Journal of Sensors http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Electrophoretic Deposition of SnO2 Nanoparticles and Its LPG Sensing Characteristics Wed, 27 May 2015 13:04:16 +0000 http://www.hindawi.com/journals/js/2015/971473/ Homogenized nanoparticles (60 nm) in acetylacetone mediums, both with and without iodine, were deposited onto platinum coated alumina substrate and interdigital electrodes using the electrophoretic deposition (EPD) method for gas sensor applications. Homogeneous and porous film layers were processed and analyzed at various coating times and voltages. The structure of the deposited films was characterized by a scanning electron microscopy (SEM). The gas sensing properties of the films were investigated using liquid petroleum gas (LPG) for various lower explosive limits (LEL). The results showed that porous, crack-free, and homogeneous films were achieved for 5 and 15 sec at 100 and 150 V EPD parameters using an iodine-free acetylacetone based suspension. The optimum sintering for the deposited nanoparticles was observed at 500°C for 5 min. The results showed that the sensitivity of the films was increased with the operating temperature. The coated films with EPD demonstrated a better sensitivity for the 20 LEL LPG concentrations at a 450°C operating temperature. The maximum sensitivity of the sensors at 450°C to 20 LEL LPG was 30. Göktuğ Günkaya, Mevlüt Gürbüz, and Aydın Doğan Copyright © 2015 Göktuğ Günkaya et al. All rights reserved. A Method for Measurement of Absolute Angular Position and Application in a Novel Electromagnetic Encoder System Wed, 27 May 2015 13:00:05 +0000 http://www.hindawi.com/journals/js/2015/503852/ For the encoders, especially the sine-cosine magnetic ones, a new method to measure absolute angular position is proposed in the paper. In the method, the code disc of the encoder has only two circle tracks and each one was divided into and () equal code cells. The cell angles, changing from 0° to 360° between any two neighboring code cells, are defined to represent any position on the code disc. The position value of the same point can be represented by different cell angle values of different tracks and the absolute angular position of the point can be obtained by the difference value between the cell angle value of the outer track and the inner one. To validate the correctness of the method theoretically, the derivation process of the method was provided. An electromagnetic encoder system was designed and the experimental platform was established to test the method. The experimental results indicate that the electromagnetic encoder can measure the absolute angular position. Besides, it shows that the method is easy to be realized in algorithm and can reduce computational complexity and decrease dimension of the encoder. Zijian Zhang, Yangyang Dong, Fenglei Ni, Minghe Jin, and Hong Liu Copyright © 2015 Zijian Zhang et al. All rights reserved. Removal of False Blood Vessels Using Shape Based Features and Image Inpainting Tue, 26 May 2015 14:23:08 +0000 http://www.hindawi.com/journals/js/2015/839894/ Automated quantification of blood vessels in human retina is the fundamental step in designing any computer-aided diagnosis system for ophthalmic disorders. Detection and analysis of variations in blood vessels can be used to diagnose several ocular diseases like diabetic retinopathy. Diabetic Retinopathy is a progressive vascular disorder caused due to variations in blood vessels of retina. These variations bring different abnormalities like lesions, exudates, and hemorrhages in human retina which make the vessel detection problematic. Therefore, automated retinal analysis is required to cater the effect of lesions while segmenting blood vessels. The proposed framework presents two improved approaches to carry out vessel segmentation in the presence of lesions. The paper mainly aims to extract true vessels by reducing the effect of abnormal structures significantly. First method is a supervised approach which extracts true vessels by performing region based analysis of retinal image, while second method intends to remove lesions before extracting blood vessels by using an inpainting technique. Both methods are evaluated on STARE and DRIVE and on our own database AFIO. Experimental results demonstrate the excellence of the proposed system. Amna Waheed, Zahra Waheed, M. Usman Akram, and Arslan Shaukat Copyright © 2015 Amna Waheed et al. All rights reserved. Using Bayesian Inference Framework towards Identifying Gas Species and Concentration from High Temperature Resistive Sensor Array Data Mon, 25 May 2015 13:17:58 +0000 http://www.hindawi.com/journals/js/2015/351940/ High temperature gas sensors have been highly demanded for combustion process optimization and toxic emissions control, which usually suffer from poor selectivity. In order to solve this selectivity issue and identify unknown reducing gas species (CO, CH4, and CH8) and concentrations, a high temperature resistive sensor array data set was built in this study based on 5 reported sensors. As each sensor showed specific responses towards different types of reducing gas with certain concentrations, based on which calibration curves were fitted, providing benchmark