Journal of Sensors The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Sensors Technologies and Methods for Perception Systems in Intelligent Vehicles Tue, 19 Jul 2016 13:32:20 +0000 Yassine Ruichek, Fadi Dornaika, and Maan El Badaoui El Najjar Copyright © 2016 Yassine Ruichek et al. All rights reserved. Sensors for Environmental Monitoring Tue, 19 Jul 2016 09:06:47 +0000 Liling Fu, Panagiotis Dallas, Virender K. Sharma, and Kewei Zhang Copyright © 2016 Liling Fu et al. All rights reserved. A Gyro Signal Characteristics Analysis Method Based on Empirical Mode Decomposition Mon, 18 Jul 2016 16:31:23 +0000 It is difficult to analyze the nonstationary gyro signal in detail for the Allan variance (AV) analysis method. A novel approach in the time-frequency domain for gyro signal characteristics analysis is proposed based on the empirical mode decomposition and Allan variance (EMDAV). The output signal of gyro is decomposed by empirical mode decomposition (EMD) first, and then the decomposed signal is analyzed by AV algorithm. Consequently, the gyro noise characteristics are demonstrated in the time-frequency domain with a three-dimensional (3D) manner. Practical data of fiber optic gyro (FOG) and MEMS gyro are processed by the AV method and the EMDAV algorithm separately. The results indicate that the details of gyro signal characteristics in different frequency bands can be described with the help of EMDAV, and the analysis dimensions are extended compared with the common AV. The proposed EMDAV, as a complementary tool of the AV, which provides a theoretical reference for the gyro signal preprocessing, is a general approach for the analysis and evaluation of gyro performance. Qinghua Zeng, Shanshan Gu, Jianye Liu, Sheng Liu, and Weina Chen Copyright © 2016 Qinghua Zeng et al. All rights reserved. Analysis and Implementation of Noncontact Level Sensing for a Pressurized Cylinder Mon, 18 Jul 2016 12:51:27 +0000 Fluid level detection for a sealed and pressurized mobile container is very useful for the provider to schedule the delivery of a new one before it runs out of the liquid. This study suggested using the frequencies of tone generated by knocking on the outside surface of the container to detect the liquid level inside. A detailed model based on Euler-Bernoulli beam theory has been proposed to study the feasibility of this method for a cylinder with complicated but practical structure. Household gas cylinders were used to validate the proposed model and the results show that experimental data agree well with the theoretical analysis. The results indicate that the proposed model can accurately explain the behavior of the vibratory frequencies under different liquid levels. An apparatus has been successfully implemented to automatically sense the near empty condition of the gas cylinder. Hsien-Huang P. Wu, Chung-Wen Hung, Shih-Hsin Chang, and Zong-Hao Yang Copyright © 2016 Hsien-Huang P. Wu et al. All rights reserved. Vision-Based Autonomous Underwater Vehicle Navigation in Poor Visibility Conditions Using a Model-Free Robust Control Mon, 18 Jul 2016 09:42:01 +0000 This paper presents a vision-based navigation system for an autonomous underwater vehicle in semistructured environments with poor visibility. In terrestrial and aerial applications, the use of visual systems mounted in robotic platforms as a control sensor feedback is commonplace. However, robotic vision-based tasks for underwater applications are still not widely considered as the images captured in this type of environments tend to be blurred and/or color depleted. To tackle this problem, we have adapted the color space to identify features of interest in underwater images even in extreme visibility conditions. To guarantee the stability of the vehicle at all times, a model-free robust control is used. We have validated the performance of our visual navigation system in real environments showing the feasibility of our approach. Ricardo Pérez-Alcocer, L. Abril Torres-Méndez, Ernesto Olguín-Díaz, and A. Alejandro Maldonado-Ramírez Copyright © 2016 Ricardo Pérez-Alcocer et al. All rights reserved. System for Malicious Node Detection in IPv6-Based Wireless Sensor Networks Mon, 18 Jul 2016 08:16:48 +0000 The trend of implementing the IPv6 into wireless sensor networks (WSNs) has recently occurred as a consequence of a tendency of their integration with other types of IP-based networks. The paper deals with the security aspects of these IPv6-based WSNs. A brief analysis of security threats and attacks which are present in the IPv6-based WSN is given. The solution to an adaptive distributed system for malicious node detection in the IPv6-based WSN is proposed. The proposed intrusion detection system is based on