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11 pages, 6328 KiB

Open AccessArticle

Development of PZT Actuated Valveless Micropump

by Fathima Rehana Munas^1,*, Gehan Melroy¹, Chamitha Bhagya Abeynayake¹, Hiniduma Liyanage Chathuranga¹, Ranjith Amarasinghe¹, Pubudu Kumarage¹, Van Thanh Dau²

and Dzung Viet Dao³

¹ Faculty of Engineering, University of Moratuwa, Moratuwa 10400, Sri Lanka

² Research Group (Environmental Health), Sumitomo Chemical, Hyogo 665-8555, Japan

³ Queensland Micro- and Nanotechnology Centre, Griffith University, Gold Coast, Queensland 4215, Australia

Sensors 2018, 18(5), 1302; https://doi.org/10.3390/s18051302 - 24 Apr 2018

Cited by 67 | Viewed by 7428

Abstract

A piezoelectrically actuated valveless micropump has been designed and developed. The principle components of this system are piezoelectrically actuated (PZT) metal diaphragms and a complete fluid flow system. The design of this pump mainly focuses on a cross junction, which is generated by [...] Read more.

A piezoelectrically actuated valveless micropump has been designed and developed. The principle components of this system are piezoelectrically actuated (PZT) metal diaphragms and a complete fluid flow system. The design of this pump mainly focuses on a cross junction, which is generated by a nozzle jet attached to a pump chamber and the intersection of two inlet channels and an outlet channel respectively. During each PZT diaphragm vibration cycle, the junction connecting the inlet and outlet channels with the nozzle jet permits consistencies in fluidic momentum and resistances in order to facilitate complete fluidic path throughout the system, in the absence of any physical valves. The entire micropump structure is fabricated as a plate-by-plate element of polymethyl methacrylate (PMMA) sheets and sandwiched to get required fluidic network as well as the overall device. In order to identify the flow characteristics, and to validate the test results with numerical simulation data, FEM analysis using ANSYS was carried out and an eigenfrequency analysis was performed to the PZT diaphragm using COMSOL Multiphysics. In addition, the control system of the pump was designed and developed to change the applied frequency to the piezoelectric diaphragms. The experimental data revealed that the maximum flow rate is 31.15 mL/min at a frequency of 100 Hz. Our proposed design is not only for a specific application but also useful in a wide range of biomedical applications. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 2556 KiB

Open AccessArticle

An Improved Fast Self-Calibration Method for Hybrid Inertial Navigation System under Stationary Condition

by Bingqi Liu^1,2, Shihui Wei², Guohua Su², Jiping Wang² and Jiazhen Lu^2,*

¹ High-Tech Institute of Xi’an, Xi’an 710025, China

² The Science and Technology on Inertial Laboratory, School of Instrumentation Science and Opto-electronics Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, China

Sensors 2018, 18(5), 1303; https://doi.org/10.3390/s18051303 - 24 Apr 2018

Cited by 26 | Viewed by 5514

Abstract

The navigation accuracy of the inertial navigation system (INS) can be greatly improved when the inertial measurement unit (IMU) is effectively calibrated and compensated, such as gyro drifts and accelerometer biases. To reduce the requirement for turntable precision in the classical calibration method, [...] Read more.

The navigation accuracy of the inertial navigation system (INS) can be greatly improved when the inertial measurement unit (IMU) is effectively calibrated and compensated, such as gyro drifts and accelerometer biases. To reduce the requirement for turntable precision in the classical calibration method, a continuous dynamic self-calibration method based on a three-axis rotating frame for the hybrid inertial navigation system is presented. First, by selecting a suitable IMU frame, the error models of accelerometers and gyros are established. Then, by taking the navigation errors during rolling as the observations, the overall twenty-one error parameters of hybrid inertial navigation system (HINS) are identified based on the calculation of the intermediate parameter. The actual experiment verifies that the method can identify all error parameters of HINS and this method has equivalent accuracy to the classical calibration on a high-precision turntable. In addition, this method is rapid, simple and feasible. Full article

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

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14 pages, 7270 KiB

Open AccessArticle

Displacement and Strain Measurement up to 1000 °C Using a Hollow Coaxial Cable Fabry-Perot Resonator

by Chen Zhu

, Yizheng Chen, Yiyang Zhuang and Jie Huang^*

Department of Electrical and Computer Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA

Sensors 2018, 18(5), 1304; https://doi.org/10.3390/s18051304 - 24 Apr 2018

Cited by 32 | Viewed by 5396

Abstract

We present a hollow coaxial cable Fabry-Perot resonator for displacement and strain measurement up to 1000 °C. By employing a novel homemade hollow coaxial cable made of stainless steel as a sensing platform, the high-temperature tolerance of the sensor is dramatically improved. A [...] Read more.

We present a hollow coaxial cable Fabry-Perot resonator for displacement and strain measurement up to 1000 °C. By employing a novel homemade hollow coaxial cable made of stainless steel as a sensing platform, the high-temperature tolerance of the sensor is dramatically improved. A Fabry-Perot resonator is implemented on this hollow coaxial cable by introducing two highly-reflective reflectors along the cable. Based on a nested structure design, the external displacement and strain can be directly correlated to the cavity length of the resonator. By tracking the shift of the amplitude reflection spectrum of the microwave resonator, the applied displacement and strain can be determined. The displacement measurement experiment showed that the sensor could function properly up to 1000 °C. The sensor was also employed to measure the thermal strain of a steel plate during the heating process. The stability of the novel sensor was also investigated. The developed sensing platform and sensing configurations are robust, cost-effective, easy to manufacture, and can be flexibly designed for many other measurement applications in harsh high-temperature environments. Full article

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

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18 pages, 53209 KiB

Open AccessArticle

Spoofing Detection Using GNSS/INS/Odometer Coupling for Vehicular Navigation

by Ali Broumandan^* and Gérard Lachapelle

Position, Location and Navigation (PLAN) Group, Schulich School of Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada

Sensors 2018, 18(5), 1305; https://doi.org/10.3390/s18051305 - 24 Apr 2018

Cited by 73 | Viewed by 8060

Abstract

Location information is one of the most vital information required to achieve intelligent and context-aware capability for various applications such as driverless cars. However, related security and privacy threats are a major holdback. With increasing focus on using Global Navigation Satellite Systems (GNSS) [...] Read more.

Location information is one of the most vital information required to achieve intelligent and context-aware capability for various applications such as driverless cars. However, related security and privacy threats are a major holdback. With increasing focus on using Global Navigation Satellite Systems (GNSS) for autonomous navigation and related applications, it is important to provide robust navigation solutions, yet signal spoofing for illegal or covert transportation and misleading receiver timing is increasing and now frequent. Hence, detection and mitigation of spoofing attacks has become an important topic. Several contributions on spoofing detection have been made, focusing on different layers of a GNSS receiver. This paper focuses on spoofing detection utilizing self-contained sensors, namely inertial measurement units (IMUs) and vehicle odometer outputs. A spoofing detection approach based on a consistency check between GNSS and IMU/odometer mechanization is proposed. To detect a spoofing attack, the method analyses GNSS and IMU/odometer measurements independently during a pre-selected observation window and cross checks the solutions provided by GNSS and inertial navigation solution (INS)/odometer mechanization. The performance of the proposed method is verified in real vehicular environments. Mean spoofing detection time and detection performance in terms of receiver operation characteristics (ROC) in sub-urban and dense urban environments are evaluated. Full article

(This article belongs to the Special Issue GNSS and Fusion with Other Sensors)

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16 pages, 841 KiB

Open AccessArticle

Learning Perfectly Secure Cryptography to Protect Communications with Adversarial Neural Cryptography

by Murilo Coutinho^1,†

, Robson De Oliveira Albuquerque^1,†

, Fábio Borges^2,†

, Luis Javier García Villalba^3,*,†

and Tai-Hoon Kim^4,†

¹ Cybersecurity INCT Unit 6, Decision Technologies Laboratory—LATITUDE, Electrical Engineering Department (ENE), Technology College, University of Brasília (UnB), 70.910-900 Brasília-DF, Brazil

² National Laboratory for Scientific Computing; 25.651-075 Petrópolis-RJ, Brazil

³ Group of Analysis, Security and Systems (GASS), Department of Software Engineering and Artificial Intelligence (DISIA), Faculty of Computer Science and Engineering, Office 431, Universidad Complutense de Madrid (UCM), Calle Profesor José García Santesmases, 9, Ciudad Universitaria, 28040 Madrid, Spain

⁴ Department of Convergence Security, Sungshin Women’s University, 249-1 Dongseon-Dong 3-ga, Seoul 136-742, Korea

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1306; https://doi.org/10.3390/s18051306 - 24 Apr 2018

Cited by 50 | Viewed by 7851

Abstract

Researches in Artificial Intelligence (AI) have achieved many important breakthroughs, especially in recent years. In some cases, AI learns alone from scratch and performs human tasks faster and better than humans. With the recent advances in AI, it is natural to wonder whether [...] Read more.

Researches in Artificial Intelligence (AI) have achieved many important breakthroughs, especially in recent years. In some cases, AI learns alone from scratch and performs human tasks faster and better than humans. With the recent advances in AI, it is natural to wonder whether Artificial Neural Networks will be used to successfully create or break cryptographic algorithms. Bibliographic review shows the main approach to this problem have been addressed throughout complex Neural Networks, but without understanding or proving the security of the generated model. This paper presents an analysis of the security of cryptographic algorithms generated by a new technique called Adversarial Neural Cryptography (ANC). Using the proposed network, we show limitations and directions to improve the current approach of ANC. Training the proposed Artificial Neural Network with the improved model of ANC, we show that artificially intelligent agents can learn the unbreakable One-Time Pad (OTP) algorithm, without human knowledge, to communicate securely through an insecure communication channel. This paper shows in which conditions an AI agent can learn a secure encryption scheme. However, it also shows that, without a stronger adversary, it is more likely to obtain an insecure one. Full article

(This article belongs to the Special Issue Advances on Resources Management for Multi-Platform Infrastructures)

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14 pages, 2264 KiB

Open AccessArticle

Residual Error Based Anomaly Detection Using Auto-Encoder in SMD Machine Sound

by Dong Yul Oh¹ and Il Dong Yun^2,*

¹ Department of Digital Information Engineering, Hankuk University of Foreign Studies, Yongin 17035, Korea

² Division of Computer & Electronic System Engineering, Hankuk University of Foreign Studies, Yongin 17035, Korea

Sensors 2018, 18(5), 1308; https://doi.org/10.3390/s18051308 - 24 Apr 2018

Cited by 109 | Viewed by 12716

Abstract

Detecting an anomaly or an abnormal situation from given noise is highly useful in an environment where constantly verifying and monitoring a machine is required. As deep learning algorithms are further developed, current studies have focused on this problem. However, there are too [...] Read more.

Detecting an anomaly or an abnormal situation from given noise is highly useful in an environment where constantly verifying and monitoring a machine is required. As deep learning algorithms are further developed, current studies have focused on this problem. However, there are too many variables to define anomalies, and the human annotation for a large collection of abnormal data labeled at the class-level is very labor-intensive. In this paper, we propose to detect abnormal operation sounds or outliers in a very complex machine along with reducing the data-driven annotation cost. The architecture of the proposed model is based on an auto-encoder, and it uses the residual error, which stands for its reconstruction quality, to identify the anomaly. We assess our model using Surface-Mounted Device (SMD) machine sound, which is very complex, as experimental data, and state-of-the-art performance is successfully achieved for anomaly detection. Full article

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

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18 pages, 2942 KiB

Open AccessArticle

Towards an Electrochemical Immunosensor System with Temperature Control for Cytokine Detection

by Julia Metzner^1,2,*, Katrin Luckert¹, Karin Lemuth¹, Martin Hämmerle² and Ralf Moos²

¹ Robert Bosch GmbH, Corporate Research, Robert-Bosch-Campus 1, D-71272 Renningen, Germany

² Department of Functional Materials, University of Bayreuth, Universitätsstraße 30, D-95440 Bayreuth, Germany

Sensors 2018, 18(5), 1309; https://doi.org/10.3390/s18051309 - 24 Apr 2018

Cited by 7 | Viewed by 5126

Abstract

The cytokine interleukin-13 (IL-13) plays a major role in airway inflammation and is a target of new anti-asthmatic drugs. Hence, IL-13 determination could be interesting in assessing therapy success. Thus, in this work an electrochemical immunosensor for IL-13 was developed and integrated into [...] Read more.

The cytokine interleukin-13 (IL-13) plays a major role in airway inflammation and is a target of new anti-asthmatic drugs. Hence, IL-13 determination could be interesting in assessing therapy success. Thus, in this work an electrochemical immunosensor for IL-13 was developed and integrated into a fluidic system with temperature control for read-out. Therefore, two sets of results are presented. First, the sensor was set up in sandwich format on single-walled carbon nanotube electrodes and was read out by applying the hydrogen peroxide–hydroquinone–horseradish peroxidase (HRP) system. Second, a fluidic system was built up with an integrated heating function realized by Peltier elements that allowed a temperature-controlled read-out of the immunosensor in order to study the influence of temperature on the amperometric read-out. The sensor was characterized at the temperature optimum of HRP at 30 °C and at 12 °C as a reference for lower performance. These results were compared to a measurement without temperature control. At the optimum operation temperature of 30 °C, the highest sensitivity (slope) was obtained compared to lower temperatures and a limit of detection of 5.4 ng/mL of IL-13 was calculated. Taken together, this approach is a first step towards an automated electrochemical immunosensor platform and shows the potential of a temperature-controlled read-out. Full article

(This article belongs to the Section Biosensors)

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11 pages, 3273 KiB

Open AccessArticle

Stand-Off Detection of Alcohol Vapors Exhaled by Humans

by Jaroslaw Mlynczak^*

, Jan Kubicki and Krzysztof Kopczynski

Institute of Optoelectronics, Military University of Technology, Gen. Witolda Urbanowicza 2, 00-908 Warsaw, Poland

Sensors 2018, 18(5), 1310; https://doi.org/10.3390/s18051310 - 24 Apr 2018

Cited by 5 | Viewed by 3399

Abstract

Early detection of humans under the influence of alcohol in public places (workplace, public gathering) is particularly important for safety reasons. In this article, the theoretical analysis of stand-off detection of alcohol in the air exhaled by humans as well as experimental results [...] Read more.

Early detection of humans under the influence of alcohol in public places (workplace, public gathering) is particularly important for safety reasons. In this article, the theoretical analysis of stand-off detection of alcohol in the air exhaled by humans as well as experimental results of the developed experimental setup is presented. The concept of differential absorption of two laser beams at different wavelengths was used. The idea of using standard deviation of the relative difference of the amplitudes of two signals to detect the alcohol was applied for the first time. The idea was verified by the experiments and it was shown that a reliable device can be developed that can efficiently detect alcohol concentration in the exhaled air at the level of 0.3 mg/L (0.63‰). Moreover, the concept of such device examining humans entering a specific area was proposed. The results of this article may be useful to scientists or engineers working on alcohol detection in human blood. Full article

(This article belongs to the Section Chemical Sensors)

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23 pages, 6781 KiB

Open AccessArticle

Body Weight Estimation for Dose-Finding and Health Monitoring of Lying, Standing and Walking Patients Based on RGB-D Data

by Christian Pfitzner^1,2,*

, Stefan May¹ and Andreas Nüchter^2,*

¹ Department of Electrical Engineering, Precision Engineering, Information Technology at the Techniche Hochschule Nürnberg Georg Simon Ohm; Keßlerplatz 12, 90489 Nuremberg, Germany

² Department of Informatics VII: Robotics and Telematics at the Julius-Maximilians University Würzburg, Am Hubland, 97074 Wuerzburg, Germany

Sensors 2018, 18(5), 1311; https://doi.org/10.3390/s18051311 - 24 Apr 2018

Cited by 23 | Viewed by 7560

Abstract

This paper describes the estimation of the body weight of a person in front of an RGB-D camera. A survey of different methods for body weight estimation based on depth sensors is given. First, an estimation of people standing in front of a [...] Read more.

This paper describes the estimation of the body weight of a person in front of an RGB-D camera. A survey of different methods for body weight estimation based on depth sensors is given. First, an estimation of people standing in front of a camera is presented. Second, an approach based on a stream of depth images is used to obtain the body weight of a person walking towards a sensor. The algorithm first extracts features from a point cloud and forwards them to an artificial neural network (ANN) to obtain an estimation of body weight. Besides the algorithm for the estimation, this paper further presents an open-access dataset based on measurements from a trauma room in a hospital as well as data from visitors of a public event. In total, the dataset contains 439 measurements. The article illustrates the efficiency of the approach with experiments with persons lying down in a hospital, standing persons, and walking persons. Applicable scenarios for the presented algorithm are body weight-related dosing of emergency patients. Full article

(This article belongs to the Special Issue Optical Methods in Sensing and Imaging for Medical and Biological Applications)

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24 pages, 2954 KiB

Open AccessArticle

Infrastructure for Integration of Legacy Electrical Equipment into a Smart-Grid Using Wireless Sensor Networks

by Paulo Régis C. De Araújo¹, Raimir Holanda Filho², Joel J. P. C. Rodrigues^3,4,5,*

, João P. C. M. Oliveira¹ and Stephanie A. Braga¹

¹ Federal Institute of Ceará (IFCE), 60040-215 Fortaleza, Brazil

² PPGIA, University of Fortaleza (UNIFOR), 60811-905 Fortaleza, Brazil

³ National Institute of Telecommunications (INATEL), 37540-000 Santa Rita do Sapucaí, Brazil

⁴ Instituto de Telecomunicações, 1049-001 Lisbon, Portugal

⁵ ITMO University, 197101 Saint Petersburg, Russia

Sensors 2018, 18(5), 1312; https://doi.org/10.3390/s18051312 - 24 Apr 2018

Cited by 28 | Viewed by 7255

Abstract

At present, the standardisation of electrical equipment communications is on the rise. In particular, manufacturers are releasing equipment for the smart grid endowed with communication protocols such as DNP3, IEC 61850, and MODBUS. However, there are legacy equipment operating in the electricity distribution [...] Read more.

At present, the standardisation of electrical equipment communications is on the rise. In particular, manufacturers are releasing equipment for the smart grid endowed with communication protocols such as DNP3, IEC 61850, and MODBUS. However, there are legacy equipment operating in the electricity distribution network that cannot communicate using any of these protocols. Thus, we propose an infrastructure to allow the integration of legacy electrical equipment to smart grids by using wireless sensor networks (WSNs). In this infrastructure, each legacy electrical device is connected to a sensor node, and the sink node runs a middleware that enables the integration of this device into a smart grid based on suitable communication protocols. This middleware performs tasks such as the translation of messages between the power substation control centre (PSCC) and electrical equipment in the smart grid. Moreover, the infrastructure satisfies certain requirements for communication between the electrical equipment and the PSCC, such as enhanced security, short response time, and automatic configuration. The paper’s contributions include a solution that enables electrical companies to integrate their legacy equipment into smart-grid networks relying on any of the above mentioned communication protocols. This integration will reduce the costs related to the modernisation of power substations. Full article

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

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19 pages, 4763 KiB

Open AccessArticle

Design and Performance of a 1 ms High-Speed Vision Chip with 3D-Stacked 140 GOPS Column-Parallel PEs ^†

by Atsushi Nose^1,*, Tomohiro Yamazaki¹, Hironobu Katayama¹, Shuji Uehara¹, Masatsugu Kobayashi¹, Sayaka Shida¹, Masaki Odahara², Kenichi Takamiya², Shizunori Matsumoto², Leo Miyashita³, Yoshihiro Watanabe³, Takashi Izawa¹, Yoshinori Muramatsu¹, Yoshikazu Nitta¹ and Masatoshi Ishikawa³

¹ Sony Semiconductor Solutions, Japan, 4-14-1 Asahi-cho, Atsugi-shi, Kanagawa 243-0014, Japan

² Sony LSI Design, Japan, 4-16-1 Okada, Atsugi-shi, Kanagawa 243-0021, Japan

³ Graduate School of Information Science and Technology, The University of Tokyo, 7 Chome-3-1 Hongo, Bunkyō, Tokyo 113-8654, Japan

Sensors 2018, 18(5), 1313; https://doi.org/10.3390/s18051313 - 24 Apr 2018

Cited by 18 | Viewed by 7333

Abstract

We have developed a high-speed vision chip using 3D stacking technology to address the increasing demand for high-speed vision chips in diverse applications. The chip comprises a 1/3.2-inch, 1.27 Mpixel, 500 fps (0.31 Mpixel, 1000 fps, 2 × 2 binning) vision chip with [...] Read more.

We have developed a high-speed vision chip using 3D stacking technology to address the increasing demand for high-speed vision chips in diverse applications. The chip comprises a 1/3.2-inch, 1.27 Mpixel, 500 fps (0.31 Mpixel, 1000 fps, 2 × 2 binning) vision chip with 3D-stacked column-parallel Analog-to-Digital Converters (ADCs) and 140 Giga Operation per Second (GOPS) programmable Single Instruction Multiple Data (SIMD) column-parallel PEs for new sensing applications. The 3D-stacked structure and column parallel processing architecture achieve high sensitivity, high resolution, and high-accuracy object positioning. Full article

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

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11 pages, 5242 KiB

Open AccessArticle

High Sensitive pH Sensor Based on AlInN/GaN Heterostructure Transistor

by Yan Dong^1,2

, Dong-Hyeok Son², Quan Dai², Jun-Hyeok Lee², Chul-Ho Won², Jeong-Gil Kim², Dunjun Chen^1,*, Jung-Hee Lee^2,*, Hai Lu¹, Rong Zhang¹ and Youdou Zheng¹

¹ School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China

² School of Electronics Engineering, Kyungpook National University, Daegu 702-701, Korea

Sensors 2018, 18(5), 1314; https://doi.org/10.3390/s18051314 - 24 Apr 2018

Cited by 16 | Viewed by 6270

Abstract

The AlInN/GaN high-electron-mobility-transistor (HEMT) indicates better performances compared with the traditional AlGaN/GaN HEMTs. The present work investigated the pH sensor functionality of an analogous HEMT AlInN/GaN device with an open gate. It was shown that the Al_0.83In_0.17N/GaN device demonstrates [...] Read more.

The AlInN/GaN high-electron-mobility-transistor (HEMT) indicates better performances compared with the traditional AlGaN/GaN HEMTs. The present work investigated the pH sensor functionality of an analogous HEMT AlInN/GaN device with an open gate. It was shown that the Al_0.83In_0.17N/GaN device demonstrates excellent pH sense functionality in aqueous solutions, exhibiting higher sensitivity (−30.83 μA/pH for AlInN/GaN and −4.6 μA/pH for AlGaN/GaN) and a faster response time, lower degradation and good stability with respect to the AlGaN/GaN device, which is attributed to higher two-dimensional electron gas (2DEG) density and a thinner barrier layer in Al_0.83In_0.17N/GaN owning to lattice matching. On the other hand, the open gate geometry was found to affect the pH sensitivity obviously. Properly increasing the width and shortening the length of the open gate area could enhance the sensitivity. However, when the open gate width is too larger or too small, the pH sensitivity would be suppressed conversely. Designing an optimal ratio of the width to the length is important for achieving high sensitivity. This work suggests that the AlInN/GaN-based 2DEG carrier modulated devices would be good candidates for high-performance pH sensors and other related applications. Full article

(This article belongs to the Special Issue Potentiometric Chemical Sensors)

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30 pages, 4998 KiB

Open AccessArticle

Presentation Attack Detection for Iris Recognition System Using NIR Camera Sensor

by Dat Tien Nguyen, Na Rae Baek, Tuyen Danh Pham 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(5), 1315; https://doi.org/10.3390/s18051315 - 24 Apr 2018

Cited by 18 | Viewed by 7617

Abstract

Among biometric recognition systems such as fingerprint, finger-vein, or face, the iris recognition system has proven to be effective for achieving a high recognition accuracy and security level. However, several recent studies have indicated that an iris recognition system can be fooled by [...] Read more.

Among biometric recognition systems such as fingerprint, finger-vein, or face, the iris recognition system has proven to be effective for achieving a high recognition accuracy and security level. However, several recent studies have indicated that an iris recognition system can be fooled by using presentation attack images that are recaptured using high-quality printed images or by contact lenses with printed iris patterns. As a result, this potential threat can reduce the security level of an iris recognition system. In this study, we propose a new presentation attack detection (PAD) method for an iris recognition system (iPAD) using a near infrared light (NIR) camera image. To detect presentation attack images, we first localized the iris region of the input iris image using circular edge detection (CED). Based on the result of iris localization, we extracted the image features using deep learning-based and handcrafted-based methods. The input iris images were then classified into real and presentation attack categories using support vector machines (SVM). Through extensive experiments with two public datasets, we show that our proposed method effectively solves the iris recognition presentation attack detection problem and produces detection accuracy superior to previous studies. Full article

(This article belongs to the Special Issue Visual Sensors)

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15 pages, 1805 KiB

Open AccessArticle

Deep Kalman Filter: Simultaneous Multi-Sensor Integration and Modelling; A GNSS/IMU Case Study

by Siavash Hosseinyalamdary

Department of Earth Observation Science (EOS), Faculty of Geo-information Science and Earth Observation (ITC), University of Twente, Enschede 7514AE, The Netherlands

Sensors 2018, 18(5), 1316; https://doi.org/10.3390/s18051316 - 24 Apr 2018

Cited by 59 | Viewed by 13578

Abstract

Bayes filters, such as the Kalman and particle filters, have been used in sensor fusion to integrate two sources of information and obtain the best estimate of unknowns. The efficient integration of multiple sensors requires deep knowledge of their error sources. Some sensors, [...] Read more.

Bayes filters, such as the Kalman and particle filters, have been used in sensor fusion to integrate two sources of information and obtain the best estimate of unknowns. The efficient integration of multiple sensors requires deep knowledge of their error sources. Some sensors, such as Inertial Measurement Unit (IMU), have complicated error sources. Therefore, IMU error modelling and the efficient integration of IMU and Global Navigation Satellite System (GNSS) observations has remained a challenge. In this paper, we developed deep Kalman filter to model and remove IMU errors and, consequently, improve the accuracy of IMU positioning. To achieve this, we added a modelling step to the prediction and update steps of the Kalman filter, so that the IMU error model is learned during integration. The results showed our deep Kalman filter outperformed the conventional Kalman filter and reached a higher level of accuracy. Full article

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

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22 pages, 1819 KiB

Open AccessArticle

Multi-Layer Artificial Neural Networks Based MPPT-Pitch Angle Control of a Tidal Stream Generator

by Khaoula Ghefiri^1,2,*

, Soufiene Bouallègue¹, Izaskun Garrido²

, Aitor J. Garrido² and Joseph Haggège¹

¹ Laboratory of Research in Automatic Control—LA.R.A, National Engineering School of Tunis (ENIT), University of Tunis El Manar, BP 37, Le Belvédère, Tunis 1002, Tunisia

² Automatic Control Group—ACG, Department of Automatic Control and Systems Engineering, Engineering School of Bilbao, University of the Basque Country, 48012 Bilbao, Spain

Sensors 2018, 18(5), 1317; https://doi.org/10.3390/s18051317 - 24 Apr 2018

Cited by 11 | Viewed by 5647

Abstract

Artificial intelligence technologies are widely investigated as a promising technique for tackling complex and ill-defined problems. In this context, artificial neural networks methodology has been considered as an effective tool to handle renewable energy systems. Thereby, the use of Tidal Stream Generator (TSG) [...] Read more.

Artificial intelligence technologies are widely investigated as a promising technique for tackling complex and ill-defined problems. In this context, artificial neural networks methodology has been considered as an effective tool to handle renewable energy systems. Thereby, the use of Tidal Stream Generator (TSG) systems aim to provide clean and reliable electrical power. However, the power captured from tidal currents is highly disturbed due to the swell effect and the periodicity of the tidal current phenomenon. In order to improve the quality of the generated power, this paper focuses on the power smoothing control. For this purpose, a novel Artificial Neural Network (ANN) is investigated and implemented to provide the proper rotational speed reference and the blade pitch angle. The ANN supervisor adequately switches the system in variable speed and power limitation modes. In order to recover the maximum power from the tides, a rotational speed control is applied to the rotor side converter following the Maximum Power Point Tracking (MPPT) generated from the ANN block. In case of strong tidal currents, a pitch angle control is set based on the ANN approach to keep the system operating within safe limits. Two study cases were performed to test the performance of the output power. Simulation results demonstrate that the implemented control strategies achieve a smoothed generated power in the case of swell disturbances. Full article

(This article belongs to the Special Issue New Trends in Ambient Intelligence Applications)

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12 pages, 1630 KiB

Open AccessArticle

Depth Reconstruction from Single Images Using a Convolutional Neural Network and a Condition Random Field Model

by Dan Liu^1,*, Xuejun Liu^2,* and Yiguang Wu²

¹ Faculty of Geomatics, East China University of Technology, Nanchang 330013, China

² Key Laboratory of Virtual Geographic Environment, Nanjing Normal University, Nanjing 210023, China

Sensors 2018, 18(5), 1318; https://doi.org/10.3390/s18051318 - 24 Apr 2018

Cited by 8 | Viewed by 6155

Abstract

This paper presents an effective approach for depth reconstruction from a single image through the incorporation of semantic information and local details from the image. A unified framework for depth acquisition is constructed by joining a deep Convolutional Neural Network (CNN) and a [...] Read more.

This paper presents an effective approach for depth reconstruction from a single image through the incorporation of semantic information and local details from the image. A unified framework for depth acquisition is constructed by joining a deep Convolutional Neural Network (CNN) and a continuous pairwise Conditional Random Field (CRF) model. Semantic information and relative depth trends of local regions inside the image are integrated into the framework. A deep CNN network is firstly used to automatically learn a hierarchical feature representation of the image. To get more local details in the image, the relative depth trends of local regions are incorporated into the network. Combined with semantic information of the image, a continuous pairwise CRF is then established and is used as the loss function of the unified model. Experiments on real scenes demonstrate that the proposed approach is effective and that the approach obtains satisfactory results. Full article

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

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14 pages, 2881 KiB

Open AccessArticle

Label-Free Impedance Sensing of Aflatoxin B₁ with Polyaniline Nanofibers/Au Nanoparticle Electrode Array

by Ajay Kumar Yagati

, Sachin Ganpat Chavan

, Changyoon Baek, Min-Ho Lee^*

and Junhong Min^*

School of Integrative Engineering, Chung-Ang University, Heukseok-dong, Dongjak-gu, Seoul 06974, Korea

Sensors 2018, 18(5), 1320; https://doi.org/10.3390/s18051320 - 24 Apr 2018

Cited by 47 | Viewed by 6268

Abstract

Aflatoxin B₁ (AFB₁) is produced by the Aspergillus flavus and Aspergillus parasiticus group of fungi which is most hepatotoxic and hepatocarcinogenic and occurs as a contaminant in a variety of foods. AFB₁ is mutagenic, teratogenic, and causes immunosuppression in [...] Read more.

Aflatoxin B₁ (AFB₁) is produced by the Aspergillus flavus and Aspergillus parasiticus group of fungi which is most hepatotoxic and hepatocarcinogenic and occurs as a contaminant in a variety of foods. AFB₁ is mutagenic, teratogenic, and causes immunosuppression in animals and is mostly found in peanuts, corn, and food grains. Therefore, novel methodologies of sensitive and expedient strategy are often required to detect mycotoxins at the lowest level. Herein, we report an electrochemical impedance sensor that selectively detects AFB₁ at the lowest level by utilizing polyaniline nanofibers (PANI) coated with gold (Au) nanoparticles composite based indium tin oxide (ITO) disk electrodes. The Au-PANI nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, and electrochemical impedance spectroscopy (EIS). The composite electrode exhibited a 14-fold decrement in |Z|_{1 Hz} in comparison with the bare electrode. The Au-PANI acted as an effective sensing platform having high surface area, electrochemical conductivity, and biocompatibility which enabled greater loading deposits of capture antibodies. As a result, the presence of AFB₁ was screened with high sensitivity and stability by monitoring the changes in impedance magnitude (|Z|) in the presence of a standard iron probe which was target specific and proportional to logarithmic AFB₁ concentrations (C_AFB1). The sensor exhibits a linear range 0.1 to 100 ng/mL with a detection limit (3σ) of 0.05 ng/mL and possesses good reproducibility and high selectivity against another fungal mycotoxin, Ochratoxin A (OTA). With regard to the practicability, the proposed sensor was successfully applied to spiked corn samples and proved excellent potential for AFB₁ detection and development of point-of-care (POC) disease sensing applications. Full article

(This article belongs to the Section Biosensors)

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13 pages, 3296 KiB

Open AccessArticle

Prediction of Fatigue Crack Growth in Gas Turbine Engine Blades Using Acoustic Emission

by Zhiheng Zhang, Guoan Yang^* and Kun Hu

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

Sensors 2018, 18(5), 1321; https://doi.org/10.3390/s18051321 - 25 Apr 2018

Cited by 36 | Viewed by 7709

Abstract

Fatigue failure is the main type of failure that occurs in gas turbine engine blades and an online monitoring method for detecting fatigue cracks in blades is urgently needed. Therefore, in this present study, we propose the use of acoustic emission (AE) monitoring [...] Read more.

Fatigue failure is the main type of failure that occurs in gas turbine engine blades and an online monitoring method for detecting fatigue cracks in blades is urgently needed. Therefore, in this present study, we propose the use of acoustic emission (AE) monitoring for the online identification of the blade status. Experiments on fatigue crack propagation based on the AE monitoring of gas turbine engine blades and TC11 titanium alloy plates were conducted. The relationship between the cumulative AE hits and the fatigue crack length was established, before a method of using the AE parameters to determine the crack propagation stage was proposed. A method for predicting the degree of crack propagation and residual fatigue life based on the AE energy was obtained. The results provide a new method for the online monitoring of cracks in the gas turbine engine blade. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 8959 KiB

Open AccessArticle

A Novel Approach to the Identification of Compromised Pulmonary Systems in Smokers by Exploiting Tidal Breathing Patterns

by Raj Rakshit^*, Anwesha Khasnobish^*

, Arijit Chowdhury, Arijit Sinharay^*, Arpan Pal and Tapas Chakravarty

TCS Research and Innovation, Kolkata-700156, India

Sensors 2018, 18(5), 1322; https://doi.org/10.3390/s18051322 - 25 Apr 2018

Cited by 3 | Viewed by 4089

Abstract

Smoking causes unalterable physiological abnormalities in the pulmonary system. This is emerging as a serious threat worldwide. Unlike spirometry, tidal breathing does not require subjects to undergo forceful breathing maneuvers and is progressing as a new direction towards pulmonary health assessment. The aim [...] Read more.

Smoking causes unalterable physiological abnormalities in the pulmonary system. This is emerging as a serious threat worldwide. Unlike spirometry, tidal breathing does not require subjects to undergo forceful breathing maneuvers and is progressing as a new direction towards pulmonary health assessment. The aim of the paper is to evaluate whether tidal breathing signatures can indicate deteriorating adult lung condition in an otherwise healthy person. If successful, such a system can be used as a pre-screening tool for all people before some of them need to undergo a thorough clinical checkup. This work presents a novel systematic approach to identify compromised pulmonary systems in smokers from acquired tidal breathing patterns. Tidal breathing patterns are acquired during restful breathing of adult participants. Thereafter, physiological attributes are extracted from the acquired tidal breathing signals. Finally, a unique classification approach of locally weighted learning with ridge regression (LWL-ridge) is implemented, which handles the subjective variations in tidal breathing data without performing feature normalization. The LWL-ridge classifier recognized compromised pulmonary systems in smokers with an average classification accuracy of 86.17% along with a sensitivity of 80% and a specificity of 92%. The implemented approach outperformed other variants of LWL as well as other standard classifiers and generated comparable results when applied on an external cohort. This end-to-end automated system is suitable for pre-screening people routinely for early detection of lung ailments as a preventive measure in an infrastructure-agnostic way. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 5687 KiB

Open AccessArticle

Optical and Acoustic Sensor-Based 3D Ball Motion Estimation for Ball Sport Simulators †

by Sang-Woo Seo^1,*

, Myunggyu Kim¹ and Yejin Kim²

¹ Creative Content Research Division, Electronics and Telecommunications Research Institute, 218 Gajeong-ro, Yuseong-gu, Daejeon 34129, Korea

² School of Games, Hongik University, 2639 Sejong-ro, Jochiwon-eup, Sejong 30016, Korea

^† This paper is an extended version of Seo, S.-W. and Kim, M. Estimation of 3D ball motion using an infrared and acoustic vector sensor. In Proceedings of the 2017 International Conference on Information and Communication Technology Convergence (ICTC), Jeju, Korea, 18–20 October 2017.

Sensors 2018, 18(5), 1323; https://doi.org/10.3390/s18051323 - 25 Apr 2018

Cited by 6 | Viewed by 6695

Abstract

Estimation of the motion of ball-shaped objects is essential for the operation of ball sport simulators. In this paper, we propose an estimation system for 3D ball motion, including speed and angle of projection, by using acoustic vector and infrared (IR) scanning sensors. [...] Read more.

Estimation of the motion of ball-shaped objects is essential for the operation of ball sport simulators. In this paper, we propose an estimation system for 3D ball motion, including speed and angle of projection, by using acoustic vector and infrared (IR) scanning sensors. Our system is comprised of three steps to estimate a ball motion: sound-based ball firing detection, sound source localization, and IR scanning for motion analysis. First, an impulsive sound classification based on the mel-frequency cepstrum and feed-forward neural network is introduced to detect the ball launch sound. An impulsive sound source localization using a 2D microelectromechanical system (MEMS) microphones and delay-and-sum beamforming is presented to estimate the firing position. The time and position of a ball in 3D space is determined from a high-speed infrared scanning method. Our experimental results demonstrate that the estimation of ball motion based on sound allows a wider activity area than similar camera-based methods. Thus, it can be practically applied to various simulations in sports such as soccer and baseball. Full article

(This article belongs to the Special Issue Selected Papers from the Eighth International Conference on ICT Convergence (ICTC 2017))

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15 pages, 3083 KiB

Open AccessArticle

Theoretical Design of a Two-Photon Fluorescent Probe for Nitric Oxide with Enhanced Emission Induced by Photoninduced Electron Transfer

by Yujin Zhang^1,†

, Jiancai Leng^1,† and Wei Hu^2,*

¹ School of Science, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China

² Hefei National Laboratory for Physical Sciences at the Microscale, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China

^† These authors contribute equally to this work.

Sensors 2018, 18(5), 1324; https://doi.org/10.3390/s18051324 - 25 Apr 2018

Cited by 17 | Viewed by 5277

Abstract

In the present work, we systematically investigate the sensing abilities of two recently literature-reported two-photon fluorescent NO probes, i.e., the o-phenylenediamine derivative of Nile Red and the p-phenylenediamine derivative of coumarin. The recognition mechanisms of these probes are studied by using the molecular [...] Read more.

In the present work, we systematically investigate the sensing abilities of two recently literature-reported two-photon fluorescent NO probes, i.e., the o-phenylenediamine derivative of Nile Red and the p-phenylenediamine derivative of coumarin. The recognition mechanisms of these probes are studied by using the molecular orbital classifying method, which demonstrates the photoinduced electron transfer process. In addition, we have designed two new probes by swapping receptor units present on fluorophores, i.e., the p-phenylenediamine derivative of Nile Red and the o-phenylenediamine derivative of coumarin. However, it illustrates that only the latter has ability to function as off-on typed fluorescent probe for NO. More importantly, calculations on the two-photon absorption properties of the probes demonstrate that both receptor derivatives of coumarin possess larger TPA cross-sections than Nile Red derivatives, which makes a better two photon fluorescent probe. Our theoretical investigations reveal that the underlying mechanism satisfactorily explain the experimental results, providing a theoretical basis on the structure-property relationships which is beneficial to developing new two-photon fluorescent probes for NO. Full article

(This article belongs to the Special Issue Novel Sensors for Bioimaging)

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19 pages, 11014 KiB

Open AccessArticle

Multi-Frequency Signal Detection Based on Frequency Exchange and Re-Scaling Stochastic Resonance and Its Application to Weak Fault Diagnosis

by Jinjun Liu¹

, Yonggang Leng^1,*, Zhihui Lai²

and Shengbo Fan¹

¹ School of Mechanical Engineering, Tianjin University, Tianjin 300350, China

² School of Mechatronics Engineering, Nanchang University, Nanchang 330031, China

Sensors 2018, 18(5), 1325; https://doi.org/10.3390/s18051325 - 25 Apr 2018

Cited by 31 | Viewed by 4623

Abstract

Mechanical fault diagnosis usually requires not only identification of the fault characteristic frequency, but also detection of its second and/or higher harmonics. However, it is difficult to detect a multi-frequency fault signal through the existing Stochastic Resonance (SR) methods, because the characteristic frequency [...] Read more.

Mechanical fault diagnosis usually requires not only identification of the fault characteristic frequency, but also detection of its second and/or higher harmonics. However, it is difficult to detect a multi-frequency fault signal through the existing Stochastic Resonance (SR) methods, because the characteristic frequency of the fault signal as well as its second and higher harmonics frequencies tend to be large parameters. To solve the problem, this paper proposes a multi-frequency signal detection method based on Frequency Exchange and Re-scaling Stochastic Resonance (FERSR). In the method, frequency exchange is implemented using filtering technique and Single SideBand (SSB) modulation. This new method can overcome the limitation of "sampling ratio" which is the ratio of the sampling frequency to the frequency of target signal. It also ensures that the multi-frequency target signals can be processed to meet the small-parameter conditions. Simulation results demonstrate that the method shows good performance for detecting a multi-frequency signal with low sampling ratio. Two practical cases are employed to further validate the effectiveness and applicability of this method. Full article

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

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19 pages, 6875 KiB

Open AccessArticle

A Low-Ambiguity Signal Waveform for Pseudolite Positioning Systems Based on Chirp

by Qing Liu^1,*

, Zhigang Huang¹, Yanhong Kou¹ and Jinling Wang²

¹ School of Electronic and Information Engineering, Beihang University, Beijing 100083, China

² School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia

Sensors 2018, 18(5), 1326; https://doi.org/10.3390/s18051326 - 25 Apr 2018

Cited by 7 | Viewed by 4404

Abstract

Signal modulation is an essential design factor of a positioning system, which directly impacts the system’s potential performance. Chirp compressions have been widely applied in the fields of communication, radar, and indoor positioning owing to their high compression gain and good resistance to [...] Read more.

Signal modulation is an essential design factor of a positioning system, which directly impacts the system’s potential performance. Chirp compressions have been widely applied in the fields of communication, radar, and indoor positioning owing to their high compression gain and good resistance to narrowband interferences and multipath fading. Based on linear chirp, we present a modulation method named chirped pseudo-noise (ChPN). The mathematical model of the ChPN signal is provided with its auto-correlation function (ACF) and the power spectrum density (PSD) derived. The ChPN with orthogonal chirps is also discussed, which has better resistance to near-far effect. Then the generation and detection methods as well as the performances of ChPN are discussed by theoretical analysis and simulation. The results show that, for ChPN signals with the same main-lobe bandwidth (MLB), generally, the signal with a larger sweep bandwidth has better tracking precision and multipath resistance. ChPN yields slighter ACF peaks ambiguity due to its lower ACF side-peaks, although its tracking precision is a little worse than that of a binary offset carrier (BOC) with the same MLB. Moreover, ChPN provides better overall anti-multipath performance than BOC. For the ChPN signals with the same code rate, a signal with a larger sweep bandwidth has better performance in most aspects. In engineering practice, a ChPN receiver can be implemented by minor modifications of a BOC receiver. Thus, ChPN modulation shows promise for future positioning applications. Full article

(This article belongs to the Special Issue GNSS and Fusion with Other Sensors)

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16 pages, 1760 KiB

Open AccessArticle

Ultrasound Pulse-Echo Coupled with a Tracking Technique for Simultaneous Measurement of Multiple Bubbles

by Antonin Povolny^1,*

, Hiroshige Kikura¹ and Tomonori Ihara²

¹ Laboratory for Advanced Nuclear Energy, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan

² Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, Etchujima, Tokyo 135-8533, Japan

Sensors 2018, 18(5), 1327; https://doi.org/10.3390/s18051327 - 25 Apr 2018

Cited by 10 | Viewed by 5881

Abstract

Bubbly flows are commonly used in various applications and their measurement is an important research topic. The ultrasound pulse-echo technique allows for the detection of each bubble and the measurement of the position of its surface. However, so far it has been used [...] Read more.

Bubbly flows are commonly used in various applications and their measurement is an important research topic. The ultrasound pulse-echo technique allows for the detection of each bubble and the measurement of the position of its surface. However, so far it has been used only to measure single bubbles. This paper investigates whether the pulse-echo technique can be applied for measuring multiple bubbles concurrently. The ultrasonic transducer wavelength and diameter were selected based on expected bubble diameters so that each bubble produced a strong reflection. The pulse-echo was implemented to obtain good accuracy without sacrificing the signal processing speed. A tracking technique was developed for the purpose of connecting detected reflections to trajectories. The technique was tested experimentally by measuring the horizontal position of rising air bubbles in a water tank. The results show that the pulse-echo technique can detect multiple bubbles concurrently. The pulse-echo technique detected almost the same number of bubbles as a high-speed video. For average void fractions up to around

1 %

(and instantaneous void fraction reaching

5.3 %

), the rate of bubbles missed by the pulse-echo and the rate of noise trajectories both stayed less than 5%. The error rate increased with the void fraction, limiting the technique’s application range. Full article

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

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18 pages, 3278 KiB

Open AccessArticle

On-Board, Real-Time Preprocessing System for Optical Remote-Sensing Imagery

by Baogui Qi¹, Hao Shi^1,2,*

, Yin Zhuang¹, He Chen¹ and Liang Chen¹

¹ Beijing Key Laboratory of Embedded Real-Time Information Processing Technology, Beijing Institute of Technology, Beijing 100081, China

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

Sensors 2018, 18(5), 1328; https://doi.org/10.3390/s18051328 - 25 Apr 2018

Cited by 40 | Viewed by 5737

Abstract

With the development of remote-sensing technology, optical remote-sensing imagery processing has played an important role in many application fields, such as geological exploration and natural disaster prevention. However, relative radiation correction and geometric correction are key steps in preprocessing because raw image data [...] Read more.

With the development of remote-sensing technology, optical remote-sensing imagery processing has played an important role in many application fields, such as geological exploration and natural disaster prevention. However, relative radiation correction and geometric correction are key steps in preprocessing because raw image data without preprocessing will cause poor performance during application. Traditionally, remote-sensing data are downlinked to the ground station, preprocessed, and distributed to users. This process generates long delays, which is a major bottleneck in real-time applications for remote-sensing data. Therefore, on-board, real-time image preprocessing is greatly desired. In this paper, a real-time processing architecture for on-board imagery preprocessing is proposed. First, a hierarchical optimization and mapping method is proposed to realize the preprocessing algorithm in a hardware structure, which can effectively reduce the computation burden of on-board processing. Second, a co-processing system using a field-programmable gate array (FPGA) and a digital signal processor (DSP; altogether, FPGA-DSP) based on optimization is designed to realize real-time preprocessing. The experimental results demonstrate the potential application of our system to an on-board processor, for which resources and power consumption are limited. Full article

(This article belongs to the Section Remote Sensors)

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20 pages, 4274 KiB

Open AccessArticle

Textile Retrieval Based on Image Content from CDC and Webcam Cameras in Indoor Environments

by Oscar García-Olalla¹, Enrique Alegre^1,3

, Laura Fernández-Robles^2,3

, Eduardo Fidalgo^1,3,*

and Surajit Saikia^1,3

¹ Department of Electrical, Systems and Automation, Universidad de León, 24071 León, Spain

² Department of Mechanical, Computer Science and Aerospace Engineering, Universidad de León, 24071 León, Spain

³ Researcher at INCIBE (Spanish National Cybersecurity Institute), 24005 León, Spain

Sensors 2018, 18(5), 1329; https://doi.org/10.3390/s18051329 - 25 Apr 2018

Cited by 14 | Viewed by 6419

Abstract

Textile based image retrieval for indoor environments can be used to retrieve images that contain the same textile, which may indicate that scenes are related. This makes up a useful approach for law enforcement agencies who want to find evidence based on matching [...] Read more.

Textile based image retrieval for indoor environments can be used to retrieve images that contain the same textile, which may indicate that scenes are related. This makes up a useful approach for law enforcement agencies who want to find evidence based on matching between textiles. In this paper, we propose a novel pipeline that allows searching and retrieving textiles that appear in pictures of real scenes. Our approach is based on first obtaining regions containing textiles by using MSER on high pass filtered images of the RGB, HSV and Hue channels of the original photo. To describe the textile regions, we demonstrated that the combination of HOG and HCLOSIB is the best option for our proposal when using the correlation distance to match the query textile patch with the candidate regions. Furthermore, we introduce a new dataset, TextilTube, which comprises a total of 1913 textile regions labelled within 67 classes. We yielded 84.94% of success in the 40 nearest coincidences and 37.44% of precision taking into account just the first coincidence, which outperforms the current deep learning methods evaluated. Experimental results show that this pipeline can be used to set up an effective textile based image retrieval system in indoor environments. Full article

(This article belongs to the Special Issue Visual Sensors)

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11 pages, 1182 KiB

Open AccessArticle

Rapid, High Affinity Binding by a Fluorescein Templated Copolymer Combining Covalent, Hydrophobic, and Acid–Base Noncovalent Crosslinks

by Casey J. Grenier¹

, Anthony Timberman², Rongfang Yang², John Csoros²

, Alex Papantones³, Leila F. Deravi⁴

and W. Rudolf Seitz^2,*

¹ Tekscan, Inc., 307 W. First St., Boston, MA 02127, USA

² Department of Chemistry, University of New Hampshire, Durham NH 03824, USA

³ Boston Analytical, 14 Manor Parkway, Salem, NH 03079, USA

⁴ Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA

Sensors 2018, 18(5), 1330; https://doi.org/10.3390/s18051330 - 25 Apr 2018

Cited by 9 | Viewed by 4175

Abstract

A new type of biomimetic templated copolymer has been prepared by reverse addition fragmentation chain transfer polymerization (RAFT) in dioxane. The initial formulation includes the template fluorescein, N-isopropylacrylamide (NIPAM, 84 mol %), methacrylic acid (MAA, 5-mol %), 4-vinylpyridine (4-VP, 9 mmol %), [...] Read more.

A new type of biomimetic templated copolymer has been prepared by reverse addition fragmentation chain transfer polymerization (RAFT) in dioxane. The initial formulation includes the template fluorescein, N-isopropylacrylamide (NIPAM, 84 mol %), methacrylic acid (MAA, 5-mol %), 4-vinylpyridine (4-VP, 9 mmol %), and N,N′-methylenebis(acrylamide) (MBA, 2 mol %). PolyNIPAM is a thermosensitive polymer that comes out of aqueous solution above its lower critical solution temperature forming hydrophobic ‘crosslinks’. MAA and 4-VP interact in dioxane forming acid–base crosslinks. The excess 4-VP serves as a recognition monomer organizing around the template fluorescein to form a binding site that is held in place by the noncovalent and covalent crosslinks. The MBA is a covalent crosslinker. The RAFT agent in the resulting copolylmer was reduced to a thiol and attached to gold nanoparticles. The gold nanoparticle bound copolymer binds fluorescein completely in less than two seconds with an affinity constant greater than 10⁸ M⁻¹. A reference copolymer prepared with the same monomers by the same procedure binds fluorescein much more weakly. Full article

(This article belongs to the Special Issue Polymer-Based Sensors for Bioanalytes)

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14 pages, 4113 KiB

Open AccessArticle

Feasibility of Optical Coherence Tomography (OCT) for Intra-Operative Detection of Blood Flow during Gastric Tube Reconstruction

by Sanne M. Jansen^1,2,*,†, Mitra Almasian^1,†, Leah S. Wilk¹, Daniel M. De Bruin¹, Mark I. Van Berge Henegouwen³, Simon D. Strackee², Paul R. Bloemen¹

, Sybren L. Meijer⁴, Suzanne S. Gisbertz³

and Ton G. Van Leeuwen¹

¹ Department of Biomedical Engineering & Physics, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands

² Department of Plastic, Reconstructive & Hand Surgery, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands

³ Department of Surgery, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands

⁴ Department of Pathology, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1331; https://doi.org/10.3390/s18051331 - 25 Apr 2018

Cited by 13 | Viewed by 5052

Abstract

In this study; an OCT-based intra-operative imaging method for blood flow detection during esophagectomy with gastric tube reconstruction is investigated. Change in perfusion of the gastric tube tissue can lead to ischemia; with a high morbidity and mortality as a result. Anastomotic leakage [...] Read more.

In this study; an OCT-based intra-operative imaging method for blood flow detection during esophagectomy with gastric tube reconstruction is investigated. Change in perfusion of the gastric tube tissue can lead to ischemia; with a high morbidity and mortality as a result. Anastomotic leakage (incidence 5–20%) is one of the most severe complications after esophagectomy with gastric tube reconstruction. Optical imaging techniques provide for minimal-invasive and real-time visualization tools that can be used in intraoperative settings. By implementing an optical technique for blood flow detection during surgery; perfusion can be imaged and quantified and; if needed; perfusion can be improved by either a surgical intervention or the administration of medication. The feasibility of imaging gastric microcirculation in vivo using optical coherence tomography (OCT) during surgery of patients with esophageal cancer by visualizing blood flow based on the speckle contrast from M-mode OCT images is studied. The percentage of pixels exhibiting a speckle contrast value indicative of flow was quantified to serve as an objective parameter to assess blood flow at 4 locations on the reconstructed gastric tube. Here; it was shown that OCT can be used for direct blood flow imaging during surgery and may therefore aid in improving surgical outcomes for patients. Full article

(This article belongs to the Special Issue Optical Methods in Sensing and Imaging for Medical and Biological Applications)

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12 pages, 4180 KiB

Open AccessArticle

The Application of an Ultrasound Tomography Algorithm in a Novel Ring 3D Ultrasound Imaging System

by Chang Liu^1,2,3, Chenyang Xue^1,2,*, Binzhen Zhang^1,2,*, Guojun Zhang^1,2 and Changde He^1,2

¹ Key Laboratory of Instrumentation Science & Dynamic Measurement, North University of China, Ministry of Education, Taiyuan 030051, China

² Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China

³ School of Electrical and Electronic Engineering, Dalian Vocational Technical College, Dalian 116037, China

Sensors 2018, 18(5), 1332; https://doi.org/10.3390/s18051332 - 25 Apr 2018

Cited by 25 | Viewed by 7728

Abstract

Currently, breast cancer is one of the most common cancers in women all over the world. A novel 3D breast ultrasound imaging ring system using the linear array transducer is proposed to decrease costs, reduce processing difficulties, and improve patient comfort as compared [...] Read more.

Currently, breast cancer is one of the most common cancers in women all over the world. A novel 3D breast ultrasound imaging ring system using the linear array transducer is proposed to decrease costs, reduce processing difficulties, and improve patient comfort as compared to modern day breast screening systems. The 1 × 128 Piezoelectric Micromachined Ultrasonic Transducer (PMUT) linear array is placed 90 degrees cross-vertically. The transducer surrounds the mammary gland, which allows for non-contact detection. Once the experimental platform is built, the breast model is placed through the electric rotary table opening and into a water tank that is at a constant temperature of 32 °C. The electric rotary table performs a 360° scan either automatically or mechanically. Pulse echo signals are captured through a circular scanning method at discrete angles. Subsequently, an ultrasonic tomography algorithm is designed, and a horizontal slice imaging is realized. The experimental results indicate that the preliminary detection of mass is realized by using this ring system. Circular scanning imaging is obtained by using a rotatable linear array instead of a cylindrical array, which allows the size and location of the mass to be recognized. The resolution of breast imaging is improved through the adjustment of the angle interval (>0.05°) and multiple slices are gained through different transducer array elements (1 × 128). These results validate the feasibility of the system design as well as the algorithm, and encourage us to implement our concept with a clinical study in the future. Full article

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

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16 pages, 15570 KiB

Open AccessArticle

Smart System for Bicarbonate Control in Irrigation for Hydroponic Precision Farming

by Carlos Cambra¹, Sandra Sendra^1,2,*

, Jaime Lloret¹

and Raquel Lacuesta³

¹ Instituto de Investigación para la Gestión Integrada de zonas Costeras, Universitat Politècnica de València, 46730 Valencia, Spain

² Department of Signal Theory, Telematics and Communications, Universidad de Granada, 18071 Granada, Spain

³ Department of Computer Science and Engineering, Universidad de Zaragoza, 50018 Zaragoza, Spain

Sensors 2018, 18(5), 1333; https://doi.org/10.3390/s18051333 - 25 Apr 2018

Cited by 78 | Viewed by 15374

Abstract

Improving the sustainability in agriculture is nowadays an important challenge. The automation of irrigation processes via low-cost sensors can to spread technological advances in a sector very influenced by economical costs. This article presents an auto-calibrated pH sensor able to detect and adjust [...] Read more.

Improving the sustainability in agriculture is nowadays an important challenge. The automation of irrigation processes via low-cost sensors can to spread technological advances in a sector very influenced by economical costs. This article presents an auto-calibrated pH sensor able to detect and adjust the imbalances in the pH levels of the nutrient solution used in hydroponic agriculture. The sensor is composed by a pH probe and a set of micropumps that sequentially pour the different liquid solutions to maintain the sensor calibration and the water samples from the channels that contain the nutrient solution. To implement our architecture, we use an auto-calibrated pH sensor connected to a wireless node. Several nodes compose our wireless sensor networks (WSN) to control our greenhouse. The sensors periodically measure the pH level of each hydroponic support and send the information to a data base (DB) which stores and analyzes the data to warn farmers about the measures. The data can then be accessed through a user-friendly, web-based interface that can be accessed through the Internet by using desktop or mobile devices. This paper also shows the design and test bench for both the auto-calibrated pH sensor and the wireless network to check their correct operation. Full article

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

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16 pages, 5358 KiB

Open AccessArticle

Gait Shear and Plantar Pressure Monitoring: A Non-Invasive OFS Based Solution for e-Health Architectures

by Cátia Tavares^1,2,*

, M. Fátima Domingues^1,3

, Anselmo Frizera-Neto⁴

, Tiago Leite², Cátia Leitão^1,2

, Nélia Alberto¹

, Carlos Marques¹

, Ayman Radwan¹

, Eduardo Rocon³

, Paulo André⁵ and Paulo Antunes^1,2

¹ Instituto de Telecomunicações, Campus Universitário de Santiago, Aveiro 3810-193, Portugal

² Department of Physics & I3N, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal

³ CSIC-UPM, Ctra. Campo Real, Arganda del Rey 28500, Madrid, Spain

⁴ Telecommunications Laboratory, Electrical Engineering Department, Federal University of Espírito Santo, Espírito Santo 29075-910, Brazil

⁵ Department of Electrical and Computer Engineering and Instituto de Telecomunicações, Instituto Superior Técnico, University of Lisbon, Lisbon 1049-001, Portugal

Sensors 2018, 18(5), 1334; https://doi.org/10.3390/s18051334 - 25 Apr 2018

Cited by 51 | Viewed by 6635

Abstract

In an era of unprecedented progress in sensing technology and communication, health services are now able to closely monitor patients and elderly citizens without jeopardizing their daily routines through health applications on their mobile devices in what is known as e-Health. Within this [...] Read more.

In an era of unprecedented progress in sensing technology and communication, health services are now able to closely monitor patients and elderly citizens without jeopardizing their daily routines through health applications on their mobile devices in what is known as e-Health. Within this field, we propose an optical fiber sensor (OFS) based system for the simultaneous monitoring of shear and plantar pressure during gait movement. These parameters are considered to be two key factors in gait analysis that can help in the early diagnosis of multiple anomalies, such as diabetic foot ulcerations or in physical rehabilitation scenarios. The proposed solution is a biaxial OFS based on two in-line fiber Bragg gratings (FBGs), which were inscribed in the same optical fiber and placed individually in two adjacent cavities, forming a small sensing cell. Such design presents a more compact and resilient solution with higher accuracy when compared to the existing electronic systems. The implementation of the proposed elements into an insole is also described, showcasing the compactness of the sensing cells, which can easily be integrated into a non-invasive mobile e-Health solution for continuous remote gait monitoring of patients and elder citizens. The reported results show that the proposed system outperforms existing solutions, in the sense that it is able to dynamically discriminate shear and plantar pressure during gait. Full article

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

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10 pages, 3041 KiB

Open AccessArticle

Exploring on the Sensitivity Changes of the LC Resonance Magnetic Sensors Affected by Superposed Ringing Signals

by Tingting Lin^1,2

, Kun Zhou^1,2, Sijia Yu^1,2, Pengfei Wang^1,2, Ling Wan^1,2 and Jing Zhao^1,2,*

¹ College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130061, China

² Key Laboratory of Geo-Exploration Instruments, Ministry of Education of China, Changchun 130061, China

Sensors 2018, 18(5), 1335; https://doi.org/10.3390/s18051335 - 25 Apr 2018

Cited by 3 | Viewed by 4874

Abstract

LC resonance magnetic sensors are widely used in low-field nuclear magnetic resonance (LF-NMR) and surface nuclear magnetic resonance (SNMR) due to their high sensitivity, low cost and simple design. In magnetically shielded rooms, LC resonance magnetic sensors can exhibit sensitivities at the fT/√Hz [...] Read more.

LC resonance magnetic sensors are widely used in low-field nuclear magnetic resonance (LF-NMR) and surface nuclear magnetic resonance (SNMR) due to their high sensitivity, low cost and simple design. In magnetically shielded rooms, LC resonance magnetic sensors can exhibit sensitivities at the fT/√Hz level in the kHz range. However, since the equivalent magnetic field noise of this type of sensor is greatly affected by the environment, weak signals are often submerged in practical applications, resulting in relatively low signal-to-noise ratios (SNRs). To determine why noise increases in unshielded environments, we analysed the noise levels of an LC resonance magnetic sensor (L ≠ 0) and a Hall sensor (L ≈ 0) in different environments. The experiments and simulations indicated that the superposed ringing of the LC resonance magnetic sensors led to the observed increase in white noise level caused by environmental interference. Nevertheless, ringing is an inherent characteristic of LC resonance magnetic sensors. It cannot be eliminated when environmental interference exists. In response to this problem, we proposed a method that uses matching resistors with various values to adjust the quality factor Q of the LC resonance magnetic sensor in different measurement environments to obtain the best sensitivity. The LF-NMR experiment in the laboratory showed that the SNR is improved significantly when the LC resonance magnetic sensor with the best sensitivity is selected for signal acquisition in the light of the test environment. (When the matching resistance is 10 kΩ, the SNR is 3.46 times that of 510 Ω). This study improves LC resonance magnetic sensors for nuclear magnetic resonance (NMR) detection in a variety of environments. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 692 KiB

Open AccessArticle

Wearable Sensors and the Assessment of Frailty among Vulnerable Older Adults: An Observational Cohort Study

by Javad Razjouyan^1,2

, Aanand D. Naik^1,3,4

, Molly J. Horstman^1,3, Mark E. Kunik^1,3,4, Mona Amirmazaheri², He Zhou²

, Amir Sharafkhaneh³ and Bijan Najafi^2,3,*

¹ VA HSR&D, Center for Innovations in Quality, Effectiveness and Safety, Michael E. DeBakey VA Medical Center, Houston, TX 77030, USA

² Interdisciplinary Consortium on Advanced Motion Performance (iCAMP), Division of Vascular Surgery and Endovascular Therapy, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, One Baylor Plaza, MS: BCM390, Houston, TX 77030, USA; Mona Amirmazaheri@bcm.edu (M.A.)

³ Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA

⁴ South Central Mental Illness Research, Education and Clinical Center (MIRECC), Houston, TX 77030, USA

Sensors 2018, 18(5), 1336; https://doi.org/10.3390/s18051336 - 26 Apr 2018

Cited by 84 | Viewed by 10023

Abstract

Background: The geriatric syndrome of frailty is one of the greatest challenges facing the U.S. aging population. Frailty in older adults is associated with higher adverse outcomes, such as mortality and hospitalization. Identifying precise early indicators of pre-frailty and measures of specific frailty [...] Read more.

Background: The geriatric syndrome of frailty is one of the greatest challenges facing the U.S. aging population. Frailty in older adults is associated with higher adverse outcomes, such as mortality and hospitalization. Identifying precise early indicators of pre-frailty and measures of specific frailty components are of key importance to enable targeted interventions and remediation. We hypothesize that sensor-derived parameters, measured by a pendant accelerometer device in the home setting, are sensitive to identifying pre-frailty. Methods: Using the Fried frailty phenotype criteria, 153 community-dwelling, ambulatory older adults were classified as pre-frail (51%), frail (22%), or non-frail (27%). A pendant sensor was used to monitor the at home physical activity, using a chest acceleration over 48 h. An algorithm was developed to quantify physical activity pattern (PAP), physical activity behavior (PAB), and sleep quality parameters. Statistically significant parameters were selected to discriminate the pre-frail from frail and non-frail adults. Results: The stepping parameters, walking parameters, PAB parameters (sedentary and moderate-to-vigorous activity), and the combined parameters reached and area under the curve of 0.87, 0.85, 0.85, and 0.88, respectively, for identifying pre-frail adults. No sleep parameters discriminated the pre-frail from the rest of the adults. Conclusions: This study demonstrates that a pendant sensor can identify pre-frailty via daily home monitoring. These findings may open new opportunities in order to remotely measure and track frailty via telehealth technologies. Full article

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

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10 pages, 269 KiB

Open AccessArticle

A Distance Bounding Protocol for Location-Cloaked Applications

by Cristián Molina-Martínez^1,†, Patricio Galdames^2,*,†

and Cristian Duran-Faundez³

¹ Magister en Ciencias de la Computación, Universidad del Bío-Bío, Concepción 4051381, Chile

² Departamento de Ciencias de la Computación, Universidad del Bío-Bío, Concepción 4051381, Chile

³ Departamento de Ingeniería Eléctrica y Electrónica, Universidad del Bío-Bío, Concepción 4051381, Chile

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1337; https://doi.org/10.3390/s18051337 - 26 Apr 2018

Cited by 1 | Viewed by 2930

Abstract

Location-based services (LBSs) assume that users are willing to release trustworthy and useful details about their whereabouts. However, many location privacy concerns have arisen. For location privacy protection, several algorithms build a cloaking region to hide a user’s location. However, many applications may [...] Read more.

Location-based services (LBSs) assume that users are willing to release trustworthy and useful details about their whereabouts. However, many location privacy concerns have arisen. For location privacy protection, several algorithms build a cloaking region to hide a user’s location. However, many applications may not operate adequately on cloaked locations. For example, a traditional distance bounding protocol (DBP)—which is run by two nodes called the prover and the verifier—may conclude an untight and useless distance between these two entities. An LBS (verifier) may use this distance as a metric of usefulness and trustworthiness of the location claimed by the user (prover). However, we show that if a tight distance is desired, traditional DBP can refine a user’s cloaked location and compromise its location privacy. To find a proper balance, we propose a location-privacy-aware DBP protocol. Our solution consists of adding some small delays before submitting any user’s response. We show that several issues arise when a certain delay is chosen, and we propose some solutions. The effectiveness of our techniques in balancing location refinement and utility is demonstrated through simulation. Full article

(This article belongs to the Section Sensor Networks)

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15 pages, 6248 KiB

Open AccessArticle

Highly Stable and Flexible Pressure Sensors with Modified Multi-Walled Carbon Nanotube/Polymer Composites for Human Monitoring

by Yin He^1,2,3, Yue Ming¹, Wei Li¹, Yafang Li¹, Maoqi Wu¹, Jinzhong Song⁴, Xiaojiu Li^1,2 and Hao Liu^1,3,*

¹ School of Textiles, Tianjin Polytechnic University, Tianjin 300387, China

² School of Fashion and Art, Tianjin Polytechnic University, Tianjin 300387, China

³ Institute of Smart Wearable Electronic Textiles, Tianjin Polytechnic University, Tianjin 300387, China

⁴ College of Biomedical Engineering & Instrument Science, Zhejiang University, Zhejiang 310027, China

Sensors 2018, 18(5), 1338; https://doi.org/10.3390/s18051338 - 26 Apr 2018

Cited by 54 | Viewed by 6130

Abstract

A facile method for preparing an easy processing, repeatable and flexible pressure sensor was presented via the synthesis of modified multi-walled carbon nanotubes (m-MWNTs) and polyurethane (PU) films. The surface modification of multi-walled carbon nanotubes (MWNTs) simultaneously used a silane coupling agent (KH550) [...] Read more.

A facile method for preparing an easy processing, repeatable and flexible pressure sensor was presented via the synthesis of modified multi-walled carbon nanotubes (m-MWNTs) and polyurethane (PU) films. The surface modification of multi-walled carbon nanotubes (MWNTs) simultaneously used a silane coupling agent (KH550) and sodium dodecyl benzene sulfonate (SDBS) to improve the dispersibility and compatibility of the MWNTs in a polymer matrix. The electrical property and piezoresistive behavior of the m-MWNT/PU composites were compared with raw multi-walled carbon nanotube (raw MWNT)/PU composites. Under linear uniaxial pressure, the m-MWNT/PU composite exhibited 4.282%kPa⁻¹ sensitivity within the pressure of 1 kPa. The nonlinear error, hysteresis error and repeatability error of the piezoresistivity of m-MWNT/PU decreased 9%, 16.72% and 54.95% relative to raw MWNT/PU respectively. Therefore, the piezoresistive response of m-MWNT/PU had better stability than that of raw MWNT/PU composites. The m-MWNT/PU sensors could be utilized in wearable devices for body movement detection, monitoring of respiration and pressure detection in garments. Full article

(This article belongs to the Section Physical Sensors)

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27 pages, 1276 KiB

Open AccessArticle

Cross-Participant EEG-Based Assessment of Cognitive Workload Using Multi-Path Convolutional Recurrent Neural Networks

by Ryan Hefron¹, Brett Borghetti^1,*

, Christine Schubert Kabban², James Christensen³ and Justin Estepp³

¹ Department of Electrical & Computer Engineering, Air Force Institute of Technology, WPAFB, Dayton, OH 45433, USA

² Department of Mathematics & Statistics, Air Force Institute of Technology, WPAFB, Dayton, OH 45433, USA

³ Air Force Research Laboratory, WPAFB, Dayton, OH 45433, USA

Sensors 2018, 18(5), 1339; https://doi.org/10.3390/s18051339 - 26 Apr 2018

Cited by 40 | Viewed by 5791

Abstract

Applying deep learning methods to electroencephalograph (EEG) data for cognitive state assessment has yielded improvements over previous modeling methods. However, research focused on cross-participant cognitive workload modeling using these techniques is underrepresented. We study the problem of cross-participant state estimation in a non-stimulus-locked [...] Read more.

Applying deep learning methods to electroencephalograph (EEG) data for cognitive state assessment has yielded improvements over previous modeling methods. However, research focused on cross-participant cognitive workload modeling using these techniques is underrepresented. We study the problem of cross-participant state estimation in a non-stimulus-locked task environment, where a trained model is used to make workload estimates on a new participant who is not represented in the training set. Using experimental data from the Multi-Attribute Task Battery (MATB) environment, a variety of deep neural network models are evaluated in the trade-space of computational efficiency, model accuracy, variance and temporal specificity yielding three important contributions: (1) The performance of ensembles of individually-trained models is statistically indistinguishable from group-trained methods at most sequence lengths. These ensembles can be trained for a fraction of the computational cost compared to group-trained methods and enable simpler model updates. (2) While increasing temporal sequence length improves mean accuracy, it is not sufficient to overcome distributional dissimilarities between individuals’ EEG data, as it results in statistically significant increases in cross-participant variance. (3) Compared to all other networks evaluated, a novel convolutional-recurrent model using multi-path subnetworks and bi-directional, residual recurrent layers resulted in statistically significant increases in predictive accuracy and decreases in cross-participant variance. Full article

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

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13 pages, 3464 KiB

Open AccessArticle

Adaptive Monostatic System for Measuring Microwave Reflections from the Breast

by Jeremie Bourqui^1,*

, Martin Kuhlmann^1,2, Douglas J. Kurrant¹, Benjamin R. Lavoie¹

and Elise C. Fear^1,*

¹ Schulich School of Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada

² College of Engineering and Architecture of Fribourg, 1700 Fribourg, Switzerland

Sensors 2018, 18(5), 1340; https://doi.org/10.3390/s18051340 - 26 Apr 2018

Cited by 24 | Viewed by 4600

Abstract

A second-generation monostatic radar system to measure microwave reflections from the human breast is presented and analyzed. The present system can measure the outline of the breast with an accuracy of ±1 mm and precisely place the microwave sensor in an adaptive matter [...] Read more.

A second-generation monostatic radar system to measure microwave reflections from the human breast is presented and analyzed. The present system can measure the outline of the breast with an accuracy of ±1 mm and precisely place the microwave sensor in an adaptive matter such that microwaves are normally incident on the skin. Microwave reflections are measured between 10 MHz to 12 GHz with sensitivity of 65 to 75 dB below the input power and a total scan time of 30 min for 140 locations. The time domain reflections measured from a volunteer show fidelity above 0.98 for signals in a single scan. Finally, multiple scans of a breast phantoms demonstrate the consistency of the system in terms of recorded reflection, outline measurement, and image reconstruction. Full article

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

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22 pages, 5272 KiB

Open AccessArticle

Artificial Intelligence-Based Semantic Internet of Things in a User-Centric Smart City

by Kun Guo, Yueming Lu^*, Hui Gao and Ruohan Cao

Key Laboratory of Trustworthy Distributed Computing and Service, Ministry of Education, Beijing University of Posts and Telecommunications, Beijing 100876, China

Sensors 2018, 18(5), 1341; https://doi.org/10.3390/s18051341 - 26 Apr 2018

Cited by 96 | Viewed by 15612

Abstract

Smart city (SC) technologies can provide appropriate services according to citizens’ demands. One of the key enablers in a SC is the Internet of Things (IoT) technology, which enables a massive number of devices to connect with each other. However, these devices usually [...] Read more.

Smart city (SC) technologies can provide appropriate services according to citizens’ demands. One of the key enablers in a SC is the Internet of Things (IoT) technology, which enables a massive number of devices to connect with each other. However, these devices usually come from different manufacturers with different product standards, which confront interactive control problems. Moreover, these devices will produce large amounts of data, and efficiently analyzing these data for intelligent services. In this paper, we propose a novel artificial intelligence-based semantic IoT (AI-SIoT) hybrid service architecture to integrate heterogeneous IoT devices to support intelligent services. In particular, the proposed architecture is empowered by semantic and AI technologies, which enable flexible connections among heterogeneous devices. The AI technology can support very implement efficient data analysis and make accurate decisions on service provisions in various kinds. Furthermore, we also present several practical use cases of the proposed AI-SIoT architecture and the opportunities and challenges to implement the proposed AI-SIoT for future SCs are also discussed. 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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17 pages, 27653 KiB

Open AccessArticle

Three-Dimensional Terahertz Coded-Aperture Imaging Based on Matched Filtering and Convolutional Neural Network

by Shuo Chen

, Chenggao Luo^*, Hongqiang Wang^*, Bin Deng, Yongqiang Cheng and Zhaowen Zhuang

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

Sensors 2018, 18(5), 1342; https://doi.org/10.3390/s18051342 - 26 Apr 2018

Cited by 11 | Viewed by 4428

Abstract

As a promising radar imaging technique, terahertz coded-aperture imaging (TCAI) can achieve high-resolution, forward-looking, and staring imaging by producing spatiotemporal independent signals with coded apertures. However, there are still two problems in three-dimensional (3D) TCAI. Firstly, the large-scale reference-signal matrix based on meshing [...] Read more.

As a promising radar imaging technique, terahertz coded-aperture imaging (TCAI) can achieve high-resolution, forward-looking, and staring imaging by producing spatiotemporal independent signals with coded apertures. However, there are still two problems in three-dimensional (3D) TCAI. Firstly, the large-scale reference-signal matrix based on meshing the 3D imaging area creates a heavy computational burden, thus leading to unsatisfactory efficiency. Secondly, it is difficult to resolve the target under low signal-to-noise ratio (SNR). In this paper, we propose a 3D imaging method based on matched filtering (MF) and convolutional neural network (CNN), which can reduce the computational burden and achieve high-resolution imaging for low SNR targets. In terms of the frequency-hopping (FH) signal, the original echo is processed with MF. By extracting the processed echo in different spike pulses separately, targets in different imaging planes are reconstructed simultaneously to decompose the global computational complexity, and then are synthesized together to reconstruct the 3D target. Based on the conventional TCAI model, we deduce and build a new TCAI model based on MF. Furthermore, the convolutional neural network (CNN) is designed to teach the MF-TCAI how to reconstruct the low SNR target better. The experimental results demonstrate that the MF-TCAI achieves impressive performance on imaging ability and efficiency under low SNR. Moreover, the MF-TCAI has learned to better resolve the low-SNR 3D target with the help of CNN. In summary, the proposed 3D TCAI can achieve: (1) low-SNR high-resolution imaging by using MF; (2) efficient 3D imaging by downsizing the large-scale reference-signal matrix; and (3) intelligent imaging with CNN. Therefore, the TCAI based on MF and CNN has great potential in applications such as security screening, nondestructive detection, medical diagnosis, etc. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 3890 KiB

Open AccessArticle

Electrochemical Biosensor for Nitrite Based on Polyacrylic-Graphene Composite Film with Covalently Immobilized Hemoglobin

by Raja Zaidatul Akhmar Raja Jamaluddin¹, Lee Yook Heng^1,2,*, Ling Ling Tan² and Kwok Feng Chong³

¹ School of Chemical Sciences and Food Technology, Faculty of Science and Technology, University Kebangsaan Malaysia (UKM), Bangi 43600, Selangor D. E., Malaysia

² Southeast Asia Disaster Prevention Research Initiative (SEADPRI-UKM), Institute for Environment and Development (LESTARI), Universiti Kebangsaan Malaysia (UKM), Bangi 43600, Selangor D. E., Malaysia

³ Faculty of Industrial Sciences & Technology, Universiti Malaysia Pahang, Lebuhraya Tun Razak, Gambang, Kuantan 26300, Pahang Darul Makmur, Malaysia

Sensors 2018, 18(5), 1343; https://doi.org/10.3390/s18051343 - 26 Apr 2018

Cited by 24 | Viewed by 4817

Abstract

A new biosensor for the analysis of nitrite in food was developed based on hemoglobin (Hb) covalently immobilized on the succinimide functionalized poly(n-butyl acrylate)-graphene [poly(nBA)-rGO] composite film deposited on a carbon-paste screen-printed electrode (SPE). The immobilized Hb on the poly(nBA)-rGO conducting matrix exhibited [...] Read more.

A new biosensor for the analysis of nitrite in food was developed based on hemoglobin (Hb) covalently immobilized on the succinimide functionalized poly(n-butyl acrylate)-graphene [poly(nBA)-rGO] composite film deposited on a carbon-paste screen-printed electrode (SPE). The immobilized Hb on the poly(nBA)-rGO conducting matrix exhibited electrocatalytic ability for the reduction of nitrite with significant enhancement in the reduction peak at −0.6 V versus Ag/AgCl reference electrode. Thus, direct determination of nitrite can be achieved by monitoring the cathodic peak current signal of the proposed polyacrylic-graphene hybrid film-based voltammetric nitrite biosensor. The nitrite biosensor exhibited a reproducible dynamic linear response range from 0.05–5 mg L⁻¹ nitrite and a detection limit of 0.03 mg L⁻¹. No significant interference was observed by potential interfering ions such as Ca²⁺, Na⁺, K⁺, NH₄⁺, Mg²⁺, and NO₃⁻ ions. Analysis of nitrite in both raw and processed edible bird’s nest (EBN) samples demonstrated recovery of close to 100%. The covalent immobilization of Hb on poly(nBA)-rGO composite film has improved the performance of the electrochemical nitrite biosensor in terms of broader detection range, lower detection limit, and prolonged biosensor stability. Full article

(This article belongs to the Special Issue Polymer-Based Sensors for Bioanalytes)

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21 pages, 4416 KiB

Open AccessArticle

Smart Web-Based Platform to Support Physical Rehabilitation

by Yves Rybarczyk^1,2,*

, Jan Kleine Deters³, Clément Cointe⁴

and Danilo Esparza¹

¹ Intelligent & Interactive Lab (SI² Lab), Universidad de Las Américas, Quito 170124, Ecuador

² Department of Electrical Engineering, CTS/UNINOVA, Nova University of Lisbon, 2829-516 Monte de Caparica, Portugal

³ Faculty of Electrical Engineering, University of Twente, 217 7500 Enschede, The Netherlands

⁴ Ecole Normale Supérieure de Paris-Saclay, 94235 Cachan, France

Sensors 2018, 18(5), 1344; https://doi.org/10.3390/s18051344 - 26 Apr 2018

Cited by 20 | Viewed by 5335

Abstract

The enhancement of ubiquitous and pervasive computing brings new perspectives in medical rehabilitation. In that sense, the present study proposes a smart, web-based platform to promote the reeducation of patients after hip replacement surgery. This project focuses on two fundamental aspects in the [...] Read more.

The enhancement of ubiquitous and pervasive computing brings new perspectives in medical rehabilitation. In that sense, the present study proposes a smart, web-based platform to promote the reeducation of patients after hip replacement surgery. This project focuses on two fundamental aspects in the development of a suitable tele-rehabilitation application, which are: (i) being based on an affordable technology, and (ii) providing the patients with a real-time assessment of the correctness of their movements. A probabilistic approach based on the development and training of ten Hidden Markov Models (HMMs) is used to discriminate in real time the main faults in the execution of the therapeutic exercises. Two experiments are designed to evaluate the precision of the algorithm for classifying movements performed in the laboratory and clinical settings, respectively. A comparative analysis of the data shows that the models are as reliable as the physiotherapists to discriminate and identify the motion errors. The results are discussed in terms of the required setup for a successful application in the field and further implementations to improve the accuracy and usability of the system. Full article

(This article belongs to the Special Issue Sensors Applied in Multimodal Systems—Selected Papers from the Second Ecuador Technical Chapters Meeting (IEEE-ETCM))

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30 pages, 1212 KiB

Open AccessArticle

Appdaptivity: An Internet of Things Device-Decoupled System for Portable Applications in Changing Contexts

by Cristian Martín^1,*

, Jeroen Hoebeke²

, Jen Rossey²

, Manuel Díaz¹, Bartolomé Rubio¹ and Floris Van den Abeele²

¹ Department of Languages and Computer Science, University of Málaga, Boulevar Louis Pasteur 35, 29071 Málaga, Spain

² IDLab, Department of Information Technology (INTEC), Ghent University-IMEC, Technologiepark-Zwijnaarde 15, 9052 Ghent, Belgium

Sensors 2018, 18(5), 1345; https://doi.org/10.3390/s18051345 - 26 Apr 2018

Cited by 5 | Viewed by 4886

Abstract

Currently, applications in the Internet of Things (IoT) are tightly coupled to the underlying physical devices. As a consequence, upon adding a device, device replacement or user’s relocation to a different physical space, application developers have to re-perform installation and configuration processes to [...] Read more.

Currently, applications in the Internet of Things (IoT) are tightly coupled to the underlying physical devices. As a consequence, upon adding a device, device replacement or user’s relocation to a different physical space, application developers have to re-perform installation and configuration processes to reconfigure applications, which bears costs in time and knowledge of low-level details. In the emerging IoT field, this issue is even more challenging due to its current unpredictable growth in term of applications and connected devices. In addition, IoT applications can be personalised to each end user and can be present in different environments. As a result, IoT scenarios are very changeable, presenting a challenge for IoT applications. In this paper we present Appdaptivity, a system that enables the development of portable device-decoupled applications that can be adapted to changing contexts. Through Appdaptivity, application developers can intuitively create portable and personalised applications, disengaging from the underlying physical infrastructure. Results confirms a good scalability of the system in terms of connected users and components involved. Full article

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

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13 pages, 4261 KiB

Open AccessArticle

Using the Transient Response of WO₃ Nanoneedles under Pulsed UV Light in the Detection of NH₃ and NO₂

by Oriol Gonzalez, Tesfalem G. Welearegay

, Xavier Vilanova^*

and Eduard Llobet

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

Sensors 2018, 18(5), 1346; https://doi.org/10.3390/s18051346 - 26 Apr 2018

Cited by 20 | Viewed by 4110

Abstract

Here we report on the use of pulsed UV light for activating the gas sensing response of metal oxides. Under pulsed UV light, the resistance of metal oxides presents a ripple due to light-induced transient adsorption and desorption phenomena. This methodology has been [...] Read more.

Here we report on the use of pulsed UV light for activating the gas sensing response of metal oxides. Under pulsed UV light, the resistance of metal oxides presents a ripple due to light-induced transient adsorption and desorption phenomena. This methodology has been applied to tungsten oxide nanoneedle gas sensors operated either at room temperature or under mild heating (50 °C or 100 °C). It has been found that by analyzing the rate of resistance change caused by pulsed UV light, a fast determination of gas concentration is achieved (ten-fold improvement in response time). The technique is useful for detecting both oxidizing (NO₂) and reducing (NH₃) gases, even in the presence of different levels of ambient humidity. Room temperature operated sensors under pulsed UV light show good response towards ammonia and nitrogen dioxide at low power consumption levels. Increasing their operating temperature to 50 °C or 100 °C has the effect of further increasing sensitivity. Full article

(This article belongs to the Section Chemical Sensors)

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13 pages, 6586 KiB

Open AccessArticle

Real-Time Vision-Based Stiffness Mapping ^†

by Angela Faragasso^1,*,‡

, João Bimbo²

, Agostino Stilli³

, Helge Arne Wurdemann⁴

, Kaspar Althoefer⁵ and Hajime Asama¹

¹ Department of Precision Engineering, School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan

² Istituto Italiano di Tecnologia (IIT), Via Morego, 30 16163 Genova, Italy

³ Department of Computer Science, University College London, London WC1E 6BT, UK

⁴ Department of Mechanical Engineering, University College London, London WC1E 7JE, UK

⁵ Centre for Advanced Robotics at Queen Mary (ARQ), Faculty of Science & Engineering, Queen Mary University of London, Mile End Road, London E1 4NS, UK

^† This paper is an extended version of our paper published in IEEE/RSJ International Conference on Intelligent Robots and Systems, 2015, A. Faragasso et al. “Multi-axis stiffness sensing device for medical palpation”.

^‡ Current address: Department of Precision Engineering, School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan.

Sensors 2018, 18(5), 1347; https://doi.org/10.3390/s18051347 - 26 Apr 2018

Cited by 10 | Viewed by 5704

Abstract

This paper presents new findings concerning a hand-held stiffness probe for the medical diagnosis of abnormalities during palpation of soft-tissue. Palpation is recognized by the medical community as an essential and low-cost method to detect and diagnose disease in soft-tissue. However, differences are [...] Read more.

This paper presents new findings concerning a hand-held stiffness probe for the medical diagnosis of abnormalities during palpation of soft-tissue. Palpation is recognized by the medical community as an essential and low-cost method to detect and diagnose disease in soft-tissue. However, differences are often subtle and clinicians need to train for many years before they can conduct a reliable diagnosis. The probe presented here fills this gap providing a means to easily obtain stiffness values of soft tissue during a palpation procedure. Our stiffness sensor is equipped with a multi degree of freedom (DoF) Aurora magnetic tracker, allowing us to track and record the 3D position of the probe whilst examining a tissue area, and generate a 3D stiffness map in real-time. The stiffness probe was integrated in a robotic arm and tested in an artificial environment representing a good model of soft tissue organs; the results show that the sensor can accurately measure and map the stiffness of a silicon phantom embedded with areas of varying stiffness. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 2871 KiB

Open AccessArticle

Plasmonic Multichannel Refractive Index Sensor Based on Subwavelength Tangent-Ring Metal–Insulator–Metal Waveguide

by Zicong Guo, Kunhua Wen^*, Qinyang Hu, Wenhui Lai, Jiyan Lin and Yihong Fang

School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, Guangdong, China

Sensors 2018, 18(5), 1348; https://doi.org/10.3390/s18051348 - 26 Apr 2018

Cited by 79 | Viewed by 4635

Abstract

In this paper, a multichannel refractive index sensor based on a subwavelength metal–insulator–metal (MIM) waveguide coupled with tangent-ring resonators is proposed. When two tangent-ring resonators were placed above the MIM waveguide, Fano resonance with asymmetrical line shape appeared in the transmission spectrum due [...] Read more.