sensor array response database, then Bayesian inference framework was utilized to process the sensor array data and build a sample selection program to simultaneously identify gas species and concentration, by formulating proper likelihood between input measured sensor array response pattern of an unknown gas and each sampled sensor array response pattern in benchmark database. This algorithm shows good robustness which can accurately identify gas species and predict gas concentration with a small error of less than 10% based on limited amount of experiment data. These features indicate that Bayesian probabilistic approach is a simple and efficient way to process sensor array data, which can significantly reduce the required computational overhead and training data. Yixin Liu, Kai Zhou, and Yu Lei Copyright © 2015 Yixin Liu et al. All rights reserved. Autonomic Context-Aware Wireless Sensor Networks Mon, 25 May 2015 11:24:33 +0000 http://www.hindawi.com/journals/js/2015/621326/ Autonomic Computing allows systems like wireless sensor networks (WSN) to self-manage computing resources in order to extend their autonomy as much as possible. In addition, contextualization tasks can fuse two or more different sensor data into a more meaningful information. Since these tasks usually run in a single centralized context server (e.g., sink node), the massive volume of data generated by the wireless sensors can lead to a huge information overload in such server. Here we propose DAIM, a distributed autonomic inference machine distributed which allows the sensor nodes to do self-management and contextualization tasks based on fuzzy logic. We have evaluated DAIM in a real sensor network taking into account other inference machines. Experimental results illustrate that DAIM is an energy-efficient contextualization method for WSN, reducing 48.8% of the number of messages sent to the context servers while saving 19.5% of the total amount of energy spent in the network. Nídia G. S. Campos, Danielo G. Gomes, Flávia C. Delicato, Augusto J. V. Neto, Luci Pirmez, and José Neuman de Souza Copyright © 2015 Nídia G. S. Campos et al. All rights reserved. Towards a Carbon Nanotube Intermodulation Product Sensor for Nonlinear Energy Harvesting Mon, 25 May 2015 06:52:35 +0000 http://www.hindawi.com/journals/js/2015/983697/ It is critically important in designing RF receiver front ends to handle high power jammers and other strong interferers. Instead of blocking incoming energy or dissipating it as heat, we investigate the possibility of redirecting that energy for harvesting and storage. The approach is based on channelizing a high power signal into a previously unknown circuit element which serves as a passive intermodulation device. This intermodulation component must produce a hysteretic current-voltage curve to be useful as an energy harvester. Here we demonstrate a method by which carbon nanotube transistors produce the necessary hysteretic - curves. Such devices can be tailored to the desired frequency by introducing functional groups to the nanotubes. These effects controllably enhance the desired behavior, namely, hysteretic nonlinearity in the transistors’ - characteristic. Combining these components with an RF energy harvester may one day enable the reuse of inbound jamming energy for standard back end radio components. Mitchell B. Lerner, Brett Goldsmith, John Rockway, and Israel Perez Copyright © 2015 Mitchell B. Lerner et al. All rights reserved. A Low-Power and Low-Voltage Power Management Strategy for On-Chip Micro Solar Cells Sun, 24 May 2015 07:19:07 +0000 http://www.hindawi.com/journals/js/2015/739871/ Fundamental characteristics of on-chip micro solar cell (MSC) structures were investigated in this study. Several MSC structures using different layers in three different CMOS processes were designed and fabricated. Effects of PN junction structure and process technology on solar cell performance were measured. Parameters for low-power and low-voltage implementation of power management strategy and boost converter based circuits utilizing fractional voltage maximum power point tracking (FVMPPT) algorithm were determined. The FVMPPT algorithm works based on the fraction between the maximum power point operation voltage and the open circuit voltage of the solar cell structure. This ratio is typically between 0.72 and 0.78 for commercially available poly crystalline silicon solar cells that produce several watts of power under typical daylight illumination. Measurements showed that the fractional voltage ratio is much higher and fairly constant between 0.82 and 0.85 for on-chip mono crystalline silicon micro solar cell structures that produce micro watts of power. Mono crystalline silicon solar cell structures were observed to result in better power fill factor (PFF) that is higher than 74% indicating a higher energy harvesting efficiency. Ismail Cevik and Suat U. Ay Copyright © 2015 Ismail Cevik and Suat U. Ay. All rights reserved. Parameter Modeling Analysis and Experimental Verification on Magnetic Shielding Cylinder of All-Optical Atomic Spin Magnetometer Thu, 21 May 2015 13:33:17 +0000 http://www.hindawi.com/journals/js/2015/491746/ The ultrahigh sensitivity atomic spin magnetometer as the