distributed algorithms and a collective decision-making process. It introduces an innovative concept of probability estimation for malicious behaviour of sensor nodes. The proposed system is implemented and tested through several different scenarios in three different network topologies. Finally, the performed analysis showed that the proposed system is energy efficient and has a good capability to detect malicious nodes. Kresimir Grgic, Drago Zagar, and Visnja Krizanovic Cik Copyright © 2016 Kresimir Grgic et al. All rights reserved. A Novel Dynamic Measurement System for Evaluating the Braking Coordination of Articulated Vehicles Sun, 17 Jul 2016 14:25:16 +0000 The braking coordination between tractor and semitrailer is vital to the safety of articulated vehicles. Traditional evaluation about braking coordination is based on the pressure measurement along air braking pipeline, which needs to change original braking structure to install gauges and cannot directly reflect the final braking coordination of different wheels. To overcome these limitations, this paper proposes a novel dynamic measurement system for evaluating the braking coordination of articulated vehicles. During the brake test, all wheel velocities of the whole articulated vehicle are synchronously obtained through a specially designed distributed acquisition platform. To effectively eliminate gross errors and noises in wheel angular velocity data, a 3-order autoregressive (AR) model and an improved-thresholding wavelet filtering algorithm are developed. Further, a novel direct evaluation method about braking coordination is proposed according to the differences in angular velocity dropping time of all wheels. Finally, the overall system is assessed through real field tests. The results validate the feasibility and effectiveness of the proposed system. Xu Li, Wei Chen, and Qimin Xu Copyright © 2016 Xu Li et al. All rights reserved. Adaptive Cross-Layer Multipath Routing Protocol for Mobile Ad Hoc Networks Sun, 17 Jul 2016 06:52:43 +0000 Mobile ad hoc networks (MANETs) are generally created for temporary scenarios. In such scenarios, where nodes are in mobility, efficient routing is a challenging task. In this paper, we propose an adaptive and cross-layer multipath routing protocol for such changing scenarios. Our routing mechanisms operate keeping in view the type of applications. For simple applications, the proposed protocol is inspired from traditional on-demand routing protocols by searching shortest routes from source to destination using default parameters. In case of multimedia applications, the proposed mechanism considers such routes which are capable of providing more data rates having less packet loss ratio. For those applications which need security, the proposed mechanism searches such routes which are more secure in nature as compared to others. Cross-layer methodology is used in proposed routing scheme so as to exchange different parameters across the protocol stack for better decision-making at network layer. Our approach is efficient and fault tolerant in a variety of scenarios that we simulated and tested. Zeeshan Iqbal, S. Khan, Amjad Mehmood, Jaime Lloret, and Nabil Ali Alrajeh Copyright © 2016 Zeeshan Iqbal et al. All rights reserved. Measurement of Prestressing Force in Pretensioned UHPC Deck Using a Fiber Optic FBG Sensor Embedded in a 7-Wire Strand Thu, 14 Jul 2016 07:05:59 +0000 This paper presents the results of the performance test and long-term monitoring of the prestressing force inside concrete performed on a pretensioned Ultra-High Performance Concrete (UHPC) deck. The force is measured by applying a 7-wire strand embedded with an FBG (Fiber Bragg Grating) sensor. The performance test was conducted on a 3.7 m × 1.8 m pretensioned deck specimen through wheel loading tests to verify the applicability of the measurement method. In addition, a 12.3 m long and 4.8 m wide bridge with a pretensioned UHPC deck was erected and long-term monitoring was conducted over three years to verify the applicability of the method to real bridges. The effectiveness of the measurement method of the prestressing force inside concrete is verified, and the long-term monitoring data are used to investigate various temperature compensation methods. The results show that the proposed method enables effective measurement of small changes in the prestressing force inside the concrete. These changes are caused by the external forces acting on the bridge in service and provide sufficient durability for long-term sensing. The analysis of the prestressing force obtained through long-term monitoring reveals the necessity of conducting temperature compensation for the consistency of the data acquired using the