Sensors

23 pages, 7492 KiB

Open AccessArticle

A Wireless Sensor Network with Soft Computing Localization Techniques for Track Cycling Applications

by Sadik Kamel Gharghan^1,2,*, Rosdiadee Nordin¹

and Mahamod Ismail¹

¹ Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor 43600, Malaysia

² College of Electrical and Electronic Engineering Techniques, Middle Technical University, Al Doura 10022, Baghdad, Iraq

Sensors 2016, 16(8), 1043; https://doi.org/10.3390/s16081043 - 6 Aug 2016

Cited by 55 | Viewed by 9780

Abstract

In this paper, we propose two soft computing localization techniques for wireless sensor networks (WSNs). The two techniques, Neural Fuzzy Inference System (ANFIS) and Artificial Neural Network (ANN), focus on a range-based localization method which relies on the measurement of the received signal [...] Read more.

In this paper, we propose two soft computing localization techniques for wireless sensor networks (WSNs). The two techniques, Neural Fuzzy Inference System (ANFIS) and Artificial Neural Network (ANN), focus on a range-based localization method which relies on the measurement of the received signal strength indicator (RSSI) from the three ZigBee anchor nodes distributed throughout the track cycling field. The soft computing techniques aim to estimate the distance between bicycles moving on the cycle track for outdoor and indoor velodromes. In the first approach the ANFIS was considered, whereas in the second approach the ANN was hybridized individually with three optimization algorithms, namely Particle Swarm Optimization (PSO), Gravitational Search Algorithm (GSA), and Backtracking Search Algorithm (BSA). The results revealed that the hybrid GSA-ANN outperforms the other methods adopted in this paper in terms of accuracy localization and distance estimation accuracy. The hybrid GSA-ANN achieves a mean absolute distance estimation error of 0.02 m and 0.2 m for outdoor and indoor velodromes, respectively. Full article

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

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16 pages, 4292 KiB

Open AccessArticle

An Omnidirectional Polarization Detector Based on a Metamaterial Absorber

by Binzhen Zhang^1,2,†, Yong Zhang^1,2,*,†, Junping Duan^1,2,†, Wendong Zhang^1,2

and Wanjun Wang³

¹ Science and Technology on Electronic Test & Measurement Laboratory, North University of China, Taiyuan 030051, China

² School of Instrument and Electronics, North University of China, Taiyuan 030051, China

³ Department of Mechanical Engineering, Louisiana State University, Baton Rouge, LA 70803, USA

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1153; https://doi.org/10.3390/s16081153 - 23 Jul 2016

Cited by 21 | Viewed by 5752

Abstract

The theory, design, simulation, fabrication, and performance of an omnidirectional polarization detector (PD) with two resonances located in the X and Ka ranges based on a metamaterial absorber (MMA) are presented in this paper. The sandwich structure of PD is composed of 0.1 [...] Read more.

The theory, design, simulation, fabrication, and performance of an omnidirectional polarization detector (PD) with two resonances located in the X and Ka ranges based on a metamaterial absorber (MMA) are presented in this paper. The sandwich structure of PD is composed of 0.1 μm periodic “I” shaped patches on the metasurface, a dielectric of 200 μm FR-4 on the interlayer, and a 0.3 μm copper film on the substrate. PD absorptivity is first used to reflect and describe the polarization of the incident wave. The numerical results, derived from the standard full wave finite integration technology (FIT) of CST 2015, indicates that the designed PD shows polarization sensitivity at all incidence angles. The effects on absorptivity produced by the incidence angles, polarization angles, and materials are investigated. The amplitude of absorptivity change caused by polarization reaches 99.802%. A laser ablation process is adopted to prepare the designed PD on a FR-4 board coated with copper on the double plane with a thickness that was 1/93 and 1/48 of wavelength at a resonance frequency of 16.055 GHz and 30.9 GHz, respectively. The sample test results verify the designed PD excellent detectability on the polarization of the incident waves. The proposed PD, which greatly enriches the applications of metamaterials in bolometers, thermal images, stealth materials, microstructure measurements, and electromagnetic devices, is easy to mass produce and market because of its strong detectability, ultrathin thickness, effective cost, and convenient process. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 10876 KiB

Open AccessArticle

A Network Coverage Information-Based Sensor Registry System for IoT Environments

by Hyunjun Jung¹, Dongwon Jeong^2,*, Sukhoon Lee³

, Byung-Won On² and Doo-Kwon Baik^4,*

¹ Department of Computer and Radio Communications Engineering, Korea University, Anam-dong, Seongbuk-Gu, Seoul 136-701, Korea

² Department of Statistics and Computer Science, Kunsan National University, Miryong-dong, Gunsan-si, Jeollabuk-do 573-701, Korea

³ Department of Biomedical Informatics, Ajou University School of Medicine, Woncheon-dong, Yeongtong-gu, Suwon 433-721, Korea

⁴ Department of Computer Science and Engineering, Korea University, Anam-dong, Seongbuk-Gu, Seoul 136-701, Korea

Sensors 2016, 16(8), 1154; https://doi.org/10.3390/s16081154 - 25 Jul 2016

Cited by 4 | Viewed by 6121

Abstract

The Internet of Things (IoT) is expected to provide better services through the interaction of physical objects via the Internet. However, its limitations cause an interoperability problem when the sensed data are exchanged between the sensor nodes in wireless sensor networks (WSNs), which [...] Read more.

The Internet of Things (IoT) is expected to provide better services through the interaction of physical objects via the Internet. However, its limitations cause an interoperability problem when the sensed data are exchanged between the sensor nodes in wireless sensor networks (WSNs), which constitute the core infrastructure of the IoT. To address this problem, a Sensor Registry System (SRS) is used. By using a SRS, the information of the heterogeneous sensed data remains pure. If users move along a road, their mobile devices predict their next positions and obtain the sensed data for that position from the SRS. If the WSNs in the location in which the users move are unstable, the sensed data will be lost. Consider a situation where the user passes through dangerous areas. If the user’s mobile device cannot receive information, they cannot be warned about the dangerous situation. To avoid this, two novel SRSs that use network coverage information have been proposed: one uses OpenSignal and the other uses the probabilistic distribution of the users accessing SRS. The empirical study showed that the proposed method can seamlessly provide services related to sensing data under any abnormal circumstance. Full article

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

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15 pages, 1247 KiB

Open AccessArticle

State Estimation for a Class of Non-Uniform Sampling Systems with Missing Measurements

by Honglei Lin and Shuli Sun^*

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

Sensors 2016, 16(8), 1155; https://doi.org/10.3390/s16081155 - 23 Jul 2016

Cited by 29 | Viewed by 5223

Abstract

This paper is concerned with the state estimation problem for a class of non-uniform sampling systems with missing measurements where the state is updated uniformly and the measurements are sampled randomly. A new state model is developed to depict the dynamics at the [...] Read more.

This paper is concerned with the state estimation problem for a class of non-uniform sampling systems with missing measurements where the state is updated uniformly and the measurements are sampled randomly. A new state model is developed to depict the dynamics at the measurement sampling points within a state update period. A non-augmented state estimator dependent on the missing rate is presented by applying an innovation analysis approach. It can provide the state estimates at the state update points and at the measurement sampling points within a state update period. Compared with the augmented method, the proposed algorithm can reduce the computational burden with the increase of the number of measurement samples within a state update period. It can deal with the optimal estimation problem for single and multi-sensor systems in a unified way. To improve the reliability, a distributed suboptimal fusion estimator at the state update points is also given for multi-sensor systems by using the covariance intersection fusion algorithm. The simulation research verifies the effectiveness of the proposed algorithms. Full article

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

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13 pages, 2143 KiB

Open AccessArticle

Test-Retest Reliability of an Automated Infrared-Assisted Trunk Accelerometer-Based Gait Analysis System

by Chia-Yu Hsu^1,2, Yuh-Show Tsai^2,*, Cheng-Shiang Yau², Hung-Hai Shie³ and Chu-Ming Wu¹

¹ Department of Rehabilitation Medicine, Ten-Chan General Hospital, No. 155, Yanping Rd., Zhongli Dist., Taoyuan City 320, Taiwan

² Department of Biomedical Engineering, Chung Yuan Christian University, No. 200, Zhongbei Rd., Zhongli Dist., Taoyuan City 320, Taiwan

³ Department of Physiotherapy, Ten-Chan General Hospital, No. 155, Yanping Rd., Zhongli Dist., Taoyuan City 320, Taiwan

Sensors 2016, 16(8), 1156; https://doi.org/10.3390/s16081156 - 23 Jul 2016

Cited by 13 | Viewed by 6372

Abstract

The aim of this study was to determine the test-retest reliability of an automated infrared-assisted, trunk accelerometer-based gait analysis system for measuring gait parameters of healthy subjects in a hospital. Thirty-five participants (28 of them females; age range, 23–79 years) performed a 5-m [...] Read more.

The aim of this study was to determine the test-retest reliability of an automated infrared-assisted, trunk accelerometer-based gait analysis system for measuring gait parameters of healthy subjects in a hospital. Thirty-five participants (28 of them females; age range, 23–79 years) performed a 5-m walk twice using an accelerometer-based gait analysis system with infrared assist. Measurements of spatiotemporal gait parameters (walking speed, step length, and cadence) and trunk control (gait symmetry, gait regularity, acceleration root mean square (RMS), and acceleration root mean square ratio (RMSR)) were recorded in two separate walking tests conducted 1 week apart. Relative and absolute test-retest reliability was determined by calculating the intra-class correlation coefficient (ICC_3,1) and smallest detectable difference (SDD), respectively. The test-retest reliability was excellent for walking speed (ICC = 0.87, 95% confidence interval = 0.74–0.93, SDD = 13.4%), step length (ICC = 0.81, 95% confidence interval = 0.63–0.91, SDD = 12.2%), cadence (ICC = 0.81, 95% confidence interval = 0.63–0.91, SDD = 10.8%), and trunk control (step and stride regularity in anterior-posterior direction, acceleration RMS and acceleration RMSR in medial-lateral direction, and acceleration RMS and stride regularity in vertical direction). An automated infrared-assisted, trunk accelerometer-based gait analysis system is a reliable tool for measuring gait parameters in the hospital environment. Full article

(This article belongs to the Special Issue Wearable Biomedical Sensors)

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20 pages, 5385 KiB

Open AccessArticle

Real Time 3D Facial Movement Tracking Using a Monocular Camera

by Yanchao Dong^1,*

, Yanming Wang¹, Jiguang Yue¹ and Zhencheng Hu²

¹ School of Electronics and Information Engineering, Tongji University, Caoan Road 4800, Shanghai 201804, China

² Department of Electrical and Electronics, Kumamoto University, 2-39-1 Kurokami, Kumamoto shi 8608555, Japan

Sensors 2016, 16(8), 1157; https://doi.org/10.3390/s16081157 - 25 Jul 2016

Cited by 7 | Viewed by 6905

Abstract

The paper proposes a robust framework for 3D facial movement tracking in real time using a monocular camera. It is designed to estimate the 3D face pose and local facial animation such as eyelid movement and mouth movement. The framework firstly utilizes the [...] Read more.

The paper proposes a robust framework for 3D facial movement tracking in real time using a monocular camera. It is designed to estimate the 3D face pose and local facial animation such as eyelid movement and mouth movement. The framework firstly utilizes the Discriminative Shape Regression method to locate the facial feature points on the 2D image and fuses the 2D data with a 3D face model using Extended Kalman Filter to yield 3D facial movement information. An alternating optimizing strategy is adopted to fit to different persons automatically. Experiments show that the proposed framework could track the 3D facial movement across various poses and illumination conditions. Given the real face scale the framework could track the eyelid with an error of 1 mm and mouth with an error of 2 mm. The tracking result is reliable for expression analysis or mental state inference. Full article

(This article belongs to the Section Physical Sensors)

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21 pages, 15466 KiB

Open AccessArticle

System Description and First Application of an FPGA-Based Simultaneous Multi-Frequency Electrical Impedance Tomography

by Susana Aguiar Santos^*

, Anne Robens, Anna Boehm

, Steffen Leonhardt

and Daniel Teichmann

Philips Chair for Medical Information Technology, RWTH Aachen University, Pauwelsstrasse 20, Aachen 52074, Germany

Sensors 2016, 16(8), 1158; https://doi.org/10.3390/s16081158 - 25 Jul 2016

Cited by 33 | Viewed by 9156

Abstract

A new prototype of a multi-frequency electrical impedance tomography system is presented. The system uses a field-programmable gate array as a main controller and is configured to measure at different frequencies simultaneously through a composite waveform. Both real and imaginary components of the [...] Read more.

A new prototype of a multi-frequency electrical impedance tomography system is presented. The system uses a field-programmable gate array as a main controller and is configured to measure at different frequencies simultaneously through a composite waveform. Both real and imaginary components of the data are computed for each frequency and sent to the personal computer over an ethernet connection, where both time-difference imaging and frequency-difference imaging are reconstructed and visualized. The system has been tested for both time-difference and frequency-difference imaging for diverse sets of frequency pairs in a resistive/capacitive test unit and in self-experiments. To our knowledge, this is the first work that shows preliminary frequency-difference images of in-vivo experiments. Results of time-difference imaging were compared with simulation results and shown that the new prototype performs well at all frequencies in the tested range of 60 kHz–960 kHz. For frequency-difference images, further development of algorithms and an improved normalization process is required to correctly reconstruct and interpreted the resulting images. Full article

(This article belongs to the Special Issue Noninvasive Biomedical Sensors)

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20 pages, 2321 KiB

Open AccessArticle

Wideband Fully-Programmable Dual-Mode CMOS Analogue Front-End for Electrical Impedance Spectroscopy

by Virgilio Valente^* and Andreas Demosthenous

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

Sensors 2016, 16(8), 1159; https://doi.org/10.3390/s16081159 - 25 Jul 2016

Cited by 22 | Viewed by 8587

Abstract

This paper presents a multi-channel dual-mode CMOS analogue front-end (AFE) for electrochemical and bioimpedance analysis. Current-mode and voltage-mode readouts, integrated on the same chip, can provide an adaptable platform to correlate single-cell biosensor studies with large-scale tissue or organ analysis for real-time cancer [...] Read more.

This paper presents a multi-channel dual-mode CMOS analogue front-end (AFE) for electrochemical and bioimpedance analysis. Current-mode and voltage-mode readouts, integrated on the same chip, can provide an adaptable platform to correlate single-cell biosensor studies with large-scale tissue or organ analysis for real-time cancer detection, imaging and characterization. The chip, implemented in a 180-nm CMOS technology, combines two current-readout (CR) channels and four voltage-readout (VR) channels suitable for both bipolar and tetrapolar electrical impedance spectroscopy (EIS) analysis. Each VR channel occupies an area of 0.48 mm

^{2}

, is capable of an operational bandwidth of 8 MHz and a linear gain in the range between −6 dB and 42 dB. The gain of the CR channel can be set to 10 kΩ, 50 kΩ or 100 kΩ and is capable of 80-dB dynamic range, with a very linear response for input currents between 10 nA and 100

μ

A. Each CR channel occupies an area of 0.21 mm

^{2}

. The chip consumes between 530

μ

A and 690

μ

A per channel and operates from a 1.8-V supply. The chip was used to measure the impedance of capacitive interdigitated electrodes in saline solution. Measurements show close matching with results obtained using a commercial impedance analyser. The chip will be part of a fully flexible and configurable fully-integrated dual-mode EIS system for impedance sensors and bioimpedance analysis. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 2696 KiB

Open AccessArticle

Robust Decentralized Nonlinear Control for a Twin Rotor MIMO System

by Lidia María Belmonte¹, Rafael Morales^1,*

, Antonio Fernández-Caballero¹

and José Andrés Somolinos²

¹ Escuela de Ingenieros Industriales de Albacete, Universidad de Castilla-La Mancha, 02071 Albacete, Spain

² Escuela Técnica Superior de Ingenieros Navales, Universidad Politécnica de Madrid, 28040 Madrid, Spain

Sensors 2016, 16(8), 1160; https://doi.org/10.3390/s16081160 - 27 Jul 2016

Cited by 24 | Viewed by 11983

Abstract

This article presents the design of a novel decentralized nonlinear multivariate control scheme for an underactuated, nonlinear and multivariate laboratory helicopter denominated the twin rotor MIMO system (TRMS). The TRMS is characterized by a coupling effect between rotor dynamics and the body of [...] Read more.

This article presents the design of a novel decentralized nonlinear multivariate control scheme for an underactuated, nonlinear and multivariate laboratory helicopter denominated the twin rotor MIMO system (TRMS). The TRMS is characterized by a coupling effect between rotor dynamics and the body of the model, which is due to the action-reaction principle originated in the acceleration and deceleration of the motor-propeller groups. The proposed controller is composed of two nested loops that are utilized to achieve stabilization and precise trajectory tracking tasks for the controlled position of the generalized coordinates of the TRMS. The nonlinear internal loop is used to control the electrical dynamics of the platform, and the nonlinear external loop allows the platform to be perfectly stabilized and positioned in space. Finally, we illustrate the theoretical control developments with a set of experiments in order to verify the effectiveness of the proposed nonlinear decentralized feedback controller, in which a comparative study with other controllers is performed, illustrating the excellent performance of the proposed robust decentralized control scheme in both stabilization and trajectory tracking tasks. Full article

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

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25 pages, 2208 KiB

Open AccessArticle

An Analysis on Sensor Locations of the Human Body for Wearable Fall Detection Devices: Principles and Practice

by Ahmet Turan Özdemir

Department of Electrical and Electronics Engineering, Erciyes University, Kayseri 38039, Turkey

Sensors 2016, 16(8), 1161; https://doi.org/10.3390/s16081161 - 25 Jul 2016

Cited by 153 | Viewed by 14384

Abstract

Wearable devices for fall detection have received attention in academia and industry, because falls are very dangerous, especially for elderly people, and if immediate aid is not provided, it may result in death. However, some predictive devices are not easily worn by elderly [...] Read more.

Wearable devices for fall detection have received attention in academia and industry, because falls are very dangerous, especially for elderly people, and if immediate aid is not provided, it may result in death. However, some predictive devices are not easily worn by elderly people. In this work, a huge dataset, including 2520 tests, is employed to determine the best sensor placement location on the body and to reduce the number of sensor nodes for device ergonomics. During the tests, the volunteer’s movements are recorded with six groups of sensors each with a triaxial (accelerometer, gyroscope and magnetometer) sensor, which is placed tightly on different parts of the body with special straps: head, chest, waist, right-wrist, right-thigh and right-ankle. The accuracy of individual sensor groups with their location is investigated with six machine learning techniques, namely the k-nearest neighbor (k-NN) classifier, Bayesian decision making (BDM), support vector machines (SVM), least squares method (LSM), dynamic time warping (DTW) and artificial neural networks (ANNs). Each technique is applied to single, double, triple, quadruple, quintuple and sextuple sensor configurations. These configurations create 63 different combinations, and for six machine learning techniques, a total of 63 × 6 = 378 combinations is investigated. As a result, the waist region is found to be the most suitable location for sensor placement on the body with 99.96% fall detection sensitivity by using the k-NN classifier, whereas the best sensitivity achieved by the wrist sensor is 97.37%, despite this location being highly preferred for today’s wearable applications. Full article

(This article belongs to the Special Issue Wearable Biomedical Sensors)

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14 pages, 4037 KiB

Open AccessArticle

Substrate and Passivation Techniques for Flexible Amorphous Silicon-Based X-ray Detectors

by Michael A. Marrs^1,* and Gregory B. Raupp²

¹ Flexible Electronics and Display Center, Arizona State University, Tempe, AZ 85284, USA

² School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287, USA

Sensors 2016, 16(8), 1162; https://doi.org/10.3390/s16081162 - 26 Jul 2016

Cited by 7 | Viewed by 8782

Abstract

Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si) PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. [...] Read more.

Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si) PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. This paper examines how altering device structuring and diode passivation layers can greatly improve the electrical performance and the mechanical reliability of the device, thereby eliminating one of the major weaknesses of a-Si PIN diodes in comparison to alternative photodetector technology, such as organic bulk heterojunction photodiodes and amorphous selenium. A dark current of 0.5 pA/mm² and photodiode quantum efficiency of 74% are possible with a pixelated diode structure with a silicon nitride/SU-8 bilayer passivation structure on a 20 µm-thick polyimide substrate. Full article

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

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11 pages, 2731 KiB

Open AccessArticle

A Sensor Array for the Detection and Discrimination of Methane and Other Environmental Pollutant Gases

by Ami Hannon^1,2, Yijiang Lu^1,3, Jing Li¹ and M. Meyyappan^1,*

¹ NASA Ames Research Center, Moffett Field, CA 94035, USA

² Analtyical Mechanics Associates, Inc. at NASA Ames Research Center, Moffett Field, CA 94035, USA

³ ELORET Corporation at NASA Ames Research Center, Moffett Field, CA 94035, USA

Sensors 2016, 16(8), 1163; https://doi.org/10.3390/s16081163 - 25 Jul 2016

Cited by 55 | Viewed by 10385

Abstract

We address the sensitive detection and discrimination of gases impacting the environment, such as CH₄, NH₃, SO₂, and CO, using a sensor array and aided by principal component analysis (PCA). A 32-element chemiresistive sensor array consisting of [...] Read more.

We address the sensitive detection and discrimination of gases impacting the environment, such as CH₄, NH₃, SO₂, and CO, using a sensor array and aided by principal component analysis (PCA). A 32-element chemiresistive sensor array consisting of nine different sensor materials including seven types of modified single-walled carbon nanotubes and two types of polymers has been constructed. PCA results demonstrate excellent discriminating ability of the chemiresistor sensor chip in the 1–30 ppm concentration range. The accuracy of the sensor was verified against data collected using cavity ring down spectroscopy. The sensor chip has also been integrated with a smartphone and has been shown to reproduce the sensing performance obtained with the laboratory measurement system. Full article

(This article belongs to the Special Issue Gas Nanosensors)

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31 pages, 3832 KiB

Open AccessReview

Distributed Fiber-Optic Sensors for Vibration Detection

by Xin Liu, Baoquan Jin

, Qing Bai

, Yu Wang

, Dong Wang and Yuncai Wang^*

Key Laboratory of Advanced Transducers and Intelligent Control Systems, Ministry of Education, Taiyuan University of Technology, No. 79 Yingzexi Street, Taiyuan 030024, China

Sensors 2016, 16(8), 1164; https://doi.org/10.3390/s16081164 - 26 Jul 2016

Cited by 239 | Viewed by 23524

Abstract

Distributed fiber-optic vibration sensors receive extensive investigation and play a significant role in the sensor panorama. Optical parameters such as light intensity, phase, polarization state, or light frequency will change when external vibration is applied on the sensing fiber. In this paper, various [...] Read more.

Distributed fiber-optic vibration sensors receive extensive investigation and play a significant role in the sensor panorama. Optical parameters such as light intensity, phase, polarization state, or light frequency will change when external vibration is applied on the sensing fiber. In this paper, various technologies of distributed fiber-optic vibration sensing are reviewed, from interferometric sensing technology, such as Sagnac, Mach–Zehnder, and Michelson, to backscattering-based sensing technology, such as phase-sensitive optical time domain reflectometer, polarization-optical time domain reflectometer, optical frequency domain reflectometer, as well as some combinations of interferometric and backscattering-based techniques. Their operation principles are presented and recent research efforts are also included. Finally, the applications of distributed fiber-optic vibration sensors are summarized, which mainly include structural health monitoring and perimeter security, etc. Overall, distributed fiber-optic vibration sensors possess the advantages of large-scale monitoring, good concealment, excellent flexibility, and immunity to electromagnetic interference, and thus show considerable potential for a variety of practical applications. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 6461 KiB

Open AccessArticle

Optical Analog to Electromagnetically Induced Transparency in Cascaded Ring-Resonator Systems

by Yonghua Wang

, Hua Zheng, Chenyang Xue^* and Wendong Zhang

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

Sensors 2016, 16(8), 1165; https://doi.org/10.3390/s16081165 - 25 Jul 2016

Cited by 4 | Viewed by 5683

Abstract

The analogue of electromagnetically induced transparency in optical methods has shown great potential in slow light and sensing applications. Here, we experimentally demonstrated a coupled resonator induced transparency system with three cascaded ring coupled resonators in a silicon chip. The structure was modeled [...] Read more.

The analogue of electromagnetically induced transparency in optical methods has shown great potential in slow light and sensing applications. Here, we experimentally demonstrated a coupled resonator induced transparency system with three cascaded ring coupled resonators in a silicon chip. The structure was modeled by using the transfer matrix method. Influences of various parameters including coupling ratio of couplers, waveguide loss and additional loss of couplers on transmission characteristic and group index have been investigated theoretically and numerically in detail. The transmission character of the system was measured by the vertical grating coupling method. The enhanced quality factor reached 1.22 × 10⁵. In addition, we further test the temperature performance of the device. The results provide a new method for the manipulation of light in highly integrated optical circuits and sensing applications. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 791 KiB

Open AccessArticle

Computation and Communication Evaluation of an Authentication Mechanism for Time-Triggered Networked Control Systems

by Goncalo Martins¹, Arul Moondra², Abhishek Dubey², Anirban Bhattacharjee² and Xenofon D. Koutsoukos^2,*

¹ Department of Electrical and Computer Engineering, University of Denver, Denver, CO 80208, USA

² Institute for Software Integrated Systems (ISIS), Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN 37212, USA

Sensors 2016, 16(8), 1166; https://doi.org/10.3390/s16081166 - 25 Jul 2016

Cited by 7 | Viewed by 5096

Abstract

In modern networked control applications, confidentiality and integrity are important features to address in order to prevent against attacks. Moreover, network control systems are a fundamental part of the communication components of current cyber-physical systems (e.g., automotive communications). Many networked control systems employ [...] Read more.

In modern networked control applications, confidentiality and integrity are important features to address in order to prevent against attacks. Moreover, network control systems are a fundamental part of the communication components of current cyber-physical systems (e.g., automotive communications). Many networked control systems employ Time-Triggered (TT) architectures that provide mechanisms enabling the exchange of precise and synchronous messages. TT systems have computation and communication constraints, and with the aim to enable secure communications in the network, it is important to evaluate the computational and communication overhead of implementing secure communication mechanisms. This paper presents a comprehensive analysis and evaluation of the effects of adding a Hash-based Message Authentication (HMAC) to TT networked control systems. The contributions of the paper include (1) the analysis and experimental validation of the communication overhead, as well as a scalability analysis that utilizes the experimental result for both wired and wireless platforms and (2) an experimental evaluation of the computational overhead of HMAC based on a kernel-level Linux implementation. An automotive application is used as an example, and the results show that it is feasible to implement a secure communication mechanism without interfering with the existing automotive controller execution times. The methods and results of the paper can be used for evaluating the performance impact of security mechanisms and, thus, for the design of secure wired and wireless TT networked control systems. Full article

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

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22 pages, 6326 KiB

Open AccessArticle

Fuzzy Adaptive Cubature Kalman Filter for Integrated Navigation Systems

by Chien-Hao Tseng¹, Sheng-Fuu Lin¹ and Dah-Jing Jwo^2,*

¹ Institute of Electrical Control Engineering, National Chiao Tung University, Hsinchu 300, Taiwan

² Department of Communications, Navigation and Control Engineering, National Taiwan Ocean University, Keelung 202, Taiwan

Sensors 2016, 16(8), 1167; https://doi.org/10.3390/s16081167 - 26 Jul 2016

Cited by 42 | Viewed by 7640

Abstract

This paper presents a sensor fusion method based on the combination of cubature Kalman filter (CKF) and fuzzy logic adaptive system (FLAS) for the integrated navigation systems, such as the GPS/INS (Global Positioning System/inertial navigation system) integration. The third-degree spherical-radial cubature rule applied [...] Read more.

This paper presents a sensor fusion method based on the combination of cubature Kalman filter (CKF) and fuzzy logic adaptive system (FLAS) for the integrated navigation systems, such as the GPS/INS (Global Positioning System/inertial navigation system) integration. The third-degree spherical-radial cubature rule applied in the CKF has been employed to avoid the numerically instability in the system model. In processing navigation integration, the performance of nonlinear filter based estimation of the position and velocity states may severely degrade caused by modeling errors due to dynamics uncertainties of the vehicle. In order to resolve the shortcoming for selecting the process noise covariance through personal experience or numerical simulation, a scheme called the fuzzy adaptive cubature Kalman filter (FACKF) is presented by introducing the FLAS to adjust the weighting factor of the process noise covariance matrix. The FLAS is incorporated into the CKF framework as a mechanism for timely implementing the tuning of process noise covariance matrix based on the information of degree of divergence (DOD) parameter. The proposed FACKF algorithm shows promising accuracy improvement as compared to the extended Kalman filter (EKF), unscented Kalman filter (UKF), and CKF approaches. Full article

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

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12 pages, 7236 KiB

Open AccessArticle

Computing the Deflection of the Vertical for Improving Aerial Surveys: A Comparison between EGM2008 and ITALGEO05 Estimates

by Riccardo Barzaghi^1,*, Daniela Carrion¹

, Massimiliano Pepe²

and Giuseppina Prezioso³

¹ Department of Civil and Environmental Engineering (DICA), Politecnico di Milano, Milan 20133, Italy

² Architecture, Built environment and Construction engineering (ABC), Politecnico di Milano, Mantova 46100, Italy

³ Department of Science and Technology (DIST), University of Naples “Parthenope”, Naples 80143, Italy

Sensors 2016, 16(8), 1168; https://doi.org/10.3390/s16081168 - 26 Jul 2016

Cited by 24 | Viewed by 5948

Abstract

Recent studies on the influence of the anomalous gravity field in GNSS/INS applications have shown that neglecting the impact of the deflection of vertical in aerial surveys induces horizontal and vertical errors in the measurement of an object that is part of the [...] Read more.

Recent studies on the influence of the anomalous gravity field in GNSS/INS applications have shown that neglecting the impact of the deflection of vertical in aerial surveys induces horizontal and vertical errors in the measurement of an object that is part of the observed scene; these errors can vary from a few tens of centimetres to over one meter. The works reported in the literature refer to vertical deflection values based on global geopotential model estimates. In this paper we compared this approach with the one based on local gravity data and collocation methods. In particular, denoted by ξ and η, the two mutually-perpendicular components of the deflection of the vertical vector (in the north and east directions, respectively), their values were computed by collocation in the framework of the Remove-Compute-Restore technique, applied to the gravity database used for estimating the ITALGEO05 geoid. Following this approach, these values have been computed at different altitudes that are relevant in aerial surveys. The (ξ, η) values were then also estimated using the high degree EGM2008 global geopotential model and compared with those obtained in the previous computation. The analysis of the differences between the two estimates has shown that the (ξ, η) global geopotential model estimate can be reliably used in aerial navigation applications that require the use of sensors connected to a GNSS/INS system only above a given height (e.g., 3000 m in this paper) that must be defined by simulations. Full article

(This article belongs to the Section Remote Sensors)

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24 pages, 7494 KiB

Open AccessReview

Short-Range Noncontact Sensors for Healthcare and Other Emerging Applications: A Review

by Changzhan Gu

Google Inc., Mountain View, CA 94043, USA

Sensors 2016, 16(8), 1169; https://doi.org/10.3390/s16081169 - 26 Jul 2016

Cited by 112 | Viewed by 14570

Abstract

Short-range noncontact sensors are capable of remotely detecting the precise movements of the subjects or wirelessly estimating the distance from the sensor to the subject. They find wide applications in our day lives such as noncontact vital sign detection of heart beat and [...] Read more.

Short-range noncontact sensors are capable of remotely detecting the precise movements of the subjects or wirelessly estimating the distance from the sensor to the subject. They find wide applications in our day lives such as noncontact vital sign detection of heart beat and respiration, sleep monitoring, occupancy sensing, and gesture sensing. In recent years, short-range noncontact sensors are attracting more and more efforts from both academia and industry due to their vast applications. Compared to other radar architectures such as pulse radar and frequency-modulated continuous-wave (FMCW) radar, Doppler radar is gaining more popularity in terms of system integration and low-power operation. This paper reviews the recent technical advances in Doppler radars for healthcare applications, including system hardware improvement, digital signal processing, and chip integration. This paper also discusses the hybrid FMCW-interferometry radars and the emerging applications and the future trends. Full article

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

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15 pages, 6321 KiB

Open AccessArticle

Design of a New Built-in UHF Multi-Frequency Antenna Sensor for Partial Discharge Detection in High-Voltage Switchgears

by Xiaoxing Zhang^1,2,*, Zheng Cheng¹ and Yingang Gui¹

¹ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, China

² School of Electrical Engineering, Wuhan University, Wuhan 430072, China

Sensors 2016, 16(8), 1170; https://doi.org/10.3390/s16081170 - 26 Jul 2016

Cited by 27 | Viewed by 7557

Abstract

In this study a new built-in ultrahigh frequency (UHF) antenna sensor was designed and applied in a high-voltage switchgear for partial discharge (PD) detection. The casing of the switchgear was initially used as the ground plane of the antenna sensor, which integrated the [...] Read more.

In this study a new built-in ultrahigh frequency (UHF) antenna sensor was designed and applied in a high-voltage switchgear for partial discharge (PD) detection. The casing of the switchgear was initially used as the ground plane of the antenna sensor, which integrated the sensor into the high-voltage switchgear. The Koch snowflake patch was adopted as the radiation patch of the antenna to overcome the disadvantages of common microstrip antennas, and the feed position and the dielectric layer thickness were simulated in detail. Simulation results show that the antenna sensor possessed four resonant points with good impedance matching from 300 MHz to 1000 MHz, and it also presented good multi-frequency performance in the entire working frequency band. PD detection experiments were conducted in the high-voltage switchgear, and the fabricated antenna sensor was effectively built into the high-voltage switchgear. In order to reflect the advantages of the built-in antenna sensor, another external UHF antenna sensor was used as a comparison to simultaneously detect PD. Experimental results demonstrated that the built-in antenna sensor possessed high detection sensitivity and strong anti-interference capacity, which ensured the practicability of the design. In addition, it had more high-voltage switchgear PD detection advantages than the external sensor. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 5376 KiB

Open AccessArticle

A Spray-On Carbon Nanotube Artificial Neuron Strain Sensor for Composite Structural Health Monitoring

by Gyeongrak Choi¹

, Jong Won Lee², Ju Young Cha³, Young-Ju Kim⁴

, Yeon-Sun Choi⁵, Mark J. Schulz⁶, Chang Kwon Moon⁷, Kwon Tack Lim⁷, Sung Yong Kim⁷

and Inpil Kang^7,*

¹ Manufacturing Automation R & BD Group, Korea Institute of Industrial Technology, Chonan 143-701, Korea

² Department of Architectural Engineering, Namseoul University, Cheonan 331-707, Korea

³ Department of Medical Device, Korea Institute of Machinery & Materials, Daegu 711-880, Korea

⁴ Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350, Korea

⁵ School of Mechanical Engineering, Sungkyunkwan University, Suwon 440-746, Korea

⁶ Smart Structures and Bio-Nanotechnology Laboratory, University of Cincinnati, Cincinnati, OH 45221, USA

⁷ Graduate School of Pukyong National University, Busan 608-739, Korea

Sensors 2016, 16(8), 1171; https://doi.org/10.3390/s16081171 - 26 Jul 2016

Cited by 24 | Viewed by 7111

Abstract

We present a nanocomposite strain sensor (NCSS) to develop a novel structural health monitoring (SHM) sensor that can be easily installed in a composite structure. An NCSS made of a multi-walled carbon nanotubes (MWCNT)/epoxy composite was installed on a target structure with facile [...] Read more.

We present a nanocomposite strain sensor (NCSS) to develop a novel structural health monitoring (SHM) sensor that can be easily installed in a composite structure. An NCSS made of a multi-walled carbon nanotubes (MWCNT)/epoxy composite was installed on a target structure with facile processing. We attempted to evaluate the NCSS sensing characteristics and benchmark compared to those of a conventional foil strain gauge. The response of the NCSS was fairly good and the result was nearly identical to the strain gauge. A neuron, which is a biomimetic long continuous NCSS, was also developed, and its vibration response was investigated for structural damage detection of a composite cantilever. The vibration response for damage detection was measured by tracking the first natural frequency, which demonstrated good result that matched the finite element (FE) analysis. Full article

(This article belongs to the Special Issue Integrated Structural Health Monitoring in Polymeric Composites)

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30 pages, 8740 KiB

Open AccessReview

Recent Progress on Cellulose-Based Electro-Active Paper, Its Hybrid Nanocomposites and Applications

by Asif Khan^1,†, Zafar Abas^1,†, Heung Soo Kim^1,*

and Jaehwan Kim^2,†

¹ Department of Mechanical, Robotics and Energy Engineering, Dongguk University-Seoul, 30 Pildong-ro 1-gil, Jung-gu, Seoul 04620, Korea

² Center for EAPap Actuator, Department of Mechanical Engineering, Inha University, 253 Yonghyun-dong, Nam-Gu, Incheon 22212, Korea

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1172; https://doi.org/10.3390/s16081172 - 26 Jul 2016

Cited by 68 | Viewed by 12085

Abstract

We report on the recent progress and development of research into cellulose-based electro-active paper for bending actuators, bioelectronics devices, and electromechanical transducers. The cellulose electro-active paper is characterized in terms of its biodegradability, chirality, ample chemically modifying capacity, light weight, actuation capability, and [...] Read more.

We report on the recent progress and development of research into cellulose-based electro-active paper for bending actuators, bioelectronics devices, and electromechanical transducers. The cellulose electro-active paper is characterized in terms of its biodegradability, chirality, ample chemically modifying capacity, light weight, actuation capability, and ability to form hybrid nanocomposites. The mechanical, electrical, and chemical characterizations of the cellulose-based electro-active paper and its hybrid composites such as blends or coatings with synthetic polymers, biopolymers, carbon nanotubes, chitosan, and metal oxides, are explained. In addition, the integration of cellulose electro-active paper is highlighted to form various functional devices including but not limited to bending actuators, flexible speaker, strain sensors, energy harvesting transducers, biosensors, chemical sensors and transistors for electronic applications. The frontiers in cellulose paper devices are reviewed together with the strategies and perspectives of cellulose electro-active paper and cellulose nanocomposite research and 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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19 pages, 1895 KiB

Open AccessReview

Revealing Nucleic Acid Mutations Using Förster Resonance Energy Transfer-Based Probes

by Nina P. L. Junager, Jacob Kongsted and Kira Astakhova^*

Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark

Sensors 2016, 16(8), 1173; https://doi.org/10.3390/s16081173 - 27 Jul 2016

Cited by 19 | Viewed by 9809

Abstract

Nucleic acid mutations are of tremendous importance in modern clinical work, biotechnology and in fundamental studies of nucleic acids. Therefore, rapid, cost-effective and reliable detection of mutations is an object of extensive research. Today, Förster resonance energy transfer (FRET) probes are among the [...] Read more.

Nucleic acid mutations are of tremendous importance in modern clinical work, biotechnology and in fundamental studies of nucleic acids. Therefore, rapid, cost-effective and reliable detection of mutations is an object of extensive research. Today, Förster resonance energy transfer (FRET) probes are among the most often used tools for the detection of nucleic acids and in particular, for the detection of mutations. However, multiple parameters must be taken into account in order to create efficient FRET probes that are sensitive to nucleic acid mutations. In this review; we focus on the design principles for such probes and available computational methods that allow for their rational design. Applications of advanced, rationally designed FRET probes range from new insights into cellular heterogeneity to gaining new knowledge of nucleic acid structures directly in living cells. Full article

(This article belongs to the Special Issue FRET Biosensors)

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27 pages, 49651 KiB

Open AccessArticle

Autonomous Underwater Navigation and Optical Mapping in Unknown Natural Environments

by Juan David Hernández^*

, Klemen Istenič^*, Nuno Gracias

, Narcís Palomeras

, Ricard Campos

, Eduard Vidal, Rafael García and Marc Carreras

Underwater Vision and Robotics Research Center (CIRS), Computer Vision and Robotics Institute (VICOROB), University of Girona, C\Pic de Peguera, 13 (La Creueta), 17003 Girona, Spain

Sensors 2016, 16(8), 1174; https://doi.org/10.3390/s16081174 - 26 Jul 2016

Cited by 59 | Viewed by 11297

Abstract

We present an approach for navigating in unknown environments while, simultaneously, gathering information for inspecting underwater structures using an autonomous underwater vehicle (AUV). To accomplish this, we first use our pipeline for mapping and planning collision-free paths online, which endows an AUV with [...] Read more.

We present an approach for navigating in unknown environments while, simultaneously, gathering information for inspecting underwater structures using an autonomous underwater vehicle (AUV). To accomplish this, we first use our pipeline for mapping and planning collision-free paths online, which endows an AUV with the capability to autonomously acquire optical data in close proximity. With that information, we then propose a reconstruction pipeline to create a photo-realistic textured 3D model of the inspected area. These 3D models are also of particular interest to other fields of study in marine sciences, since they can serve as base maps for environmental monitoring, thus allowing change detection of biological communities and their environment over time. Finally, we evaluate our approach using the Sparus II, a torpedo-shaped AUV, conducting inspection missions in a challenging, real-world and natural scenario. Full article

(This article belongs to the Special Issue Robotic Sensory Systems for Environment Protection and Conservation)

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18 pages, 2841 KiB

Open AccessReview

Microfluidic Surface Plasmon Resonance Sensors: From Principles to Point-of-Care Applications

by Da-Shin Wang and Shih-Kang Fan^*

Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan

Sensors 2016, 16(8), 1175; https://doi.org/10.3390/s16081175 - 27 Jul 2016

Cited by 125 | Viewed by 14564

Abstract

Surface plasmon resonance (SPR) is a label-free, highly-sensitive, and real-time sensing technique. Conventional SPR sensors, which involve a planar thin gold film, have been widely exploited in biosensing; various miniaturized formats have been devised for portability purposes. Another type of SPR sensor which [...] Read more.

Surface plasmon resonance (SPR) is a label-free, highly-sensitive, and real-time sensing technique. Conventional SPR sensors, which involve a planar thin gold film, have been widely exploited in biosensing; various miniaturized formats have been devised for portability purposes. Another type of SPR sensor which utilizes localized SPR (LSPR), is based on metal nanostructures with surface plasmon modes at the structural interface. The resonance condition is sensitive to the refractive index change of the local medium. The principles of these two types of SPR sensors are reviewed and their integration with microfluidic platforms is described. Further applications of microfluidic SPR sensors to point-of-care (POC) diagnostics are discussed. Full article

(This article belongs to the Special Issue Micro/Nano Fluidic Devices and Bio-MEMS)

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20 pages, 5493 KiB

Open AccessArticle

High-Accuracy Self-Calibration for Smart, Optical Orbiting Payloads Integrated with Attitude and Position Determination

by Jin Li^1,2,3,4

, Fei Xing^1,2,3,*, Daping Chu^4,*

and Zilong Liu^1,2,3

¹ Department of Precision Instrument, Tsinghua University, Beijing 100084, China

² State Key Laboratory of Precision Measurement Technology and Instruments, Beijing 100084, China

³ Collaborative Innovation Center for Micro/Nano Fabrication, Device and System, Beijing 100084, China

⁴ Photonics and Sensors Group, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK

Sensors 2016, 16(8), 1176; https://doi.org/10.3390/s16081176 - 27 Jul 2016

Cited by 23 | Viewed by 7970

Abstract

A high-accuracy space smart payload integrated with attitude and position (SSPIAP) is a new type of optical remote sensor that can autonomously complete image positioning. Inner orientation parameters (IOPs) are a prerequisite for image position determination of an SSPIAP. The calibration of IOPs [...] Read more.

