Sensors

10 pages, 3275 KiB

Open AccessArticle

Color Change of Phenol Red by Integrated Smart Phone Camera as a Tool for the Determination of Neurotoxic Compounds

by Adam Kostelnik¹, Alexander Cegan¹ and Miroslav Pohanka^2,*

¹ Faculty of Chemical Technology, University of Pardubice, Studentska 95, Pardubice CZ-53210, Czech Republic

² Faculty of Military Health Sciences, University of Defense, Trebesska 1575, Hradec Kralove CZ-50001, Czech Republic

Sensors 2016, 16(9), 1212; https://doi.org/10.3390/s16091212 - 7 Sep 2016

Cited by 10 | Viewed by 7526

Abstract

The use of a cell phone as a detection system is easy, simple and does not require trained personnel, which is in contrast to standard laboratory instruments. This paper deals with immobilization of acetylcholinesterase (AChE) in a gelatin matrix, and phenol red, as [...] Read more.

The use of a cell phone as a detection system is easy, simple and does not require trained personnel, which is in contrast to standard laboratory instruments. This paper deals with immobilization of acetylcholinesterase (AChE) in a gelatin matrix, and phenol red, as an indicator of AChE activity, is used in order to establish a method that is easily compatible with a camera device. AChE splits acetylcholine into choline and acetic acid, which changes the pH of a medium, resulting in a phenol red color change. The coloration changed in presence of an AChE inhibitor. Measurements were performed on 3D-printed, tube-shaped holder, and digital photography, with subsequent analysis of red-green-blue (RGB), served for assay purposes. Calibration of AChE inhibitors, tacrine and galantamine, was performed, with limit of detection equal to 1.1 nM and 1.28 µM, respectively. Interferences were also measured, resulting in a proof-of-method stability. The method was further successfully validated for the standard Ellman’s assay, and verified on murine plasma samples spiked with inhibitors. Full article

(This article belongs to the Section Biosensors)

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8 pages, 1743 KiB

Open AccessArticle

Performance and Durability of Thin Film Thermocouple Array on a Porous Electrode

by Erdogan Guk, Manoj Ranaweera, Vijay Venkatesan and Jung-Sik Kim^*

Aeronautical & Automotive Engineering Department, Loughborough University, Loughborough LE11 3TU, UK

Sensors 2016, 16(9), 1329; https://doi.org/10.3390/s16091329 - 23 Aug 2016

Cited by 25 | Viewed by 7289

Abstract

Management of solid oxide fuel cell (SOFC) thermal gradients is vital to limit thermal expansion mismatch and thermal stress. However, owing to harsh operation conditions of SOFCs and limited available space in stack configuration, the number of techniques available to obtain temperature distribution [...] Read more.

Management of solid oxide fuel cell (SOFC) thermal gradients is vital to limit thermal expansion mismatch and thermal stress. However, owing to harsh operation conditions of SOFCs and limited available space in stack configuration, the number of techniques available to obtain temperature distribution from the cell surface is limited. The authors previously developed and studied a thermocouple array pattern to detect surface temperature distribution on an SOFC in open circuit conditions. In this study, the performance in terms of mechanical durability and oxidation state of the thin film thermoelements of the thermocouple array on the porous SOFC cathode is investigated. A thin-film multi-junction thermocouple array was sputter deposited using a magnetron sputter coater. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) characterisation techniques were carried out to understand characteristics of the thin film before and after temperature (20 °C–800 °C) measurement. Temperature readings from the sensor agreed well with the closely placed commercial thermocouple during heating segments. However, a sensor failure occurred at around 350 °C during the cooling segment. The SEM and XPS tests revealed cracks on the thin film thermoelements and oxidation to the film thickness direction. Full article

(This article belongs to the Special Issue Integrated Sensor Arrays and Array Signal Processing)

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37 pages, 2530 KiB

Open AccessArticle

Querying and Extracting Timeline Information from Road Traffic Sensor Data

by Ardi Imawan¹, Fitri Indra Indikawati¹

, Joonho Kwon^1,*

and Praveen Rao²

¹ Department of Big Data, Pusan National University, Busan 46241, Korea

² Department of Computer Science & Electrical Engineering, University of Missouri-Kansas City, Kansas City, MO 64110, USA

Sensors 2016, 16(9), 1340; https://doi.org/10.3390/s16091340 - 23 Aug 2016

Cited by 8 | Viewed by 10309

Abstract

The escalation of traffic congestion in urban cities has urged many countries to use intelligent transportation system (ITS) centers to collect historical traffic sensor data from multiple heterogeneous sources. By analyzing historical traffic data, we can obtain valuable insights into traffic behavior. Many [...] Read more.

The escalation of traffic congestion in urban cities has urged many countries to use intelligent transportation system (ITS) centers to collect historical traffic sensor data from multiple heterogeneous sources. By analyzing historical traffic data, we can obtain valuable insights into traffic behavior. Many existing applications have been proposed with limited analysis results because of the inability to cope with several types of analytical queries. In this paper, we propose the QET (querying and extracting timeline information) system—a novel analytical query processing method based on a timeline model for road traffic sensor data. To address query performance, we build a TQ-index (timeline query-index) that exploits spatio-temporal features of timeline modeling. We also propose an intuitive timeline visualization method to display congestion events obtained from specified query parameters. In addition, we demonstrate the benefit of our system through a performance evaluation using a Busan ITS dataset and a Seattle freeway dataset. Full article

(This article belongs to the Special Issue Vehicular Sensor Networks: Technical Challenges, Supports, and Application Experiences)

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14 pages, 2522 KiB

Open AccessArticle

Sensitive Bioanalysis Based on in-Situ Droplet Anodic Stripping Voltammetric Detection of CdS Quantum Dots Label after Enhanced Cathodic Preconcentration

by Xiaoli Qin¹, Linchun Wang² and Qingji Xie^1,*

¹ Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research (Ministry of Education of China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, China

² Liuzhou Traditional Chinese Medicine Hospital, Liuzhou 545001, China

Sensors 2016, 16(9), 1342; https://doi.org/10.3390/s16091342 - 23 Aug 2016

Cited by 10 | Viewed by 7509

Abstract

We report a protocol of CdS-labeled sandwich-type amperometric bioanalysis with high sensitivity, on the basis of simultaneous chemical-dissolution/cathodic-enrichment of the CdS quantum dot biolabel and anodic stripping voltammetry (ASV) detection of Cd directly on the bioelectrode. We added a microliter droplet of 0.1 [...] Read more.

We report a protocol of CdS-labeled sandwich-type amperometric bioanalysis with high sensitivity, on the basis of simultaneous chemical-dissolution/cathodic-enrichment of the CdS quantum dot biolabel and anodic stripping voltammetry (ASV) detection of Cd directly on the bioelectrode. We added a microliter droplet of 0.1 M aqueous HNO₃ to dissolve CdS on the bioelectrode and simultaneously achieved the potentiostatic cathodic preconcentration of Cd by starting the potentiostatic operation before HNO₃ addition, which can largely increase the ASV signal. Our protocol was used for immunoanalysis and aptamer-based bioanalysis of several proteins, giving limits of detection of 4.5 fg·mL⁻¹ for human immunoglobulin G, 3.0 fg·mL⁻¹ for human carcinoembryonic antigen (CEA), 4.9 fg·mL⁻¹ for human α-fetoprotein (AFP), and 0.9 fM for thrombin, which are better than many reported results. The simultaneous and sensitive analysis of CEA and AFP at two screen-printed carbon electrodes was also conducted by our protocol. Full article

(This article belongs to the Special Issue Nanobiosensing for Sensors)

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13 pages, 3885 KiB

Open AccessArticle

Remote Bridge Deflection Measurement Using an Advanced Video Deflectometer and Actively Illuminated LED Targets

by Long Tian and Bing Pan^*

Institute of Solid Mechanics, Beihang University, Beijing 100191, China

Sensors 2016, 16(9), 1344; https://doi.org/10.3390/s16091344 - 23 Aug 2016

Cited by 87 | Viewed by 10013

Abstract

An advanced video deflectometer using actively illuminated LED targets is proposed for remote, real-time measurement of bridge deflection. The system configuration, fundamental principles, and measuring procedures of the video deflectometer are first described. To address the challenge of remote and accurate deflection measurement [...] Read more.

An advanced video deflectometer using actively illuminated LED targets is proposed for remote, real-time measurement of bridge deflection. The system configuration, fundamental principles, and measuring procedures of the video deflectometer are first described. To address the challenge of remote and accurate deflection measurement of large engineering structures without being affected by ambient light, the novel idea of active imaging, which combines high-brightness monochromatic LED targets with coupled bandpass filter imaging, is introduced. Then, to examine the measurement accuracy of the proposed advanced video deflectometer in outdoor environments, vertical motions of an LED target with precisely-controlled translations were measured and compared with prescribed values. Finally, by tracking six LED targets mounted on the bridge, the developed video deflectometer was applied for field, remote, and multipoint deflection measurement of the Wuhan Yangtze River Bridge, one of the most prestigious and most publicized constructions in China, during its routine safety evaluation tests. Since the proposed video deflectometer using actively illuminated LED targets offers prominent merits of remote, contactless, real-time, and multipoint deflection measurement with strong robustness against ambient light changes, it has great potential in the routine safety evaluation of various bridges and other large-scale engineering structures. Full article

(This article belongs to the Section Remote Sensors)

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22 pages, 20040 KiB

Open AccessArticle

An Adaptive Ship Detection Scheme for Spaceborne SAR Imagery

by Xiangguang Leng

, Kefeng Ji^*, Shilin Zhou, Xiangwei Xing and Huanxin Zou

School of Electronic Science and Engineering, National University of Defense Technology, Sanyi Avenue, Changsha 410073, China

Sensors 2016, 16(9), 1345; https://doi.org/10.3390/s16091345 - 23 Aug 2016

Cited by 53 | Viewed by 9518

Abstract

With the rapid development of spaceborne synthetic aperture radar (SAR) and the increasing need of ship detection, research on adaptive ship detection in spaceborne SAR imagery is of great importance. Focusing on practical problems of ship detection, this paper presents a highly adaptive [...] Read more.

With the rapid development of spaceborne synthetic aperture radar (SAR) and the increasing need of ship detection, research on adaptive ship detection in spaceborne SAR imagery is of great importance. Focusing on practical problems of ship detection, this paper presents a highly adaptive ship detection scheme for spaceborne SAR imagery. It is able to process a wide range of sensors, imaging modes and resolutions. Two main stages are identified in this paper, namely: ship candidate detection and ship discrimination. Firstly, this paper proposes an adaptive land masking method using ship size and pixel size. Secondly, taking into account the imaging mode, incidence angle, and polarization channel of SAR imagery, it implements adaptive ship candidate detection in spaceborne SAR imagery by applying different strategies to different resolution SAR images. Finally, aiming at different types of typical false alarms, this paper proposes a comprehensive ship discrimination method in spaceborne SAR imagery based on confidence level and complexity analysis. Experimental results based on RADARSAT-1, RADARSAT-2, TerraSAR-X, RS-1, and RS-3 images demonstrate that the adaptive scheme proposed in this paper is able to detect ship targets in a fast, efficient and robust way. Full article

(This article belongs to the Special Issue Synthetic Aperture Radars: Models, Algorithms, Techniques and Tools for Data Exploitation)

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22 pages, 1110 KiB

Open AccessArticle

Practical Performance Analysis for Multiple Information Fusion Based Scalable Localization System Using Wireless Sensor Networks

by Yubin Zhao^1,2,‡, Xiaofan Li^2,*,†,‡, Sha Zhang^2,†, Tianhui Meng^3,‡ and Yiwen Zhang¹

¹ Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China

² Shenzhen Institute of Radio Testing & Tech., Shenzhen 518000, China

³ Department of Mathematics and Computer Science, Freie Universität Berlin, Berlin 14195, Germany

Sensors 2016, 16(9), 1346; https://doi.org/10.3390/s16091346 - 23 Aug 2016

Cited by 4 | Viewed by 5523

Abstract

In practical localization system design, researchers need to consider several aspects to make the positioning efficiently and effectively, e.g., the available auxiliary information, sensing devices, equipment deployment and the environment. Then, these practical concerns turn out to be the technical problems, e.g., the [...] Read more.

In practical localization system design, researchers need to consider several aspects to make the positioning efficiently and effectively, e.g., the available auxiliary information, sensing devices, equipment deployment and the environment. Then, these practical concerns turn out to be the technical problems, e.g., the sequential position state propagation, the target-anchor geometry effect, the Non-line-of-sight (NLOS) identification and the related prior information. It is necessary to construct an efficient framework that can exploit multiple available information and guide the system design. In this paper, we propose a scalable method to analyze system performance based on the Cramér–Rao lower bound (CRLB), which can fuse all of the information adaptively. Firstly, we use an abstract function to represent all of the wireless localization system model. Then, the unknown vector of the CRLB consists of two parts: the first part is the estimated vector, and the second part is the auxiliary vector, which helps improve the estimation accuracy. Accordingly, the Fisher information matrix is divided into two parts: the state matrix and the auxiliary matrix. Unlike the theoretical analysis, our CRLB can be a practical fundamental limit to denote the system that fuses multiple information in the complicated environment, e.g., recursive Bayesian estimation based on the hidden Markov model, the map matching method and the NLOS identification and mitigation methods. Thus, the theoretical results are approaching the real case more. In addition, our method is more adaptable than other CRLBs when considering more unknown important factors. We use the proposed method to analyze the wireless sensor network-based indoor localization system. The influence of the hybrid LOS/NLOS channels, the building layout information and the relative height differences between the target and anchors are analyzed. It is demonstrated that our method exploits all of the available information for the indoor localization systems and serves as an indicator for practical system evaluation. Full article

(This article belongs to the Special Issue Scalable Localization in Wireless Sensor Networks)

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12 pages, 9733 KiB

Open AccessArticle

A New Approach of Oil Spill Detection Using Time-Resolved LIF Combined with Parallel Factors Analysis for Laser Remote Sensing

by Deqing Liu^1,2, Xiaoning Luan¹, Jinjia Guo¹, Tingwei Cui², Jubai An³ and Ronger Zheng^1,*

¹ Optics and Optoelectronics Laboratory, Ocean University of China, Qingdao 266100, China

² First Institute of Oceanography, State Oceanic Administration, Qingdao 266100, China

³ Information Science & Technology College, Dalian Maritime University, Dalian 116026, China

Sensors 2016, 16(9), 1347; https://doi.org/10.3390/s16091347 - 23 Aug 2016

Cited by 17 | Viewed by 6543

Abstract

In hope of developing a method for oil spill detection in laser remote sensing, a series of refined and crude oil samples were investigated using time-resolved fluorescence in conjunction with parallel factors analysis (PARAFAC). The time resolved emission spectra of those investigated samples [...] Read more.

In hope of developing a method for oil spill detection in laser remote sensing, a series of refined and crude oil samples were investigated using time-resolved fluorescence in conjunction with parallel factors analysis (PARAFAC). The time resolved emission spectra of those investigated samples were taken by a laser remote sensing system on a laboratory basis with a detection distance of 5 m. Based on the intensity-normalized spectra, both refined and crude oil samples were well classified without overlapping, by the approach of PARAFAC with four parallel factors. Principle component analysis (PCA) has also been operated as a comparison. It turned out that PCA operated well in classification of broad oil type categories, but with severe overlapping among the crude oil samples from different oil wells. Apart from the high correct identification rate, PARAFAC has also real-time capabilities, which is an obvious advantage especially in field applications. The obtained results suggested that the approach of time-resolved fluorescence combined with PARAFAC would be potentially applicable in oil spill field detection and identification. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 1333 KiB

Open AccessArticle

Queuing Theory Based Co-Channel Interference Analysis Approach for High-Density Wireless Local Area Networks

by Jie Zhang

, Guangjie Han^*

and Yujie Qian

College of Internet of Things, Hohai University, Changzhou 213022, China

Sensors 2016, 16(9), 1348; https://doi.org/10.3390/s16091348 - 23 Aug 2016

Cited by 19 | Viewed by 8483

Abstract

Increased co-channel interference (CCI) in wireless local area networks (WLANs) is bringing serious resource constraints to today’s high-density wireless environments. CCI in IEEE 802.11-based networks is inevitable due to the nature of the carrier sensing mechanism however can be reduced by resource optimization [...] Read more.

Increased co-channel interference (CCI) in wireless local area networks (WLANs) is bringing serious resource constraints to today’s high-density wireless environments. CCI in IEEE 802.11-based networks is inevitable due to the nature of the carrier sensing mechanism however can be reduced by resource optimization approaches. That means the CCI analysis is basic, but also crucial for an efficient resource management. In this article, we present a novel CCI analysis approach based on the queuing theory, which considers the randomness of end users’ behavior and the irregularity and complexity of network traffic in high-density WLANs that adopts the M/M/c queuing model for CCI analysis. Most of the CCIs occur when multiple networks overlap and trigger channel contentions; therefore, we use the ratio of signal-overlapped areas to signal coverage as a probabilistic factor to the queuing model to analyze the CCI impacts in highly overlapped WLANs. With the queuing model, we perform simulations to see how the CCI influences the quality of service (QoS) in high-density WLANs. Full article

(This article belongs to the Special Issue New Paradigms in Cyber-Physical Social Sensing)

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7 pages, 744 KiB

Open AccessArticle

A Wideband Circularly Polarized Pixelated Dielectric Resonator Antenna

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 2016, 16(9), 1349; https://doi.org/10.3390/s16091349 - 23 Aug 2016

Cited by 29 | Viewed by 7107

Abstract

The design of a wideband circularly polarized pixelated dielectric resonator antenna using a real-coded genetic algorithm (GA) is presented for far-field wireless power transfer applications. The antenna consists of a dielectric resonator (DR) which is discretized into 8 × 8 grid DR bars. [...] Read more.

The design of a wideband circularly polarized pixelated dielectric resonator antenna using a real-coded genetic algorithm (GA) is presented for far-field wireless power transfer applications. The antenna consists of a dielectric resonator (DR) which is discretized into 8 × 8 grid DR bars. The real-coded GA is utilized to estimate the optimal heights of the 64 DR bars to realize circular polarization. The proposed antenna is excited by a narrow rectangular slot etched on the ground plane. A prototype of the proposed antenna is fabricated and tested. The measured −10 dB reflection and 3 dB axial ratio bandwidths are 32.32% (2.62–3.63 GHz) and 14.63% (2.85–3.30 GHz), respectively. A measured peak gain of 6.13 dBic is achieved at 3.2 GHz. Full article

(This article belongs to the Special Issue Resonator Sensors)

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4 pages, 150 KiB

Open AccessEditorial

Introduction to the Special Issue on “State-of-the-Art Sensor Technology in Japan 2015”

by Masahiro Tokumitsu¹ and Yoshiteru Ishida^2,*

¹ Department of Electrical and Control Engineering, National Institute of Technology, Yonago College, 4448 Hikonacho, Yonago 683-0854, Tottori, Japan

² Department of Computer Science and Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi 441-8580, Aichi, Japan

Sensors 2016, 16(9), 1350; https://doi.org/10.3390/s16091350 - 23 Aug 2016

Viewed by 4538

Abstract

This Special Issue, “State-of-the-Art Sensor Technology in Japan 2015”, collected papers on different kinds of sensing technology: fundamental technology for intelligent sensors, information processing for monitoring humans, and information processing for adaptive and survivable sensor systems.[...] Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan 2015)

28 pages, 6232 KiB

Open AccessReview

Towards a Graphene-Based Low Intensity Photon Counting Photodetector

by Jamie O. D. Williams^1,*, Jack A. Alexander-Webber², Jon S. Lapington¹

, Mervyn Roy¹, Ian B. Hutchinson¹, Abhay A. Sagade², Marie-Blandine Martin², Philipp Braeuninger-Weimer², Andrea Cabrero-Vilatela², Ruizhi Wang², Andrea De Luca²

, Florin Udrea² and Stephan Hofmann²

¹ Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK

² Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK

Sensors 2016, 16(9), 1351; https://doi.org/10.3390/s16091351 - 23 Aug 2016

Cited by 6 | Viewed by 10513

Abstract

Graphene is a highly promising material in the development of new photodetector technologies, in particular due its tunable optoelectronic properties, high mobilities and fast relaxation times coupled to its atomic thinness and other unique electrical, thermal and mechanical properties. Optoelectronic applications and graphene-based [...] Read more.

Graphene is a highly promising material in the development of new photodetector technologies, in particular due its tunable optoelectronic properties, high mobilities and fast relaxation times coupled to its atomic thinness and other unique electrical, thermal and mechanical properties. Optoelectronic applications and graphene-based photodetector technology are still in their infancy, but with a range of device integration and manufacturing approaches emerging this field is progressing quickly. In this review we explore the potential of graphene in the context of existing single photon counting technologies by comparing their performance to simulations of graphene-based single photon counting and low photon intensity photodetection technologies operating in the visible, terahertz and X-ray energy regimes. We highlight the theoretical predictions and current graphene manufacturing processes for these detectors. We show initial experimental implementations and discuss the key challenges and next steps in the development of these technologies. Full article

(This article belongs to the Special Issue Photon-Counting Image Sensors)

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20 pages, 4341 KiB

Open AccessArticle

The Finite Element Analysis for a Mini-Conductance Probe in Horizontal Oil-Water Two-Phase Flow

by Weihang Kong^1,†, Lingfu Kong^1,2,*, Lei Li^1,3,†, Xingbin Liu³, Ronghua Xie⁴, Jun Li³ and Haitao Tang³

¹ School of Information Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China

² Key Laboratory for Computer Virtual Technology and System Integration of Hebei Province, Qinhuangdao 066004, Hebei, China

³ Logging and Testing Services Company, Daqing Oilfield Limited Company, Daqing 163453, Heilongjiang, China

⁴ Daqing Oilfield Limited Company, Daqing 163453, Heilongjiang, China

Sensors 2016, 16(9), 1352; https://doi.org/10.3390/s16091352 - 24 Aug 2016

Cited by 13 | Viewed by 6203

Abstract

Oil-water two-phase flow is widespread in petroleum industry processes. The study of oil-water two-phase flow in horizontal pipes and the liquid holdup measurement of oil-water two-phase flow are of great importance for the optimization of the oil production process. This paper presents a [...] Read more.

Oil-water two-phase flow is widespread in petroleum industry processes. The study of oil-water two-phase flow in horizontal pipes and the liquid holdup measurement of oil-water two-phase flow are of great importance for the optimization of the oil production process. This paper presents a novel sensor, i.e., a mini-conductance probe (MCP) for measuring pure-water phase conductivity of oil-water segregated flow in horizontal pipes. The MCP solves the difficult problem of obtaining the pure-water correction for water holdup measurements by using a ring-shaped conductivity water-cut meter (RSCWCM). Firstly, using the finite element method (FEM), the spatial sensitivity field of the MCP is investigated and the optimized MCP geometry structure is determined in terms of the characteristic parameters. Then, the responses of the MCP for the oil-water segregated flow are calculated, and it is found that the MCP has better stability and sensitivity to the variation of water-layer thickness in the condition of high water holdup and low flow velocity. Finally, the static experiments for the oil-water segregated flow were carried out and a novel calibration method for pure-water phase conductivity measurements was presented. The validity of the pure-water phase conductivity measurement with segregated flow in horizontal pipes was verified by experimental results. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 1273 KiB

Open AccessArticle

Influence of Experimental Conditions on Electronic Tongue Results—Case of Valsartan Minitablets Dissolution

by Małgorzata Wesoły^1,*, Anna Kluk², Małgorzata Sznitowska²

, Patrycja Ciosek^1,* and Wojciech Wróblewski¹

¹ Department of Microbioanalytics, Warsaw University of Technology, Noakowskiego 3, Warsaw 00-664, Poland

² Department of Applied Pharmacy, Gdańsk Medical University, Al. Gen. J. Hallera 107, Gdansk 80-416, Poland

Sensors 2016, 16(9), 1353; https://doi.org/10.3390/s16091353 - 23 Aug 2016

Cited by 17 | Viewed by 5976

Abstract

A potentiometric electronic tongue was applied to study the release of valsartan from pharmaceutical formulations, i.e., minitablets uncoated and coated with Eudragit E. Special attention was paid to evaluate the influence of medium temperature and composition, as well as to compare the performances [...] Read more.

A potentiometric electronic tongue was applied to study the release of valsartan from pharmaceutical formulations, i.e., minitablets uncoated and coated with Eudragit E. Special attention was paid to evaluate the influence of medium temperature and composition, as well as to compare the performances of the sensor arrays working in various hydrodynamic conditions. The drug dissolution profiles registered with the ion-sensitive electrodes were compared with standard dissolution tests performed with USP Apparatus 2 (paddle). Moreover, the signal changes of all sensors were processed by principal component analysis to visualize the release modifications, related to the presence of the coating agent. Finally, the importance and influence of the experimental conditions on the results obtained using potentiometric sensor arrays were discussed. Full article

(This article belongs to the Special Issue Olfactory and Gustatory Sensors)

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15 pages, 4266 KiB

Open AccessArticle

Ultrasensitive, Label Free, Chemiresistive Nanobiosensor Using Multiwalled Carbon Nanotubes Embedded Electrospun SU-8 Nanofibers

by Matta Durga Prakash¹, Siva Rama Krishna Vanjari^1,*, Chandra Shekhar Sharma² and Shiv Govind Singh¹

¹ Department of Electrical Engineering, Indian Institute of Technology Hyderabad, Hyderabad 502205, India

² Department of Chemical Engineering, Indian Institute of Technology Hyderabad, Hyderabad 502205, India

Sensors 2016, 16(9), 1354; https://doi.org/10.3390/s16091354 - 23 Aug 2016

Cited by 26 | Viewed by 8078

Abstract

This paper reports the synthesis and fabrication of aligned electrospun nanofibers derived out of multiwalled carbon nanotubes (MWCNTs) embedded SU-8 photoresist, which are targeted towards ultrasensitive biosensor applications. The ultrasensitivity (detection in the range of fg/mL) and the specificity of these biosensors were [...] Read more.

This paper reports the synthesis and fabrication of aligned electrospun nanofibers derived out of multiwalled carbon nanotubes (MWCNTs) embedded SU-8 photoresist, which are targeted towards ultrasensitive biosensor applications. The ultrasensitivity (detection in the range of fg/mL) and the specificity of these biosensors were achieved by complementing the inherent advantages of MWCNTs such as high surface to volume ratio and excellent electrical and transduction properties with the ease of surface functionalization of SU-8. The electrospinning process was optimized to precisely align nanofibers in between two electrodes of a copper microelectrode array. MWCNTs not only enhance the conductivity of SU-8 nanofibers but also act as transduction elements. In this paper, MWCNTs were embedded way beyond the percolation threshold and the optimum percentage loading of MWCNTs for maximizing the conductivity of nanofibers was figured out experimentally. As a proof of concept, the detection of myoglobin, an important biomarker for on-set of Acute Myocardial Infection (AMI) has been demonstrated by functionalizing the nanofibers with anti-myoglobin antibodies and carrying out detection using a chemiresistive method. This simple and robust device yielded a detection limit of 6 fg/mL. Full article

(This article belongs to the Special Issue Carbon MEMS and NEMS for Sensor Applications)

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10 pages, 1171 KiB

Open AccessArticle

Bioethanol in Biofuels Checked by an Amperometric Organic Phase Enzyme Electrode (OPEE) Working in “Substrate Antagonism” Format

by Mauro Tomassetti^*

, Gabriele Spuri Capesciotti, Riccardo Angeloni, Elisabetta Martini and Luigi Campanella

Department of Chemistry, University of Rome “Sapienza”, P.le A. Moro 5, Rome 00185, Italy

Sensors 2016, 16(9), 1355; https://doi.org/10.3390/s16091355 - 25 Aug 2016

Cited by 4 | Viewed by 5482

Abstract

The bioethanol content of two samples of biofuels was determined directly, after simple dilution in decane, by means of an amperometric catalase enzyme biosensor working in the organic phase, based on substrate antagonisms format. The results were good from the point of view [...] Read more.

The bioethanol content of two samples of biofuels was determined directly, after simple dilution in decane, by means of an amperometric catalase enzyme biosensor working in the organic phase, based on substrate antagonisms format. The results were good from the point of view of accuracy, and satisfactory for what concerns the recovery test by the standard addition method. Limit of detection (LOD) was on the order of 2.5 × 10⁻⁵ M. Full article

(This article belongs to the Special Issue Amperometric Biosensors)

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20 pages, 7972 KiB

Open AccessArticle

Design Methodology for Magnetic Field-Based Soft Tri-Axis Tactile Sensors

by Hongbo Wang^1,*, Greg De Boer², Junwai Kow¹, Ali Alazmani¹

, Mazdak Ghajari³, Robert Hewson²

and Peter Culmer¹

¹ School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK

² Department of Aeronautics, Imperial College London, London SW7 2AZ, UK

³ Dyson School of Design Engineering, Imperial College London, London SW7 2AZ, UK

Sensors 2016, 16(9), 1356; https://doi.org/10.3390/s16091356 - 24 Aug 2016

Cited by 135 | Viewed by 19604

Abstract

Tactile sensors are essential if robots are to safely interact with the external world and to dexterously manipulate objects. Current tactile sensors have limitations restricting their use, notably being too fragile or having limited performance. Magnetic field-based soft tactile sensors offer a potential [...] Read more.

Tactile sensors are essential if robots are to safely interact with the external world and to dexterously manipulate objects. Current tactile sensors have limitations restricting their use, notably being too fragile or having limited performance. Magnetic field-based soft tactile sensors offer a potential improvement, being durable, low cost, accurate and high bandwidth, but they are relatively undeveloped because of the complexities involved in design and calibration. This paper presents a general design methodology for magnetic field-based three-axis soft tactile sensors, enabling researchers to easily develop specific tactile sensors for a variety of applications. All aspects (design, fabrication, calibration and evaluation) of the development of tri-axis soft tactile sensors are presented and discussed. A moving least square approach is used to decouple and convert the magnetic field signal to force output to eliminate non-linearity and cross-talk effects. A case study of a tactile sensor prototype, MagOne, was developed. This achieved a resolution of 1.42 mN in normal force measurement (0.71 mN in shear force), good output repeatability and has a maximum hysteresis error of 3.4%. These results outperform comparable sensors reported previously, highlighting the efficacy of our methodology for sensor design. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 4174 KiB

Open AccessArticle

Investigation of a Fiberoptic Device Based on a Long Period Grating in a Ring Resonator

by Cinzia Corcione

, Benedetto Troia, Francesco De Leonardis and Vittorio M. N. Passaro^*

Photonics Research Group, Department of Electrical and Information Engineering, Politecnico di Bari, via E. Orabona n. 4, Bari 70125, Italy

Sensors 2016, 16(9), 1357; https://doi.org/10.3390/s16091357 - 24 Aug 2016

Cited by 3 | Viewed by 6518

Abstract

A fiberoptic architecture based on a ring resonator (RR) including a typical long period grating (LPG) was investigated. The interactions between the fundamental core mode (LP₀₁ or HE₁₁) coupled to the RR and the cladding mode (LP₀₈ [...] Read more.

A fiberoptic architecture based on a ring resonator (RR) including a typical long period grating (LPG) was investigated. The interactions between the fundamental core mode (LP₀₁ or HE₁₁) coupled to the RR and the cladding mode (LP₀₈), excited into the cavity by means of the LPG, allow a peculiar spectral response characterized by two splitting resonances to be achieved. The new LPGRR architecture is investigated theoretically and a mathematical modelling based on the transfer matrix method (TMM) is proposed. The theoretical results are compared with the experiments measured by an open-loop LPG, while the performance of the relative LPGRR was estimated by a theoretical parametric analysis. Finally, an overview of the possible LPGRR sensing applications is provided by investigating the features of a strain sensor operating in different environmental conditions. Full article

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

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7 pages, 3780 KiB

Open AccessArticle

Interference Confocal Microscope Integrated with Spatial Phase Shifter

by Weibo Wang^1,2

, Kang Gu¹, Xiaoyu You¹, Jiubin Tan¹ and Jian Liu^1,*

¹ Institute of Ultra-precision Optoelectronic Instrument Engineering, Harbin Institute of Technology, Harbin 150001, China

² Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK

Sensors 2016, 16(9), 1358; https://doi.org/10.3390/s16091358 - 24 Aug 2016

Cited by 2 | Viewed by 6497

Abstract

We present an interference confocal microscope (ICM) with a new single-body four-step simultaneous phase-shifter device designed to obtain high immunity to vibration. The proposed ICM combines the respective advantages of simultaneous phase shifting interferometry and bipolar differential confocal microscopy to obtain high axis [...] Read more.

We present an interference confocal microscope (ICM) with a new single-body four-step simultaneous phase-shifter device designed to obtain high immunity to vibration. The proposed ICM combines the respective advantages of simultaneous phase shifting interferometry and bipolar differential confocal microscopy to obtain high axis resolution, large dynamic range, and reduce the sensitivity to vibration and reflectance disturbance seamlessly. A compact single body spatial phase shifter is added to capture four phase-shifted interference signals simultaneously without time delay and construct a stable and space-saving simplified interference confocal microscope system. The test result can be obtained by combining the interference phase response and the bipolar property of differential confocal microscopy without phase unwrapping. Experiments prove that the proposed microscope is capable of providing stable measurements with 1 nm of axial depth resolution for either low- or high-numerical aperture objective lenses. Full article

(This article belongs to the Section Physical Sensors)

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25 pages, 12758 KiB

Open AccessReview

Recent Advances of MEMS Resonators for Lorentz Force Based Magnetic Field Sensors: Design, Applications and Challenges

by Agustín Leobardo Herrera-May^1,*

, Juan Carlos Soler-Balcazar², Héctor Vázquez-Leal³

, Jaime Martínez-Castillo¹

, Marco Osvaldo Vigueras-Zuñiga² and Luz Antonio Aguilera-Cortés⁴

¹ Micro and Nanotechnology Research Center, Universidad Veracruzana, Calzada Ruiz Cortines 455, Boca del Río, Veracruz 94294, Mexico

² Engineering Faculty, Universidad Veracruzana, Calzada Ruiz Cortines 455, Boca del Río, Veracruz 94294, Mexico

³ Electronic Instrumentation Faculty, Universidad Veracruzana, Cto. Gonzálo Aguirre Beltran S/N, Xalapa, Veracruz 91000, Mexico

⁴ Departamento de Ingeniería Mecánica, DICIS, Universidad de Guanajuato, Carr. Salamanca-Valle de Santiago km 3.5+1.8 km, Palo Blanco, Salamanca, Guanajuato 36885, Mexico

Sensors 2016, 16(9), 1359; https://doi.org/10.3390/s16091359 - 24 Aug 2016

Cited by 57 | Viewed by 18735

Abstract

Microelectromechanical systems (MEMS) resonators have allowed the development of magnetic field sensors with potential applications such as biomedicine, automotive industry, navigation systems, space satellites, telecommunications and non-destructive testing. We present a review of recent magnetic field sensors based on MEMS resonators, which operate [...] Read more.

Microelectromechanical systems (MEMS) resonators have allowed the development of magnetic field sensors with potential applications such as biomedicine, automotive industry, navigation systems, space satellites, telecommunications and non-destructive testing. We present a review of recent magnetic field sensors based on MEMS resonators, which operate with Lorentz force. These sensors have a compact structure, wide measurement range, low energy consumption, high sensitivity and suitable performance. The design methodology, simulation tools, damping sources, sensing techniques and future applications of magnetic field sensors are discussed. The design process is fundamental in achieving correct selection of the operation principle, sensing technique, materials, fabrication process and readout systems of the sensors. In addition, the description of the main sensing systems and challenges of the MEMS sensors are discussed. To develop the best devices, researches of their mechanical reliability, vacuum packaging, design optimization and temperature compensation circuits are needed. Future applications will require multifunctional sensors for monitoring several physical parameters (e.g., magnetic field, acceleration, angular ratio, humidity, temperature and gases). Full article

(This article belongs to the Special Issue Resonator Sensors)

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17 pages, 4003 KiB

Open AccessArticle

A Participatory Agent-Based Simulation for Indoor Evacuation Supported by Google Glass

by Jesús M. Sánchez¹, Álvaro Carrera^1,*, Carlos Á. Iglesias¹

and Emilio Serrano²

¹ Departamento de Ingeniería de Sistemas Telemáticos, Escuela Técnica Superior de Ingenieros de Telecomunicación, Universidad Politécnica de Madrid, 28040 Madrid, Spain

² Departamento de Inteligencia Artificial, Escuela Técnica Superior de Ingenieros Informáticos, Universidad Politécnica de Madrid, Boadilla del Monte, 28660 Madrid, Spain

Sensors 2016, 16(9), 1360; https://doi.org/10.3390/s16091360 - 24 Aug 2016

Cited by 11 | Viewed by 9228

Abstract

Indoor evacuation systems are needed for rescue and safety management. One of the challenges is to provide users with personalized evacuation routes in real time. To this end, this project aims at exploring the possibilities of Google Glass technology for participatory multiagent indoor [...] Read more.

Indoor evacuation systems are needed for rescue and safety management. One of the challenges is to provide users with personalized evacuation routes in real time. To this end, this project aims at exploring the possibilities of Google Glass technology for participatory multiagent indoor evacuation simulations. Participatory multiagent simulation combines scenario-guided agents and humans equipped with Google Glass that coexist in a shared virtual space and jointly perform simulations. The paper proposes an architecture for participatory multiagent simulation in order to combine devices (Google Glass and/or smartphones) with an agent-based social simulator and indoor tracking services. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 4020 KiB

Open AccessArticle

Are We Ready to Build a System for Assisting Blind People in Tactile Exploration of Bas-Reliefs?

by Francesco Buonamici, Monica Carfagni, Rocco Furferi^*

, Lapo Governi

and Yary Volpe

Department of Industrial Engineering, University of Florence, Florence 50139, Italy

Sensors 2016, 16(9), 1361; https://doi.org/10.3390/s16091361 - 24 Aug 2016

Cited by 16 | Viewed by 6734

Abstract

Nowadays, the creation of methodologies and tools for facilitating the 3D reproduction of artworks and, contextually, to make their exploration possible and more meaningful for blind users is becoming increasingly relevant in society. Accordingly, the creation of integrated systems including both tactile media [...] Read more.

Nowadays, the creation of methodologies and tools for facilitating the 3D reproduction of artworks and, contextually, to make their exploration possible and more meaningful for blind users is becoming increasingly relevant in society. Accordingly, the creation of integrated systems including both tactile media (e.g., bas-reliefs) and interfaces capable of providing the users with an experience cognitively comparable to the one originally envisioned by the artist, may be considered the next step for enhancing artworks exploration. In light of this, the present work provides a description of a first-attempt system designed to aid blind people (BP) in the tactile exploration of bas-reliefs. In detail, consistent hardware layout, comprising a hand-tracking system based on Kinect^® sensor and an audio device, together with a number of methodologies, algorithms and information related to physical design are proposed. Moreover, according to experimental test on the developed system related to the device position, some design alternatives are suggested so as to discuss pros and cons. Full article

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

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21 pages, 8739 KiB

Open AccessArticle

Proof-of-Concept of a Millimeter-Wave Integrated Heterogeneous Network for 5G Cellular

by Shozo Okasaka^1,*

, Richard J. Weiler², Wilhelm Keusgen², Andrey Pudeyev³, Alexander Maltsev^3,4, Ingolf Karls⁵ and Kei Sakaguchi^2,6

¹ AVC Networks Company, Panasonic Corporation, Yokohama 224-8539, Japan

² Department of Wireless Communications and Networks, Fraunhofer Heinrich Hertz Institute, Berlin 10587, Germany

³ Intel Corporation, Turgeneva Street, 30, Nizhny Novgorod 603024, Russia

⁴ Department of Bionics and Statistical Radiophysics, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod 603950, Russia

⁵ Intel Deutschland GmbH, Am Campeon 10–12, Neubiberg 85579, Germany

⁶ Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Tokyo 152-8552, Japan

Sensors 2016, 16(9), 1362; https://doi.org/10.3390/s16091362 - 25 Aug 2016

Cited by 34 | Viewed by 11629

Abstract

The fifth-generation mobile networks (5G) will not only enhance mobile broadband services, but also enable connectivity for a massive number of Internet-of-Things devices, such as wireless sensors, meters or actuators. Thus, 5G is expected to achieve a 1000-fold or more increase in capacity [...] Read more.

The fifth-generation mobile networks (5G) will not only enhance mobile broadband services, but also enable connectivity for a massive number of Internet-of-Things devices, such as wireless sensors, meters or actuators. Thus, 5G is expected to achieve a 1000-fold or more increase in capacity over 4G. The use of the millimeter-wave (mmWave) spectrum is a key enabler to allowing 5G to achieve such enhancement in capacity. To fully utilize the mmWave spectrum, 5G is expected to adopt a heterogeneous network (HetNet) architecture, wherein mmWave small cells are overlaid onto a conventional macro-cellular network. In the mmWave-integrated HetNet, splitting of the control plane (CP) and user plane (UP) will allow continuous connectivity and increase the capacity of the mmWave small cells. mmWave communication can be used not only for access linking, but also for wireless backhaul linking, which will facilitate the installation of mmWave small cells. In this study, a proof-of-concept (PoC) was conducted to demonstrate the practicality of a prototype mmWave-integrated HetNet, using mmWave technologies for both backhaul and access. Full article

(This article belongs to the Special Issue Millimeter Wave Wireless Communications and Networks)

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9 pages, 664 KiB

Open AccessArticle

Experimental Evaluation of Three Designs of Electrodynamic Flexural Transducers

by Tobias J. R. Eriksson^1,*, Michael Laws¹, Lei Kang¹, Yichao Fan¹, Sivaram N. Ramadas^1,2 and Steve Dixon¹

¹ Physics Department, University of Warwick, Coventry CV4 7AL, UK

² Elster Metering Limited, Stafford ST16 3EF, UK

Sensors 2016, 16(9), 1363; https://doi.org/10.3390/s16091363 - 25 Aug 2016

Cited by 9 | Viewed by 5650

Abstract

Three designs for electrodynamic flexural transducers (EDFT) for air-coupled ultrasonics are presented and compared. An all-metal housing was used for robustness, which makes the designs more suitable for industrial applications. The housing is designed such that there is a thin metal plate at [...] Read more.

Three designs for electrodynamic flexural transducers (EDFT) for air-coupled ultrasonics are presented and compared. An all-metal housing was used for robustness, which makes the designs more suitable for industrial applications. The housing is designed such that there is a thin metal plate at the front, with a fundamental flexural vibration mode at ∼50 kHz. By using a flexural resonance mode, good coupling to the load medium was achieved without the use of matching layers. The front radiating plate is actuated electrodynamically by a spiral coil inside the transducer, which produces an induced magnetic field when an AC current is applied to it. The transducers operate without the use of piezoelectric materials, which can simplify manufacturing and prolong the lifetime of the transducers, as well as open up possibilities for high-temperature applications. The results show that different designs perform best for the generation and reception of ultrasound. All three designs produced large acoustic pressure outputs, with a recorded sound pressure level (SPL) above 120 dB at a 40 cm distance from the highest output transducer. The sensitivity of the transducers was low, however, with single shot signal-to-noise ratio

(SNR) ≃ 15

dB in transmit–receive mode, with transmitter and receiver 40 cm apart. Full article

(This article belongs to the Special Issue Ultrasonic Sensors)

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17 pages, 13846 KiB

Open AccessArticle

A Bevel Gear Quality Inspection System Based on Multi-Camera Vision Technology

by Ruiling Liu^*

, Dexing Zhong

, Hongqiang Lyu and Jiuqiang Han

School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2016, 16(9), 1364; https://doi.org/10.3390/s16091364 - 25 Aug 2016

Cited by 13 | Viewed by 11315

Abstract

Surface defect detection and dimension measurement of automotive bevel gears by manual inspection are costly, inefficient, low speed and low accuracy. In order to solve these problems, a synthetic bevel gear quality inspection system based on multi-camera vision technology is developed. The system [...] Read more.

Surface defect detection and dimension measurement of automotive bevel gears by manual inspection are costly, inefficient, low speed and low accuracy. In order to solve these problems, a synthetic bevel gear quality inspection system based on multi-camera vision technology is developed. The system can detect surface defects and measure gear dimensions simultaneously. Three efficient algorithms named Neighborhood Average Difference (NAD), Circle Approximation Method (CAM) and Fast Rotation-Position (FRP) are proposed. The system can detect knock damage, cracks, scratches, dents, gibbosity or repeated cutting of the spline, etc. The smallest detectable defect is 0.4 mm × 0.4 mm and the precision of dimension measurement is about 40–50 μm. One inspection process takes no more than 1.3 s. Both precision and speed meet the requirements of real-time online inspection in bevel gear production. Full article

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

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11 pages, 3773 KiB

Open AccessArticle

Patterned Array of Poly(ethylene glycol) Silane Monolayer for Label-Free Detection of Dengue

by Nor Zida Rosly¹, Shahrul Ainliah Alang Ahmad^1,2,*, Jaafar Abdullah¹

and Nor Azah Yusof^1,2

¹ Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang 43400, Selangor, Malaysia

² Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, Serdang 43400, Selangor, Malaysia

Sensors 2016, 16(9), 1365; https://doi.org/10.3390/s16091365 - 25 Aug 2016

Cited by 2 | Viewed by 7827

Abstract

In the present study, the construction of arrays on silicon for naked-eye detection of DNA dengue was demonstrated. The array was created by exposing a polyethylene glycol (PEG) silane monolayer to 254 nm ultraviolet (UV) light through a photomask. Formation of the PEG [...] Read more.

In the present study, the construction of arrays on silicon for naked-eye detection of DNA dengue was demonstrated. The array was created by exposing a polyethylene glycol (PEG) silane monolayer to 254 nm ultraviolet (UV) light through a photomask. Formation of the PEG silane monolayer and photomodifed surface properties was thoroughly characterized by using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The results of XPS confirmed that irradiation of ultraviolet (UV) light generates an aldehyde functional group that offers conjugation sites of amino DNA probe for detection of a specific dengue virus target DNA. Employing a gold enhancement process after inducing the electrostatic interaction between positively charged gold nanoparticles and the negatively charged target DNA hybridized to the DNA capture probe allowed to visualize the array with naked eye. The developed arrays demonstrated excellent performance in diagnosis of dengue with a detection limit as low as 10 pM. The selectivity of DNA arrays was also examined using a single base mismatch and noncomplementary target DNA. Full article

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

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14 pages, 3217 KiB

Open AccessArticle

Quantitative Inspection of Remanence of Broken Wire Rope Based on Compressed Sensing

by Juwei Zhang^1,2,* and Xiaojiang Tan^1,2

¹ College of Electrical Engineering, Henan University of Science and Technology, Luoyang 471023, China

² Power Electronics Device and System Engineering Laboratory of Henan, Henan University of Science and Technology, Luoyang 471023, China

Sensors 2016, 16(9), 1366; https://doi.org/10.3390/s16091366 - 25 Aug 2016

Cited by 42 | Viewed by 9188

Abstract

Most traditional strong magnetic inspection equipment has disadvantages such as big excitation devices, high weight, low detection precision, and inconvenient operation. This paper presents the design of a giant magneto-resistance (GMR) sensor array collection system. The remanence signal is collected to acquire two-dimensional [...] Read more.