FBG sensor. Moreover, the selection of the thermal expansion coefficient appears also to be of critical importance for temperature compensation. Jae-min Kim, Hyun-woo Kim, Song-yi Choi, and Sung-yong Park Copyright © 2016 Jae-min Kim et al. All rights reserved. Edge Detection from RGB-D Image Based on Structured Forests Thu, 14 Jul 2016 06:56:14 +0000 This paper looks into the fundamental problem in computer vision: edge detection. We propose a new edge detector using structured random forests as the classifier, which can make full use of RGB-D image information from Kinect. Before classification, the adaptive bilateral filter is used for the denoising processing of the depth image. As data sources, information of 13 channels from RGB-D image is computed. In order to train the random forest classifier, the approximation measurement of the information gain is used. All the structured labels at a given node are mapped to a discrete set of labels using the Principal Component Analysis (PCA) method. NYUD2 dataset is used to train our structured random forests. The random forest algorithm is used to classify the RGB-D image information for extracting the edge of the image. In addition to the proposed methodology, the quantitative comparisons of different algorithms are presented. The results of the experiments demonstrate the significant improvements of our algorithm over the state of the art. Heng Zhang, Zhenqiang Wen, Yanli Liu, and Gang Xu Copyright © 2016 Heng Zhang et al. All rights reserved. Evaluation of the Degradation on a COTS Linear CCD Induced by Total Ionizing Dose Radiation Damage Tue, 12 Jul 2016 11:34:01 +0000 The evaluation of the degradation on a COTS linear Charge Coupled Device (CCD) induced by total ionizing dose (TID) radiation damage was presented. The radiation experiments were carried out at a 60Co γ-ray source. The parameters of DALSA’s linear CCD were measured at the CCD test systems as the EMVA1288 standard before and after the radiation. The dark current, dark signal nonuniformity (DSNU), photo response nonuniformity (PRNU), saturation output, full-well capacity (FWC), quantum efficiency (QE), and responsivity versus the TID were analyzed. The behavior of the tested CCD had shown a remarkable degradation after radiation. The degradation mechanisms of the CCD induced by TID damage were also discussed. Zujun Wang, Baoping He, Wuying Ma, Zhibin Yao, Shaoyan Huang, Minbo Liu, and Jiangkun Sheng Copyright © 2016 Zujun Wang et al. All rights reserved. Object-Based Distinction between Building Shadow and Water in High-Resolution Imagery Using Fuzzy-Rule Classification and Artificial Bee Colony Optimization Mon, 11 Jul 2016 09:29:04 +0000 Due to the high similarity of the spectra of urban water and building shadows, high-resolution satellite imagery often confuses and wrongly classifies these features. To address this problem, we propose an object-based method for distinguishing building shadow from water using an artificial bee colony algorithm. In the method, four spectral ratio bands are first calculated as additional input parameters for improving the accuracy of segmentation results. During the segmentation, a series of statistical factors, such as spectrum, ratio, and sharp features, are calculated to make up for defects in the high-resolution imagery. Finally, we propose a fuzzy-rule-based classifier to generate extraction rules. The classifier is based on artificial bee colony optimization, which employs the geometric mean (-mean) as fitness function. The proposed method was carried out on two test sites in Xiamen City. The experimental results based on GF-1 satellite date show that, compared with SVM method, the proposed method improved the overall accuracy of extraction by approximately 6% to 15% and the kappa coefficient values by approximately 0.1 to 0.2. The analysis of the extraction rules also proves that the red/NIR band and the length-width ratio band are significantly influenced by the distinction between building shadow and water. Yuanrong He, Xinxin Zhang, and Lizhong Hua Copyright © 2016 Yuanrong He et al. All rights reserved. Sink-to-Sink Coordination Framework Using RPL: Routing Protocol for Low Power and Lossy Networks Sun, 10 Jul 2016 06:34:55 +0000 RPL (Routing Protocol for low power and Lossy networks) is recommended by Internet Engineering Task Force (IETF) for IPv6-based LLNs (Low Power and Lossy Networks). RPL uses a proactive routing approach and each node always maintains an active path to the sink node. Sink-to-sink coordination defines syntax and semantics for the exchange of any network defined parameters among sink nodes like network size, traffic load, mobility of a sink, and so forth. The coordination allows sink to learn