Sensors

Editorial

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2 pages, 146 KiB

Open AccessEditorial

Advances in Multi-Sensor Information Fusion: Theory and Applications 2017

by Xue-Bo Jin^1,*

, Shuli Sun²

, Hong Wei³ and Feng-Bao Yang⁴

¹ School of Computer Information and Engineering, Beijing Technology and Business University, Beijing 100048, China

² School of Electronics Engineering, Heilongjiang University, Harbin 150080, China

³ Department of computer science, University of Reading, RG6 6AY Reading, UK

⁴ School of Information and Communication Engineering, North University of China, Taiyuan 030051, China

Sensors 2018, 18(4), 1162; https://doi.org/10.3390/s18041162 - 11 Apr 2018

Cited by 20 | Viewed by 4133

Abstract

The information fusion technique can integrate a large amount of data and knowledge representing the same real-world object and obtain a consistent, accurate, and useful representation of that object. The data may be independent or redundant, and can be obtained by different sensors [...] Read more.

The information fusion technique can integrate a large amount of data and knowledge representing the same real-world object and obtain a consistent, accurate, and useful representation of that object. The data may be independent or redundant, and can be obtained by different sensors at the same time or at different times. A suitable combination of investigative methods can substantially increase the profit of information in comparison with that from a single sensor. Multi-sensor information fusion has been a key issue in sensor research since the 1970s, and it has been applied in many fields. For example, manufacturing and process control industries can generate a lot of data, which have real, actionable business value. The fusion of these data can greatly improve productivity through digitization. The goal of this special issue is to report innovative ideas and solutions for multi-sensor information fusion in the emerging applications era, focusing on development, adoption, and applications. Full article

(This article belongs to the Special Issue Advances in Multi-Sensor Information Fusion: Theory and Applications 2017)

Research

Jump to: Editorial, Review, Other

20 pages, 2529 KiB

Open AccessArticle

An Internet of Things System for Underground Mine Air Quality Pollutant Prediction Based on Azure Machine Learning

by ByungWan Jo and Rana Muhammad Asad Khan^*

Department of Civil and Environmental Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Korea

Sensors 2018, 18(4), 930; https://doi.org/10.3390/s18040930 - 21 Mar 2018

Cited by 80 | Viewed by 13526

Abstract

The implementation of wireless sensor networks (WSNs) for monitoring the complex, dynamic, and harsh environment of underground coal mines (UCMs) is sought around the world to enhance safety. However, previously developed smart systems are limited to monitoring or, in a few cases, can [...] Read more.

The implementation of wireless sensor networks (WSNs) for monitoring the complex, dynamic, and harsh environment of underground coal mines (UCMs) is sought around the world to enhance safety. However, previously developed smart systems are limited to monitoring or, in a few cases, can report events. Therefore, this study introduces a reliable, efficient, and cost-effective internet of things (IoT) system for air quality monitoring with newly added features of assessment and pollutant prediction. This system is comprised of sensor modules, communication protocols, and a base station, running Azure Machine Learning (AML) Studio over it. Arduino-based sensor modules with eight different parameters were installed at separate locations of an operational UCM. Based on the sensed data, the proposed system assesses mine air quality in terms of the mine environment index (MEI). Principal component analysis (PCA) identified CH₄, CO, SO₂, and H₂S as the most influencing gases significantly affecting mine air quality. The results of PCA were fed into the ANN model in AML studio, which enabled the prediction of MEI. An optimum number of neurons were determined for both actual input and PCA-based input parameters. The results showed a better performance of the PCA-based ANN for MEI prediction, with R² and RMSE values of 0.6654 and 0.2104, respectively. Therefore, the proposed Arduino and AML-based system enhances mine environmental safety by quickly assessing and predicting mine air quality. Full article

(This article belongs to the Special Issue Artificial Intelligence and Machine Learning in Sensors Networks)

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11 pages, 15027 KiB

Open AccessArticle

Comparison between Modelled and Measured Magnetic Field Scans of Different Planar Coil Topologies for Stress Sensor Applications

by Robert Gibbs

, Gregory Moreton, Turgut Meydan^*

and Paul Williams

Cardiff School of Engineering, Cardiff University, Queen’s Buildings, Cardiff CF24 3AA, UK

Sensors 2018, 18(4), 931; https://doi.org/10.3390/s18040931 - 21 Mar 2018

Cited by 6 | Viewed by 7819

Abstract

The investigation of planar coils of differing topologies, when combined with a magnetostrictive amorphous ribbon to form a stress-sensitive self-inductor, is an active research area for applications as stress or pressure sensors. Four topologies of planar coil (Circular, Mesh, Meander, and Square) have [...] Read more.

The investigation of planar coils of differing topologies, when combined with a magnetostrictive amorphous ribbon to form a stress-sensitive self-inductor, is an active research area for applications as stress or pressure sensors. Four topologies of planar coil (Circular, Mesh, Meander, and Square) have been constructed using copper track on 30 mm wide PCB substrate. The coils are energized to draw 0.4 A and the resulting magnetic field distribution is observed with a newly developed three-dimensional magnetic field scanner. The system is based on a variably angled Micromagnetics^® STJ-020 tunneling magneto-resistance sensor with a spatial resolution of 5–10 µm and sensitivity to fields of less than 10 A/m. These experimental results are compared with the fields computed by ANSYS Maxwell^® finite element modelling of the same topologies. Measured field shape and strength correspond well with the results of modelling, including direct observation of corner and edge effects. Three-dimensional analysis of the field shape produced by the square coil, isolating the components H_(x) and H_(z), is compared with the three-dimensional field solutions from modelling. The finite element modelling is validated and the accuracy and utility of the new system for three-dimensional scanning of general stray fields is confirmed. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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13 pages, 9062 KiB

Open AccessArticle

A Newly Designed Fiber-Optic Based Earth Pressure Transducer with Adjustable Measurement Range

by Hou-Zhen Wei¹, Dong-Sheng Xu^2,*

and Qing-Shan Meng^1,*

¹ State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China

² School of Civil Engineering and Mechanics, Huazhong University of Science and Technology, 1037 Luoyu Rd., Wuhan 430074, China

Sensors 2018, 18(4), 932; https://doi.org/10.3390/s18040932 - 21 Mar 2018

Cited by 29 | Viewed by 5930

Abstract

A novel fiber-optic based earth pressure sensor (FPS) with an adjustable measurement range and high sensitivity is developed to measure earth pressures for civil infrastructures. The new FPS combines a cantilever beam with fiber Bragg grating (FBG) sensors and a flexible membrane. Compared [...] Read more.

A novel fiber-optic based earth pressure sensor (FPS) with an adjustable measurement range and high sensitivity is developed to measure earth pressures for civil infrastructures. The new FPS combines a cantilever beam with fiber Bragg grating (FBG) sensors and a flexible membrane. Compared with a traditional pressure transducer with a dual diaphragm design, the proposed FPS has a larger measurement range and shows high accuracy. The working principles, parameter design, fabrication methods, and laboratory calibration tests are explained in this paper. A theoretical solution is derived to obtain the relationship between the applied pressure and strain of the FBG sensors. In addition, a finite element model is established to analyze the mechanical behavior of the membrane and the cantilever beam and thereby obtain optimal parameters. The cantilever beam is 40 mm long, 15 mm wide, and 1 mm thick. The whole FPS has a diameter of 100 mm and a thickness of 30 mm. The sensitivity of the FPS is 0.104 kPa/με. In addition, automatic temperature compensation can be achieved. The FPS’s sensitivity, physical properties, and response to applied pressure are extensively examined through modeling and experiments. The results show that the proposed FPS has numerous potential applications in soil pressure measurement. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Based Sensors)

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19 pages, 19395 KiB

Open AccessArticle

Robust Spacecraft Component Detection in Point Clouds

by Quanmao Wei^1,2, Zhiguo Jiang^1,2 and Haopeng Zhang^1,2,*

¹ Image Processing Center, School of Astronautics, Beihang University, Beijing 100191, China

² Beijing Key Laboratory of Digital Media, Beijing 100191, China

Sensors 2018, 18(4), 933; https://doi.org/10.3390/s18040933 - 21 Mar 2018

Cited by 11 | Viewed by 4751

Abstract

Automatic component detection of spacecraft can assist in on-orbit operation and space situational awareness. Spacecraft are generally composed of solar panels and cuboidal or cylindrical modules. These components can be simply represented by geometric primitives like plane, cuboid and cylinder. Based on this [...] Read more.

Automatic component detection of spacecraft can assist in on-orbit operation and space situational awareness. Spacecraft are generally composed of solar panels and cuboidal or cylindrical modules. These components can be simply represented by geometric primitives like plane, cuboid and cylinder. Based on this prior, we propose a robust automatic detection scheme to automatically detect such basic components of spacecraft in three-dimensional (3D) point clouds. In the proposed scheme, cylinders are first detected in the iteration of the energy-based geometric model fitting and cylinder parameter estimation. Then, planes are detected by Hough transform and further described as bounded patches with their minimum bounding rectangles. Finally, the cuboids are detected with pair-wise geometry relations from the detected patches. After successive detection of cylinders, planar patches and cuboids, a mid-level geometry representation of the spacecraft can be delivered. We tested the proposed component detection scheme on spacecraft 3D point clouds synthesized by computer-aided design (CAD) models and those recovered by image-based reconstruction, respectively. Experimental results illustrate that the proposed scheme can detect the basic geometric components effectively and has fine robustness against noise and point distribution density. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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11 pages, 3702 KiB

Open AccessArticle

The Effect of Vibration Characteristics on the Atomization Rate in a Micro-Tapered Aperture Atomizer

by Qiufeng Yan^1,2, Jianhui Zhang^1,2,*, Jun Huang^3,* and Ying Wang⁴

¹ State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

² College of Mechanical and Electrical Engineering, Guangzhou University, Guanzhou 510006, China

³ Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013, China

⁴ Taizhou Polytechnical Institute, Taizhou 225300, China

Sensors 2018, 18(4), 934; https://doi.org/10.3390/s18040934 - 21 Mar 2018

Cited by 23 | Viewed by 5427

Abstract

Because little is known about the atomization theory of a micro-tapered aperture atomizer, we investigated the vibration characteristics of this type of atomizer. The atomization mechanism of a micro-tapered aperture atomizer was described, and the atomization rate equation was deduced. As observed via [...] Read more.

Because little is known about the atomization theory of a micro-tapered aperture atomizer, we investigated the vibration characteristics of this type of atomizer. The atomization mechanism of a micro-tapered aperture atomizer was described, and the atomization rate equation was deduced. As observed via microscopy, the angle of the micro-tapered aperture changes with the applied voltage, which proved the existence of a dynamic cone angle. The forward and reverse atomization rates were measured at various voltages, and the influence of the micro-tapered aperture and its variation on the atomization rate was characterized. The resonance frequency of the piezoelectric vibrator was obtained using a laser vibrometer, and the atomization rates were measured at each resonance frequency. From experiments, we found that the atomization rates at the first five resonance frequencies increased as the working frequency increased. At the fifth resonance frequency (121.1 kHz), the atomization rate was maximized (0.561 mL/min), and at the sixth resonance frequency (148.3 kHz), the atomization rate decreased significantly (0.198 mL/min). The experimental results show that the vibration characteristics of the piezoelectric vibrator have a relatively strong impact on the atomization rate. This research is expected to contribute to the manufacture of micro-tapered aperture atomizers. Full article

(This article belongs to the Special Issue Ultrasonic Sensors 2018)

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9 pages, 6871 KiB

Open AccessArticle

Detection and Compensation of Degeneracy Cases for IMU-Kinect Integrated Continuous SLAM with Plane Features

by HyunGi Cho¹, Suyong Yeon², Hyunga Choi¹ and Nakju Doh^1,3,*

¹ School of Electrical Engineering, Korea University, Seoul 02841, Korea

² Naver Labs, Gyeonggi-do 13494, Korea

³ TeeVR Inc., Seoul 02857, Korea

Sensors 2018, 18(4), 935; https://doi.org/10.3390/s18040935 - 22 Mar 2018

Cited by 20 | Viewed by 5228

Abstract

In a group of general geometric primitives, plane-based features are widely used for indoor localization because of their robustness against noises. However, a lack of linearly independent planes may lead to a non-trivial estimation. This in return can cause a degenerate state from [...] Read more.

In a group of general geometric primitives, plane-based features are widely used for indoor localization because of their robustness against noises. However, a lack of linearly independent planes may lead to a non-trivial estimation. This in return can cause a degenerate state from which all states cannot be estimated. To solve this problem, this paper first proposed a degeneracy detection method. A compensation method that could fix orientations by projecting an inertial measurement unit’s (IMU) information was then explained. Experiments were conducted using an IMU-Kinect v2 integrated sensor system prone to fall into degenerate cases owing to its narrow field-of-view. Results showed that the proposed framework could enhance map accuracy by successful detection and compensation of degenerated orientations. Full article

(This article belongs to the Section Remote Sensors)

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21 pages, 4591 KiB

Open AccessArticle

Resonance-Based Time-Frequency Manifold for Feature Extraction of Ship-Radiated Noise

by Jiaquan Yan^1,2

, Haixin Sun^1,2, Hailan Chen^1,3, Naveed Ur Rehman Junejo^1,2 and En Cheng^1,2,*

¹ Key Laboratory of Underwater Acoustic Communication and Marine Information Technology, Ministry of Education, Xiamen University, Xiamen 361005, China

² School of Information Science and Engineering, Xiamen University, Xiamen 361005, China

³ School of Science, Jimei University, Xiamen 361021, China

Sensors 2018, 18(4), 936; https://doi.org/10.3390/s18040936 - 22 Mar 2018

Cited by 27 | Viewed by 5173

Abstract

In this paper, a novel time-frequency signature using resonance-based sparse signal decomposition (RSSD), phase space reconstruction (PSR), time-frequency distribution (TFD) and manifold learning is proposed for feature extraction of ship-radiated noise, which is called resonance-based time-frequency manifold (RTFM). This is suitable for analyzing [...] Read more.

In this paper, a novel time-frequency signature using resonance-based sparse signal decomposition (RSSD), phase space reconstruction (PSR), time-frequency distribution (TFD) and manifold learning is proposed for feature extraction of ship-radiated noise, which is called resonance-based time-frequency manifold (RTFM). This is suitable for analyzing signals with oscillatory, non-stationary and non-linear characteristics in a situation of serious noise pollution. Unlike the traditional methods which are sensitive to noise and just consider one side of oscillatory, non-stationary and non-linear characteristics, the proposed RTFM can provide the intact feature signature of all these characteristics in the form of a time-frequency signature by the following steps: first, RSSD is employed on the raw signal to extract the high-oscillatory component and abandon the low-oscillatory component. Second, PSR is performed on the high-oscillatory component to map the one-dimensional signal to the high-dimensional phase space. Third, TFD is employed to reveal non-stationary information in the phase space. Finally, manifold learning is applied to the TFDs to fetch the intrinsic non-linear manifold. A proportional addition of the top two RTFMs is adopted to produce the improved RTFM signature. All of the case studies are validated on real audio recordings of ship-radiated noise. Case studies of ship-radiated noise on different datasets and various degrees of noise pollution manifest the effectiveness and robustness of the proposed method. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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16 pages, 823 KiB

Open AccessArticle

Source Localization in Acoustic Sensor Networks via Constrained Least-Squares Optimization Using AOA and GROA Measurements

by Ji-An Luo^1,*, Si-Wei Pan¹, Dong-Liang Peng¹, Zhi Wang² and Yan-Jun Li³

¹ Key Lab for IOT and Information Fusion Technology of Zhejiang, Hangzhou Dianzi University, Hangzhou 310018, China

² The State Key Laboratory of Industrial Control Technology, Zhejiang University, Hangzhou 310027, China

³ School of Computer Science and Technology, Zhejiang University of Technology, Hangzhou 310023, China

Sensors 2018, 18(4), 937; https://doi.org/10.3390/s18040937 - 22 Mar 2018

Cited by 6 | Viewed by 4383

Abstract

A constrained least-squares (CLS) 3D source localization method is presented for acoustic sensor networks with sensor position errors. The proposed approach uses angles of arrivals (AOAs) and gain ratios of arrival (GROAs) measured simultaneously at each node to estimate the source position jointly. [...] Read more.

A constrained least-squares (CLS) 3D source localization method is presented for acoustic sensor networks with sensor position errors. The proposed approach uses angles of arrivals (AOAs) and gain ratios of arrival (GROAs) measured simultaneously at each node to estimate the source position jointly. Compared to AOA-only localization methods, the GROAs can be used in conjunction with AOA measurements so as to get more accurate results by exploiting the geometrical relationship between these two measurements. Compared to time difference of arrival localization methods, the proposed algorithm does not require accurate time synchronization over different nodes. The theoretical mean-square error matrices of the proposed approach are derived and they are exactly equal to the Cramér–Rao bound for Gaussian noise under the small error condition. Simulations validate the performance of the proposed estimator. Full article

(This article belongs to the Section Sensor Networks)

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19 pages, 5120 KiB

Open AccessArticle

Application of Least-Squares Support Vector Machines for Quantitative Evaluation of Known Contaminant in Water Distribution System Using Online Water Quality Parameters

by Kexin Wang, Xiang Wen, Dibo Hou^*, Dezhan Tu, Naifu Zhu, Pingjie Huang, Guangxin Zhang and Hongjian Zhang

State Key Laboratory of Industrial Control Technology, College of Control Science and Engineering, Zhejiang University, Hangzhou 310027, China

Sensors 2018, 18(4), 938; https://doi.org/10.3390/s18040938 - 22 Mar 2018

Cited by 23 | Viewed by 5302

Abstract

In water-quality, early warning systems and qualitative detection of contaminants are always challenging. There are a number of parameters that need to be measured which are not entirely linearly related to pollutant concentrations. Besides the complex correlations between variable water parameters that need [...] Read more.

In water-quality, early warning systems and qualitative detection of contaminants are always challenging. There are a number of parameters that need to be measured which are not entirely linearly related to pollutant concentrations. Besides the complex correlations between variable water parameters that need to be analyzed also impairs the accuracy of quantitative detection. In aspects of these problems, the application of least-squares support vector machines (LS-SVM) is used to evaluate the water contamination and various conventional water quality sensors quantitatively. The various contaminations may cause different correlative responses of sensors, and also the degree of response is related to the concentration of the injected contaminant. Therefore to enhance the reliability and accuracy of water contamination detection a new method is proposed. In this method, a new relative response parameter is introduced to calculate the differences between water quality parameters and their baselines. A variety of regression models has been examined, as result of its high performance, the regression model based on genetic algorithm (GA) is combined with LS-SVM. In this paper, the practical application of the proposed method is considered, controlled experiments are designed, and data is collected from the experimental setup. The measured data is applied to analyze the water contamination concentration. The evaluation of results validated that the LS-SVM model can adapt to the local nonlinear variations between water quality parameters and contamination concentration with the excellent generalization ability and accuracy. The validity of the proposed approach in concentration evaluation for potassium ferricyanide is proven to be more than 0.5 mg/L in water distribution systems. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 646 KiB

Open AccessArticle

Visual Odometry and Place Recognition Fusion for Vehicle Position Tracking in Urban Environments

by Safa Ouerghi^1,*, Rémi Boutteau²

, Xavier Savatier² and Fethi Tlili¹

¹ Carthage University, SUP’COM, GRESCOM, El Ghazela 2083, Tunisia

² Normandie University, UNIROUEN, ESIGELEC, IRSEEM, 76000 Rouen, France

Sensors 2018, 18(4), 939; https://doi.org/10.3390/s18040939 - 22 Mar 2018

Cited by 12 | Viewed by 4834

Abstract

In this paper, we address the problem of vehicle localization in urban environments. We rely on visual odometry, calculating the incremental motion, to track the position of the vehicle and on place recognition to correct the accumulated drift of visual odometry, whenever a [...] Read more.

In this paper, we address the problem of vehicle localization in urban environments. We rely on visual odometry, calculating the incremental motion, to track the position of the vehicle and on place recognition to correct the accumulated drift of visual odometry, whenever a location is recognized. The algorithm used as a place recognition module is SeqSLAM, addressing challenging environments and achieving quite remarkable results. Specifically, we perform the long-term navigation of a vehicle based on the fusion of visual odometry and SeqSLAM. The template library for this latter is created online using navigation information from the visual odometry module. That is, when a location is recognized, the corresponding information is used as an observation of the filter. The fusion is done using the EKF and the UKF, the well-known nonlinear state estimation methods, to assess the superior alternative. The algorithm is evaluated using the KITTI dataset and the results show the reduction of the navigation errors by loop-closure detection. The overall position error of visual odometery with SeqSLAM is 0.22% of the trajectory, which is much smaller than the navigation errors of visual odometery alone 0.45%. In addition, despite the superiority of the UKF in a variety of estimation problems, our results indicate that the UKF performs as efficiently as the EKF at the expense of an additional computational overhead. This leads to the conclusion that the EKF is a better choice for fusing visual odometry and SeqSlam in a long-term navigation context. Full article

(This article belongs to the Section Intelligent Sensors)

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21 pages, 945 KiB

Open AccessArticle

Explicit Content Caching at Mobile Edge Networks with Cross-Layer Sensing

by Lingyu Chen^1,*, Youxing Su¹, Wenbin Luo¹, Xuemin Hong^1,2 and Jianghong Shi^1,2

¹ School of Information Science and Technology, Xiamen University, Xiamen 361005, China

² Key Lab of Underwater Acoustic Communication and Marine Information Technology, Ministry of Education, Xiamen 361005, China

Sensors 2018, 18(4), 940; https://doi.org/10.3390/s18040940 - 22 Mar 2018

Cited by 6 | Viewed by 4001

Abstract

The deployment density and computational power of small base stations (BSs) are expected to increase significantly in the next generation mobile communication networks. These BSs form the mobile edge network, which is a pervasive and distributed infrastructure that can empower a variety of [...] Read more.

The deployment density and computational power of small base stations (BSs) are expected to increase significantly in the next generation mobile communication networks. These BSs form the mobile edge network, which is a pervasive and distributed infrastructure that can empower a variety of edge/fog computing applications. This paper proposes a novel edge-computing application called explicit caching, which stores selective contents at BSs and exposes such contents to local users for interactive browsing and download. We formulate the explicit caching problem as a joint content recommendation, caching, and delivery problem, which aims to maximize the expected user quality-of-experience (QoE) with varying degrees of cross-layer sensing capability. Optimal and effective heuristic algorithms are presented to solve the problem. The theoretical performance bounds of the explicit caching system are derived in simplified scenarios. The impacts of cache storage space, BS backhaul capacity, cross-layer information, and user mobility on the system performance are simulated and discussed in realistic scenarios. Results suggest that, compared with conventional implicit caching schemes, explicit caching can better exploit the mobile edge network infrastructure for personalized content dissemination. Full article

(This article belongs to the Special Issue New Paradigms in Data Sensing and Processing for Edge Computing)

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16 pages, 10127 KiB

Open AccessArticle

A High-Resolution SAR Focusing Experiment Based on GF-3 Staring Data

by Mingyang Shang^1,2,3, Bing Han^1,2,*, Chibiao Ding^1,2,3,4, Jili Sun², Tao Zhang^1,2,3

, Lijia Huang^1,2 and Dadi Meng^1,2

¹ Key Laboratory of Technology in Geo-Spatial Information Processing and Application Systems, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

² Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

³ School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China

⁴ National Key Laboratory of Microwave Imaging Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

Sensors 2018, 18(4), 943; https://doi.org/10.3390/s18040943 - 22 Mar 2018

Cited by 10 | Viewed by 4869

Abstract

Spotlight synthetic aperture radar (SAR) is a proven technique, which can provide high-resolution images as compared to those produced by traditional stripmap SAR. This paper addresses a high-resolution SAR focusing experiment based on Gaofen-3 satellite (GF-3) staring data with about 55 cm azimuth [...] Read more.

Spotlight synthetic aperture radar (SAR) is a proven technique, which can provide high-resolution images as compared to those produced by traditional stripmap SAR. This paper addresses a high-resolution SAR focusing experiment based on Gaofen-3 satellite (GF-3) staring data with about 55 cm azimuth resolution and 240 MHz range bandwidth. In staring spotlight (ST) mode, the antenna always illuminates the same scene on the ground, which can extend the synthetic aperture. Based on a two-step processing algorithm, some special aspects such as curved-orbit model error correction, stop-and-go correction, and antenna pattern demodulation must be considered in image focusing. We provide detailed descriptions of all these aspects and put forward corresponding solutions. Using these suggested methods directly in an imaging module without any modification for other data processing software can make the most of the existing ground data processor. Finally, actual data acquired in GF-3 ST mode is used to validate these methodologies, and a well-focused, high-resolution image is obtained as a result of this focusing experiment. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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17 pages, 5595 KiB

Open AccessArticle

Aerial Mapping of Forests Affected by Pathogens Using UAVs, Hyperspectral Sensors, and Artificial Intelligence

by Juan Sandino^1,*

, Geoff Pegg²

, Felipe Gonzalez¹

and Grant Smith³

¹ Insitute for Future Environments; Robotics and Autonomous Systems, Queensland University of Technology (QUT), 2 George St, Brisbane City, QLD 4000, Australia

² Horticulture & Forestry Science, Department of Agriculture & Fisheries, Ecosciences Precinct, 41 Boggo Rd Dutton Park, QLD 4102, Australia

³ BioProtection Technologies, The New Zealand Institute for Plant & Food Research Limited, Gerald St, Lincoln 7608, New Zealand

Sensors 2018, 18(4), 944; https://doi.org/10.3390/s18040944 - 22 Mar 2018

Cited by 94 | Viewed by 13717

Abstract

The environmental and economic impacts of exotic fungal species on natural and plantation forests have been historically catastrophic. Recorded surveillance and control actions are challenging because they are costly, time-consuming, and hazardous in remote areas. Prolonged periods of testing and observation of site-based [...] Read more.

The environmental and economic impacts of exotic fungal species on natural and plantation forests have been historically catastrophic. Recorded surveillance and control actions are challenging because they are costly, time-consuming, and hazardous in remote areas. Prolonged periods of testing and observation of site-based tests have limitations in verifying the rapid proliferation of exotic pathogens and deterioration rates in hosts. Recent remote sensing approaches have offered fast, broad-scale, and affordable surveys as well as additional indicators that can complement on-ground tests. This paper proposes a framework that consolidates site-based insights and remote sensing capabilities to detect and segment deteriorations by fungal pathogens in natural and plantation forests. This approach is illustrated with an experimentation case of myrtle rust (Austropuccinia psidii) on paperbark tea trees (Melaleuca quinquenervia) in New South Wales (NSW), Australia. The method integrates unmanned aerial vehicles (UAVs), hyperspectral image sensors, and data processing algorithms using machine learning. Imagery is acquired using a Headwall Nano-Hyperspec

^{®}

camera, orthorectified in Headwall SpectralView

^{®}

, and processed in Python programming language using eXtreme Gradient Boosting (XGBoost), Geospatial Data Abstraction Library (GDAL), and Scikit-learn third-party libraries. In total, 11,385 samples were extracted and labelled into five classes: two classes for deterioration status and three classes for background objects. Insights reveal individual detection rates of 95% for healthy trees, 97% for deteriorated trees, and a global multiclass detection rate of 97%. The methodology is versatile to be applied to additional datasets taken with different image sensors, and the processing of large datasets with freeware tools. Full article

(This article belongs to the Special Issue UAV or Drones for Remote Sensing Applications)

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23 pages, 15475 KiB

Open AccessArticle

Sensor Buoy System for Monitoring Renewable Marine Energy Resources

by Emilio García, Eduardo Quiles^*

, Antonio Correcher

and Francisco Morant

Instituto de Automática e Informática Industrial, Universitat Politècnica de València, 46022 Valencia, Spain

Sensors 2018, 18(4), 945; https://doi.org/10.3390/s18040945 - 22 Mar 2018

Cited by 24 | Viewed by 8820

Abstract

In this paper we present a multi-sensor floating system designed to monitor marine energy parameters, in order to sample wind, wave, and marine current energy resources. For this purpose, a set of dedicated sensors to measure the height and period of the waves, [...] Read more.

In this paper we present a multi-sensor floating system designed to monitor marine energy parameters, in order to sample wind, wave, and marine current energy resources. For this purpose, a set of dedicated sensors to measure the height and period of the waves, wind, and marine current intensity and direction have been selected and installed in the system. The floating device incorporates wind and marine current turbines for renewable energy self-consumption and to carry out complementary studies on the stability of such a system. The feasibility, safety, sensor communications, and buoy stability of the floating device have been successfully checked in real operating conditions. Full article

(This article belongs to the Section Remote Sensors)

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10 pages, 1825 KiB

Open AccessArticle

Real-Time Tau Protein Detection by Sandwich-Based Piezoelectric Biosensing: Exploring Tubulin as a Mass Enhancer

by Dujuan Li¹

, Simona Scarano^2,*

, Samuele Lisi², Pasquale Palladino²

and Maria Minunni²

¹ College of Life Information Science & Instrument Engineering, Hangzhou Dianzi University, 115 Wenyi Rd, Hangzhou 310000, China

² Department of Chemistry “Ugo Schiff”, University of Florence, via della Lastruccia 3-13, Sesto Fiorentino, 50019 Firenze, Italy

Sensors 2018, 18(4), 946; https://doi.org/10.3390/s18040946 - 22 Mar 2018

Cited by 20 | Viewed by 6336

Abstract

Human tau protein is one of the most advanced and accepted biomarkers for AD and tauopathies diagnosis in general. In this work, a quartz crystal balance (QCM) immunosensor was developed for the detection of human tau protein in buffer and artificial cerebrospinal fluid [...] Read more.

Human tau protein is one of the most advanced and accepted biomarkers for AD and tauopathies diagnosis in general. In this work, a quartz crystal balance (QCM) immunosensor was developed for the detection of human tau protein in buffer and artificial cerebrospinal fluid (aCSF), through both direct and sandwich assays. Starting from a conventional immuno-based sandwich strategy, two monoclonal antibodies recognizing different epitopes of tau protein were used, achieving a detection limit for the direct assay in nanomolar range both in HBES-EP and aCSF. Afterward, for exploring alternative specific receptors as secondary recognition elements for tau protein biosensing, we tested tubulin and compared its behavior to a conventional secondary antibody in the sandwich assay. Tau–tubulin binding has shown an extended working range coupled to a signal improvement in comparison with the conventional secondary antibody-based approach, showing a dose–response trend at lower tau concentration than is usually investigated and closer to the physiological levels in the reference matrix for protein tau biomarker. Our results open up new and encouraging perspectives for the use of tubulin as an alternative receptor for tau protein with interesting features due to the possibility of taking advantage of its polymerization and reversible binding to this key hallmark of Alzheimer’s disease. Full article

(This article belongs to the Special Issue Label-Free Biosensors)

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17 pages, 12253 KiB

Open AccessArticle

An Equivalent Circuit of Longitudinal Vibration for a Piezoelectric Structure with Losses

by Tao Yuan^*, Chaodong Li and Pingqing Fan

School of Mechatronic Engineering and Automation, Shanghai University, Shanghai 200072, China

Sensors 2018, 18(4), 947; https://doi.org/10.3390/s18040947 - 22 Mar 2018

Cited by 4 | Viewed by 4910

Abstract

Equivalent circuits of piezoelectric structures such as bimorphs and unimorphs conventionally focus on the bending vibration modes. However, the longitudinal vibration modes are rarely considered even though they also play a remarkable role in piezoelectric devices. Losses, especially elastic loss in the metal [...] Read more.

Equivalent circuits of piezoelectric structures such as bimorphs and unimorphs conventionally focus on the bending vibration modes. However, the longitudinal vibration modes are rarely considered even though they also play a remarkable role in piezoelectric devices. Losses, especially elastic loss in the metal substrate, are also generally neglected, which leads to discrepancies compared with experiments. In this paper, a novel equivalent circuit with four kinds of losses is proposed for a beamlike piezoelectric structure under the longitudinal vibration mode. This structure consists of a slender beam as the metal substrate, and a piezoelectric patch which covers a partial length of the beam. In this approach, first, complex numbers are used to deal with four kinds of losses—elastic loss in the metal substrate, and piezoelectric, dielectric, and elastic losses in the piezoelectric patch. Next in this approach, based on Mason’s model, a new equivalent circuit is developed. Using MATLAB, impedance curves of this structure are simulated by the equivalent circuit method. Experiments are conducted and good agreements are revealed between experiments and equivalent circuit results. It is indicated that the introduction of four losses in an equivalent circuit can increase the result accuracy considerably. Full article

(This article belongs to the Special Issue Piezoelectric Micro- and Nano-Devices)

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11 pages, 12830 KiB

Open AccessArticle

Remarkably Enhanced Room-Temperature Hydrogen Sensing of SnO₂ Nanoflowers via Vacuum Annealing Treatment

by Gao Liu¹, Zhao Wang^1,*

, Zihui Chen¹, Shulin Yang^1,2, Xingxing Fu¹, Rui Huang¹, Xiaokang Li¹, Juan Xiong¹, Yongming Hu¹ and Haoshuang Gu^1,*

¹ Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials—Hubei Key Laboratory of Ferro & Piezoelectric Materials and Devices, Faculty of Physics & Electronic Sciences, Hubei University, Wuhan 430062, China

² School of Electronic Information, Huanggang Normal University, Huanggang 438000, China

Sensors 2018, 18(4), 949; https://doi.org/10.3390/s18040949 - 23 Mar 2018

Cited by 32 | Viewed by 4536

Abstract

In this work, SnO₂ nanoflowers synthesized by a hydrothermal method were employed as hydrogen sensing materials. The as-synthesized SnO₂ nanoflowers consisted of cuboid-like SnO₂ nanorods with tetragonal structures. A great increase in the relative content of surface-adsorbed oxygen was observed [...] Read more.

In this work, SnO₂ nanoflowers synthesized by a hydrothermal method were employed as hydrogen sensing materials. The as-synthesized SnO₂ nanoflowers consisted of cuboid-like SnO₂ nanorods with tetragonal structures. A great increase in the relative content of surface-adsorbed oxygen was observed after the vacuum annealing treatment, and this increase could have been due to the increase in surface oxygen vacancies serving as preferential adsorption sites for oxygen species. Annealing treatment resulted in an 8% increase in the specific surface area of the samples. Moreover, the conductivity of the sensors decreased after the annealing treatment, which should be attributed to the increase in electron scattering around the defects and the compensated donor behavior of the oxygen vacancies due to the surface oxygen adsorption. The hydrogen sensors of the annealed samples, compared to those of the unannealed samples, exhibited a much higher sensitivity and faster response rate. The sensor response factor and response rate increased from 27.1% to 80.2% and 0.34%/s to 1.15%/s, respectively. This remarkable enhancement in sensing performance induced by the annealing treatment could be attributed to the larger specific surface areas and higher amount of surface-adsorbed oxygen, which provides a greater reaction space for hydrogen. Moreover, the sensors with annealed SnO₂ nanoflowers also exhibited high selectivity towards hydrogen against CH₄, CO, and ethanol. Full article

(This article belongs to the Section Chemical Sensors)

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18 pages, 3083 KiB

Open AccessArticle

Localization of an Underwater Control Network Based on Quasi-Stable Adjustment

by Jianhu Zhao^1,2

, Xinhua Chen^1,2,*, Hongmei Zhang³ and Jie Feng^1,2

¹ School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan 430079, China

² Institute of Marine Science and Technology, Wuhan University, Wuhan 430079, China

³ Automation Department, School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China

Sensors 2018, 18(4), 950; https://doi.org/10.3390/s18040950 - 23 Mar 2018

Cited by 12 | Viewed by 3744

Abstract

There exists a common problem in the localization of underwater control networks that the precision of the absolute coordinates of known points obtained by marine absolute measurement is poor, and it seriously affects the precision of the whole network in traditional constraint adjustment. [...] Read more.

There exists a common problem in the localization of underwater control networks that the precision of the absolute coordinates of known points obtained by marine absolute measurement is poor, and it seriously affects the precision of the whole network in traditional constraint adjustment. Therefore, considering that the precision of underwater baselines is good, we use it to carry out quasi-stable adjustment to amend known points before constraint adjustment so that the points fit the network shape better. In addition, we add unconstrained adjustment for quality control of underwater baselines, the observations of quasi-stable adjustment and constrained adjustment, to eliminate the unqualified baselines and improve the results’ accuracy of the two adjustments. Finally, the modified method is applied to a practical LBL (Long Baseline) experiment and obtains a mean point location precision of 0.08 m, which improves by 38% compared with the traditional method. Full article

(This article belongs to the Special Issue Dependable Monitoring in Wireless Sensor Networks)

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17 pages, 4576 KiB

Open AccessArticle

Micro-Doppler Effect Removal in ISAR Imaging by Promoting Joint Sparsity in Time-Frequency Domain

by Lin Sun

and Weidong Chen^*

Key Laboratory of Electromagnetic Space Information of the Chinese Academy of Sciences, University of Science and Technology of China, Hefei 230027, China

Sensors 2018, 18(4), 951; https://doi.org/10.3390/s18040951 - 23 Mar 2018

Cited by 10 | Viewed by 4524

Abstract

For micromotion scatterers with small rotating radii, the micro-Doppler (m-D) effect interferes with cross-range compression in inverse synthetic aperture radar (ISAR) imaging and leads to a blurred main body image. In this paper, a novel method is proposed to remove the m-D effect [...] Read more.

For micromotion scatterers with small rotating radii, the micro-Doppler (m-D) effect interferes with cross-range compression in inverse synthetic aperture radar (ISAR) imaging and leads to a blurred main body image. In this paper, a novel method is proposed to remove the m-D effect by promoting the joint sparsity in the time-frequency domain. Firstly, to obtain the time-frequency representations of the limited measurements, the short-time Fourier transform (STFT) was modelled by an underdetermined equation. Then, a new objective function was used to measure the joint sparsity of the STFT entries so that the joint sparse recovery problem could be formulated as a constrained minimization problem. Similar to the smoothed

l_{0}

(SL0) algorithm, a steepest descend approach was used to minimize the new objective function, where the projection step was tailored to make it suitable for m-D effect removal. Finally, we utilized the recovered STFT entries to obtain the main body echoes, based on which cross-range compression could be realized without m-D interference. After all contaminated range cells were processed by the proposed method, a clear main body image could be achieved. Experiments using both the point-scattering model and electromagnetic (EM) computation validated the performance of the proposed method. Full article

(This article belongs to the Special Issue Automatic Target Recognition of High Resolution SAR/ISAR Images)

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13 pages, 4649 KiB

Open AccessArticle

Competitive Deep-Belief Networks for Underwater Acoustic Target Recognition

by Honghui Yang^*

, Sheng Shen, Xiaohui Yao, Meiping Sheng and Chen Wang

School of Marine Science and Technology, Northwestern Polytechnical University, 127 West Youyi Road, Beilin District, Xi’an 710072, China

Sensors 2018, 18(4), 952; https://doi.org/10.3390/s18040952 - 23 Mar 2018

Cited by 85 | Viewed by 5996

Abstract

Underwater acoustic target recognition based on ship-radiated noise belongs to the small-sample-size recognition problems. A competitive deep-belief network is proposed to learn features with more discriminative information from labeled and unlabeled samples. The proposed model consists of four stages: (1) A standard restricted [...] Read more.

Underwater acoustic target recognition based on ship-radiated noise belongs to the small-sample-size recognition problems. A competitive deep-belief network is proposed to learn features with more discriminative information from labeled and unlabeled samples. The proposed model consists of four stages: (1) A standard restricted Boltzmann machine is pretrained using a large number of unlabeled data to initialize its parameters; (2) the hidden units are grouped according to categories, which provides an initial clustering model for competitive learning; (3) competitive training and back-propagation algorithms are used to update the parameters to accomplish the task of clustering; (4) by applying layer-wise training and supervised fine-tuning, a deep neural network is built to obtain features. Experimental results show that the proposed method can achieve classification accuracy of 90.89%, which is 8.95% higher than the accuracy obtained by the compared methods. In addition, the highest accuracy of our method is obtained with fewer features than other methods. Full article

(This article belongs to the Section Intelligent Sensors)

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21 pages, 4499 KiB

Open AccessArticle

Stretchable, Flexible, Scalable Smart Skin Sensors for Robotic Position and Force Estimation

by John O’Neill^*

, Jason Lu, Rodney Dockter and Timothy Kowalewski

Department of Mechanical Engineering, University of Minnesota, 111 Church St SE, Minneapolis, MN 55401, USA

Sensors 2018, 18(4), 953; https://doi.org/10.3390/s18040953 - 23 Mar 2018

Cited by 33 | Viewed by 8868

Abstract

The design and validation of a continuously stretchable and flexible skin sensor for collaborative robotic applications is outlined. The skin consists of a PDMS skin doped with Carbon Nanotubes and the addition of conductive fabric, connected by only five wires to a simple [...] Read more.

The design and validation of a continuously stretchable and flexible skin sensor for collaborative robotic applications is outlined. The skin consists of a PDMS skin doped with Carbon Nanotubes and the addition of conductive fabric, connected by only five wires to a simple microcontroller. The accuracy is characterized in position as well as force, and the skin is also tested under uniaxial stretch. There are also two examples of practical implementations in collaborative robotic applications. The stationary position estimate has an RMSE of

7.02

mm, and the sensor error stays within

2.5 \pm 1.5

mm even under stretch. The skin consistently provides an emergency stop command at only

0.5

N of force and is shown to maintain a collaboration force of 10 N in a collaborative control experiment. Full article

(This article belongs to the Section Intelligent Sensors)

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20 pages, 6150 KiB

Open AccessArticle

A Framework to Design the Computational Load Distribution of Wireless Sensor Networks in Power Consumption Constrained Environments

by David Sánchez-Álvarez^*, Marino Linaje

and Francisco-Javier Rodríguez-Pérez

School of Technology, University of Extremadura, 10003 Caceres, Spain

Sensors 2018, 18(4), 954; https://doi.org/10.3390/s18040954 - 23 Mar 2018

Cited by 9 | Viewed by 4572

Abstract

In this paper, we present a work based on the computational load distribution among the homogeneous nodes and the Hub/Sink of Wireless Sensor Networks (WSNs). The main contribution of the paper is an early decision support framework helping WSN designers to take decisions [...] Read more.

In this paper, we present a work based on the computational load distribution among the homogeneous nodes and the Hub/Sink of Wireless Sensor Networks (WSNs). The main contribution of the paper is an early decision support framework helping WSN designers to take decisions about computational load distribution for those WSNs where power consumption is a key issue (when we refer to “framework” in this work, we are considering it as a support tool to make decisions where the executive judgment can be included along with the set of mathematical tools of the WSN designer; this work shows the need to include the load distribution as an integral component of the WSN system for making early decisions regarding energy consumption). The framework takes advantage of the idea that balancing sensors nodes and Hub/Sink computational load can lead to improved energy consumption for the whole or at least the battery-powered nodes of the WSN. The approach is not trivial and it takes into account related issues such as the required data distribution, nodes, and Hub/Sink connectivity and availability due to their connectivity features and duty-cycle. For a practical demonstration, the proposed framework is applied to an agriculture case study, a sector very relevant in our region. In this kind of rural context, distances, low costs due to vegetable selling prices and the lack of continuous power supplies may lead to viable or inviable sensing solutions for the farmers. The proposed framework systematize and facilitates WSN designers the required complex calculations taking into account the most relevant variables regarding power consumption, avoiding full/partial/prototype implementations, and measurements of different computational load distribution potential solutions for a specific WSN. Full article

(This article belongs to the Special Issue Sensors in Agriculture)

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17 pages, 561 KiB

Open AccessArticle

Supporting Beacon and Event-Driven Messages in Vehicular Platoons through Token-Based Strategies

by Ali Balador^1,2,*

, Elisabeth Uhlemann¹, Carlos T. Calafate³

and Juan-Carlos Cano³

¹ Innovation, Design and Technology (IDT), Mälardalen University, 72123 Västerås, Sweden

² RISE SICS Västerås, Stora gatan 36, 722 12 Västerås, Sweden

³ Department of Computer Engineering (DISCA), Universitat Politècnica de València, 46022 València, Spain

Sensors 2018, 18(4), 955; https://doi.org/10.3390/s18040955 - 23 Mar 2018

Cited by 18 | Viewed by 5178

Abstract

Timely and reliable inter-vehicle communications is a critical requirement to support traffic safety applications, such as vehicle platooning. Furthermore, low-delay communications allow the platoon to react quickly to unexpected events. In this scope, having a predictable and highly effective medium access control (MAC) [...] Read more.

Timely and reliable inter-vehicle communications is a critical requirement to support traffic safety applications, such as vehicle platooning. Furthermore, low-delay communications allow the platoon to react quickly to unexpected events. In this scope, having a predictable and highly effective medium access control (MAC) method is of utmost importance. However, the currently available IEEE 802.11p technology is unable to adequately address these challenges. In this paper, we propose a MAC method especially adapted to platoons, able to transmit beacons within the required time constraints, but with a higher reliability level than IEEE 802.11p, while concurrently enabling efficient dissemination of event-driven messages. The protocol circulates the token within the platoon not in a round-robin fashion, but based on beacon data age, i.e., the time that has passed since the previous collection of status information, thereby automatically offering repeated beacon transmission opportunities for increased reliability. In addition, we propose three different methods for supporting event-driven messages co-existing with beacons. Analysis and simulation results in single and multi-hop scenarios showed that, by providing non-competitive channel access and frequent retransmission opportunities, our protocol can offer beacon delivery within one beacon generation interval while fulfilling the requirements on low-delay dissemination of event-driven messages for traffic safety applications. Full article

(This article belongs to the Special Issue Smart Vehicular Mobile Sensing)

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11 pages, 46764 KiB

Open AccessArticle

Gas Sensing Properties of p-Co₃O₄/n-TiO₂ Nanotube Heterostructures

by Onur Alev, Alp Kılıç, Çiğdem Çakırlar, Serkan Büyükköse and Zafer Ziya Öztürk^*

Department of Physics, Gebze Technical University, 41400 Kocaeli, Turkey

Sensors 2018, 18(4), 956; https://doi.org/10.3390/s18040956 - 23 Mar 2018

Cited by 38 | Viewed by 6273

Abstract

In this paper, we fabricated p-Co₃O₄/n-TiO₂ heterostructures and investigated their gas sensing properties. The structural and morphological characterization were performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy analysis (XPS). The electrical properties of [...] Read more.

In this paper, we fabricated p-Co₃O₄/n-TiO₂ heterostructures and investigated their gas sensing properties. The structural and morphological characterization were performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy analysis (XPS). The electrical properties of the heterostructure were studied within the temperature range from 293 K to 423 K. Changes in electrical properties and sensing behavior against reducing and oxidizing gases were attributed to the formation of p–n heterojunctions at the Co₃O₄ and TiO₂ interface. In comparison with sensing performed with pristine TiO₂ nanotubes (NTs), a significant improvement in H₂ sensing at 200 °C was observed, while the sensing response against NO₂ decreased for the heterostructures. Additionally, a response against toluene gas, in contrast to pristine TiO₂ NTs, appeared in the Co₃O₄/TiO₂ heterostructure samples. Full article

(This article belongs to the Special Issue I3S 2017 Selected Papers)

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22 pages, 22265 KiB

Open AccessArticle

Convolutional Neural Network-Based Classification of Driver’s Emotion during Aggressive and Smooth Driving Using Multi-Modal Camera Sensors

by Kwan Woo Lee, Hyo Sik Yoon, Jong Min Song and Kang Ryoung Park^*

Division of Electronics and Electrical Engineering, Dongguk University, 30 Pildong-ro 1-gil, Jung-gu, Seoul 100-715, Korea

Sensors 2018, 18(4), 957; https://doi.org/10.3390/s18040957 - 23 Mar 2018

Cited by 61 | Viewed by 7145

Abstract

Because aggressive driving often causes large-scale loss of life and property, techniques for advance detection of adverse driver emotional states have become important for the prevention of aggressive driving behaviors. Previous studies have primarily focused on systems for detecting aggressive driver emotion via [...] Read more.

Because aggressive driving often causes large-scale loss of life and property, techniques for advance detection of adverse driver emotional states have become important for the prevention of aggressive driving behaviors. Previous studies have primarily focused on systems for detecting aggressive driver emotion via smart-phone accelerometers and gyro-sensors, or they focused on methods of detecting physiological signals using electroencephalography (EEG) or electrocardiogram (ECG) sensors. Because EEG and ECG sensors cause discomfort to drivers and can be detached from the driver’s body, it becomes difficult to focus on bio-signals to determine their emotional state. Gyro-sensors and accelerometers depend on the performance of GPS receivers and cannot be used in areas where GPS signals are blocked. Moreover, if driving on a mountain road with many quick turns, a driver’s emotional state can easily be misrecognized as that of an aggressive driver. To resolve these problems, we propose a convolutional neural network (CNN)-based method of detecting emotion to identify aggressive driving using input images of the driver’s face, obtained using near-infrared (NIR) light and thermal camera sensors. In this research, we conducted an experiment using our own database, which provides a high classification accuracy for detecting driver emotion leading to either aggressive or smooth (i.e., relaxed) driving. Our proposed method demonstrates better performance than existing methods. Full article

(This article belongs to the Special Issue Advances in Infrared Imaging: Sensing, Exploitation and Applications)

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9 pages, 10191 KiB

Open AccessArticle

A Highly Thermostable In₂O₃/ITO Thin Film Thermocouple Prepared via Screen Printing for High Temperature Measurements

by Yantao Liu^1,3, Wei Ren^1,*, Peng Shi^1,*, Dan Liu¹, Yijun Zhang¹, Ming Liu¹, Zuo-Guang Ye^1,4

, Weixuan Jing², Bian Tian² and Zhuangde Jiang²

¹ Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, China

² International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technologies, Xi’an Jiaotong University, Xi’an 710049, China

³ Department of Electronic Engineering, Xi’an University of Technology, Xi’an 710048, China

⁴ Department of Chemistry and 4D LABS, Simon Fraser University, Burnaby, BC V5A 1S6, Canada

Sensors 2018, 18(4), 958; https://doi.org/10.3390/s18040958 - 23 Mar 2018

Cited by 58 | Viewed by 6886

Abstract

An In₂O₃/ITO thin film thermocouple was prepared via screen printing. Glass additives were added to improve the sintering process and to increase the density of the In₂O₃/ITO films. The surface and cross-sectional images indicate that [...] Read more.

An In₂O₃/ITO thin film thermocouple was prepared via screen printing. Glass additives were added to improve the sintering process and to increase the density of the In₂O₃/ITO films. The surface and cross-sectional images indicate that both the grain size and densification of the ITO and In₂O₃ films increased with the increase in annealing time. The thermoelectric voltage of the In₂O₃/ITO thermocouple was 53.5 mV at 1270 °C at the hot junction. The average Seebeck coefficient of the thermocouple was calculated as 44.5 μV/°C. The drift rate of the In₂O₃/ITO thermocouple was 5.44 °C/h at a measuring time of 10 h at 1270 °C. Full article

(This article belongs to the Special Issue Sensors and Materials for Harsh Environments)

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13 pages, 3506 KiB

Open AccessArticle

Sensor-Based Optimization Model for Air Quality Improvement in Home IoT

by Jonghyuk Kim¹ and Hyunwoo Hwangbo^1,2,*

¹ Big Data Analytics Team, Kolon Benit Co., Ltd., 11 Kolon-ro, Gwacheon-si 13837, Gyeonggi-do, Korea

² Department of Data & Knowledge Service Engineering, Dankook University, 152, Jukjeon-ro, Suji-gu, Yongin-si 16890, Gyeonggi-do, Korea

Sensors 2018, 18(4), 959; https://doi.org/10.3390/s18040959 - 23 Mar 2018

Cited by 24 | Viewed by 6835

Abstract

We introduce current home Internet of Things (IoT) technology and present research on its various forms and applications in real life. In addition, we describe IoT marketing strategies as well as specific modeling techniques for improving air quality, a key home IoT service. [...] Read more.

We introduce current home Internet of Things (IoT) technology and present research on its various forms and applications in real life. In addition, we describe IoT marketing strategies as well as specific modeling techniques for improving air quality, a key home IoT service. To this end, we summarize the latest research on sensor-based home IoT, studies on indoor air quality, and technical studies on random data generation. In addition, we develop an air quality improvement model that can be readily applied to the market by acquiring initial analytical data and building infrastructures using spectrum/density analysis and the natural cubic spline method. Accordingly, we generate related data based on user behavioral values. We integrate the logic into the existing home IoT system to enable users to easily access the system through the Web or mobile applications. We expect that the present introduction of a practical marketing application method will contribute to enhancing the expansion of the home IoT market. Full article

(This article belongs to the Special Issue Sensor Networks for Collaborative and Secure Internet of Things)

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19 pages, 13314 KiB

Open AccessArticle

Convolutional Neural Network-Based Shadow Detection in Images Using Visible Light Camera Sensor

by Dong Seop Kim, Muhammad Arsalan

and Kang Ryoung Park^*

Division of Electronics and Electrical Engineering, Dongguk University, 30 Pildong-Ro 1-Gil, Jung-Gu, Seoul 100-715, Korea

Sensors 2018, 18(4), 960; https://doi.org/10.3390/s18040960 - 23 Mar 2018

Cited by 24 | Viewed by 6058

Abstract

Recent developments in intelligence surveillance camera systems have enabled more research on the detection, tracking, and recognition of humans. Such systems typically use visible light cameras and images, in which shadows make it difficult to detect and recognize the exact human area. Near-infrared [...] Read more.

Recent developments in intelligence surveillance camera systems have enabled more research on the detection, tracking, and recognition of humans. Such systems typically use visible light cameras and images, in which shadows make it difficult to detect and recognize the exact human area. Near-infrared (NIR) light cameras and thermal cameras are used to mitigate this problem. However, such instruments require a separate NIR illuminator, or are prohibitively expensive. Existing research on shadow detection in images captured by visible light cameras have utilized object and shadow color features for detection. Unfortunately, various environmental factors such as illumination change and brightness of background cause detection to be a difficult task. To overcome this problem, we propose a convolutional neural network-based shadow detection method. Experimental results with a database built from various outdoor surveillance camera environments, and from the context-aware vision using image-based active recognition (CAVIAR) open database, show that our method outperforms previous works. Full article

(This article belongs to the Special Issue Sensors Signal Processing and Visual Computing)

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15 pages, 4238 KiB

Open AccessArticle

A Multi-Hop Clustering Mechanism for Scalable IoT Networks

by Yoonyoung Sung

, Sookyoung Lee^*

and Meejeong Lee^*

Department of Computer Science and Engineering, Ewha Womans University, Seoul 03760, Korea

Sensors 2018, 18(4), 961; https://doi.org/10.3390/s18040961 - 23 Mar 2018

Cited by 30 | Viewed by 4769

Abstract

It is expected that up to 26 billion Internet of Things (IoT) equipped with sensors and wireless communication capabilities will be connected to the Internet by 2020 for various purposes. With a large scale IoT network, having each node connected to the Internet [...] Read more.

It is expected that up to 26 billion Internet of Things (IoT) equipped with sensors and wireless communication capabilities will be connected to the Internet by 2020 for various purposes. With a large scale IoT network, having each node connected to the Internet with an individual connection may face serious scalability issues. The scalability problem of the IoT network may be alleviated by grouping the nodes of the IoT network into clusters and having a representative node in each cluster connect to the Internet on behalf of the other nodes in the cluster instead of having a per-node Internet connection and communication. In this paper, we propose a multi-hop clustering mechanism for IoT networks to minimize the number of required Internet connections. Specifically, the objective of proposed mechanism is to select the minimum number of coordinators, which take the role of a representative node for the cluster, i.e., having the Internet connection on behalf of the rest of the nodes in the cluster and to map a partition of the IoT nodes onto the selected set of coordinators to minimize the total distance between the nodes and their respective coordinator under a certain constraint in terms of maximum hop count between the IoT nodes and their respective coordinator. Since this problem can be mapped into a set cover problem which is known as NP-hard, we pursue a heuristic approach to solve the problem and analyze the complexity of the proposed solution. Through a set of experiments with varying parameters, the proposed scheme shows 63–87.3% reduction of the Internet connections depending on the number of the IoT nodes while that of the optimal solution is 65.6–89.9% in a small scale network. Moreover, it is shown that the performance characteristics of the proposed mechanism coincide with expected performance characteristics of the optimal solution in a large-scale network. Full article

(This article belongs to the Special Issue Next Generation Technologies for Sensor Networks and Internet of Things)

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26 pages, 88099 KiB

Open AccessArticle

Sensor Fusion to Estimate the Depth and Width of the Weld Bead in Real Time in GMAW Processes

by Guillermo Alvarez Bestard^1,2,*

, Renato Coral Sampaio³, José A. R. Vargas⁴ and Sadek C. Absi Alfaro⁵

¹ Postgraduate Program in Mechatronic Systems (PPMEC), Faculty of Technology, University of Brasilia, Campus Darcy Ribeiro, Brasilia 70910-900, Brazil

² Department of Automatic Control, Institute of Cybernetics, Mathematics and Physics, Havana 10400, Cuba

³ Software Engineering Group, Faculty of Gama, University of Brasilia, Brasilia 72444-240, Brazil

⁴ Department of Electrical Engineering, Faculty of Technology, University of Brasilia, Brasilia 70910-900, Brazil

⁵ Department of Mechanical and Mechatronic Engineering, Faculty of Technology, University of Brasilia, Brasilia 70910-900, Brazil

Sensors 2018, 18(4), 962; https://doi.org/10.3390/s18040962 - 23 Mar 2018

Cited by 30 | Viewed by 8822

Abstract

The arc welding process is widely used in industry but its automatic control is limited by the difficulty in measuring the weld bead geometry and closing the control loop on the arc, which has adverse environmental conditions. To address this problem, this work [...] Read more.

The arc welding process is widely used in industry but its automatic control is limited by the difficulty in measuring the weld bead geometry and closing the control loop on the arc, which has adverse environmental conditions. To address this problem, this work proposes a system to capture the welding variables and send stimuli to the Gas Metal Arc Welding (GMAW) conventional process with a constant voltage power source, which allows weld bead geometry estimation with an open-loop control. Dynamic models of depth and width estimators of the weld bead are implemented based on the fusion of thermographic data, welding current and welding voltage in a multilayer perceptron neural network. The estimators were trained and validated off-line with data from a novel algorithm developed to extract the features of the infrared image, a laser profilometer was implemented to measure the bead dimensions and an image processing algorithm that measures depth by making a longitudinal cut in the weld bead. These estimators are optimized for embedded devices and real-time processing and were implemented on a Field-Programmable Gate Array (FPGA) device. Experiments to collect data, train and validate the estimators are presented and discussed. The results show that the proposed method is useful in industrial and research environments. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 7438 KiB

Open AccessArticle

MFAM: Multiple Frequency Adaptive Model-Based Indoor Localization Method

by Jure Tuta^*

and Matjaz B. Juric

Faculty of Computer and Information Science, University of Ljubljana, Vecna pot 113, SI-1000 Ljubljana, Slovenia

Sensors 2018, 18(4), 963; https://doi.org/10.3390/s18040963 - 24 Mar 2018

Cited by 6 | Viewed by 5062

Abstract

This paper presents MFAM (Multiple Frequency Adaptive Model-based localization method), a novel model-based indoor localization method that is capable of using multiple wireless signal frequencies simultaneously. It utilizes indoor architectural model and physical properties of wireless signal propagation through objects and space. The [...] Read more.

This paper presents MFAM (Multiple Frequency Adaptive Model-based localization method), a novel model-based indoor localization method that is capable of using multiple wireless signal frequencies simultaneously. It utilizes indoor architectural model and physical properties of wireless signal propagation through objects and space. The motivation for developing multiple frequency localization method lies in the future Wi-Fi standards (e.g., 802.11ah) and the growing number of various wireless signals present in the buildings (e.g., Wi-Fi, Bluetooth, ZigBee, etc.). Current indoor localization methods mostly rely on a single wireless signal type and often require many devices to achieve the necessary accuracy. MFAM utilizes multiple wireless signal types and improves the localization accuracy over the usage of a single frequency. It continuously monitors signal propagation through space and adapts the model according to the changes indoors. Using multiple signal sources lowers the required number of access points for a specific signal type while utilizing signals, already present in the indoors. Due to the unavailability of the 802.11ah hardware, we have evaluated proposed method with similar signals; we have used 2.4 GHz Wi-Fi and 868 MHz HomeMatic home automation signals. We have performed the evaluation in a modern two-bedroom apartment and measured mean localization error 2.0 to 2.3 m and median error of 2.0 to 2.2 m. Based on our evaluation results, using two different signals improves the localization accuracy by 18% in comparison to 2.4 GHz Wi-Fi-only approach. Additional signals would improve the accuracy even further. We have shown that MFAM provides better accuracy than competing methods, while having several advantages for real-world usage. Full article

(This article belongs to the Section Sensor Networks)

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15 pages, 5010 KiB

Open AccessArticle

Green, Hydrothermal Synthesis of Fluorescent Carbon Nanodots from Gardenia, Enabling the Detection of Metronidazole in Pharmaceuticals and Rabbit Plasma

by Xiupei Yang^1,*, Mingxian Liu¹, Yanru Yin¹, Fenglin Tang¹, Hua Xu¹ and Xiangjun Liao²

¹ College of Chemistry and Chemical Engineering, Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, China West Normal University, Nanchong 637000, China

² Exposure and Biomonitoring Division, Health Canada, 50 Colombine Driveway, Ottawa, ON K1A 0K9, Canada

Sensors 2018, 18(4), 964; https://doi.org/10.3390/s18040964 - 24 Mar 2018

Cited by 40 | Viewed by 5959

Abstract

Strong fluorescent carbon nanodots (FCNs) were synthesized with a green approach using gardenia as a carbon source through a one-step hydrothermal method. FCNs were characterized by their UV-vis absorption spectra, photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR) as well as X-ray photoelectron spectroscopy [...] Read more.

Strong fluorescent carbon nanodots (FCNs) were synthesized with a green approach using gardenia as a carbon source through a one-step hydrothermal method. FCNs were characterized by their UV-vis absorption spectra, photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR) as well as X-ray photoelectron spectroscopy (XPS). We further explored the use of as-synthesized FCNs as an effective probe for the detection of metronidazole (MNZ), which is based on MNZ-induced fluorescence quenching of FCNs. The proposed method displayed a wide linear range from 0.8 to 225.0 µM with a correlation coefficient of 0.9992 and a limit of detection as low as 279 nM. It was successfully applied to the determination of MNZ in commercial tablets and rabbit plasma with excellent sensitivity and selectivity, which indicates its potential applications in clinical analysis and biologically related studies. Full article

(This article belongs to the Special Issue Optical Chemical Nanosensors)

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27 pages, 1830 KiB

Open AccessArticle

Efficient Proximity Computation Techniques Using ZIP Code Data for Smart Cities

by Muhammad Harist Murdani, Joonho Kwon^*

, Yoon-Ho Choi

and Bonghee Hong

¹ School of Computer Science and Engineering, Pusan National University, Busan 46241, Korea

^‡ Current address: Wijaya Putra University, Surabaya, Indonesia.

Sensors 2018, 18(4), 965; https://doi.org/10.3390/s18040965 - 24 Mar 2018

Cited by 2 | Viewed by 5115

Abstract

In this paper, we are interested in computing ZIP code proximity from two perspectives, proximity between two ZIP codes (Ad-Hoc) and neighborhood proximity (Top-K). Such a computation can be used for ZIP code-based target marketing as one of the [...] Read more.

In this paper, we are interested in computing ZIP code proximity from two perspectives, proximity between two ZIP codes (Ad-Hoc) and neighborhood proximity (Top-K). Such a computation can be used for ZIP code-based target marketing as one of the smart city applications. A naïve approach to this computation is the usage of the distance between ZIP codes. We redefine a distance metric combining the centroid distance with the intersecting road network between ZIP codes by using a weighted sum method. Furthermore, we prove that the results of our combined approach conform to the characteristics of distance measurement. We have proposed a general and heuristic approach for computing Ad-Hoc proximity, while for computing Top-K proximity, we have proposed a general approach only. Our experimental results indicate that our approaches are verifiable and effective in reducing the execution time and search space. Full article

(This article belongs to the Special Issue Smart Cities)

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16 pages, 26122 KiB

Open AccessArticle

Building Change Detection from Bi-Temporal Dense-Matching Point Clouds and Aerial Images

by Shiyan Pang^1,2, Xiangyun Hu^1,3,*, Zhongliang Cai², Jinqi Gong³ and Mi Zhang³

¹ Collaborative Innovation Center of Geospatial Technology, Wuhan University, Wuhan 430079, China

² School of Resource and Environmental Sciences, Wuhan University, Wuhan 430079, China

³ School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China

Sensors 2018, 18(4), 966; https://doi.org/10.3390/s18040966 - 24 Mar 2018

Cited by 20 | Viewed by 4943

Abstract

In this work, a novel building change detection method from bi-temporal dense-matching point clouds and aerial images is proposed to address two major problems, namely, the robust acquisition of the changed objects above ground and the automatic classification of changed objects into buildings [...] Read more.

In this work, a novel building change detection method from bi-temporal dense-matching point clouds and aerial images is proposed to address two major problems, namely, the robust acquisition of the changed objects above ground and the automatic classification of changed objects into buildings or non-buildings. For the acquisition of changed objects above ground, the change detection problem is converted into a binary classification, in which the changed area above ground is regarded as the foreground and the other area as the background. For the gridded points of each period, the graph cuts algorithm is adopted to classify the points into foreground and background, followed by the region-growing algorithm to form candidate changed building objects. A novel structural feature that was extracted from aerial images is constructed to classify the candidate changed building objects into buildings and non-buildings. The changed building objects are further classified as “newly built”, “taller”, “demolished”, and “lower” by combining the classification and the digital surface models of two periods. Finally, three typical areas from a large dataset are used to validate the proposed method. Numerous experiments demonstrate the effectiveness of the proposed algorithm. Full article

(This article belongs to the Section Remote Sensors)

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25 pages, 24350 KiB

Open AccessArticle

Optimize the Coverage Probability of Prediction Interval for Anomaly Detection of Sensor-Based Monitoring Series

by Jingyue Pang

, Datong Liu^*, Yu Peng and Xiyuan Peng

School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150080, China

Sensors 2018, 18(4), 967; https://doi.org/10.3390/s18040967 - 24 Mar 2018

Cited by 27 | Viewed by 5196

Abstract

Effective anomaly detection of sensing data is essential for identifying potential system failures. Because they require no prior knowledge or accumulated labels, and provide uncertainty presentation, the probability prediction methods (e.g., Gaussian process regression (GPR) and relevance vector machine (RVM)) are especially adaptable [...] Read more.

Effective anomaly detection of sensing data is essential for identifying potential system failures. Because they require no prior knowledge or accumulated labels, and provide uncertainty presentation, the probability prediction methods (e.g., Gaussian process regression (GPR) and relevance vector machine (RVM)) are especially adaptable to perform anomaly detection for sensing series. Generally, one key parameter of prediction models is coverage probability (CP), which controls the judging threshold of the testing sample and is generally set to a default value (e.g., 90% or 95%). There are few criteria to determine the optimal CP for anomaly detection. Therefore, this paper designs a graphic indicator of the receiver operating characteristic curve of prediction interval (ROC-PI) based on the definition of the ROC curve which can depict the trade-off between the PI width and PI coverage probability across a series of cut-off points. Furthermore, the Youden index is modified to assess the performance of different CPs, by the minimization of which the optimal CP is derived by the simulated annealing (SA) algorithm. Experiments conducted on two simulation datasets demonstrate the validity of the proposed method. Especially, an actual case study on sensing series from an on-orbit satellite illustrates its significant performance in practical application. Full article

(This article belongs to the Section Remote Sensors)

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25 pages, 917 KiB

Open AccessArticle

Analysis of Known Linear Distributed Average Consensus Algorithms on Cycles and Paths

by Jesús Gutiérrez-Gutiérrez^*

, Marta Zárraga-Rodríguez and Xabier Insausti

Department of Biomedical Engineering and Sciences, Tecnun, University of Navarra, Manuel Lardizábal 13, 20018 San Sebastián, Spain

Sensors 2018, 18(4), 968; https://doi.org/10.3390/s18040968 - 24 Mar 2018

Cited by 12 | Viewed by 4086

Abstract

In this paper, we compare six known linear distributed average consensus algorithms on a sensor network in terms of convergence time (and therefore, in terms of the number of transmissions required). The selected network topologies for the analysis (comparison) are the cycle and [...] Read more.

In this paper, we compare six known linear distributed average consensus algorithms on a sensor network in terms of convergence time (and therefore, in terms of the number of transmissions required). The selected network topologies for the analysis (comparison) are the cycle and the path. Specifically, in the present paper, we compute closed-form expressions for the convergence time of four known deterministic algorithms and closed-form bounds for the convergence time of two known randomized algorithms on cycles and paths. Moreover, we also compute a closed-form expression for the convergence time of the fastest deterministic algorithm considered on grids. Full article

(This article belongs to the Collection Smart Communication Protocols and Algorithms for Sensor Networks)

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17 pages, 5686 KiB

Open AccessArticle

Green Grape Detection and Picking-Point Calculation in a Night-Time Natural Environment Using a Charge-Coupled Device (CCD) Vision Sensor with Artificial Illumination

by Juntao Xiong^*, Zhen Liu, Rui Lin

, Rongbin Bu, Zhiliang He, Zhengang Yang^* and Cuixiao Liang

College of Mathematics and Informatics, South China Agricultural University, Guangzhou 510642, China

Sensors 2018, 18(4), 969; https://doi.org/10.3390/s18040969 - 25 Mar 2018

Cited by 47 | Viewed by 7148

Abstract

Night-time fruit-picking technology is important to picking robots. This paper proposes a method of night-time detection and picking-point positioning for green grape-picking robots to solve the difficult problem of green grape detection and picking in night-time conditions with artificial lighting systems. Taking a [...] Read more.

Night-time fruit-picking technology is important to picking robots. This paper proposes a method of night-time detection and picking-point positioning for green grape-picking robots to solve the difficult problem of green grape detection and picking in night-time conditions with artificial lighting systems. Taking a representative green grape named Centennial Seedless as the research object, daytime and night-time grape images were captured by a custom-designed visual system. Detection was conducted employing the following steps: (1) The RGB (red, green and blue). Color model was determined for night-time green grape detection through analysis of color features of grape images under daytime natural light and night-time artificial lighting. The R component of the RGB color model was rotated and the image resolution was compressed; (2) The improved Chan–Vese (C–V) level set model and morphological processing method were used to remove the background of the image, leaving out the grape fruit; (3) Based on the character of grape vertical suspension, combining the principle of the minimum circumscribed rectangle of fruit and the Hough straight line detection method, straight-line fitting for the fruit stem was conducted and the picking point was calculated using the stem with an angle of fitting line and vertical line less than 15°. The visual detection experiment results showed that the accuracy of grape fruit detection was 91.67% and the average running time of the proposed algorithm was 0.46 s. The picking-point calculation experiment results showed that the highest accuracy for the picking-point calculation was 92.5%, while the lowest was 80%. The results demonstrate that the proposed method of night-time green grape detection and picking-point calculation can provide technical support to the grape-picking robots. Full article

(This article belongs to the Special Issue Charge-Coupled Device (CCD) Sensors)

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15 pages, 4233 KiB

Open AccessFeature PaperArticle

A Novel Laser and Video-Based Displacement Transducer to Monitor Bridge Deflections

by Miguel A. Vicente^1,2,*, Dorys C. Gonzalez^1,2, Jesus Minguez¹ and Thomas Schumacher³

¹ Department of Civil Engineering, University of Burgos, c/Villadiego, s/n. 09001 Burgos, Spain

² Department of Civil Engineering, Parks College of Engineering, Aviation and Technology, Saint Louis University, 3540 Lindell Blvd, Saint Louis, MO 63103, USA

³ Department of Civil and Environmental Engineering, Portland State University, 1930 SW 4th Ave, Portland, OR 97201, USA

Sensors 2018, 18(4), 970; https://doi.org/10.3390/s18040970 - 25 Mar 2018

Cited by 61 | Viewed by 6688

Abstract

The measurement of static vertical deflections on bridges continues to be a first-level technological challenge. These data are of great interest, especially for the case of long-term bridge monitoring; in fact, they are perhaps more valuable than any other measurable parameter. This is [...] Read more.

The measurement of static vertical deflections on bridges continues to be a first-level technological challenge. These data are of great interest, especially for the case of long-term bridge monitoring; in fact, they are perhaps more valuable than any other measurable parameter. This is because material degradation processes and changes of the mechanical properties of the structure due to aging (for example creep and shrinkage in concrete bridges) have a direct impact on the exhibited static vertical deflections. This paper introduces and evaluates an approach to monitor displacements and rotations of structures using a novel laser and video-based displacement transducer (LVBDT). The proposed system combines the use of laser beams, LED lights, and a digital video camera, and was especially designed to capture static and slow-varying displacements. Contrary to other video-based approaches, the camera is located on the bridge, hence allowing to capture displacements at one location. Subsequently, the sensing approach and the procedure to estimate displacements and the rotations are described. Additionally, laboratory and in-service field testing carried out to validate the system are presented and discussed. The results demonstrate that the proposed sensing approach is robust, accurate, and reliable, and also inexpensive, which are essential for field implementation. Full article

(This article belongs to the Special Issue I3S 2017 Selected Papers)

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16 pages, 9682 KiB

Open AccessArticle

Nondestructive Estimation of Muscle Contributions to STS Training with Different Loadings Based on Wearable Sensor System

by Kun Liu

, Yong Liu

, Jianchao Yan^*

and Zhenyuan Sun

School of Mechanical Science and Engineering, Jilin University, Changchun 130025, China

Sensors 2018, 18(4), 971; https://doi.org/10.3390/s18040971 - 25 Mar 2018

Cited by 5 | Viewed by 5695

Abstract

Partial body weight support or loading sit-to-stand (STS) rehabilitation can be useful for persons with lower limb dysfunction to achieve movement again based on the internal residual muscle force and external assistance. To explicate how the muscles contribute to the kinetics and kinematics [...] Read more.

Partial body weight support or loading sit-to-stand (STS) rehabilitation can be useful for persons with lower limb dysfunction to achieve movement again based on the internal residual muscle force and external assistance. To explicate how the muscles contribute to the kinetics and kinematics of STS performance by non-invasive in vitro detection and to nondestructively estimate the muscle contributions to STS training with different loadings, a wearable sensor system was developed with ground reaction force (GRF) platforms, motion capture inertial sensors and electromyography (EMG) sensors. To estimate the internal moments of hip, knee and ankle joints and quantify the contributions of individual muscle and gravity to STS movement, the inverse dynamics analysis on a simplified STS biomechanical model with external loading is proposed. The functional roles of the lower limb individual muscles (rectus femoris (RF), gluteus maximus (GM), vastus lateralis (VL), tibialis anterior (TA) and gastrocnemius (GAST)) during STS motion and the mechanism of the muscles’ synergies to perform STS-specific subtasks were analyzed. The muscle contributions to the biomechanical STS subtasks of vertical propulsion, anteroposterior (AP) braking and propulsion for body balance in the sagittal plane were quantified by experimental studies with EMG, kinematic and kinetic data. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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21 pages, 4168 KiB

Open AccessArticle

Correction of Visual Perception Based on Neuro-Fuzzy Learning for the Humanoid Robot TEO

by Juan Hernandez-Vicen

, Santiago Martinez^*

, Juan Miguel Garcia-Haro

and Carlos Balaguer

Systems Engineering and Automation Department, Universidad Carlos III de Madrid, Avd. Universidad, 30, Leganés, 28903 Madrid, Spain

Sensors 2018, 18(4), 972; https://doi.org/10.3390/s18040972 - 25 Mar 2018

Cited by 9 | Viewed by 4864

Abstract

New applications related to robotic manipulation or transportation tasks, with or without physical grasping, are continuously being developed. To perform these activities, the robot takes advantage of different kinds of perceptions. One of the key perceptions in robotics is vision. However, some problems [...] Read more.

New applications related to robotic manipulation or transportation tasks, with or without physical grasping, are continuously being developed. To perform these activities, the robot takes advantage of different kinds of perceptions. One of the key perceptions in robotics is vision. However, some problems related to image processing makes the application of visual information within robot control algorithms difficult. Camera-based systems have inherent errors that affect the quality and reliability of the information obtained. The need of correcting image distortion slows down image parameter computing, which decreases performance of control algorithms. In this paper, a new approach to correcting several sources of visual distortions on images in only one computing step is proposed. The goal of this system/algorithm is the computation of the tilt angle of an object transported by a robot, minimizing image inherent errors and increasing computing speed. After capturing the image, the computer system extracts the angle using a Fuzzy filter that corrects at the same time all possible distortions, obtaining the real angle in only one processing step. This filter has been developed by the means of Neuro-Fuzzy learning techniques, using datasets with information obtained from real experiments. In this way, the computing time has been decreased and the performance of the application has been improved. The resulting algorithm has been tried out experimentally in robot transportation tasks in the humanoid robot TEO (Task Environment Operator) from the University Carlos III of Madrid. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 1211 KiB

Open AccessArticle

A Portable Wireless Communication Platform Based on a Multi-Material Fiber Sensor for Real-Time Breath Detection

by Mourad Roudjane¹

, Simon Bellemare-Rousseau², Mazen Khalil^1,2, Stepan Gorgutsa¹

, Amine Miled²

and Younes Messaddeq^1,*

¹ Center for Optics, Photonics and Lasers (COPL), Department of Physics, Université Laval, Québec, QC G1V 0A6, Canada

² LABioTRON Bioengineering Research Laboratory, Department of Electrical and Computer Engineering, Research Centre for Advanced Materials (CERMA), Université Laval, Québec, QC G1V 0A6, Canada

Sensors 2018, 18(4), 973; https://doi.org/10.3390/s18040973 - 25 Mar 2018

Cited by 28 | Viewed by 9178

Abstract

In this paper, we present a new mobile wireless communication platform for real-time monitoring of an individual’s breathing rate. The platform takes the form of a wearable stretching T-shirt featuring a sensor and a detection base station. The sensor is formed by a [...] Read more.

In this paper, we present a new mobile wireless communication platform for real-time monitoring of an individual’s breathing rate. The platform takes the form of a wearable stretching T-shirt featuring a sensor and a detection base station. The sensor is formed by a spiral-shaped antenna made from a multi-material fiber connected to a compact transmitter. Based on the resonance frequency of the antenna at approximately 2.4 GHz, the breathing sensor relies on its Bluetooth transmitter. The contactless and non-invasive sensor is designed without compromising the user’s comfort. The sensing mechanism of the system is based on the detection of the signal amplitude transmitted wirelessly by the sensor, which is found to be sensitive to strain. We demonstrate the capability of the platform to detect the breathing rates of four male volunteers who are not in movement. The breathing pattern is obtained through the received signal strength indicator (RSSI) which is filtered and analyzed with home-made algorithms in the portable system. Numerical simulations of human breath are performed to support the experimental detection, and both results are in a good agreement. Slow, fast, regular, irregular, and shallow breathing types are successfully recorded within a frequency interval of 0.16–1.2 Hz, leading to a breathing rate varying from 10 to 72 breaths per minute. Full article

(This article belongs to the Special Issue Wearable Smart Devices)

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26 pages, 7170 KiB

Open AccessArticle

An Indoor Positioning-Based Mobile Payment System Using Bluetooth Low Energy Technology

by Alexander Yohan

, Nai-Wei Lo^*

and Doni Winata

Department of Information Management, National Taiwan University of Science and Technology, Taipei 10607, Taiwan

Sensors 2018, 18(4), 974; https://doi.org/10.3390/s18040974 - 25 Mar 2018

Cited by 17 | Viewed by 9224

Abstract

The development of information technology has paved the way for faster and more convenient payment process flows and new methodology for the design and implementation of next generation payment systems. The growth of smartphone usage nowadays has fostered a new and popular mobile [...] Read more.

The development of information technology has paved the way for faster and more convenient payment process flows and new methodology for the design and implementation of next generation payment systems. The growth of smartphone usage nowadays has fostered a new and popular mobile payment environment. Most of the current generation smartphones support Bluetooth Low Energy (BLE) technology to communicate with nearby BLE-enabled devices. It is plausible to construct an Over-the-Air BLE-based mobile payment system as one of the payment methods for people living in modern societies. In this paper, a secure indoor positioning-based mobile payment authentication protocol with BLE technology and the corresponding mobile payment system design are proposed. The proposed protocol consists of three phases: initialization phase, session key construction phase, and authentication phase. When a customer moves toward the POS counter area, the proposed mobile payment system will automatically detect the position of the customer to confirm whether the customer is ready for the checkout process. Once the system has identified the customer is standing within the payment-enabled area, the payment system will invoke authentication process between POS and the customer’s smartphone through BLE communication channel to generate a secure session key and establish an authenticated communication session to perform the payment transaction accordingly. A prototype is implemented to assess the performance of the proposed design for mobile payment system. In addition, security analysis is conducted to evaluate the security strength of the proposed protocol. Full article

(This article belongs to the Special Issue Mobile Sensing Applications)

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15 pages, 10656 KiB

Open AccessArticle

Non-Invasive Methodology to Estimate Polyphenol Content in Extra Virgin Olive Oil Based on Stepwise Multilinear Regression

by Diego Manuel Martínez Gila^*

, Pablo Cano Marchal, Juan Gómez Ortega and Javier Gámez García

Robotics, Automation and Computer Vision Group, University of Jaen, Campus Las Lagunillas s/n, ES-23071 Jaen, Spain

Sensors 2018, 18(4), 975; https://doi.org/10.3390/s18040975 - 25 Mar 2018

Cited by 6 | Viewed by 4829

Abstract

Normally the olive oil quality is assessed by chemical analysis according to international standards. These norms define chemical and organoleptic markers, and depending on the markers, the olive oil can be labelled as lampante, virgin, or extra virgin olive oil (EVOO), the last [...] Read more.

Normally the olive oil quality is assessed by chemical analysis according to international standards. These norms define chemical and organoleptic markers, and depending on the markers, the olive oil can be labelled as lampante, virgin, or extra virgin olive oil (EVOO), the last being an indicator of top quality. The polyphenol content is related to EVOO organoleptic features, and different scientific works have studied the positive influence that these compounds have on human health. The works carried out in this paper are focused on studying relations between the polyphenol content in olive oil samples and its spectral response in the near infrared spectra. In this context, several acquisition parameters have been assessed to optimize the measurement process within the virgin olive oil production process. The best regression model reached a mean error value of 156.14 mg/kg in leave one out cross validation, and the higher regression coefficient was 0.81 through holdout validation. Full article

(This article belongs to the Special Issue Spectroscopy Based Sensors)

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8 pages, 10008 KiB

Open AccessArticle

Ultra-Long-Distance Hybrid BOTDA/Ф-OTDR

by Yun Fu¹, Zinan Wang^1,2,*

, Richeng Zhu¹, Naitian Xue¹, Jialin Jiang¹

, Chongyu Lu¹, Bin Zhang¹, Le Yang¹, David Atubga¹ and Yunjiang Rao^1,*

¹ Key Laboratory of Optical Fiber Sensing and Communications (Ministry of Education), University of Electronic Science and Technology of China (UESTC), Chengdu 611731, China

² Center for Information Geoscience, UESTC, Chengdu 611731, China

Sensors 2018, 18(4), 976; https://doi.org/10.3390/s18040976 - 25 Mar 2018

Cited by 59 | Viewed by 7148

Abstract

In the distributed optical fiber sensing (DOFS) domain, simultaneous measurement of vibration and temperature/strain based on Rayleigh scattering and Brillouin scattering in fiber could have wide applications. However, there are certain challenges for the case of ultra-long sensing range, including the interplay of [...] Read more.

In the distributed optical fiber sensing (DOFS) domain, simultaneous measurement of vibration and temperature/strain based on Rayleigh scattering and Brillouin scattering in fiber could have wide applications. However, there are certain challenges for the case of ultra-long sensing range, including the interplay of different scattering mechanisms, the interaction of two types of sensing signals, and the competition of pump power. In this paper, a hybrid DOFS system, which can simultaneously measure temperature/strain and vibration over 150 km, is elaborately designed via integrating the Brillouin optical time-domain analyzer (BOTDA) and phase-sensitive optical time-domain reflectometry (Ф-OTDR). Distributed Raman and Brillouin amplifications, frequency division multiplexing (FDM), wavelength division multiplexing (WDM), and time division multiplexing (TDM) are delicately fused to accommodate ultra-long-distance BOTDA and Ф-OTDR. Consequently, the sensing range of the hybrid system is 150.62 km, and the spatial resolution of BOTDA and Ф-OTDR are 9 m and 30 m, respectively. The measurement uncertainty of the BOTDA is ± 0.82 MHz. To the best of our knowledge, this is the first time that such hybrid DOFS is realized with a hundred-kilometer length scale. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 25009 KiB

Open AccessArticle

Multi-Aperture-Based Probabilistic Noise Reduction of Random Telegraph Signal Noise and Photon Shot Noise in Semi-Photon-Counting Complementary-Metal-Oxide-Semiconductor Image Sensor

by Haruki Ishida¹, Keiichiro Kagawa^2,*, Takashi Komuro³, Bo Zhang², Min-Woong Seo², Taishi Takasawa², Keita Yasutomi² and Shoji Kawahito²

¹ Department of Engineering, Shizuoka University, 3-5-1, Johoku, Nakaku, Hamamatu, Shizuoka 432-8011, Japan

² Research Institute of Electronics, Shizuoka University, 3-5-1, Johoku, Nakaku, Hamamatu, Shizuoka 432-8011, Japan

³ Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan

Sensors 2018, 18(4), 977; https://doi.org/10.3390/s18040977 - 26 Mar 2018

Cited by 1 | Viewed by 6400

Abstract

A probabilistic method to remove the random telegraph signal (RTS) noise and to increase the signal level is proposed, and was verified by simulation based on measured real sensor noise. Although semi-photon-counting-level (SPCL) ultra-low noise complementary-metal-oxide-semiconductor (CMOS) image sensors (CISs) with high conversion [...] Read more.

A probabilistic method to remove the random telegraph signal (RTS) noise and to increase the signal level is proposed, and was verified by simulation based on measured real sensor noise. Although semi-photon-counting-level (SPCL) ultra-low noise complementary-metal-oxide-semiconductor (CMOS) image sensors (CISs) with high conversion gain pixels have emerged, they still suffer from huge RTS noise, which is inherent to the CISs. The proposed method utilizes a multi-aperture (MA) camera that is composed of multiple sets of an SPCL CIS and a moderately fast and compact imaging lens to emulate a very fast single lens. Due to the redundancy of the MA camera, the RTS noise is removed by the maximum likelihood estimation where noise characteristics are modeled by the probability density distribution. In the proposed method, the photon shot noise is also relatively reduced because of the averaging effect, where the pixel values of all the multiple apertures are considered. An extremely low-light condition that the maximum number of electrons per aperture was the only 2

e^{-}

was simulated. PSNRs of a test image for simple averaging, selective averaging (our previous method), and the proposed method were 11.92 dB, 11.61 dB, and 13.14 dB, respectively. The selective averaging, which can remove RTS noise, was worse than the simple averaging because it ignores the pixels with RTS noise and photon shot noise was less improved. The simulation results showed that the proposed method provided the best noise reduction performance. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 71530 KiB

Open AccessArticle

Research on Strong Clutter Suppression for Gaofen-3 Dual-Channel SAR/GMTI

by Mingjie Zheng^1,*, He Yan²

, Lei Zhang¹, Weidong Yu¹, Yunkai Deng¹ and Robert Wang¹

¹ Space Microwave Remote Sensing System Department, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

² Institute of Electronic Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210006, China

Sensors 2018, 18(4), 978; https://doi.org/10.3390/s18040978 - 26 Mar 2018

Cited by 13 | Viewed by 5308

Abstract

In spaceborne synthetic aperture radar (SAR), moving targets are almost buried in ground clutter due to the wide clutter Doppler spectrum and the restricted pulse repetition frequency (PRF), which increases the difficulty of moving target detection. Clutter suppression is one of the key [...] Read more.

In spaceborne synthetic aperture radar (SAR), moving targets are almost buried in ground clutter due to the wide clutter Doppler spectrum and the restricted pulse repetition frequency (PRF), which increases the difficulty of moving target detection. Clutter suppression is one of the key issues in the spaceborne SAR moving target indicator operation. In this paper, we describe the clutter suppression principle and analyze the influence of amplitude and phase error on clutter suppression. In the following, a novel dual-channel SAR clutter suppression algorithm is proposed, which is suitable for the Gaofen-3(GF-3) SAR sensor. The proposed algorithm consists of three technique steps, namely adaptive two-dimensional (2D) channel calibration, refined amplitude error correction and refined phase error correction. After channel error is corrected by these procedures, the clutter component, especially a strong clutter component, can be well suppressed. The validity of the proposed algorithm is verified by GF-3 SAR real data which demonstrates the ground moving-target indication (GMTI) capability of GF-3 SAR sensor. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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12 pages, 37870 KiB

Open AccessArticle

Development of Implantable Wireless Sensor Nodes for Animal Husbandry and MedTech Innovation

by Jian Lu^1,*, Lan Zhang¹, Dapeng Zhang¹, Sohei Matsumoto¹, Hiroshi Hiroshima¹, Ryutaro Maeda¹, Mizuho Sato², Atsushi Toyoda², Takafumi Gotoh^3,4 and Nobuhiro Ohkohchi⁵

¹ Research Center for Ubiquitous MEMS and Micro Engineering (UMEMSME), National Institute of Advanced Industrial Science and Technology (AIST), Namiki 1-2-1, Tsukuba 305-8564, Japan

² College of Agriculture Ibaraki University, Chuo Ami Inashiki 3-21-1, Mito 300-0393, Japan

³ Kuju Agricultural Research Center, Graduate School of Agriculture, Kyushu University, Fukuoka 878-0201, Japan

⁴ Department of Agricultural Sciences and Natural Resources, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan

⁵ Faculty of Medicine, University of Tsukuba, Tennoudai 1-1-1, Tsukuba 305-8577, Japan

Sensors 2018, 18(4), 979; https://doi.org/10.3390/s18040979 - 26 Mar 2018

Cited by 12 | Viewed by 6994

Abstract

In this paper, we report the development, evaluation, and application of ultra-small low-power wireless sensor nodes for advancing animal husbandry, as well as for innovation of medical technologies. A radio frequency identification (RFID) chip with hybrid interface and neglectable power consumption was introduced [...] Read more.