A high-accuracy space smart payload integrated with attitude and position (SSPIAP) is a new type of optical remote sensor that can autonomously complete image positioning. Inner orientation parameters (IOPs) are a prerequisite for image position determination of an SSPIAP. The calibration of IOPs significantly influences the precision of image position determination of SSPIAPs. IOPs can be precisely measured and calibrated in a laboratory. However, they may drift to a significant degree because of vibrations during complicated launches and on-orbit functioning. Therefore, laboratory calibration methods are not suitable for on-orbit functioning. We propose an on-orbit self-calibration method for SSPIAPs. Our method is based on an auto-collimating dichroic filter combined with a micro-electro-mechanical system (MEMS) point-source focal plane. A MEMS procedure is used to manufacture a light transceiver focal plane, which integrates with point light sources and a complementary metal oxide semiconductor (CMOS) sensor. A dichroic filter is used to fabricate an auto-collimation light reflection element. The dichroic filter and the MEMS point light sources focal plane are integrated into an SSPIAP so it can perform integrated self-calibration. Experiments show that our method can achieve micrometer-level precision, which is good enough to complete real-time calibration without temporal or spatial limitations. Full article

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

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15 pages, 2361 KiB

Open AccessArticle

Near-Space TOPSAR Large-Scene Full-Aperture Imaging Scheme Based on Two-Step Processing

by Qianghui Zhang^†, Junjie Wu^*,†, Wenchao Li, Yulin Huang, Jianyu Yang and Haiguang Yang

¹ School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1177; https://doi.org/10.3390/s16081177 - 27 Jul 2016

Cited by 4 | Viewed by 6095

Abstract

Free of the constraints of orbit mechanisms, weather conditions and minimum antenna area, synthetic aperture radar (SAR) equipped on near-space platform is more suitable for sustained large-scene imaging compared with the spaceborne and airborne counterparts. Terrain observation by progressive scans (TOPS), which is [...] Read more.

Free of the constraints of orbit mechanisms, weather conditions and minimum antenna area, synthetic aperture radar (SAR) equipped on near-space platform is more suitable for sustained large-scene imaging compared with the spaceborne and airborne counterparts. Terrain observation by progressive scans (TOPS), which is a novel wide-swath imaging mode and allows the beam of SAR to scan along the azimuth, can reduce the time of echo acquisition for large scene. Thus, near-space TOPS-mode SAR (NS-TOPSAR) provides a new opportunity for sustained large-scene imaging. An efficient full-aperture imaging scheme for NS-TOPSAR is proposed in this paper. In this scheme, firstly, two-step processing (TSP) is adopted to eliminate the Doppler aliasing of the echo. Then, the data is focused in two-dimensional frequency domain (FD) based on Stolt interpolation. Finally, a modified TSP (MTSP) is performed to remove the azimuth aliasing. Simulations are presented to demonstrate the validity of the proposed imaging scheme for near-space large-scene imaging application. Full article

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

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21 pages, 3155 KiB

Open AccessArticle

Defect Detection in Textures through the Use of Entropy as a Means for Automatically Selecting the Wavelet Decomposition Level

by Pedro J. Navarro^1,†

, Carlos Fernández-Isla^1,†, Pedro María Alcover^1,*,†

and Juan Suardíaz^2,†

¹ División de Sistemas e Ingeniería Electrónica (DSIE), Universidad Politécnica de Cartagena, Campus Muralla del Mar, s/n, Cartagena E-30202, Spain

² División de Innovación en Sistemas Telemáticos y Tecnología Electrónica (DINTEL), Universidad Politécnica de Cartagena, Campus Muralla del Mar, s/n, Cartagena E-30202, Spain

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1178; https://doi.org/10.3390/s16081178 - 27 Jul 2016

Cited by 24 | Viewed by 7746

Abstract

This paper presents a robust method for defect detection in textures, entropy-based automatic selection of the wavelet decomposition level (EADL), based on a wavelet reconstruction scheme, for detecting defects in a wide variety of structural and statistical textures. Two main features are presented. [...] Read more.

This paper presents a robust method for defect detection in textures, entropy-based automatic selection of the wavelet decomposition level (EADL), based on a wavelet reconstruction scheme, for detecting defects in a wide variety of structural and statistical textures. Two main features are presented. One of the new features is an original use of the normalized absolute function value (NABS) calculated from the wavelet coefficients derived at various different decomposition levels in order to identify textures where the defect can be isolated by eliminating the texture pattern in the first decomposition level. The second is the use of Shannon’s entropy, calculated over detail subimages, for automatic selection of the band for image reconstruction, which, unlike other techniques, such as those based on the co-occurrence matrix or on energy calculation, provides a lower decomposition level, thus avoiding excessive degradation of the image, allowing a more accurate defect segmentation. A metric analysis of the results of the proposed method with nine different thresholding algorithms determined that selecting the appropriate thresholding method is important to achieve optimum performance in defect detection. As a consequence, several different thresholding algorithms depending on the type of texture are proposed. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 7659 KiB

Open AccessArticle

All-Fiber Configuration Laser Self-Mixing Doppler Velocimeter Based on Distributed Feedback Fiber Laser

by Shuang Wu¹, Dehui Wang¹, Rong Xiang¹, Junfeng Zhou¹, Yangcheng Ma¹, Huaqiao Gui², Jianguo Liu²

, Huanqin Wang³, Liang Lu^1,* and Benli Yu¹

¹ Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education, Anhui University, Jiulong Road 111#, Hefei 230601, China

² Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China

³ State Key Laboratory of Transducer Technology, Institute of Intelligent Machines, Chinese Academy of Sciences, 350 Shu Shang Hu Road, Hefei 230031, China

Sensors 2016, 16(8), 1179; https://doi.org/10.3390/s16081179 - 27 Jul 2016

Cited by 21 | Viewed by 6171

Abstract

In this paper, a novel velocimeter based on laser self-mixing Doppler technology has been developed for speed measurement. The laser employed in our experiment is a distributed feedback (DFB) fiber laser, which is an all-fiber structure using only one Fiber Bragg Grating to [...] Read more.

In this paper, a novel velocimeter based on laser self-mixing Doppler technology has been developed for speed measurement. The laser employed in our experiment is a distributed feedback (DFB) fiber laser, which is an all-fiber structure using only one Fiber Bragg Grating to realize optical feedback and wavelength selection. Self-mixing interference for optical velocity sensing is experimentally investigated in this novel system, and the experimental results show that the Doppler frequency is linearly proportional to the velocity of a moving target, which agrees with the theoretical analysis commendably. In our experimental system, the velocity measurement can be achieved in the range of 3.58 mm/s–2216 mm/s with a relative error under one percent, demonstrating that our novel all-fiber configuration velocimeter can implement wide-range velocity measurements with high accuracy. Full article

(This article belongs to the Section Physical Sensors)

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26 pages, 15165 KiB

Open AccessArticle

Object Detection Applied to Indoor Environments for Mobile Robot Navigation

by Alejandra Carolina Hernández, Clara Gómez, Jonathan Crespo

and Ramón Barber^*

Department of Systems Engineering and Automation, Carlos III University of Madrid, Madrid 28911, Spain

Sensors 2016, 16(8), 1180; https://doi.org/10.3390/s16081180 - 28 Jul 2016

Cited by 40 | Viewed by 12617

Abstract

To move around the environment, human beings depend on sight more than their other senses, because it provides information about the size, shape, color and position of an object. The increasing interest in building autonomous mobile systems makes the detection and recognition of [...] Read more.

To move around the environment, human beings depend on sight more than their other senses, because it provides information about the size, shape, color and position of an object. The increasing interest in building autonomous mobile systems makes the detection and recognition of objects in indoor environments a very important and challenging task. In this work, a vision system to detect objects considering usual human environments, able to work on a real mobile robot, is developed. In the proposed system, the classification method used is Support Vector Machine (SVM) and as input to this system, RGB and depth images are used. Different segmentation techniques have been applied to each kind of object. Similarly, two alternatives to extract features of the objects are explored, based on geometric shape descriptors and bag of words. The experimental results have demonstrated the usefulness of the system for the detection and location of the objects in indoor environments. Furthermore, through the comparison of two proposed methods for extracting features, it has been determined which alternative offers better performance. The final results have been obtained taking into account the proposed problem and that the environment has not been changed, that is to say, the environment has not been altered to perform the tests. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 758 KiB

Open AccessArticle

Time-Varying Vocal Folds Vibration Detection Using a 24 GHz Portable Auditory Radar

by Hong Hong^1,†, Heng Zhao^1,†

, Zhengyu Peng^2,†, Hui Li¹, Chen Gu¹, Changzhi Li^2,* and Xiaohua Zhu¹

¹ School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

² Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX 79409, USA

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1181; https://doi.org/10.3390/s16081181 - 28 Jul 2016

Cited by 20 | Viewed by 6975

Abstract

Time-varying vocal folds vibration information is of crucial importance in speech processing, and the traditional devices to acquire speech signals are easily smeared by the high background noise and voice interference. In this paper, we present a non-acoustic way to capture the human [...] Read more.

Time-varying vocal folds vibration information is of crucial importance in speech processing, and the traditional devices to acquire speech signals are easily smeared by the high background noise and voice interference. In this paper, we present a non-acoustic way to capture the human vocal folds vibration using a 24-GHz portable auditory radar. Since the vocal folds vibration only reaches several millimeters, the high operating frequency and the 4 × 4 array antennas are applied to achieve the high sensitivity. The Variational Mode Decomposition (VMD) based algorithm is proposed to decompose the radar-detected auditory signal into a sequence of intrinsic modes firstly, and then, extract the time-varying vocal folds vibration frequency from the corresponding mode. Feasibility demonstration, evaluation, and comparison are conducted with tonal and non-tonal languages, and the low relative errors show a high consistency between the radar-detected auditory time-varying vocal folds vibration and acoustic fundamental frequency, except that the auditory radar significantly improves the frequency-resolving power. Full article

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

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23 pages, 12899 KiB

Open AccessArticle

Fast Object Motion Estimation Based on Dynamic Stixels

by Néstor Morales^*

, Antonio Morell, Jonay Toledo and Leopoldo Acosta

Departamento de Ingeniería Informática, Universidad de La Laguna, Avda. Astrofísico Francisco Sánchez, s/n, San Cristóbal de La Laguna 38271, Spain

Sensors 2016, 16(8), 1182; https://doi.org/10.3390/s16081182 - 28 Jul 2016

Cited by 6 | Viewed by 5761

Abstract

The stixel world is a simplification of the world in which obstacles are represented as vertical instances, called stixels, standing on a surface assumed to be planar. In this paper, previous approaches for stixel tracking are extended using a two-level scheme. In the [...] Read more.

The stixel world is a simplification of the world in which obstacles are represented as vertical instances, called stixels, standing on a surface assumed to be planar. In this paper, previous approaches for stixel tracking are extended using a two-level scheme. In the first level, stixels are tracked by matching them between frames using a bipartite graph in which edges represent a matching cost function. Then, stixels are clustered into sets representing objects in the environment. These objects are matched based on the number of stixels paired inside them. Furthermore, a faster, but less accurate approach is proposed in which only the second level is used. Several configurations of our method are compared to an existing state-of-the-art approach to show how our methodology outperforms it in several areas, including an improvement in the quality of the depth reconstruction. Full article

(This article belongs to the Special Issue Sensors for Autonomous Road Vehicles)

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22 pages, 1036 KiB

Open AccessArticle

Exact Distributions of Finite Random Matrices and Their Applications to Spectrum Sensing

by Wensheng Zhang^1,*, Cheng-Xiang Wang², Xiaofeng Tao³ and Piya Patcharamaneepakorn²

¹ School of Information Science and Engineering, Shandong University, Jinan 250100, China

² Institute of Sensors, Signals and Systems, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK

³ Wireless Technology Innovation Institute, Beijing University of Posts and Telecommunications, Beijing 100876, China

Sensors 2016, 16(8), 1183; https://doi.org/10.3390/s16081183 - 29 Jul 2016

Cited by 9 | Viewed by 5596

Abstract

The exact and simple distributions of finite random matrix theory (FRMT) are critically important for cognitive radio networks (CRNs). In this paper, we unify some existing distributions of the FRMT with the proposed coefficient matrices (vectors) and represent the distributions with the coefficient-based [...] Read more.

The exact and simple distributions of finite random matrix theory (FRMT) are critically important for cognitive radio networks (CRNs). In this paper, we unify some existing distributions of the FRMT with the proposed coefficient matrices (vectors) and represent the distributions with the coefficient-based formulations. A coefficient reuse mechanism is studied, i.e., the same coefficient matrices (vectors) can be exploited to formulate different distributions. For instance, the same coefficient matrices can be used by the largest eigenvalue (LE) and the scaled largest eigenvalue (SLE); the same coefficient vectors can be used by the smallest eigenvalue (SE) and the Demmel condition number (DCN). A new and simple cumulative distribution function (CDF) of the DCN is also deduced. In particular, the dimension boundary between the infinite random matrix theory (IRMT) and the FRMT is initially defined. The dimension boundary provides a theoretical way to divide random matrices into infinite random matrices and finite random matrices. The FRMT-based spectrum sensing (SS) schemes are studied for CRNs. The SLE-based scheme can be considered as an asymptotically-optimal SS scheme when the dimension K is larger than two. Moreover, the standard condition number (SCN)-based scheme achieves the same sensing performance as the SLE-based scheme for dual covariance matrix

K = 2

. The simulation results verify that the coefficient-based distributions can fit the empirical results very well, and the FRMT-based schemes outperform the IRMT-based schemes and the conventional SS schemes. Full article

(This article belongs to the Section Physical Sensors)

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8 pages, 3275 KiB

Open AccessReview

Three-Dimensional Photon Counting Imaging with Axially Distributed Sensing

by Myungjin Cho^1,* and Bahram Javidi²

¹ Department of Electrical, Electronic, and Control Engineering, Institute of Information Telecommunication Convergence (IITC), Hankyong National University, 327 Chungang-ro, Anseong-si, Kyonggi-do 456-749, Korea

² Electrical and Computer Engineering Department, University of Connecticut, Unit 4157, Storrs, CT 06269, USA

Sensors 2016, 16(8), 1184; https://doi.org/10.3390/s16081184 - 28 Jul 2016

Cited by 8 | Viewed by 5909

Abstract

In this paper, we review three-dimensional (3D) photon counting imaging with axially distributed sensing. Under severely photon-starved conditions, we have proposed various imaging and algorithmic approaches to reconstruct a scene in 3D, which are not possible by using conventional imaging system due to [...] Read more.

In this paper, we review three-dimensional (3D) photon counting imaging with axially distributed sensing. Under severely photon-starved conditions, we have proposed various imaging and algorithmic approaches to reconstruct a scene in 3D, which are not possible by using conventional imaging system due to lack of sufficient number of photons. In this paper, we present an overview of optical sensing and imaging system along with dedicated algorithms for reconstructing 3D scenes by photon counting axially distributed sensing, which may be implemented by moving a single image sensor along its optical axis. To visualize the 3D image, statistical estimation methods and computational reconstruction of axially distributed sensing is applied. Full article

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

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14 pages, 4471 KiB

Open AccessArticle

Monolithic Cylindrical Fused Silica Resonators with High Q Factors

by Yao Pan, Dongya Wang, Yanyan Wang, Jianping Liu, Suyong Wu, Tianliang Qu^*

, Kaiyong Yang and Hui Luo^*

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

Sensors 2016, 16(8), 1185; https://doi.org/10.3390/s16081185 - 28 Jul 2016

Cited by 40 | Viewed by 8330

Abstract

The cylindrical resonator gyroscope (CRG) is a typical Coriolis vibratory gyroscope whose performance is determined by the Q factor and frequency mismatch of the cylindrical resonator. Enhancing the Q factor is crucial for improving the rate sensitivity and noise performance of the CRG. [...] Read more.

The cylindrical resonator gyroscope (CRG) is a typical Coriolis vibratory gyroscope whose performance is determined by the Q factor and frequency mismatch of the cylindrical resonator. Enhancing the Q factor is crucial for improving the rate sensitivity and noise performance of the CRG. In this paper, for the first time, a monolithic cylindrical fused silica resonator with a Q factor approaching 8 × 10⁵ (ring-down time over 1 min) is reported. The resonator is made of fused silica with low internal friction and high isotropy, with a diameter of 25 mm and a center frequency of 3974.35 Hz. The structure of the resonator is first briefly introduced, and then the experimental non-contact characterization method is presented. In addition, the post-fabrication experimental procedure of Q factor improvement, including chemical and thermal treatment, is demonstrated. The Q factor improvement by both treatments is compared and the primary loss mechanism is analyzed. To the best of our knowledge, the work presented in this paper represents the highest reported Q factor for a cylindrical resonator. The proposed monolithic cylindrical fused silica resonator may enable high performance inertial sensing with standard manufacturing process and simple post-fabrication treatment. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 3177 KiB

Open AccessArticle

A Long-Term Performance Enhancement Method for FOG-Based Measurement While Drilling

by Chunxi Zhang and Tie Lin^*

School of Instrumentation Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China

Sensors 2016, 16(8), 1186; https://doi.org/10.3390/s16081186 - 28 Jul 2016

Cited by 15 | Viewed by 5905

Abstract

In the oil industry, the measurement-while-drilling (MWD) systems are usually used to provide the real-time position and orientation of the bottom hole assembly (BHA) during drilling. However, the present MWD systems based on magnetic surveying technology can barely ensure good performance because of [...] Read more.

In the oil industry, the measurement-while-drilling (MWD) systems are usually used to provide the real-time position and orientation of the bottom hole assembly (BHA) during drilling. However, the present MWD systems based on magnetic surveying technology can barely ensure good performance because of magnetic interference phenomena. In this paper, a MWD surveying system based on a fiber optic gyroscope (FOG) was developed to replace the magnetic surveying system. To accommodate the size of the downhole drilling conditions, a new design method is adopted. In order to realize long-term and high position precision and orientation surveying, an integrated surveying algorithm is proposed based on inertial navigation system (INS) and drilling features. In addition, the FOG-based MWD error model is built and the drilling features are analyzed. The state-space system model and the observation updates model of the Kalman filter are built. To validate the availability and utility of the algorithm, the semi-physical simulation is conducted under laboratory conditions. The results comparison with the traditional algorithms show that the errors were suppressed and the measurement precision of the proposed algorithm is better than the traditional ones. In addition, the proposed method uses a lot less time than the zero velocity update (ZUPT) method. Full article

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

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8 pages, 3677 KiB

Open AccessArticle

A Robust Distributed Multipoint Fiber Optic Gas Sensor System Based on AGC Amplifier Structure

by Cunguang Zhu, Rende Wang, Xuechen Tao, Guangwei Wang and Pengpeng Wang^*

School of Physics and Technology, University of Jinan, Jinan 250022, China

Sensors 2016, 16(8), 1187; https://doi.org/10.3390/s16081187 - 28 Jul 2016

Cited by 4 | Viewed by 6721

Abstract

A harsh environment-oriented distributed multipoint fiber optic gas sensor system realized by automatic gain control (AGC) technology is proposed. To improve the photoelectric signal reliability, the electronic variable gain can be modified in real time by an AGC closed-loop feedback structure to compensate [...] Read more.

A harsh environment-oriented distributed multipoint fiber optic gas sensor system realized by automatic gain control (AGC) technology is proposed. To improve the photoelectric signal reliability, the electronic variable gain can be modified in real time by an AGC closed-loop feedback structure to compensate for optical transmission loss which is caused by the fiber bend loss or other reasons. The deviation of the system based on AGC structure is below 4.02% when photoelectric signal decays due to fiber bending loss for bending radius of 5 mm, which is 20 times lower than the ordinary differential system. In addition, the AGC circuit with the same electric parameters can keep the baseline intensity of signals in different channels of the distributed multipoint sensor system at the same level. This avoids repetitive calibrations and streamlines the installation process. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 5287 KiB

Open AccessArticle

Safety and Traceability in Patient Healthcare through the Integration of RFID Technology for Intravenous Mixtures in the Prescription-Validation-Elaboration-Dispensation-Administration Circuit to Day Hospital Patients

by María Martínez Pérez^1,*

, Guillermo Vázquez González² and Carlos Dafonte¹

¹ Department of Information and Communications Technologies, Faculty of Computer Science, Campus Elviña S/N, University of A Coruña, E-15071 A Coruña, Spain

² A Coruña Universitary Hospital, Xubias de Arriba 84, E-15006 A Coruña, Spain

Sensors 2016, 16(8), 1188; https://doi.org/10.3390/s16081188 - 28 Jul 2016

Cited by 18 | Viewed by 11737

Abstract

This work presents the integration of the RFID technology with the aim of ensuring the traceability of patients and minimization of adverse events during the process of prescription-validation-elaboration-dispensation-administration of medication by means of the implementation of various passive and active WIFI RFID systems [...] Read more.

This work presents the integration of the RFID technology with the aim of ensuring the traceability of patients and minimization of adverse events during the process of prescription-validation-elaboration-dispensation-administration of medication by means of the implementation of various passive and active WIFI RFID systems in the Pharmacy and Day Hospital services of the Complejo Hospitalario Universitario A Coruña. Obtaining patient traceability and using the patient/drug binomial during this process allows us to minimize the occurrence of adverse events. The key points in this work are the unmistakably unique identification and accurate real time location of the controlled items (patients and medication). RFID technology has proved to be invaluable in assisting with the everyday clinical practice of a hospital, and has been successfully implemented in this environment and others. In services such as the day hospital, the implementation of said technology is further justified by the high costs of the service and the high risk to the patient. Full article

(This article belongs to the Special Issue Selected Papers from UCAmI, IWAAL and AmIHEALTH 2015)

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14 pages, 5671 KiB

Open AccessArticle

Fiber-Optic Surface Temperature Sensor Based on Modal Interference

by Frédéric Musin^*,†, Patrice Mégret and Marc Wuilpart^†

¹ Electromagnetism & Telecom Department, University of Mons, Boulevard Dolez 31, Mons B-7000, Belgium

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1189; https://doi.org/10.3390/s16081189 - 28 Jul 2016

Cited by 13 | Viewed by 5927

Abstract

Spatially-integrated surface temperature sensing is highly useful when it comes to controlling processes, detecting hazardous conditions or monitoring the health and safety of equipment and people. Fiber-optic sensing based on modal interference has shown great sensitivity to temperature variation, by means of cost-effective [...] Read more.

Spatially-integrated surface temperature sensing is highly useful when it comes to controlling processes, detecting hazardous conditions or monitoring the health and safety of equipment and people. Fiber-optic sensing based on modal interference has shown great sensitivity to temperature variation, by means of cost-effective image-processing of few-mode interference patterns. New developments in the field of sensor configuration, as described in this paper, include an innovative cooling and heating phase discrimination functionality and more precise measurements, based entirely on the image processing of interference patterns. The proposed technique was applied to the measurement of the integrated surface temperature of a hollow cylinder and compared with a conventional measurement system, consisting of an infrared camera and precision temperature probe. As a result, the optical technique is in line with the reference system. Compared with conventional surface temperature probes, the optical technique has the following advantages: low heat capacity temperature measurement errors, easier spatial deployment, and replacement of multiple angle infrared camera shooting and the continuous monitoring of surfaces that are not visually accessible. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 2506 KiB

Open AccessArticle

Practical Application of Electrochemical Nitrate Sensor under Laboratory and Forest Nursery Conditions

by William-Olivier Caron¹, Mohammed S. Lamhamedi², Jeff Viens³ and Younès Messaddeq^1,3,4,*

¹ Department of Chemistry, Laval University, Quebec, QC G1V 0A6, Canada

² Ministère des Forêts, de la Faune et des Parcs, Direction de la recherché forestière, Quebec, QC G1P 3W8, Canada

³ Centre for Optics, Photonics and Lasers (COPL), Laval University, Quebec, QC G1V 0A6, Canada

⁴ JIRU Instituto de Quimica, Araraquara-SP 14800-060, Brazil

Sensors 2016, 16(8), 1190; https://doi.org/10.3390/s16081190 - 28 Jul 2016

Cited by 10 | Viewed by 7320

Abstract

The reduction of nitrate leaching to ensure greater protection of groundwater quality has become a global issue. The development of new technologies for more accurate dosing of nitrates helps optimize fertilization programs. This paper presents the practical application of a newly developed electrochemical [...] Read more.

The reduction of nitrate leaching to ensure greater protection of groundwater quality has become a global issue. The development of new technologies for more accurate dosing of nitrates helps optimize fertilization programs. This paper presents the practical application of a newly developed electrochemical sensor designed for in situ quantification of nitrate. To our knowledge, this paper is the first to report the use of electrochemical impedance to determine nitrate concentrations in growing media under forest nursery conditions. Using impedance measurements, the sensor has been tested in laboratory and compared to colorimetric measurements of the nitrate. The developed sensor has been used in water-saturated growing medium and showed good correlation to certified methods, even in samples obtained over a multi-ion fertilisation season. A linear and significant relationship was observed between the resistance and the concentration of nitrates (R² = 0.972), for a range of concentrations of nitrates. We also observed stability of the sensor after exposure of one month to the real environmental conditions of the forest nursery. Full article

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

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19 pages, 1127 KiB

Open AccessArticle

Micromechanical Characterization of Polysilicon Films through On-Chip Tests

by Ramin Mirzazadeh

, Saeed Eftekhar Azam and Stefano Mariani^*

Dipartimento di Ingegneria Civile e Ambientale, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy

Sensors 2016, 16(8), 1191; https://doi.org/10.3390/s16081191 - 28 Jul 2016

Cited by 25 | Viewed by 5363

Abstract

When the dimensions of polycrystalline structures become comparable to the average grain size, some reliability issues can be reported for the moving parts of inertial microelectromechanical systems (MEMS). Not only the overall behavior of the device turns out to be affected by a [...] Read more.

When the dimensions of polycrystalline structures become comparable to the average grain size, some reliability issues can be reported for the moving parts of inertial microelectromechanical systems (MEMS). Not only the overall behavior of the device turns out to be affected by a large scattering, but also the sensitivity to imperfections gets enhanced. In this work, through on-chip tests, we experimentally investigate the behavior of thin polysilicon samples using standard electrostatic actuation/sensing. The discrepancy between the target and actual responses of each sample has then been exploited to identify: (i) the overall stiffness of the film and, according to standard continuum elasticity, a morphology-based value of its Young’s modulus; (ii) the relevant over-etch induced by the fabrication process. To properly account for the aforementioned stochastic features at the micro-scale, the identification procedure has been based on particle filtering. A simple analytical reduced-order model of the moving structure has been also developed to account for the nonlinearities in the electrical field, up to pull-in. Results are reported for a set of ten film samples of constant slenderness, and the effects of different actuation mechanisms on the identified micromechanical features are thoroughly discussed. 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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12 pages, 4327 KiB

Open AccessArticle

Eigenspace-Based Generalized Sidelobe Canceler Beamforming Applied to Medical Ultrasound Imaging

by Jiake Li

, Xiaodong Chen^*, Yi Wang, Wei Li and Daoyin Yu

School of Precision Instrument & Opto-electronics Engineering, Tianjin University, Key Laboratory of Opto-electronics Information Technology (Tianjin University), Ministry of Education, Tianjin 300072, China

Sensors 2016, 16(8), 1192; https://doi.org/10.3390/s16081192 - 28 Jul 2016

Cited by 23 | Viewed by 5518

Abstract

The use of a generalized sidelobe canceler (GSC) can significantly improve the lateral resolution of medical ultrasound systems, but the contrast improvement isn’t satisfactory. Thus a new Eigenspace-based generalized sidelobe canceler (EBGSC) approach is proposed for medical ultrasound imaging, which can improve both [...] Read more.

The use of a generalized sidelobe canceler (GSC) can significantly improve the lateral resolution of medical ultrasound systems, but the contrast improvement isn’t satisfactory. Thus a new Eigenspace-based generalized sidelobe canceler (EBGSC) approach is proposed for medical ultrasound imaging, which can improve both the lateral resolution and contrast of the system. The weight vector of the EBGSC is obtained by projecting the GSC weight vector onto a vector subspace constructed from the eigenstructure of the covariance matrix, and using the new weight vector instead of the GSC ones leads to reduced sidelobe level and improved contrast. Simulated and experimental data are used to evaluate the performance of the proposed method. The Field II software is applied to obtain the simulated echo data of scattering points and circular cysts. Imaging of scattering points show that EBGSC has the same full width at half maximum (FWHM) as GSC, while the lateral resolution improves by 35.3% and 52.7% compared with synthetic aperture (SA) and delay-and-sum (DS), respectively. Compared with GSC, SA and DS, EBGSC improves the peak sidelobe level (PSL) by 23.55, 33.11 and 50.38 dB, respectively. Also the cyst contrast increase by EBGSC was calculated as 16.77, 12.43 and 26.73 dB, when compared with GSC, SA and DS, respectively. Finally, an experiment is conducted on the basis of the complete echo data collected by a medical ultrasonic imaging system. Results show that the proposed method can produce better lateral resolution and contrast than non-adaptive beamformers. Full article

(This article belongs to the Special Issue Ultrasonic Sensors)

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17 pages, 2550 KiB

Open AccessArticle

Gaussian Process Regression Plus Method for Localization Reliability Improvement

by Kehan Liu¹, Zhaopeng Meng² and Chung-Ming Own^1,*

¹ School of Computer Software, Tianjin University, Tianjin 300350, China

² School of Computer Software, Tianjin University of Traditional Chinese Medicine, Tianjin 300193, China

Sensors 2016, 16(8), 1193; https://doi.org/10.3390/s16081193 - 29 Jul 2016

Cited by 15 | Viewed by 5608

Abstract

Location data are among the most widely used context data in context-aware and ubiquitous computing applications. Many systems with distinct deployment costs and positioning accuracies have been developed over the past decade for indoor positioning. The most useful method is focused on the [...] Read more.

Location data are among the most widely used context data in context-aware and ubiquitous computing applications. Many systems with distinct deployment costs and positioning accuracies have been developed over the past decade for indoor positioning. The most useful method is focused on the received signal strength and provides a set of signal transmission access points. However, compiling a manual measuring Received Signal Strength (RSS) fingerprint database involves high costs and thus is impractical in an online prediction environment. The system used in this study relied on the Gaussian process method, which is a nonparametric model that can be characterized completely by using the mean function and the covariance matrix. In addition, the Naive Bayes method was used to verify and simplify the computation of precise predictions. The authors conducted several experiments on simulated and real environments at Tianjin University. The experiments examined distinct data size, different kernels, and accuracy. The results showed that the proposed method not only can retain positioning accuracy but also can save computation time in location predictions. Full article

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

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33 pages, 1224 KiB

Open AccessArticle

A Design Method of Code Correlation Reference Waveform in GNSS Based on Least-Squares Fitting

by Chengtao Xu, Zhe Liu, Xiaomei Tang and Feixue Wang^*

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

Sensors 2016, 16(8), 1194; https://doi.org/10.3390/s16081194 - 29 Jul 2016

Cited by 13 | Viewed by 5144

Abstract

The multipath effect is one of the main error sources in the Global Satellite Navigation Systems (GNSSs). The code correlation reference waveform (CCRW) technique is an effective multipath mitigation algorithm for the binary phase shift keying (BPSK) signal. However, it encounters the false [...] Read more.

The multipath effect is one of the main error sources in the Global Satellite Navigation Systems (GNSSs). The code correlation reference waveform (CCRW) technique is an effective multipath mitigation algorithm for the binary phase shift keying (BPSK) signal. However, it encounters the false lock problem in code tracking, when applied to the binary offset carrier (BOC) signals. A least-squares approximation method of the CCRW design scheme is proposed, utilizing the truncated singular value decomposition method. This algorithm was performed for the BPSK signal, BOC(1,1) signal, BOC(2,1) signal, BOC(6,1) and BOC(7,1) signal. The approximation results of CCRWs were presented. Furthermore, the performances of the approximation results are analyzed in terms of the multipath error envelope and the tracking jitter. The results show that the proposed method can realize coherent and non-coherent CCRW discriminators without false lock points. Generally, there is performance degradation in the tracking jitter, if compared to the CCRW discriminator. However, the performance promotions in the multipath error envelope for the BOC(1,1) and BPSK signals makes the discriminator attractive, and it can be applied to high-order BOC signals. Full article

(This article belongs to the Section Remote Sensors)

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15 pages, 3872 KiB

Open AccessArticle

Applying High-Speed Vision Sensing to an Industrial Robot for High-Performance Position Regulation under Uncertainties

by Shouren Huang^*

, Niklas Bergström, Yuji Yamakawa, Taku Senoo

and Masatoshi Ishikawa

Graduate School of Information Science and Technology, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Sensors 2016, 16(8), 1195; https://doi.org/10.3390/s16081195 - 29 Jul 2016

Cited by 18 | Viewed by 7577

Abstract

It is traditionally difficult to implement fast and accurate position regulation on an industrial robot in the presence of uncertainties. The uncertain factors can be attributed either to the industrial robot itself (e.g., a mismatch of dynamics, mechanical defects such as backlash, etc.) [...] Read more.

It is traditionally difficult to implement fast and accurate position regulation on an industrial robot in the presence of uncertainties. The uncertain factors can be attributed either to the industrial robot itself (e.g., a mismatch of dynamics, mechanical defects such as backlash, etc.) or to the external environment (e.g., calibration errors, misalignment or perturbations of a workpiece, etc.). This paper proposes a systematic approach to implement high-performance position regulation under uncertainties on a general industrial robot (referred to as the main robot) with minimal or no manual teaching. The method is based on a coarse-to-fine strategy that involves configuring an add-on module for the main robot’s end effector. The add-on module consists of a 1000 Hz vision sensor and a high-speed actuator to compensate for accumulated uncertainties. The main robot only focuses on fast and coarse motion, with its trajectories automatically planned by image information from a static low-cost camera. Fast and accurate peg-and-hole alignment in one dimension was implemented as an application scenario by using a commercial parallel-link robot and an add-on compensation module with one degree of freedom (DoF). Experimental results yielded an almost 100% success rate for fast peg-in-hole manipulation (with regulation accuracy at about 0.1 mm) when the workpiece was randomly placed. Full article

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

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16 pages, 6766 KiB

Open AccessArticle

A Novel Single-Excitation Capacitive Angular Position Sensor Design

by Bo Hou, Bin Zhou^*, Mingliang Song, Zhihui Lin and Rong Zhang^*

Engineering Research Center for Navigation Technology, Department of Precision Instrument, Tsinghua University, Beijing 100084, China

Sensors 2016, 16(8), 1196; https://doi.org/10.3390/s16081196 - 29 Jul 2016

Cited by 39 | Viewed by 10853

Abstract

This paper presents a high-precision capacitive angular position sensor (CAPS). The CAPS is designed to be excited by a single voltage to eliminate the matching errors of multi-excitations, and it is mainly composed of excitation electrodes, coupling electrodes, petal-form sensitive electrodes and a [...] Read more.

This paper presents a high-precision capacitive angular position sensor (CAPS). The CAPS is designed to be excited by a single voltage to eliminate the matching errors of multi-excitations, and it is mainly composed of excitation electrodes, coupling electrodes, petal-form sensitive electrodes and a set of collection electrodes. A sinusoidal voltage is applied on the excitation electrodes, then the voltage couples to the coupling electrodes and sensitive electrodes without contact. The sensitive electrodes together with the set of collection electrodes encode the angular position to amplitude-modulated signals, and in order to increase the scale factor, the sensitive electrodes are patterned in the shape of petal-form sinusoidal circles. By utilizing a resolver demodulation method, the amplitude-modulated signals are digitally decoded to get the angular position. A prototype of the CAPS is fabricated and tested. The measurement results show that the accuracy of the sensor is 0.0036°, the resolution is 0.0009° and the nonlinearity over the full range is 0.008° (after compensation), indicating that the CAPS has great potential to be applied in high-precision applications with a low cost. Full article

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

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10 pages, 1838 KiB

Open AccessArticle

Integrating a DNA Strand Displacement Reaction with a Whispering Gallery Mode Sensor for Label-Free Mercury (II) Ion Detection

by Fengchi Wu^1,2,3, Yuqiang Wu³, Zhongwei Niu¹ and Frank Vollmer^3,4,*

¹ Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China

² University of Chinese Academy of Sciences, Beijing 100080, China

³ Laboratory of Nanophotonics & Biosensing, Max Planck Institute for the Science of Light, Erlangen D-91058, Germany

⁴ Division of Biomedical Engineering, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA

Sensors 2016, 16(8), 1197; https://doi.org/10.3390/s16081197 - 29 Jul 2016

Cited by 23 | Viewed by 8904

Abstract

Mercury is an extremely toxic chemical pollutant of our environment. It has attracted the world’s attention due to its high mobility and the ease with which it accumulates in organisms. Sensitive devices and methods specific for detecting mercury ions are, hence, in great [...] Read more.

Mercury is an extremely toxic chemical pollutant of our environment. It has attracted the world’s attention due to its high mobility and the ease with which it accumulates in organisms. Sensitive devices and methods specific for detecting mercury ions are, hence, in great need. Here, we have integrated a DNA strand displacement reaction with a whispering gallery mode (WGM) sensor for demonstrating the detection of Hg²⁺ ions. Our approach relies on the displacement of a DNA hairpin structure, which forms after the binding of mercury ions to an aptamer DNA sequence. The strand displacement reaction of the DNA aptamer provides highly specific and quantitative means for determining the mercury ion concentration on a label-free WGM sensor platform. Our approach also shows the possibility for manipulating the kinetics of a strand displacement reaction with specific ionic species. Full article

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

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13 pages, 7122 KiB

Open AccessArticle

Development of a Distributed Crack Sensor Using Coaxial Cable

by Zhi Zhou^1,2,*, Tong Jiao^1,2

, Peng Zhao^1,2, Jia Liu^1,2 and Hai Xiao³

¹ School of Civil Engineering, Dalian University of Technology, Dalian 116024, China

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

³ Electrical and Computer Engineering Department, Clemson University, Clemson, SC 29634, USA

Sensors 2016, 16(8), 1198; https://doi.org/10.3390/s16081198 - 29 Jul 2016

Cited by 15 | Viewed by 7745

Abstract

Cracks, the important factor of structure failure, reflect structural damage directly. Thus, it is significant to realize distributed, real-time crack monitoring. To overcome the shortages of traditional crack detectors, such as the inconvenience of installation, vulnerability, and low measurement range, etc., an improved [...] Read more.

Cracks, the important factor of structure failure, reflect structural damage directly. Thus, it is significant to realize distributed, real-time crack monitoring. To overcome the shortages of traditional crack detectors, such as the inconvenience of installation, vulnerability, and low measurement range, etc., an improved topology-based cable sensor with a shallow helical groove on the outside surface of a coaxial cable is proposed in this paper. The sensing mechanism, fabrication method, and performances are investigated both numerically and experimentally. Crack monitoring experiments of the reinforced beams are also presented in this paper, illustrating the utility of this sensor in practical applications. These studies show that the sensor can identify a minimum crack width of 0.02 mm and can measure multiple cracks with a spatial resolution of 3 mm. In addition, it is also proved that the sensor performs well to detect the initiation and development of cracks until structure failure. Full article

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

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15 pages, 2626 KiB

Open AccessArticle

A Portable Real-Time Ringdown Breath Acetone Analyzer: Toward Potential Diabetic Screening and Management

by Chenyu Jiang¹

, Meixiu Sun¹, Zhennan Wang¹, Zhuying Chen¹, Xiaomeng Zhao¹, Yuan Yuan¹, Yingxin Li^1,* and Chuji Wang^1,2,*

¹ Institute of Biomedical Engineering, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin 300192, China

² Department of Physics and Astronomy, Mississippi State University, Starkville, MS 39759, USA

Sensors 2016, 16(8), 1199; https://doi.org/10.3390/s16081199 - 30 Jul 2016

Cited by 53 | Viewed by 8435

Abstract

Breath analysis has been considered a suitable tool to evaluate diseases of the respiratory system and those that involve metabolic changes, such as diabetes. Breath acetone has long been known as a biomarker for diabetes. However, the results from published data by far [...] Read more.

Breath analysis has been considered a suitable tool to evaluate diseases of the respiratory system and those that involve metabolic changes, such as diabetes. Breath acetone has long been known as a biomarker for diabetes. However, the results from published data by far have been inconclusive regarding whether breath acetone is a reliable index of diabetic screening. Large variations exist among the results of different studies because there has been no “best-practice method” for breath-acetone measurements as a result of technical problems of sampling and analysis. In this mini-review, we update the current status of our development of a laser-based breath acetone analyzer toward real-time, one-line diabetic screening and a point-of-care instrument for diabetic management. An integrated standalone breath acetone analyzer based on the cavity ringdown spectroscopy technique has been developed. The instrument was validated by using the certificated gas chromatography-mass spectrometry. The linear fittings suggest that the obtained acetone concentrations via both methods are consistent. Breath samples from each individual subject under various conditions in total, 1257 breath samples were taken from 22 Type 1 diabetic (T1D) patients, 312 Type 2 diabetic (T2D) patients, which is one of the largest numbers of T2D subjects ever used in a single study, and 52 non-diabetic healthy subjects. Simultaneous blood glucose (BG) levels were also tested using a standard diabetic management BG meter. The mean breath acetone concentrations were determined to be 4.9 ± 16 ppm (22 T1D), and 1.5 ± 1.3 ppm (312 T2D), which are about 4.5 and 1.4 times of the one in the 42 non-diabetic healthy subjects, 1.1 ± 0.5 ppm, respectively. A preliminary quantitative correlation (R = 0.56, p < 0.05) between the mean individual breath acetone concentration and the mean individual BG levels does exist in 20 T1D subjects with no ketoacidosis. No direct correlation is observed in T1D subjects, T2D subjects, and healthy subjects. The results from a relatively large number of subjects tested indicate that an elevated mean breath acetone concentration exists in diabetic patients in general. Although many physiological parameters affect breath acetone, under a specifically controlled condition fast (<1 min) and portable breath acetone measurement can be used for screening abnormal metabolic status including diabetes, for point-of-care monitoring status of ketone bodies which have the signature smell of breath acetone, and for breath acetone related clinical studies requiring a large number of tests. Full article

(This article belongs to the Special Issue Glucose Sensors: Revolution in Diabetes Management 2016)

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20 pages, 1237 KiB

Open AccessArticle

Design of an HF-Band RFID System with Multiple Readers and Passive Tags for Indoor Mobile Robot Self-Localization

by Jian Mi^*,† and Yasutake Takahashi^†

¹ Department of Human and Artificial Intelligent Systems, Graduate School of Engineering, University of Fukui, 3-9-1, Bunkyo, Fukui 910-8507, Japan

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1200; https://doi.org/10.3390/s16081200 - 29 Jul 2016

Cited by 25 | Viewed by 7099

Abstract

Radio frequency identification (RFID) technology has already been explored for efficient self-localization of indoor mobile robots. A mobile robot equipped with RFID readers detects passive RFID tags installed on the floor in order to locate itself. The Monte-Carlo localization (MCL) method enables the [...] Read more.

Radio frequency identification (RFID) technology has already been explored for efficient self-localization of indoor mobile robots. A mobile robot equipped with RFID readers detects passive RFID tags installed on the floor in order to locate itself. The Monte-Carlo localization (MCL) method enables the localization of a mobile robot equipped with an RFID system with reasonable accuracy, sufficient robustness and low computational cost. The arrangements of RFID readers and tags and the size of antennas are important design parameters for realizing accurate and robust self-localization using a low-cost RFID system. The design of a likelihood model of RFID tag detection is also crucial for the accurate self-localization. This paper presents a novel design and arrangement of RFID readers and tags for indoor mobile robot self-localization. First, by considering small-sized and large-sized antennas of an RFID reader, we show how the design of the likelihood model affects the accuracy of self-localization. We also design a novel likelihood model by taking into consideration the characteristics of the communication range of an RFID system with a large antenna. Second, we propose a novel arrangement of RFID tags with eight RFID readers, which results in the RFID system configuration requiring much fewer readers and tags while retaining reasonable accuracy of self-localization. We verify the performances of MCL-based self-localization realized using the high-frequency (HF)-band RFID system with eight RFID readers and a lower density of RFID tags installed on the floor based on MCL in simulated and real environments. The results of simulations and real environment experiments demonstrate that our proposed low-cost HF-band RFID system realizes accurate and robust self-localization of an indoor mobile robot. Full article

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

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26 pages, 1026 KiB

Open AccessArticle

Maximum Data Collection Rate Routing Protocol Based on Topology Control for Rechargeable Wireless Sensor Networks

by Haifeng Lin¹, Di Bai^2,*, Demin Gao^1,3 and Yunfei Liu¹

¹ College of Information Science and Technology, Nanjing Forestry University, Nanjing 210037, China

² College of Engineering, Nanjing Agricultural University, Nanjing 210009, China

³ School of Computer Science and Engineering, Southeast University, Nanjing 211189, China

Sensors 2016, 16(8), 1201; https://doi.org/10.3390/s16081201 - 30 Jul 2016

Cited by 29 | Viewed by 6261

Abstract

In Rechargeable Wireless Sensor Networks (R-WSNs), in order to achieve the maximum data collection rate it is critical that sensors operate in very low duty cycles because of the sporadic availability of energy. A sensor has to stay in a dormant state in [...] Read more.

