Journal of Sensors http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Human Respiration Localization Method Using UWB Linear Antenna Array Sat, 28 Feb 2015 08:42:18 +0000 http://www.hindawi.com/journals/js/2015/601926/ Human respiration is the basic vital sign in remote monitoring. There has been remarkable progress in this area, but some challenges still remain to obtain the angle-of-arrival (AOA) and distinguish the individual signals. This paper presents a 2D noncontact human respiration localization method using Ultra-Wideband (UWB) 1D linear antenna array. The imaging reconstruction based on beamforming is used to estimate the AOA of the human chest. The distance-slow time 2D matrix at the estimated AOA is processed to obtain the distance and respiration frequency of the vital sign. The proposed method can be used to isolate signals from individual targets when more than one human object is located in the surveillance space. The feasibility of the proposed method is demonstrated via the simulation and experiment results. Yuan Liu, Shiyou Wu, Jie Chen, Guangyou Fang, and Hejun Yin Copyright © 2015 Yuan Liu et al. All rights reserved. 3D Palmprint Recognition Using Dempster-Shafer Fusion Theory Thu, 26 Feb 2015 10:04:36 +0000 http://www.hindawi.com/journals/js/2015/252086/ This paper proposed a novel 3D palmprint recognition algorithm by combining 3D palmprint features using D-S fusion theory. Firstly, the structured light imaging is used to acquire the 3D palmprint data. Secondly, two types of unique features, including mean curvature feature and Gaussian curvature feature, are extracted. Thirdly, the belief function of the mean curvature recognition and the Gaussian curvature recognition was assigned, respectively. Fourthly, the fusion belief function from the proposed method was determined by the Dempster-shafer (D-S) fusion theory. Finally, palmprint recognition was accomplished according to the classification criteria. A 3D palmprint database with 1000 range images from 100 individuals was established, on which extensive experiments were performed. The results show that the proposed method 3D palmprint recognition is much more robust to illumination variations and condition changes of palmprint than MCR and GCR. Meanwhile, by fusing mean curvature and Gaussian curvature feature, the experimental results are promising (the average equal error rate of 0.404%). In the future, imaging technique needs further improvement for a better recognition performance. Jianyun Ni, Jing Luo, and Wubin Liu Copyright © 2015 Jianyun Ni et al. All rights reserved. Significance of the Nanograin Size on the H2S-Sensing Ability of CuO-SnO2 Composite Nanofibers Tue, 24 Feb 2015 15:36:52 +0000 http://www.hindawi.com/journals/js/2015/387641/ CuO-SnO2 composite nanofibers with various nanograin sizes were synthesized for investigating their sensing properties with respect to H2S gas. The nanograin size in the CuO-SnO2 composite nanofibers was controlled by changing the thermal treatment duration under isothermal conditions. The nanograin size was found to be critical for the sensing ability of the composite nanofibers. The CuO-SnO2 composite nanofibers comprised of small-sized nanograins were more sensitive to H2S than those with larger-sized nanograins. The superior sensing properties of the CuO-SnO2 composite nanofibers with the smaller nanograins were attributed to the formation of the larger number of p-CuO-n-SnO2 junctions and their transformation to metallic-CuS-n-SnO2 contacts upon exposure to H2S gas. The results suggest that smaller nanograins are conducive to obtaining superior H2S-sensing properties in CuO-SnO2 composite nanofibers. Akash Katoch, Jae-Hun Kim, and Sang Sub Kim Copyright © 2015 Akash Katoch et al. All rights reserved. Gas Sensors Based on Locally Heated Multiwall Carbon Nanotubes Decorated with Metal Nanoparticles Sun, 22 Feb 2015 12:36:25 +0000 http://www.hindawi.com/journals/js/2015/260382/ We report the design and fabrication of microreactors and sensors based on metal nanoparticle-decorated carbon nanotubes. Titanium adhesion layers and gold films were sputtered onto Si/SiO2 substrates for obtaining the electrical contacts. The gold layers were electrochemically thickened until 1 m and the electrodes were patterned using photolithography and wet chemical etching. Before the dielectrophoretic deposition of the nanotubes, a gap 1 m wide and 5 m deep was milled in the middle of the metallic line by focused ion beam, allowing the fabrication of sensors based on suspended nanotubes bridging the electrodes. Subsequently, the sputtering technique was used for decorating the nanotubes with metallic nanoparticles. In order to test the as-obtained sensors, microreactors (100 L volume) were machined from a single