In this paper, a multichannel refractive index sensor based on a subwavelength metal–insulator–metal (MIM) waveguide coupled with tangent-ring resonators is proposed. When two tangent-ring resonators were placed above the MIM waveguide, Fano resonance with asymmetrical line shape appeared in the transmission spectrum due to the interference between the light–dark resonant modes. The sensitivity and figure of merit were as high as 880 nm/RIU and 964, respectively. Through adding more tangent-ring resonators, multiple Fano resonances with ultrasharp peaks/dips were achieved in the wavelength range of 800–2000 nm. Besides, negative group delays were also observed in the Fano resonant dips. Two-dimensional finite-difference time-domain (FDTD) method was used to simulate and analyze the performances of the proposed structures. These kinds of multiring structures can find important applications in the on-chip optical sensing and optical communication areas. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 10027 KiB

Open AccessArticle

Comparing Building and Neighborhood-Scale Variability of CO₂ and O₃ to Inform Deployment Considerations for Low-Cost Sensor System Use

by Ashley Collier-Oxandale^1,*, Evan Coffey², Jacob Thorson², Jill Johnston³ and Michael Hannigan²

¹ Environmental Engineering, University of Colorado Boulder, Boulder, CO 80309, USA

² Mechanical Engineering, University of Colorado Boulder, Boulder, CO 80309, USA

³ Preventive Medicine, University of Southern California, Los Angeles, CA 90089, USA

Sensors 2018, 18(5), 1349; https://doi.org/10.3390/s18051349 - 26 Apr 2018

Cited by 13 | Viewed by 4268

Abstract

The increased use of low-cost air quality sensor systems, particularly by communities, calls for the further development of best-practices to ensure these systems collect usable data. One area identified as requiring more attention is that of deployment logistics, that is, how to select [...] Read more.

The increased use of low-cost air quality sensor systems, particularly by communities, calls for the further development of best-practices to ensure these systems collect usable data. One area identified as requiring more attention is that of deployment logistics, that is, how to select deployment sites and how to strategically place sensors at these sites. Given that sensors are often placed at homes and businesses, ideal placement is not always possible. Considerations such as convenience, access, aesthetics, and safety are also important. To explore this issue, we placed multiple sensor systems at an existing field site allowing us to examine both neighborhood-level and building-level variability during a concurrent period for CO₂ (a primary pollutant) and O₃ (a secondary pollutant). In line with previous studies, we found that local and transported emissions as well as thermal differences in sensor systems drive variability, particularly for high-time resolution data. While this level of variability is unlikely to affect data on larger averaging scales, this variability could impact analysis if the user is interested in high-time resolution or examining local sources. However, with thoughtful placement and thorough documentation, high-time resolution data at the neighborhood level has the potential to provide us with entirely new information on local air quality trends and emissions. Full article

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

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28 pages, 1504 KiB

Open AccessArticle

Improving Fall Detection Using an On-Wrist Wearable Accelerometer

by Samad Barri Khojasteh^1,†

, José R. Villar^2,*,†,‡

, Camelia Chira^3,†, Víctor M. González^2,†

and Enrique De la Cal^2,†

¹ Sakarya University, 54050 Sakarya, Turkey

² Electric, Electronic, Computers and Systems Engineering Department, University of Oviedo, 33003 Oviedo, Spain

³ Computer SCience Department, Babes-Bolyai University, 400084 Cluj-Napoca, Romania

^† These authors contributed equally to this work.

^‡ Current address: University of Oviedo, Computer Science Department, EIMEM, c/Independencia 13, 33004 Oviedo, Spain.

Sensors 2018, 18(5), 1350; https://doi.org/10.3390/s18051350 - 26 Apr 2018

Cited by 123 | Viewed by 12395

Abstract

Fall detection is a very important challenge that affects both elderly people and the carers. Improvements in fall detection would reduce the aid response time. This research focuses on a method for fall detection with a sensor placed on the wrist. Falls are [...] Read more.

Fall detection is a very important challenge that affects both elderly people and the carers. Improvements in fall detection would reduce the aid response time. This research focuses on a method for fall detection with a sensor placed on the wrist. Falls are detected using a published threshold-based solution, although a study on threshold tuning has been carried out. The feature extraction is extended in order to balance the dataset for the minority class. Alternative models have been analyzed to reduce the computational constraints so the solution can be embedded in smart-phones or smart wristbands. Several published datasets have been used in the Materials and Methods section. Although these datasets do not include data from real falls of elderly people, a complete comparison study of fall-related datasets shows statistical differences between the simulated falls and real falls from participants suffering from impairment diseases. Given the obtained results, the rule-based systems represent a promising research line as they perform similarly to neural networks, but with a reduced computational cost. Furthermore, support vector machines performed with a high specificity. However, further research to validate the proposal in real on-line scenarios is needed. Furthermore, a slight improvement should be made to reduce the number of false alarms. Full article

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

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24 pages, 5850 KiB

Open AccessArticle

Cooperative Monocular-Based SLAM for Multi-UAV Systems in GPS-Denied Environments

by Juan-Carlos Trujillo¹

, Rodrigo Munguia¹

, Edmundo Guerra² and Antoni Grau^2,*

¹ Department of Computer Science, CUCEI, University of Guadalajara, Guadalajara 44430, Mexico

² Department of Automatic Control, Technical University of Catalonia UPC, 08034 Barcelona, Spain

Sensors 2018, 18(5), 1351; https://doi.org/10.3390/s18051351 - 26 Apr 2018

Cited by 39 | Viewed by 6278

Abstract

This work presents a cooperative monocular-based SLAM approach for multi-UAV systems that can operate in GPS-denied environments. The main contribution of the work is to show that, using visual information obtained from monocular cameras mounted onboard aerial vehicles flying in formation, the observability [...] Read more.

This work presents a cooperative monocular-based SLAM approach for multi-UAV systems that can operate in GPS-denied environments. The main contribution of the work is to show that, using visual information obtained from monocular cameras mounted onboard aerial vehicles flying in formation, the observability properties of the whole system are improved. This fact is especially notorious when compared with other related visual SLAM configurations. In order to improve the observability properties, some measurements of the relative distance between the UAVs are included in the system. These relative distances are also obtained from visual information. The proposed approach is theoretically validated by means of a nonlinear observability analysis. Furthermore, an extensive set of computer simulations is presented in order to validate the proposed approach. The numerical simulation results show that the proposed system is able to provide a good position and orientation estimation of the aerial vehicles flying in formation. Full article

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

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11 pages, 764 KiB

Open AccessArticle

Fused Microknot Optical Resonators in Folded Photonic Tapers for in-Liquid Durable Sensing

by Alexandra Logvinova^1,*, Shir Shahal², Moti Fridman²

and Yoav Linzon^1,*

¹ School of Mechanical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel

² Faculty of Engineering and the Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel

Sensors 2018, 18(5), 1352; https://doi.org/10.3390/s18051352 - 26 Apr 2018

Cited by 8 | Viewed by 3559

Abstract

Optical microknot fibers (OMFs) serve as localized devices, where photonic resonances (PRs) enable self-interfering elements sensitive to their environment. However, typical fragility and drifting of the knot severely limit the performance and durability of microknots as sensors in aqueous settings. Herein we present [...] Read more.

Optical microknot fibers (OMFs) serve as localized devices, where photonic resonances (PRs) enable self-interfering elements sensitive to their environment. However, typical fragility and drifting of the knot severely limit the performance and durability of microknots as sensors in aqueous settings. Herein we present the fabrication, electrical fusing, preparation, and persistent detection of volatile liquids in multiple wetting–dewetting cycles of volatile compounds and quantify the persistent phase shifts with a simple model relating to the ambient liquid, enabling durable in-liquid sensing employing OMF PRs. Full article

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

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12 pages, 6511 KiB

Open AccessArticle

All-Optical Photoacoustic Sensors for Steel Rebar Corrosion Monitoring

by Cong Du¹, Jones Owusu Twumasi²

, Qixiang Tang², Xu Guo¹, Jingcheng Zhou¹, Tzuyang Yu² and Xingwei Wang^1,*

¹ Department of Electrical and Computer Engineering, University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854, USA

² Department of Civil and Environmental Engineering, University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854, USA

Sensors 2018, 18(5), 1353; https://doi.org/10.3390/s18051353 - 27 Apr 2018

Cited by 19 | Viewed by 6591

Abstract

This article presents an application of an active all-optical photoacoustic sensing system with four elements for steel rebar corrosion monitoring. The sensor utilized a photoacoustic mechanism of gold nanocomposites to generate 8 MHz broadband ultrasound pulses in 0.4 mm compact space. A nanosecond [...] Read more.

This article presents an application of an active all-optical photoacoustic sensing system with four elements for steel rebar corrosion monitoring. The sensor utilized a photoacoustic mechanism of gold nanocomposites to generate 8 MHz broadband ultrasound pulses in 0.4 mm compact space. A nanosecond 532 nm pulsed laser and 400 μm multimode fiber were employed to incite an ultrasound reaction. The fiber Bragg gratings were used as distributed ultrasound detectors. Accelerated corrosion testing was applied to four sections of a single steel rebar with four different corrosion degrees. Our results demonstrated that the mass loss of steel rebar displayed an exponential growth with ultrasound frequency shifts. The sensitivity of the sensing system was such that 0.175 MHz central frequency reduction corresponded to 0.02 g mass loss of steel rebar corrosion. It was proved that the all-optical photoacoustic sensing system can actively evaluate the corrosion of steel rebar via ultrasound spectrum. This multipoint all-optical photoacoustic method is promising for embedment into a concrete structure for distributed corrosion monitoring. Full article

(This article belongs to the Special Issue Optical Sensors Using Microstructured and Photonics Crystal Fibers)

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13 pages, 8057 KiB

Open AccessArticle

An Improved BeiDou-2 Satellite-Induced Code Bias Estimation Method

by Jingyang Fu^*, Guangyun Li and Li Wang

Zhengzhou Institute of Surveying and Mapping Zhengzhou 450000, China

Sensors 2018, 18(5), 1354; https://doi.org/10.3390/s18051354 - 27 Apr 2018

Cited by 2 | Viewed by 4442

Abstract

Different from GPS, GLONASS, GALILEO and BeiDou-3, it is confirmed that the code multipath bias (CMB), which originate from the satellite end and can be over 1 m, are commonly found in the code observations of BeiDou-2 (BDS) IGSO and MEO satellites. In [...] Read more.

Different from GPS, GLONASS, GALILEO and BeiDou-3, it is confirmed that the code multipath bias (CMB), which originate from the satellite end and can be over 1 m, are commonly found in the code observations of BeiDou-2 (BDS) IGSO and MEO satellites. In order to mitigate their adverse effects on absolute precise applications which use the code measurements, we propose in this paper an improved correction model to estimate the CMB. Different from the traditional model which considering the correction values are orbit-type dependent (estimating two sets of values for IGSO and MEO, respectively) and modeling the CMB as a piecewise linear function with a elevation node separation of 10°, we estimate the corrections for each BDS IGSO + MEO satellite on one hand, and a denser elevation node separation of 5° is used to model the CMB variations on the other hand. Currently, the institutions such as IGS-MGEX operate over 120 stations which providing the daily BDS observations. These large amounts of data provide adequate support to refine the CMB estimation satellite by satellite in our improved model. One month BDS observations from MGEX are used for assessing the performance of the improved CMB model by means of precise point positioning (PPP). Experimental results show that for the satellites on the same orbit type, obvious differences can be found in the CMB at the same node and frequency. Results show that the new correction model can improve the wide-lane (WL) ambiguity usage rate for WL fractional cycle bias estimation, shorten the WL and narrow-lane (NL) time to first fix (TTFF) in PPP ambiguity resolution (AR) as well as improve the PPP positioning accuracy. With our improved correction model, the usage of WL ambiguity is increased from 94.1% to 96.0%, the WL and NL TTFF of PPP AR is shorten from 10.6 to 9.3 min, 67.9 to 63.3 min, respectively, compared with the traditional correction model. In addition, both the traditional and improved CMB model have a better performance in these aspects compared with the model which does not account for the CMB correction. Full article

(This article belongs to the Collection Positioning and Navigation)

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20 pages, 5307 KiB

Open AccessArticle

Feasibility Study on S-Band Microwave Radiation and 3D-Thermal Infrared Imaging Sensor-Aided Recognition of Polymer Materials from End-of-Life Vehicles

by Jiu Huang^1,2,*, Zhuangzhuang Zhu¹, Chuyuan Tian¹ and Zhengfu Bian¹

¹ School of Environment Science and Spatial Informatics, China University of Mining and Technology, Xuzhou 221116, China

² State Key Laboratory for Geomechnics and Deep Underground Engineering, Xuzhou 221116, China

Sensors 2018, 18(5), 1355; https://doi.org/10.3390/s18051355 - 27 Apr 2018

Viewed by 3947

Abstract

With the increase the worldwide consumption of vehicles, end-of-life vehicles (ELVs) have kept rapidly increasing in the last two decades. Metallic parts and materials of ELVs can be easily reused and recycled, but the automobile shredder residues (ASRs), of which elastomer and plastic [...] Read more.

With the increase the worldwide consumption of vehicles, end-of-life vehicles (ELVs) have kept rapidly increasing in the last two decades. Metallic parts and materials of ELVs can be easily reused and recycled, but the automobile shredder residues (ASRs), of which elastomer and plastic materials make up the vast majority, are difficult to recycle. ASRs are classified as hazardous materials in the main industrial countries, and are required to be materially recycled up to 85–95% by mass until 2020. However, there is neither sufficient theoretical nor practical experience for sorting ASR polymers. In this research, we provide a novel method by using S-Band microwave irradiation together with 3D scanning as well as infrared thermal imaging sensors for the recognition and sorting of typical plastics and elastomers from the ASR mixture. In this study, an industrial magnetron array with 2.45 GHz irradiation was utilized as the microwave source. Seven kinds of ELV polymer (PVC, ABS, PP, EPDM, NBR, CR, and SBR) crushed scrap residues were tested. After specific power microwave irradiation for a certain time, the tested polymer materials were heated up to different extents corresponding to their respective sensitivities to microwave irradiation. Due to the variations in polymer chemical structure and additive agents, polymers have different sensitivities to microwave radiation, which leads to differences in temperature rises. The differences of temperature increase were obtained by a thermal infrared sensor, and the position and geometrical features of the tested scraps were acquired by a 3D imaging sensor. With this information, the scrap material could be recognized and then sorted. The results showed that this method was effective when the tested polymer materials were heated up to more than 30 °C. For full recognition of the tested polymer scraps, the minimum temperature variations of 5 °C and 10.5 °C for plastics and elastomers were needed, respectively. The sorting efficiency was independent of particle sizes but depended on the power and time of the microwave irradiation. Generally, more than 75% (mass) of the tested polymer materials could be successfully recognized and sorted under an irradiation power of 3 kW. Plastics were much more insensitive to microwave irradiation than elastomers. With this method, the tested mixture of the plastic group (PVC, ABS, PP) and the mixture of elastomer group (EPDM, NBR, CR, and SBR) could be fully separated with an efficiency of 100%. Full article

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

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13 pages, 2436 KiB

Open AccessArticle

On the Nature of Energy-Feasible Wireless Nanosensor Networks

by Sebastian Canovas-Carrasco, Antonio-Javier Garcia-Sanchez^* and Joan Garcia-Haro

Department of Information and Communication Technologies, Technical University of Cartagena, 30202 Cartagena, Spain

Sensors 2018, 18(5), 1356; https://doi.org/10.3390/s18051356 - 27 Apr 2018

Cited by 30 | Viewed by 4270

Abstract

Electromagnetic nanocommunications, understood as the communication between electronic nanoscale devices through electromagnetic waves in the terahertz band, has attracted increasing attention in recent years. In this regard, several solutions have already been proposed. However, many of them do not sufficiently capture the significance [...] Read more.

Electromagnetic nanocommunications, understood as the communication between electronic nanoscale devices through electromagnetic waves in the terahertz band, has attracted increasing attention in recent years. In this regard, several solutions have already been proposed. However, many of them do not sufficiently capture the significance of the limitations in nanodevice energy-gathering and storing capacity. In this paper, we address key factors affecting the energy consumption of nanodevices, highlighting the effect of the communication scheme employed. Then, we also examine how nanodevices are powered, focusing on the main parameters governing the powering nanosystem. Different mathematical expressions are derived to analyze the impact of these parameters on its performance. Based on these expressions, the functionality of a nanogenerator is evaluated to gain insight into the conditions under which a wireless nanosensor network (WNSN) is viable from the energetic point of view. The results reveal that a micrometer-sized piezoelectric system in high-lossy environments (exceeding 100 dB/mm) becomes inoperative for transmission distances over 1.5 mm by its inability to harvest and store the amount of energy required to overcome the path loss. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2018)

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9 pages, 2630 KiB

Open AccessArticle

Colorimetric Humidity Sensor Using Inverse Opal Photonic Gel in Hydrophilic Ionic Liquid

by Seulki Kim¹, Sung Gu Han¹, Young Gook Koh², Hyunjung Lee³

and Wonmok Lee^1,2,*

¹ Department of Chemistry, Sejong University, 209 Neungdong-ro, Gwngjin-gu, Seoul 05006, Korea

² Engain Co. Ltd. Korea Bio Park BLD C-201, Seongnam 13488, Korea

³ School of Advanced Materials Engineering, Kookmin University, 77 Jeongneung-ro, Seongbuk-gu, Seoul 02707, Korea

Sensors 2018, 18(5), 1357; https://doi.org/10.3390/s18051357 - 27 Apr 2018

Cited by 25 | Viewed by 5967

Abstract

We demonstrate a fast response colorimetric humidity sensor using a crosslinked poly(2-hydroxyethyl methacrylate) (PHEMA) in the form of inverse opal photonic gel (IOPG) soaked in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM⁺][BF₄⁻]), a non-volatile hydrophilic room temperature ionic liquid (IL). An evaporative [...] Read more.

We demonstrate a fast response colorimetric humidity sensor using a crosslinked poly(2-hydroxyethyl methacrylate) (PHEMA) in the form of inverse opal photonic gel (IOPG) soaked in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM⁺][BF₄⁻]), a non-volatile hydrophilic room temperature ionic liquid (IL). An evaporative colloidal assembly enabled the fabrication of highly crystalline opal template, and a subsequent photopolymerization of PHEMA followed by solvent-etching and final soaking in IL produced a humidity-responsive IOPG showing highly reflective structural color by Bragg diffraction. Three IOPG sensors with different crosslinking density were fabricated on a single chip, where a lightly crosslinked IOPG exhibited the color change response over entire visible spectrum with respect to the humidity changes from 0 to 80% RH. As the water content increased in IL, thermodynamic interactions between PHEMA and [BMIM⁺][BF₄⁻] became more favorable, to show a red-shifted structural color owing to a longitudinal swelling of IOPG. Highly porous IO structure enabled fast humidity-sensing kinetics with the response times of ~1 min for both swelling and deswelling. Temperature-dependent swelling of PHEMA in [BMIM⁺][BF₄⁻] revealed that the current system follows an upper critical solution temperature (UCST) behavior with the diffraction wavelength change as small as 1% at the temperature changes from 10 °C to 30 °C. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 2715 KiB

Open AccessArticle

Empirical Determination of Efficient Sensing Frequencies for Magnetometer-Based Continuous Human Contact Monitoring

by Seungho Kuk, Junha Kim, Yongtae Park and Hyogon Kim^*

Department of Computer Science and Engineering, Korea University, Anam-Dong, Sungbuk-Gu, Seoul 02841, Korea

Sensors 2018, 18(5), 1358; https://doi.org/10.3390/s18051358 - 27 Apr 2018

Cited by 7 | Viewed by 5214

Abstract

The high linear correlation between the smartphone magnetometer readings in close proximity can be exploited for physical human contact detection, which could be useful for such applications as infectious disease contact tracing or social behavior monitoring. Alternative approaches using other capabilities in smartphones [...] Read more.

The high linear correlation between the smartphone magnetometer readings in close proximity can be exploited for physical human contact detection, which could be useful for such applications as infectious disease contact tracing or social behavior monitoring. Alternative approaches using other capabilities in smartphones have aspects that do not fit well with the human contact detection. Using Wi-Fi or cellular fingerprints have larger localization errors than close human contact distances. Bluetooth beacons could reveal the identity of the transmitter, threatening the privacy of the user. Also, using sensors such as GPS does not work for indoor contacts. However, the magnetometer correlation check works best in human contact distances that matter in infectious disease transmissions or social interactions. The omni-present geomagnetism makes it work both indoors and outdoors, and the measured magnetometer values do not easily reveal the identity and the location of the smartphone. One issue with the magnetometer-based contact detection, however, is the energy consumption. Since the contacts can take place anytime, the magnetometer sensing and recording should be running continuously. Therefore, how we address the energy requirement for the extended and continuous operation can decide the viability of the whole idea. However, then, we note that almost all existing magnetometer-based applications such as indoor location and navigation have used high sensing frequencies, ranging from 10 Hz to 200 Hz. At these frequencies, we measure that the time to complete battery drain in a typical smartphone is shortened by three to twelve hours. The heavy toll raises the question as to whether the magnetometer-based contact detection can avoid such high sensing rates while not losing the contact detection accuracy. In order to answer the question, we conduct a measurement-based study using independently produced magnetometer traces from three different countries. Specifically, we gradually remove high frequency components in the traces, while observing the correlation changes. As a result, we find that the human coexistence detection indeed tends to be no less, if not more, effective at the sampling frequency of 1 Hz or even less. This is because unlike the other applications that require centimeter-level precision, the human contacts detected anywhere within a couple of meters are valid for our purpose. With the typical smartphone battery capacity and at the 1 Hz sensing, the battery consumption is well below an hour, which is smaller by more than two hours compared with 10 Hz sampling and by almost eleven hours compared with 200 Hz sampling. With other tasks running simultaneously on smartphones, the energy saving aspect will only become more critical. Therefore, we conclude that sensing the ambient magnetic field at 1 Hz is sufficient for the human contact monitoring purpose. We expect that this finding will have a significant practicability implication in the smartphone magnetometer-based contact monitoring applications in general. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 16522 KiB

Open AccessArticle

Performance Analysis of Satellite Missions for Multi-Temporal SAR Interferometry

by Fabio Bovenga^1,*

, Antonella Belmonte¹, Alberto Refice¹

, Guido Pasquariello¹

, Raffaele Nutricato², Davide O. Nitti²

and Maria T. Chiaradia³

¹ Research National Council of Italy, ISSIA, 70126 Bari, Italy

² GAP S. R. L., 70125 Bari, Italy

³ Dipartimento di Fisica “M. Merlin”, Politecnico di Bari, 70125 Bari, Italy

Sensors 2018, 18(5), 1359; https://doi.org/10.3390/s18051359 - 27 Apr 2018

Cited by 30 | Viewed by 5000

Abstract

Multi-temporal InSAR (MTI) applications pose challenges related to the availability of coherent scattering from the ground surface, the complexity of the ground deformations, atmospheric artifacts, and visibility problems related to ground elevation. Nowadays, several satellite missions are available providing interferometric SAR data at [...] Read more.

Multi-temporal InSAR (MTI) applications pose challenges related to the availability of coherent scattering from the ground surface, the complexity of the ground deformations, atmospheric artifacts, and visibility problems related to ground elevation. Nowadays, several satellite missions are available providing interferometric SAR data at different wavelengths, spatial resolutions, and revisit time. A new and interesting opportunity is provided by Sentinel-1, which has a spatial resolution comparable to that of previous ESA C-band sensors, and revisit times improved by up to 6 days. According to these different SAR space-borne missions, the present work discusses current and future opportunities of MTI applications in terms of ground instability monitoring. Issues related to coherent target detection, mean velocity precision, and product geo-location are addressed through a simple theoretical model assuming backscattering mechanisms related to point scatterers. The paper also presents an example of a multi-sensor ground instability investigation over Lesina Marina, a village in Southern Italy lying over a gypsum diapir, where a hydration process, involving the underlying anhydride, causes a smooth uplift and the formation of scattered sinkholes. More than 20 years of MTI SAR data have been processed, coming from both legacy ERS and ENVISAT missions, and latest-generation RADARSAT-2, COSMO-SkyMed, and Sentinel-1A sensors. Results confirm the presence of a rather steady uplift process, with limited to null variations throughout the whole monitored time-period. 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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16 pages, 12439 KiB

Open AccessArticle

A Coarse-to-Fine Geometric Scale-Invariant Feature Transform for Large Size High Resolution Satellite Image Registration

by Xueli Chang^1,2, Siliang Du³, Yingying Li⁴ and Shenghui Fang^3,*

¹ School of Resource and Environmental Sciences, Wuhan University, Wuhan 430074, China

² Collaborative Innovation Center Of Geospatial Technology, Wuhan University, Wuhan 430074, China

³ School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430074, China

⁴ Institute of Remote Sensing Information of Beijing, Beijing 100000, China

Sensors 2018, 18(5), 1360; https://doi.org/10.3390/s18051360 - 27 Apr 2018

Cited by 25 | Viewed by 4673

Abstract

Large size high resolution (HR) satellite image matching is a challenging task due to local distortion, repetitive structures, intensity changes and low efficiency. In this paper, a novel matching approach is proposed for the large size HR satellite image registration, which is based [...] Read more.

Large size high resolution (HR) satellite image matching is a challenging task due to local distortion, repetitive structures, intensity changes and low efficiency. In this paper, a novel matching approach is proposed for the large size HR satellite image registration, which is based on coarse-to-fine strategy and geometric scale-invariant feature transform (SIFT). In the coarse matching step, a robust matching method scale restrict (SR) SIFT is implemented at low resolution level. The matching results provide geometric constraints which are then used to guide block division and geometric SIFT in the fine matching step. The block matching method can overcome the memory problem. In geometric SIFT, with area constraints, it is beneficial for validating the candidate matches and decreasing searching complexity. To further improve the matching efficiency, the proposed matching method is parallelized using OpenMP. Finally, the sensing image is rectified to the coordinate of reference image via Triangulated Irregular Network (TIN) transformation. Experiments are designed to test the performance of the proposed matching method. The experimental results show that the proposed method can decrease the matching time and increase the number of matching points while maintaining high registration accuracy. Full article

(This article belongs to the Special Issue Remote Sensing and Its Applications in the Bio-Geosciences)

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15 pages, 7192 KiB

Open AccessFeature PaperArticle

Optical Detection of Ketoprofen by Its Electropolymerization on an Indium Tin Oxide-Coated Optical Fiber Probe

by Robert Bogdanowicz¹, Paweł Niedziałkowski²

, Michał Sobaszek¹, Dariusz Burnat³

, Wioleta Białobrzeska², Zofia Cebula², Petr Sezemsky⁴, Marcin Koba^3,5, Vitezslav Stranak⁴, Tadeusz Ossowski² and Mateusz Śmietana^3,*

¹ Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland

² Department of Analytical Chemistry, Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, 80-308 Gdansk, Poland

³ Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa 75, 00-662 Warszawa, Poland

⁴ Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Branisovska 1760, 370 05 Ceske Budejovice, Czech Republic

⁵ National Institute of Telecommunications, Szachowa 1, 04-894 Warszawa, Poland

Sensors 2018, 18(5), 1361; https://doi.org/10.3390/s18051361 - 27 Apr 2018

Cited by 27 | Viewed by 5615

Abstract

In this work an application of optical fiber sensors for real-time optical monitoring of electrochemical deposition of ketoprofen during its anodic oxidation is discussed. The sensors were fabricated by reactive magnetron sputtering of indium tin oxide (ITO) on a 2.5 cm-long core of [...] Read more.

In this work an application of optical fiber sensors for real-time optical monitoring of electrochemical deposition of ketoprofen during its anodic oxidation is discussed. The sensors were fabricated by reactive magnetron sputtering of indium tin oxide (ITO) on a 2.5 cm-long core of polymer-clad silica fibers. ITO tuned in optical properties and thickness allows for achieving a lossy-mode resonance (LMR) phenomenon and it can be simultaneously applied as an electrode in an electrochemical setup. The ITO-LMR electrode allows for optical monitoring of changes occurring at the electrode during electrochemical processing. The studies have shown that the ITO-LMR sensor’s spectral response strongly depends on electrochemical modification of its surface by ketoprofen. The effect can be applied for real-time detection of ketoprofen. The obtained sensitivities reached over 1400 nm/M (nm·mg⁻¹·L) and 16,400 a.u./M (a.u.·mg⁻¹·L) for resonance wavelength and transmission shifts, respectively. The proposed method is a valuable alternative for the analysis of ketoprofen within the concentration range of 0.25–250 μg mL⁻¹, and allows for its determination at therapeutic and toxic levels. The proposed novel sensing approach provides a promising strategy for both optical and electrochemical detection of electrochemical modifications of ITO or its surface by various compounds. Full article

(This article belongs to the Special Issue Optical Methods in Sensing and Imaging for Medical and Biological Applications)

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17 pages, 5365 KiB

Open AccessArticle

Thermochromic Polymer Film Sensors for Detection of Incipient Thermal Damage in Carbon Fiber–Epoxy Composites

by Ryan Toivola^*

, Sei-Hum Jang, Shawn Baker, Alex K. -Y. Jen and Brian D. Flinn

Department of Materials Science & Engineering, University of Washington, Seattle, WA 98195, USA

Sensors 2018, 18(5), 1362; https://doi.org/10.3390/s18051362 - 27 Apr 2018

Cited by 7 | Viewed by 5156

Abstract

Carbon fiber–epoxy composites have become prevalent in the aerospace industry where mechanical properties and light weight are at a premium. The significant non-destructive evaluation challenges of composites require new solutions, especially in detecting early-stage, or incipient, thermal damage. The initial stages of thermal [...] Read more.

Carbon fiber–epoxy composites have become prevalent in the aerospace industry where mechanical properties and light weight are at a premium. The significant non-destructive evaluation challenges of composites require new solutions, especially in detecting early-stage, or incipient, thermal damage. The initial stages of thermal damage are chemical rather than physical, and can cause significant reduction in mechanical properties well before physical damage becomes detectable in ultrasonic testing. Thermochromic fluorescent probe molecules have the potential to sense incipient thermal damage more accurately than traditional inspection methods. We have designed a molecule which transitions from a colorless, non-fluorescent state to a colorful, highly fluorescent state when exposed to temperature–time combinations that can cause damage in composites. Moreover, this molecule can be dispersed in a polymer film and attached to composite parts as a removable sensor. This work presents an evaluation of the sensor performance of this thermochromic film in comparison to ultrasonic C-scan as a method to detect incipient thermal damage in one of the most widely used carbon fiber–epoxy composite systems. Composite samples exposed to varying thermal exposures were used to evaluate the fluorescent thermal sensor films, and the results are compared to the results of ultrasonic imaging and short-beam shear tests for interlaminar shear strength. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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12 pages, 2448 KiB

Open AccessArticle

Long-Period Gratings in Highly Germanium-Doped, Single-Mode Optical Fibers for Sensing Applications

by Sebastian Schlangen^1,*, Kort Bremer¹, Yulong Zheng¹, Sebastian Böhm², Michael Steinke², Felix Wellmann², Jörg Neumann², Bernhard Roth¹

and Ludger Overmeyer¹

¹ Hannover Centre for Optical Technologies, Leibniz Universität Hannover, Nienburger Str. 17, 30167 Hannover, Germany

² Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany

Sensors 2018, 18(5), 1363; https://doi.org/10.3390/s18051363 - 27 Apr 2018

Cited by 12 | Viewed by 6455

Abstract

Long-period fiber gratings (LPGs) are well known for their sensitivity to external influences, which make them interesting for a large number of sensing applications. For these applications, fibers with a high numerical aperture (i.e., fibers with highly germanium (Ge)-doped fused silica fiber cores) [...] Read more.

Long-period fiber gratings (LPGs) are well known for their sensitivity to external influences, which make them interesting for a large number of sensing applications. For these applications, fibers with a high numerical aperture (i.e., fibers with highly germanium (Ge)-doped fused silica fiber cores) are more attractive since they are intrinsically photosensitive, as well as less sensitive to bend- and microbend-induced light attenuations. In this work, we introduce a novel method to inscribe LPGs into highly Ge-doped, single-mode fibers. By tapering the optical fiber, and thus, tailoring the effective indices of the core and cladding modes, for the first time, an LPG was inscribed into such fibers using the amplitude mask technique and a KrF excimer laser. Based on this novel method, sensitive LPG-based fiber optic sensors only a few millimeters in length can be incorporated in bend-insensitive fibers for use in various monitoring applications. Moreover, by applying the described inscription method, the LPG spectrum can be influenced and tailored according to the specific demands of a particular application. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)

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21 pages, 405 KiB

Open AccessArticle

Trusted Operations on Sensor Data ^†

by Hassaan Janjua^*

, Wouter Joosen, Sam Michiels and Danny Hughes

¹ imec-DistriNet-KU Leuven, Celestijnenlaan 200A, B-3001 Heverlee, Belgium

^† This article is an expanded version of the conference paper “Trusted Operations on Mobile Phones”-MobiQuitous 2017.

Sensors 2018, 18(5), 1364; https://doi.org/10.3390/s18051364 - 27 Apr 2018

Cited by 9 | Viewed by 4891

Abstract

The widespread use of mobile devices has allowed the development of participatory sensing systems that capture various types of data using the existing or external sensors attached to mobile devices. Gathering data from such anonymous sources requires a mechanism to establish the integrity [...] Read more.

The widespread use of mobile devices has allowed the development of participatory sensing systems that capture various types of data using the existing or external sensors attached to mobile devices. Gathering data from such anonymous sources requires a mechanism to establish the integrity of sensor readings. In many cases, sensor data need to be preprocessed on the device itself before being uploaded to the target server while ensuring the chain of trust from capture to the delivery of the data. This can be achieved by a framework that provides a means to implement arbitrary operations to be performed on trusted sensor data, while guaranteeing the security and integrity of the data. This paper presents the design and implementation of a framework that allows the capture of trusted sensor data from both external and internal sensors on a mobile phone along with the development of trusted operations on sensor data while providing a mechanism for performing predefined operations on the data such that the chain of trust is maintained. The evaluation shows that the proposed system ensures the security and integrity of sensor data with minimal performance overhead. Full article

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

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13 pages, 4998 KiB

Open AccessArticle

Residential Consumer-Centric Demand-Side Management Based on Energy Disaggregation-Piloting Constrained Swarm Intelligence: Towards Edge Computing

by Yu-Hsiu Lin^*

and Yu-Chen Hu

Department of Computer Science and Information Management, Providence University, No. 200, Sec. 7, Taiwan Boulevard, Shalu Dist., Taichung City 43301, Taiwan

Sensors 2018, 18(5), 1365; https://doi.org/10.3390/s18051365 - 27 Apr 2018

Cited by 55 | Viewed by 6148

Abstract

The emergence of smart Internet of Things (IoT) devices has highly favored the realization of smart homes in a down-stream sector of a smart grid. The underlying objective of Demand Response (DR) schemes is to actively engage customers to modify their energy consumption [...] Read more.

The emergence of smart Internet of Things (IoT) devices has highly favored the realization of smart homes in a down-stream sector of a smart grid. The underlying objective of Demand Response (DR) schemes is to actively engage customers to modify their energy consumption on domestic appliances in response to pricing signals. Domestic appliance scheduling is widely accepted as an effective mechanism to manage domestic energy consumption intelligently. Besides, to residential customers for DR implementation, maintaining a balance between energy consumption cost and users’ comfort satisfaction is a challenge. Hence, in this paper, a constrained Particle Swarm Optimization (PSO)-based residential consumer-centric load-scheduling method is proposed. The method can be further featured with edge computing. In contrast with cloud computing, edge computing—a method of optimizing cloud computing technologies by driving computing capabilities at the IoT edge of the Internet as one of the emerging trends in engineering technology—addresses bandwidth-intensive contents and latency-sensitive applications required among sensors and central data centers through data analytics at or near the source of data. A non-intrusive load-monitoring technique proposed previously is utilized to automatic determination of physical characteristics of power-intensive home appliances from users’ life patterns. The swarm intelligence, constrained PSO, is used to minimize the energy consumption cost while considering users’ comfort satisfaction for DR implementation. The residential consumer-centric load-scheduling method proposed in this paper is evaluated under real-time pricing with inclining block rates and is demonstrated in a case study. The experimentation reported in this paper shows the proposed residential consumer-centric load-scheduling method can re-shape loads by home appliances in response to DR signals. Moreover, a phenomenal reduction in peak power consumption is achieved by 13.97%. Full article

(This article belongs to the Special Issue Smart Homes)

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13 pages, 4022 KiB

Open AccessArticle

Method for Compensating Signal Attenuation Using Stepped-Frequency Ground Penetrating Radar

by Tao Liu^*

, Yutao Zhu and Yi Su

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

Sensors 2018, 18(5), 1366; https://doi.org/10.3390/s18051366 - 27 Apr 2018

Cited by 9 | Viewed by 6468

Abstract

Ground penetrating radar (GPR) is a subsurface remote sensor that allows the user to detect, classify, and identify the buried target and structures. The radar signals are rapidly attenuated as they propagate into the ground; therefore, attenuation compensation is necessary for the visualization [...] Read more.

Ground penetrating radar (GPR) is a subsurface remote sensor that allows the user to detect, classify, and identify the buried target and structures. The radar signals are rapidly attenuated as they propagate into the ground; therefore, attenuation compensation is necessary for the visualization of the buried targets from GPR data. In this work, we developed a novel attenuation compensation approach based on the recently developed stepped-frequency continuous wave (SFCW) GPR system, which is a frequency domain sampling system with improved performance in dynamic range, sensitivity, and anti-interference ability. Because the regularly used time-varying gain function for compensating the attenuation of impulse GPR data does not make full use of the advancement of the SFCW modulation, an alternative procedure is proposed herein. The new approach is based the SFCW mechanism, and aims at improving the visualization of deeper targets by compensating the SFCW GPR signal attenuation. We first present the attenuation mode of the SFCW GPR echo, from which an inverse attenuation function is derived to compensate the amplitude loss. For the field measurement where the theoretical inverse attenuation function is difficult to achieve, we introduced a pseudo time–frequency distribution for estimating the inverse attenuation function. A procedure for amplitude attenuation has also been developed. Testing with both synthetic and experimental data return a good reconstruction of the signal amplitude, subsequently improving the ability for visualizing and detecting deeper targets. Full article

(This article belongs to the Section Remote Sensors)

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11 pages, 958 KiB

Open AccessArticle

Economic Analysis of the Reduction of Blood Transfusions during Surgical Procedures While Continuous Hemoglobin Monitoring Is Used

by Borja Ribed-Sánchez^1,2,*, Cristina González-Gaya¹

, Sara Varea-Díaz³, Carlos Corbacho-Fabregat⁴, Jaime Pérez-Oteyza⁵

and Cristóbal Belda-Iniesta⁶

¹ Department of Manufacturing Engineering, ETSII-Universidad Nacional de Educación a Distancia (UNED), C/Juan del Rosal 12, 28040 Madrid, Spain

² Department of Corporate Resources, HM Hospitales, Plaza Conde Valle de Suchil 2, 28015 Madrid Spain

³ Department of Hematology, HM Hospitales, Plaza Conde Valle de Suchil 2, 28015 Madrid, Spain

⁴ Department of Anesthesia, HM Hospitales, Plaza Conde Valle de Suchil 2, 28015 Madrid, Spain

⁵ School of Medicine, CEU San Pablo University, Urb. Montepríncipe, Ctra. Boadilla del Monte, Km. 5.300, 28925 Madrid, Spain

⁶ Department of R&D, HM Hospitales, Plaza Conde Valle de Suchil 2, 28015 Madrid, Spain

Sensors 2018, 18(5), 1367; https://doi.org/10.3390/s18051367 - 27 Apr 2018

Cited by 15 | Viewed by 4715

Abstract

Background: Two million transfusions are performed in Spain every year. These come at a high economic price for the health system, increasing the morbidity and mortality rates. The way of obtaining the hemoglobin concentration value is via invasive and intermittent methods, the results [...] Read more.

Background: Two million transfusions are performed in Spain every year. These come at a high economic price for the health system, increasing the morbidity and mortality rates. The way of obtaining the hemoglobin concentration value is via invasive and intermittent methods, the results of which take time to obtain. The drawbacks of this method mean that some transfusions are unnecessary. New continuous noninvasive hemoglobin measurement technology can save unnecessary transfusions. Methods: A prospective study was carried out with a historical control of two homogeneous groups. The control group used the traditional hemoglobin measurement methodology. The experimental group used the new continuous hemoglobin measurement technology. The difference was analyzed by comparing the transfused units of the groups. The economic savings was calculated by multiplying the cost of a transfusion by the difference in units, taking into account measurement costs. Results: The percentage of patients needing a transfusion decreased by 7.4%, and the number of transfused units per patient by 12.56%. Economic savings per patient were €20.59. At the national level, savings were estimated to be 13,500 transfusions (€1.736 million). Conclusions: Constant monitoring of the hemoglobin level significantly reduces the need for blood transfusions. By using this new measurement technology, health care facilities can significantly reduce costs and improve care quality. Full article

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

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15 pages, 6906 KiB

Open AccessArticle

Displacements Study of an Earth Fill Dam Based on High Precision Geodetic Monitoring and Numerical Modeling

by Luis Enrique Acosta¹, M. Clara De Lacy^2,3,*

, M. Isabel Ramos^2,3, Juan Pedro Cano⁴, Antonio Manuel Herrera², Manuel Avilés² and Antonio José Gil^2,3

¹ Departamento de Construcciones, Universidad de Holguín, Holguín 80100, Cuba

² Departamento de Ingeniería Cartográfica, Geodesia y Fotogrametría, Universidad de Jaén, Jaen 23071, Spain

³ CEACTierra—Centro de Estudios Avanzados de Ciencias de la Tierra, Jaen 23071, Spain

⁴ 4D Geoservices, Jaen 23008, Spain

Sensors 2018, 18(5), 1369; https://doi.org/10.3390/s18051369 - 27 Apr 2018

Cited by 30 | Viewed by 6678

Abstract

The aim of this paper is to study the behavior of an earth fill dam, analyzing the deformations determined by high precision geodetic techniques and those obtained by the Finite Element Method (FEM). A large number of control points were established around the [...] Read more.

The aim of this paper is to study the behavior of an earth fill dam, analyzing the deformations determined by high precision geodetic techniques and those obtained by the Finite Element Method (FEM). A large number of control points were established around the area of the dam, and the measurements of their displacements took place during several periods. In this study, high-precision leveling and GNSS (Global Navigation Satellite System) techniques were used to monitor vertical and horizontal displacements respectively. Seven surveys were carried out: February and July 2008, March and July 2013, August 2014, September 2015 and September 2016. Deformations were predicted, taking into account the general characteristics of an earth fill dam. A comparative evaluation of the results derived from predicted (FEM) and observed deformations shows the differences on average being 20 cm for vertical displacements, and 6 cm for horizontal displacements at the crest. These differences are probably due to the simplifications assumed during the FEM modeling process: critical sections are considered homogeneous along their longitude, and the properties of the materials were established according to the general characteristics of an earth fill dam. These characteristics were taken from the normative and similar studies in the country. This could also be due to the geodetic control points being anchored in the superficial layer of the slope when the construction of the dam was finished. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 2880 KiB

Open AccessArticle

Adaptive ISAR Imaging of Maneuvering Targets Based on a Modified Fourier Transform

by Binbin Wang^1,*

, Shiyou Xu¹, Wenzhen Wu¹, Pengjiang Hu¹ and Zengping Chen^1,2

¹ Science and Technology on Automatic Target Recognition Laboratory, National University of Defense Technology, Changsha 410073, China

² College of Information Engineering, Shenzhen University, Shenzhen 518060, China

Sensors 2018, 18(5), 1370; https://doi.org/10.3390/s18051370 - 27 Apr 2018

Cited by 19 | Viewed by 4207

Abstract

Focusing on the inverse synthetic aperture radar (ISAR) imaging of maneuvering targets, this paper presents a new imaging method which works well when the target’s maneuvering is not too severe. After translational motion compensation, we describe the equivalent rotation of maneuvering targets by [...] Read more.

Focusing on the inverse synthetic aperture radar (ISAR) imaging of maneuvering targets, this paper presents a new imaging method which works well when the target’s maneuvering is not too severe. After translational motion compensation, we describe the equivalent rotation of maneuvering targets by two variables—the relative chirp rate of the linear frequency modulated (LFM) signal and the Doppler focus shift. The first variable indicates the target’s motion status, and the second one represents the possible residual error of the translational motion compensation. With them, a modified Fourier transform matrix is constructed and then used for cross-range compression. Consequently, the imaging of maneuvering is converted into a two-dimensional parameter optimization problem in which a stable and clear ISAR image is guaranteed. A gradient descent optimization scheme is employed to obtain the accurate relative chirp rate and Doppler focus shift. Moreover, we designed an efficient and robust initialization process for the gradient descent method, thus, the well-focused ISAR images of maneuvering targets can be achieved adaptively. Human intervention is not needed, and it is quite convenient for practical ISAR imaging systems. Compared to precedent imaging methods, the new method achieves better imaging quality under reasonable computational cost. Simulation results are provided to validate the effectiveness and advantages of the proposed method. Full article

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

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25 pages, 2054 KiB

Open AccessArticle

Unsupervised Learning for Monaural Source Separation Using Maximization–Minimization Algorithm with Time–Frequency Deconvolution ^†

by Wai Lok Woo^1,*

, Bin Gao²

, Ahmed Bouridane³, Bingo Wing-Kuen Ling⁴ and Cheng Siong Chin⁵

¹ School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, UK

² School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China

³ Department of Computer and Information Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, UK

⁴ Faculty of Information Engineering, Guangdong University of Technology, Guangzhou 510006, China

⁵ Faculty of Science Agriculture and Engineering, Newcastle University, Singapore 599493, Singapore

^† This paper is an extended version of Yu, K.; Woo, W.L.; Dlay, S.S. Variational regularized two-dimensional nonnegative matrix factorization with the flexible β4-divergence for single channel source separation. In Proceedings of the 2nd IET International Conference in Intelligent Signal Processing (ISP), London, UK, 1–2 December 2015.

Sensors 2018, 18(5), 1371; https://doi.org/10.3390/s18051371 - 27 Apr 2018

Cited by 10 | Viewed by 5155

Abstract

This paper presents an unsupervised learning algorithm for sparse nonnegative matrix factor time–frequency deconvolution with optimized fractional

β

-divergence. The

β

-divergence is a group of cost functions parametrized by a single parameter

β

. The Itakura–Saito divergence, Kullback–Leibler divergence and Least Square [...] Read more.

This paper presents an unsupervised learning algorithm for sparse nonnegative matrix factor time–frequency deconvolution with optimized fractional

β

-divergence. The

β

-divergence is a group of cost functions parametrized by a single parameter

β

. The Itakura–Saito divergence, Kullback–Leibler divergence and Least Square distance are special cases that correspond to

β = 0, 1, 2

, respectively. This paper presents a generalized algorithm that uses a flexible range of

β

that includes fractional values. It describes a maximization–minimization (MM) algorithm leading to the development of a fast convergence multiplicative update algorithm with guaranteed convergence. The proposed model operates in the time–frequency domain and decomposes an information-bearing matrix into two-dimensional deconvolution of factor matrices that represent the spectral dictionary and temporal codes. The deconvolution process has been optimized to yield sparse temporal codes through maximizing the likelihood of the observations. The paper also presents a method to estimate the fractional

β

value. The method is demonstrated on separating audio mixtures recorded from a single channel. The paper shows that the extraction of the spectral dictionary and temporal codes is significantly more efficient by using the proposed algorithm and subsequently leads to better source separation performance. Experimental tests and comparisons with other factorization methods have been conducted to verify its efficacy. Full article

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

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18 pages, 2203 KiB

Open AccessArticle

Integration of 24 Feature Types to Accurately Detect and Predict Seizures Using Scalp EEG Signals

by Yinda Zhang^†, Shuhan Yang^†, Yang Liu, Yexian Zhang, Bingfeng Han and Fengfeng Zhou^*

¹ College of Computer Science and Technology, and Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, Jilin University, Changchun 130012, China

^† The first two authors contributed equally to this work.

Sensors 2018, 18(5), 1372; https://doi.org/10.3390/s18051372 - 28 Apr 2018

Cited by 54 | Viewed by 9128

Abstract

The neurological disorder epilepsy causes substantial problems to the patients with uncontrolled seizures or even sudden deaths. Accurate detection and prediction of epileptic seizures will significantly improve the life quality of epileptic patients. Various feature extraction algorithms were proposed to describe the EEG [...] Read more.

The neurological disorder epilepsy causes substantial problems to the patients with uncontrolled seizures or even sudden deaths. Accurate detection and prediction of epileptic seizures will significantly improve the life quality of epileptic patients. Various feature extraction algorithms were proposed to describe the EEG signals in frequency or time domains. Both invasive intracranial and non-invasive scalp EEG signals have been screened for the epileptic seizure patterns. This study extracted a comprehensive list of 24 feature types from the scalp EEG signals and found 170 out of the 2794 features for an accurate classification of epileptic seizures. An accuracy (Acc) of 99.40% was optimized for detecting epileptic seizures from the scalp EEG signals. A balanced accuracy (bAcc) was calculated as the average of sensitivity and specificity and our seizure detection model achieved 99.61% in bAcc. The same experimental procedure was applied to predict epileptic seizures in advance, and the model achieved Acc = 99.17% for predicting epileptic seizures 10 s before happening. Full article

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

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19 pages, 3903 KiB

Open AccessArticle

Hybrid Multi-Channel MAC Protocol for WBANs with Inter-WBAN Interference Mitigation

by Thien Thi Thanh Le and Sangman Moh^*

Department of Computer Engineering, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju 61452, Korea

Sensors 2018, 18(5), 1373; https://doi.org/10.3390/s18051373 - 28 Apr 2018

Cited by 31 | Viewed by 4210

Abstract

Herein, we propose a hybrid multi-channel medium access control (HM-MAC) protocol for wireless body area networks (WBANs) that mitigates inter-WBAN interference significantly. In HM-MAC, a superframe consists of a random access phase and a scheduled access phase. That is, a carrier sensing multiple [...] Read more.

Herein, we propose a hybrid multi-channel medium access control (HM-MAC) protocol for wireless body area networks (WBANs) that mitigates inter-WBAN interference significantly. In HM-MAC, a superframe consists of a random access phase and a scheduled access phase. That is, a carrier sensing multiple access with collision avoidance (CSMA/CA) phase and a time division multiple access (TDMA) phase are included in a superframe. The random access phase allows higher-priority users to transmit data packets with low latency and high reliability. The retransmission of data packets is also performed in the random access phase. The periodic data are transmitted in the scheduled phase, resulting in no contention and high reliability. A channel selection algorithm is also proposed to avoid collision between neighboring WBANs. The HM-MAC protocol allows multiple transmissions simultaneously on different channels, resulting in high throughput and low collision. The sensor nodes update idle channels by listening to the beacon signal; consequently, the sensor nodes can change the working channel to reduce inter-WBAN interference. According to our simulation results, HM-MAC achieves a higher packet delivery ratio and higher throughput with lower energy consumption than the conventional scheme in multi-WBAN scenarios. HM-MAC also causes lower end-to-end delays for higher-priority users. Full article

(This article belongs to the Section Sensor Networks)

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12 pages, 375 KiB

Open AccessArticle

Using Sleep Time Data from Wearable Sensors for Early Detection of Migraine Attacks

by Pekka Siirtola^*

, Heli Koskimäki, Henna Mönttinen and Juha Röning

Biomimetics and Intelligent Systems Group, University of Oulu, P.O. BOX 4500, Oulu FI-90014, Finland

Sensors 2018, 18(5), 1374; https://doi.org/10.3390/s18051374 - 28 Apr 2018

Cited by 36 | Viewed by 9576

Abstract

The migraine is a chronic, incapacitating neurovascular disorder, characterized by attacks of severe headache and autonomic nervous system dysfunction. Among the working age population, the costs of migraine are 111 billion euros in Europe alone. The early detection of migraine attacks would reduce [...] Read more.

The migraine is a chronic, incapacitating neurovascular disorder, characterized by attacks of severe headache and autonomic nervous system dysfunction. Among the working age population, the costs of migraine are 111 billion euros in Europe alone. The early detection of migraine attacks would reduce these costs, as it would shorten the migraine attack by enabling correct timing when taking preventive medication. In this article, whether it is possible to detect migraine attacks beforehand using wearable sensors is studied, and t preliminary results about how accurate the recognition can be are provided. The data for the study were collected from seven study subjects using a wrist-worn Empatica E4 sensor, which measures acceleration, galvanic skin response, blood volume pulse, heart rate and heart rate variability, and temperature. Only sleep time data were used in this study. A novel method to increase the number of training samples is introduced, and the results show that, using personal recognition models and quadratic discriminant analysis as a classifier, balanced accuracy for detecting attacks one night prior is over 84%. While this detection rate is high, the results also show that balance accuracy varies greatly between study subjects, which shows how complicated the problem actually is. However, at this point, the results are preliminary as the data set contains only seven study subjects, so these do not cover all migraine types. If the findings of this article can be confirmed in a larger population, it may potentially contribute to early diagnosis of migraine attacks. Full article

(This article belongs to the Special Issue Wearable and Ambient Sensors for Healthcare and Wellness Applications 2018)

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13 pages, 2107 KiB

Open AccessArticle

Sensor Fault Detection and System Reconfiguration for DC-DC Boost Converter

by Jian Li, Zhigang Zhang and Bo Li^*

School of Automation Engineering, Northeast Electric Power University, Jilin 132012, China

Sensors 2018, 18(5), 1375; https://doi.org/10.3390/s18051375 - 28 Apr 2018

Cited by 11 | Viewed by 4213

Abstract

This paper presents a effective sensor fault detection and system reconfiguration approach for DC-DC Boost converter. We consider to design a Luenberger observer to solve the problem of the sensor fault detection of the DC-DC Boost converter. We establish mathematical model according to [...] Read more.

This paper presents a effective sensor fault detection and system reconfiguration approach for DC-DC Boost converter. We consider to design a Luenberger observer to solve the problem of the sensor fault detection of the DC-DC Boost converter. We establish mathematical model according to the state of the switch . Luenberger observer is designed to produce residual errors and analyse faults. We detect three types of sensor faults online and compare residuals with thresholds. The system is able to maintain stability by taking system reconfiguration approach. The effectiveness of this approach is demonstrated by simulations. Full article

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

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10 pages, 3081 KiB

Open AccessArticle

Self-Reference Refractive Index Sensor Based on Independently Controlled Double Resonances in Side-Coupled U-Shaped Resonators

by Xiaobin Ren¹, Kun Ren^2,*

and Chengguo Ming¹

¹ School of Science, Tianjin University of Science and Technology, Tianjin 300222, China

² College of Precision Instrument and Opto-Electronics Engineering, Key Laboratory of Opto-Electronics Information Technology (Tianjin University), Ministry of Education, Tianjin 300072, China

Sensors 2018, 18(5), 1376; https://doi.org/10.3390/s18051376 - 28 Apr 2018

Cited by 34 | Viewed by 4284

Abstract

A plasmonic, refractive, index nanosensor is investigated theoretically and numerically in two U-shaped cavities side-coupled to a metal–dielectric–metal (MDM) waveguide. A transparency window between two transmission dips is observed. The physical origin of the transmission phenomenon is revealed by mapping the magnetic field [...] Read more.

A plasmonic, refractive, index nanosensor is investigated theoretically and numerically in two U-shaped cavities side-coupled to a metal–dielectric–metal (MDM) waveguide. A transparency window between two transmission dips is observed. The physical origin of the transmission phenomenon is revealed by mapping the magnetic field distribution. Independent double resonances are realized through the proposed design. Double resonances showed diverse responses to the variations of the structural dimensions. In particular, they presented different dependences on a refraction index of the medium in an individual resonator. One resonance exhibited a remarkable shift with the increase of the refraction index; however, the other resonance remained unchanged. On the basis of this unique characteristic of differing sensitivities, self-reference sensing is discussed. The nanosensor yielded a high sensitivity of 917 nm/RIU and a figure of merit of 180 RIU⁻¹. This work is helpful in terms of the design of on-chip optical sensors with high sensitivity and improved detection accuracy in complicated environments. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 9390 KiB

Open AccessFeature PaperArticle

Damage Detection of a Concrete Column Subject to Blast Loads Using Embedded Piezoceramic Transducers

by Kai Xu¹

, Qingshan Deng¹, Lujun Cai^2,*, Siuchun Ho³ and Gangbing Song^3,*

¹ College of Urban Construction, Wuhan University of Science and Technology, Wuhan 430065, China

² College of Science, Wuhan University of Science and Technology, Wuhan 430065, China

³ Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA

Sensors 2018, 18(5), 1377; https://doi.org/10.3390/s18051377 - 28 Apr 2018

Cited by 77 | Viewed by 6564

Abstract

Some of the most severe structural loadings come in the form of blast loads, which may be caused by severe accidents or even terrorist activities. Most commonly after exposure to explosive forces, a structure will suffer from different degrees of damage, and even [...] Read more.

Some of the most severe structural loadings come in the form of blast loads, which may be caused by severe accidents or even terrorist activities. Most commonly after exposure to explosive forces, a structure will suffer from different degrees of damage, and even progress towards a state of collapse. Therefore, damage detection of a structure subject to explosive loads is of importance. This paper proposes a new approach to damage detection of a concrete column structure subjected to blast loads using embedded piezoceramic smart aggregates (SAs). Since the sensors are embedded in the structure, the proposed active-sensing based approach is more sensitive to internal or through cracks than surface damage. In the active sensing approach, the embedded SAs act as actuators and sensors, that can respectively generate and detect stress waves. If the stress wave propagates across a crack, the energy of the wave attenuates, and the reduction of the energy compared to the healthy baseline is indicative of a damage. With a damage index matrix constructed by signals obtained from an array of SAs, cracks caused by blast loads can be detected throughout the structure. Conventional sensing methods such as the measurement of dynamic strain and acceleration were included in the experiment. Since columns are critical elements needed to prevent structural collapse, knowledge of their integrity and damage conditions is essential for safety after exposure to blast loads. In this research, a concrete column with embedded SAs was chosen as the specimen, and a series of explosive tests were conducted on the column. Experimental results reveal that surface damages, though appear severe, cause minor changes in the damage index, and through cracks result in significant increase of the damage index, demonstrating the effectiveness of the active sensing, enabled by embedded SAs, in damage monitoring of the column under blast loads, and thus providing a reliable indication of structural integrity in the event of blast loads. Full article

(This article belongs to the Special Issue Smart Sensors and Smart Structures)

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18 pages, 7385 KiB

Open AccessArticle

Unsupervised Indoor Localization Based on Smartphone Sensors, iBeacon and Wi-Fi

by Jing Chen^1,2,*, Yi Zhang¹ and Wei Xue¹

¹ Jiangnan University, School of Internet of Thing Engineering, Wuxi 214122, China

² Engineering Research Center of Internet of Things Technology Applications, Ministry of Education, Wuxi 214122, China

Sensors 2018, 18(5), 1378; https://doi.org/10.3390/s18051378 - 28 Apr 2018

Cited by 36 | Viewed by 5468

Abstract

In this paper, we propose UILoc, an unsupervised indoor localization scheme that uses a combination of smartphone sensors, iBeacons and Wi-Fi fingerprints for reliable and accurate indoor localization with zero labor cost. Firstly, compared with the fingerprint-based method, the UILoc system can build [...] Read more.

In this paper, we propose UILoc, an unsupervised indoor localization scheme that uses a combination of smartphone sensors, iBeacons and Wi-Fi fingerprints for reliable and accurate indoor localization with zero labor cost. Firstly, compared with the fingerprint-based method, the UILoc system can build a fingerprint database automatically without any site survey and the database will be applied in the fingerprint localization algorithm. Secondly, since the initial position is vital to the system, UILoc will provide the basic location estimation through the pedestrian dead reckoning (PDR) method. To provide accurate initial localization, this paper proposes an initial localization module, a weighted fusion algorithm combined with a k-nearest neighbors (KNN) algorithm and a least squares algorithm. In UILoc, we have also designed a reliable model to reduce the landmark correction error. Experimental results show that the UILoc can provide accurate positioning, the average localization error is about 1.1 m in the steady state, and the maximum error is 2.77 m. Full article

(This article belongs to the Special Issue Selected Papers from UPINLBS 2018)

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21 pages, 4562 KiB

Open AccessArticle

Flight State Identification of a Self-Sensing Wing via an Improved Feature Selection Method and Machine Learning Approaches

by Xi Chen^1,*, Fotis Kopsaftopoulos²

, Qi Wu³, He Ren¹ and Fu-Kuo Chang⁴

¹ Shanghai Engineering Research Center of Civil Aircraft Health Monitoring, Shanghai Aircraft Customer Service Co., Ltd., Shanghai 200241, China

² Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA

³ School of Electronic, Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

⁴ Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305, USA

Sensors 2018, 18(5), 1379; https://doi.org/10.3390/s18051379 - 29 Apr 2018

Cited by 19 | Viewed by 5744

Abstract

In this work, a data-driven approach for identifying the flight state of a self-sensing wing structure with an embedded multi-functional sensing network is proposed. The flight state is characterized by the structural vibration signals recorded from a series of wind tunnel experiments under [...] Read more.

In this work, a data-driven approach for identifying the flight state of a self-sensing wing structure with an embedded multi-functional sensing network is proposed. The flight state is characterized by the structural vibration signals recorded from a series of wind tunnel experiments under varying angles of attack and airspeeds. A large feature pool is created by extracting potential features from the signals covering the time domain, the frequency domain as well as the information domain. Special emphasis is given to feature selection in which a novel filter method is developed based on the combination of a modified distance evaluation algorithm and a variance inflation factor. Machine learning algorithms are then employed to establish the mapping relationship from the feature space to the practical state space. Results from two case studies demonstrate the high identification accuracy and the effectiveness of the model complexity reduction via the proposed method, thus providing new perspectives of self-awareness towards the next generation of intelligent air vehicles. Full article

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

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17 pages, 3823 KiB

Open AccessArticle

Social Sentiment Sensor in Twitter for Predicting Cyber-Attacks Using ℓ₁ Regularization

by Aldo Hernandez-Suarez¹

, Gabriel Sanchez-Perez¹, Karina Toscano-Medina¹, Victor Martinez-Hernandez¹, Hector Perez-Meana^1,*

, Jesus Olivares-Mercado¹ and Victor Sanchez²

¹ Instituto Politecnico Nacional, ESIME Culhuacan, Mexico City 04440, Mexico

² Department of Computer Science, University of Warwick, Coventry CV4 7AL, UK

Sensors 2018, 18(5), 1380; https://doi.org/10.3390/s18051380 - 29 Apr 2018

Cited by 53 | Viewed by 8905

Abstract

In recent years, online social media information has been the subject of study in several data science fields due to its impact on users as a communication and expression channel. Data gathered from online platforms such as Twitter has the potential to facilitate [...] Read more.

In recent years, online social media information has been the subject of study in several data science fields due to its impact on users as a communication and expression channel. Data gathered from online platforms such as Twitter has the potential to facilitate research over social phenomena based on sentiment analysis, which usually employs Natural Language Processing and Machine Learning techniques to interpret sentimental tendencies related to users’ opinions and make predictions about real events. Cyber-attacks are not isolated from opinion subjectivity on online social networks. Various security attacks are performed by hacker activists motivated by reactions from polemic social events. In this paper, a methodology for tracking social data that can trigger cyber-attacks is developed. Our main contribution lies in the monthly prediction of tweets with content related to security attacks and the incidents detected based on

ℓ_{1}

regularization. Full article

(This article belongs to the Special Issue Social Sensing)

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20 pages, 3638 KiB

Open AccessArticle

Building-in-Briefcase: A Rapidly-Deployable Environmental Sensor Suite for the Smart Building

by Kevin Weekly, Ming Jin, Han Zou, Christopher Hsu, Chris Soyza, Alexandre Bayen and Costas Spanos^*

Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720, USA

Sensors 2018, 18(5), 1381; https://doi.org/10.3390/s18051381 - 29 Apr 2018

Cited by 31 | Viewed by 7632

Abstract

A building’s environment has profound influence on occupant comfort and health. Continuous monitoring of building occupancy and environment is essential to fault detection, intelligent control, and building commissioning. Though many solutions for environmental measuring based on wireless sensor networks exist, they are not [...] Read more.

A building’s environment has profound influence on occupant comfort and health. Continuous monitoring of building occupancy and environment is essential to fault detection, intelligent control, and building commissioning. Though many solutions for environmental measuring based on wireless sensor networks exist, they are not easily accessible to households and building owners who may lack time or technical expertise needed to set up a system and get quick and detailed overview of environmental conditions. Building-in-Briefcase (BiB) is a portable sensor network platform that is trivially easy to deploy in any building environment. Once the sensors are distributed, the environmental data is collected and communicated to the BiB router via the Transmission Control Protocol/Internet Protocol (TCP/IP) and WiFi technology, which then forwards the data to the central database securely over the internet through a 3G radio. The user, with minimal effort, can access the aggregated data and visualize the trends in real time on the BiB web portal. Paramount to the adoption and continued operation of an indoor sensing platform is battery lifetime. This design has achieved a multi-year lifespan by careful selection of components, an efficient binary communications protocol and data compression. Our BiB sensor is capable of collecting a rich set of environmental parameters, and is expandable to measure others, such as CO

_{2}

. This paper describes the power characteristics of BiB sensors and their occupancy estimation and activity recognition functionality. We have demonstrated large-scale deployment of BiB throughout Singapore. Our vision is that, by monitoring thousands of buildings through BiB, it would provide ample research opportunities and opportunities to identify ways to improve the building environment and energy efficiency. Full article

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

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17 pages, 9627 KiB

Open AccessArticle

A CMOS Self-Contained Quadrature Signal Generator for SoC Impedance Spectroscopy

by Alejandro Márquez^*

, Jorge Pérez-Bailón

, Belén Calvo, Nicolás Medrano

and Pedro A. Martínez

Group of Electronic Design, Aragon Institute for Engineering Research (GDE-I3A), University of Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain

Sensors 2018, 18(5), 1382; https://doi.org/10.3390/s18051382 - 30 Apr 2018

Cited by 9 | Viewed by 5378

Abstract

This paper presents a low-power fully integrated quadrature signal generator for system-on-chip (SoC) impedance spectroscopy applications. It has been designed in a 0.18 μm-1.8 V CMOS technology as a self-contained oscillator, without the need for an external reference clock. The frequency can be [...] Read more.

This paper presents a low-power fully integrated quadrature signal generator for system-on-chip (SoC) impedance spectroscopy applications. It has been designed in a 0.18 μm-1.8 V CMOS technology as a self-contained oscillator, without the need for an external reference clock. The frequency can be digitally tuned from 10 to 345 kHz with 12-bit accuracy and a relative mean error below 1.7%, thus supporting a wide range of impedance sensing applications. The proposal is experimentally validated in two impedance spectrometry examples, achieving good magnitude and phase recovery results compared to the results obtained using a commercial LCR-meter. Besides the wide frequency tuning range, the proposed programmable oscillator features a total power consumption lower than 0.77 mW and an active area of 0.129 mm², thus constituting a highly suitable choice as stimulation module for instrument-on-a-chip devices. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 3408 KiB

Open AccessArticle

Electroencephalography Based Fusion Two-Dimensional (2D)-Convolution Neural Networks (CNN) Model for Emotion Recognition System

by Yea-Hoon Kwon, Sae-Byuk Shin and Shin-Dug Kim^*

Department of Computer Science, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea

Sensors 2018, 18(5), 1383; https://doi.org/10.3390/s18051383 - 30 Apr 2018

Cited by 176 | Viewed by 10857

Abstract

The purpose of this study is to improve human emotional classification accuracy using a convolution neural networks (CNN) model and to suggest an overall method to classify emotion based on multimodal data. We improved classification performance by combining electroencephalogram (EEG) and galvanic skin [...] Read more.

The purpose of this study is to improve human emotional classification accuracy using a convolution neural networks (CNN) model and to suggest an overall method to classify emotion based on multimodal data. We improved classification performance by combining electroencephalogram (EEG) and galvanic skin response (GSR) signals. GSR signals are preprocessed using by the zero-crossing rate. Sufficient EEG feature extraction can be obtained through CNN. Therefore, we propose a suitable CNN model for feature extraction by tuning hyper parameters in convolution filters. The EEG signal is preprocessed prior to convolution by a wavelet transform while considering time and frequency simultaneously. We use a database for emotion analysis using the physiological signals open dataset to verify the proposed process, achieving 73.4% accuracy, showing significant performance improvement over the current best practice models. Full article

(This article belongs to the Special Issue Recent Advances in Artificial Intelligence and Deep Learning for Sensor Information Fusion)

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23 pages, 602 KiB

Open AccessArticle

Optimization of Deep Neural Networks Using SoCs with OpenCL

by Rafael Gadea-Gironés^*

, Ricardo Colom-Palero and Vicente Herrero-Bosch

Department of Electronic Engineering, Universitat Politècnica de València, Camino de Vera, s/n, 46022 València, Spain

Sensors 2018, 18(5), 1384; https://doi.org/10.3390/s18051384 - 30 Apr 2018

Cited by 5 | Viewed by 3783

Abstract

In the optimization of deep neural networks (DNNs) via evolutionary algorithms (EAs) and the implementation of the training necessary for the creation of the objective function, there is often a trade-off between efficiency and flexibility. Pure software solutions implemented on general-purpose processors tend [...] Read more.

In the optimization of deep neural networks (DNNs) via evolutionary algorithms (EAs) and the implementation of the training necessary for the creation of the objective function, there is often a trade-off between efficiency and flexibility. Pure software solutions implemented on general-purpose processors tend to be slow because they do not take advantage of the inherent parallelism of these devices, whereas hardware realizations based on heterogeneous platforms (combining central processing units (CPUs), graphics processing units (GPUs) and/or field-programmable gate arrays (FPGAs)) are designed based on different solutions using methodologies supported by different languages and using very different implementation criteria. This paper first presents a study that demonstrates the need for a heterogeneous (CPU-GPU-FPGA) platform to accelerate the optimization of artificial neural networks (ANNs) using genetic algorithms. Second, the paper presents implementations of the calculations related to the individuals evaluated in such an algorithm on different (CPU- and FPGA-based) platforms, but with the same source files written in OpenCL. The implementation of individuals on remote, low-cost FPGA systems on a chip (SoCs) is found to enable the achievement of good efficiency in terms of performance per watt. Full article

(This article belongs to the Section Intelligent Sensors)

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23 pages, 8899 KiB

Open AccessArticle

Geometric Integration of Hybrid Correspondences for RGB-D Unidirectional Tracking

by Shengjun Tang¹, Wu Chen², Weixi Wang¹, Xiaoming Li¹, Walid Darwish²

, Wenbin Li², Zhengdong Huang¹, Han Hu^2,3 and Renzhong Guo^1,*

¹ Research Institute for Smart Cities, School of Architecture and Urban Planning, Shenzhen University, Shenzhen 518060, China

² Department of Land Surveying & Geo-Informatics, The Hong Kong Polytechnic University, Hung Hom 999077, Hong Kong, China

³ Faculty of Geosciences and Environmental Engineering of Southwest Jiaotong University, Chengdu 611756, China

Sensors 2018, 18(5), 1385; https://doi.org/10.3390/s18051385 - 1 May 2018

Cited by 8 | Viewed by 5540

Abstract

Traditionally, visual-based RGB-D SLAM systems only use correspondences with valid depth values for camera tracking, thus ignoring the regions without 3D information. Due to the strict limitation on measurement distance and view angle, such systems adopt only short-range constraints which may introduce larger [...] Read more.

Traditionally, visual-based RGB-D SLAM systems only use correspondences with valid depth values for camera tracking, thus ignoring the regions without 3D information. Due to the strict limitation on measurement distance and view angle, such systems adopt only short-range constraints which may introduce larger drift errors during long-distance unidirectional tracking. In this paper, we propose a novel geometric integration method that makes use of both 2D and 3D correspondences for RGB-D tracking. Our method handles the problem by exploring visual features both when depth information is available and when it is unknown. The system comprises two parts: coarse pose tracking with 3D correspondences, and geometric integration with hybrid correspondences. First, the coarse pose tracking generates the initial camera pose using 3D correspondences with frame-by-frame registration. The initial camera poses are then used as inputs for the geometric integration model, along with 3D correspondences, 2D-3D correspondences and 2D correspondences identified from frame pairs. The initial 3D location of the correspondence is determined in two ways, from depth image and by using the initial poses to triangulate. The model improves the camera poses and decreases drift error during long-distance RGB-D tracking iteratively. Experiments were conducted using data sequences collected by commercial Structure Sensors. The results verify that the geometric integration of hybrid correspondences effectively decreases the drift error and improves mapping accuracy. Furthermore, the model enables a comparative and synergistic use of datasets, including both 2D and 3D features. Full article

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

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19 pages, 6884 KiB

Open AccessArticle

H-SLAM: Rao-Blackwellized Particle Filter SLAM Using Hilbert Maps

by Guillem Vallicrosa^*

and Pere Ridao

Underwater Robotics Research Center (CIRS), Computer Vision and Robotics Institute (VICOROB), Universitat de Girona, 17004 Girona, Spain

Sensors 2018, 18(5), 1386; https://doi.org/10.3390/s18051386 - 1 May 2018

Cited by 32 | Viewed by 7471

Abstract

Occupancy Grid maps provide a probabilistic representation of space which is important for a variety of robotic applications like path planning and autonomous manipulation. In this paper, a SLAM (Simultaneous Localization and Mapping) framework capable of obtaining this representation online is presented. The [...] Read more.

Occupancy Grid maps provide a probabilistic representation of space which is important for a variety of robotic applications like path planning and autonomous manipulation. In this paper, a SLAM (Simultaneous Localization and Mapping) framework capable of obtaining this representation online is presented. The H-SLAM (Hilbert Maps SLAM) is based on Hilbert Map representation and uses a Particle Filter to represent the robot state. Hilbert Maps offer a continuous probabilistic representation with a small memory footprint. We present a series of experimental results carried both in simulation and with real AUVs (Autonomous Underwater Vehicles). These results demonstrate that our approach is able to represent the environment more consistently while capable of running online. Full article

(This article belongs to the Special Issue Underwater Sensing, Communication, Networking and Systems)

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24 pages, 1602 KiB

Open AccessArticle

On the Beat Detection Performance in Long-Term ECG Monitoring Scenarios

by Francisco-Manuel Melgarejo-Meseguer^1,*

, Estrella Everss-Villalba¹

, Francisco-Javier Gimeno-Blanes^2,*

, Manuel Blanco-Velasco³

, Zaida Molins-Bordallo¹

, José-Antonio Flores-Yepes²

, José-Luis Rojo-Álvarez^4,5,*

and Arcadi García-Alberola¹

¹ Cardiology Service, Arrhythmia Unit, Hospital General Universitario Virgen de la Arrixaca, El Palmar, 30120 Murcia, Spain

² Department of Signal Theory and Communications, Miguel Hernández University, Elche, 03202 Alicante, Spain

³ Department of Signal Theory and Communications, University of Alcalá, Alcalá de Henares, 28805 Madrid, Spain

⁴ Center for Computational Simulation, Universidad Politécnica de Madrid, Boadilla, 28223 Madrid, Spain

⁵ Department of Signal Theory and Communications, Rey Juan Carlos University, Fuenlabrada, 28943 Madrid, Spain

Sensors 2018, 18(5), 1387; https://doi.org/10.3390/s18051387 - 1 May 2018

Cited by 16 | Viewed by 5695

Abstract

Despite the wide literature on R-wave detection algorithms for ECG Holter recordings, the long-term monitoring applications are bringing new requirements, and it is not clear that the existing methods can be straightforwardly used in those scenarios. Our aim in this work was twofold: [...] Read more.

Despite the wide literature on R-wave detection algorithms for ECG Holter recordings, the long-term monitoring applications are bringing new requirements, and it is not clear that the existing methods can be straightforwardly used in those scenarios. Our aim in this work was twofold: First, we scrutinized the scope and limitations of existing methods for Holter monitoring when moving to long-term monitoring; Second, we proposed and benchmarked a beat detection method with adequate accuracy and usefulness in long-term scenarios. A longitudinal study was made with the most widely used waveform analysis algorithms, which allowed us to tune the free parameters of the required blocks, and a transversal study analyzed how these parameters change when moving to different databases. With all the above, the extension to long-term monitoring in a database of 7-day Holter monitoring was proposed and analyzed, by using an optimized simultaneous-multilead processing. We considered both own and public databases. In this new scenario, the noise-avoid mechanisms are more important due to the amount of noise that exists in these recordings, moreover, the computational efficiency is a key parameter in order to export the algorithm to the clinical practice. The method based on a Polling function outperformed the others in terms of accuracy and computational efficiency, yielding 99.48% sensitivity, 99.54% specificity, 99.69% positive predictive value, 99.46% accuracy, and 0.85% error for MIT-BIH arrhythmia database. We conclude that the method can be used in long-term Holter monitoring systems. Full article

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

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20 pages, 3856 KiB

Open AccessArticle

Virtual Sensor of Surface Electromyography in a New Extensive Fault-Tolerant Classification System

by Karina De O. A. De Moura^*

and Alexandre Balbinot

Electrical Engineering, Instrumentation Laboratory, Federal University of Rio Grande do Sul (UFRGS), Avenue Osvaldo Aranha 103, Porto Alegre, RS 90035-190, Brazil

Sensors 2018, 18(5), 1388; https://doi.org/10.3390/s18051388 - 1 May 2018

Cited by 20 | Viewed by 4461

Abstract

A few prosthetic control systems in the scientific literature obtain pattern recognition algorithms adapted to changes that occur in the myoelectric signal over time and, frequently, such systems are not natural and intuitive. These are some of the several challenges for myoelectric prostheses [...] Read more.

A few prosthetic control systems in the scientific literature obtain pattern recognition algorithms adapted to changes that occur in the myoelectric signal over time and, frequently, such systems are not natural and intuitive. These are some of the several challenges for myoelectric prostheses for everyday use. The concept of the virtual sensor, which has as its fundamental objective to estimate unavailable measures based on other available measures, is being used in other fields of research. The virtual sensor technique applied to surface electromyography can help to minimize these problems, typically related to the degradation of the myoelectric signal that usually leads to a decrease in the classification accuracy of the movements characterized by computational intelligent systems. This paper presents a virtual sensor in a new extensive fault-tolerant classification system to maintain the classification accuracy after the occurrence of the following contaminants: ECG interference, electrode displacement, movement artifacts, power line interference, and saturation. The Time-Varying Autoregressive Moving Average (TVARMA) and Time-Varying Kalman filter (TVK) models are compared to define the most robust model for the virtual sensor. Results of movement classification were presented comparing the usual classification techniques with the method of the degraded signal replacement and classifier retraining. The experimental results were evaluated for these five noise types in 16 surface electromyography (sEMG) channel degradation case studies. The proposed system without using classifier retraining techniques recovered of mean classification accuracy was of 4% to 38% for electrode displacement, movement artifacts, and saturation noise. The best mean classification considering all signal contaminants and channel combinations evaluated was the classification using the retraining method, replacing the degraded channel by the virtual sensor TVARMA model. This method recovered the classification accuracy after the degradations, reaching an average of 5.7% below the classification of the clean signal, that is the signal without the contaminants or the original signal. Moreover, the proposed intelligent technique minimizes the impact of the motion classification caused by signal contamination related to degrading events over time. There are improvements in the virtual sensor model and in the algorithm optimization that need further development to provide an increase the clinical application of myoelectric prostheses but already presents robust results to enable research with virtual sensors on biological signs with stochastic behavior. Full article

(This article belongs to the Special Issue Assistance Robotics and Biosensors)

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14 pages, 2899 KiB

Open AccessArticle

Optimal Sub-Band Analysis Based on the Envelope Power Spectrum for Effective Fault Detection in Bearing under Variable, Low Speeds

by Hung Ngoc Nguyen, Jaeyoung Kim and Jong-Myon Kim^*

School of Computer Engineering and Information Technology, University of Ulsan, Ulsan 44611, Korea

Sensors 2018, 18(5), 1389; https://doi.org/10.3390/s18051389 - 1 May 2018

Cited by 22 | Viewed by 4572

Abstract

Early identification of failures in rolling element bearings is an important research issue in mechanical systems. In this study, a reliable methodology for bearing fault detection is proposed, which is based on an optimal sub-band selection scheme using the discrete wavelet packet transform [...] Read more.

Early identification of failures in rolling element bearings is an important research issue in mechanical systems. In this study, a reliable methodology for bearing fault detection is proposed, which is based on an optimal sub-band selection scheme using the discrete wavelet packet transform (DWPT) and envelope power analysis techniques. A DWPT-based decomposition is first performed to extract the characteristic defect features from the acquired acoustic emission (AE) signals. The envelope power spectrum (EPS) of each sub-band signal is then calculated to detect the characteristic defect frequencies to reveal abnormal symptoms in bearings. The selection of an appropriate sub-band is essential for effective fault diagnosis, as it can reveal intrinsically explicit information about different types of bearing faults. To address this issue, we propose a Gaussian distribution model-based health-related index (HI) that is a powerful quantitative parameter to accurately estimate the severity of bearing defects. The most optimal sub-band for fault detection is determined using two dimensional (2D) visualization analysis. The efficiency of the proposed approach is validated using several experiments in which different defect conditions are identified under variable, and low operational speeds. Full article

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

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12 pages, 4191 KiB

Open AccessArticle

Heading Estimation of Robot Combine Harvesters during Turning Maneuveres

by Md Mostafizar Rahman^1,2 and Kazunobu Ishii^3,*

¹ Graduate School of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan

² Department of Food Engineering and Tea Technology, Shahjalal University of Science and Technology, Sylhet 3114, Bangladesh

³ Research Faculty of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan

Sensors 2018, 18(5), 1390; https://doi.org/10.3390/s18051390 - 1 May 2018

Cited by 8 | Viewed by 6387

Abstract

Absolute heading is an important parameter for a robot combine harvester or a robot tracked combine harvester, especially while it is turning, but due to the rapid turning of robot combine harvesters, its inertial measurement unit gives a gyro measurement bias that causes [...] Read more.

Absolute heading is an important parameter for a robot combine harvester or a robot tracked combine harvester, especially while it is turning, but due to the rapid turning of robot combine harvesters, its inertial measurement unit gives a gyro measurement bias that causes heading drift. Our research goal is to estimate the absolute heading of robot combine harvesters by compensating this gyro measurement bias during non-linear turning maneuvers. A sensor fusion method like the extended Kalman filter combined with the tracked combine harvester dynamic model and sensor measurements was used to estimate the absolute heading of a robot combine harvester. Circular, sinusoidal and concave shapes were used to evaluate the estimated heading produced by the sensor fusion method. The results indicate that the estimated heading is better than measured heading which was calculated from the integration of yaw rate gyro measurements, and the root mean square errors (RMSEs) for estimated headings are smaller than the measured headings. In practics, the target of this paper is thus the estimation of a heading or absolute heading that is bias compensated, and can be further used to calculate the exact crop periphery for automatic path planning of robot combine harvesters. Full article

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

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18 pages, 2682 KiB

Open AccessArticle

Robust Pedestrian Dead Reckoning Based on MEMS-IMU for Smartphones

by Jian Kuang, Xiaoji Niu^* and Xingeng Chen

GNSS Research Center, Wuhan University, 129 Luoyu Road, Wuhan 430079, China

Sensors 2018, 18(5), 1391; https://doi.org/10.3390/s18051391 - 1 May 2018

Cited by 132 | Viewed by 12229

Abstract

This paper proposes a pedestrian dead reckoning (PDR) algorithm based on the strap-down inertial navigation system (SINS) using the gyros, accelerometers, and magnetometers on smartphones. In addition to using a gravity vector, magnetic field vector, and quasi-static attitude, this algorithm employs a gait [...] Read more.

This paper proposes a pedestrian dead reckoning (PDR) algorithm based on the strap-down inertial navigation system (SINS) using the gyros, accelerometers, and magnetometers on smartphones. In addition to using a gravity vector, magnetic field vector, and quasi-static attitude, this algorithm employs a gait model and motion constraint to provide pseudo-measurements (i.e., three-dimensional velocity and two-dimensional position increment) instead of using only pseudo-velocity measurement for a more robust PDR algorithm. Several walking tests show that the advanced algorithm can maintain good position estimation compare to the existing SINS-based PDR method in the four basic smartphone positions, i.e., handheld, calling near the ear, swaying in the hand, and in a pants pocket. In addition, we analyze the navigation performance difference between the advanced algorithm and the existing gait-model-based PDR algorithm from three aspects, i.e., heading estimation, position estimation, and step detection failure, in the four basic phone positions. Test results show that the proposed algorithm achieves better position estimation when a pedestrian holds a smartphone in a swaying hand and step detection is unsuccessful. Full article

(This article belongs to the Collection Positioning and Navigation)

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19 pages, 7250 KiB

Open AccessArticle

Heart Rate Estimated from Body Movements at Six Degrees of Freedom by Convolutional Neural Networks

by Hyunwoo Lee¹

and Mincheol Whang^2,*

¹ Department of Emotion Engineering, University of Sangmyung, Seoul 03016, Korea

² Department of Intelligence Informatics Engineering, University of Sangmyung, Seoul 03016, Korea

Sensors 2018, 18(5), 1392; https://doi.org/10.3390/s18051392 - 1 May 2018

Cited by 15 | Viewed by 4922

Abstract

Cardiac activity has been monitored continuously in daily life by virtue of advanced medical instruments with microelectromechanical system (MEMS) technology. Seismocardiography (SCG) has been considered to be free from the burden of measurement for cardiac activity, but it has been limited in its [...] Read more.

Cardiac activity has been monitored continuously in daily life by virtue of advanced medical instruments with microelectromechanical system (MEMS) technology. Seismocardiography (SCG) has been considered to be free from the burden of measurement for cardiac activity, but it has been limited in its application in daily life. The most important issues regarding SCG are to overcome the limitations of motion artifacts due to the sensitivity of motion sensor. Although novel adaptive filters for noise cancellation have been developed, they depend on the researcher’s subjective decision. Convolutional neural networks (CNNs) can extract significant features from data automatically without a researcher’s subjective decision, so that signal processing has been recently replaced as CNNs. Thus, this study aimed to develop a novel method to enhance heart rate estimation from thoracic movement by CNNs. Thoracic movement was measured by six-axis accelerometer and gyroscope signals using a wearable sensor that can be worn by simply clipping on clothes. The dataset was collected from 30 participants (15 males, 15 females) using 12 measurement conditions according to two physical conditions (i.e., relaxed and aroused conditions), three body postures (i.e., sitting, standing, and supine), and six movement speeds (i.e., 3.2, 4.5, 5.8, 6.4, 8.5, and 10.3 km/h). The motion data (i.e., six-axis accelerometer and gyroscope) and heart rate (i.e., electrocardiogram (ECG)) were determined as the input data and labels in the dataset, respectively. The CNN model was developed based on VGG Net and optimized by testing according to network depth and data augmentation. The ensemble network of the VGG-16 without data augmentation and the VGG-19 with data augmentation was determined as optimal architecture for generalization. As a result, the proposed method showed higher accuracy than the previous SCG method using signal processing in most measurement conditions. The three main contributions are as follows: (1) the CNN model enhanced heart rate estimation with the benefits of automatic feature extraction from the data; (2) the proposed method was compared with the previous SCG method using signal processing; (3) the method was tested in 12 measurement conditions related to daily motion for a more practical application. Full article

(This article belongs to the Special Issue Wearable and Ambient Sensors for Healthcare and Wellness Applications 2018)

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29 pages, 7729 KiB

Open AccessArticle

Double-Group Particle Swarm Optimization and Its Application in Remote Sensing Image Segmentation

by Liang Shen^*, Xiaotao Huang and Chongyi Fan

College of Electronic Science, National University of Defense Technology, Changsha 410000, China

Sensors 2018, 18(5), 1393; https://doi.org/10.3390/s18051393 - 1 May 2018

Cited by 20 | Viewed by 4218

Abstract

Particle Swarm Optimization (PSO) is a well-known meta-heuristic. It has been widely used in both research and engineering fields. However, the original PSO generally suffers from premature convergence, especially in multimodal problems. In this paper, we propose a double-group PSO (DG-PSO) algorithm to [...] Read more.