In this paper, we report the development, evaluation, and application of ultra-small low-power wireless sensor nodes for advancing animal husbandry, as well as for innovation of medical technologies. A radio frequency identification (RFID) chip with hybrid interface and neglectable power consumption was introduced to enable switching of ON/OFF and measurement mode after implantation. A wireless power transmission system with a maximum efficiency of 70% and an access distance of up to 5 cm was developed to allow the sensor node to survive for a duration of several weeks from a few minutes’ remote charge. The results of field tests using laboratory mice and a cow indicated the high accuracy of the collected biological data and bio-compatibility of the package. As a result of extensive application of the above technologies, a fully solid wireless pH sensor and a surgical navigation system using artificial magnetic field and a 3D MEMS magnetic sensor are introduced in this paper, and the preliminary experimental results are presented and discussed. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 85745 KiB

Open AccessArticle

Embedded Distributed Optical Fiber Sensors in Reinforced Concrete Structures—A Case Study

by António Barrias^1,*

, Joan R. Casas¹

and Sergi Villalba²

¹ Department of Civil and Environmental Engineering, Technical University of Catalonia (UPC), c/Jordi Girona 1-3, 08034 Barcelona, Spain

² Department of Engineering and Construction Projects, Technical University of Catalonia (UPC), c/Colom 11, Ed. TR5, 08022 Terrassa, Spain

Sensors 2018, 18(4), 980; https://doi.org/10.3390/s18040980 - 26 Mar 2018

Cited by 117 | Viewed by 10750

Abstract

When using distributed optical fiber sensors (DOFS) on reinforced concrete structures, a compromise must be achieved between the protection requirements and robustness of the sensor deployment and the accuracy of the measurements both in the uncracked and cracked stages and under loading, unloading [...] Read more.

When using distributed optical fiber sensors (DOFS) on reinforced concrete structures, a compromise must be achieved between the protection requirements and robustness of the sensor deployment and the accuracy of the measurements both in the uncracked and cracked stages and under loading, unloading and reloading processes. With this in mind the authors have carried out an experiment where polyimide-coated DOFS were installed on two concrete beams, both embedded in the rebar elements and also bonded to the concrete surface. The specimens were subjected to a three-point load test where after cracking, they are unloaded and reloaded again to assess the capability of the sensor when applied to a real loading scenarios in concrete structures. Rayleigh Optical Frequency Domain Reflectometry (OFDR) was used as the most suitable technique for crack detection in reinforced concrete elements. To verify the reliability and accuracy of the DOFS measurements, additional strain gauges were also installed at three locations along the rebar. The results show the feasibility of using a thin coated polyimide DOFS directly bonded on the reinforcing bar without the need of indention or mechanization. A proposal for a Spectral Shift Quality (SSQ) threshold is also obtained and proposed for future works when using polyimide-coated DOFS bonded to rebars with cyanoacrylate adhesive. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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22 pages, 2675 KiB

Open AccessArticle

A Resource Service Model in the Industrial IoT System Based on Transparent Computing

by Weimin Li^1,2

, Bin Wang¹, Jinfang Sheng^1,*, Ke Dong¹, Zitong Li³ and Yixiang Hu¹

¹ School of Information Science and Engineering, Central South University, Changsha 410083, China

² School of Information, Hunan University of Humanities, Science and Technology, Loudi 417000, China

³ Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China

Sensors 2018, 18(4), 981; https://doi.org/10.3390/s18040981 - 26 Mar 2018

Cited by 20 | Viewed by 5090

Abstract

The Internet of Things (IoT) has received a lot of attention, especially in industrial scenarios. One of the typical applications is the intelligent mine, which actually constructs the Six-Hedge underground systems with IoT platforms. Based on a case study of the Six Systems [...] Read more.

The Internet of Things (IoT) has received a lot of attention, especially in industrial scenarios. One of the typical applications is the intelligent mine, which actually constructs the Six-Hedge underground systems with IoT platforms. Based on a case study of the Six Systems in the underground metal mine, this paper summarizes the main challenges of industrial IoT from the aspects of heterogeneity in devices and resources, security, reliability, deployment and maintenance costs. Then, a novel resource service model for the industrial IoT applications based on Transparent Computing (TC) is presented, which supports centralized management of all resources including operating system (OS), programs and data on the server-side for the IoT devices, thus offering an effective, reliable, secure and cross-OS IoT service and reducing the costs of IoT system deployment and maintenance. The model has five layers: sensing layer, aggregation layer, network layer, service and storage layer and interface and management layer. We also present a detailed analysis on the system architecture and key technologies of the model. Finally, the efficiency of the model is shown by an experiment prototype system. Full article

(This article belongs to the Section Internet of Things)

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12 pages, 19368 KiB

Open AccessArticle

Integrated Optoelectronic Position Sensor for Scanning Micromirrors

by Xiang Cheng^1,*, Xinglin Sun¹, Yan Liu¹, Lijun Zhu¹, Xiaoyang Zhang², Liang Zhou² and Huikai Xie²

¹ School of Aerospace Engineering, Xiamen University, Xiamen 361005, China

² Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611, USA

Sensors 2018, 18(4), 982; https://doi.org/10.3390/s18040982 - 26 Mar 2018

Cited by 16 | Viewed by 5642

Abstract

Scanning micromirrors have been used in a wide range of areas, but many of them do not have position sensing built in, which significantly limits their application space. This paper reports an integrated optoelectronic position sensor (iOE-PS) that can measure the linear displacement [...] Read more.

Scanning micromirrors have been used in a wide range of areas, but many of them do not have position sensing built in, which significantly limits their application space. This paper reports an integrated optoelectronic position sensor (iOE-PS) that can measure the linear displacement and tilting angle of electrothermal MEMS (Micro-electromechanical Systems) scanning mirrors. The iOE-PS integrates a laser diode and its driving circuits, a quadrant photo-detector (QPD) and its readout circuits, and a band-gap reference all on a single chip, and it has been fabricated in a standard 0.5 μm CMOS (Complementary Metal Oxide Semiconductor) process. The footprint of the iOE-PS chip is 5 mm × 5 mm. Each quadrant of the QPD has a photosensitive area of 500 µm × 500 µm and the spacing between adjacent quadrants is 500 μm. The iOE-PS chip is simply packaged underneath of an electrothermally-actuated MEMS mirror. Experimental results show that the iOE-PS has a linear response when the MEMS mirror plate moves vertically between 2.0 mm and 3.0 mm over the iOE-PS chip or scans from −5 to +5°. Such MEMS scanning mirrors integrated with the iOE-PS can greatly reduce the complexity and cost of the MEMS mirrors-enabled modules and systems. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 43941 KiB

Open AccessArticle

An Experimental Study of a Micro-Projection Enabled Optical Terminal for Short-Range Bidirectional Multi-Wavelength Visible Light Communications

by Hsi-Hsir Chou^*

, Cheng-Yu Tsai and Jhih-Shan Jiang

Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan

Sensors 2018, 18(4), 983; https://doi.org/10.3390/s18040983 - 26 Mar 2018

Cited by 1 | Viewed by 4124

Abstract

A micro-projection enabled short-range communication (SRC) approach using red-, green- and blue-based light-emitting diodes (RGB-LEDs) has experimentally demonstrated recently that micro-projection and high-speed data transmission can be performed simultaneously. In this research, a reconfigurable design of a polarization modulated image system based on [...] Read more.

A micro-projection enabled short-range communication (SRC) approach using red-, green- and blue-based light-emitting diodes (RGB-LEDs) has experimentally demonstrated recently that micro-projection and high-speed data transmission can be performed simultaneously. In this research, a reconfigurable design of a polarization modulated image system based on the use of a Liquid Crystal on Silicon based Spatial Light Modulator (LCoS-based SLM) serving as a portable optical terminal capable of micro-projection and bidirectional multi-wavelength communications is proposed and experimentally demonstrated. For the proof of concept, the system performance was evaluated through a bidirectional communication link at a transmission distance over 0.65 m. In order to make the proposed communication system architecture compatible with the data modulation format of future possible wireless communication system, baseband modulation scheme, i.e., Non-Return-to-Zero On-Off-Keying (NRZ_OOK), M-ary Phase Shift Keying (M-PSK) and M-ary Quadrature Amplitude Modulation (M-QAM) were used to investigate the system transmission performance. The experimental results shown that an acceptable BER (satisfying the limitation of Forward Error Correction, FEC standard) and crosstalk can all be achieved in the bidirectional multi-wavelength communication scenario. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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12 pages, 6342 KiB

Open AccessArticle

Analytical Method to Estimate the Complex Permittivity of Oil Samples

by Lijuan Su¹, Javier Mata-Contreras¹, Paris Vélez^1,*

, Armando Fernández-Prieto²

and Ferran Martín¹

¹ CIMITEC, Departament d’Enginyeria Electrònica, Universitat Autònoma de Barcelona, Bellaterra, 08193 Cerdanyola del Valldès, Spain

² Departamento de Electrónica y Electromagnetismo, Universidad de Sevilla, Av. Reina Mercedes s/n, 41012 Sevilla, Spain

Sensors 2018, 18(4), 984; https://doi.org/10.3390/s18040984 - 26 Mar 2018

Cited by 152 | Viewed by 7075

Abstract

In this paper, an analytical method to estimate the complex dielectric constant of liquids is presented. The method is based on the measurement of the transmission coefficient in an embedded microstrip line loaded with a complementary split ring resonator (CSRR), which is etched [...] Read more.

In this paper, an analytical method to estimate the complex dielectric constant of liquids is presented. The method is based on the measurement of the transmission coefficient in an embedded microstrip line loaded with a complementary split ring resonator (CSRR), which is etched in the ground plane. From this response, the dielectric constant and loss tangent of the liquid under test (LUT) can be extracted, provided that the CSRR is surrounded by such LUT, and the liquid level extends beyond the region where the electromagnetic fields generated by the CSRR are present. For that purpose, a liquid container acting as a pool is added to the structure. The main advantage of this method, which is validated from the measurement of the complex dielectric constant of olive and castor oil, is that reference samples for calibration are not required. Full article

(This article belongs to the Section Physical Sensors)

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21 pages, 34837 KiB

Open AccessArticle

Design and Processing of a Novel Chaos-Based Stepped Frequency Synthesized Wideband Radar Signal

by Tao Zeng¹, Shaoqiang Chang¹, Huayu Fan² and Quanhua Liu^1,3,*

¹ Radar Research Laboratory, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China

² Department of Electronic Engineering, Tsinghua University, Beijing 100084, China

³ Key Laboratory of Electronic and Information Technology in Satellite Navigation, (Beijing Institute of Technology), Ministry of Education, Beijing 100081, China

Sensors 2018, 18(4), 985; https://doi.org/10.3390/s18040985 - 26 Mar 2018

Cited by 17 | Viewed by 5004

Abstract

The linear stepped frequency and linear frequency shift keying (FSK) signal has been widely used in radar systems. However, such linear modulation signals suffer from the range–Doppler coupling that degrades radar multi-target resolution. Moreover, the fixed frequency-hopping or frequency-coded sequence can be easily [...] Read more.

The linear stepped frequency and linear frequency shift keying (FSK) signal has been widely used in radar systems. However, such linear modulation signals suffer from the range–Doppler coupling that degrades radar multi-target resolution. Moreover, the fixed frequency-hopping or frequency-coded sequence can be easily predicted by the interception receiver in the electronic countermeasures (ECM) environments, which limits radar anti-jamming performance. In addition, the single FSK modulation reduces the radar low probability of intercept (LPI) performance, for it cannot achieve a large time–bandwidth product. To solve such problems, we propose a novel chaos-based stepped frequency (CSF) synthesized wideband signal in this paper. The signal introduces chaotic frequency hopping between the coherent stepped frequency pulses, and adopts a chaotic frequency shift keying (CFSK) and phase shift keying (PSK) composited coded modulation in a subpulse, called CSF-CFSK/PSK. Correspondingly, the processing method for the signal has been proposed. According to our theoretical analyses and the simulations, the proposed signal and processing method achieve better multi-target resolution and LPI performance. Furthermore, flexible modulation is able to increase the robustness against identification of the interception receiver and improve the anti-jamming performance of the radar. Full article

(This article belongs to the Section Remote Sensors)

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13 pages, 63558 KiB

Open AccessArticle

Coupling Vibration Analysis of Trapped-Energy Rectangular Quartz Resonators by Variational Formulation of Mindlin’s Theory

by Nian Li

, Bin Wang and Zhenghua Qian^*

State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Sensors 2018, 18(4), 986; https://doi.org/10.3390/s18040986 - 26 Mar 2018

Cited by 5 | Viewed by 3668

Abstract

Mindlin’s two-dimensional theory has been derived and applied to research on quartz resonators for a long time. However, most works have focused on vibrations varying only in two directions, including thickness direction, while the effect of other directions like the length or width [...] Read more.

Mindlin’s two-dimensional theory has been derived and applied to research on quartz resonators for a long time. However, most works have focused on vibrations varying only in two directions, including thickness direction, while the effect of other directions like the length or width direction is normally neglected. Besides, researchers often model quartz resonators as fully electroded plates because of the resulting simplicity. Since a real device is finite in all directions and is only centrally electroded, results obtained in such works cannot offer quantitative information on vibrations with enough accuracy. In this paper, a theoretical analysis of a rectangular trapped-energy resonator of AT-cut quartz is studied using the Ritz method, associated with the variational formulation of Mindlin’s first-order equations. Frequency spectra and mode shapes of a real-scaled trapped-energy resonator, which is finite in all directions, are obtained with the consideration of mode couplings among thickness-shear mode, thickness-twist mode, and flexural mode. Results show the existence of an energy-trapping and coupling phenomenon and are helpful for thorough and accurate understanding of quartz resonator vibrations. Detailed discussions on the effects of structural parameters on mode couplings and energy trapping are provided, and the results can helpfully guide the selection of aspect ratio, length/thickness ratio, and electrode inertia in device design. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 26690 KiB

Open AccessArticle

2D Analytical Model for the Directivity Prediction of Ultrasonic Contact Type Transducers in the Generation of Guided Waves

by Kumar Anubhav Tiwari^*

, Renaldas Raisutis, Liudas Mazeika and Vykintas Samaitis

Prof. K. Barsauskas Ultrasound Research Institute, Kaunas University of Technology, K. Baršausko St. 59, LT-51423 Kaunas, Lithuania

Sensors 2018, 18(4), 987; https://doi.org/10.3390/s18040987 - 26 Mar 2018

Cited by 15 | Viewed by 6024

Abstract

In this paper, a novel 2D analytical model based on the Huygens’s principle of wave propagation is proposed in order to predict the directivity patterns of contact type ultrasonic transducers in the generation of guided waves (GWs). The developed model is able to [...] Read more.

In this paper, a novel 2D analytical model based on the Huygens’s principle of wave propagation is proposed in order to predict the directivity patterns of contact type ultrasonic transducers in the generation of guided waves (GWs). The developed model is able to estimate the directivity patterns at any distance, at any excitation frequency and for any configuration and shape of the transducers with prior information of phase dispersive characteristics of the guided wave modes and the behavior of transducer. This, in turn, facilitates to choose the appropriate transducer or arrays of transducers, suitable guided wave modes and excitation frequency for the nondestructive testing (NDT) and structural health monitoring (SHM) applications. The model is demonstrated for P1-type macro-fiber composite (MFC) transducer glued on a 2 mm thick aluminum (Al) alloy plate. The directivity patterns of MFC transducer in the generation of fundamental guided Lamb modes (the S0 and A0) and shear horizontal mode (the SH0) are successfully obtained at 80 kHz, 5-period excitation signal. The results are verified using 3D finite element (FE) modelling and experimental investigation. The results obtained using the proposed model shows the good agreement with those obtained using numerical simulations and experimental analysis. The calculation time using the analytical model was significantly shorter as compared to the time spent in experimental analysis and FE numerical modelling. Full article

(This article belongs to the Special Issue Ultrasonic Sensors 2018)

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13 pages, 8442 KiB

Open AccessArticle

Temperature and Vibration Dependence of the Faraday Effect of Gd₂O₃ NPs-Doped Alumino-Silicate Glass Optical Fiber

by Seongmin Ju¹

, Jihun Kim¹, Kadathala Linganna², Pramod R. Watekar¹, Seong Gu Kang¹, Bok Hyeon Kim¹, Seongjae Boo³, Youjin Lee⁴

, Yong Ho An⁴, Cheol Jin Kim⁵ and Won-Taek Han^1,*

¹ School of Electrical Engineering and Computer Science/Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, Korea

² Advanced Optical Lens Research Center, Korea Photonics Technology Institute, Gwangju 61007, Korea

³ Solar City Center, Korea Institute of Industrial Technology, Gwangju 61012, Korea

⁴ Power System Laboratory, Korea Electric Power Corporation Research Institute, Daejeon 34056, Korea

⁵ Department of Nano and Advanced Materials Engineering, Gyeongsang National University, Jinju 52828, Korea

Sensors 2018, 18(4), 988; https://doi.org/10.3390/s18040988 - 27 Mar 2018

Cited by 16 | Viewed by 4965

Abstract

All-optical fiber magnetic field sensor based on the Gd₂O₃ nano-particles (NPs)-doped alumino-silicate glass optical fiber was developed, and its temperature and vibration dependence on the Faraday Effect were investigated. Uniformly embedded Gd₂O₃ NPs were identified to form [...] Read more.

All-optical fiber magnetic field sensor based on the Gd₂O₃ nano-particles (NPs)-doped alumino-silicate glass optical fiber was developed, and its temperature and vibration dependence on the Faraday Effect were investigated. Uniformly embedded Gd₂O₃ NPs were identified to form in the core of the fiber, and the measured absorption peaks of the fiber appearing at 377 nm, 443 nm, and 551 nm were attributed to the Gd₂O₃ NPs incorporated in the fiber core. The Faraday rotation angle (FRA) of the linearly polarized light was measured at 650 nm with the induced magnetic field by the solenoid. The Faraday rotation angle was found to increase linearly with the magnetic field, and it was about 18.16° ± 0.048° at 0.142 Tesla (T) at temperatures of 25 °C–120 °C, by which the estimated Verdet constant was 3.19 rad/(T∙m) ± 0.01 rad/(T∙m). The variation of the FRA with time at 0.142 T and 120 °C was negligibly small (−9.78 × 10⁻⁴ °/min). The variation of the FRA under the mechanical vibration with the acceleration below 10 g and the frequency above 50 Hz was within 0.5°. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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10 pages, 37663 KiB

Open AccessArticle

Printing and Folding: A Solution for High-Throughput Processing of Organic Thin-Film Thermoelectric Devices

by Seyedmohammad Mortazavinatanzi^*, Alireza Rezaniakolaei^*

and Lasse Rosendahl

Department of Energy Technology, Aalborg University, Pontoppidanstraede 111, DK-9220 Aalborg, Denmark

Sensors 2018, 18(4), 989; https://doi.org/10.3390/s18040989 - 27 Mar 2018

Cited by 19 | Viewed by 6306

Abstract

Wearable electronics are rapidly expanding, especially in applications like health monitoring through medical sensors and body area networks (BANs). Thermoelectric generators (TEGs) have been the main candidate among the different types of energy harvesting methods for body-mounted or even implantable sensors. Introducing new [...] Read more.

Wearable electronics are rapidly expanding, especially in applications like health monitoring through medical sensors and body area networks (BANs). Thermoelectric generators (TEGs) have been the main candidate among the different types of energy harvesting methods for body-mounted or even implantable sensors. Introducing new semiconductor materials like organic thermoelectric materials and advancing manufacturing techniques are paving the way to overcome the barriers associated with the bulky and inflexible nature of the common TEGs and are making it possible to fabricate flexible and biocompatible modules. Yet, the lower efficiency of these materials in comparison with bulk-inorganic counterparts as well as applying them mostly in the form of thin layers on flexible substrates limits their applications. This research aims to improve the functionality of thin and flexible organic thermoelectric generators (OTEs) by utilizing a novel design concept inspired by origami. The effects of critical geometric parameters are investigated using COMSOL Multiphysics to further prove the concept of printing and folding as an approach for the system level optimization of printed thin film TEGs. Full article

(This article belongs to the Special Issue I3S 2017 Selected Papers)

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8 pages, 5663 KiB

Open AccessArticle

Electronic Detection of DNA Hybridization by Coupling Organic Field-Effect Transistor-Based Sensors and Hairpin-Shaped Probes

by Corrado Napoli^1,*

, Stefano Lai¹, Ambra Giannetti²

, Sara Tombelli²

, Francesco Baldini²

, Massimo Barbaro¹

and Annalisa Bonfiglio¹

¹ Department of Electrical and Electronic Engineering, Università di Cagliari, 09123 Cagliari, Italy

² Istituto di Fisica Applicata “Nello Carrara”, Consiglio Nazionale delle Ricerche, 50019 Sesto Fiorentino, Italy

Sensors 2018, 18(4), 990; https://doi.org/10.3390/s18040990 - 27 Mar 2018

Cited by 23 | Viewed by 7114

Abstract

In this paper, the electronic transduction of DNA hybridization is presented by coupling organic charge-modulated field-effect transistors (OCMFETs) and hairpin-shaped probes. These probes have shown interesting properties in terms of sensitivity and selectivity in other kinds of assays, in the form of molecular [...] Read more.

In this paper, the electronic transduction of DNA hybridization is presented by coupling organic charge-modulated field-effect transistors (OCMFETs) and hairpin-shaped probes. These probes have shown interesting properties in terms of sensitivity and selectivity in other kinds of assays, in the form of molecular beacons (MBs). Their integration with organic-transistor based sensors, never explored before, paves the way to a new class of low-cost, easy-to-use, and portable genetic sensors with enhanced performances. Thanks to the peculiar characteristics of the employed sensor, measurements can be performed at relatively high ionic strengths, thus optimizing the probes’ functionality without affecting the detection ability of the device. A complete electrical characterization of the sensor is reported, including calibration with different target concentrations in the measurement environment and selectivity evaluation. In particular, DNA hybridization detection for target concentration as low as 100 pM is demonstrated. Full article

(This article belongs to the Special Issue Label-Free Biosensors)

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16 pages, 20945 KiB

Open AccessArticle

An Improved Positioning Method for Two Base Stations in AIS

by Yi Jiang

, Jiani Wu^* and Shufang Zhang

Key Laboratory of Intelligent Waterway Transport Ministry of Transport, Information Science and Technology College, Dalian Maritime University, Dalian 116026, China

Sensors 2018, 18(4), 991; https://doi.org/10.3390/s18040991 - 27 Mar 2018

Cited by 10 | Viewed by 5435

Abstract

Resilient position, navigation, and timing (PNT) data is indispensable information in the field of e-navigation. An automatic identification system (AIS) based ranging mode (R-Mode) is put forward to develop a terrestrial backup system in order to overcome the vulnerability of the global navigation [...] Read more.

Resilient position, navigation, and timing (PNT) data is indispensable information in the field of e-navigation. An automatic identification system (AIS) based ranging mode (R-Mode) is put forward to develop a terrestrial backup system in order to overcome the vulnerability of the global navigation satellite system (GNSS). In general, at least three base stations are required in the traditional R-Mode positioning method. However, the geometric distribution of existing base stations is not considered for positioning, as AIS is a communication system. In some cases, a vessel can only receive signals from two base stations. In this paper, an improved position estimation method based on displacement correction is therefore proposed to solve this problem. Compared with the prior displacement correction position estimation (DCPE) method, the proposed method can improve positioning accuracy effectively by adopting a more precise motion model for the vessel, including an accelerated motion and a turning motion model. Moreover, the motion model is employed adaptively to correct the displacement of the vessel. Finally, the proposed method is verified and the performance is analyzed and compared by simulation. This study can extend the application region of AIS R-Mode. Full article

(This article belongs to the Special Issue Smart Vehicular Mobile Sensing)

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16 pages, 16673 KiB

Open AccessArticle

A Robust Real Time Direction-of-Arrival Estimation Method for Sequential Movement Events of Vehicles

by Huawei Liu^1,2, Baoqing Li¹, Xiaobing Yuan^1,*, Qianwei Zhou³ and Jingchang Huang⁴

¹ Science and Technology on Microsystem Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 201800, China

² University of Chinese Academy of Science, Beijing 100049, China

³ College of Computer Science and Technology, Zhejiang University of Technology, Hangzhou 310023, China

⁴ IBM-Research China, Shanghai 201203, China

Sensors 2018, 18(4), 992; https://doi.org/10.3390/s18040992 - 27 Mar 2018

Cited by 8 | Viewed by 4868

Abstract

Parameters estimation of sequential movement events of vehicles is facing the challenges of noise interferences and the demands of portable implementation. In this paper, we propose a robust direction-of-arrival (DOA) estimation method for the sequential movement events of vehicles based on a small [...] Read more.

Parameters estimation of sequential movement events of vehicles is facing the challenges of noise interferences and the demands of portable implementation. In this paper, we propose a robust direction-of-arrival (DOA) estimation method for the sequential movement events of vehicles based on a small Micro-Electro-Mechanical System (MEMS) microphone array system. Inspired by the incoherent signal-subspace method (ISM), the method that is proposed in this work employs multiple sub-bands, which are selected from the wideband signals with high magnitude-squared coherence to track moving vehicles in the presence of wind noise. The field test results demonstrate that the proposed method has a better performance in emulating the DOA of a moving vehicle even in the case of severe wind interference than the narrowband multiple signal classification (MUSIC) method, the sub-band DOA estimation method, and the classical two-sided correlation transformation (TCT) method. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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17 pages, 14521 KiB

Open AccessArticle

Comparison of Portable and Bench-Top Spectrometers for Mid-Infrared Diffuse Reflectance Measurements of Soils

by Christopher Hutengs^1,2,*, Bernard Ludwig³, András Jung⁴

, Andreas Eisele⁵ and Michael Vohland^1,2

¹ Geoinformatics and Remote Sensing, Institute for Geography, Leipzig University, Johannisallee 19a, 04103 Leipzig, Germany

² German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany

³ Deparatment of Environmental Chemistry, Kassel University, Nordbahnhofstr. 1a, 37213 Witzenhausen, Germany

⁴ Technical Department, Szent István University, Villányi út 29-43, 1118 Budapest, Hungary

⁵ SphereOptics GmbH, Gewerbestrasse 13, 82211 Herrsching, Germany

Sensors 2018, 18(4), 993; https://doi.org/10.3390/s18040993 - 27 Mar 2018

Cited by 56 | Viewed by 8555

Abstract

Mid-infrared (MIR) spectroscopy has received widespread interest as a method to complement traditional soil analysis. Recently available portable MIR spectrometers additionally offer potential for on-site applications, given sufficient spectral data quality. We therefore tested the performance of the Agilent 4300 Handheld FTIR (DRIFT [...] Read more.

Mid-infrared (MIR) spectroscopy has received widespread interest as a method to complement traditional soil analysis. Recently available portable MIR spectrometers additionally offer potential for on-site applications, given sufficient spectral data quality. We therefore tested the performance of the Agilent 4300 Handheld FTIR (DRIFT spectra) in comparison to a Bruker Tensor 27 bench-top instrument in terms of (i) spectral quality and measurement noise quantified by wavelet analysis; (ii) accuracy of partial least squares (PLS) calibrations for soil organic carbon (SOC), total nitrogen (N), pH, clay and sand content with a repeated cross-validation analysis; and (iii) key spectral regions for these soil properties identified with a Monte Carlo spectral variable selection approach. Measurements and multivariate calibrations with the handheld device were as good as or slightly better than Bruker equipped with a DRIFT accessory, but not as accurate as with directional hemispherical reflectance (DHR) data collected with an integrating sphere. Variations in noise did not markedly affect the accuracy of multivariate PLS calibrations. Identified key spectral regions for PLS calibrations provided a good match between Agilent and Bruker DHR data, especially for SOC and N. Our findings suggest that portable FTIR instruments are a viable alternative for MIR measurements in the laboratory and offer great potential for on-site applications. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 61489 KiB

Open AccessArticle

Self-Sensing of Position-Related Loads in Continuous Carbon Fibers-Embedded 3D-Printed Polymer Structures Using Electrical Resistance Measurement

by Congcong Luan^1,2, Xinhua Yao^1,2,*

, Hongyao Shen^1,2 and Jianzhong Fu^1,2

¹ State Key Laboratory of Fluid Power and Mechatronic Systems, School of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China

² Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, School of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China

Sensors 2018, 18(4), 994; https://doi.org/10.3390/s18040994 - 27 Mar 2018

Cited by 41 | Viewed by 5348

Abstract

Condition monitoring in polymer composites and structures based on continuous carbon fibers show overwhelming advantages over other potentially competitive sensing technologies in long-gauge measurements due to their great electromechanical behavior and excellent reinforcement property. Although carbon fibers have been developed as strain- or [...] Read more.

Condition monitoring in polymer composites and structures based on continuous carbon fibers show overwhelming advantages over other potentially competitive sensing technologies in long-gauge measurements due to their great electromechanical behavior and excellent reinforcement property. Although carbon fibers have been developed as strain- or stress-sensing agents in composite structures through electrical resistance measurements, the electromechanical behavior under flexural loads in terms of different loading positions still lacks adequate research, which is the most common situation in practical applications. This study establishes the relationship between the fractional change in electrical resistance of carbon fibers and the external loads at different loading positions along the fibers’ longitudinal direction. An approach for real-time monitoring of flexural loads at different loading positions was presented simultaneously based on this relationship. The effectiveness and feasibility of the approach were verified by experiments on carbon fiber-embedded three-dimensional (3D) printed thermoplastic polymer beam. The error in using the provided approach to monitor the external loads at different loading positions was less than 1.28%. The study fully taps the potential of continuous carbon fibers as long-gauge sensory agents and reinforcement in the 3D-printed polymer structures. Full article

(This article belongs to the Special Issue Printed Sensors 2018)

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8 pages, 9028 KiB

Open AccessArticle

Infrared Hollow Optical Fiber Probe for Localized Carbon Dioxide Measurement in Respiratory Tracts

by Takashi Katagiri¹, Kyosuke Shibayama², Takeru Iida² and Yuji Matsuura^2,*

¹ Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Sendai 980-8579, Japan

² Graduate School of Biomedical Engineering, Tohoku University, 6-6-05 Aoba, Sendai 980-8579, Japan

Sensors 2018, 18(4), 995; https://doi.org/10.3390/s18040995 - 27 Mar 2018

Cited by 16 | Viewed by 5614

Abstract

A real-time gas monitoring system based on optical absorption spectroscopy is proposed for localized carbon dioxide (CO₂) measurement in respiratory tracts. In this system, a small gas cell is attached to the end of a hollow optical fiber that delivers mid-infrared [...] Read more.

A real-time gas monitoring system based on optical absorption spectroscopy is proposed for localized carbon dioxide (CO₂) measurement in respiratory tracts. In this system, a small gas cell is attached to the end of a hollow optical fiber that delivers mid-infrared light with small transmission loss. The diameters of the fiber and the gas cell are smaller than 1.2 mm so that the probe can be inserted into a working channel of common bronchoscopes. The dimensions of the gas cell are designed based on absorption spectra of CO₂ standard gases in the 4.2 μm wavelength region, which are measured using a Fourier-transform infrared spectrometer. A miniature gas cell that is comprised of a stainless-steel tube with slots for gas inlet and a micro-mirror is fabricated. A compact probing system with a quantum cascade laser (QCL) light source is built using a gas cell with a hollow optical fiber for monitoring CO₂ concentration. Experimental results using human breaths show the feasibility of the system for in-situ measurement of localized CO₂ concentration in human airways. Full article

(This article belongs to the Special Issue Biomedical Infrared Imaging: From Sensors to Applications)

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18 pages, 23024 KiB

Open AccessArticle

Computationally Efficient Automatic Coast Mode Target Tracking Based on Occlusion Awareness in Infrared Images

by Sohyun Kim^1,*, Gwang-Il Jang¹, Sungho Kim²

and Junmo Kim³

¹ Agency for Defense Development, P.O. Box 35, Yuseong, Daejeon 34186, Korea

² Department of Electronic Engineering, Yeungnam University, 280 Daehak-ro, Gyeongsan, Gyeongbuk 38541, Korea

³ Department of Electrical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea

Sensors 2018, 18(4), 996; https://doi.org/10.3390/s18040996 - 27 Mar 2018

Cited by 5 | Viewed by 6114

Abstract

This paper proposes the automatic coast mode tracking of centroid trackers for infrared images to overcome the target occlusion status. The centroid tracking method, using only the brightness information of an image, is still widely used in infrared imaging tracking systems because it [...] Read more.

This paper proposes the automatic coast mode tracking of centroid trackers for infrared images to overcome the target occlusion status. The centroid tracking method, using only the brightness information of an image, is still widely used in infrared imaging tracking systems because it is difficult to extract meaningful features from infrared images. However, centroid trackers are likely to lose the track because they are highly vulnerable to screened status by the clutter or background. Coast mode, one of the tracking modes, maintains the servo slew rate with the tracking rate right before the loss of track. The proposed automatic coast mode tracking method makes decisions regarding entering coast mode by the prediction of target occlusion and tries to re-lock the target and resume the tracking after blind time. This algorithm comprises three steps. The first step is the prediction process of the occlusion by checking both matters which have target-likelihood brightness and which may screen the target despite different brightness. The second step is the process making inertial tracking commands to the servo. The last step is the process of re-locking a target based on the target modeling of histogram ratio. The effectiveness of the proposed algorithm is addressed by presenting experimental results based on computer simulation with various test imagery sequences compared to published tracking algorithms. The proposed algorithm is tested under a real environment with a naval electro-optical tracking system (EOTS) and airborne EO/IR system. Full article

(This article belongs to the Special Issue Sensors Signal Processing and Visual Computing)

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20 pages, 30424 KiB

Open AccessArticle

Feasibility of Using Elastic Wave Velocity Monitoring for Early Warning of Rainfall-Induced Slope Failure

by Yulong Chen^1,2,*, Muhammad Irfan³

, Taro Uchimura² and Ke Zhang^4,*

¹ State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China

² Department of Civil Engineering, The University of Tokyo, Tokyo 113-8656, Japan

³ Department of Civil Engineering, University of Engineering & Technology Lahore, Lahore 54890, Pakistan

⁴ Faculty of Electric Power Engineering, Kunming University of Science and Technology, Yunnan 650500, China

Sensors 2018, 18(4), 997; https://doi.org/10.3390/s18040997 - 27 Mar 2018

Cited by 26 | Viewed by 5192

Abstract

Rainfall-induced landslides are one of the most widespread slope instability phenomena posing a serious risk to public safety worldwide so that their temporal prediction is of great interest to establish effective warning systems. The objective of this study is to determine the effectiveness [...] Read more.

Rainfall-induced landslides are one of the most widespread slope instability phenomena posing a serious risk to public safety worldwide so that their temporal prediction is of great interest to establish effective warning systems. The objective of this study is to determine the effectiveness of elastic wave velocities in the surface layer of the slope in monitoring, prediction and early warning of landslide. The small-scale fixed and varied, and large-scale slope model tests were conducted. Analysis of the results has established that the elastic wave velocity continuously decreases in response of moisture content and deformation and there was a distinct surge in the decrease rate of wave velocity when failure was initiated. Based on the preliminary results of this analysis, the method using the change in elastic wave velocity proves superior for landslide early warning and suggests that a warning be issued at switch of wave velocity decrease rate. Full article

(This article belongs to the Special Issue Remote Sensing and GIS for Geo-Hazards and Disasters)

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20 pages, 1596 KiB

Open AccessArticle

ABS-SmartComAgri: An Agent-Based Simulator of Smart Communication Protocols in Wireless Sensor Networks for Debugging in Precision Agriculture

by Iván García-Magariño^1,2,*

, Raquel Lacuesta^1,2

and Jaime Lloret³

¹ Department of Computer Science and Engineering of Systems, University of Zaragoza, 44003 Teruel, Spain

² Instituto de Investigación Sanitaria Aragón, University of Zaragoza, 50009 Zaragoza, Spain

³ Integrated Management Coastal Research Institute, Universitat Politècnica de València, 46022 València, Spain

Sensors 2018, 18(4), 998; https://doi.org/10.3390/s18040998 - 27 Mar 2018

Cited by 13 | Viewed by 4971

Abstract

Smart communication protocols are becoming a key mechanism for improving communication performance in networks such as wireless sensor networks. However, the literature lacks mechanisms for simulating smart communication protocols in precision agriculture for decreasing production costs. In this context, the current work presents [...] Read more.

Smart communication protocols are becoming a key mechanism for improving communication performance in networks such as wireless sensor networks. However, the literature lacks mechanisms for simulating smart communication protocols in precision agriculture for decreasing production costs. In this context, the current work presents an agent-based simulator of smart communication protocols for efficiently managing pesticides. The simulator considers the needs of electric power, crop health, percentage of alive bugs and pesticide consumption. The current approach is illustrated with three different communication protocols respectively called (a) broadcast, (b) neighbor and (c) low-cost neighbor. The low-cost neighbor protocol obtained a statistically-significant reduction in the need of electric power over the neighbor protocol, with a very large difference according to the common interpretations about the Cohen’s d effect size. The presented simulator is called ABS-SmartComAgri and is freely distributed as open-source from a public research data repository. It ensures the reproducibility of experiments and allows other researchers to extend the current approach. Full article

(This article belongs to the Special Issue Intelligent Sensor Systems for Environmental Monitoring)

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12 pages, 21182 KiB

Open AccessArticle

Flexible Gas Sensors Employing Octahedral Indium Oxide Films

by Miriam Alvarado

, Èric Navarrete

, Alfonso Romero, José Luis Ramírez and Eduard Llobet^*

MINOS-EMaS, Universitat Rovira i Virgili, Avda. Països Catalans, 26, 43007 Tarragona, Spain

Sensors 2018, 18(4), 999; https://doi.org/10.3390/s18040999 - 28 Mar 2018

Cited by 21 | Viewed by 6056

Abstract

Indium oxide octahedral nanopowders were obtained from an ionic precursor compound after an oxidation process conducted under a low-oxygen atmosphere. This method was found to produce contamination-free indium oxide nanomaterial with very similar morphological and crystalline properties to the one produced by vapor-phase [...] Read more.

Indium oxide octahedral nanopowders were obtained from an ionic precursor compound after an oxidation process conducted under a low-oxygen atmosphere. This method was found to produce contamination-free indium oxide nanomaterial with very similar morphological and crystalline properties to the one produced by vapor-phase transport, but at significantly lower temperatures and higher yield. The as-synthesized indium oxide was mixed to an organic vehicle and microdrop deposited to form a film bridging the interdigitated silver electrodes patterned on top of a flexible, polyimide (Kapton^®), substrate. The gas sensing properties of the flexible chemoresistors towards ammonia vapors, hydrogen, and nitrogen dioxide were investigated. It was found that these sensors were remarkably sensitive to nitrogen dioxide at a low operating temperature of 150 °C. These results are consistent with the performance of vapor-phase transport synthesized indium oxide octahedra sensors on rigid, ceramic substrates. Therefore, the results presented here pave the way for the mass production of inexpensive gas sensors onto flexible substrates via additive manufacturing. Full article

(This article belongs to the Special Issue Gas Sensors based on Semiconducting Metal Oxides)

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20 pages, 92592 KiB

Open AccessArticle

Image Registration-Based Bolt Loosening Detection of Steel Joints

by Xiangxiong Kong^*

and Jian Li

Department of Civil, Environmental, and Architectural Engineering, University of Kansas, Lawrence, KS 66045, USA

Sensors 2018, 18(4), 1000; https://doi.org/10.3390/s18041000 - 28 Mar 2018

Cited by 94 | Viewed by 10936

Abstract

Self-loosening of bolts caused by repetitive loads and vibrations is one of the common defects that can weaken the structural integrity of bolted steel joints in civil structures. Many existing approaches for detecting loosening bolts are based on physical sensors and, hence, require [...] Read more.

Self-loosening of bolts caused by repetitive loads and vibrations is one of the common defects that can weaken the structural integrity of bolted steel joints in civil structures. Many existing approaches for detecting loosening bolts are based on physical sensors and, hence, require extensive sensor deployment, which limit their abilities to cost-effectively detect loosened bolts in a large number of steel joints. Recently, computer vision-based structural health monitoring (SHM) technologies have demonstrated great potential for damage detection due to the benefits of being low cost, easy to deploy, and contactless. In this study, we propose a vision-based non-contact bolt loosening detection method that uses a consumer-grade digital camera. Two images of the monitored steel joint are first collected during different inspection periods and then aligned through two image registration processes. If the bolt experiences rotation between inspections, it will introduce differential features in the registration errors, serving as a good indicator for bolt loosening detection. The performance and robustness of this approach have been validated through a series of experimental investigations using three laboratory setups including a gusset plate on a cross frame, a column flange, and a girder web. The bolt loosening detection results are presented for easy interpretation such that informed decisions can be made about the detected loosened bolts. Full article

(This article belongs to the Special Issue Novel Methodologies to Interpret Non-Destructive Testing and Structural Health Monitoring Data)

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9 pages, 19811 KiB

Open AccessArticle

Direct Printing of Stretchable Elastomers for Highly Sensitive Capillary Pressure Sensors

by Wenguang Liu¹

and Chaoyi Yan^1,2,*

¹ School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen 518055, China

² College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China

Sensors 2018, 18(4), 1001; https://doi.org/10.3390/s18041001 - 28 Mar 2018

Cited by 26 | Viewed by 6276

Abstract

We demonstrate the successful fabrication of highly sensitive capillary pressure sensors using an innovative 3D printing method. Unlike conventional capacitive pressure sensors where the capacitance changes were due to the pressure-induced interspace variations between the parallel plate electrodes, in our capillary sensors the [...] Read more.

We demonstrate the successful fabrication of highly sensitive capillary pressure sensors using an innovative 3D printing method. Unlike conventional capacitive pressure sensors where the capacitance changes were due to the pressure-induced interspace variations between the parallel plate electrodes, in our capillary sensors the capacitance was determined by the extrusion and extraction of liquid medium and consequent changes of dielectric constants. Significant pressure sensitivity advances up to 547.9 KPa⁻¹ were achieved. Moreover, we suggest that our innovative capillary pressure sensors can adopt a wide range of liquid mediums, such as ethanol, deionized water, and their mixtures. The devices also showed stable performances upon repeated pressing cycles. The direct and versatile printing method combined with the significant performance advances are expected to find important applications in future stretchable and wearable electronics. Full article

(This article belongs to the Special Issue Printed Sensors 2018)

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14 pages, 3130 KiB

Open AccessArticle

Linear Feature Projection-Based Sensory Event Detection from the Multiunit Activity of Dorsal Root Ganglion Recordings

by Sungmin Han¹

and Inchan Youn^1,2,*

¹ Biomedical Research Institute, Korea Institute of Science and Technology, 5, Hwarang-ro 14-gil, Seongbuk-gu, Seoul 02791, Korea

² Division of Bio-Medical Science &Technology, KIST School, Korea Institute of Science and Technology, 5, Hwarang-ro 14-gil, Seongbuk-gu, Seoul 02791, Korea

Sensors 2018, 18(4), 1002; https://doi.org/10.3390/s18041002 - 28 Mar 2018

Cited by 2 | Viewed by 5199

Abstract

Afferent signals recorded from the dorsal root ganglion can be used to extract sensory information to provide feedback signals in a functional electrical stimulation (FES) system. The goal of this study was to propose an efficient feature projection method for detecting sensory events [...] Read more.

Afferent signals recorded from the dorsal root ganglion can be used to extract sensory information to provide feedback signals in a functional electrical stimulation (FES) system. The goal of this study was to propose an efficient feature projection method for detecting sensory events from multiunit activity-based feature vectors of tactile afferent activity. Tactile afferent signals were recorded from the L4 dorsal root ganglion using a multichannel microelectrode for three types of sensory events generated by mechanical stimulation on the rat hind paw. The multiunit spikes (MUSs) were extracted as multiunit activity-based feature vectors and projected using a linear feature projection method which consisted of projection pursuit and negentropy maximization (PP/NEM). Finally, a multilayer perceptron classifier was used to detect sensory events. The proposed method showed a detection accuracy superior to those of other linear and nonlinear feature projection methods and all processes were completed within real-time constraints. Results suggest that the proposed method could be useful to detect sensory events in real time. We have demonstrated the methodology for an efficient feature projection method to detect real-time sensory events from the multiunit activity of dorsal root ganglion recordings. The proposed method could be applied to provide real-time sensory feedback signals in closed-loop FES systems. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 32301 KiB

Open AccessArticle

A Sparsity-Promoted Method Based on Majorization-Minimization for Weak Fault Feature Enhancement

by Bangyue Ren¹

, Yansong Hao¹, Huaqing Wang^1,*

, Liuyang Song^1,2, Gang Tang¹ and Hongfang Yuan³

¹ College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China

² Graduate School of Environmental Science and Technology, Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514-8507, Japan

³ College of Information Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China

Sensors 2018, 18(4), 1003; https://doi.org/10.3390/s18041003 - 28 Mar 2018

Cited by 22 | Viewed by 3998

Abstract

Fault transient impulses induced by faulty components in rotating machinery usually contain substantial interference. Fault features are comparatively weak in the initial fault stage, which renders fault diagnosis more difficult. In this case, a sparse representation method based on the Majorzation-Minimization (MM) algorithm [...] Read more.

Fault transient impulses induced by faulty components in rotating machinery usually contain substantial interference. Fault features are comparatively weak in the initial fault stage, which renders fault diagnosis more difficult. In this case, a sparse representation method based on the Majorzation-Minimization (MM) algorithm is proposed to enhance weak fault features and extract the features from strong background noise. However, the traditional MM algorithm suffers from two issues, which are the choice of sparse basis and complicated calculations. To address these challenges, a modified MM algorithm is proposed in which a sparse optimization objective function is designed firstly. Inspired by the Basis Pursuit (BP) model, the optimization function integrates an impulsive feature-preserving factor and a penalty function factor. Second, a modified Majorization iterative method is applied to address the convex optimization problem of the designed function. A series of sparse coefficients can be achieved through iterating, which only contain transient components. It is noteworthy that there is no need to select the sparse basis in the proposed iterative method because it is fixed as a unit matrix. Then the reconstruction step is omitted, which can significantly increase detection efficiency. Eventually, envelope analysis of the sparse coefficients is performed to extract weak fault features. Simulated and experimental signals including bearings and gearboxes are employed to validate the effectiveness of the proposed method. In addition, comparisons are made to prove that the proposed method outperforms the traditional MM algorithm in terms of detection results and efficiency. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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19 pages, 1715 KiB

Open AccessArticle

Evaluating Muscle Activation Models for Elbow Motion Estimation

by Tyler Desplenter¹

and Ana Luisa Trejos^1,2,*

¹ Department of Electrical and Computer Engineering, Western University, London, ON N6A 5B9, Canada

² Canadian Surgical Technologies and Advanced Robotics, Lawson Health Research Institute, London, ON N6A 5A5, Canada

Sensors 2018, 18(4), 1004; https://doi.org/10.3390/s18041004 - 28 Mar 2018

Cited by 23 | Viewed by 5144

Abstract

Adoption of wearable assistive technologies relies heavily on improvement of existing control system models. Knowing which models to use and how to improve them is difficult to determine due to the number of proposed solutions with relatively little broad comparisons. One type of [...] Read more.

Adoption of wearable assistive technologies relies heavily on improvement of existing control system models. Knowing which models to use and how to improve them is difficult to determine due to the number of proposed solutions with relatively little broad comparisons. One type of these models, muscle activation models, describes the nonlinear relationship between neural inputs and mechanical activation of the muscle. Many muscle activation models can be found in the literature, but no comparison is available to guide the community on limitations and improvements. In this research, an EMG-driven elbow motion model is developed for the purpose of evaluating muscle activation models. Seven muscle activation models are used in an optimization procedure to determine which model has the best performance. Root mean square errors in muscle torque estimation range from 1.67–2.19 Nm on average over varying input trajectories. The computational resource demand was also measured during the optimization procedure, as it is an important aspect for determining if a model is feasible for use in a particular wearable assistive device. This study provides insight into the ability of these models to estimate elbow motion and the trade-off between estimation accuracy and computational demand. Full article

(This article belongs to the Special Issue Smart Sensors for Mechatronic and Robotic Systems)

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15 pages, 1284 KiB

Open AccessArticle

Individual Biometric Identification Using Multi-Cycle Electrocardiographic Waveform Patterns

by Wonki Lee, Seulgee Kim and Daeeun Kim^*

School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Korea

Sensors 2018, 18(4), 1005; https://doi.org/10.3390/s18041005 - 28 Mar 2018

Cited by 21 | Viewed by 4921

Abstract

The electrocardiogram (ECG) waveform conveys information regarding the electrical property of the heart. The patterns vary depending on the individual heart characteristics. ECG features can be potentially used for biometric recognition. This study presents a new method using the entire ECG waveform pattern [...] Read more.

The electrocardiogram (ECG) waveform conveys information regarding the electrical property of the heart. The patterns vary depending on the individual heart characteristics. ECG features can be potentially used for biometric recognition. This study presents a new method using the entire ECG waveform pattern for matching and demonstrates that the approach can potentially be employed for individual biometric identification. Multi-cycle ECG signals were assessed using an ECG measuring circuit, and three electrodes can be patched on the wrists or fingers for considering various measurements. For biometric identification, our-fold cross validation was used in the experiments for assessing how the results of a statistical analysis will generalize to an independent data set. Four different pattern matching algorithms, i.e., cosine similarity, cross correlation, city block distance, and Euclidean distances, were tested to compare the individual identification performances with a single channel of ECG signal (3-wire ECG). To evaluate the pattern matching for biometric identification, the ECG recordings for each subject were partitioned into training and test set. The suggested method obtained a maximum performance of 89.9% accuracy with two heartbeats of ECG signals measured on the wrist and 93.3% accuracy with three heartbeats for 55 subjects. The performance rate with ECG signals measured on the fingers improved up to 99.3% with two heartbeats and 100% with three heartbeats of signals for 20 subjects. Full article

(This article belongs to the Section Biosensors)

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17 pages, 16978 KiB

Open AccessArticle

PSPICE Hybrid Modeling and Simulation of Capacitive Micro-Gyroscopes

by Yan Su^1,2, Xin Tong^1,2, Nan Liu^2,3, Guowei Han³, Chaowei Si^3,*, Jin Ning^3,4,5, Zhaofeng Li^3,6,* and Fuhua Yang^1,6,*

¹ State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China

² College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China

³ Engineering Research Center for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China

⁴ State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Beijing 100083, China

⁵ School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China

⁶ School of Microelectronics, University of Chinese Academy of Sciences, Beijing 100049, China

Sensors 2018, 18(4), 1006; https://doi.org/10.3390/s18041006 - 28 Mar 2018

Viewed by 5667

Abstract

With an aim to reduce the cost of prototype development, this paper establishes a PSPICE hybrid model for the simulation of capacitive microelectromechanical systems (MEMS) gyroscopes. This is achieved by modeling gyroscopes in different modules, then connecting them in accordance with the corresponding [...] Read more.

With an aim to reduce the cost of prototype development, this paper establishes a PSPICE hybrid model for the simulation of capacitive microelectromechanical systems (MEMS) gyroscopes. This is achieved by modeling gyroscopes in different modules, then connecting them in accordance with the corresponding principle diagram. Systematic simulations of this model are implemented along with a consideration of details of MEMS gyroscopes, including a capacitance model without approximation, mechanical thermal noise, and the effect of ambient temperature. The temperature compensation scheme and optimization of interface circuits are achieved based on the hybrid closed-loop simulation of MEMS gyroscopes. The simulation results show that the final output voltage is proportional to the angular rate input, which verifies the validity of this model. Full article

(This article belongs to the Collection Modeling, Testing and Reliability Issues in MEMS Engineering)

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17 pages, 4492 KiB

Open AccessArticle

A Novel GMM-Based Behavioral Modeling Approach for Smartwatch-Based Driver Authentication

by Ching-Han Yang^1,3,*

, Chin-Chun Chang² and Deron Liang^1,3

¹ Department of Computer Science and Information Engineering, National Central University, Taoyuan City 32001, Taiwan, drliang@csie.ncu.edu.tw

² Department of Computer Science and Engineering, National Taiwan Ocean University, Keelung City 20224, Taiwan, cvml@mail.ntou.edu.tw

³ Software Research Center, National Central University, Taoyuan City 32001, Taiwan

Sensors 2018, 18(4), 1007; https://doi.org/10.3390/s18041007 - 28 Mar 2018

Cited by 9 | Viewed by 4291

Abstract

All drivers have their own distinct driving habits, and usually hold and operate the steering wheel differently in different driving scenarios. In this study, we proposed a novel Gaussian mixture model (GMM)-based method that can improve the traditional GMM in modeling driving behavior. [...] Read more.

All drivers have their own distinct driving habits, and usually hold and operate the steering wheel differently in different driving scenarios. In this study, we proposed a novel Gaussian mixture model (GMM)-based method that can improve the traditional GMM in modeling driving behavior. This new method can be applied to build a better driver authentication system based on the accelerometer and orientation sensor of a smartwatch. To demonstrate the feasibility of the proposed method, we created an experimental system that analyzes driving behavior using the built-in sensors of a smartwatch. The experimental results for driver authentication—an equal error rate (EER) of 4.62% in the simulated environment and an EER of 7.86% in the real-traffic environment—confirm the feasibility of this approach. Full article

(This article belongs to the Special Issue Wearable Smart Devices)

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17 pages, 4447 KiB

Open AccessArticle

Sparse Unorganized Point Cloud Based Relative Pose Estimation for Uncooperative Space Target

by Fang Yin^1,*

, Wusheng Chou^1,2, Yun Wu³, Guang Yang¹ and Song Xu¹

¹ School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, China

² State Key Laboratory of Virtual Reality Technology and Systems, Beihang University, Beijing 100191, China

³ Beijing Institute of Control Engineering, Beijing 100080, China

Sensors 2018, 18(4), 1009; https://doi.org/10.3390/s18041009 - 28 Mar 2018

Cited by 30 | Viewed by 4313

Abstract

This paper proposes an autonomous algorithm to determine the relative pose between the chaser spacecraft and the uncooperative space target, which is essential in advanced space applications, e.g., on-orbit serving missions. The proposed method, named Congruent Tetrahedron Align (CTA) algorithm, uses the very [...] Read more.

This paper proposes an autonomous algorithm to determine the relative pose between the chaser spacecraft and the uncooperative space target, which is essential in advanced space applications, e.g., on-orbit serving missions. The proposed method, named Congruent Tetrahedron Align (CTA) algorithm, uses the very sparse unorganized 3D point cloud acquired by a LIDAR sensor, and does not require any prior pose information. The core of the method is to determine the relative pose by looking for the congruent tetrahedron in scanning point cloud and model point cloud on the basis of its known model. The two-level index hash table is built for speeding up the search speed. In addition, the Iterative Closest Point (ICP) algorithm is used for pose tracking after CTA. In order to evaluate the method in arbitrary initial attitude, a simulated system is presented. Specifically, the performance of the proposed method to provide the initial pose needed for the tracking algorithm is demonstrated, as well as their robustness against noise. Finally, a field experiment is conducted and the results demonstrated the effectiveness of the proposed method. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 12971 KiB

Open AccessArticle

Single-Kernel FT-NIR Spectroscopy for Detecting Supersweet Corn (Zea mays L. Saccharata Sturt) Seed Viability with Multivariate Data Analysis

by Guangjun Qiu¹

, Enli Lü^1,*, Huazhong Lu², Sai Xu³, Fanguo Zeng¹ and Qin Shui¹

¹ College of Engineering, South China Agricultural University, Guangzhou 510640, China

² Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China

³ Public Monitoring Center for Agro-Products of Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China

Sensors 2018, 18(4), 1010; https://doi.org/10.3390/s18041010 - 28 Mar 2018

Cited by 55 | Viewed by 8142

Abstract

The viability and vigor of crop seeds are crucial indicators for evaluating seed quality, and high-quality seeds can increase agricultural yield. The conventional methods for assessing seed viability are time consuming, destructive, and labor intensive. Therefore, a rapid and nondestructive technique for testing [...] Read more.

The viability and vigor of crop seeds are crucial indicators for evaluating seed quality, and high-quality seeds can increase agricultural yield. The conventional methods for assessing seed viability are time consuming, destructive, and labor intensive. Therefore, a rapid and nondestructive technique for testing seed viability has great potential benefits for agriculture. In this study, single-kernel Fourier transform near-infrared (FT-NIR) spectroscopy with a wavelength range of 1000–2500 nm was used to distinguish viable and nonviable supersweet corn seeds. Various preprocessing algorithms coupled with partial least squares discriminant analysis (PLS-DA) were implemented to test the performance of classification models. The FT-NIR spectroscopy technique successfully differentiated viable seeds from seeds that were nonviable due to overheating or artificial aging. Correct classification rates for both heat-damaged kernels and artificially aged kernels reached 98.0%. The comprehensive model could also attain an accuracy of 98.7% when combining heat-damaged samples and artificially aged samples into one category. Overall, the FT-NIR technique with multivariate data analysis methods showed great potential capacity in rapidly and nondestructively detecting seed viability in supersweet corn. Full article

(This article belongs to the Special Issue Infrared Sensors and Technologies)

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11 pages, 8346 KiB

Open AccessArticle

Diaphragm-Free Fiber-Optic Fabry-Perot Interferometric Gas Pressure Sensor for High Temperature Application

by Hao Liang, Pinggang Jia^*

, Jia Liu, Guocheng Fang, Zhe Li, Yingping Hong, Ting Liang and Jijun Xiong

Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China

Sensors 2018, 18(4), 1011; https://doi.org/10.3390/s18041011 - 28 Mar 2018

Cited by 65 | Viewed by 8666

Abstract

A diaphragm-free fiber-optic Fabry-Perot (FP) interferometric gas pressure sensor is designed and experimentally verified in this paper. The FP cavity was fabricated by inserting a well-cut fiber Bragg grating (FBG) and hollow silica tube (HST) from both sides into a silica casing. The [...] Read more.

A diaphragm-free fiber-optic Fabry-Perot (FP) interferometric gas pressure sensor is designed and experimentally verified in this paper. The FP cavity was fabricated by inserting a well-cut fiber Bragg grating (FBG) and hollow silica tube (HST) from both sides into a silica casing. The FP cavity length between the ends of the SMF and HST changes with the gas density. Using temperature decoupling method to improve the accuracy of the pressure sensor in high temperature environments. An experimental system for measuring the pressure under different temperatures was established to verify the performance of the sensor. The pressure sensitivity of the FP gas pressure sensor is 4.28 nm/MPa with a high linear pressure response over the range of 0.1–0.7 MPa, and the temperature sensitivity is 14.8 pm/°C under the range of 20–800 °C. The sensor has less than 1.5% non-linearity at different temperatures by using temperature decoupling method. The simple fabrication and low-cost will help sensor to maintain the excellent features required by pressure measurement in high temperature applications. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 9674 KiB

Open AccessArticle

Experimental Study of the Oriented Immobilization of Antibodies on Photonic Sensing Structures by Using Protein A as an Intermediate Layer

by Raffaele Caroselli¹

, Javier García Castelló¹, Jorge Escorihuela²

, María José Bañuls²

, Ángel Maquieira² and Jaime García-Rupérez^1,*

¹ Nanophotonics Technology Center, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain

² Departamento de Química, Instituto Universitario de Investigación de Reconocimiento Molecular y Desarrollo Tecnológico (IDM), Universitat Politècnica de València, Universitat de València, 46022 Valencia, Spain

Sensors 2018, 18(4), 1012; https://doi.org/10.3390/s18041012 - 28 Mar 2018

Cited by 16 | Viewed by 5427

Abstract

A proper antibody immobilization on a biosensor is a crucial step in order to obtain a high sensitivity to be able to detect low target analyte concentrations. In this paper, we present an experimental study of the immobilization process of antibodies as bioreceptors [...] Read more.

A proper antibody immobilization on a biosensor is a crucial step in order to obtain a high sensitivity to be able to detect low target analyte concentrations. In this paper, we present an experimental study of the immobilization process of antibodies as bioreceptors on a photonic ring resonator sensor. A protein A intermediate layer was created on the sensor surface in order to obtain an oriented immobilization of the antibodies, which enhances the interaction with the target antigens to be detected. The anti-bovine serum albumin (antiBSA)-bovine serum albumin (BSA) pair was used as a model for our study. An opto-fluidic setup was developed in order to flow the different reagents and, simultaneously, to monitor in real-time the spectral response of the photonic sensing structure. The antiBSA immobilization and the BSA detection, their repeatability, and specificity were studied in different conditions of the sensor surface. Finally, an experimental limit of detection for BSA recognition of only 1 ng/mL was obtained. Full article

(This article belongs to the Special Issue Protein-Based Biosensors)

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14 pages, 14454 KiB

Open AccessArticle

A Simultaneous and Continuous Excitation Method for High-Speed Electrical Impedance Tomography with Reduced Transients and Noise Sensitivity

by Antoine Dupré^1,*

and Saba Mylvaganam²

¹ Private Practice, Jouquetti, 05400 Furmeyer, France

² Department of Electrical Engineering, IT and Cybernetics, Faculty of Technology, Natural Sciences and Maritime Sciences, University College of Southeast Norway, 3901 Porsgrunn, Norway

Sensors 2018, 18(4), 1013; https://doi.org/10.3390/s18041013 - 28 Mar 2018

Cited by 11 | Viewed by 4239

Abstract

This paper presents a concept for soft field tomographic scan of all the projections of electromagnetic waves emanating from an array of electrodes. Instead of the sequential excitation of all pairs of electrodes in the list of all projections, the new method present [...] Read more.

This paper presents a concept for soft field tomographic scan of all the projections of electromagnetic waves emanating from an array of electrodes. Instead of the sequential excitation of all pairs of electrodes in the list of all projections, the new method present here consists of a single and continuous excitation. This excitation signal is the linear combination of the excitation signals in the projection set at different AC frequencies. The response to a given projection is discriminated by selecting the corresponding AC frequency component in the signal spectra of the digitally demodulated signals. The main advantage of this method is the suppression of transients after each projection, which is particularly problematic in electrical impedance tomography due to contact impedance phenomena and skin effect. The second benefit over the sequential scan method is the increased number of samples for each measurement for reduced noise sensitivity with digital demodulation. The third benefit is the increased temporal resolution in high-speed applications. The main drawback is the increased number of signal sources required (one per electrode). This paper focuses on electrical impedance tomography, based on earlier work by the authors. An experimental proof-of-concept using a simple 4-electrodes electrical impedance tomographic system is presented using simulations and laboratory data. The method presented here may be extended to other modalities (ultrasonic, microwave, optical, etc.). Full article

(This article belongs to the Section State-of-the-Art Sensors Technologies)

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17 pages, 40592 KiB

Open AccessArticle

A New FPGA Architecture of FAST and BRIEF Algorithm for On-Board Corner Detection and Matching

by Jingjin Huang¹, Guoqing Zhou^1,2,*, Xiang Zhou³ and Rongting Zhang¹

¹ School of Precision Instrument & Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China

² Guangxi Key Laboratory for Spatial Information and Geomatics, Guilin University of Technology, Guilin 541004, China

³ School of Microelectronics, Tianjin University, Tianjin 300072, China

Sensors 2018, 18(4), 1014; https://doi.org/10.3390/s18041014 - 28 Mar 2018

Cited by 38 | Viewed by 7203

Abstract

Although some researchers have proposed the Field Programmable Gate Array (FPGA) architectures of Feature From Accelerated Segment Test (FAST) and Binary Robust Independent Elementary Features (BRIEF) algorithm, there is no consideration of image data storage in these traditional architectures that will result in [...] Read more.

Although some researchers have proposed the Field Programmable Gate Array (FPGA) architectures of Feature From Accelerated Segment Test (FAST) and Binary Robust Independent Elementary Features (BRIEF) algorithm, there is no consideration of image data storage in these traditional architectures that will result in no image data that can be reused by the follow-up algorithms. This paper proposes a new FPGA architecture that considers the reuse of sub-image data. In the proposed architecture, a remainder-based method is firstly designed for reading the sub-image, a FAST detector and a BRIEF descriptor are combined for corner detection and matching. Six pairs of satellite images with different textures, which are located in the Mentougou district, Beijing, China, are used to evaluate the performance of the proposed architecture. The Modelsim simulation results found that: (i) the proposed architecture is effective for sub-image reading from DDR3 at a minimum cost; (ii) the FPGA implementation is corrected and efficient for corner detection and matching, such as the average value of matching rate of natural areas and artificial areas are approximately 67% and 83%, respectively, which are close to PC’s and the processing speed by FPGA is approximately 31 and 2.5 times faster than those by PC processing and by GPU processing, respectively. Full article

(This article belongs to the Section Remote Sensors)

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28 pages, 5547 KiB

Open AccessArticle

Diagnosing a Strong-Fault Model by Conflict and Consistency

by Wenfeng Zhang¹

, Qi Zhao¹

, Hongbo Zhao^1,*

, Gan Zhou² and Wenquan Feng¹

¹ Electronic and Information Engineering, Beihang University, Beijing 100191, China

² The 6th Research Institute of China Electronics Corporation, Beijing 100083, China

Sensors 2018, 18(4), 1016; https://doi.org/10.3390/s18041016 - 29 Mar 2018

Cited by 1 | Viewed by 3149

Abstract

The diagnosis method for a weak-fault model with only normal behaviors of each component has evolved over decades. However, many systems now demand a strong-fault models, the fault modes of which have specific behaviors as well. It is difficult to diagnose a strong-fault [...] Read more.

The diagnosis method for a weak-fault model with only normal behaviors of each component has evolved over decades. However, many systems now demand a strong-fault models, the fault modes of which have specific behaviors as well. It is difficult to diagnose a strong-fault model due to its non-monotonicity. Currently, diagnosis methods usually employ conflicts to isolate possible fault and the process can be expedited when some observed output is consistent with the model’s prediction where the consistency indicates probably normal components. This paper solves the problem of efficiently diagnosing a strong-fault model by proposing a novel Logic-based Truth Maintenance System (LTMS) with two search approaches based on conflict and consistency. At the beginning, the original a strong-fault model is encoded by Boolean variables and converted into Conjunctive Normal Form (CNF). Then the proposed LTMS is employed to reason over CNF and find multiple minimal conflicts and maximal consistencies when there exists fault. The search approaches offer the best candidate efficiency based on the reasoning result until the diagnosis results are obtained. The completeness, coverage, correctness and complexity of the proposals are analyzed theoretically to show their strength and weakness. Finally, the proposed approaches are demonstrated by applying them to a real-world domain—the heat control unit of a spacecraft—where the proposed methods are significantly better than best first and conflict directly with A* search methods. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 19199 KiB

Open AccessArticle

Modeling and Assessment of Precise Time Transfer by Using BeiDou Navigation Satellite System Triple-Frequency Signals

by Rui Tu^1,2,3,4,*

, Pengfei Zhang^1,3, Rui Zhang^1,2, Jinhai Liu^1,3 and Xiaochun Lu^1,2,3

¹ National Time Service Center, Chinese Academy of Sciences, Shu Yuan Road, Xi’an 710600, China

² Key Laboratory of Precision Navigation and Timing Technology, Chinese Academy of Sciences, Shu Yuan Road, Xi’an 710600, China

³ University of Chinese Academy of Sciences, Yu Quan Road, Beijing 100049, China

⁴ State Key Laboratory of Geo-Information Engineering, Yan Ta Road, Xi’an 710054, China

Sensors 2018, 18(4), 1017; https://doi.org/10.3390/s18041017 - 29 Mar 2018

Cited by 27 | Viewed by 3549

Abstract

This study proposes two models for precise time transfer using the BeiDou Navigation Satellite System triple-frequency signals: ionosphere-free (IF) combined precise point positioning (PPP) model with two dual-frequency combinations (IF-PPP1) and ionosphere-free combined PPP model with a single triple-frequency combination (IF-PPP2). A dataset [...] Read more.

This study proposes two models for precise time transfer using the BeiDou Navigation Satellite System triple-frequency signals: ionosphere-free (IF) combined precise point positioning (PPP) model with two dual-frequency combinations (IF-PPP1) and ionosphere-free combined PPP model with a single triple-frequency combination (IF-PPP2). A dataset with a short baseline (with a common external time frequency) and a long baseline are used for performance assessments. The results show that IF-PPP1 and IF-PPP2 models can both be used for precise time transfer using BeiDou Navigation Satellite System (BDS) triple-frequency signals, and the accuracy and stability of time transfer is the same in both cases, except for a constant system bias caused by the hardware delay of different frequencies, which can be removed by the parameter estimation and prediction with long time datasets or by a priori calibration. Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 29491 KiB

Open AccessArticle

Semi-Automated Air-Coupled Impact-Echo Method for Large-Scale Parkade Structure

by Tyler Epp, Dagmar Svecova and Young-Jin Cha^*

Department of Civil Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

Sensors 2018, 18(4), 1018; https://doi.org/10.3390/s18041018 - 29 Mar 2018

Cited by 17 | Viewed by 3775

Abstract

Structural Health Monitoring (SHM) has moved to data-dense systems, utilizing numerous sensor types to monitor infrastructure, such as bridges and dams, more regularly. One of the issues faced in this endeavour is the scale of the inspected structures and the time it takes [...] Read more.

Structural Health Monitoring (SHM) has moved to data-dense systems, utilizing numerous sensor types to monitor infrastructure, such as bridges and dams, more regularly. One of the issues faced in this endeavour is the scale of the inspected structures and the time it takes to carry out testing. Installing automated systems that can provide measurements in a timely manner is one way of overcoming these obstacles. This study proposes an Artificial Neural Network (ANN) application that determines intact and damaged locations from a small training sample of impact-echo data, using air-coupled microphones from a reinforced concrete beam in lab conditions and data collected from a field experiment in a parking garage. The impact-echo testing in the field is carried out in a semi-autonomous manner to expedite the front end of the in situ damage detection testing. The use of an ANN removes the need for a user-defined cutoff value for the classification of intact and damaged locations when a least-square distance approach is used. It is postulated that this may contribute significantly to testing time reduction when monitoring large-scale civil Reinforced Concrete (RC) structures. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 14759 KiB

Open AccessArticle

Poisson–Gaussian Noise Analysis and Estimation for Low-Dose X-ray Images in the NSCT Domain

by Sangyoon Lee, Min Seok Lee and Moon Gi Kang^*

School of Electrical and Electronics Engineering, Yonsei University, 50 Yonsei-Ro, Seodaemun-Gu, Seoul 03722, Korea

Sensors 2018, 18(4), 1019; https://doi.org/10.3390/s18041019 - 29 Mar 2018

Cited by 45 | Viewed by 9449

Abstract

The noise distribution of images obtained by X-ray sensors in low-dosage situations can be analyzed using the Poisson and Gaussian mixture model. Multiscale conversion is one of the most popular noise reduction methods used in recent years. Estimation of the noise distribution of [...] Read more.

The noise distribution of images obtained by X-ray sensors in low-dosage situations can be analyzed using the Poisson and Gaussian mixture model. Multiscale conversion is one of the most popular noise reduction methods used in recent years. Estimation of the noise distribution of each subband in the multiscale domain is the most important factor in performing noise reduction, with non-subsampled contourlet transform (NSCT) representing an effective method for scale and direction decomposition. In this study, we use artificially generated noise to analyze and estimate the Poisson–Gaussian noise of low-dose X-ray images in the NSCT domain. The noise distribution of the subband coefficients is analyzed using the noiseless low-band coefficients and the variance of the noisy subband coefficients. The noise-after-transform also follows a Poisson–Gaussian distribution, and the relationship between the noise parameters of the subband and the full-band image is identified. We then analyze noise of actual images to validate the theoretical analysis. Comparison of the proposed noise estimation method with an existing noise reduction method confirms that the proposed method outperforms traditional methods. Full article

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17 pages, 919 KiB

Open AccessArticle

An Effective Hybrid Routing Algorithm in WSN: Ant Colony Optimization in combination with Hop Count Minimization

by Ailian Jiang¹

and Lihong Zheng^2,*

¹ Department of Computer Science, Taiyuan University of Technology, Taiyuan 030600, China

² School of Computing and Maths, Charles Sturt University, Wagga Wagga, NSW 2678, Australia

Sensors 2018, 18(4), 1020; https://doi.org/10.3390/s18041020 - 29 Mar 2018

Cited by 52 | Viewed by 6625

Abstract

Low cost, high reliability and easy maintenance are key criteria in the design of routing protocols for wireless sensor networks (WSNs). This paper investigates the existing ant colony optimization (ACO)-based WSN routing algorithms and the minimum hop count WSN routing algorithms by reviewing [...] Read more.

Low cost, high reliability and easy maintenance are key criteria in the design of routing protocols for wireless sensor networks (WSNs). This paper investigates the existing ant colony optimization (ACO)-based WSN routing algorithms and the minimum hop count WSN routing algorithms by reviewing their strengths and weaknesses. We also consider the critical factors of WSNs, such as energy constraint of sensor nodes, network load balancing and dynamic network topology. Then we propose a hybrid routing algorithm that integrates ACO and a minimum hop count scheme. The proposed algorithm is able to find the optimal routing path with minimal total energy consumption and balanced energy consumption on each node. The algorithm has unique superiority in terms of searching for the optimal path, balancing the network load and the network topology maintenance. The WSN model and the proposed algorithm have been implemented using C++. Extensive simulation experimental results have shown that our algorithm outperforms several other WSN routing algorithms on such aspects that include the rate of convergence, the success rate in searching for global optimal solution, and the network lifetime. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 30295 KiB

Open AccessArticle

A Comparison of Inductive Sensors in the Characterization of Partial Discharges and Electrical Noise Using the Chromatic Technique

by Jorge Alfredo Ardila-Rey^1,*

, Johny Montaña², Bruno Albuquerque De Castro³

, Roger Schurch², José Alfredo Covolan Ulson³, Firdaus Muhammad-Sukki⁴

and Nurul Aini Bani⁵

¹ Department of Electrical Engineering, Universidad Técnica Federico Santa María, Av. Vicuña Mackenna 3939, Santiago de Chile 8940000, Chile

² Department of Electrical Engineering, Universidad Técnica Federico Santa María, Av. España 1680, Valparaiso 2340000, Chile

³ Department of Electrical Engineering, São Paulo State University, Av. Eng. Luiz Edmundo Carrijo Coube 14-01, Bauru 17033-360, Brazil

⁴ School of Engineering, Robert Gordon University, Garthdee Road, Aberdeen AB10 7GJ, UK

⁵ UTM Razak School of Engineering and Advanced Technology, Universiti Teknologi Malaysia, Kuala Lumpur 54100, Malaysia

Sensors 2018, 18(4), 1021; https://doi.org/10.3390/s18041021 - 29 Mar 2018

Cited by 33 | Viewed by 5597

Abstract

Partial discharges (PDs) are one of the most important classes of ageing processes that occur within electrical insulation. PD detection is a standardized technique to qualify the state of the insulation in electric assets such as machines and power cables. Generally, the classical [...] Read more.

Partial discharges (PDs) are one of the most important classes of ageing processes that occur within electrical insulation. PD detection is a standardized technique to qualify the state of the insulation in electric assets such as machines and power cables. Generally, the classical phase-resolved partial discharge (PRPD) patterns are used to perform the identification of the type of PD source when they are related to a specific degradation process and when the electrical noise level is low compared to the magnitudes of the PD signals. However, in practical applications such as measurements carried out in the field or in industrial environments, several PD sources and large noise signals are usually present simultaneously. In this study, three different inductive sensors have been used to evaluate and compare their performance in the detection and separation of multiple PD sources by applying the chromatic technique to each of the measured signals. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 18568 KiB

Open AccessArticle

Non-Invasive Electromagnetic Skin Patch Sensor to Measure Intracranial Fluid–Volume Shifts

by Jacob Griffith¹, Kim Cluff^1,*, Brandon Eckerman¹, Jessica Aldrich¹, Ryan Becker¹, Peer Moore-Jansen² and Jeremy Patterson^3,4

¹ Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA

² Department of Anthropology, Wichita State University, Wichita, KS 67260, USA

³ Human Performance Studies, Wichita State University, Wichita, KS 67260, USA

⁴ Institute of Interdisciplinary Creativity, Wichita State University, Wichita, KS 67260, USA

Sensors 2018, 18(4), 1022; https://doi.org/10.3390/s18041022 - 29 Mar 2018

Cited by 47 | Viewed by 10033

Abstract

Elevated intracranial fluid volume can drive intracranial pressure increases, which can potentially result in numerous neurological complications or death. This study’s focus was to develop a passive skin patch sensor for the head that would non-invasively measure cranial fluid volume shifts. The sensor [...] Read more.

Elevated intracranial fluid volume can drive intracranial pressure increases, which can potentially result in numerous neurological complications or death. This study’s focus was to develop a passive skin patch sensor for the head that would non-invasively measure cranial fluid volume shifts. The sensor consists of a single baseline component configured into a rectangular planar spiral with a self-resonant frequency response when impinged upon by external radio frequency sweeps. Fluid volume changes (10 mL increments) were detected through cranial bone using the sensor on a dry human skull model. Preliminary human tests utilized two sensors to determine feasibility of detecting fluid volume shifts in the complex environment of the human body. The correlation between fluid volume changes and shifts in the first resonance frequency using the dry human skull was classified as a second order polynomial with R² = 0.97. During preliminary and secondary human tests, a ≈24 MHz and an average of ≈45.07 MHz shifts in the principal resonant frequency were measured respectively, corresponding to the induced cephalad bio-fluid shifts. This electromagnetic resonant sensor may provide a non-invasive method to monitor shifts in fluid volume and assist with medical scenarios including stroke, cerebral hemorrhage, concussion, or monitoring intracranial pressure. Full article

(This article belongs to the Special Issue Internet of Wearable and Implantable Medical Things: Theory and Applications)

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14 pages, 15548 KiB

Open AccessArticle

Investigating Water Movement Within and Near Wells Using Active Point Heating and Fiber Optic Distributed Temperature Sensing

by Frank Selker^1,* and John S. Selker^1,2,*

¹ SelkerMetrics, LLC., 4225 SW Agate Lane, Portland, OR 97239, USA

² Department of Biological and Ecological Engineering, Oregon State University, Corvallis, OR 97331, USA

Sensors 2018, 18(4), 1023; https://doi.org/10.3390/s18041023 - 29 Mar 2018

Cited by 29 | Viewed by 5779

Abstract

There are few methods to provide high-resolution in-situ characterization of flow in aquifers and reservoirs. We present a method that has the potential to quantify lateral and vertical (magnitude and direction) components of flow with spatial resolution of about one meter and temporal [...] Read more.

There are few methods to provide high-resolution in-situ characterization of flow in aquifers and reservoirs. We present a method that has the potential to quantify lateral and vertical (magnitude and direction) components of flow with spatial resolution of about one meter and temporal resolution of about one day. A fiber optic distributed temperature sensor is used with a novel heating system. Temperatures before heating may be used to evaluate background geothermal gradient and vertical profile of thermal diffusivity. The innovation presented is the use of variable energy application along the well, in this case concentrated heating at equally-spaced (2 m) localized areas (0.5 m). Relative to uniform warming this offers greater opportunity to estimate water movement, reduces required heating power, and increases practical length that can be heated. Numerical simulations are presented which illustrate expected behaviors. We estimate relative advection rates near the well using the times at which various locations diverge from a heating trajectory expected for pure conduction in the absence of advection. The concept is demonstrated in a grouted 600 m borehole with 300 heated patches, though evidence of vertical water movement was not seen. Full article

(This article belongs to the Special Issue Optical Sensors based on Micro/Nanofibres)

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10 pages, 8040 KiB

Open AccessArticle

Volterra Kernel Estimation of White Light LEDs in the Time Domain

by Grzegorz Stepniak^*

, Marcin Kowalczyk

and Jerzy Siuzdak

Institute of Telecommunications, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warsaw, Poland

Sensors 2018, 18(4), 1024; https://doi.org/10.3390/s18041024 - 29 Mar 2018

Cited by 9 | Viewed by 4410

Abstract

In this paper, we present a time domain method for extracting coefficients of nonlinear Volterra-series kernels for white light-emitting diodes (LED) used both for illumination and visible light communications. We show that this method may have several advantages over the thus far more [...] Read more.

In this paper, we present a time domain method for extracting coefficients of nonlinear Volterra-series kernels for white light-emitting diodes (LED) used both for illumination and visible light communications. We show that this method may have several advantages over the thus far more popular frequency domain method. We successfully apply the measured kernel coefficients up to the 3rd order for the modeling of nonlinear distortion impact on advanced modulation formats: pulse amplitude modulation, carrierless amplitude phase and orthogonal frequency division multiplexing. The impact of blue filtering on dynamic nonlinearity is also presented. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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20 pages, 68690 KiB

Open AccessArticle

Statistical Platform for Individualized Behavioral Analyses Using Biophysical Micro-Movement Spikes

by Elizabeth B. Torres^1,2,*, Joe Vero³

and Richa Rai¹

¹ Psychology Department, Rutgers University, Piscataway, NJ 08854, USA

² Computer Science Department, Computational Biomedicine Imaging and Modeling, Rutgers Center for Cognitive Science, Rutgers University, Piscataway, NJ 08854, USA

³ Bioengineering Department, Rutgers University, Piscataway, NJ 08854, USA

Sensors 2018, 18(4), 1025; https://doi.org/10.3390/s18041025 - 29 Mar 2018

Cited by 14 | Viewed by 7471

Abstract

Wearable biosensors, such as those embedded in smart phones, can provide data to assess neuro-motor control in mobile settings, at homes, schools, workplaces and clinics. However, because most machine learning algorithms currently used to analyze such data require several steps that depend on [...] Read more.

Wearable biosensors, such as those embedded in smart phones, can provide data to assess neuro-motor control in mobile settings, at homes, schools, workplaces and clinics. However, because most machine learning algorithms currently used to analyze such data require several steps that depend on human heuristics, the analyses become computationally expensive and rather subjective. Further, there is no standardized scale or set of tasks amenable to take advantage of such technology in ways that permit broad dissemination and reproducibility of results. Indeed, there is a critical need for fully objective automated analytical methods that easily handle the deluge of data these sensors output, while providing standardized scales amenable to apply across large sections of the population, to help promote personalized-mobile medicine. Here we use an open-access data set from Kaggle.com to illustrate the use of a new statistical platform and standardized data types applied to smart phone accelerometer and gyroscope data from 30 participants, performing six different activities. We report full distinction without confusion of the activities from the Kaggle set using a single parameter (linear acceleration or angular speed). We further extend the use of our platform to characterize data from commercially available smart shoes, using gait patterns within a set of experiments that probe nervous systems functioning and levels of motor control. Full article

(This article belongs to the Special Issue Point of Care Sensors)

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12 pages, 45238 KiB

Open AccessArticle

Tunable Nanosensor Based on Fano Resonances Created by Changing the Deviation Angle of the Metal Core in a Plasmonic Cavity

by Qiong Wang^1,2, Zhengbiao Ouyang^1,2,*, Yiling Sun^1,2, Mi Lin^1,2, Qiang Liu^1,2, Guoliang Zheng^1,2 and Junxing Fan^1,2

¹ THz Technical Research Center of Shenzhen University, Shenzhen University, Shenzhen 518060, China

² College of Electronic Science &Technology, Shenzhen University, Shenzhen 518060, China

Sensors 2018, 18(4), 1026; https://doi.org/10.3390/s18041026 - 29 Mar 2018

Cited by 11 | Viewed by 4197

Abstract

In this paper, a type of tunable plasmonic refractive index nanosensor based on Fano resonance is proposed and investigated. The sensor comprises a metal-insulator-metal (MIM) nanocavity with a center-deviated metal core and two side-coupled waveguides. By carefully adjusting the deviation angle and distance [...] Read more.

In this paper, a type of tunable plasmonic refractive index nanosensor based on Fano resonance is proposed and investigated. The sensor comprises a metal-insulator-metal (MIM) nanocavity with a center-deviated metal core and two side-coupled waveguides. By carefully adjusting the deviation angle and distance of the metal core in the cavity, Fano resonances can be obtained and modulated. The Fano resonances can be considered as results induced by the symmetry-breaking or geometric effect that affects the field distribution intensity at the coupling region between the right waveguide and the cavity. Such a field-distribution pattern change can be regarded as being caused by the interference between the waveguide modes and the cavity modes. The investigations demonstrate that the spectral positions and modulation depths of Fano resonances are highly sensitive to the deviation parameters. Furthermore, the figure of merit (FOM) value is calculated for different deviation angle. The result shows that this kind of tunable sensor has compact structure, high transmission, sharp Fano lineshape, and high sensitivity to the change in background refractive index. This work provides an effective method for flexibly tuning Fano resonance, which has wide applications in designing on-chip plasmonic nanosensors or other relevant devices, such as information modulators, optical filters, and ultra-fast switches. Full article

(This article belongs to the Special Issue Optical Waveguide Based Sensors)

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15 pages, 13503 KiB

Open AccessArticle

Comparative Performance Analysis of Support Vector Machine, Random Forest, Logistic Regression and k-Nearest Neighbours in Rainbow Trout (Oncorhynchus Mykiss) Classification Using Image-Based Features

by Mohammadmehdi Saberioon^1,*

, Petr Císař¹, Laurent Labbé², Pavel Souček¹, Pablo Pelissier² and Thierry Kerneis²

¹ Institute of Complex Systems, South Bohemian Research Centre of Aquaculture and Biodiversity of Hydrocenoses, Faculty of Fisheries and Protection of Waters, University of South Bohemia in České Budějovice, Zámek 136, Nové Hrady 37 333, Czech Republic

² Institut National de la Recherche Agronomique (INRA), UE 0937 PEIMA (Pisciculture Expérimentale INRA des Monts d’Arrée), 29450 Sizun, France

Sensors 2018, 18(4), 1027; https://doi.org/10.3390/s18041027 - 29 Mar 2018

Cited by 59 | Viewed by 8890

Abstract

The main aim of this study was to develop a new objective method for evaluating the impacts of different diets on the live fish skin using image-based features. In total, one-hundred and sixty rainbow trout (Oncorhynchus mykiss) were fed either a [...] Read more.

The main aim of this study was to develop a new objective method for evaluating the impacts of different diets on the live fish skin using image-based features. In total, one-hundred and sixty rainbow trout (Oncorhynchus mykiss) were fed either a fish-meal based diet (80 fish) or a 100% plant-based diet (80 fish) and photographed using consumer-grade digital camera. Twenty-three colour features and four texture features were extracted. Four different classification methods were used to evaluate fish diets including Random forest (RF), Support vector machine (SVM), Logistic regression (LR) and k-Nearest neighbours (k-NN). The SVM with radial based kernel provided the best classifier with correct classification rate (CCR) of 82% and Kappa coefficient of 0.65. Although the both LR and RF methods were less accurate than SVM, they achieved good classification with CCR 75% and 70% respectively. The k-NN was the least accurate (40%) classification model. Overall, it can be concluded that consumer-grade digital cameras could be employed as the fast, accurate and non-invasive sensor for classifying rainbow trout based on their diets. Furthermore, these was a close association between image-based features and fish diet received during cultivation. These procedures can be used as non-invasive, accurate and precise approaches for monitoring fish status during the cultivation by evaluating diet’s effects on fish skin. Full article

(This article belongs to the Special Issue Artificial Intelligence and Machine Learning in Sensors Networks)

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9 pages, 959 KiB

Open AccessArticle

Quantifying the Accuracy of Digital Hemispherical Photography for Leaf Area Index Estimates on Broad-Leaved Tree Species

by Carlo Gilardelli^1,*, Francesca Orlando², Ermes Movedi¹ and Roberto Confalonieri^1,*

¹ Cassandra Lab, Università degli Studi di Milano, DESP, via Celoria 2, I-20133 Milan, Italy

² Department of Agricultural and Environmental Sciences—Production, Landscape, Agroenergy, Università degli Studi di Milano, DESP, via Celoria 2, I-20133 Milan, Italy

Sensors 2018, 18(4), 1028; https://doi.org/10.3390/s18041028 - 29 Mar 2018

Cited by 9 | Viewed by 3636

Abstract

Digital hemispherical photography (DHP) has been widely used to estimate leaf area index (LAI) in forestry. Despite the advancement in the processing of hemispherical images with dedicated tools, several steps are still manual and thus easily affected by user’s experience and sensibility. The [...] Read more.