In Rechargeable Wireless Sensor Networks (R-WSNs), in order to achieve the maximum data collection rate it is critical that sensors operate in very low duty cycles because of the sporadic availability of energy. A sensor has to stay in a dormant state in most of the time in order to recharge the battery and use the energy prudently. In addition, a sensor cannot always conserve energy if a network is able to harvest excessive energy from the environment due to its limited storage capacity. Therefore, energy exploitation and energy saving have to be traded off depending on distinct application scenarios. Since higher data collection rate or maximum data collection rate is the ultimate objective for sensor deployment, surplus energy of a node can be utilized for strengthening packet delivery efficiency and improving the data generating rate in R-WSNs. In this work, we propose an algorithm based on data aggregation to compute an upper data generation rate by maximizing it as an optimization problem for a network, which is formulated as a linear programming problem. Subsequently, a dual problem by introducing Lagrange multipliers is constructed, and subgradient algorithms are used to solve it in a distributed manner. At the same time, a topology controlling scheme is adopted for improving the network’s performance. Through extensive simulation and experiments, we demonstrate that our algorithm is efficient at maximizing the data collection rate in rechargeable wireless sensor networks. Full article

(This article belongs to the Special Issue Topology Control in Emerging Sensor Networks)

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13 pages, 3053 KiB

Open AccessArticle

Dynamic Calibration and Verification Device of Measurement System for Dynamic Characteristic Coefficients of Sliding Bearing

by Runlin Chen^*

, Yangyang Wei, Zhaoyang Shi and Xiaoyang Yuan

Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi’an Jiaotong University, Xi’an 41049, China

Sensors 2016, 16(8), 1202; https://doi.org/10.3390/s16081202 - 30 Jul 2016

Cited by 4 | Viewed by 5233

Abstract

The identification accuracy of dynamic characteristics coefficients is difficult to guarantee because of the errors of the measurement system itself. A novel dynamic calibration method of measurement system for dynamic characteristics coefficients is proposed in this paper to eliminate the errors of the [...] Read more.

The identification accuracy of dynamic characteristics coefficients is difficult to guarantee because of the errors of the measurement system itself. A novel dynamic calibration method of measurement system for dynamic characteristics coefficients is proposed in this paper to eliminate the errors of the measurement system itself. Compared with the calibration method of suspension quality, this novel calibration method is different because the verification device is a spring-mass system, which can simulate the dynamic characteristics of sliding bearing. The verification device is built, and the calibration experiment is implemented in a wide frequency range, in which the bearing stiffness is simulated by the disc springs. The experimental results show that the amplitude errors of this measurement system are small in the frequency range of 10 Hz–100 Hz, and the phase errors increase along with the increasing of frequency. It is preliminarily verified by the simulated experiment of dynamic characteristics coefficients identification in the frequency range of 10 Hz–30 Hz that the calibration data in this frequency range can support the dynamic characteristics test of sliding bearing in this frequency range well. The bearing experiments in greater frequency ranges need higher manufacturing and installation precision of calibration device. Besides, the processes of calibration experiments should be improved. Full article

(This article belongs to the Section Physical Sensors)

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30 pages, 2575 KiB

Open AccessArticle

On-Ground Processing of Yaogan-24 Remote Sensing Satellite Attitude Data and Verification Using Geometric Field Calibration

by Mi Wang¹, Chengcheng Fan^1,*, Bo Yang^2,3, Shuying Jin¹

and Jun Pan¹

¹ State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, 129 Luoyu Road, Wuhan 430079, China

² Computer School, Wuhan University, 129 Luoyu Road, Wuhan 430079, China

³ Collaborative Innovation Center of Geospatial Technology, Wuhan University, 129 Luoyu Road, Wuhan 430079, China

Sensors 2016, 16(8), 1203; https://doi.org/10.3390/s16081203 - 30 Jul 2016

Cited by 8 | Viewed by 6363

Abstract

Satellite attitude accuracy is an important factor affecting the geometric processing accuracy of high-resolution optical satellite imagery. To address the problem whereby the accuracy of the Yaogan-24 remote sensing satellite’s on-board attitude data processing is not high enough and thus cannot meet its [...] Read more.

Satellite attitude accuracy is an important factor affecting the geometric processing accuracy of high-resolution optical satellite imagery. To address the problem whereby the accuracy of the Yaogan-24 remote sensing satellite’s on-board attitude data processing is not high enough and thus cannot meet its image geometry processing requirements, we developed an approach involving on-ground attitude data processing and digital orthophoto (DOM) and the digital elevation model (DEM) verification of a geometric calibration field. The approach focuses on three modules: on-ground processing based on bidirectional filter, overall weighted smoothing and fitting, and evaluation in the geometric calibration field. Our experimental results demonstrate that the proposed on-ground processing method is both robust and feasible, which ensures the reliability of the observation data quality, convergence and stability of the parameter estimation model. In addition, both the Euler angle and quaternion could be used to build a mathematical fitting model, while the orthogonal polynomial fitting model is more suitable for modeling the attitude parameter. Furthermore, compared to the image geometric processing results based on on-board attitude data, the image uncontrolled and relative geometric positioning result accuracy can be increased by about 50%. Full article

(This article belongs to the Section Remote Sensors)

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20 pages, 9778 KiB

Open AccessArticle

Genetic Particle Swarm Optimization–Based Feature Selection for Very-High-Resolution Remotely Sensed Imagery Object Change Detection

by Qiang Chen^1,2

, Yunhao Chen^1,2,*

and Weiguo Jiang^2,3,*

¹ State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China

² College of Resources Science and Technology, Beijing Normal University, Beijing 100875, China

³ Academy of Disaster Reduction and Emergency Management Ministry of Civil and Ministry of Education, Beijing Normal University, Beijing 100875, China

Sensors 2016, 16(8), 1204; https://doi.org/10.3390/s16081204 - 30 Jul 2016

Cited by 35 | Viewed by 6803

Abstract

In the field of multiple features Object-Based Change Detection (OBCD) for very-high-resolution remotely sensed images, image objects have abundant features and feature selection affects the precision and efficiency of OBCD. Through object-based image analysis, this paper proposes a Genetic Particle Swarm Optimization (GPSO)-based [...] Read more.

In the field of multiple features Object-Based Change Detection (OBCD) for very-high-resolution remotely sensed images, image objects have abundant features and feature selection affects the precision and efficiency of OBCD. Through object-based image analysis, this paper proposes a Genetic Particle Swarm Optimization (GPSO)-based feature selection algorithm to solve the optimization problem of feature selection in multiple features OBCD. We select the Ratio of Mean to Variance (RMV) as the fitness function of GPSO, and apply the proposed algorithm to the object-based hybrid multivariate alternative detection model. Two experiment cases on Worldview-2/3 images confirm that GPSO can significantly improve the speed of convergence, and effectively avoid the problem of premature convergence, relative to other feature selection algorithms. According to the accuracy evaluation of OBCD, GPSO is superior at overall accuracy (84.17% and 83.59%) and Kappa coefficient (0.6771 and 0.6314) than other algorithms. Moreover, the sensitivity analysis results show that the proposed algorithm is not easily influenced by the initial parameters, but the number of features to be selected and the size of the particle swarm would affect the algorithm. The comparison experiment results reveal that RMV is more suitable than other functions as the fitness function of GPSO-based feature selection algorithm. Full article

(This article belongs to the Section Remote Sensors)

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17 pages, 7095 KiB

Open AccessArticle

Modeling and Experimental Analysis on the Temperature Response of AlN-Film Based SAWRs

by Shuo Chen^1,2 and Zheng You^1,2,*

¹ Department of Precision Instrument, Tsinghua University, Beijing 100084, China

² State Key Laboratory of Precision Measurement Technology and Instruments, Tsinghua University, Beijing 100084, China

Sensors 2016, 16(8), 1205; https://doi.org/10.3390/s16081205 - 30 Jul 2016

Cited by 6 | Viewed by 5090

Abstract

The temperature responses of aluminum nitride (AlN) based surface acoustic wave resonator (SAWR) are modeled and tested. The modeling of the electrical performance is based on a modified equivalent circuit model introduced in this work. For SAWR consisting of piezoelectric film and semiconducting [...] Read more.

The temperature responses of aluminum nitride (AlN) based surface acoustic wave resonator (SAWR) are modeled and tested. The modeling of the electrical performance is based on a modified equivalent circuit model introduced in this work. For SAWR consisting of piezoelectric film and semiconducting substrate, parasitic parameters from the substrate is taken into consideration for the modeling. By utilizing the modified model, the high temperature electrical performance of the AlN/Si and AlN/6H-SiC based SAWRs can be predicted, indicating that a substrate with a wider band gap will lead to a more stable high temperature behavior, which is further confirmed experimentally by high temperature testing from 300 K to 725 K with SAWRs having a wavelength of 12 μm. Temperature responses of SAWR’s center frequency are also calculated and tested, with experimental temperature coefficient factors (TCF) of center frequency being −29 ppm/K and −26 ppm/K for the AlN/Si and AlN/6H-SiC based SAWRs, which are close to the predicted values. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 6232 KiB

Open AccessArticle

Analysis on Node Position of Imperfect Resonators for Cylindrical Shell Gyroscopes

by Zidan Wang, Yulie Wu^*, Xiang Xi, Yongmeng Zhang and Xuezhong Wu^*

College of Mechatronics Engineering and Automation, National University of Defense Technology, Changsha 410073, China

Sensors 2016, 16(8), 1206; https://doi.org/10.3390/s16081206 - 30 Jul 2016

Cited by 8 | Viewed by 5168

Abstract

For cylindrical shell gyroscopes, node position of their operating eigenmodes has an important influence on the gyroscopes’ performance. It is considered that the nodes are equally separated from each other by 90° when the resonator vibrates in the standing wave eigenmode. However, we [...] Read more.

For cylindrical shell gyroscopes, node position of their operating eigenmodes has an important influence on the gyroscopes’ performance. It is considered that the nodes are equally separated from each other by 90° when the resonator vibrates in the standing wave eigenmode. However, we found that, due to manufacturing errors and trimming, the nodes may not be equally distributed. This paper mainly analyzes the influences of unbalanced masses on the cylindrical resonators’ node position, by using FEM simulation and experimental measurement. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 6243 KiB

Open AccessArticle

Passive Wireless Hermetic Environment Monitoring System for Spray Painting Workshop

by Lifeng Wang^1,*, Jingjing Ma², Yan Huang¹, Dan Tang¹ and Qing-An Huang¹

¹ Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 210096, China

² Smart Integrated Sensor Engineering Center, Jiangsu R & D Center for Internet of Things, Wuxi 214135, China

Sensors 2016, 16(8), 1207; https://doi.org/10.3390/s16081207 - 1 Aug 2016

Cited by 4 | Viewed by 5111

Abstract

Passive wireless sensors have the advantages of operating without a power supply and remote sensing capability. Hence, they are very suitable for some harsh environments, such as hermetic environments, rotating parts, or very high temperature environments. The spray painting workshop is such a [...] Read more.

Passive wireless sensors have the advantages of operating without a power supply and remote sensing capability. Hence, they are very suitable for some harsh environments, such as hermetic environments, rotating parts, or very high temperature environments. The spray painting workshop is such a harsh environment, containing a large amount of flammable paint mist and organic gas. Aiming at this special environment of spray painting workshop, a passive wireless hermetic environment monitoring system was designed, fabricated, and demonstrated. The proposed system is composed of a transponder and a reader, and the circuit design of each part is given in detail in this paper. The power and the data transmission between the transponder and the reader are realized by the inductive coupling mechanism. Utilizing the back scatter modulation and channel multiplexing, the frequency signals generated by three different environmental sensors—together with their interfaces in the transponder—are wirelessly read out by the reader. Because of the harsh environment of the spray painting room, the package of the monitoring system is quite important. Three different kinds of filter films for the system package were compared. The experimental results show that the composite filter film aluminum anodic oxide/polytetrafluoroethylene (AAO/PTFE) has the best performance. After fabrication, the measured temperature, humidity, and pressure sensitivities were measured and found to be 180 Hz/°C in the range of 0~60 °C, 100 Hz/%RH in the range of 15~95 %RH, and 42 Hz/hPa in the range of 600~1100 hPa, respectively. Additionally, the remote sensing distance of the monitoring system reaches 4 cm. Finally, the passive wireless hermetic environment monitoring system was installed on the glass wall of the spray painting workshop and was successfully demonstrated. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 1833 KiB

Open AccessArticle

Preprocessing the Nintendo Wii Board Signal to Derive More Accurate Descriptors of Statokinesigrams

by Julien Audiffren^1,2,* and Emile Contal^1,2

¹ CMLA, ENS Cachan, CNRS, Université Paris-Saclay, 94235 Cachan, France

² Cognac-G, CNRS, Université Paris Descartes, 75006 Paris, France

Sensors 2016, 16(8), 1208; https://doi.org/10.3390/s16081208 - 1 Aug 2016

Cited by 26 | Viewed by 5730

Abstract

During the past few years, the Nintendo Wii Balance Board (WBB) has been used in postural control research as an affordable but less reliable replacement for laboratory grade force platforms. However, the WBB suffers some limitations, such as a lower accuracy and an [...] Read more.

During the past few years, the Nintendo Wii Balance Board (WBB) has been used in postural control research as an affordable but less reliable replacement for laboratory grade force platforms. However, the WBB suffers some limitations, such as a lower accuracy and an inconsistent sampling rate. In this study, we focus on the latter, namely the non uniform acquisition frequency. We show that this problem, combined with the poor signal to noise ratio of the WBB, can drastically decrease the quality of the obtained information if not handled properly. We propose a new resampling method, Sliding Window Average with Relevance Interval Interpolation (SWARII), specifically designed with the WBB in mind, for which we provide an open source implementation. We compare it with several existing methods commonly used in postural control, both on synthetic and experimental data. The results show that some methods, such as linear and piecewise constant interpolations should definitely be avoided, particularly when the resulting signal is differentiated, which is necessary to estimate speed, an important feature in postural control. Other methods, such as averaging on sliding windows or SWARII, perform significantly better on synthetic dataset, and produce results more similar to the laboratory-grade AMTI force plate (AFP) during experiments. Those methods should be preferred when resampling data collected from a WBB. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 4578 KiB

Open AccessArticle

Examination of Inertial Sensor-Based Estimation Methods of Lower Limb Joint Moments and Ground Reaction Force: Results for Squat and Sit-to-Stand Movements in the Sagittal Plane

by Jun Kodama¹ and Takashi Watanabe^2,*

¹ Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan

² Graduate School of Biomedical Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan

Sensors 2016, 16(8), 1209; https://doi.org/10.3390/s16081209 - 1 Aug 2016

Cited by 22 | Viewed by 9283

Abstract

Joint moment estimation by a camera-based motion measurement system and a force plate has a limitation of measurement environment and is costly. The purpose of this paper is to evaluate quantitatively inertial sensor-based joint moment estimation methods with five-link, four-link and three-link rigid [...] Read more.

Joint moment estimation by a camera-based motion measurement system and a force plate has a limitation of measurement environment and is costly. The purpose of this paper is to evaluate quantitatively inertial sensor-based joint moment estimation methods with five-link, four-link and three-link rigid body models using different trunk segmented models. Joint moments, ground reaction forces (GRF) and center of pressure (CoP) were estimated for squat and sit-to-stand movements in the sagittal plane measured with six healthy subjects. The five-link model and the four-link model that the trunk was divided at the highest point of the iliac crest (four-link-IC model) were appropriate for joint moment estimation with inertial sensors, which showed average RMS values of about 0.1 Nm/kg for all lower limb joints and average correlation coefficients of about 0.98 for hip and knee joints and about 0.80 for ankle joint. Average root mean square (RMS) errors of horizontal and vertical GRFs and CoP were about 10 N, 15 N and 2 cm, respectively. Inertial sensor-based method was suggested to be an option for estimating joint moments of the trunk segments. Inertial sensors were also shown to be useful for the bottom-up estimation method using measured GRFs, in which average RMS values and average correlation coefficients were about 0.06 Nm/kg and larger than about 0.98 for all joints. Full article

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

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12 pages, 3259 KiB

Open AccessArticle

Transducer Development and Characterization for Underwater Acoustic Neutrino Detection Calibration

by María Saldaña^*, Carlos D. Llorens, Ivan Felis

, Juan Antonio Martínez-Mora and Miguel Ardid^*

Institut d’Investigació per a la Gestió Integrada de les Zones Costaneres (IGIC), Universitat Politècnica de València (UPV), 46730 Gandia, Spain

Sensors 2016, 16(8), 1210; https://doi.org/10.3390/s16081210 - 2 Aug 2016

Cited by 11 | Viewed by 6431

Abstract

A short bipolar pressure pulse with “pancake” directivity is produced and propagated when an Ultra-High Energy (UHE) neutrino interacts with a nucleus in water. Nowadays, acoustic sensor networks are being deployed in deep seas to detect this phenomenon as a first step toward [...] Read more.

A short bipolar pressure pulse with “pancake” directivity is produced and propagated when an Ultra-High Energy (UHE) neutrino interacts with a nucleus in water. Nowadays, acoustic sensor networks are being deployed in deep seas to detect this phenomenon as a first step toward building a neutrino telescope. In order to study the feasibility of the method, it is critical to have a calibrator that is able to mimic the neutrino signature. In previous works the possibility of using the acoustic parametric technique for this aim was proven. In this study, the array is operated at a high frequency and, by means of the parametric effect, the emission of the low-frequency acoustic bipolar pulse is generated mimicking the UHE neutrino acoustic pulse. To this end, the development of the transducer to be used in the parametric array is described in all its phases. The transducer design process, the characterization tests for the bare piezoelectric ceramic, and the addition of backing and matching layers are presented. The efficiencies and directivity patterns obtained for both primary and parametric beams confirm that the design of the proposed calibrator meets all the requirements for the emitter. 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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14 pages, 6357 KiB

Open AccessArticle

Seasonal Mass Changes and Crustal Vertical Deformations Constrained by GPS and GRACE in Northeastern Tibet

by Yuanjin Pan¹

, Wen-Bin Shen^1,2,*, Cheinway Hwang^1,3

, Chaoming Liao⁴, Tengxu Zhang¹ and Guoqing Zhang¹

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

² State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China

³ Department of Civil Engineering, National Chiao Tung University, Hsinchu 300, Taiwan

⁴ School of Land Resources and Surveying, Guangxi Teachers Education University, Nanning 530001, China

Sensors 2016, 16(8), 1211; https://doi.org/10.3390/s16081211 - 2 Aug 2016

Cited by 31 | Viewed by 6665

Abstract

Surface vertical deformation includes the Earth’s elastic response to mass loading on or near the surface. Continuous Global Positioning System (CGPS) stations record such deformations to estimate seasonal and secular mass changes. We used 41 CGPS stations to construct a time series of [...] Read more.

Surface vertical deformation includes the Earth’s elastic response to mass loading on or near the surface. Continuous Global Positioning System (CGPS) stations record such deformations to estimate seasonal and secular mass changes. We used 41 CGPS stations to construct a time series of coordinate changes, which are decomposed by empirical orthogonal functions (EOFs), in northeastern Tibet. The first common mode shows clear seasonal changes, indicating seasonal surface mass re-distribution around northeastern Tibet. The GPS-derived result is then assessed in terms of the mass changes observed in northeastern Tibet. The GPS-derived common mode vertical change and the stacked Gravity Recovery and Climate Experiment (GRACE) mass change are consistent, suggesting that the seasonal surface mass variation is caused by changes in the hydrological, atmospheric and non-tidal ocean loads. The annual peak-to-peak surface mass changes derived from GPS and GRACE results show seasonal oscillations in mass loads, and the corresponding amplitudes are between 3 and 35 mm/year. There is an apparent gradually increasing gravity between 0.1 and 0.9 μGal/year in northeast Tibet. Crustal vertical deformation is determined after eliminating the surface load effects from GRACE, without considering Glacial Isostatic Adjustment (GIA) contribution. It reveals crustal uplift around northeastern Tibet from the corrected GPS vertical velocity. The unusual uplift of the Longmen Shan fault indicates tectonically sophisticated processes in northeastern Tibet. Full article

(This article belongs to the Section Remote Sensors)

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18 pages, 7435 KiB

Open AccessArticle

Sine Rotation Vector Method for Attitude Estimation of an Underwater Robot

by Nak Yong Ko^1,*

, Seokki Jeong^2,† and Youngchul Bae^3,†

¹ School of Electronic and Information Engineering, Chosun University, 375 Seosuk-dong Dong-gu, Gwangju 501-759, Korea

² Department of Control and Instrumentation Engineering, Graduate school, Chosun University, 375 Seosuk-dong Dong-gu, Gwangju 501-759, Korea

³ Division of Electrical, Electronic Communication and Computer Engineering, Chonnam National University, 50 Daehak-ro, Yeosu, Jeonnam 550-749, Korea

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1213; https://doi.org/10.3390/s16081213 - 2 Aug 2016

Cited by 15 | Viewed by 6155

Abstract

This paper describes a method for estimating the attitude of an underwater robot. The method employs a new concept of sine rotation vector and uses both an attitude heading and reference system (AHRS) and a Doppler velocity log (DVL) for the purpose of [...] Read more.

This paper describes a method for estimating the attitude of an underwater robot. The method employs a new concept of sine rotation vector and uses both an attitude heading and reference system (AHRS) and a Doppler velocity log (DVL) for the purpose of measurement. First, the acceleration and magnetic-field measurements are transformed into sine rotation vectors and combined. The combined sine rotation vector is then transformed into the differences between the Euler angles of the measured attitude and the predicted attitude; the differences are used to correct the predicted attitude. The method was evaluated according to field-test data and simulation data and compared to existing methods that calculate angular differences directly without a preceding sine rotation vector transformation. The comparison verifies that the proposed method improves the attitude estimation performance. Full article

(This article belongs to the Special Issue Selected Papers From the 16th International Symposium on Advanced Intelligent Systems (ISIS))

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11 pages, 3702 KiB

Open AccessArticle

Modeling and Analysis of Phase Fluctuation in a High-Precision Roll Angle Measurement Based on a Heterodyne Interferometer

by Junhui Huang^1,*

, Zhao Wang^1,*, Jianmin Gao² and Bao Yu¹

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(8), 1214; https://doi.org/10.3390/s16081214 - 2 Aug 2016

Cited by 10 | Viewed by 5382

Abstract

Heterodyne interferometry is a high-precision method applied in roll angle measurements. Phase metering is essential for high precision. During a high-precision measurement, a phase fluctuation appears even when the roll angle does not vary, which has never been analyzed before. Herein, the reason [...] Read more.

Heterodyne interferometry is a high-precision method applied in roll angle measurements. Phase metering is essential for high precision. During a high-precision measurement, a phase fluctuation appears even when the roll angle does not vary, which has never been analyzed before. Herein, the reason for the phase fluctuation is revealed, which results from the frequency-difference fluctuation and time difference between measurement and reference beams. A mathematical model of that phase-fluctuation mechanism is established, and that model provides a theoretical basis for analyzing and reducing the phase fluctuation. The impact that the main factors have on the phase metering is analyzed quantitatively, and experiments are carried out to validate the model. Finally, the phase fluctuation decreases to 0.02° by frequency reduction, which conversely verifies the theoretical model. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 2174 KiB

Open AccessArticle

INS/GNSS Tightly-Coupled Integration Using Quaternion-Based AUPF for USV

by Guoqing Xia and Guoqing Wang^*

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

Sensors 2016, 16(8), 1215; https://doi.org/10.3390/s16081215 - 2 Aug 2016

Cited by 17 | Viewed by 5861

Abstract

This paper addresses the problem of integration of Inertial Navigation System (INS) and Global Navigation Satellite System (GNSS) for the purpose of developing a low-cost, robust and highly accurate navigation system for unmanned surface vehicles (USVs). A tightly-coupled integration approach is one of [...] Read more.

This paper addresses the problem of integration of Inertial Navigation System (INS) and Global Navigation Satellite System (GNSS) for the purpose of developing a low-cost, robust and highly accurate navigation system for unmanned surface vehicles (USVs). A tightly-coupled integration approach is one of the most promising architectures to fuse the GNSS data with INS measurements. However, the resulting system and measurement models turn out to be nonlinear, and the sensor stochastic measurement errors are non-Gaussian and distributed in a practical system. Particle filter (PF), one of the most theoretical attractive non-linear/non-Gaussian estimation methods, is becoming more and more attractive in navigation applications. However, the large computation burden limits its practical usage. For the purpose of reducing the computational burden without degrading the system estimation accuracy, a quaternion-based adaptive unscented particle filter (AUPF), which combines the adaptive unscented Kalman filter (AUKF) with PF, has been proposed in this paper. The unscented Kalman filter (UKF) is used in the algorithm to improve the proposal distribution and generate a posterior estimates, which specify the PF importance density function for generating particles more intelligently. In addition, the computational complexity of the filter is reduced with the avoidance of the re-sampling step. Furthermore, a residual-based covariance matching technique is used to adapt the measurement error covariance. A trajectory simulator based on a dynamic model of USV is used to test the proposed algorithm. Results show that quaternion-based AUPF can significantly improve the overall navigation accuracy and reliability. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 2386 KiB

Open AccessArticle

Quantitative Determination of Fluorine Content in Blends of Polylactide (PLA)–Talc Using Near Infrared Spectroscopy

by Elena Tamburini^1,*

, Chiara Tagliati², Tiziano Bonato², Stefania Costa¹

, Chiara Scapoli¹ and Paola Pedrini¹

¹ Department of Life Science and Biotechnology, University of Ferrara, Via L. Borsari, Ferrara 46 | 44121, Italy

² Lab Control Srl, Chemical Analysis and Technological Services, Via Cà Donà, San Martino di Venezze, Rovigo 545 | 45030, Italy

Sensors 2016, 16(8), 1216; https://doi.org/10.3390/s16081216 - 2 Aug 2016

Cited by 5 | Viewed by 6096

Abstract

Near-infrared spectroscopy (NIRS) has been widely used for quantitative and/or qualitative determination of a wide range of matrices. The objective of this study was to develop a NIRS method for the quantitative determination of fluorine content in polylactide (PLA)-talc blends. A blending profile [...] Read more.

Near-infrared spectroscopy (NIRS) has been widely used for quantitative and/or qualitative determination of a wide range of matrices. The objective of this study was to develop a NIRS method for the quantitative determination of fluorine content in polylactide (PLA)-talc blends. A blending profile was obtained by mixing different amounts of PLA granules and talc powder. The calibration model was built correlating wet chemical data (alkali digestion method) and NIR spectra. Using FT (Fourier Transform)-NIR technique, a Partial Least Squares (PLS) regression model was set-up, in a concentration interval of 0 ppm of pure PLA to 800 ppm of pure talc. Fluorine content prediction (R²_cal = 0.9498; standard error of calibration, SEC = 34.77; standard error of cross-validation, SECV = 46.94) was then externally validated by means of a further 15 independent samples (R²_EX.V = 0.8955; root mean standard error of prediction, RMSEP = 61.08). A positive relationship between an inorganic component as fluorine and NIR signal has been evidenced, and used to obtain quantitative analytical information from the spectra. Full article

(This article belongs to the Section Chemical Sensors)

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29 pages, 6945 KiB

Open AccessArticle

Bindings and RESTlets: A Novel Set of CoAP-Based Application Enablers to Build IoT Applications

by Girum Ketema Teklemariam^1,2,*, Floris Van Den Abeele¹, Ingrid Moerman¹

, Piet Demeester¹ and Jeroen Hoebeke¹

¹ Department of Information Technology (INTEC), Ghent University—iMinds, Technologiepark-Zwijnaarde 15, 9052 Ghent, Belgium

² Information Communication Technology Development Directorate, Jimma University, P.O. Box 378, Jimma, Ethiopia

Sensors 2016, 16(8), 1217; https://doi.org/10.3390/s16081217 - 2 Aug 2016

Cited by 6 | Viewed by 6110

Abstract

Sensors and actuators are becoming important components of Internet of Things (IoT) applications. Today, several approaches exist to facilitate communication of sensors and actuators in IoT applications. Most communications go through often proprietary gateways requiring availability of the gateway for each and every [...] Read more.

Sensors and actuators are becoming important components of Internet of Things (IoT) applications. Today, several approaches exist to facilitate communication of sensors and actuators in IoT applications. Most communications go through often proprietary gateways requiring availability of the gateway for each and every interaction between sensors and actuators. Sometimes, the gateway does some processing of the sensor data before triggering actuators. Other approaches put this processing logic further in the cloud. These approaches introduce significant latencies and increased number of packets. In this paper, we introduce a CoAP-based mechanism for direct binding of sensors and actuators. This flexible binding solution is utilized further to build IoT applications through RESTlets. RESTlets are defined to accept inputs and produce outputs after performing some processing tasks. Sensors and actuators could be associated with RESTlets (which can be hosted on any device) through the flexible binding mechanism we introduced. This approach facilitates decentralized IoT application development by placing all or part of the processing logic in Low power and Lossy Networks (LLNs). We run several tests to compare the performance of our solution with existing solutions and found out that our solution reduces communication delay and number of packets in the LLN. Full article

(This article belongs to the Special Issue Intelligent Internet of Things (IoT) Networks)

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9 pages, 1877 KiB

Open AccessArticle

Identification of Quorum-Sensing Signal Molecules and a Biosynthetic Gene in Alicycliphilus sp. Isolated from Activated Sludge

by Tomohiro Morohoshi^1,*

, Noriya Okutsu¹, Xiaonan Xie² and Tsukasa Ikeda^1,*

¹ Department of Material and Environmental Chemistry, Graduate School of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585, Japan

² Center for Bioscience Research and Education, Utsunomiya University, 350 Mine-machi, Utsunomiya, Tochigi 321-8505, Japan

Sensors 2016, 16(8), 1218; https://doi.org/10.3390/s16081218 - 2 Aug 2016

Cited by 10 | Viewed by 5342

Abstract

Activated sludge is a complicated mixture of various microorganisms that is used to treat sewage and industrial wastewater. Many bacteria produce N-acylhomoserine lactone (AHL) as a quorum-sensing signal molecule to regulate the expression of the exoenzymes used for wastewater treatment. Here, we [...] Read more.

Activated sludge is a complicated mixture of various microorganisms that is used to treat sewage and industrial wastewater. Many bacteria produce N-acylhomoserine lactone (AHL) as a quorum-sensing signal molecule to regulate the expression of the exoenzymes used for wastewater treatment. Here, we isolated an AHL-producing bacteria from an activated sludge sample collected from an electronic component factory, which we named Alicycliphilus sp. B1. Clone library analysis revealed that Alicycliphilus was a subdominant genus in this sample. When we screened the activated sludge sample for AHL-producing strains, 12 of 14 the AHL-producing isolates were assigned to the genus Alicycliphilus. A putative AHL-synthase gene, ALISP_0667, was cloned from the genome of B1 and transformed into Escherichia coli DH5α. The AHLs were extracted from the culture supernatants of the B1 strain and E. coli DH5α cells harboring the ALISP_0667 gene and were identified by liquid chromatography-mass spectrometry as N-(3-hydroxydecanoyl)-l-homoserine lactone and N-(3-hydroxydodecanoyl)-l-homoserine lactone. The results of comparative genomic analysis suggested that the quorum-sensing genes in the B1 strain might have been acquired by horizontal gene transfer within activated sludge. Full article

(This article belongs to the Section Biosensors)

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24 pages, 9011 KiB

Open AccessArticle

Analysis and Optimization of Four-Coil Planar Magnetically Coupled Printed Spiral Resonators

by Sadeque Reza Khan

and GoangSeog Choi^*

Department of Information and Communication Engineering, SoC Design Laboratory, Chosun University, Gwangju 61452, Korea

Sensors 2016, 16(8), 1219; https://doi.org/10.3390/s16081219 - 3 Aug 2016

Cited by 55 | Viewed by 10512

Abstract

High-efficiency power transfer at a long distance can be efficiently established using resonance-based wireless techniques. In contrast to the conventional two-coil-based inductive links, this paper presents a magnetically coupled fully planar four-coil printed spiral resonator-based wireless power-transfer system that compensates the adverse effect [...] Read more.

High-efficiency power transfer at a long distance can be efficiently established using resonance-based wireless techniques. In contrast to the conventional two-coil-based inductive links, this paper presents a magnetically coupled fully planar four-coil printed spiral resonator-based wireless power-transfer system that compensates the adverse effect of low coupling and improves efficiency by using high quality-factor coils. A conformal architecture is adopted to reduce the transmitter and receiver sizes. Both square architecture and circular architectures are analyzed and optimized to provide maximum efficiency at a certain operating distance. Furthermore, their performance is compared on the basis of the power-transfer efficiency and power delivered to the load. Square resonators can produce higher measured power-transfer efficiency (79.8%) than circular resonators (78.43%) when the distance between the transmitter and receiver coils is 10 mm of air medium at a resonant frequency of 13.56 MHz. On the other hand, circular coils can deliver higher power (443.5 mW) to the load than the square coils (396 mW) under the same medium properties. The performance of the proposed structures is investigated by simulation using a three-layer human-tissue medium and by experimentation. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 4463 KiB

Open AccessArticle

A Smart Wearable Sensor System for Counter-Fighting Overweight in Teenagers

by Carlo Emilio Standoli^1,*, Maria Renata Guarneri¹, Paolo Perego¹

, Marco Mazzola², Alessandra Mazzola¹ and Giuseppe Andreoni¹

¹ Politecnico di Milano, Dipartimento di Design, via Giovanni Durando, 38/A, 20158 Milano, Italy

² Neosperience S.p.a, Corso Indipendenza 5, 20125 Milano, Italy

Sensors 2016, 16(8), 1220; https://doi.org/10.3390/s16081220 - 10 Aug 2016

Cited by 16 | Viewed by 7467

Abstract

PEGASO is a FP7-funded project whose goal is to develop an ICT and mobile-based platform together with an appropriate strategy to tackle the diffusion of obesity and other lifestyle-related illnesses among teenagers. Indeed, the design of an engaging strategy, leveraging a complementary set [...] Read more.

PEGASO is a FP7-funded project whose goal is to develop an ICT and mobile-based platform together with an appropriate strategy to tackle the diffusion of obesity and other lifestyle-related illnesses among teenagers. Indeed, the design of an engaging strategy, leveraging a complementary set of technologies, is the approach proposed by the project to promote the adoption of healthy habits such as active lifestyle and balanced nutrition and to effectively counter-fight the emergence of overweight and obesity in the younger population. A technological key element of such a strategy sees the adoption of wearable sensors to monitor teenagers’ activities, which is at the basis of developing awareness about the current lifestyle. This paper describes the experience carried out in the framework of the PEGASO project in developing and evaluating wearable monitoring systems addressed to adolescents. The paper describes the methodological approach based on the co-designing of such a wearable system and the main results that, in the first phase, involved a total of 407 adolescents across Europe in a series of focus groups conducted in three countries for the requirements definition phase. Moreover, it describes an evaluation process of signal reliability during the usage of the wearable system. The main results described here are: (a) a prototype of the standardized experimental protocol that has been developed and applied to test signal reliability in smart garments; (b) the requirements definition methodology through a co-design activity and approach to address user requirements and preferences and not only technological specifications. Such co-design approach is able to support a higher system acceptance and usability together with a sustained adoption of the solution with respect to the traditional technology push system development strategy. 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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10 pages, 2927 KiB

Open AccessArticle

Wearable Sensors for eLearning of Manual Tasks: Using Forearm EMG in Hand Hygiene Training

by Ekaterina Kutafina^1,2,*, David Laukamp¹, Ralf Bettermann¹, Ulrik Schroeder³

and Stephan M. Jonas¹

¹ Department of Medical Informatics, Uniklinik RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen, Germany

² Faculty of Applied Mathematics, AGH University of Science and Technology, Mickiewicza 30, 30-059 Cracow, Poland

³ Computer Supported Learning Group, RWTH Aachen University, Ahornstrasse 55, 52074 Aachen, Germany

Sensors 2016, 16(8), 1221; https://doi.org/10.3390/s16081221 - 3 Aug 2016

Cited by 32 | Viewed by 10062 | Correction

Abstract

In this paper, we propose a novel approach to eLearning that makes use of smart wearable sensors. Traditional eLearning supports the remote and mobile learning of mostly theoretical knowledge. Here we discuss the possibilities of eLearning to support the training of manual skills. [...] Read more.

In this paper, we propose a novel approach to eLearning that makes use of smart wearable sensors. Traditional eLearning supports the remote and mobile learning of mostly theoretical knowledge. Here we discuss the possibilities of eLearning to support the training of manual skills. We employ forearm armbands with inertial measurement units and surface electromyography sensors to detect and analyse the user’s hand motions and evaluate their performance. Hand hygiene is chosen as the example activity, as it is a highly standardized manual task that is often not properly executed. The World Health Organization guidelines on hand hygiene are taken as a model of the optimal hygiene procedure, due to their algorithmic structure. Gesture recognition procedures based on artificial neural networks and hidden Markov modeling were developed, achieving recognition rates of

98.30 %

(

\pm 1.26 %

) for individual gestures. Our approach is shown to be promising for further research and application in the mobile eLearning of manual skills. Full article

(This article belongs to the Section Sensor Networks)

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23 pages, 26252 KiB

Open AccessArticle

DeepFruits: A Fruit Detection System Using Deep Neural Networks

by Inkyu Sa^*, Zongyuan Ge, Feras Dayoub, Ben Upcroft, Tristan Perez and Chris McCool

Science and Engineering Faculty, Queensland University of Technology, Brisbane 4000, Australia

Sensors 2016, 16(8), 1222; https://doi.org/10.3390/s16081222 - 3 Aug 2016

Cited by 965 | Viewed by 66477

Abstract

This paper presents a novel approach to fruit detection using deep convolutional neural networks. The aim is to build an accurate, fast and reliable fruit detection system, which is a vital element of an autonomous agricultural robotic platform; it is a key element [...] Read more.

This paper presents a novel approach to fruit detection using deep convolutional neural networks. The aim is to build an accurate, fast and reliable fruit detection system, which is a vital element of an autonomous agricultural robotic platform; it is a key element for fruit yield estimation and automated harvesting. Recent work in deep neural networks has led to the development of a state-of-the-art object detector termed Faster Region-based CNN (Faster R-CNN). We adapt this model, through transfer learning, for the task of fruit detection using imagery obtained from two modalities: colour (RGB) and Near-Infrared (NIR). Early and late fusion methods are explored for combining the multi-modal (RGB and NIR) information. This leads to a novel multi-modal Faster R-CNN model, which achieves state-of-the-art results compared to prior work with the F1 score, which takes into account both precision and recall performances improving from

0.807

to

0.838

for the detection of sweet pepper. In addition to improved accuracy, this approach is also much quicker to deploy for new fruits, as it requires bounding box annotation rather than pixel-level annotation (annotating bounding boxes is approximately an order of magnitude quicker to perform). The model is retrained to perform the detection of seven fruits, with the entire process taking four hours to annotate and train the new model per fruit. Full article

(This article belongs to the Special Issue Vision-Based Sensors in Field Robotics)

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15 pages, 2578 KiB

Open AccessArticle

A Bionic Polarization Navigation Sensor and Its Calibration Method

by Huijie Zhao and Wujian Xu^*

School of Instrument Science and Opto-Electronics Engineering, Beihang University, No. 37 Xueyuan RD, Haidian, Beijing 100191, China

Sensors 2016, 16(8), 1223; https://doi.org/10.3390/s16081223 - 3 Aug 2016

Cited by 31 | Viewed by 6231

Abstract

The polarization patterns of skylight which arise due to the scattering of sunlight in the atmosphere can be used by many insects for deriving compass information. Inspired by insects’ polarized light compass, scientists have developed a new kind of navigation method. One of [...] Read more.

The polarization patterns of skylight which arise due to the scattering of sunlight in the atmosphere can be used by many insects for deriving compass information. Inspired by insects’ polarized light compass, scientists have developed a new kind of navigation method. One of the key techniques in this method is the polarimetric sensor which is used to acquire direction information from skylight. In this paper, a polarization navigation sensor is proposed which imitates the working principles of the polarization vision systems of insects. We introduce the optical design and mathematical model of the sensor. In addition, a calibration method based on variable substitution and non-linear curve fitting is proposed. The results obtained from the outdoor experiments provide support for the feasibility and precision of the sensor. The sensor’s signal processing can be well described using our mathematical model. A relatively high degree of accuracy in polarization measurement can be obtained without any error compensation. Full article

(This article belongs to the Section Physical Sensors)

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29 pages, 9577 KiB

Open AccessArticle

A Semantic Approach with Decision Support for Safety Service in Smart Home Management

by Xiaoci Huang^1,2,*

, Jianjun Yi^2,*, Xiaomin Zhu² and Shaoli Chen²

¹ Shanghai University of Engineering Science, Shanghai 201620, China

² Department of Mechanical Engineering, East China University of Science and Technology, Shanghai 200237, China

Sensors 2016, 16(8), 1224; https://doi.org/10.3390/s16081224 - 3 Aug 2016

Cited by 17 | Viewed by 6690

Abstract

Research on smart homes (SHs) has increased significantly in recent years because of the convenience provided by having an assisted living environment. The functions of SHs as mentioned in previous studies, particularly safety services, are seldom discussed or mentioned. Thus, this study proposes [...] Read more.

Research on smart homes (SHs) has increased significantly in recent years because of the convenience provided by having an assisted living environment. The functions of SHs as mentioned in previous studies, particularly safety services, are seldom discussed or mentioned. Thus, this study proposes a semantic approach with decision support for safety service in SH management. The focus of this contribution is to explore a context awareness and reasoning approach for risk recognition in SH that enables the proper decision support for flexible safety service provision. The framework of SH based on a wireless sensor network is described from the perspective of neighbourhood management. This approach is based on the integration of semantic knowledge in which a reasoner can make decisions about risk recognition and safety service. We present a management ontology for a SH and relevant monitoring contextual information, which considers its suitability in a pervasive computing environment and is service-oriented. We also propose a rule-based reasoning method to provide decision support through reasoning techniques and context-awareness. A system prototype is developed to evaluate the feasibility, time response and extendibility of the approach. The evaluation of our approach shows that it is more effective in daily risk event recognition. The decisions for service provision are shown to be accurate. Full article

(This article belongs to the Special Issue Smart City: Vision and Reality)

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18 pages, 8477 KiB

Open AccessArticle

Physical Behavior in Older Persons during Daily Life: Insights from Instrumented Shoes

by Christopher Moufawad el Achkar¹, Constanze Lenoble-Hoskovec², Anisoara Paraschiv-Ionescu¹, Kristof Major², Christophe Büla² and Kamiar Aminian^1,*

¹ Laboratory of Movement Analysis and Measurement, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland

² Centre Hospitalier Universitaire Vaudois (CHUV), Service de gériatrie et réadaptation gériatrique, 1011 Lausanne, Switzerland

Sensors 2016, 16(8), 1225; https://doi.org/10.3390/s16081225 - 3 Aug 2016

Cited by 40 | Viewed by 6934

Abstract

Activity level and gait parameters during daily life are important indicators for clinicians because they can provide critical insights into modifications of mobility and function over time. Wearable activity monitoring has been gaining momentum in daily life health assessment. Consequently, this study seeks [...] Read more.