Most traditional strong magnetic inspection equipment has disadvantages such as big excitation devices, high weight, low detection precision, and inconvenient operation. This paper presents the design of a giant magneto-resistance (GMR) sensor array collection system. The remanence signal is collected to acquire two-dimensional magnetic flux leakage (MFL) data on the surface of wire ropes. Through the use of compressed sensing wavelet filtering (CSWF), the image expression of wire ropes MFL on the surface was obtained. Then this was taken as the input of the designed back propagation (BP) neural network to extract three kinds of MFL image geometry features and seven invariant moments of defect images. Good results were obtained. The experimental results show that nondestructive inspection through the use of remanence has higher accuracy and reliability compared with traditional inspection devices, along with smaller volume, lighter weight and higher precision. Full article

(This article belongs to the Special Issue Giant Magnetoresistive Sensors)

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9 pages, 879 KiB

Open AccessCommunication

A Low-Complexity ESPRIT-Based DOA Estimation Method for Co-Prime Linear Arrays

by Fenggang Sun^1,2,†

, Bin Gao², Lizhen Chen¹ and Peng Lan^1,*,†

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

² College of Communications Engineering, PLA University of Science and Technology, Nanjing 210007, China

Sensors 2016, 16(9), 1367; https://doi.org/10.3390/s16091367 - 25 Aug 2016

Cited by 66 | Viewed by 6627

Abstract

The problem of direction-of-arrival (DOA) estimation is investigated for co-prime array, where the co-prime array consists of two uniform sparse linear subarrays with extended inter-element spacing. For each sparse subarray, true DOAs are mapped into several equivalent angles impinging on the traditional uniform [...] Read more.

The problem of direction-of-arrival (DOA) estimation is investigated for co-prime array, where the co-prime array consists of two uniform sparse linear subarrays with extended inter-element spacing. For each sparse subarray, true DOAs are mapped into several equivalent angles impinging on the traditional uniform linear array with half-wavelength spacing. Then, by applying the estimation of signal parameters via rotational invariance technique (ESPRIT), the equivalent DOAs are estimated, and the candidate DOAs are recovered according to the relationship among equivalent and true DOAs. Finally, the true DOAs are estimated by combining the results of the two subarrays. The proposed method achieves a better complexity–performance tradeoff as compared to other existing methods. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 5134 KiB

Open AccessArticle

Tracking Control of a Magnetic Shape Memory Actuator Using an Inverse Preisach Model with Modified Fuzzy Sliding Mode Control

by Jhih-Hong Lin and Mao-Hsiung Chiang^*

Department of Engineering Science and Ocean Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan

Sensors 2016, 16(9), 1368; https://doi.org/10.3390/s16091368 - 25 Aug 2016

Cited by 11 | Viewed by 6781

Abstract

Magnetic shape memory (MSM) alloys are a new class of smart materials with extraordinary strains up to 12% and frequencies in the range of 1 to 2 kHz. The MSM actuator is a potential device which can achieve high performance electromagnetic actuation by [...] Read more.

Magnetic shape memory (MSM) alloys are a new class of smart materials with extraordinary strains up to 12% and frequencies in the range of 1 to 2 kHz. The MSM actuator is a potential device which can achieve high performance electromagnetic actuation by using the properties of MSM alloys. However, significant non-linear hysteresis behavior is a significant barrier to control the MSM actuator. In this paper, the Preisach model was used, by capturing experiments from different input signals and output responses, to model the hysteresis of MSM actuator, and the inverse Preisach model, as a feedforward control, provided compensational signals to the MSM actuator to linearize the hysteresis non-linearity. The control strategy for path tracking combined the hysteresis compensator and the modified fuzzy sliding mode control (MFSMC) which served as a path controller. Based on the experimental results, it was verified that a tracking error in the order of micrometers was achieved. Full article

(This article belongs to the Section Physical Sensors)

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21 pages, 18039 KiB

Open AccessArticle

On-Chip Magnetic Bead Manipulation and Detection Using a Magnetoresistive Sensor-Based Micro-Chip: Design Considerations and Experimental Characterization

by Chinthaka P. Gooneratne^*, Rimantas Kodzius

, Fuquan Li, Ian G. Foulds and Jürgen Kosel

Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia

Sensors 2016, 16(9), 1369; https://doi.org/10.3390/s16091369 - 26 Aug 2016

Cited by 17 | Viewed by 10205

Abstract

The remarkable advantages micro-chip platforms offer over cumbersome, time-consuming equipment currently in use for bio-analysis are well documented. In this research, a micro-chip that includes a unique magnetic actuator (MA) for the manipulation of superparamagnetic beads (SPBs), and a magnetoresistive sensor for the [...] Read more.

The remarkable advantages micro-chip platforms offer over cumbersome, time-consuming equipment currently in use for bio-analysis are well documented. In this research, a micro-chip that includes a unique magnetic actuator (MA) for the manipulation of superparamagnetic beads (SPBs), and a magnetoresistive sensor for the detection of SPBs is presented. A design methodology, which takes into account the magnetic volume of SPBs, diffusion and heat transfer phenomena, is presented with the aid of numerical analysis to optimize the parameters of the MA. The MA was employed as a magnetic flux generator and experimental analysis with commercially available COMPEL™ and Dynabeads^® demonstrated the ability of the MA to precisely transport a small number of SPBs over long distances and concentrate SPBs to a sensing site for detection. Moreover, the velocities of COMPEL™ and Dynabead^® SPBs were correlated to their magnetic volumes and were in good agreement with numerical model predictions. We found that 2.8 μm Dynabeads^® travel faster, and can be attracted to a magnetic source from a longer distance, than 6.2 μm COMPEL™ beads at magnetic flux magnitudes of less than 10 mT. The micro-chip system could easily be integrated with electronic circuitry and microfluidic functions, paving the way for an on-chip biomolecule quantification device. Full article

(This article belongs to the Special Issue Giant Magnetoresistive Sensors)

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8 pages, 1417 KiB

Open AccessArticle

Label-Free Ag⁺ Detection by Enhancing DNA Sensitized Tb³⁺ Luminescence

by Kimberly Kleinke^†, Runjhun Saran^† and Juewen Liu^*

Department of Chemistry and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L 3G1, Canada

Sensors 2016, 16(9), 1370; https://doi.org/10.3390/s16091370 - 26 Aug 2016

Cited by 17 | Viewed by 6805

Abstract

In this work, the effect of Ag⁺ on DNA sensitized Tb³⁺ luminescence was studied initially using the Ag⁺-specific RNA-cleaving DNAzyme, Ag10c. While we expected to observe luminescence quenching by Ag⁺, a significant enhancement was produced. Based on [...] Read more.

In this work, the effect of Ag⁺ on DNA sensitized Tb³⁺ luminescence was studied initially using the Ag⁺-specific RNA-cleaving DNAzyme, Ag10c. While we expected to observe luminescence quenching by Ag⁺, a significant enhancement was produced. Based on this observation, simple DNA oligonucleotide homopolymers were used with systematically varied sequence and length. We discovered that both poly-G and poly-T DNA have a significant emission enhancement by Ag⁺, while the absolute intensity is stronger with the poly-G DNA, indicating that a G-quadruplex DNA is not required for this enhancement. Using the optimized length of the G7 DNA (an oligo constituted with seven guanines), Ag⁺ was measured with a detection limit of 57.6 nM. The signaling kinetics, G7 DNA conformation, and the binding affinity of Tb³⁺ to the DNA in the presence or absence of Ag⁺ are also studied to reveal the mechanism of emission enhancement. This observation is useful not only for label-free detection of Ag⁺, but also interesting for the rational design of new biosensors using Tb³⁺ luminescence. Full article

(This article belongs to the Special Issue Nanobiosensing for Sensors)

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8 pages, 2452 KiB

Open AccessArticle

Embedded Ceria Nanoparticles in Crosslinked PVA Electrospun Nanofibers as Optical Sensors for Radicals

by Nader Shehata^1,2,3,*, Effat Samir^2,4, Soha Gaballah^2,5, Aya Hamed^1,2 and Asmaa Elrasheedy^2,5

¹ Department of Engineering Mathematics and Physics, Faculty of Engineering, Alexandria University, Alexandria 21544, Egypt

² Center of Smart Nanotechnology and Photonics (CSNP), Smart CI Research Center, Alexandria University, Alexandria 21544, Egypt

³ USTAR Bioinnovations Center, Utah State University, Logan, UT 84341, USA

⁴ Department of Electrical Engineering, Faculty of Engineering, Alexandria University, Alexandria 21544, Egypt

⁵ Department of Chemical Engineering, Faculty of Engineering, Alexandria University, Alexandria 21544, Egypt

Sensors 2016, 16(9), 1371; https://doi.org/10.3390/s16091371 - 26 Aug 2016

Cited by 20 | Viewed by 5874

Abstract

This work presents a new nanocomposite of cerium oxide (ceria) nanoparticles embedded in electrospun PVA nanofibers for optical sensing of radicals in solutions. Our ceria nanoparticles are synthesized to have O-vacancies which are the receptors for the radicals extracted from peroxide in water [...] Read more.

This work presents a new nanocomposite of cerium oxide (ceria) nanoparticles embedded in electrospun PVA nanofibers for optical sensing of radicals in solutions. Our ceria nanoparticles are synthesized to have O-vacancies which are the receptors for the radicals extracted from peroxide in water solution. Ceria nanoparticles are embedded insitu in PVA solution and then formed as nanofibers using an electrospinning technique. The formed nanocomposite emits visible fluorescent emissions under 430 nm excitation, due to the active ceria nanoparticles with fluorescent Ce³⁺ ionization states. When the formed nanocomposite is in contact with peroxide solution, the fluorescence emission intensity peak has been found to be reduced with increasing concentration of peroxide or the corresponding radicals through a fluorescence quenching mechanism. The fluorescence intensity peak is found to be reduced to more than 30% of its original value at a peroxide weight concentration up to 27%. This work could be helpful in further applications of radicals sensing using a solid mat through biomedical and environmental monitoring applications. Full article

(This article belongs to the Special Issue The Use of New and/or Improved Materials for Sensing Applications)

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21 pages, 1218 KiB

Open AccessArticle

Target Coverage in Wireless Sensor Networks with Probabilistic Sensors

by Anxing Shan¹, Xianghua Xu^1,* and Zongmao Cheng²

¹ School of Computer Science, Hangzhou Dianzi University, Hangzhou 310018, China

² School of Science, Hangzhou Dianzi University, Hangzhou 310018, China

Sensors 2016, 16(9), 1372; https://doi.org/10.3390/s16091372 - 27 Aug 2016

Cited by 44 | Viewed by 7493

Abstract

Sensing coverage is a fundamental problem in wireless sensor networks (WSNs), which has attracted considerable attention. Conventional research on this topic focuses on the 0/1 coverage model, which is only a coarse approximation to the practical sensing model. In this paper, we study [...] Read more.

Sensing coverage is a fundamental problem in wireless sensor networks (WSNs), which has attracted considerable attention. Conventional research on this topic focuses on the 0/1 coverage model, which is only a coarse approximation to the practical sensing model. In this paper, we study the target coverage problem, where the objective is to find the least number of sensor nodes in randomly-deployed WSNs based on the probabilistic sensing model. We analyze the joint detection probability of target with multiple sensors. Based on the theoretical analysis of the detection probability, we formulate the minimum ϵ-detection coverage problem. We prove that the minimum ϵ-detection coverage problem is NP-hard and present an approximation algorithm called the Probabilistic Sensor Coverage Algorithm (PSCA) with provable approximation ratios. To evaluate our design, we analyze the performance of PSCA theoretically and also perform extensive simulations to demonstrate the effectiveness of our proposed algorithm. Full article

(This article belongs to the Section Sensor Networks)

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15 pages, 5132 KiB

Open AccessArticle

Hybrid SnO₂/TiO₂ Nanocomposites for Selective Detection of Ultra-Low Hydrogen Sulfide Concentrations in Complex Backgrounds

by Alexander Larin^1,2, Phillip C. Womble¹ and Vladimir Dobrokhotov^3,*

¹ VAON LLC, KY, USA, Bowling Green, KY 42101, USA

³ Applied Physics Institute, Western Kentucky University, Bowling Green, KY 42101, USA

² Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292, USA

Sensors 2016, 16(9), 1373; https://doi.org/10.3390/s16091373 - 27 Aug 2016

Cited by 34 | Viewed by 7932

Abstract

In this paper, we present a chemiresistive metal oxide (MOX) sensor for detection of hydrogen sulfide. Compared to the previous reports, the overall sensor performance was improved in multiple characteristics, including: sensitivity, selectivity, stability, activation time, response time, recovery time, and activation temperature. [...] Read more.

In this paper, we present a chemiresistive metal oxide (MOX) sensor for detection of hydrogen sulfide. Compared to the previous reports, the overall sensor performance was improved in multiple characteristics, including: sensitivity, selectivity, stability, activation time, response time, recovery time, and activation temperature. The superior sensor performance was attributed to the utilization of hybrid SnO₂/TiO₂ oxides as interactive catalytic layers deposited using a magnetron radio frequency (RF) sputtering technique. The unique advantage of the RF sputtering for sensor fabrication is the ability to create ultra-thin films with precise control of geometry, morphology and chemical composition of the product of synthesis. Chemiresistive films down to several nanometers can be fabricated as sensing elements. The RF sputtering technique was found to be very robust for bilayer and multilayer oxide structure fabrication. The geometry, morphology, chemical composition and electronic structure of interactive layers were evaluated in relation to their gas sensing performance, using scanning electron microscopy (SEM), X-ray diffraction technique (XRD), atomic force microscopy (AFM), Energy Dispersive X-ray Spectroscopy (EDAX), UV visible spectroscopy, and Kelvin probe measurements. A sensor based on multilayer SnO₂/TiO₂ catalytic layer with 10% vol. content of TiO₂ demonstrated the best gas sensing performance in all characteristics. Based on the pattern relating material’s characteristics to gas sensing performance, the optimization strategy for hydrogen sulfide sensor fabrication was suggested. Full article

(This article belongs to the Section Chemical Sensors)

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19 pages, 2958 KiB

Open AccessArticle

Automatic Authorship Detection Using Textual Patterns Extracted from Integrated Syntactic Graphs

by Helena Gómez-Adorno^1,*, Grigori Sidorov¹, David Pinto², Darnes Vilariño² and Alexander Gelbukh¹

¹ Instituto Politécnico Nacional, Centro de Investigación en Computación, Av. Juan de Dios Bátiz S/N, Mexico City 07738, Mexico

² Benemérita Universidad Autónoma de Puebla, Facultad de Ciencias de la Computación, Av. San Claudio y 14 Sur, Puebla 72570, Mexico,

Sensors 2016, 16(9), 1374; https://doi.org/10.3390/s16091374 - 29 Aug 2016

Cited by 25 | Viewed by 6882

Abstract

We apply the integrated syntactic graph feature extraction methodology to the task of automatic authorship detection. This graph-based representation allows integrating different levels of language description into a single structure. We extract textual patterns based on features obtained from shortest path walks over [...] Read more.

We apply the integrated syntactic graph feature extraction methodology to the task of automatic authorship detection. This graph-based representation allows integrating different levels of language description into a single structure. We extract textual patterns based on features obtained from shortest path walks over integrated syntactic graphs and apply them to determine the authors of documents. On average, our method outperforms the state of the art approaches and gives consistently high results across different corpora, unlike existing methods. Our results show that our textual patterns are useful for the task of authorship attribution. Full article

(This article belongs to the Special Issue Advances in Artificial Intelligence: Selected Papers from MICAI 2013, 2014 and 2015—12th, 13th and 14th Mexican International Conferences on Artificial Intelligence)

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15 pages, 2882 KiB

Open AccessArticle

Identifying Plant Part Composition of Forest Logging Residue Using Infrared Spectral Data and Linear Discriminant Analysis

by Gifty E. Acquah^1,*

, Brian K. Via¹, Nedret Billor², Oladiran O. Fasina³ and Lori G. Eckhardt⁴

¹ Forest Products Development Center, School of Forestry and Wildlife Sciences, Auburn University, 520 Devall Drive, Auburn, AL 36849, USA

² Department of Mathematics and Statistics, Auburn University, Auburn, AL 36849, USA

³ Center for Bioenergy and Bioproducts, Department of Biosystems Engineering, Auburn University, 350 Mell Street, Auburn, AL 36849, USA

⁴ Forest Health Dynamics Laboratory, School of Forestry and Wildlife Sciences, Auburn University, 602 Duncan Drive, Auburn, AL 36849, USA

Sensors 2016, 16(9), 1375; https://doi.org/10.3390/s16091375 - 27 Aug 2016

Cited by 28 | Viewed by 6602

Abstract

As new markets, technologies and economies evolve in the low carbon bioeconomy, forest logging residue, a largely untapped renewable resource will play a vital role. The feedstock can however be variable depending on plant species and plant part component. This heterogeneity can influence [...] Read more.

As new markets, technologies and economies evolve in the low carbon bioeconomy, forest logging residue, a largely untapped renewable resource will play a vital role. The feedstock can however be variable depending on plant species and plant part component. This heterogeneity can influence the physical, chemical and thermochemical properties of the material, and thus the final yield and quality of products. Although it is challenging to control compositional variability of a batch of feedstock, it is feasible to monitor this heterogeneity and make the necessary changes in process parameters. Such a system will be a first step towards optimization, quality assurance and cost-effectiveness of processes in the emerging biofuel/chemical industry. The objective of this study was therefore to qualitatively classify forest logging residue made up of different plant parts using both near infrared spectroscopy (NIRS) and Fourier transform infrared spectroscopy (FTIRS) together with linear discriminant analysis (LDA). Forest logging residue harvested from several Pinus taeda (loblolly pine) plantations in Alabama, USA, were classified into three plant part components: clean wood, wood and bark and slash (i.e., limbs and foliage). Five-fold cross-validated linear discriminant functions had classification accuracies of over 96% for both NIRS and FTIRS based models. An extra factor/principal component (PC) was however needed to achieve this in FTIRS modeling. Analysis of factor loadings of both NIR and FTIR spectra showed that, the statistically different amount of cellulose in the three plant part components of logging residue contributed to their initial separation. This study demonstrated that NIR or FTIR spectroscopy coupled with PCA and LDA has the potential to be used as a high throughput tool in classifying the plant part makeup of a batch of forest logging residue feedstock. Thus, NIR/FTIR could be employed as a tool to rapidly probe/monitor the variability of forest biomass so that the appropriate online adjustments to parameters can be made in time to ensure process optimization and product quality. Full article

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

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20 pages, 3377 KiB

Open AccessArticle

Mixed Criticality Scheduling for Industrial Wireless Sensor Networks

by Xi Jin¹

, Changqing Xia¹, Huiting Xu², Jintao Wang^1,3 and Peng Zeng^1,*

¹ Laboratory of Networked Control Systems, Shenyang Institute of Automation, Chinese Academy of Science, Shenyang 110016, China

² College of Information Science and Engineering, Northeastern University, Shenyang 110819, China

³ School of Computer and Control Engineering, University of Chinese Academy of Science, Beijing 100049, China

Sensors 2016, 16(9), 1376; https://doi.org/10.3390/s16091376 - 29 Aug 2016

Cited by 27 | Viewed by 6595

Abstract

Wireless sensor networks (WSNs) have been widely used in industrial systems. Their real-time performance and reliability are fundamental to industrial production. Many works have studied the two aspects, but only focus on single criticality WSNs. Mixed criticality requirements exist in many advanced applications [...] Read more.

Wireless sensor networks (WSNs) have been widely used in industrial systems. Their real-time performance and reliability are fundamental to industrial production. Many works have studied the two aspects, but only focus on single criticality WSNs. Mixed criticality requirements exist in many advanced applications in which different data flows have different levels of importance (or criticality). In this paper, first, we propose a scheduling algorithm, which guarantees the real-time performance and reliability requirements of data flows with different levels of criticality. The algorithm supports centralized optimization and adaptive adjustment. It is able to improve both the scheduling performance and flexibility. Then, we provide the schedulability test through rigorous theoretical analysis. We conduct extensive simulations, and the results demonstrate that the proposed scheduling algorithm and analysis significantly outperform existing ones. Full article

(This article belongs to the Special Issue Real-Time and Cyber-Physical Systems)

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22 pages, 7368 KiB

Open AccessArticle

A Saliency Guided Semi-Supervised Building Change Detection Method for High Resolution Remote Sensing Images

by Bin Hou, Yunhong Wang and Qingjie Liu^*

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

Sensors 2016, 16(9), 1377; https://doi.org/10.3390/s16091377 - 27 Aug 2016

Cited by 36 | Viewed by 6826

Abstract

Characterizations of up to date information of the Earth’s surface are an important application providing insights to urban planning, resources monitoring and environmental studies. A large number of change detection (CD) methods have been developed to solve them by utilizing remote sensing (RS) [...] Read more.

Characterizations of up to date information of the Earth’s surface are an important application providing insights to urban planning, resources monitoring and environmental studies. A large number of change detection (CD) methods have been developed to solve them by utilizing remote sensing (RS) images. The advent of high resolution (HR) remote sensing images further provides challenges to traditional CD methods and opportunities to object-based CD methods. While several kinds of geospatial objects are recognized, this manuscript mainly focuses on buildings. Specifically, we propose a novel automatic approach combining pixel-based strategies with object-based ones for detecting building changes with HR remote sensing images. A multiresolution contextual morphological transformation called extended morphological attribute profiles (EMAPs) allows the extraction of geometrical features related to the structures within the scene at different scales. Pixel-based post-classification is executed on EMAPs using hierarchical fuzzy clustering. Subsequently, the hierarchical fuzzy frequency vector histograms are formed based on the image-objects acquired by simple linear iterative clustering (SLIC) segmentation. Then, saliency and morphological building index (MBI) extracted on difference images are used to generate a pseudo training set. Ultimately, object-based semi-supervised classification is implemented on this training set by applying random forest (RF). Most of the important changes are detected by the proposed method in our experiments. This study was checked for effectiveness using visual evaluation and numerical evaluation. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 6318 KiB

Open AccessArticle

Novel Robotic Platforms for the Accurate Sampling and Monitoring of Water Columns

by Roemi Fernández^*

, Andrey Apalkov and Manuel Armada

Centre for Automation and Robotics (CAR) CSIC-UPM, Carretera de Campo Real, Km. 0,200, La Poveda, Arganda del Rey, Madrid 28500, Spain

Sensors 2016, 16(9), 1378; https://doi.org/10.3390/s16091378 - 29 Aug 2016

Cited by 2 | Viewed by 6265

Abstract

The hydrosphere contains large amounts of suspended particulate material, including living and non-living material that can be found in different compositions and concentrations, and that can be composed of particles of different sizes. The study of this particulate material along water columns plays [...] Read more.

The hydrosphere contains large amounts of suspended particulate material, including living and non-living material that can be found in different compositions and concentrations, and that can be composed of particles of different sizes. The study of this particulate material along water columns plays a key role in understanding a great variety of biological, chemical, and physical processes. This paper presents the conceptual design of two patented robotic platforms that have been conceived for carrying out studies of water properties at desired depths with very high accuracy in the vertical positioning. One platform has been specially designed for operating near to a reservoir bottom, while the other is intended to be used near the surface. Several experimental tests have been conducted in order to validate the proposed approaches. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

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13 pages, 1741 KiB

Open AccessArticle

Dynamic Layered Dual-Cluster Heads Routing Algorithm Based on Krill Herd Optimization in UWSNs

by Peng Jiang^*, Yang Feng, Feng Wu, Shanen Yu and Huan Xu

College of Automation, Hangzhou Dianzi University, Hangzhou 310018, China

Sensors 2016, 16(9), 1379; https://doi.org/10.3390/s16091379 - 29 Aug 2016

Cited by 13 | Viewed by 5299

Abstract

Aimed at the limited energy of nodes in underwater wireless sensor networks (UWSNs) and the heavy load of cluster heads in clustering routing algorithms, this paper proposes a dynamic layered dual-cluster routing algorithm based on Krill Herd optimization in UWSNs. Cluster size is [...] Read more.

Aimed at the limited energy of nodes in underwater wireless sensor networks (UWSNs) and the heavy load of cluster heads in clustering routing algorithms, this paper proposes a dynamic layered dual-cluster routing algorithm based on Krill Herd optimization in UWSNs. Cluster size is first decided by the distance between the cluster head nodes and sink node, and a dynamic layered mechanism is established to avoid the repeated selection of the same cluster head nodes. Using Krill Herd optimization algorithm selects the optimal and second optimal cluster heads, and its Lagrange model directs nodes to a high likelihood area. It ultimately realizes the functions of data collection and data transition. The simulation results show that the proposed algorithm can effectively decrease cluster energy consumption, balance the network energy consumption, and prolong the network lifetime. Full article

(This article belongs to the Section Sensor Networks)

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18 pages, 446 KiB

Open AccessArticle

A Game Theoretic Optimization Method for Energy Efficient Global Connectivity in Hybrid Wireless Sensor Networks

by JongHyup Lee and Dohyun Pak^*

Department of Mathematical Finance, Gachon University, 1342 Seongnamdaero, Seongnam-si 13120, Korea

Sensors 2016, 16(9), 1380; https://doi.org/10.3390/s16091380 - 29 Aug 2016

Cited by 6 | Viewed by 4976

Abstract

For practical deployment of wireless sensor networks (WSN), WSNs construct clusters, where a sensor node communicates with other nodes in its cluster, and a cluster head support connectivity between the sensor nodes and a sink node. In hybrid WSNs, cluster heads have cellular [...] Read more.

For practical deployment of wireless sensor networks (WSN), WSNs construct clusters, where a sensor node communicates with other nodes in its cluster, and a cluster head support connectivity between the sensor nodes and a sink node. In hybrid WSNs, cluster heads have cellular network interfaces for global connectivity. However, when WSNs are active and the load of cellular networks is high, the optimal assignment of cluster heads to base stations becomes critical. Therefore, in this paper, we propose a game theoretic model to find the optimal assignment of base stations for hybrid WSNs. Since the communication and energy cost is different according to cellular systems, we devise two game models for TDMA/FDMA and CDMA systems employing power prices to adapt to the varying efficiency of recent wireless technologies. The proposed model is defined on the assumptions of the ideal sensing field, but our evaluation shows that the proposed model is more adaptive and energy efficient than local selections. Full article

(This article belongs to the Section Sensor Networks)

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33 pages, 7216 KiB

Open AccessFeature PaperReview

Surface Plasmon Resonance-Based Fiber Optic Sensors Utilizing Molecular Imprinting

by Banshi D. Gupta^*, Anand M. Shrivastav

and Sruthi P. Usha

Physics Department, Indian Institute of Technology Delhi, New Delhi 110016, India

Sensors 2016, 16(9), 1381; https://doi.org/10.3390/s16091381 - 29 Aug 2016

Cited by 105 | Viewed by 19492

Abstract

Molecular imprinting is earning worldwide attention from researchers in the field of sensing and diagnostic applications, due to its properties of inevitable specific affinity for the template molecule. The fabrication of complementary template imprints allows this technique to achieve high selectivity for the [...] Read more.

Molecular imprinting is earning worldwide attention from researchers in the field of sensing and diagnostic applications, due to its properties of inevitable specific affinity for the template molecule. The fabrication of complementary template imprints allows this technique to achieve high selectivity for the analyte to be sensed. Sensors incorporating this technique along with surface plasmon or localized surface plasmon resonance (SPR/LSPR) provide highly sensitive real time detection with quick response times. Unfolding these techniques with optical fiber provide the additional advantages of miniaturized probes with ease of handling, online monitoring and remote sensing. In this review a summary of optical fiber sensors using the combined approaches of molecularly imprinted polymer (MIP) and the SPR/LSPR technique is discussed. An overview of the fundamentals of SPR/LSPR implementation on optical fiber is provided. The review also covers the molecular imprinting technology (MIT) with its elementary study, synthesis procedures and its applications for chemical and biological anlayte detection with different sensing methods. In conclusion, we explore the advantages, challenges and the future perspectives of developing highly sensitive and selective methods for the detection of analytes utilizing MIT with the SPR/LSPR phenomenon on optical fiber platforms. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2016)

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17 pages, 5195 KiB

Open AccessArticle

Magnetoelastic Effect-Based Transmissive Stress Detection for Steel Strips: Theory and Experiment

by Qingdong Zhang, Yuanxiao Su, Liyuan Zhang^*, Jia Bi and Jiang Luo

School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China

Sensors 2016, 16(9), 1382; https://doi.org/10.3390/s16091382 - 29 Aug 2016

Cited by 8 | Viewed by 6653

Abstract

For the deficiencies of traditional stress detection methods for steel strips in industrial production, this paper proposes a non-contact stress detection scheme based on the magnetoelastic effect. The theoretical model of the transmission-type stress detection is established, in which the output voltage and [...] Read more.

For the deficiencies of traditional stress detection methods for steel strips in industrial production, this paper proposes a non-contact stress detection scheme based on the magnetoelastic effect. The theoretical model of the transmission-type stress detection is established, in which the output voltage and the tested stress obey a linear relation. Then, a stress detection device is built for the experiment, and Q235 steel under uniaxial tension is tested as an example. The result shows that the output voltage rises linearly with the increase of the tensile stress, consistent with the theoretical prediction. To ensure the accuracy of the stress detection method in actual application, the temperature compensation, magnetic shielding and some other key technologies are investigated to reduce the interference of the external factors, such as environment temperature and surrounding magnetic field. The present research develops the theoretical and experimental foundations for the magnetic stress detection system, which can be used for online non-contact monitoring of strip flatness-related stress (tension distribution or longitudinal residual stress) in the steel strip rolling process, the quality evaluation of strip flatness after rolling, the life and safety assessment of metal construction and other industrial production links. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 2445 KiB

Open AccessArticle

Target Capturing Control for Space Robots with Unknown Mass Properties: A Self-Tuning Method Based on Gyros and Cameras

by Zhenyu Li^*

, Bin Wang^* and Hong Liu

State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin 150000, China

Sensors 2016, 16(9), 1383; https://doi.org/10.3390/s16091383 - 30 Aug 2016

Cited by 7 | Viewed by 6018

Abstract

Satellite capturing with free-floating space robots is still a challenging task due to the non-fixed base and unknown mass property issues. In this paper gyro and eye-in-hand camera data are adopted as an alternative choice for solving this problem. For this improved system, [...] Read more.

Satellite capturing with free-floating space robots is still a challenging task due to the non-fixed base and unknown mass property issues. In this paper gyro and eye-in-hand camera data are adopted as an alternative choice for solving this problem. For this improved system, a new modeling approach that reduces the complexity of system control and identification is proposed. With the newly developed model, the space robot is equivalent to a ground-fixed manipulator system. Accordingly, a self-tuning control scheme is applied to handle such a control problem including unknown parameters. To determine the controller parameters, an estimator is designed based on the least-squares technique for identifying the unknown mass properties in real time. The proposed method is tested with a credible 3-dimensional ground verification experimental system, and the experimental results confirm the effectiveness of the proposed control scheme. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

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20 pages, 6647 KiB

Open AccessArticle

Implementation and Analysis of a Wireless Sensor Network-Based Pet Location Monitoring System for Domestic Scenarios

by Erik Aguirre¹, Peio Lopez-Iturri¹

, Leyre Azpilicueta²

, José Javier Astrain³

, Jesús Villadangos³

, Daniel Santesteban¹ and Francisco Falcone^1,*

¹ Electrical and Electronic Engineering Department, Public University of Navarre, 31006 Pamplona, Spain

² School of Engineering and Sciences, Tecnologico de Monterrey, 64849 Monterrey, Mexico

³ Mathematical Engineering and Computer Science Department, Institute of Smart Cities, Public University of Navarre, 31006 Pamplona, Spain

Sensors 2016, 16(9), 1384; https://doi.org/10.3390/s16091384 - 30 Aug 2016

Cited by 20 | Viewed by 9235

Abstract

The flexibility of new age wireless networks and the variety of sensors to measure a high number of variables, lead to new scenarios where anything can be monitored by small electronic devices, thereby implementing Wireless Sensor Networks (WSN). Thanks to ZigBee, RFID or [...] Read more.

The flexibility of new age wireless networks and the variety of sensors to measure a high number of variables, lead to new scenarios where anything can be monitored by small electronic devices, thereby implementing Wireless Sensor Networks (WSN). Thanks to ZigBee, RFID or WiFi networks the precise location of humans or animals as well as some biological parameters can be known in real-time. However, since wireless sensors must be attached to biological tissues and they are highly dispersive, propagation of electromagnetic waves must be studied to deploy an efficient and well-working network. The main goal of this work is to study the influence of wireless channel limitations in the operation of a specific pet monitoring system, validated at physical channel as well as at functional level. In this sense, radio wave propagation produced by ZigBee devices operating at the ISM 2.4 GHz band is studied through an in-house developed 3D Ray Launching simulation tool, in order to analyze coverage/capacity relations for the optimal system selection as well as deployment strategy in terms of number of transceivers and location. Furthermore, a simplified dog model is developed for simulation code, considering not only its morphology but also its dielectric properties. Relevant wireless channel information such as power distribution, power delay profile and delay spread graphs are obtained providing an extensive wireless channel analysis. A functional dog monitoring system is presented, operating over the implemented ZigBee network and providing real time information to Android based devices. The proposed system can be scaled in order to consider different types of domestic pets as well as new user based functionalities. Full article

(This article belongs to the Special Issue Selected Papers from the 2nd International Electronic Conference on Sensors and Applications)

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16 pages, 2150 KiB

Open AccessArticle

Adaptive Sampling-Based Information Collection for Wireless Body Area Networks

by Xiaobin Xu^1,*, Fang Zhao¹, Wendong Wang² and Hui Tian²

¹ School of Software Engineering, Beijing University of Posts and Telecommunications, Beijing 10087, China

² State Key Laboratory of Networking and Switch Technology, Beijing University of Posts and Telecommunications, Beijing 10087, China

Sensors 2016, 16(9), 1385; https://doi.org/10.3390/s16091385 - 31 Aug 2016

Cited by 4 | Viewed by 4670

Abstract

To collect important health information, WBAN applications typically sense data at a high frequency. However, limited by the quality of wireless link, the uploading of sensed data has an upper frequency. To reduce upload frequency, most of the existing WBAN data collection approaches [...] Read more.

To collect important health information, WBAN applications typically sense data at a high frequency. However, limited by the quality of wireless link, the uploading of sensed data has an upper frequency. To reduce upload frequency, most of the existing WBAN data collection approaches collect data with a tolerable error. These approaches can guarantee precision of the collected data, but they are not able to ensure that the upload frequency is within the upper frequency. Some traditional sampling based approaches can control upload frequency directly, however, they usually have a high loss of information. Since the core task of WBAN applications is to collect health information, this paper aims to collect optimized information under the limitation of upload frequency. The importance of sensed data is defined according to information theory for the first time. Information-aware adaptive sampling is proposed to collect uniformly distributed data. Then we propose Adaptive Sampling-based Information Collection (ASIC) which consists of two algorithms. An adaptive sampling probability algorithm is proposed to compute sampling probabilities of different sensed values. A multiple uniform sampling algorithm provides uniform samplings for values in different intervals. Experiments based on a real dataset show that the proposed approach has higher performance in terms of data coverage and information quantity. The parameter analysis shows the optimized parameter settings and the discussion shows the underlying reason of high performance in the proposed approach. Full article

(This article belongs to the Special Issue Advances on Data Transmission and Analysis for Wearable Sensors Systems)

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15 pages, 2840 KiB

Open AccessArticle

Estimation Accuracy on Execution Time of Run-Time Tasks in a Heterogeneous Distributed Environment

by Qi Liu^1,2, Weidong Cai^2,*, Dandan Jin², Jian Shen³, Zhangjie Fu³, Xiaodong Liu⁴ and Nigel Linge⁵

¹ Jiangsu Collaborative Innovation Centre of Atmospheric Environment and Equipment Technology (CICAEET), Nanjing University of Information Science & Technology, Nanjing 210044, China

² School of Computer & Software, Nanjing University of Information Science & Technology, Nanjing 210044, China

³ Jiangsu Engineering Centre of Network Monitoring, Nanjing University of Information Science and Technology, Nanjing 210044, China

⁴ School of Computing, Edinburgh Napier University, 10 Colinton Road, Edinburgh EH10 5DT, UK

⁵ Computer Networking and Telecommunications Research Centre, University of Salford, Salford, Greater Manchester M5 4WT, UK

Sensors 2016, 16(9), 1386; https://doi.org/10.3390/s16091386 - 30 Aug 2016

Cited by 17 | Viewed by 6738

Abstract

Distributed Computing has achieved tremendous development since cloud computing was proposed in 2006, and played a vital role promoting rapid growth of data collecting and analysis models, e.g., Internet of things, Cyber-Physical Systems, Big Data Analytics, etc. Hadoop has become a data convergence [...] Read more.

Distributed Computing has achieved tremendous development since cloud computing was proposed in 2006, and played a vital role promoting rapid growth of data collecting and analysis models, e.g., Internet of things, Cyber-Physical Systems, Big Data Analytics, etc. Hadoop has become a data convergence platform for sensor networks. As one of the core components, MapReduce facilitates allocating, processing and mining of collected large-scale data, where speculative execution strategies help solve straggler problems. However, there is still no efficient solution for accurate estimation on execution time of run-time tasks, which can affect task allocation and distribution in MapReduce. In this paper, task execution data have been collected and employed for the estimation. A two-phase regression (TPR) method is proposed to predict the finishing time of each task accurately. Detailed data of each task have drawn interests with detailed analysis report being made. According to the results, the prediction accuracy of concurrent tasks’ execution time can be improved, in particular for some regular jobs. Full article

(This article belongs to the Special Issue Big Data and Cloud Computing for Sensor Networks)

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35 pages, 9797 KiB

Open AccessReview

Advanced Spatial-Division Multiplexed Measurement Systems Propositions—From Telecommunication to Sensing Applications: A Review

by Yi Weng^1,2,*, Ezra Ip¹, Zhongqi Pan² and Ting Wang¹

¹ NEC Laboratories America, Inc., Princeton, NJ 08540, USA

² Department of Electrical & Computer Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504, USA

Sensors 2016, 16(9), 1387; https://doi.org/10.3390/s16091387 - 30 Aug 2016

Cited by 45 | Viewed by 11701

Abstract

The concepts of spatial-division multiplexing (SDM) technology were first proposed in the telecommunications industry as an indispensable solution to reduce the cost-per-bit of optical fiber transmission. Recently, such spatial channels and modes have been applied in optical sensing applications where the returned echo [...] Read more.

The concepts of spatial-division multiplexing (SDM) technology were first proposed in the telecommunications industry as an indispensable solution to reduce the cost-per-bit of optical fiber transmission. Recently, such spatial channels and modes have been applied in optical sensing applications where the returned echo is analyzed for the collection of essential environmental information. The key advantages of implementing SDM techniques in optical measurement systems include the multi-parameter discriminative capability and accuracy improvement. In this paper, to help readers without a telecommunication background better understand how the SDM-based sensing systems can be incorporated, the crucial components of SDM techniques, such as laser beam shaping, mode generation and conversion, multimode or multicore elements using special fibers and multiplexers are introduced, along with the recent developments in SDM amplifiers, opto-electronic sources and detection units of sensing systems. The examples of SDM-based sensing systems not only include Brillouin optical time-domain reflectometry or Brillouin optical time-domain analysis (BOTDR/BOTDA) using few-mode fibers (FMF) and the multicore fiber (MCF) based integrated fiber Bragg grating (FBG) sensors, but also involve the widely used components with their whole information used in the full multimode constructions, such as the whispering gallery modes for fiber profiling and chemical species measurements, the screw/twisted modes for examining water quality, as well as the optical beam shaping to improve cantilever deflection measurements. Besides, the various applications of SDM sensors, the cost efficiency issue, as well as how these complex mode multiplexing techniques might improve the standard fiber-optic sensor approaches using single-mode fibers (SMF) and photonic crystal fibers (PCF) have also been summarized. Finally, we conclude with a prospective outlook for the opportunities and challenges of SDM technologies in optical sensing industry. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2016)

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18 pages, 3662 KiB

Open AccessArticle

A High Precision Approach to Calibrate a Structured Light Vision Sensor in a Robot-Based Three-Dimensional Measurement System

by Defeng Wu^1,2,*, Tianfei Chen³ and Aiguo Li⁴

¹ School of Marine Engineering, Jimei University, Xiamen 361021, China

² Fujian Provincial Key Laboratory of Naval Architecture and Ocean Engineering, Xiamen 361021, China

³ School of Electrical Engineering, Henan University of Technology, Zhengzhou 450001, China

⁴ School of Information Science and Technology, Dalian Maritime University, Dalian 116026, China

Sensors 2016, 16(9), 1388; https://doi.org/10.3390/s16091388 - 30 Aug 2016

Cited by 36 | Viewed by 8454

Abstract

A robot-based three-dimensional (3D) measurement system is presented. In the presented system, a structured light vision sensor is mounted on the arm of an industrial robot. Measurement accuracy is one of the most important aspects of any 3D measurement system. To improve the [...] Read more.

A robot-based three-dimensional (3D) measurement system is presented. In the presented system, a structured light vision sensor is mounted on the arm of an industrial robot. Measurement accuracy is one of the most important aspects of any 3D measurement system. To improve the measuring accuracy of the structured light vision sensor, a novel sensor calibration approach is proposed to improve the calibration accuracy. The approach is based on a number of fixed concentric circles manufactured in a calibration target. The concentric circle is employed to determine the real projected centres of the circles. Then, a calibration point generation procedure is used with the help of the calibrated robot. When enough calibration points are ready, the radial alignment constraint (RAC) method is adopted to calibrate the camera model. A multilayer perceptron neural network (MLPNN) is then employed to identify the calibration residuals after the application of the RAC method. Therefore, the hybrid pinhole model and the MLPNN are used to represent the real camera model. Using a standard ball to validate the effectiveness of the presented technique, the experimental results demonstrate that the proposed novel calibration approach can achieve a highly accurate model of the structured light vision sensor. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 3868 KiB

Open AccessArticle

Drain Current Modulation of a Single Drain MOSFET by Lorentz Force for Magnetic Sensing Application

by Prasenjit Chatterjee^*, Hwang-Cherng Chow^* and Wu-Shiung Feng

Graduate Institute of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan

Sensors 2016, 16(9), 1389; https://doi.org/10.3390/s16091389 - 30 Aug 2016

Cited by 3 | Viewed by 6027

Abstract

This paper reports a detailed analysis of the drain current modulation of a single-drain normal-gate n channel metal-oxide semiconductor field effect transistor (n-MOSFET) under an on-chip magnetic field. A single-drain n-MOSFET has been fabricated and placed in the center of a square-shaped metal [...] Read more.

This paper reports a detailed analysis of the drain current modulation of a single-drain normal-gate n channel metal-oxide semiconductor field effect transistor (n-MOSFET) under an on-chip magnetic field. A single-drain n-MOSFET has been fabricated and placed in the center of a square-shaped metal loop which generates the on-chip magnetic field. The proposed device designed is much smaller in size with respect to the metal loop, which ensures that the generated magnetic field is approximately uniform. The change of drain current and change of bulk current per micron device width has been measured. The result shows that the difference drain current is about 145 µA for the maximum applied magnetic field. Such changes occur from the applied Lorentz force to push out the carriers from the channel. Based on the drain current difference, the change in effective mobility has been detected up to 4.227%. Furthermore, a detailed investigation reveals that the device behavior is quite different in subthreshold and saturation region. A change of 50.24 µA bulk current has also been measured. Finally, the device has been verified for use as a magnetic sensor with sensitivity 4.084% (29.6 T⁻¹), which is very effective as compared to other previously reported works for a single device. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 4496 KiB

Open AccessArticle

An Effective Cuckoo Search Algorithm for Node Localization in Wireless Sensor Network

by Jing Cheng and Linyuan Xia^*

Guangdong Key Laboratory for Urbanization and Geo-simulation, School of Geography and Planning, Sun Yat-Sen University, Guangzhou 510275, China

Sensors 2016, 16(9), 1390; https://doi.org/10.3390/s16091390 - 31 Aug 2016

Cited by 51 | Viewed by 7833

Abstract

Localization is an essential requirement in the increasing prevalence of wireless sensor network (WSN) applications. Reducing the computational complexity, communication overhead in WSN localization is of paramount importance in order to prolong the lifetime of the energy-limited sensor nodes and improve localization performance. [...] Read more.

Localization is an essential requirement in the increasing prevalence of wireless sensor network (WSN) applications. Reducing the computational complexity, communication overhead in WSN localization is of paramount importance in order to prolong the lifetime of the energy-limited sensor nodes and improve localization performance. This paper proposes an effective Cuckoo Search (CS) algorithm for node localization. Based on the modification of step size, this approach enables the population to approach global optimal solution rapidly, and the fitness of each solution is employed to build mutation probability for avoiding local convergence. Further, the approach restricts the population in the certain range so that it can prevent the energy consumption caused by insignificant search. Extensive experiments were conducted to study the effects of parameters like anchor density, node density and communication range on the proposed algorithm with respect to average localization error and localization success ratio. In addition, a comparative study was conducted to realize the same localization task using the same network deployment. Experimental results prove that the proposed CS algorithm can not only increase convergence rate but also reduce average localization error compared with standard CS algorithm and Particle Swarm Optimization (PSO) algorithm. Full article

(This article belongs to the Section Sensor Networks)

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28 pages, 1284 KiB

Open AccessArticle

On Reliable and Efficient Data Gathering Based Routing in Underwater Wireless Sensor Networks

by Tayyaba Liaqat¹, Mariam Akbar², Nadeem Javaid^2,*

, Umar Qasim³

, Zahoor Ali Khan⁴

, Qaisar Javaid⁵, Turki Ali Alghamdi⁶ and Iftikhar Azim Niaz²

¹ Institute of Space Technology, Islamabad 44000, Pakistan

² COMSATS Institute of Information Technology, Park Road, Islamabad 44000, Pakistan

³ Cameron Library, University of Alberta, Edmonton, AB T6G 2J8, Canada

⁴ Internetworking Program, FE, Dalhousie University, Halifax, NS B3J 4R2, Canada

⁵ International Islamic University, Islamabad 44000, Pakistan

⁶ College of CIS, Umm AlQura University, Makkah 11692, Saudi Arabia

Sensors 2016, 16(9), 1391; https://doi.org/10.3390/s16091391 - 30 Aug 2016

Cited by 9 | Viewed by 6086

Abstract

This paper presents cooperative routing scheme to improve data reliability. The proposed protocol achieves its objective, however, at the cost of surplus energy consumption. Thus sink mobility is introduced to minimize the energy consumption cost of nodes as it directly collects data from [...] Read more.

This paper presents cooperative routing scheme to improve data reliability. The proposed protocol achieves its objective, however, at the cost of surplus energy consumption. Thus sink mobility is introduced to minimize the energy consumption cost of nodes as it directly collects data from the network nodes at minimized communication distance. We also present delay and energy optimized versions of our proposed RE-AEDG to further enhance its performance. Simulation results prove the effectiveness of our proposed RE-AEDG in terms of the selected performance matrics. Full article

(This article belongs to the Special Issue Scalable Localization in Wireless Sensor Networks)

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21 pages, 9122 KiB

Open AccessArticle

Trajectory Correction and Locomotion Analysis of a Hexapod Walking Robot with Semi-Round Rigid Feet

by Yaguang Zhu^1,*

, Bo Jin², Yongsheng Wu¹, Tong Guo¹ and Xiangmo Zhao³

¹ Key Laboratory of Road Construction Technology and Equipment of MOE, Chang’an University, Xi’an 710064, China

² State Key Laboratory of Fluid Power & Mechatronic Systems, Zhejiang University, Hangzhou 310028, China

³ School of Information Engineering, Chang’an University, Xi’an 710064, China

Sensors 2016, 16(9), 1392; https://doi.org/10.3390/s16091392 - 31 Aug 2016

Cited by 16 | Viewed by 7549

Abstract

Aimed at solving the misplaced body trajectory problem caused by the rolling of semi-round rigid feet when a robot is walking, a legged kinematic trajectory correction methodology based on the Least Squares Support Vector Machine (LS-SVM) is proposed. The concept of ideal foothold [...] Read more.