Digital hemispherical photography (DHP) has been widely used to estimate leaf area index (LAI) in forestry. Despite the advancement in the processing of hemispherical images with dedicated tools, several steps are still manual and thus easily affected by user’s experience and sensibility. The purpose of this study was to quantify the impact of user’s subjectivity on DHP LAI estimates for broad-leaved woody canopies using the software Can-Eye. Following the ISO 5725 protocol, we quantified the repeatability and reproducibility of the method, thus defining its precision for a wide range of broad-leaved canopies markedly differing for their structure. To get a complete evaluation of the method accuracy, we also quantified its trueness using artificial canopy images with known canopy cover. Moreover, the effect of the segmentation method was analysed. The best results for precision (restrained limits of repeatability and reproducibility) were obtained for high LAI values (>5) with limits corresponding to a variation of 22% in the estimated LAI values. Poorer results were obtained for medium and low LAI values, with a variation of the estimated LAI values that exceeded the 40%. Regardless of the LAI range explored, satisfactory results were achieved for trees in row-structured plantations (limits almost equal to the 30% of the estimated LAI). Satisfactory results were achieved for trueness, regardless of the canopy structure. The paired t-test revealed that the effect of the segmentation method on LAI estimates was significant. Despite a non-negligible user effect, the accuracy metrics for DHP are consistent with those determined for other indirect methods for LAI estimates, confirming the overall reliability of DHP in broad-leaved woody canopies. Full article

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14 pages, 11464 KiB

Open AccessArticle

A Novel Model to Simulate Flexural Complements in Compliant Sensor Systems

by Hongyan Tang^1,2, Dan Zhang^1,2,*, Sheng Guo¹ and Haibo Qu¹

¹ School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, China

² Lassonde School of Engineering, York University, Toronto, ON M3J 1P3, Canada

Sensors 2018, 18(4), 1029; https://doi.org/10.3390/s18041029 - 29 Mar 2018

Cited by 3 | Viewed by 4286

Abstract

The main challenge in analyzing compliant sensor systems is how to calculate the large deformation of flexural complements. Our study proposes a new model that is called the spline pseudo-rigid-body model (spline PRBM). It combines dynamic spline and the pseudo-rigid-body model (PRBM) to [...] Read more.

The main challenge in analyzing compliant sensor systems is how to calculate the large deformation of flexural complements. Our study proposes a new model that is called the spline pseudo-rigid-body model (spline PRBM). It combines dynamic spline and the pseudo-rigid-body model (PRBM) to simulate the flexural complements. The axial deformations of flexural complements are modeled by using dynamic spline. This makes it possible to consider the nonlinear compliance of the system using four control points. Three rigid rods connected by two revolute (R) pins with two torsion springs replace the three lines connecting the four control points. The kinematic behavior of the system is described using Lagrange equations. Both the optimization and the numerical fitting methods are used for resolving the characteristic parameters of the new model. An example is given of a compliant mechanism to modify the accuracy of the model. The spline PRBM is important in expanding the applications of the PRBM to the design and simulation of flexural force sensors. Full article

(This article belongs to the Special Issue Sensors for MEMS and Microsystems)

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17 pages, 9054 KiB

Open AccessArticle

Range Sensor-Based Efficient Obstacle Avoidance through Selective Decision-Making

by Youngbo Shim¹

and Gon-Woo Kim^2,*

¹ Mechanical Technology Research Center, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea

² School of Electronics Engineering, Chungbuk National University, Chungbuk 28644, Korea

Sensors 2018, 18(4), 1030; https://doi.org/10.3390/s18041030 - 29 Mar 2018

Cited by 6 | Viewed by 4538

Abstract

In this paper, we address a collision avoidance method for mobile robots. Many conventional obstacle avoidance methods have been focused solely on avoiding obstacles. However, this can cause instability when passing through a narrow passage, and can also generate zig-zag motions. We define [...] Read more.

In this paper, we address a collision avoidance method for mobile robots. Many conventional obstacle avoidance methods have been focused solely on avoiding obstacles. However, this can cause instability when passing through a narrow passage, and can also generate zig-zag motions. We define two strategies for obstacle avoidance, known as Entry mode and Bypass mode. Entry mode is a pattern for passing through the gap between obstacles, while Bypass mode is a pattern for making a detour around obstacles safely. With these two modes, we propose an efficient obstacle avoidance method based on the Expanded Guide Circle (EGC) method with selective decision-making. The simulation and experiment results show the validity of the proposed method. Full article

(This article belongs to the Section Intelligent Sensors)

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19 pages, 27629 KiB

Open AccessArticle

Robust Sliding Mode Control of PMSM Based on Rapid Nonlinear Tracking Differentiator and Disturbance Observer

by Zhanmin Zhou^1,2,*, Bao Zhang¹ and Dapeng Mao¹

¹ Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China

² University of Chinese Academy of Sciences, No.19, Yuquan Rd., Beijing 100049, China

Sensors 2018, 18(4), 1031; https://doi.org/10.3390/s18041031 - 29 Mar 2018

Cited by 45 | Viewed by 6604

Abstract

Torque ripples caused by cogging torque, flux harmonics, and current measurement error seriously restrict the application of a permanent magnet synchronous motor (PMSM), which has been paid more and more attention for the use in inertial stabilized platforms. Sliding mode control (SMC), in [...] Read more.

Torque ripples caused by cogging torque, flux harmonics, and current measurement error seriously restrict the application of a permanent magnet synchronous motor (PMSM), which has been paid more and more attention for the use in inertial stabilized platforms. Sliding mode control (SMC), in parallel with the classical proportional integral (PI) controller, has a high advantage to suppress the torque ripples as its invariance to disturbances. However, since the high switching gain tends to cause chattering and it requires derivative of signals which is not readily obtainable without an acceleration signal sensor. Therefore, this paper proposes a robust SMC scheme based on a rapid nonlinear tracking differentiator (NTD) and a disturbance observer (DOB) to further improve the performance of the SMC. The NTD is employed to providing the derivative of the signal, and the DOB is utilized to estimate the system lumped disturbances, including parameter variations and external disturbances. On the one hand, DOB can compensate the robust SMC speed controller, it can reduce the chattering of SMC on the other hand. Experiments were carried out on an ARM and DSP-based platform. The obtained experimental results demonstrate that the robust SMC scheme has an improved performance with inertia stability and it exhibits a satisfactory anti-disturbance performance compared to the traditional methods. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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34 pages, 1079 KiB

Open AccessArticle

Real-Time Processing Library for Open-Source Hardware Biomedical Sensors

by Alberto J. Molina-Cantero^*

, Juan A. Castro-García

, Clara Lebrato-Vázquez, Isabel M. Gómez-González

and Manuel Merino-Monge

Departamento de Tecnología Electrónica, ETS, Ingeniería Informática, Universidad de Sevilla, 41012 Sevilla, Spain

Sensors 2018, 18(4), 1033; https://doi.org/10.3390/s18041033 - 29 Mar 2018

Cited by 10 | Viewed by 9077

Abstract

Applications involving data acquisition from sensors need samples at a preset frequency rate, the filtering out of noise and/or analysis of certain frequency components. We propose a novel software architecture based on open-software hardware platforms which allows programmers to create data streams from [...] Read more.

Applications involving data acquisition from sensors need samples at a preset frequency rate, the filtering out of noise and/or analysis of certain frequency components. We propose a novel software architecture based on open-software hardware platforms which allows programmers to create data streams from input channels and easily implement filters and frequency analysis objects. The performances of the different classes given in the size of memory allocated and execution time (number of clock cycles) were analyzed in the low-cost platform Arduino Genuino. In addition, 11 people took part in an experiment in which they had to implement several exercises and complete a usability test. Sampling rates under 250 Hz (typical for many biomedical applications) makes it feasible to implement filters, sliding windows and Fourier analysis, operating in real time. Participants rated software usability at 70.2 out of 100 and the ease of use when implementing several signal processing applications was rated at just over 4.4 out of 5. Participants showed their intention of using this software because it was percieved as useful and very easy to use. The performances of the library showed that it may be appropriate for implementing small biomedical real-time applications or for human movement monitoring, even in a simple open-source hardware device like Arduino Genuino. The general perception about this library is that it is easy to use and intuitive. Full article

(This article belongs to the Section Biosensors)

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18 pages, 428 KiB

Open AccessArticle

Optimally Distributed Kalman Filtering with Data-Driven Communication

by Katharina Dormann^1,‡, Benjamin Noack^2,*,‡

and Uwe D. Hanebeck²

¹ Robert Bosch GmbH, 71636 Ludwigsburg, Germany

² Intelligent Sensor-Actuator-Systems Laboratory (ISAS), Institute for Anthropomatics and Robotics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany

^‡ These authors contributed equally to this work.

Sensors 2018, 18(4), 1034; https://doi.org/10.3390/s18041034 - 29 Mar 2018

Cited by 15 | Viewed by 5166

Abstract

For multisensor data fusion, distributed state estimation techniques that enable a local processing of sensor data are the means of choice in order to minimize storage and communication costs. In particular, a distributed implementation of the optimal Kalman filter has recently been developed. [...] Read more.

For multisensor data fusion, distributed state estimation techniques that enable a local processing of sensor data are the means of choice in order to minimize storage and communication costs. In particular, a distributed implementation of the optimal Kalman filter has recently been developed. A significant disadvantage of this algorithm is that the fusion center needs access to each node so as to compute a consistent state estimate, which requires full communication each time an estimate is requested. In this article, different extensions of the optimally distributed Kalman filter are proposed that employ data-driven transmission schemes in order to reduce communication expenses. As a first relaxation of the full-rate communication scheme, it can be shown that each node only has to transmit every second time step without endangering consistency of the fusion result. Also, two data-driven algorithms are introduced that even allow for lower transmission rates, and bounds are derived to guarantee consistent fusion results. Simulations demonstrate that the data-driven distributed filtering schemes can outperform a centralized Kalman filter that requires each measurement to be sent to the center node. Full article

(This article belongs to the Special Issue Selected Papers from MFI 2017 - International Conference on Multisensor Fusion and Integration for Intelligent Systems)

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19 pages, 93130 KiB

Open AccessArticle

Object-Based Dense Matching Method for Maintaining Structure Characteristics of Linear Buildings

by Nan Su^1,*

, Yiming Yan^1,*, Mingjie Qiu², Chunhui Zhao¹ and Liguo Wang¹

¹ College of information and communication engineering, Harbin Engineering University, Harbin 150001, China

² School of electronics and information engineering, Harbin Institute of Technology, Harbin 150001, China

Sensors 2018, 18(4), 1035; https://doi.org/10.3390/s18041035 - 29 Mar 2018

Cited by 5 | Viewed by 3557

Abstract

In this paper, we proposed a novel object-based dense matching method specially for the high-precision disparity map of building objects in urban areas, which can maintain accurate object structure characteristics. The proposed framework mainly includes three stages. Firstly, an improved edge line extraction [...] Read more.

In this paper, we proposed a novel object-based dense matching method specially for the high-precision disparity map of building objects in urban areas, which can maintain accurate object structure characteristics. The proposed framework mainly includes three stages. Firstly, an improved edge line extraction method is proposed for the edge segments to fit closely to building outlines. Secondly, a fusion method is proposed for the outlines under the constraint of straight lines, which can maintain the building structural attribute with parallel or vertical edges, which is very useful for the dense matching method. Finally, we proposed an edge constraint and outline compensation (ECAOC) dense matching method to maintain building object structural characteristics in the disparity map. In the proposed method, the improved edge lines are used to optimize matching search scope and matching template window, and the high-precision building outlines are used to compensate the shape feature of building objects. Our method can greatly increase the matching accuracy of building objects in urban areas, especially at building edges. For the outline extraction experiments, our fusion method verifies the superiority and robustness on panchromatic images of different satellites and different resolutions. For the dense matching experiments, our ECOAC method shows great advantages for matching accuracy of building objects in urban areas compared with three other methods. Full article

(This article belongs to the Section Remote Sensors)

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25 pages, 17593 KiB

Open AccessArticle

Vehicle Mode and Driving Activity Detection Based on Analyzing Sensor Data of Smartphones

by Dang-Nhac Lu^1,2, Duc-Nhan Nguyen³, Thi-Hau Nguyen^1,*

and Ha-Nam Nguyen^4,*

¹ University of Engineering and Technology, Vietnam National University in Hanoi (VNU-UET), Hanoi 123105, Vietnam

² Academy of Journalism and Communication, Hanoi 123105, Vietnam

³ Posts and Telecommunications Institute of Technology in Hanoi (PTIT), Hanoi 151100, Vietnam

⁴ Information Technology Institute, Vietnam National University in Hanoi (VNU-ITI), Hanoi 123105, Vietnam

Sensors 2018, 18(4), 1036; https://doi.org/10.3390/s18041036 - 29 Mar 2018

Cited by 42 | Viewed by 12222

Abstract

In this paper, we present a flexible combined system, namely the Vehicle mode-driving Activity Detection System (VADS), that is capable of detecting either the current vehicle mode or the current driving activity of travelers. Our proposed system is designed to be lightweight in [...] Read more.

In this paper, we present a flexible combined system, namely the Vehicle mode-driving Activity Detection System (VADS), that is capable of detecting either the current vehicle mode or the current driving activity of travelers. Our proposed system is designed to be lightweight in computation and very fast in response to the changes of travelers’ vehicle modes or driving events. The vehicle mode detection module is responsible for recognizing both motorized vehicles, such as cars, buses, and motorbikes, and non-motorized ones, for instance, walking, and bikes. It relies only on accelerometer data in order to minimize the energy consumption of smartphones. By contrast, the driving activity detection module uses the data collected from the accelerometer, gyroscope, and magnetometer of a smartphone to detect various driving activities, i.e., stopping, going straight, turning left, and turning right. Furthermore, we propose a method to compute the optimized data window size and the optimized overlapping ratio for each vehicle mode and each driving event from the training datasets. The experimental results show that this strategy significantly increases the overall prediction accuracy. Additionally, numerous experiments are carried out to compare the impact of different feature sets (time domain features, frequency domain features, Hjorth features) as well as the impact of various classification algorithms (Random Forest, Naïve Bayes, Decision tree J48, K Nearest Neighbor, Support Vector Machine) contributing to the prediction accuracy. Our system achieves an average accuracy of 98.33% in detecting the vehicle modes and an average accuracy of 98.95% in recognizing the driving events of motorcyclists when using the Random Forest classifier and a feature set containing time domain features, frequency domain features, and Hjorth features. Moreover, on a public dataset of HTC company in New Taipei, Taiwan, our framework obtains the overall accuracy of 97.33% that is considerably higher than that of the state-of the art. Full article

(This article belongs to the Section Intelligent Sensors)

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18 pages, 24742 KiB

Open AccessArticle

Design and Implementation of a Dual-Mass MEMS Gyroscope with High Shock Resistance

by Yang Gao^1,2

, Libin Huang^1,2, Xukai Ding^1,2

and Hongsheng Li^1,2,*

¹ School of Instrument Science and Engineering, Southeast University, Nanjing 210096, China

² Key Laboratory of Micro-Inertial Instruments and Advanced Navigation Technology, Ministry of Education, Nanjing 210096, China

Sensors 2018, 18(4), 1037; https://doi.org/10.3390/s18041037 - 30 Mar 2018

Cited by 12 | Viewed by 6654

Abstract

This paper presents the design and implementation of a dual-mass MEMS gyroscope with high shock resistance by improving the in-phase frequency of the gyroscope and by using a two-stage elastic stopper mechanism and proposes a Simulink shock model of the gyroscope equipped with [...] Read more.

This paper presents the design and implementation of a dual-mass MEMS gyroscope with high shock resistance by improving the in-phase frequency of the gyroscope and by using a two-stage elastic stopper mechanism and proposes a Simulink shock model of the gyroscope equipped with the two-stage stopper mechanism, which is a very efficient method to evaluate the shock resistance of the gyroscope. The structural design takes into account both the mechanical sensitivity and the shock resistance. The design of the primary structure and the analysis of the stopper mechanism are first introduced. Based on the expression of the restoring force of the stopper beam, the analytical shock response model of the gyroscope is obtained. By this model, the shock response of the gyroscope is theoretically analyzed, and the appropriate structural parameters are obtained. Then, the correctness of the model is verified by finite element (FE) analysis, where the contact collision analysis is introduced in detail. The simulation results show that the application of the two-stage elastic stopper mechanism can effectively improve the shock resistance by more than 1900 g and 1500 g in the x- and y-directions, respectively. Finally, experimental verifications are carried out by using a machete hammer on the micro-gyroscope prototype fabricated by the deep dry silicon on glass (DDSOG) technology. The results show that the shock resistance of the prototype along the x-, y- and z-axes all exceed 10,000 g. Moreover, the output of the gyroscope can return to normal in about 2 s. Full article

(This article belongs to the Special Issue Integrated MEMS Sensors for the IoT Era)

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20 pages, 9905 KiB

Open AccessArticle

Sensor-Based Optimized Control of the Full Load Instability in Large Hydraulic Turbines

by Alexandre Presas, David Valentin^*

, Mònica Egusquiza

, Carme Valero and Eduard Egusquiza

Center for Industrial Diagnostics and Fluid Dynamics (CDIF), Polytechnic University of Catalonia (UPC), Av. Diagonal, 647, ETSEIB, 08028 Barcelona, Spain

Sensors 2018, 18(4), 1038; https://doi.org/10.3390/s18041038 - 30 Mar 2018

Cited by 15 | Viewed by 4649

Abstract

Hydropower plants are of paramount importance for the integration of intermittent renewable energy sources in the power grid. In order to match the energy generated and consumed, Large hydraulic turbines have to work under off-design conditions, which may lead to dangerous unstable operating [...] Read more.

Hydropower plants are of paramount importance for the integration of intermittent renewable energy sources in the power grid. In order to match the energy generated and consumed, Large hydraulic turbines have to work under off-design conditions, which may lead to dangerous unstable operating points involving the hydraulic, mechanical and electrical system. Under these conditions, the stability of the grid and the safety of the power plant itself can be compromised. For many Francis Turbines one of these critical points, that usually limits the maximum output power, is the full load instability. Therefore, these machines usually work far away from this unstable point, reducing the effective operating range of the unit. In order to extend the operating range of the machine, working closer to this point with a reasonable safety margin, it is of paramount importance to monitor and to control relevant parameters of the unit, which have to be obtained with an accurate sensor acquisition strategy. Within the framework of a large EU project, field tests in a large Francis Turbine located in Canada (rated power of 444 MW) have been performed. Many different sensors were used to monitor several working parameters of the unit for all its operating range. Particularly for these tests, more than 80 signals, including ten type of different sensors and several operating signals that define the operating point of the unit, were simultaneously acquired. The present study, focuses on the optimization of the acquisition strategy, which includes type, number, location, acquisition frequency of the sensors and corresponding signal analysis to detect the full load instability and to prevent the unit from reaching this point. A systematic approach to determine this strategy has been followed. It has been found that some indicators obtained with different types of sensors are linearly correlated with the oscillating power. The optimized strategy has been determined based on the correlation characteristics (linearity, sensitivity and reactivity), the simplicity of the installation and the acquisition frequency necessary. Finally, an economic and easy implementable protection system based on the resulting optimized acquisition strategy is proposed. This system, which can be used in a generic Francis turbine with a similar full load instability, permits one to extend the operating range of the unit by working close to the instability with a reasonable safety margin. Full article

(This article belongs to the Special Issue I3S 2017 Selected Papers)

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11 pages, 18538 KiB

Open AccessArticle

The Height-Adaptive Parameterized Step Length Measurement Method and Experiment Based on Motion Parameters

by Yanshun Zhang¹, Yingyue Li^1,*, Chuang Peng¹, Dong Mou², Ming Li¹ and Wei Wang¹

¹ School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, China

² Electronic Engineering Research Institute, China Academy of Engineering Physics, Mianyang 621900, China

Sensors 2018, 18(4), 1039; https://doi.org/10.3390/s18041039 - 30 Mar 2018

Cited by 25 | Viewed by 6652

Abstract

In order to tackle the inaccurate step length measurement of people with different heights and in different motion states, a height-adaptive method of step length measurement based on motion parameters is proposed in this paper. This method takes people’s height, stride frequency, and [...] Read more.

In order to tackle the inaccurate step length measurement of people with different heights and in different motion states, a height-adaptive method of step length measurement based on motion parameters is proposed in this paper. This method takes people’s height, stride frequency, and changing accelerometer output while walking into integrated consideration, and builds a dynamic and parameterized model of their step length. In this study, these parameters were calibrated with thirty sets of experiment data from people with different heights and in different motion states, which were then verified experimentally by motion data of randomly selected subjects, regardless of speed and height. The experiment results indicate that the height-adaptive step length measurement was realized, thus eliminating the influence of height exerted on step length measurement. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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17 pages, 13649 KiB

Open AccessArticle

Discrete Indoor Three-Dimensional Localization System Based on Neural Networks Using Visible Light Communication

by Itziar Alonso-González^1,2,†

, David Sánchez-Rodríguez^1,2,*,†

, Carlos Ley-Bosch^1,2,† and Miguel A. Quintana-Suárez^2,†

¹ Institute for Technological Development and Innovation in Communications, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira, 35017 Las Palmas de Gran Canaria, Spain

² Telematic Engineering Department, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira, 35017 Las Palmas de Gran Canaria, Spain

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1040; https://doi.org/10.3390/s18041040 - 30 Mar 2018

Cited by 44 | Viewed by 5437

Abstract

Indoor localization estimation has become an attractive research topic due to growing interest in location-aware services. Many research works have proposed solving this problem by using wireless communication systems based on radiofrequency. Nevertheless, those approaches usually deliver an accuracy of up to two [...] Read more.

Indoor localization estimation has become an attractive research topic due to growing interest in location-aware services. Many research works have proposed solving this problem by using wireless communication systems based on radiofrequency. Nevertheless, those approaches usually deliver an accuracy of up to two metres, since they are hindered by multipath propagation. On the other hand, in the last few years, the increasing use of light-emitting diodes in illumination systems has provided the emergence of Visible Light Communication technologies, in which data communication is performed by transmitting through the visible band of the electromagnetic spectrum. This brings a brand new approach to high accuracy indoor positioning because this kind of network is not affected by electromagnetic interferences and the received optical power is more stable than radio signals. Our research focus on to propose a fingerprinting indoor positioning estimation system based on neural networks to predict the device position in a 3D environment. Neural networks are an effective classification and predictive method. The localization system is built using a dataset of received signal strength coming from a grid of different points. From the these values, the position in Cartesian coordinates

(x, y, z)

is estimated. The use of three neural networks is proposed in this work, where each network is responsible for estimating the position by each axis. Experimental results indicate that the proposed system leads to substantial improvements to accuracy over the widely-used traditional fingerprinting methods, yielding an accuracy above 99% and an average error distance of 0.4 mm. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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14 pages, 23684 KiB

Open AccessArticle

A Hybrid Bionic Image Sensor Achieving FOV Extension and Foveated Imaging

by Qun Hao¹, Zihan Wang¹, Jie Cao^1,2,* and Fanghua Zhang¹

¹ School of optics and photonics, Beijing Institute of Technology, Key Laboratory of Biomimetic Robots and Systems, Ministry of Education, Beijing 100081, China

² NUS Suzhou Research Institute (NUSRI), Suzhou Industrial Park, Suzhou 215123, China

Sensors 2018, 18(4), 1042; https://doi.org/10.3390/s18041042 - 30 Mar 2018

Cited by 24 | Viewed by 5949

Abstract

Based on bionic compound eye and human foveated imaging mechanisms, a hybrid bionic image sensor (HBIS) is proposed in this paper to extend the field of view (FOV) with high resolution. First, the hybrid bionic imaging model was developed and the structure parameters [...] Read more.

Based on bionic compound eye and human foveated imaging mechanisms, a hybrid bionic image sensor (HBIS) is proposed in this paper to extend the field of view (FOV) with high resolution. First, the hybrid bionic imaging model was developed and the structure parameters of the HBIS were deduced. Second, the properties of the HBIS were simulated, including FOV extension, super-resolution imaging, foveal ratio and so on. Third, a prototype of the HBIS was developed to validate the theory. Imaging experiments were carried out, and the results are in accordance with the simulations, proving the potential of the HBIS for large FOV and high-resolution imaging with low cost. Full article

(This article belongs to the Special Issue Bio-Inspiring Sensing)

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9 pages, 10374 KiB

Open AccessArticle

Eight-Channel AC Magnetosusceptometer of Magnetic Nanoparticles for High-Throughput and Ultra-High-Sensitivity Immunoassay

by Jen-Jie Chieh^1,*, Wen-Chun Wei¹, Shu-Hsien Liao¹

, Hsin-Hsein Chen², Yen-Fu Lee², Feng-Chun Lin², Ming-Hsien Chiang¹, Ming-Jang Chiu^3,4,5,6, Herng-Er Horng^1,* and Shieh-Yueh Yang²

¹ Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taipei 116, Taiwan

² MagQu Co., Ltd., New Taipei 231, Taiwan

³ Departments of Neurology, National Taiwan University Hospital, Taipei 100, Taiwan

⁴ Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei 100, Taiwan

⁵ Department of Psychology, National Taiwan University, Taipei 106, Taiwan

⁶ Graduate Institute of Biomedical Engineering and Bio-informatics, National Taiwan University, Taipei 106, Taiwan

Sensors 2018, 18(4), 1043; https://doi.org/10.3390/s18041043 - 30 Mar 2018

Cited by 20 | Viewed by 4238

Abstract

An alternating-current magnetosusceptometer of antibody-functionalized magnetic nanoparticles (MNPs) was developed for immunomagnetic reduction (IMR). A high-sensitivity, high-critical-temperature superconducting quantum interference device was used in the magnetosusceptometer. Minute levels of biomarkers of early-stage neurodegeneration diseases were detectable in serum, but measuring each biomarker required [...] Read more.

An alternating-current magnetosusceptometer of antibody-functionalized magnetic nanoparticles (MNPs) was developed for immunomagnetic reduction (IMR). A high-sensitivity, high-critical-temperature superconducting quantum interference device was used in the magnetosusceptometer. Minute levels of biomarkers of early-stage neurodegeneration diseases were detectable in serum, but measuring each biomarker required approximately 4 h. Hence, an eight-channel platform was developed in this study to fit minimal screening requirements for Alzheimer’s disease. Two consistent results were measured for three biomarkers, namely Aβ40, Aβ42, and tau protein, per human specimen. This paper presents the instrument configuration as well as critical characteristics, such as the low noise level variations among channels, a high signal-to-noise ratio, and the coefficient of variation for the biomarkers’ IMR values. The instrument’s ultrahigh sensitivity levels for the three biomarkers and the substantially shorter total measurement time in comparison with the previous single- and four-channels platforms were also demonstrated in this study. Thus, the eight-channel instrument may serve as a powerful tool for clinical high-throughput screening of Alzheimer’s disease. Full article

(This article belongs to the Special Issue Magnetic Materials Based Biosensors)

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23 pages, 22999 KiB

Open AccessArticle

Polar Cooperative Navigation Algorithm for Multi-Unmanned Underwater Vehicles Considering Communication Delays

by Zheping Yan, Lu Wang^*, Tongda Wang, Zewen Yang, Tao Chen and Jian Xu

College of Automation, Harbin Engineering University, Harbin 150001, China

Sensors 2018, 18(4), 1044; https://doi.org/10.3390/s18041044 - 30 Mar 2018

Cited by 32 | Viewed by 5773

Abstract

To solve the navigation accuracy problems of multi-Unmanned Underwater Vehicles (multi-UUVs) in the polar region, a polar cooperative navigation algorithm for multi-UUVs considering communication delays is proposed in this paper. UUVs are important pieces of equipment in ocean engineering for marine development. For [...] Read more.

To solve the navigation accuracy problems of multi-Unmanned Underwater Vehicles (multi-UUVs) in the polar region, a polar cooperative navigation algorithm for multi-UUVs considering communication delays is proposed in this paper. UUVs are important pieces of equipment in ocean engineering for marine development. For UUVs to complete missions, precise navigation is necessary. It is difficult for UUVs to establish true headings because of the rapid convergence of Earth meridians and the severe polar environment. Based on the polar grid navigation algorithm, UUV navigation in the polar region can be accomplished with the Strapdown Inertial Navigation System (SINS) in the grid frame. To save costs, a leader-follower type of system is introduced in this paper. The leader UUV helps the follower UUVs to achieve high navigation accuracy. Follower UUVs correct their own states based on the information sent by the leader UUV and the relative position measured by ultra-short baseline (USBL) acoustic positioning. The underwater acoustic communication delay is quantized by the model. In this paper, considering underwater acoustic communication delay, the conventional adaptive Kalman filter (AKF) is modified to adapt to polar cooperative navigation. The results demonstrate that the polar cooperative navigation algorithm for multi-UUVs that considers communication delays can effectively navigate the sailing of multi-UUVs in the polar region. Full article

(This article belongs to the Special Issue Sensors, Wireless Connectivity and Systems for Autonomous Vehicles and Smart Mobility)

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17 pages, 3978 KiB

Open AccessArticle

Accurate Object Pose Estimation Using Depth Only

by Mingyu Li^*

and Koichi Hashimoto

Graduate School of Information Sciences, Tohoku University, Aramaki Aza Aoba 6-6-01, Aoba-Ku, Sendai 980-8579, Japan

Sensors 2018, 18(4), 1045; https://doi.org/10.3390/s18041045 - 30 Mar 2018

Cited by 19 | Viewed by 6693

Abstract

Object recognition and pose estimation is an important task in computer vision. A pose estimation algorithm using only depth information is proposed in this paper. Foreground and background points are distinguished based on their relative positions with boundaries. Model templates are selected using [...] Read more.

Object recognition and pose estimation is an important task in computer vision. A pose estimation algorithm using only depth information is proposed in this paper. Foreground and background points are distinguished based on their relative positions with boundaries. Model templates are selected using synthetic scenes to make up for the point pair feature algorithm. An accurate and fast pose verification method is introduced to select result poses from thousands of poses. Our algorithm is evaluated against a large number of scenes and proved to be more accurate than algorithms using both color information and depth information. Full article

(This article belongs to the Special Issue Depth Sensors and 3D Vision)

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16 pages, 1148 KiB

Open AccessArticle

Classification of Incomplete Data Based on Evidence Theory and an Extreme Learning Machine in Wireless Sensor Networks

by Yang Zhang¹, Yun Liu^1,*, Han-Chieh Chao^2,3,4,5, Zhenjiang Zhang⁶ and Zhiyuan Zhang¹

¹ Key Laboratory of Communication and Information Systems, Beijing Municipal Commission of Education, School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing 100044, China

² School of Information Science and Engineering, Fujian University of Technology, Fuzhou 350118, China

³ School of Mathematics and Computer Science, Wuhan Polytechnic University, Wuhan 430024, China

⁴ Department of Electrical Engineering, National Dong Hwa University, Hualien 97401, Taiwan

⁵ Department of Computer Science and Information Engineering, National Ilan University, Yilan 26047, Taiwan

⁶ School of Software Engineering, Beijing Jiaotong University, Beijing 100044, China

Sensors 2018, 18(4), 1046; https://doi.org/10.3390/s18041046 - 30 Mar 2018

Cited by 17 | Viewed by 4264

Abstract

In wireless sensor networks, the classification of incomplete data reported by sensor nodes is an open issue because it is difficult to accurately estimate the missing values. In many cases, the misclassification is unacceptable considering that it probably brings catastrophic damages to the [...] Read more.

In wireless sensor networks, the classification of incomplete data reported by sensor nodes is an open issue because it is difficult to accurately estimate the missing values. In many cases, the misclassification is unacceptable considering that it probably brings catastrophic damages to the data users. In this paper, a novel classification approach of incomplete data is proposed to reduce the misclassification errors. This method uses the regularized extreme learning machine to estimate the potential values of missing data at first, and then it converts the estimations into multiple classification results on the basis of the distance between interval numbers. Finally, an evidential reasoning rule is adopted to fuse these classification results. The final decision is made according to the combined basic belief assignment. The experimental results show that this method has better performance than other traditional classification methods of incomplete data. Full article

(This article belongs to the Special Issue Sensor Networks for Collaborative and Secure Internet of Things)

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10 pages, 19314 KiB

Open AccessArticle

A Monolithic Electrochemical Micro Seismic Sensor Capable of Monitoring Three-Dimensional Vibrations

by Lianhong Chen^1,2, Zhenyuan Sun^1,2

, Guanglei Li^1,2, Deyong Chen^1,2,*, Junbo Wang^1,2 and Jian Chen^1,2

¹ State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, 100190 Beijing, China

² School of Electronic, Electrical and Communication Engineering, Chinese Academy of Sciences, 100190 Beijing, China

Sensors 2018, 18(4), 1047; https://doi.org/10.3390/s18041047 - 31 Mar 2018

Cited by 6 | Viewed by 5176

Abstract

A monolithic electrochemical micro seismic sensor capable of monitoring three-axial vibrations was proposed in this paper. The proposed micro sensor mainly consisted of four sensing units interconnected within flow channels and by interpreting the voltage outputs of the sensing units, vibrations with arbitrary [...] Read more.

A monolithic electrochemical micro seismic sensor capable of monitoring three-axial vibrations was proposed in this paper. The proposed micro sensor mainly consisted of four sensing units interconnected within flow channels and by interpreting the voltage outputs of the sensing units, vibrations with arbitrary directions can be quantified. The proposed seismic sensors are fabricated based on MEMS technologies and characterized, which produced sensitivities along x, y, and z axes as 2473.2 ± 184.5 V/(m/s), 2261.7 ± 119.6 V/(m/s), and 3480.7 ± 417.2 V/(m/s) at 30 Hz. In addition, the vibrations in x-y, x-z, and y-z planes were applied to the developed seismic sensors, leading to comparable monitoring results after decoupling calculations with the input velocities. Furthermore, the results have shown its feasibilities for seismic data recording. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 40877 KiB

Open AccessArticle

Mapping Soil Salinity/Sodicity by using Landsat OLI Imagery and PLSR Algorithm over Semiarid West Jilin Province, China

by Hao Yu^1,2,†

, Mingyue Liu^1,2,†, Baojia Du¹, Zongming Wang^1,*

, Liangjun Hu^3,*

and Bai Zhang^1,*

¹ Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Key Laboratory of Wetland Ecology and Environment, Changchun 130102, China

² University of Chinese Academy of Sciences, Beijing 100049, China

³ Northeast Normal University, Key Laboratory for Vegetation Ecology Science of Ministry of Education, Changchun 130021, China

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1048; https://doi.org/10.3390/s18041048 - 31 Mar 2018

Cited by 73 | Viewed by 7160

Abstract

Soil salinity and sodicity can significantly reduce the value and the productivity of affected lands, posing degradation, and threats to sustainable development of natural resources on earth. This research attempted to map soil salinity/sodicity via disentangling the relationships between Landsat 8 Operational Land [...] Read more.

Soil salinity and sodicity can significantly reduce the value and the productivity of affected lands, posing degradation, and threats to sustainable development of natural resources on earth. This research attempted to map soil salinity/sodicity via disentangling the relationships between Landsat 8 Operational Land Imager (OLI) imagery and in-situ measurements (EC, pH) over the west Jilin of China. We established the retrieval models for soil salinity and sodicity using Partial Least Square Regression (PLSR). Spatial distribution of the soils that were subjected to hybridized salinity and sodicity (HSS) was obtained by overlay analysis using maps of soil salinity and sodicity in geographical information system (GIS) environment. We analyzed the severity and occurring sizes of soil salinity, sodicity, and HSS with regard to specified soil types and land cover. Results indicated that the models’ accuracy was improved by combining the reflectance bands and spectral indices that were mathematically transformed. Therefore, our results stipulated that the OLI imagery and PLSR method applied to mapping soil salinity and sodicity in the region. The mapping results revealed that the areas of soil salinity, sodicity, and HSS were 1.61 × 10⁶ hm², 1.46 × 10⁶ hm², and 1.36 × 10⁶ hm², respectively. Also, the occurring area of moderate and intensive sodicity was larger than that of salinity. This research may underpin efficiently mapping regional salinity/sodicity occurrences, understanding the linkages between spectral reflectance and ground measurements of soil salinity and sodicity, and provide tools for soil salinity monitoring and the sustainable utilization of land resources. Full article

(This article belongs to the Section Remote Sensors)

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20 pages, 6611 KiB

Open AccessArticle

Positioning Locality Using Cognitive Directions Based on Indoor Landmark Reference System

by Yankun Wang^1,2, Hong Fan^1,2,*, Ruizhi Chen^1,2

, Huan Li^3,4, Luyao Wang^1,2, Kang Zhao^1,2 and Wu Du^1,2

¹ State Key Lab for Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, 129 Luoyu Road, Wuhan 430079, China

² Collaborative Innovation Center of Geospatial Technology, Wuhan University, 129 Luoyu Road, Wuhan 430079, China

³ State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China

⁴ Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China

Sensors 2018, 18(4), 1049; https://doi.org/10.3390/s18041049 - 31 Mar 2018

Cited by 9 | Viewed by 4190

Abstract

Locality descriptions are generally communicated using reference objects and spatial relations that reflect human spatial cognition. However, uncertainty is inevitable in locality descriptions. Positioning locality with locality description, with a mapping mechanism between the qualitative and quantitative data, is one of the important [...] Read more.

Locality descriptions are generally communicated using reference objects and spatial relations that reflect human spatial cognition. However, uncertainty is inevitable in locality descriptions. Positioning locality with locality description, with a mapping mechanism between the qualitative and quantitative data, is one of the important research issues in next-generation geographic information sciences. Spatial relations play an important role in the uncertainty of positioning locality. In indoor landmark reference systems, the nearest landmarks can be selected when describing localities by using direction relations indoors. By using probability operation, we combine a set of uncertainties, that is, near and direction relations to positioning locality. Some definitions are proposed from cognitive and computational perspectives. We evaluate the performance of our method through indoor cognitive experiments. Test results demonstrate that a positioning accuracy of 3.55 m can be achieved with the semantically derived direction relationships in indoor landmark reference systems. Full article

(This article belongs to the Section Remote Sensors)

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13 pages, 15189 KiB

Open AccessArticle

Assessing the Crop-Water Status in Almond (Prunus dulcis Mill.) Trees via Thermal Imaging Camera Connected to Smartphone

by Iván Francisco García-Tejero^1,*, Carlos José Ortega-Arévalo¹, Manuel Iglesias-Contreras¹, José Manuel Moreno¹, Luciene Souza^1,2, Simón Cuadros Tavira³

and Víctor Hugo Durán-Zuazo¹

¹ Instituto Andaluz de Investigación y Formación Agraria y Pesquera (IFAPA), Centro “Las Torres-Tomejil”, Ctra. Sevilla-Cazalla km. 12,2, 41.200 Alcalá del Río (Sevilla), Spain

² Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000 Campos dos Goytacazes, RJ, Brazil

³ Departamento de Ingeniería Forestal, Universidad de Córdoba, Campus de Rabanales, E-14071 Córdoba, Spain

Sensors 2018, 18(4), 1050; https://doi.org/10.3390/s18041050 - 31 Mar 2018

Cited by 46 | Viewed by 6235

Abstract

Different tools are being implemented in order to improve the water management in agricultural irrigated areas of semiarid environments. Thermography has been progressively introduced as a promising technique for irrigation scheduling and the assessing of crop-water status, especially when deficit irrigation is being [...] Read more.

Different tools are being implemented in order to improve the water management in agricultural irrigated areas of semiarid environments. Thermography has been progressively introduced as a promising technique for irrigation scheduling and the assessing of crop-water status, especially when deficit irrigation is being implemented. However, an important limitation is related to the cost of the actual cameras, this being a severe limitation to its practical usage by farmers and technicians. This work evaluates the potential and the robustness of a thermal imaging camera that is connected to smartphone (Flir One) recently developed by Flir Systems Inc. as a first step to assess the crop water status. The trial was developed in mature almond (Prunus dulcis Mill.) trees that are subjected to different irrigation treatments. Thermal information obtained by the Flir One camera was deal with the thermal information obtained with a conventional Thermal Camera (Flir SC660) with a high resolution, and subsequently, confronted with other related plant physiological parameters (leaf water potential, Ψ_leaf, and stomatal conductance, g_s). Thermal imaging camera connected to smartphone provided useful information in estimating the crop-water status in almond trees, being a potential promising tool to accelerate the monitoring process and thereby enhance water-stress management of almond orchards. Full article

(This article belongs to the Special Issue Application of Satellite and Proximal Sensors in Precision Agriculture)

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17 pages, 62953 KiB

Open AccessArticle

Assessment of Spatiotemporal Fusion Algorithms for Planet and Worldview Images

by Chiman Kwan^1,*

, Xiaolin Zhu², Feng Gao³

, Bryan Chou¹, Daniel Perez⁴

, Jiang Li⁴

, Yuzhong Shen⁴, Krzysztof Koperski⁵ and Giovanni Marchisio⁵

¹ Applied Research LLC, Rockville, MD 20850, USA

² Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Kowloon, Hong Kong 999077, China

³ Hydrology & Remote Sensing Lab, USDA ARS, Beltsville, MD 20704, USA

⁴ Department of Electrical & Computer Engineering, Old Dominion University, Norfolk, VA 23529, USA

⁵ Digital Globe, Inc., Herndon, VA 20171, USA

Sensors 2018, 18(4), 1051; https://doi.org/10.3390/s18041051 - 31 Mar 2018

Cited by 39 | Viewed by 5708

Abstract

Although Worldview-2 (WV) images (non-pansharpened) have 2-m resolution, the re-visit times for the same areas may be seven days or more. In contrast, Planet images are collected using small satellites that can cover the whole Earth almost daily. However, the resolution of Planet [...] Read more.

Although Worldview-2 (WV) images (non-pansharpened) have 2-m resolution, the re-visit times for the same areas may be seven days or more. In contrast, Planet images are collected using small satellites that can cover the whole Earth almost daily. However, the resolution of Planet images is 3.125 m. It would be ideal to fuse these two satellites images to generate high spatial resolution (2 m) and high temporal resolution (1 or 2 days) images for applications such as damage assessment, border monitoring, etc. that require quick decisions. In this paper, we evaluate three approaches to fusing Worldview (WV) and Planet images. These approaches are known as Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM), Flexible Spatiotemporal Data Fusion (FSDAF), and Hybrid Color Mapping (HCM), which have been applied to the fusion of MODIS and Landsat images in recent years. Experimental results using actual Planet and Worldview images demonstrated that the three aforementioned approaches have comparable performance and can all generate high quality prediction images. Full article

(This article belongs to the Special Issue Sensors Signal Processing and Visual Computing)

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12 pages, 23631 KiB

Open AccessArticle

New Digital Metal-Oxide (MOx) Sensor Platform

by Daniel Rüffer^*, Felix Hoehne and Johannes Bühler

Sensirion AG, CH-8712 Stäfa, Switzerland

Sensors 2018, 18(4), 1052; https://doi.org/10.3390/s18041052 - 31 Mar 2018

Cited by 92 | Viewed by 18220

Abstract

The application of metal oxide gas sensors in Internet of Things (IoT) devices and mobile platforms like wearables and mobile phones offers new opportunities for sensing applications. Metal-oxide (MOx) sensors are promising candidates for such applications, thanks to the scientific progresses achieved in [...] Read more.

The application of metal oxide gas sensors in Internet of Things (IoT) devices and mobile platforms like wearables and mobile phones offers new opportunities for sensing applications. Metal-oxide (MOx) sensors are promising candidates for such applications, thanks to the scientific progresses achieved in recent years. For the widespread application of MOx sensors, viable commercial offerings are required. In this publication, the authors show that with the new Sensirion Gas Platform (SGP) a milestone in the commercial application of MOx technology has been reached. The architecture of the new platform and its performance in selected applications are presented. Full article

(This article belongs to the Special Issue Gas Sensors based on Semiconducting Metal Oxides)

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13 pages, 4453 KiB

Open AccessArticle

A Power-Frequency Electric Field Sensor for Portable Measurement

by Dongping Xiao^*, Qichao Ma, Yutong Xie, Qi Zheng and Zhanlong Zhang

State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, China

Sensors 2018, 18(4), 1053; https://doi.org/10.3390/s18041053 - 31 Mar 2018

Cited by 17 | Viewed by 5864

Abstract

In this paper, a new type of electric field sensor is proposed for the health and safety protection of inspection staff in high-voltage environments. Compared with the traditional power frequency electric field measurement instruments, the portable instrument has some special performance requirements and, [...] Read more.

In this paper, a new type of electric field sensor is proposed for the health and safety protection of inspection staff in high-voltage environments. Compared with the traditional power frequency electric field measurement instruments, the portable instrument has some special performance requirements and, thus, a new kind of double spherical shell sensor is presented. First, the mathematical relationships between the induced voltage of the sensor, the output voltage of the measurement circuit, and the original electric field in free space are deduced theoretically. These equations show the principle of the proposed sensor to measure the electric field and the effect factors of the measurement. Next, the characteristics of the sensor are analyzed through simulation. The simulation results are in good agreement with the theoretical analysis. The influencing rules of the size and material of the sensor on the measurement results are summarized. Then, the proposed sensor and the matching measurement system are used in a physical experiment. After calibration, the error of the measurement system is discussed. Lastly, the directional characteristic of the proposed sensor is experimentally tested. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 734 KiB

Open AccessArticle

A Distance Boundary with Virtual Nodes for the Weighted Centroid Localization Algorithm

by Kwang-Yul Kim

and Yoan Shin^*

School of Electronic Engineering, Soongsil University, Seoul 06978, Korea

Sensors 2018, 18(4), 1054; https://doi.org/10.3390/s18041054 - 1 Apr 2018

Cited by 25 | Viewed by 4758

Abstract

In wireless sensor networks, accurate location information is important for precise tracking of targets. In order to satisfy hardware installation cost and localization accuracy requirements, a weighted centroid localization (WCL) algorithm, which is considered a promising localization algorithm, was introduced. In our previous [...] Read more.

In wireless sensor networks, accurate location information is important for precise tracking of targets. In order to satisfy hardware installation cost and localization accuracy requirements, a weighted centroid localization (WCL) algorithm, which is considered a promising localization algorithm, was introduced. In our previous research, we proposed a test node-based WCL algorithm using a distance boundary to improve the localization accuracy in the corner and side areas. The proposed algorithm estimates the target location by averaging the test node locations that exactly match with the number of anchor nodes in the distribution map. However, since the received signal strength has large variability in real channel conditions, the number of anchor nodes is not exactly matched and the localization accuracy may deteriorate. Thus, we propose an intersection threshold to compensate for the localization accuracy in this paper. The simulation results show that the proposed test node-based WCL algorithm provides higher-precision location information than the conventional WCL algorithm in entire areas, with a reduced number of physical anchor nodes. Moreover, we show that the localization accuracy is improved by using the intersection threshold when considering small-scale fading channel conditions. Full article

(This article belongs to the Section Sensor Networks)

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24 pages, 3951 KiB

Open AccessArticle

Divide and Conquer-Based 1D CNN Human Activity Recognition Using Test Data Sharpening

by Heeryon Cho

and Sang Min Yoon^*

HCI Lab., College of Computer Science, Kookmin University, 77, Jeongneung-ro, Seongbuk-gu, Seoul 02707, Korea

Sensors 2018, 18(4), 1055; https://doi.org/10.3390/s18041055 - 1 Apr 2018

Cited by 156 | Viewed by 19569

Abstract

Human Activity Recognition (HAR) aims to identify the actions performed by humans using signals collected from various sensors embedded in mobile devices. In recent years, deep learning techniques have further improved HAR performance on several benchmark datasets. In this paper, we propose one-dimensional [...] Read more.

Human Activity Recognition (HAR) aims to identify the actions performed by humans using signals collected from various sensors embedded in mobile devices. In recent years, deep learning techniques have further improved HAR performance on several benchmark datasets. In this paper, we propose one-dimensional Convolutional Neural Network (1D CNN) for HAR that employs a divide and conquer-based classifier learning coupled with test data sharpening. Our approach leverages a two-stage learning of multiple 1D CNN models; we first build a binary classifier for recognizing abstract activities, and then build two multi-class 1D CNN models for recognizing individual activities. We then introduce test data sharpening during prediction phase to further improve the activity recognition accuracy. While there have been numerous researches exploring the benefits of activity signal denoising for HAR, few researches have examined the effect of test data sharpening for HAR. We evaluate the effectiveness of our approach on two popular HAR benchmark datasets, and show that our approach outperforms both the two-stage 1D CNN-only method and other state of the art approaches. Full article

(This article belongs to the Special Issue Selected Papers from MFI 2017 - International Conference on Multisensor Fusion and Integration for Intelligent Systems)

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16 pages, 11824 KiB

Open AccessArticle

Development and On-Field Testing of Low-Cost Portable System for Monitoring PM2.5 Concentrations

by Konstantinos N. Genikomsakis¹

, Nikolaos-Fivos Galatoulas¹, Panagiotis I. Dallas², Luis Miguel Candanedo Ibarra¹, Dimitris Margaritis³ and Christos S. Ioakimidis^1,*

¹ European Research Area Chair (*Holder) ‘Net-Zero Energy Efficiency on City Districts, NZED’ Unit, Research Institute for Energy, University of Mons, Rue de l’Epargne, 56, 7000 Mons, Belgium

² Wireless Network Systems Division, INTRACOM Telecom S.A., 19.7 km Markopoulo Ave., Peania, 19002 Athens, Greece

³ Centre for Research and Technology Hellas (CERTH), Hellenic Institute of Transport (HIT), 6th km Charilaou-Thermi, 57001 Thermi, Thessaloniki, Greece

Sensors 2018, 18(4), 1056; https://doi.org/10.3390/s18041056 - 1 Apr 2018

Cited by 52 | Viewed by 9351

Abstract

Recent developments in the field of low-cost sensors enable the design and implementation of compact, inexpensive and portable sensing units for air pollution monitoring with fine-detailed spatial and temporal resolution, in order to support applications of wider interest in the area of intelligent [...] Read more.

Recent developments in the field of low-cost sensors enable the design and implementation of compact, inexpensive and portable sensing units for air pollution monitoring with fine-detailed spatial and temporal resolution, in order to support applications of wider interest in the area of intelligent transportation systems (ITS). In this context, the present work advances the concept of developing a low-cost portable air pollution monitoring system (APMS) for measuring the concentrations of particulate matter (PM), in particular fine particles with a diameter of 2.5 μm or less (PM2.5). Specifically, this paper presents the on-field testing of the proposed low-cost APMS implementation using roadside measurements from a mobile laboratory equipped with a calibrated instrument as the basis of comparison and showcases its accuracy on characterizing the PM2.5 concentrations on 1 min resolution in an on-road trial. Moreover, it demonstrates the intended application of collecting fine-grained spatio-temporal PM2.5 profiles by mounting the developed APMS on an electric bike as a case study in the city of Mons, Belgium. Full article

(This article belongs to the Special Issue Intelligent Sensor Systems for Environmental Monitoring)

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21 pages, 11732 KiB

Open AccessArticle

Design of Dual-Mode Local Oscillators Using CMOS Technology for Motion Detection Sensors

by Keum-Won Ha¹

, Jeong-Yun Lee¹, Jeong-Geun Kim² and Donghyun Baek^1,*

¹ Microwave Embedded Circuit & System (MECAS) Lab., School of Electrical Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjack-gu, Seoul 06974, Korea

² Integrated Radar Lab., Department of Electronic Engineering, KwangWoon University, 20 Gwangun-ro, Nowon-gu, Seoul 01897, Korea

Sensors 2018, 18(4), 1057; https://doi.org/10.3390/s18041057 - 1 Apr 2018

Cited by 6 | Viewed by 7117

Abstract

Recently, studies have been actively carried out to implement motion detecting sensors by applying radar techniques. Doppler radar or frequency-modulated continuous wave (FMCW) radar are mainly used, but each type has drawbacks. In Doppler radar, no signal is detected when the movement is [...] Read more.

Recently, studies have been actively carried out to implement motion detecting sensors by applying radar techniques. Doppler radar or frequency-modulated continuous wave (FMCW) radar are mainly used, but each type has drawbacks. In Doppler radar, no signal is detected when the movement is stopped. Also, FMCW radar cannot function when the detection object is near the sensor. Therefore, by implementing a single continuous wave (CW) radar for operating in dual-mode, the disadvantages in each mode can be compensated for. In this paper, a dual mode local oscillator (LO) is proposed that makes a CW radar operate as a Doppler or FMCW radar. To make the dual-mode LO, a method that controls the division ratio of the phase locked loop (PLL) is used. To support both radar mode easily, the proposed LO is implemented by adding a frequency sweep generator (FSG) block to a fractional-N PLL. The operation mode of the LO is determined by according to whether this block is operating or not. Since most radar sensors are used in conjunction with microcontroller units (MCUs), the proposed architecture is capable of dual-mode operation by changing only the input control code. In addition, all components such as VCO, LDO, and loop filter are integrated into the chip, so complexity and interface issues can be solved when implementing radar sensors. Thus, the proposed dual-mode LO is suitable as a radar sensor. Full article

(This article belongs to the Special Issue Sensors for Microwave Imaging and Detection)

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13 pages, 21463 KiB

Open AccessArticle

Sensitive and Selective NH₃ Monitoring at Room Temperature Using ZnO Ceramic Nanofibers Decorated with Poly(styrene sulfonate)

by Rafaela S. Andre^1,2,3, Dongwook Kwak⁴, Qiuchen Dong⁵, Wei Zhong⁶, Daniel S. Correa^2,3,*

, Luiz H. C. Mattoso^2,3 and Yu Lei^1,*

¹ Department of Chemical and Biomolecular Engineering, University of Connecticut, 191 Auditorium Road, Storrs, CT 06269, USA

² Nanotechnology National Laboratory for Agriculture (LNNA), Embrapa Instrumentação, São Carlos 13560-970, SP, Brazil

³ PPGQ, Department of Chemistry, Center for Exact Sciences and Technology, Federal University of São Carlos (UFSCar), São Carlos 13565-905, SP, Brazil

⁴ Department of Materials Science and Engineering, University of Connecticut, 97 North Eagleville Road, Storrs, CT 06269, USA

⁵ Department of Biomedical Engineering, University of Connecticut, 260 Glenbrook Road, Storrs, CT 06269, USA

⁶ Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, CT 06269, USA

Sensors 2018, 18(4), 1058; https://doi.org/10.3390/s18041058 - 1 Apr 2018

Cited by 51 | Viewed by 6917

Abstract

Ammonia (NH₃) gas is a prominent air pollutant that is frequently found in industrial and livestock production environments. Due to the importance in controlling pollution and protecting public health, the development of new platforms for sensing NH₃ at room temperature [...] Read more.

Ammonia (NH₃) gas is a prominent air pollutant that is frequently found in industrial and livestock production environments. Due to the importance in controlling pollution and protecting public health, the development of new platforms for sensing NH₃ at room temperature has attracted great attention. In this study, a sensitive NH₃ gas device with enhanced selectivity is developed based on zinc oxide nanofibers (ZnO NFs) decorated with poly(styrene sulfonate) (PSS) and operated at room temperature. ZnO NFs were prepared by electrospinning followed by calcination at 500 °C for 3 h. The electrospun ZnO NFs are characterized to evaluate the properties of the as-prepared sensing materials. The loading of PSS to prepare ZnO NFs/PSS composite is also optimized based on the best sensing performance. Under the optimal composition, ZnO NFs/PSS displays rapid, reversible, and sensitive response upon NH₃ exposure at room temperature. The device shows a dynamic linear range up to 100 ppm and a limit of detection of 3.22 ppm and enhanced selectivity toward NH₃ in synthetic air, against NO₂ and CO, compared to pure ZnO NFs. Additionally, a sensing mechanism is proposed to illustrate the sensing performance using ZnO NFs/PSS composite. Therefore, this study provides a simple methodology to design a sensitive platform for NH₃ monitoring at room temperature. Full article

(This article belongs to the Section Chemical Sensors)

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23 pages, 41316 KiB

Open AccessArticle

A Teleo-Reactive Node for Implementing Internet of Things Systems

by Pedro Sánchez^*

, Bárbara Álvarez, Elías Antolinos

, Diego Fernández and Andrés Iborra

División de Sistemas e Ingeniería Electrónica (DSIE), Universidad Politécnica de Cartagena, Campus Muralla del Mar, s/n, 30202 Cartagena, Murcia, Spain

Sensors 2018, 18(4), 1059; https://doi.org/10.3390/s18041059 - 1 Apr 2018

Cited by 2 | Viewed by 5605

Abstract

The Internet of Things (IoT) is one of today’s main disruptive technologies and, although massive research has been carried out in recent years, there are still some open issues such as the consideration of software engineering methods and tools. We propose the adoption [...] Read more.

The Internet of Things (IoT) is one of today’s main disruptive technologies and, although massive research has been carried out in recent years, there are still some open issues such as the consideration of software engineering methods and tools. We propose the adoption of the Teleo-Reactive approach in order to facilitate the development of Internet of Things systems as a set of communicating Teleo-Reactive nodes. The software behavior of the nodes is specified in terms of goals, perceptions and actions over the environment, achieving higher abstraction than using general-purpose programming languages and therefore, enhancing the involvement of non-technical users in the specification process. Throughout this paper, we describe the elements of a Teleo-Reactive node and a systematic procedure for translating Teleo-Reactive specifications into executable code for Internet of Things devices. The case study of a robotic agent is used in order to validate the whole approach. Full article

(This article belongs to the Section Internet of Things)

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18 pages, 3917 KiB

Open AccessArticle

Sky Detection in Hazy Image

by Yingchao Song^1,2,3,*, Haibo Luo^1,3, Junkai Ma^1,2,3, Bin Hui^1,3 and Zheng Chang^1,3

¹ Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016, China

² University of Chinese Academy of Sciences, Beijing 100049, China

³ Key Laboratory of Opto-Electronic Information Processing, Chinese Academy of Sciences, Shenyang 110016, China

Sensors 2018, 18(4), 1060; https://doi.org/10.3390/s18041060 - 1 Apr 2018

Cited by 17 | Viewed by 5429

Abstract

Sky detection plays an essential role in various computer vision applications. Most existing sky detection approaches, being trained on ideal dataset, may lose efficacy when facing unfavorable conditions like the effects of weather and lighting conditions. In this paper, a novel algorithm for [...] Read more.

Sky detection plays an essential role in various computer vision applications. Most existing sky detection approaches, being trained on ideal dataset, may lose efficacy when facing unfavorable conditions like the effects of weather and lighting conditions. In this paper, a novel algorithm for sky detection in hazy images is proposed from the perspective of probing the density of haze. We address the problem by an image segmentation and a region-level classification. To characterize the sky of hazy scenes, we unprecedentedly introduce several haze-relevant features that reflect the perceptual hazy density and the scene depth. Based on these features, the sky is separated by two imbalance SVM classifiers and a similarity measurement. Moreover, a sky dataset (named HazySky) with 500 annotated hazy images is built for model training and performance evaluation. To evaluate the performance of our method, we conducted extensive experiments both on our HazySky dataset and the SkyFinder dataset. The results demonstrate that our method performs better on the detection accuracy than previous methods, not only under hazy scenes, but also under other weather conditions. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 4798 KiB

Open AccessArticle

Double-Windows-Based Motion Recognition in Multi-Floor Buildings Assisted by a Built-In Barometer

by Maolin Liu¹

, Huaiyu Li^1,2,*

, Yuan Wang¹, Fei Li¹ and Xiuwan Chen¹

¹ Institute of Remote Sensing and GIS, Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871, China

² China Ship Research and Development Academy, No. 2, Shuangquanbao, Chaoyang District, Beijing 100101, China

Sensors 2018, 18(4), 1061; https://doi.org/10.3390/s18041061 - 1 Apr 2018

Cited by 7 | Viewed by 4618

Abstract

Accelerometers, gyroscopes and magnetometers in smartphones are often used to recognize human motions. Since it is difficult to distinguish between vertical motions and horizontal motions in the data provided by these built-in sensors, the vertical motion recognition accuracy is relatively low. The emergence [...] Read more.

Accelerometers, gyroscopes and magnetometers in smartphones are often used to recognize human motions. Since it is difficult to distinguish between vertical motions and horizontal motions in the data provided by these built-in sensors, the vertical motion recognition accuracy is relatively low. The emergence of a built-in barometer in smartphones improves the accuracy of motion recognition in the vertical direction. However, there is a lack of quantitative analysis and modelling of the barometer signals, which is the basis of barometer’s application to motion recognition, and a problem of imbalanced data also exists. This work focuses on using the barometers inside smartphones for vertical motion recognition in multi-floor buildings through modelling and feature extraction of pressure signals. A novel double-windows pressure feature extraction method, which adopts two sliding time windows of different length, is proposed to balance recognition accuracy and response time. Then, a random forest classifier correlation rule is further designed to weaken the impact of imbalanced data on recognition accuracy. The results demonstrate that the recognition accuracy can reach 95.05% when pressure features and the improved random forest classifier are adopted. Specifically, the recognition accuracy of the stair and elevator motions is significantly improved with enhanced response time. The proposed approach proves effective and accurate, providing a robust strategy for increasing accuracy of vertical motions. Full article

(This article belongs to the Special Issue Ubiquitous Massive Sensing Using Smartphones)

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29 pages, 1169 KiB

Open AccessArticle

Mobile Sinks Assisted Geographic and Opportunistic Routing Based Interference Avoidance for Underwater Wireless Sensor Network

by Farwa Ahmed¹, Zahid Wadud², Nadeem Javaid¹

, Nabil Alrajeh^3,*, Mohamad Souheil Alabed³ and Umar Qasim⁴

¹ COMSATS Institute of Information Technology, Islamabad 44000, Pakistan

² University of Engineering and Technology Peshawar, Peshawar 25000, Pakistan

³ Biomedical Technology Department, CAMS, King Saud University, Riyadh 11633, Saudi Arabia

⁴ Cameron Library, University of Alberta, Edmonton, AB T6G 2J8, Canada

Sensors 2018, 18(4), 1062; https://doi.org/10.3390/s18041062 - 2 Apr 2018

Cited by 53 | Viewed by 5444

Abstract

The distinctive features of acoustic communication channel-like high propagation delay, multi-path fading, quick attenuation of acoustic signal, etc. limit the utilization of underwater wireless sensor networks (UWSNs). The immutable selection of forwarder node leads to dramatic death of node resulting in imbalanced energy [...] Read more.

The distinctive features of acoustic communication channel-like high propagation delay, multi-path fading, quick attenuation of acoustic signal, etc. limit the utilization of underwater wireless sensor networks (UWSNs). The immutable selection of forwarder node leads to dramatic death of node resulting in imbalanced energy depletion and void hole creation. To reduce the probability of void occurrence and imbalance energy dissipation, in this paper, we propose mobility assisted geo-opportunistic routing paradigm based on interference avoidance for UWSNs. The network volume is divided into logical small cubes to reduce the interference and to make more informed routing decisions for efficient energy consumption. Additionally, an optimal number of forwarder nodes is elected from each cube based on its proximity with respect to the destination to avoid void occurrence. Moreover, the data packets are recovered from void regions with the help of mobile sinks which also reduce the data traffic on intermediate nodes. Extensive simulations are performed to verify that our proposed work maximizes the network lifetime and packet delivery ratio. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 1820 KiB

Open AccessArticle

Delving Deep into Multiscale Pedestrian Detection via Single Scale Feature Maps

by Xinchuan Fu^1,*

, Rui Yu², Weinan Zhang³, Jie Wu⁴ and Shihai Shao¹

¹ National Key Laboratory of Science and Technology on Communications, University of Electronic Science and Technology of China, Chengdu 611731, China

² Department of Computer Science, University College London, London WC1E 6BT, UK

³ Department of Computer Science & Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

⁴ Department of MOE Research Center for Software/Hardware Co-Design Engineering and Application, East China Normal University, Shanghai 200062, China

Sensors 2018, 18(4), 1063; https://doi.org/10.3390/s18041063 - 2 Apr 2018

Cited by 6 | Viewed by 5258

Abstract

The standard pipeline in pedestrian detection is sliding a pedestrian model on an image feature pyramid to detect pedestrians of different scales. In this pipeline, feature pyramid construction is time consuming and becomes the bottleneck for fast detection. Recently, a method called multiresolution [...] Read more.

The standard pipeline in pedestrian detection is sliding a pedestrian model on an image feature pyramid to detect pedestrians of different scales. In this pipeline, feature pyramid construction is time consuming and becomes the bottleneck for fast detection. Recently, a method called multiresolution filtered channels (MRFC) was proposed which only used single scale feature maps to achieve fast detection. However, there are two shortcomings in MRFC which limit its accuracy. One is that the receptive field correspondence in different scales is weak. Another is that the features used are not scale invariance. In this paper, two solutions are proposed to tackle with the two shortcomings respectively. Specifically, scale-aware pooling is proposed to make a better receptive field correspondence, and soft decision tree is proposed to relive scale variance problem. When coupled with efficient sliding window classification strategy, our detector achieves fast detecting speed at the same time with state-of-the-art accuracy. Full article

(This article belongs to the Special Issue Visual Sensors)

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18 pages, 3745 KiB

Open AccessArticle

Automatic Fabric Defect Detection with a Multi-Scale Convolutional Denoising Autoencoder Network Model

by Shuang Mei^†

, Yudan Wang^† and Guojun Wen^*,†

¹ School of Mechanical Engineering and Electronic Information, China University of Geosciences, Wuhan 430074, China

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1064; https://doi.org/10.3390/s18041064 - 2 Apr 2018

Cited by 269 | Viewed by 21762

Abstract

Fabric defect detection is a necessary and essential step of quality control in the textile manufacturing industry. Traditional fabric inspections are usually performed by manual visual methods, which are low in efficiency and poor in precision for long-term industrial applications. In this paper, [...] Read more.

Fabric defect detection is a necessary and essential step of quality control in the textile manufacturing industry. Traditional fabric inspections are usually performed by manual visual methods, which are low in efficiency and poor in precision for long-term industrial applications. In this paper, we propose an unsupervised learning-based automated approach to detect and localize fabric defects without any manual intervention. This approach is used to reconstruct image patches with a convolutional denoising autoencoder network at multiple Gaussian pyramid levels and to synthesize detection results from the corresponding resolution channels. The reconstruction residual of each image patch is used as the indicator for direct pixel-wise prediction. By segmenting and synthesizing the reconstruction residual map at each resolution level, the final inspection result can be generated. This newly developed method has several prominent advantages for fabric defect detection. First, it can be trained with only a small amount of defect-free samples. This is especially important for situations in which collecting large amounts of defective samples is difficult and impracticable. Second, owing to the multi-modal integration strategy, it is relatively more robust and accurate compared to general inspection methods (the results at each resolution level can be viewed as a modality). Third, according to our results, it can address multiple types of textile fabrics, from simple to more complex. Experimental results demonstrate that the proposed model is robust and yields good overall performance with high precision and acceptable recall rates. Full article

(This article belongs to the Special Issue Sensors Signal Processing and Visual Computing)

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14 pages, 23625 KiB

Open AccessArticle

A New Design of a Single-Device 3D Hall Sensor: Cross-Shaped 3D Hall Sensor

by Wei Tang¹, Fei Lyu², Dunhui Wang¹ and Hongbing Pan^2,*

¹ School of Physics, Nanjing University, Nanjing 210093, China

² School of Electric Science & Engineering, Nanjing University, Nanjing 210093, China

Sensors 2018, 18(4), 1065; https://doi.org/10.3390/s18041065 - 2 Apr 2018

Cited by 11 | Viewed by 6624

Abstract

In this paper, a new single-device three-dimensional (3D) Hall sensor called a cross-shaped 3D Hall device is designed based on the five-contact vertical Hall device. Some of the device parameters are based on 0.18 μm BCDlite^TM technology provided by GLOBALFOUNDRIES. Two-dimensional (2D) [...] Read more.

In this paper, a new single-device three-dimensional (3D) Hall sensor called a cross-shaped 3D Hall device is designed based on the five-contact vertical Hall device. Some of the device parameters are based on 0.18 μm BCDlite^TM technology provided by GLOBALFOUNDRIES. Two-dimensional (2D) and 3D finite element models implemented in COMSOL are applied to understand the device behavior under a constant magnetic field. Besides this, the influence of the sensing contacts, active region’s depth, and P-type layers are taken into account by analyzing the distribution of the voltage along the top edge and the current density inside the devices. Due to the short-circuiting effect, the sensing contacts lead to degradation in sensitivities. The P-type layers and a deeper active region in turn are responsible for the improvement of sensitivities. To distinguish the P-type layer from the active region which plays the dominant role in reducing the short-circuiting effect, the current-related sensitivity of the top edge (S_top) is defined. It is found that the short-circuiting effect fades as the depth of the active region grows. Despite the P-type layers, the behavior changes a little. When the depth of the active region is 7 μm and the thickness of the P-type layers is 3 μm, the sensitivities in the x, y, and z directions can reach 91.70 V/AT, 92.36 V/AT, and 87.10 V/AT, respectively. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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17 pages, 49231 KiB

Open AccessArticle

Sparse Reconstruction Based Robust Near-Field Source Localization Algorithm

by Sen Li, Bing Li, Bin Lin, Xiaofang Tang and Rongxi He^*

College of Information and Science Technology, Dalian Maritime University, Dalian 116026, China

Sensors 2018, 18(4), 1066; https://doi.org/10.3390/s18041066 - 2 Apr 2018

Cited by 11 | Viewed by 3740

Abstract

Non-Gaussian impulsive noise widely exists in the real world, this paper takes the α-stable distribution as the mathematical model of non-Gaussian impulsive noise and works on the joint direction-of-arrival (DOA) and range estimation problem of near-field signals in impulsive noise environment. Since the [...] Read more.

Non-Gaussian impulsive noise widely exists in the real world, this paper takes the α-stable distribution as the mathematical model of non-Gaussian impulsive noise and works on the joint direction-of-arrival (DOA) and range estimation problem of near-field signals in impulsive noise environment. Since the conventional algorithms based on the classical second order correlation statistics degenerate severely in the impulsive noise environment, this paper adopts two robust correlations, the fractional lower order correlation (FLOC) and the nonlinear transform correlation (NTC), and presents two related near-field localization algorithms. In our proposed algorithms, by exploring the symmetrical characteristic of the array, we construct the robust far-field approximate correlation vector in relation with the DOA only, which allows for bearing estimation based on the sparse reconstruction. With the estimated bearing, the range can consequently be obtained by the sparse reconstruction of the output of a virtual array. The proposed algorithms have the merits of good noise suppression ability, and their effectiveness is demonstrated by the computer simulation results. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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18 pages, 29678 KiB

Open AccessArticle

Artifact Noise Removal Techniques on Seismocardiogram Using Two Tri-Axial Accelerometers

by Loc Luu and Anh Dinh^*

Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada

Sensors 2018, 18(4), 1067; https://doi.org/10.3390/s18041067 - 2 Apr 2018

Cited by 15 | Viewed by 5346

Abstract

The aim of this study is on the investigation of motion noise removal techniques using two-accelerometer sensor system and various placements of the sensors on gentle movement and walking of the patients. A Wi-Fi based data acquisition system and a framework on Matlab [...] Read more.

The aim of this study is on the investigation of motion noise removal techniques using two-accelerometer sensor system and various placements of the sensors on gentle movement and walking of the patients. A Wi-Fi based data acquisition system and a framework on Matlab are developed to collect and process data while the subjects are in motion. The tests include eight volunteers who have no record of heart disease. The walking and running data on the subjects are analyzed to find the minimal-noise bandwidth of the SCG signal. This bandwidth is used to design filters in the motion noise removal techniques and peak signal detection. There are two main techniques of combining signals from the two sensors to mitigate the motion artifact: analog processing and digital processing. The analog processing comprises analog circuits performing adding or subtracting functions and bandpass filter to remove artifact noises before entering the data acquisition system. The digital processing processes all the data using combinations of total acceleration and z-axis only acceleration. The two techniques are tested on three placements of accelerometer sensors including horizontal, vertical, and diagonal on gentle motion and walking. In general, the total acceleration and z-axis acceleration are the best techniques to deal with gentle motion on all sensor placements which improve average systolic signal-noise-ratio (SNR) around 2 times and average diastolic SNR around 3 times comparing to traditional methods using only one accelerometer. With walking motion, ADDER and z-axis acceleration are the best techniques on all placements of the sensors on the body which enhance about 7 times of average systolic SNR and about 11 times of average diastolic SNR comparing to only one accelerometer method. Among the sensor placements, the performance of horizontal placement of the sensors is outstanding comparing with other positions on all motions. Full article

(This article belongs to the Section Biosensors)

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17 pages, 26498 KiB

Open AccessArticle

A High Throughput Integrated Hyperspectral Imaging and 3D Measurement System

by Huijie Zhao, Lunbao Xu, Shaoguang Shi, Hongzhi Jiang^* and Da Chen

School of Instrumentation Science and Opto-electronics Engineering, Beihang University, Beijing 100191, China

Sensors 2018, 18(4), 1068; https://doi.org/10.3390/s18041068 - 2 Apr 2018

Cited by 17 | Viewed by 6061

Abstract

Hyperspectral and three-dimensional measurements can obtain the intrinsic physicochemical properties and external geometrical characteristics of objects, respectively. The combination of these two kinds of data can provide new insights into objects, which has gained attention in the fields of agricultural management, plant phenotyping, [...] Read more.

Hyperspectral and three-dimensional measurements can obtain the intrinsic physicochemical properties and external geometrical characteristics of objects, respectively. The combination of these two kinds of data can provide new insights into objects, which has gained attention in the fields of agricultural management, plant phenotyping, cultural heritage conservation, and food production. Currently, a variety of sensors are integrated into a system to collect spectral and morphological information in agriculture. However, previous experiments were usually performed with several commercial devices on a single platform. Inadequate registration and synchronization among instruments often resulted in mismatch between spectral and 3D information of the same target. In addition, using slit-based spectrometers and point-based 3D sensors extends the working hours in farms due to the narrow field of view (FOV). Therefore, we propose a high throughput prototype that combines stereo vision and grating dispersion to simultaneously acquire hyperspectral and 3D information. Furthermore, fiber-reformatting imaging spectrometry (FRIS) is adopted to acquire the hyperspectral images. Test experiments are conducted for the verification of the system accuracy, and vegetation measurements are carried out to demonstrate its feasibility. The proposed system is an improvement in multiple data acquisition and has the potential to improve plant phenotyping. Full article

(This article belongs to the Special Issue Multispectral and Hyperspectral Instrumentation)

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10 pages, 3623 KiB

Open AccessArticle

Detection of Metallothionein in Javanese Medaka (Oryzias javanicus), Using a scFv-Immobilized Protein Chip

by Euiyeon Lee^1,†, Hyunjin Jeon^1,†, Chungwon Kang¹, Seonock Woo^2,3, Seungshic Yum^2,3 and Youngeun Kwon^1,*

¹ Department of Biomedical Engineering, Dongguk University, Seoul 04620, Korea

² Faculty of Marine Environmental Science, University of Science and Technology (UST), Geoje 53201, Korea

³ South Sea Environment Research Center, Korea Institute of Ocean Science and Technology (KIOST), Geoje 53201, Korea

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1069; https://doi.org/10.3390/s18041069 - 2 Apr 2018

Cited by 5 | Viewed by 5598

Abstract

Environmental pollution by various industrial chemicals and biological agents poses serious risks to human health. Especially, marine contamination by potentially toxic elements (PTEs) has become a global concern in recent years. Many efforts have been undertaken to monitor the PTE contamination of the [...] Read more.

Environmental pollution by various industrial chemicals and biological agents poses serious risks to human health. Especially, marine contamination by potentially toxic elements (PTEs) has become a global concern in recent years. Many efforts have been undertaken to monitor the PTE contamination of the aquatic environment. However, there are few approaches available to assess the PTE exposure of aquatic organisms. In this research, we developed a strategy to evaluate the heavy metal exposure of marine organisms, by measuring the expression levels of metallothionein protein derived from Oryzias javanicus (OjaMT). OjaMT is a biomarker of heavy metal exposure because the expression level increases upon heavy metal exposure. The developed assay is based on a real-time, label-free surface plasmon resonance (SPR) measurement. Anti-OjaMT antibody and anti-OjaMT single-chain fragment of variable region (scFv) were used as detection probes. Two types of SPR sensor chips were fabricated, by immobilizing antibody or Cys3-tagged scFv (scFv-Cys3) in a controlled orientation and were tested for in situ label-free OjaMT detection. Compared to the antibody-presenting sensor chips, the scFv-presenting sensor chips showed improved performance, displaying enhanced sensitivity and enabling semi-quantitative detection. The portable SPR system combined with scFv-immobilized sensor chips is expected to provide an excellent point-of-care testing system that can monitor target biomarkers in real time. Full article

(This article belongs to the Special Issue Environmental Monitoring Biosensors)

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14 pages, 19468 KiB

Open AccessArticle

Quantitative Detection of Cracks in Steel Using Eddy Current Pulsed Thermography

by Zhanqun Shi, Xiaoyu Xu, Jiaojiao Ma, Dong Zhen^*

and Hao Zhang

School of Mechanical Engineering, Hebei University of Technology, Tianjin 300130, China

Sensors 2018, 18(4), 1070; https://doi.org/10.3390/s18041070 - 2 Apr 2018

Cited by 34 | Viewed by 5305

Abstract

Small cracks are common defects in steel and often lead to catastrophic accidents in industrial applications. Various nondestructive testing methods have been investigated for crack detection; however, most current methods focus on qualitative crack identification and image processing. In this study, eddy current [...] Read more.

Small cracks are common defects in steel and often lead to catastrophic accidents in industrial applications. Various nondestructive testing methods have been investigated for crack detection; however, most current methods focus on qualitative crack identification and image processing. In this study, eddy current pulsed thermography (ECPT) was applied for quantitative crack detection based on derivative analysis of temperature variation. The effects of the incentive parameters on the temperature variation were analyzed in the simulation study. The crack profile and position are identified in the thermal image based on the Canny edge detection algorithm. Then, one or more trajectories are determined through the crack profile in order to determine the crack boundary through its temperature distribution. The slope curve along the trajectory is obtained. Finally, quantitative analysis of the crack sizes was performed by analyzing the features of the slope curves. The experimental verification showed that the crack sizes could be quantitatively detected with errors of less than 1%. Therefore, the proposed ECPT method was demonstrated to be a feasible and effective nondestructive approach for quantitative crack detection. Full article

(This article belongs to the Special Issue Intelligent Sensing Technologies for Nondestructive Evaluation 2018)

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12 pages, 12861 KiB

Open AccessArticle

Naked-Eye Detection of Glucose in Saliva with Bienzymatic Paper-Based Sensor

by Luis A. Santana-Jiménez¹, Alfredo Márquez-Lucero², Velia Osuna³

, Ivan Estrada-Moreno³

and Rocio B. Dominguez^3,*

¹ Center for Research in Advanced Materials (CIMAV S.C.), Miguel de Cervantes 120, 31136 Chihuahua, Mexico

² CIMAV S.C., Ejido Arroyo Seco, 34147 Durango, Mexico

³ CONACyT-CIMAV S.C., Miguel de Cervantes 120, 31136 Chihuahua, Mexico

Sensors 2018, 18(4), 1071; https://doi.org/10.3390/s18041071 - 3 Apr 2018

Cited by 54 | Viewed by 9408

Abstract

The high incidence of Diabetes Mellitus in low-income regions has promoted the development of low-cost alternatives to replace blood-based procedures. In this work, we present a bienzymatic paper-based sensor suitable for the naked-eye detection of glucose in saliva samples. The sensor was obtained [...] Read more.

The high incidence of Diabetes Mellitus in low-income regions has promoted the development of low-cost alternatives to replace blood-based procedures. In this work, we present a bienzymatic paper-based sensor suitable for the naked-eye detection of glucose in saliva samples. The sensor was obtained by a stamping procedure and modified with chitosan to improve the colorimetric readout. The bienzymatic reaction of GOx-HRP coupled with 2,4,6-tribromo-3-hydroxy benzoic acid was applied for the detection of glucose within a range from 0 to 180 mgdL⁻¹ in buffer and artificial saliva solutions. The visual readout was perceived by the naked eye and registered with an office scanner to evaluate the analytical performance. The results showed a limit of detection of 0.37 mgdL⁻¹ (S/N = 3) with an R.S.D. of 1.69% and a linear range from 1 to 22.5 mgdL⁻¹ with an R² of 0.99235. The analysis of human saliva samples was performed without pre-processing, achieving recoveries from 92 to 114%. The naked-eye detection was evaluated under two different light settings, showing average recoveries of 108.58 and 90.65% for standard and low illumination. The proposed device showed potential for easy-to-use, sensitive, low-cost, fast, and device-free detection of salivary glucose suitable for untrained personnel operation and limited facilities. Full article

(This article belongs to the Section Biosensors)

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13 pages, 11669 KiB

Open AccessArticle

Effects of Cable Sway, Electrode Surface Area, and Electrode Mass on Electroencephalography Signal Quality during Motion

by Evangelia-Regkina Symeonidou^1,2,3,*, Andrew D. Nordin¹, W. David Hairston⁴ and Daniel P. Ferris¹

¹ J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611, USA

² Max Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany

³ International Max Planck Research School for Cognitive and Systems Neuroscience, 72074 Tübingen, Germany

⁴ U. S. Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, MD 21005, USA

Sensors 2018, 18(4), 1073; https://doi.org/10.3390/s18041073 - 3 Apr 2018

Cited by 83 | Viewed by 10401

Abstract

More neuroscience researchers are using scalp electroencephalography (EEG) to measure electrocortical dynamics during human locomotion and other types of movement. Motion artifacts corrupt the EEG and mask underlying neural signals of interest. The cause of motion artifacts in EEG is often attributed to [...] Read more.

More neuroscience researchers are using scalp electroencephalography (EEG) to measure electrocortical dynamics during human locomotion and other types of movement. Motion artifacts corrupt the EEG and mask underlying neural signals of interest. The cause of motion artifacts in EEG is often attributed to electrode motion relative to the skin, but few studies have examined EEG signals under head motion. In the current study, we tested how motion artifacts are affected by the overall mass and surface area of commercially available electrodes, as well as how cable sway contributes to motion artifacts. To provide a ground-truth signal, we used a gelatin head phantom with embedded antennas broadcasting electrical signals, and recorded EEG with a commercially available electrode system. A robotic platform moved the phantom head through sinusoidal displacements at different frequencies (0–2 Hz). Results showed that a larger electrode surface area can have a small but significant effect on improving EEG signal quality during motion and that cable sway is a major contributor to motion artifacts. These results have implications in the development of future hardware for mobile brain imaging with EEG. Full article

(This article belongs to the Special Issue Novel Sensors for Bioimaging)

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19 pages, 16377 KiB

Open AccessArticle

Semantic Edge Based Disparity Estimation Using Adaptive Dynamic Programming for Binocular Sensors

by Dongchen Zhu^1,2,*, Jiamao Li¹, Xianshun Wang^1,2, Jingquan Peng^1,2,3, Wenjun Shi^1,2 and Xiaolin Zhang¹

¹ Bio-Vision System Laboratory, State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China

² University of Chinese Academy of Sciences, Beijing 100049, China

³ School of Information Science and Technology, ShanghaiTech University, Shanghai 201210, China

Sensors 2018, 18(4), 1074; https://doi.org/10.3390/s18041074 - 3 Apr 2018

Cited by 6 | Viewed by 4529

Abstract

Disparity calculation is crucial for binocular sensor ranging. The disparity estimation based on edges is an important branch in the research of sparse stereo matching and plays an important role in visual navigation. In this paper, we propose a robust sparse stereo matching [...] Read more.

Disparity calculation is crucial for binocular sensor ranging. The disparity estimation based on edges is an important branch in the research of sparse stereo matching and plays an important role in visual navigation. In this paper, we propose a robust sparse stereo matching method based on the semantic edges. Some simple matching costs are used first, and then a novel adaptive dynamic programming algorithm is proposed to obtain optimal solutions. This algorithm makes use of the disparity or semantic consistency constraint between the stereo images to adaptively search parameters, which can improve the robustness of our method. The proposed method is compared quantitatively and qualitatively with the traditional dynamic programming method, some dense stereo matching methods, and the advanced edge-based method respectively. Experiments show that our method can provide superior performance on the above comparison. Full article

(This article belongs to the Section Intelligent Sensors)

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10 pages, 18508 KiB

Open AccessArticle

Radio Frequency Detection and Characterization of Water-Ethanol Solution through Spiral-Coupled Passive Micro-Resonator Sensor

by Gyan Raj Koirala¹

, Rajendra Dhakal^1,2

, Eun-Seong Kim¹

, Zhao Yao¹ and Nam-Young Kim^1,*

¹ RFIC Lab, Department of Electronic Engineering, Kwangwoon University, 01897 Seoul, Korea

² Department of Computer Science and Engineering, Sejong University, 05006 Seoul, Korea

Sensors 2018, 18(4), 1075; https://doi.org/10.3390/s18041075 - 3 Apr 2018

Cited by 11 | Viewed by 6392

Abstract

We present a microfabricated spiral-coupled passive resonator sensor realized through integrated passive device (IPD) technology for the sensitive detection and characterization of water-ethanol solutions. In order to validate the performance of the proposed device, we explicitly measured and analyzed the radio frequency (RF) [...] Read more.

We present a microfabricated spiral-coupled passive resonator sensor realized through integrated passive device (IPD) technology for the sensitive detection and characterization of water-ethanol solutions. In order to validate the performance of the proposed device, we explicitly measured and analyzed the radio frequency (RF) characteristics of various water-ethanol solution compositions. The measured results showed a drift in the resonance frequency from 1.16 GHz for deionized (DI) water to 1.68 GHz for the solution containing 50% ethanol, whereas the rejection level given by the reflection coefficient decreased from −29.74 dB to −14.81 dB. The obtained limit of detection was 3.82% volume composition of ethanol in solution. The derived loaded capacitance was 21.76 pF for DI water, which gradually decreased to 8.70 pF for the 50% ethanol solution, and the corresponding relative permittivity of the solution decreased from 80.14 to 47.79. The dissipation factor increased with the concentration of ethanol in the solution. We demonstrated the reproducibility of the proposed sensor through iterative measures of the samples and the study of surface morphology. Successive measurement of different samples had no overlapping and had very minimum bias between RF characteristics for each measured sample. The surface profile for bare sensors was retained after the sample test, resulting a root mean square (RMS) value of 11.416 nm as compared to 10.902 nm for the bare test. The proposed sensor was shown to be a viable alternative to existing sensors for highly sensitive water-ethanol concentration detection. Full article

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17 pages, 29268 KiB

Open AccessArticle

Noise Source Visualization Using a Digital Voice Recorder and Low-Cost Sensors

by Yong Thung Cho

Division of Mechanical and Automotive Engineering, Kongju National University, Cheonan, Chungnam 31080, Korea

Sensors 2018, 18(4), 1076; https://doi.org/10.3390/s18041076 - 3 Apr 2018

Cited by 1 | Viewed by 5047

Abstract

Accurate sound visualization of noise sources is required for optimal noise control. Typically, noise measurement systems require microphones, an analog-digital converter, cables, a data acquisition system, etc., which may not be affordable for potential users. Also, many such systems are not highly portable [...] Read more.

Accurate sound visualization of noise sources is required for optimal noise control. Typically, noise measurement systems require microphones, an analog-digital converter, cables, a data acquisition system, etc., which may not be affordable for potential users. Also, many such systems are not highly portable and may not be convenient for travel. Handheld personal electronic devices such as smartphones and digital voice recorders with relatively lower costs and higher performance have become widely available recently. Even though such devices are highly portable, directly implementing them for noise measurement may lead to erroneous results since such equipment was originally designed for voice recording. In this study, external microphones were connected to a digital voice recorder to conduct measurements and the input received was processed for noise visualization. In this way, a low cost, compact sound visualization system was designed and introduced to visualize two actual noise sources for verification with different characteristics: an enclosed loud speaker and a small air compressor. Reasonable accuracy of noise visualization for these two sources was shown over a relatively wide frequency range. This very affordable and compact sound visualization system can be used for many actual noise visualization applications in addition to educational purposes. Full article

(This article belongs to the Section Sensor Networks)

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11 pages, 8935 KiB

Open AccessArticle

Three-Dimensional Modeling of Weed Plants Using Low-Cost Photogrammetry

by Dionisio Andújar^1,*, Mikel Calle²

, César Fernández-Quintanilla¹, Ángela Ribeiro³

and José Dorado¹

¹ Institute of Agricultural Sciences, CSIC, 28006 Madrid, Spain

² National Museum of Natural Sciences, CSIC, 28006 Madrid, Spain

³ Centre for Automation and Robotics, CSIC-UPM, Arganda del Rey, 28500 Madrid, Spain

Sensors 2018, 18(4), 1077; https://doi.org/10.3390/s18041077 - 3 Apr 2018

Cited by 48 | Viewed by 6772

Abstract

Sensing advances in plant phenotyping are of vital importance in basic and applied plant research. Plant phenotyping enables the modeling of complex shapes, which is useful, for example, in decision-making for agronomic management. In this sense, 3D processing algorithms for plant modeling is [...] Read more.

Sensing advances in plant phenotyping are of vital importance in basic and applied plant research. Plant phenotyping enables the modeling of complex shapes, which is useful, for example, in decision-making for agronomic management. In this sense, 3D processing algorithms for plant modeling is expanding rapidly with the emergence of new sensors and techniques designed to morphologically characterize. However, there are still some technical aspects to be improved, such as an accurate reconstruction of end-details. This study adapted low-cost techniques, Structure from Motion (SfM) and MultiView Stereo (MVS), to create 3D models for reconstructing plants of three weed species with contrasting shape and plant structures. Plant reconstruction was developed by applying SfM algorithms to an input set of digital images acquired sequentially following a track that was concentric and equidistant with respect to the plant axis and using three different angles, from a perpendicular to top view, which guaranteed the necessary overlap between images to obtain high precision 3D models. With this information, a dense point cloud was created using MVS, from which a 3D polygon mesh representing every plants’ shape and geometry was generated. These 3D models were validated with ground truth values (e.g., plant height, leaf area (LA) and plant dry biomass) using regression methods. The results showed, in general, a good consistency in the correlation equations between the estimated values in the models and the actual values measured in the weed plants. Indeed, 3D modeling using SfM algorithms proved to be a valuable methodology for weed phenotyping, since it accurately estimated the actual values of plant height and LA. Additionally, image processing using the SfM method was relatively fast. Consequently, our results indicate the potential of this budget system for plant reconstruction at high detail, which may be usable in several scenarios, including outdoor conditions. Future research should address other issues, such as the time-cost relationship and the need for detail in the different approaches. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2018)

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18 pages, 7888 KiB

Open AccessArticle

Multi-GNSS PPP-RTK: From Large- to Small-Scale Networks

by Nandakumaran Nadarajah¹, Amir Khodabandeh¹

, Kan Wang¹

, Mazher Choudhury¹ and Peter J. G. Teunissen^1,2,*

¹ GNSS Research Centre, Department of Spatial Sciences, Curtin University, Perth, WA 6845, Australia

² Department of Geoscience and Remote Sensing, Delft University of Technology, 2628 CN, Delft, The Netherlands

Sensors 2018, 18(4), 1078; https://doi.org/10.3390/s18041078 - 3 Apr 2018

Cited by 78 | Viewed by 8388

Abstract

Precise point positioning (PPP) and its integer ambiguity resolution-enabled variant, PPP-RTK (real-time kinematic), can benefit enormously from the integration of multiple global navigation satellite systems (GNSS). In such a multi-GNSS landscape, the positioning convergence time is expected to be reduced considerably as compared [...] Read more.