Particle Swarm Optimization (PSO) is a well-known meta-heuristic. It has been widely used in both research and engineering fields. However, the original PSO generally suffers from premature convergence, especially in multimodal problems. In this paper, we propose a double-group PSO (DG-PSO) algorithm to improve the performance. DG-PSO uses a double-group based evolution framework. The individuals are divided into two groups: an advantaged group and a disadvantaged group. The advantaged group works according to the original PSO, while two new strategies are developed for the disadvantaged group. The proposed algorithm is firstly evaluated by comparing it with the other five popular PSO variants and two state-of-the-art meta-heuristics on various benchmark functions. The results demonstrate that DG-PSO shows a remarkable performance in terms of accuracy and stability. Then, we apply DG-PSO to multilevel thresholding for remote sensing image segmentation. The results show that the proposed algorithm outperforms five other popular algorithms in meta-heuristic-based multilevel thresholding, which verifies the effectiveness of the proposed algorithm. Full article

(This article belongs to the Section Remote Sensors)

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13 pages, 4213 KiB

Open AccessArticle

Handheld Real-Time LED-Based Photoacoustic and Ultrasound Imaging System for Accurate Visualization of Clinical Metal Needles and Superficial Vasculature to Guide Minimally Invasive Procedures

by Wenfeng Xia^1,2,*,†

, Mithun Kuniyil Ajith Singh^3,*,†, Efthymios Maneas^1,2, Naoto Sato⁴, Yusuke Shigeta⁴, Toshitaka Agano⁴, Sebastian Ourselin^1,5, Simeon J. West⁶ and Adrien E. Desjardins^1,2

¹ Wellcome/EPSRC Centre for Interventional and Surgical Sciences, University College London, Charles Bell House, 67-73 Riding House Street, London W1W 7EJ, UK

² Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, UK

³ Research and Business Development Division, PreXion Corporation, Stationsplein 45 A4.004, 3013AK Rotterdam, The Netherlands

⁴ Research and Development Division, 1-14-1, Kandasudacho, Chiyoda-ku, Tokyo 101-0041, Japan

⁵ Centre for Medical Imaging Computing, University College London, Gower Street, London WC1E 6BT, UK

⁶ Department of Anaesthesia, University College Hospital, Main Theatres, Maple Bridge Link Corridor, Podium 3, 235 Euston Road, London NW1 2BU, UK

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1394; https://doi.org/10.3390/s18051394 - 1 May 2018

Cited by 96 | Viewed by 10551

Abstract

Ultrasound imaging is widely used to guide minimally invasive procedures, but the visualization of the invasive medical device and the procedure’s target is often challenging. Photoacoustic imaging has shown great promise for guiding minimally invasive procedures, but clinical translation of this technology has [...] Read more.

Ultrasound imaging is widely used to guide minimally invasive procedures, but the visualization of the invasive medical device and the procedure’s target is often challenging. Photoacoustic imaging has shown great promise for guiding minimally invasive procedures, but clinical translation of this technology has often been limited by bulky and expensive excitation sources. In this work, we demonstrate the feasibility of guiding minimally invasive procedures using a dual-mode photoacoustic and ultrasound imaging system with excitation from compact arrays of light-emitting diodes (LEDs) at 850 nm. Three validation experiments were performed. First, clinical metal needles inserted into biological tissue were imaged. Second, the imaging depth of the system was characterized using a blood-vessel-mimicking phantom. Third, the superficial vasculature in human volunteers was imaged. It was found that photoacoustic imaging enabled needle visualization with signal-to-noise ratios that were 1.2 to 2.2 times higher than those obtained with ultrasound imaging, over insertion angles of 26 to 51 degrees. With the blood vessel mimicking phantom, the maximum imaging depth was 38 mm. The superficial vasculature of a human middle finger and a human wrist were clearly visualized in real-time. We conclude that the LED-based system is promising for guiding minimally invasive procedures with peripheral tissue targets. Full article

(This article belongs to the Special Issue Photoacoustic Sensing and Imaging in Biomedicine)

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10 pages, 1087 KiB

Open AccessArticle

Assessment of Performance of the Industrial Process of Bulk Vacuum Packaging of Raw Meat with Nondestructive Optical Oxygen Sensing Systems

by Caroline A. Kelly¹, Malco Cruz-Romero²

, Joseph P. Kerry² and Dmitri P. Papkovsky^1,*

¹ School of Biochemistry and Cell Biology, University College Cork, Cavanagh Pharmacy Building, College Road, Cork T12 K8AF, Ireland

² Food Packaging Group, School of Food and Nutritional Sciences, University College Cork, Food Science Building, College Road, Cork T12 K8AF, Ireland

Sensors 2018, 18(5), 1395; https://doi.org/10.3390/s18051395 - 2 May 2018

Cited by 10 | Viewed by 3953

Abstract

The commercially-available optical oxygen-sensing system Optech-O₂ Platinum was applied to nondestructively assess the in situ performance of bulk, vacuum-packaged raw beef in three ~300 kg containers. Twenty sensors were attached to the inner surface of the standard bin-contained laminate bag (10 on [...] Read more.

The commercially-available optical oxygen-sensing system Optech-O₂ Platinum was applied to nondestructively assess the in situ performance of bulk, vacuum-packaged raw beef in three ~300 kg containers. Twenty sensors were attached to the inner surface of the standard bin-contained laminate bag (10 on the front and back sides), such that after filling with meat and sealing under vacuum, the sensors were accessible for optical interrogation with the external reader device. After filling and sealing each bag, the sensors were measured repetitively and nondestructively over a 15-day storage period at 1 °C, thus tracking residual oxygen distribution in the bag and changes during storage. The sensors revealed a number of unidentified meat quality and processing issues, and helped to improve the packaging process by pouring flakes of dry ice into the bag. Sensor utility in mapping the distribution of residual O₂ in sealed bulk containers and optimising and improving the packaging process, including handling and storage of bulk vacuum-packaged meat bins, was evident. Full article

(This article belongs to the Section Chemical Sensors)

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13 pages, 6122 KiB

Open AccessArticle

Quantitative Study on Corrosion of Steel Strands Based on Self-Magnetic Flux Leakage

by Runchuan Xia¹, Jianting Zhou^1,*, Hong Zhang¹

, Leng Liao², Ruiqiang Zhao² and Zeyu Zhang³

¹ College of Civil Engineering, Chongqing Jiaotong University, Chongqing 400074, China

² School of Materials Science and Engineering, Chongqing Jiaotong University, Chongqing 400074, China

³ Guizhou Expressway Group Co., Ltd., Guiyang 550000, China

Sensors 2018, 18(5), 1396; https://doi.org/10.3390/s18051396 - 2 May 2018

Cited by 60 | Viewed by 5172

Abstract

This paper proposed a new computing method to quantitatively and non-destructively determine the corrosion of steel strands by analyzing the self-magnetic flux leakage (SMFL) signals from them. The magnetic dipole model and three growth models (Logistic model, Exponential model, and Linear model) were [...] Read more.

This paper proposed a new computing method to quantitatively and non-destructively determine the corrosion of steel strands by analyzing the self-magnetic flux leakage (SMFL) signals from them. The magnetic dipole model and three growth models (Logistic model, Exponential model, and Linear model) were proposed to theoretically analyze the characteristic value of SMFL. Then, the experimental study on the corrosion detection by the magnetic sensor was carried out. The setup of the magnetic scanning device and signal collection method were also introduced. The results show that the Logistic Growth model is verified as the optimal model for calculating the magnetic field with good fitting effects. Combined with the experimental data analysis, the amplitudes of the calculated values (B_xL(x,z) curves) agree with the measured values in general. This method provides significant application prospects for the evaluation of the corrosion and the residual bearing capacity of steel strand. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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16 pages, 4430 KiB

Open AccessArticle

Comparison of Resonance Frequency Analysis and of Quantitative Ultrasound to Assess Dental Implant Osseointegration

by Romain Vayron¹, Vu-Hieu Nguyen¹, Benoît Lecuelle², Hugues Albini Lomami¹, Jean-Paul Meningaud^3,4, Romain Bosc^3,4 and Guillaume Haiat^1,*

¹ CNRS, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR CNRS 8208, 61, Avenue du Général de Gaulle, 94010 Créteil CEDEX, France

² Centre de Recherche BioMédicale, Ecole Nationale Vétérinaire d’Alfort, 7 Avenue du Général de Gaulle, 94700 Maisons-Alfort, France

³ Service de Chirurgie Orthopédique et Traumatologique, Hôpital Henri Mondor AP-HP, CHU Paris 12, Université Paris-Est, 51 Avenue du Maréchal de Lattre de Tassigny, 94000 Créteil, France

⁴ Équipe 10, Groupe 5, IMRB U955, INSERM/UPEC, 8 rue du Général Sarrail, 94000 Créteil, France

Sensors 2018, 18(5), 1397; https://doi.org/10.3390/s18051397 - 2 May 2018

Cited by 38 | Viewed by 6759

Abstract

Dental implants are widely used in the clinic. However, there remain risks of failure, which depend on the implant stability. The aim of this paper is to compare two methods based on resonance frequency analysis (RFA) and on quantitative ultrasound (QUS) and that [...] Read more.

Dental implants are widely used in the clinic. However, there remain risks of failure, which depend on the implant stability. The aim of this paper is to compare two methods based on resonance frequency analysis (RFA) and on quantitative ultrasound (QUS) and that aim at assessing implant stability. Eighty-one identical dental implants were inserted in the iliac crests of 11 sheep. The QUS and RFA measurements were realized after different healing times (0, 5, 7, and 15 weeks). The results obtained with the QUS (respectively RFA) method were significantly different when comparing two consecutive healing time for 97% (respectively, 18%) of the implants. The error made on the estimation of the healing time when analyzing the results obtained with the QUS technique was around 10 times lower than that made when using the RFA technique. The results corresponding to the dependence of the ISQ versus healing time were significantly different when comparing two directions of RFA measurement. The results show that the QUS method allows a more accurate determination of the evolution of dental implant stability when compared to the RFA method. This study paves the way towards the development of a medical device, thus providing a decision support system to dental surgeons. Full article

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

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15 pages, 4289 KiB

Open AccessArticle

Dispersed Sensing Networks in Nano-Engineered Polymer Composites: From Static Strain Measurement to Ultrasonic Wave Acquisition

by Yehai Li^†, Kai Wang^† and Zhongqing Su^*

¹ Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR 999077, China

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1398; https://doi.org/10.3390/s18051398 - 2 May 2018

Cited by 19 | Viewed by 5596

Abstract

Self-sensing capability of composite materials has been the core of intensive research over the years and particularly boosted up by the recent quantum leap in nanotechnology. The capacity of most existing self-sensing approaches is restricted to static strains or low-frequency structural vibration. In [...] Read more.

Self-sensing capability of composite materials has been the core of intensive research over the years and particularly boosted up by the recent quantum leap in nanotechnology. The capacity of most existing self-sensing approaches is restricted to static strains or low-frequency structural vibration. In this study, a new breed of functionalized epoxy-based composites is developed and fabricated, with a graphene nanoparticle-enriched, dispersed sensing network, whereby to self-perceive broadband elastic disturbance from static strains, through low-frequency vibration to guided waves in an ultrasonic regime. Owing to the dispersed and networked sensing capability, signals can be captured at any desired part of the composites. Experimental validation has demonstrated that the functionalized composites can self-sense strains, outperforming conventional metal foil strain sensors with a significantly enhanced gauge factor and a much broader response bandwidth. Precise and fast self-response of the composites to broadband ultrasonic signals (up to 440 kHz) has revealed that the composite structure itself can serve as ultrasound sensors, comparable to piezoceramic sensors in performance, whereas avoiding the use of bulky cables and wires as used in a piezoceramic sensor network. This study has spotlighted promising potentials of the developed approach to functionalize conventional composites with a self-sensing capability of high-sensitivity yet minimized intrusion to original structures. Full article

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

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17 pages, 1520 KiB

Open AccessArticle

Force Trends and Pulsatility for Catheter Contact Identification in Intracardiac Electrograms during Arrhythmia Ablation

by David Rivas-Lalaleo^1,2,*

, Sergio Muñoz-Romero^2,3, Mónica Huerta⁴

, Mayra Erazo-Rodas¹

, Juan José Sánchez-Muñoz⁵, José Luis Rojo-Álvarez^2,3

and Arcadi García-Alberola⁵

¹ Departamento de Eléctrica y Electrónica, Universidad de las Fuerzas Armadas ESPE, Av. General Rumiñahui s/n, 170501 Sangolquí, Ecuador

² Department of Signal Theory and Communications and Telematic Systems and Computation, Rey Juan Carlos University, Fuenlabrada, 28943 Madrid, Spain

³ Center for Computational Simulation, Universidad Politécnica de Madrid; Boadilla, 28223 Madrid, Spain

⁴ Universidad Politécnica Salesiana, 010105 Cuenca, Ecuador

⁵ Arrhythmia Unit, University Clinic Hospital Virgen de la Arrixaca, El Palmar, 30120 Murcia, Spain

Sensors 2018, 18(5), 1399; https://doi.org/10.3390/s18051399 - 2 May 2018

Cited by 2 | Viewed by 4411

Abstract

The intracardiac electrical activation maps are commonly used as a guide in the ablation of cardiac arrhythmias. The use of catheters with force sensors has been proposed in order to know if the electrode is in contact with the tissue during the registration [...] Read more.

The intracardiac electrical activation maps are commonly used as a guide in the ablation of cardiac arrhythmias. The use of catheters with force sensors has been proposed in order to know if the electrode is in contact with the tissue during the registration of intracardiac electrograms (EGM). Although threshold criteria on force signals are often used to determine the catheter contact, this may be a limited criterion due to the complexity of the heart dynamics and cardiac vorticity. The present paper is devoted to determining the criteria and force signal profiles that guarantee the contact of the electrode with the tissue. In this study, we analyzed 1391 force signals and their associated EGM recorded during 2 and 8 s, respectively, in 17 patients (82 ± 60 points per patient). We aimed to establish a contact pattern by first visually examining and classifying the signals, according to their likely-contact joint profile and following the suggestions from experts in the doubtful cases. First, we used Principal Component Analysis to scrutinize the force signal dynamics by analyzing the main eigen-directions, first globally and then grouped according to the certainty of their tissue-catheter contact. Second, we used two different linear classifiers (Fisher discriminant and support vector machines) to identify the most relevant components of the previous signal models. We obtained three main types of eigenvectors, namely, pulsatile relevant, non-pulsatile relevant, and irrelevant components. The classifiers reached a moderate to sufficient discrimination capacity (areas under the curve between 0.84 and 0.95 depending on the contact certainty and on the classifier), which allowed us to analyze the relevant properties in the force signals. We conclude that the catheter-tissue contact profiles in force recordings are complex and do not depend only on the signal intensity being above a threshold at a single time instant, but also on time pulsatility and trends. These findings pave the way towards a subsystem which can be included in current intracardiac navigation systems assisted by force contact sensors, and it can provide the clinician with an estimate of the reliability on the tissue-catheter contact in the point-by-point EGM acquisition procedure. Full article

(This article belongs to the Section Biosensors)

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10 pages, 3763 KiB

Open AccessArticle

A Flexible Temperature Sensor Based on Reduced Graphene Oxide for Robot Skin Used in Internet of Things

by Guanyu Liu^1,2, Qiulin Tan^1,2,*

, Hairong Kou^1,2, Lei Zhang^1,2, Jinqi Wang^1,2, Wen Lv^1,2, Helei Dong^1,2 and Jijun Xiong^1,2

¹ Key Laboratory of Instrumentation Science & Dynamic Measurement, Ministry of Education, North University of China, Taiyuan 030051, China

² Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China

Sensors 2018, 18(5), 1400; https://doi.org/10.3390/s18051400 - 2 May 2018

Cited by 232 | Viewed by 14580

Abstract

Flexible electronics, which can be distributed on any surface we need, are highly demanded in the development of Internet of Things (IoT), robot technology and electronic skins. Temperature is a fundamental physical parameter, and it is an important indicator in many applications. Therefore, [...] Read more.

Flexible electronics, which can be distributed on any surface we need, are highly demanded in the development of Internet of Things (IoT), robot technology and electronic skins. Temperature is a fundamental physical parameter, and it is an important indicator in many applications. Therefore, a flexible temperature sensor is required. Here, we report a simple method to fabricate three lightweight, low-cost and flexible temperature sensors, whose sensitive materials are reduced graphene oxide (r-GO), single-walled carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs). By comparing linearity, sensitive and repeatability, we found that the r-GO temperature sensor had the most balanced performance. Furthermore, the r-GO temperature sensor showed good mechanical properties and it could be bent in different angles with negligible resistance change. In addition, the performance of the r-GO temperature sensor remained stable under different kinds of pressure and was unaffected by surrounding environments, like humidity or other gases, because of the insulating layer on its sensitive layer. The easy-fabricated process and economy, together with the remarkable performance of the r-GO temperature sensor, suggest that it is suitable for use as a robot skin or used in the environment of IoT. Full article

(This article belongs to the Special Issue Temperature Sensors)

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12 pages, 3223 KiB

Open AccessArticle

Response of a Bell–Bloom Magnetometer to a Magnetic Field of Arbitrary Direction

by Zhichao Ding, Jie Yuan and Xingwu Long^*

College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(5), 1401; https://doi.org/10.3390/s18051401 - 2 May 2018

Cited by 13 | Viewed by 5987

Abstract

The Bell–Bloom magnetometer in response to a magnetic field of arbitrary direction is observed theoretically and experimentally. A theoretical model is built from a macroscopic view to simulate the magnetometer frequency response to an external magnetic field of arbitrary direction. Based on the [...] Read more.

The Bell–Bloom magnetometer in response to a magnetic field of arbitrary direction is observed theoretically and experimentally. A theoretical model is built from a macroscopic view to simulate the magnetometer frequency response to an external magnetic field of arbitrary direction. Based on the simulation results, the magnetometer characteristics, including the signal phase and amplitude at resonance, the linewidth, and the magnetometer sensitivity, are analyzed, and the dependencies of these characteristics on the external magnetic field direction are obtained, which are verified by the experiment. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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21 pages, 5282 KiB

Open AccessArticle

New-Generation BeiDou (BDS-3) Experimental Satellite Precise Orbit Determination with an Improved Cycle-Slip Detection and Repair Algorithm

by Chao Hu^1,2,*, Qianxin Wang^1,2,3, Zhongyuan Wang^1,2,* and Alberto Hernández Moraleda²

¹ NASG Key Laboratory of Land Environment and Disaster Monitoring, China University of Mining and Technology, Xuzhou 221116, China

² School of Environment Science and Spatial Informatics, China University of Mining and Technology, Xuzhou 221116, China

³ Satellite Positioning for Atmosphere, Climate and Environment (SPACE) Research Centre, School of Science, Mathematical and Geospatial Sciences, RMIT University, Melbourne, VIC 3001, Australia

Sensors 2018, 18(5), 1402; https://doi.org/10.3390/s18051402 - 2 May 2018

Cited by 24 | Viewed by 5853

Abstract

Currently, five new-generation BeiDou (BDS-3) experimental satellites are working in orbit and broadcast B1I, B3I, and other new signals. Precise satellite orbit determination of the BDS-3 is essential for the future global services of the BeiDou system. However, BDS-3 experimental satellites are mainly [...] Read more.

Currently, five new-generation BeiDou (BDS-3) experimental satellites are working in orbit and broadcast B1I, B3I, and other new signals. Precise satellite orbit determination of the BDS-3 is essential for the future global services of the BeiDou system. However, BDS-3 experimental satellites are mainly tracked by the international GNSS Monitoring and Assessment Service (iGMAS) network. Under the current constraints of the limited data sources and poor data quality of iGMAS, this study proposes an improved cycle-slip detection and repair algorithm, which is based on a polynomial prediction of ionospheric delays. The improved algorithm takes the correlation of ionospheric delays into consideration to accurately estimate and repair cycle slips in the iGMAS data. Moreover, two methods of BDS-3 experimental satellite orbit determination, namely, normal equation stacking (NES) and step-by-step (SS), are designed to strengthen orbit estimations and to make full use of the BeiDou observations in different tracking networks. In addition, a method to improve computational efficiency based on a matrix eigenvalue decomposition algorithm is derived in the NES. Then, one-year of BDS-3 experimental satellite precise orbit determinations were conducted based on iGMAS and Multi-GNSS Experiment (MGEX) networks. Furthermore, the orbit accuracies were analyzed from the discrepancy of overlapping arcs and satellite laser range (SLR) residuals. The results showed that the average three-dimensional root-mean-square error (3D RMS) of one-day overlapping arcs for BDS-3 experimental satellites (C31, C32, C33, and C34) acquired by NES and SS are 31.0, 36.0, 40.3, and 50.1 cm, and 34.6, 39.4, 43.4, and 55.5 cm, respectively; the RMS of SLR residuals are 55.1, 49.6, 61.5, and 70.9 cm and 60.5, 53.6, 65.8, and 73.9 cm, respectively. Finally, one month of observations were used in four schemes of BDS-3 experimental satellite orbit determination to further investigate the reliability and advantages of the improved methods. It was suggested that the scheme with improved cycle-slip detection and repair algorithm based on NES was optimal, which improved the accuracy of BDS-3 experimental satellite orbits by 34.07%, 41.05%, 72.29%, and 74.33%, respectively, compared with the widely-used strategy. Therefore, improved methods for the BDS-3 experimental satellites proposed in this study are very beneficial for the determination of new-generation BeiDou satellite precise orbits. Full article

(This article belongs to the Special Issue GNSS and Fusion with Other Sensors)

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17 pages, 1749 KiB

Open AccessArticle

VeLoc: Finding Your Car in Indoor Parking Structures

by Ruipeng Gao^1,*

, Fangpu He¹ and Teng Li²

¹ School of Software Engineering, Beijing Jiaotong University, Beijing 100044, China

² Department of Electrical Engineering and Computer Science, Syracuse University, Syracuse, NY 13244, USA

Sensors 2018, 18(5), 1403; https://doi.org/10.3390/s18051403 - 2 May 2018

Cited by 4 | Viewed by 4519

Abstract

While WiFi-based indoor localization is attractive, there are many indoor places without WiFi coverage with a strong demand for localization capability. This paper describes a system and associated algorithms to address the indoor vehicle localization problem without the installation of additional infrastructure. In [...] Read more.

While WiFi-based indoor localization is attractive, there are many indoor places without WiFi coverage with a strong demand for localization capability. This paper describes a system and associated algorithms to address the indoor vehicle localization problem without the installation of additional infrastructure. In this paper, we propose VeLoc, which utilizes the sensor data of smartphones in the vehicle together with the floor map of the parking structure to track the vehicle in real time. VeLoc simultaneously harnesses constraints imposed by the map and environment sensing. All these cues are codified into a novel augmented particle filtering framework to estimate the position of the vehicle. Experimental results show that VeLoc performs well when even the initial position and the initial heading direction of the vehicle are completely unknown. Full article

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

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15 pages, 3849 KiB

Open AccessArticle

An Optimal Enhanced Kalman Filter for a ZUPT-Aided Pedestrian Positioning Coupling Model

by Qigao Fan, Hai Zhang^*, Yan Sun, Yixin Zhu, Xiangpeng Zhuang, Jie Jia and Pengsong Zhang

College of Internet of Things Engineering, Jiangnan University, Wuxi 214000, China

Sensors 2018, 18(5), 1404; https://doi.org/10.3390/s18051404 - 2 May 2018

Cited by 32 | Viewed by 5011

Abstract

Aimed at overcoming the problems of cumulative errors and low positioning accuracy in single Inertial Navigation Systems (INS), an Optimal Enhanced Kalman Filter (OEKF) is proposed in this paper to achieve accurate positioning of pedestrians within an enclosed environment. Firstly, the errors of [...] Read more.

Aimed at overcoming the problems of cumulative errors and low positioning accuracy in single Inertial Navigation Systems (INS), an Optimal Enhanced Kalman Filter (OEKF) is proposed in this paper to achieve accurate positioning of pedestrians within an enclosed environment. Firstly, the errors of the inertial sensors are analyzed, modeled, and reconstructed. Secondly, the cumulative errors in attitude and velocity are corrected using the attitude fusion filtering algorithm and Zero Velocity Update algorithm (ZUPT), respectively. Then, the OEKF algorithm is described in detail. Finally, a pedestrian indoor positioning experimental platform is established to verify the performance of the proposed positioning system. Experimental results show that the accuracy of the pedestrian indoor positioning system can reach 0.243 m, giving it a high practical value. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 10972 KiB

Open AccessArticle

A 0.18 μm CMOS LDO Regulator for an On-Chip Sensor Array Impedance Measurement System

by Jorge Pérez-Bailón^*

, Alejandro Márquez

, Belén Calvo and Nicolás Medrano

Group of Electronic Design, Aragon Institute for Engineering Research, I3A, University of Zaragoza, 50009 Zaragoza, Spain

Sensors 2018, 18(5), 1405; https://doi.org/10.3390/s18051405 - 2 May 2018

Cited by 9 | Viewed by 8590

Abstract

This paper presents a fully integrated 0.18 μm CMOS Low-Dropout (LDO) Voltage Regulator specifically designed to meet the stringent requirements of a battery-operated impedance spectrometry multichannel CMOS micro-instrument. The proposed LDO provides a regulated 1.8 V voltage from a 3.6 V to 1.94 [...] Read more.

This paper presents a fully integrated 0.18 μm CMOS Low-Dropout (LDO) Voltage Regulator specifically designed to meet the stringent requirements of a battery-operated impedance spectrometry multichannel CMOS micro-instrument. The proposed LDO provides a regulated 1.8 V voltage from a 3.6 V to 1.94 V battery voltage over a −40 °C to 100 °C temperature range, with a compact topology (<0.10 mm² area) and a constant quiescent current of only 7.45 μA with 99.985% current efficiency, achieving remarkable state-of-art Figures of Merit (FoMs) for the regulating–transient performance. Experimental measurements validate its suitability for the target application, paving the way towards the future achievement of a truly portable System on Chip (SoC) platform for impedance sensors. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 6367 KiB

Open AccessArticle

Substrate Integrated Waveguide (SIW)-Based Wireless Temperature Sensor for Harsh Environments

by Qiulin Tan^1,2,*,†

, Yanjie Guo^1,2,†, Lei Zhang^1,2, Fei Lu^1,2

, Helei Dong^1,2 and Jijun Xiong^1,2

¹ Key Laboratory of Instrumentation Science & Dynamic Measurement, Ministry of Education, North University of China, Taiyuan 030051, China

² Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1406; https://doi.org/10.3390/s18051406 - 3 May 2018

Cited by 24 | Viewed by 5699

Abstract

This paper presents a new wireless sensor structure based on a substrate integrated circular waveguide (SICW) for the temperature test in harsh environments. The sensor substrate material is 99% alumina ceramic, and the SICW structure is composed of upper and lower metal plates [...] Read more.

This paper presents a new wireless sensor structure based on a substrate integrated circular waveguide (SICW) for the temperature test in harsh environments. The sensor substrate material is 99% alumina ceramic, and the SICW structure is composed of upper and lower metal plates and a series of metal cylindrical sidewall vias. A rectangular aperture antenna integrated on the surface of the SICW resonator is used for electromagnetic wave transmission between the sensor and the external antenna. The resonant frequency of the temperature sensor decreases when the temperature increases, because the relative permittivity of the alumina ceramic increases with temperature. The temperature sensor presented in this paper was tested four times at a range of 30–1200 °C, and a broad band coplanar waveguide (CPW)-fed antenna was used as an interrogation antenna during the test process. The resonant frequency changed from 2.371 to 2.141 GHz as the temperature varied from 30 to 1200 °C, leading to a sensitivity of 0.197 MHz/°C. The quality factor of the sensor changed from 3444.6 to 35.028 when the temperature varied from 30 to 1000 °C. Full article

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

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14 pages, 2344 KiB

Open AccessArticle

Fast Potentiometric Analysis of Lead in Aqueous Medium under Competitive Conditions Using an Acridono-Crown Ether Neutral Ionophore

by Ádám Golcs¹, Viola Horváth²

, Péter Huszthy¹

and Tünde Tóth^1,3,*

¹ Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, P.O. Box 91, H-1521 Budapest, Hungary

² MTA-BME Computation Driven Chemistry Research Group, P.O. Box 91, H-1521 Budapest, Hungary

³ Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary

Sensors 2018, 18(5), 1407; https://doi.org/10.3390/s18051407 - 3 May 2018

Cited by 26 | Viewed by 5186

Abstract

Lead is a particularly toxic heavy metal that is present above acceptable levels in the water of many countries. This article describes a quick detection method of lead(II) ions using a polyvinyl chloride (PVC)-based ion-selective membrane electrode containing an acridono-crown ether ionophore by [...] Read more.

Lead is a particularly toxic heavy metal that is present above acceptable levels in the water of many countries. This article describes a quick detection method of lead(II) ions using a polyvinyl chloride (PVC)-based ion-selective membrane electrode containing an acridono-crown ether ionophore by potentiometry. The electrochemical cell exhibits a Nernstian response for lead(II) ions between the concentration range of 10⁻⁴ to 10⁻² M, and can be used in the pH range of 4–7. The applicability of this sensor was verified by measuring a multicomponent aqueous sample. Under the given conditions, this electrode is suitable for the selective quantitative analysis of lead(II) ions in the presence of many additional metal ions. Full article

(This article belongs to the Section Chemical Sensors)

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17 pages, 7945 KiB

Open AccessArticle

Automated Inspection of Defects in Optical Fiber Connector End Face Using Novel Morphology Approaches

by Shuang Mei¹

, Yudan Wang¹, Guojun Wen^1,* and Yang Hu²

¹ School of Mechanical Engineering and Electronic Infomation, China University of Geosciences, Wuhan 430074, China

² Wuhan Second Ship Design and Research Institute, Wuhan 430205, China

Sensors 2018, 18(5), 1408; https://doi.org/10.3390/s18051408 - 3 May 2018

Cited by 7 | Viewed by 7402

Abstract

Increasing deployment of optical fiber networks and the need for reliable high bandwidth make the task of inspecting optical fiber connector end faces a crucial process that must not be neglected. Traditional end face inspections are usually performed by manual visual methods, which [...] Read more.

Increasing deployment of optical fiber networks and the need for reliable high bandwidth make the task of inspecting optical fiber connector end faces a crucial process that must not be neglected. Traditional end face inspections are usually performed by manual visual methods, which are low in efficiency and poor in precision for long-term industrial applications. More seriously, the inspection results cannot be quantified for subsequent analysis. Aiming at the characteristics of typical defects in the inspection process for optical fiber end faces, we propose a novel method, “difference of min-max ranking filtering” (DO2MR), for detection of region-based defects, e.g., dirt, oil, contamination, pits, and chips, and a special model, a “linear enhancement inspector” (LEI), for the detection of scratches. The DO2MR is a morphology method that intends to determine whether a pixel belongs to a defective region by comparing the difference of gray values of pixels in the neighborhood around the pixel. The LEI is also a morphology method that is designed to search for scratches at different orientations with a special linear detector. These two approaches can be easily integrated into optical inspection equipment for automatic quality verification. As far as we know, this is the first time that complete defect detection methods for optical fiber end faces are available in the literature. Experimental results demonstrate that the proposed DO2MR and LEI models yield good comprehensive performance with high precision and accepted recall rates, and the image-level detection accuracies reach 96.0 and 89.3%, respectively. Full article

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

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9 pages, 3776 KiB

Open AccessArticle

Demonstration of a Speckle Based Sensing with Pulse-Doppler Radar for Vibration Detection

by Nisan Ozana^1,*, Reuven Bauer^1,2, Koby Ashkenazy², Nissim Sasson², Ariel Schwarz¹, Amir Shemer¹ and Zeev Zalevsky¹

¹ Faculty of Engineering and the Nano Technology Center, Bar-Ilan University, Ramat-Gan 52900, Israel

² ELTA Systems Ltd., P.O.B. 330 Ashdod 7710202, Israel

Sensors 2018, 18(5), 1409; https://doi.org/10.3390/s18051409 - 3 May 2018

Cited by 6 | Viewed by 3704

Abstract

In previous works, an optical technique for extraction and separation of remote static vibrations has been demonstrated. In this paper, we will describe an approach in which RF speckle movement is used to extract remote vibrations of a static target. The use of [...] Read more.

In previous works, an optical technique for extraction and separation of remote static vibrations has been demonstrated. In this paper, we will describe an approach in which RF speckle movement is used to extract remote vibrations of a static target. The use of conventional radar Doppler methods is not suitable for detecting vibrations of static targets. In addition, the speckle method has an important advantage, in that it is able to detect vibrations at far greater distances than what is normally detected in classical optical methods. The experiment described in this paper was done using a motorized vehicle, which engine was turned on and off. The results showed that the system was able to distinguish between the different engine states, and in addition, was able to determine the vibration frequency of the engine. The first step towards real time detection of human vital signs using RF speckle patterns is presented. Full article

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

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16 pages, 2522 KiB

Open AccessArticle

Radio-Frequency Localization of Multiple Partial Discharges Sources with Two Receivers

by Guillermo Robles^*

, José Manuel Fresno

and Juan Manuel Martínez-Tarifa

Department of Electrical Engineering, Universidad Carlos III de Madrid, Avda, Universidad, 30, Leganés, 28911 Madrid, Spain

Sensors 2018, 18(5), 1410; https://doi.org/10.3390/s18051410 - 3 May 2018

Cited by 6 | Viewed by 4303

Abstract

Spatial localization of emitting sources is especially interesting in different fields of application. The focus of an earthquake, the determination of cracks in solid structures, or the position of bones inside a body are some examples of the use of multilateration techniques applied [...] Read more.

Spatial localization of emitting sources is especially interesting in different fields of application. The focus of an earthquake, the determination of cracks in solid structures, or the position of bones inside a body are some examples of the use of multilateration techniques applied to acoustic and vibratory signals. Radar, GPS and wireless sensors networks location are based on radiofrequency emissions and the techniques are the same as in the case of acoustic emissions. This paper is focused on the determination of the position of sources of partial discharges in electrical insulation for maintenance based on the condition of the electrical equipment. The use of this phenomenon is a mere example of the capabilities of the proposed method but it is very representative because the emission can be electromagnetic in the VHF and UHF ranges or acoustic. This paper presents a method to locate more than one source in space with only two receivers, one of them in a fixed position and the other describing a circumference around the first one. The signals arriving from the different sources to the antennas are first separated using a classification technique based on their spectral components. Then, the individualized time differences of arrival (TDOA) from the sources collected at different angles describe a function, angle versus TDOA, that has all the geometric information needed to locate the source. The paper will show how to derive these functions for any source analytically with the position of the source as unknown parameters. Then, it will be demonstrated that it is possible to fit the curve with experimental measurements of the TDOA to obtain the parameters of the position of each source. Finally, the technique is extended to the localization of the emitter in three dimensions. 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, 5720 KiB

Open AccessArticle

Low-Cost, Distributed Environmental Monitors for Factory Worker Health

by Geb W. Thomas^1,*, Sinan Sousan², Marcus Tatum¹, Xiaoxing Liu^1,3

, Christopher Zuidema⁴

, Mitchell Fitzpatrick¹, Kirsten A. Koehler⁴ and Thomas M. Peters²

¹ Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, IA 52242, USA

² Department of Occupational and Environmental Health, The University of Iowa, Iowa City, IA 52242, USA

³ Department of Mathematics and Computer Science, Adelphi University, New York, NY 11530, USA

⁴ Department of Environmental Health & Engineering, Johns Hopkins University, Baltimore, MD 21205, USA

Sensors 2018, 18(5), 1411; https://doi.org/10.3390/s18051411 - 3 May 2018

Cited by 49 | Viewed by 6186

Abstract

An integrated network of environmental monitors was developed to continuously measure several airborne hazards in a manufacturing facility. The monitors integrated low-cost sensors to measure particulate matter, carbon monoxide, ozone and nitrogen dioxide, noise, temperature and humidity. The monitors were developed and tested [...] Read more.

An integrated network of environmental monitors was developed to continuously measure several airborne hazards in a manufacturing facility. The monitors integrated low-cost sensors to measure particulate matter, carbon monoxide, ozone and nitrogen dioxide, noise, temperature and humidity. The monitors were developed and tested in situ for three months in several overlapping deployments, before a full cohort of 40 was deployed in a heavy vehicle manufacturing facility for a year of data collection. The monitors collect data from each sensor and report them to a central database every 5 min. The work includes an experimental validation of the particle, gas and noise monitors. The R² for the particle sensor ranges between 0.98 and 0.99 for particle mass densities up to 300 μg/m³. The R² for the carbon monoxide sensor is 0.99 for concentrations up to 15 ppm. The R² for the oxidizing gas sensor is 0.98 over the sensitive range from 20 to 180 ppb. The noise monitor is precise within 1% between 65 and 95 dBA. This work demonstrates the capability of distributed monitoring as a means to examine exposure variability in both space and time, building an important preliminary step towards a new approach for workplace hazard monitoring. Full article

(This article belongs to the Section Sensor Networks)

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22 pages, 6894 KiB

Open AccessArticle

Manipulation of Unknown Objects to Improve the Grasp Quality Using Tactile Information

by Andrés Montaño

and Raúl Suárez^*

Institute of Industrial and Control Engineering (IOC), Universitat Politècnica de Catalunya (UPC), 08028 Barcelona, Spain

Sensors 2018, 18(5), 1412; https://doi.org/10.3390/s18051412 - 3 May 2018

Cited by 22 | Viewed by 4511

Abstract

This work presents a novel and simple approach in the area of manipulation of unknown objects considering both geometric and mechanical constraints of the robotic hand. Starting with an initial blind grasp, our method improves the grasp quality through manipulation considering the three [...] Read more.

This work presents a novel and simple approach in the area of manipulation of unknown objects considering both geometric and mechanical constraints of the robotic hand. Starting with an initial blind grasp, our method improves the grasp quality through manipulation considering the three common goals of the manipulation process: improving the hand configuration, the grasp quality and the object positioning, and, at the same time, prevents the object from falling. Tactile feedback is used to obtain local information of the contacts between the fingertips and the object, and no additional exteroceptive feedback sources are considered in the approach. The main novelty of this work lies in the fact that the grasp optimization is performed on-line as a reactive procedure using the tactile and kinematic information obtained during the manipulation. Experimental results are shown to illustrate the efficiency of the approach. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 2956 KiB

Open AccessArticle

Energy Aware Cluster-Based Routing in Flying Ad-Hoc Networks

by Farhan Aadil¹

, Ali Raza¹, Muhammad Fahad Khan¹, Muazzam Maqsood¹

, Irfan Mehmood^2,*

and Seungmin Rho³

¹ Department of Computer Science, COMSATS Institute of Information Technology, Attock 43600, Pakistan

² Department of Software, Sejong University, Seoul 143-747, Korea

³ Department of Media Software, Sungkyul University, Anyang 430-742, Korea

Sensors 2018, 18(5), 1413; https://doi.org/10.3390/s18051413 - 3 May 2018

Cited by 138 | Viewed by 7951

Abstract

Flying ad-hoc networks (FANETs) are a very vibrant research area nowadays. They have many military and civil applications. Limited battery energy and the high mobility of micro unmanned aerial vehicles (UAVs) represent their two main problems, i.e., short flight time and inefficient routing. [...] Read more.

Flying ad-hoc networks (FANETs) are a very vibrant research area nowadays. They have many military and civil applications. Limited battery energy and the high mobility of micro unmanned aerial vehicles (UAVs) represent their two main problems, i.e., short flight time and inefficient routing. In this paper, we try to address both of these problems by means of efficient clustering. First, we adjust the transmission power of the UAVs by anticipating their operational requirements. Optimal transmission range will have minimum packet loss ratio (PLR) and better link quality, which ultimately save the energy consumed during communication. Second, we use a variant of the K-Means Density clustering algorithm for selection of cluster heads. Optimal cluster heads enhance the cluster lifetime and reduce the routing overhead. The proposed model outperforms the state of the art artificial intelligence techniques such as Ant Colony Optimization-based clustering algorithm and Grey Wolf Optimization-based clustering algorithm. The performance of the proposed algorithm is evaluated in term of number of clusters, cluster building time, cluster lifetime and energy consumption. Full article

(This article belongs to the Special Issue Advances on Vehicular Networks: From Sensing to Autonomous Driving)

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10 pages, 4200 KiB

Open AccessArticle

A Sequential Multiplicative Extended Kalman Filter for Attitude Estimation Using Vector Observations

by Fangjun Qin¹, Lubin Chang^1,*

, Sai Jiang² and Feng Zha¹

¹ Department of Navigation Engineering, Naval University of Engineering, Wuhan 430000, China

² Office of Research and Development, Naval University of Engineering, Wuhan 430000, China

Sensors 2018, 18(5), 1414; https://doi.org/10.3390/s18051414 - 3 May 2018

Cited by 16 | Viewed by 6118

Abstract

In this paper, a sequential multiplicative extended Kalman filter (SMEKF) is proposed for attitude estimation using vector observations. In the proposed SMEKF, each of the vector observations is processed sequentially to update the attitude, which can make the measurement model linearization more accurate [...] Read more.

In this paper, a sequential multiplicative extended Kalman filter (SMEKF) is proposed for attitude estimation using vector observations. In the proposed SMEKF, each of the vector observations is processed sequentially to update the attitude, which can make the measurement model linearization more accurate for the next vector observation. This is the main difference to Murrell’s variation of the MEKF, which does not update the attitude estimate during the sequential procedure. Meanwhile, the covariance is updated after all the vector observations have been processed, which is used to account for the special characteristics of the reset operation necessary for the attitude update. This is the main difference to the traditional sequential EKF, which updates the state covariance at each step of the sequential procedure. The numerical simulation study demonstrates that the proposed SMEKF has more consistent and accurate performance in a wide range of initial estimate errors compared to the MEKF and its traditional sequential forms. Full article

(This article belongs to the Collection Positioning and Navigation)

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15 pages, 2478 KiB

Open AccessArticle

Compact FTICR Mass Spectrometry for Real Time Monitoring of Volatile Organic Compounds

by Joël Lemaire^1,*

, Sébastien Thomas², Allan Lopes¹, Essyllt Louarn¹

, Hélène Mestdagh¹, Hubert Latappy^1,2, Julien Leprovost² and Michel Heninger^1,2,*

¹ Laboratoire de Chimie Physique, CNRS, Univ. Paris Sud, Université Paris Saclay, 91405 Orsay, France

² AlyXan, Centre Hoche, 91260 Juvisy-sur-Orge, France

Sensors 2018, 18(5), 1415; https://doi.org/10.3390/s18051415 - 3 May 2018

Cited by 17 | Viewed by 6191

Abstract

In this paper, we present a compact Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS) designed for real time analysis of volatile organic compounds (VOCs) in air or in water. The spectrometer is based on a structured permanent magnet made with NdFeB segments. [...] Read more.

In this paper, we present a compact Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS) designed for real time analysis of volatile organic compounds (VOCs) in air or in water. The spectrometer is based on a structured permanent magnet made with NdFeB segments. Chemical ionization is implemented inside the ICR cell. The most widely used reaction is the proton transfer reaction using H₃O⁺ precursor ions, but other ionic precursors can be used to extend the range of species that can be detected. Complex mixtures are studied by switching automatically from one precursor to another. The accuracy obtained on the mass to charge ratio (Δm/z 5 × 10⁻³), allows a precise identification of the VOCs present and the limit of detection is 200 ppb without accumulation. The time resolution is a few seconds, mainly limited by the time necessary to come back to background pressure after the gas pulses. The real time measurement will be illustrated by the monitoring of VOCs produced during the thermal degradation of a polymer and by an example where three different precursor ions are used alternatively to monitor a gas sample. Full article

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

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12 pages, 2908 KiB

Open AccessArticle

The Use of Drones in Spain: Towards a Platform for Controlling UAVs in Urban Environments

by Pablo Chamoso^1,*

, Alfonso González-Briones¹

, Alberto Rivas^1,*

, Federico Bueno De Mata² and Juan Manuel Corchado^1,3,4

¹ BISITE Digital Innovation Hub, University of Salamanca, Edificio Multiusos I+D+i, Calle Espejo 2, 37007 Salamanca, Spain

² Faculty of Law, University of Salamanca, C. Miguel de Unamuno. P. Francisco Tomás y Valiente, s/n. 37007 Salamanca, Spain

³ Department of Electronics, Information and Communication, Faculty of Engineering, Osaka Institute of Technology, Osaka 535-8585, Japan

⁴ Pusat Komputeran dan Informatik, Universiti Malaysia Kelantan, Karung Berkunci 36, Pengkaan Chepa, Kota Bharu 16100, Kelantan, Malaysia

Sensors 2018, 18(5), 1416; https://doi.org/10.3390/s18051416 - 3 May 2018

Cited by 22 | Viewed by 6189

Abstract

Rapid advances in technology make it necessary to prepare our society in every aspect. Some of the most significant technological developments of the last decade are the UAVs (Unnamed Aerial Vehicles) or drones. UAVs provide a wide range of new possibilities and have [...] Read more.

Rapid advances in technology make it necessary to prepare our society in every aspect. Some of the most significant technological developments of the last decade are the UAVs (Unnamed Aerial Vehicles) or drones. UAVs provide a wide range of new possibilities and have become a tool that we now use on a daily basis. However, if their use is not controlled, it could entail several risks, which make it necessary to legislate and monitor UAV flights to ensure, inter alia, the security and privacy of all citizens. As a result of this problem, several laws have been passed which seek to regulate their use; however, no proposals have been made with regards to the control of airspace from a technological point of view. This is exactly what we propose in this article: a platform with different modes designed to control UAVs and monitor their status. The features of the proposed platform provide multiple advantages that make the use of UAVs more secure, such as prohibiting UAVs’ access to restricted areas or avoiding collisions between vehicles. The platform has been successfully tested in Salamanca, Spain. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2018)

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24 pages, 14211 KiB

Open AccessArticle

Direct Reflectance Measurements from Drones: Sensor Absolute Radiometric Calibration and System Tests for Forest Reflectance Characterization

by Teemu Hakala¹, Lauri Markelin^1,*

, Eija Honkavaara¹

, Barry Scott², Theo Theocharous², Olli Nevalainen¹

, Roope Näsi¹

, Juha Suomalainen¹

, Niko Viljanen¹

, Claire Greenwell² and Nigel Fox²

¹ Finnish Geospatial Research Institute FGI, National Land Survey of Finland, Geodeetinrinne 2, 02430 Masala, Finland

² National Physical Laboratory NPL, Teddington TW11-0LW, UK

Sensors 2018, 18(5), 1417; https://doi.org/10.3390/s18051417 - 3 May 2018

Cited by 69 | Viewed by 11069

Abstract

Drone-based remote sensing has evolved rapidly in recent years. Miniaturized hyperspectral imaging sensors are becoming more common as they provide more abundant information of the object compared to traditional cameras. Reflectance is a physically defined object property and therefore often preferred output of [...] Read more.

Drone-based remote sensing has evolved rapidly in recent years. Miniaturized hyperspectral imaging sensors are becoming more common as they provide more abundant information of the object compared to traditional cameras. Reflectance is a physically defined object property and therefore often preferred output of the remote sensing data capture to be used in the further processes. Absolute calibration of the sensor provides a possibility for physical modelling of the imaging process and enables efficient procedures for reflectance correction. Our objective is to develop a method for direct reflectance measurements for drone-based remote sensing. It is based on an imaging spectrometer and irradiance spectrometer. This approach is highly attractive for many practical applications as it does not require in situ reflectance panels for converting the sensor radiance to ground reflectance factors. We performed SI-traceable spectral and radiance calibration of a tuneable Fabry-Pérot Interferometer -based (FPI) hyperspectral camera at the National Physical Laboratory NPL (Teddington, UK). The camera represents novel technology by collecting 2D format hyperspectral image cubes using time sequential spectral scanning principle. The radiance accuracy of different channels varied between ±4% when evaluated using independent test data, and linearity of the camera response was on average 0.9994. The spectral response calibration showed side peaks on several channels that were due to the multiple orders of interference of the FPI. The drone-based direct reflectance measurement system showed promising results with imagery collected over Wytham Forest (Oxford, UK). Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 949 KiB

Open AccessArticle

A Method for Estimating the Polarimetric Scattering Matrix of Moving Target for Simultaneous Fully Polarimetric Radar

by Fulai Wang^*

, Chao Li, Chen Pang, Yongzhen Li and Xuesong Wang

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

Sensors 2018, 18(5), 1418; https://doi.org/10.3390/s18051418 - 3 May 2018

Cited by 4 | Viewed by 3246

Abstract

To precisely obtain the polarimetric scattering matrix (PSM) of moving target, a measurement model for the simultaneous fully polarimetric radar is formulated. The calibration errors and isolation of the transmitted waveforms are considered. To address the decline in performance of the traditional PSM [...] Read more.

To precisely obtain the polarimetric scattering matrix (PSM) of moving target, a measurement model for the simultaneous fully polarimetric radar is formulated. The calibration errors and isolation of the transmitted waveforms are considered. To address the decline in performance of the traditional PSM estimation methods when the target moves, a novel method with measurement selection is proposed. Numerical experiments are conducted to demonstrate and validate the superiority of the proposed method, especially for the PSM estimation of the target with non-uniform motion. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 5155 KiB

Open AccessArticle

Distributed Fast Self-Organized Maps for Massive Spectrophotometric Data Analysis ^†

by Carlos Dafonte^1,*

, Daniel Garabato^1,*

, Marco A. Álvarez¹

and Minia Manteiga²

¹ CITIC—Department of Computer Science, University of A Coruña, Campus de Elviña s/n, 15071 A Coruña, Spain

² CITIC—Astronomy and Astrophysics, University of A Coruña, Campus de Elviña s/n, 15071 A Coruña, Spain

^† This paper is an extended version of our paper published in Garabato, D., Dafonte, C., Álvarez, M. A., Manteiga, M. Distributed Unsupervised Clustering for Outlier Analysis in the Biggest Milky Way Survey: ESA Gaia Mission. In Proceedings of the 11th International Conference on Ubiquitous Computing and Ambient Intelligence, Philadelphia, PA, USA, 7–10 November 2017.

Sensors 2018, 18(5), 1419; https://doi.org/10.3390/s18051419 - 3 May 2018

Cited by 6 | Viewed by 3834

Abstract

Analyzing huge amounts of data becomes essential in the era of Big Data, where databases are populated with hundreds of Gigabytes that must be processed to extract knowledge. Hence, classical algorithms must be adapted towards distributed computing methodologies that leverage the underlying computational [...] Read more.

Analyzing huge amounts of data becomes essential in the era of Big Data, where databases are populated with hundreds of Gigabytes that must be processed to extract knowledge. Hence, classical algorithms must be adapted towards distributed computing methodologies that leverage the underlying computational power of these platforms. Here, a parallel, scalable, and optimized design for self-organized maps (SOM) is proposed in order to analyze massive data gathered by the spectrophotometric sensor of the European Space Agency (ESA) Gaia spacecraft, although it could be extrapolated to other domains. The performance comparison between the sequential implementation and the distributed ones based on Apache Hadoop and Apache Spark is an important part of the work, as well as the detailed analysis of the proposed optimizations. Finally, a domain-specific visualization tool to explore astronomical SOMs is presented. 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, 2842 KiB

Open AccessArticle

A Finite State Machine Approach to Algorithmic Lateral Inhibition for Real-Time Motion Detection ^†

by María T. López, Aurelio Bermúdez

, Francisco Montero, José L. Sánchez and Antonio Fernández-Caballero^*

¹ Departamento de Sistemas Informáticos, Universidad de Castilla-La Mancha, 02071-Albacete, Spain

^† Homage to the memory of Prof José Mira, our close master and friend, 10 years after his death.

Sensors 2018, 18(5), 1420; https://doi.org/10.3390/s18051420 - 3 May 2018

Cited by 2 | Viewed by 4037

Abstract

Many researchers have explored the relationship between recurrent neural networks and finite state machines. Finite state machines constitute the best-characterized computational model, whereas artificial neural networks have become a very successful tool for modeling and problem solving. The neurally-inspired lateral inhibition method, and [...] Read more.

Many researchers have explored the relationship between recurrent neural networks and finite state machines. Finite state machines constitute the best-characterized computational model, whereas artificial neural networks have become a very successful tool for modeling and problem solving. The neurally-inspired lateral inhibition method, and its application to motion detection tasks, have been successfully implemented in recent years. In this paper, control knowledge of the algorithmic lateral inhibition (ALI) method is described and applied by means of finite state machines, in which the state space is constituted from the set of distinguishable cases of accumulated charge in a local memory. The article describes an ALI implementation for a motion detection task. For the implementation, we have chosen to use one of the members of the 16-nm Kintex UltraScale+ family of Xilinx FPGAs. FPGAs provide the necessary accuracy, resolution, and precision to run neural algorithms alongside current sensor technologies. The results offered in this paper demonstrate that this implementation provides accurate object tracking performance on several datasets, obtaining a high F-score value (0.86) for the most complex sequence used. Moreover, it outperforms implementations of a complete ALI algorithm and a simplified version of the ALI algorithm—named “accumulative computation”—which was run about ten years ago, now reaching real-time processing times that were simply not achievable at that time for ALI. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2018)

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21 pages, 1051 KiB

Open AccessArticle

Defense Strategies for Asymmetric Networked Systems with Discrete Components

by Nageswara S. V. Rao^1,*,†, Chris Y. T. Ma^2,†, Kjell Hausken^3,†, Fei He^4,†, David K. Y. Yau^5,† and Jun Zhuang^6,†

¹ Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

² Hang Seng Management College, Hong Kong

³ Faculty of Social Sciences, University of Stavanger, 4036 Stavanger, Norway

⁴ Department of Mechanical and Industrial Engineering, Texas A&M University, Kingsville, TX 78363, USA

⁵ Information Systems Technology and Design Clusteer, Singapore University of Technology and Design, Singapore 487372, Singapore

⁶ Department of Industrial and Systems Engineering, University at Buffalo, Buffalo, NY 14260, USA

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1421; https://doi.org/10.3390/s18051421 - 3 May 2018

Cited by 15 | Viewed by 3743

Abstract

We consider infrastructures consisting of a network of systems, each composed of discrete components. The network provides the vital connectivity between the systems and hence plays a critical, asymmetric role in the infrastructure operations. The individual components of the systems can be attacked [...] Read more.

We consider infrastructures consisting of a network of systems, each composed of discrete components. The network provides the vital connectivity between the systems and hence plays a critical, asymmetric role in the infrastructure operations. The individual components of the systems can be attacked by cyber and physical means and can be appropriately reinforced to withstand these attacks. We formulate the problem of ensuring the infrastructure performance as a game between an attacker and a provider, who choose the numbers of the components of the systems and network to attack and reinforce, respectively. The costs and benefits of attacks and reinforcements are characterized using the sum-form, product-form and composite utility functions, each composed of a survival probability term and a component cost term. We present a two-level characterization of the correlations within the infrastructure: (i) the aggregate failure correlation function specifies the infrastructure failure probability given the failure of an individual system or network, and (ii) the survival probabilities of the systems and network satisfy first-order differential conditions that capture the component-level correlations using multiplier functions. We derive Nash equilibrium conditions that provide expressions for individual system survival probabilities and also the expected infrastructure capacity specified by the total number of operational components. We apply these results to derive and analyze defense strategies for distributed cloud computing infrastructures using cyber-physical models. Full article

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

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41 pages, 6654 KiB

Open AccessArticle

A Cross-Layer Optimized Opportunistic Routing Scheme for Loss-and-Delay Sensitive WSNs

by Xin Xu¹, Minjiao Yuan¹, Xiao Liu^1,*, Anfeng Liu^1,2

, Neal N. Xiong³

, Zhiping Cai⁴ and Tian Wang⁵

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, OK 74464, USA, xiongnaixue@gmail.com

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

⁵ School of Computer Science, National Huaqiao University, Quanzhou 362000 China

Sensors 2018, 18(5), 1422; https://doi.org/10.3390/s18051422 - 3 May 2018

Cited by 28 | Viewed by 4032

Abstract

In wireless sensor networks (WSNs), communication links are typically error-prone and unreliable, so providing reliable and timely data routing for loss- and delay-sensitive applications in WSNs it is a challenge issue. Additionally, with specific thresholds in practical applications, the loss and delay sensitivity [...] Read more.

In wireless sensor networks (WSNs), communication links are typically error-prone and unreliable, so providing reliable and timely data routing for loss- and delay-sensitive applications in WSNs it is a challenge issue. Additionally, with specific thresholds in practical applications, the loss and delay sensitivity implies requirements for high reliability and low delay. Opportunistic Routing (OR) has been well studied in WSNs to improve reliability for error-prone and unreliable wireless communication links where the transmission power is assumed to be identical in the whole network. In this paper, a Cross-layer Optimized Opportunistic Routing (COOR) scheme is proposed to improve the communication link reliability and reduce delay for loss-and-delay sensitive WSNs. The main contribution of the COOR scheme is making full use of the remaining energy in networks to increase the transmission power of most nodes, which will provide a higher communication reliability or further transmission distance. Two optimization strategies referred to as COOR(R) and COOR(P) of the COOR scheme are proposed to improve network performance. In the case of increasing the transmission power, the COOR(R) strategy chooses a node that has a higher communication reliability with same distance in comparison to the traditional opportunistic routing when selecting the next hop candidate node. Since the reliability of data transmission is improved, the delay of the data reaching the sink is reduced by shortening the time of communication between candidate nodes. On the other hand, the COOR(P) strategy prefers a node that has the same communication reliability with longer distance. As a result, network performance can be improved for the following reasons: (a) the delay is reduced as fewer hops are needed while the packet reaches the sink in longer transmission distance circumstances; (b) the reliability can be improved since it is the product of the reliability of every hop of the routing path, and the count is reduced while the reliability of each hop is the same as the traditional method. After analyzing the energy consumption of the network in detail, the value of optimized transmission power in different areas is given. On the basis of a large number of experimental and theoretical analyses, the results show that the COOR scheme will increase communication reliability by 36.62–87.77%, decrease delay by 21.09–52.48%, and balance the energy consumption of 86.97% of the nodes in the WSNs. Full article

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

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13 pages, 2037 KiB

Open AccessArticle

Construction and Functionality of a Ceramic Resonant Pressure Sensor for Operation at Elevated Temperatures

by Matej Sadl^1,2,*

, Andraz Bradesko^1,2

, Darko Belavic^1,3,4, Andreja Bencan^1,2, Barbara Malic^1,2 and Tadej Rojac^1,2

¹ Electronic Ceramics Department, Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia

² Jozef Stefan International Postgraduate School, Jamova cesta 39, 1000 Ljubljana, Slovenia

³ Centre of Excellence NAMASTE, Jamova cesta 39, 1000 Ljubljana, Slovenia

⁴ HIPOT-RR, Šentpeter 18, 8222 Otočec, Slovenia

Sensors 2018, 18(5), 1423; https://doi.org/10.3390/s18051423 - 3 May 2018

Cited by 8 | Viewed by 5068

Abstract

Piezoelectric ceramic resonant pressure sensors have shown potential as sensing elements for harsh environments, such as elevated temperatures. For operating temperatures exceeding ~250 °C, conventional and widely used Pb(Zr,Ti)O₃ (PZT) piezoelectrics should be replaced. Here, a ceramic pressure sensor from low-temperature co-fired [...] Read more.

Piezoelectric ceramic resonant pressure sensors have shown potential as sensing elements for harsh environments, such as elevated temperatures. For operating temperatures exceeding ~250 °C, conventional and widely used Pb(Zr,Ti)O₃ (PZT) piezoelectrics should be replaced. Here, a ceramic pressure sensor from low-temperature co-fired ceramics (LTCC) was constructed by integrating a piezoelectric actuator made from bismuth ferrite (BiFeO₃) on a diaphragm. This ferroelectric material was selected because of its high Curie temperature (T_C = 825 °C) and as a lead-free piezoelectric extensively investigated for high-temperature applications. In order to construct a sensor with suitable pressure sensitivity, numerical simulations were used to define the optimum construction dimensions. The functionality of the pressure sensor was tested up to 201 °C. The measurements confirmed a pressure sensitivity, i.e., resonance frequency shift of the sensor per unit of pressure, of −8.7 Hz/kPa up to 171 °C. It was suggested that the main reason for the hindered operation at the elevated temperatures could lie in the thermo-mechanical properties of the diaphragm and the adhesive bonding at the actuator-diaphragm interconnection. Full article

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

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7 pages, 705 KiB

Open AccessArticle

Evaluation of Meropenem Pharmacokinetics in an Experimental Acute Respiratory Distress Syndrome (ARDS) Model during Extracorporeal Membrane Oxygenation (ECMO) by Using a PenP β-Lactamase Biosensor

by Max Andresen^1,*, Joaquin Araos¹, Kwok-Yin Wong², Yun-Chung Leung², Lok-Yan So²

, Wai-Ting Wong², Salvador Cabrera³, Camila Silva¹, Leyla Alegria¹, Alejandro Bruhn¹

and Dagoberto Soto¹

¹ Laboratory 103B, Centro de Investigaciones Médicas, Departamento de Medicina Intensiva, Facultad de Medicina y Hospital Clínico, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago 8330024, Chile

² State Key Laboratory of Chirosciences, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China

³ Departamento de Farmacia, Facultad de Farmacia, Universidad de Concepción, Víctor Lamas 1290, Concepción 4070386, Chile

Sensors 2018, 18(5), 1424; https://doi.org/10.3390/s18051424 - 4 May 2018

Cited by 11 | Viewed by 4827

Abstract

Introduction: The use of antibiotics is mandatory in patients during extracorporeal membrane oxygenation (ECMO) support. Clinical studies have shown high variability in the antibiotic concentrations, as well as sequestration of them by the ECMO circuit, suggesting that the doses and/or interval administration used [...] Read more.

Introduction: The use of antibiotics is mandatory in patients during extracorporeal membrane oxygenation (ECMO) support. Clinical studies have shown high variability in the antibiotic concentrations, as well as sequestration of them by the ECMO circuit, suggesting that the doses and/or interval administration used during ECMO may not be adequate. Thus, a fast response sensor to estimate antibiotic concentrations in this setting would contribute to improve dose adjustments. The biosensor PenP has been shown to have a dynamic range, sensitivity and specificity useful for pharmacokinetic (PK) tests in healthy subjects. However, the use of this biosensor in the context of a complex critical condition, such as ECMO during acute respiratory distress syndrome (ARDS), has not been tested. Objectives: To describe, by using PenP Biosensor, the pharmacokinetic of meropenem in a 24-h animal ARDS/ECMO model. Methods: The PK of meropenem was evaluated in a swine model before and during ECMO. Results: The PK parameters such as maximum concentration (Cmax), elimination rate constant (Ke), and cleareance (Cl), were not significantly altered during ECMO support. Conclusions: (a) ECMO does not affect the PK of meropenem, at least during the first 24 h; and (b) PenP has the potential to become an effective tool for making medical decisions associated with the dose model of antibiotics in a critical patient context. Full article

(This article belongs to the Section Biosensors)

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18 pages, 7291 KiB

Open AccessArticle

Partial Discharge Ultrasound Detection Using the Sagnac Interferometer System

by Yu Wang¹

, Xiaomin Li², Yan Gao², Hongjuan Zhang², Dong Wang¹ and Baoquan Jin^1,3,*

¹ Key Laboratory of Advanced Transducers and Intelligent Control Systems (Ministry of Education and Shanxi Province), College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China

² College of Electrical and Power Engineering, Taiyuan University of Technology, Taiyuan 030024, China

³ State Key Laboratory of Coal and CBM Co-mining, Jincheng, Shanxi 048000, China

Sensors 2018, 18(5), 1425; https://doi.org/10.3390/s18051425 - 4 May 2018

Cited by 57 | Viewed by 9597

Abstract

Partial discharge detection is crucial for electrical cable safety evaluation. The ultrasonic signals frequently generated in the partial discharge process contains important characteristic information. However, traditional ultrasonic transducers are easily subject to strong electromagnetic interference in environments with high voltages and strong magnetic [...] Read more.

Partial discharge detection is crucial for electrical cable safety evaluation. The ultrasonic signals frequently generated in the partial discharge process contains important characteristic information. However, traditional ultrasonic transducers are easily subject to strong electromagnetic interference in environments with high voltages and strong magnetic fields. In order to overcome this problem, an optical fiber Sagnac interferometer system is proposed for partial discharge ultrasound detection. Optical fiber sensing and time-frequency analysis of the ultrasonic signals excited by the piezoelectric ultrasonic transducer is realized for the first time. The effective frequency band of the Sagnac interferometer system was up to 175 kHz with the help of a designed 10 kV partial discharge simulator device. Using the cumulative histogram method, the characteristic ultrasonic frequency band of the partial discharges was between 28.9 kHz and 57.6 kHz for this optical fiber partial discharge detection system. This new ultrasound sensor can be used as an ideal ultrasonic source for the intrinsically safe detection of partial discharges in an explosive environment. Full article

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29 pages, 1381 KiB

Open AccessArticle

Do Monetary Incentives Influence Users’ Behavior in Participatory Sensing?

by Ngo Manh Khoi^1,*

, Sven Casteleyn¹

, M. Mehdi Moradi¹

and Edzer Pebesma²

¹ GEOTEC, Institute of New Imaging Technologies (INIT), Universitat Jaume I, 12071 Castellón, Spain

² Institute for Geoinformatics, Universität Münster, 48149 Münster, Germany

Sensors 2018, 18(5), 1426; https://doi.org/10.3390/s18051426 - 4 May 2018

Cited by 14 | Viewed by 5425

Abstract

Participatory sensing combines the powerful sensing capabilities of current mobile devices with the mobility and intelligence of human beings, and as such has to potential to collect various types of information at a high spatial and temporal resolution. Success, however, entirely relies on [...] Read more.

Participatory sensing combines the powerful sensing capabilities of current mobile devices with the mobility and intelligence of human beings, and as such has to potential to collect various types of information at a high spatial and temporal resolution. Success, however, entirely relies on the willingness and motivation of the users to carry out sensing tasks, and thus it is essential to incentivize the users’ active participation. In this article, we first present an open, generic participatory sensing framework (Citizense) which aims to make participatory sensing more accessible, flexible and transparent. Within the context of this framework we adopt three monetary incentive mechanisms which prioritize the fairness for the users while maintaining their simplicity and portability: fixed micro-payment, variable micro-payment and lottery. This incentive-enabled framework is then deployed on a large scale, real-world case study, where 230 participants were exposed to 44 different sensing campaigns. By randomly distributing incentive mechanisms among participants and a subset of campaigns, we study the behaviors of the overall population as well as the behaviors of different subgroups divided by demographic information with respect to the various incentive mechanisms. As a result of our study, we can conclude that (1) in general, monetary incentives work to improve participation rate; (2) for the overall population, a general descending order in terms of effectiveness of the incentive mechanisms can be established: fixed micro-payment first, then lottery-style payout and finally variable micro-payment. These two conclusions hold for all the demographic subgroups, even though different different internal distances between the incentive mechanisms are observed for different subgroups. Finally, a negative correlation between age and participation rate was found: older participants contribute less compared to their younger peers. Full article

(This article belongs to the Special Issue Smart Cities)

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14 pages, 2501 KiB

Open AccessArticle

An Embodied Multi-Sensor Fusion Approach to Visual Motion Estimation Using Unsupervised Deep Networks

by E. Jared Shamwell^1,*

, William D. Nothwang¹ and Donald Perlis²

¹ Sensors and Electron Devices Directorate, US Army Research Laboratory, 2800 Powder Mill Rd, Adelphi MD 20783, USA

² Department of Computer Science, University of Maryland, A.V. Williams Building, College Park, MD 20740, USA

Sensors 2018, 18(5), 1427; https://doi.org/10.3390/s18051427 - 4 May 2018

Cited by 3 | Viewed by 4067

Abstract

Aimed at improving size, weight, and power (SWaP)-constrained robotic vision-aided state estimation, we describe our unsupervised, deep convolutional-deconvolutional sensor fusion network, Multi-Hypothesis DeepEfference (MHDE). MHDE learns to intelligently combine noisy heterogeneous sensor data to predict several probable hypotheses for the dense, pixel-level correspondence [...] Read more.

Aimed at improving size, weight, and power (SWaP)-constrained robotic vision-aided state estimation, we describe our unsupervised, deep convolutional-deconvolutional sensor fusion network, Multi-Hypothesis DeepEfference (MHDE). MHDE learns to intelligently combine noisy heterogeneous sensor data to predict several probable hypotheses for the dense, pixel-level correspondence between a source image and an unseen target image. We show how our multi-hypothesis formulation provides increased robustness against dynamic, heteroscedastic sensor and motion noise by computing hypothesis image mappings and predictions at 76–357 Hz depending on the number of hypotheses being generated. MHDE fuses noisy, heterogeneous sensory inputs using two parallel, inter-connected architectural pathways and n (1–20 in this work) multi-hypothesis generating sub-pathways to produce n global correspondence estimates between a source and a target image. We evaluated MHDE on the KITTI Odometry dataset and benchmarked it against the vision-only DeepMatching and Deformable Spatial Pyramids algorithms and were able to demonstrate a significant runtime decrease and a performance increase compared to the next-best performing method. Full article

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

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17 pages, 4279 KiB

Open AccessArticle

Implementation of Cyber-Physical Production Systems for Quality Prediction and Operation Control in Metal Casting

by JuneHyuck Lee, Sang Do Noh, Hyun-Jung Kim and Yong-Shin Kang^*

Department of Systems Management Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Korea

Sensors 2018, 18(5), 1428; https://doi.org/10.3390/s18051428 - 4 May 2018

Cited by 123 | Viewed by 11672

Abstract

The prediction of internal defects of metal casting immediately after the casting process saves unnecessary time and money by reducing the amount of inputs into the next stage, such as the machining process, and enables flexible scheduling. Cyber-physical production systems (CPPS) perfectly fulfill [...] Read more.

The prediction of internal defects of metal casting immediately after the casting process saves unnecessary time and money by reducing the amount of inputs into the next stage, such as the machining process, and enables flexible scheduling. Cyber-physical production systems (CPPS) perfectly fulfill the aforementioned requirements. This study deals with the implementation of CPPS in a real factory to predict the quality of metal casting and operation control. First, a CPPS architecture framework for quality prediction and operation control in metal-casting production was designed. The framework describes collaboration among internet of things (IoT), artificial intelligence, simulations, manufacturing execution systems, and advanced planning and scheduling systems. Subsequently, the implementation of the CPPS in actual plants is described. Temperature is a major factor that affects casting quality, and thus, temperature sensors and IoT communication devices were attached to casting machines. The well-known NoSQL database, HBase and the high-speed processing/analysis tool, Spark, are used for IoT repository and data pre-processing, respectively. Many machine learning algorithms such as decision tree, random forest, artificial neural network, and support vector machine were used for quality prediction and compared with R software. Finally, the operation of the entire system is demonstrated through a CPPS dashboard. In an era in which most CPPS-related studies are conducted on high-level abstract models, this study describes more specific architectural frameworks, use cases, usable software, and analytical methodologies. In addition, this study verifies the usefulness of CPPS by estimating quantitative effects. This is expected to contribute to the proliferation of CPPS in the industry. Full article

(This article belongs to the Special Issue Design and Implementation of Future CPS)

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16 pages, 3729 KiB

Open AccessArticle

A Novel Fault Diagnosis Method for Rotating Machinery Based on a Convolutional Neural Network

by Sheng Guo

, Tao Yang^*, Wei Gao and Chen Zhang

School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

Sensors 2018, 18(5), 1429; https://doi.org/10.3390/s18051429 - 4 May 2018

Cited by 213 | Viewed by 11042

Abstract

Fault diagnosis is critical to ensure the safety and reliable operation of rotating machinery. Most methods used in fault diagnosis of rotating machinery extract a few feature values from vibration signals for fault diagnosis, which is a dimensionality reduction from the original signal [...] Read more.

Fault diagnosis is critical to ensure the safety and reliable operation of rotating machinery. Most methods used in fault diagnosis of rotating machinery extract a few feature values from vibration signals for fault diagnosis, which is a dimensionality reduction from the original signal and may omit some important fault messages in the original signal. Thus, a novel diagnosis method is proposed involving the use of a convolutional neural network (CNN) to directly classify the continuous wavelet transform scalogram (CWTS), which is a time-frequency domain transform of the original signal and can contain most of the information of the vibration signals. In this method, CWTS is formed by discomposing vibration signals of rotating machinery in different scales using wavelet transform. Then the CNN is trained to diagnose faults, with CWTS as the input. A series of experiments is conducted on the rotor experiment platform using this method. The results indicate that the proposed method can diagnose the faults accurately. To verify the universality of this method, the trained CNN was also used to perform fault diagnosis for another piece of rotor equipment, and a good result was achieved. Full article

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

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17 pages, 3569 KiB

Open AccessArticle

Analysis and Compensation of Modulation Angular Rate Error Based on Missile-Borne Rotation Semi-Strapdown Inertial Navigation System

by Jiayu Zhang^1,2, Jie Li^1,2,*, Xi Zhang^1,2, Xiaorui Che^1,2, Yugang Huang³ and Kaiqiang Feng^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

³ The 60th Research Institute of General Staff Dept of P.L.A, Nanjing 210000, China

Sensors 2018, 18(5), 1430; https://doi.org/10.3390/s18051430 - 4 May 2018

Cited by 15 | Viewed by 4682

Abstract

The Semi-Strapdown Inertial Navigation System (SSINS) provides a new solution to attitude measurement of a high-speed rotating missile. However, micro-electro-mechanical-systems (MEMS) inertial measurement unit (MIMU) outputs are corrupted by significant sensor errors. In order to improve the navigation precision, a rotation modulation technology [...] Read more.

The Semi-Strapdown Inertial Navigation System (SSINS) provides a new solution to attitude measurement of a high-speed rotating missile. However, micro-electro-mechanical-systems (MEMS) inertial measurement unit (MIMU) outputs are corrupted by significant sensor errors. In order to improve the navigation precision, a rotation modulation technology method called Rotation Semi-Strapdown Inertial Navigation System (RSSINS) is introduced into SINS. In fact, the stability of the modulation angular rate is difficult to achieve in a high-speed rotation environment. The changing rotary angular rate has an impact on the inertial sensor error self-compensation. In this paper, the influence of modulation angular rate error, including acceleration-deceleration process, and instability of the angular rate on the navigation accuracy of RSSINS is deduced and the error characteristics of the reciprocating rotation scheme are analyzed. A new compensation method is proposed to remove or reduce sensor errors so as to make it possible to maintain high precision autonomous navigation performance by MIMU when there is no external aid. Experiments have been carried out to validate the performance of the method. In addition, the proposed method is applicable for modulation angular rate error compensation under various dynamic conditions. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 3793 KiB

Open AccessArticle

A Flexible Interdigital Electrode Used in Skin Penetration Promotion and Evaluation with Electroporation and Reverse Iontophoresis Synergistically

by Rongjian Zhao^1,2, Chenshuo Wang^1,2, Fei Lu^1,2, Lidong Du¹

, Zhen Fang^1,2, Xiuhua Guo^3,4, Jen-Tsai Liu², Ching-Jung Chen² and Zhan Zhao^1,2,*

¹ State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100080, China

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

³ School of Public Health, Capital Medical University, Beijing 100069, China

⁴ Beijing Municipal Key Laboratory of Clinical Epidemiology, Beijing 100069, China

Sensors 2018, 18(5), 1431; https://doi.org/10.3390/s18051431 - 4 May 2018

Cited by 13 | Viewed by 6958

Abstract

Skin penetration is related to efficiencies of drug delivery or ISF extraction. Normally, the macro-electrode is employed in skin permeability promotion and evaluation, which has the disadvantages of easily causing skin damage when using electroporation or reverse iontophoresis by alone; furthermore, it has [...] Read more.

Skin penetration is related to efficiencies of drug delivery or ISF extraction. Normally, the macro-electrode is employed in skin permeability promotion and evaluation, which has the disadvantages of easily causing skin damage when using electroporation or reverse iontophoresis by alone; furthermore, it has large measurement error, low sensitivity, and difficulty in integration. To resolve these issues, this paper presents a flexible interdigital microelectrode for evaluating skin penetration by sensing impedance and a method of synergistical combination of electroporation and reverse iontophoresis to promote skin penetration. First, a flexible interdigital microelectrode was designed with a minimal configuration circuit of electroporation and reverse iontophoresis for future wearable application. Due to the variation of the skin impedance correlated with many factors, relative changes of it were recorded at the end of supply, different voltage, or constant current, times, and duration. It is found that the better results can be obtained by using electroporation for 5 min then reverse iontophoresis for 12 min. By synergistically using electroporation and reverse iontophoresis, the penetration of skin is promoted. The results tested in vivo suggest that the developed microelectrode can be applied to evaluate and promote the skin penetration and the designed method promises to leave the skin without damage. The electrode and the method may be beneficial for designing noninvasive glucose sensors. Full article

(This article belongs to the Section Biosensors)

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12 pages, 1802 KiB

Open AccessArticle

Mixed Incoherent Far-Field and Near-Field Source Localization under Uniform Circular Array

by Xiaolong Su

, Zhen Liu^*

, Xin Chen and Xiang Li

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

Sensors 2018, 18(5), 1432; https://doi.org/10.3390/s18051432 - 4 May 2018

Cited by 10 | Viewed by 3981

Abstract

A high-accuracy algorithm is presented for the localization of mixed incoherent near-field and far-field narrow-band sources under uniform circular array (UCA). Herein, considering that it is difficult to classify the mixed sources, we first decouple mixed sources’ angles and ranges by calculating centro-symmetric [...] Read more.

A high-accuracy algorithm is presented for the localization of mixed incoherent near-field and far-field narrow-band sources under uniform circular array (UCA). Herein, considering that it is difficult to classify the mixed sources, we first decouple mixed sources’ angles and ranges by calculating centro-symmetric sensors’ phase differences. Then, as the phase differences including only sources’ angles can be transformed as indefinite equations, each source’s azimuth angle and elevation angle are obtained by performing the least squares method. After that, on the basis of the estimated angles of the mixed sources, one-dimensional (1-D) multiple signal classification (MUSIC) method and corresponding spatial spectrum are utilized to identify the mixed sources and estimate the ranges of the near-field sources. Finally, simulation and comparison results verify the superior performance of our proposed algorithm. Full article

(This article belongs to the Special Issue Applications of Wireless Sensors in Localization and Tracking)

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20 pages, 4556 KiB

Open AccessArticle

Impact Assessment of GNSS Spoofing Attacks on INS/GNSS Integrated Navigation System

by Yang Liu^*

, Sihai Li, Qiangwen Fu and Zhenbo Liu

School of Automation, Northwestern Polytechnical University, Xi’an 710072, China

Sensors 2018, 18(5), 1433; https://doi.org/10.3390/s18051433 - 4 May 2018

Cited by 67 | Viewed by 9248

Abstract

In the face of emerging Global Navigation Satellite System (GNSS) spoofing attacks, there is a need to give a comprehensive analysis on how the inertial navigation system (INS)/GNSS integrated navigation system responds to different kinds of spoofing attacks. A better understanding of the [...] Read more.

In the face of emerging Global Navigation Satellite System (GNSS) spoofing attacks, there is a need to give a comprehensive analysis on how the inertial navigation system (INS)/GNSS integrated navigation system responds to different kinds of spoofing attacks. A better understanding of the integrated navigation system’s behavior with spoofed GNSS measurements gives us valuable clues to develop effective spoofing defenses. This paper focuses on an impact assessment of GNSS spoofing attacks on the integrated navigation system Kalman filter’s error covariance, innovation sequence and inertial sensor bias estimation. A simple and straightforward measurement-level trajectory spoofing simulation framework is presented, serving as the basis for an impact assessment of both unsynchronized and synchronized spoofing attacks. Recommendations are given for spoofing detection and mitigation based on our findings in the impact assessment process. Full article

(This article belongs to the Special Issue GNSS and Fusion with Other Sensors)

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25 pages, 3885 KiB

Open AccessArticle

A New Path-Constrained Rendezvous Planning Approach for Large-Scale Event-Driven Wireless Sensor Networks

by Ahmadreza Vajdi¹

, Gongxuan Zhang¹, Junlong Zhou^1,*

, Tongquan Wei²

, Yongli Wang¹ and Tianshu Wang¹

¹ School of Computer Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

² Department of Computer Science and Technology, East China Normal University, Shanghai 200062, China

Sensors 2018, 18(5), 1434; https://doi.org/10.3390/s18051434 - 4 May 2018

Cited by 8 | Viewed by 3950

Abstract

We study the problem of employing a mobile-sink into a large-scale Event-Driven Wireless Sensor Networks (EWSNs) for the purpose of data harvesting from sensor-nodes. Generally, this employment improves the main weakness of WSNs that is about energy-consumption in battery-driven sensor-nodes. The main motivation [...] Read more.

We study the problem of employing a mobile-sink into a large-scale Event-Driven Wireless Sensor Networks (EWSNs) for the purpose of data harvesting from sensor-nodes. Generally, this employment improves the main weakness of WSNs that is about energy-consumption in battery-driven sensor-nodes. The main motivation of our work is to address challenges which are related to a network’s topology by adopting a mobile-sink that moves in a predefined trajectory in the environment. Since, in this fashion, it is not possible to gather data from sensor-nodes individually, we adopt the approach of defining some of the sensor-nodes as Rendezvous Points (RPs) in the network. We argue that RP-planning in this case is a tradeoff between minimizing the number of RPs while decreasing the number of hops for a sensor-node that needs data transformation to the related RP which leads to minimizing average energy consumption in the network. We address the problem by formulating the challenges and expectations as a Mixed Integer Linear Programming (MILP). Henceforth, by proving the NP-hardness of the problem, we propose three effective and distributed heuristics for RP-planning, identifying sojourn locations, and constructing routing trees. Finally, experimental results prove the effectiveness of our approach. Full article

(This article belongs to the Section Sensor Networks)

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14 pages, 10707 KiB

Open AccessArticle

Liquefied Petroleum Gas Monitoring System Based on Polystyrene Coated Long Period Grating

by Flavio Esposito¹

, Aldobenedetto Zotti²

, Giovanna Palumbo¹, Simona Zuppolini², Marco Consales^3,4, Antonello Cutolo³, Anna Borriello², Stefania Campopiano¹

, Mauro Zarrelli^2,*

and Agostino Iadicicco^1,*

¹ Department of Engineering, University of Naples “Parthenope”, 80143 Napoli, Italy

² Institute for Polymers, Composites and Biomaterials (IPCB)-CNR, 80055 Portici, Italy

³ Optoelectronics group, Department of Engineering, University of Sannio, 82100 Benevento, Italy

⁴ Centro Regionale Information Communication Technology-CeRICT scrl, 82100 Benevento, Italy

Sensors 2018, 18(5), 1435; https://doi.org/10.3390/s18051435 - 5 May 2018

Cited by 18 | Viewed by 5213

Abstract

In this work, we report the in-field demonstration of a liquefied petroleum gas monitoring system based on optical fiber technology. Long-period grating coated with a thin layer of atactic polystyrene (aPS) was employed as a gas sensor, and an array comprising two different [...] Read more.

In this work, we report the in-field demonstration of a liquefied petroleum gas monitoring system based on optical fiber technology. Long-period grating coated with a thin layer of atactic polystyrene (aPS) was employed as a gas sensor, and an array comprising two different fiber Bragg gratings was set for the monitoring of environmental conditions such as temperature and humidity. A custom package was developed for the sensors, ensuring their suitable installation and operation in harsh conditions. The developed system was installed in a real railway location scenario (i.e., a southern Italian operative railway tunnel), and tests were performed to validate the system performances in operational mode. Daytime normal working operations of the railway line and controlled gas expositions, at very low concentrations, were the searched realistic conditions for an out-of-lab validation of the developed system. Encouraging results were obtained with a precise indication of the gas concentration and external conditioning of the sensor. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 2589 KiB

Open AccessArticle

Investigating the Strain, Temperature and Humidity Sensitivity of a Multimode Graded-Index Perfluorinated Polymer Optical Fiber with Bragg Grating

by Yulong Zheng^*, Kort Bremer and Bernhard Roth

Hannover Centre for Optical Technologies (HOT), Leibniz University Hannover, 30167 Hannover, Germany

Sensors 2018, 18(5), 1436; https://doi.org/10.3390/s18051436 - 5 May 2018

Cited by 47 | Viewed by 5198

Abstract

In this work we investigate the strain, temperature and humidity sensitivity of a Fiber Bragg Grating (FBG) inscribed in a near infrared low-loss multimode perfluorinated polymer optical fiber based on cyclic transparent optical polymer (CYTOP). For this purpose, FBGs were inscribed into the [...] Read more.

In this work we investigate the strain, temperature and humidity sensitivity of a Fiber Bragg Grating (FBG) inscribed in a near infrared low-loss multimode perfluorinated polymer optical fiber based on cyclic transparent optical polymer (CYTOP). For this purpose, FBGs were inscribed into the multimode CYTOP fiber with a core diameter of 50 µm by using a krypton fluoride (KrF) excimer laser and the phase mask method. The evolution of the reflection spectrum of the FBG detected with a multimode interrogation technique revealed a single reflection peak with a full width at half maximum (FHWM) bandwidth of about 9 nm. Furthermore, the spectral envelope of the single FBG reflection peak can be optimized depending on the KrF excimer laser irradiation time. A linear shift of the Bragg wavelength due to applied strain, temperature and humidity was measured. Furthermore, depending on irradiation time of the KrF excimer laser, both the failure strain and strain sensitivity of the multimode fiber with FBG can be controlled. The inherent low light attenuation in the near infrared wavelength range (telecommunication window) of the multimode CYTOP fiber and the single FBG reflection peak when applying the multimode interrogation set-up will allow for new applications in the area of telecommunication and optical sensing. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)

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12 pages, 3525 KiB

Open AccessArticle

Evaluating Post-Earthquake Building Safety Using Economical MEMS Seismometers

by Ting-Yu Hsu^1,*

, Ren-Cheng Yin² and Yih-Min Wu²

¹ Department of Civil and Construction Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan

² Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan

Sensors 2018, 18(5), 1437; https://doi.org/10.3390/s18051437 - 5 May 2018

Cited by 23 | Viewed by 5616

Abstract

The earthquake early warning (EEW)-research group at National Taiwan University has been developing a microelectromechanical system-based accelerometer called “P-Alert”, designed for issuing EEWs. The main advantage of P-Alert is that it is a relatively economical seismometer. However, because of the expensive nature of [...] Read more.

The earthquake early warning (EEW)-research group at National Taiwan University has been developing a microelectromechanical system-based accelerometer called “P-Alert”, designed for issuing EEWs. The main advantage of P-Alert is that it is a relatively economical seismometer. However, because of the expensive nature of commercial hardware for structural health monitoring (SHM) systems, the application of SHM to buildings remains limited. To determine the performance of P-Alert for evaluating post-earthquake building safety, we conducted a series of steel-frame shaking table tests with incremental damage. We used the fragility curves of different damage levels and the interstory drift ratios (calculated by the measured acceleration of each story using double integration and a filter) to gauge the potential damage levels. We concluded that the acceptable detection of damage for an entire building is possible. With improvements to the synchronization of the P-Alert sensors, we also anticipate a damage localization feature for the stories of a building. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 4148 KiB

Open AccessArticle

A Microwave Method for Dielectric Characterization Measurement of Small Liquids Using a Metamaterial-Based Sensor

by Weina Liu¹, Haoran Sun²

and Lei Xu^3,*

¹ College of Electric and Electrical Engineering, Henan Normal University, Xinxiang 453007, China

² College of Electronic Engineering, Chengdu University of Information Technology, Chengdu 610225, China

³ School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China

Sensors 2018, 18(5), 1438; https://doi.org/10.3390/s18051438 - 5 May 2018

Cited by 66 | Viewed by 5626

Abstract

We present a microwave method for the dielectric characterization of small liquids based on a metamaterial-based sensor The proposed sensor consists of a micro-strip line and a double split-ring resonator (SRR). A large electric field is observed on the two splits of the [...] Read more.