Aimed at solving the misplaced body trajectory problem caused by the rolling of semi-round rigid feet when a robot is walking, a legged kinematic trajectory correction methodology based on the Least Squares Support Vector Machine (LS-SVM) is proposed. The concept of ideal foothold is put forward for the three-dimensional kinematic model modification of a robot leg, and the deviation value between the ideal foothold and real foothold is analyzed. The forward/inverse kinematic solutions between the ideal foothold and joint angular vectors are formulated and the problem of direct/inverse kinematic nonlinear mapping is solved by using the LS-SVM. Compared with the previous approximation method, this correction methodology has better accuracy and faster calculation speed with regards to inverse kinematics solutions. Experiments on a leg platform and a hexapod walking robot are conducted with multi-sensors for the analysis of foot tip trajectory, base joint vibration, contact force impact, direction deviation, and power consumption, respectively. The comparative analysis shows that the trajectory correction methodology can effectively correct the joint trajectory, thus eliminating the contact force influence of semi-round rigid feet, significantly improving the locomotion of the walking robot and reducing the total power consumption of the system. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 2730 KiB

Open AccessArticle

A Ground-Based Near Infrared Camera Array System for UAV Auto-Landing in GPS-Denied Environment

by Tao Yang^1,*

, Guangpo Li¹, Jing Li², Yanning Zhang¹, Xiaoqiang Zhang¹, Zhuoyue Zhang¹ and Zhi Li¹

¹ ShaanXi Provincial Key Laboratory of Speech and Image Information Processing, School of Computer Science, Northwestern Polytechnical University, Xi’an 710129, China

² School of Telecommunications Engineering, Xidian University, Xi’an 710071, China

Sensors 2016, 16(9), 1393; https://doi.org/10.3390/s16091393 - 30 Aug 2016

Cited by 57 | Viewed by 12040

Abstract

This paper proposes a novel infrared camera array guidance system with capability to track and provide real time position and speed of a fixed-wing Unmanned air vehicle (UAV) during a landing process. The system mainly include three novel parts: (1) Infrared camera array [...] Read more.

This paper proposes a novel infrared camera array guidance system with capability to track and provide real time position and speed of a fixed-wing Unmanned air vehicle (UAV) during a landing process. The system mainly include three novel parts: (1) Infrared camera array and near infrared laser lamp based cooperative long range optical imaging module; (2) Large scale outdoor camera array calibration module; and (3) Laser marker detection and 3D tracking module. Extensive automatic landing experiments with fixed-wing flight demonstrate that our infrared camera array system has the unique ability to guide the UAV landing safely and accurately in real time. Moreover, the measurement and control distance of our system is more than 1000 m. The experimental results also demonstrate that our system can be used for UAV automatic accurate landing in Global Position System (GPS)-denied environments. Full article

(This article belongs to the Special Issue Infrared and THz Sensing and Imaging)

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9 pages, 2519 KiB

Open AccessArticle

Internal and External Temperature Monitoring of a Li-Ion Battery with Fiber Bragg Grating Sensors

by Susana Novais^1,*

, Micael Nascimento¹

, Lorenzo Grande², Maria Fátima Domingues³

, Paulo Antunes⁴

, Nélia Alberto⁵

, Cátia Leitão⁴

, Ricardo Oliveira⁶

, Stephan Koch², Guk Tae Kim², Stefano Passerini²

and João Pinto⁴

¹ Department of Physics & I3N, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal

² Helmholtz Institute Ulm (HIU) Electrochemistry I, Helmholtzstraße 11, 89081 Ulm, Germany and Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021 Karsruhe, Germany

³ Instituto de Telecomunicações and I3N, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal

⁴ Instituto de Telecomunicações and Department of Physics & I3N, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal

⁵ Instituto de Telecomunicações and Centre for Mechanical Technology and Automation, Department of Mechanical Engineering, University of Aveiro, 3810-193 Aveiro, Portugal

⁶ Instituto de Telecomunicações, Campus de Santiago, 3810-193 Aveiro, Portugal

Sensors 2016, 16(9), 1394; https://doi.org/10.3390/s16091394 - 30 Aug 2016

Cited by 162 | Viewed by 13983

Abstract

The integration of fiber Bragg grating (FBG) sensors in lithium-ion cells for in-situ and in-operando temperature monitoring is presented herein. The measuring of internal and external temperature variations was performed through four FBG sensors during galvanostatic cycling at C-rates ranging from 1C to [...] Read more.

The integration of fiber Bragg grating (FBG) sensors in lithium-ion cells for in-situ and in-operando temperature monitoring is presented herein. The measuring of internal and external temperature variations was performed through four FBG sensors during galvanostatic cycling at C-rates ranging from 1C to 8C. The FBG sensors were placed both outside and inside the cell, located in the center of the electrochemically active area and at the tab-electrode connection. The internal sensors recorded temperature variations of 4.0 ± 0.1 °C at 5C and 4.7 ± 0.1 °C at 8C at the center of the active area, and 3.9 ± 0.1 °C at 5C and 4.0 ± 0.1 °C at 8C at the tab-electrode connection, respectively. This study is intended to contribute to detection of a temperature gradient in real time inside a cell, which can determine possible damage in the battery performance when it operates under normal and abnormal operating conditions, as well as to demonstrate the technical feasibility of the integration of in-operando microsensors inside Li-ion cells. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 3567 KiB

Open AccessArticle

A Web Service Protocol Realizing Interoperable Internet of Things Tasking Capability

by Chih-Yuan Huang^1,* and Cheng-Hung Wu²

¹ Center for Space and Remote Sensing Research, National Central University, Taoyuan 320, Taiwan

² Department of Civil Engineering, National Central University, Taoyuan 320, Taiwan

Sensors 2016, 16(9), 1395; https://doi.org/10.3390/s16091395 - 31 Aug 2016

Cited by 20 | Viewed by 5985

Abstract

The Internet of Things (IoT) is an infrastructure that interconnects uniquely-identifiable devices using the Internet. By interconnecting everyday appliances, various monitoring, and physical mashup applications can be constructed to improve human’s daily life. In general, IoT devices provide two main capabilities: sensing and [...] Read more.

The Internet of Things (IoT) is an infrastructure that interconnects uniquely-identifiable devices using the Internet. By interconnecting everyday appliances, various monitoring, and physical mashup applications can be constructed to improve human’s daily life. In general, IoT devices provide two main capabilities: sensing and tasking capabilities. While the sensing capability is similar to the World-Wide Sensor Web, this research focuses on the tasking capability. However, currently, IoT devices created by different manufacturers follow different proprietary protocols and are locked in many closed ecosystems. This heterogeneity issue impedes the interconnection between IoT devices and damages the potential of the IoT. To address this issue, this research aims at proposing an interoperable solution called tasking capability description that allows users to control different IoT devices using a uniform web service interface. This paper demonstrates the contribution of the proposed solution by interconnecting different IoT devices for different applications. In addition, the proposed solution is integrated with the OGC SensorThings API standard, which is a Web service standard defined for the IoT sensing capability. Consequently, the Extended SensorThings API can realize both IoT sensing and tasking capabilities in an integrated and interoperable manner. Full article

(This article belongs to the Special Issue Data in the IoT: from Sensing to Meaning)

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22 pages, 7488 KiB

Open AccessArticle

Empirical Study on Designing of Gaze Tracking Camera Based on the Information of User’s Head Movement

by Weiyuan Pan, Dongwook Jung, Hyo Sik Yoon, Dong Eun Lee, Rizwan Ali Naqvi, Kwan Woo Lee and Kang Ryoung Park^*

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

Sensors 2016, 16(9), 1396; https://doi.org/10.3390/s16091396 - 31 Aug 2016

Cited by 7 | Viewed by 6707

Abstract

Gaze tracking is the technology that identifies a region in space that a user is looking at. Most previous non-wearable gaze tracking systems use a near-infrared (NIR) light camera with an NIR illuminator. Based on the kind of camera lens used, the viewing [...] Read more.

Gaze tracking is the technology that identifies a region in space that a user is looking at. Most previous non-wearable gaze tracking systems use a near-infrared (NIR) light camera with an NIR illuminator. Based on the kind of camera lens used, the viewing angle and depth-of-field (DOF) of a gaze tracking camera can be different, which affects the performance of the gaze tracking system. Nevertheless, to our best knowledge, most previous researches implemented gaze tracking cameras without ground truth information for determining the optimal viewing angle and DOF of the camera lens. Eye-tracker manufacturers might also use ground truth information, but they do not provide this in public. Therefore, researchers and developers of gaze tracking systems cannot refer to such information for implementing gaze tracking system. We address this problem providing an empirical study in which we design an optimal gaze tracking camera based on experimental measurements of the amount and velocity of user’s head movements. Based on our results and analyses, researchers and developers might be able to more easily implement an optimal gaze tracking system. Experimental results show that our gaze tracking system shows high performance in terms of accuracy, user convenience and interest. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 2423 KiB

Open AccessArticle

A Simple BODIPY-Based Viscosity Probe for Imaging of Cellular Viscosity in Live Cells

by Dongdong Su^1,†, Chai Lean Teoh^1,†, Nengyue Gao², Qing-Hua Xu² and Young-Tae Chang^1,2,*

¹ Singapore Bioimaging Consortium, Agency for Science, Technology and Research (A*STAR), Singapore 138667, Singapore

² Department of Chemistry, National University of Singapore, Singapore 117543, Singapore

Sensors 2016, 16(9), 1397; https://doi.org/10.3390/s16091397 - 31 Aug 2016

Cited by 72 | Viewed by 12913

Abstract

Intracellular viscosity is a fundamental physical parameter that indicates the functioning of cells. In this work, we developed a simple boron-dipyrromethene (BODIPY)-based probe, BTV, for cellular mitochondria viscosity imaging by coupling a simple BODIPY rotor with a mitochondria-targeting unit. The BTV exhibited [...] Read more.

Intracellular viscosity is a fundamental physical parameter that indicates the functioning of cells. In this work, we developed a simple boron-dipyrromethene (BODIPY)-based probe, BTV, for cellular mitochondria viscosity imaging by coupling a simple BODIPY rotor with a mitochondria-targeting unit. The BTV exhibited a significant fluorescence intensity enhancement of more than 100-fold as the solvent viscosity increased. Also, the probe showed a direct linear relationship between the fluorescence lifetime and the media viscosity, which makes it possible to trace the change of the medium viscosity. Furthermore, it was demonstrated that BTV could achieve practical applicability in the monitoring of mitochondrial viscosity changes in live cells through fluorescence lifetime imaging microscopy (FLIM). Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensor)

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10 pages, 1019 KiB

Open AccessArticle

An H₂S Sensor Based on Electrochemistry for Chicken Coops

by Lihua Zeng^1,2,3, Mei He^1,3, Huihui Yu^1,3 and Daoliang Li^1,3,*

¹ Beijing Engineering and Technology Research Center for Internet of Things in Agriculture, China Agricultural University, Beijing 100083, China

² College of Mechanical and Electrical Engineering, Agricultural University of Hebei, Baoding 071001, China

³ Key Laboratory of Agricultural Information Acquisition Technology, Ministry of Agriculture, China Agricultural University, Beijing 100083, China

Sensors 2016, 16(9), 1398; https://doi.org/10.3390/s16091398 - 31 Aug 2016

Cited by 15 | Viewed by 9979

Abstract

The recent modernization of the livestock industry lags behind the scale of the livestock industry, particularly in indoor environmental monitoring. In particular, the H₂S gas concentration in chicken coops affects the growth and reproductive capacity of the chickens and threatens their [...] Read more.

The recent modernization of the livestock industry lags behind the scale of the livestock industry, particularly in indoor environmental monitoring. In particular, the H₂S gas concentration in chicken coops affects the growth and reproductive capacity of the chickens and threatens their health. Therefore, the research and development of a low-cost, environmentally friendly sensor that can achieve on-line monitoring of H₂S gas has a notably important practical significance. This paper reports the design of an H₂S gas sensor, with selection of an electrochemical probe with high accuracy and wide measurement range using the relatively mature technology of electrochemical sensors. Although the probe of the sensor is the main factor that affects the sensor accuracy, the probe must be combined with a specifically designed signal condition circuit that can overcome the lack of an electrode to satisfy the requirements for the interconnection and matching between the output signal and the test instrument. Because the output current of the electrochemical electrode is small and likely to be disturbed by noise, we designed signal-conditioning modules. Through the signal-conditioning circuit, the output signal of the current electrode can be converted into a voltage and amplified. In addition, we designed a power control module because a bias voltage is necessary for the electrode. Finally, after the calibration experiment, the accurate concentration of H₂S gas can be measured. Based on the experimental analysis, the sensor shows good linearity and selectivity, comparatively high sensitivity, perfect stability and an extremely long operating life of up to two years. Full article

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

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13 pages, 2789 KiB

Open AccessArticle

Cardinality Balanced Multi-Target Multi-Bernoulli Filter with Error Compensation

by Xiangyu He^1,2 and Guixi Liu^1,*

¹ School of Mechano-electronic Engineering, Xidian University, Xi’an 710071, China

² School of Physics and Electronic Information, Luoyang Normal University, Luoyang 471934, China

Sensors 2016, 16(9), 1399; https://doi.org/10.3390/s16091399 - 31 Aug 2016

Cited by 4 | Viewed by 4823

Abstract

The cardinality balanced multi-target multi-Bernoulli (CBMeMBer) filter developed recently has been proved an effective multi-target tracking (MTT) algorithm based on the random finite set (RFS) theory, and it can jointly estimate the number of targets and their states from a sequence of sensor [...] Read more.

The cardinality balanced multi-target multi-Bernoulli (CBMeMBer) filter developed recently has been proved an effective multi-target tracking (MTT) algorithm based on the random finite set (RFS) theory, and it can jointly estimate the number of targets and their states from a sequence of sensor measurement sets. However, because of the existence of systematic errors in sensor measurements, the CBMeMBer filter can easily produce different levels of performance degradation. In this paper, an extended CBMeMBer filter, in which the joint probability density function of target state and systematic error is recursively estimated, is proposed to address the MTT problem based on the sensor measurements with systematic errors. In addition, an analytic implementation of the extended CBMeMBer filter is also presented for linear Gaussian models. Simulation results confirm that the proposed algorithm can track multiple targets with better performance. Full article

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

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18 pages, 26261 KiB

Open AccessArticle

A Sensor Fusion Method Based on an Integrated Neural Network and Kalman Filter for Vehicle Roll Angle Estimation

by Leandro Vargas-Meléndez¹

, Beatriz L. Boada^1,*,†

, María Jesús L. Boada^1,†

, Antonio Gauchía^2,† and Vicente Díaz^1,†

¹ Mechanical Engineering Department, Universidad Carlos III de Madrid, Avda. de la Universidad 30, Madrid 28911, Spain

² Mechanical Engineering-Engineering Mechanics Department, Michigan Tech University, 1400 Townsend Drive, Houghton 49931, Michigan, MI, USA

Sensors 2016, 16(9), 1400; https://doi.org/10.3390/s16091400 - 31 Aug 2016

Cited by 56 | Viewed by 11205

Abstract

This article presents a novel estimator based on sensor fusion, which combines the Neural Network (NN) with a Kalman filter in order to estimate the vehicle roll angle. The NN estimates a “pseudo-roll angle” through variables that are easily measured from Inertial Measurement [...] Read more.

This article presents a novel estimator based on sensor fusion, which combines the Neural Network (NN) with a Kalman filter in order to estimate the vehicle roll angle. The NN estimates a “pseudo-roll angle” through variables that are easily measured from Inertial Measurement Unit (IMU) sensors. An IMU is a device that is commonly used for vehicle motion detection, and its cost has decreased during recent years. The pseudo-roll angle is introduced in the Kalman filter in order to filter noise and minimize the variance of the norm and maximum errors’ estimation. The NN has been trained for J-turn maneuvers, double lane change maneuvers and lane change maneuvers at different speeds and road friction coefficients. The proposed method takes into account the vehicle non-linearities, thus yielding good roll angle estimation. Finally, the proposed estimator has been compared with one that uses the suspension deflections to obtain the pseudo-roll angle. Experimental results show the effectiveness of the proposed NN and Kalman filter-based estimator. Full article

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

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18 pages, 14051 KiB

Open AccessArticle

Through Wall Radar Classification of Human Micro-Doppler Using Singular Value Decomposition Analysis

by Matthew Ritchie^1,*, Matthew Ash¹, Qingchao Chen² and Kevin Chetty²

¹ Department of Electronic and Electrical Engineering, University College London, London, WC1E 7JE, UK

² Department of Security and Crime Science, University College London, London, WC1H 9EZ, UK

Sensors 2016, 16(9), 1401; https://doi.org/10.3390/s16091401 - 31 Aug 2016

Cited by 40 | Viewed by 11079

Abstract

The ability to detect the presence as well as classify the activities of individuals behind visually obscuring structures is of significant benefit to police, security and emergency services in many situations. This paper presents the analysis from a series of experimental results generated [...] Read more.

The ability to detect the presence as well as classify the activities of individuals behind visually obscuring structures is of significant benefit to police, security and emergency services in many situations. This paper presents the analysis from a series of experimental results generated using a through-the-wall (TTW) Frequency Modulated Continuous Wave (FMCW) C-Band radar system named Soprano. The objective of this analysis was to classify whether an individual was carrying an item in both hands or not using micro-Doppler information from a FMCW sensor. The radar was deployed at a standoff distance, of approximately 0.5 m, outside a residential building and used to detect multiple people walking within a room. Through the application of digital filtering, it was shown that significant suppression of the primary wall reflection is possible, significantly enhancing the target signal to clutter ratio. Singular Value Decomposition (SVD) signal processing techniques were then applied to the micro-Doppler signatures from different individuals. Features from the SVD information have been used to classify whether the person was carrying an item or walking free handed. Excellent performance of the classifier was achieved in this challenging scenario with accuracies up to 94%, suggesting that future through wall radar sensors may have the ability to reliably recognize many different types of activities in TTW scenarios using these techniques. Full article

(This article belongs to the Special Issue Non-Contact Sensing)

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16 pages, 7193 KiB

Open AccessArticle

Combining Remote Temperature Sensing with in-Situ Sensing to Track Marine/Freshwater Mixing Dynamics

by Margaret McCaul¹, Jack Barland¹, John Cleary², Conor Cahalane³

, Tim McCarthy³

and Dermot Diamond^1,*

¹ Insight Centre for Data Analytics, National Centre for Sensor Research, Dublin City University, Dublin 9, Ireland

² Carlow Institute of Technology, Carlow, Ireland

³ National Centre for Geocomputation Ireland, Maynooth, Ireland

Sensors 2016, 16(9), 1402; https://doi.org/10.3390/s16091402 - 31 Aug 2016

Cited by 21 | Viewed by 6313

Abstract

The ability to track the dynamics of processes in natural water bodies on a global scale, and at a resolution that enables highly localised behaviour to be visualized, is an ideal scenario for understanding how local events can influence the global environment. While [...] Read more.

The ability to track the dynamics of processes in natural water bodies on a global scale, and at a resolution that enables highly localised behaviour to be visualized, is an ideal scenario for understanding how local events can influence the global environment. While advances in in-situ chem/bio-sensing continue to be reported, costs and reliability issues still inhibit the implementation of large-scale deployments. In contrast, physical parameters like surface temperature can be tracked on a global scale using satellite remote sensing, and locally at high resolution via flyovers and drones using multi-spectral imaging. In this study, we show how a much more complete picture of submarine and intertidal groundwater discharge patterns in Kinvara Bay, Galway can be achieved using a fusion of data collected from the Earth Observation satellite (Landsat 8), small aircraft and in-situ sensors. Over the course of the four-day field campaign, over 65,000 in-situ temperatures, salinity and nutrient measurements were collected in parallel with high-resolution thermal imaging from aircraft flyovers. The processed in-situ data show highly correlated patterns between temperature and salinity at the southern end of the bay where freshwater springs can be identified at low tide. Salinity values range from 1 to 2 ppt at the southern end of the bay to 30 ppt at the mouth of the bay, indicating the presence of a freshwater wedge. The data clearly show that temperature differences can be used to track the dynamics of freshwater and seawater mixing in the inner bay region. This outcome suggests that combining the tremendous spatial density and wide geographical reach of remote temperature sensing (using drones, flyovers and satellites) with ground-truthing via appropriately located in-situ sensors (temperature, salinity, chemical, and biological) can produce a much more complete and accurate picture of the water dynamics than each modality used in isolation. Full article

(This article belongs to the Section Remote Sensors)

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23 pages, 13398 KiB

Open AccessArticle

Analysis of the Dynamic Sensitivity of Hemisphere-Shaped Electrostatic Sensors’ Circular Array for Charged Particle Monitoring

by Xin Tang, Zhong-Sheng Chen^*, Yue Li, Zheng Hu and Yong-Min Yang

Science and Technology on Integrated Logistics Support Laboratory, National University of Defense Technology, Changsha 410073, China

Sensors 2016, 16(9), 1403; https://doi.org/10.3390/s16091403 - 31 Aug 2016

Cited by 17 | Viewed by 4977

Abstract

Electrostatic sensor arrays (ESAs) are promising in industrial applications related to charged particle monitoring. Sensitivity is a fundamental and commonly-used sensing characteristic of an ESA. However, the usually used spatial sensitivity, which is called static sensitivity here, is not proper for moving particles [...] Read more.

Electrostatic sensor arrays (ESAs) are promising in industrial applications related to charged particle monitoring. Sensitivity is a fundamental and commonly-used sensing characteristic of an ESA. However, the usually used spatial sensitivity, which is called static sensitivity here, is not proper for moving particles or capable of reflecting array signal processing algorithms integrated in an ESA. Besides, reports on ESAs for intermittent particles are scarce yet, especially lacking suitable array signal processing algorithms. To solve the problems, the dynamic sensitivity of ESA is proposed, and a hemisphere-shaped electrostatic sensors’ circular array (HSESCA) along with its application in intermittent particle monitoring are taken as an example. In detail, a sensing model of the HSESCA is built. On this basis, its array signals are analyzed; the dynamic sensitivity is thereupon defined by analyzing the processing of the array signals. Besides, a component extraction-based array signal processing algorithm for intermittent particles is proposed, and the corresponding dynamic sensitivity is analyzed quantitatively. Moreover, simulated and experimental results are discussed, which validate the accuracy of the models and the effectiveness of the relevant approaches. The proposed dynamic sensitivity of ESA, as well as the array signal processing algorithm are expected to provide references in modeling, designing and using ESAs. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 9728 KiB

Open AccessArticle

Carded Tow Real-Time Color Assessment: A Spectral Camera-Based System

by Rocco Furferi^*

, Lapo Governi

, Yary Volpe

and Monica Carfagni

Department of Industrial Engineering, University of Florence (Italy), Firenze 50139, Italy

Sensors 2016, 16(9), 1404; https://doi.org/10.3390/s16091404 - 31 Aug 2016

Viewed by 6344

Abstract

One of the most important parameters to be controlled during the production of textile yarns obtained by mixing pre-colored fibers, is the color correspondence between the manufactured yarn and a given reference, usually provided by a designer or a customer. Obtaining yarns from [...] Read more.

One of the most important parameters to be controlled during the production of textile yarns obtained by mixing pre-colored fibers, is the color correspondence between the manufactured yarn and a given reference, usually provided by a designer or a customer. Obtaining yarns from raw pre-colored fibers is a complex manufacturing process entailing a number of steps such as laboratory sampling, color recipe corrections, blowing, carding and spinning. Carding process is the one devoted to transform a “fuzzy mass” of tufted fibers into a regular mass of untwisted fibers, named “tow”. During this process, unfortunately, the correspondence between the color of the tow and the target one cannot be assured, thus leading to yarns whose color differs from the one used for reference. To solve this issue, the main aim of this work is to provide a system able to perform a spectral camera-based real-time measurement of a carded tow, to assess its color correspondence with a reference carded fabric and, at the same time, to monitor the overall quality of the tow during the carding process. Tested against a number of differently colored carded fabrics, the proposed system proved its effectiveness in reliably assessing color correspondence in real-time. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technologies in Italy 2016)

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10 pages, 1829 KiB

Open AccessArticle

Resonance Frequency of Optical Microbubble Resonators: Direct Measurements and Mitigation of Fluctuations

by Alessandro Cosci^1,2,*, Simone Berneschi², Ambra Giannetti²

, Daniele Farnesi^1,2, Franco Cosi², Francesco Baldini²

, Gualtiero Nunzi Conti^1,2, Silvia Soria²

, Andrea Barucci²

, Giancarlo Righini^1,2 and Stefano Pelli^1,2

¹ Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Piazza del Viminale 1, Rome 00184, Italy

² IFAC-CNR, Istituto di Fisica Applicata “Nello Carrara”, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, Sesto Fiorentino 50019, Italy

Sensors 2016, 16(9), 1405; https://doi.org/10.3390/s16091405 - 31 Aug 2016

Cited by 9 | Viewed by 5004

Abstract

This work shows the improvements in the sensing capabilities and precision of an Optical Microbubble Resonator due to the introduction of an encaging poly(methyl methacrylate) (PMMA) box. A frequency fluctuation parameter σ was defined as a score of resonance stability and was evaluated [...] Read more.

This work shows the improvements in the sensing capabilities and precision of an Optical Microbubble Resonator due to the introduction of an encaging poly(methyl methacrylate) (PMMA) box. A frequency fluctuation parameter σ was defined as a score of resonance stability and was evaluated in the presence and absence of the encaging system and in the case of air- or water-filling of the cavity. Furthermore, the noise interference introduced by the peristaltic and the syringe pumping system was studied. The measurements showed a reduction of σ in the presence of the encaging PMMA box and when the syringe pump was used as flowing system. Full article

(This article belongs to the Special Issue SPR, WGM & Nano-Sensors: Advantages and Prospects)

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22 pages, 8136 KiB

Open AccessArticle

Onboard Robust Visual Tracking for UAVs Using a Reliable Global-Local Object Model

by Changhong Fu^1,2

, Ran Duan^1,2, Dogan Kircali^1,2

and Erdal Kayacan^1,*

¹ School of Mechanical and Aerospace Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 639798, Singapore

² ST Engineering-NTU Corporate Laboratory, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore

Sensors 2016, 16(9), 1406; https://doi.org/10.3390/s16091406 - 31 Aug 2016

Cited by 51 | Viewed by 8171

Abstract

In this paper, we present a novel onboard robust visual algorithm for long-term arbitrary 2D and 3D object tracking using a reliable global-local object model for unmanned aerial vehicle (UAV) applications, e.g., autonomous tracking and chasing a moving target. The first main approach [...] Read more.

In this paper, we present a novel onboard robust visual algorithm for long-term arbitrary 2D and 3D object tracking using a reliable global-local object model for unmanned aerial vehicle (UAV) applications, e.g., autonomous tracking and chasing a moving target. The first main approach in this novel algorithm is the use of a global matching and local tracking approach. In other words, the algorithm initially finds feature correspondences in a way that an improved binary descriptor is developed for global feature matching and an iterative Lucas–Kanade optical flow algorithm is employed for local feature tracking. The second main module is the use of an efficient local geometric filter (LGF), which handles outlier feature correspondences based on a new forward-backward pairwise dissimilarity measure, thereby maintaining pairwise geometric consistency. In the proposed LGF module, a hierarchical agglomerative clustering, i.e., bottom-up aggregation, is applied using an effective single-link method. The third proposed module is a heuristic local outlier factor (to the best of our knowledge, it is utilized for the first time to deal with outlier features in a visual tracking application), which further maximizes the representation of the target object in which we formulate outlier feature detection as a binary classification problem with the output features of the LGF module. Extensive UAV flight experiments show that the proposed visual tracker achieves real-time frame rates of more than thirty-five frames per second on an i7 processor with 640 × 512 image resolution and outperforms the most popular state-of-the-art trackers favorably in terms of robustness, efficiency and accuracy. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

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23 pages, 543 KiB

Open AccessArticle

Multi-Sensor Consensus Estimation of State, Sensor Biases and Unknown Input

by Jie Zhou, Yan Liang^*, Feng Yang, Linfeng Xu and Quan Pan

Key Laboratory of Information Fusion Technology, Ministry of Education, School of Automation, Northwestern Polytechnical University, Xi’an 710129, China

Sensors 2016, 16(9), 1407; https://doi.org/10.3390/s16091407 - 1 Sep 2016

Cited by 6 | Viewed by 5679

Abstract

This paper addresses the problem of the joint estimation of system state and generalized sensor bias (GSB) under a common unknown input (UI) in the case of bias evolution in a heterogeneous sensor network. First, the equivalent UI-free GSB dynamic model is derived [...] Read more.

This paper addresses the problem of the joint estimation of system state and generalized sensor bias (GSB) under a common unknown input (UI) in the case of bias evolution in a heterogeneous sensor network. First, the equivalent UI-free GSB dynamic model is derived and the local optimal estimates of system state and sensor bias are obtained in each sensor node; Second, based on the state and bias estimates obtained by each node from its neighbors, the UI is estimated via the least-squares method, and then the state estimates are fused via consensus processing; Finally, the multi-sensor bias estimates are further refined based on the consensus estimate of the UI. A numerical example of distributed multi-sensor target tracking is presented to illustrate the proposed filter. Full article

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

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20 pages, 5284 KiB

Open AccessArticle

PSO-SVM-Based Online Locomotion Mode Identification for Rehabilitation Robotic Exoskeletons

by Yi Long¹, Zhi-Jiang Du¹, Wei-Dong Wang¹

, Guang-Yu Zhao², Guo-Qiang Xu², Long He², Xi-Wang Mao² and Wei Dong^1,*

¹ State Key Laboratory of Robotics and System, Harbin Institute of Technology (HIT), Harbin 150001, China

² Weapon Equipment Research Institute, China Ordnance Industries Group, Beijing 102202, China

Sensors 2016, 16(9), 1408; https://doi.org/10.3390/s16091408 - 2 Sep 2016

Cited by 69 | Viewed by 8546

Abstract

Locomotion mode identification is essential for the control of a robotic rehabilitation exoskeletons. This paper proposes an online support vector machine (SVM) optimized by particle swarm optimization (PSO) to identify different locomotion modes to realize a smooth and automatic locomotion transition. A PSO [...] Read more.

Locomotion mode identification is essential for the control of a robotic rehabilitation exoskeletons. This paper proposes an online support vector machine (SVM) optimized by particle swarm optimization (PSO) to identify different locomotion modes to realize a smooth and automatic locomotion transition. A PSO algorithm is used to obtain the optimal parameters of SVM for a better overall performance. Signals measured by the foot pressure sensors integrated in the insoles of wearable shoes and the MEMS-based attitude and heading reference systems (AHRS) attached on the shoes and shanks of leg segments are fused together as the input information of SVM. Based on the chosen window whose size is 200 ms (with sampling frequency of 40 Hz), a three-layer wavelet packet analysis (WPA) is used for feature extraction, after which, the kernel principal component analysis (kPCA) is utilized to reduce the dimension of the feature set to reduce computation cost of the SVM. Since the signals are from two types of different sensors, the normalization is conducted to scale the input into the interval of [0, 1]. Five-fold cross validation is adapted to train the classifier, which prevents the classifier over-fitting. Based on the SVM model obtained offline in MATLAB, an online SVM algorithm is constructed for locomotion mode identification. Experiments are performed for different locomotion modes and experimental results show the effectiveness of the proposed algorithm with an accuracy of 96.00% ± 2.45%. To improve its accuracy, majority vote algorithm (MVA) is used for post-processing, with which the identification accuracy is better than 98.35% ± 1.65%. The proposed algorithm can be extended and employed in the field of robotic rehabilitation and assistance. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 2399 KiB

Open AccessArticle

Low-Rank Matrix Recovery Approach for Clutter Rejection in Real-Time IR-UWB Radar-Based Moving Target Detection

by Donatien Sabushimike¹, Seung You Na^1,*

, Jin Young Kim¹, Ngoc Nam Bui², Kyung Sik Seo² and Gil Gyeom Kim²

¹ Department of Electronics and Computer Engineering, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186, Korea

² MOMED Solution, Gwangju 61008, Korea

Sensors 2016, 16(9), 1409; https://doi.org/10.3390/s16091409 - 1 Sep 2016

Cited by 15 | Viewed by 7054

Abstract

The detection of a moving target using an IR-UWB Radar involves the core task of separating the waves reflected by the static background and by the moving target. This paper investigates the capacity of the low-rank and sparse matrix decomposition approach to separate [...] Read more.

The detection of a moving target using an IR-UWB Radar involves the core task of separating the waves reflected by the static background and by the moving target. This paper investigates the capacity of the low-rank and sparse matrix decomposition approach to separate the background and the foreground in the trend of UWB Radar-based moving target detection. Robust PCA models are criticized for being batched-data-oriented, which makes them inconvenient in realistic environments where frames need to be processed as they are recorded in real time. In this paper, a novel method based on overlapping-windows processing is proposed to cope with online processing. The method consists of processing a small batch of frames which will be continually updated without changing its size as new frames are captured. We prove that RPCA (via its Inexact Augmented Lagrange Multiplier (IALM) model) can successfully separate the two subspaces, which enhances the accuracy of target detection. The overlapping-windows processing method converges on the optimal solution with its batch counterpart (i.e., processing batched data with RPCA), and both methods prove the robustness and efficiency of the RPCA over the classic PCA and the commonly used exponential averaging method. Full article

(This article belongs to the Special Issue Non-Contact Sensing)

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12 pages, 10833 KiB

Open AccessArticle

Coseismic Gravity and Displacement Signatures Induced by the 2013 Okhotsk Mw8.3 Earthquake

by Guoqing Zhang^1,2, Wenbin Shen^1,3,*, Changyi Xu⁴ and Yiqing Zhu²

¹ School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China

² The Second Monitoring and Application Center, China Earthquake Administration, Xi’an 710043, China

³ State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China

⁴ Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China

Sensors 2016, 16(9), 1410; https://doi.org/10.3390/s16091410 - 1 Sep 2016

Cited by 7 | Viewed by 5394

Abstract

In this study, Gravity Recovery and Climate Experiment (GRACE) RL05 data from January 2003 to October 2014 were used to extract the coseismic gravity changes induced by the 24 May 2013 Okhotsk Mw8.3 deep-focus earthquake using the difference and least square [...] Read more.

In this study, Gravity Recovery and Climate Experiment (GRACE) RL05 data from January 2003 to October 2014 were used to extract the coseismic gravity changes induced by the 24 May 2013 Okhotsk Mw8.3 deep-focus earthquake using the difference and least square fitting methods. The gravity changes obtained from GRACE data agreed well with those from dislocation theory in both magnitude and spatial pattern. Positive and negative gravity changes appeared on both sides of the epicenter. The positive signature appeared on the western side, and the peak value was approximately 0.4 microgal (1 microgal = 10⁻⁸ m/s²), whereas on the eastern side, the gravity signature was negative, and the peak value was approximately −1.1 microgal. It demonstrates that deep-focus earthquakes Mw ≤ 8.5 are detectable by GRACE observations. Moreover, the coseismic displacements of 20 Global Positioning System (GPS) stations on the Earth’s surface were simulated using an elastic dislocation theory in a spherical earth model, and the results are consistent with the GPS results, especially the near-field results. We also estimated the gravity contributions from the coseismic vertical displacements and density changes, analyzed the proportion of these two gravity change factors (based on an elastic dislocation theory in a spherical earth model) in this deep-focus earthquake. The gravity effect from vertical displacement is four times larger than that caused by density redistribution. Full article

(This article belongs to the Section Remote Sensors)

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19 pages, 1375 KiB

Open AccessArticle

Concurrent Reflectance Confocal Microscopy and Laser Doppler Flowmetry to Improve Skin Cancer Imaging: A Monte Carlo Model and Experimental Validation

by Alireza Mowla¹

, Thomas Taimre², Yah Leng Lim¹, Karl Bertling¹

, Stephen J. Wilson¹, Tarl W. Prow³, H. Peter Soyer³

and Aleksandar D. Rakić^1,*

¹ School of Information Technology and Electrical Engineering, The University of Queensland, St. Lucia, Brisbane 4072, Australia

² School of Mathematics and Physics, The University of Queensland, St. Lucia, Brisbane 4072, Australia

³ Dermatology Research Centre, The University of Queensland, School of Medicine, Translational Research Institute, Brisbane 4102, Australia

Sensors 2016, 16(9), 1411; https://doi.org/10.3390/s16091411 - 1 Sep 2016

Cited by 10 | Viewed by 7443

Abstract

Optical interrogation of suspicious skin lesions is standard care in the management of skin cancer worldwide. Morphological and functional markers of malignancy are often combined to improve expert human diagnostic power. We propose the evaluation of the combination of two independent optical biomarkers [...] Read more.

Optical interrogation of suspicious skin lesions is standard care in the management of skin cancer worldwide. Morphological and functional markers of malignancy are often combined to improve expert human diagnostic power. We propose the evaluation of the combination of two independent optical biomarkers of skin tumours concurrently. The morphological modality of reflectance confocal microscopy (RCM) is combined with the functional modality of laser Doppler flowmetry, which is capable of quantifying tissue perfusion. To realize the idea, we propose laser feedback interferometry as an implementation of RCM, which is able to detect the Doppler signal in addition to the confocal reflectance signal. Based on the proposed technique, we study numerical models of skin tissue incorporating two optical biomarkers of malignancy: (i) abnormal red blood cell velocities and concentrations and (ii) anomalous optical properties manifested through tissue confocal reflectance, using Monte Carlo simulation. We also conduct a laboratory experiment on a microfluidic channel containing a dynamic turbid medium, to validate the efficacy of the technique. We quantify the performance of the technique by examining a signal to background ratio (SBR) in both the numerical and experimental models, and it is shown that both simulated and experimental SBRs improve consistently using this technique. This work indicates the feasibility of an optical instrument, which may have a role in enhanced imaging of skin malignancies. Full article

(This article belongs to the Special Issue Laser Sensors for Displacement, Distance, Flow, Velocity and Vibrations Measurements)

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19 pages, 4003 KiB

Open AccessArticle

Weak and Dynamic GNSS Signal Tracking Strategies for Flight Missions in the Space Service Volume

by Shuai Jing

, Xingqun Zhan^*, Baoyu Liu and Maolin Chen

School of Aeronautics and Astronautics, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Shanghai 200240, China

Sensors 2016, 16(9), 1412; https://doi.org/10.3390/s16091412 - 2 Sep 2016

Cited by 14 | Viewed by 6303

Abstract

Weak-signal and high-dynamics are of two primary concerns of space navigation using GNSS (Global Navigation Satellite System) in the space service volume (SSV). The paper firstly defines a reference assumption third-order phase-locked loop (PLL) as the baseline of an onboard GNSS receiver, and [...] Read more.

Weak-signal and high-dynamics are of two primary concerns of space navigation using GNSS (Global Navigation Satellite System) in the space service volume (SSV). The paper firstly defines a reference assumption third-order phase-locked loop (PLL) as the baseline of an onboard GNSS receiver, and proves the incompetence of this conventional architecture. Then an adaptive four-state Kalman filter (KF)-based algorithm is introduced to realize the optimization of loop noise bandwidth, which can adaptively regulate its filter gain according to the received signal power and line-of-sight (LOS) dynamics. To overcome the matter of losing lock in weak-signal and high-dynamic environments, an open loop tracking strategy aided by an inertial navigation system (INS) is recommended, and the traditional maximum likelihood estimation (MLE) method is modified in a non-coherent way by reconstructing the likelihood cost function. Furthermore, a typical mission with combined orbital maneuvering and non-maneuvering arcs is taken as a destination object to test the two proposed strategies. Finally, the experiment based on computer simulation identifies the effectiveness of an adaptive four-state KF-based strategy under non-maneuvering conditions and the virtue of INS-assisted methods under maneuvering conditions. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

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19 pages, 5326 KiB

Open AccessArticle

Aspect-Aided Dynamic Non-Negative Sparse Representation-Based Microwave Image Classification

by Xinzheng Zhang^1,*

, Qiuyue Yang¹, Miaomiao Liu¹, Yunjian Jia¹, Shujun Liu¹ and Guojun Li²

¹ College of Communication Engineering, Chongqing University, Chongqing 400044, China

² Department of Communication Commanding, Chongqing Communication Institute, Chongqing 400035, China

Sensors 2016, 16(9), 1413; https://doi.org/10.3390/s16091413 - 2 Sep 2016

Cited by 1 | Viewed by 5759

Abstract

Classification of target microwave images is an important application in much areas such as security, surveillance, etc. With respect to the task of microwave image classification, a recognition algorithm based on aspect-aided dynamic non-negative least square (ADNNLS) sparse representation is proposed. Firstly, an [...] Read more.

Classification of target microwave images is an important application in much areas such as security, surveillance, etc. With respect to the task of microwave image classification, a recognition algorithm based on aspect-aided dynamic non-negative least square (ADNNLS) sparse representation is proposed. Firstly, an aspect sector is determined, the center of which is the estimated aspect angle of the testing sample. The training samples in the aspect sector are divided into active atoms and inactive atoms by smooth self-representative learning. Secondly, for each testing sample, the corresponding active atoms are selected dynamically, thereby establishing dynamic dictionary. Thirdly, the testing sample is represented with

ℓ_{1}

-regularized non-negative sparse representation under the corresponding dynamic dictionary. Finally, the class label of the testing sample is identified by use of the minimum reconstruction error. Verification of the proposed algorithm was conducted using the Moving and Stationary Target Acquisition and Recognition (MSTAR) database which was acquired by synthetic aperture radar. Experiment results validated that the proposed approach was able to capture the local aspect characteristics of microwave images effectively, thereby improving the classification performance. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 4719 KiB

Open AccessArticle

Dynamic Aberration Correction for Conformal Window of High-Speed Aircraft Using Optimized Model-Based Wavefront Sensorless Adaptive Optics

by Bing Dong^1,*

, Yan Li², Xin-li Han¹ and Bin Hu²

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

² Beijing Institute of Space Mechanics & Electricity, Beijing 100090, China

Sensors 2016, 16(9), 1414; https://doi.org/10.3390/s16091414 - 2 Sep 2016

Cited by 19 | Viewed by 6337

Abstract

For high-speed aircraft, a conformal window is used to optimize the aerodynamic performance. However, the local shape of the conformal window leads to large amounts of dynamic aberrations varying with look angle. In this paper, deformable mirror (DM) and model-based wavefront sensorless adaptive [...] Read more.

For high-speed aircraft, a conformal window is used to optimize the aerodynamic performance. However, the local shape of the conformal window leads to large amounts of dynamic aberrations varying with look angle. In this paper, deformable mirror (DM) and model-based wavefront sensorless adaptive optics (WSLAO) are used for dynamic aberration correction of an infrared remote sensor equipped with a conformal window and scanning mirror. In model-based WSLAO, aberration is captured using Lukosz mode, and we use the low spatial frequency content of the image spectral density as the metric function. Simulations show that aberrations induced by the conformal window are dominated by some low-order Lukosz modes. To optimize the dynamic correction, we can only correct dominant Lukosz modes and the image size can be minimized to reduce the time required to compute the metric function. In our experiment, a 37-channel DM is used to mimic the dynamic aberration of conformal window with scanning rate of 10 degrees per second. A 52-channel DM is used for correction. For a 128 × 128 image, the mean value of image sharpness during dynamic correction is 1.436 × 10⁻⁵ in optimized correction and is 1.427 × 10⁻⁵ in un-optimized correction. We also demonstrated that model-based WSLAO can achieve convergence two times faster than traditional stochastic parallel gradient descent (SPGD) method. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 4100 KiB

Open AccessArticle

A Direct and Non-Singular UKF Approach Using Euler Angle Kinematics for Integrated Navigation Systems

by Changyan Ran^1,2,3

and Xianghong Cheng^1,3,*

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

² College of Computer and Information Technology, Three Gorges University, Yichang 443000, China

³ Key Laboratory of Micro-Inertial Instrument and Advanced Navigation Technology, Ministry of Education, Southeast University, Nanjing 210096, China

Sensors 2016, 16(9), 1415; https://doi.org/10.3390/s16091415 - 2 Sep 2016

Cited by 11 | Viewed by 6401

Abstract

This paper presents a direct and non-singular approach based on an unscented Kalman filter (UKF) for the integration of strapdown inertial navigation systems (SINSs) with the aid of velocity. The state vector includes velocity and Euler angles, and the system model contains Euler [...] Read more.

This paper presents a direct and non-singular approach based on an unscented Kalman filter (UKF) for the integration of strapdown inertial navigation systems (SINSs) with the aid of velocity. The state vector includes velocity and Euler angles, and the system model contains Euler angle kinematics equations. The measured velocity in the body frame is used as the filter measurement. The quaternion nonlinear equality constraint is eliminated, and the cross-noise problem is overcome. The filter model is simple and easy to apply without linearization. Data fusion is performed by an UKF, which directly estimates and outputs the navigation information. There is no need to process navigation computation and error correction separately because the navigation computation is completed synchronously during the filter time updating. In addition, the singularities are avoided with the help of the dual-Euler method. The performance of the proposed approach is verified by road test data from a land vehicle equipped with an odometer aided SINS, and a singularity turntable test is conducted using three-axis turntable test data. The results show that the proposed approach can achieve higher navigation accuracy than the commonly-used indirect approach, and the singularities can be efficiently removed as the result of dual-Euler method. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 6624 KiB

Open AccessArticle

The Front-End Readout as an Encoder IC for Magneto-Resistive Linear Scale Sensors

by Trong-Hieu Tran, Paul Chang-Po Chao^*

and Ping-Chieh Chien

Department of Electrical Engineering, National Chiao Tung University, Hsinchu 200, Taiwan

Sensors 2016, 16(9), 1416; https://doi.org/10.3390/s16091416 - 2 Sep 2016

Cited by 11 | Viewed by 11165

Abstract

This study proposes a front-end readout circuit as an encoder chip for magneto-resistance (MR) linear scales. A typical MR sensor consists of two major parts: one is its base structure, also called the magnetic scale, which is embedded with multiple grid MR electrodes, [...] Read more.