Kovar piece, being equipped with electrical connections and 1/4′′ Swagelok-compatible gas inlet and outlets for controlling the atmosphere in the testing chamber. The sensors, electrically connected to the contact pins by wire-bonding, were tested in the 10−5 to 10−2 W working power interval using oxygen as target gas. The small chamber volume allowed the measurement of fast characteristic times (response/recovery), with the sensors showing good sensitivity. R. Savu, J. V. Silveira, A. Alaferdov, E. Joanni, A. L. Gobbi, M. A. Canesqui, D. S. de Lara, A. G. Souza Filho, and S. A. Moshkalev Copyright © 2015 R. Savu et al. All rights reserved. Noncontact Detection and Analysis of Respiratory Function Using Microwave Doppler Radar Tue, 17 Feb 2015 13:26:43 +0000 http://www.hindawi.com/journals/js/2015/548136/ Real-time respiratory measurement with Doppler Radar has an important advantage in the monitoring of certain conditions such as sleep apnoea, sudden infant death syndrome (SIDS), and many other general clinical uses requiring fast nonwearable and non-contact measurement of the respiratory function. In this paper, we demonstrate the feasibility of using Doppler Radar in measuring the basic respiratory frequencies (via fast Fourier transform) for four different types of breathing scenarios: normal breathing, rapid breathing, slow inhalation-fast exhalation, and fast inhalation-slow exhalation conducted in a laboratory environment. A high correlation factor was achieved between the Doppler Radar-based measurements and the conventional measurement device, a respiration strap. We also extended this work from basic signal acquisition to extracting detailed features of breathing function (I : E ratio). This facilitated additional insights into breathing activity and is likely to trigger a number of new applications in respiratory medicine. Yee Siong Lee, Pubudu N. Pathirana, Robin J. Evans, and Christopher L. Steinfort Copyright © 2015 Yee Siong Lee et al. All rights reserved. Sensing of Tooth Microleakage Based on Dental Optical Coherence Tomography Sun, 15 Feb 2015 08:36:58 +0000 http://www.hindawi.com/journals/js/2015/984627/ This study describes microleakage sensing based on swept-source optical coherence tomography (SS-OCT). With a handheld scanning probe, the SS-OCT system can provide portable real-time imaging for clinical diagnosis. Radiography is the traditional clinical imaging instrument used for dentistry; however, it does not provide good contrast images between filling material and the enamel of treated teeth with microleakage. The results of this study show that microleakage can be detected with oral probing using SS-OCT in vivo. The calculated microleakage length was 401 μm and the width is 148 μm, which is consistent with the related histological biopsy measurements. The diagnosis of microleakage in teeth could be useful for prevention of secondary caries in the clinical treatment plans developed in the field of oral medicine. Chia-Wei Sun, Yi-Ching Ho, and Shyh-Yuan Lee Copyright © 2015 Chia-Wei Sun et al. All rights reserved. Self-Noise of the MET Angular Motion Seismic Sensors Tue, 10 Feb 2015 14:25:56 +0000 http://www.hindawi.com/journals/js/2015/512645/ Interest to angular motion seismic sensors is generated by an expectation that direct measurement of the rotations, associated with seismic signals, would allow obtaining more detailed and accurate information from them. Due to the seismic signals low intensity a self-noise of the sensors is one of the most crucial parameters, characterizing their performance. In seismic applications the molecular-electronic transfer (MET) technology is considered as one of the most promising technologies for the rotations measurements. In this research we have developed a noise model for the MET angular sensors. The experimental part of the research which fully agrees with theoretical data includes the instrument self-noise measurement in quite locations. Based on the modelling we have revealed the directions of further research to improve the MET angular sensors performance. Egor V. Egorov, Ivan V. Egorov, and Vadim M. Agafonov Copyright © 2015 Egor V. Egorov et al. All rights reserved. An eHealth System for Pressure Ulcer Risk Assessment Based on Accelerometer and Pressure Data Tue, 10 Feb 2015 07:43:53 +0000 http://www.hindawi.com/journals/js/2015/106537/ Pressure ulcers are a common skin disease which is associated with pain, reduced autonomy, social isolation, and reduced quality of life. There are several systems for monitoring of pressure ulcer-related risk factors on the market, but up to now no satisfactory solution is available, especially for people with medium pressure ulcer risk. We present a novel pressure ulcer risk assessment and prevention system, which