Sensors

Editorial

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4 pages, 165 KiB

Open AccessEditorial

Smart Sensing Technologies for Personalised e-Coaching

by Oresti Banos^1,2,*

, Hermie Hermens^1,3, Christopher Nugent⁴

and Hector Pomares²

¹ Biomedical Signals and Systems Group, University of Twente, 7522 NB Enschede, The Netherlands

² CITIC-UGR, University of Granada, E-18015 Granada, Spain

³ Telemedicine Group, Roessingh Research and Development, 7500 AH Enschede, The Netherlands

⁴ Smart Environments Research Group, Ulster University, Newtownabbey BT37 0QB, UK

Sensors 2018, 18(6), 1751; https://doi.org/10.3390/s18061751 - 29 May 2018

Cited by 4 | Viewed by 5608

Abstract

People living in both developed and developing countries face serious health challenges related to sedentary lifestyles. It is therefore essential to find new ways to improve health so that people can live longer and age well. With an ever-growing number of smart sensing [...] Read more.

People living in both developed and developing countries face serious health challenges related to sedentary lifestyles. It is therefore essential to find new ways to improve health so that people can live longer and age well. With an ever-growing number of smart sensing systems developed and deployed across the globe, experts are primed to help coach people to have healthier behaviors. The increasing accountability associated with app- and device-based behavior tracking not only provides timely and personalized information and support, but also gives us an incentive to set goals and do more. This paper outlines some of the recent efforts made towards automatic and autonomous identification and coaching of troublesome behaviors to procure lasting, beneficial behavioral changes. Full article

(This article belongs to the Special Issue Smart Sensing Technologies for Personalised Coaching)

Research

Jump to: Editorial, Review, Other

14 pages, 2555 KiB

Open AccessArticle

Differentiation Between Organic and Non-Organic Apples Using Diffraction Grating and Image Processing—A Cost-Effective Approach

by Nanfeng Jiang¹, Weiran Song², Hui Wang², Gongde Guo^1,* and Yuanyuan Liu¹

¹ Digit Fujian Internet-of-Things Laboratory of Environmental Monitoring, School of Mathematics and Informatics, Fujian Normal University, Fuzhou 350007, China

² School of Computing, Ulster University, Belfast, BT37 0QB, UK

Sensors 2018, 18(6), 1667; https://doi.org/10.3390/s18061667 - 23 May 2018

Cited by 9 | Viewed by 5057

Abstract

As the expectation for higher quality of life increases, consumers have higher demands for quality food. Food authentication is the technical means of ensuring food is what it says it is. A popular approach to food authentication is based on spectroscopy, which has [...] Read more.

As the expectation for higher quality of life increases, consumers have higher demands for quality food. Food authentication is the technical means of ensuring food is what it says it is. A popular approach to food authentication is based on spectroscopy, which has been widely used for identifying and quantifying the chemical components of an object. This approach is non-destructive and effective but expensive. This paper presents a computer vision-based sensor system for food authentication, i.e., differentiating organic from non-organic apples. This sensor system consists of low-cost hardware and pattern recognition software. We use a flashlight to illuminate apples and capture their images through a diffraction grating. These diffraction images are then converted into a data matrix for classification by pattern recognition algorithms, including k-nearest neighbors (k-NN), support vector machine (SVM) and three partial least squares discriminant analysis (PLS-DA)- based methods. We carry out experiments on a reasonable collection of apple samples and employ a proper pre-processing, resulting in a highest classification accuracy of 94%. Our studies conclude that this sensor system has the potential to provide a viable solution to empower consumers in food authentication. Full article

(This article belongs to the Section Intelligent Sensors)

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9 pages, 1995 KiB

Open AccessArticle

Multilayer Black Phosphorus Near-Infrared Photodetectors

by Chaojian Hou¹, Lijun Yang^1,*, Bo Li², Qihan Zhang², Yuefeng Li³, Qiuyang Yue², Yang Wang¹, Zhan Yang^4,*

and Lixin Dong^2,*

¹ A Key Laboratory of Microsystems and Microstructures Manufacturing, Ministry of Education, School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China

² Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA

³ Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA

⁴ School of Mechatronics Engineering, Soochow University, Soochow 215000, China

Sensors 2018, 18(6), 1668; https://doi.org/10.3390/s18061668 - 23 May 2018

Cited by 31 | Viewed by 6673

Abstract

Black phosphorus (BP), owing to its distinguished properties, has become one of the most competitive candidates for photodetectors. However, there has been little attention paid on photo-response performance of multilayer BP nanoflakes with large layer thickness. In fact, multilayer BP nanoflakes with large [...] Read more.

Black phosphorus (BP), owing to its distinguished properties, has become one of the most competitive candidates for photodetectors. However, there has been little attention paid on photo-response performance of multilayer BP nanoflakes with large layer thickness. In fact, multilayer BP nanoflakes with large layer thickness have greater potential from the fabrication viewpoint as well as due to the physical properties than single or few layer ones. In this report, the thickness-dependence of the intrinsic property of BP photodetectors in the dark was initially investigated. Then the photo-response performance (including responsivity, photo-gain, photo-switching time, noise equivalent power, and specific detectivity) of BP photodetectors with relative thicker thickness was explored under a near-infrared laser beam (λ_IR = 830 nm). Our experimental results reveal the impact of BP’s thickness on the current intensity of the channel and show degenerated p-type BP is beneficial for larger current intensity. More importantly, the photo-response of our thicker BP photodetectors exhibited a larger responsivity up to 2.42 A/W than the few-layer ones and a fast response photo-switching speed (response time is ~2.5 ms) comparable to thinner BP nanoflakes was obtained, indicating BP nanoflakes with larger layer thickness are also promising for application for ultra-fast and ultra-high near-infrared photodetectors. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 24853 KiB

Open AccessArticle

Wave Propagation in Aluminum Honeycomb Plate and Debonding Detection Using Scanning Laser Vibrometer

by Jingjing Zhao, Fucai Li^*, Xiao Cao and Hongguang Li

State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai 200240, China

Sensors 2018, 18(6), 1669; https://doi.org/10.3390/s18061669 - 23 May 2018

Cited by 14 | Viewed by 4659

Abstract

Both the aerospace and marine industry have widely relied on a honeycomb sandwich structure (HSS) because of its high strength-to-weight ratio. However, the intrinsic nature of an adhesively bonded multi-layer structure increases the risk of debonding when the structure is under strain or [...] Read more.

Both the aerospace and marine industry have widely relied on a honeycomb sandwich structure (HSS) because of its high strength-to-weight ratio. However, the intrinsic nature of an adhesively bonded multi-layer structure increases the risk of debonding when the structure is under strain or exposed to varying temperatures. Such defects are normally concealed under the surface but can significantly compromise the strength and stiffness of a structure. In this paper, the guided wave method is used to detect debondings which are located between the skin and the honeycomb in sandwich plates. The propagation of guided waves in honeycomb plates is investigated via numerical techniques, with emphasis placed on demonstrating the behavior of structure-based wave interactions (SWIs). The SWI technique is effective to distinguish heterogeneous structures from homogeneous structures. The excitation frequency is necessary to generate obvious SWIs in HSSs; accordingly, a novel strategy is proposed to select the optimal excitation frequencies. A series of experiments are conducted, the results of which show that the presented procedure can be used to effectively detect the locations and the sizes of single- and multi-damage zones in HSSs. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 3425 KiB

Open AccessArticle

Electron-Beam-Lithographed Nanostructures as Reference Materials for Label-Free Scattered-Light Biosensing of Single Filoviruses

by Anant Agrawal^1,*

, Joseph Majdi¹, Kathleen A. Clouse² and Tzanko Stantchev²

¹ Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD 20993, USA

² Division of Biotechnology Review and Research I, Office of Biotechnology Products, Office of Pharmaceutical Quality, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD 20993, USA

Sensors 2018, 18(6), 1670; https://doi.org/10.3390/s18061670 - 23 May 2018

Cited by 5 | Viewed by 3932

Abstract

Optical biosensors based on scattered-light measurements are being developed for rapid and label-free detection of single virions captured from body fluids. Highly controlled, stable, and non-biohazardous reference materials producing virus-like signals are valuable tools to calibrate, evaluate, and refine the performance of these [...] Read more.

Optical biosensors based on scattered-light measurements are being developed for rapid and label-free detection of single virions captured from body fluids. Highly controlled, stable, and non-biohazardous reference materials producing virus-like signals are valuable tools to calibrate, evaluate, and refine the performance of these new optical biosensing methods. To date, spherical polymer nanoparticles have been the only non-biological reference materials employed with scattered-light biosensing techniques. However, pathogens like filoviruses, including the Ebola virus, are far from spherical and their shape strongly affects scattered-light signals. Using electron beam lithography, we fabricated nanostructures resembling individual filamentous virions attached to a biosensing substrate (silicon wafer overlaid with silicon oxide film) and characterized their dimensions with scanning electron and atomic force microscopes. To assess the relevance of these nanostructures, we compared their signals across the visible spectrum to signals recorded from Ebola virus-like particles which exhibit characteristic filamentous morphology. We demonstrate the highly stable nature of our nanostructures and use them to obtain new insights into the relationship between virion dimensions and scattered-light signal. Full article

(This article belongs to the Special Issue Label-free Optical Nanobiosensors)

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20 pages, 930 KiB

Open AccessArticle

A General Cross-Layer Cloud Scheduling Framework for Multiple IoT Computer Tasks

by Guanlin Wu^1,*, Weidong Bao¹, Xiaomin Zhu^1,2 and Xiongtao Zhang¹

¹ College of Systems Engineering, National University of Defense Technology, Changsha 410073, China

² State Key Laboratory of High Performance Computing, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(6), 1671; https://doi.org/10.3390/s18061671 - 23 May 2018

Cited by 7 | Viewed by 3544

Abstract

The diversity of IoT services and applications brings enormous challenges to improving the performance of multiple computer tasks’ scheduling in cross-layer cloud computing systems. Unfortunately, the commonly-employed frameworks fail to adapt to the new patterns on the cross-layer cloud. To solve this issue, [...] Read more.

The diversity of IoT services and applications brings enormous challenges to improving the performance of multiple computer tasks’ scheduling in cross-layer cloud computing systems. Unfortunately, the commonly-employed frameworks fail to adapt to the new patterns on the cross-layer cloud. To solve this issue, we design a new computer task scheduling framework for multiple IoT services in cross-layer cloud computing systems. Specifically, we first analyze the features of the cross-layer cloud and computer tasks. Then, we design the scheduling framework based on the analysis and present detailed models to illustrate the procedures of using the framework. With the proposed framework, the IoT services deployed in cross-layer cloud computing systems can dynamically select suitable algorithms and use resources more effectively to finish computer tasks with different objectives. Finally, the algorithms are given based on the framework, and extensive experiments are also given to validate its effectiveness, as well as its superiority. Full article

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

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20 pages, 478 KiB

Open AccessArticle

Time and Memory Efficient Online Piecewise Linear Approximation of Sensor Signals

by Florian Grützmacher^1,*

, Benjamin Beichler¹

, Albert Hein²

, Thomas Kirste² and Christian Haubelt¹

¹ Institute of Applied Microelectronics and Computer Engineering, University of Rostock, 18051 Rostock, Germany

² Institute of Computer Science, University of Rostock, 18051 Rostock, Germany

Sensors 2018, 18(6), 1672; https://doi.org/10.3390/s18061672 - 23 May 2018

Cited by 20 | Viewed by 4705

Abstract

Piecewise linear approximation of sensor signals is a well-known technique in the fields of Data Mining and Activity Recognition. In this context, several algorithms have been developed, some of them with the purpose to be performed on resource constrained microcontroller architectures of wireless [...] Read more.

Piecewise linear approximation of sensor signals is a well-known technique in the fields of Data Mining and Activity Recognition. In this context, several algorithms have been developed, some of them with the purpose to be performed on resource constrained microcontroller architectures of wireless sensor nodes. While microcontrollers are usually constrained in computational power and memory resources, all state-of-the-art piecewise linear approximation techniques either need to buffer sensor data or have an execution time depending on the segment’s length. In the paper at hand, we propose a novel piecewise linear approximation algorithm, with a constant computational complexity as well as a constant memory complexity. Our proposed algorithm’s worst-case execution time is one to three orders of magnitude smaller and its average execution time is three to seventy times smaller compared to the state-of-the-art Piecewise Linear Approximation (PLA) algorithms in our experiments. In our evaluations, we show that our algorithm is time and memory efficient without sacrificing the approximation quality compared to other state-of-the-art piecewise linear approximation techniques, while providing a maximum error guarantee per segment, a small parameter space of only one parameter, and a maximum latency of one sample period plus its worst-case execution time. Full article

(This article belongs to the Section Sensor Networks)

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12 pages, 2405 KiB

Open AccessArticle

Angle Measurement of Objects outside the Linear Field of View of a Strapdown Semi-Active Laser Seeker

by Yongbin Zheng^*

, Huimin Chen and Zongtan Zhou

College of Intelligence Science and Technology, National university of Defense Technology, Changsha 410073, China

Sensors 2018, 18(6), 1673; https://doi.org/10.3390/s18061673 - 23 May 2018

Cited by 7 | Viewed by 5494

Abstract

The accurate angle measurement of objects outside the linear field of view (FOV) is a challenging task for a strapdown semi-active laser seeker and is not yet well resolved. Considering the fact that the strapdown semi-active laser seeker is equipped with GPS and [...] Read more.

The accurate angle measurement of objects outside the linear field of view (FOV) is a challenging task for a strapdown semi-active laser seeker and is not yet well resolved. Considering the fact that the strapdown semi-active laser seeker is equipped with GPS and an inertial navigation system (INS) on a missile, in this work, we present an angle measurement method based on the fusion of the seeker’s data and GPS and INS data for a strapdown semi-active laser seeker. When an object is in the nonlinear FOV or outside the FOV, by solving the problems of space consistency and time consistency, the pitch angle and yaw angle of the object can be calculated via the fusion of the last valid angles measured by the seeker and the corresponding GPS and INS data. The numerical simulation results demonstrate the correctness and effectiveness of the proposed method. Full article

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

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19 pages, 3543 KiB

Open AccessArticle

Holey-Cavity-Based Compressive Sensing for Ultrasound Imaging

by Ashkan Ghanbarzadeh-Dagheyan¹

, Chang Liu¹, Ali Molaei², Juan Heredia^1,2 and Jose Martinez Lorenzo^1,2,*

¹ Mechanical Engineering Department, Northeastern University, Boston, MA 02115, USA

² Electrical Engineering Department, Northeastern University, Boston, MA 02115, USA

Sensors 2018, 18(6), 1674; https://doi.org/10.3390/s18061674 - 23 May 2018

Cited by 10 | Viewed by 4684

Abstract

The use of solid cavities around electromagnetic sources has been recently reported as a mechanism to provide enhanced images at microwave frequencies. These cavities are used as measurement randomizers; and they compress the wave fields at the physical layer. As a result of [...] Read more.

The use of solid cavities around electromagnetic sources has been recently reported as a mechanism to provide enhanced images at microwave frequencies. These cavities are used as measurement randomizers; and they compress the wave fields at the physical layer. As a result of this compression, the amount of information collected by the sensing array through the different excited modes inside the resonant cavity is increased when compared to that obtained by no-cavity approaches. In this work, a two-dimensional cavity, having multiple openings, is used to perform such a compression for ultrasound imaging. Moreover, compressive sensing techniques are used for sparse signal retrieval with a limited number of operating transceivers. As a proof-of-concept of this theoretical investigation, two point-like targets located in a uniform background medium are imaged in the presence and the absence of the cavity. In addition, an analysis of the sensing capacity and the shape of the point spread function is also carried out for the aforementioned cases. The cavity is designed to have the maximum sensing capacity given different materials and opening sizes. It is demonstrated that the use of a cavity, whether it is made of plastic or metal, can significantly enhance the sensing capacity and the point spread function of a focused beam. The imaging performance is also improved in terms cross-range resolution when compared to the no-cavity case. Full article

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

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11 pages, 1853 KiB

Open AccessArticle

Power Consumption and Calculation Requirement Analysis of AES for WSN IoT

by Chung-Wen Hung^*

and Wen-Ting Hsu

Department of Electrical Engineering, National Yunlin University of Science & Technology, 123 University Road, Section 3, Douliou 64002, Yunlin, Taiwan

Sensors 2018, 18(6), 1675; https://doi.org/10.3390/s18061675 - 23 May 2018

Cited by 37 | Viewed by 6944

Abstract

Because of the ubiquity of Internet of Things (IoT) devices, the power consumption and security of IoT systems have become very important issues. Advanced Encryption Standard (AES) is a block cipher algorithm is commonly used in IoT devices. In this paper, the power [...] Read more.

Because of the ubiquity of Internet of Things (IoT) devices, the power consumption and security of IoT systems have become very important issues. Advanced Encryption Standard (AES) is a block cipher algorithm is commonly used in IoT devices. In this paper, the power consumption and cryptographic calculation requirement for different payload lengths and AES encryption types are analyzed. These types include software-based AES-CB, hardware-based AES-ECB (Electronic Codebook Mode), and hardware-based AES-CCM (Counter with CBC-MAC Mode). The calculation requirement and power consumption for these AES encryption types are measured on the Texas Instruments LAUNCHXL-CC1310 platform. The experimental results show that the hardware-based AES performs better than the software-based AES in terms of power consumption and calculation cycle requirements. In addition, in terms of AES mode selection, the AES-CCM-MIC64 mode may be a better choice if the IoT device is considering security, encryption calculation requirement, and low power consumption at the same time. However, if the IoT device is pursuing lower power and the payload length is generally less than 16 bytes, then AES-ECB could be considered. Full article

(This article belongs to the Special Issue Security, Trust and Privacy for Sensor Networks)

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18 pages, 6518 KiB

Open AccessArticle

Collaborative Working Architecture for IoT-Based Applications

by Higinio Mora^1,*

, María Teresa Signes-Pont¹, David Gil¹

and Magnus Johnsson^2,3,4

¹ Department of Computer Science Technology and Computation, University of Alicante, 03690 Alicante, Spain

² Department of Intelligent Cybernetic Systems, NRNU MEPhI, 115409 Moscow, Russia

³ Department of Philosophy, Lund University Cognitive Science, 22362 Lund, Sweden

⁴ Magnus Johnsson AI Research AB, 24334 Höör, Sweden

Sensors 2018, 18(6), 1676; https://doi.org/10.3390/s18061676 - 23 May 2018

Cited by 22 | Viewed by 7099

Abstract

The new sensing applications need enhanced computing capabilities to handle the requirements of complex and huge data processing. The Internet of Things (IoT) concept brings processing and communication features to devices. In addition, the Cloud Computing paradigm provides resources and infrastructures for performing [...] Read more.

The new sensing applications need enhanced computing capabilities to handle the requirements of complex and huge data processing. The Internet of Things (IoT) concept brings processing and communication features to devices. In addition, the Cloud Computing paradigm provides resources and infrastructures for performing the computations and outsourcing the work from the IoT devices. This scenario opens new opportunities for designing advanced IoT-based applications, however, there is still much research to be done to properly gear all the systems for working together. This work proposes a collaborative model and an architecture to take advantage of the available computing resources. The resulting architecture involves a novel network design with different levels which combines sensing and processing capabilities based on the Mobile Cloud Computing (MCC) paradigm. An experiment is included to demonstrate that this approach can be used in diverse real applications. The results show the flexibility of the architecture to perform complex computational tasks of advanced applications. 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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15 pages, 5495 KiB

Open AccessArticle

Real-Time Hand Position Sensing Technology Based on Human Body Electrostatics

by Kai Tang, Pengfei Li, Chuang Wang, Yifei Wang and Xi Chen^*

State Key Laboratory of Mechatronics Engineering and Control, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(6), 1677; https://doi.org/10.3390/s18061677 - 23 May 2018

Cited by 8 | Viewed by 4428

Abstract

Non-contact human-computer interactions (HCI) based on hand gestures have been widely investigated. Here, we present a novel method to locate the real-time position of the hand using the electrostatics of the human body. This method has many advantages, including a delay of less [...] Read more.

Non-contact human-computer interactions (HCI) based on hand gestures have been widely investigated. Here, we present a novel method to locate the real-time position of the hand using the electrostatics of the human body. This method has many advantages, including a delay of less than one millisecond, low cost, and does not require a camera or wearable devices. A formula is first created to sense array signals with five spherical electrodes. Next, a solving algorithm for the real-time measured hand position is introduced and solving equations for three-dimensional coordinates of hand position are obtained. A non-contact real-time hand position sensing system was established to perform verification experiments, and the principle error of the algorithm and the systematic noise were also analyzed. The results show that this novel technology can determine the dynamic parameters of hand movements with good robustness to meet the requirements of complicated HCI. Full article

(This article belongs to the Special Issue Innovative Sensor Technology for Intelligent System and Computing)

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21 pages, 3061 KiB

Open AccessArticle

Evaluation of Image Reconstruction Algorithms for Confocal Microwave Imaging: Application to Patient Data

by Muhammad Adnan Elahi^1,*

, Declan O’Loughlin¹

, Benjamin R. Lavoie²

, Martin Glavin¹

, Edward Jones¹, Elise C. Fear²

and Martin O’Halloran¹

¹ Electrical and Electronic Engineering, National University of Ireland Galway, H91 TK33 Galway, Ireland

² Department of Electrical and Computer Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada

Sensors 2018, 18(6), 1678; https://doi.org/10.3390/s18061678 - 23 May 2018

Cited by 71 | Viewed by 6254

Abstract

Confocal Microwave Imaging (CMI) for the early detection of breast cancer has been under development for over two decades and is currently going through early-phase clinical evaluation. The image reconstruction algorithm is a key signal processing component of any CMI-based breast imaging system [...] Read more.

Confocal Microwave Imaging (CMI) for the early detection of breast cancer has been under development for over two decades and is currently going through early-phase clinical evaluation. The image reconstruction algorithm is a key signal processing component of any CMI-based breast imaging system and impacts the efficacy of CMI in detecting breast cancer. Several image reconstruction algorithms for CMI have been developed since its inception. These image reconstruction algorithms have been previously evaluated and compared, using both numerical and physical breast models, and healthy volunteer data. However, no study has been performed to evaluate the performance of image reconstruction algorithms using clinical patient data. In this study, a variety of imaging algorithms, including both data-independent and data-adaptive algorithms, were evaluated using data obtained from a small-scale patient study conducted at the University of Calgary. Six imaging algorithms were applied to reconstruct 3D images of five clinical patients. Reconstructed images for each algorithm and each patient were compared to the available clinical reports, in terms of abnormality detection and localisation. The imaging quality of each algorithm was evaluated using appropriate quality metrics. The results of the conventional Delay-and-Sum algorithm and the Delay-Multiply-and-Sum (DMAS) algorithm were found to be consistent with the clinical information, with DMAS producing better quality images compared to all other algorithms. Full article

(This article belongs to the Special Issue Sensors for Microwave Imaging and Detection)

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22 pages, 3532 KiB

Open AccessArticle

Pulse Based Time-of-Flight Range Sensing

by Hamed Sarbolandi^*, Markus Plack

and Andreas Kolb

Institute for Vision and Graphics, University of Siegen, 57068 Siegen, Germany

Sensors 2018, 18(6), 1679; https://doi.org/10.3390/s18061679 - 23 May 2018

Cited by 38 | Viewed by 12365

Abstract

Pulse-based Time-of-Flight (PB-ToF) cameras are an attractive alternative range imaging approach, compared to the widely commercialized Amplitude Modulated Continuous-Wave Time-of-Flight (AMCW-ToF) approach. This paper presents an in-depth evaluation of a PB-ToF camera prototype based on the Hamamatsu area sensor S11963-01CR. We evaluate different [...] Read more.

Pulse-based Time-of-Flight (PB-ToF) cameras are an attractive alternative range imaging approach, compared to the widely commercialized Amplitude Modulated Continuous-Wave Time-of-Flight (AMCW-ToF) approach. This paper presents an in-depth evaluation of a PB-ToF camera prototype based on the Hamamatsu area sensor S11963-01CR. We evaluate different ToF-related effects, i.e., temperature drift, systematic error, depth inhomogeneity, multi-path effects, and motion artefacts. Furthermore, we evaluate the systematic error of the system in more detail, and introduce novel concepts to improve the quality of range measurements by modifying the mode of operation of the PB-ToF camera. Finally, we describe the means of measuring the gate response of the PB-ToF sensor and using this information for PB-ToF sensor simulation. Full article

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

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16 pages, 4690 KiB

Open AccessArticle

Laser Spectroscopic Sensors for the Development of Anthropomorphic Robot Sensitivity

by Oleg Bukin^1,*, Dmitriy Proschenko^1,2, Alexey Chekhlenok¹, Sergey Golik^2,3, Ilya Bukin¹, Alexander Mayor^2,3 and Victoriya Yurchik¹

¹ Maritime State University Named after G.I. Nevelskoy, Verkhneportovaya 50A St., 690059 Vladivostok, Russia

² Far Eastern Federal University, Sukhanova 8 St., 690091 Vladivostok, Russia

³ Institute of Automation and Control Processes FEBRAS, Radio 5 St., 690041 Vladivostok, Russia

Sensors 2018, 18(6), 1680; https://doi.org/10.3390/s18061680 - 23 May 2018

Cited by 11 | Viewed by 5248

Abstract

The development of underwater robotics sensitivity, which is based on the sensors of laser spectroscopy methods, have been discussed. The ways to improve Laser Induced Fluorescence (LIF) and Laser Induced Breakdown Spectroscopy (LIBS) methods were investigated in order to develop and create laser [...] Read more.

The development of underwater robotics sensitivity, which is based on the sensors of laser spectroscopy methods, have been discussed. The ways to improve Laser Induced Fluorescence (LIF) and Laser Induced Breakdown Spectroscopy (LIBS) methods were investigated in order to develop and create laser sensitivity for underwater robotics. A brief overview is done in the article, where LIF and LIBS spectroscopy in underwater robotics are used as spectroscopy sensors in order to investigate underwater environments by means of underwater vehicles. Limit of Detection (LoD) of oil and oil product solutions in the seawater have been detected by means of nanosecond and femtosecond spectroscopy LIF. All results, which had been received by laser pulses of different duration, were compared. The same experiments have been provided in order to measure concentrations of elements in the seawater and solutions by the LIBS method. It was discovered that the LoD of a group of elements was reduced when the femtosecond LIBS was used. Anthropomorphic complexes were under discussion in order to adopt laser spectroscopy sensors for underwater environments. The submersible module, which was constructed to investigate and examine laser spectroscopy sensors, has been described. Full article

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

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18 pages, 5849 KiB

Open AccessArticle

Development of a Cloud Computing-Based Pier Type Port Structure Stability Evaluation Platform Using Fiber Bragg Grating Sensors

by Byung Wan Jo, Jun Ho Jo^*

, Rana Muhammad Asad Khan

, Jung Hoon Kim and Yun Sung Lee

Department of Civil and Environmental Engineering, Hanyang University, Seoul 04763, Korea

Sensors 2018, 18(6), 1681; https://doi.org/10.3390/s18061681 - 23 May 2018

Cited by 11 | Viewed by 4095

Abstract

Structure Health Monitoring is a topic of great interest in port structures due to the ageing of structures and the limitations of evaluating structures. This paper presents a cloud computing-based stability evaluation platform for a pier type port structure using Fiber Bragg Grating [...] Read more.

Structure Health Monitoring is a topic of great interest in port structures due to the ageing of structures and the limitations of evaluating structures. This paper presents a cloud computing-based stability evaluation platform for a pier type port structure using Fiber Bragg Grating (FBG) sensors in a system consisting of a FBG strain sensor, FBG displacement gauge, FBG angle meter, gateway, and cloud computing-based web server. The sensors were installed on core components of the structure and measurements were taken to evaluate the structures. The measurement values were transmitted to the web server via the gateway to analyze and visualize them. All data were analyzed and visualized in the web server to evaluate the structure based on the safety evaluation index (SEI). The stability evaluation platform for pier type port structures involves the efficient monitoring of the structures which can be carried out easily anytime and anywhere by converging new technologies such as cloud computing and FBG sensors. In addition, the platform has been successfully implemented at “Maryang Harbor” situated in Maryang-Meyon of Korea to test its durability. Full article

(This article belongs to the Section Internet of Things)

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16 pages, 5040 KiB

Open AccessArticle

A PVDF-Based Sensor for Internal Stress Monitoring of a Concrete-Filled Steel Tubular (CFST) Column Subject to Impact Loads

by Guofeng Du¹, Zhao Li¹

and Gangbing Song^2,*

¹ School of Urban Construction, Yangtze University, Jingzhou 434023, China

² Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA

Sensors 2018, 18(6), 1682; https://doi.org/10.3390/s18061682 - 23 May 2018

Cited by 51 | Viewed by 9330

Abstract

Impact loads can have major adverse effects on the safety of civil engineering structures, such as concrete-filled steel tubular (CFST) columns. The study of mechanical behavior and stress analysis of CFST columns under impact loads is very important to ensure their safety against [...] Read more.

Impact loads can have major adverse effects on the safety of civil engineering structures, such as concrete-filled steel tubular (CFST) columns. The study of mechanical behavior and stress analysis of CFST columns under impact loads is very important to ensure their safety against such loads. At present, the internal stress monitoring of the concrete cores CFST columns under impact loads is still a very challenging subject. In this paper, a PVDF (Polyvinylidene Fluoride) piezoelectric smart sensor was developed and successfully applied to the monitoring of the internal stress of the concrete core of a CFST column under impact loads. The smart sensor consists of a PVDF piezoelectric film sandwiched between two thin steel plates through epoxy. The protection not only prevents the PVDF film from impact damages but also ensures insulation and waterproofing. The smart sensors were embedded into the circular concrete-filled steel tube specimen during concrete pouring. The specimen was tested against impact loads, and testing data were collected. The time history of the stress obtained from the PVDF smart sensor revealed the evolution of core concrete internal stress under impact loads when compared with the impact force–time curve of the hammer. Nonlinear finite element simulations of the impact process were also carried out. The results of FEM simulations had good agreement with the test results. The results showed that the proposed PVDF piezoelectric smart sensors can effectively monitor the internal stress of concrete-filled steel tubular columns under impact loads. Full article

(This article belongs to the Special Issue Recent Advances of Piezoelectric Transducers and Applications)

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15 pages, 5781 KiB

Open AccessArticle

Electrolyte Magnetohydrondyamics Flow Sensing in an Open Annular Channel—A Vision System for Validation of the Mathematical Model

by Mónica Valenzuela-Delgado, Wendy Flores-Fuentes^*

, Moisés Rivas-López

, Oleg Sergiyenko

, Lars Lindner, Daniel Hernández-Balbuena and Julio C. Rodríguez-Quiñonez

Facultad de Ingeniería, Universidad Autónoma de Baja California, Mexicali C.P. 21280, Baja California, Mexico

Sensors 2018, 18(6), 1683; https://doi.org/10.3390/s18061683 - 24 May 2018

Cited by 13 | Viewed by 3963

Abstract

Magnetohydrodynamics (MHD) is becoming more popular every day among developers of applications based on microfluidics, such as “lab on a chip” (LOC) and/or “micro-total analysis systems” (micro-TAS). Its physical properties enable fluid manipulation for tasks such as pumping, networking, propelling, stirring, mixing, and [...] Read more.

Magnetohydrodynamics (MHD) is becoming more popular every day among developers of applications based on microfluidics, such as “lab on a chip” (LOC) and/or “micro-total analysis systems” (micro-TAS). Its physical properties enable fluid manipulation for tasks such as pumping, networking, propelling, stirring, mixing, and even cooling without the need for mechanical components, and its non-intrusive nature provides a solution to mechanical systems issues. However, these are not easy tasks. They all require precise flow control, which depends on several parameters, like microfluidics conductivity, the microfluidics conduit (channel) shape and size configuration, and the interaction between magnetic and electric fields. This results in a mathematical model that needs to be validated theoretically and experimentally. The present paper introduces the design of a 3D laminar flow involving an electrolyte in an annular open channel driven by a Lorentz force. For an organized description, first of all is provided an introduction to MHD applied in microfluidics, then an overall description of the proposed MHD microfluidic system is given, after that is focused in the theoretical validation of the mathematical model, next is described the experimental validation of the mathematical model using a customized vision system, and finally conclusions and future work are stated. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 5258 KiB

Open AccessArticle

Comparison between Different Types of Sensors Used in the Real Operational Environment Based on Optical Scanning System

by Wendy Flores-Fuentes¹

, Jesús Elías Miranda-Vega^2,*, Moisés Rivas-López²

, Oleg Sergiyenko²

, Julio C. Rodríguez-Quiñonez¹ and Lars Lindner²

¹ Facultad de Ingeniería, Universidad Autónoma de Baja California, Mexicali, Baja California 21280, Mexico

² Instituto de Ingeniería, Universidad Autónoma de Baja California, Mexicali, Baja California 21280, Mexico

Sensors 2018, 18(6), 1684; https://doi.org/10.3390/s18061684 - 24 May 2018

Cited by 17 | Viewed by 5689

Abstract

The present paper describes the experimentation in a controlled environment and a real environment using different photosensors, such as infrared light emitting diode (IRLED-as receiver), photodiode, light dependent resistor (LDR), and blue LED for the purpose of selecting those devices, which can be [...] Read more.

The present paper describes the experimentation in a controlled environment and a real environment using different photosensors, such as infrared light emitting diode (IRLED-as receiver), photodiode, light dependent resistor (LDR), and blue LED for the purpose of selecting those devices, which can be employed in adverse conditions, such as sunlight or artificial sources. The experiments that are described in this paper confirmed that the blue LED and phototransistor could be used as a photosensor of an Optical Scanning System (OSS), because they were less sensitive to sunlight radiation. Moreover, they are appropriate as reference sources that are selected for the experiment (blue LED flashlight and light bulb). The best experimental results that were obtained contained a digital filter that was applied to the output of the photosensor, which reduced the standard deviation for the best case for the phototransistor LED from 100.26 to 0.15. For the best case, using the blue LED, the standard deviation was reduced from 86.08 to 0.11. Using these types of devices the cost of the Optical Scanning System can be reduced and a considerable increase in resolution and accuracy. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 2020 KiB

Open AccessArticle

Label-Free Detection of Salivary Pepsin Using Gold Nanoparticle/Polypyrrole Nanocoral Modified Screen-Printed Electrode

by Doyeon Lee¹, Young Ju Lee², Young-Gyu Eun³ and Gi-Ja Lee^1,2,*

¹ Department of Medical Engineering, Graduate School, Kyung Hee University, Seoul 130-701, Korea

² Department of Biomedical Engineering, College of Medicine, Kyung Hee University, Seoul 130-701, Korea

³ Department of Otolaryngology-Head and Neck Surgery, Kyung Hee University Medical Center, Seoul 130-702, Korea

Sensors 2018, 18(6), 1685; https://doi.org/10.3390/s18061685 - 24 May 2018

Cited by 22 | Viewed by 6169

Abstract

Detection of salivary pepsin has been given attention as a new diagnostic tool for laryngopharyngeal reflux (LPR) disease, because saliva collection is non-invasive and relatively comfortable. In this study, we prepared polypyrrole nanocorals (PPNCs) on a screen-printed carbon electrode (SPCE) by a soft [...] Read more.

Detection of salivary pepsin has been given attention as a new diagnostic tool for laryngopharyngeal reflux (LPR) disease, because saliva collection is non-invasive and relatively comfortable. In this study, we prepared polypyrrole nanocorals (PPNCs) on a screen-printed carbon electrode (SPCE) by a soft template synthesis method, using β-naphthalenesulfonic acid (NSA) (for short, PPNCs/SPCE). Gold nanoparticles (GNPs) were then decorated on PPNCs/SPCE by electrodeposition (for short, GNP/PPNCs/SPCE). To construct the immunosensor, pepsin antibody was immobilized on GNP/PPNCs/SPCE. Next, citric acid was applied to prevent non-specific binding and change the electrode surface charge before pepsin incubation. Electrochemical stepwise characterization was performed using cyclic voltammetry, and immunosensor response toward different pepsin concentrations was measured by differential pulsed voltammetry. As a result, our electrochemical immunosensor showed a sensitive detection performance toward pepsin with a linear range from 6.25 to 100 ng/mL and high specificity toward pepsin, as well as a low limit of detection of 2.2 ng/mL. Finally, we quantified the pepsin levels in saliva samples of LPR patients (n = 2), showing that the results were concordant with those of a conventional ELISA method. Therefore, we expect that this electrochemical immunosensor could be helpful for preliminarily diagnosing LPR through the detection of pepsin in saliva. Full article

(This article belongs to the Special Issue Biosensors for the Detection of Biomarkers)

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19 pages, 842 KiB

Open AccessArticle

Cooperative Computing System for Heavy-Computation and Low-Latency Processing in Wireless Sensor Networks

by Jongtack Jung^†

, Woonghee Lee^†

and Hwangnam Kim^*

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

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1686; https://doi.org/10.3390/s18061686 - 24 May 2018

Cited by 6 | Viewed by 3225

Abstract

Over the past decades, hardware and software technologies for wireless sensor networks (WSNs) have significantly progressed, and WSNs are widely used in various areas including Internet of Things (IoT). In general, existing WSNs are mainly used for applications that require delay-tolerance and low-computation [...] Read more.

Over the past decades, hardware and software technologies for wireless sensor networks (WSNs) have significantly progressed, and WSNs are widely used in various areas including Internet of Things (IoT). In general, existing WSNs are mainly used for applications that require delay-tolerance and low-computation due to the poor resources of traditional sensor nodes in WSNs. However, compared to the traditional sensor nodes, today’s devices for WSNs have more powerful resource. Thus, sensor nodes these days not only conduct sensing and transmitting data to servers but also are able to process many operations, so more diverse applications can be applied to WSNs. Especially, many applications using audio data have been proposed because audio is one of the most widely used data types, and many mobile devices already have a built-in microphone. However, many of the applications have a requirement that heavy-operations should be done by a tight deadline, so it is difficult for a single node in WSNs to run relatively heavy applications by itself. In this paper, to overcome this limitation of WSNs, we propose a new emerging system, HeaLow, a cooperative computing system for heavy-computation and low-latency processing in WSNs. We designed HeaLow and carried out the practical implementation on real devices. We confirmed the effectiveness of HeaLow through various experiments using the real devices and simulations. Using HeaLow, nodes in WSNs are able to perform heavy-computation processes while satisfying a completion time requirement. Full article

(This article belongs to the Special Issue Internet of Things and Ubiquitous Sensing)

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13 pages, 6583 KiB

Open AccessArticle

FEM Analysis of Sezawa Mode SAW Sensor for VOC Based on CMOS Compatible AlN/SiO₂/Si Multilayer Structure

by Muhammad Zubair Aslam^1,*, Varun Jeoti¹, Saravanan Karuppanan², Aamir Farooq Malik¹ and Asif Iqbal¹

¹ Department of Electrical and Electronics Engineering, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia

² Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia

Sensors 2018, 18(6), 1687; https://doi.org/10.3390/s18061687 - 24 May 2018

Cited by 35 | Viewed by 8020

Abstract

A Finite Element Method (FEM) simulation study is conducted, aiming to scrutinize the sensitivity of Sezawa wave mode in a multilayer AlN/SiO₂/Si Surface Acoustic Wave (SAW) sensor to low concentrations of Volatile Organic Compounds (VOCs), that is, trichloromethane, trichloroethylene, carbon tetrachloride [...] Read more.

A Finite Element Method (FEM) simulation study is conducted, aiming to scrutinize the sensitivity of Sezawa wave mode in a multilayer AlN/SiO₂/Si Surface Acoustic Wave (SAW) sensor to low concentrations of Volatile Organic Compounds (VOCs), that is, trichloromethane, trichloroethylene, carbon tetrachloride and tetrachloroethene. A Complimentary Metal-Oxide Semiconductor (CMOS) compatible AlN/SiO₂/Si based multilayer SAW resonator structure is taken into account for this purpose. In this study, first, the influence of AlN and SiO₂ layers’ thicknesses over phase velocities and electromechanical coupling coefficients (k²) of two SAW modes (i.e., Rayleigh and Sezawa) is analyzed and the optimal thicknesses of AlN and SiO₂ layers are opted for best propagation characteristics. Next, the study is further extended to analyze the mass loading effect on resonance frequencies of SAW modes by coating a thin Polyisobutylene (PIB) polymer film over the AlN surface. Finally, the sensitivity of the two SAW modes is examined for VOCs. This study concluded that the sensitivity of Sezawa wave mode for 1 ppm of selected volatile organic gases is twice that of the Rayleigh wave mode. Full article

(This article belongs to the Special Issue Surface Acoustic Wave Sensors)

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9 pages, 3134 KiB

Open AccessArticle

Multiband Imaging CMOS Image Sensor with Multi-Storied Photodiode Structure ^†

by Yoshiaki Takemoto^*

, Mitsuhiro Tsukimura, Hideki Kato, Shunsuke Suzuki, Jun Aoki, Toru Kondo, Haruhisa Saito, Yuichi Gomi, Seisuke Matsuda and Yoshitaka Tadaki

¹ Olympus Corporation, Tokyo 163-0914, Japan

^† This paper is an expanded version of our published paper: Takemoto, Y.; Kobayashi, K.; Tsukimura, M.; Takazawa, N.; Kato, H.; Suzuki, S.; Aoki, J.; Kondo, T.; Saito, H.; Gomi, Y.; Matsuda, S.; Tadaki Y. Optical characteristics of multi-storied photodiode CMOS image sensor with 3D stacking technology. In Proceedings of the 2017 International Image Sensor Workshop, Hiroshima, Japan, 30 May–2 June 2017.

Sensors 2018, 18(6), 1688; https://doi.org/10.3390/s18061688 - 24 May 2018

Cited by 1 | Viewed by 14744

Abstract

We developed a multiband imaging CMOS image sensor (CIS) with a multi-storied photodiode structure, which comprises two photodiode (PD) arrays that capture two different images, visible red, green, and blue (RGB) and near infrared (NIR) images at the same time. The sensor enables [...] Read more.

We developed a multiband imaging CMOS image sensor (CIS) with a multi-storied photodiode structure, which comprises two photodiode (PD) arrays that capture two different images, visible red, green, and blue (RGB) and near infrared (NIR) images at the same time. The sensor enables us to capture a wide variety of multiband images which is not limited to conventional visible RGB images taken with a Bayer filter or to invisible NIR images. Its wiring layers between two PD arrays can have an optically optimized effect by modifying its material and thickness on the bottom PD array. The incident light angle on the bottom PD depends on the thickness and structure of the wiring and bonding layer, and the structure can act as an optical filter. Its wide-range sensitivity and optimized optical filtering structure enable us to create the images of specific bands of light waves in addition to visible RGB images without designated pixels for IR among same pixel arrays without additional optical components. Our sensor will push the envelope of capturing a wide variety of multiband images. Full article

(This article belongs to the Special Issue Special Issue on the 2017 International Image Sensor Workshop (IISW))

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27 pages, 12620 KiB

Open AccessArticle

A Service-Oriented Middleware for Integrated Management of Crowdsourced and Sensor Data Streams in Disaster Management

by Luiz Fernando F. G. de Assis^1,*

, Flávio E. A. Horita^1,4

, Edison P. de Freitas²

, Jó Ueyama¹

and João Porto De Albuquerque^1,3

¹ Institute of Mathematics and Computer Science (ICMC), University of São Paulo (USP), São Carlos/SP 13566-590, Brazil

² Federal University of Rio Grande do Sul, Porto Alegre/RS 90040-060, Brazil

³ Centre for Interdisciplinary Methodologies, University of Warwick, Coventry CV4 7AL, UK

⁴ Center for Mathematics, Computation and Cognition, Federal University of ABC, Santo André/SP 09210-580, Brazil

Sensors 2018, 18(6), 1689; https://doi.org/10.3390/s18061689 - 24 May 2018

Cited by 11 | Viewed by 6247

Abstract

The increasing number of sensors used in diverse applications has provided a massive number of continuous, unbounded, rapid data and requires the management of distinct protocols, interfaces and intermittent connections. As traditional sensor networks are error-prone and difficult to maintain, the study highlights [...] Read more.

The increasing number of sensors used in diverse applications has provided a massive number of continuous, unbounded, rapid data and requires the management of distinct protocols, interfaces and intermittent connections. As traditional sensor networks are error-prone and difficult to maintain, the study highlights the emerging role of “citizens as sensors” as a complementary data source to increase public awareness. To this end, an interoperable, reusable middleware for managing spatial, temporal, and thematic data using Sensor Web Enablement initiative services and a processing engine was designed, implemented, and deployed. The study found that its approach provided effective sensor data-stream access, publication, and filtering in dynamic scenarios such as disaster management, as well as it enables batch and stream management integration. Also, an interoperability analytics testing of a flood citizen observatory highlighted even variable data such as those provided by the crowd can be integrated with sensor data stream. Our approach, thus, offers a mean to improve near-real-time applications. Full article

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

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16 pages, 615 KiB

Open AccessArticle

Vehicle Classification Using an Imbalanced Dataset Based on a Single Magnetic Sensor

by Chang Xu^1,2,*

, Yingguan Wang¹, Xinghe Bao¹ and Fengrong Li¹

¹ Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China

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

Sensors 2018, 18(6), 1690; https://doi.org/10.3390/s18061690 - 24 May 2018

Cited by 37 | Viewed by 5813

Abstract

This paper aims to improve the accuracy of automatic vehicle classifiers for imbalanced datasets. Classification is made through utilizing a single anisotropic magnetoresistive sensor, with the models of vehicles involved being classified into hatchbacks, sedans, buses, and multi-purpose vehicles (MPVs). Using time domain [...] Read more.

This paper aims to improve the accuracy of automatic vehicle classifiers for imbalanced datasets. Classification is made through utilizing a single anisotropic magnetoresistive sensor, with the models of vehicles involved being classified into hatchbacks, sedans, buses, and multi-purpose vehicles (MPVs). Using time domain and frequency domain features in combination with three common classification algorithms in pattern recognition, we develop a novel feature extraction method for vehicle classification. These three common classification algorithms are the k-nearest neighbor, the support vector machine, and the back-propagation neural network. Nevertheless, a problem remains with the original vehicle magnetic dataset collected being imbalanced, and may lead to inaccurate classification results. With this in mind, we propose an approach called SMOTE, which can further boost the performance of classifiers. Experimental results show that the k-nearest neighbor (KNN) classifier with the SMOTE algorithm can reach a classification accuracy of 95.46%, thus minimizing the effect of the imbalance. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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15 pages, 1964 KiB

Open AccessArticle

A Statistical Approach to Detect Jamming Attacks in Wireless Sensor Networks

by Opeyemi Osanaiye^1,*, Attahiru S. Alfa^1,2

and Gerhard P. Hancke¹

¹ Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa

² Department of Electrical and Computer Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

Sensors 2018, 18(6), 1691; https://doi.org/10.3390/s18061691 - 24 May 2018

Cited by 115 | Viewed by 10030

Abstract

Wireless Sensor Networks (WSNs), in recent times, have become one of the most promising network solutions with a wide variety of applications in the areas of agriculture, environment, healthcare and the military. Notwithstanding these promising applications, sensor nodes in WSNs are vulnerable to [...] Read more.

Wireless Sensor Networks (WSNs), in recent times, have become one of the most promising network solutions with a wide variety of applications in the areas of agriculture, environment, healthcare and the military. Notwithstanding these promising applications, sensor nodes in WSNs are vulnerable to different security attacks due to their deployment in hostile and unattended areas and their resource constraints. One of such attacks is the DoS jamming attack that interferes and disrupts the normal functions of sensor nodes in a WSN by emitting radio frequency signals to jam legitimate signals to cause a denial of service. In this work we propose a step-wise approach using a statistical process control technique to detect these attacks. We deploy an exponentially weighted moving average (EWMA) to detect anomalous changes in the intensity of a jamming attack event by using the packet inter-arrival feature of the received packets from the sensor nodes. Results obtained from a trace-driven simulation show that the proposed solution can efficiently and accurately detect jamming attacks in WSNs with little or no overhead. Full article

(This article belongs to the Collection Smart Industrial Wireless Sensor Networks)

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15 pages, 2927 KiB

Open AccessFeature PaperArticle

Dynamical Properties of Postural Control in Obese Community-Dwelling Older Adults

by Christopher W. Frames^1,2, Rahul Soangra³

, Thurmon E. Lockhart^1,*

, John Lach⁴

, Dong Sam Ha⁵, Karen A. Roberto⁶

and Abraham Lieberman²

¹ School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85281, USA

² Muhammad Ali Parkinson Center (MAPC), Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA

³ Department of Physical Therapy, Crean College of Health and Behavioral Sciences, Chapman University, Orange, CA 92866, USA

⁴ Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA 22904, USA

⁵ The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA

⁶ Center for Gerontology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA

Sensors 2018, 18(6), 1692; https://doi.org/10.3390/s18061692 - 24 May 2018

Cited by 27 | Viewed by 5638

Abstract

Postural control is a key aspect in preventing falls. The aim of this study was to determine if obesity affected balance in community-dwelling older adults and serve as an indicator of fall risk. The participants were randomly assigned to receive a comprehensive geriatric [...] Read more.

Postural control is a key aspect in preventing falls. The aim of this study was to determine if obesity affected balance in community-dwelling older adults and serve as an indicator of fall risk. The participants were randomly assigned to receive a comprehensive geriatric assessment followed by a longitudinal assessment of their fall history. The standing postural balance was measured for 98 participants with a Body Mass Index (BMI) ranging from 18 to 63 kg/m², using a force plate and an inertial measurement unit affixed at the sternum. Participants’ fall history was recorded over 2 years and participants with at least one fall in the prior year were classified as fallers. The results suggest that body weight/BMI is an additional risk factor for falling in elderly persons and may be an important marker for fall risk. The linear variables of postural analysis suggest that the obese fallers have significantly higher sway area and sway ranges, along with higher root mean square and standard deviation of time series. Additionally, it was found that obese fallers have lower complexity of anterior-posterior center of pressure time series. Future studies should examine more closely the combined effect of aging and obesity on dynamic balance. Full article

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

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16 pages, 2551 KiB

Open AccessArticle

Acquiring Respiration Rate from Photoplethysmographic Signal by Recursive Bayesian Tracking of Intrinsic Modes in Time-Frequency Spectra

by Mikko Pirhonen^*

, Mikko Peltokangas

and Antti Vehkaoja

BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Tampere University of Technology, 33720 Tampere, Finland

Sensors 2018, 18(6), 1693; https://doi.org/10.3390/s18061693 - 24 May 2018

Cited by 26 | Viewed by 5839

Abstract

Respiration rate (RR) provides useful information for assessing the status of a patient. We propose RR estimation based on photoplethysmography (PPG) because the blood perfusion dynamics are known to carry information on breathing, as respiration-induced modulations in the PPG signal. We studied the [...] Read more.

Respiration rate (RR) provides useful information for assessing the status of a patient. We propose RR estimation based on photoplethysmography (PPG) because the blood perfusion dynamics are known to carry information on breathing, as respiration-induced modulations in the PPG signal. We studied the use of amplitude variability of transmittance mode finger PPG signal in RR estimation by comparing four time-frequency (TF) representation methods of the signal cascaded with a particle filter. The TF methods compared were short-time Fourier transform (STFT) and three types of synchrosqueezing methods. The public VORTAL database was used in this study. The results indicate that the advanced frequency reallocation methods based on synchrosqueezing approach may present improvement over linear methods, such as STFT. The best results were achieved using wavelet synchrosqueezing transform, having a mean absolute error and median error of 2.33 and 1.15 breaths per minute, respectively. Synchrosqueezing methods were generally more accurate than STFT on most of the subjects when particle filtering was applied. While TF analysis combined with particle filtering is a promising alternative for real-time estimation of RR, artefacts and non-respiration-related frequency components remain problematic and impose requirements for further studies in the areas of signal processing algorithms an PPG instrumentation. Full article

(This article belongs to the Special Issue Advanced Physiological Sensing)

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11 pages, 3671 KiB

Open AccessArticle

Piezoelectric Actuator with Frequency Characteristics for a Middle-Ear Implant

by Dong Ho Shin and Jin-Ho Cho^*

Institute of Biomedical Engineering Research, Kyungpook National University, 680, Gukchaebosang-ro, Jung-gu, Daegu 41944, Korea

Sensors 2018, 18(6), 1694; https://doi.org/10.3390/s18061694 - 24 May 2018

Cited by 18 | Viewed by 9815

Abstract

The design and implementation of a novel piezoelectric-based actuator for an implantable middle-ear hearing aid is described in this paper. The proposed actuator has excellent low-frequency output characteristics, and can generate high output in a specific frequency band by adjusting the mechanical resonance. [...] Read more.

The design and implementation of a novel piezoelectric-based actuator for an implantable middle-ear hearing aid is described in this paper. The proposed actuator has excellent low-frequency output characteristics, and can generate high output in a specific frequency band by adjusting the mechanical resonance. The actuator consists of a piezoelectric element, a miniature bellows, a cantilever membrane, a metal ring support, a ceramic tip, and titanium housing. The optimal structure of the cantilever-membrane design, which determines the frequency characteristics of the piezoelectric actuator, was derived through finite element analysis. Based on the results, the piezoelectric actuator was implemented, and its performance was verified through a cadaveric experiment. It was confirmed that the proposed actuator provides better performance than currently used actuators, in terms of frequency characteristics. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 5983 KiB

Open AccessArticle

Group Sparse Representation Based on Nonlocal Spatial and Local Spectral Similarity for Hyperspectral Imagery Classification

by Haoyang Yu^1,2, Lianru Gao^1,*

, Wenzhi Liao³

and Bing Zhang^1,2

¹ Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China

² College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China

³ Department of Telecommunications and Information Processing, IMEC-TELIN-Ghent University, 9000 Ghent, Belgium

Sensors 2018, 18(6), 1695; https://doi.org/10.3390/s18061695 - 24 May 2018

Cited by 16 | Viewed by 4382

Abstract

Spectral-spatial classification has been widely applied for remote sensing applications, especially for hyperspectral imagery. Traditional methods mainly focus on local spatial similarity and neglect nonlocal spatial similarity. Recently, nonlocal self-similarity (NLSS) has gradually gained support since it can be used to support spatial [...] Read more.

Spectral-spatial classification has been widely applied for remote sensing applications, especially for hyperspectral imagery. Traditional methods mainly focus on local spatial similarity and neglect nonlocal spatial similarity. Recently, nonlocal self-similarity (NLSS) has gradually gained support since it can be used to support spatial coherence tasks. However, these methods are biased towards the direct use of spatial information as a whole, while discriminative spectral information is not well exploited. In this paper, we propose a novel method to couple both nonlocal spatial and local spectral similarity together in a single framework. In particular, the proposed approach exploits nonlocal spatial similarities by searching non-overlapped patches, whereas spectral similarity is analyzed locally within the locally discovered patches. By fusion of nonlocal and local information, we then apply group sparse representation (GSR) for classification based on a group structured prior. Experimental results on three real hyperspectral data sets demonstrate the efficiency of the proposed approach, and the improvements are significant over the methods that consider either nonlocal or local similarity. Full article

(This article belongs to the Special Issue Spatial Analysis and Remote Sensing)

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11 pages, 1294 KiB

Open AccessArticle

Accurate Traffic Flow Prediction in Heterogeneous Vehicular Networks in an Intelligent Transport System Using a Supervised Non-Parametric Classifier

by Hesham El-Sayed^1,*

, Sharmi Sankar², Yousef-Awwad Daraghmi³, Prayag Tiwari⁴

, Ekarat Rattagan⁵, Manoranjan Mohanty⁶

, Deepak Puthal⁷ and Mukesh Prasad^8,*

¹ College of Information Technology, UAE University, Al Ain 15551, United Arab Emirates

² Department of Information Technology, Ibri College of Applied Sciences (MoHE), Ibri 516, Sultanate of Oman

³ Department of Computer Systems Engineering, Palestine Technical University, Tulkarem 007, Palestine

⁴ Department of Information Engineering, University of Padova, 35131 Padova, Italy

⁵ Faculty of Information Science and Technology, Mahanakorn University of Technology, Bangkok 10530, Thailand

⁶ Department of Computer Science, University of Auckland, Auckland 1010, New Zealand

⁷ School of Electrical and Data Engineering, FEIT, University of Technology Sydney, Sydney 2007, Australia

⁸ Centre for Artificial Intelligence, School of Software, FEIT, University of Technology Sydney, Sydney 2007, Australia

Sensors 2018, 18(6), 1696; https://doi.org/10.3390/s18061696 - 24 May 2018

Cited by 20 | Viewed by 6006

Abstract

Heterogeneous vehicular networks (HETVNETs) evolve from vehicular ad hoc networks (VANETs), which allow vehicles to always be connected so as to obtain safety services within intelligent transportation systems (ITSs). The services and data provided by HETVNETs should be neither interrupted nor delayed. Therefore, [...] Read more.

Heterogeneous vehicular networks (HETVNETs) evolve from vehicular ad hoc networks (VANETs), which allow vehicles to always be connected so as to obtain safety services within intelligent transportation systems (ITSs). The services and data provided by HETVNETs should be neither interrupted nor delayed. Therefore, Quality of Service (QoS) improvement of HETVNETs is one of the topics attracting the attention of researchers and the manufacturing community. Several methodologies and frameworks have been devised by researchers to address QoS-prediction service issues. In this paper, to improve QoS, we evaluate various traffic characteristics of HETVNETs and propose a new supervised learning model to capture knowledge on all possible traffic patterns. This model is a refinement of support vector machine (SVM) kernels with a radial basis function (RBF). The proposed model produces better results than SVMs, and outperforms other prediction methods used in a traffic context, as it has lower computational complexity and higher prediction accuracy. Full article

(This article belongs to the Special Issue Sensors for Green Computing)

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22 pages, 2530 KiB

Open AccessArticle

Maglev Train Signal Processing Architecture Based on Nonlinear Discrete Tracking Differentiator

by Zhiqiang Wang¹

, Xiaolong Li¹, Yunde Xie² and Zhiqiang Long^1,*

¹ Maglev Engineering Research Center, National University of Defense Technology, Changsha 410073, China

² Beijing Enterprises Holdings Maglev Technology Development Co. Ltd., Beijing 100124, China

Sensors 2018, 18(6), 1697; https://doi.org/10.3390/s18061697 - 24 May 2018

Cited by 11 | Viewed by 6566

Abstract

In a maglev train levitation system, signal processing plays an important role for the reason that some sensor signals are prone to be corrupted by noise due to the harsh installation and operation environment of sensors and some signals cannot be acquired directly [...] Read more.

In a maglev train levitation system, signal processing plays an important role for the reason that some sensor signals are prone to be corrupted by noise due to the harsh installation and operation environment of sensors and some signals cannot be acquired directly via sensors. Based on these concerns, an architecture based on a new type of nonlinear second-order discrete tracking differentiator is proposed. The function of this signal processing architecture includes filtering signal noise and acquiring needed signals for levitation purposes. The proposed tracking differentiator possesses the advantages of quick convergence, no fluttering, and simple calculation. Tracking differentiator’s frequency characteristics at different parameter values are studied in this paper. The performance of this new type of tracking differentiator is tested in a MATLAB simulation and this tracking-differentiator is implemented in Very-High-Speed Integrated Circuit Hardware Description Language (VHDL). In the end, experiments are conducted separately on a test board and a maglev train model. Simulation and experiment results show that the performance of this novel signal processing architecture can fulfill the real system requirement. Full article

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

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30 pages, 878 KiB

Open AccessArticle

Towards an Online Seizure Advisory System—An Adaptive Seizure Prediction Framework Using Active Learning Heuristics

by Vignesh Raja Karuppiah Ramachandran^*, Huibert J. Alblas^†, Duc V. Le^†

and Nirvana Meratnia^†

¹ Pervasive Systems Research Group, University of Twente, Drienerlolaan 5, 7522 NB Enschede, The Netherlands

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1698; https://doi.org/10.3390/s18061698 - 24 May 2018

Cited by 13 | Viewed by 5624

Abstract

In the last decade, seizure prediction systems have gained a lot of attention because of their enormous potential to largely improve the quality-of-life of the epileptic patients. The accuracy of the prediction algorithms to detect seizure in real-world applications is largely limited because [...] Read more.

In the last decade, seizure prediction systems have gained a lot of attention because of their enormous potential to largely improve the quality-of-life of the epileptic patients. The accuracy of the prediction algorithms to detect seizure in real-world applications is largely limited because the brain signals are inherently uncertain and affected by various factors, such as environment, age, drug intake, etc., in addition to the internal artefacts that occur during the process of recording the brain signals. To deal with such ambiguity, researchers transitionally use active learning, which selects the ambiguous data to be annotated by an expert and updates the classification model dynamically. However, selecting the particular data from a pool of large ambiguous datasets to be labelled by an expert is still a challenging problem. In this paper, we propose an active learning-based prediction framework that aims to improve the accuracy of the prediction with a minimum number of labelled data. The core technique of our framework is employing the Bernoulli-Gaussian Mixture model (BGMM) to determine the feature samples that have the most ambiguity to be annotated by an expert. By doing so, our approach facilitates expert intervention as well as increasing medical reliability. We evaluate seven different classifiers in terms of the classification time and memory required. An active learning framework built on top of the best performing classifier is evaluated in terms of required annotation effort to achieve a high level of prediction accuracy. The results show that our approach can achieve the same accuracy as a Support Vector Machine (SVM) classifier using only

20 %

of the labelled data and also improve the prediction accuracy even under the noisy condition. Full article

(This article belongs to the Special Issue Sensors for Health Monitoring and Disease Diagnosis)

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22 pages, 1345 KiB

Open AccessArticle

Influence of Different Coupling Modes on the Robustness of Smart Grid under Targeted Attack

by WenJie Kang^1,†

, Gang Hu^1,†, PeiDong Zhu^2,†, Qiang Liu^1,†, Zhi Hang^3,† and Xin Liu^4,*,†

¹ College of Computer, National University of Defense Technology, Changsha 410073, China

² Department of Electronic Information and Electrical Engineering, Changsha University, Changsha 410022, China

³ Key Laboratory of Hunan Province for Mobile Business Intelligence, Changsha 410205, China

⁴ Department of Computer Engineering & Applied Math, Changsha University, Changsha 410022, China

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1699; https://doi.org/10.3390/s18061699 - 24 May 2018

Cited by 7 | Viewed by 3695

Abstract

Many previous works only focused on the cascading failure of global coupling of one-to-one structures in interdependent networks, but the local coupling of dual coupling structures has rarely been studied due to its complex structure. This will result in a serious consequence that [...] Read more.

Many previous works only focused on the cascading failure of global coupling of one-to-one structures in interdependent networks, but the local coupling of dual coupling structures has rarely been studied due to its complex structure. This will result in a serious consequence that many conclusions of the one-to-one structure may be incorrect in the dual coupling network and do not apply to the smart grid. Therefore, it is very necessary to subdivide the dual coupling link into a top-down coupling link and a bottom-up coupling link in order to study their influence on network robustness by combining with different coupling modes. Additionally, the power flow of the power grid can cause the load of a failed node to be allocated to its neighboring nodes and trigger a new round of load distribution when the load of these nodes exceeds their capacity. This means that the robustness of smart grids may be affected by four factors, i.e., load redistribution, local coupling, dual coupling link and coupling mode; however, the research on the influence of those factors on the network robustness is missing. In this paper, firstly, we construct the smart grid as a two-layer network with a dual coupling link and divide the power grid and communication network into many subnets based on the geographical location of their nodes. Secondly, we define node importance (

N I

) as an evaluation index to access the impact of nodes on the cyber or physical network and propose three types of coupling modes based on

N I

of nodes in the cyber and physical subnets, i.e., Assortative Coupling in Subnets (ACIS), Disassortative Coupling in Subnets (DCIS), and Random Coupling in Subnets (RCIS). Thirdly, a cascading failure model is proposed for studying the effect of local coupling of dual coupling link in combination with ACIS, DCIS, and RCIS on the robustness of the smart grid against a targeted attack, and the survival rate of functional nodes is used to assess the robustness of the smart grid. Finally, we use the IEEE 118-Bus System and the Italian High-Voltage Electrical Transmission Network to verify our model and obtain the same conclusions: (I) DCIS applied to the top-down coupling link is better able to enhance the robustness of the smart grid against a targeted attack than RCIS or ACIS, (II) ACIS applied to a bottom-up coupling link is better able to enhance the robustness of the smart grid against a targeted attack than RCIS or DCIS, and (III) the robustness of the smart grid can be improved by increasing the tolerance

α

. This paper provides some guidelines for slowing down the speed of the cascading failures in the design of architecture and optimization of interdependent networks, such as a top-down link with DCIS, a bottom-up link with ACIS, and an increased tolerance

α

. Full article

(This article belongs to the Special Issue Security in IoT Enabled Sensors)

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17 pages, 14950 KiB

Open AccessArticle

Digital Self-Interference Cancellation for Asynchronous In-Band Full-Duplex Underwater Acoustic Communication

by Gang Qiao^1,2,3, Shuwei Gan^1,2,3, Songzuo Liu^1,2,3,*, Lu Ma^1,2,3 and Zongxin Sun^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

Sensors 2018, 18(6), 1700; https://doi.org/10.3390/s18061700 - 24 May 2018

Cited by 44 | Viewed by 4397

Abstract

To improve the throughput of underwater acoustic (UWA) networking, the In-band full-duplex (IBFD) communication is one of the most vital pieces of research. The major drawback of IBFD-UWA communication is Self-Interference (SI). This paper presents a digital SI cancellation algorithm for asynchronous IBFD-UWA [...] Read more.

To improve the throughput of underwater acoustic (UWA) networking, the In-band full-duplex (IBFD) communication is one of the most vital pieces of research. The major drawback of IBFD-UWA communication is Self-Interference (SI). This paper presents a digital SI cancellation algorithm for asynchronous IBFD-UWA communication system. We focus on two issues: one is asynchronous communication dissimilar to IBFD radio communication, the other is nonlinear distortion caused by power amplifier (PA). First, we discuss asynchronous IBFD-UWA signal model with the nonlinear distortion of PA. Then, we design a scheme for asynchronous IBFD-UWA communication utilizing the non-overlapping region between SI and intended signal to estimate the nonlinear SI channel. To cancel the nonlinear distortion caused by PA, we propose an Over-Parameterization based Recursive Least Squares (RLS) algorithm (OPRLS) to estimate the nonlinear SI channel. Furthermore, we present the OPRLS with a sparse constraint to estimate the SI channel, which reduces the requirement of the length of the non-overlapping region. Finally, we verify our concept through simulation and the pool experiment. Results demonstrate that the proposed digital SI cancellation scheme can cancel SI efficiently. Full article

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

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21 pages, 2787 KiB

Open AccessArticle

Geometric Positioning Accuracy Improvement of ZY-3 Satellite Imagery Based on Statistical Learning Theory

by Niangang Jiao^1,2,3,*, Feng Wang^1,2, Hongjian You^1,2,3, Mudan Yang^1,2,3 and Xinghui Yao^1,2,3

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

Sensors 2018, 18(6), 1701; https://doi.org/10.3390/s18061701 - 24 May 2018

Cited by 5 | Viewed by 3443

Abstract

With the increasing demand for high-resolution remote sensing images for mapping and monitoring the Earth’s environment, geometric positioning accuracy improvement plays a significant role in the image preprocessing step. Based on the statistical learning theory, we propose a new method to improve the [...] Read more.

With the increasing demand for high-resolution remote sensing images for mapping and monitoring the Earth’s environment, geometric positioning accuracy improvement plays a significant role in the image preprocessing step. Based on the statistical learning theory, we propose a new method to improve the geometric positioning accuracy without ground control points (GCPs). Multi-temporal images from the ZY-3 satellite are tested and the bias-compensated rational function model (RFM) is applied as the block adjustment model in our experiment. An easy and stable weight strategy and the fast iterative shrinkage-thresholding (FIST) algorithm which is widely used in the field of compressive sensing are improved and utilized to define the normal equation matrix and solve it. Then, the residual errors after traditional block adjustment are acquired and tested with the newly proposed inherent error compensation model based on statistical learning theory. The final results indicate that the geometric positioning accuracy of ZY-3 satellite imagery can be improved greatly with our proposed method. Full article

(This article belongs to the Section Remote Sensors)

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20 pages, 3326 KiB

Open AccessArticle

Outlier-Detection Methodology for Structural Identification Using Sparse Static Measurements

by Marco Proverbio^1,2,*, Numa J. Bertola^1,2

and Ian F. C. Smith²

¹ ETH Zurich, Future Cities Laboratory, Singapore-ETH Centre, 1 CREATE Way, CREATE Tower, Singapore 138602, Singapore

² Applied Computing and Mechanics Laboratory (IMAC), School of Architecture, Civil and Environmental Engineering (ENAC), Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland

Sensors 2018, 18(6), 1702; https://doi.org/10.3390/s18061702 - 24 May 2018

Cited by 13 | Viewed by 3621

Abstract

The aim of structural identification is to provide accurate knowledge of the behaviour of existing structures. In most situations, finite-element models are updated using behaviour measurements and field observations. Error-domain model falsification (EDMF) is a multi-model approach that compares finite-element model predictions with [...] Read more.

The aim of structural identification is to provide accurate knowledge of the behaviour of existing structures. In most situations, finite-element models are updated using behaviour measurements and field observations. Error-domain model falsification (EDMF) is a multi-model approach that compares finite-element model predictions with sensor measurements while taking into account epistemic and stochastic uncertainties—including the systematic bias that is inherent in the assumptions behind structural models. Compared with alternative model-updating strategies such as residual minimization and traditional Bayesian methodologies, EDMF is easy-to-use for practising engineers and does not require precise knowledge of values for uncertainty correlations. However, wrong parameter identification and flawed extrapolation may result when undetected outliers occur in the dataset. Moreover, when datasets consist of a limited number of static measurements rather than continuous monitoring data, the existing signal-processing and statistics-based algorithms provide little support for outlier detection. This paper introduces a new model-population methodology for outlier detection that is based on the expected performance of the as-designed sensor network. Thus, suspicious measurements are identified even when few measurements, collected with a range of sensors, are available. The structural identification of a full-scale bridge in Exeter (UK) is used to demonstrate the applicability of the proposed methodology and to compare its performance with existing algorithms. The results show that outliers, capable of compromising EDMF accuracy, are detected. Moreover, a metric that separates the impact of powerful sensors from the effects of measurement outliers have been included in the framework. Finally, the impact of outlier occurrence on parameter identification and model extrapolation (for example, reserve capacity assessment) is evaluated. Full article

(This article belongs to the Section Sensor Networks)

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30 pages, 13062 KiB

Open AccessArticle

LightDenseYOLO: A Fast and Accurate Marker Tracker for Autonomous UAV Landing by Visible Light Camera Sensor on Drone

by Phong Ha Nguyen, Muhammad Arsalan

, Ja Hyung Koo, Rizwan Ali Naqvi, Noi Quang Truong 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(6), 1703; https://doi.org/10.3390/s18061703 - 24 May 2018

Cited by 70 | Viewed by 13419

Abstract

Autonomous landing of an unmanned aerial vehicle or a drone is a challenging problem for the robotics research community. Previous researchers have attempted to solve this problem by combining multiple sensors such as global positioning system (GPS) receivers, inertial measurement unit, and multiple [...] Read more.

Autonomous landing of an unmanned aerial vehicle or a drone is a challenging problem for the robotics research community. Previous researchers have attempted to solve this problem by combining multiple sensors such as global positioning system (GPS) receivers, inertial measurement unit, and multiple camera systems. Although these approaches successfully estimate an unmanned aerial vehicle location during landing, many calibration processes are required to achieve good detection accuracy. In addition, cases where drones operate in heterogeneous areas with no GPS signal should be considered. To overcome these problems, we determined how to safely land a drone in a GPS-denied environment using our remote-marker-based tracking algorithm based on a single visible-light-camera sensor. Instead of using hand-crafted features, our algorithm includes a convolutional neural network named lightDenseYOLO to extract trained features from an input image to predict a marker’s location by visible light camera sensor on drone. Experimental results show that our method significantly outperforms state-of-the-art object trackers both using and not using convolutional neural network in terms of both accuracy and processing time. Full article

(This article belongs to the Special Issue Emerging Algorithms and Applications in Vision Sensors System based on Artificial Intelligence)

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20 pages, 7158 KiB

Open AccessArticle

Electrical Resistance Tomography for Visualization of Moving Objects Using a Spatiotemporal Total Variation Regularization Algorithm

by Bo Chen¹, Juan F. P. J. Abascal²

and Manuchehr Soleimani^1,*

¹ Engineering Tomography Lab (ETL), Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK

² Univ Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1206 Lyon, France

Sensors 2018, 18(6), 1704; https://doi.org/10.3390/s18061704 - 24 May 2018

Cited by 29 | Viewed by 5068

Abstract

Electrical resistance tomography (ERT) has been considered as a data collection and image reconstruction method in many multi-phase flow application areas due to its advantages of high speed, low cost and being non-invasive. In order to improve the quality of the reconstructed images, [...] Read more.

Electrical resistance tomography (ERT) has been considered as a data collection and image reconstruction method in many multi-phase flow application areas due to its advantages of high speed, low cost and being non-invasive. In order to improve the quality of the reconstructed images, the Total Variation algorithm attracts abundant attention due to its ability to solve large piecewise and discontinuous conductivity distributions. In industrial processing tomography (IPT), techniques such as ERT have been used to extract important flow measurement information. For a moving object inside a pipe, a velocity profile can be calculated from the cross correlation between signals generated from ERT sensors. Many previous studies have used two sets of 2D ERT measurements based on pixel-pixel cross correlation, which requires two ERT systems. In this paper, a method for carrying out flow velocity measurement using a single ERT system is proposed. A novel spatiotemporal total variation regularization approach is utilised to exploit sparsity both in space and time in 4D, and a voxel-voxel cross correlation method is adopted for measurement of flow profile. Result shows that the velocity profile can be calculated with a single ERT system and that the volume fraction and movement can be monitored using the proposed method. Both semi-dynamic experimental and static simulation studies verify the suitability of the proposed method. For in plane velocity profile, a 3D image based on temporal 2D images produces velocity profile with accuracy of less than 1% error and a 4D image for 3D velocity profiling shows an error of 4%. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 6734 KiB

Open AccessArticle

Spectral Kurtosis Entropy and Weighted SaE-ELM for Bogie Fault Diagnosis under Variable Conditions

by Zhipeng Wang^1,2,3,*

, Limin Jia^1,2,3, Linlin Kou^1,2,3 and Yong Qin^1,2,3

¹ State Key Lab of Rail Traffic Control and Safety, Beijing Jiaotong University, Beijing 100044, China

² National Engineering Laboratory for System Safety and Operation Assurance of Urban Rail Transit, Guangzhou 510000, China

³ Beijing Research Center of Urban Traffic Information Sensing and Service Technologies, Beijing Jiaotong University, Beijing 100044, China

Sensors 2018, 18(6), 1705; https://doi.org/10.3390/s18061705 - 24 May 2018

Cited by 15 | Viewed by 4569

Abstract

Bogies are crucial for the safe operation of rail transit systems and usually work under uncertain and variable operating conditions. However, the diagnosis of bogie faults under variable conditions has barely been discussed until now. Thus, it is valuable to develop effective methods [...] Read more.