This study proposes a front-end readout circuit as an encoder chip for magneto-resistance (MR) linear scales. A typical MR sensor consists of two major parts: one is its base structure, also called the magnetic scale, which is embedded with multiple grid MR electrodes, while another is an “MR reader” stage with magnets inside and moving on the rails of the base. As the stage is in motion, the magnetic interaction between the moving stage and the base causes the variation of the magneto-resistances of the grid electrodes. In this study, a front-end readout IC chip is successfully designed and realized to acquire temporally-varying resistances in electrical signals as the stage is in motions. The acquired signals are in fact sinusoids and co-sinusoids, which are further deciphered by the front-end readout circuit via newly-designed programmable gain amplifiers (PGAs) and analog-to-digital converters (ADCs). The PGA is particularly designed to amplify the signals up to full dynamic ranges and up to 1 MHz. A 12-bit successive approximation register (SAR) ADC for analog-to-digital conversion is designed with linearity performance of ±1 in the least significant bit (LSB) over the input range of 0.5–2.5 V from peak to peak. The chip was fabricated by the Taiwan Semiconductor Manufacturing Company (TSMC) 0.35-micron complementary metal oxide semiconductor (CMOS) technology for verification with a chip size of 6.61 mm², while the power consumption is 56 mW from a 5-V power supply. The measured integral non-linearity (INL) is −0.79–0.95 LSB while the differential non-linearity (DNL) is −0.68–0.72 LSB. The effective number of bits (ENOB) of the designed ADC is validated as 10.86 for converting the input analog signal to digital counterparts. Experimental validation was conducted. A digital decoder is orchestrated to decipher the harmonic outputs from the ADC via interpolation to the position of the moving stage. It was found that the displacement measurement error is within ±15 µm for a measuring range of 10 mm. Full article

(This article belongs to the Special Issue Applications of Advanced Materials on Microelectronic and Optical Sensors)

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13 pages, 9274 KiB

Open AccessArticle

Using Custom Fiber Bragg Grating-Based Sensors to Monitor Artificial Landslides

by Qinghua Zhang^1,2,3

, Yuan Wang^1,2,*, Yangyang Sun^1,2, Lei Gao^1,2, Zhenglin Zhang^1,2, Wenyuan Zhang^1,2, Pengchong Zhao^1,2 and Yin Yue^1,2

¹ College of Defense Engineering, PLA University of Science and Technology, Nanjing 210007, China

² State Key Laboratory of Disaster Prevention and Mitigation of Explosion and Impact, Nanjing 210007, China

³ College of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

Sensors 2016, 16(9), 1417; https://doi.org/10.3390/s16091417 - 2 Sep 2016

Cited by 34 | Viewed by 7230

Abstract

Four custom fiber Bragg grating (FBG)-based sensors are developed to monitor an artificial landslide located in Nanjing, China. The sensors are composed of a rod and two FBGs. Based on the strength of the rods, two sensors are referred to as “hard sensors” [...] Read more.

Four custom fiber Bragg grating (FBG)-based sensors are developed to monitor an artificial landslide located in Nanjing, China. The sensors are composed of a rod and two FBGs. Based on the strength of the rods, two sensors are referred to as “hard sensors” (Sensor 1 and Sensor 2), the other two are referred to as “soft sensors” (Sensor 3 and Sensor 4). The two FBGs are fixed on each sensor rod at distances of 50 cm and 100 cm from the top of the rod (an upper FBG and a lower FBG). In the experiment presented in this paper, the sensors are installed on a slope on which an artificial landslide is generated through both machine-based and manual excavation. The fiber sensing system consists of the four custom FBG-based sensors, optical fiber, a static fiber grating demodulation instrument (SM125), and a PC with the necessary software. Experimental data was collected in the presence of an artificial landslide, and the results show that the lower FBGs are more sensitive than the upper FBGs for all four of the custom sensors. It was also found that Sensor 2 and Sensor 4 are more capable of monitoring small-scale landslides than Sensor 1 and Sensor 3, and this is mainly due to their placement location with respect to the landslide. The stronger rods used in the hard sensors make them more adaptable to the harsh environments of large landslides. Thus, hard sensors should be fixed near the landslide, while soft sensors should be placed farther away from the landslide. In addition, a clear tendency of strain variation can be detected by the soft sensors, which can be used to predict landslides and raise a hazard alarm. Full article

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

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15 pages, 4125 KiB

Open AccessArticle

A Disposable Microfluidic Device with a Screen Printed Electrode for Mimicking Phase II Metabolism

by Rafaela Vasiliadou^1,*, Mohammad Mehdi Nasr Esfahani², Nathan J. Brown² and Kevin J. Welham¹

¹ Department of Chemistry, University of Hull, Cottingham Road, Hull HU6 7RX, UK

² Department of Engineering, University of Hull, Cottingham Road, Hull HU6 7RX, UK

Sensors 2016, 16(9), 1418; https://doi.org/10.3390/s16091418 - 2 Sep 2016

Cited by 14 | Viewed by 9022

Abstract

Human metabolism is investigated using several in vitro methods. However, the current methodologies are often expensive, tedious and complicated. Over the last decade, the combination of electrochemistry (EC) with mass spectrometry (MS) has a simpler and a cheaper alternative to mimic the human [...] Read more.

Human metabolism is investigated using several in vitro methods. However, the current methodologies are often expensive, tedious and complicated. Over the last decade, the combination of electrochemistry (EC) with mass spectrometry (MS) has a simpler and a cheaper alternative to mimic the human metabolism. This paper describes the development of a disposable microfluidic device with a screen-printed electrode (SPE) for monitoring phase II GSH reactions. The proposed chip has the potential to be used as a primary screening tool, thus complementing the current in vitro methods. Full article

(This article belongs to the Special Issue Recent Advances in Biosensors Based Screen Printed Platforms)

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13 pages, 2890 KiB

Open AccessArticle

Characterization of the ER-Targeted Low Affinity Ca²⁺ Probe D4ER

by Elisa Greotti^1,2,†

, Andrea Wong^1,†,‡

, Tullio Pozzan^1,2,3

, Diana Pendin^1,2,*

and Paola Pizzo^1,2

¹ Department of Biomedical Sciences, University of Padua, Via U. Bassi 58/B, Padua 35121, Italy

² Neuroscience Institute—Italian National Research Council (CNR), Padua 35121, Italy

³ Venetian Institute of Molecular Medicine, Padua 35121, Italy

Sensors 2016, 16(9), 1419; https://doi.org/10.3390/s16091419 - 2 Sep 2016

Cited by 32 | Viewed by 9094

Abstract

Calcium ion (Ca²⁺) is a ubiquitous intracellular messenger and changes in its concentration impact on nearly every aspect of cell life. Endoplasmic reticulum (ER) represents the major intracellular Ca²⁺ store and the free Ca²⁺ concentration ([Ca²⁺]) within [...] Read more.

Calcium ion (Ca²⁺) is a ubiquitous intracellular messenger and changes in its concentration impact on nearly every aspect of cell life. Endoplasmic reticulum (ER) represents the major intracellular Ca²⁺ store and the free Ca²⁺ concentration ([Ca²⁺]) within its lumen ([Ca²⁺]_ER) can reach levels higher than 1 mM. Several genetically-encoded ER-targeted Ca²⁺ sensors have been developed over the last years. However, most of them are non-ratiometric and, thus, their signal is difficult to calibrate in live cells and is affected by shifts in the focal plane and artifactual movements of the sample. On the other hand, existing ratiometric Ca²⁺ probes are plagued by different drawbacks, such as a double dissociation constant (K_d) for Ca²⁺, low dynamic range, and an affinity for the cation that is too high for the levels of [Ca²⁺] in the ER lumen. Here, we report the characterization of a recently generated ER-targeted, Förster resonance energy transfer (FRET)-based, Cameleon probe, named D4ER, characterized by suitable Ca²⁺ affinity and dynamic range for monitoring [Ca²⁺] variations within the ER. As an example, resting [Ca²⁺]_ER have been evaluated in a known paradigm of altered ER Ca²⁺ homeostasis, i.e., in cells expressing a mutated form of the familial Alzheimer’s Disease-linked protein Presenilin 2 (PS2). The lower Ca²⁺ affinity of the D4ER probe, compared to that of the previously generated D1ER, allowed the detection of a conspicuous, more clear-cut, reduction in ER Ca²⁺ content in cells expressing mutated PS2, compared to controls. Full article

(This article belongs to the Special Issue FRET Biosensors)

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24 pages, 5203 KiB

Open AccessArticle

Numerical Analysis of Orbital Perturbation Effects on Inclined Geosynchronous SAR

by Xichao Dong^1,*, Cheng Hu¹, Teng Long^1,2 and Yuanhao Li¹

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

² Beijing Key Laboratory of Embedded Real-time Information Processing Technology, Beijing 100081, China

Sensors 2016, 16(9), 1420; https://doi.org/10.3390/s16091420 - 2 Sep 2016

Cited by 12 | Viewed by 8538

Abstract

The geosynchronous synthetic aperture radar (GEO SAR) is susceptible to orbit perturbations, leading to orbit drifts and variations. The influences behave very differently from those in low Earth orbit (LEO) SAR. In this paper, the impacts of perturbations on GEO SAR orbital elements [...] Read more.

The geosynchronous synthetic aperture radar (GEO SAR) is susceptible to orbit perturbations, leading to orbit drifts and variations. The influences behave very differently from those in low Earth orbit (LEO) SAR. In this paper, the impacts of perturbations on GEO SAR orbital elements are modelled based on the perturbed dynamic equations, and then, the focusing is analyzed theoretically and numerically by using the Systems Tool Kit (STK) software. The accurate GEO SAR slant range histories can be calculated according to the perturbed orbit positions in STK. The perturbed slant range errors are mainly the first and second derivatives, leading to image drifts and defocusing. Simulations of the point target imaging are performed to validate the aforementioned analysis. In the GEO SAR with an inclination of 53° and an argument of perigee of 90°, the Doppler parameters and the integration time are different and dependent on the geometry configurations. Thus, the influences are varying at different orbit positions: at the equator, the first-order phase errors should be mainly considered; at the perigee and apogee, the second-order phase errors should be mainly considered; at other positions, first-order and second-order exist simultaneously. Full article

(This article belongs to the Special Issue Synthetic Aperture Radars: Models, Algorithms, Techniques and Tools for Data Exploitation)

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24 pages, 642 KiB

Open AccessArticle

Performance Optimization of Priority Assisted CSMA/CA Mechanism of 802.15.6 under Saturation Regime

by Mustafa Shakir¹

, Obaid Ur Rehman¹, Mudassir Rahim¹, Nabil Alrajeh², Zahoor Ali Khan^3,4

, Mahmood Ashraf Khan¹, Iftikhar Azim Niaz¹

and Nadeem Javaid^1,*

¹ COMSATS Institute of Information Technology, Islamabad 44000, Pakistan

² Biomedical Technology Department, College of Applied Medical Sciences, King Saud University, Riyadh 11633, Saudi Arabia

³ CIS, Higher Colleges of Technology, Fujairah, P.O. Box 4114, United Arab Emirates

⁴ Department of Engineering Maths and Internetworking, Dalhousie University, Halifax, NS B3J 4R2, Canada

Sensors 2016, 16(9), 1421; https://doi.org/10.3390/s16091421 - 2 Sep 2016

Cited by 19 | Viewed by 7114

Abstract

Due to the recent development in the field of Wireless Sensor Networks (WSNs), the Wireless Body Area Networks (WBANs) have become a major area of interest for the developers and researchers. Human body exhibits postural mobility due to which distance variation occurs and [...] Read more.

Due to the recent development in the field of Wireless Sensor Networks (WSNs), the Wireless Body Area Networks (WBANs) have become a major area of interest for the developers and researchers. Human body exhibits postural mobility due to which distance variation occurs and the status of connections amongst sensors change time to time. One of the major requirements of WBAN is to prolong the network lifetime without compromising on other performance measures, i.e., delay, throughput and bandwidth efficiency. Node prioritization is one of the possible solutions to obtain optimum performance in WBAN. IEEE 802.15.6 CSMA/CA standard splits the nodes with different user priorities based on Contention Window (CW) size. Smaller CW size is assigned to higher priority nodes. This standard helps to reduce delay, however, it is not energy efficient. In this paper, we propose a hybrid node prioritization scheme based on IEEE 802.15.6 CSMA/CA to reduce energy consumption and maximize network lifetime. In this scheme, optimum performance is achieved by node prioritization based on CW size as well as power in respective user priority. Our proposed scheme reduces the average back off time for channel access due to CW based prioritization. Additionally, power based prioritization for a respective user priority helps to minimize required number of retransmissions. Furthermore, we also compare our scheme with IEEE 802.15.6 CSMA/CA standard (CW assisted node prioritization) and power assisted node prioritization under postural mobility in WBAN. Mathematical expressions are derived to determine the accurate analytical model for throughput, delay, bandwidth efficiency, energy consumption and life time for each node prioritization scheme. With the intention of analytical model validation, we have performed the simulations in OMNET++/MIXIM framework. Analytical and simulation results show that our proposed hybrid node prioritization scheme outperforms other node prioritization schemes in terms of average network delay, average throughput, average bandwidth efficiency and network lifetime. Full article

(This article belongs to the Section Sensor Networks)

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22 pages, 16738 KiB

Open AccessArticle

A 72 × 60 Angle-Sensitive SPAD Imaging Array for Lens-less FLIM

by Changhyuk Lee^1,2, Ben Johnson^1,3, TaeSung Jung^1,2 and Alyosha Molnar^1,*

¹ School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA

² Department of Electrical Engineering, Columbia University, New York, NY 10027, USA

³ Cortera Neurotechnologies, 2150 Shattuck Ave., PH, Berkeley, CA 94704, USA

Sensors 2016, 16(9), 1422; https://doi.org/10.3390/s16091422 - 2 Sep 2016

Cited by 21 | Viewed by 12060

Abstract

We present a 72 × 60, angle-sensitive single photon avalanche diode (A-SPAD) array for lens-less 3D fluorescence lifetime imaging. An A-SPAD pixel consists of (1) a SPAD to provide precise photon arrival time where a time-resolved operation is utilized to avoid stimulus-induced saturation, [...] Read more.

We present a 72 × 60, angle-sensitive single photon avalanche diode (A-SPAD) array for lens-less 3D fluorescence lifetime imaging. An A-SPAD pixel consists of (1) a SPAD to provide precise photon arrival time where a time-resolved operation is utilized to avoid stimulus-induced saturation, and (2) integrated diffraction gratings on top of the SPAD to extract incident angles of the incoming light. The combination enables mapping of fluorescent sources with different lifetimes in 3D space down to micrometer scale. Futhermore, the chip presented herein integrates pixel-level counters to reduce output data-rate and to enable a precise timing control. The array is implemented in standard 180 nm complementary metal-oxide-semiconductor (CMOS) technology and characterized without any post-processing. Full article

(This article belongs to the Special Issue Photon-Counting Image Sensors)

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13 pages, 1096 KiB

Open AccessArticle

Step-Detection and Adaptive Step-Length Estimation for Pedestrian Dead-Reckoning at Various Walking Speeds Using a Smartphone

by Ngoc-Huynh Ho, Phuc Huu Truong and Gu-Min Jeong^*

School of Electrical Engineering, Kookmin University, 861-1 Jeongnung-dong, Seongbuk-gu, Seoul 136-702, Korea

Sensors 2016, 16(9), 1423; https://doi.org/10.3390/s16091423 - 2 Sep 2016

Cited by 150 | Viewed by 13531

Abstract

We propose a walking distance estimation method based on an adaptive step-length estimator at various walking speeds using a smartphone. First, we apply a fast Fourier transform (FFT)-based smoother on the acceleration data collected by the smartphone to remove the interference signals. Then, [...] Read more.

We propose a walking distance estimation method based on an adaptive step-length estimator at various walking speeds using a smartphone. First, we apply a fast Fourier transform (FFT)-based smoother on the acceleration data collected by the smartphone to remove the interference signals. Then, we analyze these data using a set of step-detection rules in order to detect walking steps. Using an adaptive estimator, which is based on a model of average step speed, we accurately obtain the walking step length. To evaluate the accuracy of the proposed method, we examine the distance estimation for four different distances and three speed levels. The experimental results show that the proposed method significantly outperforms conventional estimation methods in terms of accuracy. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 2542 KiB

Open AccessReview

Research Progress on F-P Interference—Based Fiber-Optic Sensors

by Yi Wen Huang¹, Jin Tao² and Xu Guang Huang^1,3,*

¹ Guangzhou Key Laboratory for Special Fiber Photonic Devices and Applications, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China

² State Key Laboratory of Optical Communication Technologies and Networks, Wuhan Research Institute of Posts Telecommunications, Wuhan 430074, China

³ Specially Functional Fiber Engineering Technology Research Center of Guangdong Higher Education Institutes, Guangdong Provincial Engineering Technology Research Center for Microstructured Functional Fibers and Devices, South China Normal University, Guangzhou 510006, China

Sensors 2016, 16(9), 1424; https://doi.org/10.3390/s16091424 - 3 Sep 2016

Cited by 60 | Viewed by 8877

Abstract

We review our works on Fabry-Perot (F-P) interferometric fiber-optic sensors with various applications. We give a general model of F-P interferometric optical fiber sensors including diffraction loss caused by the beam divergence and the Gouy phase shift. Based on different structures of an [...] Read more.

We review our works on Fabry-Perot (F-P) interferometric fiber-optic sensors with various applications. We give a general model of F-P interferometric optical fiber sensors including diffraction loss caused by the beam divergence and the Gouy phase shift. Based on different structures of an F-P cavity formed on the end of a single-mode fiber, the F-P interferometric optical sensor has been extended to measurements of the refractive index (RI) of liquids and solids, temperature as well as small displacement. The RI of liquids and solids can be obtained by monitoring the fringe contrast related to Fresnel reflections, while the ambient temperature and small displacement can be obtained by monitoring the wavelength shift of the interference fringes. The F-P interferometric fiber-optic sensors can be used for many scientific and technological applications. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 6821 KiB

Open AccessArticle

Sparse Reconstruction for Temperature Distribution Using DTS Fiber Optic Sensors with Applications in Electrical Generator Stator Monitoring

by João Paulo Bazzo¹, Daniel Rodrigues Pipa¹

, Erlon Vagner Da Silva², Cicero Martelli¹ and Jean Carlos Cardozo da Silva^1,*

¹ Graduate Program in Electrical and Computer Engineering (CPGEI)/Federal University of Technology-Parana, Curitiba 80230-901, Brazil

² Engie Brasil Energia, Saudades do Iguaçu 85568-000, Brazil

Sensors 2016, 16(9), 1425; https://doi.org/10.3390/s16091425 - 7 Sep 2016

Cited by 4 | Viewed by 6126

Abstract

This paper presents an image reconstruction method to monitor the temperature distribution of electric generator stators. The main objective is to identify insulation failures that may arise as hotspots in the structure. The method is based on temperature readings of fiber optic distributed [...] Read more.

This paper presents an image reconstruction method to monitor the temperature distribution of electric generator stators. The main objective is to identify insulation failures that may arise as hotspots in the structure. The method is based on temperature readings of fiber optic distributed sensors (DTS) and a sparse reconstruction algorithm. Thermal images of the structure are formed by appropriately combining atoms of a dictionary of hotspots, which was constructed by finite element simulation with a multi-physical model. Due to difficulties for reproducing insulation faults in real stator structure, experimental tests were performed using a prototype similar to the real structure. The results demonstrate the ability of the proposed method to reconstruct images of hotspots with dimensions down to 15 cm, representing a resolution gain of up to six times when compared to the DTS spatial resolution. In addition, satisfactory results were also obtained to detect hotspots with only 5 cm. The application of the proposed algorithm for thermal imaging of generator stators can contribute to the identification of insulation faults in early stages, thereby avoiding catastrophic damage to the structure. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 9277 KiB

Open AccessArticle

Analysis and Compensation for Lateral Chromatic Aberration in a Color Coding Structured Light 3D Measurement System

by Junhui Huang^1,*

, Qi Xue^1,*, Zhao Wang¹ and Jianmin Gao²

¹ School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049, China

² State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2016, 16(9), 1426; https://doi.org/10.3390/s16091426 - 3 Sep 2016

Cited by 18 | Viewed by 7360

Abstract

While color-coding methods have improved the measuring efficiency of a structured light three-dimensional (3D) measurement system, they decreased the measuring accuracy significantly due to lateral chromatic aberration (LCA). In this study, the LCA in a structured light measurement system is analyzed, and a [...] Read more.

While color-coding methods have improved the measuring efficiency of a structured light three-dimensional (3D) measurement system, they decreased the measuring accuracy significantly due to lateral chromatic aberration (LCA). In this study, the LCA in a structured light measurement system is analyzed, and a method is proposed to compensate the error caused by the LCA. Firstly, based on the projective transformation, a 3D error map of LCA is constructed in the projector images by using a flat board and comparing the image coordinates of red, green and blue circles with the coordinates of white circles at preselected sample points within the measurement volume. The 3D map consists of the errors, which are the equivalent errors caused by LCA of the camera and projector. Then in measurements, error values of LCA are calculated and compensated to correct the projector image coordinates through the 3D error map and a tri-linear interpolation method. Eventually, 3D coordinates with higher accuracy are re-calculated according to the compensated image coordinates. The effectiveness of the proposed method is verified in the following experiments. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 3132 KiB

Open AccessArticle

Continuous Indoor Positioning Fusing WiFi, Smartphone Sensors and Landmarks

by Zhi-An Deng^1,*, Guofeng Wang¹, Danyang Qin²

, Zhenyu Na¹, Yang Cui³ and Juan Chen¹

¹ School of Information Science and Technology, Dalian Maritime University, Dalian 116026, China

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

³ School of Computer Science and Technology, Harbin Institute of Technology, Harbin 150001, China

Sensors 2016, 16(9), 1427; https://doi.org/10.3390/s16091427 - 5 Sep 2016

Cited by 45 | Viewed by 8142

Abstract

To exploit the complementary strengths of WiFi positioning, pedestrian dead reckoning (PDR), and landmarks, we propose a novel fusion approach based on an extended Kalman filter (EKF). For WiFi positioning, unlike previous fusion approaches setting measurement noise parameters empirically, we deploy a kernel [...] Read more.

To exploit the complementary strengths of WiFi positioning, pedestrian dead reckoning (PDR), and landmarks, we propose a novel fusion approach based on an extended Kalman filter (EKF). For WiFi positioning, unlike previous fusion approaches setting measurement noise parameters empirically, we deploy a kernel density estimation-based model to adaptively measure the related measurement noise statistics. Furthermore, a trusted area of WiFi positioning defined by fusion results of previous step and WiFi signal outlier detection are exploited to reduce computational cost and improve WiFi positioning accuracy. For PDR, we integrate a gyroscope, an accelerometer, and a magnetometer to determine the user heading based on another EKF model. To reduce accumulation error of PDR and enable continuous indoor positioning, not only the positioning results but also the heading estimations are recalibrated by indoor landmarks. Experimental results in a realistic indoor environment show that the proposed fusion approach achieves substantial positioning accuracy improvement than individual positioning approaches including PDR and WiFi positioning. Full article

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

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11 pages, 2430 KiB

Open AccessArticle

Noise Suppression on the Tunable Laser for Precise Cavity Length Displacement Measurement

by Radek Šmíd^*, Martin Čížek, Břetislav Mikel, Jan Hrabina, Josef Lazar and Ondřej Číp

Institute of Scientific Instruments of Academy of Sciences of Czech Republic, v.v.i., Brno 61264, Czech Republic

Sensors 2016, 16(9), 1428; https://doi.org/10.3390/s16091428 - 6 Sep 2016

Cited by 3 | Viewed by 5410

Abstract

The absolute distance between the mirrors of a Fabry-Perot cavity with a spacer from an ultra low expansion material was measured by an ultra wide tunable laser diode. The DFB laser diode working at 1542 nm with 1.5 MHz linewidth and 2 nm [...] Read more.

The absolute distance between the mirrors of a Fabry-Perot cavity with a spacer from an ultra low expansion material was measured by an ultra wide tunable laser diode. The DFB laser diode working at 1542 nm with 1.5 MHz linewidth and 2 nm tuning range has been suppressed with an unbalanced heterodyne fiber interferometer. The frequency noise of laser has been suppressed by 40 dB across the Fourier frequency range 30–300 Hz and by 20 dB up to 4 kHz and the linewidth of the laser below 300 kHz. The relative resolution of the measurement was

10^{- 9}

that corresponds to 0.3 nm (sub-nm) for 0.178 m long cavity with ability of displacement measurement of 0.5 mm. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 8243 KiB

Open AccessArticle

Neural Network-Based Self-Tuning PID Control for Underwater Vehicles

by Rodrigo Hernández-Alvarado^1,*,†,‡, Luis Govinda García-Valdovinos^1,‡, Tomás Salgado-Jiménez^1,‡, Alfonso Gómez-Espinosa^2,‡

and Fernando Fonseca-Navarro^1,‡

¹ Energy Division, Center for Engineering and Industrial Development-CIDESI, Santiago de Queretaro, Queretaro 76125, Mexico

² Tecnologico de Monterrey, Campus Queretaro, Ave. Epigmenio González 500, Fracc. San Pablo, Santiago de Queretaro, Queretaro 76130, Mexico

Sensors 2016, 16(9), 1429; https://doi.org/10.3390/s16091429 - 5 Sep 2016

Cited by 176 | Viewed by 17573

Abstract

For decades, PID (Proportional + Integral + Derivative)-like controllers have been successfully used in academia and industry for many kinds of plants. This is thanks to its simplicity and suitable performance in linear or linearized plants, and under certain conditions, in nonlinear ones. [...] Read more.

For decades, PID (Proportional + Integral + Derivative)-like controllers have been successfully used in academia and industry for many kinds of plants. This is thanks to its simplicity and suitable performance in linear or linearized plants, and under certain conditions, in nonlinear ones. A number of PID controller gains tuning approaches have been proposed in the literature in the last decades; most of them off-line techniques. However, in those cases wherein plants are subject to continuous parametric changes or external disturbances, online gains tuning is a desirable choice. This is the case of modular underwater ROVs (Remotely Operated Vehicles) where parameters (weight, buoyancy, added mass, among others) change according to the tool it is fitted with. In practice, some amount of time is dedicated to tune the PID gains of a ROV. Once the best set of gains has been achieved the ROV is ready to work. However, when the vehicle changes its tool or it is subject to ocean currents, its performance deteriorates since the fixed set of gains is no longer valid for the new conditions. Thus, an online PID gains tuning algorithm should be implemented to overcome this problem. In this paper, an auto-tune PID-like controller based on Neural Networks (NN) is proposed. The NN plays the role of automatically estimating the suitable set of PID gains that achieves stability of the system. The NN adjusts online the controller gains that attain the smaller position tracking error. Simulation results are given considering an underactuated 6 DOF (degrees of freedom) underwater ROV. Real time experiments on an underactuated mini ROV are conducted to show the effectiveness of the proposed scheme. Full article

(This article belongs to the Section Sensor Networks)

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18 pages, 3270 KiB

Open AccessArticle

Effect of Sensors on the Reliability and Control Performance of Power Circuits in the Web of Things (WoT)

by Sungwoo Bae¹ and Myungchin Kim^2,*

¹ Department of Electrical Engineering, Yeungnam University, Gyeongsan 38541, Korea

² Agency for Defense Development, Daejeon 34186, Korea

Sensors 2016, 16(9), 1430; https://doi.org/10.3390/s16091430 - 6 Sep 2016

Cited by 1 | Viewed by 6312

Abstract

In order to realize a true WoT environment, a reliable power circuit is required to ensure interconnections among a range of WoT devices. This paper presents research on sensors and their effects on the reliability and response characteristics of power circuits in WoT [...] Read more.

In order to realize a true WoT environment, a reliable power circuit is required to ensure interconnections among a range of WoT devices. This paper presents research on sensors and their effects on the reliability and response characteristics of power circuits in WoT devices. The presented research can be used in various power circuit applications, such as energy harvesting interfaces, photovoltaic systems, and battery management systems for the WoT devices. As power circuits rely on the feedback from voltage/current sensors, the system performance is likely to be affected by the sensor failure rates, sensor dynamic characteristics, and their interface circuits. This study investigated how the operational availability of the power circuits is affected by the sensor failure rates by performing a quantitative reliability analysis. In the analysis process, this paper also includes the effects of various reconstruction and estimation techniques used in power processing circuits (e.g., energy harvesting circuits and photovoltaic systems). This paper also reports how the transient control performance of power circuits is affected by sensor interface circuits. With the frequency domain stability analysis and circuit simulation, it was verified that the interface circuit dynamics may affect the transient response characteristics of power circuits. The verification results in this paper showed that the reliability and control performance of the power circuits can be affected by the sensor types, fault tolerant approaches against sensor failures, and the response characteristics of the sensor interfaces. The analysis results were also verified by experiments using a power circuit prototype. Full article

(This article belongs to the Special Issue Recent Advances in Sensor Technologies and Applications in the Web of Things (WoT))

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23 pages, 26027 KiB

Open AccessArticle

Web of Objects Based Ambient Assisted Living Framework for Emergency Psychiatric State Prediction

by Md Golam Rabiul Alam, Sarder Fakhrul Abedin, Moshaddique Al Ameen and Choong Seon Hong^*

Computer Science and Engineering, Kyung Hee University, 1732 Deokyoungdaero, Gilheung-gu, Yongin-si 446-701, Korea

Sensors 2016, 16(9), 1431; https://doi.org/10.3390/s16091431 - 6 Sep 2016

Cited by 20 | Viewed by 7964

Abstract

Ambient assisted living can facilitate optimum health and wellness by aiding physical, mental and social well-being. In this paper, patients’ psychiatric symptoms are collected through lightweight biosensors and web-based psychiatric screening scales in a smart home environment and then analyzed through machine learning [...] Read more.

Ambient assisted living can facilitate optimum health and wellness by aiding physical, mental and social well-being. In this paper, patients’ psychiatric symptoms are collected through lightweight biosensors and web-based psychiatric screening scales in a smart home environment and then analyzed through machine learning algorithms to provide ambient intelligence in a psychiatric emergency. The psychiatric states are modeled through a Hidden Markov Model (HMM), and the model parameters are estimated using a Viterbi path counting and scalable Stochastic Variational Inference (SVI)-based training algorithm. The most likely psychiatric state sequence of the corresponding observation sequence is determined, and an emergency psychiatric state is predicted through the proposed algorithm. Moreover, to enable personalized psychiatric emergency care, a service a web of objects-based framework is proposed for a smart-home environment. In this framework, the biosensor observations and the psychiatric rating scales are objectified and virtualized in the web space. Then, the web of objects of sensor observations and psychiatric rating scores are used to assess the dweller’s mental health status and to predict an emergency psychiatric state. The proposed psychiatric state prediction algorithm reported 83.03 percent prediction accuracy in an empirical performance study. Full article

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

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28 pages, 1966 KiB

Open AccessArticle

A Greedy Scanning Data Collection Strategy for Large-Scale Wireless Sensor Networks with a Mobile Sink

by Chuan Zhu¹

, Sai Zhang¹, Guangjie Han^1,*

, Jinfang Jiang¹ and Joel J. P. C. Rodrigues^2,3,4

¹ Department of Information and Communication Systems, Hohai University, Changzhou 213000, China

² National Institute of Telecommunications (Inatel), Minas Gerais 30000-000, Brazil

³ The Instituto de Telecomunicações, Universidade da Beira Interior, Covilhã 6200-062, Portugal

⁴ The University ITMO, St. Petersburg 190000, Russia

Sensors 2016, 16(9), 1432; https://doi.org/10.3390/s16091432 - 6 Sep 2016

Cited by 16 | Viewed by 6062

Abstract

Mobile sink is widely used for data collection in wireless sensor networks. It can avoid ‘hot spot’ problems but energy consumption caused by multihop transmission is still inefficient in real-time application scenarios. In this paper, a greedy scanning data collection strategy (GSDCS) is [...] Read more.

Mobile sink is widely used for data collection in wireless sensor networks. It can avoid ‘hot spot’ problems but energy consumption caused by multihop transmission is still inefficient in real-time application scenarios. In this paper, a greedy scanning data collection strategy (GSDCS) is proposed, and we focus on how to reduce routing energy consumption by shortening total length of routing paths. We propose that the mobile sink adjusts its trajectory dynamically according to the changes of network, instead of predetermined trajectory or random walk. Next, the mobile sink determines which area has more source nodes, then it moves toward this area. The benefit of GSDCS is that most source nodes are no longer needed to upload sensory data for long distances. Especially in event-driven application scenarios, when event area changes, the mobile sink could arrive at the new event area where most source nodes are located currently. Hence energy can be saved. Analytical and simulation results show that compared with existing work, our GSDCS has a better performance in specific application scenarios. Full article

(This article belongs to the Special Issue New Paradigms in Cyber-Physical Social Sensing)

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14 pages, 790 KiB

Open AccessArticle

Modeling of Distributed Sensing of Elastic Waves by Fiber-Optic Interferometry

by Just Agbodjan Prince¹, Franz Kohl¹ and Thilo Sauter^1,2,*

¹ Center for Integrated Sensor Systems, Danube University Krems, Viktor Kaplan Straße 2, 2700 Wr. Neustadt, Austria

² Institute of Computer Technology, Vienna University of Technology, Gußhausstraße 27-29/384, 1040 Vienna, Austria

Sensors 2016, 16(9), 1433; https://doi.org/10.3390/s16091433 - 6 Sep 2016

Cited by 3 | Viewed by 5368

Abstract

This paper deals with the transduction of strain accompanying elastic waves in solids by firmly attached optical fibers. Stretching sections of optical fibers changes the time required by guided light to pass such sections. Exploiting interferometric techniques, highly sensitive fiber-optic strain transducers are [...] Read more.

This paper deals with the transduction of strain accompanying elastic waves in solids by firmly attached optical fibers. Stretching sections of optical fibers changes the time required by guided light to pass such sections. Exploiting interferometric techniques, highly sensitive fiber-optic strain transducers are feasible based on this fiber-intrinsic effect. The impact on the actual strain conversion of the fiber segment’s shape and size, as well as its inclination to the elastic wavefront is studied. FEM analyses show that severe distortions of the interferometric response occur when the attached fiber length spans a noticeable fraction of the elastic wavelength. Analytical models of strain transduction are presented for typical transducer shapes. They are used to compute input-output relationships for the transduction of narrow-band strain pulses as a function of the mechanical wavelength. The described approach applies to many transducers depending on the distributed interaction with the investigated object. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 2089 KiB

Open AccessArticle

Enhancement of Kinematic Accelerations by Wavenumber Correlation Filtering

by Chang-Ki Hong¹

and Jay Hyoun Kwon^2,*

¹ Department of Geoinformatics Engineering, Kyungil University, Daegu 38428, Korea

² Department of Geoinformatics, University of Seoul, Seoul 02504, Korea

Sensors 2016, 16(9), 1434; https://doi.org/10.3390/s16091434 - 6 Sep 2016

Cited by 1 | Viewed by 3432

Abstract

To obtain kinematic accelerations with high accuracy and reliability, multiple Global Positioning System (GPS) receivers with a single antenna can be used for airborne gravimetry. The data collected from each receiver can be processed for kinematic accelerations that may be combined using simple [...] Read more.

To obtain kinematic accelerations with high accuracy and reliability, multiple Global Positioning System (GPS) receivers with a single antenna can be used for airborne gravimetry. The data collected from each receiver can be processed for kinematic accelerations that may be combined using simple averaging. Here, however, uncorrelated errors from instrument errors in each receiver also will be included that degrade the final solutions. Therefore, in this study, the wavenumber correlation filter (WCF) is applied to extract only the higher positively correlated wavenumber components of the kinematic accelerations for the enhancement of the final solution. The in situ airborne GPS data from two receivers were wavenumber-correlation-filtered to show about 0.07835 Gal improvement in accuracy relative to the solution from the raw kinematic accelerations. Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 2740 KiB

Open AccessArticle

Testing the Suitability of a Terrestrial 2D LiDAR Scanner for Canopy Characterization of Greenhouse Tomato Crops

by Jordi Llop¹, Emilio Gil^1,*

, Jordi Llorens²

, Antonio Miranda-Fuentes²

and Montserrat Gallart¹

¹ Department of Agrifood Engineering and Biotechnology, Polytechnic University of Catalonia, Esteve Terradas, 8, Castelldefels 08860, Spain

² Department of Rural Engineering, Area of Rural Mechanization and Technology, University of Cordoba, Córdoba 14005, Spain

Sensors 2016, 16(9), 1435; https://doi.org/10.3390/s16091435 - 6 Sep 2016

Cited by 37 | Viewed by 9917

Abstract

Canopy characterization is essential for pesticide dosage adjustment according to vegetation volume and density. It is especially important for fresh exportable vegetables like greenhouse tomatoes. These plants are thin and tall and are planted in pairs, which makes their characterization with electronic methods [...] Read more.

Canopy characterization is essential for pesticide dosage adjustment according to vegetation volume and density. It is especially important for fresh exportable vegetables like greenhouse tomatoes. These plants are thin and tall and are planted in pairs, which makes their characterization with electronic methods difficult. Therefore, the accuracy of the terrestrial 2D LiDAR sensor is evaluated for determining canopy parameters related to volume and density and established useful correlations between manual and electronic parameters for leaf area estimation. Experiments were performed in three commercial tomato greenhouses with a paired plantation system. In the electronic characterization, a LiDAR sensor scanned the plant pairs from both sides. The canopy height, canopy width, canopy volume, and leaf area were obtained. From these, other important parameters were calculated, like the tree row volume, leaf wall area, leaf area index, and leaf area density. Manual measurements were found to overestimate the parameters compared with the LiDAR sensor. The canopy volume estimated with the scanner was found to be reliable for estimating the canopy height, volume, and density. Moreover, the LiDAR scanner could assess the high variability in canopy density along rows and hence is an important tool for generating canopy maps. Full article

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

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7 pages, 1519 KiB

Open AccessArticle

Effects of AlN Coating Layer on High Temperature Characteristics of Langasite SAW Sensors

by Lin Shu¹

, Bin Peng^1,*, Yilin Cui¹, Dongdong Gong¹, Zhengbing Yang², Xingzhao Liu¹ and Wanli Zhang¹

¹ State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China

² China Gas Turbine Establishment, Jiangyou 621703, China

Sensors 2016, 16(9), 1436; https://doi.org/10.3390/s16091436 - 6 Sep 2016

Cited by 29 | Viewed by 5795

Abstract

High temperature characteristics of langasite surface acoustic wave (SAW) devices coated with an AlN thin film have been investigated in this work. The AlN films were deposited on the prepared SAW devices by mid-frequency magnetron sputtering. The SAW devices coated with AlN films [...] Read more.

High temperature characteristics of langasite surface acoustic wave (SAW) devices coated with an AlN thin film have been investigated in this work. The AlN films were deposited on the prepared SAW devices by mid-frequency magnetron sputtering. The SAW devices coated with AlN films were measured from room temperature to 600 °C. The results show that the SAW devices can work up to 600 °C. The AlN coating layer can protect and improve the performance of the SAW devices at high temperature. The SAW velocity increases with increasing AlN coating layer thickness. The temperature coefficients of frequency (TCF) of the prepared SAW devices decrease with increasing thickness of AlN coating layers, while the electromechanical coupling coefficient (K²) of the SAW devices increases with increasing AlN film thickness. The K² of the SAW devices increases by about 20% from room temperature to 600 °C. The results suggest that AlN coating layer can not only protect the SAW devices from environmental contamination, but also improve the K² of the SAW devices. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 12578 KiB

Open AccessCommunication

Selectivity Enhancement by Using Double-Layer MOX-Based Gas Sensors Prepared by Flame Spray Pyrolysis (FSP)

by Julia Rebholz¹, Katharina Grossmann¹, David Pham², Suman Pokhrel², Lutz Mädler², Udo Weimar¹ and Nicolae Barsan^1,*

¹ Institute of Physical Chemistry, University of Tübingen, Auf der Morgenstelle 15, Tübingen 72076, Germany

² IWT Foundation Institute of Materials Science, University of Bremen, Badgasteiner Str. 3, Bremen 28359, Germany

Sensors 2016, 16(9), 1437; https://doi.org/10.3390/s16091437 - 6 Sep 2016

Cited by 16 | Viewed by 6356

Abstract

Here we present a novel concept for the selective recognition of different target gases with a multilayer semiconducting metal oxide (SMOX)-based sensor device. Direct current (DC) electrical resistance measurements were performed during exposure to CO and ethanol as single gases and mixtures of [...] Read more.

Here we present a novel concept for the selective recognition of different target gases with a multilayer semiconducting metal oxide (SMOX)-based sensor device. Direct current (DC) electrical resistance measurements were performed during exposure to CO and ethanol as single gases and mixtures of highly porous metal oxide double- and single-layer sensors obtained by flame spray pyrolysis. The results show that the calculated resistance ratios of the single- and double-layer sensors are a good indicator for the presence of specific gases in the atmosphere, and can constitute some building blocks for the development of chemical logic devices. Due to the inherent lack of selectivity of SMOX-based gas sensors, such devices could be especially relevant for domestic applications. Full article

(This article belongs to the Special Issue Gas Nanosensors)

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19 pages, 3513 KiB

Open AccessArticle

An Optimized Hidden Node Detection Paradigm for Improving the Coverage and Network Efficiency in Wireless Multimedia Sensor Networks

by Adwan Alanazi^* and Khaled Elleithy

Computer Science and Engineering Department, University of Bridgeport, 126 Park Ave, Bridgeport, CT 06604, USA

Sensors 2016, 16(9), 1438; https://doi.org/10.3390/s16091438 - 7 Sep 2016

Cited by 7 | Viewed by 4693

Abstract

Successful transmission of online multimedia streams in wireless multimedia sensor networks (WMSNs) is a big challenge due to their limited bandwidth and power resources. The existing WSN protocols are not completely appropriate for multimedia communication. The effectiveness of WMSNs varies, and it depends [...] Read more.

Successful transmission of online multimedia streams in wireless multimedia sensor networks (WMSNs) is a big challenge due to their limited bandwidth and power resources. The existing WSN protocols are not completely appropriate for multimedia communication. The effectiveness of WMSNs varies, and it depends on the correct location of its sensor nodes in the field. Thus, maximizing the multimedia coverage is the most important issue in the delivery of multimedia contents. The nodes in WMSNs are either static or mobile. Thus, the node connections change continuously due to the mobility in wireless multimedia communication that causes an additional energy consumption, and synchronization loss between neighboring nodes. In this paper, we introduce an Optimized Hidden Node Detection (OHND) paradigm. The OHND consists of three phases: hidden node detection, message exchange, and location detection. These three phases aim to maximize the multimedia node coverage, and improve energy efficiency, hidden node detection capacity, and packet delivery ratio. OHND helps multimedia sensor nodes to compute the directional coverage. Furthermore, an OHND is used to maintain a continuous node– continuous neighbor discovery process in order to handle the mobility of the nodes. We implement our proposed algorithms by using a network simulator (NS2). The simulation results demonstrate that nodes are capable of maintaining direct coverage and detecting hidden nodes in order to maximize coverage and multimedia node mobility. To evaluate the performance of our proposed algorithms, we compared our results with other known approaches. Full article

(This article belongs to the Section Sensor Networks)

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9 pages, 4774 KiB

Open AccessArticle

The Non-Destructive Test of Steel Corrosion in Reinforced Concrete Bridges Using a Micro-Magnetic Sensor

by Hong Zhang¹, Leng Liao², Ruiqiang Zhao², Jianting Zhou^1,*

, Mao Yang³ and Runchuan Xia¹

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 College of Civil Engineering, Chongqing Three Gorges University, Chongqing 404100, China

Sensors 2016, 16(9), 1439; https://doi.org/10.3390/s16091439 - 6 Sep 2016

Cited by 92 | Viewed by 9510

Abstract

This paper presents a non-destructive test method for steel corrosion in reinforced concrete bridges by using a 3-dimensional digital micro-magnetic sensor to detect and analyze the self-magnetic field leakage from corroded reinforced concrete. The setup of the magnetic scanning device and the measurement [...] Read more.

This paper presents a non-destructive test method for steel corrosion in reinforced concrete bridges by using a 3-dimensional digital micro-magnetic sensor to detect and analyze the self-magnetic field leakage from corroded reinforced concrete. The setup of the magnetic scanning device and the measurement mode of the micro-magnetic sensor are introduced. The numerical analysis model is also built based on the linear magnetic charge theory. Compared to the self-magnetic field leakage data obtained from magnetic sensor-based measurement and numerical calculation, it is shown that the curves of tangential magnetic field at different lift-off height all intersect near the edge of the steel corrosion zone. The result indicates that the intersection of magnetic field curves can be used to detect and evaluate the range of the inner steel corrosion in engineering structures. The findings of this work propose a new and effective non-destructive test method for steel corrosion, and therefore enlarge the application of the micro-magnetic sensor. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 5708 KiB

Open AccessArticle

A Study of Dispersion Compensation of Polarization Multiplexing-Based OFDM-OCDMA for Radio-over-Fiber Transmissions

by Chih-Ta Yen^* and Wen-Bin Chen

Department of Electrical Engineering, National Formosa University, Yunlin County 632, Taiwan

Sensors 2016, 16(9), 1440; https://doi.org/10.3390/s16091440 - 7 Sep 2016

Cited by 5 | Viewed by 7517

Abstract

Chromatic dispersion from optical fiber is the most important problem that produces temporal skews and destroys the rectangular structure of code patterns in the spectra-amplitude-coding-based optical code-division multiple-access (SAC-OCDMA) system. Thus, the balance detection scheme does not work perfectly to cancel multiple access [...] Read more.

Chromatic dispersion from optical fiber is the most important problem that produces temporal skews and destroys the rectangular structure of code patterns in the spectra-amplitude-coding-based optical code-division multiple-access (SAC-OCDMA) system. Thus, the balance detection scheme does not work perfectly to cancel multiple access interference (MAI) and the system performance will be degraded. Orthogonal frequency-division multiplexing (OFDM) is the fastest developing technology in the academic and industrial fields of wireless transmission. In this study, the radio-over-fiber system is realized by integrating OFDM and OCDMA via polarization multiplexing scheme. The electronic dispersion compensation (EDC) equalizer element of OFDM integrated with the dispersion compensation fiber (DCF) is used in the proposed radio-over-fiber (RoF) system, which can efficiently suppress the chromatic dispersion influence in long-haul transmitted distance. A set of length differences for 10 km-long single-mode fiber (SMF) and 4 km-long DCF is to verify the compensation scheme by relative equalizer algorithms and constellation diagrams. In the simulation result, the proposed dispersion mechanism successfully compensates the dispersion from SMF and the system performance with dispersion equalizer is highly improved. Full article

(This article belongs to the Special Issue Applications of Advanced Materials on Microelectronic and Optical Sensors)

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17 pages, 530 KiB

Open AccessArticle

Single-Side Two-Location Spotlight Imaging for Building Based on MIMO Through-Wall-Radar

by Yong Jia¹

, Xiaoling Zhong^1,*

, Jiangang Liu² and Yong Guo¹

¹ College of Information Science and Technology, Chengdu University of Technology, Chengdu 610059, China

² School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China

Sensors 2016, 16(9), 1441; https://doi.org/10.3390/s16091441 - 7 Sep 2016

Cited by 14 | Viewed by 5567

Abstract

Through-wall-radar imaging is of interest for mapping the wall layout of buildings and for the detection of stationary targets within buildings. In this paper, we present an easy single-side two-location spotlight imaging method for both wall layout mapping and stationary target detection by [...] Read more.