We present a microwave method for the dielectric characterization of small liquids based on a metamaterial-based sensor The proposed sensor consists of a micro-strip line and a double split-ring resonator (SRR). A large electric field is observed on the two splits of the double SRRs at the resonance frequency (1.9 GHz). The dielectric property data of the samples under test (SUTs) were obtained with two measurements. One is with the sensor loaded with the reference liquid (REF) and the other is with the sensor loaded with the SUTs. Additionally, the principle of extracting permittivity from measured changes of resonance characteristics changes of the sensor loaded with REF and SUTs is given. Some measurements were carried out at 1.9 GHz, and the calculated results of methanol–water mixtures with different molar fractions agree well with the time-domain reflectometry method. Moreover, the proposed sensor is compact and highly sensitive for use of sub-wavelength resonance. In comparison with literature data, relative errors are less than 3% for the real parts and 2% for the imaginary parts of complex permittivity. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 5511 KiB

Open AccessArticle

Study of Current Measurement Method Based on Circular Magnetic Field Sensing Array

by Zhenhua Li^1,2,*

, Siqiu Zhang¹

, Zhengtian Wu³, Ahmed Abu-Siada⁴

and Yuan Tao¹

¹ College of Electrical Engineering & New Energy, China Three Gorges University, Yichang 443002, China

² Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, China Three Gorges University, Yichang 443002, China

³ School of Electronic and Information Engineering, Suzhou University of Science and Technology, Suzhou 215009, China

⁴ Electrical and Computer Engineering Department, Curtin University, Perth 6000, WA, Australia

Sensors 2018, 18(5), 1439; https://doi.org/10.3390/s18051439 - 5 May 2018

Cited by 18 | Viewed by 4374

Abstract

Classic core-based instrument transformers are more prone to magnetic saturation. This affects the measurement accuracy of such transformers and limits their applications in measuring large direct current (DC). Moreover, protection and control systems may exhibit malfunctions due to such measurement errors. This paper [...] Read more.

Classic core-based instrument transformers are more prone to magnetic saturation. This affects the measurement accuracy of such transformers and limits their applications in measuring large direct current (DC). Moreover, protection and control systems may exhibit malfunctions due to such measurement errors. This paper presents a more accurate method for current measurement based on a circular magnetic field sensing array. The proposed measurement approach utilizes multiple hall sensors that are evenly distributed on a circle. The average value of all hall sensors is regarded as the final measurement. The calculation model is established in the case of magnetic field interference of the parallel wire, and the simulation results show that the error decreases significantly when the number of hall sensors n is greater than 8. The measurement error is less than 0.06% when the wire spacing is greater than 2.5 times the radius of the sensor array. A simulation study on the off-center primary conductor is conducted, and a kind of hall sensor compensation method is adopted to improve the accuracy. The simulation and test results indicate that the measurement error of the system is less than 0.1%. Full article

(This article belongs to the Section Intelligent Sensors)

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15 pages, 5118 KiB

Open AccessFeature PaperArticle

Visible and Extended Near-Infrared Multispectral Imaging for Skin Cancer Diagnosis

by Laura Rey-Barroso^1,*, Francisco J. Burgos-Fernández¹

, Xana Delpueyo¹, Miguel Ares¹, Santiago Royo¹

, Josep Malvehy², Susana Puig² and Meritxell Vilaseca¹

¹ Centre for Sensors, Instruments and Systems Development, Technical University of Catalonia, Terrassa 08222, Spain

² Dermatology Department of the Hospital Clinic of Barcelona, IDIBAPS; Barcelona 08036, Spain

Sensors 2018, 18(5), 1441; https://doi.org/10.3390/s18051441 - 5 May 2018

Cited by 57 | Viewed by 9321

Abstract

With the goal of diagnosing skin cancer in an early and noninvasive way, an extended near infrared multispectral imaging system based on an InGaAs sensor with sensitivity from 995 nm to 1613 nm was built to evaluate deeper skin layers thanks to the [...] Read more.

With the goal of diagnosing skin cancer in an early and noninvasive way, an extended near infrared multispectral imaging system based on an InGaAs sensor with sensitivity from 995 nm to 1613 nm was built to evaluate deeper skin layers thanks to the higher penetration of photons at these wavelengths. The outcomes of this device were combined with those of a previously developed multispectral system that works in the visible and near infrared range (414 nm–995 nm). Both provide spectral and spatial information from skin lesions. A classification method to discriminate between melanomas and nevi was developed based on the analysis of first-order statistics descriptors, principal component analysis, and support vector machine tools. The system provided a sensitivity of 78.6% and a specificity of 84.6%, the latter one being improved with respect to that offered by silicon sensors. Full article

(This article belongs to the Special Issue Optical Methods in Sensing and Imaging for Medical and Biological Applications)

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18 pages, 772 KiB

Open AccessArticle

A BLE-Based Pedestrian Navigation System for Car Searching in Indoor Parking Garages

by Sheng-Shih Wang

Department of Information Management, Minghsin University of Science and Technology, Hsinchu 30401, Taiwan

Sensors 2018, 18(5), 1442; https://doi.org/10.3390/s18051442 - 5 May 2018

Cited by 20 | Viewed by 5541

Abstract

The continuous global increase in the number of cars has led to an increase in parking issues, particularly with respect to the search for available parking spaces and finding cars. In this paper, we propose a navigation system for car owners to find [...] Read more.

The continuous global increase in the number of cars has led to an increase in parking issues, particularly with respect to the search for available parking spaces and finding cars. In this paper, we propose a navigation system for car owners to find their cars in indoor parking garages. The proposed system comprises a car-searching mobile app and a positioning-assisting subsystem. The app guides car owners to their cars based on a “turn-by-turn” navigation strategy, and has the ability to correct the user’s heading orientation. The subsystem uses beacon technology for indoor positioning, supporting self-guidance of the car-searching mobile app. This study also designed a local coordinate system to support the identification of the locations of parking spaces and beacon devices. We used Android as the platform to implement the proposed car-searching mobile app, and used Bytereal HiBeacon devices to implement the proposed positioning-assisting subsystem. We also deployed the system in a parking lot in our campus for testing. The experimental results verified that the proposed system not only works well, but also provides the car owner with the correct route guidance information. Full article

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

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41 pages, 7608 KiB

Open AccessArticle

Developing a Mixed Neural Network Approach to Forecast the Residential Electricity Consumption Based on Sensor Recorded Data

by Simona-Vasilica Oprea¹

, Alexandru Pîrjan^2,*

, George Căruțașu²

, Dana-Mihaela Petroșanu^2,3

, Adela Bâra¹, Justina-Lavinia Stănică² and Cristina Coculescu²

¹ Department of Economic Informatics and Cybernetics, The Bucharest Academy of Economic Studies, Romana Square 6, Bucharest 010374, Romania

² Department of Informatics, Statistics and Mathematics, Romanian-American University, Expoziției 1B, Bucharest 012101, Romania

³ Department of Mathematics-Informatics, University Politehnica of Bucharest, Splaiul Independenței 313, Bucharest 060042, Romania

Sensors 2018, 18(5), 1443; https://doi.org/10.3390/s18051443 - 5 May 2018

Cited by 22 | Viewed by 5245

Abstract

In this paper, we report a study having as a main goal the obtaining of a method that can provide an accurate forecast of the residential electricity consumption, refining it up to the appliance level, using sensor recorded data, for residential smart homes [...] Read more.

In this paper, we report a study having as a main goal the obtaining of a method that can provide an accurate forecast of the residential electricity consumption, refining it up to the appliance level, using sensor recorded data, for residential smart homes complexes that use renewable energy sources as a part of their consumed electricity, overcoming the limitations of not having available historical meteorological data and the unwillingness of the contractor to acquire such data periodically in the future accurate short-term forecasts from a specialized institute due to the implied costs. In this purpose, we have developed a mixed artificial neural network (ANN) approach using both non-linear autoregressive with exogenous input (NARX) ANNs and function fitting neural networks (FITNETs). We have used a large dataset containing detailed electricity consumption data recorded by sensors, monitoring a series of individual appliances, while in the NARX case we have also used timestamps datasets as exogenous variables. After having developed and validated the forecasting method, we have compiled it in view of incorporating it into a cloud solution, being delivered to the contractor that can provide it as a service for a monthly fee to both the operators and residential consumers. Full article

(This article belongs to the Special Issue Smart Homes)

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24 pages, 2284 KiB

Open AccessArticle

Simultaneous Mean and Covariance Correction Filter for Orbit Estimation

by Xiaoxu Wang^1,*

, Quan Pan¹, Zhengtao Ding² and Zhengya Ma¹

¹ School of Automation, Northwestern Polytechnical University, Xi’an 710072, China

² School of Electrical and Electronic Engineering, The University of Manchester, Manchester M13 9PL, UK

Sensors 2018, 18(5), 1444; https://doi.org/10.3390/s18051444 - 5 May 2018

Cited by 2 | Viewed by 3582

Abstract

This paper proposes a novel filtering design, from a viewpoint of identification instead of the conventional nonlinear estimation schemes (NESs), to improve the performance of orbit state estimation for a space target. First, a nonlinear perturbation is viewed or modeled as an unknown [...] Read more.

This paper proposes a novel filtering design, from a viewpoint of identification instead of the conventional nonlinear estimation schemes (NESs), to improve the performance of orbit state estimation for a space target. First, a nonlinear perturbation is viewed or modeled as an unknown input (UI) coupled with the orbit state, to avoid the intractable nonlinear perturbation integral (INPI) required by NESs. Then, a simultaneous mean and covariance correction filter (SMCCF), based on a two-stage expectation maximization (EM) framework, is proposed to simply and analytically fit or identify the first two moments (FTM) of the perturbation (viewed as UI), instead of directly computing such the INPI in NESs. Orbit estimation performance is greatly improved by utilizing the fit UI-FTM to simultaneously correct the state estimation and its covariance. Third, depending on whether enough information is mined, SMCCF should outperform existing NESs or the standard identification algorithms (which view the UI as a constant independent of the state and only utilize the identified UI-mean to correct the state estimation, regardless of its covariance), since it further incorporates the useful covariance information in addition to the mean of the UI. Finally, our simulations demonstrate the superior performance of SMCCF via an orbit estimation example. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 3254 KiB

Open AccessArticle

Theory and Measurement of Signal-to-Noise Ratio in Continuous-Wave Noise Radar

by Bronisław Stec and Waldemar Susek^*

Faculty of Electronics, Military University of Technology, Gen. Urbanowicz St. No 2, 00-908 Warsaw, Poland

Sensors 2018, 18(5), 1445; https://doi.org/10.3390/s18051445 - 6 May 2018

Cited by 15 | Viewed by 6437

Abstract

Determination of the signal power-to-noise power ratio on the input and output of reception systems is essential to the estimation of their quality and signal reception capability. This issue is especially important in the case when both signal and noise have the same [...] Read more.

Determination of the signal power-to-noise power ratio on the input and output of reception systems is essential to the estimation of their quality and signal reception capability. This issue is especially important in the case when both signal and noise have the same characteristic as Gaussian white noise. This article considers the problem of how a signal-to-noise ratio is changed as a result of signal processing in the correlation receiver of a noise radar in order to determine the ability to detect weak features in the presence of strong clutter-type interference. These studies concern both theoretical analysis and practical measurements of a noise radar with a digital correlation receiver for 9.2 GHz bandwidth. Firstly, signals participating individually in the correlation process are defined and the terms signal and interference are ascribed to them. Further studies show that it is possible to distinguish a signal and a noise on the input and output of a correlation receiver, respectively, when all the considered noises are in the form of white noise. Considering the above, a measurement system is designed in which it is possible to represent the actual conditions of noise radar operation and power measurement of a useful noise signal and interference noise signals—in particular the power of an internal leakage signal between a transmitter and a receiver of the noise radar. The proposed measurement stands and the obtained results show that it is possible to optimize with the use of the equipment and not with the complex processing of a noise signal. The radar parameters depend on its prospective application, such as short- and medium-range radar, ground-penetrating radar, and through-the-wall detection radar. Full article

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

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15 pages, 4073 KiB

Open AccessArticle

Least Squares Neural Network-Based Wireless E-Nose System Using an SnO₂ Sensor Array

by Areej Shahid, Jong-Hyeok Choi, Abu Ul Hassan Sarwar Rana and Hyun-Seok Kim^*

Division of Electronics and Electrical Engineering, Dongguk University-Seoul, Seoul 04620, Korea

Sensors 2018, 18(5), 1446; https://doi.org/10.3390/s18051446 - 6 May 2018

Cited by 52 | Viewed by 7546

Abstract

Over the last few decades, the development of the electronic nose (E-nose) for detection and quantification of dangerous and odorless gases, such as methane (CH₄) and carbon monoxide (CO), using an array of SnO₂ gas sensors has attracted considerable attention. [...] Read more.

Over the last few decades, the development of the electronic nose (E-nose) for detection and quantification of dangerous and odorless gases, such as methane (CH₄) and carbon monoxide (CO), using an array of SnO₂ gas sensors has attracted considerable attention. This paper addresses sensor cross sensitivity by developing a classifier and estimator using an artificial neural network (ANN) and least squares regression (LSR), respectively. Initially, the ANN was implemented using a feedforward pattern recognition algorithm to learn the collective behavior of an array as the signature of a particular gas. In the second phase, the classified gas was quantified by minimizing the mean square error using LSR. The combined approach produced 98.7% recognition probability, with 95.5 and 94.4% estimated gas concentration accuracies for CH₄ and CO, respectively. The classifier and estimator parameters were deployed in a remote microcontroller for the actualization of a wireless E-nose system. Full article

(This article belongs to the Section Chemical Sensors)

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23 pages, 16756 KiB

Open AccessArticle

Active Sensor for Microwave Tissue Imaging with Bias-Switched Arrays

by Farzad Foroutan^*,†

and Natalia K. Nikolova^†

¹ Department of Electrical and Computer Engineering, McMaster University, Hamilton, ON L8S 4L8, Canada

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1447; https://doi.org/10.3390/s18051447 - 6 May 2018

Cited by 23 | Viewed by 5850

Abstract

A prototype of a bias-switched active sensor was developed and measured to establish the achievable dynamic range in a new generation of active arrays for microwave tissue imaging. The sensor integrates a printed slot antenna, a low-noise amplifier (LNA) and an active mixer [...] Read more.

A prototype of a bias-switched active sensor was developed and measured to establish the achievable dynamic range in a new generation of active arrays for microwave tissue imaging. The sensor integrates a printed slot antenna, a low-noise amplifier (LNA) and an active mixer in a single unit, which is sufficiently small to enable inter-sensor separation distance as small as 12 mm. The sensor’s input covers the bandwidth from 3 GHz to

7.5

GHz. Its output intermediate frequency (IF) is 30 MHz. The sensor is controlled by a simple bias-switching circuit, which switches ON and OFF the bias of the LNA and the mixer simultaneously. It was demonstrated experimentally that the dynamic range of the sensor, as determined by its ON and OFF states, is 109 dB and 118 dB at resolution bandwidths of 1 kHz and 100 Hz, respectively. Full article

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

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12 pages, 3965 KiB

Open AccessArticle

Centrifugal Deposited Au-Pd Core-Shell Nanoparticle Film for Room-Temperature Optical Detection of Hydrogen Gas

by Han Song^1,*

, Zhijie Luo¹, Mingyao Liu¹, Gang Zhang², Wang Peng², Boyi Wang³ and Yong Zhu³

¹ School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan 430070, China

² School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

³ School of Engineering, Griffith University, Nathan, QLD 4222, Australia

Sensors 2018, 18(5), 1448; https://doi.org/10.3390/s18051448 - 6 May 2018

Cited by 19 | Viewed by 5407

Abstract

In the present work, centrifugal deposited Au-Pd core-shell nanoparticle (NP) film was proposed for the room-temperature optical detection of hydrogen gas. The size dimension of 44, 48, 54, and 62 nm Au-Pd core-shell nanocubes with 40 nm Au core were synthesized following a [...] Read more.

In the present work, centrifugal deposited Au-Pd core-shell nanoparticle (NP) film was proposed for the room-temperature optical detection of hydrogen gas. The size dimension of 44, 48, 54, and 62 nm Au-Pd core-shell nanocubes with 40 nm Au core were synthesized following a solution-based seed-mediated growth method. Compared to a pure Pd NP, this core-shell structure with an inert Au core could decrease the H diffusion length in the Pd shell. Through a modified centrifugal deposition process, continues film samples with different core-shell NPs were deposited on 10 mm diameter quartz substrates. Under various hydrogen concentration conditions, the optical response properties of these samples were characterized by an intensity-based optical fiber bundle sensor. Experimental results show that the continues film that was composed of 62 nm Au-Pd core-shell NPs has achieved a stable and repeatable reflectance response with low zero drift in the range of 4 to 0.1% hydrogen after a stress relaxation mechanism at first few loading/unloading cycles. Because of the short H diffusion length due to the thinner Pd shell, the film sample composed of 44 nm Au-Pd NPs has achieved a dramatically decreased response/recovery time to 4 s/30 s. The experiments present the promising prospect of this simple method to fabricate optical hydrogen sensors with controllable high sensitivity and response rate at low cost. Full article

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

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12 pages, 2859 KiB

Open AccessArticle

Fast Sparse Coding for Range Data Denoising with Sparse Ridges Constraint

by Zhi Gao^1,*

, Mingjie Lao¹, Yongsheng Sang², Fei Wen³, Bharath Ramesh¹

and Ruifang Zhai⁴

¹ Temasek Laboratories, National University of Singapore, 117411 Singapore

² College of Computer Science, Sichuan University, Chengdu 610065, China

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

⁴ College of Informatics, Huazhong Agricultural University, Wuhan 430070, China

Sensors 2018, 18(5), 1449; https://doi.org/10.3390/s18051449 - 6 May 2018

Cited by 4 | Viewed by 4102

Abstract

Light detection and ranging (LiDAR) sensors have been widely deployed on intelligent systems such as unmanned ground vehicles (UGVs) and unmanned aerial vehicles (UAVs) to perform localization, obstacle detection, and navigation tasks. Thus, research into range data processing with competitive performance in terms [...] Read more.

Light detection and ranging (LiDAR) sensors have been widely deployed on intelligent systems such as unmanned ground vehicles (UGVs) and unmanned aerial vehicles (UAVs) to perform localization, obstacle detection, and navigation tasks. Thus, research into range data processing with competitive performance in terms of both accuracy and efficiency has attracted increasing attention. Sparse coding has revolutionized signal processing and led to state-of-the-art performance in a variety of applications. However, dictionary learning, which plays the central role in sparse coding techniques, is computationally demanding, resulting in its limited applicability in real-time systems. In this study, we propose sparse coding algorithms with a fixed pre-learned ridge dictionary to realize range data denoising via leveraging the regularity of laser range measurements in man-made environments. Experiments on both synthesized data and real data demonstrate that our method obtains accuracy comparable to that of sophisticated sparse coding methods, but with much higher computational efficiency. Full article

(This article belongs to the Section Remote Sensors)

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8 pages, 2595 KiB

Open AccessArticle

Infrared Thermography Approach for Effective Shielding Area of Field Smoke Based on Background Subtraction and Transmittance Interpolation

by Runze Tang, Tonglai Zhang, Yongpeng Chen, Hao Liang, Bingyang Li and Zunning Zhou^*

State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(5), 1450; https://doi.org/10.3390/s18051450 - 6 May 2018

Cited by 5 | Viewed by 4673

Abstract

Effective shielding area is a crucial indicator for the evaluation of the infrared smoke-obscuring effectiveness on the battlefield. The conventional methods for assessing the shielding area of the smoke screen are time-consuming and labor intensive, in addition to lacking precision. Therefore, an efficient [...] Read more.

Effective shielding area is a crucial indicator for the evaluation of the infrared smoke-obscuring effectiveness on the battlefield. The conventional methods for assessing the shielding area of the smoke screen are time-consuming and labor intensive, in addition to lacking precision. Therefore, an efficient and convincing technique for testing the effective shielding area of the smoke screen has great potential benefits in the smoke screen applications in the field trial. In this study, a thermal infrared sensor with a mid-wavelength infrared (MWIR) range of 3 to 5 μm was first used to capture the target scene images through clear as well as obscuring smoke, at regular intervals. The background subtraction in motion detection was then applied to obtain the contour of the smoke cloud at each frame. The smoke transmittance at each pixel within the smoke contour was interpolated based on the data that was collected from the image. Finally, the smoke effective shielding area was calculated, based on the accumulation of the effective shielding pixel points. One advantage of this approach is that it utilizes only one thermal infrared sensor without any other additional equipment in the field trial, which significantly contributes to the efficiency and its convenience. Experiments have been carried out to demonstrate that this approach can determine the effective shielding area of the field infrared smoke both practically and efficiently. Full article

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

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15 pages, 1292 KiB

Open AccessArticle

by Ali Mohydeen¹

, Pascal Chargé¹, Yide Wang¹

, Oussama Bazzi² and Yuehua Ding^3,*

¹ Institute of Electronics and Telecommunications of Rennes (IETR), UMR CNRS 6164, Polytech Nantes, Rue Christian Pauc, BP 50609, 44306 Nantes CEDEX 3, France

² Department of Physics and Electronics, Faculty of Sciences 1, Lebanese University, Hadath, Beirut 14/6573, Lebanon

³ School of Electronic and Information Engineering, South China University of Technology, Wushan Road, Tianhe District, Guangzhou 510641, China

Sensors 2018, 18(5), 1451; https://doi.org/10.3390/s18051451 - 6 May 2018

Cited by 2 | Viewed by 4436

Abstract

A parametric scheme for spatially correlated sparse multiple-input multiple-output (MIMO) channel path delay estimation in scattering environments is presented in this paper. In MIMO outdoor communication scenarios, channel impulse responses (CIRs) of different transmit–receive antenna pairs are often supposed to be sparse due [...] Read more.

A parametric scheme for spatially correlated sparse multiple-input multiple-output (MIMO) channel path delay estimation in scattering environments is presented in this paper. In MIMO outdoor communication scenarios, channel impulse responses (CIRs) of different transmit–receive antenna pairs are often supposed to be sparse due to a few significant scatterers, and share a common sparse pattern, such that path delays are assumed to be equal for every transmit–receive antenna pair. In some existing works, an exact common support condition is exploited, where the path delays are considered equal for every transmit–receive antenna pair, meanwhile ignoring the influence of scattering. A more realistic channel model is proposed in this paper, where due to scatterers in the environment, the received signals are modeled as clusters of multi-rays around a nominal or mean time delay at different antenna elements, resulting in a non-strictly exact common support phenomenon. A method for estimating the channel mean path delays is then derived based on the subspace approach, and the tracking of the effective dimension of the signal subspace that changes due to the wireless environment. The proposed method shows an improved channel mean path delays estimation performance in comparison with the conventional estimation methods. Full article

(This article belongs to the Section Physical Sensors)

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30 pages, 12122 KiB

Open AccessArticle

An Ultra-Low-Power RFID/NFC Frontend IC Using 0.18 μm CMOS Technology for Passive Tag Applications

by Mayukh Bhattacharyya^1,*

, Waldemar Gruenwald¹, Dirk Jansen¹, Leonhard Reindl²

and Jasmin Aghassi-Hagmann^1,3

¹ Institute for Applied Research, University of Applied Sciences Offenburg, 77652 Offenburg, Germany

² Department of Microsystems Engineering, University of Freiburg, 79098 Freiburg, Germany

³ Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-vom-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

Sensors 2018, 18(5), 1452; https://doi.org/10.3390/s18051452 - 7 May 2018

Cited by 13 | Viewed by 10324

Abstract

Battery-less passive sensor tags based on RFID or NFC technology have achieved much popularity in recent times. Passive tags are widely used for various applications like inventory control or in biotelemetry. In this paper, we present a new RFID/NFC frontend IC (integrated circuit) [...] Read more.

Battery-less passive sensor tags based on RFID or NFC technology have achieved much popularity in recent times. Passive tags are widely used for various applications like inventory control or in biotelemetry. In this paper, we present a new RFID/NFC frontend IC (integrated circuit) for 13.56 MHz passive tag applications. The design of the frontend IC is compatible with the standard ISO 15693/NFC 5. The paper discusses the analog design part in details with a brief overview of the digital interface and some of the critical measured parameters. A novel approach is adopted for the demodulator design, to demodulate the 10% ASK (amplitude shift keying) signal. The demodulator circuit consists of a comparator designed with a preset offset voltage. The comparator circuit design is discussed in detail. The power consumption of the bandgap reference circuit is used as the load for the envelope detection of the ASK modulated signal. The sub-threshold operation and low-supply-voltage are used extensively in the analog design—to keep the power consumption low. The IC was fabricated using 0.18

μ

m CMOS technology in a die area of 1.5 mm × 1.5 mm and an effective area of 0.7

m m^{2}

. The minimum supply voltage desired is 1.2 V, for which the total power consumption is 107

μ

W. The analog part of the design consumes only 36

μ

W, which is low in comparison to other contemporary passive tags ICs. Eventually, a passive tag is developed using the frontend IC, a microcontroller, a temperature and a pressure sensor. A smart NFC device is used to readout the sensor data from the tag employing an Android-based application software. The measurement results demonstrate the full passive operational capability. The IC is suitable for low-power and low-cost industrial or biomedical battery-less sensor applications. A figure-of-merit (FOM) is proposed in this paper which is taken as a reference for comparison with other related state-of-the-art researches. Full article

(This article belongs to the Special Issue RFID-Based Sensors for IoT Applications)

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15 pages, 1095 KiB

Open AccessArticle

Privacy-Preserving Authentication Using a Double Pseudonym for Internet of Vehicles

by Jie Cui^1,2

, Wenyu Xu^1,2, Hong Zhong^1,2,*

, Jing Zhang^1,2, Yan Xu^1,2 and Lu Liu³

¹ School of Computer Science and Technology, Anhui University, Hefei 230039, China

² Anhui Engineering Laboratory of IoT Security Technologies, Anhui University, Hefei 230039, China

³ Department of Computing and Mathematics, University of Derby, Derby DE22 1GB, UK

Sensors 2018, 18(5), 1453; https://doi.org/10.3390/s18051453 - 7 May 2018

Cited by 25 | Viewed by 5019

Abstract

The Internet of Vehicles (IoV) plays an important role in smart transportation to reduce the drivers’s risk of having an accident and help them manage small emergencies. Therefore, security and privacy issues of the message in the tamper proof device (TPD) broadcasted to [...] Read more.

The Internet of Vehicles (IoV) plays an important role in smart transportation to reduce the drivers’s risk of having an accident and help them manage small emergencies. Therefore, security and privacy issues of the message in the tamper proof device (TPD) broadcasted to other vehicles and roadside units (RSUs) have become an important research subject in the field of smart transportation. Many authentication schemes are proposed to tackle the challenges above and most of them are heavy in computation and communication. In this paper, we propose a novel authentication scheme that utilizes the double pseudonym method to hide the real identity of vehicles and adopts the dynamic update technology to periodically update the information (such as member secret, authentication key, internal pseudo-identity) stored in the tamper-proof device to prevent the side-channel attack. Because of not using bilinear pairing, our scheme yields a better performance in terms of computation overhead and communication overhead, and is more suitable to be applied in the Internet of Vehicles. Full article

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

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15 pages, 6937 KiB

Open AccessArticle

A Range Ambiguity Suppression Processing Method for Spaceborne SAR with Up and Down Chirp Modulation

by Xuejiao Wen¹, Xiaolan Qiu^2,*

, Bing Han², Chibiao Ding², Bin Lei² and Qi Chen³

¹ Laboratory of spatial information intelligent processing system, Institute of Electronics, Chinese Academy of Sciences, Suzhou 215000, China

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

³ China Center for Resources Satellite Data and Application, Beijing 100094, China

Sensors 2018, 18(5), 1454; https://doi.org/10.3390/s18051454 - 7 May 2018

Cited by 16 | Viewed by 5897

Abstract

Range ambiguity is one of the factors which affect the SAR image quality. Alternately transmitting up and down chirp modulation pulses is one of the methods used to suppress the range ambiguity. However, the defocusing range ambiguous signal can still hold the stronger [...] Read more.

Range ambiguity is one of the factors which affect the SAR image quality. Alternately transmitting up and down chirp modulation pulses is one of the methods used to suppress the range ambiguity. However, the defocusing range ambiguous signal can still hold the stronger backscattering intensity than the mainlobe imaging area in some case, which has a severe impact on visual effects and subsequent applications. In this paper, a novel hybrid range ambiguity suppression method for up and down chirp modulation is proposed. The method can obtain the ambiguity area image and reduce the ambiguity signal power appropriately, by applying pulse compression using a contrary modulation rate and CFAR detecting method. The effectiveness and correctness of the approach is demonstrated by processing the archive images acquired by Chinese Gaofen-3 SAR sensor in full-polarization mode. Full article

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

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17 pages, 4734 KiB

Open AccessArticle

Filter Selection for Optimizing the Spectral Sensitivity of Broadband Multispectral Cameras Based on Maximum Linear Independence

by Sui-Xian Li^1,2

¹ Flying College, Binzhou University, Binzhou 256600, China

² Aeronautic Information Technology Research Center, Binzhou University, Binzhou 256600, China

Sensors 2018, 18(5), 1455; https://doi.org/10.3390/s18051455 - 7 May 2018

Cited by 16 | Viewed by 4693

Abstract

Previous research has shown that the effectiveness of selecting filter sets from among a large set of commercial broadband filters by a vector analysis method based on maximum linear independence (MLI). However, the traditional MLI approach is suboptimal due to the need to [...] Read more.

Previous research has shown that the effectiveness of selecting filter sets from among a large set of commercial broadband filters by a vector analysis method based on maximum linear independence (MLI). However, the traditional MLI approach is suboptimal due to the need to predefine the first filter of the selected filter set to be the maximum ℓ₂ norm among all available filters. An exhaustive imaging simulation with every single filter serving as the first filter is conducted to investigate the features of the most competent filter set. From the simulation, the characteristics of the most competent filter set are discovered. Besides minimization of the condition number, the geometric features of the best-performed filter set comprise a distinct transmittance peak along the wavelength axis of the first filter, a generally uniform distribution for the peaks of the filters and substantial overlaps of the transmittance curves of the adjacent filters. Therefore, the best-performed filter sets can be recognized intuitively by simple vector analysis and just a few experimental verifications. A practical two-step framework for selecting optimal filter set is recommended, which guarantees a significant enhancement of the performance of the systems. This work should be useful for optimizing the spectral sensitivity of broadband multispectral imaging sensors. Full article

(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)

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19 pages, 4139 KiB

Open AccessArticle

An Innovative Strategy for Accurate Thermal Compensation of Gyro Bias in Inertial Units by Exploiting a Novel Augmented Kalman Filter

by Rita Fontanella¹

, Domenico Accardo^1,*

, Rosario Schiano Lo Moriello¹

, Leopoldo Angrisani²

and Domenico De Simone³

¹ Department of Industrial Engineering, University of Naples Federico II, Piazzale Tecchio 80, I80125 Naples, Italy

² Department of Electrical Engineering and Information Technology, University of Naples Federico II, Via Claudio 21, I80125 Naples, Italy

³ Generale Meccatronica Applicata S.p.A., via Salvatore Piccolo, I80014 Giugliano, Italy

Sensors 2018, 18(5), 1457; https://doi.org/10.3390/s18051457 - 7 May 2018

Cited by 34 | Viewed by 6217

Abstract

This paper presents an innovative model for integrating thermal compensation of gyro bias error into an augmented state Kalman filter. The developed model is applied in the Zero Velocity Update filter for inertial units manufactured by exploiting Micro Electro-Mechanical System (MEMS) gyros. It [...] Read more.

This paper presents an innovative model for integrating thermal compensation of gyro bias error into an augmented state Kalman filter. The developed model is applied in the Zero Velocity Update filter for inertial units manufactured by exploiting Micro Electro-Mechanical System (MEMS) gyros. It is used to remove residual bias at startup. It is a more effective alternative to traditional approach that is realized by cascading bias thermal correction by calibration and traditional Kalman filtering for bias tracking. This function is very useful when adopted gyros are manufactured using MEMS technology. These systems have significant limitations in terms of sensitivity to environmental conditions. They are characterized by a strong correlation of the systematic error with temperature variations. The traditional process is divided into two separated algorithms, i.e., calibration and filtering, and this aspect reduces system accuracy, reliability, and maintainability. This paper proposes an innovative Zero Velocity Update filter that just requires raw uncalibrated gyro data as input. It unifies in a single algorithm the two steps from the traditional approach. Therefore, it saves time and economic resources, simplifying the management of thermal correction process. In the paper, traditional and innovative Zero Velocity Update filters are described in detail, as well as the experimental data set used to test both methods. The performance of the two filters is compared both in nominal conditions and in the typical case of a residual initial alignment bias. In this last condition, the innovative solution shows significant improvements with respect to the traditional approach. This is the typical case of an aircraft or a car in parking conditions under solar input. Full article

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

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18 pages, 1704 KiB

Open AccessArticle

An INS/WiFi Indoor Localization System Based on the Weighted Least Squares

by Jian Chen, Gang Ou, Ao Peng^*

, Lingxiang Zheng and Jianghong Shi

School of Information Science and Engineering, Xiamen University, Xiamen 361001, China

Sensors 2018, 18(5), 1458; https://doi.org/10.3390/s18051458 - 7 May 2018

Cited by 45 | Viewed by 6209

Abstract

For smartphone indoor localization, an INS/WiFi hybrid localization system is proposed in this paper. Acceleration and angular velocity are used to estimate step lengths and headings. The problem with INS is that positioning errors grow with time. Using radio signal strength as a [...] Read more.

For smartphone indoor localization, an INS/WiFi hybrid localization system is proposed in this paper. Acceleration and angular velocity are used to estimate step lengths and headings. The problem with INS is that positioning errors grow with time. Using radio signal strength as a fingerprint is a widely used technology. The main problem with fingerprint matching is mismatching due to noise. Taking into account the different shortcomings and advantages, inertial sensors and WiFi from smartphones are integrated into indoor positioning. For a hybrid localization system, pre-processing techniques are used to enhance the WiFi signal quality. An inertial navigation system limits the range of WiFi matching. A Multi-dimensional Dynamic Time Warping (MDTW) is proposed to calculate the distance between the measured signals and the fingerprint in the database. A MDTW-based weighted least squares (WLS) is proposed for fusing multiple fingerprint localization results to improve positioning accuracy and robustness. Using four modes (calling, dangling, handheld and pocket), we carried out walking experiments in a corridor, a study room and a library stack room. Experimental results show that average localization accuracy for the hybrid system is about 2.03 m. Full article

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

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21 pages, 1143 KiB

Open AccessArticle

A Telerehabilitation System for the Selection, Evaluation and Remote Management of Therapies

by David Anton^1,*, Idoia Berges², Jesús Bermúdez², Alfredo Goñi² and Arantza Illarramendi²

¹ Department of Electrical Engineering & Computer Sciences, University of California, Berkeley, CA 94720, USA

² Department of Languages and Information Systems, University of the Basque Country UPV/EHU, 20018 Donostia-San Sebastián, Spain

Sensors 2018, 18(5), 1459; https://doi.org/10.3390/s18051459 - 8 May 2018

Cited by 68 | Viewed by 11287

Abstract

Telerehabilitation systems that support physical therapy sessions anywhere can help save healthcare costs while also improving the quality of life of the users that need rehabilitation. The main contribution of this paper is to present, as a whole, all the features supported by [...] Read more.

Telerehabilitation systems that support physical therapy sessions anywhere can help save healthcare costs while also improving the quality of life of the users that need rehabilitation. The main contribution of this paper is to present, as a whole, all the features supported by the innovative Kinect-based Telerehabilitation System (KiReS). In addition to the functionalities provided by current systems, it handles two new ones that could be incorporated into them, in order to give a step forward towards a new generation of telerehabilitation systems. The knowledge extraction functionality handles knowledge about the physical therapy record of patients and treatment protocols described in an ontology, named TrhOnt, to select the adequate exercises for the rehabilitation of patients. The teleimmersion functionality provides a convenient, effective and user-friendly experience when performing the telerehabilitation, through a two-way real-time multimedia communication. The ontology contains about 2300 classes and 100 properties, and the system allows a reliable transmission of Kinect video depth, audio and skeleton data, being able to adapt to various network conditions. Moreover, the system has been tested with patients who suffered from shoulder disorders or total hip replacement. Full article

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

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21 pages, 9834 KiB

Open AccessArticle

Ultrasonic Phased Array Compressive Imaging in Time and Frequency Domain: Simulation, Experimental Verification and Real Application

by Zhiliang Bai, Shili Chen^*, Lecheng Jia and Zhoumo Zeng

State Key Laboratory of Precision Measurement Technology and Instrument, Tianjin University, Tianjin 300072, China

Sensors 2018, 18(5), 1460; https://doi.org/10.3390/s18051460 - 8 May 2018

Cited by 11 | Viewed by 4616

Abstract

Embracing the fact that one can recover certain signals and images from far fewer measurements than traditional methods use, compressive sensing (CS) provides solutions to huge amounts of data collection in phased array-based material characterization. This article describes how a CS framework can [...] Read more.

Embracing the fact that one can recover certain signals and images from far fewer measurements than traditional methods use, compressive sensing (CS) provides solutions to huge amounts of data collection in phased array-based material characterization. This article describes how a CS framework can be utilized to effectively compress ultrasonic phased array images in time and frequency domains. By projecting the image onto its Discrete Cosine transform domain, a novel scheme was implemented to verify the potentiality of CS for data reduction, as well as to explore its reconstruction accuracy. The results from CIVA simulations indicate that both time and frequency domain CS can accurately reconstruct array images using samples less than the minimum requirements of the Nyquist theorem. For experimental verification of three types of artificial flaws, although a considerable data reduction can be achieved with defects clearly preserved, it is currently impossible to break Nyquist limitation in the time domain. Fortunately, qualified recovery in the frequency domain makes it happen, meaning a real breakthrough for phased array image reconstruction. As a case study, the proposed CS procedure is applied to the inspection of an engine cylinder cavity containing different pit defects and the results show that orthogonal matching pursuit (OMP)-based CS guarantees the performance for real application. Full article

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

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24 pages, 2732 KiB

Open AccessArticle

Managing Emergency Situations in VANET Through Heterogeneous Technologies Cooperation

by Amilcare Francesco Santamaria

, Mauro Tropea

, Peppino Fazio^*

and Floriano De Rango

Dimes Department, University of Calabria, 87036 Rende, Cosenza, Italy

Sensors 2018, 18(5), 1461; https://doi.org/10.3390/s18051461 - 8 May 2018

Cited by 37 | Viewed by 5306

Abstract

Nowadays, the research on vehicular computing enhanced a very huge amount of services and protocols, aimed to vehicles security and comfort. The investigation of the IEEE802.11p, Wireless Access in Vehicular Environments (WAVE) and Dedicated Short Range Communication (DSRC) standards gave to the scientific [...] Read more.

Nowadays, the research on vehicular computing enhanced a very huge amount of services and protocols, aimed to vehicles security and comfort. The investigation of the IEEE802.11p, Wireless Access in Vehicular Environments (WAVE) and Dedicated Short Range Communication (DSRC) standards gave to the scientific world the chance to integrate new services, protocols, algorithms and devices inside vehicles. This opportunity attracted the attention of private/public organizations, which spent lot of resources and money to promote vehicular technologies. In this paper, the attention is focused on the design of a new approach for vehicular environments able to gather information during mobile node trips, for advising dangerous or emergency situations by exploiting on-board sensors. It is assumed that each vehicle has an integrated on-board unit composed of several sensors and Global Position System (GPS) device, able to spread alerting messages around the network, regarding warning and dangerous situations/conditions. On-board units, based on the standard communication protocols, share the collected information with the surrounding road-side units, while the sensing platform is able to recognize the environment that vehicles are passing through (obstacles, accidents, emergencies, dangerous situations, etc.). Finally, through the use of the GPS receiver, the exact location of the caught event is determined and spread along the network. In this way, if an accident occurs, the arriving cars will, probably, avoid delay and danger situations. Full article

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

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36 pages, 5410 KiB

Open AccessArticle

Geomagnetism-Aided Indoor Wi-Fi Radio-Map Construction via Smartphone Crowdsourcing

by Wen Li^1,2, Dongyan Wei^1,*, Qifeng Lai^1,2, Xianghong Li^1,2 and Hong Yuan¹

¹ Academy of Opto-Electronics, Chinese Academy of Sciences, Beijing 100094, China

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

Sensors 2018, 18(5), 1462; https://doi.org/10.3390/s18051462 - 8 May 2018

Cited by 15 | Viewed by 5625

Abstract

Wi-Fi radio-map construction is an important phase in indoor fingerprint localization systems. Traditional methods for Wi-Fi radio-map construction have the problems of being time-consuming and labor-intensive. In this paper, an indoor Wi-Fi radio-map construction method is proposed which utilizes crowdsourcing data contributed by [...] Read more.

Wi-Fi radio-map construction is an important phase in indoor fingerprint localization systems. Traditional methods for Wi-Fi radio-map construction have the problems of being time-consuming and labor-intensive. In this paper, an indoor Wi-Fi radio-map construction method is proposed which utilizes crowdsourcing data contributed by smartphone users. We draw indoor pathway map and construct Wi-Fi radio-map without requiring manual site survey, exact floor layout and extra infrastructure support. The key novelty is that it recognizes road segments from crowdsourcing traces by a cluster based on magnetism sequence similarity and constructs an indoor pathway map with Wi-Fi signal strengths annotated on. Through experiments in real world indoor areas, the method is proved to have good performance on magnetism similarity calculation, road segment clustering and pathway map construction. The Wi-Fi radio maps constructed by crowdsourcing data are validated to provide competitive indoor localization accuracy. Full article

(This article belongs to the Collection Positioning and Navigation)

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11 pages, 1696 KiB

Open AccessArticle

Non-Invasive Detection of Respiration and Heart Rate with a Vehicle Seat Sensor

by Grace Wusk^* and Hampton Gabler

Department of Biomedical Engineering and Mechanics, Virginia Tech, 325 Stanger Street, Blacksburg, VA 24061, USA

Sensors 2018, 18(5), 1463; https://doi.org/10.3390/s18051463 - 8 May 2018

Cited by 40 | Viewed by 7108

Abstract

This study demonstrates the feasibility of using a seat sensor designed for occupant classification from a production passenger vehicle to measure an occupant’s respiration rate (RR) and heart rate (HR) in a laboratory setting. Relaying occupant vital signs after a crash could improve [...] Read more.

This study demonstrates the feasibility of using a seat sensor designed for occupant classification from a production passenger vehicle to measure an occupant’s respiration rate (RR) and heart rate (HR) in a laboratory setting. Relaying occupant vital signs after a crash could improve emergency response by adding a direct measure of the occupant state to an Advanced Automatic Collision Notification (AACN) system. Data was collected from eleven participants with body weights ranging from 42 to 91 kg using a Ford Mustang passenger seat and seat sensor. Using a ballistocardiography (BCG) approach, the data was processed by time domain filtering and frequency domain analysis using the fast Fourier transform to yield RR and HR in a 1-min sliding window. Resting rates over the 30-min data collection and continuous RR and HR signals were compared to laboratory physiological instruments using the Bland-Altman approach. Differences between the seat sensor and reference sensor were within 5 breaths per minute for resting RR and within 15 beats per minute for resting HR. The time series comparisons for RR and HR were promising with the frequency analysis technique outperforming the peak detection technique. However, future work is necessary for more accurate and reliable real-time monitoring of RR and HR outside the laboratory setting. Full article

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

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19 pages, 2659 KiB

Open AccessArticle

Pido: Predictive Delay Optimization for Intertidal Wireless Sensor Networks

by Xinyan Zhou¹

, Xiaoyu Ji^1,*, Bin Wang², Yushi Cheng¹, Zhuoran Ma¹, Francis Choi³, Brian Helmuth³

and Wenyuan Xu¹

¹ College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China

² Hangzhou Hikvision Digital Technology Co Ltd., 310051 Hangzhou, China

³ Department of Marine and Environmental Sciences and School of Public Policy and Urban Affairs, Northeastern University Marine Science Center, Nahant, MA 01908, USA

Sensors 2018, 18(5), 1464; https://doi.org/10.3390/s18051464 - 8 May 2018

Cited by 11 | Viewed by 5165

Abstract

Intertidal habitats are among the harshest environments on the planet, and have emerged as a model system for exploring the ecological impacts of global climate change. Deploying reliable instrumentation to measure environmental conditions such as temperature is challenging in this environment. The application [...] Read more.

Intertidal habitats are among the harshest environments on the planet, and have emerged as a model system for exploring the ecological impacts of global climate change. Deploying reliable instrumentation to measure environmental conditions such as temperature is challenging in this environment. The application of wireless sensor networks (WSNs) shows considerable promise as a means of optimizing continuous data collection, but poor link quality and unstable connections between nodes, caused by harsh physical environmental conditions, bring about a delay problem. In this paper, we model and analyze the components of delays in an intertidal wireless sensor network system (IT-WSN). We show that, by properly selecting routing pathways, it is feasible to improve delay. To this end, we propose a Predictive Delay Optimization (Pido) framework, which provides a new metric for routing path selection. Pido incorporates delay introduced by both link quality and node conditions, and designs a classifier to predict future conditions of nodes, i.e., the likely time of aerial exposure at low tide in this case. We evaluate the performance of Pido in both a real IT-WSN system and a large-scale simulation, the result demonstrates that Pido decreases up to 73% of delays on average with limited overhead. Full article

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

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24 pages, 6267 KiB

Open AccessArticle

Smart Waste Collection System with Low Consumption LoRaWAN Nodes and Route Optimization

by Álvaro Lozano^1,*

, Javier Caridad¹

, Juan Francisco De Paz¹, Gabriel Villarrubia González¹

and Javier Bajo²

¹ Faculty of Science, University of Salamanca, Plaza de la Merced s/n, 37002 Salamanca, Spain

² Department of Artificial Intelligence, Polytechnic University of Madrid, Campus Montegancedo s/n, Boadilla del Monte, 28660 Madrid, Spain

Sensors 2018, 18(5), 1465; https://doi.org/10.3390/s18051465 - 8 May 2018

Cited by 77 | Viewed by 15242

Abstract

New solutions for managing waste have emerged due to the rise of Smart Cities and the Internet of Things. These solutions can also be applied in rural environments, but they require the deployment of a low cost and low consumption sensor network which [...] Read more.

New solutions for managing waste have emerged due to the rise of Smart Cities and the Internet of Things. These solutions can also be applied in rural environments, but they require the deployment of a low cost and low consumption sensor network which can be used by different applications. Wireless technologies such as LoRa and low consumption microcontrollers, such as the SAM L21 family make the implementation and deployment of this kind of sensor network possible. This paper introduces a waste monitoring and management platform used in rural environments. A prototype of a low consumption wireless node is developed to obtain measurements of the weight, filling volume and temperature of a waste container. This monitoring allows the progressive filling data of every town container to be gathered and analysed as well as creating alerts in case of incidence. The platform features a module for optimising waste collection routes. This module dynamically generates routes from data obtained through the deployed nodes to save energy, time and consequently, costs. It also features a mobile application for the collection fleet which guides every driver through the best route—previously calculated for each journey. This paper presents a case study performed in the region of Salamanca to evaluate the efficiency and the viability of the system’s implementation. Data used for this case study come from open data sources, the report of the Castilla y León waste management plan and data from public tender procedures in the region of Salamanca. The results of the case study show a developed node with a great lifetime of operation, a large coverage with small deployment of antennas in the region, and a route optimization system which uses weight and volume measured by the node, and provides savings in cost, time and workforce compared to a static collection route approach. Full article

(This article belongs to the Special Issue Smart Decision-Making)

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21 pages, 19994 KiB

Open AccessArticle

Multiband Envelope Spectra Extraction for Fault Diagnosis of Rolling Element Bearings

by Jie Duan¹

, Tielin Shi^1,*, Hongdi Zhou², Jianping Xuan¹ and Yongxiang Zhang³

¹ State Key Lab of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China

² School of Mechanical Engineering, Hubei University of Technology, Wuhan 430068, China

³ Department of Power Engineering, Naval University of Engineering, Wuhan 430033, China

Sensors 2018, 18(5), 1466; https://doi.org/10.3390/s18051466 - 8 May 2018

Cited by 27 | Viewed by 4573

Abstract

Bearing fault features are presented as repetitive transient impulses in vibration signals. Narrowband demodulation methods have been widely used to extract the repetitive transients in bearing fault diagnosis, for which the key factor is to accurately locate the optimal band. A multitude of [...] Read more.

Bearing fault features are presented as repetitive transient impulses in vibration signals. Narrowband demodulation methods have been widely used to extract the repetitive transients in bearing fault diagnosis, for which the key factor is to accurately locate the optimal band. A multitude of criteria have been constructed to determine the optimal frequency band for demodulation. However, these criteria can only describe the strength of transient impulses, and cannot differentiate fault-related impulses and interference impulses that are cyclically generated in the signals. Additionally, these criteria are easily affected by the independent transitions and background noise in industrial locales. Therefore, the large values of the criteria may not appear in the optimal frequency band. To overcome these problems, a new method, referred to as multiband envelope spectra extraction (MESE), is proposed in this paper, which can extract all repetitive transient features in the signals. The novelty of MESE lies in the following aspects: (1) it can fuse envelope spectra at multiple narrow bands. The potential bands are selected based on Jarque-Bera statistics of narrowband envelope spectra; and (2) fast independent component analysis (fastICA) is introduced to extract the independent source spectra, which are fault- or interference-related. The multi-band strategy will preserve all impulse features and make the method more robust. Meanwhile, as a blind source separation technique, the fastICA can suppress some in-band noise and make the diagnosis more accurate. Several simulated and experimental signals are used to validate the efficiency of the proposed method. The results show that MESE is effective for enhanced fault diagnosis of rolling element bearings. Bearing faults can be detected even in a harsh environment. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 2813 KiB

Open AccessArticle

Speech Enhancement of Mobile Devices Based on the Integration of a Dual Microphone Array and a Background Noise Elimination Algorithm

by Yung-Yue Chen

Department of Systems and Naval Mechatronic Engineering, National Cheng Kung University, Tainan City 701, Taiwan

Sensors 2018, 18(5), 1467; https://doi.org/10.3390/s18051467 - 8 May 2018

Cited by 8 | Viewed by 5265

Abstract

Mobile devices are often used in our daily lives for the purposes of speech and communication. The speech quality of mobile devices is always degraded due to the environmental noises surrounding mobile device users. Regretfully, an effective background noise reduction solution cannot easily [...] Read more.

Mobile devices are often used in our daily lives for the purposes of speech and communication. The speech quality of mobile devices is always degraded due to the environmental noises surrounding mobile device users. Regretfully, an effective background noise reduction solution cannot easily be developed for this speech enhancement problem. Due to these depicted reasons, a methodology is systematically proposed to eliminate the effects of background noises for the speech communication of mobile devices. This methodology integrates a dual microphone array with a background noise elimination algorithm. The proposed background noise elimination algorithm includes a whitening process, a speech modelling method and an H₂ estimator. Due to the adoption of the dual microphone array, a low-cost design can be obtained for the speech enhancement of mobile devices. Practical tests have proven that this proposed method is immune to random background noises, and noiseless speech can be obtained after executing this denoise process. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICICE 2017)

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14 pages, 799 KiB

Open AccessArticle

A Hybrid DV-Hop Algorithm Using RSSI for Localization in Large-Scale Wireless Sensor Networks

by Omar Cheikhrouhou^1,*,†, Ghulam M. Bhatti² and Roobaea Alroobaea²

¹ Department of IT, College of Computers and Information Technology, Taif University, At Taif 26571, Saudi Arabia

² Department of Computer Science, College of Computers and Information Technology, Taif University, At Taif 26571, Saudi Arabia

^† Current Address: ISIMA, University of Monastir, Avenue Habib Bourguiba, Sidi Massoud -BP 49, Mahdia 5111, Tunisia.

Sensors 2018, 18(5), 1469; https://doi.org/10.3390/s18051469 - 8 May 2018

Cited by 91 | Viewed by 5942

Abstract

With the increasing realization of the Internet-of-Things (IoT) and rapid proliferation of wireless sensor networks (WSN), estimating the location of wireless sensor nodes is emerging as an important issue. Traditional ranging based localization algorithms use triangulation for estimating the physical location of only [...] Read more.

With the increasing realization of the Internet-of-Things (IoT) and rapid proliferation of wireless sensor networks (WSN), estimating the location of wireless sensor nodes is emerging as an important issue. Traditional ranging based localization algorithms use triangulation for estimating the physical location of only those wireless nodes that are within one-hop distance from the anchor nodes. Multi-hop localization algorithms, on the other hand, aim at localizing the wireless nodes that can physically be residing at multiple hops away from anchor nodes. These latter algorithms have attracted a growing interest from research community due to the smaller number of required anchor nodes. One such algorithm, known as DV-Hop (Distance Vector Hop), has gained popularity due to its simplicity and lower cost. However, DV-Hop suffers from reduced accuracy due to the fact that it exploits only the network topology (i.e., number of hops to anchors) rather than the distances between pairs of nodes. In this paper, we propose an enhanced DV-Hop localization algorithm that also uses the RSSI values associated with links between one-hop neighbors. Moreover, we exploit already localized nodes by promoting them to become additional anchor nodes. Our simulations have shown that the proposed algorithm significantly outperforms the original DV-Hop localization algorithm and two of its recently published variants, namely RSSI Auxiliary Ranging and the Selective 3-Anchor DV-hop algorithm. More precisely, in some scenarios, the proposed algorithm improves the localization accuracy by almost 95%, 90% and 70% as compared to the basic DV-Hop, Selective 3-Anchor, and RSSI DV-Hop algorithms, respectively. Full article

(This article belongs to the Special Issue Applications of Wireless Sensors in Localization and Tracking)

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12 pages, 2728 KiB

Open AccessArticle

Application of a Portable Multi-Analyte Biosensor for Organic Acid Determination in Silage

by Johanna Pilas^1,2, Yasemen Yazici¹, Thorsten Selmer¹, Michael Keusgen² and Michael J. Schöning^1,3,*

¹ Institute of Nano- and Biotechnologies (INB), FH Aachen, Heinrich-Mußmann-Straße 1, 52428 Jülich, Germany

² Institute of Pharmaceutical Chemistry, Philipps-Universität Marburg, 35037 Marburg, Germany

³ Institute of Complex Systems 8 (ICS-8); Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße 1, 52425 Jülich, Germany

Sensors 2018, 18(5), 1470; https://doi.org/10.3390/s18051470 - 8 May 2018

Cited by 17 | Viewed by 6431

Abstract

Multi-analyte biosensors may offer the opportunity to perform cost-effective and rapid analysis with reduced sample volume, as compared to electrochemical biosensing of each analyte individually. This work describes the development of an enzyme-based biosensor system for multi-parametric determination of four different organic acids. [...] Read more.

Multi-analyte biosensors may offer the opportunity to perform cost-effective and rapid analysis with reduced sample volume, as compared to electrochemical biosensing of each analyte individually. This work describes the development of an enzyme-based biosensor system for multi-parametric determination of four different organic acids. The biosensor array comprises five working electrodes for simultaneous sensing of ethanol, formate, d-lactate, and l-lactate, and an integrated counter electrode. Storage stability of the biosensor was evaluated under different conditions (stored at +4 °C in buffer solution and dry at −21 °C, +4 °C, and room temperature) over a period of 140 days. After repeated and regular application, the individual sensing electrodes exhibited the best stability when stored at −21 °C. Furthermore, measurements in silage samples (maize and sugarcane silage) were conducted with the portable biosensor system. Comparison with a conventional photometric technique demonstrated successful employment for rapid monitoring of complex media. Full article

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

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13 pages, 5046 KiB

Open AccessArticle

A Four-Feet Walking-Type Rotary Piezoelectric Actuator with Minute Step Motion

by Yingxiang Liu^*

, Yun Wang

, Junkao Liu, Dongmei Xu, Kai Li, Xiaobiao Shan and Jie Deng

State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin 150001, China

Sensors 2018, 18(5), 1471; https://doi.org/10.3390/s18051471 - 8 May 2018

Cited by 18 | Viewed by 4893

Abstract

A four-feet walking-type rotary piezoelectric actuator with minute step motion was proposed. The proposed actuator used the rectangular motions of four driving feet to push the rotor step-by-step; this operating principle was different with the previous non-resonant actuators using direct-driving, inertial-driving, and inchworm-type [...] Read more.

A four-feet walking-type rotary piezoelectric actuator with minute step motion was proposed. The proposed actuator used the rectangular motions of four driving feet to push the rotor step-by-step; this operating principle was different with the previous non-resonant actuators using direct-driving, inertial-driving, and inchworm-type mechanisms. The mechanism of the proposed actuator was discussed in detail. Transient analyses were accomplished by ANSYS software to simulate the motion trajectory of the driving foot and to find the response characteristics. A prototype was manufactured to verify the mechanism and to test the mechanical characteristics. A minimum resolution of 0.095 μrad and a maximum torque of 49 N·mm were achieved by the prototype, and the output speed was varied by changing the driving voltage and working frequency. This work provides a new mechanism for the design of a rotary piezoelectric actuator with minute step motion. Full article

(This article belongs to the Section Physical Sensors)

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35 pages, 9559 KiB

Open AccessArticle

A Cooperative Search and Coverage Algorithm with Controllable Revisit and Connectivity Maintenance for Multiple Unmanned Aerial Vehicles

by Zhong Liu^*, Xiaoguang Gao and Xiaowei Fu

School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710072, China

Sensors 2018, 18(5), 1472; https://doi.org/10.3390/s18051472 - 8 May 2018

Cited by 48 | Viewed by 5607

Abstract

In this paper, we mainly study a cooperative search and coverage algorithm for a given bounded rectangle region, which contains several unknown stationary targets, by a team of unmanned aerial vehicles (UAVs) with non-ideal sensors and limited communication ranges. Our goal is to [...] Read more.

In this paper, we mainly study a cooperative search and coverage algorithm for a given bounded rectangle region, which contains several unknown stationary targets, by a team of unmanned aerial vehicles (UAVs) with non-ideal sensors and limited communication ranges. Our goal is to minimize the search time, while gathering more information about the environment and finding more targets. For this purpose, a novel cooperative search and coverage algorithm with controllable revisit mechanism is presented. Firstly, as the representation of the environment, the cognitive maps that included the target probability map (TPM), the uncertain map (UM), and the digital pheromone map (DPM) are constituted. We also design a distributed update and fusion scheme for the cognitive map. This update and fusion scheme can guarantee that each one of the cognitive maps converges to the same one, which reflects the targets’ true existence or absence in each cell of the search region. Secondly, we develop a controllable revisit mechanism based on the DPM. This mechanism can concentrate the UAVs to revisit sub-areas that have a large target probability or high uncertainty. Thirdly, in the frame of distributed receding horizon optimizing, a path planning algorithm for the multi-UAVs cooperative search and coverage is designed. In the path planning algorithm, the movement of the UAVs is restricted by the potential fields to meet the requirements of avoiding collision and maintaining connectivity constraints. Moreover, using the minimum spanning tree (MST) topology optimization strategy, we can obtain a tradeoff between the search coverage enhancement and the connectivity maintenance. The feasibility of the proposed algorithm is demonstrated by comparison simulations by way of analyzing the effects of the controllable revisit mechanism and the connectivity maintenance scheme. The Monte Carlo method is employed to validate the influence of the number of UAVs, the sensing radius, the detection and false alarm probabilities, and the communication range on the proposed algorithm. Full article

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

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17 pages, 4419 KiB

Open AccessArticle

PS-CARA: Context-Aware Resource Allocation Scheme for Mobile Public Safety Networks

by Zeeshan Kaleem¹

, Muhammad Zubair Khaliq¹

, Ajmal Khan², Ishtiaq Ahmad³ and Trung Q. Duong^4,*

¹ Department of Electrical Engineering, COMSATS University, Wah Campus, Wah Cantonment 47040, Pakistan

² Department of Electrical Engineering, COMSATS University, Attock Campus, Attock 43600, Pakistan

³ Department of Electronics Engineering, Inha University, Incheon 22212, Korea

⁴ School of Electronics, Electrical Engineering and Computer Science, Queen’s University Belfast, University Rd, Belfast BT7 1NN, UK

Sensors 2018, 18(5), 1473; https://doi.org/10.3390/s18051473 - 8 May 2018

Cited by 22 | Viewed by 5609

Abstract

The fifth-generation (5G) communications systems are expecting to support users with diverse quality-of-service (QoS) requirements. Beside these requirements, the task with utmost importance is to support the emergency communication services during natural or man-made disasters. Most of the conventional base stations are not [...] Read more.

The fifth-generation (5G) communications systems are expecting to support users with diverse quality-of-service (QoS) requirements. Beside these requirements, the task with utmost importance is to support the emergency communication services during natural or man-made disasters. Most of the conventional base stations are not properly functional during a disaster situation, so deployment of emergency base stations such as mobile personal cell (mPC) is crucial. An mPC having moving capability can move in the disaster area to provide emergency communication services. However, mPC deployment causes severe co-channel interference to the users in its vicinity. The problem in the existing resource allocation schemes is its support for static environment, that does not fit well for mPC. So, a resource allocation scheme for mPC users is desired that can dynamically allocate resources based on users’ location and its connection establishment priority. In this paper, we propose a public safety users priority-based context-aware resource allocation (PS-CARA) scheme for users sum-rate maximization in disaster environment. Simulations results demonstrate that the proposed PS-CARA scheme can increase the user average and edge rate around 10.3% and 32.8% , respectively because of context information availability and by prioritizing the public safety users. The simulation results ensure that call blocking probability is also reduced considerably under the PS-CARA scheme. Full article

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

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27 pages, 6047 KiB

Open AccessArticle

Poaching Detection Technologies—A Survey

by Jacob Kamminga

, Eyuel Ayele

, Nirvana Meratnia and Paul Havinga^*

Pervasive Systems Group, University of Twente, Enschede 7522 NB, The Netherlands

Sensors 2018, 18(5), 1474; https://doi.org/10.3390/s18051474 - 8 May 2018

Cited by 51 | Viewed by 18131

Abstract

Between 1960 and 1990, 95% of the black rhino population in the world was killed. In South Africa, a rhino was killed every 8 h for its horn throughout 2016. Wild animals, rhinos and elephants, in particular, are facing an ever increasing poaching [...] Read more.

Between 1960 and 1990, 95% of the black rhino population in the world was killed. In South Africa, a rhino was killed every 8 h for its horn throughout 2016. Wild animals, rhinos and elephants, in particular, are facing an ever increasing poaching crisis. In this paper, we review poaching detection technologies that aim to save endangered species from extinction. We present requirements for effective poacher detection and identify research challenges through the survey. We describe poaching detection technologies in four domains: perimeter based, ground based, aerial based, and animal tagging based technologies. Moreover, we discuss the different types of sensor technologies that are used in intruder detection systems such as: radar, magnetic, acoustic, optic, infrared and thermal, radio frequency, motion, seismic, chemical, and animal sentinels. The ultimate long-term solution for the poaching crisis is to remove the drivers of demand by educating people in demanding countries and raising awareness of the poaching crisis. Until prevention of poaching takes effect, there will be a continuous urgent need for new (combined) approaches that take up the research challenges and provide better protection against poaching in wildlife areas. Full article

(This article belongs to the Section Sensor Networks)

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10 pages, 3348 KiB

Open AccessArticle

Manufacturing a Long-Period Grating with Periodic Thermal Diffusion Technology on High-NA Fiber and Its Application as a High-Temperature Sensor

by Xiang Shen, Bin Dai, Yingbin Xing, Luyun Yang, Haiqing Li, Jinyan Li and Jingang Peng^*

Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China

Sensors 2018, 18(5), 1475; https://doi.org/10.3390/s18051475 - 8 May 2018

Cited by 8 | Viewed by 4628

Abstract

We demonstrated a kind of long-period fiber grating (LPFG), which is manufactured with a thermal diffusion treatment. The LPFG was inscribed on an ultrahigh-numerical-aperture (UHNA) fiber, highly doped with Ge and P, which was able to easily diffuse at high temperatures within a [...] Read more.

We demonstrated a kind of long-period fiber grating (LPFG), which is manufactured with a thermal diffusion treatment. The LPFG was inscribed on an ultrahigh-numerical-aperture (UHNA) fiber, highly doped with Ge and P, which was able to easily diffuse at high temperatures within a few seconds. We analyzed how the elements diffused at a high temperature over 1300 °C in the UHNA fiber. Then we developed a periodically heated technology with a CO₂ laser, which was able to cause the diffusion of the elements to constitute the modulations of an LPFG. With this technology, there is little damage to the outer structure of the fiber, which is different from the traditional LPFG, as it is periodically tapered. Since the LPFG itself was manufactured under high temperature, it can withstand higher temperatures than traditional LPFGs. Furthermore, the LPFG presents a higher sensitivity to high temperature due to the large amount of Ge doping, which is approximately 100 pm/°C. In addition, the LPFG shows insensitivity to the changing of the environment’s refractive index and strain. Full article

(This article belongs to the Special Issue Optical Sensors Using Microstructured and Photonics Crystal Fibers)

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12 pages, 1644 KiB

Open AccessArticle

Robust Adaptive Beamforming with Sensor Position Errors Using Weighted Subspace Fitting-Based Covariance Matrix Reconstruction

by Peng Chen

, Yixin Yang^*, Yong Wang

and Yuanliang Ma

School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China

Sensors 2018, 18(5), 1476; https://doi.org/10.3390/s18051476 - 8 May 2018

Cited by 23 | Viewed by 3746

Abstract

When sensor position errors exist, the performance of recently proposed interference-plus-noise covariance matrix (INCM)-based adaptive beamformers may be severely degraded. In this paper, we propose a weighted subspace fitting-based INCM reconstruction algorithm to overcome sensor displacement for linear arrays. By estimating the rough [...] Read more.

When sensor position errors exist, the performance of recently proposed interference-plus-noise covariance matrix (INCM)-based adaptive beamformers may be severely degraded. In this paper, we propose a weighted subspace fitting-based INCM reconstruction algorithm to overcome sensor displacement for linear arrays. By estimating the rough signal directions, we construct a novel possible mismatched steering vector (SV) set. We analyze the proximity of the signal subspace from the sample covariance matrix (SCM) and the space spanned by the possible mismatched SV set. After solving an iterative optimization problem, we reconstruct the INCM using the estimated sensor position errors. Then we estimate the SV of the desired signal by solving an optimization problem with the reconstructed INCM. The main advantage of the proposed algorithm is its robustness against SV mismatches dominated by unknown sensor position errors. Numerical examples show that even if the position errors are up to half of the assumed sensor spacing, the output signal-to-interference-plus-noise ratio is only reduced by 4 dB. Beam patterns plotted using experiment data show that the interference suppression capability of the proposed beamformer outperforms other tested beamformers. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 5992 KiB

Open AccessArticle

PCANet-Based Structural Representation for Nonrigid Multimodal Medical Image Registration

by Xingxing Zhu¹, Mingyue Ding¹, Tao Huang², Xiaomeng Jin¹ and Xuming Zhang^1,*

¹ Department of Biomedical Engineering, School of Life Science and Technology, Ministry of Education Key Laboratory of Molecular Biophysics, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074, China

² State Food and Drug Administration Hubei Center for Medical Devices Quality Supervision and Testing, No. 507, Hi-Tech Avenue, Donghu Hi-Tech Development District, Wuhan 430075, China

Sensors 2018, 18(5), 1477; https://doi.org/10.3390/s18051477 - 8 May 2018

Cited by 30 | Viewed by 5933

Abstract

Nonrigid multimodal image registration remains a challenging task in medical image processing and analysis. The structural representation (SR)-based registration methods have attracted much attention recently. However, the existing SR methods cannot provide satisfactory registration accuracy due to the utilization of hand-designed features for [...] Read more.

Nonrigid multimodal image registration remains a challenging task in medical image processing and analysis. The structural representation (SR)-based registration methods have attracted much attention recently. However, the existing SR methods cannot provide satisfactory registration accuracy due to the utilization of hand-designed features for structural representation. To address this problem, the structural representation method based on the improved version of the simple deep learning network named PCANet is proposed for medical image registration. In the proposed method, PCANet is firstly trained on numerous medical images to learn convolution kernels for this network. Then, a pair of input medical images to be registered is processed by the learned PCANet. The features extracted by various layers in the PCANet are fused to produce multilevel features. The structural representation images are constructed for two input images based on nonlinear transformation of these multilevel features. The Euclidean distance between structural representation images is calculated and used as the similarity metrics. The objective function defined by the similarity metrics is optimized by L-BFGS method to obtain parameters of the free-form deformation (FFD) model. Extensive experiments on simulated and real multimodal image datasets show that compared with the state-of-the-art registration methods, such as modality-independent neighborhood descriptor (MIND), normalized mutual information (NMI), Weber local descriptor (WLD), and the sum of squared differences on entropy images (ESSD), the proposed method provides better registration performance in terms of target registration error (TRE) and subjective human vision. Full article

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

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14 pages, 22186 KiB

Open AccessArticle

Extrinsic Calibration of a Laser Galvanometric Setup and a Range Camera

by Seppe Sels^1,*

, Boris Bogaerts¹

, Steve Vanlanduit¹ and Rudi Penne^1,2

¹ Departement Electromechanics, Faculty of Applied Engineering, University of Antwerp, 2020 Antwerpen, Belgium

² Departement of Mathematics, University of Antwerp, 2020 Antwerpen, Belgium

Sensors 2018, 18(5), 1478; https://doi.org/10.3390/s18051478 - 8 May 2018

Cited by 8 | Viewed by 6345

Abstract

Currently, galvanometric scanning systems (like the one used in a scanning laser Doppler vibrometer) rely on a planar calibration procedure between a two-dimensional (2D) camera and the laser galvanometric scanning system to automatically aim a laser beam at a particular point on an [...] Read more.

Currently, galvanometric scanning systems (like the one used in a scanning laser Doppler vibrometer) rely on a planar calibration procedure between a two-dimensional (2D) camera and the laser galvanometric scanning system to automatically aim a laser beam at a particular point on an object. In the case of nonplanar or moving objects, this calibration is not sufficiently accurate anymore. In this work, a three-dimensional (3D) calibration procedure that uses a 3D range sensor is proposed. The 3D calibration is valid for all types of objects and retains its accuracy when objects are moved between subsequent measurement campaigns. The proposed 3D calibration uses a Non-Perspective-n-Point (NPnP) problem solution. The 3D range sensor is used to calculate the position of the object under test relative to the laser galvanometric system. With this extrinsic calibration, the laser galvanometric scanning system can automatically aim a laser beam to this object. In experiments, the mean accuracy of aiming the laser beam on an object is below 10 mm for 95% of the measurements. This achieved accuracy is mainly determined by the accuracy and resolution of the 3D range sensor. The new calibration method is significantly better than the original 2D calibration method, which in our setup achieves errors below 68 mm for 95% of the measurements. Full article

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

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17 pages, 5085 KiB

Open AccessArticle

Direct Position Determination of Multiple Non-Circular Sources with a Moving Coprime Array

by Yankui Zhang

, Bin Ba^*, Daming Wang, Wei Geng and Haiyun Xu

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

Sensors 2018, 18(5), 1479; https://doi.org/10.3390/s18051479 - 8 May 2018

Cited by 16 | Viewed by 4040

Abstract

Direct position determination (DPD) is currently a hot topic in wireless localization research as it is more accurate than traditional two-step positioning. However, current DPD algorithms are all based on uniform arrays, which have an insufficient degree of freedom and limited estimation accuracy. [...] Read more.

Direct position determination (DPD) is currently a hot topic in wireless localization research as it is more accurate than traditional two-step positioning. However, current DPD algorithms are all based on uniform arrays, which have an insufficient degree of freedom and limited estimation accuracy. To improve the DPD accuracy, this paper introduces a coprime array to the position model of multiple non-circular sources with a moving array. To maximize the advantages of this coprime array, we reconstruct the covariance matrix by vectorization, apply a spatial smoothing technique, and converge the subspace data from each measuring position to establish the cost function. Finally, we obtain the position coordinates of the multiple non-circular sources. The complexity of the proposed method is computed and compared with that of other methods, and the Cramer–Rao lower bound of DPD for multiple sources with a moving coprime array, is derived. Theoretical analysis and simulation results show that the proposed algorithm is not only applicable to circular sources, but can also improve the positioning accuracy of non-circular sources. Compared with existing two-step positioning algorithms and DPD algorithms based on uniform linear arrays, the proposed technique offers a significant improvement in positioning accuracy with a slight increase in complexity. Full article

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

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22 pages, 1084 KiB

Open AccessArticle

Distributed Power Allocation for Wireless Sensor Network Localization: A Potential Game Approach

by Mingxing Ke^1,2,*

, Ding Li³, Shiwei Tian¹, Yuli Zhang^1,2, Kaixiang Tong¹ and Yuhua Xu^1,2

¹ The College of Communications Engineering, PLA Army Engineering University, Nanjing 210007, China

² Science and Technology on Communication Networks Laboratory, Shijiazhuang 050002, China

³ Modern Educational and Technological Center, Agricultural University of South China, Guangzhou 510642, China

Sensors 2018, 18(5), 1480; https://doi.org/10.3390/s18051480 - 8 May 2018

Cited by 8 | Viewed by 3486

Abstract

The problem of distributed power allocation in wireless sensor network (WSN) localization systems is investigated in this paper, using the game theoretic approach. Existing research focuses on the minimization of the localization errors of individual agent nodes over all anchor nodes subject to [...] Read more.

The problem of distributed power allocation in wireless sensor network (WSN) localization systems is investigated in this paper, using the game theoretic approach. Existing research focuses on the minimization of the localization errors of individual agent nodes over all anchor nodes subject to power budgets. When the service area and the distribution of target nodes are considered, finding the optimal trade-off between localization accuracy and power consumption is a new critical task. To cope with this issue, we propose a power allocation game where each anchor node minimizes the square position error bound (SPEB) of the service area penalized by its individual power. Meanwhile, it is proven that the power allocation game is an exact potential game which has one pure Nash equilibrium (NE) at least. In addition, we also prove the existence of an

ϵ

-equilibrium point, which is a refinement of NE and the better response dynamic approach can reach the end solution. Analytical and simulation results demonstrate that: (i) when prior distribution information is available, the proposed strategies have better localization accuracy than the uniform strategies; (ii) when prior distribution information is unknown, the performance of the proposed strategies outperforms power management strategies based on the second-order cone program (SOCP) for particular agent nodes after obtaining the estimated distribution of agent nodes. In addition, proposed strategies also provide an instructional trade-off between power consumption and localization accuracy. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 2803 KiB

Open AccessArticle

Robust Target Tracking with Multi-Static Sensors under Insufficient TDOA Information

by Hyunhak Shin¹, Bonhwa Ku¹, Jill K. Nelson² and Hanseok Ko^1,*

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

² Department of Electrical and Computer Engineering, George Mason University, Fairfax, VA 22030, USA

Sensors 2018, 18(5), 1481; https://doi.org/10.3390/s18051481 - 8 May 2018

Cited by 11 | Viewed by 5603

Abstract

This paper focuses on underwater target tracking based on a multi-static sonar network composed of passive sonobuoys and an active ping. In the multi-static sonar network, the location of the target can be estimated using TDOA (Time Difference of Arrival) measurements. However, since [...] Read more.

This paper focuses on underwater target tracking based on a multi-static sonar network composed of passive sonobuoys and an active ping. In the multi-static sonar network, the location of the target can be estimated using TDOA (Time Difference of Arrival) measurements. However, since the sensor network may obtain insufficient and inaccurate TDOA measurements due to ambient noise and other harsh underwater conditions, target tracking performance can be significantly degraded. We propose a robust target tracking algorithm designed to operate in such a scenario. First, track management with track splitting is applied to reduce performance degradation caused by insufficient measurements. Second, a target location is estimated by a fusion of multiple TDOA measurements using a Gaussian Mixture Model (GMM). In addition, the target trajectory is refined by conducting a stack-based data association method based on multiple-frames measurements in order to more accurately estimate target trajectory. The effectiveness of the proposed method is verified through simulations. Full article

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

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11 pages, 4287 KiB

Open AccessArticle

A Double Dwell High Sensitivity GPS Acquisition Scheme Using Binarized Convolution Neural Network

by Zhen Wang, Yuan Zhuang^*, Jun Yang, Hengfeng Zhang, Wei Dong, Min Wang, Luchi Hua, Bo Liu and Longxing Shi

National ASIC System Engineering Research Center, Southeast University, 2 Sipailou, Nanjing 210096, China

Sensors 2018, 18(5), 1482; https://doi.org/10.3390/s18051482 - 9 May 2018

Cited by 7 | Viewed by 4425

Abstract

Conventional GPS acquisition methods, such as Max selection and threshold crossing (MAX/TC), estimate GPS code/Doppler by its correlation peak. Different from MAX/TC, a multi-layer binarized convolution neural network (BCNN) is proposed to recognize the GPS acquisition correlation envelope in this article. The proposed [...] Read more.

Conventional GPS acquisition methods, such as Max selection and threshold crossing (MAX/TC), estimate GPS code/Doppler by its correlation peak. Different from MAX/TC, a multi-layer binarized convolution neural network (BCNN) is proposed to recognize the GPS acquisition correlation envelope in this article. The proposed method is a double dwell acquisition in which a short integration is adopted in the first dwell and a long integration is applied in the second one. To reduce the search space for parameters, BCNN detects the possible envelope which contains the auto-correlation peak in the first dwell to compress the initial search space to 1/1023. Although there is a long integration in the second dwell, the acquisition computation overhead is still low due to the compressed search space. Comprehensively, the total computation overhead of the proposed method is only 1/5 of conventional ones. Experiments show that the proposed double dwell/correlation envelope identification (DD/CEI) neural network achieves 2 dB improvement when compared with the MAX/TC under the same specification. Full article

(This article belongs to the Collection Positioning and Navigation)

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14 pages, 7855 KiB

Open AccessArticle

Use of the Stockwell Transform in the Detection of P300 Evoked Potentials with Low-Cost Brain Sensors

by Alan F. Pérez-Vidal^1,*, Carlos D. Garcia-Beltran¹

, Albino Martínez-Sibaja² and Rubén Posada-Gómez²

¹ Tecnológico Nacional de México-CENIDET, Interior Internado Palmira S/N, Col. Palmira, Cuernavaca, Morelos, C.P. 62490, México

² Tecnológico Nacional de México-Instituto Tecnológico de Orizaba, Av. Oriente 9 N° 852, Col. Emiliano Zapata, Orizaba, C.P. 94320, México

Sensors 2018, 18(5), 1483; https://doi.org/10.3390/s18051483 - 9 May 2018

Cited by 14 | Viewed by 5394

Abstract

The evoked potential is a neuronal activity that originates when a stimulus is presented. To achieve its detection, various techniques of brain signal processing can be used. One of the most studied evoked potentials is the P300 brain wave, which usually appears between [...] Read more.

The evoked potential is a neuronal activity that originates when a stimulus is presented. To achieve its detection, various techniques of brain signal processing can be used. One of the most studied evoked potentials is the P300 brain wave, which usually appears between 300 and 500 ms after the stimulus. Currently, the detection of P300 evoked potentials is of great importance due to its unique properties that allow the development of applications such as spellers, lie detectors, and diagnosis of psychiatric disorders. The present study was developed to demonstrate the usefulness of the Stockwell transform in the process of identifying P300 evoked potentials using a low-cost electroencephalography (EEG) device with only two brain sensors. The acquisition of signals was carried out using the Emotiv EPOC^® device—a wireless EEG headset. In the feature extraction, the Stockwell transform was used to obtain time-frequency information. The algorithms of linear discriminant analysis and a support vector machine were used in the classification process. The experiments were carried out with 10 participants; men with an average age of 25.3 years in good health. In general, a good performance (75–92%) was obtained in identifying P300 evoked potentials. Full article

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

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17 pages, 3021 KiB

Open AccessArticle

State Recognition of Bone Drilling Based on Acoustic Emission in Pedicle Screw Operation

by Fengqing Guan^1,2, Yu Sun^1,2

, Xiaozhi Qi^1,*

, Ying Hu^1,*, Gang Yu² and Jianwei Zhang³

¹ Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China

² Harbin Institute of Technology at Shenzhen, Shenzhen 518052, China

³ Department of Informatics, University of Hamburg, 22527 Hamburg, Germany

Sensors 2018, 18(5), 1484; https://doi.org/10.3390/s18051484 - 9 May 2018

Cited by 30 | Viewed by 5328

Abstract

Pedicle drilling is an important step in pedicle screw fixation and the most significant challenge in this operation is how to determine a key point in the transition region between cancellous and inner cortical bone. The purpose of this paper is to find [...] Read more.

Pedicle drilling is an important step in pedicle screw fixation and the most significant challenge in this operation is how to determine a key point in the transition region between cancellous and inner cortical bone. The purpose of this paper is to find a method to achieve the recognition for the key point. After acquiring acoustic emission (AE) signals during the drilling process, this paper proposed a novel frequency distribution-based algorithm (FDB) to analyze the AE signals in the frequency domain after certain processes. Then we select a specific frequency domain of the signal for standard operations and choose a fitting function to fit the obtained sequence. Characters of the fitting function are extracted as outputs for identification of different bone layers. The results, which are obtained by detecting force signal and direct measurement, are given in the paper. Compared with the results above, the results obtained by AE signals are distinguishable for different bone layers and are more accurate and precise. The results of the algorithm are trained and identified by a neural network and the recognition rate reaches 84.2%. The proposed method is proved to be efficient and can be used for bone layer identification in pedicle screw fixation. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 5270 KiB

Open AccessArticle

Development of a Wireless Unified-Maintenance System for the Structural Health Monitoring of Civil Structures

by Gwanghee Heo¹

, Byungjik Son¹, Chunggil Kim¹

, Seunggon Jeon² and Joonryong Jeon^1,*

¹ Department of International Civil and Plant Engineering, Konyang University, 121 Daehak-ro, Nonsan, Chungnam 32992, Korea

² Department of Civil Engineering, Chungnam National University, Daejeon 34134, Korea

Sensors 2018, 18(5), 1485; https://doi.org/10.3390/s18051485 - 9 May 2018

Cited by 9 | Viewed by 4145

Abstract

A disaster preventive structural health monitoring (SHM) system needs to be equipped with the following abilities: First, it should be able to simultaneously measure diverse types of data (e.g., displacement, velocity, acceleration, strain, load, temperature, humidity, etc.) for accurate diagnosis. Second, it also [...] Read more.

A disaster preventive structural health monitoring (SHM) system needs to be equipped with the following abilities: First, it should be able to simultaneously measure diverse types of data (e.g., displacement, velocity, acceleration, strain, load, temperature, humidity, etc.) for accurate diagnosis. Second, it also requires standalone power supply to guarantee its immediate response in crisis (e.g., sudden interruption of normal AC power in disaster situations). Furthermore, it should be capable of prompt processing and realtime wireless communication of a huge amount of data. Therefore, this study is aimed at developing a wireless unified-maintenance system (WUMS) that would satisfy all the requirements for a disaster preventive SHM system of civil structures. The WUMS is designed to measure diverse types of structural responses in realtime based on wireless communication, allowing users to selectively use WiFi RF band and finally working in standalone mode by means of the field-programmable gate array (FPGA) technology. To verify its performance, the following tests were performed: (i) A test to see how far communication is possible in open field, (ii) a test on a shaker to see how accurate responses are, (iii) a modal test on a bridge to see how exactly characteristic real-time dynamic responses are of structures. The test results proved that the WUMS was able to secure stable communication far up to nearly 800 m away by acquiring wireless responses in realtime accurately, when compared to the displacement and acceleration responses which were acquired through wired communication. The analysis of dynamic characteristics also showed that the wireless acceleration responses in real-time represented satisfactorily the dynamic properties of structures. Therefore, the WUMS is proved valid as a SHM, and its outstanding performance is also proven. Full article

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

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9 pages, 1312 KiB

Open AccessArticle

Rapid Iodine Sensing on Mechanically Treated Carbon Nanofibers

by Eunbyul Cho¹, Alexandra Perebikovsky², Olivia Benice³, Sunshine Holmberg⁴, Marc Madou⁴ and Maziar Ghazinejad^4,5,*

¹ Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA

² Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA

³ Department of Chemistry, University of California, Irvine, CA 92697, USA

⁴ Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA 92697, USA

⁵ Department of Mechanical Engineering, California State University, Fresno, CA 93740, USA

Sensors 2018, 18(5), 1486; https://doi.org/10.3390/s18051486 - 9 May 2018

Cited by 23 | Viewed by 7595

Abstract

In this work, we report on a rapid, efficient electrochemical iodine sensor based on mechanically treated carbon nanofiber (MCNF) electrodes. The electrode’s highly graphitic content, unique microstructure, and the presence of nitrogen heteroatoms in its atomic lattice contribute to increased heterogeneous electron transfer [...] Read more.

In this work, we report on a rapid, efficient electrochemical iodine sensor based on mechanically treated carbon nanofiber (MCNF) electrodes. The electrode’s highly graphitic content, unique microstructure, and the presence of nitrogen heteroatoms in its atomic lattice contribute to increased heterogeneous electron transfer and improved kinetics compared to conventional pyrolytic carbons. The electrode demonstrates selectivity for iodide ions in the presence of both interfering agents and high salt concentrations. The sensor exhibits clinically relevant limits of detection of 0.59 µM and 1.41 µM, in 1X PBS and synthetic urine, respectively, and a wide dynamic range between 5 µM and 700 µM. These results illustrate the advantages of the material’s unique electrochemical properties for iodide sensing, in addition to its simple, inexpensive fabrication. The reported iodine sensor eliminates the need for specimen processing, revealing its aptitude for applications in point-of-care diagnostics. Full article

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

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20 pages, 559 KiB

Open AccessArticle

A Weighted Combination Method for Conflicting Evidence in Multi-Sensor Data Fusion

by Fuyuan Xiao^*

and Bowen Qin

School of Computer and Information Science, Southwest University, No.2 Tiansheng Road, BeiBei District, Chongqing 400715, China

Sensors 2018, 18(5), 1487; https://doi.org/10.3390/s18051487 - 9 May 2018

Cited by 80 | Viewed by 5479

Abstract

Dempster–Shafer evidence theory is widely applied in various fields related to information fusion. However, how to avoid the counter-intuitive results is an open issue when combining highly conflicting pieces of evidence. In order to handle such a problem, a weighted combination method for [...] Read more.

Dempster–Shafer evidence theory is widely applied in various fields related to information fusion. However, how to avoid the counter-intuitive results is an open issue when combining highly conflicting pieces of evidence. In order to handle such a problem, a weighted combination method for conflicting pieces of evidence in multi-sensor data fusion is proposed by considering both the interplay between the pieces of evidence and the impacts of the pieces of evidence themselves. First, the degree of credibility of the evidence is determined on the basis of the modified cosine similarity measure of basic probability assignment. Then, the degree of credibility of the evidence is adjusted by leveraging the belief entropy function to measure the information volume of the evidence. Finally, the final weight of each piece of evidence generated from the above steps is obtained and adopted to modify the bodies of evidence before using Dempster’s combination rule. A numerical example is provided to illustrate that the proposed method is reasonable and efficient in handling the conflicting pieces of evidence. In addition, applications in data classification and motor rotor fault diagnosis validate the practicability of the proposed method with better accuracy. Full article

(This article belongs to the Collection Multi-Sensor Information Fusion)

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17 pages, 3093 KiB

Open AccessArticle

Long-Term Deflection Prediction from Computer Vision-Measured Data History for High-Speed Railway Bridges

by Jaebeom Lee¹, Kyoung-Chan Lee^2,*

and Young-Joo Lee^1,*

¹ School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea

² Advanced Railroad Civil Engineering Division, Korea Railroad Research Institute, Uiwang 16105, Korea

Sensors 2018, 18(5), 1488; https://doi.org/10.3390/s18051488 - 9 May 2018

Cited by 25 | Viewed by 6589

Abstract

Management of the vertical long-term deflection of a high-speed railway bridge is a crucial factor to guarantee traffic safety and passenger comfort. Therefore, there have been efforts to predict the vertical deflection of a railway bridge based on physics-based models representing various influential [...] Read more.