Bogies are crucial for the safe operation of rail transit systems and usually work under uncertain and variable operating conditions. However, the diagnosis of bogie faults under variable conditions has barely been discussed until now. Thus, it is valuable to develop effective methods to deal with variable conditions. Besides, considering that the normal data for training are much more than the faulty data in practice, there is another problem in that only a small amount of data is available that includes faults. Concerning these issues, this paper proposes two new algorithms: (1) A novel feature parameter named spectral kurtosis entropy (SKE) is proposed based on the protrugram. The SKE not only avoids the manual post-processing of the protrugram but also has strong robustness to the operating conditions and parameter configurations, which have been validated by a simulation experiment in this paper. In this paper, the SKE, in conjunction with variational mode decomposition (VMD), is employed for feature extraction under variable conditions. (2) A new learning algorithm named weighted self-adaptive evolutionary extreme learning machine (WSaE-ELM) is proposed. WSaE-ELM gives each sample an extra sample weight to rebalance the training data and optimizes these weights along with the parameters of hidden neurons by means of the self-adaptive differential evolution algorithm. Finally, the hybrid method based on VMD, SKE, and WSaE-ELM is verified by using the vibration signals gathered from real bogies with speed variations. It is demonstrated that the proposed method of bogie fault diagnosis outperforms the conventional methods by up to 4.42% and 6.22%, respectively, in percentages of accuracy under variable conditions. Full article

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

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19 pages, 1688 KiB

Open AccessArticle

Marker-Based Multi-Sensor Fusion Indoor Localization System for Micro Air Vehicles

by Boyang Xing¹, Quanmin Zhu²

, Feng Pan^1,3 and Xiaoxue Feng^1,*

¹ School of Automation, Beijing Institute of Technology, Beijing 100081, China

² Faculty of Computing, Engineering and Mathematical Sciences, University of the West of England, Bristol BS16 1QY, UK

³ Kunming-BIT Industry Technology Research Institute INC, Kunming 650106, China

Sensors 2018, 18(6), 1706; https://doi.org/10.3390/s18061706 - 25 May 2018

Cited by 36 | Viewed by 8117

Abstract

A novel multi-sensor fusion indoor localization algorithm based on ArUco marker is designed in this paper. The proposed ArUco mapping algorithm can build and correct the map of markers online with Grubbs criterion and K-mean clustering, which avoids the map distortion due to [...] Read more.

A novel multi-sensor fusion indoor localization algorithm based on ArUco marker is designed in this paper. The proposed ArUco mapping algorithm can build and correct the map of markers online with Grubbs criterion and K-mean clustering, which avoids the map distortion due to lack of correction. Based on the conception of multi-sensor information fusion, the federated Kalman filter is utilized to synthesize the multi-source information from markers, optical flow, ultrasonic and the inertial sensor, which can obtain a continuous localization result and effectively reduce the position drift due to the long-term loss of markers in pure marker localization. The proposed algorithm can be easily implemented in a hardware of one Raspberry Pi Zero and two STM32 micro controllers produced by STMicroelectronics (Geneva, Switzerland). Thus, a small-size and low-cost marker-based localization system is presented. The experimental results show that the speed estimation result of the proposed system is better than Px4flow, and it has the centimeter accuracy of mapping and positioning. The presented system not only gives satisfying localization precision, but also has the potential to expand other sensors (such as visual odometry, ultra wideband (UWB) beacon and lidar) to further improve the localization performance. The proposed system can be reliably employed in Micro Aerial Vehicle (MAV) visual localization and robotics control. Full article

(This article belongs to the Section Sensor Networks)

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18 pages, 6804 KiB

Open AccessFeature PaperArticle

Numerical Simulation of a Novel Sensing Approach Based on Abnormal Blocking by Periodic Grating Strips near the Silicon Wire Waveguide

by Andrei Tsarev^1,2, Eugeny Kolosovsky¹, Francesco De Leonardis³ and Vittorio M. N. Passaro^3,*

¹ Laboratory of Optical Materials and Structures, Rzhanov Institute of Semiconductor Physics, SB RAS, 630090 Novosibirsk, Russia

² Laboratory of Semiconductor and Dielectric Materials, Physics Department, Novosibirsk State University, 630090 Novosibirsk, Russia

³ Photonics Research Group, Dipartimento di Ingegneria Elettrica e dell’Informazione, Politecnico di Bari, Via E. Orabona 4, 70125 Bari, Italy

Sensors 2018, 18(6), 1707; https://doi.org/10.3390/s18061707 - 25 May 2018

Cited by 4 | Viewed by 5478

Abstract

This paper discusses the physical nature and the numerical modeling of a novel approach of periodic structures for applications as photonic sensors. The sensing is based on the high sensitivity to the cover index change of the notch wavelength. This sensitivity is due [...] Read more.

This paper discusses the physical nature and the numerical modeling of a novel approach of periodic structures for applications as photonic sensors. The sensing is based on the high sensitivity to the cover index change of the notch wavelength. This sensitivity is due to the effect of abnormal blocking of the guided wave propagating along the silicon wire with periodic strips overhead it through the silica buffer. The structure sensing is numerically modeled by 2D and 3D finite difference time domain (FDTD) method, taking into account the waveguide dispersion. The modeling of the long structures (more than 1000 strips) is accomplished by the 2D method of lines (MoL) with a maximal implementation of the analytical feature of the method. It is proved that the effect of abnormal blocking could be used for the construction of novel types of optical sensors. Full article

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

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13 pages, 899 KiB

Open AccessArticle

Differentiation of Apple Varieties and Investigation of Organic Status Using Portable Visible Range Reflectance Spectroscopy

by Jordan Vincent^1,*

, Hui Wang¹, Omar Nibouche¹ and Paul Maguire²

¹ School of Computing and Mathematics, University of Ulster, Shore Rd, Newtownabbey BT37 0QB, UK

² School of Engineering, University of Ulster, Shore Rd, Newtownabbey BT37 0QB, UK

Sensors 2018, 18(6), 1708; https://doi.org/10.3390/s18061708 - 25 May 2018

Cited by 18 | Viewed by 3773

Abstract

Food fraud, the sale of goods that have in some way been mislabelled or tampered with, is an increasing concern, with a number of high profile documented incidents in recent years. These recent incidents and their scope show that there are gaps in [...] Read more.

Food fraud, the sale of goods that have in some way been mislabelled or tampered with, is an increasing concern, with a number of high profile documented incidents in recent years. These recent incidents and their scope show that there are gaps in the food chain where food authentication methods are not applied or otherwise not sufficient and more accessible detection methods would be beneficial. This paper investigates the utility of affordable and portable visible range spectroscopy hardware with partial least squares discriminant analysis (PLS-DA) when applied to the differentiation of apple types and organic status. This method has the advantage that it is accessible throughout the supply chain, including at the consumer level. Scans were acquired of 132 apples of three types, half of which are organic and the remaining non-organic. The scans were preprocessed with zero correction, normalisation and smoothing. Two tests were used to determine accuracy, the first using 10-fold cross-validation and the second using a test set collected in different ambient conditions. Overall, the system achieved an accuracy of 94% when predicting the type of apple and 66% when predicting the organic status. Additionally, the resulting models were analysed to find the regions of the spectrum that had the most significance. Then, the accuracy when using three-channel information (RGB) is presented and shows the improvement provided by spectroscopic data. Full article

(This article belongs to the Section Intelligent Sensors)

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21 pages, 1761 KiB

Open AccessArticle

Performance Evaluation of Energy-Autonomous Sensors Using Power-Harvesting Beacons for Environmental Monitoring in Internet of Things (IoT)

by George Dan Moiş^1,*,†

, Teodora Sanislav^1,†

, Silviu Corneliu Folea^1,†

and Sherali Zeadally^2,†

¹ Department of Automation, Faculty of Automation and Computer Science, Technical University of Cluj-Napoca, 400114 Cluj-Napoca, Romania

² College of Communication and Information at the University of Kentucky, Lexington, KY 40506-0224, USA

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1709; https://doi.org/10.3390/s18061709 - 25 May 2018

Cited by 29 | Viewed by 9124

Abstract

Environmental conditions and air quality monitoring have become crucial today due to the undeniable changes of the climate and accelerated urbanization. To efficiently monitor environmental parameters such as temperature, humidity, and the levels of pollutants, such as fine particulate matter (PM2.5) and volatile [...] Read more.

Environmental conditions and air quality monitoring have become crucial today due to the undeniable changes of the climate and accelerated urbanization. To efficiently monitor environmental parameters such as temperature, humidity, and the levels of pollutants, such as fine particulate matter (PM2.5) and volatile organic compounds (VOCs) in the air, and to collect data covering vast geographical areas, the development of cheap energy-autonomous sensors for large scale deployment and fine-grained data acquisition is required. Rapid advances in electronics and communication technologies along with the emergence of paradigms such as Cyber-Physical Systems (CPSs) and the Internet of Things (IoT) have led to the development of low-cost sensor devices that can operate unattended for long periods of time and communicate using wired or wireless connections through the Internet. We investigate the energy efficiency of an environmental monitoring system based on Bluetooth Low Energy (BLE) beacons that operate in the IoT environment. The beacons developed measure the temperature, the relative humidity, the light intensity, and the CO₂ and VOC levels in the air. Based on our analysis we have developed efficient sleep scheduling algorithms that allow the sensor nodes developed to operate autonomously without requiring the replacement of the power supply. The experimental results show that low-power sensors communicating using BLE technology can operate autonomously (from the energy perspective) in applications that monitor the environment or the air quality in indoor or outdoor settings. Full article

(This article belongs to the Special Issue Low Energy Wireless Sensor Networks: Protocols, Architectures and Solutions)

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15 pages, 2328 KiB

Open AccessArticle

DE-Sync: A Doppler-Enhanced Time Synchronization for Mobile Underwater Sensor Networks

by Feng Zhou^1,2,3,†, Qi Wang^1,2,3,†

, DongHu Nie^1,2,3,*,†

and Gang Qiao^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

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1710; https://doi.org/10.3390/s18061710 - 25 May 2018

Cited by 24 | Viewed by 3732

Abstract

Time synchronization is the foundation of cooperative work among nodes of underwater sensor networks; it takes a critical role in the research and application of underwater sensor networks. Although numerous time synchronization protocols have been proposed for terrestrial wireless sensor networks, they cannot [...] Read more.

Time synchronization is the foundation of cooperative work among nodes of underwater sensor networks; it takes a critical role in the research and application of underwater sensor networks. Although numerous time synchronization protocols have been proposed for terrestrial wireless sensor networks, they cannot be directly applied to underwater sensor networks. This is because most of them typically assume that the propagation delay among sensor nodes is negligible, which is not the case in underwater sensor networks. Time synchronization is mainly affected by a long propagation delay among sensor nodes due to the low propagation speed of acoustic signals. Furthermore, sensor nodes in underwater tend to experience some degree of mobility due to wind or ocean current, or some other nodes are on self-propelled vehicles, such as autonomous underwater vehicles (AUVs). In this paper, we propose a Doppler-enhanced time synchronization scheme for mobile underwater sensor networks, called DE-Sync. Our new scheme considers the effect of the clock skew during the process of estimating the Doppler scale factor and directly substitutes the Doppler scale factor into linear regression to achieve the estimation of the clock skew and offset. Simulation results show that DE-Sync outperforms existing time synchronization protocols in both accuracy and energy efficiency. Full article

(This article belongs to the Section Sensor Networks)

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20 pages, 6369 KiB

Open AccessArticle

Real-Time Analysis of a Sensor’s Data for Automated Decision Making in an IoT-Based Smart Home

by Nida Saddaf Khan^1,*, Sayeed Ghani¹

and Sajjad Haider²

¹ Telecommunication Research Lab, Department of Computer Science, Institute of Business Administration, Garden/Kayani Shaheed Road, Karachi 74400, Pakistan

² Artificial Intelligence Lab, Department of Computer Science, Institute of Business Administration, Garden/Kayani Shaheed Road, Karachi 74400, Pakistan

Sensors 2018, 18(6), 1711; https://doi.org/10.3390/s18061711 - 25 May 2018

Cited by 31 | Viewed by 7584

Abstract

IoT devices frequently generate large volumes of streaming data and in order to take advantage of this data, their temporal patterns must be learned and identified. Streaming data analysis has become popular after being successfully used in many applications including forecasting electricity load, [...] Read more.

IoT devices frequently generate large volumes of streaming data and in order to take advantage of this data, their temporal patterns must be learned and identified. Streaming data analysis has become popular after being successfully used in many applications including forecasting electricity load, stock market prices, weather conditions, etc. Artificial Neural Networks (ANNs) have been successfully utilized in understanding the embedded interesting patterns/behaviors in the data and forecasting the future values based on it. One such pattern is modelled and learned in the present study to identify the occurrence of a specific pattern in a Water Management System (WMS). This prediction aids in making an automatic decision support system, to switch OFF a hydraulic suction pump at the appropriate time. Three types of ANN, namely Multi-Input Multi-Output (MIMO), Multi-Input Single-Output (MISO), and Recurrent Neural Network (RNN) have been compared, for multi-step-ahead forecasting, on a sensor’s streaming data. Experiments have shown that RNN has the best performance among three models and based on its prediction, a system can be implemented to make the best decision with 86% accuracy. Full article

(This article belongs to the Special Issue Advanced Technology for Smart Home Automation and Entertainment Using IoT and Sensor Networks)

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20 pages, 1322 KiB

Open AccessArticle

HiMeter: Telling You the Height Rather than the Altitude

by Haibo Ye^1,*, Kai Dong² and Tao Gu³

¹ College of Computer Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China

² School of Computer Science and Engineering, Southeast University, Nanjing 211189, China

³ School of Computer Science and IT, RMIT University, VIC 3000 Melbourne, Australia

Sensors 2018, 18(6), 1712; https://doi.org/10.3390/s18061712 - 25 May 2018

Cited by 22 | Viewed by 5699

Abstract

The altitude of a moving user is important context information for mobile technologies and applications. However, with the increasing pervasiveness of smartphones and abundant mobile applications, developers and users have gradually discovered that the height is more useful than altitude in many situations. [...] Read more.

The altitude of a moving user is important context information for mobile technologies and applications. However, with the increasing pervasiveness of smartphones and abundant mobile applications, developers and users have gradually discovered that the height is more useful than altitude in many situations. The height is often a relative value, which is the vertical distance to the ground rather than the vertical distance to sea level, and we believe that it is useful in many applications, such as localization/navigation, sport/health and tourism/travel. In this paper, we first carried out a nation-wide online survey to confirm the desirability for the height information in mobile applications, and the result is positive. Then, we proposed HiMeter, an effective and accurate approach to calculating the height of the smartphone. HiMeter makes use of a low-power barometer on the smartphone and does not require GPS or back-server support. We concentrate on the vertical moving pattern of the user and designed several novel techniques, resulting in HiMeter not needing any reference points, and the complex process of calculating the absolute altitude can be avoided. The field studies show that HiMeter can achieve an accuracy of within 5 m in 90% of cases indoors and an accuracy of 10 m in 83% of cases outdoors. Compared to the existing works, HiMeter is more accurate and practical and is more suitable for usage in many mobile applications. Full article

(This article belongs to the Special Issue Advances in Sensing, Processing and Transmission for IoT-Oriented Sensors Networks)

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11 pages, 9177 KiB

Open AccessArticle

Large Scale Triboelectric Nanogenerator and Self-Powered Flexible Sensor for Human Sleep Monitoring

by Xiaoheng Ding^1,2,*, Hailin Cao², Xinghong Zhang¹, Mingyu Li² and Yuntian Liu³

¹ School of Material Science and Engineering, Harbin Institute of Technology, Harbin 150001, China

² Shenzhen Academy of Aerospace Technology, Shenzhen 518000, China

³ Department of Physics, University of Science and Technology of China, Hefei 230000, China

Sensors 2018, 18(6), 1713; https://doi.org/10.3390/s18061713 - 25 May 2018

Cited by 75 | Viewed by 8354

Abstract

The triboelectric nanogenerator (TENG) and its application as a sensor is a popular research subject. There is demand for self-powered, flexible sensors with high sensitivity and high power-output for the next generation of consumer electronics. In this study, a 300 mm × 300 [...] Read more.

The triboelectric nanogenerator (TENG) and its application as a sensor is a popular research subject. There is demand for self-powered, flexible sensors with high sensitivity and high power-output for the next generation of consumer electronics. In this study, a 300 mm × 300 mm carbon nanotube (CNT)-doped porous PDMS film was successfully fabricated wherein the CNT influenced the micropore structure. A self-powered TENG tactile sensor was established according to triboelectric theory. The CNT-doped porous TENG showed a voltage output seven times higher than undoped porous TENG and 16 times higher than TENG with pure PDMS, respectively. The TENG successfully acquired human motion signals, breath signals, and heartbeat signals during a sleep monitoring experiment. The results presented here may provide an effective approach for fabricating large-scale and low-cost flexible TENG sensors. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 4667 KiB

Open AccessArticle

Simulation of Graphene Field-Effect Transistor Biosensors for Bacterial Detection

by Guangfu Wu^1,2,3

, M. Meyyappan⁴ and King Wai Chiu Lai^1,2,*

¹ Department of Mechanical and Biomedical Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, China

² Centre for Robotics and Automation, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, China

³ Shanghai Key Laboratory of Modern Optical System, Engineering Research Center of Optical Instrument and System (Ministry of Education), University of Shanghai for Science and Technology, Shanghai 200093, China

⁴ NASA Ames Research Center, Moffett Field, Mountain View, CA 94035, USA

Sensors 2018, 18(6), 1715; https://doi.org/10.3390/s18061715 - 25 May 2018

Cited by 25 | Viewed by 10057

Abstract

Foodborne illness is correlated with the existence of infectious pathogens such as bacteria in food and drinking water. Probe-modified graphene field effect transistors (G-FETs) have been shown to be suitable for Escherichia coli (E. coli) detection. Here, the G-FETs for bacterial [...] Read more.

Foodborne illness is correlated with the existence of infectious pathogens such as bacteria in food and drinking water. Probe-modified graphene field effect transistors (G-FETs) have been shown to be suitable for Escherichia coli (E. coli) detection. Here, the G-FETs for bacterial detection are modeled and simulated with COMSOL Multiphysics to understand the operation of the biosensors. The motion of E. coli cells in electrolyte and the surface charge of graphene induced by E. coli are systematically investigated. The comparison between the simulation and experimental data proves the sensing probe size to be a key parameter affecting the surface charge of graphene induced by bacteria. Finally, the relationship among the change in source-drain current (∆I_ds), graphene-bacteria distance and bacterial concentration is established. The shorter graphene-bacteria distance and higher bacterial concentration give rise to better sensing performance (larger ∆I_ds) of the G-FETs biosensors. The simulation here could serve as a guideline for the design and optimization of G-FET biosensors for various applications. Full article

(This article belongs to the Special Issue Carbon Materials Based Sensors and the Application)

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16 pages, 906 KiB

Open AccessArticle

Contention-Aware Adaptive Data Rate for Throughput Optimization in LoRaWAN

by Sungryul Kim

and Younghwan Yoo^*

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

Sensors 2018, 18(6), 1716; https://doi.org/10.3390/s18061716 - 25 May 2018

Cited by 41 | Viewed by 4673

Abstract

In Long Range Wide Area Network (LoRaWAN), the data rate of the devices can be adjusted to optimize the throughput by changing the spreading factor. However, the adaptive data rate has to be carefully utilized because the collision probability, which directly affects the [...] Read more.

In Long Range Wide Area Network (LoRaWAN), the data rate of the devices can be adjusted to optimize the throughput by changing the spreading factor. However, the adaptive data rate has to be carefully utilized because the collision probability, which directly affects the throughput, is changed according to the use of spreading factors. Namely, the greater the number of devices using the same spreading factor, the greater the probability of collision, resulting in a decrease of total throughput. Nevertheless, in the current system, the only criteria to determine the data rate to be adjusted is a link quality. Therefore, contention-aware adaptive data rate should be designed for the throughput optimization. Here, the number of devices which can use a specific data rate is restricted, and accordingly the optimization problem can be regarded as constrained optimization. To find an optimal solution, we adopt the gradient projection method. By adjusting the data rate based on the retrieved set of optimal data rate, the system performance can be significantly improved. The numerical results demonstrate that the proposed method outperforms the comparisons regardless of the number of devices and is close to the theoretical upper bound of throughput. Full article

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

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16 pages, 3716 KiB

Open AccessArticle

A Dual-Channel Acquisition Method Based on Extended Replica Folding Algorithm for Long Pseudo-Noise Code in Inter-Satellite Links

by Hongbo Zhao^*

, Yuying Chen, Wenquan Feng and Chen Zhuang

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

Sensors 2018, 18(6), 1717; https://doi.org/10.3390/s18061717 - 25 May 2018

Cited by 3 | Viewed by 2949

Abstract

Inter-satellite links are an important component of the new generation of satellite navigation systems, characterized by low signal-to-noise ratio (SNR), complex electromagnetic interference and the short time slot of each satellite, which brings difficulties to the acquisition stage. The inter-satellite link in both [...] Read more.

Inter-satellite links are an important component of the new generation of satellite navigation systems, characterized by low signal-to-noise ratio (SNR), complex electromagnetic interference and the short time slot of each satellite, which brings difficulties to the acquisition stage. The inter-satellite link in both Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) adopt the long code spread spectrum system. However, long code acquisition is a difficult and time-consuming task due to the long code period. Traditional folding methods such as extended replica folding acquisition search technique (XFAST) and direct average are largely restricted because of code Doppler and additional SNR loss caused by replica folding. The dual folding method (DF-XFAST) and dual-channel method have been proposed to achieve long code acquisition in low SNR and high dynamic situations, respectively, but the former is easily affected by code Doppler and the latter is not fast enough. Considering the environment of inter-satellite links and the problems of existing algorithms, this paper proposes a new long code acquisition algorithm named dual-channel acquisition method based on the extended replica folding algorithm (DC-XFAST). This method employs dual channels for verification. Each channel contains an incoming signal block. Local code samples are folded and zero-padded to the length of the incoming signal block. After a circular FFT operation, the correlation results contain two peaks of the same magnitude and specified relative position. The detection process is eased through finding the two largest values. The verification takes all the full and partial peaks into account. Numerical results reveal that the DC-XFAST method can improve acquisition performance while acquisition speed is guaranteed. The method has a significantly higher acquisition probability than folding methods XFAST and DF-XFAST. Moreover, with the advantage of higher detection probability and lower false alarm probability, it has a lower mean acquisition time than traditional XFAST, DF-XFAST and zero-padding. Full article

(This article belongs to the Section Remote Sensors)

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20 pages, 4997 KiB

Open AccessArticle

On Applicability of Network Coding Technique for 6LoWPAN-based Sensor Networks

by Marek Amanowicz¹ and Jaroslaw Krygier^2,*

¹ NASK—National Research Institute, Kolska 12, Warsaw 01-045, Poland

² Faculty of Electronics, Military University of Technology, Urbanowicza 2, Warsaw 00-908, Poland

Sensors 2018, 18(6), 1718; https://doi.org/10.3390/s18061718 - 26 May 2018

Cited by 12 | Viewed by 3194

Abstract

In this paper, the applicability of the network coding technique in 6LoWPAN-based sensor multihop networks is examined. The 6LoWPAN is one of the standards proposed for the Internet of Things architecture. Thus, we can expect the significant growth of traffic in such networks, [...] Read more.

In this paper, the applicability of the network coding technique in 6LoWPAN-based sensor multihop networks is examined. The 6LoWPAN is one of the standards proposed for the Internet of Things architecture. Thus, we can expect the significant growth of traffic in such networks, which can lead to overload and decrease in the sensor network lifetime. The authors propose the inter-session network coding mechanism that can be implemented in resource-limited sensor motes. The solution reduces the overall traffic in the network, and in consequence, the energy consumption is decreased. Used procedures take into account deep header compressions of the native 6LoWPAN packets and the hop-by-hop changes of the header structure. Applied simplifications reduce signaling traffic that is typically occurring in network coding deployments, keeping the solution usefulness for the wireless sensor networks with limited resources. The authors validate the proposed procedures in terms of end-to-end packet delay, packet loss ratio, traffic in the air, total energy consumption, and network lifetime. The solution has been tested in a real wireless sensor network. The results confirm the efficiency of the proposed technique, mostly in delay-tolerant sensor networks. Full article

(This article belongs to the Section Sensor Networks)

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15 pages, 3662 KiB

Open AccessArticle

Analysis of Consistency of Transthoracic Bioimpedance Measurements Acquired with Dry Carbon Black PDMS Electrodes, Adhesive Electrodes, and Wet Textile Electrodes

by Hugo F. Posada-Quintero^1,*

, Natasa Reljin¹

, Caitlin Eaton-Robb¹, Yeonsik Noh^2,3, Jarno Riistama⁴ and Ki H. Chon¹

¹ Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269 USA

² College of Nursing, University of Massachusetts Amherst, Amherst, MA 01003, USA

³ Department of Electrical and Computer Engineering, University of Massachusetts Amherst, Amherst, MA 01003, USA

⁴ Philips Research, 5656 Eindhoven, The Netherlands

Sensors 2018, 18(6), 1719; https://doi.org/10.3390/s18061719 - 26 May 2018

Cited by 15 | Viewed by 4776

Abstract

The detection of intrathoracic volume retention could be crucial to the early detection of decompensated heart failure (HF). Transthoracic Bioimpedance (TBI) measurement is an indirect, promising approach to assessing intrathoracic fluid volume. Gel-based adhesive electrodes can produce skin irritation, as the patient needs [...] Read more.

The detection of intrathoracic volume retention could be crucial to the early detection of decompensated heart failure (HF). Transthoracic Bioimpedance (TBI) measurement is an indirect, promising approach to assessing intrathoracic fluid volume. Gel-based adhesive electrodes can produce skin irritation, as the patient needs to place them daily in the same spots. Textile electrodes can reduce skin irritation; however, they inconveniently require wetting before each use and provide poor adherence to the skin. Previously, we developed waterproof reusable dry carbon black polydimethylsiloxane (CB/PDMS) electrodes that exhibited a good response to motion artifacts. We examined whether these CB/PDMS electrodes were suitable sensing components to be embedded into a monitoring vest for measuring TBI and the electrocardiogram (ECG). We recruited N = 20 subjects to collect TBI and ECG data. The TBI parameters were different between the various types of electrodes. Inter-subject variability for copper-mesh CB/PDMS electrodes and Ag/AgCl electrodes was lower compared to textile electrodes, and the intra-subject variability was similar between the copper-mesh CB/PDMS and Ag/AgCl. We concluded that the copper mesh CB/PDMS (CM/CB/PDMS) electrodes are a suitable alternative for textile electrodes for TBI measurements, but with the benefit of better skin adherence and without the requirement of wetting the electrodes, which can often be forgotten by the stressed HF subjects. Full article

(This article belongs to the Special Issue Sensors for Biosignal Processing)

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21 pages, 8568 KiB

Open AccessArticle

Development of Virtual Resource Based IoT Proxy for Bridging Heterogeneous Web Services in IoT Networks

by Wenquan Jin

and DoHyeun Kim^*

Department of Computer Engineering, Jeju National University, Jeju 63243, Korea

Sensors 2018, 18(6), 1721; https://doi.org/10.3390/s18061721 - 26 May 2018

Cited by 24 | Viewed by 5714

Abstract

The Internet of Things is comprised of heterogeneous devices, applications, and platforms using multiple communication technologies to connect the Internet for providing seamless services ubiquitously. With the requirement of developing Internet of Things products, many protocols, program libraries, frameworks, and standard specifications have [...] Read more.

The Internet of Things is comprised of heterogeneous devices, applications, and platforms using multiple communication technologies to connect the Internet for providing seamless services ubiquitously. With the requirement of developing Internet of Things products, many protocols, program libraries, frameworks, and standard specifications have been proposed. Therefore, providing a consistent interface to access services from those environments is difficult. Moreover, bridging the existing web services to sensor and actuator networks is also important for providing Internet of Things services in various industry domains. In this paper, an Internet of Things proxy is proposed that is based on virtual resources to bridge heterogeneous web services from the Internet to the Internet of Things network. The proxy enables clients to have transparent access to Internet of Things devices and web services in the network. The proxy is comprised of server and client to forward messages for different communication environments using the virtual resources which include the server for the message sender and the client for the message receiver. We design the proxy for the Open Connectivity Foundation network where the virtual resources are discovered by the clients as Open Connectivity Foundation resources. The virtual resources represent the resources which expose services in the Internet by web service providers. Although the services are provided by web service providers from the Internet, the client can access services using the consistent communication protocol in the Open Connectivity Foundation network. For discovering the resources to access services, the client also uses the consistent discovery interface to discover the Open Connectivity Foundation devices and virtual resources. Full article

(This article belongs to the Special Issue Advances in Sensing, Processing and Transmission for IoT-Oriented Sensors Networks)

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27 pages, 1989 KiB

Open AccessArticle

Indoor Pedestrian Localization Using iBeacon and Improved Kalman Filter

by Kwangjae Sung

, Dong Kyu ‘Roy’ Lee and Hwangnam Kim^*

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

Sensors 2018, 18(6), 1722; https://doi.org/10.3390/s18061722 - 26 May 2018

Cited by 34 | Viewed by 4522

Abstract

The reliable and accurate indoor pedestrian positioning is one of the biggest challenges for location-based systems and applications. Most pedestrian positioning systems have drift error and large bias due to low-cost inertial sensors and random motions of human being, as well as unpredictable [...] Read more.

The reliable and accurate indoor pedestrian positioning is one of the biggest challenges for location-based systems and applications. Most pedestrian positioning systems have drift error and large bias due to low-cost inertial sensors and random motions of human being, as well as unpredictable and time-varying radio-frequency (RF) signals used for position determination. To solve this problem, many indoor positioning approaches that integrate the user’s motion estimated by dead reckoning (DR) method and the location data obtained by RSS fingerprinting through Bayesian filter, such as the Kalman filter (KF), unscented Kalman filter (UKF), and particle filter (PF), have recently been proposed to achieve higher positioning accuracy in indoor environments. Among Bayesian filtering methods, PF is the most popular integrating approach and can provide the best localization performance. However, since PF uses a large number of particles for the high performance, it can lead to considerable computational cost. This paper presents an indoor positioning system implemented on a smartphone, which uses simple dead reckoning (DR), RSS fingerprinting using iBeacon and machine learning scheme, and improved KF. The core of the system is the enhanced KF called a sigma-point Kalman particle filter (SKPF), which localize the user leveraging both the unscented transform of UKF and the weighting method of PF. The SKPF algorithm proposed in this study is used to provide the enhanced positioning accuracy by fusing positional data obtained from both DR and fingerprinting with uncertainty. The SKPF algorithm can achieve better positioning accuracy than KF and UKF and comparable performance compared to PF, and it can provide higher computational efficiency compared with PF. iBeacon in our positioning system is used for energy-efficient localization and RSS fingerprinting. We aim to design the localization scheme that can realize the high positioning accuracy, computational efficiency, and energy efficiency through the SKPF and iBeacon indoors. Empirical experiments in real environments show that the use of the SKPF algorithm and iBeacon in our indoor localization scheme can achieve very satisfactory performance in terms of localization accuracy, computational cost, and energy efficiency. Full article

(This article belongs to the Section Sensor Networks)

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21 pages, 6441 KiB

Open AccessArticle

Improved Spatial Registration and Target Tracking Method for Sensors on Multiple Missiles

by Xiaodong Lu, Yuting Xie^* and Jun Zhou

Institute of Precision Guidance and Control, Northwestern Polytechnical University, Xi’an 710072, China

Sensors 2018, 18(6), 1723; https://doi.org/10.3390/s18061723 - 27 May 2018

Cited by 9 | Viewed by 3279

Abstract

Inspired by the problem that the current spatial registration methods are unsuitable for three-dimensional (3-D) sensor on high-dynamic platform, this paper focuses on the estimation for the registration errors of cooperative missiles and motion states of maneuvering target. There are two types of [...] Read more.

Inspired by the problem that the current spatial registration methods are unsuitable for three-dimensional (3-D) sensor on high-dynamic platform, this paper focuses on the estimation for the registration errors of cooperative missiles and motion states of maneuvering target. There are two types of errors being discussed: sensor measurement biases and attitude biases. Firstly, an improved Kalman Filter on Earth-Centered Earth-Fixed (ECEF-KF) coordinate algorithm is proposed to estimate the deviations mentioned above, from which the outcomes are furtherly compensated to the error terms. Secondly, the Pseudo Linear Kalman Filter (PLKF) and the nonlinear scheme the Unscented Kalman Filter (UKF) with modified inputs are employed for target tracking. The convergence of filtering results are monitored by a position-judgement logic, and a low-pass first order filter is selectively introduced before compensation to inhibit the jitter of estimations. In the simulation, the ECEF-KF enhancement is proven to improve the accuracy and robustness of the space alignment, while the conditional-compensation-based PLKF method is demonstrated to be the optimal performance in target tracking. Full article

(This article belongs to the Section Physical Sensors)

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25 pages, 1304 KiB

Open AccessArticle

Maximum Correntropy Unscented Kalman Filter for Ballistic Missile Navigation System based on SINS/CNS Deeply Integrated Mode

by Bowen Hou¹, Zhangming He^1,2, Dong Li³, Haiyin Zhou¹ and Jiongqi Wang^1,2,*

¹ Department of System Science, College of Liberal Arts and Science, National University of Defense Technology, Fuyuan Road No.1, Changsha 410072, China

² Beijing Institute of Control Engineering, China Academy of Space Technology, Beijing 100080, China

³ Unit 94, PLA 91550, Dalian 116023, China

Sensors 2018, 18(6), 1724; https://doi.org/10.3390/s18061724 - 27 May 2018

Cited by 42 | Viewed by 5296

Abstract

Strap-down inertial navigation system/celestial navigation system (SINS/CNS) integrated navigation is a high precision navigation technique for ballistic missiles. The traditional navigation method has a divergence in the position error. A deeply integrated mode for SINS/CNS navigation system is proposed to improve the navigation [...] Read more.

Strap-down inertial navigation system/celestial navigation system (SINS/CNS) integrated navigation is a high precision navigation technique for ballistic missiles. The traditional navigation method has a divergence in the position error. A deeply integrated mode for SINS/CNS navigation system is proposed to improve the navigation accuracy of ballistic missile. The deeply integrated navigation principle is described and the observability of the navigation system is analyzed. The nonlinearity, as well as the large outliers and the Gaussian mixture noises, often exists during the actual navigation process, leading to the divergence phenomenon of the navigation filter. The new nonlinear Kalman filter on the basis of the maximum correntropy theory and unscented transformation, named the maximum correntropy unscented Kalman filter, is deduced, and the computational complexity is analyzed. The unscented transformation is used for restricting the nonlinearity of the system equation, and the maximum correntropy theory is used to deal with the non-Gaussian noises. Finally, numerical simulation illustrates the superiority of the proposed filter compared with the traditional unscented Kalman filter. The comparison results show that the large outliers and the influence of non-Gaussian noises for SINS/CNS deeply integrated navigation is significantly reduced through the proposed filter. Full article

(This article belongs to the Special Issue Sensor Fusion and Novel Technologies in Positioning and Navigation)

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10 pages, 297 KiB

Open AccessArticle

Reduced Dimension Based Two-Dimensional DOA Estimation with Full DOFs for Generalized Co-Prime Planar Arrays

by Fenggang Sun^1,*

, Peng Lan^1,* and Guowei Zhang²

¹ College of Information Science and Engineering, Shandong Agricultural University, Tai’an 271018, China

² Information School, Shandong University of Political Science and Law, Jinan 250014, China

Sensors 2018, 18(6), 1725; https://doi.org/10.3390/s18061725 - 27 May 2018

Cited by 14 | Viewed by 3528

Abstract

In this paper, we investigate the problem of two-dimensional (2D) direction-of-arrival (DOA) estimation for generalized co-prime planar arrays. The classic multiple signal classification (MUSIC)-based methods can provide a superior estimation performance, but suffer from a tremendous computational burden caused by the 2D spectral [...] Read more.

In this paper, we investigate the problem of two-dimensional (2D) direction-of-arrival (DOA) estimation for generalized co-prime planar arrays. The classic multiple signal classification (MUSIC)-based methods can provide a superior estimation performance, but suffer from a tremendous computational burden caused by the 2D spectral search. To this end, we reduce the 2D problem into a one-dimensional (1D) one and propose a reduced dimension partial spectral search estimation method, which can compress the search region into a small 1D sector. Moreover, the proposed method can utilize the full information of the entire array without degrees-of-freedom loss. Furthermore, an iterative approach is also proposed to reduce complexity and improve performance. Simulation results show that the proposed methods can provide improved performance with substantially reduced complexity, as compared to other state-of-the-art methods. Full article

(This article belongs to the Special Issue Recent Advances in Array Processing for Wireless Applications)

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8 pages, 1439 KiB

Open AccessArticle

A Simplified Hollow-Core Photonic Crystal Fiber SERS Probe with a Fully Filled Photoreduction Silver Nanoprism

by Youfu Geng^1,*

, Yiwen Xu¹, Xiaoling Tan², Lina Wang¹, Xuejin Li^1,3, Yu Du¹ and Xueming Hong¹

¹ Collage of Physics and Energy, Shenzhen Key Lab. of Sensor Technol., Shenzhen University, Shenzhen 518060, China

² The Electronic Communication Department, Shenzhen Institute of Information Technology, Shenzhen 518172, China

³ School of Science and Engineering, The Chinese University of Hong Kong (Shenzhen), Shenzhen 518172, China

Sensors 2018, 18(6), 1726; https://doi.org/10.3390/s18061726 - 28 May 2018

Cited by 10 | Viewed by 3887

Abstract

In this paper, a simplified hollow-core photonic crystal fiber surface-enhanced Raman scattering (SERS) probe is presented. Silver nanoprisms are grown with a photoreduction method and account for the SERS, which have better electromagnetic enhancement than spherical silver nanoparticles at 785 nm. Due to [...] Read more.

In this paper, a simplified hollow-core photonic crystal fiber surface-enhanced Raman scattering (SERS) probe is presented. Silver nanoprisms are grown with a photoreduction method and account for the SERS, which have better electromagnetic enhancement than spherical silver nanoparticles at 785 nm. Due to the antiresonant reflecting guidance mechanism, the excited laser and SERS signal are effectively guided in such a fully filled hollow-core photonic crystal fiber SERS probe and complicated selective filling with target sample is avoided. Rhodamine 6G molecules are used as probe molecules and the simplified hollow-core photonic crystal fiber SERS probe is test. Detection of low concentration Rhodamine 6G down to 10⁻⁸ M is achieved with a short integration time of 300 ms. Full article

(This article belongs to the Section Chemical Sensors)

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17 pages, 8471 KiB

Open AccessArticle

Health Monitoring of Bolted Spherical Joint Connection Based on Active Sensing Technique Using Piezoceramic Transducers

by Jing Xu^1,2, Chenyu Wang³, Hongnan Li^2,4, Chunwei Zhang¹, Jiajia Hao¹ and Shuli Fan^2,*

¹ School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China

² State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China

³ Department of Mechanical Engineering, University of Houston, Houston, TX 77004, USA

⁴ College of Civil Engineering, Shenyang Jianzhu University, Shenyang 110168, China

Sensors 2018, 18(6), 1727; https://doi.org/10.3390/s18061727 - 28 May 2018

Cited by 65 | Viewed by 8662

Abstract

Bolted spherical joints are widely used to form space steel structures. The stiffness and load capacity of the structures are affected by the looseness of bolted spherical joint connections in the structures. The looseness of the connections, which can be caused by fabrication [...] Read more.

Bolted spherical joints are widely used to form space steel structures. The stiffness and load capacity of the structures are affected by the looseness of bolted spherical joint connections in the structures. The looseness of the connections, which can be caused by fabrication error, low modeling accuracy, and “false twist” in the installation process, may negatively impact the load capacity of the structure and even lead to severe accidents. Furthermore, it is difficult to detect bolted spherical joint connection looseness from the outside since the bolts connect spheres with rods together from the inside. Active sensing methods are proposed in this paper to monitor the tightness status of the bolted spherical connection using piezoceramic transducers. A triangle-on-triangle offset grid composed of bolted spherical joints and steel tube bars was fabricated as the specimen and was used to validate the active sensing methods. Lead Zirconate Titanate (PZT) patches were used as sensors and actuators to monitor the bolted spherical joint tightness status. One PZT patch mounted on the central bolted sphere at the upper chord was used as an actuator to generate a stress wave. Another PZT patch mounted on the bar was used as a sensor to detect the propagated waves through the bolted spherical connection. The looseness of the connection can impact the energy of the stress wave propagated through the connection. The wavelet packet analysis and time reversal (TR) method were used to quantify the energy of the transmitted signal between the PZT patches by which the tightness status of the connection can be detected. In order to verify the effectiveness, repeatability, and consistency of the proposed methods, the experiments were repeated six times in different bolted spherical connection positions. The experimental results showed that the wavelet packet analysis and TR method are effective in detecting the tightness status of the connections. The proposed active monitoring method using PZT transducers can monitor the tightness levels of bolted spherical joint connections efficiently and shows its potential to guarantee the safety of space steel structures in construction and service. Full article

(This article belongs to the Special Issue Recent Advances of Piezoelectric Transducers and Applications)

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15 pages, 451 KiB

Open AccessArticle

Energy Modeling of IoT Mobile Terminals on WiFi Environmental Impacts ^†

by Yuxia Sun^1,*

, Junxian Chen¹, Yong Tang² and Yanjia Chen¹

¹ Department of Computer Science, Jinan University, Guangzhou 510630, China

² College of Computing, South China Normal University, Guangzhou 510630, China

^† This article is an extended version of the paper entitled “Modeling the Impacts of WiFi Signals on Energy Consumption of Smartphones”, presented at CollaborateCom 2017, Edinburgh, UK, 11–13 December 2017.

Sensors 2018, 18(6), 1728; https://doi.org/10.3390/s18061728 - 28 May 2018

Cited by 5 | Viewed by 3683

Abstract

With the popularity of various IoT mobile terminals such as mobile phones and sensors, the energy problems of IoT mobile terminals have attracted increasingly more attention. In this paper, we explore the impacts of some important factors of WiFi environments on the energy [...] Read more.

With the popularity of various IoT mobile terminals such as mobile phones and sensors, the energy problems of IoT mobile terminals have attracted increasingly more attention. In this paper, we explore the impacts of some important factors of WiFi environments on the energy consumption of mobile phones, which are typical IoT end devices. The factors involve the WiFi signal strength under good signal conditions, the type and the amount of protocol packets that are initiated by WiFi APs (Access Points) to maintain basic network communication with the phones. Controlled experiments are conducted to quantitatively study the phone energy impacts by the above WiFi environmental factors. To describe such impacts, we construct a time-based signal strength-aware energy model and packet type/amount-aware energy models. The models constructed in the paper corroborate the following user experience on phone energy consumption: (1) a phone’s energy is drawn faster under higher WiFi signal strengths than under lower ones even in normal signal conditions; (2) phones consume energy faster in a public WiFi network than in a private one even in the basic phone state. The energy modeling methods proposed in the paper enable ordinary developers to analyze phone energy draw conveniently by utilizing inexpensive power meters as measurement tools. The modeling methods are general and are able to be used for phones of any type and any platform. Full article

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

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13 pages, 4257 KiB

Open AccessArticle

Miniaturized Sensors Registering the Long-Term Course of Suture Tension In Vivo under Varying Intra-Abdominal Pressure

by Jörg Höer^1,* and Oliver Wetter²

¹ Hochtaunuskliniken Bad Homburg, Department of General and Visceral Surgery, Zeppelinstrasse 20, D-61352 Bad Homburg, Germany

² Fachhochschule Bielefeld, Campus Minden, Fachbereich Technik, Artilleriestrasse 9, D-32427 Minden, Germany

Sensors 2018, 18(6), 1729; https://doi.org/10.3390/s18061729 - 28 May 2018

Cited by 9 | Viewed by 3940

Abstract

Background: Failure of laparotomy closure develops after up to 20% of abdominal operations. Suture tension has an influence on the quality of tissue regeneration. No sensors are available to register suture tension dynamics in vivo. Methods: In a series of animal experiments, the [...] Read more.

Background: Failure of laparotomy closure develops after up to 20% of abdominal operations. Suture tension has an influence on the quality of tissue regeneration. No sensors are available to register suture tension dynamics in vivo. Methods: In a series of animal experiments, the effect of suture tension on the ultrastructure of the healing incision was examined. Surgeons’ ability to suture with target tension was tested. An implantable sensor and data logger were developed and tested experimentally in sutures closing midline laparotomies in pigs both under normal and elevated intra-abdominal pressure. Results: High suture tension has a negative influence on the regeneration of laparotomy incisions. Running sutures for laparotomy closure lose 45% of their initial tension over periods of 23 h. Intermittent elevation of intra-abdominal pressure to 30 mm Hg leads to a near total loss of suture tension after 23 h. Conclusion: Surgeons are not able to control and reproduce suture tension. Suture tension dynamics can be measured in vivo by the sensor developed. Further research is needed to define a tissue-specific suture tension optimum to reduce the incidence of complications after laparotomy. Techniques for laparotomy closure need to be modified. Full article

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

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21 pages, 5659 KiB

Open AccessArticle

Precision Agriculture Design Method Using a Distributed Computing Architecture on Internet of Things Context

by Francisco Javier Ferrández-Pastor^*

, Juan Manuel García-Chamizo, Mario Nieto-Hidalgo

and José Mora-Martínez

Department of Computer Technology, University of Alicante, P.O. Box 99, E-03080 Alicante, Spain

Sensors 2018, 18(6), 1731; https://doi.org/10.3390/s18061731 - 28 May 2018

Cited by 172 | Viewed by 20577

Abstract

The Internet of Things (IoT) has opened productive ways to cultivate soil with the use of low-cost hardware (sensors/actuators) and communication (Internet) technologies. Remote equipment and crop monitoring, predictive analytic, weather forecasting for crops or smart logistics and warehousing are some examples of [...] Read more.

The Internet of Things (IoT) has opened productive ways to cultivate soil with the use of low-cost hardware (sensors/actuators) and communication (Internet) technologies. Remote equipment and crop monitoring, predictive analytic, weather forecasting for crops or smart logistics and warehousing are some examples of these new opportunities. Nevertheless, farmers are agriculture experts but, usually, do not have experience in IoT applications. Users who use IoT applications must participate in its design, improving the integration and use. In this work, different industrial agricultural facilities are analysed with farmers and growers to design new functionalities based on IoT paradigms deployment. User-centred design model is used to obtain knowledge and experience in the process of introducing technology in agricultural applications. Internet of things paradigms are used as resources to facilitate the decision making. IoT architecture, operating rules and smart processes are implemented using a distributed model based on edge and fog computing paradigms. A communication architecture is proposed using these technologies. The aim is to help farmers to develop smart systems both, in current and new facilities. Different decision trees to automate the installation, designed by the farmer, can be easily deployed using the method proposed in this document. 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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17 pages, 2834 KiB

Open AccessArticle

Design of Compressed Sensing Algorithm for Coal Mine IoT Moving Measurement Data Based on a Multi-Hop Network and Total Variation

by Gang Wang^1,2

, Zhikai Zhao^1,2,* and Yongjie Ning²

¹ The National Joint Engineering Laboratory of Internet Applied Technology of Mines, Xuzhou 221000, China

² IOT Perception Mine Research Center, China University of Mining and Technology, Xuzhou 221000, China

Sensors 2018, 18(6), 1732; https://doi.org/10.3390/s18061732 - 28 May 2018

Cited by 11 | Viewed by 4460

Abstract

As the application of a coal mine Internet of Things (IoT), mobile measurement devices, such as intelligent mine lamps, cause moving measurement data to be increased. How to transmit these large amounts of mobile measurement data effectively has become an urgent problem. This [...] Read more.

As the application of a coal mine Internet of Things (IoT), mobile measurement devices, such as intelligent mine lamps, cause moving measurement data to be increased. How to transmit these large amounts of mobile measurement data effectively has become an urgent problem. This paper presents a compressed sensing algorithm for the large amount of coal mine IoT moving measurement data based on a multi-hop network and total variation. By taking gas data in mobile measurement data as an example, two network models for the transmission of gas data flow, namely single-hop and multi-hop transmission modes, are investigated in depth, and a gas data compressed sensing collection model is built based on a multi-hop network. To utilize the sparse characteristics of gas data, the concept of total variation is introduced and a high-efficiency gas data compression and reconstruction method based on Total Variation Sparsity based on Multi-Hop (TVS-MH) is proposed. According to the simulation results, by using the proposed method, the moving measurement data flow from an underground distributed mobile network can be acquired and transmitted efficiently. Full article

(This article belongs to the Special Issue Data and Information Fusion for Wireless Sensor Networks)

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16 pages, 3868 KiB

Open AccessArticle

A Capsule-Type Electromagnetic Acoustic Transducer for Fast Screening of External Corrosion in Nonmagnetic Pipes

by Yong Li^1,*

, Rui Cai¹, Bei Yan¹, Ilham Mukriz Zainal Abidin², Haoqing Jing¹ and Yi Wang¹

¹ State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Engineering Research Center of NDT and Structural Integrity Evaluation, School of Aerospace Engineering, Xi’an Jiaotong University, Xi’an 710049, China

² Leading Edge NDT Technology (LENDT) Group, Malaysian Nuclear Agency, Bangi, Kajang 43000, Malaysia

Sensors 2018, 18(6), 1733; https://doi.org/10.3390/s18061733 - 28 May 2018

Cited by 10 | Viewed by 4600

Abstract

For fuel transmission and structural strengthening, small-diameter pipes of nonmagnetic materials are extensively adopted in engineering fields including aerospace, energy, transportation, etc. However, the hostile and corrosive environment leaves them vulnerable to external corrosion which poses a severe threat to structural integrity of [...] Read more.

For fuel transmission and structural strengthening, small-diameter pipes of nonmagnetic materials are extensively adopted in engineering fields including aerospace, energy, transportation, etc. However, the hostile and corrosive environment leaves them vulnerable to external corrosion which poses a severe threat to structural integrity of pipes. Therefore, it is imperative to nondestructively detect and evaluate the external corrosion in nonmagnetic pipes. In light of this, a capsule-type Electromagnetic Acoustic Transducer (EMAT) for in-situ nondestructive evaluation of nonmagnetic pipes and fast screening of external corrosion is proposed in this paper. A 3D hybrid model for efficient prediction of responses from the proposed transducer to external corrosion is established. Closed-form expressions of field quantities of electromagnetics and EMAT signals are formulated. Simulations based on the hybrid model indicate feasibility of the proposed transducer in detection and evaluation of external corrosion in nonmagnetic pipes. In parallel, experiments with the fabricated transducer have been carried out. Experimental results are supportive of the conclusion drawn from simulations. The investigation via simulations and experiments implies that the proposed capsule-type EMAT is capable of fast screening of external corrosion, which is beneficial to the in-situ nondestructive evaluation of small-diameter nonmagnetic pipes. Full article

(This article belongs to the Special Issue Ultrasound Transducers)

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15 pages, 7103 KiB

Open AccessArticle

Planetary Gear Fault Diagnosis via Feature Image Extraction Based on Multi Central Frequencies and Vibration Signal Frequency Spectrum

by Yong Li¹, Gang Cheng^1,*, Yusong Pang²

and Moshen Kuai¹

¹ School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou 221116, China

² Faculty Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft 2628, The Netherlands

Sensors 2018, 18(6), 1735; https://doi.org/10.3390/s18061735 - 28 May 2018

Cited by 44 | Viewed by 5696

Abstract

Poor working environment leads to frequent failures of planetary gear trains. However, complex structure and variable transmission make the vibration signal strongly non-linear and non-stationary, which brings big problems to fault diagnosis. A method of planetary gear fault diagnosis via feature image extraction [...] Read more.

Poor working environment leads to frequent failures of planetary gear trains. However, complex structure and variable transmission make the vibration signal strongly non-linear and non-stationary, which brings big problems to fault diagnosis. A method of planetary gear fault diagnosis via feature image extraction based on multi central frequencies and vibration signal frequency spectrum is proposed. The original vibration signal is decomposed by variational mode decomposition (VMD), and four components with narrow bands and independent central frequencies are decomposed. In order to retain the feature spectrum of the original vibration signal as far as possible, the corresponding feature bands are intercepted from the frequency spectrum of original vibration signal based on the central frequency of each component. Then, the feature images of fault signals are constructed as the inputs of the convolution neural network (CNN), and the parameters of the neural network are optimized by sample training. Finally, the optimized CNN is used to identify fault signals. The overall fault recognition rate is up to 98.75%. Compared with the feature bands extracted directly from the component spectrums, the extraction method of the feature bands proposed in this paper needs fewer iterations under the same network structure. The method of planetary gear fault diagnosis proposed in this paper is effective. Full article

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

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12 pages, 3205 KiB

Open AccessArticle

Detection of Hemiplegic Walking Using a Wearable Inertia Sensing Device

by Junseok Lee^1,†, Sooji Park^2,† and Hangsik Shin^1,2,*

¹ Interdisciplinary Program in Biomedical Engineering, Chonnam National University, 77, Yongbong-ro, Buk-gu, Gwangju 61186, Korea

² Department of Biomedical Engineering, Chonnam National University, 50, Daehak-ro, Yeosu, Jeonnam 59626, Korea

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1736; https://doi.org/10.3390/s18061736 - 28 May 2018

Cited by 16 | Viewed by 4978

Abstract

Hemiplegia is a symptom that is caused by reduced sensory and motor ability on one side of the body due to stroke-related neural defects. Muscular weakness and abnormal sensation that is induced by hemiplegia usually lead to motor impairments, such as difficulty in [...] Read more.

Hemiplegia is a symptom that is caused by reduced sensory and motor ability on one side of the body due to stroke-related neural defects. Muscular weakness and abnormal sensation that is induced by hemiplegia usually lead to motor impairments, such as difficulty in controlling the trunk, unstable balance, and poor walking ability. Therefore, most hemiplegia patients show defective and asymmetric gait pattern. The purpose of this study is to distinguish hemiplegic gait by extracting simple characteristics of acceleration signals that are caused by asymmetry during walking using a wearable system. The devised wearable system was equipped with a three-axis accelerometer and a three-axis gyroscope. We selected 165 candidate features without step detection. A random forest algorithm was used for the classification, and the forward search algorithm was also used for optimal feature selection. The developed system and algorithms were verified clinically in 15 normal subjects and 20 hemiplegia patients that were undergoing stroke treatment, and 26 subject’s data was used for training, including validation, and nine subject’s data used for test. As a result of test set, the accuracy, sensitivity, specificity and positive predictive value were 100.0%, with the two classification attributes of standard deviation of points perpendicular to the axis of line of identity of Poincaré plot of angular velocity around vertical axis and kurtosis of frequency of angular velocity around longitudinal axis. Full article

(This article belongs to the Collection Sensors for Globalized Healthy Living and Wellbeing)

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15 pages, 3759 KiB

Open AccessArticle

Estimation of Temporal Gait Parameters Using a Human Body Electrostatic Sensing-Based Method

by Mengxuan Li, Pengfei Li, Shanshan Tian, Kai Tang and Xi Chen^*

State Key Laboratory of Mechatronics Engineering and Control, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(6), 1737; https://doi.org/10.3390/s18061737 - 28 May 2018

Cited by 21 | Viewed by 4712

Abstract

Accurate estimation of gait parameters is essential for obtaining quantitative information on motor deficits in Parkinson’s disease and other neurodegenerative diseases, which helps determine disease progression and therapeutic interventions. Due to the demand for high accuracy, unobtrusive measurement methods such as optical motion [...] Read more.

Accurate estimation of gait parameters is essential for obtaining quantitative information on motor deficits in Parkinson’s disease and other neurodegenerative diseases, which helps determine disease progression and therapeutic interventions. Due to the demand for high accuracy, unobtrusive measurement methods such as optical motion capture systems, foot pressure plates, and other systems have been commonly used in clinical environments. However, the high cost of existing lab-based methods greatly hinders their wider usage, especially in developing countries. In this study, we present a low-cost, noncontact, and an accurate temporal gait parameters estimation method by sensing and analyzing the electrostatic field generated from human foot stepping. The proposed method achieved an average 97% accuracy on gait phase detection and was further validated by comparison to the foot pressure system in 10 healthy subjects. Two results were compared using the Pearson coefficient r and obtained an excellent consistency (r = 0.99, p < 0.05). The repeatability of the purposed method was calculated between days by intraclass correlation coefficients (ICC), and showed good test-retest reliability (ICC = 0.87, p < 0.01). The proposed method could be an affordable and accurate tool to measure temporal gait parameters in hospital laboratories and in patients’ home environments. Full article

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

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14 pages, 2537 KiB

Open AccessArticle

Multifunctionalized Reduced Graphene Oxide Biosensors for Simultaneous Monitoring of Structural Changes in Amyloid-β 40

by Dahye Jeong^1,2,†, Jinsik Kim^3,†, Myung-Sic Chae¹, Wonseok Lee⁴, Seung-Hoon Yang⁵

, YoungSoo Kim⁶, Seung Min Kim⁷, Jin San Lee⁸, Jeong Hoon Lee⁹

, Jungkyu Choi²

, Dae Sung Yoon^10,* and Kyo Seon Hwang^1,*

¹ Department of Clinical Pharmacology and Therapeutics, College of Medicine, Kyung Hee University, Seoul 02447, Korea

² Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Korea

³ Department of Biomedical Engineering, Dongguk University, Seoul 04620, Korea

⁴ Department of Biomedical Engineering, Yonsei University, Wonju 26493, Korea

⁵ Systems Biotechnology Research Center, Korea Institute of Science and Technology (KIST), Gangnueung 25451, Korea

⁶ Department of Pharmacy & Intergrated Science and Engineering Division, Yonsei University, Incheon 21983, Korea

⁷ Center for Institute of Advanced Composite Materials, Korea Institute of Science and Technology (KIST), Jeonbuk 55324, Korea

⁸ Department of Neurology, Kyung Hee University Hospital, Seoul 02447, Korea

⁹ Department of Electrical Engineering, Kwangwoon University, Seoul 01897, Korea

¹⁰ Department of Biomedical Engineering, Korea University, Seoul 02841, Korea

^† These authors contributed equally to this work.

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Sensors 2018, 18(6), 1738; https://doi.org/10.3390/s18061738 - 28 May 2018

Cited by 18 | Viewed by 4518

Abstract

Determination of the conformation (monomer, oligomer, or fibril) of amyloid peptide aggregates in the human brain is essential for the diagnosis and treatment of Alzheimer’s disease (AD). Accordingly, systematic investigation of amyloid conformation using analytical tools is essential for precisely quantifying the relative [...] Read more.

Determination of the conformation (monomer, oligomer, or fibril) of amyloid peptide aggregates in the human brain is essential for the diagnosis and treatment of Alzheimer’s disease (AD). Accordingly, systematic investigation of amyloid conformation using analytical tools is essential for precisely quantifying the relative amounts of the three conformations of amyloid peptide. Here, we developed a reduced graphene oxide (rGO) based multiplexing biosensor that could be used to monitor the relative amounts of the three conformations of various amyloid-β 40 (Aβ40) fluids. The electrical rGO biosensor was composed of a multichannel sensor array capable of individual detection of monomers, oligomers, and fibrils in a single amyloid fluid sample. From the performance test of each sensor, we showed that this method had good analytical sensitivity (1 pg/mL) and a fairly wide dynamic range (1 pg/mL to 10 ng/mL) for each conformation of Aβ40. To verify whether the rGO biosensor could be used to evaluate the relative amounts of the three conformations, various amyloid solutions (monomeric Aβ40, aggregated Aβ40, and disaggregated Aβ40 solutions) were employed. Notably, different trends in the relative amounts of the three conformations were observed in each amyloid solution, indicating that this information could serve as an important parameter in the clinical setting. Accordingly, our analytical tool could precisely detect the relative amounts of the three conformations of Aβ40 and may have potential applications as a diagnostic system for AD. Full article

(This article belongs to the Section Biosensors)

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22 pages, 4085 KiB

Open AccessArticle

An Unambiguous Delay-And-Multiply Acquisition Scheme for GPS L1C Signals

by Duk-Sun Shim^* and Jin-Seok Jeon

School of Electrical and Electronics Engineering, Chung-Ang University, 84 Huksuk-ro, Dongjak-ku, Seoul 06974, Korea

Sensors 2018, 18(6), 1739; https://doi.org/10.3390/s18061739 - 28 May 2018

Cited by 14 | Viewed by 3301

Abstract

The GPS provides positioning information almost anytime and anywhere on Earth, regardless of the weather conditions, and has become an essential technology for positioning and navigation. As a modernization program, the fourth civil GPS signal, denoted as L1C, will be transmitted from Block [...] Read more.

The GPS provides positioning information almost anytime and anywhere on Earth, regardless of the weather conditions, and has become an essential technology for positioning and navigation. As a modernization program, the fourth civil GPS signal, denoted as L1C, will be transmitted from Block III satellites. One distinction of the L1C signal from the former signals is the use of binary offset carrier (BOC) modulation, which is necessary for compatibility and the reduction of interference between the legacy L1 signal and L1C signal, despite their use of the same carrier frequency. One drawback of using BOC modulation is the ambiguity problem, which comes from the multiple peaks in the correlation function and causes difficulties finding the code phase in the acquisition process. In this paper we suggest two delay-and-multiply (DM) methods for the L1C signal to solve the ambiguity problem. For the DM acquisition schemes we suggest the optimal delay time for the delay signal, and prove that the correlation function of the received DM signal and the generated DM signal has a triangular shape, as seen in the legacy GPS L1 signal. The noise characteristics of the decision variable are obtained and the performance of the DM acquisition scheme is given in terms of the probability of detection, and compared with that of the conventional method. We provide the procedure to find the Doppler frequency after obtaining the code phase through the proposed DM method. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 7508 KiB

Open AccessArticle

Research on a Novel MEMS Sensor for Spatial DC Electric Field Measurements in an Ion Flows Field

by Ya Mou¹, Zhanqing Yu^1,*, Kaitian Huang², Qing Ma³, Rong Zeng^1,* and Zheyao Wang³

¹ State Key Lab of Power Systems, Department of Electrical Engineering, Tsinghua University, Beijing 100084, China

² Electric Power Research Institute, China Southern Power Grid, Guangzhou 510000, China

³ Department of Microelectronics and Nanoelectronics, Tsinghua University, Beijing 100084, China

Sensors 2018, 18(6), 1740; https://doi.org/10.3390/s18061740 - 28 May 2018

Cited by 27 | Viewed by 5236

Abstract

Thus far, despite the development of electric field sensors (EFSs) such as field mills, optoelectronic EFSs and microelectromechanical system (MEMS)-based EFSs, no sensor can accurately measure an electric field in space due to the existence of space charge and the influence of charge [...] Read more.

Thus far, despite the development of electric field sensors (EFSs) such as field mills, optoelectronic EFSs and microelectromechanical system (MEMS)-based EFSs, no sensor can accurately measure an electric field in space due to the existence of space charge and the influence of charge attachment. To measure a spatial synthetic electric field in an ion flow field, a double potential independent differential EFS based on MEMS is proposed. Compared with other EFSs, this method has the advantages of independent potential (without grounding) and the ability to support the measurement of the synthetic ion flow electric field in space. First, to analyse the charge distribution after the sensor is involved exposed to an electric field, a simulation model was constructed. Then, given the redistribution of the spatial electric field in space and the influence of the surface charge on the sensor, the quantitative relationship between the electric field to be measured and that measured by the proposed sensor was obtained. To improve the performance of the EFS, a set of synthetic field strength sensor calibration systems that consider spatial ion flow injection was established. Furthermore, the parameter λ, which is related to the relative position of the differential chips, was determined. Finally, a series of comparative experiments indicated that the differential EFS highlighted in the present study exhibits good linearity and accuracy. Full article

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

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14 pages, 3724 KiB

Open AccessArticle

Two-Dimensional Direction-of-Arrival Fast Estimation of Multiple Signals with Matrix Completion Theory in Coprime Planar Array

by Haiyun Xu

, Yankui Zhang

, Bin Ba^*, Daming Wang and Xiangzhi Li

National Digital System Engineering and Technological Research R&D Center, Zhengzhou 450001, China

Sensors 2018, 18(6), 1741; https://doi.org/10.3390/s18061741 - 28 May 2018

Cited by 9 | Viewed by 3230

Abstract

In estimating the two-dimensional (2D) direction-of-arrival (DOA) using a coprime planar array, the main issues are the high complexity of spectral peak search and the limited degree of freedom imposed by the number of sensors. In this paper, we present an algorithm based [...] Read more.

In estimating the two-dimensional (2D) direction-of-arrival (DOA) using a coprime planar array, the main issues are the high complexity of spectral peak search and the limited degree of freedom imposed by the number of sensors. In this paper, we present an algorithm based on the matrix completion theory in coprime planar array that reduces the computational complexity and obtains a high degree of freedom. The algorithm first analyzes the covariance matrix of received signals to estimate the covariance matrix of a virtual uniform rectangular array, which has the same aperture as the coprime planar array. Matrix completion theory is then applied to estimate the missing elements of the virtual array covariance matrix. Finally, a closed-form DOA solution is obtained using the unitary estimation signal parameters via rotational invariance techniques (Unitary-ESPRIT). Simulation results show that the proposed algorithm has a high degree of freedom, enabling the estimation of more signal DOAs than the number of sensors. The proposed algorithm has reduced computational complexity because the spectral peak search is replaced by Unitary-ESPRIT, but attains similarly high levels accuracy to those of the 2D multiple signal classification algorithm. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 1796 KiB

Open AccessArticle

Waveform Optimization for Target Estimation by Cognitive Radar with Multiple Antennas

by Yu Yao^1,*, Junhui Zhao¹

and Lenan Wu²

¹ School of Information Engineering, East China Jiaotong University, Nanchang 330031, China

² School of Information Science and Engineering, Southeast University, Nanjing 210096, China

Sensors 2018, 18(6), 1743; https://doi.org/10.3390/s18061743 - 29 May 2018

Cited by 15 | Viewed by 3720

Abstract

A new scheme based on Kalman filtering to optimize the waveforms of an adaptive multi-antenna radar system for target impulse response (TIR) estimation is presented. This work aims to improve the performance of TIR estimation by making use of the temporal correlation between [...] Read more.

A new scheme based on Kalman filtering to optimize the waveforms of an adaptive multi-antenna radar system for target impulse response (TIR) estimation is presented. This work aims to improve the performance of TIR estimation by making use of the temporal correlation between successive received signals, and minimize the mean square error (MSE) of TIR estimation. The waveform design approach is based upon constant learning from the target feature at the receiver. Under the multiple antennas scenario, a dynamic feedback loop control system is established to real-time monitor the change in the target features extracted form received signals. The transmitter adapts its transmitted waveform to suit the time-invariant environment. Finally, the simulation results show that, as compared with the waveform design method based on the MAP criterion, the proposed waveform design algorithm is able to improve the performance of TIR estimation for extended targets with multiple iterations, and has a relatively lower level of complexity. Full article

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

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9 pages, 2303 KiB

Open AccessArticle

Temporal Stability of GPS Transmitter Group Delay Variations

by Susanne Beer^* and Lambert Wanninger

Geodätisches Institut, Technische Universität Dresden, 01062 Dresden, Germany

Sensors 2018, 18(6), 1744; https://doi.org/10.3390/s18061744 - 29 May 2018

Cited by 6 | Viewed by 3088

Abstract

The code observable of global navigation satellite systems (GNSS) is influenced by group delay variations (GDV) of transmitter and receiver antennas. For the Global Positioning System (GPS), the variations can sum up to 1 m in the ionosphere-free linear combination and thus can [...] Read more.

The code observable of global navigation satellite systems (GNSS) is influenced by group delay variations (GDV) of transmitter and receiver antennas. For the Global Positioning System (GPS), the variations can sum up to 1 m in the ionosphere-free linear combination and thus can significantly affect precise code applications. The contribution of the GPS transmitters can amount to 0.8 m peak-to-peak over the entire nadir angle range. To verify the assumption of their time-invariance, we determined daily individual satellite GDV for GPS transmitter antennas over a period of more than two years. Dual-frequency observations of globally distributed reference stations and their multipath combination form the basis for our analysis. The resulting GPS GDV are stable on the level of a few centimeters for C1, P2, and for the ionosphere-free linear combination. Our study reveals that the inconsistencies of the GDV of space vehicle number (SVN) 55 with respect to earlier studies are not caused by temporal instabilities, but are rather related to receiver properties. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 5506 KiB

Open AccessArticle

Inverse Piezoresistive Nanocomposite Sensors for Identifying Human Sitting Posture

by Zhe Qian^1,2, Anton E. Bowden^2,3,*

, Dong Zhang^1,2, Jia Wan^1,2, Wei Liu^1,2, Xiao Li¹, Daniel Baradoy³ and David T. Fullwood³

¹ School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510006, China

² SYSU-CMU Shunde International Joint Research Institute, Shunde, Foshan 528399, China

³ Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602, USA

Sensors 2018, 18(6), 1745; https://doi.org/10.3390/s18061745 - 29 May 2018

Cited by 20 | Viewed by 5515

Abstract

Sitting posture is the position in which one holds his/her body upright against gravity while sitting. Poor sitting posture is regarded as an aggravating factor for various diseases. In this paper, we present an inverse piezoresistive nanocomposite sensor, and related deciphering neural network, [...] Read more.

Sitting posture is the position in which one holds his/her body upright against gravity while sitting. Poor sitting posture is regarded as an aggravating factor for various diseases. In this paper, we present an inverse piezoresistive nanocomposite sensor, and related deciphering neural network, as a new tool to identify human sitting postures accurately. As a low power consumption device, the proposed tool has simple structure, and is easy to use. The strain gauge is attached to the back of the user to acquire sitting data. A three-layer BP neural network is employed to distinguish normal sitting posture, slight hunchback and severe hunchback according to the acquired data. Experimental results show that our method is both realizable and effective, achieving 98.75% posture identification accuracy. This successful application of inverse piezoresistive nanocomposite sensors reveals that the method could potentially be used for monitoring of diverse physiological parameters in the future. Full article

(This article belongs to the Special Issue Sensor Applications in Medical Monitoring and Assistive Devices)

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24 pages, 7553 KiB

Open AccessArticle

A Kinect-Based Segmentation of Touching-Pigs for Real-Time Monitoring

by Miso Ju, Younchang Choi, Jihyun Seo, Jaewon Sa

, Sungju Lee

, Yongwha Chung^* and Daihee Park

Department of Computer Convergence Software, Korea University, Sejong City 30019, Korea

Sensors 2018, 18(6), 1746; https://doi.org/10.3390/s18061746 - 29 May 2018

Cited by 44 | Viewed by 5710

Abstract

Segmenting touching-pigs in real-time is an important issue for surveillance cameras intended for the 24-h tracking of individual pigs. However, methods to do so have not yet been reported. We particularly focus on the segmentation of touching-pigs in a crowded pig room with [...] Read more.

Segmenting touching-pigs in real-time is an important issue for surveillance cameras intended for the 24-h tracking of individual pigs. However, methods to do so have not yet been reported. We particularly focus on the segmentation of touching-pigs in a crowded pig room with low-contrast images obtained using a Kinect depth sensor. We reduce the execution time by combining object detection techniques based on a convolutional neural network (CNN) with image processing techniques instead of applying time-consuming operations, such as optimization-based segmentation. We first apply the fastest CNN-based object detection technique (i.e., You Only Look Once, YOLO) to solve the separation problem for touching-pigs. If the quality of the YOLO output is not satisfied, then we try to find the possible boundary line between the touching-pigs by analyzing the shape. Our experimental results show that this method is effective to separate touching-pigs in terms of both accuracy (i.e., 91.96%) and execution time (i.e., real-time execution), even with low-contrast images obtained using a Kinect depth sensor. Full article

(This article belongs to the Special Issue Sensors in Agriculture 2018)

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14 pages, 2108 KiB

Open AccessArticle

Magnetic Detection Structure for Lab-on-Chip Applications Based on the Frequency Mixing Technique

by Amine Rabehi¹, Benjamin Garlan¹, Stefan Achtsnicht²

, Hans-Joachim Krause^2,*

, Andreas Offenhäusser²

, Kieu Ngo³, Sophie Neveu⁴, Stephanie Graff-Dubois⁵

and Hamid Kokabi¹

¹ Laboratoire d’Electronique et d’Electromagnétisme, Sorbonne Université, L2E, 75252 Paris, France

² Institute of Bioelectronics (ICS-8), Forschungszentrum Jülich, 52428 Jülich, Germany

³ Laboratoire Interfaces et Systèmes Électrochimiques, LISE, Sorbonne Université, CNRS, F 75005 Paris, France

⁴ PHENIX, Sorbonne Université, CNRS, F 75005 Paris, France

⁵ Faculte de Medecine, Sorbonne Université, CIMI-PARIS, UMRS CR7-Inserm U1135-CNRS ERL 8255, 75013 Paris, France

Sensors 2018, 18(6), 1747; https://doi.org/10.3390/s18061747 - 29 May 2018

Cited by 30 | Viewed by 4734

Abstract

A magnetic frequency mixing technique with a set of miniaturized planar coils was investigated for use with a completely integrated Lab-on-Chip (LoC) pathogen sensing system. The system allows the detection and quantification of superparamagnetic beads. Additionally, in terms of magnetic nanoparticle characterization ability, [...] Read more.

A magnetic frequency mixing technique with a set of miniaturized planar coils was investigated for use with a completely integrated Lab-on-Chip (LoC) pathogen sensing system. The system allows the detection and quantification of superparamagnetic beads. Additionally, in terms of magnetic nanoparticle characterization ability, the system can be used for immunoassays using the beads as markers. Analytical calculations and simulations for both excitation and pick-up coils are presented; the goal was to investigate the miniaturization of simple and cost-effective planar spiral coils. Following these calculations, a Printed Circuit Board (PCB) prototype was designed, manufactured, and tested for limit of detection, linear response, and validation of theoretical concepts. Using the magnetic frequency mixing technique, a limit of detection of 15 µg/mL of 20 nm core-sized nanoparticles was achieved without any shielding. Full article

(This article belongs to the Section Biosensors)

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13 pages, 6275 KiB

Open AccessArticle

Stand-Alone Wearable System for Ubiquitous Real-Time Monitoring of Muscle Activation Potentials

by Ivan Mazzetta¹, Paolo Gentile^1,2

, Marco Pessione³, Antonio Suppa^4,5

, Alessandro Zampogna⁴

, Edoardo Bianchini⁴ and Fernanda Irrera^1,*

¹ Department of Information Engineering, Electronics and Telecommunications DIET, “Sapienza” University of Rome, via Eudossiana 18, 00184 Rome, Italy

² ABB Italy Electrification Products, Via Pescaria 5, 24123 Bergamo, Italy

³ STMicroelectronics, Via Olivetti 2, 20864 Agrate Brianza MI, Italy

⁴ Department of Human Neuroscience, “Sapienza” University of Rome, Piazzale Aldo Moro, 00185 Rome, Italy

⁵ IRCSS-NEUROMED, via Atinense 18, 86077 Pozzilli, IS, Italy

Sensors 2018, 18(6), 1748; https://doi.org/10.3390/s18061748 - 29 May 2018

Cited by 22 | Viewed by 5303

Abstract

Wearable technology is attracting most attention in healthcare for the acquisition of physiological signals. We propose a stand-alone wearable surface ElectroMyoGraphy (sEMG) system for monitoring the muscle activity in real time. With respect to other wearable sEMG devices, the proposed system includes circuits [...] Read more.