combines the advantages of accelerometer and pressure sensors for monitoring pressure ulcer risk factors. Sensors are used for detection of repositionings of the person lying on the mattress. Sensor data are sent to a tablet where they are analysed and presented graphically. The system was evaluated in a long-term test at the homes of people of the target group. Results indicate that the system is able to detect movements of persons while lying in bed. Weak correlation in between mobility and Braden pressure ulcer risk was found (correlation factor = 0.31). From our data, long-term trends could be visualized as well as 24 h mobility profiles. Such graphical illustrations might be helpful for caregivers in order to optimize care of people with medium to high pressure ulcer risk. Dieter Hayn, Markus Falgenhauer, Jürgen Morak, Karin Wipfler, Viktoria Willner, Walter Liebhart, and Günter Schreier Copyright © 2015 Dieter Hayn et al. All rights reserved. Developing an Ontology-Based Cold Chain Logistics Monitoring and Decision System Tue, 10 Feb 2015 06:17:49 +0000 http://www.hindawi.com/journals/js/2015/231706/ Nowadays the cold chain logistics for perishable goods is increasingly complex, while most of the research works are focusing on the monitoring of temperature and humidity but seldom on the assessment and decision support for the monitored cold chain quality. In this context, a monitoring and decision system based on wireless sensor networks (WSN) and ontology is proposed in this paper which consists of sensing layer, network layer, and application layer. Ontology, as a shared concept model, can describe the objective world better with its own syntax and provides the general understanding of the specialized knowledge in a domain. Therefore, cold chain quality assessment software based on ontology has been developed; consequently, assessment and diagnosis for cold chain quality can be achieved, which can provide constructive advice and suggestions for its treatment. A demonstration of the system along a rabies vaccine logistics chain is validated in this paper. These results proved that this system presents important advantages such as effective regulation, low power consumption, and accurate ontology-based analysis. Yujun Wang, Jianjun Yi, Xiaomin Zhu, Jinlong Luo, and Baiyang Ji Copyright © 2015 Yujun Wang et al. All rights reserved. Microwave Sensors Based on Symmetry Properties of Resonator-Loaded Transmission Lines Mon, 09 Feb 2015 10:08:21 +0000 http://www.hindawi.com/journals/js/2015/741853/ This review paper is focused on the design of microwave sensors using symmetry properties of transmission lines loaded with symmetric resonators. The operating principle of these sensors is presented and then several prototype devices are reported, including linear and angular displacement sensors and rotation speed sensors. The main advantage of the proposed sensors is the robustness against changing environmental conditions. Jordi Naqui and Ferran Martín Copyright © 2015 Jordi Naqui and Ferran Martín. All rights reserved. Multiobjective Dynamic Vehicle Routing Problem and Time Seed Based Solution Using Particle Swarm Optimization Mon, 02 Feb 2015 13:21:35 +0000 http://www.hindawi.com/journals/js/2015/189832/ A multiobjective dynamic vehicle routing problem (M-DVRP) has been identified and a time seed based solution using particle swarm optimization (TS-PSO) for M-DVRP has been proposed. M-DVRP considers five objectives, namely, geographical ranking of the request, customer ranking, service time, expected reachability time, and satisfaction level of the customers. The multiobjective function of M-DVRP has four components, namely, number of vehicles, expected reachability time, and profit and satisfaction level. Three constraints of the objective function are vehicle, capacity, and reachability. In TS-PSO, first of all, the problem is partitioned into smaller size DVRPs. Secondly, the time horizon of each smaller size DVRP is divided into time seeds and the problem is solved in each time seed using particle swarm optimization. The proposed solution has been simulated in ns-2 considering real road network of New Delhi, India, and results are compared with those obtained from genetic algorithm (GA) simulations. The comparison confirms that TS-PSO optimizes the multiobjective function of the identified problem better than what is offered by GA solution. Omprakash Kaiwartya, Sushil Kumar, D. K. Lobiyal, Pawan Kumar Tiwari, Abdul Hanan Abdullah, and Ahmed Nazar Hassan Copyright © 2015 Omprakash Kaiwartya et al. All rights reserved. ACO-Based Sweep Coverage Scheme in Wireless Sensor Networks Sun, 01 Feb 2015 09:42:21 +0000 http://www.hindawi.com/journals/js/2015/484902/ Coverage problem is one of the major issues in wireless