Through-wall-radar imaging is of interest for mapping the wall layout of buildings and for the detection of stationary targets within buildings. In this paper, we present an easy single-side two-location spotlight imaging method for both wall layout mapping and stationary target detection by utilizing multiple-input multiple-output (MIMO) through-wall-radar. Rather than imaging for building walls directly, the images of all building corners are generated to speculate wall layout indirectly by successively deploying the MIMO through-wall-radar at two appropriate locations on only one side of the building and then carrying out spotlight imaging with two different squint-views. In addition to the ease of implementation, the single-side two-location squint-view detection also has two other advantages for stationary target imaging. The first one is the fewer multi-path ghosts, and the second one is the smaller region of side-lobe interferences from the corner images in comparison to the wall images. Based on Computer Simulation Technology (CST) electromagnetic simulation software, we provide multiple sets of validation results where multiple binary panorama images with clear images of all corners and stationary targets are obtained by combining two single-location images with the use of incoherent additive fusion and two-dimensional cell-averaging constant-false-alarm-rate (2D CA-CFAR) detection. Full article

(This article belongs to the Section Remote Sensors)

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10 pages, 3782 KiB

Open AccessArticle

Dispersion Curve Engineering of TiO₂/Silver Hybrid Substrates for Enhanced Surface Plasmon Resonance Detection

by Sherif H. El-Gohary¹, Munsik Choi¹, Young L. Kim^2,3,* and Kyung Min Byun^1,*

¹ Department of Biomedical Engineering, Kyung Hee University, Yongin 17104, Korea

² Department of Computer Science and Engineering, Kyung Hee University, Yongin 17104, Korea

³ Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA

Sensors 2016, 16(9), 1442; https://doi.org/10.3390/s16091442 - 7 Sep 2016

Cited by 13 | Viewed by 7917

Abstract

As surface plasmon resonance (SPR)-based biosensors are well translated into biological, chemical, environmental, and clinical fields, it is critical to further realize stable and sustainable systems, avoiding oxidation susceptibility of metal films—in particular, silver substrates. We report an enhanced SPR detection performance by [...] Read more.

As surface plasmon resonance (SPR)-based biosensors are well translated into biological, chemical, environmental, and clinical fields, it is critical to further realize stable and sustainable systems, avoiding oxidation susceptibility of metal films—in particular, silver substrates. We report an enhanced SPR detection performance by incorporating a TiO₂ layer on top of a thin silver film. A uniform TiO₂ film fabricated by electron beam evaporation at room temperature is an effective alternative in bypassing oxidation of a silver film. Based on our finding that the sensor sensitivity is strongly correlated with the slope of dispersion curves, SPR sensing results obtained by parylene film deposition shows that TiO₂/silver hybrid substrates provide notable sensitivity improvement compared to a conventional bare silver film, which confirms the possibility of engineering the dispersion characteristic according to the incidence wavelength. The reported SPR structures with TiO₂ films enhance the sensitivity significantly in water and air environments and its overall qualitative trend in sensitivity improvement is consistent with numerical simulations. Thus, we expect that our approach can extend the applicability of TiO₂-mediated SPR biosensors to highly sensitive detection for biomolecular binding events of low concentrations, while serving a practical and reliable biosensing platform. Full article

(This article belongs to the Section Biosensors)

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14 pages, 2061 KiB

Open AccessArticle

Real-Time Robust Tracking for Motion Blur and Fast Motion via Correlation Filters

by Lingyun Xu^1,2,3,*

, Haibo Luo^1,2, Bin Hui^1,2 and Zheng Chang^1,2

¹ Key Laboratory of Opto-Electronic Information Processing, Chinese Academy of Sciences, Shenyang 110016, China

² Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016, China

³ University of Chinese Academy of Science, Beijing 100049, China

Sensors 2016, 16(9), 1443; https://doi.org/10.3390/s16091443 - 7 Sep 2016

Cited by 11 | Viewed by 6551

Abstract

Visual tracking has extensive applications in intelligent monitoring and guidance systems. Among state-of-the-art tracking algorithms, Correlation Filter methods perform favorably in robustness, accuracy and speed. However, it also has shortcomings when dealing with pervasive target scale variation, motion blur and fast motion. In [...] Read more.

Visual tracking has extensive applications in intelligent monitoring and guidance systems. Among state-of-the-art tracking algorithms, Correlation Filter methods perform favorably in robustness, accuracy and speed. However, it also has shortcomings when dealing with pervasive target scale variation, motion blur and fast motion. In this paper we proposed a new real-time robust scheme based on Kernelized Correlation Filter (KCF) to significantly improve performance on motion blur and fast motion. By fusing KCF and STC trackers, our algorithm also solve the estimation of scale variation in many scenarios. We theoretically analyze the problem for CFs towards motions and utilize the point sharpness function of the target patch to evaluate the motion state of target. Then we set up an efficient scheme to handle the motion and scale variation without much time consuming. Our algorithm preserves the properties of KCF besides the ability to handle special scenarios. In the end extensive experimental results on benchmark of VOT datasets show our algorithm performs advantageously competed with the top-rank trackers. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

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16 pages, 925 KiB

Open AccessArticle

A Network Coding Based Hybrid ARQ Protocol for Underwater Acoustic Sensor Networks

by Hao Wang, Shilian Wang^*, Eryang Zhang and Jianbin Zou

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

Sensors 2016, 16(9), 1444; https://doi.org/10.3390/s16091444 - 7 Sep 2016

Cited by 18 | Viewed by 5249

Abstract

Underwater Acoustic Sensor Networks (UASNs) have attracted increasing interest in recent years due to their extensive commercial and military applications. However, the harsh underwater channel causes many challenges for the design of reliable underwater data transport protocol. In this paper, we propose an [...] Read more.

Underwater Acoustic Sensor Networks (UASNs) have attracted increasing interest in recent years due to their extensive commercial and military applications. However, the harsh underwater channel causes many challenges for the design of reliable underwater data transport protocol. In this paper, we propose an energy efficient data transport protocol based on network coding and hybrid automatic repeat request (NCHARQ) to ensure reliability, efficiency and availability in UASNs. Moreover, an adaptive window length estimation algorithm is designed to optimize the throughput and energy consumption tradeoff. The algorithm can adaptively change the code rate and can be insensitive to the environment change. Extensive simulations and analysis show that NCHARQ significantly reduces energy consumption with short end-to-end delay. Full article

(This article belongs to the Section Sensor Networks)

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16 pages, 4692 KiB

Open AccessArticle

Study of Intrinsic Dissipation Due to Thermoelastic Coupling in Gyroscope Resonators

by Changlong Li, Shiqiao Gao, Shaohua Niu^* and Haipeng Liu

State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China

Sensors 2016, 16(9), 1445; https://doi.org/10.3390/s16091445 - 7 Sep 2016

Cited by 3 | Viewed by 4417

Abstract

This paper presents analytical models, as well as numerical and experimental verification of intrinsic dissipation due to thermoelastic loss in tuning-fork resonator. The thermoelastic analytical governing equations are created for resonator vibrating at drive-mode and sense-mode, and thermoelastic vibration field quantities are deduced. [...] Read more.

This paper presents analytical models, as well as numerical and experimental verification of intrinsic dissipation due to thermoelastic loss in tuning-fork resonator. The thermoelastic analytical governing equations are created for resonator vibrating at drive-mode and sense-mode, and thermoelastic vibration field quantities are deduced. Moreover, the theoretical values are verified that coincided well with finite element analysis (FEM) simulation results. Also, the comparison of vibration field quantities is made to investigate the effect of different conditions on resonator thermoelastic vibration behavior. The significant parameters of thermoelastic damping and quality factor are subsequently deduced to analyze the energy dissipation situation in the vibration process. Meanwhile, the corresponding conclusions from other studies are used to verify our theoretical model and numerical results. By comparing with the experimental quality factor, the numerical values are validated. The combination of the theoretical expressions, numerical results and experimental data leads to an important insight into the achievable quality factor value of tuning-fork resonator, namely, that the thermoelastic damping is the main loss mechanism in the micro-comb finger structure and the quality factor varies under different vibration modes. The results demonstrate that the critical geometry dimensions of tuning-fork resonator can be well designed with the assistance of this study. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 1521 KiB

Open AccessArticle

Pretreated Butterfly Wings for Tuning the Selective Vapor Sensing

by Gábor Piszter^1,*

, Krisztián Kertész¹

, Zsolt Bálint² and László Péter Biró¹

¹ Institute of Technical Physics and Materials Science, Centre for Energy Research, H-1525 Budapest, P.O. Box 49, Hungary

² Hungarian Natural History Museum, H-1088 Budapest, Baross utca 13, Hungary

Sensors 2016, 16(9), 1446; https://doi.org/10.3390/s16091446 - 7 Sep 2016

Cited by 17 | Viewed by 5463

Abstract

Photonic nanoarchitectures occurring in the scales of Blue butterflies are responsible for their vivid blue wing coloration. These nanoarchitectures are quasi-ordered nanocomposites which are constituted from a chitin matrix with embedded air holes. Therefore, they can act as chemically selective sensors due to [...] Read more.

Photonic nanoarchitectures occurring in the scales of Blue butterflies are responsible for their vivid blue wing coloration. These nanoarchitectures are quasi-ordered nanocomposites which are constituted from a chitin matrix with embedded air holes. Therefore, they can act as chemically selective sensors due to their color changes when mixing volatile vapors in the surrounding atmosphere which condensate into the nanoarchitecture through capillary condensation. Using a home-built vapor-mixing setup, the spectral changes caused by the different air + vapor mixtures were efficiently characterized. It was found that the spectral shift is vapor-specific and proportional with the vapor concentration. We showed that the conformal modification of the scale surface by atomic layer deposition and by ethanol pretreatment can significantly alter the optical response and chemical selectivity, which points the way to the efficient production of sensor arrays based on the knowledge obtained through the investigation of modified butterfly wings. Full article

(This article belongs to the Section Chemical Sensors)

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20 pages, 8398 KiB

Open AccessArticle

An Indoor Pedestrian Positioning Method Using HMM with a Fuzzy Pattern Recognition Algorithm in a WLAN Fingerprint System

by Yepeng Ni^1,*

, Jianbo Liu², Shan Liu²

and Yaxin Bai³

¹ Computer and Network Center, Communication University of China, No. 1 Dingfuzhuang East Street, Chaoyang District, Beijing 100024, China

² Information Engineering Institute, Science and Technology Department, Communication University of China, No. 1 Dingfuzhuang East Street, Chaoyang District, Beijing 100024, China

³ School of Journalism, Faculty of Journalism and Communication, Communication University of China, No. 1 Dingfuzhuang East Street, Chaoyang District, Beijing 100024, China

Sensors 2016, 16(9), 1447; https://doi.org/10.3390/s16091447 - 8 Sep 2016

Cited by 15 | Viewed by 5160

Abstract

With the rapid development of smartphones and wireless networks, indoor location-based services have become more and more prevalent. Due to the sophisticated propagation of radio signals, the Received Signal Strength Indicator (RSSI) shows a significant variation during pedestrian walking, which introduces critical errors [...] Read more.

With the rapid development of smartphones and wireless networks, indoor location-based services have become more and more prevalent. Due to the sophisticated propagation of radio signals, the Received Signal Strength Indicator (RSSI) shows a significant variation during pedestrian walking, which introduces critical errors in deterministic indoor positioning. To solve this problem, we present a novel method to improve the indoor pedestrian positioning accuracy by embedding a fuzzy pattern recognition algorithm into a Hidden Markov Model. The fuzzy pattern recognition algorithm follows the rule that the RSSI fading has a positive correlation to the distance between the measuring point and the AP location even during a dynamic positioning measurement. Through this algorithm, we use the RSSI variation trend to replace the specific RSSI value to achieve a fuzzy positioning. The transition probability of the Hidden Markov Model is trained by the fuzzy pattern recognition algorithm with pedestrian trajectories. Using the Viterbi algorithm with the trained model, we can obtain a set of hidden location states. In our experiments, we demonstrate that, compared with the deterministic pattern matching algorithm, our method can greatly improve the positioning accuracy and shows robust environmental adaptability. Full article

(This article belongs to the Section Physical Sensors)

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31 pages, 5315 KiB

Open AccessArticle

A Tagless Indoor Localization System Based on Capacitive Sensing Technology

by Alireza Ramezani Akhmareh^*,†, Mihai Teodor Lazarescu^†

, Osama Bin Tariq and Luciano Lavagno

Politecnico di Torino, Corso Duca degli Abruzzi, Torino 24-10129, Italy

Sensors 2016, 16(9), 1448; https://doi.org/10.3390/s16091448 - 7 Sep 2016

Cited by 29 | Viewed by 9762

Abstract

Accurate indoor person localization is essential for several services, such as assisted living. We introduce a tagless indoor person localization system based on capacitive sensing and localization algorithms that can determine the location with less than 0.2 m average error in a 3 [...] Read more.

Accurate indoor person localization is essential for several services, such as assisted living. We introduce a tagless indoor person localization system based on capacitive sensing and localization algorithms that can determine the location with less than 0.2 m average error in a 3 m × 3 m room and has recall and precision better than 70%. We also discuss the effects of various noise types on the measurements and ways to reduce them using filters suitable for on-sensor implementation to lower communication energy consumption. We also compare the performance of several standard localization algorithms in terms of localization error, recall, precision, and accuracy of detection of the movement trajectory. Full article

(This article belongs to the Special Issue Data in the IoT: from Sensing to Meaning)

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16 pages, 4334 KiB

Open AccessArticle

Real-Time Tracking Framework with Adaptive Features and Constrained Labels

by Daqun Li¹, Tingfa Xu^1,2,*, Shuoyang Chen¹, Jizhou Zhang¹ and Shenwang Jiang¹

¹ School of Optoelectronics, Image Engineering & Video Technology Lab, Beijing Institute of Technology, Beijing 100081, China

² Key Laboratory of Photoelectronic Imaging Technology and System, Ministry of Education of China, Beijing 100081, China

Sensors 2016, 16(9), 1449; https://doi.org/10.3390/s16091449 - 8 Sep 2016

Cited by 3 | Viewed by 4315

Abstract

This paper proposes a novel tracking framework with adaptive features and constrained labels (AFCL) to handle illumination variation, occlusion and appearance changes caused by the variation of positions. The novel ensemble classifier, including the Forward–Backward error and the location constraint is applied, to [...] Read more.

This paper proposes a novel tracking framework with adaptive features and constrained labels (AFCL) to handle illumination variation, occlusion and appearance changes caused by the variation of positions. The novel ensemble classifier, including the Forward–Backward error and the location constraint is applied, to get the precise coordinates of the promising bounding boxes. The Forward–Backward error can enhance the adaptation and accuracy of the binary features, whereas the location constraint can overcome the label noise to a certain degree. We use the combiner which can evaluate the online templates and the outputs of the classifier to accommodate the complex situation. Evaluation of the widely used tracking benchmark shows that the proposed framework can significantly improve the tracking accuracy, and thus reduce the processing time. The proposed framework has been tested and implemented on the embedded system using TMS320C6416 and Cyclone Ⅲ kernel processors. The outputs show that achievable and satisfying results can be obtained. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 3288 KiB

Open AccessArticle

Planar Microwave Sensor for Theranostic Therapy of Organic Tissue Based on Oval Split Ring Resonators

by Carolin Reimann^1,*, Margarita Puentes¹, Matthias Maasch², Frank Hübner³, Babak Bazrafshan³, Thomas J. Vogl³, Christian Damm² and Rolf Jakoby¹

¹ Institute for Microwave Engineering and Photonics, Technische Universität Darmstadt, Merckstr. 25, Darmstadt 64283, Germany

² Terahertz Sensors Group, Technische Universität Darmstadt, Merckstr. 25, Darmstadt 64283, Germany

³ Institute of Diagnostic and Interventional Radiology, Goethe University, Theodor-Stern-Kai 7, Frankfurt am Main 60590, Germany

Sensors 2016, 16(9), 1450; https://doi.org/10.3390/s16091450 - 8 Sep 2016

Cited by 20 | Viewed by 7288

Abstract

Microwave sensors in medical environments play a significant role due to the contact-less and non-invasive sensing mechanism to determine dielectric properties of tissue. In this work, a theranostic sensor based on Split Ring Resonators (SRRs) is presented that provides two operation modes to [...] Read more.

Microwave sensors in medical environments play a significant role due to the contact-less and non-invasive sensing mechanism to determine dielectric properties of tissue. In this work, a theranostic sensor based on Split Ring Resonators (SRRs) is presented that provides two operation modes to detect and treat tumor cells, exemplary in the liver. For the detection mode, resonance frequency changes due to abnormalities are evaluated, and in the treatment mode, microwave ablation is performed. The planar sensor structure can be integrated into a needle like a surgery tool that evokes challenges concerning size limitations and biocompatibility. To meet the size requirements and provide a reasonable operating frequency, properties of oval shaped SRRs are investigated. By elongating the radius of the SRR in one direction, the resonance frequency can be decreased significantly compared to circular SRR by a factor of two below 12 GHz. In order to validate the detection and treatment characteristics of the sensor, full wave simulations and measurements are examined. Clear resonance shifts are detected for loading the sensor structures with phantoms mimicking healthy and malignant tissue. For treatment mode evaluation, ex vivo beef liver tissue was ablated leading to a lesion zone 1.2 cm × 1 cm × 0.3 cm with a three minute exposure of maximum 2.1 W. Full article

(This article belongs to the Special Issue Advanced Technologies and Techniques for Microwave and Wireless Sensors)

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19 pages, 6393 KiB

Open AccessArticle

Experimental Study on Rebar Corrosion Using the Galvanic Sensor Combined with the Electronic Resistance Technique

by Yunze Xu^1,*

, Kaiqiang Li², Liang Liu¹, Lujia Yang¹, Xiaona Wang^2,* and Yi Huang^1,*

¹ School of Naval Architecture and Ocean Engineering, Dalian University of Technology, Dalian 116024, China

² School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China

Sensors 2016, 16(9), 1451; https://doi.org/10.3390/s16091451 - 8 Sep 2016

Cited by 27 | Viewed by 7382

Abstract

In this paper, a new kind of carbon steel (CS) and stainless steel (SS) galvanic sensor system was developed for the study of rebar corrosion in different pore solution conditions. Through the special design of the CS and SS electronic coupons, the electronic [...] Read more.

In this paper, a new kind of carbon steel (CS) and stainless steel (SS) galvanic sensor system was developed for the study of rebar corrosion in different pore solution conditions. Through the special design of the CS and SS electronic coupons, the electronic resistance (ER) method and zero resistance ammeter (ZRA) technique were used simultaneously for the measurement of both the galvanic current and the corrosion depth. The corrosion processes in different solution conditions were also studied by linear polarization resistance (LPR) and the measurements of polarization curves. The test result shows that the galvanic current noise can provide detailed information of the corrosion processes. When localized corrosion occurs, the corrosion rate measured by the ER method is lower than the real corrosion rate. However, the value measured by the LPR method is higher than the real corrosion rate. The galvanic current and the corrosion current measured by the LPR method shows linear correlation in chloride-containing saturated Ca(OH)₂ solution. The relationship between the corrosion current differences measured by the CS electronic coupons and the galvanic current between the CS and SS electronic coupons can also be used to evaluate the localized corrosion in reinforced concrete. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 1205 KiB

Open AccessArticle

RSS-Based Method for Sensor Localization with Unknown Transmit Power and Uncertainty in Path Loss Exponent

by Jiyan Huang^1,2,*

, Peng Liu³, Wei Lin¹ and Guan Gui⁴

¹ School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China

² Institute of Electronic and Information Engineering in Dongguan UESTC, Dongguan 523808, China

³ Space Star Technology Co., Ltd. and State Key Laboratory of Space-Ground Integrated Information Technology, Beijing 100191, China

⁴ Department of Electronics and Information Systems, Akita Prefectural University, Akita 015-0055, Japan

Sensors 2016, 16(9), 1452; https://doi.org/10.3390/s16091452 - 8 Sep 2016

Cited by 22 | Viewed by 5420

Abstract

The localization of a sensor in wireless sensor networks (WSNs) has now gained considerable attention. Since the transmit power and path loss exponent (PLE) are two critical parameters in the received signal strength (RSS) localization technique, many RSS-based location methods, considering the case [...] Read more.

The localization of a sensor in wireless sensor networks (WSNs) has now gained considerable attention. Since the transmit power and path loss exponent (PLE) are two critical parameters in the received signal strength (RSS) localization technique, many RSS-based location methods, considering the case that both the transmit power and PLE are unknown, have been proposed in the literature. However, these methods require a search process, and cannot give a closed-form solution to sensor localization. In this paper, a novel RSS localization method with a closed-form solution based on a two-step weighted least squares estimator is proposed for the case with the unknown transmit power and uncertainty in PLE. Furthermore, the complete performance analysis of the proposed method is given in the paper. Both the theoretical variance and Cramer-Rao lower bound (CRLB) are derived. The relationships between the deterministic CRLB and the proposed stochastic CRLB are presented. The paper also proves that the proposed method can reach the stochastic CRLB. Full article

(This article belongs to the Special Issue Advanced Algorithms for Mobile Sensing: from Wireless Sensor Networks to Mobile Crowd Sensing)

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14 pages, 3880 KiB

Open AccessArticle

Channel-Based Key Generation for Encrypted Body-Worn Wireless Sensor Networks

by Patrick Van Torre

Department of Information Technology, Ghent University/iMinds, Technologiepark-Zwijnaarde 15, 9052 Gent, Belgium

Sensors 2016, 16(9), 1453; https://doi.org/10.3390/s16091453 - 8 Sep 2016

Cited by 10 | Viewed by 4574

Abstract

Body-worn sensor networks are important for rescue-workers, medical and many other applications. Sensitive data are often transmitted over such a network, motivating the need for encryption. Body-worn sensor networks are deployed in conditions where the wireless communication channel varies dramatically due to fading [...] Read more.

Body-worn sensor networks are important for rescue-workers, medical and many other applications. Sensitive data are often transmitted over such a network, motivating the need for encryption. Body-worn sensor networks are deployed in conditions where the wireless communication channel varies dramatically due to fading and shadowing, which is considered a disadvantage for communication. Interestingly, these channel variations can be employed to extract a common encryption key at both sides of the link. Legitimate users share a unique physical channel and the variations thereof provide data series on both sides of the link, with highly correlated values. An eavesdropper, however, does not share this physical channel and cannot extract the same information when intercepting the signals. This paper documents a practical wearable communication system implementing channel-based key generation, including an implementation and a measurement campaign comprising indoor as well as outdoor measurements. The results provide insight into the performance of channel-based key generation in realistic practical conditions. Employing a process known as key reconciliation, error free keys are generated in all tested scenarios. The key-generation system is computationally simple and therefore compatible with the low-power micro controllers and low-data rate transmissions commonly used in wireless sensor networks. Full article

(This article belongs to the Special Issue Recent Advances in Sensor Technologies and Applications in the Web of Things (WoT))

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17 pages, 309 KiB

Open AccessArticle

Distributed Particle Filter for Target Tracking: With Reduced Sensor Communications

by Tadesse Ghirmai

School of STEM, Division of Engineering and Mathematics, University of Washington Bothell, Bothell, WA 98011, USA

Sensors 2016, 16(9), 1454; https://doi.org/10.3390/s16091454 - 9 Sep 2016

Cited by 20 | Viewed by 5795

Abstract

For efficient and accurate estimation of the location of objects, a network of sensors can be used to detect and track targets in a distributed manner. In nonlinear and/or non-Gaussian dynamic models, distributed particle filtering methods are commonly applied to develop target tracking [...] Read more.

For efficient and accurate estimation of the location of objects, a network of sensors can be used to detect and track targets in a distributed manner. In nonlinear and/or non-Gaussian dynamic models, distributed particle filtering methods are commonly applied to develop target tracking algorithms. An important consideration in developing a distributed particle filtering algorithm in wireless sensor networks is reducing the size of data exchanged among the sensors because of power and bandwidth constraints. In this paper, we propose a distributed particle filtering algorithm with the objective of reducing the overhead data that is communicated among the sensors. In our algorithm, the sensors exchange information to collaboratively compute the global likelihood function that encompasses the contribution of the measurements towards building the global posterior density of the unknown location parameters. Each sensor, using its own measurement, computes its local likelihood function and approximates it using a Gaussian function. The sensors then propagate only the mean and the covariance of their approximated likelihood functions to other sensors, reducing the communication overhead. The global likelihood function is computed collaboratively from the parameters of the local likelihood functions using an average consensus filter or a forward-backward propagation information exchange strategy. Full article

(This article belongs to the Special Issue New Paradigms in Cyber-Physical Social Sensing)

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25 pages, 14668 KiB

Open AccessArticle

Drift Reduction in Pedestrian Navigation System by Exploiting Motion Constraints and Magnetic Field

by Muhammad Ilyas¹, Kuk Cho², Seung-Ho Baeg^2,* and Sangdeok Park²

¹ Department of Robotics and Virtual Engineering, University of Science and Technology (UST), Daejon 305-333, Korea

² Robotics R & BD Group, Korea Institute of Industrial Technology (KITECH), Ansan 426-791, Korea

Sensors 2016, 16(9), 1455; https://doi.org/10.3390/s16091455 - 9 Sep 2016

Cited by 44 | Viewed by 8508

Abstract

Pedestrian navigation systems (PNS) using foot-mounted MEMS inertial sensors use zero-velocity updates (ZUPTs) to reduce drift in navigation solutions and estimate inertial sensor errors. However, it is well known that ZUPTs cannot reduce all errors, especially as heading error is not observable. Hence, [...] Read more.

Pedestrian navigation systems (PNS) using foot-mounted MEMS inertial sensors use zero-velocity updates (ZUPTs) to reduce drift in navigation solutions and estimate inertial sensor errors. However, it is well known that ZUPTs cannot reduce all errors, especially as heading error is not observable. Hence, the position estimates tend to drift and even cyclic ZUPTs are applied in updated steps of the Extended Kalman Filter (EKF). This urges the use of other motion constraints for pedestrian gait and any other valuable heading reduction information that is available. In this paper, we exploit two more motion constraints scenarios of pedestrian gait: (1) walking along straight paths; (2) standing still for a long time. It is observed that these motion constraints (called “virtual sensor”), though considerably reducing drift in PNS, still need an absolute heading reference. One common absolute heading estimation sensor is the magnetometer, which senses the Earth’s magnetic field and, hence, the true heading angle can be calculated. However, magnetometers are susceptible to magnetic distortions, especially in indoor environments. In this work, an algorithm, called magnetic anomaly detection (MAD) and compensation is designed by incorporating only healthy magnetometer data in the EKF updating step, to reduce drift in zero-velocity updated INS. Experiments are conducted in GPS-denied and magnetically distorted environments to validate the proposed algorithms. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

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14 pages, 2059 KiB

Open AccessArticle

Target Tracking Using SePDAF under Ambiguous Angles for Distributed Array Radar

by Teng Long¹, Honggang Zhang¹

, Tao Zeng¹, Xinliang Chen¹, Quanhua Liu^1,* and Le Zheng²

¹ Beijing Key Laboratory of Embedded Real-time Information Processing Technology, Radar Research Laboratory, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China

² Electrical Engineering Department, Columbia University, New York, NY 10027, USA

Sensors 2016, 16(9), 1456; https://doi.org/10.3390/s16091456 - 9 Sep 2016

Cited by 7 | Viewed by 5438

Abstract

Distributed array radar can improve radar detection capability and measurement accuracy. However, it will suffer cyclic ambiguity in its angle estimates according to the spatial Nyquist sampling theorem since the large sparse array is undersampling. Consequently, the state estimation accuracy and track validity [...] Read more.

Distributed array radar can improve radar detection capability and measurement accuracy. However, it will suffer cyclic ambiguity in its angle estimates according to the spatial Nyquist sampling theorem since the large sparse array is undersampling. Consequently, the state estimation accuracy and track validity probability degrades when the ambiguous angles are directly used for target tracking. This paper proposes a second probability data association filter (SePDAF)-based tracking method for distributed array radar. Firstly, the target motion model and radar measurement model is built. Secondly, the fusion result of each radar’s estimation is employed to the extended Kalman filter (EKF) to finish the first filtering. Thirdly, taking this result as prior knowledge, and associating with the array-processed ambiguous angles, the SePDAF is applied to accomplish the second filtering, and then achieving a high accuracy and stable trajectory with relatively low computational complexity. Moreover, the azimuth filtering accuracy will be promoted dramatically and the position filtering accuracy will also improve. Finally, simulations illustrate the effectiveness of the proposed method. Full article

(This article belongs to the Special Issue Non-Contact Sensing)

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17 pages, 2944 KiB

Open AccessArticle

Online Learners’ Reading Ability Detection Based on Eye-Tracking Sensors

by Zehui Zhan^1,*, Lei Zhang^2,*

, Hu Mei^3,* and Patrick S. W. Fong^4,*

¹ Center of Educational Information Technology, South China Normal University, Guangzhou 510631, China

² College of Communication Engineering, Chongqing University, Chongqing 400044, China

³ School of Economics & Management, South China Normal University, Guangzhou 510006, China

⁴ Department of Building & Real Estate, The Hong Kong Polytechnic University, Hong Kong 999077, China

Sensors 2016, 16(9), 1457; https://doi.org/10.3390/s16091457 - 10 Sep 2016

Cited by 41 | Viewed by 12215

Abstract

The detection of university online learners’ reading ability is generally problematic and time-consuming. Thus the eye-tracking sensors have been employed in this study, to record temporal and spatial human eye movements. Learners’ pupils, blinks, fixation, saccade, and regression are recognized as primary indicators [...] Read more.

The detection of university online learners’ reading ability is generally problematic and time-consuming. Thus the eye-tracking sensors have been employed in this study, to record temporal and spatial human eye movements. Learners’ pupils, blinks, fixation, saccade, and regression are recognized as primary indicators for detecting reading abilities. A computational model is established according to the empirical eye-tracking data, and applying the multi-feature regularization machine learning mechanism based on a Low-rank Constraint. The model presents good generalization ability with an error of only 4.9% when randomly running 100 times. It has obvious advantages in saving time and improving precision, with only 20 min of testing required for prediction of an individual learner’s reading ability. Full article

(This article belongs to the Section Physical Sensors)

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27 pages, 9301 KiB

Open AccessArticle

Fuzzy Sets in Dynamic Adaptation of Parameters of a Bee Colony Optimization for Controlling the Trajectory of an Autonomous Mobile Robot

by Leticia Amador-Angulo^1,*

, Olivia Mendoza², Juan R. Castro², Antonio Rodríguez-Díaz², Patricia Melin¹ and Oscar Castillo¹

¹ Division of Graduate Studies and Research, Tijuana Institute of Technology, Tijuana 22414, Mexico

² Universidad Autónoma de Baja California, Tijuana 22390, Mexico

Sensors 2016, 16(9), 1458; https://doi.org/10.3390/s16091458 - 9 Sep 2016

Cited by 85 | Viewed by 7115

Abstract

A hybrid approach composed by different types of fuzzy systems, such as the Type-1 Fuzzy Logic System (T1FLS), Interval Type-2 Fuzzy Logic System (IT2FLS) and Generalized Type-2 Fuzzy Logic System (GT2FLS) for the dynamic adaptation of the alpha and beta parameters of a [...] Read more.

A hybrid approach composed by different types of fuzzy systems, such as the Type-1 Fuzzy Logic System (T1FLS), Interval Type-2 Fuzzy Logic System (IT2FLS) and Generalized Type-2 Fuzzy Logic System (GT2FLS) for the dynamic adaptation of the alpha and beta parameters of a Bee Colony Optimization (BCO) algorithm is presented. The objective of the work is to focus on the BCO technique to find the optimal distribution of the membership functions in the design of fuzzy controllers. We use BCO specifically for tuning membership functions of the fuzzy controller for trajectory stability in an autonomous mobile robot. We add two types of perturbations in the model for the Generalized Type-2 Fuzzy Logic System to better analyze its behavior under uncertainty and this shows better results when compared to the original BCO. We implemented various performance indices; ITAE, IAE, ISE, ITSE, RMSE and MSE to measure the performance of the controller. The experimental results show better performances using GT2FLS then by IT2FLS and T1FLS in the dynamic adaptation the parameters for the BCO algorithm. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

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17 pages, 555 KiB

Open AccessArticle

Fuzzy C-Means Clustering and Energy Efficient Cluster Head Selection for Cooperative Sensor Network

by Dost Muhammad Saqib Bhatti¹

, Nasir Saeed²

and Haewoon Nam^1,*

¹ Department of Electronics and Communication Engineering, Hanyang University, Ansan 15588, Korea

² Faculty of Computer Science, Iqra National University, Peshawar, Pakistan

Sensors 2016, 16(9), 1459; https://doi.org/10.3390/s16091459 - 9 Sep 2016

Cited by 57 | Viewed by 8874

Abstract

We propose a novel cluster based cooperative spectrum sensing algorithm to save the wastage of energy, in which clusters are formed using fuzzy c-means (FCM) clustering and a cluster head (CH) is selected based on a sensor’s location within each cluster, its location [...] Read more.

We propose a novel cluster based cooperative spectrum sensing algorithm to save the wastage of energy, in which clusters are formed using fuzzy c-means (FCM) clustering and a cluster head (CH) is selected based on a sensor’s location within each cluster, its location with respect to fusion center (FC), its signal-to-noise ratio (SNR) and its residual energy. The sensing information of a single sensor is not reliable enough due to shadowing and fading. To overcome these issues, cooperative spectrum sensing schemes were proposed to take advantage of spatial diversity. For cooperative spectrum sensing, all sensors sense the spectrum and report the sensed energy to FC for the final decision. However, it increases the energy consumption of the network when a large number of sensors need to cooperate; in addition to that, the efficiency of the network is also reduced. The proposed algorithm makes the cluster and selects the CHs such that very little amount of network energy is consumed and the highest efficiency of the network is achieved. Using the proposed algorithm maximum probability of detection under an imperfect channel is accomplished with minimum energy consumption as compared to conventional clustering schemes. Full article

(This article belongs to the Section Sensor Networks)

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8 pages, 3095 KiB

Open AccessArticle

A Small U-Shaped Bending-Induced Interference Optical Fiber Sensor for the Measurement of Glucose Solutions

by Yu-Lin Fang, Chen-Tung Wang and Chia-Chin Chiang^*

Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan

Sensors 2016, 16(9), 1460; https://doi.org/10.3390/s16091460 - 9 Sep 2016

Cited by 38 | Viewed by 7576

Abstract

The study proposes a small U-shaped bending-induced interference optical fiber sensor; this novel sensor is a probe-type sensor manufactured using a mechanical device, a heat source, optical fiber and a packaging module. This probe-type sensor overcomes the shortcomings of conventional optical fibers, including [...] Read more.

The study proposes a small U-shaped bending-induced interference optical fiber sensor; this novel sensor is a probe-type sensor manufactured using a mechanical device, a heat source, optical fiber and a packaging module. This probe-type sensor overcomes the shortcomings of conventional optical fibers, including being difficult to repair and a tendency to be influenced by external forces. We manufactured three types of sensors with different curvature radiuses. Specifically, sensors with three radiuses (1.5 mm, 2.0 mm, and 3.0 mm) were used to measure common water and glucose solutions with concentrations of between 6% and 30% (the interval between concentrations was 4%). The results show that the maximal sensitivity was 0.85 dB/% and that the linearly-dependent coefficient was 0.925. The results further show that not only can the small U-shaped bending-induced interference optical fiber sensor achieve high sensitivity in the measurement of glucose solutions, but that it can also achieve great stability and repeatability. Full article

(This article belongs to the Special Issue Applications of Advanced Materials on Microelectronic and Optical Sensors)

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31 pages, 33445 KiB

Open AccessArticle

Sediment Sampling in Estuarine Mudflats with an Aerial-Ground Robotic Team

by Pedro Deusdado^1,*, Magno Guedes¹, André Silva¹, Francisco Marques²

, Eduardo Pinto², Paulo Rodrigues², André Lourenço²

, Ricardo Mendonça²

, Pedro Santana^3,4

, José Corisco⁵, Susana Marta Almeida⁵

, Luís Portugal⁶, Raquel Caldeira¹, José Barata²

and Luis Flores¹

¹ INTROSYS SA, Introsys—Global Control System Designers, Parkim- Parque Industrial da Moita Rua dos Girassóis, n°1, Lote 6, Armazém A3, 2860-274 Moita, Portugal

² CTS-UNINOVA, Universidade Nova de Lisboa (UNL), FCT Campus, 2829-516 Caparica, Portugal

³ ISCTE-Instituto Universitário de Lisboa (ISCTE-IUL), 1649-026 Lisboa, Portugal

⁴ Instituto de Telecomunicações (IT), 1049-001 Lisboa, Portugal

⁵ Centro de Ciências e Tecnologias Nucleares (C2TN), Instituto Superior Técnico, Universidade de Lisboa, E.N. 10 km 139.7, 2695-066 Bobadela LRS, Portugal

⁶ Agência Portuguesa do Ambiente (APA), Agência Portuguesa do Ambiente, I.P., Rua da Murgueira, 9/9A-Zambujal, Ap. 7585, 2610-124 Amadora, Portugal

Sensors 2016, 16(9), 1461; https://doi.org/10.3390/s16091461 - 9 Sep 2016

Cited by 12 | Viewed by 11213

Abstract

This paper presents a robotic team suited for bottom sediment sampling and retrieval in mudflats, targeting environmental monitoring tasks. The robotic team encompasses a four-wheel-steering ground vehicle, equipped with a drilling tool designed to be able to retain wet soil, and a multi-rotor [...] Read more.

This paper presents a robotic team suited for bottom sediment sampling and retrieval in mudflats, targeting environmental monitoring tasks. The robotic team encompasses a four-wheel-steering ground vehicle, equipped with a drilling tool designed to be able to retain wet soil, and a multi-rotor aerial vehicle for dynamic aerial imagery acquisition. On-demand aerial imagery, properly fused on an aerial mosaic, is used by remote human operators for specifying the robotic mission and supervising its execution. This is crucial for the success of an environmental monitoring study, as often it depends on human expertise to ensure the statistical significance and accuracy of the sampling procedures. Although the literature is rich on environmental monitoring sampling procedures, in mudflats, there is a gap as regards including robotic elements. This paper closes this gap by also proposing a preliminary experimental protocol tailored to exploit the capabilities offered by the robotic system. Field trials in the south bank of the river Tagus’ estuary show the ability of the robotic system to successfully extract and transport bottom sediment samples for offline analysis. The results also show the efficiency of the extraction and the benefits when compared to (conventional) human-based sampling. Full article

(This article belongs to the Special Issue Robotic Sensory Systems for Environment Protection and Conservation)

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18 pages, 2598 KiB

Open AccessArticle

A Novel Semi-Supervised Method of Electronic Nose for Indoor Pollution Detection Trained by M-S4VMs

by Tailai Huang, Pengfei Jia^*, Peilin He, Shukai Duan, Jia Yan

and Lidan Wang

College of Electronic and Information Engineering, Southwest University, Chongqing 400715, China

Sensors 2016, 16(9), 1462; https://doi.org/10.3390/s16091462 - 10 Sep 2016

Cited by 5 | Viewed by 5051

Abstract

Electronic nose (E-nose), as a device intended to detect odors or flavors, has been widely used in many fields. Many labeled samples are needed to gain an ideal E-nose classification model. However, the labeled samples are not easy to obtain and there are [...] Read more.

Electronic nose (E-nose), as a device intended to detect odors or flavors, has been widely used in many fields. Many labeled samples are needed to gain an ideal E-nose classification model. However, the labeled samples are not easy to obtain and there are some cases where the gas samples in the real world are complex and unlabeled. As a result, it is necessary to make an E-nose that cannot only classify unlabeled samples, but also use these samples to modify its classification model. In this paper, we first introduce a semi-supervised learning algorithm called S4VMs and improve its use within a multi-classification algorithm to classify the samples for an E-nose. Then, we enhance its performance by adding the unlabeled samples that it has classified to modify its model and by using an optimization algorithm called quantum-behaved particle swarm optimization (QPSO) to find the optimal parameters for classification. The results of comparing this with other semi-supervised learning algorithms show that our multi-classification algorithm performs well in the classification system of an E-nose after learning from unlabeled samples. Full article

(This article belongs to the Section Physical Sensors)

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27 pages, 500 KiB

Open AccessArticle

Privacy-Enhanced and Multifunctional Health Data Aggregation under Differential Privacy Guarantees

by Hao Ren¹

, Hongwei Li^1,2,*, Xiaohui Liang³, Shibo He⁴, Yuanshun Dai¹ and Lian Zhao⁵

¹ School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China

² State Key Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, Beijing 100093, China

³ Department of Computer Science, University of Massachusetts at Boston, MA 02125, USA

⁴ State Key Laboratory of Industrial Control Technology, Zhejiang University, Hangzhou 310027, China

⁵ Department of Electrical and Computer Engineering, Ryerson University, Toronto, ON M5B 2K3, Canada

Sensors 2016, 16(9), 1463; https://doi.org/10.3390/s16091463 - 10 Sep 2016

Cited by 24 | Viewed by 7011

Abstract

With the rapid growth of the health data scale, the limited storage and computation resources of wireless body area sensor networks (WBANs) is becoming a barrier to their development. Therefore, outsourcing the encrypted health data to the cloud has been an appealing strategy. [...] Read more.

With the rapid growth of the health data scale, the limited storage and computation resources of wireless body area sensor networks (WBANs) is becoming a barrier to their development. Therefore, outsourcing the encrypted health data to the cloud has been an appealing strategy. However, date aggregation will become difficult. Some recently-proposed schemes try to address this problem. However, there are still some functions and privacy issues that are not discussed. In this paper, we propose a privacy-enhanced and multifunctional health data aggregation scheme (PMHA-DP) under differential privacy. Specifically, we achieve a new aggregation function, weighted average (WAAS), and design a privacy-enhanced aggregation scheme (PAAS) to protect the aggregated data from cloud servers. Besides, a histogram aggregation scheme with high accuracy is proposed. PMHA-DP supports fault tolerance while preserving data privacy. The performance evaluation shows that the proposal leads to less communication overhead than the existing one. Full article

(This article belongs to the Special Issue Security and Privacy in Sensor Networks)

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16 pages, 1042 KiB

Open AccessArticle

Human Movement Recognition Based on the Stochastic Characterisation of Acceleration Data

by Mario Munoz-Organero^1,*

and Ahmad Lotfi²

¹ Telematics Engineering Department, Universidad Carlos III de Madrid, Avda de la Universidad, 30, E-28911 Leganés, Madrid, Spain

² School of Science and Technology, Nottingham Trent University, Nottingham NG11 8NS, UK

Sensors 2016, 16(9), 1464; https://doi.org/10.3390/s16091464 - 9 Sep 2016

Cited by 20 | Viewed by 8050

Abstract

Human activity recognition algorithms based on information obtained from wearable sensors are successfully applied in detecting many basic activities. Identified activities with time-stationary features are characterised inside a predefined temporal window by using different machine learning algorithms on extracted features from the measured [...] Read more.

Human activity recognition algorithms based on information obtained from wearable sensors are successfully applied in detecting many basic activities. Identified activities with time-stationary features are characterised inside a predefined temporal window by using different machine learning algorithms on extracted features from the measured data. Better accuracy, precision and recall levels could be achieved by combining the information from different sensors. However, detecting short and sporadic human movements, gestures and actions is still a challenging task. In this paper, a novel algorithm to detect human basic movements from wearable measured data is proposed and evaluated. The proposed algorithm is designed to minimise computational requirements while achieving acceptable accuracy levels based on characterising some particular points in the temporal series obtained from a single sensor. The underlying idea is that this algorithm would be implemented in the sensor device in order to pre-process the sensed data stream before sending the information to a central point combining the information from different sensors to improve accuracy levels. Intra- and inter-person validation is used for two particular cases: single step detection and fall detection and classification using a single tri-axial accelerometer. Relevant results for the above cases and pertinent conclusions are also presented. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 1374 KiB

Open AccessReview

A Survey on Node Clustering in Cognitive Radio Wireless Sensor Networks

by Gyanendra Prasad Joshi

and Sung Won Kim^*

Department of Information and Communication Engineering, Yeungnam University, 280 Daehak-Ro, Gyeongsan, Geongbuk 38541, Korea

Sensors 2016, 16(9), 1465; https://doi.org/10.3390/s16091465 - 10 Sep 2016

Cited by 45 | Viewed by 6741

Abstract

Cognitive radio wireless sensor networks (CR-WSNs) have attracted a great deal of attention recently due to the emerging spectrum scarcity issue. This work attempts to provide a detailed analysis of the role of node clustering in CR-WSNs. We outline the objectives, requirements, and [...] Read more.

Cognitive radio wireless sensor networks (CR-WSNs) have attracted a great deal of attention recently due to the emerging spectrum scarcity issue. This work attempts to provide a detailed analysis of the role of node clustering in CR-WSNs. We outline the objectives, requirements, and advantages of node clustering in CR-WSNs. We describe how a CR-WSN with node clustering differs from conventional wireless sensor networks, and we discuss its characteristics, architecture, and topologies. We survey the existing clustering algorithms and compare their objectives and features. We suggest how clustering issues and challenges can be handled. Full article

(This article belongs to the Section Sensor Networks)

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18 pages, 2368 KiB

Open AccessArticle

A Study of LoRa: Long Range & Low Power Networks for the Internet of Things

by Aloÿs Augustin¹, Jiazi Yi^1,*, Thomas Clausen¹

and William Mark Townsley²

¹ École polytechnique Route de Saclay, 91128 Palaiseau, France

² Cisco Paris Innovation and Research Laboratory (PIRL), 11 Rue Camille Desmoulins, 92782 Issy les Moulineaux, France

Sensors 2016, 16(9), 1466; https://doi.org/10.3390/s16091466 - 9 Sep 2016

Cited by 1236 | Viewed by 80844

Abstract

LoRa is a long-range, low-power, low-bitrate, wireless telecommunications system, promoted as an infrastructure solution for the Internet of Things: end-devices use LoRa across a single wireless hop to communicate to gateway(s), connected to the Internet and which act as transparent bridges and relay [...] Read more.

LoRa is a long-range, low-power, low-bitrate, wireless telecommunications system, promoted as an infrastructure solution for the Internet of Things: end-devices use LoRa across a single wireless hop to communicate to gateway(s), connected to the Internet and which act as transparent bridges and relay messages between these end-devices and a central network server. This paper provides an overview of LoRa and an in-depth analysis of its functional components. The physical and data link layer performance is evaluated by field tests and simulations. Based on the analysis and evaluations, some possible solutions for performance enhancements are proposed. Full article

(This article belongs to the Special Issue Enabling the Move from Wireless Sensor Networks to Internet of Things and Cyber-Physical Systems)

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13 pages, 541 KiB

Open AccessArticle

A Hybrid Algorithm for Missing Data Imputation and Its Application to Electrical Data Loggers

by Concepción Crespo Turrado¹, Fernando Sánchez Lasheras^2,*

, José Luis Calvo-Rollé³

, Andrés-José Piñón-Pazos³, Manuel G. Melero⁴ and Francisco Javier De Cos Juez⁵

¹ Maintenance Department, University of Oviedo, San Francisco 3, Oviedo 33007, Spain

² Department of Construction and Manufacturing Engineering, University of Oviedo, Campus de Viesques, Gijón 33204, Spain

³ Departamento de Ingeniería Industrial, University of A Coruña, A Coruña 15405, Spain

⁴ Electrical Engineering Department, University of Oviedo, Campus de Viesques, Gijón 33204, Spain

⁵ Prospecting and Exploitation of Mines Department, University of Oviedo, Oviedo 33004, Spain

Sensors 2016, 16(9), 1467; https://doi.org/10.3390/s16091467 - 10 Sep 2016

Cited by 5 | Viewed by 4447

Abstract

The storage of data is a key process in the study of electrical power networks related to the search for harmonics and the finding of a lack of balance among phases. The presence of missing data of any of the main electrical variables [...] Read more.