Wearable technology is attracting most attention in healthcare for the acquisition of physiological signals. We propose a stand-alone wearable surface ElectroMyoGraphy (sEMG) system for monitoring the muscle activity in real time. With respect to other wearable sEMG devices, the proposed system includes circuits for detecting the muscle activation potentials and it embeds the complete real-time data processing, without using any external device. The system is optimized with respect to power consumption, with a measured battery life that allows for monitoring the activity during the day. Thanks to its compactness and energy autonomy, it can be used outdoor and it provides a pathway to valuable diagnostic data sets for patients during their own day-life. Our system has performances that are comparable to state-of-art wired equipment in the detection of muscle contractions with the advantage of being wearable, compact, and ubiquitous. Full article

(This article belongs to the Special Issue Smart Sensing System for Real-Time Monitoring)

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18 pages, 6981 KiB

Open AccessArticle

Adaptive Obstacle Detection for Mobile Robots in Urban Environments Using Downward-Looking 2D LiDAR

by Cong Pang¹, Xunyu Zhong^1,*

, Huosheng Hu²

, Jun Tian¹, Xiafu Peng¹ and Jianping Zeng¹

¹ Department of Automation, Xiamen University, Xiamen 361102, China

² School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK

Sensors 2018, 18(6), 1749; https://doi.org/10.3390/s18061749 - 29 May 2018

Cited by 31 | Viewed by 6309

Abstract

Environment perception is important for collision-free motion planning of outdoor mobile robots. This paper presents an adaptive obstacle detection method for outdoor mobile robots using a single downward-looking LiDAR sensor. The method begins by extracting line segments from the raw sensor data, and [...] Read more.

Environment perception is important for collision-free motion planning of outdoor mobile robots. This paper presents an adaptive obstacle detection method for outdoor mobile robots using a single downward-looking LiDAR sensor. The method begins by extracting line segments from the raw sensor data, and then estimates the height and the vector of the scanned road surface at each moment. Subsequently, the segments are divided into either road ground or obstacles based on the average height of each line segment and the deviation between the line segment and the road vector estimated from the previous measurements. A series of experiments have been conducted in several scenarios, including normal scenes and complex scenes. The experimental results show that the proposed approach can accurately detect obstacles on roads and could effectively deal with the different heights of obstacles in urban road environments. Full article

(This article belongs to the Section Remote Sensors)

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45 pages, 38814 KiB

Open AccessArticle

Caching Joint Shortcut Routing to Improve Quality of Service for Information-Centric Networking

by Baixiang Huang¹, Anfeng Liu^1,2

, Chengyuan Zhang^1,*

, Naixue Xiong³

, Zhiwen Zeng¹ and Zhiping Cai⁴

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 Department of Mathematics and Computer Science, Northeastern State University, Tahlequah, OK 74464, USA

⁴ Department of Network Engineering, School of Computer, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(6), 1750; https://doi.org/10.3390/s18061750 - 29 May 2018

Cited by 20 | Viewed by 5223

Abstract

Hundreds of thousands of ubiquitous sensing (US) devices have provided an enormous number of data for Information-Centric Networking (ICN), which is an emerging network architecture that has the potential to solve a great variety of issues faced by the traditional network. A Caching [...] Read more.

Hundreds of thousands of ubiquitous sensing (US) devices have provided an enormous number of data for Information-Centric Networking (ICN), which is an emerging network architecture that has the potential to solve a great variety of issues faced by the traditional network. A Caching Joint Shortcut Routing (CJSR) scheme is proposed in this paper to improve the Quality of service (QoS) for ICN. The CJSR scheme mainly has two innovations which are different from other in-network caching schemes: (1) Two routing shortcuts are set up to reduce the length of routing paths. Because of some inconvenient transmission processes, the routing paths of previous schemes are prolonged, and users can only request data from Data Centers (DCs) until the data have been uploaded from Data Producers (DPs) to DCs. Hence, the first kind of shortcut is built from DPs to users directly. This shortcut could release the burden of whole network and reduce delay. Moreover, in the second shortcut routing method, a Content Router (CR) which could yield shorter length of uploading routing path from DPs to DCs is chosen, and then data packets are uploaded through this chosen CR. In this method, the uploading path shares some segments with the pre-caching path, thus the overall length of routing paths is reduced. (2) The second innovation of the CJSR scheme is that a cooperative pre-caching mechanism is proposed so that QoS could have a further increase. Besides being used in downloading routing, the pre-caching mechanism can also be used when data packets are uploaded towards DCs. Combining uploading and downloading pre-caching, the cooperative pre-caching mechanism exhibits high performance in different situations. Furthermore, to address the scarcity of storage size, an algorithm that could make use of storage from idle CRs is proposed. After comparing the proposed scheme with five existing schemes via simulations, experiments results reveal that the CJSR scheme could reduce the total number of processed interest packets by 54.8%, enhance the cache hits of each CR and reduce the number of total hop counts by 51.6% and cut down the length of routing path for users to obtain their interested data by 28.6–85.7% compared with the traditional NDN scheme. Moreover, the length of uploading routing path could be decreased by 8.3–33.3%. Full article

(This article belongs to the Special Issue Internet of Things and Ubiquitous Sensing)

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18 pages, 473 KiB

Open AccessArticle

Supervoxels-Based Histon as a New Alzheimer’s Disease Imaging Biomarker

by César A. Ortiz Toro^*

, Consuelo Gonzalo-Martín^*,†

, Angel García-Pedrero

and Ernestina Menasalvas Ruiz^†

¹ Centro de Tecnología Biomédica, Campus de Montegancedo, Universidad Politécnica de Madrid, 28233 Pozuelo de Alarcón, Spain

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1752; https://doi.org/10.3390/s18061752 - 29 May 2018

Cited by 13 | Viewed by 8566

Abstract

Alzheimer’s disease (AD) represents the prevalent type of dementia in the elderly, and is characterized by the presence of neurofibrillary tangles and amyloid plaques that eventually leads to the loss of neurons, resulting in atrophy in specific brain areas. Although the process of [...] Read more.

Alzheimer’s disease (AD) represents the prevalent type of dementia in the elderly, and is characterized by the presence of neurofibrillary tangles and amyloid plaques that eventually leads to the loss of neurons, resulting in atrophy in specific brain areas. Although the process of degeneration can be visualized through various modalities of medical imaging and has proved to be a valuable biomarker, the accurate diagnosis of Alzheimer’s disease remains a challenge, especially in its early stages. In this paper, we propose a novel classification method for Alzheimer’s disease/cognitive normal discrimination in structural magnetic resonance images (MRI), based on the extension of the concept of histons to volumetric images. The proposed method exploits the relationship between grey matter, white matter and cerebrospinal fluid degeneration by means of a segmentation using supervoxels. The calculated histons are then processed for a reduction in dimensionality using principal components analysis (PCA) and the resulting vector is used to train an support vector machine (SVM) classifier. Experimental results using the OASIS-1 database have proven to be a significant improvement compared to a baseline classification made using the pipeline provided by Clinica software. Full article

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

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18 pages, 1726 KiB

Open AccessArticle

Estimating Angle-of-Arrival and Time-of-Flight for Multipath Components Using WiFi Channel State Information

by Afaz Uddin Ahmed^1,2,*

, Reza Arablouei²

, Frank De Hoog², Branislav Kusy², Raja Jurdak² and Neil Bergmann¹

¹ School of Information Technology and Electrical Engineering, University of Queensland, St Lucia, QLD 4072, Australia

² Data61, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Pullenvale, QLD 4069, Australia

Sensors 2018, 18(6), 1753; https://doi.org/10.3390/s18061753 - 29 May 2018

Cited by 33 | Viewed by 8479

Abstract

Channel state information (CSI) collected during WiFi packet transmissions can be used for localization of commodity WiFi devices in indoor environments with multipath propagation. To this end, the angle of arrival (AoA) and time of flight (ToF) for all dominant multipath components need [...] Read more.

Channel state information (CSI) collected during WiFi packet transmissions can be used for localization of commodity WiFi devices in indoor environments with multipath propagation. To this end, the angle of arrival (AoA) and time of flight (ToF) for all dominant multipath components need to be estimated. A two-dimensional (2D) version of the multiple signal classification (MUSIC) algorithm has been shown to solve this problem using 2D grid search, which is computationally expensive and is therefore not suited for real-time localisation. In this paper, we propose using a modified matrix pencil (MMP) algorithm instead. Specifically, we show that the AoA and ToF estimates can be found independently of each other using the one-dimensional (1D) MMP algorithm and the results can be accurately paired to obtain the AoA–ToF pairs for all multipath components. Thus, the 2D estimation problem reduces to running 1D estimation multiple times, substantially reducing the computational complexity. We identify and resolve the problem of degenerate performance when two or more multipath components have the same AoA. In addition, we propose a packet aggregation model that uses the CSI data from multiple packets to improve the performance under noisy conditions. Simulation results show that our algorithm achieves two orders of magnitude reduction in the computational time over the 2D MUSIC algorithm while achieving similar accuracy. High accuracy and low computation complexity of our approach make it suitable for applications that require location estimation to run on resource-constrained embedded devices in real time. Full article

(This article belongs to the Section Sensor Networks)

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16 pages, 4942 KiB

Open AccessArticle

Accurate Fall Detection in a Top View Privacy Preserving Configuration

by Manola Ricciuti^*

, Susanna Spinsante

and Ennio Gambi

Dipartimento di Ingegneria dell’Informazione, Università Politecnica delle Marche via Brecce Bianche 12, 60131 Ancona, Italy

Sensors 2018, 18(6), 1754; https://doi.org/10.3390/s18061754 - 29 May 2018

Cited by 13 | Viewed by 3641

Abstract

Fall detection is one of the most investigated themes in the research on assistive solutions for aged people. In particular, a false-alarm-free discrimination between falls and non-falls is indispensable, especially to assist elderly people living alone. Current technological solutions designed to monitor several [...] Read more.

Fall detection is one of the most investigated themes in the research on assistive solutions for aged people. In particular, a false-alarm-free discrimination between falls and non-falls is indispensable, especially to assist elderly people living alone. Current technological solutions designed to monitor several types of activities in indoor environments can guarantee absolute privacy to the people that decide to rely on them. Devices integrating RGB and depth cameras, such as the Microsoft Kinect, can ensure privacy and anonymity, since the depth information is considered to extract only meaningful information from video streams. In this paper, we propose an accurate fall detection method investigating the depth frames of the human body using a single device in a top-view configuration, with the subjects located under the device inside a room. Features extracted from depth frames train a classifier based on a binary support vector machine learning algorithm. The dataset includes 32 falls and 8 activities considered for comparison, for a total of 800 sequences performed by 20 adults. The system showed an accuracy of 98.6% and only one false positive. Full article

(This article belongs to the Special Issue Smart Homes)

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21 pages, 1068 KiB

Open AccessArticle

Vibration-Induced Errors in MEMS Tuning Fork Gyroscopes with Imbalance

by Xiang Fang¹, Linxi Dong^1,2,*, Wen-Sheng Zhao¹

, Haixia Yan^3,4,*, Kwok Siong Teh⁵ and Gaofeng Wang¹

¹ The Key Laboratory of RF Circuits and System of Ministry of Education, College of Electronic and Information, Hangzhou Dianzi University, Hangzhou 310018, China

² State Key Laboratory of Functional Materials for Informatics, Chinese Academy of Sciences, Shanghai 200050, China

³ Department of Mechanics, School of Information Engineering, Hangzhou Dianzi University, Hangzhou 310018, China

⁴ State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, China

⁵ Department of Mechanics, School of Engineering, San Francisco State University, San Francisco, CA 94132, USA

Sensors 2018, 18(6), 1755; https://doi.org/10.3390/s18061755 - 29 May 2018

Cited by 7 | Viewed by 3721

Abstract

This paper discusses the vibration-induced error in non-ideal MEMS tuning fork gyroscopes (TFGs). Ideal TFGs which are thought to be immune to vibrations do not exist, and imbalance between two gyros of TFGs is an inevitable phenomenon. Three types of fabrication imperfections (i.e., [...] Read more.

This paper discusses the vibration-induced error in non-ideal MEMS tuning fork gyroscopes (TFGs). Ideal TFGs which are thought to be immune to vibrations do not exist, and imbalance between two gyros of TFGs is an inevitable phenomenon. Three types of fabrication imperfections (i.e., stiffness imbalance, mass imbalance, and damping imbalance) are studied, considering different imbalance radios. We focus on the coupling types of two gyros of TFGs in both drive and sense directions, and the vibration sensitivities of four TFG designs with imbalance are simulated and compared. It is found that non-ideal TFGs with two gyros coupled both in drive and sense directions (type CC TFGs) are the most insensitive to vibrations with frequencies close to the TFG operating frequencies. However, sense-axis vibrations with in-phase resonant frequencies of a coupled gyros system result in severe error outputs to TFGs with two gyros coupled in the sense direction, which is mainly attributed to the sense capacitance nonlinearity. With increasing stiffness coupled ratio of the coupled gyros system, the sensitivity to vibrations with operating frequencies is cut down, yet sensitivity to vibrations with in-phase frequencies is amplified. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 2408 KiB

Open AccessArticle

Phenol-Formaldehyde Resin for Optical-Chemical Temperature Sensing

by Steven Claucherty

and Hirotaka Sakaue^*

Department of Aerospace and Mechanical Engineering, University of Notre Dame, Hessert Laboratory, Notre Dame, IN 46556, USA

Sensors 2018, 18(6), 1756; https://doi.org/10.3390/s18061756 - 30 May 2018

Cited by 11 | Viewed by 4231

Abstract

The application of phenol-formaldehyde (PF) resin as an optical temperature sensor is investigated. Recent developments in optical luminescent sensors allow for global measurements to be made over the surface of a test article, extending beyond conventional point measurements. Global temperature distributions are particularly [...] Read more.

The application of phenol-formaldehyde (PF) resin as an optical temperature sensor is investigated. Recent developments in optical luminescent sensors allow for global measurements to be made over the surface of a test article, extending beyond conventional point measurements. Global temperature distributions are particularly helpful when validating computational models or when mapping temperature over complex geometries, and can be used to calculate surface heat flux values. Temperature-sensitive paint (TSP) is a novel chemical approach to obtaining these global temperature measurements, but there are still challenges to overcome to make it a reliable tool. A sensor with a wide range of temperature sensitivity is desired to provide the maximum amount of utility, especially for tests spanning large temperature gradients. Naturally luminescent materials such as PF resin provide an attractive alternative to chemical sensor coatings, and PF resin is studied for this reason. Static tests of different PF resin samples are conducted using two binder materials to strengthen the material: cloth and paper. The material shows temperature sensitivities up to −0.8%/K, demonstrating the usefulness of PF resin as a temperature sensor. Full article

(This article belongs to the Section Chemical Sensors)

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12 pages, 4588 KiB

Open AccessArticle

Evaluation of Dry Electrodes in Canine Heart Rate Monitoring

by Juhani Virtanen^1,*

, Sanni Somppi², Heini Törnqvist², Vala Jeyhani¹, Patrique Fiedler³

, Yulia Gizatdinova⁴, Päivi Majaranta⁴, Heli Väätäjä⁴, Anna Valldeoriola Cardó²

, Jukka Lekkala¹, Sampo Tuukkanen¹

, Veikko Surakka⁴, Outi Vainio² and Antti Vehkaoja¹

¹ BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Tampere University of Technology (TUT), P.O. Box 692, FI-33101 Tampere, Finland

² Department of Equine and Small Animal Medicine, University of Helsinki (UH), P.O. Box 57 (Viikintie 49), FI-00014 Helsinki, Finland

³ Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau, Gustav-Kirchhoff-Straße 2, 98693 Ilmenau, Germany

⁴ Research Group for Emotions, Sociality, and Computing, Faculty of Communication Sciences, University of Tampere (UTA), Pinni B Building, Kanslerinrinne 1, FI-33014 Tampere, Finland

Sensors 2018, 18(6), 1757; https://doi.org/10.3390/s18061757 - 30 May 2018

Cited by 9 | Viewed by 6490

Abstract

The functionality of three dry electrocardiogram electrode constructions was evaluated by measuring canine heart rate during four different behaviors: Standing, sitting, lying and walking. The testing was repeated (n = 9) in each of the 36 scenarios with three dogs. Two of the [...] Read more.

The functionality of three dry electrocardiogram electrode constructions was evaluated by measuring canine heart rate during four different behaviors: Standing, sitting, lying and walking. The testing was repeated (n = 9) in each of the 36 scenarios with three dogs. Two of the electrodes were constructed with spring-loaded test pins while the third electrode was a molded polymer electrode with Ag/AgCl coating. During the measurement, a specifically designed harness was used to attach the electrodes to the dogs. The performance of the electrodes was evaluated and compared in terms of heartbeat detection coverage. The effect on the respective heart rate coverage was studied by computing the heart rate coverage from the measured electrocardiogram signal using a pattern-matching algorithm to extract the R-peaks and further the beat-to-beat heart rate. The results show that the overall coverage ratios regarding the electrodes varied between 45–95% in four different activity modes. The lowest coverage was for lying and walking and the highest was for standing and sitting. Full article

(This article belongs to the Special Issue Advanced Physiological Sensing)

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19 pages, 18204 KiB

Open AccessArticle

An Enhanced Hidden Markov Map Matching Model for Floating Car Data

by Mingliang Che, Yingli Wang^*, Chi Zhang and Xinliang Cao

School of Geographic Science, Nantong University, Nantong 226019, Jiangsu, China

Sensors 2018, 18(6), 1758; https://doi.org/10.3390/s18061758 - 31 May 2018

Cited by 21 | Viewed by 3911

Abstract

The map matching (MM) model plays an important role in revising the locations of floating car data (FCD) on a digital map. However, most existing MM models have multiple shortcomings, such as a low matching accuracy for complex roads, long running times, an [...] Read more.

The map matching (MM) model plays an important role in revising the locations of floating car data (FCD) on a digital map. However, most existing MM models have multiple shortcomings, such as a low matching accuracy for complex roads, long running times, an inability to take full advantage of historical FCD information, and challenges in maintaining the topological adjacency and obeying traffic rules. To address these issues, an enhanced hidden Markov map matching (EHMM) model is proposed by adopting explicit topological expressions, using historical FCD information and introducing traffic rules. The EHMM model was validated against areal ground dataset at various sampling intervals and compared with the spatial and temporal matching model and the ordinary hidden Markov matching model. The empirical results reveal that the matching accuracy of the EHMM model is significantly higher than that of the reference models regarding real FCD trajectories at medium and high sampling rates. The running time of the EHMM model was notably shorter than those of the reference models. The matching results of the EHMM model retained topological adjacency and complied with traffic regulations better than the reference models. Full article

(This article belongs to the Section Sensor Networks)

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14 pages, 6081 KiB

Open AccessArticle

Effect of Surface Coverage of Gold Nanoparticles on the Refractive Index Sensitivity in Fiber-Optic Nanoplasmonic Sensing

by Wei-Te Wu^1,*, Chien-Hsing Chen²

, Chang-Yue Chiang² and Lai-Kwan Chau^2,*

¹ Department of Biomechatronics Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan

² Department of Chemistry and Biochemistry and Center for Nano Bio-Detection, National Chung Cheng University, Chiayi 621, Taiwan

Sensors 2018, 18(6), 1759; https://doi.org/10.3390/s18061759 - 31 May 2018

Cited by 49 | Viewed by 8879

Abstract

A simple theoretical model was developed to analyze the extinction spectrum of gold nanoparticles (AuNPs) on the fiber core and glass surfaces in order to aid the determination of the surface coverage and surface distribution of the AuNPs on the fiber core surface [...] Read more.

A simple theoretical model was developed to analyze the extinction spectrum of gold nanoparticles (AuNPs) on the fiber core and glass surfaces in order to aid the determination of the surface coverage and surface distribution of the AuNPs on the fiber core surface for sensitivity optimization of the fiber optic particle plasmon resonance (FOPPR) sensor. The extinction spectrum of AuNPs comprises of the interband absorption of AuNPs, non-interacting plasmon resonance (PR) band due to isolated AuNPs, and coupled PR band of interacting AuNPs. When the surface coverage is smaller than 12.2%, the plasmon coupling effect can almost be ignored. This method is also applied to understand the refractive index sensitivity of the FOPPR sensor with respect to the non-interacting PR band and the coupled PR band. In terms of wavelength sensitivity at a surface coverage of 18.6%, the refractive index sensitivity of the coupled PR band (205.5 nm/RIU) is greater than that of the non-interacting PR band (349.1 nm/RIU). In terms of extinction sensitivity, refractive index sensitivity of the coupled PR band (−3.86/RIU) is similar to that of the non-interacting PR band (−3.93/RIU). Both maximum wavelength and extinction sensitivities were found at a surface coverage of 15.2%. Full article

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

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16 pages, 4957 KiB

Open AccessArticle

Analysis of Wide-Lane Ambiguities Derived from Geometry-Free and Geometry-Based Precise Point Positioning Models and Their Implication for Orbit and Clock Quality

by Gang Chen¹, Sijing Liu^1,2,* and Qile Zhao^3,*

¹ College of Maritime Science and Technology, China University of Geosciences, Wuhan 430074, China

² Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074, China

³ GNSS Research Center, Wuhan University, Wuhan 430079, China

Sensors 2018, 18(6), 1760; https://doi.org/10.3390/s18061760 - 31 May 2018

Cited by 3 | Viewed by 3253

Abstract

Orbit and clock products are used in real-time global navigation satellite systems (GNSS) precise point positioning (PPP) without knowing their quality. This study develops a new approach to detect orbit and clock errors through comparing geometry-free and geometry-based wide-lane ambiguities in a PPP [...] Read more.

Orbit and clock products are used in real-time global navigation satellite systems (GNSS) precise point positioning (PPP) without knowing their quality. This study develops a new approach to detect orbit and clock errors through comparing geometry-free and geometry-based wide-lane ambiguities in a PPP model. The reparameterization and estimation procedures of the geometry-free and geometry-based ambiguities are described in detail. The effects of orbit and clock errors on ambiguities are given in analytical expressions. The numerical similarity and differences of geometry-free and geometry-based wide-lane ambiguities are analyzed using different orbit and clock products. Furthermore, two types of typical errors in orbit and clock are simulated and their effects on wide-lane ambiguities are numerically produced and analyzed. The contribution discloses that the geometry-free and geometry-based wide-lane ambiguities are equivalent in terms of their formal errors. Although they are very close in terms of their estimates when the used orbit and clock for geometry-based ambiguities are precise enough, they are not the same, in particular, in the case that the used orbit and clock, as a combination, contain significant errors. It is discovered that the discrepancies of geometry-free and geometry-based wide-lane ambiguities coincide with the actual time-variant errors in the used orbit and clock at the line-of-sight direction. This provides a quality index for real-time users to detect the errors in real-time orbit and clock products, which potentially improves the accuracy of positioning. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 563 KiB

Open AccessArticle

Compressed Sensing mm-Wave SAR for Non-Destructive Testing Applications Using Multiple Weighted Side Information

by Mathias Becquaert^1,2,*

, Edison Cristofani^1,2

, Huynh Van Luong², Marijke Vandewal¹, Johan Stiens² and Nikos Deligiannis^2,3

¹ CISS Department, Royal Military Academy, 30 Av. de la Renaissance, B-1000 Brussels, Belgium

² ETRO Department, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium

³ IMEC, Kapeldreef 75, 3001 Leuven, Belgium

Sensors 2018, 18(6), 1761; https://doi.org/10.3390/s18061761 - 31 May 2018

Cited by 6 | Viewed by 3230

Abstract

This work explores an innovative strategy for increasing the efficiency of compressed sensing applied on mm-wave SAR sensing using multiple weighted side information. The approach is tested on synthetic and on real non-destructive testing measurements performed on a 3D-printed object with defects while [...] Read more.

This work explores an innovative strategy for increasing the efficiency of compressed sensing applied on mm-wave SAR sensing using multiple weighted side information. The approach is tested on synthetic and on real non-destructive testing measurements performed on a 3D-printed object with defects while taking advantage of multiple previous SAR images of the object with different degrees of similarity. The tested algorithm attributes autonomously weights to the side information at two levels: (1) between the components inside the side information and (2) between the different side information. The reconstruction is thereby almost immune to poor quality side information while exploiting the relevant components hidden inside the added side information. The presented results prove that, in contrast to common compressed sensing, good SAR image reconstruction is achieved at subsampling rates far below the Nyquist rate. Moreover, the algorithm is shown to be much more robust for low quality side information compared to coherent background subtraction. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 1888 KiB

Open AccessArticle

Toward Smart Footwear to Track Frailty Phenotypes—Using Propulsion Performance to Determine Frailty

by Hadi Rahemi^1,2,†, Hung Nguyen^1,†

, Hyoki Lee^1,3

and Bijan Najafi^1,*

¹ Interdisciplinary Consortium on Advanced Motion Performance (iCAMP), Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, TX 77030, USA

² Circulation Concepts Inc., Houston, TX 77030, USA

³ BioSensics LLC, Watertown, MA 02472, USA

^† These authors contributed equally to the manuscript.

Sensors 2018, 18(6), 1763; https://doi.org/10.3390/s18061763 - 1 Jun 2018

Cited by 19 | Viewed by 5989

Abstract

Frailty assessment is dependent on the availability of trained personnel and it is currently limited to clinic and supervised setting. The growing aging population has made it necessary to find phenotypes of frailty that can be measured in an unsupervised setting for translational [...] Read more.

Frailty assessment is dependent on the availability of trained personnel and it is currently limited to clinic and supervised setting. The growing aging population has made it necessary to find phenotypes of frailty that can be measured in an unsupervised setting for translational application in continuous, remote, and in-place monitoring during daily living activity, such as walking. We analyzed gait performance of 161 older adults using a shin-worn inertial sensor to investigate the feasibility of developing a foot-worn sensor to assess frailty. Sensor-derived gait parameters were extracted and modeled to distinguish different frailty stages, including non-frail, pre-frail, and frail, as determined by Fried Criteria. An artificial neural network model was implemented to evaluate the accuracy of an algorithm using a proposed set of gait parameters in predicting frailty stages. Changes in discriminating power was compared between sensor data extracted from the left and right shin sensor. The aim was to investigate the feasibility of developing a foot-worn sensor to assess frailty. The results yielded a highly accurate model in predicting frailty stages, irrespective of sensor location. The independent predictors of frailty stages were propulsion duration and acceleration, heel-off and toe-off speed, mid stance and mid swing speed, and speed norm. The proposed model enables discriminating different frailty stages with area under curve ranging between 83.2–95.8%. Furthermore, results from the neural network suggest the potential of developing a single-shin worn sensor that would be ideal for unsupervised application and footwear integration for continuous monitoring during walking. Full article

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

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15 pages, 1692 KiB

Open AccessArticle

Detection of Sclerotinia Stem Rot on Oilseed Rape (Brassica napus L.) Leaves Using Hyperspectral Imaging

by Wenwen Kong^1,†, Chu Zhang^2,3,†

, Feng Cao^2,3, Fei Liu^2,3

, Shaoming Luo⁴, Yu Tang^4,* and Yong He^2,3,*

¹ School of Information Engineering, Zhejiang A & F University, Hangzhou 311300, China

² College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China

³ Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture, Hangzhou 310058, China

⁴ College of Automation, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China

^† These two authors contributed equally to this work and should be considered co-first authors.

Sensors 2018, 18(6), 1764; https://doi.org/10.3390/s18061764 - 1 Jun 2018

Cited by 32 | Viewed by 3919

Abstract

Hyperspectral imaging was explored to detect Sclerotinia stem rot (SSR) on oilseed rape leaves with chemometric methods, and the influences of variable selection, machine learning, and calibration transfer methods on detection performances were evaluated. Three different sample sets containing healthy and infected oilseed [...] Read more.

Hyperspectral imaging was explored to detect Sclerotinia stem rot (SSR) on oilseed rape leaves with chemometric methods, and the influences of variable selection, machine learning, and calibration transfer methods on detection performances were evaluated. Three different sample sets containing healthy and infected oilseed rape leaves were acquired under different imaging acquisition parameters. Four discriminant models were built using full spectra, including partial least squares-discriminant analysis (PLS-DA), support vector machine (SVM), soft independent modeling of class analogies (SIMCA), and k-nearest neighbors (KNN). PLS-DA and SVM models were also built with the optimal wavelengths selected by principal component analysis (PCA) loadings, second derivative spectra, competitive adaptive reweighted sampling (CARS), and successive projections algorithm (SPA). The optimal wavelengths selected for each sample set by different methods were different; however, the optimal wavelengths selected by PCA loadings and second derivative spectra showed similarity between different sample sets. Direct standardization (DS) was successfully applied to reduce spectral differences among different sample sets. Overall, the results demonstrated that using hyperspectral imaging with chemometrics for plant disease detection can be efficient and will also help in the selection of optimal variable selection, machine learning, and calibration transfer methods for fast and accurate plant disease detection. Full article

(This article belongs to the Section Remote Sensors)

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12 pages, 2459 KiB

Open AccessArticle

A Multi-Region Magnetoimpedance-Based Bio-Analytical System for Ultrasensitive Simultaneous Determination of Cardiac Biomarkers Myoglobin and C-Reactive Protein

by Zhen Yang^1,2,*

, Huanhuan Wang^1,2, Pengfei Guo^1,2, Yuanyuan Ding^1,2, Chong Lei³ and Yongsong Luo^1,2

¹ School of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China

² Key Laboratory of Microelectronics and Energy of Henan Province, Xinyang Normal University, Xinyang 464000, China

³ Department of Micro/Nano Electronics, School of electronic information and electrical engineering, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China

Sensors 2018, 18(6), 1765; https://doi.org/10.3390/s18061765 - 1 Jun 2018

Cited by 21 | Viewed by 4043

Abstract

Cardiac biomarkers (CBs) are substances that appear in the blood when the heart is damaged or stressed. Measurements of the level of CBs can be used in course of diagnostics or monitoring the state of the health of group risk persons. A multi-region [...] Read more.

Cardiac biomarkers (CBs) are substances that appear in the blood when the heart is damaged or stressed. Measurements of the level of CBs can be used in course of diagnostics or monitoring the state of the health of group risk persons. A multi-region bio-analytical system (MRBAS) based on magnetoimpedance (MI) changes was proposed for ultrasensitive simultaneous detection of CBs myoglobin (Mb) and C-reactive protein (CRP). The microfluidic device was designed and developed using standard microfabrication techniques for their usage in different regions, which were pre-modified with specific antibody for specified detection. Mb and CRP antigens labels attached to commercial Dynabeads with selected concentrations were trapped in different detection regions. The MI response of the triple sensitive element was carefully evaluated in initial state and in the presence of biomarkers. The results showed that the MI-based bio-sensing system had high selectivity and sensitivity for detection of CBs. Compared with the control region, ultrasensitive detections of CRP and Mb were accomplished with the detection limits of 1.0 pg/mL and 0.1 pg/mL, respectively. The linear detection range contained low concentration detection area and high concentration detection area, which were 1 pg/mL–10 ng/mL, 10–100 ng/mL for CRP, and 0.1 pg/mL–1 ng/mL, 1 n/mL–80 ng/mL for Mb. The measurement technique presented here provides a new methodology for multi-target biomolecules rapid testing. Full article

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

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9 pages, 3150 KiB

Open AccessArticle

Temperature Insensitivity Polarization-Controlled Orbital Angular Momentum Mode Converter Based on an LPFG Induced in Four-Mode Fiber

by Shen Liu^1,†, Yan Zhang^1,†, Cailing Fu¹, Zhiyong Bai¹

, Ziliang Li¹, Changrui Liao¹, Ying Wang¹, Jun He¹

, Yu Liu^2,* and Yiping Wang^1,*

¹ Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China

² School of Optoelectronic Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1766; https://doi.org/10.3390/s18061766 - 1 Jun 2018

Cited by 11 | Viewed by 3421

Abstract

We propose a novel method for generating ±1-order orbital angular momentum (OAM) in long-period fiber gratings (LPFGs) by adjusting a polarization controller (PC). An LPFG, inscribed in a four-mode fiber (4MF) using a CO₂ laser, was used to generate OAM_±1 across [...] Read more.

We propose a novel method for generating ±1-order orbital angular momentum (OAM) in long-period fiber gratings (LPFGs) by adjusting a polarization controller (PC). An LPFG, inscribed in a four-mode fiber (4MF) using a CO₂ laser, was used to generate OAM_±1 across a broad range of wavelengths from 1530 nm to 1630 nm. Additionally, the OAM vortex phase remained stable while the temperature increased from 23 °C to 50 °C. The LPFG, as a temperature sensor, and its temperature sensitivity was measured to be 38.6 ± 0.37 pm/°C at the resonant wavelength of 1625 nm. This design offers simple fabrication and several properties which are highly beneficial for all-fiber optical communications based on the OAM mode-division multiplexing technique. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 1851 KiB

Open AccessArticle

Magnetically-Actuated Mixing and Merging of Acid-Base Micro-Droplets on Open Surfaces: Preliminary Study

by Mei-Kum Khaw^1,2

, Faisal Mohd-Yasin^1,*

and Nam-Trung Nguyen¹

¹ Queensland Micro-and Nanotechnology Centre, Griffith University, Nathan QLD 4111, Australia

² Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Bandar Sungai Long, Kajang 43000, Selangor, Malaysia

Sensors 2018, 18(6), 1767; https://doi.org/10.3390/s18061767 - 1 Jun 2018

Cited by 2 | Viewed by 3264

Abstract

We present the mixing and merging of two reactive droplets on top of an open surface. A mobile droplet (1.0 M HCl solution + iron oxide particles) is magnetically-actuated to merge with a sessile droplet (1.0 M NaOH + phenolphthalein). The heat from [...] Read more.

We present the mixing and merging of two reactive droplets on top of an open surface. A mobile droplet (1.0 M HCl solution + iron oxide particles) is magnetically-actuated to merge with a sessile droplet (1.0 M NaOH + phenolphthalein). The heat from the exothermic reaction is detected by a thermocouple. We vary the droplet volume (1, 5 and 10 μL), the magnet speed (1.86, 2.79, 3.72 and 4.65 mm/s) and the iron oxide concentration (0.010, 0.020 and 0.040 g/mL) to study their influences on the mixing time, peak temperature and cooling time. The sampled recording of these processes are provided as supplementary files. We observe the following trends. First, the lower volume of droplet and higher speed of magnet lead to shorter mixing time. Second, the peak temperature increases and cooling time decreases at the increasing speed of magnet. Third, the peak temperature is similar for bigger droplets, and they take longer to cool down. Finally, we also discuss the limitations of this preliminary study and propose improvements. These observations could be used to improve the sensitivity of the open chamber system in measuring the exothermic reaction of biological samples. Full article

(This article belongs to the Section Biosensors)

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11 pages, 2110 KiB

Open AccessArticle

Parameter Estimation of SAR Signal Based on SVD for the Nyquist Folding Receiver

by Tao Li, Qian Zhu^* and Zengping Chen

College of Electronic Science, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(6), 1768; https://doi.org/10.3390/s18061768 - 1 Jun 2018

Cited by 7 | Viewed by 4046

Abstract

The Nyquist Folding Receiver (NYFR) is a novel ultra-wideband (UWB) receiver structure that can realize wideband signal monitoring with fewer components. The NYFR induces a Nyquist zone (NZ)-dependent sinusoidal frequency modulation (SFM) by a modulated local oscillator (LOS), and the intercepted linear frequency [...] Read more.

The Nyquist Folding Receiver (NYFR) is a novel ultra-wideband (UWB) receiver structure that can realize wideband signal monitoring with fewer components. The NYFR induces a Nyquist zone (NZ)-dependent sinusoidal frequency modulation (SFM) by a modulated local oscillator (LOS), and the intercepted linear frequency modulated (LFM) synthetic aperture radar (SAR) signal will be converted into an LFM/SFM hybrid modulated signal. In this paper, a parameter estimation algorithm is proposed for the complicated NYFR output signal. According to the NYFR prior information, a chirp singular value ratio (CSVR) spectrum method based on singular value decomposition (SVD) is proposed to estimate the chirp rate directly before estimating the NZ index. Then, a fast search algorithm based on golden section method for the CSVR spectrum is analyzed, which can obviously reduce the computational complexity. The simulation shows that the presented algorithm can accurately estimate the parameters of the LFM/SFM hybrid modulated output signal by the NYFR. Full article

(This article belongs to the Special Issue Synthetic Aperture Radar (SAR) Technology: New Perspectives Offered by New-Generation and Forthcoming SAR Sensors)

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10 pages, 3110 KiB

Open AccessArticle

A Label-Free Aptasensor for Ochratoxin a Detection Based on the Structure Switch of Aptamer

by Feng Liu, Ailing Ding, Jiushang Zheng, Jiucun Chen^* and Bin Wang^*

Institute for Clean Energy and Advanced Materials, Faculty of Materials and Energy, Southwest University, Chongqing 400715, China

Sensors 2018, 18(6), 1769; https://doi.org/10.3390/s18061769 - 1 Jun 2018

Cited by 31 | Viewed by 7062

Abstract

A label-free sensing platform is developed based on switching the structure of aptamer for highly sensitive and selective fluorescence detection of ochratoxin A (OTA). OTA induces the structure of aptamer, transforms into G-quadruplex and produces strong fluorescence in the presence of zinc(II)-protoporphyrin IX [...] Read more.

A label-free sensing platform is developed based on switching the structure of aptamer for highly sensitive and selective fluorescence detection of ochratoxin A (OTA). OTA induces the structure of aptamer, transforms into G-quadruplex and produces strong fluorescence in the presence of zinc(II)-protoporphyrin IX probe due to the specific bind to G-quadruplex. The simple method exhibits high sensitivity towards OTA with a detection limit of 0.03 nM and excellent selectivity over other mycotoxins. In addition, the successful detection of OTA in real samples represents a promising application in food safety. Full article

(This article belongs to the Special Issue Aptamers and Applications)

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21 pages, 4464 KiB

Open AccessArticle

Registration of Aerial Optical Images with LiDAR Data Using the Closest Point Principle and Collinearity Equations

by Rongyong Huang^1,2,3,*

, Shunyi Zheng^4,5 and Kun Hu^6,7,8

¹ Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Guangxi University, Nanning 530004, China

² School of Marine Sciences, Guangxi University, Nanning 530004, China

³ Coral Reef Research Centre of China, Guangxi University, Nanning 530004, China

⁴ School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China

⁵ Collaborative Innovation Center for Geospatial Technology, Wuhan University, Wuhan 430079, China

⁶ Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

⁷ Key Laboratory of Technology in Geo-Spatial Information Processing and Application System, Chinese Academy of Sciences, Beijing 100190, China

⁸ Department of Civil, Environmental and Geodetic Engineering, Ohio State University, Columbus, OH 43210, USA

Sensors 2018, 18(6), 1770; https://doi.org/10.3390/s18061770 - 1 Jun 2018

Cited by 28 | Viewed by 7481

Abstract

Registration of large-scale optical images with airborne LiDAR data is the basis of the integration of photogrammetry and LiDAR. However, geometric misalignments still exist between some aerial optical images and airborne LiDAR point clouds. To eliminate such misalignments, we extended a method for [...] Read more.

Registration of large-scale optical images with airborne LiDAR data is the basis of the integration of photogrammetry and LiDAR. However, geometric misalignments still exist between some aerial optical images and airborne LiDAR point clouds. To eliminate such misalignments, we extended a method for registering close-range optical images with terrestrial LiDAR data to a variety of large-scale aerial optical images and airborne LiDAR data. The fundamental principle is to minimize the distances from the photogrammetric matching points to the terrestrial LiDAR data surface. Except for the satisfactory efficiency of about 79 s per 6732 × 8984 image, the experimental results also show that the unit weighted root mean square (RMS) of the image points is able to reach a sub-pixel level (0.45 to 0.62 pixel), and the actual horizontal and vertical accuracy can be greatly improved to a high level of 1/4–1/2 (0.17–0.27 m) and 1/8–1/4 (0.10–0.15 m) of the average LiDAR point distance respectively. Finally, the method is proved to be more accurate, feasible, efficient, and practical in variety of large-scale aerial optical image and LiDAR data. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 3526 KiB

Open AccessFeature PaperArticle

Sensor Network Configuration Learning for Maximizing Application Performance

by Joel Helkey and Lawrence Holder^*

School of Electrical Engineering and Computer Science, Washington State University, Pullman, WA 99164, USA

Sensors 2018, 18(6), 1771; https://doi.org/10.3390/s18061771 - 1 Jun 2018

Cited by 3 | Viewed by 2970

Abstract

Numerous applications rely on data obtained from a wireless sensor network where application performance is of utmost importance. However, energy usage is also important, and oftentimes, a subset of sensors can be selected to maximize application performance. We cast the problem of sensor [...] Read more.

Numerous applications rely on data obtained from a wireless sensor network where application performance is of utmost importance. However, energy usage is also important, and oftentimes, a subset of sensors can be selected to maximize application performance. We cast the problem of sensor selection as a local search optimization problem and solve it using a variant of stochastic hill climbing extended with novel heuristics. This paper introduces sensor network configuration learning, a feedback-based heuristic algorithm that dynamically reconfigures the sensor network to maximize the performance of the target application. The proposed algorithm is described in detail, along with experiments conducted and a scalability study. A quick method for launching the algorithm from a better starting point than random is also detailed. The performance of the algorithm is compared to that of two other well-known algorithms and randomness. Our simulation results obtained from running sensor network configuration learning on a number of scenarios show the effectiveness and scalability of our approach. Full article

(This article belongs to the Section Sensor Networks)

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23 pages, 911 KiB

Open AccessArticle

Improved Multitarget Tracking in Clutter Using Bearings-Only Measurements

by Yifang Shi¹, Mengfan Xue¹, Yuemin Ding^2,* and Dongliang Peng¹

¹ School of Automation, Hangzhou Dianzi University, Xiasha Higher Education Zone, 2nd Street, Hangzhou 310018, China

² School of Computer Science and Engineering, Tianjin University of Technology, 391 Bingshuixi Road, Xiqing District, Tianjin 300384, China

Sensors 2018, 18(6), 1772; https://doi.org/10.3390/s18061772 - 1 Jun 2018

Cited by 1 | Viewed by 2615

Abstract

Multitarget tracking in clutter using bearings-only measurements is a challenging problem. In this paper, a performance improved nonlinear filter is proposed on the basis of the Random Finite Set (RFS) theory and is named as Gaussian mixture measurements-based cardinality probability hypothesis density (GMMbCPHD) [...] Read more.

Multitarget tracking in clutter using bearings-only measurements is a challenging problem. In this paper, a performance improved nonlinear filter is proposed on the basis of the Random Finite Set (RFS) theory and is named as Gaussian mixture measurements-based cardinality probability hypothesis density (GMMbCPHD) filter. The GMMbCPHD filter enables to address two main issues: measurement-origin-uncertainty and measurement nonlinearity, which constitutes the key problems in bearings-only multitarget tracking in clutter. For the measurement-origin-uncertainty issue, the proposed filter estimates the intensity of RFS of multiple targets as well as propagates the posterior cardinality distribution. For the measurement-origin-nonlinearity issue, the GMMbCPHD approximates the measurement likelihood function using a Gaussian mixture rather than a single Gaussian distribution as used in extended Kalman filter (EKF). The superiority of the proposed GMMbCPHD are validated by comparing with several state-of-the-art algorithms via intensive simulation studies. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 3200 KiB

Open AccessArticle

A Low-Profile Dual-Layer Patch Antenna with a Circular Polarizer Consisting of Dual Semicircular Resonators

by Li Guo

, Ming-Chun Tang^* and Mei Li

College of Communication Engineering, Chongqing University, Chongqing 400044, China

Sensors 2018, 18(6), 1773; https://doi.org/10.3390/s18061773 - 1 Jun 2018

Cited by 10 | Viewed by 4860

Abstract

In this paper, a circular polarizer comprising dual semicircular split-rings (DSSRs) is presented. By placing it above an elliptical radiator that radiates linearly polarized (LP) waves, dual-layer patch antennas capable of radiating right-hand (RH) or left-hand (LH) circularly polarized (CP) waves are achieved [...] Read more.

In this paper, a circular polarizer comprising dual semicircular split-rings (DSSRs) is presented. By placing it above an elliptical radiator that radiates linearly polarized (LP) waves, dual-layer patch antennas capable of radiating right-hand (RH) or left-hand (LH) circularly polarized (CP) waves are achieved in terms of the different offset direction of the bottom splits of the DSSRs. Because of both the capacitive coupling to the radiator and the degenerate modes existing in the excited DSSRs, the DSSRs collaboratively result in a circularly polarized radiation, successfully converting incident LP waves into CP ones. Simulated results show that the impedance, axial ratio (AR), and gain frequency response of both proposed CP antennas are identical, with a simulated 3-dB AR bandwidth of 72 MHz covering 2.402–2.474 GHz and a gain enhanced by 3.9 dB. The proposed antennas were fabricated and measured, revealing an operational bandwidth of 65 MHz (2.345–2.41 GHz) and a peak gain up to 9 dBi. Moreover, a low profile of 0.063λ₀ is maintained. The proposed CP antennas could be as a candidate for wireless target detection applications in terms of their identical frequency response property. Full article

(This article belongs to the Special Issue Passive Electromagnetic Sensors for Autonomous Wireless Networks)

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21 pages, 10769 KiB

Open AccessArticle

Combining Motion Compensation with Spatiotemporal Constraint for Video Deblurring

by Jing Li, Weiguo Gong^* and Weihong Li

Key Lab of Optoelectronic Technology & Systems of Education Ministry, Chongqing University, Chongqing 400044, China

Sensors 2018, 18(6), 1774; https://doi.org/10.3390/s18061774 - 1 Jun 2018

Cited by 2 | Viewed by 3508

Abstract

We propose a video deblurring method by combining motion compensation with spatiotemporal constraint for restoring blurry video caused by camera shake. The proposed method makes effective full use of the spatiotemporal information not only in the blur kernel estimation, but also in the [...] Read more.

We propose a video deblurring method by combining motion compensation with spatiotemporal constraint for restoring blurry video caused by camera shake. The proposed method makes effective full use of the spatiotemporal information not only in the blur kernel estimation, but also in the latent sharp frame restoration. Firstly, we estimate a motion vector between the current and the previous blurred frames, and introduce the estimated motion vector for deriving the motion-compensated frame with the previous restored frame. Secondly, we proposed a blur kernel estimation strategy by applying the derived motion-compensated frame to an improved regularization model for improving the quality of the estimated blur kernel and reducing the processing time. Thirdly, we propose a spatiotemporal constraint algorithm that can not only enhance temporal consistency, but also suppress noise and ringing artifacts of the deblurred video through introducing a temporal regularization term. Finally, we extend Fast Total Variation de-convolution (FTVd) for solving the minimization problem of the proposed spatiotemporal constraint energy function. Extensive experiments demonstrate that the proposed method achieve the state-of-the-art results either in subjective vision or objective evaluation. Full article

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

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11 pages, 364 KiB

Open AccessArticle

Development of A Low-Cost FPGA-Based Measurement System for Real-Time Processing of Acoustic Emission Data: Proof of Concept Using Control of Pulsed Laser Ablation in Liquids

by Sebastian F. Wirtz^1,*, Adauto P. A. Cunha¹, Marc Labusch^2,3, Galina Marzun², Stephan Barcikowski² and Dirk Söffker¹

¹ Chair of Dynamics and Control, University of Duisburg-Essen, 47057 Duisburg, Germany

² Center for Nanointegration Duisburg-Essen (CENIDE), Nano Energy Technic Center (NETZ), Technical Chemistry I, University of Duisburg-Essen, 47057 Duisburg, Germany

³ Institute for Coatings and Surface Chemistry (ILOC), Hochschule Niederrhein University of Applied Sciences, 47798 Krefeld, Germany

Sensors 2018, 18(6), 1775; https://doi.org/10.3390/s18061775 - 1 Jun 2018

Cited by 19 | Viewed by 6340

Abstract

Today, the demand for continuous monitoring of valuable or safety critical equipment is increasing in many industrial applications due to safety and economical requirements. Therefore, reliable in-situ measurement techniques are required for instance in Structural Health Monitoring (SHM) as well as process monitoring [...] Read more.

Today, the demand for continuous monitoring of valuable or safety critical equipment is increasing in many industrial applications due to safety and economical requirements. Therefore, reliable in-situ measurement techniques are required for instance in Structural Health Monitoring (SHM) as well as process monitoring and control. Here, current challenges are related to the processing of sensor data with a high data rate and low latency. In particular, measurement and analyses of Acoustic Emission (AE) are widely used for passive, in-situ inspection. Advantages of AE are related to its sensitivity to different micro-mechanical mechanisms on the material level. However, online processing of AE waveforms is computationally demanding. The related equipment is typically bulky, expensive, and not well suited for permanent installation. The contribution of this paper is the development of a Field Programmable Gate Array (FPGA)-based measurement system using ZedBoard devlopment kit with Zynq-7000 system on chip for embedded implementation of suitable online processing algorithms. This platform comprises a dual-core Advanced Reduced Instruction Set Computer Machine (ARM) architecture running a Linux operating system and FPGA fabric. A FPGA-based hardware implementation of the discrete wavelet transform is realized to accelerate processing the AE measurements. Key features of the system are low cost, small form factor, and low energy consumption, which makes it suitable to serve as field-deployed measurement and control device. For verification of the functionality, a novel automatically realized adjustment of the working distance during pulsed laser ablation in liquids is established as an example. A sample rate of 5 MHz is achieved at 16 bit resolution. 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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15 pages, 3558 KiB

Open AccessArticle

Pitfall of the Strongest Cells in Static Random Access Memory Physical Unclonable Functions

by Mingyang Gong, Hailong Liu, Run Min and Zhenglin Liu^*

School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China

Sensors 2018, 18(6), 1776; https://doi.org/10.3390/s18061776 - 1 Jun 2018

Cited by 7 | Viewed by 3613

Abstract

Static Random Access Memory (SRAM) Physical Unclonable Functions (PUFs) are some of the most popular PUFs that provide a highly-secured solution for secret key storage. Given that PUF responses are noisy, the key reconstruction must use error correcting code (ECC) to reduce the [...] Read more.

Static Random Access Memory (SRAM) Physical Unclonable Functions (PUFs) are some of the most popular PUFs that provide a highly-secured solution for secret key storage. Given that PUF responses are noisy, the key reconstruction must use error correcting code (ECC) to reduce the noise. Repetition code is widely used in resource constrained systems as it is concise and lightweight, however, research has shown that repetition codes can lead to information leakage. In this paper we found that the strongest cell distribution in a SRAM array may leak information of the responses of SRAM PUF when the repetition code is directly applied. Experimentally, on an ASIC platform with the HHGRACE 0.13 μm process, we recovered 8.3% of the measured response using the strongest cells revealed by the helper data, and we finally obtained a clone response 79% similar to weak response using the public helper data. We therefore propose Error Resistant Fuzzy Extractor (ERFE), a 4-bit error tolerant fuzzy extractor, that extracts the value of the sum of the responses as a unique key and reduces the failure rate to 1.8 × 10⁻⁸ with 256 bit entropy. Full article

(This article belongs to the Special Issue Scalable and Efficient Networking and Communication Architectures in IoT Domain)

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13 pages, 14102 KiB

Open AccessArticle

A Design of Small Area, 0.95 mW, 612–1152 MHz Open Loop Injection-Locked Frequency Multiplier for IoT Sensor Applications

by SungJin Kim¹, Dong-Gyu Kim¹, Chanho Kim¹, Dong Soo Lee¹, Behnam Samadpoor Rikan¹, YoungGun Pu¹, Sang-Sun Yoo², Minjae Lee³, KeumCheol Hwang¹

, Youngoo Yang¹ and Kang-Yoon Lee^1,*

¹ College of Information and Communication Engineering, Sungkyunkwan University, Suwon 16419, Korea

² Department of Smart Automobile, Pyeongtaek University, Pyeongtaek 17869, Korea

³ School of Information and Communications, Gwangju Institute of Science and Technology, Gwangju 61005, Korea

Sensors 2018, 18(6), 1777; https://doi.org/10.3390/s18061777 - 1 Jun 2018

Cited by 3 | Viewed by 5286

Abstract

This paper presents a 612–1152 MHz Injection-Locked Frequency Multiplier (ILFM). The proposed ILFM is used to send an input signal to a receiver in only the I/Q mismatch calibration mode. Adopting a Phase-Locked Loop (PLL) to calibrate the receiver places a burden on [...] Read more.

This paper presents a 612–1152 MHz Injection-Locked Frequency Multiplier (ILFM). The proposed ILFM is used to send an input signal to a receiver in only the I/Q mismatch calibration mode. Adopting a Phase-Locked Loop (PLL) to calibrate the receiver places a burden on this system because of the additional area and power consumption that is required. Instead of the PLL, to satisfy high-frequency, low-jitter and low-area requirements, a Ring Oscillator is adopted in the system. The free-running frequency of the ILFM is automatically and digitally calibrated to reflect the frequency of the injected signal from the harmonics of the reference clock. To control the frequency of the ILFM, the load current is digitally tuned with a 6-bit digital control signal. The proposed ILFM locks to the target frequency using a digitally controlled Frequency Locked Loop (FLL). This chip is fabricated using 1-poly 6-metal 0.18 µm CMOS and has achieved the wide tuning range of 612–1152 MHz. The power consumption is 0.95 mW from a supply voltage of 1.8 V. The measured phase noise of the ILFM is −108 dBc/Hz at a 1 MHz offset. Full article

(This article belongs to the Special Issue Advances in Sensing, Processing and Transmission for IoT-Oriented Sensors Networks)

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20 pages, 658 KiB

Open AccessArticle

Spatio-Temporal Field Estimation Using Kriged Kalman Filter (KKF) with Sparsity-Enforcing Sensor Placement

by Venkat Roy^1,*, Andrea Simonetto² and Geert Leus³

¹ NXP Semiconductors, High Tech Campus 46, 5656 AE Eindhoven, The Netherlands

² Optimisation and Control group, IBM Research Ireland, Dublin 15, Ireland

³ Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherlands

Sensors 2018, 18(6), 1778; https://doi.org/10.3390/s18061778 - 1 Jun 2018

Cited by 15 | Viewed by 3985

Abstract

We propose a sensor placement method for spatio-temporal field estimation based on a kriged Kalman filter (KKF) using a network of static or mobile sensors. The developed framework dynamically designs the optimal constellation to place the sensors. We combine the estimation error (for [...] Read more.

We propose a sensor placement method for spatio-temporal field estimation based on a kriged Kalman filter (KKF) using a network of static or mobile sensors. The developed framework dynamically designs the optimal constellation to place the sensors. We combine the estimation error (for the stationary as well as non-stationary component of the field) minimization problem with a sparsity-enforcing penalty to design the optimal sensor constellation in an economic manner. The developed sensor placement method can be directly used for a general class of covariance matrices (ill-conditioned or well-conditioned) modelling the spatial variability of the stationary component of the field, which acts as a correlated observation noise, while estimating the non-stationary component of the field. Finally, a KKF estimator is used to estimate the field using the measurements from the selected sensing locations. Numerical results are provided to exhibit the feasibility of the proposed dynamic sensor placement followed by the KKF estimation method. Full article

(This article belongs to the Special Issue Sensor Networks for Environmental Observations)

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15 pages, 4293 KiB

Open AccessArticle

Study of the Home-Auxiliary Robot Based on BCI

by Fuwang Wang^1,*

, Xiaolei Zhang¹, Rongrong Fu² and Guangbin Sun³

¹ School of Mechanic Engineering, Northeast Electric Power University, Jilin 132012, China

² College of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China

³ Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences, Beijing 100094, China

Sensors 2018, 18(6), 1779; https://doi.org/10.3390/s18061779 - 1 Jun 2018

Cited by 18 | Viewed by 4305

Abstract

A home-auxiliary robot platform is developed in the current study which could assist patients with physical disabilities and older persons with mobility impairments. The robot, mainly controlled by brain computer interface (BCI) technology, can not only perform actions in a person’s field of [...] Read more.

A home-auxiliary robot platform is developed in the current study which could assist patients with physical disabilities and older persons with mobility impairments. The robot, mainly controlled by brain computer interface (BCI) technology, can not only perform actions in a person’s field of vision, but also work outside the field of vision. The wavelet decomposition (WD) is used in this study to extract the δ (0~4 Hz) and θ (4~8 Hz) sub-bands of subjects’ electroencephalogram (EEG) signals. The correlation between pairs of 14 EEG channels is determined with synchronization likelihood (SL), and the brain network structure is generated. Then, the motion characteristics are analyzed using the brain network parameters clustering coefficient (C) and global efficiency (G). Meanwhile, the eye movement characteristics in the F3 and F4 channels are identified. Finally, the motion characteristics identified by brain networks and eye movement characteristics can be used to control the home-auxiliary robot platform. The experimental result shows that the accuracy rate of left and right motion recognition using this method is more than 93%. Additionally, the similarity between that autonomous return path and the real path of the home-auxiliary robot reaches up to 0.89. Full article

(This article belongs to the Special Issue Sensors for Biosignal Processing)

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16 pages, 10289 KiB

Open AccessArticle

A High-Sensitivity Flexible Eddy Current Array Sensor for Crack Monitoring of Welded Structures under Varying Environment

by Tao Chen^*, Yuting He and Jinqiang Du

Aeronautic Engineering College, Air Force Engineering University, 1 Baling Road, Xi’an 710038, China

Sensors 2018, 18(6), 1780; https://doi.org/10.3390/s18061780 - 1 Jun 2018

Cited by 48 | Viewed by 4749

Abstract

This paper develops a high-sensitivity flexible eddy current array (HS-FECA) sensor for crack monitoring of welded structures under varying environment. Firstly, effects of stress, temperature and crack on output signals of the traditional flexible eddy current array (FECA) sensor were investigated by experiments [...] Read more.

This paper develops a high-sensitivity flexible eddy current array (HS-FECA) sensor for crack monitoring of welded structures under varying environment. Firstly, effects of stress, temperature and crack on output signals of the traditional flexible eddy current array (FECA) sensor were investigated by experiments that show both stress and temperature have great influences on the crack monitoring performance of the sensor. A 3-D finite element model was established using Comsol AC/DC module to analyze the perturbation effects of crack on eddy currents and output signals of the sensor, which showed perturbation effect of cracks on eddy currents is reduced by the current loop when crack propagates. Then, the HS-FECA sensor was proposed to boost the sensitivity to cracks. Simulation results show that perturbation effect of cracks on eddy currents excited by the HS-FECA sensor gradually grows stronger when the crack propagates, resulting in much higher sensitivity to cracks. Experimental result further shows that the sensitivity of the new sensor is at least 19 times that of the original one. In addition, both stress and temperature variations have little effect on signals of the new sensor. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 543 KiB

Open AccessArticle

Energy Harvesting over Rician Fading Channel: A Performance Analysis for Half-Duplex Bidirectional Sensor Networks under Hardware Impairments

by Tan N. Nguyen^1,2, Tran Hoang Quang Minh³, Phuong T. Tran^1,*

and Miroslav Vozňák²

¹ Wireless Communications Research Group, Faculty of Electrical and Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

² Faculty of Electrical Engineering and Computer Science, VŠB-Technical University of Ostrava, 17. Listopadu 15/2172, 708 00 Ostrava, Czech Republic

³ Optoelectronics Research Group, Faculty of Electrical and Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

Sensors 2018, 18(6), 1781; https://doi.org/10.3390/s18061781 - 1 Jun 2018

Cited by 62 | Viewed by 5532

Abstract

In this paper, a rigorous analysis of the performance of time-switching energy harvesting strategy that is applied for a half-duplex bidirectional wireless sensor network with intermediate relay over a Rician fading channel is presented to provide the exact-form expressions of the outage probability, [...] Read more.

In this paper, a rigorous analysis of the performance of time-switching energy harvesting strategy that is applied for a half-duplex bidirectional wireless sensor network with intermediate relay over a Rician fading channel is presented to provide the exact-form expressions of the outage probability, achievable throughput and the symbol-error-rate (SER) of the system under the hardware impairment condition. Using the proposed probabilistic models for wireless channels between mobile nodes as well as for the hardware noises, we derive the outage probability of the system, and then the throughput and SER can be obtained as a result. Both exact analysis and asymptotic analysis at high signal-power-to-noise-ratio regime are provided. Monte Carlo simulation is also conducted to verify the analysis. This work confirms the effectiveness of energy harvesting applied in wireless sensor networks over a Rician fading channel, and can provide an insightful understanding about the effect of various parameters on the system performance. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 7219 KiB

Open AccessFeature PaperArticle

Influence of Axial Load on Electromechanical Impedance (EMI) of Embedded Piezoceramic Transducers in Steel Fiber Concrete

by Zhijie Wang¹, Dongdong Chen^2,†, Liqiong Zheng², Linsheng Huo^2,*

and Gangbing Song^3,*

¹ Department of Underground Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China

² Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China

³ Smart Materials and Structures Laboratory, Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA

^† The co-first author who has equal contribution with the first author.

Sensors 2018, 18(6), 1782; https://doi.org/10.3390/s18061782 - 1 Jun 2018

Cited by 37 | Viewed by 4487

Abstract

With the advantages of high tensile, bending, and shear strength, steel fiber concrete structures have been widely used in civil engineering. The health monitoring of concrete structures, including steel fiber concrete structures, receives increasing attention, and the Electromechanical Impedance (EMI)-based method is commonly [...] Read more.

With the advantages of high tensile, bending, and shear strength, steel fiber concrete structures have been widely used in civil engineering. The health monitoring of concrete structures, including steel fiber concrete structures, receives increasing attention, and the Electromechanical Impedance (EMI)-based method is commonly used. Structures are often subject to changing axial load and ignoring the effect of axial forces may introduce error to Structural Health Monitoring (SHM), including the EMI-based method. However, many of the concrete structure monitoring algorithms do not consider the effects of axial loading. To investigate the influence of axial load on the EMI of a steel fiber concrete structure, concrete specimens with different steel fiber content (0, 30, 60, 90, 120) (kg/m³) were casted and the Lead Zirconate Titanate (PZT)-based Smart Aggregate (SA) was used as the EMI sensor. During tests, the step-by-step loading procedure was applied on different steel fiber content specimens, and the electromechanical impedance values were measured. The Normalized root-mean-square deviation Index (NI) was developed to analyze the EMI information and evaluate the test results. The results show that the normalized root-mean-square deviation index increases with the increase of the axial load, which clearly demonstrates the influence of axial load on the EMI values for steel fiber concrete and this influence should be considered during a monitoring or damage detection procedure if the axial load changes. In addition, testing results clearly reveal that the steel fiber content, often at low mass and volume percentage, has no obvious influence on the PZT’s EMI values. Furthermore, experiments to test the repeatability of the proposed method were conducted. The repeating test results show that the EMI-based indices are repeatable and there is a great linearity between the NI and the applied loading. Full article

(This article belongs to the Special Issue Recent Advances of Piezoelectric Transducers and Applications)

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11 pages, 464 KiB

Open AccessArticle

Disentangling the Contribution of Spatial Reference Frames to Executive Functioning in Healthy and Pathological Aging: An Experimental Study with Virtual Reality

by Silvia Serino^1,2,*, Francesca Morganti³

, Desirée Colombo⁴, Elisa Pedroli¹, Pietro Cipresso^1,2

and Giuseppe Riva^1,2

¹ Applied Technology for Neuro-Psychology Lab, IRCCS Istituto Auxologico Italiano, Via Magnasco 2, 20149 Milan, Italy

² Department of Psychology, Università Cattolica del Sacro Cuore, Largo Gemelli 1, 20100 Milan, Italy

³ Department of Human and Social Sciences, University of Bergamo, Piazzale S. Agostino 2, 24129 Bergamo, Italy

⁴ Department of Basic Psychology, Clinic and Psychobiology, Universitat Jaume I, Av. Sos Baynat, s/n, 12071 Castellón, Spain

Sensors 2018, 18(6), 1783; https://doi.org/10.3390/s18061783 - 1 Jun 2018

Cited by 10 | Viewed by 5019

Abstract

A growing body of evidence pointed out that a decline in effectively using spatial reference frames for categorizing information occurs both in normal and pathological aging. Moreover, it is also known that executive deficits primarily characterize the cognitive profile of older individuals. Acknowledging [...] Read more.

A growing body of evidence pointed out that a decline in effectively using spatial reference frames for categorizing information occurs both in normal and pathological aging. Moreover, it is also known that executive deficits primarily characterize the cognitive profile of older individuals. Acknowledging this literature, the current study was aimed to specifically disentangle the contribution of the cognitive abilities related to the use of spatial reference frames to executive functioning in both healthy and pathological aging. 48 healthy elderly individuals and 52 elderly suffering from probable Alzheimer’s Disease (AD) took part in the study. We exploited the potentiality of Virtual Reality to specifically measure the abilities in retrieving and syncing between different spatial reference frames, and then we administrated different neuropsychological tests for evaluating executive functions. Our results indicated that allocentric functions contributed significantly to the planning abilities, while syncing abilities influenced the attentional ones. The findings were discussed in terms of previous literature exploring relationships between cognitive deficits in the first phase of AD. Full article

(This article belongs to the Special Issue New Trends in Psychophysiology and Mental Health)

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17 pages, 7572 KiB

Open AccessArticle

Assessing the Performance of GPS Precise Point Positioning Under Different Geomagnetic Storm Conditions during Solar Cycle 24

by Xiaomin Luo¹, Shengfeng Gu^1,*, Yidong Lou¹, Chao Xiong², Biyan Chen³ and Xueyuan Jin⁴

¹ GNSS Research Centre, Wuhan University, Luoyu Road 129, Wuhan 430079, China

² GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany

³ School of Geosciences and Info-Physics, Central South University, Changsha 410083, China

⁴ School of Geodesy and Geomatics, Wuhan University, Luoyu Road 129, Wuhan 430079, China

Sensors 2018, 18(6), 1784; https://doi.org/10.3390/s18061784 - 1 Jun 2018

Cited by 57 | Viewed by 5205

Abstract

The geomagnetic storm, which is an abnormal space weather phenomenon, can sometimes severely affect GPS signal propagation, thereby impacting the performance of GPS precise point positioning (PPP). However, the investigation of GPS PPP accuracy over the global scale under different geomagnetic storm conditions [...] Read more.

The geomagnetic storm, which is an abnormal space weather phenomenon, can sometimes severely affect GPS signal propagation, thereby impacting the performance of GPS precise point positioning (PPP). However, the investigation of GPS PPP accuracy over the global scale under different geomagnetic storm conditions is very limited. This paper for the first time presents the performance of GPS dual-frequency (DF) and single-frequency (SF) PPP under moderate, intense, and super storms conditions during solar cycle 24 using a large data set collected from about 500 international GNSS services (IGS) stations. The global root mean square (RMS) maps of GPS PPP results show that stations with degraded performance are mainly distributed at high-latitude, and the degradation level generally depends on the storm intensity. The three-dimensional (3D) RMS of GPS DF PPP for high-latitude during moderate, intense, and super storms are 0.393 m, 0.680 m and 1.051 m, respectively, with respect to only 0.163 m on quiet day. RMS errors of mid- and low-latitudes show less dependence on the storm intensities, with values less than 0.320 m, compared to 0.153 m on quiet day. Compared with DF PPP, the performance of GPS SF PPP is inferior regardless of quiet or disturbed conditions. The degraded performance of GPS positioning during geomagnetic storms is attributed to the increased ionospheric disturbances, which have been confirmed by our global rate of TEC index (ROTI) maps. Ionospheric disturbances not only lead to the deteriorated ionospheric correction but also to the frequent cycle-slip occurrence. Statistical results show that, compared with that on quiet day, the increased cycle-slip occurrence are 13.04%, 56.52%, and 69.57% under moderate, intense, and super storms conditions, respectively. Full article

(This article belongs to the Section Remote Sensors)

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18 pages, 3144 KiB

Open AccessArticle

A Linear-Quadratic Model for the Quantification of a Mixture of Two Diluted Gases with a Single Metal Oxide Sensor

by Stéphanie Madrolle¹, Pierre Grangeat^1,*

and Christian Jutten²

¹ Univ. Grenoble Alpes, CEA, LETI, MINATEC Campus, Micro-technologies for Biology and Healthcare Division, F-38054 Grenoble, France

² GIPSA-lab, Univ. Grenoble Alpes, CNRS, Grenoble INP, F-38000 Grenoble, France

Sensors 2018, 18(6), 1785; https://doi.org/10.3390/s18061785 - 1 Jun 2018

Cited by 16 | Viewed by 3410

Abstract

The aim of our work is to quantify two gases (acetone and ethanol) diluted in an air buffer using only a single metal oxide (MOX) sensor. We took advantage of the low selectivity of the MOX sensor, exploiting a dual-temperature mode. Working at [...] Read more.

The aim of our work is to quantify two gases (acetone and ethanol) diluted in an air buffer using only a single metal oxide (MOX) sensor. We took advantage of the low selectivity of the MOX sensor, exploiting a dual-temperature mode. Working at two temperatures of the MOX sensitive layer allowed us to obtain diversity in the measures. Two virtual sensors were created to characterize our gas mixture. We presented a linear-quadratic mixture sensing model which was closer to the experimental data. To validate this model and the experimental protocol, we inverted the system of quadratic equations to quantify a mixture of the two gases. The linear-quadratic model was compared to the bilinear model proposed in the literature. We presented an experimental evaluation on mixtures made of a few ppm of acetone and ethanol, and we obtained a precision close to the ppm. This is an important step towards medical applications, particularly in terms of diabetes, to deliver a non-invasive measure with a low-cost device. Full article

(This article belongs to the Section Chemical Sensors)

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18 pages, 6918 KiB

Open AccessArticle

Design and Manufacturing of an Ultra-Low-Cost Custom Torque Sensor for Robotics

by Rodrigo Pérez Ubeda^1,*

, Santiago C. Gutiérrez Rubert¹, Ranko Zotovic Stanisic²

and Ángel Perles Ivars³

¹ Department of Mechanical and Materials Engineering, Universitat Politècnica de València, Valencia 46022, Spain

² Department of Systems Engineering and Automation, Universitat Politècnica de València, Valencia 46022, Spain

³ Department of Computer Systems and Computation, Universitat Politècnica de València, Valencia 46022, Spain

Sensors 2018, 18(6), 1786; https://doi.org/10.3390/s18061786 - 1 Jun 2018

Cited by 37 | Viewed by 8509

Abstract

This article describes a new, very low-cost torque sensor. It was designed to obtain a geometric shape suitable for very affordable manufacturing by machining. The torque sensor was developed under the principle of measurement by strain gauges. It has been designed in order [...] Read more.

This article describes a new, very low-cost torque sensor. It was designed to obtain a geometric shape suitable for very affordable manufacturing by machining. The torque sensor was developed under the principle of measurement by strain gauges. It has been designed in order to make manufacturing operations as simple as possible. Optimization was achieved through finite element analysis. Three test sensors for 1, 5, and 20 Nm were designed and machined. Calibration of the three sensors has been carried out obtaining excellent results. An analysis of the dimensional quality of the product and associated costs demonstrates that manufacturing is possible with very simple machining operations, standard tools, and economic equipment. Full article

(This article belongs to the Section Physical Sensors)

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21 pages, 1128 KiB

Open AccessArticle

A Survey on Proactive, Active and Passive Fault Diagnosis Protocols for WSNs: Network Operation Perspective

by Amjad Mehmood^1,3,*,†

, Nabil Alrajeh^2,†, Mithun Mukherjee^3,†, Salwani Abdullah^4,† and Houbing Song^5,†

¹ Institute of Information Technology, Kohat University of Science Technology, Kohat KP 26000, Pakistan

² Traffic Safety Technologies Chair, Urban Planning Department, College of Architecture and Planning, King Saud University, Riyadh 14511, Saudi Arabia

³ Guangdong Provincial Key Lab of Petrochemical Equipment Fault Diagnosis, Guangdong University of Petrochemical Technology, Maoming 525000, China

⁴ Faculty of Information Science and Technology (Bangi Campus), Universiti Kebangsaan Malaysia, Bangi Selangor 43600, Malaysia

⁵ Department of Electrical, Computer, Software, and Systems Engineering, Embry-Riddle Aeronautical University, Daytona Beach, FL 32114, USA

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1787; https://doi.org/10.3390/s18061787 - 1 Jun 2018

Cited by 17 | Viewed by 3861

Abstract

Although wireless sensor networks (WSNs) have been the object of research focus for the past two decades, fault diagnosis in these networks has received little attention. This is an essential requirement for wireless networks, especially in WSNs, because of their ad-hoc nature, deployment [...] Read more.

Although wireless sensor networks (WSNs) have been the object of research focus for the past two decades, fault diagnosis in these networks has received little attention. This is an essential requirement for wireless networks, especially in WSNs, because of their ad-hoc nature, deployment requirements and resource limitations. Therefore, in this paper we survey fault diagnosis from the perspective of network operations. To the best of our knowledge, this is the first survey from such a perspective. We survey the proactive, active and passive fault diagnosis schemes that have appeared in the literature to date, accenting their advantages and limitations of each scheme. In addition to illuminating the details of past efforts, this survey also reveals new research challenges and strengthens our understanding of the field of fault diagnosis. Full article

(This article belongs to the Section Sensor Networks)

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33 pages, 18991 KiB

Open AccessArticle

Realistic Indoor Radio Propagation for Sub-GHz Communication

by Ben Bellekens^1,*

, Rudi Penne² and Maarten Weyn¹

¹ IDLab, Faculty of Applied Engineering, University of Antwerp-imec, Groenenborgerlaan 171, 2000 Antwerp, Belgium

² Op3Mech, Faculty of Mathematics and Applied Engineering, University of Antwerp, Groenenborgerlaan 171, 2000 Antwerp, Belgium

Sensors 2018, 18(6), 1788; https://doi.org/10.3390/s18061788 - 1 Jun 2018

Cited by 4 | Viewed by 2758

Abstract

This research article proposes a novel ray-launching propagation loss model that is able to use an environment model that contains the real geometry. This environment model is made by applying a Simultaneous Localization and Mapping (SLAM) algorithm. As a solution to the rising [...] Read more.

This research article proposes a novel ray-launching propagation loss model that is able to use an environment model that contains the real geometry. This environment model is made by applying a Simultaneous Localization and Mapping (SLAM) algorithm. As a solution to the rising demands of Internet of Things applications for indoor environments, this deterministic radio propagation loss model is able to simulate an accurate coverage map that can be used for localization applications or network optimizations. Since this propagation loss model uses a 2D environment model that was captured by a moving robot, an automated validation model is developed so that a wireless sensor network can be used for validating the propagation loss model. We validated the propagation loss model by evaluated two environment models towards the lowest Root Mean Square Error (RMSE), the Mean Absolute Error (MAE), and the Mean Error (ME). Furthermore, the correlation between the number of rays and the RMSE is analyzed and the correlation between the number of reflections versus the RMSE is also analyzed. Finally, the performance of the radio propagation loss model is analyzed. Full article

(This article belongs to the Section Sensor Networks)

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19 pages, 8072 KiB

Open AccessArticle

A Silicon-on-Insulator-Based Dual-Gain Charge-Sensitive Pixel Detector for Low-Noise X-ray Imaging for Future Astronomical Satellite Missions

by Sumeet Shrestha¹

, Shoji Kawahito^1,*, Hiroki Kamehama², Syunta Nakanishi¹, Keita Yasutomi¹, Keiichiro Kagawa¹, Nobukazu Teranishi¹, Ayaki Takeda³, Takeshi Go Tsuru⁴

, Ikuo Kurachi⁵ and Yasuo Arai⁵

¹ Research Institute of Electronics, Shizuoka University, Hamamatsu, Shizuoka 432-8011, Japan

² Information and Communication Systems Engineering, National Institute of Technology, Okinawa College, Okinawa 905-2171, Japan

³ Department of Applied Physics and Electronic Engineering, University of Miyazaki, Miyazaki 889-2192, Japan

⁴ Department of Physics, Kyoto University, Kyoto 606-8502, Japan

⁵ High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan

Sensors 2018, 18(6), 1789; https://doi.org/10.3390/s18061789 - 1 Jun 2018

Cited by 6 | Viewed by 4733

Abstract

In this paper, we report on the development of a monolithic active pixel sensor for X-ray imaging using 0.2 µm fully depleted silicon-on-insulator (SOI)-based technology to support next generation astronomical satellite missions. Detail regarding low-noise dual-gain SOI based pixels with a charge sensitive [...] Read more.