magnetic measurement sensor has received much concern. The performance of the magnetic shielding cylinder is one of the key factors constraining the atomic spin magnetometer’s sensitivity. In order to effectively improve the performances of the magnetic shielding, the parameter optimization models of the magnetic shielding cylinder were established in this paper. Under the condition of changing only one parameter while the others keeping constant, the effects of various parameters influencing the axial shielding coefficient were comprehensively analyzed, and the results showed that the smaller the innermost length, the innermost radius, and the radial spacing were, and the greater the axial spacing was, the better the shielding performance could be obtained. According to these results and the actual needs, the magnetic shielding cylinder was optimally designed, and then the shielding effects were simulated via the software Ansoft. The simulation results showed that the optimized magnetic shielding cylinder had the advantages of small size, high shielding performance, and lager uniformity than that of the nonoptimized one. The actual measurement results showed that the residual magnetism in the optimized magnetic shielding cylinder was below 0.1 nT, which was 2~4 times lower than the nonoptimized one. Hong Zhang, Sheng Zou, Xi-Yuan Chen, and Wei Quan Copyright © 2015 Hong Zhang et al. All rights reserved. Characterization and Optimization of a Single-Transistor Active Pixel Image Sensor with Floating Junction Connected to Floating Gate Thu, 21 May 2015 11:38:52 +0000 http://www.hindawi.com/journals/js/2015/167145/ The application of semifloating gate transistor (SFGT) as the single-transistor active pixel image sensor (APS) is investigated in this paper. This single-transistor (1T) APS can realize the functions of the conventional 3T CMOS image sensor. The device operation mechanism, optimization methods, and transient behavior measurements will be discussed. Because the floating junction of this device is connected to the floating gate, special behaviors such as floating gate voltage pinning effects were observed. The transient time measurement emulating the exposure procedure also confirmed the light sensing function as a single-transistor image sensor. Xin-Yan Liu, Jun Wu, Xiao-Yong Liu, Shuai Zhang, Xi Lin, Chun-Min Zhang, Peng-Fei Wang, and David Wei Zhang Copyright © 2015 Xin-Yan Liu et al. All rights reserved. EEG Signal Quality of a Subcutaneous Recording System Compared to Standard Surface Electrodes Wed, 20 May 2015 06:57:24 +0000 http://www.hindawi.com/journals/js/2015/341208/ Purpose. We provide a comprehensive verification of a new subcutaneous EEG recording device which promises robust and unobtrusive measurements over ultra-long time periods. The approach is evaluated against a state-of-the-art surface EEG electrode technology. Materials and Methods. An electrode powered by an inductive link was subcutaneously implanted on five subjects. Surface electrodes were placed at sites corresponding to the subcutaneous electrodes, and the EEG signals were evaluated with both quantitative (power spectral density and coherence analysis) and qualitative (blinded subjective scoring by neurophysiologists) analysis. Results. The power spectral density and coherence analysis were very similar during measurements of resting EEG. The scoring by neurophysiologists showed a higher EEG quality for the implanted system for different subject states (eyes open and eyes closed). This was most likely due to higher amplitude of the subcutaneous signals. During periods with artifacts, such as chewing, blinking, and eye movement, the two systems performed equally well. Conclusions. Subcutaneous measurements of EEG with the test device showed high quality as measured by both quantitative and more subjective qualitative methods. The signal might be superior to surface EEG in some aspects and provides a method of ultra-long term EEG recording in situations where this is required and where a small number of EEG electrodes are sufficient. Jonas Duun-Henriksen, Troels Wesenberg Kjaer, David Looney, Mary Doreen Atkins, Jens Ahm Sørensen, Martin Rose, Danilo P. Mandic, Rasmus Elsborg Madsen, and Claus Bogh Juhl Copyright © 2015 Jonas Duun-Henriksen et al. All rights reserved. Experimental Results for Direction of Arrival Estimation with a Single Acoustic Vector Sensor in Shallow Water Tue, 19 May 2015 13:11:54 +0000 http://www.hindawi.com/journals/js/2015/401353/ We study the performances of several computationally efficient and simple techniques for estimating direction of arrival (DOA) of an underwater acoustic source using a single acoustic vector sensor (AVS) in shallow water. Underwater AVS is a compact device, which consists of one hydrophone and three accelerometers in a packaged form, measuring scalar pressure and three-dimensional acceleration simultaneously at a single position. A very controlled experimental setup is prepared to test how well-known techniques, namely, arctan-based, intensity-based, time domain beamforming, and frequency domain beamforming methods, perform in estimating DOA of a source in different circumstances. Experimental results reveal that for almost all cases