about the network condition of neighboring sinks. As a result, sinks can make coordinated decision to increase/decrease their network size for optimizing over all network performance in terms of load sharing, increasing network lifetime, and lowering end-to-end latency of communication. Currently, RPL does not provide any coordination framework that can define message exchange between different sink nodes for enhancing the network performance. In this paper, a sink-to-sink coordination framework is proposed which utilizes the periodic route maintenance messages issued by RPL to exchange network status observed at a sink with its neighboring sinks. The proposed framework distributes network load among sink nodes for achieving higher throughputs and longer network’s life time. Meer M. Khan, M. Ali Lodhi, Abdul Rehman, Abid Khan, and Faisal Bashir Hussain Copyright © 2016 Meer M. Khan et al. All rights reserved. FastSLAM Using Compressed Occupancy Grids Tue, 05 Jul 2016 11:58:31 +0000 Robotic vehicles working in unknown environments require the ability to determine their location while learning about obstacles located around them. In this paper a method of solving the SLAM problem that makes use of compressed occupancy grids is presented. The presented approach is an extension of the FastSLAM algorithm which stores a compressed form of the occupancy grid to reduce the amount of memory required to store the set of occupancy grids maintained by the particle filter. The performance of the algorithm is presented using experimental results obtained using a small inexpensive ground vehicle equipped with LiDAR, compass, and downward facing camera that provides the vehicle with visual odometry measurements. The presented results demonstrate that although with our approach the occupancy grid maintained by each particle uses only of the data needed to store the uncompressed occupancy grid, we can still achieve almost identical results to the approach where each particle filter stores the full occupancy grid. Christopher Cain and Alexander Leonessa Copyright © 2016 Christopher Cain and Alexander Leonessa. All rights reserved. Design and Evaluation of a Fiber-Optic Grip Force Sensor with Compliant 3D-Printable Structure for (f)MRI Applications Mon, 04 Jul 2016 12:26:48 +0000 Grip force sensors compatible with magnetic resonance imaging (MRI) are used in human motor control and decision-making research, providing objective and sensitive behavioral outcome measures. Commercial sensors are expensive, cover limited force ranges, rely on pneumatic force transmission that cannot detect fast force changes, or are electrically active, which increases the risk of electromagnetic interference. We present the design and evaluation of a low-cost, 3D-printed, inherently MRI-compatible grip force sensor based on a commercial intensity-based fiber-optic sensor. A compliant monobloc structure with flexible hinges transduces grip force to a linear displacement captured by the fiber-optic sensor. The structure can easily be adapted for different force ranges by changing the hinge thickness. A prototype designed for forces up to 800 N was manufactured and showed a highly linear behavior (nonlinearity of 2.37%) and an accuracy of 1.57% in a range between zero and 500 N. It can be printed and assembled within one day and for less than $300. Accurate performance was confirmed, both inside and outside a 3 T MRI scanner within a pilot study. Given its simple design allowing for customization of sensing properties and ergonomics for different applications and requirements, the proposed grip force handle offers researchers a valuable scientific tool. Tobias L. Bützer, Mike D. Rinderknecht, Gunda H. Johannes, Werner L. Popp, Rea Lehner, Olivier Lambercy, and Roger Gassert Copyright © 2016 Tobias L. Bützer et al. All rights reserved. Security Analysis and Improvements of Session Key Establishment for Clustered Sensor Networks Thu, 30 Jun 2016 08:18:16 +0000 WSN (wireless sensor network) is one of the main technologies in IoT (Internet of Things) applications or services. To date, several schemes have been proposed to establish a pair-wise key between two nodes in WSN, and most of them are designed to establish long-term keys used throughout the network lifetime. However, in the near future, if WSN will be used for information infrastructures in various fields such as manufacturing, distribution, or public facilities management and its life cycle can be as long as that of other common networks, it will definitely be advantageous in terms of security to encrypt messages using session keys instead of long-term keys. In this paper, we propose a session key establishment scheme for clustered sensor networks that is