Precise point positioning (PPP) and its integer ambiguity resolution-enabled variant, PPP-RTK (real-time kinematic), can benefit enormously from the integration of multiple global navigation satellite systems (GNSS). In such a multi-GNSS landscape, the positioning convergence time is expected to be reduced considerably as compared to the one obtained by a single-GNSS setup. It is therefore the goal of the present contribution to provide numerical insights into the role taken by the multi-GNSS integration in delivering fast and high-precision positioning solutions (sub-decimeter and centimeter levels) using PPP-RTK. To that end, we employ the Curtin PPP-RTK platform and process data-sets of GPS, BeiDou Navigation Satellite System (BDS) and Galileo in stand-alone and combined forms. The data-sets are collected by various receiver types, ranging from high-end multi-frequency geodetic receivers to low-cost single-frequency mass-market receivers. The corresponding stations form a large-scale (Australia-wide) network as well as a small-scale network with inter-station distances less than 30 km. In case of the Australia-wide GPS-only ambiguity-float setup, 90% of the horizontal positioning errors (kinematic mode) are shown to become less than five centimeters after 103 min. The stated required time is reduced to 66 min for the corresponding GPS + BDS + Galieo setup. The time is further reduced to 15 min by applying single-receiver ambiguity resolution. The outcomes are supported by the positioning results of the small-scale network. Full article

(This article belongs to the Section Remote Sensors)

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23 pages, 3456 KiB

Open AccessArticle

Clustering and Flow Conservation Monitoring Tool for Software Defined Networks

by Jesús Antonio Puente Fernández^1,†, Luis Javier García Villalba^1,*,†

and Tai-Hoon Kim^2,†

¹ Group of Analysis, Security and Systems (GASS), Department of Software Engineering and Artificial Intelligence (DISIA), Faculty of Computer Science and Engineering, Office 431, Universidad Complutense de Madrid (UCM), Calle Profesor José García Santesmases 9, Ciudad Universitaria, 28040 Madrid, Spain

² Department of Convergence Security, Sungshin Women’s University, 249-1 Dongseon-Dong 3-ga, Seoul 136-742, Korea

^† Those authors contributed equally to this work.

Sensors 2018, 18(4), 1079; https://doi.org/10.3390/s18041079 - 3 Apr 2018

Cited by 3 | Viewed by 4317

Abstract

Prediction systems present some challenges on two fronts: the relation between video quality and observed session features and on the other hand, dynamics changes on the video quality. Software Defined Networks (SDN) is a new concept of network architecture that provides the separation [...] Read more.

Prediction systems present some challenges on two fronts: the relation between video quality and observed session features and on the other hand, dynamics changes on the video quality. Software Defined Networks (SDN) is a new concept of network architecture that provides the separation of control plane (controller) and data plane (switches) in network devices. Due to the existence of the southbound interface, it is possible to deploy monitoring tools to obtain the network status and retrieve a statistics collection. Therefore, achieving the most accurate statistics depends on a strategy of monitoring and information requests of network devices. In this paper, we propose an enhanced algorithm for requesting statistics to measure the traffic flow in SDN networks. Such an algorithm is based on grouping network switches in clusters focusing on their number of ports to apply different monitoring techniques. Such grouping occurs by avoiding monitoring queries in network switches with common characteristics and then, by omitting redundant information. In this way, the present proposal decreases the number of monitoring queries to switches, improving the network traffic and preventing the switching overload. We have tested our optimization in a video streaming simulation using different types of videos. The experiments and comparison with traditional monitoring techniques demonstrate the feasibility of our proposal maintaining similar values decreasing the number of queries to the switches. Full article

(This article belongs to the Special Issue Advances on Resources Management for Multi-Platform Infrastructures)

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30 pages, 2828 KiB

Open AccessArticle

TwitterSensing: An Event-Based Approach for Wireless Sensor Networks Optimization Exploiting Social Media in Smart City Applications

by Daniel G. Costa^1,*,†

, Cristian Duran-Faundez^2,†

, Daniel C. Andrade^1,†

, João B. Rocha-Junior^3,†

and João Paulo Just Peixoto^3,†

¹ Department of Technology, State University of Feira de Santana, Feira de Santana 44036-900, Brazil

² Department of Electrical and Electronic Engineering, University of the Bio-Bio, Collao, Region del Bio Bio, Concepcion 1202, Chile

³ Department of Exact Sciences, State University of Feira de Santana, Feira de Santana 44036-900, Brazil

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1080; https://doi.org/10.3390/s18041080 - 3 Apr 2018

Cited by 32 | Viewed by 9284

Abstract

Modern cities are subject to periodic or unexpected critical events, which may bring economic losses or even put people in danger. When some monitoring systems based on wireless sensor networks are deployed, sensing and transmission configurations of sensor nodes may be adjusted exploiting [...] Read more.

Modern cities are subject to periodic or unexpected critical events, which may bring economic losses or even put people in danger. When some monitoring systems based on wireless sensor networks are deployed, sensing and transmission configurations of sensor nodes may be adjusted exploiting the relevance of the considered events, but efficient detection and classification of events of interest may be hard to achieve. In Smart City environments, several people spontaneously post information in social media about some event that is being observed and such information may be mined and processed for detection and classification of critical events. This article proposes an integrated approach to detect and classify events of interest posted in social media, notably in Twitter, and the assignment of sensing priorities to source nodes. By doing so, wireless sensor networks deployed in Smart City scenarios can be optimized for higher efficiency when monitoring areas under the influence of the detected events. Full article

(This article belongs to the Special Issue The Architectures, Systems, and Applications of Internet of Things for Smart Cities)

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18 pages, 39360 KiB

Open AccessArticle

An Azimuth Antenna Pattern Estimation Method Based on Doppler Spectrum in SAR Ocean Images

by Hui Meng^1,2,3

, Xiaoqing Wang^4,* and Jinsong Chong^1,2,*

¹ National Key Laboratory of Science and Technology on Microwave Imaging, Beijing 100190, China

² Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

³ School of Electronics, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China

⁴ Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China

Sensors 2018, 18(4), 1081; https://doi.org/10.3390/s18041081 - 3 Apr 2018

Cited by 4 | Viewed by 5006

Abstract

In synthetic aperture radar (SAR) ocean remote sensing, it is very difficult to estimate an accurate azimuth antenna pattern (AAP) from low-scattering SAR images without strong scattering targets. Therefore, an azimuth antenna pattern estimation method based on Doppler spectrum in SAR ocean images [...] Read more.

In synthetic aperture radar (SAR) ocean remote sensing, it is very difficult to estimate an accurate azimuth antenna pattern (AAP) from low-scattering SAR images without strong scattering targets. Therefore, an azimuth antenna pattern estimation method based on Doppler spectrum in SAR ocean images is proposed in this paper. In order to preserve the complete AAP information, an azimuth unweighted matched filter is used to re-image the SAR raw data in the proposed method. Then, the shape factor of AAP can be obtained by linear statistics of the relationship between Doppler center and edge frequency spectrum in Doppler spectrum of each distance gate. In addition, the impact of the uniformity and signal-to-noise ratio of SAR ocean images on the estimation results are also analyzed by simulation. Finally, the feasibility of proposed method is verified by data from ERS-2 (European remote sensing satellite (ERS) was the European Space Agency’s first Earth-observing satellite). Experimental results show that the AAP estimated by proposed method has a good estimation result. Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 13266 KiB

Open AccessArticle

Rapid Determination of Thiabendazole Pesticides in Rape by Surface Enhanced Raman Spectroscopy

by Lei Lin^1,2,†, Tao Dong^1,2,†

, Pengcheng Nie^1,2,3, Fangfang Qu^1,2, Yong He^1,2,*

, Bingquan Chu^1,2 and Shupei Xiao^1,2

¹ College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China

² Key Laboratory of Sensors Sensing, Ministry of Agriculture, Hangzhou 310058, China

³ State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310058, China

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1082; https://doi.org/10.3390/s18041082 - 4 Apr 2018

Cited by 51 | Viewed by 7284

Abstract

Thiabendazole is widely used in sclerotium blight, downy mildew and black rot prevention and treatment in rape. Accurate monitoring of thiabendazole pesticides in plants will prevent potential adverse effects to the Environment and human health. Surface Enhanced Raman Spectroscopy (SERS) is a highly [...] Read more.

Thiabendazole is widely used in sclerotium blight, downy mildew and black rot prevention and treatment in rape. Accurate monitoring of thiabendazole pesticides in plants will prevent potential adverse effects to the Environment and human health. Surface Enhanced Raman Spectroscopy (SERS) is a highly sensitive fingerprint with the advantages of simple operation, convenient portability and high detection efficiency. In this paper, a rapid determination method of thiabendazole pesticides in rape was conducted combining SERS with chemometric methods. The original SERS were pretreated and the partial least squares (PLS) was applied to establish the prediction model between SERS and thiabendazole pesticides in rape. As a result, the SERS enhancing effect based on silver Nano-substrate was better than that of gold Nano-substrate, where the detection limit of thiabendazole pesticides in rape could reach 0.1 mg/L. Moreover, 782, 1007 and 1576 cm⁻¹ could be determined as thiabendazole pesticides Raman characteristic peaks in rape. The prediction effect of thiabendazole pesticides in rape was the best (

R_{p}^{2}

= 0.94, RMSEP = 3.17 mg/L) after the original spectra preprocessed with 1st-Derivative, and the linear relevance between thiabendazole pesticides concentration and Raman peak intensity at 782 cm⁻¹ was the highest (R² = 0.91). Furthermore, five rape samples with unknown thiabendazole pesticides concentration were used to verify the accuracy and reliability of this method. It was showed that prediction relative standard deviation was 0.70–9.85%, recovery rate was 94.71–118.92% and t value was −1.489. In conclusion, the thiabendazole pesticides in rape could be rapidly and accurately detected by SERS, which was beneficial to provide a rapid, accurate and reliable scheme for the detection of pesticides residues in agriculture products. Full article

(This article belongs to the Special Issue Applications of Raman Spectroscopy in Sensors)

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12 pages, 17537 KiB

Open AccessArticle

Micro-Capillary Coatings Based on Spiropyran Polymeric Brushes for Metal Ion Binding, Detection, and Release in Continuous Flow

by Aishling Dunne¹, Colm Delaney¹

, Aoife McKeon^1,†, Pavel Nesterenko²

, Brett Paull², Fernando Benito-Lopez^3,*, Dermot Diamond¹

and Larisa Florea^1,*

¹ Insight Centre for Data Analytics, National Centre for Sensor Research, Dublin City University, Dublin 9, Ireland

² Australian Centre for Research on Separation Science, and ARC Centre of Excellence for Electromaterials Science, Hobart, Tasmania 7001, Australia

³ Analytical Microsystems & Materials for Lab-on-a-Chip (AMMa-LOAC) Group, Microfluidics Cluster UPV/EHU, Analytical Chemistry Department, University of the Basque Country UPV/EHU, Vitoria-Gasteiz 01006, Spain

^† Current Address: Centre for Synthesis and Chemical Biology, Department of Pharmaceutical and Medicinal Chemistry, Royal College of Surgeons in Ireland, 123 St. Stephens Green, Dublin 2 D02 YN77, Ireland.

Sensors 2018, 18(4), 1083; https://doi.org/10.3390/s18041083 - 4 Apr 2018

Cited by 16 | Viewed by 6253

Abstract

Micro-capillaries, capable of light-regulated binding and qualitative detection of divalent metal ions in continuous flow, have been realised through functionalisation with spiropyran photochromic brush-type coatings. Upon irradiation with UV light, the coating switches from the passive non-binding spiropyran form to the active merocyanine [...] Read more.

Micro-capillaries, capable of light-regulated binding and qualitative detection of divalent metal ions in continuous flow, have been realised through functionalisation with spiropyran photochromic brush-type coatings. Upon irradiation with UV light, the coating switches from the passive non-binding spiropyran form to the active merocyanine form, which binds different divalent metal ions (Zn²⁺, Co²⁺, Cu²⁺, Ni²⁺, Cd²⁺), as they pass through the micro-capillary. Furthermore, the merocyanine visible absorbance spectrum changes upon metal ion binding, enabling the ion uptake to be detected optically. Irradiation with white light causes reversion of the merocyanine to the passive spiropyran form, with simultaneous release of the bound metal ion from the micro-capillary coating. Full article

(This article belongs to the Special Issue I3S 2017 Selected Papers)

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19 pages, 1715 KiB

Open AccessArticle

An In-Vitro Optical Sensor Designed to Estimate Glycated Hemoglobin Levels

by Sanghamitra Mandal^* and M. O. Manasreh

Department of Electrical Engineering, University of Arkansas, Fayetteville, AR 72701, USA

Sensors 2018, 18(4), 1084; https://doi.org/10.3390/s18041084 - 4 Apr 2018

Cited by 26 | Viewed by 6974

Abstract

The purpose of this research was to design an optical sensor for evaluating glycated hemoglobin (HbA1c) percentages in hemoglobin. The A1c sensors available in the market use invasive methods, while our device offers the possibility of non-invasive monitoring of HbA1c levels in diabetic [...] Read more.

The purpose of this research was to design an optical sensor for evaluating glycated hemoglobin (HbA1c) percentages in hemoglobin. The A1c sensors available in the market use invasive methods, while our device offers the possibility of non-invasive monitoring of HbA1c levels in diabetic patients. A prototype is assembled using two light emitting diodes with peak emission wavelengths of 535 nm and 593 nm, a photodiode, and a microcontroller. The proposed sensor measures the transmitted intensity in the form of an output voltage. We devise an approach to estimate the percentage of HbA1c in hemoglobin for a given solution. This estimation is based on the relative change in absorbance due to change in path length and molar absorption coefficients of hemoglobin and HbA1c, at the two wavelengths. We calculate the molar absorption coefficient of HbA1c at 535 nm and 593 nm wavelengths using the sensor, which is performed by a multiple variable regression analysis algorithm fed through the microcontroller. Specifically, the sensor output voltage with respect to the sample concentration is fitted to an exponentially decaying equation model. We used a commercial chemical assay called Control FD Glycohemoglobin A1c with known percentage HbA1c levels to verify our device measurements. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 2710 KiB

Open AccessArticle

Wide-Baseline Stereo-Based Obstacle Mapping for Unmanned Surface Vehicles

by Xiaozheng Mou^* and Han Wang

School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore

Sensors 2018, 18(4), 1085; https://doi.org/10.3390/s18041085 - 4 Apr 2018

Cited by 23 | Viewed by 4881

Abstract

This paper proposes a wide-baseline stereo-based static obstacle mapping approach for unmanned surface vehicles (USVs). The proposed approach eliminates the complicated calibration work and the bulky rig in our previous binocular stereo system, and raises the ranging ability from 500 to 1000 m [...] Read more.

This paper proposes a wide-baseline stereo-based static obstacle mapping approach for unmanned surface vehicles (USVs). The proposed approach eliminates the complicated calibration work and the bulky rig in our previous binocular stereo system, and raises the ranging ability from 500 to 1000 m with a even larger baseline obtained from the motion of USVs. Integrating a monocular camera with GPS and compass information in this proposed system, the world locations of the detected static obstacles are reconstructed while the USV is traveling, and an obstacle map is then built. To achieve more accurate and robust performance, multiple pairs of frames are leveraged to synthesize the final reconstruction results in a weighting model. Experimental results based on our own dataset demonstrate the high efficiency of our system. To the best of our knowledge, we are the first to address the task of wide-baseline stereo-based obstacle mapping in a maritime environment. Full article

(This article belongs to the Section Remote Sensors)

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18 pages, 19829 KiB

Open AccessArticle

3D Laser Scanner for Underwater Manipulation

by Albert Palomer^1,*

, Pere Ridao¹

, Dina Youakim¹

, David Ribas²

, Josep Forest¹

and Yvan Petillot³

¹ Computer Vision and Robotics Research Institute (VICOROB), Universitat de Girona, 17003 Girona, Spain

² IQUA Robotics, 17003 Girona, Spain

³ Ocean Systems Laboratory, Heriot-Watt University, Edinburgh EH14 4AS, UK

Sensors 2018, 18(4), 1086; https://doi.org/10.3390/s18041086 - 4 Apr 2018

Cited by 53 | Viewed by 9723

Abstract

Nowadays, research in autonomous underwater manipulation has demonstrated simple applications like picking an object from the sea floor, turning a valve or plugging and unplugging a connector. These are fairly simple tasks compared with those already demonstrated by the mobile robotics community, which [...] Read more.

Nowadays, research in autonomous underwater manipulation has demonstrated simple applications like picking an object from the sea floor, turning a valve or plugging and unplugging a connector. These are fairly simple tasks compared with those already demonstrated by the mobile robotics community, which include, among others, safe arm motion within areas populated with a priori unknown obstacles or the recognition and location of objects based on their 3D model to grasp them. Kinect-like 3D sensors have contributed significantly to the advance of mobile manipulation providing 3D sensing capabilities in real-time at low cost. Unfortunately, the underwater robotics community is lacking a 3D sensor with similar capabilities to provide rich 3D information of the work space. In this paper, we present a new underwater 3D laser scanner and demonstrate its capabilities for underwater manipulation. In order to use this sensor in conjunction with manipulators, a calibration method to find the relative position between the manipulator and the 3D laser scanner is presented. Then, two different advanced underwater manipulation tasks beyond the state of the art are demonstrated using two different manipulation systems. First, an eight Degrees of Freedom (DoF) fixed-base manipulator system is used to demonstrate arm motion within a work space populated with a priori unknown fixed obstacles. Next, an eight DoF free floating Underwater Vehicle-Manipulator System (UVMS) is used to autonomously grasp an object from the bottom of a water tank. Full article

(This article belongs to the Special Issue Underwater Sensing, Communication, Networking and Systems)

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15 pages, 5095 KiB

Open AccessArticle

Parameter Estimation of Multiple Frequency-Hopping Signals with Two Sensors

by Le Zuo^1,2,*

, Jin Pan¹ and Boyuan Ma¹

¹ Department of Microwave Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China

² School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore

Sensors 2018, 18(4), 1088; https://doi.org/10.3390/s18041088 - 4 Apr 2018

Cited by 7 | Viewed by 3788

Abstract

This paper essentially focuses on parameter estimation of multiple wideband emitting sources with time-varying frequencies, such as two-dimensional (2-D) direction of arrival (DOA) and signal sorting, with a low-cost circular synthetic array (CSA) consisting of only two rotating sensors. Our basic idea is [...] Read more.

This paper essentially focuses on parameter estimation of multiple wideband emitting sources with time-varying frequencies, such as two-dimensional (2-D) direction of arrival (DOA) and signal sorting, with a low-cost circular synthetic array (CSA) consisting of only two rotating sensors. Our basic idea is to decompose the received data, which is a superimposition of phase measurements from multiple sources into separated groups and separately estimate the DOA associated with each source. Motivated by joint parameter estimation, we propose to adopt the expectation maximization (EM) algorithm in this paper; our method involves two steps, namely, the expectation-step (E-step) and the maximization (M-step). In the E-step, the correspondence of each signal with its emitting source is found. Then, in the M-step, the maximum-likelihood (ML) estimates of the DOA parameters are obtained. These two steps are iteratively and alternatively executed to jointly determine the DOAs and sort multiple signals. Closed-form DOA estimation formulae are developed by ML estimation based on phase data, which also realize an optimal estimation. Directional ambiguity is also addressed by another ML estimation method based on received complex responses. The Cramer-Rao lower bound is derived for understanding the estimation accuracy and performance comparison. The verification of the proposed method is demonstrated with simulations. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 59259 KiB

Open AccessArticle

Joint Center Estimation Using Single-Frame Optimization: Part 1: Numerical Simulation

by Eric Frick¹ and Salam Rahmatalla^1,2,*

¹ Center for Computer-Aided Design, College of Engineering, The University of Iowa, Iowa City, IA 52242, USA

² Department of Civil and Environmental Engineering, College of Engineering, The University of Iowa, Iowa City, IA 52242, USA

Sensors 2018, 18(4), 1089; https://doi.org/10.3390/s18041089 - 4 Apr 2018

Cited by 11 | Viewed by 3960

Abstract

The biomechanical models used to refine and stabilize motion capture processes are almost invariably driven by joint center estimates, and any errors in joint center calculation carry over and can be compounded when calculating joint kinematics. Unfortunately, accurate determination of joint centers is [...] Read more.

The biomechanical models used to refine and stabilize motion capture processes are almost invariably driven by joint center estimates, and any errors in joint center calculation carry over and can be compounded when calculating joint kinematics. Unfortunately, accurate determination of joint centers is a complex task, primarily due to measurements being contaminated by soft-tissue artifact (STA). This paper proposes a novel approach to joint center estimation implemented via sequential application of single-frame optimization (SFO). First, the method minimizes the variance of individual time frames’ joint center estimations via the developed variance minimization method to obtain accurate overall initial conditions. These initial conditions are used to stabilize an optimization-based linearization of human motion that determines a time-varying joint center estimation. In this manner, the complex and nonlinear behavior of human motion contaminated by STA can be captured as a continuous series of unique rigid-body realizations without requiring a complex analytical model to describe the behavior of STA. This article intends to offer proof of concept, and the presented method must be further developed before it can be reasonably applied to human motion. Numerical simulations were introduced to verify and substantiate the efficacy of the proposed methodology. When directly compared with a state-of-the-art inertial method, SFO reduced the error due to soft-tissue artifact in all cases by more than 45%. Instead of producing a single vector value to describe the joint center location during a motion capture trial as existing methods often do, the proposed method produced time-varying solutions that were highly correlated (r > 0.82) with the true, time-varying joint center solution. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 35707 KiB

Open AccessFeature PaperArticle

A Fiber Optic Interferometric Sensor Platform for Determining Gas Diffusivity in Zeolite Films

by Ruidong Yang¹, Zhi Xu¹, Shixuan Zeng¹, Wenheng Jing², Adam Trontz¹ and Junhang Dong^1,*

¹ Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221, USA

² State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, 5 Xinmofan Road, Nanjing 210009, China

Sensors 2018, 18(4), 1090; https://doi.org/10.3390/s18041090 - 4 Apr 2018

Cited by 8 | Viewed by 5370

Abstract

Fiber optic interferometer (FOI) sensors have been fabricated by directly growing pure-silica MFI-type zeolite (i.e., silicalite) films on straight-cut endfaces of single-mode communication optical fibers. The FOI sensor has been demonstrated for determining molecular diffusivity in the zeolite by monitoring the temporal response [...] Read more.

Fiber optic interferometer (FOI) sensors have been fabricated by directly growing pure-silica MFI-type zeolite (i.e., silicalite) films on straight-cut endfaces of single-mode communication optical fibers. The FOI sensor has been demonstrated for determining molecular diffusivity in the zeolite by monitoring the temporal response of light interference from the zeolite film during the dynamic process of gas adsorption. The optical thickness of the zeolite film depends on the amount of gas adsorption that causes the light interference to shift upon loading molecules into the zeolitic channels. Thus, the time-dependence of the optical signal reflected from the coated zeolite film can represent the adsorption uptake curve, which allows computation of the diffusivity using models derived from the Fick’s Law equations. In this study, the diffusivity of isobutane in silicalite has been determined by the new FOI sensing method, and the results are in good agreement with literature values obtained by various conventional macroscopic techniques. The FOI sensor platform, because of its robustness and small size, could be useful for studying molecular diffusion in zeolitic materials under conditions that are inaccessible to the existing techniques. Full article

(This article belongs to the Collection Gas Sensors)

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24 pages, 2622 KiB

Open AccessArticle

Robust Stride Segmentation of Inertial Signals Based on Local Cyclicity Estimation

by Sebastijan Šprager^*,†

and Matjaž B. Jurič^†

¹ Faculty of Computer and Information Science, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1091; https://doi.org/10.3390/s18041091 - 4 Apr 2018

Cited by 9 | Viewed by 3989

Abstract

A novel approach for stride segmentation, gait sequence extraction, and gait event detection for inertial signals is presented. The approach operates by combining different local cyclicity estimators and sensor channels, and can additionally employ a priori knowledge on the fiducial points of gait [...] Read more.

A novel approach for stride segmentation, gait sequence extraction, and gait event detection for inertial signals is presented. The approach operates by combining different local cyclicity estimators and sensor channels, and can additionally employ a priori knowledge on the fiducial points of gait events. The approach is universal as it can work on signals acquired by different inertial measurement unit (IMU) sensor types, is template-free, and operates unsupervised. A thorough evaluation was performed with two datasets: our own collected FRIgait dataset available for open use, containing long-term inertial measurements collected from 57 subjects using smartphones within the span of more than one year, and an FAU eGait dataset containing inertial data from shoe-mounted sensors collected from three cohorts of subjects: healthy, geriatric, and Parkinson’s disease patients. The evaluation was performed in controlled and uncontrolled conditions. When compared to the ground truth of the labelled FRIgait and eGait datasets, the results of our evaluation revealed the high robustness, efficiency (F-measure of about 98%), and accuracy (mean absolute error MAE in about the range of one sample) of the proposed approach. Based on these results, we conclude that the proposed approach shows great potential for its applicability in procedures and algorithms for movement analysis. Full article

(This article belongs to the Section Physical Sensors)

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28 pages, 1741 KiB

Open AccessArticle

Spatiotemporal Local-Remote Senor Fusion (ST-LRSF) for Cooperative Vehicle Positioning

by Han-You Jeong^1,*

, Hoa-Hung Nguyen¹

and Adhitya Bhawiyuga²

¹ School of Electrical and Computer Engineering, Pusan National University, 46241 Busan, Korea

² Faculty of Computer Science, Brawijaya University, 65145 Malang, Indonesia

Sensors 2018, 18(4), 1092; https://doi.org/10.3390/s18041092 - 4 Apr 2018

Cited by 8 | Viewed by 4611

Abstract

Vehicle positioning plays an important role in the design of protocols, algorithms, and applications in the intelligent transport systems. In this paper, we present a new framework of spatiotemporal local-remote sensor fusion (ST-LRSF) that cooperatively improves the accuracy of absolute vehicle positioning based [...] Read more.

Vehicle positioning plays an important role in the design of protocols, algorithms, and applications in the intelligent transport systems. In this paper, we present a new framework of spatiotemporal local-remote sensor fusion (ST-LRSF) that cooperatively improves the accuracy of absolute vehicle positioning based on two state estimates of a vehicle in the vicinity: a local sensing estimate, measured by the on-board exteroceptive sensors, and a remote sensing estimate, received from neighbor vehicles via vehicle-to-everything communications. Given both estimates of vehicle state, the ST-LRSF scheme identifies the set of vehicles in the vicinity, determines the reference vehicle state, proposes a spatiotemporal dissimilarity metric between two reference vehicle states, and presents a greedy algorithm to compute a minimal weighted matching (MWM) between them. Given the outcome of MWM, the theoretical position uncertainty of the proposed refinement algorithm is proven to be inversely proportional to the square root of matching size. To further reduce the positioning uncertainty, we also develop an extended Kalman filter model with the refined position of ST-LRSF as one of the measurement inputs. The numerical results demonstrate that the proposed ST-LRSF framework can achieve high positioning accuracy for many different scenarios of cooperative vehicle positioning. Full article

(This article belongs to the Special Issue Smart Vehicular Mobile Sensing)

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20 pages, 6331 KiB

Open AccessArticle

Postharvest Monitoring of Tomato Ripening Using the Dynamic Laser Speckle

by Piotr Mariusz Pieczywek^1,*, Małgorzata Nowacka²

, Magdalena Dadan²

, Artur Wiktor²

, Katarzyna Rybak², Dorota Witrowa-Rajchert²

and Artur Zdunek¹

¹ Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland

² Department of Food Engineering and Process Management, Faculty of Food Sciences, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159c, 02-776 Warsaw, Poland

Sensors 2018, 18(4), 1093; https://doi.org/10.3390/s18041093 - 4 Apr 2018

Cited by 21 | Viewed by 7203

Abstract

The dynamic laser speckle (biospeckle) method was tested as a potential tool for the assessment and monitoring of the maturity stage of tomatoes. Two tomato cultivars—Admiro and Starbuck—were tested. The process of climacteric maturation of tomatoes was monitored during a shelf life storage [...] Read more.

The dynamic laser speckle (biospeckle) method was tested as a potential tool for the assessment and monitoring of the maturity stage of tomatoes. Two tomato cultivars—Admiro and Starbuck—were tested. The process of climacteric maturation of tomatoes was monitored during a shelf life storage experiment. The biospeckle phenomena were captured using 640 nm and 830 nm laser light wavelength, and analysed using two activity descriptors based on biospeckle pattern decorrelation—C4 and ε. The well-established optical parameters of tomatoes skin were used as a reference method (luminosity, a*/b*, chroma). Both methods were tested with respect to their prediction capabilities of the maturity and destructive indicators of tomatoes—firmness, chlorophyll and carotenoids content. The statistical significance of the tested relationships were investigated by means of linear regression models. The climacteric maturation of tomato fruit was associated with an increase in biospckle activity. Compared to the 830 nm laser wavelength the biospeckle activity measured at 640 nm enabled more accurate predictions of firmness, chlorophyll and carotenoids content. At 640 nm laser wavelength both activity descriptors (C4 and ε) provided similar results, while at 830 nm the ε showed slightly better performance. The linear regression models showed that biospeckle activity descriptors had a higher correlation with chlorophyll and carotenoids content than the a*/b* ratio and luminosity. The results for chroma were comparable with the results for both biospeckle activity indicators. The biospeckle method showed very good results in terms of maturation monitoring and the prediction of the maturity indices of tomatoes, proving the possibility of practical implementation of this method for the determination of the maturity stage of tomatoes. Full article

(This article belongs to the Collection Sensors in Agriculture and Forestry)

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11 pages, 22603 KiB

Open AccessArticle

Structural Health Monitoring in Composite Structures by Fiber-Optic Sensors

by Alfredo Güemes^1,*, Antonio Fernández-López¹

, Patricia F. Díaz-Maroto¹, Angel Lozano¹ and Julian Sierra-Perez²

¹ Department Aeronautics, Polytechnic University of Madrid, 28040 Madrid, Spain

² Ingeniería Aeroespacial, Universidad Pontificia Bolivariana, Medellín 050031, Colombia

Sensors 2018, 18(4), 1094; https://doi.org/10.3390/s18041094 - 4 Apr 2018

Cited by 132 | Viewed by 10822

Abstract

Fiber-optic sensors cannot measure damage; to get information about damage from strain measurements, additional strategies are needed, and several alternatives are available in the existing literature. This paper discusses two independent procedures. The first is based on detecting new strains appearing around a [...] Read more.

Fiber-optic sensors cannot measure damage; to get information about damage from strain measurements, additional strategies are needed, and several alternatives are available in the existing literature. This paper discusses two independent procedures. The first is based on detecting new strains appearing around a damage spot. The structure does not need to be under loads, the technique is very robust, and damage detectability is high, but it requires sensors to be located very close to the damage, so it is a local technique. The second approach offers wider coverage of the structure; it is based on identifying the changes caused by damage on the strain field in the whole structure for similar external loads. Damage location does not need to be known a priori, and detectability is dependent upon the sensor’s network density, the damage size, and the external loads. Examples of application to real structures are given. Full article

(This article belongs to the Special Issue Selected Papers from IWSHM 2017)

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23 pages, 10729 KiB

Open AccessArticle

A Student’s t Mixture Probability Hypothesis Density Filter for Multi-Target Tracking with Outliers

by Zhuowei Liu¹

, Shuxin Chen¹, Hao Wu^1,*, Renke He¹ and Lin Hao²

¹ Information and Navigation College Air Force Engineering University, Xi’an 710077, China

² Unit 93786, Chinese People’s Liberation Army (PLA), Zhangjiakou 075000, China

Sensors 2018, 18(4), 1095; https://doi.org/10.3390/s18041095 - 4 Apr 2018

Cited by 17 | Viewed by 4119

Abstract

In multi-target tracking, the outliers-corrupted process and measurement noises can reduce the performance of the probability hypothesis density (PHD) filter severely. To solve the problem, this paper proposed a novel PHD filter, called Student’s t mixture PHD (STM-PHD) filter. The proposed filter models [...] Read more.

In multi-target tracking, the outliers-corrupted process and measurement noises can reduce the performance of the probability hypothesis density (PHD) filter severely. To solve the problem, this paper proposed a novel PHD filter, called Student’s t mixture PHD (STM-PHD) filter. The proposed filter models the heavy-tailed process noise and measurement noise as a Student’s t distribution as well as approximates the multi-target intensity as a mixture of Student’s t components to be propagated in time. Then, a closed PHD recursion is obtained based on Student’s t approximation. Our approach can make full use of the heavy-tailed characteristic of a Student’s t distribution to handle the situations with heavy-tailed process and the measurement noises. The simulation results verify that the proposed filter can overcome the negative effect generated by outliers and maintain a good tracking accuracy in the simultaneous presence of process and measurement outliers. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 2058 KiB

Open AccessArticle

A Weighted Deep Representation Learning Model for Imbalanced Fault Diagnosis in Cyber-Physical Systems

by Zhenyu Wu^1,*

, Yang Guo², Wenfang Lin², Shuyang Yu² and Yang Ji^1,2

¹ Engineering Research Center of Information Network, Ministry of Education, Beijing University of Posts and Telecommunications, Beijing 100876, China

² Key Laboratory of Universal Wireless Communications, Ministry of Education, Beijing University of Posts and Telecommunications, Beijing 100876, China

Sensors 2018, 18(4), 1096; https://doi.org/10.3390/s18041096 - 5 Apr 2018

Cited by 73 | Viewed by 6611

Abstract

Predictive maintenance plays an important role in modern Cyber-Physical Systems (CPSs) and data-driven methods have been a worthwhile direction for Prognostics Health Management (PHM). However, two main challenges have significant influences on the traditional fault diagnostic models: one is that extracting hand-crafted features [...] Read more.

Predictive maintenance plays an important role in modern Cyber-Physical Systems (CPSs) and data-driven methods have been a worthwhile direction for Prognostics Health Management (PHM). However, two main challenges have significant influences on the traditional fault diagnostic models: one is that extracting hand-crafted features from multi-dimensional sensors with internal dependencies depends too much on expertise knowledge; the other is that imbalance pervasively exists among faulty and normal samples. As deep learning models have proved to be good methods for automatic feature extraction, the objective of this paper is to study an optimized deep learning model for imbalanced fault diagnosis for CPSs. Thus, this paper proposes a weighted Long Recurrent Convolutional LSTM model with sampling policy (wLRCL-D) to deal with these challenges. The model consists of 2-layer CNNs, 2-layer inner LSTMs and 2-Layer outer LSTMs, with under-sampling policy and weighted cost-sensitive loss function. Experiments are conducted on PHM 2015 challenge datasets, and the results show that wLRCL-D outperforms other baseline methods. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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21 pages, 1298 KiB

Open AccessArticle

QuantifyMe: An Open-Source Automated Single-Case Experimental Design Platform

by Sara Taylor^*,‡

, Akane Sano^*,‡, Craig Ferguson, Akshay Mohan and Rosalind W. Picard

¹ Affective Computing Group, MIT Media Lab, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

^‡ These authors contributed equally to this work.

Sensors 2018, 18(4), 1097; https://doi.org/10.3390/s18041097 - 5 Apr 2018

Cited by 12 | Viewed by 7272

Abstract

Smartphones and wearable sensors have enabled unprecedented data collection, with many products now providing feedback to users about recommended step counts or sleep durations. However, these recommendations do not provide personalized insights that have been shown to be best suited for a specific [...] Read more.

Smartphones and wearable sensors have enabled unprecedented data collection, with many products now providing feedback to users about recommended step counts or sleep durations. However, these recommendations do not provide personalized insights that have been shown to be best suited for a specific individual. A scientific way to find individualized recommendations and causal links is to conduct experiments using single-case experimental design; however, properly designed single-case experiments are not easy to conduct on oneself. We designed, developed, and evaluated a novel platform, QuantifyMe, for novice self-experimenters to conduct proper-methodology single-case self-experiments in an automated and scientific manner using their smartphones. We provide software for the platform that we used (available for free on GitHub), which provides the methodological elements to run many kinds of customized studies. In this work, we evaluate its use with four different kinds of personalized investigations, examining how variables such as sleep duration and regularity, activity, and leisure time affect personal happiness, stress, productivity, and sleep efficiency. We conducted a six-week pilot study (N = 13) to evaluate QuantifyMe. We describe the lessons learned developing the platform and recommendations for its improvement, as well as its potential for enabling personalized insights to be scientifically evaluated in many individuals, reducing the high administrative cost for advancing human health and wellbeing. Full article

(This article belongs to the Special Issue Selected Papers from 7th EAI International Conference on Wireless Mobile Communication and Healthcare)

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14 pages, 14667 KiB

Open AccessArticle

Dynamically Rough Boundary Scattering Effect on a Propagating Continuous Acoustical Wave in a Circular Pipe with Flow

by Anna V. Romanova^1,*, Kirill V. Horoshenkov²

and Anton Krynkin²

¹ Faculty of Engineering & Science, University of Greenwich, Central Avenue, Chatham, Kent ME4 4TB, UK

² Department of Mechanical Engineering, University of Sheffield, Mappin Steet, Sheffield, South Yorkshire S1 3JD, UK

Sensors 2018, 18(4), 1098; https://doi.org/10.3390/s18041098 - 5 Apr 2018

Cited by 3 | Viewed by 5190

Abstract

The pattern of the free surface of the turbulent flow in a partially filled circular pipe contains information on the underlying hydraulic processes. However, the roughness of the free surface of flow and its temporal variation in a pipe is a dynamic and [...] Read more.

The pattern of the free surface of the turbulent flow in a partially filled circular pipe contains information on the underlying hydraulic processes. However, the roughness of the free surface of flow and its temporal variation in a pipe is a dynamic and non-stationary process that is difficult to measure directly. This work examines a new acoustic method that is used to study the characteristics of the free surface roughness under controlled laboratory conditions. The acoustic method makes use of a continuous sine wave that is transmitted through the air above the turbulent flow of water over a section of the pipe instrumented with an array of wave probes and microphones. The results obtained for a representative range of flow regimes and variety of pipe bed conditions illustrate that it is possible to unambiguously relate variations in the recorded acoustic field to the standard deviation in the free surface roughness and mean flow depth. These variations are clearly linked to the hydraulic friction factor of the pipe, which is shown to be related to airborne acoustic data obtained non-invasively. Full article

(This article belongs to the Special Issue Surface Acoustic Wave and Bulk Acoustic Wave Sensors)

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19 pages, 23081 KiB

Open AccessArticle

A Vehicular Mobile Standard Instrument for Field Verification of Traffic Speed Meters Based on Dual-Antenna Doppler Radar Sensor

by Lei Du^*

, Qiao Sun, Changqing Cai, Jie Bai, Zhe Fan and Yue Zhang

Division of Mechanics and Acoustics, National Institute of Metrology, Beijing 100029, China

Sensors 2018, 18(4), 1099; https://doi.org/10.3390/s18041099 - 5 Apr 2018

Cited by 17 | Viewed by 6178

Abstract

Traffic speed meters are important legal measuring instruments specially used for traffic speed enforcement and must be tested and verified in the field every year using a vehicular mobile standard speed-measuring instrument to ensure speed-measuring performances. The non-contact optical speed sensor and the [...] Read more.

Traffic speed meters are important legal measuring instruments specially used for traffic speed enforcement and must be tested and verified in the field every year using a vehicular mobile standard speed-measuring instrument to ensure speed-measuring performances. The non-contact optical speed sensor and the GPS speed sensor are the two most common types of standard speed-measuring instruments. The non-contact optical speed sensor requires extremely high installation accuracy, and its speed-measuring error is nonlinear and uncorrectable. The speed-measuring accuracy of the GPS speed sensor is rapidly reduced if the amount of received satellites is insufficient enough, which often occurs in urban high-rise regions, tunnels, and mountainous regions. In this paper, a new standard speed-measuring instrument using a dual-antenna Doppler radar sensor is proposed based on a tradeoff between the installation accuracy requirement and the usage region limitation, which has no specified requirements for its mounting distance and no limitation on usage regions and can automatically compensate for the effect of an inclined installation angle on its speed-measuring accuracy. Theoretical model analysis, simulated speed measurement results, and field experimental results compared with a GPS speed sensor with high accuracy showed that the dual-antenna Doppler radar sensor is effective and reliable as a new standard speed-measuring instrument. Full article

(This article belongs to the Special Issue Smart Vehicular Mobile Sensing)

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12 pages, 7536 KiB

Open AccessArticle

Dual-Polarization Ku-Band Compact Spaceborne Antenna Based on Dual-Reflectarray Optics

by Carolina Tienda^1,*, Jose A. Encinar²

, Mariano Barba² and Manuel Arrebola³

¹ Airbus Defence and Space, Gunnels Wood Road, Stevenage SG1 2AS, UK

² Information, Processing and Telecommunications Center, Universidad Politécnica de Madrid (UPM), 28040 Madrid, Spain

³ Department of Electrical Engineering, University of Oviedo, 33203 Gijón, Spain

Sensors 2018, 18(4), 1100; https://doi.org/10.3390/s18041100 - 5 Apr 2018

Cited by 6 | Viewed by 6140

Abstract

This article demonstrated an accurate analysis technique for dual-reflectarray antennas that take into account the angle of incidence of the impinging electric field on the main reflectarray cells. The reflected field on the sub and the main reflectarray surfaces is computed using Method [...] Read more.

This article demonstrated an accurate analysis technique for dual-reflectarray antennas that take into account the angle of incidence of the impinging electric field on the main reflectarray cells. The reflected field on the sub and the main reflectarray surfaces is computed using Method of Moments in the spectral domain and assuming local periodicity. The sub-reflectarray is divided into groups of elements and the field radiated by each group is used to compute the incident and reflected field on the main reflectarray cells. A 50-cm demonstrator in Ku-band that provides European coverage has been designed, manufactured and tested to validate the analysis technique. The measured radiation patterns match the simulations and they fulfill the coverage requirements, achieving a cross-polar discrimination better than 25 dB in the frequency range: 12.975–14.25 GHz. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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18 pages, 2745 KiB

Open AccessArticle

Real-Life/Real-Time Elderly Fall Detection with a Triaxial Accelerometer

by Angela Sucerquia^1,*

, José David López²

and Jesús Francisco Vargas-Bonilla²

¹ Facultad de Ingeniería, Institución Universitaria ITM, Cra. 65, 98A-75 Medellín, Colombia

² SISTEMIC, Facultad de Ingeniería, Universidad de Antiquia UDEA, Calle 70, No. 52-21 Medellín, Colombia

Sensors 2018, 18(4), 1101; https://doi.org/10.3390/s18041101 - 5 Apr 2018

Cited by 91 | Viewed by 10756

Abstract

The consequences of a fall on an elderly person can be reduced if the accident is attended by medical personnel within the first hour. Independent elderly people often stay alone for long periods of time, being in more risk if they suffer a [...] Read more.

The consequences of a fall on an elderly person can be reduced if the accident is attended by medical personnel within the first hour. Independent elderly people often stay alone for long periods of time, being in more risk if they suffer a fall. The literature offers several approaches for detecting falls with embedded devices or smartphones using a triaxial accelerometer. Most of these approaches have not been tested with the target population or cannot be feasibly implemented in real-life conditions. In this work, we propose a fall detection methodology based on a non-linear classification feature and a Kalman filter with a periodicity detector to reduce the false positive rate. This methodology requires a sampling rate of only 25 Hz; it does not require large computations or memory and it is robust among devices. We tested our approach with the SisFall dataset achieving 99.4% of accuracy. We then validated it with a new round of simulated activities with young adults and an elderly person. Finally, we give the devices to three elderly persons for full-day validations. They continued with their normal life and the devices behaved as expected. Full article

(This article belongs to the Special Issue Wearable and Ambient Sensors for Healthcare and Wellness Applications 2018)

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12 pages, 22810 KiB

Open AccessArticle

Motor Subtypes of Parkinson’s Disease Can Be Identified by Frequency Component of Postural Stability

by Saba Rezvanian¹

, Thurmon Lockhart^1,*

, Christopher Frames^1,2, Rahul Soangra³

and Abraham Lieberman²

¹ School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85281, USA

² Barrow Neurological Institute, Phoenix, AZ 85013, USA

³ Department of Physical Therapy, Crean College of Health and Behavioral Sciences, Chapman University, Orange, CA 92866, USA

Sensors 2018, 18(4), 1102; https://doi.org/10.3390/s18041102 - 5 Apr 2018

Cited by 22 | Viewed by 5925

Abstract

Parkinson’s disease (PD) can be divided into two subtypes based on clinical features—namely tremor dominant (TD) and postural instability and gait difficulty (PIGD). This categorization is important at the early stage of PD, since identifying the subtypes can help to predict the clinical [...] Read more.

Parkinson’s disease (PD) can be divided into two subtypes based on clinical features—namely tremor dominant (TD) and postural instability and gait difficulty (PIGD). This categorization is important at the early stage of PD, since identifying the subtypes can help to predict the clinical progression of the disease. Accordingly, correctly diagnosing subtypes is critical in initiating appropriate early interventions and tracking the progression of the disease. However, as the disease progresses, it becomes increasingly difficult to further distinguish those attributes that are relevant to the subtypes. In this study, we investigated whether a method using the standing center of pressure (COP) time series data can separate two subtypes of PD by looking at the frequency component of COP (i.e., COP position and speed). Thirty-six participants diagnosed with PD were evaluated, with their bare feet on the force platform, and were instructed to stand upright with their arms by their sides for 20 s (with their eyes open and closed), which is consistent with the traditional COP measures. Fast Fourier transform (FFT) and wavelet transform (WT) were performed to distinguish between the motor subtypes using the COP measures. The TD group exhibited larger amplitudes at the frequency range of 3–7 Hz when compared to the PIGD group. Both the FFT and WT methods were able to differentiate the subtypes. COP time series information can be used to differentiate between the two motor subtypes of PD, using the frequency component of postural stability. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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19 pages, 891 KiB

Open AccessArticle

The Cramér–Rao Bounds and Sensor Selection for Nonlinear Systems with Uncertain Observations

by Zhiguo Wang

, Xiaojing Shen^*

, Ping Wang and Yunmin Zhu

School of Mathematics, Sichuan University, Chengdu 610064, China

Sensors 2018, 18(4), 1103; https://doi.org/10.3390/s18041103 - 5 Apr 2018

Cited by 9 | Viewed by 3807

Abstract

This paper considers the problems of the posterior Cramér–Rao bound and sensor selection for multi-sensor nonlinear systems with uncertain observations. In order to effectively overcome the difficulties caused by uncertainty, we investigate two methods to derive the posterior Cramér–Rao bound. The first method [...] Read more.

This paper considers the problems of the posterior Cramér–Rao bound and sensor selection for multi-sensor nonlinear systems with uncertain observations. In order to effectively overcome the difficulties caused by uncertainty, we investigate two methods to derive the posterior Cramér–Rao bound. The first method is based on the recursive formula of the Cramér–Rao bound and the Gaussian mixture model. Nevertheless, it needs to compute a complex integral based on the joint probability density function of the sensor measurements and the target state. The computation burden of this method is relatively high, especially in large sensor networks. Inspired by the idea of the expectation maximization algorithm, the second method is to introduce some 0–1 latent variables to deal with the Gaussian mixture model. Since the regular condition of the posterior Cramér–Rao bound is unsatisfied for the discrete uncertain system, we use some continuous variables to approximate the discrete latent variables. Then, a new Cramér–Rao bound can be achieved by a limiting process of the Cramér–Rao bound of the continuous system. It avoids the complex integral, which can reduce the computation burden. Based on the new posterior Cramér–Rao bound, the optimal solution of the sensor selection problem can be derived analytically. Thus, it can be used to deal with the sensor selection of a large-scale sensor networks. Two typical numerical examples verify the effectiveness of the proposed methods. Full article

(This article belongs to the Section Sensor Networks)

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26 pages, 12260 KiB

Open AccessArticle

A Lightweight Continuous Authentication Protocol for the Internet of Things

by Yo-Hsuan Chuang¹, Nai-Wei Lo¹

, Cheng-Ying Yang^2,* and Ssu-Wei Tang¹

¹ Department of Information Management, National Taiwan University of Science and Technology, Taipei 10607, Taiwan

² Department of Computer Science, University of Taipei, Taipei 10048, Taiwan

Sensors 2018, 18(4), 1104; https://doi.org/10.3390/s18041104 - 5 Apr 2018

Cited by 75 | Viewed by 9401

Abstract

Modern societies are moving toward an information-oriented environment. To gather and utilize information around people’s modern life, tiny devices with all kinds of sensing devices and various sizes of gateways need to be deployed and connected with each other through the Internet or [...] Read more.

Modern societies are moving toward an information-oriented environment. To gather and utilize information around people’s modern life, tiny devices with all kinds of sensing devices and various sizes of gateways need to be deployed and connected with each other through the Internet or proxy-based wireless sensor networks (WSNs). Within this kind of Internet of Things (IoT) environment, how to authenticate each other between two communicating devices is a fundamental security issue. As a lot of IoT devices are powered by batteries and they need to transmit sensed data periodically, it is necessary for IoT devices to adopt a lightweight authentication protocol to reduce their energy consumption when a device wants to authenticate and transmit data to its targeted peer. In this paper, a lightweight continuous authentication protocol for sensing devices and gateway devices in general IoT environments is introduced. The concept of valid authentication time period is proposed to enhance robustness of authentication between IoT devices. To construct the proposed lightweight continuous authentication protocol, token technique and dynamic features of IoT devices are adopted in order to reach the design goals: the reduction of time consumption for consecutive authentications and energy saving for authenticating devices through by reducing the computation complexity during session establishment of continuous authentication. Security analysis is conducted to evaluate security strength of the proposed protocol. In addition, performance analysis has shown the proposed protocol is a strong competitor among existing protocols for device-to-device authentication in IoT environments. Full article

(This article belongs to the Special Issue Mobile Sensing Applications)

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26 pages, 43584 KiB

Open AccessArticle

Adaptive LINE-P: An Adaptive Linear Energy Prediction Model for Wireless Sensor Network Nodes

by Faisal Ahmed^1,*, Gert Tamberg²

, Yannick Le Moullec^1,*

and Paul Annus¹

¹ Thomas Johann Seebeck Department of Electronics, Tallinn University of Technology, Tallinn 12616, Estonia

² Department of Cybernetics, Tallinn University of Technology, Tallinn 12616, Estonia

Sensors 2018, 18(4), 1105; https://doi.org/10.3390/s18041105 - 5 Apr 2018

Cited by 8 | Viewed by 4577

Abstract

In the context of wireless sensor networks, energy prediction models are increasingly useful tools that can facilitate the power management of the wireless sensor network (WSN) nodes. However, most of the existing models suffer from the so-called fixed weighting parameter, which limits their [...] Read more.

In the context of wireless sensor networks, energy prediction models are increasingly useful tools that can facilitate the power management of the wireless sensor network (WSN) nodes. However, most of the existing models suffer from the so-called fixed weighting parameter, which limits their applicability when it comes to, e.g., solar energy harvesters with varying characteristics. Thus, in this article we propose the Adaptive LINE-P (all cases) model that calculates adaptive weighting parameters based on the stored energy profiles. Furthermore, we also present a profile compression method to reduce the memory requirements. To determine the performance of our proposed model, we have used real data for the solar and wind energy profiles. The simulation results show that our model achieves 90–94% accuracy and that the compressed method reduces memory overheads by 50% as compared to state-of-the-art models. Full article

(This article belongs to the Special Issue Low Energy Wireless Sensor Networks: Protocols, Architectures and Solutions)

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21 pages, 1322 KiB

Open AccessArticle

A Two-Stage Reconstruction Processor for Human Detection in Compressive Sensing CMOS Radar

by Kuei-Chi Tsao¹, Ling Lee², Ta-Shun Chu¹ and Yuan-Hao Huang^2,*

¹ Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan

² Institute of Communications Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan

Sensors 2018, 18(4), 1106; https://doi.org/10.3390/s18041106 - 5 Apr 2018

Cited by 4 | Viewed by 4493

Abstract

Complementary metal-oxide-semiconductor (CMOS) radar has recently gained much research attraction because small and low-power CMOS devices are very suitable for deploying sensing nodes in a low-power wireless sensing system. This study focuses on the signal processing of a wireless CMOS impulse radar system [...] Read more.

Complementary metal-oxide-semiconductor (CMOS) radar has recently gained much research attraction because small and low-power CMOS devices are very suitable for deploying sensing nodes in a low-power wireless sensing system. This study focuses on the signal processing of a wireless CMOS impulse radar system that can detect humans and objects in the home-care internet-of-things sensing system. The challenges of low-power CMOS radar systems are the weakness of human signals and the high computational complexity of the target detection algorithm. The compressive sensing-based detection algorithm can relax the computational costs by avoiding the utilization of matched filters and reducing the analog-to-digital converter bandwidth requirement. The orthogonal matching pursuit (OMP) is one of the popular signal reconstruction algorithms for compressive sensing radar; however, the complexity is still very high because the high resolution of human respiration leads to high-dimension signal reconstruction. Thus, this paper proposes a two-stage reconstruction algorithm for compressive sensing radar. The proposed algorithm not only has lower complexity than the OMP algorithm by 75% but also achieves better positioning performance than the OMP algorithm especially in noisy environments. This study also designed and implemented the algorithm by using Vertex-7 FPGA chip (Xilinx, San Jose, CA, USA). The proposed reconstruction processor can support the

256 \times 13

real-time radar image display with a throughput of 28.2 frames per second. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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20 pages, 29325 KiB

Open AccessArticle

A Temperature-Hardened Sensor Interface with a 12-Bit Digital Output Using a Novel Pulse Width Modulation Technique

by Emna Chabchoub^1,2,3,*

, Franck Badets¹, Frédérick Mailly²

, Pascal Nouet²

and Mohamed Masmoudi³

¹ Grenoble Alpes University, CEA, LETI, F-38000 Grenoble, France

² Laboratory of Informatics, Robotics and Microelectronics of Montpellier, University of Montpellier, CNRS, 34000 Montpellier, France

³ METS Research Group, National Engineers School of Sfax, Sfax University, Sfax 3029, Tunisia

Sensors 2018, 18(4), 1107; https://doi.org/10.3390/s18041107 - 5 Apr 2018

Cited by 2 | Viewed by 4564

Abstract

A fully integrated sensor interface for a wide operational temperature range is presented. It translates the sensor signal into a pulse width modulated (PWM) signal that is then converted into a 12-bit digital output. The sensor interface is based on a pair of [...] Read more.

A fully integrated sensor interface for a wide operational temperature range is presented. It translates the sensor signal into a pulse width modulated (PWM) signal that is then converted into a 12-bit digital output. The sensor interface is based on a pair of injection locked oscillators used to implement a differential time-domain architecture with low sensitivity to temperature variations. A prototype has been fabricated using a 180 nm partially depleted silicon-on-insulator (SOI) technology. Experimental results demonstrate a thermal stability as low as 65 ppm/°C over a large temperature range from −20 °C up to 220 °C. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 44622 KiB

Open AccessArticle

Cu(OH)₂ and CuO Nanorod Synthesis on Piezoresistive Cantilevers for the Selective Detection of Nitrogen Dioxide

by Laurent Schlur^1,*

, Manuel Hofer², Ahmad Ahmad², Karine Bonnot¹, Mathias Holz² and Denis Spitzer¹

¹ Nanomatériaux pour les Systèmes Sous Sollicitations Extrêmes (NS3E), UMR 3208 ISL/CNRS/UNISTRA, French-German Research Institute of Saint-Louis, 5, rue du Général Cassagnou, 68300 Saint-Louis, France

² Nano analytik GmbH, Ehrenbergstraße 1, 98693 Ilmenau, Germany

Sensors 2018, 18(4), 1108; https://doi.org/10.3390/s18041108 - 5 Apr 2018

Cited by 19 | Viewed by 8145

Abstract

Self-controlled active oscillating microcantilevers with a piezoresistive readout are very promising sensitive sensors, despite their small surface. In order to increase this surface and consequently their sensitivity, we nanostructured them with copper hydroxide (Cu(OH)₂) or with copper oxide (CuO) nanorods. The [...] Read more.

Self-controlled active oscillating microcantilevers with a piezoresistive readout are very promising sensitive sensors, despite their small surface. In order to increase this surface and consequently their sensitivity, we nanostructured them with copper hydroxide (Cu(OH)₂) or with copper oxide (CuO) nanorods. The Cu(OH)₂ rods were grown, on a homogeneous copper layer previously evaporated on the top of the cantilever. The CuO nanorods were further obtained by the annealing of the copper hydroxide nanostructures. Then, these copper based nanorods were used to detect several molecules vapors. The results showed no chemical affinity (no formation of a chemical bond) between the CuO cantilevers and the tested molecules. The cantilever with Cu(OH)₂ nanorods is selective to nitrogen dioxide (NO₂) in presence of humidity. Indeed, among all the tested analytes, copper hydroxide has only an affinity with NO₂. Despite the absence of affinity, the cantilevers could even so condensate explosives (1,3,5-trinitro-1,3,5-triazinane (RDX) and pentaerythritol tetranitrate (PETN) on their surface when the cantilever temperature was lower than the explosives source, allowing their detection. We proved that in condensation conditions, the cantilever surface material has no importance and that the nanostructuration is useless because a raw silicon cantilever detects as well as the nanostructured ones. Full article

(This article belongs to the Special Issue Gas Sensors based on Semiconducting Metal Oxides)

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13 pages, 30168 KiB

Open AccessArticle

Statistical Analysis of SSMIS Sea Ice Concentration Threshold at the Arctic Sea Ice Edge during Summer Based on MODIS and Ship-Based Observational Data

by Qing Ji¹

, Fei Li^1,*, Xiaoping Pang¹ and Cong Luo²

¹ Chinese Antarctic Center of Surveying and Mapping, Wuhan University, Wuhan 430079, China

² School of Resource and Environmental Sciences, Wuhan University, Wuhan 430079, China

Sensors 2018, 18(4), 1109; https://doi.org/10.3390/s18041109 - 5 Apr 2018

Cited by 8 | Viewed by 3958

Abstract

The threshold of sea ice concentration (SIC) is the basis for accurately calculating sea ice extent based on passive microwave (PM) remote sensing data. However, the PM SIC threshold at the sea ice edge used in previous studies and released sea ice products [...] Read more.

The threshold of sea ice concentration (SIC) is the basis for accurately calculating sea ice extent based on passive microwave (PM) remote sensing data. However, the PM SIC threshold at the sea ice edge used in previous studies and released sea ice products has not always been consistent. To explore the representable value of the PM SIC threshold corresponding on average to the position of the Arctic sea ice edge during summer in recent years, we extracted sea ice edge boundaries from the Moderate-resolution Imaging Spectroradiometer (MODIS) sea ice product (MOD29 with a spatial resolution of 1 km), MODIS images (250 m), and sea ice ship-based observation points (1 km) during the fifth (CHINARE-2012) and sixth (CHINARE-2014) Chinese National Arctic Research Expeditions, and made an overlay and comparison analysis with PM SIC derived from Special Sensor Microwave Imager Sounder (SSMIS, with a spatial resolution of 25 km) in the summer of 2012 and 2014. Results showed that the average SSMIS SIC threshold at the Arctic sea ice edge based on ice-water boundary lines extracted from MOD29 was 33%, which was higher than that of the commonly used 15% discriminant threshold. The average SIC threshold at sea ice edge based on ice-water boundary lines extracted by visual interpretation from four scenes of the MODIS image was 35% when compared to the average value of 36% from the MOD29 extracted ice edge pixels for the same days. The average SIC of 31% at the sea ice edge points extracted from ship-based observations also confirmed that choosing around 30% as the SIC threshold during summer is recommended for sea ice extent calculations based on SSMIS PM data. These results can provide a reference for further studying the variation of sea ice under the rapidly changing Arctic. Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 9086 KiB

Open AccessArticle

Recognition of Broken Wire Rope Based on Remanence using EEMD and Wavelet Methods

by Juwei Zhang^1,2,*, Pengbo Zheng^1,2,* and Xiaojiang Tan^1,2

¹ College of Electrical Engineering, Henan University of Science and Technology, Luoyang 471023, China

² Power Electronics Device and System Engineering Laboratory of Henan, Henan University of Science and Technology, Luoyang 471023, China

Sensors 2018, 18(4), 1110; https://doi.org/10.3390/s18041110 - 5 Apr 2018

Cited by 33 | Viewed by 6551

Abstract

The magnetic flux leakage method is widely used for non-destructive testing in wire rope applications. A non-destructive testing device for wire rope based on remanence was designed to solve the problems of large volume, low accuracy, and complex operations seen in traditional devices. [...] Read more.

The magnetic flux leakage method is widely used for non-destructive testing in wire rope applications. A non-destructive testing device for wire rope based on remanence was designed to solve the problems of large volume, low accuracy, and complex operations seen in traditional devices. A wavelet denoising method based on ensemble empirical mode decomposition was proposed to reduce the system noise in broken wire rope testing. After extracting the defects image, the wavelet super-resolution reconstruction technique was adopted to improve the resolution of defect grayscale. A back propagation neural network was designed to classify defects by the feature vectors of area, rectangle, stretch length, and seven invariant moments. The experimental results show that the device was not only highly precise and sensitive, but also easy to operate; noise is effectively suppressed by the proposed filtering algorithm, and broken wires are classified by the network. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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22 pages, 43042 KiB

Open AccessArticle

Evaluation for Bearing Wear States Based on Online Oil Multi-Parameters Monitoring

by Si-Yuan Wang^†

, Ding-Xin Yang^*,†

and Hai-Feng Hu

¹ Science and Technology on Integrated Logistics Support Laboratory, National University of Defense Technology, Changsha 410073, China

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1111; https://doi.org/10.3390/s18041111 - 5 Apr 2018

Cited by 11 | Viewed by 5821

Abstract

As bearings are critical components of a mechanical system, it is important to characterize their wear states and evaluate health conditions. In this paper, a novel approach for analyzing the relationship between online oil multi-parameter monitoring samples and bearing wear states has been [...] Read more.

As bearings are critical components of a mechanical system, it is important to characterize their wear states and evaluate health conditions. In this paper, a novel approach for analyzing the relationship between online oil multi-parameter monitoring samples and bearing wear states has been proposed based on an improved gray k-means clustering model (G-KCM). First, an online monitoring system with multiple sensors for bearings is established, obtaining oil multi-parameter data and vibration signals for bearings through the whole lifetime. Secondly, a gray correlation degree distance matrix is generated using a gray correlation model (GCM) to express the relationship of oil monitoring samples at different times and then a KCM is applied to cluster the matrix. Analysis and experimental results show that there is an obvious correspondence that state changing coincides basically in time between the lubricants’ multi-parameters and the bearings’ wear states. It also has shown that online oil samples with multi-parameters have early wear failure prediction ability for bearings superior to vibration signals. It is expected to realize online oil monitoring and evaluation for bearing health condition and to provide a novel approach for early identification of bearing-related failure modes. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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13 pages, 23334 KiB

Open AccessArticle

Vibration and Noise in Magnetic Resonance Imaging of the Vocal Tract: Differences between Whole-Body and Open-Air Devices

by Jiří Přibil^1,*, Anna Přibilová² and Ivan Frollo¹

¹ Institute of Measurement Science, Slovak Academy of Sciences, 841 04 Bratislava, Slovak Republic

² Faculty of Electrical Engineering and Information Technology, Slovak University of Technology in Bratislava, 812 19 Bratislava, Slovak Republic

Sensors 2018, 18(4), 1112; https://doi.org/10.3390/s18041112 - 5 Apr 2018

Cited by 5 | Viewed by 7229

Abstract

This article compares open-air and whole-body magnetic resonance imaging (MRI) equipment working with a weak magnetic field as regards the methods of its generation, spectral properties of mechanical vibration and acoustic noise produced by gradient coils during the scanning process, and the measured [...] Read more.

This article compares open-air and whole-body magnetic resonance imaging (MRI) equipment working with a weak magnetic field as regards the methods of its generation, spectral properties of mechanical vibration and acoustic noise produced by gradient coils during the scanning process, and the measured noise intensity. These devices are used for non-invasive MRI reconstruction of the human vocal tract during phonation with simultaneous speech recording. In this case, the vibration and noise have negative influence on quality of speech signal. Two basic measurement experiments were performed within the paper: mapping sound pressure levels in the MRI device vicinity and picking up vibration and noise signals in the MRI scanning area. Spectral characteristics of these signals are then analyzed statistically and compared visually and numerically. Full article

(This article belongs to the Special Issue Optical Methods in Sensing and Imaging for Medical and Biological Applications)

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20 pages, 11173 KiB

Open AccessArticle

3D-Subspace-Based Auto-Paired Azimuth Angle, Elevation Angle, and Range Estimation for 24G FMCW Radar with an L-Shaped Array

by HyungSoo Nam¹, Ying-Chun Li²

, ByungGil Choi¹ and Daegun Oh^1,*

¹ Collaborative Robots Research Center, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Korea

² Department of Electronic Engineering, Hanyang University, Seoul 04763, Korea

Sensors 2018, 18(4), 1113; https://doi.org/10.3390/s18041113 - 5 Apr 2018

Cited by 9 | Viewed by 6275

Abstract

In this paper, a three-dimensional (3D)-subspace-based azimuth angle, elevation angle, and range estimation method with auto-pairing is proposed for frequency-modulated continuous waveform (FMCW) radar with an L-shaped array. The proposed method is designed to exploit the 3D shift-invariant structure of the stacked Hankel [...] Read more.

In this paper, a three-dimensional (3D)-subspace-based azimuth angle, elevation angle, and range estimation method with auto-pairing is proposed for frequency-modulated continuous waveform (FMCW) radar with an L-shaped array. The proposed method is designed to exploit the 3D shift-invariant structure of the stacked Hankel snapshot matrix for auto-paired azimuth angle, elevation angle, and range estimation. The effectiveness of the proposed method is verified through a variety of experiments conducted in a chamber. For the realization of the proposed method, K-band FMCW radar is implemented with an L-shaped antenna. Full article

(This article belongs to the Section Remote Sensors)

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10 pages, 47090 KiB

Open AccessArticle

Oil Motion Control by an Extra Pinning Structure in Electro-Fluidic Display

by Yingying Dou^1,2, Biao Tang^1,2,*, Jan Groenewold^2,3, Fahong Li², Qiao Yue^1,2, Rui Zhou^1,2, Hui Li^1,2, Lingling Shui^1,2, Alex Henzen² and Guofu Zhou^1,2,4,5,*

¹ Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China

² National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou 510006, China

³ Van’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Research Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands

⁴ Shenzhen Guohua Optoelectronics Tech. Co. Ltd., Shenzhen 518110, China

⁵ Academy of Shenzhen Guohua Optoelectronics, Shenzhen 518110, China

Sensors 2018, 18(4), 1114; https://doi.org/10.3390/s18041114 - 6 Apr 2018

Cited by 19 | Viewed by 5064

Abstract

Oil motion control is the key for the optical performance of electro-fluidic displays (EFD). In this paper, we introduced an extra pinning structure (EPS) into the EFD pixel to control the oil motion inside for the first time. The pinning structure canbe fabricated [...] Read more.

Oil motion control is the key for the optical performance of electro-fluidic displays (EFD). In this paper, we introduced an extra pinning structure (EPS) into the EFD pixel to control the oil motion inside for the first time. The pinning structure canbe fabricated together with the pixel wall by a one-step lithography process. The effect of the relative location of the EPS in pixels on the oil motion was studied by a series of optoelectronic measurements. EPS showed good control of oil rupture position. The properly located EPS effectively guided the oil contraction direction, significantly accelerated switching on process, and suppressed oil overflow, without declining in aperture ratio. An asymmetrically designed EPS off the diagonal is recommended. This study provides a novel and facile way for oil motion control within an EFD pixel in both direction and timescale. Full article

(This article belongs to the Special Issue Microfluidic Sensors)

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9 pages, 1122 KiB

Open AccessArticle

Low-Cost GRIN-Lens-Based Nephelometric Turbidity Sensing in the Range of 0.1–1000 NTU

by Michael Metzger^1,2, Alexander Konrad², Felix Blendinger¹, Andreas Modler³, Alfred J. Meixner², Volker Bucher¹ and Marc Brecht^2,4,*

¹ Institute for Applied Research, Faculty for Mechanical and Medical Engineering, Furtwangen University, 78054 Villingen-Schwenningen, Germany

² Institute of Physical and Theoretical Chemistry, University of Tuebingen, 72076 Tuebingen, Germany

³ Department of Mathematics, Physics and Chemistry, Beuth University of Applied Sciences, 13353 Berlin, Germany

⁴ Process Analysis and Technology (PA&T), Reutlingen Research Institute, Reutlingen University, 72762 Reutlingen, Germany

Sensors 2018, 18(4), 1115; https://doi.org/10.3390/s18041115 - 6 Apr 2018

Cited by 25 | Viewed by 9465

Abstract

Turbidity sensing is very common in the control of drinking water. Furthermore, turbidity measurements are applied in the chemical (e.g., process monitoring), pharmaceutical (e.g., drug discovery), and food industries (e.g., the filtration of wine and beer). The most common measurement technique is nephelometric [...] Read more.

Turbidity sensing is very common in the control of drinking water. Furthermore, turbidity measurements are applied in the chemical (e.g., process monitoring), pharmaceutical (e.g., drug discovery), and food industries (e.g., the filtration of wine and beer). The most common measurement technique is nephelometric turbidimetry. A nephelometer is a device for measuring the amount of scattered light of suspended particles in a liquid by using a light source and a light detector orientated in 90° to each other. Commercially available nephelometers cost usually—depending on the measurable range, reliability, and precision—thousands of euros. In contrast, our new developed GRIN-lens-based nephelometer, called GRINephy, combines low costs with excellent reproducibility and precision, even at very low turbidity levels, which is achieved by its ability to rotate the sample. Thereby, many cuvette positions can be measured, which results in a more precise average value for the turbidity calculated by an algorithm, which also eliminates errors caused by scratches and contaminations on the cuvettes. With our compact and cheap Arduino-based sensor, we are able to measure in the range of 0.1–1000 NTU and confirm the ISO 7027-1:2016 for low turbidity values. Full article

(This article belongs to the Special Issue Sensors for Emerging Environmental Markers and Contaminants)

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15 pages, 44588 KiB

Open AccessArticle

Soil Water Measurement Using Actively Heated Fiber Optics at Field Scale

by Duminda N. Vidana Gamage¹

, Asim Biswas^2,*

, Ian B. Strachan¹ and Viacheslav I. Adamchuk³

¹ Department of Natural Resource Sciences, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada

² School of Environmental Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada

³ Department of Bioresource Engineering, McGill University, 21111 Lakeshore Road, Ste Anne-de-Bellevue, QC H9X 3V9, Canada

Sensors 2018, 18(4), 1116; https://doi.org/10.3390/s18041116 - 6 Apr 2018

Cited by 25 | Viewed by 6212

Abstract

Several studies have demonstrated the potential of actively heated fiber optics (AHFO) to measure soil water content (SWC) at high spatial and temporal resolutions. This study tested the feasibility of the AHFO technique to measure soil water in the surface soil of a [...] Read more.

Several studies have demonstrated the potential of actively heated fiber optics (AHFO) to measure soil water content (SWC) at high spatial and temporal resolutions. This study tested the feasibility of the AHFO technique to measure soil water in the surface soil of a crop grown field over a growing season using an in-situ calibration approach. Heat pulses of five minutes duration were applied at a rate of 7.28 W m⁻¹ along eighteen fiber optic cable transects installed at three depths (0.05, 0.10 and 0.20 m) at six-hour intervals. Cumulative temperature increase (T_cum) during heat pulses was calculated at locations along the cable. While predicting commercial sensor measurements, the AHFO showed root mean square errors (RMSE) of 2.8, 3.7 and 3.7% for 0.05, 0.10 and 0.20 m depths, respectively. Further, the coefficients of determination (R²) for depth specific relationships were 0.87 (0.05 m depth), 0.46 (0.10 m depth), 0.86 (0.20 m depth) and 0.66 (all depths combined). This study showed a great potential of the AHFO technique to measure soil water at high spatial resolutions (<1 m) and to monitor soil water dynamics of surface soil in a crop grown field over a cropping season with a reasonable compromise between accuracy and practicality. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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17 pages, 5416 KiB

Open AccessArticle

Collision Detection for Underwater ROV Manipulator Systems

by Satja Sivčev^1,2,*,†

, Matija Rossi^1,2,†, Joseph Coleman^1,2

, Edin Omerdić^1,2

, Gerard Dooly^1,2 and Daniel Toal^1,2

¹ MaREI – Marine and Renewable Energy Ireland, Cork, Ireland

² Department of Electronic and Computer Engineering, University of Limerick, Limerick, Ireland

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1117; https://doi.org/10.3390/s18041117 - 6 Apr 2018

Cited by 40 | Viewed by 7788

Abstract

Work-class ROVs equipped with robotic manipulators are extensively used for subsea intervention operations. Manipulators are teleoperated by human pilots relying on visual feedback from the worksite. Operating in a remote environment, with limited pilot perception and poor visibility, manipulator collisions which may cause [...] Read more.

Work-class ROVs equipped with robotic manipulators are extensively used for subsea intervention operations. Manipulators are teleoperated by human pilots relying on visual feedback from the worksite. Operating in a remote environment, with limited pilot perception and poor visibility, manipulator collisions which may cause significant damage are likely to happen. This paper presents a real-time collision detection algorithm for marine robotic manipulation. The proposed collision detection mechanism is developed, integrated into a commercial ROV manipulator control system, and successfully evaluated in simulations and experimental setup using a real industry standard underwater manipulator. The presented collision sensing solution has a potential to be a useful pilot assisting tool that can reduce the task load, operational time, and costs of subsea inspection, repair, and maintenance operations. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 5691 KiB

Open AccessArticle

Smart City Pilot Projects Using LoRa and IEEE802.15.4 Technologies

by Gianni Pasolini^1,*

, Chiara Buratti¹, Luca Feltrin¹

, Flavio Zabini¹, Cristina De Castro², Roberto Verdone¹ and Oreste Andrisano¹

¹ DEI, University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy

² IEIIT, National Research Council, Viale Risorgimento 2, 40136 Bologna, Italy

Sensors 2018, 18(4), 1118; https://doi.org/10.3390/s18041118 - 6 Apr 2018

Cited by 150 | Viewed by 14505

Abstract

Information and Communication Technologies (ICTs), through wireless communications and the Internet of Things (IoT) paradigm, are the enabling keys for transforming traditional cities into smart cities, since they provide the core infrastructure behind public utilities and services. However, to be effective, IoT-based services [...] Read more.

Information and Communication Technologies (ICTs), through wireless communications and the Internet of Things (IoT) paradigm, are the enabling keys for transforming traditional cities into smart cities, since they provide the core infrastructure behind public utilities and services. However, to be effective, IoT-based services could require different technologies and network topologies, even when addressing the same urban scenario. In this paper, we highlight this aspect and present two smart city testbeds developed in Italy. The first one concerns a smart infrastructure for public lighting and relies on a heterogeneous network using the IEEE 802.15.4 short-range communication technology, whereas the second one addresses smart-building applications and is based on the LoRa low-rate, long-range communication technology. The smart lighting scenario is discussed providing the technical details and the economic benefits of a large-scale (around 3000 light poles) flexible and modular implementation of a public lighting infrastructure, while the smart-building testbed is investigated, through measurement campaigns and simulations, assessing the coverage and the performance of the LoRa technology in a real urban scenario. Results show that a proper parameter setting is needed to cover large urban areas while maintaining the airtime sufficiently low to keep packet losses at satisfactory levels. Full article

(This article belongs to the Special Issue The Architectures, Systems, and Applications of Internet of Things for Smart Cities)

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14 pages, 28808 KiB

Open AccessArticle

Optimization Strategies for Responsivity Control of Microgel Assisted Lab-On-Fiber Optrodes

by Martino Giaquinto¹

, Alberto Micco¹, Anna Aliberti¹, Eugenia Bobeico², Vera La Ferrara², Menotti Ruvo³, Armando Ricciardi^1,*

and Andrea Cusano^1,*

¹ Optoelectronics Group, Department of Engineering, University of Sannio, I-82100 Benevento, Italy

² ENEA, Portici Research Center, P. le E. Fermi 1, Portici, I-80055 Napoli, Italy

³ Institute of Biostructure and Bioimaging, National Research Council, I-80143 Napoli, Italy

Sensors 2018, 18(4), 1119; https://doi.org/10.3390/s18041119 - 6 Apr 2018

Cited by 24 | Viewed by 4576

Abstract

Integrating multi-responsive polymers such as microgels onto optical fiber tips, in a controlled fashion, enables unprecedented functionalities to Lab-on-fiber optrodes. The creation of a uniform microgel monolayer with a specific coverage factor is crucial for enhancing the probes responsivity to a pre-defined target [...] Read more.

Integrating multi-responsive polymers such as microgels onto optical fiber tips, in a controlled fashion, enables unprecedented functionalities to Lab-on-fiber optrodes. The creation of a uniform microgel monolayer with a specific coverage factor is crucial for enhancing the probes responsivity to a pre-defined target parameter. Here we report a reliable fabrication strategy, based on the dip coating technique, for the controlled realization of microgel monolayer onto unconventional substrates, such as the optical fiber tip. The latter was previously covered by a plasmonic nanostructure to make it sensitive to superficial environment changes. Microgels have been prepared using specific Poly(N-isopropylacrylamide)-based monomers that enable bulky size changes in response to both temperature and pH variations. The formation of the microgel monolayer is efficiently controlled through the selection of suitable operating pH, temperature and concentration of particle dispersions used during the dipping procedure. The effect of each parameter has been evaluated, and the validity of our procedure is confirmed by means of both morphological and optical characterizations. We demonstrate that when the coverage factor exceeds 90%, the probe responsivity to microgels swelling/collapsing is significantly improved. Our study opens new paradigms for the development of engineered microgels assisted Lab-on-Fiber probes for biochemical applications. Full article

(This article belongs to the Special Issue Lab on Fiber Optrodes for Chemical and Biological Sensing: Recent Trends and Advances)

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18 pages, 49622 KiB

Open AccessArticle

Retrieval of Winter Wheat Leaf Area Index from Chinese GF-1 Satellite Data Using the PROSAIL Model

by He Li¹, Gaohuan Liu¹, Qingsheng Liu¹, Zhongxin Chen² and Chong Huang^1,*

¹ State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

² Key Laboratory of Agricultural Remote Sensing, Ministry of Agriculture/Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China

Sensors 2018, 18(4), 1120; https://doi.org/10.3390/s18041120 - 6 Apr 2018

Cited by 38 | Viewed by 4882

Abstract

Leaf area index (LAI) is one of the key biophysical parameters in crop structure. The accurate quantitative estimation of crop LAI is essential to verify crop growth and health. The PROSAIL radiative transfer model (RTM) is one of the most established methods for [...] Read more.

Leaf area index (LAI) is one of the key biophysical parameters in crop structure. The accurate quantitative estimation of crop LAI is essential to verify crop growth and health. The PROSAIL radiative transfer model (RTM) is one of the most established methods for estimating crop LAI. In this study, a look-up table (LUT) based on the PROSAIL RTM was first used to estimate winter wheat LAI from GF-1 data, which accounted for some available prior knowledge relating to the distribution of winter wheat characteristics. Next, the effects of 15 LAI-LUT strategies with reflectance bands and 10 LAI-LUT strategies with vegetation indexes on the accuracy of the winter wheat LAI retrieval with different phenological stages were evaluated against in situ LAI measurements. The results showed that the LUT strategies of LAI-GNDVI were optimal and had the highest accuracy with a root mean squared error (RMSE) value of 0.34, and a coefficient of determination (R²) of 0.61 during the elongation stages, and the LUT strategies of LAI-Green were optimal with a RMSE of 0.74, and R² of 0.20 during the grain-filling stages. The results demonstrated that the PROSAIL RTM had great potential in winter wheat LAI inversion with GF-1 satellite data and the performance could be improved by selecting the appropriate LUT inversion strategies in different growth periods. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 7517 KiB

Open AccessArticle

Energy-Efficient Data Collection Method for Sensor Networks by Integrating Asymmetric Communication and Wake-Up Radio

by Masanari Iwata, Suhua Tang and Sadao Obana^*

Graduate School of Informatics and Engineering, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan

Sensors 2018, 18(4), 1121; https://doi.org/10.3390/s18041121 - 6 Apr 2018

Cited by 15 | Viewed by 4319

Abstract

In large-scale wireless sensor networks (WSNs), nodes close to sink nodes consume energy more quickly than other nodes due to packet forwarding. A mobile sink is a good solution to this issue, although it causes two new problems to nodes: (i) overhead of [...] Read more.

In large-scale wireless sensor networks (WSNs), nodes close to sink nodes consume energy more quickly than other nodes due to packet forwarding. A mobile sink is a good solution to this issue, although it causes two new problems to nodes: (i) overhead of updating routing information; and (ii) increased operating time due to aperiodic query. To solve these problems, this paper proposes an energy-efficient data collection method, Sink-based Centralized transmission Scheduling (SC-Sched), by integrating asymmetric communication and wake-up radio. Specifically, each node is equipped with a low-power wake-up receiver. The sink node determines transmission scheduling, and transmits a wake-up message using a large transmission power, directly activating a pair of nodes simultaneously which will communicate with a normal transmission power. This paper further investigates how to deal with frame loss caused by fading and how to mitigate the impact of the wake-up latency of communication modules. Simulation evaluations confirm that using multiple channels effectively reduces data collection time and SC-Sched works well with a mobile sink. Compared with the conventional duty-cycling method, SC-Sched greatly reduces total energy consumption and improves the network lifetime by 7.47 times in a WSN with 4 data collection points and 300 sensor nodes. Full article

(This article belongs to the Special Issue QoS in Wireless Sensor Networks)

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19 pages, 18905 KiB

Open AccessArticle

Latent Factors Limiting the Performance of sEMG-Interfaces

by Sergey Lobov^1,*, Nadia Krilova¹, Innokentiy Kastalskiy¹

, Victor Kazantsev¹ and Valeri A. Makarov^1,2,*

¹ Lobachevsky State University of Nizhny Novgorod, Gagarin Ave. 23, 603950 Nizhny Novgorod, Russia

² Department of Applied Mathematics, Instituto de Matemática Interdisciplinar, Universidad Complutense de Madrid, 28040 Madrid, Spain

Sensors 2018, 18(4), 1122; https://doi.org/10.3390/s18041122 - 6 Apr 2018

Cited by 84 | Viewed by 10302

Abstract

Recent advances in recording and real-time analysis of surface electromyographic signals (sEMG) have fostered the use of sEMG human–machine interfaces for controlling personal computers, prostheses of upper limbs, and exoskeletons among others. Despite a relatively high mean performance, sEMG-interfaces still exhibit strong variance [...] Read more.

Recent advances in recording and real-time analysis of surface electromyographic signals (sEMG) have fostered the use of sEMG human–machine interfaces for controlling personal computers, prostheses of upper limbs, and exoskeletons among others. Despite a relatively high mean performance, sEMG-interfaces still exhibit strong variance in the fidelity of gesture recognition among different users. Here, we systematically study the latent factors determining the performance of sEMG-interfaces in synthetic tests and in an arcade game. We show that the degree of muscle cooperation and the amount of the body fatty tissue are the decisive factors in synthetic tests. Our data suggest that these factors can only be adjusted by long-term training, which promotes fine-tuning of low-level neural circuits driving the muscles. Short-term training has no effect on synthetic tests, but significantly increases the game scoring. This implies that it works at a higher decision-making level, not relevant for synthetic gestures. We propose a procedure that enables quantification of the gestures’ fidelity in a dynamic gaming environment. For each individual subject, the approach allows identifying “problematic” gestures that decrease gaming performance. This information can be used for optimizing the training strategy and for adapting the signal processing algorithms to individual users, which could be a way for a qualitative leap in the development of future sEMG-interfaces. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 9604 KiB

Open AccessArticle

On-Chip Cell Staining and Counting Platform for the Rapid Detection of Blood Cells in Cerebrospinal Fluid

by Yujin Lee^†, Byeongyeon Kim^† and Sungyoung Choi^*

¹ Department of Biomedical Engineering, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, Korea

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1124; https://doi.org/10.3390/s18041124 - 7 Apr 2018

Cited by 15 | Viewed by 8213

Abstract

Counting blood cells in cerebrospinal fluid (CSF) is indispensable for diagnosing several pathological conditions in the central nervous system, such as meningitis, even though collecting CSF samples is invasive. Cell counting methods, such as hemocytometer chambers and flow cytometers, have been used for [...] Read more.

Counting blood cells in cerebrospinal fluid (CSF) is indispensable for diagnosing several pathological conditions in the central nervous system, such as meningitis, even though collecting CSF samples is invasive. Cell counting methods, such as hemocytometer chambers and flow cytometers, have been used for CSF cell counting, but they often lack the sensitivity to detect low blood cell numbers. They also depend on off-chip, manual sample preparation or require bulky, costly equipment, thereby limiting their clinical utility. Here, we present a portable cell counting platform for simple, rapid CSF cell counting that integrates a microfluidic cell counting chamber with a miniaturized microscope. The microfluidic chamber is designed not only to be a reagent container for on-chip cell staining but also to have a large control volume for accurate cell counting. The proposed microscope miniaturizes both bright-field and fluorescence microscopy with a simple optical setup and a custom cell-counting program, thereby allowing rapid and automated cell counting of nucleated white blood cells and non-nucleated red blood cells in fluorescence and bright-field images. Using these unique features, we successfully demonstrate the ability of our counting platform to measure low CSF cell counts without sample preparation. Full article

(This article belongs to the Special Issue Microfluidic Sensors)

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16 pages, 2122 KiB

Open AccessArticle

Mobile User Connectivity in Relay-Assisted Visible Light Communications

by Petr Pešek^1,*, Stanislav Zvanovec¹

, Petr Chvojka¹, Manav R. Bhatnagar², Zabih Ghassemlooy³

and Prakriti Saxena²

¹ Department of Electromagnetic Field, Faculty of Electrical Engineering, Czech Technical University in Prague, 2 Technicka, 16627 Prague, Czech Republic

² Department of Electrical Engineering, Indian Institute of Technology Delhi, Hauz Khas, IN-110016 New Delhi, India

³ Optical Communications Research Group, NCRLab, Faculty of Engineering and Environment, Northumbria University, NE1 8ST Newcastle upon Tyne, UK

Sensors 2018, 18(4), 1125; https://doi.org/10.3390/s18041125 - 7 Apr 2018

Cited by 25 | Viewed by 5862

Abstract

In this paper, we investigate relay-assisted visible light communications (VLC) where a mobile user acts as a relay and forwards data from a transmitter to the end mobile user. We analyse the utilization of the amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes. The [...] Read more.

In this paper, we investigate relay-assisted visible light communications (VLC) where a mobile user acts as a relay and forwards data from a transmitter to the end mobile user. We analyse the utilization of the amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes. The focus of the paper is on analysis of the behavior of the mobile user acting as a relay while considering a realistic locations of the receivers and transmitters on a standard mobile phone, more specifically with two photodetectors on both sides of a mobile phone and a transmitting LED array located upright. We also investigate dependency of the bit error rate (BER) performance on the azimuth and elevation angles of the mobile relay device within a typical office environment. We provide a new analytical description of BER for AF and DF-based relays in VLC. In addition we compare AF and DF-based systems and show that DF offers a marginal improvement in the coverage area with a BER < 10^–3 and a data rate of 100 Mb/s. Numerical results also illustrate that relay-based systems offer a significant improvement in terms of the coverage compared to direct non-line of sight VLC links. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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14 pages, 12873 KiB

Open AccessArticle

Application of Deep Learning Architectures for Accurate and Rapid Detection of Internal Mechanical Damage of Blueberry Using Hyperspectral Transmittance Data

by Zhaodi Wang

, Menghan Hu^* and Guangtao Zhai^*

Institute of Image Communication and Information Processing, Shanghai Jiao Tong University, Shanghai 200240, China

Sensors 2018, 18(4), 1126; https://doi.org/10.3390/s18041126 - 7 Apr 2018

Cited by 145 | Viewed by 11348

Abstract

Deep learning has become a widely used powerful tool in many research fields, although not much so yet in agriculture technologies. In this work, two deep convolutional neural networks (CNN), viz. Residual Network (ResNet) and its improved version named ResNeXt, are used to [...] Read more.