beamforming techniques perform best. Moreover, arctan-based method, which is the simplest of all, provides satisfactory results for practical purposes. Alper Bereketli, Mehmet B. Guldogan, Taner Kolcak, Tamer Gudu, and Ahmet Levent Avsar Copyright © 2015 Alper Bereketli et al. All rights reserved. Structure Analysis and Decoupling Research of a Novel Flexible Tactile Sensor Array Mon, 18 May 2015 13:58:38 +0000 http://www.hindawi.com/journals/js/2015/476403/ This paper presents a novel flexible tactile sensor structure and proposes an efficient decoupling algorithm for the tactile sensor. Firstly, structure of the sensor model is introduced, and the sensing mechanism of the sensor array based on force-sensitive conductive rubber is analyzed. Then the mapping relation between the resistances of conductive pillars and the three-dimensional force is deduced. After that, the force applied on the tactile sensor is decoupled from the resistance information by the improved Back Propagation Neural Network (BPNN) algorithm with the number of hidden layer nodes optimized. The flexible tactile sensor model achieves the decomposition of the three-dimensional information from the structure with its unique design, avoids the direct interference between electrodes of the sensor array, reduces the structural complexity and the nonlinear degree, improves the decoupling accuracy, and accelerates the decoupling rate. Feilu Wang, Yang Song, Zhenya Zhang, and Wanli Chen Copyright © 2015 Feilu Wang et al. All rights reserved. Measuring Conductance of Phenylenediamine as a Molecular Sensor Thu, 14 May 2015 14:56:48 +0000 http://www.hindawi.com/journals/js/2015/353095/ We report experimental measurements of molecular conductance as a single molecular sensor by using scanning tunneling microscope-based break-junction (STM-BJ) technique. The gap was created after Au atomic point contact was ruptured, and the target molecule was inserted and bonded to the top and bottom electrodes. We successfully measured the conductance for a series of amine-terminated oligophenyl molecules by forming the molecular junctions with Au electrodes. The measured conductance decays exponentially with molecular backbone length, enabling us to detect the type of molecules as a molecular sensor. Furthermore, we demonstrated reversible binary switching in a molecular junction by mechanical control of the gap between the electrodes. Since our method allows us to measure the conductance of a single molecule in ambient conditions, it should open up various practical molecular sensing applications. Taekyeong Kim and Tae Hyun Kim Copyright © 2015 Taekyeong Kim and Tae Hyun Kim. All rights reserved. Utilizing Smart Textiles-Enabled Sensorized Toy and Playful Interactions for Assessment of Psychomotor Development on Children Sun, 10 May 2015 07:07:11 +0000 http://www.hindawi.com/journals/js/2015/898047/ Emerging pervasive technologies like smart textiles make it possible to develop new and more accessible healthcare services for patients independently of their location or time. However, none of these new e-health solutions guarantee a complete user acceptance, especially in cases requiring extensive interaction between the user and the solution. So far, researchers have focused their efforts on new interactions techniques to improve the perception of privacy and confidence of the people using e-health services. In this way, the use of smart everyday objects arises as an interesting approach to facilitate the required interaction and increase user acceptance. Such Smart Daily Objects together with smart textiles provide researchers with a novel way to introduce sophisticated sensor technology in the daily life of people. This work presents a sensorized smart toy for assessment of psychomotor development in early childhood. The aim of this work is to design, develop, and evaluate the usability and playfulness of a smart textile-enabled sensorized toy that facilitates the user engagement in a personalized monitoring healthcare activity. To achieve this objective the monitoring is based on a smart textile sensorized toy as catalyzer of acceptance and multimodal sensing sources to monitor psychomotor development activities during playtime. Mario Vega-Barbas, Iván Pau, Javier Ferreira, Evelyn Lebis, and Fernando Seoane Copyright © 2015 Mario Vega-Barbas et al. All rights reserved. Towards Extremely Sensitive Ultraviolet-Light Sensors Employing Photochromic Optical Microfiber Wed, 06 May 2015 12:56:55 +0000 http://www.hindawi.com/journals/js/2015/586318/ We propose an extremely responsive ultraviolet-light sensor (−1.39 × 106 dB/(W/cm2)) based on photochromic optical microfiber. A densely packed planar coil of ZBLAN optical microfiber is doped with photochromic dyes. Under ultraviolet radiation, the photochromic microfiber experiences temporary photodarkening, and the change in the transmission of the probe light provides a measure of the incident ultraviolet light. This novel design grants an enhancement in sensitivity (3.13 nW/cm2) by at least one order of magnitude compared to traditional electrical counterparts. George Y. Chen and Zilong Wang Copyright © 2015 George Y. Chen and Zilong Wang. All rights reserved. Linear Time Approximation