In this paper, we report on the development of a monolithic active pixel sensor for X-ray imaging using 0.2 µm fully depleted silicon-on-insulator (SOI)-based technology to support next generation astronomical satellite missions. Detail regarding low-noise dual-gain SOI based pixels with a charge sensitive amplifier and pinned depleted diode sensor structure is presented. The proposed multi-well sensor structure underneath the fully-depleted SOI allows the design of a detector with low node capacitance and high charge collection efficiency. Configurations for achieving very high charge-to-voltage conversion gain of 52 µV/e⁻ and 187 µV/e⁻ are demonstrated. Furthermore, in-pixel dual gain selection is used for low-noise and wide dynamic range X-ray energy detection. A technique to improve the noise performance by removing correlated system noise leads to an improvement in the spectroscopic performance of the measured X-ray energy. Taken together, the implemented chip has low dark current (44.8 pA/cm² at −30 °C), improved noise performance (8.5 e⁻ rms for high gain and 11.7 e⁻ rms for low gain), and better energy resolution of 2.89% (171 eV FWHM) at 5.9 keV using ⁵⁵Fe and 1.67% (234 eV FWHM) at 13.95 keV using ²⁴¹Am. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 6468 KiB

Open AccessArticle

Development of a Fault Monitoring Technique for Wind Turbines Using a Hidden Markov Model

by Sung-Hwan Shin^1,*, SangRyul Kim² and Yun-Ho Seo²

¹ Department of Automotive Engineering, Kookmin University, 77 Jeongneung-ro, Seongbuk-gu, Seoul 02707, Korea

² System Dynamics Lab, Korea Institute of Machinery & Materials, 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 34103, Korea

Sensors 2018, 18(6), 1790; https://doi.org/10.3390/s18061790 - 2 Jun 2018

Cited by 13 | Viewed by 3291

Abstract

Regular inspection for the maintenance of the wind turbines is difficult because of their remote locations. For this reason, condition monitoring systems (CMSs) are typically installed to monitor their health condition. The purpose of this study is to propose a fault detection algorithm [...] Read more.

Regular inspection for the maintenance of the wind turbines is difficult because of their remote locations. For this reason, condition monitoring systems (CMSs) are typically installed to monitor their health condition. The purpose of this study is to propose a fault detection algorithm for the mechanical parts of the wind turbine. To this end, long-term vibration data were collected over two years by a CMS installed on a 3 MW wind turbine. The vibration distribution at a specific rotating speed of main shaft is approximated by the Weibull distribution and its cumulative distribution function is utilized for determining the threshold levels that indicate impending failure of mechanical parts. A Hidden Markov model (HMM) is employed to propose the statistical fault detection algorithm in the time domain and the method whereby the input sequence for HMM is extracted is also introduced by considering the threshold levels and the correlation between the signals. Finally, it was demonstrated that the proposed HMM algorithm achieved a greater than 95% detection success rate by using the long-term signals. Full article

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

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20 pages, 20154 KiB

Open AccessArticle

Temperature Resistant Fiber Bragg Gratings for On-Line and Structural Health Monitoring of the Next-Generation of Nuclear Reactors

by Guillaume Laffont^*, Romain Cotillard, Nicolas Roussel, Rudy Desmarchelier and Stéphane Rougeault

CEA, List, F-91191 Gif-sur-Yvette CEDEX, France

Sensors 2018, 18(6), 1791; https://doi.org/10.3390/s18061791 - 2 Jun 2018

Cited by 86 | Viewed by 7481

Abstract

The harsh environment associated with the next generation of nuclear reactors is a great challenge facing all new sensing technologies to be deployed for on-line monitoring purposes and for the implantation of SHM methods. Sensors able to resist sustained periods at very high [...] Read more.

The harsh environment associated with the next generation of nuclear reactors is a great challenge facing all new sensing technologies to be deployed for on-line monitoring purposes and for the implantation of SHM methods. Sensors able to resist sustained periods at very high temperatures continuously as is the case within sodium-cooled fast reactors require specific developments and evaluations. Among the diversity of optical fiber sensing technologies, temperature resistant fiber Bragg gratings are increasingly being considered for the instrumentation of future nuclear power plants, especially for components exposed to high temperature and high radiation levels. Research programs are supporting the developments of optical fiber sensors under mixed high temperature and radiative environments leading to significant increase in term of maturity. This paper details the development of temperature-resistant wavelength-multiplexed fiber Bragg gratings for temperature and strain measurements and their characterization for on-line monitoring into the liquid sodium used as a coolant for the next generation of fast reactors. Full article

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

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20 pages, 4322 KiB

Open AccessFeature PaperArticle

Inertial Sensor-Based Variables Are Indicators of Frailty and Adverse Post-Operative Outcomes in Cardiovascular Disease Patients

by Rahul Soangra¹

and Thurmon E. Lockhart^2,*

¹ Department of Physical Therapy, Crean College of Health and Behavioral Sciences, Chapman University, Orange, CA 92866, USA

² School of Biological and Health Systems Engineering, Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, AZ 85287, USA

Sensors 2018, 18(6), 1792; https://doi.org/10.3390/s18061792 - 2 Jun 2018

Cited by 18 | Viewed by 4247

Abstract

Cardiovascular disease (CVD) patients with intrinsic cardiac cause for falling have been found to be frail and submissive to morbidity and mortality as post-operative outcomes. In these older CVD patients, gait speed is conjectured by the Society of Thoracic Surgeons (STS) as an [...] Read more.

Cardiovascular disease (CVD) patients with intrinsic cardiac cause for falling have been found to be frail and submissive to morbidity and mortality as post-operative outcomes. In these older CVD patients, gait speed is conjectured by the Society of Thoracic Surgeons (STS) as an independent predictor of post-operative morbidity and mortality. However, this guideline by STS has not been studied adequately with a large sample size; rather it is based largely on expert opinions of cardiac surgeons and researchers. Although one’s gait speed is not completely associated with one’s risk of falls, gait speed is a quick robust measure to classify frail/non-frail CVD patients and undoubtedly frail individuals are more prone to falls. Thus, this study examines the effects of inertial sensor-based quick movement variability characteristics in identifying CVD patients likely to have an adverse post-operative outcome. This study establishes a relationship with gait and postural predictor variables with patient’s post-operative adverse outcomes. Accordingly, inertial sensors embedded inside smartphones are indispensable for the assessment of elderly patients in clinical environments and may be necessary for quick objective assessment. Sixteen elderly CVD patients (Age 76.1 ± 3.6 years) who were scheduled for cardiac surgery the next day were recruited for this study. Based on STS recommendation guidelines, eight of the CVD patients were classified as frail (prone to adverse outcomes with gait speed ≤ 0.833 m/s) and the other eight patients as non-frail (gait speed > 0.833 m/s). Smartphone-derived walking velocity was found to be significantly lower in frail patients than that in non-frail patients (p < 0.01). Mean Center of Pressure (COP) radius (p < 0.01), COP Area (p < 0.01), COP path length (p < 0.05) and mean COP velocity (p < 0.05) were found to be significantly higher in frail patients than that in the non-frail patient group. Nonlinear variability measures such as sample entropy were significantly lower in frail participants in anterior-posterior (p < 0.01) and resultant sway direction (p < 0.01) than in the non-frail group. This study identified numerous postural and movement variability parameters that offer insights into predictive inertial sensor-based variables and post-operative adverse outcomes among CVD patients. In future, smartphone-based clinical measurement systems could serve as a clinical decision support system for assessing patients quickly in the perioperative period. Full article

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

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16 pages, 5839 KiB

Open AccessArticle

Adaptive Unscented Kalman Filter Phase Unwrapping Method and Its Application on Gaofen-3 Interferometric SAR Data

by Yandong Gao¹

, Shubi Zhang¹, Tao Li^2,*, Qianfu Chen², Shijin Li¹ and Pengfei Meng¹

¹ School of Environment Science and Spatial Informatics, China University of Miningand Technology, Xuzhou 221116, China

² Satellite Surveying and Mapping Application Center, National Administration of Surveying, Mapping and Geo-Information, Haidian District, Beijing 100048, China

Sensors 2018, 18(6), 1793; https://doi.org/10.3390/s18061793 - 2 Jun 2018

Cited by 20 | Viewed by 4981

Abstract

Phase unwrapping (PU) is a key step in the reconstruction of digital elevation models (DEMs) and the monitoring of surface deformation from interferometric synthetic aperture radar (SAR, InSAR) data. In this paper, an improved PU method that combines an amended matrix pencil model, [...] Read more.

Phase unwrapping (PU) is a key step in the reconstruction of digital elevation models (DEMs) and the monitoring of surface deformation from interferometric synthetic aperture radar (SAR, InSAR) data. In this paper, an improved PU method that combines an amended matrix pencil model, an adaptive unscented kalman filter (AUKF), an efficient quality-guided strategy based on heapsort, and a circular median filter is proposed. PU theory and the existing UKFPU method are covered. Then, the improved method is presented with emphasis on the AUKF and the circular median filter. AUKF has been well used in other fields, but it is for the first time applied to interferometric images PU, to the best of our knowledge. First, the amended matrix pencil model is used to estimate the phase gradient. Then, an AUKF model is used to unwrap the interferometric phase based on an efficient quality-guided strategy based on heapsort. Finally, the key results are obtained by filtering the results using a circular median. The proposed method is compared with the minimum cost network flow (MCF), statistical cost network flow (SNAPHU), regularized phase tracking technique (RPTPU), and UKFPU methods using two sets of simulated data and two sets of experimental GF-3 SAR data. The improved method is shown to yield the greatest accuracy in the interferometric phase maps compared to the methods considered in this paper. Furthermore, the improved method is shown to be the most robust to noise and is thus most suitable for PU of GF-3 SAR data in high-noise and low-coherence regions. Full article

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

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19 pages, 5324 KiB

Open AccessArticle

FPGA-Based On-Board Geometric Calibration for Linear CCD Array Sensors

by Guoqing Zhou^1,2,3,*, Linjun Jiang⁴, Jingjin Huang², Rongting Zhang², Dequan Liu⁵

, Xiang Zhou^1,5 and Oktay Baysal⁶

¹ Guangxi Key Laboratory for Spatial Information and Geomatics, Guilin University of Technology, Guilin 541004, China

² School of Precision Instrument & Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China

³ The Center for Remote Sensing, Tianjin University, Tianjin 300072 China

⁴ Guangxi Institute of Geoinformation, Surveying and Mapping, Liuzhou 545006, China

⁵ School of Microelectronics, Tianjin University, Tianjin 300072, China

⁶ Mechanical & Aerospace Engineering, Old Dominion University, Norfolk, VA 23529, USA

Sensors 2018, 18(6), 1794; https://doi.org/10.3390/s18061794 - 2 Jun 2018

Cited by 15 | Viewed by 4077

Abstract

With increasing demands in real-time or near real-time remotely sensed imagery applications in such as military deployments, quick response to terrorist attacks and disaster rescue, the on-board geometric calibration problem has attracted the attention of many scientists in recent years. This paper presents [...] Read more.

With increasing demands in real-time or near real-time remotely sensed imagery applications in such as military deployments, quick response to terrorist attacks and disaster rescue, the on-board geometric calibration problem has attracted the attention of many scientists in recent years. This paper presents an on-board geometric calibration method for linear CCD sensor arrays using FPGA chips. The proposed method mainly consists of four modules—Input Data, Coefficient Calculation, Adjustment Computation and Comparison—in which the parallel computations for building the observation equations and least squares adjustment, are implemented using FPGA chips, for which a decomposed matrix inversion method is presented. A Xilinx Virtex-7 FPGA VC707 chip is selected and the MOMS-2P data used for inflight geometric calibration from DLR (Köln, Germany), are employed for validation and analysis. The experimental results demonstrated that: (1) When the widths of floating-point data from 44-bit to 64-bit are adopted, the FPGA resources, including the utilizations of FF, LUT, memory LUT, I/O and DSP48, are consumed at a fast increasing rate; thus, a 50-bit data width is recommended for FPGA-based geometric calibration. (2) Increasing number of ground control points (GCPs) does not significantly consume the FPGA resources, six GCPs is therefore recommended for geometric calibration. (3) The FPGA-based geometric calibration can reach approximately 24 times faster speed than the PC-based one does. (4) The accuracy from the proposed FPGA-based method is almost similar to the one from the inflight calibration if the calibration model and GCPs number are the same. Full article

(This article belongs to the Section Remote Sensors)

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32 pages, 9108 KiB

Open AccessArticle

A Mission Planning Approach for Precision Farming Systems Based on Multi-Objective Optimization

by Zhaoyu Zhai^*

, José-Fernán Martínez Ortega, Néstor Lucas Martínez

and Jesús Rodríguez-Molina

Departamento de Ingeniería Telemática y Electrónica (DTE), Escuela Técnica Superior de Ingeniería y Sistemas de Telecomunicación (ETSIST), Universidad Politécnica de Madrid (UPM), C/Nikola Tesla, s/n, 28031 Madrid, Spain

Sensors 2018, 18(6), 1795; https://doi.org/10.3390/s18061795 - 2 Jun 2018

Cited by 38 | Viewed by 6904

Abstract

As the demand for food grows continuously, intelligent agriculture has drawn much attention due to its capability of producing great quantities of food efficiently. The main purpose of intelligent agriculture is to plan agricultural missions properly and use limited resources reasonably with minor [...] Read more.

As the demand for food grows continuously, intelligent agriculture has drawn much attention due to its capability of producing great quantities of food efficiently. The main purpose of intelligent agriculture is to plan agricultural missions properly and use limited resources reasonably with minor human intervention. This paper proposes a Precision Farming System (PFS) as a Multi-Agent System (MAS). Components of PFS are treated as agents with different functionalities. These agents could form several coalitions to complete the complex agricultural missions cooperatively. In PFS, mission planning should consider several criteria, like expected benefit, energy consumption or equipment loss. Hence, mission planning could be treated as a Multi-objective Optimization Problem (MOP). In order to solve MOP, an improved algorithm, MP-PSOGA, is proposed, taking advantages of the Genetic Algorithms and Particle Swarm Optimization. A simulation, called precise pesticide spraying mission, is performed to verify the feasibility of the proposed approach. Simulation results illustrate that the proposed approach works properly. This approach enables the PFS to plan missions and allocate scarce resources efficiently. The theoretical analysis and simulation is a good foundation for the future study. Once the proposed approach is applied to a real scenario, it is expected to bring significant economic improvement. Full article

(This article belongs to the Special Issue Smart Decision-Making)

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18 pages, 2502 KiB

Open AccessArticle

Crack Damage Detection Method via Multiple Visual Features and Efficient Multi-Task Learning Model

by Baoxian Wang¹, Weigang Zhao^1,*, Po Gao², Yufeng Zhang³ and Zhe Wang³

¹ Structure Health Monitoring and Control Institute, Shijiazhuang Tiedao University, Shijiazhuang 050043, China

² School of Technology, Beijing Forestry University, Beijing 100083, China

³ School of Electrical and Electronic Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, China

Sensors 2018, 18(6), 1796; https://doi.org/10.3390/s18061796 - 2 Jun 2018

Cited by 32 | Viewed by 6252

Abstract

This paper proposes an effective and efficient model for concrete crack detection. The presented work consists of two modules: multi-view image feature extraction and multi-task crack region detection. Specifically, multiple visual features (such as texture, edge, etc.) of image regions are calculated, which [...] Read more.

This paper proposes an effective and efficient model for concrete crack detection. The presented work consists of two modules: multi-view image feature extraction and multi-task crack region detection. Specifically, multiple visual features (such as texture, edge, etc.) of image regions are calculated, which can suppress various background noises (such as illumination, pockmark, stripe, blurring, etc.). With the computed multiple visual features, a novel crack region detector is advocated using a multi-task learning framework, which involves restraining the variability for different crack region features and emphasizing the separability between crack region features and complex background ones. Furthermore, the extreme learning machine is utilized to construct this multi-task learning model, thereby leading to high computing efficiency and good generalization. Experimental results of the practical concrete images demonstrate that the developed algorithm can achieve favorable crack detection performance compared with traditional crack detectors. Full article

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

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18 pages, 18769 KiB

Open AccessArticle

A Fog Computing and Cloudlet Based Augmented Reality System for the Industry 4.0 Shipyard

by Tiago M. Fernández-Caramés^1,*

, Paula Fraga-Lamas^1,*

, Manuel Suárez-Albela¹

and Miguel Vilar-Montesinos²

¹ Unidade Mixta de Investigación Navantia-UDC, Universidade da Coruña, Edificio Talleres Tecnológicos, Mendizábal s/n, Ferrol 15403, Spain

² Navantia S. A., Astillero Ría de Ferrol, Taxonera, s/n, Ferrol 15403, Spain

Sensors 2018, 18(6), 1798; https://doi.org/10.3390/s18061798 - 2 Jun 2018

Cited by 124 | Viewed by 9731

Abstract

Augmented Reality (AR) is one of the key technologies pointed out by Industry 4.0 as a tool for enhancing the next generation of automated and computerized factories. AR can also help shipbuilding operators, since they usually need to interact with information (e.g., product [...] Read more.

Augmented Reality (AR) is one of the key technologies pointed out by Industry 4.0 as a tool for enhancing the next generation of automated and computerized factories. AR can also help shipbuilding operators, since they usually need to interact with information (e.g., product datasheets, instructions, maintenance procedures, quality control forms) that could be handled easily and more efficiently through AR devices. This is the reason why Navantia, one of the 10 largest shipbuilders in the world, is studying the application of AR (among other technologies) in different shipyard environments in a project called “Shipyard 4.0”. This article presents Navantia’s industrial AR (IAR) architecture, which is based on cloudlets and on the fog computing paradigm. Both technologies are ideal for supporting physically-distributed, low-latency and QoS-aware applications that decrease the network traffic and the computational load of traditional cloud computing systems. The proposed IAR communications architecture is evaluated in real-world scenarios with payload sizes according to demanding Microsoft HoloLens applications and when using a cloud, a cloudlet and a fog computing system. The results show that, in terms of response delay, the fog computing system is the fastest when transferring small payloads (less than 128 KB), while for larger file sizes, the cloudlet solution is faster than the others. Moreover, under high loads (with many concurrent IAR clients), the cloudlet in some cases is more than four times faster than the fog computing system in terms of response delay. Full article

(This article belongs to the Special Issue Sensor Networks and Systems to Enable Industry 4.0 Environments)

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12 pages, 3285 KiB

Open AccessArticle

Study on the Optimal Groove Shape and Glue Material for Fiber Bragg Grating Measuring Bolts

by Yiming Zhao^1,2, Nong Zhang^1,*

, Guangyao Si^3,4,* and Xuehua Li¹

¹ Key Laboratory of Deep Coal Resource Mining of the Ministry of Education, School of Mines, China University of Mining and Technology, Xuzhou 221116, China

² Shenzhen Oceanpower Co. Ltd., Shenzhen 518040, China

³ School of Minerals and Energy Resources Engineering, University of New South Wales, Sydney, NSW 2052, Australia

⁴ State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou 221116, China

Sensors 2018, 18(6), 1799; https://doi.org/10.3390/s18061799 - 2 Jun 2018

Cited by 14 | Viewed by 4791

Abstract

Fiber Bragg grating (FBG) measuring bolts, as a useful tool to evaluate the behaviors of steel bolts in underground engineering, can be manufactured by gluing the FBG sensors inside the grooves, which are usually symmetrical cuts along the steel bolt rod. The selection [...] Read more.

Fiber Bragg grating (FBG) measuring bolts, as a useful tool to evaluate the behaviors of steel bolts in underground engineering, can be manufactured by gluing the FBG sensors inside the grooves, which are usually symmetrical cuts along the steel bolt rod. The selection of the cut shape and the glue types could perceivably affect the final supporting strength of the bolts. Unfortunately, the impact of cut shape and glue type on bolting strength is not yet clear. In this study, based on direct tension tests, full tensile load–displacement curves of rock bolts with different groove shapes were obtained and analyzed. The effects of groove shape on the bolt strength were discussed, and the stress redistribution in the cross-section of a rock bolt with different grooves was simulated using ANSYS. The results indicated that the trapezoidal groove is best for manufacturing the FBG bolt due to its low reduction of supporting strength. Four types of glues commonly used for the FBG sensors were assessed by conducting tensile tests on the mechanical testing and simulation system and the static and dynamic optical interrogators system. Using linear regression analysis, the relationship between the reflected wavelength of FBG sensors and tensile load was obtained. Practical recommendations for glue selection in engineering practice are also provided. Full article

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

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22 pages, 10500 KiB

Open AccessArticle

Design of Low-Cost Vehicle Roll Angle Estimator Based on Kalman Filters and an IoT Architecture

by Javier Garcia Guzman^1,*,†

, Lisardo Prieto Gonzalez^1,†

, Jonatan Pajares Redondo^2,†

, Susana Sanz Sanchez^2,†

and Beatriz L. Boada^2,†

¹ Computer Science Department, Institute for Automotive Vehicle Safety (ISVA), Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganés, Madrid, Spain

² Mechanical Engineering Department, Institute for Automotive Vehicle Safety (ISVA), Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganés, Madrid, Spain

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1800; https://doi.org/10.3390/s18061800 - 3 Jun 2018

Cited by 19 | Viewed by 4562

Abstract

In recent years, there have been many advances in vehicle technologies based on the efficient use of real-time data provided by embedded sensors. Some of these technologies can help you avoid or reduce the severity of a crash such as the Roll Stability [...] Read more.

In recent years, there have been many advances in vehicle technologies based on the efficient use of real-time data provided by embedded sensors. Some of these technologies can help you avoid or reduce the severity of a crash such as the Roll Stability Control (RSC) systems for commercial vehicles. In RSC, several critical variables to consider such as sideslip or roll angle can only be directly measured using expensive equipment. These kind of devices would increase the price of commercial vehicles. Nevertheless, sideslip or roll angle or values can be estimated using MEMS sensors in combination with data fusion algorithms. The objectives stated for this research work consist of integrating roll angle estimators based on Linear and Unscented Kalman filters to evaluate the precision of the results obtained and determining the fulfillment of the hard real-time processing constraints to embed this kind of estimators in IoT architectures based on low-cost equipment able to be deployed in commercial vehicles. An experimental testbed composed of a van with two sets of low-cost kits was set up, the first one including a Raspberry Pi 3 Model B, and the other having an Intel Edison System on Chip. This experimental environment was tested under different conditions for comparison. The results obtained from low-cost experimental kits, based on IoT architectures and including estimators based on Kalman filters, provide accurate roll angle estimation. Also, these results show that the processing time to get the data and execute the estimations based on Kalman Filters fulfill hard real time constraints. Full article

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

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17 pages, 7362 KiB

Open AccessArticle

Use of Energy Efficient Sensor Networks to Enhance Dynamic Data Gathering Systems: A Comparative Study between Bluetooth and ZigBee

by Razvan Andrei Gheorghiu^*

and Valentin Iordache

Transports Faculty, Politehnica University of Bucharest, Bucharest 060042, Romania

Sensors 2018, 18(6), 1801; https://doi.org/10.3390/s18061801 - 3 Jun 2018

Cited by 10 | Viewed by 4117

Abstract

As road traffic conditions worsen due to the constantly increasing number of cars, traffic management systems are struggling to provide a suitable environment, by gathering all the relevant information from the road network. However, in most cases these are obtained via traffic detectors [...] Read more.

As road traffic conditions worsen due to the constantly increasing number of cars, traffic management systems are struggling to provide a suitable environment, by gathering all the relevant information from the road network. However, in most cases these are obtained via traffic detectors placed near road junctions, thus providing no information on the conditions in between. A large-scale sensor network using detectors on the majority of vehicles would certainly be capable of providing useful data, but has two major impediments: the equipment installed on the vehicles should be cheap enough (assuming the willingness of private car owners to be a part of the network) and be capable of transferring the required amount of data in due time, as the vehicle passes by the road side unit that acts as interface with the traffic management system. These restrictions reduce the number of technologies that can be used. In this article a series of comprehensive tests have been performed to evaluate the Bluetooth and ZigBee protocols for this purpose from many points of view: handshake time, static and dynamic data transfer (in laboratory conditions and in real traffic conditions). An assessment of the environmental conditions (during tests and probable to be encountered in real conditions) was also provided. Full article

(This article belongs to the Special Issue Advances on Vehicular Networks: From Sensing to Autonomous Driving)

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18 pages, 4088 KiB

Open AccessArticle

Non-Contact Heart Rate and Blood Pressure Estimations from Video Analysis and Machine Learning Modelling Applied to Food Sensory Responses: A Case Study for Chocolate

by Claudia Gonzalez Viejo

, Sigfredo Fuentes^*

, Damir D. Torrico and Frank R. Dunshea

School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, VIC 3010, Australia

Sensors 2018, 18(6), 1802; https://doi.org/10.3390/s18061802 - 3 Jun 2018

Cited by 64 | Viewed by 10087

Abstract

Traditional methods to assess heart rate (HR) and blood pressure (BP) are intrusive and can affect results in sensory analysis of food as participants are aware of the sensors. This paper aims to validate a non-contact method to measure HR using the photoplethysmography [...] Read more.

Traditional methods to assess heart rate (HR) and blood pressure (BP) are intrusive and can affect results in sensory analysis of food as participants are aware of the sensors. This paper aims to validate a non-contact method to measure HR using the photoplethysmography (PPG) technique and to develop models to predict the real HR and BP based on raw video analysis (RVA) with an example application in chocolate consumption using machine learning (ML). The RVA used a computer vision algorithm based on luminosity changes on the different RGB color channels using three face-regions (forehead and both cheeks). To validate the proposed method and ML models, a home oscillometric monitor and a finger sensor were used. Results showed high correlations with the G color channel (R² = 0.83). Two ML models were developed using three face-regions: (i) Model 1 to predict HR and BP using the RVA outputs with R = 0.85 and (ii) Model 2 based on time-series prediction with HR, magnitude and luminosity from RVA inputs to HR values every second with R = 0.97. An application for the sensory analysis of chocolate showed significant correlations between changes in HR and BP with chocolate hardness and purchase intention. Full article

(This article belongs to the Section Biosensors)

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31 pages, 14229 KiB

Open AccessArticle

Optimal Representation of Anuran Call Spectrum in Environmental Monitoring Systems Using Wireless Sensor Networks

by Amalia Luque^1,*

, Jesús Gómez-Bellido¹, Alejandro Carrasco²

and Julio Barbancho³

¹ Ingeniería del Diseño, Escuela Politécnica Superior, Universidad de Sevilla, 41004 Sevilla, Spain

² Tecnología Electrónica, Escuela Ingeniería Informática, Universidad de Sevilla, 41004 Sevilla, Spain

³ Tecnología Electrónica, Escuela Politécnica Superior, Universidad de Sevilla, 41004 Sevilla, Spain

Sensors 2018, 18(6), 1803; https://doi.org/10.3390/s18061803 - 3 Jun 2018

Cited by 19 | Viewed by 4221

Abstract

The analysis and classification of the sounds produced by certain animal species, notably anurans, have revealed these amphibians to be a potentially strong indicator of temperature fluctuations and therefore of the existence of climate change. Environmental monitoring systems using Wireless Sensor Networks are [...] Read more.

The analysis and classification of the sounds produced by certain animal species, notably anurans, have revealed these amphibians to be a potentially strong indicator of temperature fluctuations and therefore of the existence of climate change. Environmental monitoring systems using Wireless Sensor Networks are therefore of interest to obtain indicators of global warming. For the automatic classification of the sounds recorded on such systems, the proper representation of the sound spectrum is essential since it contains the information required for cataloguing anuran calls. The present paper focuses on this process of feature extraction by exploring three alternatives: the standardized MPEG-7, the Filter Bank Energy (FBE), and the Mel Frequency Cepstral Coefficients (MFCC). Moreover, various values for every option in the extraction of spectrum features have been considered. Throughout the paper, it is shown that representing the frame spectrum with pure FBE offers slightly worse results than using the MPEG-7 features. This performance can easily be increased, however, by rescaling the FBE in a double dimension: vertically, by taking the logarithm of the energies; and, horizontally, by applying mel scaling in the filter banks. On the other hand, representing the spectrum in the cepstral domain, as in MFCC, has shown additional marginal improvements in classification performance. Full article

(This article belongs to the Special Issue Sensor Networks for Environmental Observations)

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27 pages, 737 KiB

Open AccessArticle

Average Accumulative Based Time Variant Model for Early Diagnosis and Prognosis of Slowly Varying Faults

by Funa Zhou^1,2,*

, Ju H. Park^2,*

, Chenglin Wen³ and Po Hu¹

¹ School of Computer and Information Engineering, Henan University, Kaifeng 475004, China

² Department of Electrical Engineering, Yeungnam University, 280 Daehak-Ro, Kyongsan 38541, Korea

³ School of Automatic, Hangzhou Dianzi University, Hangzhou 310018, China

Sensors 2018, 18(6), 1804; https://doi.org/10.3390/s18061804 - 3 Jun 2018

Cited by 10 | Viewed by 3323

Abstract

Early detection of slowly varying small faults is an essential step for fault prognosis. In this paper, we first propose an average accumulative (AA) based time varying principal component analysis (PCA) model for early detection of slowly varying faults. The AA based method [...] Read more.

Early detection of slowly varying small faults is an essential step for fault prognosis. In this paper, we first propose an average accumulative (AA) based time varying principal component analysis (PCA) model for early detection of slowly varying faults. The AA based method can increase the fault size as well as decrease the noise energy. Then, designated component analysis (DCA) is introduced for developing an AA-DCA method to diagnose the root cause of the fault, which is helpful for the operator to make maintenance decisions. Combining the advantage of the cumulative sum (CUSUM) based method and the AA based method, a CUSUM-AA based method is developed to detect faults at earlier times. Finally, the remaining useful life (RUL) prediction model with error correction is established by nonlinear fitting. Once online fault size defined by detection statistics is obtained by an early diagnosis algorithm, real-time RUL prediction can be directly estimated without extra recursive regression. Full article

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

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25 pages, 8242 KiB

Open AccessArticle

Sensing and Storing the Blood Pressure Measure by Patients through A Platform and Mobile Devices ^†

by Vladimir Villarreal^*

, Mel Nielsen and Manuel Samudio

Department of Computer Systems Engineering, Technological University of Panama, El Dorado 0819-07289 Panama City, Republic of Panama

Sensors 2018, 18(6), 1805; https://doi.org/10.3390/s18061805 - 3 Jun 2018

Cited by 6 | Viewed by 5111

Abstract

In this article, we present a platform that allows for the integration of different applications for the follow-up of patients with chronic diseases. We developed two elements: a mobile and a web application. The mobile application allows the capture and processing of vital [...] Read more.

In this article, we present a platform that allows for the integration of different applications for the follow-up of patients with chronic diseases. We developed two elements: a mobile and a web application. The mobile application allows the capture and processing of vital signs for patients with high blood pressure (hypertension). This application allows for the patient to store the data obtained, provides historical information and trends of the stored measures, and provides alerts and recommendations according to ranges of measures that were obtained. The web application allows the doctor and patients to obtain updated information of the disease behavior through the measures obtained. We used different biometric devices including an efimomanometer, glucometer, scale, and a thermometer with a wi-fi connection. Through this web application, we also generated information about average measures at a given time, by age, by region, and by a specific date. The developed system was evaluated in a medical center with different types of patients. 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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16 pages, 7309 KiB

Open AccessArticle

Distributed ISAR Subimage Fusion of Nonuniform Rotating Target Based on Matching Fourier Transform

by Yuanyuan Li^*

, Yaowen Fu

and Wenpeng Zhang

College of Electronic Science, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(6), 1806; https://doi.org/10.3390/s18061806 - 4 Jun 2018

Cited by 7 | Viewed by 2886

Abstract

In real applications, the image quality of the conventional monostatic Inverse Synthetic Aperture Radar (ISAR) for the maneuvering target is subject to the strong fluctuation of Radar Cross Section (RCS), as the target aspect varies enormously. Meanwhile, the maneuvering target introduces nonuniform rotation [...] Read more.

In real applications, the image quality of the conventional monostatic Inverse Synthetic Aperture Radar (ISAR) for the maneuvering target is subject to the strong fluctuation of Radar Cross Section (RCS), as the target aspect varies enormously. Meanwhile, the maneuvering target introduces nonuniform rotation after translation motion compensation which degrades the imaging performance of the conventional Fourier Transform (FT)-based method in the cross-range dimension. In this paper, a method which combines the distributed ISAR technique and the Matching Fourier Transform (MFT) is proposed to overcome these problems. Firstly, according to the characteristics of the distributed ISAR, the multiple channel echoes of the nonuniform rotation target from different observation angles can be acquired. Then, by applying the MFT to the echo of each channel, the defocused problem of nonuniform rotation target which is inevitable by using the FT-based imaging method can be avoided. Finally, after preprocessing, scaling and rotation of all subimages, the noncoherent fusion image containing all the RCS information in all channels can be obtained. The accumulation coefficients of all subimages are calculated adaptively according to the their image qualities. Simulation and experimental data are used to validate the effectiveness of the proposed approach, and fusion image with improved recognizability can be obtained. Therefore, by using the distributed ISAR technique and MFT, subimages of high-maneuvering target from different observation angles can be obtained. Meanwhile, by employing the adaptive subimage fusion method, the RCS fluctuation can be alleviated and more recognizable final image can be obtained. Full article

(This article belongs to the Section Remote Sensors)

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9 pages, 769 KiB

Open AccessArticle

Considerations about the Determination of the Depolarization Calibration Profile of a Two-Telescope Lidar and Its Implications for Volume Depolarization Ratio Retrieval

by Adolfo Comerón¹

, Alejandro Rodríguez-Gómez^1,*

, Michaël Sicard^1,2

, Rubén Barragán^1,2, Constantino Muñoz-Porcar¹

, Francesc Rocadenbosch^1,2 and María José Granados-Muñoz¹

¹ CommSensLab, Department of Signal Theory and Communications, Universitat Politècnica de Catalunya (BarcelonaTech-UPC), 08034 Barcelona, Spain

² Ciències i Tecnologies de l’Espai—Centre de Recerca de l’Aeronàutica i de l’Espai/Institut d’Estudis Espacials de Catalunya (CTE-CRAE/IEEC), Universitat Politècnica de Catalunya, 08034 Barcelona, Spain

Sensors 2018, 18(6), 1807; https://doi.org/10.3390/s18061807 - 4 Jun 2018

Cited by 4 | Viewed by 2625

Abstract

We propose a new method for calculating the volume depolarization ratio of light backscattered by the atmosphere and a lidar system that employs an auxiliary telescope to detect the depolarized component. It takes into account the possible error in the positioning of the [...] Read more.

We propose a new method for calculating the volume depolarization ratio of light backscattered by the atmosphere and a lidar system that employs an auxiliary telescope to detect the depolarized component. It takes into account the possible error in the positioning of the polarizer used in the auxiliary telescope. The theory of operation is presented and then applied to a few cases for which the actual position of the polarizer is estimated, and the improvement of the volume depolarization ratio in the molecular region is quantified. In comparison to the method used before, i.e., without correction, the agreement between the volume depolarization ratio with correction and the theoretical value in the molecular region is improved by a factor of 2–2.5. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 568 KiB

Open AccessArticle

Tailored Algorithm for Sensitivity Enhancement of Gas Concentration Sensors Based on Tunable Laser Absorption Spectroscopy

by Everardo Vargas-Rodriguez^*

, Ana Dinora Guzman-Chavez^* and Roberto Baeza-Serrato

Departamento de Estudios Multidisciplinarios, División de Ingenierías, Universidad de Guanajuato, Av. Universidad s/n, Col. Yacatitas, Yuriria, Gto C.P. 38940, Mexico

Sensors 2018, 18(6), 1808; https://doi.org/10.3390/s18061808 - 4 Jun 2018

Cited by 2 | Viewed by 2952

Abstract

In this work, a novel tailored algorithm to enhance the overall sensitivity of gas concentration sensors based on the Direct Absorption Tunable Laser Absorption Spectroscopy (DA-ATLAS) method is presented. By using this algorithm, the sensor sensitivity can be custom-designed to be quasi constant [...] Read more.

In this work, a novel tailored algorithm to enhance the overall sensitivity of gas concentration sensors based on the Direct Absorption Tunable Laser Absorption Spectroscopy (DA-ATLAS) method is presented. By using this algorithm, the sensor sensitivity can be custom-designed to be quasi constant over a much larger dynamic range compared with that obtained by typical methods based on a single statistics feature of the sensor signal output (peak amplitude, area under the curve, mean or RMS). Additionally, it is shown that with our algorithm, an optimal function can be tailored to get a quasi linear relationship between the concentration and some specific statistics features over a wider dynamic range. In order to test the viability of our algorithm, a basic C

_{2}

H

_{2}

sensor based on DA-ATLAS was implemented, and its experimental measurements support the simulated results provided by our algorithm. Full article

(This article belongs to the Section Chemical Sensors)

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14 pages, 1120 KiB

Open AccessArticle

Cooperative Feedback Bits Allocation and Transmit Power Control in Underlay Cognitive Radio Networks

by Deokhui Lee

and Jaewoo So^*

Department of Electronic Engineering, Sogang University, Seoul 04107, Korea

Sensors 2018, 18(6), 1809; https://doi.org/10.3390/s18061809 - 4 Jun 2018

Cited by 6 | Viewed by 2846

Abstract

In this paper, we consider an underlay cognitive radio network where the spectrum is shared with the primary network. Due to the coexistence of primary and secondary networks, primary users (PUs) are interfered with by the inter-network interference, at the same time secondary [...] Read more.

In this paper, we consider an underlay cognitive radio network where the spectrum is shared with the primary network. Due to the coexistence of primary and secondary networks, primary users (PUs) are interfered with by the inter-network interference, at the same time secondary users (SUs) counteract the intra-network (inter-user) interference. Based on the cooperative feedback between the primary network and the secondary network, the secondary transmitter (ST) applies the cognitive beamforming to suppress the interference to PUs while improving the sum rate of SUs. We herein propose an adaptive feedback bits allocation among multiple PUs and SUs where the quantized channel direction information (CDI) for the interference channel is forwarded to the ST in order to utilize the beamforming. Moreover, based on the cognitive beamforming, we adjust the transmit power of the ST under the constraint of the average interference at PUs. To jointly solve the feedback bits allocation and the transmit power control problems, we formulate an optimization problem which requires a little iterations compared with the separated feedback bits allocation and the transmit power control problems. Numerical results show that the proposed scheme significantly improves the sum rate of SUs while satisfying the average interference constraint at PUs. Full article

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

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17 pages, 4475 KiB

Open AccessFeature PaperArticle

A Comparison between the Decimated Padé Approximant and Decimated Signal Diagonalization Methods for Leak Detection in Pipelines Equipped with Pressure Sensors

by Aimé Lay-Ekuakille^1,*

, Laura Fabbiano², Gaetano Vacca², Joël Kidiamboko Kitoko³, Patrice Bibala Kulapa⁴ and Vito Telesca⁵

¹ Department of Innovation Engineering, University of Salento, 73100 Lecce, Italy

² Department of Mechanics Mathematics & Management, Polytechnic of Bari, 70100 Bari, Italy

³ Faculty of Engineering, Bel Campus University of Technology, 01 Kinshasa, DR Congo

⁴ Department of Electronics, ISTA University, 01 Kinshasa, DR Congo

⁵ School of Engineering, University of Basilicata, 85100 Potenza, Italy

Sensors 2018, 18(6), 1810; https://doi.org/10.3390/s18061810 - 4 Jun 2018

Cited by 5 | Viewed by 3434

Abstract

Pipelines conveying fluids are considered strategic infrastructures to be protected and maintained. They generally serve for transportation of important fluids such as drinkable water, waste water, oil, gas, chemicals, etc. Monitoring and continuous testing, especially on-line, are necessary to assess the condition of [...] Read more.

Pipelines conveying fluids are considered strategic infrastructures to be protected and maintained. They generally serve for transportation of important fluids such as drinkable water, waste water, oil, gas, chemicals, etc. Monitoring and continuous testing, especially on-line, are necessary to assess the condition of pipelines. The paper presents findings related to a comparison between two spectral response algorithms based on the decimated signal diagonalization (DSD) and decimated Padé approximant (DPA) techniques that allow to one to process signals delivered by pressure sensors mounted on an experimental pipeline. Full article

(This article belongs to the Special Issue Intelligent Sensing Technologies for Nondestructive Evaluation 2018)

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24 pages, 8748 KiB

Open AccessArticle

Pedestrian Dead Reckoning Based on Motion Mode Recognition Using a Smartphone

by Boyuan Wang¹, Xuelin Liu^1,*, Baoguo Yu^2,3, Ruicai Jia^2,3 and Xingli Gan^2,3

¹ College of Information and Communication Engineering, Harbin Engineering University, Harbin 150001, China

² State Key Laboratory of Satellite Navigation System and Equipment Technology, Shijiazhuang 050081, China

³ The 54th Research Institute of China Electronics Technology Group Corporation, Shijiazhuang 050081, China

Sensors 2018, 18(6), 1811; https://doi.org/10.3390/s18061811 - 4 Jun 2018

Cited by 82 | Viewed by 8186

Abstract

This paper presents a pedestrian dead reckoning (PDR) approach based on motion mode recognition using a smartphone. The motion mode consists of pedestrian movement state and phone pose. With the support vector machine (SVM) and the decision tree (DT), the arbitrary combinations of [...] Read more.

This paper presents a pedestrian dead reckoning (PDR) approach based on motion mode recognition using a smartphone. The motion mode consists of pedestrian movement state and phone pose. With the support vector machine (SVM) and the decision tree (DT), the arbitrary combinations of movement state and phone pose can be recognized successfully. In the traditional principal component analysis based (PCA-based) method, the obtained horizontal accelerations in one stride time interval cannot be guaranteed to be horizontal and the pedestrian’s direction vector will be influenced. To solve this problem, we propose a PCA-based method with global accelerations (PCA-GA) to infer pedestrian’s headings. Besides, based on the further analysis of phone poses, an ambiguity elimination method is also developed to calibrate the obtained headings. The results indicate that the recognition accuracy of the combinations of movement states and phone poses can be 92.4%. The 50% and 75% absolute estimation errors of pedestrian’s headings are 5.6° and 9.2°, respectively. This novel PCA-GA based method can achieve higher accuracy than traditional PCA-based method and heading offset method. The localization error can reduce to around 3.5 m in a trajectory of 164 m for different movement states and phone poses. Full article

(This article belongs to the Special Issue Sensor Fusion and Novel Technologies in Positioning and Navigation)

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13 pages, 1945 KiB

Open AccessArticle

Thermal Analysis of a Disposable, Instrument-Free DNA Amplification Lab-on-a-Chip Platform

by Tamás Pardy^1,2,*

, Toomas Rang¹ and Indrek Tulp^2,3

¹ Thomas Johann Seebeck Department of Electronics, Tallinn University of Technology, 12616 Tallinn, Estonia

² Selfdiagnostics Deutschland GmbH, 04103 Leipzig, Germany

³ Institute of Technology, University of Tartu, 50411 Tartu, Estonia

Sensors 2018, 18(6), 1812; https://doi.org/10.3390/s18061812 - 4 Jun 2018

Cited by 9 | Viewed by 4720

Abstract

Novel second-generation rapid diagnostics based on nucleic acid amplification tests (NAAT) offer performance metrics on par with clinical laboratories in detecting infectious diseases at the point of care. The diagnostic assay is typically performed within a Lab-on-a-Chip (LoC) component with integrated temperature regulation. [...] Read more.

Novel second-generation rapid diagnostics based on nucleic acid amplification tests (NAAT) offer performance metrics on par with clinical laboratories in detecting infectious diseases at the point of care. The diagnostic assay is typically performed within a Lab-on-a-Chip (LoC) component with integrated temperature regulation. However, constraints on device dimensions, cost and power supply inherent with the device format apply to temperature regulation as well. Thermal analysis on simplified thermal models for the device can help overcome these barriers by speeding up thermal optimization. In this work, we perform experimental thermal analysis on the simplified thermal model for our instrument-free, single-use LoC NAAT platform. The system is evaluated further by finite element modelling. Steady-state as well as transient thermal analysis are performed to evaluate the performance of a self-regulating polymer resin heating element in the proposed device geometry. Reaction volumes in the target temperature range of the amplification reaction are estimated in the simulated model to assess compliance with assay requirements. Using the proposed methodology, we demonstrated our NAAT device concept capable of performing loop-mediated isothermal amplification in the 20–25 °C ambient temperature range with 32 min total assay time. Full article

(This article belongs to the Special Issue Lab-on-a-Chip–From Point of Care to Precision Medicine)

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15 pages, 1308 KiB

Open AccessArticle

Centralized Duplicate Removal Video Storage System with Privacy Preservation in IoT

by Hongyang Yan¹, Xuan Li^2,*, Yu Wang³ and Chunfu Jia¹

¹ College of Computer and Control Engineering, Nankai University, Tianjin 300071, China

² College of Mathematics and Informatics, Fujian Normal University, Fuzhou 350117, China

³ School of Computer Science, Guangzhou University, Guangzhou 510006, China

Sensors 2018, 18(6), 1814; https://doi.org/10.3390/s18061814 - 4 Jun 2018

Cited by 49 | Viewed by 5315

Abstract

In recent years, the Internet of Things (IoT) has found wide application and attracted much attention. Since most of the end-terminals in IoT have limited capabilities for storage and computing, it has become a trend to outsource the data from local to cloud [...] Read more.

In recent years, the Internet of Things (IoT) has found wide application and attracted much attention. Since most of the end-terminals in IoT have limited capabilities for storage and computing, it has become a trend to outsource the data from local to cloud computing. To further reduce the communication bandwidth and storage space, data deduplication has been widely adopted to eliminate the redundant data. However, since data collected in IoT are sensitive and closely related to users’ personal information, the privacy protection of users’ information becomes a challenge. As the channels, like the wireless channels between the terminals and the cloud servers in IoT, are public and the cloud servers are not fully trusted, data have to be encrypted before being uploaded to the cloud. However, encryption makes the performance of deduplication by the cloud server difficult because the ciphertext will be different even if the underlying plaintext is identical. In this paper, we build a centralized privacy-preserving duplicate removal storage system, which supports both file-level and block-level deduplication. In order to avoid the leakage of statistical information of data, Intel Software Guard Extensions (SGX) technology is utilized to protect the deduplication process on the cloud server. The results of the experimental analysis demonstrate that the new scheme can significantly improve the deduplication efficiency and enhance the security. It is envisioned that the duplicated removal system with privacy preservation will be of great use in the centralized storage environment of IoT. Full article

(This article belongs to the Special Issue Threat Identification and Defence for Internet-of-Things)

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20 pages, 882 KiB

Open AccessArticle

Sparse Method for Direction of Arrival Estimation Using Denoised Fourth-Order Cumulants Vector

by Yangyu Fan, Jianshu Wang^*

, Rui Du and Guoyun Lv

School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710129, China

Sensors 2018, 18(6), 1815; https://doi.org/10.3390/s18061815 - 4 Jun 2018

Cited by 10 | Viewed by 3239

Abstract

Fourth-order cumulants (FOCs) vector-based direction of arrival (DOA) estimation methods of non-Gaussian sources may suffer from poor performance for limited snapshots or difficulty in setting parameters. In this paper, a novel FOCs vector-based sparse DOA estimation method is proposed. Firstly, by utilizing the [...] Read more.

Fourth-order cumulants (FOCs) vector-based direction of arrival (DOA) estimation methods of non-Gaussian sources may suffer from poor performance for limited snapshots or difficulty in setting parameters. In this paper, a novel FOCs vector-based sparse DOA estimation method is proposed. Firstly, by utilizing the concept of a fourth-order difference co-array (FODCA), an advanced FOCs vector denoising or dimension reduction procedure is presented for arbitrary array geometries. Then, a novel single measurement vector (SMV) model is established by the denoised FOCs vector, and efficiently solved by an off-grid sparse Bayesian inference (OGSBI) method. The estimation errors of FOCs are integrated in the SMV model, and are approximately estimated in a simple way. A necessary condition regarding the number of identifiable sources of our method is presented that, in order to uniquely identify all sources, the number of sources K must fulfill

K \leq (M^{4} - 2 M^{3} + 7 M^{2} - 6 M) / 8

. The proposed method suits any geometry, does not need prior knowledge of the number of sources, is insensitive to associated parameters, and has maximum identifiability

O (M^{4})

, where M is the number of sensors in the array. Numerical simulations illustrate the superior performance of the proposed method. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 18303 KiB

Open AccessArticle

Real-Time Monitoring for BDS Signal-In-Space Anomalies Using Ground Observation Data

by Hu Jiang^1,2

, Haitao Wang^2,*, Zemin Wang¹ and Yunbin Yuan²

¹ Chinese Antarctic Center of Surveying and Mapping, Wuhan University, Wuhan 430079, China

² State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China

Sensors 2018, 18(6), 1816; https://doi.org/10.3390/s18061816 - 4 Jun 2018

Cited by 11 | Viewed by 3898

Abstract

Signal-in-space (SIS) User Range Error (URE) is one of the major error sources for BeiDou Navigation Satellite System (BDS) applications and can reach tens of meters or even more. Therefore, real-time monitoring of SIS anomalies has a great realistic significance to guarantee the [...] Read more.

Signal-in-space (SIS) User Range Error (URE) is one of the major error sources for BeiDou Navigation Satellite System (BDS) applications and can reach tens of meters or even more. Therefore, real-time monitoring of SIS anomalies has a great realistic significance to guarantee the safety of users. According to an analysis of the BDS navigation messages, it showed that the User Range Accuracy (URA) index could not reflect the change of URE when it was abnormal. The conventional models using the relationship between URA and URE to monitor SIS anomalies are not suitable to the present BDS. Therefore, we use a prior information of SIS URE derived from ground observational data instead of URA to monitor BDS SIS anomalies. In order to realize the corresponding functions, we analysed the distribution of SIS UREs and obtained their prior models. Then, the monitoring threshold is determined using the prior models and a confidence interval instead of URA. The scheme was tested by applying to BDS SIS anomalies monitoring based on 13 ground tracking stations. The performance of this method was assessed by comparison with the satellite-health indicators from broadcast ephemeris. The results confirm that the method developed in this paper can rightly and timely detect abnormal SIS. Full article

(This article belongs to the Special Issue GNSS and Fusion with Other Sensors)

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32 pages, 8814 KiB

Open AccessArticle

Dynamics and Embedded Internet of Things Input Shaping Control for Overhead Cranes Transporting Multibody Payloads

by Gerardo Peláez^1,*,†, Joshua Vaugan^2,†, Pablo Izquierdo^1,†, Higinio Rubio^3,†

and Juan Carlos García-Prada^3,†

¹ Department of Mechanical Engineering, Universidade de Vigo, 36310 Pontevedra, Spain

² Department of Mechanical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504, USA

³ Department of Mechanical Engineering, Universidad Carlos III de Madrid, 28903 Madrid, Spain

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1817; https://doi.org/10.3390/s18061817 - 4 Jun 2018

Cited by 13 | Viewed by 4885

Abstract

Input shaping is an Optimal Control feedforward strategy whose ability to define how and when a flexible dynamical system defined by Ordinary Differential Equations (ODEs) and computer controlled would move into its operative space, without command induced unwanted dynamics, has been exhaustively demonstrated. [...] Read more.

Input shaping is an Optimal Control feedforward strategy whose ability to define how and when a flexible dynamical system defined by Ordinary Differential Equations (ODEs) and computer controlled would move into its operative space, without command induced unwanted dynamics, has been exhaustively demonstrated. This work examines the issue of Embedded Internet of Things (IoT) Input Shaping with regard to real time control of multibody oscillatory systems whose dynamics are better described by differential algebraic equations (DAEs). An overhead crane hanging a double link multibody payload has been appointed as a benchmark case; it is a multibody, multimode system. This might be worst scenario to implement Input Shaping. The reasons can be found in the wide array of constraints that arise. Firstly, the reliability of the multibody model was tested on a Functional Mock-Up Interface (FMI) with the two link payload suspended from the trolley by comparing the experimental video tapping signals in time domain faced with the signals extracted from the multibody model. The FFTs of the simulated and the experimental signal contain the same frequency harmonics only with somewhat different power due to the real world light damping in the joints. The application of this approach may be extended to other cases i.e., the usefulness of mobile hydraulic cranes is limited because the payload is supported by an overhead cable under tension that allows oscillation to occur during crane motion. If the payload size is not negligible small when compared with the cable length may introduce an additional oscillatory mode that creates a multibody double pendulum. To give the insight into the double pendulum dynamics by Lagrangian methods two slender rods as payloads are analyzed dealing with the overhead crane and a composite revolute-revolute joint is proposed to model the cable of the hydraulic crane, both assumptions facilitates an affordable analysis. This allows developing a general study of this type of multibody payloads dynamics including its normal modes, modes ratios plus ranges of frequencies expected. Input Shapers were calculated for those multimodes of vibration by convolving Specified Insensitivity (SI) shapers for each mode plus a novel Direct SI-SI shaper well suited to reduce the computational requirements, i.e., the number of the shaper taps, to carry out the convolution sum in real time by the IoT device based on a single microcontroller working as the command generator. Several comparisons are presented for the shaped and unshaped responses using both the multibody model, the experimental FMI set-up and finally a real world hydraulic crane under slewing motion commanded by an analog Joystick connected by two RF modules 802.15.4 to the IoT device that carry out the convolution sum in real time. Input Shaping improves the performances for all the cases. Full article

(This article belongs to the Section Internet of Things)

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19 pages, 800 KiB

Open AccessArticle

Sequence-Based Indoor Localization with Channel Status Information

by Zhongqiu Wang, Ying Chen^*

and Hai Wang

School of Computer Science and Technology, China University of Mining and Technology, Xuzhou 221116, China

Sensors 2018, 18(6), 1818; https://doi.org/10.3390/s18061818 - 4 Jun 2018

Cited by 10 | Viewed by 3172

Abstract

Most of the indoor localization systems nowadays are based on received signal strength indication (RSSI), which has further increased the importance of precise localization of access points (AP) in a wireless local area network (WLAN). Since most existing AP localization algorithms suffer from [...] Read more.

Most of the indoor localization systems nowadays are based on received signal strength indication (RSSI), which has further increased the importance of precise localization of access points (AP) in a wireless local area network (WLAN). Since most existing AP localization algorithms suffer from a high error rate in practical scenarios due to multipath fading and temporal dynamics, we propose an AP localization algorithm based on the channel status information (CSI) sequence-based localization (SBL-CSI). The proposed algorithm SBL-CSI is an efficient localization method that consists of the following three major steps: Firstly, a 2D localization space is divided by special APs into distinct regions, and each region has a unique location sequence that represents the distance ranks of special APs to that region and constructs the location sequence table. Then, the relative distance of the ordinary AP, served in the location sequence, is obtained by using CSI between the ordinary AP and special AP. Finally, the “nearest” feasible sequence of the ordinary AP in the location sequence table is searched, and the centroid of the corresponding region is the ordinary AP’s localization. Compared with the traditional localization algorithm based on RSSI, the experiment results demonstrate that the positioning accuracy is improved approximately 24.31%. Full article

(This article belongs to the Section Sensor Networks)

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13 pages, 2667 KiB

Open AccessArticle

Sensor Design Optimization for Ultrasonic Spectroscopy Cure Monitoring

by Christian Pommer^*

and Michael Sinapius

Institut for Adaptronics and Function Integration, Technische Universität Braunschweig, Langer Kamp 6, 38106 Braunschweig, Germany

Sensors 2018, 18(6), 1819; https://doi.org/10.3390/s18061819 - 4 Jun 2018

Cited by 1 | Viewed by 2960

Abstract

In the field of cure monitoring, resonant ultrasonic cure monitoring is a unique technique to measure the progression of cure of composites in fully or partially closed tools. It allows for the use of electronic hardware that is less sophisticated than traditional pulse-based [...] Read more.

In the field of cure monitoring, resonant ultrasonic cure monitoring is a unique technique to measure the progression of cure of composites in fully or partially closed tools. It allows for the use of electronic hardware that is less sophisticated than traditional pulse-based ultrasonic systems to obtain accurate results. While this technique is not new, it has been used very rarely. One reason for this is the lack of optimized sensors. Commercially available sensors are optimized for pulse-based ultrasonic testing. This paper establishes a possible optimized sensor design for resonant ultrasound cure monitoring using a multi-parameter FE model. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 3513 KiB

Open AccessArticle

Humanoid Identification of Fabric Material Properties by Vibration Spectrum Analysis

by Shuyang Ding, Yunlu Pan^*

and Xuezeng Zhao

Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Ministry of Education and School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China

Sensors 2018, 18(6), 1820; https://doi.org/10.3390/s18061820 - 5 Jun 2018

Cited by 5 | Viewed by 6750

Abstract

In daily contexts, fabrics embodied in garments are in contact with human body all the time. Since fabric material properties—such as softness or fineness—can be easily sensed by human fingertips, fabric materials can be roughly identified by fingertip sliding. Identification by simply touching [...] Read more.

In daily contexts, fabrics embodied in garments are in contact with human body all the time. Since fabric material properties—such as softness or fineness—can be easily sensed by human fingertips, fabric materials can be roughly identified by fingertip sliding. Identification by simply touching and sliding is convenient and fast, although the room for error is always very large. In this study, a highly discernible fabric humanoid identification method with a fingertip structure inspired tactile sensor is designed to investigate the fabric material properties by characterizing the power spectrum integral of vibration signal basing on fast Fourier transform integral S(FFT), which is generated from a steel ball probe rubbing against a fabric surface at an increasing sliding velocity and normal load, respectively. kv and kw are defined as the slope values to identify the fabric surface roughness and hardness. A sample of 21 pieces of fabric categorized by yarn weight, weave pattern, and material were tested by this method. It was proved that the proposed humanoid sensing method has more efficient compared with fingertip sliding while it is also much more accurate for fabric material identification. Our study would be discussed in light of textile design and has a great number of potential applications in humanoid tactile perception technology. Full article

(This article belongs to the Special Issue I3S 2018 Selected Papers)

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13 pages, 2586 KiB

Open AccessArticle

Functionalized Fiber End Superstructure Fiber Bragg Grating Refractive Index Sensor for Heavy Metal Ion Detection

by Rex Xiao Tan^1,*

, Stephanie Hui Kit Yap¹

, Yung Chuen Tan², Swee Chuan Tjin¹, Morten Ibsen³, Ken Tye Yong¹ and Wenn Jing Lai²

¹ School of EEE, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore

² Temasek Laboratories@NTU, 50 Nanyang Avenue, Research Techno Plaza, Singapore 637553, Singapore

³ Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK

Sensors 2018, 18(6), 1821; https://doi.org/10.3390/s18061821 - 5 Jun 2018

Cited by 23 | Viewed by 5452

Abstract

We present a novel superstructure fiber Bragg grating fiber end sensor capable of detecting variations in refractive index (RI) of liquids and potentially that of gases, and demonstrated an application in the detection of heavy metal ions in water. The sensor is capable [...] Read more.

We present a novel superstructure fiber Bragg grating fiber end sensor capable of detecting variations in refractive index (RI) of liquids and potentially that of gases, and demonstrated an application in the detection of heavy metal ions in water. The sensor is capable of sensing RI variations in the range of 1.333 to 1.470 with good sensitivity of up to 230 dB/RIU achieved for the RI range of 1.370 to 1.390. The sensor is capable of simultaneously measuring variations in ambient temperature along with RI. A simple chemical coating was employed as a chelating agent for heavy metal ion detection at the fiber end to demonstrate an possible application of the sensor. The coated fiber sensor can conclusively detect the presence of heavy metal ions with concentrations upwards of 100 ppm. RI sensing capability of the sensor is neither affected by temperature nor strain and is both robust and easily reproducible. Full article

(This article belongs to the Special Issue Advanced Sensors for the Detection of Heavy Metals)

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17 pages, 7534 KiB

Open AccessArticle

Suitability of Inexpensive Eye-Tracking Device for User Experience Evaluations

by Gregor Burger^*, Jože Guna

and Matevž Pogačnik

Faculty of Electrical Engineering, University of Ljubljana, 1000 Ljubljana, Slovenia

Sensors 2018, 18(6), 1822; https://doi.org/10.3390/s18061822 - 5 Jun 2018

Cited by 14 | Viewed by 4330

Abstract

We present the results of a study evaluating the suitability of an inexpensive eye-tracking device for the enhancement of user experience evaluations. Ensuring a comfortable user experience is an important part of the mobile application design process. Evaluation of user experience is usually [...] Read more.

We present the results of a study evaluating the suitability of an inexpensive eye-tracking device for the enhancement of user experience evaluations. Ensuring a comfortable user experience is an important part of the mobile application design process. Evaluation of user experience is usually done through questionnaires and interviews, but it can be improved using eye tracking sensors for user experience studies. We conducted a user experience study of DriveGreen, a mobile application devoted to ecodriving for a transition to a low-carbon society. We used an inexpensive eye-tracking device in addition to standard User Experience Questionnaire and Single Ease Question questionnaires. The results show that the inexpensive eye-tracking device data correlate with data from User Experience Questionnaire and Single Ease Question questionnaires and interviews with users. We conclude that an enhancement of user experience evaluations with inexpensive eye-tracking device is possible. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 18033 KiB

Open AccessArticle

Molecular Assembly of a Durable HRP-AuNPs/PEDOT:BSA/Pt Biosensor with Detailed Characterizations

by Fangcheng Xu^1,†, Shuaibin Ren^1,2,†, Jiansin Li², Xiang Bi² and Yesong Gu^2,*

¹ Department of Chemical and Biochemical Engineering, Xiamen University, Xiamen 361005, China

² Department of Chemical and Materials Engineering, Tunghai University, Taichung 407, Taiwan

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1823; https://doi.org/10.3390/s18061823 - 5 Jun 2018

Cited by 17 | Viewed by 3885

Abstract

In this study, we provided the detailed characterizations of our recent HRP-AuNPs/PEDOT:BSA/Pt biosensor, constructed through a simple fabrication procedure with improved stability and good sensitivity. Raman and Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy not only confirmed the synthesis of conductive PEDOT [...] Read more.

In this study, we provided the detailed characterizations of our recent HRP-AuNPs/PEDOT:BSA/Pt biosensor, constructed through a simple fabrication procedure with improved stability and good sensitivity. Raman and Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy not only confirmed the synthesis of conductive PEDOT where BSA was the template for the polymerization, but also provided further insights into the stable immobilization of AuNP on the PEDOT:BSA film. Scanning electron microscopy revealed that the attachment of AuNPs were stable under a high salt environment. The current technology demonstrates a feasible procedure to form a functional AuNPs/PEDOT:BSA film that has potential applications in the fabrication of various biosensors and electric devices. Full article

(This article belongs to the Special Issue Development of Enzymatic Electrochemical Biosensors and Applications)

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18 pages, 5904 KiB

Open AccessArticle

Distributed Systematic Network Coding for Reliable Content Uploading in Wireless Multimedia Sensor Networks

by Phuc Chau¹

, Jitae Shin^1,*

and Jaehoon (Paul) Jeong²

¹ School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon 16419, Korea

² Department of Interaction Science, Sungkyunkwan University, Suwon 16419, Korea

Sensors 2018, 18(6), 1824; https://doi.org/10.3390/s18061824 - 5 Jun 2018

Cited by 3 | Viewed by 3046

Abstract

Recently, the wireless sensor network paradigm is shifting toward research aimed at enabling the robust delivery of multimedia content. A challenge is to deliver multimedia content with predefined levels of Quality of Service (QoS) under resource constraints such as bandwidth, energy, and delay. [...] Read more.

Recently, the wireless sensor network paradigm is shifting toward research aimed at enabling the robust delivery of multimedia content. A challenge is to deliver multimedia content with predefined levels of Quality of Service (QoS) under resource constraints such as bandwidth, energy, and delay. In this paper, we propose a distributed systematic network coding (DSNC) scheme for reliable multimedia content uploading over wireless multimedia sensor networks, in which a large number of multimedia sensor nodes upload their own content to a sink through a cluster head node. The design objective is to increase the reliability and bandwidth-efficient utilization in uploading with low decoding complexity. The proposed scheme consists of two phases: in the first phase, each sensor node distributedly encodes the content into systematic network coding packets and transmits them to the cluster head; then in the second phase, the cluster head encodes all successfully decoded incoming packets from multiple sensor nodes into innovative systematic network coding packets and transmits them to the sink. A bandwidth-efficient and channel-aware error control algorithm is proposed to enhance the bandwidth-efficient utilization by dynamically determining the optimal number of innovative coded packets. For performance analysis and evaluation, we firstly derive the closed-form equations of decoding probability to validate the effectiveness of the proposed uploading scheme. Furthermore, we perform various simulations along with a discussion in terms of three performance metrics: decoding probability, redundancy, and image quality measurement. The analytical and experimental results demonstrate that the performance of our proposed DSNC outperforms the existing uploading schemes. Full article

(This article belongs to the Section Sensor Networks)

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10 pages, 2754 KiB

Open AccessFeature PaperArticle

Optical Fiber-Tip Sensors Based on In-Situ µ-Printed Polymer Suspended-Microbeams

by Mian Yao^1,2, Xia Ouyang²

, Jushuai Wu², A. Ping Zhang^2,*, Hwa-Yaw Tam² and P. K. A. Wai¹

¹ Photonics Research Centre, Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Hong Kong, China

² Photonics Research Centre, Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong, China

Sensors 2018, 18(6), 1825; https://doi.org/10.3390/s18061825 - 5 Jun 2018

Cited by 26 | Viewed by 6472

Abstract

Miniature optical fiber-tip sensors based on directly µ-printed polymer suspended-microbeams are presented. With an in-house optical 3D μ-printing technology, SU-8 suspended-microbeams are fabricated in situ to form Fabry–Pérot (FP) micro-interferometers on the end face of standard single-mode optical fiber. Optical reflection spectra of [...] Read more.

Miniature optical fiber-tip sensors based on directly µ-printed polymer suspended-microbeams are presented. With an in-house optical 3D μ-printing technology, SU-8 suspended-microbeams are fabricated in situ to form Fabry–Pérot (FP) micro-interferometers on the end face of standard single-mode optical fiber. Optical reflection spectra of the fabricated FP micro-interferometers are measured and fast Fourier transform is applied to analyze the cavity of micro-interferometers. The applications of the optical fiber-tip sensors for refractive index (RI) sensing and pressure sensing, which showed 917.3 nm/RIU to RI change and 4.29 nm/MPa to pressure change, respectively, are demonstrated in the experiments. The sensors and their optical µ-printing method unveil a new strategy to integrate complicated microcomponents on optical fibers toward ‘lab-on-fiber’ devices and 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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21 pages, 1504 KiB

Open AccessArticle

Joint Cache Content Placement and Task Offloading in C-RAN Enabled by Multi-Layer MEC

by Haibo Mei^1,*, Kezhi Wang² and Kun Yang^1,3

¹ School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China

² Department of Computer and Information Sciences, Northumbria University, Newcastle upon Tyne NE2 1XE, UK

³ School of Computer Sciences and Electrical Engineering, University of Essex, Colchester CO4 3SQ, UK

Sensors 2018, 18(6), 1826; https://doi.org/10.3390/s18061826 - 5 Jun 2018

Cited by 14 | Viewed by 4205

Abstract

In this paper, we work on a Cache and Multi-layer MEC enabled C-RAN (CMM-CRAN) to handle various user tasks with minimized latency and energy cost. We intend to solve two particular problems of CMM-CRAN. First, because CMM-CRAN has to maximally cache the most [...] Read more.

In this paper, we work on a Cache and Multi-layer MEC enabled C-RAN (CMM-CRAN) to handle various user tasks with minimized latency and energy cost. We intend to solve two particular problems of CMM-CRAN. First, because CMM-CRAN has to maximally cache the most frequently requested data from Service Provide Server (SPS) to Remote Radio Head (RRH) and later offered to proximity mobile users, the cache content placement from SPSs to RRHs becomes a many-to-many matching problem with peer effects. Second, because of multi-layer MEC, a user task has to be dynamically controlled to be offloaded to the best fit cloud, i.e., either local MEC or remote MEC, to get served. This dynamic task offloading is a Multi-Dimension Multiple-Choice Knapsack (MMCK) problem. To solve these two problems, we provide a Joint Cache content placement and task Offloading Solution (JCOS) to CMM-CRAN that utilizes Proportional Fairness (PF) as the user scheduling policy. JCOS applies a Gale-Shaply (GS) method to work out the cache content placement, and a Population Evolution (PE) game theory coupled with a use of Analytic Hierarchy Process(AHP) to work out the dynamic user task offloading. According to the simulation results, CMM-CRAN with JCOS is proved to be able to provide highly desired low-latency communication and computation services with decreased energy cost to mobile users. Full article

(This article belongs to the Special Issue Advanced Technologies on Green Radio Networks)

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16 pages, 3746 KiB

Open AccessArticle

Improvement of Information Transfer Rates Using a Hybrid EEG-NIRS Brain-Computer Interface with a Short Trial Length: Offline and Pseudo-Online Analyses

by Jaeyoung Shin^1,†

, Do-Won Kim^2,†, Klaus-Robert Müller^3,4,5,* and Han-Jeong Hwang^6,*

¹ Department of Biomedical Engineering, Hanyang University, Seoul 04763, Korea

² Department of Biomedical Engineering, Chonnam National University, Yeosu 59626, Korea

³ Machine Learning Group, Berlin Institute of Technology (TU Berlin), 10623 Berlin, Germany

⁴ Department of Brain and Cognitive Engineering, Korea University, Seoul 02841, Korea

⁵ Max Planck Institute for Informatics, Stuhlsatzenhausweg, Saarbrücken 66123, Germany

⁶ Department of Medical IT Convergence Engineering, Kumoh National Institute of Technology, Gumi 39177, Korea

^† These authors contributed equally to this study.

Sensors 2018, 18(6), 1827; https://doi.org/10.3390/s18061827 - 5 Jun 2018

Cited by 29 | Viewed by 5181

Abstract

Electroencephalography (EEG) and near-infrared spectroscopy (NIRS) are non-invasive neuroimaging methods that record the electrical and metabolic activity of the brain, respectively. Hybrid EEG-NIRS brain-computer interfaces (hBCIs) that use complementary EEG and NIRS information to enhance BCI performance have recently emerged to overcome the [...] Read more.

Electroencephalography (EEG) and near-infrared spectroscopy (NIRS) are non-invasive neuroimaging methods that record the electrical and metabolic activity of the brain, respectively. Hybrid EEG-NIRS brain-computer interfaces (hBCIs) that use complementary EEG and NIRS information to enhance BCI performance have recently emerged to overcome the limitations of existing unimodal BCIs, such as vulnerability to motion artifacts for EEG-BCI or low temporal resolution for NIRS-BCI. However, with respect to NIRS-BCI, in order to fully induce a task-related brain activation, a relatively long trial length (≥10 s) is selected owing to the inherent hemodynamic delay that lowers the information transfer rate (ITR; bits/min). To alleviate the ITR degradation, we propose a more practical hBCI operated by intuitive mental tasks, such as mental arithmetic (MA) and word chain (WC) tasks, performed within a short trial length (5 s). In addition, the suitability of the WC as a BCI task was assessed, which has so far rarely been used in the BCI field. In this experiment, EEG and NIRS data were simultaneously recorded while participants performed MA and WC tasks without preliminary training and remained relaxed (baseline; BL). Each task was performed for 5 s, which was a shorter time than previous hBCI studies. Subsequently, a classification was performed to discriminate MA-related or WC-related brain activations from BL-related activations. By using hBCI in the offline/pseudo-online analyses, average classification accuracies of 90.0 ± 7.1/85.5 ± 8.1% and 85.8 ± 8.6/79.5 ± 13.4% for MA vs. BL and WC vs. BL, respectively, were achieved. These were significantly higher than those of the unimodal EEG- or NIRS-BCI in most cases. Given the short trial length and improved classification accuracy, the average ITRs were improved by more than 96.6% for MA vs. BL and 87.1% for WC vs. BL, respectively, compared to those reported in previous studies. The suitability of implementing a more practical hBCI based on intuitive mental tasks without preliminary training and with a shorter trial length was validated when compared to previous studies. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 14263 KiB

Open AccessArticle

An Efficient Neural-Network-Based Microseismic Monitoring Platform for Hydraulic Fracture on an Edge Computing Architecture

by Xiaopu Zhang^1,2, Jun Lin^1,2, Zubin Chen^1,2, Feng Sun^1,2,3,*, Xi Zhu³ and Gengfa Fang³

¹ College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130061, China

² Key Laboratory of Geophysical Exploration Equipment, Ministry of Education, Jilin University, Changchun 130061, China

³ School of Electrical and Data Engineering, University of Technology Sydney, Sydney, NSW 2007, Australia

Sensors 2018, 18(6), 1828; https://doi.org/10.3390/s18061828 - 5 Jun 2018

Cited by 20 | Viewed by 6494

Abstract

Microseismic monitoring is one of the most critical technologies for hydraulic fracturing in oil and gas production. To detect events in an accurate and efficient way, there are two major challenges. One challenge is how to achieve high accuracy due to a poor [...] Read more.

Microseismic monitoring is one of the most critical technologies for hydraulic fracturing in oil and gas production. To detect events in an accurate and efficient way, there are two major challenges. One challenge is how to achieve high accuracy due to a poor signal-to-noise ratio (SNR). The other one is concerned with real-time data transmission. Taking these challenges into consideration, an edge-computing-based platform, namely Edge-to-Center LearnReduce, is presented in this work. The platform consists of a data center with many edge components. At the data center, a neural network model combined with convolutional neural network (CNN) and long short-term memory (LSTM) is designed and this model is trained by using previously obtained data. Once the model is fully trained, it is sent to edge components for events detection and data reduction. At each edge component, a probabilistic inference is added to the neural network model to improve its accuracy. Finally, the reduced data is delivered to the data center. Based on experiment results, a high detection accuracy (over 96%) with less transmitted data (about 90%) was achieved by using the proposed approach on a microseismic monitoring system. These results show that the platform can simultaneously improve the accuracy and efficiency of microseismic monitoring. Full article

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

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21 pages, 22593 KiB

Open AccessArticle

Enabling Autonomous Navigation for Affordable Scooters

by Kaikai Liu^*

and Rajathswaroop Mulky

Computer Engineering, San Jose State University, San Jose, CA 95123, USA

Sensors 2018, 18(6), 1829; https://doi.org/10.3390/s18061829 - 5 Jun 2018

Cited by 8 | Viewed by 5719

Abstract

Despite the technical success of existing assistive technologies, for example, electric wheelchairs and scooters, they are still far from effective enough in helping those in need navigate to their destinations in a hassle-free manner. In this paper, we propose to improve the safety [...] Read more.

Despite the technical success of existing assistive technologies, for example, electric wheelchairs and scooters, they are still far from effective enough in helping those in need navigate to their destinations in a hassle-free manner. In this paper, we propose to improve the safety and autonomy of navigation by designing a cutting-edge autonomous scooter, thus allowing people with mobility challenges to ambulate independently and safely in possibly unfamiliar surroundings. We focus on indoor navigation scenarios for the autonomous scooter where the current location, maps, and nearby obstacles are unknown. To achieve semi-LiDAR functionality, we leverage the gyros-based pose data to compensate the laser motion in real time and create synthetic mapping of simple environments with regular shapes and deep hallways. Laser range finders are suitable for long ranges with limited resolution. Stereo vision, on the other hand, provides 3D structural data of nearby complex objects. To achieve simultaneous fine-grained resolution and long range coverage in the mapping of cluttered and complex environments, we dynamically fuse the measurements from the stereo vision camera system, the synthetic laser scanner, and the LiDAR. We propose solutions to self-correct errors in data fusion and create a hybrid map to assist the scooter in achieving collision-free navigation in an indoor environment. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 4219 KiB

Open AccessArticle

Ultrasonic Phased Array Sparse-TFM Imaging Based on Sparse Array Optimization and New Edge-Directed Interpolation

by Hongwei Hu¹, Jian Du¹, Chengbao Ye¹ and Xiongbing Li^2,*

¹ College of Automotive and Mechanical Engineering, Changsha University of Science and Technology, Changsha 410114, China

² School of Traffic and Transportation Engineering, Central South University, Changsha 410075, China

Sensors 2018, 18(6), 1830; https://doi.org/10.3390/s18061830 - 5 Jun 2018

Cited by 28 | Viewed by 6427

Abstract

The ultrasonic phased array total focusing method (TFM) has the advantages of full-range dynamic focusing and high imaging resolution, but the problem of long imaging time limits its practically industrial applications. To reduce the imaging calculation demand of TFM, the locations of active [...] Read more.