The storage of data is a key process in the study of electrical power networks related to the search for harmonics and the finding of a lack of balance among phases. The presence of missing data of any of the main electrical variables (phase-to-neutral voltage, phase-to-phase voltage, current in each phase and power factor) affects any time series study in a negative way that has to be addressed. When this occurs, missing data imputation algorithms are required. These algorithms are able to substitute the data that are missing for estimated values. This research presents a new algorithm for the missing data imputation method based on Self-Organized Maps Neural Networks and Mahalanobis distances and compares it not only with a well-known technique called Multivariate Imputation by Chained Equations (MICE) but also with an algorithm previously proposed by the authors called Adaptive Assignation Algorithm (AAA). The results obtained demonstrate how the proposed method outperforms both algorithms. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 4991 KiB

Open AccessArticle

The Simulation of the Recharging Method Based on Solar Radiation for an Implantable Biosensor

by Yun Li¹, Yong Song^1,*, Xianyue Kong¹, Maoyuan Li¹, Yufei Zhao¹, Qun Hao¹ and Tianxin Gao²

¹ School of Opto-Electronics, Beijing Institute of Technology, Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology, Beijing 100081, China

² School of Life Science, Beijing Institute of Technology, Beijing 100081, China

Sensors 2016, 16(9), 1468; https://doi.org/10.3390/s16091468 - 10 Sep 2016

Viewed by 4559

Abstract

A method of recharging implantable biosensors based on solar radiation is proposed. Firstly, the models of the proposed method are developed. Secondly, the recharging processes based on solar radiation are simulated using Monte Carlo (MC) method and the energy distributions of sunlight within [...] Read more.

A method of recharging implantable biosensors based on solar radiation is proposed. Firstly, the models of the proposed method are developed. Secondly, the recharging processes based on solar radiation are simulated using Monte Carlo (MC) method and the energy distributions of sunlight within the different layers of human skin have been achieved and discussed. Finally, the simulation results are verified experimentally, which indicates that the proposed method will contribute to achieve a low-cost, convenient and safe method for recharging implantable biosensors. Full article

(This article belongs to the Section Biosensors)

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18 pages, 951 KiB

Open AccessArticle

Improved Bearings-Only Multi-Target Tracking with GM-PHD Filtering

by Qian Zhang and Taek Lyul Song^*

Department of Electronic Systems Engineering, Hanyang University, Ansan, Gyeonggi-do 15588, Korea

Sensors 2016, 16(9), 1469; https://doi.org/10.3390/s16091469 - 10 Sep 2016

Cited by 27 | Viewed by 6219

Abstract

In this paper, an improved nonlinear Gaussian mixture probability hypothesis density (GM-PHD) filter is proposed to address bearings-only measurements in multi-target tracking. The proposed method, called the Gaussian mixture measurements-probability hypothesis density (GMM-PHD) filter, not only approximates the posterior intensity using a Gaussian [...] Read more.

In this paper, an improved nonlinear Gaussian mixture probability hypothesis density (GM-PHD) filter is proposed to address bearings-only measurements in multi-target tracking. The proposed method, called the Gaussian mixture measurements-probability hypothesis density (GMM-PHD) filter, not only approximates the posterior intensity using a Gaussian mixture, but also models the likelihood function with a Gaussian mixture instead of a single Gaussian distribution. Besides, the target birth model of the GMM-PHD filter is assumed to be partially uniform instead of a Gaussian mixture. Simulation results show that the proposed filter outperforms the GM-PHD filter embedded with the extended Kalman filter (EKF) and the unscented Kalman filter (UKF). Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 8366 KiB

Open AccessArticle

Real-Time Deflection Monitoring for Milling of a Thin-Walled Workpiece by Using PVDF Thin-Film Sensors with a Cantilevered Beam as a Case Study

by Ming Luo^*

, Dongsheng Liu and Huan Luo

Key Laboratory of Contemporary Design and Integrated Manufacturing Technology, Ministry of Education, Northwestern Polytechnical University, Xi’an 710072, China

Sensors 2016, 16(9), 1470; https://doi.org/10.3390/s16091470 - 10 Sep 2016

Cited by 26 | Viewed by 10090

Abstract

Thin-walled workpieces, such as aero-engine blisks and casings, are usually made of hard-to-cut materials. The wall thickness is very small and it is easy to deflect during milling process under dynamic cutting forces, leading to inaccurate workpiece dimensions and poor surface integrity. To [...] Read more.

Thin-walled workpieces, such as aero-engine blisks and casings, are usually made of hard-to-cut materials. The wall thickness is very small and it is easy to deflect during milling process under dynamic cutting forces, leading to inaccurate workpiece dimensions and poor surface integrity. To understand the workpiece deflection behavior in a machining process, a new real-time nonintrusive method for deflection monitoring is presented, and a detailed analysis of workpiece deflection for different machining stages of the whole machining process is discussed. The thin-film polyvinylidene fluoride (PVDF) sensor is attached to the non-machining surface of the workpiece to copy the deflection excited by the dynamic cutting force. The relationship between the input deflection and the output voltage of the monitoring system is calibrated by testing. Monitored workpiece deflection results show that the workpiece experiences obvious vibration during the cutter entering the workpiece stage, and vibration during the machining process can be easily tracked by monitoring the deflection of the workpiece. During the cutter exiting the workpiece stage, the workpiece experiences forced vibration firstly, and free vibration exists until the amplitude reduces to zero after the cutter exits the workpiece. Machining results confirmed the suitability of the deflection monitoring system for machining thin-walled workpieces with the application of PVDF sensors. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 4382 KiB

Open AccessArticle

A Novel Slope Method for Measurement of Fluid Density with a Micro-cantilever under Flexural and Torsional Vibrations

by Libo Zhao^1,*, Yingjie Hu¹, Rahman Hebibul², Jianjun Ding¹, Tongdong Wang¹, Tingzhong Xu¹, Xixiang Liu¹, Yulong Zhao¹ and Zhuangde Jiang¹

¹ State Key Laboratory for Manufacturing Systems Engineering, Collaborative Innovation Center of Suzhou Nano Science and Technology, Xi’an Jiaotong University, Xi’an 710049, China

² School of Automotive, Mechanical and Electrical Engineering, Xinjiang Vocational & Technical College of Communications, Urumqi 831401, China

Sensors 2016, 16(9), 1471; https://doi.org/10.3390/s16091471 - 11 Sep 2016

Cited by 7 | Viewed by 6548

Abstract

A novel method, which was called a slope method, has been proposed to measure fluid density by the micro-cantilever sensing chip. The theoretical formulas of the slope method were discussed and established when the micro-cantilever sensing chip was under flexural and torsional vibrations. [...] Read more.

A novel method, which was called a slope method, has been proposed to measure fluid density by the micro-cantilever sensing chip. The theoretical formulas of the slope method were discussed and established when the micro-cantilever sensing chip was under flexural and torsional vibrations. The slope was calculated based on the fitted curve between the excitation and output voltages of sensing chip under the nonresonant status. This measuring method need not sweep frequency to find the accurate resonant frequency. Therefore, the fluid density was measured easily based on the calculated slope. In addition, the micro-cantilver was drived by double sided excitation and free end excitation to oscillate under flexural and torsional vibrations, respectively. The corresponding experiments were carried out to measure the fluid density by the slope method. The measurement results were also analyzed when the sensing chip was under flexural and torsional nonresonant vibrations separately. The measurement accuracies under these vibrations were all better than 1.5%, and the density measuring sensitivity under torsional nonresonant vibration was about two times higher than that under flexural nonresonant vibration. Full article

(This article belongs to the Special Issue Resonator Sensors)

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15 pages, 2403 KiB

Open AccessArticle

Performance Analysis of Amplify-and-Forward Systems with Single Relay Selection in Correlated Environments

by Binh Van Nguyen¹

and Kiseon Kim^2,*

¹ Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 61005, Korea

² School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, Gwangju 61005, Korea

Sensors 2016, 16(9), 1472; https://doi.org/10.3390/s16091472 - 11 Sep 2016

Cited by 11 | Viewed by 5063

Abstract

In this paper, we consider amplify-and-forward (AnF) cooperative systems under correlated fading environments. We first present a brief overview of existing works on the effect of channel correlations on the system performance. We then focus on our main contribution which is analyzing the [...] Read more.

In this paper, we consider amplify-and-forward (AnF) cooperative systems under correlated fading environments. We first present a brief overview of existing works on the effect of channel correlations on the system performance. We then focus on our main contribution which is analyzing the outage probability of a multi-AnF-relay system with the best relay selection (BRS) scheme under a condition that two channels of each relay, source-relay and relay-destination channels, are correlated. Using lower and upper bounds on the end-to-end received signal-to-noise ratio (SNR) at the destination, we derive corresponding upper and lower bounds on the system outage probability. We prove that the system can achieve a diversity order (DO) equal to the number of relays. In addition, and importantly, we show that the considered correlation form has a constructive effect on the system performance. In other words, the larger the correlation coefficient, the better system performance. Our analytic results are corroborated by extensive Monte-Carlo simulations. Full article

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7 pages, 2691 KiB

Open AccessArticle

Orientation-Dependent Displacement Sensor Using an Inner Cladding Fiber Bragg Grating

by Tingting Yang

, Xueguang Qiao^*, Qiangzhou Rong^* and Weijia Bao

Physics Department, Northwest University, Xi’an 710069, China

Sensors 2016, 16(9), 1473; https://doi.org/10.3390/s16091473 - 11 Sep 2016

Cited by 19 | Viewed by 5175

Abstract

An orientation-dependent displacement sensor based on grating inscription over a fiber core and inner cladding has been demonstrated. The device comprises a short piece of multi-cladding fiber sandwiched between two standard single-mode fibers (SMFs). The grating structure is fabricated by a femtosecond laser [...] Read more.

An orientation-dependent displacement sensor based on grating inscription over a fiber core and inner cladding has been demonstrated. The device comprises a short piece of multi-cladding fiber sandwiched between two standard single-mode fibers (SMFs). The grating structure is fabricated by a femtosecond laser side-illumination technique. Two well-defined resonances are achieved by the downstream both core and cladding fiber Bragg gratings (FBGs). The cladding resonance presents fiber bending dependence, together with a strong orientation dependence because of asymmetrical distribution of the “cladding” FBG along the fiber cross-section. Full article

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12 pages, 4056 KiB

Open AccessArticle

A Microflow Cytometer with a Rectangular Quasi-Flat-Top Laser Spot

by Jingjing Zhao^1,2,3 and Zheng You^1,2,3,*

¹ State Key Laboratory of Precision Measurement Technology and Instrument, Tsinghua University, Beijing 100084, China

² Department of Precision Instrument, Tsinghua University, Beijing 100084, China

³ Beijing Laboratory for Biomedical Detection Technology and Instrument, Tsinghua University, Beijing 100084, China

Sensors 2016, 16(9), 1474; https://doi.org/10.3390/s16091474 - 11 Sep 2016

Cited by 19 | Viewed by 6607

Abstract

This work develops a microflow cytometer, based on a microfluidic chip for three-dimensional (3D) hydrodynamic focusing and a binary optical element (BOE) for shaping and homogenizing a laser beam. The microfluidic chip utilizes sheath flows to confine the sample flow along the channel [...] Read more.

This work develops a microflow cytometer, based on a microfluidic chip for three-dimensional (3D) hydrodynamic focusing and a binary optical element (BOE) for shaping and homogenizing a laser beam. The microfluidic chip utilizes sheath flows to confine the sample flow along the channel centerline with a narrow cross section. In addition to hydrodynamic focusing, secondary flows are generated to strengthen the focusing in the vertical direction. In experiments, the chip was able to focus the sample flow with cross sections of 15 μm high and 8–30 μm wide at 5 m/s, under the condition of the sample flow rates between 10 and 120 μL/min. Instead of using the conventional elliptical Gaussian spot for optical detection, we used a specially designed BOE and obtained a 50 μm × 10 μm rectangular quasi-flat-top spot. The microflow cytometer combining the chip and the BOE was tested to count 3, 5, and 7 μm fluorescence microbeads, and the experimental results were comparable to or better than those derived from two commercial instruments. Full article

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22 pages, 2875 KiB

Open AccessArticle

Cooperative Game-Based Energy Efficiency Management over Ultra-Dense Wireless Cellular Networks

by Ming Li^1,*

, Pengpeng Chen¹ and Shouwan Gao^1,2

¹ School of Computer Science and Technology, China University of Mining and Technology, Xuzhou 221116, China

² Key Laboratory of Gas and Fire Control for Coal Mines, China University of Mining and Technology, Xuzhou 221116, China

Sensors 2016, 16(9), 1475; https://doi.org/10.3390/s16091475 - 13 Sep 2016

Cited by 7 | Viewed by 5882

Abstract

Ultra-dense wireless cellular networks have been envisioned as a promising technique for handling the explosive increase of wireless traffic volume. With the extensive deployment of small cells in wireless cellular networks, the network spectral efficiency (SE) is improved with the use of limited [...] Read more.

Ultra-dense wireless cellular networks have been envisioned as a promising technique for handling the explosive increase of wireless traffic volume. With the extensive deployment of small cells in wireless cellular networks, the network spectral efficiency (SE) is improved with the use of limited frequency. However, the mutual inter-tier and intra-tier interference between or among small cells and macro cells becomes serious. On the other hand, more chances for potential cooperation among different cells are introduced. Energy efficiency (EE) has become one of the most important problems for future wireless networks. This paper proposes a cooperative bargaining game-based method for comprehensive EE management in an ultra-dense wireless cellular network, which highlights the complicated interference influence on energy-saving challenges and the power-coordination process among small cells and macro cells. Especially, a unified EE utility with the consideration of the interference mitigation is proposed to jointly address the SE, the deployment efficiency (DE), and the EE. In particular, closed-form power-coordination solutions for the optimal EE are derived to show the convergence property of the algorithm. Moreover, a simplified algorithm is presented to reduce the complexity of the signaling overhead, which is significant for ultra-dense small cells. Finally, numerical simulations are provided to illustrate the efficiency of the proposed cooperative bargaining game-based and simplified schemes. Full article

(This article belongs to the Section Sensor Networks)

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22 pages, 1062 KiB

Open AccessArticle

Machine-Learning Based Channel Quality and Stability Estimation for Stream-Based Multichannel Wireless Sensor Networks

by Waqas Rehan^1,*

, Stefan Fischer¹

and Maaz Rehan²

¹ Institute of Telematics (ITM), University of Luebeck, 23562 Luebeck, Germany

² COMSATS Institute of Information Technology (CIIT), Quaid Avenue, 47040 Wah Cantt, Pakistan

Sensors 2016, 16(9), 1476; https://doi.org/10.3390/s16091476 - 12 Sep 2016

Cited by 22 | Viewed by 7537

Abstract

Wireless sensor networks (WSNs) have become more and more diversified and are today able to also support high data rate applications, such as multimedia. In this case, per-packet channel handshaking/switching may result in inducing additional overheads, such as energy consumption, delays and, therefore, [...] Read more.

Wireless sensor networks (WSNs) have become more and more diversified and are today able to also support high data rate applications, such as multimedia. In this case, per-packet channel handshaking/switching may result in inducing additional overheads, such as energy consumption, delays and, therefore, data loss. One of the solutions is to perform stream-based channel allocation where channel handshaking is performed once before transmitting the whole data stream. Deciding stream-based channel allocation is more critical in case of multichannel WSNs where channels of different quality/stability are available and the wish for high performance requires sensor nodes to switch to the best among the available channels. In this work, we will focus on devising mechanisms that perform channel quality/stability estimation in order to improve the accommodation of stream-based communication in multichannel wireless sensor networks. For performing channel quality assessment, we have formulated a composite metric, which we call channel rank measurement (CRM), that can demarcate channels into good, intermediate and bad quality on the basis of the standard deviation of the received signal strength indicator (RSSI) and the average of the link quality indicator (LQI) of the received packets. CRM is then used to generate a data set for training a supervised machine learning-based algorithm (which we call Normal Equation based Channel quality prediction (NEC) algorithm) in such a way that it may perform instantaneous channel rank estimation of any channel. Subsequently, two robust extensions of the NEC algorithm are proposed (which we call Normal Equation based Weighted Moving Average Channel quality prediction (NEWMAC) algorithm and Normal Equation based Aggregate Maturity Criteria with Beta Tracking based Channel weight prediction (NEAMCBTC) algorithm), that can perform channel quality estimation on the basis of both current and past values of channel rank estimation. In the end, simulations are made using MATLAB, and the results show that the Extended version of NEAMCBTC algorithm (Ext-NEAMCBTC) outperforms the compared techniques in terms of channel quality and stability assessment. It also minimizes channel switching overheads (in terms of switching delays and energy consumption) for accommodating stream-based communication in multichannel WSNs. Full article

(This article belongs to the Section Sensor Networks)

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23 pages, 1150 KiB

Open AccessArticle

Ambient Sound-Based Collaborative Localization of Indeterministic Devices

by Jacob Kamminga^1,2,*

, Duc Le¹

and Paul Havinga¹

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

² ASTRON, Dwingeloo 7991 PD, The Netherlands

Sensors 2016, 16(9), 1478; https://doi.org/10.3390/s16091478 - 14 Sep 2016

Cited by 2 | Viewed by 4798

Abstract

Localization is essential in wireless sensor networks. To our knowledge, no prior work has utilized low-cost devices for collaborative localization based on only ambient sound, without the support of local infrastructure. The reason may be the fact that most low-cost devices are indeterministic [...] Read more.

Localization is essential in wireless sensor networks. To our knowledge, no prior work has utilized low-cost devices for collaborative localization based on only ambient sound, without the support of local infrastructure. The reason may be the fact that most low-cost devices are indeterministic and suffer from uncertain input latencies. This uncertainty makes accurate localization challenging. Therefore, we present a collaborative localization algorithm (Cooperative Localization on Android with ambient Sound Sources (CLASS)) that simultaneously localizes the position of indeterministic devices and ambient sound sources without local infrastructure. The CLASS algorithm deals with the uncertainty by splitting the devices into subsets so that outliers can be removed from the time difference of arrival values and localization results. Since Android is indeterministic, we select Android devices to evaluate our approach. The algorithm is evaluated with an outdoor experiment and achieves a mean Root Mean Square Error (RMSE) of 2.18 m with a standard deviation of 0.22 m. Estimated directions towards the sound sources have a mean RMSE of

17.5

° and a standard deviation of

2.3

°. These results show that it is feasible to simultaneously achieve a relative positioning of both devices and sound sources with sufficient accuracy, even when using non-deterministic devices and platforms, such as Android. Full article

(This article belongs to the Special Issue Scalable Localization in Wireless Sensor Networks)

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21 pages, 5066 KiB

Open AccessArticle

Mechatronic Development and Vision Feedback Control of a Nanorobotics Manipulation System inside SEM for Nanodevice Assembly

by Zhan Yang^1,2

, Yaqiong Wang¹, Bin Yang³, Guanghui Li¹, Tao Chen^1,2,*, Masahiro Nakajima⁴, Lining Sun^1,2 and Toshio Fukuda^4,5

¹ Jiangsu Key Laboratory for Advanced Robotics, Soochow University, Suzhou 215123, China

² Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, China

³ School of Mechatronic Engineering and Automation, Shanghai University, Shanghai 200072, China

⁴ Department of Micro-Nano Systems Engineering, Nagoya University, Nagoya 464-8603, Japan

⁵ Intelligent Robotics Institute, School of Mechatronic Engineering, Beijing Institute of Technology, Beijing 100081, China

Sensors 2016, 16(9), 1479; https://doi.org/10.3390/s16091479 - 14 Sep 2016

Cited by 15 | Viewed by 8307

Abstract

Carbon nanotubes (CNT) have been developed in recent decades for nanodevices such as nanoradios, nanogenerators, carbon nanotube field effect transistors (CNTFETs) and so on, indicating that the application of CNTs for nanoscale electronics may play a key role in the development of nanotechnology. [...] Read more.

Carbon nanotubes (CNT) have been developed in recent decades for nanodevices such as nanoradios, nanogenerators, carbon nanotube field effect transistors (CNTFETs) and so on, indicating that the application of CNTs for nanoscale electronics may play a key role in the development of nanotechnology. Nanorobotics manipulation systems are a promising method for nanodevice construction and assembly. For the purpose of constructing three-dimensional CNTFETs, a nanorobotics manipulation system with 16 DOFs was developed for nanomanipulation of nanometer-scale objects inside the specimen chamber of a scanning electron microscope (SEM). Nanorobotics manipulators are assembled into four units with four DOFs (X-Y-Z-θ) individually. The rotational one is actuated by a picomotor. That means a manipulator has four DOFs including three linear motions in the X, Y, Z directions and a 360-degree rotational one (X-Y-Z-θ stage, θ is along the direction rotating with X or Y axis). Manipulators are actuated by picomotors with better than 30 nm linear resolution and <1 micro-rad rotary resolution. Four vertically installed AFM cantilevers (the axis of the cantilever tip is vertical to the axis of electronic beam of SEM) served as the end-effectors to facilitate the real-time observation of the operations. A series of kinematic derivations of these four manipulators based on the Denavit-Hartenberg (D-H) notation were established. The common working space of the end-effectors is 2.78 mm by 4.39 mm by 6 mm. The manipulation strategy and vision feedback control for multi-manipulators operating inside the SEM chamber were been discussed. Finally, application of the designed nanorobotics manipulation system by successfully testing of the pickup-and-place manipulation of an individual CNT onto four probes was described. The experimental results have shown that carbon nanotubes can be successfully picked up with this nanorobotics manipulation system. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

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25 pages, 18629 KiB

Open AccessArticle

A Precise Visual Method for Narrow Butt Detection in Specular Reflection Workpiece Welding

by Jinle Zeng

, Baohua Chang

, Dong Du^*, Yuxiang Hong

, Shuhe Chang and Yirong Zou

Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Department of Mechanial Engineering, Tsinghua University, Beijing 100084, China

Sensors 2016, 16(9), 1480; https://doi.org/10.3390/s16091480 - 13 Sep 2016

Cited by 27 | Viewed by 6450

Abstract

During the complex path workpiece welding, it is important to keep the welding torch aligned with the groove center using a visual seam detection method, so that the deviation between the torch and the groove can be corrected automatically. However, when detecting the [...] Read more.

During the complex path workpiece welding, it is important to keep the welding torch aligned with the groove center using a visual seam detection method, so that the deviation between the torch and the groove can be corrected automatically. However, when detecting the narrow butt of a specular reflection workpiece, the existing methods may fail because of the extremely small groove width and the poor imaging quality. This paper proposes a novel detection method to solve these issues. We design a uniform surface light source to get high signal-to-noise ratio images against the specular reflection effect, and a double-line laser light source is used to obtain the workpiece surface equation relative to the torch. Two light sources are switched on alternately and the camera is synchronized to capture images when each light is on; then the position and pose between the torch and the groove can be obtained nearly at the same time. Experimental results show that our method can detect the groove effectively and efficiently during the welding process. The image resolution is 12.5 μm and the processing time is less than 10 ms per frame. This indicates our method can be applied to real-time narrow butt detection during high-speed welding process. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 4100 KiB

Open AccessArticle

Weak Fault Feature Extraction of Rolling Bearings Based on an Improved Kurtogram

by Xianglong Chen^1,*, Fuzhou Feng¹ and Bingzhi Zhang²

¹ Department of Mechanical Engineering, Academy of Armored Forces Engineering, Beijing 100072, China

² Beijing Special Vehicle Research Institute, Beijing 100072, China

Sensors 2016, 16(9), 1482; https://doi.org/10.3390/s16091482 - 13 Sep 2016

Cited by 39 | Viewed by 5925

Abstract

Kurtograms have been verified to be an efficient tool in bearing fault detection and diagnosis because of their superiority in extracting transient features. However, the short-time Fourier Transform is insufficient in time-frequency analysis and kurtosis is deficient in detecting cyclic transients. Those factors [...] Read more.

Kurtograms have been verified to be an efficient tool in bearing fault detection and diagnosis because of their superiority in extracting transient features. However, the short-time Fourier Transform is insufficient in time-frequency analysis and kurtosis is deficient in detecting cyclic transients. Those factors weaken the performance of the original kurtogram in extracting weak fault features. Correlated Kurtosis (CK) is then designed, as a more effective solution, in detecting cyclic transients. Redundant Second Generation Wavelet Packet Transform (RSGWPT) is deemed to be effective in capturing more detailed local time-frequency description of the signal, and restricting the frequency aliasing components of the analysis results. The authors in this manuscript, combining the CK with the RSGWPT, propose an improved kurtogram to extract weak fault features from bearing vibration signals. The analysis of simulation signals and real application cases demonstrate that the proposed method is relatively more accurate and effective in extracting weak fault features. Full article

(This article belongs to the Section Physical Sensors)

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26 pages, 9627 KiB

Open AccessArticle

Mathematical Model and Calibration Procedure of a PSD Sensor Used in Local Positioning Systems

by David Rodríguez-Navarro^1,*, José Luis Lázaro-Galilea¹

, Ignacio Bravo-Muñoz¹

, Alfredo Gardel-Vicente¹

, Francisco Domingo-Perez¹ and Georgios Tsirigotis²

¹ Department of electronics, University of Alcalá, Alcalá de Henares, Madrid 28801, Spain

² Informatics Engineering Department, Eastern Macedonia and Thrace Institute of Technology, Kvala 65404, Greece

Sensors 2016, 16(9), 1484; https://doi.org/10.3390/s16091484 - 15 Sep 2016

Cited by 24 | Viewed by 9815

Abstract

Here, we propose a mathematical model and a calibration procedure for a PSD (position sensitive device) sensor equipped with an optical system, to enable accurate measurement of the angle of arrival of one or more beams of light emitted by infrared (IR) transmitters [...] Read more.

Here, we propose a mathematical model and a calibration procedure for a PSD (position sensitive device) sensor equipped with an optical system, to enable accurate measurement of the angle of arrival of one or more beams of light emitted by infrared (IR) transmitters located at distances of between 4 and 6 m. To achieve this objective, it was necessary to characterize the intrinsic parameters that model the system and obtain their values. This first approach was based on a pin-hole model, to which system nonlinearities were added, and this was used to model the points obtained with the nA currents provided by the PSD. In addition, we analyzed the main sources of error, including PSD sensor signal noise, gain factor imbalances and PSD sensor distortion. The results indicated that the proposed model and method provided satisfactory calibration and yielded precise parameter values, enabling accurate measurement of the angle of arrival with a low degree of error, as evidenced by the experimental results. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 4701 KiB

Open AccessArticle

Modeling and Analysis of a 2-DOF Spherical Parallel Manipulator

by Xuechao Duan^1,2,*

, Yongzhi Yang¹ and Bi Cheng¹

¹ Key Laboratory of Electronic Equipment Structure Design, Ministry of Education of China, Xidian University, Xi’an 710126, China

² Collaborative Innovation Center of Information Sensing and Understanding, Xidian University, Xi’an 710126, China

Sensors 2016, 16(9), 1485; https://doi.org/10.3390/s16091485 - 13 Sep 2016

Cited by 24 | Viewed by 12809

Abstract

The kinematics of a two rotational degrees-of-freedom (DOF) spherical parallel manipulator (SPM) is developed based on the coordinate transformation approach and the cosine rule of a trihedral angle. The angular displacement, angular velocity, and angular acceleration between the actuators and end-effector are thus [...] Read more.

The kinematics of a two rotational degrees-of-freedom (DOF) spherical parallel manipulator (SPM) is developed based on the coordinate transformation approach and the cosine rule of a trihedral angle. The angular displacement, angular velocity, and angular acceleration between the actuators and end-effector are thus determined. Moreover, the dynamic model of the 2-DOF SPM is established by using the virtual work principle and the first-order influence coefficient matrix of the manipulator. Eventually, a typical motion plan and simulations are carried out, and the actuating torque needed for these motions are worked out by employing the derived inverse dynamic equations. In addition, an analysis of the mechanical characteristics of the parallel manipulator is made. This study lays a solid base for the control of the 2-DOF SPM, and also provides the possibility of using this kind of spherical manipulator as a 2-DOF orientation, angular velocity, or even torque sensor. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

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20 pages, 4154 KiB

Open AccessArticle

Automated As-Built Model Generation of Subway Tunnels from Mobile LiDAR Data

by Mostafa Arastounia

Department of Geomatics Engineering, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada

Sensors 2016, 16(9), 1486; https://doi.org/10.3390/s16091486 - 13 Sep 2016

Cited by 31 | Viewed by 8049

Abstract

This study proposes fully-automated methods for as-built model generation of subway tunnels employing mobile Light Detection and Ranging (LiDAR) data. The employed dataset is acquired by a Velodyne HDL 32E and covers 155 m of a subway tunnel containing six million points. First, [...] Read more.

This study proposes fully-automated methods for as-built model generation of subway tunnels employing mobile Light Detection and Ranging (LiDAR) data. The employed dataset is acquired by a Velodyne HDL 32E and covers 155 m of a subway tunnel containing six million points. First, the tunnel’s main axis and cross sections are extracted. Next, a preliminary model is created by fitting an ellipse to each extracted cross section. The model is refined by employing residual analysis and Baarda’s data snooping method to eliminate outliers. The final model is then generated by applying least squares adjustment to outlier-free data. The obtained results indicate that the tunnel’s main axis and 1551 cross sections at 0.1 m intervals are successfully extracted. Cross sections have an average semi-major axis of 7.8508 m with a standard deviation of 0.2 mm and semi-minor axis of 7.7509 m with a standard deviation of 0.1 mm. The average normal distance of points from the constructed model (average absolute error) is also 0.012 m. The developed algorithm is applicable to tunnels with any horizontal orientation and degree of curvature since it makes no assumptions, nor does it use any a priori knowledge regarding the tunnel’s curvature and horizontal orientation. Full article

(This article belongs to the Special Issue Urban Remote Sensing: Monitoring, Synthesis and Modeling in the Urban Environment)

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24 pages, 1939 KiB

Open AccessReview

A Guide to Fluorescent Protein FRET Pairs

by Bryce T. Bajar^1,†, Emily S. Wang^2,†, Shu Zhang³, Michael Z. Lin⁴ and Jun Chu^3,*

¹ Medical Scientist Training Program, University of California, Los Angeles, CA 90095, USA

² Harvard College, Cambridge, MA 02138, USA

³ Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China

⁴ Departments of Bioengineering and Neurobiology, Stanford University, CA 94305, USA

Sensors 2016, 16(9), 1488; https://doi.org/10.3390/s16091488 - 14 Sep 2016

Cited by 358 | Viewed by 43602

Abstract

Förster or fluorescence resonance energy transfer (FRET) technology and genetically encoded FRET biosensors provide a powerful tool for visualizing signaling molecules in live cells with high spatiotemporal resolution. Fluorescent proteins (FPs) are most commonly used as both donor and acceptor fluorophores in FRET [...] Read more.

Förster or fluorescence resonance energy transfer (FRET) technology and genetically encoded FRET biosensors provide a powerful tool for visualizing signaling molecules in live cells with high spatiotemporal resolution. Fluorescent proteins (FPs) are most commonly used as both donor and acceptor fluorophores in FRET biosensors, especially since FPs are genetically encodable and live-cell compatible. In this review, we will provide an overview of methods to measure FRET changes in biological contexts, discuss the palette of FP FRET pairs developed and their relative strengths and weaknesses, and note important factors to consider when using FPs for FRET studies. Full article

(This article belongs to the Special Issue FRET Biosensors)

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13 pages, 2961 KiB

Open AccessArticle

A Microchip for Integrated Single-Cell Gene Expression Profiling and Genotoxicity Detection

by Hui Dong and Hao Sun^*

School of Mechanical Engineering and Automation, Fuzhou University, Fujian 350116, China

Sensors 2016, 16(9), 1489; https://doi.org/10.3390/s16091489 - 14 Sep 2016

Cited by 6 | Viewed by 7124

Abstract

Microfluidics-based single-cell study is an emerging approach in personalized treatment or precision medicine studies. Single-cell gene expression holds a potential to provide treatment selections with maximized efficacy to help cancer patients based on a genetic understanding of their disease. This work presents a [...] Read more.

Microfluidics-based single-cell study is an emerging approach in personalized treatment or precision medicine studies. Single-cell gene expression holds a potential to provide treatment selections with maximized efficacy to help cancer patients based on a genetic understanding of their disease. This work presents a multi-layer microchip for single-cell multiplexed gene expression profiling and genotoxicity detection. Treated by three drug reagents (i.e., methyl methanesulfonate, docetaxel and colchicine) with varied concentrations and time lengths, individual human cancer cells (MDA-MB-231) are lysed on-chip, and the released mRNA templates are captured and reversely transcribed into single strand DNA. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), cyclin-dependent kinase inhibitor 1A (CDKN1A), and aurora kinase A (AURKA) genes from single cells are amplified and real-time quantified through multiplex polymerase chain reaction. The microchip is capable of integrating all steps of single-cell multiplexed gene expression profiling, and providing precision detection of drug induced genotoxic stress. Throughput has been set to be 18, and can be further increased following the same approach. Numerical simulation of on-chip single cell trapping and heat transfer has been employed to evaluate the chip design and operation. Full article

(This article belongs to the Special Issue Biomicrofluidics)

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23 pages, 16118 KiB

Open AccessArticle

Design and Experimental Validation of a USBL Underwater Acoustic Positioning System

by Joel Reis^1,2,*, Marco Morgado², Pedro Batista², Paulo Oliveira^2,3

and Carlos Silvestre^1,2,†

¹ Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macao, China

² Institute for Systems and Robotics, Instituto Superior Técnico, Universidade de Lisboa, Lisboa 1049-001, Portugal

³ LAETA—Associated Laboratory for Energy, Transports and Aeronautics, IDMEC—Institute of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Lisboa 1049-001, Portugal

Sensors 2016, 16(9), 1491; https://doi.org/10.3390/s16091491 - 14 Sep 2016

Cited by 43 | Viewed by 12718

Abstract

This paper presents the steps for developing a low-cost POrtableNavigation Tool for Underwater Scenarios (PONTUS) to be used as a localization device for subsea targets. PONTUS consists of an integrated ultra-short baseline acoustic positioning system aided by an inertial navigation system. Built on [...] Read more.

This paper presents the steps for developing a low-cost POrtableNavigation Tool for Underwater Scenarios (PONTUS) to be used as a localization device for subsea targets. PONTUS consists of an integrated ultra-short baseline acoustic positioning system aided by an inertial navigation system. Built on a practical design, it can be mounted on an underwater robotic vehicle or be operated by a scuba diver. It also features a graphical user interface that provides information on the tracking of the designated target, in addition to some details on the physical properties inside PONTUS. A full disclosure of the architecture of the tool is first presented, followed by thorough technical descriptions of the hardware components ensemble and the software development process. A series of experiments was carried out to validate the developed prototype, and the results are presented herein, which allow assessing its overall performance. Full article

(This article belongs to the Special Issue Sensing Technologies for Autonomy and Cooperation in Underwater Networked Robot Systems)

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21 pages, 3931 KiB

Open AccessArticle

Pose Self-Calibration of Stereo Vision Systems for Autonomous Vehicle Applications

by Basam Musleh^*

, David Martín

, José María Armingol and Arturo De la Escalera

Intelligent Systems Laboratory, Universidad Carlos III de Madrid/Avda de la Universidad 30, Leganés, Madrid 28911, Spain

Sensors 2016, 16(9), 1492; https://doi.org/10.3390/s16091492 - 14 Sep 2016

Cited by 6 | Viewed by 7386

Abstract

Nowadays, intelligent systems applied to vehicles have grown very rapidly; their goal is not only the improvement of safety, but also making autonomous driving possible. Many of these intelligent systems are based on making use of computer vision in order to know the [...] Read more.

Nowadays, intelligent systems applied to vehicles have grown very rapidly; their goal is not only the improvement of safety, but also making autonomous driving possible. Many of these intelligent systems are based on making use of computer vision in order to know the environment and act accordingly. It is of great importance to be able to estimate the pose of the vision system because the measurement matching between the perception system (pixels) and the vehicle environment (meters) depends on the relative position between the perception system and the environment. A new method of camera pose estimation for stereo systems is presented in this paper, whose main contribution regarding the state of the art on the subject is the estimation of the pitch angle without being affected by the roll angle. The validation of the self-calibration method is accomplished by comparing it with relevant methods of camera pose estimation, where a synthetic sequence is used in order to measure the continuous error with a ground truth. This validation is enriched by the experimental results of the method in real traffic environments. Full article

(This article belongs to the Special Issue Sensors for Autonomous Road Vehicles)

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10 pages, 10042 KiB

Open AccessArticle

Long-Term Continuous Double Station Observation of Faint Meteor Showers

by Stanislav Vítek^1,*

, Petr Páta¹

, Pavel Koten² and Karel Fliegel¹

¹ Faculty of Electrical Engineering, Czech Technical University in Prague, Technická 2, 166 27 Prague, Czech Republic

² Astronomical Institute of the Academy of Sciences of the Czech Republic, Fričova 298, 251 65 Ondřejov, Czech Republic

Sensors 2016, 16(9), 1493; https://doi.org/10.3390/s16091493 - 14 Sep 2016

Cited by 6 | Viewed by 5413

Abstract

Meteor detection and analysis is an essential topic in the field of astronomy. In this paper, a high-sensitivity and high-time-resolution imaging device for the detection of faint meteoric events is presented. The instrument is based on a fast CCD camera and an image [...] Read more.

Meteor detection and analysis is an essential topic in the field of astronomy. In this paper, a high-sensitivity and high-time-resolution imaging device for the detection of faint meteoric events is presented. The instrument is based on a fast CCD camera and an image intensifier. Two such instruments form a double-station observation network. The MAIA (Meteor Automatic Imager and Analyzer) system has been in continuous operation since 2013 and has successfully captured hundreds of meteors belonging to different meteor showers, as well as sporadic meteors. A data processing pipeline for the efficient processing and evaluation of the massive amount of video sequences is also introduced in this paper. Full article

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

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10 pages, 2137 KiB

Open AccessArticle

Fast and Robust Real-Time Estimation of Respiratory Rate from Photoplethysmography

by Hodam Kim

, Jeong-Youn Kim and Chang-Hwan Im^*

Department of Biomedical Engineering, Hanyang University, Seoul 04763, Korea

Sensors 2016, 16(9), 1494; https://doi.org/10.3390/s16091494 - 14 Sep 2016

Cited by 21 | Viewed by 7092

Abstract

Respiratory rate (RR) is a useful vital sign that can not only provide auxiliary information on physiological changes within the human body, but also indicate early symptoms of various diseases. Recently, methods for the estimation of RR from photoplethysmography (PPG) have attracted increased [...] Read more.

Respiratory rate (RR) is a useful vital sign that can not only provide auxiliary information on physiological changes within the human body, but also indicate early symptoms of various diseases. Recently, methods for the estimation of RR from photoplethysmography (PPG) have attracted increased interest, because PPG can be readily recorded using wearable sensors such as smart watches and smart bands. In the present study, we propose a new method for the fast and robust real-time estimation of RR using an adaptive infinite impulse response (IIR) notch filter, which has not yet been applied to the PPG-based estimation of RR. In our offline simulation study, the performance of the proposed method was compared to that of recently developed RR estimation methods called an adaptive lattice-type RR estimator and a Smart Fusion. The results of the simulation study show that the proposed method could not only estimate RR more quickly and more accurately than the conventional methods, but also is most suitable for online RR monitoring systems, as it does not use any overlapping moving windows that require increased computational costs. In order to demonstrate the practical applicability of the proposed method, an online RR estimation system was implemented. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 9407 KiB

Open AccessArticle

Surface Subsidence Analysis by Multi-Temporal InSAR and GRACE: A Case Study in Beijing

by Jiming Guo^1,2,3

, Lv Zhou^1,2,3,*, Chaolong Yao^1,3 and Jiyuan Hu¹

¹ School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China

² Key Laboratory of Precise Engineering and Industry Surveying of National Administration of Surveying, Mapping and Geoinformation, Wuhan University, Wuhan 430079, China

³ Guangxi Key Laboratory of Spatial Information and Geomatics, Guilin University of Technology, Guilin 541004, China

Sensors 2016, 16(9), 1495; https://doi.org/10.3390/s16091495 - 14 Sep 2016

Cited by 49 | Viewed by 7293

Abstract

The aim of this study was to investigate the relationship between surface subsidence and groundwater changes. To investigate this relationship, we first analyzed surface subsidence. This paper presents the results of a case study of surface subsidence in Beijing from 1 August 2007 [...] Read more.

The aim of this study was to investigate the relationship between surface subsidence and groundwater changes. To investigate this relationship, we first analyzed surface subsidence. This paper presents the results of a case study of surface subsidence in Beijing from 1 August 2007 to 29 September 2010. The Multi-temporal Interferometric Synthetic Aperture Radar (multi-temporal InSAR) technique, which can simultaneously detect point-like stable reflectors (PSs) and distributed scatterers (DSs), was used to retrieve the subsidence magnitude and distribution in Beijing using 18 ENVISAT ASAR images. The multi-temporal InSAR-derived subsidence was verified by leveling at an accuracy better than 5 mm/year. Based on the verified multi-temporal InSAR results, a prominent uneven subsidence was identified in Beijing. Specifically, most of the subsidence velocities in the downtown area were within 10 mm/year, and the largest subsidence was detected in Tongzhou, with velocities exceeding 140 mm/year. Furthermore, Gravity Recovery and Climate Experiment (GRACE) data were used to derive the groundwater change series and trend. By comparison with the multi-temporal InSAR-derived subsidence results, the long-term decreasing trend between groundwater changes and surface subsidence showed a relatively high consistency, and a significant impact of groundwater changes on the surface subsidence was identified. Additionally, the spatial distribution of the subsidence funnel was partially consistent with that of groundwater depression, i.e., the former possessed a wider range than the latter. Finally, the relationship between surface subsidence and groundwater changes was determined. Full article

(This article belongs to the Special Issue Synthetic Aperture Radars: Models, Algorithms, Techniques and Tools for Data Exploitation)

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17 pages, 2554 KiB

Open AccessArticle

A Novel 2-D Coherent DOA Estimation Method Based on Dimension Reduction Sparse Reconstruction for Orthogonal Arrays

by Xiuhong Wang^1,2, Xingpeng Mao^1,4,*

, Yiming Wang^1,3

, Naitong Zhang^1,4 and Bo Li²

¹ School of Electronics and Information Engineering, Harbin Institute of Technology, Harbin 150001, China

² School of Information and Electrical Engineering, Harbin Institute of Technology (Weihai), Weihai 264209, China

³ First Institute of Oceanography, SOA, Qingdao 266061, China

⁴ Collaborative Innovation Center of Information Sensing and Understanding at Harbin Institute of Technology, Harbin 150001, China

Sensors 2016, 16(9), 1496; https://doi.org/10.3390/s16091496 - 15 Sep 2016

Cited by 8 | Viewed by 5281

Abstract

Based on sparse representations, the problem of two-dimensional (2-D) direction of arrival (DOA) estimation is addressed in this paper. A novel sparse 2-D DOA estimation method, called Dimension Reduction Sparse Reconstruction (DRSR), is proposed with pairing by Spatial Spectrum Reconstruction of Sub-Dictionary (SSRSD). [...] Read more.

Based on sparse representations, the problem of two-dimensional (2-D) direction of arrival (DOA) estimation is addressed in this paper. A novel sparse 2-D DOA estimation method, called Dimension Reduction Sparse Reconstruction (DRSR), is proposed with pairing by Spatial Spectrum Reconstruction of Sub-Dictionary (SSRSD). By utilizing the angle decoupling method, which transforms a 2-D estimation into two independent one-dimensional (1-D) estimations, the high computational complexity induced by a large 2-D redundant dictionary is greatly reduced. Furthermore, a new angle matching scheme, SSRSD, which is less sensitive to the sparse reconstruction error with higher pair-matching probability, is introduced. The proposed method can be applied to any type of orthogonal array without requirement of a large number of snapshots and a priori knowledge of the number of signals. The theoretical analyses and simulation results show that the DRSR-SSRSD method performs well for coherent signals, which performance approaches Cramer–Rao bound (CRB), even under a single snapshot and low signal-to-noise ratio (SNR) condition. Full article

(This article belongs to the Section Physical Sensors)

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21 pages, 2387 KiB

Open AccessArticle

A Movement-Assisted Deployment of Collaborating Autonomous Sensors for Indoor and Outdoor Environment Monitoring

by Ewa Niewiadomska-Szynkiewicz^1,2, Andrzej Sikora¹ and Michał Marks^1,*

¹ Research and Academic Computer Network, Warsaw 01-045, Poland

² Institute of Control and Computation Engineering, Warsaw University of Technology, Warsaw 00-665, Poland

Sensors 2016, 16(9), 1497; https://doi.org/10.3390/s16091497 - 14 Sep 2016

Cited by 8 | Viewed by 4968

Abstract

Using mobile robots or unmanned vehicles to assist optimal wireless sensors deployment in a working space can significantly enhance the capability to investigate unknown environments. This paper addresses the issues of the application of numerical optimization and computer simulation techniques to on-line calculation [...] Read more.

Using mobile robots or unmanned vehicles to assist optimal wireless sensors deployment in a working space can significantly enhance the capability to investigate unknown environments. This paper addresses the issues of the application of numerical optimization and computer simulation techniques to on-line calculation of a wireless sensor network topology for monitoring and tracking purposes. We focus on the design of a self-organizing and collaborative mobile network that enables a continuous data transmission to the data sink (base station) and automatically adapts its behavior to changes in the environment to achieve a common goal. The pre-defined and self-configuring approaches to the mobile-based deployment of sensors are compared and discussed. A family of novel algorithms for the optimal placement of mobile wireless devices for permanent monitoring of indoor and outdoor dynamic environments is described. They employ a network connectivity-maintaining mobility model utilizing the concept of the virtual potential function for calculating the motion trajectories of platforms carrying sensors. Their quality and utility have been justified through simulation experiments and are discussed in the final part of the paper. Full article

(This article belongs to the Special Issue Advanced Algorithms for Mobile Sensing: from Wireless Sensor Networks to Mobile Crowd Sensing)

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15 pages, 1021 KiB

Open AccessArticle

Multimodal Learning and Intelligent Prediction of Symptom Development in Individual Parkinson’s Patients

by Andrzej W. Przybyszewski^1,2,*, Mark Kon³, Stanislaw Szlufik⁴, Artur Szymanski¹, Piotr Habela¹ and Dariusz M. Koziorowski⁴

¹ Polish-Japanese Academy of Information Technology, 02-008 Warszawa, Poland

² Department Neurology, University of Massachusetts Medical School, Worcester, MA 01655, USA

³ Mathematics and Statistics, Boston University, Boston, MA 02215, USA

⁴ Neurology, Faculty of Health Science, Medical University of Warsaw, Warszawa 03-242, Poland

Sensors 2016, 16(9), 1498; https://doi.org/10.3390/s16091498 - 14 Sep 2016

Cited by 35 | Viewed by 6128

Abstract

We still do not know how the brain and its computations are affected by nerve cell deaths and their compensatory learning processes, as these develop in neurodegenerative diseases (ND). Compensatory learning processes are ND symptoms usually observed at a point when the disease [...] Read more.