sensor networks (WSN). In order to optimize the network coverage, different coverage formulations have been proposed. Recently, a newly emerging coverage scheme in wireless sensor networks, sweep coverage, which uses mobile sensors to monitor certain points of interest (POIs), is proposed. However, the data delivery to sink, an important problem in WSN, is not considered in original sweep coverage and many of the existing works did not consider it yet. In this work, a novel algorithm named ACOSC (ACO-based sweep coverage) to solve the sweep coverage problem considering periodical coverage of POIs and delivery of data simultaneously is proposed. The evaluation results show that our algorithm has better performance than existing schemes. Peng Huang, Feng Lin, Chang Liu, Jian Gao, and Ji-liu Zhou Copyright © 2015 Peng Huang et al. All rights reserved. Ultrasensitive NO2 Gas Sensor Based on Epitaxial Graphene Thu, 29 Jan 2015 15:29:24 +0000 http://www.hindawi.com/journals/js/2015/108581/ We report about technology of fabrication and optimization of a gas sensor based on epitaxial graphene. Optimized graphene/metal contact configuration exhibited low contact resistance. Complementary annealing of graphene sensor after each gas exposure led to significant improvement in the sensing performance. The response of the annealed sensor to the nitrogen dioxide (NO2) was tenfold higher than that of an as-fabricated graphene sensor. NO2 concentration as low as 0.2 parts per billion (ppb) was easily detectable. Devices have high signal-to-noise ratio. The detection limit of the graphene sensor was estimated to be 0.6 ppt (parts per trillion). The present technology with additional annealing improves the performance of the graphene based sensor and makes it suitable for the environmental nitrogen dioxide gas monitoring. S. Novikov, N. Lebedeva, and A. Satrapinski Copyright © 2015 S. Novikov et al. All rights reserved. Self-Referenced Plasmon Waveguide Resonance Sensor Using Different Waveguide Modes Wed, 28 Jan 2015 07:11:55 +0000 http://www.hindawi.com/journals/js/2015/945908/ We report a plasmon waveguide resonance (PWR) sensing structure supporting two waveguide modes for self-referenced measurement. We show theoretically the dual mode PWR sensing structure owns unique opportunities for self-referenced measurement, and the accuracy and cross sensitivity can be optimized by simply varying the gold film thickness or dielectric layer thickness or dielectric film refractive index. This structure may provide an approach owning good compatibility with the surface plasmon resonance and PWR biosensors for self-referenced biosensing. Pengfei Zhang, Le Liu, Yonghong He, Yanhong Ji, and Hui Ma Copyright © 2015 Pengfei Zhang et al. All rights reserved. Resolution Enhancement Method Used for Force Sensing Resistor Array Tue, 27 Jan 2015 12:01:16 +0000 http://www.hindawi.com/journals/js/2015/647427/ Tactile sensors are one of the major devices that enable robotic systems to interact with the surrounding environment. This research aims to propose a mathematical model to describe the behavior of a tactile sensor based on experimental and statistical analyses and moreover to develop a versatile algorithm that can be applied to different tactile sensor arrays to enhance the limited resolution. With the proposed algorithm, the resolution can be increased up to twenty times if multiple measurements are available. To verify if the proposed algorithm can be used for tactile sensor arrays that are used in robotic system, a force sensing array (FSR) is adopted. The acquired two-dimensional measurements were processed by a resolution enhancement method (REM) to enhance the resolution, which can be used to improve the resolution for single image or multiple measurements. As a result, the resolution of the sensor is increased and it can be used as synthetic skin to identify accurate shapes of objects and applied forces. Karen Flores De Jesus, Marvin H. Cheng, Lei Jiang, and Ezzat G. Bakhoum Copyright © 2015 Karen Flores De Jesus et al. All rights reserved. Rate Allocation for Wireless Multimedia Sensor Networks Using Pricing Mechanism Thu, 22 Jan 2015 10:43:46 +0000 http://www.hindawi.com/journals/js/2015/738565/ A bandwidth allocation algorithm for wireless multimedia sensor networks is proposed in this paper. On the premise of Initial allocation algorithm based on distortion and congestion model to provide an efficient system performance, the allocation algorithm based on pricing mechanism we proposed balances the real-time requirement of different users by adjusting the bandwidth price in each network and each slot. Simulation results show that the proposed algorithm balances the bandwidth ratio of different users according to the video complexity, and