Activity level and gait parameters during daily life are important indicators for clinicians because they can provide critical insights into modifications of mobility and function over time. Wearable activity monitoring has been gaining momentum in daily life health assessment. Consequently, this study seeks to validate an algorithm for the classification of daily life activities and to provide a detailed gait analysis in older adults. A system consisting of an inertial sensor combined with a pressure sensing insole has been developed. Using an algorithm that we previously validated during a semi structured protocol, activities in 10 healthy elderly participants were recorded and compared to a wearable reference system over a 4 h recording period at home. Detailed gait parameters were calculated from inertial sensors. Dynamics of physical behavior were characterized using barcodes that express the measure of behavioral complexity. Activity classification based on the algorithm led to a 93% accuracy in classifying basic activities of daily life, i.e., sitting, standing, and walking. Gait analysis emphasizes the importance of metrics such as foot clearance in daily life assessment. Results also underline that measures of physical behavior and gait performance are complementary, especially since gait parameters were not correlated to complexity. Participants gave positive feedback regarding the use of the instrumented shoes. These results extend previous observations in showing the concurrent validity of the instrumented shoes compared to a body-worn reference system for daily-life physical behavior monitoring in older adults. Full article

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

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19 pages, 2850 KiB

Open AccessArticle

Towards a Real-Time Embedded System for Water Monitoring Installed in a Robotic Sailboat

by Andouglas Goncalves da Silva Junior^1,2,†, Sarah Thomaz de Lima Sa^1,†, Davi Henrique dos Santos¹, Álvaro Pinto Ferrnandes de Negreiros¹, João Moreno Vilas Boas de Souza Silva³, Justo Emílio Álvarez Jácobo¹ and Luiz Marcos Garcia Gonçalves^1,*

¹ Departamento de Engenharia de Computação e Automação, Universidade Federal do Rio Grande do Norte, DCA-CT-UFRN, Campus Universitário, Lagoa Nova, CEP 59078-970 Natal, RN, Brazil

² Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Norte, Campus Mossoró, Rua Raimundo Firmino de Oliveira, 400, Conj. Ulrick Graff, CEP 59628-330 Mossoró, RN, Brazil

³ Diretoria Acadêmica de Gestão e Tecnologia da Informação, Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Norte, Av. Sen. Salgado Filho, 1559, Tirol, CEP 59015-000 Natal, RN, Brazil

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1226; https://doi.org/10.3390/s16081226 - 8 Aug 2016

Cited by 16 | Viewed by 6586

Abstract

Problems related to quality (and quantity) of water in natural resources or in artificial reservoirs are frequently arising and are at the center of attention of authorities and governments around the world. Many times the monitoring is not performed in an efficient time [...] Read more.

Problems related to quality (and quantity) of water in natural resources or in artificial reservoirs are frequently arising and are at the center of attention of authorities and governments around the world. Many times the monitoring is not performed in an efficient time frame and a precise manner, whereas the adoption of fast and punctual solutions would undoubtedly improve the water quality and consequently enhance the life of people. To minimize or diminish such kinds of problems, we propose an architecture for sensors installed in a robotic platform, an autonomous sail boat, able to acquire raw data relative to water quality, to process and make them available to people that might be interested in such information. The main contributions are the sensors architecture itself, which uses low cost sensors, with practical experimentation done with a prototype. Results show data collected for points in lakes and rivers in the northeast of Brazil. This embedded system is fixed in the sailboat robot with the intention to facilitate the study of water quality for long endurance missions. This robot can help monitoring water bodies in a more consistent manner. Nonetheless the system can also be used with fixed vases or buoys in strategic points. Full article

(This article belongs to the Special Issue Robotic Sensory Systems for Environment Protection and Conservation)

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59 pages, 19529 KiB

Open AccessArticle

SensoTube: A Scalable Hardware Design Architecture for Wireless Sensors and Actuators Networks Nodes in the Agricultural Domain

by Dimitrios Piromalis^1,2,* and Konstantinos Arvanitis¹

¹ Department of Natural Resources Management and Agricultural Engineering, Agricultural University of Athens, Iera Odoos 75, Athens 11855, Greece

² Department of Automation Engineering, Piraeus University of Applied Sciences (TEI of Piraeus), P. Ralli and Thivon 250, Egaleo 12244, Greece

Sensors 2016, 16(8), 1227; https://doi.org/10.3390/s16081227 - 4 Aug 2016

Cited by 23 | Viewed by 10125

Abstract

Wireless Sensor and Actuators Networks (WSANs) constitute one of the most challenging technologies with tremendous socio-economic impact for the next decade. Functionally and energy optimized hardware systems and development tools maybe is the most critical facet of this technology for the achievement of [...] Read more.

Wireless Sensor and Actuators Networks (WSANs) constitute one of the most challenging technologies with tremendous socio-economic impact for the next decade. Functionally and energy optimized hardware systems and development tools maybe is the most critical facet of this technology for the achievement of such prospects. Especially, in the area of agriculture, where the hostile operating environment comes to add to the general technological and technical issues, reliable and robust WSAN systems are mandatory. This paper focuses on the hardware design architectures of the WSANs for real-world agricultural applications. It presents the available alternatives in hardware design and identifies their difficulties and problems for real-life implementations. The paper introduces SensoTube, a new WSAN hardware architecture, which is proposed as a solution to the various existing design constraints of WSANs. The establishment of the proposed architecture is based, firstly on an abstraction approach in the functional requirements context, and secondly, on the standardization of the subsystems connectivity, in order to allow for an open, expandable, flexible, reconfigurable, energy optimized, reliable and robust hardware system. The SensoTube implementation reference model together with its encapsulation design and installation are analyzed and presented in details. Furthermore, as a proof of concept, certain use cases have been studied in order to demonstrate the benefits of migrating existing designs based on the available open-source hardware platforms to SensoTube architecture. Full article

(This article belongs to the Section Sensor Networks)

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10 pages, 1297 KiB

Open AccessArticle

Real-Time Identification of Smoldering and Flaming Combustion Phases in Forest Using a Wireless Sensor Network-Based Multi-Sensor System and Artificial Neural Network

by Xiaofei Yan¹, Hong Cheng², Yandong Zhao^1,*, Wenhua Yu¹, Huan Huang¹ and Xiaoliang Zheng¹

¹ School of Technology, Beijing Forestry University, Beijing 100083, China

² College of Information Science and Technology, Agricultural University of Hebei, Baoding 071001, China

Sensors 2016, 16(8), 1228; https://doi.org/10.3390/s16081228 - 4 Aug 2016

Cited by 33 | Viewed by 10316

Abstract

Diverse sensing techniques have been developed and combined with machine learning method for forest fire detection, but none of them referred to identifying smoldering and flaming combustion phases. This study attempts to real-time identify different combustion phases using a developed wireless sensor network [...] Read more.

Diverse sensing techniques have been developed and combined with machine learning method for forest fire detection, but none of them referred to identifying smoldering and flaming combustion phases. This study attempts to real-time identify different combustion phases using a developed wireless sensor network (WSN)-based multi-sensor system and artificial neural network (ANN). Sensors (CO, CO₂, smoke, air temperature and relative humidity) were integrated into one node of WSN. An experiment was conducted using burning materials from residual of forest to test responses of each node under no, smoldering-dominated and flaming-dominated combustion conditions. The results showed that the five sensors have reasonable responses to artificial forest fire. To reduce cost of the nodes, smoke, CO₂ and temperature sensors were chiefly selected through correlation analysis. For achieving higher identification rate, an ANN model was built and trained with inputs of four sensor groups: smoke; smoke and CO₂; smoke and temperature; smoke, CO₂ and temperature. The model test results showed that multi-sensor input yielded higher predicting accuracy (≥82.5%) than single-sensor input (50.9%–92.5%). Based on these, it is possible to reduce the cost with a relatively high fire identification rate and potential application of the system can be tested in future under real forest condition. Full article

(This article belongs to the Collection Sensors in Agriculture and Forestry)

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14 pages, 6819 KiB

Open AccessArticle

Frequency Splitting Analysis and Compensation Method for Inductive Wireless Powering of Implantable Biosensors

by Matthew Schormans^*, Virgilio Valente and Andreas Demosthenous

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

Sensors 2016, 16(8), 1229; https://doi.org/10.3390/s16081229 - 4 Aug 2016

Cited by 29 | Viewed by 9027

Abstract

Inductive powering for implanted medical devices, such as implantable biosensors, is a safe and effective technique that allows power to be delivered to implants wirelessly, avoiding the use of transcutaneous wires or implanted batteries. Wireless powering is very sensitive to a number of [...] Read more.

Inductive powering for implanted medical devices, such as implantable biosensors, is a safe and effective technique that allows power to be delivered to implants wirelessly, avoiding the use of transcutaneous wires or implanted batteries. Wireless powering is very sensitive to a number of link parameters, including coil distance, alignment, shape, and load conditions. The optimum drive frequency of an inductive link varies depending on the coil spacing and load. This paper presents an optimum frequency tracking (OFT) method, in which an inductive power link is driven at a frequency that is maintained at an optimum value to ensure that the link is working at resonance, and the output voltage is maximised. The method is shown to provide significant improvements in maintained secondary voltage and system efficiency for a range of loads when the link is overcoupled. The OFT method does not require the use of variable capacitors or inductors. When tested at frequencies around a nominal frequency of 5 MHz, the OFT method provides up to a twofold efficiency improvement compared to a fixed frequency drive. The system can be readily interfaced with passive implants or implantable biosensors, and lends itself to interfacing with designs such as distributed implanted sensor networks, where each implant is operating at a different frequency. Full article

(This article belongs to the Section Biosensors)

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3 pages, 155 KiB

Open AccessCorrection

Correction: Gao, Q. et al. A Context-Aware Mobile User Behavior-Based Neighbor Finding Approach for Preference Profile Construction. Sensors 2016, 16, 143

by Qian Gao^1,*

, Deqian Fu² and Xiangjun Dong¹

¹ School of Information, Qilu University of Technology, #3501 Daxue Road, Changqing District, Jinan 250353, China

² School of Informatics, Linyi University, Shuangling Rd., Lanshan, Linyi 276005, China

Sensors 2016, 16(8), 1230; https://doi.org/10.3390/s16081230 - 4 Aug 2016

Cited by 1 | Viewed by 3891

Abstract

At ﬁrst, may I offer my profoundest respects to the previous work obtained by the author Shi, whose work enlarged our view and set a good research direction for us and enlightened the initial idea of our paper.[...] Full article

(This article belongs to the Special Issue Integration of Sensors in Complex, Intelligent Systems—Selected Papers from the CHARMS 2015 Workshop)

12 pages, 1624 KiB

Open AccessArticle

A Novel One-Step Fabricated, Droplet-Based Electrochemical Sensor for Facile Biochemical Assays

by Yong Yao and Chunsun Zhang^*

MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China

Sensors 2016, 16(8), 1231; https://doi.org/10.3390/s16081231 - 4 Aug 2016

Cited by 10 | Viewed by 6542

Abstract

A simple, novel concept for the one-step fabrication of a low-cost, easy-to-use droplet-based electrochemical (EC) sensor is described, in which the EC reagents are contained in a droplet and the droplet assay is operated on a simple planar surface instead of in a [...] Read more.

A simple, novel concept for the one-step fabrication of a low-cost, easy-to-use droplet-based electrochemical (EC) sensor is described, in which the EC reagents are contained in a droplet and the droplet assay is operated on a simple planar surface instead of in a complicated closed channel/chamber. In combination with an elegant carbon electrode configuration, screen-printed on a widely available polyethylene terephthalate (PET) substrate, the developed sensor exhibits a stable solution-restriction capacity and acceptable EC response, and thus can be used directly for the detection of different analytes (including ascorbic acid (AA), copper ions (Cu²⁺), 2′-deoxyguanosine 5′-triphosphate (dGTP) and ferulic acid (FA)), without any pretreatment. The obtained, acceptable linear ranges/detection limits for AA, Cu²⁺, dGTP and FA are 0.5–10/0.415 mM, (0.0157–0.1574 and 0.1574–1.5736)/0.011 mM, 0.01–0.1/0.008 mM and 0.0257–0.515/0.024 mM, respectively. Finally, the utility of the droplet-based EC sensor was demonstrated for the determination of AA in two commercial beverages, and of Cu²⁺ in two water samples, with reliable recovery and good stability. The applicability of the droplet-based sensor demonstrates that the proposed EC strategy is potentially a cost-effective solution for a series of biochemical sensing applications in public health, environmental monitoring, and the developing world. Full article

(This article belongs to the Section Biosensors)

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21 pages, 1972 KiB

Open AccessReview

A Review: Origins of the Dielectric Properties of Proteins and Potential Development as Bio-Sensors

by Fabien Bibi¹, Maud Villain¹, Carole Guillaume¹, Brice Sorli^2,* and Nathalie Gontard¹

¹ Joint Research Unit Agropolymers Engineering and Emerging Technologies, UMR 1208 INRA/SupAgroM/UMII/CIRAD, 2 Place Pierre Viala, Montpellier 34060, France

² B. SORLI, Institut d’Electronique et des Systèmes, Université Montpellier 2, 860 Rue Saint-Priest, Montpellier 34090, France

Sensors 2016, 16(8), 1232; https://doi.org/10.3390/s16081232 - 4 Aug 2016

Cited by 124 | Viewed by 11123

Abstract

Polymers can be classified as synthetic polymers and natural polymers, and are often characterized by their most typical functions namely their high mechanical resistivity, electrical conductivity and dielectric properties. This bibliography report consists in: (i) Defining the origins of the dielectric properties of [...] Read more.

Polymers can be classified as synthetic polymers and natural polymers, and are often characterized by their most typical functions namely their high mechanical resistivity, electrical conductivity and dielectric properties. This bibliography report consists in: (i) Defining the origins of the dielectric properties of natural polymers by reviewing proteins. Despite their complex molecular chains, proteins present several points of interest, particularly, their charge content conferring their electrical and dielectric properties; (ii) Identifying factors influencing the dielectric properties of protein films. The effects of vapors and gases such as water vapor, oxygen, carbon dioxide, ammonia and ethanol on the dielectric properties are put forward; (iii) Finally, potential development of protein films as bio-sensors coated on electronic devices for detection of environmental changes particularly humidity or carbon dioxide content in relation with dielectric properties variations are discussed. As the study of the dielectric properties implies imposing an electric field to the material, it was necessary to evaluate the impact of frequency on the polymers and subsequently on their structure. Characterization techniques, on the one hand dielectric spectroscopy devoted for the determination of the glass transition temperature among others, and on the other hand other techniques such as infra-red spectroscopy for structure characterization as a function of moisture content for instance are also introduced. Full article

(This article belongs to the Section Biosensors)

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12 pages, 2021 KiB

Open AccessArticle

Optical Feedback Interferometry for Velocity Measurement of Parallel Liquid-Liquid Flows in a Microchannel

by Evelio E. Ramírez-Miquet^1,2, Julien Perchoux^1,*

, Karine Loubière³, Clément Tronche¹, Laurent Prat³ and Oscar Sotolongo-Costa^4,5

¹ LAAS-CNRS, Université de Toulouse, CNRS, INP, Toulouse F-31400, France

² Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Calle 30 No. 502, Miramar, La Habana 11300, Cuba

³ Laboratoire de Génie Chimique, Université de Toulouse, CNRS, INPT, UPS, 4 allée Emile Monso, BP 84234, Toulouse F-31432, France

⁴ Instituto de Investigación en Ciencias Básicas y Aplicadas, Universidad Autónoma del Estado de Morelos, Cuernavaca 62209, Mexico

⁵ Cátedra de Sistemas Complejos Henri Poincaré, Universidad de La Habana, La Habana 10400, Cuba

Sensors 2016, 16(8), 1233; https://doi.org/10.3390/s16081233 - 4 Aug 2016

Cited by 22 | Viewed by 6405

Abstract

Optical feedback interferometry (OFI) is a compact sensing technique with recent implementation for flow measurements in microchannels. We propose implementing OFI for the analysis at the microscale of multiphase flows starting with the case of parallel flows of two immiscible fluids. The velocity [...] Read more.

Optical feedback interferometry (OFI) is a compact sensing technique with recent implementation for flow measurements in microchannels. We propose implementing OFI for the analysis at the microscale of multiphase flows starting with the case of parallel flows of two immiscible fluids. The velocity profiles in each phase were measured and the interface location estimated for several operating conditions. To the authors knowledge, this sensing technique is applied here for the first time to multiphase flows. Theoretical profiles issued from a model based on the Couette viscous flow approximation reproduce fairly well the experimental results. The sensing system and the analysis presented here provide a new tool for studying more complex interactions between immiscible fluids (such as liquid droplets flowing in a microchannel). Full article

(This article belongs to the Special Issue Microfluidic Sensors and Control Devices)

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9 pages, 8622 KiB

Open AccessArticle

A Miniaturized On-Chip Colorimeter for Detecting NPK Elements

by Rui-Tao Liu^1,2, Lu-Qi Tao^1,2, Bo Liu^1,2, Xiang-Guang Tian^1,2, Mohammad Ali Mohammad^1,3, Yi Yang^1,2 and Tian-Ling Ren^1,2,*

¹ Institute of Microelectronics, Tsinghua University, Beijing 100084, China

² Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China

³ School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan

Sensors 2016, 16(8), 1234; https://doi.org/10.3390/s16081234 - 4 Aug 2016

Cited by 21 | Viewed by 10062

Abstract

Recently, precision agriculture has become a globally attractive topic. As one of the most important factors, the soil nutrients play an important role in estimating the development of precision agriculture. Detecting the content of nitrogen, phosphorus and potassium (NPK) elements more efficiently is [...] Read more.

Recently, precision agriculture has become a globally attractive topic. As one of the most important factors, the soil nutrients play an important role in estimating the development of precision agriculture. Detecting the content of nitrogen, phosphorus and potassium (NPK) elements more efficiently is one of the key issues. In this paper, a novel chip-level colorimeter was fabricated to detect the NPK elements for the first time. A light source–microchannel photodetector in a sandwich structure was designed to realize on-chip detection. Compared with a commercial colorimeter, all key parts are based on MEMS (Micro-Electro-Mechanical System) technology so that the volume of this on-chip colorimeter can be minimized. Besides, less error and high precision are achieved. The cost of this colorimeter is two orders of magnitude less than that of a commercial one. All these advantages enable a low-cost and high-precision sensing operation in a monitoring network. The colorimeter developed herein has bright prospects for environmental and biological applications. Full article

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

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22 pages, 2892 KiB

Open AccessArticle

CoDA: Collaborative Data Aggregation in Emerging Sensor Networks Using Bio-Level Voronoi Diagrams

by Chengpei Tang^1,2,* and Nian Yang¹

¹ School of Engineering, Sun Yat-Sen University, Guangzhou 510006, China

² Research Institute of Sun Yat-Sen University in Shenzhen, Shenzhen 510006, China

Sensors 2016, 16(8), 1235; https://doi.org/10.3390/s16081235 - 5 Aug 2016

Cited by 3 | Viewed by 5877

Abstract

To implement minimum power consumption of the link, cluster heads adopt the multi-hop manner for inter-cluster communication so as to forward the aggregation data to the relay nodes. This paper proposes a collaborative data aggregation in emerging sensor networks using a bio-level Voronoi [...] Read more.

To implement minimum power consumption of the link, cluster heads adopt the multi-hop manner for inter-cluster communication so as to forward the aggregation data to the relay nodes. This paper proposes a collaborative data aggregation in emerging sensor networks using a bio-level Voronoi diagram, which is an energy-efficient data aggregation protocol that integrates topology control, Multiple Access Control (MAC) and routing. The sensor nodes situated in the lower level of the diagram are responsible for listening and gathering data, and should be organized by optimal clustering node. In the inter-cluster communication stage, a particle swarm optimization algorithm is addressed to seek optimal transmission path which could simultaneously achieve the minimization of the maximum next hop distance between two nodes in the routing path and the minimization of the maximum hop count, so the minimization of whole network energy consumption is realized. The results of theoretical analysis and simulation results show that energy efficiency and synchronization accuracy of the proposed algorithm can be much better than with traditional routing protocols, and the energy consumption of nodes in the whole network can be more balanced. Full article

(This article belongs to the Special Issue Topology Control in Emerging Sensor Networks)

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17 pages, 1033 KiB

Open AccessArticle

Performance Characterization of a Hybrid Satellite-Terrestrial System with Co-Channel Interference over Generalized Fading Channels

by Umer Javed^*, Di He and Peilin Liu

Shanghai Key Laboratory of Navigation and Location-Based Services, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China

Sensors 2016, 16(8), 1236; https://doi.org/10.3390/s16081236 - 5 Aug 2016

Cited by 9 | Viewed by 4376

Abstract

The transmission of signals in a hybrid satellite-terrestrial system (HSTS) in the presence of co-channel interference (CCI) is considered in this study. Specifically, we examine the problem of amplify-and-forward (AF)-based relaying in a hybrid satellite-terrestrial link, where the relay node is operating in [...] Read more.

The transmission of signals in a hybrid satellite-terrestrial system (HSTS) in the presence of co-channel interference (CCI) is considered in this study. Specifically, we examine the problem of amplify-and-forward (AF)-based relaying in a hybrid satellite-terrestrial link, where the relay node is operating in the presence of a dominant co-channel interferer. It is assumed that direct connection between a source node (satellite) and a destination node (terrestrial receiver) is not available due to masking by obstacles in the surrounding. The destination node is only able to receive signals from the satellite with the help of a relay node located at the ground. In the proposed HSTS, the satellite-relay channel follows the shadowed Rice fading; and the channels of interferer-relay and relay-destination links experience generalized Nakagami-m fading. For the considered AF-based HSTS, we first develop the analytical expression for the moment generating function (MGF) of the overall output signal-to-interference-plus-noise ratio (SINR). Then, based on the derived exact MGF, we derive novel expressions for the average symbol error rate (SER) of the considered HSTS for the following digital modulation techniques: M-ary phase shift keying (M-PSK), M-ary quadrature amplitude modulation (M-QAM) and M-ary pulse amplitude modulation (M-PAM). To significantly reduce the computational complexity for utility in system-level simulations, simple analytical approximation for the exact SER in the high signal-to-noise ratio (SNR) regime is presented to provide key insights. Finally, numerical results and the corresponding analysis are presented to demonstrate the effectiveness of the developed performance evaluation framework and to view the impact of CCI on the considered HSTS under varying channel conditions and with different modulation schemes. Full article

(This article belongs to the Section Remote Sensors)

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11 pages, 3052 KiB

Open AccessArticle

A Non-Intrusive Pressure Sensor by Detecting Multiple Longitudinal Waves

by Hongliang Zhou^1,*, Weibin Lin¹, Xiaocheng Ge² and Jian Zhou³

¹ State Key Laboratory of Industrial Control Technology, College of Control Science and Engineering, Zhejiang University, Hangzhou 310027, China

² School of Computing and Engineering, University of Huddersfield, Huddersfield HD1 3DH, UK

³ College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China

Sensors 2016, 16(8), 1237; https://doi.org/10.3390/s16081237 - 5 Aug 2016

Cited by 7 | Viewed by 7700

Abstract

Pressure vessels are widely used in industrial fields, and some of them are safety-critical components in the system—for example, those which contain flammable or explosive material. Therefore, the pressure of these vessels becomes one of the critical measurements for operational management. In the [...] Read more.

Pressure vessels are widely used in industrial fields, and some of them are safety-critical components in the system—for example, those which contain flammable or explosive material. Therefore, the pressure of these vessels becomes one of the critical measurements for operational management. In the paper, we introduce a new approach to the design of non-intrusive pressure sensors, based on ultrasonic waves. The model of this sensor is built based upon the travel-time change of the critically refracted longitudinal wave (L_CR wave) and the reflected longitudinal waves with the pressure. To evaluate the model, experiments are carried out to compare the proposed model with other existing models. The results show that the proposed model can improve the accuracy compared to models based on a single wave. Full article

(This article belongs to the Special Issue Ultrasonic Sensors)

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18 pages, 2760 KiB

Open AccessArticle

Passive Mixing Capabilities of Micro- and Nanofibres When Used in Microfluidic Systems

by Lauren Matlock-Colangelo¹, Nicholas W. Colangelo², Christoph Fenzl³, Margaret W. Frey⁴ and Antje J. Baeumner^1,3,*

¹ Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA

² Department of Radiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA

³ Institute for Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, Regensburg 93040, Germany

⁴ Department of Fibre Science and Apparel Design, Cornell University, Ithaca, NY 14853, USA

Sensors 2016, 16(8), 1238; https://doi.org/10.3390/s16081238 - 5 Aug 2016

Cited by 15 | Viewed by 6159

Abstract

Nanofibres are increasingly being used in the field of bioanalytics due to their large surface-area-to-volume ratios and easy-to-functionalize surfaces. To date, nanofibres have been studied as effective filters, concentrators, and immobilization matrices within microfluidic devices. In addition, they are frequently used as optical [...] Read more.

Nanofibres are increasingly being used in the field of bioanalytics due to their large surface-area-to-volume ratios and easy-to-functionalize surfaces. To date, nanofibres have been studied as effective filters, concentrators, and immobilization matrices within microfluidic devices. In addition, they are frequently used as optical and electrochemical transduction materials. In this work, we demonstrate that electrospun nanofibre mats cause appreciable passive mixing and therefore provide dual functionality when incorporated within microfluidic systems. Specifically, electrospun nanofibre mats were integrated into Y-shaped poly(methyl methacrylate) microchannels and the degree of mixing was quantified using fluorescence microscopy and ImageJ analysis. The degree of mixing afforded in relationship to fibre diameter, mat height, and mat length was studied. We observed that the most mixing was caused by small diameter PVA nanofibres (450–550 nm in diameter), producing up to 71% mixing at the microchannel outlet, compared to up to 51% with polystyrene microfibres (0.8–2.7 μm in diameter) and 29% mixing in control channels containing no fibres. The mixing afforded by the PVA nanofibres is caused by significant inhomogeneity in pore size and distribution leading to percolation. As expected, within all the studies, fluid mixing increased with fibre mat height, which corresponds to the vertical space of the microchannel occupied by the fibre mats. Doubling the height of the fibre mat led to an average increase in mixing of 14% for the PVA nanofibres and 8% for the PS microfibres. Overall, mixing was independent of the length of the fibre mat used (3–10 mm), suggesting that most mixing occurs as fluid enters and exits the fibre mat. The mixing effects observed within the fibre mats were comparable to or better than many passive mixers reported in literature. Since the nanofibre mats can be further functionalized to couple analyte concentration, immobilization, and detection with enhanced fluid mixing, they are a promising nanomaterial providing dual-functionality within lab-on-a-chip devices. Full article

(This article belongs to the Special Issue Microfluidics-Based Microsystem Integration Research)

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11 pages, 1743 KiB

Open AccessArticle

Soil Water Content Sensor Response to Organic Matter Content under Laboratory Conditions

by Ali Fares^*

, Ripendra Awal

and Haimanote K. Bayabil

College of Agriculture and Human Sciences, Prairie View A&M University, Prairie View, TX 77446, USA

Sensors 2016, 16(8), 1239; https://doi.org/10.3390/s16081239 - 5 Aug 2016

Cited by 17 | Viewed by 7667

Abstract

Studies show that the performance of soil water content monitoring (SWCM) sensors is affected by soil physical and chemical properties. However, the effect of organic matter on SWCM sensor responses remains less understood. Therefore, the objectives of this study are to (i) assess [...] Read more.

Studies show that the performance of soil water content monitoring (SWCM) sensors is affected by soil physical and chemical properties. However, the effect of organic matter on SWCM sensor responses remains less understood. Therefore, the objectives of this study are to (i) assess the effect of organic matter on the accuracy and precision of SWCM sensors using a commercially available soil water content monitoring sensor; and (ii) account for the organic matter effect on the sensor’s accuracy. Sand columns with seven rates of oven-dried sawdust (2%, 4%, 6%, 8%, 10%, 12% and 18% v/v, used as an organic matter amendment), thoroughly mixed with quartz sand, and a control without sawdust were prepared by packing quartz sand in two-liter glass containers. Sand was purposely chosen because of the absence of any organic matter or salinity, and also because sand has a relatively low cation exchange capacity that will not interfere with the treatment effect of the current work. Sensor readings (raw counts) were monitored at seven water content levels (0, 0.02, 0.04, 0.08, 0.12, 0.18, 0.24, and 0.30 cm³ cm⁻³) by uniformly adding the corresponding volumes of deionized water in addition to the oven-dry one. Sensor readings were significantly (p < 0.05) affected by the organic matter level and water content. Sensor readings were strongly correlated with the organic matter level (R² = 0.92). In addition, the default calibration equation underestimated the water content readings at the lower water content range (<0.05 cm³ cm⁻³), while it overestimated the water content at the higher water content range (>0.05 cm³ cm⁻³). A new polynomial calibration equation that uses raw count and organic matter content as covariates improved the accuracy of the sensor (RMSE = 0.01 cm³ cm⁻³). Overall, findings of this study highlight the need to account for the effect of soil organic matter content to improve the accuracy and precision of the tested sensor under different soils and environmental conditions. Full article

(This article belongs to the Section Physical Sensors)

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21 pages, 11964 KiB

Open AccessArticle

Rigorous Performance Evaluation of Smartphone GNSS/IMU Sensors for ITS Applications

by Vassilis Gikas^* and Harris Perakis

School of Rural and Surveying Engineering, National Technical University of Athens (NTUA), Zographos 15780, Greece

Sensors 2016, 16(8), 1240; https://doi.org/10.3390/s16081240 - 5 Aug 2016

Cited by 57 | Viewed by 9812

Abstract

With the rapid growth in smartphone technologies and improvement in their navigation sensors, an increasing amount of location information is now available, opening the road to the provision of new Intelligent Transportation System (ITS) services. Current smartphone devices embody miniaturized Global Navigation Satellite [...] Read more.

With the rapid growth in smartphone technologies and improvement in their navigation sensors, an increasing amount of location information is now available, opening the road to the provision of new Intelligent Transportation System (ITS) services. Current smartphone devices embody miniaturized Global Navigation Satellite System (GNSS), Inertial Measurement Unit (IMU) and other sensors capable of providing user position, velocity and attitude. However, it is hard to characterize their actual positioning and navigation performance capabilities due to the disparate sensor and software technologies adopted among manufacturers and the high influence of environmental conditions, and therefore, a unified certification process is missing. This paper presents the analysis results obtained from the assessment of two modern smartphones regarding their positioning accuracy (i.e., precision and trueness) capabilities (i.e., potential and limitations) based on a practical but rigorous methodological approach. Our investigation relies on the results of several vehicle tracking (i.e., cruising and maneuvering) tests realized through comparing smartphone obtained trajectories and kinematic parameters to those derived using a high-end GNSS/IMU system and advanced filtering techniques. Performance testing is undertaken for the HTC One S (Android) and iPhone 5s (iOS). Our findings indicate that the deviation of the smartphone locations from ground truth (trueness) deteriorates by a factor of two in obscured environments compared to those derived in open sky conditions. Moreover, it appears that iPhone 5s produces relatively smaller and less dispersed error values compared to those computed for HTC One S. Also, the navigation solution of the HTC One S appears to adapt faster to changes in environmental conditions, suggesting a somewhat different data filtering approach for the iPhone 5s. Testing the accuracy of the accelerometer and gyroscope sensors for a number of maneuvering (speeding, turning, etc.,) events reveals high consistency between smartphones, whereas the small deviations from ground truth verify their high potential even for critical ITS safety applications. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 4126 KiB

Open AccessArticle

Generation of Localized Surface Plasmon Resonance Using Hybrid Au–Ag Nanoparticle Arrays as a Sensor of Polychlorinated Biphenyls Detection

by Jing Liu¹, Haoyuan Cai², Chaoyang Chen¹, Guangsong Yang¹ and Cheng-Fu Yang^3,*

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

² State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou 310027, China

³ Department of Chemical and Materials Engineering, National University of Kaohsiung, No. 700, Kaohsiung University Rd., Nan-Tzu District, Kaohsiung 811, Taiwan

Sensors 2016, 16(8), 1241; https://doi.org/10.3390/s16081241 - 5 Aug 2016

Cited by 8 | Viewed by 6343

Abstract

In this study, the hybrid Au–Ag hexagonal lattice of triangular and square lattice of quadrate periodic nanoparticle arrays (PNAs) were designed to investigate their extinction spectra of the localized surface plasmon resonances (LSPRs). First, their simulating extinction spectra were calculated by discrete dipole [...] Read more.

In this study, the hybrid Au–Ag hexagonal lattice of triangular and square lattice of quadrate periodic nanoparticle arrays (PNAs) were designed to investigate their extinction spectra of the localized surface plasmon resonances (LSPRs). First, their simulating extinction spectra were calculated by discrete dipole approximation (DDA) numerical method by changing the media refractive index. Simulation results showed that as the media refractive index was changed from 1.0 to 1.2, the maximum peak intensity of LSPRs spectra had no apparent change and the wavelength to reveal the maximum peak intensity of LSPRs spectra was shifted lower value. Polystyrene (PS) nanospheres with two differently arranged structures were used as the templates to deposit the hybrid Au–Ag hexagonal lattice of triangular and square lattice of quadrate periodic PNAs by evaporation method. The hybrid Au–Ag hexagonal lattice of triangular and square lattice of quadrate PNAs were grown on single crystal silicon (c-Si) substrates, and their measured extinction spectra were compared with the calculated results. Finally, the fabricated hexagonal lattices of triangular PNAs were investigated as a sensor of polychlorinated biphenyl solution (PCB-77) by observing the wavelength to reveal the maximum extinction efficiency (λ_max). We show that the adhesion of β-cyclodextrins (SH-β-CD) on the hybrid Au–Ag hexagonal lattice of triangular PNAs could be used to increase the variation of λ_max. We also demonstrate that the adhesion of SH-β-CD increases the sensitivity and detection effect of PCB-77 in hexagonal lattice of triangular PNAs. Full article

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

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18 pages, 3591 KiB

Open AccessArticle

Stochastic Modeling and Analysis of Multiple Nonlinear Accelerated Degradation Processes through Information Fusion

by Fuqiang Sun^1,2, Le Liu¹

, Xiaoyang Li¹

and Haitao Liao^2,*

¹ Science and Technology on Reliability and Environmental Engineering Laboratory, School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China

² Department of Industrial Engineering, University of Arkansas, Fayetteville, AR 72701, USA

Sensors 2016, 16(8), 1242; https://doi.org/10.3390/s16081242 - 6 Aug 2016

Cited by 44 | Viewed by 6302

Abstract

Accelerated degradation testing (ADT) is an efficient technique for evaluating the lifetime of a highly reliable product whose underlying failure process may be traced by the degradation of the product’s performance parameters with time. However, most research on ADT mainly focuses on a [...] Read more.

Accelerated degradation testing (ADT) is an efficient technique for evaluating the lifetime of a highly reliable product whose underlying failure process may be traced by the degradation of the product’s performance parameters with time. However, most research on ADT mainly focuses on a single performance parameter. In reality, the performance of a modern product is usually characterized by multiple parameters, and the degradation paths are usually nonlinear. To address such problems, this paper develops a new s-dependent nonlinear ADT model for products with multiple performance parameters using a general Wiener process and copulas. The general Wiener process models the nonlinear ADT data, and the dependency among different degradation measures is analyzed using the copula method. An engineering case study on a tuner’s ADT data is conducted to demonstrate the effectiveness of the proposed method. The results illustrate that the proposed method is quite effective in estimating the lifetime of a product with s-dependent performance parameters. Full article

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

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20 pages, 5780 KiB

Open AccessArticle

Improved Feature Matching for Mobile Devices with IMU

by Andrea Masiero^*

and Antonio Vettore

CIRGEO (Interdepartmental Research Center of Geomatics), University of Padova, via dell’Università 16, 35020 Legnaro (PD), Italy

Sensors 2016, 16(8), 1243; https://doi.org/10.3390/s16081243 - 5 Aug 2016

Cited by 20 | Viewed by 5043

Abstract

Thanks to the recent diffusion of low-cost high-resolution digital cameras and to the development of mostly automated procedures for image-based 3D reconstruction, the popularity of photogrammetry for environment surveys is constantly increasing in the last years. Automatic feature matching is an important step [...] Read more.

Thanks to the recent diffusion of low-cost high-resolution digital cameras and to the development of mostly automated procedures for image-based 3D reconstruction, the popularity of photogrammetry for environment surveys is constantly increasing in the last years. Automatic feature matching is an important step in order to successfully complete the photogrammetric 3D reconstruction: this step is the fundamental basis for the subsequent estimation of the geometry of the scene. This paper reconsiders the feature matching problem when dealing with smart mobile devices (e.g., when using the standard camera embedded in a smartphone as imaging sensor). More specifically, this paper aims at exploiting the information on camera movements provided by the inertial navigation system (INS) in order to make the feature matching step more robust and, possibly, computationally more efficient. First, a revised version of the affine scale-invariant feature transform (ASIFT) is considered: this version reduces the computational complexity of the original ASIFT, while still ensuring an increase of correct feature matches with respect to the SIFT. Furthermore, a new two-step procedure for the estimation of the essential matrix E (and the camera pose) is proposed in order to increase its estimation robustness and computational efficiency. Full article

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10 pages, 4065 KiB

Open AccessArticle

Novel Low-Cost Sensor for Human Bite Force Measurement

by Jarred Fastier-Wooller¹

, Hoang-Phuong Phan²

, Toan Dinh², Tuan-Khoa Nguyen², Andrew Cameron³

, Andreas Öchsner¹

and Dzung Viet Dao^1,2,*

¹ School of Engineering, Griffith University, Queensland 4215, Australia

² Queensland Micro- and Nanotechnology Centre, Griffith University, Queensland 4111, Australia

³ School of Dentistry, Griffith University, Queensland 4215, Australia

Sensors 2016, 16(8), 1244; https://doi.org/10.3390/s16081244 - 6 Aug 2016

Cited by 28 | Viewed by 12767

Abstract

This paper presents the design and development of a low cost and reliable maximal voluntary bite force sensor which can be manufactured in-house by using an acrylic laser cutting machine. The sensor has been designed for ease of fabrication, assembly, calibration, and safe [...] Read more.

This paper presents the design and development of a low cost and reliable maximal voluntary bite force sensor which can be manufactured in-house by using an acrylic laser cutting machine. The sensor has been designed for ease of fabrication, assembly, calibration, and safe use. The sensor is capable of use within an hour of commencing production, allowing for rapid prototyping/modifications and practical implementation. The measured data shows a good linear relationship between the applied force and the electrical resistance of the sensor. The output signal has low drift, excellent repeatability, and a large measurable range of 0 to 700 N. A high signal-to-noise response to human bite forces was observed, indicating the high potential of the proposed sensor for human bite force measurement. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 23627 KiB

Open AccessArticle

Spatiotemporal Interpolation for Environmental Modelling

by Ferry Susanto^1,2,*, Paulo De Souza, Jr.¹ and Jing He²

¹ Data61, CSIRO, College Road, Sandy Bay TAS 7005, Australia

² College of Engineering and Science, Victoria University, Footscray VIC 3011, Australia

Sensors 2016, 16(8), 1245; https://doi.org/10.3390/s16081245 - 6 Aug 2016

Cited by 35 | Viewed by 8669

Abstract

A variation of the reduction-based approach to spatiotemporal interpolation (STI), in which time is treated independently from the spatial dimensions, is proposed in this paper. We reviewed and compared three widely-used spatial interpolation techniques: ordinary kriging, inverse distance weighting and the triangular irregular [...] Read more.

A variation of the reduction-based approach to spatiotemporal interpolation (STI), in which time is treated independently from the spatial dimensions, is proposed in this paper. We reviewed and compared three widely-used spatial interpolation techniques: ordinary kriging, inverse distance weighting and the triangular irregular network. We also proposed a new distribution-based distance weighting (DDW) spatial interpolation method. In this study, we utilised one year of Tasmania’s South Esk Hydrology model developed by CSIRO. Root mean squared error statistical methods were performed for performance evaluations. Our results show that the proposed reduction approach is superior to the extension approach to STI. However, the proposed DDW provides little benefit compared to the conventional inverse distance weighting (IDW) method. We suggest that the improved IDW technique, with the reduction approach used for the temporal dimension, is the optimal combination for large-scale spatiotemporal interpolation within environmental modelling applications. Full article

(This article belongs to the Section Sensor Networks)

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10 pages, 3804 KiB

Open AccessArticle

A Fluidically Tunable Metasurface Absorber for Flexible Large-Scale Wireless Ethanol Sensor Applications

by Hyung Ki Kim

, Dongju Lee and Sungjoon Lim^*

School of Electrical and Electronics Engineering, College of Engineering, Chung-Ang University, 221 Heukseok-dong, Dongjak-gu, Seoul 156-756, Korea

Sensors 2016, 16(8), 1246; https://doi.org/10.3390/s16081246 - 6 Aug 2016

Cited by 84 | Viewed by 8545

Abstract

In this paper, a novel flexible tunable metasurface absorber is proposed for large-scale remote ethanol sensor applications. The proposed metasurface absorber consists of periodic split-ring-cross resonators (SRCRs) and microfluidic channels. The SRCR patterns are inkjet-printed on paper using silver nanoparticle inks. The microfluidic [...] Read more.

In this paper, a novel flexible tunable metasurface absorber is proposed for large-scale remote ethanol sensor applications. The proposed metasurface absorber consists of periodic split-ring-cross resonators (SRCRs) and microfluidic channels. The SRCR patterns are inkjet-printed on paper using silver nanoparticle inks. The microfluidic channels are laser-etched on polydimethylsiloxane (PDMS) material. The proposed absorber can detect changes in the effective permittivity for different liquids. Therefore, the absorber can be used for a remote chemical sensor by detecting changes in the resonant frequencies. The performance of the proposed absorber is demonstrated with full-wave simulation and measurement results. The experimental results show the resonant frequency increases from 8.9 GHz to 10.04 GHz when the concentration of ethanol is changed from 0% to 100%. In addition, the proposed absorber shows linear frequency shift from 20% to 80% of the different concentrations of ethanol. Full article

(This article belongs to the Special Issue Microfluidics-Based Microsystem Integration Research)

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25 pages, 12905 KiB

Open AccessArticle

Implementation and Analysis of ISM 2.4 GHz Wireless Sensor Network Systems in Judo Training Venues

by Peio Lopez-Iturri¹

, Erik Aguirre¹

, Leyre Azpilicueta²

, José Javier Astrain³

, Jesús Villadangos³

and Francisco Falcone^1,*

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

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

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

Sensors 2016, 16(8), 1247; https://doi.org/10.3390/s16081247 - 6 Aug 2016

Cited by 8 | Viewed by 5780

Abstract

In this work, the performance of ISM 2.4 GHz Wireless Sensor Networks (WSNs) deployed in judo training venues is analyzed. Judo is a very popular martial art, which is practiced by thousands of people not only at the competition level, but also as [...] Read more.

In this work, the performance of ISM 2.4 GHz Wireless Sensor Networks (WSNs) deployed in judo training venues is analyzed. Judo is a very popular martial art, which is practiced by thousands of people not only at the competition level, but also as part of physical education programs at different school levels. There is a great variety of judo training venues, and each one has specific morphological aspects, making them unique scenarios in terms of radio propagation due to the presence of furniture, columns, equipment and the presence of human beings, which is a major issue as the person density within this kind of scenarios could be high. Another key aspect is the electromagnetic interference created by other wireless systems, such as WiFi or other WSNs, which make the radio planning a complex task in terms of coexistence. In order to analyze the impact of these features on the radio propagation and the performance of WSNs, an in-house developed 3D ray launching algorithm has been used. The obtained simulation results have been validated with a measurement campaign carried out in the sport facilities of the Public University of Navarre. The analysis is completed with the inclusion of an application designed to monitor biological constants of judokas, aimed to improve their training procedures. The application, that allows the simultaneous monitoring of multiple judokas (collective workouts) minimizing the efforts of the coach and medical supervisor, is based on commercial off-the-shelf products. The presented assessment of the presence of interfering wireless systems and the presence of human beings within judo training venues shows that an in-depth radio planning is required as these issues can have a great impact in the overall performance of a ISM 2.4 GHz WSN, affecting negatively the potential applications supported by wireless channel. 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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14 pages, 3797 KiB

Open AccessArticle

Design and Fabrication of Double-Focused Ultrasound Transducers to Achieve Tight Focusing

by Jihun Jang¹

and Jin Ho Chang^1,2,3,*

¹ Department of Electronic Engineering, Sogang University, Seoul 04107, Korea

² Department of Biomedical Engineering, Sogang University, Seoul 04107, Korea

³ Sogang Institutes of Advanced Technology, Sogang University, Seoul 04107, Korea

Sensors 2016, 16(8), 1248; https://doi.org/10.3390/s16081248 - 6 Aug 2016

Cited by 32 | Viewed by 13022

Abstract

Beauty treatment for skin requires a high-intensity focused ultrasound (HIFU) transducer to generate coagulative necrosis in a small focal volume (e.g., 1 mm³) placed at a shallow depth (3–4.5 mm from the skin surface). For this, it is desirable to make [...] Read more.