Management of the vertical long-term deflection of a high-speed railway bridge is a crucial factor to guarantee traffic safety and passenger comfort. Therefore, there have been efforts to predict the vertical deflection of a railway bridge based on physics-based models representing various influential factors to vertical deflection such as concrete creep and shrinkage. However, it is not an easy task because the vertical deflection of a railway bridge generally involves several sources of uncertainty. This paper proposes a probabilistic method that employs a Gaussian process to construct a model to predict the vertical deflection of a railway bridge based on actual vision-based measurement and temperature. To deal with the sources of uncertainty which may cause prediction errors, a Gaussian process is modeled with multiple kernels and hyperparameters. Once the hyperparameters are identified through the Gaussian process regression using training data, the proposed method provides a 95% prediction interval as well as a predictive mean about the vertical deflection of the bridge. The proposed method is applied to an arch bridge under operation for high-speed trains in South Korea. The analysis results obtained from the proposed method show good agreement with the actual measurement data on the vertical deflection of the example bridge, and the prediction results can be utilized for decision-making on railway bridge maintenance. 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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19 pages, 5221 KiB

Open AccessArticle

A Vision-Based Counting and Recognition System for Flying Insects in Intelligent Agriculture

by Yuanhong Zhong^*, Junyuan Gao, Qilun Lei and Yao Zhou

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

Sensors 2018, 18(5), 1489; https://doi.org/10.3390/s18051489 - 9 May 2018

Cited by 190 | Viewed by 18286

Abstract

Rapid and accurate counting and recognition of flying insects are of great importance, especially for pest control. Traditional manual identification and counting of flying insects is labor intensive and inefficient. In this study, a vision-based counting and classification system for flying insects is [...] Read more.

Rapid and accurate counting and recognition of flying insects are of great importance, especially for pest control. Traditional manual identification and counting of flying insects is labor intensive and inefficient. In this study, a vision-based counting and classification system for flying insects is designed and implemented. The system is constructed as follows: firstly, a yellow sticky trap is installed in the surveillance area to trap flying insects and a camera is set up to collect real-time images. Then the detection and coarse counting method based on You Only Look Once (YOLO) object detection, the classification method and fine counting based on Support Vector Machines (SVM) using global features are designed. Finally, the insect counting and recognition system is implemented on Raspberry PI. Six species of flying insects including bee, fly, mosquito, moth, chafer and fruit fly are selected to assess the effectiveness of the system. Compared with the conventional methods, the test results show promising performance. The average counting accuracy is 92.50% and average classifying accuracy is 90.18% on Raspberry PI. The proposed system is easy-to-use and provides efficient and accurate recognition data, therefore, it can be used for intelligent agriculture applications. Full article

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

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19 pages, 1795 KiB

Open AccessArticle

Convolutional Neural Network Based on Extreme Learning Machine for Maritime Ships Recognition in Infrared Images

by Atmane Khellal^1,*, Hongbin Ma^1,2,* and Qing Fei^1,2

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

² State Key Laboratory of Intelligent Control and Decision of Complex Systems, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(5), 1490; https://doi.org/10.3390/s18051490 - 9 May 2018

Cited by 62 | Viewed by 6621

Abstract

The success of Deep Learning models, notably convolutional neural networks (CNNs), makes them the favorable solution for object recognition systems in both visible and infrared domains. However, the lack of training data in the case of maritime ships research leads to poor performance [...] Read more.

The success of Deep Learning models, notably convolutional neural networks (CNNs), makes them the favorable solution for object recognition systems in both visible and infrared domains. However, the lack of training data in the case of maritime ships research leads to poor performance due to the problem of overfitting. In addition, the back-propagation algorithm used to train CNN is very slow and requires tuning many hyperparameters. To overcome these weaknesses, we introduce a new approach fully based on Extreme Learning Machine (ELM) to learn useful CNN features and perform a fast and accurate classification, which is suitable for infrared-based recognition systems. The proposed approach combines an ELM based learning algorithm to train CNN for discriminative features extraction and an ELM based ensemble for classification. The experimental results on VAIS dataset, which is the largest dataset of maritime ships, confirm that the proposed approach outperforms the state-of-the-art models in term of generalization performance and training speed. For instance, the proposed model is up to 950 times faster than the traditional back-propagation based training of convolutional neural networks, primarily for low-level features extraction. Full article

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

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19 pages, 1296 KiB

Open AccessArticle

Optimal Control for Aperiodic Dual-Rate Systems With Time-Varying Delays

by Ernesto Aranda-Escolástico^1,*

, Julián Salt², María Guinaldo¹, Jesús Chacón¹ and Sebastián Dormido¹

¹ Departamento de Informática y Automática, Universidad Nacional de Educación a Distancia, 28040 Madrid, Spain

² Departamento de Ingeniería de Sistemas y Automática, Instituto Universitario de Automática e Informática Industrial, Universitat Politécnica de Valéncia, 46022 Valencia, Spain

Sensors 2018, 18(5), 1491; https://doi.org/10.3390/s18051491 - 9 May 2018

Cited by 5 | Viewed by 3171

Abstract

In this work, we consider a dual-rate scenario with slow input and fast output. Our objective is the maximization of the decay rate of the system through the suitable choice of the n-input signals between two measures (periodic sampling) and their times [...] Read more.

In this work, we consider a dual-rate scenario with slow input and fast output. Our objective is the maximization of the decay rate of the system through the suitable choice of the n-input signals between two measures (periodic sampling) and their times of application. The optimization algorithm is extended for time-varying delays in order to make possible its implementation in networked control systems. We provide experimental results in an air levitation system to verify the validity of the algorithm in a real plant. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 7633 KiB

Open AccessArticle

A Novel Nonlinear Piezoelectric Energy Harvesting System Based on Linear-Element Coupling: Design, Modeling and Dynamic Analysis

by Shengxi Zhou^1,3,*, Bo Yan^2,* and Daniel J. Inman³

¹ School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China

² Faculty of Mechanical Engineering & Automation, Zhejiang Sci-Tech University, Hangzhou 310018, China

³ Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109-2140, USA

Sensors 2018, 18(5), 1492; https://doi.org/10.3390/s18051492 - 9 May 2018

Cited by 42 | Viewed by 5690

Abstract

This paper presents a novel nonlinear piezoelectric energy harvesting system which consists of linear piezoelectric energy harvesters connected by linear springs. In principle, the presented nonlinear system can improve broadband energy harvesting efficiency where magnets are forbidden. The linear spring inevitably produces the [...] Read more.

This paper presents a novel nonlinear piezoelectric energy harvesting system which consists of linear piezoelectric energy harvesters connected by linear springs. In principle, the presented nonlinear system can improve broadband energy harvesting efficiency where magnets are forbidden. The linear spring inevitably produces the nonlinear spring force on the connected harvesters, because of the geometrical relationship and the time-varying relative displacement between two adjacent harvesters. Therefore, the presented nonlinear system has strong nonlinear characteristics. A theoretical model of the presented nonlinear system is deduced, based on Euler-Bernoulli beam theory, Kirchhoff’s law, piezoelectric theory and the relevant geometrical relationship. The energy harvesting enhancement of the presented nonlinear system (when n = 2, 3) is numerically verified by comparing with its linear counterparts. In the case study, the output power area of the presented nonlinear system with two and three energy harvesters is 268.8% and 339.8% of their linear counterparts, respectively. In addition, the nonlinear dynamic response characteristics are analyzed via bifurcation diagrams, Poincare maps of the phase trajectory, and the spectrum of the output voltage. Full article

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

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19 pages, 40946 KiB

Open AccessArticle

Real-Time Large-Scale Dense Mapping with Surfels

by Xingyin Fu^1,2,3,4,*, Feng Zhu^1,3,4, Qingxiao Wu^1,3,4, Yunlei Sun^1,2,3,4, Rongrong Lu^1,2,3,4 and Ruigang Yang^5,6

¹ Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016, China

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

³ Key Laboratory of Opto-Electronic Information Processing, CAS, Shenyang 110016, China

⁴ The Key Lab of Image Understanding and Computer Vision, Shenyang 110016, China

⁵ Baidu Inc., Beijing 100193, China

⁶ National Engineering Laboratory of Deep Learning Technology and Application, Beijing 100193, China

Sensors 2018, 18(5), 1493; https://doi.org/10.3390/s18051493 - 9 May 2018

Cited by 11 | Viewed by 6442

Abstract

Real-time dense mapping systems have been developed since the birth of consumer RGB-D cameras. Currently, there are two commonly used models in dense mapping systems: truncated signed distance function (TSDF) and surfel. The state-of-the-art dense mapping systems usually work fine with small-sized regions. [...] Read more.

Real-time dense mapping systems have been developed since the birth of consumer RGB-D cameras. Currently, there are two commonly used models in dense mapping systems: truncated signed distance function (TSDF) and surfel. The state-of-the-art dense mapping systems usually work fine with small-sized regions. The generated dense surface may be unsatisfactory around the loop closures when the system tracking drift grows large. In addition, the efficiency of the system with surfel model slows down when the number of the model points in the map becomes large. In this paper, we propose to use two maps in the dense mapping system. The RGB-D images are integrated into a local surfel map. The old surfels that reconstructed in former times and far away from the camera frustum are moved from the local map to the global map. The updated surfels in the local map when every frame arrives are kept bounded. Therefore, in our system, the scene that can be reconstructed is very large, and the frame rate of our system remains high. We detect loop closures and optimize the pose graph to distribute system tracking drift. The positions and normals of the surfels in the map are also corrected using an embedded deformation graph so that they are consistent with the updated poses. In order to deal with large surface deformations, we propose a new method for constructing constraints with system trajectories and loop closure keyframes. The proposed new method stabilizes large-scale surface deformation. Experimental results show that our novel system behaves better than the prior state-of-the-art dense mapping systems. Full article

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

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10 pages, 3548 KiB

Open AccessArticle

Filament Advance Detection Sensor for Fused Deposition Modelling 3D Printers

by Enrique Soriano Heras^1,*

, Fernando Blaya Haro²

, José M. De Agustín del Burgo², Manuel Islán Marcos² and Roberto D’Amato²

¹ Departamento de Ingeniería Mecánica, Universidad Carlos III de Madrid, Avda. de la Universidad, 30, 28911 Leganés, 28012 Madrid, Spain

² Escuela Técnica Superior de Ingeniería y Diseño Industrial, Universidad Politécnica de Madrid, Ronda de Valencia, 3, 28012 Madrid, Spain

Sensors 2018, 18(5), 1495; https://doi.org/10.3390/s18051495 - 9 May 2018

Cited by 26 | Viewed by 6830

Abstract

The main purpose of this paper is to present a system to detect extrusion failures in fused deposition modelling (FDM) 3D printers by sensing that the filament is moving forward properly. After several years using these kind of machines, authors detected that there [...] Read more.

The main purpose of this paper is to present a system to detect extrusion failures in fused deposition modelling (FDM) 3D printers by sensing that the filament is moving forward properly. After several years using these kind of machines, authors detected that there is not any system to detect the main problem in FDM machines. Authors thought in different sensors and used the weighted objectives method, one of the most common evaluation methods, for comparing design concepts based on an overall value per design concept. Taking into account the obtained scores of each specification, the best choice for this work is the optical encoder. Once the sensor is chosen, it is necessary to design de part where it will be installed without interfering with the normal function of the machine. To do it, photogrammetry scanning methodology was employed. The developed device perfectly detects the advance of the filament without affecting the normal operation of the machine. Also, it is achieved the primary objective of the system, avoiding loss of material, energy, and mechanical wear, keeping the premise of making a low-cost product that does not significantly increase the cost of the machine. This development has made it possible to use the printer with remains of coil filaments, which were not spent because they were not sufficient to complete an impression. Also, printing models in two colours with only one extruder has been enabled by this development. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 7047 KiB

Open AccessArticle

Discriminating between Different Heavy Metal Ions with Fullerene-Derived Nanoparticles

by Erica Ciotta¹

, Paolo Prosposito^1,2

, Pietro Tagliatesta³

, Chiara Lorecchio³, Lorenzo Stella³

, Saulius Kaciulis⁴

, Peiman Soltani⁴

, Ernesto Placidi⁵

and Roberto Pizzoferrato^1,*

¹ Department of Industrial Engineering, University of Rome Tor Vergata, 00133 Rome, Italy

² INSTM and CiMER, University of Rome Tor Vergata, 00133 Rome, Italy

³ Department of Chemical Sciences and Technology, University of Rome Tor Vergata, 00133 Rome, Italy

⁴ Institute for the Study of Nanostructured Materials, CNR of Italy, Monterotondo Stazione, 00015 Rome, Italy

⁵ CNR—Istituto di Struttura della Materia, Via Fosso del Cavaliere 100, 00133 Roma, Italy

Sensors 2018, 18(5), 1496; https://doi.org/10.3390/s18051496 - 10 May 2018

Cited by 33 | Viewed by 5332

Abstract

A novel type of graphene-like nanoparticle, synthesized by oxidation and unfolding of C₆₀ buckminsterfullerene fullerene, showed multiple and reproducible sensitivity to Cu²⁺, Pb²⁺, Cd²⁺, and As(III) through different degrees of fluorescence quenching or, in the case [...] Read more.

A novel type of graphene-like nanoparticle, synthesized by oxidation and unfolding of C₆₀ buckminsterfullerene fullerene, showed multiple and reproducible sensitivity to Cu²⁺, Pb²⁺, Cd²⁺, and As(III) through different degrees of fluorescence quenching or, in the case of Cd²⁺, through a remarkable fluorescence enhancement. Most importantly, only for Cu²⁺ and Pb²⁺, the fluorescence intensity variations came with distinct modifications of the optical absorption spectrum. Time-resolved fluorescence study confirmed that the common origin of these diverse behaviors lies in complexation of the metal ions by fullerene-derived carbon layers, even though further studies are required for a complete explanation of the involved processes. Nonetheless, the different response of fluorescence and optical absorbance towards distinct cationic species makes it possible to discriminate between the presence of Cu²⁺, Pb²⁺, Cd²⁺, and As(III), through two simple optical measurements. To this end, the use of a three-dimensional calibration plot is discussed. This property makes fullerene-derived nanoparticles a promising material in view of the implementation of a selective, colorimetric/fluorescent detection system. Full article

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

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12 pages, 4180 KiB

Open AccessArticle

Electrochemical Detection of E. coli O157:H7 in Water after Electrocatalytic and Ultraviolet Treatments Using a Polyguanine-Labeled Secondary Bead Sensor

by Michael G. Beeman^1,*, Ugochukwu C. Nze¹

, Himanshu J. Sant^1,2,*, Hammad Malik³, Swomitra Mohanty^3,4, Bruce K Gale^1,2

and Krista Carlson³

¹ Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112, USA

² Espira Inc., 825 N 300 W Suite N-223, Salt Lake City, UT 84103, USA

³ Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112, USA

⁴ Department of Chemical Engineering, University of Utah, Salt Lake City, UT 84112, USA

Sensors 2018, 18(5), 1497; https://doi.org/10.3390/s18051497 - 10 May 2018

Cited by 16 | Viewed by 5598

Abstract

The availability of clean drinking water is a significant problem worldwide. Many technologies exist for purifying drinking water, however, many of these methods require chemicals or use simple methods, such as boiling and filtering, which may or may not be effective in removing [...] Read more.

The availability of clean drinking water is a significant problem worldwide. Many technologies exist for purifying drinking water, however, many of these methods require chemicals or use simple methods, such as boiling and filtering, which may or may not be effective in removing waterborne pathogens. Present methods for detecting pathogens in point-of-use (POU) sterilized water are typically time prohibitive or have limited ability differentiating between active and inactive cells. This work describes a rapid electrochemical sensor to differentially detect the presence of active Escherichia coli (E. coli) O157:H7 in samples that have been partially or completely sterilized using a new POU electrocatalytic water purification technology based on superradicals generated by defect laden titania (TiO₂) nanotubes. The sensor was also used to detect pathogens sterilized by UV-C radiation for a comparison of different modes of cell death. The sensor utilizes immunomagnetic bead separation to isolate active bacteria by forming a sandwich assay comprised of antibody functionalized secondary magnetic beads, E. coli O157:H7, and polyguanine (polyG) oligonucleotide functionalized secondary polystyrene beads as an electrochemical tag. The assay is formed by the attachment of antibodies to active receptors on the membrane of E. coli, allowing the sensor to differentially detect viable cells. Ultravioloet (UV)-C radiation and an electrocatalytic reactor (ER) with integrated defect-laden titania nanotubes were used to examine the sensors’ performance in detecting sterilized cells under different modes of cell death. Plate counts and flow cytometry were used to quantify disinfection efficacy and cell damage. It was found that the ER treatments shredded the bacteria into multiple fragments, while UV-C treatments inactivated the bacteria but left the cell membrane mostly intact. Full article

(This article belongs to the Special Issue Immunosensors - 2018 Trends and Perspective)

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11 pages, 6108 KiB

Open AccessArticle

Investigation of the Temperature Fluctuation of Single-Phase Fluid Based Microchannel Heat Sink

by Tao Wang^1,2,*,†, Jiejun Wang^1,2,†, Jian He^1,2, Chuangui Wu^1,2, Wenbo Luo^1,2, Yao Shuai^1,2, Wanli Zhang^1,2 and Chengkuo Lee³

¹ School of Electronic Science and Engineering, University of Electronic Science and Technology of China, 2006 Xiyuan Avenue, Chengdu 611731, China

² State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, 2006 Xiyuan Avenue, Chengdu 611731, China

³ Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Singapore

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1498; https://doi.org/10.3390/s18051498 - 10 May 2018

Cited by 7 | Viewed by 5224

Abstract

The temperature fluctuation in a single-phase microchannel heat sink (MCHS) is investigated using the integrated temperature sensors with deionized water as the coolant. Results show that the temperature fluctuation in single phase is not negligible. The causes of the temperature fluctuation are revealed [...] Read more.

The temperature fluctuation in a single-phase microchannel heat sink (MCHS) is investigated using the integrated temperature sensors with deionized water as the coolant. Results show that the temperature fluctuation in single phase is not negligible. The causes of the temperature fluctuation are revealed based on both simulation and experiment. It is found that the inlet temperature fluctuation and the gas bubbles separated out from coolant are the main causes. The effect of the inlet temperature fluctuation is global, where the temperatures at different locations change simultaneously. Meanwhile, the gas bubble effect is localized where the temperature changes at different locations are not synchronized. In addition, the relation between temperature fluctuation and temperature gradient is established. The temperature fluctuation increases with the temperature gradient accordingly. Full article

(This article belongs to the Special Issue Integrated Sensors)

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20 pages, 577 KiB

Open AccessArticle

An Emotion Aware Task Automation Architecture Based on Semantic Technologies for Smart Offices

by Sergio Muñoz^*

, Oscar Araque

, J. Fernando Sánchez-Rada

and Carlos A. Iglesias

Intelligent Systems Group, Universidad Politécnica de Madrid, 28040 Madrid, Spain

Sensors 2018, 18(5), 1499; https://doi.org/10.3390/s18051499 - 10 May 2018

Cited by 21 | Viewed by 5976

Abstract

The evolution of the Internet of Things leads to new opportunities for the contemporary notion of smart offices, where employees can benefit from automation to maximize their productivity and performance. However, although extensive research has been dedicated to analyze the impact of workers’ [...] Read more.

The evolution of the Internet of Things leads to new opportunities for the contemporary notion of smart offices, where employees can benefit from automation to maximize their productivity and performance. However, although extensive research has been dedicated to analyze the impact of workers’ emotions on their job performance, there is still a lack of pervasive environments that take into account emotional behaviour. In addition, integrating new components in smart environments is not straightforward. To face these challenges, this article proposes an architecture for emotion aware automation platforms based on semantic event-driven rules to automate the adaptation of the workplace to the employee’s needs. The main contributions of this paper are: (i) the design of an emotion aware automation platform architecture for smart offices; (ii) the semantic modelling of the system; and (iii) the implementation and evaluation of the proposed architecture in a real scenario. Full article

(This article belongs to the Section Intelligent Sensors)

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17 pages, 462 KiB

Open AccessArticle

Marginal Contribution-Based Distributed Subchannel Allocation in Small Cell Networks

by Shashi Shah^1,2,*

, Somsak Kittipiyakul¹, Yuto Lim² and Yasuo Tan²

¹ School of Information, Computer, and Communication Technology, Sirindhorn International Institute of Technology (SIIT), Thammasat University (TU), Pathum Thani 12121, Thailand

² School of Information Science, Japan Advanced Institute of Science and Technology (JAIST), Ishikawa 923-1292, Japan

Sensors 2018, 18(5), 1500; https://doi.org/10.3390/s18051500 - 10 May 2018

Cited by 2 | Viewed by 3246

Abstract

The paper presents a game theoretic solution for distributed subchannel allocation problem in small cell networks (SCNs) analyzed under the physical interference model. The objective is to find a distributed solution that maximizes the welfare of the SCNs, defined as the total system [...] Read more.

The paper presents a game theoretic solution for distributed subchannel allocation problem in small cell networks (SCNs) analyzed under the physical interference model. The objective is to find a distributed solution that maximizes the welfare of the SCNs, defined as the total system capacity. Although the problem can be addressed through best-response (BR) dynamics, the existence of a steady-state solution, i.e., a pure strategy Nash equilibrium (NE), cannot be guaranteed. Potential games (PGs) ensure convergence to a pure strategy NE when players rationally play according to some specified learning rules. However, such a performance guarantee comes at the expense of complete knowledge of the SCNs. To overcome such requirements, properties of PGs are exploited for scalable implementations, where we utilize the concept of marginal contribution (MC) as a tool to design learning rules of players’ utility and propose the marginal contribution-based best-response (MCBR) algorithm of low computational complexity for the distributed subchannel allocation problem. Finally, we validate and evaluate the proposed scheme through simulations for various performance metrics. Full article

(This article belongs to the Section Sensor Networks)

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30 pages, 6054 KiB

Open AccessArticle

IrisDenseNet: Robust Iris Segmentation Using Densely Connected Fully Convolutional Networks in the Images by Visible Light and Near-Infrared Light Camera Sensors

by Muhammad Arsalan

, Rizwan Ali Naqvi, Dong Seop Kim, Phong Ha Nguyen, Muhammad Owais

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(5), 1501; https://doi.org/10.3390/s18051501 - 10 May 2018

Cited by 111 | Viewed by 9505

Abstract

The recent advancements in computer vision have opened new horizons for deploying biometric recognition algorithms in mobile and handheld devices. Similarly, iris recognition is now much needed in unconstraint scenarios with accuracy. These environments make the acquired iris image exhibit occlusion, low resolution, [...] Read more.

The recent advancements in computer vision have opened new horizons for deploying biometric recognition algorithms in mobile and handheld devices. Similarly, iris recognition is now much needed in unconstraint scenarios with accuracy. These environments make the acquired iris image exhibit occlusion, low resolution, blur, unusual glint, ghost effect, and off-angles. The prevailing segmentation algorithms cannot cope with these constraints. In addition, owing to the unavailability of near-infrared (NIR) light, iris recognition in visible light environment makes the iris segmentation challenging with the noise of visible light. Deep learning with convolutional neural networks (CNN) has brought a considerable breakthrough in various applications. To address the iris segmentation issues in challenging situations by visible light and near-infrared light camera sensors, this paper proposes a densely connected fully convolutional network (IrisDenseNet), which can determine the true iris boundary even with inferior-quality images by using better information gradient flow between the dense blocks. In the experiments conducted, five datasets of visible light and NIR environments were used. For visible light environment, noisy iris challenge evaluation part-II (NICE-II selected from UBIRIS.v2 database) and mobile iris challenge evaluation (MICHE-I) datasets were used. For NIR environment, the institute of automation, Chinese academy of sciences (CASIA) v4.0 interval, CASIA v4.0 distance, and IIT Delhi v1.0 iris datasets were used. Experimental results showed the optimal segmentation of the proposed IrisDenseNet and its excellent performance over existing algorithms for all five datasets. Full article

(This article belongs to the Special Issue Visual Sensors)

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9 pages, 1949 KiB

Open AccessArticle

Investigation of Grating-Assisted Trimodal Interferometer Biosensors Based on a Polymer Platform

by Yuxin Liang^1,2

, Mingshan Zhao²

, Zhenlin Wu² and Geert Morthier^1,*

¹ Photonics Research Group, Department of Information and Technology, Ghent University, 9000 Ghent, Belgium

² School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian116023, China

Sensors 2018, 18(5), 1502; https://doi.org/10.3390/s18051502 - 10 May 2018

Cited by 11 | Viewed by 3217

Abstract

A grating-assisted trimodal interferometer biosensor is proposed and numerically analyzed. A long period grating coupler, for adjusting the power between the fundamental mode and the second higher order mode, is investigated, and is shown to act as a conventional directional coupler for adjusting [...] Read more.

A grating-assisted trimodal interferometer biosensor is proposed and numerically analyzed. A long period grating coupler, for adjusting the power between the fundamental mode and the second higher order mode, is investigated, and is shown to act as a conventional directional coupler for adjusting the power between the two arms. The trimodal interferometer can achieve maximal fringe visibility when the powers of the two modes are adjusted to the same value by the grating coupler, which means that a better limit of detection can be expected. In addition, the second higher order mode typically has a larger evanescent tail than the first higher order mode in bimodal interferometers, resulting in a higher sensitivity of the trimodal interferometer. The influence of fabrication tolerances on the performance of the designed interferometer is also investigated. The power difference between the two modes shows inertia to the fill factor of the grating, but high sensitivity to the modulation depth. Finally, a 2050 2π/RIU (refractive index unit) sensitivity and 43 dB extinction ratio of the output power are achieved. Full article

(This article belongs to the Section Biosensors)

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13 pages, 2461 KiB

Open AccessArticle

Quantitative Determining of Ultra-Trace Aluminum Ion in Environmental Samples by Liquid Phase Microextraction Assisted Anodic Stripping Voltammetry

by Liuyang Zhang^1,†, Jinju Luo^1,†, Xinyu Shen², Chunya Li¹, Xian Wang¹, Bei Nie¹ and Huaifang Fang^1,*

¹ Key Laboratory of Analytical Chemistry of the State Ethnic Affairs Commission, College of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan 430074, China

² Key Laboratory of Analytical Chemistry for Biology and Medicine, Wuhan University, Ministry of Education, Wuhan 430072, China

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1503; https://doi.org/10.3390/s18051503 - 10 May 2018

Cited by 7 | Viewed by 3813

Abstract

Direct detecting of trace amount Al(III) in aqueous solution by stripping voltammetry is often frustrated by its irreversible reduction, resided at −1.75 V (vs. Ag/AgCl reference), which is in a proximal potential of proton reduction. Here, we described an electroanalytical approach, combined with [...] Read more.

Direct detecting of trace amount Al(III) in aqueous solution by stripping voltammetry is often frustrated by its irreversible reduction, resided at −1.75 V (vs. Ag/AgCl reference), which is in a proximal potential of proton reduction. Here, we described an electroanalytical approach, combined with liquid phase microextraction (LPME) using ionic liquid (IL), to quantitatively assess trace amount aluminum in environmental samples. The Al(III) was caged by 8-hydroxyquinoline, forming a superb hydrophobic metal–chelate, which sequentially transfers and concentrates in the bottom layer of IL-phase during LPME. The preconcentrated Al(III) was further analyzed by a square-wave anodic stripping voltammetry (SW-ASV). The resulting Al-deposited electrodes were characterized by scanning electron microscopy and powder X-ray diffraction, showing the intriguing amorphous nanostructures. The method developed provides a linear calibration ranging from 0.1 to 1.2 ng L⁻¹ with a correlation coefficient of 0.9978. The LOD attains as low as 1 pmol L⁻¹, which reaches the lowest report for Al(III) detection using electroanalytical techniques. The applicable methodology was implemented for monitoring Al(III) in commercial distilled water. Full article

(This article belongs to the Section Chemical Sensors)

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15 pages, 1643 KiB

Open AccessArticle

An RFID Indoor Positioning Algorithm Based on Support Vector Regression

by He Xu^1,2,*

, Manxing Wu^1,2, Peng Li^1,2

, Feng Zhu^1,2 and Ruchuan Wang^1,2

¹ School of Computer Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

² Jiangsu High Technology Research Key Laboratory for Wireless Sensor Networks, Nanjing 210003, China

Sensors 2018, 18(5), 1504; https://doi.org/10.3390/s18051504 - 10 May 2018

Cited by 86 | Viewed by 6732

Abstract

Nowadays, location-based services, which include services to identify the location of a person or an object, have many uses in social life. Though traditional GPS positioning can provide high quality positioning services in outdoor environments, due to the shielding of buildings and the [...] Read more.

Nowadays, location-based services, which include services to identify the location of a person or an object, have many uses in social life. Though traditional GPS positioning can provide high quality positioning services in outdoor environments, due to the shielding of buildings and the interference of indoor environments, researchers and enterprises have paid more attention to how to perform high precision indoor positioning. There are many indoor positioning technologies, such as WiFi, Bluetooth, UWB and RFID. RFID positioning technology is favored by researchers because of its lower cost and higher accuracy. One of the methods that is applied to indoor positioning is the LANDMARC algorithm, which uses RFID tags and readers to implement an Indoor Positioning System (IPS). However, the accuracy of the LANDMARC positioning algorithm relies on the density of reference tags and the performance of RFID readers. In this paper, we introduce the weighted path length and support vector regression algorithm to improve the positioning precision of LANDMARC. The results show that the proposed algorithm is effective. Full article

(This article belongs to the Section Sensor Networks)

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13 pages, 1072 KiB

Open AccessArticle

Nordic Walking Performance Analysis with an Integrated Monitoring System

by Francesco Mocera^*

, Giuseppe Aquilino and Aurelio Somà

Department of Mechanical and Aerospace Engineering, Politecnico di Torino, 10129 Torino, Italy

Sensors 2018, 18(5), 1505; https://doi.org/10.3390/s18051505 - 10 May 2018

Cited by 18 | Viewed by 5798

Abstract

There is a growing interest in Nordic walking both from the fitness and medical point of views due to its possible therapeutic applications. The proper execution of the technique is an essential requirement to maximize the benefits of this practice. This is the [...] Read more.

There is a growing interest in Nordic walking both from the fitness and medical point of views due to its possible therapeutic applications. The proper execution of the technique is an essential requirement to maximize the benefits of this practice. This is the reason why a monitoring system for outdoor Nordic walking activity was developed. Using data obtained from synchronized sensors, it is possible to have a complete overview of the users’ movements. The system described in this paper is able to measure: the pole angle during the pushing phase, the arms cycle frequency and synchronization and the pushing force applied to the ground. Furthermore, data from a GPS module give an image of the environment where the activity session takes place, in terms of the distance, slope, as well as the ground typology. A heart rate sensor is used to monitor the effort of the user through his/her Beats Per Minute (BPM). In this work, the developed monitoring system is presented, explaining how to use the gathered data to obtain the main feedback parameters for Nordic walking performance analysis. The comparison between left and right arm measurements allowed validating the system as a tool for technique evaluation. Finally, a procedure to estimate the peak pushing force from acceleration measurements is proposed. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2017)

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32 pages, 12727 KiB

Open AccessArticle

Unifying Terrain Awareness for the Visually Impaired through Real-Time Semantic Segmentation

by Kailun Yang¹, Kaiwei Wang^1,*, Luis M. Bergasa²

, Eduardo Romera², Weijian Hu¹, Dongming Sun³, Junwei Sun⁴, Ruiqi Cheng¹

, Tianxue Chen⁵ and Elena López²

¹ State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China

² Department of Electronics, University of Alcalá, Madrid 28805, Spain

³ Department of Computing, Imperial College London, London SW7 2AZ, UK

⁴ KR-VISION Technology Co., Ltd., Hangzhou 310023, China

⁵ Department of Electrical and Computer Engineering, University of California, Los Angeles, CA 90095, USA

Sensors 2018, 18(5), 1506; https://doi.org/10.3390/s18051506 - 10 May 2018

Cited by 100 | Viewed by 13524

Abstract

Navigational assistance aims to help visually-impaired people to ambulate the environment safely and independently. This topic becomes challenging as it requires detecting a wide variety of scenes to provide higher level assistive awareness. Vision-based technologies with monocular detectors or depth sensors have sprung [...] Read more.

Navigational assistance aims to help visually-impaired people to ambulate the environment safely and independently. This topic becomes challenging as it requires detecting a wide variety of scenes to provide higher level assistive awareness. Vision-based technologies with monocular detectors or depth sensors have sprung up within several years of research. These separate approaches have achieved remarkable results with relatively low processing time and have improved the mobility of impaired people to a large extent. However, running all detectors jointly increases the latency and burdens the computational resources. In this paper, we put forward seizing pixel-wise semantic segmentation to cover navigation-related perception needs in a unified way. This is critical not only for the terrain awareness regarding traversable areas, sidewalks, stairs and water hazards, but also for the avoidance of short-range obstacles, fast-approaching pedestrians and vehicles. The core of our unification proposal is a deep architecture, aimed at attaining efficient semantic understanding. We have integrated the approach in a wearable navigation system by incorporating robust depth segmentation. A comprehensive set of experiments prove the qualified accuracy over state-of-the-art methods while maintaining real-time speed. We also present a closed-loop field test involving real visually-impaired users, demonstrating the effectivity and versatility of the assistive framework. Full article

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

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15 pages, 2467 KiB

Open AccessArticle

High-Speed Lateral Flow Strategy for a Fast Biosensing with an Improved Selectivity and Binding Affinity

by Dong Guk Cho¹, Haneul Yoo¹, Haein Lee², Yeol Kyo Choi²

, Minju Lee¹

, Dong June Ahn^2,* and Seunghun Hong^1,*

¹ Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea

² Department of Chemical & Biological Engineering, KU-KIST Graduate School of Converging Science & Technology, Korea University, Seoul 02841, Korea

Sensors 2018, 18(5), 1507; https://doi.org/10.3390/s18051507 - 10 May 2018

Cited by 14 | Viewed by 5171

Abstract

We report a high-speed lateral flow strategy for a fast biosensing with an improved selectivity and binding affinity even under harsh conditions. In this strategy, biosensors were fixed at a location away from the center of a round shape disk, and the disk [...] Read more.

We report a high-speed lateral flow strategy for a fast biosensing with an improved selectivity and binding affinity even under harsh conditions. In this strategy, biosensors were fixed at a location away from the center of a round shape disk, and the disk was rotated to create the lateral flow of a target solution on the biosensors during the sensing measurements. Experimental results using the strategy showed high reaction speeds, high binding affinity, and low nonspecific adsorptions of target molecules to biosensors. Furthermore, binding affinity between target molecules and sensing molecules was enhanced even in harsh conditions such as low pH and low ionic strength conditions. These results show that the strategy can improve the performance of conventional biosensors by generating high-speed lateral flows on a biosensor surface. Therefore, our strategy can be utilized as a simple but powerful tool for versatile bio and medical applications. Full article

(This article belongs to the Section Biosensors)

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16 pages, 36479 KiB

Open AccessArticle

Self-Tuning Method for Increased Obstacle Detection Reliability Based on Internet of Things LiDAR Sensor Models

by Fernando Castaño^1,*

, Gerardo Beruvides¹

, Alberto Villalonga^1,2

and Rodolfo E. Haber¹

¹ Centre for Automation and Robotics, UPM—CSIC, 28500 Arganda del Rey, Spain

² Research Centre of Advanced and Sustainable Manufacturing, UM, Matanzas 44100, Cuba

Sensors 2018, 18(5), 1508; https://doi.org/10.3390/s18051508 - 10 May 2018

Cited by 47 | Viewed by 9283

Abstract

On-chip LiDAR sensors for vehicle collision avoidance are a rapidly expanding area of research and development. The assessment of reliable obstacle detection using data collected by LiDAR sensors has become a key issue that the scientific community is actively exploring. The design of [...] Read more.

On-chip LiDAR sensors for vehicle collision avoidance are a rapidly expanding area of research and development. The assessment of reliable obstacle detection using data collected by LiDAR sensors has become a key issue that the scientific community is actively exploring. The design of a self-tuning methodology and its implementation are presented in this paper, to maximize the reliability of LiDAR sensors network for obstacle detection in the ‘Internet of Things’ (IoT) mobility scenarios. The Webots Automobile 3D simulation tool for emulating sensor interaction in complex driving environments is selected in order to achieve that objective. Furthermore, a model-based framework is defined that employs a point-cloud clustering technique, and an error-based prediction model library that is composed of a multilayer perceptron neural network, and k-nearest neighbors and linear regression models. Finally, a reinforcement learning technique, specifically a Q-learning method, is implemented to determine the number of LiDAR sensors that are required to increase sensor reliability for obstacle localization tasks. In addition, a IoT driving assistance user scenario, connecting a five LiDAR sensor network is designed and implemented to validate the accuracy of the computational intelligence-based framework. The results demonstrated that the self-tuning method is an appropriate strategy to increase the reliability of the sensor network while minimizing detection thresholds. Full article

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

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34 pages, 10420 KiB

Open AccessArticle

An Adaption Broadcast Radius-Based Code Dissemination Scheme for Low Energy Wireless Sensor Networks

by Shidi Yu¹, Xiao Liu^1,*, Anfeng Liu^1,2

, Naixue Xiong³

, Zhiping Cai⁴ and Tian Wang⁵

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

⁵ School of Computer Science, National Huaqiao University, Quanzhou 362000, China

Sensors 2018, 18(5), 1509; https://doi.org/10.3390/s18051509 - 10 May 2018

Cited by 27 | Viewed by 4269

Abstract

Due to the Software Defined Network (SDN) technology, Wireless Sensor Networks (WSNs) are getting wider application prospects for sensor nodes that can get new functions after updating program codes. The issue of disseminating program codes to every node in the network with minimum [...] Read more.

Due to the Software Defined Network (SDN) technology, Wireless Sensor Networks (WSNs) are getting wider application prospects for sensor nodes that can get new functions after updating program codes. The issue of disseminating program codes to every node in the network with minimum delay and energy consumption have been formulated and investigated in the literature. The minimum-transmission broadcast (MTB) problem, which aims to reduce broadcast redundancy, has been well studied in WSNs where the broadcast radius is assumed to be fixed in the whole network. In this paper, an Adaption Broadcast Radius-based Code Dissemination (ABRCD) scheme is proposed to reduce delay and improve energy efficiency in duty cycle-based WSNs. In the ABCRD scheme, a larger broadcast radius is set in areas with more energy left, generating more optimized performance than previous schemes. Thus: (1) with a larger broadcast radius, program codes can reach the edge of network from the source in fewer hops, decreasing the number of broadcasts and at the same time, delay. (2) As the ABRCD scheme adopts a larger broadcast radius for some nodes, program codes can be transmitted to more nodes in one broadcast transmission, diminishing the number of broadcasts. (3) The larger radius in the ABRCD scheme causes more energy consumption of some transmitting nodes, but radius enlarging is only conducted in areas with an energy surplus, and energy consumption in the hot-spots can be reduced instead due to some nodes transmitting data directly to sink without forwarding by nodes in the original hot-spot, thus energy consumption can almost reach a balance and network lifetime can be prolonged. The proposed ABRCD scheme first assigns a broadcast radius, which doesn’t affect the network lifetime, to nodes having different distance to the code source, then provides an algorithm to construct a broadcast backbone. In the end, a comprehensive performance analysis and simulation result shows that the proposed ABRCD scheme shows better performance in different broadcast situations. Compared to previous schemes, the transmission delay is reduced by 41.11~78.42%, the number of broadcasts is reduced by 36.18~94.27% and the energy utilization ratio is improved up to 583.42%, while the network lifetime can be prolonged up to 274.99%. Full article

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

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23 pages, 7010 KiB

Open AccessArticle

Experiments and Analysis of Close-Shot Identification of On-Branch Citrus Fruit with RealSense

by Jizhan Liu^1,*, Yan Yuan¹, Yao Zhou², Xinxin Zhu¹ and Tabinda Naz Syed¹

¹ Key Laboratory of Modern Agricultural Equipment and Technology, Ministry of Education, Jiangsu University, Jiangsu 212013, China

² College of Information Science and Technology, Nanjing Forestry University, Nanjing 210037, China

Sensors 2018, 18(5), 1510; https://doi.org/10.3390/s18051510 - 11 May 2018

Cited by 22 | Viewed by 5316

Abstract

Fruit recognition based on depth information has been a hot topic due to its advantages. However, the present equipment and methods cannot meet the requirements of rapid and reliable recognition and location of fruits in close shot for robot harvesting. To solve this [...] Read more.

Fruit recognition based on depth information has been a hot topic due to its advantages. However, the present equipment and methods cannot meet the requirements of rapid and reliable recognition and location of fruits in close shot for robot harvesting. To solve this problem, we propose a recognition algorithm for citrus fruit based on RealSense. This method effectively utilizes depth-point cloud data in a close-shot range of 160 mm and different geometric features of the fruit and leaf to recognize fruits with a intersection curve cut by the depth-sphere. Experiments with close-shot recognition of six varieties of fruit under different conditions were carried out. The detection rates of little occlusion and adhesion were from 80–100%. However, severe occlusion and adhesion still have a great influence on the overall success rate of on-branch fruits recognition, the rate being 63.8%. The size of the fruit has a more noticeable impact on the success rate of detection. Moreover, due to close-shot near-infrared detection, there was no obvious difference in recognition between bright and dark conditions. The advantages of close-shot limited target detection with RealSense, fast foreground and background removal and the simplicity of the algorithm with high precision may contribute to high real-time vision-servo operations of harvesting robots. Full article

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

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31 pages, 4399 KiB

Open AccessArticle

Agent-Based Intelligent Interface for Wheelchair Movement Control

by Alberto L. Barriuso^*

, Javier Pérez-Marcos

, Diego M. Jiménez-Bravo

, Gabriel Villarrubia González

and Juan F. De Paz

BISITE Digital Innovation Hub., University of Salamanca, Edificio Multiusos I+D+i, C/Espejo SN, 37007 Salamanca, Spain

Sensors 2018, 18(5), 1511; https://doi.org/10.3390/s18051511 - 11 May 2018

Cited by 17 | Viewed by 7156

Abstract

People who suffer from any kind of motor difficulty face serious complications to autonomously move in their daily lives. However, a growing number research projects which propose different powered wheelchairs control systems are arising. Despite of the interest of the research community in [...] Read more.

People who suffer from any kind of motor difficulty face serious complications to autonomously move in their daily lives. However, a growing number research projects which propose different powered wheelchairs control systems are arising. Despite of the interest of the research community in the area, there is no platform that allows an easy integration of various control methods that make use of heterogeneous sensors and computationally demanding algorithms. In this work, an architecture based on virtual organizations of agents is proposed that makes use of a flexible and scalable communication protocol that allows the deployment of embedded agents in computationally limited devices. In order to validate the proper functioning of the proposed system, it has been integrated into a conventional wheelchair and a set of alternative control interfaces have been developed and deployed, including a portable electroencephalography system, a voice interface or as specifically designed smartphone application. A set of tests were conducted to test both the platform adequacy and the accuracy and ease of use of the proposed control systems yielding positive results that can be useful in further wheelchair interfaces design and implementation. Full article

(This article belongs to the Special Issue Smart Decision-Making)

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15 pages, 2350 KiB

Open AccessArticle

Real-Time Adaptive Control of a Magnetic Levitation System with a Large Range of Load Disturbance

by Zhizhou Zhang^1,* and Xiaolong Li²

¹ College of Aerospace Science, National University of Defense Technology, Changsha 410073, China

² College of Intelligence Science, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(5), 1512; https://doi.org/10.3390/s18051512 - 11 May 2018

Cited by 30 | Viewed by 4666

Abstract

In an idle light-load or a full-load condition, the change of the load mass of a suspension system is very significant. If the control parameters of conventional control methods remain unchanged, the suspension performance of the control system deteriorates rapidly or even loses [...] Read more.

In an idle light-load or a full-load condition, the change of the load mass of a suspension system is very significant. If the control parameters of conventional control methods remain unchanged, the suspension performance of the control system deteriorates rapidly or even loses stability when the load mass changes in a large range. In this paper, a real-time adaptive control method for a magnetic levitation system with large range of mass changes is proposed. First, the suspension control system model of the maglev train is built up, and the stability of the closed-loop system is analyzed. Then, a fast inner current-loop is used to simplify the design of the suspension control system, and an adaptive control method is put forward to ensure that the system is still in a stable state when the load mass varies in a wide range. Simulations and experiments show that when the load mass of the maglev system varies greatly, the adaptive control method is effective to suspend the system stably with a given displacement. Full article

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

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14 pages, 7943 KiB

Open AccessArticle

Microwave Metamaterial-Based Sensor for Dielectric Characterization of Liquids

by André Soffiatti^*

, Yuri Max

, Sandro G. Silva

and Laércio M. de Mendonça

Department of Communication Engineering, Federal University of Rio Grande do Norte, Campus Universitário, Natal RN 59078-900, Brazil

Sensors 2018, 18(5), 1513; https://doi.org/10.3390/s18051513 - 11 May 2018

Cited by 48 | Viewed by 6084

Abstract

This article proposed to build a system founded on metamaterial sensor antennas, which can be used to evaluate impurities in aqueous substances according to the quality of transmission between the sensor antennas. In order to do this, a dedicated setup with tests in [...] Read more.

This article proposed to build a system founded on metamaterial sensor antennas, which can be used to evaluate impurities in aqueous substances according to the quality of transmission between the sensor antennas. In order to do this, a dedicated setup with tests in several frequencies was deployed so as to monitor the behavior of transmission variation between sensors. These sensors are microstrip antennas with a ground plane of resonant cleaved metallic rings; the substrate functions as a metamaterial for the irradiating element. In this study, an analysis was made of transmission between the sensors, looking for variation in angles of incidence of signal and of distance between the antennas. The sensor was tested at various operating frequencies, as such 1.8 GHz, 2.4 GHz, 3.4 GHz and 4.1 GHz, resulting in different values of sensitivity. The prototypes were constructed and tested so as to analyze the dielectric effects of the impurities on NaCl and C₂H₄O₂ substances. The research aims to use these control systems of impurities in industrial premises. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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18 pages, 1598 KiB

Open AccessArticle

Analysis of Soot Propensity in Combustion Processes Using Optical Sensors and Video Magnification

by Hugo O. Garcés^1,*,†

, Andrés Fuentes^2,†, Pedro Reszka^3,†

and Gonzalo Carvajal^4,*,†

¹ Computer Science Department, Universidad Católica de la Santísima Concepción, Concepción 4090541, Chile

² Departamento de Industrias, Universidad Técnica Federico Santa María, Valparaíso 2390123, Chile

³ Faculty of Engineering and Sciences, Universidad Adolfo Ibáñez, Peñalolén, Santiago 7941169, Chile

⁴ Departamento de Electrónica, Universidad Técnica Federico Santa María, Valparaíso 2390123, Chile

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1514; https://doi.org/10.3390/s18051514 - 11 May 2018

Cited by 6 | Viewed by 4923

Abstract

Industrial combustion processes are an important source of particulate matter, causing significant pollution problems that affect human health, and are a major contributor to global warming. The most common method for analyzing the soot emission propensity in flames is the Smoke Point Height [...] Read more.

Industrial combustion processes are an important source of particulate matter, causing significant pollution problems that affect human health, and are a major contributor to global warming. The most common method for analyzing the soot emission propensity in flames is the Smoke Point Height (SPH) analysis, which relates the fuel flow rate to a critical flame height at which soot particles begin to leave the reactive zone through the tip of the flame. The SPH and is marked by morphological changes on the flame tip. SPH analysis is normally done through flame observations with the naked eye, leading to high bias. Other techniques are more accurate, but are not practical to implement in industrial settings, such as the Line Of Sight Attenuation (LOSA), which obtains soot volume fractions within the flame from the attenuation of a laser beam. We propose the use of Video Magnification techniques to detect the flame morphological changes and thus determine the SPH minimizing observation bias. We have applied for the first time Eulerian Video Magnification (EVM) and Phase-based Video Magnification (PVM) on an ethylene laminar diffusion flame. The results were compared with LOSA measurements, and indicate that EVM is the most accurate method for SPH determination. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 7550 KiB

Open AccessArticle

A BDS Interference Suppression Technique Based on Linear Phase Adaptive IIR Notch Filters

by Hongbo Zhao^*

, Yinan Hu, Hua Sun and Wenquan Feng

School of Electronic and Information Engineering, Beihang University, No. 37 Xueyuan Road, Haidian District, Beijing 100191, China

Sensors 2018, 18(5), 1515; https://doi.org/10.3390/s18051515 - 11 May 2018

Cited by 9 | Viewed by 3449

Abstract

The continuous wave interferences (CWIs) and the narrow-band interferences (NBIs) have significantly impacted the acquisition, tracking and positioning accuracy of Beidou Navigation Satellite System (BDS) receivers. As an interference suppression technology with a simple structure and low hardware cost, the adaptive infinite-duration impulse [...] Read more.

The continuous wave interferences (CWIs) and the narrow-band interferences (NBIs) have significantly impacted the acquisition, tracking and positioning accuracy of Beidou Navigation Satellite System (BDS) receivers. As an interference suppression technology with a simple structure and low hardware cost, the adaptive infinite-duration impulse response (IIR) notch filter has been widely employed in the receivers to mitigate the CWIs and the NBIs. However, the nonlinear phase characteristics introduced by the IIR notch filters into the navigation receivers, may cause the distortion of navigation signals. It also leads to amplitude and phase distortion of the correlation peak in acquisition and loop tracking, which consequently brings on positioning errors in the measurement domain. This problem, however, has been ignored by many previous papers. Meanwhile, some other researchers came up with the idea of equalizers and all-pass networks compensating the distortion, which is also highly infeasible. Therefore, we propose a new method of an adaptive linear phase IIR notch filter with low hardware cost which is composed of three parts—the complex IIR notch filters, the IIR linear phase structure, and the adaptive and variable step-size algorithms. Applying this method, interference suppression and the correlation peak distortion compensation can be achieved with a modest increase hardware cost. This paper compares the performance of the new method with other IIR filters in both CWI and NBI scene and presents the effects of its parameters on the anti-jamming performance. Simulation results show that the proposed module has better anti-jamming performance in NBI scene and can compensate for the correlation peak distortion in the meantime. Full article

(This article belongs to the Section Remote Sensors)

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15 pages, 4666 KiB

Open AccessArticle

Polyimide-Based Capacitive Humidity Sensor

by Jamila Boudaden^1,2,*

, Matthias Steinmaßl^1,3,4

, Hanns-Erik Endres¹

, Andreas Drost¹, Ignaz Eisele¹, Christoph Kutter^1,4 and Peter Müller-Buschbaum³

¹ Fraunhofer EMFT, Research Institution for Microsystems and Solid State Technologies EMFT, Hansastraße 27d, D-80686 Munich, Germany

² Institute of Electronic and Sensor Materials, Technische Universität Bergakademie Freiberg, Gustav-Zeuner-Str. 3, D-09599 Freiberg, Germany

³ Physik-Department, Lehrstuhl für Funktionelle Materialien, Technische Universität München, James-Franck-Strasse 1, D-85748 Garching, Germany

⁴ Physik-Department, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, D-85579 Neubiberg, Germany

Sensors 2018, 18(5), 1516; https://doi.org/10.3390/s18051516 - 11 May 2018

Cited by 119 | Viewed by 10981

Abstract

The development of humidity sensors with simple transduction principles attracts considerable interest by both scientific researchers and industrial companies. Capacitive humidity sensors, based on polyimide sensing material with different thickness and surface morphologies, are prepared. The surface morphology of the sensing layer is [...] Read more.

The development of humidity sensors with simple transduction principles attracts considerable interest by both scientific researchers and industrial companies. Capacitive humidity sensors, based on polyimide sensing material with different thickness and surface morphologies, are prepared. The surface morphology of the sensing layer is varied from flat to rough and then to nanostructure called nanograss by using an oxygen plasma etch process. The relative humidity (RH) sensor selectively responds to the presence of water vapor by a capacitance change. The interaction between polyimide and water molecules is studied by FTIR spectroscopy. The complete characterization of the prepared capacitive humidity sensor performance is realized using a gas mixing setup and an evaluation kit. A linear correlation is found between the measured capacitance and the RH level in the range of 5 to 85%. The morphology of the humidity sensing layer is revealed as an important parameter influencing the sensor performance. It is proved that a nanograss-like structure is the most effective for detecting RH, due to its rapid response and recovery times, which are comparable to or even better than the ones of commercial polymer-based sensors. This work demonstrates the readiness of the developed RH sensor technology for industrialization. Full article

(This article belongs to the Section Chemical Sensors)

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17 pages, 1158 KiB

Open AccessArticle

Heterogeneous Wireless Networks for Smart Grid Distribution Systems: Advantages and Limitations

by Tarek Khalifa¹, Atef Abdrabou^2,*, Khaled Shaban³

and A. M. Gaouda⁴

¹ Computer Engineering Department, American University of the Middle East, PO 220 Dasman 15453, Kuwait

² Department of Electrical Engineering, UAE University, Al-Ain, Abu Dhabi PO 15551, UAE

³ Department of Computer Science and Engineering, Qatar University, Doha PO 2713, Qatar

⁴ Electrical Engineering Department, American University of the Middle East, PO 220 Dasman 15453, Kuwait

Sensors 2018, 18(5), 1517; https://doi.org/10.3390/s18051517 - 11 May 2018

Cited by 17 | Viewed by 4624

Abstract

Supporting a conventional power grid with advanced communication capabilities is a cornerstone to transferring it to a smart grid. A reliable communication infrastructure with a high throughput can lay the foundation towards the ultimate objective of a fully automated power grid with self-healing [...] Read more.

Supporting a conventional power grid with advanced communication capabilities is a cornerstone to transferring it to a smart grid. A reliable communication infrastructure with a high throughput can lay the foundation towards the ultimate objective of a fully automated power grid with self-healing capabilities. In order to realize this objective, the communication infrastructure of a power distribution network needs to be extended to cover all substations including medium/low voltage ones. This shall enable information exchange among substations for a variety of system automation purposes with a low latency that suits time critical applications. This paper proposes the integration of two heterogeneous wireless technologies (such as WiFi and cellular 3G/4G) to provide reliable and fast communication among primary and secondary distribution substations. This integration allows the transmission of different data packets (not packet replicas) over two radio interfaces, making these interfaces act like a one data pipe. Thus, the paper investigates the applicability and effectiveness of employing heterogeneous wireless networks (HWNs) in achieving the desired reliability and timeliness requirements of future smart grids. We study the performance of HWNs in a realistic scenario under different data transfer loads and packet loss ratios. Our findings reveal that HWNs can be a viable data transfer option for smart grids. Full article

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

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13 pages, 2635 KiB

Open AccessFeature PaperArticle

Hypersensitivity and Applications of Cladding Modes of Optical Fibers Coated with Nanoscale Metal Layers

by Jacques Albert^*

, Fu Liu and Violeta Marquez-Cruz

Department of Electronics, Carleton University, Ottawa, ON K1S 5B6, Canada

Sensors 2018, 18(5), 1518; https://doi.org/10.3390/s18051518 - 11 May 2018

Cited by 8 | Viewed by 3883

Abstract

Theoretical and experimental results are presented to show that the complex effective index of the modes of optical fibers coated with non-uniform metal coatings of gold, silver, copper, or palladium, with thicknesses between 0 and 20 nm, acquire a greatly enhanced sensitivity to [...] Read more.

Theoretical and experimental results are presented to show that the complex effective index of the modes of optical fibers coated with non-uniform metal coatings of gold, silver, copper, or palladium, with thicknesses between 0 and 20 nm, acquire a greatly enhanced sensitivity to various forms of perturbations. Thickness changes of less than 1 nm can be measured as well as the binding of record low concentrations of chemical and biochemical species. Full article

(This article belongs to the Special Issue Optical Biochemical Sensor Systems and Applications)

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20 pages, 992 KiB

Open AccessArticle

Data Gathering and Energy Transfer Dilemma in UAV-Assisted Flying Access Network for IoT

by Sara Arabi¹, Essaid Sabir^1,*

, Halima Elbiaze²

and Mohamed Sadik¹

¹ NEST Research Group, Laboratoire de Recherche en Ingénierie (LRI), ENSEM, Hassan II University of Casablanca, Casablanca 8118, Morocco

² Computer Science Department Research Group, University of Quebec at Montreal (UQAM), Montreal, QC H2L 2C4, Canada

Sensors 2018, 18(5), 1519; https://doi.org/10.3390/s18051519 - 11 May 2018

Cited by 33 | Viewed by 5248

Abstract

Recently, Unmanned Aerial Vehicles (UAVs) have emerged as an alternative solution to assist wireless networks, thanks to numerous advantages they offer in comparison to terrestrial fixed base stations. For instance, a UAV can be used to embed a flying base station providing an [...] Read more.

Recently, Unmanned Aerial Vehicles (UAVs) have emerged as an alternative solution to assist wireless networks, thanks to numerous advantages they offer in comparison to terrestrial fixed base stations. For instance, a UAV can be used to embed a flying base station providing an on-demand nomadic access to network services. A UAV can also be used to wirelessly recharge out-of-battery ground devices. In this paper, we aim to deal with both data collection and recharging depleted ground Internet-of-Things (IoT) devices through a UAV station used as a flying base station. To extend the network lifetime, we present a novel use of UAV with energy harvesting module and wireless recharging capabilities. However, the UAV is used as an energy source to empower depleted IoT devices. On one hand, the UAV charges depleted ground IoT devices under three policies: (1) low-battery first scheme; (2) high-battery first scheme; and (3) random scheme. On the other hand, the UAV station collects data from IoT devices that have sufficient energy to transmit their packets, and in the same phase, the UAV exploits the Radio Frequency (RF) signals transmitted by IoT devices to extract and harvest energy. Furthermore, and as the UAV station has a limited coverage time due to its energy constraints, we propose and investigate an efficient trade-off between ground users recharging time and data gathering time. Furthermore, we suggest to control and optimize the UAV trajectory in order to complete its travel within a minimum time, while minimizing the energy spent and/or enhancing the network lifetime. Extensive numerical results and simulations show how the system behaves under different scenarios and using various metrics in which we examine the added value of UAV with energy harvesting module. Full article

(This article belongs to the Special Issue Unmanned Aerial Vehicle Networks, Systems and Applications)

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17 pages, 2546 KiB

Open AccessArticle

An Energy Centric Cluster-Based Routing Protocol for Wireless Sensor Networks

by A. S. M. Sanwar Hosen and Gi Hwan Cho^*

Division of Computer Science and Engineering, Chonbuk National University, Jeonju 54896, Jeonbuk, Korea

Sensors 2018, 18(5), 1520; https://doi.org/10.3390/s18051520 - 11 May 2018

Cited by 48 | Viewed by 5627

Abstract

Clustering is an effective way to prolong the lifetime of a wireless sensor network (WSN). The common approach is to elect cluster heads to take routing and controlling duty, and to periodically rotate each cluster head’s role to distribute energy consumption among nodes. [...] Read more.

Clustering is an effective way to prolong the lifetime of a wireless sensor network (WSN). The common approach is to elect cluster heads to take routing and controlling duty, and to periodically rotate each cluster head’s role to distribute energy consumption among nodes. However, a significant amount of energy dissipates due to control messages overhead, which results in a shorter network lifetime. This paper proposes an energy-centric cluster-based routing mechanism in WSNs. To begin with, cluster heads are elected based on the higher ranks of the nodes. The rank is defined by residual energy and average distance from the member nodes. With the role of data aggregation and data forwarding, a cluster head acts as a caretaker for cluster-head election in the next round, where the ranks’ information are piggybacked along with the local data sending during intra-cluster communication. This reduces the number of control messages for the cluster-head election as well as the cluster formation in detail. Simulation results show that our proposed protocol saves the energy consumption among nodes and achieves a significant improvement in the network lifetime. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 7624 KiB

Open AccessArticle

Structural Health Monitoring of a Composite Panel Based on PZT Sensors and a Transfer Impedance Framework

by Michal Dziendzikowski^*, Patryk Niedbala, Artur Kurnyta, Kamil Kowalczyk

and Krzysztof Dragan

Air Force Institute of Technology, ul. Ks, Boleslawa 6, 01-494 Warszawa, Poland

Sensors 2018, 18(5), 1521; https://doi.org/10.3390/s18051521 - 11 May 2018

Cited by 40 | Viewed by 4958

Abstract

One of the ideas for development of Structural Health Monitoring (SHM) systems is based on excitation of elastic waves by a network of PZT piezoelectric transducers integrated with the structure. In the paper, a variant of the so-called Transfer Impedance (TI) approach to [...] Read more.

One of the ideas for development of Structural Health Monitoring (SHM) systems is based on excitation of elastic waves by a network of PZT piezoelectric transducers integrated with the structure. In the paper, a variant of the so-called Transfer Impedance (TI) approach to SHM is followed. Signal characteristics, called the Damage Indices (DIs), were proposed for data presentation and analysis. The idea underlying the definition of DIs was to maintain most of the information carried by the voltage induced on PZT sensors by elastic waves. In particular, the DIs proposed in the paper should be sensitive to all types of damage which can influence the amplitude or the phase of the voltage induced on the sensor. Properties of the proposed DIs were investigated experimentally using a GFRP composite panel equipped with PZT networks attached to its surface and embedded into its internal structure. Repeatability and stability of DI indications under controlled conditions were verified in tests. Also, some performance indicators for surface-attached and structure-embedded sensors were obtained. The DIs’ behavior was dependent mostly on the presence of a simulated damage in the structure. Anisotropy of mechanical properties of the specimen, geometrical properties of PZT network as well as, to some extent, the technology of sensor integration with the structure were irrelevant for damage indication. This property enables the method to be used for damage detection and classification. Full article

(This article belongs to the Special Issue Sensor Technologies for Health Monitoring of Composite Structures)

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19 pages, 3389 KiB

Open AccessArticle

A Strategy toward Collaborative Filter Recommended Location Service for Privacy Protection

by Peng Wang^1,2, Jing Yang^1,* and Jianpei Zhang¹

¹ College of Computer Science and Technology, Harbin Engineering University, Harbin 150000, China

² College of Information Engineering, Suihua University, Suihua 152000, China

Sensors 2018, 18(5), 1522; https://doi.org/10.3390/s18051522 - 11 May 2018

Cited by 7 | Viewed by 3442

Abstract

A new collaborative filtered recommendation strategy was proposed for existing privacy and security issues in location services. In this strategy, every user establishes his/her own position profiles according to their daily position data, which is preprocessed using a density clustering method. Then, density [...] Read more.

A new collaborative filtered recommendation strategy was proposed for existing privacy and security issues in location services. In this strategy, every user establishes his/her own position profiles according to their daily position data, which is preprocessed using a density clustering method. Then, density prioritization was used to choose similar user groups as service request responders and the neighboring users in the chosen groups recommended appropriate location services using a collaborative filter recommendation algorithm. The two filter algorithms based on position profile similarity and position point similarity measures were designed in the recommendation, respectively. At the same time, the homomorphic encryption method was used to transfer location data for effective protection of privacy and security. A real location dataset was applied to test the proposed strategy and the results showed that the strategy provides better location service and protects users’ privacy. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 8997 KiB

Open AccessArticle

Planetary Gears Feature Extraction and Fault Diagnosis Method Based on VMD and CNN

by Chang Liu¹

, Gang Cheng^1,*, Xihui Chen² and Yusong Pang³

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

² College of Mechanical and Electrical Engineering, Hohai University, Changzhou 213022, China

³ Faculty Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft 2628 CD, The Netherlands

Sensors 2018, 18(5), 1523; https://doi.org/10.3390/s18051523 - 11 May 2018

Cited by 104 | Viewed by 7120

Abstract

Given local weak feature information, a novel feature extraction and fault diagnosis method for planetary gears based on variational mode decomposition (VMD), singular value decomposition (SVD), and convolutional neural network (CNN) is proposed. VMD was used to decompose the original vibration signal to [...] Read more.

Given local weak feature information, a novel feature extraction and fault diagnosis method for planetary gears based on variational mode decomposition (VMD), singular value decomposition (SVD), and convolutional neural network (CNN) is proposed. VMD was used to decompose the original vibration signal to mode components. The mode matrix was partitioned into a number of submatrices and local feature information contained in each submatrix was extracted as a singular value vector using SVD. The singular value vector matrix corresponding to the current fault state was constructed according to the location of each submatrix. Finally, by training a CNN using singular value vector matrices as inputs, planetary gear fault state identification and classification was achieved. The experimental results confirm that the proposed method can successfully extract local weak feature information and accurately identify different faults. The singular value vector matrices of different fault states have a distinct difference in element size and waveform. The VMD-based partition extraction method is better than ensemble empirical mode decomposition (EEMD), resulting in a higher CNN total recognition rate of 100% with fewer training times (14 times). Further analysis demonstrated that the method can also be applied to the degradation recognition of planetary gears. Thus, the proposed method is an effective feature extraction and fault diagnosis technique for planetary gears. Full article

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

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19 pages, 6973 KiB

Open AccessArticle

A High-Speed Imaging Method Based on Compressive Sensing for Sound Extraction Using a Low-Speed Camera

by Ge Zhu¹, Xu-Ri Yao^2,*, Zhi-Bin Sun^2,3, Peng Qiu^2,3, Chao Wang², Guang-Jie Zhai^2,3 and Qing Zhao^1,*

¹ Center for Quantum Technology Research, School of Physics, Beijing Institute of Technology, Beijing 100081, China

² Key Laboratory of Electronics and Information Technology for Space Systems, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China

³ University of Chinese Academy of Sciences, Beijing 100049, China

Sensors 2018, 18(5), 1524; https://doi.org/10.3390/s18051524 - 11 May 2018

Cited by 9 | Viewed by 5167

Abstract

This paper reports an efficient method for sound extraction from high-speed light spot videos reconstructed from the coded light spot images captured with a low-speed camera based on compressive sensing, but at the expense of consuming time. The proposed method first gets the [...] Read more.

This paper reports an efficient method for sound extraction from high-speed light spot videos reconstructed from the coded light spot images captured with a low-speed camera based on compressive sensing, but at the expense of consuming time. The proposed method first gets the high-speed video of the light spot that is illuminated on the vibrating target caused by sound. Then the centroid of the light spot is used to recover the sound. Simulations of the proposed method are carried out and experimental results are demonstrated. The results show that high-speed videos with a frame rate of 2000 Hz can be reconstructed with a low-speed (100 Hz) charge-coupled device (CCD) camera, which is randomly modulated by a digital micro-mirror device (DMD) 20 times during each exposure time. This means a speed improvement of 20 times is achieved. The effects of synchronization between CCD image recording and DMD modulation, the optimal sampling patterns of DMD, and sound vibration amplitudes on the performance of the proposed method are evaluated. Using this compressive camera, speech (counting from one to four in Chinese) was recovered well. This has been confirmed by directly listening to the recovered sound, and the intelligibility value (0–1) that evaluated the similarity between them was 0.8185. Although we use this compressive camera for sound detection, we expect it to be useful in applications related to vibration and motion. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 584 KiB

Open AccessArticle

Biometric Authentication Using the PPG: A Long-Term Feasibility Study

by Jorge Sancho^*

, Álvaro Alesanco

and José García

Aragón Institute of Engineering Research (I3A), University of Zaragoza, 50018 Zaragoza, Spain

Sensors 2018, 18(5), 1525; https://doi.org/10.3390/s18051525 - 11 May 2018

Cited by 56 | Viewed by 6543

Abstract

The photoplethysmogram (PPG) is a biomedical signal that can be used to estimate volumetric blood flow changes in the peripheral circulation. During the past few years, several works have been published in order to assess the potential for PPGs to be used in [...] Read more.

The photoplethysmogram (PPG) is a biomedical signal that can be used to estimate volumetric blood flow changes in the peripheral circulation. During the past few years, several works have been published in order to assess the potential for PPGs to be used in biometric authentication systems, but results are inconclusive. In this paper we perform an analysis of the feasibility of using the PPG as a realistic biometric alternative in the long term. Several feature extractors (based on the time domain and the Karhunen–Loève transform) and matching metrics (Manhattan and Euclidean distances) have been tested using four different PPG databases (PRRB, MIMIC-II, Berry, and Nonin). We show that the false match rate (FMR) and false non-match rate (FNMR) values remain constant in different time instances for a selected threshold, which is essential for using the PPG for biometric authentication purposes. On the other hand, obtained equal error rate (EER) values for signals recorded during the same session range from 1.0% for high-quality signals recorded in controlled conditions to 8% for those recorded in conditions closer to real-world scenarios. Moreover, in certain scenarios, EER values rise up to 23.2% for signals recorded over different days, signaling that performance degradation could take place with time. Full article

(This article belongs to the Section Biosensors)

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16 pages, 4584 KiB

Open AccessArticle

Quantitative Analysis of Nutrient Elements in Soil Using Single and Double-Pulse Laser-Induced Breakdown Spectroscopy

by Yong He^1,2

, Xiaodan Liu^1,2

, Yangyang Lv¹, Fei Liu^1,2,*

, Jiyu Peng¹

, Tingting Shen¹, Yun Zhao^1,3, Yu Tang⁴ and Shaoming Luo⁴

¹ College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China

² Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture, Hangzhou 310058, China

³ School of information and electronic engineering, Zhejiang University of Science and Technology, 318 Liuhe Road, Hangzhou 310023, China

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

Sensors 2018, 18(5), 1526; https://doi.org/10.3390/s18051526 - 11 May 2018

Cited by 64 | Viewed by 6934

Abstract

Rapid detection of soil nutrient elements is beneficial to the evaluation of crop yield, and it’s of great significance in agricultural production. The aim of this work was to compare the detection ability of single-pulse (SP) and collinear double-pulse (DP) laser-induced breakdown spectroscopy [...] Read more.

Rapid detection of soil nutrient elements is beneficial to the evaluation of crop yield, and it’s of great significance in agricultural production. The aim of this work was to compare the detection ability of single-pulse (SP) and collinear double-pulse (DP) laser-induced breakdown spectroscopy (LIBS) for soil nutrient elements and obtain an accurate and reliable method for rapid detection of soil nutrient elements. 63 soil samples were collected for SP and collinear DP signal acquisition, respectively. Macro-nutrients (K, Ca, Mg) and micro-nutrients (Fe, Mn, Na) were analyzed. Three main aspects of all elements were investigated, including spectral intensity, signal stability, and detection sensitivity. Signal-to-noise ratio (SNR) and relative standard deviation (RSD) of elemental spectra were applied to evaluate the stability of SP and collinear DP signals. In terms of detection sensitivity, the performance of chemometrics models (univariate and multivariate analysis models) and the limit of detection (LOD) of elements were analyzed, and the results indicated that the DP-LIBS technique coupled with PLSR could be an accurate and reliable method in the quantitative determination of soil nutrient elements. Full article

(This article belongs to the Section Remote Sensors)

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22 pages, 1289 KiB

Open AccessArticle

Cellular-V2X Communications for Platooning: Design and Evaluation

by Giovanni Nardini¹

, Antonio Virdis¹

, Claudia Campolo²

, Antonella Molinaro^2,*

and Giovanni Stea¹

¹ Dipartimento di Ingegneria dell Informazione, University of Pisa, Largo Lucio Lazzarino 1, 56122 Pisa, Italy

² Dipartimento DIIES, University Mediterranea di Reggio Calabria, Via Graziella, Loc. Feo di Vito, 89122 Reggio Calabria, Italy

Sensors 2018, 18(5), 1527; https://doi.org/10.3390/s18051527 - 11 May 2018

Cited by 83 | Viewed by 10920

Abstract

Platooning is a cooperative driving application where autonomous/semi-autonomous vehicles move on the same lane in a train-like manner, keeping a small constant inter-vehicle distance, in order to reduce fuel consumption and gas emissions and to achieve safe and efficient transport. To this aim, [...] Read more.

Platooning is a cooperative driving application where autonomous/semi-autonomous vehicles move on the same lane in a train-like manner, keeping a small constant inter-vehicle distance, in order to reduce fuel consumption and gas emissions and to achieve safe and efficient transport. To this aim, they may exploit multiple on-board sensors (e.g., radars, LiDARs, positioning systems) and direct vehicle-to-vehicle communications to synchronize their manoeuvres. The main objective of this paper is to discuss the design choices and factors that determine the performance of a platooning application, when exploiting the emerging cellular vehicle-to-everything (C-V2X) communication technology and considering the scheduled mode, specified by 3GPP for communications over the sidelink assisted by the eNodeB. Since no resource management algorithm is currently mandated by 3GPP for this new challenging context, we focus on analyzing the feasibility and performance of the dynamic scheduling approach, with platoon members asking for radio resources on a per-packet basis. We consider two ways of implementing dynamic scheduling, currently unspecified by 3GPP: the sequential mode, that is somehow reminiscent of time division multiple access solutions based on IEEE 802.11p—till now the only investigated access technology for platooning—and the simultaneous mode with spatial frequency reuse enabled by the eNodeB. The evaluation conducted through system-level simulations provides helpful insights about the proposed configurations and C-V2X parameter settings that mainly affect the reliability and latency performance of data exchange in platoons, under different load settings. Achieved results show that the proposed simultaneous mode succeeds in reducing the latency in the update cycle in each vehicle’s controller, thus enabling future high-density platooning scenarios. Full article

(This article belongs to the Special Issue Sensor Networks for Smart Roads)

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16 pages, 28492 KiB

Open AccessArticle

The First Result of Relative Positioning and Velocity Estimation Based on CAPS

by Jiaojiao Zhao^1,2, Zishen Li^1,3,*

, Jian Ge¹, Liang Wang^1,2, Ningbo Wang¹, Kai Zhou¹ and Hong Yuan¹

¹ Academy of Opto-Electronics, Chinese Academy of Sciences, No.9 Dengzhuang South Road, Haidian District, 100094 Beijing, China

² School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, No.19A Yuquan Road, Shijingshan District, 100049 Beijing, China

³ State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, No.340 Xudong Road, Wuchang District, 430077 Wuhan, China

Sensors 2018, 18(5), 1528; https://doi.org/10.3390/s18051528 - 12 May 2018

Cited by 5 | Viewed by 3557

Abstract

The Chinese Area Positioning System (CAPS) is a new positioning system developed by the Chinese Academy of Sciences based on the communication satellites in geosynchronous orbit. The CAPS has been regarded as a pilot system to test the new technology for the design, [...] Read more.

The Chinese Area Positioning System (CAPS) is a new positioning system developed by the Chinese Academy of Sciences based on the communication satellites in geosynchronous orbit. The CAPS has been regarded as a pilot system to test the new technology for the design, construction and update of the BeiDou Navigation Satellite System (BDS). The system structure of CAPS, including the space, ground control station and user segments, is almost like the traditional Global Navigation Satellite Systems (GNSSs), but with the clock on the ground, the navigation signal in C waveband, and different principles of operation. The major difference is that the CAPS navigation signal is first generated at the ground control station, before being transmitted to the satellite in orbit and finally forwarded by the communication satellite transponder to the user. This design moves the clock from the satellite in orbit to the ground. The clock error can therefore be easily controlled and mitigated to improve the positioning accuracy. This paper will present the performance of CAPS-based relative positioning and velocity estimation as assessed in Beijing, China. The numerical results show that, (1) the accuracies of relative positioning, using only code measurements, are 1.25 and 1.8 m in the horizontal and vertical components, respectively; (2) meanwhile, they are about 2.83 and 3.15 cm in static mode and 6.31 and 10.78 cm in kinematic mode, respectively, when using the carrier-phase measurements with ambiguities fixed; and (3) the accuracy of the velocity estimation is about 0.04 and 0.11 m/s in static and kinematic modes, respectively. These results indicate the potential application of CAPS for high-precision positioning and velocity estimation and the availability of a new navigation mode based on communication satellites. Full article

(This article belongs to the Section Remote Sensors)

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34 pages, 2897 KiB

Open AccessArticle

DOW-PR DOlphin and Whale Pods Routing Protocol for Underwater Wireless Sensor Networks (UWSNs)

by Zahid Wadud¹, Khadem Ullah²

, Sajjad Hussain³, Xiaodong Yang^4,* and Abdul Baseer Qazi⁵

¹ Department of Electrical Engineering, Capital University of Science and Technology, Islamabad 44000, Pakistan

² Department of Computer Systems Engineering, University of Engineering and Technology, Peshawar 25000, Pakistan

³ School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK

⁴ School of Electronic Engineering, Xidian University, Xi’an 710071, China

⁵ Department of Software Engineering, Bahria University, Islamabad 44000, Pakistan

Sensors 2018, 18(5), 1529; https://doi.org/10.3390/s18051529 - 12 May 2018

Cited by 18 | Viewed by 6779

Abstract

Underwater Wireless Sensor Networks (UWSNs) have intrinsic challenges that include long propagation delays, high mobility of sensor nodes due to water currents, Doppler spread, delay variance, multipath, attenuation and geometric spreading. The existing Weighting Depth and Forwarding Area Division Depth Based Routing (WDFAD-DBR) [...] Read more.

Underwater Wireless Sensor Networks (UWSNs) have intrinsic challenges that include long propagation delays, high mobility of sensor nodes due to water currents, Doppler spread, delay variance, multipath, attenuation and geometric spreading. The existing Weighting Depth and Forwarding Area Division Depth Based Routing (WDFAD-DBR) protocol considers the weighting depth of the two hops in order to select the next Potential Forwarding Node (PFN). To improve the performance of WDFAD-DBR, we propose DOlphin and Whale Pod Routing protocol (DOW-PR). In this scheme, we divide the transmission range into a number of transmission power levels and at the same time select the next PFNs from forwarding and suppressed zones. In contrast to WDFAD-DBR, our scheme not only considers the packet upward advancement, but also takes into account the number of suppressed nodes and number of PFNs at the first and second hops. Consequently, reasonable energy reduction is observed while receiving and transmitting packets. Moreover, our scheme also considers the hops count of the PFNs from the sink. In the absence of PFNs, the proposed scheme will select the node from the suppressed region for broadcasting and thus ensures minimum loss of data. Besides this, we also propose another routing scheme (whale pod) in which multiple sinks are placed at water surface, but one sink is embedded inside the water and is physically connected with the surface sink through high bandwidth connection. Simulation results show that the proposed scheme has high Packet Delivery Ratio (PDR), low energy tax, reduced Accumulated Propagation Distance (APD) and increased the network lifetime. Full article

(This article belongs to the Section Sensor Networks)

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23 pages, 4382 KiB

Open AccessArticle

Convolutional Neural Network-Based Embarrassing Situation Detection under Camera for Social Robot in Smart Homes

by Guanci Yang^1,*

, Jing Yang¹

, Weihua Sheng², Francisco Erivaldo Fernandes Junior² and Shaobo Li^1,*

¹ Key Laboratory of Advanced Manufacturing Technology of Ministry of Education, Guizhou University, Guiyang 550025, China

² School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, OK 74074, USA

Sensors 2018, 18(5), 1530; https://doi.org/10.3390/s18051530 - 12 May 2018

Cited by 41 | Viewed by 7720

Abstract

Recent research has shown that the ubiquitous use of cameras and voice monitoring equipment in a home environment can raise privacy concerns and affect human mental health. This can be a major obstacle to the deployment of smart home systems for elderly or [...] Read more.

Recent research has shown that the ubiquitous use of cameras and voice monitoring equipment in a home environment can raise privacy concerns and affect human mental health. This can be a major obstacle to the deployment of smart home systems for elderly or disabled care. This study uses a social robot to detect embarrassing situations. Firstly, we designed an improved neural network structure based on the You Only Look Once (YOLO) model to obtain feature information. By focusing on reducing area redundancy and computation time, we proposed a bounding-box merging algorithm based on region proposal networks (B-RPN), to merge the areas that have similar features and determine the borders of the bounding box. Thereafter, we designed a feature extraction algorithm based on our improved YOLO and B-RPN, called F-YOLO, for our training datasets, and then proposed a real-time object detection algorithm based on F-YOLO (RODA-FY). We implemented RODA-FY and compared models on our MAT social robot. Secondly, we considered six types of situations in smart homes, and developed training and validation datasets, containing 2580 and 360 images, respectively. Meanwhile, we designed three types of experiments with four types of test datasets composed of 960 sample images. Thirdly, we analyzed how a different number of training iterations affects our prediction estimation, and then we explored the relationship between recognition accuracy and learning rates. Our results show that our proposed privacy detection system can recognize designed situations in the smart home with an acceptable recognition accuracy of 94.48%. Finally, we compared the results among RODA-FY, Inception V3, and YOLO, which indicate that our proposed RODA-FY outperforms the other comparison models in recognition accuracy. Full article

(This article belongs to the Special Issue Smart Homes)

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15 pages, 7140 KiB

Open AccessArticle

Vibro-Perception of Optical Bio-Inspired Fiber-Skin

by Tao Li^1,†

, Sheng Zhang^2,*,†

, Guo-Wei Lu^1,*,†

and Yuta Sunami^2,3

¹ Institute of Innovative Science and Technology, Tokai University, Hiratsuka-shi 259-1292, Japan

² Micro/Nano Technology Center, Tokai University, Hiratsuka-shi 259-1292, Japan

³ Department of Mechanical Engineering, Tokai University, Hiratsuka-shi 259-1292, Japan

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1531; https://doi.org/10.3390/s18051531 - 12 May 2018

Cited by 9 | Viewed by 4824

Abstract

In this research, based on the principle of optical interferometry, the Mach-Zehnder and Optical Phase-locked Loop (OPLL) vibro-perception systems of bio-inspired fiber-skin are designed to mimic the tactile perception of human skin. The fiber-skin is made of the optical fiber embedded in the [...] Read more.

In this research, based on the principle of optical interferometry, the Mach-Zehnder and Optical Phase-locked Loop (OPLL) vibro-perception systems of bio-inspired fiber-skin are designed to mimic the tactile perception of human skin. The fiber-skin is made of the optical fiber embedded in the silicone elastomer. The optical fiber is an instinctive and alternative sensor for tactile perception with high sensitivity and reliability, also low cost and susceptibility to the magnetic interference. The silicone elastomer serves as a substrate with high flexibility and biocompatibility, and the optical fiber core serves as the vibro-perception sensor to detect physical motions like tapping and sliding. According to the experimental results, the designed optical fiber-skin demonstrates the ability to detect the physical motions like tapping and sliding in both the Mach-Zehnder and OPLL vibro-perception systems. For direct contact condition, the OPLL vibro-perception system shows better performance compared with the Mach-Zehnder vibro-perception system. However, the Mach-Zehnder vibro-perception system is preferable to the OPLL system in the indirect contact experiment. In summary, the fiber-skin is validated to have light touch character and excellent repeatability, which is highly-suitable for skin-mimic sensing. Full article

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

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20 pages, 2420 KiB

Open AccessArticle

Combining Fog Computing with Sensor Mote Machine Learning for Industrial IoT

by Mehrzad Lavassani

, Stefan Forsström

, Ulf Jennehag and Tingting Zhang^*

Department of Information Systems and Technology, Mid Sweden University, 851 70 Sundsvall, Sweden

Sensors 2018, 18(5), 1532; https://doi.org/10.3390/s18051532 - 12 May 2018

Cited by 57 | Viewed by 9003

Abstract

Digitalization is a global trend becoming ever more important to our connected and sustainable society. This trend also affects industry where the Industrial Internet of Things is an important part, and there is a need to conserve spectrum as well as energy when [...] Read more.

Digitalization is a global trend becoming ever more important to our connected and sustainable society. This trend also affects industry where the Industrial Internet of Things is an important part, and there is a need to conserve spectrum as well as energy when communicating data to a fog or cloud back-end system. In this paper we investigate the benefits of fog computing by proposing a novel distributed learning model on the sensor device and simulating the data stream in the fog, instead of transmitting all raw sensor values to the cloud back-end. To save energy and to communicate as few packets as possible, the updated parameters of the learned model at the sensor device are communicated in longer time intervals to a fog computing system. The proposed framework is implemented and tested in a real world testbed in order to make quantitative measurements and evaluate the system. Our results show that the proposed model can achieve a 98% decrease in the number of packets sent over the wireless link, and the fog node can still simulate the data stream with an acceptable accuracy of 97%. We also observe an end-to-end delay of 180 ms in our proposed three-layer framework. Hence, the framework shows that a combination of fog and cloud computing with a distributed data modeling at the sensor device for wireless sensor networks can be beneficial for Industrial Internet of Things applications. Full article

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

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24 pages, 7480 KiB

Open AccessArticle

Speckle Filtering of GF-3 Polarimetric SAR Data with Joint Restriction Principle

by Jinwei Xie¹

, Zhenfang Li^1,*, Chaowei Zhou¹, Yuyuan Fang¹ and Qingjun Zhang²

¹ National Laboratory of Radar Signal Processing, Xidian University, Xi’an 710071, China

² Beijing Institute of Spacecraft System Engineering, China Academy of Space Technology, Beijing 100094, China

Sensors 2018, 18(5), 1533; https://doi.org/10.3390/s18051533 - 12 May 2018

Cited by 8 | Viewed by 4587

Abstract

Polarimetric SAR (PolSAR) scattering characteristics of imagery are always obtained from the second order moments estimation of multi-polarization data, that is, the estimation of covariance or coherency matrices. Due to the extra-paths that signal reflected from separate scatterers within the resolution cell has [...] Read more.

Polarimetric SAR (PolSAR) scattering characteristics of imagery are always obtained from the second order moments estimation of multi-polarization data, that is, the estimation of covariance or coherency matrices. Due to the extra-paths that signal reflected from separate scatterers within the resolution cell has to travel, speckle noise always exists in SAR images and has a severe impact on the scattering performance, especially on single look complex images. In order to achieve high accuracy in estimating covariance or coherency matrices, three aspects are taken into consideration: (1) the edges and texture of the scene are distinct after speckle filtering; (2) the statistical characteristic should be similar to the object pixel; and (3) the polarimetric scattering signature should be preserved, in addition to speckle reduction. In this paper, a joint restriction principle is proposed to meet the requirement. Three different restriction principles are introduced to the processing of speckle filtering. First, a new template, which is more suitable for the point or line targets, is designed to ensure the morphological consistency. Then, the extent sigma filter is used to restrict the pixels in the template aforementioned to have an identical statistic characteristic. At last, a polarimetric similarity factor is applied to the same pixels above, to guarantee the similar polarimetric features amongst the optional pixels. This processing procedure is named as speckle filtering with joint restriction principle and the approach is applied to GF-3 polarimetric SAR data acquired in San Francisco, CA, USA. Its effectiveness of keeping the image sharpness and preserving the scattering mechanism as well as speckle reduction is validated by the comparison with boxcar filters and refined Lee filter. Full article

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

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15 pages, 3967 KiB

Open AccessArticle

Polarization Smoothing Generalized MUSIC Algorithm with Polarization Sensitive Array for Low Angle Estimation

by Jun Tan^*

and Zaiping Nie

School of Electronic Science and Engineering (National Exemplary School of Microelectronics), University of Electronic Science and Technology of China, Shahe Campus, Section 2, North Jianshe Road, Chengdu 610054, China

Sensors 2018, 18(5), 1534; https://doi.org/10.3390/s18051534 - 12 May 2018

Cited by 14 | Viewed by 4292

Abstract

Direction of Arrival (DOA) estimation of low-altitude targets is difficult due to the multipath coherent interference from the ground reflection image of the targets, especially for very high frequency (VHF) radars, which have antennae that are severely restricted in terms of aperture and [...] Read more.