The ultrasonic phased array total focusing method (TFM) has the advantages of full-range dynamic focusing and high imaging resolution, but the problem of long imaging time limits its practically industrial applications. To reduce the imaging calculation demand of TFM, the locations of active array elements in the sparse array are optimized by combining almost different sets with the genetic algorithm (ADSGA), and corrected based on the consistency of the effective aperture with the equivalent point diffusion function. At the same time, to further increase the imaging efficiency, a sparse-TFM image with lower resolution is obtained by reducing the number of focus points and then interpolated by the new edge-directed interpolation algorithm (NEDI) to obtain a high quality sparse-TFM image. Compared with TFM, the experimental results show that the quantitative accuracy of the proposed method is only decreased by 1.09% when the number of sparse transmitting elements reaches 8 for a 32-element transducer, and the imaging speed is improved by about 16 times with the same final pixel resolution. Full article

(This article belongs to the Special Issue Intelligent Sensing Technologies for Nondestructive Evaluation 2018)

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14 pages, 4014 KiB

Open AccessArticle

Electrical and Thermal Properties of Heater-Sensor Microsystems Patterned in TCO Films for Wide-Range Temperature Applications from 15 K to 350 K

by Ryszard Pawlak^* and Marcin Lebioda

Institute of Electrical Engineering Systems, Lodz University of Technology, Lodz 90-924, Poland

Sensors 2018, 18(6), 1831; https://doi.org/10.3390/s18061831 - 5 Jun 2018

Cited by 11 | Viewed by 6358

Abstract

This paper presents an analysis of the electrical and thermal properties of miniature transparent heaters for use in a wide range of temperature applications, from 15 K to 350 K. The heater structures were produced in transparent conducting oxide (TCO) layers: indium tin [...] Read more.

This paper presents an analysis of the electrical and thermal properties of miniature transparent heaters for use in a wide range of temperature applications, from 15 K to 350 K. The heater structures were produced in transparent conducting oxide (TCO) layers: indium tin oxide (ITO) and ITO/Ag/ITO on polymer substrates-polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), by direct laser patterning. Thermo-resistors for temperature measurement were created in the same process, with geometry corresponding to the shape of the heating path. The thermo-resistors integrated with the heating structure allowed easy control of the thermal state of the heaters. Laser patterning provided high precision and repeatability in terms of the geometry and electrical properties of the heater-sensor structures. Measurements at temperatures from 15 K to above room temperature (350 K) confirmed the excellent dynamics of the heating and cooling processes, due to current flow. The largest value for surface heating power was over 3 W/cm². A heater-sensor structure equipped with a small capacity chamber was successfully applied for controlled heating of small volumes of different liquids. Such structures have potential for use in research and measurements, where for various reasons controlled and accurate heating of small volumes of liquids is required. Full article

(This article belongs to the Special Issue Temperature Sensors)

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8 pages, 2117 KiB

Open AccessArticle

Design and Fabrication of Full Wheatstone-Bridge-Based Angular GMR Sensors

by Shaohua Yan¹, Zhiqiang Cao², Zongxia Guo², Zhenyi Zheng¹, Anni Cao¹, Yue Qi³, Qunwen Leng^2,4,* and Weisheng Zhao^1,2,*

¹ Fert Beijing Institute, BDBC, School of Electronic and Information Engineering, Beihang University, Beijing 100191, China

² Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao 266000, China

³ State Key Laboratory of Virtual Reality Technology and Systems, Beihang University, Beijing 100191, China

⁴ Goertek Inc., Weifang 261031, China

Sensors 2018, 18(6), 1832; https://doi.org/10.3390/s18061832 - 5 Jun 2018

Cited by 33 | Viewed by 8136

Abstract

Since the discovery of the giant magnetoresistive (GMR) effect, GMR sensors have gained much attention in last decades due to their high sensitivity, small size, and low cost. The full Wheatstone-bridge-based GMR sensor is most useful in terms of the application point of [...] Read more.

Since the discovery of the giant magnetoresistive (GMR) effect, GMR sensors have gained much attention in last decades due to their high sensitivity, small size, and low cost. The full Wheatstone-bridge-based GMR sensor is most useful in terms of the application point of view. However, its manufacturing process is usually complex. In this paper, we present an efficient and concise approach to fabricate a full Wheatstone-bridge-based angular GMR sensor by depositing one GMR film stack, utilizing simple patterned processes, and a concise post-annealing procedure based on a special layout. The angular GMR sensor is of good linear performance and achieves a sensitivity of 0.112 mV/V/Oe at the annealing temperature of 260 °C in the magnetic field range from −50 to +50 Oe. This work provides a design and method for GMR-sensor manufacturing that is easy for implementation and suitable for mass production. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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18 pages, 805 KiB

Open AccessArticle

Enhancing LoRaWAN Security through a Lightweight and Authenticated Key Management Approach

by Ramon Sanchez-Iborra^1,*

, Jesús Sánchez-Gómez¹

, Salvador Pérez¹

, Pedro J. Fernández¹

, José Santa¹

, José L. Hernández-Ramos^1,2

and Antonio F. Skarmeta¹

¹ Department of Information and Communications Engineering, University of Murcia, 30100 Murcia, Spain

² European Commission, Joint Research Centre, 21027 Ispra, Italy

Sensors 2018, 18(6), 1833; https://doi.org/10.3390/s18061833 - 5 Jun 2018

Cited by 71 | Viewed by 8454

Abstract

Luckily, new communication technologies and protocols are nowadays designed considering security issues. A clear example of this can be found in the Internet of Things (IoT) field, a quite recent area where communication technologies such as ZigBee or IPv6 over Low power Wireless [...] Read more.

Luckily, new communication technologies and protocols are nowadays designed considering security issues. A clear example of this can be found in the Internet of Things (IoT) field, a quite recent area where communication technologies such as ZigBee or IPv6 over Low power Wireless Personal Area Networks (6LoWPAN) already include security features to guarantee authentication, confidentiality and integrity. More recent technologies are Low-Power Wide-Area Networks (LP-WAN), which also consider security, but present initial approaches that can be further improved. An example of this can be found in Long Range (LoRa) and its layer-two supporter LoRa Wide Area Network (LoRaWAN), which include a security scheme based on pre-shared cryptographic material lacking flexibility when a key update is necessary. Because of this, in this work, we evaluate the security vulnerabilities of LoRaWAN in the area of key management and propose different alternative schemes. Concretely, the application of an approach based on the recently specified Ephemeral Diffie–Hellman Over COSE (EDHOC) is found as a convenient solution, given its flexibility in the update of session keys, its low computational cost and the limited message exchanges needed. A comparative conceptual analysis considering the overhead of different security schemes for LoRaWAN is carried out in order to evaluate their benefits in the challenging area of LP-WAN. Full article

(This article belongs to the Special Issue Security, Trust and Privacy for Sensor Networks)

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11 pages, 2097 KiB

Open AccessArticle

Research on Strain Measurements of Core Positions for the Chinese Space Station

by Jingshi Shen^1,2, Xiaodong Zeng¹, Yuxiang Luo², Changqing Cao^1,* and Ting Wang¹

¹ School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China

² Shandong Institute of Space Electronic Technology, Yantai 264670, China

Sensors 2018, 18(6), 1834; https://doi.org/10.3390/s18061834 - 5 Jun 2018

Cited by 14 | Viewed by 4606

Abstract

The Chinese space station is designed to carry out manned spaceflight, space science research, and so on. In serious applications, it is a common operation to inject gas into the hull, which can produce strain of the bulkhead. Accurate measurement of strain for [...] Read more.

The Chinese space station is designed to carry out manned spaceflight, space science research, and so on. In serious applications, it is a common operation to inject gas into the hull, which can produce strain of the bulkhead. Accurate measurement of strain for the bulkhead is one of the key tasks in evaluating the health condition of the space station. This is the first work to perform strain detection for the Chinese space station bulkhead by using optical fiber Bragg grating. In the period of measurements, the resistance strain gauge is used as the strain standard. The measurement error of the fiber optical sensor in the circumferential direction is very small, being less than 4.52 με. However, the error in the axial direction is very large with the highest value of 28.93 με. Because the measurement error of bare fiber in the axial direction is very small, the transverse effect of the substrate of the fiber optical sensor likely plays a role. The comparison of the theoretical and experimental results of the transverse effect coefficients shows that they are fairly consistent, with values of 0.0271 and 0.0287, respectively. After the transverse effect is compensated, the strain deviation in the axial detection is smaller than 2.04 με. It is of great significance to carry out real-time health assessment for the bulkhead of the space station. Full article

(This article belongs to the Special Issue Optoelectronic and Photonic Sensors)

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13 pages, 4341 KiB

Open AccessArticle

An Evaluation System for the Contact Electrification of a Single Microparticle Using Microelectromechanical-Based Actuated Tweezers

by Daichi Yamaguchi

RICOH Company, Ltd., 810 Shimo-Imaizumi, Ebina-shi, Kanagawa 243-040, Japan

Sensors 2018, 18(6), 1835; https://doi.org/10.3390/s18061835 - 5 Jun 2018

Cited by 1 | Viewed by 3061

Abstract

The image quality of laser and multi-function printers that make use of electrophotography depends on the amount of surface charge generated by contact electrification on the toner particles. However, because it has been impossible to experimentally evaluate such amounts under controlled contact conditions [...] Read more.

The image quality of laser and multi-function printers that make use of electrophotography depends on the amount of surface charge generated by contact electrification on the toner particles. However, because it has been impossible to experimentally evaluate such amounts under controlled contact conditions using macroscopic measurements, theoretical elucidation of the contact electrification mechanism has not progressed sufficiently. In the present study, we have developed a system to experimentally evaluate the contact electrification of a single particle using atomic force microscopy (AFM) and nanotweezers (microelectromechanical systems (MEMS)-based actuated tweezers). This system performs, in succession, (i) a contact test that makes use of the nanotweezers and three piezoelectric stages, and (ii) an image force measurement using the AFM cantilever. Using this system, contact electrification was evaluated under controlled conditions, such as the contact number and the indentation depth. In addition, differences in contact electrification due to the amount of external surface additives were investigated. The results reveal that a coating with external additives leads to a decrease in the amount of contact electrification due to a reduction in the contact area with the substrate. Full article

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

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11 pages, 1837 KiB

Open AccessArticle

A Molecularly Imprinted Polymer on a Plasmonic Plastic Optical Fiber to Detect Perfluorinated Compounds in Water

by Nunzio Cennamo^1,*

, Girolamo D’Agostino², Gianni Porto², Adriano Biasiolo², Chiara Perri²

, Francesco Arcadio¹ and Luigi Zeni^1,3

¹ Department of Engineering, University of Campania “Luigi Vanvitelli”, via Roma 29, 81031 Aversa, Italy

² Copernico S.r.l., Via Monte Hermada 75, 33100 Udine, Italy

³ IREA-CNR, Via Diocleziano 328, 80124 Napoli, Italy

Sensors 2018, 18(6), 1836; https://doi.org/10.3390/s18061836 - 5 Jun 2018

Cited by 79 | Viewed by 8412

Abstract

A novel Molecularly Imprinted Polymer (MIP) able to bind perfluorinated compounds, combined with a surface plasmon resonance (SPR) optical fiber platform, is presented. The new MIP receptor has been deposited on a D-shaped plastic optical fiber (POF) covered with a photoresist buffer layer [...] Read more.

A novel Molecularly Imprinted Polymer (MIP) able to bind perfluorinated compounds, combined with a surface plasmon resonance (SPR) optical fiber platform, is presented. The new MIP receptor has been deposited on a D-shaped plastic optical fiber (POF) covered with a photoresist buffer layer and a thin gold film. The experimental results have shown that the developed SPR-POF-MIP sensor makes it possible to selectively detect the above compounds. In this work, we present the results obtained with perfluorooctanoate (PFOA) compound, and they hold true when obtained with a perfluorinated alkylated substances (PFAs) mixture sample. The sensor’s response is the same for PFOA, perfluorooctanesulfonate (PFOS) or PFA contaminants in the C₄–C₁₁ range. We have also tested a sensor based on a non-imprinted polymer (NIP) on the same SPR in a D-shaped POF platform. The limit of detection (LOD) of the developed chemical sensor was 0.13 ppb. It is similar to the one obtained by the configuration based on a specific antibody for PFOA/PFOS exploiting the same SPR-POF platform, already reported in literature. The advantage of an MIP receptor is that it presents a better stability out of the native environment, very good reproducibility, low cost and, furthermore, it can be directly deposited on the gold layer, without modifying the metal surface by functionalizing procedures. Full article

(This article belongs to the Special Issue Label-free Optical Nanobiosensors)

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20 pages, 9577 KiB

Open AccessArticle

Space Subdivision in Indoor Mobile Laser Scanning Point Clouds Based on Scanline Analysis

by Yi Zheng^1,2, Michael Peter²

, Ruofei Zhong^1,*, Sander Oude Elberink²

and Quan Zhou¹

¹ Beijing Advanced Innovation Center for Imaging Technology, College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China

² Faculty of Geo-Information Science and Earth Observation, University of Twente, P.O. Box 217, 7514 AE Enschede, The Netherlands

Sensors 2018, 18(6), 1838; https://doi.org/10.3390/s18061838 - 5 Jun 2018

Cited by 18 | Viewed by 4685

Abstract

Indoor space subdivision is an important aspect of scene analysis that provides essential information for many applications, such as indoor navigation and evacuation route planning. Until now, most proposed scene understanding algorithms have been based on whole point clouds, which has led to [...] Read more.

Indoor space subdivision is an important aspect of scene analysis that provides essential information for many applications, such as indoor navigation and evacuation route planning. Until now, most proposed scene understanding algorithms have been based on whole point clouds, which has led to complicated operations, high computational loads and low processing speed. This paper presents novel methods to efficiently extract the location of openings (e.g., doors and windows) and to subdivide space by analyzing scanlines. An opening detection method is demonstrated that analyses the local geometric regularity in scanlines to refine the extracted opening. Moreover, a space subdivision method based on the extracted openings and the scanning system trajectory is described. Finally, the opening detection and space subdivision results are saved as point cloud labels which will be used for further investigations. The method has been tested on a real dataset collected by ZEB-REVO. The experimental results validate the completeness and correctness of the proposed method for different indoor environment and scanning paths. Full article

(This article belongs to the Special Issue Indoor LiDAR/Vision Systems)

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15 pages, 1447 KiB

Open AccessArticle

Wideband Spectrum Sensing: A Bayesian Compressive Sensing Approach

by Youness Arjoune^* and Naima Kaabouch

Electrical Engineering Department, University of North Dakota, Grand Forks, ND 58202, USA

Sensors 2018, 18(6), 1839; https://doi.org/10.3390/s18061839 - 5 Jun 2018

Cited by 24 | Viewed by 4976

Abstract

Sensing the wideband spectrum is an important process for next-generation wireless communication systems. Spectrum sensing primarily aims at detecting unused spectrum holes over wide frequency bands so that secondary users can use them to meet their requirements in terms of quality-of-service. However, this [...] Read more.

Sensing the wideband spectrum is an important process for next-generation wireless communication systems. Spectrum sensing primarily aims at detecting unused spectrum holes over wide frequency bands so that secondary users can use them to meet their requirements in terms of quality-of-service. However, this sensing process requires a great deal of time, which is not acceptable for timely communications. In addition, the sensing measurements are often affected by uncertainty. In this paper, we propose an approach based on Bayesian compressive sensing to speed up the process of sensing and to handle uncertainty. This approach takes only a few measurements using a Toeplitz matrix, recovers the wideband signal from a few measurements using Bayesian compressive sensing via fast Laplace prior, and detects either the presence or absence of the primary user using an autocorrelation-based detection method. The proposed approach was implemented using GNU Radio software and Universal Software Radio Peripheral units and was tested on real-world signals. The results show that the proposed approach speeds up the sensing process by minimizing the number of samples while achieving the same performance as Nyquist-based sensing techniques regarding both the probabilities of detection and false alarm. Full article

(This article belongs to the Section Sensor Networks)

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20 pages, 663 KiB

Open AccessArticle

An Image Focusing Method for Sparsity-Driven Radar Imaging of Rotating Targets

by Ngoc Hung Nguyen^1,*

, Kutluyıl Doğançay¹

, Hai-Tan Tran² and Paul Berry²

¹ School of Engineering, University of South Australia, Mawson Lakes, SA 5095, Australia

² National Security and ISR Division, Defence Science and Technology Group, Edinburgh, SA 5111, Australia

Sensors 2018, 18(6), 1840; https://doi.org/10.3390/s18061840 - 5 Jun 2018

Cited by 10 | Viewed by 2795

Abstract

This paper presents a new image focusing algorithm for sparsity-driven radar imaging of rotating targets. In the general formulation of off-grid scatterers, the sparse reconstruction algorithms may result in blurred and low-contrast images due to dictionary mismatch. Motivated by the natural clustering of [...] Read more.

This paper presents a new image focusing algorithm for sparsity-driven radar imaging of rotating targets. In the general formulation of off-grid scatterers, the sparse reconstruction algorithms may result in blurred and low-contrast images due to dictionary mismatch. Motivated by the natural clustering of atoms in the sparsity-based reconstructed images, the proposed algorithm first partitions the atoms into separate clusters, and then the true off-grid scatterers associated with each cluster are estimated. Being a post-processing technique, the proposed algorithm is computationally simple, while at the same time being capable of producing a sharp and correct-contrast image, and attaining a scatterer parameter estimation performance close to the Cramér–Rao lower bound. Numerical simulations are presented to corroborate the effectiveness of the proposed algorithm. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 4515 KiB

Open AccessArticle

Elastic MCF Rubber with Photovoltaics and Sensing for Use as Artificial or Hybrid Skin (H-Skin): 1st Report on Dry-Type Solar Cell Rubber with Piezoelectricity for Compressive Sensing

by Kunio Shimada

Faculty of Symbiotic Systems Sciences, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan

Sensors 2018, 18(6), 1841; https://doi.org/10.3390/s18061841 - 5 Jun 2018

Cited by 12 | Viewed by 4568

Abstract

Ordinary solar cells are very difficult to bend, squash by compression, or extend by tensile strength. However, if they were to possess elastic, flexible, and extensible properties, in addition to piezo-electricity and resistivity, they could be put to effective use as artificial skin [...] Read more.

Ordinary solar cells are very difficult to bend, squash by compression, or extend by tensile strength. However, if they were to possess elastic, flexible, and extensible properties, in addition to piezo-electricity and resistivity, they could be put to effective use as artificial skin installed over human-like robots or humanoids. Further, it could serve as a husk that generates electric power from solar energy and perceives any force or temperature changes. Therefore, we propose a new type of artificial skin, called hybrid skin (H-Skin), for a humanoid robot having hybrid functions. In this study, a novel elastic solar cell is developed from natural rubber that is electrolytically polymerized with a configuration of magnetic clusters of metal particles incorporated into the rubber, by applying a magnetic field. The material thus produced is named magnetic compound fluid rubber (MCF rubber) that is elastic, flexible, and extensible. The present report deals with a dry-type MCF rubber solar cell that uses photosensitized dye molecules. First, the photovoltaic mechanism in the material is investigated. Next, the changes in the photovoltaic properties of its molecules due to irradiation by visible light are measured under compression. The effect of the compression on its piezoelectric properties is investigated. 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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11 pages, 1917 KiB

Open AccessArticle

Gas Flow to Enhance the Detection of Alpha-Induced Air Radioluminescence Based on a UVTron Flame Sensor

by Anita J. Crompton^1,*

, Kelum A. A. Gamage²

, Steven Bell³, Andrew P. Wilson⁴, Alex W. Jenkins⁵ and Divyesh Trivedi⁶

¹ Engineering Department, Lancaster University, Lancaster LA1 4YW, UK

² School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK

³ Nuclear Metrology Group, National Physical Laboratory, Teddington TW11 0LW, UK

⁴ Independent Researcher

⁵ Characterisation, Inspection & Decontamination Group, Sellafield Ltd., Cumbria CA20 1PG, UK

⁶ The National Nuclear Laboratory, Warrington WA3 6AE, UK

Sensors 2018, 18(6), 1842; https://doi.org/10.3390/s18061842 - 5 Jun 2018

Cited by 14 | Viewed by 3981

Abstract

In many field applications where alpha-induced radioluminescence (or so-called UV fluorescence) could potentially be used for stand-off detection of alpha-emitting materials, it may not be possible to create a fully purged gas atmosphere. Hence, an alternative gas delivery method to utilise the radioluminescence [...] Read more.

In many field applications where alpha-induced radioluminescence (or so-called UV fluorescence) could potentially be used for stand-off detection of alpha-emitting materials, it may not be possible to create a fully purged gas atmosphere. Hence, an alternative gas delivery method to utilise the radioluminescence enhancing properties of gases has been investigated, with the novel results from this presented herewithin. A solar blind ultraviolet C (UVC) sensor (UVTron R9533, Hamamatsu, Japan) has been used to detect changes in the signal in the UVC wavelength range (180–280 nm), where gases of Ar, Xe, Ne, N₂, Kr, and P-10 were flowed over a 6.95 MBq ²¹⁰Po source using a narrow diameter pipe close to the source. In comparison with an air atmosphere, there was an increase in signal in all instances, the greatest being the flow of Xe, which in one instance greater than doubled the average counts per second. This increase in signal could prove beneficial in the design of a stand-off alpha detector to detect the very small UVC radioluminescence signals from alpha-emitting materials found in nuclear decommissioning environments. Full article

(This article belongs to the Section Chemical Sensors)

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24 pages, 899 KiB

Open AccessArticle

Performance Evaluation of Relay Selection Schemes in Beacon-Assisted Dual-Hop Cognitive Radio Wireless Sensor Networks under Impact of Hardware Noises

by Tran Dinh Hieu^1,†

, Tran Trung Duy²

, Le The Dung^1,†

and Seong Gon Choi^1,*,†

¹ Department of Radio and Communication Engineering, Chungbuk National University, Cheongju City 362763, Korea

² Posts Department of Telecommunications, Posts and Telecommunications Institute of Technology, Ho Chi Minh City 70000, Vietnam

^† Current address: Room 618, Building E-10, Chungbuk National University, Chungbuk 28644, Korea.

^‡ All the authors contributed equally to this work.

Sensors 2018, 18(6), 1843; https://doi.org/10.3390/s18061843 - 5 Jun 2018

Cited by 29 | Viewed by 4428

Abstract

To solve the problem of energy constraints and spectrum scarcity for cognitive radio wireless sensor networks (CR-WSNs), an underlay decode-and-forward relaying scheme is considered, where the energy constrained secondary source and relay nodes are capable of harvesting energy from a multi-antenna power beacon [...] Read more.

To solve the problem of energy constraints and spectrum scarcity for cognitive radio wireless sensor networks (CR-WSNs), an underlay decode-and-forward relaying scheme is considered, where the energy constrained secondary source and relay nodes are capable of harvesting energy from a multi-antenna power beacon (PB) and using that harvested energy to forward the source information to the destination. Based on the time switching receiver architecture, three relaying protocols, namely, hybrid partial relay selection (H-PRS), conventional opportunistic relay selection (C-ORS), and best opportunistic relay selection (B-ORS) protocols are considered to enhance the end-to-end performance under the joint impact of maximal interference constraint and transceiver hardware impairments. For performance evaluation and comparison, we derive the exact and asymptotic closed-form expressions of outage probability (OP) and throughput (TP) to provide significant insights into the impact of our proposed protocols on the system performance over Rayleigh fading channel. Finally, simulation results validate the theoretical results. Full article

(This article belongs to the Section Sensor Networks)

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22 pages, 2700 KiB

Open AccessArticle

A Correlation Driven Approach with Edge Services for Predictive Industrial Maintenance

by Meiling Zhu^1,2,3,* and Chen Liu^2,3

¹ School of Computer Science and Technology, Tianjin University, Tianjin 300350, China

² Beijing Key Laboratory on Integration and Analysis of Large-Scale Stream Data, North China University of Technology, Beijing 100144, China

³ Institute of Data Engineering, North China University of Technology, Beijing 100144, China

Sensors 2018, 18(6), 1844; https://doi.org/10.3390/s18061844 - 5 Jun 2018

Cited by 10 | Viewed by 3693

Abstract

Predictive industrial maintenance promotes proactive scheduling of maintenance to minimize unexpected device anomalies/faults. Almost all current predictive industrial maintenance techniques construct a model based on prior knowledge or data at build-time. However, anomalies/faults will propagate among sensors and devices along correlations hidden among [...] Read more.

Predictive industrial maintenance promotes proactive scheduling of maintenance to minimize unexpected device anomalies/faults. Almost all current predictive industrial maintenance techniques construct a model based on prior knowledge or data at build-time. However, anomalies/faults will propagate among sensors and devices along correlations hidden among sensors. These correlations can facilitate maintenance. This paper makes an attempt on predicting the anomaly/fault propagation to perform predictive industrial maintenance by considering the correlations among faults. The main challenge is that an anomaly/fault may propagate in multiple ways owing to various correlations. This is called as the uncertainty of anomaly/fault propagation. This present paper proposes a correlation-based event routing approach for predictive industrial maintenance by improving our previous works. Our previous works mapped physical sensors into a soft-ware-defined abstraction, called proactive data service. In the service model, anomalies/faults are encapsulated into events. We also proposed a service hyperlink model to encapsulate the correlations among anomalies/faults. This paper maps the anomalies/faults propagation into event routing and proposes a heuristic algorithm based on service hyperlinks to route events among services. The experiment results show that, our approach can reach 100% precision and 88.89% recall at most. Full article

(This article belongs to the Special Issue Internet of Things and Ubiquitous Sensing)

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13 pages, 668 KiB

Open AccessArticle

Directional Paging for 5G Communications Based on Partitioned User ID

by Mamta Agiwal and Hu Jin^*

Department of Electrical and Electronics Engineering, Hanyang University, Ansan 15588, Korea

Sensors 2018, 18(6), 1845; https://doi.org/10.3390/s18061845 - 5 Jun 2018

Cited by 15 | Viewed by 6798

Abstract

The millimeter-wave (mmWave) spectrum is one of the important propositions of 5G mobile networks due to its ability to accommodate massive traffic demands and an ever-increasing number of wireless devices. The beam-formed directional technique overcomes the propagation and path loss challenges of mmWave [...] Read more.

The millimeter-wave (mmWave) spectrum is one of the important propositions of 5G mobile networks due to its ability to accommodate massive traffic demands and an ever-increasing number of wireless devices. The beam-formed directional technique overcomes the propagation and path loss challenges of mmWave high frequencies. Though the directional convergence is expected to unleash new possibilities, it cannot be implemented with conventional power-saving solutions optimized over omnidirectional communications. Paging broadcast, for users in Idle Discontinuous Reception (IDRX) mode for energy saving, is one such necessary function in a wireless communication that needs modification in highly directional beam-based transmissions. Due to the limited spatial coverage of directional beams, the paging transmission takes place over multiple beams, which increases the paging resource overheads of the network substantially. In this article, we present a novel paging mechanism for the directional air interface in mmWave-enabled 5G communications. Numerical analysis of the proposed Partitioned UE ID-based Directional Paging (PIDP) mechanism reduces the paging resource overheads of the network, resulting in a

15 %

gain in power savings compared to directional paging transmission without the UE ID partition. Full article

(This article belongs to the Special Issue Advanced Technologies on Green Radio Networks)

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14 pages, 3536 KiB

Open AccessArticle

A Novel Strategy for Improving the Aeromagnetic Compensation Performance of Helicopters

by Luzhao Chen^1,2,*, Peilin Wu^1,2

, Wanhua Zhu^1,3, Yongqiang Feng^1,2,3 and Guangyou Fang^1,3

¹ Key Laboratory of Electromagnetic Radiation and Sensing Technology, Chinese Academy of Sciences, Beijing 100190, China

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

³ Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

Sensors 2018, 18(6), 1846; https://doi.org/10.3390/s18061846 - 6 Jun 2018

Cited by 16 | Viewed by 4483

Abstract

An aeromagnetic survey is an important method in magnetic anomaly detection and geophysical prospecting. The magnetic field is typically measured by optically pumped magnetometers (OPM) installed on the aircraft. The measurement accuracy of the OPM is easily affected by the platform-generated magnetic fields. [...] Read more.

An aeromagnetic survey is an important method in magnetic anomaly detection and geophysical prospecting. The magnetic field is typically measured by optically pumped magnetometers (OPM) installed on the aircraft. The measurement accuracy of the OPM is easily affected by the platform-generated magnetic fields. Therefore, aeromagnetic compensation is necessary. The traditional compensation model only considers the permanent, induced, and eddy current interference magnetic field of the aircraft platform. However, the interference field produced by the avionics system, and the relative motion between the aircraft and the magnetometer, are still not taken into account. To address this issue, we proposed a novel strategy to eliminate the additional interference of the platform with two OPMs. Among them, the OPM located farther away from the aircraft serves as a sensing magnetometer, whereas the near OPM serves as a reference magnetometer. The coherent noise suppression method is used to process the residual magnetic field interference after compensation. By establishing the interference magnetic transfer function between the two sensors, the interference field can be suppressed. The results of the experiments demonstrate the effectiveness of the novel strategy, and the standard deviation of residual interference drops from 0.065 nT to 0.045 nT. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 3682 KiB

Open AccessArticle

Detecting and Monitoring the Flavor of Tomato (Solanum lycopersicum) under the Impact of Postharvest Handlings by Physicochemical Parameters and Electronic Nose

by Sai Xu^1,4, Xiuxiu Sun³, Huazhong Lu^2,4,*, Hui Yang¹, Qingsong Ruan⁴, Hao Huang⁴ and Minglin Chen⁴

¹ Public Monitoring Center for Agro-Product of Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China

² Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China

³ Indian River Research and Education Center, University of Florida, Ft. Pierce, FL 34845, USA

⁴ College of Engineering, South China Agricultural University, Guangzhou 510640, China

Sensors 2018, 18(6), 1847; https://doi.org/10.3390/s18061847 - 6 Jun 2018

Cited by 35 | Viewed by 4940

Abstract

The objective of this study was to detect and monitor the flavor of tomatoes, as impacted by different postharvest handlings, including chilling storage (CS) and blanching treatment (BT). CS tomatoes were stored in a refrigerator at 5 °C and tested at storage day [...] Read more.

The objective of this study was to detect and monitor the flavor of tomatoes, as impacted by different postharvest handlings, including chilling storage (CS) and blanching treatment (BT). CS tomatoes were stored in a refrigerator at 5 °C and tested at storage day 0, 3, and 7. BT tomatoes were dipped in 50 or 100 °C water for 1 min, and tested immediately. The taste, mouth feel, and aroma of tomatoes were evaluated by testing the total soluble solid content (TSS), titratable acidity (TA), ratio of TSS and TA (TSS/TA), firmness, and electronic nose (E-nose) response to tomatoes. The experimental results showed that the CS can prevent taste and firmness loss to a certain extent, but the sensory results indicated that CS accelerated flavor loss due to the TSS/TA of CS tomatoes increasing slower than control. The taste and firmness of tomatoes were impacted slightly by 50 °C BT, and were significantly impacted by 100 °C BT. Based on physicochemical parameters, different postharvest handling treatments for tomatoes could not be classified except for the 100 °C BT treated tomatoes, which were significantly impacted in terms of taste and mouth feel. The E-nose is an efficient way to detect differences in postharvest handling treatments for tomatoes, and indicated significant aroma changes for CS and BT treated tomato fruit. The classification of tomatoes after different postharvest handling treatments, based on comprehensive flavor (physicochemical parameters and E-nose combined data), is better than that based on single physicochemical parameters or E-nose, and the comprehensive flavor of 100 °C BT tomatoes changed the most. Even so, the tomato flavor change during postharvest handlings is suggested to be detected and monitored by single E-nose data. The E-nose has also been proved as a feasible way to predict the TSS and firmness of tomato fruit rather than TA or TSS/TA, during the postharvest handing process. Full article

(This article belongs to the Special Issue Sensors in Agriculture 2018)

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23 pages, 12379 KiB

Open AccessArticle

Elastic MCF Rubber with Photovoltaics and Sensing on Hybrid Skin (H-Skin) for Artificial Skin by Utilizing Natural Rubber: 2nd Report on the Effect of Tension and Compression on the Hybrid Photo- and Piezo-Electricity Properties in Wet-Type Solar Cell Rubber

by Kunio Shimada

Faculty of Symbiotic Systems Sciences, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan

Sensors 2018, 18(6), 1848; https://doi.org/10.3390/s18061848 - 6 Jun 2018

Cited by 8 | Viewed by 3828

Abstract

In contrast to ordinary solid-state solar cells, a flexible, elastic, extensible and light-weight solar cell has the potential to be extremely useful in many new engineering applications, such as in the field of robotics. Therefore, we propose a new type of artificial skin [...] Read more.

In contrast to ordinary solid-state solar cells, a flexible, elastic, extensible and light-weight solar cell has the potential to be extremely useful in many new engineering applications, such as in the field of robotics. Therefore, we propose a new type of artificial skin for humanoid robots with hybrid functions, which we have termed hybrid skin (H-Skin). To realize the fabrication of such a solar cell, we have continued to utilize the principles of ordinary solid-state wet-type or dye-sensitized solar rubber as a follow-up study to the first report. In the first report, we dealt with both photovoltaic- and piezo-effects for dry-type magnetic compound fluid (MCF) rubber solar cells, which were generated because the polyisoprene, oleic acid of the magnetic fluid (MF), and water served as p- and n- semiconductors. In the present report, we deal with wet-type MCF rubber solar cells by using sensitized dyes and electrolytes. Photoreactions generated through the synthesis of these components were investigated by an experiment using irradiation with visible and ultraviolet light. In addition, magnetic clusters were formed by the aggregation of Fe₃O₄ in the MF and the metal particles created the hetero-junction structure of the semiconductors. In the MCF rubber solar cell, both photo- and piezo-electricity were generated using a physical model. The effects of tension and compression on their electrical properties were evaluated. Finally, we experimentally demonstrated the effect of the distance between the electrodes of the solar cell on photoelectricity and built-in electricity. 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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20 pages, 3904 KiB

Open AccessArticle

Depletion-of-Battery Attack: Specificity, Modelling and Analysis

by Vladimir Shakhov¹ and Insoo Koo^2,*

¹ Automobile/Ship Electronics Convergence Center, University of Ulsan, Ulsan 680-749, Korea

² The School of Electrical Engineering, University of Ulsan, Ulsan 680-749, Korea

Sensors 2018, 18(6), 1849; https://doi.org/10.3390/s18061849 - 6 Jun 2018

Cited by 38 | Viewed by 5445

Abstract

The emerging Internet of Things (IoT) has great potential; however, the societal costs of the IoT can outweigh its benefits. To unlock IoT potential, there needs to be improvement in the security of IoT applications. There are several standardization initiatives for sensor networks, [...] Read more.

The emerging Internet of Things (IoT) has great potential; however, the societal costs of the IoT can outweigh its benefits. To unlock IoT potential, there needs to be improvement in the security of IoT applications. There are several standardization initiatives for sensor networks, which eventually converge with the Internet of Things. As sensor-based applications are deployed, security emerges as an essential requirement. One of the critical issues of wireless sensor technology is limited sensor resources, including sensor batteries. This creates a vulnerability to battery-exhausting attacks. Rapid exhaustion of sensor battery power is not only explained by intrusions, but can also be due to random failure of embedded sensor protocols. Thus, most wireless sensor applications, without tools to defend against rash battery exhausting, would be unable to function during prescribed times. In this paper, we consider a special type of threat, in which the harm is malicious depletion of sensor battery power. In contrast to the traditional denial-of-service attack, quality of service under the considered attack is not necessarily degraded. Moreover, the quality of service can increase up to the moment of the sensor set crashes. We argue that this is a distinguishing type of attack. Hence, the application of a traditional defense mechanism against this threat is not always possible. Therefore, effective methods should be developed to counter the threat. We first discuss the feasibility of rash depletion of battery power. Next, we propose a model for evaluation of energy consumption when under attack. Finally, a technique to counter the attack is discussed. Full article

(This article belongs to the Special Issue Security in IoT Enabled Sensors)

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17 pages, 1341 KiB

Open AccessArticle

A User-Adaptive Algorithm for Activity Recognition Based on K-Means Clustering, Local Outlier Factor, and Multivariate Gaussian Distribution

by Shizhen Zhao, Wenfeng Li^* and Jingjing Cao

School of Logistics Engineering, Wuhan University of Technology, Wuhan 430070, China

Sensors 2018, 18(6), 1850; https://doi.org/10.3390/s18061850 - 6 Jun 2018

Cited by 55 | Viewed by 6078

Abstract

Mobile activity recognition is significant to the development of human-centric pervasive applications including elderly care, personalized recommendations, etc. Nevertheless, the distribution of inertial sensor data can be influenced to a great extent by varying users. This means that the performance of an activity [...] Read more.

Mobile activity recognition is significant to the development of human-centric pervasive applications including elderly care, personalized recommendations, etc. Nevertheless, the distribution of inertial sensor data can be influenced to a great extent by varying users. This means that the performance of an activity recognition classifier trained by one user’s dataset will degenerate when transferred to others. In this study, we focus on building a personalized classifier to detect four categories of human activities: light intensity activity, moderate intensity activity, vigorous intensity activity, and fall. In order to solve the problem caused by different distributions of inertial sensor signals, a user-adaptive algorithm based on K-Means clustering, local outlier factor (LOF), and multivariate Gaussian distribution (MGD) is proposed. To automatically cluster and annotate a specific user’s activity data, an improved K-Means algorithm with a novel initialization method is designed. By quantifying the samples’ informative degree in a labeled individual dataset, the most profitable samples can be selected for activity recognition model adaption. Through experiments, we conclude that our proposed models can adapt to new users with good recognition performance. Full article

(This article belongs to the Special Issue Wearable and Ambient Sensors for Healthcare and Wellness Applications 2018)

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18 pages, 1265 KiB

Open AccessArticle

Wearable Sensors Integrated with Internet of Things for Advancing eHealth Care

by Jose-Luis Bayo-Monton^1,*

, Antonio Martinez-Millana¹

, Weisi Han², Carlos Fernandez-Llatas^1,3

, Yan Sun²

and Vicente Traver^1,3

¹ Instituto Universitario de Investigación de Aplicaciones de las Tecnologías de la Información y de las Comunicaciones Avanzadas (ITACA), Universitat Politècnica de València, Camino de Vera S/N, Valencia 46022, Spain

² School of Electronic Engineering and Computer Science, Queen Mary University of London, London E1 4NS, UK

³ Unidad Mixta de Reingeniería de Procesos Sociosanitarios (eRPSS), Instituto de Investigación Sanitaria del Hospital Universitario y Politecnico La Fe, Bulevar Sur S/N, Valencia 46026, Spain

Sensors 2018, 18(6), 1851; https://doi.org/10.3390/s18061851 - 6 Jun 2018

Cited by 81 | Viewed by 9989

Abstract

Health and sociological indicators alert that life expectancy is increasing, hence so are the years that patients have to live with chronic diseases and co-morbidities. With the advancement in ICT, new tools and paradigms are been explored to provide effective and efficient health [...] Read more.

Health and sociological indicators alert that life expectancy is increasing, hence so are the years that patients have to live with chronic diseases and co-morbidities. With the advancement in ICT, new tools and paradigms are been explored to provide effective and efficient health care. Telemedicine and health sensors stand as indispensable tools for promoting patient engagement, self-management of diseases and assist doctors to remotely follow up patients. In this paper, we evaluate a rapid prototyping solution for information merging based on five health sensors and two low-cost ubiquitous computing components: Arduino and Raspberry Pi. Our study, which is entirely described with the purpose of reproducibility, aimed to evaluate the extent to which portable technologies are capable of integrating wearable sensors by comparing two deployment scenarios: Raspberry Pi 3 and Personal Computer. The integration is implemented using a choreography engine to transmit data from sensors to a display unit using web services and a simple communication protocol with two modes of data retrieval. Performance of the two set-ups is compared by means of the latency in the wearable data transmission and data loss. PC has a delay of 0.051 ± 0.0035 s (max = 0.2504 s), whereas the Raspberry Pi yields a delay of 0.0175 ± 0.149 s (max = 0.294 s) for N = 300. Our analysis confirms that portable devices (

p < < 0.01

) are suitable to support the transmission and analysis of biometric signals into scalable telemedicine systems. Full article

(This article belongs to the Special Issue Data Analytics and Applications of the Wearable Sensors in Healthcare)

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11 pages, 3097 KiB

Open AccessArticle

A Non-Destructive and Direction-Insensitive Method Using a Strain Sensor and Two Single Axis Angle Sensors for Evaluating Corn Stalk Lodging Resistance

by Qingqian Guo^1,2, Ruipeng Chen¹, Xiaoquan Sun³, Min Jiang⁴, Haifeng Sun¹, Shun Wang¹, Liuzheng Ma¹, Yatao Yang¹ and Jiandong Hu^1,2,*

¹ Collage of Mechanical and Electrical Engineering, Henan Agricultural University, Zhengzhou 450002, China

² State Key Laboratory of Wheat and Maize Crop Science, Zhengzhou 450002, China

³ Henan Institute of Metrology, Zhengzhou 450008, China

⁴ College of Life Sciences, Henan Agricultural University, Zhengzhou 450002, China

Sensors 2018, 18(6), 1852; https://doi.org/10.3390/s18061852 - 6 Jun 2018

Cited by 15 | Viewed by 4021

Abstract

Corn stalk lodging is caused by different factors, including severe wind storms, stalk cannibalization, and stalk rots, and it leads to yield loss. Determining how to rapidly evaluate corn lodging resistance will assist scientists in the field of crop breeding to understand the [...] Read more.

Corn stalk lodging is caused by different factors, including severe wind storms, stalk cannibalization, and stalk rots, and it leads to yield loss. Determining how to rapidly evaluate corn lodging resistance will assist scientists in the field of crop breeding to understand the contributing factors in managing the moisture, chemical fertilizer, and weather conditions for corn growing. This study proposes a non-destructive and direction-insensitive method, using a strain sensor and two single axis angle sensors to measure the corn stalk lodging resistance in the field. An equivalent force whose direction is perpendicular to the stalk is utilized to evaluate the corn lodging properties when a pull force is applied on the corn stalk. A novel measurement device is designed to obtain the equivalent force with the coefficient of variation (CV) of 4.85%. Five corn varieties with two different planting densities are arranged to conduct the experiment using the novel measurement device. The experimental results show that the maximum equivalent force could reach up to 44 N. A strong relationship with the square of the correlation coefficient of 0.88 was obtained between the maximum equivalent forces and the corn field’s stalk lodging rates. Moreover, the stalk lodging angles corresponding to the different pull forces over a measurement time of 20 s shift monotonically along the equivalent forces. Thus, the non-destructive and direction-insensitive method is an excellent tool for rapid analysis of stalk lodging resistance in corn, providing critical information on in-situ lodging dynamics. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 7422 KiB

Open AccessArticle

Elastic MCF Rubber with Photovoltaics and Sensing on Hybrid Skin (H-Skin) for Artificial Skin by Utilizing Natural Rubber: Third Report on Electric Charge and Storage under Tension and Compression

by Kunio Shimada

Faculty of Symbiotic Systems Sciences, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan

Sensors 2018, 18(6), 1853; https://doi.org/10.3390/s18061853 - 6 Jun 2018

Cited by 5 | Viewed by 3601

Abstract

In the series of studies on new types of elastic and compressible artificial skins with hybrid sensing functions, photovoltaics, and battery, we have proposed a hybrid skin (H-Skin) by utilizing an electrolytically polymerized magnetic compound fluid (MCF) made of natural rubber latex (NR-latex). [...] Read more.

In the series of studies on new types of elastic and compressible artificial skins with hybrid sensing functions, photovoltaics, and battery, we have proposed a hybrid skin (H-Skin) by utilizing an electrolytically polymerized magnetic compound fluid (MCF) made of natural rubber latex (NR-latex). By using the experimental results in the first and second reports, we have clarified the feasibility of electric charge at irradiation, and that without illumination under compression and elongation. The former was explained in a wet-type MCF rubber solar cell by developing a tunneling theory together with an equivalent electric circuit model. The latter corresponds to the battery rather than to the solar cell. As for the MCF rubber battery, depending on the selected agent type, we can make the MCF rubber have higher electricity and lighter weight. Therefore, the MCF rubber has an electric charge and storage whether at irradiation or not. 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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17 pages, 1744 KiB

Open AccessArticle

Comparative Study of the Dual Layer Magnet Array in a Moving-Coil Tubular Linear PM Motor

by Liang Yan^*, Lu Zhang, Lei Peng and Zongxia Jiao

School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China

Sensors 2018, 18(6), 1854; https://doi.org/10.3390/s18061854 - 6 Jun 2018

Cited by 2 | Viewed by 4549

Abstract

Conventional single-layer magnet arrays are widely utilized in electromagnetic linear machines. The objective of this paper is to analyze various types of novel dual-layer magnet arrays, either in similar or different patterns, to compare their flux field distribution and increase flux density in [...] Read more.

Conventional single-layer magnet arrays are widely utilized in electromagnetic linear machines. The objective of this paper is to analyze various types of novel dual-layer magnet arrays, either in similar or different patterns, to compare their flux field distribution and increase flux density in the machine. High flux density helps to improve the sensitivity of electromagnetic displacement sensors or actuator thrust. The design concept of magnet arrays are presented. The machine space is divided into several regions according to the magnetic properties. The corresponding magnetic field distribution is formulated based on magnetic vector potential and Laplace’s equations. Numerical computation is conducted to validate the developed magnetic field model. A systematic comparison of magnetic field of various magnet arrays is carried out. It shows that the dual Halbach magnet array can generate relatively high and constant flux density, which may help to produce strong signals. A research prototype and an experimental testbed are developed to validate the analytical model of dual Halbach array. This study provides a general framework for the design and analysis of dual-layer magnet arrays with various magnetization patterns. It can be extended to multiple-layer designs in radial direction. Full article

(This article belongs to the Special Issue Mechatronic Systems for Automatic Vehicles)

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19 pages, 3398 KiB

Open AccessArticle

A Self-Organizing Spatial Clustering Approach to Support Large-Scale Network RTK Systems

by Lili Shen¹, Jiming Guo^1,*

and Lei Wang^2,*

¹ School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China

² State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China

Sensors 2018, 18(6), 1855; https://doi.org/10.3390/s18061855 - 6 Jun 2018

Cited by 3 | Viewed by 3538

Abstract

The network real-time kinematic (RTK) technique can provide centimeter-level real time positioning solutions and play a key role in geo-spatial infrastructure. With ever-increasing popularity, network RTK systems will face issues in the support of large numbers of concurrent users. In the past, high-precision [...] Read more.

The network real-time kinematic (RTK) technique can provide centimeter-level real time positioning solutions and play a key role in geo-spatial infrastructure. With ever-increasing popularity, network RTK systems will face issues in the support of large numbers of concurrent users. In the past, high-precision positioning services were oriented towards professionals and only supported a few concurrent users. Currently, precise positioning provides a spatial foundation for artificial intelligence (AI), and countless smart devices (autonomous cars, unmanned aerial-vehicles (UAVs), robotic equipment, etc.) require precise positioning services. Therefore, the development of approaches to support large-scale network RTK systems is urgent. In this study, we proposed a self-organizing spatial clustering (SOSC) approach which automatically clusters online users to reduce the computational load on the network RTK system server side. The experimental results indicate that both the SOSC algorithm and the grid algorithm can reduce the computational load efficiently, while the SOSC algorithm gives a more elastic and adaptive clustering solution with different datasets. The SOSC algorithm determines the cluster number and the mean distance to cluster center (MDTCC) according to the data set, while the grid approaches are all predefined. The side-effects of clustering algorithms on the user side are analyzed with real global navigation satellite system (GNSS) data sets. The experimental results indicate that 10 km can be safely used as the cluster radius threshold for the SOSC algorithm without significantly reducing the positioning precision and reliability on the user side. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 8198 KiB

Open AccessArticle

Virtual Deformable Image Sensors: Towards to a General Framework for Image Sensors with Flexible Grids and Forms

by Wei Wen

and Siamak Khatibi^*

Blekinge Institute of Technology, 37179 Karlskrona, Sweden

Sensors 2018, 18(6), 1856; https://doi.org/10.3390/s18061856 - 6 Jun 2018

Cited by 4 | Viewed by 3800

Abstract

Our vision system has a combination of different sensor arrangements from hexagonal to elliptical ones. Inspired from this variation in type of arrangements we propose a general framework by which it becomes feasible to create virtual deformable sensor arrangements. In the framework for [...] Read more.

Our vision system has a combination of different sensor arrangements from hexagonal to elliptical ones. Inspired from this variation in type of arrangements we propose a general framework by which it becomes feasible to create virtual deformable sensor arrangements. In the framework for a certain sensor arrangement a configuration of three optional variables are used which includes the structure of arrangement, the pixel form and the gap factor. We show that the histogram of gradient orientations of a certain sensor arrangement has a specific distribution (called ANCHOR) which is obtained by using at least two generated images of the configuration. The results showed that ANCHORs change their patterns by the change of arrangement structure. In this relation pixel size changes have 10-fold more impact on ANCHORs than gap factor changes. A set of 23 images; randomly chosen from a database of 1805 images, are used in the evaluation where each image generates twenty-five different images based on the sensor configuration. The robustness of ANCHORs properties is verified by computing ANCHORs for totally 575 images with different sensor configurations. We believe by using the framework and ANCHOR it becomes feasible to plan a sensor arrangement in the relation to a specific application and its requirements where the sensor arrangement can be planed even as combination of different ANCHORs. Full article

(This article belongs to the Special Issue Image Sensors)

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15 pages, 3146 KiB

Open AccessArticle

One-Step Laser Patterned Highly Uniform Reduced Graphene Oxide Thin Films for Circuit-Enabled Tattoo and Flexible Humidity Sensor Application

by Rowoon Park^1,†, Hyesu Kim^1,†, Saifullah Lone^1,†, Sangheon Jeon¹, Young Woo Kwon², Bosung Shin^1,* and Suck Won Hong^1,*

¹ Department of Cogno-Mechatronics Engineering, Department of Optics and Mechatronics Engineering, College of Nanoscience and Nanotechnology, Pusan National University, Busan 46241, Korea

² Department of Nano-Fusion Technology, College of Nanoscience and Nanotechnology, Pusan National University, Busan 46241, Korea

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1857; https://doi.org/10.3390/s18061857 - 6 Jun 2018

Cited by 42 | Viewed by 9752

Abstract

The conversion of graphene oxide (GO) into reduced graphene oxide (rGO) is imperative for the electronic device applications of graphene-based materials. Efficient and cost-effective fabrication of highly uniform GO films and the successive reduction into rGO on a large area is still a [...] Read more.

The conversion of graphene oxide (GO) into reduced graphene oxide (rGO) is imperative for the electronic device applications of graphene-based materials. Efficient and cost-effective fabrication of highly uniform GO films and the successive reduction into rGO on a large area is still a cumbersome task through conventional protocols. Improved film casting of GO sheets on a polymeric substrate with quick and green reduction processes has a potential that may establish a path to the practical flexible electronics. Herein, we report a facile deposition process of GO on flexible polymer substrates to create highly uniform thin films over a large area by a flow-enabled self-assembly approach. The self-assembly of GO sheets was successfully performed by dragging the trapped solution of GO in confined geometry, which consisted of an upper stationary blade and a lower moving substrate on a motorized translational stage. The prepared GO thin films could be selectively reduced and facilitated from the simple laser direct writing process for programmable circuit printing with the desired configuration and less sample damage due to the non-contact mode operation without the use of photolithography, toxic chemistry, or high-temperature reduction methods. Furthermore, two different modes of the laser operating system for the reduction of GO films turned out to be valuable for the construction of novel graphene-based high-throughput electrical circuit boards compatible with integrating electronic module chips and flexible humidity sensors. Full article

(This article belongs to the Special Issue Tattoo Sensors)

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19 pages, 3642 KiB

Open AccessArticle

Automatic Detection and Classification of Audio Events for Road Surveillance Applications

by Noor Almaadeed^1,*, Muhammad Asim¹, Somaya Al-Maadeed¹

, Ahmed Bouridane² and Azeddine Beghdadi³

¹ Department of Computer Science and Engineering, College of Engineering, Qatar University, Doha 2713, Qatar

² Department of Computer and Information Sciences, Northumbria University Newcastle, Newcastle upon Tyne NE1 8ST, UK

³ L2TI, Institut Galilée, Université Paris 13, Sorbonne Paris Cité 99, Avenue J.B. Clément, 93430 Villetaneuse, France

Sensors 2018, 18(6), 1858; https://doi.org/10.3390/s18061858 - 6 Jun 2018

Cited by 57 | Viewed by 6757

Abstract

This work investigates the problem of detecting hazardous events on roads by designing an audio surveillance system that automatically detects perilous situations such as car crashes and tire skidding. In recent years, research has shown several visual surveillance systems that have been proposed [...] Read more.

This work investigates the problem of detecting hazardous events on roads by designing an audio surveillance system that automatically detects perilous situations such as car crashes and tire skidding. In recent years, research has shown several visual surveillance systems that have been proposed for road monitoring to detect accidents with an aim to improve safety procedures in emergency cases. However, the visual information alone cannot detect certain events such as car crashes and tire skidding, especially under adverse and visually cluttered weather conditions such as snowfall, rain, and fog. Consequently, the incorporation of microphones and audio event detectors based on audio processing can significantly enhance the detection accuracy of such surveillance systems. This paper proposes to combine time-domain, frequency-domain, and joint time-frequency features extracted from a class of quadratic time-frequency distributions (QTFDs) to detect events on roads through audio analysis and processing. Experiments were carried out using a publicly available dataset. The experimental results conform the effectiveness of the proposed approach for detecting hazardous events on roads as demonstrated by 7% improvement of accuracy rate when compared against methods that use individual temporal and spectral features. Full article

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

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12 pages, 3514 KiB

Open AccessArticle

Coupling of PZT Thin Films with Bimetallic Strip Heat Engines for Thermal Energy Harvesting

by Jihane Boughaleb^1,2,3,*, Arthur Arnaud¹, Benoit Guiffard⁴

, Daniel Guyomar², Raynald Seveno⁴

, Stéphane Monfray¹, Thomas Skotnicki¹ and Pierre-Jean Cottinet²

¹ STMicroelectronics (Crolles 2) SAS, 850 Rue Jean Monnet, 38926 Crolles CEDEX, France

² Univ Lyon, INSA-Lyon, LGEF, EA682, F-69621 Villeurbanne, France

³ CEA Liten, 17 Rue des Martyrs, 38054 Grenoble CEDEX 9, France

⁴ Université Bretagne Loire, Université de Nantes, IETR UMR CNRS 6164, 44322 Nantes, France

Sensors 2018, 18(6), 1859; https://doi.org/10.3390/s18061859 - 6 Jun 2018

Cited by 3 | Viewed by 6404

Abstract

A thermal energy harvester based on a double transduction mechanism and which converts thermal energy into electrical energy by means of piezoelectric membranes and bimetals, has previously been developed and widely presented in the literature In such a device, the thermo-mechanical conversion is [...] Read more.

A thermal energy harvester based on a double transduction mechanism and which converts thermal energy into electrical energy by means of piezoelectric membranes and bimetals, has previously been developed and widely presented in the literature In such a device, the thermo-mechanical conversion is ensured by a bimetal whereas the electro-mechanical conversion is generated by a piezoelectric ceramic. However, it has been shown that only 19% of the mechanical energy delivered by the bimetal during its snap is converted into electrical energy. To extract more energy from the bimetallic strip and to increase the transduction efficiency, a new way to couple piezoelectric materials with bimetals has thus been explored through direct deposition of piezoelectric layers on bimetals. This paper consequently presents an alternative way to harvest heat, based on piezoelectric bimetallic strip heat engines and presents a proof of concept of such a system. In this light, different PZT (Lead zirconate titanate) thin films were synthesized directly on aluminium foils and were attached to the bimetals using conductive epoxy. The fabrication process of each sample is presented herein as well as the experimental tests carried out on the devices. Throughout this study, different thicknesses of the piezoelectric layers and substrates were tested to determine the most powerful configuration. Finally, the study also gives some guidelines for future improvements of piezoelectric bimetals. Full article

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

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10 pages, 1892 KiB

Open AccessArticle

Design of Sparse FIR Decision Feedback Equalizers in MIMO Systems Using Hybrid l₁/l₂ Norm Minimization and the OMP Algorithm

by Lihong Yu¹, Jiaxiang Zhao^2,*, Wei Xu³ and Haiyuan Liu²

¹ College of Computer and Control Engineering, Nankai University, Tianjin 300350, China

² Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network Technology, College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China

³ College of Electronic and Information Engineering, Tianjin Polytechnic University, Tianjin 300387, China

Sensors 2018, 18(6), 1860; https://doi.org/10.3390/s18061860 - 6 Jun 2018

Cited by 1 | Viewed by 3746

Abstract

In this paper, a novel scheme using hybrid l₁/l₂ norm minimization and the orthogonal matching pursuit (OMP) algorithm is proposed to design the sparse finite impulse response (FIR) decision feedback equalizers (DFE) in multiple input multiple output (MIMO) systems. [...] Read more.

In this paper, a novel scheme using hybrid l₁/l₂ norm minimization and the orthogonal matching pursuit (OMP) algorithm is proposed to design the sparse finite impulse response (FIR) decision feedback equalizers (DFE) in multiple input multiple output (MIMO) systems. To reduce the number of nonzero taps for the FIR DFE while ensuring its design accuracy, the problem of designing a sparse FIR DFE is transformed into an l₀ norm minimization problem, and then the proposed scheme is used to obtain the sparse solution. In the proposed scheme, a sequence of minimum weighted l₂ norm problems is solved using the OMP algorithm. The nonzero taps positions can be corrected with the different weights in the diagonal weighting matrix which is computed through the hybrid l₁/l₂ norm minimization. The simulation results verify that the sparse FIR MIMO DFEs designed by the proposed scheme get a significant reduction in the number of nonzero taps with a small performance loss compared to the non-sparse optimum DFE under the minimum mean square error (MMSE) criterion. In addition, the proposed scheme provides better design accuracy than the OMP algorithm with the same sparsity level. Full article

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

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16 pages, 2277 KiB

Open AccessArticle

Two-Dimensional DOA Estimation for Three-Parallel Nested Subarrays via Sparse Representation

by Weijian Si, Zhanli Peng, Changbo Hou^* and Fuhong Zeng

College of Information and Communication Engineering, Harbin Engineering University, No. 145 Nantong Street, Harbin 150001, China

Sensors 2018, 18(6), 1861; https://doi.org/10.3390/s18061861 - 7 Jun 2018

Cited by 20 | Viewed by 3236

Abstract

Nested arrays are considered attractive due to their hole-free performance, and have the ability to resolve

O (N^{2})

sources with

O (N)

physical sensors. Inspired by nested arrays, two kinds of three-parallel nested subarrays (TPNAs), which are composed [...] Read more.

Nested arrays are considered attractive due to their hole-free performance, and have the ability to resolve

O (N^{2})

sources with

O (N)

physical sensors. Inspired by nested arrays, two kinds of three-parallel nested subarrays (TPNAs), which are composed of three parallel sparse linear subarrays with different inter-element spacings, are proposed for two-dimensional (2-D) direction-of-arrival (DOA) estimation in this paper. We construct two cross-correlation matrices and combine them as one augmented matrix in the first step. Then, by vectorizing the augmented matrix, a hole-free difference coarray with larger degrees of freedom (DOFs) is achieved. Meanwhile, sparse representation and the total least squares technique are presented to transform the problem of 2-D DOA searching into 1-D searching. Accordingly, we can obtain the paired 2-D angles automatically and improve the 2-D DOA estimation performance. In addition, we derive closed form expressions of sensor positions, as well as number of sensors for different subarrays of two kinds of TPNA to maximize the DOFs. In the end, the simulation results verify the superiority of the proposed TPNAs and 2-D DOA estimation method. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 2909 KiB

Open AccessArticle

Acoustic–Seismic Mixed Feature Extraction Based on Wavelet Transform for Vehicle Classification in Wireless Sensor Networks

by Heng Zhang^*, Zhongming Pan and Wenna Zhang

College of Artificial Intelligence, National University of Defense Technology, Changsha, Hunan 410073, China

Sensors 2018, 18(6), 1862; https://doi.org/10.3390/s18061862 - 7 Jun 2018

Cited by 15 | Viewed by 3415

Abstract

An acoustic–seismic mixed feature extraction method based on the wavelet coefficient energy ratio (WCER) of the target signal is proposed in this study for classifying vehicle targets in wireless sensor networks. The signal was decomposed into a set of wavelet coefficients using the [...] Read more.

An acoustic–seismic mixed feature extraction method based on the wavelet coefficient energy ratio (WCER) of the target signal is proposed in this study for classifying vehicle targets in wireless sensor networks. The signal was decomposed into a set of wavelet coefficients using the à trous algorithm, which is a concise method used to implement the wavelet transform of a discrete signal sequence. After the wavelet coefficients of the target acoustic and seismic signals were obtained, the energy ratio of each layer coefficient was calculated as the feature vector of the target signals. Subsequently, the acoustic and seismic features were merged into an acoustic–seismic mixed feature to improve the target classification accuracy after the acoustic and seismic WCER features of the target signal were simplified using the hierarchical clustering method. We selected the support vector machine method for classification and utilized the data acquired from a real-world experiment to validate the proposed method. The calculated results show that the WCER feature extraction method can effectively extract the target features from target signals. Feature simplification can reduce the time consumption of feature extraction and classification, with no effect on the target classification accuracy. The use of acoustic–seismic mixed features effectively improved target classification accuracy by approximately 12% compared with either acoustic signal or seismic signal alone. Full article

(This article belongs to the Section Sensor Networks)

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21 pages, 13249 KiB

Open AccessArticle

New Energy Efficient Multi-Hop Routing Techniques for Wireless Sensor Networks: Static and Dynamic Techniques

by Emad Alnawafa^* and Ion Marghescu

Department of Telecommunications, University Politehnica of Bucharest, Bucharest 060042, Romania

Sensors 2018, 18(6), 1863; https://doi.org/10.3390/s18061863 - 7 Jun 2018

Cited by 62 | Viewed by 6147

Abstract

The performance of Wireless Sensor Networks (WSNs) faces a number of challenges. Of these challenges, energy consumption is considered a hot research area. Most WSN energy is used in transmitting the data from the sensor nodes either among each other or to a [...] Read more.

The performance of Wireless Sensor Networks (WSNs) faces a number of challenges. Of these challenges, energy consumption is considered a hot research area. Most WSN energy is used in transmitting the data from the sensor nodes either among each other or to a Base Station (BS). For this reason, many routing protocols have been developed to facilitate the data dissemination in the WSNs. One of these protocols, Low Energy Adaptive Clustering Hierarchy (LEACH) has provided a distinctive hierarchical approach that efficiently forwards the nodes data to the BS, but it suffers from increased energy consumption and a significant decline in the network performance in the case of large-scale networks. This paper aims to present a new approach for splitting the whole sensor network into several levels. Thus, every node will be acting accordingly on its position and status. Further, two techniques, a static one and a dynamic one, have been developed to route the data between the levels. The simulation results demonstrated that the proposed techniques prolong the lifespan, improve the stability and raise the throughput of the network compared with the LEACH, the Improved MHT-LEACH (IMHT-LEACH), and the Enhancing DMHT-LEACH (EDMHT-LEACH) protocols. Full article

(This article belongs to the Special Issue Low Energy Wireless Sensor Networks: Protocols, Architectures and Solutions)

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22 pages, 15046 KiB

Open AccessArticle

A Self-Organized Reciprocal Decision Approach for Sensing Coverage with Multi-UAV Swarms

by Runfeng Chen, Ning Xu and Jie Li^*

College of Mechatronics and Automation, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(6), 1864; https://doi.org/10.3390/s18061864 - 7 Jun 2018

Cited by 14 | Viewed by 3487

Abstract

This paper tackles the problem of sensing coverage for multiple Unmanned Aerial Vehicles (UAVs) with an approach that takes into account the reciprocal between neighboring UAVs to reduce the oscillation of their trajectories. The proposed reciprocal decision approach, which is performed in three [...] Read more.

This paper tackles the problem of sensing coverage for multiple Unmanned Aerial Vehicles (UAVs) with an approach that takes into account the reciprocal between neighboring UAVs to reduce the oscillation of their trajectories. The proposed reciprocal decision approach, which is performed in three steps, is self-organized, distributed and autonomous. First, in contrast to the traditional method modeled and optimized in configuration space, the sensing coverage problem is directly presented as an optimal reciprocal coverage velocity (ORCV) in velocity space that is concise and effective. Second, the ORCV is determined by adjusting the action velocity out of weak coverage velocity relative to neighboring UAVs to demonstrate that the ORCV supports a collision-avoiding assembly. Third, a corresponding random probability method is proposed for determining the optimal velocity in the ORCV. The results from the simulation indicate that the proposed method has a high coverage rate, rapid convergence rate and low deadweight loss. In addition, for up to 10³-size UAVs, the proposed method has excellent scalability and collision-avoiding ability. Full article

(This article belongs to the Special Issue Unmanned Aerial Vehicle Networks, Systems and Applications)

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13 pages, 2178 KiB

Open AccessArticle

Construction of Chitosan-Zn-Based Electrochemical Biosensing Platform for Rapid and Accurate Assay of Actin

by Chong Sun¹, Ye Zou¹, Daoying Wang^1,2,*, Zhiming Geng¹, Weimin Xu¹, Fang Liu¹ and Jinxuan Cao^3,*

¹ Institute of Agricultural Products Processing, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China

² Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base of Ministry of Science and Technology, Nanjing 210014, China

³ Key Laboratory of Animal Protein Food Processing Technology of Zhejiang Province, Ningbo University, Ningbo 315211, China

Sensors 2018, 18(6), 1865; https://doi.org/10.3390/s18061865 - 7 Jun 2018

Cited by 9 | Viewed by 3275

Abstract

This work reports a study on the development of a sensitive immunosensor for the assay of actin, which is fabricated using sensing material chitosan-Zn nanoparticles (NPs) and anti-actin modified on glassy carbon electrode respectively. The prepared materials were characterized using transmission electron microscope [...] Read more.

This work reports a study on the development of a sensitive immunosensor for the assay of actin, which is fabricated using sensing material chitosan-Zn nanoparticles (NPs) and anti-actin modified on glassy carbon electrode respectively. The prepared materials were characterized using transmission electron microscope (TEM), fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) spectra, and circular dichroism (CD) techniques. Meanwhile, the electrochemical properties were studied by linear sweep voltammetric (LSV), electrochemical impedance spectra (EIS), and differential pulse voltammetry (DPV). According to the experiments, under the optimum conditions, the linear fitting equation was I (μA) = −17.31 + 78.97c (R² = 0.9948). The linear range was from 0.0001 to 0.1 mg/mL and the detection limit (LOD, S/N = 3) was 21.52 ng/mL. The interference studies were also performed for checking the sensors’ selectivity to actin. With better properties of the chitosan-Zn NPs, the modified electrode is considered as a better candidate than Western blot or immunohistochemical method for real-time usability. The detection limit reported is the lowest till date and this method provides a new approach for quality evaluation. Full article

(This article belongs to the Section Biosensors)

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14 pages, 5364 KiB

Open AccessArticle

Fabrication of Long Period Gratings by Periodically Removing the Coating of Cladding-Etched Single Mode Optical Fiber Towards Optical Fiber Sensor Development

by Joaquin Ascorbe^1,*

, Jesus M. Corres^1,2

, Ignacio Del Villar^1,2 and Ignacio R. Matias^1,2

¹ Department of Electrical, Electronic and Communication Engineering, Public University of Navarra, 31006 Pamplona, Spain

² Institute of Smart Cities, Public University of Navarra, 31006 Pamplona, Spain

Sensors 2018, 18(6), 1866; https://doi.org/10.3390/s18061866 - 7 Jun 2018

Cited by 11 | Viewed by 3366

Abstract

Here, we present a novel method to fabricate long period gratings using standard single mode optical fibers (SMF). These optical devices were fabricated in a three-step process, which consisted of etching the SMF, then coating it with a thin-film and, the final step, [...] Read more.

Here, we present a novel method to fabricate long period gratings using standard single mode optical fibers (SMF). These optical devices were fabricated in a three-step process, which consisted of etching the SMF, then coating it with a thin-film and, the final step, which involved removing sections of the coating periodically by laser ablation. Tin dioxide was chosen as the material for this study and it was sputtered using a pulsed DC sputtering system. Theoretical simulations were performed in order to select the appropriate parameters for the experiments. The responses of two different devices to different external refractive indices was studied, and the maximum sensitivity obtained was 6430 nm/RIU for external refractive indices ranging from 1.37 to 1.39. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 3801 KiB

Open AccessArticle

A Low-Noise Direct Incremental A/D Converter for FET-Based THz Imaging Detectors

by Moustafa Khatib^*

and Matteo Perenzoni

Center for Materials and Microsystems, Integrated Radiation and Image Sensors Group, Fondazione Bruno Kessler, Trento 38122, Italy

Sensors 2018, 18(6), 1867; https://doi.org/10.3390/s18061867 - 7 Jun 2018

Cited by 8 | Viewed by 5075

Abstract

This paper presents the design, implementation and characterization results of a pixel-level readout chain integrated with a FET-based terahertz (THz) detector for imaging applications. The readout chain is fabricated in a standard 150-nm CMOS technology and contains a cascade of a preamplification and [...] Read more.

This paper presents the design, implementation and characterization results of a pixel-level readout chain integrated with a FET-based terahertz (THz) detector for imaging applications. The readout chain is fabricated in a standard 150-nm CMOS technology and contains a cascade of a preamplification and noise reduction stage based on a parametric chopper amplifier and a direct analog-to-digital conversion by means of an incremental

Σ Δ

converter, performing a lock-in operation with modulated sources. The FET detector is integrated with an on-chip antenna operating in the frequency range of 325–375 GHz and compliant with all process design rules. The cascade of the FET THz detector and readout chain is evaluated in terms of responsivity and Noise Equivalent Power (NEP) measurements. The measured readout input-referred noise of 1.6

μ

V

_{r m s}

allows preserving the FET detector sensitivity by achieving a minimum NEP of 376 pW/

\sqrt{Hz}

in the optimum bias condition, while directly providing a digital output. The integrated readout chain features 65-dB peak-SNR and 80-

μ

W power consumption from a 1.8-V supply. The area of the antenna-coupled FET detector and the readout chain fits a pixel pitch of 455

μ

m, which is suitable for pixel array implementation. The proposed THz pixel has been successfully applied for imaging of concealed objects in a paper envelope under continuous-wave illumination. Full article

(This article belongs to the Special Issue Image Sensors)

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21 pages, 5142 KiB

Open AccessArticle

Optical Tracking Data Validation and Orbit Estimation for Sparse Observations of Satellites by the OWL-Net

by Jin Choi^1,2

, Jung Hyun Jo^1,2,*

, Hong-Suh Yim¹, Eun-Jung Choi¹, Sungki Cho¹ and Jang-Hyun Park¹

¹ Center for Space Situational Awareness, Korea Astronomy and Space Science Institute, 776, Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Korea

² Astronomy and Space Science Department, University of Science and Technology, 217, Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea

Sensors 2018, 18(6), 1868; https://doi.org/10.3390/s18061868 - 7 Jun 2018

Cited by 13 | Viewed by 6438

Abstract

An Optical Wide-field patroL-Network (OWL-Net) has been developed for maintaining Korean low Earth orbit (LEO) satellites’ orbital ephemeris. The OWL-Net consists of five optical tracking stations. Brightness signals of reflected sunlight of the targets were detected by a charged coupled device (CCD). A [...] Read more.

An Optical Wide-field patroL-Network (OWL-Net) has been developed for maintaining Korean low Earth orbit (LEO) satellites’ orbital ephemeris. The OWL-Net consists of five optical tracking stations. Brightness signals of reflected sunlight of the targets were detected by a charged coupled device (CCD). A chopper system was adopted for fast astrometric data sampling, maximum 50 Hz, within a short observation time. The astrometric accuracy of the optical observation data was validated with precise orbital ephemeris such as Consolidated Prediction File (CPF) data and precise orbit determination result with onboard Global Positioning System (GPS) data from the target satellite. In the optical observation simulation of the OWL-Net for 2017, an average observation span for a single arc of 11 LEO observation targets was about 5 min, while an average optical observation separation time was 5 h. We estimated the position and velocity with an atmospheric drag coefficient of LEO observation targets using a sequential-batch orbit estimation technique after multi-arc batch orbit estimation. Post-fit residuals for the multi-arc batch orbit estimation and sequential-batch orbit estimation were analyzed for the optical measurements and reference orbit (CPF and GPS data). The post-fit residuals with reference show few tens-of-meters errors for in-track direction for multi-arc batch and sequential-batch orbit estimation results. Full article

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

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19 pages, 5558 KiB

Open AccessArticle

Design and Vibration Suppression Control of a Modular Elastic Joint

by Hong Liu, Shipeng Cui, Yiwei Liu^*, Yi Ren and Yongjun Sun

State Key Laboratory of Robotics and System, Harbin Institute of Technology, West Dazhi Street, Harbin 150001, China

Sensors 2018, 18(6), 1869; https://doi.org/10.3390/s18061869 - 7 Jun 2018

Cited by 22 | Viewed by 6210

Abstract

In this paper, a novel mechatronic design philosophy is introduced to develop a compact modular rotary elastic joint for a humanoid manipulator. The designed elastic joint is mainly composed of a brushless direct current (DC) motor, harmonic reducer, customized torsional spring, and fail-safe [...] Read more.

In this paper, a novel mechatronic design philosophy is introduced to develop a compact modular rotary elastic joint for a humanoid manipulator. The designed elastic joint is mainly composed of a brushless direct current (DC) motor, harmonic reducer, customized torsional spring, and fail-safe brake. The customized spring considerably reduces the volume of the elastic joint and facilitates the construction of a humanoid manipulator which employs this joint. The large central hole along the joint axis brings convenience for cabling and the fail-safe brake can guarantee safety when the power is off. In order to reduce the computational burden on the central controller and simplify system maintenance, an expandable electrical system, which has a double-layer control structure, is introduced. Furthermore, a robust position controller for the elastic joint is proposed and interpreted in detail. Vibration of the elastic joint is suppressed by means of resonance ratio control (RRC). In this method, the ratio between the resonant and anti-resonant frequency can be arbitrarily designated according to the feedback of the nominal spring torsion. Instead of using an expensive torque sensor, the spring torque can be obtained by calculating the product of spring stiffness and deformation, due to the high linearity of the customized spring. In addition, to improve the system robustness, a motor-side disturbance observer (DOb) and an arm-side DOb are employed to estimate and compensate for external disturbances and system uncertainties, such as model variation, friction, and unknown external load. Validity of the DOb-based RRC is demonstrated in the simulation results. Experimental results show the performance of the modular elastic joint and the viability of the proposed controller further. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 2257 KiB

Open AccessArticle

Reproducible Molecularly Imprinted Piezoelectric Sensor for Accurate and Sensitive Detection of Ractopamine in Swine and Feed Products

by Mingfei Pan, Rui Li, Leling Xu, Jingying Yang, Xiaoyuan Cui and Shuo Wang^*

Key Laboratory of Food Nutrition and Safety, Ministry of Education of China, Tianjin University of Science and Technology, Tianjin 300457, China

Sensors 2018, 18(6), 1870; https://doi.org/10.3390/s18061870 - 7 Jun 2018

Cited by 14 | Viewed by 3607

Abstract

This paper describes the development of a reproducible molecularly imprinted piezoelectric sensor for the accurate and sensitive detection of ractopamine (RAC) in swine and feed products. The synthesized molecularly imprinted polymer (MIP) was directly immobilized on the surface of a quartz crystal microbalance [...] Read more.