Beauty treatment for skin requires a high-intensity focused ultrasound (HIFU) transducer to generate coagulative necrosis in a small focal volume (e.g., 1 mm³) placed at a shallow depth (3–4.5 mm from the skin surface). For this, it is desirable to make the F-number as small as possible under the largest possible aperture in order to generate ultrasound energy high enough to induce tissue coagulation in such a small focal volume. However, satisfying both conditions at the same time is demanding. To meet the requirements, this paper, therefore, proposes a double-focusing technique, in which the aperture of an ultrasound transducer is spherically shaped for initial focusing and an acoustic lens is used to finally focus ultrasound on a target depth of treatment; it is possible to achieve the F-number of unity or less while keeping the aperture of a transducer as large as possible. In accordance with the proposed method, we designed and fabricated a 7-MHz double-focused ultrasound transducer. The experimental results demonstrated that the fabricated double-focused transducer had a focal length of 10.2 mm reduced from an initial focal length of 15.2 mm and, thus, the F-number changed from 1.52 to 1.02. Based on the results, we concluded that the proposed double-focusing method is suitable to decrease F-number while maintaining a large aperture size. Full article

(This article belongs to the Special Issue Ultrasonic Sensors)

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14 pages, 2171 KiB

Open AccessArticle

Comparative Study of Two Different TiO₂ Film Sensors on Response to H₂ under UV Light and Room Temperature

by Xiaoying Peng^1,2, Zhongming Wang^1,2, Pan Huang², Xun Chen^1,2, Xianzhi Fu^1,2 and Wenxin Dai^1,2,*

¹ State Key Laboratory of Photocatalysis on Energy and Environment, Research Institute of Photocatalysis, Fuzhou University, Fuzhou 350002, China

² College of Chemistry, Fuzhou University, Fuzhou 350108, China

Sensors 2016, 16(8), 1249; https://doi.org/10.3390/s16081249 - 8 Aug 2016

Cited by 45 | Viewed by 8194

Abstract

An anatase TiO₂ film sensor was prepared by a facile in-situ method on the interdigitated Au electrode deposited on the alumina substrate. The structure, morphology and the optical properties of the in-situ TiO₂ film sensor were characterized by X-ray diffraction, Scanning [...] Read more.

An anatase TiO₂ film sensor was prepared by a facile in-situ method on the interdigitated Au electrode deposited on the alumina substrate. The structure, morphology and the optical properties of the in-situ TiO₂ film sensor were characterized by X-ray diffraction, Scanning Electron Microscopy, and UV-vis diffuse reflectance spectra. The photo-assisted gas sensitivities of the prepared film towards H₂ gas were evaluated at room temperature in N₂ and synthetic air atmospheres. As compared to TiO₂ film sensor prepared by drop-coating method, this in-situ TiO₂ film sensor exhibited a more compact structure composed of uniform TiO₂ microspheres as well as a better gas sensitivity towards H₂ under UV irradiation, especially in synthetic air. The photo-electrochemical measurements suggest that these improvements may be associated with the efficient charge transfer in the TiO₂ interface induced by the TiO₂ microsphere structure. This study might offer a feasible approach to develop photo-assisted gas sensors at ambient temperature. Full article

(This article belongs to the Section Chemical Sensors)

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19 pages, 3908 KiB

Open AccessArticle

Evaluation of an Extended Autocorrelation Phase Estimator for Ultrasonic Velocity Profiles Using Nondestructive Testing Systems

by César Yutaka Ofuchi^1,*, Fabio Rizental Coutinho¹, Flávio Neves¹, Lucia Valéria Ramos De Arruda¹

and Rigoberto Eleazar Melgarejo Morales²

¹ Graduate School of Electrical Engineering and Computer Science (CPGEI), Federal University of Technology-Paraná (UTFPR), Avenida 7 de Setembro 3165, Curitiba 80230-901, Paraná, Brazil

² Mechanical & Materials Engineering Postgraduate Program (PPGEM), Federal University of Technology-Paraná (UTFPR), Avenida 7 de Setembro 3165, Curitiba 80230-901, Paraná, Brazil

Sensors 2016, 16(8), 1250; https://doi.org/10.3390/s16081250 - 9 Aug 2016

Cited by 4 | Viewed by 5720

Abstract

In this paper the extended autocorrelation velocity estimator is evaluated and compared using a nondestructive ultrasonic device. For this purpose, three velocity estimators are evaluated and compared. The autocorrelation method (ACM) is the most used and well established in current ultrasonic velocity profiler [...] Read more.

In this paper the extended autocorrelation velocity estimator is evaluated and compared using a nondestructive ultrasonic device. For this purpose, three velocity estimators are evaluated and compared. The autocorrelation method (ACM) is the most used and well established in current ultrasonic velocity profiler technology, however, the technique suffers with phase aliasing (also known as the Nyquist limit) at higher velocities. The cross-correlation method (CCM) is also well known and does not suffer with phase aliasing as it relies on time shift measurements between emissions. The problem of this method is the large computational burden due to several required mathematical operations. Recently, an extended autocorrelation method (EAM) which combines both ACM and CCM was developed. The technique is not well known within the fluid engineering community, but it can measure velocities beyond the Nyquist limit without the ACM phase aliasing issues and with a lower computational cost than CCM. In this work, all three velocity estimation methods are used to measure a uniform flow of the liquid inside a controlled rotating cylinder. The root-mean-square deviation variation coefficient (CV_RMSD) of the velocity estimate and the reference cylinder velocity was used to evaluate the three different methods. Results show that EAM correctly measures velocities below the Nyquist limit with less than 2% CV_RMSD. Velocities beyond the Nyquist limit are only measured well by EAM and CCM, with the advantage of the former of being computationally 15 times faster. Furthermore, the maximum value of measurable velocity is also investigated considering the number of times the velocity surpasses the Nyquist limit. The combination of number of pulses and number of samples, which highly affects the results, are also studied in this work. Velocities up to six times the Nyquist limit could be measurable with CCM and EAM using a set of parameters as suggested in this work. The results validate the use of the NDT tool to measure velocities even beyond Nyquist limit by using EAM. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 7679 KiB

Open AccessArticle

A Study of a Handrim-Activated Power-Assist Wheelchair Based on a Non-Contact Torque Sensor

by Ki-Tae Nam

, Dae-Jin Jang, Yong Chol Kim, Yoon Heo and Eung-Pyo Hong^*

Korea Orthopedics & Rehabilitation Engineering Center, 26, Gyeongin-ro 10beon-gil, Bupyeong-gu, Incheon 21417, Korea

Sensors 2016, 16(8), 1251; https://doi.org/10.3390/s16081251 - 8 Aug 2016

Cited by 5 | Viewed by 9276

Abstract

Demand for wheelchairs is increasing with growing numbers of aged and disabled persons. Manual wheelchairs are the most commonly used assistive device for mobility because they are convenient to transport. Manual wheelchairs have several advantages but are not easy to use for the [...] Read more.

Demand for wheelchairs is increasing with growing numbers of aged and disabled persons. Manual wheelchairs are the most commonly used assistive device for mobility because they are convenient to transport. Manual wheelchairs have several advantages but are not easy to use for the elderly or those who lack muscular strength. Therefore, handrim-activated power-assist wheelchairs (HAPAW) that can aid driving power with a motor by detecting user driving intentions through the handrim are being researched. This research will be on HAPAW that judge user driving intentions by using non-contact torque sensors. To deliver the desired motion, which is sensed from handrim rotation relative to a fixed controller, a new driving wheel mechanism is designed by applying a non-contact torque sensor, and corresponding torques are simulated. Torques are measured by a driving wheel prototype and compared with simulation results. The HAPAW prototype was developed using the wheels and a driving control algorithm that uses left and right input torques and time differences are used to check if the non-contact torque sensor can distinguish users’ driving intentions. Through this procedure, it was confirmed that the proposed sensor can be used effectively in HAPAW. Full article

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

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22 pages, 6080 KiB

Open AccessArticle

Analysis of the Bias on the Beidou GEO Multipath Combinations

by Yafei Ning^1,2,*, Yunbin Yuan¹, Yanju Chai¹ and Yong Huang³

¹ State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and Geophysics, 340 Xudong Rd., Wuhan 430077, China

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

³ School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ 85282, USA

Sensors 2016, 16(8), 1252; https://doi.org/10.3390/s16081252 - 8 Aug 2016

Cited by 11 | Viewed by 5074

Abstract

The Beidou navigation satellite system is a very important sensor for positioning in the Asia-Pacific region. The Beidou inclined geosynchronous orbit (IGSO) and medium Earth orbit (MEO) satellites have been analysed in some studies previously conducted by other researchers; this paper seeks to [...] Read more.

The Beidou navigation satellite system is a very important sensor for positioning in the Asia-Pacific region. The Beidou inclined geosynchronous orbit (IGSO) and medium Earth orbit (MEO) satellites have been analysed in some studies previously conducted by other researchers; this paper seeks to gain more insight regarding the geostationary earth orbit (GEO) satellites. Employing correlation analysis, Fourier transformation and wavelet decomposition, we validate whether there is a systematic bias in their multipath combinations. These biases can be observed clearly in satellites C01, C02 and C04 and have a great correlation with time series instead of elevation, being significantly different from those of the Beidou IGSO and MEO satellites. We propose a correction model to mitigate this bias based on its daily periodicity characteristic. After the model has been applied, the performance of the positioning estimations of the eight stations distributed in the Asia-Pacific region is evaluated and compared. The results show that residuals of multipath series behaves random noise; for the single point positioning (SPP) and precise point positioning (PPP) approaches, the positioning accuracy in the upward direction can be improved by 8 cm and 6 mm, respectively, and by 2 cm and 4 mm, respectively, for the horizontal component. Full article

(This article belongs to the Section Remote Sensors)

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27 pages, 4523 KiB

Open AccessArticle

Thermal Image Sensing Model for Robotic Planning and Search

by Lídice E. Castro Jiménez and Edgar A. Martínez-García^*

Laboratorio de Robótica, Institute of Engineering and Technology, Universidad Autónoma de Ciudad Juárez, Cd. Juárez, Chih. 32310, Mexico

Sensors 2016, 16(8), 1253; https://doi.org/10.3390/s16081253 - 8 Aug 2016

Cited by 5 | Viewed by 6212

Abstract

This work presents a search planning system for a rolling robot to find a source of infra-red (IR) radiation at an unknown location. Heat emissions are observed by a low-cost home-made IR passive visual sensor. The sensor capability for detection of radiation spectra [...] Read more.

This work presents a search planning system for a rolling robot to find a source of infra-red (IR) radiation at an unknown location. Heat emissions are observed by a low-cost home-made IR passive visual sensor. The sensor capability for detection of radiation spectra was experimentally characterized. The sensor data were modeled by an exponential model to estimate the distance as a function of the IR image’s intensity, and, a polynomial model to estimate temperature as a function of IR intensities. Both theoretical models are combined to deduce a subtle nonlinear exact solution via distance-temperature. A planning system obtains feed back from the IR camera (position, intensity, and temperature) to lead the robot to find the heat source. The planner is a system of nonlinear equations recursively solved by a Newton-based approach to estimate the IR-source in global coordinates. The planning system assists an autonomous navigation control in order to reach the goal and avoid collisions. Trigonometric partial differential equations were established to control the robot’s course towards the heat emission. A sine function produces attractive accelerations toward the IR source. A cosine function produces repulsive accelerations against the obstacles observed by an RGB-D sensor. Simulations and real experiments of complex indoor are presented to illustrate the convenience and efficacy of the proposed approach. Full article

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

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9 pages, 4826 KiB

Open AccessArticle

Reversed Three-Dimensional Visible Light Indoor Positioning Utilizing Annular Receivers with Multi-Photodiodes

by Yinfan Xu

, Jiaqi Zhao, Jianyang Shi and Nan Chi^*

Key Laboratory for Information Science of Electromagnetic Waves (MoE), Department of Communication Science and Engineering, Fudan University, No. 220, Handan Road, Shanghai 200433, China

Sensors 2016, 16(8), 1254; https://doi.org/10.3390/s16081254 - 8 Aug 2016

Cited by 31 | Viewed by 7187

Abstract

Exploiting the increasingly wide use of light emitting diodes (LEDs) lighting, in this paper we propose a reversed indoor positioning system (IPS) based on LED visible light communication (VLC) in order to improve indoor positioning accuracy. Unlike other VLC positioning systems, we employ [...] Read more.

Exploiting the increasingly wide use of light emitting diodes (LEDs) lighting, in this paper we propose a reversed indoor positioning system (IPS) based on LED visible light communication (VLC) in order to improve indoor positioning accuracy. Unlike other VLC positioning systems, we employ two annular receivers with multi-photodiodes installed on the ceiling to locate the persons who carry LEDs. The basic idea is using multi-photodiodes to calculate the angle while using the received signal strength (RSS) method to calculate the distance. The experiment results show that the effective positioning range of the proposed system is 1.8 m when the distance between two receivers is 1.2 m. Moreover, a positioning error less than 0.2 m can be achieved under the condition that the radius of the PIN circle is between 0.16 m and 0.2 m, and the distance of the transmitter-receiver plane is less than 1.8 m, which will be effective in practice. Full article

(This article belongs to the Special Issue Image Sensor Based Optical Wireless Communications– Selected Papers from the 7th International Conference on Ubiquitous and Future Networks and the 3rd International Workshop on Optical-Wireless LED Communication Networks)

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18 pages, 8877 KiB

Open AccessArticle

A Novel Cloud-Based Service Robotics Application to Data Center Environmental Monitoring

by Ludovico Orlando Russo^1,*

, Stefano Rosa¹

, Marcello Maggiora² and Basilio Bona¹

¹ Department of Control and Computer Engineering, Politecnico di Torino, Corso Duca Abruzzi 24, Turin 10129, Italy

² Infrastructure IT Division, Politecnico di Torino, Corso Duca Abruzzi 24, Turin 10129, Italy

Sensors 2016, 16(8), 1255; https://doi.org/10.3390/s16081255 - 8 Aug 2016

Cited by 23 | Viewed by 7014

Abstract

This work presents a robotic application aimed at performing environmental monitoring in data centers. Due to the high energy density managed in data centers, environmental monitoring is crucial for controlling air temperature and humidity throughout the whole environment, in order to improve power [...] Read more.

This work presents a robotic application aimed at performing environmental monitoring in data centers. Due to the high energy density managed in data centers, environmental monitoring is crucial for controlling air temperature and humidity throughout the whole environment, in order to improve power efficiency, avoid hardware failures and maximize the life cycle of IT devices. State of the art solutions for data center monitoring are nowadays based on environmental sensor networks, which continuously collect temperature and humidity data. These solutions are still expensive and do not scale well in large environments. This paper presents an alternative to environmental sensor networks that relies on autonomous mobile robots equipped with environmental sensors. The robots are controlled by a centralized cloud robotics platform that enables autonomous navigation and provides a remote client user interface for system management. From the user point of view, our solution simulates an environmental sensor network. The system can easily be reconfigured in order to adapt to management requirements and changes in the layout of the data center. For this reason, it is called the virtual sensor network. This paper discusses the implementation choices with regards to the particular requirements of the application and presents and discusses data collected during a long-term experiment in a real scenario. Full article

(This article belongs to the Special Issue Robotic Sensory Systems for Environment Protection and Conservation)

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14 pages, 3240 KiB

Open AccessArticle

Accurate Behavioral Simulator of All-Digital Time-Domain Smart Temperature Sensors by Using SIMULINK

by Chun-Chi Chen^*

, Chao-Lieh Chen

and You-Ting Lin

Department of Electronic Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung 811, Taiwan

Sensors 2016, 16(8), 1256; https://doi.org/10.3390/s16081256 - 8 Aug 2016

Cited by 3 | Viewed by 6279

Abstract

This study proposes a new behavioral simulator that uses SIMULINK for all-digital CMOS time-domain smart temperature sensors (TDSTSs) for performing rapid and accurate simulations. Inverter-based TDSTSs offer the benefits of low cost and simple structure for temperature-to-digital conversion and have been developed. Typically, [...] Read more.

This study proposes a new behavioral simulator that uses SIMULINK for all-digital CMOS time-domain smart temperature sensors (TDSTSs) for performing rapid and accurate simulations. Inverter-based TDSTSs offer the benefits of low cost and simple structure for temperature-to-digital conversion and have been developed. Typically, electronic design automation tools, such as HSPICE, are used to simulate TDSTSs for performance evaluations. However, such tools require extremely long simulation time and complex procedures to analyze the results and generate figures. In this paper, we organize simple but accurate equations into a temperature-dependent model (TDM) by which the TDSTSs evaluate temperature behavior. Furthermore, temperature-sensing models of a single CMOS NOT gate were devised using HSPICE simulations. Using the TDM and these temperature-sensing models, a novel simulator in SIMULINK environment was developed to substantially accelerate the simulation and simplify the evaluation procedures. Experiments demonstrated that the simulation results of the proposed simulator have favorable agreement with those obtained from HSPICE simulations, showing that the proposed simulator functions successfully. This is the first behavioral simulator addressing the rapid simulation of TDSTSs. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 6110 KiB

Open AccessArticle

Probing the Kinetic Anabolism of Poly-Beta-Hydroxybutyrate in Cupriavidus necator H16 Using Single-Cell Raman Spectroscopy

by Zhanhua Tao¹, Lixin Peng¹, Pengfei Zhang², Yong-Qing Li³ and Guiwen Wang^1,*

¹ Guangxi Academy of Sciences, Nanning 530007, Guangxi, China

² Optical Imaging Laboratory at Washington University in St. Louis, One Brookings Drive, St Louis, MO 63130, USA

³ Department of Physics, East Carolina University, Greenville, NC 27858, USA

Sensors 2016, 16(8), 1257; https://doi.org/10.3390/s16081257 - 8 Aug 2016

Cited by 13 | Viewed by 7704

Abstract

Poly-beta-hydroxybutyrate (PHB) can be formed in large amounts in Cupriavidus necator and is important for the industrial production of biodegradable plastics. In this investigation, laser tweezers Raman spectroscopy (LTRS) was used to characterize dynamic changes in PHB content—as well as in the contents [...] Read more.

Poly-beta-hydroxybutyrate (PHB) can be formed in large amounts in Cupriavidus necator and is important for the industrial production of biodegradable plastics. In this investigation, laser tweezers Raman spectroscopy (LTRS) was used to characterize dynamic changes in PHB content—as well as in the contents of other common biomolecule—in C. necator during batch growth at both the population and single-cell levels. PHB accumulation began in the early stages of bacterial growth, and the maximum PHB production rate occurred in the early and middle exponential phases. The active biosynthesis of DNA, RNA, and proteins occurred in the lag and early exponential phases, whereas the levels of these molecules decreased continuously during the remaining fermentation process until the minimum values were reached. The PHB content inside single cells was relatively homogenous in the middle stage of fermentation; during the late growth stage, the variation in PHB levels between cells increased. In addition, bacterial cells in various growth phases could be clearly discriminated when principle component analysis was performed on the spectral data. These results suggest that LTRS is a valuable single-cell analysis tool that can provide more comprehensive information about the physiological state of a growing microbial population. Full article

(This article belongs to the Special Issue Applications of Raman Spectroscopy in Biosensors)

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13 pages, 4738 KiB

Open AccessArticle

Biomechanical Characterization of Cardiomyocyte Using PDMS Pillar with Microgrooves

by Nomin-Erdene Oyunbaatar¹, Deok-Hyu Lee¹, Swati J. Patil¹, Eung-Sam Kim² and Dong-Weon Lee^1,*

¹ MEMS and Nanotechnology Laboratory, Mechanical Engineering, Chonnam National University, Gwangju 61186, Korea

² Department of Biological Sciences, Chonnam National University, Gwangju 61186, Korea

Sensors 2016, 16(8), 1258; https://doi.org/10.3390/s16081258 - 9 Aug 2016

Cited by 56 | Viewed by 9026

Abstract

This paper describes the surface-patterned polydimethylsiloxane (PDMS) pillar arrays for enhancing cell alignment and contraction force in cardiomyocytes. The PDMS micropillar (μpillar) arrays with microgrooves (μgrooves) were fabricated using a unique micro-mold made using SU-8 double layer processes. The spring constant of the [...] Read more.

This paper describes the surface-patterned polydimethylsiloxane (PDMS) pillar arrays for enhancing cell alignment and contraction force in cardiomyocytes. The PDMS micropillar (μpillar) arrays with microgrooves (μgrooves) were fabricated using a unique micro-mold made using SU-8 double layer processes. The spring constant of the μpillar arrays was experimentally confirmed using atomic force microscopy (AFM). After culturing cardiac cells on the two different types of μpillar arrays, with and without grooves on the top of μpillar, the characteristics of the cardiomyocytes were analyzed using a custom-made image analysis system. The alignment of the cardiomyocytes on the μgrooves of the μpillars was clearly observed using a DAPI staining process. The mechanical force generated by the contraction force of the cardiomyocytes was derived from the displacement of the μpillar arrays. The contraction force of the cardiomyocytes aligned on the μgrooves was 20% higher than that of the μpillar arrays without μgrooves. The experimental results prove that applied geometrical stimulus is an effective method for aligning and improving the contraction force of cardiomyocytes. Full article

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

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9 pages, 1005 KiB

Open AccessArticle

Upconversion Nanoparticle-Based Förster Resonance Energy Transfer for Detecting DNA Methylation

by Seockjune Kim¹

, Sang-Hyun Hwang^2,3,*

, Su-Gyeong Im², Min-Ki Lee⁴, Chang-Hun Lee⁵, Sang Jun Son⁶ and Heung-Bum Oh^1,*

¹ Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul 05505, Korea

² Department of Laboratory Medicine, Center for Diagnostic Oncology, Research Institute and Hospital, National Cancer Center, Goyang-si 10408, Korea

³ Hematologic Malignancy Branch, Research Institute and Hospital, National Cancer Center, Goyang-si 10408, Korea

⁴ Department of Internal Medicine, Pusan National University School of Medicine and Biomedical Research Institute, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan 602-739, Korea

⁵ Department of Pathology, Pusan National University School of Medicine and Biomedical Research Institute, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan 602-739, Korea

⁶ Department of Chemistry, Gachon University, Seongnam, Gyeonggi, and Gachon Medical Research Institute, Gil Medical Center, Inchon 461-701, Korea

Sensors 2016, 16(8), 1259; https://doi.org/10.3390/s16081259 - 9 Aug 2016

Cited by 14 | Viewed by 6726

Abstract

Aberrant methylation of a crucial CpG island is the main mechanism for the inactivation of CDKN2A in the early stages of carcinogenesis. Therefore, the detection of DNA methylation with high sensitivity and specificity is important, and various detection methods have been developed. Recently, [...] Read more.

Aberrant methylation of a crucial CpG island is the main mechanism for the inactivation of CDKN2A in the early stages of carcinogenesis. Therefore, the detection of DNA methylation with high sensitivity and specificity is important, and various detection methods have been developed. Recently, upconversion nanoparticles (UCNPs) have been found to display a high signal-to-noise ratio and no photobleaching, making them useful for diagnostic applications. In this pilot study, we applied UCNPs to the detection of CDKN2A methylation and evaluated the feasibility of this system for use in molecular diagnostics. DNA PCR was performed using biotinylated primers, and the PCR amplicon was then intercalated with SYTOX Orange dye, followed by incubation with streptavidin-conjugated UCNPs. Fluorescence detection of the Förster resonance energy transfer (FRET) of the UCNPs (MS-UC-FRET) was then performed, and the results were compared to those from real-time PCR (RQ-PCR) and pyrosequencing. Detection by MS-UC-FRET was more sensitive than that by either RQ-PCR or pyrosequencing. Our results confirmed the success of our MS-UC-FRET system for detecting DNA methylation and demonstrated the potential application of this system in molecular diagnostics. Full article

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

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25 pages, 7848 KiB

Open AccessReview

The Quanta Image Sensor: Every Photon Counts

by Eric R. Fossum^*

, Jiaju Ma, Saleh Masoodian, Leo Anzagira and Rachel Zizza

Thayer School of Engineering at Dartmouth, Dartmouth College, Hanover, NH 03755, USA

Sensors 2016, 16(8), 1260; https://doi.org/10.3390/s16081260 - 10 Aug 2016

Cited by 95 | Viewed by 25801

Abstract

The Quanta Image Sensor (QIS) was conceived when contemplating shrinking pixel sizes and storage capacities, and the steady increase in digital processing power. In the single-bit QIS, the output of each field is a binary bit plane, where each bit represents the presence [...] Read more.

The Quanta Image Sensor (QIS) was conceived when contemplating shrinking pixel sizes and storage capacities, and the steady increase in digital processing power. In the single-bit QIS, the output of each field is a binary bit plane, where each bit represents the presence or absence of at least one photoelectron in a photodetector. A series of bit planes is generated through high-speed readout, and a kernel or “cubicle” of bits (x, y, t) is used to create a single output image pixel. The size of the cubicle can be adjusted post-acquisition to optimize image quality. The specialized sub-diffraction-limit photodetectors in the QIS are referred to as “jots” and a QIS may have a gigajot or more, read out at 1000 fps, for a data rate exceeding 1 Tb/s. Basically, we are trying to count photons as they arrive at the sensor. This paper reviews the QIS concept and its imaging characteristics. Recent progress towards realizing the QIS for commercial and scientific purposes is discussed. This includes implementation of a pump-gate jot device in a 65 nm CIS BSI process yielding read noise as low as 0.22 e− r.m.s. and conversion gain as high as 420 µV/e−, power efficient readout electronics, currently as low as 0.4 pJ/b in the same process, creating high dynamic range images from jot data, and understanding the imaging characteristics of single-bit and multi-bit QIS devices. The QIS represents a possible major paradigm shift in image capture. Full article

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

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13 pages, 4671 KiB

Open AccessArticle

Real-Time Single Frequency Precise Point Positioning Using SBAS Corrections

by Liang Li^1,2,*, Chun Jia^1,*, Lin Zhao¹, Jianhua Cheng¹, Jianxu Liu¹ and Jicheng Ding¹

¹ College of Automation, Harbin Engineering University, Harbin 150001, China

² Acdemy of Opto-electroncis, Chinse Academy of Sciences, Beijing 100094, China

Sensors 2016, 16(8), 1261; https://doi.org/10.3390/s16081261 - 10 Aug 2016

Cited by 43 | Viewed by 5529

Abstract

Real-time single frequency precise point positioning (PPP) is a promising technique for high-precision navigation with sub-meter or even centimeter-level accuracy because of its convenience and low cost. The navigation performance of single frequency PPP heavily depends on the real-time availability and quality of [...] Read more.

Real-time single frequency precise point positioning (PPP) is a promising technique for high-precision navigation with sub-meter or even centimeter-level accuracy because of its convenience and low cost. The navigation performance of single frequency PPP heavily depends on the real-time availability and quality of correction products for satellite orbits and satellite clocks. Satellite-based augmentation system (SBAS) provides the correction products in real-time, but they are intended to be used for wide area differential positioning at 1 meter level precision. By imposing the constraints for ionosphere error, we have developed a real-time single frequency PPP method by sufficiently utilizing SBAS correction products. The proposed PPP method are tested with static and kinematic data, respectively. The static experimental results show that the position accuracy of the proposed PPP method can reach decimeter level, and achieve an improvement of at least 30% when compared with the traditional SBAS method. The positioning convergence of the proposed PPP method can be achieved in 636 epochs at most in static mode. In the kinematic experiment, the position accuracy of the proposed PPP method can be improved by at least 20 cm relative to the SBAS method. Furthermore, it has revealed that the proposed PPP method can achieve decimeter level convergence within 500 s in the kinematic mode. Full article

(This article belongs to the Section Remote Sensors)

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18 pages, 7843 KiB

Open AccessArticle

Design and Fabrication of a Differential Electrostatic Accelerometer for Space-Station Testing of the Equivalence Principle

by Fengtian Han^*

, Tianyi Liu, Linlin Li and Qiuping Wu

Department of Precision Instrument, Tsinghua University, Beijing 100084, China

Sensors 2016, 16(8), 1262; https://doi.org/10.3390/s16081262 - 10 Aug 2016

Cited by 8 | Viewed by 6856

Abstract

The differential electrostatic space accelerometer is an equivalence principle (EP) experiment instrument proposed to operate onboard China’s space station in the 2020s. It is designed to compare the spin-spin interaction between two rotating extended bodies and the Earth to a precision of 10 [...] Read more.

The differential electrostatic space accelerometer is an equivalence principle (EP) experiment instrument proposed to operate onboard China’s space station in the 2020s. It is designed to compare the spin-spin interaction between two rotating extended bodies and the Earth to a precision of 10⁻¹², which is five orders of magnitude better than terrestrial experiment results to date. To achieve the targeted test accuracy, the sensitive space accelerometer will use the very soft space environment provided by a quasi-drag-free floating capsule and long-time observation of the free-fall mass motion for integration of the measurements over 20 orbits. In this work, we describe the design and capability of the differential accelerometer to test weak space acceleration. Modeling and simulation results of the electrostatic suspension and electrostatic motor are presented based on attainable space microgravity condition. Noise evaluation shows that the electrostatic actuation and residual non-gravitational acceleration are two major noise sources. The evaluated differential acceleration noise is 1.01 × 10⁻⁹ m/s²/Hz^1/2 at the NEP signal frequency of 0.182 mHz, by neglecting small acceleration disturbances. The preliminary work on development of the first instrument prototype is introduced for on-ground technological assessments. This development has already confirmed several crucial fabrication processes and measurement techniques and it will open the way to the construction of the final differential space accelerometer. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 5639 KiB

Open AccessArticle

Research on a Defects Detection Method in the Ferrite Phase Shifter Cementing Process Based on a Multi-Sensor Prognostic and Health Management (PHM) System

by Bo Wan^1,*, Guicui Fu¹, Yanruoyue Li¹ and Youhu Zhao²

¹ School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China

² Dipartimento di Energia, Politecnico di Milano, Milano 20133, Italy

Sensors 2016, 16(8), 1263; https://doi.org/10.3390/s16081263 - 10 Aug 2016

Cited by 1 | Viewed by 5657

Abstract

The cementing manufacturing process of ferrite phase shifters has the defect that cementing strength is insufficient and fractures always appear. A detection method of these defects was studied utilizing the multi-sensors Prognostic and Health Management (PHM) theory. Aiming at these process defects, the [...] Read more.

The cementing manufacturing process of ferrite phase shifters has the defect that cementing strength is insufficient and fractures always appear. A detection method of these defects was studied utilizing the multi-sensors Prognostic and Health Management (PHM) theory. Aiming at these process defects, the reasons that lead to defects are analyzed in this paper. In the meanwhile, the key process parameters were determined and Differential Scanning Calorimetry (DSC) tests during the cure process of resin cementing were carried out. At the same time, in order to get data on changing cementing strength, multiple-group cementing process tests of different key process parameters were designed and conducted. A relational model of cementing strength and cure temperature, time and pressure was established, by combining data of DSC and process tests as well as based on the Avrami formula. Through sensitivity analysis for three process parameters, the on-line detection decision criterion and the process parameters which have obvious impact on cementing strength were determined. A PHM system with multiple temperature and pressure sensors was established on this basis, and then, on-line detection, diagnosis and control for ferrite phase shifter cementing process defects were realized. It was verified by subsequent process that the on-line detection system improved the reliability of the ferrite phase shifter cementing process and reduced the incidence of insufficient cementing strength defects. Full article

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

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19 pages, 1982 KiB

Open AccessArticle

Human Behavior Analysis by Means of Multimodal Context Mining

by Oresti Banos^1,2, Claudia Villalonga^1,3

, Jaehun Bang¹, Taeho Hur¹, Donguk Kang¹

, Sangbeom Park¹

, Thien Huynh-The¹, Vui Le-Ba¹, Muhammad Bilal Amin¹, Muhammad Asif Razzaq¹, Wahajat Ali Khan¹, Choong Seon Hong^1,* and Sungyoung Lee¹

¹ Department of Computer Engineering, Kyung Hee University, Yongin-si 446-701, Korea

² Telemedicine Group, Center for Telematics and Information Technology, University of Twente, Enschede 7500AE, The Netherlands

³ Department of Computer Architecture and Computer Technology, Research Center on Information and Communications Technology, University of Granada, Granada E18071, Spain

Sensors 2016, 16(8), 1264; https://doi.org/10.3390/s16081264 - 10 Aug 2016

Cited by 34 | Viewed by 8406

Abstract

There is sufficient evidence proving the impact that negative lifestyle choices have on people’s health and wellness. Changing unhealthy behaviours requires raising people’s self-awareness and also providing healthcare experts with a thorough and continuous description of the user’s conduct. Several monitoring techniques have [...] Read more.

There is sufficient evidence proving the impact that negative lifestyle choices have on people’s health and wellness. Changing unhealthy behaviours requires raising people’s self-awareness and also providing healthcare experts with a thorough and continuous description of the user’s conduct. Several monitoring techniques have been proposed in the past to track users’ behaviour; however, these approaches are either subjective and prone to misreporting, such as questionnaires, or only focus on a specific component of context, such as activity counters. This work presents an innovative multimodal context mining framework to inspect and infer human behaviour in a more holistic fashion. The proposed approach extends beyond the state-of-the-art, since it not only explores a sole type of context, but also combines diverse levels of context in an integral manner. Namely, low-level contexts, including activities, emotions and locations, are identified from heterogeneous sensory data through machine learning techniques. Low-level contexts are combined using ontological mechanisms to derive a more abstract representation of the user’s context, here referred to as high-level context. An initial implementation of the proposed framework supporting real-time context identification is also presented. The developed system is evaluated for various realistic scenarios making use of a novel multimodal context open dataset and data on-the-go, demonstrating prominent context-aware capabilities at both low and high levels. Full article

(This article belongs to the Special Issue Selected Papers from UCAmI, IWAAL and AmIHEALTH 2015)

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21 pages, 6975 KiB

Open AccessArticle

Feature-Based Laser Scan Matching and Its Application for Indoor Mapping

by Jiayuan Li²

, Ruofei Zhong¹, Qingwu Hu^2,*

and Mingyao Ai^2,3

¹ Beijing Advanced Innovation Center for Imaging Technology, Capital Normal University, Beijing 100048, China

² School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China

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

Sensors 2016, 16(8), 1265; https://doi.org/10.3390/s16081265 - 10 Aug 2016

Cited by 56 | Viewed by 9379

Abstract

Scan matching, an approach to recover the relative position and orientation of two laser scans, is a very important technique for indoor positioning and indoor modeling. The iterative closest point (ICP) algorithm and its variants are the most well-known techniques for such a [...] Read more.

Scan matching, an approach to recover the relative position and orientation of two laser scans, is a very important technique for indoor positioning and indoor modeling. The iterative closest point (ICP) algorithm and its variants are the most well-known techniques for such a problem. However, ICP algorithms rely highly on the initial guess of the relative transformation, which will reduce its power for practical applications. In this paper, an initial-free 2D laser scan matching method based on point and line features is proposed. We carefully design a framework for the detection of point and line feature correspondences. First, distinct feature points are detected based on an extended 1D SIFT, and line features are extracted via a modified Split-and-Merge algorithm. In this stage, we also give an effective strategy for discarding unreliable features. The point and line features are then described by a distance histogram; the pairs achieving best matching scores are accepted as potential correct correspondences. The histogram cluster technique is adapted to filter outliers and provide an accurate initial value of the rigid transformation. We also proposed a new relative pose estimation method that is robust to outliers. We use the lq-norm (0 < q < 1) metric in this approach, in contrast to classic optimization methods whose cost function is based on the l₂-norm of residuals. Extensive experiments on real data demonstrate that the proposed method is almost as accurate as ICPs and is initial free. We also show that our scan matching method can be integrated into a simultaneous localization and mapping (SLAM) system for indoor mapping. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 6956 KiB

Open AccessArticle

Partial Discharge Monitoring in Power Transformers Using Low-Cost Piezoelectric Sensors

by Bruno Castro

, Guilherme Clerice, Caio Ramos

, André Andreoli, Fabricio Baptista^*

, Fernando Campos and José Ulson

Faculdade de Engenharia, UNESP-Univ. Estadual Paulista, Bauru, Departamento de Engenharia Elétrica, Av. Eng. Luiz Edmundo C. Coube 14-01, 17033-360 Bauru–SP, Brazil

Sensors 2016, 16(8), 1266; https://doi.org/10.3390/s16081266 - 10 Aug 2016

Cited by 67 | Viewed by 9522

Abstract

Power transformers are crucial in an electric power system. Failures in transformers can affect the quality and cause interruptions in the power supply. Partial discharges are a phenomenon that can cause failures in the transformers if not properly monitored. Typically, the monitoring requires [...] Read more.

Power transformers are crucial in an electric power system. Failures in transformers can affect the quality and cause interruptions in the power supply. Partial discharges are a phenomenon that can cause failures in the transformers if not properly monitored. Typically, the monitoring requires high-cost corrective maintenance or even interruptions of the power system. Therefore, the development of online non-invasive monitoring systems to detect partial discharges in power transformers has great relevance since it can reduce significant maintenance costs. Although commercial acoustic emission sensors have been used to monitor partial discharges in power transformers, they still represent a significant cost. In order to overcome this drawback, this paper presents a study of the feasibility of low-cost piezoelectric sensors to identify partial discharges in mineral insulating oil of power transformers. The analysis of the feasibility of the proposed low-cost sensor is performed by its comparison with a commercial acoustic emission sensor commonly used to detect partial discharges. The comparison between the responses in the time and frequency domain of both sensors was carried out and the experimental results indicate that the proposed piezoelectric sensors have great potential in the detection of acoustic waves generated by partial discharges in insulation oil, contributing for the popularization of this noninvasive technique. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 2003 KiB

Open AccessArticle

Correction of Dynamic Errors of a Gas Sensor Based on a Parametric Method and a Neural Network Technique

by Jerzy Roj

Institute of Measurement Science, Electronics and Control, Silesian University of Technology, Gliwice 44-100, Poland

Sensors 2016, 16(8), 1267; https://doi.org/10.3390/s16081267 - 10 Aug 2016

Cited by 6 | Viewed by 5702

Abstract

The paper presents two methods of dynamic error correction applied to transducers used for the measurement of gas concentration. One of them is based on a parametric model of the transducer dynamics, and the second one uses the artificial neural network (ANN) technique. [...] Read more.

The paper presents two methods of dynamic error correction applied to transducers used for the measurement of gas concentration. One of them is based on a parametric model of the transducer dynamics, and the second one uses the artificial neural network (ANN) technique. This article describes research of the dynamic properties of the gas concentration measuring transducer with a typical sensor based on tin dioxide. Its response time is about 8 min, which may be not acceptable in many applications. On the basis of these studies, a parametric model of the transducer dynamics and an adequate correction algorithm has been developed. The results obtained in the research of the transducer were also used for learning and testing ANN, which were implemented in the dynamic correction task. Despite the simplicity of the used models, both methods allowed a significant reduction of the transducer’s response time. For the algorithm based on the parametric model the response time was shorter by approximately eight-fold (reduced up to 40–80 s, i.e., about 2–4 sample periods), whereas with the use of an ANN the output signal was practically fixed after a time equal to one sampling period, i.e., 20 s. In addition, the use of ANN has allowed reducing the impact of the transducer dynamic non-linearity on the correction effectiveness. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 26314 KiB

Open AccessArticle

Vertical Corner Feature Based Precise Vehicle Localization Using 3D LIDAR in Urban Area

by Jun-Hyuck Im¹

, Sung-Hyuck Im² and Gyu-In Jee^1,*

¹ Department of Electronic Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea

² Satellite Navigation Team, Korea Aerospace Research Institute, 169-84 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Korea

Sensors 2016, 16(8), 1268; https://doi.org/10.3390/s16081268 - 10 Aug 2016

Cited by 54 | Viewed by 11390

Abstract

Tall buildings are concentrated in urban areas. The outer walls of buildings are vertically erected to the ground and almost flat. Therefore, the vertical corners that meet the vertical planes are present everywhere in urban areas. These corners act as convenient landmarks, which [...] Read more.

Tall buildings are concentrated in urban areas. The outer walls of buildings are vertically erected to the ground and almost flat. Therefore, the vertical corners that meet the vertical planes are present everywhere in urban areas. These corners act as convenient landmarks, which can be extracted by using the light detection and ranging (LIDAR) sensor. A vertical corner feature based precise vehicle localization method is proposed in this paper and implemented using 3D LIDAR (Velodyne HDL-32E). The vehicle motion is predicted by accumulating the pose increment output from the iterative closest point (ICP) algorithm based on the geometric relations between the scan data of the 3D LIDAR. The vertical corner is extracted using the proposed corner extraction method. The vehicle position is then corrected by matching the prebuilt corner map with the extracted corner. The experiment was carried out in the Gangnam area of Seoul, South Korea. In the experimental results, the maximum horizontal position error is about 0.46 m and the 2D Root Mean Square (RMS) horizontal error is about 0.138 m. Full article

(This article belongs to the Special Issue Sensors for Autonomous Road Vehicles)

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19 pages, 7208 KiB

Open AccessArticle

A Multi-Robot Sense-Act Approach to Lead to a Proper Acting in Environmental Incidents

by Jesús Conesa-Muñoz¹

, João Valente^2,3, Jaime Del Cerro²

, Antonio Barrientos²

and Angela Ribeiro^1,*

¹ Centre for Automation and Robotics, CSIC-UPM, Arganda del Rey, Madrid 28500, Spain

² Centre for Automation and Robotics, UPM-CSIC, José Gutierrez Abascal 2, Madrid 28006, Spain

³ Department of Systems Engineering & Automation, Carlos III University, Av. Universidad 30, Leganés 28911, Spain

Sensors 2016, 16(8), 1269; https://doi.org/10.3390/s16081269 - 10 Aug 2016

Cited by 30 | Viewed by 7580

Abstract

Many environmental incidents affect large areas, often in rough terrain constrained by natural obstacles, which makes intervention difficult. New technologies, such as unmanned aerial vehicles, may help address this issue due to their suitability to reach and easily cover large areas. Thus, unmanned [...] Read more.

Many environmental incidents affect large areas, often in rough terrain constrained by natural obstacles, which makes intervention difficult. New technologies, such as unmanned aerial vehicles, may help address this issue due to their suitability to reach and easily cover large areas. Thus, unmanned aerial vehicles may be used to inspect the terrain and make a first assessment of the affected areas; however, nowadays they do not have the capability to act. On the other hand, ground vehicles rely on enough power to perform the intervention but exhibit more mobility constraints. This paper proposes a multi-robot sense-act system, composed of aerial and ground vehicles. This combination allows performing autonomous tasks in large outdoor areas by integrating both types of platforms in a fully automated manner. Aerial units are used to easily obtain relevant data from the environment and ground units use this information to carry out interventions more efficiently. This paper describes the platforms and sensors required by this multi-robot sense-act system as well as proposes a software system to automatically handle the workflow for any generic environmental task. The proposed system has proved to be suitable to reduce the amount of herbicide applied in agricultural treatments. Although herbicides are very polluting, they are massively deployed on complete agricultural fields to remove weeds. Nevertheless, the amount of herbicide required for treatment is radically reduced when it is accurately applied on patches by the proposed multi-robot system. Thus, the aerial units were employed to scout the crop and build an accurate weed distribution map which was subsequently used to plan the task of the ground units. The whole workflow was executed in a fully autonomous way, without human intervention except when required by Spanish law due to safety reasons. Full article

(This article belongs to the Special Issue Robotic Sensory Systems for Environment Protection and Conservation)

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26 pages, 5082 KiB

Open AccessArticle

Regular Deployment of Wireless Sensors to Achieve Connectivity and Information Coverage

by Wei Cheng^*, Yong Li, Yi Jiang and Xipeng Yin

School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710072, Shaanxi, China

Sensors 2016, 16(8), 1270; https://doi.org/10.3390/s16081270 - 12 Aug 2016

Cited by 12 | Viewed by 4671

Abstract

Coverage and connectivity are two of the most critical research subjects in WSNs, while regular deterministic deployment is an important deployment strategy and results in some pattern-based lattice WSNs. Some studies of optimal regular deployment for generic values of r_c/r [...] Read more.