Direction of Arrival (DOA) estimation of low-altitude targets is difficult due to the multipath coherent interference from the ground reflection image of the targets, especially for very high frequency (VHF) radars, which have antennae that are severely restricted in terms of aperture and height. The polarization smoothing generalized multiple signal classification (MUSIC) algorithm, which combines polarization smoothing and generalized MUSIC algorithm for polarization sensitive arrays (PSAs), was proposed to solve this problem in this paper. Firstly, the polarization smoothing pre-processing was exploited to eliminate the coherence between the direct and the specular signals. Secondly, we constructed the generalized MUSIC algorithm for low angle estimation. Finally, based on the geometry information of the symmetry multipath model, the proposed algorithm was introduced to convert the two-dimensional searching into one-dimensional searching, thus reducing the computational burden. Numerical results were provided to verify the effectiveness of the proposed method, showing that the proposed algorithm has significantly improved angle estimation performance in the low-angle area compared with the available methods, especially when the grazing angle is near zero. Full article

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

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28 pages, 4807 KiB

Open AccessArticle

An Effective Delay Reduction Approach through a Portion of Nodes with a Larger Duty Cycle for Industrial WSNs

by Minrui Wu¹, Yanhui Wu², Chuyao Liu³, Zhiping Cai⁴, Neal N. Xiong⁵

, Anfeng Liu^1,6,*

and Ming Ma⁷

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

² College of computer and information engineering, Hunan University of Commerce, Changsha 410205, China

³ School of Software, Central South University, Changsha 410075, China

⁴ College of Computer, National University of Defense Technology, Changsha 410073, China

⁵ Department of Mathematics and Computer Science, Northeastern State University, Tahlequah, OK 74464, USA

⁶ The State Key Laboratory of Industrial Control Technology, Zhejiang University, Hangzhou 310027, China

⁷ Department of Computer Science, Stony Brook University, Stony Brook, NY 11794, USA

Sensors 2018, 18(5), 1535; https://doi.org/10.3390/s18051535 - 12 May 2018

Cited by 30 | Viewed by 4666

Abstract

For Industrial Wireless Sensor Networks (IWSNs), sending data with timely style to the stink (or control center, CC) that is monitored by sensor nodes is a challenging issue. However, in order to save energy, wireless sensor networks based on a duty cycle are [...] Read more.

For Industrial Wireless Sensor Networks (IWSNs), sending data with timely style to the stink (or control center, CC) that is monitored by sensor nodes is a challenging issue. However, in order to save energy, wireless sensor networks based on a duty cycle are widely used in the industrial field, which can bring great delay to data transmission. We observe that if the duty cycle of a small number of nodes in the network is set to 1, the sleep delay caused by the duty cycle can be effectively reduced. Thus, in this paper, a novel Portion of Nodes with Larger Duty Cycle (PNLDC) scheme is proposed to reduce delay and optimize energy efficiency for IWSNs. In the PNLDC scheme, a portion of nodes are selected to set their duty cycle to 1, and the proportion of nodes with the duty cycle of 1 is determined according to the energy abundance of the area in which the node is located. The more the residual energy in the region, the greater the proportion of the selected nodes. Because there are a certain proportion of nodes with the duty cycle of 1 in the network, the PNLDC scheme can effectively reduce delay in IWSNs. The performance analysis and experimental results show that the proposed scheme significantly reduces the delay for forwarding data by 8.9~26.4% and delay for detection by 2.1~24.6% without reducing the network lifetime when compared with the fixed duty cycle method. Meanwhile, compared with the dynamic duty cycle strategy, the proposed scheme has certain advantages in terms of energy utilization and delay reduction. Full article

(This article belongs to the Special Issue Sensor Networks and Systems to Enable Industry 4.0 Environments)

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16 pages, 4881 KiB

Open AccessArticle

Sparsity-Driven Reconstruction Technique for Microwave/Millimeter-Wave Computational Imaging

by Thomas Fromenteze^1,*, Cyril Decroze¹, Sana Abid¹ and Okan Yurduseven²

¹ XLIM UMR 7252, Université de Limoges/CNRS, 87060 Limoges, France

² Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA

Sensors 2018, 18(5), 1536; https://doi.org/10.3390/s18051536 - 12 May 2018

Cited by 19 | Viewed by 4237

Abstract

Numerous prototypes of computational imaging systems have recently been presented in the microwave and millimeter-wave domains, enabling the simplification of associated active architectures through the use of radiating cavities and metasurfaces that can multiplex signals encoded in the physical layer. This paper presents [...] Read more.

Numerous prototypes of computational imaging systems have recently been presented in the microwave and millimeter-wave domains, enabling the simplification of associated active architectures through the use of radiating cavities and metasurfaces that can multiplex signals encoded in the physical layer. This paper presents a new reconstruction technique leveraging the sparsity of the signals in the time-domain and decomposition of the sensing matrix by support detection, the size of the computational inverse problem being reduced significantly without compromising the image quality. Full article

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

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22 pages, 4470 KiB

Open AccessArticle

A Hybrid TDMA/CSMA-Based Wireless Sensor and Data Transmission Network for ORS Intra-Microsatellite Applications

by Long Wang^1,2,3,*, Yong Liu^1,3 and Zengshan Yin^1,2,3

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

³ Shanghai Engineering Center for Microsatellites, Chinese Academy of Sciences, Shanghai 201210, China

Sensors 2018, 18(5), 1537; https://doi.org/10.3390/s18051537 - 12 May 2018

Cited by 7 | Viewed by 4420

Abstract

To achieve launch-on-demand for Operationally Responsive Space (ORS) missions, in this article, an intra-satellite wireless network (ISWN) is presented. It provides a wireless and modularized scheme for intra-spacecraft sensing and data buses. By removing the wired data bus, the commercial off-the-shelf (COTS) based [...] Read more.

To achieve launch-on-demand for Operationally Responsive Space (ORS) missions, in this article, an intra-satellite wireless network (ISWN) is presented. It provides a wireless and modularized scheme for intra-spacecraft sensing and data buses. By removing the wired data bus, the commercial off-the-shelf (COTS) based wireless modular architecture will reduce both the volume and weight of the satellite platform, thus achieving rapid design and cost savings in development and launching. Based on the on-orbit data demand analysis, a hybrid time division multiple access/carrier sense multiple access (TDMA/CSMA) protocol is proposed. It includes an improved clear channel assessment (CCA) mechanism and a traffic adaptive slot allocation method. To analyze the access process, a Markov model is constructed. Then a detailed calculation is given in which the unsaturated cases are considered. Through simulations, the proposed protocol is proved to commendably satisfy the demands and performs better than existing schemes. It helps to build a full-wireless satellite instead of the current wired ones, and will contribute to provide dynamic space capabilities for ORS missions. Full article

(This article belongs to the Section Sensor Networks)

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18 pages, 4107 KiB

Open AccessArticle

Hybrid Transverse Polar Navigation for High-Precision and Long-Term INSs

by Ruonan Wu

, Qiuping Wu^*, Fengtian Han^*

, Rong Zhang, Peida Hu and Haixia Li

Department of Precision Instrument, Tsinghua University, Beijing 100084, China

Sensors 2018, 18(5), 1538; https://doi.org/10.3390/s18051538 - 12 May 2018

Cited by 11 | Viewed by 4281

Abstract

Transverse navigation has been proposed to help inertial navigation systems (INSs) fill the gap of polar navigation ability. However, as the transverse system does not have the ability of navigate globally, a complicated switch between the transverse and the traditional algorithms is necessary [...] Read more.

Transverse navigation has been proposed to help inertial navigation systems (INSs) fill the gap of polar navigation ability. However, as the transverse system does not have the ability of navigate globally, a complicated switch between the transverse and the traditional algorithms is necessary when the system moves across the polar circles. To maintain the inner continuity and consistency of the core algorithm, a hybrid transverse polar navigation is proposed in this research based on a combination of Earth-fixed-frame mechanization and transverse-frame outputs. Furthermore, a thorough analysis of kinematic error characteristics, proper damping technology and corresponding long-term contributions of main error sources is conducted for the high-precision INSs. According to the analytical expressions of the long-term navigation errors in polar areas, the 24-h period symmetrical oscillation with a slowly divergent amplitude dominates the transverse horizontal position errors, and the first-order drift dominates the transverse azimuth error, which results from the

g^{0}

gyro drift coefficients that occur in corresponding directions. Simulations are conducted to validate the theoretical analysis and the deduced analytical expressions. The results show that the proposed hybrid transverse navigation can ensure the same accuracy and oscillation characteristics in polar areas as the traditional algorithm in low and mid latitude regions. Full article

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

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23 pages, 3480 KiB

Open AccessArticle

A Key Pre-Distribution Scheme Based on µ-PBIBD for Enhancing Resilience in Wireless Sensor Networks

by Qi Yuan^1,2, Chunguang Ma^1,*, Haitao Yu³ and Xuefen Bian⁴

¹ College of Computer Science and Technology, Harbin Engineering University, Harbin 150001, China

² College of Communication and Electronic Engineering, Qiqihar University, Qiqihar 161006, China

³ College of Tourism, Guilin University of Technology, Guilin 541004, China

⁴ College of Data Science and Technology, Heilongjiang University, Harbin 150080, China

Sensors 2018, 18(5), 1539; https://doi.org/10.3390/s18051539 - 12 May 2018

Cited by 15 | Viewed by 3036

Abstract

Many key pre-distribution (KPD) schemes based on combinatorial design were proposed for secure communication of wireless sensor networks (WSNs). Due to complexity of constructing the combinatorial design, it is infeasible to generate key rings using the corresponding combinatorial design in large scale deployment [...] Read more.

Many key pre-distribution (KPD) schemes based on combinatorial design were proposed for secure communication of wireless sensor networks (WSNs). Due to complexity of constructing the combinatorial design, it is infeasible to generate key rings using the corresponding combinatorial design in large scale deployment of WSNs. In this paper, we present a definition of new combinatorial design, termed “µ-partially balanced incomplete block design (µ-PBIBD)”, which is a refinement of partially balanced incomplete block design (PBIBD), and then describe a 2-D construction of µ-PBIBD which is mapped to KPD in WSNs. Our approach is of simple construction which provides a strong key connectivity and a poor network resilience. To improve the network resilience of KPD based on 2-D µ-PBIBD, we propose a KPD scheme based on 3-D Ex-µ-PBIBD which is a construction of µ-PBIBD from 2-D space to 3-D space. Ex-µ-PBIBD KPD scheme improves network scalability and resilience while has better key connectivity. Theoretical analysis and comparison with the related schemes show that key pre-distribution scheme based on Ex-µ-PBIBD provides high network resilience and better key scalability, while it achieves a trade-off between network resilience and network connectivity. Full article

(This article belongs to the Section Sensor Networks)

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10 pages, 2842 KiB

Open AccessArticle

A Novel Mach-Zehnder Interferometer Using Eccentric-Core Fiber Design for Optical Coherence Tomography

by Qiao Xiong^1,2, Xinglin Tong^1,2,*, Chengwei Deng¹, Cui Zhang¹, Pengfei Wang^1,2, Zhiyuan Zheng¹ and Fang Liu^1,2

¹ National Engineering Laboratory for Fiber Optic Sensing Technology, Wuhan University of Technology, Wuhan 430074, China

² School of Information Engineering, Wuhan University of Technology, Wuhan 430074, China

Sensors 2018, 18(5), 1540; https://doi.org/10.3390/s18051540 - 13 May 2018

Cited by 5 | Viewed by 4005

Abstract

A novel Mach-Zehnder interferometer using eccentric-core fiber (ECF) design for optical coherence tomography (OCT) is proposed and demonstrated. Instead of the commercial single-mode fiber (SMF), the ECF is used as one interference arm of the implementation. Because of the offset location of the [...] Read more.

A novel Mach-Zehnder interferometer using eccentric-core fiber (ECF) design for optical coherence tomography (OCT) is proposed and demonstrated. Instead of the commercial single-mode fiber (SMF), the ECF is used as one interference arm of the implementation. Because of the offset location of the eccentric core, it is sensitive to directional bending and the optical path difference (OPD) of two interference arms can be adjusted with high precision. The birefringence of ECF is calculated and experimentally measured, which demonstrates the polarization sensitivity of the ECF proposed in the paper is similar to that of SMF. Such a structure can replace the reference optical delay line to form an all-fiber passive device. A mirror is used as a sample for analyzing the ECF bending responses of the system. Besides, four pieces of overlapping glass slides as sample are experimentally measured as well. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 6961 KiB

Open AccessArticle

Monitoring of Cardiorespiratory Signals Using Thermal Imaging: A Pilot Study on Healthy Human Subjects

by Carina Barbosa Pereira^1,*,†

, Michael Czaplik^2,†

, Vladimir Blazek^1,3, Steffen Leonhardt¹

and Daniel Teichmann¹

¹ Chair for Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstr. 20, D-52074 Aachen, Germany

² Department of Anesthesiology, University Hospital RWTH Aachen, Pauwelsstr. 30, D-52074 Aachen, Germany

³ Czech Institute of Informatics, Robotics and Cybernetics (CIIRC), CTU Prague, Zikova street 1903/4, 166 36 Prague, Czech Republic

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1541; https://doi.org/10.3390/s18051541 - 13 May 2018

Cited by 44 | Viewed by 7168

Abstract

Heart rate (HR) and respiratory rate (RR) are important parameters for patient assessment. However, current measurement techniques require attachment of sensors to the patient’s body, often leading to discomfort, stress and even pain. A new algorithm is presented for monitoring both HR and [...] Read more.

Heart rate (HR) and respiratory rate (RR) are important parameters for patient assessment. However, current measurement techniques require attachment of sensors to the patient’s body, often leading to discomfort, stress and even pain. A new algorithm is presented for monitoring both HR and RR using thermal imaging. The cyclical ejection of blood flow from the heart to the head (through carotid arteries and thoracic aorta) leads to periodic movements of the head; these vertical movements are used to assess HR. Respiratory rate is estimated by using temperature fluctuations under the nose during the respiratory cycle. To test the viability and feasibility of this approach, a pilot study was conducted with 20 healthy subjects (aged 18–36 and 1 aged 50 years). The study consisted of two phases: phase A (frontal view acquisitions) and phase B (side view acquisitions). To validate the results, photoplethysmography and thoracic effort (piezoplethysmography) were simultaneously recorded. High agreement between infrared thermography and ground truth/gold standard was achieved. For HR, the root-mean-square errors (RMSE) for phases A and B were 3.53 ± 1.53 and 3.43 ± 1.61 beats per minute, respectively. For RR, the RMSE between thermal imaging and piezoplethysmography stayed around 0.71 ± 0.30 breaths per minute (phase A). This study demonstrates that infrared thermography may be a promising, clinically relevant alternative for the assessment of HR and RR. Full article

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

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9 pages, 4832 KiB

Open AccessArticle

Frequency Invariability of (Pb,La)(Zr,Ti)O₃ Antiferroelectric Thick-Film Micro-Cantilevers

by Kun An^1,*

, Xuechen Jin¹, Jiang Meng², Xiao Li¹ and Yifeng Ren¹

¹ School of Electrical and Control Engineering, North University of China, Taiyuan 030051, China

² Advanced Manufacturing Technology of Provincial Key Laboratory, North University of China, Taiyuan 030051, China

Sensors 2018, 18(5), 1542; https://doi.org/10.3390/s18051542 - 13 May 2018

Cited by 2 | Viewed by 3453

Abstract

Micro-electromechanical systems comprising antiferroelectric layers can offer both actuation and transduction to integrated technologies. Micro-cantilevers based on the (Pb_0.97La_0.02)(Zr_0.95Ti_0.05)O₃ (PLZT) antiferroelectric thick film are fabricated by the micro-nano manufacturing process, to utilize the effect [...] Read more.

Micro-electromechanical systems comprising antiferroelectric layers can offer both actuation and transduction to integrated technologies. Micro-cantilevers based on the (Pb_0.97La_0.02)(Zr_0.95Ti_0.05)O₃ (PLZT) antiferroelectric thick film are fabricated by the micro-nano manufacturing process, to utilize the effect of phase transition induced strain and sharp phase switch of antiferroelectric materials. When micro-cantilevers made of antiferroelectric thick films were driven by sweep voltages, there were two resonant peaks corresponding to the natural frequency shift from 27.8 to 27.0 kHz, before and after phase transition. This is the compensation principle for the PLZT micro-cantilever to tune the natural frequency by the amplitude modulation of driving voltage, rather than of frequency modulation. Considering the natural frequency shift about 0.8 kHz and the frequency tuning ability about 156 Hz/V before the phase transition, this can compensate the frequency shift caused by increasing temperature by tuning only the amplitude of driving voltage, when the ultrasonic micro-transducer made of antiferroelectric thick films works for such a long period. Therefore, antiferroelectric thick films with hetero-structures incorporated into PLZT micro-cantilevers not only require a lower driving voltage (no more than 40 V) than rival bulk piezoelectric ceramics, but also exhibit better performance of frequency invariability, based on the amplitude modulation. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 15924 KiB

Open AccessArticle

Integral Sensor Fault Detection and Isolation for Railway Traction Drive

by Fernando Garramiola^*

, Jon Del Olmo, Javier Poza, Patxi Madina and Gaizka Almandoz

Faculty of Engineering, Mondragon Unibertsitatea, 20500 Arrasate - Mondragón, Spain

Sensors 2018, 18(5), 1543; https://doi.org/10.3390/s18051543 - 13 May 2018

Cited by 30 | Viewed by 6492

Abstract

Due to the increasing importance of reliability and availability of electric traction drives in Railway applications, early detection of faults has become an important key for Railway traction drive manufacturers. Sensor faults are important sources of failures. Among the different fault diagnosis approaches, [...] Read more.

Due to the increasing importance of reliability and availability of electric traction drives in Railway applications, early detection of faults has become an important key for Railway traction drive manufacturers. Sensor faults are important sources of failures. Among the different fault diagnosis approaches, in this article an integral diagnosis strategy for sensors in traction drives is presented. Such strategy is composed of an observer-based approach for direct current (DC)-link voltage and catenary current sensors, a frequency analysis approach for motor current phase sensors and a hardware redundancy solution for speed sensors. None of them requires any hardware change requirement in the actual traction drive. All the fault detection and isolation approaches have been validated in a Hardware-in-the-loop platform comprising a Real Time Simulator and a commercial Traction Control Unit for a tram. In comparison to safety-critical systems in Aerospace applications, Railway applications do not need instantaneous detection, and the diagnosis is validated in a short time period for reliable decision. Combining the different approaches and existing hardware redundancy, an integral fault diagnosis solution is provided, to detect and isolate faults in all the sensors installed in the traction drive. Full article

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

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17 pages, 7785 KiB

Open AccessArticle

Design of an Inertial-Sensor-Based Data Glove for Hand Function Evaluation

by Bor-Shing Lin¹

, I-Jung Lee^1,2

, Shu-Yu Yang³, Yi-Chiang Lo⁴, Junghsi Lee⁴ and Jean-Lon Chen^5,6,7,*

¹ Department of Computer Science and Information Engineering, National Taipei University, New Taipei City 23741, Taiwan

² College of Electrical Engineering and Computer Science, National Taipei University, New Taipei City 23741, Taiwan

³ Department of Physical Medicine and Rehabilitation, Chi-Mei Medical Center, Tainan 71004, Taiwan

⁴ Department of Electrical Engineering, Yuan Ze University, Taoyuan City 32003, Taiwan

⁵ Department of Physical Medicine & Rehabilitation, Taoyuan Chang Gung Memorial Hospital, Taoyuan City 333, Taiwan

⁶ Center for Healthy and Aging Research, Chang Gung University, Taoyuan City 33302, Taiwan

⁷ School of Medicine, Medical College, Chang Gung University, Taoyuan City 33302, Taiwan

Sensors 2018, 18(5), 1545; https://doi.org/10.3390/s18051545 - 13 May 2018

Cited by 86 | Viewed by 8742

Abstract

Capturing hand motions for hand function evaluations is essential in the medical field. Various data gloves have been developed for rehabilitation and manual dexterity assessments. This study proposed a modular data glove with 9-axis inertial measurement units (IMUs) to obtain static and dynamic [...] Read more.

Capturing hand motions for hand function evaluations is essential in the medical field. Various data gloves have been developed for rehabilitation and manual dexterity assessments. This study proposed a modular data glove with 9-axis inertial measurement units (IMUs) to obtain static and dynamic parameters during hand function evaluation. A sensor fusion algorithm is used to calculate the range of motion of joints. The data glove is designed to have low cost, easy wearability, and high reliability. Owing to the modular design, the IMU board is independent and extensible and can be used with various microcontrollers to realize more medical applications. This design greatly enhances the stability and maintainability of the glove. Full article

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

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17 pages, 4790 KiB

Open AccessArticle

Application and Comparison of the MODIS-Derived Enhanced Vegetation Index to VIIRS, Landsat 5 TM and Landsat 8 OLI Platforms: A Case Study in the Arid Colorado River Delta, Mexico

by Christopher J. Jarchow^1,2,*, Kamel Didan³

, Armando Barreto-Muñoz³, Pamela L. Nagler²

and Edward P. Glenn⁴

¹ Soil, Water, and Environmental Science (SWES), University of Arizona, Tucson, AZ 85719, USA

² US Geological Survey, Southwest Biological Science Center, University of Arizona, 520 N. Park Avenue, Tucson, AZ 85719, USA

³ Biosystems Engineering, University of Arizona, Tucson, AZ 85719, USA

⁴ Environmental Research Laboratory, University of Arizona, Tucson, AZ 85719, USA

Sensors 2018, 18(5), 1546; https://doi.org/10.3390/s18051546 - 13 May 2018

Cited by 52 | Viewed by 6785

Abstract

The Enhanced Vegetation Index (EVI) is a key Earth science parameter used to assess vegetation, originally developed and calibrated for the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra and Aqua satellites. With the impending decommissioning of the MODIS sensors by the year [...] Read more.

The Enhanced Vegetation Index (EVI) is a key Earth science parameter used to assess vegetation, originally developed and calibrated for the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra and Aqua satellites. With the impending decommissioning of the MODIS sensors by the year 2020/2022, alternative platforms will need to be used to estimate EVI. We compared Landsat 5 (2000–2011), 8 (2013–2016) and the Visible Infrared Imaging Radiometer Suite (VIIRS; 2013–2016) to MODIS EVI (2000–2016) over a 420,083-ha area of the arid lower Colorado River Delta in Mexico. Over large areas with mixed land cover or agricultural fields, we found high correspondence between Landsat and MODIS EVI (R² = 0.93 for the entire area studied and 0.97 for agricultural fields), but the relationship was weak over bare soil (R² = 0.27) and riparian vegetation (R² = 0.48). The correlation between MODIS and Landsat EVI was higher over large, homogeneous areas and was generally lower in narrow riparian areas. VIIRS and MODIS EVI were highly similar (R² = 0.99 for the entire area studied) and did not show the same decrease in performance in smaller, narrower regions as Landsat. Landsat and VIIRS provide EVI estimates of similar quality and characteristics to MODIS, but scale, seasonality and land cover type(s) should be considered before implementing Landsat EVI in a particular area. Full article

(This article belongs to the Section Remote Sensors)

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11 pages, 2403 KiB

Open AccessArticle

CNT Foam-Embedded Micro Gas Preconcentrator for Low-Concentration Ethane Measurements

by Janghyeon Lee¹

and Si-Hyung Lim^2,*

¹ Department of Mechanics and Design, Kookmin University, Seoul 136-702, Korea

² School of Mechanical Engineering, Kookmin University, Seoul 136-702, Korea

Sensors 2018, 18(5), 1547; https://doi.org/10.3390/s18051547 - 14 May 2018

Cited by 14 | Viewed by 4324

Abstract

Breath analysis has become increasingly important as a noninvasive process for the clinical diagnosis of patients suffering from various diseases. Many commercial gas preconcentration instruments are already being used to overcome the detection limits of commercial gas sensors for gas concentrations which are [...] Read more.

Breath analysis has become increasingly important as a noninvasive process for the clinical diagnosis of patients suffering from various diseases. Many commercial gas preconcentration instruments are already being used to overcome the detection limits of commercial gas sensors for gas concentrations which are as low as ~100 ppb in exhaled breath. However, commercial instruments are large and expensive, and they require high power consumption and intensive maintenance. In the proposed study, a micro gas preconcentrator (μ-PC) filled with a carbon nanotube (CNT) foam as an adsorbing material was designed and fabricated for the detection of low-concentration ethane, which is known to be one of the most important biomarkers related to chronic obstructive pulmonary disease (COPD) and asthma. A comparison of the performance of two gas-adsorbing materials, i.e., the proposed CNT foam and commercial adsorbing material, was performed using the developed μ-PC. The experimental results showed that the synthesized CNT foam performs better than a commercial adsorbing material owing to its lower pressure drop and greater preconcentration efficiency in the μ-PC. The present results show that the application of CNT foam-embedded μ-PC in portable breath analysis systems holds great promise. Full article

(This article belongs to the Section Chemical Sensors)

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20 pages, 7110 KiB

Open AccessArticle

Development and Performance Evaluation of Image-Based Robotic Waxing System for Detailing Automobiles

by Chi-Ying Lin^*

and Bing-Cheng Hsu

Department of Mechanical Engineering, National Taiwan University of Science and Technology, No. 43, Keelung Rd., Sec. 4, Taipei 106, Taiwan

Sensors 2018, 18(5), 1548; https://doi.org/10.3390/s18051548 - 14 May 2018

Viewed by 3888

Abstract

Waxing is an important aspect of automobile detailing, aimed at protecting the finish of the car and preventing rust. At present, this delicate work is conducted manually due to the need for iterative adjustments to achieve acceptable quality. This paper presents a robotic [...] Read more.

Waxing is an important aspect of automobile detailing, aimed at protecting the finish of the car and preventing rust. At present, this delicate work is conducted manually due to the need for iterative adjustments to achieve acceptable quality. This paper presents a robotic waxing system in which surface images are used to evaluate the quality of the finish. An RGB-D camera is used to build a point cloud that details the sheet metal components to enable path planning for a robot manipulator. The robot is equipped with a multi-axis force sensor to measure and control the forces involved in the application and buffing of wax. Images of sheet metal components that were waxed by experienced car detailers were analyzed using image processing algorithms. A Gaussian distribution function and its parameterized values were obtained from the images for use as a performance criterion in evaluating the quality of surfaces prepared by the robotic waxing system. Waxing force and dwell time were optimized using a mathematical model based on the image-based criterion used to measure waxing performance. Experimental results demonstrate the feasibility of the proposed robotic waxing system and image-based performance evaluation scheme. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 5830 KiB

Open AccessArticle

A Novel Strain Sensor with Large Measurement Range Based on All Fiber Mach-Zehnder Interferometer

by Xinran Dong, Haifeng Du, Xiaoyan Sun^*, Zhi Luo^*

and Ji’an Duan

State Key Laboratory of High Performance Complex Manufacturing, College of Mechanical and Electrical Engineering, Central South University, 932 South Lushan Street, Changsha 410083, China

Sensors 2018, 18(5), 1549; https://doi.org/10.3390/s18051549 - 14 May 2018

Cited by 56 | Viewed by 5066

Abstract

We have proposed a high sensitive photonic crystal fiber (PCF) strain sensor based on the Mach-Zehnder interferometer (MZI). The sensing head is formed by all-fiber in-line single mode-multimode-photonic-crystal-single mode fiber (SMPS) structure, using only the splicing method. Such a strain sensor exhibited a [...] Read more.

We have proposed a high sensitive photonic crystal fiber (PCF) strain sensor based on the Mach-Zehnder interferometer (MZI). The sensing head is formed by all-fiber in-line single mode-multimode-photonic-crystal-single mode fiber (SMPS) structure, using only the splicing method. Such a strain sensor exhibited a high sensitivity of −2.21 pm/με within a large measurement range of up to 5000 με and a large fringe visibility of up to 24 dB. Moreover, it was found that the strain sensitivity was weekly dependent of the length of PCF or MMF. In addition, the sensor exhibited the advantages of simplicity of fabrication, high sensitivity and larger fringe visibility. Full article

(This article belongs to the Special Issue Integrated Sensors)

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12 pages, 2134 KiB

Open AccessArticle

Determination of Tumor Marker Carcinoembryonic Antigen with Biosensor Based on Optical Quantum Weak Measurements

by Tian Guan^1,2,*, Xiangnan Wang^1,2, Dongmei Li^2,3, Yilong Zhang^2,3, Yonghong He^2,3,*, Lixuan Shi^2,3, Yiqing Liu^1,2, Yuxuan Yang^1,2, Yang Xu^2,3 and Rui Cui⁴

¹ Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, China

² Shenzhen Key Laboratory for Minimal Invasive Medical Technologies, Institute of Optical Imaging and Sensing, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China

³ Department of Physics, Tsinghua University, Beijing 100084, China

⁴ Shenzhen Maternity & Child Healthcare Hospital, Shenzhen 518055, China

Sensors 2018, 18(5), 1550; https://doi.org/10.3390/s18051550 - 14 May 2018

Cited by 14 | Viewed by 4001

Abstract

A phase-sensitive weak measurement biosensor was proposed for the detection of carcinoembryonic antigen (CEA), one common category of tumor markers. The total internal reflection (TIR) at the interface of the prism without precious metal coating was exploited to introduce the phase delay between [...] Read more.

A phase-sensitive weak measurement biosensor was proposed for the detection of carcinoembryonic antigen (CEA), one common category of tumor markers. The total internal reflection (TIR) at the interface of the prism without precious metal coating was exploited to introduce the phase delay between horizontal and vertical polarizations, which can be determined through the central wavelength shift of output spectra for the sensing of the refractive index of the sample. In the weak measurement analysis, the specific binding reaction of tumor markers with a refractive index change on the surface of the prism can be monitored in real time through the central wavelength shift. With the specific absorption measurement, the feasibility of this weak measurement-based biosensor was experimentally demonstrated. We provide a low cost and convenient approach for tumor marker detection. Full article

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

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13 pages, 1139 KiB

Open AccessArticle

Hand-Held Refractometer-Based Measurement and Excess Permittivity Analysis Method for Detection of Diesel Oils Adulterated by Kerosene in Field Conditions

by Boniphace Kanyathare^*

and Kai-Erik Peiponen^*

Department of Physics and Mathematics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland

Sensors 2018, 18(5), 1551; https://doi.org/10.3390/s18051551 - 14 May 2018

Cited by 21 | Viewed by 4317

Abstract

Adulteration of fuels is a major problem, especially in developing and third world countries. One such case is the adulteration of diesel oil by kerosene. This problem contributes to air pollution, which leads to other far-reaching adverse effects, such as climate change. The [...] Read more.

Adulteration of fuels is a major problem, especially in developing and third world countries. One such case is the adulteration of diesel oil by kerosene. This problem contributes to air pollution, which leads to other far-reaching adverse effects, such as climate change. The objective of this study was to develop a relatively easy measurement method based on an inexpensive, handheld Abbe refractometer for the detection of adulteration and estimation of the ascending order of the amount of kerosene present in adulterated samples in field conditions. We achieved this by increasing the volume of pure diesel sample in the adulterated diesel oil, and measuring the trend of refractive index change, and next, exploiting the true and ideal permittivities of the binary mixture. The permittivity can be obtained with the aid of the measured refractive index of a liquid. Due to the molecular interactions, the true and ideal permittivities of diesel–kerosene binary liquid mixture have a mismatch which can be used to screen for adulterated diesel oils. The difference between the true and the ideal permittivity is the so-called excess permittivity. We first investigated a training set of diesel oils in laboratory in Finland, using the accurate table model Abbe refractometer and depicting the behavior of the excess permittivity of the mixture of diesel oil and kerosene. Then, we measured same samples in the laboratory using a handheld refractometer. Finally, preliminary field measurements using the handheld device were performed in Tanzania to assess the accuracy and possibility of applying the suggested method in field conditions. We herein show that it is not only possible to detect even relatively low adulteration levels of diesel in kerosene—namely, 5%, 10%, and 15%—but also it is possible to monitor the ascending order of adulteration for different adulterated diesel samples. We propose that the method of increasing the volume of an unknown (suspected) diesel oil sample by adding a known authentic diesel sample and monitoring excess permittivity is useful for the screening of adulterated diesel oil in field measurement conditions. Full article

(This article belongs to the Section Chemical Sensors)

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14 pages, 3705 KiB

Open AccessArticle

A Combined Gravity Compensation Method for INS Using the Simplified Gravity Model and Gravity Database

by Xiao Zhou^1,2,*, Gongliu Yang^1,2, Jing Wang³ and Zeyang Wen^1,2

¹ School of Instrument Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China

² Science and Technology on Inertial Laboratory, Beihang University, Beijing 100191, China

³ School of Mechatronices and Information Engineering, China Mining University, Beijing 100083, China

Sensors 2018, 18(5), 1552; https://doi.org/10.3390/s18051552 - 14 May 2018

Cited by 11 | Viewed by 3993

Abstract

In recent decades, gravity compensation has become an important way to reduce the position error of an inertial navigation system (INS), especially for a high-precision INS, because of the extensive application of high precision inertial sensors (accelerometers and gyros). This paper first deducts [...] Read more.

In recent decades, gravity compensation has become an important way to reduce the position error of an inertial navigation system (INS), especially for a high-precision INS, because of the extensive application of high precision inertial sensors (accelerometers and gyros). This paper first deducts the INS’s solution error considering gravity disturbance and simulates the results. Meanwhile, this paper proposes a combined gravity compensation method using a simplified gravity model and gravity database. This new combined method consists of two steps all together. Step 1 subtracts the normal gravity using a simplified gravity model. Step 2 first obtains the gravity disturbance on the trajectory of the carrier with the help of ELM training based on the measured gravity data (provided by Institute of Geodesy and Geophysics; Chinese Academy of sciences), and then compensates it into the error equations of the INS, considering the gravity disturbance, to further improve the navigation accuracy. The effectiveness and feasibility of this new gravity compensation method for the INS are verified through vehicle tests in two different regions; one is in flat terrain with mild gravity variation and the other is in complex terrain with fierce gravity variation. During 2 h vehicle tests, the positioning accuracy of two tests can improve by 20% and 38% respectively, after the gravity is compensated by the proposed method. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 3837 KiB

Open AccessArticle

Time-Sharing-Based Synchronization and Performance Evaluation of Color-Independent Visual-MIMO Communication

by Tae-Ho Kwon, Jai-Eun Kim

and Ki-Doo Kim^*

Department of Electronic Engineering, Kookmin University, Seongbuk-gu, Seoul 02707, Korea

Sensors 2018, 18(5), 1553; https://doi.org/10.3390/s18051553 - 14 May 2018

Cited by 12 | Viewed by 3763

Abstract

In the field of communication, synchronization is always an important issue. The communication between a light-emitting diode (LED) array (LEA) and a camera is known as visual multiple-input multiple-output (MIMO), for which the data transmitter and receiver must be synchronized for seamless communication. [...] Read more.

In the field of communication, synchronization is always an important issue. The communication between a light-emitting diode (LED) array (LEA) and a camera is known as visual multiple-input multiple-output (MIMO), for which the data transmitter and receiver must be synchronized for seamless communication. In visual-MIMO, LEDs generally have a faster data rate than the camera. Hence, we propose an effective time-sharing-based synchronization technique with its color-independent characteristics providing the key to overcome this synchronization problem in visual-MIMO communication. We also evaluated the performance of our synchronization technique by varying the distance between the LEA and camera. A graphical analysis is also presented to compare the symbol error rate (SER) at different distances. Full article

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

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15 pages, 2259 KiB

Open AccessArticle

A Lightweight Protocol for Secure Video Streaming

by Algimantas Venčkauskas^1,*

, Nerijus Morkevicius¹

, Kazimieras Bagdonas¹, Robertas Damaševičius²

and Rytis Maskeliūnas³

¹ Department of Computers Science, Kaunas University of Technology, Studentu 50-212, LT-51368 Kaunas, Lithuania

² Department of Software Engineering, Kaunas University of Technology, Studentu 50-212, LT-51368 Kaunas, Lithuania

³ Department of Multimedia Engineering, Kaunas University of Technology, Studentu 50-212, LT-51368 Kaunas, Lithuania

Sensors 2018, 18(5), 1554; https://doi.org/10.3390/s18051554 - 14 May 2018

Cited by 27 | Viewed by 4565

Abstract

The Internet of Things (IoT) introduces many new challenges which cannot be solved using traditional cloud and host computing models. A new architecture known as fog computing is emerging to address these technological and security gaps. Traditional security paradigms focused on providing perimeter-based [...] Read more.

The Internet of Things (IoT) introduces many new challenges which cannot be solved using traditional cloud and host computing models. A new architecture known as fog computing is emerging to address these technological and security gaps. Traditional security paradigms focused on providing perimeter-based protections and client/server point to point protocols (e.g., Transport Layer Security (TLS)) are no longer the best choices for addressing new security challenges in fog computing end devices, where energy and computational resources are limited. In this paper, we present a lightweight secure streaming protocol for the fog computing “Fog Node-End Device” layer. This protocol is lightweight, connectionless, supports broadcast and multicast operations, and is able to provide data source authentication, data integrity, and confidentiality. The protocol is based on simple and energy efficient cryptographic methods, such as Hash Message Authentication Codes (HMAC) and symmetrical ciphers, and uses modified User Datagram Protocol (UDP) packets to embed authentication data into streaming data. Data redundancy could be added to improve reliability in lossy networks. The experimental results summarized in this paper confirm that the proposed method efficiently uses energy and computational resources and at the same time provides security properties on par with the Datagram TLS (DTLS) standard. Full article

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

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19 pages, 6418 KiB

Open AccessArticle

Design of a Low-Power, Small-Area AEC-Q100-Compliant SENT Transmitter in Signal Conditioning IC for Automotive Pressure and Temperature Complex Sensors in 180 Nm CMOS Technology

by Imran Ali¹

, Behnam Samadpoor Rikhan¹, Dong-Gyu Kim¹, Dong-Soo Lee¹, Muhammad Riaz Ur Rehman¹, Hamed Abbasizadeh¹, Muhammad Asif¹, Minjae Lee², Keum Cheol Hwang¹

, Youngoo Yang¹ and Kang-Yoon Lee^1,*

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

² School of Information and Communications, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea

Sensors 2018, 18(5), 1555; https://doi.org/10.3390/s18051555 - 14 May 2018

Cited by 10 | Viewed by 6699

Abstract

In this paper, a low-power and small-area Single Edge Nibble Transmission (SENT) transmitter design is proposed for automotive pressure and temperature complex sensor applications. To reduce the cost and size of the hardware, the pressure and temperature information is processed with a single [...] Read more.

In this paper, a low-power and small-area Single Edge Nibble Transmission (SENT) transmitter design is proposed for automotive pressure and temperature complex sensor applications. To reduce the cost and size of the hardware, the pressure and temperature information is processed with a single integrated circuit (IC) and transmitted at the same time to the electronic control unit (ECU) through SENT. Due to its digital nature, it is immune to noise, has reduced sensitivity to electromagnetic interference (EMI), and generates low EMI. It requires only one PAD for its connectivity with ECU, and thus reduces the pin requirements, simplifies the connectivity, and minimizes the printed circuit board (PCB) complexity. The design is fully synthesizable, and independent of technology. The finite state machine-based approach is employed for area efficient implementation, and to translate the proposed architecture into hardware. The IC is fabricated in 1P6M 180 nm CMOS process with an area of (116 μm × 116 μm) and 4.314 K gates. The current consumption is 50 μA from a 1.8 V supply with a total 90 μW power. For compliance with AEC-Q100 for automotive reliability, a reverse and over voltage protection circuit is also implemented with human body model (HBM) electro-static discharge (ESD) of +6 kV, reverse voltage of −16 V to 0 V, over voltage of 8.2 V to 16 V, and fabricated area of 330 μm × 680 μm. The extensive testing, measurement, and simulation results prove that the design is fully compliant with SAE J2716 standard. Full article

(This article belongs to the Section Physical Sensors)

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32 pages, 4213 KiB

Open AccessArticle

A Personalized QoS Prediction Approach for CPS Service Recommendation Based on Reputation and Location-Aware Collaborative Filtering

by Li Kuang^*

, Long Yu

, Lan Huang, Yin Wang, Pengju Ma, Chuanbin Li and Yujia Zhu

School of Software, Central South University, Changsha 410075, China

Sensors 2018, 18(5), 1556; https://doi.org/10.3390/s18051556 - 14 May 2018

Cited by 57 | Viewed by 4966

Abstract

With the rapid development of cyber-physical systems (CPS), building cyber-physical systems with high quality of service (QoS) has become an urgent requirement in both academia and industry. During the procedure of building Cyber-physical systems, it has been found that a large number of [...] Read more.

With the rapid development of cyber-physical systems (CPS), building cyber-physical systems with high quality of service (QoS) has become an urgent requirement in both academia and industry. During the procedure of building Cyber-physical systems, it has been found that a large number of functionally equivalent services exist, so it becomes an urgent task to recommend suitable services from the large number of services available in CPS. However, since it is time-consuming, and even impractical, for a single user to invoke all of the services in CPS to experience their QoS, a robust QoS prediction method is needed to predict unknown QoS values. A commonly used method in QoS prediction is collaborative filtering, however, it is hard to deal with the data sparsity and cold start problem, and meanwhile most of the existing methods ignore the data credibility issue. Thence, in order to solve both of these challenging problems, in this paper, we design a framework of QoS prediction for CPS services, and propose a personalized QoS prediction approach based on reputation and location-aware collaborative filtering. Our approach first calculates the reputation of users by using the Dirichlet probability distribution, so as to identify untrusted users and process their unreliable data, and then it digs out the geographic neighborhood in three levels to improve the similarity calculation of users and services. Finally, the data from geographical neighbors of users and services are fused to predict the unknown QoS values. The experiments using real datasets show that our proposed approach outperforms other existing methods in terms of accuracy, efficiency, and robustness. Full article

(This article belongs to the Special Issue Advances on Resources Management for Multi-Platform Infrastructures)

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20 pages, 591 KiB

Open AccessArticle

Degree-of-Freedom Strengthened Cascade Array for DOD-DOA Estimation in MIMO Array Systems

by Bobin Yao^1,*

, Zhi Dong², Weile Zhang³, Wei Wang^3,† and Qisheng Wu¹

¹ School of Electronic and Control Engineering, Chang’an University, Xi’an 710064, China

² School of Highway, Chang’an University, Xi’an 710064, China

³ School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China

^† current address: School of Information Engineering, Xijing University, Xi’an 710123, China

Sensors 2018, 18(5), 1557; https://doi.org/10.3390/s18051557 - 14 May 2018

Cited by 11 | Viewed by 4025

Abstract

In spatial spectrum estimation, difference co-array can provide extra degrees-of-freedom (DOFs) for promoting parameter identifiability and parameter estimation accuracy. For the sake of acquiring as more DOFs as possible with a given number of physical sensors, we herein design a novel sensor array [...] Read more.

In spatial spectrum estimation, difference co-array can provide extra degrees-of-freedom (DOFs) for promoting parameter identifiability and parameter estimation accuracy. For the sake of acquiring as more DOFs as possible with a given number of physical sensors, we herein design a novel sensor array geometry named cascade array. This structure is generated by systematically connecting a uniform linear array (ULA) and a non-uniform linear array, and can provide more DOFs than some exist array structures but less than the upper-bound indicated by minimum redundant array (MRA). We further apply this cascade array into multiple input multiple output (MIMO) array systems, and propose a novel joint direction of departure (DOD) and direction of arrival (DOA) estimation algorithm, which is based on a reduced-dimensional weighted subspace fitting technique. The algorithm is angle auto-paired and computationally efficient. Theoretical analysis and numerical simulations prove the advantages and effectiveness of the proposed array structure and the related algorithm. Full article

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

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18 pages, 2349 KiB

Open AccessArticle

Modelling of Cavity Optomechanical Magnetometers

by Yimin Yu, Stefan Forstner, Halina Rubinsztein-Dunlop

and Warwick Paul Bowen^*

ARC Centre for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4072, Australia

Sensors 2018, 18(5), 1558; https://doi.org/10.3390/s18051558 - 14 May 2018

Cited by 13 | Viewed by 5828

Abstract

Cavity optomechanical magnetic field sensors, constructed by coupling a magnetostrictive material to a micro-toroidal optical cavity, act as ultra-sensitive room temperature magnetometers with tens of micrometre size and broad bandwidth, combined with a simple operating scheme. Here, we develop a general recipe for [...] Read more.

Cavity optomechanical magnetic field sensors, constructed by coupling a magnetostrictive material to a micro-toroidal optical cavity, act as ultra-sensitive room temperature magnetometers with tens of micrometre size and broad bandwidth, combined with a simple operating scheme. Here, we develop a general recipe for predicting the field sensitivity of these devices. Several geometries are analysed, with a highest predicted sensitivity of 180 p

T / \sqrt{Hz}

at 28

μ

m resolution limited by thermal noise in good agreement with previous experimental observations. Furthermore, by adjusting the composition of the magnetostrictive material and its annealing process, a sensitivity as good as 20 p

T / \sqrt{Hz}

may be possible at the same resolution. This method paves a way for future design of magnetostrictive material based optomechanical magnetometers, possibly allowing both scalar and vectorial magnetometers. Full article

(This article belongs to the Special Issue Sensors Based on Quantum Phenomena)

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18 pages, 3237 KiB

Open AccessArticle

Multi-Touch Tabletop System Using Infrared Image Recognition for User Position Identification

by Shota Suto^1,2, Toshiya Watanabe³, Susumu Shibusawa^4,* and Masaru Kamada⁵

¹ Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki 316-8511, Japan

² East Japan Institute of Technology Co., Ltd., Hitachi, Ibaraki 319-1221, Japan

³ National Institute of Technology, Gunma College, Maebashi, Gunma 371-8530, Japan

⁴ Hitachi Campus, Ibaraki University, Hitachi, Ibaraki 316-8511, Japan

⁵ College of Engineering, Ibaraki University, Hitachi, Ibaraki 316-8511, Japan

Sensors 2018, 18(5), 1559; https://doi.org/10.3390/s18051559 - 14 May 2018

Cited by 7 | Viewed by 5000

Abstract

A tabletop system can facilitate multi-user collaboration in a variety of settings, including small meetings, group work, and education and training exercises. The ability to identify the users touching the table and their positions can promote collaborative work among participants, so methods have [...] Read more.

A tabletop system can facilitate multi-user collaboration in a variety of settings, including small meetings, group work, and education and training exercises. The ability to identify the users touching the table and their positions can promote collaborative work among participants, so methods have been studied that involve attaching sensors to the table, chairs, or to the users themselves. An effective method of recognizing user actions without placing a burden on the user would be some type of visual process, so the development of a method that processes multi-touch gestures by visual means is desired. This paper describes the development of a multi-touch tabletop system using infrared image recognition for user position identification and presents the results of touch-gesture recognition experiments and a system-usability evaluation. Using an inexpensive FTIR touch panel and infrared light, this system picks up the touch areas and the shadow area of the user’s hand by an infrared camera to establish an association between the hand and table touch points and estimate the position of the user touching the table. The multi-touch gestures prepared for this system include an operation to change the direction of an object to face the user and a copy operation in which two users generate duplicates of an object. The system-usability evaluation revealed that prior learning was easy and that system operations could be easily performed. Full article

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

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17 pages, 1831 KiB

Open AccessArticle

A Novel DFT-Based DOA Estimation by a Virtual Array Extension Using Simple Multiplications for FMCW Radar

by Bongseok Kim, Sangdong Kim and Jonghun Lee^*

Advanced Radar Technology Laboratory (ART Lab.), Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea

Sensors 2018, 18(5), 1560; https://doi.org/10.3390/s18051560 - 14 May 2018

Cited by 42 | Viewed by 5810

Abstract

We propose a novel discrete Fourier transform (DFT)-based direction of arrival (DOA) estimation by a virtual array extension using simple multiplications for frequency modulated continuous wave (FMCW) radar. DFT-based DOA estimation is usually employed in radar systems because it provides the advantage of [...] Read more.

We propose a novel discrete Fourier transform (DFT)-based direction of arrival (DOA) estimation by a virtual array extension using simple multiplications for frequency modulated continuous wave (FMCW) radar. DFT-based DOA estimation is usually employed in radar systems because it provides the advantage of low complexity for real-time signal processing. In order to enhance the resolution of DOA estimation or to decrease the missing detection probability, it is essential to have a considerable number of channel signals. However, due to constraints of space and cost, it is not easy to increase the number of channel signals. In order to address this issue, we increase the number of effective channel signals by generating virtual channel signals using simple multiplications of the given channel signals. The increase in channel signals allows the proposed scheme to detect DOA more accurately than the conventional scheme while using the same number of channel signals. Simulation results show that the proposed scheme achieves improved DOA estimation compared to the conventional DFT-based method. Furthermore, the effectiveness of the proposed scheme in a practical environment is verified through the experiment. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 1568 KiB

Open AccessArticle

Hyperspectral Imaging and Spectrometry-Derived Spectral Features for Bitter Pit Detection in Storage Apples

by Sanaz Jarolmasjed¹, Lav R. Khot^1,2 and Sindhuja Sankaran^1,2,*

¹ Department of Biological Systems Engineering, Washington State University, PO Box 646120, Pullman, WA 99164, USA

² Center for Precision and Automated Agricultural Systems, Washington State University, 24106 North Bunn Road, Prosser, WA 99350, USA

Sensors 2018, 18(5), 1561; https://doi.org/10.3390/s18051561 - 15 May 2018

Cited by 16 | Viewed by 4872

Abstract

Bitter pit is one of the most important disorders in apples. Some of the fresh market apple varieties are susceptible to bitter pit disorder. In this study, visible–near-infrared spectrometry-based reflectance spectral data (350–2500 nm) were acquired from 2014, 2015 and 2016 harvest produce [...] Read more.

Bitter pit is one of the most important disorders in apples. Some of the fresh market apple varieties are susceptible to bitter pit disorder. In this study, visible–near-infrared spectrometry-based reflectance spectral data (350–2500 nm) were acquired from 2014, 2015 and 2016 harvest produce after 63 days of storage at 5 °C. Selected spectral features from 2014 season were used to classify the healthy and bitter pit samples from three years. In addition, these spectral features were also validated using hyperspectral imagery data collected on 2016 harvest produce after storage in a commercial storage facility for 5 months. The hyperspectral images were captured from either sides of apples in the range of 550–1700 nm. These images were analyzed to extract additional set of spectral features that were effective in bitter pit detection. Based on these features, an automated spatial data analysis algorithm was developed to detect bitter pit points. The pit area was extracted, and logistic regression was used to define the categorizing threshold. This method was able to classify the healthy and bitter pit apples with an accuracy of 85%. Finally, hyperspectral imagery derived spectral features were re-evaluated on the visible–near-infrared reflectance data acquired with spectrometer. The pertinent partial least square regression classification accuracies were in the range of 90–100%. Overall, the study identified salient spectral features based on both hyperspectral spectrometry and imaging techniques that can be used to develop a sensing solution to sort the fruit on the packaging lines. Full article

(This article belongs to the Section Remote Sensors)

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9 pages, 1964 KiB

Open AccessArticle

Multivariate Analysis as a Tool to Identify Concentrations from Strongly Overlapping Gas Spectra

by Yannick Saalberg^1,2 and Marcus Wolff^1,*

¹ Heinrich Blasius Institute of Physical Technologies, Hamburg University of Applied Sciences, Berliner Tor 21, 20099 Hamburg, Germany

² School of Engineering and Computing, University of the West of Scotland, High Street, Paisley PA1 2BE, UK

Sensors 2018, 18(5), 1562; https://doi.org/10.3390/s18051562 - 15 May 2018

Cited by 8 | Viewed by 3658

Abstract

We applied a multivariate analysis (MVA) to spectroscopic data of gas mixtures in the mid-IR in order to calculate the concentrations of the single components which exhibit strongly overlapping absorption spectra. This is a common challenge in broadband spectroscopy. Photoacoustic (PA) measurements of [...] Read more.

We applied a multivariate analysis (MVA) to spectroscopic data of gas mixtures in the mid-IR in order to calculate the concentrations of the single components which exhibit strongly overlapping absorption spectra. This is a common challenge in broadband spectroscopy. Photoacoustic (PA) measurements of different volatile organic compounds (VOCs) in the wavelength region of 3250 nm to 3550 nm served as the exemplary detection technique. Partial least squares regression (PLS) was used to calculate concentrations from the PA spectra. After calibration, the PLS model was able to determine concentrations of single VOCs with a relative accuracy of 2.60%. Full article

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

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11 pages, 5905 KiB

Open AccessArticle

A Feasibility Study on Timber Damage Detection Using Piezoceramic-Transducer-Enabled Active Sensing

by Jicheng Zhang¹, Yongshui Huang¹ and Yu Zheng^2,*

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

² School of Environment and Civil Engineering, Dongguan University of Technology, Dongguan 523808, China

Sensors 2018, 18(5), 1563; https://doi.org/10.3390/s18051563 - 15 May 2018

Cited by 51 | Viewed by 4800

Abstract

In recent years, piezoelectric-based transducers and technologies have made significant progress towards structural health monitoring and damage evaluation for various metal and concrete structures. Timber is still commonly used as a construction material in practical engineering; however, there is a lack of research [...] Read more.

In recent years, piezoelectric-based transducers and technologies have made significant progress towards structural health monitoring and damage evaluation for various metal and concrete structures. Timber is still commonly used as a construction material in practical engineering; however, there is a lack of research on the health monitoring of timber-based structures using piezoelectric-based transducers and methods. This paper conducts a feasibility study on timber damage detection using surface-mounted piezoelectric patches, which enable the stress-wave-based active sensing approach. Typical damage modes in timber frame structures, such as surface cracks and holes, were investigated in this study. In the active sensing approach, one piezoceramic transducer is used as an actuator to generate stress waves, which propagate along the surface of the timber structure, and other piezoceramic transducers function as sensors to detect the propagating stress waves. Defects, such as a crack or a hole, induce additional attenuation to the propagating stress wave. Based on this attenuation, the proposed method can detect the defects using the wavelet-packet-based damage index, demonstrating its implementation potential for real-time timber damage detection. Full article

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

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19 pages, 6273 KiB

Open AccessArticle

Calibrating an Ionosonde for Ionospheric Attenuation Measurements

by Lorenzo Gilli, Umberto Sciacca^*

and Enrico Zuccheretti

Istituto Nazionale di Geofisica e Vulcanologia, 00143 Rome, Italy

Sensors 2018, 18(5), 1564; https://doi.org/10.3390/s18051564 - 15 May 2018

Cited by 4 | Viewed by 3060

Abstract

Vertical ionospheric soundings have been performed at almost all ionospheric observatories with little attention to measuring the attenuation of the signal between transmission and reception. When the absorption has been determined, this has been achieved by comparing the received power after the first [...] Read more.

Vertical ionospheric soundings have been performed at almost all ionospheric observatories with little attention to measuring the attenuation of the signal between transmission and reception. When the absorption has been determined, this has been achieved by comparing the received power after the first and second reflections, but this method has some limitations due to the unknown reflection coefficient of the ground and the non-continuous presence of the second reflection. This paper deals with a different method based on precise calibration of the sounding system, allowing determination of absolute signal attenuation after a single reflection. This approach is affected by a systematic error due to imperfect calibration of the antennas, but when the focus of interest is to measure a trend over a specified period, it is very accurate. The article describes how calibration was implemented, the measurement output formats, and finally it presents some results from a meaningful set of measurements in order to demonstrate what this method can accomplish. Full article

(This article belongs to the Section Remote Sensors)

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12 pages, 3140 KiB

Open AccessArticle

A Comparison of ACQ, AIE and AEE-Based Polymers Loaded on Polyurethane Foams as Sensors for Explosives Detection

by Zhiwei Chu¹, Zhuxin Fan¹, Xiang Zhang¹, Xiaofeng Tan², Dongxu Li¹

, Guohua Chen¹ and Qinghua Zhao^1,*

¹ College of Materials Science and Engineering, Huaqiao University, Xiamen 361021, China

² Department of Polymer Chemistry and Technology, Kaunas University of Technology, K. Barsauskog. 59, 51423 Kaunas, Lithuania

Sensors 2018, 18(5), 1565; https://doi.org/10.3390/s18051565 - 15 May 2018

Cited by 19 | Viewed by 5059

Abstract

An aggregation-caused quenching (ACQ)-active polymer (PF), an aggregation-induced emission (AIE)-active polymer (PFTPE) and an aggregation-enhanced emission (AEE)-active polymer (PTTPE) were synthesized by tetraphenylethane (TPE), fluorene and thiophene moieties. Polyurethane (PU) foams modified by PF, PFTPE and PTTPE, namely PU-PF, PU-PFTPE and PU-PTTPE, using [...] Read more.

An aggregation-caused quenching (ACQ)-active polymer (PF), an aggregation-induced emission (AIE)-active polymer (PFTPE) and an aggregation-enhanced emission (AEE)-active polymer (PTTPE) were synthesized by tetraphenylethane (TPE), fluorene and thiophene moieties. Polyurethane (PU) foams modified by PF, PFTPE and PTTPE, namely PU-PF, PU-PFTPE and PU-PTTPE, using ultrasonication-assisted method have been prepared. A comparative study of PU-PF, PU-PFTPE and PU-PTTPE for detection explosives had been performed, and significant fluorescence quenching was observed with the introduction of PA solutions. The as-prepared PU-PF, PU-PFTPE and PU-PTTPE sensors exhibited a superior sensitivity for PA solutions with different concentrations. Remarkably, PU-PF gave a quenching efficiency of 96.2%, higher than 93.5% for PU-PFTPE and 86.7% for PU-PTTPE at a PA concentration of 180 µg·mL⁻¹ in methanol, which was attributed to the effective energy transfer from the fluorophore (PF) to the nitro explosive (PA). This suggested that some ACQ polymers, applied to detect explosives, could afford better performances than AIE or AEE polymers through modification of structures and selection of adequate carriers. At the same time, these chemical sensors can be recycled many times. Full article

(This article belongs to the Section Chemical Sensors)

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22 pages, 4035 KiB

Open AccessArticle

A Crowdsensing Based Analytical Framework for Perceptional Degradation of OTT Web Browsing

by Ke Li^1,*, Hai Wang¹, Xiaolong Xu¹, Yu Du², Yuansheng Liu² and M. Omair Ahmad³

¹ College of Smart City, Beijing Union University, Beijing 100101, China

² College of Robotics, Beijing Union University, Beijing 100101, China

³ Department of Electrical and Computer Engineering, Concordia University, Montreal, QC H3G IM8, Canada

Sensors 2018, 18(5), 1566; https://doi.org/10.3390/s18051566 - 15 May 2018

Cited by 2 | Viewed by 2908

Abstract

Service perception analysis is crucial for understanding both user experiences and network quality as well as for maintaining and optimizing of mobile networks. Given the rapid development of mobile Internet and over-the-top (OTT) services, the conventional network-centric mode of network operation and maintenance [...] Read more.

Service perception analysis is crucial for understanding both user experiences and network quality as well as for maintaining and optimizing of mobile networks. Given the rapid development of mobile Internet and over-the-top (OTT) services, the conventional network-centric mode of network operation and maintenance is no longer effective. Therefore, developing an approach to evaluate and optimizing users’ service perceptions has become increasingly important. Meanwhile, the development of a new sensing paradigm, mobile crowdsensing (MCS), makes it possible to evaluate and analyze the user’s OTT service perception from end-user’s point of view other than from the network side. In this paper, the key factors that impact users’ end-to-end OTT web browsing service perception are analyzed by monitoring crowdsourced user perceptions. The intrinsic relationships among the key factors and the interactions between key quality indicators (KQI) are evaluated from several perspectives. Moreover, an analytical framework of perceptional degradation and a detailed algorithm are proposed whose goal is to identify the major factors that impact the perceptional degradation of web browsing service as well as their significance of contribution. Finally, a case study is presented to show the effectiveness of the proposed method using a dataset crowdsensed from a large number of smartphone users in a real mobile network. The proposed analytical framework forms a valuable solution for mobile network maintenance and optimization and can help improve web browsing service perception and network quality. Full article

(This article belongs to the Special Issue Crowd-Sensing and Remote Sensing Technologies for Smart Cities)

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13 pages, 3796 KiB

Open AccessArticle

A Facile Electrochemical Sensor Based on PyTS–CNTs for Simultaneous Determination of Cadmium and Lead Ions

by Ruyuan Jiang¹, Niantao Liu¹, Sanshuang Gao², Xamxikamar Mamat^2,*, Yuhong Su^1,*, Thomas Wagberg³, Yongtao Li², Xun Hu⁴ and Guangzhi Hu^2,*

¹ Key Laboratory of Oil/Gas Fine Chemical Engineering, Ministry of Education and Autonomous Region, College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046, China

² Key Laboratory of Chemistry of Plant Resources in Arid Regions, State Key Laboratory Basis of Xinjiang Indigenous Medicinal Plants Resource Utilization, The Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011, China

³ Department of Physics, Umeå University, Umeå 90187, Sweden

⁴ School of Material Science and Engineering, University of Jinan, Jinan 250022, China

Sensors 2018, 18(5), 1567; https://doi.org/10.3390/s18051567 - 15 May 2018

Cited by 45 | Viewed by 5991

Abstract

A simple and easy method was implemented for the contemporary detection of cadmium (Cd²⁺) and lead (Pb²⁺) ions using 1,3,6,8-pyrenetetrasulfonic acid sodium salt-functionalized carbon nanotubes nanocomposites (PyTS–CNTs). The morphology and composition of the obtained PyTS–CNTs were characterized using scanning [...] Read more.

A simple and easy method was implemented for the contemporary detection of cadmium (Cd²⁺) and lead (Pb²⁺) ions using 1,3,6,8-pyrenetetrasulfonic acid sodium salt-functionalized carbon nanotubes nanocomposites (PyTS–CNTs). The morphology and composition of the obtained PyTS–CNTs were characterized using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS). The experimental results confirmed that the fabricated PyTS–CNTs exhibited good selectivity and sensitivity for metal ion-sensing owing to the insertion of sulfonic acid groups. For Cd²⁺ and Pb²⁺, some of the electrochemical sensing parameters were evaluated by varying data such as the PyTS–CNT quantity loaded on the pyrolytic graphite electrode (PGE), pH of the acetate buffer, deposition time, and deposition potential. These parameters were optimized with differential pulse anodic sweeping voltammetry (DPASV). Under the optimal condition, the stripping peak current of the PyTS–CNTs/Nafion/PGE varies linearly with the heavy metal ion concentration, ranging from 1.0 μg L⁻¹ to 90 μg L⁻¹ for Cd²⁺ and from 1.0 μg L⁻¹ to 110 μg L⁻¹ for Pb²⁺. The limits of detection were estimated to be approximately 0.8 μg L⁻¹ for Cd²⁺ and 0.02 μg L⁻¹ for Pb²⁺. The proposed PyTS–CNTs/Nafion/PGE can be used as a rapid, simple, and controllable electrochemical sensor for the determination of toxic Cd²⁺ and Pb²⁺. Full article

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

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12 pages, 3133 KiB

Open AccessArticle

A High Aspect Ratio Bifurcated 128-Microchannel Microfluidic Device for Environmental Monitoring of Explosives

by Paul T. Charles^*, Varun Wadhwa, Amara Kouyate, Kelly J. Mesa-Donado, Andre A. Adams, Jeffrey R. Deschamps and Anne W. Kusterbeck

Center for Bio/Molecular Science and Engineering, Code 6900, U.S. Naval Research Laboratory, Washington, DC 20375, USA

Sensors 2018, 18(5), 1568; https://doi.org/10.3390/s18051568 - 15 May 2018

Cited by 16 | Viewed by 4937

Abstract

Design and evolution of explosives monitoring and detection platforms to address the challenges of trace level chemical identification have led investigations into the use of intricately designed microfluidic devices. Microfluidic devices are unique tools that possess distinct characteristics that, when designed properly and [...] Read more.

Design and evolution of explosives monitoring and detection platforms to address the challenges of trace level chemical identification have led investigations into the use of intricately designed microfluidic devices. Microfluidic devices are unique tools that possess distinct characteristics that, when designed properly and configured with optical and fluidic components, can produce detection platforms with unmatched performance levels. Herein, we report the design, fabrication and integration of a bifurcated high aspect ratio microfluidic device containing 128 microchannels (40 mm × 40 μm × 250 μm; L × W × H) for explosives detection at trace levels. Aspect ratios measuring >6:1 support improved receptor-target molecule interactions, higher throughput and extremely low limits of detection (LOD). In addition to superior assay sensitivity, the bifurcated microfluidic device provides greater durability and versatility for substrate modification. Using the explosive 2,4,6-trinitrotoluene (TNT) as the model compound in a fluorescence-based displacement immunoassay, we report LODs for TNT at 10 parts-per-trillion (pptr) using a neutravidin-coated biotinylated anti-TNT microfluidic device. Solution to wall interactions were also simulated in COMSOL Multiphysics to understand fluid flow characteristics. Reynolds numbers were calculated to be 0.27–2.45 with a maximum pressure of 1.2 × 10⁻² psi. Full article

(This article belongs to the Special Issue Environmental Monitoring Biosensors)

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27 pages, 24496 KiB

Open AccessArticle

m-Health: Lessons Learned by m-Experiences

by José Bravo^*, Ramón Hervás

, Jesús Fontecha

and Iván González

MAmI Research Lab, University of Castilla-La Mancha, Ciudad Real 13071, Spain

Sensors 2018, 18(5), 1569; https://doi.org/10.3390/s18051569 - 15 May 2018

Cited by 25 | Viewed by 7043

Abstract

m-Health is an emerging area that is transforming how people take part in the control of their wellness condition. This vision is changing traditional health processes by discharging hospitals from the care of people. Important advantages of continuous monitoring can be reached but, [...] Read more.

m-Health is an emerging area that is transforming how people take part in the control of their wellness condition. This vision is changing traditional health processes by discharging hospitals from the care of people. Important advantages of continuous monitoring can be reached but, in order to transform this vision into a reality, some factors need to be addressed. m-Health applications should be shared by patients and hospital staff to perform proper supervised health monitoring. Furthermore, the uses of smartphones for health purposes should be transformed to achieve the objectives of this vision. In this work, we analyze the m-Health features and lessons learned by the experiences of systems developed by MAmI Research Lab. We have focused on three main aspects: m-interaction, use of frameworks, and physical activity recognition. For the analysis of the previous aspects, we have developed some approaches to: (1) efficiently manage patient medical records for nursing and healthcare environments by introducing the NFC technology; (2) a framework to monitor vital signs, obesity and overweight levels, rehabilitation and frailty aspects by means of accelerometer-enabled smartphones and, finally; (3) a solution to analyze daily gait activity in the elderly, carrying a single inertial wearable close to the first thoracic vertebra. 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, 9178 KiB

Open AccessArticle

Remote Sensing of Wildland Fire-Induced Risk Assessment at the Community Level

by M. Razu Ahmed

, Khan Rubayet Rahaman

and Quazi K. Hassan^*

Department of Geomatics Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada

Sensors 2018, 18(5), 1570; https://doi.org/10.3390/s18051570 - 15 May 2018

Cited by 25 | Viewed by 6693

Abstract

Wildland fires are some of the critical natural hazards that pose a significant threat to the communities located in the vicinity of forested/vegetated areas. In this paper, our overall objective was to study the structural damages due to the 2016 Horse River Fire [...] Read more.

Wildland fires are some of the critical natural hazards that pose a significant threat to the communities located in the vicinity of forested/vegetated areas. In this paper, our overall objective was to study the structural damages due to the 2016 Horse River Fire (HRF) that happened in Fort McMurray (Alberta, Canada) by employing primarily very high spatial resolution optical satellite data, i.e., WorldView-2. Thus, our activities included the: (i) estimation of the structural damages; and (ii) delineation of the wildland-urban interface (WUI) and its associated buffers at certain intervals, and their utilization in assessing potential risks. Our proposed method of remote sensing-based estimates of the number of structural damages was compared with the ground-based information available from the Planning and Development Recovery Committee Task Force of Regional Municipality of Wood Buffalo (RMWB); and found a strong linear relationship (i.e., r² value of 0.97 with a slope of 0.97). Upon delineating the WUI and its associated buffer zones at 10 m, 30 m, 50 m, 70 m and 100 m distances; we found existence of vegetation within the 30 m buffers from the WUI for all of the damaged structures. In addition, we noticed that the relevant authorities had removed vegetation in some areas between 30 m and 70 m buffers from the WUI, which was proven to be effective in order to protect the structures in the adjacent communities. Furthermore, we mapped the wildland fire-induced vulnerable areas upon considering the WUI and its associated buffers. Our analysis revealed that approximately 30% of the areas within the buffer zones of 10 m and 30 m were vulnerable due to the presence of vegetation; in which, approximately 7% were burned during the 2016 HRF event that led the structural damages. Consequently, we suggest to remove the existing vegetation within these critical zones and also monitor the region at a regular interval in order to reduce the wildland fire-induced risk. Full article

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

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24 pages, 7606 KiB

Open AccessArticle

Features of Cross-Correlation Analysis in a Data-Driven Approach for Structural Damage Assessment

by Jhonatan Camacho Navarro^1,*,†, Magda Ruiz^1,‡, Rodolfo Villamizar^2,‡, Luis Mujica^1,‡ and Jabid Quiroga^2,‡

¹ Department of Mathematics, Escola d’Enginyeria de Barcelona Est. (EEBE), Universitat Politécnica de Catalunya (UPC) Barcelonatech, Campus Diagonal Besòs, Edifici A, C. Eduard Maristany, 10-14, 08019 Barcelona, Spain

² CEMOS Research Group, Electrical, Electronics and Telecommunications Engineering School, Universidad Industrial de Santander (UIS), Bucaramanga 680002, Colombia

^† Current address: Campus Diagonal Besòs, Edifici A, C. Eduard Maristany, 6-12. 08930 St Adrià de Besòs, Barcelona, Spain.

^‡ These authors contributed equally to this work.

Sensors 2018, 18(5), 1571; https://doi.org/10.3390/s18051571 - 15 May 2018

Cited by 12 | Viewed by 5003

Abstract

This work discusses the advantage of using cross-correlation analysis in a data-driven approach based on principal component analysis (PCA) and piezodiagnostics to obtain successful diagnosis of events in structural health monitoring (SHM). In this sense, the identification of noisy data and outliers, as [...] Read more.

This work discusses the advantage of using cross-correlation analysis in a data-driven approach based on principal component analysis (PCA) and piezodiagnostics to obtain successful diagnosis of events in structural health monitoring (SHM). In this sense, the identification of noisy data and outliers, as well as the management of data cleansing stages can be facilitated through the implementation of a preprocessing stage based on cross-correlation functions. Additionally, this work evidences an improvement in damage detection when the cross-correlation is included as part of the whole damage assessment approach. The proposed methodology is validated by processing data measurements from piezoelectric devices (PZT), which are used in a piezodiagnostics approach based on PCA and baseline modeling. Thus, the influence of cross-correlation analysis used in the preprocessing stage is evaluated for damage detection by means of statistical plots and self-organizing maps. Three laboratory specimens were used as test structures in order to demonstrate the validity of the methodology: (i) a carbon steel pipe section with leak and mass damage types, (ii) an aircraft wing specimen, and (iii) a blade of a commercial aircraft turbine, where damages are specified as mass-added. As the main concluding remark, the suitability of cross-correlation features combined with a PCA-based piezodiagnostic approach in order to achieve a more robust damage assessment algorithm is verified for SHM tasks. Full article

(This article belongs to the Special Issue Sensor Technologies for Health Monitoring of Composite Structures)

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13 pages, 335 KiB

Open AccessArticle

Optimal Resource Allocation for NOMA-TDMA Scheme with α-Fairness in Industrial Internet of Things

by Yanjing Sun^1,*, Yiyu Guo¹, Song Li¹, Dapeng Wu² and Bin Wang³

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

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

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

Sensors 2018, 18(5), 1572; https://doi.org/10.3390/s18051572 - 15 May 2018

Cited by 21 | Viewed by 4526

Abstract

In this paper, a joint non-orthogonal multiple access and time division multiple access (NOMA-TDMA) scheme is proposed in Industrial Internet of Things (IIoT), which allowed multiple sensors to transmit in the same time-frequency resource block using NOMA. The user scheduling, time slot allocation, [...] Read more.

In this paper, a joint non-orthogonal multiple access and time division multiple access (NOMA-TDMA) scheme is proposed in Industrial Internet of Things (IIoT), which allowed multiple sensors to transmit in the same time-frequency resource block using NOMA. The user scheduling, time slot allocation, and power control are jointly optimized in order to maximize the system

α

-fair utility under transmit power constraint and minimum rate constraint. The optimization problem is nonconvex because of the fractional objective function and the nonconvex constraints. To deal with the original problem, we firstly convert the objective function in the optimization problem into a difference of two convex functions (D.C.) form, and then propose a NOMA-TDMA-DC algorithm to exploit the global optimum. Numerical results show that the NOMA-TDMA scheme significantly outperforms the traditional orthogonal multiple access scheme in terms of both spectral efficiency and user fairness. Full article

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

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23 pages, 1481 KiB

Open AccessArticle

PCPA: A Practical Certificateless Conditional Privacy Preserving Authentication Scheme for Vehicular Ad Hoc Networks

by Yang Ming^1,*

and Xiaoqin Shen²

¹ School of Information Engineering, Chang’an University, Xi’an 710064, China

² School of Sciences, Xi’an University of Technology, Xi’an 710054, China

Sensors 2018, 18(5), 1573; https://doi.org/10.3390/s18051573 - 15 May 2018

Cited by 57 | Viewed by 5502

Abstract

Vehicle ad hoc networks (VANETs) is a promising network scenario for greatly improving traffic efficiency and safety, in which smart vehicles can communicate with other vehicles or roadside units. For the availability of VANETs, it is very important to deal with the security [...] Read more.

Vehicle ad hoc networks (VANETs) is a promising network scenario for greatly improving traffic efficiency and safety, in which smart vehicles can communicate with other vehicles or roadside units. For the availability of VANETs, it is very important to deal with the security and privacy problems for VANETs. In this paper, based on certificateless cryptography and elliptic curve cryptography, we present a certificateless signature with message recovery (CLS-MR), which we believe are of independent interest. Then, a practical certificateless conditional privacy preserving authentication (PCPA) scheme is proposed by incorporating the proposed CLS-MR scheme. Furthermore, the security analysis shows that PCPA satisfies all security and privacy requirements. The evaluation results indicate that PCPA achieves low computation and communication costs because there is no need to use the bilinear pairing and map-to-point hash operations. Moreover, extensive simulations show that PCPA is feasible and achieves prominent performances in terms of message delay and message loss ratio, and thus is more suitable for the deployment and adoption of VANETs. Full article

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

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18 pages, 595 KiB

Open AccessArticle

Performance Analysis of Two-Way Satellite Multi-Terrestrial Relay Networks with Hardware Impairments

by Kefeng Guo^1,†

, Kang An^2,†, Bangning Zhang^1,† and Daoxing Guo^1,*

¹ College of Communication Engineering, Army Engineering University of PLA (Its Old Name Is PLA University of Science and Technology), Nanjing 210007, China

² National University of Defense Technology, Nanjing 210016, China

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1574; https://doi.org/10.3390/s18051574 - 15 May 2018

Cited by 15 | Viewed by 3065

Abstract

In this paper, we investigate the performance of a two-way hybrid satellite multi-terrestrial cooperative network with hardware impairments (HIs). Particularly, opportunistic relay selection scheme is employed in the considered network, which can substantially enhance the spectral efficiency and spatial diversity gain. By considering [...] Read more.

In this paper, we investigate the performance of a two-way hybrid satellite multi-terrestrial cooperative network with hardware impairments (HIs). Particularly, opportunistic relay selection scheme is employed in the considered network, which can substantially enhance the spectral efficiency and spatial diversity gain. By considering both the amplify-and-forward (AF) and decode-and-forward (DF) relay protocols, the closed-form expressions of the outage probability (OP) and throughput for the system are derived. Furthermore, in order to observe the effects of HIs level and the number of terrestrial relays on the system performance at high signal-to-noise ratios (SNRs), the asymptotic expressions of the system performance are also derived. Finally, computer results are presented to reveal the correctness of the analytical results. Full article

(This article belongs to the Section Sensor Networks)

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26 pages, 6146 KiB

Open AccessArticle

An Effective Palmprint Recognition Approach for Visible and Multispectral Sensor Images

by Abdu Gumaei^1,*

, Rachid Sammouda¹, Abdul Malik Al-Salman¹ and Ahmed Alsanad²

¹ Department of Computer Science, College of Computer and Information Sciences, King Saud University, Riyadh 11543, Saudi Arabia

² Department of Information Systems, College of Computer and Information Sciences, King Saud University, Riyadh 11543, Saudi Arabia

Sensors 2018, 18(5), 1575; https://doi.org/10.3390/s18051575 - 15 May 2018

Cited by 30 | Viewed by 4945

Abstract

Among several palmprint feature extraction methods the HOG-based method is attractive and performs well against changes in illumination and shadowing of palmprint images. However, it still lacks the robustness to extract the palmprint features at different rotation angles. To solve this problem, this [...] Read more.

Among several palmprint feature extraction methods the HOG-based method is attractive and performs well against changes in illumination and shadowing of palmprint images. However, it still lacks the robustness to extract the palmprint features at different rotation angles. To solve this problem, this paper presents a hybrid feature extraction method, named HOG-SGF that combines the histogram of oriented gradients (HOG) with a steerable Gaussian filter (SGF) to develop an effective palmprint recognition approach. The approach starts by processing all palmprint images by David Zhang’s method to segment only the region of interests. Next, we extracted palmprint features based on the hybrid HOG-SGF feature extraction method. Then, an optimized auto-encoder (AE) was utilized to reduce the dimensionality of the extracted features. Finally, a fast and robust regularized extreme learning machine (RELM) was applied for the classification task. In the evaluation phase of the proposed approach, a number of experiments were conducted on three publicly available palmprint databases, namely MS-PolyU of multispectral palmprint images and CASIA and Tongji of contactless palmprint images. Experimentally, the results reveal that the proposed approach outperforms the existing state-of-the-art approaches even when a small number of training samples are used. Full article

(This article belongs to the Special Issue Advances on Sensor Pattern Noise used in Multimedia Forensics and Counter Forensic)

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12 pages, 1754 KiB

Open AccessArticle

Broadband Circularly Polarized Slot Antenna Loaded by a Multiple-Circular-Sector Patch

by Son Trinh-Van

, Youngoo Yang, Kang-Yoon Lee and Keum Cheol Hwang^*

School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon 440-746, Korea

Sensors 2018, 18(5), 1576; https://doi.org/10.3390/s18051576 - 15 May 2018

Cited by 14 | Viewed by 4043

Abstract

In this paper, a microstrip-fed broadband circularly polarized (CP) slot antenna is presented. CP operation can be attained simply by embedding an S-shaped strip. By loading with a multiple-circular-sector patch, which consists of 12 circular-sector patches with identical central angles of 30° and [...] Read more.

In this paper, a microstrip-fed broadband circularly polarized (CP) slot antenna is presented. CP operation can be attained simply by embedding an S-shaped strip. By loading with a multiple-circular-sector patch, which consists of 12 circular-sector patches with identical central angles of 30° and different radii, the 3 dB axial ratio (AR) bandwidth is significantly broadened. To validate the performance of the proposed antenna, an antenna prototype is fabricated and tested. The fabricated antenna is 54 mm × 54 mm × 0.8 mm in size. The measured −10 dB reflection and 3 dB AR bandwidths are 81.06% (1.68–3.97 GHz) and 70.55% (1.89–3.95 GHz), respectively. Within the 3 dB AR bandwidth, the measured peak gain is 3.81 dBic. Reasonable agreement is also obtained between the measured and simulated results. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 1757 KiB

Open AccessArticle

Biomechanical Gait Variable Estimation Using Wearable Sensors after Unilateral Total Knee Arthroplasty

by Ik-Hyun Youn^1,*, Jong-Hoon Youn², Joseph A. Zeni³ and Brian A. Knarr⁴

¹ Division of Navigation & Information Systems, Mokpo National Maritime University, Mokpo 58628, Korea

² Department of Computer Science, University of Nebraska Omaha, Omaha, NE 68182, USA

³ Department of Physical Therapy, University of Delaware, Newark, DE 19716, USA

⁴ Department of Biomechanics, University of Nebraska Omaha, Omaha, NE 68182, USA

Sensors 2018, 18(5), 1577; https://doi.org/10.3390/s18051577 - 15 May 2018

Cited by 23 | Viewed by 6241

Abstract

Total knee arthroplasty is a common surgical treatment for end-stage osteoarthritis of the knee. The majority of existing studies that have explored the relationship between recovery and gait biomechanics have been conducted in laboratory settings. However, seamless gait parameter monitoring in real-world conditions [...] Read more.

Total knee arthroplasty is a common surgical treatment for end-stage osteoarthritis of the knee. The majority of existing studies that have explored the relationship between recovery and gait biomechanics have been conducted in laboratory settings. However, seamless gait parameter monitoring in real-world conditions may provide a better understanding of recovery post-surgery. The purpose of this study was to estimate kinematic and kinetic gait variables using two ankle-worn wearable sensors in individuals after unilateral total knee arthroplasty. Eighteen subjects at least six months post-unilateral total knee arthroplasty participated in this study. Four biomechanical gait variables were measured using an instrumented split-belt treadmill and motion capture systems. Concurrently, eleven inertial gait variables were extracted from two ankle-worn accelerometers. Subsets of the inertial gait variables for each biomechanical gait variable estimation were statistically selected. Then, hierarchical regressions were created to determine the directional contributions of the inertial gait variables for biomechanical gait variable estimations. Selected inertial gait variables significantly predicted trial-averaged biomechanical gait variables. Moreover, strong directionally-aligned relationships were observed. Wearable-based gait monitoring of multiple and sequential kinetic gait variables in daily life could provide a more accurate understanding of the relationships between movement patterns and recovery from total knee arthroplasty. Full article

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

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27 pages, 1329 KiB

Open AccessArticle

Leveraging Energy Harvesting and Wake-Up Receivers for Long-Term Wireless Sensor Networks

by Fayçal Ait Aoudia¹, Matthieu Gautier^1,*, Michele Magno², Olivier Berder¹

and Luca Benini²

¹ University of Rennes, CNRS, IRISA, 6 rue Kerampont, F-22305 Lannion CEDEX, France

² ETH Zurich, Integrated Systems Laboratory, Gloriastrasse 35, 8092 Zurich, Switzerland

Sensors 2018, 18(5), 1578; https://doi.org/10.3390/s18051578 - 15 May 2018

Cited by 32 | Viewed by 4286

Abstract

Wireless sensor nodes are traditionally powered by individual batteries, and a significant effort has been devoted to maximizing the lifetime of these devices. However, as the batteries can only store a finite amount of energy, the network is still doomed to die, and [...] Read more.

Wireless sensor nodes are traditionally powered by individual batteries, and a significant effort has been devoted to maximizing the lifetime of these devices. However, as the batteries can only store a finite amount of energy, the network is still doomed to die, and changing the batteries is not always possible. A promising solution is to enable each node to harvest energy directly in its environment, using individual energy harvesters. Moreover, novel ultra-low power wake-up receivers, which allow continuous listening of the channel with negligible power consumption, are emerging. These devices enable asynchronous communication, further reducing the power consumption related to communication, which is typically one the most energy-consuming tasks in wireless sensor networks. Energy harvesting and wake-up receivers can be combined to significantly increase the energy efficiency of sensor networks. In this paper, we propose an energy manager for energy harvesting wireless sensor nodes and an asynchronous medium access control protocol, which exploits ultra-low power wake-up receivers. The two components are designed to work together and especially to fit the stringent constraints of wireless sensor nodes. The proposed approach has been implemented on a real hardware platform and tested in the field. Experimental results demonstrate the benefits of the proposed approach in terms of energy efficiency, power consumption and throughput, which can be up to more than two-times higher compared to traditional schemes. Full article

(This article belongs to the Section Sensor Networks)

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10 pages, 2259 KiB

Open AccessArticle

Thermoelectric Array Sensors with Selective Combustion Catalysts for Breath Gas Monitoring

by Woosuck Shin^1,*, Tomoyo Goto²

, Daisuke Nagai¹, Toshio Itoh¹, Akihiro Tsuruta¹, Takafumi Akamatsu¹ and Kazuo Sato³

¹ National Institute of Advanced Industrial Science and Technology (AIST), Shimo-Shidami, Moriyama-ku, Nagoya 463-8560, Japan

² The Institute of Scientific and Industrial Research, Osaka University, Ibaraki 567-0047, Japan

³ Department of Mechanical Engineering, Aichi Institute of Technology, Toyota 470-0392, Japan

Sensors 2018, 18(5), 1579; https://doi.org/10.3390/s18051579 - 16 May 2018

Cited by 13 | Viewed by 4373

Abstract

Inflammable breath gases such as H₂ and CH₄ are used as bio markers for monitoring the condition of the colon. However, their typical concentrations of below 100 ppm pose sensitivity and selectivity challenges to current gas sensing systems without the use [...] Read more.

Inflammable breath gases such as H₂ and CH₄ are used as bio markers for monitoring the condition of the colon. However, their typical concentrations of below 100 ppm pose sensitivity and selectivity challenges to current gas sensing systems without the use of chromatography. We fabricated a compact, gas-selective thermoelectric array sensor (TAS) that uses micro-machined sensor devices with three different combustion catalysts to detect gases such as H₂, CO, and CH₄ in breath. Using Pt/Pt-W thin-film micro-heater meanders, Pd/Al₂O₃, Pt,Pd,Au/Co₃O₄, and Pt/Al₂O₃ catalysts were heated to 320, 200, and 125 °C, respectively, and the gas sensing performances of the TAS for each gas and for a model breath gas mixture of 100 ppm H₂, 25 ppm CO, 50 ppm CH₄, and 199 ppm CO₂ in air were investigated. Owing to its high catalyst temperature, the Pd/Al₂O₃ catalyst burned all three gases, while the Pt,Pd,Au/Co₃O₄ burned CO and H₂ and the Pt/Al₂O₃ burned H₂ selectively. To calibrate the gas concentration of the mixture gas without the use of a gas separation tool, linear discriminant analysis was applied to measure the sensing performance of TAS. To enhance the gas selectivity against H₂, a double catalyst structure was integrated into the TAS sensor. Full article

(This article belongs to the Special Issue VOC Sensors Applicable to IoT and Healthcare)

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13 pages, 10322 KiB

Open AccessArticle

Weed Growth Stage Estimator Using Deep Convolutional Neural Networks

by Nima Teimouri^1,2, Mads Dyrmann^1,*

, Per Rydahl Nielsen³, Solvejg Kopp Mathiassen⁴, Gayle J. Somerville⁴

and Rasmus Nyholm Jørgensen¹

¹ Department of Engineering-Signal Processing, Faculty of Science and Technology, Aarhus University, DK-8000 Aarhus C, Denmark

² Department of Biosystems Engineering, University of Tehran, Tehran 1417466191, Iran

³ IPM Consult ApS, DK-4295 Stenlille, Denmark

⁴ Department of Agroecology, Aarhus University, DK-4200 Slagelse, Denmark

Sensors 2018, 18(5), 1580; https://doi.org/10.3390/s18051580 - 16 May 2018

Cited by 92 | Viewed by 9620

Abstract

This study outlines a new method of automatically estimating weed species and growth stages (from cotyledon until eight leaves are visible) of in situ images covering 18 weed species or families. Images of weeds growing within a variety of crops were gathered across [...] Read more.