This paper describes the development of a reproducible molecularly imprinted piezoelectric sensor for the accurate and sensitive detection of ractopamine (RAC) in swine and feed products. The synthesized molecularly imprinted polymer (MIP) was directly immobilized on the surface of a quartz crystal microbalance (QCM) Au chip as the recognition element. The experimental parameters in the fabrication, measurement and regeneration process were evaluated in detail to produce an MIP-based piezoelectric sensor with high sensing capability. The developed piezoelectric sensor was verified to perform favorably in the RAC analysis of swine and feed products, with acceptable accuracy (recovery: 75.9–93.3%), precision [relative standard deviation (n = 3): 2.3–6.4%], and sensitivity [limit of detection: 0.46 ng g⁻¹ (swine) and 0.38 ng g⁻¹ (feed)]. This portable MIP-based chip for the piezoelectric sensing of RAC could be reused for at least 30 cycles and easily stored for a long time. These results demonstrated that the developed MIP-based piezoelectric sensor presents an accurate, sensitive and cost-effective method for the quantitative detection of RAC in complex samples. This research offers a promising strategy for the development of novel effective devices used for use in food safety analysis. Full article

(This article belongs to the Section Chemical Sensors)

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19 pages, 7560 KiB

Open AccessArticle

A Case Study on Attribute Recognition of Heated Metal Mark Image Using Deep Convolutional Neural Networks

by Keming Mao ^1,*

, Duo Lu ¹, Dazhi E ² and Zhenhua Tan ¹

¹ College of Software, Northeastern University, Shenyang 110004, China

² Shenyang Fire Research Institute, Ministry of Public Security, Shenyang 110034, China

Sensors 2018, 18(6), 1871; https://doi.org/10.3390/s18061871 - 7 Jun 2018

Cited by 9 | Viewed by 3454

Abstract

Heated metal mark is an important trace to identify the cause of fire. However, traditional methods mainly focus on the knowledge of physics and chemistry for qualitative analysis and make it still a challenging problem. This paper presents a case study on attribute [...] Read more.

Heated metal mark is an important trace to identify the cause of fire. However, traditional methods mainly focus on the knowledge of physics and chemistry for qualitative analysis and make it still a challenging problem. This paper presents a case study on attribute recognition of the heated metal mark image using computer vision and machine learning technologies. The proposed work is composed of three parts. Material is first generated. According to national standards, actual needs and feasibility, seven attributes are selected for research. Data generation and organization are conducted, and a small size benchmark dataset is constructed. A recognition model is then implemented. Feature representation and classifier construction methods are introduced based on deep convolutional neural networks. Finally, the experimental evaluation is carried out. Multi-aspect testings are performed with various model structures, data augments, training modes, optimization methods and batch sizes. The influence of parameters, recognitio efficiency and execution time are also analyzed. The results show that with a fine-tuned model, the recognition rate of attributes metal type, heating mode, heating temperature, heating duration, cooling mode, placing duration and relative humidity are 0.925, 0.908, 0.835, 0.917, 0.928, 0.805 and 0.92, respectively. The proposed method recognizes the attribute of heated metal mark with preferable effect, and it can be used in practical application. Full article

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

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23 pages, 840 KiB

Open AccessArticle

Satellite Launcher Navigation with One Versus Three IMUs: Sensor Positioning and Data Fusion Model Analysis

by Yanick Beaudoin^1,*, André Desbiens¹

, Eric Gagnon² and René Landry, Jr.³

¹ Département de Génie Électrique et de Génie Informatique, Université Laval, 1065 Avenue de la Médecine, Québec, QC G1V 0A6, Canada

² Defence Research and Development Canada, 2459 Route de la Bravoure, Québec, QC G3J 1X5, Canada

³ Département de Génie Électrique, École de Technologie Supérieure, 1100 Rue Notre-Dame Ouest, Montréal, QC H3C 1K3, Canada

Sensors 2018, 18(6), 1872; https://doi.org/10.3390/s18061872 - 7 Jun 2018

Cited by 5 | Viewed by 4720

Abstract

Using multiple IMUs allows both their distribution along vehicle structures and a reliance on integration methods, which is not possible with a single IMU. This paper addresses the issue of relying on three IMUs instead of only one of a higher quality in [...] Read more.

Using multiple IMUs allows both their distribution along vehicle structures and a reliance on integration methods, which is not possible with a single IMU. This paper addresses the issue of relying on three IMUs instead of only one of a higher quality in the context of a satellite launcher. The impact of the IMU positions was tested by comparing collocated IMUs against IMUs installed in the head of each launcher stage. For multi-IMU configurations, three integration methods were tested: all IMUs fused in a single INS, multiple INSs fused in a stacked filter, and multiple INSs fused in a stacked filter with geometrical constraints. All navigation solutions were aided by a three-axis attitude reference sensor and were tested with and without a GPS receiver. The results show that distributing IMUs along the launcher structure does not improve navigation performances compared to having them collocated. The fusion of multiple IMUs in one INS provides equivalent results as one IMU. However, fusing multiple INSs greatly reduces estimation errors. Performances are further improved with the addition of geometrical constraints. During long GPS outages, relative velocity and position constraints should not be exploited, as they may lead to filter divergence. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 3837 KiB

Open AccessArticle

Indirect Measurement of Rotor Dynamic Imbalance for Control Moment Gyroscopes via Gimbal Disturbance Observer

by Liya Huang, Zhong Wu^*

and Kan Wang

School of Instrumentation Science and Optoelectronics Engineering, Beihang University, Beijing 100191, China

Sensors 2018, 18(6), 1873; https://doi.org/10.3390/s18061873 - 7 Jun 2018

Cited by 10 | Viewed by 4178

Abstract

The high-precision speed control of gimbal servo systems is the key to generating high-precision torque for control moment gyroscopes (CMGs) in spacecrafts. However, the control performance of gimbal servo systems may be degraded significantly by disturbances, especially a dynamic imbalance disturbance with the [...] Read more.

The high-precision speed control of gimbal servo systems is the key to generating high-precision torque for control moment gyroscopes (CMGs) in spacecrafts. However, the control performance of gimbal servo systems may be degraded significantly by disturbances, especially a dynamic imbalance disturbance with the same frequency as the high-speed rotor. For assembled CMGs, it is very difficult to measure the rotor imbalance directly by using a dynamic balancing machine. In this paper, a gimbal disturbance observer is proposed to estimate the dynamic imbalance of the rotor assembled in the CMG. First, a third-order dynamical system is established to describe the disturbance dynamics of the gimbal servo system, in which the rotor dynamic imbalance torque along the gimbal axis and the other disturbances are modeled to be periodic and bounded, respectively. Then, the gimbal disturbance observer is designed for the third-order dynamical system by using the total disturbance as a virtual measurement. Since the virtual measurement is derived from the inverse dynamics of the gimbal servo system, the information of the rotor dynamic imbalance can be obtained indirectly only using the measurements of gimbal speed and three-phase currents. Semi-physical experimental results demonstrate the effectiveness of the observer by using a CMG simulator. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 2685 KiB

Open AccessArticle

An Improved Heuristic Drift Elimination Method for Indoor Pedestrian Positioning

by Zhihong Deng^*

, Yun Cao

, Pengyu Wang

and Bo Wang

School of Automation, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(6), 1874; https://doi.org/10.3390/s18061874 - 7 Jun 2018

Cited by 10 | Viewed by 3774

Abstract

Indoor positioning is currently a research hotspot. In recent years, Pedestrian Dead Reckoning (PDR) has been widely used in indoor positioning. However, the positioning error caused by heading drifts will accumulate as the walking distance increases, so some methods need to be used [...] Read more.

Indoor positioning is currently a research hotspot. In recent years, Pedestrian Dead Reckoning (PDR) has been widely used in indoor positioning. However, the positioning error caused by heading drifts will accumulate as the walking distance increases, so some methods need to be used to correct the heading angle. Heuristic Drift Elimination (HDE) is an effective heading correction algorithm, which only uses the information of a building’s dominant directions to reduce the heading error, but it does not apply to the non-dominant direction condition. In this paper, we propose a heading drift suppressing method for the limitation of HDE. Firstly, the method constructs membership functions to judge the pedestrian’s motion according to the result of comprehensive evaluation. Then, it further determines by a threshold condition whether the pedestrian walks along the dominant directions, and a heading error measurement is introduced for heading correction. Finally, we verify by experiments that the proposed method can correct heading angles properly for different conditions, which indicates an adaptability to the environment. Full article

(This article belongs to the Special Issue Smart Sensors and Smart Structures)

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19 pages, 706 KiB

Open AccessArticle

Analysis of the Scalability of UWB Indoor Localization Solutions for High User Densities

by Matteo Ridolfi^1,*

, Samuel Van de Velde², Heidi Steendam²

and Eli De Poorter¹

¹ IDLab, Department of Information Technology, Ghent University—IMEC, 9000 Gent, Belgium

² Department of Telecommunications and Information Processing, Ghent University, 9000 Gent, Belgium

Sensors 2018, 18(6), 1875; https://doi.org/10.3390/s18061875 - 7 Jun 2018

Cited by 93 | Viewed by 8919

Abstract

Radio frequency (RF) technologies are often used to track assets in indoor environments. Among others, ultra-wideband (UWB) has constantly gained interest thanks to its capability to obtain typical errors of 30 cm or lower, making it more accurate than other wireless technologies such [...] Read more.

Radio frequency (RF) technologies are often used to track assets in indoor environments. Among others, ultra-wideband (UWB) has constantly gained interest thanks to its capability to obtain typical errors of 30 cm or lower, making it more accurate than other wireless technologies such as WiFi, which normally can predict the location with several meters accuracy. However, mainly due to technical requirements that are part of the standard, conventional medium access strategies such as clear channel assessment, are not straightforward to implement. Since most scientific papers focus on UWB accuracy improvements of a single user, it is not clear to which extend this limitation and other design choices impact the scalability of UWB indoor positioning systems. We investigated the scalability of indoor localization solutions, to prove that UWB can be used when hundreds of tags are active in the same system. This paper provides mathematical models that calculate the theoretical supported user density for multiple localization approaches, namely Time Difference of Arrival (TDoA) and Two-Way Ranging (TWR) with different MAC protocol combinations, i.e., ALOHA and TDMA. Moreover, this paper applies these formulas to a number of realistic UWB configurations to study the impact of different UWB schemes and settings. When applied to the 802.15.4a compliant Decawave DW1000 chip, the scalability dramatically degrades if the system operates with uncoordinated protocols and two-way communication schemes. In the best case scenario, UWB DW1000 chips can actively support up to 6171 tags in a single domain cell (no handover) with well-selected settings and choices, i.e., when adopting the combination of TDoA (one-way link) and TDMA. As a consequence, UWB can be used to simultaneously localize thousands of nodes in a dense network. However, we also show that the number of supported devices varies greatly depending on the MAC and PHY configuration choices. Full article

(This article belongs to the Special Issue Sensor Fusion and Novel Technologies in Positioning and Navigation)

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17 pages, 19843 KiB

Open AccessArticle

Monitoring Highway Stability in Permafrost Regions with X-band Temporary Scatterers Stacking InSAR

by Keren Dai^1,2

, Guoxiang Liu^3,*, Zhenhong Li⁴

, Deying Ma^3,5, Xiaowen Wang³, Bo Zhang³, Jia Tang⁶ and Guangyu Li³

¹ College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China

² State Key Laboratory of Geohazard Prevention and Geoenviroment Protection, Chengdu University of Technology, Chengdu 610059, China

³ Department of Surveying and Geo-Informatics, Southwest Jiaotong University, Chengdu 610031, China

⁴ COMET, School of Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, UK

⁵ School of Civil Engineering and Architecture, Southwest Petroleum University, Chengdu 610500, China

⁶ Sichuan No. 1 Surveying and Mapping Engineering Institute, Chengdu 610100, China

Sensors 2018, 18(6), 1876; https://doi.org/10.3390/s18061876 - 8 Jun 2018

Cited by 55 | Viewed by 6130

Abstract

Interferograms with short wavelength (e.g., X-band) are usually prone to temporal decorrelation in permafrost regions, leading to the unavailability of sufficient high-coherence interferograms for performing conventional time series InSAR analysis. This paper proposes the utilization of temporary scatterers for the stacking InSAR method, [...] Read more.

Interferograms with short wavelength (e.g., X-band) are usually prone to temporal decorrelation in permafrost regions, leading to the unavailability of sufficient high-coherence interferograms for performing conventional time series InSAR analysis. This paper proposes the utilization of temporary scatterers for the stacking InSAR method, thus enabling extraction of subsidence in a permafrost region with limited SAR images and limited high-coherence interferograms. Such method is termed as the temporary scatterers stacking InSAR (TSS-InSAR). Taking the Gonghe-Yushu highway (about 30 km), part of G214 National Highway in Qinghai province (in a permafrost region), as a case study, this TSS-InSAR approach was demonstrated in detail and implemented. With 10 TerraSAR-X images acquired during the period from May 2015 to August 2015, the subsidence along this highway was extracted. In this case the lack of a consistent number of SAR acquisitions limits the possibility to perform other conventional time series InSAR analysis. The results show that the middle part of this highway is in the thermokarst and seasonal frozen soil area, and its accumulated subsidence reach up to 10 cm in 110 days. The thawing phenomena is still the main reason for the instability of highway. The results demonstrate that the TSS-InSAR method can effectively extract the subsidence information in a challenging scenario with limited X-band SAR images and limited high-coherence interferograms, where other time series InSAR-based techniques cannot be applied in a simple way. Full article

(This article belongs to the Special Issue Synthetic Aperture Radar (SAR) Technology: New Perspectives Offered by New-Generation and Forthcoming SAR Sensors)

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30 pages, 5520 KiB

Open AccessArticle

FPGA-Based High-Performance Embedded Systems for Adaptive Edge Computing in Cyber-Physical Systems: The ARTICo³ Framework

by Alfonso Rodríguez^1,*

, Juan Valverde², Jorge Portilla¹

, Andrés Otero¹

, Teresa Riesgo¹

and Eduardo De la Torre¹

¹ Centro de Electrónica Industrial, Universidad Politécnica de Madrid, José Gutiérrez Abascal 2, 28006 Madrid, Spain

² United Technologies Research Centre (UTRC), Penrose Wharf, Cork T23 XN53, Ireland

Sensors 2018, 18(6), 1877; https://doi.org/10.3390/s18061877 - 8 Jun 2018

Cited by 76 | Viewed by 8777

Abstract

Cyber-Physical Systems are experiencing a paradigm shift in which processing has been relocated to the distributed sensing layer and is no longer performed in a centralized manner. This approach, usually referred to as Edge Computing, demands the use of hardware platforms that are [...] Read more.

Cyber-Physical Systems are experiencing a paradigm shift in which processing has been relocated to the distributed sensing layer and is no longer performed in a centralized manner. This approach, usually referred to as Edge Computing, demands the use of hardware platforms that are able to manage the steadily increasing requirements in computing performance, while keeping energy efficiency and the adaptability imposed by the interaction with the physical world. In this context, SRAM-based FPGAs and their inherent run-time reconfigurability, when coupled with smart power management strategies, are a suitable solution. However, they usually fail in user accessibility and ease of development. In this paper, an integrated framework to develop FPGA-based high-performance embedded systems for Edge Computing in Cyber-Physical Systems is presented. This framework provides a hardware-based processing architecture, an automated toolchain, and a runtime to transparently generate and manage reconfigurable systems from high-level system descriptions without additional user intervention. Moreover, it provides users with support for dynamically adapting the available computing resources to switch the working point of the architecture in a solution space defined by computing performance, energy consumption and fault tolerance. Results show that it is indeed possible to explore this solution space at run time and prove that the proposed framework is a competitive alternative to software-based edge computing platforms, being able to provide not only faster solutions, but also higher energy efficiency for computing-intensive algorithms with significant levels of data-level parallelism. Full article

(This article belongs to the Special Issue Green Communications and Networking for IoT)

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15 pages, 11563 KiB

Open AccessArticle

Ultrasensitive Electrochemical Detection of Clostridium perfringens DNA Based Morphology-Dependent DNA Adsorption Properties of CeO₂ Nanorods in Dairy Products

by Xingcan Qian¹, Qing Qu^1,*, Lei Li^2,*, Xin Ran¹, Limei Zuo¹, Rui Huang³ and Qiang Wang³

¹ School of Chemical Science and Technology, Yunnan University, Kunming 650091, China

² Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming 650091, China

³ Sino-Pipeline International Company Limited, Beijing 100000, China

Sensors 2018, 18(6), 1878; https://doi.org/10.3390/s18061878 - 8 Jun 2018

Cited by 43 | Viewed by 5492

Abstract

Foodborne pathogens such as Clostridium perfringens can cause diverse illnesses and seriously threaten to human health, yet far less attention has been given to detecting these pathogenic bacteria. Herein, two morphologies of nanoceria were synthesized via adjusting the concentration of NaOH, and CeO [...] Read more.

Foodborne pathogens such as Clostridium perfringens can cause diverse illnesses and seriously threaten to human health, yet far less attention has been given to detecting these pathogenic bacteria. Herein, two morphologies of nanoceria were synthesized via adjusting the concentration of NaOH, and CeO₂ nanorod has been utilized as sensing material to achieve sensitive and selective detection of C. perfringens DNA sequence due to its strong adsorption ability towards DNA compared to nanoparticle. The DNA probe was tightly immobilized on CeO₂/chitosan modified electrode surface via metal coordination, and the DNA surface density was 2.51 × 10⁻¹⁰ mol/cm². Under optimal experimental conditions, the electrochemical impedance biosensor displays favorable selectivity toward target DNA in comparison with base-mismatched and non-complementary DNA. The dynamic linear range of the proposed biosensor for detecting oligonucleotide sequence of Clostridium perfringens was from 1.0 × 10⁻¹⁴ to 1.0 × 10⁻⁷ mol/L. The detection limit was 7.06 × 10⁻¹⁵ mol/L. In comparison, differential pulse voltammetry (DPV) method quantified the target DNA with a detection limit of 1.95 × 10⁻¹⁵ mol/L. Moreover, the DNA biosensor could detect C. perfringens extracted DNA in dairy products and provided a potential application in food quality control. Full article

(This article belongs to the Special Issue The Applications of Sensors and Biosensors in Investigating Drugs, Nutraceuticals and Foods)

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15 pages, 2450 KiB

Open AccessArticle

Dynamic Model Updating for Bridge Structures Using the Kriging Model and PSO Algorithm Ensemble with Higher Vibration Modes

by Shiqiang Qin¹, Yazhou Zhang¹

, Yun-Lai Zhou^2,*

and Juntao Kang¹

¹ School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan 430070, China

² Department of Civil and Environmental Engineering, National University of Singapore, 2 Engineering Drive 2, Singapore 117576, Singapore

Sensors 2018, 18(6), 1879; https://doi.org/10.3390/s18061879 - 8 Jun 2018

Cited by 75 | Viewed by 5598

Abstract

This study applied the kriging model and particle swarm optimization (PSO) algorithm for the dynamic model updating of bridge structures using the higher vibration modes under large-amplitude initial conditions. After addressing the higher mode identification theory using time-domain operational modal analysis, the kriging [...] Read more.

This study applied the kriging model and particle swarm optimization (PSO) algorithm for the dynamic model updating of bridge structures using the higher vibration modes under large-amplitude initial conditions. After addressing the higher mode identification theory using time-domain operational modal analysis, the kriging model is then established based on Latin hypercube sampling and regression analysis. The kriging model performs as a surrogate model for a complex finite element model in order to predict analytical responses. An objective function is established to express the relative difference between analytically predicted responses and experimentally measured ones, and the initial finite element (FE) model is hereinafter updated using the PSO algorithm. The Jalón viaduct—a concrete continuous railway bridge—is applied to verify the proposed approach. The results show that the kriging model can accurately predict the responses and reduce computational time as well. Full article

(This article belongs to the Special Issue Bridge Structural Health Monitoring and Damage Identification)

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12 pages, 4623 KiB

Open AccessArticle

Atmospheric Pollution Monitoring in Urban Area by Employing a 450-nm Lidar System

by Zheng Kong, Zhi Liu, Lishan Zhang, Peng Guan, Limei Li and Liang Mei^*

School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, China

Sensors 2018, 18(6), 1880; https://doi.org/10.3390/s18061880 - 8 Jun 2018

Cited by 26 | Viewed by 7038

Abstract

In past decades, lidar techniques have become main tools for atmospheric remote sensing. However, traditional pulsed lidar systems are relatively expensive and require considerable maintenance. These shortcomings may be overcome by the development of a blue band Scheimpflug lidar system in Dalian, Northern [...] Read more.

In past decades, lidar techniques have become main tools for atmospheric remote sensing. However, traditional pulsed lidar systems are relatively expensive and require considerable maintenance. These shortcomings may be overcome by the development of a blue band Scheimpflug lidar system in Dalian, Northern China. Atmospheric remote measurements were carried out for 10 days in an urban area to validate the feasibility and performance of a 450-nm Scheimpflug lidar system. A 24-h continuous measurement was achieved in winter on a near horizontal path with an elevation angle of about 6.4°. The aerosol extinction coefficient retrieved by the Fernald-inversion algorithm shows good agreement with the variation of PM10/PM2.5 concentrations recorded by a national pollution monitoring station. The experimental result reveals that the linear ratio between the aerosol extinction coefficient and the PM10 concentration under high relative humidity (75–90%) is about two-times that in low relative humidity (≤75%) when the PM10 concentrations are less than 100 µg/m³. Full article

(This article belongs to the Special Issue Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing)

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14 pages, 1603 KiB

Open AccessArticle

Application of Crack Identification Techniques for an Aging Concrete Bridge Inspection Using an Unmanned Aerial Vehicle

by In-Ho Kim¹

, Haemin Jeon^2,*, Seung-Chan Baek³, Won-Hwa Hong⁴ and Hyung-Jo Jung^5,*

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

² Department of Civil and Environmental Engineering, Hanbat National University, Daejeon 34158, Korea

³ Division of Electronics and Info-Communication Engineering, YeungJin College, Daegu 41527, Korea

⁴ School of Architecture, Civil, Environmental and Energy Engineering, Kyungpook National University, Daegu 41566, Korea

⁵ Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea

Sensors 2018, 18(6), 1881; https://doi.org/10.3390/s18061881 - 8 Jun 2018

Cited by 244 | Viewed by 12292

Abstract

Bridge inspection using unmanned aerial vehicles (UAV) with high performance vision sensors has received considerable attention due to its safety and reliability. As bridges become obsolete, the number of bridges that need to be inspected increases, and they require much maintenance cost. Therefore, [...] Read more.

Bridge inspection using unmanned aerial vehicles (UAV) with high performance vision sensors has received considerable attention due to its safety and reliability. As bridges become obsolete, the number of bridges that need to be inspected increases, and they require much maintenance cost. Therefore, a bridge inspection method based on UAV with vision sensors is proposed as one of the promising strategies to maintain bridges. In this paper, a crack identification method by using a commercial UAV with a high resolution vision sensor is investigated in an aging concrete bridge. First, a point cloud-based background model is generated in the preliminary flight. Then, cracks on the structural surface are detected with the deep learning algorithm, and their thickness and length are calculated. In the deep learning method, region with convolutional neural networks (R-CNN)-based transfer learning is applied. As a result, a new network for the 384 collected crack images of 256 × 256 pixel resolution is generated from the pre-trained network. A field test is conducted to verify the proposed approach, and the experimental results proved that the UAV-based bridge inspection is effective at identifying and quantifying the cracks on the structures. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 1821 KiB

Open AccessArticle

An Auto-Calibrating Knee Flexion-Extension Axis Estimator Using Principal Component Analysis with Inertial Sensors

by Timothy McGrath^1,*

, Richard Fineman²

and Leia Stirling^1,3

¹ Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

² Harvard-MIT Division of Health Sciences & Technology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

³ Institute for Medical Engineering Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

Sensors 2018, 18(6), 1882; https://doi.org/10.3390/s18061882 - 8 Jun 2018

Cited by 59 | Viewed by 7182 | Correction

Abstract

Inertial measurement units (IMUs) have been demonstrated to reliably measure human joint angles—an essential quantity in the study of biomechanics. However, most previous literature proposed IMU-based joint angle measurement systems that required manual alignment or prescribed calibration motions. This paper presents a simple, [...] Read more.

Inertial measurement units (IMUs) have been demonstrated to reliably measure human joint angles—an essential quantity in the study of biomechanics. However, most previous literature proposed IMU-based joint angle measurement systems that required manual alignment or prescribed calibration motions. This paper presents a simple, physically-intuitive method for IMU-based measurement of the knee flexion/extension angle in gait without requiring alignment or discrete calibration, based on computationally-efficient and easy-to-implement Principle Component Analysis (PCA). The method is compared against an optical motion capture knee flexion/extension angle modeled through OpenSim. The method is evaluated using both measured and simulated IMU data in an observational study (n = 15) with an absolute root-mean-square-error (RMSE) of 9.24

^{\circ}

and a zero-mean RMSE of 3.49

^{\circ}

. Variation in error across subjects was found, made emergent by the larger subject population than previous literature considers. Finally, the paper presents an explanatory model of RMSE on IMU mounting location. The observational data suggest that RMSE of the method is a function of thigh IMU perturbation and axis estimation quality. However, the effect size for these parameters is small in comparison to potential gains from improved IMU orientation estimations. Results also highlight the need to set relevant datums from which to interpret joint angles for both truth references and estimated data. Full article

(This article belongs to the Special Issue Wearable Biomedical Sensors 2019)

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14 pages, 4298 KiB

Open AccessArticle

Real-Time Phase-Sensitive OTDR Based on Data Matrix Matching Method

by Xin Liu¹, Yu Wang¹

, Ruidong Wu¹, Dong Wang¹, Qing Bai¹

and Baoquan Jin^1,2,*

¹ Key Laboratory of Advanced Transducers and Intelligent Control Systems, Taiyuan University of Technology, Ministry of Education and Shanxi Province, Taiyuan 030024, China

² State Key Laboratory of Coal and CBM Co-mining, Jincheng 048012, China

Sensors 2018, 18(6), 1883; https://doi.org/10.3390/s18061883 - 8 Jun 2018

Cited by 8 | Viewed by 3807

Abstract

Phase-sensitive optical time-domain reflectometry (Φ-OTDR) is an effective technique to accomplish fully distributed vibration measurement along the entire fiber link. In this paper, a novel data matrix matching method is proposed and successfully employed in the Φ-OTDR system for real-time vibration detection and [...] Read more.

Phase-sensitive optical time-domain reflectometry (Φ-OTDR) is an effective technique to accomplish fully distributed vibration measurement along the entire fiber link. In this paper, a novel data matrix matching method is proposed and successfully employed in the Φ-OTDR system for real-time vibration detection and type identification. By using the novel method, the quantized response time is presented and improved to millisecond level for the first time. Meanwhile, the data can be extracted completely without packet loss, thus allowing vibration type identification to be obtained while maintaining the system simplicity. The experimental results demonstrate that the vibration signals can be detected and located with an average response time of 50.1 ms, under a data transmission speed which can go up to 77.824 Mbps. Moreover, different vibration types such as sine waves and square waves which are applied to the sensing fiber through a piezoelectric ceramic (PZT) cylinder can also be successfully identified. This method provides an efficient solution for real-time vibration location and type identification, thus exhibiting considerable application potential in many practical situations. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 1340 KiB

Open AccessArticle

Strain Sensitivity Control of an In-Series Silica and Polymer FBG

by Ricardo Oliveira^1,*

, Lúcia Bilro^1,2

and Rogério Nogueira¹

¹ Instituto de Telecomunicações, Campus de Santiago, 3810-193 Aveiro, Portugal

² Instituto de Telecomunicações and I3N/FSCOSD, Institute of Nanostructures, Nanomodelling and Nanofabrication, Physics Department of University of Aveiro, 3810-193 Aveiro, Portugal

Sensors 2018, 18(6), 1884; https://doi.org/10.3390/s18061884 - 8 Jun 2018

Cited by 5 | Viewed by 3064

Abstract

This work reports on the use of an in-series silica and polymer fiber Bragg grating (FBG) to control the FBG strain sensitivities and enhance in the case of the polymer fiber Bragg grating (PFBG). Due to differences in the Young’s Modulus of the [...] Read more.

This work reports on the use of an in-series silica and polymer fiber Bragg grating (FBG) to control the FBG strain sensitivities and enhance in the case of the polymer fiber Bragg grating (PFBG). Due to differences in the Young’s Modulus of the fibers employed, the amount of strain is unequally distributed in each fiber section. By acting on the silica fiber length, it was possible to control the strain sensitivity of the two FBGs, allowing a polymer FBG strain sensitivity much higher than the one found in the elementary fiber to be obtained. The influence of the diameter of the polymer fiber on the strain sensitivities of the FBGs was also investigated. Results have shown that, besides the strain sensitivity control, an even greater improvement in the PFBG strain sensitivity can be achieved. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 2154 KiB

Open AccessArticle

Improved Cross-Ratio Invariant-Based Intrinsic Calibration of A Hyperspectral Line-Scan Camera

by Daobilige Su^*

, Asher Bender

and Salah Sukkarieh

Australian Centre for Filed Robotics (ACFR), The University of Sydney, Sydney, NSW 2006, Australia

Sensors 2018, 18(6), 1885; https://doi.org/10.3390/s18061885 - 8 Jun 2018

Cited by 14 | Viewed by 5033

Abstract

Hyperspectral line-scan cameras are increasingly being deployed on mobile platforms operating in unstructured environments. To generate geometrically accurate hyperspectral composites, the intrinsic parameters of these cameras must be resolved. This article describes a method for determining the intrinsic parameters of a hyperspectral line-scan [...] Read more.

Hyperspectral line-scan cameras are increasingly being deployed on mobile platforms operating in unstructured environments. To generate geometrically accurate hyperspectral composites, the intrinsic parameters of these cameras must be resolved. This article describes a method for determining the intrinsic parameters of a hyperspectral line-scan camera. The proposed method is based on a cross-ratio invariant calibration routine and is able to estimate the focal length, principal point, and radial distortion parameters in a hyperspectral line-scan camera. Compared to previous methods that use similar calibration targets, our approach extends the camera model to include radial distortion. It is able to utilize calibration data recorded from multiple camera view angles by optimizing the re-projection error of all calibration data jointly. The proposed method also includes an additional signal processing step that automatically detects calibration points in hyperspectral imagery of the calibration target. These contributions result in accurate estimates of the intrinsic parameters with minimal supervision. The proposed method is validated through comprehensive simulation and demonstrated on real hyperspectral line-scans. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 1035 KiB

Open AccessArticle

Boosting a Low-Cost Smart Home Environment with Usage and Access Control Rules

by Paolo Barsocchi^*

, Antonello Calabrò, Erina Ferro, Claudio Gennaro

, Eda Marchetti

and Claudio Vairo

Institute of Information Science and Technologies of CNR (CNR-ISTI)-Italy, 56124 Pisa, Italy

Sensors 2018, 18(6), 1886; https://doi.org/10.3390/s18061886 - 8 Jun 2018

Cited by 35 | Viewed by 5631

Abstract

Smart Home has gained widespread attention due to its flexible integration into everyday life. Pervasive sensing technologies are used to recognize and track the activities that people perform during the day, and to allow communication and cooperation of physical objects. Usually, the available [...] Read more.

Smart Home has gained widespread attention due to its flexible integration into everyday life. Pervasive sensing technologies are used to recognize and track the activities that people perform during the day, and to allow communication and cooperation of physical objects. Usually, the available infrastructures and applications leveraging these smart environments have a critical impact on the overall cost of the Smart Home construction, require to be preferably installed during the home construction and are still not user-centric. In this paper, we propose a low cost, easy to install, user-friendly, dynamic and flexible infrastructure able to perform runtime resources management by decoupling the different levels of control rules. The basic idea relies on the usage of off-the-shelf sensors and technologies to guarantee the regular exchange of critical information, without the necessity from the user to develop accurate models for managing resources or regulating their access/usage. This allows us to simplify the continuous updating and improvement, to reduce the maintenance effort and to improve residents’ living and security. A first validation of the proposed infrastructure on a case study is also presented. Full article

(This article belongs to the Special Issue Smart Homes)

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17 pages, 2550 KiB

Open AccessArticle

Multi-Focus Fusion Technique on Low-Cost Camera Images for Canola Phenotyping

by Thang Cao¹, Anh Dinh^1,*, Khan A. Wahid¹

, Karim Panjvani¹ and Sally Vail²

¹ Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada

² Agriculture and Agri-Food Canada, Ottawa, ON K1A 0C5, Canada

Sensors 2018, 18(6), 1887; https://doi.org/10.3390/s18061887 - 8 Jun 2018

Cited by 10 | Viewed by 5567

Abstract

To meet the high demand for supporting and accelerating progress in the breeding of novel traits, plant scientists and breeders have to measure a large number of plants and their characteristics accurately. Imaging methodologies are being deployed to acquire data for quantitative studies [...] Read more.

To meet the high demand for supporting and accelerating progress in the breeding of novel traits, plant scientists and breeders have to measure a large number of plants and their characteristics accurately. Imaging methodologies are being deployed to acquire data for quantitative studies of complex traits. Images are not always good quality, in particular, they are obtained from the field. Image fusion techniques can be helpful for plant breeders with more comfortable access plant characteristics by improving the definition and resolution of color images. In this work, the multi-focus images were loaded and then the similarity of visual saliency, gradient, and color distortion were measured to obtain weight maps. The maps were refined by a modified guided filter before the images were reconstructed. Canola images were obtained by a custom built mobile platform for field phenotyping and were used for testing in public databases. The proposed method was also tested against the five common image fusion methods in terms of quality and speed. Experimental results show good re-constructed images subjectively and objectively performed by the proposed technique. The findings contribute to a new multi-focus image fusion that exhibits a competitive performance and outperforms some other state-of-the-art methods based on the visual saliency maps and gradient domain fast guided filter. The proposed fusing technique can be extended to other fields, such as remote sensing and medical image fusion applications. Full article

(This article belongs to the Collection Multi-Sensor Information Fusion)

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32 pages, 11144 KiB

Open AccessArticle

An Enhanced LoRaWAN Security Protocol for Privacy Preservation in IoT with a Case Study on a Smart Factory-Enabled Parking System

by Ilsun You

, Soonhyun Kwon, Gaurav Choudhary, Vishal Sharma^*

and Jung Taek Seo

Department of Information Security Engineering, Soonchunhyang University, Asan 31538, Korea

Sensors 2018, 18(6), 1888; https://doi.org/10.3390/s18061888 - 8 Jun 2018

Cited by 63 | Viewed by 10659

Abstract

The Internet of Things (IoT) utilizes algorithms to facilitate intelligent applications across cities in the form of smart-urban projects. As the majority of devices in IoT are battery operated, their applications should be facilitated with a low-power communication setup. Such facility is possible [...] Read more.

The Internet of Things (IoT) utilizes algorithms to facilitate intelligent applications across cities in the form of smart-urban projects. As the majority of devices in IoT are battery operated, their applications should be facilitated with a low-power communication setup. Such facility is possible through the Low-Power Wide-Area Network (LPWAN), but at a constrained bit rate. For long-range communication over LPWAN, several approaches and protocols are adopted. One such protocol is the Long-Range Wide Area Network (LoRaWAN), which is a media access layer protocol for long-range communication between the devices and the application servers via LPWAN gateways. However, LoRaWAN comes with fewer security features as a much-secured protocol consumes more battery because of the exorbitant computational overheads. The standard protocol fails to support end-to-end security and perfect forward secrecy while being vulnerable to the replay attack that makes LoRaWAN limited in supporting applications where security (especially end-to-end security) is important. Motivated by this, an enhanced LoRaWAN security protocol is proposed, which not only provides the basic functions of connectivity between the application server and the end device, but additionally averts these listed security issues. The proposed protocol is developed with two options, the Default Option (DO) and the Security-Enhanced Option (SEO). The protocol is validated through Burrows–Abadi–Needham (BAN) logic and the Automated Validation of Internet Security Protocols and Applications (AVISPA) tool. The proposed protocol is also analyzed for overheads through system-based and low-power device-based evaluations. Further, a case study on a smart factory-enabled parking system is considered for its practical application. The results, in terms of network latency with reliability fitting and signaling overheads, show paramount improvements and better performance for the proposed protocol compared with the two handshake options, Pre-Shared Key (PSK) and Elliptic Curve Cryptography (ECC), of Datagram Transport Layer Security (DTLS). 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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22 pages, 1335 KiB

Open AccessArticle

Modeling and Identification for Vector Propulsion of an Unmanned Surface Vehicle: Three Degrees of Freedom Model and Response Model

by Dongdong Mu

, Guofeng Wang^*, Yunsheng Fan

, Xiaojie Sun and Bingbing Qiu

School of Marine Electrical Engineering, Dalian Maritime University, Dalian 116026, China

Sensors 2018, 18(6), 1889; https://doi.org/10.3390/s18061889 - 8 Jun 2018

Cited by 45 | Viewed by 4867

Abstract

This paper presents a complete scheme for research on the three degrees of freedom model and response model of the vector propulsion of an unmanned surface vehicle. The object of this paper is “Lanxin”, an unmanned surface vehicle (7.02 m × 2.6 m), [...] Read more.

This paper presents a complete scheme for research on the three degrees of freedom model and response model of the vector propulsion of an unmanned surface vehicle. The object of this paper is “Lanxin”, an unmanned surface vehicle (7.02 m × 2.6 m), which is equipped with a single vector propulsion device. First, the “Lanxin” unmanned surface vehicle and the related field experiments (turning test and zig-zag test) are introduced and experimental data are collected through various sensors. Then, the thrust of the vector thruster is estimated by the empirical formula method. Third, using the hypothesis and simplification, the three degrees of freedom model and the response model of USV are deduced and established, respectively. Fourth, the parameters of the models (three degrees of freedom model, response model and thruster servo model) are obtained by system identification, and we compare the simulated turning test and zig-zag test with the actual data to verify the accuracy of the identification results. Finally, the biggest advantage of this paper is that it combines theory with practice. Based on identified response model, simulation and practical course keeping experiments are carried out to further verify feasibility and correctness of modeling and identification. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 3792 KiB

Open AccessArticle

Fairness-Aware Resource Allocation in Multi-Hop Wireless Powered Communication Networks with User Cooperation

by Ming Lei, Xingjun Zhang^*, Han Ding and Bocheng Yu

Department of Computer Science and Technology, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2018, 18(6), 1890; https://doi.org/10.3390/s18061890 - 8 Jun 2018

Cited by 13 | Viewed by 3702

Abstract

In wireless powered communication networks (WPCNs), the harvested energy varies greatly among user nodes (UNs), resulting in throughput unfairness. Since the harvested energy is limited, each UN must strategically allocate the energy used for forwarding the other nodes’ information and for transmitting its [...] Read more.

In wireless powered communication networks (WPCNs), the harvested energy varies greatly among user nodes (UNs), resulting in throughput unfairness. Since the harvested energy is limited, each UN must strategically allocate the energy used for forwarding the other nodes’ information and for transmitting its own information, which further aggravates the global unfairness in terms of throughput. In this paper, we leverage user cooperation in multi-hop transmission to improve the throughput fairness. We formulate the fairness problem as the max-min throughput with resource allocation, which is NP-hard. We design an approximate algorithm to address this problem. The theoretical proof and the simulation results both show that the proposed algorithm provides tight upper and lower bounds for the optimal solution. Compared with the benchmark methods, our proposed method significantly enhances the throughput fairness for WPCNs. Full article

(This article belongs to the Section Sensor Networks)

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12 pages, 3059 KiB

Open AccessArticle

A Microelectrode Array with Reproducible Performance Shows Loss of Consistency Following Functionalization with a Self-Assembled 6-Mercapto-1-hexanol Layer

by Damion K. Corrigan^1,2

, Vincent Vezza², Holger Schulze³

, Till T. Bachmann³, Andrew R. Mount¹, Anthony J. Walton⁴

and Jonathan G. Terry^4,*

¹ EaStCHEM, School of Chemistry, The University of Edinburgh, Joseph Black Building, The King’s Buildings, West Mains Road, Edinburgh EH9 3FJ, UK

² Department of Biomedical Engineering, University of Strathclyde, Glasgow G4 0NS, UK

³ Division of Infection and Pathway Medicine, Edinburgh Medical School, The University of Edinburgh, Chancellor’s Building, Little France Crescent, Edinburgh EH16 4SB, UK

⁴ Institute for Integrated Micro and Nano Systems, School of Engineering, The University of Edinburgh, The King’s Buildings, Alexander Crum Brown Road, Edinburgh EH9 3FF, UK

Sensors 2018, 18(6), 1891; https://doi.org/10.3390/s18061891 - 9 Jun 2018

Cited by 8 | Viewed by 5798

Abstract

For analytical applications involving label-free biosensors and multiple measurements, i.e., across an electrode array, it is essential to develop complete sensor systems capable of functionalization and of producing highly consistent responses. To achieve this, a multi-microelectrode device bearing twenty-four equivalent 50 µm diameter [...] Read more.

For analytical applications involving label-free biosensors and multiple measurements, i.e., across an electrode array, it is essential to develop complete sensor systems capable of functionalization and of producing highly consistent responses. To achieve this, a multi-microelectrode device bearing twenty-four equivalent 50 µm diameter Pt disc microelectrodes was designed in an integrated 3-electrode system configuration and then fabricated. Cyclic voltammetry and electrochemical impedance spectroscopy were used for initial electrochemical characterization of the individual working electrodes. These confirmed the expected consistency of performance with a high degree of measurement reproducibility for each microelectrode across the array. With the aim of assessing the potential for production of an enhanced multi-electrode sensor for biomedical use, the working electrodes were then functionalized with 6-mercapto-1-hexanol (MCH). This is a well-known and commonly employed surface modification process, which involves the same principles of thiol attachment chemistry and self-assembled monolayer (SAM) formation commonly employed in the functionalization of electrodes and the formation of biosensors. Following this SAM formation, the reproducibility of the observed electrochemical signal between electrodes was seen to decrease markedly, compromising the ability to achieve consistent analytical measurements from the sensor array following this relatively simple and well-established surface modification. To successfully and consistently functionalize the sensors, it was necessary to dilute the constituent molecules by a factor of ten thousand to support adequate SAM formation on microelectrodes. The use of this multi-electrode device therefore demonstrates in a high throughput manner irreproducibility in the SAM formation process at the higher concentration, even though these electrodes are apparently functionalized simultaneously in the same film formation environment, confirming that the often seen significant electrode-to-electrode variation in label-free SAM biosensing films formed under such conditions is not likely to be due to variation in film deposition conditions, but rather kinetically controlled variation in the SAM layer formation process at these microelectrodes. Full article

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

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16 pages, 4952 KiB

Open AccessArticle

Design and Implementation of a Wireless Sensor and Actuator Network to Support the Intelligent Control of Efficient Energy Usage

by Jesús Blanco^1,*

, Andrés García² and Javier De las Morenas³

¹ AutoLog Group, Polytechnic School of Cuenca, University of Castilla-La Mancha, Cuenca 16071, Spain

² AutoLog Group, School of Industrial Engineering, University of Castilla-La Mancha, Ciudad Real 13071, Spain

³ AutoLog Group, School of Mining and Industrial Engineering, University of Castilla-La Mancha, Almadén 13400, Spain

Sensors 2018, 18(6), 1892; https://doi.org/10.3390/s18061892 - 9 Jun 2018

Cited by 22 | Viewed by 8081

Abstract

Energy saving has become a major concern for the developed society of our days. This paper presents a Wireless Sensor and Actuator Network (WSAN) designed to provide support to an automatic intelligent system, based on the Internet of Things (IoT), which enables a [...] Read more.

Energy saving has become a major concern for the developed society of our days. This paper presents a Wireless Sensor and Actuator Network (WSAN) designed to provide support to an automatic intelligent system, based on the Internet of Things (IoT), which enables a responsible consumption of energy. The proposed overall system performs an efficient energetic management of devices, machines and processes, optimizing their operation to achieve a reduction in their overall energy usage at any given time. For this purpose, relevant data is collected from intelligent sensors, which are in-stalled at the required locations, as well as from the energy market through the Internet. This information is analysed to provide knowledge about energy utilization, and to improve efficiency. The system takes autonomous decisions automatically, based on the available information and the specific requirements in each case. The proposed system has been implanted and tested in a food factory. Results show a great optimization of energy efficiency and a substantial improvement on energy and costs savings. Full article

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

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24 pages, 2023 KiB

Open AccessArticle

Proprioceptive Sensors’ Fault Tolerant Control Strategy for an Autonomous Vehicle

by Mohamed Riad Boukhari^1,2,*

, Ahmed Chaibet², Moussa Boukhnifer²

and Sébastien Glaser³

¹ Institut VEDECOM, 77 Rue des Chantiers, Versailles 78000, France

² ESTACA, 12 Rue Paul Delouvrier, Montigny-le-Bretonneux 78180, France

³ Centre for Accident Research and Road Safety (CARRS-Q), Queensland University of Technology (QUT), Brisbane City, QLD 4000, Australia

Sensors 2018, 18(6), 1893; https://doi.org/10.3390/s18061893 - 9 Jun 2018

Cited by 27 | Viewed by 6252

Abstract

In this contribution, a fault-tolerant control strategy for the longitudinal dynamics of an autonomous vehicle is presented. The aim is to be able to detect potential failures of the vehicle’s speed sensor and then to keep the vehicle in a safe state. For [...] Read more.

In this contribution, a fault-tolerant control strategy for the longitudinal dynamics of an autonomous vehicle is presented. The aim is to be able to detect potential failures of the vehicle’s speed sensor and then to keep the vehicle in a safe state. For this purpose, the separation principle, composed of a static output feedback controller and fault estimation observers, is designed. Indeed, two observer techniques were proposed: the proportional and integral observer and the descriptor observer. The effectiveness of the proposed scheme is validated by means of the experimental demonstrator of the VEDECOM (Véhicle Décarboné et Communinicant) Institut. Full article

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

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13 pages, 3061 KiB

Open AccessArticle

Experimental Demonstration of Low-Uncertainty Calibration Methods for Bragg Grating Interrogators

by José Luis De Miguel^1,*

, Juan Galindo-Santos¹, Concepción Pulido de Torres², Pedro Salgado³, Aitor V. Velasco¹ and Pedro Corredera¹

¹ Instituto de Óptica, CSIC, C/Serrano 121, 28006 Madrid, Spain

² Instituto de Estructura de la Materia, CSIC, Serrano 123, 28006 Madrid, Spain

³ Instituto Mexicano del Petróleo—IMP, Ciudad de México 07730, México

Sensors 2018, 18(6), 1895; https://doi.org/10.3390/s18061895 - 10 Jun 2018

Cited by 4 | Viewed by 3544

Abstract

In this paper we propose and demonstrate two alternative methods for the high-precision calibration of fiber Bragg grating (FBG) interrogators. The first method is based on the direct comparison between the wavelength measurements of the interrogator under test and a calibrated wavemeter, while [...] Read more.

In this paper we propose and demonstrate two alternative methods for the high-precision calibration of fiber Bragg grating (FBG) interrogators. The first method is based on the direct comparison between the wavelength measurements of the interrogator under test and a calibrated wavemeter, while analyzing a simulated symmetric Bragg grating constructed by a tunable filter and a fiber mirror. This first method is applicable to most commercial systems but presents an uncertainty limited by the spectral width and the wavelength stability of the tunable filter. The second method consists in measuring multiple reference absorption lines of calibrated absorption gas cells. This second method presents lower uncertainties, limited only by the optical resolution of the interrogator and the wavelength uncertainty of the reference cell absorption lines. However, it imposes more restrictive requirements on the interrogator software. Both methods were experimentally demonstrated by calibrating multiple commercial systems, reaching uncertainties down to 0.63 pm at a central wavelength of 1550 nm. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 1809 KiB

Open AccessArticle

MineLoC: A Rapid Production of Lab-on-a-Chip Biosensors Using 3D Printer and the Sandbox Game, Minecraft

by Kyukwang Kim^1,†, Hyeongkeun Kim^2,†

, Seunggyu Kim²

and Jessie S. Jeon^2,3,*

¹ Robotics Program, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Daejeon 34141, Korea

² Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Daejeon 34141, Korea

³ KAIST Institute for Health Science and Technology, 291 Daehak-ro, Daejeon 34141, Korea

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1896; https://doi.org/10.3390/s18061896 - 10 Jun 2018

Cited by 5 | Viewed by 7069

Abstract

Here, MineLoC is described as a pipeline developed to generate 3D printable models of master templates for Lab-on-a-Chip (LoC) by using a popular multi-player sandbox game “Minecraft”. The user can draw a simple diagram describing the channels and chambers of the Lab-on-a-Chip devices [...] Read more.

Here, MineLoC is described as a pipeline developed to generate 3D printable models of master templates for Lab-on-a-Chip (LoC) by using a popular multi-player sandbox game “Minecraft”. The user can draw a simple diagram describing the channels and chambers of the Lab-on-a-Chip devices with pre-registered color codes which indicate the height of the generated structure. MineLoC converts the diagram into large chunks of blocks (equal sized cube units composing every object in the game) in the game world. The user and co-workers can simultaneously access the game and edit, modify, or review, which is a feature not generally supported by conventional design software. Once the review is complete, the resultant structure can be exported into a stereolithography (STL) file which can be used in additive manufacturing. Then, the Lab-on-a-Chip device can be fabricated by the standard protocol to produce a Lab-on-a-Chip. The simple polydimethylsiloxane (PDMS) device for the bacterial growth measurement used in the previous research was copied by the proposed method. The error calculation by a 3D model comparison showed an accuracy of 86%. It is anticipated that this work will facilitate more use of 3D printer-based Lab-on-a-Chip fabrication, which greatly lowers the entry barrier in the field of Lab-on-a-Chip research. Full article

(This article belongs to the Section Biosensors)

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13 pages, 2097 KiB

Open AccessArticle

An IBeacon-Based Location System for Smart Home Control

by Qinghe Liu¹, Xinshuang Yang¹ and Lizhen Deng^2,*

¹ Bell Honors School, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

² School of communication and information engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

Sensors 2018, 18(6), 1897; https://doi.org/10.3390/s18061897 - 11 Jun 2018

Cited by 28 | Viewed by 5709

Abstract

Indoor location and intelligent control system can bring convenience to people’s daily life. In this paper, an indoor control system is designed to achieve equipment remote control by using low-energy Bluetooth (BLE) beacon and Internet of Things (IoT) technology. The proposed system consists [...] Read more.

Indoor location and intelligent control system can bring convenience to people’s daily life. In this paper, an indoor control system is designed to achieve equipment remote control by using low-energy Bluetooth (BLE) beacon and Internet of Things (IoT) technology. The proposed system consists of five parts: web server, home gateway, smart terminal, smartphone app and BLE beacons. In the web server, fingerprint matching based on RSSI stochastic characteristic and posture recognition model based on geomagnetic sensing are used to establish a more efficient equipment control system, combined with Pedestrian Dead Reckoning (PDR) technology to improve the accuracy of location. A personalized menu of remote “one-click” control is finally offered to users in a smartphone app. This smart home control system has been implemented by hardware, and precision and stability tests have been conducted, which proved the practicability and good user experience of this solution. Full article

(This article belongs to the Special Issue Smart Homes)

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13 pages, 6702 KiB

Open AccessArticle

Coastline Detection with Gaofen-3 SAR Images Using an Improved FCM Method

by Meng An¹, Qian Sun^2,3,*, Jun Hu^1,4

, Yuqi Tang^1,4 and Ziwei Zhu¹

¹ School of Geosciences and Info-physics, Central South University, Changsha 410083, China

² College of Resources and Environmental Science, Hunan Normal University, Changsha 410081, China

³ Key Laboratory of Geospatial Big Data Mining and Application, Hunan Normal University, Changsha 410081, China

⁴ Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha 410083, China

Sensors 2018, 18(6), 1898; https://doi.org/10.3390/s18061898 - 11 Jun 2018

Cited by 24 | Viewed by 4640

Abstract

The coastline detection is one of the main applications of the Gaofen-3 satellite in the ocean field. However, the capability of Gaofen-3 SAR image in coastline detection has not yet been validated. In this paper, two Gaofen-3 SAR images, acquired in 2016, were [...] Read more.

The coastline detection is one of the main applications of the Gaofen-3 satellite in the ocean field. However, the capability of Gaofen-3 SAR image in coastline detection has not yet been validated. In this paper, two Gaofen-3 SAR images, acquired in 2016, were used to extract the coastlines of the regions of Bohai and Taihu in China, respectively. The classical Fuzzy C-means (FCM) method was used in the coastline detection, but had been improved by combining the Wavelet decomposition algorithm to better suppress the inherent speckle noises of SAR image. Coastline detection results obtained from two Sentinel-1 SAR images acquired on the same regions were compared with those of the Gaofen-3 images. By using the manually delineated coastlines as the standards in the qualitative evaluations, improvements of about 12.0%, 8.3%, 23.8%, and 9.4% can be achieved by the improved FCM method with respect to the indicators of mean, RMSE, PGSD, and P90%, respectively; demonstrating that the Gaofen-3 data is superior to the Sentinel-1 data in the detection of coastline. Full article

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

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13 pages, 8252 KiB

Open AccessArticle

Fiber Bragg Grating Displacement Sensor with High Abrasion Resistance for a Steel Spring Floating Slab Damping Track

by Yongxing Guo^1,2,*

, Wenlong Liu^1,2, Li Xiong^1,2, Yi Kuang^1,2, Heng Wu^1,2 and Honghai Liu³

¹ Key Laboratory of Metallurgical Equipment and Control Technology, Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081, China

² Hubei Key Laboratory of Mechanical Transmission and Manufacturing Engineering, Wuhan University of Science and Technology, Wuhan 430081, China

³ State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Sensors 2018, 18(6), 1899; https://doi.org/10.3390/s18061899 - 11 Jun 2018

Cited by 24 | Viewed by 5042

Abstract

This paper presents a fiber Bragg grating (FBG) displacement sensor with high abrasion resistance for displacement monitoring of a steel spring floating slab damping track. A wedge-shaped sliding block and an equal-strength beam form a conversion mechanism to transfer displacement to the deflection [...] Read more.

This paper presents a fiber Bragg grating (FBG) displacement sensor with high abrasion resistance for displacement monitoring of a steel spring floating slab damping track. A wedge-shaped sliding block and an equal-strength beam form a conversion mechanism to transfer displacement to the deflection of the beam, and the deflection-induced strain is exerted on two FBGs. A special linear guide rail-slider and a precision rolling bearing have been adopted onto the conversion mechanism, which turned sliding friction into rolling friction and thus significantly reduced the friction during frequent alternating displacement measuring. Sensing principle and the corresponding theoretical derivation have been demonstrated. Experiment results show that the sensor has a sensitivity of 34.32 pm/mm and a high resolution of 0.0029 mm within a measurement range of 0~90 mm. Besides, the sensor has also a good measurement capability for micro-displacement within a range of 0~3 mm. The repeatability error and hysteresis error are 1.416% and 0.323%, respectively. Good creep resistance and high abrasion resistance for alternating displacement measurement have also been presented by a performance test. These excellent performances satisfy the requirements of high precision and long-term stability in structural health monitoring for machinery equipment and civil engineering, especially in the displacement monitoring of a floating slab damping track. Full article

(This article belongs to the Special Issue Fiber Optic Sensors for Structural and Geotechnical Monitoring)

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15 pages, 963 KiB

Open AccessArticle

Human Part Segmentation in Depth Images with Annotated Part Positions

by Andrew Hynes^*

and Stephen Czarnuch

Department of Electrical and Computer Engineering, Memorial University, St. John’s, NL A1B 3X5, Canada

Sensors 2018, 18(6), 1900; https://doi.org/10.3390/s18061900 - 11 Jun 2018

Cited by 7 | Viewed by 7259

Abstract

We present a method of segmenting human parts in depth images, when provided the image positions of the body parts. The goal is to facilitate per-pixel labelling of large datasets of human images, which are used for training and testing algorithms for pose [...] Read more.

We present a method of segmenting human parts in depth images, when provided the image positions of the body parts. The goal is to facilitate per-pixel labelling of large datasets of human images, which are used for training and testing algorithms for pose estimation and automatic segmentation. A common technique in image segmentation is to represent an image as a two-dimensional grid graph, with one node for each pixel and edges between neighbouring pixels. We introduce a graph with distinct layers of nodes to model occlusion of the body by the arms. Once the graph is constructed, the annotated part positions are used as seeds for a standard interactive segmentation algorithm. Our method is evaluated on two public datasets containing depth images of humans from a frontal view. It produces a mean per-class accuracy of 93.55% on the first dataset, compared to 87.91% (random forest and graph cuts) and 90.31% (random forest and Markov random field). It also achieves a per-class accuracy of 90.60% on the second dataset. Future work can experiment with various methods for creating the graph layers to accurately model occlusion. Full article

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

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16 pages, 3306 KiB

Open AccessArticle

Partial Least Square Discriminant Analysis Based on Normalized Two-Stage Vegetation Indices for Mapping Damage from Rice Diseases Using PlanetScope Datasets

by Yue Shi^1,2

, Wenjiang Huang^1,3,4,*

, Huichun Ye^1,3, Chao Ruan^1,5, Naichen Xing^1,2, Yun Geng^1,2, Yingying Dong¹ and Dailiang Peng¹

¹ Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Science, Beijing 100094, China

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

³ Key Laboratory of Earth Observation, Sanya 572029, China

⁴ State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China

⁵ School of Electronics and Information Engineering, Anhui University, Hefei 230601, China

Sensors 2018, 18(6), 1901; https://doi.org/10.3390/s18061901 - 11 Jun 2018

Cited by 53 | Viewed by 6490

Abstract

In recent decades, rice disease co-epidemics have caused tremendous damage to crop production in both China and Southeast Asia. A variety of remote sensing based approaches have been developed and applied to map diseases distribution using coarse- to moderate-resolution imagery. However, the detection [...] Read more.

In recent decades, rice disease co-epidemics have caused tremendous damage to crop production in both China and Southeast Asia. A variety of remote sensing based approaches have been developed and applied to map diseases distribution using coarse- to moderate-resolution imagery. However, the detection and discrimination of various disease species infecting rice were seldom assessed using high spatial resolution data. The aims of this study were (1) to develop a set of normalized two-stage vegetation indices (VIs) for characterizing the progressive development of different diseases with rice; (2) to explore the performance of combined normalized two-stage VIs in partial least square discriminant analysis (PLS-DA); and (3) to map and evaluate the damage caused by rice diseases at fine spatial scales, for the first time using bi-temporal, high spatial resolution imagery from PlanetScope datasets at a 3 m spatial resolution. Our findings suggest that the primary biophysical parameters caused by different disease (e.g., changes in leaf area, pigment contents, or canopy morphology) can be captured using combined normalized two-stage VIs. PLS-DA was able to classify rice diseases at a sub-field scale, with an overall accuracy of 75.62% and a Kappa value of 0.47. The approach was successfully applied during a typical co-epidemic outbreak of rice dwarf (Rice dwarf virus, RDV), rice blast (Magnaporthe oryzae), and glume blight (Phyllosticta glumarum) in Guangxi Province, China. Furthermore, our approach highlighted the feasibility of the method in capturing heterogeneous disease patterns at fine spatial scales over the large spatial extents. Full article

(This article belongs to the Special Issue Application of Satellite and Proximal Sensors in Precision Agriculture)

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15 pages, 324 KiB

Open AccessArticle

An Extension to Deng’s Entropy in the Open World Assumption with an Application in Sensor Data Fusion

by Yongchuan Tang^1,2,*

, Deyun Zhou¹ and Felix T. S. Chan^2,*

¹ School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710072, China

² Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hong Kong, China

Sensors 2018, 18(6), 1902; https://doi.org/10.3390/s18061902 - 11 Jun 2018

Cited by 23 | Viewed by 4203

Abstract

Quantification of uncertain degree in the Dempster-Shafer evidence theory (DST) framework with belief entropy is still an open issue, even a blank field for the open world assumption. Currently, the existed uncertainty measures in the DST framework are limited to the closed world [...] Read more.

Quantification of uncertain degree in the Dempster-Shafer evidence theory (DST) framework with belief entropy is still an open issue, even a blank field for the open world assumption. Currently, the existed uncertainty measures in the DST framework are limited to the closed world where the frame of discernment (FOD) is assumed to be complete. To address this issue, this paper focuses on extending a belief entropy to the open world by considering the uncertain information represented as the FOD and the nonzero mass function of the empty set simultaneously. An extension to Deng’s entropy in the open world assumption (EDEOW) is proposed as a generalization of the Deng’s entropy and it can be degenerated to the Deng entropy in the closed world wherever necessary. In order to test the reasonability and effectiveness of the extended belief entropy, an EDEOW-based information fusion approach is proposed and applied to sensor data fusion under uncertainty circumstance. The experimental results verify the usefulness and applicability of the extended measure as well as the modified sensor data fusion method. In addition, a few open issues still exist in the current work: the necessary properties for a belief entropy in the open world assumption, whether there exists a belief entropy that satisfies all the existed properties, and what is the most proper fusion frame for sensor data fusion under uncertainty. Full article

(This article belongs to the Collection Multi-Sensor Information Fusion)

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20 pages, 3075 KiB

Open AccessArticle

A Robust Method for Detecting Parking Areas in Both Indoor and Outdoor Environments

by Wenhao Zong

and Qijun Chen^*

Department of Control Science & Engineering, Tongji University, 4800 Cao’an Hwy, Shanghai 201804, China

Sensors 2018, 18(6), 1903; https://doi.org/10.3390/s18061903 - 11 Jun 2018

Cited by 15 | Viewed by 5871

Abstract

Although an automatic parking system has been installed in many vehicles recently, it is still hard for the system to confirm by itself whether a vacant parking area truly exists or not. In this paper, we introduced a robust vision-based vacancy parking area [...] Read more.

Although an automatic parking system has been installed in many vehicles recently, it is still hard for the system to confirm by itself whether a vacant parking area truly exists or not. In this paper, we introduced a robust vision-based vacancy parking area detecting method for both indoor and outdoor environments. The main contribution of this paper is given as follows. First, an automatic image stitching method is proposed. Secondly, the problem of environment illuminating change and line color difference is considered and solved. Thirdly, the proposed algorithm is insensitive to the shadow and scene diversity, which means the detecting result satisfies most of the environment. Finally, a vehicle model is considered for tracking and reconfirming the detecting results to eliminate most of the false positives. Full article

(This article belongs to the Section Intelligent Sensors)

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16 pages, 898 KiB

Open AccessArticle

Energy-Aware RFID Anti-Collision Protocol

by Laura Arjona^*

, Hugo Landaluce Simon

and Asier Perallos Ruiz

Faculty of Engineering, University of Deusto and DeustoTech-Fundacion Deusto, Deusto Foundation, 48007 Bilbao, Spain

Sensors 2018, 18(6), 1904; https://doi.org/10.3390/s18061904 - 11 Jun 2018

Cited by 8 | Viewed by 4361

Abstract

The growing interest in mobile devices is transforming wireless identification technologies. Mobile and battery-powered Radio Frequency Identification (RFID) readers, such as hand readers and smart phones, are are becoming increasingly attractive. These RFID readers require energy-efficient anti-collision protocols to minimize the tag collisions [...] Read more.

The growing interest in mobile devices is transforming wireless identification technologies. Mobile and battery-powered Radio Frequency Identification (RFID) readers, such as hand readers and smart phones, are are becoming increasingly attractive. These RFID readers require energy-efficient anti-collision protocols to minimize the tag collisions and to expand the reader’s battery life. Furthermore, there is an increasing interest in RFID sensor networks with a growing number of RFID sensor tags. Thus, RFID application developers must be mindful of tag anti-collision protocols. Energy-efficient protocols involve a low reader energy consumption per tag. This work presents a thorough study of the reader energy consumption per tag and analyzes the main factor that affects this metric: the frame size update strategy. Using the conclusion of this analysis, the anti-collision protocol Energy-Aware Slotted Aloha (EASA) is presented to decrease the energy consumption per tag. The frame size update strategy of EASA is configured to minimize the energy consumption per tag. As a result, EASA presents an energy-aware frame. The performance of the proposed protocol is evaluated and compared with several state of the art Aloha-based anti-collision protocols based on the current RFID standard. Simulation results show that EASA, with an average of 15 mJ consumed per tag identified, achieves a 6% average improvement in the energy consumption per tag in relation to the strategies of the comparison. Full article

(This article belongs to the Special Issue RFID-Based Sensors for IoT Applications)

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19 pages, 447 KiB

Open AccessArticle

A Globally Generalized Emotion Recognition System Involving Different Physiological Signals

by Mouhannad Ali^1,*

, Fadi Al Machot²

, Ahmad Haj Mosa¹, Midhat Jdeed¹, Elyan Al Machot³ and Kyandoghere Kyamakya¹

¹ Department of Smart Systems Technologies, Alpen-Adira University, Klagenfurt 9020, Austria

² Research Center Borstel—Leibniz Center for Medicine and Biosciences, Borstel 23845, Germany

³ Carl Gustav Carus Faculty of Medicine, Dresden University of Technology, Dresden 01069, Germany

Sensors 2018, 18(6), 1905; https://doi.org/10.3390/s18061905 - 11 Jun 2018

Cited by 39 | Viewed by 6121

Abstract

Machine learning approaches for human emotion recognition have recently demonstrated high performance. However, only/mostly for subject-dependent approaches, in a variety of applications like advanced driver assisted systems, smart homes and medical environments. Therefore, now the focus is shifted more towards subject-independent approaches, which [...] Read more.

Machine learning approaches for human emotion recognition have recently demonstrated high performance. However, only/mostly for subject-dependent approaches, in a variety of applications like advanced driver assisted systems, smart homes and medical environments. Therefore, now the focus is shifted more towards subject-independent approaches, which are more universal and where the emotion recognition system is trained using a specific group of subjects and then tested on totally new persons and thereby possibly while using other sensors of same physiological signals in order to recognize their emotions. In this paper, we explore a novel robust subject-independent human emotion recognition system, which consists of two major models. The first one is an automatic feature calibration model and the second one is a classification model based on Cellular Neural Networks (CNN). The proposed system produces state-of-the-art results with an accuracy rate between

80 %

and

89 %

when using the same elicitation materials and physiological sensors brands for both training and testing and an accuracy rate of

71.05 %

when the elicitation materials and physiological sensors brands used in training are different from those used in training. Here, the following physiological signals are involved: ECG (Electrocardiogram), EDA (Electrodermal activity) and ST (Skin-Temperature). Full article

(This article belongs to the Special Issue From Sensors to Ambient Intelligence for Health and Social Care)

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22 pages, 3097 KiB

Open AccessArticle

A Bayesian Scene-Prior-Based Deep Network Model for Face Verification

by Huafeng Wang^1,2,*,†

, Wenfeng Song^2,†, Wanquan Liu^3,*,†, Ning Song^2,*,†, Yuehai Wang^1,† and Haixia Pan^2,*

¹ Department of Electronics and Information Engineering, North China University of Technology, Beijing 100144, China

² Department of Software, Beihang University, Beijing 100191, China

³ Department of Computing, Curtin University, Perth, WA 6102, Australia

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1906; https://doi.org/10.3390/s18061906 - 11 Jun 2018

Cited by 6 | Viewed by 4219

Abstract

Face recognition/verification has received great attention in both theory and application for the past two decades. Deep learning has been considered as a very powerful tool for improving the performance of face recognition/verification recently. With large labeled training datasets, the features obtained from [...] Read more.

Face recognition/verification has received great attention in both theory and application for the past two decades. Deep learning has been considered as a very powerful tool for improving the performance of face recognition/verification recently. With large labeled training datasets, the features obtained from deep learning networks can achieve higher accuracy in comparison with shallow networks. However, many reported face recognition/verification approaches rely heavily on the large size and complete representative of the training set, and most of them tend to suffer serious performance drop or even fail to work if fewer training samples per person are available. Hence, the small number of training samples may cause the deep features to vary greatly. We aim to solve this critical problem in this paper. Inspired by recent research in scene domain transfer, for a given face image, a new series of possible scenarios about this face can be deduced from the scene semantics extracted from other face individuals in a face dataset. We believe that the “scene” or background in an image, that is, samples with more different scenes for a given person, may determine the intrinsic features among the faces of the same individual. In order to validate this belief, we propose a Bayesian scene-prior-based deep learning model in this paper with the aim to extract important features from background scenes. By learning a scene model on the basis of a labeled face dataset via the Bayesian idea, the proposed method transforms a face image into new face images by referring to the given face with the learnt scene dictionary. Because the new derived faces may have similar scenes to the input face, the face-verification performance can be improved without having background variance, while the number of training samples is significantly reduced. Experiments conducted on the Labeled Faces in the Wild (LFW) dataset view #2 subset illustrated that this model can increase the verification accuracy to 99.2% by means of scenes’ transfer learning (99.12% in literature with an unsupervised protocol). Meanwhile, our model can achieve 94.3% accuracy for the YouTube Faces database (DB) (93.2% in literature with an unsupervised protocol). Full article

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

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16 pages, 6735 KiB

Open AccessFeature PaperArticle

Strain Transfer for Optimal Performance of Sensing Sheet

by Matthew Gerber, Campbell Weaver

, Levent E. Aygun, Naveen Verma, James C. Sturm and Branko Glišić^*

Departments of Civil and Environmental Engineering, and Electrical Engineering, Princeton University, Princeton, NJ 08544, USA

Sensors 2018, 18(6), 1907; https://doi.org/10.3390/s18061907 - 12 Jun 2018

Cited by 13 | Viewed by 4400

Abstract

Sensing sheets based on Large Area Electronics (LAE) and Integrated Circuits (ICs) are novel sensors designed to enable reliable early-stage detection of local unusual structural behaviors. Such a device consists of a dense array of strain sensors, patterned onto a flexible polyimide substrate [...] Read more.

Sensing sheets based on Large Area Electronics (LAE) and Integrated Circuits (ICs) are novel sensors designed to enable reliable early-stage detection of local unusual structural behaviors. Such a device consists of a dense array of strain sensors, patterned onto a flexible polyimide substrate along with associated electronics. Previous tests performed on steel specimens equipped with sensing sheet prototypes and subjected to fatigue cracking pointed to a potential issue: individual sensors that were on or near a crack would immediately be damaged by the crack, thereby rendering them useless in assessing the size of the crack opening or to monitor future crack growth. In these tests, a stiff adhesive was used to bond the sensing sheet prototype to the steel specimen. Such an adhesive provided excellent strain transfer, but it also caused premature failure of individual sensors within the sheet. Therefore, the aim of this paper is to identify an alternative adhesive that survives minor damage, yet provides strain transfer that is sufficient for reliable early-stage crack detection. A sensor sheet prototype is then calibrated for use with the selected adhesive. Full article

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

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11 pages, 1980 KiB

Open AccessArticle

Numerical and Experimental Evaluation of High-Frequency Unfocused Polymer Transducer Arrays

by Anowarul Habib^*, Sanat Wagle, Adit Decharat and Frank Melandsø

Department of Physics and Technology, UiT The Arctic University of Norway, 9037 Tromsø, Norway

Sensors 2018, 18(6), 1908; https://doi.org/10.3390/s18061908 - 12 Jun 2018

Cited by 3 | Viewed by 4522

Abstract

High-frequency unfocused polymer array transducers are developed using an adhesive-free layer-by-layer assembly method. The current paper focuses on experimental and numerical methods for measuring the acoustic performance of these types of array transducers. Two different types of numerical approaches were used to simulate [...] Read more.

High-frequency unfocused polymer array transducers are developed using an adhesive-free layer-by-layer assembly method. The current paper focuses on experimental and numerical methods for measuring the acoustic performance of these types of array transducers. Two different types of numerical approaches were used to simulate the transducer performance, including a finite element method (FEM) study of the transducer response done in COMSOL 5.2a Multiphysics, and modeling of the excited ultrasonic pressure fields using the open source software k-Wave 1.2.1. The experimental characterization also involves two methods (narrow and broadband pulses), which are measurements of the acoustic reflections picked up by the transducer elements. Later on, measurements were undertaken of the ultrasonic pressure fields in a water-scanning tank using a hydrophone system. Ultrasonic pressure field measurements were visualized at various distances from the transducer surface and compared with the numerical findings. Full article

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

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17 pages, 2318 KiB

Open AccessArticle

Enhancing the Discrimination Ability of a Gas Sensor Array Based on a Novel Feature Selection and Fusion Framework

by Changjian Deng¹, Kun Lv², Debo Shi³, Bo Yang¹, Song Yu¹, Zhiyi He¹ and Jia Yan^1,*

¹ College of Electronic and Information Engineering, Southwest University, Chongqing 400715, China

² High Tech Department, China International Engineering Consulting Corporation, Beijing 100048, China

³ Westa College, Southwest University, Chongqing 400715, China

Sensors 2018, 18(6), 1909; https://doi.org/10.3390/s18061909 - 12 Jun 2018

Cited by 25 | Viewed by 3596

Abstract

In this paper, a novel feature selection and fusion framework is proposed to enhance the discrimination ability of gas sensor arrays for odor identification. Firstly, we put forward an efficient feature selection method based on the separability and the dissimilarity to determine the [...] Read more.

In this paper, a novel feature selection and fusion framework is proposed to enhance the discrimination ability of gas sensor arrays for odor identification. Firstly, we put forward an efficient feature selection method based on the separability and the dissimilarity to determine the feature selection order for each type of feature when increasing the dimension of selected feature subsets. Secondly, the K-nearest neighbor (KNN) classifier is applied to determine the dimensions of the optimal feature subsets for different types of features. Finally, in the process of establishing features fusion, we come up with a classification dominance feature fusion strategy which conducts an effective basic feature. Experimental results on two datasets show that the recognition rates of Database I and Database II achieve 97.5% and 80.11%, respectively, when k = 1 for KNN classifier and the distance metric is correlation distance (COR), which demonstrates the superiority of the proposed feature selection and fusion framework in representing signal features. The novel feature selection method proposed in this paper can effectively select feature subsets that are conducive to the classification, while the feature fusion framework can fuse various features which describe the different characteristics of sensor signals, for enhancing the discrimination ability of gas sensors and, to a certain extent, suppressing drift effect. Full article

(This article belongs to the Section Chemical Sensors)

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20 pages, 4806 KiB

Open AccessArticle

Data Fusion Architectures for Orthogonal Redundant Inertial Measurement Units

by Eric Gagnon^1,*, Alexandre Vachon² and Yanick Beaudoin³

¹ Defence Research and Development Canada, Quebec, QC G3J 1X5, Canada

² Numérica Technologies Inc., Quebec, QC G2E 4P8, Canada

³ Département de génie électrique et génie informatique, Université Laval, Quebec, QC G1V 0A6, Canada

Sensors 2018, 18(6), 1910; https://doi.org/10.3390/s18061910 - 12 Jun 2018

Cited by 3 | Viewed by 3748

Abstract

This work looks at the exploitation of large numbers of orthogonal redundant inertial measurement units. Specifically, the paper analyses centralized and distributed architectures in the context of data fusion algorithms for those sensors. For both architectures, data fusion algorithms based on Kalman filter [...] Read more.