Coverage and connectivity are two of the most critical research subjects in WSNs, while regular deterministic deployment is an important deployment strategy and results in some pattern-based lattice WSNs. Some studies of optimal regular deployment for generic values of r_c/r_s were shown recently. However, most of these deployments are subject to a disk sensing model, and cannot take advantage of data fusion. Meanwhile some other studies adapt detection techniques and data fusion to sensing coverage to enhance the deployment scheme. In this paper, we provide some results on optimal regular deployment patterns to achieve information coverage and connectivity as a variety of r_c/r_s, which are all based on data fusion by sensor collaboration, and propose a novel data fusion strategy for deployment patterns. At first the relation between variety of r_c/r_s and density of sensors needed to achieve information coverage and connectivity is derived in closed form for regular pattern-based lattice WSNs. Then a dual triangular pattern deployment based on our novel data fusion strategy is proposed, which can utilize collaborative data fusion more efficiently. The strip-based deployment is also extended to a new pattern to achieve information coverage and connectivity, and its characteristics are deduced in closed form. Some discussions and simulations are given to show the efficiency of all deployment patterns, including previous patterns and the proposed patterns, to help developers make more impactful WSN deployment decisions. Full article

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

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20 pages, 4952 KiB

Open AccessArticle

Mathematical Model and Calibration Experiment of a Large Measurement Range Flexible Joints 6-UPUR Six-Axis Force Sensor

by Yanzhi Zhao^1,2,*, Caifeng Zhang^1,2, Dan Zhang³, Zhongpan Shi^1,2 and Tieshi Zhao^1,2

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 M3J1P3, Canada

Sensors 2016, 16(8), 1271; https://doi.org/10.3390/s16081271 - 11 Aug 2016

Cited by 40 | Viewed by 7382

Abstract

Nowadays improving the accuracy and enlarging the measuring range of six-axis force sensors for wider applications in aircraft landing, rocket thrust, and spacecraft docking testing experiments has become an urgent objective. However, it is still difficult to achieve high accuracy and large measuring [...] Read more.

Nowadays improving the accuracy and enlarging the measuring range of six-axis force sensors for wider applications in aircraft landing, rocket thrust, and spacecraft docking testing experiments has become an urgent objective. However, it is still difficult to achieve high accuracy and large measuring range with traditional parallel six-axis force sensors due to the influence of the gap and friction of the joints. Therefore, to overcome the mentioned limitations, this paper proposed a 6-Universal-Prismatic-Universal-Revolute (UPUR) joints parallel mechanism with flexible joints to develop a large measurement range six-axis force sensor. The structural characteristics of the sensor are analyzed in comparison with traditional parallel sensor based on the Stewart platform. The force transfer relation of the sensor is deduced, and the force Jacobian matrix is obtained using screw theory in two cases of the ideal state and the state of flexibility of each flexible joint is considered. The prototype and loading calibration system are designed and developed. The K value method and least squares method are used to process experimental data, and in errors of kind Ι and kind II linearity are obtained. The experimental results show that the calibration error of the K value method is more than 13.4%, and the calibration error of the least squares method is 2.67%. The experimental results prove the feasibility of the sensor and the correctness of the theoretical analysis which are expected to be adopted in practical applications. Full article

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

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13 pages, 947 KiB

Open AccessArticle

Utility of Ochrobactrum anthropi YC152 in a Microbial Fuel Cell as an Early Warning Device for Hexavalent Chromium Determination

by Guey-Horng Wang^1,†, Chiu-Yu Cheng^2,†, Man-Hai Liu³, Tzu-Yu Chen², Min-Chi Hsieh² and Ying-Chien Chung^2,*

¹ Fujian Provincial Key Laboratory of Biological Engineering on Traditional Herbs and Research Center of Natural Cosmeceuticals Engineering, Xiamen Medical College, Xiamen 361008, China

² Department of Biological Science and Technology, China University of Science and Technology, Taipei 11581, Taiwan

³ Department of Food Science, China University of Science and Technology, Taipei 11581, Taiwan

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1272; https://doi.org/10.3390/s16081272 - 16 Aug 2016

Cited by 42 | Viewed by 6244

Abstract

Fast hexavalent chromium (Cr(VI)) determination is important for environmental risk and health-related considerations. We used a microbial fuel cell-based biosensor inoculated with a facultatively anaerobic, Cr(VI)-reducing, and exoelectrogenic Ochrobactrum anthropi YC152 to determine the Cr(VI) concentration in water. The results indicated that O. [...] Read more.

Fast hexavalent chromium (Cr(VI)) determination is important for environmental risk and health-related considerations. We used a microbial fuel cell-based biosensor inoculated with a facultatively anaerobic, Cr(VI)-reducing, and exoelectrogenic Ochrobactrum anthropi YC152 to determine the Cr(VI) concentration in water. The results indicated that O. anthropi YC152 exhibited high adaptability to pH, temperature, salinity, and water quality under anaerobic conditions. The stable performance of the microbial fuel cell (MFC)-based biosensor indicated its potential as a reliable biosensor system. The MFC voltage decreased as the Cr(VI) concentration in the MFC increased. Two satisfactory linear relationships were observed between the Cr(VI) concentration and voltage output for various Cr(VI) concentration ranges (0.0125–0.3 mg/L and 0.3–5 mg/L). The MFC biosensor is a simple device that can accurately measure Cr(VI) concentrations in drinking water, groundwater, and electroplating wastewater in 45 min with low deviations (<10%). The use of the biosensor can help in preventing the violation of effluent regulations and the maximum allowable concentration of Cr(VI) in water. Thus, the developed MFC biosensor has potential as an early warning detection device for Cr(VI) determination even if O. anthropi YC152 is a possible opportunistic pathogen. Full article

(This article belongs to the Special Issue Sensors for Biomedical, Environmental and Food Monitoring Applications)

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15 pages, 2914 KiB

Open AccessArticle

Baseline Signal Reconstruction for Temperature Compensation in Lamb Wave-Based Damage Detection

by Guoqiang Liu^1,*, Yingchun Xiao², Hua Zhang² and Gexue Ren¹

¹ School of Aerospace Engineering, Tsinghua University, Beijing 100084, China

² Aircraft Strength Research Institute of China, Xi’an 710065, China

Sensors 2016, 16(8), 1273; https://doi.org/10.3390/s16081273 - 11 Aug 2016

Cited by 37 | Viewed by 7564

Abstract

Temperature variations have significant effects on propagation of Lamb wave and therefore can severely limit the damage detection for Lamb wave. In order to mitigate the temperature effect, a temperature compensation method based on baseline signal reconstruction is developed for Lamb wave-based damage [...] Read more.

Temperature variations have significant effects on propagation of Lamb wave and therefore can severely limit the damage detection for Lamb wave. In order to mitigate the temperature effect, a temperature compensation method based on baseline signal reconstruction is developed for Lamb wave-based damage detection. The method is a reconstruction of a baseline signal at the temperature of current signal. In other words, it compensates the baseline signal to the temperature of current signal. The Hilbert transform is used to compensate the phase of baseline signal. The Orthogonal matching pursuit (OMP) is used to compensate the amplitude of baseline signal. Experiments were conducted on two composite panels to validate the effectiveness of the proposed method. Results show that the proposed method could effectively work for temperature intervals of at least 18 °C with the baseline signal temperature as the center, and can be applied to the actual damage detection. Full article

(This article belongs to the Special Issue Ultrasonic Sensors)

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12 pages, 2212 KiB

Open AccessArticle

Label Free QCM Immunobiosensor for AFB1 Detection Using Monoclonal IgA Antibody as Recognition Element

by Özlem Ertekin^1,2,*

, Selma Öztürk¹ and Zafer Ziya Öztürk³

¹ TÜBİTAK, The Scientific and Technological Research Council of Turkey, Marmara Research Center, Genetic Engineering and Biotechnology Institute, Gebze, 41470 Kocaeli, Turkey

² Department of Molecular Biology and Genetics, Gebze Technical University, 41400 Kocaeli, Turkey

³ Department of Physics, Gebze Technical University, 41400 Kocaeli, Turkey

Sensors 2016, 16(8), 1274; https://doi.org/10.3390/s16081274 - 11 Aug 2016

Cited by 29 | Viewed by 7913

Abstract

This study introduces the use of an IgA isotype aflatoxin (AF) specific monoclonal antibody for the development of a highly sensitive Quartz Crystal Microbalance (QCM) immunobiosensor for the detection of AF in inhibitory immunoassay format. The higher molecular weight of IgA antibodies proved [...] Read more.

This study introduces the use of an IgA isotype aflatoxin (AF) specific monoclonal antibody for the development of a highly sensitive Quartz Crystal Microbalance (QCM) immunobiosensor for the detection of AF in inhibitory immunoassay format. The higher molecular weight of IgA antibodies proved an advantage over commonly used IgG antibodies in label free immunobiosensor measurements. IgA and IgG antibodies with similar affinity for AF were used in the comparative studies. Sensor surface was prepared by covalent immobilization of AFB1, using self assembled monolayer (SAM) formed on gold coated Quartz Crystal, with 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxy succinimide (EDC/NHS) method using a diamine linker. Nonspecific binding to the surface was decreased by minimizing the duration of EDC/NHS activation. Sensor surface was chemically blocked after AF immobilization without any need for protein blocking. This protein free sensor chip endured harsh solutions with strong ionic detergent at high pH, which is required for the regeneration of the high affinity antibody-antigen interaction. According to the obtained results, the detection range with IgA antibodies was higher than IgG antibodies in QCM immunosensor developed for AFB1. Full article

(This article belongs to the Section Biosensors)

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15 pages, 2170 KiB

Open AccessArticle

A Novel Optimization Technique to Improve Gas Recognition by Electronic Noses Based on the Enhanced Krill Herd Algorithm

by Li Wang, Pengfei Jia^*, Tailai Huang, Shukai Duan, Jia Yan

and Lidan Wang

College of Electronic and Information Engineering, Southwest University, Chongqing 400715, China

Sensors 2016, 16(8), 1275; https://doi.org/10.3390/s16081275 - 12 Aug 2016

Cited by 14 | Viewed by 6551

Abstract

An electronic nose (E-nose) is an intelligent system that we will use in this paper to distinguish three indoor pollutant gases (benzene (C₆H₆), toluene (C₇H₈), formaldehyde (CH₂O)) and carbon monoxide (CO). The algorithm [...] Read more.

An electronic nose (E-nose) is an intelligent system that we will use in this paper to distinguish three indoor pollutant gases (benzene (C₆H₆), toluene (C₇H₈), formaldehyde (CH₂O)) and carbon monoxide (CO). The algorithm is a key part of an E-nose system mainly composed of data processing and pattern recognition. In this paper, we employ support vector machine (SVM) to distinguish indoor pollutant gases and two of its parameters need to be optimized, so in order to improve the performance of SVM, in other words, to get a higher gas recognition rate, an effective enhanced krill herd algorithm (EKH) based on a novel decision weighting factor computing method is proposed to optimize the two SVM parameters. Krill herd (KH) is an effective method in practice, however, on occasion, it cannot avoid the influence of some local best solutions so it cannot always find the global optimization value. In addition its search ability relies fully on randomness, so it cannot always converge rapidly. To address these issues we propose an enhanced KH (EKH) to improve the global searching and convergence speed performance of KH. To obtain a more accurate model of the krill behavior, an updated crossover operator is added to the approach. We can guarantee the krill group are diversiform at the early stage of iterations, and have a good performance in local searching ability at the later stage of iterations. The recognition results of EKH are compared with those of other optimization algorithms (including KH, chaotic KH (CKH), quantum-behaved particle swarm optimization (QPSO), particle swarm optimization (PSO) and genetic algorithm (GA)), and we can find that EKH is better than the other considered methods. The research results verify that EKH not only significantly improves the performance of our E-nose system, but also provides a good beginning and theoretical basis for further study about other improved krill algorithms’ applications in all E-nose application areas. Full article

(This article belongs to the Special Issue E-noses: Sensors and Applications)

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19 pages, 26361 KiB

Open AccessArticle

Efficient Lane Boundary Detection with Spatial-Temporal Knowledge Filtering

by Zhixiong Nan, Ping Wei^*, Linhai Xu and Nanning Zheng

Institute of Artificial Intelligence and Robotics, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2016, 16(8), 1276; https://doi.org/10.3390/s16081276 - 12 Aug 2016

Cited by 24 | Viewed by 10622

Abstract

Lane boundary detection technology has progressed rapidly over the past few decades. However, many challenges that often lead to lane detection unavailability remain to be solved. In this paper, we propose a spatial-temporal knowledge filtering model to detect lane boundaries in videos. To [...] Read more.

Lane boundary detection technology has progressed rapidly over the past few decades. However, many challenges that often lead to lane detection unavailability remain to be solved. In this paper, we propose a spatial-temporal knowledge filtering model to detect lane boundaries in videos. To address the challenges of structure variation, large noise and complex illumination, this model incorporates prior spatial-temporal knowledge with lane appearance features to jointly identify lane boundaries. The model first extracts line segments in video frames. Two novel filters—the Crossing Point Filter (CPF) and the Structure Triangle Filter (STF)—are proposed to filter out the noisy line segments. The two filters introduce spatial structure constraints and temporal location constraints into lane detection, which represent the spatial-temporal knowledge about lanes. A straight line or curve model determined by a state machine is used to fit the line segments to finally output the lane boundaries. We collected a challenging realistic traffic scene dataset. The experimental results on this dataset and other standard dataset demonstrate the strength of our method. The proposed method has been successfully applied to our autonomous experimental vehicle. Full article

(This article belongs to the Special Issue Sensors for Autonomous Road Vehicles)

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11 pages, 903 KiB

Open AccessArticle

Inertial Sensor Based Analysis of Lie-to-Stand Transfers in Younger and Older Adults

by Lars Schwickert^1,*, Ronald Boos¹, Jochen Klenk^1,2

, Alan Bourke³

, Clemens Becker¹ and Wiebren Zijlstra⁴

¹ Department of Clinical Gerontology, Robert-Bosch Hospital, Stuttgart 70376, Germany

² Institute of Epidemiology and Medical Biometry, Ulm University, Ulm 89081, Germany

³ Department of Neuroscience, Norwegian University of Science and Technology, Trondheim NO-7491, Norway

⁴ Institute of Movement and Sport Gerontology, German Sport University Cologne, Cologne 50933, Germany

Sensors 2016, 16(8), 1277; https://doi.org/10.3390/s16081277 - 12 Aug 2016

Cited by 12 | Viewed by 5279

Abstract

Many older adults lack the capacity to stand up again after a fall. Therefore, to analyse falls it is relevant to understand recovery patterns, including successful and failed attempts to get up from the floor in general. This study analysed different kinematic features [...] Read more.

Many older adults lack the capacity to stand up again after a fall. Therefore, to analyse falls it is relevant to understand recovery patterns, including successful and failed attempts to get up from the floor in general. This study analysed different kinematic features of standing up from the floor. We used inertial sensors to describe the kinematics of lie-to-stand transfer patterns of younger and healthy older adults. Fourteen younger (20–50 years of age, 50% men) and 10 healthy older community dwellers (≥60 years; 50% men) conducted four lie-to-stand transfers from different initial lying postures. The analysed temporal, kinematic, and elliptic fitting complexity measures of transfer performance were significantly different between younger and older subjects (i.e., transfer duration, angular velocity (RMS), maximum vertical acceleration, maximum vertical velocity, smoothness, fluency, ellipse width, angle between ellipses). These results show the feasibility and potential of analysing kinematic features to describe the lie-to-stand transfer performance, to help design interventions and detection approaches to prevent long lies after falls. It is possible to describe age-related differences in lie-to-stand transfer performance using inertial sensors. The kinematic analysis remains to be tested on patterns after real-world falls. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 9785 KiB

Open AccessArticle

On the Dynamic RSS Feedbacks of Indoor Fingerprinting Databases for Localization Reliability Improvement

by Xiaoyang Wen¹, Wenyuan Tao¹, Chung-Ming Own^1,* and Zhenjiang Pan²

¹ School of Computer Software, Tianjin University, Tianjin 300072, China

² Bohai Securities Co., Ltd., Tianjin 300072, China

Sensors 2016, 16(8), 1278; https://doi.org/10.3390/s16081278 - 15 Aug 2016

Cited by 14 | Viewed by 4902

Abstract

Location data is one of the most widely used context data types in context-aware and ubiquitous computing applications. To support locating applications in indoor environments, numerous systems with different deployment costs and positioning accuracies have been developed over the past decade. One useful [...] Read more.

Location data is one of the most widely used context data types in context-aware and ubiquitous computing applications. To support locating applications in indoor environments, numerous systems with different deployment costs and positioning accuracies have been developed over the past decade. One useful method, based on received signal strength (RSS), provides a set of signal transmission access points. However, compiling a remeasurement RSS database involves a high cost, which is impractical in dynamically changing environments, particularly in highly crowded areas. In this study, we propose a dynamic estimation resampling method for certain locations chosen from a set of remeasurement fingerprinting databases. Our proposed method adaptively applies different, newly updated and offline fingerprinting points according to the temporal and spatial strength of the location. To achieve accuracy within a simulated area, the proposed method requires approximately 3% of the feedback to attain a double correctness probability comparable to similar methods; in a real environment, our proposed method can obtain excellent 1 m accuracy errors in the positioning system. Full article

(This article belongs to the Special Issue Identification, Information & Knowledge in the Internet of Things)

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23 pages, 9135 KiB

Open AccessArticle

The Positioning Accuracy of BAUV Using Fusion of Data from USBL System and Movement Parameters Measurements

by Naus Krzysztof^1,*

and Nowak Aleksander²

¹ Faculty of Navigation and Naval Weapons, Polish Naval Academy, Smidowicza 69, Gdynia 81-103, Poland

² Faculty of Civil and Environmental Engineering, Department of Geodesy, Gdansk University of Technology, Narutowicza 11/12, Gdansk 80-233, Poland

Sensors 2016, 16(8), 1279; https://doi.org/10.3390/s16081279 - 15 Aug 2016

Cited by 20 | Viewed by 5964

Abstract

The article presents a study of the accuracy of estimating the position coordinates of BAUV (Biomimetic Autonomous Underwater Vehicle) by the extended Kalman filter (EKF) method. The fusion of movement parameters measurements and position coordinates fixes was applied. The movement parameters measurements are [...] Read more.

The article presents a study of the accuracy of estimating the position coordinates of BAUV (Biomimetic Autonomous Underwater Vehicle) by the extended Kalman filter (EKF) method. The fusion of movement parameters measurements and position coordinates fixes was applied. The movement parameters measurements are carried out by on-board navigation devices, while the position coordinates fixes are done by the USBL (Ultra Short Base Line) system. The problem of underwater positioning and the conceptual design of the BAUV navigation system constructed at the Naval Academy (Polish Naval Academy—PNA) are presented in the first part of the paper. The second part consists of description of the evaluation results of positioning accuracy, the genesis of the problem of selecting method for underwater positioning, and the mathematical description of the method of estimating the position coordinates using the EKF method by the fusion of measurements with on-board navigation and measurements obtained with the USBL system. The main part contains a description of experimental research. It consists of a simulation program of navigational parameter measurements carried out during the BAUV passage along the test section. Next, the article covers the determination of position coordinates on the basis of simulated parameters, using EKF and DR methods and the USBL system, which are then subjected to a comparative analysis of accuracy. The final part contains systemic conclusions justifying the desirability of applying the proposed fusion method of navigation parameters for the BAUV positioning. Full article

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

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18 pages, 5717 KiB

Open AccessArticle

High Accuracy Passive Magnetic Field-Based Localization for Feedback Control Using Principal Component Analysis

by Shaohui Foong^1,*

and Zhenglong Sun²

¹ Engineering Product Development (EPD) Pillar, Singapore University of Technology & Design (SUTD), Singapore 487372, Singapore

² International Design Centre (IDC), Singapore University of Technology & Design (SUTD), Singapore 487372, Singapore

Sensors 2016, 16(8), 1280; https://doi.org/10.3390/s16081280 - 12 Aug 2016

Cited by 4 | Viewed by 5456

Abstract

In this paper, a novel magnetic field-based sensing system employing statistically optimized concurrent multiple sensor outputs for precise field-position association and localization is presented. This method capitalizes on the independence between simultaneous spatial field measurements at multiple locations to induce unique correspondences between [...] Read more.

In this paper, a novel magnetic field-based sensing system employing statistically optimized concurrent multiple sensor outputs for precise field-position association and localization is presented. This method capitalizes on the independence between simultaneous spatial field measurements at multiple locations to induce unique correspondences between field and position. This single-source-multi-sensor configuration is able to achieve accurate and precise localization and tracking of translational motion without contact over large travel distances for feedback control. Principal component analysis (PCA) is used as a pseudo-linear filter to optimally reduce the dimensions of the multi-sensor output space for computationally efficient field-position mapping with artificial neural networks (ANNs). Numerical simulations are employed to investigate the effects of geometric parameters and Gaussian noise corruption on PCA assisted ANN mapping performance. Using a 9-sensor network, the sensing accuracy and closed-loop tracking performance of the proposed optimal field-based sensing system is experimentally evaluated on a linear actuator with a significantly more expensive optical encoder as a comparison. Full article

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

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9 pages, 2583 KiB

Open AccessArticle

Plasma-Modified, Epitaxial Fabricated Graphene on SiC for the Electrochemical Detection of TNT

by Scott A. Trammell^*, Sandra C. Hernández, Rachael L. Myers-Ward, Daniel Zabetakis, David A. Stenger, D. Kurt Gaskill and Scott G. Walton

U.S. Naval Research Laboratory, Washington, DC 20375, USA

Sensors 2016, 16(8), 1281; https://doi.org/10.3390/s16081281 - 12 Aug 2016

Cited by 17 | Viewed by 4888

Abstract

Using square wave voltammetry, we show an increase in the electrochemical detection of trinitrotoluene (TNT) with a working electrode constructed from plasma modified graphene on a SiC surface vs. unmodified graphene. The graphene surface was chemically modified using electron beam generated plasmas produced [...] Read more.

Using square wave voltammetry, we show an increase in the electrochemical detection of trinitrotoluene (TNT) with a working electrode constructed from plasma modified graphene on a SiC surface vs. unmodified graphene. The graphene surface was chemically modified using electron beam generated plasmas produced in oxygen or nitrogen containing backgrounds to introduce oxygen or nitrogen moieties. The use of this chemical modification route enabled enhancement of the electrochemical signal for TNT, with the oxygen treatment showing a more pronounced detection than the nitrogen treatment. For graphene modified with oxygen, the electrochemical response to TNT can be fit to a two-site Langmuir isotherm suggesting different sites on the graphene surface with different affinities for TNT. We estimate a limit of detection for TNT equal to 20 ppb based on the analytical standard S/N ratio of 3. In addition, this approach to sensor fabrication is inherently a high-throughput, high-volume process amenable to industrial applications. High quality epitaxial graphene is easily grown over large area SiC substrates, while plasma processing is a rapid approach to large area substrate processing. This combination facilitates low cost, mass production of sensors. Full article

(This article belongs to the Section Chemical Sensors)

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9 pages, 4130 KiB

Open AccessArticle

Optical Inspection and Morphological Analysis of Diospyros kaki Plant Leaves for the Detection of Circular Leaf Spot Disease

by Ruchire Eranga Wijesinghe^1,†, Seung-Yeol Lee^2,†, Pilun Kim³, Hee-Young Jung^2,*, Mansik Jeon^1,* and Jeehyun Kim¹

¹ School of Electronics Engineering, College of IT Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, Korea

² School of Applied Biosciences, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, Korea

³ OZ Tec, No. 901, IT Convergence Industrial building, 47, Gyeongdae-ro, 17-gil, Buk-gu, Daegu 41566, Korea

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1282; https://doi.org/10.3390/s16081282 - 12 Aug 2016

Cited by 25 | Viewed by 7411

Abstract

The feasibility of using the bio-photonic imaging technique to assess symptoms of circular leaf spot (CLS) disease in Diospyros kaki (persimmon) leaf samples was investigated. Leaf samples were selected from persimmon plantations and were categorized into three groups: healthy leaf samples, infected leaf [...] Read more.

The feasibility of using the bio-photonic imaging technique to assess symptoms of circular leaf spot (CLS) disease in Diospyros kaki (persimmon) leaf samples was investigated. Leaf samples were selected from persimmon plantations and were categorized into three groups: healthy leaf samples, infected leaf samples, and healthy-looking leaf samples from infected trees. Visually non-identifiable reduction of the palisade parenchyma cell layer thickness is the main initial symptom, which occurs at the initial stage of the disease. Therefore, we established a non-destructive bio-photonic inspection method using a 1310 nm swept source optical coherence tomography (SS-OCT) system. These results confirm that this method is able to identify morphological differences between healthy leaves from infected trees and leaves from healthy and infected trees. In addition, this method has the potential to generate significant cost savings and good control of CLS disease in persimmon fields. Full article

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

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14 pages, 8554 KiB

Open AccessArticle

CO Gas Sensing Properties of Pure and Cu-Incorporated SnO₂ Nanoparticles: A Study of Cu-Induced Modifications

by Tangirala Venkata Krishna Karthik^1,*

, María De la Luz Olvera¹, Arturo Maldonado¹ and Heberto Gómez Pozos²

¹ Departamento de Ingeniería Eléctrica-SEES, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, CINVESTAV-IPN, 14740 Apartado, Mexico

² Área académica de Computación y Electrónica, ICBI, Universidad Autónoma del Estado de Hidalgo, Mineral de la Reforma, 56092 Hidalgo, Mexico

Sensors 2016, 16(8), 1283; https://doi.org/10.3390/s16081283 - 15 Aug 2016

Cited by 40 | Viewed by 8687

Abstract

Pure and copper (Cu)-incorporated tin oxide (SnO₂) pellet gas sensors with characteristics provoking gas sensitivity were fabricated and used for measuring carbon monoxide (CO) atmospheres. Non-spherical pure SnO₂ nano-structures were prepared by using urea as the precipitation agent. The resultant [...] Read more.

Pure and copper (Cu)-incorporated tin oxide (SnO₂) pellet gas sensors with characteristics provoking gas sensitivity were fabricated and used for measuring carbon monoxide (CO) atmospheres. Non-spherical pure SnO₂ nano-structures were prepared by using urea as the precipitation agent. The resultant SnO₂ powders were ball milled and incorporated with a transition metal, Cu, via chemical synthesis method. The incorporation is confirmed by high-resolution transmission electron microscope (HRTEM) analysis. By utilizing Cu-incorporated SnO₂ pellets an increase in the CO sensitivity by an order of three, and a decrease in the response and recovery times by an order of two, were obtained. This improvement in the sensitivity is due to two factors that arise due to Cu incorporation: necks between the microparticles and stacking faults in the grains. These two factors increased the conductivity and oxygen adsorption, respectively, at the pellets’ surface of SnO₂ which, in turn, raised the CO sensitivity. Full article

(This article belongs to the Special Issue Chemiresistive Sensors)

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16 pages, 3721 KiB

Open AccessArticle

Enhanced Positioning Algorithm of ARPS for Improving Accuracy and Expanding Service Coverage

by Kyuman Lee¹

, Hoki Baek² and Jaesung Lim^1,*

¹ Department of Computer Engineering, Ajou University, 206 World cup-ro, Yeongtong-gu, Suwon 16499, Korea

² Department of Military Digital Convergence, Ajou University, 206 World cup-ro, Yeongtong-gu, Suwon 16499, Korea

Sensors 2016, 16(8), 1284; https://doi.org/10.3390/s16081284 - 12 Aug 2016

Cited by 2 | Viewed by 4296

Abstract

The airborne relay-based positioning system (ARPS), which employs the relaying of navigation signals, was proposed as an alternative positioning system. However, the ARPS has limitations, such as relatively large vertical error and service restrictions, because firstly, the user position is estimated based on [...] Read more.

The airborne relay-based positioning system (ARPS), which employs the relaying of navigation signals, was proposed as an alternative positioning system. However, the ARPS has limitations, such as relatively large vertical error and service restrictions, because firstly, the user position is estimated based on airborne relays that are located in one direction, and secondly, the positioning is processed using only relayed navigation signals. In this paper, we propose an enhanced positioning algorithm to improve the performance of the ARPS. The main idea of the enhanced algorithm is the adaptable use of either virtual or direct measurements of reference stations in the calculation process based on the structural features of the ARPS. Unlike the existing two-step algorithm for airborne relay and user positioning, the enhanced algorithm is divided into two cases based on whether the required number of navigation signals for user positioning is met. In the first case, where the number of signals is greater than four, the user first estimates the positions of the airborne relays and its own initial position. Then, the user position is re-estimated by integrating a virtual measurement of a reference station that is calculated using the initial estimated user position and known reference positions. To prevent performance degradation, the re-estimation is performed after determining its requirement through comparing the expected position errors. If the navigation signals are insufficient, such as when the user is outside of airborne relay coverage, the user position is estimated by additionally using direct signal measurements of the reference stations in place of absent relayed signals. The simulation results demonstrate that a higher accuracy level can be achieved because the user position is estimated based on the measurements of airborne relays and a ground station. Furthermore, the service coverage is expanded by using direct measurements of reference stations for user positioning. Full article

(This article belongs to the Section Remote Sensors)

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15 pages, 6126 KiB

Open AccessArticle

RGB-D SLAM Based on Extended Bundle Adjustment with 2D and 3D Information

by Kaichang Di¹, Qiang Zhao^1,2, Wenhui Wan^1,*, Yexin Wang¹ and Yunjun Gao¹

¹ State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, No. 20A, Datun Road, Chaoyang District, Beijing 100101, China

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

Sensors 2016, 16(8), 1285; https://doi.org/10.3390/s16081285 - 13 Aug 2016

Cited by 27 | Viewed by 7795

Abstract

In the study of SLAM problem using an RGB-D camera, depth information and visual information as two types of primary measurement data are rarely tightly coupled during refinement of camera pose estimation. In this paper, a new method of RGB-D camera SLAM is [...] Read more.

In the study of SLAM problem using an RGB-D camera, depth information and visual information as two types of primary measurement data are rarely tightly coupled during refinement of camera pose estimation. In this paper, a new method of RGB-D camera SLAM is proposed based on extended bundle adjustment with integrated 2D and 3D information on the basis of a new projection model. First, the geometric relationship between the image plane coordinates and the depth values is constructed through RGB-D camera calibration. Then, 2D and 3D feature points are automatically extracted and matched between consecutive frames to build a continuous image network. Finally, extended bundle adjustment based on the new projection model, which takes both image and depth measurements into consideration, is applied to the image network for high-precision pose estimation. Field experiments show that the proposed method has a notably better performance than the traditional method, and the experimental results demonstrate the effectiveness of the proposed method in improving localization accuracy. Full article

(This article belongs to the Special Issue Vision-Based Sensors in Field Robotics)

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13 pages, 5925 KiB

Open AccessArticle

A Micromachined Piezoresistive Pressure Sensor with a Shield Layer

by Gang Cao¹, Xiaoping Wang¹, Yong Xu² and Sheng Liu^3,*

¹ School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

² Department of Electrical and Computer Engineering, Wayne State University, Detroit, MI 48202, USA

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

Sensors 2016, 16(8), 1286; https://doi.org/10.3390/s16081286 - 13 Aug 2016

Cited by 9 | Viewed by 7456

Abstract

This paper presents a piezoresistive pressure sensor with a shield layer for improved stability. Compared with the conventional piezoresistive pressure sensors, the new one reported in this paper has an n-type shield layer that covers p-type piezoresistors. This shield layer aims to minimize [...] Read more.

This paper presents a piezoresistive pressure sensor with a shield layer for improved stability. Compared with the conventional piezoresistive pressure sensors, the new one reported in this paper has an n-type shield layer that covers p-type piezoresistors. This shield layer aims to minimize the impact of electrical field and reduce the temperature sensitivity of piezoresistors. The proposed sensors have been successfully fabricated by bulk-micromachining techniques. A sensitivity of 0.022 mV/V/kPa and a maximum non-linearity of 0.085% FS are obtained in a pressure range of 1 MPa. After numerical simulation, the role of the shield layer has been experimentally investigated. It is demonstrated that the shield layer is able to reduce the drift caused by electrical field and ambient temperature variation. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 3759 KiB

Open AccessArticle

Ontology-Based Architecture for Intelligent Transportation Systems Using a Traffic Sensor Network

by Susel Fernandez^1,2,*

, Rafik Hadfi¹, Takayuki Ito¹, Ivan Marsa-Maestre²

and Juan R. Velasco²

¹ Department of Computer Science and Engineering, Nagoya Institute of Technology, Nagoya 466-0054, Japan

² Department of Computing Engineering, University of Alcala, Madrid 28805, Spain

Sensors 2016, 16(8), 1287; https://doi.org/10.3390/s16081287 - 15 Aug 2016

Cited by 46 | Viewed by 11896

Abstract

Intelligent transportation systems are a set of technological solutions used to improve the performance and safety of road transportation. A crucial element for the success of these systems is the exchange of information, not only between vehicles, but also among other components in [...] Read more.

Intelligent transportation systems are a set of technological solutions used to improve the performance and safety of road transportation. A crucial element for the success of these systems is the exchange of information, not only between vehicles, but also among other components in the road infrastructure through different applications. One of the most important information sources in this kind of systems is sensors. Sensors can be within vehicles or as part of the infrastructure, such as bridges, roads or traffic signs. Sensors can provide information related to weather conditions and traffic situation, which is useful to improve the driving process. To facilitate the exchange of information between the different applications that use sensor data, a common framework of knowledge is needed to allow interoperability. In this paper an ontology-driven architecture to improve the driving environment through a traffic sensor network is proposed. The system performs different tasks automatically to increase driver safety and comfort using the information provided by the sensors. Full article

(This article belongs to the Special Issue Sensors for Autonomous Road Vehicles)

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14 pages, 17433 KiB

Open AccessArticle

Hyperspectral Imaging Using Flexible Endoscopy for Laryngeal Cancer Detection

by Bianca Regeling^1,*, Boris Thies¹, Andreas O. H. Gerstner², Stephan Westermann³, Nina A. Müller³, Jörg Bendix¹

and Wiebke Laffers³

¹ Laboratory for Climatology and Remote Sensing, Faculty of Geography, University of Marburg, Deutschhausstr. 12, Marburg 35032, Germany

² Klinikum Braunschweig, ENT-Clinic, Holwedestr. 16, Braunschweig 38118, Germany

³ Department of Otorhinolaryngology/Head and Neck Surgery, University of Bonn, Sigmund-Freud-Str. 25, Bonn 53127, Germany

Sensors 2016, 16(8), 1288; https://doi.org/10.3390/s16081288 - 13 Aug 2016

Cited by 49 | Viewed by 8428

Abstract

Hyperspectral imaging (HSI) is increasingly gaining acceptance in the medical field. Up until now, HSI has been used in conjunction with rigid endoscopy to detect cancer in vivo. The logical next step is to pair HSI with flexible endoscopy, since it improves access [...] Read more.

Hyperspectral imaging (HSI) is increasingly gaining acceptance in the medical field. Up until now, HSI has been used in conjunction with rigid endoscopy to detect cancer in vivo. The logical next step is to pair HSI with flexible endoscopy, since it improves access to hard-to-reach areas. While the flexible endoscope’s fiber optic cables provide the advantage of flexibility, they also introduce an interfering honeycomb-like pattern onto images. Due to the substantial impact this pattern has on locating cancerous tissue, it must be removed before the HS data can be further processed. Thereby, the loss of information is to minimize avoiding the suppression of small-area variations of pixel values. We have developed a system that uses flexible endoscopy to record HS cubes of the larynx and designed a special filtering technique to remove the honeycomb-like pattern with minimal loss of information. We have confirmed its feasibility by comparing it to conventional filtering techniques using an objective metric and by applying unsupervised and supervised classifications to raw and pre-processed HS cubes. Compared to conventional techniques, our method successfully removes the honeycomb-like pattern and considerably improves classification performance, while preserving image details. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 2679 KiB

Open AccessArticle

Sensor Fusion of Gaussian Mixtures for Ballistic Target Tracking in the Re-Entry Phase

by Kelin Lu^*

and Rui Zhou

School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China

Sensors 2016, 16(8), 1289; https://doi.org/10.3390/s16081289 - 15 Aug 2016

Cited by 6 | Viewed by 4940

Abstract

A sensor fusion methodology for the Gaussian mixtures model is proposed for ballistic target tracking with unknown ballistic coefficients. To improve the estimation accuracy, a track-to-track fusion architecture is proposed to fuse tracks provided by the local interacting multiple model filters. During the [...] Read more.

A sensor fusion methodology for the Gaussian mixtures model is proposed for ballistic target tracking with unknown ballistic coefficients. To improve the estimation accuracy, a track-to-track fusion architecture is proposed to fuse tracks provided by the local interacting multiple model filters. During the fusion process, the duplicate information is removed by considering the first order redundant information between the local tracks. With extensive simulations, we show that the proposed algorithm improves the tracking accuracy in ballistic target tracking in the re-entry phase applications. Full article

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

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22 pages, 5867 KiB

Open AccessArticle

Time Domain Strain/Stress Reconstruction Based on Empirical Mode Decomposition: Numerical Study and Experimental Validation

by Jingjing He^1,*, Yibin Zhou², Xuefei Guan³, Wei Zhang¹, Weifang Zhang¹ and Yongming Liu⁴

¹ School of Reliability and System Engineering, Beihang University, Beijing 100191, China

² School of Energy and Power Engineering, Beihang University, Beijing 100191, China

³ Siemens Corporation, Corporate Technology, 755 College Rd. E., Princeton, NJ 08540, USA

⁴ School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ 85281, USA

Sensors 2016, 16(8), 1290; https://doi.org/10.3390/s16081290 - 16 Aug 2016

Cited by 67 | Viewed by 5974

Abstract

Structural health monitoring has been studied by a number of researchers as well as various industries to keep up with the increasing demand for preventive maintenance routines. This work presents a novel method for reconstruct prompt, informed strain/stress responses at the hot spots [...] Read more.

Structural health monitoring has been studied by a number of researchers as well as various industries to keep up with the increasing demand for preventive maintenance routines. This work presents a novel method for reconstruct prompt, informed strain/stress responses at the hot spots of the structures based on strain measurements at remote locations. The structural responses measured from usage monitoring system at available locations are decomposed into modal responses using empirical mode decomposition. Transformation equations based on finite element modeling are derived to extrapolate the modal responses from the measured locations to critical locations where direct sensor measurements are not available. Then, two numerical examples (a two-span beam and a 19956-degree of freedom simplified airfoil) are used to demonstrate the overall reconstruction method. Finally, the present work investigates the effectiveness and accuracy of the method through a set of experiments conducted on an aluminium alloy cantilever beam commonly used in air vehicle and spacecraft. The experiments collect the vibration strain signals of the beam via optical fiber sensors. Reconstruction results are compared with theoretical solutions and a detailed error analysis is also provided. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 2019 KiB

Open AccessArticle

Assessment of the Minimum Sampling Frequency to Avoid Measurement Redundancy in Microclimate Field Surveys in Museum Buildings

by Fernando-Juan García-Diego^1,2,*, Elena Verticchio³, Pedro Beltrán¹ and Anna Maria Siani³

¹ Department of Applied Physics, Universitat Politècnica de València, Av. de los Naranjos s/n, Valencia 46022, Spain

² Centro de Tecnologías Físicas, Universitat Politècnica de València, Av. de los Naranjos s/n, Valencia 46022, Spain

³ Department of Physics, Sapienza Università di Roma, P.le A. Moro 2, Rome 00185, Italy

Sensors 2016, 16(8), 1291; https://doi.org/10.3390/s16081291 - 15 Aug 2016

Cited by 21 | Viewed by 5355

Abstract

Monitoring temperature and relative humidity of the environment to which artefacts are exposed is fundamental in preventive conservation studies. The common approach in setting measuring instruments is the choice of a high sampling rate to detect short fluctuations and increase the accuracy of [...] Read more.

Monitoring temperature and relative humidity of the environment to which artefacts are exposed is fundamental in preventive conservation studies. The common approach in setting measuring instruments is the choice of a high sampling rate to detect short fluctuations and increase the accuracy of statistical analysis. However, in recent cultural heritage standards the evaluation of variability is based on moving average and short fluctuations and therefore massive acquisition of data in slowly-changing indoor environments could end up being redundant. In this research, the sampling frequency to set a datalogger in a museum room and inside a microclimate frame is investigated by comparing the outcomes obtained from datasheets associated with different sampling conditions. Thermo-hygrometric data collected in the Sorolla room of the Pio V Museum of Valencia (Spain) were used and the widely consulted recommendations issued in UNI 10829:1999 and EN 15757:2010 standards and in the American Society of Heating, Air-Conditioning and Refrigerating Engineers (ASHRAE) guidelines were applied. Hourly sampling proved effective in obtaining highly reliable results. Furthermore, it was found that in some instances daily means of data sampled every hour can lead to the same conclusions as those of high frequency. This allows us to improve data logging design and manageability of the resulting datasheets. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 4581 KiB

Open AccessArticle

Low-Cost Soil Moisture Profile Probe Using Thin-Film Capacitors and a Capacitive Touch Sensor

by Yuki Kojima^1,*, Ryo Shigeta², Naoya Miyamoto³, Yasutomo Shirahama², Kazuhiro Nishioka³, Masaru Mizoguchi³ and Yoshihiro Kawahara²

¹ Faculty of Engineering, Gifu University, Gifu 501-1193, Japan

² Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 113-8656, Japan

³ Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan

Sensors 2016, 16(8), 1292; https://doi.org/10.3390/s16081292 - 15 Aug 2016

Cited by 65 | Viewed by 18352

Abstract

Soil moisture is an important property for agriculture, but currently commercialized soil moisture sensors are too expensive for many farmers. The objective of this study is to develop a low-cost soil moisture sensor using capacitors on a film substrate and a capacitive touch [...] Read more.

Soil moisture is an important property for agriculture, but currently commercialized soil moisture sensors are too expensive for many farmers. The objective of this study is to develop a low-cost soil moisture sensor using capacitors on a film substrate and a capacitive touch integrated circuit. The performance of the sensor was evaluated in two field experiments: a grape field and a mizuna greenhouse field. The developed sensor captured dynamic changes in soil moisture at 10, 20, and 30 cm depth, with a period of 10–14 days required after sensor installation for the contact between capacitors and soil to settle down. The measured soil moisture showed the influence of individual sensor differences, and the influence masked minor differences of less than 0.05 m³·m⁻³ in the soil moisture at different locations. However, the developed sensor could detect large differences of more than 0.05 m³·m⁻³, as well as the different magnitude of changes, in soil moisture. The price of the developed sensor was reduced to 300 U.S. dollars and can be reduced even more by further improvements suggested in this study and by mass production. Therefore, the developed sensor will be made more affordable to farmers as it requires low financial investment, and it can be utilized for decision-making in irrigation. Full article

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

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11 pages, 2382 KiB

Open AccessArticle

Through-Wall Multiple Targets Vital Signs Tracking Based on VMD Algorithm

by Jiaming Yan^†

, Hong Hong^†, Heng Zhao^†

, Yusheng Li, Chen Gu and Xiaohua Zhu^*

¹ School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1293; https://doi.org/10.3390/s16081293 - 15 Aug 2016

Cited by 84 | Viewed by 8371

Abstract

Targets located at the same distance are easily neglected in most through-wall multiple targets detecting applications which use the single-input single-output (SISO) ultra-wideband (UWB) radar system. In this paper, a novel multiple targets vital signs tracking algorithm for through-wall detection using SISO UWB [...] Read more.