We still do not know how the brain and its computations are affected by nerve cell deaths and their compensatory learning processes, as these develop in neurodegenerative diseases (ND). Compensatory learning processes are ND symptoms usually observed at a point when the disease has already affected large parts of the brain. We can register symptoms of ND such as motor and/or mental disorders (dementias) and even provide symptomatic relief, though the structural effects of these are in most cases not yet understood. It is very important to obtain early diagnosis, which can provide several years in which we can monitor and partly compensate for the disease’s symptoms, with the help of various therapies. In the case of Parkinson’s disease (PD), in addition to classical neurological tests, measurements of eye movements are diagnostic. We have performed measurements of latency, amplitude, and duration in reflexive saccades (RS) of PD patients. We have compared the results of our measurement-based diagnoses with standard neurological ones. The purpose of our work was to classify how condition attributes predict the neurologist’s diagnosis. For n = 10 patients, the patient age and parameters based on RS gave a global accuracy in predictions of neurological symptoms in individual patients of about 80%. Further, by adding three attributes partly related to patient ‘well-being’ scores, our prediction accuracies increased to 90%. Our predictive algorithms use rough set theory, which we have compared with other classifiers such as Naïve Bayes, Decision Trees/Tables, and Random Forests (implemented in KNIME/WEKA). We have demonstrated that RS are powerful biomarkers for assessment of symptom progression in PD. Full article

(This article belongs to the Special Issue Advances in Artificial Intelligence: Selected Papers from MICAI 2013, 2014 and 2015—12th, 13th and 14th Mexican International Conferences on Artificial Intelligence)

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9 pages, 5755 KiB

Open AccessArticle

Fabrication of a Miniaturized ZnO Nanowire Accelerometer and Its Performance Tests

by Hyun Chan Kim

, Sangho Song and Jaehwan Kim^*

Creative Research Center for Nanocellulose Future Composites, Department of Mechanical Engineering, Inha University, 100 Inha-Ro, Nam-Ku, Incheon 22212, Korea

Sensors 2016, 16(9), 1499; https://doi.org/10.3390/s16091499 - 14 Sep 2016

Cited by 16 | Viewed by 7825

Abstract

This paper reports a miniaturized piezoelectric accelerometer suitable for a small haptic actuator array. The accelerometer is made with zinc oxide (ZnO) nanowire (NW) grown on a copper wafer by a hydrothermal process. The size of the accelerometer is 1.5 × 1.5 mm [...] Read more.

This paper reports a miniaturized piezoelectric accelerometer suitable for a small haptic actuator array. The accelerometer is made with zinc oxide (ZnO) nanowire (NW) grown on a copper wafer by a hydrothermal process. The size of the accelerometer is 1.5 × 1.5 mm², thus fitting the 1.8 × 1.8 mm² haptic actuator array cell. The detailed fabrication process of the miniaturized accelerometer is illustrated. Performance evaluation of the fabricated accelerometer is conducted by comparing it with a commercial piezoelectric accelerometer. The output current of the fabricated accelerometer increases linearly with the acceleration. The miniaturized ZnO NW accelerometer is feasible for acceleration measurement of small and lightweight devices. Full article

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

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14 pages, 11052 KiB

Open AccessArticle

Real-Time Measurement of Width and Height of Weld Beads in GMAW Processes

by Jesús Emilio Pinto-Lopera¹

, José Mauricio S. T. Motta² and Sadek Crisostomo Absi Alfaro^2,*

¹ Universidad Católica de Manizales, Facultad de Ingeniería y Arquitectura, Unidad Académica de Ciencias Naturales y Matemáticas, Manizales 170001, Colombia

² Automation and Control Group in Manufacturing Processes—GRACO, Department of Mechanical Engineering, University of Brasilia, Brasilia DF 7191090, Brazil

Sensors 2016, 16(9), 1500; https://doi.org/10.3390/s16091500 - 15 Sep 2016

Cited by 65 | Viewed by 12198

Abstract

Associated to the weld quality, the weld bead geometry is one of the most important parameters in welding processes. It is a significant requirement in a welding project, especially in automatic welding systems where a specific width, height, or penetration of weld bead [...] Read more.

Associated to the weld quality, the weld bead geometry is one of the most important parameters in welding processes. It is a significant requirement in a welding project, especially in automatic welding systems where a specific width, height, or penetration of weld bead is needed. This paper presents a novel technique for real-time measuring of the width and height of weld beads in gas metal arc welding (GMAW) using a single high-speed camera and a long-pass optical filter in a passive vision system. The measuring method is based on digital image processing techniques and the image calibration process is based on projective transformations. The measurement process takes less than 3 milliseconds per image, which allows a transfer rate of more than 300 frames per second. The proposed methodology can be used in any metal transfer mode of a gas metal arc welding process and does not have occlusion problems. The responses of the measurement system, presented here, are in a good agreement with off-line data collected by a common laser-based 3D scanner. Each measurement is compare using a statistical Welch’s t-test of the null hypothesis, which, in any case, does not exceed the threshold of significance level α = 0.01, validating the results and the performance of the proposed vision system. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 1786 KiB

Open AccessArticle

Semantic Framework of Internet of Things for Smart Cities: Case Studies

by Ningyu Zhang

, Huajun Chen^*, Xi Chen and Jiaoyan Chen

Computer Science and Technology Institute, Zhejiang University, Hangzhou 310058, China

Sensors 2016, 16(9), 1501; https://doi.org/10.3390/s16091501 - 14 Sep 2016

Cited by 62 | Viewed by 10984

Abstract

In recent years, the advancement of sensor technology has led to the generation of heterogeneous Internet-of-Things (IoT) data by smart cities. Thus, the development and deployment of various aspects of IoT-based applications are necessary to mine the potential value of data to the [...] Read more.

In recent years, the advancement of sensor technology has led to the generation of heterogeneous Internet-of-Things (IoT) data by smart cities. Thus, the development and deployment of various aspects of IoT-based applications are necessary to mine the potential value of data to the benefit of people and their lives. However, the variety, volume, heterogeneity, and real-time nature of data obtained from smart cities pose considerable challenges. In this paper, we propose a semantic framework that integrates the IoT with machine learning for smart cities. The proposed framework retrieves and models urban data for certain kinds of IoT applications based on semantic and machine-learning technologies. Moreover, we propose two case studies: pollution detection from vehicles and traffic pattern detection. The experimental results show that our system is scalable and capable of accommodating a large number of urban regions with different types of IoT applications. Full article

(This article belongs to the Special Issue Smart City: Vision and Reality)

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12 pages, 3998 KiB

Open AccessArticle

A Self-Powered Insole for Human Motion Recognition

by Yingzhou Han^1,2,3, Yalu Cao^1,2,3, Jingjing Zhao^1,2,3, Yajiang Yin^1,2,3, Liangchen Ye^1,2,3

, Xiaofeng Wang^1,2,3,* and Zheng You^1,2,3,*

¹ Collaborative Innovation Center for Micro/Nano Fabrication, Device and System, Tsinghua University, Beijing 100084, China

² State Key Laboratory of Precision Measurement Technology and Instruments, Tsinghua University, Beijing 100084, China

³ Department of Precision Instrument, Tsinghua University, Beijing 100084, China

Sensors 2016, 16(9), 1502; https://doi.org/10.3390/s16091502 - 15 Sep 2016

Cited by 40 | Viewed by 10276

Abstract

Biomechanical energy harvesting is a feasible solution for powering wearable sensors by directly driving electronics or acting as wearable self-powered sensors. A wearable insole that not only can harvest energy from foot pressure during walking but also can serve as a self-powered human [...] Read more.

Biomechanical energy harvesting is a feasible solution for powering wearable sensors by directly driving electronics or acting as wearable self-powered sensors. A wearable insole that not only can harvest energy from foot pressure during walking but also can serve as a self-powered human motion recognition sensor is reported. The insole is designed as a sandwich structure consisting of two wavy silica gel film separated by a flexible piezoelectric foil stave, which has higher performance compared with conventional piezoelectric harvesters with cantilever structure. The energy harvesting insole is capable of driving some common electronics by scavenging energy from human walking. Moreover, it can be used to recognize human motion as the waveforms it generates change when people are in different locomotion modes. It is demonstrated that different types of human motion such as walking and running are clearly classified by the insole without any external power source. This work not only expands the applications of piezoelectric energy harvesters for wearable power supplies and self-powered sensors, but also provides possible approaches for wearable self-powered human motion monitoring that is of great importance in many fields such as rehabilitation and sports science. Full article

(This article belongs to the Special Issue Wearable Biomedical Sensors)

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20 pages, 8108 KiB

Open AccessArticle

Spiking Cortical Model Based Multimodal Medical Image Fusion by Combining Entropy Information with Weber Local Descriptor

by Xuming Zhang^*

, Jinxia Ren, Zhiwen Huang and Fei Zhu

Department of Biomedical Engineering, School of Life Science and Technology, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074, China

Sensors 2016, 16(9), 1503; https://doi.org/10.3390/s16091503 - 15 Sep 2016

Cited by 5 | Viewed by 6140

Abstract

Multimodal medical image fusion (MIF) plays an important role in clinical diagnosis and therapy. Existing MIF methods tend to introduce artifacts, lead to loss of image details or produce low-contrast fused images. To address these problems, a novel spiking cortical model (SCM) based [...] Read more.

Multimodal medical image fusion (MIF) plays an important role in clinical diagnosis and therapy. Existing MIF methods tend to introduce artifacts, lead to loss of image details or produce low-contrast fused images. To address these problems, a novel spiking cortical model (SCM) based MIF method has been proposed in this paper. The proposed method can generate high-quality fused images using the weighting fusion strategy based on the firing times of the SCM. In the weighting fusion scheme, the weight is determined by combining the entropy information of pulse outputs of the SCM with the Weber local descriptor operating on the firing mapping images produced from the pulse outputs. The extensive experiments on multimodal medical images show that compared with the numerous state-of-the-art MIF methods, the proposed method can preserve image details very well and avoid the introduction of artifacts effectively, and thus it significantly improves the quality of fused images in terms of human vision and objective evaluation criteria such as mutual information, edge preservation index, structural similarity based metric, fusion quality index, fusion similarity metric and standard deviation. Full article

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

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23 pages, 9447 KiB

Open AccessDiscussion

Finite Element Modelling of a Field-Sensed Magnetic Suspended System for Accurate Proximity Measurement Based on a Sensor Fusion Algorithm with Unscented Kalman Filter

by Amor Chowdhury¹ and Andrej Sarjaš^2,*

¹ Margento R&D, Gosposvetska cesta 84, Maribor 2000, Slovenia

² Faculty of Electrical Engineering and Computer Science, University of Maribor, Smetanova 17, Maribor 2000, Slovenia

Sensors 2016, 16(9), 1504; https://doi.org/10.3390/s16091504 - 15 Sep 2016

Cited by 6 | Viewed by 9218

Abstract

The presented paper describes accurate distance measurement for a field-sensed magnetic suspension system. The proximity measurement is based on a Hall effect sensor. The proximity sensor is installed directly on the lower surface of the electro-magnet, which means that it is very sensitive [...] Read more.

The presented paper describes accurate distance measurement for a field-sensed magnetic suspension system. The proximity measurement is based on a Hall effect sensor. The proximity sensor is installed directly on the lower surface of the electro-magnet, which means that it is very sensitive to external magnetic influences and disturbances. External disturbances interfere with the information signal and reduce the usability and reliability of the proximity measurements and, consequently, the whole application operation. A sensor fusion algorithm is deployed for the aforementioned reasons. The sensor fusion algorithm is based on the Unscented Kalman Filter, where a nonlinear dynamic model was derived with the Finite Element Modelling approach. The advantage of such modelling is a more accurate dynamic model parameter estimation, especially in the case when the real structure, materials and dimensions of the real-time application are known. The novelty of the paper is the design of a compact electro-magnetic actuator with a built-in low cost proximity sensor for accurate proximity measurement of the magnetic object. The paper successively presents a modelling procedure with the finite element method, design and parameter settings of a sensor fusion algorithm with Unscented Kalman Filter and, finally, the implementation procedure and results of real-time operation. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 1612 KiB

Open AccessArticle

D-Shaped Polarization Maintaining Fiber Sensor for Strain and Temperature Monitoring

by Hummad Habib Qazi¹, Abu Bakar Mohammad^1,*, Harith Ahmad² and Mohd Zamani Zulkifli²

¹ Faculty of Electrical Engineering, Universiti Teknologi Malaysia, UTM, Skudai, 81310 Johor, Malaysia

² Photonics Research Centre, University of Malaya, 50603 Kuala Lumpur, Malaysia

Sensors 2016, 16(9), 1505; https://doi.org/10.3390/s16091505 - 15 Sep 2016

Cited by 39 | Viewed by 7845

Abstract

A D-shaped polarization-maintaining fiber (PMF) as fiber optic sensor for the simultaneous monitoring of strain and the surrounding temperature is presented. A mechanical end and edge polishing system with aluminum oxide polishing film is utilized to perform sequential polishing on one side (lengthwise) [...] Read more.

A D-shaped polarization-maintaining fiber (PMF) as fiber optic sensor for the simultaneous monitoring of strain and the surrounding temperature is presented. A mechanical end and edge polishing system with aluminum oxide polishing film is utilized to perform sequential polishing on one side (lengthwise) of the PMF in order to fabricate a D-shaped cross-section. Experimental results show that the proposed sensor has high sensitivity of 46 pm/µε and 130 pm/°C for strain and temperature, respectively, which is significantly higher than other recently reported work (mainly from 2013) related to fiber optic sensors. The easy fabrication method, high sensitivity, and good linearity make this sensing device applicable in various applications such as health monitoring and spatial analysis of engineering structures. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 9411 KiB

Open AccessArticle

Decoupling Principle Analysis and Development of a Parallel Three-Dimensional Force Sensor

by Yanzhi Zhao^1,2,*, Leihao Jiao^1,2, Dacheng Weng^1,2, Dan Zhang³ and Rencheng Zheng⁴

¹ Key Laboratory of Parallel Robot and Mechatronic System of Hebei Province, Yanshan University, Qinhuangdao 066004, China

² Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education of China, Yanshan University, Qinhuangdao 066004, China

³ Department of Mechanical Engineering, Lassonde School of Engineering, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada

⁴ Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505, Japan

Sensors 2016, 16(9), 1506; https://doi.org/10.3390/s16091506 - 15 Sep 2016

Cited by 18 | Viewed by 8466

Abstract

In the development of the multi-dimensional force sensor, dimension coupling is the ubiquitous factor restricting the improvement of the measurement accuracy. To effectively reduce the influence of dimension coupling on the parallel multi-dimensional force sensor, a novel parallel three-dimensional force sensor is proposed [...] Read more.

In the development of the multi-dimensional force sensor, dimension coupling is the ubiquitous factor restricting the improvement of the measurement accuracy. To effectively reduce the influence of dimension coupling on the parallel multi-dimensional force sensor, a novel parallel three-dimensional force sensor is proposed using a mechanical decoupling principle, and the influence of the friction on dimension coupling is effectively reduced by making the friction rolling instead of sliding friction. In this paper, the mathematical model is established by combining with the structure model of the parallel three-dimensional force sensor, and the modeling and analysis of mechanical decoupling are carried out. The coupling degree (ε) of the designed sensor is defined and calculated, and the calculation results show that the mechanical decoupling parallel structure of the sensor possesses good decoupling performance. A prototype of the parallel three-dimensional force sensor was developed, and FEM analysis was carried out. The load calibration and data acquisition experiment system are built, and then calibration experiments were done. According to the calibration experiments, the measurement accuracy is less than 2.86% and the coupling accuracy is less than 3.02%. The experimental results show that the sensor system possesses high measuring accuracy, which provides a basis for the applied research of the parallel multi-dimensional force sensor. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

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24 pages, 10424 KiB

Open AccessArticle

The Effect of Assistive Anchor-Like Grousers on Wheeled Rover Performance over Unconsolidated Sandy Dune Inclines

by Ahmad Najmuddin Ibrahim¹, Shinichi Aoshima², Naoji Shiroma² and Yasuhiro Fukuoka^2,*

¹ Graduate School of Science and Engineering, College of Engineering, Ibaraki University, Hitachi 316-8511, Japan

² Department of Intelligent Systems Engineering, College of Engineering, Ibaraki University, Hitachi 316-8511, Japan

Sensors 2016, 16(9), 1507; https://doi.org/10.3390/s16091507 - 15 Sep 2016

Cited by 12 | Viewed by 6680

Abstract

Typical rovers with wheels equipped with conventional grousers are prone to getting stuck in unconsolidated sandy dune inclines as the wheels tend to sink into the sand. This phenomenon is caused by the motion of the grouser through the sand during the latter [...] Read more.

Typical rovers with wheels equipped with conventional grousers are prone to getting stuck in unconsolidated sandy dune inclines as the wheels tend to sink into the sand. This phenomenon is caused by the motion of the grouser through the sand during the latter half of the rotation, in which the grouser pushes the sand from underneath the wheel upwards and towards the backside of the wheel. This creates a space that the wheel can sink into. To minimize sand movement and subsequent sinkage, we propose the concept of using an “assistive grouser”, which is attached to the side of a conventional rover wheel. The assistive grouser is designed to be able to autonomously maintain a uniform angle relative to the rover body independent of the rotation of the wheels. Rotating the wheel causes the assistive grousers to automatically penetrate into the sand slope surface at a constant angle of attack, thereby acting as an anchor and providing traction for the wheel. Maintaining a uniform grouser angle as opposed to a rotating motion also assists in extracting the grouser out of the sand without moving the sand towards the back of the wheel. Moreover, the angle of the assistive grousers is held constantly by a single dedicated motor, meaning that the angle of the assistive grousers can be optimized to provide the least amount of sinkage for each slope angle. The experimental results showed that for slope angles of 0–30 degrees, the rover equipped with the proposed assistive grousers experienced significantly less sinkage and consumed less current compared to the rover equipped with conventional grousers. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

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15 pages, 5824 KiB

Open AccessArticle

A Differential Reflective Intensity Optical Fiber Angular Displacement Sensor

by Binghui Jia^1,2,*, Lei He¹, Guodong Yan¹ and Yong Feng¹

¹ School of Mechanical Engineering, Nanjing Institute of Technology, Nanjing 211167, China

² Key Laboratory of Road Construction Technology and Equipment, Chang’an University, Xi’an 710064, China

Sensors 2016, 16(9), 1508; https://doi.org/10.3390/s16091508 - 16 Sep 2016

Cited by 22 | Viewed by 10004

Abstract

In this paper, a novel differential reflective intensity optical fiber angular displacement sensor was proposed. This sensor can directly measure the angular and axial linear displacement of a flat surface. The structure of the sensor probe is simple and its basic principle was [...] Read more.

In this paper, a novel differential reflective intensity optical fiber angular displacement sensor was proposed. This sensor can directly measure the angular and axial linear displacement of a flat surface. The structure of the sensor probe is simple and its basic principle was first analyzed according to the intensity modulation mechanisms. Secondly, in order to trim the dark output voltage to zero, the photoelectric conversion circuit was developed to adjust the signals. Then, the sensor model including the photoelectric conversion circuit has been established, and the influence of design parameters on the sensor output characteristic has been simulated. Finally, the design parameters of the sensor structure were obtained based on the simulation results; and an experimental test system was built for the sensor calibration. Experimental results show that the linear angular range and the sensitivity of the sensor were 74.4 and 0.051 V/°, respectively. Its change rules confirm the operating principle of the sensor well. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2016)

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22 pages, 1113 KiB

Open AccessArticle

Sensor Data Fusion with Z-Numbers and Its Application in Fault Diagnosis

by Wen Jiang^*

, Chunhe Xie, Miaoyan Zhuang, Yehang Shou and Yongchuan Tang

School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710072, Shanxi, China

Sensors 2016, 16(9), 1509; https://doi.org/10.3390/s16091509 - 15 Sep 2016

Cited by 143 | Viewed by 10213

Abstract

Sensor data fusion technology is widely employed in fault diagnosis. The information in a sensor data fusion system is characterized by not only fuzziness, but also partial reliability. Uncertain information of sensors, including randomness, fuzziness, etc., has been extensively studied recently. However, the [...] Read more.

Sensor data fusion technology is widely employed in fault diagnosis. The information in a sensor data fusion system is characterized by not only fuzziness, but also partial reliability. Uncertain information of sensors, including randomness, fuzziness, etc., has been extensively studied recently. However, the reliability of a sensor is often overlooked or cannot be analyzed adequately. A Z-number, Z = (A, B), can represent the fuzziness and the reliability of information simultaneously, where the first component A represents a fuzzy restriction on the values of uncertain variables and the second component B is a measure of the reliability of A. In order to model and process the uncertainties in a sensor data fusion system reasonably, in this paper, a novel method combining the Z-number and Dempster–Shafer (D-S) evidence theory is proposed, where the Z-number is used to model the fuzziness and reliability of the sensor data and the D-S evidence theory is used to fuse the uncertain information of Z-numbers. The main advantages of the proposed method are that it provides a more robust measure of reliability to the sensor data, and the complementary information of multi-sensors reduces the uncertainty of the fault recognition, thus enhancing the reliability of fault detection. Full article

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

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19 pages, 4240 KiB

Open AccessArticle

Using Crowdsourced Trajectories for Automated OSM Data Entry Approach

by Anahid Basiri^1,*, Pouria Amirian² and Peter Mooney³

¹ The Nottingham Geospatial Institute, The University of Nottingham, Nottingham NG7 2TU, UK

² Ordnance Survey GB, Southampton SO16 0AS, UK

³ Department of Computer Science, Maynooth University, Maynooth W23 F2H6, Ireland

Sensors 2016, 16(9), 1510; https://doi.org/10.3390/s16091510 - 15 Sep 2016

Cited by 23 | Viewed by 9726

Abstract

The concept of crowdsourcing is nowadays extensively used to refer to the collection of data and the generation of information by large groups of users/contributors. OpenStreetMap (OSM) is a very successful example of a crowd-sourced geospatial data project. Unfortunately, it is often the [...] Read more.

The concept of crowdsourcing is nowadays extensively used to refer to the collection of data and the generation of information by large groups of users/contributors. OpenStreetMap (OSM) is a very successful example of a crowd-sourced geospatial data project. Unfortunately, it is often the case that OSM contributor inputs (including geometry and attribute data inserts, deletions and updates) have been found to be inaccurate, incomplete, inconsistent or vague. This is due to several reasons which include: (1) many contributors with little experience or training in mapping and Geographic Information Systems (GIS); (2) not enough contributors familiar with the areas being mapped; (3) contributors having different interpretations of the attributes (tags) for specific features; (4) different levels of enthusiasm between mappers resulting in different number of tags for similar features and (5) the user-friendliness of the online user-interface where the underlying map can be viewed and edited. This paper suggests an automatic mechanism, which uses raw spatial data (trajectories of movements contributed by contributors to OSM) to minimise the uncertainty and impact of the above-mentioned issues. This approach takes the raw trajectory datasets as input and analyses them using data mining techniques. In addition, we extract some patterns and rules about the geometry and attributes of the recognised features for the purpose of insertion or editing of features in the OSM database. The underlying idea is that certain characteristics of user trajectories are directly linked to the geometry and the attributes of geographic features. Using these rules successfully results in the generation of new features with higher spatial quality which are subsequently automatically inserted into the OSM database. Full article

(This article belongs to the Special Issue Advanced Algorithms for Mobile Sensing: from Wireless Sensor Networks to Mobile Crowd Sensing)

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19 pages, 12504 KiB

Open AccessArticle

Stripe-PZT Sensor-Based Baseline-Free Crack Diagnosis in a Structure with a Welded Stiffener

by Yun-Kyu An^1,2,*

, Zhiqi Shen¹ and Zhishen Wu¹

¹ International Institute for Urban Systems Engineering, Southeast University, Nanjing 210096, China

² Department of Architectural Engineering, Sejong University, Seoul 05006, Korea

Sensors 2016, 16(9), 1511; https://doi.org/10.3390/s16091511 - 16 Sep 2016

Cited by 7 | Viewed by 4879

Abstract

This paper proposes a stripe-PZT sensor-based baseline-free crack diagnosis technique in the heat affected zone (HAZ) of a structure with a welded stiffener. The proposed technique enables one to identify and localize a crack in the HAZ using only current data measured using [...] Read more.

This paper proposes a stripe-PZT sensor-based baseline-free crack diagnosis technique in the heat affected zone (HAZ) of a structure with a welded stiffener. The proposed technique enables one to identify and localize a crack in the HAZ using only current data measured using a stripe-PZT sensor. The use of the stripe-PZT sensor makes it possible to significantly improve the applicability to real structures and minimize man-made errors associated with the installation process by embedding multiple piezoelectric sensors onto a printed circuit board. Moreover, a new frequency-wavenumber analysis-based baseline-free crack diagnosis algorithm minimizes false alarms caused by environmental variations by avoiding simple comparison with the baseline data accumulated from the pristine condition of a target structure. The proposed technique is numerically as well as experimentally validated using a plate-like structure with a welded stiffener, reveling that it successfully identifies and localizes a crack in HAZ. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 5725 KiB

Open AccessArticle

Optimization and Validation of Rotating Current Excitation with GMR Array Sensors for Riveted Structures Inspection

by Chaofeng Ye^*

, Lalita Udpa and Satish Udpa

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

Sensors 2016, 16(9), 1512; https://doi.org/10.3390/s16091512 - 16 Sep 2016

Cited by 18 | Viewed by 5485

Abstract

In eddy current non-destructive testing of a multi-layered riveted structure, rotating current excitation, generated by orthogonal coils, is advantageous in providing sensitivity to defects of all orientations. However, when used with linear array sensors, the exciting magnetic flux density (

B_{x}

) [...] Read more.

In eddy current non-destructive testing of a multi-layered riveted structure, rotating current excitation, generated by orthogonal coils, is advantageous in providing sensitivity to defects of all orientations. However, when used with linear array sensors, the exciting magnetic flux density (

B_{x}

) of the orthogonal coils is not uniform over the sensor region, resulting in an output signal magnitude that depends on the relative location of the defect to the sensor array. In this paper, the rotating excitation coil is optimized to achieve a uniform

B_{x}

field in the sensor array area and minimize the probe size. The current density distribution of the coil is optimized using the polynomial approximation method. A non-uniform coil design is derived from the optimized current density distribution. Simulation results, using both an optimized coil and a conventional coil, are generated using the finite element method (FEM) model. The signal magnitude for an optimized coil is seen to be more robust with respect to offset of defects from the coil center. A novel multilayer coil structure, fabricated on a multi-layer printed circuit board, is used to build the optimized coil. A prototype probe with the optimized coil and 32 giant magnetoresistive (GMR) sensors is built and tested on a two-layer riveted aluminum sample. Experimental results show that the optimized probe has better defect detection capability compared with a conventional non-optimized coil. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 1909 KiB

Open AccessArticle

Modeling and Implementation of Multi-Position Non-Continuous Rotation Gyroscope North Finder

by Jun Luo^1,2, Zhiqian Wang^1,*, Chengwu Shen^1,2, Arjan Kuijper^3,4

, Zhuoman Wen^1,2 and Shaojin Liu¹

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

² University of the Chinese Academy of Sciences, Beijing 10049, China

³ Fraunhofer Institute for Computer Graphics Research, Darmstadt 64283, Germany

⁴ Mathematical and Applied Visual Computing, Technische Universität Darmstadt, Darmstadt 64283, Germany

Sensors 2016, 16(9), 1513; https://doi.org/10.3390/s16091513 - 20 Sep 2016

Cited by 10 | Viewed by 8464

Abstract

Even when the Global Positioning System (GPS) signal is blocked, a rate gyroscope (gyro) north finder is capable of providing the required azimuth reference information to a certain extent. In order to measure the azimuth between the observer and the north direction very [...] Read more.

Even when the Global Positioning System (GPS) signal is blocked, a rate gyroscope (gyro) north finder is capable of providing the required azimuth reference information to a certain extent. In order to measure the azimuth between the observer and the north direction very accurately, we propose a multi-position non-continuous rotation gyro north finding scheme. Our new generalized mathematical model analyzes the elements that affect the azimuth measurement precision and can thus provide high precision azimuth reference information. Based on the gyro’s principle of detecting a projection of the earth rotation rate on its sensitive axis and the proposed north finding scheme, we are able to deduct an accurate mathematical model of the gyro outputs against azimuth with the gyro and shaft misalignments. Combining the gyro outputs model and the theory of propagation of uncertainty, some approaches to optimize north finding are provided, including reducing the gyro bias error, constraining the gyro random error, increasing the number of rotation points, improving rotation angle measurement precision, decreasing the gyro and the shaft misalignment angles. According them, a north finder setup is built and the azimuth uncertainty of 18” is obtained. This paper provides systematic theory for analyzing the details of the gyro north finder scheme from simulation to implementation. The proposed theory can guide both applied researchers in academia and advanced practitioners in industry for designing high precision robust north finder based on different types of rate gyroscopes. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 2937 KiB

Open AccessReview

Combined Dielectrophoresis and Impedance Systems for Bacteria Analysis in Microfluidic On-Chip Platforms

by Cristina Páez-Avilés^1,*

, Esteve Juanola-Feliu¹, Jaime Punter-Villagrasa¹

, Beatriz Del Moral Zamora¹, Antoni Homs-Corbera^1,2,3

, Jordi Colomer-Farrarons¹, Pere Lluís Miribel-Català¹ and Josep Samitier^1,2,3

¹ Department of Electronics, Bioelectronics and Nanobioengineering Research Group (SIC-BIO), University of Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain

² IBEC-Institute of Bioengineering of Catalonia, Nanobioengineering Research Group, Baldiri Reixac 10-12, 08028 Barcelona, Spain

³ CIBER-BBN-Biomedical Research Networking Centre for Bioengineering, Biomaterials and Nanomedicine, María de Luna 11, Edificio CEEI, 50018 Zaragoza, Spain

Sensors 2016, 16(9), 1514; https://doi.org/10.3390/s16091514 - 16 Sep 2016

Cited by 43 | Viewed by 16505

Abstract

Bacteria concentration and detection is time-consuming in regular microbiology procedures aimed to facilitate the detection and analysis of these cells at very low concentrations. Traditional methods are effective but often require several days to complete. This scenario results in low bioanalytical and diagnostic [...] Read more.

Bacteria concentration and detection is time-consuming in regular microbiology procedures aimed to facilitate the detection and analysis of these cells at very low concentrations. Traditional methods are effective but often require several days to complete. This scenario results in low bioanalytical and diagnostic methodologies with associated increased costs and complexity. In recent years, the exploitation of the intrinsic electrical properties of cells has emerged as an appealing alternative approach for concentrating and detecting bacteria. The combination of dielectrophoresis (DEP) and impedance analysis (IA) in microfluidic on-chip platforms could be key to develop rapid, accurate, portable, simple-to-use and cost-effective microfluidic devices with a promising impact in medicine, public health, agricultural, food control and environmental areas. The present document reviews recent DEP and IA combined approaches and the latest relevant improvements focusing on bacteria concentration and detection, including selectivity, sensitivity, detection time, and conductivity variation enhancements. Furthermore, this review analyses future trends and challenges which need to be addressed in order to successfully commercialize these platforms resulting in an adequate social return of public-funded investments. Full article

(This article belongs to the Special Issue Microfluidics-Based Microsystem Integration Research)

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13 pages, 7892 KiB

Open AccessArticle

Flexible Touch Sensors Made of Two Layers of Printed Conductive Flexible Adhesives

by Sungwon Seo¹

, Seonggi Kim^1,2, Jiyeon Jung³, Rujun Ma⁴, Seunghyun Baik¹ and Hyungpil Moon^1,*

¹ School of Mechanical Engineering, Sungkyunkwan University, Suwon 440-746, Korea

² Department of Nature-Inspired Nano Convergence Systems, Korea Institute of Machinery and Materials, Daejeon 34103, Korea

³ Hyundai Motor Company, Hwaseong 440-130, Korea

⁴ Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea

Sensors 2016, 16(9), 1515; https://doi.org/10.3390/s16091515 - 16 Sep 2016

Cited by 11 | Viewed by 5834

Abstract

Touch sensors are crucial in controlling robotic manipulation when a robot interacts with environmental objects. In this study, multilayer flexible touch sensors in the form of an array were developed. The sensors use ink-type conductive flexible adhesives as electrodes which were printed on [...] Read more.

Touch sensors are crucial in controlling robotic manipulation when a robot interacts with environmental objects. In this study, multilayer flexible touch sensors in the form of an array were developed. The sensors use ink-type conductive flexible adhesives as electrodes which were printed on polyethylene terephthalate (PET) films in a parallel equidistance stripe pattern. Between the two printed layers, a double-sided adhesive film was used to combine each layer and was perforated at the junctions of the top and bottom electrodes with different-sized circles. These holes represent switching mechanisms between the top and bottom electrodes, and their sizes make the sensor respond to different levels of external pressure. We showed the durability of the fabricated sensor with 1 mm diameter holes by repeated experiments of exerting normal pressure ranging from 0 to 159.15 kPa for 1000 cycles. In case of 1 mm diameter holes, the state of each sensor node was reliably determined by the threshold pressures of 127.3 kPa for increasing pressure and 111.4 kPa for decreasing pressure. On the other hand, decreasing the hole size from 3 to 0.5 mm caused an increase in the threshold pressure from 1.41 to 214 kPa. The relation between the hole size and the threshold pressure was analyzed by a mechanical model. The sensor performance was also verified on curved surfaces up to 60 mm radius of curvatures. Additionally, we fabricated a sensor with three levels of sensitivity with a conventional method which was a thermal evaporation to show the extendibility of the idea. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 3520 KiB

Open AccessArticle

Navigation Aiding by a Hybrid Laser-Camera Motion Estimator for Micro Aerial Vehicles

by Jamal Atman^1,*, Manuel Popp¹, Jan Ruppelt¹ and Gert F. Trommer^1,2

¹ Institute of Systems Optimization (ITE), Karlsruhe Institute of Technology (KIT), Karlsruhe 76049, Germany

² ITMO University, Saint Petersburg 197046, Russia

Sensors 2016, 16(9), 1516; https://doi.org/10.3390/s16091516 - 16 Sep 2016

Cited by 16 | Viewed by 6550

Abstract

Micro Air Vehicles (MAVs) equipped with various sensors are able to carry out autonomous flights. However, the self-localization of autonomous agents is mostly dependent on Global Navigation Satellite Systems (GNSS). In order to provide an accurate navigation solution in absence of GNSS signals, [...] Read more.

Micro Air Vehicles (MAVs) equipped with various sensors are able to carry out autonomous flights. However, the self-localization of autonomous agents is mostly dependent on Global Navigation Satellite Systems (GNSS). In order to provide an accurate navigation solution in absence of GNSS signals, this article presents a hybrid sensor. The hybrid sensor is a deep integration of a monocular camera and a 2D laser rangefinder so that the motion of the MAV is estimated. This realization is expected to be more flexible in terms of environments compared to laser-scan-matching approaches. The estimated ego-motion is then integrated in the MAV’s navigation system. However, first, the knowledge about the pose between both sensors is obtained by proposing an improved calibration method. For both calibration and ego-motion estimation, 3D-to-2D correspondences are used and the Perspective-3-Point (P3P) problem is solved. Moreover, the covariance estimation of the relative motion is presented. The experiments show very accurate calibration and navigation results. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

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20 pages, 10956 KiB

Open AccessArticle

Probe and Sensors Development for Level Measurement of Fats, Oils and Grease in Grease Boxes

by José Faria¹, André Sousa²

, Arsénio Reis^2,*

, Vitor Filipe² and João Barroso²

¹ ECT, Universidade de Trás-os-Montes e Alto Douro, Vila Real 5000, Portugal

² INESC TEC and Universidade de Trás-os-Montes e Alto Douro, Vila Real 5000, Portugal

Sensors 2016, 16(9), 1517; https://doi.org/10.3390/s16091517 - 16 Sep 2016

Cited by 3 | Viewed by 7452

Abstract

The wide spread of food outlets has become an environmental and sanitation infrastructure problem, due to Fats, Oils and Grease (FOG). A grease box is used at the industrials facilities to collect the FOG, in a specific time window, while its quality is [...] Read more.

The wide spread of food outlets has become an environmental and sanitation infrastructure problem, due to Fats, Oils and Grease (FOG). A grease box is used at the industrials facilities to collect the FOG, in a specific time window, while its quality is good for recycling (e.g., biodiesel) and it is economically valuable. After this period, it will be disposed at a cost. For the proper management of the grease boxes, it is necessary to know the quantity of FOG inside the boxes, which is a major problem, as the boxes are sealed and permanently filled with water. The lack of homogeneity of the FOG renders it not detectable by current probes for level detection in liquids. In this article, the design, development and testing of a set of probes for FOG level measurement, based on the principles used in sensors for the detection of liquids inside containers, is described. The most suitable probe, based on the capacitance principle, together with the necessary hardware and software modules for data acquisition and transmission, was developed and tested. After the development phase, the probe was integrated on a metropolitan system for FOG collection and grease box management in partnership with a grease box management company. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 3335 KiB

Open AccessTechnical Note

Forward-Looking Infrared Cameras for Micrometeorological Applications within Vineyards

by Marwan Katurji^* and Peyman Zawar-Reza

Center for Atmopsheric Research, University of Canterbury, Christchurch 8140, New Zealand

Sensors 2016, 16(9), 1518; https://doi.org/10.3390/s16091518 - 18 Sep 2016

Cited by 6 | Viewed by 5595

Abstract

We apply the principles of atmospheric surface layer dynamics within a vineyard canopy to demonstrate the use of forward-looking infrared cameras measuring surface brightness temperature (spectrum bandwidth of 7.5 to 14 μm) at a relatively high temporal rate of 10 s. The temporal [...] Read more.

We apply the principles of atmospheric surface layer dynamics within a vineyard canopy to demonstrate the use of forward-looking infrared cameras measuring surface brightness temperature (spectrum bandwidth of 7.5 to 14 μm) at a relatively high temporal rate of 10 s. The temporal surface brightness signal over a few hours of the stable nighttime boundary layer, intermittently interrupted by periods of turbulent heat flux surges, was shown to be related to the observed meteorological measurements by an in situ eddy-covariance system, and reflected the above-canopy wind variability. The infrared raster images were collected and the resultant self-organized spatial cluster provided the meteorological context when compared to in situ data. The spatial brightness temperature pattern was explained in terms of the presence or absence of nighttime cloud cover and down-welling of long-wave radiation and the canopy turbulent heat flux. Time sequential thermography as demonstrated in this research provides positive evidence behind the application of thermal infrared cameras in the domain of micrometeorology, and to enhance our spatial understanding of turbulent eddy interactions with the surface. Full article

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

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14 pages, 6001 KiB

Open AccessArticle

An Improved InSAR Image Co-Registration Method for Pairs with Relatively Big Distortions or Large Incoherent Areas

by Zhenwei Chen¹

, Lei Zhang²

and Guo Zhang^3,*

¹ School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China

² Department of Land Surveying and Geo-Informatics, Hong Kong Polytechnic University, Hong Kong, China

³ State Key Laboratory of Information Engineering in Survey, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China

Sensors 2016, 16(9), 1519; https://doi.org/10.3390/s16091519 - 17 Sep 2016

Cited by 18 | Viewed by 6427

Abstract

Co-registration is one of the most important steps in interferometric synthetic aperture radar (InSAR) data processing. The standard offset-measurement method based on cross-correlating uniformly distributed patches takes no account of specific geometric transformation between images or characteristics of ground scatterers. Hence, it is [...] Read more.

Co-registration is one of the most important steps in interferometric synthetic aperture radar (InSAR) data processing. The standard offset-measurement method based on cross-correlating uniformly distributed patches takes no account of specific geometric transformation between images or characteristics of ground scatterers. Hence, it is inefficient and difficult to obtain satisfying co-registration results for image pairs with relatively big distortion or large incoherent areas. Given this, an improved co-registration strategy is proposed in this paper which takes both the geometric features and image content into consideration. Firstly, some geometric transformations including scale, flip, rotation, and shear between images were eliminated based on the geometrical information, and the initial co-registration polynomial was obtained. Then the registration points were automatically detected by integrating the signal-to-clutter-ratio (SCR) thresholds and the amplitude information, and a further co-registration process was performed to refine the polynomial. Several comparison experiments were carried out using 2 TerraSAR-X data from the Hong Kong airport and 21 PALSAR data from the Donghai Bridge. Experiment results demonstrate that the proposed method brings accuracy and efficiency improvements for co-registration and processing abilities in the cases of big distortion between images or large incoherent areas in the images. For most co-registrations, the proposed method can enhance the reliability and applicability of co-registration and thus promote the automation to a higher level. Full article

(This article belongs to the Section Remote Sensors)

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19 pages, 4946 KiB

Open AccessArticle

Research on the Conductivity-Based Detection Principles of Bubbles in Two-Phase Flows and the Design of a Bubble Sensor for CBM Wells

by Chuan Wu¹, Guojun Wen^2,*, Lei Han² and Xiaoming Wu¹

¹ Faculty of Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China

² Faculty of Mechanical and Electronic Information, China University of Geosciences (Wuhan), Wuhan 430074, China

Sensors 2016, 16(9), 1520; https://doi.org/10.3390/s16091520 - 17 Sep 2016

Cited by 9 | Viewed by 6759

Abstract

The parameters of gas-liquid two-phase flow bubbles in field coalbed methane (CBM) wells are of great significance for analyzing coalbed methane output, judging faults in CBM wells, and developing gas drainage and extraction processes, which stimulates an urgent need for detecting bubble parameters [...] Read more.

The parameters of gas-liquid two-phase flow bubbles in field coalbed methane (CBM) wells are of great significance for analyzing coalbed methane output, judging faults in CBM wells, and developing gas drainage and extraction processes, which stimulates an urgent need for detecting bubble parameters for CBM wells in the field. However, existing bubble detectors cannot meet the requirements of the working environments of CBM wells. Therefore, this paper reports findings on the principles of measuring the flow pattern, velocity, and volume of two-phase flow bubbles based on conductivity, from which a new bubble sensor was designed. The structural parameters and other parameters of the sensor were then computed, the “water film phenomenon” produced by the sensor was analyzed, and the appropriate materials for making the sensor were tested and selected. After the sensor was successfully devised, laboratory tests and field tests were performed, and the test results indicated that the sensor was highly reliable and could detect the flow patterns of two-phase flows, as well as the quantities, velocities, and volumes of bubbles. With a velocity measurement error of ±5% and a volume measurement error of ±7%, the sensor can meet the requirements of field use. Finally, the characteristics and deficiencies of the bubble sensor are summarized based on an analysis of the measurement errors and a comparison of existing bubble-measuring devices and the designed sensor. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 6523 KiB

Open AccessArticle

Mechanical Enhancement of Sensitivity in Natural Rubber Using Electrolytic Polymerization Aided by a Magnetic Field and MCF for Application in Haptic Sensors

by Kunio Shimada^1,*

and Norihiko Saga²

¹ Faculty of Symbiotic Systems Sciences, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan

² Department of Human System Interaction, Kansai Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan

Sensors 2016, 16(9), 1521; https://doi.org/10.3390/s16091521 - 18 Sep 2016

Cited by 22 | Viewed by 7066

Abstract

Sensors are essential to the fulfillment of every condition of haptic technology, and they need simultaneously to sense shear stress as well as normal force, and temperature. They also must have a strong and simple structure, softness, and large extension. To achieve these [...] Read more.

Sensors are essential to the fulfillment of every condition of haptic technology, and they need simultaneously to sense shear stress as well as normal force, and temperature. They also must have a strong and simple structure, softness, and large extension. To achieve these conditions simultaneously, we enhanced the sensitivity of sensors utilizing natural rubber (NR)-latex through the application of electrolytic polymerization focused on the isoprene C=C bonds in natural rubbers such as NR-latex, and then applied a magnetic field and magnetic compound fluid (MCF) as magnetically responsive fluid. When an electric field alone was used in the rubber, the effect of electrolytic polymerization was very small compared to the effect in well-known conductive polymer solution such as plastic. The MCF developed by Shimada in 2001 involved magnetite and metal particles, and acts as a filler in NR-latex. By utilizing the magnetic, electric fields and the MCF, we aligned the electrolytically polymerized C=C along the magnetic field line with the magnetic clusters formed by the aggregation of magnetite and metal particles so as to enhance the effect of electrolytic polymerization. We then demonstrated the effectiveness of the new method of rubber vulcanization on the sensitivity of the rubber by experimentally investigating its electric and dynamic characteristics. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 420 KiB

Open AccessArticle

Combating QR-Code-Based Compromised Accounts in Mobile Social Networks

by Dong Guo^1,2, Jian Cao^1,2, Xiaoqi Wang^1,2, Qiang Fu^1,2 and Qiang Li^1,2,*

¹ College of Computer Science and Technology, Jilin University, Changchun 130012, China

² Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, Jilin University, Changchun 130012, China

Sensors 2016, 16(9), 1522; https://doi.org/10.3390/s16091522 - 20 Sep 2016

Cited by 5 | Viewed by 7008

Abstract

Cyber Physical Social Sensing makes mobile social networks (MSNs) popular with users. However, such attacks are rampant as malicious URLs are spread covertly through quick response (QR) codes to control compromised accounts in MSNs to propagate malicious messages. Currently, there are generally two [...] Read more.

Cyber Physical Social Sensing makes mobile social networks (MSNs) popular with users. However, such attacks are rampant as malicious URLs are spread covertly through quick response (QR) codes to control compromised accounts in MSNs to propagate malicious messages. Currently, there are generally two types of methods to identify compromised accounts in MSNs: one type is to analyze the potential threats on wireless access points and the potential threats on handheld devices’ operation systems so as to stop compromised accounts from spreading malicious messages; the other type is to apply the method of detecting compromised accounts in online social networks to MSNs. The above types of methods above focus neither on the problems of MSNs themselves nor on the interaction of sensors’ messages, which leads to the restrictiveness of platforms and the simplification of methods. In order to stop the spreading of compromised accounts in MSNs effectively, the attacks have to be traced to their sources first. Through sensors, users exchange information in MSNs and acquire information by scanning QR codes. Therefore, analyzing the traces of sensor-related information helps to identify the compromised accounts in MSNs. This paper analyzes the diversity of information sending modes of compromised accounts and normal accounts, analyzes the regularity of GPS (Global Positioning System)-based location information, and introduces the concepts of entropy and conditional entropy so as to construct an entropy-based model based on machine learning strategies. To achieve the goal, about 500,000 accounts of Sina Weibo and about 100 million corresponding messages are collected. Through the validation, the accuracy rate of the model is proved to be as high as 87.6%, and the false positive rate is only 3.7%. Meanwhile, the comparative experiments of the feature sets prove that sensor-based location information can be applied to detect the compromised accounts in MSNs. Full article

(This article belongs to the Special Issue New Paradigms in Cyber-Physical Social Sensing)

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17 pages, 2373 KiB

Open AccessArticle

Friendly-Sharing: Improving the Performance of City Sensoring through Contact-Based Messaging Applications

by Jorge Herrera-Tapia, Enrique Hernández-Orallo

, Andrés Tomás, Pietro Manzoni^*

, Carlos Tavares Calafate

and Juan-Carlos Cano

Department of Computing Engineering, Universitat Politècnica de València, Valencia 46022, Spain

Sensors 2016, 16(9), 1523; https://doi.org/10.3390/s16091523 - 18 Sep 2016

Cited by 13 | Viewed by 8470

Abstract

Regular citizens equipped with smart devices are being increasingly used as “sensors” by Smart Cities applications. Using contacts among users, data in the form of messages is obtained and shared. Contact-based messaging applications are based on establishing a short-range communication directly between mobile [...] Read more.