Algorithms for the Relay Node Placement Problem in Wireless Sensor Networks with Hexagon Tessellation Sun, 03 May 2015 12:21:47 +0000 http://www.hindawi.com/journals/js/2015/565983/ The relay node placement problem in wireless sensor network (WSN) aims at deploying the minimum number of relay nodes over the network so that each sensor can communicate with at least one relay node. When the deployed relay nodes are homogeneous and their communication ranges are circular, one way to solve the WSN relay node placement problem is to solve the minimum geometric disk cover (MGDC) problem first and place the relay nodes at the centers of the covering disks and then, if necessary, deploy additional relay nodes to meet the connection requirement of relay nodes. It is known that the MGDC problem is NP-complete. A novel linear time approximation algorithm for the MGDC problem is proposed, which identifies covering disks using the regular hexagon tessellation of the plane with bounded area. The approximation ratio of the proposed algorithm is (), where . Experimental results show that the worst case is rare, and on average the proposed algorithm uses less than 1.7 times the optimal disks of the MGDC problem. In cases where quick deployment is necessary, this study provides a fast 7-approximation algorithm which uses on average less than twice the optimal number of relay nodes in the simulation. Chi-Chang Chen, Chi-Yu Chang, and Po-Ying Chen Copyright © 2015 Chi-Chang Chen et al. All rights reserved. A Method of Vehicle Route Prediction Based on Social Network Analysis Thu, 30 Apr 2015 13:47:55 +0000 http://www.hindawi.com/journals/js/2015/210298/ A method of vehicle route prediction based on social network analysis is proposed in this paper. The difference from proposed work is that, according to our collected vehicles’ past trips, we build a relationship model between different road segments rather than find the driving regularity of vehicles to predict upcoming routes. In this paper, firstly we depend on graph theory to build an initial road network model and modify related model parameters based on the collected data set. Then we transform the model into a matrix. Secondly, two concepts from social network analysis are introduced to describe the meaning of the matrix and we process it by current software of social network analysis. Thirdly, we design the algorithm of vehicle route prediction based on the above processing results. Finally, we use the leave-one-out approach to verify the efficiency of our algorithm. Ning Ye, Zhong-qin Wang, Reza Malekian, Ying-ya Zhang, and Ru-chuan Wang Copyright © 2015 Ning Ye et al. All rights reserved. Development of In Situ Sensors for Chlorophyll Concentration Measurement Thu, 30 Apr 2015 11:40:08 +0000 http://www.hindawi.com/journals/js/2015/903509/ Chlorophyll fluorescence measurement is a sensitive and effective method to quantify and analyze freshwater and sea water phytoplankton in situ. Major improvements in optical design, electronic technology, and calibration protocol have increased the accuracy and reliability of the fluorometer. This review briefly describes the improvement of probe design, excitation light sources, detectors, and calibrations of in situ fluorometers. Firstly, various optical designs for increasing the efficiency of fluorescence measurement are discussed. Next, the development of electronic technology to meet and improve in situ measurement, including various light sources, detectors, and corresponding measurement protocols, is described. In addition, various calibration materials, procedures, and methods are recommended for different kinds of water. The conclusion discusses key trends and future perspectives for in situ fluorescence sensors. Lihua Zeng and Daoliang Li Copyright © 2015 Lihua Zeng and Daoliang Li. All rights reserved. An Efficient Bypassing Void Routing Algorithm for Wireless Sensor Network Thu, 30 Apr 2015 11:07:00 +0000 http://www.hindawi.com/journals/js/2015/686809/ Since the sensor node’s distribution in a wireless sensor network (WSN) is irregular, geographic routing protocols using the greedy algorithm can cause local minima problem. This problem may fail due to routing voids and lead to failure of data transmission. Based on the virtual coordinate mapping, this paper proposes an efficient bypassing void routing protocol to solve the control packet overhead and transmission delay in routing void of WSN, which is called EBVRPVCM. The basic idea is to transfer the random structure of void edge to a regular one through mapping the coordinates on a virtual circle. In EBVRPVCM, some strategies, executed in different regions, are selected through virtual coordinates to bypass routing void efficiently. The regular edge is established by coordinate mapping that can shorten the average routing path length and decrease the transmission delay. The virtual coordinate mapping is not affected by the real geographic node position, and the control packet overhead can be reduced accordingly. Compared with RGP and GPSR, simulation results demonstrate that EBVRPVCM can successfully find the shortest routing path with higher delivery ratio and less control packet overhead and energy consumption. Xunli Fan and Feifei Du