This study outlines a new method of automatically estimating weed species and growth stages (from cotyledon until eight leaves are visible) of in situ images covering 18 weed species or families. Images of weeds growing within a variety of crops were gathered across variable environmental conditions with regards to soil types, resolution and light settings. Then, 9649 of these images were used for training the computer, which automatically divided the weeds into nine growth classes. The performance of this proposed convolutional neural network approach was evaluated on a further set of 2516 images, which also varied in term of crop, soil type, image resolution and light conditions. The overall performance of this approach achieved a maximum accuracy of 78% for identifying Polygonum spp. and a minimum accuracy of 46% for blackgrass. In addition, it achieved an average 70% accuracy rate in estimating the number of leaves and 96% accuracy when accepting a deviation of two leaves. These results show that this new method of using deep convolutional neural networks has a relatively high ability to estimate early growth stages across a wide variety of weed species. Full article

(This article belongs to the Special Issue Application of Satellite and Proximal Sensors in Precision Agriculture)

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20 pages, 4077 KiB

Open AccessArticle

An Efficient Framework for Development of Task-Oriented Dialog Systems in a Smart Home Environment

by Youngmin Park¹, Sangwoo Kang^2,* and Jungyun Seo¹

¹ Department of Engineering, Computer Science, Sogang University, Seoul 04107, Korea

² Department of Software, Gachon University, Gyeonggi-do 13120, Korea

Sensors 2018, 18(5), 1581; https://doi.org/10.3390/s18051581 - 16 May 2018

Cited by 5 | Viewed by 6498

Abstract

In recent times, with the increasing interest in conversational agents for smart homes, task-oriented dialog systems are being actively researched. However, most of these studies are focused on the individual modules of such a system, and there is an evident lack of research [...] Read more.

In recent times, with the increasing interest in conversational agents for smart homes, task-oriented dialog systems are being actively researched. However, most of these studies are focused on the individual modules of such a system, and there is an evident lack of research on a dialog framework that can integrate and manage the entire dialog system. Therefore, in this study, we propose a framework that enables the user to effectively develop an intelligent dialog system. The proposed framework ontologically expresses the knowledge required for the task-oriented dialog system’s process and can build a dialog system by editing the dialog knowledge. In addition, the framework provides a module router that can indirectly run externally developed modules. Further, it enables a more intelligent conversation by providing a hierarchical argument structure (HAS) to manage the various argument representations included in natural language sentences. To verify the practicality of the framework, an experiment was conducted in which developers without any previous experience in developing a dialog system developed task-oriented dialog systems using the proposed framework. The experimental results show that even beginner dialog system developers can develop a high-level task-oriented dialog system. Full article

(This article belongs to the Special Issue Smart Homes)

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14 pages, 4438 KiB

Open AccessArticle

Three-Dimensional Terahertz Coded-Aperture Imaging Based on Geometric Measures

by Shuo Chen, Xiaoqiang Hua, Hongqiang Wang^*, Chenggao Luo^*, Yongqiang Cheng and Bin Deng

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

Sensors 2018, 18(5), 1582; https://doi.org/10.3390/s18051582 - 16 May 2018

Cited by 5 | Viewed by 3267

Abstract

For synthetic aperture radars, it is difficult to achieve forward-looking and staring imaging with high resolution. Fortunately, terahertz coded-aperture imaging (TCAI), an advanced radar imaging technology, can solve this problem by producing various irradiation patterns with coded apertures. However, three-dimensional (3D) TCAI has [...] Read more.

For synthetic aperture radars, it is difficult to achieve forward-looking and staring imaging with high resolution. Fortunately, terahertz coded-aperture imaging (TCAI), an advanced radar imaging technology, can solve this problem by producing various irradiation patterns with coded apertures. However, three-dimensional (3D) TCAI has two problems, including a heavy computational burden caused by a large-scale reference signal matrix, and poor resolving ability at low signal-to-noise ratios (SNRs). This paper proposes a 3D imaging method based on geometric measures (GMs), which can reduce the computational burden and achieve high-resolution imaging for low SNR targets. At extremely low SNRs, it is difficult to detect the range cells containing scattering information with an ordinary range profile. However, this difficulty can be overcome through GMs, which can enhance the useful signal and restrain the noise. By extracting useful data from the range profile, target information in different imaging cells can be simultaneously reconstructed. Thus, the computational complexity is distinctly reduced when the 3D image is obtained by combining reconstructed 2D imaging results. Based on the conventional TCAI (C-TCAI) model, we deduce and build a GM-based TCAI (GM-TCAI) model. Compared with C-TCAI, the experimental results demonstrate that GM-TCAI achieves a more impressive performance with regards to imaging ability and efficiency. Furthermore, GM-TCAI can be widely applied in close-range imaging fields, for instance, medical diagnosis, nondestructive detection, security screening, etc. Full article

(This article belongs to the Section Remote Sensors)

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21 pages, 2512 KiB

Open AccessArticle

Speed Consistency in the Smart Tachograph

by Daniele Borio^*

, Eduardo Cano and Gianmarco Baldini

European Commission, Joint Research Centre (JRC) Directorate for Space, Security and Migration, Via Enrico Fermi 2749, 21027 Ispra (VA), Italy

Sensors 2018, 18(5), 1583; https://doi.org/10.3390/s18051583 - 16 May 2018

Cited by 4 | Viewed by 5013

Abstract

In the transportation sector, safety risks can be significantly reduced by monitoring the behaviour of drivers and by discouraging possible misconducts that entail fatigue and can increase the possibility of accidents. The Smart Tachograph (ST), the new revision of the Digital Tachograph (DT), [...] Read more.

In the transportation sector, safety risks can be significantly reduced by monitoring the behaviour of drivers and by discouraging possible misconducts that entail fatigue and can increase the possibility of accidents. The Smart Tachograph (ST), the new revision of the Digital Tachograph (DT), has been designed with this purpose: to verify that speed limits and compulsory rest periods are respected by drivers. In order to operate properly, the ST periodically checks the consistency of data from different sensors, which can be potentially manipulated to avoid the monitoring of the driver behaviour. In this respect, the ST regulation specifies a test procedure to detect motion conflicts originating from inconsistencies between Global Navigation Satellite System (GNSS) and odometry data. This paper provides an experimental evaluation of the speed verification procedure specified by the ST regulation. Several hours of data were collected using three vehicles and considering light urban and highway environments. The vehicles were equipped with an On-Board Diagnostics (OBD) data reader and a GPS/Galileo receiver. The tests prescribed by the regulation were implemented with specific focus on synchronization aspects. The experimental analysis also considered aspects such as the impact of tunnels and the presence of data gaps. The analysis shows that the metrics selected for the tests are resilient to data gaps, latencies between GNSS and odometry data and simplistic manipulations such as data scaling. The new ST forces an attacker to falsify data from both sensors at the same time and in a coherent way. This makes more difficult the implementation of frauds in comparison to the current version of the DT. Full article

(This article belongs to the Special Issue GNSS and Fusion with Other Sensors)

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15 pages, 6159 KiB

Open AccessArticle

Effects of Proof Mass Geometry on Piezoelectric Vibration Energy Harvesters

by Abdul Hafiz Alameh

, Mathieu Gratuze

, Mohannad Y. Elsayed and Frederic Nabki^*

Department of Electrical Engineering, École de Technologie Supérieure, Montréal, QC H3C 1K3, Canada

Sensors 2018, 18(5), 1584; https://doi.org/10.3390/s18051584 - 16 May 2018

Cited by 41 | Viewed by 6669

Abstract

Piezoelectric energy harvesters have proven to have the potential to be a power source in a wide range of applications. As the harvester dimensions scale down, the resonance frequencies of these devices increase drastically. Proof masses are essential in micro-scale devices in order [...] Read more.

Piezoelectric energy harvesters have proven to have the potential to be a power source in a wide range of applications. As the harvester dimensions scale down, the resonance frequencies of these devices increase drastically. Proof masses are essential in micro-scale devices in order to decrease the resonance frequency and increase the strain along the beam to increase the output power. In this work, the effects of proof mass geometry on piezoelectric energy harvesters are studied. Different geometrical dimension ratios have significant impact on the resonance frequency, e.g., beam to mass lengths, and beam to mass widths. A piezoelectric energy harvester has been fabricated and tested operating at a frequency of about 4 kHz within the audible range. The responses of various prototypes were studied, and an optimized T-shaped piezoelectric vibration energy harvester design is presented for improved performance. Full article

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

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17 pages, 4401 KiB

Open AccessArticle

Attention-Based Recurrent Temporal Restricted Boltzmann Machine for Radar High Resolution Range Profile Sequence Recognition

by Yifan Zhang, Xunzhang Gao^*, Xuan Peng

, Jiaqi Ye and Xiang Li

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

Sensors 2018, 18(5), 1585; https://doi.org/10.3390/s18051585 - 16 May 2018

Cited by 14 | Viewed by 3836

Abstract

The High Resolution Range Profile (HRRP) recognition has attracted great concern in the field of Radar Automatic Target Recognition (RATR). However, traditional HRRP recognition methods failed to model high dimensional sequential data efficiently and have a poor anti-noise ability. To deal with these [...] Read more.

The High Resolution Range Profile (HRRP) recognition has attracted great concern in the field of Radar Automatic Target Recognition (RATR). However, traditional HRRP recognition methods failed to model high dimensional sequential data efficiently and have a poor anti-noise ability. To deal with these problems, a novel stochastic neural network model named Attention-based Recurrent Temporal Restricted Boltzmann Machine (ARTRBM) is proposed in this paper. RTRBM is utilized to extract discriminative features and the attention mechanism is adopted to select major features. RTRBM is efficient to model high dimensional HRRP sequences because it can extract the information of temporal and spatial correlation between adjacent HRRPs. The attention mechanism is used in sequential data recognition tasks including machine translation and relation classification, which makes the model pay more attention to the major features of recognition. Therefore, the combination of RTRBM and the attention mechanism makes our model effective for extracting more internal related features and choose the important parts of the extracted features. Additionally, the model performs well with the noise corrupted HRRP data. Experimental results on the Moving and Stationary Target Acquisition and Recognition (MSTAR) dataset show that our proposed model outperforms other traditional methods, which indicates that ARTRBM extracts, selects, and utilizes the correlation information between adjacent HRRPs effectively and is suitable for high dimensional data or noise corrupted data. Full article

(This article belongs to the Section Remote Sensors)

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27 pages, 21585 KiB

Open AccessArticle

Energy Efficient GNSS Signal Acquisition Using Singular Value Decomposition (SVD)

by Juan Carlos Bermúdez Ordoñez^*

, Rosa María Arnaldo Valdés^*

and Fernando Gómez Comendador^*

School of Aeronautical and Space Engineering, Universidad Politécnica de Madrid, Plaza Cardenal Cisneros 3, 28040 Madrid, Spain

Sensors 2018, 18(5), 1586; https://doi.org/10.3390/s18051586 - 16 May 2018

Cited by 8 | Viewed by 6124

Abstract

A significant challenge in global navigation satellite system (GNSS) signal processing is a requirement for a very high sampling rate. The recently-emerging compressed sensing (CS) theory makes processing GNSS signals at a low sampling rate possible if the signal has a sparse representation [...] Read more.

A significant challenge in global navigation satellite system (GNSS) signal processing is a requirement for a very high sampling rate. The recently-emerging compressed sensing (CS) theory makes processing GNSS signals at a low sampling rate possible if the signal has a sparse representation in a certain space. Based on CS and SVD theories, an algorithm for sampling GNSS signals at a rate much lower than the Nyquist rate and reconstructing the compressed signal is proposed in this research, which is validated after the output from that process still performs signal detection using the standard fast Fourier transform (FFT) parallel frequency space search acquisition. The sparse representation of the GNSS signal is the most important precondition for CS, by constructing a rectangular Toeplitz matrix (TZ) of the transmitted signal, calculating the left singular vectors using SVD from the TZ, to achieve sparse signal representation. Next, obtaining the M-dimensional observation vectors based on the left singular vectors of the SVD, which are equivalent to the sampler operator in standard compressive sensing theory, the signal can be sampled below the Nyquist rate, and can still be reconstructed via

ℓ_{1}

minimization with accuracy using convex optimization. As an added value, there is a GNSS signal acquisition enhancement effect by retaining the useful signal and filtering out noise by projecting the signal into the most significant proper orthogonal modes (PODs) which are the optimal distributions of signal power. The algorithm is validated with real recorded signals, and the results show that the proposed method is effective for sampling, reconstructing intermediate frequency (IF) GNSS signals in the time discrete domain. Full article

(This article belongs to the Special Issue GNSS and Fusion with Other Sensors)

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21 pages, 9090 KiB

Open AccessArticle

Observing APOD with the AuScope VLBI Array

by Andreas Hellerschmied^1,*

, Lucia McCallum²

, Jamie McCallum²

, Jing Sun³, Johannes Böhm¹

and Jianfeng Cao⁴

¹ Department of Geodesy and Geoinformation, Technische Universität Wien, Gußhausstraße 27–29/E120.4, A-1040 Vienna, Austria

² School of Physical Science, University of Tasmania, Private Bag 25, Hobart TAS 7001, Australia

³ National Astronomic Observatory, 20A Datun Road, Beijing 100012, China

⁴ Beijing Aerospace Control Center, 26 Beiqing Road, Beijing 100094, China

Sensors 2018, 18(5), 1587; https://doi.org/10.3390/s18051587 - 16 May 2018

Cited by 18 | Viewed by 4883

Abstract

The possibility to observe satellites with the geodetic Very Long Baseline Interferometry (VLBI) technique is vividly discussed in the geodetic community, particularly with regard to future co-location satellite missions. The Chinese APOD-A nano satellite can be considered as a first prototype—suitable for practical [...] Read more.

The possibility to observe satellites with the geodetic Very Long Baseline Interferometry (VLBI) technique is vividly discussed in the geodetic community, particularly with regard to future co-location satellite missions. The Chinese APOD-A nano satellite can be considered as a first prototype—suitable for practical observation tests—combining the techniques Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS) and VLBI on a single platform in a Low Earth Orbit (LEO). Unfortunately, it has hardly been observed by VLBI, so major studies towards actual frame ties could not be performed. The main reason for the lack of observations was that VLBI observations of satellites are non-standard, and suitable observing strategies were not in place for this mission. This work now presents the first serious attempt to observe the satellite with a VLBI network over multiple passes. We introduce a series of experiments with the AuScope geodetic VLBI array which were carried out in November 2016, and describe all steps integrated in the established process chain: the experiment design and observation planning, the antenna tracking and control scheme, correlation and derivation of baseline-delays, and the data analysis yielding delay residuals on the level of 10 ns. The developed procedure chain can now serve as reference for future experiments, hopefully enabling the global VLBI network to be prepared for the next co-location satellite mission. Full article

(This article belongs to the Section Remote Sensors)

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11 pages, 2969 KiB

Open AccessArticle

Tactile Estimation of Molded Plastic Plates Based on the Estimated Impulse Responses of Mechanoreceptive Units

by Lisako Nobuyama¹, Yuta Kurashina²

, Kei Kawauchi³, Koji Matsui³ and Kenjiro Takemura^2,*

¹ Graduate School of Science for Open and Environmental Systems, Keio University, Yokohama 223-8522, Japan

² Department of Mechanical Engineering, Keio University, Yokohama 223-8522, Japan

³ Kato Tech Co., Ltd., Kyoto 601-8447, Japan

Sensors 2018, 18(5), 1588; https://doi.org/10.3390/s18051588 - 16 May 2018

Cited by 10 | Viewed by 4127

Abstract

This study proposes a tactile estimation method of molded plastic plates based on human tactile perception characteristics. Plastic plates are often used in consumer products. The tactile evaluation plays an important role in product development. However, physical quantities not taking into account human [...] Read more.

This study proposes a tactile estimation method of molded plastic plates based on human tactile perception characteristics. Plastic plates are often used in consumer products. The tactile evaluation plays an important role in product development. However, physical quantities not taking into account human tactile perception have been employed in previous tactile estimation procedures. Hence, in this study, we adopted the vibrational thresholds of the mechanoreceptive units—FA I, FA II, SA I and SA II—for stimuli detection and developed a tactile estimation method for plastic plates that clarified the mechanoreceptive units related to tactile sensation. The developed tactile sensor consists of a base and a silicone rubber pad that contains strain gauges in it. We detected vibration during touch by the sensor and calculated the estimation of the firing values of the cutaneous mechanoreceptors, which are the essential data obtained by humans during tactile perception, in comparison to the amplitude spectrum of the vibration with the threshold amplitude of each mechanoreceptive unit. Simultaneously, we calculated the relationship between the normal and tangential forces recorded while the sensor ran over the samples. As a result of stepwise linear regression analysis using these values as explanatory variables, the evaluation scores for Soft were successfully estimated using the firing value of FA II and the relationship between normal/tangential forces, and the evaluation scores for Rough were estimated using the SA I firing value. Full article

(This article belongs to the Special Issue Tactile Sensors and Applications)

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13 pages, 5617 KiB

Open AccessArticle

Sidelobe Suppression with Resolution Maintenance for SAR Images via Sparse Representation

by Xiaoxiang Zhu¹, Feng He^1,*, Fan Ye¹, Zhen Dong¹ and Manqing Wu²

¹ College of Electronic Science, National University of Defense Technology, No. 109 De Ya Road, Changsha 410073, China

² China Electronic Technology Group Corporation (CETC), Wan Shou Road, Beijing 100000, China

Sensors 2018, 18(5), 1589; https://doi.org/10.3390/s18051589 - 16 May 2018

Cited by 19 | Viewed by 5455

Abstract

Severe sidelobe interference is one of the major problems with traditional Synthetic Aperture Radar (SAR) imaging. In the observation scene of sea areas, the number of targets in the observation scene is so small that targets can be regarded as sparse. Taking this [...] Read more.

Severe sidelobe interference is one of the major problems with traditional Synthetic Aperture Radar (SAR) imaging. In the observation scene of sea areas, the number of targets in the observation scene is so small that targets can be regarded as sparse. Taking this into account, a method of sidelobe suppression, on the basis of sparsity constraint regularization, is proposed to reduce sidelobes of Gaofen-3 (GF-3) images in sea areas of the image domain. This proposed method has a prominent sidelobe suppression effect with resolution maintenance and without destruction of amplitude and phase information. This method can also be applied to SAR images of other satellites. In addition to the employment of peak sidelobe ratio (PSLR) and integrated sidelobe ratio (ISLR) in evaluating sidelobe suppression level, AE (amplitude error) and PE (phase error) are firstly defined for the evaluation of amplitude and phase-preserving quality, respectively. Through the proposed method, AE and PE values are nearly unchanged and the PSLR and ISLR are significantly reduced. The method, as an important part of the quality-improvement project of GF-3, has been successfully applied to the sidelobe suppression of GF-3 data. Full article

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

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12 pages, 4530 KiB

Open AccessArticle

Developing an Acoustic Sensing Yarn for Health Surveillance in a Military Setting

by Theodore Hughes-Riley^*

and Tilak Dias

Advanced Textiles Research Group, School of Art & Design, Nottingham Trent University, Bonington Building, Dryden Street, Nottingham NG1 4GG, UK

Sensors 2018, 18(5), 1590; https://doi.org/10.3390/s18051590 - 17 May 2018

Cited by 24 | Viewed by 6934

Abstract

Overexposure to high levels of noise can cause permanent hearing disorders, which have a significant adverse effect on the quality of life of those affected. Injury due to noise can affect people in a variety of careers including construction workers, factory workers, and [...] Read more.

Overexposure to high levels of noise can cause permanent hearing disorders, which have a significant adverse effect on the quality of life of those affected. Injury due to noise can affect people in a variety of careers including construction workers, factory workers, and members of the armed forces. By monitoring the noise exposure of workers, overexposure can be avoided and suitable protective equipment can be provided. This work focused on the creation of a noise dosimeter suitable for use by members of the armed forces, where a discrete dosimeter was integrated into a textile helmet cover. In this way the sensing elements could be incorporated very close to the ears, providing a highly representative indication of the sound level entering the body, and also creating a device that would not interfere with military activities. This was achieved by utilising commercial microelectromechanical system microphones integrated within the fibres of yarn to create an acoustic sensing yarn. The acoustic sensing yarns were fully characterised over a range of relevant sound levels and frequencies at each stage in the yarn production process. The yarns were ultimately integrated into a knitted helmet cover to create a functional acoustic sensing helmet cover prototype. Full article

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

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15 pages, 4809 KiB

Open AccessFeature PaperArticle

Damage Evaluation of Concrete Column under Impact Load Using a Piezoelectric-Based EMI Technique

by Shuli Fan¹

, Shaoyu Zhao¹

, Baoxin Qi²

and Qingzhao Kong^3,*

¹ State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China

² School of Civil Engineering, Shenyang Jianzhu University, Shenyang 110168, China

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

Sensors 2018, 18(5), 1591; https://doi.org/10.3390/s18051591 - 17 May 2018

Cited by 65 | Viewed by 5838

Abstract

One of the major causes of damage to column-supported concrete structures, such as bridges and highways, are collisions from moving vehicles, such as cars and ships. It is essential to quantify the collision damage of the column so that appropriate actions can be [...] Read more.

One of the major causes of damage to column-supported concrete structures, such as bridges and highways, are collisions from moving vehicles, such as cars and ships. It is essential to quantify the collision damage of the column so that appropriate actions can be taken to prevent catastrophic events. A widely used method to assess structural damage is through the root-mean-square deviation (RMSD) damage index established by the collected data; however, the RMSD index does not truly provide quantitative information about the structure. Conversely, the damage volume ratio that can only be obtained via simulation provides better detail about the level of damage in a structure. Furthermore, as simulation can also provide the RMSD index relating to that particular damage volume ratio, the empirically obtained RMSD index can thus be related to the structural damage degree through comparison of the empirically obtained RMSD index to numerically-obtained RMSD. Thus, this paper presents a novel method in which the impact-induced damage to a structure is simulated in order to obtain the relationship between the damage volume ratio to the RMSD index, and the relationship can be used to predict the true damage degree by comparison to the empirical RMSD index. In this paper, the collision damage of a bridge column by moving vehicles was simulated by using a concrete beam model subjected to continuous impact loadings by a freefalling steel ball. The variation in admittance signals measured by the surface attached lead zirconate titanate (PZT) patches was used to establish the RMSD index. The results demonstrate that the RMSD index and the damage ratio of concrete have a linear relationship for the particular simulation model. Full article

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

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23 pages, 849 KiB

Open AccessArticle

Improving UWB-Based Localization in IoT Scenarios with Statistical Models of Distance Error

by Stefania Monica¹ and Gianluigi Ferrari^2,*

¹ Department of Mathematics, Physics and Computer Science, University of Parma, 43124 Parma, Italy

² Department of Engineering and Architecture, University of Parma, 43124 Parma, Italy

Sensors 2018, 18(5), 1592; https://doi.org/10.3390/s18051592 - 17 May 2018

Cited by 23 | Viewed by 4414

Abstract

Interest in the Internet of Things (IoT) is rapidly increasing, as the number of connected devices is exponentially growing. One of the application scenarios envisaged for IoT technologies involves indoor localization and context awareness. In this paper, we focus on a localization approach [...] Read more.

Interest in the Internet of Things (IoT) is rapidly increasing, as the number of connected devices is exponentially growing. One of the application scenarios envisaged for IoT technologies involves indoor localization and context awareness. In this paper, we focus on a localization approach that relies on a particular type of communication technology, namely Ultra Wide Band (UWB). UWB technology is an attractive choice for indoor localization, owing to its high accuracy. Since localization algorithms typically rely on estimated inter-node distances, the goal of this paper is to evaluate the improvement brought by a simple (linear) statistical model of the distance error. On the basis of an extensive experimental measurement campaign, we propose a general analytical framework, based on a Least Square (LS) method, to derive a novel statistical model for the range estimation error between a pair of UWB nodes. The proposed statistical model is then applied to improve the performance of a few illustrative localization algorithms in various realistic scenarios. The obtained experimental results show that the use of the proposed statistical model improves the accuracy of the considered localization algorithms with a reduction of the localization error up to 66%. Full article

(This article belongs to the Section Internet of Things)

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22 pages, 6964 KiB

Open AccessArticle

SOBER-MCS: Sociability-Oriented and Battery Efficient Recruitment for Mobile Crowd-Sensing

by Fazel Anjomshoa^1,† and Burak Kantarci^2,*,†

¹ Department of Electrical and Computer Engineering, Clarkson University, Potsdam, NY 13699, USA

² School of Electrical Engineering and Computer Science, University of Ottawa, Ottawa, ON K1N 6N5, Canada

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1593; https://doi.org/10.3390/s18051593 - 17 May 2018

Cited by 18 | Viewed by 3951

Abstract

The Internet of Things (IoT) concept is aiming at being an integral part of the next generation networking services by introducing pervasiveness and ubiquitous interconnectivity of uniquely-identifiable objects. The massive availability of personalized smart devices such as smartphones and wearables enable their penetration [...] Read more.

The Internet of Things (IoT) concept is aiming at being an integral part of the next generation networking services by introducing pervasiveness and ubiquitous interconnectivity of uniquely-identifiable objects. The massive availability of personalized smart devices such as smartphones and wearables enable their penetration into the IoT ecosystem with their built-in sensors, particularly in Mobile Crowd-Sensing (MCS) campaigns. The MCS systems achieve the objectives of the large-scale non-dedicated sensing concept in the IoT if a sufficient number of participants are engaged to the collaborative data acquisition process. Therefore, user recruitment is a key challenge in MCS, which requires effective incentivization of cooperative, truthful and trustworthy users. A grand concern for the participants is the battery drain on the mobile devices. It is a known fact that battery drain in a smartphone is a function of the user activity, which can be modeled under various contexts. With this in mind, we propose a new social activity-aware recruitment policy, namely Sociability-Oriented and Battery-Efficient Recruitment for Mobile Crowd-Sensing (SOBER-MCS). SOBER-MCS uses sociability and the residual power of the participant smartphones as two primary criteria in the selection of participating devices. The former is an indicator of the participant willingness toward sensing campaigns, whereas the latter is used to prioritize personal use over crowd-sensing under critical battery levels. We use sociability profiles that were obtained in our previous work and use those values to simulate the sociability behavior of a large pool of participants in an MCS environment. Through simulations, we show that SOBER-MCS is able to introduce battery savings up to 18.5% while improving user and platform utilities by 12% and 20%, respectively. Full article

(This article belongs to the Special Issue Realization of Large-Scale Mobile Crowd Sensing Experiments)

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15 pages, 4174 KiB

Open AccessArticle

Resource Optimization Techniques and Security Levels for Wireless Sensor Networks Based on the ARSy Framework

by Jumadi Mabe Parenreng^1,2,*

and Akio Kitagawa^1,*

¹ Electrical Engineering and Computer Science, Kanazawa University, Ishikawa 920-1192, Japan

² Informatic Engineering and Computer Education, State University of Makassar, Makassar 90222, South of Sulawesi, Indonesia

Sensors 2018, 18(5), 1594; https://doi.org/10.3390/s18051594 - 17 May 2018

Cited by 14 | Viewed by 4421

Abstract

Wireless Sensor Networks (WSNs) with limited battery, central processing units (CPUs), and memory resources are a widely implemented technology for early warning detection systems. The main advantage of WSNs is their ability to be deployed in areas that are difficult to access by [...] Read more.

Wireless Sensor Networks (WSNs) with limited battery, central processing units (CPUs), and memory resources are a widely implemented technology for early warning detection systems. The main advantage of WSNs is their ability to be deployed in areas that are difficult to access by humans. In such areas, regular maintenance may be impossible; therefore, WSN devices must utilize their limited resources to operate for as long as possible, but longer operations require maintenance. One method of maintenance is to apply a resource adaptation policy when a system reaches a critical threshold. This study discusses the application of a security level adaptation model, such as an ARSy Framework, for using resources more efficiently. A single node comprising a Raspberry Pi 3 Model B and a DS18B20 temperature sensor were tested in a laboratory under normal and stressful conditions. The result shows that under normal conditions, the system operates approximately three times longer than under stressful conditions. Maintaining the stability of the resources also enables the security level of a network’s data output to stay at a high or medium level. Full article

(This article belongs to the Section Sensor Networks)

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10 pages, 2986 KiB

Open AccessArticle

Visual and Colorimetric Sensing of Metsulfuron-Methyl by Exploiting Hydrogen Bond-Induced Anti-Aggregation of Gold Nanoparticles in the Presence of Melamine

by Guangyang Liu^1,2, Ruonan Zhang², Xiaodong Huang², Lingyun Li², Naixin Liu^1,*, Jing Wang³ and Donghui Xu^2,*

¹ Quality and Safety Risk Assessment Laboratory for Sugar Crops Products, the Ministry of Agriculture, Heilongjiang University, Harbin 150080, China

² Key Laboratory of Vegetables Quality and Safety Control, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Ministry of Agriculture of China, Beijing 100081, China

³ Key Laboratory of Agrifood Safety and Quality, Institute of Quality Standard and Testing Technology for Agro Products, Chinese Academy of Agricultural Sciences, Ministry of Agriculture of China, Beijing 100081, China

Sensors 2018, 18(5), 1595; https://doi.org/10.3390/s18051595 - 17 May 2018

Cited by 18 | Viewed by 4895

Abstract

Various highly sensitive and selective analytical methods have been used to monitor metsulfuron-methyl residue in the environment. However, these methods involve costly instruments and complex, time-consuming operations performed in laboratories. Here, a rapid, convenient, and sensitive colorimetric sensor based on anti-aggregation of gold [...] Read more.

Various highly sensitive and selective analytical methods have been used to monitor metsulfuron-methyl residue in the environment. However, these methods involve costly instruments and complex, time-consuming operations performed in laboratories. Here, a rapid, convenient, and sensitive colorimetric sensor based on anti-aggregation of gold nanoparticles (AuNPs) is demonstrated for the rapid detection of metsulfuron-methyl in agricultural irrigation water. The AuNPs could be induced to aggregate in the presence of melamine and exhibited a distinct color change from wine-red to blue. The aggregation was suppressed by a strong hydrogen-bonding interaction between metsulfuron-methyl and melamine. The differences of the absorbance at 523 nm (ΔA523) and the color change was linearly related to metsulfuron-methyl concentration over the range 0.1–100 mg/L, as observed visually and by UV-vis (Ultraviolet-visible) spectrometry. The detection limit of the sensor was as low as 0.05 mg/L (signal/noise = 3), and was used to determine metsulfuron-methyl in spiked water and in agricultural irrigation water samples. Recoveries were in the range of 71.2–100.4%, suggesting that the colorimetric sensor was suitable for the determination of metsulfuron-methyl in agricultural water samples. Full article

(This article belongs to the Section Chemical Sensors)

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26 pages, 2050 KiB

Open AccessArticle

An Energy Balanced and Lifetime Extended Routing Protocol for Underwater Sensor Networks

by Hao Wang¹

, Shilian Wang^1,*, Eryang Zhang¹ and Luxi Lu²

¹ College of Electronic Science and Engineering, National University of Defense Technology, Changsha 410073, China

² National Key Laboratory of Science and Technology on Blind Signal Processing, Chengdu 610000, China

Sensors 2018, 18(5), 1596; https://doi.org/10.3390/s18051596 - 17 May 2018

Cited by 34 | Viewed by 5497

Abstract

Energy limitation is an adverse problem in designing routing protocols for underwater sensor networks (UWSNs). To prolong the network lifetime with limited battery power, an energy balanced and efficient routing protocol, called energy balanced and lifetime extended routing protocol (EBLE), is proposed in [...] Read more.

Energy limitation is an adverse problem in designing routing protocols for underwater sensor networks (UWSNs). To prolong the network lifetime with limited battery power, an energy balanced and efficient routing protocol, called energy balanced and lifetime extended routing protocol (EBLE), is proposed in this paper. The proposed EBLE not only balances traffic loads according to the residual energy, but also optimizes data transmissions by selecting low-cost paths. Two phases are operated in the EBLE data transmission process: (1) candidate forwarding set selection phase and (2) data transmission phase. In candidate forwarding set selection phase, nodes update candidate forwarding nodes by broadcasting the position and residual energy level information. The cost value of available nodes is calculated and stored in each sensor node. Then in data transmission phase, high residual energy and relatively low-cost paths are selected based on the cost function and residual energy level information. We also introduce detailed analysis of optimal energy consumption in UWSNs. Numerical simulation results on a variety of node distributions and data load distributions prove that EBLE outperforms other routing protocols (BTM, BEAR and direct transmission) in terms of network lifetime and energy efficiency. Full article

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

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11 pages, 2259 KiB

Open AccessArticle

Overlap Spectrum Fiber Bragg Grating Sensor Based on Light Power Demodulation

by Hao Zhang^1,*,†, Junzhen Jiang^2,†, Shuang Liu¹, Huaixi Chen³, Xiaoqian Zheng¹ and Yishen Qiu²

¹ Department of Electronic Information Science, Fujian Jiangxia University, Fuzhou 350007, China

² Fujian Provincial Key Laboratory for Photonics Technology, Fujian Normal University, Fuzhou 350007, China

³ Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China

^† The authors contributed equally to this work.

Sensors 2018, 18(5), 1597; https://doi.org/10.3390/s18051597 - 17 May 2018

Cited by 14 | Viewed by 4203

Abstract

Demodulation is a bottleneck for applications involving fiber Bragg gratings (FBGs). An overlap spectrum FBG sensor based on a light power demodulation method is presented in this paper. The demodulation method uses two chirp FBGs (cFBGs) of which the reflection spectra partially overlap [...] Read more.

Demodulation is a bottleneck for applications involving fiber Bragg gratings (FBGs). An overlap spectrum FBG sensor based on a light power demodulation method is presented in this paper. The demodulation method uses two chirp FBGs (cFBGs) of which the reflection spectra partially overlap each other. The light power variation of the overlap spectrum can be linked to changes in the measurand, and the sensor function can be realized via this relationship. A temperature experiment showed that the relationship between the overlap power spectrum of the FBG sensor and temperature had good linearity and agreed with the theoretical analysis. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 1159 KiB

Open AccessArticle

AMID: Accurate Magnetic Indoor Localization Using Deep Learning

by Namkyoung Lee

, Sumin Ahn and Dongsoo Han^*

School of Computing, Korea Institute of Science and Technology, Daejeon 34141, Korea

Sensors 2018, 18(5), 1598; https://doi.org/10.3390/s18051598 - 17 May 2018

Cited by 72 | Viewed by 8648

Abstract

Geomagnetic-based indoor positioning has drawn a great attention from academia and industry due to its advantage of being operable without infrastructure support and its reliable signal characteristics. However, it must overcome the problems of ambiguity that originate with the nature of geomagnetic data. [...] Read more.

Geomagnetic-based indoor positioning has drawn a great attention from academia and industry due to its advantage of being operable without infrastructure support and its reliable signal characteristics. However, it must overcome the problems of ambiguity that originate with the nature of geomagnetic data. Most studies manage this problem by incorporating particle filters along with inertial sensors. However, they cannot yield reliable positioning results because the inertial sensors in smartphones cannot precisely predict the movement of users. There have been attempts to recognize the magnetic sequence pattern, but these attempts are proven only in a one-dimensional space, because magnetic intensity fluctuates severely with even a slight change of locations. This paper proposes accurate magnetic indoor localization using deep learning (AMID), an indoor positioning system that recognizes magnetic sequence patterns using a deep neural network. Features are extracted from magnetic sequences, and then the deep neural network is used for classifying the sequences by patterns that are generated by nearby magnetic landmarks. Locations are estimated by detecting the landmarks. AMID manifested the proposed features and deep learning as an outstanding classifier, revealing the potential of accurate magnetic positioning with smartphone sensors alone. The landmark detection accuracy was over 80% in a two-dimensional environment. Full article

(This article belongs to the Collection Positioning and Navigation)

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15 pages, 3985 KiB

Open AccessArticle

Automated Geo/Co-Registration of Multi-Temporal Very-High-Resolution Imagery

by Youkyung Han¹

and Jaehong Oh^2,*

¹ School of Convergence & Fusion System Engineering, Kyungpook National University, Sangju 37224, Korea

² Department of Civil Engineering, Korea Maritime and Ocean University, Busan 49112, Korea

Sensors 2018, 18(5), 1599; https://doi.org/10.3390/s18051599 - 17 May 2018

Cited by 15 | Viewed by 4583

Abstract

For time-series analysis using very-high-resolution (VHR) multi-temporal satellite images, both accurate georegistration to the map coordinates and subpixel-level co-registration among the images should be conducted. However, applying well-known matching methods, such as scale-invariant feature transform and speeded up robust features for VHR multi-temporal [...] Read more.

For time-series analysis using very-high-resolution (VHR) multi-temporal satellite images, both accurate georegistration to the map coordinates and subpixel-level co-registration among the images should be conducted. However, applying well-known matching methods, such as scale-invariant feature transform and speeded up robust features for VHR multi-temporal images, has limitations. First, they cannot be used for matching an optical image to heterogeneous non-optical data for georegistration. Second, they produce a local misalignment induced by differences in acquisition conditions, such as acquisition platform stability, the sensor’s off-nadir angle, and relief displacement of the considered scene. Therefore, this study addresses the problem by proposing an automated geo/co-registration framework for full-scene multi-temporal images acquired from a VHR optical satellite sensor. The proposed method comprises two primary steps: (1) a global georegistration process, followed by (2) a fine co-registration process. During the first step, two-dimensional multi-temporal satellite images are matched to three-dimensional topographic maps to assign the map coordinates. During the second step, a local analysis of registration noise pixels extracted between the multi-temporal images that have been mapped to the map coordinates is conducted to extract a large number of well-distributed corresponding points (CPs). The CPs are finally used to construct a non-rigid transformation function that enables minimization of the local misalignment existing among the images. Experiments conducted on five Kompsat-3 full scenes confirmed the effectiveness of the proposed framework, showing that the georegistration performance resulted in an approximately pixel-level accuracy for most of the scenes, and the co-registration performance further improved the results among all combinations of the georegistered Kompsat-3 image pairs by increasing the calculated cross-correlation values. Full article

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

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9 pages, 684 KiB

Open AccessArticle

63 km BOFDA for Temperature and Strain Monitoring

by Thomas Kapa^*

, Andy Schreier

and Katerina Krebber

Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 44-46, 12203 Berlin, Germany

Sensors 2018, 18(5), 1600; https://doi.org/10.3390/s18051600 - 17 May 2018

Cited by 27 | Viewed by 4571

Abstract

We demonstrate (and are the first to do so) 63 km Brillouin Optical Frequency-Domain Analysis (BOFDA) for temperature and strain monitoring using a 100 km fiber loop. The use of BOFDA for long-range applications can be considered a novel approach, as previous investigations [...] Read more.

We demonstrate (and are the first to do so) 63 km Brillouin Optical Frequency-Domain Analysis (BOFDA) for temperature and strain monitoring using a 100 km fiber loop. The use of BOFDA for long-range applications can be considered a novel approach, as previous investigations focused on the utilization of Brillouin Optical Time-Domain Reflectometry and Analysis (BOTDR and BOTDA, respectively). At 51.7 km, a 100 m hotspot (37

^{\circ}

C) was detected without using distributed Raman amplification or image processing. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 1676 KiB

Open AccessArticle

RCSS: A Real-Time On-Demand Charging Scheduling Scheme for Wireless Rechargeable Sensor Networks

by Ping Zhong

, Yiwen Zhang, Shuaihua Ma, Xiaoyan Kui and Jianliang Gao^*

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

Sensors 2018, 18(5), 1601; https://doi.org/10.3390/s18051601 - 17 May 2018

Cited by 47 | Viewed by 4688

Abstract

With the emergence of edge computing, a large number of devices such as sensor nodes have been deployed in the edge network to sense and process data. However, how to provide real-time on-demand energy for these edge devices is a new challenge issue [...] Read more.

With the emergence of edge computing, a large number of devices such as sensor nodes have been deployed in the edge network to sense and process data. However, how to provide real-time on-demand energy for these edge devices is a new challenge issue of edge networks. In real-world applications of edge computing, sensor nodes usually have different task burdens due to the environmental impact, which results in a dynamic change of the energy consumption rate at different nodes. Therefore, the traditional periodical charging mode cannot meet the nodes charging demand that have dynamic energy consumption. In this paper, we propose a real-time on-demand charging scheduling scheme (RCSS) under the condition of limited mobile charger capacity. In the process of building the charging path, RCSS adequately considers the dynamic energy consumption of different node, and puts forward the next node selection algorithm. At the same time, a method to determine the feasibility of charging circuit is also proposed to ensure the charging efficiency. During the charging process, RCSS is based on adaptive charging threshold to reduce node mortality. Compared with existing approaches, the proposed RCSS achieves better performance in the number of survival nodes, the average service time and charging efficiency. Full article

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

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18 pages, 2532 KiB

Open AccessArticle

Integrated Method for Personal Thermal Comfort Assessment and Optimization through Users’ Feedback, IoT and Machine Learning: A Case Study ^†

by Francesco Salamone^1,*

, Lorenzo Belussi¹

, Cristian Currò², Ludovico Danza¹, Matteo Ghellere¹, Giulia Guazzi¹, Bruno Lenzi², Valentino Megale² and Italo Meroni¹

¹ ITC-CNR, Construction Technologies Institute-National Research Council of Italy, Lombardia St., 49-20098 San Giuliano M.se, Italy

² SCS, SoftCare Studios Srls, Franco Sacchetti St., 52-00137 Roma, Italy

Sensors 2018, 18(5), 1602; https://doi.org/10.3390/s18051602 - 17 May 2018

Cited by 86 | Viewed by 10220

Abstract

Thermal comfort has become a topic issue in building performance assessment as well as energy efficiency. Three methods are mainly recognized for its assessment. Two of them based on standardized methodologies, face the problem by considering the indoor environment in steady-state conditions (PMV [...] Read more.

Thermal comfort has become a topic issue in building performance assessment as well as energy efficiency. Three methods are mainly recognized for its assessment. Two of them based on standardized methodologies, face the problem by considering the indoor environment in steady-state conditions (PMV and PPD) and users as active subjects whose thermal perception is influenced by outdoor climatic conditions (adaptive approach). The latter method is the starting point to investigate thermal comfort from an overall perspective by considering endogenous variables besides the traditional physical and environmental ones. Following this perspective, the paper describes the results of an in-field investigation of thermal conditions through the use of nearable and wearable solutions, parametric models and machine learning techniques. The aim of the research is the exploration of the reliability of IoT-based solutions combined with advanced algorithms, in order to create a replicable framework for the assessment and improvement of user thermal satisfaction. For this purpose, an experimental test in real offices was carried out involving eight workers. Parametric models are applied for the assessment of thermal comfort; IoT solutions are used to monitor the environmental variables and the users’ parameters; the machine learning CART method allows to predict the users’ profile and the thermal comfort perception respect to the indoor environment. 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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14 pages, 36779 KiB

Open AccessArticle

Effective Crack Detection in Railway Axles Using Vibration Signals and WPT Energy

by María Jesús Gómez^*

, Eduardo Corral

, Cristina Castejón

and Juan Carlos García-Prada

Mechanical Engineering Department，Universidad Carlos III de Madrid, 28911 Madrid, Spain

Sensors 2018, 18(5), 1603; https://doi.org/10.3390/s18051603 - 17 May 2018

Cited by 38 | Viewed by 7292

Abstract

Crack detection for railway axles is key to avoiding catastrophic accidents. Currently, non-destructive testing is used for that purpose. The present work applies vibration signal analysis to diagnose cracks in real railway axles installed on a real Y21 bogie working on a rig. [...] Read more.

Crack detection for railway axles is key to avoiding catastrophic accidents. Currently, non-destructive testing is used for that purpose. The present work applies vibration signal analysis to diagnose cracks in real railway axles installed on a real Y21 bogie working on a rig. Vibration signals were obtained from two wheelsets with cracks at the middle section of the axle with depths from 5.7 to 15 mm, at several conditions of load and speed. Vibration signals were processed by means of wavelet packet transform energy. Energies obtained were used to train an artificial neural network, with reliable diagnosis results. The success rate of 5.7 mm defects was 96.27%, and the reliability in detecting larger defects reached almost 100%, with a false alarm ratio lower than 5.5%. Full article

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

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20 pages, 9626 KiB

Open AccessArticle

A Preliminary Analysis of Wind Retrieval, Based on GF-3 Wave Mode Data

by Lei Wang^1,2,3, Bing Han^1,2,*, Xinzhe Yuan⁴, Bin Lei^1,2, Chibiao Ding^1,2,3,5, Yulin Yao⁶ and Qi Chen⁶

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

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

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

⁴ National Satellite Ocean Application Service, State Oceanic Administration, Beijing 100081, China

⁵ National Key Laboratory of Microwave Imaging Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

⁶ China Centre for Resource Satellite Data and Application, Beijing 100094, China

Sensors 2018, 18(5), 1604; https://doi.org/10.3390/s18051604 - 17 May 2018

Cited by 17 | Viewed by 4096

Abstract

This paper presents an analysis of measurements of the normalized radar cross-(NRCS) in Wave Mode for Chinese C-band Gaofen-3(GF-3) synthetic aperture radar (SAR). Based on 2779 images from GF-3 quad-polarization SAR in Wave Mode and collocated wind vectors from ERA-Interim, this experiment verifies [...] Read more.

This paper presents an analysis of measurements of the normalized radar cross-(NRCS) in Wave Mode for Chinese C-band Gaofen-3(GF-3) synthetic aperture radar (SAR). Based on 2779 images from GF-3 quad-polarization SAR in Wave Mode and collocated wind vectors from ERA-Interim, this experiment verifies the feasibility of using ocean surface wind fields and VV-polarized NRCS to perform normalized calibration. The method uses well-validated empirical C-band geophysical model function (CMOD4) to estimate the calibration constant for each beam. In addition, the relationship between cross-pol NRCS and wind vectors is discussed. The cross-pol NRCS increases linearly with wind speed and it is obviously modulated by the wind direction when the wind speed is greater than 8 m/s. Furthermore, the properties of the polarization ratio, denoted PR, are also investigated. The PR is dependent on incidence angle and azimuth angle. Two empirical models of the PR are fitted, one as a function of incidence angle only, the other with additional dependence on azimuth angle. Assessments show that the

σ_{VV}^{0}

retrieved from new PR models as well as

σ_{HH}^{0}

is in good agreement with

σ_{VV}^{0}

extracted from SAR images directly. Full article

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

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16 pages, 3318 KiB

Open AccessArticle

Measurement of Wall Shear Stress in High Speed Air Flow Using Shear-Sensitive Liquid Crystal Coating

by Jisong Zhao

College of Astronautics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Sensors 2018, 18(5), 1605; https://doi.org/10.3390/s18051605 - 17 May 2018

Cited by 9 | Viewed by 6331

Abstract

Wall shear stress is an important quantity in fluid mechanics, but its measurement is a challenging task. An approach to measure wall shear stress vector distribution using shear-sensitive liquid crystal coating (SSLCC) is described. The wall shear stress distribution on the test surface [...] Read more.

Wall shear stress is an important quantity in fluid mechanics, but its measurement is a challenging task. An approach to measure wall shear stress vector distribution using shear-sensitive liquid crystal coating (SSLCC) is described. The wall shear stress distribution on the test surface beneath high speed jet flow is measured while using the proposed technique. The flow structures inside the jet flow are captured and the results agree well with the streakline pattern that was visualized using the oil-flow technique. In addition, the shock diamonds inside the supersonic jet flow are visualized clearly using SSLCC and the results are compared with the velocity contour that was measured using the particle image velocimetry (PIV) technique. The work of this paper demonstrates the application of SSLCC in the measurement/visualization of wall shear stress in high speed flow. Full article

(This article belongs to the Special Issue New Sensors for Metrology for Aerospace)

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15 pages, 2832 KiB

Open AccessArticle

Improving the Energy Saving Process with High-Resolution Data: A Case Study in a University Building

by Jeongyun Han¹, Eunjung Lee¹, Hyunghun Cho¹, Yoonjin Yoon², Hyoseop Lee³ and Wonjong Rhee^1,*

¹ Department of Transdisciplinary Studies, Seoul National University, Seoul 08826, Korea

² Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea

³ Encored Technologies Inc., Seoul 06109, Korea

Sensors 2018, 18(5), 1606; https://doi.org/10.3390/s18051606 - 17 May 2018

Cited by 8 | Viewed by 6423

Abstract

In this paper, we provide findings from an energy saving experiment in a university building, where an IoT platform with 1 Hz sampling sensors was deployed to collect electric power consumption data. The experiment was a reward setup with daily feedback delivered by [...] Read more.

In this paper, we provide findings from an energy saving experiment in a university building, where an IoT platform with 1 Hz sampling sensors was deployed to collect electric power consumption data. The experiment was a reward setup with daily feedback delivered by an energy delegate for one week, and energy saving of 25.4% was achieved during the experiment. Post-experiment sustainability, defined as 10% or more of energy saving, was also accomplished for 44 days without any further intervention efforts. The saving was possible mainly because of the data-driven intervention designs with high-resolution data in terms of sampling frequency and number of sensors, and the high-resolution data turned out to be pivotal for an effective waste behavior investigation. While the quantitative result was encouraging, we also noticed many uncontrollable factors, such as exams, papers due, office allocation shuffling, graduation, and new-comers, that affected the result in the campus environment. To confirm that the quantitative result was due to behavior changes, rather than uncontrollable factors, we developed several data-driven behavior detection measures. With these measures, it was possible to analyze behavioral changes, as opposed to simply analyzing quantitative fluctuations. Overall, we conclude that the space-time resolution of data can be crucial for energy saving, and potentially for many other data-driven energy applications. Full article

(This article belongs to the Section Internet of Things)

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12 pages, 2998 KiB

Open AccessArticle

Sensitivity Enhancement of FBG-Based Strain Sensor

by Ruiya Li^1,2

, Yiyang Chen¹, Yuegang Tan^1,*, Zude Zhou¹, Tianliang Li³

and Jian Mao¹

¹ School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan 430070, China

² School of Engineering, University of Birmingham, Birmingham B15 2TT, UK

³ Department of Biomedical Engineering, National University of Singapore, Singapore 117576, Singapore

Sensors 2018, 18(5), 1607; https://doi.org/10.3390/s18051607 - 17 May 2018

Cited by 90 | Viewed by 9596

Abstract

A novel fiber Bragg grating (FBG)-based strain sensor with a high-sensitivity is presented in this paper. The proposed FBG-based strain sensor enhances sensitivity by pasting the FBG on a substrate with a lever structure. This typical mechanical configuration mechanically amplifies the strain of [...] Read more.

A novel fiber Bragg grating (FBG)-based strain sensor with a high-sensitivity is presented in this paper. The proposed FBG-based strain sensor enhances sensitivity by pasting the FBG on a substrate with a lever structure. This typical mechanical configuration mechanically amplifies the strain of the FBG to enhance overall sensitivity. As this mechanical configuration has a high stiffness, the proposed sensor can achieve a high resonant frequency and a wide dynamic working range. The sensing principle is presented, and the corresponding theoretical model is derived and validated. Experimental results demonstrate that the developed FBG-based strain sensor achieves an enhanced strain sensitivity of 6.2 pm/με, which is consistent with the theoretical analysis result. The strain sensitivity of the developed sensor is 5.2 times of the strain sensitivity of a bare fiber Bragg grating strain sensor. The dynamic characteristics of this sensor are investigated through the finite element method (FEM) and experimental tests. The developed sensor exhibits an excellent strain-sensitivity-enhancing property in a wide frequency range. The proposed high-sensitivity FBG-based strain sensor can be used for small-amplitude micro-strain measurement in harsh industrial environments. Full article

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

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12 pages, 3382 KiB

Open AccessArticle

Determination of the Maximum Temperature in a Non-Uniform Hot Zone by Line-of-Site Absorption Spectroscopy with a Single Diode Laser

by Vladimir V. Liger¹, Vladimir R. Mironenko¹, Yurii A. Kuritsyn¹

and Mikhail A. Bolshov^1,2,*

¹ Institute for Spectroscopy, Russian Academy of Sciences, 5 Fizicheskaya Str., Troitsk, 108840 Moscow, Russia

² Chemistry Department, Analytical Chemistry Division, Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow, Russia

Sensors 2018, 18(5), 1608; https://doi.org/10.3390/s18051608 - 17 May 2018

Cited by 11 | Viewed by 4050

Abstract

A new algorithm for the estimation of the maximum temperature in a non-uniform hot zone by a sensor based on absorption spectrometry with a diode laser is developed. The algorithm is based on the fitting of the absorption spectrum with a test molecule [...] Read more.

A new algorithm for the estimation of the maximum temperature in a non-uniform hot zone by a sensor based on absorption spectrometry with a diode laser is developed. The algorithm is based on the fitting of the absorption spectrum with a test molecule in a non-uniform zone by linear combination of two single temperature spectra simulated using spectroscopic databases. The proposed algorithm allows one to better estimate the maximum temperature of a non-uniform zone and can be useful if only the maximum temperature rather than a precise temperature profile is of primary interest. The efficiency and specificity of the algorithm are demonstrated in numerical experiments and experimentally proven using an optical cell with two sections. Temperatures and water vapor concentrations could be independently regulated in both sections. The best fitting was found using a correlation technique. A distributed feedback (DFB) diode laser in the spectral range around 1.343 µm was used in the experiments. Because of the significant differences between the temperature dependences of the experimental and theoretical absorption spectra in the temperature range 300–1200 K, a database was constructed using experimentally detected single temperature spectra. Using the developed algorithm the maximum temperature in the two-section cell was estimated with accuracy better than 30 K. Full article

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

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38 pages, 4672 KiB

Open AccessArticle

Secure Data Access Control for Fog Computing Based on Multi-Authority Attribute-Based Signcryption with Computation Outsourcing and Attribute Revocation

by Qian Xu^*, Chengxiang Tan, Zhijie Fan, Wenye Zhu, Ya Xiao and Fujia Cheng

Department of Computer Science and Technology, Tongji University, Cao An Highway, Shanghai 201804, China

Sensors 2018, 18(5), 1609; https://doi.org/10.3390/s18051609 - 17 May 2018

Cited by 40 | Viewed by 5444

Abstract

Nowadays, fog computing provides computation, storage, and application services to end users in the Internet of Things. One of the major concerns in fog computing systems is how fine-grained access control can be imposed. As a logical combination of attribute-based encryption and attribute-based [...] Read more.

Nowadays, fog computing provides computation, storage, and application services to end users in the Internet of Things. One of the major concerns in fog computing systems is how fine-grained access control can be imposed. As a logical combination of attribute-based encryption and attribute-based signature, Attribute-based Signcryption (ABSC) can provide confidentiality and anonymous authentication for sensitive data and is more efficient than traditional “encrypt-then-sign” or “sign-then-encrypt” strategy. Thus, ABSC is suitable for fine-grained access control in a semi-trusted cloud environment and is gaining more and more attention recently. However, in many existing ABSC systems, the computation cost required for the end users in signcryption and designcryption is linear with the complexity of signing and encryption access policy. Moreover, only a single authority that is responsible for attribute management and key generation exists in the previous proposed ABSC schemes, whereas in reality, mostly, different authorities monitor different attributes of the user. In this paper, we propose OMDAC-ABSC, a novel data access control scheme based on Ciphertext-Policy ABSC, to provide data confidentiality, fine-grained control, and anonymous authentication in a multi-authority fog computing system. The signcryption and designcryption overhead for the user is significantly reduced by outsourcing the undesirable computation operations to fog nodes. The proposed scheme is proven to be secure in the standard model and can provide attribute revocation and public verifiability. The security analysis, asymptotic complexity comparison, and implementation results indicate that our construction can balance the security goals with practical efficiency in computation. Full article

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

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23 pages, 3849 KiB

Open AccessArticle

A Framework of Covariance Projection on Constraint Manifold for Data Fusion ^†

by Muhammad Abu Bakr and Sukhan Lee^*

¹ Intelligent Systems Research Institute, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Korea

^† This paper is an extended version of the paper entitled “A general framework for data fusion and outlier removal in distributed sensor networks”, presented at IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems, Daegu, Korea, 16–18 November 2017.

Sensors 2018, 18(5), 1610; https://doi.org/10.3390/s18051610 - 17 May 2018

Cited by 6 | Viewed by 3745

Abstract

A general framework of data fusion is presented based on projecting the probability distribution of true states and measurements around the predicted states and actual measurements onto the constraint manifold. The constraint manifold represents the constraints to be satisfied among true states and [...] Read more.

A general framework of data fusion is presented based on projecting the probability distribution of true states and measurements around the predicted states and actual measurements onto the constraint manifold. The constraint manifold represents the constraints to be satisfied among true states and measurements, which is defined in the extended space with all the redundant sources of data such as state predictions and measurements considered as independent variables. By the general framework, we mean that it is able to fuse any correlated data sources while directly incorporating constraints and identifying inconsistent data without any prior information. The proposed method, referred to here as the Covariance Projection (CP) method, provides an unbiased and optimal solution in the sense of minimum mean square error (MMSE), if the projection is based on the minimum weighted distance on the constraint manifold. The proposed method not only offers a generalization of the conventional formula for handling constraints and data inconsistency, but also provides a new insight into data fusion in terms of a geometric-algebraic point of view. Simulation results are provided to show the effectiveness of the proposed method in handling constraints and data inconsistency. Full article

(This article belongs to the Collection Multi-Sensor Information Fusion)

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16 pages, 32991 KiB

Open AccessArticle

A Novel Locating System for Cereal Plant Stem Emerging Points’ Detection Using a Convolutional Neural Network

by Hadi Karimi^1,2,*

, Søren Skovsen²

, Mads Dyrmann²

and Rasmus Nyholm Jørgensen²

¹ Department of Biosystems Engineering, Faculty of Agriculture, University of Tabriz, Tabriz 29 Bahman Boulevard, Tabriz 5166616471, Iran

² Department of Engineering—Signal Processing, Aarhus University, DK-8000 Aarhus C, Denmark

Sensors 2018, 18(5), 1611; https://doi.org/10.3390/s18051611 - 18 May 2018

Cited by 7 | Viewed by 3906

Abstract

Determining the individual location of a plant, besides evaluating sowing performance, would make subsequent treatment for each plant across a field possible. In this study, a system for locating cereal plant stem emerging points (PSEPs) has been developed. In total, 5719 images were [...] Read more.

Determining the individual location of a plant, besides evaluating sowing performance, would make subsequent treatment for each plant across a field possible. In this study, a system for locating cereal plant stem emerging points (PSEPs) has been developed. In total, 5719 images were gathered from several cereal fields. In 212 of these images, the PSEPs of the cereal plants were marked manually and used to train a fully-convolutional neural network. In the training process, a cost function was made, which incorporates predefined penalty regions and PSEPs. The penalty regions were defined based on fault prediction of the trained model without penalty region assignment. By adding penalty regions to the training, the network’s ability to precisely locate emergence points of the cereal plants was enhanced significantly. A coefficient of determination of about 87 percent between the predicted PSEP number of each image and the manually marked one implies the ability of the system to count PSEPs. With regard to the obtained results, it was concluded that the developed model can give a reliable clue about the quality of PSEPs’ distribution and the performance of seed drills in fields. Full article

(This article belongs to the Special Issue Application of Satellite and Proximal Sensors in Precision Agriculture)

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12 pages, 1119 KiB

Open AccessArticle

A Model for Remote Depth Estimation of Buried Radioactive Wastes Using CdZnTe Detector

by Ikechukwu Kevin Ukaegbu^1,*

and Kelum A. A. Gamage²

¹ Engineering Department, Lancaster University, Lancaster LA1 4YW, UK

² School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK

Sensors 2018, 18(5), 1612; https://doi.org/10.3390/s18051612 - 18 May 2018

Cited by 6 | Viewed by 4068

Abstract

This paper presents the results of an attenuation model for remote depth estimation of buried radioactive wastes using a Cadmium Zinc Telluride (CZT) detector. Previous research using an organic liquid scintillator detector system showed that the model is able to estimate the depth [...] Read more.

This paper presents the results of an attenuation model for remote depth estimation of buried radioactive wastes using a Cadmium Zinc Telluride (CZT) detector. Previous research using an organic liquid scintillator detector system showed that the model is able to estimate the depth of a 329-kBq Cs-137 radioactive source buried up to 12 cm in sand with an average count rate of 100 cps. The results presented in this paper showed that the use of the CZT detector extended the maximum detectable depth of the same radioactive source to 18 cm in sand with a significantly lower average count rate of 14 cps. Furthermore, the model also successfully estimated the depth of a 9-kBq Co-60 source buried up to 3 cm in sand. This confirms that this remote depth estimation method can be used with other radionuclides and wastes with very low activity. Finally, the paper proposes a performance parameter for evaluating radiation detection systems that implement this remote depth estimation method. Full article

(This article belongs to the Section Remote Sensors)

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12 pages, 4686 KiB

Open AccessArticle

Design and Evaluation of an Aerosol Electrometer with Low Noise and a Wide Dynamic Range

by Yixin Yang^1,2, Tongzhu Yu^1,2,*, Jiaoshi Zhang^1,3, Wenyu Wang^1,2, Huaqiao Gui^1,3, Peng Du¹ and Jianguo Liu^1,2,3,*

¹ Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China

² Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230026, China

³ CAS Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China

Sensors 2018, 18(5), 1614; https://doi.org/10.3390/s18051614 - 18 May 2018

Cited by 13 | Viewed by 5146

Abstract

A low-noise aerosol electrometer with a wide dynamic range has been designed for measuring the total net charge on high concentration aerosol particles within the range of −500 pA to +500 pA. The performance of the aerosol electrometer was evaluated by a series [...] Read more.

A low-noise aerosol electrometer with a wide dynamic range has been designed for measuring the total net charge on high concentration aerosol particles within the range of −500 pA to +500 pA. The performance of the aerosol electrometer was evaluated by a series of experiments to determine linearity, sensitivity and noise. The relative errors were controlled within 5.0%, 1.0% and 0.3% at the range of −40 pA to +40 pA, ±40 pA to ±100 pA, and ±100 pA to ±500 pA respectively. The stability of the designed aerosol electrometer was found to be highly sensitive to temperature variations, but under temperature control, the root mean square noise and the peak-to-peak noise were 1.040 fA and 5.2 fA respectively, which are very close to the calculated theoretical limit of the current noise. The excellent correlation and the advantage of a wide dynamic range have been demonstrated by comparing with the designed aerosol electrometer to a commercial aerosol electrometer. A 99.7% (R²) statistical correlation was obtained; meanwhile, the designed aerosol electrometer operated well even when an overrange phenomenon appeared in the commercial aerosol electrometer. Full article

(This article belongs to the Special Issue Sensors for Emerging Environmental Markers and Contaminants)

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17 pages, 332 KiB

Open AccessArticle

Feature Extraction and Selection for Myoelectric Control Based on Wearable EMG Sensors

by Angkoon Phinyomark^1,*

, Rami N. Khushaba²

and Erik Scheme¹

¹ Institute of Biomedical Engineering, University of New Brunswick, Fredericton, NB E3B 5A3, Canada

² Faculty of Engineering and Information Technology, University of Technology, Sydney 2007, NSW, Australia

Sensors 2018, 18(5), 1615; https://doi.org/10.3390/s18051615 - 18 May 2018

Cited by 245 | Viewed by 14562

Abstract

Specialized myoelectric sensors have been used in prosthetics for decades, but, with recent advancements in wearable sensors, wireless communication and embedded technologies, wearable electromyographic (EMG) armbands are now commercially available for the general public. Due to physical, processing, and cost constraints, however, these [...] Read more.

Specialized myoelectric sensors have been used in prosthetics for decades, but, with recent advancements in wearable sensors, wireless communication and embedded technologies, wearable electromyographic (EMG) armbands are now commercially available for the general public. Due to physical, processing, and cost constraints, however, these armbands typically sample EMG signals at a lower frequency (e.g., 200 Hz for the Myo armband) than their clinical counterparts. It remains unclear whether existing EMG feature extraction methods, which largely evolved based on EMG signals sampled at 1000 Hz or above, are still effective for use with these emerging lower-bandwidth systems. In this study, the effects of sampling rate (low: 200 Hz vs. high: 1000 Hz) on the classification of hand and finger movements were evaluated for twenty-six different individual features and eight sets of multiple features using a variety of datasets comprised of both able-bodied and amputee subjects. The results show that, on average, classification accuracies drop significantly (

p <

0.05) from 2% to 56% depending on the evaluated features when using the lower sampling rate, and especially for transradial amputee subjects. Importantly, for these subjects, no number of existing features can be combined to compensate for this loss in higher-frequency content. From these results, we identify two new sets of recommended EMG features (along with a novel feature, L-scale) that provide better performance for these emerging low-sampling rate systems. Full article

(This article belongs to the Special Issue Wearable and Ambient Sensors for Healthcare and Wellness Applications 2018)

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15 pages, 2051 KiB

Open AccessArticle

Application of a Novel S3 Nanowire Gas Sensor Device in Parallel with GC-MS for the Identification of Rind Percentage of Grated Parmigiano Reggiano

by Marco Abbatangelo^1,*

, Estefanía Núñez-Carmona¹

, Veronica Sberveglieri^2,3

, Dario Zappa¹, Elisabetta Comini^1,3 and Giorgio Sberveglieri^1,3

¹ Department of Information Engineering, University of Brescia, Via Branze 38, 25123 Brescia, Italy

² CNR-IBBR, Institute of Biosciences and Bioresources, Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI), Italy

³ NANO SENSOR SYSTEMS S.r.l., Via Branze 38, 25123 Brescia, Italy

Sensors 2018, 18(5), 1617; https://doi.org/10.3390/s18051617 - 18 May 2018

Cited by 29 | Viewed by 4541

Abstract

Parmigiano Reggiano cheese is one of the most appreciated and consumed foods worldwide, especially in Italy, for its high content of nutrients and taste. However, these characteristics make this product subject to counterfeiting in different forms. In this study, a novel method based [...] Read more.

Parmigiano Reggiano cheese is one of the most appreciated and consumed foods worldwide, especially in Italy, for its high content of nutrients and taste. However, these characteristics make this product subject to counterfeiting in different forms. In this study, a novel method based on an electronic nose has been developed to investigate the potentiality of this tool to distinguish rind percentages in grated Parmigiano Reggiano packages that should be lower than 18%. Different samples, in terms of percentage, seasoning and rind working process, were considered to tackle the problem at 360°. In parallel, GC-MS technique was used to give a name to the compounds that characterize Parmigiano and to relate them to sensors responses. Data analysis consisted of two stages: Multivariate analysis (PLS) and classification made in a hierarchical way with PLS-DA ad ANNs. Results were promising, in terms of correct classification of the samples. The correct classification rate (%) was higher for ANNs than PLS-DA, with correct identification approaching 100 percent. Full article

(This article belongs to the Special Issue Artificial Olfaction and Taste)

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12 pages, 1581 KiB

Open AccessArticle

Estimating Respiratory Rate in Post-Anesthesia Care Unit Patients Using Infrared Thermography: An Observational Study

by Nadine Hochhausen^1,*

, Carina Barbosa Pereira², Steffen Leonhardt²

, Rolf Rossaint¹ and Michael Czaplik¹

¹ Department of Anesthesiology, Medical Faculty, RWTH Aachen University, 52074 Aachen, Germany

² Philips Chair for Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, 52074 Aachen, Germany

Sensors 2018, 18(5), 1618; https://doi.org/10.3390/s18051618 - 18 May 2018

Cited by 38 | Viewed by 5391

Abstract

The post-anesthesia care unit (PACU) is the central hub for recovery after surgery, especially when the surgery is performed under general anesthesia. Aside from clinical aspects, respiratory impairment is one of the major causes of morbidity and affected recovery in the PACU and [...] Read more.

The post-anesthesia care unit (PACU) is the central hub for recovery after surgery, especially when the surgery is performed under general anesthesia. Aside from clinical aspects, respiratory impairment is one of the major causes of morbidity and affected recovery in the PACU and should therefore be monitored. In previous studies, infrared thermography was applied to assess the breathing rate (BR) of healthy volunteers. Here, the transferability of published methods for postoperative patients in the PACU was examined. Video recordings of 28 patients were acquired using a long-wave infrared camera, and analyzed offline. For validation purposes, BRs derived from body surface electrocardiography were measured simultaneously. In general, a close agreement between the two techniques (r = 0.607, p = 0.002 upon arrival, and r = 0.849, p < 0.001 upon discharge from the PACU) was obtained. In conclusion, the algorithm was demonstrated to be feasible and reliable under these challenging conditions. Full article

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

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30 pages, 350 KiB

Open AccessArticle

Routing Protocols for Underwater Wireless Sensor Networks: Taxonomy, Research Challenges, Routing Strategies and Future Directions

by Anwar Khan^1,2,*

, Ihsan Ali^3,*

, Abdullah Ghani^3,4,*, Nawsher Khan^5,6

, Mohammed Alsaqer⁵, Atiq Ur Rahman⁷

and Hasan Mahmood²

¹ Department of Electronics, University of Peshawar, Peshawar KPK 25000, Pakistan

² Department of Electronics, Quaid-i-Azam University, Islamabad 44000, Pakistan

³ Department of Computer System and Technology, Faculty of Computer Science and Information Technology, University of Malaya, Kualalumpur 50603, Malaysia

⁴ School of Computing and IT, Taylor’s University, Kualalumpur 50603, Malaysia

⁵ Collage of Computer Science, King Khalid University, Abha 61421, Saudi Arabia

⁶ Department of Computer Science, Abdul Wali Khan University, Mardan 23200, Pakistan

⁷ Faculty of Computing and Information Technology, Northern Border University, Rafha 11351, Saudi Arabia

Sensors 2018, 18(5), 1619; https://doi.org/10.3390/s18051619 - 18 May 2018

Cited by 95 | Viewed by 9198

Abstract

Recent research in underwater wireless sensor networks (UWSNs) has gained the attention of researchers in academia and industry for a number of applications. They include disaster and earthquake prediction, water quality and environment monitoring, leakage and mine detection, military surveillance and underwater navigation. [...] Read more.

Recent research in underwater wireless sensor networks (UWSNs) has gained the attention of researchers in academia and industry for a number of applications. They include disaster and earthquake prediction, water quality and environment monitoring, leakage and mine detection, military surveillance and underwater navigation. However, the aquatic medium is associated with a number of limitations and challenges: long multipath delay, high interference and noise, harsh environment, low bandwidth and limited battery life of the sensor nodes. These challenges demand research techniques and strategies to be overcome in an efficient and effective fashion. The design of routing protocols for UWSNs is one of the promising solutions to cope with these challenges. This paper presents a survey of the routing protocols for UWSNs. For the ease of description, the addressed routing protocols are classified into two groups: localization-based and localization-free protocols. These groups are further subdivided according to the problems they address or the major parameters they consider during routing. Unlike the existing surveys, this survey considers only the latest and state-of-the-art routing protocols. In addition, every protocol is described in terms of its routing strategy and the problem it addresses and solves. The merit(s) of each protocol is (are) highlighted along with the cost. A description of the protocols in this fashion has a number of advantages for researchers, as compared to the existing surveys. Firstly, the description of the routing strategy of each protocol makes its routing operation easily understandable. Secondly, the demerit(s) of a protocol provides (provide) insight into overcoming its flaw(s) in future investigation. This, in turn, leads to the foundation of new protocols that are more intelligent, robust and efficient with respect to the desired parameters. Thirdly, a protocol can be selected for the appropriate application based on its described merit(s). Finally, open challenges and research directions are presented for future investigation. Full article

(This article belongs to the Special Issue Underwater Sensing, Communication, Networking and Systems)

9 pages, 31273 KiB

Open AccessArticle

A Tube-Integrated Painted Biosensor for Glucose and Lactate

by Weihua Shi, Xiaojin Luo and Yue Cui^*

College of Engineering, Peking University, Beijing 100871, China

Sensors 2018, 18(5), 1620; https://doi.org/10.3390/s18051620 - 18 May 2018

Cited by 13 | Viewed by 3947

Abstract

Developing a simple and direct approach for sensitive, specific, and rapid detection of metabolic compounds is of great importance for a variety of biological, medical, and food applications. Tubes are a highly portable and accessible container shape which are widely used for scientific [...] Read more.

Developing a simple and direct approach for sensitive, specific, and rapid detection of metabolic compounds is of great importance for a variety of biological, medical, and food applications. Tubes are a highly portable and accessible container shape which are widely used for scientific research in cell biology and chemical synthesis, and which are also of great use in domestic health care applications. Here, we show for the first time the development of a tube-based painted amperometric biosensor for the detection of glucose and lactate. The sensor was prepared by printing carbon graphite and silver/silver chloride inks on the interior wall of the tube and then immobilizing glucose oxidase or lactate oxidase on the sensor. The sensor showed a sensitive, rapid, and reliable detection of glucose and lactate. We anticipate that these results could open new avenues for the development of painted biosensors, and toward advanced biosensor applications. Full article

(This article belongs to the Section Biosensors)

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13 pages, 2689 KiB

Open AccessArticle

Grating-Coupled Surface Plasmon Resonance (GC-SPR) Optimization for Phase-Interrogation Biosensing in a Microfluidic Chamber

by Stefano Rossi^1,2,3, Enrico Gazzola¹, Pietro Capaldo⁴, Giulia Borile^1,2,3,*,† and Filippo Romanato^1,2,3,4,†

¹ Department of Physics and Astronomy “G. Galilei”, University of Padua, Via Marzolo 8, 35131 Padua, Italy

² Laboratory for Nanofabrication of Nanodevices, Corso Stati Uniti 4, 35127 Padua, Italy

³ Fondazione Institute of Pediatric Research Città della Speranza, Corso Stati Uniti 4, 35127 Padua, Italy

⁴ CNR-INFM TASC IOM National Laboratory, Area Science Park S.S. 14 km 163.5, 34012 Trieste, Italy

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1621; https://doi.org/10.3390/s18051621 - 18 May 2018

Cited by 53 | Viewed by 6362

Abstract

Surface Plasmon Resonance (SPR)-based sensors have the advantage of being label-free, enzyme-free and real-time. However, their spreading in multidisciplinary research is still mostly limited to prism-coupled devices. Plasmonic gratings, combined with a simple and cost-effective instrumentation, have been poorly developed compared to prism-coupled [...] Read more.

Surface Plasmon Resonance (SPR)-based sensors have the advantage of being label-free, enzyme-free and real-time. However, their spreading in multidisciplinary research is still mostly limited to prism-coupled devices. Plasmonic gratings, combined with a simple and cost-effective instrumentation, have been poorly developed compared to prism-coupled system mainly due to their lower sensitivity. Here we describe the optimization and signal enhancement of a sensing platform based on phase-interrogation method, which entails the exploitation of a nanostructured sensor. This technique is particularly suitable for integration of the plasmonic sensor in a lab-on-a-chip platform and can be used in a microfluidic chamber to ease the sensing procedures and limit the injected volume. The careful optimization of most suitable experimental parameters by numerical simulations leads to a 30–50% enhancement of SPR response, opening new possibilities for applications in the biomedical research field while maintaining the ease and versatility of the configuration. Full article

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

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31 pages, 10014 KiB

Open AccessArticle

A Multimodal Deep Log-Based User Experience (UX) Platform for UX Evaluation

by Jamil Hussain¹

, Wajahat Ali Khan¹, Taeho Hur¹, Hafiz Syed Muhammad Bilal¹, Jaehun Bang¹

, Anees Ul Hassan¹, Muhammad Afzal²

and Sungyoung Lee^1,*

¹ Ubiquitous Computing Lab, Department of Computer Science and Engineering, Kyung Hee University, Giheung-gu, Yongin-si, Gyeonggi-do, Seoul 446-701, Korea

² Department of Software, College of Electronics and Information Engineering, Sejong University, Seoul 05006, Korea

Sensors 2018, 18(5), 1622; https://doi.org/10.3390/s18051622 - 18 May 2018

Cited by 47 | Viewed by 13094

Abstract

The user experience (UX) is an emerging field in user research and design, and the development of UX evaluation methods presents a challenge for both researchers and practitioners. Different UX evaluation methods have been developed to extract accurate UX data. Among UX evaluation [...] Read more.

The user experience (UX) is an emerging field in user research and design, and the development of UX evaluation methods presents a challenge for both researchers and practitioners. Different UX evaluation methods have been developed to extract accurate UX data. Among UX evaluation methods, the mixed-method approach of triangulation has gained importance. It provides more accurate and precise information about the user while interacting with the product. However, this approach requires skilled UX researchers and developers to integrate multiple devices, synchronize them, analyze the data, and ultimately produce an informed decision. In this paper, a method and system for measuring the overall UX over time using a triangulation method are proposed. The proposed platform incorporates observational and physiological measurements in addition to traditional ones. The platform reduces the subjective bias and validates the user’s perceptions, which are measured by different sensors through objectification of the subjective nature of the user in the UX assessment. The platform additionally offers plug-and-play support for different devices and powerful analytics for obtaining insight on the UX in terms of multiple participants. Full article

(This article belongs to the Collection Multi-Sensor Information Fusion)

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14 pages, 4026 KiB

Open AccessArticle

Microfluidic Cultivation and Laser Tweezers Raman Spectroscopy of E. coli under Antibiotic Stress

by Zdeněk Pilát^1,*, Silvie Bernatová¹, Jan Ježek¹, Johanna Kirchhoff^2,3,4, Astrid Tannert^2,4, Ute Neugebauer^2,3,4

, Ota Samek¹ and Pavel Zemánek¹

¹ Institute of Scientific Instruments (ISI), Czech Academy of Sciences, v.v.i., Kralovopolska 147, 612 64 Brno, Czech Republic

² Center for Sepsis Control and Care (CSCC), Jena University Hospital, Am Klinikum 1, D-07747 Jena, Germany

³ Institute of Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, D-07743 Jena, Germany

⁴ Leibniz Institute of Photonic Technology (Leibniz IPHT), Albert-Einstein-Str. 9, D-07745 Jena, Germany

Sensors 2018, 18(5), 1623; https://doi.org/10.3390/s18051623 - 18 May 2018

Cited by 42 | Viewed by 8575

Abstract

Analyzing the cells in various body fluids can greatly deepen the understanding of the mechanisms governing the cellular physiology. Due to the variability of physiological and metabolic states, it is important to be able to perform such studies on individual cells. Therefore, we [...] Read more.

Analyzing the cells in various body fluids can greatly deepen the understanding of the mechanisms governing the cellular physiology. Due to the variability of physiological and metabolic states, it is important to be able to perform such studies on individual cells. Therefore, we developed an optofluidic system in which we precisely manipulated and monitored individual cells of Escherichia coli. We tested optical micromanipulation in a microfluidic chamber chip by transferring individual bacteria into the chambers. We then subjected the cells in the chambers to antibiotic cefotaxime and we observed the changes by using time-lapse microscopy. Separately, we used laser tweezers Raman spectroscopy (LTRS) in a different micro-chamber chip to manipulate and analyze individual cefotaxime-treated E. coli cells. Additionally, we performed conventional Raman micro-spectroscopic measurements of E. coli cells in a micro-chamber. We found observable changes in the cellular morphology (cell elongation) and in Raman spectra, which were consistent with other recently published observations. The principal component analysis (PCA) of Raman data distinguished between the cefotaxime treated cells and control. We tested the capabilities of the optofluidic system and found it to be a reliable and versatile solution for this class of microbiological experiments. Full article

(This article belongs to the Special Issue Applications of Raman Spectroscopy in Sensors)

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16 pages, 1484 KiB

Open AccessArticle

Quadratic Frequency Modulation Signals Parameter Estimation Based on Two-Dimensional Product Modified Parameterized Chirp Rate-Quadratic Chirp Rate Distribution

by Zhiyu Qu^†, Fuxin Qu^†, Changbo Hou^* and Fulong Jing^†

¹ College of Information and Communication Engineering, Harbin Engineering University, Harbin 150001, China

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1624; https://doi.org/10.3390/s18051624 - 19 May 2018

Cited by 10 | Viewed by 3752

Abstract

In an inverse synthetic aperture radar (ISAR) imaging system for targets with complex motion, the azimuth echo signals of the target are always modeled as multicomponent quadratic frequency modulation (QFM) signals. The chirp rate (CR) and quadratic chirp rate (QCR) estimation of QFM [...] Read more.

In an inverse synthetic aperture radar (ISAR) imaging system for targets with complex motion, the azimuth echo signals of the target are always modeled as multicomponent quadratic frequency modulation (QFM) signals. The chirp rate (CR) and quadratic chirp rate (QCR) estimation of QFM signals is very important to solve the ISAR image defocus problem. For multicomponent QFM (multi-QFM) signals, the conventional QR and QCR estimation algorithms suffer from the cross-term and poor anti-noise ability. This paper proposes a novel estimation algorithm called a two-dimensional product modified parameterized chirp rate-quadratic chirp rate distribution (2D-PMPCRD) for QFM signals parameter estimation. The 2D-PMPCRD employs a multi-scale parametric symmetric self-correlation function and modified nonuniform fast Fourier transform-Fast Fourier transform to transform the signals into the chirp rate-quadratic chirp rate (CR-QCR) domains. It can greatly suppress the cross-terms while strengthening the auto-terms by multiplying different CR-QCR domains with different scale factors. Compared with high order ambiguity function-integrated cubic phase function and modified Lv’s distribution, the simulation results verify that the 2D-PMPCRD acquires higher anti-noise performance and obtains better cross-terms suppression performance for multi-QFM signals with reasonable computation cost. Full article

(This article belongs to the Section Remote Sensors)

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11 pages, 2655 KiB

Open AccessArticle

A 3D-Printed Multichannel Viscometer for High-Throughput Analysis of Frying Oil Quality

by Sein Oh^†, Byeongyeon Kim^† and Sungyoung Choi^*

¹ Department of Biomedical Engineering, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, Korea

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1625; https://doi.org/10.3390/s18051625 - 19 May 2018

Cited by 7 | Viewed by 5216

Abstract

Viscosity as a sensitive measure of material changes is a potential quality-control parameter for simple and rapid assessment of frying oil quality. However, conventional viscometers require improvements in throughput, portability, cost-effectiveness and usability to be widely adopted for quality-control applications. Here we present [...] Read more.

Viscosity as a sensitive measure of material changes is a potential quality-control parameter for simple and rapid assessment of frying oil quality. However, conventional viscometers require improvements in throughput, portability, cost-effectiveness and usability to be widely adopted for quality-control applications. Here we present a 3D-printed multichannel viscometer for simple, inexpensive and multiplexed viscosity measurement. The multichannel viscometer enables both parallel actuation of multiple fluid flows by pressing the plunger of the viscometer by hand and direct measurement of their relative volumes dispensed with naked eye. Thus, the unknown viscosities of test fluids can be simultaneously determined by the volume ratios between a reference fluid of known viscosity and the test fluids of unknown viscosity. With a 4-plex version of the multichannel viscometer, we demonstrated that the viscometer is effective for rapid examination of the degradation of a vegetable oil during deep frying of potato strips and the recovery of used frying oil after treatment with an adsorbent agent to remove frying by-products. The measurement results obtained by the multichannel viscometer were highly correlated with those obtained using a commercial oil tester. We also demonstrated the multiplexing capability of the viscometer, fabricating a 10-plex version of the viscometer and measuring the viscosities of ten test liquids at the same time. Collectively, these results indicate that the 3D-printed multichannel viscometer represents a valuable tool for high-throughput examination of frying oil quality in resource-limited settings. Full article

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

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18 pages, 5484 KiB

Open AccessArticle

Etracker: A Mobile Gaze-Tracking System with Near-Eye Display Based on a Combined Gaze-Tracking Algorithm

by Bin Li^1,2,3, Hong Fu^3,*, Desheng Wen¹ and WaiLun LO³

¹ Xi’an Institute of Optics and Precision Mechanics of CAS, Xi’an 710119, China

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

³ Department of Computer Science, Chu Hai College of Higher Education, Tuen Mun, Hong Kong, China

Sensors 2018, 18(5), 1626; https://doi.org/10.3390/s18051626 - 19 May 2018

Cited by 34 | Viewed by 7727

Abstract

Eye tracking technology has become increasingly important for psychological analysis, medical diagnosis, driver assistance systems, and many other applications. Various gaze-tracking models have been established by previous researchers. However, there is currently no near-eye display system with accurate gaze-tracking performance and a convenient [...] Read more.

Eye tracking technology has become increasingly important for psychological analysis, medical diagnosis, driver assistance systems, and many other applications. Various gaze-tracking models have been established by previous researchers. However, there is currently no near-eye display system with accurate gaze-tracking performance and a convenient user experience. In this paper, we constructed a complete prototype of the mobile gaze-tracking system ‘Etracker’ with a near-eye viewing device for human gaze tracking. We proposed a combined gaze-tracking algorithm. In this algorithm, the convolutional neural network is used to remove blinking images and predict coarse gaze position, and then a geometric model is defined for accurate human gaze tracking. Moreover, we proposed using the mean value of gazes to resolve pupil center changes caused by nystagmus in calibration algorithms, so that an individual user only needs to calibrate it the first time, which makes our system more convenient. The experiments on gaze data from 26 participants show that the eye center detection accuracy is 98% and Etracker can provide an average gaze accuracy of 0.53° at a rate of 30–60 Hz. Full article

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

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18 pages, 6054 KiB

Open AccessArticle

Traceability in Patient Healthcare through the Integration of RFID Technology in an ICU in a Hospital

by María Martínez Pérez^*

, Carlos Dafonte

and Ángel Gómez

CITIC—Department of Computer Science, University of A Coruña, Campus de Elviña s/n, 15071 A Coruña, Spain

Sensors 2018, 18(5), 1627; https://doi.org/10.3390/s18051627 - 19 May 2018

Cited by 28 | Viewed by 6509

Abstract

Patient safety is a principal concern for health professionals in the care process and it is, therefore, necessary to provide information management systems to each unit of the hospital, capable of tracking patients and medication to reduce the occurrence of adverse events and [...] Read more.

Patient safety is a principal concern for health professionals in the care process and it is, therefore, necessary to provide information management systems to each unit of the hospital, capable of tracking patients and medication to reduce the occurrence of adverse events and therefore increase the quality of care received by patients during their stay in hospital. This work presents a tool for the Intensive Care Unit (ICU), a key service with special characteristics, which computerises and tracks admissions, care plans, vital monitoring, the prescription and medication administration process for patients in this service. To achieve this, it is essential that innovative and cutting-edge technologies are implemented such as Near Field Communication (NFC) technology which is now being implemented in diverse environments bringing a range of benefits to the tasks for which it is employed. 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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11 pages, 1678 KiB

Open AccessArticle

A High-Q AFM Sensor Using a Balanced Trolling Quartz Tuning Fork in the Liquid

by Yingxu Zhang^1,2

, Yingzi Li^2,3,*, Zihang Song^2,3, Rui Lin^2,3

, Yifu Chen^2,3 and Jianqiang Qian^2,3

¹ School of Instrumentation Science and Opto-electronics Engineering, Beihang University, Beijing 100191, China

² Key Laboratory of Micro-nano Measurement-Manipulation and Physics, Beihang University, Beijing 100191, China

³ School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191, China

Sensors 2018, 18(5), 1628; https://doi.org/10.3390/s18051628 - 19 May 2018

Cited by 13 | Viewed by 4158

Abstract

A quartz tuning fork (QTF) has been widely used as a force sensor of the frequency modulation atomic force microscope due to its ultrahigh stiffness, high quality factor and self-sensing nature. However, due to the bulky structure and exposed surface electrode arrangement, its [...] Read more.

A quartz tuning fork (QTF) has been widely used as a force sensor of the frequency modulation atomic force microscope due to its ultrahigh stiffness, high quality factor and self-sensing nature. However, due to the bulky structure and exposed surface electrode arrangement, its application is limited, especially in liquid imaging of in situ biological samples, ionic liquids, electrochemical reaction, etc. Although the complication can be resolved by coating insulating materials on the QTF surface and then immersing the whole QTF into the liquid, it would result in a sharp drop of the quality factor, which will reduce the sensitivity of the QTF. To solve the problem, a novel method, called the balanced trolling quartz tuning fork (BT-QTF), is introduced here. In this method, two same probes are glued on both prongs of the QTF separately while only one probe immersed in the liquid. With the method, the hydrodynamic interaction can be reduced, thus the BT-QTF can retain a high quality factor and constant resonance frequency. The stable small vibration of the BT-QTF can be achieved in the liquid. Initially, a theoretical model is presented to analyze the sensing performance of the BT-QTF in the liquid. Then, the sensing performance analysis experiments of the BT-QTF have been performed. At last, the proposed method is applied to atomic force microscope imaging different samples in the liquid, which proves its feasibility. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 3400 KiB

Open AccessArticle

Study of CMOS-SOI Integrated Temperature Sensing Circuits for On-Chip Temperature Monitoring

by Maria Malits^*, Igor Brouk and Yael Nemirovsky

Department of Electrical Engineering, Technion—Israel Institute of Technology, Haifa 3200003, Israel

Sensors 2018, 18(5), 1629; https://doi.org/10.3390/s18051629 - 19 May 2018

Cited by 14 | Viewed by 7759

Abstract

This paper investigates the concepts, performance and limitations of temperature sensing circuits realized in complementary metal-oxide-semiconductor (CMOS) silicon on insulator (SOI) technology. It is shown that the MOSFET threshold voltage (V_t) can be used to accurately measure the chip local [...] Read more.