based on elliptic curve Diffie-Hellman (ECDH) key exchange and hash chain. The proposed scheme eliminates vulnerabilities of existing schemes for WSN and has improved security. The proposed scheme is efficient in terms of energy costs compared to related schemes. Jiye Kim, Jongho Moon, Jaewook Jung, and Dongho Won Copyright © 2016 Jiye Kim et al. All rights reserved. Investigation on a Novel Capacitive Electrode for Geophysical Surveys Wed, 29 Jun 2016 12:51:04 +0000 Nonpolarizable electrodes are applied widely in the electric field measurement for geophysical surveys. However, there are two major problems: (1) systematic errors caused by poor electrical contact in the high resistive terrains and (2) environmental damage associated with using nonpolarizable electrodes. A new alternative structure of capacitive electrode, which is capable of sensing surface potential through weak capacitive coupling, is presented to solve the above problems. A technique is introduced to neutralize distributed capacitance and input capacitance of the detection circuit. With the capacitance neutralization technique, the transmission coefficient of capacitive electrode remains stable when environmental conditions change. The simulation and field test results indicate that the new capacitive electrode has an operating bandwidth range from 0.1 Hz to 1 kHz. The capacitive electrodes have a good prospect of the applications in geophysical prospecting, especially in resistive terrains. Zhiyu Wang, Shun Wang, Guangyou Fang, and Qunying Zhang Copyright © 2016 Zhiyu Wang et al. All rights reserved. An Algorithmic Approach to Wireless Sensor Networks Localization Using Rigid Graphs Wed, 29 Jun 2016 11:11:46 +0000 In this work estimating the position coordinates of Wireless Sensor Network nodes using the concept of rigid graphs is carried out in detail. The range based localization approaches use the distance information measured by the RSSI, which is prone to noise, due to effects of path loss, shadowing, and so forth. In this work, both the distance and the bearing information are used for localization using the trilateration technique. Rigid graph theory is employed to analyze the localizability, that is, whether the nodes of the WSN are uniquely localized. The WSN graph is divided into rigid patches by varying appropriately the communication power range of the WSN nodes and then localizing the patches by trilateration. The main advantage of localizing the network using rigid graph approach is that it overcomes the effect of noisy perturbed distance. Our approach gives a better performance compared to robust quads in terms of percentage of localizable nodes and computational complexity. Shamantha Rai B and Shirshu Varma Copyright © 2016 Shamantha Rai B and Shirshu Varma. All rights reserved. Handwriting Recognition in Free Space Using WIMU-Based Hand Motion Analysis Wed, 29 Jun 2016 11:05:14 +0000 We present a wireless-inertial-measurement-unit- (WIMU-) based hand motion analysis technique for handwriting recognition in three-dimensional (3D) space. The proposed handwriting recognition system is not bounded by any limitations or constraints; users have the freedom and flexibility to write characters in free space. It uses hand motion analysis to segment hand motion data from a WIMU device that incorporates magnetic, angular rate, and gravity sensors (MARG) and a sensor fusion algorithm to automatically distinguish segments that represent handwriting from nonhandwriting data in continuous hand motion data. Dynamic time warping (DTW) recognition algorithm is used to recognize handwriting in real-time. We demonstrate that a user can freely write in air using an intuitive WIMU as an input and hand motion analysis device to recognize the handwriting in 3D space. The experimental results for recognizing handwriting in free space show that the proposed method is effective and efficient for other natural interaction techniques, such as in computer games and real-time hand gesture recognition applications. Shashidhar Patil, Dubeom Kim, Seongsill Park, and Youngho Chai Copyright © 2016 Shashidhar Patil et al. All rights reserved. Computer Vision-Based Portable System for Nitroaromatics Discrimination Wed, 29 Jun 2016 09:49:31 +0000 A computer vision-based portable measurement system is presented in this report. The system is based on a compact reader unit composed of a microcamera and a Raspberry Pi board as control unit. This reader can acquire and process images of a sensor array formed by four nonselective sensing chemistries. Processing these array images it is possible to identify and quantify eight different nitroaromatic compounds (both explosives and related compounds) by using chromatic coordinates of