Copyright © 2015 Xunli Fan and Feifei Du. All rights reserved. Variable Step-Size Method Based on a Reference Separation System for Source Separation Thu, 30 Apr 2015 09:35:57 +0000 http://www.hindawi.com/journals/js/2015/964098/ Traditional variable step-size methods are effective to solve the problem of choosing step-size in adaptive blind source separation process. But the initial setting of learning rate is vital, and the convergence speed is still low. This paper proposes a novel variable step-size method based on reference separation system for online blind source separation. The correlation between the estimated source signals and original source signals increases along with iteration. Therefore, we introduce a reference separation system to approximately estimate the correlation in terms of mean square error (MSE), which is utilized to update the step-size. The use of “minibatches” for the computation of MSE can reduce the complexity of the algorithm to some extent. Moreover, simulations demonstrate that the proposed method exhibits superior convergence and better steady-state performance over the fixed step-size method in the noise-free case, while converging faster than classical variable step-size methods in both stationary and nonstationary environments. Pengcheng Xu, Zhigang Yuan, Wei Jian, and Wei Zhao Copyright © 2015 Pengcheng Xu et al. All rights reserved. A Framework for Real Time Processing of Sensor Data in the Cloud Wed, 29 Apr 2015 06:49:39 +0000 http://www.hindawi.com/journals/js/2015/468047/ We describe IoTCloud, a platform to connect smart devices to cloud services for real time data processing and control. A device connected to IoTCloud can communicate with real time data analysis frameworks deployed in the cloud via messaging. The platform design is scalable in connecting devices as well as transferring and processing data. With IoTCloud, a user can develop real time data processing algorithms in an abstract framework without concern for the underlying details of how the data is distributed and transferred. For this platform, we primarily consider real time robotics applications such as autonomous robot navigation, where there are strict requirements on processing latency and demand for scalable processing. To demonstrate the effectiveness of the system, a robotic application is developed on top of the framework. The system and the robotics application characteristics are measured to show that data processing in central servers is feasible for real time sensor applications. Supun Kamburugamuve, Leif Christiansen, and Geoffrey Fox Copyright © 2015 Supun Kamburugamuve et al. All rights reserved. Cost-Effective Location Management for Mobile Agents on the Internet Tue, 28 Apr 2015 13:13:32 +0000 http://www.hindawi.com/journals/js/2015/915648/ Many mobile agent system-related services and applications require interacting with a mobile agent by passing messages. However, an agent’s mobility raises several challenges in delivering messages to a mobile agent accurately. Consisting of tracking and message delivery phases, most mobile agent location management schemes create or receive many update messages and interaction messages to ensure the effectiveness of the schemes. In addition to downgrading the overall performance of a mobile agent location management scheme, excessive transmission of messages increases the network load. The migration locality of a mobile agent and the interaction rate between mobile agents significantly affect the performance of a mobile agent location management scheme with respect to location management cost. This work presents a novel Dual Home based Scheme (DHS) that can lower the location management costs in terms of migration locality and interaction rate. While the DHS scheme uniquely adopts dual home location management architecture, a selective update strategy based on that architecture is also designed for cost-effective location management of mobile agents. Moreover, DHS is compared with available schemes based on formulations and simulation experiments from the perspective of location management costs. Simulation results demonstrate that the proposed DHS scheme performs satisfactorily in terms of migration locality and interaction rate. Chien-Sheng Chen, Jiing-Dong Hwang, Chyuan-Der Lu, and Ting-Yuan Yeh Copyright © 2015 Chien-Sheng Chen et al. All rights reserved. A Novel Method of Adaptive Traffic Image Enhancement for Complex Environments Tue, 28 Apr 2015 07:08:42 +0000 http://www.hindawi.com/journals/js/2015/516326/ There exist two main drawbacks for traffic images in classic image enhancement methods. First is the performance degradation that occurs under frontlight, backlight, and extremely dark conditions. The second drawback is complicated manual settings, such as transform functions and multiple parameter selection mechanisms. Thus, this paper proposes an effective and adaptive parameter optimization enhancement algorithm based on adaptive brightness baseline drift (ABBD) for color traffic images under different luminance conditions. This method consists of two parts: brightness baseline model acquisition and adaptive color image compensation. The brightness baseline model can be attained by analyzing changes in