Deep learning has become a widely used powerful tool in many research fields, although not much so yet in agriculture technologies. In this work, two deep convolutional neural networks (CNN), viz. Residual Network (ResNet) and its improved version named ResNeXt, are used to detect internal mechanical damage of blueberries using hyperspectral transmittance data. The original structure and size of hypercubes are adapted for the deep CNN training. To ensure that the models are applicable to hypercube, we adjust the number of filters in the convolutional layers. Moreover, a total of 5 traditional machine learning algorithms, viz. Sequential Minimal Optimization (SMO), Linear Regression (LR), Random Forest (RF), Bagging and Multilayer Perceptron (MLP), are performed as the comparison experiments. In terms of model assessment, k-fold cross validation is used to indicate that the model performance does not vary with the different combination of dataset. In real-world application, selling damaged berries will lead to greater interest loss than discarding the sound ones. Thus, precision, recall, and F1-score are also used as the evaluation indicators alongside accuracy to quantify the false positive rate. The first three indicators are seldom used by investigators in the agricultural engineering domain. Furthermore, ROC curves and Precision-Recall curves are plotted to visualize the performance of classifiers. The fine-tuned ResNet/ResNeXt achieve average accuracy and F1-score of 0.8844/0.8784 and 0.8952/0.8905, respectively. Classifiers SMO/ LR/RF/Bagging/MLP obtain average accuracy and F1-score of 0.8082/0.7606/0.7314/0.7113/0.7827 and 0.8268/0.7796/0.7529/0.7339/0.7971, respectively. Two deep learning models achieve better classification performance than the traditional machine learning methods. Classification for each testing sample only takes 5.2 ms and 6.5 ms respectively for ResNet and ResNeXt, indicating that the deep learning framework has great potential for online fruit sorting. The results of this study demonstrate the potential of deep CNN application on analyzing the internal mechanical damage of fruit. Full article

(This article belongs to the Special Issue Artificial Intelligence and Machine Learning in Sensors Networks)

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18 pages, 75395 KiB

Open AccessArticle

Efficient Visible Light Communication Transmitters Based on Switching-Mode dc-dc Converters

by Juan Rodríguez^1,*

, Diego G. Lamar¹

, Daniel G. Aller¹

, Pablo F. Miaja²

and Javier Sebastián¹

¹ Power Supply Group, Electrical Engineering Department, University of Oviedo, Gijón 33204, Spain

² Power Systems Division, European Space Agency (ESA), Noordwijk 2201AZ, The Netherlands

Sensors 2018, 18(4), 1127; https://doi.org/10.3390/s18041127 - 7 Apr 2018

Cited by 24 | Viewed by 6921

Abstract

Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting [...] Read more.

Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting diodes (LEDs) enable. The switching-mode dc-to-dc converter (SMC_dc-dc) must be the cornerstone of the LED driver of VLC transmitters in order to incorporate the communication functionality into LED lighting, keeping high power efficiency. However, the new requirements related to the communication, especially the high bandwidth that the LED driver must achieve, converts the design of the SMC_dc-dc into a very challenging task. In this work, three different methods for achieving such a high bandwidth with an SMC_dc-dc are presented: increasing the order of the SMC_dc-dc output filter, increasing the number of voltage inputs, and increasing the number of phases. These three strategies are combinable and the optimum design depends on the particular VLC application, which determines the requirements of the VLC transmitter. As an example, an experimental VLC transmitter based on a two-phase buck converter with a fourth-order output filter will demonstrate that a bandwidth of several hundred kilohertz (kHz) can be achieved with output power levels close to 10 W and power efficiencies between 85% and 90%. In conclusion, the design strategy presented allows us to incorporate VLC into SSL, achieving high bit rates without damaging the power efficiency of LED lighting. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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22 pages, 23648 KiB

Open AccessArticle

Bearing Fault Diagnosis by a Robust Higher-Order Super-Twisting Sliding Mode Observer

by Farzin Piltan¹

and Jong-Myon Kim^2,*

¹ Department of Electrical, Electronics and Computer Engineering, University of Ulsan, Ulsan 680-479, Korea

² School of IT Convergence, University of Ulsan, Ulsan 680-479, Korea

Sensors 2018, 18(4), 1128; https://doi.org/10.3390/s18041128 - 7 Apr 2018

Cited by 44 | Viewed by 5435

Abstract

An effective bearing fault detection and diagnosis (FDD) model is important for ensuring the normal and safe operation of machines. This paper presents a reliable model-reference observer technique for FDD based on modeling of a bearing’s vibration data by analyzing the dynamic properties [...] Read more.

An effective bearing fault detection and diagnosis (FDD) model is important for ensuring the normal and safe operation of machines. This paper presents a reliable model-reference observer technique for FDD based on modeling of a bearing’s vibration data by analyzing the dynamic properties of the bearing and a higher-order super-twisting sliding mode observation (HOSTSMO) technique for making diagnostic decisions using these data models. The HOSTSMO technique can adaptively improve the performance of estimating nonlinear failures in rolling element bearings (REBs) over a linear approach by modeling 5 degrees of freedom under normal and faulty conditions. The effectiveness of the proposed technique is evaluated using a vibration dataset provided by Case Western Reserve University, which consists of vibration acceleration signals recorded for REBs with inner, outer, ball, and no faults, i.e., normal. Experimental results indicate that the proposed technique outperforms the ARX-Laguerre proportional integral observation (ALPIO) technique, yielding 18.82%, 16.825%, and 17.44% performance improvements for three levels of crack severity of 0.007, 0.014, and 0.021 inches, respectively. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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15 pages, 18450 KiB

Open AccessArticle

Non-Mutually Exclusive Deep Neural Network Classifier for Combined Modes of Bearing Fault Diagnosis

by Bach Phi Duong

and Jong-Myon Kim^*

School of Electrical, Electronics and Computer Engineering, University of Ulsan, 44610 Ulsan, Korea

Sensors 2018, 18(4), 1129; https://doi.org/10.3390/s18041129 - 7 Apr 2018

Cited by 33 | Viewed by 5326

Abstract

The simultaneous occurrence of various types of defects in bearings makes their diagnosis more challenging owing to the resultant complexity of the constituent parts of the acoustic emission (AE) signals. To address this issue, a new approach is proposed in this paper for [...] Read more.

The simultaneous occurrence of various types of defects in bearings makes their diagnosis more challenging owing to the resultant complexity of the constituent parts of the acoustic emission (AE) signals. To address this issue, a new approach is proposed in this paper for the detection of multiple combined faults in bearings. The proposed methodology uses a deep neural network (DNN) architecture to effectively diagnose the combined defects. The DNN structure is based on the stacked denoising autoencoder non-mutually exclusive classifier (NMEC) method for combined modes. The NMEC-DNN is trained using data for a single fault and it classifies both single faults and multiple combined faults. The results of experiments conducted on AE data collected through an experimental test-bed demonstrate that the DNN achieves good classification performance with a maximum accuracy of 95%. The proposed method is compared with a multi-class classifier based on support vector machines (SVMs). The NMEC-DNN yields better diagnostic performance in comparison to the multi-class classifier based on SVM. The NMEC-DNN reduces the number of necessary data collections and improves the bearing fault diagnosis performance. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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20 pages, 11681 KiB

Open AccessArticle

Study and Development of a Fluorescence Based Sensor System for Monitoring Oxygen in Wine Production: The WOW Project

by Nicola Trivellin^1,3, Diego Barbisan¹, Denis Badocco², Paolo Pastore², Gaudenzio Meneghesso³

, Matteo Meneghini³

, Enrico Zanoni³, Giuseppe Belgioioso^3,† and Angelo Cenedese^3,*

¹ LightCube Srl, Viale della Navigazione Interna, 51-35129 Padova, Italy

² Department of Chemical Science, University of Padova, Via Marzolo, 1-35131 Padova, Italy

³ Department of Information Engineering, University of Padova, Via Gradenigo, 6/B-35131 Padova, Italy

^† Current affiliation: Department of Electrical Engineering, Eindhoven University of Technology, De Zaale, 5612 AJ Eindhoven.

Sensors 2018, 18(4), 1130; https://doi.org/10.3390/s18041130 - 7 Apr 2018

Cited by 24 | Viewed by 6652

Abstract

The importance of oxygen in the winemaking process is widely known, as it affects the chemical aspects and therefore the organoleptic characteristics of the final product. Hence, it is evident the usefulness of a continuous and real-time measurements of the levels of oxygen [...] Read more.

The importance of oxygen in the winemaking process is widely known, as it affects the chemical aspects and therefore the organoleptic characteristics of the final product. Hence, it is evident the usefulness of a continuous and real-time measurements of the levels of oxygen in the various stages of the winemaking process, both for monitoring and for control. The WOW project (Deployment of WSAN technology for monitoring Oxygen in Wine products) has focused on the design and the development of an innovative device for monitoring the oxygen levels in wine. This system is based on the use of an optical fiber to measure the luminescent lifetime variation of a reference metal/porphyrin complex, which decays in presence of oxygen. The developed technology results in a high sensitivity and low cost sensor head that can be employed for measuring the dissolved oxygen levels at several points inside a wine fermentation or aging tank. This system can be complemented with dynamic modeling techniques to provide predictive behavior of the nutrient evolution in space and time given few sampled measuring points, for both process monitoring and control purposes. The experimental validation of the technology has been first performed in a controlled laboratory setup to attain calibration and study sensitivity with respect to different photo-luminescent compounds and alcoholic or non-alcoholic solutions, and then in an actual case study during a measurement campaign at a renown Italian winery. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2017)

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11 pages, 15389 KiB

Open AccessArticle

3D Copper Foam-Supported CuCo₂O₄ Nanosheet Arrays as Electrode for Enhanced Non-Enzymatic Glucose Sensing

by Fangqing Liu, Yi Zhuang, Mingliang Guo, Yongjun Chen, Jinchun Tu and Lei Ding^*

State Key Laboratory of Marine Resource Utilization in South China Sea, College of Materials and Chemical Engineering, Hainan University, Haikou 570228, China

Sensors 2018, 18(4), 1131; https://doi.org/10.3390/s18041131 - 8 Apr 2018

Cited by 17 | Viewed by 6423

Abstract

CuCo₂O₄ anchored on Cu foam (CuCo₂O₄/CF) with polycrystalline features was fabricated by a mild process based on solvothermal reaction and subsequent calcination in this work. The structure and morphology of the obtained materials were thoroughly characterized [...] Read more.

CuCo₂O₄ anchored on Cu foam (CuCo₂O₄/CF) with polycrystalline features was fabricated by a mild process based on solvothermal reaction and subsequent calcination in this work. The structure and morphology of the obtained materials were thoroughly characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy. According to the above analysis, the morphology of the CuCo₂O₄ was nanosheet arrays. Meanwhile, the CuCo₂O₄ was grown on Cu foam successfully. The CuCo₂O₄/CF displayed good electrochemical properties for glucose detection at a linear range from 0 mM to 1.0 mM. Meanwhile, the detection limit was as low as 1 μM (S/N = 3), and the sensitivity was 20,981 μA·mM⁻¹·cm⁻². Moreover, the selectivity and the stability were tested with excellent results. This nanomaterial could show great potential application in electrochemical sensors. Full article

(This article belongs to the Section Biosensors)

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15 pages, 27349 KiB

Open AccessArticle

Real-Time Seismic Data from the Bottom Sea

by Xavier Roset^1,†, Enric Trullols¹, Carola Artero-Delgado¹, Joana Prat¹, Joaquin Del Río¹

, Immaculada Massana¹, Montserrat Carbonell¹, Jaime Barco de la Torre² and Daniel Mihai Toma^1,*,†

¹ SARTI Research Group, Universitat Politècnica de Catalunya (UPC), 08800 Vilanova i la Geltrú, Spain

² Instituto Geográfico Nacional C/General Ibáñez de Íbero 3, 28003 Madrid, Spain

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1132; https://doi.org/10.3390/s18041132 - 8 Apr 2018

Cited by 5 | Viewed by 5905

Abstract

An anchored marine seismometer, acquiring real-time seismic data, has been built and tested. The system consists of an underwater seismometer, a surface buoy, and a mooring line that connects them. Inductive communication through the mooring line provides an inexpensive, reliable, and flexible solution. [...] Read more.

An anchored marine seismometer, acquiring real-time seismic data, has been built and tested. The system consists of an underwater seismometer, a surface buoy, and a mooring line that connects them. Inductive communication through the mooring line provides an inexpensive, reliable, and flexible solution. Prior to the deployment the dynamics of the system have been simulated numerically in order to find optimal materials, cables, buoys, and connections under critical marine conditions. The seismometer used is a high sensitivity triaxial broadband geophone able to measure low vibrational signals produced by the underwater seismic events. The power to operate the surface buoy is provided by solar panels. Additional batteries are needed for the underwater unit. In this paper we also present the first results and an earthquake detection of a prototype system that demonstrates the feasibility of this concept. The seismometer transmits continuous data at a rate of 1000 bps to a controller equipped with a radio link in the surface buoy. A GPS receiver on the surface buoy has been configured to perform accurate timestamps on the seismic data, which makes it possible to integrate the seismic data from these marine seismometers into the existing seismic network. Full article

(This article belongs to the Special Issue Underwater Sensing, Communication, Networking and Systems)

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24 pages, 7916 KiB

Open AccessArticle

Drawing Inspiration from Human Brain Networks: Construction of Interconnected Virtual Networks

by Masaya Murakami^1,*

, Daichi Kominami², Kenji Leibnitz³

and Masayuki Murata¹

¹ Graduate School of Information Science and Technology, Osaka University, 1-5, Yamadaoka, Suita 565-0871, Osaka, Japan

² Graduate School of Economics, Osaka University, 1-7, Machikaneyama-cho, Toyonaka 560-0043, Osaka, Japan

³ Center for Information and Neural Networks (CiNet), 1-4, Yamadaoka, Suita 565-0871, Osaka, Japan

Sensors 2018, 18(4), 1133; https://doi.org/10.3390/s18041133 - 8 Apr 2018

Cited by 9 | Viewed by 4611

Abstract

Virtualization of wireless sensor networks (WSN) is widely considered as a foundational block of edge/fog computing, which is a key technology that can help realize next-generation Internet of things (IoT) networks. In such scenarios, multiple IoT devices and service modules will be virtually [...] Read more.

Virtualization of wireless sensor networks (WSN) is widely considered as a foundational block of edge/fog computing, which is a key technology that can help realize next-generation Internet of things (IoT) networks. In such scenarios, multiple IoT devices and service modules will be virtually deployed and interconnected over the Internet. Moreover, application services are expected to be more sophisticated and complex, thereby increasing the number of modifications required for the construction of network topologies. Therefore, it is imperative to establish a method for constructing a virtualized WSN (VWSN) topology that achieves low latency on information transmission and high resilience against network failures, while keeping the topological construction cost low. In this study, we draw inspiration from inter-modular connectivity in human brain networks, which achieves high performance when dealing with large-scale networks composed of a large number of modules (i.e., regions) and nodes (i.e., neurons). We propose a method for assigning inter-modular links based on a connectivity model observed in the cerebral cortex of the brain, known as the exponential distance rule (EDR) model. We then choose endpoint nodes of these links by controlling inter-modular assortativity, which characterizes the topological connectivity of brain networks. We test our proposed methods using simulation experiments. The results show that the proposed method based on the EDR model can construct a VWSN topology with an optimal combination of communication efficiency, robustness, and construction cost. Regarding the selection of endpoint nodes for the inter-modular links, the results also show that high assortativity enhances the robustness and communication efficiency because of the existence of inter-modular links of two high-degree nodes. Full article

(This article belongs to the Section Sensor Networks)

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10 pages, 12063 KiB

Open AccessArticle

Click Access to a Cyclodextrin-Based Spatially Confined AIE Material for Hydrogenase Recognition

by Rui Zhao¹

, Bin Li², Yong Wang^1,3,* and Wenping Hu^1,3

¹ Tianjin Key Laboratory of Molecular Optoelectronic Science, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China

² School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China

³ Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China

Sensors 2018, 18(4), 1134; https://doi.org/10.3390/s18041134 - 8 Apr 2018

Cited by 4 | Viewed by 4414

Abstract

The spatial confinement of conjugated phenyl rotators is a compulsory requirement for the fluorescence enhancement of aggregation induced emission (AIE) molecules. This work reports a novel spatially confined AIE material by restricting several tetraphenylethylene (TPE) molecules around the primary face of β-cyclodextrin (CD) [...] Read more.

The spatial confinement of conjugated phenyl rotators is a compulsory requirement for the fluorescence enhancement of aggregation induced emission (AIE) molecules. This work reports a novel spatially confined AIE material by restricting several tetraphenylethylene (TPE) molecules around the primary face of β-cyclodextrin (CD) via a Cu(I) catalytic 1,3-dipolar cycloaddition reaction (click chemistry). The spatial confinement effect was found to significantly enhance the fluorescence emission when compared with a single TPE modified CD. In addition, the emission maxima took place with the dimethyl sulfoxide volume ratio of 30% in a water mixture, which is remarkably different from traditional AIE molecules. Benefiting from the CD’s complexation effect, this material exhibits a selective fluorescence quenching property in certain hydrogenases and can be used as a fluorescence probe for hydrogenase sensing. This demonstrates the potential of the spatially confined AIECD for practical applications. Full article

(This article belongs to the Section Chemical Sensors)

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15 pages, 3101 KiB

Open AccessArticle

Defocus Blur Detection and Estimation from Imaging Sensors

by Jinyang Li^*, Zhijing Liu and Yong Yao

School of Computer Science and Technology, Xidian University, Xi’an 710071, Shannxi, China

Sensors 2018, 18(4), 1135; https://doi.org/10.3390/s18041135 - 8 Apr 2018

Cited by 6 | Viewed by 7408

Abstract

Sparse representation has been proven to be a very effective technique for various image restoration applications. In this paper, an improved sparse representation based method is proposed to detect and estimate defocus blur of imaging sensors. Considering the fact that the patterns usually [...] Read more.

Sparse representation has been proven to be a very effective technique for various image restoration applications. In this paper, an improved sparse representation based method is proposed to detect and estimate defocus blur of imaging sensors. Considering the fact that the patterns usually vary remarkably across different images or different patches in a single image, it is unstable and time-consuming for sparse representation over an over-complete dictionary. We propose an adaptive domain selection scheme to prelearn a set of compact dictionaries and adaptively select the optimal dictionary to each image patch. Then, with nonlocal structure similarity, the proposed method learns nonzero-mean coefficients’ distributions that are much more closer to the real ones. More accurate sparse coefficients can be obtained and further improve the performance of results. Experimental results validate that the proposed method outperforms existing defocus blur estimation approaches, both qualitatively and quantitatively. Full article

(This article belongs to the Special Issue Sensors Signal Processing and Visual Computing)

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14 pages, 18098 KiB

Open AccessArticle

Effects of tDCS on Real-Time BCI Detection of Pedaling Motor Imagery

by Maria De la Soledad Rodriguez-Ugarte^*, Eduardo Iáñez, Mario Ortiz-Garcia

and José M. Azorín

Brain-Machine Interface Systems Lab, Miguel Hernández University of Elche, Avda. de la Universidad S/N Ed. Innova, Elche, 03202 Alicante, Spain

Sensors 2018, 18(4), 1136; https://doi.org/10.3390/s18041136 - 8 Apr 2018

Cited by 21 | Viewed by 6012

Abstract

The purpose of this work is to strengthen the cortical excitability over the primary motor cortex (M1) and the cerebro-cerebellar pathway by means of a new transcranial direct current stimulation (tDCS) configuration to detect lower limb motor imagery (MI) in real time using [...] Read more.

The purpose of this work is to strengthen the cortical excitability over the primary motor cortex (M1) and the cerebro-cerebellar pathway by means of a new transcranial direct current stimulation (tDCS) configuration to detect lower limb motor imagery (MI) in real time using two different cognitive neural states: relax and pedaling MI. The anode is located over the primary motor cortex in Cz, and the cathode over the right cerebro-cerebellum. The real-time brain–computer interface (BCI) designed is based on finding, for each electrode selected, the power at the particular frequency where the most difference between the two mental tasks is observed. Electroencephalographic (EEG) electrodes are placed over the brain’s premotor area (PM), M1, supplementary motor area (SMA) and primary somatosensory cortex (S1). A single-blind study is carried out, where fourteen healthy subjects are separated into two groups: sham and active tDCS. Each subject is experimented on for five consecutive days. On all days, the results achieved by the active tDCS group were over 60% in real-time detection accuracy, with a five-day average of 62.6%. The sham group eventually reached those levels of accuracy, but it needed three days of training to do so. Full article

(This article belongs to the Special Issue Assistance Robotics and Biosensors)

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17 pages, 45533 KiB

Open AccessArticle

Visual Servoing-Based Nanorobotic System for Automated Electrical Characterization of Nanotubes inside SEM

by Huiyang Ding^1,†, Chaoyang Shi^2,†, Li Ma^1,*,‡, Zhan Yang^3,4,*,‡

, Mingyu Wang³, Yaqiong Wang³, Tao Chen^3,4, Lining Sun^3,4 and Fukuda Toshio⁵

¹ School of Mechatronic Engineering and Automation, Shanghai University, Shanghai 200072, China

² Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON M5S 3G8, Canada

³ Provincial Jiangsu Key Laboratory for Advanced Robotics, Soochow University, Suzhou 215123, China; 20165229031@stu.suda.edu.cn (M.W.)

⁴ Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, China

⁵ Intelligent Robotics Institute, School of Mechatronic Engineering, Beijing Institute of Technology, Beijing 100081, China

^† H. Ding and C. Shi contribute equally to this work and are co-first authors.

^‡ Denotes equal contribution and joint first authorship.

Sensors 2018, 18(4), 1137; https://doi.org/10.3390/s18041137 - 8 Apr 2018

Cited by 23 | Viewed by 5129

Abstract

The maneuvering and electrical characterization of nanotubes inside a scanning electron microscope (SEM) has historically been time-consuming and laborious for operators. Before the development of automated nanomanipulation-enabled techniques for the performance of pick-and-place and characterization of nanoobjects, these functions were still incomplete and [...] Read more.

The maneuvering and electrical characterization of nanotubes inside a scanning electron microscope (SEM) has historically been time-consuming and laborious for operators. Before the development of automated nanomanipulation-enabled techniques for the performance of pick-and-place and characterization of nanoobjects, these functions were still incomplete and largely operated manually. In this paper, a dual-probe nanomanipulation system vision-based feedback was demonstrated to automatically perform 3D nanomanipulation tasks, to investigate the electrical characterization of nanotubes. The XY-position of Atomic Force Microscope (AFM) cantilevers and individual carbon nanotubes (CNTs) were precisely recognized via a series of image processing operations. A coarse-to-fine positioning strategy in the Z-direction was applied through the combination of the sharpness-based depth estimation method and the contact-detection method. The use of nanorobotic magnification-regulated speed aided in improving working efficiency and reliability. Additionally, we proposed automated alignment of manipulator axes by visual tracking the movement trajectory of the end effector. The experimental results indicate the system’s capability for automated measurement electrical characterization of CNTs. Furthermore, the automated nanomanipulation system has the potential to be extended to other nanomanipulation tasks. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 28732 KiB

Open AccessArticle

DCT-Based Preprocessing Approach for ICA in Hyperspectral Data Analysis

by Kamel Boukhechba^*

, Huayi Wu and Razika Bazine

The State Key Laboratory of Information Engineering in Surveying, Mapping, and Remote Sensing, Wuhan University, Wuhan 430079, China

Sensors 2018, 18(4), 1138; https://doi.org/10.3390/s18041138 - 8 Apr 2018

Cited by 20 | Viewed by 6164

Abstract

The huge quantity of information and the high spectral resolution of hyperspectral imagery present a challenge when performing traditional processing techniques such as classification. Dimensionality and noise reduction improves both efficiency and accuracy, while retaining essential information. Among the many dimensionality reduction methods, [...] Read more.

The huge quantity of information and the high spectral resolution of hyperspectral imagery present a challenge when performing traditional processing techniques such as classification. Dimensionality and noise reduction improves both efficiency and accuracy, while retaining essential information. Among the many dimensionality reduction methods, Independent Component Analysis (ICA) is one of the most popular techniques. However, ICA is computationally costly, and given the absence of specific criteria for component selection, constrains its application in high-dimension data analysis. To overcome this limitation, we propose a novel approach that applies Discrete Cosine Transform (DCT) as preprocessing for ICA. Our method exploits the unique capacity of DCT to pack signal energy in few low-frequency coefficients, thus reducing noise and computation time. Subsequently, ICA is applied on this reduced data to make the output components as independent as possible for subsequent hyperspectral classification. To evaluate this novel approach, the reduced data using (1) ICA without preprocessing; (2) ICA with the commonly used preprocessing techniques which is Principal Component Analysis (PCA); and (3) ICA with DCT preprocessing are tested with Support Vector Machine (SVM) and K-Nearest Neighbor (K-NN) classifiers on two real hyperspectral datasets. Experimental results in both instances indicate that data after our proposed DCT preprocessing method combined with ICA yields superior hyperspectral classification accuracy. Full article

(This article belongs to the Special Issue Advances in Remote Sensing of Land-Cover and Land-Use Changes)

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24 pages, 85022 KiB

Open AccessArticle

FPGA Based Adaptive Rate and Manifold Pattern Projection for Structured Light 3D Camera System

by Muhammad Atif

and Sukhan Lee^*

Intelligent Systems Research Institute (ISRI), College of Information and Communication Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Korea

Sensors 2018, 18(4), 1139; https://doi.org/10.3390/s18041139 - 8 Apr 2018

Cited by 4 | Viewed by 6686

Abstract

The quality of the captured point cloud and the scanning speed of a structured light 3D camera system depend upon their capability of handling the object surface of a large reflectance variation in the trade-off of the required number of patterns to be [...] Read more.

The quality of the captured point cloud and the scanning speed of a structured light 3D camera system depend upon their capability of handling the object surface of a large reflectance variation in the trade-off of the required number of patterns to be projected. In this paper, we propose and implement a flexible embedded framework that is capable of triggering the camera single or multiple times for capturing single or multiple projections within a single camera exposure setting. This allows the 3D camera system to synchronize the camera and projector even for miss-matched frame rates such that the system is capable of projecting different types of patterns for different scan speed applications. This makes the system capturing a high quality of 3D point cloud even for the surface of a large reflectance variation while achieving a high scan speed. The proposed framework is implemented on the Field Programmable Gate Array (FPGA), where the camera trigger is adaptively generated in such a way that the position and the number of triggers are automatically determined according to camera exposure settings. In other words, the projection frequency is adaptive to different scanning applications without altering the architecture. In addition, the proposed framework is unique as it does not require any external memory for storage because pattern pixels are generated in real-time, which minimizes the complexity and size of the application-specific integrated circuit (ASIC) design and implementation. Full article

(This article belongs to the Special Issue Selected Papers from MFI 2017 - International Conference on Multisensor Fusion and Integration for Intelligent Systems)

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16 pages, 47907 KiB

Open AccessArticle

A Fiber Bragg Grating Interrogation System with Self-Adaption Threshold Peak Detection Algorithm

by Weifang Zhang¹, Yingwu Li¹, Bo Jin², Feifei Ren¹, Hongxun Wang^1,*

and Wei Dai¹

¹ School of Reliability and Systems Engineering, Beihang University, Haidian Dist., Beijing 100191, China

² School of Energy and Power Engineering, Beihang University, Haidian Dist., Beijing 100191, China

Sensors 2018, 18(4), 1140; https://doi.org/10.3390/s18041140 - 8 Apr 2018

Cited by 12 | Viewed by 5653

Abstract

A Fiber Bragg Grating (FBG) interrogation system with a self-adaption threshold peak detection algorithm is proposed and experimentally demonstrated in this study. This system is composed of a field programmable gate array (FPGA) and advanced RISC machine (ARM) platform, tunable Fabry–Perot (F–P) filter [...] Read more.

A Fiber Bragg Grating (FBG) interrogation system with a self-adaption threshold peak detection algorithm is proposed and experimentally demonstrated in this study. This system is composed of a field programmable gate array (FPGA) and advanced RISC machine (ARM) platform, tunable Fabry–Perot (F–P) filter and optical switch. To improve system resolution, the F–P filter was employed. As this filter is non-linear, this causes the shifting of central wavelengths with the deviation compensated by the parts of the circuit. Time-division multiplexing (TDM) of FBG sensors is achieved by an optical switch, with the system able to realize the combination of 256 FBG sensors. The wavelength scanning speed of 800 Hz can be achieved by a FPGA+ARM platform. In addition, a peak detection algorithm based on a self-adaption threshold is designed and the peak recognition rate is 100%. Experiments with different temperatures were conducted to demonstrate the effectiveness of the system. Four FBG sensors were examined in the thermal chamber without stress. When the temperature changed from 0 °C to 100 °C, the degree of linearity between central wavelengths and temperature was about 0.999 with the temperature sensitivity being 10 pm/°C. The static interrogation precision was able to reach 0.5 pm. Through the comparison of different peak detection algorithms and interrogation approaches, the system was verified to have an optimum comprehensive performance in terms of precision, capacity and speed. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Based Sensors)

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16 pages, 36482 KiB

Open AccessArticle

ECCM Scheme against Interrupted Sampling Repeater Jammer Based on Parameter-Adjusted Waveform Design

by Zhenhua Wei¹, Zhen Liu^2,*

, Bo Peng² and Rui Shen²

¹ Rocket Force University of Engineering, Xi’an 710025, China

² College of Electronic Science, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(4), 1141; https://doi.org/10.3390/s18041141 - 8 Apr 2018

Cited by 58 | Viewed by 4790

Abstract

Interrupted sampling repeater jamming (ISRJ) is an effective way of deceiving coherent radar sensors, especially for linear frequency modulated (LFM) radar. In this paper, for a simplified scenario with a single jammer, we propose a dynamic electronic counter-counter measure (ECCM) scheme based on [...] Read more.

Interrupted sampling repeater jamming (ISRJ) is an effective way of deceiving coherent radar sensors, especially for linear frequency modulated (LFM) radar. In this paper, for a simplified scenario with a single jammer, we propose a dynamic electronic counter-counter measure (ECCM) scheme based on jammer parameter estimation and transmitted signal design. Firstly, the LFM waveform is transmitted to estimate the main jamming parameters by investigating the discontinuousness of the ISRJ’s time-frequency (TF) characteristics. Then, a parameter-adjusted intra-pulse frequency coded signal, whose ISRJ signal after matched filtering only forms a single false target, is designed adaptively according to the estimated parameters, i.e., sampling interval, sampling duration and repeater times. Ultimately, for typical jamming scenes with different jamming signal ratio (JSR) and duty cycle, we propose two particular ISRJ suppression approaches. Simulation results validate the effective performance of the proposed scheme for countering the ISRJ, and the trade-off relationship between the two approaches is demonstrated. Full article

(This article belongs to the Section Remote Sensors)

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9 pages, 9005 KiB

Open AccessArticle

An Intelligent Monitoring Network for Detection of Cracks in Anvils of High-Press Apparatus

by Hao Tian^1,2,3, Zhaoli Yan^1,2,* and Jun Yang^1,2

¹ Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China

² Key Laboratory of Noise and Vibration Research, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China

³ University of Chinese Academy of Sciences, Beijing 100049, China

Sensors 2018, 18(4), 1142; https://doi.org/10.3390/s18041142 - 9 Apr 2018

Cited by 2 | Viewed by 2826

Abstract

Due to the endurance of alternating high pressure and temperature, the carbide anvils of the high-press apparatus, which are widely used in the synthetic diamond industry, are prone to crack. In this paper, an acoustic method is used to monitor the crack events, [...] Read more.

Due to the endurance of alternating high pressure and temperature, the carbide anvils of the high-press apparatus, which are widely used in the synthetic diamond industry, are prone to crack. In this paper, an acoustic method is used to monitor the crack events, and the intelligent monitoring network is proposed to classify the sound samples. The pulse sound signals produced by such cracking are first extracted based on a short-time energy threshold. Then, the signals are processed with the proposed intelligent monitoring network to identify the operation condition of the anvil of the high-pressure apparatus. The monitoring network is an improved convolutional neural network that solves the problems that may occur in practice. The length of pulse sound excited by the crack growth is variable, so a spatial pyramid pooling layer is adopted to solve the variable-length input problem. An adaptive weighted algorithm for loss function is proposed in this method to handle the class imbalance problem. The good performance regarding the accuracy and balance of the proposed intelligent monitoring network is validated through the experiments finally. Full article

(This article belongs to the Section Sensor Networks)

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11 pages, 3940 KiB

Open AccessArticle

Absolute Measurement of the Refractive Index of Water by a Mode-Locked Laser at 518 nm

by Zhaopeng Meng¹, Xiaoyu Zhai^1,2, Jianguo Wei¹, Zhiyang Wang³ and Hanzhong Wu^3,*

¹ School of Computer Software, Tianjin University, Tianjin 300072, China

² National Ocean Technology Center, Tianjin 300112, China

³ School of Marine Science and Technology, Tianjin University, Tianjin 300072, China

Sensors 2018, 18(4), 1143; https://doi.org/10.3390/s18041143 - 9 Apr 2018

Cited by 13 | Viewed by 6632

Abstract

In this paper, we demonstrate a method using a frequency comb, which can precisely measure the refractive index of water. We have developed a simple system, in which a Michelson interferometer is placed into a quartz-glass container with a low expansion coefficient, and [...] Read more.

In this paper, we demonstrate a method using a frequency comb, which can precisely measure the refractive index of water. We have developed a simple system, in which a Michelson interferometer is placed into a quartz-glass container with a low expansion coefficient, and for which compensation of the thermal expansion of the water container is not required. By scanning a mirror on a moving stage, a pair of cross-correlation patterns can be generated. We can obtain the length information via these cross-correlation patterns, with or without water in the container. The refractive index of water can be measured by the resulting lengths. Long-term experimental results show that our method can measure the refractive index of water with a high degree of accuracy—measurement uncertainty at 10⁻⁵ level has been achieved, compared with the values calculated by the empirical formula. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 1295 KiB

Open AccessArticle

Multi-Objectives Optimization of Ventilation Controllers for Passive Cooling in Residential Buildings

by Krzysztof Grygierek^1,* and Joanna Ferdyn-Grygierek²

¹ Faculty of Civil Engineering, The Silesian University of Technology, Akademicka 5, 44-100 Gliwice, Poland

² Faculty of Energy and Environmental Engineering, The Silesian University of Technology, Konarskiego 18, 44-100 Gliwice, Poland

Sensors 2018, 18(4), 1144; https://doi.org/10.3390/s18041144 - 9 Apr 2018

Cited by 22 | Viewed by 3903

Abstract

An inappropriate indoor climate, mostly indoor temperature, may cause occupants’ discomfort. There are a great number of air conditioning systems that make it possible to maintain the required thermal comfort. Their installation, however, involves high investment costs and high energy demand. The study [...] Read more.

An inappropriate indoor climate, mostly indoor temperature, may cause occupants’ discomfort. There are a great number of air conditioning systems that make it possible to maintain the required thermal comfort. Their installation, however, involves high investment costs and high energy demand. The study analyses the possibilities of limiting too high a temperature in residential buildings using passive cooling by means of ventilation with ambient cool air. A fuzzy logic controller whose aim is to control mechanical ventilation has been proposed and optimized. In order to optimize the controller, the modified Multiobjective Evolutionary Algorithm, based on the Strength Pareto Evolutionary Algorithm, has been adopted. The optimization algorithm has been implemented in MATLAB^®, which is coupled by MLE+ with EnergyPlus for performing dynamic co-simulation between the programs. The example of a single detached building shows that the occupants’ thermal comfort in a transitional climate may improve significantly owing to mechanical ventilation controlled by the suggested fuzzy logic controller. When the system is connected to the traditional cooling system, it may further bring about a decrease in cooling demand. Full article

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19 pages, 3124 KiB

Open AccessArticle

A SINS/SRS/GNS Autonomous Integrated Navigation System Based on Spectral Redshift Velocity Measurements

by Wenhui Wei^1,2,*, Zhaohui Gao¹, Shesheng Gao¹ and Ke Jia¹

¹ School of Automatics, Northwestern Polytechnical University, 710072 Xi’an, China

² School of Geological Engineering and Surveying and Mapping, Chang’an University, 710064 Xi’an, China

Sensors 2018, 18(4), 1145; https://doi.org/10.3390/s18041145 - 9 Apr 2018

Cited by 29 | Viewed by 6869

Abstract

In order to meet the requirements of autonomy and reliability for the navigation system, combined with the method of measuring speed by using the spectral redshift information of the natural celestial bodies, a new scheme, consisting of Strapdown Inertial Navigation System (SINS)/Spectral Redshift [...] Read more.

In order to meet the requirements of autonomy and reliability for the navigation system, combined with the method of measuring speed by using the spectral redshift information of the natural celestial bodies, a new scheme, consisting of Strapdown Inertial Navigation System (SINS)/Spectral Redshift (SRS)/Geomagnetic Navigation System (GNS), is designed for autonomous integrated navigation systems. The principle of this SINS/SRS/GNS autonomous integrated navigation system is explored, and the corresponding mathematical model is established. Furthermore, a robust adaptive central difference particle filtering algorithm is proposed for this autonomous integrated navigation system. The simulation experiments are conducted and the results show that the designed SINS/SRS/GNS autonomous integrated navigation system possesses good autonomy, strong robustness and high reliability, thus providing a new solution for autonomous navigation technology. Full article

(This article belongs to the Special Issue Sensor Fusion and Novel Technologies in Positioning and Navigation)

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16 pages, 8871 KiB

Open AccessArticle

Three-Dimensional Registration for Handheld Profiling Systems Based on Multiple Shot Structured Light

by Shirazi Muhammad Ayaz¹, Danish Khan¹

and Min Young Kim^1,2,*

¹ School of Electronics Engineering, IT College, Kyungpook National University, 1370 Sankyuk-dong, Buk-gu, Daegu 41566, Korea

² Research Center for Neurosurgical Robotic System, Kyungpook National University, 1370 Sankyuk-dong, Buk-gu, Daegu 41566, Korea

Sensors 2018, 18(4), 1146; https://doi.org/10.3390/s18041146 - 9 Apr 2018

Cited by 6 | Viewed by 6133

Abstract

In this article, a multi-view registration approach for the 3D handheld profiling system based on the multiple shot structured light technique is proposed. The multi-view registration approach is categorized into coarse registration and point cloud refinement using the iterative closest point (ICP) algorithm. [...] Read more.

In this article, a multi-view registration approach for the 3D handheld profiling system based on the multiple shot structured light technique is proposed. The multi-view registration approach is categorized into coarse registration and point cloud refinement using the iterative closest point (ICP) algorithm. Coarse registration of multiple point clouds was performed using relative orientation and translation parameters estimated via homography-based visual navigation. The proposed system was evaluated using an artificial human skull and a paper box object. For the quantitative evaluation of the accuracy of a single 3D scan, a paper box was reconstructed, and the mean errors in its height and breadth were found to be 9.4 μm and 23 μm, respectively. A comprehensive quantitative evaluation and comparison of proposed algorithm was performed with other variants of ICP. The root mean square error for the ICP algorithm to register a pair of point clouds of the skull object was also found to be less than 1 mm. Full article

(This article belongs to the Special Issue Depth Sensors and 3D Vision)

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17 pages, 30980 KiB

Open AccessArticle

Maritime over the Horizon Sensor Integration: High Frequency Surface-Wave-Radar and Automatic Identification System Data Integration Algorithm

by Dejan Nikolic^*

, Nikola Stojkovic and Nikola Lekic

Vlatacom Institute, Bulevar Milutina Milankovića 5, Beograd 11070, Serbia

Sensors 2018, 18(4), 1147; https://doi.org/10.3390/s18041147 - 9 Apr 2018

Cited by 22 | Viewed by 5658

Abstract

To obtain the complete operational picture of the maritime situation in the Exclusive Economic Zone (EEZ) which lies over the horizon (OTH) requires the integration of data obtained from various sensors. These sensors include: high frequency surface-wave-radar (HFSWR), satellite automatic identification system (SAIS) [...] Read more.

To obtain the complete operational picture of the maritime situation in the Exclusive Economic Zone (EEZ) which lies over the horizon (OTH) requires the integration of data obtained from various sensors. These sensors include: high frequency surface-wave-radar (HFSWR), satellite automatic identification system (SAIS) and land automatic identification system (LAIS). The algorithm proposed in this paper utilizes radar tracks obtained from the network of HFSWRs, which are already processed by a multi-target tracking algorithm and associates SAIS and LAIS data to the corresponding radar tracks, thus forming an integrated data pair. During the integration process, all HFSWR targets in the vicinity of AIS data are evaluated and the one which has the highest matching factor is used for data association. On the other hand, if there is multiple AIS data in the vicinity of a single HFSWR track, the algorithm still makes only one data pair which consists of AIS and HFSWR data with the highest mutual matching factor. During the design and testing, special attention is given to the latency of AIS data, which could be very high in the EEZs of developing countries. The algorithm is designed, implemented and tested in a real working environment. The testing environment is located in the Gulf of Guinea and includes a network of HFSWRs consisting of two HFSWRs, several coastal sites with LAIS receivers and SAIS data provided by provider of SAIS data. Full article

(This article belongs to the Section Sensor Networks)

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12 pages, 3846 KiB

Open AccessArticle

Near-Field Chipless Radio-Frequency Identification (RFID) Sensing and Identification System with Switching Reading

by Ferran Paredes^1,*

, Cristian Herrojo¹

, Javier Mata-Contreras¹, Miquel Moras², Alba Núñez²

, Eloi Ramon² and Ferran Martín¹

¹ GEMMA/CIMITEC, Departament d’Enginyeria Electrònica, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain

² Institut de Microelectrònica de Barcelona, IMB-CNM (CSIC), 08193 Bellaterra, Spain

Sensors 2018, 18(4), 1148; https://doi.org/10.3390/s18041148 - 9 Apr 2018

Cited by 19 | Viewed by 6715

Abstract

A chipless radio-frequency identification (chipless-RFID) and sensing system, where tags are read by proximity (near-field) through a switch, is presented. The tags consist of a set of identical resonant elements (split-ring resonators or SRRs), printed or etched at predefined and equidistant positions, forming [...] Read more.

A chipless radio-frequency identification (chipless-RFID) and sensing system, where tags are read by proximity (near-field) through a switch, is presented. The tags consist of a set of identical resonant elements (split-ring resonators or SRRs), printed or etched at predefined and equidistant positions, forming a linear chain, each SRR providing a bit of information. The logic state (‘1’ or ‘0’) associated with each resonator depends on whether it is present or not in the predefined position. The reader is an array of power splitters used to feed a set of SRR-loaded transmission lines (in equal number to the number of resonant elements, or bits, of the tag). The feeding (interrogation) signal is a harmonic (single-tone) signal tuned to a frequency in the vicinity of the fundamental resonance of the SRRs. The set of SRR-loaded lines must be designed so that the corresponding SRRs are in perfect alignment with the SRRs of the tag, provided the tag is positioned on top of the reader. Thus, in a reading operation, as long as the tag is very close to the reader, the SRRs of the tag modify (decrease) the transmission coefficient of the corresponding reader line (through electromagnetic coupling between both SRRs), and the amplitude of the output signal is severely reduced. Therefore, the identification (ID) code of the tag is contained in the amplitudes of the output signals of the SRR-loaded lines, which can be inferred sequentially by means of a switching system. Unlike previous chipless-RFID systems based on near-field and sequential bit reading, the tags in the proposed system can be merely positioned on top of the reader, conveniently aligned, without the need to mechanically place them across the reader. Since tag reading is only possible if the tag is very close to the reader, this system can be also used as a proximity sensor with applications such as target identification. The proposed chipless-RFID and sensing approach is validated by reading a designed 4-bit tag. For identification purposes, this system is of special interest in applications where a low number of bits suffice, and tag reading by proximity is acceptable (or even convenient). Applications mostly related to secure paper, particularly involving a limited number of items (e.g., exams, ballots, etc.), in order to provide authenticity and avoid counterfeiting, are envisaged. As a proximity sensor, the system may be of use in detecting and distinguishing different targets in applications such as smart packaging. Full article

(This article belongs to the Special Issue RFID-Based Sensors for IoT Applications)

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17 pages, 34176 KiB

Open AccessArticle

Statistical Multipath Model Based on Experimental GNSS Data in Static Urban Canyon Environment

by Yuze Wang

, Xin Chen^*

and Peilin Liu

Shanghai Key Laboratory of Navigation and Location Based Service, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Sensors 2018, 18(4), 1149; https://doi.org/10.3390/s18041149 - 10 Apr 2018

Cited by 42 | Viewed by 6636

Abstract

A deep understanding of multipath characteristics is essential to design signal simulators and receivers in global navigation satellite system applications. As a new constellation is deployed and more applications occur in the urban environment, the statistical multipath models of navigation signal need further [...] Read more.

A deep understanding of multipath characteristics is essential to design signal simulators and receivers in global navigation satellite system applications. As a new constellation is deployed and more applications occur in the urban environment, the statistical multipath models of navigation signal need further study. In this paper, we present statistical distribution models of multipath time delay, multipath power attenuation, and multipath fading frequency based on the experimental data in the urban canyon environment. The raw data of multipath characteristics are obtained by processing real navigation signal to study the statistical distribution. By fitting the statistical data, it shows that the probability distribution of time delay follows a gamma distribution which is related to the waiting time of Poisson distributed events. The fading frequency follows an exponential distribution, and the mean of multipath power attenuation decreases linearly with an increasing time delay. In addition, the detailed statistical characteristics for different elevations and orbits satellites is studied, and the parameters of each distribution are quite different. The research results give useful guidance for navigation simulator and receiver designers. Full article

(This article belongs to the Section Remote Sensors)

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11 pages, 18812 KiB

Open AccessArticle

Polyacrylonitrile Nanofiber-Based Quartz Crystal Microbalance for Sensitive Detection of Safrole

by Aditya Rianjanu^1,*

, Roto Roto^2,3

, Trisna Julian¹, Shidiq Nur Hidayat¹, Ahmad Kusumaatmaja^1,3

, Eko Agus Suyono⁴ and Kuwat Triyana^1,3,*

¹ Department of Physics, Universitas Gadjah Mada, Sekip Utara, Yogyakarta 55281, Indonesia

² Department of Chemistry, Universitas Gadjah Mada, Sekip Utara, Yogyakarta 55281, Indonesia

³ Nanomaterial Research Group, Universitas Gadjah Mada, Sekip Utara, Yogyakarta 55281, Indonesia

⁴ Department of Biology, Universitas Gadjah Mada, Sekip Utara, Yogyakarta 55281, Indonesia

Sensors 2018, 18(4), 1150; https://doi.org/10.3390/s18041150 - 10 Apr 2018

Cited by 41 | Viewed by 8299

Abstract

Safrole is the main precursor for producing the amphetamine-type stimulant (ATS) drug, N-methyl-3,4-methylenedioxyamphetamine (MDMA), also known as ecstasy. We devise a polyacrylonitrile (PAN) nanofiber-based quartz crystal microbalance (QCM) for detecting safrole. The PAN nanofibers were fabricated by direct electrospinning to modify the [...] Read more.

Safrole is the main precursor for producing the amphetamine-type stimulant (ATS) drug, N-methyl-3,4-methylenedioxyamphetamine (MDMA), also known as ecstasy. We devise a polyacrylonitrile (PAN) nanofiber-based quartz crystal microbalance (QCM) for detecting safrole. The PAN nanofibers were fabricated by direct electrospinning to modify the QCM chips. The PAN nanofiber on the QCM chips has a diameter of 240 ± 10 nm. The sensing of safrole by QCM modified with PAN nanofiber shows good reversibility and an apparent sensitivity of 4.6 Hz·L/mg. The proposed method is simple, inexpensive, and convenient for detecting safrole, and can be an alternative to conventional instrumental analytical methods for general volatile compounds. Full article

(This article belongs to the Section Chemical Sensors)

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22 pages, 42959 KiB

Open AccessArticle

New Analysis Scheme of Flow-Acoustic Coupling for Gas Ultrasonic Flowmeter with Vortex near the Transducer

by Yanzhao Sun^*

, Tao Zhang^* and Dandan Zheng

School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China

Sensors 2018, 18(4), 1151; https://doi.org/10.3390/s18041151 - 10 Apr 2018

Cited by 20 | Viewed by 7104

Abstract

Ultrasonic flowmeters with a small or medium diameter are widely used in process industries. The flow field disturbance on acoustic propagation caused by a vortex near the transducer inside the sensor as well as the mechanism and details of flow-acoustic interaction are needed [...] Read more.

Ultrasonic flowmeters with a small or medium diameter are widely used in process industries. The flow field disturbance on acoustic propagation caused by a vortex near the transducer inside the sensor as well as the mechanism and details of flow-acoustic interaction are needed to strengthen research. For that reason, a new hybrid scheme is proposed; the theories of computational fluid dynamics (CFD), wave acoustics, and ray acoustics are used comprehensively by a new step-by-step method. The flow field with a vortex near the transducer, and its influence on sound propagation, receiving, and flowmeter performance are analyzed in depth. It was found that, firstly, the velocity and vortex intensity distribution were asymmetric on the sensor cross-section and acoustic path. Secondly, when passing through the vortex zone, the central ray trajectory was deflected significantly. The sound pressure on the central line of the sound path also changed. Thirdly, the pressure deviation becomes larger with as the flow velocity increases. The deviation was up to 17% for different velocity profiles in a range of 0.6 m/s to 53 m/s. Lastly, in comparison to the theoretical value, the relative deviation of the instrument coefficient for the velocity profile with a vortex near the transducer reached up to −17%. In addition, the rationality of the simulation was proved by experiments. Full article

(This article belongs to the Special Issue Ultrasonic Sensors 2018)

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11 pages, 5637 KiB

Open AccessArticle

Measuring the Human Ultra-Weak Photon Emission Distribution Using an Electron-Multiplying, Charge-Coupled Device as a Sensor

by Fernando Ortega-Ojeda^1,2, Matías Calcerrada¹, Alejandro Ferrero³, Joaquín Campos³ and Carmen Garcia-Ruiz^1,2,*

¹ Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Multipurpose Building of Chemistry, University of Alcalá, Alcalá de Henares, 28871 Madrid, Spain

² University Institute of Research in Police Sciences (IUICP), Law Faculty, University of Alcalá, Alcalá de Henares, 28801 Madrid, Spain

³ Institute of Optics “Daza de Valdés”, IO-CSIC, Calle Serrano 121, 28006 Madrid, Spain

Sensors 2018, 18(4), 1152; https://doi.org/10.3390/s18041152 - 10 Apr 2018

Cited by 13 | Viewed by 7636

Abstract

Ultra-weak photon emission (UPE) is the spontaneous emission from living systems mainly attributed to oxidation reactions, in which reactive oxygen species (ROS) may play a major role. Given the capability of the next-generation electron-multiplying CCD (EMCCD) sensors and the easy use of liquid [...] Read more.

Ultra-weak photon emission (UPE) is the spontaneous emission from living systems mainly attributed to oxidation reactions, in which reactive oxygen species (ROS) may play a major role. Given the capability of the next-generation electron-multiplying CCD (EMCCD) sensors and the easy use of liquid crystal tunable filters (LCTF), the aim of this work was to explore the potential of a simple UPE spectrometer to measure the UPE from a human hand. Thus, an easy setup was configured based on a dark box for inserting the subject’s hand prior to LCTF as a monochromator and an EMCCD sensor working in the full vertical binning mode (FVB) as a spectra detector. Under controlled conditions, both dark signals and left hand UPE were acquired by registering the UPE intensity at different selected wavelengths (400, 450, 500, 550, 600, 650, and 700 nm) during a period of 10 min each. Then, spurious signals were filtered out by ignoring the pixels whose values were clearly outside of the Gaussian distribution, and the dark signal was subtracted from the subject hand signal. The stepped spectrum with a peak of approximately 880 photons at 500 nm had a shape that agreed somewhat with previous reports, and agrees with previous UPE research that reported UPE from 420 to 570 nm, or 260 to 800 nm, with a range from 1 to 1000 photons s⁻¹ cm⁻². Obtaining the spectral distribution instead of the total intensity of the UPE represents a step forward in this field, as it may provide extra information about a subject’s personal states and relationship with ROS. A new generation of CCD sensors with lower dark signals, and spectrographs with a more uniform spectral transmittance, will open up new possibilities for configuring measuring systems in portable formats. Full article

(This article belongs to the Special Issue Optical Biochemical Sensor Systems and Applications)

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18 pages, 4379 KiB

Open AccessArticle

δ-Generalized Labeled Multi-Bernoulli Filter Using Amplitude Information of Neighboring Cells

by Chao Liu, Jinping Sun

, Peng Lei^* and Yaolong Qi

School of Electronic and Information Engineering, Beihang University, Beijing 100191, China

Sensors 2018, 18(4), 1153; https://doi.org/10.3390/s18041153 - 10 Apr 2018

Cited by 9 | Viewed by 3610

Abstract

The amplitude information (AI) of echoed signals plays an important role in radar target detection and tracking. A lot of research shows that the introduction of AI enables the tracking algorithm to distinguish targets from clutter better and then improves the performance of [...] Read more.

The amplitude information (AI) of echoed signals plays an important role in radar target detection and tracking. A lot of research shows that the introduction of AI enables the tracking algorithm to distinguish targets from clutter better and then improves the performance of data association. The current AI-aided tracking algorithms only consider the signal amplitude in the range-azimuth cell where measurement exists. However, since radar echoes always contain backscattered signals from multiple cells, the useful information of neighboring cells would be lost if directly applying those existing methods. In order to solve this issue, a new δ-generalized labeled multi-Bernoulli (δ-GLMB) filter is proposed. It exploits the AI of radar echoes from neighboring cells to construct a united amplitude likelihood ratio, and then plugs it into the update process and the measurement-track assignment cost matrix of the δ-GLMB filter. Simulation results show that the proposed approach has better performance in target’s state and number estimation than that of the δ-GLMB only using single-cell AI in low signal-to-clutter-ratio (SCR) environment. Full article

(This article belongs to the Section Intelligent Sensors)

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19 pages, 2351 KiB

Open AccessArticle

Coherent and Noncoherent Joint Processing of Sonar for Detection of Small Targets in Shallow Water

by Xiang Pan^1,*

, Jingning Jiang¹, Si Li¹, Zhenping Ding¹, Chen Pan² and Xianyi Gong¹

¹ College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China

² Hangzhou Xuejun High School, Hangzhou 310012, China

Sensors 2018, 18(4), 1154; https://doi.org/10.3390/s18041154 - 10 Apr 2018

Cited by 6 | Viewed by 4855

Abstract

A coherent-noncoherent joint processing framework is proposed for active sonar to combine diversity gain and beamforming gain for detection of a small target in shallow water environments. Sonar utilizes widely-spaced arrays to sense environments and illuminate a target of interest from multiple angles. [...] Read more.

A coherent-noncoherent joint processing framework is proposed for active sonar to combine diversity gain and beamforming gain for detection of a small target in shallow water environments. Sonar utilizes widely-spaced arrays to sense environments and illuminate a target of interest from multiple angles. Meanwhile, it exploits spatial diversity for time-reversal focusing to suppress reverberation, mainly strong bottom reverberation. For enhancement of robustness of time-reversal focusing, an adaptive iterative strategy is utilized in the processing framework. A probing signal is firstly transmitted and echoes of a likely target are utilized as steering vectors for the second transmission. With spatial diversity, target bearing and range are estimated using a broadband signal model. Numerical simulations show that the novel sonar outperforms the traditional phased-array sonar due to benefits of spatial diversity. The effectiveness of the proposed framework has been validated by localization of a small target in at-lake experiments. Full article

(This article belongs to the Special Issue Ultrasonic Sensors 2018)

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29 pages, 23295 KiB

Open AccessArticle

Analysis of a Smartphone-Based Architecture with Multiple Mobility Sensors for Fall Detection with Supervised Learning

by José Antonio Santoyo-Ramón, Eduardo Casilari^*

and José Manuel Cano-García

Departamento de Tecnología Electrónica, Universidad de Málaga, ETSI Telecomunicación, 29071 Málaga, Spain

Sensors 2018, 18(4), 1155; https://doi.org/10.3390/s18041155 - 10 Apr 2018

Cited by 58 | Viewed by 8256

Abstract

This paper describes a wearable Fall Detection System (FDS) based on a body-area network consisting of four nodes provided with inertial sensors and Bluetooth wireless interfaces. The signals captured by the nodes are sent to a smartphone which simultaneously acts as another sensing [...] Read more.

This paper describes a wearable Fall Detection System (FDS) based on a body-area network consisting of four nodes provided with inertial sensors and Bluetooth wireless interfaces. The signals captured by the nodes are sent to a smartphone which simultaneously acts as another sensing point. In contrast to many FDSs proposed by the literature (which only consider a single sensor), the multisensory nature of the prototype is utilized to investigate the impact of the number and the positions of the sensors on the effectiveness of the production of the fall detection decision. In particular, the study assesses the capability of four popular machine learning algorithms to discriminate the dynamics of the Activities of Daily Living (ADLs) and falls generated by a set of experimental subjects, when the combined use of the sensors located on different parts of the body is considered. Prior to this, the election of the statistics that optimize the characterization of the acceleration signals and the efficacy of the FDS is also investigated. As another important methodological novelty in this field, the statistical significance of all the results (an aspect which is usually neglected by other works) is validated by an analysis of variance (ANOVA). Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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16 pages, 6570 KiB

Open AccessArticle

Influence of Waveform Characteristics on LiDAR Ranging Accuracy and Precision

by Xiaolu Li^1,2

, Bingwei Yang¹, Xinhao Xie¹, Duan Li¹ and Lijun Xu^1,2,*

¹ School of Instrumentation Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China

² Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Beijing 100191, China

Sensors 2018, 18(4), 1156; https://doi.org/10.3390/s18041156 - 10 Apr 2018

Cited by 66 | Viewed by 7820

Abstract

Time of flight (TOF) based light detection and ranging (LiDAR) is a technology for calculating distance between start/stop signals of time of flight. In lab-built LiDAR, two ranging systems for measuring flying time between start/stop signals include time-to-digital converter (TDC) that counts time [...] Read more.

Time of flight (TOF) based light detection and ranging (LiDAR) is a technology for calculating distance between start/stop signals of time of flight. In lab-built LiDAR, two ranging systems for measuring flying time between start/stop signals include time-to-digital converter (TDC) that counts time between trigger signals and analog-to-digital converter (ADC) that processes the sampled start/stop pulses waveform for time estimation. We study the influence of waveform characteristics on range accuracy and precision of two kinds of ranging system. Comparing waveform based ranging (WR) with analog discrete return system based ranging (AR), a peak detection method (WR-PK) shows the best ranging performance because of less execution time, high ranging accuracy, and stable precision. Based on a novel statistic mathematical method maximal information coefficient (MIC), WR-PK precision has a high linear relationship with the received pulse width standard deviation. Thus keeping the received pulse width of measuring a constant distance as stable as possible can improve ranging precision. Full article

(This article belongs to the Section Remote Sensors)

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22 pages, 10320 KiB

Open AccessArticle

Predicting Key Agronomic Soil Properties with UV-Vis Fluorescence Measurements Combined with Vis-NIR-SWIR Reflectance Spectroscopy: A Farm-Scale Study in a Mediterranean Viticultural Agroecosystem

by Emmanuelle Vaudour^1,*

, Zoran G. Cerovic², Dav M. Ebengo¹ and Gwendal Latouche²

¹ UMR ECOSYS, AgroParisTech, INRA, Université Paris-Saclay, 78850 Thiverval-Grignon, France

² Ecologie, Systématique et Evolution (UMR 8079), CNRS, Univ. Paris-Sud, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France

Sensors 2018, 18(4), 1157; https://doi.org/10.3390/s18041157 - 10 Apr 2018

Cited by 17 | Viewed by 5853

Abstract

For adequate crop and soil management, rapid and accurate techniques for monitoring soil properties are particularly important when a farmer starts up his activities and needs a diagnosis of his cultivated fields. This study aimed to evaluate the potential of fluorescence measured directly [...] Read more.

For adequate crop and soil management, rapid and accurate techniques for monitoring soil properties are particularly important when a farmer starts up his activities and needs a diagnosis of his cultivated fields. This study aimed to evaluate the potential of fluorescence measured directly on 146 whole soil solid samples, for predicting key soil properties at the scale of a 6 ha Mediterranean wine estate with contrasting soils. UV-Vis fluorescence measurements were carried out in conjunction with reflectance measurements in the Vis-NIR-SWIR range. Combining PLSR predictions from Vis-NIR-SWIR reflectance spectra and from a set of fluorescence signals enabled us to improve the power of prediction of a number of key agronomic soil properties including SOC, N_tot, CaCO₃, iron, fine particle-sizes (clay, fine silt, fine sand), CEC, pH and exchangeable Ca²⁺ with cross-validation RPD ≥ 2 and R² ≥ 0.75, while exchangeable K⁺, Na⁺, Mg²⁺, coarse silt and coarse sand contents were fairly predicted (1.42 ≤ RPD < 2 and 0.54 ≤ R² < 0.75). Predictions of SOC, N_tot, CaCO₃, iron contents, and pH were still good (RPD ≥ 1.8, R² ≥ 0.68) when using a single fluorescence signal or index such as SFR_R or FERARI, highlighting the unexpected importance of red excitations and indices derived from plant studies. The predictive ability of single fluorescence indices or original signals was very significant for topsoil: this is very important for a farmer who wishes to update information on soil nutrient for the purpose of fertility diagnosis and particularly nitrogen fertilization. These results open encouraging perspectives for using miniaturized fluorescence devices enabling red excitation coupled with red or far-red fluorescence emissions directly in the field. Full article

(This article belongs to the Section Chemical Sensors)

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12 pages, 24100 KiB

Open AccessArticle

A Novel Strategy of Ambiguity Correction for the Improved Faraday Rotation Estimator in Linearly Full-Polarimetric SAR Data

by Jinhui Li, Yifei Ji, Yongsheng Zhang^*, Qilei Zhang, Haifeng Huang and Zhen Dong

College of Electronic Science and Engineering, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(4), 1158; https://doi.org/10.3390/s18041158 - 10 Apr 2018

Cited by 8 | Viewed by 3447

Abstract

Spaceborne synthetic aperture radar (SAR) missions operating at low frequencies, such as L-band or P-band, are significantly influenced by the ionosphere. As one of the serious ionosphere effects, Faraday rotation (FR) is a remarkable distortion source for the polarimetric SAR (PolSAR) application. Various [...] Read more.

Spaceborne synthetic aperture radar (SAR) missions operating at low frequencies, such as L-band or P-band, are significantly influenced by the ionosphere. As one of the serious ionosphere effects, Faraday rotation (FR) is a remarkable distortion source for the polarimetric SAR (PolSAR) application. Various published FR estimators along with an improved one have been introduced to solve this issue, all of which are implemented by processing a set of PolSAR real data. The improved estimator exhibits optimal robustness based on performance analysis, especially in term of the system noise. However, all published estimators, including the improved estimator, suffer from a potential FR angle (FRA) ambiguity. A novel strategy of the ambiguity correction for those FR estimators is proposed and shown as a flow process, which is divided into pixel-level and image-level correction. The former is not yet recognized and thus is considered in particular. Finally, the validation experiments show a prominent performance of the proposed strategy. Full article

(This article belongs to the Section Remote Sensors)

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25 pages, 5785 KiB

Open AccessArticle

PL-VIO: Tightly-Coupled Monocular Visual–Inertial Odometry Using Point and Line Features

by Yijia He^1,2,*

, Ji Zhao³, Yue Guo^1,2, Wenhao He¹ and Kui Yuan¹

¹ Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China

² University of Chinese Academy of Sciences, Beijing 100049, China

³ The ReadSense Ltd., Shanghai 200040, China

Sensors 2018, 18(4), 1159; https://doi.org/10.3390/s18041159 - 10 Apr 2018

Cited by 275 | Viewed by 21973

Abstract

To address the problem of estimating camera trajectory and to build a structural three-dimensional (3D) map based on inertial measurements and visual observations, this paper proposes point–line visual–inertial odometry (PL-VIO), a tightly-coupled monocular visual–inertial odometry system exploiting both point and line features. Compared [...] Read more.

To address the problem of estimating camera trajectory and to build a structural three-dimensional (3D) map based on inertial measurements and visual observations, this paper proposes point–line visual–inertial odometry (PL-VIO), a tightly-coupled monocular visual–inertial odometry system exploiting both point and line features. Compared with point features, lines provide significantly more geometrical structure information on the environment. To obtain both computation simplicity and representational compactness of a 3D spatial line, Plücker coordinates and orthonormal representation for the line are employed. To tightly and efficiently fuse the information from inertial measurement units (IMUs) and visual sensors, we optimize the states by minimizing a cost function which combines the pre-integrated IMU error term together with the point and line re-projection error terms in a sliding window optimization framework. The experiments evaluated on public datasets demonstrate that the PL-VIO method that combines point and line features outperforms several state-of-the-art VIO systems which use point features only. Full article

(This article belongs to the Special Issue Sensor Fusion and Novel Technologies in Positioning and Navigation)

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20 pages, 1106 KiB

Open AccessArticle

Non-Invasive Blood Pressure Estimation from ECG Using Machine Learning Techniques

by Monika Simjanoska^1,*,†

, Martin Gjoreski^2,†

, Matjaž Gams^2,† and Ana Madevska Bogdanova^1,†

¹ Faculty of Computer Science and Engineering, Ss. Cyril and Methodius University, Rugjer Boshkovikj 16, 1000 Skopje, Macedonia

² Department of Intelligent Systems, Jožef Stefan Institute, Jožef Stefan International Postgraduate School, Jamova cesta 39, 1000 Ljubljana, Slovenia

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1160; https://doi.org/10.3390/s18041160 - 11 Apr 2018

Cited by 141 | Viewed by 14408

Abstract

Background: Blood pressure (BP) measurements have been used widely in clinical and private environments. Recently, the use of ECG monitors has proliferated; however, they are not enabled with BP estimation. We have developed a method for BP estimation using only electrocardiogram (ECG) signals. [...] Read more.

Background: Blood pressure (BP) measurements have been used widely in clinical and private environments. Recently, the use of ECG monitors has proliferated; however, they are not enabled with BP estimation. We have developed a method for BP estimation using only electrocardiogram (ECG) signals. Methods: Raw ECG data are filtered and segmented, and, following this, a complexity analysis is performed for feature extraction. Then, a machine-learning method is applied, combining a stacking-based classification module and a regression module for building systolic BP (SBP), diastolic BP (DBP), and mean arterial pressure (MAP) predictive models. In addition, the method allows a probability distribution-based calibration to adapt the models to a particular user. Results: Using ECG recordings from 51 different subjects, 3129 30-s ECG segments are constructed, and seven features are extracted. Using a train-validation-test evaluation, the method achieves a mean absolute error (MAE) of 8.64 mmHg for SBP, 18.20 mmHg for DBP, and 13.52 mmHg for the MAP prediction. When models are calibrated, the MAE decreases to 7.72 mmHg for SBP, 9.45 mmHg for DBP and 8.13 mmHg for MAP. Conclusion: The experimental results indicate that, when a probability distribution-based calibration is used, the proposed method can achieve results close to those of a certified medical device for BP estimation. Full article

(This article belongs to the Special Issue Non-Invasive Biomedical Sensors)

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14 pages, 3459 KiB

Open AccessArticle

Label-Free QCM Immunosensor for the Detection of Ochratoxin A

by Şerife Şeyda Pirinçci^1,2,*,†

, Özlem Ertekin^1,*,†, Duygu Ercan Laguna^1,‡, Fehime Şeyma Özen^1,‡, Zafer Ziya Öztürk³ and Selma Öztürk¹

¹ TÜBİTAK, The Scientific and Technological Research Council of Turkey, Marmara Research Center, Genetic Engineering and Biotechnology Institute, Gebze, Kocaeli 41400, Turkey

² Department of Medical Genetics and Molecular Biology, Kocaeli University, Umuttepe, Kocaeli 41100, Turkey

³ Department of Physics, Gebze Technical University, Gebze, Kocaeli 41400, Turkey

^† These authors contributed equally to this work.

^‡ The two authors are out of work now.

Sensors 2018, 18(4), 1161; https://doi.org/10.3390/s18041161 - 11 Apr 2018

Cited by 37 | Viewed by 6249

Abstract

Ochratoxin A (OTA) is a potent mycotoxin that poses a risk in food and feed moieties and subject to worldwide regulation. Laboratory-based analytical methods are traditionally employed for reliable OTA quantification, but these methods cannot provide rapid and on-site analysis, where biosensors fill [...] Read more.

Ochratoxin A (OTA) is a potent mycotoxin that poses a risk in food and feed moieties and subject to worldwide regulation. Laboratory-based analytical methods are traditionally employed for reliable OTA quantification, but these methods cannot provide rapid and on-site analysis, where biosensors fill this gap. In this study a label-free quartz crystal microbalance (QCM)-based immunosensor for the detection of OTA, which is one of the most important small molecule contaminants, was developed by direct immobilization of OTA to amine-bearing sensor surfaces using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-Hydroxysuccinimide (NHS) chemistry. The protein-free sensor surface enabled regeneration of sensor surface with 50 mM NaOH and 1% SDS up to 13 times without loss of performance, which would disrupt a protein-containing sensor surface. We developed a QCM immunosensor using the developed sensor surface with a 17.2–200 ng/mL detection range which can be used for on-site detection of feedstuffs. Full article

(This article belongs to the Special Issue I3S 2017 Selected Papers)

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11 pages, 13559 KiB

Open AccessArticle

A Novel “Off-On” Fluorescent Probe Based on Carbon Nitride Nanoribbons for the Detection of Citrate Anion and Live Cell Imaging

by Yanling Hu¹, Dongliang Yang¹

, Chen Yang¹, Ning Feng¹, Zhouwei Shao¹, Lei Zhang¹

, Xiaodong Wang¹, Lixing Weng², Zhimin Luo¹ and Lianhui Wang^1,*

¹ Key Laboratory for Organic Electronics & Information Displays (KLOEID) and Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, 9 Wenyuan Road, Nanjing 210023, China

² College of Geography and Biological Information, Nanjing University of Posts and Telecommunications, 9 Wenyuan Road, Nanjing 210023, China

Sensors 2018, 18(4), 1163; https://doi.org/10.3390/s18041163 - 11 Apr 2018

Cited by 6 | Viewed by 3986

Abstract

A novel fluorescent “off-on” probe based on carbon nitride (C₃N₄) nanoribbons was developed for citrate anion (C₆H₅O₇³⁻) detection. The fluorescence of C₃N₄ nanoribbons can be quenched by Cu²⁺ [...] Read more.

A novel fluorescent “off-on” probe based on carbon nitride (C₃N₄) nanoribbons was developed for citrate anion (C₆H₅O₇³⁻) detection. The fluorescence of C₃N₄ nanoribbons can be quenched by Cu²⁺ and then recovered by the addition of C₆H₅O₇³⁻, because the chelation between C₆H₅O₇³⁻ and Cu²⁺ blocks the electron transfer between Cu²⁺ and C₃N₄ nanoribbons. The turn-on fluorescent sensor using this fluorescent “off-on” probe can detect C₆H₅O₇³⁻ rapidly and selectively, showing a wide detection linear range (1~400 μM) and a low detection limit (0.78 μM) in aqueous solutions. Importantly, this C₃N₄ nanoribbon-based “off-on” probe exhibits good biocompatibility and can be used as fluorescent visualizer for exogenous C₆H₅O₇³⁻ in HeLa cells. Full article

(This article belongs to the Section Chemical Sensors)

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13 pages, 2604 KiB

Open AccessArticle

Edge-Aware Unidirectional Total Variation Model for Stripe Non-Uniformity Correction

by Ayoub Boutemedjet

, Chenwei Deng^*

and Baojun Zhao

School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(4), 1164; https://doi.org/10.3390/s18041164 - 11 Apr 2018

Cited by 33 | Viewed by 4604

Abstract

The problem of stripe non-uniformity in array-based infrared imaging systems has been the focus of many research studies. Among the proposed correction techniques, total variation models have been proven to significantly reduce the effect of this type of noise on the captured image. [...] Read more.

The problem of stripe non-uniformity in array-based infrared imaging systems has been the focus of many research studies. Among the proposed correction techniques, total variation models have been proven to significantly reduce the effect of this type of noise on the captured image. However, they also cause the loss of some image details and textures due to over-smoothing effect. In this paper, a correction scheme is proposed based on unidirectional variation model to exploit the direction characteristic of the stripe noise, in which an edge-aware weighting is incorporated to convey image structure retaining ability to the overall algorithm. Moreover, a statistical-based regularization is also introduced to further enhance correction performance around strong edges. The proposed approach is thoroughly scrutinized and compared to the state-of-the-art de-striping techniques using real stripe non-uniform images. Results demonstrate a significant improvement in edge preservation with better correction performance. Full article

(This article belongs to the Special Issue Advances in Infrared Imaging: Sensing, Exploitation and Applications)

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10 pages, 8344 KiB

Open AccessArticle

A Flexible Sensing Unit Manufacturing Method of Electrochemical Seismic Sensor

by Guanglei Li^1,2,†, Zhenyuan Sun^3,†, Junbo Wang^1,2,*, Deyong Chen^1,2, Jian Chen^1,2

, Lianhong Chen^1,2, Chao Xu^1,2, Wenjie Qi^1,2 and Yu Zheng⁴

¹ University of Chinese Academy of Sciences, Beijing 100049, China

² Institute of Electronics, Chinese Academy of Sciences, Beijing 100010, China

³ Tsinghua University, Beijing 100084, China

⁴ Affiliated High School of Peking University, Beijing 100080, China

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1165; https://doi.org/10.3390/s18041165 - 11 Apr 2018

Cited by 10 | Viewed by 3945

Abstract

This paper presents an electrochemical seismic sensor in which paraylene was used as a substrate and insulating layer of micro-fabricated electrodes, enabling the detection of seismic signals with enhanced sensitivities in comparison to silicon-based counterparts. Based on microfabrication, paralene-based electrochemical seismic sensors were [...] Read more.

This paper presents an electrochemical seismic sensor in which paraylene was used as a substrate and insulating layer of micro-fabricated electrodes, enabling the detection of seismic signals with enhanced sensitivities in comparison to silicon-based counterparts. Based on microfabrication, paralene-based electrochemical seismic sensors were fabricated in which the thickness of the insulating spacer was 6.7 μm. Compared to silicon-based counterparts with ~100 μm insulating layers, the parylene-based devices produced higher sensitivities of 490.3 ± 6.1 V/(m/s) vs. 192.2 ± 1.9 V/(m/s) at 0.1 Hz, 4764.4 ± 18 V/(m/s) vs. 318.9 ± 6.5 V/(m/s) at 1 Hz, and 4128.1 ± 38.3 V/(m/s) vs. 254.5 ± 4.2 V/(m/s) at 10 Hz. In addition, the outputs of the parylene vs. silicon devices in response to two transit inputs were compared, producing peak responses of 2.97 V vs. 0.22 V and 2.41 V vs. 0.19 V, respectively. Furthermore, the self-noises of parylene vs. silicon-based devices were compared as follows: −82.3 ± 3.9 dB vs. −90.4 ± 9.4 dB at 0.1 Hz, −75.7 ± 7.3 dB vs. −98.2 ± 9.9 dB at 1 Hz, and −62.4 ± 7.7 dB vs. −91.1 ± 8.1 dB at 10 Hz. The developed parylene-based electrochemical seismic sensors may function as an enabling technique for further detection of seismic motions in various applications. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 26646 KiB

Open AccessArticle

High Dynamic Range Imaging at the Quantum Limit with Single Photon Avalanche Diode-Based Image Sensors

by Neale A.W. Dutton^1,*

, Tarek Al Abbas²

, Istvan Gyongy²

, Francescopaolo Mattioli Della Rocca^1,2 and Robert K. Henderson²

¹ STMicroelectronics Imaging Division, Tanfield, Edinburgh EH3 5DA, UK

² School of Engineering, The University of Edinburgh, Edinburgh EH9 3JL, UK

Sensors 2018, 18(4), 1166; https://doi.org/10.3390/s18041166 - 11 Apr 2018

Cited by 38 | Viewed by 10030

Abstract

This paper examines methods to best exploit the High Dynamic Range (HDR) of the single photon avalanche diode (SPAD) in a high fill-factor HDR photon counting pixel that is scalable to megapixel arrays. The proposed method combines multi-exposure HDR with temporal oversampling in-pixel. [...] Read more.

This paper examines methods to best exploit the High Dynamic Range (HDR) of the single photon avalanche diode (SPAD) in a high fill-factor HDR photon counting pixel that is scalable to megapixel arrays. The proposed method combines multi-exposure HDR with temporal oversampling in-pixel. We present a silicon demonstration IC with 96 × 40 array of 8.25 µm pitch 66% fill-factor SPAD-based pixels achieving >100 dB dynamic range with 3 back-to-back exposures (short, mid, long). Each pixel sums 15 bit-planes or binary field images internally to constitute one frame providing 3.75× data compression, hence the 1k frames per second (FPS) output off-chip represents 45,000 individual field images per second on chip. Two future projections of this work are described: scaling SPAD-based image sensors to HDR 1 MPixel formats and shrinking the pixel pitch to 1–3 µm. Full article

(This article belongs to the Special Issue Special Issue on the 2017 International Image Sensor Workshop (IISW))

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15 pages, 32022 KiB

Open AccessArticle

A Novel Well Drill Assisted with High-Frequency Vibration Using the Bending Mode

by Xinda Qi, Weishan Chen, Yingxiang Liu^*

, Xintian Tang and Shengjun Shi

State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin 150001, China

Sensors 2018, 18(4), 1167; https://doi.org/10.3390/s18041167 - 11 Apr 2018

Cited by 11 | Viewed by 5025

Abstract

It is important for companies to increase the efficiency of drilling as well as prolong the lifetime of the drilling tool. Since some previous investigations indicated that a superposition of well drilling with an additional vibration increases the drilling efficiency, this paper introduces [...] Read more.

It is important for companies to increase the efficiency of drilling as well as prolong the lifetime of the drilling tool. Since some previous investigations indicated that a superposition of well drilling with an additional vibration increases the drilling efficiency, this paper introduces a novel well drill which is assisted with additional vibrations by means of piezoelectric sandwich bending vibration transducer. The proposed drill uses bending vibrations in two different directions to from an elliptical trajectory movement, which can help the drill to break the surface of hard material more efficiently and clean away the lithic fragments more easily. The proposed well drill with bending vibration transducer is designed to have a resonance frequency of the first bending vibration mode of about 1779 Hz. The motion equation of the particle on the edge of the drill bit is developed and analyzed. The vibration trajectory of the particle on the edge of the drill bit is calculated by using finite element method. A prototype of the proposed drill using bending vibrations is fabricated and tested to verify the aim of drilling efficiency increase. The feed speed of the vibration assisted drilling is tested to be about 0.296 mm/s when the excitation voltage of the transducer is 300 V, while this speed decreases to about 0.195 mm/s when no vibration is added. This comparison shows that the feed speed of the vibration assisted drilling is about 52% higher than that of the normal drilling, which means the proposed drill has a better efficiency and it is important to consider vibration superimposition in well drilling. In addition, the surface of the drill hole gained by the vibration assisted drilling is smoother than that of the normal drilling, which makes the clearance easier. Full article

(This article belongs to the Special Issue Piezoelectric Micro- and Nano-Devices)

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8 pages, 11184 KiB

Open AccessArticle

Phase-Shifted Eccentric Core Fiber Bragg Grating Fabricated by Electric Arc Discharge for Directional Bending Measurement

by Yang Ouyang^1,2

, Jianxia Liu³, Xiaofeng Xu^1,2, Yujia Zhao^1,2 and Ai Zhou^1,*

¹ National Engineering Laboratory for Fiber Optic Sensing Technology, Wuhan University of Technology, Wuhan 430074, China

² School of Information Engineering, Wuhan University of Technology, Wuhan 430074, China

³ School of Electrical and Information Engineering, Hubei University of Science and Technology, Xianning 437100, China

Sensors 2018, 18(4), 1168; https://doi.org/10.3390/s18041168 - 11 Apr 2018

Cited by 18 | Viewed by 4334

Abstract

A phase-shifted eccentric core fiber Bragg grating (PS-ECFBG) fabricated by electric arc discharge (EAD) is presented and demonstrated. It is composed of a fraction of eccentric core fiber fusion spliced in between two pieces of commercial single mode fibers, where a PS-FBG was [...] Read more.

A phase-shifted eccentric core fiber Bragg grating (PS-ECFBG) fabricated by electric arc discharge (EAD) is presented and demonstrated. It is composed of a fraction of eccentric core fiber fusion spliced in between two pieces of commercial single mode fibers, where a PS-FBG was written. The EAD in this work could flexibly change the amount of phase-shift by changing the discharge number or discharge duration. Because of the offset location of the eccentric core and the ultra-narrow resonant peak of the PS-ECFBG, it has a higher accuracy for measuring the directional bend. The elongation and compression of the eccentric core keep the magnitude of phase shift still unchanged during the bending process. The bending sensitivities of the PS-ECFBG at two opposite most sensitive directions are 57.4 pm/m⁻¹ and −51.5 pm/m⁻¹, respectively. Besides, the PS-ECFBG has the potential to be a tunable narrow bandpass filter, which has a wider bi-directional adjustable range because of the bending responses. The strain and temperature sensitivities of the PS-ECFBG are experimentally measured as well, which are 0.70 pm/με and 8.85 pm/°C, respectively. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 21821 KiB

Open AccessArticle

Infrared and Visible Image Fusion Based on Different Constraints in the Non-Subsampled Shearlet Transform Domain

by Yan Huang^1,2,*, Duyan Bi¹ and Dongpeng Wu³

¹ Aeronautics and Astronautics Engineering College, Air Force Engineering University, Xi’an 710038, Shaanxi, China

² School of Management Engineering, Xi’an University of Finance and Economics, Xi’an 710100, Shaanxi, China

³ The 93575 Unit of PLA, Chengde 067000, Hebei, China

Sensors 2018, 18(4), 1169; https://doi.org/10.3390/s18041169 - 11 Apr 2018

Cited by 33 | Viewed by 4489

Abstract

There are many artificial parameters when fuse infrared and visible images, to overcome the lack of detail in the fusion image because of the artifacts, a novel fusion algorithm for infrared and visible images that is based on different constraints in non-subsampled shearlet [...] Read more.

There are many artificial parameters when fuse infrared and visible images, to overcome the lack of detail in the fusion image because of the artifacts, a novel fusion algorithm for infrared and visible images that is based on different constraints in non-subsampled shearlet transform (NSST) domain is proposed. There are high bands and low bands of images that are decomposed by the NSST. After analyzing the characters of the bands, fusing the high level bands by the gradient constraint, the fused image can obtain more details; fusing the low bands by the constraint of saliency in the images, the targets are more salient. Before the inverse NSST, the Nash equilibrium is used to update the coefficient. The fused images and the quantitative results demonstrate that our method is more effective in reserving details and highlighting the targets when compared with other state-of-the-art methods. Full article

(This article belongs to the Special Issue Advances in Infrared Imaging: Sensing, Exploitation and Applications)

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29 pages, 13400 KiB

Open AccessArticle

Drone Mission Definition and Implementation for Automated Infrastructure Inspection Using Airborne Sensors

by Juan A. Besada¹, Luca Bergesio¹, Iván Campaña¹, Diego Vaquero-Melchor¹, Jaime López-Araquistain¹

, Ana M. Bernardos^1,2,* and José R. Casar¹

¹ Information Processing and Telecommunication Center, Universidad Politécnica de Madrid, 28040 Madrid, Spain

² C-315.1, ETSI Telecomunicación, Avenida Complutense 30, 28040 Madrid, Spain

Sensors 2018, 18(4), 1170; https://doi.org/10.3390/s18041170 - 11 Apr 2018

Cited by 107 | Viewed by 14129

Abstract

This paper describes a Mission Definition System and the automated flight process it enables to implement measurement plans for discrete infrastructure inspections using aerial platforms, and specifically multi-rotor drones. The mission definition aims at improving planning efficiency with respect to state-of-the-art waypoint-based techniques, [...] Read more.

This paper describes a Mission Definition System and the automated flight process it enables to implement measurement plans for discrete infrastructure inspections using aerial platforms, and specifically multi-rotor drones. The mission definition aims at improving planning efficiency with respect to state-of-the-art waypoint-based techniques, using high-level mission definition primitives and linking them with realistic flight models to simulate the inspection in advance. It also provides flight scripts and measurement plans which can be executed by commercial drones. Its user interfaces facilitate mission definition, pre-flight 3D synthetic mission visualisation and flight evaluation. Results are delivered for a set of representative infrastructure inspection flights, showing the accuracy of the flight prediction tools in actual operations using automated flight control. Full article

(This article belongs to the Section Sensor Networks)

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9 pages, 8248 KiB

Open AccessFeature PaperArticle

Development of a Waterproof Crack-Based Stretchable Strain Sensor Based on PDMS Shielding

by Seong Kyung Hong^1,†, Seongjin Yang^1,†, Seong J. Cho²

, Hyungkook Jeon^1,*

and Geunbae Lim^1,*

¹ Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang 790-784, Korea

² School of Mechanical Engineering, Chungnam National University (CNU), 99 Daehak-Ro, Yuseong-Gu, Daejeon 305-764, Korea

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1171; https://doi.org/10.3390/s18041171 - 12 Apr 2018

Cited by 38 | Viewed by 8296

Abstract

This paper details the design of a poly(dimethylsiloxane) (PDMS)-shielded waterproof crack-based stretchable strain sensor, in which the electrical characteristics and sensing performance are not influenced by changes in humidity. This results in a higher number of potential applications for the sensor. A previously [...] Read more.

This paper details the design of a poly(dimethylsiloxane) (PDMS)-shielded waterproof crack-based stretchable strain sensor, in which the electrical characteristics and sensing performance are not influenced by changes in humidity. This results in a higher number of potential applications for the sensor. A previously developed omni-purpose stretchable strain (OPSS) sensor was used as the basis for this work, which utilizes a metal cracking structure and provides a wide sensing range and high sensitivity. Changes in the conductivity of the OPSS sensor, based on humidity conditions, were investigated along with the potential possibility of using the design as a humidity sensor. However, to prevent conductivity variation, which can decrease the reliability and sensing ability of the OPSS sensor, PDMS was utilized as a shielding layer over the OPSS sensor. The PDMS-shielded OPSS sensor showed approximately the same electrical characteristics as previous designs, including in a high humidity environment, while maintaining its strain sensing capabilities. The developed sensor shows promise for use under high humidity conditions and in underwater applications. Therefore, considering its unique features and reliable sensing performance, the developed PDMS-shielded waterproof OPSS sensor has potential utility in a wide range of applications, such as motion monitoring, medical robotics and wearable healthcare devices. Full article

(This article belongs to the Special Issue Smart Sensing System for Real-Time Monitoring)

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19 pages, 2378 KiB

Open AccessArticle

Optimized Multi-Spectral Filter Array Based Imaging of Natural Scenes

by Yuqi Li^1,2,*, Aditi Majumder³, Hao Zhang³ and M. Gopi³

¹ College of Information Science and Engineering, Ningbo University, Ningbo 315000, China

² College of Computer Science and Technology, Zhejiang University, Hangzhou 310000, China

³ Department of Computer Science, University of California, Irvine, CA 92697-3425, USA

Sensors 2018, 18(4), 1172; https://doi.org/10.3390/s18041172 - 12 Apr 2018

Cited by 24 | Viewed by 6732

Abstract

Multi-spectral imaging using a camera with more than three channels is an efficient method to acquire and reconstruct spectral data and is used extensively in tasks like object recognition, relighted rendering, and color constancy. Recently developed methods are used to only guide content-dependent [...] Read more.

Multi-spectral imaging using a camera with more than three channels is an efficient method to acquire and reconstruct spectral data and is used extensively in tasks like object recognition, relighted rendering, and color constancy. Recently developed methods are used to only guide content-dependent filter selection where the set of spectral reflectances to be recovered are known a priori. We present the first content-independent spectral imaging pipeline that allows optimal selection of multiple channels. We also present algorithms for optimal placement of the channels in the color filter array yielding an efficient demosaicing order resulting in accurate spectral recovery of natural reflectance functions. These reflectance functions have the property that their power spectrum statistically exhibits a power-law behavior. Using this property, we propose power-law based error descriptors that are minimized to optimize the imaging pipeline. We extensively verify our models and optimizations using large sets of commercially available wide-band filters to demonstrate the greater accuracy and efficiency of our multi-spectral imaging pipeline over existing methods. Full article

(This article belongs to the Special Issue Snapshot Multi-Band Spectral and Polarization Imaging Systems)

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16 pages, 8176 KiB

Open AccessArticle

Optical DNA Biosensor Based on Square-Planar Ethyl Piperidine Substituted Nickel(II) Salphen Complex for Dengue Virus Detection

by Eda Yuhana Ariffin¹, Ling Ling Tan^2,*, Nurul Huda Abd. Karim¹ and Lee Yook Heng^1,2

¹ School of Chemical Sciences and Food Technology, Faculty of Science and Technology, University Kebangsaan Malaysia, Bangi 43600, Selangor D.E., Malaysia

² Southeast Asia Disaster Prevention Research Initiative (SEADPRI-UKM), Institute for Environment and Development (LESTARI), Universiti Kebangsaan Malaysia, Bangi 43600, Selangor D.E., Malaysia

Sensors 2018, 18(4), 1173; https://doi.org/10.3390/s18041173 - 12 Apr 2018

Cited by 21 | Viewed by 5801

Abstract

A sensitive and selective optical DNA biosensor was developed for dengue virus detection based on novel square-planar piperidine side chain-functionalized N,N′-bis-4-(hydroxysalicylidene)-phenylenediamine-nickel(II), which was able to intercalate via nucleobase stacking within DNA and be functionalized as an optical DNA hybridization marker. [...] Read more.