a color space. The system is also capable of sending the obtained information after the processing by a WiFi link to a smartphone in order to present the analysis result to the final user. The identification and quantification algorithm programmed in the Raspberry board is easy and quick enough to allow real time analysis. Nitroaromatic compounds analyzed in the range of mg/L were picric acid, 2,4-dinitrotoluene (2,4-DNT), 1,3-dinitrobenzene (1,3-DNB), 3,5-dinitrobenzonitrile (3,5-DNBN), 2-chloro-3,5-dinitrobenzotrifluoride (2-C-3,5-DNBF), 1,3,5-trinitrobenzene (TNB), 2,4,6-trinitrotoluene (TNT), and tetryl (TT). Nuria López-Ruiz, Miguel M. Erenas, Ignacio de Orbe-Payá, Luis F. Capitán-Vallvey, Alberto J. Palma, and Antonio Martínez-Olmos Copyright © 2016 Nuria López-Ruiz et al. All rights reserved. Test Verification and Application of a Longitudinal Temperature Force Testing Method for Long Seamless Rails Using FBG Strain Sensor Wed, 29 Jun 2016 09:21:41 +0000 In order to evaluate the health status of continuous welded rail accurately, a deduction on the FBG sensing principle has been made with regard to the temperature variation of test specimens under different constraint conditions. A long seamless rail testing solution and its on-site application are designed based on this deduction. According to the verification experiments of sensing principle inside, the effect of the reference temperature on the FBG temperature and strain sensitivity coefficient within −30°C~30°C is not higher than 0.05%; the maximum relative error of single point between the tested and theoretical results of test specimen under constrained condition is 3.2%; and the maximum relative error of slopes of fitted straight lines based on the tested and theoretical results within the entire test temperature range is 2.3%, verifying the deduced FBG sensing principle with regard to the test specimen under constrained condition. The maximum error of the longitudinal temperature force between the on-site tested results and calculated results in long seamless rails is only 6.1 kN, the corresponding rail temperature variation is 0.3°C, and the accumulated error is controllable within 5%. Ping Wang, Kaize Xie, Rong Chen, Liyang Shao, Lianshan Yan, Hao Liu, and Meng Zhang Copyright © 2016 Ping Wang et al. All rights reserved. RESH: A Secure Authentication Algorithm Based on Regeneration Encoding Self-Healing Technology in WSN Wed, 29 Jun 2016 09:21:34 +0000 In the real application environment of wireless sensor networks (WSNs), the uncertain factor of data storage makes the authentication information be easily forged and destroyed by illegal attackers. As a result, it is hard for secure managers to conduct forensics on transmitted information in WSN. This work considers the regeneration encoding self-healing and secret sharing techniques and proposes an effective scheme to authenticate data in WSN. The data is encoded by regeneration codes and then distributed to other redundant nodes in the form of fragments. When the network is attacked, the scheme has the ability against tampering attack or collusion attack. Furthermore, the damaged fragments can be restored as well. Parts of fragments, encoded by regeneration code, are required for secure authentication of the original distributed data. Experimental results show that the proposed scheme reduces hardware communication overhead by five percent in comparison. Additionally, the performance of local recovery achieves ninety percent. Wei Liang, Zhiqiang Ruan, Yuntao Wang, and Xiaoyan Chen Copyright © 2016 Wei Liang et al. All rights reserved. Numerical Study on Mass Sensitivity of Magnetoelastic Biosensors with Concentrated Mass Load under Different Resonance Modes Tue, 28 Jun 2016 06:18:56 +0000 Magnetoelastic biosensors are an important type of resonant mode based mass-sensing device, for which mass sensitivity is a critical parameter to evaluate their performance. In this work, the effect of concentrated mass position on mass sensitivity () of a magnetoelastic sensor under different resonance modes was theoretically studied. The effect of magnitude of loading mass on mass sensitivity for the first resonance mode was also studied. The results indicated that mass sensitivity as the function of loading position for all resonance modes was consistent with the law of function . By comparing the mass sensitivity for the sensor attached with concentrated mass and uniform mass, it was found that mass sensitivity was linearly proportional to the sum of the squares of the displacement of each loading point. For the first resonance mode, when the loading position satisfied or , mass sensitivity decreased with loading mass increasing. The opposite trend was observed when