light along a timeline. The adaptive color image compensation involves color space remapping and adaptive compensation specific color components. Our experiments were tested on various traffic images under frontlight, backlight, and during nighttime. The experimental results show that the proposed method achieved better effects compared with other available methods under different luminance conditions, which also effectively reduced the influence of the weather. Cao Liu, Hong Zheng, Dian Yu, and Xiaohang Xu Copyright © 2015 Cao Liu et al. All rights reserved. Study of the Effect of Damage on the Electrical Impedance of Carbon Nanotube Reinforced Epoxy Nanocomposites Mon, 27 Apr 2015 09:11:10 +0000 http://www.hindawi.com/journals/js/2015/805303/ Within the scope of this work is the study of the effect of damage on the electrical hysteretic behaviour of carbon nanotube (CNT) reinforced epoxy nanocomposites. For that purpose CNT reinforced epoxy nanocomposites were subjected to different levels of damage and their response to an AC voltage excitation was monitored. The correlation between frequency dependent impedance properties and level of damage was extensively studied. The AC frequency response of the interrogated specimens from 10 Hz up to 0.5 MHz revealed a strong correlation between the level of damage and the hysteresis of the studied materials. Dimitrios G. Bekas and Alkiviadis S. Paipetis Copyright © 2015 Dimitrios G. Bekas and Alkiviadis S. Paipetis. All rights reserved. Energy Analysis of Contention Tree-Based Access Protocols in Dense Machine-to-Machine Area Networks Wed, 22 Apr 2015 14:05:16 +0000 http://www.hindawi.com/journals/js/2015/685164/ Machine-to-Machine (M2M) area networks aim at connecting an M2M gateway with a large number of energy-constrained devices that must operate autonomously for years. Therefore, attaining high energy efficiency is essential in the deployment of M2M networks. In this paper, we consider a dense M2M area network composed of hundreds or thousands of devices that periodically transmit data upon request from a gateway or coordinator. We theoretically analyse the devices’ energy consumption using two Medium Access Control (MAC) protocols which are based on a tree-splitting algorithm to resolve collisions among devices: the Contention Tree Algorithm (CTA) and the Distributed Queuing (DQ) access. We have carried out computer-based simulations to validate the accuracy of the theoretical models and to compare the energy performance using DQ, CTA, and Frame Slotted-ALOHA (FSA) in M2M area networks with devices in compliance with the IEEE 802.15.4 physical layer. Results show that the performance of DQ is totally independent of the number of contending devices, and it can reduce the energy consumed per device in more than 35% with respect to CTA and in more than 80% with respect to FSA. Francisco Vázquez-Gallego, Luis Alonso, and Jesus Alonso-Zarate Copyright © 2015 Francisco Vázquez-Gallego et al. All rights reserved. Lifetime Optimization of a Multiple Sink Wireless Sensor Network through Energy Balancing Sun, 19 Apr 2015 09:58:31 +0000 http://www.hindawi.com/journals/js/2015/921250/ The wireless sensor network consists of small limited energy sensors which are connected to one or more sinks. The maximum energy consumption takes place in communicating the data from the nodes to the sink. Multiple sink WSN has an edge over the single sink WSN where very less energy is utilized in sending the data to the sink, as the number of hops is reduced. If the energy consumed by a node is balanced between the other nodes, the lifetime of the network is considerably increased. The network lifetime optimization is achieved by restructuring the network by modifying the neighbor nodes of a sink. Only those nodes are connected to a sink which makes the total energy of the sink less than the threshold. This energy balancing through network restructuring optimizes the network lifetime. This paper depicts this fact through simulations done in MATLAB. Tapan Kumar Jain, Davinder Singh Saini, and Sunil Vidya Bhooshan Copyright © 2015 Tapan Kumar Jain et al. All rights reserved. Efficient Multiway Relaying for Data Sharing in Energy Harvesting Sensor Networks Wed, 15 Apr 2015 13:08:12 +0000 http://www.hindawi.com/journals/js/2015/285056/ In a wireless sensor network (WSN), sensors often need to share their measurements for applications like distributed estimation and detection or data aggregation. Here, we suggest using multiway relaying (MWR) for data sharing between energy harvesting sensors that cannot directly communicate with each other. We first start by studying the achievable data rate of amplify-and-forward (AF) MWR for energy harvesting sensors. Then, we show that, by backing off the transmit power at the sensors, not only better energy efficiency and longer lifetime are achieved, but also the data sharing rate increases. Based on this result, we further improve the performance of AF MWR in the assumed WSN by smartly adjusting the transmit power at the sensors. Our power allocation is devised in a way to improve the energy efficiency of MWR and increase the sum rate of data sharing between the sensors over the network lifetime. Simulation results are