A sensitive and selective optical DNA biosensor was developed for dengue virus detection based on novel square-planar piperidine side chain-functionalized N,N′-bis-4-(hydroxysalicylidene)-phenylenediamine-nickel(II), which was able to intercalate via nucleobase stacking within DNA and be functionalized as an optical DNA hybridization marker. 3-Aminopropyltriethoxysilane (APTS)-modified porous silica nanospheres (PSiNs), was synthesized with a facile mini-emulsion method to act as a high capacity DNA carrier matrix. The Schiff base salphen complexes-labelled probe to target nucleic acid on the PSiNs renders a colour change of the DNA biosensor to a yellow background colour, which could be quantified via a reflectance transduction method. The reflectometric DNA biosensor demonstrated a wide linear response range to target DNA over the concentration range of 1.0 × 10⁻¹⁶–1.0 × 10⁻¹⁰ M (R² = 0.9879) with an ultralow limit of detection (LOD) at 0.2 aM. The optical DNA biosensor response was stable and maintainable at 92.8% of its initial response for up to seven days of storage duration with a response time of 90 min. The reflectance DNA biosensor obtained promising recovery values of close to 100% for the detection of spiked synthetic dengue virus serotypes 2 (DENV-2) DNA concentration in non-invasive human samples, indicating the high accuracy of the proposed DNA analytical method for early diagnosis of all potential infectious diseases or pathological genotypes. Full article

(This article belongs to the Section Biosensors)

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16 pages, 24211 KiB

Open AccessArticle

Pure FPGA Implementation of an HOG Based Real-Time Pedestrian Detection System

by Jian Hua Luo

and Chang Hong Lin^*

Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, #43, Sec. 4, Keelung Rd., Taipei 106, Taiwan

Sensors 2018, 18(4), 1174; https://doi.org/10.3390/s18041174 - 12 Apr 2018

Cited by 32 | Viewed by 6226

Abstract

In this study, we propose a real-time pedestrian detection system using a FPGA with a digital image sensor. Comparing with some prior works, the proposed implementation realizes both the histogram of oriented gradients (HOG) and the trained support vector machine (SVM) classification on [...] Read more.

In this study, we propose a real-time pedestrian detection system using a FPGA with a digital image sensor. Comparing with some prior works, the proposed implementation realizes both the histogram of oriented gradients (HOG) and the trained support vector machine (SVM) classification on a FPGA. Moreover, the implementation does not use any external memory or processors to assist the implementation. Although the implementation implements both the HOG algorithm and the SVM classification in hardware without using any external memory modules and processors, the proposed implementation’s resource utilization of the FPGA is lower than most of the prior art. The main reasons resulting in the lower resource usage are: (1) simplification in the Getting Bin sub-module; (2) distributed writing and two shift registers in the Cell Histogram Generation sub-module; (3) reuse of each sum of the cell histogram in the Block Histogram Normalization sub-module; and (4) regarding a window of the SVM classification as 105 blocks of the SVM classification. Moreover, compared to Dalal and Triggs’s pure software HOG implementation, the proposed implementation‘s average detection rate is just about 4.05% less, but can achieve a much higher frame rate. Full article

(This article belongs to the Section Intelligent Sensors)

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19 pages, 1514 KiB

Open AccessArticle

A Convex Constraint Variational Method for Restoring Blurred Images in the Presence of Alpha-Stable Noises

by Zhenzhen Yang^1,2, Zhen Yang^1,2 and Guan Gui^1,2,*

¹ National Engineering Research Center of Communication and Network Technology, Nanjing University of Posts and Telecommunications, Nanjing 210003, China

² Key Lab of Broadband Wireless Communication and Sensor Network Technology, Nanjing University of Posts and Telecommunications, Ministry of Education, Nanjing 210003, China

Sensors 2018, 18(4), 1175; https://doi.org/10.3390/s18041175 - 12 Apr 2018

Cited by 9 | Viewed by 3979

Abstract

Blurred image restoration poses a great challenge under the non-Gaussian noise environments in various communication systems. In order to restore images from blur and alpha-stable noise while also preserving their edges, this paper proposes a variational method to restore the blurred images with [...] Read more.

Blurred image restoration poses a great challenge under the non-Gaussian noise environments in various communication systems. In order to restore images from blur and alpha-stable noise while also preserving their edges, this paper proposes a variational method to restore the blurred images with alpha-stable noises based on the property of the meridian distribution and the total variation (TV). Since the variational model is non-convex, it cannot guarantee a global optimal solution. To overcome this drawback, we also incorporate an additional penalty term into the deblurring and denoising model and propose a strictly convex variational method. Due to the convexity of our model, the primal-dual algorithm is adopted to solve this convex variational problem. Our simulation results validate the proposed method. Full article

(This article belongs to the Special Issue Software-Defined Networking Based Mobile Networks)

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9 pages, 5058 KiB

Open AccessArticle

Discrimination of Temperature and Strain in Brillouin Optical Time Domain Analysis Using a Multicore Optical Fiber

by Mohamed A. S. Zaghloul^1,*, Mohan Wang¹, Giovanni Milione², Ming-Jun Li³, Shenping Li³, Yue-Kai Huang², Ting Wang² and Kevin P. Chen^1,*

¹ Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA

² Optical Networking and Sensing Department, NEC Laboratories America, Inc., Princeton, NJ 08540, USA

³ Corning Research and Development Corporation, Corning, NY 14831, USA

Sensors 2018, 18(4), 1176; https://doi.org/10.3390/s18041176 - 12 Apr 2018

Cited by 27 | Viewed by 5357

Abstract

Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a [...] Read more.

Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores’ temperature and strain coefficients are such that temperature (strain) changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11

μ ϵ

/MHz), which is 2.63 (3.67) times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain) changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%). Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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15 pages, 1269 KiB

Open AccessArticle

Vehicular Visible Light Networks for Urban Mobile Crowd Sensing

by Barbara M. Masini^*

, Alessandro Bazzi

and Alberto Zanella

CNR-IEIIT, v.le Risorgimento, 2, 40136 Bologna, Italy

Sensors 2018, 18(4), 1177; https://doi.org/10.3390/s18041177 - 12 Apr 2018

Cited by 47 | Viewed by 5923

Abstract

Crowd sensing is a powerful tool to map and predict interests and events. In the future, it could be boosted by an increasing number of connected vehicles sharing information and intentions. This will be made available by on board wireless connected devices able [...] Read more.

Crowd sensing is a powerful tool to map and predict interests and events. In the future, it could be boosted by an increasing number of connected vehicles sharing information and intentions. This will be made available by on board wireless connected devices able to continuously communicate with other vehicles and with the environment. Among the enabling technologies, visible light communication (VLC) represents a low cost solution in the short term. In spite of the fact that vehicular communications cannot rely on the sole VLC due to the limitation provided by the light which allows communications in visibility only, VLC can however be considered to complement other wireless communication technologies which could be overloaded in dense scenarios. In this paper we evaluate the performance of VLC connected vehicles when urban crowd sensing is addressed and we compare the performance of sole vehicular visible light networks with that of VLC as a complementary technology of IEEE 802.11p. Results, obtained through a realistic simulation tool taking into account both the roadmap constraints and the technologies protocols, help to understand when VLC provides the major improvement in terms of delivered data varying the number and position of RSUs and the FOV of the receiver. Full article

(This article belongs to the Special Issue Smart Vehicular Mobile Sensing)

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22 pages, 18480 KiB

Open AccessArticle

Self-Alignment MEMS IMU Method Based on the Rotation Modulation Technique on a Swing Base

by Haifeng Xing

, Zhiyong Chen, Haotian Yang

, Chengbin Wang, Zhihui Lin and Meifeng Guo^*

Engineering Research Center for Navigation Technology, Department of Precision Instruments, Tsinghua University, Beijing 100084, China

Sensors 2018, 18(4), 1178; https://doi.org/10.3390/s18041178 - 12 Apr 2018

Cited by 20 | Viewed by 6731

Abstract

The micro-electro-mechanical-system (MEMS) inertial measurement unit (IMU) has been widely used in the field of inertial navigation due to its small size, low cost, and light weight, but aligning MEMS IMUs remains a challenge for researchers. MEMS IMUs have been conventionally aligned on [...] Read more.

The micro-electro-mechanical-system (MEMS) inertial measurement unit (IMU) has been widely used in the field of inertial navigation due to its small size, low cost, and light weight, but aligning MEMS IMUs remains a challenge for researchers. MEMS IMUs have been conventionally aligned on a static base, requiring other sensors, such as magnetometers or satellites, to provide auxiliary information, which limits its application range to some extent. Therefore, improving the alignment accuracy of MEMS IMU as much as possible under swing conditions is of considerable value. This paper proposes an alignment method based on the rotation modulation technique (RMT), which is completely self-aligned, unlike the existing alignment techniques. The effect of the inertial sensor errors is mitigated by rotating the IMU. Then, inertial frame-based alignment using the rotation modulation technique (RMT-IFBA) achieved coarse alignment on the swing base. The strong tracking filter (STF) further improved the alignment accuracy. The performance of the proposed method was validated with a physical experiment, and the results of the alignment showed that the standard deviations of pitch, roll, and heading angle were 0.0140

°

, 0.0097

°,

and 0.91

°

, respectively, which verified the practicality and efficacy of the proposed method for the self-alignment of the MEMS IMU on a swing base. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 22909 KiB

Open AccessArticle

In Situ 3D Monitoring of Geometric Signatures in the Powder-Bed-Fusion Additive Manufacturing Process via Vision Sensing Methods

by Zhongwei Li¹, Xingjian Liu^1,*, Shifeng Wen¹, Piyao He¹, Kai Zhong^1,*, Qingsong Wei¹, Yusheng Shi¹ and Sheng Liu^2,3,*

¹ State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, China

² The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China

³ School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China

Sensors 2018, 18(4), 1180; https://doi.org/10.3390/s18041180 - 12 Apr 2018

Cited by 112 | Viewed by 13718

Abstract

Lack of monitoring of the in situ process signatures is one of the challenges that has been restricting the improvement of Powder-Bed-Fusion Additive Manufacturing (PBF AM). Among various process signatures, the monitoring of the geometric signatures is of high importance. This paper presents [...] Read more.

Lack of monitoring of the in situ process signatures is one of the challenges that has been restricting the improvement of Powder-Bed-Fusion Additive Manufacturing (PBF AM). Among various process signatures, the monitoring of the geometric signatures is of high importance. This paper presents the use of vision sensing methods as a non-destructive in situ 3D measurement technique to monitor two main categories of geometric signatures: 3D surface topography and 3D contour data of the fusion area. To increase the efficiency and accuracy, an enhanced phase measuring profilometry (EPMP) is proposed to monitor the 3D surface topography of the powder bed and the fusion area reliably and rapidly. A slice model assisted contour detection method is developed to extract the contours of fusion area. The performance of the techniques is demonstrated with some selected measurements. Experimental results indicate that the proposed method can reveal irregularities caused by various defects and inspect the contour accuracy and surface quality. It holds the potential to be a powerful in situ 3D monitoring tool for manufacturing process optimization, close-loop control, and data visualization. Full article

(This article belongs to the Special Issue Depth Sensors and 3D Vision)

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20 pages, 966 KiB

Open AccessArticle

Hadoop Oriented Smart Cities Architecture

by Vlad Diaconita^*

, Ana-Ramona Bologa

and Razvan Bologa

Department of Computer Science and Cybernetics, Bucharest University of Economic Studies, Bucharest 010374, Romania

Sensors 2018, 18(4), 1181; https://doi.org/10.3390/s18041181 - 12 Apr 2018

Cited by 20 | Viewed by 8466

Abstract

A smart city implies a consistent use of technology for the benefit of the community. As the city develops over time, components and subsystems such as smart grids, smart water management, smart traffic and transportation systems, smart waste management systems, smart security systems, [...] Read more.

A smart city implies a consistent use of technology for the benefit of the community. As the city develops over time, components and subsystems such as smart grids, smart water management, smart traffic and transportation systems, smart waste management systems, smart security systems, or e-governance are added. These components ingest and generate a multitude of structured, semi-structured or unstructured data that may be processed using a variety of algorithms in batches, micro batches or in real-time. The ICT architecture must be able to handle the increased storage and processing needs. When vertical scaling is no longer a viable solution, Hadoop can offer efficient linear horizontal scaling, solving storage, processing, and data analyses problems in many ways. This enables architects and developers to choose a stack according to their needs and skill-levels. In this paper, we propose a Hadoop-based architectural stack that can provide the ICT backbone for efficiently managing a smart city. On the one hand, Hadoop, together with Spark and the plethora of NoSQL databases and accompanying Apache projects, is a mature ecosystem. This is one of the reasons why it is an attractive option for a Smart City architecture. On the other hand, it is also very dynamic; things can change very quickly, and many new frameworks, products and options continue to emerge as others decline. To construct an optimized, modern architecture, we discuss and compare various products and engines based on a process that takes into consideration how the products perform and scale, as well as the reusability of the code, innovations, features, and support and interest in online communities. Full article

(This article belongs to the Section Sensor Networks)

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23 pages, 17355 KiB

Open AccessArticle

A Three-Dimensional Target Depth-Resolution Method with a Single-Vector Sensor

by Anbang Zhao^1,2,3,4, Xuejie Bi^1,2,3, Juan Hui^1,2,3,*, Caigao Zeng^1,2,3 and Lin Ma^1,2,3

¹ Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China

² Key Laboratory of Marine Information Acquisition and Security, Harbin Engineering University, Ministry of Industry and Information Technology, Harbin 150001, China

³ College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China

⁴ National Key Laboratory of Science and Technology on Underwater Acoustic Antagonizing, China State Shipbuilding Corporation Systems Engineering Research Institute, Beijing 100036, China

Sensors 2018, 18(4), 1182; https://doi.org/10.3390/s18041182 - 12 Apr 2018

Cited by 4 | Viewed by 3239

Abstract

This paper mainly studies and verifies the target number category-resolution method in multi-target cases and the target depth-resolution method of aerial targets. Firstly, target depth resolution is performed by using the sign distribution of the reactive component of the vertical complex acoustic intensity; [...] Read more.

This paper mainly studies and verifies the target number category-resolution method in multi-target cases and the target depth-resolution method of aerial targets. Firstly, target depth resolution is performed by using the sign distribution of the reactive component of the vertical complex acoustic intensity; the target category and the number resolution in multi-target cases is realized with a combination of the bearing-time recording information; and the corresponding simulation verification is carried out. The algorithm proposed in this paper can distinguish between the single-target multi-line spectrum case and the multi-target multi-line spectrum case. This paper presents an improved azimuth-estimation method for multi-target cases, which makes the estimation results more accurate. Using the Monte Carlo simulation, the feasibility of the proposed target number and category-resolution algorithm in multi-target cases is verified. In addition, by studying the field characteristics of the aerial and surface targets, the simulation results verify that there is only amplitude difference between the aerial target field and the surface target field under the same environmental parameters, and an aerial target can be treated as a special case of a surface target; the aerial target category resolution can then be realized based on the sign distribution of the reactive component of the vertical acoustic intensity so as to realize three-dimensional target depth resolution. By processing data from a sea experiment, the feasibility of the proposed aerial target three-dimensional depth-resolution algorithm is verified. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 4641 KiB

Open AccessArticle

Crowdsourcing-Assisted Radio Environment Database for V2V Communication

by Keita Katagiri^1,*,‡, Koya Sato^2,‡

and Takeo Fujii^1,‡

¹ Advanced Wireless and Communication Research Center (AWCC), The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu-shi, Tokyo 182–8585, Japan

² Department of Electrical Engineering, Faculty of Engineering, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585, Japan

^‡ These authors contributed equally to this work.

Sensors 2018, 18(4), 1183; https://doi.org/10.3390/s18041183 - 12 Apr 2018

Cited by 20 | Viewed by 4963

Abstract

In order to realize reliable Vehicle-to-Vehicle (V2V) communication systems for autonomous driving, the recognition of radio propagation becomes an important technology. However, in the current wireless distributed network systems, it is difficult to accurately estimate the radio propagation characteristics because of the locality [...] Read more.

In order to realize reliable Vehicle-to-Vehicle (V2V) communication systems for autonomous driving, the recognition of radio propagation becomes an important technology. However, in the current wireless distributed network systems, it is difficult to accurately estimate the radio propagation characteristics because of the locality of the radio propagation caused by surrounding buildings and geographical features. In this paper, we propose a measurement-based radio environment database for improving the accuracy of the radio environment estimation in the V2V communication systems. The database first gathers measurement datasets of the received signal strength indicator (RSSI) related to the transmission/reception locations from V2V systems. By using the datasets, the average received power maps linked with transmitter and receiver locations are generated. We have performed measurement campaigns of V2V communications in the real environment to observe RSSI for the database construction. Our results show that the proposed method has higher accuracy of the radio propagation estimation than the conventional path loss model-based estimation. Full article

(This article belongs to the Special Issue Smart Vehicular Mobile Sensing)

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27 pages, 13796 KiB

Open AccessArticle

A Multi-Technology Communication Platform for Urban Mobile Sensing

by Rodrigo Almeida^1,*, Rui Oliveira^1,2, Miguel Luís¹

, Carlos Senna¹

and Susana Sargento^1,2

¹ Instituto de Telecomunicações, 3810-193 Aveiro, Portugal

² Departamento de Eletrónica, Telecomunicações e Informática, University of Aveiro, 3810-193 Aveiro, Portugal

Sensors 2018, 18(4), 1184; https://doi.org/10.3390/s18041184 - 12 Apr 2018

Cited by 18 | Viewed by 5902

Abstract

A common concern in smart cities is the focus on sensing procedures to provide city-wide information to city managers and citizens. To meet the growing demands of smart cities, the network must provide the ability to handle a large number of mobile sensors/devices, [...] Read more.

A common concern in smart cities is the focus on sensing procedures to provide city-wide information to city managers and citizens. To meet the growing demands of smart cities, the network must provide the ability to handle a large number of mobile sensors/devices, with high heterogeneity and unpredictable mobility, by collecting and delivering the sensed information for future treatment. This work proposes a multi-wireless technology communication platform for opportunistic data gathering and data exchange with respect to smart cities. Through the implementation of a proprietary long-range (LoRa) network and an urban sensor network, our platform addresses the heterogeneity of Internet of Things (IoT) devices while conferring communications in an opportunistic manner, increasing the interoperability of our platform. It implements and evaluates a medium access communication (MAC) protocol for LoRa networks with multiple gateways. It also implements mobile Opportunistic VEhicular (mOVE), a delay-tolerant network (DTN)-based architecture to address the mobility dimension. The platform provides vehicle-to-everything (V2X) communication with support for highly reliable and actionable information flows. Moreover, taking into account the high mobility pattern that a smart city scenario presents, we propose and evaluate two forwarding strategies for the opportunistic sensor network. Full article

(This article belongs to the Special Issue Smart Vehicular Mobile Sensing)

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14 pages, 26700 KiB

Open AccessArticle

Improving Efficiency of Passive RFID Tag Anti-Collision Protocol Using Dynamic Frame Adjustment and Optimal Splitting

by Muhammad Qasim Memon¹

, Jingsha He^1,*, Mirza Ammar Yasir² and Aasma Memon³

¹ Faculty of Information Technology & Beijing Engineering Research Center for IoT Software and Systems, Beijing University of Technology, Beijing 100124, China

² Institute of Information & Communication Technology, Mehran University of Engineering & Technology, Jamshoro 76062, Pakistan

³ School of Economics and Management, Beijing University of Technology, Beijing 100124, China

Sensors 2018, 18(4), 1185; https://doi.org/10.3390/s18041185 - 12 Apr 2018

Cited by 8 | Viewed by 5322

Abstract

Radio frequency identification is a wireless communication technology, which enables data gathering and identifies recognition from any tagged object. The number of collisions produced during wireless communication would lead to a variety of problems including unwanted number of iterations and reader-induced idle slots, [...] Read more.

Radio frequency identification is a wireless communication technology, which enables data gathering and identifies recognition from any tagged object. The number of collisions produced during wireless communication would lead to a variety of problems including unwanted number of iterations and reader-induced idle slots, computational complexity in terms of estimation as well as recognition of the number of tags. In this work, dynamic frame adjustment and optimal splitting are employed together in the proposed algorithm. In the dynamic frame adjustment method, the length of frames is based on the quantity of tags to yield optimal efficiency. The optimal splitting method is conceived with smaller duration of idle slots using an optimal value for splitting level

M_{o p t}

, where (M > 2), to vary slot sizes to get the minimal identification time for the idle slots. The application of the proposed algorithm offers the advantages of not going for the cumbersome estimation of the quantity of tags incurred and the size (number) of tags has no effect on its performance efficiency. Our experiment results show that using the proposed algorithm, the efficiency curve remains constant as the number of tags varies from 50 to 450, resulting in an overall theoretical gain in the efficiency of 0.032 compared to system efficiency of 0.441 and thus outperforming both dynamic binary tree slotted ALOHA (DBTSA) and binary splitting protocols. Full article

(This article belongs to the Special Issue RFID-Based Sensors for IoT Applications)

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21 pages, 5363 KiB

Open AccessArticle

Practical 3-D Beam Pattern Based Channel Modeling for Multi-Polarized Massive MIMO Systems

by Saeid Aghaeinezhadfirouzja¹, Hui Liu¹ and Ali Balador^2,3,*

¹ Department of Electronics Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

² Department of Innovation, Design and Technology (IDT), Mälardalen University, 72123 Västerås, Sweden

³ RISE SICS Västerås, Stora gatan 36, 722 12 Västerås, Sweden

Sensors 2018, 18(4), 1186; https://doi.org/10.3390/s18041186 - 12 Apr 2018

Cited by 3 | Viewed by 6354

Abstract

In this paper, a practical non-stationary three-dimensional (3-D) channel models for massive multiple-input multiple-output (MIMO) systems, considering beam patterns for different antenna elements, is proposed. The beam patterns using dipole antenna elements with different phase excitation toward the different direction of travels (DoTs) [...] Read more.

In this paper, a practical non-stationary three-dimensional (3-D) channel models for massive multiple-input multiple-output (MIMO) systems, considering beam patterns for different antenna elements, is proposed. The beam patterns using dipole antenna elements with different phase excitation toward the different direction of travels (DoTs) contributes various correlation weights for rays related towards/from the cluster, thus providing different elevation angle of arrivals (EAoAs) and elevation angle of departures (EAoDs) for each antenna element. These include the movements of the user that makes our channel to be a non-stationary model of clusters at the receiver (RX) on both the time and array axes. In addition, their impacts on 3-D massive MIMO channels are investigated via statistical properties including received spatial correlation. Additionally, the impact of elevation/azimuth angles of arrival on received spatial correlation is discussed. Furthermore, experimental validation of the proposed 3-D channel models on azimuth and elevation angles of the polarized antenna are specifically evaluated and compared through simulations. The proposed 3-D generic models are verified using relevant measurement data. Full article

(This article belongs to the Special Issue Smart Vehicular Mobile Sensing)

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14 pages, 28382 KiB

Open AccessArticle

A Novel LiDAR-Based Instrument for High-Throughput, 3D Measurement of Morphological Traits in Maize and Sorghum

by Suresh Thapa¹, Feiyu Zhu², Harkamal Walia³, Hongfeng Yu² and Yufeng Ge^1,*

¹ Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA

² Department of Computer Science and Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA

³ Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE 68583, USA

Sensors 2018, 18(4), 1187; https://doi.org/10.3390/s18041187 - 13 Apr 2018

Cited by 115 | Viewed by 11466

Abstract

Recently, imaged-based approaches have developed rapidly for high-throughput plant phenotyping (HTPP). Imaging reduces a 3D plant into 2D images, which makes the retrieval of plant morphological traits challenging. We developed a novel LiDAR-based phenotyping instrument to generate 3D point clouds of single plants. [...] Read more.

Recently, imaged-based approaches have developed rapidly for high-throughput plant phenotyping (HTPP). Imaging reduces a 3D plant into 2D images, which makes the retrieval of plant morphological traits challenging. We developed a novel LiDAR-based phenotyping instrument to generate 3D point clouds of single plants. The instrument combined a LiDAR scanner with a precision rotation stage on which an individual plant was placed. A LabVIEW program was developed to control the scanning and rotation motion, synchronize the measurements from both devices, and capture a 360° view point cloud. A data processing pipeline was developed for noise removal, voxelization, triangulation, and plant leaf surface reconstruction. Once the leaf digital surfaces were reconstructed, plant morphological traits, including individual and total leaf area, leaf inclination angle, and leaf angular distribution, were derived. The system was tested with maize and sorghum plants. The results showed that leaf area measurements by the instrument were highly correlated with the reference methods (R² > 0.91 for individual leaf area; R² > 0.95 for total leaf area of each plant). Leaf angular distributions of the two species were also derived. This instrument could fill a critical technological gap for indoor HTPP of plant morphological traits in 3D. Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 46236 KiB

Open AccessArticle

Research on a Visual Electronic Nose System Based on Spatial Heterodyne Spectrometer

by Wenli Zhang, Fengchun Tian^*

, An Song and Youwen Hu

College of Communication Engineering, Chongqing University, 174 Sha Pingba, Chongqing 400044, China

Sensors 2018, 18(4), 1188; https://doi.org/10.3390/s18041188 - 13 Apr 2018

Cited by 4 | Viewed by 4014

Abstract

Light absorption gas sensing technology has the characteristics of massive parallelism, cross-sensitivity and extensive responsiveness, which make it suitable for the sensing task of an electronic nose (e-nose). With the performance of hyperspectral resolution, spatial heterodyne spectrometer (SHS) can present absorption spectra of [...] Read more.

Light absorption gas sensing technology has the characteristics of massive parallelism, cross-sensitivity and extensive responsiveness, which make it suitable for the sensing task of an electronic nose (e-nose). With the performance of hyperspectral resolution, spatial heterodyne spectrometer (SHS) can present absorption spectra of the gas in the form of a two dimensional (2D) interferogram which facilitates the analysis of gases with mature image processing techniques. Therefore, a visual e-nose system based on SHS was proposed. Firstly, a theoretical model of the visual e-nose system was constructed and its visual maps were obtained by an experiment. Then the local binary pattern (LBP) and Gray-Level Co-occurrence Matrix (GLCM) were used for feature extraction. Finally, classification algorithms based on distance similarity (Correlation coefficient (CC); Euclidean distance to centroids (EDC)) were chosen to carry on pattern recognition analysis to verify the feasibility of the visual e-nose system. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 5909 KiB

Open AccessArticle

Edge-Based Efficient Search over Encrypted Data Mobile Cloud Storage

by Yeting Guo¹

, Fang Liu^2,*, Zhiping Cai¹, Nong Xiao¹ and Ziming Zhao¹

¹ College of Computer, National University of Defense Technology, Changsha 410073, China

² School of Data and Computer Science, Sun Yat-Sen University, Guangzhou 510006, China

Sensors 2018, 18(4), 1189; https://doi.org/10.3390/s18041189 - 13 Apr 2018

Cited by 30 | Viewed by 6130

Abstract

Smart sensor-equipped mobile devices sense, collect, and process data generated by the edge network to achieve intelligent control, but such mobile devices usually have limited storage and computing resources. Mobile cloud storage provides a promising solution owing to its rich storage resources, great [...] Read more.

Smart sensor-equipped mobile devices sense, collect, and process data generated by the edge network to achieve intelligent control, but such mobile devices usually have limited storage and computing resources. Mobile cloud storage provides a promising solution owing to its rich storage resources, great accessibility, and low cost. But it also brings a risk of information leakage. The encryption of sensitive data is the basic step to resist the risk. However, deploying a high complexity encryption and decryption algorithm on mobile devices will greatly increase the burden of terminal operation and the difficulty to implement the necessary privacy protection algorithm. In this paper, we propose ENSURE (EfficieNt and SecURE), an efficient and secure encrypted search architecture over mobile cloud storage. ENSURE is inspired by edge computing. It allows mobile devices to offload the computation intensive task onto the edge server to achieve a high efficiency. Besides, to protect data security, it reduces the information acquisition of untrusted cloud by hiding the relevance between query keyword and search results from the cloud. Experiments on a real data set show that ENSURE reduces the computation time by 15% to 49% and saves the energy consumption by 38% to 69% per query. Full article

(This article belongs to the Special Issue New Paradigms in Data Sensing and Processing for Edge Computing)

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13 pages, 12309 KiB

Open AccessArticle

Easy-to-Build Textile Pressure Sensor

by Francisco Pizarro^*, Piero Villavicencio, Daniel Yunge

, Mauricio Rodríguez

, Gabriel Hermosilla and Ariel Leiva

Pontificia Universidad Católica de Valparaíso, Escuela de Ingeniería Eléctrica, Avenida Brasil 2147, Valparaíso 2362804, Chile

Sensors 2018, 18(4), 1190; https://doi.org/10.3390/s18041190 - 13 Apr 2018

Cited by 49 | Viewed by 12412

Abstract

This article presents the design, construction, and evaluation of an easy-to-build textile pressure resistive sensor created from low-cost conventional anti-static sheets and conductive woven fabrics. The sensor can be built quickly using standard household tools, and its thinness makes it especially suitable for [...] Read more.

This article presents the design, construction, and evaluation of an easy-to-build textile pressure resistive sensor created from low-cost conventional anti-static sheets and conductive woven fabrics. The sensor can be built quickly using standard household tools, and its thinness makes it especially suitable for wearable applications. Five sensors constructed under such conditions were evaluated, presenting a stable and linear characteristic in the range 1 to 70 kPa. The linear response was modeled and fitted for each sensor individually for comparison purposes, confirming a low variability due to the simple manufacturing process. Besides, the recovery times of the sensors were measured for pressures in the linear range, observing, for example, an average time of 1 s between the moment in which a pressure of 8 kPa was no longer applied, and the resistance variation at the 90% of its nominal value. Finally, we evaluated the proposed sensor design on a classroom application consisting of a smart glove that measured the pressure applied by each finger. From the evaluated characteristics, we concluded that the proposed design is suitable for didactic, healthcare and lifestyle applications in which the sensing of pressure variations, e.g., for activity assessment, is more valuable than accurate pressure sensing. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 3613 KiB

Open AccessArticle

Fabrication of Flexible Microneedle Array Electrodes for Wearable Bio-Signal Recording

by Lei Ren^1,†, Shujia Xu^1,†, Jie Gao¹, Zi Lin¹, Zhipeng Chen¹, Bin Liu¹, Liang Liang² and Lelun Jiang^1,*

¹ Guangdong Provincial Key Laboratory of Sensor Technology and Biomedical Instrument, Sun Yat-Sen University, Guangzhou 510006, China

² School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1191; https://doi.org/10.3390/s18041191 - 13 Apr 2018

Cited by 83 | Viewed by 11906

Abstract

Laser-direct writing (LDW) and magneto-rheological drawing lithography (MRDL) have been proposed for the fabrication of a flexible microneedle array electrode (MAE) for wearable bio-signal monitoring. Conductive patterns were directly written onto the flexible polyethylene terephthalate (PET) substrate by LDW. The microneedle array was [...] Read more.

Laser-direct writing (LDW) and magneto-rheological drawing lithography (MRDL) have been proposed for the fabrication of a flexible microneedle array electrode (MAE) for wearable bio-signal monitoring. Conductive patterns were directly written onto the flexible polyethylene terephthalate (PET) substrate by LDW. The microneedle array was rapidly drawn and formed from the droplets of curable magnetorheological fluid with the assistance of an external magnetic field by MRDL. A flexible MAE can maintain a stable contact interface with curved human skin due to the flexibility of the PET substrate. Compared with Ag/AgCl electrodes and flexible dry electrodes (FDE), the electrode–skin interface impedance of flexible MAE was the minimum even after a 50-cycle bending test. Flexible MAE can record electromyography (EMG), electroencephalography (EEG) and static electrocardiography (ECG) signals with good fidelity. The main features of the dynamic ECG signal recorded by flexible MAE are the most distinguishable with the least moving artifacts. Flexible MAE is an attractive candidate electrode for wearable bio-signal monitoring. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 15954 KiB

Open AccessArticle

A Fast and On-Machine Measuring System Using the Laser Displacement Sensor for the Contour Parameters of the Drill Pipe Thread

by Zhixu Dong^1,*

, Xingwei Sun¹, Changzheng Chen¹ and Mengnan Sun²

¹ School of Mechanical Engineering, Shenyang University of Technology, Shenyang 110870, China

² School of Mechanical Engineering & Automation, Northeastern University, Shenyang 110819, China

Sensors 2018, 18(4), 1192; https://doi.org/10.3390/s18041192 - 13 Apr 2018

Cited by 27 | Viewed by 6604

Abstract

The inconvenient loading and unloading of a long and heavy drill pipe gives rise to the difficulty in measuring the contour parameters of its threads at both ends. To solve this problem, in this paper we take the SCK230 drill pipe thread-repairing machine [...] Read more.

The inconvenient loading and unloading of a long and heavy drill pipe gives rise to the difficulty in measuring the contour parameters of its threads at both ends. To solve this problem, in this paper we take the SCK230 drill pipe thread-repairing machine tool as a carrier to design and achieve a fast and on-machine measuring system based on a laser probe. This system drives a laser displacement sensor to acquire the contour data of a certain axial section of the thread by using the servo function of a CNC machine tool. To correct the sensor’s measurement errors caused by the measuring point inclination angle, an inclination error model is built to compensate data in real time. To better suppress random error interference and ensure real contour information, a new wavelet threshold function is proposed to process data through the wavelet threshold denoising. Discrete data after denoising is segmented according to the geometrical characteristics of the drill pipe thread, and the regression model of the contour data in each section is fitted by using the method of weighted total least squares (WTLS). Then, the thread parameters are calculated in real time to judge the processing quality. Inclination error experiments show that the proposed compensation model is accurate and effective, and it can improve the data acquisition accuracy of a sensor. Simulation results indicate that the improved threshold function is of better continuity and self-adaptability, which makes sure that denoising effects are guaranteed, and, meanwhile, the complete elimination of real data distorted in random errors is avoided. Additionally, NC50 thread-testing experiments show that the proposed on-machine measuring system can complete the measurement of a 25 mm thread in 7.8 s, with a measurement accuracy of ±8 μm and repeatability limit ≤ 4 μm (high repeatability), and hence the accuracy and efficiency of measurement are both improved. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 11277 KiB

Open AccessArticle

Fabrication of Composite Microneedle Array Electrode for Temperature and Bio-Signal Monitoring

by Yiwei Sun^1,†, Lei Ren^1,†, Lelun Jiang¹, Yong Tang² and Bin Liu^1,*

¹ School of Engineering, Guangdong Provincial Key Laboratory of Sensor Technology and Biomedical Instrument, Sun Yat-Sen University, Guangzhou 510006, China

² Guangdong Provincial Key Laboratory of Precision Equipment and Manufacturing Technology, South China University of Technology, Guangzhou 510640, China

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1193; https://doi.org/10.3390/s18041193 - 13 Apr 2018

Cited by 28 | Viewed by 6740

Abstract

Body temperature and bio-signals are important health indicators that reflect the human health condition. However, monitoring these indexes is inconvenient and time-consuming, requires various instruments, and needs professional skill. In this study, a composite microneedle array electrode (CMAE) was designed and fabricated. It [...] Read more.

Body temperature and bio-signals are important health indicators that reflect the human health condition. However, monitoring these indexes is inconvenient and time-consuming, requires various instruments, and needs professional skill. In this study, a composite microneedle array electrode (CMAE) was designed and fabricated. It simultaneously detects body temperature and bio-signals. The CMAE consists of a 6 × 6 microneedles array with a height of 500 μm and a base diameter of 200 μm. Multiple insertion experiments indicate that the CMAE possesses excellent mechanical properties. The CMAE can pierce porcine skin 100 times without breaking or bending. A linear calibration relationship between temperature and voltage are experimentally obtained. Armpit temperature (35.8 °C) and forearm temperature (35.3 °C) are detected with the CMAE, and the measurements agree well with the data acquired with a clinical thermometer. Bio-signals including EII, ECG, and EMG are recorded and compared with those obtained by a commercial Ag/AgCl electrode. The CMAE continuously monitors bio-signals and is more convenient to apply because it does not require skin preparation and gel usage. The CMAE exhibits good potential for continuous and repetitive monitoring of body temperature and bio-signals. Full article

(This article belongs to the Special Issue Sensors for Health Monitoring and Disease Diagnosis)

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10 pages, 3456 KiB

Open AccessArticle

Super-Resolution for “Jilin-1” Satellite Video Imagery via a Convolutional Network

by Aoran Xiao¹

, Zhongyuan Wang^2,*, Lei Wang¹ and Yexian Ren¹

¹ State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing (LIESMARS), Wuhan University, Wuhan 430079, China

² National Engineering Research Center for Multimedia Software, School of Computer, Wuhan University, Wuhan 430072, China

Sensors 2018, 18(4), 1194; https://doi.org/10.3390/s18041194 - 13 Apr 2018

Cited by 64 | Viewed by 8487

Abstract

Super-resolution for satellite video attaches much significance to earth observation accuracy, and the special imaging and transmission conditions on the video satellite pose great challenges to this task. The existing deep convolutional neural-network-based methods require pre-processing or post-processing to be adapted to a [...] Read more.

Super-resolution for satellite video attaches much significance to earth observation accuracy, and the special imaging and transmission conditions on the video satellite pose great challenges to this task. The existing deep convolutional neural-network-based methods require pre-processing or post-processing to be adapted to a high-resolution size or pixel format, leading to reduced performance and extra complexity. To this end, this paper proposes a five-layer end-to-end network structure without any pre-processing and post-processing, but imposes a reshape or deconvolution layer at the end of the network to retain the distribution of ground objects within the image. Meanwhile, we formulate a joint loss function by combining the output and high-dimensional features of a non-linear mapping network to precisely learn the desirable mapping relationship between low-resolution images and their high-resolution counterparts. Also, we use satellite video data itself as a training set, which favors consistency between training and testing images and promotes the method’s practicality. Experimental results on “Jilin-1” satellite video imagery show that this method demonstrates a superior performance in terms of both visual effects and measure metrics over competing methods. Full article

(This article belongs to the Special Issue Sensors Signal Processing and Visual Computing)

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21 pages, 6174 KiB

Open AccessArticle

Verifying Safety Messages Using Relative-Time and Zone Priority in Vehicular Ad Hoc Networks

by Sam Banani¹, Steven Gordon^2,*

, Surapa Thiemjarus³ and Somsak Kittipiyakul¹

¹ School of Information, Computer, and Communication Technology, Sirindhorn International Institute of Technology, Thammasat University, Pathum Thani 12000, Thailand

² School of Engineering and Technology, CQUniversity, Cairns QLD 4870, Australia

³ National Electronics and Computer Technology Center, Pathum Thani 12120, Thailand

Sensors 2018, 18(4), 1195; https://doi.org/10.3390/s18041195 - 13 Apr 2018

Cited by 23 | Viewed by 4481

Abstract

In high-density road networks, with each vehicle broadcasting multiple messages per second, the arrival rate of safety messages can easily exceed the rate at which digital signatures can be verified. Since not all messages can be verified, algorithms for selecting which messages to [...] Read more.

In high-density road networks, with each vehicle broadcasting multiple messages per second, the arrival rate of safety messages can easily exceed the rate at which digital signatures can be verified. Since not all messages can be verified, algorithms for selecting which messages to verify are required to ensure that each vehicle receives appropriate awareness about neighbouring vehicles. This paper presents a novel scheme to select important safety messages for verification in vehicular ad hoc networks (VANETs). The proposed scheme uses location and direction of the sender, as well as proximity and relative-time between vehicles, to reduce the number of irrelevant messages verified (i.e., messages from vehicles that are unlikely to cause an accident). Compared with other existing schemes, the analysis results show that the proposed scheme can verify messages from nearby vehicles with lower inter-message delay and reduced packet loss and thus provides high level of awareness of the nearby vehicles. Full article

(This article belongs to the Special Issue Sensors, Wireless Connectivity and Systems for Autonomous Vehicles and Smart Mobility)

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15 pages, 2238 KiB

Open AccessArticle

Ship Detection from Ocean SAR Image Based on Local Contrast Variance Weighted Information Entropy

by Weibo Huo^*

, Yulin Huang, Jifang Pei, Qian Zhang, Qin Gu and Jianyu Yang

School of Communication and Information Engineering, University of Electronic Science and Technology of China, 2006 Xiyuan Road, Gaoxin Western District, Chengdu 611731, China

Sensors 2018, 18(4), 1196; https://doi.org/10.3390/s18041196 - 13 Apr 2018

Cited by 56 | Viewed by 6058

Abstract

Ship detection from synthetic aperture radar (SAR) images is one of the crucial issues in maritime surveillance. However, due to the varying ocean waves and the strong echo of the sea surface, it is very difficult to detect ships from heterogeneous and strong [...] Read more.

Ship detection from synthetic aperture radar (SAR) images is one of the crucial issues in maritime surveillance. However, due to the varying ocean waves and the strong echo of the sea surface, it is very difficult to detect ships from heterogeneous and strong clutter backgrounds. In this paper, an innovative ship detection method is proposed to effectively distinguish the vessels from complex backgrounds from a SAR image. First, the input SAR image is pre-screened by the maximally-stable extremal region (MSER) method, which can obtain the ship candidate regions with low computational complexity. Then, the proposed local contrast variance weighted information entropy (LCVWIE) is adopted to evaluate the complexity of those candidate regions and the dissimilarity between the candidate regions with their neighborhoods. Finally, the LCVWIE values of the candidate regions are compared with an adaptive threshold to obtain the final detection result. Experimental results based on measured ocean SAR images have shown that the proposed method can obtain stable detection performance both in strong clutter and heterogeneous backgrounds. Meanwhile, it has a low computational complexity compared with some existing detection methods. Full article

(This article belongs to the Special Issue Automatic Target Recognition of High Resolution SAR/ISAR Images)

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12 pages, 3838 KiB

Open AccessArticle

Intercomparison on Four Irrigated Cropland Maps in Mainland China

by Yizhu Liu¹, Wenbin Wu^1,*, Hailan Li², Muhammad Imtiaz³, Zhaoliang Li¹ and Qingbo Zhou¹

¹ Institute of Agriculture Resources and Regional Planning, Chinese Academy of Agriculture Sciences, Beijing 100081, China

² Institute of Agricultural Products Processing and Nuclear Agriculture Technology Research, Hubei Academy of Agricultural Sciences, Wuhan 430070, China

³ School of Geographical Science, Guangzhou University, Guangzhou 510006, China

Sensors 2018, 18(4), 1197; https://doi.org/10.3390/s18041197 - 13 Apr 2018

Cited by 10 | Viewed by 3954

Abstract

Wide-coverage spatial information on irrigated croplands is a vital foundation for food security and water resources studies at the regional level. Several global irrigated-cropland maps have been released to the public over the past decade due to the efforts of the remote sensing [...] Read more.

Wide-coverage spatial information on irrigated croplands is a vital foundation for food security and water resources studies at the regional level. Several global irrigated-cropland maps have been released to the public over the past decade due to the efforts of the remote sensing community. However, the consistency and discrepancy between these maps is largely unknown because of a lack of comparative studies, limiting their use and improvement. To close this knowledge gap, we compared the latest four irrigated-cropland datasets (GMIA, GRIPC, GlobCover, and GFSAD) in mainland China. First, the four maps were compared quantitatively and neutral regional- and provincial-level statistics of the relative proportions of irrigated land were obtained through regression analysis. Second, we compared the similarities and discrepancies of the datasets on spatial grids. Furthermore, the contributions of mosaic cropland pixels in GlobCover and GFSAD were also analyzed because of their extensive distribution and ambiguous content. Results showed that GMIA has the lowest dispersion and best statistical correlation followed by GRIPC, while the corresponding features of GlobCover and GFSAD are approximately equal. Spatial agreement of the four maps is higher in eastern than western China, and disagreement is contributed mostly by GlobCover and GFSAD. However, divergence exists in the ratios of the different agreement levels, as well as their sources, on a regional scale. Mosaic pixels provide more than half of the irrigated areas for GlobCover and GFSAD, and they include both correct and incorrect information. Our results indicate a need for a uniform quantitative classification system and for greater focus on heterogeneous regions. Furthermore, the results demonstrate the advantage of numerical restriction in the calculations. Therefore, special attention should be paid to integrating databases and to exploring remote sensing features and methods for spatial reconstruction and identification of untypical irrigation areas. Full article

(This article belongs to the Section Remote Sensors)

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21 pages, 6439 KiB

Open AccessArticle

Optimizing the Energy and Throughput of a Water-Quality Monitoring System

by Segun O. Olatinwo^* and Trudi-H. Joubert

Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Pretoria 0001, South Africa

Sensors 2018, 18(4), 1198; https://doi.org/10.3390/s18041198 - 13 Apr 2018

Cited by 39 | Viewed by 5321

Abstract

This work presents a new approach to the maximization of energy and throughput in a wireless sensor network (WSN), with the intention of applying the approach to water-quality monitoring. Water-quality monitoring using WSN technology has become an interesting research area. Energy scarcity is [...] Read more.

This work presents a new approach to the maximization of energy and throughput in a wireless sensor network (WSN), with the intention of applying the approach to water-quality monitoring. Water-quality monitoring using WSN technology has become an interesting research area. Energy scarcity is a critical issue that plagues the widespread deployment of WSN systems. Different power supplies, harvesting energy from sustainable sources, have been explored. However, when energy-efficient models are not put in place, energy harvesting based WSN systems may experience an unstable energy supply, resulting in an interruption in communication, and low system throughput. To alleviate these problems, this paper presents the joint maximization of the energy harvested by sensor nodes and their information-transmission rate using a sum-throughput technique. A wireless information and power transfer (WIPT) method is considered by harvesting energy from dedicated radio frequency sources. Due to the doubly near–far condition that confronts WIPT systems, a new WIPT system is proposed to improve the fairness of resource utilization in the network. Numerical simulation results are presented to validate the mathematical formulations for the optimization problem, which maximize the energy harvested and the overall throughput rate. Defining the performance metrics of achievable throughput and fairness in resource sharing, the proposed WIPT system outperforms an existing state-of-the-art WIPT system, with the comparison based on numerical simulations of both systems. The improved energy efficiency of the proposed WIPT system contributes to addressing the problem of energy scarcity. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 19375 KiB

Open AccessArticle

Performance Analysis of BDS Medium-Long Baseline RTK Positioning Using an Empirical Troposphere Model

by Bao Shu¹

, Hui Liu^1,2,*, Longwei Xu¹, Chuang Qian¹, Xiaopeng Gong¹ and Xiangdong An¹

¹ GNSS Research Center, Wuhan University, No. 129 Luoyu Road, Wuhan 430079, China

² Collaborative Innovation Center of Geospatial Technology, Wuhan University, No. 129 Luoyu Road, Wuhan 430079, China

Sensors 2018, 18(4), 1199; https://doi.org/10.3390/s18041199 - 14 Apr 2018

Cited by 21 | Viewed by 3687

Abstract

For GPS medium-long baseline real-time kinematic (RTK) positioning, the troposphere parameter is introduced along with coordinates, and the model is ill-conditioned due to its strong correlation with the height parameter. For BeiDou Navigation Satellite System (BDS), additional difficulties occur due to its special [...] Read more.

For GPS medium-long baseline real-time kinematic (RTK) positioning, the troposphere parameter is introduced along with coordinates, and the model is ill-conditioned due to its strong correlation with the height parameter. For BeiDou Navigation Satellite System (BDS), additional difficulties occur due to its special satellite constellation. In fact, relative zenith troposphere delay (RZTD) derived from high-precision empirical zenith troposphere models can be introduced. Thus, the model strength can be improved, which is also called the RZTD-constrained RTK model. In this contribution, we first analyze the factors affecting the precision of BDS medium-long baseline RTK; thereafter, 15 baselines ranging from 38 km to 167 km in different troposphere conditions are processed to assess the performance of RZTD-constrained RTK. Results show that the troposphere parameter is difficult to distinguish from the height component, even with long time filtering for BDS-only RTK. Due to the lack of variation in geometry for the BDS geostationary Earth orbit satellite, the long convergence time of ambiguity parameters may reduce the height precision of GPS/BDS-combined RTK in the initial period. When the RZTD-constrained model was used in BDS and GPS/BDS-combined situations compared with the traditional RTK, the standard deviation of the height component for the fixed solution was reduced by 52.4% and 34.0%, respectively. Full article

(This article belongs to the Section Remote Sensors)

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18 pages, 18459 KiB

Open AccessArticle

An Embedded Sensory System for Worker Safety: Prototype Development and Evaluation

by Chunhee Cho and JeeWoong Park^*

Department of Civil and Environmental Engineering and Construction, The University of Nevada, Las Vegas, NV 89154, USA

Sensors 2018, 18(4), 1200; https://doi.org/10.3390/s18041200 - 14 Apr 2018

Cited by 17 | Viewed by 4972

Abstract

At a construction site, workers mainly rely on two senses, which are sight and sound, in order to perceive their physical surroundings. However, they are often hindered by the nature of most construction sites, which are usually dynamic, loud, and complicated. To overcome [...] Read more.

At a construction site, workers mainly rely on two senses, which are sight and sound, in order to perceive their physical surroundings. However, they are often hindered by the nature of most construction sites, which are usually dynamic, loud, and complicated. To overcome these challenges, this research explored a method using an embedded sensory system that might offer construction workers an artificial sensing ability to better perceive their surroundings. This study identified three parameters (i.e., intensity, signal length, and delay between consecutive pulses) needed for tactile-based signals for the construction workers to communicate quickly. We developed a prototype system based on these parameters, conducted experimental studies to quantify and validate the sensitivity of the parameters for quick communication, and analyzed test data to reveal what was added by this method in order to perceive information from the tactile signals. The findings disclosed that the parameters of tactile-based signals and their distinguishable ranges could be perceived in a short amount of time (i.e., a fraction of a second). Further experimentation demonstrated the capability of the identified unit signals combined with a signal mapping technique to effectively deliver simple information to individuals and offer an additional sense of awareness to the surroundings. The findings of this study could serve as a basis for future research in exploring advanced tactile-based messages to overcome challenges in environments for which communication is a struggle. Full article

(This article belongs to the Section Intelligent Sensors)

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0 pages, 32357 KiB

Open AccessArticle

Design and Investigation of Optical Properties of N-(Rhodamine-B)-Lactam-Ethylenediamine (RhB-EDA) Fluorescent Probe

by Eva Soršak^1,2, Julija Volmajer Valh¹, Špela Korent Urek³ and Aleksandra Lobnik^1,3,*

¹ Institute of Engineering Materials and Design, Faculty of Mechanical Engineering, University of Maribor, Smetanova 17, 2000 Maribor, Slovenia

² Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia

³ Institute for Environmental Protection and Sensors, Beloruska 7, 2000 Maribor, Slovenia

Sensors 2018, 18(4), 1201; https://doi.org/10.3390/s18041201 - 14 Apr 2018

Cited by 13 | Viewed by 6548 | Correction

Abstract

This study presents chemical modification of a Rhodamine B (RhB) sensor probe by ethylenediamine (EDA), and investigation of its spectral as well as sensor properties to the various metals. The synthesised N-(Rhodamine-B)-lactam-ethylenediamine (RhB-EDA) fluorescent probe shows interesting optical sensor properties, and high [...] Read more.

This study presents chemical modification of a Rhodamine B (RhB) sensor probe by ethylenediamine (EDA), and investigation of its spectral as well as sensor properties to the various metals. The synthesised N-(Rhodamine-B)-lactam-ethylenediamine (RhB-EDA) fluorescent probe shows interesting optical sensor properties, and high sensitivity and selectivity to Ag⁺ ions among all the tested metal ions (K⁺, Mg²⁺, Cu²⁺, Ni²⁺, Fe²⁺, Pb²⁺, Na⁺, Mn²⁺, Li⁺, Al³⁺, Co²⁺, Hg²⁺, Sr²⁺, Ca²⁺, Ag⁺, Cd²⁺ and Zn²⁺), while the well-known Rhodamine B (RhB) fluorescent probe shows much less sensitivity to Ag⁺ ions, but high sensitivity to Fe²⁺ ions. The novel fluorescent sensor probe RhB-EDA has the capabilities to sense Ag⁺ ions up to µM ranges by using the fluorescence quenching approach. The probe displayed a dynamic response to Ag⁺ in the range of 0.43 × 10⁻³–10⁻⁶ M with a detection limit of 0.1 μM. The sensing system of an RhB-EDA novel fluorescent probe was optimised according to the spectral properties, effect of pH and buffer, photostability, incubation time, sensitivity, and selectivity. Since all the spectral and sensing properties were tested in green aqueous media, although many other similar sensor systems rely on organic solvent solutions, the RhB-EDA sensing probe may be a good candidate for measuring Ag⁺ ions in real-life applications. Full article

(This article belongs to the Section Chemical Sensors)

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22 pages, 1983 KiB

Open AccessArticle

Using Ontologies for the Online Recognition of Activities of Daily Living

by Alberto G. Salguero^1,*

, Macarena Espinilla²

, Pablo Delatorre¹

and Javier Medina²

¹ Department of Computer Science, University of Cádiz, Cádiz 11519, Spain

² Department of Computer Science, University of Jaén, Jaén 23071, Spain

Sensors 2018, 18(4), 1202; https://doi.org/10.3390/s18041202 - 14 Apr 2018

Cited by 18 | Viewed by 4480

Abstract

The recognition of activities of daily living is an important research area of interest in recent years. The process of activity recognition aims to recognize the actions of one or more people in a smart environment, in which a set of sensors has [...] Read more.

The recognition of activities of daily living is an important research area of interest in recent years. The process of activity recognition aims to recognize the actions of one or more people in a smart environment, in which a set of sensors has been deployed. Usually, all the events produced during each activity are taken into account to develop the classification models. However, the instant in which an activity started is unknown in a real environment. Therefore, only the most recent events are usually used. In this paper, we use statistics to determine the most appropriate length of that interval for each type of activity. In addition, we use ontologies to automatically generate features that serve as the input for the supervised learning algorithms that produce the classification model. The features are formed by combining the entities in the ontology, such as concepts and properties. The results obtained show a significant increase in the accuracy of the classification models generated with respect to the classical approach, in which only the state of the sensors is taken into account. Moreover, the results obtained in a simulation of a real environment under an event-based segmentation also show an improvement in most activities. Full article

(This article belongs to the Special Issue Selected Papers from UCAmI 2017 – the 11th International Conference on Ubiquitous Computing and Ambient Intelligence)

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19 pages, 16764 KiB

Open AccessArticle

Rolling Bearing Fault Diagnosis Based on an Improved HTT Transform

by Bin Pang^*

, Guiji Tang, Tian Tian and Chong Zhou

School of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071000, China

Sensors 2018, 18(4), 1203; https://doi.org/10.3390/s18041203 - 14 Apr 2018

Cited by 59 | Viewed by 6424

Abstract

When rolling bearing failure occurs, vibration signals generally contain different signal components, such as impulsive fault feature signals, background noise and harmonic interference signals. One of the most challenging aspects of rolling bearing fault diagnosis is how to inhibit noise and harmonic interference [...] Read more.

When rolling bearing failure occurs, vibration signals generally contain different signal components, such as impulsive fault feature signals, background noise and harmonic interference signals. One of the most challenging aspects of rolling bearing fault diagnosis is how to inhibit noise and harmonic interference signals, while enhancing impulsive fault feature signals. This paper presents a novel bearing fault diagnosis method, namely an improved Hilbert time–time (IHTT) transform, by combining a Hilbert time–time (HTT) transform with principal component analysis (PCA). Firstly, the HTT transform was performed on vibration signals to derive a HTT transform matrix. Then, PCA was employed to de-noise the HTT transform matrix in order to improve the robustness of the HTT transform. Finally, the diagonal time series of the de-noised HTT transform matrix was extracted as the enhanced impulsive fault feature signal and the contained fault characteristic information was identified through further analyses of amplitude and envelope spectrums. Both simulated and experimental analyses validated the superiority of the presented method for detecting bearing failures. Full article

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21 pages, 1173 KiB

Open AccessArticle

Big Data Clustering via Community Detection and Hyperbolic Network Embedding in IoT Applications

by Vasileios Karyotis^1,*,†

, Konstantinos Tsitseklis^1,†

, Konstantinos Sotiropoulos^1,2,‡ and Symeon Papavassiliou^1,†

¹ Institute of Communication and Computer Systems (ICCS), School of Electrical and Computer Engineering, National Technical University of Athens (NTUA), Athens 157 80, Greece

² Department of Computer Science, Boston University, Boston, MA 02215, USA

^† Current address: Iroon Polytechniou 9, Zografou, Athens 157 80, Greece.

^‡ The author was with the Institute of Communication and Computer Systems (ICCS), School of Electrical and Computer Engineering, National Technical University of Athens (NTUA), Greece, for the main part of this work. He is now with Boston University, MA, USA. Current address: 111 Cummington Mall, Boston, MA 02215, USA.

Sensors 2018, 18(4), 1205; https://doi.org/10.3390/s18041205 - 15 Apr 2018

Cited by 10 | Viewed by 4775

Abstract

In this paper, we present a novel data clustering framework for big sensory data produced by IoT applications. Based on a network representation of the relations among multi-dimensional data, data clustering is mapped to node clustering over the produced data graphs. To address [...] Read more.

In this paper, we present a novel data clustering framework for big sensory data produced by IoT applications. Based on a network representation of the relations among multi-dimensional data, data clustering is mapped to node clustering over the produced data graphs. To address the potential very large scale of such datasets/graphs that test the limits of state-of-the-art approaches, we map the problem of data clustering to a community detection one over the corresponding data graphs. Specifically, we propose a novel computational approach for enhancing the traditional Girvan–Newman (GN) community detection algorithm via hyperbolic network embedding. The data dependency graph is embedded in the hyperbolic space via Rigel embedding, allowing more efficient computation of edge-betweenness centrality needed in the GN algorithm. This allows for more efficient clustering of the nodes of the data graph in terms of modularity, without sacrificing considerable accuracy. In order to study the operation of our approach with respect to enhancing GN community detection, we employ various representative types of artificial complex networks, such as scale-free, small-world and random geometric topologies, and frequently-employed benchmark datasets for demonstrating its efficacy in terms of data clustering via community detection. Furthermore, we provide a proof-of-concept evaluation by applying the proposed framework over multi-dimensional datasets obtained from an operational smart-city/building IoT infrastructure provided by the Federated Interoperable Semantic IoT/cloud Testbeds and Applications (FIESTA-IoT) testbed federation. It is shown that the proposed framework can be indeed used for community detection/data clustering and exploited in various other IoT applications, such as performing more energy-efficient smart-city/building sensing. Full article

(This article belongs to the Section Sensor Networks)

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15 pages, 12633 KiB

Open AccessFeature PaperArticle

“What Is a Step?” Differences in How a Step Is Detected among Three Popular Activity Monitors That Have Impacted Physical Activity Research

by Dinesh John^1,*, Alvin Morton²

, Diego Arguello¹, Kate Lyden³ and David Bassett²

¹ Department of Health Sciences, Northeastern University, Boston, MA 02115, USA

² Department of Kinesiology, Recreation, and Sport Studies, University of Tennessee, Knoxville, TN 37996 USA

³ KAL Research/Consulting, Denver, CO 80206, USA

Sensors 2018, 18(4), 1206; https://doi.org/10.3390/s18041206 - 15 Apr 2018

Cited by 64 | Viewed by 6700

Abstract

(1) Background: This study compared manually-counted treadmill walking steps from the hip-worn DigiwalkerSW200 and OmronHJ720ITC, and hip and wrist-worn ActiGraph GT3X+ and GT9X; determined brand-specific acceleration amplitude (g) and/or frequency (Hz) step-detection thresholds; and quantified key features of the acceleration signal during walking. [...] Read more.

(1) Background: This study compared manually-counted treadmill walking steps from the hip-worn DigiwalkerSW200 and OmronHJ720ITC, and hip and wrist-worn ActiGraph GT3X+ and GT9X; determined brand-specific acceleration amplitude (g) and/or frequency (Hz) step-detection thresholds; and quantified key features of the acceleration signal during walking. (2) Methods: Twenty participants (Age: 26.7 ± 4.9 years) performed treadmill walking between 0.89-to-1.79 m/s (2–4 mph) while wearing a hip-worn DigiwalkerSW200, OmronHJ720ITC, GT3X+ and GT9X, and a wrist-worn GT3X+ and GT9X. A DigiwalkerSW200 and OmronHJ720ITC underwent shaker testing to determine device-specific frequency and amplitude step-detection thresholds. Simulated signal testing was used to determine thresholds for the ActiGraph step algorithm. Steps during human testing were compared using bias and confidence intervals. (3) Results: The OmronHJ720ITC was most accurate during treadmill walking. Hip and wrist-worn ActiGraph outputs were significantly different from the criterion. The DigiwalkerSW200 records steps for movements with a total acceleration of ≥1.21 g. The OmronHJ720ITC detects a step when movement has an acceleration ≥0.10 g with a dominant frequency of ≥1 Hz. The step-threshold for the ActiLife algorithm is variable based on signal frequency. Acceleration signals at the hip and wrist have distinctive patterns during treadmill walking. (4) Conclusions: Three common research-grade physical activity monitors employ different step-detection strategies, which causes variability in step output. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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10 pages, 4486 KiB

Open AccessArticle

Continuous-Wave Fiber Cavity Ringdown Pressure Sensing Based on Frequency-Shifted Interferometry

by Yiwen Ou^1,2, Chunfu Cheng^1,2,*, Zehao Chen^1,2, Zhangyong Yang^1,2, Hui Lv^1,2 and Li Qian³

¹ Hubei Collaborative Innovation Center for High-Efficiency Utilization of Solar Energy, Hubei University of Technology, Wuhan 430068, China

² School of Science, Hubei University of Technology, Wuhan 430068, China

³ Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON M5S 3G4, Canada

Sensors 2018, 18(4), 1207; https://doi.org/10.3390/s18041207 - 16 Apr 2018

Cited by 16 | Viewed by 3623

Abstract

We present a continuous-wave fiber cavity ringdown (FCRD) pressure-sensing method based on frequency-shifted interferometry (FSI). Compared with traditional CRD or FCRD techniques, this FSI-FCRD scheme deduces pressure by measuring the decay rate of continuous light exiting the fiber ringdown cavity (RDC) in the [...] Read more.

We present a continuous-wave fiber cavity ringdown (FCRD) pressure-sensing method based on frequency-shifted interferometry (FSI). Compared with traditional CRD or FCRD techniques, this FSI-FCRD scheme deduces pressure by measuring the decay rate of continuous light exiting the fiber ringdown cavity (RDC) in the spatial domain (i.e., the CRD distance), without the requirement for optical pulsation and fast electronics. By using a section of fiber with the buffer layer stripped in the fiber RDC as the sensor head, pressures were measured within the range from 0 to 10.4 MPa. The sensitivity of 0.02356/(km∙MPa) was obtained with a measurement error of 0.1%, and the corresponding pressure resolution was 0.05 MPa. It was found that the measurement sensitivity can be improved by enlarging the interaction length of the sensor head. The results show the proposed sensor has the advantages of simple structure, low cost, high sensitivity, and high stability in pressure detection. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 45969 KiB

Open AccessArticle

Comparative Analysis of Warp Function for Digital Image Correlation-Based Accurate Single-Shot 3D Shape Measurement

by Xiao Yang^1,2

, Xiaobo Chen^1,2 and Juntong Xi^1,2,3,*

¹ School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

² Shanghai Key Laboratory of Advanced Manufacturing Environment, Shanghai 200030, China

³ State Key Laboratory of Mechanical System and Vibration, Shanghai 200240, China

Sensors 2018, 18(4), 1208; https://doi.org/10.3390/s18041208 - 16 Apr 2018

Cited by 9 | Viewed by 4727

Abstract

Digital image correlation (DIC)-based stereo 3D shape measurement is a kind of single-shot method, which can achieve high precision and is robust to vibration as well as environment noise. The efficiency of DIC has been greatly improved with the proposal of inverse compositional [...] Read more.

Digital image correlation (DIC)-based stereo 3D shape measurement is a kind of single-shot method, which can achieve high precision and is robust to vibration as well as environment noise. The efficiency of DIC has been greatly improved with the proposal of inverse compositional Gauss-Newton (IC-GN) operators for both first-order and second-order warp functions. Without the algorithm itself, both the registration accuracy and efficiency of DIC-based stereo matching for shapes with different complexities are closely related to the selection of warp function, subset size, and convergence criteria. Understanding the similarity and difference of the impacts of prescribed subset size and convergence criteria on first-order and second-order warp functions, and how to choose a proper warp function and set optimal subset size as well as convergence criteria for different shapes are fundamental problems in realizing efficient and accurate 3D shape measurement. In this work, we present a comparative analysis of first-order and second-order warp functions for DIC-based 3D shape measurement using IC-GN algorithm. The effects of subset size and convergence criteria of first-order and second-order warp functions on the accuracy and efficiency of DIC are comparatively examined with both simulation tests and real experiments. Reference standards for the selection of warp function for different kinds of 3D shape measurement and the setting of proper convergence criteria are recommended. The effects of subset size on the measuring precision using different warp functions are also concluded. Full article

(This article belongs to the Special Issue Visual Sensors)

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25 pages, 1953 KiB

Open AccessArticle

Escalator: An Autonomous Scheduling Scheme for Convergecast in TSCH

by Sukho Oh¹, DongYeop Hwang¹, Ki-Hyung Kim^2,* and Kangseok Kim²

¹ Department of Computer Engineering, Graduate School of Ajou University, Suwon 16499, Korea

² Department of Cyber Security, Ajou University, Suwon 16499, Korea

Sensors 2018, 18(4), 1209; https://doi.org/10.3390/s18041209 - 16 Apr 2018

Cited by 37 | Viewed by 5187

Abstract

Time Slotted Channel Hopping (TSCH) is widely used in the industrial wireless sensor networks due to its high reliability and energy efficiency. Various timeslot and channel scheduling schemes have been proposed for achieving high reliability and energy efficiency for TSCH networks. Recently proposed [...] Read more.

Time Slotted Channel Hopping (TSCH) is widely used in the industrial wireless sensor networks due to its high reliability and energy efficiency. Various timeslot and channel scheduling schemes have been proposed for achieving high reliability and energy efficiency for TSCH networks. Recently proposed autonomous scheduling schemes provide flexible timeslot scheduling based on the routing topology, but do not take into account the network traffic and packet forwarding delays. In this paper, we propose an autonomous scheduling scheme for convergecast in TSCH networks with RPL as a routing protocol, named Escalator. Escalator generates a consecutive timeslot schedule along the packet forwarding path to minimize the packet transmission delay. The schedule is generated autonomously by utilizing only the local routing topology information without any additional signaling with other nodes. The generated schedule is guaranteed to be conflict-free, in that all nodes in the network could transmit packets to the sink in every slotframe cycle. We implement Escalator and evaluate its performance with existing autonomous scheduling schemes through a testbed and simulation. Experimental results show that the proposed Escalator has lower end-to-end delay and higher packet delivery ratio compared to the existing schemes regardless of the network topology. Full article

(This article belongs to the Section Sensor Networks)

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21 pages, 20255 KiB

Open AccessArticle

Multi-Fault Diagnosis of Rolling Bearings via Adaptive Projection Intrinsically Transformed Multivariate Empirical Mode Decomposition and High Order Singular Value Decomposition

by Rui Yuan^1,2

, Yong Lv^1,2,* and Gangbing Song^3,*

¹ Key Laboratory of Metallurgical Equipment and Control Technology, Wuhan University of Science and Technology, Ministry of Education, Wuhan 430081, China

² Hubei Key Laboratory of Mechanical Transmission and Manufacturing Engineering, Wuhan University of Science and Technology, Wuhan 430081, China

³ Smart Material and Structure Laboratory, Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA

Sensors 2018, 18(4), 1210; https://doi.org/10.3390/s18041210 - 16 Apr 2018

Cited by 44 | Viewed by 5166

Abstract

Rolling bearings are important components in rotary machinery systems. In the field of multi-fault diagnosis of rolling bearings, the vibration signal collected from single channels tends to miss some fault characteristic information. Using multiple sensors to collect signals at different locations on the [...] Read more.

Rolling bearings are important components in rotary machinery systems. In the field of multi-fault diagnosis of rolling bearings, the vibration signal collected from single channels tends to miss some fault characteristic information. Using multiple sensors to collect signals at different locations on the machine to obtain multivariate signal can remedy this problem. The adverse effect of a power imbalance between the various channels is inevitable, and unfavorable for multivariate signal processing. As a useful, multivariate signal processing method, Adaptive-projection has intrinsically transformed multivariate empirical mode decomposition (APIT-MEMD), and exhibits better performance than MEMD by adopting adaptive projection strategy in order to alleviate power imbalances. The filter bank properties of APIT-MEMD are also adopted to enable more accurate and stable intrinsic mode functions (IMFs), and to ease mode mixing problems in multi-fault frequency extractions. By aligning IMF sets into a third order tensor, high order singular value decomposition (HOSVD) can be employed to estimate the fault number. The fault correlation factor (FCF) analysis is used to conduct correlation analysis, in order to determine effective IMFs; the characteristic frequencies of multi-faults can then be extracted. Numerical simulations and the application of multi-fault situation can demonstrate that the proposed method is promising in multi-fault diagnoses of multivariate rolling bearing signal. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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12 pages, 3026 KiB

Open AccessArticle

Energy Consumption Research of Mobile Data Collection Protocol for Underwater Nodes Using an USV

by Zhichao Lv¹

, Jie Zhang², Jiucai Jin^2,*, Qi Li¹ and Baoru Gao³

¹ Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China

² First Institute of Oceanography, State Oceanic Administration, Qingdao 266100, China

³ College of Engineering, Ocean University of China, Qingdao 266100, China

Sensors 2018, 18(4), 1211; https://doi.org/10.3390/s18041211 - 16 Apr 2018

Cited by 11 | Viewed by 4362

Abstract

The Unmanned Surface Vehicle (USV) integrated with an acoustic modem is a novel mobile vehicle for data collection, which has an advantage in terms of mobility, efficiency, and collection cost. In the scenario of data collection, the USV is controlled autonomously along the [...] Read more.

The Unmanned Surface Vehicle (USV) integrated with an acoustic modem is a novel mobile vehicle for data collection, which has an advantage in terms of mobility, efficiency, and collection cost. In the scenario of data collection, the USV is controlled autonomously along the planning trajectory and the data of underwater nodes are dynamically collected. In order to improve the efficiency of data collection and extend the life of the underwater nodes, a mobile data collection protocol for underwater nodes using the USV was proposed. In the protocol, the stop-and-wait ARQ transmission mechanism is adopted, where the duty cycle is designed considering the ratio between the sleep mode and the detection mode, and the transmission ratio is defined by the duty cycle, wake-up signal cycles, and USV’s speed. According to protocol, the evaluation index for energy consumption is constructed based on the duty cycle and the transmission ratio. The energy consumption of the protocol is simulated and analyzed using the mobile communication experiment data of USV, taking into consideration USV’s speed, data sequence length, and duty cycle. Optimized protocol parameters are identified, which in turn denotes the proposed protocol’s feasibility and effectiveness. Full article

(This article belongs to the Special Issue Underwater Sensing, Communication, Networking and Systems)

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21 pages, 85723 KiB

Open AccessArticle

A Universal Vacant Parking Slot Recognition System Using Sensors Mounted on Off-the-Shelf Vehicles

by Jae Kyu Suhr¹

and Ho Gi Jung^2,*

¹ School of Intelligent Mechatronics Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea

² Department of Electronic Engineering, Korea National University of Transportation, 50 Daehak-ro, Chungju-si, Chungbuk 27469, Korea

Sensors 2018, 18(4), 1213; https://doi.org/10.3390/s18041213 - 16 Apr 2018

Cited by 31 | Viewed by 8407

Abstract

An automatic parking system is an essential part of autonomous driving, and it starts by recognizing vacant parking spaces. This paper proposes a method that can recognize various types of parking slot markings in a variety of lighting conditions including daytime, nighttime, and [...] Read more.

An automatic parking system is an essential part of autonomous driving, and it starts by recognizing vacant parking spaces. This paper proposes a method that can recognize various types of parking slot markings in a variety of lighting conditions including daytime, nighttime, and underground. The proposed method can readily be commercialized since it uses only those sensors already mounted on off-the-shelf vehicles: an around-view monitor (AVM) system, ultrasonic sensors, and in-vehicle motion sensors. This method first detects separating lines by extracting parallel line pairs from AVM images. Parking slot candidates are generated by pairing separating lines based on the geometric constraints of the parking slot. These candidates are confirmed by recognizing their entrance positions using line and corner features and classifying their occupancies using ultrasonic sensors. For more reliable recognition, this method uses the separating lines and parking slots not only found in the current image but also found in previous images by tracking their positions using the in-vehicle motion-sensor-based vehicle odometry. The proposed method was quantitatively evaluated using a dataset obtained during the day, night, and underground, and it outperformed previous methods by showing a 95.24% recall and a 97.64% precision. Full article

(This article belongs to the Section Intelligent Sensors)

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15 pages, 56074 KiB

Open AccessArticle

Improved Seam-Line Searching Algorithm for UAV Image Mosaic with Optical Flow

by Weilong Zhang¹, Bingxuan Guo^1,2,*, Ming Li^1,2,3,*

, Xuan Liao¹ and Wenzhuo Li¹

¹ State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China

² Collaborative Innovation Center of Geospatial Technology, Wuhan University, Wuhan 430079, China

³ School of Resource and Environmental Science, Wuhan University, Wuhan 430079, China

Sensors 2018, 18(4), 1214; https://doi.org/10.3390/s18041214 - 16 Apr 2018

Cited by 26 | Viewed by 6416

Abstract

Ghosting and seams are two major challenges in creating unmanned aerial vehicle (UAV) image mosaic. In response to these problems, this paper proposes an improved method for UAV image seam-line searching. First, an image matching algorithm is used to extract and match the [...] Read more.

Ghosting and seams are two major challenges in creating unmanned aerial vehicle (UAV) image mosaic. In response to these problems, this paper proposes an improved method for UAV image seam-line searching. First, an image matching algorithm is used to extract and match the features of adjacent images, so that they can be transformed into the same coordinate system. Then, the gray scale difference, the gradient minimum, and the optical flow value of pixels in adjacent image overlapped area in a neighborhood are calculated, which can be applied to creating an energy function for seam-line searching. Based on that, an improved dynamic programming algorithm is proposed to search the optimal seam-lines to complete the UAV image mosaic. This algorithm adopts a more adaptive energy aggregation and traversal strategy, which can find a more ideal splicing path for adjacent UAV images and avoid the ground objects better. The experimental results show that the proposed method can effectively solve the problems of ghosting and seams in the panoramic UAV images. Full article

(This article belongs to the Special Issue Visual Sensors)

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22 pages, 2137 KiB

Open AccessArticle

Automated Quality Control for Sensor Based Symptom Measurement Performed Outside the Lab

by Reham Badawy^1,*,†

, Yordan P. Raykov^1,†

, Luc J. W. Evers^2,3

, Bastiaan R. Bloem³

, Marjan J. Faber⁴

, Andong Zhan⁵

, Kasper Claes⁶

and Max A. Little^1,7

¹ School of Engineering and Applied Sciences, Aston University, Birmingham B4 7ET, UK

² Institute for Computing and Information Sciences, Radboud University, 6525 EC Nijmegen, The Netherlands

³ Department of Neurology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525 HR Nijmegen, The Netherlands

⁴ Radboud Institute for Health Sciences, Scientific Center for Quality of Healthcare, Radboud University Medical Center, 6525 EZ Nijmegen, The Netherlands

⁵ Department of Computer Science, Johns Hopkins University, Baltimore, MD 21218, USA

⁶ UCB Biopharma, B–1070 Brussels, Belgium

⁷ Media Lab, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1215; https://doi.org/10.3390/s18041215 - 16 Apr 2018

Cited by 17 | Viewed by 7684

Abstract

The use of wearable sensing technology for objective, non-invasive and remote clinimetric testing of symptoms has considerable potential. However, the accuracy achievable with such technology is highly reliant on separating the useful from irrelevant sensor data. Monitoring patient symptoms using digital sensors outside [...] Read more.

The use of wearable sensing technology for objective, non-invasive and remote clinimetric testing of symptoms has considerable potential. However, the accuracy achievable with such technology is highly reliant on separating the useful from irrelevant sensor data. Monitoring patient symptoms using digital sensors outside of controlled, clinical lab settings creates a variety of practical challenges, such as recording unexpected user behaviors. These behaviors often violate the assumptions of clinimetric testing protocols, where these protocols are designed to probe for specific symptoms. Such violations are frequent outside the lab and affect the accuracy of the subsequent data analysis and scientific conclusions. To address these problems, we report on a unified algorithmic framework for automated sensor data quality control, which can identify those parts of the sensor data that are sufficiently reliable for further analysis. Combining both parametric and nonparametric signal processing and machine learning techniques, we demonstrate that across 100 subjects and 300 clinimetric tests from three different types of behavioral clinimetric protocols, the system shows an average segmentation accuracy of around 90%. By extracting reliable sensor data, it is possible to strip the data of confounding factors in the environment that may threaten reproducibility and replicability. Full article

(This article belongs to the Special Issue Sensors for Health Monitoring and Disease Diagnosis)

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28 pages, 6179 KiB

Open AccessArticle

Adaptive Aggregation Routing to Reduce Delay for Multi-Layer Wireless Sensor Networks

by Xujing Li¹, Anfeng Liu^1,2

, Mande Xie^3,*, Neal N. Xiong⁴

, Zhiwen Zeng¹ and Zhiping Cai⁵

¹ School of Information Science and Engineering, Central South University, Changsha 410083, China

² The State Key Laboratory of Industrial Control Technology, Zhejiang University, Hangzhou 310027, China

³ School of Computer Science and Information Engineering, Zhejiang Gongshang University, Hangzhou 310018, China

⁴ Department of Mathematics and Computer Science, Northeastern State University, Tahlequah, OK 74464, USA

⁵ Department of Network Engineering, School of Computer, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(4), 1216; https://doi.org/10.3390/s18041216 - 16 Apr 2018

Cited by 33 | Viewed by 5259

Abstract

The quality of service (QoS) regarding delay, lifetime and reliability is the key to the application of wireless sensor networks (WSNs). Data aggregation is a method to effectively reduce the data transmission volume and improve the lifetime of a network. In the previous [...] Read more.

The quality of service (QoS) regarding delay, lifetime and reliability is the key to the application of wireless sensor networks (WSNs). Data aggregation is a method to effectively reduce the data transmission volume and improve the lifetime of a network. In the previous study, a common strategy required that data wait in the queue. When the length of the queue is greater than or equal to the predetermined aggregation threshold (

N_{t}

) or the waiting time is equal to the aggregation timer (

T_{t}

), data are forwarded at the expense of an increase in the delay. The primary contributions of the proposed Adaptive Aggregation Routing (AAR) scheme are the following: (a) the senders select the forwarding node dynamically according to the length of the data queue, which effectively reduces the delay. In the AAR scheme, the senders send data to the nodes with a long data queue. The advantages are that first, the nodes with a long data queue need a small amount of data to perform aggregation; therefore, the transmitted data can be fully utilized to make these nodes aggregate. Second, this scheme balances the aggregating and data sending load; thus, the lifetime increases. (b) An improved AAR scheme is proposed to improve the QoS. The aggregation deadline (

T_{t}

) and the aggregation threshold (

N_{t}

) are dynamically changed in the network. In WSNs, nodes far from the sink have residual energy because these nodes transmit less data than the other nodes. In the improved AAR scheme, the nodes far from the sink have a small value of

T_{t}

and

N_{t}

to reduce delay, and the nodes near the sink are set to a large value of

T_{t}

and

N_{t}

to reduce energy consumption. Thus, the end to end delay is reduced, a longer lifetime is achieved, and the residual energy is fully used. Simulation results demonstrate that compared with the previous scheme, the performance of the AAR scheme is improved. This scheme reduces the delay by 14.91%, improves the lifetime by 30.91%, and increases energy efficiency by 76.40%. Full article

(This article belongs to the Special Issue QoS in Wireless Sensor Networks)

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11 pages, 47090 KiB

Open AccessArticle

Glucose Sensor Using U-Shaped Optical Fiber Probe with Gold Nanoparticles and Glucose Oxidase

by Kuan-Chieh Chen¹, Yu-Le Li¹, Chao-Wei Wu² and Chia-Chin Chiang^1,*

¹ Department of Mechanical Engineering, National Kaohsiung University of Science and Technology, No. 415, Jiangong Rd., Sanmin Dist., Kaohsiung City 807, Taiwan

² Department of Aeronautical and Mechanical Engineering, Air Force Academy, Academy, No. Sisou 1, Jieshou W. Road, Kaohsiung 820, Taiwan

Sensors 2018, 18(4), 1217; https://doi.org/10.3390/s18041217 - 16 Apr 2018

Cited by 49 | Viewed by 8176

Abstract

In this study, we proposed a U-shaped optical fiber probe fabricated using a flame heating method. The probe was packaged in glass tube to reduce human factors during experimental testing of the probe as a glucose sensor. The U-shaped fiber probe was found [...] Read more.

In this study, we proposed a U-shaped optical fiber probe fabricated using a flame heating method. The probe was packaged in glass tube to reduce human factors during experimental testing of the probe as a glucose sensor. The U-shaped fiber probe was found to have high sensitivity in detecting the very small molecule. When the sensor was dipped in solutions with different refractive indexes, its wavelength or transmission loss changed. We used electrostatic self-assembly to bond gold nanoparticles and glucose oxidase (GOD) onto the sensor’s surface. The results over five cycles of the experiment showed that, as the glucose concentration increased, the refractive index of the sensor decreased and its spectrum wavelength shifted. The best wavelength sensitivity was 2.899 nm/%, and the linearity was 0.9771. The best transmission loss sensitivity was 5.101 dB/%, and the linearity was 0.9734. Therefore, the proposed U-shaped optical fiber probe with gold nanoparticles and GOD has good potential for use as a blood sugar sensor in the future. Full article

(This article belongs to the Special Issue Selected Sensor Related Papers from ICI2017)

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16 pages, 3802 KiB

Open AccessArticle

Detection of Ultrasonic Stress Waves in Structures Using 3D Shaped Optic Fiber Based on a Mach–Zehnder Interferometer

by Chengming Lan¹

, Wensong Zhou^2,3,4,*

and Yawen Xie^2,3,4

¹ School of Civil and Resource Engineering, University of Science & Technology Beijing, Beijing 100083, China

² Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Harbin Institute of Technology, Harbin 150090, China

³ Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology, Harbin Institute of Technology, Harbin 150090, China

⁴ School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China

Sensors 2018, 18(4), 1218; https://doi.org/10.3390/s18041218 - 16 Apr 2018

Cited by 24 | Viewed by 5273

Abstract

This work proposes a 3D shaped optic fiber sensor for ultrasonic stress waves detection based on the principle of a Mach–Zehnder interferometer. This sensor can be used to receive acoustic emission signals in the passive damage detection methods and other types of ultrasonic [...] Read more.

This work proposes a 3D shaped optic fiber sensor for ultrasonic stress waves detection based on the principle of a Mach–Zehnder interferometer. This sensor can be used to receive acoustic emission signals in the passive damage detection methods and other types of ultrasonic signals propagating in the active damage detection methods, such as guided wave-based methods. The sensitivity of an ultrasonic fiber sensor based on the Mach–Zehnder interferometer mainly depends on the length of the sensing optical fiber; therefore, the proposed sensor achieves the maximum possible sensitivity by wrapping an optical fiber on a hollow cylinder with a base. The deformation of the optical fiber is produced by the displacement field of guided waves in the hollow cylinder. The sensor was first analyzed using the finite element method, which demonstrated its basic sensing capacity, and the simulation signals have the same characteristics in the frequency domain as the excitation signal. Subsequently, the primary investigations were conducted via a series of experiments. The sensor was used to detect guided wave signals excited by a piezoelectric wafer in an aluminum plate, and subsequently it was tested on a reinforced concrete beam, which produced acoustic emission signals via impact loading and crack extension when it was loaded to failure. The signals obtained from a piezoelectric acoustic emission sensor were used for comparison, and the results indicated that the proposed 3D fiber optic sensor can detect ultrasonic signals in the specific frequency response range. Full article

(This article belongs to the Special Issue Ultrasonic Sensors 2018)

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23 pages, 904 KiB

Open AccessArticle

Secure and Usable User-in-a-Context Continuous Authentication in Smartphones Leveraging Non-Assisted Sensors

by Jose Maria De Fuentes^*

, Lorena Gonzalez-Manzano and Arturo Ribagorda

Computer Security Lab (COSEC), Universidad Carlos III de Madrid, ES-28911 Madrid, Spain

Sensors 2018, 18(4), 1219; https://doi.org/10.3390/s18041219 - 16 Apr 2018

Cited by 16 | Viewed by 5266

Abstract

Smartphones are equipped with a set of sensors that describe the environment (e.g., GPS, noise, etc.) and their current status and usage (e.g., battery consumption, accelerometer readings, etc.). Several works have already addressed how to leverage such data for user-in-a-context continuous authentication, i.e., [...] Read more.

Smartphones are equipped with a set of sensors that describe the environment (e.g., GPS, noise, etc.) and their current status and usage (e.g., battery consumption, accelerometer readings, etc.). Several works have already addressed how to leverage such data for user-in-a-context continuous authentication, i.e., determining if the porting user is the authorized one and resides in his regular physical environment. This can be useful for an early reaction against robbery or impersonation. However, most previous works depend on assisted sensors, i.e., they rely upon immutable elements (e.g., cell towers, satellites, magnetism), thus being ineffective in their absence. Moreover, they focus on accuracy aspects, neglecting usability ones. For this purpose, in this paper, we explore the use of four non-assisted sensors, namely battery, transmitted data, ambient light and noise. Our approach leverages data stream mining techniques and offers a tunable security-usability trade-off. We assess the accuracy, immediacy, usability and readiness of the proposal. Results on 50 users over 24 months show that battery readings alone achieve 97.05% of accuracy and 81.35% for audio, light and battery all together. Moreover, when usability is at stake, robbery is detected in 100 s for the case of battery and in 250 s when audio, light and battery are applied. Remarkably, these figures are obtained with moderate training and storage needs, thus making the approach suitable for current devices. Full article

(This article belongs to the Special Issue Security, Trust and Privacy for Sensor Networks)

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15 pages, 6382 KiB

Open AccessArticle

Multi-Sensor Registration in High-Precision CMM Based on a Composite Standard

by Yan Zhao¹, Yiwen Wang¹, Xiuling Ye¹, Zhong Wang¹, Luhua Fu^1,*, Changjie Liu¹ and Zhiwei Wang²

¹ State Key Laboratory of Precision Measuring Technology and Instrument, School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China

² TZTEK Technology Co. Ltd., Suzhou 215153, China

Sensors 2018, 18(4), 1220; https://doi.org/10.3390/s18041220 - 16 Apr 2018

Cited by 10 | Viewed by 4211

Abstract

Registration is a critical step in multi-sensor dimensional measurement. As the accuracy of registration directly impacts the quality of final results, a reference sphere as a common standard is problematic in high-precision registration. In this paper, a novel method based on a composite [...] Read more.

Registration is a critical step in multi-sensor dimensional measurement. As the accuracy of registration directly impacts the quality of final results, a reference sphere as a common standard is problematic in high-precision registration. In this paper, a novel method based on a composite standard is proposed to fuse the multiple heterogeneous sensors in high-precision coordinate measuring machines (CMMs), which will void the drawbacks of a reference sphere. The composite standard consists of a cone and cylinder, which share a same central axis. To ensure high precision in the submicron range, or better, the standard is manufactured by an ultra-precision machine. Three features of the composite standard are inspected by three sensors: a video camera (VC), a tactile probe (TP), and a chromatic confocal displacement sensor (CC). All features will concentrate on a common point through which the relation between the three sensors will be obtained. The errors of each measurement were analyzed theoretically, and simulations and real experiments were carried out to verify the composite standard. This study demonstrates that the proposed registration method is stable and that the standard has potential use for the registration of multiple sensors in high-precision dimensional measurement. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 7835 KiB

Open AccessArticle

Intelligent Fault Diagnosis of HVCB with Feature Space Optimization-Based Random Forest

by Suliang Ma^†, Mingxuan Chen^†

, Jianwen Wu^*, Yuhao Wang, Bowen Jia and Yuan Jiang

¹ School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1221; https://doi.org/10.3390/s18041221 - 16 Apr 2018

Cited by 45 | Viewed by 5231

Abstract

Mechanical faults of high-voltage circuit breakers (HVCBs) always happen over long-term operation, so extracting the fault features and identifying the fault type have become a key issue for ensuring the security and reliability of power supply. Based on wavelet packet decomposition technology and [...] Read more.

Mechanical faults of high-voltage circuit breakers (HVCBs) always happen over long-term operation, so extracting the fault features and identifying the fault type have become a key issue for ensuring the security and reliability of power supply. Based on wavelet packet decomposition technology and random forest algorithm, an effective identification system was developed in this paper. First, compared with the incomplete description of Shannon entropy, the wavelet packet time-frequency energy rate (WTFER) was adopted as the input vector for the classifier model in the feature selection procedure. Then, a random forest classifier was used to diagnose the HVCB fault, assess the importance of the feature variable and optimize the feature space. Finally, the approach was verified based on actual HVCB vibration signals by considering six typical fault classes. The comparative experiment results show that the classification accuracy of the proposed method with the origin feature space reached 93.33% and reached up to 95.56% with optimized input feature vector of classifier. This indicates that feature optimization procedure is successful, and the proposed diagnosis algorithm has higher efficiency and robustness than traditional methods. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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9 pages, 24378 KiB

Open AccessArticle

Development of a 2 MHz Sonar Sensor for Inspection of Bridge Substructures

by Chul Park¹, Youngseok Kim^1,*

, Heungsu Lee¹, Sangsik Choi¹ and Haewook Jung²

¹ Daum Engineering Co., Ltd., Seongnam-si 13493, Korea

² Woori Engineering Co., Ltd., Sejong-si 30054, Korea

Sensors 2018, 18(4), 1222; https://doi.org/10.3390/s18041222 - 16 Apr 2018

Cited by 8 | Viewed by 4553

Abstract

Hydraulic factors account for a large part of the causes of bridge collapse. Due to the nature of the underwater environment, quick and accurate inspection is required when damage occurs. In this study, we developed a 2 MHz side scan sonar sensor module [...] Read more.