or . When the concentrated mass was loaded at the nodal point (i.e., ), mass sensitivity was always zero no matter how the loading mass changed. Kewei Zhang and Yuesheng Chai Copyright © 2016 Kewei Zhang and Yuesheng Chai. All rights reserved. Study of Wireless Authentication Center with Mixed Encryption in WSN Mon, 27 Jun 2016 14:27:04 +0000 WSN (wireless sensor network) has been used in a wide range of applications nowadays. Sensor networks may often relay critical data; thus, security must be a high priority. However, due to their limited computational, energy, and storage resources, sensor nodes are vulnerable to attack. So how to protect sensor nodes from attacks without raising computational capability and energy consumption is a worthwhile issue. A WAC (wireless authentication center) with mixed encryption named “MEWAC” is proposed. MEWAC is based on MCU (Microcontroller Unit) and WiFi (Wireless Fidelity) module and uses RSA, AES (Advanced Encryption Standard), and SHA-1 (Secure Hash Algorithm 1) to provide high performance authentication and data encryption services for sensor nodes. The experimental results show that MEWAC has the advantages of low cost, low power consumption, good performance, and stability; moreover, the authentication protocol improves the security of WSN and reduces the overhead in node authentication. Yiqin Lu, Jing Zhai, Ronghuan Zhu, and Jiancheng Qin Copyright © 2016 Yiqin Lu et al. All rights reserved. Multilevel Modeling of Distributed Denial of Service Attacks in Wireless Sensor Networks Mon, 27 Jun 2016 14:19:31 +0000 The growing popularity of wireless sensor networks increases the risk of security attacks. One of the most common and dangerous types of attack that takes place these days in any electronic society is a distributed denial of service attack. Due to the resource constraint nature of mobile sensors, DDoS attacks have become a major threat to its stability. In this paper, we established a model of a structural health monitoring network, being disturbed by one of the most common types of DDoS attacks, the flooding attack. Through a set of simulations, we explore the scope of flood-based DDoS attack problem, assessing the performance and the lifetime of the network under the attack condition. To conduct our research, we utilized the Quality of Protection Modeling Language. With the proposed approach, it was possible to examine numerous network configurations, parameters, attack options, and scenarios. The results of the carefully performed multilevel analysis allowed us to identify a new kind of DDoS attack, the delayed distributed denial of service, by the authors, referred to as DDDoS attack. Multilevel approach to DDoS attack analysis confirmed that, examining endangered environments, it is significant to take into account many characteristics at once, just to not overlook any important aspect. Katarzyna Mazur, Bogdan Ksiezopolski, and Radoslaw Nielek Copyright © 2016 Katarzyna Mazur et al. All rights reserved. Enhancing Energy Efficiency of Wireless Sensor Network through the Design of Energy Efficient Routing Protocol Sun, 26 Jun 2016 09:04:40 +0000 Wireless Sensor Network (WSN) is known to be a highly resource constrained class of network where energy consumption is one of the prime concerns. In this research, a cross layer design methodology was adopted to design an energy efficient routing protocol entitled “Position Responsive Routing Protocol” (PRRP). PRRP is designed to minimize energy consumed in each node by (1) reducing the amount of time in which a sensor node is in an idle listening state and (2) reducing the average communication distance over the network. The performance of the proposed PRRP was critically evaluated in the context of network lifetime, throughput, and energy consumption of the network per individual basis and per data packet basis. The research results were analyzed and benchmarked against the well-known LEACH and CELRP protocols. The outcomes show a significant improvement in the WSN in terms of energy efficiency and the overall performance of WSN. Noor Zaman, Low Tang Jung, and Muhammad Mehboob Yasin Copyright © 2016 Noor Zaman et al. All rights reserved. Research on the Calibration Method of Micro Inertial Measurement Unit for Engineering Application Thu, 23 Jun 2016 14:58:40 +0000 With rapid development of micro fabrication technology, the production level of micro inertial devices has increased, which promoted the performance improvement of Micro Inertial Measurement Unit (MIMU). Measurement precision of MIMU is one of the most significant indexes, especially for the application of the guided spinning projectiles. In order to improve the measurement precision of MIMU, this paper presents