it can provide a good system performance guaranteeing the fairness among the users. Zhang Jian Ming, Wang YI, Xie Ze Ming, Tang Shi Yi, and Ou Hao Yuan Copyright © 2015 Zhang Jian Ming et al. All rights reserved. Fiber-Optic Temperature and Pressure Sensors Applied to Radiofrequency Thermal Ablation in Liver Phantom: Methodology and Experimental Measurements Tue, 20 Jan 2015 06:22:38 +0000 http://www.hindawi.com/journals/js/2015/909012/ Radiofrequency thermal ablation (RFA) is a procedure aimed at interventional cancer care and is applied to the treatment of small- and midsize tumors in lung, kidney, liver, and other tissues. RFA generates a selective high-temperature field in the tissue; temperature values and their persistency are directly related to the mortality rate of tumor cells. Temperature measurement in up to 3–5 points, using electrical thermocouples, belongs to the present clinical practice of RFA and is the foundation of a physical model of the ablation process. Fiber-optic sensors allow extending the detection of biophysical parameters to a vast plurality of sensing points, using miniature and noninvasive technologies that do not alter the RFA pattern. This work addresses the methodology for optical measurement of temperature distribution and pressure using four different fiber-optic technologies: fiber Bragg gratings (FBGs), linearly chirped FBGs (LCFBGs), Rayleigh scattering-based distributed temperature system (DTS), and extrinsic Fabry-Perot interferometry (EFPI). For each instrument, methodology for ex vivo sensing, as well as experimental results, is reported, leading to the application of fiber-optic technologies in vivo. The possibility of using a fiber-optic sensor network, in conjunction with a suitable ablation device, can enable smart ablation procedure whereas ablation parameters are dynamically changed. Daniele Tosi, Edoardo Gino Macchi, and Alfredo Cigada Copyright © 2015 Daniele Tosi et al. All rights reserved. ETARP: An Energy Efficient Trust-Aware Routing Protocol for Wireless Sensor Networks Sun, 18 Jan 2015 09:11:36 +0000 http://www.hindawi.com/journals/js/2015/469793/ This paper presents a new routing protocol called Secure and Energy Aware Routing Protocol (ETARP) designed for energy efficiency and security for wireless sensor networks (WSNs). ETARP attempts to deal with WSN applications operating in extreme environments such as the battlefield. The key part of the routing protocol is route selection based on utility theory. The concept of utility is a novel approach to simultaneously factor energy efficiency and trustworthiness of routes in the routing protocol. ETARP discovers and selects routes on the basis of maximum utility with incurring additional cost in overhead compared to the common AODV (Ad Hoc On Demand Distance Vector) routing protocol. Simulation results show that, in comparison to previously proposed routing protocols, namely, AODV-EHA and LTB-AODV (Light-Weight Trust-Based Routing Protocol), the proposed ETARP can keep the same security level while achieving more energy efficiency for data packet delivery. Pu Gong, Thomas M. Chen, and Quan Xu Copyright © 2015 Pu Gong et al. All rights reserved. A Feasibility Study of a Noncontact Torque Sensor with Multiple Hall Sensors Tue, 13 Jan 2015 14:17:48 +0000 http://www.hindawi.com/journals/js/2015/126935/ The feasibility of a noncontact sensor is investigated. This type of sensor can potentially be used for torque measurement in a speed-variable power transmission system. Torque can be read by examining the phase difference between two induction signals from respective magnetic sensors that detect the magnetic field intensity of permanent magnets mounted on the surface of a shaft in rotation. A real-time measuring algorithm that includes filtering and calibration is adopted to measure the torque magnitude. It is shown that this new torque sensor can perform well under rotation speeds ranging from 300 rpm to 500 rpm. As an interim report rather than a complete development, this work demonstrates the feasibility of noncontact torque measurement by monitoring a magnetic field. The result shows an error of less than 2% within the full test range, which is a sufficient competitive performance for commercial sensors. The price is very low compared to competitors in the marketplace, and the device does not require special handling of the shaft of the surface. Kyungshik Lee and Chongdu Cho Copyright © 2015 Kyungshik Lee and Chongdu Cho. All rights reserved. Defect Automatic Identification of Eddy Current Pulsed Thermography Wed, 31 Dec 2014 06:29:59 +0000 http://www.hindawi.com/journals/js/2014/326316/ Eddy current pulsed thermography (ECPT) is an effective nondestructive testing and evaluation (NDT&E) technique, and has been