Targets located at the same distance are easily neglected in most through-wall multiple targets detecting applications which use the single-input single-output (SISO) ultra-wideband (UWB) radar system. In this paper, a novel multiple targets vital signs tracking algorithm for through-wall detection using SISO UWB radar has been proposed. Taking advantage of the high-resolution decomposition of the Variational Mode Decomposition (VMD) based algorithm, the respiration signals of different targets can be decomposed into different sub-signals, and then, we can track the time-varying respiration signals accurately when human targets located in the same distance. Intensive evaluation has been conducted to show the effectiveness of our scheme with a 0.15 m thick concrete brick wall. Constant, piecewise-constant and time-varying vital signs could be separated and tracked successfully with the proposed VMD based algorithm for two targets, even up to three targets. For the multiple targets’ vital signs tracking issues like urban search and rescue missions, our algorithm has superior capability in most detection applications. Full article

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

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12 pages, 4160 KiB

Open AccessArticle

Development of Gated Pinned Avalanche Photodiode Pixels for High-Speed Low-Light Imaging

by Tomislav Resetar^1,2,*, Koen De Munck², Luc Haspeslagh², Maarten Rosmeulen², Andreas Süss², Robert Puers^1,2

and Chris Van Hoof^1,2

¹ KU Leuven, ESAT, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium

² Imec, Kapeldreef 75, B-3001 Leuven, Belgium

Sensors 2016, 16(8), 1294; https://doi.org/10.3390/s16081294 - 15 Aug 2016

Cited by 7 | Viewed by 7471

Abstract

This work explores the benefits of linear-mode avalanche photodiodes (APDs) in high-speed CMOS imaging as compared to different approaches present in literature. Analysis of APDs biased below their breakdown voltage employed in single-photon counting mode is also discussed, showing a potentially interesting alternative [...] Read more.

This work explores the benefits of linear-mode avalanche photodiodes (APDs) in high-speed CMOS imaging as compared to different approaches present in literature. Analysis of APDs biased below their breakdown voltage employed in single-photon counting mode is also discussed, showing a potentially interesting alternative to existing Geiger-mode APDs. An overview of the recently presented gated pinned avalanche photodiode pixel concept is provided, as well as the first experimental results on a 8 × 16 pixel test array. Full feasibility of the proposed pixel concept is not demonstrated; however, informative data is obtained from the sensor operating under −32 V substrate bias and clearly exhibiting wavelength-dependent gain in frontside illumination. The readout of the chip designed in standard 130 nm CMOS technology shows no dependence on the high-voltage bias. Readout noise level of 15

e^{-}

rms, full well capacity of 8000

e^{-}

, and the conversion gain of 75 µV

/ e^{-}

are extracted from the photon-transfer measurements. The gain characteristics of the avalanche junction are characterized on separate test diodes showing a multiplication factor of 1.6 for red light in frontside illumination. Full article

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

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11 pages, 4435 KiB

Open AccessArticle

High Sensitivity Refractometer Based on TiO₂-Coated Adiabatic Tapered Optical Fiber via ALD Technology

by Shan Zhu¹, Fufei Pang^1,*, Sujuan Huang¹, Fang Zou^1,2, Qiang Guo¹, Jianxiang Wen¹ and Tingyun Wang¹

¹ Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, 149 Yanchang Road, Shanghai 200072, China

² Hebei GEO University, 136 East Huaian Road, Shijiazhuang 050031, China

Sensors 2016, 16(8), 1295; https://doi.org/10.3390/s16081295 - 15 Aug 2016

Cited by 27 | Viewed by 8081

Abstract

Atomic layer deposition (ALD) technology is introduced to fabricate a high sensitivity refractometer based on an adiabatic tapered optical fiber. Different thicknesses of titanium dioxide (TiO₂) nanofilm were coated around the tapered fiber precisely and uniformly under different deposition cycles. Attributed [...] Read more.

Atomic layer deposition (ALD) technology is introduced to fabricate a high sensitivity refractometer based on an adiabatic tapered optical fiber. Different thicknesses of titanium dioxide (TiO₂) nanofilm were coated around the tapered fiber precisely and uniformly under different deposition cycles. Attributed to the higher refractive index of the TiO₂ nanofilm compared to that of silica, an asymmetric Fabry–Perot (F-P) resonator could be constructed along the fiber taper. The central wavelength of the F-P resonator could be controlled by adjusting the thickness of the TiO₂ nanofilm. Such a F-P resonator is sensitive to changes in the surrounding refractive index (SRI), which is utilized to realize a high sensitivity refractometer. The refractometer developed by depositing 50.9-nm-thickness TiO₂ on the tapered fiber shows SRI sensitivity as high as 7096 nm/RIU in the SRI range of 1.3373–1.3500. Due to TiO₂’s advantages of high refractive index, lack of toxicity, and good biocompatibility, this refractometer is expected to have wide applications in the biochemical sensing field. Full article

(This article belongs to the Section Chemical Sensors)

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15 pages, 1673 KiB

Open AccessArticle

Robust Pedestrian Classification Based on Hierarchical Kernel Sparse Representation

by Rui Sun^1,*

, Guanghai Zhang¹, Xiaoxing Yan² and Jun Gao¹

¹ School of Computer and Information, Hefei University of Technology, Tunxi Road 193, Hefei 230009, China

² Academy of Optoelectronic Technology, Hefei University of Technology, Tunxi Road 193, Hefei 230009, China

Sensors 2016, 16(8), 1296; https://doi.org/10.3390/s16081296 - 16 Aug 2016

Cited by 5 | Viewed by 5390

Abstract

Vision-based pedestrian detection has become an active topic in computer vision and autonomous vehicles. It aims at detecting pedestrians appearing ahead of the vehicle using a camera so that autonomous vehicles can assess the danger and take action. Due to varied illumination and [...] Read more.

Vision-based pedestrian detection has become an active topic in computer vision and autonomous vehicles. It aims at detecting pedestrians appearing ahead of the vehicle using a camera so that autonomous vehicles can assess the danger and take action. Due to varied illumination and appearance, complex background and occlusion pedestrian detection in outdoor environments is a difficult problem. In this paper, we propose a novel hierarchical feature extraction and weighted kernel sparse representation model for pedestrian classification. Initially, hierarchical feature extraction based on a CENTRIST descriptor is used to capture discriminative structures. A max pooling operation is used to enhance the invariance of varying appearance. Then, a kernel sparse representation model is proposed to fully exploit the discrimination information embedded in the hierarchical local features, and a Gaussian weight function as the measure to effectively handle the occlusion in pedestrian images. Extensive experiments are conducted on benchmark databases, including INRIA, Daimler, an artificially generated dataset and a real occluded dataset, demonstrating the more robust performance of the proposed method compared to state-of-the-art pedestrian classification methods. Full article

(This article belongs to the Special Issue Sensors for Autonomous Road Vehicles)

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31 pages, 2669 KiB

Open AccessArticle

On Event-Triggered Adaptive Architectures for Decentralized and Distributed Control of Large-Scale Modular Systems

by Ali Albattat¹, Benjamin C. Gruenwald² and Tansel Yucelen^2,*

¹ Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA

² Laboratory for Autonomy, Control, Information, and Systems (LACIS), Department of Mechanical Engineering, University of South Florida, Tampa, FL 33620, USA

Sensors 2016, 16(8), 1297; https://doi.org/10.3390/s16081297 - 16 Aug 2016

Cited by 16 | Viewed by 4995

Abstract

The last decade has witnessed an increased interest in physical systems controlled over wireless networks (networked control systems). These systems allow the computation of control signals via processors that are not attached to the physical systems, and the feedback loops are closed over [...] Read more.

The last decade has witnessed an increased interest in physical systems controlled over wireless networks (networked control systems). These systems allow the computation of control signals via processors that are not attached to the physical systems, and the feedback loops are closed over wireless networks. The contribution of this paper is to design and analyze event-triggered decentralized and distributed adaptive control architectures for uncertain networked large-scale modular systems; that is, systems consist of physically-interconnected modules controlled over wireless networks. Specifically, the proposed adaptive architectures guarantee overall system stability while reducing wireless network utilization and achieving a given system performance in the presence of system uncertainties that can result from modeling and degraded modes of operation of the modules and their interconnections between each other. In addition to the theoretical findings including rigorous system stability and the boundedness analysis of the closed-loop dynamical system, as well as the characterization of the effect of user-defined event-triggering thresholds and the design parameters of the proposed adaptive architectures on the overall system performance, an illustrative numerical example is further provided to demonstrate the efficacy of the proposed decentralized and distributed control approaches. Full article

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

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43 pages, 1078 KiB

Open AccessReview

A Comprehensive Review on Water Quality Parameters Estimation Using Remote Sensing Techniques

by Mohammad Haji Gholizadeh¹

, Assefa M. Melesse^2,*

and Lakshmi Reddi¹

¹ Department of Civil Engineering, Florida International University, Miami, FL 33174, USA

² Department of Earth and Environment, Florida International University, Miami, FL 33199, USA

Sensors 2016, 16(8), 1298; https://doi.org/10.3390/s16081298 - 16 Aug 2016

Cited by 844 | Viewed by 63898

Abstract

Remotely sensed data can reinforce the abilities of water resources researchers and decision makers to monitor waterbodies more effectively. Remote sensing techniques have been widely used to measure the qualitative parameters of waterbodies (i.e., suspended sediments, colored dissolved organic matter (CDOM), chlorophyll-a [...] Read more.

Remotely sensed data can reinforce the abilities of water resources researchers and decision makers to monitor waterbodies more effectively. Remote sensing techniques have been widely used to measure the qualitative parameters of waterbodies (i.e., suspended sediments, colored dissolved organic matter (CDOM), chlorophyll-a, and pollutants). A large number of different sensors on board various satellites and other platforms, such as airplanes, are currently used to measure the amount of radiation at different wavelengths reflected from the water’s surface. In this review paper, various properties (spectral, spatial and temporal, etc.) of the more commonly employed spaceborne and airborne sensors are tabulated to be used as a sensor selection guide. Furthermore, this paper investigates the commonly used approaches and sensors employed in evaluating and quantifying the eleven water quality parameters. The parameters include: chlorophyll-a (chl-a), colored dissolved organic matters (CDOM), Secchi disk depth (SDD), turbidity, total suspended sediments (TSS), water temperature (WT), total phosphorus (TP), sea surface salinity (SSS), dissolved oxygen (DO), biochemical oxygen demand (BOD) and chemical oxygen demand (COD). Full article

(This article belongs to the Special Issue Sensors and Sensing in Water Quality Assessment and Monitoring)

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30 pages, 447 KiB

Open AccessArticle

An Anonymous User Authentication and Key Agreement Scheme Based on a Symmetric Cryptosystem in Wireless Sensor Networks

by Jaewook Jung¹

, Jiye Kim¹, Younsung Choi² and Dongho Won^1,*

¹ Department of Computer Engineering, Sungkyunkwan University, 2066 Seoburo, Suwon, Gyeonggido 440-746, Korea

² Department of Cyber Security, Howon University, 64 Howon University 3 Gil, Impi-Myeon, Gunsan-Si, Jeonrabuk-Do 54058, Korea

Sensors 2016, 16(8), 1299; https://doi.org/10.3390/s16081299 - 16 Aug 2016

Cited by 43 | Viewed by 6853

Abstract

In wireless sensor networks (WSNs), a registered user can login to the network and use a user authentication protocol to access data collected from the sensor nodes. Since WSNs are typically deployed in unattended environments and sensor nodes have limited resources, many researchers [...] Read more.

In wireless sensor networks (WSNs), a registered user can login to the network and use a user authentication protocol to access data collected from the sensor nodes. Since WSNs are typically deployed in unattended environments and sensor nodes have limited resources, many researchers have made considerable efforts to design a secure and efficient user authentication process. Recently, Chen et al. proposed a secure user authentication scheme using symmetric key techniques for WSNs. They claim that their scheme assures high efficiency and security against different types of attacks. After careful analysis, however, we find that Chen et al.’s scheme is still vulnerable to smart card loss attack and is susceptible to denial of service attack, since it is invalid for verification to simply compare an entered ID and a stored ID in smart card. In addition, we also observe that their scheme cannot preserve user anonymity. Furthermore, their scheme cannot quickly detect an incorrect password during login phase, and this flaw wastes both communication and computational overheads. In this paper, we describe how these attacks work, and propose an enhanced anonymous user authentication and key agreement scheme based on a symmetric cryptosystem in WSNs to address all of the aforementioned vulnerabilities in Chen et al.’s scheme. Our analysis shows that the proposed scheme improves the level of security, and is also more efficient relative to other related schemes. Full article

(This article belongs to the Section Sensor Networks)

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19 pages, 2160 KiB

Open AccessArticle

A Matrix-Based Proactive Data Relay Algorithm for Large Distributed Sensor Networks

by Yang Xu^*

, Xuemei Hu, Haixiao Hu and Ming Liu

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

Sensors 2016, 16(8), 1300; https://doi.org/10.3390/s16081300 - 16 Aug 2016

Viewed by 4389

Abstract

In large-scale distributed sensor networks, sensed data is required to be relayed around the network so that one or few sensors can gather adequate relative data to produce high quality information for decision-making. In regards to very high energy-constraint sensor nodes, data transmission [...] Read more.

In large-scale distributed sensor networks, sensed data is required to be relayed around the network so that one or few sensors can gather adequate relative data to produce high quality information for decision-making. In regards to very high energy-constraint sensor nodes, data transmission should be extremely economical. However, traditional data delivery protocols are potentially inefficient relaying unpredictable sensor readings for data fusion in large distributed networks for either overwhelming query transmissions or unnecessary data coverage. By building sensors’ local model from their previously transmitted data in three matrixes, we have developed a novel energy-saving data relay algorithm, which allows sensors to proactively make broadcast decisions by using a neat matrix computation to provide balance between transmission and energy-saving. In addition, we designed a heuristic maintenance algorithm to efficiently update these three matrices. This can easily be deployed to large-scale mobile networks in which decisions of sensors are based on their local matrix models no matter how large the network is, and the local models of these sensors are updated constantly. Compared with some traditional approaches based on our simulations, the efficiency of this approach is manifested in uncertain environment. The results show that our approach is scalable and can effectively balance aggregating data with minimizing energy consumption. Full article

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

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9 pages, 2145 KiB

Open AccessCommunication

Using a Hexagonal Mirror for Varying Light Intensity in the Measurement of Small-Angle Variation

by Meng-Chang Hsieh¹, Jiun-You Lin² and Chia-Ou Chang^1,3,*

¹ Institute of Applied Mechanics, National Taiwan University, No. 1, Sec. 4 Roosevelt Road, Taipei 10617, Taiwan

² Department of Mechatronics Engineering, National Changhua University of Education, 2, Shi-Da Road, Changhua 50074, Taiwan

³ College of Mechanical Engineering, Guangxi University, 100, University Road, Nanning 530004, China

Sensors 2016, 16(8), 1301; https://doi.org/10.3390/s16081301 - 16 Aug 2016

Cited by 4 | Viewed by 5382

Abstract

Precision positioning and control are critical to industrial-use processing machines. In order to have components fabricated with excellent precision, the measurement of small-angle variations must be as accurate as possible. To achieve this goal, this study provides a new and simple optical mechanism [...] Read more.

Precision positioning and control are critical to industrial-use processing machines. In order to have components fabricated with excellent precision, the measurement of small-angle variations must be as accurate as possible. To achieve this goal, this study provides a new and simple optical mechanism by varying light intensity. A He-Ne laser beam was passed through an attenuator and into a beam splitter. The reflected light was used as an intensity reference for calibrating the measurement. The transmitted light as a test light entered the optical mechanism hexagonal mirror, the optical mechanism of which was created by us, and then it entered the power detector after four consecutive reflections inside the mirror. When the hexagonal mirror was rotated by a small angle, the laser beam was parallel shifted. Once the laser beam was shifted, the hitting area on the detector was changed; it might be partially outside the sensing zone and would cause the variation of detection intensity. This variation of light intensity can be employed to measure small-angle variations. The experimental results demonstrate the feasibility of this method. The resolution and sensitivity are 3 × 10⁻⁴⁰ and 4 mW/° in the angular range of 0.6°, respectively, and 9.3 × 10⁻⁵⁰ and 13 mW/° in the angular range of 0.25°. Full article

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

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16 pages, 3555 KiB

Open AccessArticle

Conditional Random Field-Based Offline Map Matching for Indoor Environments

by Safaa Bataineh^1,*, Alfonso Bahillo¹

, Luis Enrique Díez¹, Enrique Onieva^1,2

and Ikram Bataineh³

¹ Faculty of Engineering, University of Deusto, Av. Universidades, 24, Bilbao 48007, Spain

² DeustoTech-Fundación Deusto, Fundación Deusto, Av. Universidades, 24, Bilbao 48007, Spain

³ Department of Architecture, Jordan University of Science and Technology, Irbid 22110, Jordan

Sensors 2016, 16(8), 1302; https://doi.org/10.3390/s16081302 - 16 Aug 2016

Cited by 16 | Viewed by 6610

Abstract

In this paper, we present an offline map matching technique designed for indoor localization systems based on conditional random fields (CRF). The proposed algorithm can refine the results of existing indoor localization systems and match them with the map, using loose coupling between [...] Read more.

In this paper, we present an offline map matching technique designed for indoor localization systems based on conditional random fields (CRF). The proposed algorithm can refine the results of existing indoor localization systems and match them with the map, using loose coupling between the existing localization system and the proposed map matching technique. The purpose of this research is to investigate the efficiency of using the CRF technique in offline map matching problems for different scenarios and parameters. The algorithm was applied to several real and simulated trajectories of different lengths. The results were then refined and matched with the map using the CRF algorithm. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 4509 KiB

Open AccessArticle

Research on the Error Characteristics of a 110 kV Optical Voltage Transformer under Three Conditions: In the Laboratory, Off-Line in the Field and During On-Line Operation

by Xia Xiao^1,*, Haoliang Hu², Yan Xu¹, Min Lei² and Qianzhu Xiong²

¹ School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430070, China

² State Grid Electric Power Research Institute, Wuhan 430070, China

Sensors 2016, 16(8), 1303; https://doi.org/10.3390/s16081303 - 16 Aug 2016

Cited by 5 | Viewed by 5963

Abstract

Optical voltage transformers (OVTs) have been applied in power systems. When performing accuracy performance tests of OVTs large differences exist between the electromagnetic environment and the temperature variation in the laboratory and on-site. Therefore, OVTs may display different error characteristics under different conditions. [...] Read more.

Optical voltage transformers (OVTs) have been applied in power systems. When performing accuracy performance tests of OVTs large differences exist between the electromagnetic environment and the temperature variation in the laboratory and on-site. Therefore, OVTs may display different error characteristics under different conditions. In this paper, OVT prototypes with typical structures were selected to be tested for the error characteristics with the same testing equipment and testing method. The basic accuracy, the additional error caused by temperature and the adjacent phase in the laboratory, the accuracy in the field off-line, and the real-time monitoring error during on-line operation were tested. The error characteristics under the three conditions—laboratory, in the field off-line and during on-site operation—were compared and analyzed. The results showed that the effect of the transportation process, electromagnetic environment and the adjacent phase on the accuracy of OVTs could be ignored for level 0.2, but the error characteristics of OVTs are dependent on the environmental temperature and are sensitive to the temperature gradient. The temperature characteristics during on-line operation were significantly superior to those observed in the laboratory. Full article

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

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28 pages, 959 KiB

Open AccessReview

A Review of Classification Techniques of EMG Signals during Isotonic and Isometric Contractions

by Nurhazimah Nazmi^1,2, Mohd Azizi Abdul Rahman^1,*

, Shin-Ichiroh Yamamoto², Siti Anom Ahmad³

, Hairi Zamzuri¹ and Saiful Amri Mazlan¹

¹ Malaysia Japan International Institute of Technology, Universiti Teknologi Malaysia, Jalan Sultan Yahya Petra, Kuala Lumpur 54100, Malaysia

² Department of Bio-Science and Engineering, College of Systems Engineering and Science, Shibaura Institute of Technology, Fukasaku 307, Saitama-City 337-8570, Japan

³ Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang 43400, Malaysia

Sensors 2016, 16(8), 1304; https://doi.org/10.3390/s16081304 - 17 Aug 2016

Cited by 317 | Viewed by 28313

Abstract

In recent years, there has been major interest in the exposure to physical therapy during rehabilitation. Several publications have demonstrated its usefulness in clinical/medical and human machine interface (HMI) applications. An automated system will guide the user to perform the training during rehabilitation [...] Read more.

In recent years, there has been major interest in the exposure to physical therapy during rehabilitation. Several publications have demonstrated its usefulness in clinical/medical and human machine interface (HMI) applications. An automated system will guide the user to perform the training during rehabilitation independently. Advances in engineering have extended electromyography (EMG) beyond the traditional diagnostic applications to also include applications in diverse areas such as movement analysis. This paper gives an overview of the numerous methods available to recognize motion patterns of EMG signals for both isotonic and isometric contractions. Various signal analysis methods are compared by illustrating their applicability in real-time settings. This paper will be of interest to researchers who would like to select the most appropriate methodology in classifying motion patterns, especially during different types of contractions. For feature extraction, the probability density function (PDF) of EMG signals will be the main interest of this study. Following that, a brief explanation of the different methods for pre-processing, feature extraction and classifying EMG signals will be compared in terms of their performance. The crux of this paper is to review the most recent developments and research studies related to the issues mentioned above. Full article

(This article belongs to the Special Issue Sensing Technology for Healthcare System)

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16 pages, 2249 KiB

Open AccessArticle

High-Resolution Time-Frequency Spectrum-Based Lung Function Test from a Smartphone Microphone

by Tharoeun Thap¹, Heewon Chung¹, Changwon Jeong², Ki-Eun Hwang³, Hak-Ryul Kim³, Kwon-Ha Yoon^4,*

and Jinseok Lee^1,*

¹ Department of Biomedical Engineering, Wonkwang University School of Medicine, 460 Iksandeaero, Iksan, Jeonbuk 570-749, Korea

² Imaging Science based Lung and Bone Disease Research Center, Wonkwang University, 460 Iksandeaero, Iksan, Jeonbuk 570-749, Korea

³ Department of Internal Medicine, Wonkwang University School of Medicine, 460 Iksandeaero, Iksan, Jeonbuk 570-749, Korea

⁴ Department of Radiology, Wonkwang University School of Medicine, 460 Iksandeaero, Iksan, Jeonbuk 570-749, Korea

Sensors 2016, 16(8), 1305; https://doi.org/10.3390/s16081305 - 17 Aug 2016

Cited by 29 | Viewed by 10343

Abstract

In this paper, a smartphone-based lung function test, developed to estimate lung function parameters using a high-resolution time-frequency spectrum from a smartphone built-in microphone is presented. A method of estimation of the forced expiratory volume in 1 s divided by forced vital capacity [...] Read more.

In this paper, a smartphone-based lung function test, developed to estimate lung function parameters using a high-resolution time-frequency spectrum from a smartphone built-in microphone is presented. A method of estimation of the forced expiratory volume in 1 s divided by forced vital capacity (FEV₁/FVC) based on the variable frequency complex demodulation method (VFCDM) is first proposed. We evaluated our proposed method on 26 subjects, including 13 healthy subjects and 13 chronic obstructive pulmonary disease (COPD) patients, by comparing with the parameters clinically obtained from pulmonary function tests (PFTs). For the healthy subjects, we found that an absolute error (AE) and a root mean squared error (RMSE) of the FEV₁/FVC ratio were 4.49% ± 3.38% and 5.54%, respectively. For the COPD patients, we found that AE and RMSE from COPD patients were 10.30% ± 10.59% and 14.48%, respectively. For both groups, we compared the results using the continuous wavelet transform (CWT) and short-time Fourier transform (STFT), and found that VFCDM was superior to CWT and STFT. Further, to estimate other parameters, including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), and peak expiratory flow (PEF), regression analysis was conducted to establish a linear transformation. However, the parameters FVC, FEV1, and PEF had correlation factor r values of 0.323, 0.275, and −0.257, respectively, while FEV₁/FVC had an r value of 0.814. The results obtained suggest that only the FEV1/FVC ratio can be accurately estimated from a smartphone built-in microphone. The other parameters, including FVC, FEV1, and PEF, were subjective and dependent on the subject’s familiarization with the test and performance of forced exhalation toward the microphone. Full article

(This article belongs to the Special Issue Smartphone-Based Sensors for Non-Invasive Physiological Monitoring)

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19 pages, 6463 KiB

Open AccessArticle

A Self-Provisioning Mechanism in OpenStack for IoT Devices

by Antonio Solano

, Raquel Dormido^*

, Natividad Duro and Juan Miguel Sánchez

Departamento Informatica y Automatica, ETSI Informatica, UNED Juan del Rosal 16, 28040 Madrid, Spain

Sensors 2016, 16(8), 1306; https://doi.org/10.3390/s16081306 - 17 Aug 2016

Cited by 16 | Viewed by 9480

Abstract

The aim of this paper is to introduce a plug-and-play mechanism for an Internet of Things (IoT) device to instantiate a Software as a Service (SaaS) application in a private cloud, built up with OpenStack. The SaaS application is the digital avatar of [...] Read more.

The aim of this paper is to introduce a plug-and-play mechanism for an Internet of Things (IoT) device to instantiate a Software as a Service (SaaS) application in a private cloud, built up with OpenStack. The SaaS application is the digital avatar of a physical object connected to Internet. As a proof of concept, a Vending Machine is retrofitted and connected to Internet with and Arduino Open Hardware device. Once the self-configuration mechanism is completed, it is possible to order a product from a mobile communication device. Full article

(This article belongs to the Special Issue Intelligent Internet of Things (IoT) Networks)

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14 pages, 1720 KiB

Open AccessArticle

Virtual Control Policy for Binary Ordered Resources Petri Net Class

by Carlos A. Rovetto^*, Tomás J. Concepción^* and Elia Esther Cano^*

Computer Systems Engineering Department, Technological University of Panama, 0819-07289, El Dorado, Panama City, Republic of Panama

Sensors 2016, 16(8), 1307; https://doi.org/10.3390/s16081307 - 18 Aug 2016

Cited by 1 | Viewed by 4949

Abstract

Prevention and avoidance of deadlocks in sensor networks that use the wormhole routing algorithm is an active research domain. There are diverse control policies that will address this problem being our approach a new method. In this paper we present a virtual control [...] Read more.

Prevention and avoidance of deadlocks in sensor networks that use the wormhole routing algorithm is an active research domain. There are diverse control policies that will address this problem being our approach a new method. In this paper we present a virtual control policy for the new specialized Petri net subclass called Binary Ordered Resources Petri Net (BORPN). Essentially, it is an ordinary class constructed from various state machines that share unitary resources in a complex form, which allows branching and joining of processes. The reduced structure of this new class gives advantages that allow analysis of the entire system’s behavior, which is a prohibitive task for large systems because of the complexity and routing algorithms. Full article

(This article belongs to the Special Issue Selected Papers from UCAmI, IWAAL and AmIHEALTH 2015)

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29 pages, 1493 KiB

Open AccessReview

Estimation of Soil Moisture from Optical and Thermal Remote Sensing: A Review

by Dianjun Zhang^1,2 and Guoqing Zhou^3,*

¹ The Center for Remote Sensing, Tianjin University, Tianjin 300072, China

² College of Earth Sciences, Guilin University of Technology, Guilin 541004, China

³ Guangxi Key Laboratory for Spatial Information and Geomatics, Guilin University of Technology, Guilin 541004, China

Sensors 2016, 16(8), 1308; https://doi.org/10.3390/s16081308 - 17 Aug 2016

Cited by 257 | Viewed by 17489

Abstract

As an important parameter in recent and numerous environmental studies, soil moisture (SM) influences the exchange of water and energy at the interface between the land surface and atmosphere. Accurate estimate of the spatio-temporal variations of SM is critical for numerous large-scale terrestrial [...] Read more.

As an important parameter in recent and numerous environmental studies, soil moisture (SM) influences the exchange of water and energy at the interface between the land surface and atmosphere. Accurate estimate of the spatio-temporal variations of SM is critical for numerous large-scale terrestrial studies. Although microwave remote sensing provides many algorithms to obtain SM at large scale, such as SMOS and SMAP etc., resulting in many data products, they are almost low resolution and not applicable in small catchment or field scale. Estimations of SM from optical and thermal remote sensing have been studied for many years and significant progress has been made. In contrast to previous reviews, this paper presents a new, comprehensive and systematic review of using optical and thermal remote sensing for estimating SM. The physical basis and status of the estimation methods are analyzed and summarized in detail. The most important and latest advances in soil moisture estimation using temporal information have been shown in this paper. SM estimation from optical and thermal remote sensing mainly depends on the relationship between SM and the surface reflectance or vegetation index. The thermal infrared remote sensing methods uses the relationship between SM and the surface temperature or variations of surface temperature/vegetation index. These approaches often have complex derivation processes and many approximations. Therefore, combinations of optical and thermal infrared remotely sensed data can provide more valuable information for SM estimation. Moreover, the advantages and weaknesses of different approaches are compared and applicable conditions as well as key issues in current soil moisture estimation algorithms are discussed. Finally, key problems and suggested solutions are proposed for future research. Full article

(This article belongs to the Section Remote Sensors)

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20 pages, 4104 KiB

Open AccessArticle

SiDIVS: Simple Detection of Inductive Vehicle Signatures with a Multiplex Resonant Sensor

by José J. Lamas-Seco^†, Paula M. Castro^*,†, Adriana Dapena^† and Francisco J. Vazquez-Araujo^†

¹ Department of Electronics and Systems, University of A Coruña, 15071 A Coruña, Spain

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1309; https://doi.org/10.3390/s16081309 - 17 Aug 2016

Cited by 9 | Viewed by 6308

Abstract

This work provides a system capable of obtaining simultaneous inductive signatures of vehicles traveling on a roadway with minimal cost. Based on Time-Division Multiplexing (TDM) with multiple oscillators, one for each inductive loop, the proposed system detects the presence of vehicles by means [...] Read more.

This work provides a system capable of obtaining simultaneous inductive signatures of vehicles traveling on a roadway with minimal cost. Based on Time-Division Multiplexing (TDM) with multiple oscillators, one for each inductive loop, the proposed system detects the presence of vehicles by means of a shift in the oscillation period of the selected loop and registers the signature of the detected vehicles by measuring the duration of a fixed number of oscillator pulses. In order to test the system in an actual environment, we implement a prototype that we denote as SiDIVS (Simple Detection of Inductive Vehicle Signatures) and acquire different vehicle inductive signatures under real scenarios. We also test the robustness of the detector by simulating the effect of noise on the signature acquisition. Full article

(This article belongs to the Section Physical Sensors)

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29 pages, 1992 KiB

Open AccessReview

Airborne Optical and Thermal Remote Sensing for Wildfire Detection and Monitoring

by Robert S. Allison^1,*

, Joshua M. Johnston², Gregory Craig³ and Sion Jennings³

¹ Centre for Vision Research, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada

² Great Lakes Forestry Centre, Canadian Forest Service, 1219 Queen Street East, Sault Ste Marie, ON P6A 2E5, Canada

³ Flight Research Lab, National Research Council of Canada, 1200 Montreal Road, M-3, Ottawa, ON K1A 0R6, Canada

Sensors 2016, 16(8), 1310; https://doi.org/10.3390/s16081310 - 18 Aug 2016

Cited by 239 | Viewed by 26380

Abstract

For decades detection and monitoring of forest and other wildland fires has relied heavily on aircraft (and satellites). Technical advances and improved affordability of both sensors and sensor platforms promise to revolutionize the way aircraft detect, monitor and help suppress wildfires. Sensor systems [...] Read more.

For decades detection and monitoring of forest and other wildland fires has relied heavily on aircraft (and satellites). Technical advances and improved affordability of both sensors and sensor platforms promise to revolutionize the way aircraft detect, monitor and help suppress wildfires. Sensor systems like hyperspectral cameras, image intensifiers and thermal cameras that have previously been limited in use due to cost or technology considerations are now becoming widely available and affordable. Similarly, new airborne sensor platforms, particularly small, unmanned aircraft or drones, are enabling new applications for airborne fire sensing. In this review we outline the state of the art in direct, semi-automated and automated fire detection from both manned and unmanned aerial platforms. We discuss the operational constraints and opportunities provided by these sensor systems including a discussion of the objective evaluation of these systems in a realistic context. Full article

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

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24 pages, 1077 KiB

Open AccessArticle

Mining IP to Domain Name Interactions to Detect DNS Flood Attacks on Recursive DNS Servers

by Roberto Alonso^1,2

, Raúl Monroy¹

and Luis A. Trejo^1,*

¹ Escuela de Ingeniería y Ciencias, Tecnologico de Monterrey, Carretera al Lago de Guadalupe Km. 3.5, Atizapán, Estado de México 52926, Mexico

² Department of Informatics, Technical University of Munich, Boltzmannstr. 3, 85748 Garching, Germany

Sensors 2016, 16(8), 1311; https://doi.org/10.3390/s16081311 - 17 Aug 2016

Cited by 13 | Viewed by 9413

Abstract

The Domain Name System (DNS) is a critical infrastructure of any network, and, not surprisingly a common target of cybercrime. There are numerous works that analyse higher level DNS traffic to detect anomalies in the DNS or any other network service. By contrast, [...] Read more.

The Domain Name System (DNS) is a critical infrastructure of any network, and, not surprisingly a common target of cybercrime. There are numerous works that analyse higher level DNS traffic to detect anomalies in the DNS or any other network service. By contrast, few efforts have been made to study and protect the recursive DNS level. In this paper, we introduce a novel abstraction of the recursive DNS traffic to detect a flooding attack, a kind of Distributed Denial of Service (DDoS). The crux of our abstraction lies on a simple observation: Recursive DNS queries, from IP addresses to domain names, form social groups; hence, a DDoS attack should result in drastic changes on DNS social structure. We have built an anomaly-based detection mechanism, which, given a time window of DNS usage, makes use of features that attempt to capture the DNS social structure, including a heuristic that estimates group composition. Our detection mechanism has been successfully validated (in a simulated and controlled setting) and with it the suitability of our abstraction to detect flooding attacks. To the best of our knowledge, this is the first time that work is successful in using this abstraction to detect these kinds of attacks at the recursive level. Before concluding the paper, we motivate further research directions considering this new abstraction, so we have designed and tested two additional experiments which exhibit promising results to detect other types of anomalies in recursive DNS servers. 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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13 pages, 6143 KiB

Open AccessArticle

Imaging of Metabolic Status in 3D Cultures with an Improved AMPK FRET Biosensor for FLIM

by George Chennell^1,2,3,*

, Robin J. W. Willows¹, Sean C. Warren⁶

, David Carling^1,2,†, Paul M. W. French^3,†, Chris Dunsby^3,4,† and Alessandro Sardini^2,5,†

¹ Cellular Stress Group, MRC Clinical Sciences Centre (CSC), Du Cane Road, London W12 0NN, UK

² Institute of Clinical Sciences (ICS), Department of Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK

³ Photonics Group, Department of Physics, Imperial College London, London SW7 2AZ, UK

⁴ Centre for Pathology, Department of Medicine, Imperial College London, London W12 0NN, UK

⁵ Whole Animal Physiology and Imaging, MRC Clinical Sciences Centre (CSC), Du Cane Road, London W12 0NN, UK

⁶ The Kinghorn Cancer Centre, Garvan Institute of Medical Research and St Vincent’s Clinical School, University of New South Wales, Darlinghurst, NSW 2010, Australia

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1312; https://doi.org/10.3390/s16081312 - 19 Aug 2016

Cited by 13 | Viewed by 9349

Abstract

We describe an approach to non-invasively map spatiotemporal biochemical and physiological changes in 3D cell culture using Forster Resonance Energy Transfer (FRET) biosensors expressed in tumour spheroids. In particular, we present an improved Adenosine Monophosphate (AMP) Activated Protein Kinase (AMPK) FRET biosensor, mTurquoise2 [...] Read more.

We describe an approach to non-invasively map spatiotemporal biochemical and physiological changes in 3D cell culture using Forster Resonance Energy Transfer (FRET) biosensors expressed in tumour spheroids. In particular, we present an improved Adenosine Monophosphate (AMP) Activated Protein Kinase (AMPK) FRET biosensor, mTurquoise2 AMPK Activity Reporter (T2AMPKAR), for fluorescence lifetime imaging (FLIM) readouts that we have evaluated in 2D and 3D cultures. Our results in 2D cell culture indicate that replacing the FRET donor, enhanced Cyan Fluorescent Protein (ECFP), in the original FRET biosensor, AMPK activity reporter (AMPKAR), with mTurquoise2 (mTq2FP), increases the dynamic range of the response to activation of AMPK, as demonstrated using the direct AMPK activator, 991. We demonstrated 3D FLIM of this T2AMPKAR FRET biosensor expressed in tumour spheroids using two-photon excitation. Full article

(This article belongs to the Special Issue FRET Biosensors)

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23 pages, 9895 KiB

Open AccessArticle

Road Lane Detection by Discriminating Dashed and Solid Road Lanes Using a Visible Light Camera Sensor

by Toan Minh Hoang, Hyung Gil Hong, Husan Vokhidov 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(8), 1313; https://doi.org/10.3390/s16081313 - 18 Aug 2016

Cited by 45 | Viewed by 16022

Abstract

With the increasing need for road lane detection used in lane departure warning systems and autonomous vehicles, many studies have been conducted to turn road lane detection into a virtual assistant to improve driving safety and reduce car accidents. Most of the previous [...] Read more.

With the increasing need for road lane detection used in lane departure warning systems and autonomous vehicles, many studies have been conducted to turn road lane detection into a virtual assistant to improve driving safety and reduce car accidents. Most of the previous research approaches detect the central line of a road lane and not the accurate left and right boundaries of the lane. In addition, they do not discriminate between dashed and solid lanes when detecting the road lanes. However, this discrimination is necessary for the safety of autonomous vehicles and the safety of vehicles driven by human drivers. To overcome these problems, we propose a method for road lane detection that distinguishes between dashed and solid lanes. Experimental results with the Caltech open database showed that our method outperforms conventional methods. Full article

(This article belongs to the Special Issue Sensors for Autonomous Road Vehicles)

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29 pages, 5614 KiB

Open AccessArticle

Recognizing the Operating Hand and the Hand-Changing Process for User Interface Adjustment on Smartphones

by Hansong Guo¹

, He Huang^2,*, Liusheng Huang¹ and Yu-E Sun^3,4

¹ School of Computer Science and Technology, University of Science and Technology of China, Hefei 230000, China

² School of Computer Science and Technology, Soochow University, Soochow 215000, China

³ School of Urban Rail Transportation, Soochow University, Soochow 215000, China

⁴ School of Computer and Software, Nanjing University of Information Science and Technology, Nanjing 210000, China

Sensors 2016, 16(8), 1314; https://doi.org/10.3390/s16081314 - 20 Aug 2016

Cited by 6 | Viewed by 6424

Abstract

As the size of smartphone touchscreens has become larger and larger in recent years, operability with a single hand is getting worse, especially for female users. We envision that user experience can be significantly improved if smartphones are able to recognize the current [...] Read more.

As the size of smartphone touchscreens has become larger and larger in recent years, operability with a single hand is getting worse, especially for female users. We envision that user experience can be significantly improved if smartphones are able to recognize the current operating hand, detect the hand-changing process and then adjust the user interfaces subsequently. In this paper, we proposed, implemented and evaluated two novel systems. The first one leverages the user-generated touchscreen traces to recognize the current operating hand, and the second one utilizes the accelerometer and gyroscope data of all kinds of activities in the user’s daily life to detect the hand-changing process. These two systems are based on two supervised classifiers constructed from a series of refined touchscreen trace, accelerometer and gyroscope features. As opposed to existing solutions that all require users to select the current operating hand or confirm the hand-changing process manually, our systems follow much more convenient and practical methods and allow users to change the operating hand frequently without any harm to the user experience. We conduct extensive experiments on Samsung Galaxy S4 smartphones, and the evaluation results demonstrate that our proposed systems can recognize the current operating hand and detect the hand-changing process with 94.1% and 93.9% precision and 94.1% and 93.7% True Positive Rates (TPR) respectively, when deciding with a single touchscreen trace or accelerometer-gyroscope data segment, and the False Positive Rates (FPR) are as low as 2.6% and 0.7% accordingly. These two systems can either work completely independently and achieve pretty high accuracies or work jointly to further improve the recognition accuracy. 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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24 pages, 22500 KiB

Open AccessArticle

Accurate Mobile Urban Mapping via Digital Map-Based SLAM

by Hyunchul Roh¹, Jinyong Jeong², Younggun Cho² and Ayoung Kim^2,*

¹ Robotics Program, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea

² Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea

Sensors 2016, 16(8), 1315; https://doi.org/10.3390/s16081315 - 18 Aug 2016

Cited by 33 | Viewed by 11911

Abstract

This paper presents accurate urban map generation using digital map-based Simultaneous Localization and Mapping (SLAM). Throughout this work, our main objective is generating a 3D and lane map aiming for sub-meter accuracy. In conventional mapping approaches, achieving extremely high accuracy was performed by [...] Read more.

This paper presents accurate urban map generation using digital map-based Simultaneous Localization and Mapping (SLAM). Throughout this work, our main objective is generating a 3D and lane map aiming for sub-meter accuracy. In conventional mapping approaches, achieving extremely high accuracy was performed by either (i) exploiting costly airborne sensors or (ii) surveying with a static mapping system in a stationary platform. Mobile scanning systems recently have gathered popularity but are mostly limited by the availability of the Global Positioning System (GPS). We focus on the fact that the availability of GPS and urban structures are both sporadic but complementary. By modeling both GPS and digital map data as measurements and integrating them with other sensor measurements, we leverage SLAM for an accurate mobile mapping system. Our proposed algorithm generates an efficient graph SLAM and achieves a framework running in real-time and targeting sub-meter accuracy with a mobile platform. Integrated with the SLAM framework, we implement a motion-adaptive model for the Inverse Perspective Mapping (IPM). Using motion estimation derived from SLAM, the experimental results show that the proposed approaches provide stable bird’s-eye view images, even with significant motion during the drive. Our real-time map generation framework is validated via a long-distance urban test and evaluated at randomly sampled points using Real-Time Kinematic (RTK)-GPS. Full article

(This article belongs to the Section Remote Sensors)

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27 pages, 1400 KiB

Open AccessArticle

Data-Aware Retrodiction for Asynchronous Harmonic Measurement in a Cyber-Physical Energy System

by Youda Liu, Xue Wang^*, Yanchi Liu and Sujin Cui

State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing 100084, China

Sensors 2016, 16(8), 1316; https://doi.org/10.3390/s16081316 - 18 Aug 2016

Cited by 5 | Viewed by 5781

Abstract

Cyber-physical energy systems provide a networked solution for safety, reliability and efficiency problems in smart grids. On the demand side, the secure and trustworthy energy supply requires real-time supervising and online power quality assessing. Harmonics measurement is necessary in power quality evaluation. However, [...] Read more.