This work looks at the exploitation of large numbers of orthogonal redundant inertial measurement units. Specifically, the paper analyses centralized and distributed architectures in the context of data fusion algorithms for those sensors. For both architectures, data fusion algorithms based on Kalman filter are developed. Some of those algorithms consider sensors location, whereas the others do not, but all estimate the sensors bias. A fault detection algorithm, based on residual analysis, is also proposed. Monte-Carlo simulations show better performance for the centralized architecture with an algorithm considering sensors location. Due to a better estimation of the sensors bias, the latter provides the most precise and accurate estimates and the best fault detection. However, it requires a much longer computational time. An analysis of the sensors bias correlation is also done. Based on the simulations, the biases correlation has a small effect on the attitude rate estimation, but a very significant one on the acceleration estimation. Full article

(This article belongs to the Collection Multi-Sensor Information Fusion)

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12 pages, 3670 KiB

Open AccessArticle

Sensitive and Selective Detection of Tartrazine Based on TiO₂-Electrochemically Reduced Graphene Oxide Composite-Modified Electrodes

by Quanguo He^1,2,3,†

, Jun Liu^1,3,†, Xiaopeng Liu^2,3, Guangli Li^1,3, Peihong Deng^2,3,*, Jing Liang^2,3 and Dongchu Chen^1,*

¹ School of Materials Science and Energy Engineering, Foshan University, Foshan 528000, China

² Department of Chemistry and Material Science, Hengyang Normal University, Hengyang 421008, China

³ Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Sciences and Chemistry, Hunan University of Technology, Zhuzhou 412007, China

^† These authors contributed equally.

Sensors 2018, 18(6), 1911; https://doi.org/10.3390/s18061911 - 12 Jun 2018

Cited by 75 | Viewed by 5007

Abstract

TiO₂-reduced graphene oxide composite-modified glassy carbon electrodes (TiO₂–ErGO–GCE) for the sensitive detection of tartrazine were prepared by drop casting followed by electrochemical reduction. The as-prepared material was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Cyclic voltammetry [...] Read more.

TiO₂-reduced graphene oxide composite-modified glassy carbon electrodes (TiO₂–ErGO–GCE) for the sensitive detection of tartrazine were prepared by drop casting followed by electrochemical reduction. The as-prepared material was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Cyclic voltammetry and second-order derivative linear scan voltammetry were performed to analyze the electrochemical sensing of tartrazine on different electrodes. The determination conditions (including pH, accumulation potential, and accumulation time) were optimized systematically. The results showed that the TiO₂–ErGO composites increased the electrochemical active area of the electrode and enhanced the electrochemical responses to tartrazine significantly. Under the optimum detection conditions, the peak current was found to be linear for tartrazine concentrations in the range of 2.0 × 10⁻⁸–2.0 × 10⁻⁵ mol/L, with a lower detection limit of 8.0 × 10⁻⁹ mol/L (S/N = 3). Finally, the proposed TiO₂–ErGO–GCEs were successfully applied for the detection of trace tartrazine in carbonated beverage samples. Full article

(This article belongs to the Section Chemical Sensors)

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10 pages, 7665 KiB

Open AccessArticle

Microwave Metamaterial Absorber for Non-Destructive Sensing Applications of Grain

by Yin Zhang^1,2

, Junming Zhao², Jie Cao^1,* and Bo Mao¹

¹ Collaborative Innovation Center for Modern Grain Circulation and Safety, School of Information Engineering, Nanjing University of Finance and Economics, Nanjing 210046, China

² Department of Electronic Engineering, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China

Sensors 2018, 18(6), 1912; https://doi.org/10.3390/s18061912 - 12 Jun 2018

Cited by 66 | Viewed by 7059

Abstract

In this work, we propose a metamaterial absorber at microwave frequencies with significant sensitivity and non-destructive sensing capability for grain samples. This absorber is composed of cross-resonators periodically arranged on an ultrathin substrate, a sensing layer filled with grain samples, and a metal [...] Read more.

In this work, we propose a metamaterial absorber at microwave frequencies with significant sensitivity and non-destructive sensing capability for grain samples. This absorber is composed of cross-resonators periodically arranged on an ultrathin substrate, a sensing layer filled with grain samples, and a metal ground. The cross-resonator array is fabricated using the printed circuit board process on an FR-4 board. The performance of the proposed metamaterial is demonstrated with both full-wave simulation and measurement results, and the working mechanism is revealed through multi-reflection interference theory. It can serve as a non-contact sensor for food quality control such as adulteration, variety, etc. by detecting shifts in the resonant frequencies. As a direct application, it is shown that the resonant frequency displays a significant blue shift from 7.11 GHz to 7.52 GHz when the mass fraction of stale rice in the mixture of fresh and stale rice is changed from 0% to 100%. In addition, the absorber shows a distinct difference in the resonant absorption frequency for different varieties of grain, which also makes it a candidate for a grain classification sensor. The presented scheme could open up opportunities for microwave metamaterial absorbers to be applied as efficient sensors in the non-destructive evaluation of agricultural and food product quality. Full article

(This article belongs to the Special Issue Antenna Technologies for Microwave Sensors)

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15 pages, 2701 KiB

Open AccessArticle

Effective Vehicle-Based Kangaroo Detection for Collision Warning Systems Using Region-Based Convolutional Networks

by Khaled Saleh^*, Mohammed Hossny and Saeid Nahavandi

Institute for Intelligent Systems Research and Innovation (IISRI), Deakin University, Waurn Ponds, Victoria 3216, Australia

Sensors 2018, 18(6), 1913; https://doi.org/10.3390/s18061913 - 12 Jun 2018

Cited by 19 | Viewed by 4768

Abstract

Traffic collisions between kangaroos and motorists are on the rise on Australian roads. According to a recent report, it was estimated that there were more than 20,000 kangaroo vehicle collisions that occurred only during the year 2015 in Australia. In this work, we [...] Read more.

Traffic collisions between kangaroos and motorists are on the rise on Australian roads. According to a recent report, it was estimated that there were more than 20,000 kangaroo vehicle collisions that occurred only during the year 2015 in Australia. In this work, we are proposing a vehicle-based framework for kangaroo detection in urban and highway traffic environment that could be used for collision warning systems. Our proposed framework is based on region-based convolutional neural networks (RCNN). Given the scarcity of labeled data of kangaroos in traffic environments, we utilized our state-of-the-art data generation pipeline to generate 17,000 synthetic depth images of traffic scenes with kangaroo instances annotated in them. We trained our proposed RCNN-based framework on a subset of the generated synthetic depth images dataset. The proposed framework achieved a higher average precision (AP) score of 92% over all the testing synthetic depth image datasets. We compared our proposed framework against other baseline approaches and we outperformed it with more than 37% in AP score over all the testing datasets. Additionally, we evaluated the generalization performance of the proposed framework on real live data and we achieved a resilient detection accuracy without any further fine-tuning of our proposed RCNN-based framework. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 1892 KiB

Open AccessArticle

Transilient Response to Acetone Gas Using the Interlocking p+n Field-Effect Transistor Circuit

by Xinyuan Zhou^1,2,3, Jinxiao Wang⁴, Zhou Wang¹, Yuzhi Bian^1,2, Ying Wang¹, Ning Han^1,3,*

and Yunfa Chen^1,3,*

¹ State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China

² College of Chemical Engineering, University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China

³ Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China

⁴ College of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2018, 18(6), 1914; https://doi.org/10.3390/s18061914 - 12 Jun 2018

Cited by 12 | Viewed by 4378

Abstract

Low concentration acetone gas detection is significantly important for diabetes diagnosis as 1.8–10 ppm of acetone exists in exhaled breath from diabetes patients. A new interlocking p+n field-effect transistor (FET) circuit has been proposed for Mn-doped ZnO nanoparticles (MZO) to detect the acetone [...] Read more.

Low concentration acetone gas detection is significantly important for diabetes diagnosis as 1.8–10 ppm of acetone exists in exhaled breath from diabetes patients. A new interlocking p+n field-effect transistor (FET) circuit has been proposed for Mn-doped ZnO nanoparticles (MZO) to detect the acetone gas at low concentration, especially close to 1.8 ppm. It is noteworthy that MZO in this interlocking amplification circuit shows a low voltage signal of <0.3 V to the acetone <2 ppm while it displays a transilient response with voltage signal >4.0 V to >2 ppm acetone. In other words, the response to acetone from 1 ppm to 2 ppm increases by ~1233%, which is competent to separate diabetic patients from healthy people. Moreover, the response to 2 ppm acetone is hardly influenced by high relative humidity of 85%. In the meanwhile, MZO in this interlocking circuit possesses a high acetone selectivity compared to formaldehyde, acetaldehyde, toluene and ethanol, suggesting a promising technology for the widespread qualitative screening of diabetes. Importantly, this interlocking circuit is also applicable to other types of metal oxide semiconductor gas sensors. The resistance jump of p- and n-FETs induced by the change of their gate voltages is deemed to make this interlocking circuit produce the transilient response. Full article

(This article belongs to the Section Chemical Sensors)

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19 pages, 10486 KiB

Open AccessArticle

Automatic Railway Traffic Object Detection System Using Feature Fusion Refine Neural Network under Shunting Mode

by Tao Ye^1,*

, Baocheng Wang², Ping Song³

and Juan Li³

¹ Beijing Institute of Remote Sensing and Equipment, 52 Yongding Road, Haidian District, Beijing 100039, China

² College of Computer and Science Technology, North China University of Technology, 5 Jin Yuan Zhuang Road, Shijingshan District, Beijing 100144, China

³ School of Instrumentation Science and Opto-Electronics Engineering, Key Laboratory of Precision Opto-Mechatronics Technology, Ministry of Education, Beihang University, Beijing 100191, China

Sensors 2018, 18(6), 1916; https://doi.org/10.3390/s18061916 - 12 Jun 2018

Cited by 60 | Viewed by 9754 | Correction

Abstract

Many accidents happen under shunting mode when the speed of a train is below 45 km/h. In this mode, train attendants observe the railway condition ahead using the traditional manual method and tell the observation results to the driver in order to avoid [...] Read more.

Many accidents happen under shunting mode when the speed of a train is below 45 km/h. In this mode, train attendants observe the railway condition ahead using the traditional manual method and tell the observation results to the driver in order to avoid danger. To address this problem, an automatic object detection system based on convolutional neural network (CNN) is proposed to detect objects ahead in shunting mode, which is called Feature Fusion Refine neural network (FR-Net). It consists of three connected modules, i.e., the depthwise-pointwise convolution, the coarse detection module, and the object detection module. Depth-wise-pointwise convolutions are used to improve the detection in real time. The coarse detection module coarsely refine the locations and sizes of prior anchors to provide better initialization for the subsequent module and also reduces search space for the classification, whereas the object detection module aims to regress accurate object locations and predict the class labels for the prior anchors. The experimental results on the railway traffic dataset show that FR-Net achieves 0.8953 mAP with 72.3 FPS performance on a machine with a GeForce GTX1080Ti with the input size of 320 × 320 pixels. The results imply that FR-Net takes a good tradeoff both on effectiveness and real time performance. The proposed method can meet the needs of practical application in shunting mode. Full article

(This article belongs to the Section Physical Sensors)

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28 pages, 3071 KiB

Open AccessArticle

Two-Phase Framework for Indoor Positioning Systems Using Visible Light ^†

by Gregary B. Prince^* and Thomas D. C. Little

¹ Department of Electrical and Computer Engineering, College of Engineering, Boston University, Boston, MA 02215, USA

^† This work was presented partially at “Prince, G.B.; Little, T.D. A two phase hybrid RSS/AoA algorithm for indoor device localization using visible light. In Proceedings of 2012 IEEE Global Communications Conference (GLOBECOM), Anaheim, CA, USA, 3–7 December 2012; pp. 3347–3352.” and “Prince, G.B.; Little, T.D. Latency constrained device positioning using a visible light communication two-phase received signal strength—angle of arrival algorithm. In Proceedings of the 2015 International Conference on Indoor Positioning and Indoor Navigation (IPIN), Banff, AB, Canada, 13–16 October 2015; pp. 1–7”.

Sensors 2018, 18(6), 1917; https://doi.org/10.3390/s18061917 - 12 Jun 2018

Cited by 13 | Viewed by 4574

Abstract

Recently with the advancement of solid state lighting and the application thereof to Visible Light Communications (VLC), the concept of Visible Light Positioning (VLP) has been targeted as a very attractive indoor positioning system (IPS) due to its ubiquity, directionality, spatial reuse, and [...] Read more.

Recently with the advancement of solid state lighting and the application thereof to Visible Light Communications (VLC), the concept of Visible Light Positioning (VLP) has been targeted as a very attractive indoor positioning system (IPS) due to its ubiquity, directionality, spatial reuse, and relatively high modulation bandwidth. IPSs, in general, have four major components: (1) a modulation, (2) a multiple access scheme, (3) a channel measurement, and (4) a positioning algorithm. A number of VLP approaches have been proposed in the literature and primarily focus on a fixed combination of these elements and moreover evaluate the quality of the contribution often by accuracy or precision alone. In this article, we provide a novel two-phase indoor positioning algorithmic framework that is able to increase robustness when subject to insufficient anchor luminaries and also incorporate any combination of the four major IPS components. Full article

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

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19 pages, 1485 KiB

Open AccessArticle

Using Temporal Covariance of Motion and Geometric Features via Boosting for Human Fall Detection

by Syed Farooq Ali¹

, Reamsha Khan¹, Arif Mahmood²

, Malik Tahir Hassan¹

and Moongu Jeon^3,*

¹ Department of Software Engineering, University of Management and Technology, UMT Road, C-II Johar Town, Lahore 54000, Pakistan

² Department of Computer Science, Information Technology University (ITU), 346-B, Ferozepur Road, Lahore, Punjab 54000, Pakistan

³ School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea

Sensors 2018, 18(6), 1918; https://doi.org/10.3390/s18061918 - 12 Jun 2018

Cited by 29 | Viewed by 5763

Abstract

Fall induced damages are serious incidences for aged as well as young persons. A real-time automatic and accurate fall detection system can play a vital role in timely medication care which will ultimately help to decrease the damages and complications. In this paper, [...] Read more.

Fall induced damages are serious incidences for aged as well as young persons. A real-time automatic and accurate fall detection system can play a vital role in timely medication care which will ultimately help to decrease the damages and complications. In this paper, we propose a fast and more accurate real-time system which can detect people falling in videos captured by surveillance cameras. Novel temporal and spatial variance-based features are proposed which comprise the discriminatory motion, geometric orientation and location of the person. These features are used along with ensemble learning strategy of boosting with J48 and Adaboost classifiers. Experiments have been conducted on publicly available standard datasets including Multiple Cameras Fall (with 2 classes and 3 classes) and UR Fall Detection achieving percentage accuracies of 99.2, 99.25 and 99.0, respectively. Comparisons with nine state-of-the-art methods demonstrate the effectiveness of the proposed approach on both datasets. Full article

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

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22 pages, 5764 KiB

Open AccessArticle

An Improved Strong Tracking Cubature Kalman Filter for GPS/INS Integrated Navigation Systems

by Kaiqiang Feng^1,2, Jie Li^1,2,*, Xi Zhang^1,2, Xiaoming Zhang^1,2, Chong Shen^1,2

, Huiliang Cao^1,2, Yanyu Yang^1,2 and Jun Liu^1,2

¹ Key Laboratory of Instrumentation Science & Dynamic Measurement, Ministry of Education, North University of China, Taiyuan 030051, China

² National Key Laboratory for Electronic Measurement Technology, North University of China, Taiyuan 030051, China

Sensors 2018, 18(6), 1919; https://doi.org/10.3390/s18061919 - 12 Jun 2018

Cited by 45 | Viewed by 5235

Abstract

The cubature Kalman filter (CKF) is widely used in the application of GPS/INS integrated navigation systems. However, its performance may decline in accuracy and even diverge in the presence of process uncertainties. To solve the problem, a new algorithm named improved strong tracking [...] Read more.

The cubature Kalman filter (CKF) is widely used in the application of GPS/INS integrated navigation systems. However, its performance may decline in accuracy and even diverge in the presence of process uncertainties. To solve the problem, a new algorithm named improved strong tracking seventh-degree spherical simplex-radial cubature Kalman filter (IST-7thSSRCKF) is proposed in this paper. In the proposed algorithm, the effect of process uncertainty is mitigated by using the improved strong tracking Kalman filter technique, in which the hypothesis testing method is adopted to identify the process uncertainty and the prior state estimate covariance in the CKF is further modified online according to the change in vehicle dynamics. In addition, a new seventh-degree spherical simplex-radial rule is employed to further improve the estimation accuracy of the strong tracking cubature Kalman filter. In this way, the proposed comprehensive algorithm integrates the advantage of 7thSSRCKF’s high accuracy and strong tracking filter’s strong robustness against process uncertainties. The GPS/INS integrated navigation problem with significant dynamic model errors is utilized to validate the performance of proposed IST-7thSSRCKF. Results demonstrate that the improved strong tracking cubature Kalman filter can achieve higher accuracy than the existing CKF and ST-CKF, and is more robust for the GPS/INS integrated navigation system. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 3770 KiB

Open AccessArticle

Fault Diagnosis Method for a Mine Hoist in the Internet of Things Environment

by Juanli Li^1,2,*, Jiacheng Xie¹, Zhaojian Yang¹ and Junjie Li¹

¹ Shanxi Key Laboratory of Fully Mechanized Coal Mining Equipment, College of Mechanical Engineering, Taiyuan University of Technology, Taiyuan 030024, China

² Post-Doctoral Scientific Research Station, Shanxi Coking Coal Group Co., Ltd., Taiyuan 030024, China

Sensors 2018, 18(6), 1920; https://doi.org/10.3390/s18061920 - 13 Jun 2018

Cited by 30 | Viewed by 7042

Abstract

To reduce the difficulty of acquiring and transmitting data in mining hoist fault diagnosis systems and to mitigate the low efficiency and unreasonable reasoning process problems, a fault diagnosis method for mine hoisting equipment based on the Internet of Things (IoT) is proposed [...] Read more.

To reduce the difficulty of acquiring and transmitting data in mining hoist fault diagnosis systems and to mitigate the low efficiency and unreasonable reasoning process problems, a fault diagnosis method for mine hoisting equipment based on the Internet of Things (IoT) is proposed in this study. The IoT requires three basic architectural layers: a perception layer, network layer, and application layer. In the perception layer, we designed a collaborative acquisition system based on the ZigBee short distance wireless communication technology for key components of the mine hoisting equipment. Real-time data acquisition was achieved, and a network layer was created by using long-distance wireless General Packet Radio Service (GPRS) transmission. The transmission and reception platforms for remote data transmission were able to transmit data in real time. A fault diagnosis reasoning method is proposed based on the improved Dezert-Smarandache Theory (DSmT) evidence theory, and fault diagnosis reasoning is performed. Based on interactive technology, a humanized and visualized fault diagnosis platform is created in the application layer. The method is then verified. A fault diagnosis test of the mine hoisting mechanism shows that the proposed diagnosis method obtains complete diagnostic data, and the diagnosis results have high accuracy and reliability. Full article

(This article belongs to the Special Issue Advances in Sensing, Processing and Transmission for IoT-Oriented Sensors Networks)

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18 pages, 4314 KiB

Open AccessArticle

Error Analysis of Magnetohydrodynamic Angular Rate Sensor Combing with Coriolis Effect at Low Frequency

by Yue Ji^1,*, Mengjie Xu², Xingfei Li³, Tengfei Wu³, Weixiao Tuo³, Jun Wu⁴ and Jiuzhi Dong⁵

¹ Key Laboratory of Advanced Electrical Engineering and Energy Technology, Tianjin Polytechnic University, Tianjin 300387, China

² School of Instrument Science and Opto-Electronics Engineering, Hefei University of Technology, Hefei 230009, China

³ State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China

⁴ Aviation Engineering Institute, Civil Aviation University of China, Tianjin 300300, China

⁵ Advanced Mechatronics Equipment Technology Tianjin Area Major Laboratory, Tianjin Polytechnic University, Tianjin 300160, China

Sensors 2018, 18(6), 1921; https://doi.org/10.3390/s18061921 - 13 Jun 2018

Cited by 15 | Viewed by 4734

Abstract

The magnetohydrodynamic (MHD) angular rate sensor (ARS) with low noise level in ultra-wide bandwidth is developed in lasing and imaging applications, especially the line-of-sight (LOS) system. A modified MHD ARS combined with the Coriolis effect was studied in this paper to expand the [...] Read more.

The magnetohydrodynamic (MHD) angular rate sensor (ARS) with low noise level in ultra-wide bandwidth is developed in lasing and imaging applications, especially the line-of-sight (LOS) system. A modified MHD ARS combined with the Coriolis effect was studied in this paper to expand the sensor’s bandwidth at low frequency (<1 Hz), which is essential for precision LOS pointing and wide-bandwidth LOS jitter suppression. The model and the simulation method were constructed and a comprehensive solving method based on the magnetic and electric interaction methods was proposed. The numerical results on the Coriolis effect and the frequency response of the modified MHD ARS were detailed. In addition, according to the experimental results of the designed sensor consistent with the simulation results, an error analysis of model errors was discussed. Our study provides an error analysis method of MHD ARS combined with the Coriolis effect and offers a framework for future studies to minimize the error. Full article

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

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14 pages, 3550 KiB

Open AccessFeature PaperArticle

Classification of Bitter Orange Essential Oils According to Fruit Ripening Stage by Untargeted Chemical Profiling and Machine Learning

by Saeedeh Taghadomi-Saberi^1,2

, Sílvia Mas Garcia^2,*, Amin Allah Masoumi¹, Morteza Sadeghi¹ and Santiago Marco^2,3

¹ Department of Biosystems Engineering, College of Agriculture, Isfahan University of Technology, Isfahan P.O. Box 84156-83111, Iran

² Signal and Information Processing for Sensing Systems, Institute for Bioengineering of Catalonia, The Barcelona Institute for Science and Technology, Baldiri Reixac 4-8, 08028 Barcelona, Spain

³ Department of Electronics and Biomedical Engineering, Universitat de Barcelona, Marti i Franqués 1, 08028 Barcelona, Spain

Sensors 2018, 18(6), 1922; https://doi.org/10.3390/s18061922 - 13 Jun 2018

Cited by 18 | Viewed by 8866

Abstract

The quality and composition of bitter orange essential oils (EOs) strongly depend on the ripening stage of the citrus fruit. The concentration of volatile compounds and consequently its organoleptic perception varies. While this can be detected by trained humans, we propose an objective [...] Read more.

The quality and composition of bitter orange essential oils (EOs) strongly depend on the ripening stage of the citrus fruit. The concentration of volatile compounds and consequently its organoleptic perception varies. While this can be detected by trained humans, we propose an objective approach for assessing the bitter orange from the volatile composition of their EO. The method is based on the combined use of headspace gas chromatography–mass spectrometry (HS-GC-MS) and artificial neural networks (ANN) for predictive modeling. Data obtained from the analysis of HS-GC-MS were preprocessed to select relevant peaks in the total ion chromatogram as input features for ANN. Results showed that key volatile compounds have enough predictive power to accurately classify the EO, according to their ripening stage for different applications. A sensitivity analysis detected the key compounds to identify the ripening stage. This study provides a novel strategy for the quality control of bitter orange EO without subjective methods. Full article

(This article belongs to the Special Issue Multivariate Data Analysis for Sensors and Sensor Arrays)

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14 pages, 8374 KiB

Open AccessArticle

Online 3D Displacement Measurement Using Speckle Interferometer with a Single Illumination-Detection Path

by Min Lu^*, Shengjia Wang, Laura Bilgeri, Xian Song, Martin Jakobi

and Alexander W. Koch

Institute for Measurement Systems and Sensor Technology, Technical University of Munich, Theresienstraße 90/N5, 80333 Munich, Germany

Sensors 2018, 18(6), 1923; https://doi.org/10.3390/s18061923 - 13 Jun 2018

Cited by 25 | Viewed by 6885

Abstract

Measurement systems for online nondestructive full-field three-dimensional (3D) displacement based on the single-shot and multiplexing techniques attract more and more interest, especially throughout the manufacturing industries. This paper proposes an accurate and easy-to-implement method based on an electronic speckle pattern interferometer (ESPI) with [...] Read more.

Measurement systems for online nondestructive full-field three-dimensional (3D) displacement based on the single-shot and multiplexing techniques attract more and more interest, especially throughout the manufacturing industries. This paper proposes an accurate and easy-to-implement method based on an electronic speckle pattern interferometer (ESPI) with single illumination-detection path to realize the online nondestructive full-field 3D displacement measurement. The simple and compact optical system generates three different sensitivity vectors to enable the evaluation of the three orthogonal displacement components. By applying the spatial carrier phase-shifting technique, the desired information can be obtained in real time. The theoretical analysis and the measurement results have proven the feasibility of this ESPI system and quantified its relative measurement error. Full article

(This article belongs to the Section Physical Sensors)

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26 pages, 18046 KiB

Open AccessArticle

A Direct Position-Determination Approach for Multiple Sources Based on Neural Network Computation

by Xin Chen^1,2

, Ding Wang^1,2,*

, Jiexin Yin^1,2

and Ying Wu^1,2

¹ National Digital Switching System Engineering and Technology Research Center, Zhengzhou 450002, China

² Zhengzhou Information Science and Technology Institute, Zhengzhou 450002, China

Sensors 2018, 18(6), 1925; https://doi.org/10.3390/s18061925 - 13 Jun 2018

Cited by 20 | Viewed by 3812

Abstract

The most widely used localization technology is the two-step method that localizes transmitters by measuring one or more specified positioning parameters. Direct position determination (DPD) is a promising technique that directly localizes transmitters from sensor outputs and can offer superior localization performance. However, [...] Read more.

The most widely used localization technology is the two-step method that localizes transmitters by measuring one or more specified positioning parameters. Direct position determination (DPD) is a promising technique that directly localizes transmitters from sensor outputs and can offer superior localization performance. However, existing DPD algorithms such as maximum likelihood (ML)-based and multiple signal classification (MUSIC)-based estimations are computationally expensive, making it difficult to satisfy real-time demands. To solve this problem, we propose the use of a modular neural network for multiple-source DPD. In this method, the area of interest is divided into multiple sub-areas. Multilayer perceptron (MLP) neural networks are employed to detect the presence of a source in a sub-area and filter sources in other sub-areas, and radial basis function (RBF) neural networks are utilized for position estimation. Simulation results show that a number of appropriately trained neural networks can be successfully used for DPD. The performance of the proposed MLP-MLP-RBF method is comparable to the performance of the conventional MUSIC-based DPD algorithm for various signal-to-noise ratios and signal power ratios. Furthermore, the MLP-MLP-RBF network is less computationally intensive than the classical DPD algorithm and is therefore an attractive choice for real-time applications. Full article

(This article belongs to the Section Sensor Networks)

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21 pages, 2825 KiB

Open AccessArticle

A Smart Collaborative Routing Protocol for Reliable Data Diffusion in IoT Scenarios

by Zheng-Yang Ai¹, Yu-Tong Zhou² and Fei Song^1,*

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

² Institute of Education and Economy Research, University of International Business and Economics, Beijing 100029, China

Sensors 2018, 18(6), 1926; https://doi.org/10.3390/s18061926 - 13 Jun 2018

Cited by 68 | Viewed by 5722

Abstract

It is knotty for current routing protocols to meet the needs of reliable data diffusion during the Internet of Things (IoT) deployments. Due to the random placement, limited resources and unattended features of existing sensor nodes, the wireless transmissions are easily exposed to [...] Read more.

It is knotty for current routing protocols to meet the needs of reliable data diffusion during the Internet of Things (IoT) deployments. Due to the random placement, limited resources and unattended features of existing sensor nodes, the wireless transmissions are easily exposed to unauthorized users, which becomes a vulnerable area for various malicious attacks, such as wormhole and Sybil attacks. However, the scheme based on geographic location is a suitable candidate to defend against them. This paper is inspired to propose a smart collaborative routing protocol, Geographic energy aware routing and Inspecting Node (GIN), for guaranteeing the reliability of data exchanging. The proposed protocol integrates the directed diffusion routing, Greedy Perimeter Stateless Routing (GPSR), and the inspecting node mechanism. We first discuss current wireless routing protocols from three diverse perspectives (improving transmission rate, shortening transmission range and reducing transmission consumption). Then, the details of GIN, including the model establishment and implementation processes, are presented by means of the theoretical analysis. Through leveraging the game theory, the inspecting node is elected to monitor the network behaviors. Thirdly, we evaluate the network performances, in terms of transmission delay, packet loss ratio, and throughput, between GIN and three traditional schemes (i.e., Flooding, GPSR, and GEAR). The simulation results illustrate that the proposed protocol is able to outperform the others. Full article

(This article belongs to the Special Issue Security, Trust and Privacy for Sensor Networks)

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17 pages, 8182 KiB

Open AccessArticle

Thermal Energy Harvesting on the Bodily Surfaces of Arms and Legs through a Wearable Thermo-Electric Generator

by Antonino Proto¹

, Daniele Bibbo², Martin Cerny¹

, David Vala¹, Vladimir Kasik¹, Lukas Peter¹, Silvia Conforto², Maurizio Schmid²

and Marek Penhaker^1,*

¹ Department of Cybernetics and Biomedical Engineering, VŠB-Technical University of Ostrava, 17. listopadu 15, 70833 Ostrava-Poruba, Czech Republic

² Department of Engineering, University of Roma Tre, Via Vito Volterra, 62, 00146 Rome, Italy

Sensors 2018, 18(6), 1927; https://doi.org/10.3390/s18061927 - 13 Jun 2018

Cited by 51 | Viewed by 7033

Abstract

This work analyzes the results of measurements on thermal energy harvesting through a wearable Thermo-electric Generator (TEG) placed on the arms and legs. Four large skin areas were chosen as locations for the placement of the TEGs. In order to place the generator [...] Read more.

This work analyzes the results of measurements on thermal energy harvesting through a wearable Thermo-electric Generator (TEG) placed on the arms and legs. Four large skin areas were chosen as locations for the placement of the TEGs. In order to place the generator on the body, a special manufactured band guaranteed the proper contact between the skin and TEG. Preliminary measurements were performed to find out the value of the resistor load which maximizes the power output. Then, an experimental investigation was conducted for the measurement of harvested energy while users were performing daily activities, such as sitting, walking, jogging, and riding a bike. The generated power values were in the range from 5 to 50 μW. Moreover, a preliminary hypothesis based on the obtained results indicates the possibility to use TEGs on leg for the recognition of locomotion activities. It is due to the rather high and different biomechanical work, produced by the gastrocnemius muscle, while the user is walking rather than jogging or riding a bike. This result reflects a difference between temperatures associated with the performance of different activities. Full article

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

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18 pages, 6287 KiB

Open AccessArticle

Preload Monitoring of Bolted L-Shaped Lap Joints Using Virtual Time Reversal Method

by Fei Du¹

, Chao Xu^1,*

, Guannan Wu^1,2 and Jie Zhang³

¹ School of Astronautics, Northwestern Polytechnical University, Xi’an 710072, China

² Mechanical Engineering Department, University of Maryland Baltimore County, Baltimore, MD 21250, USA

³ Department of Mechanical Engineering, University of Bristol, Bristol BS81TR, UK

Sensors 2018, 18(6), 1928; https://doi.org/10.3390/s18061928 - 13 Jun 2018

Cited by 35 | Viewed by 5001

Abstract

L-shaped bolt lap joints are commonly used in aerospace and civil structures. However, bolt joints are frequently subjected to loosening, and this has a significant effect on the safety and reliability of these structures. Therefore, bolt preload monitoring is very important, especially at [...] Read more.

L-shaped bolt lap joints are commonly used in aerospace and civil structures. However, bolt joints are frequently subjected to loosening, and this has a significant effect on the safety and reliability of these structures. Therefore, bolt preload monitoring is very important, especially at the early stage of loosening. In this paper, a virtual time reversal guided wave method is presented to monitor preload of bolted L-shaped lap joints accurately and simply. In this method, a referenced reemitting signal (RRS) is extracted from the bolted structure in fully tightened condition. Then the RRS is utilized as the excitation signal for the bolted structure in loosening states, and the normalized peak amplitude of refocused wave packet is used as the tightness index (TI_A). The proposed method is experimentally validated by L-shaped bolt joints with single and multiple bolts. Moreover, the selections of guided wave frequency and tightness index are also discussed. The results demonstrate that the relationship between TI_A and bolt preload is linear. The detection sensitivity is improved significantly compared with time reversal (TR) method, particularly when bolt loosening is at its embryo stage. The results also show that TR method is an effective method for detection of the number of loosening 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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15 pages, 2194 KiB

Open AccessArticle

Design of Event-Triggered Fault-Tolerant Control for Stochastic Systems with Time-Delays

by Yi Gao^1,2, YunJi Li^1,†, Li Peng^1,3,*,†

and Junyu Liu⁴

¹ Engineering Research Center of Internet of Things Technology Applications Ministry of Education, Jiangnan University, Wuxi 214122, China

² Jiangsu Provincial Sensor Network Engineering Technology Research Center, Wuxi Institute of Technology, Wuxi 214121, China

³ Jiangsu Key Laboratory of IOT Application Technology, Taihu University of Wuxi, Wuxi 214064, China

⁴ Dublin Institute of Technology, 19A Lower Kevin Street, Dublin 8, Ireland

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1929; https://doi.org/10.3390/s18061929 - 13 Jun 2018

Cited by 10 | Viewed by 3637

Abstract

This paper proposes two novel, event-triggered fault-tolerant control strategies for a class of stochastic systems with state delays. The plant is disturbed by a Gaussian process, actuator faults, and unknown disturbances. First, a special case about fault signals that are coupled to the [...] Read more.

This paper proposes two novel, event-triggered fault-tolerant control strategies for a class of stochastic systems with state delays. The plant is disturbed by a Gaussian process, actuator faults, and unknown disturbances. First, a special case about fault signals that are coupled to the unknown disturbances is discussed, and then a fault-tolerant strategy is designed based on an event condition on system states. Subsequently, a send-on-delta transmission framework is established to deal with the problem of fault-tolerant control strategy against fault signals separated from the external disturbances. Two criteria are provided to design feedback controllers in order to guarantee that the systems are exponentially mean-square stable, and the corresponding

H_{\infty}

-norm disturbance attenuation levels are achieved. Two theorems were obtained by synthesizing the feedback control gains and the desired event conditions in terms of linear matrix inequalities (LMIs). Finally, two numerical examples are provided to illustrate the effectiveness of the proposed theoretical results. Full article

(This article belongs to the Special Issue Intelligent Computing, Networking, Security and Robustness in Internet of Things)

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19 pages, 1737 KiB

Open AccessArticle

Fast Convolution Filter-Bank Based Non-Orthogonal Multiplexed Cognitive Radio (NOMCR) Receiver Design Using Cyclostationarity Based FRESH Filtering

by Jayanta Datta^1,* and Hsin-Piao Lin²

¹ Department of Electrical Engineering and Computer Science, National Taipei University of Technology , Daan District, Taipei City 10608, Taiwan

² Department of Electronic Engineering, National Taipei University of Technology, Daan District, Taipei City 10608, Taiwan

Sensors 2018, 18(6), 1930; https://doi.org/10.3390/s18061930 - 13 Jun 2018

Cited by 3 | Viewed by 3926

Abstract

Non-orthogonal multiple access (NOMA) systems are being considered as candidates for 5G wireless systems due to their promise of improved spectral efficiency. NOMA schemes are being combined with popular multicarrier schemes such as orthogonal frequency division multiplexing (OFDM) to take advantage of the [...] Read more.

Non-orthogonal multiple access (NOMA) systems are being considered as candidates for 5G wireless systems due to their promise of improved spectral efficiency. NOMA schemes are being combined with popular multicarrier schemes such as orthogonal frequency division multiplexing (OFDM) to take advantage of the benefits of multicarrier signals. A variant of the power domain NOMA is Layer Division Multiplexing (LDM). The most commonly deployed power domain LDM scheme involves successive interference cancellation (SIC) based decoding at the receiver. Fast convolution based filtered-OFDM (FC-F-OFDM) systems are becoming popular among 5G wireless access technologies due to their ability to process 5G physical layer signals efficiently. In this work, firstly, a cognitive multicarrier non-orthogonal multiplexed system based on the concept of LDM is discussed, which uses FC-F-OFDM and conventional OFDM as its component layers. Secondly, cyclostationary FREquency SHift (FRESH) filter based SIC decoding is used at the receiver side, which also utilizes artificial neural network (ANN) processing. Computer simulations indicate that the system provides good bit error rate (BER) performance under frequency selective Rayleigh fading channels. Full article

(This article belongs to the Special Issue Non-Orthogonal Multi-User Transmissions for 5G Networks)

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22 pages, 3336 KiB

Open AccessArticle

Evaluation of the Continuous Wavelet Transform for Detection of Single-Point Rub in Aeroderivative Gas Turbines with Accelerometers

by Alejandro Silva¹

, Alejandro Zarzo^1,*, Juan M. Munoz-Guijosa²

and Francesco Miniello³

¹ Department of Applied Mathematics, Escuela Técnica Superior de Ingenieros Industriales, Universidad Politécnica de Madrid, Calle de José Gutiérrez Abascal 2, 28006 Madrid, Spain

² Department of Mechanical Engineering, Escuela Técnica Superior de Ingenieros Industriales, Universidad Politécnica de Madrid, Calle de José Gutiérrez Abascal 2, 28006 Madrid, Spain

³ Baker Hughes, a GE Company—Bently Nevada, Calle Josefa Valcárcel 26, 28027 Madrid, Spain

Sensors 2018, 18(6), 1931; https://doi.org/10.3390/s18061931 - 13 Jun 2018

Cited by 12 | Viewed by 5462

Abstract

A common fault in turbomachinery is rotor–casing rub. Shaft vibration, measured with proximity probes, is the most powerful indicator of rotor–stator rub. However, in machines such as aeroderivative turbines, with increasing industrial relevance in power generation, constructive reasons prevent the use of those [...] Read more.

A common fault in turbomachinery is rotor–casing rub. Shaft vibration, measured with proximity probes, is the most powerful indicator of rotor–stator rub. However, in machines such as aeroderivative turbines, with increasing industrial relevance in power generation, constructive reasons prevent the use of those sensors, being only acceleration signals at selected casing locations available. This implies several shortcomings in the characterization of the machinery condition, associated with a lower information content about the machine dynamics. In this work, we evaluated the performance of Continuous Wavelet Transform to isolate the accelerometer signal features that characterize rotor–casing rub in an aeroderivative turbine. The evaluation is carried out on a novel rotor model of a rotor–flexible casing system. Due to damped transients and other short-lived features that rub induces in the signals, the Continuous Wavelet Transform proves being more effective than both Fourier and Cepstrum Analysis. This creates the chance for enabling early fault diagnosis of rub before it may cause machine shutdown or damage. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 6934 KiB

Open AccessArticle

Immuno Nanosensor for the Ultrasensitive Naked Eye Detection of Tuberculosis

by Noremylia Mohd Bakhori¹, Nor Azah Yusof^1,2,*, Jaafar Abdullah²

, Helmi Wasoh³, Siti Suraiya Md Noor⁴, Nurul Hanun Ahmad Raston⁵ and Faruq Mohammad^6,*

¹ Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Malaysia

² Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Malaysia

³ Faculty of Biotechnology and Biomolecule Science, Universiti Putra Malaysia, 43400 UPM Serdang, Malaysia

⁴ School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, 16150 Kelantan, Malaysia

⁵ School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Malaysia

⁶ Surfactant Research Chair, Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia

Sensors 2018, 18(6), 1932; https://doi.org/10.3390/s18061932 - 14 Jun 2018

Cited by 30 | Viewed by 4555

Abstract

In the present study, a beneficial approach for the ultrasensitive and affordable naked eye detection and diagnosis of tuberculosis (TB) by utilizing plasmonic enzyme-linked immunosorbent assay (ELISA) via antibody-antigen interaction was studied. Here, the biocatalytic cycle of the intracellular enzymes links to the [...] Read more.

In the present study, a beneficial approach for the ultrasensitive and affordable naked eye detection and diagnosis of tuberculosis (TB) by utilizing plasmonic enzyme-linked immunosorbent assay (ELISA) via antibody-antigen interaction was studied. Here, the biocatalytic cycle of the intracellular enzymes links to the formation and successive growth of the gold nanoparticles (GNPs) for ultrasensitive detection. The formation of different colored solutions by the plasmonic nanoparticles in the presence of enzyme labels links directly to the existence or non-existence of the TB analytes in the sample solutions. For disease detection, the adapted protocol is based mainly on the conventional ELISA procedure that involves catalase-labeled antibodies, i.e., the enzymes consume hydrogen peroxide and further produce GNPs with the addition of gold (III) chloride. The amount of hydrogen peroxide remaining in the solution determines whether the GNPs solution is to be formed in the color blue or the color red, as it serves as a confirmation for the naked eye detection of TB analytes. However, the conventional ELISA method only shows tonal colors that need a high concentration of analyte to achieve high confidence levels for naked eye detection. Also, in this research, we proposed the incorporation of protein biomarker, Mycobacterium tuberculosis ESAT-6-like protein esxB (CFP-10), as a means of TB detection using plasmonic ELISA. With the use of this technique, the CFP-10 detection limit can be lowered to 0.01 µg/mL by the naked eye. Further, our developed technique was successfully tested and confirmed with sputum samples from patients diagnosed with positive TB, thereby providing enough evidence for the utilization of our technique in the early diagnosis of TB disease. Full article

(This article belongs to the Section Biosensors)

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11 pages, 2031 KiB

Open AccessArticle

Effects of Fire Suppression Agents and Weathering in the Analysis of Fire Debris by HS-MS eNose

by Barbara Falatová¹

, Marta Ferreiro-González^2,*

, Carlos Martín-Alberca³

, Danica Kačíková¹

, Štefan Galla⁴, Miguel Palma² and Carmelo G. Barroso²

¹ Department of Fire Protection, Faculty of Wood Sciences and Technology, Technical University in Zvolen, ul.T. G. Masaryka 2117/24, 960 53 Zvolen, Slovakia

² Department of Analytical Chemistry, Faculty of Sciences, University of Cadiz, Agrifood Campus of International Excellence (ceiA3), IVAGRO, P.O. Box 40, 11510 Puerto Real, Cadiz, Spain

³ Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Edificio Polivalente de Química, and University Institute of Research in Police Sciences (IUICP), 28871 Alcalá de Henares, Madrid, Spain

⁴ Fire Research Institute of the Ministry of Interior, Rožňavská 11, 831 04 Bratislava, Slovakia

Sensors 2018, 18(6), 1933; https://doi.org/10.3390/s18061933 - 14 Jun 2018

Cited by 16 | Viewed by 4976

Abstract

In arson attacks the detection of ignitable liquid residues (ILRs) at fire scenes provides key evidence since ignitable liquids, such as gasoline, are commonly used to initiate the fire. In most forensic laboratories gas chromatography-mass spectrometry is employed for the analysis of ILRs. [...] Read more.

In arson attacks the detection of ignitable liquid residues (ILRs) at fire scenes provides key evidence since ignitable liquids, such as gasoline, are commonly used to initiate the fire. In most forensic laboratories gas chromatography-mass spectrometry is employed for the analysis of ILRs. When a fire occurs, suppression agents are used to extinguish the fire and, before the scene is investigated, the samples at the scene are subjected to a variety of processes such as weathering, which can significantly modify the chemical composition and thus lead to erroneous conclusions. In order to avoid this possibility, the application of chemometric tools that help the analyst to extract useful information from data is very advantageous. The study described here concerned the application of a headspace-mass spectrometry electronic nose (HS-MS eNose) combined with chemometric tools to determine the presence/absence of gasoline in weathered fire debris samples. The effect of applying two suppression agents (Cafoam Aquafoam AF-6 and Pyro-chem PK-80 Powder) and delays in the sampling time (from 0 to 48 h) were studied. It was found that, although the suppression systems affect the mass spectra, the HS-MS eNose in combination with suitable pattern recognition chemometric tools, such as linear discriminant analysis, is able to identify the presence of gasoline in any of the studied situations (100% correct classification). Full article

(This article belongs to the Section Chemical Sensors)

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23 pages, 5876 KiB

Open AccessArticle

A Novel Bearing Multi-Fault Diagnosis Approach Based on Weighted Permutation Entropy and an Improved SVM Ensemble Classifier

by Shenghan Zhou¹

, Silin Qian¹

, Wenbing Chang^1,*, Yiyong Xiao¹

and Yang Cheng²

¹ School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China

² Center for Industrial Production, Aalborg University, 9220 Aalborg, Denmark

Sensors 2018, 18(6), 1934; https://doi.org/10.3390/s18061934 - 14 Jun 2018

Cited by 101 | Viewed by 5965

Abstract

Timely and accurate state detection and fault diagnosis of rolling element bearings are very critical to ensuring the reliability of rotating machinery. This paper proposes a novel method of rolling bearing fault diagnosis based on a combination of ensemble empirical mode decomposition (EEMD), [...] Read more.

Timely and accurate state detection and fault diagnosis of rolling element bearings are very critical to ensuring the reliability of rotating machinery. This paper proposes a novel method of rolling bearing fault diagnosis based on a combination of ensemble empirical mode decomposition (EEMD), weighted permutation entropy (WPE) and an improved support vector machine (SVM) ensemble classifier. A hybrid voting (HV) strategy that combines SVM-based classifiers and cloud similarity measurement (CSM) was employed to improve the classification accuracy. First, the WPE value of the bearing vibration signal was calculated to detect the fault. Secondly, if a bearing fault occurred, the vibration signal was decomposed into a set of intrinsic mode functions (IMFs) by EEMD. The WPE values of the first several IMFs were calculated to form the fault feature vectors. Then, the SVM ensemble classifier was composed of binary SVM and the HV strategy to identify the bearing multi-fault types. Finally, the proposed model was fully evaluated by experiments and comparative studies. The results demonstrate that the proposed method can effectively detect bearing faults and maintain a high accuracy rate of fault recognition when a small number of training samples are available. Full article

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

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14 pages, 5180 KiB

Open AccessArticle

A Distributed Model for Stressors Monitoring Based on Environmental Smart Sensors

by Alberto De Ramón-Fernández, Daniel Ruiz-Fernández^*

, Diego Marcos-Jorquera

and Virgilio Gilart-Iglesias

Department of Computer Technology, University of Alicante, 03690 San Vicente del Raspeig, Alicante, Spain

Sensors 2018, 18(6), 1935; https://doi.org/10.3390/s18061935 - 14 Jun 2018

Cited by 3 | Viewed by 3158

Abstract

Nowadays, in many countries, stress is becoming a problem that increasingly affects the health of people. Suffering stress continuously can lead to serious behavioral disorders such as anxiety or depression. Every person, in his daily routine, can face many factors which can contribute [...] Read more.

Nowadays, in many countries, stress is becoming a problem that increasingly affects the health of people. Suffering stress continuously can lead to serious behavioral disorders such as anxiety or depression. Every person, in his daily routine, can face many factors which can contribute to increase his stress level. This paper describes a flexible and distributed model to monitor environmental variables associated with stress, which provides adaptability to any environment in an agile way. This model was designed to transform stress environmental variables in value added information (key stress indicator) and to provide it to external systems, in both proactive and reactive mode. Thus, this value-added information will assist organizations and users in a personalized way helping in the detection and prevention of acute stress cases. Our proposed model is supported by an architecture that achieves the features above mentioned, in addition to interoperability, robustness, scalability, autonomy, efficient, low cost and consumption, and information availability in real time. Finally, a prototype of the system was implemented, allowing the validation of the proposal in different environments at the University of Alicante. 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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10 pages, 1749 KiB

Open AccessArticle

High-Speed Terahertz Waveform Measurement for Intense Terahertz Light Using 100-kHz Yb-Doped Fiber Laser

by Masaaki Tsubouchi^*

and Keisuke Nagashima

Kansai Photon Science Institute (KPSI), National Institutes for Quantum and Radiological Science and Technology (QST), 8-1-7 Umimedai, Kizugawa, Kyoto 619-0215, Japan

Sensors 2018, 18(6), 1936; https://doi.org/10.3390/s18061936 - 14 Jun 2018

Cited by 2 | Viewed by 4030

Abstract

We demonstrate a high-speed terahertz (THz) waveform measurement system for intense THz light with a scan rate of 100 Hz. To realize the high scan rate, a loudspeaker vibrating at 50 Hz is employed to scan the delay time between THz light and [...] Read more.

We demonstrate a high-speed terahertz (THz) waveform measurement system for intense THz light with a scan rate of 100 Hz. To realize the high scan rate, a loudspeaker vibrating at 50 Hz is employed to scan the delay time between THz light and electro-optic sampling light. Because the fast scan system requires a high data sampling rate, we develop an Yb-doped fiber laser with a repetition rate of 100 kHz optimized for effective THz light generation with the output electric field of 1 kV/cm. The present system drastically reduces the measurement time of the THz waveform from several minutes to 10 ms. Full article

(This article belongs to the Special Issue THz Imaging Systems and Sensors)

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24 pages, 8331 KiB

Open AccessArticle

An Improved Randomized Local Binary Features for Keypoints Recognition

by Jinming Zhang^1,*

, Zuren Feng¹, Jinpeng Zhang² and Gang Li¹

¹ State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, No. 28 Xianning West Road, Beilin District, Xi’an 710049, China

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

Sensors 2018, 18(6), 1937; https://doi.org/10.3390/s18061937 - 14 Jun 2018

Cited by 5 | Viewed by 3570

Abstract

In this paper, we carry out researches on randomized local binary features. Randomized local binary features have been used in many methods like RandomForests, RandomFerns, BRIEF, ORB and AKAZE to matching keypoints. However, in those existing methods, the randomness of feature operators only [...] Read more.

In this paper, we carry out researches on randomized local binary features. Randomized local binary features have been used in many methods like RandomForests, RandomFerns, BRIEF, ORB and AKAZE to matching keypoints. However, in those existing methods, the randomness of feature operators only reflects in sampling position. In this paper, we find the quality of the binary feature space can be greatly improved by increasing the randomness of the basic sampling operator. The key idea of our method is to use a Randomized Intensity Difference operator (we call it RID operator) as a basic sampling operator to observe image patches. The randomness of RID operators are reflected in five aspects: grids, position, aperture, weights and channels. Comparing with the traditional incompletely randomized binary features (we call them RIT features), a completely randomized sampling manner can generate higher quality binary feature space. The RID operator can be used on both gray and color images. We embed different kinds of RID operators into RandomFerns and RandomForests classifiers to test their recognition rate on both image and video datasets. The experiment results show the excellent quality of our feature method. We also propose the evaluation criteria for robustness and distinctiveness to observe the effects of randomization on binary feature space. Full article

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

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23 pages, 592 KiB

Open AccessArticle

A Novel Friendly Jamming Scheme in Industrial Crowdsensing Networks against Eavesdropping Attack

by Xuran Li¹, Qiu Wang¹, Hong-Ning Dai^1,*

and Hao Wang^2,*

¹ Faculty of Information Technology, Macau University of Science and Technology, Macau SAR, China

² Department of ICT and Natural Sciences, Faculty of Information Technology and Electrical Engineering, Norwegian University of Science and Technology, Postboks 1517, NO-6025 Aalesund, Norway

Sensors 2018, 18(6), 1938; https://doi.org/10.3390/s18061938 - 14 Jun 2018

Cited by 15 | Viewed by 4444

Abstract

Eavesdropping attack is one of the most serious threats in industrial crowdsensing networks. In this paper, we propose a novel anti-eavesdropping scheme by introducing friendly jammers to an industrial crowdsensing network. In particular, we establish a theoretical framework considering both the probability of [...] Read more.

Eavesdropping attack is one of the most serious threats in industrial crowdsensing networks. In this paper, we propose a novel anti-eavesdropping scheme by introducing friendly jammers to an industrial crowdsensing network. In particular, we establish a theoretical framework considering both the probability of eavesdropping attacks and the probability of successful transmission to evaluate the effectiveness of our scheme. Our framework takes into account various channel conditions such as path loss, Rayleigh fading, and the antenna type of friendly jammers. Our results show that using jammers in industrial crowdsensing networks can effectively reduce the eavesdropping risk while having no significant influence on legitimate communications. Full article

(This article belongs to the Special Issue Recent Advances in Crowdsensing and Its Security, Privacy and Trust Challenges)

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17 pages, 2076 KiB

Open AccessArticle

AVSS: Airborne Video Surveillance System

by Jongtack Jung^†

, Seungho Yoo^†

, Woong Gyu La

, Dongkyu Roy Lee

, Mungyu Bae

and Hwangnam Kim^*

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

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1939; https://doi.org/10.3390/s18061939 - 14 Jun 2018

Cited by 25 | Viewed by 5019

Abstract

Most surveillance systems only contain CCTVs. CCTVs, however, provide only limited maneuverability against dynamic targets and are inefficient for short term surveillance. Such limitations do not raise much concern in some cases, but for the scenario in which traditional surveillance systems do not [...] Read more.

Most surveillance systems only contain CCTVs. CCTVs, however, provide only limited maneuverability against dynamic targets and are inefficient for short term surveillance. Such limitations do not raise much concern in some cases, but for the scenario in which traditional surveillance systems do not suffice, adopting a fleet of UAVs can help overcoming the limitations. In this paper, we present a surveillance system implemented with a fleet of unmanned aerial vehicles (UAVs). A surveillance system implemented with a fleet of UAVs is easy to deploy and maintain. A UAV fleet requires little time to deploy and set up, and removing the surveillance is also virtually instant. The system we propose deploys UAVs to the target area for installation and perform surveillance operations. The camera mounted UAVs act as surveillance probes, the server provides overall control of the surveillance system, and the fleet platform provides fleet-wise control of the UAVs. In the proposed system, the UAVs establish a network and enable multi-hop communication, which allows the system to widen its coverage area. The operator of the system can control the fleet of UAVs via the fleet platform and receive surveillance information gathered by the UAVs. The proposed system is described in detail along with the algorithm for effective placement of the UAVs. The prototype of the system is presented, and the experiment carried out shows that the system can successfully perform surveillance over an area set by the system. Full article

(This article belongs to the Special Issue Unmanned Aerial Vehicle Networks, Systems and Applications)

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8 pages, 1810 KiB

Open AccessArticle

Accuracy of a Basketball Indoor Tracking System Based on Standard Bluetooth Low Energy Channels (NBN23^®)

by Bruno Figueira^1,2,*, Bruno Gonçalves^2,3

, Hugo Folgado^2,4

, Nerijus Masiulis¹, Julio Calleja-González⁵ and Jaime Sampaio^2,3

¹ Faculty of Sports Biomedicine, Lithuanian Sports University, 44221 Kaunas, Lithuania

² Research Center in Sports Sciences, Health Sciences and Human Development, CIDESD, 5000-801 Vila Real, Portugal

³ Sport Sciences Department, Universidade de Trás-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal

⁴ Departamento de Desporto e Saúde, Escola de Ciências e Tecnologia, Universidade de Évora, 7000 Évora, Portugal

⁵ Department of Physical Activity and Sport Science, University of Basque Country, 1007 Vitoria, Alava, Spain

Sensors 2018, 18(6), 1940; https://doi.org/10.3390/s18061940 - 14 Jun 2018

Cited by 21 | Viewed by 6057

Abstract

The present study aims to identify the accuracy of the NBN23^® system, an indoor tracking system based on radio-frequency and standard Bluetooth Low Energy channels. Twelve capture tags were attached to a custom cart with fixed distances of 0.5, 1.0, 1.5, and [...] Read more.

The present study aims to identify the accuracy of the NBN23^® system, an indoor tracking system based on radio-frequency and standard Bluetooth Low Energy channels. Twelve capture tags were attached to a custom cart with fixed distances of 0.5, 1.0, 1.5, and 1.8 m. The cart was pushed along a predetermined course following the lines of a standard dimensions Basketball court. The course was performed at low speed (<10.0 km/h), medium speed (>10.0 km/h and <20.0 km/h) and high speed (>20.0 km/h). Root mean square error (RMSE) and percentage of variance accounted for (%VAF) were used as accuracy measures. The obtained data showed acceptable accuracy results for both RMSE and %VAF, despite the expected degree of error in position measurement at higher speeds. The RMSE for all the distances and velocities presented an average absolute error of 0.30 ± 0.13 cm with 90.61 ± 8.34 of %VAF, in line with most available systems, and considered acceptable for indoor sports. The processing of data with filter correction seemed to reduce the noise and promote a lower relative error, increasing the %VAF for each measured distance. Research using positional-derived variables in Basketball is still very scarce; thus, this independent test of the NBN23^® tracking system provides accuracy details and opens up opportunities to develop new performance indicators that help to optimize training adaptations and performance. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 2414 KiB

Open AccessArticle

A Model Design for Risk Assessment of Line Tripping Caused by Wildfires

by Shuzhu Shi¹

, Chunjing Yao^1,*

, Shiwei Wang² and Wenjun Han³

¹ School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China

² School of Electronic Information, Wuhan University, Wuhan 430072, China

³ State Grid Economic and Technological Research Institute Co. Ltd., Beijing 102209, China

Sensors 2018, 18(6), 1941; https://doi.org/10.3390/s18061941 - 14 Jun 2018

Cited by 22 | Viewed by 3943

Abstract

A power line is particularly vulnerable to wildfires in its vicinity, and various damage including line tripping can be caused by wildfires. Using remote sensing techniques, a novel model developed to assess the risk of line tripping caused by the wildfire occurrence in [...] Read more.

A power line is particularly vulnerable to wildfires in its vicinity, and various damage including line tripping can be caused by wildfires. Using remote sensing techniques, a novel model developed to assess the risk of line tripping caused by the wildfire occurrence in high-voltage power line corridors is presented. This model mainly contains the wildfire risk assessment for power line corridors and the estimation of the probability of line tripping when a wildfire occurs in power line corridors. For the wildfire risk assessment, high-resolution satellite data, Moderate Resolution Imaging Spectroradiometer (MODIS) data, meteorological data, and digital elevation model (DEM) data were employed to infer the natural factors. Human factors were also included to achieve good reliability. In the estimation of the probability of line tripping, vegetation characteristics, meteorological status, topographic conditions, and transmission line parameters were chosen as influencing factors. According to the above input variables and observed historical datasets, the risk levels for wildfire occurrence and line tripping were obtained with a logic regression approach. The experimental results demonstrate that the developed model can provide good results in predicting wildfire occurrence and line tripping for high-voltage power line corridors. Full article

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

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10 pages, 3138 KiB

Open AccessArticle

A Submerged Optical Fiber Ultrasonic Sensor Using Matched Fiber Bragg Gratings

by Xiaohong Bai

, Manli Hu^*, Tingting Gang and Qiangzhou Rong^*

School of Physics, Northwest University, Xi’an 710127, China

Sensors 2018, 18(6), 1942; https://doi.org/10.3390/s18061942 - 14 Jun 2018

Cited by 12 | Viewed by 3962

Abstract

A novel kind of fiber optic ultrasonic sensor based on matching fiber Bragg gratings (FBGs) is proposed and demonstrated. The sensors consist of a pair of matching FBGs fixed to a special bracket. The bracket plays a role in stretching and squeezing the [...] Read more.

A novel kind of fiber optic ultrasonic sensor based on matching fiber Bragg gratings (FBGs) is proposed and demonstrated. The sensors consist of a pair of matching FBGs fixed to a special bracket. The bracket plays a role in stretching and squeezing the FBGs, with the push–pull effect efficiently coupling the ultrasonic signal to the sensor, thus, improving the sensor’s sensitivity. Side-band filtering technology-based intensity interrogation was used to detect ultrasounds in water. With the synergic effect of the matching FBGs, the sensor performed with a high signal-to-noise ratio (56.9 dB at 300 KHz, 53 dB at 1 MHz and 31.8 dB at 5 MHz) and the observed ultrasonic sinusoidal signals were undistorted and distinguishable in the time domain. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 4027 KiB

Open AccessArticle

Hybrid Histogram Descriptor: A Fusion Feature Representation for Image Retrieval

by Qinghe Feng¹

, Qiaohong Hao², Yuqi Chen³, Yugen Yi³, Ying Wei^1,* and Jiangyan Dai^4,*

¹ College of Information Science and Engineering, Northeastern University, Shenyang 110004, China

² School of Computer Science and Technology, Tianjin University, Tianjin 300350, China

³ School of Software, Jiangxi Normal University, Nanchang 330022, China

⁴ School of Computer Engineering, Weifang University, Weifang 261061, China

Sensors 2018, 18(6), 1943; https://doi.org/10.3390/s18061943 - 15 Jun 2018

Cited by 18 | Viewed by 4441

Abstract

Currently, visual sensors are becoming increasingly affordable and fashionable, acceleratingly the increasing number of image data. Image retrieval has attracted increasing interest due to space exploration, industrial, and biomedical applications. Nevertheless, designing effective feature representation is acknowledged as a hard yet fundamental issue. [...] Read more.

Currently, visual sensors are becoming increasingly affordable and fashionable, acceleratingly the increasing number of image data. Image retrieval has attracted increasing interest due to space exploration, industrial, and biomedical applications. Nevertheless, designing effective feature representation is acknowledged as a hard yet fundamental issue. This paper presents a fusion feature representation called a hybrid histogram descriptor (HHD) for image retrieval. The proposed descriptor comprises two histograms jointly: a perceptually uniform histogram which is extracted by exploiting the color and edge orientation information in perceptually uniform regions; and a motif co-occurrence histogram which is acquired by calculating the probability of a pair of motif patterns. To evaluate the performance, we benchmarked the proposed descriptor on RSSCN7, AID, Outex-00013, Outex-00014 and ETHZ-53 datasets. Experimental results suggest that the proposed descriptor is more effective and robust than ten recent fusion-based descriptors under the content-based image retrieval framework. The computational complexity was also analyzed to give an in-depth evaluation. Furthermore, compared with the state-of-the-art convolutional neural network (CNN)-based descriptors, the proposed descriptor also achieves comparable performance, but does not require any training process. Full article

(This article belongs to the Special Issue Visual Sensors)

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15 pages, 2787 KiB

Open AccessArticle

Detection of Oil Chestnuts Infected by Blue Mold Using Near-Infrared Hyperspectral Imaging Combined with Artificial Neural Networks

by Lei Feng^1,2, Susu Zhu^1,2, Fucheng Lin³, Zhenzhu Su^3,*, Kangpei Yuan⁴, Yiying Zhao^1,2, Yong He^1,2

and Chu Zhang^1,2

¹ College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China

² Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture, Hangzhou 310058, China

³ State Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China

⁴ College of Life Sciences, Zhejiang University, Hangzhou 310058, China

Sensors 2018, 18(6), 1944; https://doi.org/10.3390/s18061944 - 15 Jun 2018

Cited by 24 | Viewed by 4444

Abstract

Mildew damage is a major reason for chestnut poor quality and yield loss. In this study, a near-infrared hyperspectral imaging system in the 874–1734 nm spectral range was applied to detect the mildew damage to chestnuts caused by blue mold. Principal component analysis [...] Read more.

Mildew damage is a major reason for chestnut poor quality and yield loss. In this study, a near-infrared hyperspectral imaging system in the 874–1734 nm spectral range was applied to detect the mildew damage to chestnuts caused by blue mold. Principal component analysis (PCA) scored images were firstly employed to qualitatively and intuitively distinguish moldy chestnuts from healthy chestnuts. Spectral data were extracted from the hyperspectral images. A successive projections algorithm (SPA) was used to select 12 optimal wavelengths. Artificial neural networks, including back propagation neural network (BPNN), evolutionary neural network (ENN), extreme learning machine (ELM), general regression neural network (GRNN) and radial basis neural network (RBNN) were used to build models using the full spectra and optimal wavelengths to distinguish moldy chestnuts. BPNN and ENN models using full spectra and optimal wavelengths obtained satisfactory performances, with classification accuracies all surpassing 99%. The results indicate the potential for the rapid and non-destructive detection of moldy chestnuts by hyperspectral imaging, which would help to develop online detection system for healthy and blue mold infected chestnuts. Full article

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

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12 pages, 428 KiB

Open AccessArticle

Energy-Aware Computation Offloading of IoT Sensors in Cloudlet-Based Mobile Edge Computing

by Xiao Ma¹, Chuang Lin¹, Han Zhang^2,* and Jianwei Liu²

¹ Tsinghua National Laboratory for Information Science and Technology, Department of Computer Science and Technology, Tsinghua University, Beijing 100084, China

² School of Cyber Science and Technology, Beihang University, Beijing 100191, China

Sensors 2018, 18(6), 1945; https://doi.org/10.3390/s18061945 - 15 Jun 2018

Cited by 39 | Viewed by 4767

Abstract

Mobile edge computing is proposed as a promising computing paradigm to relieve the excessive burden of data centers and mobile networks, which is induced by the rapid growth of Internet of Things (IoT). This work introduces the cloud-assisted multi-cloudlet framework to provision scalable [...] Read more.

Mobile edge computing is proposed as a promising computing paradigm to relieve the excessive burden of data centers and mobile networks, which is induced by the rapid growth of Internet of Things (IoT). This work introduces the cloud-assisted multi-cloudlet framework to provision scalable services in cloudlet-based mobile edge computing. Due to the constrained computation resources of cloudlets and limited communication resources of wireless access points (APs), IoT sensors with identical computation offloading decisions interact with each other. To optimize the processing delay and energy consumption of computation tasks, theoretic analysis of the computation offloading decision problem of IoT sensors is presented in this paper. In more detail, the computation offloading decision problem of IoT sensors is formulated as a computation offloading game and the condition of Nash equilibrium is derived by introducing the tool of a potential game. By exploiting the finite improvement property of the game, the Computation Offloading Decision (COD) algorithm is designed to provide decentralized computation offloading strategies for IoT sensors. Simulation results demonstrate that the COD algorithm can significantly reduce the system cost compared with the random-selection algorithm and the cloud-first algorithm. Furthermore, the COD algorithm can scale well with increasing IoT sensors. Full article

(This article belongs to the Special Issue Software-Defined Networking Based Mobile Networks)

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11 pages, 2517 KiB

Open AccessArticle

A Sensitive Electrochemical Immunosensor Based on PAMAM Dendrimer-Encapsulated Au for Detection of Norfloxacin in Animal-Derived Foods

by Bing Liu^*, Min Li, Yaoshuai Zhao, Mingfei Pan, Ying Gu, Wei Sheng, Guozhen Fang and Shuo Wang^*

State Key Laboratory of Food Nutrition and Safety, Ministry of Education of China, Tianjin University of Science and Technology, No. 29 The Thirteenth Road, Tianjin Economy and Technology Development Area, Tianjin 300457, China

Sensors 2018, 18(6), 1946; https://doi.org/10.3390/s18061946 - 15 Jun 2018

Cited by 49 | Viewed by 4866

Abstract

In this work, a sensitive electrochemical immunosensor has been reported for the determination of norfloxacin in animal-derived foods. The poly (amidoamine) dendrimer encapsulated gold nanoparticles (PAMAM-Au) played dual roles in the proposed sensing platform which not only accelerated the electron transfer process of [...] Read more.

In this work, a sensitive electrochemical immunosensor has been reported for the determination of norfloxacin in animal-derived foods. The poly (amidoamine) dendrimer encapsulated gold nanoparticles (PAMAM-Au) played dual roles in the proposed sensing platform which not only accelerated the electron transfer process of sensing, but also increased the efficiency of the immobilized antibody. The HRP-labeled antigen, as the signal labels in the immunosensor, was introduced to catalyze the following reaction of the substrate hydroquinone with the aid of H₂O₂ in the competitive reaction. On the basis of the signal amplification of PAMAM-Au, the signal intensity was linearly related to the concentration of norfloxacin in the range of 1 μg·L⁻¹–10 mg·L⁻¹. All the results showed that the proposed strategy with low LOD (0.3837 μg·L⁻¹) and favorable recovery (91.6–106.1%) in the practical sample, and it could provide a suitable protocol for norfloxacin detection in animal-derived foods with high sensitivity, good accuracy, and stability. Full article

(This article belongs to the Section Biosensors)

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18 pages, 572 KiB

Open AccessArticle

Exploring the Exponentially Decaying Merit of an Out-of-Sequence Observation

by Josiah Yoder^1,*, Stanley Baek²

, Hyukseong Kwon³ and Daniel Pack⁴

¹ Department of Electrical Engineering and Computer Science, Milwaukee School of Engineering, Milwaukee, WI 53202, USA

² Department of Electrical and Computer Engineering, University of Michigan-Dearborn, Dearborn, MI 48128, USA

³ HRL Laboratories, Malibu, CA 90265, USA

⁴ College of Engineering and Computer Science, University of Tennessee at Chattanooga, Chattanooga, TN 37403, USA

Sensors 2018, 18(6), 1947; https://doi.org/10.3390/s18061947 - 15 Jun 2018

Viewed by 2294

Abstract

It is well known that in a Kalman filtering framework, all sensor observations or measurements contribute toward improving the accuracy of state estimation, but, as observations become older, their impact toward improving estimations becomes smaller to the point that they offer no practical [...] Read more.

It is well known that in a Kalman filtering framework, all sensor observations or measurements contribute toward improving the accuracy of state estimation, but, as observations become older, their impact toward improving estimations becomes smaller to the point that they offer no practical benefit. In this paper, we provide an practical technique for determining the merit of an old observation using system parameters. We demonstrate that the benefit provided by an old observation decreases exponentially with the number of observations captured and processed after it. To quantify the merit of an old observation, we use the filter gain for the delayed observation, found by re-processing all past measurements between the delayed observation and the current time estimate, a high cost task. We demonstrate the value of the proposed technique to system designers using both nearly-constant position (random walk) and nearly-constant velocity (discrete white-noise acceleration, DWNA) cases. In these cases, the merit (that is, gain) of an old observation can be computed in closed-form without iteration. The analysis technique incorporates the state transition function, the observation function, the state transition noise, and the observation noise to quantify the merit of an old observation. Numerical simulations demonstrate the accuracy of these predictions even when measurements arrive randomly according to a Poisson distribution. Simulations confirm that our approach correctly predicts which observations increase estimation accuracy based on their delay by comparing a single-step out-of-sequence Kalman filter with a selective version that drops out-of-sequence observations. This approach may be used in system design to evaluate feasibility of a multi-agent target tracking system, and when selecting system parameters including sensor rates and network latencies. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 7744 KiB

Open AccessArticle

Scale Estimation and Correction of the Monocular Simultaneous Localization and Mapping (SLAM) Based on Fusion of 1D Laser Range Finder and Vision Data

by Zhuang Zhang^1,2, Rujin Zhao^1,*, Enhai Liu¹, Kun Yan^1,2 and Yuebo Ma^1,2

¹ Institute of Optics and Electronics of Chinese Academy of Sciences, Chengdu 610209, China

² University of Chinese Academy of Sciences, Beijing 100149, China

Sensors 2018, 18(6), 1948; https://doi.org/10.3390/s18061948 - 15 Jun 2018

Cited by 41 | Viewed by 6374

Abstract

This article presents a new sensor fusion method for visual simultaneous localization and mapping (SLAM) through integration of a monocular camera and a 1D-laser range finder. Such as a fusion method provides the scale estimation and drift correction and it is not limited [...] Read more.

This article presents a new sensor fusion method for visual simultaneous localization and mapping (SLAM) through integration of a monocular camera and a 1D-laser range finder. Such as a fusion method provides the scale estimation and drift correction and it is not limited by volume, e.g., the stereo camera is constrained by the baseline and overcomes the limited depth range problem associated with SLAM for RGBD cameras. We first present the analytical feasibility for estimating the absolute scale through the fusion of 1D distance information and image information. Next, the analytical derivation of the laser-vision fusion is described in detail based on the local dense reconstruction of the image sequences. We also correct the scale drift of the monocular SLAM using the laser distance information which is independent of the drift error. Finally, application of this approach to both indoor and outdoor scenes is verified by the Technical University of Munich dataset of RGBD and self-collected data. We compare the effects of the scale estimation and drift correction of the proposed method with the SLAM for a monocular camera and a RGBD camera. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 1951 KiB

Open AccessArticle

Preliminary Study on Biosensor-Type Time-Temperature Integrator for Intelligent Food Packaging

by A. T. M. Mijanur Rahman, Do Hyeon Kim, Han Dong Jang, Jung Hwa Yang and Seung Ju Lee^*

Center for Intelligent Agro-Food Packaging (CIFP), Department of Food Science and Biotechnology, Dongguk University, Seoul 10326, Korea

Sensors 2018, 18(6), 1949; https://doi.org/10.3390/s18061949 - 15 Jun 2018

Cited by 36 | Viewed by 6141

Abstract

A glucose biosensor was utilized as a platform for the time-temperature integrator (TTI), a device for intelligent food packaging. The TTI system is composed of glucose oxidase, glucose, a pH indicator, and a three-electrode potentiostat, which produces an electrical signal as well as [...] Read more.

A glucose biosensor was utilized as a platform for the time-temperature integrator (TTI), a device for intelligent food packaging. The TTI system is composed of glucose oxidase, glucose, a pH indicator, and a three-electrode potentiostat, which produces an electrical signal as well as color development. The reaction kinetics of these response variables were analyzed under isothermal conditions. The reaction rates of the electrical current and color changes were 0.0360 ± 0.0020 (95% confidence limit), 0.0566 ± 0.0026, 0.0716 ± 0.0024, 0.1073 ± 0.0028 µA/min, and 0.0187 ± 0.0005, 0.0293 ± 0.0018, 0.0363 ± 0.0012, 0.0540 ± 0.0019 1/min, at 5, 15, 25, and 35 °C, respectively. The Arrhenius activation energy of the current reaction (Ea_current) was 25.0 ± 1.6 kJ/mol and the Ea_color of the color reactions was 24.2 ± 0.6 kJ/mol. The similarity of these Ea shows agreement in the prediction of food qualities between the electrical signal and color development. Consequently, the function of the new time-temperature integrator system could be extended to that of a biosensor compatible with any electrical utilization equipment. Full article

(This article belongs to the Special Issue The Applications of Sensors and Biosensors in Investigating Drugs, Nutraceuticals and Foods)

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16 pages, 899 KiB

Open AccessArticle

An Optimization Routing Algorithm for Green Communication in Underground Mines

by Heng Xu

, Qiyue Li, Jianping Wang, Guojun Luo, Chenghui Zhu and Wei Sun^*

School of Electrical Engineering and Automation, Hefei University of Technology, Hefei 230009, China

Sensors 2018, 18(6), 1950; https://doi.org/10.3390/s18061950 - 15 Jun 2018

Cited by 7 | Viewed by 3913

Abstract

With the long-term dependence of humans on ore-based energy, underground mines are utilized around the world, and underground mining is often dangerous. Therefore, many underground mines have established networks that manage and acquire information from sensor nodes deployed on miners and in other [...] Read more.

With the long-term dependence of humans on ore-based energy, underground mines are utilized around the world, and underground mining is often dangerous. Therefore, many underground mines have established networks that manage and acquire information from sensor nodes deployed on miners and in other places. Since the power supplies of many mobile sensor nodes are batteries, green communication is an effective approach of reducing the energy consumption of a network and extending its longevity. To reduce the energy consumption of networks, all factors that negatively influence the lifetime should be considered. The degree constraint minimum spanning tree (DCMST) is introduced in this study to consider all the heterogeneous factors and assign weights for the next step of the evaluation. Then, a genetic algorithm (GA) is introduced to cluster sensor nodes in the network and balance energy consumption according to several heterogeneous factors and routing paths from DCMST. Based on a comparison of the simulation results, the optimization routing algorithm proposed in this study for use in green communication in underground mines can effectively reduce the network energy consumption and extend the lifetimes of networks. Full article

(This article belongs to the Special Issue Low Energy Wireless Sensor Networks: Protocols, Architectures and Solutions)

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16 pages, 2529 KiB

Open AccessArticle

Cloud-Based Behavioral Monitoring in Smart Homes

by Niccolò Mora^*

, Guido Matrella

and Paolo Ciampolini

Dipartimento di Ingegneria e Architettura, Università degli Studi di Parma, 43124 Parma, Italy

Sensors 2018, 18(6), 1951; https://doi.org/10.3390/s18061951 - 15 Jun 2018

Cited by 32 | Viewed by 5407

Abstract

Environmental sensors are exploited in smart homes for many purposes. Sensor data inherently carries behavioral information, possibly useful to infer wellness and health-related insights in an indirect fashion. In order to exploit such features, however, powerful analytics are needed to convert raw sensor [...] Read more.