Hydraulic factors account for a large part of the causes of bridge collapse. Due to the nature of the underwater environment, quick and accurate inspection is required when damage occurs. In this study, we developed a 2 MHz side scan sonar sensor module and effective operation technique by improving the limitations of existing sonar. Through field tests, we analyzed the correlation of factors affecting the resolution of the sonar data such as the angle of survey, the distance from the underwater structure and the water depth. The effect of the distance and the water depth and the structure on the survey angle was 66~82%. We also derived the relationship between these factors as a regression model for effective operating techniques. It is considered that application of the developed 2 MHz side scan sonar and its operation method could contribute to prevention of bridge collapses and disasters by quickly and accurately checking the damage of bridge substructures due to hydraulic factors. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 4184 KiB

Open AccessArticle

Electrochemical Determination of Norepinephrine by Means of Modified Glassy Carbon Electrodes with Carbon Nanotubes and Magnetic Nanoparticles of Cobalt Ferrite

by Daniely Ferreira de Queiroz^1,*, Tony Rogério de Lima Dadamos²

, Sergio Antonio Spinola Machado¹ and Marco Antonio Utrera Martines³

¹ Laboratório de Materiais Coloidais, Departamento de Físico Química, Instituto de Química, Universidade de São Paulo, Av. Trabalhador São Carlense, C.P. 780, São Carlos 13560-970, SP, Brazil

² Instituto de Biociências, Letras e Ciências Exatas, Campus de São José do Rio Preto, Universidade Estadual Paulista, R. Cristóvão Colombo, 2265, Jardim Nazareth, São José do Rio Preto 15054-000, SP, Brazil

³ Laboratório de Química de Superfície e Moléculas Bioativas, Departamento de Química, Universidade Federal do Mato Grosso do Sul, Av. Senador Filinto Müller, 1555, Campo Grande 79074-460, MS, Brazil

Sensors 2018, 18(4), 1223; https://doi.org/10.3390/s18041223 - 16 Apr 2018

Cited by 40 | Viewed by 6215

Abstract

This study describes the electrochemical preparation of the electrocatalytic oxidation/reduction of noradrenaline in modified glassy carbon of cobalt ferrite nanoparticles and carbon nanotubes (GC/MWCNT/FCo₉₈). The cobalt ferrite powder was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The optimum [...] Read more.

This study describes the electrochemical preparation of the electrocatalytic oxidation/reduction of noradrenaline in modified glassy carbon of cobalt ferrite nanoparticles and carbon nanotubes (GC/MWCNT/FCo₉₈). The cobalt ferrite powder was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The optimum conditions found in an electrode composition were 4 μL of cobalt ferrite and 10 μL of carbon nanotubes in 0.1 mol L⁻¹ PBS at pH 7.0. The electrode displays electrochemical behavior in a wide potential range (−0.4 to 1.0 V vs. Ag/AgCl), high conductivity, and electrode stability/durability in 0.1 mol L⁻¹ PBS. Catalytic oxidation of noradrenaline was performed at the unmodified GC electrode at +0.60 V vs. Ag/AgCl and current of 0.17 μA and modified GC with cobalt ferrite nanoparticles and carbon nanotubes at +0.54 V vs. Ag/AgCl and current of 0.23 mA. With regard to the anodic peak current (I_pa) versus noradrenaline concentration by means of the amperometric method at the modified electrode, (which is linear in the 0.16 and 1.91 mmol L⁻¹ concentration range), the concentration limit was 0.76 μmol L⁻¹. In this way, the modified electrode GC/MWCNT/FCo₉₈ was found to be a promising application for the determination of this neurotransmitter in the area of neuroscience. Full article

(This article belongs to the Special Issue Carbon Materials Based Sensors and the Application)

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19 pages, 69029 KiB

Open AccessArticle

Monitoring of Carbon Fiber-Reinforced Old Timber Beams via Strain and Multiresonant Acoustic Emission Sensors

by Francisco J. Rescalvo¹, Ignacio Valverde-Palacios², Elisabet Suarez^1,*

, Andrés Roldán³

and Antolino Gallego¹

¹ Department of Applied Physics, University of Granada, Campus Fuentenueva s/n, 18071 Granada, Spain

² Department of Building Constructions, University of Granada, Campus Fuentenueva s/n, 18071 Granada, Spain

³ Department of Electronics and Computer Technology, University of Granada, Campus Fuentenueva s/n, 18071 Granada, Spain

Sensors 2018, 18(4), 1224; https://doi.org/10.3390/s18041224 - 17 Apr 2018

Cited by 24 | Viewed by 4794

Abstract

This paper proposes the monitoring of old timber beams with natural defects (knots, grain deviations, fissures and wanes), reinforced using carbon composite materials (CFRP). Reinforcement consisted of the combination of a CFRP laminate strip and a carbon fabric discontinuously wrapping the timber element. [...] Read more.

This paper proposes the monitoring of old timber beams with natural defects (knots, grain deviations, fissures and wanes), reinforced using carbon composite materials (CFRP). Reinforcement consisted of the combination of a CFRP laminate strip and a carbon fabric discontinuously wrapping the timber element. Monitoring considered the use and comparison of two types of sensors: strain gauges and multi-resonant acoustic emission (AE) sensors. Results demonstrate that: (1) the mechanical behavior of the beams can be considerably improved by means of the use of CFRP (160% in bending load capacity and 90% in stiffness); (2) Acoustic emission sensors provide comparable information to strain gauges. This fact points to the great potential of AE techniques for in-service damage assessment in real wood structures. Full article

(This article belongs to the Special Issue Ultrasonic Sensors 2018)

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22 pages, 13617 KiB

Open AccessArticle

Feature Extraction for Track Section Status Classification Based on UGW Signals

by Lei Yuan^1,2

, Yuan Yang^1,*, Álvaro Hernández²

and Lin Shi¹

¹ Electronics Department, Xi’an University of Technology, Xi’an 710048, China

² Electronics Department, University of Alcala, Alcalá de Henares, Madrid 28805, Spain

Sensors 2018, 18(4), 1225; https://doi.org/10.3390/s18041225 - 17 Apr 2018

Cited by 9 | Viewed by 3834

Abstract

Track status classification is essential for the stability and safety of railway operations nowadays, when railway networks are becoming more and more complex and broad. In this situation, monitoring systems are already a key element in applications dedicated to evaluating the status of [...] Read more.

Track status classification is essential for the stability and safety of railway operations nowadays, when railway networks are becoming more and more complex and broad. In this situation, monitoring systems are already a key element in applications dedicated to evaluating the status of a certain track section, often determining whether it is free or occupied by a train. Different technologies have already been involved in the design of monitoring systems, including ultrasonic guided waves (UGW). This work proposes the use of the UGW signals captured by a track monitoring system to extract the features that are relevant for determining the corresponding track section status. For that purpose, three features of UGW signals have been considered: the root mean square value, the energy, and the main frequency components. Experimental results successfully validated how these features can be used to classify the track section status into free, occupied and broken. Furthermore, spatial and temporal dependencies among these features were analysed in order to show how they can improve the final classification performance. Finally, a preliminary high-level classification system based on deep learning networks has been envisaged for future works. Full article

(This article belongs to the Section Sensor Networks)

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16 pages, 8920 KiB

Open AccessArticle

A Novel Detection Model and Its Optimal Features to Classify Falls from Low- and High-Acceleration Activities of Daily Life Using an Insole Sensor System

by Benjamin Cates^1,†, Taeyong Sim^1,†, Hyun Mu Heo¹, Bori Kim², Hyunggun Kim^1,* and Joung Hwan Mun^1,*

¹ Department of Bio-Mechatronic Engineering, College of Biotechnology and Bioengineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi 16419, Korea

² Department of Research and Development, Biomaterial Team, Medical Device Development Center, KBIO HEALTH, 123 Osongsaengmyung-ro, Osong-eub, Heungdeok-gu, Cheongju, Chungbuk 28160, Korea

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1227; https://doi.org/10.3390/s18041227 - 17 Apr 2018

Cited by 27 | Viewed by 5293

Abstract

In order to overcome the current limitations in current threshold-based and machine learning-based fall detectors, an insole system and novel fall classification model were created. Because high-acceleration activities have a high risk for falls, and because of the potential damage that is associated [...] Read more.

In order to overcome the current limitations in current threshold-based and machine learning-based fall detectors, an insole system and novel fall classification model were created. Because high-acceleration activities have a high risk for falls, and because of the potential damage that is associated with falls during high-acceleration activities, four low-acceleration activities, four high-acceleration activities, and eight types of high-acceleration falls were performed by twenty young male subjects. Encompassing a total of 800 falls and 320 min of activities of daily life (ADLs), the created Support Vector Machine model’s Leave-One-Out cross-validation provides a fall detection sensitivity (0.996), specificity (1.000), and accuracy (0.999). These classification results are similar or superior to other fall detection models in the literature, while also including high-acceleration ADLs to challenge the classification model, and simultaneously reducing the burden that is associated with wearable sensors and increasing user comfort by inserting the insole system into the shoe. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 4763 KiB

Open AccessArticle

Trellis Tone Modulation Multiple-Access for Peer Discovery in D2D Networks

by Chiwoo Lim¹, Min Jang²

and Sang-Hyo Kim^1,*

¹ College of Information and Communication Engineering, Sungkyunkwan University, Suwon 16419, Korea

² Samsung Electronics Co., Ltd., Suwon 16677, Korea

Sensors 2018, 18(4), 1228; https://doi.org/10.3390/s18041228 - 17 Apr 2018

Cited by 5 | Viewed by 3821

Abstract

In this paper, a new non-orthogonal multiple-access scheme, trellis tone modulation multiple-access (TTMMA), is proposed for peer discovery of distributed device-to-device (D2D) communication. The range and capacity of discovery are important performance metrics in peer discovery. The proposed trellis tone modulation uses single-tone [...] Read more.

In this paper, a new non-orthogonal multiple-access scheme, trellis tone modulation multiple-access (TTMMA), is proposed for peer discovery of distributed device-to-device (D2D) communication. The range and capacity of discovery are important performance metrics in peer discovery. The proposed trellis tone modulation uses single-tone transmission and achieves a long discovery range due to its low Peak-to-Average Power Ratio (PAPR). The TTMMA also exploits non-orthogonal resource assignment to increase the discovery capacity. For the multi-user detection of superposed multiple-access signals, a message-passing algorithm with supplementary schemes are proposed. With TTMMA and its message-passing demodulation, approximately 1.5 times the number of devices are discovered compared to the conventional frequency division multiple-access (FDMA)-based discovery. Full article

(This article belongs to the Special Issue Non-Orthogonal Multi-User Transmissions for 5G Networks)

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18 pages, 4815 KiB

Open AccessArticle

LiteNet: Lightweight Neural Network for Detecting Arrhythmias at Resource-Constrained Mobile Devices

by Ziyang He¹

, Xiaoqing Zhang¹, Yangjie Cao^1,2,*, Zhi Liu³, Bo Zhang²

and Xiaoyan Wang⁴

¹ Collaborative Innovation Center for Internet Healthcare, Zhengzhou University, 75 University North Road, Erqi District, Zhengzhou 450000, China

² School of Software Engineering, Zhengzhou University, 97 Culture Road, Jinshui District, Zhengzhou 450000, China

³ Department of Mathematical and Systems Engineering, Shizuoka University, 5-627, 3-5-1 Johoku Hamamatsu 432-8561, Japan

⁴ College of Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi, Ibaraki 316-8511, Japan

Sensors 2018, 18(4), 1229; https://doi.org/10.3390/s18041229 - 17 Apr 2018

Cited by 43 | Viewed by 7323

Abstract

By running applications and services closer to the user, edge processing provides many advantages, such as short response time and reduced network traffic. Deep-learning based algorithms provide significantly better performances than traditional algorithms in many fields but demand more resources, such as higher [...] Read more.

By running applications and services closer to the user, edge processing provides many advantages, such as short response time and reduced network traffic. Deep-learning based algorithms provide significantly better performances than traditional algorithms in many fields but demand more resources, such as higher computational power and more memory. Hence, designing deep learning algorithms that are more suitable for resource-constrained mobile devices is vital. In this paper, we build a lightweight neural network, termed LiteNet which uses a deep learning algorithm design to diagnose arrhythmias, as an example to show how we design deep learning schemes for resource-constrained mobile devices. Compare to other deep learning models with an equivalent accuracy, LiteNet has several advantages. It requires less memory, incurs lower computational cost, and is more feasible for deployment on resource-constrained mobile devices. It can be trained faster than other neural network algorithms and requires less communication across different processing units during distributed training. It uses filters of heterogeneous size in a convolutional layer, which contributes to the generation of various feature maps. The algorithm was tested using the MIT-BIH electrocardiogram (ECG) arrhythmia database; the results showed that LiteNet outperforms comparable schemes in diagnosing arrhythmias, and in its feasibility for use at the mobile devices. Full article

(This article belongs to the Special Issue New Paradigms in Data Sensing and Processing for Edge Computing)

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18 pages, 47348 KiB

Open AccessArticle

Finding the Key Periods for Assimilating HJ-1A/B CCD Data and the WOFOST Model to Evaluate Heavy Metal Stress in Rice

by Shuang Zhao¹, Xu Qian², Xiangnan Liu^1,* and Zhao Xu³

¹ School of Information Engineering, China University of Geosciences, Haidian District, Beijing 100083, China

² 96669 Troops, Changping District, Beijing 102208, China

³ State Grid Energy Research Institute, Changping District, Beijing 102209, China

Sensors 2018, 18(4), 1230; https://doi.org/10.3390/s18041230 - 17 Apr 2018

Cited by 5 | Viewed by 3568

Abstract

Accurately monitoring heavy metal stress in crops is vital for food security and agricultural production. The assimilation of remote sensing images into the World Food Studies (WOFOST) model provides an efficient way to solve this problem. In this study, we aimed at investigating [...] Read more.

Accurately monitoring heavy metal stress in crops is vital for food security and agricultural production. The assimilation of remote sensing images into the World Food Studies (WOFOST) model provides an efficient way to solve this problem. In this study, we aimed at investigating the key periods of the assimilation framework for continuous monitoring of heavy metal stress in rice. The Harris algorithm was used for the leaf area index (LAI) curves to select the key period for an optimized assimilation. To obtain accurate LAI values, the measured dry weight of rice roots (WRT), which have been proven to be the most stress-sensitive indicator of heavy metal stress, were incorporated into the improved WOFOST model. Finally, the key periods, which contain four dominant time points, were used to select remote sensing images for the RS-WOFOST model for continuous monitoring of heavy metal stress. Compared with the key period which contains all the available remote sensing images, the results showed that the optimal key period can significantly improve the time efficiency of the assimilation framework by shortening the model operation time by more than 50%, while maintaining its accuracy. This result is highly significant when monitoring heavy metals in rice on a large-scale. Furthermore, it can also offer a reference for the timing of field measurements in monitoring heavy metal stress in rice. Full article

(This article belongs to the Section Remote Sensors)

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12 pages, 15325 KiB

Open AccessArticle

An Energy-Efficient Compressive Image Coding for Green Internet of Things (IoT)

by Ran Li^*

, Xiaomeng Duan, Xu Li, Wei He and Yanling Li

School of Computer and Information Technology, Xinyang Normal University, Xinyang 464000, China

Sensors 2018, 18(4), 1231; https://doi.org/10.3390/s18041231 - 17 Apr 2018

Cited by 9 | Viewed by 4079

Abstract

Aimed at a low-energy consumption of Green Internet of Things (IoT), this paper presents an energy-efficient compressive image coding scheme, which provides compressive encoder and real-time decoder according to Compressive Sensing (CS) theory. The compressive encoder adaptively measures each image block based on [...] Read more.

Aimed at a low-energy consumption of Green Internet of Things (IoT), this paper presents an energy-efficient compressive image coding scheme, which provides compressive encoder and real-time decoder according to Compressive Sensing (CS) theory. The compressive encoder adaptively measures each image block based on the block-based gradient field, which models the distribution of block sparse degree, and the real-time decoder linearly reconstructs each image block through a projection matrix, which is learned by Minimum Mean Square Error (MMSE) criterion. Both the encoder and decoder have a low computational complexity, so that they only consume a small amount of energy. Experimental results show that the proposed scheme not only has a low encoding and decoding complexity when compared with traditional methods, but it also provides good objective and subjective reconstruction qualities. In particular, it presents better time-distortion performance than JPEG. Therefore, the proposed compressive image coding is a potential energy-efficient scheme for Green IoT. Full article

(This article belongs to the Special Issue Green Communications and Networking for IoT)

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19 pages, 10388 KiB

Open AccessArticle

Reconstruction-Based Change Detection with Image Completion for a Free-Moving Camera

by Tsubasa Minematsu^1,*, Atsushi Shimada¹, Hideaki Uchiyama¹, Vincent Charvillat² and Rin-ichiro Taniguchi¹

¹ Graduate School of Information Science and Electrical Engineering, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-0395, Japan

² IRIT, Université de Toulouse, CNRS, 31000 Toulouse, France

Sensors 2018, 18(4), 1232; https://doi.org/10.3390/s18041232 - 17 Apr 2018

Cited by 7 | Viewed by 4540

Abstract

Reconstruction-based change detection methods are robust for camera motion. The methods learn reconstruction of input images based on background images. Foreground regions are detected based on the magnitude of the difference between an input image and a reconstructed input image. For learning, only [...] Read more.

Reconstruction-based change detection methods are robust for camera motion. The methods learn reconstruction of input images based on background images. Foreground regions are detected based on the magnitude of the difference between an input image and a reconstructed input image. For learning, only background images are used. Therefore, foreground regions have larger differences than background regions. Traditional reconstruction-based methods have two problems. One is over-reconstruction of foreground regions. The other is that decision of change detection depends on magnitudes of differences only. It is difficult to distinguish magnitudes of differences in foreground regions when the foreground regions are completely reconstructed in patch images. We propose the framework of a reconstruction-based change detection method for a free-moving camera using patch images. To avoid over-reconstruction of foreground regions, our method reconstructs a masked central region in a patch image from a region surrounding the central region. Differences in foreground regions are enhanced because foreground regions in patch images are removed by the masking procedure. Change detection is learned from a patch image and a reconstructed image automatically. The decision procedure directly uses patch images rather than the differences between patch images. Our method achieves better accuracy compared to traditional reconstruction-based methods without masking patch images. Full article

(This article belongs to the Section Remote Sensors)

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22 pages, 43436 KiB

Open AccessArticle

IoT On-Board System for Driving Style Assessment

by Bartosz Jachimczyk^1,3,*, Damian Dziak², Jacek Czapla³, Pawel Damps³ and Wlodek J. Kulesza³

¹ BetterSolutions S.A. Al. Grunwaldzka 103, 80-244 Gdansk, Poland

² 3DPLab Do Studzienki 28, 80-227 Gdansk, Poland

³ Blekinge Institute of Technology, Department of Applied Signal Processing, 371 79 Karlskrona, Sweden

Sensors 2018, 18(4), 1233; https://doi.org/10.3390/s18041233 - 17 Apr 2018

Cited by 31 | Viewed by 8483

Abstract

The assessment of skills is essential and desirable in areas such as medicine, security, and other professions where mental, physical, and manual skills are crucial. However, often such assessments are performed by people called “experts” who may be subjective and are able to [...] Read more.

The assessment of skills is essential and desirable in areas such as medicine, security, and other professions where mental, physical, and manual skills are crucial. However, often such assessments are performed by people called “experts” who may be subjective and are able to consider a limited number of factors and indicators. This article addresses the problem of the objective assessment of driving style independent of circumstances. The proposed objective assessment of driving style is based on eight indicators, which are associated with the vehicle’s speed, acceleration, jerk, engine rotational speed and driving time. These indicators are used to estimate three driving style criteria: safety, economy, and comfort. The presented solution is based on the embedded system designed according to the Internet of Things concept. The useful data are acquired from the car diagnostic port—OBD-II—and from an additional accelerometer sensor and GPS module. The proposed driving skills assessment method has been implemented and experimentally validated on a group of drivers. The obtained results prove the system’s ability to quantitatively distinguish different driving styles. The system was verified on long-route tests for analysis and could then improve the driver’s behavior behind the wheel. Moreover, the spider diagram approach that was used established a convenient visualization platform for multidimensional comparison of the result and comprehensive assessment in an intelligible manner. Full article

(This article belongs to the Special Issue Wireless Sensors Networks in Activity Detection and Context Awareness)

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10 pages, 21591 KiB

Open AccessArticle

A Novel Nanowire Assembly Process for the Fabrication of CO Sensor

by Biyao Cheng, Shuming Yang^*, Tao Liu and Ali Vazinishayan

State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2018, 18(4), 1234; https://doi.org/10.3390/s18041234 - 17 Apr 2018

Cited by 6 | Viewed by 4865

Abstract

Nanowires have been widely studied due to their outstanding mechanical and electrical properties; however, their practical applications are limited to the lack of an effective technique for controlled assembly. In the present work, zinc oxide (ZnO) nanowire arrays were assembled via a combing [...] Read more.

Nanowires have been widely studied due to their outstanding mechanical and electrical properties; however, their practical applications are limited to the lack of an effective technique for controlled assembly. In the present work, zinc oxide (ZnO) nanowire arrays were assembled via a combing process using a makeup brush and the nanodevice was fabricated. The current–voltage (I–V) and ultraviolet (UV) characteristics of the device indicate stable and repeatable electrical properties. The carbon monoxide (CO) sensing properties were tested at operating temperatures of 200, 300 and 400 °C. It was found that ZnO based sensor exhibited the highest sensitivity to CO at 300 °C due to the change of dominant oxygen species. Comparing with others result, the sensitivity of the fabricated sensor exhibits higher sensing performance. The sensing mechanism of the CO sensor is also discussed. Full article

(This article belongs to the Special Issue Novel Sensors Based on Metal Oxide Films and Structures)

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12 pages, 6864 KiB

Open AccessArticle

Older Adults with Weaker Muscle Strength Stand up from a Sitting Position with More Dynamic Trunk Use

by Rob C. Van Lummel^1,2,*, Jordi Evers¹

, Martijn Niessen¹, Peter J. Beek²

and Jaap H. Van Dieën²

¹ McRoberts, Raamweg 43, 2596 HN The Hague, The Netherlands

² Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands

Sensors 2018, 18(4), 1235; https://doi.org/10.3390/s18041235 - 17 Apr 2018

Cited by 40 | Viewed by 8141

Abstract

The ability to stand up from a sitting position is essential for older adults to live independently. Body-fixed inertial sensors may provide an approach for quantifying the sit-to-stand (STS) in clinical settings. The aim of this study was to determine whether measurements of [...] Read more.

The ability to stand up from a sitting position is essential for older adults to live independently. Body-fixed inertial sensors may provide an approach for quantifying the sit-to-stand (STS) in clinical settings. The aim of this study was to determine whether measurements of STS movements using body-fixed sensors yield parameters that are informative regarding changes in STS performance in older adults with reduced muscle strength. In twenty-seven healthy older adults, handgrip strength was assessed as a proxy for overall muscle strength. Subjects were asked to stand up from a chair placed at three heights. Trunk movements were measured using an inertial sensor fixed to the back. Duration, angular range, and maximum angular velocity of STS phases, as well as the vertical velocity of the extension phase, were calculated. Backwards elimination using Generalized Estimating Equations was used to determine if handgrip strength predicted the STS durations and trunk kinematics. Weaker subjects (i.e., with lower handgrip strength) were slower during the STS and showed a larger flexion angular range and a larger extension angular range. In addition, weaker subjects showed a greater maximum angular velocity, which increased with lower seat heights. Measurements with a single inertial sensor did reveal that older adults with lower handgrip strength employed a different strategy to stand up from a sitting position, involving more dynamic use of the trunk. This effect was greatest when elevating body mass. Trunk kinematic parameters were more sensitive to reduced muscle strength than durations. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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20 pages, 1072 KiB

Open AccessArticle

A Closed-Form Error Model of Straight Lines for Improved Data Association and Sensor Fusing

by Volker Sommer

Department of Computer Science and Media, Beuth University of Applied Sciences, Luxemburger Str. 10, D-13353 Berlin, Germany

Sensors 2018, 18(4), 1236; https://doi.org/10.3390/s18041236 - 17 Apr 2018

Viewed by 4330

Abstract

Linear regression is a basic tool in mobile robotics, since it enables accurate estimation of straight lines from range-bearing scans or in digital images, which is a prerequisite for reliable data association and sensor fusing in the context of feature-based SLAM. This paper [...] Read more.

Linear regression is a basic tool in mobile robotics, since it enables accurate estimation of straight lines from range-bearing scans or in digital images, which is a prerequisite for reliable data association and sensor fusing in the context of feature-based SLAM. This paper discusses, extends and compares existing algorithms for line fitting applicable also in the case of strong covariances between the coordinates at each single data point, which must not be neglected if range-bearing sensors are used. Besides, in particular, the determination of the covariance matrix is considered, which is required for stochastic modeling. The main contribution is a new error model of straight lines in closed form for calculating quickly and reliably the covariance matrix dependent on just a few comprehensible and easily-obtainable parameters. The model can be applied widely in any case when a line is fitted from a number of distinct points also without a priori knowledge of the specific measurement noise. By means of extensive simulations, the performance and robustness of the new model in comparison to existing approaches is shown. Full article

(This article belongs to the Collection Multi-Sensor Information Fusion)

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17 pages, 1309 KiB

Open AccessArticle

Power-Efficient Beacon Recognition Method Based on Periodic Wake-Up for Industrial Wireless Devices

by Soonyong Song^*

, Donghun Lee, Ingook Jang, Jinchul Choi and Youngsung Son

IoT Convergence Research Department, Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon 34129, Korea

Sensors 2018, 18(4), 1237; https://doi.org/10.3390/s18041237 - 17 Apr 2018

Cited by 2 | Viewed by 3844

Abstract

Energy harvester-integrated wireless devices are attractive for generating semi-permanent power from wasted energy in industrial environments. The energy-harvesting wireless devices may have difficulty in their communication with access points due to insufficient power supply for beacon recognition during network initialization. In this manuscript, [...] Read more.

Energy harvester-integrated wireless devices are attractive for generating semi-permanent power from wasted energy in industrial environments. The energy-harvesting wireless devices may have difficulty in their communication with access points due to insufficient power supply for beacon recognition during network initialization. In this manuscript, we propose a novel method of beacon recognition based on wake-up control to reduce instantaneous power consumption in the initialization procedure. The proposed method applies a moving window for the periodic wake-up of the wireless devices. For unsynchronized wireless devices, beacons are always located in the same positions within each beacon interval even though the starting offsets are unknown. Using these characteristics, the moving window checks the existence of the beacon associated withspecified resources in a beacon interval, checks again for neighboring resources at the next beacon interval, and so on. This method can reduce instantaneous power and generates a surplus of charging time. Thus, the proposed method alleviates the problems of power insufficiency in the network initialization. The feasibility of the proposed method is evaluated using computer simulations of power shortage in various energy-harvesting conditions. Full article

(This article belongs to the Special Issue Selected Papers from the Eighth International Conference on ICT Convergence (ICTC 2017))

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12 pages, 1238 KiB

Open AccessArticle

Frequency Based Design Partitioning to Achieve Higher Throughput in Digital Cross Correlator for Aperture Synthesis Passive MMW Imager

by Muhammad Asif^*, Xiangzhou Guo, Jing Zhang and Jungang Miao

School of Electronic Information Engineering, Beihang University, No. 37, Xueyuan Road, Haidian District, Beijing 100191, China

Sensors 2018, 18(4), 1238; https://doi.org/10.3390/s18041238 - 17 Apr 2018

Cited by 7 | Viewed by 3561

Abstract

Digital cross-correlation is central to many applications including but not limited to Digital Image Processing, Satellite Navigation and Remote Sensing. With recent advancements in digital technology, the computational demands of such applications have increased enormously. In this paper we are presenting a high [...] Read more.

Digital cross-correlation is central to many applications including but not limited to Digital Image Processing, Satellite Navigation and Remote Sensing. With recent advancements in digital technology, the computational demands of such applications have increased enormously. In this paper we are presenting a high throughput digital cross correlator, capable of processing 1-bit digitized stream, at the rate of up to 2 GHz, simultaneously on 64 channels i.e., approximately 4 Trillion correlation and accumulation operations per second. In order to achieve higher throughput, we have focused on frequency based partitioning of our design and tried to minimize and localize high frequency operations. This correlator is designed for a Passive Millimeter Wave Imager intended for the detection of contraband items concealed on human body. The goals are to increase the system bandwidth, achieve video rate imaging, improve sensitivity and reduce the size. Design methodology is detailed in subsequent sections, elaborating the techniques enabling high throughput. The design is verified for Xilinx Kintex UltraScale device in simulation and the implementation results are given in terms of device utilization and power consumption estimates. Our results show considerable improvements in throughput as compared to our baseline design, while the correlator successfully meets the functional requirements. Full article

(This article belongs to the Section Remote Sensors)

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13 pages, 15108 KiB

Open AccessArticle

Ultrasensitive Mach-Zehnder Interferometric Temperature Sensor Based on Liquid-Filled D-Shaped Fiber Cavity

by Hui Zhang¹, Shecheng Gao^2,*, Yunhan Luo³, Zhenshi Chen⁴

, Songsong Xiong⁵, Lei Wan², Xincheng Huang², Bingsen Huang², Yuanhua Feng², Miao He^1,*, Weiping Liu², Zhe Chen³ and Zhaohui Li⁵

¹ School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China

² Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou 510632, China

³ Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Jinan University, Guangzhou 510632, China

⁴ Institute of Photonics Technology, Jinan University, Guangzhou 510632, China

⁵ State Key Laboratory of Optoelectronic Materials and Technologies and School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China

Sensors 2018, 18(4), 1239; https://doi.org/10.3390/s18041239 - 17 Apr 2018

Cited by 37 | Viewed by 6269

Abstract

A liquid-filled D-shaped fiber (DF) cavity serving as an in-fiber Mach–Zehnder interferometer (MZI) has been proposed and experimentally demonstrated for temperature sensing with ultrahigh sensitivity. The miniature MZI is constructed by splicing a segment of DF between two single-mode fibers (SMFs) to form [...] Read more.

A liquid-filled D-shaped fiber (DF) cavity serving as an in-fiber Mach–Zehnder interferometer (MZI) has been proposed and experimentally demonstrated for temperature sensing with ultrahigh sensitivity. The miniature MZI is constructed by splicing a segment of DF between two single-mode fibers (SMFs) to form a microcavity (MC) for filling and replacement of various refractive index (RI) liquids. By adjusting the effective RI difference between the DF and MC (the two interference arms), experimental and calculated results indicate that the interference spectra show different degrees of temperature dependence. As the effective RI of the liquid-filled MC approaches that of the DF, temperature sensitivity up to −84.72 nm/°C with a linear correlation coefficient of 0.9953 has been experimentally achieved for a device with the MC length of 456 μm, filled with liquid RI of 1.482. Apart from ultrahigh sensitivity, the proposed MCMZI device possesses additional advantages of its miniature size and simple configuration; these features make it promising and competitive in various temperature sensing applications, such as consumer electronics, biological treatments, and medical diagnosis. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 3368 KiB

Open AccessArticle

Key Processes of Silicon-On-Glass MEMS Fabrication Technology for Gyroscope Application

by Zhibo Ma^1,2,*, Yinan Wang^1,2, Qiang Shen^1,2, Han Zhang^1,2 and Xuetao Guo^1,2

¹ He Ministry of Education Key Lab of Micro/Nano Systems for Aerospace (Northwestern Polytechnical University), Ministry of Education, Xi’an 710072, China

² Shaan’xi Key Lab of MEMS/NEMS, Northwestern Polytechnical University, Xi’an 710072, China

Sensors 2018, 18(4), 1240; https://doi.org/10.3390/s18041240 - 17 Apr 2018

Cited by 15 | Viewed by 7275

Abstract

MEMS fabrication that is based on the silicon-on-glass (SOG) process requires many steps, including patterning, anodic bonding, deep reactive ion etching (DRIE), and chemical mechanical polishing (CMP). The effects of the process parameters of CMP and DRIE are investigated in this study. The [...] Read more.

MEMS fabrication that is based on the silicon-on-glass (SOG) process requires many steps, including patterning, anodic bonding, deep reactive ion etching (DRIE), and chemical mechanical polishing (CMP). The effects of the process parameters of CMP and DRIE are investigated in this study. The process parameters of CMP, such as abrasive size, load pressure, and pH value of SF1 solution are examined to optimize the total thickness variation in the structure and the surface quality. The ratio of etching and passivation cycle time and the process pressure are also adjusted to achieve satisfactory performance during DRIE. The process is optimized to avoid neither the notching nor lag effects on the fabricated silicon structures. For demonstrating the capability of the modified CMP and DRIE processes, a z-axis micro gyroscope is fabricated that is based on the SOG process. Initial test results show that the average surface roughness of silicon is below 1.13 nm and the thickness of the silicon is measured to be 50 μm. All of the structures are well defined without the footing effect by the use of the modified DRIE process. The initial performance test results of the resonant frequency for the drive and sense modes are 4.048 and 4.076 kHz, respectively. The demands for this kind of SOG MEMS device can be fulfilled using the optimized process. Full article

(This article belongs to the Collection Modeling, Testing and Reliability Issues in MEMS Engineering)

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26 pages, 3899 KiB

Open AccessArticle

New Vectorial Propulsion System and Trajectory Control Designs for Improved AUV Mission Autonomy

by Ivan Masmitja^1,*

, Julian Gonzalez¹, Cesar Galarza¹, Spartacus Gomariz¹

, Jacopo Aguzzi²

and Joaquin Del Rio¹

¹ SARTI research group, Electronics Department, Universitat Politècnica de Catalunya, 08800 Vilanova i la Geltrú, Spain

² Marine Science Institute (ICM), Consejo Superior de Investigaciones Científica (CSIC), 08003 Barcelona, Spain

Sensors 2018, 18(4), 1241; https://doi.org/10.3390/s18041241 - 17 Apr 2018

Cited by 11 | Viewed by 7145

Abstract

Autonomous Underwater Vehicles (AUV) are proving to be a promising platform design for multidisciplinary autonomous operability with a wide range of applications in marine ecology and geoscience. Here, two novel contributions towards increasing the autonomous navigation capability of a new AUV prototype (the [...] Read more.

Autonomous Underwater Vehicles (AUV) are proving to be a promising platform design for multidisciplinary autonomous operability with a wide range of applications in marine ecology and geoscience. Here, two novel contributions towards increasing the autonomous navigation capability of a new AUV prototype (the Guanay II) as a mix between a propelled vehicle and a glider are presented. Firstly, a vectorial propulsion system has been designed to provide full vehicle maneuverability in both horizontal and vertical planes. Furthermore, two controllers have been designed, based on fuzzy controls, to provide the vehicle with autonomous navigation capabilities. Due to the decoupled system propriety, the controllers in the horizontal plane have been designed separately from the vertical plane. This class of non-linear controllers has been used to interpret linguistic laws into different zones of functionality. This method provided good performance, used as interpolation between different rules or linear controls. Both improvements have been validated through simulations and field tests, displaying good performance results. Finally, the conclusion of this work is that the Guanay II AUV has a solid controller to perform autonomous navigation and carry out vertical immersions. Full article

(This article belongs to the Special Issue Mechatronic Systems for Automatic Vehicles)

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16 pages, 35557 KiB

Open AccessArticle

Evaluation of Over-The-Row Harvester Damage in a Super-High-Density Olive Orchard Using On-Board Sensing Techniques

by Manuel Pérez-Ruiz^1,*

, Pilar Rallo²

, M. Rocío Jiménez²

, Miguel Garrido-Izard³

, M. Paz Suárez², Laura Casanova², Constantino Valero³

, Jorge Martínez-Guanter¹

and Ana Morales-Sillero²

¹ Dpto. Ingeniería Aeroespacial y Mecánica de Fluidos, Área de Ingeniería Agroforestal, Escuela Técnica Superior de Ingeniería Agronómica (ETSIA), Universidad de Sevilla, 41013 Sevilla, Spain

² Dpto. Ciencias Agroforestales, Escuela Técnica Superior de Ingeniería Agronómica (ETSIA), Universidad de Sevilla, 41013 Sevilla, Spain

³ Laboratorio de Propiedades Físicas (LPF_TRAGRALIA), Universidad Politécnica de Madrid, 28040 Madrid, Spain

Sensors 2018, 18(4), 1242; https://doi.org/10.3390/s18041242 - 17 Apr 2018

Cited by 29 | Viewed by 7109

Abstract

New super-high-density (SHD) olive orchards designed for mechanical harvesting using over-the-row harvesters are becoming increasingly common around the world. Some studies regarding olive SHD harvesting have focused on the effective removal of the olive fruits; however, the energy applied to the canopy by [...] Read more.

New super-high-density (SHD) olive orchards designed for mechanical harvesting using over-the-row harvesters are becoming increasingly common around the world. Some studies regarding olive SHD harvesting have focused on the effective removal of the olive fruits; however, the energy applied to the canopy by the harvesting machine that can result in fruit damage, structural damage or extra stress on the trees has been little studied. Using conventional analyses, this study investigates the effects of different nominal speeds and beating frequencies on the removal efficiency and the potential for fruit damage, and it uses remote sensing to determine changes in the plant structures of two varieties of olive trees (‘Manzanilla Cacereña’ and ‘Manzanilla de Sevilla’) planted in SHD orchards harvested by an over-the-row harvester. ‘Manzanilla de Sevilla’ fruit was the least tolerant to damage, and for this variety, harvesting at the highest nominal speed led to the greatest percentage of fruits with cuts. Different vibration patterns were applied to the olive trees and were evaluated using triaxial accelerometers. The use of two light detection and ranging (LiDAR) sensing devices allowed us to evaluate structural changes in the studied olive trees. Before- and after-harvest measurements revealed significant differences in the LiDAR data analysis, particularly at the highest nominal speed. The results of this work show that the operating conditions of the harvester are key to minimising fruit damage and that a rapid estimate of the damage produced by an over-the-row harvester with contactless sensing could provide useful information for automatically adjusting the machine parameters in individual olive groves in the future. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2018)

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19 pages, 7137 KiB

Open AccessArticle

Mechanical Characterization of Polysilicon MEMS: A Hybrid TMCMC/POD-Kriging Approach

by Ramin Mirzazadeh¹

, Saeed Eftekhar Azam²

and Stefano Mariani^1,*

¹ Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy

² Department of Civil Engineering, University of Nebraska-Lincoln, 2200 Vine St, Lincoln, NE 68503, USA

Sensors 2018, 18(4), 1243; https://doi.org/10.3390/s18041243 - 17 Apr 2018

Cited by 31 | Viewed by 5081

Abstract

Microscale uncertainties related to the geometry and morphology of polycrystalline silicon films, constituting the movable structures of micro electro-mechanical systems (MEMS), were investigated through a joint numerical/experimental approach. An on-chip testing device was designed and fabricated to deform a compliant polysilicon beam. In [...] Read more.

Microscale uncertainties related to the geometry and morphology of polycrystalline silicon films, constituting the movable structures of micro electro-mechanical systems (MEMS), were investigated through a joint numerical/experimental approach. An on-chip testing device was designed and fabricated to deform a compliant polysilicon beam. In previous studies, we showed that the scattering in the input–output characteristics of the device can be properly described only if statistical features related to the morphology of the columnar polysilicon film and to the etching process adopted to release the movable structure are taken into account. In this work, a high fidelity finite element model of the device was used to feed a transitional Markov chain Monte Carlo (TMCMC) algorithm for the estimation of the unknown parameters governing the aforementioned statistical features. To reduce the computational cost of the stochastic analysis, a synergy of proper orthogonal decomposition (POD) and kriging interpolation was adopted. Results are reported for a batch of nominally identical tested devices, in terms of measurement error-affected probability distributions of the overall Young’s modulus of the polysilicon film and of the overetch depth. Full article

(This article belongs to the Collection Modeling, Testing and Reliability Issues in MEMS Engineering)

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32 pages, 11637 KiB

Open AccessArticle

Tightly-Coupled GNSS/Vision Using a Sky-Pointing Camera for Vehicle Navigation in Urban Areas

by Paul Verlaine Gakne^*

and Kyle O’Keefe

Position, Location and Navigation (PLAN) Group, Department of Geomatics Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive, N.W., Calgary, AB T2N 1N4, Canada

Sensors 2018, 18(4), 1244; https://doi.org/10.3390/s18041244 - 17 Apr 2018

Cited by 46 | Viewed by 8351

Abstract

This paper presents a method of fusing the ego-motion of a robot or a land vehicle estimated from an upward-facing camera with Global Navigation Satellite System (GNSS) signals for navigation purposes in urban environments. A sky-pointing camera is mounted on the top of [...] Read more.

This paper presents a method of fusing the ego-motion of a robot or a land vehicle estimated from an upward-facing camera with Global Navigation Satellite System (GNSS) signals for navigation purposes in urban environments. A sky-pointing camera is mounted on the top of a car and synchronized with a GNSS receiver. The advantages of this configuration are two-fold: firstly, for the GNSS signals, the upward-facing camera will be used to classify the acquired images into sky and non-sky (also known as segmentation). A satellite falling into the non-sky areas (e.g., buildings, trees) will be rejected and not considered for the final position solution computation. Secondly, the sky-pointing camera (with a field of view of about 90 degrees) is helpful for urban area ego-motion estimation in the sense that it does not see most of the moving objects (e.g., pedestrians, cars) and thus is able to estimate the ego-motion with fewer outliers than is typical with a forward-facing camera. The GNSS and visual information systems are tightly-coupled in a Kalman filter for the final position solution. Experimental results demonstrate the ability of the system to provide satisfactory navigation solutions and better accuracy than the GNSS-only and the loosely-coupled GNSS/vision, 20 percent and 82 percent (in the worst case) respectively, in a deep urban canyon, even in conditions with fewer than four GNSS satellites. Full article

(This article belongs to the Collection Positioning and Navigation)

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18 pages, 11304 KiB

Open AccessArticle

Lower-Order Compensation Chain Threshold-Reduction Technique for Multi-Stage Voltage Multipliers

by Francesco Dell’ Anna¹, Tao Dong^2,*, Ping Li³, Yumei Wen³, Mehdi Azadmehr², Mario Casu⁴

and Yngvar Berg²

¹ Institute of Applied Micro-Nano Science and Technology—IAMNST, Chongqing Key Laboratory of Colleges and Universities on Micro-Nano Systems Technology and Smart Transducing, Chongqing Engineering Laboratoryfor Detection, Control and Integrated System, National Research Base of Intelligent Manufacturing Service, Chongqing Technology and Business University, Nan’an District, Chongqing 400067, China

² Faculty of Engineering, Science and Maritime Studies, Department of Microsystems, Campus Vestfold, Høgskolen i Sørøst-Norge, 235 3603 Kongsberg, Norway

³ Department of Instrumentation, School of Electronic Information and Electric Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

⁴ Department of Electronics and Telecommunications (DET), Politecnico di Torino, Corso Duca degli Abruzzi No. 24, 10129 Torino, Italy

Sensors 2018, 18(4), 1245; https://doi.org/10.3390/s18041245 - 17 Apr 2018

Cited by 1 | Viewed by 4323

Abstract

This paper presents a novel threshold-compensation technique for multi-stage voltage multipliers employed in low power applications such as passive and autonomous wireless sensing nodes (WSNs) powered by energy harvesters. The proposed threshold-reduction technique enables a topological design methodology which, through an optimum control [...] Read more.

This paper presents a novel threshold-compensation technique for multi-stage voltage multipliers employed in low power applications such as passive and autonomous wireless sensing nodes (WSNs) powered by energy harvesters. The proposed threshold-reduction technique enables a topological design methodology which, through an optimum control of the trade-off among transistor conductivity and leakage losses, is aimed at maximizing the voltage conversion efficiency (VCE) for a given ac input signal and physical chip area occupation. The conducted simulations positively assert the validity of the proposed design methodology, emphasizing the exploitable design space yielded by the transistor connection scheme in the voltage multiplier chain. An experimental validation and comparison of threshold-compensation techniques was performed, adopting 2N5247 N-channel junction field effect transistors (JFETs) for the realization of the voltage multiplier prototypes. The attained measurements clearly support the effectiveness of the proposed threshold-reduction approach, which can significantly reduce the chip area occupation for a given target output performance and ac input signal. Full article

(This article belongs to the Special Issue Micro-Nano Systems Technology and Micro-Nano Intelligent Manufacture)

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18 pages, 9337 KiB

Open AccessArticle

Active and Assisted Living Ecosystem for the Elderly

by Isabel Marcelino^1,2, Rosalía Laza^3,4,5, Patrício Domingues², Silvana Gómez-Meire³

, Florentino Fdez-Riverola^3,4,5,*

and António Pereira^1,2

¹ INOV INESC INOVAÇÃO Instituto de Novas Tecnologias—Delegação de Leiria, 2411-901 Leiria, Portugal

² School of Technology and Management, Computer Science and Communications Research Centre, Polytechnic Institute of Leiria, 2411-901 Leiria, Portugal

³ ESEI: Escuela Superior de Ingeniería Informática, University of Vigo, 32004 Ourense, Spain

⁴ CINBIO: Centro de Investigaciones Biomédicas, University of Vigo, 36310 Vigo, Spain

⁵ Grupo de Investigación SING, Instituto de Investigación Sanitaria Galicia Sur (IIS Galicia Sur), SERGAS-UVIGO, 36312 Vigo, Spain

Sensors 2018, 18(4), 1246; https://doi.org/10.3390/s18041246 - 17 Apr 2018

Cited by 27 | Viewed by 6736

Abstract

A novel ecosystem to promote the physical, emotional and psychic health and well-being of the elderly is presented. Our proposal was designed to add several services developed to meet the needs of the senior population, namely services to improve social inclusion and increase [...] Read more.

A novel ecosystem to promote the physical, emotional and psychic health and well-being of the elderly is presented. Our proposal was designed to add several services developed to meet the needs of the senior population, namely services to improve social inclusion and increase contribution to society. Moreover, the solution monitors the vital signs of elderly individuals, as well as environmental parameters and behavior patterns, in order to seek eminent danger situations and predict potential hazardous issues, acting in accordance with the various alert levels specified for each individual. The platform was tested by seniors in a real scenario. The experimental results demonstrated that the proposed ecosystem was well accepted and is easy to use by seniors. Full article

(This article belongs to the Special Issue New Trends in Ambient Intelligence Applications)

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9 pages, 3049 KiB

Open AccessArticle

Study on Misalignment Angle Compensation during Scale Factor Matching for Two Pairs of Accelerometers in a Gravity Gradient Instrument

by Xiangqing Huang^1,2, Zhongguang Deng¹, Yafei Xie¹, Ji Fan^1,3, Chenyuan Hu^1,* and Liangcheng Tu^1,2,3,*

¹ MOE Key Laboratory of Fundamental Physical Quantities Measurement & Hubei Key Laboratory of Gravitation and Quantum Physics, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China

² TianQin Research Center for Gravitational Physics and School of Physics and Astronomy, Sun Yat-sen University (Zhuhai Campus), Zhuhai 519082, China

³ Institute of Geophysics, Huazhong University of Science and Technology, Wuhan 430074, China

Sensors 2018, 18(4), 1247; https://doi.org/10.3390/s18041247 - 18 Apr 2018

Cited by 17 | Viewed by 4891

Abstract

A method for automatic compensation of misalignment angles during matching the scale factors of two pairs of the accelerometers in developing the rotating accelerometer gravity gradient instrument (GGI) is proposed and demonstrated in this paper. The purpose of automatic scale factor matching of [...] Read more.

A method for automatic compensation of misalignment angles during matching the scale factors of two pairs of the accelerometers in developing the rotating accelerometer gravity gradient instrument (GGI) is proposed and demonstrated in this paper. The purpose of automatic scale factor matching of the four accelerometers in GGI is to suppress the common mode acceleration of the moving-based platforms. However, taking the full model equation of the accelerometer into consideration, the other two orthogonal axes which is the pendulous axis and the output axis, will also sense the common mode acceleration and reduce the suppression performance. The coefficients from the two axes to the output are δ_O and δ_P respectively, called the misalignment angles. The angle δ_O, coupling with the acceleration along the pendulous axis perpendicular to the rotational plane, will not be modulated by the rotation and gives little contribution to the scale factors matching. On the other hand, because of coupling with the acceleration along the centripetal direction in the rotating plane, the angle δ_P would produce a component with 90 degrees phase delay relative to the scale factor component. Hence, the δ_P component coincides exactly with the sensitive direction of the orthogonal accelerometers. To improve the common mode acceleration rejection, the misalignment angle δ_P is compensated by injecting a trimming current, which is proportional to the output of an orthogonal accelerometer, into the torque coil of the accelerometer during the scale factor matching. The experimental results show that the common linear acceleration suppression achieved three orders after the scale factors balance and five orders after the misalignment angles compensation, which is almost down to the noise level of the used accelerometers of 1~2 × 10⁻⁷ g/√Hz (1 g ≈ 9.8 m/s²). Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 8384 KiB

Open AccessArticle

Simulation Analysis of Fluid-Structure Interaction of High Velocity Environment Influence on Aircraft Wing Materials under Different Mach Numbers

by Lijun Zhang^1,*

and Changyan Sun²

¹ National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, China

² School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing 100083, China

Sensors 2018, 18(4), 1248; https://doi.org/10.3390/s18041248 - 18 Apr 2018

Cited by 10 | Viewed by 6522

Abstract

Aircraft service process is in a state of the composite load of pressure and temperature for a long period of time, which inevitably affects the inherent characteristics of some components in aircraft accordingly. The flow field of aircraft wing materials under different Mach [...] Read more.

Aircraft service process is in a state of the composite load of pressure and temperature for a long period of time, which inevitably affects the inherent characteristics of some components in aircraft accordingly. The flow field of aircraft wing materials under different Mach numbers is simulated by Fluent in order to extract pressure and temperature on the wing in this paper. To determine the effect of coupling stress on the wing’s material and structural properties, the fluid-structure interaction (FSI) method is used in ANSYS-Workbench to calculate the stress that is caused by pressure and temperature. Simulation analysis results show that with the increase of Mach number, the pressure and temperature on the wing’s surface both increase exponentially and thermal stress that is caused by temperature will be the main factor in the coupled stress. When compared with three kinds of materials, titanium alloy, aluminum alloy, and Haynes alloy, carbon fiber composite material has better performance in service at high speed, and natural frequency under coupling pre-stressing will get smaller. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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17 pages, 3607 KiB

Open AccessArticle

A Sparse-Driven Anti-Velocity Deception Jamming Strategy Based on Pulse-Doppler Radar with Random Pulse Initial Phases

by Zhen Liu¹

, Jinping Sui^1,*

, Zhenhua Wei² and Xiang Li¹

¹ College of Electronic Science, National University of Defense Technology, Changsha 410073, China

² Rocket Force University of Engineering, Xi’an 710025, China

Sensors 2018, 18(4), 1249; https://doi.org/10.3390/s18041249 - 18 Apr 2018

Cited by 18 | Viewed by 4417

Abstract

This paper focuses on developing an anti-velocity jamming strategy that enhances the ability of a pulse-Doppler (PD) radar to detect moving targets in the presence of translational and/or micro motion velocity jamming generated by the digital radio frequency memory (DRFM) repeat jammers. The [...] Read more.

This paper focuses on developing an anti-velocity jamming strategy that enhances the ability of a pulse-Doppler (PD) radar to detect moving targets in the presence of translational and/or micro motion velocity jamming generated by the digital radio frequency memory (DRFM) repeat jammers. The strategy adopts random pulse initial phase (RPIP) pulses as its transmitted signal and thus gets DRFM jammers not adaptable to the randomness of initial phase of the transmitted pulses in the pulse repetition interval (PRI) domain. The difference between the true target echo and the false target jamming signal at each PRI is then utilized to recognize the true and false target signals. In particular, an entropy based multi-channel processing scheme is designed to extract the information of the received signal without the assumption that true and false targets must be both included within one coherent processing interval (CPI). Information such as the component of the received signal (target echo only, jamming only or both) or the operating manner of DRFM repeat jammer can be gained (if jamming exists). Meanwhile, we solve the false target recognition problem under sparse theory frame and our previous work named the short-time sparse recovery (STSR) algorithm is introduced to recover the motion parameters of the true and/or false targets in the time-frequency domain. It should be pointed out that both the translational false target jamming and micro motion target jamming can be recognized in our strategy. The performance of the proposed strategy is compared with the correlated processing (CP) method used by most extant strategies. It is shown that the proposed strategy can successfully recognize the existence of true and/or false targets and keep its power in recovering corresponding motion parameters even when the jamming environment is strong. Full article

(This article belongs to the Section Remote Sensors)

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15 pages, 38333 KiB

Open AccessArticle

Non-Contact Smartphone-Based Monitoring of Thermally Stressed Structures

by Mehmet Sefa Orak^1,2

, Amir Nasrollahi¹

, Turgut Ozturk², David Mas³, Belen Ferrer⁴

and Piervincenzo Rizzo^1,*

¹ Laboratory for Nondestructive Evaluation and Structural Health Monitoring Studies, Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA

² Department of Civil Engineering, Istanbul Technical University (ITU), Maslak, Istanbul 34469, Turkey

³ Institute of Physics Applied to the Sciences and Technologies, University of Alicante, Alicante 03690, Spain

⁴ Department of Civil Engineering, University of Alicante, Alicante 03690, Spain

Sensors 2018, 18(4), 1250; https://doi.org/10.3390/s18041250 - 18 Apr 2018

Cited by 9 | Viewed by 4506

Abstract

The in-situ measurement of thermal stress in beams or continuous welded rails may prevent structural anomalies such as buckling. This study proposed a non-contact monitoring/inspection approach based on the use of a smartphone and a computer vision algorithm to estimate the vibrating characteristics [...] Read more.

The in-situ measurement of thermal stress in beams or continuous welded rails may prevent structural anomalies such as buckling. This study proposed a non-contact monitoring/inspection approach based on the use of a smartphone and a computer vision algorithm to estimate the vibrating characteristics of beams subjected to thermal stress. It is hypothesized that the vibration of a beam can be captured using a smartphone operating at frame rates higher than conventional 30 Hz, and the first few natural frequencies of the beam can be extracted using a computer vision algorithm. In this study, the first mode of vibration was considered and compared to the information obtained with a conventional accelerometer attached to the two structures investigated, namely a thin beam and a thick beam. The results show excellent agreement between the conventional contact method and the non-contact sensing approach proposed here. In the future, these findings may be used to develop a monitoring/inspection smartphone application to assess the axial stress of slender structures, to predict the neutral temperature of continuous welded rails, or to prevent thermal buckling. Full article

(This article belongs to the Special Issue Novel Methodologies to Interpret Non-Destructive Testing and Structural Health Monitoring Data)

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26 pages, 14241 KiB

Open AccessArticle

A Wearable Body Controlling Device for Application of Functional Electrical Stimulation

by Nazita Taghavi^1,*

, Greg R. Luecke^1,*

and Nicholas D. Jeffery²

¹ Department of Mechanical Engineering and Virtual Reality Applications Center, Iowa State University of Science and Technology, Ames, IA 50011, USA

² Department of Veterinary Medicine & Biological Science, Texas A&M University, College Station, TX 77843, USA

Sensors 2018, 18(4), 1251; https://doi.org/10.3390/s18041251 - 18 Apr 2018

Cited by 8 | Viewed by 6244

Abstract

In this research, we describe a new balancing device used to stabilize the rear quarters of a patient dog with spinal cord injuries. Our approach uses inertial measurement sensing and direct leg actuation to lay a foundation for eventual muscle control by means [...] Read more.

In this research, we describe a new balancing device used to stabilize the rear quarters of a patient dog with spinal cord injuries. Our approach uses inertial measurement sensing and direct leg actuation to lay a foundation for eventual muscle control by means of direct functional electrical stimulation (FES). During this phase of development, we designed and built a mechanical test-bed to develop the control and stimulation algorithms before we use the device on our animal subjects. We designed the bionic test-bed to mimic the typical walking gait of a dog and use it to develop and test the functionality of the balancing device for stabilization of patient dogs with hindquarter paralysis. We present analysis for various muscle stimulation and balancing strategies, and our device can be used by veterinarians to tailor the stimulation strength and temporal distribution for any individual patient dog. We develop stabilizing muscle stimulation strategies using the robotic test-bed to enhance walking stability. We present experimental results using the bionic test-bed to demonstrate that the balancing device can provide an effective sensing strategy and deliver the required motion control commands for stabilizing an actual dog with a spinal cord injury. Full article

(This article belongs to the Special Issue Wearable Smart Devices)

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6 pages, 907 KiB

Open AccessArticle

Improving Color Accuracy of Colorimetric Sensors

by Eric Kirchner^1,*, Pim Koeckhoven¹ and Keshav Sivakumar²

¹ Color Research Group, AkzoNobel Paints & Coatings, 2170 BA Sassenheim, The Netherlands

² Color Research Group, AkzoNobel Paints & Coatings, 562 114 Bengaluru, India

Sensors 2018, 18(4), 1252; https://doi.org/10.3390/s18041252 - 18 Apr 2018

Cited by 9 | Viewed by 7103

Abstract

Accurate measurements of reflectance and color require spectrophotometers with prices often exceeding $3000. Recently, new “color instruments” became available with much lower prices, thanks to the availability of inexpensive colorimetric sensors. We investigated the Node+ChromaPro and the Color Muse, launched in 2015 and [...] Read more.

Accurate measurements of reflectance and color require spectrophotometers with prices often exceeding $3000. Recently, new “color instruments” became available with much lower prices, thanks to the availability of inexpensive colorimetric sensors. We investigated the Node+ChromaPro and the Color Muse, launched in 2015 and 2016 by Variable Inc. Both instruments are colorimeters, combining a colorimetric sensor with LED lighting. We investigated color accuracy compared to a high-end spectrophotometer from BYK Gardner. With different sets of samples we find for the Node an average value of dE_CMC (1:1) = 1.50, and a maximum of 7.86, when comparing with the 45° geometry of the spectrophotometer. Utilizing measurement data on the Spectral Power Distributions of the LEDs, we developed three methods to improve color accuracy as compared to the spectrophotometer data. We used these methods on different sets of samples with various degrees of gloss, both for training the models underlying the methods and for independent tests of model accuracy. Average color accuracy of the Node+ChromaPro improves from dE_CMC (1:1) = 1.82 to 1.16 with respect to spectrophotometer data. The percentage of samples with dE_CMC (1:1) < 1.0 increases from 30.9% (uncorrected) to 64%. With the improved color accuracy, these sensors become useful for many more applications. Full article

(This article belongs to the Special Issue Colorimetric Nanosensors)

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25 pages, 38610 KiB

Open AccessArticle

A New Vegetation Segmentation Approach for Cropped Fields Based on Threshold Detection from Hue Histograms

by Mohamed Hassanein^1,*, Zahra Lari²

and Naser El-Sheimy¹

¹ Department of Geomatics Engineering, University of Calgary, 2500 University Dr NW, Calgary, AB T2N1N4, Canada

² Leica Geosystems Ltd.; 245 Aero Way NE, Calgary, AB T2E6K2, Canada

Sensors 2018, 18(4), 1253; https://doi.org/10.3390/s18041253 - 18 Apr 2018

Cited by 58 | Viewed by 6632

Abstract

Over the last decade, the use of unmanned aerial vehicle (UAV) technology has evolved significantly in different applications as it provides a special platform capable of combining the benefits of terrestrial and aerial remote sensing. Therefore, such technology has been established as an [...] Read more.

Over the last decade, the use of unmanned aerial vehicle (UAV) technology has evolved significantly in different applications as it provides a special platform capable of combining the benefits of terrestrial and aerial remote sensing. Therefore, such technology has been established as an important source of data collection for different precision agriculture (PA) applications such as crop health monitoring and weed management. Generally, these PA applications depend on performing a vegetation segmentation process as an initial step, which aims to detect the vegetation objects in collected agriculture fields’ images. The main result of the vegetation segmentation process is a binary image, where vegetations are presented in white color and the remaining objects are presented in black. Such process could easily be performed using different vegetation indexes derived from multispectral imagery. Recently, to expand the use of UAV imagery systems for PA applications, it was important to reduce the cost of such systems through using low-cost RGB cameras Thus, developing vegetation segmentation techniques for RGB images is a challenging problem. The proposed paper introduces a new vegetation segmentation methodology for low-cost UAV RGB images, which depends on using Hue color channel. The proposed methodology follows the assumption that the colors in any agriculture field image can be distributed into vegetation and non-vegetations colors. Therefore, four main steps are developed to detect five different threshold values using the hue histogram of the RGB image, these thresholds are capable to discriminate the dominant color, either vegetation or non-vegetation, within the agriculture field image. The achieved results for implementing the proposed methodology showed its ability to generate accurate and stable vegetation segmentation performance with mean accuracy equal to 87.29% and standard deviation as 12.5%. Full article

(This article belongs to the Special Issue Application of Satellite and Proximal Sensors in Precision Agriculture)

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11 pages, 4025 KiB

Open AccessArticle

Development and Testing of an Integrated Rotating Dynamometer Based on Fiber Bragg Grating for Four-Component Cutting Force Measurement

by Mingyao Liu¹, Junjun Bing¹, Li Xiao², Kang Yun^1,* and Liang Wan¹

¹ School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan 430070, Hubei, China

² Jianghan Machinery Research Institute Co., Ltd., CNPC, Jingzhou 430024, Hubei, China

Sensors 2018, 18(4), 1254; https://doi.org/10.3390/s18041254 - 18 Apr 2018

Cited by 22 | Viewed by 5179

Abstract

Cutting force measurement is of great importance in machining processes. Hence, various methods of measuring the cutting force have been proposed by many researchers. In this work, a novel integrated rotating dynamometer based on fiber Bragg grating (FBG) was designed, constructed, and tested [...] Read more.

Cutting force measurement is of great importance in machining processes. Hence, various methods of measuring the cutting force have been proposed by many researchers. In this work, a novel integrated rotating dynamometer based on fiber Bragg grating (FBG) was designed, constructed, and tested to measure four-component cutting force. The dynamometer consists of FBGs that are pasted on the newly designed elastic structure which is then mounted on the rotating spindle. The elastic structure is designed as two mutual-perpendicular semi-octagonal rings. The signals of the FBGs are transmitted to FBG interrogator via fiber optic rotary joints and optical fiber, and the wavelength values are displayed on a computer. In order to determine the static and dynamic characteristics, many tests have been done. The results show that it is suitable for measuring cutting force. Full article

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22 pages, 4046 KiB

Open AccessArticle

A Novel Energy-Efficient Multi-Sensor Fusion Wake-Up Control Strategy Based on a Biomimetic Infectious-Immune Mechanism for Target Tracking

by Jie Zhou¹, Yan Liang^1,*, Qiang Shen², Xiaoxue Feng³ and Quan Pan¹

¹ School of Automation & MOE Key Laboratory of Information Fusion Technology, Northwestern Polytechnical University, Xi’an 710072, China

² MOE Key Laboratory of Micro and Nano Systems for Aerospace, Northwestern Polytechnical University, Xi’an 710072, China

³ School of Automation, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(4), 1255; https://doi.org/10.3390/s18041255 - 18 Apr 2018

Cited by 5 | Viewed by 4174

Abstract

A biomimetic distributed infection-immunity model (BDIIM), inspired by the immune mechanism of an infected organism, is proposed in order to achieve a high-efficiency wake-up control strategy based on multi-sensor fusion for target tracking. The resultant BDIIM consists of six sub-processes reflecting the infection-immunity [...] Read more.

A biomimetic distributed infection-immunity model (BDIIM), inspired by the immune mechanism of an infected organism, is proposed in order to achieve a high-efficiency wake-up control strategy based on multi-sensor fusion for target tracking. The resultant BDIIM consists of six sub-processes reflecting the infection-immunity mechanism: occurrence probabilities of direct-infection (DI) and cross-infection (CI), immunity/immune-deficiency of DI and CI, pathogen amount of DI and CI, immune cell production, immune memory, and pathogen accumulation under immunity state. Furthermore, a corresponding relationship between the BDIIM and sensor wake-up control is established to form the collaborative wake-up method. Finally, joint surveillance and target tracking are formulated in the simulation, in which we show that the energy cost and position tracking error are reduced to 50.8% and 78.9%, respectively. Effectiveness of the proposed BDIIM algorithm is shown, and this model is expected to have a significant role in guiding the performance improvement of multi-sensor networks. Full article

(This article belongs to the Collection Smart Communication Protocols and Algorithms for Sensor Networks)

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16 pages, 1433 KiB

Open AccessArticle

Seeker-Azimuth Determination with Gyro Rotor and Optoelectronic Sensors

by Jian-Ming Bai^1,2, Guangshe Zhao³, Hai-Jun Rong^1,* and Xianhua Wang²

¹ State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Key Laboratory of Environment and Control for Flight Vehicle, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, China

² Optical Direction and Pointing Technique Research Department, Xi’an Institute of Optics and Precision Mechanics of CAS, Xi’an 710119, China

³ School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2018, 18(4), 1256; https://doi.org/10.3390/s18041256 - 19 Apr 2018

Cited by 2 | Viewed by 5650

Abstract

This paper presents an approach to seeker-azimuth determination using the gyro rotor and optoelectronic sensors. In the proposed method, the gyro rotor is designed with a set of black and white right spherical triangle patterns on its surface. Two pairs of optoelectronic sensors [...] Read more.

This paper presents an approach to seeker-azimuth determination using the gyro rotor and optoelectronic sensors. In the proposed method, the gyro rotor is designed with a set of black and white right spherical triangle patterns on its surface. Two pairs of optoelectronic sensors are located symmetrically around the gyro rotor. When there is an azimuth, the stripe width covering the black and white patterns changes. The optoelectronic sensors then capture the reflected optical signals from the different black and white pattern stripes on the gyro rotor and produce the duty ratio signal. The functional relationship between the measured duty ratio and the azimuth information is numerically derived, and, based on this relationship, the azimuth is determined from the measured duty ratio. Experimental results show that the proposed approach produces a large azimuth range and high measurement accuracy with the linearity error of less than 0.005. Full article

(This article belongs to the Special Issue Optoelectronic and Photonic Sensors)

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12 pages, 3213 KiB

Open AccessArticle

A Fast and Easily-Realized Concentration Sensor for Binary Gas Mixtures and Its Design Analysis

by Yu Guan

, Song Lu^*

, Dan Zhang, Yang Hu and Wei Yuan

State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230026, China

Sensors 2018, 18(4), 1257; https://doi.org/10.3390/s18041257 - 19 Apr 2018

Cited by 13 | Viewed by 4111

Abstract

A low-cost and easily-realized sensing device used for the detection of gas mixtures at different concentrations is presented. Its sensing part includes a small critical nozzle, a laminar structure, and a differential pressure sensor. When gas flows through the laminar structure, there is [...] Read more.

A low-cost and easily-realized sensing device used for the detection of gas mixtures at different concentrations is presented. Its sensing part includes a small critical nozzle, a laminar structure, and a differential pressure sensor. When gas flows through the laminar structure, there is a pressure drop between both ends of it, and for different components of gas, the pressure drop is different. Based on this feature, the concentration detection is achieved. Concentration tests for two types of fire extinguishing agents CBrF₃ and C₃HF₇ are presented. The results show the characteristics of fast response/recovery time, high accuracy, and good repeatability. Based on the theoretical analysis, the effects of the design parameters on the sensing performance to concentration detection are discussed in detail. Full article

(This article belongs to the Collection Gas Sensors)

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10 pages, 10540 KiB

Open AccessArticle

High-Contrast Imaging of Cholesterol Crystals in Rabbit Arteries Ex Vivo Using LED-Based Polarization Microscopy

by Seonghee Cho¹, Kyungmin Kim², Taehoon Kim³, Hyoeun Park³, Jin-Moo Kim³, SeungHoon Lee³, YeonSu Kang³, Kiyuk Chang^3,* and Chulhong Kim^1,2,*

¹ School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea

² Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea

³ Division of Cardiology, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea

Sensors 2018, 18(4), 1258; https://doi.org/10.3390/s18041258 - 19 Apr 2018

Cited by 7 | Viewed by 8260

Abstract

Detection of cholesterol crystals (Chcs) in atherosclerosis disease is important for understanding the pathophysiology of atherosclerosis. Polarization microscopy (PM) has been in use traditionally for detecting Chcs, but they have difficulty in distinguishing Chcs with other crystalline materials in tissue, such as collagens. [...] Read more.

Detection of cholesterol crystals (Chcs) in atherosclerosis disease is important for understanding the pathophysiology of atherosclerosis. Polarization microscopy (PM) has been in use traditionally for detecting Chcs, but they have difficulty in distinguishing Chcs with other crystalline materials in tissue, such as collagens. Thus, most studies using PM have been limited to studying cell-level samples. Although various methods have been proposed to detect Chcs with high specificity, most of them have low signal-to-noise ratios, a high system construction cost, and are difficult to operate due to a complex protocol. To address these problems, we have developed a simple and inexpensive universal serial bus (USB) PM system equipped with a 5700 K cool-white light-emitting diode (LED). In this system, Chcs are shown in a light blue color while collagen is shown in a yellow color. More importantly, the contrast between Chcs and collagens is improved by a factor of 2.3 under an aqueous condition in these PM images. These imaging results are well-matched with the ones acquired with two-photon microscopy (TPM). The system can visualize the features of atherosclerosis that cannot be visualized by the conventional hematoxylin and eosin and oil-red-o staining methods. Thus, we believe that this simple USB PM system can be widely used to identify Chcs in atherosclerosis. Full article

(This article belongs to the Special Issue Sensors for Health Monitoring and Disease Diagnosis)

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15 pages, 6821 KiB

Open AccessArticle

Development of Noninvasive Classification Methods for Different Roasting Degrees of Coffee Beans Using Hyperspectral Imaging

by Bingquan Chu¹, Keqiang Yu², Yanru Zhao^3,4 and Yong He^3,4,*

¹ School of Biological and Chemical Engineering/School of Light Industry, Zhejiang Provincial Key Laboratory of Chemical and Biological Processing Technology of Farm Products, Zhejiang Provincial Collaborative Innovation Center of Agricultural Biological Resources Biochemical Manufacturing, Zhejiang University of Science and Technology, Hangzhou 310023, China

² College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China

³ College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China

⁴ Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture, Hangzhou 310058, China

Sensors 2018, 18(4), 1259; https://doi.org/10.3390/s18041259 - 19 Apr 2018

Cited by 34 | Viewed by 7410

Abstract

This study aimed to develop an approach for quickly and noninvasively differentiating the roasting degrees of coffee beans using hyperspectral imaging (HSI). The qualitative properties of seven roasting degrees of coffee beans (unroasted, light, moderately light, light medium, medium, moderately dark, and dark) [...] Read more.

This study aimed to develop an approach for quickly and noninvasively differentiating the roasting degrees of coffee beans using hyperspectral imaging (HSI). The qualitative properties of seven roasting degrees of coffee beans (unroasted, light, moderately light, light medium, medium, moderately dark, and dark) were assayed, including moisture, crude fat, trigonelline, chlorogenic acid, and caffeine contents. These properties were influenced greatly by the respective roasting degree. Their hyperspectral images (874–1734 nm) were collected using a hyperspectral reflectance imaging system. The spectra of the regions of interest were manually extracted from the HSI images. Then, principal components analysis was employed to compress the spectral data and select the optimal wavelengths based on loading weight analysis. Meanwhile, the random frog (RF) methodology and the successive projections algorithm were also adopted to pick effective wavelengths from the spectral data. Finally, least squares support vector machine (LS-SVM) was utilized to establish discriminative models using spectral reflectance and corresponding labeled classes for each degree of roast sample. The results showed that the LS-SVM model, established by the RF selecting method, with eight wavelengths performed very well, achieving an overall classification accuracy of 90.30%. In conclusion, HSI was illustrated as a potential technique for noninvasively classifying the roasting degrees of coffee beans and might have an important application for the development of nondestructive, real-time, and portable sensors to monitor the roasting process of coffee beans. Full article

(This article belongs to the Special Issue Advances in Infrared Imaging: Sensing, Exploitation and Applications)

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11 pages, 3288 KiB

Open AccessArticle

Modelling of a Hall Effect-Based Current Sensor with an Open Core Magnetic Concentrator

by Ivan Yatchev^1,*, Mehmet Sen^1,2, Iosko Balabozov¹ and Ivan Kostov¹

¹ Faculty of Electrical Engineering, Tehcnical University of Sofia, 1000 Sofia, Bulgaria

² Vocational School of Technical Sciences, Uludağ University, 16059 Nilufer/Bursa, Turkey

Sensors 2018, 18(4), 1260; https://doi.org/10.3390/s18041260 - 19 Apr 2018

Cited by 17 | Viewed by 5972

Abstract

The present paper deals with the modelling of a Hall effect current sensor with open core magnetic concentrator. 3D magnetic field modelling is carried out using the finite element method (FEM) and Comsol Multiphysics software. Two rectangular core constructions are considered. Different geometric [...] Read more.

The present paper deals with the modelling of a Hall effect current sensor with open core magnetic concentrator. 3D magnetic field modelling is carried out using the finite element method (FEM) and Comsol Multiphysics software. Two rectangular core constructions are considered. Different geometric parameters of the magnetic concentrator are varied and their influence on the sensor characteristic is studied, with the aim of reducing the dependence on the output signal on the distance to the conductor. Of the studied parameters, core window length leads to the most significant change in the sensor characteristic. Future work can include the optimization of the sensor construction. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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22 pages, 13099 KiB

Open AccessArticle

A Method for Extracting Road Boundary Information from Crowdsourcing Vehicle GPS Trajectories

by Wei Yang, Tinghua Ai^*

and Wei Lu

School of Resource and Environmental Sciences, Wuhan University, 129 Luoyu Road, Wuhan 430079, China

Sensors 2018, 18(4), 1261; https://doi.org/10.3390/s18041261 - 19 Apr 2018

Cited by 52 | Viewed by 7179

Abstract

Crowdsourcing trajectory data is an important approach for accessing and updating road information. In this paper, we present a novel approach for extracting road boundary information from crowdsourcing vehicle traces based on Delaunay triangulation (DT). First, an optimization and interpolation method is proposed [...] Read more.

Crowdsourcing trajectory data is an important approach for accessing and updating road information. In this paper, we present a novel approach for extracting road boundary information from crowdsourcing vehicle traces based on Delaunay triangulation (DT). First, an optimization and interpolation method is proposed to filter abnormal trace segments from raw global positioning system (GPS) traces and interpolate the optimization segments adaptively to ensure there are enough tracking points. Second, constructing the DT and the Voronoi diagram within interpolated tracking lines to calculate road boundary descriptors using the area of Voronoi cell and the length of triangle edge. Then, the road boundary detection model is established integrating the boundary descriptors and trajectory movement features (e.g., direction) by DT. Third, using the boundary detection model to detect road boundary from the DT constructed by trajectory lines, and a regional growing method based on seed polygons is proposed to extract the road boundary. Experiments were conducted using the GPS traces of taxis in Beijing, China, and the results show that the proposed method is suitable for extracting the road boundary from low-frequency GPS traces, multi-type road structures, and different time intervals. Compared with two existing methods, the automatically extracted boundary information was proved to be of higher quality. Full article

(This article belongs to the Special Issue Crowd-Sensing and Remote Sensing Technologies for Smart Cities)

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11 pages, 14421 KiB

Open AccessCommunication

From the Paper to the Tablet: On the Design of an AR-Based Tool for the Inspection of Pre-Fab Buildings. Preliminary Results of the SIRAE Project

by Cristina Portalés^1,*

, Sergio Casas¹

, Jesús Gimeno¹

, Marcos Fernández¹ and Montse Poza²

¹ Institute of Robotics and Information and Communication Technologies (IRTIC), Universitat de València, 46980 València, Spain

² DRAGADOS, S.A., 28050 Madrid, Spain

Sensors 2018, 18(4), 1262; https://doi.org/10.3390/s18041262 - 19 Apr 2018

Cited by 12 | Viewed by 5331

Abstract

Energy-efficient Buildings (EeB) are demanded in today’s constructions, fulfilling the requirements for green cities. Pre-fab buildings, which are modularly fully-built in factories, are a good example of this. Although this kind of building is quite new, the in situ inspection is documented using [...] Read more.

Energy-efficient Buildings (EeB) are demanded in today’s constructions, fulfilling the requirements for green cities. Pre-fab buildings, which are modularly fully-built in factories, are a good example of this. Although this kind of building is quite new, the in situ inspection is documented using traditional tools, mainly based on paper annotations. Thus, the inspection process is not taking advantage of new technologies. In this paper, we present the preliminary results of the SIRAE project that aims to provide an Augmented Reality (AR) tool that can seamlessly aid in the regular processes of pre-fab building inspections to detect and eliminate the possible existing quality and energy efficiency deviations. In this regards, we show a description of the current inspection process and how an interactive tool can be designed and adapted to it. Our first results show the design and implementation of our tool, which is highly interactive and involves AR visualizations and 3D data-gathering, allowing the inspectors to quickly manage it without altering the way the inspection process is done. First trials on a real environment show that the tool is promising for massive inspection processes. Full article

(This article belongs to the Special Issue Advances in Sensors for Sustainable Smart Cities and Smart Buildings)

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20 pages, 1788 KiB

Open AccessArticle

Support Stiffness Monitoring of Cylindrical Structures Using Magnetostrictive Transducers and the Torsional Mode T(0,1)

by Jabid Quiroga Mendez^1,*

, Luis Mujica², Rodolfo Villamizar¹ and Magda Ruiz²

¹ Schools of Mechanical and Electric, Electronics and Telecommunications Engineering, Universidad Industrial de Santander (UIS), Universidad Industrial de Santander (UIS), Cra 27 Calle 9, Bucaramanga, Colombia

² Departament de Matemàtiques, CoDAlab, Escola d’Enginyeria de Barcelona Est (EEBE), Universitat Politècnica de Catalunya, Campus Diagonal-Besòs. C, Eduard Maristany, 6-12, St. Adrià de Besòs, 08930 Barcelona, Spain

Sensors 2018, 18(4), 1263; https://doi.org/10.3390/s18041263 - 19 Apr 2018

Cited by 8 | Viewed by 4321

Abstract

In this paper, a support stiffness monitoring scheme based on torsional guided waves for detecting loss of rigidity in a support of cylindrical structures is presented. Poor support performance in cylindrical specimens such as a pipeline setup located in a sloping terrain may [...] Read more.

In this paper, a support stiffness monitoring scheme based on torsional guided waves for detecting loss of rigidity in a support of cylindrical structures is presented. Poor support performance in cylindrical specimens such as a pipeline setup located in a sloping terrain may produce a risky operation condition in terms of the installation integrity and the possibility of human casualties. The effects of changing the contact forces between support and the waveguide have been investigated by considering variations in the load between them. Fundamental torsional

T (0, 1)

mode is produced and launched by a magnetostrictive collar in a pitch-catch configuration to study the support effect in the wavepacket propagation. Several scenarios are studied by emulating an abnormal condition in the support of a dedicated test bench. Numerical results revealed

T (0, 1)

ultrasonic energy leakage in the form of

S H_{0}

bulk waves when a mechanical coupling between the cylindrical waveguide and support is yielded. Experimental results showed that the rate of ultrasonic energy leakage depends on the magnitude of the reaction forces between pipe and support; so different levels of attenuation of

T (0, 1)

mode will be produced with different mechanical contact conditions. Thus, it is possible to relate a measured attenuation to variations in the supports condition. Results of each scenarios are presented and discussed demonstrating the feasibility and potential of tracking of the amplitude of the

T (0, 1)

as an indicator of abnormal conditions in simple supports. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 62848 KiB

Open AccessArticle

Weak Defect Identification for Centrifugal Compressor Blade Crack Based on Pressure Sensors and Genetic Algorithm

by Hongkun Li¹, Changbo He^1,2,*, Reza Malekian^3,*

and Zhixiong Li⁴

¹ School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, China

² Laboratoire Vibrations Acoustique, University of Lyon, INSA-Lyon, LVA EA677, Villeurbanne F-69621, France

³ Department of Electrical, Electronic & Computer Engineering, University of Pretoria, Pretoria 0002, South Africa

⁴ School of Mechanical, Materials, Mechatronic and Biomedical Engineering, University of Wollongong, Wollongong, NSW 2522, Australia

Sensors 2018, 18(4), 1264; https://doi.org/10.3390/s18041264 - 19 Apr 2018

Cited by 16 | Viewed by 5864

Abstract

The Centrifugal compressor is a piece of key equipment for petrochemical factories. As the core component of a compressor, the blades suffer periodic vibration and flow induced excitation mechanism, which will lead to the occurrence of crack defect. Moreover, the induced blade defect [...] Read more.

The Centrifugal compressor is a piece of key equipment for petrochemical factories. As the core component of a compressor, the blades suffer periodic vibration and flow induced excitation mechanism, which will lead to the occurrence of crack defect. Moreover, the induced blade defect usually has a serious impact on the normal operation of compressors and the safety of operators. Therefore, an effective blade crack identification method is particularly important for the reliable operation of compressors. Conventional non-destructive testing and evaluation (NDT&E) methods can detect the blade defect effectively, however, the compressors should shut down during the testing process which is time-consuming and costly. In addition, it can be known these methods are not suitable for the long-term on-line condition monitoring and cannot identify the blade defect in time. Therefore, the effective on-line condition monitoring and weak defect identification method should be further studied and proposed. Considering the blade vibration information is difficult to measure directly, pressure sensors mounted on the casing are used to sample airflow pressure pulsation signal on-line near the rotating impeller for the purpose of monitoring the blade condition indirectly in this paper. A big problem is that the blade abnormal vibration amplitude induced by the crack is always small and this feature information will be much weaker in the pressure signal. Therefore, it is usually difficult to identify blade defect characteristic frequency embedded in pressure pulsation signal by general signal processing methods due to the weakness of the feature information and the interference of strong noise. In this paper, continuous wavelet transform (CWT) is used to pre-process the sampled signal first. Then, the method of bistable stochastic resonance (SR) based on Woods-Saxon and Gaussian (WSG) potential is applied to enhance the weak characteristic frequency contained in the pressure pulsation signal. Genetic algorithm (GA) is used to obtain optimal parameters for this SR system to improve its feature enhancement performance. The analysis result of experimental signal shows the validity of the proposed method for the enhancement and identification of weak defect characteristic. In the end, strain test is carried out to further verify the accuracy and reliability of the analysis result obtained by pressure pulsation signal. Full article

(This article belongs to the Special Issue Recent Advances in Artificial Intelligence and Deep Learning for Sensor Information Fusion)

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17 pages, 19938 KiB

Open AccessArticle

Wireless Sensor Network Congestion Control Based on Standard Particle Swarm Optimization and Single Neuron PID

by Xiaoping Yang, Xueying Chen, Riting Xia and Zhihong Qian^*

School of Communication Engineering, Jilin University, Changchun 130025, China

Sensors 2018, 18(4), 1265; https://doi.org/10.3390/s18041265 - 19 Apr 2018

Cited by 58 | Viewed by 5173

Abstract

Aiming at the problem of network congestion caused by the large number of data transmissions in wireless routing nodes of wireless sensor network (WSN), this paper puts forward an algorithm based on standard particle swarm–neural PID congestion control (PNPID). Firstly, PID control theory [...] Read more.

Aiming at the problem of network congestion caused by the large number of data transmissions in wireless routing nodes of wireless sensor network (WSN), this paper puts forward an algorithm based on standard particle swarm–neural PID congestion control (PNPID). Firstly, PID control theory was applied to the queue management of wireless sensor nodes. Then, the self-learning and self-organizing ability of neurons was used to achieve online adjustment of weights to adjust the proportion, integral and differential parameters of the PID controller. Finally, the standard particle swarm optimization to neural PID (NPID) algorithm of initial values of proportion, integral and differential parameters and neuron learning rates were used for online optimization. This paper describes experiments and simulations which show that the PNPID algorithm effectively stabilized queue length near the expected value. At the same time, network performance, such as throughput and packet loss rate, was greatly improved, which alleviated network congestion and improved network QoS. Full article

(This article belongs to the Section Sensor Networks)

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25 pages, 5516 KiB

Open AccessArticle

On Target Localization Using Combined RSS and AoA Measurements

by Slavisa Tomic^1,2,*,†

, Marko Beko^1,3,†

, Rui Dinis^4,5,† and Luís Bernardo^4,5,†

¹ COPELABS, Universidade Lusófona de Humanidades e Tecnologias, Campo Grande 376, 1749-024 Lisboa, Portugal

² ISR/IST, LARSyS, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal

³ CTS/UNINOVA, Campus da FCT/UNL, Monte de Caparica, 2829-516 Caparica, Portugal

⁴ Dep.^o de Eng.^a Electrotécnica, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal

⁵ Instituto de Telecomunicações, Av. Rovisco Pais 1, Torre Norte, piso 10, 1049-001 Lisboa, Portugal

^† Those authors contributed equally to this work.

Sensors 2018, 18(4), 1266; https://doi.org/10.3390/s18041266 - 19 Apr 2018

Cited by 69 | Viewed by 7567

Abstract

This work revises existing solutions for a problem of target localization in wireless sensor networks (WSNs), utilizing integrated measurements, namely received signal strength (RSS) and angle of arrival (AoA). The problem of RSS/AoA-based target localization became very popular in the research community recently, [...] Read more.

This work revises existing solutions for a problem of target localization in wireless sensor networks (WSNs), utilizing integrated measurements, namely received signal strength (RSS) and angle of arrival (AoA). The problem of RSS/AoA-based target localization became very popular in the research community recently, owing to its great applicability potential and relatively low implementation cost. Therefore, here, a comprehensive study of the state-of-the-art (SoA) solutions and their detailed analysis is presented. The beginning of this work starts by considering the SoA approaches based on convex relaxation techniques (more computationally complex in general), and it goes through other (less computationally complex) approaches, as well, such as the ones based on the generalized trust region sub-problems framework and linear least squares. Furthermore, a detailed analysis of the computational complexity of each solution is reviewed. Furthermore, an extensive set of simulation results is presented. Finally, the main conclusions are summarized, and a set of future aspects and trends that might be interesting for future research in this area is identified. Full article

(This article belongs to the Collection Positioning and Navigation)

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13 pages, 8573 KiB

Open AccessArticle

Plasmonic Optical Fiber Sensor Based on Double Step Growth of Gold Nano-Islands

by José M. M. M. De Almeida^1,2,*

, Helena Vasconcelos¹, Pedro A. S. Jorge¹

and Luis Coelho¹

¹ CAP/INESC TEC—Technology and Science and FCUP—Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal

² Department of Physics, School of Sciences and Technology, University of Trás-os-Montes e Alto Douro, 5001-801 Vila Real, Portugal

Sensors 2018, 18(4), 1267; https://doi.org/10.3390/s18041267 - 20 Apr 2018

Cited by 10 | Viewed by 5186

Abstract

It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on [...] Read more.

It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO₂) substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS) and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of ~60 nm/RIU was calculated, for the repeated dewetting, a value of ~186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency. Full article

(This article belongs to the Section Chemical Sensors)

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24 pages, 9821 KiB

Open AccessArticle

Estimation of Longitudinal Force and Sideslip Angle for Intelligent Four-Wheel Independent Drive Electric Vehicles by Observer Iteration and Information Fusion

by Te Chen¹

, Long Chen^1,2,*, Xing Xu^1,2, Yingfeng Cai^1,2, Haobin Jiang^1,2 and Xiaoqiang Sun^1,2

¹ School of Automotive and Traffic Engineering, Jiangsu University, Zhenjiang 212013, China

² Automotive Engineering Research Institute, Jiangsu University, Zhenjiang 212013, China

Sensors 2018, 18(4), 1268; https://doi.org/10.3390/s18041268 - 20 Apr 2018

Cited by 26 | Viewed by 5543

Abstract

Exact estimation of longitudinal force and sideslip angle is important for lateral stability and path-following control of four-wheel independent driven electric vehicle. This paper presents an effective method for longitudinal force and sideslip angle estimation by observer iteration and information fusion for four-wheel [...] Read more.