applied for a wide range of conductive materials. Manual selected frames have been used for defects detection and quantification. Defects are indicated by high/low temperature in the frames. However, the variation of surface emissivity sometimes introduces illusory temperature inhomogeneity and results in false alarm. To improve the probability of detection, this paper proposes a two-heat balance states-based method which can restrain the influence of the emissivity. In addition, the independent component analysis (ICA) is also applied to automatically identify defect patterns and quantify the defects. An experiment was carried out to validate the proposed methods. Kai Chen, Libing Bai, Yifan Chen, Yuhua Cheng, Shulin Tian, and Peipei Zhu Copyright © 2014 Kai Chen et al. All rights reserved. Autonomic Wireless Sensor Networks: A Systematic Literature Review Mon, 29 Dec 2014 08:33:02 +0000 http://www.hindawi.com/journals/js/2014/782789/ Autonomic computing (AC) is a promising approach to meet basic requirements in the design of wireless sensor networks (WSNs), and its principles can be applied to efficiently manage nodes operation and optimize network resources. Middleware for WSNs supports the implementation and basic operation of such networks. In this systematic literature review (SLR) we aim to provide an overview of existing WSN middleware systems that address autonomic properties. The main goal is to identify which development approaches of AC are used for designing WSN middleware system, which allow the self-management of WSN. Another goal is finding out which interactions and behavior can be automated in WSN components. We drew the following main conclusions from the SLR results: (i) the selected studies address WSN concerns according to the self- properties of AC, namely, self-configuration, self-healing, self-optimization, and self-protection; (ii) the selected studies use different approaches for managing the dynamic behavior of middleware systems for WSN, such as policy-based reasoning, context-based reasoning, feedback control loops, mobile agents, model transformations, and code generation. Finally, we identified a lack of comprehensive system architecture designs that support the autonomy of sensor networking. Jesús M. T. Portocarrero, Flávia C. Delicato, Paulo F. Pires, Nadia Gámez, Lidia Fuentes, David Ludovino, and Paulo Ferreira Copyright © 2014 Jesús M. T. Portocarrero et al. All rights reserved. Resource Management Technique Based on Lightweight and Compressed Sensing for Mobile Internet of Things Tue, 23 Dec 2014 06:35:55 +0000 http://www.hindawi.com/journals/js/2014/690521/ In mobile Internet of Tings, based on cross-layer design and resource-aware scheduling, the combination of light weight coding and compressed sensing is used to improve the real-time performance of acquisition of system resource and reliability of resource management in this paper. Compressed sensing scheme based on the adaptive frame format definition of lightweight coding is able to set up the parameters such as sample signal, signal and hops. The nonlinear relationship matrixes between resource information of sensors or system and quality of services are built to manage the global or local network resource scheduling. Experimental results show that the proposed scheme is better than the traditional scheme or resource management based on compressed sensing alone scheme, which can make the system be able to achieve optimal resource allocation. Zhou Jianming, Liu Fan, and Lu Qiuyuan Copyright © 2014 Zhou Jianming et al. All rights reserved. Trace Detection of Pentaerythritol Tetranitrate Using Electrochemical Gas Sensors Mon, 22 Dec 2014 00:10:13 +0000 http://www.hindawi.com/journals/js/2014/234607/ Selective and sensitive detection of trace amounts of pentaerythritol tetranitrate (PETN) is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensor as the detector. A single sensor is operated in the dominant hydrocarbon (HC) and nitrogen oxides (NOx) mode by varying the sensor operating condition. The potentiometric sensor with integrated heaters was used to capture the signature of PETN. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (10 μg down to 200 ng). The ratio of the HC integrated peak area to the NOx integrated peak area is identified as an indicator of selectivity. The HC/NOx ratio is unique for PETN and has a range from 1.7 to 2.7. This detection technique has the potential to become an orthogonal technique to the existing explosive screening technologies for reducing the number of false positives/false negatives in a cost-effective manner. Praveen K. Sekhar, Jie Zhou, Hui Wang, and Eric R. Hamblin Copyright © 2014 Praveen K. Sekhar et al. All rights reserved. Use of Magnetic Fluid in Accelerometers Thu, 18 Dec 2014 09:08:14 +0000 http://www.hindawi.com/journals/js/2014/375623/ Magnetic fluid accelerometer is designed based on the special physical properties of magnetic fluid. Compared with the conventional acceleration sensors, magnetic fluid accelerometer has stronger shock resistance capability, higher sensitivity, lower energy consumption, and better performance in low frequency response. It satisfies the growing requirements of acceleration sensors. In this paper, the dynamic model and the theory of magnetic fluid accelerometers were presented. The structure characteristics of typical magnetic fluid accelerometers were investigated, and the development trend of magnetic fluid accelerometers in the future was also predicted. Besides, a novel accelerometer with linearity better than 1.5% and sensitivity better than 75 mV/g was proposed. Leping Qian and Decai Li Copyright © 2014 Leping Qian and Decai Li. All rights reserved. A Novel Subnanosecond Monocycle Pulse Generator for UWB Radar Applications Mon, 15 Dec 2014 13:57:35 +0000 http://www.hindawi.com/journals/js/2014/150549/ A novel ultra-wideband (UWB) monocycle pulse generator with good performance is designed and demonstrated in this paper. It contains a power supply circuit, a pulse drive circuit, a unique pulse forming circuit, and a novel monopolar-to-monocycle pulse transition circuit. The drive circuit employs wideband bipolar junction transistors (BJTs) and linear power amplifier transistor to produce a high amplitude drive pulse, and the pulse forming circuit uses the transition characteristics of step recovery diode (SRD) effectively to produce a negative narrow pulse. At last, the monocycle pulse forming circuit utilizes a novel inductance L short-circuited stub to generate the monocycle pulse directly. Measurement results show that the waveform of the generated monocycle pulses is over 76 V in peak-to-peak amplitude and 3.2 ns in pulse full-width. These characteristics of the monocycle pulse are advantageous for obtaining long detection range and high resolution, when it is applied to ultra-wideband radar applications. Xinfan Xia, Lihua Liu, Shengbo Ye, Hongfei Guan, and Guangyou Fang Copyright © 2014 Xinfan Xia et al. All rights reserved. Frequency Tuning of Work Modes in Z-Axis Dual-Mass Silicon Microgyroscope Mon, 15 Dec 2014 12:54:22 +0000 http://www.hindawi.com/journals/js/2014/891735/ Frequency tuning of work modes in the silicon vibratory gyroscope is studied by the theoretical, numerical, and experimental methods in this paper. First, the schematic structure and simplified kinematics model of the gyroscope were presented for deducing the natural frequencies. Then, the width and length of support beams were optimized to tune work frequencies at their designed value. Besides, the frequency difference was experimentally tested and manually tuned by varying the voltage applied on the tuning capacitors. The test on a prototype showed that the difference could be localized between −55.8 Hz and 160.2 Hz when the tuning voltage limit is 20 V. Finally, a frequency control loop was developed to automatically tune the sense frequency toward the drive frequency. Both the theoretical analysis and numeric simulation show that the difference is stabilized at 0.8 Hz when no Coriolis force or quadrature coupling force is applied. It is proved that the frequency difference is successfully tuned by modifying the size of support beams before fabrication as well as the voltage applied on the tuning capacitors after fabrication. The automatic tuning loop, used to match the work modes, is beneficial to enhance the performance of the gyroscope as well as its resistance to environment disturbances. Lu Xu, Hongsheng Li, Yunfang Ni, Jia Liu, and Libin Huang Copyright © 2014 Lu Xu et al. All rights reserved. BeTrust: A Dynamic Trust Model Based on Bayesian Inference and Tsallis Entropy for Medical Sensor Networks Wed, 03 Dec 2014 00:10:12 +0000 http://www.hindawi.com/journals/js/2014/649392/ With the rapid development and application of medical sensor networks, the security has become a big challenge to be resolved. Trust mechanism as a method of “soft security” has been proposed to guarantee the network security. Trust models to compute the trustworthiness of single node and each path are constructed, respectively, in this paper. For the trust relationship between nodes, trust value in every interval is quantified based on Bayesian inference. A node estimates the parameters of prior distribution by using the collected recommendation information and obtains the posterior distribution combined with direct interactions. Further, the weights of trust values are allocated through using the ordered weighted vector twice and overall trust degree is represented. With the associated