Environmental sensors are exploited in smart homes for many purposes. Sensor data inherently carries behavioral information, possibly useful to infer wellness and health-related insights in an indirect fashion. In order to exploit such features, however, powerful analytics are needed to convert raw sensor output into meaningful and accessible knowledge. In this paper, a complete monitoring architecture is presented, including home sensors and cloud-based back-end services. Unsupervised techniques for behavioral data analysis are presented, including: (i) regression and outlier detection models (also used as feature extractors for more complex models); (ii) statistical hypothesis testing frameworks for detecting changes in sensor-detected activities; and (iii) a clustering process, leveraging deep learning techniques, for extracting complex, multivariate patterns from daily sensor data. Such methods are discussed and evaluated on real-life data, collected within several EU-funded projects. Overall, the presented methods may prove very useful to build effective monitoring services, suitable for practical exploitation in caregiving activities, complementing conventional telemedicine techniques. Full article

(This article belongs to the Special Issue Smart Homes)

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13 pages, 1906 KiB

Open AccessArticle

A Temperature Drift Compensation Method for Pulsed Eddy Current Technology

by Biting Lei, Pengxing Yi^*, Yahui Li and Jiayun Xiang

School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China

Sensors 2018, 18(6), 1952; https://doi.org/10.3390/s18061952 - 15 Jun 2018

Cited by 14 | Viewed by 5084

Abstract

Pulsed eddy current (PEC) technology is another important non-contact nondestructive testing technology for defect detection. However, the temperature drift of the exciting coil has a considerable influence on the precision of PEC testing. The objective of this study is to investigate the temperature [...] Read more.

Pulsed eddy current (PEC) technology is another important non-contact nondestructive testing technology for defect detection. However, the temperature drift of the exciting coil has a considerable influence on the precision of PEC testing. The objective of this study is to investigate the temperature drift effect and reduce its impact. The temperature drift effect is analyzed theoretically and experimentally. The temperature drift effect on the peak-to-peak values of the output signal is investigated, and a temperature compensation method is proposed to reduce the effect of temperature variation. The results show that temperature drift has a negative impact on PEC testing and the temperature compensation method can effectively reduce the effect of temperature drift. 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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17 pages, 1690 KiB

Open AccessArticle

Polystyrene Oxygen Optodes Doped with Ir(III) and Pd(II) meso-Tetrakis(pentafluorophenyl)porphyrin Using an LED-Based High-Sensitivity Phosphorimeter

by Alexandre F. De Moraes Filho^1,*

, Pedro M. Gewehr²

, Joaquim M. Maia²

and Douglas R. Jakubiak³

¹ Federal Institute of Education, Science and Technology of Paraná (IFPR), Curitiba 80230-150, Brazil

² Graduate Program in Electrical and Computer Engineering (CPGEI), Federal University of Technology-Paraná (UTFPR), Curitiba 80230-901, Brazil

³ Department of Electronics (DAELN), Federal University of Technology-Paraná (UTFPR), Curitiba 80230-901, Brazil

Sensors 2018, 18(6), 1953; https://doi.org/10.3390/s18061953 - 15 Jun 2018

Cited by 4 | Viewed by 6490

Abstract

This paper presents a gaseous oxygen detection system based on time-resolved phosphorimetry (time-domain), which is used to investigate O

_{2}

optical transducers. The primary sensing elements were formed by incorporating iridium(III) and palladium(II) meso-tetrakis(pentafluorophenyl)porphyrin complexes (IrTFPP-CO-Cl and PdTFPP) in polystyrene (PS) solid [...] Read more.

This paper presents a gaseous oxygen detection system based on time-resolved phosphorimetry (time-domain), which is used to investigate O

_{2}

optical transducers. The primary sensing elements were formed by incorporating iridium(III) and palladium(II) meso-tetrakis(pentafluorophenyl)porphyrin complexes (IrTFPP-CO-Cl and PdTFPP) in polystyrene (PS) solid matrices. Probe excitation was obtained using a violet light-emitting diode (LED) (low power), and the resulting phosphorescence was detected by a high-sensitivity compact photomultiplier tube. The detection system performance and the preparation of the transducers are presented along with their optical properties, phosphorescence lifetimes, calibration curves and photostability. The developed lifetime measuring system showed a good signal-to-noise ratio, and reliable results were obtained from the optodes, even when exposed to moderate levels of O

_{2}

. The new IrTFPP-CO-Cl membranes exhibited room temperature phosphorescence and moderate sensitivity: <

τ_{0}

>/<

τ_{21 %}

> ratio of ≈6. A typically high degree of dynamic phosphorescence quenching was observed for the traditional indicator PdTFPP: <

τ_{0}

>/<

τ_{21 %}

> ratio of ≈36. Pulsed-source time-resolved phosphorimetry combined with a high-sensitivity photodetector can offer potential advantages such as: (i) major dynamic range, (ii) extended temporal resolution (

Δ

τ

/

Δ

[O

_{2}

]) and (iii) high operational stability. IrTFPP-CO-Cl immobilized in polystyrene is a promising alternative for O

_{2}

detection, offering adequate photostability and potentially mid-range sensitivity over Pt(II) and Pd(II) metalloporphyrins. Full article

(This article belongs to the Special Issue Luminescence and Chemiluminescence Sensors)

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13 pages, 1205 KiB

Open AccessArticle

Fire Source Range Localization Based on the Dynamic Optimization Method for Large-Space Buildings

by Guoyong Wang¹, Xiaoliang Feng^2,*

and Zhenzhong Zhang³

¹ Luoyang Institute of Science and Technology, Luoyang 471000, China

² College of Electrical Engineering, Henan University of Technology, Zhengzhou 450001, China

³ Bureau of Geophysical Prospecting, China National Petroleum Corporation, Zhuozhou 072751, China

Sensors 2018, 18(6), 1954; https://doi.org/10.3390/s18061954 - 15 Jun 2018

Cited by 4 | Viewed by 3957

Abstract

This paper is concerned to the fire localization problem for large-space buildings. Two kinds of circular fire source arrangement localization methods are proposed on the basis of the dynamic optimization technology. In the Range-Point-Range frame, a dynamic optimization localization is proposed to globally [...] Read more.

This paper is concerned to the fire localization problem for large-space buildings. Two kinds of circular fire source arrangement localization methods are proposed on the basis of the dynamic optimization technology. In the Range-Point-Range frame, a dynamic optimization localization is proposed to globally estimate the circle center of the circular arrangement to be determined based on all the point estimates of the fire source. In the Range-Range-Range frame, a dynamic optimization localization method is developed by solving a non-convex optimization problem. In this way, the circle center and the radius are obtained simultaneously. Additionally, the dynamic angle bisector method is evaluated. Finally, a simulation with three simulation scenes is provided to illustrate the effectiveness and availability of the proposed methods. Full article

(This article belongs to the Collection Multi-Sensor Information Fusion)

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17 pages, 3740 KiB

Open AccessFeature PaperArticle

Nondestructive Evaluation of Concrete Bridge Decks with Automated Acoustic Scanning System and Ground Penetrating Radar

by Hongbin Sun

, Sepehr Pashoutani

and Jinying Zhu^*

Department of Civil Engineering, University of Nebraska-Lincoln, 1110 S 67th St., Omaha, NE 68182, USA

Sensors 2018, 18(6), 1955; https://doi.org/10.3390/s18061955 - 16 Jun 2018

Cited by 56 | Viewed by 8965

Abstract

Delamanintions and reinforcement corrosion are two common problems in concrete bridge decks. No single nondestructive testing method (NDT) is able to provide comprehensive characterization of these defects. In this work, two NDT methods, acoustic scanning and Ground Penetrating Radar (GPR), were used to [...] Read more.

Delamanintions and reinforcement corrosion are two common problems in concrete bridge decks. No single nondestructive testing method (NDT) is able to provide comprehensive characterization of these defects. In this work, two NDT methods, acoustic scanning and Ground Penetrating Radar (GPR), were used to image a straight concrete bridge deck and a curved intersection ramp bridge. An acoustic scanning system has been developed for rapid delamination mapping. The system consists of metal-ball excitation sources, air-coupled sensors, and a GPS positioning system. The acoustic scanning results are presented as a two-dimensional image that is based on the energy map in the frequency range of 0.5–5 kHz. The GPR scanning results are expressed as the GPR signal attenuation map to characterize concrete deterioration and reinforcement corrosion. Signal processing algorithms for both methods are discussed. Delamination maps from the acoustic scanning are compared with deterioration maps from the GPR scanning on both bridges. The results demonstrate that combining the acoustic and GPR scanning results will provide a complementary and comprehensive evaluation of concrete bridge decks. 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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12 pages, 5557 KiB

Open AccessArticle

Laser Self-Mixing Fiber Bragg Grating Sensor for Acoustic Emission Measurement

by Bin Liu

, Yuxi Ruan

, Yanguang Yu^*, Jiangtao Xi, Qinghua Guo, Jun Tong and Ginu Rajan

School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia

Sensors 2018, 18(6), 1956; https://doi.org/10.3390/s18061956 - 16 Jun 2018

Cited by 28 | Viewed by 5234

Abstract

Fiber Bragg grating (FBG) is considered a good candidate for acoustic emission (AE) measurement. The sensing and measurement in traditional FBG-based AE systems are based on the variation in laser intensity induced by the Bragg wavelength shift. This paper presents a sensing system [...] Read more.

Fiber Bragg grating (FBG) is considered a good candidate for acoustic emission (AE) measurement. The sensing and measurement in traditional FBG-based AE systems are based on the variation in laser intensity induced by the Bragg wavelength shift. This paper presents a sensing system by combining self-mixing interference (SMI) in a laser diode and FBG for AE measurement, aiming to form a new compact and cost-effective sensing system. The measurement model of the overall system was derived. The performance of the presented system was investigated from both aspects of theory and experiment. The results show that the proposed system is able to measure AE events with high resolution and over a wide dynamic frequency range. Full article

(This article belongs to the Special Issue Laser Sensors for Displacement, Distance and Position)

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16 pages, 3060 KiB

Open AccessArticle

Adaptive Waveform Design for MIMO Radar-Communication Transceiver

by Yu Yao^1,*

, Junhui Zhao¹ and Lenan Wu²

¹ School of Information Engineering, East China Jiaotong University, Nanchang 330031, China

² School of Information Science and Engineering, Southeast University, Nanjing 210096, China

Sensors 2018, 18(6), 1957; https://doi.org/10.3390/s18061957 - 16 Jun 2018

Cited by 14 | Viewed by 4492

Abstract

The system architecture for an adaptive multiple input multiple output (MIMO) radar-communication transceiver is proposed. A waveform design approach for communication data embedding into MIMO radar pulse using M-ary position phase shift keying (MPPSK) waveforms is introduced. A waveform optimization algorithm for the [...] Read more.

The system architecture for an adaptive multiple input multiple output (MIMO) radar-communication transceiver is proposed. A waveform design approach for communication data embedding into MIMO radar pulse using M-ary position phase shift keying (MPPSK) waveforms is introduced. A waveform optimization algorithm for the adaptive system is presented. The algorithm aims to improve the target detection performance by maximizing the relative entropy (RE) between the distributions under existence and absence of the target, and minimizing the mutual information (MI) between the current received signals and the estimated signals in the next time instant. The proposed system adapts its MPPSK modulated inter-pulse duration to suit the time-varying environment. With subsequent iterations of the algorithm, simulation results show an improvement in target impulse response (TIR) estimation and target detection probability. Meanwhile, the system is able to transmit data of several Mbps with low symbol error rates. Full article

(This article belongs to the Section Remote Sensors)

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11 pages, 4026 KiB

Open AccessArticle

Design of Inkjet-Printed RFID-Based Sensor on Paper: Single- and Dual-Tag Sensor Topologies

by Sangkil Kim^1,*, Apostolos Georgiadis² and Manos M. Tentzeris³

¹ Department of Electronics Engineering, Pusan National University, Busan, 46241, Korea

² Heriot Watt University, Edinburgh Campus, Edinburgh EH14 4AS, UK

³ Department of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Dr. NW, Atlanta, GA 30332, USA

Sensors 2018, 18(6), 1958; https://doi.org/10.3390/s18061958 - 17 Jun 2018

Cited by 31 | Viewed by 6703

Abstract

The detailed design considerations for the printed RFID-based sensor system is presented in this paper. Starting from material selection and metallization method, this paper discusses types of RFID-based sensors (single- & dual-tag sensor topologies), design procedures, and performance evaluation methods for the wireless [...] Read more.

The detailed design considerations for the printed RFID-based sensor system is presented in this paper. Starting from material selection and metallization method, this paper discusses types of RFID-based sensors (single- & dual-tag sensor topologies), design procedures, and performance evaluation methods for the wireless sensor system. The electrical properties of the paper substrates (cellulose-based and synthetic papers) and the silver nano-particle-based conductive film are thoroughly characterized for RF applications up to 8 GHz. The reported technology could potentially set the foundation for truly “green”, low-cost, scalable wireless topologies for autonomous Internet-of-Things (IoT), bio-monitoring, and “smart skin” applications. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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13 pages, 2525 KiB

Open AccessArticle

Stochastic Feedback Based Continuous-Discrete Cubature Kalman Filtering for Bearings-Only Tracking

by Renke He¹, Shuxin Chen¹, Hao Wu^1,*, Lei Hong¹ and Kun Chen²

¹ Information and Navigation College, Air Force Engineering University, Xi’an 710077, China

² Air Force Harbin Flight Academy, Harbin 150006, China

Sensors 2018, 18(6), 1959; https://doi.org/10.3390/s18061959 - 17 Jun 2018

Cited by 9 | Viewed by 3335

Abstract

Bearings-only tracking only adopts measurements from angle sensors to realize target tracking, thus, the accuracy of the state prediction has a significant influence on the final results of filtering. There exist unpredictable approximation errors in the process of filtering due to state propagation, [...] Read more.

Bearings-only tracking only adopts measurements from angle sensors to realize target tracking, thus, the accuracy of the state prediction has a significant influence on the final results of filtering. There exist unpredictable approximation errors in the process of filtering due to state propagation, discretization, linearization or other adverse effects. The idea of online covariance adaption is proposed in this work, where the post covariance information is proved to be effective for the covariance adaption. With theoretical deduction, the relationship between the posterior covariance and the priori covariance is investigated; the priori covariance is modified online based on the feedback rule of covariance updating. The general framework integrates the continuous-discrete cubature Kalman filtering and the feedback rule of covariance updating. Numerical results illustrated that the proposed method has advantages over decreasing unpredictable errors and improving the computational accuracy and efficiency. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 867 KiB

Open AccessArticle

Adaptive Maximum Correntropy Gaussian Filter Based on Variational Bayes

by Guoqing Wang¹

, Zhongxing Gao^1,*, Yonggang Zhang¹ and Bin Ma²

¹ College of Automation, Harbin Engineering University, Harbin 150001, China

² Chinese Ship Research and Design Center, Wuhan 430064, China

Sensors 2018, 18(6), 1960; https://doi.org/10.3390/s18061960 - 17 Jun 2018

Cited by 29 | Viewed by 4411

Abstract

In this paper, we investigate the state estimation of systems with unknown covariance non-Gaussian measurement noise. A novel improved Gaussian filter (GF) is proposed, where the maximum correntropy criterion (MCC) is used to suppress the pollution of non-Gaussian measurement noise and its covariance [...] Read more.

In this paper, we investigate the state estimation of systems with unknown covariance non-Gaussian measurement noise. A novel improved Gaussian filter (GF) is proposed, where the maximum correntropy criterion (MCC) is used to suppress the pollution of non-Gaussian measurement noise and its covariance is online estimated through the variational Bayes (VB) approximation. MCC and VB are integrated through the fixed-point iteration to modify the estimated measurement noise covariance. As a general framework, the proposed algorithm is applicable to both linear and nonlinear systems with different rules being used to calculate the Gaussian integrals. Experimental results show that the proposed algorithm has better estimation accuracy than related robust and adaptive algorithms through a target tracking simulation example and the field test of an INS/DVL integrated navigation system. Full article

(This article belongs to the Section Physical Sensors)

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26 pages, 45012 KiB

Open AccessArticle

A Fog Computing Based Cyber-Physical System for the Automation of Pipe-Related Tasks in the Industry 4.0 Shipyard

by Tiago M. Fernández-Caramés^1,*

, Paula Fraga-Lamas^1,*

, Manuel Suárez-Albela¹

and Manuel A. Díaz-Bouza²

¹ Unidade Mixta de Investigación Navantia-UDC, Universidade da Coruña, Edificio Talleres Tecnológicos, Mendizábal s/n, 15403 Ferrol, Spain

² Navantia S. A., Astillero Ría de Ferrol, Taxonera, s/n, 15403 Ferrol, Spain

Sensors 2018, 18(6), 1961; https://doi.org/10.3390/s18061961 - 17 Jun 2018

Cited by 72 | Viewed by 8028

Abstract

Pipes are one of the key elements in the construction of ships, which usually contain between 15,000 and 40,000 of them. This huge number, as well as the variety of processes that may be performed on a pipe, require rigorous identification, quality assessment [...] Read more.

Pipes are one of the key elements in the construction of ships, which usually contain between 15,000 and 40,000 of them. This huge number, as well as the variety of processes that may be performed on a pipe, require rigorous identification, quality assessment and traceability. Traditionally, such tasks have been carried out by using manual procedures and following documentation on paper, which slows down the production processes and reduces the output of a pipe workshop. This article presents a system that allows for identifying and tracking the pipes of a ship through their construction cycle. For such a purpose, a fog computing architecture is proposed to extend cloud computing to the edge of the shipyard network. The system has been developed jointly by Navantia, one of the largest shipbuilders in the world, and the University of A Coruña (Spain), through a project that makes use of some of the latest Industry 4.0 technologies. Specifically, a Cyber-Physical System (CPS) is described, which uses active Radio Frequency Identification (RFID) tags to track pipes and detect relevant events. Furthermore, the CPS has been integrated and tested in conjunction with Siemens’ Manufacturing Execution System (MES) (Simatic IT). The experiments performed on the CPS show that, in the selected real-world scenarios, fog gateways respond faster than the tested cloud server, being such gateways are also able to process successfully more samples under high-load situations. In addition, under regular loads, fog gateways react between five and 481 times faster than the alternative cloud approach. Full article

(This article belongs to the Special Issue Sensor Networks and Systems to Enable Industry 4.0 Environments)

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22 pages, 8275 KiB

Open AccessArticle

Joint Energy Supply and Routing Path Selection for Rechargeable Wireless Sensor Networks

by Liangrui Tang, Jinqi Cai^*, Jiangyu Yan and Zhenyu Zhou

State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China

Sensors 2018, 18(6), 1962; https://doi.org/10.3390/s18061962 - 17 Jun 2018

Cited by 16 | Viewed by 4661

Abstract

The topic of network lifetime has been attracting much research attention because of its importance in prolonging the standing operation of battery-restricted wireless sensor networks, and the rechargeable wireless sensor network has emerged as a promising solution. In this paper, we propose a [...] Read more.

The topic of network lifetime has been attracting much research attention because of its importance in prolonging the standing operation of battery-restricted wireless sensor networks, and the rechargeable wireless sensor network has emerged as a promising solution. In this paper, we propose a joint energy supply and routing path selection algorithm to extend the network lifetime based on an initiative power supply. We develop a two-stage energy replenishment strategy to supplement the energy consumption of nodes as much as possible. Furthermore, the influence of charging factors on the selection of next-hop nodes in data routing is considered. The simulation results show that our algorithm effectively prolong the network lifetime, and different demands of network delay and energy consumption can be obtained by dynamically adjusting parameters. Full article

(This article belongs to the Special Issue Low Energy Wireless Sensor Networks: Protocols, Architectures and Solutions)

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11 pages, 2923 KiB

Open AccessArticle

Non-Destructive Methodology to Determine Modulus of Elasticity in Static Bending of Quercus mongolica Using Near-Infrared Spectroscopy

by Hao Liang^1,2,3, Meng Zhang^1,2,3, Chao Gao^1,2,3 and Yandong Zhao^1,2,3,*

¹ School of Technology, Beijing Forestry University, Beijing 100083, China

² Beijing Laboratory of Urban and Rural Ecological Environment, Beijing 100083, China

³ Key Lab of State Forestry Administration for Forestry Equipment and Automation, Beijing 10083, China

Sensors 2018, 18(6), 1963; https://doi.org/10.3390/s18061963 - 18 Jun 2018

Cited by 17 | Viewed by 5136

Abstract

This article presents a non-destructive methodology to determine the modulus of elasticity (MOE) in static bending of wood through the use of near-infrared (NIR) spectroscopy. Wood specimens were obtained from Quercus mongolica growing in Northeast of China. The NIR spectra of specimens were [...] Read more.

This article presents a non-destructive methodology to determine the modulus of elasticity (MOE) in static bending of wood through the use of near-infrared (NIR) spectroscopy. Wood specimens were obtained from Quercus mongolica growing in Northeast of China. The NIR spectra of specimens were acquired by using a one-chip NIR fiber optic spectrometer whose spectral range was 900~1900 nm. The raw spectra of specimens were pretreated by multiplication scatter correlation and Savitzky-Golay smoothing and differentiation filter. To reduce the dimensions of data and complexity of modeling, the synergy interval partial least squares and successive projections algorithm were applied to extract the characteristic wavelengths, which had closing relevance with the MOE of wood, and five characteristic wavelengths were selected from full 117 variables of a spectrum. Taking the characteristic wavelengths as input values, partial least square regression (PLSR) and the propagation neural network (BPNN) were implemented to establish calibration models. The predictive ability of the models was estimated by the coefficient of determination (r_p) and the root mean square error of prediction (RMSEP) and in the prediction set. In comparison with the predicted results of the models, BPNN performed better results with the higher r_p of 0.91 and lower RMSEP of 0.76. The results indicate that it is feasible to accurately determine the MOE of wood by using the NIR spectroscopy technique. Full article

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

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18 pages, 5634 KiB

Open AccessArticle

TM₀₂ Quarter-Mode Substrate-Integrated Waveguide Resonator for Dual Detection of Chemicals

by Ahmed Salim and Sungjoon Lim^*

School of Electrical and Electronics Engineering, College of Engineering, Chung-Ang University, 221, Heukseok-Dong, Dongjak-Gu, Seoul 156-756, Korea

Sensors 2018, 18(6), 1964; https://doi.org/10.3390/s18061964 - 18 Jun 2018

Cited by 25 | Viewed by 5060

Abstract

The detection of multiple fluids using a single chip has been attracting attention recently. A TM₀₂ quarter-mode substrate-integrated waveguide resonator designed at 5.81 GHz on RT/duroid 6010LM with a return loss of 13 dB and an unloaded quality factor of Q ≈ [...] Read more.

The detection of multiple fluids using a single chip has been attracting attention recently. A TM₀₂ quarter-mode substrate-integrated waveguide resonator designed at 5.81 GHz on RT/duroid 6010LM with a return loss of 13 dB and an unloaded quality factor of Q ≈ 13 generates two distinct strong electric fields that can be manipulated to simultaneously detect two chemicals. Two asymmetric channels engraved in a polydimethylsiloxane sheet are loaded with analyte to produce a unique resonance frequency in each case, regardless of the dielectric constants of the liquids. Keeping in view the nature of lossy liquids such as ethanol, the initial structure and channels are optimized to ensure a reasonable return loss even in the case of loading lossy liquids. After loading the empty channels, Q is evaluated as 43. Ethanol (E) and deionized water (DI) are simultaneously loaded to demonstrate the detection of all possible combinations: [Air, Air], [E, DI], [DI, E], [E, E], and [DI, DI]. The proposed structure is miniaturized while exhibiting a performance comparable to that of existing multichannel microwave chemical sensors. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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20 pages, 10222 KiB

Open AccessArticle

Impact of Sliding Window Length in Indoor Human Motion Modes and Pose Pattern Recognition Based on Smartphone Sensors

by Gaojing Wang¹

, Qingquan Li^1,*, Lei Wang^1,*

, Wei Wang², Mengqi Wu² and Tao Liu³

¹ State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China

² School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China

³ College of Resources and Environment, Henan University of Economics and Law, Zhengzhou 450002, China

Sensors 2018, 18(6), 1965; https://doi.org/10.3390/s18061965 - 18 Jun 2018

Cited by 56 | Viewed by 7482

Abstract

Human activity recognition (HAR) is essential for understanding people’s habits and behaviors, providing an important data source for precise marketing and research in psychology and sociology. Different approaches have been proposed and applied to HAR. Data segmentation using a sliding window is a [...] Read more.

Human activity recognition (HAR) is essential for understanding people’s habits and behaviors, providing an important data source for precise marketing and research in psychology and sociology. Different approaches have been proposed and applied to HAR. Data segmentation using a sliding window is a basic step during the HAR procedure, wherein the window length directly affects recognition performance. However, the window length is generally randomly selected without systematic study. In this study, we examined the impact of window length on smartphone sensor-based human motion and pose pattern recognition. With data collected from smartphone sensors, we tested a range of window lengths on five popular machine-learning methods: decision tree, support vector machine, K-nearest neighbor, Gaussian naïve Bayesian, and adaptive boosting. From the results, we provide recommendations for choosing the appropriate window length. Results corroborate that the influence of window length on the recognition of motion modes is significant but largely limited to pose pattern recognition. For motion mode recognition, a window length between 2.5–3.5 s can provide an optimal tradeoff between recognition performance and speed. Adaptive boosting outperformed the other methods. For pose pattern recognition, 0.5 s was enough to obtain a satisfactory result. In addition, all of the tested methods performed well. Full article

(This article belongs to the Special Issue Smartphone-Based Sensors for Posture, Movement Analysis and Human Activity Recognition)

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18 pages, 5573 KiB

Open AccessArticle

Estimation of Tri-Axial Walking Ground Reaction Forces of Left and Right Foot from Total Forces in Real-Life Environments

by Erfan Shahabpoor^1,2,*

and Aleksandar Pavic³

¹ Department of Architecture and Civil Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK

² Department of Civil & Structural Engineering, INSIGNEO Institute for In-Silico Medicine, University of Sheffield, Sheffield S1 3JD, UK

³ College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK

Sensors 2018, 18(6), 1966; https://doi.org/10.3390/s18061966 - 19 Jun 2018

Cited by 6 | Viewed by 4422

Abstract

Continuous monitoring of natural human gait in real-life environments is essential in many applications including disease monitoring, rehabilitation, and professional sports. Wearable inertial measurement units are successfully used to measure body kinematics in real-life environments and to estimate total walking ground reaction forces [...] Read more.

Continuous monitoring of natural human gait in real-life environments is essential in many applications including disease monitoring, rehabilitation, and professional sports. Wearable inertial measurement units are successfully used to measure body kinematics in real-life environments and to estimate total walking ground reaction forces

G R F (t)

using equations of motion. However, for inverse dynamics and clinical gait analysis, the

G R F (t)

of each foot is required separately. Using an experimental dataset of 1243 tri-axial separate-foot

G R F (t)

time histories measured by the authors across eight years, this study proposes the ‘Twin Polynomial Method’ (TPM) to estimate the tri-axial left and right foot

G R F (t)

signals from the total

G R F (t)

signals. For each gait cycle, TPM fits polynomials of degree five, eight, and nine to the known single-support part of the left and right foot vertical, anterior-posterior, and medial-lateral

G R F (t)

signals, respectively, to extrapolate the unknown double-support parts of the corresponding

G R F (t)

signals. Validation of the proposed method both with force plate measurements (gold standard) in the laboratory, and in real-life environment showed a peak-to-peak normalized root mean square error of less than 2.5%, 6.5% and 7.5% for the estimated

G R F (t)

signals in the vertical, anterior-posterior and medial-lateral directions, respectively. These values show considerable improvement compared with the currently available

G R F (t)

decomposition methods in the literature. Full article

(This article belongs to the Section Physical Sensors)

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32 pages, 7453 KiB

Open AccessArticle

GNSS Code Multipath Mitigation by Cascading Measurement Monitoring Techniques

by Ali Pirsiavash^*

, Ali Broumandan, Gérard Lachapelle and Kyle O’Keefe

Position, Location and Navigation (PLAN) Group, Schulich School of Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada

Sensors 2018, 18(6), 1967; https://doi.org/10.3390/s18061967 - 19 Jun 2018

Cited by 26 | Viewed by 8091

Abstract

Various measurement monitoring techniques are investigated to mitigate the effect of global navigation satellite systems (GNSS) code multipath through error correction, stochastic weighting of measurements and detection and exclusion (or de-weighting) of affected measurements. Following a comprehensive review of each approach, the paper [...] Read more.

Various measurement monitoring techniques are investigated to mitigate the effect of global navigation satellite systems (GNSS) code multipath through error correction, stochastic weighting of measurements and detection and exclusion (or de-weighting) of affected measurements. Following a comprehensive review of each approach, the paper focuses on detection/exclusion and detection/de-weighting techniques where several single and dual-frequency monitoring metrics are employed in a combination with time-averaging and the M of N detection strategy. A new Geometry-Free (GF) detection metric is proposed given its capability to be combined with a preceding Code-Minus-Carrier (CMC)-based error correction to reduce the number of excluded or de-weighted measurements and thus preserve the measurement geometry. Three geometry-based algorithms, namely measurement subset testing, consecutive exclusion and iterative change of measurement weights are investigated to address multipath scenarios with multiple simultaneously affected measurements. Experimental results are provided using GPS L1, L2C and L5 data collected in multipath environments for static and kinematic scenarios. For GPS L1, the proposed combined method shows more than 38% improvement over a conventional Carrier-to-Noise-density ratio (C/N₀)-based Least-Squares (LS) solution in all but deep urban canyons. Lower performance was observed for L2C and L5 frequencies with a limited number of satellites in view. Full article

(This article belongs to the Special Issue GNSS and Fusion with Other Sensors)

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18 pages, 4942 KiB

Open AccessArticle

Deformation Monitoring for Chinese Traditional Timber Buildings Using Fiber Bragg Grating Sensors

by Ni-Lei Li¹, Shao-Fei Jiang^1,*

, Ming-Hao Wu¹, Sheng Shen¹ and Ying Zhang²

¹ College of Civil Engineering, Fuzhou University, Fuzhou 350108, China

² College of Architecture, Fuzhou University, Fuzhou 350108, China

Sensors 2018, 18(6), 1968; https://doi.org/10.3390/s18061968 - 19 Jun 2018

Cited by 23 | Viewed by 5246

Abstract

The Fiber Bragg Grating (FBG) sensing technique is suitable for a wide variety of measurements, including temperature, pressure, acceleration, liquid level, etc., and has been applied to many bridges and buildings in the past two decades. The fact that the FBG technique can [...] Read more.

The Fiber Bragg Grating (FBG) sensing technique is suitable for a wide variety of measurements, including temperature, pressure, acceleration, liquid level, etc., and has been applied to many bridges and buildings in the past two decades. The fact that the FBG technique can only monitor and measure strain data for most cases when it is used for deformation measurements impedes application of the FBG sensing technique in civil infrastructures. This paper proposes FBG sensing-based deformation monitoring methods that are applicable to monitoring beam deflection, column inclination angle and mortise-tenon joint dislocation for Chinese traditional timber structures. On the basis of improved conjugated beam theory and geometrical trigonometric function relationship, the relationships between the FBG sensing strain values and the deflection of beam, inclination angle of column, as well as the amount of dislocation of mortise-tenon joint are deducted for Chinese traditional buildings. A series of experiments were conducted to verify the applicability and effectiveness of the proposed deformation monitoring methods. The results show that a good agreement is obtained between the values given by the methods proposed in this paper and other methods. This implies that the proposed deformation monitoring methods are applicable and effective in the health monitoring of Chinese traditional timber structures. Full article

(This article belongs to the Special Issue Smart Sensors and Smart Structures)

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17 pages, 7915 KiB

Open AccessArticle

UCMAC: A Cooperative MAC Protocol for Underwater Wireless Sensor Networks

by Hee-won Kim¹, Tae Ho Im² and Ho-Shin Cho^1,*

¹ School of Electronics Engineering, Kyungpook National University, Daegu 41566, Korea

² Oceanic IT Convergence Technology Research Center, Hoseo University, Asan 31499, Korea

Sensors 2018, 18(6), 1969; https://doi.org/10.3390/s18061969 - 19 Jun 2018

Cited by 22 | Viewed by 5114

Abstract

This paper proposes a cooperative medium access control (MAC) protocol for underwater wireless sensor networks (UWSNs) named UCMAC, which fundamentally benefits from cooperative communication. In UCMAC, a source identifies cooperators and provides its destination with a list of the cooperators while also delineating [...] Read more.

This paper proposes a cooperative medium access control (MAC) protocol for underwater wireless sensor networks (UWSNs) named UCMAC, which fundamentally benefits from cooperative communication. In UCMAC, a source identifies cooperators and provides its destination with a list of the cooperators while also delineating their proximity to the destination. For erroneous reception of data packets, the destination then requests retransmission to the cooperators in a closest-one-first manner. A designated cooperator transmits the buffered data packet it has successfully overheard from the source or other cooperators. A signaling procedure and the various waiting times of the nodes are carefully designed to address the overheads that stem from cooperation. Through computer simulation, this paper evaluates UCMAC in terms of system throughput, latency, single-hop packet delivery ratio (PDR), and energy efficiency. The results show that UCMAC performs better than existing schemes, including MACA-U and CD-MACA. Full article

(This article belongs to the Section Sensor Networks)

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23 pages, 8959 KiB

Open AccessArticle

Heading Estimation for Pedestrian Dead Reckoning Based on Robust Adaptive Kalman Filtering

by Dongjin Wu^*

, Linyuan Xia^* and Jijun Geng

School of Geography and Planning, SunYat-Sen University, 135 # Xingangxi Road, Guangzhou 510275, China

Sensors 2018, 18(6), 1970; https://doi.org/10.3390/s18061970 - 19 Jun 2018

Cited by 30 | Viewed by 6276

Abstract

Pedestrian dead reckoning (PDR) using smart phone-embedded micro-electro-mechanical system (MEMS) sensors plays a key role in ubiquitous localization indoors and outdoors. However, as a relative localization method, it suffers from the problem of error accumulation which prevents it from long term independent running. [...] Read more.

Pedestrian dead reckoning (PDR) using smart phone-embedded micro-electro-mechanical system (MEMS) sensors plays a key role in ubiquitous localization indoors and outdoors. However, as a relative localization method, it suffers from the problem of error accumulation which prevents it from long term independent running. Heading estimation error is one of the main location error sources, and therefore, in order to improve the location tracking performance of the PDR method in complex environments, an approach based on robust adaptive Kalman filtering (RAKF) for estimating accurate headings is proposed. In our approach, outputs from gyroscope, accelerometer, and magnetometer sensors are fused using the solution of Kalman filtering (KF) that the heading measurements derived from accelerations and magnetic field data are used to correct the states integrated from angular rates. In order to identify and control measurement outliers, a maximum likelihood-type estimator (M-estimator)-based model is used. Moreover, an adaptive factor is applied to resist the negative effects of state model disturbances. Extensive experiments under static and dynamic conditions were conducted in indoor environments. The experimental results demonstrate the proposed approach provides more accurate heading estimates and supports more robust and dynamic adaptive location tracking, compared with methods based on conventional KF. Full article

(This article belongs to the Special Issue Smartphone-Based Sensors for Posture, Movement Analysis and Human Activity Recognition)

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13 pages, 5064 KiB

Open AccessArticle

Processing Ultrasonic Data by Coda Wave Interferometry to Monitor Load Tests of Concrete Beams

by Ernst Niederleithinger^1,*

, Xin Wang¹, Martin Herbrand² and Matthias Müller³

¹ Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany

² RWTH Aachen University (now WTM Engineers GmbH), Templergraben 55, 52062 Aachen, Germany

³ Bundesanstalt für Straßenwesen (BASt), Bruederstr. 53, 51427 Bergisch Gladbach, Germany

Sensors 2018, 18(6), 1971; https://doi.org/10.3390/s18061971 - 19 Jun 2018

Cited by 83 | Viewed by 7653 | Correction

Abstract

Ultrasonic transmission measurements have been used for decades to monitor concrete elements, mostly on a laboratory scale. Recently, coda wave interferometry (CWI), a technique adapted from seismology, was introduced to civil engineering experiments. It can be used to reveal subtle changes in concrete [...] Read more.

Ultrasonic transmission measurements have been used for decades to monitor concrete elements, mostly on a laboratory scale. Recently, coda wave interferometry (CWI), a technique adapted from seismology, was introduced to civil engineering experiments. It can be used to reveal subtle changes in concrete laboratory samples and even large structural elements without having a transducer directly at the place where the change is taking place. Here, several load tests until failure on large posttensioned concrete beams have been monitored using networks of embedded transducers. To detect subtle effects at the beginning of the experiments and cope with severe changes due to cracking close to failure, the coda wave interferometry procedures had to be modified to an adapted step-wise approach. Using this methodology, we were able to monitor stress distribution and localize large cracks by a relatively simple technique. Implementation of this approach on selected real structures might help to make decisions in infrastructure asset management. 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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15 pages, 3553 KiB

Open AccessArticle

Improved Dynamic Mode Decomposition and Its Application to Fault Diagnosis of Rolling Bearing

by Zhang Dang^1,2,3

, Yong Lv^1,2,*, Yourong Li^1,2 and Guoqian Wei^1,2

¹ Key Laboratory of Metallurgical Equipment and Control Technology, Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081, China

² Hubei Key Laboratory of Mechanical Transmission and Manufacturing Engineering, Wuhan University of Science and Technology, Wuhan 430081, China

³ National Demonstration Center for Experimental Mechanical Education, Wuhan University of Science and Technology, Wuhan 430081, China

Sensors 2018, 18(6), 1972; https://doi.org/10.3390/s18061972 - 19 Jun 2018

Cited by 31 | Viewed by 5740

Abstract

To solve the intractable problems of optimal rank truncation threshold and dominant modes selection strategy of the standard dynamic mode decomposition (DMD), an improved DMD algorithm is introduced in this paper. Distinct from the conventional methods, a convex optimization framework is introduced by [...] Read more.

To solve the intractable problems of optimal rank truncation threshold and dominant modes selection strategy of the standard dynamic mode decomposition (DMD), an improved DMD algorithm is introduced in this paper. Distinct from the conventional methods, a convex optimization framework is introduced by applying a parameterized non-convex penalty function to obtain the optimal rank truncation number. This method is inspirited by the performance that it is more perfectible than other rank truncation methods in inhibiting noise disturbance. A hierarchical and multiresolution application similar to the process of wavelet packet decomposition in modes selection is presented so as to improve the algorithm’s performance. With the modes selection strategy, the frequency spectrum of the reconstruction signal is more readable and interference-free. The improved DMD algorithm successfully extracts the fault characteristics of rolling bearing fault signals when it is utilized for mechanical signal feature extraction. Results demonstrated that the proposed method has good application prospects in denoising and fault feature extraction for mechanical signals. Full article

(This article belongs to the Section Physical Sensors)

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26 pages, 619 KiB

Open AccessArticle

Downlink Cooperative Broadcast Transmission Based on Superposition Coding in a Relaying System for Future Wireless Sensor Networks

by Yang Liu¹, Guangjie Han^2,*

, Sulong Shi³ and Zhengquan Li¹

¹ Jiangsu Provincial Engineerinig Laboratory of Pattern Recognition and Computational Intelligence, Jiangnan University, Wuxi 214122, China

² Key Laboratory for Ubiquitous Network and Service Software of Liaoning Province, School of Software, Dalian University of Technology, Dalian 116024, China

³ Huawei Company, Nanjing 210003, China

Sensors 2018, 18(6), 1973; https://doi.org/10.3390/s18061973 - 20 Jun 2018

Cited by 7 | Viewed by 3630

Abstract

This study investigates the superiority of cooperative broadcast transmission over traditional orthogonal schemes when applied in a downlink relaying broadcast channel (RBC). Two proposed cooperative broadcast transmission protocols, one with an amplify-and-forward (AF) relay, and the other with a repetition-based decode-and-forward (DF) relay, [...] Read more.

This study investigates the superiority of cooperative broadcast transmission over traditional orthogonal schemes when applied in a downlink relaying broadcast channel (RBC). Two proposed cooperative broadcast transmission protocols, one with an amplify-and-forward (AF) relay, and the other with a repetition-based decode-and-forward (DF) relay, are investigated. By utilizing superposition coding (SupC), the source and the relay transmit the private user messages simultaneously instead of sequentially as in traditional orthogonal schemes, which means the channel resources are reused and an increased channel degree of freedom is available to each user, hence the half-duplex penalty of relaying is alleviated. To facilitate a performance evaluation, theoretical outage probability expressions of the two broadcast transmission schemes are developed, based on which, we investigate the minimum total power consumption of each scheme for a given traffic requirement by numerical simulation. The results provide details on the overall system performance and fruitful insights on the essential characteristics of cooperative broadcast transmission in RBCs. It is observed that better overall outage performances and considerable power gains can be obtained by utilizing cooperative broadcast transmissions compared to traditional orthogonal schemes. Full article

(This article belongs to the Section Sensor Networks)

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21 pages, 11785 KiB

Open AccessArticle

Accurate Smartphone Indoor Visual Positioning Based on a High-Precision 3D Photorealistic Map

by Teng Wu¹, Jingbin Liu^1,2,4,*, Zheng Li³, Keke Liu¹ and Beini Xu¹

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 Chinese Antarctic Center of Surveying and Mapping, Wuhan University, Wuhan 430079, China

⁴ Department of Remote Sensing and Photogrammetry and the Center of Excellence in Laser Scanning Research, Finnish Geospatial Research Institute, 02430 Masala, Finland

Sensors 2018, 18(6), 1974; https://doi.org/10.3390/s18061974 - 20 Jun 2018

Cited by 26 | Viewed by 5584

Abstract

Indoor positioning is in high demand in a variety of applications, and indoor environment is a challenging scene for visual positioning. This paper proposes an accurate visual positioning method for smartphones. The proposed method includes three procedures. First, an indoor high-precision 3D photorealistic [...] Read more.

Indoor positioning is in high demand in a variety of applications, and indoor environment is a challenging scene for visual positioning. This paper proposes an accurate visual positioning method for smartphones. The proposed method includes three procedures. First, an indoor high-precision 3D photorealistic map is produced using a mobile mapping system, and the intrinsic and extrinsic parameters of the images are obtained from the mapping result. A point cloud is calculated using feature matching and multi-view forward intersection. Second, top-K similar images are queried using hamming embedding with SIFT feature description. Feature matching and pose voting are used to select correctly matched image, and the relationship between image points and 3D points is obtained. Finally, outlier points are removed using P3P with the coarse focal length. Perspective-four-point with unknown focal length and random sample consensus are used to calculate the intrinsic and extrinsic parameters of the query image and then to obtain the positioning of the smartphone. Compared with established baseline methods, the proposed method is more accurate and reliable. The experiment results show that 70 percent of the images achieve location error smaller than 0.9 m in a 10 m × 15.8 m room, and the prospect of improvement is discussed. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 2919 KiB

Open AccessArticle

Directional Sensitivity of a MEMS-Based Fiber-Optic Extrinsic Fabry–Perot Ultrasonic Sensor for Partial Discharge Detection

by Wenrong Si^1,†

, Chenzhao Fu^1,†, Delin Li^2,3,†, Haoyong Li^2,3, Peng Yuan⁴ and Yiting Yu^2,3,*

¹ State Grid Shanghai Electric Power Research Institute, Shanghai 200437, China

² Key Laboratory of Micro/Nano Systems for Aerospace (Ministry of Education), Northwestern Polytechnical University, Xi’an 710072, China

³ Shaanxi Province Key Laboratory of Micro and Nano Electro-Mechanical Systems, Northwestern Polytechnical University, Xi’an 701172, China

⁴ Xi’an Maorong Power Equipment Co., Ltd., Xi’an 710048, China

^† These authors contribute equally to this work.

Sensors 2018, 18(6), 1975; https://doi.org/10.3390/s18061975 - 20 Jun 2018

Cited by 42 | Viewed by 5719

Abstract

Extrinsic Fabry–Perot (FP) interferometric sensors are being intensively applied for partial discharge (PD) detection and localization. Previous research work has mainly focused on novel structures and materials to improve the sensitivity and linear response of these sensors. However, the directional response behavior of [...] Read more.

Extrinsic Fabry–Perot (FP) interferometric sensors are being intensively applied for partial discharge (PD) detection and localization. Previous research work has mainly focused on novel structures and materials to improve the sensitivity and linear response of these sensors. However, the directional response behavior of an FP ultrasonic sensor is also of particular importance in localizing the PD source, which is rarely considered. Here, the directional sensitivity of a microelectromechanical system (MEMS)-based FP ultrasonic sensor with a 5-μm-thick micromechanical vibrating diaphragm is experimentally investigated. Ultrasonic signals from a discharge source with varying incident angles and linear distances are measured and analyzed. The results show that the sensor has a 5.90 dB amplitude fluctuation over a ±60° incident range and an exciting capability to detect weak PD signals from 3 m away due to its high signal–noise ratio. The findings are expected to optimize the configuration of a sensor array and accurately localize the PD source. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 383 KiB

Open AccessArticle

On the Coverage of Bus-Based Mobile Sensing

by Pedro Henrique Cruz Caminha¹

, Rodrigo De Souza Couto²

, Luís Henrique Maciel Kosmalski Costa^1,*

, Anne Fladenmuller³

and Marcelo Dias de Amorim³

¹ Poli/COPPE—Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos 149, Rio de Janeiro 21941-972, Brazil

² DETEL/PEL—Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, Rio de Janeiro 20550-013, Brazil

³ LIP6/CNRS—Sorbonne Université, 4 Place Jussieu, 75252 Paris, France

Sensors 2018, 18(6), 1976; https://doi.org/10.3390/s18061976 - 20 Jun 2018

Cited by 22 | Viewed by 5215

Abstract

A cost-effective approach to gather information in a smart city is to embed sensors in vehicles such as buses. To understand the limitations and opportunities of this model, it is fundamental to investigate the spatial coverage of such a network, especially in the [...] Read more.

A cost-effective approach to gather information in a smart city is to embed sensors in vehicles such as buses. To understand the limitations and opportunities of this model, it is fundamental to investigate the spatial coverage of such a network, especially in the case where only a subset of the buses have a sensing device embedded. In this paper, we propose a model to select the right subset of buses that maximizes the coverage of the city. We evaluate the model in a real scenario based on a large-scale dataset of more than 5700 buses in the city of Rio de Janeiro, Brazil. Among other findings, we observe that the fleet of buses covers approximately 5655 km of streets (approximately 47% of the streets) and show that it is possible to cover 94% of the same streets if only 18% of buses have sensing capabilities embedded. Full article

(This article belongs to the Special Issue Sensor Networks for Smart Roads)

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19 pages, 4857 KiB

Open AccessArticle

A New Method of High-Precision Positioning for an Indoor Pseudolite without Using the Known Point Initialization

by Yinzhi Zhao^1,2,3

, Peng Zhang^1,2,3,*, Jiming Guo^1,2,3,*

, Xin Li⁴

, Jinling Wang⁵

, Fei Yang^1,2,3 and Xinzhe Wang¹

¹ School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China

² Key Laboratory of Precise Engineering and Industry Surveying of National Administration of Surveying, Mapping and Geoinformation, Wuhan University, Wuhan 430079, China

³ Research Center for High Accuracy Location Awareness, Wuhan University 430079, China

⁴ College of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, China

⁵ School of Surveying and Spatial Information Systems, The University of New South Wales, Sydney 2052, Australia

Sensors 2018, 18(6), 1977; https://doi.org/10.3390/s18061977 - 20 Jun 2018

Cited by 25 | Viewed by 5010

Abstract

Due to the great influence of multipath effect, noise, clock and error on pseudorange, the carrier phase double difference equation is widely used in high-precision indoor pseudolite positioning. The initial position is determined mostly by the known point initialization (KPI) method, and then [...] Read more.

Due to the great influence of multipath effect, noise, clock and error on pseudorange, the carrier phase double difference equation is widely used in high-precision indoor pseudolite positioning. The initial position is determined mostly by the known point initialization (KPI) method, and then the ambiguities can be fixed with the LAMBDA method. In this paper, a new method without using the KPI to achieve high-precision indoor pseudolite positioning is proposed. The initial coordinates can be quickly obtained to meet the accuracy requirement of the indoor LAMBDA method. The detailed processes of the method follows: Aiming at the low-cost single-frequency pseudolite system, the static differential pseudolite system (DPL) method is used to obtain the low-accuracy positioning coordinates of the rover station quickly. Then, the ambiguity function method (AFM) is used to search for the coordinates in the corresponding epoch. The real coordinates obtained by AFM can meet the initial accuracy requirement of the LAMBDA method, so that the double difference carrier phase ambiguities can be correctly fixed. Following the above steps, high-precision indoor pseudolite positioning can be realized. Several experiments, including static and dynamic tests, are conducted to verify the feasibility of the new method. According to the results of the experiments, the initial coordinates with the accuracy of decimeter level through the DPL can be obtained. For the AFM part, both a one-meter search scope and two-centimeter or four-centimeter search steps are used to ensure the precision at the centimeter level and high search efficiency. After dealing with the problem of multiple peaks caused by the ambiguity cosine function, the coordinate information of the maximum ambiguity function value (AFV) is taken as the initial value of the LAMBDA, and the ambiguities can be fixed quickly. The new method provides accuracies at the centimeter level for dynamic experiments and at the millimeter level for static ones. Full article

(This article belongs to the Special Issue GNSS and Fusion with Other Sensors)

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15 pages, 1788 KiB

Open AccessArticle

Spectral-Spatial Feature Extraction of Hyperspectral Images Based on Propagation Filter

by Zhikun Chen^1,2,3, Junjun Jiang¹, Xinwei Jiang¹, Xiaoping Fang¹ and Zhihua Cai^1,2,*

¹ School of Computer Science, China University of Geosciences, Wuhan 430074, China

² Beibu Gulf Big Data Resources Utilisation Lab, Qinzhou University, Qinzhou 535000, China

³ Guangxi Key Laboratory of Beibu Gulf Marine Biodiversity Conservation, Qinzhou 535000, China

Sensors 2018, 18(6), 1978; https://doi.org/10.3390/s18061978 - 20 Jun 2018

Cited by 24 | Viewed by 4975

Abstract

Recently, image-filtering based hyperspectral image (HSI) feature extraction has been widely studied. However, due to limited spatial resolution and feature distribution complexity, the problems of cross-region mixing after filtering and spectral discriminative reduction still remain. To address these issues, this paper proposes a [...] Read more.

Recently, image-filtering based hyperspectral image (HSI) feature extraction has been widely studied. However, due to limited spatial resolution and feature distribution complexity, the problems of cross-region mixing after filtering and spectral discriminative reduction still remain. To address these issues, this paper proposes a spectral-spatial propagation filter (PF) based HSI feature extraction method that can effectively address the above problems. The dimensionality/band of an HSI is typically high; therefore, principal component analysis (PCA) is first used to reduce the HSI dimensionality. Then, the principal components of the HSI are filtered with the PF. When cross-region mixture occurs in the image, the filter template reduces the weight assignments of the cross-region mixed pixels to handle the issue of cross-region mixed pixels simply and effectively. To validate the effectiveness of the proposed method, experiments are carried out on three common HSIs using support vector machine (SVM) classifiers with features learned by the PF. The experimental results demonstrate that the proposed method effectively extracts the spectral-spatial features of HSIs and significantly improves the accuracy of HSI classification. Full article

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

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Review

Jump to: Editorial, Research, Other

33 pages, 836 KiB

Open AccessReview

Sensors and Functionalities of Non-Invasive Wrist-Wearable Devices: A Review

by Aida Kamišalić^*

, Iztok Fister

, Muhamed Turkanović

and Sašo Karakatič

Institute of Informatics, Faculty of Electrical Engineering and Computer Science, University of Maribor, Koroška Cesta 46, 2000 Maribor, Slovenia

Sensors 2018, 18(6), 1714; https://doi.org/10.3390/s18061714 - 25 May 2018

Cited by 218 | Viewed by 24128

Abstract

Wearable devices have recently received considerable interest due to their great promise for a plethora of applications. Increased research efforts are oriented towards a non-invasive monitoring of human health as well as activity parameters. A wide range of wearable sensors are being developed [...] Read more.

Wearable devices have recently received considerable interest due to their great promise for a plethora of applications. Increased research efforts are oriented towards a non-invasive monitoring of human health as well as activity parameters. A wide range of wearable sensors are being developed for real-time non-invasive monitoring. This paper provides a comprehensive review of sensors used in wrist-wearable devices, methods used for the visualization of parameters measured as well as methods used for intelligent analysis of data obtained from wrist-wearable devices. In line with this, the main features of commercial wrist-wearable devices are presented. As a result of this review, a taxonomy of sensors, functionalities, and methods used in non-invasive wrist-wearable devices was assembled. Full article

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

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27 pages, 2088 KiB

Open AccessReview

Bio-Signal Complexity Analysis in Epileptic Seizure Monitoring: A Topic Review

by Zhenning Mei¹, Xian Zhao¹, Hongyu Chen² and Wei Chen^1,3,*

¹ Center for Intelligent Medical Electronics (CIME), School of Information Science and Engineering, Fudan University, Shanghai 200433, China

² Department of Industrial Design, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands

³ Shanghai Key Laboratory of Medical Imaging Computing and Computer Assisted Intervention, Shanghai 200032, China

Sensors 2018, 18(6), 1720; https://doi.org/10.3390/s18061720 - 26 May 2018

Cited by 27 | Viewed by 6488

Abstract

Complexity science has provided new perspectives and opportunities for understanding a variety of complex natural or social phenomena, including brain dysfunctions like epilepsy. By delving into the complexity in electrophysiological signals and neuroimaging, new insights have emerged. These discoveries have revealed that complexity [...] Read more.

Complexity science has provided new perspectives and opportunities for understanding a variety of complex natural or social phenomena, including brain dysfunctions like epilepsy. By delving into the complexity in electrophysiological signals and neuroimaging, new insights have emerged. These discoveries have revealed that complexity is a fundamental aspect of physiological processes. The inherent nonlinearity and non-stationarity of physiological processes limits the methods based on simpler underlying assumptions to point out the pathway to a more comprehensive understanding of their behavior and relation with certain diseases. The perspective of complexity may benefit both the research and clinical practice through providing novel data analytics tools devoted for the understanding of and the intervention about epilepsies. This review aims to provide a sketchy overview of the methods derived from different disciplines lucubrating to the complexity of bio-signals in the field of epilepsy monitoring. Although the complexity of bio-signals is still not fully understood, bundles of new insights have been already obtained. Despite the promising results about epileptic seizure detection and prediction through offline analysis, we are still lacking robust, tried-and-true real-time applications. Multidisciplinary collaborations and more high-quality data accessible to the whole community are needed for reproducible research and the development of such applications. Full article

(This article belongs to the Section Intelligent Sensors)

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29 pages, 2141 KiB

Open AccessReview

Reader Architectures for Wireless Surface Acoustic Wave Sensors

by Fabian Lurz^1,*

, Thomas Ostertag², Benedict Scheiner¹

, Robert Weigel¹

and Alexander Koelpin³

¹ Institute for Electronics Engineering, Friedrich-Alexander University Erlangen-Nuremberg (FAU), 91058 Erlangen, Germany

² RSSI GmbH, Bürgermeister-Graf-Ring 1, 82538 Geretsried, Germany

³ Department of General Electrical Engineering and Measurement Technology, Brandenburg University of Technology, 03046 Cottbus, Germany

Sensors 2018, 18(6), 1734; https://doi.org/10.3390/s18061734 - 28 May 2018

Cited by 49 | Viewed by 9373

Abstract

Wireless surface acoustic wave (SAW) sensors have some unique features that make them promising for industrial metrology. Their decisive advantage lies in their purely passive operation and the wireless readout capability allowing the installation also at particularly inaccessible locations. Furthermore, they are small, [...] Read more.

Wireless surface acoustic wave (SAW) sensors have some unique features that make them promising for industrial metrology. Their decisive advantage lies in their purely passive operation and the wireless readout capability allowing the installation also at particularly inaccessible locations. Furthermore, they are small, low-cost and rugged components on highly stable substrate materials and thus particularly suited for harsh environments. Nevertheless, a sensor itself does not carry out any measurement but always requires a suitable excitation and interrogation circuit: a reader. A variety of different architectures have been presented and investigated up to now. This review paper gives a comprehensive survey of the present state of reader architectures such as time domain sampling (TDS), frequency domain sampling (FDS) and hybrid concepts for both SAW resonators and reflective SAW delay line sensors. Furthermore, critical performance parameters such as measurement accuracy, dynamic range, update rate, and hardware costs of the state of the art in science and industry are presented, compared and discussed. Full article

(This article belongs to the Special Issue Surface Acoustic Wave and Bulk Acoustic Wave Sensors)

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26 pages, 4451 KiB

Open AccessReview

Progress of Inertial Microfluidics in Principle and Application

by Yixing Gou¹, Yixuan Jia²

, Peng Wang^1,* and Changku Sun¹

¹ State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China

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

Sensors 2018, 18(6), 1762; https://doi.org/10.3390/s18061762 - 1 Jun 2018

Cited by 131 | Viewed by 13434

Abstract

Inertial microfluidics has become a popular topic in microfluidics research for its good performance in particle manipulation and its advantages of simple structure, high throughput, and freedom from an external field. Compared with traditional microfluidic devices, the flow field in inertial microfluidics is [...] Read more.

Inertial microfluidics has become a popular topic in microfluidics research for its good performance in particle manipulation and its advantages of simple structure, high throughput, and freedom from an external field. Compared with traditional microfluidic devices, the flow field in inertial microfluidics is between Stokes state and turbulence, whereas the flow is still regarded as laminar. However, many mechanical effects induced by the inertial effect are difficult to observe in traditional microfluidics, making particle motion analysis in inertial microfluidics more complicated. In recent years, the inertial migration effect in straight and curved channels has been explored theoretically and experimentally to realize on-chip manipulation with extensive applications from the ordinary manipulation of particles to biochemical analysis. In this review, the latest theoretical achievements and force analyses of inertial microfluidics and its development process are introduced, and its applications in circulating tumor cells, exosomes, DNA, and other biological particles are summarized. Finally, the future development of inertial microfluidics is discussed. Owing to its special advantages in particle manipulation, inertial microfluidics will play a more important role in integrated biochips and biomolecule analysis. Full article

(This article belongs to the Special Issue Sensors and Lab-on-a-Chip)

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21 pages, 1570 KiB

Open AccessReview

Reactive Sputtering of Aluminum Nitride (002) Thin Films for Piezoelectric Applications: A Review

by Abid Iqbal and Faisal Mohd-Yasin^*

Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, QLD 4111, Australia

Sensors 2018, 18(6), 1797; https://doi.org/10.3390/s18061797 - 2 Jun 2018

Cited by 173 | Viewed by 16380

Abstract

We summarize the recipes and describe the role of sputtering parameters in producing highly c-axis Aluminum Nitride (AlN) films for piezoelectric applications. The information is collated from the analysis of around 80 journal articles that sputtered this film on variety of substrate materials, [...] Read more.

We summarize the recipes and describe the role of sputtering parameters in producing highly c-axis Aluminum Nitride (AlN) films for piezoelectric applications. The information is collated from the analysis of around 80 journal articles that sputtered this film on variety of substrate materials, processes and equipment. This review will be a good starting point to catch up with the state-of-the-arts research on the reactive sputtering of AlN (002) thin film, as well as its evolving list of piezoelectric applications such as energy harvesters. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 2316 KiB

Open AccessReview

An Overview of High-k Oxides on Hydrogenated-Diamond for Metal-Oxide-Semiconductor Capacitors and Field-Effect Transistors

by Jiangwei Liu^1,*

and Yasuo Koide²

¹ Research Center for Functional Materials, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Ibaraki, Japan

² Research Network and Facility Services Division, National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba 305-0047, Ibaraki, Japan

Sensors 2018, 18(6), 1813; https://doi.org/10.3390/s18061813 - 4 Jun 2018

Cited by 19 | Viewed by 6251

Abstract

Thanks to its excellent intrinsic properties, diamond is promising for applications of high-power electronic devices, ultraviolet detectors, biosensors, high-temperature tolerant gas sensors, etc. Here, an overview of high-k oxides on hydrogenated-diamond (H-diamond) for metal-oxide-semiconductor (MOS) capacitors and MOS field-effect transistors (MOSFETs) is [...] Read more.

Thanks to its excellent intrinsic properties, diamond is promising for applications of high-power electronic devices, ultraviolet detectors, biosensors, high-temperature tolerant gas sensors, etc. Here, an overview of high-k oxides on hydrogenated-diamond (H-diamond) for metal-oxide-semiconductor (MOS) capacitors and MOS field-effect transistors (MOSFETs) is demonstrated. Fabrication routines for the H-diamond MOS capacitors and MOSFETs, band configurations of oxide/H-diamond heterointerfaces, and electrical properties of the MOS and MOSFETs are summarized and discussed. High-k oxide insulators are deposited using atomic layer deposition (ALD) and sputtering deposition (SD) techniques. Electrical properties of the H-diamond MOS capacitors with high-k oxides of ALD-Al₂O₃, ALD-HfO₂, ALD-HfO₂/ALD-Al₂O₃ multilayer, SD-HfO₂/ALD-HfO₂ bilayer, SD-TiO₂/ALD-Al₂O₃ bilayer, and ALD-TiO₂/ALD-Al₂O₃ bilayer are discussed. Analyses for capacitance-voltage characteristics of them show that there are low fixed and trapped charge densities for the ALD-Al₂O₃/H-diamond and SD-HfO₂/ALD-HfO₂/H-diamond MOS capacitors. The k value of 27.2 for the ALD-TiO₂/ALD-Al₂O₃ bilayer is larger than those of the other oxide insulators. Drain-source current versus voltage curves show distinct pitch-off and p-type channel characteristics for the ALD-Al₂O₃/H-diamond, SD-HfO₂/ALD-HfO₂/H-diamond, and ALD-TiO₂/ALD-Al₂O₃/H-diamond MOSFETs. Understanding of fabrication routines and electrical properties for the high-k oxide/H-diamond MOS electronic devices is meaningful for the fabrication of high-performance H-diamond MOS capacitor and MOSFET gas sensors. Full article

(This article belongs to the Special Issue Novel Sensors Based on Metal Oxide Films and Structures)

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26 pages, 897 KiB

Open AccessReview

Advances in Photopletysmography Signal Analysis for Biomedical Applications

by Jermana L. Moraes¹

, Matheus X. Rocha¹, Glauber G. Vasconcelos², José E. Vasconcelos Filho³, Victor Hugo C. De Albuquerque^3,*

and Auzuir R. Alexandria¹

¹ Programa de Pós-Graduação em Engenharia de Telecomunicações, Instituto Federal de Educação, Ciência e Tecnologia do Ceará, Fortaleza 60040-531, Ceará, Brazil

² Hospital de Messejana–Dr. Carlos Alberto Studart–Avenida Frei Cirilo, 3480–Messejana, Fortaleza 60846-190, Ceará, Brazil

³ Programa de Pós-Graduação em Informática Aplicada, Laboratório de Bioinformática, Universidade de Fortaleza, Fortaleza 60811-905, Ceará, Brazil

Sensors 2018, 18(6), 1894; https://doi.org/10.3390/s18061894 - 9 Jun 2018

Cited by 234 | Viewed by 15950

Abstract

Heart Rate Variability (HRV) is an important tool for the analysis of a patient’s physiological conditions, as well a method aiding the diagnosis of cardiopathies. Photoplethysmography (PPG) is an optical technique applied in the monitoring of the HRV and its adoption has been [...] Read more.

Heart Rate Variability (HRV) is an important tool for the analysis of a patient’s physiological conditions, as well a method aiding the diagnosis of cardiopathies. Photoplethysmography (PPG) is an optical technique applied in the monitoring of the HRV and its adoption has been growing significantly, compared to the most commonly used method in medicine, Electrocardiography (ECG). In this survey, definitions of these technique are presented, the different types of sensors used are explained, and the methods for the study and analysis of the PPG signal (linear and nonlinear methods) are described. Moreover, the progress, and the clinical and practical applicability of the PPG technique in the diagnosis of cardiovascular diseases are evaluated. In addition, the latest technologies utilized in the development of new tools for medical diagnosis are presented, such as Internet of Things, Internet of Health Things, genetic algorithms, artificial intelligence and biosensors which result in personalized advances in e-health and health care. After the study of these technologies, it can be noted that PPG associated with them is an important tool for the diagnosis of some diseases, due to its simplicity, its cost–benefit ratio, the easiness of signals acquisition, and especially because it is a non-invasive technique. Full article

(This article belongs to the Special Issue Sensor-based E-Healthcare System: Greenness and Security)

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16 pages, 1504 KiB

Open AccessReview

Recent Developments in Enzyme, DNA and Immuno-Based Biosensors

by Melis Asal¹

, Özlem Özen²

, Mert Şahinler³

and İlker Polatoğlu^4,*

¹ Department of Molecular Biology and Genetics, İzmir International Biomedicine and Genome Institute, Dokuz Eylül University, Balçova, 35340 İzmir, Turkey

² Department of Pharmacology, Ege University, Institute of Health Sciences, Bornova, 35040 İzmir, Turkey

³ Department of Bioengineering, Graduate School of Natural and Applied Sciences, Ege University, Bornova, 35040 İzmir, Turkey

⁴ Bioengineering Department, Manisa Celal Bayar University, Yunusemre, 45140 Manisa, Turkey

Sensors 2018, 18(6), 1924; https://doi.org/10.3390/s18061924 - 13 Jun 2018

Cited by 116 | Viewed by 10033

Abstract

Novel sensitive, rapid and economical biosensors are being developed in a wide range of medical environmental and food applications. In this paper, we review some of the main advances in the field over the past few years by discussing recent studies from literature. [...] Read more.

Novel sensitive, rapid and economical biosensors are being developed in a wide range of medical environmental and food applications. In this paper, we review some of the main advances in the field over the past few years by discussing recent studies from literature. A biosensor, which is defined as an analytical device consisting of a biomolecule, a transducer and an output system, can be categorized according to the type of the incorporated biomolecule. The biomolecules can be enzymes, antibodies, ssDNA, organelles, cells etc. The main biosensor categories classified according to the biomolecules are enzymatic biosensors, immunosensors and DNA-based biosensors. These sensors can measure analytes produced or reduced during reactions at lower costs compared to the conventional detection techniques. Numerous types of biosensor studies conducted over the last decade have been explored here to reveal their key applications in medical, environmental and food industries which provide comprehensive perspective to the readers. Overviews of the working principles and applications of the reviewed sensors are also summarized. Full article

(This article belongs to the Special Issue Sensors and NanoSensors for Biomedical, Environmental and Food Monitoring Applications)

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14 pages, 604 KiB

Open AccessComment

Comments to: A Novel Low-Cost Instrumentation System for Measuring the Water Content and Apparent Electrical Conductivity of Soils, Sensors, 15, 25546–25563

by Xavier Chavanne^1,*

, Alain Bruère² and Jean-Pierre Frangi¹

¹ Institut de Physique du Globe de Paris, University Paris Diderot, Sorbonne Paris Cité, UMR 7154 CNRS, Case Courrier 7011, F75205 Paris CEDEX 13, France

² CAPAAB, 4 Mail des Houssières, 92290 Chatenay Malabry, France

Sensors 2018, 18(6), 1730; https://doi.org/10.3390/s18061730 - 28 May 2018

Cited by 7 | Viewed by 3403

Abstract

The article comments on claims made by Rêgo et al. about the sensor they developed to determine soil water content and its salinity via the admittance measurement of electrodes embedded in the soil. Their sensor is not based on a self-balanced bridge, as [...] Read more.

The article comments on claims made by Rêgo et al. about the sensor they developed to determine soil water content and its salinity via the admittance measurement of electrodes embedded in the soil. Their sensor is not based on a self-balanced bridge, as stated, but on a more common technique relying on Ohm’s law. A bridge is a zero method of measurement which can provide direct voltages proportional to soil permittivity and conductivity with a high resolution. Thanks to modern electronics the method can be adapted for fast and continuous monitoring in a remote site. Because of this confusion about the different measurement techniques among available admittance or capacitance sensors, we give a succinct review of them and indicate how they compare to the two techniques under discussion. We also question the ability of Rêgo et al.’s current sensor to determine both soil water content and salinity due first to instrument biases and then to the soil complexity as a dielectric medium. In particular, the choice of sensor frequencies is crucial in the two steps. In addition, the procedure to determine and account for temperature influences on readings is not presented clearly enough. It is important to distinguish between the effect resulting from electronics sensitivity, and those that are soil-specific. The comment does not invalidate the design of the sensor, but indicates points, especially parasitic contributions, which must be dealt with to avoid major errors. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 1176 KiB

Open AccessReply

Reply to Comments: A Novel Low-Cost Instrumentation System for Measuring the Water Content and Apparent Electrical Conductivity of Soils, Sensors, 15, 25546–25563

by Alan Kardek Rêgo Segundo^1,*

, Marco Jose Da Silva^2,†, Gustavo Medeiros Freitas^3,†, Paulo Marcos De Barros Monteiro^1,† and José Helvecio Martins^4,†

¹ Department of Control and Automation Engineering (DECAT), Escola de Minas, Universidade Federal de Ouro Preto (UFOP), Morro do Cruzeiro, 35400-000 Ouro Preto, MG, Brazil

² Department of Electrical Engineering (CPGEI), Universidade Tecnológica Federal do Paraná (UTFPR), Av. Sete de Setembro, 3165, 80230-901 Curitiba, PR, Brazil

³ Instituto Tecnológico Vale (ITV), Avenida Juscelino Kubitschek, 31, Bauxita, 35400-000 Ouro Preto, MG, Brazil

⁴ Instituto de Educação Tecnológica (IETEC), 30140-138 Belo Horizonte, MG, Brazil

^† These authors contributed equally to this work.

Sensors 2018, 18(6), 1742; https://doi.org/10.3390/s18061742 - 28 May 2018

Cited by 3 | Viewed by 3086

Abstract

In this article we respond to the comments made by Chavanne et al., who have questioned: (i) the name of the technique used; (ii) the ability of the system to determine both soil water content and salinity due to potential instrument biases and [...] Read more.

In this article we respond to the comments made by Chavanne et al., who have questioned: (i) the name of the technique used; (ii) the ability of the system to determine both soil water content and salinity due to potential instrument biases and choice of sensor frequencies; and (iii) the procedure used to determine temperature effect on readings presented in the article “A Novel Low-Cost Instrumentation System for Measuring the Water Content and Apparent Electrical Conductivity of Soils” (Sensors 2015, 15, 25546–25563). We have carefully analyzed the arguments in the comment, and have concluded that they only partially affect the previous conclusions, as will be discussed in this reply. We show here that the findings and conclusions previously drawn are valid and supported by the many experiments previously conducted. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 3390 KiB

Open AccessProject Report

Modular AUV System with Integrated Real-Time Water Quality Analysis

by Mike Eichhorn^1,*

, Christoph Ament^1,†, Marco Jacobi^2,‡, Torsten Pfuetzenreuter², Divas Karimanzira², Kornelia Bley^3,§, Michael Boer³ and Henning Wehde⁴

¹ Institute for Automation and Systems Engineering, Technische Universität Ilmenau, Helmholtzplatz 5, 98693 Ilmenau, Germany

² Fraunhofer IOSB-AST, Am Vogelherd 50, 98693 Ilmenau, Germany

³ -4H- JENA Engineering GmbH, Mühlenstraße 126, 07745 Jena, Germany

⁴ Institute of Marine Research, Nordnesgaten 50, 5005 Bergen, Norway

^† The author was with the Institute for Automation and Systems Engineering for the main part of this work. He is now with University of Augsburg, Faculty of Applied Computer Science.

^‡ The author was with the Fraunhofer IOSB-AST. He is now with ATLAS Maridan ApS.

^§ The author was with the -4H- JENA engineering GmbH. She is now retired.

Sensors 2018, 18(6), 1837; https://doi.org/10.3390/s18061837 - 5 Jun 2018

Cited by 58 | Viewed by 10064

Abstract

This paper describes the concept, the technical implementation and the practical application of a miniaturized sensor system integrated into an autonomous underwater vehicle (AUV) for real-time acquisition of water quality parameters. The main application field of the presented system is the analysis of [...] Read more.

This paper describes the concept, the technical implementation and the practical application of a miniaturized sensor system integrated into an autonomous underwater vehicle (AUV) for real-time acquisition of water quality parameters. The main application field of the presented system is the analysis of the discharge of nitrates into Norwegian fjords near aqua farms. The presented system was developed within the research project SALMON (Sea Water Quality Monitoring and Management) over a three-year period. The development of the sensor system for water quality parameters represented a significant challenge for the research group, as it was to be integrated in the payload unit of the autonomous underwater vehicle in compliance with the underwater environmental conditions. The German company -4H- JENA engineering GmbH (4HJE), with experience in optical in situ-detection of nutrients, designed and built the measurement system. As a carrier platform, the remotely operated vehicle (ROV) “CWolf” from Fraunhofer-Institut für Optronik, Systemtechnik und Bildauswertung - Institutsteil Angewandte Systemtechnik (IOSB-AST) modified to an AUV was deployed. The concept presented illustrates how the measurement system can be integrated easily into the vehicle with a minimum of hard- and software technical interfaces. Full article

(This article belongs to the Special Issue Underwater Sensing, Communication, Networking and Systems)

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21 pages, 741 KiB

Open AccessTechnical Note

Measurement Uncertainty Calculations for pH Value Obtained by an Ion-Selective Electrode

by Józef Wiora^*

and Alicja Wiora

Institute of Automatic Control, Silesian University of Technology, ul. Akademicka 16, 44-100 Gliwice, Poland

Sensors 2018, 18(6), 1915; https://doi.org/10.3390/s18061915 - 12 Jun 2018

Cited by 9 | Viewed by 7216

Abstract

An assessment of measurement uncertainty is a task, which has to be the final step of every chemical assay. Apart from a commonly applied typical assessment method, Monte Carlo (MC) simulations may be used. The simulations are frequently performed by a computer program, [...] Read more.

An assessment of measurement uncertainty is a task, which has to be the final step of every chemical assay. Apart from a commonly applied typical assessment method, Monte Carlo (MC) simulations may be used. The simulations are frequently performed by a computer program, which has to be written, and therefore some programming skills are required. It is also possible to use a commonly known spreadsheet and perform such simulations without writing any code. Commercial programs dedicated for the purpose are also available. In order to show the advantages and disadvantages of the ways of uncertainty evaluation, i.e., the typical method, the MC method implemented in a program and in a spreadsheet, and commercial programs, a case of pH measurement after two-point calibration is considered in this article. The ways differ in the required mathematical transformations, degrees of software usage, the time spent for the uncertainty calculations, and cost of software. Since analysts may have different mathematical and coding skills and practice, it is impossible to point out the best way of uncertainty assessment—all of them are just as good and give comparable assessments. Full article

(This article belongs to the Special Issue Potentiometric Chemical Sensors)

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