Regular citizens equipped with smart devices are being increasingly used as “sensors” by Smart Cities applications. Using contacts among users, data in the form of messages is obtained and shared. Contact-based messaging applications are based on establishing a short-range communication directly between mobile devices, and on storing the messages in these devices for subsequent delivery to cloud-based services. An effective way to increase the number of messages that can be shared is to increase the contact duration. We thus introduce the Friendly-Sharing diffusion approach, where, during a contact, the users are aware of the time needed to interchange the messages stored in their buffers, and they can thus decide to wait more time in order to increase the message sharing probability. The performance of this approach is anyway closely related to the size of the buffer in the device. We therefore compare various policies either for the message selection at forwarding times and for message dropping when the buffer is full. We evaluate our proposal with a modified version of the Opportunistic Networking Environment (ONE) simulator and using real human mobility traces. Full article

(This article belongs to the Special Issue Smart City: Vision and Reality)

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20 pages, 6129 KiB

Open AccessArticle

A Sparsity-Promoted Decomposition for Compressed Fault Diagnosis of Roller Bearings

by Huaqing Wang¹

, Yanliang Ke¹, Liuyang Song^2,*

, Gang Tang^1,* and Peng Chen²

¹ College of Mechanical & Electrical Engineering, Beijing University of Chemical Technology Chao Yang District, Beijing 100029, China

² Graduate School of Bioresources, Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514-8507, Japan

Sensors 2016, 16(9), 1524; https://doi.org/10.3390/s16091524 - 19 Sep 2016

Cited by 29 | Viewed by 6060

Abstract

The traditional approaches for condition monitoring of roller bearings are almost always achieved under Shannon sampling theorem conditions, leading to a big-data problem. The compressed sensing (CS) theory provides a new solution to the big-data problem. However, the vibration signals are insufficiently sparse [...] Read more.

The traditional approaches for condition monitoring of roller bearings are almost always achieved under Shannon sampling theorem conditions, leading to a big-data problem. The compressed sensing (CS) theory provides a new solution to the big-data problem. However, the vibration signals are insufficiently sparse and it is difficult to achieve sparsity using the conventional techniques, which impedes the application of CS theory. Therefore, it is of great significance to promote the sparsity when applying the CS theory to fault diagnosis of roller bearings. To increase the sparsity of vibration signals, a sparsity-promoted method called the tunable Q-factor wavelet transform based on decomposing the analyzed signals into transient impact components and high oscillation components is utilized in this work. The former become sparser than the raw signals with noise eliminated, whereas the latter include noise. Thus, the decomposed transient impact components replace the original signals for analysis. The CS theory is applied to extract the fault features without complete reconstruction, which means that the reconstruction can be completed when the components with interested frequencies are detected and the fault diagnosis can be achieved during the reconstruction procedure. The application cases prove that the CS theory assisted by the tunable Q-factor wavelet transform can successfully extract the fault features from the compressed samples. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 6679 KiB

Open AccessArticle

FGG-NUFFT-Based Method for Near-Field 3-D Imaging Using Millimeter Waves

by Yingzhi Kan¹, Yongfeng Zhu^1,*, Liang Tang¹, Qiang Fu¹ and Hucheng Pei²

¹ College of Electronic Science and Engineering, National University of Defense Technology, Changsha 410073, China

² Beijing Institute of Mechanical and Electrical Engineering, Beijing 100074, China

Sensors 2016, 16(9), 1525; https://doi.org/10.3390/s16091525 - 19 Sep 2016

Cited by 11 | Viewed by 6804

Abstract

In this paper, to deal with the concealed target detection problem, an accurate and efficient algorithm for near-field millimeter wave three-dimensional (3-D) imaging is proposed that uses a two-dimensional (2-D) plane antenna array. First, a two-dimensional fast Fourier transform (FFT) is performed on [...] Read more.

In this paper, to deal with the concealed target detection problem, an accurate and efficient algorithm for near-field millimeter wave three-dimensional (3-D) imaging is proposed that uses a two-dimensional (2-D) plane antenna array. First, a two-dimensional fast Fourier transform (FFT) is performed on the scattered data along the antenna array plane. Then, a phase shift is performed to compensate for the spherical wave effect. Finally, fast Gaussian gridding based nonuniform FFT (FGG-NUFFT) combined with 2-D inverse FFT (IFFT) is performed on the nonuniform 3-D spatial spectrum in the frequency wavenumber domain to achieve 3-D imaging. The conventional method for near-field 3-D imaging uses Stolt interpolation to obtain uniform spatial spectrum samples and performs 3-D IFFT to reconstruct a 3-D image. Compared with the conventional method, our FGG-NUFFT based method is comparable in both efficiency and accuracy in the full sampled case and can obtain more accurate images with less clutter and fewer noisy artifacts in the down-sampled case, which are good properties for practical applications. Both simulation and experimental results demonstrate that the FGG-NUFFT-based near-field 3-D imaging algorithm can have better imaging performance than the conventional method for down-sampled measurements. Full article

(This article belongs to the Special Issue Synthetic Aperture Radars: Models, Algorithms, Techniques and Tools for Data Exploitation)

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16 pages, 2274 KiB

Open AccessArticle

Potential Seasonal Terrestrial Water Storage Monitoring from GPS Vertical Displacements: A Case Study in the Lower Three-Rivers Headwater Region, China

by Bao Zhang¹, Yibin Yao^1,*, Hok Sum Fok^1,*

, Yufeng Hu¹ and Qiang Chen²

¹ School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China

² Faculte des Science, de la Technologie et de la Communication, University of Luxembourg, 6 Rue Richard Coudenhove-Kalergi L-1359, Luxembourg

Sensors 2016, 16(9), 1526; https://doi.org/10.3390/s16091526 - 19 Sep 2016

Cited by 22 | Viewed by 7581

Abstract

This study uses the observed vertical displacements of Global Positioning System (GPS) time series obtained from the Crustal Movement Observation Network of China (CMONOC) with careful pre- and post-processing to estimate the seasonal crustal deformation in response to the hydrological loading in lower [...] Read more.

This study uses the observed vertical displacements of Global Positioning System (GPS) time series obtained from the Crustal Movement Observation Network of China (CMONOC) with careful pre- and post-processing to estimate the seasonal crustal deformation in response to the hydrological loading in lower three-rivers headwater region of southwest China, followed by inferring the annual EWH changes through geodetic inversion methods. The Helmert Variance Component Estimation (HVCE) and the Minimum Mean Square Error (MMSE) criterion were successfully employed. The GPS inferred EWH changes agree well qualitatively with the Gravity Recovery and Climate Experiment (GRACE)-inferred and the Global Land Data Assimilation System (GLDAS)-inferred EWH changes, with a discrepancy of 3.2–3.9 cm and 4.8–5.2 cm, respectively. In the research areas, the EWH changes in the Lancang basin is larger than in the other regions, with a maximum of 21.8–24.7 cm and a minimum of 3.1–6.9 cm. Full article

(This article belongs to the Section Remote Sensors)

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10 pages, 1501 KiB

Open AccessArticle

Spatial Ecology of Estuarine Crocodile (Crocodylus porosus) Nesting in a Fragmented Landscape

by Luke J. Evans^1,2,3,*, T. Hefin Jones^1,4, Keeyen Pang⁵, Silvester Saimin³ and Benoit Goossens^1,2,3,4,*

¹ Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK

² Danau Girang Field Centre, c/o Sabah Wildlife Department, Wisma Muis, 5th Floor, Block B, Kota Kinabalu 88100, Malaysia

³ Sabah Wildlife Department, Wisma Muis, 5th Floor, Block B, Kota Kinabalu 88100, Malaysia

⁴ Sustainable Places Research Institute, Cardiff University, 33 Park Place, Cardiff CF10 3BA, UK

⁵ Hornbill Surveys Sdn Bhd, Lot 9, Harapan Baru Light Ind Estate, Mile 8, Jalan Labuk, Sandakan 90009, Malaysia

Sensors 2016, 16(9), 1527; https://doi.org/10.3390/s16091527 - 19 Sep 2016

Cited by 32 | Viewed by 10426

Abstract

The role that oil palm plays in the Lower Kinabatangan region of Eastern Sabah is of considerable scientific and conservation interest, providing a model habitat for many tropical regions as they become increasingly fragmented. Crocodilians, as apex predators, widely distributed throughout the tropics, [...] Read more.

The role that oil palm plays in the Lower Kinabatangan region of Eastern Sabah is of considerable scientific and conservation interest, providing a model habitat for many tropical regions as they become increasingly fragmented. Crocodilians, as apex predators, widely distributed throughout the tropics, are ideal indicator species for ecosystem health. Drones (or unmanned aerial vehicles (UAVs)) were used to identify crocodile nests in a fragmented landscape. Flights were targeted through the use of fuzzy overlay models and nests located primarily in areas indicated as suitable habitat. Nests displayed a number of similarities in terms of habitat characteristics allowing for refined modelling of survey locations. As well as being more cost-effective compared to traditional methods of nesting survey, the use of drones also enabled a larger survey area to be completed albeit with a limited number of flights. The study provides a methodology for targeted nest surveying, as well as a low-cost repeatable flight methodology. This approach has potential for widespread applicability across a range of species and for a variety of study designs. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

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15 pages, 1933 KiB

Open AccessArticle

Small Moving Vehicle Detection in a Satellite Video of an Urban Area

by Tao Yang^1,*

, Xiwen Wang¹, Bowei Yao¹, Jing Li², Yanning Zhang¹, Zhannan He¹ and Wencheng Duan¹

¹ ShaanXi Provincial Key Lab of Speech and Image Infromation Processing, School of Computer Science, Northwestern Polytechnical University, Xi’an 710129, China

² School of Telecommunications Engineering, Xidian University, Xi’an 710071, China

Sensors 2016, 16(9), 1528; https://doi.org/10.3390/s16091528 - 21 Sep 2016

Cited by 85 | Viewed by 10349

Abstract

Vehicle surveillance of a wide area allows us to learn much about the daily activities and traffic information. With the rapid development of remote sensing, satellite video has become an important data source for vehicle detection, which provides a broader field of surveillance. [...] Read more.

Vehicle surveillance of a wide area allows us to learn much about the daily activities and traffic information. With the rapid development of remote sensing, satellite video has become an important data source for vehicle detection, which provides a broader field of surveillance. The achieved work generally focuses on aerial video with moderately-sized objects based on feature extraction. However, the moving vehicles in satellite video imagery range from just a few pixels to dozens of pixels and exhibit low contrast with respect to the background, which makes it hard to get available appearance or shape information. In this paper, we look into the problem of moving vehicle detection in satellite imagery. To the best of our knowledge, it is the first time to deal with moving vehicle detection from satellite videos. Our approach consists of two stages: first, through foreground motion segmentation and trajectory accumulation, the scene motion heat map is dynamically built. Following this, a novel saliency based background model which intensifies moving objects is presented to segment the vehicles in the hot regions. Qualitative and quantitative experiments on sequence from a recent Skybox satellite video dataset demonstrates that our approach achieves a high detection rate and low false alarm simultaneously. Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 2290 KiB

Open AccessArticle

Research on the Lift-off Effect of Receiving Longitudinal Mode Guided Waves in Pipes Based on the Villari Effect

by Jiang Xu^*

, Yong Sun and Jinhai Zhou

School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, China

Sensors 2016, 16(9), 1529; https://doi.org/10.3390/s16091529 - 20 Sep 2016

Cited by 11 | Viewed by 6993

Abstract

The magnetostrictive guided wave technology as a non-contact measurement can generate and receive guided waves with a large lift-off distance up to tens of millimeters. However, the lift-off distance of the receiving coil would affect the coupling efficiency from the elastic energy to [...] Read more.

The magnetostrictive guided wave technology as a non-contact measurement can generate and receive guided waves with a large lift-off distance up to tens of millimeters. However, the lift-off distance of the receiving coil would affect the coupling efficiency from the elastic energy to the electromagnetic energy. In the existing magnetomechanical models, the change of the magnetic field in the air gap was ignored since the permeability of the rod is much greater than that of air. The lift-off distance of the receiving coil will not affect the receiving signals based on these models. However, the experimental phenomenon is in contradiction with these models. To solve the contradiction, the lift-off effect of receiving the longitudinal mode guided waves in pipes is investigated based on the Villari effect. A finite element model of receiving longitudinal guided waves in pipes is obtained based on the Villari effect, which takes into account the magnetic field in the pipe wall and the air zone at the same time. The relation between the amplitude of the induced signals and the radius (lift-off distance) of the receiving coil is obtained, which is verified by experiment. The coupling efficiency of the receiver is a monotonic decline with the lift-off distance increasing. The decay rate of the low frequency wave is slower than the high frequency wave. Additionally, the results show that the rate of change of the magnetic flux in the air zone and in the pipe wall is the same order of magnitude, but opposite. However, the experimental results show that the error of the model in the large lift-off distance is obvious due to the diffusion of the magnetic field in the air, especially for the high frequency guided waves. Full article

(This article belongs to the Special Issue Non-Contact Sensing)

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16 pages, 1314 KiB

Open AccessArticle

Maximum Correntropy Unscented Kalman Filter for Spacecraft Relative State Estimation

by Xi Liu^1,*

, Hua Qu^1,2, Jihong Zhao¹, Pengcheng Yue¹ and Meng Wang²

¹ School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China

² School of Software Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2016, 16(9), 1530; https://doi.org/10.3390/s16091530 - 20 Sep 2016

Cited by 110 | Viewed by 8785

Abstract

A new algorithm called maximum correntropy unscented Kalman filter (MCUKF) is proposed and applied to relative state estimation in space communication networks. As is well known, the unscented Kalman filter (UKF) provides an efficient tool to solve the non-linear state estimate problem. However, [...] Read more.

A new algorithm called maximum correntropy unscented Kalman filter (MCUKF) is proposed and applied to relative state estimation in space communication networks. As is well known, the unscented Kalman filter (UKF) provides an efficient tool to solve the non-linear state estimate problem. However, the UKF usually plays well in Gaussian noises. Its performance may deteriorate substantially in the presence of non-Gaussian noises, especially when the measurements are disturbed by some heavy-tailed impulsive noises. By making use of the maximum correntropy criterion (MCC), the proposed algorithm can enhance the robustness of UKF against impulsive noises. In the MCUKF, the unscented transformation (UT) is applied to obtain a predicted state estimation and covariance matrix, and a nonlinear regression method with the MCC cost is then used to reformulate the measurement information. Finally, the UT is adopted to the measurement equation to obtain the filter state and covariance matrix. Illustrative examples demonstrate the superior performance of the new algorithm. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 5980 KiB

Open AccessReview

Design of Highly Selective Gas Sensors via Physicochemical Modification of Oxide Nanowires: Overview

by Hyung-Sik Woo, Chan Woong Na^† and Jong-Heun Lee^*

Department of Materials Science and Engineering, Korea University, Seoul 02841, Korea

Sensors 2016, 16(9), 1531; https://doi.org/10.3390/s16091531 - 20 Sep 2016

Cited by 74 | Viewed by 14432

Abstract

Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW) networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and [...] Read more.

Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW) networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n-type NWs such as SnO₂, ZnO, and In₂O₃ are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C₂H₅OH and NO₂, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies—such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core–shell structures—have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n-type into p-type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors. Full article

(This article belongs to the Special Issue Gas Nanosensors)

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18 pages, 5355 KiB

Open AccessArticle

Efficient Data Gathering Methods in Wireless Sensor Networks Using GBTR Matrix Completion

by Donghao Wang, Jiangwen Wan^*, Zhipeng Nie, Qiang Zhang and Zhijie Fei

School of Instrumentation Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China

Sensors 2016, 16(9), 1532; https://doi.org/10.3390/s16091532 - 21 Sep 2016

Cited by 4 | Viewed by 6424

Abstract

To obtain efficient data gathering methods for wireless sensor networks (WSNs), a novel graph based transform regularized (GBTR) matrix completion algorithm is proposed. The graph based transform sparsity of the sensed data is explored, which is also considered as a penalty term in [...] Read more.

To obtain efficient data gathering methods for wireless sensor networks (WSNs), a novel graph based transform regularized (GBTR) matrix completion algorithm is proposed. The graph based transform sparsity of the sensed data is explored, which is also considered as a penalty term in the matrix completion problem. The proposed GBTR-ADMM algorithm utilizes the alternating direction method of multipliers (ADMM) in an iterative procedure to solve the constrained optimization problem. Since the performance of the ADMM method is sensitive to the number of constraints, the GBTR-A2DM2 algorithm obtained to accelerate the convergence of GBTR-ADMM. GBTR-A2DM2 benefits from merging two constraint conditions into one as well as using a restart rule. The theoretical analysis shows the proposed algorithms obtain satisfactory time complexity. Extensive simulation results verify that our proposed algorithms outperform the state of the art algorithms for data collection problems in WSNs in respect to recovery accuracy, convergence rate, and energy consumption. Full article

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

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15 pages, 4009 KiB

Open AccessArticle

Fabrication of Micro-Needle Electrodes for Bio-Signal Recording by a Magnetization-Induced Self-Assembly Method

by Keyun Chen^1,†, Lei Ren^1,†, Zhipeng Chen¹, Chengfeng Pan¹, Wei Zhou² and Lelun Jiang^1,*

¹ Guangdong Provincial Key Laboratory of Sensor Technology and Biomedical Instrument, Sun Yat-Sen University, Guangzhou 510006, China

² Department of Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005, China

Sensors 2016, 16(9), 1533; https://doi.org/10.3390/s16091533 - 20 Sep 2016

Cited by 63 | Viewed by 12562

Abstract

Micro-needle electrodes (MEs) have attracted more and more attention for monitoring physiological electrical signals, including electrode-skin interface impedance (EII), electromyography (EMG) and electrocardiography (ECG) recording. A magnetization-induced self-assembling method (MSM) was developed to fabricate a microneedle array (MA). A MA coated with Ti/Au [...] Read more.

Micro-needle electrodes (MEs) have attracted more and more attention for monitoring physiological electrical signals, including electrode-skin interface impedance (EII), electromyography (EMG) and electrocardiography (ECG) recording. A magnetization-induced self-assembling method (MSM) was developed to fabricate a microneedle array (MA). A MA coated with Ti/Au film was assembled as a ME. The fracture and insertion properties of ME were tested by experiments. The bio-signal recording performance of the ME was measured and compared with a typical commercial wet electrode (Ag/AgCl electrode). The results show that the MA self-assembled from the magnetic droplet array under the sum of gravitational surface tension and magnetic potential energies. The ME had good toughness and could easily pierce rabbit skin without being broken or buckling. When the compression force applied on the ME was larger than 2 N, ME could stably record EII, which was a lower value than that measured by Ag/AgCl electrodes. EMG signals collected by ME varied along with the contraction of biceps brachii muscle. ME could record static ECG signals with a larger amplitude and dynamic ECG signals with more distinguishable features in comparison with a Ag/AgCl electrode, therefore, ME is an alternative electrode for bio-signal monitoring in some specific situations. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 4050 KiB

Open AccessArticle

A Laser Line Auto-Scanning System for Underwater 3D Reconstruction

by Shukai Chi, Zexiao Xie^* and Wenzhu Chen

Engineering College, Ocean University of China, 238 Songling Road, Qingdao 266100, China

Sensors 2016, 16(9), 1534; https://doi.org/10.3390/s16091534 - 20 Sep 2016

Cited by 66 | Viewed by 10890

Abstract

In this study, a laser line auto-scanning system was designed to perform underwater close-range 3D reconstructions with high accuracy and resolution. The system changes the laser plane direction with a galvanometer to perform automatic scanning and obtain continuous laser strips for underwater 3D [...] Read more.

In this study, a laser line auto-scanning system was designed to perform underwater close-range 3D reconstructions with high accuracy and resolution. The system changes the laser plane direction with a galvanometer to perform automatic scanning and obtain continuous laser strips for underwater 3D reconstruction. The system parameters were calibrated with the homography constraints between the target plane and image plane. A cost function was defined to optimize the galvanometer’s rotating axis equation. Compensation was carried out for the refraction of the incident and emitted light at the interface. The accuracy and the spatial measurement capability of the system were tested and analyzed with standard balls under laboratory underwater conditions, and the 3D surface reconstruction for a sealing cover of an underwater instrument was proved to be satisfactory. Full article

(This article belongs to the Special Issue Laser Sensors for Displacement, Distance, Flow, Velocity and Vibrations Measurements)

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15 pages, 6186 KiB

Open AccessArticle

A Novel Passive Wireless Sensor for Concrete Humidity Monitoring

by Shuangxi Zhou¹, Fangming Deng^2,3,*, Lehua Yu¹, Bing Li³, Xiang Wu² and Baiqiang Yin³

¹ School of Civil Engineering and Architecture, East China Jiaotong University, Nanchang 330013, China

² School of Electrical and Automation Engineering, East China Jiaotong University, Nanchang 330013, China

³ School of Electrical Engineering and Automation, Hefei University of Technology, Hefei 230009, China

Sensors 2016, 16(9), 1535; https://doi.org/10.3390/s16091535 - 20 Sep 2016

Cited by 38 | Viewed by 10678

Abstract

This paper presents a passive wireless humidity sensor for concrete monitoring. After discussing the transmission of electromagnetic wave in concrete, a novel architecture of wireless humidity sensor, based on Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) technology, is proposed for low-power application. The [...] Read more.

This paper presents a passive wireless humidity sensor for concrete monitoring. After discussing the transmission of electromagnetic wave in concrete, a novel architecture of wireless humidity sensor, based on Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) technology, is proposed for low-power application. The humidity sensor utilizes the top metal layer to form the interdigitated electrodes, which were then filled with polyimide as the humidity sensing layer. The sensor interface converts the humidity capacitance into a digital signal in the frequency domain. A two-stage rectifier adopts a dynamic bias-voltage generator to boost the effective gate-source voltage of the switches in differential-drive architecture. The clock generator employs a novel structure to reduce the internal voltage swing. The measurement results show that our proposed wireless humidity can achieve a high linearity with a normalized sensitivity of 0.55% %RH at 20 °C. Despite the high losses of concrete, the proposed wireless humidity sensor achieves reliable communication performances in passive mode. The maximum operating distance is 0.52 m when the proposed wireless sensor is embedded into the concrete at the depth of 8 cm. The measured results are highly consistent with the results measured by traditional methods. Full article

(This article belongs to the Special Issue Advanced Technologies and Techniques for Microwave and Wireless Sensors)

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31 pages, 2360 KiB

Open AccessArticle

Increasing the Lifetime of Mobile WSNs via Dynamic Optimization of Sensor Node Communication Activity

by Dayan Adionel Guimarães^*

, Lucas Jun Sakai, Antonio Marcos Alberti and Rausley Adriano Amaral De Souza

National Institute of Telecommunications—Inatel Av. João de Camargo 510, Santa Rita do Sapucaí, MG 37540-000, Brazil

Sensors 2016, 16(9), 1536; https://doi.org/10.3390/s16091536 - 20 Sep 2016

Cited by 6 | Viewed by 7535

Abstract

In this paper, a simple and flexible method for increasing the lifetime of fixed or mobile wireless sensor networks is proposed. Based on past residual energy information reported by the sensor nodes, the sink node or another central node dynamically optimizes the communication [...] Read more.

In this paper, a simple and flexible method for increasing the lifetime of fixed or mobile wireless sensor networks is proposed. Based on past residual energy information reported by the sensor nodes, the sink node or another central node dynamically optimizes the communication activity levels of the sensor nodes to save energy without sacrificing the data throughput. The activity levels are defined to represent portions of time or time-frequency slots in a frame, during which the sensor nodes are scheduled to communicate with the sink node to report sensory measurements. Besides node mobility, it is considered that sensors’ batteries may be recharged via a wireless power transmission or equivalent energy harvesting scheme, bringing to the optimization problem an even more dynamic character. We report large increased lifetimes over the non-optimized network and comparable or even larger lifetime improvements with respect to an idealized greedy algorithm that uses both the real-time channel state and the residual energy information. Full article

(This article belongs to the Section Sensor Networks)

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16 pages, 2021 KiB

Open AccessArticle

A Security Mechanism for Cluster-Based WSN against Selective Forwarding

by Hai Zhou, Yuanming Wu^*, Li Feng and Daolei Liu

School of Optoelectronic Information, University of Electronic Science and Technology, Chengdu 610054, China

Sensors 2016, 16(9), 1537; https://doi.org/10.3390/s16091537 - 20 Sep 2016

Cited by 32 | Viewed by 5410

Abstract

A wireless sensor network (WSN) faces a number of outsider and insider attacks, and it is difficult to detect and defend against insider attacks. In particular, an insider selective-forwarding attack, in which the attackers select some of the received packets to drop, most [...] Read more.

A wireless sensor network (WSN) faces a number of outsider and insider attacks, and it is difficult to detect and defend against insider attacks. In particular, an insider selective-forwarding attack, in which the attackers select some of the received packets to drop, most threatens a WSN. Compared to a distributed WSN, a cluster-based WSN will suffer more losses, even the whole network’s destruction, if the cluster head is attacked. In this paper, a scheme solving the above issues is proposed with three types of nodes, the Cluster Head (CH), the Inspector Node (IN) and Member Nodes (MNs). The IN monitors the CH’s transmission to protect the cluster against a selective-forwarding attack; the CH forwards packets from MNs and other CHs, and randomly checks the IN to ascertain if it works properly; and the MNs send the gathered data packets to the CH and evaluate the behaviors of the CH and IN based on their own reputation mechanism. The novelty of our scheme is that in order to take both the safety and the lifespan of a network into consideration, the composite reputation value (CRV) including forwarding rate, detecting malicious nodes, and surplus energy of the node is utilized to select CH and IN under the new suggested network arrangement, and the use of a node’s surplus energy can balance the energy consumption of a node, thereby prolonging the network lifespan. Theoretical analysis and simulation results indicate that the proposed scheme can detect the malicious node accurately and efficiently, so the false alarm rate is lowered by 25.7% compared with Watchdog and the network lifespan is prolonged by 54.84% compared with LEACH (Low Energy Adaptive Clustering Hierarchy). Full article

(This article belongs to the Section Sensor Networks)

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31 pages, 5967 KiB

Open AccessArticle

Collection and Processing of Data from Wrist Wearable Devices in Heterogeneous and Multiple-User Scenarios

by Francisco De Arriba-Pérez^*,†, Manuel Caeiro-Rodríguez^† and Juan M. Santos-Gago^†

Department of Telematics Engineering, University of Vigo, Campus Lagoas-Marcosende, Vigo 36310, Spain

Sensors 2016, 16(9), 1538; https://doi.org/10.3390/s16091538 - 21 Sep 2016

Cited by 129 | Viewed by 24270

Abstract

Over recent years, we have witnessed the development of mobile and wearable technologies to collect data from human vital signs and activities. Nowadays, wrist wearables including sensors (e.g., heart rate, accelerometer, pedometer) that provide valuable data are common in market. We are working [...] Read more.

Over recent years, we have witnessed the development of mobile and wearable technologies to collect data from human vital signs and activities. Nowadays, wrist wearables including sensors (e.g., heart rate, accelerometer, pedometer) that provide valuable data are common in market. We are working on the analytic exploitation of this kind of data towards the support of learners and teachers in educational contexts. More precisely, sleep and stress indicators are defined to assist teachers and learners on the regulation of their activities. During this development, we have identified interoperability challenges related to the collection and processing of data from wearable devices. Different vendors adopt specific approaches about the way data can be collected from wearables into third-party systems. This hinders such developments as the one that we are carrying out. This paper contributes to identifying key interoperability issues in this kind of scenario and proposes guidelines to solve them. Taking into account these topics, this work is situated in the context of the standardization activities being carried out in the Internet of Things and Machine to Machine domains. Full article

(This article belongs to the Special Issue Advances on Data Transmission and Analysis for Wearable Sensors Systems)

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13 pages, 2446 KiB

Open AccessArticle

Zwitterionic Surfactant Modified Acetylene Black Paste Electrode for Highly Facile and Sensitive Determination of Tetrabromobisphenol A

by Xiaoyun Wei¹, Qiang Zhao¹, Weixiang Wu¹, Tong Zhou¹, Shunli Jiang¹, Yeqing Tong^2,* and Qing Lu^1,*

¹ Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China

² Hubei Provincial Center for Disease Control and Prevention, Wuhan 430079, China

Sensors 2016, 16(9), 1539; https://doi.org/10.3390/s16091539 - 21 Sep 2016

Cited by 16 | Viewed by 6552

Abstract

A electrochemical sensor for the highly sensitive detection of tetrabromobisphenol A (TBBPA) was fabricated based on acetylene black paste electrode (ABPE) modified with 3-(N,N-Dimethylpalmitylammonio) propanesulfonate (SB3-16) in this study. The peak current of TBBPA was significantly enhanced at SB3-16/ABPE [...] Read more.

A electrochemical sensor for the highly sensitive detection of tetrabromobisphenol A (TBBPA) was fabricated based on acetylene black paste electrode (ABPE) modified with 3-(N,N-Dimethylpalmitylammonio) propanesulfonate (SB3-16) in this study. The peak current of TBBPA was significantly enhanced at SB3-16/ABPE compared with unmodified electrodes. To further improve the electrochemical performance of the modified electrode, corresponding experimental parameters such as the length of hydrophobic chains of zwitterionic surfactant, the concentration of SB3-16, pH value, and accumulation time were examined. The peak currents of TBBPA were found to be linearly correlated with its concentrations in the range of 1 nM to 1 µM, with a detection limit of 0.4 nM. Besides, a possible mechanism was also discussed, and the hydrophobic interaction between TBBPA and the surfactants was suggested to take a leading role in enhancing the responses. Finally, this sensor was successfully employed to detect TBBPA in water samples. Full article

(This article belongs to the Special Issue Chemiresistive Sensors)

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14 pages, 3411 KiB

Open AccessArticle

Optimization of Stripping Voltammetric Sensor by a Back Propagation Artificial Neural Network for the Accurate Determination of Pb(II) in the Presence of Cd(II)

by Guo Zhao^1,2, Hui Wang^1,2, Gang Liu^1,2,* and Zhiqiang Wang³

¹ Key Lab of Modern Precision Agriculture System Integration Research, Ministry of Education of China, China Agricultural University, Beijing 100083, China

² Key Lab of Agricultural Information Acquisition Technology, Ministry of Agricultural of China, China Agricultural University, Beijing 100083, China

³ College of Computer Science and Technology, Shandong University of Technology, Zibo 255049, China

Sensors 2016, 16(9), 1540; https://doi.org/10.3390/s16091540 - 21 Sep 2016

Cited by 21 | Viewed by 7446

Abstract

An easy, but effective, method has been proposed to detect and quantify the Pb(II) in the presence of Cd(II) based on a Bi/glassy carbon electrode (Bi/GCE) with the combination of a back propagation artificial neural network (BP-ANN) and square wave anodic stripping voltammetry [...] Read more.

An easy, but effective, method has been proposed to detect and quantify the Pb(II) in the presence of Cd(II) based on a Bi/glassy carbon electrode (Bi/GCE) with the combination of a back propagation artificial neural network (BP-ANN) and square wave anodic stripping voltammetry (SWASV) without further electrode modification. The effects of Cd(II) in different concentrations on stripping responses of Pb(II) was studied. The results indicate that the presence of Cd(II) will reduce the prediction precision of a direct calibration model. Therefore, a two-input and one-output BP-ANN was built for the optimization of a stripping voltammetric sensor, which considering the combined effects of Cd(II) and Pb(II) on the SWASV detection of Pb(II) and establishing the nonlinear relationship between the stripping peak currents of Pb(II) and Cd(II) and the concentration of Pb(II). The key parameters of the BP-ANN and the factors affecting the SWASV detection of Pb(II) were optimized. The prediction performance of direct calibration model and BP-ANN model were tested with regard to the mean absolute error (MAE), root mean square error (RMSE), average relative error (ARE), and correlation coefficient. The results proved that the BP-ANN model exhibited higher prediction accuracy than the direct calibration model. Finally, a real samples analysis was performed to determine trace Pb(II) in some soil specimens with satisfactory results. Full article

(This article belongs to the Special Issue Sensors for Environmental Monitoring 2016)

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21 pages, 1906 KiB

Open AccessArticle

Markov Task Network: A Framework for Service Composition under Uncertainty in Cyber-Physical Systems

by Abdul-Wahid Mohammed^1,2,†

, Yang Xu^1,*,†

, Haixiao Hu^1,† and Brighter Agyemang¹

¹ School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China

² School of Engineering, University for Development Studies, Tamale 00233, Northern Region, Ghana

Sensors 2016, 16(9), 1542; https://doi.org/10.3390/s16091542 - 21 Sep 2016

Cited by 7 | Viewed by 6060

Abstract

In novel collaborative systems, cooperative entities collaborate services to achieve local and global objectives. With the growing pervasiveness of cyber-physical systems, however, such collaboration is hampered by differences in the operations of the cyber and physical objects, and the need for the dynamic [...] Read more.

In novel collaborative systems, cooperative entities collaborate services to achieve local and global objectives. With the growing pervasiveness of cyber-physical systems, however, such collaboration is hampered by differences in the operations of the cyber and physical objects, and the need for the dynamic formation of collaborative functionality given high-level system goals has become practical. In this paper, we propose a cross-layer automation and management model for cyber-physical systems. This models the dynamic formation of collaborative services pursuing laid-down system goals as an ontology-oriented hierarchical task network. Ontological intelligence provides the semantic technology of this model, and through semantic reasoning, primitive tasks can be dynamically composed from high-level system goals. In dealing with uncertainty, we further propose a novel bridge between hierarchical task networks and Markov logic networks, called the Markov task network. This leverages the efficient inference algorithms of Markov logic networks to reduce both computational and inferential loads in task decomposition. From the results of our experiments, high-precision service composition under uncertainty can be achieved using this approach. Full article

(This article belongs to the Special Issue Real-Time and Cyber-Physical Systems)

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10 pages, 2036 KiB

Open AccessArticle

Biomimetic Precapillary Flow Patterns for Enhancing Blood Plasma Separation: A Preliminary Study

by Bumseok Namgung¹, Justin Kok Soon Tan¹, Peter Agustinus Wong¹, Sung-Yong Park²

, Hwa Liang Leo¹ and Sangho Kim^1,*

¹ Department of Biomedical Engineering, National University of Singapore, Singapore 117583, Singapore

² Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore

Sensors 2016, 16(9), 1543; https://doi.org/10.3390/s16091543 - 21 Sep 2016

Cited by 3 | Viewed by 7292

Abstract

In this study, a biomimetic microfluidic plasma separation device is discussed. The design of the device drew inspiration from in vivo observations of enhanced cell-free layer (CFL) formation downstream of vascular bifurcations. The working principle for the plasma separation was based on the [...] Read more.

In this study, a biomimetic microfluidic plasma separation device is discussed. The design of the device drew inspiration from in vivo observations of enhanced cell-free layer (CFL) formation downstream of vascular bifurcations. The working principle for the plasma separation was based on the plasma skimming effect in an arteriolar bifurcation, which is modulated by CFL formation. The enhancement of the CFL width was achieved by a local hematocrit reduction near the collection channel by creating an uneven hematocrit distribution at the bifurcation of the channel. The device demonstrated a high purity of separation (~99.9%) at physiological levels of hematocrit (~40%). Full article

(This article belongs to the Special Issue Biomicrofluidics)

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10 pages, 1392 KiB

Open AccessArticle

Intensity-Stabilized Fast-Scanned Direct Absorption Spectroscopy Instrumentation Based on a Distributed Feedback Laser with Detection Sensitivity down to 4 × 10⁻⁶

by Gang Zhao^1,2, Wei Tan^1,2, Mengyuan Jia^1,2, Jiajuan Hou^1,2, Weiguang Ma^1,2,3,*, Lei Dong^1,2

, Lei Zhang^1,2, Xiaoxia Feng⁴, Xuechun Wu⁵, Wangbao Yin^1,2, Liantuan Xiao^1,2, Ove Axner³ and Suotang Jia^1,2

¹ State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China

² Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China

³ Department of Physics, Umeå University, Umeå SE-901 87, Sweden

⁴ Department of Electrical Engineering and Automation, Shanxi Polytechnic College, Taiyuan 030006, China

⁵ Shanxi Guohui Optoelectronic Technology CO., Ltd., Taiyuan 030006, China

Sensors 2016, 16(9), 1544; https://doi.org/10.3390/s16091544 - 21 Sep 2016

Cited by 15 | Viewed by 7350

Abstract

A novel, intensity-stabilized, fast-scanned, direct absorption spectroscopy (IS-FS-DAS) instrumentation, based on a distributed feedback (DFB) diode laser, is developed. A fiber-coupled polarization rotator and a fiber-coupled polarizer are used to stabilize the intensity of the laser, which significantly reduces its relative intensity noise [...] Read more.

A novel, intensity-stabilized, fast-scanned, direct absorption spectroscopy (IS-FS-DAS) instrumentation, based on a distributed feedback (DFB) diode laser, is developed. A fiber-coupled polarization rotator and a fiber-coupled polarizer are used to stabilize the intensity of the laser, which significantly reduces its relative intensity noise (RIN). The influence of white noise is reduced by fast scanning over the spectral feature (at 1 kHz), followed by averaging. By combining these two noise-reducing techniques, it is demonstrated that direct absorption spectroscopy (DAS) can be swiftly performed down to a limit of detection (LOD) (1σ) of 4 × 10⁻⁶, which opens up a number of new applications. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 3032 KiB

Open AccessArticle

Features of a Self-Mixing Laser Diode Operating Near Relaxation Oscillation

by Bin Liu¹

, Yanguang Yu^1,*, Jiangtao Xi¹, Yuanlong Fan², Qinghua Guo¹, Jun Tong¹ and Roger A. Lewis²

¹ School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Northfields Ave, Wollongong, NSW 2522, Australia

² School of Physics, University of Wollongong, Wollongong, NSW 2522, Australia

Sensors 2016, 16(9), 1546; https://doi.org/10.3390/s16091546 - 21 Sep 2016

Cited by 11 | Viewed by 6749

Abstract

When a fraction of the light reflected by an external cavity re-enters the laser cavity, both the amplitude and the frequency of the lasing field can be modulated. This phenomenon is called the self-mixing effect (SME). A self-mixing laser diode (SM-LD) is a [...] Read more.

When a fraction of the light reflected by an external cavity re-enters the laser cavity, both the amplitude and the frequency of the lasing field can be modulated. This phenomenon is called the self-mixing effect (SME). A self-mixing laser diode (SM-LD) is a sensor using the SME. Usually, such LDs operate below the stability boundary where no relaxation oscillation happens. The boundary is determined by the operation condition including the injection current, optical feedback strength and external cavity length. This paper discovers the features of an SM-LD where the LD operates beyond the stability boundary, that is, near the relaxation oscillation (RO) status. We call the signals from such a SM-LD as RO-SM signals to differentiate them from the conventional SM signals reported in the literature. Firstly, simulations are made based on the well-known Lang and Kobayashi (L-K) equations. Then the experiments are conducted on different LDs to verify the simulation results. It shows that a RO-SM signal exhibits high frequency oscillation with its amplitude modulated by a slow time varying envelop which corresponds to the movement of the external target. The envelope has same fringe structure (half-wavelength displacement resolution) with the conventional SM signals. However, the amplitudes of the RO-SM signals are much higher compared to conventional SM signals. The results presented reveal that an SM-LD operating near the RO has potential for achieving sensing with improved sensitivity. Full article

(This article belongs to the Special Issue Laser Sensors for Displacement, Distance, Flow, Velocity and Vibrations Measurements)

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17 pages, 1122 KiB

Open AccessArticle

Electronic Nose Testing Procedure for the Definition of Minimum Performance Requirements for Environmental Odor Monitoring

by Lidia Eusebio

, Laura Capelli^*

and Selena Sironi

Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano 20133, Italy

Sensors 2016, 16(9), 1548; https://doi.org/10.3390/s16091548 - 21 Sep 2016

Cited by 47 | Viewed by 9993

Abstract

Despite initial enthusiasm towards electronic noses and their possible application in different fields, and quite a lot of promising results, several criticalities emerge from most published research studies, and, as a matter of fact, the diffusion of electronic noses in real-life applications is [...] Read more.

Despite initial enthusiasm towards electronic noses and their possible application in different fields, and quite a lot of promising results, several criticalities emerge from most published research studies, and, as a matter of fact, the diffusion of electronic noses in real-life applications is still very limited. In general, a first step towards large-scale-diffusion of an analysis method, is standardization. The aim of this paper is describing the experimental procedure adopted in order to evaluate electronic nose performances, with the final purpose of establishing minimum performance requirements, which is considered to be a first crucial step towards standardization of the specific case of electronic nose application for environmental odor monitoring at receptors. Based on the experimental results of the performance testing of a commercialized electronic nose type with respect to three criteria (i.e., response invariability to variable atmospheric conditions, instrumental detection limit, and odor classification accuracy), it was possible to hypothesize a logic that could be adopted for the definition of minimum performance requirements, according to the idea that these are technologically achievable. Full article

(This article belongs to the Special Issue E-noses: Sensors and Applications)

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29 pages, 2991 KiB

Open AccessArticle

Underdetermined DOA Estimation Using MVDR-Weighted LASSO

by Amgad A. Salama

, M. Omair Ahmad^* and M. N. S. Swamy

Department of Electrical and Computer Engineering, Concordia University, Montreal, PQ H3G 1M8, Canada

Sensors 2016, 16(9), 1549; https://doi.org/10.3390/s16091549 - 21 Sep 2016

Cited by 16 | Viewed by 8268

Abstract

The direction of arrival (DOA) estimation problem is formulated in a compressive sensing (CS) framework, and an extended array aperture is presented to increase the number of degrees of freedom of the array. The ordinary least square adaptable least absolute shrinkage and selection [...] Read more.

The direction of arrival (DOA) estimation problem is formulated in a compressive sensing (CS) framework, and an extended array aperture is presented to increase the number of degrees of freedom of the array. The ordinary least square adaptable least absolute shrinkage and selection operator (OLS A-LASSO) is applied for the first time for DOA estimation. Furthermore, a new LASSO algorithm, the minimum variance distortionless response (MVDR) A-LASSO, which solves the DOA problem in the CS framework, is presented. The proposed algorithm does not depend on the singular value decomposition nor on the orthogonality of the signal and the noise subspaces. Hence, the DOA estimation can be done without a priori knowledge of the number of sources. The proposed algorithm can estimate up to

((M^{2} - 2) / 2 + M - 1) / 2

sources using M sensors without any constraints or assumptions about the nature of the signal sources. Furthermore, the proposed algorithm exhibits performance that is superior compared to that of the classical DOA estimation methods, especially for low signal to noise ratios (SNR), spatially-closed sources and coherent scenarios. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 4079 KiB

Open AccessArticle

Design and Implementation of Sound Searching Robots in Wireless Sensor Networks

by Lianfu Han^1,*, Zhengguang Shen², Changfeng Fu¹ and Chao Liu¹

¹ School of Electronic Science, Northeast Petroleum University, Daqing 163318, China

² Beijing Institute of Automatic Control Equipment, Beijing 100076, China

Sensors 2016, 16(9), 1550; https://doi.org/10.3390/s16091550 - 21 Sep 2016

Cited by 14 | Viewed by 7852

Abstract

A sound target-searching robot system which includes a 4-channel microphone array for sound collection, magneto-resistive sensor for declination measurement, and a wireless sensor networks (WSN) for exchanging information is described. It has an embedded sound signal enhancement, recognition and location method, and a [...] Read more.

A sound target-searching robot system which includes a 4-channel microphone array for sound collection, magneto-resistive sensor for declination measurement, and a wireless sensor networks (WSN) for exchanging information is described. It has an embedded sound signal enhancement, recognition and location method, and a sound searching strategy based on a digital signal processor (DSP). As the wireless network nodes, three robots comprise the WSN a personal computer (PC) in order to search the three different sound targets in task-oriented collaboration. The improved spectral subtraction method is used for noise reduction. As the feature of audio signal, Mel-frequency cepstral coefficient (MFCC) is extracted. Based on the K-nearest neighbor classification method, we match the trained feature template to recognize sound signal type. This paper utilizes the improved generalized cross correlation method to estimate time delay of arrival (TDOA), and then employs spherical-interpolation for sound location according to the TDOA and the geometrical position of the microphone array. A new mapping has been proposed to direct the motor to search sound targets flexibly. As the sink node, the PC receives and displays the result processed in the WSN, and it also has the ultimate power to make decision on the received results in order to improve their accuracy. The experiment results show that the designed three-robot system implements sound target searching function without collisions and performs well. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

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8 pages, 4349 KiB

Open AccessArticle

A Portable Laser Photoacoustic Methane Sensor Based on FPGA

by Jianwei Wang^1,*, Huili Wang² and Xianyong Liu¹

¹ School of Information Engineering, Robot Technology Used for Special Environment Key Laboratory of Sichuan Province, Southwest University of Science and Technology, Mianyang 621010, China

² Joint Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology and Research Center of Laser Fusion CAEP, Mianyang 621010, China

Sensors 2016, 16(9), 1551; https://doi.org/10.3390/s16091551 - 21 Sep 2016

Cited by 15 | Viewed by 8092

Abstract

A portable laser photoacoustic sensor for methane (CH₄) detection based on a field-programmable gate array (FPGA) is reported. A tunable distributed feedback (DFB) diode laser in the 1654 nm wavelength range is used as an excitation source. The photoacoustic signal processing [...] Read more.

A portable laser photoacoustic sensor for methane (CH₄) detection based on a field-programmable gate array (FPGA) is reported. A tunable distributed feedback (DFB) diode laser in the 1654 nm wavelength range is used as an excitation source. The photoacoustic signal processing was implemented by a FPGA device. A small resonant photoacoustic cell is designed. The minimum detection limit (1σ) of 10 ppm for methane is demonstrated. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 2559 KiB

Open AccessArticle

A Small Range Six-Axis Accelerometer Designed with High Sensitivity DCB Elastic Element

by Zhibo Sun^1,2, Jinhao Liu^1,*, Chunzhan Yu¹ and Yili Zheng¹

¹ School of Technology, Beijing Forestry University, Beijing 100083, China

² Engineering Training Center, Beihang University, Beijing 102206, China

Sensors 2016, 16(9), 1552; https://doi.org/10.3390/s16091552 - 21 Sep 2016

Cited by 22 | Viewed by 8172

Abstract

This paper describes a small range six-axis accelerometer (the measurement range of the sensor is ±g) with high sensitivity DCB (Double Cantilever Beam) elastic element. This sensor is developed based on a parallel mechanism because of the reliability. The accuracy of sensors is [...] Read more.

This paper describes a small range six-axis accelerometer (the measurement range of the sensor is ±g) with high sensitivity DCB (Double Cantilever Beam) elastic element. This sensor is developed based on a parallel mechanism because of the reliability. The accuracy of sensors is affected by its sensitivity characteristics. To improve the sensitivity, a DCB structure is applied as the elastic element. Through dynamic analysis, the dynamic model of the accelerometer is established using the Lagrange equation, and the mass matrix and stiffness matrix are obtained by a partial derivative calculation and a conservative congruence transformation, respectively. By simplifying the structure of the accelerometer, a model of the free vibration is achieved, and the parameters of the sensor are designed based on the model. Through stiffness analysis of the DCB structure, the deflection curve of the beam is calculated. Compared with the result obtained using a finite element analysis simulation in ANSYS Workbench, the coincidence rate of the maximum deflection is 89.0% along the x-axis, 88.3% along the y-axis and 87.5% along the z-axis. Through strain analysis of the DCB elastic element, the sensitivity of the beam is obtained. According to the experimental result, the accuracy of the theoretical analysis is found to be 90.4% along the x-axis, 74.9% along the y-axis and 78.9% along the z-axis. The measurement errors of linear accelerations a_x, a_y and a_z in the experiments are 2.6%, 0.6% and 1.31%, respectively. The experiments prove that accelerometer with DCB elastic element performs great sensitive and precision characteristics. Full article

(This article belongs to the Section Physical Sensors)

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