presented to verify the enhancement achieved by using our proposed power allocation technique. Moslem Noori and Masoud Ardakani Copyright © 2015 Moslem Noori and Masoud Ardakani. All rights reserved. Locomotion Strategy Selection for a Hybrid Mobile Robot Using Time of Flight Depth Sensor Wed, 15 Apr 2015 11:38:55 +0000 http://www.hindawi.com/journals/js/2015/425732/ The performance of a mobile robot can be improved by utilizing different locomotion modes in various terrain conditions. This creates the necessity of having a supervisory controller capable of recognizing different terrain types and changing the locomotion mode of the robot accordingly. This work focuses on the locomotion strategy selection problem for a hybrid legged wheeled mobile robot. Supervisory control of the robot is accomplished by the terrain recognizer, which classifies depth images obtained from a commercial time of flight depth sensor and selects different locomotion mode subcontrollers based on the recognized terrain type. For the terrain recognizer, a database is generated consisting of five terrain classes (Uneven, Level Ground, Stair Up, Stair Down, and Nontraversable). Depth images are enhanced using confidence map based filtering. The accuracy of the terrain classification using Support Vector Machine classifier for the testing database in five-class terrain recognition problem is 97%. Real-world experiments assess the locomotion abilities of the quadruped and the capability of the terrain recognizer in real-time settings. The results of these experiments show depth images processed in real time using machine learning algorithms can be used for the supervisory control of hybrid robots with legged and wheeled locomotion capabilities. Artur Saudabayev, Farabi Kungozhin, Damir Nurseitov, and Huseyin Atakan Varol Copyright © 2015 Artur Saudabayev et al. All rights reserved. Fabrication of Porous Silicon Based Humidity Sensing Elements on Paper Thu, 09 Apr 2015 07:34:07 +0000 http://www.hindawi.com/journals/js/2015/927396/ A roll-to-roll compatible fabrication process of porous silicon (pSi) based sensing elements for a real-time humidity monitoring is described. The sensing elements, consisting of printed interdigitated silver electrodes and a spray-coated pSi layer, were fabricated on a coated paper substrate by a two-step process. Capacitive and resistive responses of the sensing elements were examined under different concentrations of humidity. More than a three orders of magnitude reproducible decrease in resistance was measured when the relative humidity (RH) was increased from 0% to 90%. A relatively fast recovery without the need of any refreshing methods was observed with a change in RH. Humidity background signal and hysteresis arising from the paper substrate were dependent on the thickness of sensing pSi layer. Hysteresis in most optimal sensing element setup (a thick pSi layer) was still noticeable but not detrimental for the sensing. In addition to electrical characterization of sensing elements, thermal degradation and moisture adsorption properties of the paper substrate were examined in connection to the fabrication process of the silver electrodes and the moisture sensitivity of the paper. The results pave the way towards the development of low-cost humidity sensors which could be utilized, for example, in smart packaging applications or in smart cities to monitor the environment. Tero Jalkanen, Anni Määttänen, Ermei Mäkilä, Jaani Tuura, Martti Kaasalainen, Vesa-Pekka Lehto, Petri Ihalainen, Jouko Peltonen, and Jarno Salonen Copyright © 2015 Tero Jalkanen et al. All rights reserved. Optimization of an Accelerometer and Gyroscope-Based Fall Detection Algorithm Thu, 09 Apr 2015 06:40:33 +0000 http://www.hindawi.com/journals/js/2015/452078/ Falling is a common and significant cause of injury in elderly adults (>65 yrs old), often leading to disability and death. In the USA, one in three of the elderly suffers from fall injuries annually. This study’s purpose is to develop, optimize, and assess the efficacy of a falls detection algorithm based upon a wireless, wearable sensor system (WSS) comprised of a 3-axis accelerometer and gyroscope. For this study, the WSS is placed at the chest center to collect real-time motion data of various simulated daily activities (i.e., walking, running, stepping, and falling). Tests were conducted on 36 human subjects with a total of 702 different movements collected in a laboratory setting. Half of the dataset was used for development of the fall detection algorithm including investigations of critical sensor thresholds and the remaining dataset was used for assessment of algorithm sensitivity and specificity. Experimental results show that the algorithm detects falls compared to other daily movements with a sensitivity and specificity of 96.3% and 96.2%, respectively. The addition of gyroscope information enhances sensitivity dramatically from results in the literature as angular velocity changes provide further delineation of a fall event from other activities that may also experience high acceleration peaks. Quoc T. Huynh, Uyen D. Nguyen, Lucia B. Irazabal, Nazanin Ghassemian, and Binh Q. Tran Copyright © 2015 Quoc T. Huynh et al. All rights reserved.