Exact estimation of longitudinal force and sideslip angle is important for lateral stability and path-following control of four-wheel independent driven electric vehicle. This paper presents an effective method for longitudinal force and sideslip angle estimation by observer iteration and information fusion for four-wheel independent drive electric vehicles. The electric driving wheel model is introduced into the vehicle modeling process and used for longitudinal force estimation, the longitudinal force reconstruction equation is obtained via model decoupling, the a Luenberger observer and high-order sliding mode observer are united for longitudinal force observer design, and the Kalman filter is applied to restrain the influence of noise. Via the estimated longitudinal force, an estimation strategy is then proposed based on observer iteration and information fusion, in which the Luenberger observer is applied to achieve the transcendental estimation utilizing less sensor measurements, the extended Kalman filter is used for a posteriori estimation with higher accuracy, and a fuzzy weight controller is used to enhance the adaptive ability of observer system. Simulations and experiments are carried out, and the effectiveness of proposed estimation method is verified. Full article

(This article belongs to the Special Issue Advances on Vehicular Networks: From Sensing to Autonomous Driving)

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15 pages, 2414 KiB

Open AccessArticle

Assessment of Dry Epidermal Electrodes for Long-Term Electromyography Measurements

by Momona Yamagami¹

, Keshia M. Peters², Ivana Milovanovic², Irene Kuang³, Zeyu Yang⁴, Nanshu Lu⁵ and Katherine M. Steele^2,*

¹ Department of Electrical Engineering, University of Washington, Seattle, WA 98195, USA

² Department of Mechanical Engineering, University of Washington, Seattle, WA 98195, USA

³ Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

⁴ Chengdu Rotex Technology Company Ltd., Chengdu 610041, China

⁵ Department of Biomedical Engineering, Aerospace Engineering and Engineering Mechanics, University of Texas, Austin, TX 78712, USA

Sensors 2018, 18(4), 1269; https://doi.org/10.3390/s18041269 - 20 Apr 2018

Cited by 41 | Viewed by 7792

Abstract

Commercially available electrodes can only provide quality surface electromyography (sEMG) measurements for a limited duration due to user discomfort and signal degradation, but in many applications, collecting sEMG data for a full day or longer is desirable to enhance clinical care. Few studies [...] Read more.

Commercially available electrodes can only provide quality surface electromyography (sEMG) measurements for a limited duration due to user discomfort and signal degradation, but in many applications, collecting sEMG data for a full day or longer is desirable to enhance clinical care. Few studies for long-term sEMG have assessed signal quality of electrodes using clinically relevant tests. The goal of this research was to evaluate flexible, gold-based epidermal sensor system (ESS) electrodes for long-term sEMG recordings. We collected sEMG and impedance data from eight subjects from ESS and standard clinical electrodes on upper extremity muscles during maximum voluntary isometric contraction tests, dynamic range of motion tests, the Jebsen Taylor Hand Function Test, and the Box & Block Test. Four additional subjects were recruited to test the stability of ESS signals over four days. Signals from the ESS and traditional electrodes were strongly correlated across tasks. Measures of signal quality, such as signal-to-noise ratio and signal-to-motion ratio, were also similar for both electrodes. Over the four-day trial, no significant decrease in signal quality was observed in the ESS electrodes, suggesting that thin, flexible electrodes may provide a robust tool that does not inhibit movement or irritate the skin for long-term measurements of muscle activity in rehabilitation and other applications. Full article

(This article belongs to the Special Issue Sensors for Health Monitoring and Disease Diagnosis)

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13 pages, 7088 KiB

Open AccessArticle

Flow Channel Influence of a Collision-Based Piezoelectric Jetting Dispenser on Jet Performance

by Can Zhou^1,2,3

, Guiling Deng^1,3,*, Junhui Li^1,3,* and Ji’an Duan^1,3,*

¹ School of Mechanical and Electronical Engineering, Central South University, No. 932, South Lushan Road, Changsha 410083, China

² School of Information Science and Engineering, No.932, South Lushan Road, Changsha 410083, China

³ State Key Laboratory of High Performance Complex Manufacturing, No. 932, South Lushan Road, Changsha 410083, China

Sensors 2018, 18(4), 1270; https://doi.org/10.3390/s18041270 - 20 Apr 2018

Cited by 28 | Viewed by 5686

Abstract

To improve the jet performance of a bi-piezoelectric jet dispenser, mathematical and simulation models were established according to the operating principle. In order to improve the accuracy and reliability of the simulation calculation, a viscosity model of the fluid was fitted to a [...] Read more.

To improve the jet performance of a bi-piezoelectric jet dispenser, mathematical and simulation models were established according to the operating principle. In order to improve the accuracy and reliability of the simulation calculation, a viscosity model of the fluid was fitted to a fifth-order function with shear rate based on rheological test data, and the needle displacement model was fitted to a nine-order function with time based on real-time displacement test data. The results show that jet performance is related to the diameter of the nozzle outlet and the cone angle of the nozzle, and the impacts of the flow channel structure were confirmed. The approach of numerical simulation is confirmed by the testing results of droplet volume. It will provide a reliable simulation platform for mechanical collision-based jet dispensing and a theoretical basis for micro jet valve design and improvement. Full article

(This article belongs to the Special Issue Piezoelectric Micro- and Nano-Devices)

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23 pages, 1592 KiB

Open AccessArticle

Detection of Anomalous Noise Events on Low-Capacity Acoustic Nodes for Dynamic Road Traffic Noise Mapping within an Hybrid WASN

by Rosa Ma Alsina-Pagès^*

, Francesc Alías

, Joan Claudi Socoró

and Ferran Orga

GTM—Grup de recerca en Tecnologies Mèdia, La Salle—Universitat Ramon Llull, Quatre Camins, 30, 08022 Barcelona, Spain

Sensors 2018, 18(4), 1272; https://doi.org/10.3390/s18041272 - 20 Apr 2018

Cited by 19 | Viewed by 7725

Abstract

One of the main aspects affecting the quality of life of people living in urban and suburban areas is the continuous exposure to high road traffic noise (RTN) levels. Nowadays, thanks to Wireless Acoustic Sensor Networks (WASN) noise in Smart Cities has started [...] Read more.

One of the main aspects affecting the quality of life of people living in urban and suburban areas is the continuous exposure to high road traffic noise (RTN) levels. Nowadays, thanks to Wireless Acoustic Sensor Networks (WASN) noise in Smart Cities has started to be automatically mapped. To obtain a reliable picture of the RTN, those anomalous noise events (ANE) unrelated to road traffic (sirens, horns, people, etc.) should be removed from the noise map computation by means of an Anomalous Noise Event Detector (ANED). In Hybrid WASNs, with master-slave architecture, ANED should be implemented in both high-capacity (Hi-Cap) and low-capacity (Lo-Cap) sensors, following the same principle to obtain consistent results. This work presents an ANED version to run in real-time on

μ

Controller-based Lo-Cap sensors of a hybrid WASN, discriminating RTN from ANE through their Mel-based spectral energy differences. The experiments, considering 9 h and 8 min of real-life acoustic data from both urban and suburban environments, show the feasibility of the proposal both in terms of computational load and in classification accuracy. Specifically, the ANED Lo-Cap requires around

\frac{1}{6}

of the computational load of the ANED Hi-Cap, while classification accuracies are slightly lower (around 10%). However, preliminary analyses show that these results could be improved in around 4% in the future by means of considering optimal frequency selection. Full article

(This article belongs to the Special Issue Selected Papers from the 4th International Electronic Conference on Sensors and Applications)

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16 pages, 7237 KiB

Open AccessArticle

Two New Shrinking-Circle Methods for Source Localization Based on TDoA Measurements

by Mingzhi Luo, Xiang Chen^*, Shuai Cao and Xu Zhang

Department of Electronic Science and Technology, University of Science and Technology of China (USTC), Hefei 230026, China

Sensors 2018, 18(4), 1274; https://doi.org/10.3390/s18041274 - 20 Apr 2018

Cited by 12 | Viewed by 5200

Abstract

Time difference of arrival (TDoA) measurement is a promising approach for target localization based on a set of nodes with known positions, with high accuracy and low complexity. Common localization algorithms include the maximum-likelihood, non-linear least-squares and weighted least-squares methods. These methods have [...] Read more.

Time difference of arrival (TDoA) measurement is a promising approach for target localization based on a set of nodes with known positions, with high accuracy and low complexity. Common localization algorithms include the maximum-likelihood, non-linear least-squares and weighted least-squares methods. These methods have shortcomings such as high computational complexity, requiring an initial guess position, or having difficulty in finding the optimal solution. From the point of view of geometrical analysis, this study proposes two new shrinking-circle methods (SC-1 and SC-2) to solve the TDoA-based localization problem in a two-dimensional (2-D) space. In both methods, an optimal radius is obtained by shrinking the radius with a dichotomy algorithm, and the position of the target is determined by the optimal radius. The difference of the two methods is that a distance parameter is defined in SC-1, while an error function is introduced in SC-2 to guide the localization procedure. Simulations and indoor-localization experiments based on acoustic transducers were conducted to compare the performance differences between the proposed methods, algorithms based on weighted least-squares as well as the conventional shrinking-circle method. The experimental results demonstrate that the proposed methods can realize high-precision target localization based on TDoA measurements using three nodes, and have the advantages of speed and high robustness. Full article

(This article belongs to the Special Issue Applications of Wireless Sensors in Localization and Tracking)

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14 pages, 1113 KiB

Open AccessArticle

Dual-Task Elderly Gait of Prospective Fallers and Non-Fallers: A Wearable-Sensor Based Analysis

by Jennifer Howcroft¹, Edward D. Lemaire^2,3

, Jonathan Kofman^1,* and William E. McIlroy⁴

¹ Department of Systems Design Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada

² Centre for Rehabilitation Research and Development, Ottawa Hospital Research Institute, Ottawa, ON K1H 8M2, Canada

³ Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada

⁴ Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1, Canada

Sensors 2018, 18(4), 1275; https://doi.org/10.3390/s18041275 - 21 Apr 2018

Cited by 28 | Viewed by 6619

Abstract

Wearable sensors could facilitate point of care, clinically feasible assessments of dynamic stability and associated fall risk through an assessment of single-task (ST) and dual-task (DT) walking. This study investigated gait changes between ST and DT walking and between older adult prospective fallers [...] Read more.

Wearable sensors could facilitate point of care, clinically feasible assessments of dynamic stability and associated fall risk through an assessment of single-task (ST) and dual-task (DT) walking. This study investigated gait changes between ST and DT walking and between older adult prospective fallers and non-fallers. The results were compared to a study based on retrospective fall occurrence. Seventy-five individuals (75.2 ± 6.6 years; 47 non-fallers, 28 fallers; 6 month prospective fall occurrence) walked 7.62 m under ST and DT conditions while wearing pressure-sensing insoles and accelerometers at the head, pelvis, and on both shanks. DT-induced gait changes included changes in temporal measures, centre of pressure (CoP) path stance deviations and coefficient of variation, acceleration descriptive statistics, Fast Fourier Transform (FFT) first quartile, ratio of even to odd harmonics, and maximum Lyapunov exponent. Compared to non-fallers, prospective fallers had significantly lower DT anterior–posterior CoP path stance coefficient of variation, DT head anterior–posterior FFT first quartile, ST left shank medial–lateral FFT first quartile, and ST right shank superior maximum acceleration. DT-induced gait changes were consistent regardless of faller status or when the fall occurred (retrospective or prospective). Gait differences between fallers and non-fallers were dependent on retrospective or prospective faller identification. Full article

(This article belongs to the Special Issue Point of Care Sensors)

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14 pages, 2719 KiB

Open AccessArticle

Synchronized High-Speed Vision Sensor Network for Expansion of Field of View

by Akihito Noda^1,*

, Satoshi Tabata², Masatoshi Ishikawa³ and Yuji Yamakawa⁴

¹ Department of Mechatronics, Nanzan University, 18 Yamazato-cho, Showa-ku, Nagoya 466-8673, Japan

² Department of Information Physics and Computing, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

³ Department of Creative Informatics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

⁴ Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan

Sensors 2018, 18(4), 1276; https://doi.org/10.3390/s18041276 - 21 Apr 2018

Cited by 2 | Viewed by 6712

Abstract

We propose a 500-frames-per-second high-speed vision (HSV) sensor network that acquires frames at a timing that is precisely synchronized across the network. Multiple vision sensor nodes, individually comprising a camera and a PC, are connected via Ethernet for data transmission and for clock [...] Read more.

We propose a 500-frames-per-second high-speed vision (HSV) sensor network that acquires frames at a timing that is precisely synchronized across the network. Multiple vision sensor nodes, individually comprising a camera and a PC, are connected via Ethernet for data transmission and for clock synchronization. A network of synchronized HSV sensors provides a significantly expanded field-of-view compared with that of each individual HSV sensor. In the proposed system, the shutter of each camera is controlled based on the clock of the PC locally provided inside the node, and the shutters are globally synchronized using the Precision Time Protocol (PTP) over the network. A theoretical analysis and experiment results indicate that the shutter trigger skew among the nodes is a few tens of microseconds at most, which is significantly smaller than the frame interval of 1000-fps-class high-speed cameras. Experimental results obtained with the proposed system comprising four nodes demonstrated the ability to capture the propagation of a small displacement along a large-scale structure. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan 2017)

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18 pages, 5456 KiB

Open AccessArticle

Sigma Routing Metric for RPL Protocol

by Paul Sanmartin^1,2,*

, Aldo Rojas¹, Luis Fernandez¹, Karen Avila²

, Daladier Jabba²

and Sebastian Valle²

¹ Departamento de Ingeniería de Sistemas, Universidad Simón Bolívar, Barranquilla 080001, Colombia

² Departamento de Ingeniería de Sistemas, Universidad del Norte, Barranquilla 080001, Colombia

Sensors 2018, 18(4), 1277; https://doi.org/10.3390/s18041277 - 21 Apr 2018

Cited by 65 | Viewed by 8336

Abstract

This paper presents the adaptation of a specific metric for the RPL protocol in the objective function MRHOF. Among the functions standardized by IETF, we find OF0, which is based on the minimum hop count, as well as MRHOF, which is based on [...] Read more.

This paper presents the adaptation of a specific metric for the RPL protocol in the objective function MRHOF. Among the functions standardized by IETF, we find OF0, which is based on the minimum hop count, as well as MRHOF, which is based on the Expected Transmission Count (ETX). However, when the network becomes denser or the number of nodes increases, both OF0 and MRHOF introduce long hops, which can generate a bottleneck that restricts the network. The adaptation is proposed to optimize both OFs through a new routing metric. To solve the above problem, the metrics of the minimum number of hops and the ETX are combined by designing a new routing metric called SIGMA-ETX, in which the best route is calculated using the standard deviation of ETX values between each node, as opposed to working with the ETX average along the route. This method ensures a better routing performance in dense sensor networks. The simulations are done through the Cooja simulator, based on the Contiki operating system. The simulations showed that the proposed optimization outperforms at a high margin in both OF0 and MRHOF, in terms of network latency, packet delivery ratio, lifetime, and power consumption. Full article

(This article belongs to the Special Issue Low Energy Wireless Sensor Networks: Protocols, Architectures and Solutions)

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17 pages, 3217 KiB

Open AccessArticle

Data Decomposition Techniques with Multi-Scale Permutation Entropy Calculations for Bearing Fault Diagnosis

by Muhammad Naveed Yasir

and Bong-Hwan Koh^*

Department of Mechanical, Robotics and Energy Engineering, Dongguk University-Seoul, 30 Pildong-ro 1 gil, Jung-gu, Seoul 04620, Korea

Sensors 2018, 18(4), 1278; https://doi.org/10.3390/s18041278 - 21 Apr 2018

Cited by 33 | Viewed by 5753

Abstract

This paper presents the local mean decomposition (LMD) integrated with multi-scale permutation entropy (MPE), also known as LMD-MPE, to investigate the rolling element bearing (REB) fault diagnosis from measured vibration signals. First, the LMD decomposed the vibration data or acceleration measurement into separate [...] Read more.

This paper presents the local mean decomposition (LMD) integrated with multi-scale permutation entropy (MPE), also known as LMD-MPE, to investigate the rolling element bearing (REB) fault diagnosis from measured vibration signals. First, the LMD decomposed the vibration data or acceleration measurement into separate product functions that are composed of both amplitude and frequency modulation. MPE then calculated the statistical permutation entropy from the product functions to extract the nonlinear features to assess and classify the condition of the healthy and damaged REB system. The comparative experimental results of the conventional LMD-based multi-scale entropy and MPE were presented to verify the authenticity of the proposed technique. The study found that LMD-MPE’s integrated approach provides reliable, damage-sensitive features when analyzing the bearing condition. The results of REB experimental datasets show that the proposed approach yields more vigorous outcomes than existing methods. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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13 pages, 8953 KiB

Open AccessArticle

A Wearable Gait Phase Detection System Based on Force Myography Techniques

by Xianta Jiang

, Kelvin H.T. Chu

, Mahta Khoshnam

and Carlo Menon^*

MENRVA lab, Schools of Mechatronic Systems and Engineering Science, Simon Fraser University, Metro Vancouver, BC V5A 1S6, Canada

Sensors 2018, 18(4), 1279; https://doi.org/10.3390/s18041279 - 21 Apr 2018

Cited by 50 | Viewed by 7531

Abstract

(1) Background: Quantitative evaluation of gait parameters can provide useful information for constructing individuals’ gait profile, diagnosing gait abnormalities, and better planning of rehabilitation schemes to restore normal gait pattern. Objective determination of gait phases in a gait cycle is a key requirement [...] Read more.

(1) Background: Quantitative evaluation of gait parameters can provide useful information for constructing individuals’ gait profile, diagnosing gait abnormalities, and better planning of rehabilitation schemes to restore normal gait pattern. Objective determination of gait phases in a gait cycle is a key requirement in gait analysis applications; (2) Methods: In this study, the feasibility of using a force myography-based technique for a wearable gait phase detection system is explored. In this regard, a force myography band is developed and tested with nine participants walking on a treadmill. The collected force myography data are first examined sample-by-sample and classified into four phases using Linear Discriminant Analysis. The gait phase events are then detected from these classified samples using a set of supervisory rules; (3) Results: The results show that the force myography band can correctly detect more than 99.9% of gait phases with zero insertions and only four deletions over 12,965 gait phase segments. The average temporal error of gait phase detection is 55.2 ms, which translates into 2.1% error with respect to the corresponding labelled stride duration; (4) Conclusions: This proof-of-concept study demonstrates the feasibility of force myography techniques as viable solutions in developing wearable gait phase detection systems. Full article

(This article belongs to the Section Biosensors)

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15 pages, 1438 KiB

Open AccessArticle

OFDM with Index Modulation for Asynchronous mMTC Networks

by Seda Doğan^1,*

, Armed Tusha¹ and Hüseyin Arslan^1,2

¹ Department of Electrical and Electronics Engineering, Istanbul Medipol University, 34810 Istanbul, Turkey

² Department of Electrical Engineering, University of South Florida, Tampa, FL 33620, USA

Sensors 2018, 18(4), 1280; https://doi.org/10.3390/s18041280 - 21 Apr 2018

Cited by 20 | Viewed by 10226

Abstract

One of the critical missions for next-generation wireless communication systems is to fulfill the high demand for massive Machine-Type Communications (mMTC). In mMTC systems, a sporadic transmission is performed between machine users and base station (BS). Lack of coordination between the users and [...] Read more.

One of the critical missions for next-generation wireless communication systems is to fulfill the high demand for massive Machine-Type Communications (mMTC). In mMTC systems, a sporadic transmission is performed between machine users and base station (BS). Lack of coordination between the users and BS in time destroys orthogonality between the subcarriers, and causes inter-carrier interference (ICI). Therefore, providing services to asynchronous massive machine users is a major challenge for Orthogonal Frequency Division Multiplexing (OFDM). In this study, OFDM with index modulation (OFDM-IM) is proposed as an eligible solution to alleviate ICI caused by asynchronous transmission in uncoordinated mMTC networks. In OFDM-IM, data transmission is performed not only by modulated subcarriers but also by the indices of active subcarriers. Unlike classical OFDM, fractional subcarrier activation leads to less ICI in OFDM-IM technology. A novel subcarrier mapping scheme (SMS) named as Inner Subcarrier Activation is proposed to further alleviate adjacent user interference in asynchronous OFDM-IM-based systems. ISA reduces inter-user interference since it gives more activation priority to inner subcarriers compared with the existing SMS-s. The superiority of the proposed SMS is shown through both theoretical analysis and computer-based simulations in comparison to existing mapping schemes for asynchronous systems. Full article

(This article belongs to the Special Issue Emerging Methodologies and Practical Solutions for M2M and D2D Communications in the Internet of Things Era)

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20 pages, 2136 KiB

Open AccessArticle

Enhanced Pedestrian Navigation Based on Course Angle Error Estimation Using Cascaded Kalman Filters

by Jin Woo Song¹

and Chan Gook Park^2,*

¹ School of Intelligent Mechatronic Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea

² Department of Mechanical and Aerospace Engineering/ASRI, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea

Sensors 2018, 18(4), 1281; https://doi.org/10.3390/s18041281 - 21 Apr 2018

Cited by 26 | Viewed by 7058

Abstract

An enhanced pedestrian dead reckoning (PDR) based navigation algorithm, which uses two cascaded Kalman filters (TCKF) for the estimation of course angle and navigation errors, is proposed. The proposed algorithm uses a foot-mounted inertial measurement unit (IMU), waist-mounted magnetic sensors, and a zero [...] Read more.

An enhanced pedestrian dead reckoning (PDR) based navigation algorithm, which uses two cascaded Kalman filters (TCKF) for the estimation of course angle and navigation errors, is proposed. The proposed algorithm uses a foot-mounted inertial measurement unit (IMU), waist-mounted magnetic sensors, and a zero velocity update (ZUPT) based inertial navigation technique with TCKF. The first stage filter estimates the course angle error of a human, which is closely related to the heading error of the IMU. In order to obtain the course measurements, the filter uses magnetic sensors and a position-trace based course angle. For preventing magnetic disturbance from contaminating the estimation, the magnetic sensors are attached to the waistband. Because the course angle error is mainly due to the heading error of the IMU, and the characteristic error of the heading angle is highly dependent on that of the course angle, the estimated course angle error is used as a measurement for estimating the heading error in the second stage filter. At the second stage, an inertial navigation system-extended Kalman filter-ZUPT (INS-EKF-ZUPT) method is adopted. As the heading error is estimated directly by using course-angle error measurements, the estimation accuracy for the heading and yaw gyro bias can be enhanced, compared with the ZUPT-only case, which eventually enhances the position accuracy more efficiently. The performance enhancements are verified via experiments, and the way-point position error for the proposed method is compared with those for the ZUPT-only case and with other cases that use ZUPT and various types of magnetic heading measurements. The results show that the position errors are reduced by a maximum of 90% compared with the conventional ZUPT based PDR algorithms. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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27 pages, 2917 KiB

Open AccessArticle

A Low Power IoT Sensor Node Architecture for Waste Management Within Smart Cities Context

by Matteo Cerchecci, Francesco Luti, Alessandro Mecocci, Stefano Parrino, Giacomo Peruzzi and Alessandro Pozzebon^*

Department of Information Engineering and Mathematical Sciences, University of Siena, 53100 Siena, Italy

Sensors 2018, 18(4), 1282; https://doi.org/10.3390/s18041282 - 21 Apr 2018

Cited by 128 | Viewed by 21708

Abstract

This paper focuses on the realization of an Internet of Things (IoT) architecture to optimize waste management in the context of Smart Cities. In particular, a novel typology of sensor node based on the use of low cost and low power components is [...] Read more.

This paper focuses on the realization of an Internet of Things (IoT) architecture to optimize waste management in the context of Smart Cities. In particular, a novel typology of sensor node based on the use of low cost and low power components is described. This node is provided with a single-chip microcontroller, a sensor able to measure the filling level of trash bins using ultrasounds and a data transmission module based on the LoRa LPWAN (Low Power Wide Area Network) technology. Together with the node, a minimal network architecture was designed, based on a LoRa gateway, with the purpose of testing the IoT node performances. Especially, the paper analyzes in detail the node architecture, focusing on the energy saving technologies and policies, with the purpose of extending the batteries lifetime by reducing power consumption, through hardware and software optimization. Tests on sensor and radio module effectiveness are also presented. Full article

(This article belongs to the Special Issue Smart Cities)

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14 pages, 2324 KiB

Open AccessArticle

Quantitative Comparison of Protein Adsorption and Conformational Changes on Dielectric-Coated Nanoplasmonic Sensing Arrays

by Abdul Rahim Ferhan¹, Joshua A. Jackman¹, Tun Naw Sut¹ and Nam-Joon Cho^1,2,*

¹ School of Materials Science and Engineering and Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive 637553, Singapore

² School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive 637459, Singapore

Sensors 2018, 18(4), 1283; https://doi.org/10.3390/s18041283 - 22 Apr 2018

Cited by 20 | Viewed by 6780

Abstract

Nanoplasmonic sensors are a popular, surface-sensitive measurement tool to investigate biomacromolecular interactions at solid-liquid interfaces, opening the door to a wide range of applications. In addition to high surface sensitivity, nanoplasmonic sensors have versatile surface chemistry options as plasmonic metal nanoparticles can be [...] Read more.

Nanoplasmonic sensors are a popular, surface-sensitive measurement tool to investigate biomacromolecular interactions at solid-liquid interfaces, opening the door to a wide range of applications. In addition to high surface sensitivity, nanoplasmonic sensors have versatile surface chemistry options as plasmonic metal nanoparticles can be coated with thin dielectric layers. Within this scope, nanoplasmonic sensors have demonstrated promise for tracking protein adsorption and substrate-induced conformational changes on oxide film-coated arrays, although existing studies have been limited to single substrates. Herein, we investigated human serum albumin (HSA) adsorption onto silica- and titania-coated arrays of plasmonic gold nanodisks by localized surface plasmon resonance (LSPR) measurements and established an analytical framework to compare responses across multiple substrates with different sensitivities. While similar responses were recorded on the two substrates for HSA adsorption under physiologically-relevant ionic strength conditions, distinct substrate-specific behavior was observed at lower ionic strength conditions. With decreasing ionic strength, larger measurement responses occurred for HSA adsorption onto silica surfaces, whereas HSA adsorption onto titania surfaces occurred independently of ionic strength condition. Complementary quartz crystal microbalance-dissipation (QCM-D) measurements were also performed, and the trend in adsorption behavior was similar. Of note, the magnitudes of the ionic strength-dependent LSPR and QCM-D measurement responses varied, and are discussed with respect to the measurement principle and surface sensitivity of each technique. Taken together, our findings demonstrate how the high surface sensitivity of nanoplasmonic sensors can be applied to quantitatively characterize protein adsorption across multiple surfaces, and outline broadly-applicable measurement strategies for biointerfacial science applications. Full article

(This article belongs to the Special Issue Biosensing for Interfacial Science)

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21 pages, 16238 KiB

Open AccessArticle

Detecting Inspection Objects of Power Line from Cable Inspection Robot LiDAR Data

by Xinyan Qin¹, Gongping Wu^1,*, Jin Lei^1,2,*

, Fei Fan¹ and Xuhui Ye¹

¹ Department of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China

² Key Laboratory of Hydraulic Machinery Transients, Wuhan University, Ministry of Education, Wuhan 430072, China

Sensors 2018, 18(4), 1284; https://doi.org/10.3390/s18041284 - 22 Apr 2018

Cited by 39 | Viewed by 7208

Abstract

Power lines are extending to complex environments (e.g., lakes and forests), and the distribution of power lines in a tower is becoming complicated (e.g., multi-loop and multi-bundle). Additionally, power line inspection is becoming heavier and more difficult. Advanced LiDAR technology is increasingly being [...] Read more.

Power lines are extending to complex environments (e.g., lakes and forests), and the distribution of power lines in a tower is becoming complicated (e.g., multi-loop and multi-bundle). Additionally, power line inspection is becoming heavier and more difficult. Advanced LiDAR technology is increasingly being used to solve these difficulties. Based on precise cable inspection robot (CIR) LiDAR data and the distinctive position and orientation system (POS) data, we propose a novel methodology to detect inspection objects surrounding power lines. The proposed method mainly includes four steps: firstly, the original point cloud is divided into single-span data as a processing unit; secondly, the optimal elevation threshold is constructed to remove ground points without the existing filtering algorithm, improving data processing efficiency and extraction accuracy; thirdly, a single power line and its surrounding data can be respectively extracted by a structured partition based on a POS data (SPPD) algorithm from “layer” to “block” according to power line distribution; finally, a partition recognition method is proposed based on the distribution characteristics of inspection objects, highlighting the feature information and improving the recognition effect. The local neighborhood statistics and the 3D region growing method are used to recognize different inspection objects surrounding power lines in a partition. Three datasets were collected by two CIR LIDAR systems in our study. The experimental results demonstrate that an average 90.6% accuracy and average 98.2% precision at the point cloud level can be achieved. The successful extraction indicates that the proposed method is feasible and promising. Our study can be used to obtain precise dimensions of fittings for modeling, as well as automatic detection and location of security risks, so as to improve the intelligence level of power line inspection. Full article

(This article belongs to the Special Issue Automatic Target Recognition of High Resolution SAR/ISAR Images)

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21 pages, 3214 KiB

Open AccessArticle

Geriatric Helper: An mHealth Application to Support Comprehensive Geriatric Assessment

by Samuel Silva^1,2,*,†

, Rafael Felgueiras^1,† and Ilídio C. Oliveira^1,2

¹ Department of Electronics, Telecommunications and Informatics, University of Aveiro, 3810-193 Aveiro, Portugal

² Institute of Electronics and Informatics Engineering of Aveiro, University of Aveiro, 3810-193 Aveiro, Portugal

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1285; https://doi.org/10.3390/s18041285 - 22 Apr 2018

Cited by 11 | Viewed by 6713

Abstract

The Comprehensive Geriatric Assessment (CGA) is a multidisciplinary diagnosis approach that considers several dimensions of fragility in older adults to develop an individualized plan to improve their overall health. Despite the evidence of its positive impact, CGA is still applied by a reduced [...] Read more.

The Comprehensive Geriatric Assessment (CGA) is a multidisciplinary diagnosis approach that considers several dimensions of fragility in older adults to develop an individualized plan to improve their overall health. Despite the evidence of its positive impact, CGA is still applied by a reduced number of professionals in geriatric care in many countries, mostly using a paper-based approach. In this context, we collaborate with clinicians to bring CGA to the attention of more healthcare professionals and to enable its easier application in clinical settings by proposing a mobile application, Geriatric Helper, to act as a pocket guide that is easy to update remotely with up-to-date information, and that acts as a tool for conducting CGA. This approach reduces the time spent on retrieving the scales documentation, the overhead of calculating the results, and works as a source of information for non-specialists. Geriatric Helper is a tool for the health professionals developed considering an iterative, User-Centred Design approach, with extensive contributions from a broad set of users including domain experts, resulting in a highly usable and accepted system. Geriatric Helper is currently being tested in Portuguese healthcare units allowing for any clinician to apply the otherwise experts-limited geriatric assessment. Full article

(This article belongs to the Special Issue Selected Papers from 7th EAI International Conference on Wireless Mobile Communication and Healthcare)

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22 pages, 4868 KiB

Open AccessArticle

Nonlinear Blind Compensation for Array Signal Processing Application

by Jialu Huang

, Hong Ma, Jiang Jin and Hua Zhang^*

School of Electronic Information and Communications, Huazhong University of Science & Technology, 1037 Luoyu Road, Wuhan 430074, China

Sensors 2018, 18(4), 1286; https://doi.org/10.3390/s18041286 - 22 Apr 2018

Cited by 4 | Viewed by 4611

Abstract

Recently, nonlinear blind compensation technique has attracted growing attention in array signal processing application. However, due to the nonlinear distortion stemming from array receiver which consists of multi-channel radio frequency (RF) front-ends, it is too difficult to estimate the parameters of array signal [...] Read more.

Recently, nonlinear blind compensation technique has attracted growing attention in array signal processing application. However, due to the nonlinear distortion stemming from array receiver which consists of multi-channel radio frequency (RF) front-ends, it is too difficult to estimate the parameters of array signal accurately. A novel nonlinear blind compensation algorithm aims at the nonlinearity mitigation of array receiver and its spurious-free dynamic range (SFDR) improvement, which will be more precise to estimate the parameters of target signals such as their two-dimensional directions of arrival (2-D DOAs). Herein, the suggested method is designed as follows: the nonlinear model parameters of any channel of RF front-end are extracted to synchronously compensate the nonlinear distortion of the entire receiver. Furthermore, a verification experiment on the array signal from a uniform circular array (UCA) is adopted to testify the validity of our approach. The real-world experimental results show that the SFDR of the receiver is enhanced, leading to a significant improvement of the 2-D DOAs estimation performance for weak target signals. And these results demonstrate that our nonlinear blind compensation algorithm is effective to estimate the parameters of weak array signal in concomitance with strong jammers. Full article

(This article belongs to the Special Issue Recent Advances in Array Processing for Wireless Applications)

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16 pages, 861 KiB

Open AccessArticle

How to Stop Disagreeing and Start Cooperatingin the Presence of Asymmetric Packet Loss

by Oscar Morales-Ponce^1,†

, Elad M. Schiller^2,*,†

and Paolo Falcone^3,†

¹ Department of Computer Engineering and Computer Science, California State University Long Beach, Long Beach, CA, 90840, USA

² Department of Computer Science and Engineering, Chalmers University of Technology, Göteborg, Sweden

³ Department of Electrical Engineering, Chalmers University of Technology, Göteborg, Sweden

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1287; https://doi.org/10.3390/s18041287 - 22 Apr 2018

Cited by 2 | Viewed by 3986

Abstract

We consider the design of a disagreement correction protocol in multi-vehicle systems. Vehicles broadcast in real-time vital information such as position, direction, speed, acceleration, intention, etc. This information is then used to identify the risks and adapt their trajectory to maintain the highest [...] Read more.

We consider the design of a disagreement correction protocol in multi-vehicle systems. Vehicles broadcast in real-time vital information such as position, direction, speed, acceleration, intention, etc. This information is then used to identify the risks and adapt their trajectory to maintain the highest performance without compromising the safety. To minimize the risk due to the use of inconsistent information, all cooperating vehicles must agree whether to use the exchanged information to operate in a cooperative mode or use the only local information to operate in an autonomous mode. However, since wireless communications are prone to failures, it is impossible to deterministically reach an agreement. Therefore, any protocol will exhibit necessary disagreement periods. In this paper, we investigate whether vehicles can still cooperate despite communication failures even in the scenario where communication is suddenly not available. We present a deterministic protocol that allows all participants to either operate a cooperative mode when vehicles can exchange all the information in a timely manner or operate in autonomous mode when messages are lost. We show formally that the disagreement time is bounded by the time that the communication channel requires to deliver messages and validate our protocol using NS-3 simulations. We explain how the proposed solution can be used in vehicular platooning to attain high performance and still guarantee high safety standards despite communication failures. Full article

(This article belongs to the Special Issue Dependable Monitoring in Wireless Sensor Networks)

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24 pages, 1902 KiB

Open AccessArticle

Evolutionary Design of Convolutional Neural Networks for Human Activity Recognition in Sensor-Rich Environments

by Alejandro Baldominos^*

, Yago Saez

and Pedro Isasi

Computer Science Department, Universidad Carlos III de Madrid, 28911 Leganes, Spain

Sensors 2018, 18(4), 1288; https://doi.org/10.3390/s18041288 - 23 Apr 2018

Cited by 33 | Viewed by 7046

Abstract

Human activity recognition is a challenging problem for context-aware systems and applications. It is gaining interest due to the ubiquity of different sensor sources, wearable smart objects, ambient sensors, etc. This task is usually approached as a supervised machine learning problem, where a [...] Read more.

Human activity recognition is a challenging problem for context-aware systems and applications. It is gaining interest due to the ubiquity of different sensor sources, wearable smart objects, ambient sensors, etc. This task is usually approached as a supervised machine learning problem, where a label is to be predicted given some input data, such as the signals retrieved from different sensors. For tackling the human activity recognition problem in sensor network environments, in this paper we propose the use of deep learning (convolutional neural networks) to perform activity recognition using the publicly available OPPORTUNITY dataset. Instead of manually choosing a suitable topology, we will let an evolutionary algorithm design the optimal topology in order to maximize the classification F1 score. After that, we will also explore the performance of committees of the models resulting from the evolutionary process. Results analysis indicates that the proposed model was able to perform activity recognition within a heterogeneous sensor network environment, achieving very high accuracies when tested with new sensor data. Based on all conducted experiments, the proposed neuroevolutionary system has proved to be able to systematically find a classification model which is capable of outperforming previous results reported in the state-of-the-art, showing that this approach is useful and improves upon previously manually-designed architectures. Full article

(This article belongs to the Special Issue Wireless Sensors Networks in Activity Detection and Context Awareness)

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11 pages, 1495 KiB

Open AccessArticle

Microplate Chemiluminescent Assay for DNA Detection Using Apoperoxidase-Oligonucleotide as Capture Conjugate and HRP-Streptavidin Signaling System

by Ivan Sakharov

Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia

Sensors 2018, 18(4), 1289; https://doi.org/10.3390/s18041289 - 23 Apr 2018

Cited by 5 | Viewed by 5955

Abstract

A covalent conjugate of horseradish apoperoxidase and amino-containing oligonucleotide was synthesized for the first time. Using the obtained conjugate as a capture reagent chemiluminescent microtiter plate-based assay for detection of 35-mer fragment of hepatitis B virus (HBV) DNA (proof-of-concept analyte) was developed. To [...] Read more.

A covalent conjugate of horseradish apoperoxidase and amino-containing oligonucleotide was synthesized for the first time. Using the obtained conjugate as a capture reagent chemiluminescent microtiter plate-based assay for detection of 35-mer fragment of hepatitis B virus (HBV) DNA (proof-of-concept analyte) was developed. To detect the target DNA, a signaling system consisted of biotinylated reporter oligonucleotide and HRP-streptavidin conjugate was used. The high sensitivity of the assay was due to the enhanced chemiluminescence reaction, where 3-(10′-phenothiazinyl)propane-1-sulfonate/N-morpholinopyridine pair was used as an enhancer. Under the optimized conditions the limit of detection and a working range of the assay were 3 pM and 6–100 pM, respectively. The assay sensitivity was 1.6 × 10⁵ RLU/pM of target. The coefficient of variation (CV) for determination of HBV DNA within the working range was lower than 6%. Full article

(This article belongs to the Special Issue Recent Advances in Nucleic Acid Sensors)

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12 pages, 1613 KiB

Open AccessArticle

Proximity-Induced Artefacts in Magnetic Imaging with Nitrogen-Vacancy Ensembles in Diamond

by Jean-Philippe Tetienne^1,*

, David A. Broadway^1,2

, Scott E. Lillie^1,2, Nikolai Dontschuk²

, Tokuyuki Teraji³, Liam T. Hall¹

, Alastair Stacey², David A. Simpson¹ and Lloyd C. L. Hollenberg^1,2

¹ School of Physics, The University of Melbourne, Melbourne 3010, Australia

² Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Melbourne 3010, Australia

³ National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan

Sensors 2018, 18(4), 1290; https://doi.org/10.3390/s18041290 - 23 Apr 2018

Cited by 21 | Viewed by 8012

Abstract

Magnetic imaging with ensembles of nitrogen-vacancy (NV) centres in diamond is a recently developed technique that allows for quantitative vector field mapping. Here we uncover a source of artefacts in the measured magnetic field in situations where the magnetic sample is placed in [...] Read more.

Magnetic imaging with ensembles of nitrogen-vacancy (NV) centres in diamond is a recently developed technique that allows for quantitative vector field mapping. Here we uncover a source of artefacts in the measured magnetic field in situations where the magnetic sample is placed in close proximity (a few tens of nm) to the NV sensing layer. Using magnetic nanoparticles as a test sample, we find that the measured field deviates significantly from the calculated field, in shape, amplitude and even in sign. By modelling the full measurement process, we show that these discrepancies are caused by the limited measurement range of NV sensors combined with the finite spatial resolution of the optical readout. We numerically investigate the role of the stand-off distance to identify an artefact-free regime, and discuss an application to ultrathin materials. This work provides a guide to predict and mitigate proximity-induced artefacts that can arise in NV-based wide-field magnetic imaging, and also demonstrates that the sensitivity of these artefacts to the sample can make them a useful tool for magnetic characterisation. Full article

(This article belongs to the Special Issue Sensors Based on Quantum Phenomena)

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12 pages, 664 KiB

Open AccessArticle

On the Energy Efficiency of On-Off Keying Transmitters with Two Distinct Types of Batteries

by Tingting Shen, Tao Wang^*, Yanzan Sun^*, Yating Wu and Yanliang Jin

Shanghai Institute for Advanced Communication and Data Science, Key laboratory of Specialty Fiber Optics and Optical Access Networks, Joint International Research Laboratory of Specialty Fiber Optics and Advanced Communication, Shanghai University, Shanghai 200444, China

Sensors 2018, 18(4), 1291; https://doi.org/10.3390/s18041291 - 23 Apr 2018

Cited by 7 | Viewed by 4599

Abstract

As nodes in wireless sensor networks are usually powered by nonrenewable batteries, energy efficient design becomes critical. This paper considers a battery-powered transmitter using on-off keying (OOK) modulation and studies its energy efficiency in terms of the battery’s energy consumption for per bit [...] Read more.

As nodes in wireless sensor networks are usually powered by nonrenewable batteries, energy efficient design becomes critical. This paper considers a battery-powered transmitter using on-off keying (OOK) modulation and studies its energy efficiency in terms of the battery’s energy consumption for per bit transmission (BECPB). In particular, the transmitter may use one of two distinct types of batteries with battery utilization factor (BUF) depending on discharge current. The first has an instantaneous discharge current (IDC)-based BUF, while the second has a mean discharge current (MDC)-based BUF. For each type of battery, a closed-form BECPB expression is derived under a Rayleigh channel when a prescribed symbol error rate (SER) is guaranteed. Then theoretical analysis is made to study the impact of battery characteristic parameter

γ

, communication distance d and bandwidth B on the BECPB. Finally, the analysis is corroborated by numerical experimental results, which reveal that: the BECPB for each type of battery increases with

γ

and d; the BECPB for the two batteries first decreases and then increases with B, and there exists the optimal bandwidth corresponding to the minimum BECPB; the battery with IDC-based BUF corresponds to a larger BECPB. When

γ

and d are large, the BECPB for each type of battery is significantly higher than that for the ideal battery whose BUF is aways 1. For instance, when

γ = 0.015

,

d = 90

m and

B = 10

kHz, the BECPB for IDC-based and MDC-based battery is nearly 60% amd 25% higher than that of the ideal battery, respectively. Full article

(This article belongs to the Special Issue Low Energy Wireless Sensor Networks: Protocols, Architectures and Solutions)

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17 pages, 5990 KiB

Open AccessArticle

Color Feature-Based Object Tracking through Particle Swarm Optimization with Improved Inertia Weight

by Siqiu Guo^1,2, Tao Zhang^1,*, Yulong Song¹ and Feng Qian¹

¹ Chinese Academy of Science, Changchun Institute of Optics Fine Mechanics and Physics, 3888 Dongnanhu Road, Changchun 130033, China

² University of Chinese Academy of Science, 19 Yuquan Road, Beijing 100049, China

Sensors 2018, 18(4), 1292; https://doi.org/10.3390/s18041292 - 23 Apr 2018

Cited by 13 | Viewed by 4844

Abstract

This paper presents a particle swarm tracking algorithm with improved inertia weight based on color features. The weighted color histogram is used as the target feature to reduce the contribution of target edge pixels in the target feature, which makes the algorithm insensitive [...] Read more.

This paper presents a particle swarm tracking algorithm with improved inertia weight based on color features. The weighted color histogram is used as the target feature to reduce the contribution of target edge pixels in the target feature, which makes the algorithm insensitive to the target non-rigid deformation, scale variation, and rotation. Meanwhile, the influence of partial obstruction on the description of target features is reduced. The particle swarm optimization algorithm can complete the multi-peak search, which can cope well with the object occlusion tracking problem. This means that the target is located precisely where the similarity function appears multi-peak. When the particle swarm optimization algorithm is applied to the object tracking, the inertia weight adjustment mechanism has some limitations. This paper presents an improved method. The concept of particle maturity is introduced to improve the inertia weight adjustment mechanism, which could adjust the inertia weight in time according to the different states of each particle in each generation. Experimental results show that our algorithm achieves state-of-the-art performance in a wide range of scenarios. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 1512 KiB

Open AccessArticle

Path Diversity Improved Opportunistic Routing for Underwater Sensor Networks

by Weigang Bai^1,2,*

, Haiyan Wang^1,2,*, Ke He^1,2 and Ruiqin Zhao^1,2

¹ Key Laboratory of Ocean Acoustics and Sensing, Northwestern Polytechnical University, Ministry of Industry and Information Technology, Xi’an 710072, China

² School of Marine Science and Technology, Northwestern Polytechnical University; Xi’an 710072, China

Sensors 2018, 18(4), 1293; https://doi.org/10.3390/s18041293 - 23 Apr 2018

Cited by 9 | Viewed by 4993

Abstract

The packets carried along a pre-defined route in underwater sensor networks are very vulnerble. Node mobility or intermittent channel availability easily leads to unreachable routing. Opportunistic routing has been proven to be a promising paradigm to design routing protocols for underwater sensor networks. [...] Read more.

The packets carried along a pre-defined route in underwater sensor networks are very vulnerble. Node mobility or intermittent channel availability easily leads to unreachable routing. Opportunistic routing has been proven to be a promising paradigm to design routing protocols for underwater sensor networks. It takes advantage of the broadcast nature of the wireless medium to combat packet losses and selects potential paths on the fly. Finding an appropriate forwarding candidate set is a key issue in opportunistic routing. Many existing solutions ignore the impact of candidates location distribution on packet forwarding. In this paper, a path diversity improved candidate selection strategy is applied in opportunistic routing to improve packet forwarding efficiency. It not only maximizes the packet forwarding advancements but also takes the candidate’s location distribution into account. Based on this strategy, we propose two effective routing protocols: position improved candidates selection (PICS) and position random candidates selection (PRCS). PICS employs two-hop neighbor information to make routing decisions. PRCS only uses one-hop neighbor information. Simulation results show that both PICS and PRCS can significantly improve network performance when compared with the previous solutions, in terms of packet delivery ratio, average energy consumption and end-to-end delay. Full article

(This article belongs to the Section Sensor Networks)

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19 pages, 12278 KiB

Open AccessArticle

A Single LiDAR-Based Feature Fusion Indoor Localization Algorithm

by Yun-Ting Wang¹, Chao-Chung Peng^1,*, Ankit A. Ravankar²

and Abhijeet Ravankar³

¹ Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 701, Taiwan

² Division of Human Mechanical Systems and Design, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan

³ Lab of Smart Systems Engineering, Kitami Institute of Technology, Hokkaido, Kitami 090-8507, Japan

Sensors 2018, 18(4), 1294; https://doi.org/10.3390/s18041294 - 23 Apr 2018

Cited by 75 | Viewed by 9432

Abstract

In past years, there has been significant progress in the field of indoor robot localization. To precisely recover the position, the robots usually relies on multiple on-board sensors. Nevertheless, this affects the overall system cost and increases computation. In this research work, we [...] Read more.

In past years, there has been significant progress in the field of indoor robot localization. To precisely recover the position, the robots usually relies on multiple on-board sensors. Nevertheless, this affects the overall system cost and increases computation. In this research work, we considered a light detection and ranging (LiDAR) device as the only sensor for detecting surroundings and propose an efficient indoor localization algorithm. To attenuate the computation effort and preserve localization robustness, a weighted parallel iterative closed point (WP-ICP) with interpolation is presented. As compared to the traditional ICP, the point cloud is first processed to extract corners and line features before applying point registration. Later, points labeled as corners are only matched with the corner candidates. Similarly, points labeled as lines are only matched with the lines candidates. Moreover, their ICP confidence levels are also fused in the algorithm, which make the pose estimation less sensitive to environment uncertainties. The proposed WP-ICP architecture reduces the probability of mismatch and thereby reduces the ICP iterations. Finally, based on given well-constructed indoor layouts, experiment comparisons are carried out under both clean and perturbed environments. It is shown that the proposed method is effective in significantly reducing computation effort and is simultaneously able to preserve localization precision. Full article

(This article belongs to the Special Issue Selected Sensor Related Papers from ICI2017)

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14 pages, 960 KiB

Open AccessArticle

Classification and Discrimination of Different Fungal Diseases of Three Infection Levels on Peaches Using Hyperspectral Reflectance Imaging Analysis

by Ye Sun, Kangli Wei, Qiang Liu, Leiqing Pan

and Kang Tu^*

College of Food Science and Technology, Nanjing Agricultural University, No. 1, Weigang Road, Nanjing 210095, China

Sensors 2018, 18(4), 1295; https://doi.org/10.3390/s18041295 - 23 Apr 2018

Cited by 45 | Viewed by 7972

Abstract

Peaches are susceptible to infection from several postharvest diseases. In order to control disease and avoid potential health risks, it is important to identify suitable treatments for each disease type. In this study, the spectral and imaging information from hyperspectral reflectance (400~1000 nm) [...] Read more.

Peaches are susceptible to infection from several postharvest diseases. In order to control disease and avoid potential health risks, it is important to identify suitable treatments for each disease type. In this study, the spectral and imaging information from hyperspectral reflectance (400~1000 nm) was used to evaluate and classify three kinds of common peach disease. To reduce the large dimensionality of the hyperspectral imaging, principal component analysis (PCA) was applied to analyse each wavelength image as a whole, and the first principal component was selected to extract the imaging features. A total of 54 parameters were extracted as imaging features for one sample. Three decayed stages (slight, moderate and severe decayed peaches) were considered for classification by deep belief network (DBN) and partial least squares discriminant analysis (PLSDA) in this study. The results showed that the DBN model has better classification results than the classification accuracy of the PLSDA model. The DBN model based on integrated information (494 features) showed the highest classification results for the three diseases, with accuracies of 82.5%, 92.5%, and 100% for slightly-decayed, moderately-decayed and severely-decayed samples, respectively. The successive projections algorithm (SPA) was used to select the optimal features from the integrated information; then, six optimal features were selected from a total of 494 features to establish the simple model. The SPA-PLSDA model showed better results which were more feasible for industrial application. The results showed that the hyperspectral reflectance imaging technique is feasible for detecting different kinds of diseased peaches, especially at the moderately- and severely-decayed levels. Full article

(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)

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11 pages, 2376 KiB

Open AccessArticle

Distinguishing Computer-Generated Graphics from Natural Images Based on Sensor Pattern Noise and Deep Learning

by Ye Yao^1,2

, Weitong Hu¹, Wei Zhang^3,*, Ting Wu^1,* and Yun-Qing Shi⁴

¹ School of CyberSpace, Hangzhou Dianzi University, Hangzhou 310018, China

² Shenzhen Key Laboratory of Media Security, Shenzhen University, Shenzhen 518060, China

³ School of Computer Science and Technology, Hangzhou Dianzi University, Hangzhou 310018, China

⁴ Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA

Sensors 2018, 18(4), 1296; https://doi.org/10.3390/s18041296 - 23 Apr 2018

Cited by 47 | Viewed by 7155

Abstract

Computer-generated graphics (CGs) are images generated by computer software. The rapid development of computer graphics technologies has made it easier to generate photorealistic computer graphics, and these graphics are quite difficult to distinguish from natural images (NIs) with the naked eye. In this [...] Read more.

Computer-generated graphics (CGs) are images generated by computer software. The rapid development of computer graphics technologies has made it easier to generate photorealistic computer graphics, and these graphics are quite difficult to distinguish from natural images (NIs) with the naked eye. In this paper, we propose a method based on sensor pattern noise (SPN) and deep learning to distinguish CGs from NIs. Before being fed into our convolutional neural network (CNN)-based model, these images—CGs and NIs—are clipped into image patches. Furthermore, three high-pass filters (HPFs) are used to remove low-frequency signals, which represent the image content. These filters are also used to reveal the residual signal as well as SPN introduced by the digital camera device. Different from the traditional methods of distinguishing CGs from NIs, the proposed method utilizes a five-layer CNN to classify the input image patches. Based on the classification results of the image patches, we deploy a majority vote scheme to obtain the classification results for the full-size images. The experiments have demonstrated that (1) the proposed method with three HPFs can achieve better results than that with only one HPF or no HPF and that (2) the proposed method with three HPFs achieves 100% accuracy, although the NIs undergo a JPEG compression with a quality factor of 75. Full article

(This article belongs to the Special Issue Advances on Sensor Pattern Noise used in Multimedia Forensics and Counter Forensic)

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18 pages, 24186 KiB

Open AccessArticle

A Refined Crop Drought Monitoring Method Based on the Chinese GF-1 Wide Field View Data

by Sheng Chang^1,2,3, Bingfang Wu^1,2,*

, Nana Yan², Jianjun Zhu^1,3, Qi Wen⁴

and Feng Xu^4,5

¹ School of Geosciences and Info-Physics, Central South University, Changsha 410083, China

² Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Olympic Village Science Park, W. Beichen Road, Beijing 100101, China

³ Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring Ministry of Education, School of Geoscience and Infophysics, Central South University, Changsha 410083, China

⁴ National Disaster Reduction Center of China, Beijing 100124, China

⁵ China Transport Telecommunications and Information Center, Beijing 100011, China

Sensors 2018, 18(4), 1297; https://doi.org/10.3390/s18041297 - 23 Apr 2018

Cited by 6 | Viewed by 4834

Abstract

In this study, modified perpendicular drought index (MPDI) models based on the red-near infrared spectral space are established for the first time through the analysis of the spectral characteristics of GF-1 wide field view (WFV) data, with a high spatial resolution of 16 [...] Read more.

In this study, modified perpendicular drought index (MPDI) models based on the red-near infrared spectral space are established for the first time through the analysis of the spectral characteristics of GF-1 wide field view (WFV) data, with a high spatial resolution of 16 m and the highest frequency as high as once every 4 days. GF-1 data was from the Chinese-made, new-generation high-resolution GF-1 remote sensing satellites. Soil-type spatial data are introduced for simulating soil lines in different soil types for reducing errors of using same soil line. Multiple vegetation indices are employed to analyze the response to the MPDI models. Relative soil moisture content (RSMC) and precipitation data acquired at selected stations are used to optimize the drought models, and the best one is the Two-band enhanced vegetation index (EVI2)-based MPDI model. The crop area that was statistically significantly affected by drought from a local governmental department, and used for validation. High correlations and small differences in drought-affected crop area was detected between the field observation data from the local governmental department and the EVI2-based MPDI results. The percentage of bias is between −21.8% and 14.7% in five sub-areas, with an accuracy above 95% when evaluating the performance via the data for the whole study region. Generally the proposed EVI2-based MPDI for GF-1 WFV data has great potential for reliably monitoring crop drought at a relatively high frequency and spatial scale. Currently there is almost no drought model based on GF-1 data, a full exploitation of the advantages of GF-1 satellite data and further improvement of the capacity to observe ground surface objects can provide high temporal and spatial resolution data source for refined monitoring of crop droughts. Full article

(This article belongs to the Section Remote Sensors)

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15 pages, 2406 KiB

Open AccessArticle

Intelligent Fault Diagnosis of Delta 3D Printers Using Attitude Sensors Based on Support Vector Machines

by Kun He^1,2

, Zhijun Yang¹, Yun Bai², Jianyu Long² and Chuan Li^1,2,*

¹ School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006, China

² School of Mechanical Engineering, Dongguan University of Technology, Dongguan 523808, China

Sensors 2018, 18(4), 1298; https://doi.org/10.3390/s18041298 - 23 Apr 2018

Cited by 47 | Viewed by 8662

Abstract

Health condition is a vital factor affecting printing quality for a 3D printer. In this work, an attitude monitoring approach is proposed to diagnose the fault of the delta 3D printer using support vector machines (SVM). An attitude sensor was mounted on the [...] Read more.

Health condition is a vital factor affecting printing quality for a 3D printer. In this work, an attitude monitoring approach is proposed to diagnose the fault of the delta 3D printer using support vector machines (SVM). An attitude sensor was mounted on the moving platform of the printer to monitor its 3-axial attitude angle, angular velocity, vibratory acceleration and magnetic field intensity. The attitude data of the working printer were collected under different conditions involving 12 fault types and a normal condition. The collected data were analyzed for diagnosing the health condition. To this end, the combination of binary classification, one-against-one with least-square SVM, was adopted for fault diagnosis modelling by using all channels of attitude monitoring data in the experiment. For comparison, each one channel of the attitude monitoring data was employed for model training and testing. On the other hand, a back propagation neural network (BPNN) was also applied to diagnose fault using the same data. The best fault diagnosis accuracy (94.44%) was obtained when all channels of the attitude monitoring data were used with SVM modelling. The results indicate that the attitude monitoring with SVM is an effective method for the fault diagnosis of delta 3D printers. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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12 pages, 1694 KiB

Open AccessArticle

Water Detection in Urban Areas from GF-3

by Xiaoyan Liu^1,2,3,4

, Long Liu^1,2,3,*

, Yun Shao^1,2,3, Quanhua Zhao⁴, Qingjun Zhang⁵

and Linjiang Lou⁶

¹ Laboratory of Target Microwave Properties, Deqing 313200, China

² Deqing Academy of Satellite Applications, Deqing 313200, China

³ Laboratory of Radar Remote Sensing Application Technology, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China

⁴ Institute of Remote Sensing Science and Application, School of Geomatics, Liaoning Technical University, Fuxin 123000, China

⁵ China Academy of Space Technology, Beijing Institute of Space System Engineering, Beijing 100086, China

⁶ Satellite Surveying and Mapping Application Center, Beijing 100048, China

Sensors 2018, 18(4), 1299; https://doi.org/10.3390/s18041299 - 23 Apr 2018

Cited by 9 | Viewed by 4925

Abstract

The rapid and accurate detection of urban water is critical for urban management, river detection, and flood disaster assessment. This study is devoted to detecting water by GaoFen-3 (GF-3) Synthetic Aperture Radar (SAR) images with high spatial resolution. There have been no effective [...] Read more.

The rapid and accurate detection of urban water is critical for urban management, river detection, and flood disaster assessment. This study is devoted to detecting water by GaoFen-3 (GF-3) Synthetic Aperture Radar (SAR) images with high spatial resolution. There have been no effective solutions that discriminate water and building shadows using a single SAR image in previous research. Inspired by the principle that every shadow has a corresponding building nearby, a new method is proposed in this study, whereby building shadows are removed depending on the correspondence of buildings and their shadows. The proposed method is demonstrated effective and efficient by experimental results on six GF-3 SAR images. The Receiver Operating Characteristic (ROC) curves of the water detection results indicate that the proposed method increases the Probability of Detection (PD) to 98.36% and decreases the Probability of False Alarm (PFA) to 1.91% compared with the thresholding method, where, at the same PFA level, the maximum PD of the thresholding method is 72.62% in all testing samples. The proposed method is capable of removing building shadows and detecting water with high precision in urban areas, which presents the great potential of high-spatial-resolution GF-3 images in terms of water resource management. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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27 pages, 1683 KiB

Open AccessArticle

Wind Gust Measurement Techniques—From Traditional Anemometry to New Possibilities

by Irene Suomi^*,†

and Timo Vihma

¹ Meteorological Research, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland

^† Current address: Erik Palménin aukio 1, 00560 Helsinki, Finland

Sensors 2018, 18(4), 1300; https://doi.org/10.3390/s18041300 - 23 Apr 2018

Cited by 48 | Viewed by 11589

Abstract

Information on wind gusts is needed for assessment of wind-induced damage and risks to safety. The measurement of wind gust speed requires a high temporal resolution of the anemometer system, because the gust is defined as a short-duration (seconds) maximum of the fluctuating [...] Read more.

Information on wind gusts is needed for assessment of wind-induced damage and risks to safety. The measurement of wind gust speed requires a high temporal resolution of the anemometer system, because the gust is defined as a short-duration (seconds) maximum of the fluctuating wind speed. Until the digitalization of wind measurements in the 1990s, the wind gust measurements suffered from limited recording and data processing resources. Therefore, the majority of continuous wind gust records date back at most only by 30 years. Although the response characteristics of anemometer systems are good enough today, the traditional measurement techniques at weather stations based on cup and sonic anemometers are limited to heights and regions where the supporting structures can reach. Therefore, existing measurements are mainly concentrated over densely-populated land areas, whereas from remote locations, such as the marine Arctic, wind gust information is available only from sparse coastal locations. Recent developments of wind gust measurement techniques based on turbulence measurements from research aircraft and from Doppler lidar can potentially provide new information from heights and locations unreachable by traditional measurement techniques. Moreover, fast-developing measurement methods based on Unmanned Aircraft Systems (UASs) may add to better coverage of wind gust measurements in the future. In this paper, we provide an overview of the history and the current status of anemometry from the perspective of wind gusts. Furthermore, a discussion on the potential future directions of wind gust measurement techniques is provided. Full article

(This article belongs to the Special Issue Earth Observation and In-Situ Sensing for Risk Assessment from Natural Threats)

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18 pages, 7147 KiB

Open AccessArticle

Development and Hybrid Position/Force Control of a Dual-Drive Macro-Fiber-Composite Microgripper

by Jin Zhang¹, Yiling Yang^1,*

, Junqiang Lou^1,*

, Yanding Wei^2,3 and Lei Fu^2,3

¹ Faculty of Mechanical Engineering and Mechanics, Ningbo University, Ningbo 315211, China

² The Key Laboratory of Advanced Manufacturing Technology of Zhejiang Province, Zhejiang University, Hangzhou 310058, China

³ State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310058, China

Sensors 2018, 18(4), 1301; https://doi.org/10.3390/s18041301 - 23 Apr 2018

Cited by 17 | Viewed by 6135

Abstract

This paper reports on the development, implementation and hybrid control of a new micro-fiber-composite microgripper with synchronous position and force control capabilities. In particular, the micro-fiber-composite actuator was composed of rectangular piezoelectric fibers covered by interdigitated electrodes and embedded in structural epoxy. Thus, [...] Read more.

This paper reports on the development, implementation and hybrid control of a new micro-fiber-composite microgripper with synchronous position and force control capabilities. In particular, the micro-fiber-composite actuator was composed of rectangular piezoelectric fibers covered by interdigitated electrodes and embedded in structural epoxy. Thus, the micro-fiber-composite microgripper had a larger displacement-volume ratio (i.e., the ratio of the output displacement to the volume of the microgripper) than that of a traditional piezoelectric one. Moreover, to regulate both the gripper position and the gripping force simultaneously, a hybrid position/force control scheme using fuzzy sliding mode control and the proportional-integral controller was developed. In particular, the fuzzy sliding mode control was used to achieve the precision position control under the influence of the system disturbances and uncertainties, and the proportional-integral controller was used to guarantee the force control accuracy of the microgripper. A series of experimental investigations was performed to verify the feasibility of the developed microgripper and the control scheme. The experimental results validated the effectiveness of the designed microgripper and hybrid control scheme. The developed microgripper was capable of precision and multiscale micromanipulation tasks. Full article

(This article belongs to the Special Issue Recent Advances of Piezoelectric Transducers and Applications)

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Review

Jump to: Editorial, Research, Other

17 pages, 5583 KiB

Open AccessReview

Comparison of Tagging Technologies for Safeguards of Copper Canisters for Nuclear Spent Fuel

by Chiara Clementi^1,2, François Littmann^1,* and Lorenzo Capineri²

¹ European Commission, Joint Research Centre, I-21027 Ispra, Italy

² Department of Information Engineering, University of Florence, 50139 Florence, Italy

Sensors 2018, 18(4), 929; https://doi.org/10.3390/s18040929 - 21 Mar 2018

Cited by 5 | Viewed by 5228

Abstract

Several countries are planning to store nuclear spent fuel in long term geological repositories, preserved by copper canisters with an iron insert. This new approach involves many challenging problems and one is to satisfy safeguards requirements: the Continuity of Knowledge (CoK) of the [...] Read more.

Several countries are planning to store nuclear spent fuel in long term geological repositories, preserved by copper canisters with an iron insert. This new approach involves many challenging problems and one is to satisfy safeguards requirements: the Continuity of Knowledge (CoK) of the fuel must be kept from the encapsulation plant up to the final repository. To date, no measurement system has been suggested for a unique identification and authentication. Following the list of the most important safeguards, safety and security requirements for copper canisters identification and authentication, a review of conventional tagging technologies and measurement systems for nuclear items is reported in this paper. The aim of this study is to verify to what extent each technology could be potentially used for keeping the CoK of copper canisters. Several tagging methods are briefly described and compared, discussing advantages and disadvantages. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2017)

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16 pages, 7713 KiB

Open AccessReview

Optical Graphene Gas Sensors Based on Microfibers: A Review

by Yu Wu^*, Baicheng Yao, Caibin Yu and Yunjiang Rao^*

Fiber Optics Research Centre, Key Laboratory of Optical Fiber Sensing and Communications (Education Ministry of China), University of Electronic Science and Technology of China, Chengdu 610054, China

Sensors 2018, 18(4), 941; https://doi.org/10.3390/s18040941 - 22 Mar 2018

Cited by 48 | Viewed by 11229

Abstract

Graphene has become a bridge across optoelectronics, mechanics, and bio-chemical sensing due to its unique photoelectric characteristics. Moreover, benefiting from its two-dimensional nature, this atomically thick film with full flexibility has been widely incorporated with optical waveguides such as fibers, realizing novel photonic [...] Read more.

Graphene has become a bridge across optoelectronics, mechanics, and bio-chemical sensing due to its unique photoelectric characteristics. Moreover, benefiting from its two-dimensional nature, this atomically thick film with full flexibility has been widely incorporated with optical waveguides such as fibers, realizing novel photonic devices including polarizers, lasers, and sensors. Among the graphene-based optical devices, sensor is one of the most important branch, especially for gas sensing, as rapid progress has been made in both sensing structures and devices in recent years. This article presents a comprehensive and systematic overview of graphene-based microfiber gas sensors regarding many aspects including sensing principles, properties, fabrication, interrogating and implementations. Full article

(This article belongs to the Special Issue Optical Sensors based on Micro/Nanofibres)

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18 pages, 4453 KiB

Open AccessFeature PaperReview

Miniaturized Bio-and Chemical-Sensors for Point-of-Care Monitoring of Chronic Kidney Diseases

by Antonio Tricoli¹ and Giovanni Neri^2,*

¹ Nanotechnolgy Research Laboratory, Research School of Engineering, Australian National University, Canberra ACT 0200, Australia

² Department of Engineering, University of Messina, I-9866 Messina, Italy

Sensors 2018, 18(4), 942; https://doi.org/10.3390/s18040942 - 22 Mar 2018

Cited by 57 | Viewed by 14783

Abstract

This review reports the latest achievements in point-of-care (POC) sensor technologies for the monitoring of ammonia, creatinine and urea in patients suffering of chronic kidney diseases (CKDs). Abnormal levels of these nitrogen biomarkers are found in the physiological fluids, such as blood, urine [...] Read more.

This review reports the latest achievements in point-of-care (POC) sensor technologies for the monitoring of ammonia, creatinine and urea in patients suffering of chronic kidney diseases (CKDs). Abnormal levels of these nitrogen biomarkers are found in the physiological fluids, such as blood, urine and sweat, of CKD patients. Delocalized at-home monitoring of CKD biomarkers via integration of miniaturized, portable, and low cost chemical- and bio-sensors in POC devices, is an emerging approach to improve patients’ health monitoring and life quality. The successful monitoring of CKD biomarkers, performed on the different body fluids by means of sensors having strict requirements in term of size, cost, large-scale production capacity, response time and simple operation procedures for use in POC devices, is reported and discussed. Full article

(This article belongs to the Special Issue Non-Invasive Biomedical Sensors)

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29 pages, 9188 KiB

Open AccessReview

Recent Progress in Technologies for Tactile Sensors

by Cheng Chi^1,2

, Xuguang Sun^1,2, Ning Xue^1,2,*, Tong Li¹ and Chang Liu^1,*

¹ State Key Laboratory of Transducer Technology, Institute of Electronics Chinese Academy of Sciences, Beijing 100190, China

² School of Electronic, Electrical, and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China

Sensors 2018, 18(4), 948; https://doi.org/10.3390/s18040948 - 22 Mar 2018

Cited by 209 | Viewed by 20920

Abstract

Over the last two decades, considerable scientific and technological efforts have been devoted to developing tactile sensing based on a variety of transducing mechanisms, with prospective applications in many fields such as human–machine interaction, intelligent robot tactile control and feedback, and tactile sensorized [...] Read more.

Over the last two decades, considerable scientific and technological efforts have been devoted to developing tactile sensing based on a variety of transducing mechanisms, with prospective applications in many fields such as human–machine interaction, intelligent robot tactile control and feedback, and tactile sensorized minimally invasive surgery. This paper starts with an introduction of human tactile systems, followed by a presentation of the basic demands of tactile sensors. State-of-the-art tactile sensors are reviewed in terms of their diverse sensing mechanisms, design consideration, and material selection. Subsequently, typical performances of the sensors, along with their advantages and disadvantages, are compared and analyzed. Two major potential applications of tactile sensing systems are discussed in detail. Lastly, we propose prospective research directions and market trends of tactile sensing systems. Full article

(This article belongs to the Special Issue Tactile Sensors and Sensing)

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18 pages, 7569 KiB

Open AccessReview

A Large-Scale Study of Fingerprint Matching Systems for Sensor Interoperability Problem

by Helala AlShehri^*

, Muhammad Hussain^*, Hatim AboAlSamh and Mansour AlZuair

College of Computer and Information Sciences, King Saud University, Riyadh 11543, Saudi Arabia

Sensors 2018, 18(4), 1008; https://doi.org/10.3390/s18041008 - 28 Mar 2018

Cited by 15 | Viewed by 8068

Abstract

The fingerprint is a commonly used biometric modality that is widely employed for authentication by law enforcement agencies and commercial applications. The designs of existing fingerprint matching methods are based on the hypothesis that the same sensor is used to capture fingerprints during [...] Read more.

The fingerprint is a commonly used biometric modality that is widely employed for authentication by law enforcement agencies and commercial applications. The designs of existing fingerprint matching methods are based on the hypothesis that the same sensor is used to capture fingerprints during enrollment and verification. Advances in fingerprint sensor technology have raised the question about the usability of current methods when different sensors are employed for enrollment and verification; this is a fingerprint sensor interoperability problem. To provide insight into this problem and assess the status of state-of-the-art matching methods to tackle this problem, we first analyze the characteristics of fingerprints captured with different sensors, which makes cross-sensor matching a challenging problem. We demonstrate the importance of fingerprint enhancement methods for cross-sensor matching. Finally, we conduct a comparative study of state-of-the-art fingerprint recognition methods and provide insight into their abilities to address this problem. We performed experiments using a public database (FingerPass) that contains nine datasets captured with different sensors. We analyzed the effects of different sensors and found that cross-sensor matching performance deteriorates when different sensors are used for enrollment and verification. In view of our analysis, we propose future research directions for this problem. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 4833 KiB

Open AccessReview

Alpha Particle Detection Using Alpha-Induced Air Radioluminescence: A Review and Future Prospects for Preliminary Radiological Characterisation for Nuclear Facilities Decommissioning

by Anita J. Crompton^1,*

, Kelum A. A. Gamage²

, Alex Jenkins³ and Charles James Taylor¹

¹ Engineering Department, Lancaster University, LA1 4YW Lancaster, UK

² School of Engineering, University of Glasgow, G12 8QQ Glasgow, UK

³ Characterisation, Inspection & Decontamination Group, Sellafield Ltd., CA20 1PG Cumbria, UK

Sensors 2018, 18(4), 1015; https://doi.org/10.3390/s18041015 - 28 Mar 2018

Cited by 27 | Viewed by 9971

Abstract

The United Kingdom (UK) has a significant legacy of nuclear installations to be decommissioned over the next 100 years and a thorough characterisation is required prior to the development of a detailed decommissioning plan. Alpha radiation detection is notoriously time consuming and difficult [...] Read more.

The United Kingdom (UK) has a significant legacy of nuclear installations to be decommissioned over the next 100 years and a thorough characterisation is required prior to the development of a detailed decommissioning plan. Alpha radiation detection is notoriously time consuming and difficult to carry out due to the short range of alpha particles in air. Long-range detection of alpha particles is therefore highly desirable and this has been attempted through the detection of secondary effects from alpha radiation, most notably the air-radioluminescence caused by ionisation. This paper evaluates alpha induced air radioluminescence detectors developed to date and looks at their potential to develop a stand-off, alpha radiation detector which can be used in the nuclear decommissioning field in daylight conditions to detect alpha contaminated materials. Full article

(This article belongs to the Special Issue Sensors and Materials for Harsh Environments)

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23 pages, 2418 KiB

Open AccessReview

Screen-Printed Electrodes Modified with “Green” Metals for Electrochemical Stripping Analysis of Toxic Elements

by Anastasios Economou

Department of Chemistry, National and Kapodistrian University of Athens, Athens 157 71, Greece

Sensors 2018, 18(4), 1032; https://doi.org/10.3390/s18041032 - 29 Mar 2018

Cited by 77 | Viewed by 7296

Abstract

This work reviews the field of screen-printed electrodes (SPEs) modified with “green” metals for electrochemical stripping analysis of toxic elements. Electrochemical stripping analysis has been established as a useful trace analysis technique offering many advantages compared to competing optical techniques. Although mercury has [...] Read more.

This work reviews the field of screen-printed electrodes (SPEs) modified with “green” metals for electrochemical stripping analysis of toxic elements. Electrochemical stripping analysis has been established as a useful trace analysis technique offering many advantages compared to competing optical techniques. Although mercury has been the preferred electrode material for stripping analysis, the toxicity of mercury and the associated legal requirements in its use and disposal have prompted research towards the development of “green” metals as alternative electrode materials. When combined with the screen-printing technology, such environment-friendly metals can lead to disposable sensors for trace metal analysis with excellent operational characteristics. This review focuses on SPEs modified with Au, Bi, Sb, and Sn for stripping analysis of toxic elements. Different modification approaches (electroplating, bulk modification, use of metal precursors, microengineering techniques) are considered and representative applications are described. A developing related field, namely biosensing based on stripping analysis of metallic nanoprobe labels, is also briefly mentioned. Full article

(This article belongs to the Special Issue Screen-Printed Electrodes)

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22 pages, 17903 KiB

Open AccessReview

Aptamer-Modified Magnetic Beads in Biosensing

by Harshvardhan Modh

, Thomas Scheper and Johanna-Gabriela Walter^*

Institute of Technical Chemistry, Leibniz University of Hannover, Hannover 30167, Germany

Sensors 2018, 18(4), 1041; https://doi.org/10.3390/s18041041 - 30 Mar 2018

Cited by 63 | Viewed by 14340

Abstract

Magnetic beads (MBs) are versatile tools for the purification, detection, and quantitative analysis of analytes from complex matrices. The superparamagnetic property of magnetic beads qualifies them for various analytical applications. To provide specificity, MBs can be decorated with ligands like aptamers, antibodies and [...] Read more.

Magnetic beads (MBs) are versatile tools for the purification, detection, and quantitative analysis of analytes from complex matrices. The superparamagnetic property of magnetic beads qualifies them for various analytical applications. To provide specificity, MBs can be decorated with ligands like aptamers, antibodies and peptides. In this context, aptamers are emerging as particular promising ligands due to a number of advantages. Most importantly, the chemical synthesis of aptamers enables straightforward and controlled chemical modification with linker molecules and dyes. Moreover, aptamers facilitate novel sensing strategies based on their oligonucleotide nature that cannot be realized with conventional peptide-based ligands. Due to these benefits, the combination of aptamers and MBs was already used in various analytical applications which are summarized in this article. Full article

(This article belongs to the Special Issue Magnetic Materials Based Biosensors)

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31 pages, 81980 KiB

Open AccessReview

Distributed Optical Fiber Sensors Based on Optical Frequency Domain Reflectometry: A review

by Zhenyang Ding^1,2,3,*

, Chenhuan Wang^1,2,3, Kun Liu^1,2,3,*, Junfeng Jiang^1,2,3, Di Yang^1,2,3, Guanyi Pan¹, Zelin Pu¹ and Tiegen Liu^1,2,3

¹ School of Precision Instrument & Optoelectronics Engineering, Tianjin University, Tianjin 300072, China

² Key Laboratory of Optoelectronics Information Technology, Ministry of Education, Tianjin 300072, China

³ Tianjin Optical Fiber Sensing Engineering Center, Institute of Optical Fiber Sensing of Tianjin University, Tianjin 300072, China

Sensors 2018, 18(4), 1072; https://doi.org/10.3390/s18041072 - 3 Apr 2018

Cited by 282 | Viewed by 22243

Abstract

Distributed optical fiber sensors (DOFS) offer unprecedented features, the most unique one of which is the ability of monitoring variations of the physical and chemical parameters with spatial continuity along the fiber. Among all these distributed sensing techniques, optical frequency domain reflectometry (OFDR) [...] Read more.

Distributed optical fiber sensors (DOFS) offer unprecedented features, the most unique one of which is the ability of monitoring variations of the physical and chemical parameters with spatial continuity along the fiber. Among all these distributed sensing techniques, optical frequency domain reflectometry (OFDR) has been given tremendous attention because of its high spatial resolution and large dynamic range. In addition, DOFS based on OFDR have been used to sense many parameters. In this review, we will survey the key technologies for improving sensing range, spatial resolution and sensing performance in DOFS based on OFDR. We also introduce the sensing mechanisms and the applications of DOFS based on OFDR including strain, stress, vibration, temperature, 3D shape, flow, refractive index, magnetic field, radiation, gas and so on. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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32 pages, 29867 KiB

Open AccessReview

Biosensing Based on Nanoparticles for Food Allergens Detection

by Lidia Nazaret Gómez-Arribas^†, Elena Benito-Peña^†

, María Del Carmen Hurtado-Sánchez and María Cruz Moreno-Bondi^*

¹ Departamento de Química Analítica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1087; https://doi.org/10.3390/s18041087 - 4 Apr 2018

Cited by 43 | Viewed by 9806

Abstract

Food allergy is one of the major health threats for sensitized individuals all over the world and, over the years, the food industry has made significant efforts and investments to offer safe foods for allergic consumers. The analysis of the concentration of food [...] Read more.

Food allergy is one of the major health threats for sensitized individuals all over the world and, over the years, the food industry has made significant efforts and investments to offer safe foods for allergic consumers. The analysis of the concentration of food allergen residues in processing equipment, in raw materials or in the final product, provides analytical information that can be used for risk assessment as well as to ensure that food-allergic consumers get accurate and useful information to make their food choices and purchasing decisions. The development of biosensors based on nanomaterials for applications in food analysis is a challenging area of growing interest in the last years. Research in this field requires the combined efforts of experts in very different areas including food chemistry, biotechnology or materials science. However, the outcome of such collaboration can be of significant impact on the food industry as well as for consumer’s safety. These nanobiosensing devices allow the rapid, selective, sensitive, cost-effective and, in some cases, in-field, online and real-time detection of a wide range of compounds, even in complex matrices. Moreover, they can also enable the design of novel allergen detection strategies. Herein we review the main advances in the use of nanoparticles for the development of biosensors and bioassays for allergen detection, in food samples, over the past few years. Research in this area is still in its infancy in comparison, for instance, to the application of nanobiosensors for clinical analysis. However, it will be of interest for the development of new technologies that reduce the gap between laboratory research and industrial applications. Full article

(This article belongs to the Special Issue Novel Approaches to Biosensing with Nanoparticles)

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18 pages, 3027 KiB

Open AccessReview

Signal Quality Improvement Algorithms for MEMS Gyroscope-Based Human Motion Analysis Systems: A Systematic Review

by Jiaying Du^1,2,*

, Christer Gerdtman² and Maria Lindén¹

¹ School of Innovation, Design and Engineering, Mälardalen University, 721 23 Västerås, Sweden

² Motion Control i Västerås AB, 721 30 Västerås, Sweden

Sensors 2018, 18(4), 1123; https://doi.org/10.3390/s18041123 - 6 Apr 2018

Cited by 29 | Viewed by 7184

Abstract

Motion sensors such as MEMS gyroscopes and accelerometers are characterized by a small size, light weight, high sensitivity, and low cost. They are used in an increasing number of applications. However, they are easily influenced by environmental effects such as temperature change, shock, [...] Read more.

Motion sensors such as MEMS gyroscopes and accelerometers are characterized by a small size, light weight, high sensitivity, and low cost. They are used in an increasing number of applications. However, they are easily influenced by environmental effects such as temperature change, shock, and vibration. Thus, signal processing is essential for minimizing errors and improving signal quality and system stability. The aim of this work is to investigate and present a systematic review of different signal error reduction algorithms that are used for MEMS gyroscope-based motion analysis systems for human motion analysis or have the potential to be used in this area. A systematic search was performed with the search engines/databases of the ACM Digital Library, IEEE Xplore, PubMed, and Scopus. Sixteen papers that focus on MEMS gyroscope-related signal processing and were published in journals or conference proceedings in the past 10 years were found and fully reviewed. Seventeen algorithms were categorized into four main groups: Kalman-filter-based algorithms, adaptive-based algorithms, simple filter algorithms, and compensation-based algorithms. The algorithms were analyzed and presented along with their characteristics such as advantages, disadvantages, and time limitations. A user guide to the most suitable signal processing algorithms within this area is presented. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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26 pages, 5936 KiB

Open AccessReview

Study on Interference Suppression Algorithms for Electronic Noses: A Review

by Zhifang Liang^1,*, Fengchun Tian^2,*

, Simon X. Yang^3,*

, Ci Zhang², Hao Sun² and Tao Liu²

¹ College of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongwen Road 2nd, Nan’an District, Chongqing 400065, China

² College of Communication Engineering, Chongqing University, 174 ShaZheng Street, ShaPingBa District, Chongqing 400044, China

³ Advanced Robotics and Intelligent Systems (ARIS) Lab, School of Engineering, University of Guelph, Guelph, ON N1G 2W1, Canada

Sensors 2018, 18(4), 1179; https://doi.org/10.3390/s18041179 - 12 Apr 2018

Cited by 47 | Viewed by 6537

Abstract

Electronic noses (e-nose) are composed of an appropriate pattern recognition system and a gas sensor array with a certain degree of specificity and broad spectrum characteristics. The gas sensors have their own shortcomings of being highly sensitive to interferences which has an impact [...] Read more.

Electronic noses (e-nose) are composed of an appropriate pattern recognition system and a gas sensor array with a certain degree of specificity and broad spectrum characteristics. The gas sensors have their own shortcomings of being highly sensitive to interferences which has an impact on the detection of target gases. When there are interferences, the performance of the e-nose will deteriorate. Therefore, it is urgent to study interference suppression techniques for e-noses. This paper summarizes the sources of interferences and reviews the advances made in recent years in interference suppression for e-noses. According to the factors which cause interference, interferences can be classified into two types: interference caused by changes of operating conditions and interference caused by hardware failures. The existing suppression methods were summarized and analyzed from these two aspects. Since the interferences of e-noses are uncertain and unstable, it can be found that some nonlinear methods have good effects for interference suppression, such as methods based on transfer learning, adaptive methods, etc. Full article

(This article belongs to the Section Chemical Sensors)

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17 pages, 6741 KiB

Open AccessReview

From Protein Features to Sensing Surfaces

by Greta Faccio

Independent Scientist, St. Gallen 9000, Switzerland

Sensors 2018, 18(4), 1204; https://doi.org/10.3390/s18041204 - 15 Apr 2018

Cited by 43 | Viewed by 7441

Abstract

Proteins play a major role in biosensors in which they provide catalytic activity and specificity in molecular recognition. However, the immobilization process is far from straightforward as it often affects the protein functionality. Extensive interaction of the protein with the surface or significant [...] Read more.

Proteins play a major role in biosensors in which they provide catalytic activity and specificity in molecular recognition. However, the immobilization process is far from straightforward as it often affects the protein functionality. Extensive interaction of the protein with the surface or significant surface crowding can lead to changes in the mobility and conformation of the protein structure. This review will provide insights as to how an analysis of the physico-chemical features of the protein surface before the immobilization process can help to identify the optimal immobilization approach. Such an analysis can help to preserve the functionality of the protein when on a biosensor surface. Full article

(This article belongs to the Special Issue Biosensing for Interfacial Science)

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24 pages, 29183 KiB

Open AccessFeature PaperReview

Sensor Technologies for Intelligent Transportation Systems

by Juan Guerrero-Ibáñez¹, Sherali Zeadally² and Juan Contreras-Castillo^1,*

¹ Faculty of Telematics, University of Colima, 333 University Avenue, Colima C.P. 28040, Mexico

² College of Communication and Information, University of Kentucky, 315 Little Library Building, Lexington, KY 40506-0224, USA

Sensors 2018, 18(4), 1212; https://doi.org/10.3390/s18041212 - 16 Apr 2018

Cited by 508 | Viewed by 73400

Abstract

Modern society faces serious problems with transportation systems, including but not limited to traffic congestion, safety, and pollution. Information communication technologies have gained increasing attention and importance in modern transportation systems. Automotive manufacturers are developing in-vehicle sensors and their applications in different areas [...] Read more.

Modern society faces serious problems with transportation systems, including but not limited to traffic congestion, safety, and pollution. Information communication technologies have gained increasing attention and importance in modern transportation systems. Automotive manufacturers are developing in-vehicle sensors and their applications in different areas including safety, traffic management, and infotainment. Government institutions are implementing roadside infrastructures such as cameras and sensors to collect data about environmental and traffic conditions. By seamlessly integrating vehicles and sensing devices, their sensing and communication capabilities can be leveraged to achieve smart and intelligent transportation systems. We discuss how sensor technology can be integrated with the transportation infrastructure to achieve a sustainable Intelligent Transportation System (ITS) and how safety, traffic control and infotainment applications can benefit from multiple sensors deployed in different elements of an ITS. Finally, we discuss some of the challenges that need to be addressed to enable a fully operational and cooperative ITS environment. Full article

(This article belongs to the Special Issue The Architectures, Systems, and Applications of Internet of Things for Smart Cities)

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27 pages, 2085 KiB

Open AccessReview

dPCR: A Technology Review

by Phenix-Lan Quan^1,†, Martin Sauzade^1,† and Eric Brouzes^1,2,*

¹ Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794, USA

² Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA

^† These authors contributed equally to this work.

Sensors 2018, 18(4), 1271; https://doi.org/10.3390/s18041271 - 20 Apr 2018

Cited by 475 | Viewed by 41984

Abstract

Digital Polymerase Chain Reaction (dPCR) is a novel method for the absolute quantification of target nucleic acids. Quantification by dPCR hinges on the fact that the random distribution of molecules in many partitions follows a Poisson distribution. Each partition acts as an individual [...] Read more.

Digital Polymerase Chain Reaction (dPCR) is a novel method for the absolute quantification of target nucleic acids. Quantification by dPCR hinges on the fact that the random distribution of molecules in many partitions follows a Poisson distribution. Each partition acts as an individual PCR microreactor and partitions containing amplified target sequences are detected by fluorescence. The proportion of PCR-positive partitions suffices to determine the concentration of the target sequence without a need for calibration. Advances in microfluidics enabled the current revolution of digital quantification by providing efficient partitioning methods. In this review, we compare the fundamental concepts behind the quantification of nucleic acids by dPCR and quantitative real-time PCR (qPCR). We detail the underlying statistics of dPCR and explain how it defines its precision and performance metrics. We review the different microfluidic digital PCR formats, present their underlying physical principles, and analyze the technological evolution of dPCR platforms. We present the novel multiplexing strategies enabled by dPCR and examine how isothermal amplification could be an alternative to PCR in digital assays. Finally, we determine whether the theoretical advantages of dPCR over qPCR hold true by perusing studies that directly compare assays implemented with both methods. Full article

(This article belongs to the Special Issue Bio-MEMS for Precision Medicine)

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Jump to: Editorial, Research, Review

2 pages, 12477 KiB

Open AccessCorrection

Correction: Schena, E.; et al. Fiber Optic Sensors for Temperature Monitoring during Thermal Treatments: an Overview. Sensors 2016, 16, 1144

by Emiliano Schena¹

, Daniele Tosi²

, Paola Saccomandi^3,*

, Elfed Lewis⁴

and Taesung Kim⁵

¹ Universita’ Campus Bio-Medico di Roma, Unit of Measurements and Biomedical Instrumentation, via Alvaro del Portillo 21, 00128 Roma, Italy

² School of Engineering, Nazarbayev University, 53 Kabanbay Batyr, 01000 Astana, Kazakhstan

³ Institute of Image-Guided Surgery (IHU), S/c Ircad, 1 place de l'Hôpital, 67091 Strasbourg Cedex, France

⁴ Optical Fibre Sensors Research Centre (OFSRC), University of Limerick, V94 T9PX Limerick, Ireland

⁵ School of Mechanical Engineering & SAINT, Sungkyunkwan University, 53 Myeongnyun-dong 3-ga, Jongno-gu, 110-745 Suwon, Korea

Sensors 2018, 18(4), 1226; https://doi.org/10.3390/s18041226 - 17 Apr 2018

Cited by 1 | Viewed by 3058

Abstract

The author wishes to make the following correction to this paper [1], and to replace Figure 2:[...] Full article

7 pages, 909 KiB

Open AccessLetter

Complex Fiber Micro-Knots

by Shir Shahal¹, Hamootal Duadi¹, Yoav Linzon² and Moti Fridman^1,*

¹ Faculty of Engineering and the Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel

² School of Mechanical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel

Sensors 2018, 18(4), 1273; https://doi.org/10.3390/s18041273 - 20 Apr 2018

Cited by 28 | Viewed by 4464

Abstract

Fiber micro-knots are a promising and a cheap solution for advanced fiber-based sensors. We investigated complex fiber micro-knots in theory and experiment. We compared the measured spectral response and present an analytical study of simple micro-knots with double twists, twin micro-knots, figure-eight micro-knots, [...] Read more.

Fiber micro-knots are a promising and a cheap solution for advanced fiber-based sensors. We investigated complex fiber micro-knots in theory and experiment. We compared the measured spectral response and present an analytical study of simple micro-knots with double twists, twin micro-knots, figure-eight micro-knots, and tangled micro-knots. This research brings the simple fabrication process and robustness of fiber micro-knots into the world of complex resonators which may lead to novel optical devices based on fiber micro-knots. Full article

(This article belongs to the Special Issue Resonator Sensors 2018)

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