properties of Tsallis entropy, the definition of path Tsallis entropy is put forward, which can comprehensively measure the uncertainty of each path. Then a method to calculate the credibility of each path is derived. The simulation results show that the proposed models can correctly reflect the dynamic of node behavior, quickly identify the malicious attacks, and effectively avoid such path containing low-trust nodes so as to enhance the robustness. Yan Gao and Wenfen Liu Copyright © 2014 Yan Gao and Wenfen Liu. All rights reserved. Boundary Detection Method for Large-Scale Coverage Holes in Wireless Sensor Network Based on Minimum Critical Threshold Constraint Mon, 01 Dec 2014 06:50:45 +0000 http://www.hindawi.com/journals/js/2014/985854/ The existing coverage hole boundary detection methods cannot detect large-scale coverage hole boundary in wireless sensor network quickly and efficiently. Aiming at this problem, a boundary detection method for large-scale coverage holes in wireless sensor network based on minimum critical threshold constraint is proposed. Firstly, the optimization problem of minimum critical threshold is highlighted, and its formulaic description is constructed according to probabilistic sensing model. On the basis of this, the distributed gradient information is used to approximately solve the optimization problem. After that, local-scale rough boundary detection algorithm incorporating the minimum critical threshold and its iterative thinning algorithm are proposed according to blocking flow theory. The experimental results show that the proposed method has low computational complexity and network overhead when detecting large-scale coverage hole boundary in wireless sensor network. Rong Jing, Lingfu Kong, and Liang Kong Copyright © 2014 Rong Jing et al. All rights reserved. TDAL: Thoroughly Data Aggregation of Low Energy Devices in Secure Heterogeneous Wireless Sensor Networks Thu, 27 Nov 2014 12:35:30 +0000 http://www.hindawi.com/journals/js/2014/938480/ The heterogeneous wireless sensor networks (HWSNs), composed of multiple types of tiny devices (sensor nodes) with wireless communication capability and suffering from computational resources constrains, enable interacting with the physical world, like never before. Innovative applications are developed for security, industrial production, monitoring, and tracking, but theoretical assumptions on these distributed data may not hold in a real scenario. In this paper, the emphasis is on accurate data and sensor nodes privacy preserving while transmitting their sensory information amongst neighbors toward the sink based on parent-child relationship in the wireless sensor network (WSN) environment, while ensuring energy saving. Data aggregation is a known energy efficient technique that is investigated through in-depth analysis of sensor communication through game theory, considering various embodiments of methods like elliptic curve cryptography for secrecy between nodes. This paper endeavors to provide new perspective for secure and energy efficient data aggregation models, where the heterogeneity of a sensor network environment makes it more complex to predict the overall network outputs. Tristan Daladier Engouang, Yun Liu, and Zhenjiang Zhang Copyright © 2014 Tristan Daladier Engouang et al. All rights reserved. Long-Stroke Nanopositioning Stage Driven by Piezoelectric Motor Mon, 24 Nov 2014 08:34:02 +0000 http://www.hindawi.com/journals/js/2014/926314/ This paper reported a biaxial nanopositioning stage single-driven by piezoelectric motor. The employed piezoelectric motor can perform two different driving modes, namely, AC drive mode to drive in long-stroke and at high-speed and DC scanning mode with the high-resolution of several nanometers, which satisfies the requirements of both long-stroke and nanoresolution. To compensate for the effects of the variable friction force and some unpredictable disturbances, a novel backward error compensation (BEC) positioning control method integrated of the two driving modes and a double closed-loop PID controller system are proposed to obtain a high-accuracy positional motion. The experiment results demonstrate that the nanopositioning stage with large travel range of 300 mm × 300 mm has a fine speed characteristic and resolution is 5 nm. In the experiments of different travels up to 15 mm, calibrated by a commercial laser vibrometer, the positioning accuracy is proved within 55 nm in x-axis and 40 nm in y-axis with standard deviation less than 40 nm in x-axis and 30 nm in y-axis and the final position locking can be limited to 10 nm, meeting the requirements of micromanipulation technology. Yong Wang, Fujun Sun, Junhui Zhu, Ming Pang, and Changhai Ru Copyright © 2014 Yong Wang et al. All rights reserved.