a novel calibration method. The calibration model is established and the derivation for parameters estimation has been introduced. By the multirate tests and multiposition tests, all the parameters in the calibration model can be well estimated. Verification experiment shows that the proposed method has the same compensation effect as the traditional method, but it can alleviate the computing burden for the system. Thus the proposed method will have a wide application prospect for the future engineering calibration. Yun Xu, Yu Wang, Yan Su, and Xinhua Zhu Copyright © 2016 Yun Xu et al. All rights reserved. Exploiting Performance of Different Low-Cost Sensors for Small Amplitude Oscillatory Motion Monitoring: Preliminary Comparisons in View of Possible Integration Tue, 21 Jun 2016 15:06:05 +0000 We address the problem of low amplitude oscillatory motion detection through different low-cost sensors: a LIS3LV02DQ MEMS accelerometer, a Microsoft Kinect v2 range camera, and a uBlox 6 GPS receiver. Several tests were performed using a one-direction vibrating table with different oscillation frequencies (in the range 1.5–3 Hz) and small challenging amplitudes (0.02 m and 0.03 m). A Mikrotron EoSens high-resolution camera was used to give reference data. A dedicated software tool was developed to retrieve Kinect v2 results. The capabilities of the VADASE algorithm were employed to process uBlox 6 GPS receiver observations. In the investigated time interval (in the order of tens of seconds) the results obtained indicate that displacements were detected with the resolution of fractions of millimeters with MEMS accelerometer and Kinect v2 and few millimeters with uBlox 6. MEMS accelerometer displays the lowest noise but a significant bias, whereas Kinect v2 and uBlox 6 appear more stable. The results suggest the possibility of sensor integration both for indoor (MEMS accelerometer + Kinect v2) and for outdoor (MEMS accelerometer + uBlox 6) applications and seem promising for structural monitoring applications. Elisa Benedetti, Roberta Ravanelli, Monica Moroni, Andrea Nascetti, and Mattia Crespi Copyright © 2016 Elisa Benedetti et al. All rights reserved. Design and Fabrication of Air-Based 1-3 Piezoelectric Composite Transducer for Air-Coupled Ultrasonic Applications Mon, 20 Jun 2016 15:07:22 +0000 The air-based 1-3 piezoelectric composite transducers are designed and fabricated in order to solve the acoustic impedance matching problem. Firstly, a finite element model using honeycomb structure as the piezoelectric composite matrix is built to reduce the acoustic impedance of the sensitive element. Three important factors, volume fraction of piezoelectric materials , the thickness , and the size of the square cross section of piezoelectric column, are examined and verified in simulation. Then, according to the result of simulation, the piezoelectric composites and the air-coupled transducers are fabricated. The honeycomb structures of resin are produced by the method of 3D printing technology, with the volume fraction of air being 30%. The impedance characteristics and the excitation/reception performance of the air-coupled transducers are measured and optimized. Meanwhile, a scanning experiment is carried out to demonstrate the crack detection process in monocrystalline silicon. mode of Lamb waves is excited and collected. The location and size of the defect will be determined by calculating the correlation coefficients of the received signals and reference signals. Finally, a 15 mm × 0.5 mm × 0.5 mm scratch is clearly distinguished. Cunfu He, Yaoyao Wang, Yan Lu, Yuepeng Liu, and Bin Wu Copyright © 2016 Cunfu He et al. All rights reserved. Hybrid Wireless Sensor Network Coverage Holes Restoring Algorithm Mon, 20 Jun 2016 10:48:18 +0000 Aiming at the perception hole caused by the necessary movement or failure of nodes in the wireless sensor actuator network, this paper proposed a kind of coverage restoring scheme based on hybrid particle swarm optimization algorithm. The scheme first introduced network coverage based on grids, transformed the coverage restoring problem into unconstrained optimization problem taking the network coverage as the optimization target, and then solved the optimization problem in the use of the hybrid particle swarm optimization algorithm with the idea of simulated annealing. Simulation results show that the probabilistic jumping property of simulated annealing algorithm could make up for the defect that particle swarm optimization algorithm is easy to fall into premature convergence, and the hybrid algorithm can effectively solve the coverage restoring problem. Liu Zhouzhou and Yanhong She Copyright © 2016 Liu Zhouzhou and Yanhong She. All rights reserved.