Cyber-physical energy systems provide a networked solution for safety, reliability and efficiency problems in smart grids. On the demand side, the secure and trustworthy energy supply requires real-time supervising and online power quality assessing. Harmonics measurement is necessary in power quality evaluation. However, under the large-scale distributed metering architecture, harmonic measurement faces the out-of-sequence measurement (OOSM) problem, which is the result of latencies in sensing or the communication process and brings deviations in data fusion. This paper depicts a distributed measurement network for large-scale asynchronous harmonic analysis and exploits a nonlinear autoregressive model with exogenous inputs (NARX) network to reorder the out-of-sequence measuring data. The NARX network gets the characteristics of the electrical harmonics from practical data rather than the kinematic equations. Thus, the data-aware network approximates the behavior of the practical electrical parameter with real-time data and improves the retrodiction accuracy. Theoretical analysis demonstrates that the data-aware method maintains a reasonable consumption of computing resources. Experiments on a practical testbed of a cyber-physical system are implemented, and harmonic measurement and analysis accuracy are adopted to evaluate the measuring mechanism under a distributed metering network. Results demonstrate an improvement of the harmonics analysis precision and validate the asynchronous measuring method in cyber-physical energy systems. Full article

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

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14 pages, 13400 KiB

Open AccessArticle

Estimation of Prestress Force Distribution in Multi-Strand System of Prestressed Concrete Structures Using Field Data Measured by Electromagnetic Sensor

by Keunhee Cho

, Jeong-Rae Cho, Sung Tae Kim, Sung Yong Park, Young-Jin Kim and Young-Hwan Park^*

Structural Engineering Research Institute, Korea Institute of Civil Engineering and Building Technology, 283 Goyangdae-Ro, Ilsanseo-Gu, Goyang-Si, Gyeonggi-Do 411-712, Korea

Sensors 2016, 16(8), 1317; https://doi.org/10.3390/s16081317 - 18 Aug 2016

Cited by 8 | Viewed by 13312

Abstract

The recently developed smart strand can be used to measure the prestress force in the prestressed concrete (PSC) structure from the construction stage to the in-service stage. The higher cost of the smart strand compared to the conventional strand renders it unaffordable to [...] Read more.

The recently developed smart strand can be used to measure the prestress force in the prestressed concrete (PSC) structure from the construction stage to the in-service stage. The higher cost of the smart strand compared to the conventional strand renders it unaffordable to replace all the strands by smart strands, and results in the application of only a limited number of smart strands in the PSC structure. However, the prestress forces developed in the strands of the multi-strand system frequently adopted in PSC structures differ from each other, which means that the prestress force in the multi-strand system cannot be obtained by simple proportional scaling using the measurement of the smart strand. Therefore, this study examines the prestress force distribution in the multi-strand system to find the correlation between the prestress force measured by the smart strand and the prestress force distribution in the multi-strand system. To that goal, the prestress force distribution was measured using electromagnetic sensors for various factors of the multi-strand system adopted on site in the fabrication of actual PSC girders. The results verified the possibility to assume normal distribution for the prestress force distribution per anchor head, and a method computing the mean and standard deviation defining the normal distribution is proposed. This paper presents a meaningful finding by proposing an estimation method of the prestress force based upon field-measured data of the prestress force distribution in the multi-strand system of actual PSC structures. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 1314 KiB

Open AccessArticle

CS²-Collector: A New Approach for Data Collection in Wireless Sensor Networks Based on Two-Dimensional Compressive Sensing

by Yong Wang¹, Zhuoshi Yang¹, Jianpei Zhang¹, Feng Li², Hongkai Wen³ and Yiran Shen^1,*

¹ College of Computer Science and Technology, Harbin Engineering University, Harbin 150001, China

² School of Computer Science and Technology, Shandong University, Jinan 250100, China

³ Department of Computer Science, University of Oxford, Oxford OX1 3QD, UK

Sensors 2016, 16(8), 1318; https://doi.org/10.3390/s16081318 - 19 Aug 2016

Cited by 9 | Viewed by 6288

Abstract

In this paper, we consider the problem of reconstructing the temporal and spatial profile of some physical phenomena monitored by large-scale Wireless Sensor Networks (WSNs) in an energy efficient manner. Compressive sensing is one of the popular choices to reduce the energy consumption [...] Read more.

In this paper, we consider the problem of reconstructing the temporal and spatial profile of some physical phenomena monitored by large-scale Wireless Sensor Networks (WSNs) in an energy efficient manner. Compressive sensing is one of the popular choices to reduce the energy consumption of the data collection in WSNs. The existing solutions only consider sparsity of sensors’ data from either temporal or spatial dimensions. In this paper, we propose a novel data collection strategy, CS²-collector, for WSNs based on the theory of Two Dimensional Compressive Sensing (2DCS). It exploits both temporal and spatial sparsity, i.e., 2D-sparsity of WSNs and achieves significant gain on the tradeoff between the compression ratio and reconstruction accuracy as the numerical simulations and evaluations on different types of sensors’ data. More intuitively, with the same given energy budget, CS²-collector provides significantly more accurate reconstruction of the profile of the physical phenomena that are temporal-spatially sparse. 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, 2843 KiB

Open AccessArticle

Colour-Based Binary Discrimination of Scarified Quercus robur Acorns under Varying Illumination

by Mirosław Jabłoński^1,*, Paweł Tylek²

, Józef Walczyk², Ryszard Tadeusiewicz¹ and Adam Piłat¹

¹ Faculty of Electrical Engineering, Automatics, Computer Science and Biomedical Engineering, AGH University of Science and Technology, 30 Mickiewicza Ave., Kraków 30-059, Poland

² Department of Forest Work Mechanisation, Faculty of Forestry, University of Agriculture in Krakow, 46 29-listopada Ave., Kraków 31-425, Poland

Sensors 2016, 16(8), 1319; https://doi.org/10.3390/s16081319 - 18 Aug 2016

Cited by 15 | Viewed by 5729

Abstract

Efforts to predict the germination ability of acorns using their shape, length, diameter and density are reported in the literature. These methods, however, are not efficient enough. As such, a visual assessment of the viability of seeds based on the appearance of cross-sections [...] Read more.

Efforts to predict the germination ability of acorns using their shape, length, diameter and density are reported in the literature. These methods, however, are not efficient enough. As such, a visual assessment of the viability of seeds based on the appearance of cross-sections of seeds following their scarification is used. This procedure is more robust but demands significant effort from experienced employees over a short period of time. In this article an automated method of acorn scarification and assessment has been announced. This type of automation requires the specific setup of a machine vision system and application of image processing algorithms for evaluation of sections of seeds in order to predict their viability. In the stage of the analysis of pathological changes, it is important to point out image features that enable efficient classification of seeds in respect of viability. The article shows the results of the binary separation of seeds into two fractions (healthy or spoiled) using average components of regular red-green-blue and perception-based hue-saturation-value colour space. Analysis of accuracy of discrimination was performed on sections of 400 scarified acorns acquired using two various setups: machine vision camera under uncontrolled varying illumination and commodity high-resolution camera under controlled illumination. The accuracy of automatic classification has been compared with predictions completed by experienced professionals. It has been shown that both automatic and manual methods reach an accuracy level of 84%, assuming that the images of the sections are properly normalised. The achieved recognition ratio was higher when referenced to predictions provided by professionals. Results of discrimination by means of Bayes classifier have been also presented as a reference. Full article

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

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15 pages, 3319 KiB

Open AccessArticle

Linearized Programming of Memristors for Artificial Neuro-Sensor Signal Processing

by Changju Yang and Hyongsuk Kim^*

Department of Electronic Engineering, College of Engineering at Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do 54896, Korea

Sensors 2016, 16(8), 1320; https://doi.org/10.3390/s16081320 - 19 Aug 2016

Cited by 2 | Viewed by 7708

Abstract

A linearized programming method of memristor-based neural weights is proposed. Memristor is known as an ideal element to implement a neural synapse due to its embedded functions of analog memory and analog multiplication. Its resistance variation with a voltage input is generally a [...] Read more.

A linearized programming method of memristor-based neural weights is proposed. Memristor is known as an ideal element to implement a neural synapse due to its embedded functions of analog memory and analog multiplication. Its resistance variation with a voltage input is generally a nonlinear function of time. Linearization of memristance variation about time is very important for the easiness of memristor programming. In this paper, a method utilizing an anti-serial architecture for linear programming is proposed. The anti-serial architecture is composed of two memristors with opposite polarities. It linearizes the variation of memristance due to complimentary actions of two memristors. For programming a memristor, additional memristor with opposite polarity is employed. The linearization effect of weight programming of an anti-serial architecture is investigated and memristor bridge synapse which is built with two sets of anti-serial memristor architecture is taken as an application example of the proposed method. Simulations are performed with memristors of both linear drift model and nonlinear model. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 1347 KiB

Open AccessArticle

Modeling and Analysis of Micro-Spacecraft Attitude Sensing with Gyrowheel

by Xiaokun Liu^*,†, Hui Zhao^†, Yu Yao^† and Fenghua He^†

¹ School of Astronautics, Harbin Institute of Technology, No. 2 Yikuang Street, Nangang District, Harbin 150080, China

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1321; https://doi.org/10.3390/s16081321 - 19 Aug 2016

Cited by 24 | Viewed by 5379

Abstract

This paper proposes two kinds of approaches of angular rate sensing for micro-spacecraft with a gyrowheel (GW), which can combine attitude sensing with attitude control into one single device to achieve a compact micro-spacecraft design. In this implementation, during the three-dimensional attitude control [...] Read more.

This paper proposes two kinds of approaches of angular rate sensing for micro-spacecraft with a gyrowheel (GW), which can combine attitude sensing with attitude control into one single device to achieve a compact micro-spacecraft design. In this implementation, during the three-dimensional attitude control torques being produced, two-dimensional spacecraft angular rates can be sensed from the signals of the GW sensors, such as the currents of the torque coils, the tilt angles of the rotor, the motor rotation, etc. This paper focuses on the problems of the angular rate sensing with the GW at large tilt angles of the rotor. For this purpose, a novel real-time linearization approach based on Lyapunov’s linearization theory is proposed, and a GW linearized measurement model at arbitrary tilt angles of the rotor is derived. Furthermore, by representing the two-dimensional rotor tilt angles and tilt control torques as complex quantities and separating the twice periodic terms about the motor spin speed, the linearized measurement model at smaller tilt angles of the rotor is given and simplified. According to the respective characteristics, the application schemes of the two measurement models are analyzed from the engineering perspective. Finally, the simulation results are presented to demonstrate the effectiveness of the proposed strategy. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 4879 KiB

Open AccessArticle

A Fuzzy Logic Prompting Mechanism Based on Pattern Recognition and Accumulated Activity Effective Index Using a Smartphone Embedded Sensor

by Chung-Tse Liu and Chia-Tai Chan^*

Department of Biomedical Engineering, National Yang-Ming University, Taipei 11221, Taiwan

Sensors 2016, 16(8), 1322; https://doi.org/10.3390/s16081322 - 19 Aug 2016

Cited by 8 | Viewed by 8361

Abstract

Sufficient physical activity can reduce many adverse conditions and contribute to a healthy life. Nevertheless, inactivity is prevalent on an international scale. Improving physical activity is an essential concern for public health. Reminders that help people change their health behaviors are widely applied [...] Read more.

Sufficient physical activity can reduce many adverse conditions and contribute to a healthy life. Nevertheless, inactivity is prevalent on an international scale. Improving physical activity is an essential concern for public health. Reminders that help people change their health behaviors are widely applied in health care services. However, timed-based reminders deliver periodic prompts suffer from flexibility and dependency issues which may decrease prompt effectiveness. We propose a fuzzy logic prompting mechanism, Accumulated Activity Effective Index Reminder (AAEIReminder), based on pattern recognition and activity effective analysis to manage physical activity. AAEIReminder recognizes activity levels using a smartphone-embedded sensor for pattern recognition and analyzing the amount of physical activity in activity effective analysis. AAEIReminder can infer activity situations such as the amount of physical activity and days spent exercising through fuzzy logic, and decides whether a prompt should be delivered to a user. This prompting system was implemented in smartphones and was used in a short-term real-world trial by seventeenth participants for validation. The results demonstrated that the AAEIReminder is feasible. The fuzzy logic prompting mechanism can deliver prompts automatically based on pattern recognition and activity effective analysis. AAEIReminder provides flexibility which may increase the prompts’ efficiency. Full article

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

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27 pages, 574 KiB

Open AccessArticle

Virtual Wireless Sensor Networks: Adaptive Brain-Inspired Configuration for Internet of Things Applications

by Shinya Toyonaga^1,*,†, Daichi Kominami^2,† and Masayuki Murata^1,†

¹ Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan

² Graduate School of Economics, Osaka University, Osaka 560-0043, Japan

^† These authors contributed equally to this work.

Sensors 2016, 16(8), 1323; https://doi.org/10.3390/s16081323 - 19 Aug 2016

Cited by 9 | Viewed by 7477

Abstract

Many researchers are devoting attention to the so-called “Internet of Things” (IoT), and wireless sensor networks (WSNs) are regarded as a critical technology for realizing the communication infrastructure of the future, including the IoT. Against this background, virtualization is a crucial technique for [...] Read more.

Many researchers are devoting attention to the so-called “Internet of Things” (IoT), and wireless sensor networks (WSNs) are regarded as a critical technology for realizing the communication infrastructure of the future, including the IoT. Against this background, virtualization is a crucial technique for the integration of multiple WSNs. Designing virtualized WSNs for actual environments will require further detailed studies. Within the IoT environment, physical networks can undergo dynamic change, and so, many problems exist that could prevent applications from running without interruption when using the existing approaches. In this paper, we show an overall architecture that is suitable for constructing and running virtual wireless sensor network (VWSN) services within a VWSN topology. Our approach provides users with a reliable VWSN network by assigning redundant resources according to each user’s demand and providing a recovery method to incorporate environmental changes. We tested this approach by simulation experiment, with the results showing that the VWSN network is reliable in many cases, although physical deployment of sensor nodes and the modular structure of the VWSN will be quite important to the stability of services within the VWSN topology. Full article

(This article belongs to the Special Issue Intelligent Internet of Things (IoT) Networks)

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15 pages, 6577 KiB

Open AccessArticle

Transportation Modes Classification Using Sensors on Smartphones

by Shih-Hau Fang¹

, Hao-Hsiang Liao¹, Yu-Xiang Fei¹, Kai-Hsiang Chen², Jen-Wei Huang², Yu-Ding Lu³ and Yu Tsao^3,*

¹ Department of Electrical Engineering, Yuan Ze University, Taoyuan 320, Taiwan

² Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan

³ Research Center for Information Technology Innovation, Academia Sinica, Taipei 115, Taiwan

Sensors 2016, 16(8), 1324; https://doi.org/10.3390/s16081324 - 19 Aug 2016

Cited by 58 | Viewed by 9618

Abstract

This paper investigates the transportation and vehicular modes classification by using big data from smartphone sensors. The three types of sensors used in this paper include the accelerometer, magnetometer, and gyroscope. This study proposes improved features and uses three machine learning algorithms including [...] Read more.

This paper investigates the transportation and vehicular modes classification by using big data from smartphone sensors. The three types of sensors used in this paper include the accelerometer, magnetometer, and gyroscope. This study proposes improved features and uses three machine learning algorithms including decision trees, K-nearest neighbor, and support vector machine to classify the user’s transportation and vehicular modes. In the experiments, we discussed and compared the performance from different perspectives including the accuracy for both modes, the executive time, and the model size. Results show that the proposed features enhance the accuracy, in which the support vector machine provides the best performance in classification accuracy whereas it consumes the largest prediction time. This paper also investigates the vehicle classification mode and compares the results with that of the transportation modes. Full article

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

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23 pages, 7344 KiB

Open AccessArticle

A Hybrid Vehicle Detection Method Based on Viola-Jones and HOG + SVM from UAV Images

by Yongzheng Xu^1,2, Guizhen Yu^1,2, Yunpeng Wang^1,2, Xinkai Wu^1,2,* and Yalong Ma^1,2

¹ Beijing Key Laboratory for Cooperative Vehicle Infrastructure Systems and Safety Control, School of Transportation Science and Engineering, Beihang University, Beijing 100191, China

² Jiangsu Province Collaborative Innovation Center of Modern Urban Traffic Technologies, SiPaiLou #2, Nanjing 210096, China

Sensors 2016, 16(8), 1325; https://doi.org/10.3390/s16081325 - 19 Aug 2016

Cited by 121 | Viewed by 13208

Abstract

A new hybrid vehicle detection scheme which integrates the Viola-Jones (V-J) and linear SVM classifier with HOG feature (HOG + SVM) methods is proposed for vehicle detection from low-altitude unmanned aerial vehicle (UAV) images. As both V-J and HOG + SVM are sensitive [...] Read more.

A new hybrid vehicle detection scheme which integrates the Viola-Jones (V-J) and linear SVM classifier with HOG feature (HOG + SVM) methods is proposed for vehicle detection from low-altitude unmanned aerial vehicle (UAV) images. As both V-J and HOG + SVM are sensitive to on-road vehicles’ in-plane rotation, the proposed scheme first adopts a roadway orientation adjustment method, which rotates each UAV image to align the roads with the horizontal direction so the original V-J or HOG + SVM method can be directly applied to achieve fast detection and high accuracy. To address the issue of descending detection speed for V-J and HOG + SVM, the proposed scheme further develops an adaptive switching strategy which sophistically integrates V-J and HOG + SVM methods based on their different descending trends of detection speed to improve detection efficiency. A comprehensive evaluation shows that the switching strategy, combined with the road orientation adjustment method, can significantly improve the efficiency and effectiveness of the vehicle detection from UAV images. The results also show that the proposed vehicle detection method is competitive compared with other existing vehicle detection methods. Furthermore, since the proposed vehicle detection method can be performed on videos captured from moving UAV platforms without the need of image registration or additional road database, it has great potentials of field applications. Future research will be focusing on expanding the current method for detecting other transportation modes such as buses, trucks, motors, bicycles, and pedestrians. Full article

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

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12 pages, 3844 KiB

Open AccessArticle

A Microfluidic Approach for Inducing Cell Rotation by Means of Hydrodynamic Forces

by Stefania Torino^1,2,*, Mario Iodice¹

, Ivo Rendina¹, Giuseppe Coppola¹

and Ethan Schonbrun²

¹ Institute for Microelectronics and Microsystems, National Research Council, Naples 80131, Italy

² Rowland Institute at Harvard, Harvard University, 100 E. Land Blvd., Cambridge, MA 02142, USA

Sensors 2016, 16(8), 1326; https://doi.org/10.3390/s16081326 - 19 Aug 2016

Cited by 22 | Viewed by 7310

Abstract

Microfluidic technology allows to realize devices in which cells can be imaged in their three-dimensional shape. However, there are still some limitations in the method, due to the fact that cells follow a straight path while they are flowing in a channel. This [...] Read more.

Microfluidic technology allows to realize devices in which cells can be imaged in their three-dimensional shape. However, there are still some limitations in the method, due to the fact that cells follow a straight path while they are flowing in a channel. This can result in a loss in information, since only one side of the cell will be visible. Our work has started from the consideration that if a cell rotates, it is possible to overcome this problem. Several approaches have been proposed for cell manipulation in microfluidics. In our approach, cells are controlled by only taking advantages of hydrodynamic forces. Two different devices have been designed, realized, and tested. The first device induces cell rotation in a plane that is parallel (in-plane) to the observation plane, while the second one induce rotation in a plane perpendicular (out-of-plane) to the observation plane. Full article

(This article belongs to the Special Issue Biomicrofluidics)

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13 pages, 1042 KiB

Open AccessArticle

The Availability of Space Service for Inter-Satellite Links in Navigation Constellations

by Yinyin Tang, Yueke Wang^* and Jianyun Chen

College of Mechatronics Engineering and Automation, National University of Defense Technology, Changsha 410073, China

Sensors 2016, 16(8), 1327; https://doi.org/10.3390/s16081327 - 19 Aug 2016

Cited by 14 | Viewed by 6626

Abstract

Global navigation satellite systems (GNSS) are widely used in low Earth orbit (LEO) satellite navigation; however, their availability is poor for users in medium Earth orbits (MEO), and high Earth orbits (HEO). With the increasing demand for navigation from MEO and HEO users, [...] Read more.

Global navigation satellite systems (GNSS) are widely used in low Earth orbit (LEO) satellite navigation; however, their availability is poor for users in medium Earth orbits (MEO), and high Earth orbits (HEO). With the increasing demand for navigation from MEO and HEO users, the inadequate coverage of GNSS has emerged. Inter-satellite links (ISLs) are used for ranging and communication between navigation satellites and can also serve space users that are outside the navigation constellation. This paper aims to summarize their application method and analyze their service performance. The mathematical model of visibility is proposed and then the availability of time division ISLs is analyzed based on global grid points. The BeiDou navigation constellation is used as an example for numerical simulation. Simulation results show that the availability can be enhanced by scheduling more satellites and larger beams, while the presence of more users lowers the availability. The availability of navigation signals will be strengthened when combined with the signals from the ISLs. ISLs can improve the space service volume (SSV) of navigation constellations, and are therefore a promising method for navigation in MEO/HEO spacecraft. Full article

(This article belongs to the Section Remote Sensors)

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15 pages, 3195 KiB

Open AccessArticle

A Method to Simultaneously Detect the Current Sensor Fault and Estimate the State of Energy for Batteries in Electric Vehicles

by Jun Xu^1,2,*

, Jing Wang^1,2, Shiying Li^1,2 and Binggang Cao^1,2

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(8), 1328; https://doi.org/10.3390/s16081328 - 19 Aug 2016

Cited by 56 | Viewed by 6825

Abstract

Recently, State of energy (SOE) has become one of the most fundamental parameters for battery management systems in electric vehicles. However, current information is critical in SOE estimation and current sensor is usually utilized to obtain the latest current information. However, if the [...] Read more.

Recently, State of energy (SOE) has become one of the most fundamental parameters for battery management systems in electric vehicles. However, current information is critical in SOE estimation and current sensor is usually utilized to obtain the latest current information. However, if the current sensor fails, the SOE estimation may be confronted with large error. Therefore, this paper attempts to make the following contributions: Current sensor fault detection and SOE estimation method is realized simultaneously. Through using the proportional integral observer (PIO) based method, the current sensor fault could be accurately estimated. By taking advantage of the accurate estimated current sensor fault, the influence caused by the current sensor fault can be eliminated and compensated. As a result, the results of the SOE estimation will be influenced little by the fault. In addition, the simulation and experimental workbench is established to verify the proposed method. The results indicate that the current sensor fault can be estimated accurately. Simultaneously, the SOE can also be estimated accurately and the estimation error is influenced little by the fault. The maximum SOE estimation error is less than 2%, even though the large current error caused by the current sensor fault still exists. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 6602 KiB

Open AccessArticle

Channel Measurement and Modeling for 5G Urban Microcellular Scenarios

by Michael Peter^1,*, Richard J. Weiler¹, Barış Göktepe¹, Wilhelm Keusgen¹ and Kei Sakaguchi^1,2

¹ Department of Wireless Communications and Networks, Fraunhofer Heinrich Hertz Institute, Berlin 10587, Germany

² Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Tokyo 152-8552, Japan

Sensors 2016, 16(8), 1330; https://doi.org/10.3390/s16081330 - 20 Aug 2016

Cited by 16 | Viewed by 7601

Abstract

In order to support the development of channel models for higher frequency bands, multiple urban microcellular measurement campaigns have been carried out in Berlin, Germany, at 60 and 10 GHz. In this paper, the collected data is uniformly analyzed with focus on the [...] Read more.

In order to support the development of channel models for higher frequency bands, multiple urban microcellular measurement campaigns have been carried out in Berlin, Germany, at 60 and 10 GHz. In this paper, the collected data is uniformly analyzed with focus on the path loss (PL) and the delay spread (DS). It reveals that the ground reflection has a dominant impact on the fading behavior. For line-of-sight conditions, the PL exponents are close to free space propagation at 60 GHz, but slightly smaller (1.62) for the street canyon at 10 GHz. The DS shows a clear dependence on the scenario (median values between 16 and 38 ns) and a strong distance dependence for the open square and the wide street canyon. The dependence is less distinct for the narrow street canyon with residential buildings. This behavior is consistent with complementary ray tracing simulations, though the simplified model tends to overestimate the DS. Full article

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

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25 pages, 5395 KiB

Open AccessArticle

Mounted Smartphones as Measurement and Control Platforms for Motor-Based Laboratory Test-Beds

by Jared A. Frank

, Anthony Brill

and Vikram Kapila^*

Department of Mechanical and Aerospace Engineering, NYU Tandon School of Engineering, Mechatronics and Control Laboratory, Brooklyn, NY 11201, USA

Sensors 2016, 16(8), 1331; https://doi.org/10.3390/s16081331 - 20 Aug 2016

Cited by 3 | Viewed by 6678

Abstract

Laboratory education in science and engineering often entails the use of test-beds equipped with costly peripherals for sensing, acquisition, storage, processing, and control of physical behavior. However, costly peripherals are no longer necessary to obtain precise measurements and achieve stable feedback control of [...] Read more.

Laboratory education in science and engineering often entails the use of test-beds equipped with costly peripherals for sensing, acquisition, storage, processing, and control of physical behavior. However, costly peripherals are no longer necessary to obtain precise measurements and achieve stable feedback control of test-beds. With smartphones performing diverse sensing and processing tasks, this study examines the feasibility of mounting smartphones directly to test-beds to exploit their embedded hardware and software in the measurement and control of the test-beds. This approach is a first step towards replacing laboratory-grade peripherals with more compact and affordable smartphone-based platforms, whose interactive user interfaces can engender wider participation and engagement from learners. Demonstrative cases are presented in which the sensing, computation, control, and user interaction with three motor-based test-beds are handled by a mounted smartphone. Results of experiments and simulations are used to validate the feasibility of mounted smartphones as measurement and feedback control platforms for motor-based laboratory test-beds, report the measurement precision and closed-loop performance achieved with such platforms, and address challenges in the development of platforms to maintain system stability. Full article

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

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13 pages, 4249 KiB

Open AccessArticle

Global Navigation Satellite System Multipath Mitigation Using a Wave-Absorbing Shield

by Haiyan Yang^1,2,3,*, Xuhai Yang^1,3, Baoqi Sun^1,3 and Hang Su^1,2,3

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

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

³ Key Laboratory of Precision Navigation and Timing Technology, National Time Service Center, Chinese Academy of Sciences, Xi’an 710600, China

Sensors 2016, 16(8), 1332; https://doi.org/10.3390/s16081332 - 22 Aug 2016

Cited by 10 | Viewed by 6182

Abstract

Code multipath is an unmanaged error source in precise global navigation satellite system (GNSS) observation processing that limits GNSS positioning accuracy. A new technique for mitigating multipath by installing a wave-absorbing shield is presented in this paper. The wave-absorbing shield was designed according [...] Read more.

Code multipath is an unmanaged error source in precise global navigation satellite system (GNSS) observation processing that limits GNSS positioning accuracy. A new technique for mitigating multipath by installing a wave-absorbing shield is presented in this paper. The wave-absorbing shield was designed according to a GNSS requirement of received signals and collected measurements to achieve good performance. The wave-absorbing shield was installed at the KUN1 and SHA1 sites of the international GNSS Monitoring and Assessment System (iGMAS). Code and carrier phase measurements of three constellations were collected on the dates of the respective installations plus and minus one week. Experiments were performed in which the multipath of the measurements obtained at different elevations was mitigated to different extents after applying the wave-absorbing shield. The results of an analysis and comparison show that the multipath was mitigated by approximately 17%–36% on all available frequencies of BeiDou Navigation Satellite System (BDS), Global Positioning System (GPS), and Global Navigation Satellite System (GLONASS) satellites. The three-dimensional accuracies of BDS, GPS, and GLONASS single-point positioning (SPP) were, respectively, improved by 1.07, 0.63 and 0.49 m for the KUN1 site, and by 0.72, 0.79 and 0.73 m for the SHA1 site. Results indicate that the multipath of the original observations was mitigated by using the wave-absorbing shield. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 11106 KiB

Open AccessArticle

Measurement Matrix Optimization and Mismatch Problem Compensation for DLSLA 3-D SAR Cross-Track Reconstruction

by Qian Bao^1,2,*, Chenglong Jiang^1,2, Yun Lin¹, Weixian Tan³, Zhirui Wang⁴

and Wen Hong¹

¹ Science and Technology on Microwave Imaging Laboratory, Institute of Electronics, Chinese Academy of Sciences (IECAS), Beijing 100190, China

² University of Chinese Academy of Sciences (UCAS), Beijing 100190, China

³ College of Information Engineering, Inner Mongolia University of Technology, Hohhot 010051, Inner Mongolia, China

⁴ Department of Electronic Engineering, Tsinghua University, Beijing 100084, China

Sensors 2016, 16(8), 1333; https://doi.org/10.3390/s16081333 - 22 Aug 2016

Cited by 10 | Viewed by 5705

Abstract

With a short linear array configured in the cross-track direction, downward looking sparse linear array three-dimensional synthetic aperture radar (DLSLA 3-D SAR) can obtain the 3-D image of an imaging scene. To improve the cross-track resolution, sparse recovery methods have been investigated in [...] Read more.

With a short linear array configured in the cross-track direction, downward looking sparse linear array three-dimensional synthetic aperture radar (DLSLA 3-D SAR) can obtain the 3-D image of an imaging scene. To improve the cross-track resolution, sparse recovery methods have been investigated in recent years. In the compressive sensing (CS) framework, the reconstruction performance depends on the property of measurement matrix. This paper concerns the technique to optimize the measurement matrix and deal with the mismatch problem of measurement matrix caused by the off-grid scatterers. In the model of cross-track reconstruction, the measurement matrix is mainly affected by the configuration of antenna phase centers (APC), thus, two mutual coherence based criteria are proposed to optimize the configuration of APCs. On the other hand, to compensate the mismatch problem of the measurement matrix, the sparse Bayesian inference based method is introduced into the cross-track reconstruction by jointly estimate the scatterers and the off-grid error. Experiments demonstrate the performance of the proposed APCs’ configuration schemes and the proposed cross-track reconstruction method. Full article

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

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14 pages, 24767 KiB

Open AccessArticle

Clustering and Beamforming for Efficient Communication in Wireless Sensor Networks

by Francisco Porcel-Rodríguez¹, Juan Valenzuela-Valdés^1,*, Pablo Padilla¹, Francisco Luna-Valero², Rafael Luque-Baena³ and Miguel Ángel López-Gordo¹

¹ Department of Signal Theory, Telematics and Communications—CITIC, University of Granada, 18071 Granada, Spain

² Department of Computer Science and Programming Languages, University of Malaga, 29071 Malaga, Spain

³ Department of Computer and Telematics Systems Engineering, University of Extremadura, 06800 Merida, Spain

Sensors 2016, 16(8), 1334; https://doi.org/10.3390/s16081334 - 20 Aug 2016

Cited by 10 | Viewed by 6302

Abstract

Energy efficiency is a critical issue for wireless sensor networks (WSNs) as sensor nodes have limited power availability. In order to address this issue, this paper tries to maximize the power efficiency in WSNs by means of the evaluation of WSN node networks [...] Read more.

Energy efficiency is a critical issue for wireless sensor networks (WSNs) as sensor nodes have limited power availability. In order to address this issue, this paper tries to maximize the power efficiency in WSNs by means of the evaluation of WSN node networks and their performance when both clustering and antenna beamforming techniques are applied. In this work, four different scenarios are defined, each one considering different numbers of sensors: 50, 20, 10, five, and two nodes per scenario, and each scenario is randomly generated thirty times in order to statistically validate the results. For each experiment, two different target directions for transmission are taken into consideration in the optimization process (φ = 0° and θ = 45°; φ = 45°, and θ = 45°). Each scenario is evaluated for two different types of antennas, an ideal isotropic antenna and a conventional dipole one. In this set of experiments two types of WSN are evaluated: in the first one, all of the sensors have the same amount of power for communications purposes; in the second one, each sensor has a different amount of power for its communications purposes. The analyzed cases in this document are focused on 2D surface and 3D space for the node location. To the authors’ knowledge, this is the first time that beamforming and clustering are simultaneously applied to increase the network lifetime in WSNs. 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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22 pages, 2694 KiB

Open AccessArticle

Subsea Cable Tracking by Autonomous Underwater Vehicle with Magnetic Sensing Guidance

by Xianbo Xiang^1,*

, Caoyang Yu¹, Zemin Niu¹ and Qin Zhang²

¹ School of Naval Architecture and Ocean Engineering, Huazhong University of Science and Technology, 1037, Luoyu Road, Wuhan 430074, China

² State Key Lab of Digital Manufacturing, Equipment and Technology, Huazhong University of Science and Technology, 1037, Luoyu Road, Wuhan 430074, China

Sensors 2016, 16(8), 1335; https://doi.org/10.3390/s16081335 - 20 Aug 2016

Cited by 112 | Viewed by 11686

Abstract

The changes of the seabed environment caused by a natural disaster or human activities dramatically affect the life span of the subsea buried cable. It is essential to track the cable route in order to inspect the condition of the buried cable and [...] Read more.

The changes of the seabed environment caused by a natural disaster or human activities dramatically affect the life span of the subsea buried cable. It is essential to track the cable route in order to inspect the condition of the buried cable and protect its surviving seabed environment. The magnetic sensor is instrumental in guiding the remotely-operated vehicle (ROV) to track and inspect the buried cable underseas. In this paper, a novel framework integrating the underwater cable localization method with the magnetic guidance and control algorithm is proposed, in order to enable the automatic cable tracking by a three-degrees-of-freedom (3-DOF) under-actuated autonomous underwater vehicle (AUV) without human beings in the loop. The work relies on the passive magnetic sensing method to localize the subsea cable by using two tri-axial magnetometers, and a new analytic formulation is presented to compute the heading deviation, horizontal offset and buried depth of the cable. With the magnetic localization, the cable tracking and inspection mission is elaborately constructed as a straight-line path following control problem in the horizontal plane. A dedicated magnetic line-of-sight (LOS) guidance is built based on the relative geometric relationship between the vehicle and the cable, and the feedback linearizing technique is adopted to design a simplified cable tracking controller considering the side-slip effects, such that the under-actuated vehicle is able to move towards the subsea cable and then inspect its buried environment, which further guides the environmental protection of the cable by setting prohibited fishing/anchoring zones and increasing the buried depth. Finally, numerical simulation results show the effectiveness of the proposed magnetic guidance and control algorithm on the envisioned subsea cable tracking and the potential protection of the seabed environment along the cable route. Full article

(This article belongs to the Special Issue Robotic Sensory Systems for Environment Protection and Conservation)

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17 pages, 2435 KiB

Open AccessArticle

Fault Diagnosis Strategies for SOFC-Based Power Generation Plants

by Paola Costamagna¹

, Andrea De Giorgi², Alberto Gotelli², Loredana Magistri³, Gabriele Moser², Emanuele Sciaccaluga² and Andrea Trucco^2,4,*

¹ Department of Civil, Chemical and Environmental Engineering (DICCA), University of Genoa, Genova 16145, Italy

² Department of Electrical, Electronic, Telecommunications Engineering, and Naval Architecture (DITEN), University of Genoa, Genova 16145, Italy

³ Department of Mechanics, Energetics, Management, and Transportation (DIME), University of Genoa, Genova 16145, Italy

⁴ Pattern Analysis & Computer Vision (PAVIS), Istituto Italiano di Tecnologia (IIT), Genova 16163, Italy

Sensors 2016, 16(8), 1336; https://doi.org/10.3390/s16081336 - 22 Aug 2016

Cited by 22 | Viewed by 6930

Abstract

The success of distributed power generation by plants based on solid oxide fuel cells (SOFCs) is hindered by reliability problems that can be mitigated through an effective fault detection and isolation (FDI) system. However, the numerous operating conditions under which such plants can [...] Read more.

The success of distributed power generation by plants based on solid oxide fuel cells (SOFCs) is hindered by reliability problems that can be mitigated through an effective fault detection and isolation (FDI) system. However, the numerous operating conditions under which such plants can operate and the random size of the possible faults make identifying damaged plant components starting from the physical variables measured in the plant very difficult. In this context, we assess two classical FDI strategies (model-based with fault signature matrix and data-driven with statistical classification) and the combination of them. For this assessment, a quantitative model of the SOFC-based plant, which is able to simulate regular and faulty conditions, is used. Moreover, a hybrid approach based on the random forest (RF) classification method is introduced to address the discrimination of regular and faulty situations due to its practical advantages. Working with a common dataset, the FDI performances obtained using the aforementioned strategies, with different sets of monitored variables, are observed and compared. We conclude that the hybrid FDI strategy, realized by combining a model-based scheme with a statistical classifier, outperforms the other strategies. In addition, the inclusion of two physical variables that should be measured inside the SOFCs can significantly improve the FDI performance, despite the actual difficulty in performing such measurements. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 3416 KiB

Open AccessArticle

Factors Influencing Continuous Breath Signal in Intubated and Mechanically-Ventilated Intensive Care Unit Patients Measured by an Electronic Nose

by Jan Hendrik Leopold^1,2,*

, Ameen Abu-Hanna²

, Camilla Colombo², Peter J. Sterk³, Marcus J. Schultz¹ and Lieuwe D. J. Bos^1,3

¹ Department of Intensive Care, Academic Medical Center, University of Amsterdam, Amsterdam 1100DD, The Netherlands

² Department of Medical Informatics, Academic Medical Center, University of Amsterdam, Amsterdam 1100DD, The Netherlands

³ Department of Respiratory Medicine, Academic Medical Center, University of Amsterdam, Amsterdam 1100DD, The Netherlands

Sensors 2016, 16(8), 1337; https://doi.org/10.3390/s16081337 - 22 Aug 2016

Cited by 6 | Viewed by 5401

Abstract

Introduction: Continuous breath analysis by electronic nose (eNose) technology in the intensive care unit (ICU) may be useful in monitoring (patho) physiological changes. However, the application of breath monitoring in a non-controlled clinical setting introduces noise into the data. We hypothesized that the [...] Read more.

Introduction: Continuous breath analysis by electronic nose (eNose) technology in the intensive care unit (ICU) may be useful in monitoring (patho) physiological changes. However, the application of breath monitoring in a non-controlled clinical setting introduces noise into the data. We hypothesized that the sensor signal is influenced by: (1) humidity in the side-stream; (2) patient-ventilator disconnections and the nebulization of medication; and (3) changes in ventilator settings and the amount of exhaled CO₂. We aimed to explore whether the aforementioned factors introduce noise into the signal, and discuss several approaches to reduce this noise. Methods: Study in mechanically-ventilated ICU patients. Exhaled breath was monitored using a continuous eNose with metal oxide sensors. Linear (mixed) models were used to study hypothesized associations. Results: In total, 1251 h of eNose data were collected. First, the initial 15 min of the signal was discarded. There was a negative association between humidity and Sensor 1 (Fixed-effect β: −0.05 ± 0.002) and a positive association with Sensors 2–4 (Fixed-effect β: 0.12 ± 0.001); the signal was corrected for this noise. Outliers were most likely due to noise and therefore removed. Sensor values were positively associated with end-tidal CO₂, tidal volume and the pressure variables. The signal was corrected for changes in these ventilator variables after which the associations disappeared. Conclusion: Variations in humidity, ventilator disconnections, nebulization of medication and changes of ventilator settings indeed influenced exhaled breath signals measured in ventilated patients by continuous eNose analysis. We discussed several approaches to reduce the effects of these noise inducing variables. Full article

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

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25 pages, 1478 KiB

Open AccessArticle

Virtualized MME Design for IoT Support in 5G Systems

by Pilar Andres-Maldonado^*,†, Pablo Ameigeiras^†, Jonathan Prados-Garzon^†

, Juan Jose Ramos-Munoz^†

and Juan Manuel Lopez-Soler^†

Department of Signal Theory, Telematics, and Communications, University of Granada, Granada 18071, Spain

Sensors 2016, 16(8), 1338; https://doi.org/10.3390/s16081338 - 22 Aug 2016

Cited by 11 | Viewed by 7273

Abstract

Cellular systems are recently being considered an option to provide support to the Internet of Things (IoT). To enable this support, the 3rd Generation Partnership Project (3GPP) has introduced new procedures specifically targeted for cellular IoT. With one of these procedures, the transmissions [...] Read more.

Cellular systems are recently being considered an option to provide support to the Internet of Things (IoT). To enable this support, the 3rd Generation Partnership Project (3GPP) has introduced new procedures specifically targeted for cellular IoT. With one of these procedures, the transmissions of small and infrequent data packets from/to the devices are encapsulated in signaling messages and sent through the control plane. However, these transmissions from/to a massive number of devices may imply a major increase of the processing load on the control plane entities of the network and in particular on the Mobility Management Entity (MME). In this paper, we propose two designs of an MME based on Network Function Virtualization (NFV) that aim at facilitating the IoT support. The first proposed design partially separates the processing resources dedicated to each traffic class. The second design includes traffic shaping to control the traffic of each class. We consider three classes: Mobile Broadband (MBB), low latency Machine to Machine communications (lM2M) and delay-tolerant M2M communications. Our proposals enable reducing the processing resources and, therefore, the cost. Additionally, results show that the proposed designs lessen the impact between classes, so they ease the compliance of the delay requirements of MBB and lM2M communications. Full article

(This article belongs to the Special Issue Intelligent Internet of Things (IoT) Networks)

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14 pages, 5954 KiB

Open AccessArticle

A Dielectric-Filled Waveguide Antenna Element for 3D Imaging Radar in High Temperature and Excessive Dust Conditions

by Ding Xu^1,*

, Zhiping Li¹, Xianzhong Chen²

, Zhengpeng Wang¹ and Jianhua Wu¹

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

² School of Automation & Electrical Engineering, University of Science and Technology Beijing, Beijing 100083, China

Sensors 2016, 16(8), 1339; https://doi.org/10.3390/s16081339 - 22 Aug 2016

Cited by 9 | Viewed by 9498

Abstract

Three-dimensional information of the burden surface in high temperature and excessive dust industrial conditions has been previously hard to obtain. This paper presents a novel microstrip-fed dielectric-filled waveguide antenna element which is resistant to dust and high temperatures. A novel microstrip-to-dielectric-loaded waveguide transition [...] Read more.

Three-dimensional information of the burden surface in high temperature and excessive dust industrial conditions has been previously hard to obtain. This paper presents a novel microstrip-fed dielectric-filled waveguide antenna element which is resistant to dust and high temperatures. A novel microstrip-to-dielectric-loaded waveguide transition was developed. A cylinder and cuboid composite structure was employed at the terminal of the antenna element, which improved the return loss performance and reduced the size. The proposed antenna element was easily integrated into a T-shape multiple-input multiple-output (MIMO) imaging radar system and tested in both the laboratory environment and real blast furnace environment. The measurement results show that the proposed antenna element works very well in industrial 3D imaging radar. Full article

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

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18 pages, 2370 KiB

Open AccessArticle

Recognition of Daily Gestures with Wearable Inertial Rings and Bracelets

by Alessandra Moschetti^*, Laura Fiorini, Dario Esposito, Paolo Dario and Filippo Cavallo

The BioRobotics Institute, Scuola Superiore Sant’Anna, Viale Rinaldo Piaggio, 34, Pontedera 56025, Italy

Sensors 2016, 16(8), 1341; https://doi.org/10.3390/s16081341 - 22 Aug 2016

Cited by 69 | Viewed by 9213

Abstract

Recognition of activities of daily living plays an important role in monitoring elderly people and helping caregivers in controlling and detecting changes in daily behaviors. Thanks to the miniaturization and low cost of Microelectromechanical systems (MEMs), in particular of Inertial Measurement Units, in [...] Read more.

Recognition of activities of daily living plays an important role in monitoring elderly people and helping caregivers in controlling and detecting changes in daily behaviors. Thanks to the miniaturization and low cost of Microelectromechanical systems (MEMs), in particular of Inertial Measurement Units, in recent years body-worn activity recognition has gained popularity. In this context, the proposed work aims to recognize nine different gestures involved in daily activities using hand and wrist wearable sensors. Additionally, the analysis was carried out also considering different combinations of wearable sensors, in order to find the best combination in terms of unobtrusiveness and recognition accuracy. In order to achieve the proposed goals, an extensive experimentation was performed in a realistic environment. Twenty users were asked to perform the selected gestures and then the data were off-line analyzed to extract significant features. In order to corroborate the analysis, the classification problem was treated using two different and commonly used supervised machine learning techniques, namely Decision Tree and Support Vector Machine, analyzing both personal model and Leave-One-Subject-Out cross validation. The results obtained from this analysis show that the proposed system is able to recognize the proposed gestures with an accuracy of 89.01% in the Leave-One-Subject-Out cross validation and are therefore promising for further investigation in real life scenarios. Full article

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

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Sensors, Volume 16, Issue 8 (August 2016) – 188 articles

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