This paper investigates the concepts, performance and limitations of temperature sensing circuits realized in complementary metal-oxide-semiconductor (CMOS) silicon on insulator (SOI) technology. It is shown that the MOSFET threshold voltage (V_t) can be used to accurately measure the chip local temperature by using a V_t extractor circuit. Furthermore, the circuit’s performance is compared to standard circuits used to generate an accurate output current or voltage proportional to the absolute temperature, i.e., proportional-to-absolute temperature (PTAT), in terms of linearity, sensitivity, power consumption, speed, accuracy and calibration needs. It is shown that the V_t extractor circuit is a better solution to determine the temperature of low power, analog and mixed-signal designs due to its accuracy, low power consumption and no need for calibration. The circuit has been designed using 1 µm partially depleted (PD) CMOS-SOI technology, and demonstrates a measurement inaccuracy of ±1.5 K across 300 K–500 K temperature range while consuming only 30 µW during operation. Full article

(This article belongs to the Special Issue CMOS Smart Temperature Sensors)

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14 pages, 5228 KiB

Open AccessArticle

An Electromagnetic/Capacitive Composite Sensor for Testing of Thermal Barrier Coatings

by Yuan Ren^*, Mengchun Pan, Dixiang Chen and Wugang Tian^*

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

Sensors 2018, 18(5), 1630; https://doi.org/10.3390/s18051630 - 19 May 2018

Cited by 16 | Viewed by 3477

Abstract

Thermal barrier coatings (TBCs) can significantly reduce the operating temperature of the aeroengine turbine blade substrate, and their testing technology is very urgently demanded. Due to their complex multi-layer structure, it is hard to evaluate TBCs with a single function sensor. In this [...] Read more.

Thermal barrier coatings (TBCs) can significantly reduce the operating temperature of the aeroengine turbine blade substrate, and their testing technology is very urgently demanded. Due to their complex multi-layer structure, it is hard to evaluate TBCs with a single function sensor. In this paper, an electromagnetic/capacitive composite sensor is proposed for the testing of thermal barrier coatings. The dielectric material is tested with planar capacitor, and the metallic material is tested with electromagnetic coils. Then, the comprehensive test and evaluation of thermal barrier coating system can be realized. The sensor is optimized by means of theoretical and simulation analysis, and the interaction between the planar capacitor and the electromagnetic coil is studied. The experimental system is built based on an impedance analyser and multiplex unit to evaluate the performance of the composite sensor. The transimpedances and capacitances are measured under different coating parameters, such as thickness and permittivity of top coating as well as bond layer conductivity. The experimental results agree with the simulation analysis, and the feasibility of the sensor is proved. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 4391 KiB

Open AccessArticle

Hysteresis Compensation in a Tactile Device for Arterial Pulse Reproduction

by Fernando Carneiro^*,†, Paulo Abreu

and Maria Teresa Restivo

¹ LAETA—INEGI, Associated Laboratory for Energy, Transports and Aeronautics—Institute of Science and Innovation in Mechanical and Industrial Engineering, University of Porto, 4200-465 Porto, Portugal

^† Current Address: Rua Dr. Roberto Frias, 400 Porto, Portugal.

Sensors 2018, 18(5), 1631; https://doi.org/10.3390/s18051631 - 19 May 2018

Cited by 7 | Viewed by 3524

Abstract

This paper describes a system for training healthcare practitioners in the identification of different arterial pulses. The driving system uses a linear solenoid in an open loop force control. Due to the large hysteresis it exhibited, a form of compensation was implemented, based [...] Read more.

This paper describes a system for training healthcare practitioners in the identification of different arterial pulses. The driving system uses a linear solenoid in an open loop force control. Due to the large hysteresis it exhibited, a form of compensation was implemented, based on the classic Preisach model of hysteresis. Implementation of said model resulted in a significant reduction of force tracking error, demonstrating the feasibility of the chosen approach for the intended application. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 568 KiB

Open AccessArticle

Integrated Framework of Load Monitoring by a Combination of Smartphone Applications, Wearables and Point-of-Care Testing Provides Feedback that Allows Individual Responsive Adjustments to Activities of Daily Living

by Peter Düking^1,*

, Silvia Achtzehn^2,3, Hans-Christer Holmberg^4,5 and Billy Sperlich¹

¹ Integrative and Experimental Exercise Science & Training, Institute for Sport Sciences, University of Würzburg, 97082 Würzburg, Germany

² Institute of Cardiology and Sports Medicine, German Sport University, 50933 Cologne, Germany

³ The German Research Centre of Elite Sport, German Sport University, 50933 Cologne, Germany

⁴ School of Sport Sciences, UiT The Arctic University of Norway, 9019 Tromso, Norway

⁵ Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, SE-831 25 Östersund, Sweden

Sensors 2018, 18(5), 1632; https://doi.org/10.3390/s18051632 - 19 May 2018

Cited by 53 | Viewed by 9882

Abstract

Athletes schedule their training and recovery in periods, often utilizing a pre-defined strategy. To avoid underperformance and/or compromised health, the external load during training should take into account the individual’s physiological and perceptual responses. No single variable provides an adequate basis for planning, [...] Read more.

Athletes schedule their training and recovery in periods, often utilizing a pre-defined strategy. To avoid underperformance and/or compromised health, the external load during training should take into account the individual’s physiological and perceptual responses. No single variable provides an adequate basis for planning, but continuous monitoring of a combination of several indicators of internal and external load during training, recovery and off-training as well may allow individual responsive adjustments of a training program in an effective manner. From a practical perspective, including that of coaches, monitoring of potential changes in health and performance should ideally be valid, reliable and sensitive, as well as time-efficient, easily applicable, non-fatiguing and as non-invasive as possible. Accordingly, smartphone applications, wearable sensors and point-of-care testing appear to offer a suitable monitoring framework allowing responsive adjustments to exercise prescription. Here, we outline 24-h monitoring of selected parameters by these technologies that (i) allows responsive adjustments of exercise programs, (ii) enhances performance and/or (iii) reduces the risk for overuse, injury and/or illness. Full article

(This article belongs to the Special Issue Wearable and Ambient Sensors for Healthcare and Wellness Applications 2018)

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21 pages, 13639 KiB

Open AccessArticle

Agreement Technologies for Energy Optimization at Home

by Alfonso González-Briones^1,*

, Pablo Chamoso^1,*

, Fernando De La Prieta¹

, Yves Demazeau²

and Juan M. Corchado^1,3,4

¹ BISITE Digital Innovation Hub, University of Salamanca, Edificio Multiusos I+D+i, 37007 Salamanca, Spain

² Centre National de le Recherche Scientifique - Laboratoire d’Informatique de Grenoble (CNRS-LIG), University of Grenoble-Alps, 38000 Grenoble, France

³ Department of Electronics, Information and Communication, Faculty of Engineering, Osaka Institute of Technology, 535-8585 Osaka, Japan

⁴ Pusat Komputeran dan Informatik, Universiti Malaysia Kelantan, Karung Berkunci 36, Pengkaan Chepa, 16100 Kota Bharu, Kelantan, Malaysia

Sensors 2018, 18(5), 1633; https://doi.org/10.3390/s18051633 - 19 May 2018

Cited by 34 | Viewed by 5634

Abstract

Nowadays, it is becoming increasingly common to deploy sensors in public buildings or homes with the aim of obtaining data from the environment and taking decisions that help to save energy. Many of the current state-of-the-art systems make decisions considering solely the environmental [...] Read more.

Nowadays, it is becoming increasingly common to deploy sensors in public buildings or homes with the aim of obtaining data from the environment and taking decisions that help to save energy. Many of the current state-of-the-art systems make decisions considering solely the environmental factors that cause the consumption of energy. These systems are successful at optimizing energy consumption; however, they do not adapt to the preferences of users and their comfort. Any system that is to be used by end-users should consider factors that affect their wellbeing. Thus, this article proposes an energy-saving system, which apart from considering the environmental conditions also adapts to the preferences of inhabitants. The architecture is based on a Multi-Agent System (MAS), its agents use Agreement Technologies (AT) to perform a negotiation process between the comfort preferences of the users and the degree of optimization that the system can achieve according to these preferences. A case study was conducted in an office building, showing that the proposed system achieved average energy savings of 17.15%. Full article

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

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17 pages, 8015 KiB

Open AccessArticle

3D Target Localization of Modified 3D MUSIC for a Triple-Channel K-Band Radar

by Ying-Chun Li¹

, Byunggil Choi², Jong-Wha Chong¹ and Daegun Oh^2,*

¹ Department Of Electronic Engineering, Hanyang University, Seoul 04763, Korea

² Collaborative Robots Research Center, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Korea

Sensors 2018, 18(5), 1634; https://doi.org/10.3390/s18051634 - 20 May 2018

Cited by 17 | Viewed by 5975

Abstract

In this paper, a modified 3D multiple signal classification (MUSIC) algorithm is proposed for joint estimation of range, azimuth, and elevation angles of K-band radar with a small 2 × 2 horn antenna array. Three channels of the 2 × 2 horn antenna [...] Read more.

In this paper, a modified 3D multiple signal classification (MUSIC) algorithm is proposed for joint estimation of range, azimuth, and elevation angles of K-band radar with a small 2 × 2 horn antenna array. Three channels of the 2 × 2 horn antenna array are utilized as receiving channels, and the other one is a transmitting antenna. The proposed modified 3D MUSIC is designed to make use of a stacked autocorrelation matrix, whose element matrices are related to each other in the spatial domain. An augmented 2D steering vector based on the stacked autocorrelation matrix is proposed for the modified 3D MUSIC, instead of the conventional 3D steering vector. The effectiveness of the proposed modified 3D MUSIC is verified through implementation with a K-band frequency-modulated continuous-wave (FMCW) radar with the 2 × 2 horn antenna array through a variety of experiments in a chamber. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 6618 KiB

Open AccessArticle

Lane Marking Detection and Reconstruction with Line-Scan Imaging Data

by Lin Li^1,*, Wenting Luo^1,*

and Kelvin C.P. Wang²

¹ School of Transportation and Civil Engineering, Fujian Agriculture and Forestry University, Fuzhou 350002, China

² School of Civil and Environmental Engineering, Oklahoma State University, Stillwater, OK 74078, USA

Sensors 2018, 18(5), 1635; https://doi.org/10.3390/s18051635 - 20 May 2018

Cited by 32 | Viewed by 8216

Abstract

Abstract: Lane marking detection and localization are crucial for autonomous driving and lane-based pavement surveys. Numerous studies have been done to detect and locate lane markings with the purpose of advanced driver assistance systems, in which image data are usually captured by [...] Read more.

Abstract: Lane marking detection and localization are crucial for autonomous driving and lane-based pavement surveys. Numerous studies have been done to detect and locate lane markings with the purpose of advanced driver assistance systems, in which image data are usually captured by vision-based cameras. However, a limited number of studies have been done to identify lane markings using high-resolution laser images for road condition evaluation. In this study, the laser images are acquired with a digital highway data vehicle (DHDV). Subsequently, a novel methodology is presented for the automated lane marking identification and reconstruction, and is implemented in four phases: (1) binarization of the laser images with a new threshold method (multi-box segmentation based threshold method); (2) determination of candidate lane markings with closing operations and a marching square algorithm; (3) identification of true lane marking by eliminating false positives (FPs) using a linear support vector machine method; and (4) reconstruction of the damaged and dash lane marking segments to form a continuous lane marking based on the geometry features such as adjacent lane marking location and lane width. Finally, a case study is given to validate effects of the novel methodology. The findings indicate the new strategy is robust in image binarization and lane marking localization. This study would be beneficial in road lane-based pavement condition evaluation such as lane-based rutting measurement and crack classification. Full article

(This article belongs to the Special Issue Visual Sensors)

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12 pages, 351 KiB

Open AccessArticle

Controller–Pilot Data Link Communication Security

by Andrei Gurtov^1,*

, Tatiana Polishchuk² and Max Wernberg²

¹ Department of Computer and Information Science, Linköping University, Campus Valla, SE-581 83 Linköping, Sweden

² Communications and Transport Systems, Linköping University, Campus Norrköping, SE-601 74 Norrköping, Sweden

Sensors 2018, 18(5), 1636; https://doi.org/10.3390/s18051636 - 20 May 2018

Cited by 29 | Viewed by 8975

Abstract

The increased utilization of the new types of cockpit communications, including controller–pilot data link communications (CPDLC), puts the airplane at higher risk of hacking or interference than ever before. We review the technological characteristics and properties of the CPDLC and construct the corresponding [...] Read more.

The increased utilization of the new types of cockpit communications, including controller–pilot data link communications (CPDLC), puts the airplane at higher risk of hacking or interference than ever before. We review the technological characteristics and properties of the CPDLC and construct the corresponding threat model. Based on the limitations imposed by the system parameters, we propose several solutions for the improved security of the data messaging communication used in air traffic management (ATM). We discuss the applicability of elliptical curve cryptography (ECC), protected aircraft communications addressing and reporting systems (PACARs) and the Host Identity Protocol (HIP) as possible countermeasures to the identified security threats. In addition, we consider identity-defined networking (IDN) as an example of a genuine security solution which implies global changes in the whole air traffic communication system. Full article

(This article belongs to the Section Internet of Things)

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17 pages, 4376 KiB

Open AccessArticle

An Interactive Real-Time Locating System Based on Bluetooth Low-Energy Beacon Network ^†

by You-Wei Lin and Chi-Yi Lin^*

¹ Department of Computer Science and Information Engineering, Tamkang University, New Taipei City 25137, Taiwan

^† This paper is an extended version of our paper published in Lin, Y.W.; Lin, C.Y. Beyond Beacons—An Interactive Positioning and Tracking System Solely Based on BLE Mesh Network. In Proceedings of the 20th International Conference on Network-Based Information Systems (NBiS-2017), Toronto, ON, Canada, 24–26 August 2017.

Sensors 2018, 18(5), 1637; https://doi.org/10.3390/s18051637 - 21 May 2018

Cited by 24 | Viewed by 12621

Abstract

The ubiquity of Bluetooth-enabled smartphones and peripherals has brought tremendous convenience to our daily life. In recent years, Bluetooth beacons have also been gaining popularity in implementing a variety of innovative location-based services such as self-guided systems in exhibition centers. However, the broadcast-based [...] Read more.

The ubiquity of Bluetooth-enabled smartphones and peripherals has brought tremendous convenience to our daily life. In recent years, Bluetooth beacons have also been gaining popularity in implementing a variety of innovative location-based services such as self-guided systems in exhibition centers. However, the broadcast-based beacon technology can only provide unidirectional communication. In case smartphone users would like to respond to the beacon messages, they have to rely on their own mobile Internet connections to send the information back to the backend system. Nevertheless, mobile Internet services may not be always available or too costly. In this work, we develop a real-time locating system based only on the Bluetooth low energy (BLE) technology to support interactive communications by combining the broadcast and mesh topology options to extend the applicability of beacon solutions. Specifically, we turn the smartphone into a beacon device and augment the beacon devices with the capability of forming a mesh network. The implementation result shows that our beacon devices can detect the presence of specific users at specific locations, and then the presence state can be sent to the application server via the relay of beacon devices. Moreover, the application server can send personalized location-based messages to the users, again via the relay of beacon devices. With the capability of relaying messages between the beacon devices, it would be convenient for developers to implement a variety of interactive applications such as tracking VIP customers at the airport, or tracking an elder with Alzheimer’s disease in the neighborhood. Full article

(This article belongs to the Section Sensor Networks)

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16 pages, 5131 KiB

Open AccessArticle

Cold-Rolled Strip Steel Stress Detection Technology Based on a Magnetoresistance Sensor and the Magnetoelastic Effect

by Ben Guan¹, Yong Zang^1,*, Xiaohui Han¹ and Kailun Zheng²

¹ School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China

² Department of Mechanical Engineering, Imperial College London, Exhibition Road, London SW7 2AZ, UK

Sensors 2018, 18(5), 1638; https://doi.org/10.3390/s18051638 - 21 May 2018

Cited by 13 | Viewed by 5778

Abstract

Driven by the demands for contactless stress detection, technologies are being used for shape control when producing cold-rolled strips. This paper presents a novel contactless stress detection technology based on a magnetoresistance sensor and the magnetoelastic effect, enabling the detection of internal stress [...] Read more.

Driven by the demands for contactless stress detection, technologies are being used for shape control when producing cold-rolled strips. This paper presents a novel contactless stress detection technology based on a magnetoresistance sensor and the magnetoelastic effect, enabling the detection of internal stress in manufactured cold-rolled strips. An experimental device was designed and produced. Characteristics of this detection technology were investigated through experiments assisted by theoretical analysis. Theoretically, a linear correlation exists between the internal stress of strip steel and the voltage output of a magneto-resistive sensor. Therefore, for this stress detection system, the sensitivity of the stress detection was adjusted by adjusting the supply voltage of the magnetoresistance sensor, detection distance, and other relevant parameters. The stress detection experimental results showed that this detection system has good repeatability and linearity. The detection error was controlled within 1.5%. Moreover, the intrinsic factors of the detected strip steel, including thickness, carbon percentage, and crystal orientation, also affected the sensitivity of the detection system. The detection technology proposed in this research enables online contactless detection and meets the requirements for cold-rolled steel strips. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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20 pages, 3121 KiB

Open AccessArticle

Recognition of a Person Wearing Sport Shoes or High Heels through Gait Using Two Types of Sensors

by Marcin Derlatka^1,* and Mariusz Bogdan²

¹ Department of Biocybernetics and Biomedical Engineering of the Faculty of Mechanical Engineering at Bialystok University of Technology, 15-351 Bialystok, Poland

² Department of Automatic Control and Robotics of the Faculty of Mechanical Engineering at Bialystok University of Technology, 15-351 Bialystok, Poland

Sensors 2018, 18(5), 1639; https://doi.org/10.3390/s18051639 - 21 May 2018

Cited by 15 | Viewed by 7680

Abstract

Biometrics is currently an area that is both very interesting as well as rapidly growing. Among various types of biometrics the human gait recognition seems to be one of the most intriguing. However, one of the greatest problems within this field of biometrics [...] Read more.

Biometrics is currently an area that is both very interesting as well as rapidly growing. Among various types of biometrics the human gait recognition seems to be one of the most intriguing. However, one of the greatest problems within this field of biometrics is the change in gait caused by footwear. A change of shoes results in a significant lowering of accuracy in recognition of people. The following work presents a method which uses data gathered by two sensors: force plates and Microsoft Kinect v2 to reduce this problem. Microsoft Kinect is utilized to measure the body height of a person which allows the reduction of the set of recognized people only to those whose height is similar to that which has been measured. The entire process is preceded by identifying the type of footwear which the person is wearing. The research was conducted on data obtained from 99 people (more than 3400 strides) and the proposed method allowed us to reach a Correct Classification Rate (CCR) greater than 88% which, in comparison to earlier methods reaching CCR’s of <80%, is a significant improvement. The work presents advantages as well as limitations of the proposed method. Full article

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

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11 pages, 3620 KiB

Open AccessArticle

Effects of Center Metals in Porphines on Nanomechanical Gas Sensing

by Huynh Thien Ngo^1,*, Kosuke Minami¹

, Gaku Imamura^1,*

, Kota Shiba¹

and Genki Yoshikawa^1,2

¹ World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan

² Materials Science and Engineering, Graduate School of Pure and Applied Science, University of Tsukuba, Tennodai 1-1-1 Tsukuba, Ibaraki 305-8571, Japan

Sensors 2018, 18(5), 1640; https://doi.org/10.3390/s18051640 - 21 May 2018

Cited by 24 | Viewed by 4811

Abstract

Porphyrin is one of the most promising materials for realizing a practical artificial olfactory sensor system. In this study, we focus on non-substituted porphyrins—porphines—as receptor materials of nanomechanical membrane-type surface stress sensors (MSS) to investigate the effect of center metals on gas sensing. [...] Read more.

Porphyrin is one of the most promising materials for realizing a practical artificial olfactory sensor system. In this study, we focus on non-substituted porphyrins—porphines—as receptor materials of nanomechanical membrane-type surface stress sensors (MSS) to investigate the effect of center metals on gas sensing. By omitting the substituents on the tetrapyrrole macrocycle of porphyrin, the peripheral interference by substituents can be avoided. Zinc, nickel, and iron were chosen for the center metals as these metalloporphines show different properties compared to free-base porphine. The present study revealed that iron insertion enhanced sensitivity to various gases, while zinc and nickel insertion led to equivalent or less sensitivity than free-base porphine. Based on the experimental results, we discuss the role of center metals for gas uptake from the view point of molecular interaction. We also report the high robustness of the iron porphine to humidity, showing the high feasibility of porphine-based nanomechanical sensor devices for practical applications in ambient conditions. Full article

(This article belongs to the Special Issue Artificial Olfaction and Taste)

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16 pages, 7941 KiB

Open AccessArticle

Research on the Forward and Reverse Calculation Based on the Adaptive Zero-Velocity Interval Adjustment for the Foot-Mounted Inertial Pedestrian-Positioning System

by Qiuying Wang, Zheng Guo, Zhiguo Sun^*, Xufei Cui and Kaiyue Liu

College of Information and Communication Engineering, Harbin Engineering University, Harbin 150001, China

Sensors 2018, 18(5), 1642; https://doi.org/10.3390/s18051642 - 21 May 2018

Cited by 26 | Viewed by 4137

Abstract

Pedestrian-positioning technology based on the foot-mounted micro inertial measurement unit (MIMU) plays an important role in the field of indoor navigation and has received extensive attention in recent years. However, the positioning accuracy of the inertial-based pedestrian-positioning method is rapidly reduced because of [...] Read more.

Pedestrian-positioning technology based on the foot-mounted micro inertial measurement unit (MIMU) plays an important role in the field of indoor navigation and has received extensive attention in recent years. However, the positioning accuracy of the inertial-based pedestrian-positioning method is rapidly reduced because of the relatively low measurement accuracy of the measurement sensor. The zero-velocity update (ZUPT) is an error correction method which was proposed to solve the cumulative error because, on a regular basis, the foot is stationary during the ordinary gait; this is intended to reduce the position error growth of the system. However, the traditional ZUPT has poor performance because the time of foot touchdown is short when the pedestrians move faster, which decreases the positioning accuracy. Considering these problems, a forward and reverse calculation method based on the adaptive zero-velocity interval adjustment for the foot-mounted MIMU location method is proposed in this paper. To solve the inaccuracy of the zero-velocity interval detector during fast pedestrian movement where the contact time of the foot on the ground is short, an adaptive zero-velocity interval detection algorithm based on fuzzy logic reasoning is presented in this paper. In addition, to improve the effectiveness of the ZUPT algorithm, forward and reverse multiple solutions are presented. Finally, with the basic principles and derivation process of this method, the MTi-G710 produced by the XSENS company is used to complete the test. The experimental results verify the correctness and applicability of the proposed method. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 694 KiB

Open AccessArticle

Analyzing Cyber-Physical Threats on Robotic Platforms

by Khalil M. Ahmad Yousef^1,*

, Anas AlMajali¹

, Salah Abu Ghalyon¹

, Waleed Dweik²

and Bassam J. Mohd¹

¹ Department of Computer Engineering, The Hashemite University, Zarqa 13115, Jordan

² Department of Computer Engineering, The University of Jordan, Amman 11942, Jordan

Sensors 2018, 18(5), 1643; https://doi.org/10.3390/s18051643 - 21 May 2018

Cited by 31 | Viewed by 9399

Abstract

Robots are increasingly involved in our daily lives. Fundamental to robots are the communication link (or stream) and the applications that connect the robots to their clients or users. Such communication link and applications are usually supported through client/server network connection. This networking [...] Read more.

Robots are increasingly involved in our daily lives. Fundamental to robots are the communication link (or stream) and the applications that connect the robots to their clients or users. Such communication link and applications are usually supported through client/server network connection. This networking system is amenable of being attacked and vulnerable to the security threats. Ensuring security and privacy for robotic platforms is thus critical, as failures and attacks could have devastating consequences. In this paper, we examine several cyber-physical security threats that are unique to the robotic platforms; specifically the communication link and the applications. Threats target integrity, availability and confidential security requirements of the robotic platforms, which use MobileEyes/arnlServer client/server applications. A robot attack tool (RAT) was developed to perform specific security attacks. An impact-oriented approach was adopted to analyze the assessment results of the attacks. Tests and experiments of attacks were conducted in simulation environment and physically on the robot. The simulation environment was based on MobileSim; a software tool for simulating, debugging and experimenting on MobileRobots/ActivMedia platforms and their environments. The robot platform PeopleBot^TM was used for physical experiments. The analysis and testing results show that certain attacks were successful at breaching the robot security. Integrity attacks modified commands and manipulated the robot behavior. Availability attacks were able to cause Denial-of-Service (DoS) and the robot was not responsive to MobileEyes commands. Integrity and availability attacks caused sensitive information on the robot to be hijacked. To mitigate security threats, we provide possible mitigation techniques and suggestions to raise awareness of threats on the robotic platforms, especially when the robots are involved in critical missions or applications. Full article

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

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14 pages, 2875 KiB

Open AccessArticle

A Novel Displacement and Tilt Detection Method Using Passive UHF RFID Technology

by Xiaozheng Lai¹, Zhirong Cai¹, Zeming Xie² and Hailong Zhu^3,*

¹ School of Computer Science & Engineering, South China University of Technology, Guangzhou 510006, China

² School of Electronic & Information, South China University of Technology, Guangzhou 510641, China

³ School of Information Engineering, Guangdong University of Technology, Guangzhou 510006, China

Sensors 2018, 18(5), 1644; https://doi.org/10.3390/s18051644 - 21 May 2018

Cited by 21 | Viewed by 6176

Abstract

The displacement and tilt angle of an object are useful information for wireless monitoring applications. In this paper, a low-cost detection method based on passive radio frequency identification (RFID) technology is proposed. This method uses a standard ultrahigh-frequency (UHF) RFID reader to measure [...] Read more.

The displacement and tilt angle of an object are useful information for wireless monitoring applications. In this paper, a low-cost detection method based on passive radio frequency identification (RFID) technology is proposed. This method uses a standard ultrahigh-frequency (UHF) RFID reader to measure the phase variation of the tag response and detect the displacement and tilt angle of RFID tags attached to the targeted object. An accurate displacement result can be detected by the RFID system with a linearly polarized (LP) reader antenna. Based on the displacement results, an accurate tilt angle can also be detected by the RFID system with a circularly polarized (CP) reader antenna, which has been proved to have a linear relationship with the phase parameter of the tag’s backscattered wave. As far as accuracy is concerned, the mean absolute error (MAE) of displacement is less than 2 mm and the MAE of the tilt angle is less than 2.5° for an RFID system with 500 mm working range. Full article

(This article belongs to the Special Issue RFID-Based Sensors for IoT Applications)

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18 pages, 11625 KiB

Open AccessArticle

A Modified Empirical Wavelet Transform for Acoustic Emission Signal Decomposition in Structural Health Monitoring

by Shaopeng Dong¹, Mei Yuan^1,2,*, Qiusheng Wang¹ and Zhiling Liang¹

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

² Collaborative Innovation Center of Advanced Aero-Engine, Beihang University, Beijing 100191, China

Sensors 2018, 18(5), 1645; https://doi.org/10.3390/s18051645 - 21 May 2018

Cited by 31 | Viewed by 6539

Abstract

The acoustic emission (AE) method is useful for structural health monitoring (SHM) of composite structures due to its high sensitivity and real-time capability. The main challenge, however, is how to classify the AE data into different failure mechanisms because the detected signals are [...] Read more.

The acoustic emission (AE) method is useful for structural health monitoring (SHM) of composite structures due to its high sensitivity and real-time capability. The main challenge, however, is how to classify the AE data into different failure mechanisms because the detected signals are affected by various factors. Empirical wavelet transform (EWT) is a solution for analyzing the multi-component signals and has been used to process the AE data. In order to solve the spectrum separation problem of the AE signals, this paper proposes a novel modified separation method based on local window maxima (LWM) algorithm. It searches the local maxima of the Fourier spectrum in a proper window, and automatically determines the boundaries of spectrum segmentations, which helps to eliminate the impact of noise interference or frequency dispersion in the detected signal and obtain the meaningful empirical modes that are more related to the damage characteristics. Additionally, both simulation signal and AE signal from the composite structures are used to verify the effectiveness of the proposed method. Finally, the experimental results indicate that the proposed method performs better than the original EWT method in identifying different damage mechanisms of composite structures. Full article

(This article belongs to the Special Issue Mechatronic Systems for Automatic Vehicles)

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29 pages, 1122 KiB

Open AccessArticle

Efficient Convex Optimization for Energy-Based Acoustic Sensor Self-Localization and Source Localization in Sensor Networks

by Yongsheng Yan^1,*, Haiyan Wang^2,3, Xiaohong Shen^2,3, Bing Leng³ and Shuangquan Li⁴

¹ Centre for Infocomm Technology (INFINITUS), School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 , Singapore

² Key Laboratory of Ocean Acoustics and Sensing, Ministry of Industry and Information Technology, Xi’an 710072, China

³ School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China

⁴ Xi’an Institute of Applied Optics, Xi’an 710065, China

Sensors 2018, 18(5), 1646; https://doi.org/10.3390/s18051646 - 21 May 2018

Cited by 86 | Viewed by 3983

Abstract

The energy reading has been an efficient and attractive measure for collaborative acoustic source localization in practical application due to its cost saving in both energy and computation capability. The maximum likelihood problems by fusing received acoustic energy readings transmitted from local sensors [...] Read more.

The energy reading has been an efficient and attractive measure for collaborative acoustic source localization in practical application due to its cost saving in both energy and computation capability. The maximum likelihood problems by fusing received acoustic energy readings transmitted from local sensors are derived. Aiming to efficiently solve the nonconvex objective of the optimization problem, we present an approximate estimator of the original problem. Then, a direct norm relaxation and semidefinite relaxation, respectively, are utilized to derive the second-order cone programming, semidefinite programming or mixture of them for both cases of sensor self-location and source localization. Furthermore, by taking the colored energy reading noise into account, several minimax optimization problems are formulated, which are also relaxed via the direct norm relaxation and semidefinite relaxation respectively into convex optimization problems. Performance comparison with the existing acoustic energy-based source localization methods is given, where the results show the validity of our proposed methods. Full article

(This article belongs to the Section Sensor Networks)

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18 pages, 21272 KiB

Open AccessArticle

Sensitivity and Resolution Improvement in RGBW Color Filter Array Sensor

by Seunghoon Jee, Ki Sun Song and Moon Gi Kang^*

Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei Road, Seodaemun-gu, Seoul 03722, Korea

Sensors 2018, 18(5), 1647; https://doi.org/10.3390/s18051647 - 21 May 2018

Cited by 11 | Viewed by 9007

Abstract

Recently, several red-green-blue-white (RGBW) color filter arrays (CFAs), which include highly sensitive W pixels, have been proposed. However, RGBW CFA patterns suffer from spatial resolution degradation owing to the sensor composition having more color components than the Bayer CFA pattern. RGBW CFA demosaicing [...] Read more.

Recently, several red-green-blue-white (RGBW) color filter arrays (CFAs), which include highly sensitive W pixels, have been proposed. However, RGBW CFA patterns suffer from spatial resolution degradation owing to the sensor composition having more color components than the Bayer CFA pattern. RGBW CFA demosaicing methods reconstruct resolution using the correlation between white (W) pixels and pixels of other colors, which does not improve the red-green-blue (RGB) channel sensitivity to the W channel level. In this paper, we thus propose a demosaiced image post-processing method to improve the RGBW CFA sensitivity and resolution. The proposed method decomposes texture components containing image noise and resolution information. The RGB channel sensitivity and resolution are improved through updating the W channel texture component with those of RGB channels. For this process, a cross multilateral filter (CMF) is proposed. It decomposes the smoothness component from the texture component using color difference information and distinguishes color components through that information. Moreover, it decomposes texture components, luminance noise, color noise, and color aliasing artifacts from the demosaiced images. Finally, by updating the texture of the RGB channels with the W channel texture components, the proposed algorithm improves the sensitivity and resolution. Results show that the proposed method is effective, while maintaining W pixel resolution characteristics and improving sensitivity from the signal-to-noise ratio value by approximately 4.5 dB. Full article

(This article belongs to the Special Issue Image Sensors)

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23 pages, 6932 KiB

Open AccessArticle

Design and Test of a Soil Profile Moisture Sensor Based on Sensitive Soil Layers

by Zhenran Gao

, Yan Zhu

, Cheng Liu, Hongzhou Qian, Weixing Cao^* and Jun Ni^*

National Engineering and Technology Center for Information Agriculture, Jiangsu Key Laboratory for Information Agriculture, Key Laboratory for Crop System Analysis and Decision Making, Ministry of Agriculture, Jiangsu Key Laboratory for Information Agriculture, Jiangsu Collaborative Innovation Center for the Technology and Application of Internet of Things, Nanjing Agricultural University, Nanjing 210095, China

Sensors 2018, 18(5), 1648; https://doi.org/10.3390/s18051648 - 21 May 2018

Cited by 43 | Viewed by 13085

Abstract

To meet the demand of intelligent irrigation for accurate moisture sensing in the soil vertical profile, a soil profile moisture sensor was designed based on the principle of high-frequency capacitance. The sensor consists of five groups of sensing probes, a data processor, and [...] Read more.

To meet the demand of intelligent irrigation for accurate moisture sensing in the soil vertical profile, a soil profile moisture sensor was designed based on the principle of high-frequency capacitance. The sensor consists of five groups of sensing probes, a data processor, and some accessory components. Low-resistivity copper rings were used as components of the sensing probes. Composable simulation of the sensor’s sensing probes was carried out using a high-frequency structure simulator. According to the effective radiation range of electric field intensity, width and spacing of copper ring were set to 30 mm and 40 mm, respectively. A parallel resonance circuit of voltage-controlled oscillator and high-frequency inductance-capacitance (LC) was designed for signal frequency division and conditioning. A data processor was used to process moisture-related frequency signals for soil profile moisture sensing. The sensor was able to detect real-time soil moisture at the depths of 20, 30, and 50 cm and conduct online inversion of moisture in the soil layer between 0–100 cm. According to the calibration results, the degree of fitting (R²) between the sensor’s measuring frequency and the volumetric moisture content of soil sample was 0.99 and the relative error of the sensor consistency test was 0–1.17%. Field tests in different loam soils showed that measured soil moisture from our sensor reproduced the observed soil moisture dynamic well, with an R² of 0.96 and a root mean square error of 0.04. In a sensor accuracy test, the R² between the measured value of the proposed sensor and that of the Diviner2000 portable soil moisture monitoring system was higher than 0.85, with a relative error smaller than 5%. The R² between measured values and inversed soil moisture values for other soil layers were consistently higher than 0.8. According to calibration test and field test, this sensor, which features low cost, good operability, and high integration, is qualified for precise agricultural irrigation with stable performance and high accuracy. Full article

(This article belongs to the Special Issue Smart Sensors for Water Systems and Networks)

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29 pages, 10180 KiB

Open AccessArticle

An Observation Capability Semantic-Associated Approach to the Selection of Remote Sensing Satellite Sensors: A Case Study of Flood Observations in the Jinsha River Basin

by Chuli Hu¹, Jie Li¹, Xin Lin^1,2, Nengcheng Chen²

and Chao Yang^1,*

¹ Faculty of Information Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China

² State Key Laboratory for Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China

Sensors 2018, 18(5), 1649; https://doi.org/10.3390/s18051649 - 21 May 2018

Cited by 9 | Viewed by 5115

Abstract

Observation schedules depend upon the accurate understanding of a single sensor’s observation capability and the interrelated observation capability information on multiple sensors. The general ontologies for sensors and observations are abundant. However, few observation capability ontologies for satellite sensors are available, and no [...] Read more.

Observation schedules depend upon the accurate understanding of a single sensor’s observation capability and the interrelated observation capability information on multiple sensors. The general ontologies for sensors and observations are abundant. However, few observation capability ontologies for satellite sensors are available, and no study has described the dynamic associations among the observation capabilities of multiple sensors used for integrated observational planning. This limitation results in a failure to realize effective sensor selection. This paper develops a sensor observation capability association (SOCA) ontology model that is resolved around the task-sensor-observation capability (TSOC) ontology pattern. The pattern is developed considering the stimulus-sensor-observation (SSO) ontology design pattern, which focuses on facilitating sensor selection for one observation task. The core aim of the SOCA ontology model is to achieve an observation capability semantic association. A prototype system called SemOCAssociation was developed, and an experiment was conducted for flood observations in the Jinsha River basin in China. The results of this experiment verified that the SOCA ontology based association method can help sensor planners intuitively and accurately make evidence-based sensor selection decisions for a given flood observation task, which facilitates efficient and effective observational planning for flood satellite sensors. Full article

(This article belongs to the Section Remote Sensors)

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15 pages, 2126 KiB

Open AccessArticle

Random Weighting, Strong Tracking, and Unscented Kalman Filter for Soft Tissue Characterization

by Jaehyun Shin^1,*

, Yongmin Zhong¹

, Denny Oetomo² and Chengfan Gu³

¹ School of Engineering, RMIT University, Bundoora, VIC 3083, Australia

² Department of Mechanical Engineering, University of Melbourne, Parkville, VIC 3010, Australia

³ City of Whittlesea, Mill Park, VIC 3082, Australia

Sensors 2018, 18(5), 1650; https://doi.org/10.3390/s18051650 - 21 May 2018

Cited by 5 | Viewed by 3714

Abstract

This paper presents a new nonlinear filtering method based on the Hunt-Crossley model for online nonlinear soft tissue characterization. This method overcomes the problem of performance degradation in the unscented Kalman filter due to contact model error. It adopts the concept of Mahalanobis [...] Read more.

This paper presents a new nonlinear filtering method based on the Hunt-Crossley model for online nonlinear soft tissue characterization. This method overcomes the problem of performance degradation in the unscented Kalman filter due to contact model error. It adopts the concept of Mahalanobis distance to identify contact model error, and further incorporates a scaling factor in predicted state covariance to compensate identified model error. This scaling factor is determined according to the principle of innovation orthogonality to avoid the cumbersome computation of Jacobian matrix, where the random weighting concept is adopted to improve the estimation accuracy of innovation covariance. A master-slave robotic indentation system is developed to validate the performance of the proposed method. Simulation and experimental results as well as comparison analyses demonstrate that the efficacy of the proposed method for online characterization of soft tissue parameters in the presence of contact model error. Full article

(This article belongs to the Section Physical Sensors)

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21 pages, 8968 KiB

Open AccessArticle

Registration of Panoramic/Fish-Eye Image Sequence and LiDAR Points Using Skyline Features

by Ningning Zhu^*, Yonghong Jia^* and Shunping Ji

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

Sensors 2018, 18(5), 1651; https://doi.org/10.3390/s18051651 - 21 May 2018

Cited by 15 | Viewed by 5735

Abstract

We propose utilizing a rigorous registration model and a skyline-based method for automatic registration of LiDAR points and a sequence of panoramic/fish-eye images in a mobile mapping system (MMS). This method can automatically optimize original registration parameters and avoid the use of manual [...] Read more.

We propose utilizing a rigorous registration model and a skyline-based method for automatic registration of LiDAR points and a sequence of panoramic/fish-eye images in a mobile mapping system (MMS). This method can automatically optimize original registration parameters and avoid the use of manual interventions in control point-based registration methods. First, the rigorous registration model between the LiDAR points and the panoramic/fish-eye image was built. Second, skyline pixels from panoramic/fish-eye images and skyline points from the MMS’s LiDAR points were extracted, relying on the difference in the pixel values and the registration model, respectively. Third, a brute force optimization method was used to search for optimal matching parameters between skyline pixels and skyline points. In the experiments, the original registration method and the control point registration method were used to compare the accuracy of our method with a sequence of panoramic/fish-eye images. The result showed: (1) the panoramic/fish-eye image registration model is effective and can achieve high-precision registration of the image and the MMS’s LiDAR points; (2) the skyline-based registration method can automatically optimize the initial attitude parameters, realizing a high-precision registration of a panoramic/fish-eye image and the MMS’s LiDAR points; and (3) the attitude correction values of the sequences of panoramic/fish-eye images are different, and the values must be solved one by one. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 7186 KiB

Open AccessArticle

A High Noise Immunity, 28 × 16-Channel Finger Touch Sensing IC Using OFDM and Frequency Translation Technique

by SangYun Kim¹, Behnam Samadpoor Rikan¹, YoungGun Pu¹, Sang-Sun Yoo², Minjae Lee³, Keum Cheol 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(5), 1652; https://doi.org/10.3390/s18051652 - 21 May 2018

Cited by 3 | Viewed by 5410

Abstract

In this paper, a high noise immunity, 28 × 16-channel finger touch sensing IC for an orthogonal frequency division multiplexing (OFDM) touch sensing scheme is presented. In order to increase the signal-to-noise ratio (SNR), the OFDM sensing scheme is proposed. The transmitter (TX) [...] Read more.

In this paper, a high noise immunity, 28 × 16-channel finger touch sensing IC for an orthogonal frequency division multiplexing (OFDM) touch sensing scheme is presented. In order to increase the signal-to-noise ratio (SNR), the OFDM sensing scheme is proposed. The transmitter (TX) transmits the orthogonal signal to each channels of the panel. The receiver (RX) detects the magnitude of the orthogonal frequency to be transmitted from the TX. Due to the orthogonal characteristics, it is robust to narrowband interference and noise. Therefore, the SNR can be improved. In order to reduce the noise effect of low frequencies, a mixer and high-pass filter are proposed as well. After the noise is filtered, the touch SNR attained is 60 dB, from 20 dB before the noise is filtered. The advantage of the proposed OFDM sensing scheme is its ability to detect channels of the panel simultaneously with the use of multiple carriers. To satisfy the linearity of the signal in the OFDM system, a high-linearity mixer and a rail-to-rail amplifier in the TX driver are designed. The proposed design is implemented in 90 nm CMOS process. The SNR is approximately 60 dB. The area is 13.6 mm², and the power consumption is 62.4 mW. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 1018 KiB

Open AccessArticle

Dual Sensor Control Scheme for Multi-Target Tracking

by Wei Li^*

and Chongzhao Han^*

MOE KLINNS Lab, Institute of Integrated Automation, School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2018, 18(5), 1653; https://doi.org/10.3390/s18051653 - 21 May 2018

Cited by 9 | Viewed by 4070

Abstract

Sensor control is a challenging issue in the field of multi-target tracking. It involves multi-target state estimation and the optimal control of the sensor. To maximize the overall utility of the surveillance system, we propose a dual sensor control scheme. This work is [...] Read more.

Sensor control is a challenging issue in the field of multi-target tracking. It involves multi-target state estimation and the optimal control of the sensor. To maximize the overall utility of the surveillance system, we propose a dual sensor control scheme. This work is formulated in the framework of partially observed Markov decision processes (POMDPs) with Mahler’s finite set statistics (FISST). To evaluate the performance associated with each control action, a key element is to design an appropriate metric. From a task-driven perspective, we utilize a metric to minimize the posterior distance between the sensor and the target. This distance-related metric promotes the design of a dual sensor control scheme. Moreover, we introduce a metric to maximize the predicted average probability of detection, which will improve the efficiency by avoiding unnecessary update processes. Simulation results indicate that the performance of the proposed algorithm is significantly superior to the existing methods. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 6877 KiB

Open AccessArticle

Suspended Carbon Nanotubes for Humidity Sensing

by Shivaram Arunachalam^*, Anubha A. Gupta, Ricardo Izquierdo and Frederic Nabki

Department of Electrical Engineering, École de Technologie Supérieure, Montreal, QC H3C 1K3, Canada

Sensors 2018, 18(5), 1655; https://doi.org/10.3390/s18051655 - 22 May 2018

Cited by 37 | Viewed by 4723

Abstract

A room temperature microfabrication technique using SU8, an epoxy-based highly functional photoresist as a sacrificial layer, is developed to obtain suspended aligned carbon nanotube beams. The humidity-sensing characteristics of aligned suspended single-walled carbon nanotube films are studied. A comparative study between suspended and [...] Read more.

A room temperature microfabrication technique using SU8, an epoxy-based highly functional photoresist as a sacrificial layer, is developed to obtain suspended aligned carbon nanotube beams. The humidity-sensing characteristics of aligned suspended single-walled carbon nanotube films are studied. A comparative study between suspended and non-suspended architectures is done by recording the resistance change in the nanotubes under humidity. For the tests, the humidity was varied from 15% to 98% RH. A comparative study between suspended and non-suspended devices shows that the response and recovery times of the suspended devices was found to be almost 3 times shorter than the non-suspended devices. The suspended devices also showed minimal hysteresis even after 10 humidity cycles, and also exhibit enhanced sensitivity. Repeatability tests were performed by subjecting the sensors to continuous humidification cycles. All tests reported here have been performed using pristine non-functionalized nanotubes. Full article

(This article belongs to the Section Biosensors)

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19 pages, 4052 KiB

Open AccessArticle

Automated Field-of-View, Illumination, and Recognition Algorithm Design of a Vision System for Pick-and-Place Considering Colour Information in Illumination and Images

by Yibing Chen¹, Taiki Ogata^2,*, Tsuyoshi Ueyama³, Toshiyuki Takada³ and Jun Ota²

¹ Department of Precision Engineering, the University of Tokyo, Tokyo 113-8656, Japan

² Research into Artifacts, Center for Engineering (RACE), The University of Tokyo, Chiba 277-8568, Japan

³ Denso Wave Incorporated, Aichi 470-2298, Japan

Sensors 2018, 18(5), 1656; https://doi.org/10.3390/s18051656 - 22 May 2018

Cited by 7 | Viewed by 4812

Abstract

Machine vision is playing an increasingly important role in industrial applications, and the automated design of image recognition systems has been a subject of intense research. This study has proposed a system for automatically designing the field-of-view (FOV) of a camera, the illumination [...] Read more.

Machine vision is playing an increasingly important role in industrial applications, and the automated design of image recognition systems has been a subject of intense research. This study has proposed a system for automatically designing the field-of-view (FOV) of a camera, the illumination strength and the parameters in a recognition algorithm. We formulated the design problem as an optimisation problem and used an experiment based on a hierarchical algorithm to solve it. The evaluation experiments using translucent plastics objects showed that the use of the proposed system resulted in an effective solution with a wide FOV, recognition of all objects and 0.32 mm and 0.4° maximal positional and angular errors when all the RGB (red, green and blue) for illumination and R channel image for recognition were used. Though all the RGB illumination and grey scale images also provided recognition of all the objects, only a narrow FOV was selected. Moreover, full recognition was not achieved by using only G illumination and a grey-scale image. The results showed that the proposed method can automatically design the FOV, illumination and parameters in the recognition algorithm and that tuning all the RGB illumination is desirable even when single-channel or grey-scale images are used for recognition. Full article

(This article belongs to the Special Issue Visual Sensors)

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20 pages, 5256 KiB

Open AccessArticle

Segment-Tube: Spatio-Temporal Action Localization in Untrimmed Videos with Per-Frame Segmentation

by Le Wang^1,*

, Xuhuan Duan¹, Qilin Zhang²

, Zhenxing Niu³, Gang Hua⁴ and Nanning Zheng¹

¹ Institute of Artificial Intelligence and Robotics, Xi’an Jiaotong University, Xi’an, Shannxi 710049, China

² HERE Technologies, Chicago, IL 60606, USA

³ Alibaba Group, Hangzhou 311121, China

⁴ Microsoft Research, Redmond, WA 98052, USA

Sensors 2018, 18(5), 1657; https://doi.org/10.3390/s18051657 - 22 May 2018

Cited by 10 | Viewed by 12603

Abstract

Inspired by the recent spatio-temporal action localization efforts with tubelets (sequences of bounding boxes), we present a new spatio-temporal action localization detector Segment-tube, which consists of sequences of per-frame segmentation masks. The proposed Segment-tube detector can temporally pinpoint the starting/ending frame of each [...] Read more.

Inspired by the recent spatio-temporal action localization efforts with tubelets (sequences of bounding boxes), we present a new spatio-temporal action localization detector Segment-tube, which consists of sequences of per-frame segmentation masks. The proposed Segment-tube detector can temporally pinpoint the starting/ending frame of each action category in the presence of preceding/subsequent interference actions in untrimmed videos. Simultaneously, the Segment-tube detector produces per-frame segmentation masks instead of bounding boxes, offering superior spatial accuracy to tubelets. This is achieved by alternating iterative optimization between temporal action localization and spatial action segmentation. Experimental results on three datasets validated the efficacy of the proposed method, including (1) temporal action localization on the THUMOS 2014 dataset; (2) spatial action segmentation on the Segtrack dataset; and (3) joint spatio-temporal action localization on the newly proposed ActSeg dataset. It is shown that our method compares favorably with existing state-of-the-art methods. Full article

(This article belongs to the Special Issue Visual Sensors)

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19 pages, 9328 KiB

Open AccessArticle

Automatic Identification of Alpine Mass Movements by a Combination of Seismic and Infrasound Sensors

by Andreas Schimmel^1,*

, Johannes Hübl¹, Brian W. McArdell² and Fabian Walter³

¹ Institute of Mountain Risk Engineering, University of Natural Resources and Life Sciences (BOKU), 1190 Vienna, Austria

² Swiss Federal Institute for Forest, Snow and Landscape Research WSL, 8903 Birmensdorf, Switzerland

³ Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zürich, 8093 Zürich, Switzerland

Sensors 2018, 18(5), 1658; https://doi.org/10.3390/s18051658 - 22 May 2018

Cited by 32 | Viewed by 5920

Abstract

The automatic detection and identification of alpine mass movements such as debris flows, debris floods, or landslides have been of increasing importance for devising mitigation measures in densely populated and intensively used alpine regions. Since these mass movements emit characteristic seismic and acoustic [...] Read more.

The automatic detection and identification of alpine mass movements such as debris flows, debris floods, or landslides have been of increasing importance for devising mitigation measures in densely populated and intensively used alpine regions. Since these mass movements emit characteristic seismic and acoustic waves in the low-frequency range (<30 Hz), several approaches have already been developed for detection and warning systems based on these signals. However, a combination of the two methods, for improving detection probability and reducing false alarms, is still applied rarely. This paper presents an update and extension of a previously published approach for a detection and identification system based on a combination of seismic and infrasound sensors. Furthermore, this work evaluates the possible early warning times at several test sites and aims to analyze the seismic and infrasound spectral signature produced by different sediment-related mass movements to identify the process type and estimate the magnitude of the event. Thus, this study presents an initial method for estimating the peak discharge and total volume of debris flows based on infrasound data. Tests on several catchments show that this system can detect and identify mass movements in real time directly at the sensor site with high accuracy and a low false alarm ratio. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 8742 KiB

Open AccessArticle

A Nonlinear Calibration Algorithm Based on Harmonic Decomposition for Two-Axis Fluxgate Sensors

by Wenguang Feng

and Shibin Liu^*

School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710072, China

Sensors 2018, 18(5), 1659; https://doi.org/10.3390/s18051659 - 22 May 2018

Cited by 6 | Viewed by 4730

Abstract

Nonlinearity is a prominent limitation to the calibration performance for two-axis fluxgate sensors. In this paper, a novel nonlinear calibration algorithm taking into account the nonlinearity of errors is proposed. In order to establish the nonlinear calibration model, the combined effort of all [...] Read more.

Nonlinearity is a prominent limitation to the calibration performance for two-axis fluxgate sensors. In this paper, a novel nonlinear calibration algorithm taking into account the nonlinearity of errors is proposed. In order to establish the nonlinear calibration model, the combined effort of all time-invariant errors is analyzed in detail, and then harmonic decomposition method is utilized to estimate the compensation coefficients. Meanwhile, the proposed nonlinear calibration algorithm is validated and compared with a classical calibration algorithm by experiments. The experimental results show that, after the nonlinear calibration, the maximum deviation of magnetic field magnitude is decreased from 1302 nT to 30 nT, which is smaller than 81 nT after the classical calibration. Furthermore, for the two-axis fluxgate sensor used as magnetic compass, the maximum error of heading is corrected from 1.86° to 0.07°, which is approximately 11% in contrast with 0.62° after the classical calibration. The results suggest an effective way to improve the calibration performance of two-axis fluxgate sensors. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 1406 KiB

Open AccessArticle

In Situ Determination of Bisphenol A in Beverage Using a Molybdenum Selenide/Reduced Graphene Oxide Nanoparticle Composite Modified Glassy Carbon Electrode

by Rongguang Shi¹, Jing Liang², Zongshan Zhao^2,*, Yi Liu^3,*

and Aifeng Liu²

¹ Key Laboratory for Environmental Factors Control of Agro-Product Quality Safety, Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China

² CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, China

³ School of Chemistry and Chemical Engineering, Yantai University, Yantai 264005, China

Sensors 2018, 18(5), 1660; https://doi.org/10.3390/s18051660 - 22 May 2018

Cited by 20 | Viewed by 4549

Abstract

Due to the endocrine disturbing effects of bisphenol A (BPA) on organisms, rapid detection has become one of the most important techniques for monitoring its levels in the aqueous solutions associated with plastics and human beings. In this paper, a glassy carbon electrode [...] Read more.

Due to the endocrine disturbing effects of bisphenol A (BPA) on organisms, rapid detection has become one of the most important techniques for monitoring its levels in the aqueous solutions associated with plastics and human beings. In this paper, a glassy carbon electrode (GCE) modified with molybdenum selenide/reduced graphene oxide (MoSe₂/rGO) was fabricated for in situ determination of bisphenol A in several beverages. The surface area of the electrode dramatically increases due to the existence of ultra-thin nanosheets in a flower-like structure of MoSe₂. Adding phosphotungstic acid in the electrolyte can significantly enhance the repeatability (RSD = 0.4%) and reproducibility (RSD = 2.2%) of the electrode. Under the optimized condition (pH = 6.5), the linear range of BPA was from 0.1 μM–100 μM and the detection limit was 0.015 μM (S/N = 3). When using the as-prepared electrode for analyzing BPA in beverage samples without any pretreatments, the recoveries ranged from 98–107%, and the concentrations were from below the detection limit to 1.7 μM, indicating its potential prospect for routine analysis of BPA. Full article

(This article belongs to the Section Chemical Sensors)

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11 pages, 605 KiB

Open AccessFeature PaperArticle

Magnetorelaxometry in the Presence of a DC Bias Field of Ferromagnetic Nanoparticles Bearing a Viscoelastic Corona

by Victor Rusakov^† and Yuriy Raikher^*,†

¹ Institute of Continuous Media Mechanics, Russian Academy of Sciences, Ural Branch, Perm 614013, Russia

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1661; https://doi.org/10.3390/s18051661 - 22 May 2018

Cited by 11 | Viewed by 3816

Abstract

With allowance for orientational Brownian motion, the magnetorelaxometry (MRX) signal, i.e., the decay of magnetization generated by an ensemble of ferromagnet nanoparticles, each of which bears a macromolecular corona (a loose layer of polymer gel) is studied. The rheology of corona is modelled [...] Read more.

With allowance for orientational Brownian motion, the magnetorelaxometry (MRX) signal, i.e., the decay of magnetization generated by an ensemble of ferromagnet nanoparticles, each of which bears a macromolecular corona (a loose layer of polymer gel) is studied. The rheology of corona is modelled by the Jeffreys scheme. The latter, although comprising only three phenomenological parameters, enables one to describe a wide spectrum of viscoelastic media: from linearly viscous liquids to weakly-fluent gels. The “transverse” configuration of MRX is considered where the system is subjected to a DC (constant bias) field, whereas the probing field is applied perpendicularly to the bias one. The analysis shows that the rate of magnetization decay strongly depends on the state of corona and slows down with enhancement of the corona elasticity. In addition, for the case of “transverse” MRX, we consider the integral time, i.e., the characteristic that is applicable to relaxation processes with an arbitrary number of decay modes. Expressions for the dependence of the integral time on the corona elasticity parameter and temperature are derived. Full article

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

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20 pages, 1808 KiB

Open AccessArticle

Flying Real-Time Network to Coordinate Disaster Relief Activities in Urban Areas

by Matias Micheletto^1,§, Vinicius Petrucci^2,§

, Rodrigo Santos^1,*,‡,§

, Javier Orozco^1,§, Daniel Mosse^3,§, Sergio F. Ochoa^4,§

and Roc Meseguer^5,§

¹ Department of Electrical and Computers, Universidad Nacional del Sur, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca 8000, Argentina

² Department of Computer Science, Universidade Federal do Bahía, Bahía 40110909, Brazil

³ Department of Computer Science, University of Pittsburgh, Pittsburgh, PA 15261, USA

⁴ Department of Computer Science, Universidad de Chile, Santiago 8370456, Chile

⁵ Department of Computer Architecture, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain

^‡ Current address: Instituto de Investigaciones en Ingeniería Eléctrica - Universidad Nacional del Surt - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Alem 1253, Bahía Blanca 8000, Argentina.

^§ These authors contributed equally to this work.

Sensors 2018, 18(5), 1662; https://doi.org/10.3390/s18051662 - 22 May 2018

Cited by 24 | Viewed by 5426

Abstract

While there have been important advances within wireless communication technology, the provision of communication support during disaster relief activities remains an open issue. The literature in disaster research reports several major restrictions to conducting first response activities in urban areas, given the limitations [...] Read more.

While there have been important advances within wireless communication technology, the provision of communication support during disaster relief activities remains an open issue. The literature in disaster research reports several major restrictions to conducting first response activities in urban areas, given the limitations of telephone networks and radio systems to provide digital communication in the field. In search-and-rescue operations, the communication requirements are increased, since the first responders need to rely on real-time and reliable communication to perform their activities and coordinate their efforts with other teams. Therefore, these limitations open the door to improvisation during disaster relief efforts. In this paper, we argue that flying ad-hoc networks can provide the communication support needed in these scenarios, and propose a new solution towards that goal. The proposal involves the use of flying witness units, implemented using drones, that act as communication gateways between first responders working at different locations of the affected area. The proposal is named the Flying Real-Time Network, and its feasibility to provide communication in a disaster scenario is shown by presenting both a real-time schedulability analysis of message delivery, as well as simulations of the communication support in a physical scenario inspired by a real incident. The obtained results were highly positive and consistent, therefore this proposal represents a step forward towards the solution of this open issue. 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, 788 KiB

Open AccessArticle

An Identity-Based Anti-Quantum Privacy-Preserving Blind Authentication in Wireless Sensor Networks

by Hongfei Zhu¹, Yu-an Tan¹

, Liehuang Zhu¹, Xianmin Wang², Quanxin Zhang¹ and Yuanzhang Li^1,*

¹ School of Computer Science and Technology, Beijing Institute of Technology, Beijing 100081, China

² School of Computer Science, Guangzhou University, Guangzhou 510006, China

Sensors 2018, 18(5), 1663; https://doi.org/10.3390/s18051663 - 22 May 2018

Cited by 31 | Viewed by 5935

Abstract

With the development of wireless sensor networks, IoT devices are crucial for the Smart City; these devices change people’s lives such as e-payment and e-voting systems. However, in these two systems, the state-of-art authentication protocols based on traditional number theory cannot defeat a [...] Read more.

With the development of wireless sensor networks, IoT devices are crucial for the Smart City; these devices change people’s lives such as e-payment and e-voting systems. However, in these two systems, the state-of-art authentication protocols based on traditional number theory cannot defeat a quantum computer attack. In order to protect user privacy and guarantee trustworthy of big data, we propose a new identity-based blind signature scheme based on number theorem research unit lattice, this scheme mainly uses a rejection sampling theorem instead of constructing a trapdoor. Meanwhile, this scheme does not depend on complex public key infrastructure and can resist quantum computer attack. Then we design an e-payment protocol using the proposed scheme. Furthermore, we prove our scheme is secure in the random oracle, and satisfies confidentiality, integrity, and non-repudiation. Finally, we demonstrate that the proposed scheme outperforms the other traditional existing identity-based blind signature schemes in signing speed and verification speed, outperforms the other lattice-based blind signature in signing speed, verification speed, and signing secret key size. Full article

(This article belongs to the Special Issue Threat Identification and Defence for Internet-of-Things)

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22 pages, 7609 KiB

Open AccessArticle

Design of a Novel MEMS Microgripper with Rotatory Electrostatic Comb-Drive Actuators for Biomedical Applications

by Luis A. Velosa-Moncada^1,2,*, Luz Antonio Aguilera-Cortés¹, Max A. González-Palacios¹

, Jean-Pierre Raskin³ and Agustin L. Herrera-May^4,5

¹ Departamento de Ingeniería Mecánica, DICIS, Universidad de Guanajuato/Carretera Salamanca-Valle de Santiago km 3.5+1.8, Salamanca 36885, Mexico

² Grupo de Investigación GIDEATIC, Universidad Popular del Cesar Seccional Aguachica, Carrera 40 via al Mar, Aguachica 25010, Colombia

³ Institute of Information and Communication Technologies, Electronics and Applied Mathematics (ICTEAM), Université catholique de Louvain (UCL), 1348 Louvain-la-Neuve, Belgium

⁴ Micro and Nanotechnology Research Center, Universidad Veracruzana, Calzada Ruíz Cortines 455, Boca del Río 94294, Mexico

⁵ Maestría en Ingeniería Aplicada, Facultad de Ingeniería de la Construcción y el Hábitat, Universidad Veracruzana, Calzada Ruíz Cortines 455, Boca del Río 94294, Mexico

Sensors 2018, 18(5), 1664; https://doi.org/10.3390/s18051664 - 22 May 2018

Cited by 47 | Viewed by 9999

Abstract

Primary tumors of patients can release circulating tumor cells (CTCs) to flow inside of their blood. The CTCs have different mechanical properties in comparison with red and white blood cells, and their detection may be employed to study the efficiency of medical treatments [...] Read more.

Primary tumors of patients can release circulating tumor cells (CTCs) to flow inside of their blood. The CTCs have different mechanical properties in comparison with red and white blood cells, and their detection may be employed to study the efficiency of medical treatments against cancer. We present the design of a novel MEMS microgripper with rotatory electrostatic comb-drive actuators for mechanical properties characterization of cells. The microgripper has a compact structural configuration of four polysilicon layers and a simple performance that control the opening and closing displacements of the microgripper tips. The microgripper has a mobile arm, a fixed arm, two different actuators and two serpentine springs, which are designed based on the SUMMiT V surface micromachining process from Sandia National Laboratories. The proposed microgripper operates at its first rotational resonant frequency and its mobile arm has a controlled displacement of 40 µm at both opening and closing directions using dc and ac bias voltages. Analytical models are developed to predict the stiffness, damping forces and first torsional resonant frequency of the microgripper. In addition, finite element method (FEM) models are obtained to estimate the mechanical behavior of the microgripper. The results of the analytical models agree very well respect to FEM simulations. The microgripper has a first rotational resonant frequency of 463.8 Hz without gripped cell and it can operate up to with maximum dc and ac voltages of 23.4 V and 129.2 V, respectively. Based on the results of the analytical and FEM models about the performance of the proposed microgripper, it could be used as a dispositive for mechanical properties characterization of circulating tumor cells (CTCs). Full article

(This article belongs to the Special Issue MEMS Resonators)

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21 pages, 2953 KiB

Open AccessArticle

Strategies to Improve Activity Recognition Based on Skeletal Tracking: Applying Restrictions Regarding Body Parts and Similarity Boundaries

by Carlos Gutiérrez-López-Franca^*, Ramón Hervás

and Esperanza Johnson

MAmI Research Lab, University of Castilla-La Mancha, Paseo de la Universidad 4, 13071 Ciudad Real, Spain

Sensors 2018, 18(5), 1665; https://doi.org/10.3390/s18051665 - 22 May 2018

Cited by 3 | Viewed by 4088

Abstract

This paper aims to improve activity recognition systems based on skeletal tracking through the study of two different strategies (and its combination): (a) specialized body parts analysis and (b) stricter restrictions for the most easily detectable activities. The study was performed using the [...] Read more.

This paper aims to improve activity recognition systems based on skeletal tracking through the study of two different strategies (and its combination): (a) specialized body parts analysis and (b) stricter restrictions for the most easily detectable activities. The study was performed using the Extended Body-Angles Algorithm, which is able to analyze activities using only a single key sample. This system allows to select, for each considered activity, which are its relevant joints, which makes it possible to monitor the body of the user selecting only a subset of the same. But this feature of the system has both advantages and disadvantages. As a consequence, in the past we had some difficulties with the recognition of activities that only have a small subset of the joints of the body as relevant. The goal of this work, therefore, is to analyze the effect produced by the application of several strategies on the results of an activity recognition system based on skeletal tracking joint oriented devices. Strategies that we applied with the purpose of improve the recognition rates of the activities with a small subset of relevant joints. Through the results of this work, we aim to give the scientific community some first indications about which considered strategy is better. 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, 6197 KiB

Open AccessArticle

Transmitting Pulse Encoding for Beyond-PRT Retransmitting Deception Jamming Detection in Spaceborne Synthetic Aperture Radar (SAR)

by Ruijia Wang^1,2,*, Sun Bing², Xing Wang¹ and Siyi Cheng¹

¹ Aeronautics Engineering College, Air Force Engineering University, Xi’an 710038, China

² School of Electronics and Information Engineering, Beihang University, Beijing 100084, China

Sensors 2018, 18(5), 1666; https://doi.org/10.3390/s18051666 - 22 May 2018

Cited by 2 | Viewed by 4589

Abstract

Retransmitting deception jamming (RDJ) degrades and misleads the Synthetic Aperture Radar (SAR) image interpretation by forming false targets. The beyond-Pulse Repetition Time (PRT) RDJ enlarges the effective jamming area without constraining the jammer location to reduce the spaceborne SAR working effectiveness. In order [...] Read more.

Retransmitting deception jamming (RDJ) degrades and misleads the Synthetic Aperture Radar (SAR) image interpretation by forming false targets. The beyond-Pulse Repetition Time (PRT) RDJ enlarges the effective jamming area without constraining the jammer location to reduce the spaceborne SAR working effectiveness. In order to detect the beyond-PRT RDJ and enhance the working efficiency in electronic countermeasure environment, the transmitting pulse encoding method for use in spaceborne SAR is proposed based on the geometry and signal models of beyond-PRT RDJ. Optimum binary codes with maximum number of detection windows are determined by the encoding procedure. The detected area is found to be proportional to the code length and the encoding efficiencies of even and odd codes are analyzed. The simulation results validate the effectiveness of the transmitting pulse encoding method for beyond-PRT RDJ detection in spaceborne SAR. 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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Review

Jump to: Research

18 pages, 2057 KiB

Open AccessReview

A Review of the Piezoelectric Electromechanical Impedance Based Structural Health Monitoring Technique for Engineering Structures

by Wongi S. Na^* and Jongdae Baek

Department of Infrastructure Safety Research, Korea Institute of Civil Engineering and Building Technology, Gyeonggi-Do 10223, Korea

Sensors 2018, 18(5), 1307; https://doi.org/10.3390/s18051307 - 24 Apr 2018

Cited by 280 | Viewed by 14081

Abstract

The birth of smart materials such as piezoelectric (PZT) transducers has aided in revolutionizing the field of structural health monitoring (SHM) based on non-destructive testing (NDT) methods. While a relatively new NDT method known as the electromechanical (EMI) technique has been investigated for [...] Read more.

The birth of smart materials such as piezoelectric (PZT) transducers has aided in revolutionizing the field of structural health monitoring (SHM) based on non-destructive testing (NDT) methods. While a relatively new NDT method known as the electromechanical (EMI) technique has been investigated for more than two decades, there are still various problems that must be solved before it is applied to real structures. The technique, which has a significant potential to contribute to the creation of one of the most effective SHM systems, involves the use of a single PZT for exciting and sensing of the host structure. In this paper, studies applied for the past decade related to the EMI technique have been reviewed to understand its trend. In addition, new concepts and ideas proposed by various authors are also surveyed, and the paper concludes with a discussion of the potential directions for future works. Full article

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

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27 pages, 2092 KiB

Open AccessReview

Direct Electron Transfer of Dehydrogenases for Development of 3rd Generation Biosensors and Enzymatic Fuel Cells

by Paolo Bollella¹

, Lo Gorton² and Riccarda Antiochia^1,*

¹ Department of Chemistry and Drug Technologies, Sapienza University of Rome P.le Aldo Moro 5, 00185 Rome, Italy

² Department of Biochemistry and Structural Biology, Lund University, P.O. Box 124, 221 00 Lund, Sweden

Sensors 2018, 18(5), 1319; https://doi.org/10.3390/s18051319 - 24 Apr 2018

Cited by 86 | Viewed by 9530

Abstract

Dehydrogenase based bioelectrocatalysis has been increasingly exploited in recent years in order to develop new bioelectrochemical devices, such as biosensors and biofuel cells, with improved performances. In some cases, dehydrogeases are able to directly exchange electrons with an appropriately designed electrode surface, without [...] Read more.

Dehydrogenase based bioelectrocatalysis has been increasingly exploited in recent years in order to develop new bioelectrochemical devices, such as biosensors and biofuel cells, with improved performances. In some cases, dehydrogeases are able to directly exchange electrons with an appropriately designed electrode surface, without the need for an added redox mediator, allowing bioelectrocatalysis based on a direct electron transfer process. In this review we briefly describe the electron transfer mechanism of dehydrogenase enzymes and some of the characteristics required for bioelectrocatalysis reactions via a direct electron transfer mechanism. Special attention is given to cellobiose dehydrogenase and fructose dehydrogenase, which showed efficient direct electron transfer reactions. An overview of the most recent biosensors and biofuel cells based on the two dehydrogenases will be presented. The various strategies to prepare modified electrodes in order to improve the electron transfer properties of the device will be carefully investigated and all analytical parameters will be presented, discussed and compared. Full article

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

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21 pages, 22287 KiB

Open AccessReview

A Review on Bacteriorhodopsin-Based Bioelectronic Devices

by Yu-Tao Li^1,2,†, Ye Tian^1,2,†, He Tian^1,2,*, Tao Tu^1,2, Guang-Yang Gou^1,2, Qian Wang^1,2, Yan-Cong Qiao^1,2, Yi Yang^1,2,* and Tian-Ling Ren^1,2,*

¹ Institute of Microelectronics, Tsinghua University, Beijing 100084, China

² Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China

^† These authors contributed equally to this work.

Sensors 2018, 18(5), 1368; https://doi.org/10.3390/s18051368 - 27 Apr 2018

Cited by 59 | Viewed by 11652

Abstract

Bacteriorhodopsin protein extracted from Halobacterium salinarum is widely used in many biohybrid electronic devices and forms a research subject known as bioelectronics, which merges biology with electronic technique. The specific molecule structure and components of bR lead to its unique photocycle characteristic, which [...] Read more.

Bacteriorhodopsin protein extracted from Halobacterium salinarum is widely used in many biohybrid electronic devices and forms a research subject known as bioelectronics, which merges biology with electronic technique. The specific molecule structure and components of bR lead to its unique photocycle characteristic, which consists of several intermediates (bR, K, L, M, N, and O) and results in proton pump function. In this review, working principles and properties of bacteriorhodopsin are briefly introduced, as well as bR layer preparation method. After that, different bR-based devices divided into photochemical and photoelectric applications are shown. Finally, outlook and conclusions are drawn to inspire new design of high-performance bR-based biohybrid electronic devices. Full article

(This article belongs to the Section Biosensors)

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21 pages, 6916 KiB

Open AccessReview

Fluorescent Nanobiosensors for Sensing Glucose

by Longyi Chen¹, Eugene Hwang² and Jin Zhang^1,2,*

¹ Department of Chemical and Biochemical Engineering, University of Western Ontario, 1151 Richmond St., London, ON N6A 5B9, Canada

² Biomedical Engineering Graduate Program, University of Western Ontario, 1151 Richmond St., London, ON N6A 5B9, Canada

Sensors 2018, 18(5), 1440; https://doi.org/10.3390/s18051440 - 5 May 2018

Cited by 98 | Viewed by 10297

Abstract

Glucose sensing in diabetes diagnosis and therapy is of great importance due to the prevalence of diabetes in the world. Furthermore, glucose sensing is also critical in the food and drug industries. Sensing glucose has been accomplished through various strategies, such as electrochemical [...] Read more.

Glucose sensing in diabetes diagnosis and therapy is of great importance due to the prevalence of diabetes in the world. Furthermore, glucose sensing is also critical in the food and drug industries. Sensing glucose has been accomplished through various strategies, such as electrochemical or optical methods. Novel transducers made with nanomaterials that integrate fluorescent techniques have allowed for the development of advanced glucose sensors with superior sensitivity and convenience. In this review, glucose sensing by fluorescent nanobiosensor systems is discussed. Firstly, typical fluorescence emitting/interacting nanomaterials utilized in various glucose assays are discussed. Secondly, strategies for integrating fluorescent nanomaterials and biological sensing elements are reviewed and discussed. In summary, this review highlights the applicability of fluorescent nanomaterials, which makes them ideal for glucose sensing. Insight on the future direction of fluorescent nanobiosensor systems is also provided. Full article

(This article belongs to the Section Biosensors)

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21 pages, 4290 KiB

Open AccessReview

3D Architectured Graphene/Metal Oxide Hybrids for Gas Sensors: A Review

by Yi Xia^1,2,3,*, Ran Li^1,4, Ruosong Chen³, Jing Wang^3,5,* and Lan Xiang^3,*

¹ Research Center for Analysis and Measurement, Kunming University of Science and Technology, Kunming 650093, China

² The Key Laboratory of Unconventional Metallurgy, Ministry of Education, Kunming 650093, China

³ Department of Chemical Engineering, Tsinghua University, Beijing 100084, China

⁴ Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China

⁵ The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, China

Sensors 2018, 18(5), 1456; https://doi.org/10.3390/s18051456 - 7 May 2018

Cited by 96 | Viewed by 9600

Abstract

Graphene/metal oxide-based materials have been demonstrated as promising candidates for gas sensing applications due to the enhanced sensing performance and synergetic effects of the two components. Plenty of metal oxides such as SnO₂, ZnO, WO₃, etc. have been hybridized [...] Read more.

Graphene/metal oxide-based materials have been demonstrated as promising candidates for gas sensing applications due to the enhanced sensing performance and synergetic effects of the two components. Plenty of metal oxides such as SnO₂, ZnO, WO₃, etc. have been hybridized with graphene to improve the gas sensing properties. However, graphene/metal oxide nanohybrid- based gas sensors still have several limitations in practical application such as the insufficient sensitivity and response rate, and long recovery time in some cases. To achieve higher sensing performances of graphene/metal oxides nanocomposites, many recent efforts have been devoted to the controllable synthesis of 3D graphene/metal oxides architectures owing to their large surface area and well-organized structure for the enhanced gas adsorption/diffusion on sensing films. This review summarizes recent advances in the synthesis, assembly, and applications of 3D architectured graphene/metal oxide hybrids for gas sensing. Full article

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

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16 pages, 2504 KiB

Open AccessReview

Shoe-Insole Technology for Injury Prevention in Walking

by Hanatsu Nagano and Rezaul K. Begg^*

Institute for Health and Sport (IHES), Victoria University, Melbourne, VIC 3032, Australia

Sensors 2018, 18(5), 1468; https://doi.org/10.3390/s18051468 - 8 May 2018

Cited by 46 | Viewed by 23728

Abstract

Impaired walking increases injury risk during locomotion, including falls-related acute injuries and overuse damage to lower limb joints. Gait impairments seriously restrict voluntary, habitual engagement in injury prevention activities, such as recreational walking and exercise. There is, therefore, an urgent need for technology-based [...] Read more.

Impaired walking increases injury risk during locomotion, including falls-related acute injuries and overuse damage to lower limb joints. Gait impairments seriously restrict voluntary, habitual engagement in injury prevention activities, such as recreational walking and exercise. There is, therefore, an urgent need for technology-based interventions for gait disorders that are cost effective, willingly taken-up, and provide immediate positive effects on walking. Gait control using shoe-insoles has potential as an effective population-based intervention, and new sensor technologies will enhance the effectiveness of these devices. Shoe-insole modifications include: (i) ankle joint support for falls prevention; (ii) shock absorption by utilising lower-resilience materials at the heel; (iii) improving reaction speed by stimulating cutaneous receptors; and (iv) preserving dynamic balance via foot centre of pressure control. Using sensor technology, such as in-shoe pressure measurement and motion capture systems, gait can be precisely monitored, allowing us to visualise how shoe-insoles change walking patterns. In addition, in-shoe systems, such as pressure monitoring and inertial sensors, can be incorporated into the insole to monitor gait in real-time. Inertial sensors coupled with in-shoe foot pressure sensors and global positioning systems (GPS) could be used to monitor spatiotemporal parameters in real-time. Real-time, online data management will enable ‘big-data’ applications to everyday gait control characteristics. Full article

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

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26 pages, 7043 KiB

Open AccessReview

Fast and Cost-Effective Biochemical Spectrophotometric Analysis of Solution of Insect “Blood” and Body Surface Elution

by Aleksandra Łoś

and Aneta Strachecka^*

Faculty of Biology, Animal Sciences and Bioeconomy, Institute of Biological Basis of Animal Production, University of Life Sciences in Lublin, Akademicka 13, 20950 Lublin, Poland

Sensors 2018, 18(5), 1494; https://doi.org/10.3390/s18051494 - 9 May 2018

Cited by 41 | Viewed by 6984

Abstract

Using insect hemolymph (“blood”) and insect body surface elutions, researchers can perform rapid and cheap biochemical analyses to determine the insect’s immunology status. The authors of this publication describe a detailed methodology for a quick marking of the concentration of total proteins and [...] Read more.

Using insect hemolymph (“blood”) and insect body surface elutions, researchers can perform rapid and cheap biochemical analyses to determine the insect’s immunology status. The authors of this publication describe a detailed methodology for a quick marking of the concentration of total proteins and evaluation of the proteolytic system activity (acid, neutral, and alkaline proteases and protease inhibitors), as well as a methodology for quick “liver” tests in insects: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and urea and glucose concentration analyses. The meaning and examples of an interpretation of the results of the presented methodology for biochemical parameter determination are described for the example of honey bees. Full article

(This article belongs to the Section Biosensors)

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30 pages, 16767 KiB

Open AccessReview

Biological Oscillators in Nanonetworks—Opportunities and Challenges

by Ethungshan Shitiri¹

, Athanasios V. Vasilakos² and Ho-Shin Cho^1,*

¹ School of Electronics, Kyungpook National University, Daegu 41566, Korea

² Department of Computer Science, Electrical and Space Engineering, Lulea University of Technology, 93187 Lulea, Sweden

Sensors 2018, 18(5), 1544; https://doi.org/10.3390/s18051544 - 13 May 2018

Cited by 14 | Viewed by 5655

Abstract

One of the major issues in molecular communication-based nanonetworks is the provision and maintenance of a common time knowledge. To stay true to the definition of molecular communication, biological oscillators are the potential solutions to achieve that goal as they generate oscillations through [...] Read more.

One of the major issues in molecular communication-based nanonetworks is the provision and maintenance of a common time knowledge. To stay true to the definition of molecular communication, biological oscillators are the potential solutions to achieve that goal as they generate oscillations through periodic fluctuations in the concentrations of molecules. Through the lens of a communication systems engineer, the scope of this survey is to explicitly classify, for the first time, existing biological oscillators based on whether they are found in nature or not, to discuss, in a tutorial fashion, the main principles that govern the oscillations in each oscillator, and to analyze oscillator parameters that are most relevant to communication engineer researchers. In addition, the survey highlights and addresses the key open research issues pertaining to several physical aspects of the oscillators and the adoption and implementation of the oscillators to nanonetworks. Moreover, key research directions are discussed. Full article

(This article belongs to the Section Biosensors)

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20 pages, 573 KiB

Open AccessReview

Type and Location of Wearable Sensors for Monitoring Falls during Static and Dynamic Tasks in Healthy Elderly: A Review

by Rosaria Rucco^1,2,*

, Antonietta Sorriso³, Marianna Liparoti^1,2, Giampaolo Ferraioli⁴, Pierpaolo Sorrentino^2,3, Michele Ambrosanio³

and Fabio Baselice³

¹ Department of Motor Sciences and Wellness, University of Naples “Parthenope”, 80133 Naples, Italy

² IDC Hermitage Capodimonte, 80133 Naples, Italy

³ Department of Engineering, University of Naples “Parthenope”, 80133 Naples, Italy

⁴ Department of Science and Technologies, University of Naples “Parthenope”, 80133 Naples, Italy

Sensors 2018, 18(5), 1613; https://doi.org/10.3390/s18051613 - 18 May 2018

Cited by 103 | Viewed by 8785 | Correction

Abstract

In recent years, the meaning of successful living has moved from extending lifetime to improving the quality of aging, mainly in terms of high cognitive and physical functioning together with avoiding diseases. In healthy elderly, falls represent an alarming accident both in terms [...] Read more.

In recent years, the meaning of successful living has moved from extending lifetime to improving the quality of aging, mainly in terms of high cognitive and physical functioning together with avoiding diseases. In healthy elderly, falls represent an alarming accident both in terms of number of events and the consequent decrease in the quality of life. Stability control is a key approach for studying the genesis of falls, for detecting the event and trying to develop methodologies to prevent it. Wearable sensors have proved to be very useful in monitoring and analyzing the stability of subjects. Within this manuscript, a review of the approaches proposed in the literature for fall risk assessment, fall prevention and fall detection in healthy elderly is provided. The review has been carried out by using the most adopted publication databases and by defining a search strategy based on keywords and boolean algebra constructs. The analysis aims at evaluating the state of the art of such kind of monitoring, both in terms of most adopted sensor technologies and of their location on the human body. The review has been extended to both dynamic and static analyses. In order to provide a useful tool for researchers involved in this field, the manuscript also focuses on the tests conducted in the analyzed studies, mainly in terms of characteristics of the population involved and of the tasks used. Finally, the main trends related to sensor typology, sensor location and tasks have been identified. Full article

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

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11 pages, 4158 KiB

Open AccessReview

SPR Biosensors in Direct Molecular Fishing: Implications for Protein Interactomics

by Anna Florinskaya

, Pavel Ershov, Yuri Mezentsev^*, Leonid Kaluzhskiy

, Evgeniy Yablokov

, Alexei Medvedev and Alexis Ivanov

Institute of Biomedical Chemistry, 119121 Moscow, Russia

Sensors 2018, 18(5), 1616; https://doi.org/10.3390/s18051616 - 18 May 2018

Cited by 21 | Viewed by 5089

Abstract

We have developed an original experimental approach based on the use of surface plasmon resonance (SPR) biosensors, applicable for investigation of potential partners involved in protein–protein interactions (PPI) as well as protein–peptide or protein–small molecule interactions. It is based on combining a SPR [...] Read more.

We have developed an original experimental approach based on the use of surface plasmon resonance (SPR) biosensors, applicable for investigation of potential partners involved in protein–protein interactions (PPI) as well as protein–peptide or protein–small molecule interactions. It is based on combining a SPR biosensor, size exclusion chromatography (SEC), mass spectrometric identification of proteins (LC-MS/MS) and direct molecular fishing employing principles of affinity chromatography for isolation of potential partner proteins from the total lysate of biological samples using immobilized target proteins (or small non-peptide compounds) as ligands. Applicability of this approach has been demonstrated within the frame of the Human Proteome Project (HPP) and PPI regulation by a small non-peptide biologically active compound, isatin. Full article

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

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25 pages, 1070 KiB

Open AccessReview

Registration of Laser Scanning Point Clouds: A Review

by Liang Cheng^1,2,3,4, Song Chen^1,2,4, Xiaoqiang Liu^1,2,4

, Hao Xu^1,2,4, Yang Wu^1,2,4, Manchun Li^1,2,3,4 and Yanming Chen^1,2,3,4,*

¹ Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, Nanjing University, Nanjing 210093, China

² Collaborative Innovation Center for the South Sea Studies, Nanjing University, Nanjing 210093, China

³ Collaborative Innovation Center of Novel Software Technology and Industrialization, Nanjing University, Nanjing 210093, China

⁴ School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093, China

Sensors 2018, 18(5), 1641; https://doi.org/10.3390/s18051641 - 21 May 2018

Cited by 235 | Viewed by 16459

Abstract

The integration of multi-platform, multi-angle, and multi-temporal LiDAR data has become important for geospatial data applications. This paper presents a comprehensive review of LiDAR data registration in the fields of photogrammetry and remote sensing. At present, a coarse-to-fine registration strategy is commonly used [...] Read more.

The integration of multi-platform, multi-angle, and multi-temporal LiDAR data has become important for geospatial data applications. This paper presents a comprehensive review of LiDAR data registration in the fields of photogrammetry and remote sensing. At present, a coarse-to-fine registration strategy is commonly used for LiDAR point clouds registration. The coarse registration method is first used to achieve a good initial position, based on which registration is then refined utilizing the fine registration method. According to the coarse-to-fine framework, this paper reviews current registration methods and their methodologies, and identifies important differences between them. The lack of standard data and unified evaluation systems is identified as a factor limiting objective comparison of different methods. The paper also describes the most commonly-used point cloud registration error analysis methods. Finally, avenues for future work on LiDAR data registration in terms of applications, data, and technology are discussed. In particular, there is a need to address registration of multi-angle and multi-scale data from various newly available types of LiDAR hardware, which will play an important role in diverse applications such as forest resource surveys, urban energy use, cultural heritage protection, and unmanned vehicles. Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 708 KiB

Open AccessFeature PaperReview

Deep Learning to Predict Falls in Older Adults Based on Daily-Life Trunk Accelerometry

by Ahmed Nait Aicha^1,*

, Gwenn Englebienne², Kimberley S. Van Schooten³

, Mirjam Pijnappels⁴

and Ben Kröse^1,5

¹ Department of Computer Science, Amsterdam University of Applied Sciences, 1091 GM Amsterdam, The Netherlands

² Human Media Interaction, University of Twente, 7522 NH Enschede, The Netherlands

³ Neuroscience Research Australia, University of New South Wales, Sydney 2031, Australia

⁴ Department of Human Movement Sciences, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands

⁵ Informatics Institute, University of Amsterdam, 1098 XH Amsterdam, The Netherlands

Sensors 2018, 18(5), 1654; https://doi.org/10.3390/s18051654 - 22 May 2018

Cited by 155 | Viewed by 12307

Abstract

Early detection of high fall risk is an essential component of fall prevention in older adults. Wearable sensors can provide valuable insight into daily-life activities; biomechanical features extracted from such inertial data have been shown to be of added value for the assessment [...] Read more.

Early detection of high fall risk is an essential component of fall prevention in older adults. Wearable sensors can provide valuable insight into daily-life activities; biomechanical features extracted from such inertial data have been shown to be of added value for the assessment of fall risk. Body-worn sensors such as accelerometers can provide valuable insight into fall risk. Currently, biomechanical features derived from accelerometer data are used for the assessment of fall risk. Here, we studied whether deep learning methods from machine learning are suited to automatically derive features from raw accelerometer data that assess fall risk. We used an existing dataset of 296 older adults. We compared the performance of three deep learning model architectures (convolutional neural network (CNN), long short-term memory (LSTM) and a combination of these two (ConvLSTM)) to each other and to a baseline model with biomechanical features on the same dataset. The results show that the deep learning models in a single-task learning mode are strong in recognition of identity of the subject, but that these models only slightly outperform the baseline method on fall risk assessment. When using multi-task learning, with gender and age as auxiliary tasks, deep learning models perform better. We also found that preprocessing of the data resulted in the best performance (AUC = 0.75). We conclude that deep learning models, and in particular multi-task learning, effectively assess fall risk on the basis of wearable sensor data. Full article

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

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