Journal of Electrical and Computer Engineering The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. A Scaling Scheme for DCT Precoded Optical Intensity-Modulated Direct Detection Systems Sun, 29 Nov 2015 10:56:05 +0000 A scaling technique is employed to improve the performance of a Discrete Cosine Transform (DCT) precoded optical intensity-modulated direct detection (IM/DD) OFDM system, which fully exploits the dynamic range of a digital-to-analog converter (DAC). The theoretical analysis shows that the proposed scaling scheme can improve the BER performance of DCT precoded and scaled OFDM systems. The experiment results also show that the proposed scheme significantly improves the BER performance without changing the receiver structure. The measured received sensitivity at a BER of 10−3 for a 4 G samples/s (2.7 Gbits/s) DCT precoded and scaled OFDM signal and after 100 km standard single-mode fiber (SMF) transmission has been improved by 3 and 1.3 dB when compared with the original OFDM system and conventional DCT precoded OFDM system, respectively. Zhongpeng Wang, Xiumin Wang, Fangni Chen, Weiwei Qiu, and Linpeng Ye Copyright © 2015 Zhongpeng Wang et al. All rights reserved. DOA Estimation Based on Sparse Signal Recovery Utilizing Double-Threshold Sigmoid Penalty Thu, 26 Nov 2015 11:59:02 +0000 This paper proposes a new algorithm based on sparse signal recovery for estimating the direction of arrival (DOA) of multiple sources. The problem model we build is about the sample covariance matrix fitting by unknown source powers. We enhance the sparsity by the double-threshold sigmoid penalty function which can approximate the norm accurately. Our method can distinguish closely spaced sources and does not need the knowledge of the number of the sources. In addition, our method can also perform well in low SNR. Besides, our method can handle more sources accurately than other methods. Simulations are done to certify the great performance of the proposed method. Hanbing Wang, Hui Li, and Bin Li Copyright © 2015 Hanbing Wang et al. All rights reserved. User Utility Oriented Queuing Model for Resource Allocation in Cloud Environment Thu, 19 Nov 2015 08:53:37 +0000 Resource allocation is one of the most important research topics in servers. In the cloud environment, there are massive hardware resources of different kinds, and many kinds of services are usually run on virtual machines of the cloud server. In addition, cloud environment is commercialized, and economical factor should also be considered. In order to deal with commercialization and virtualization of cloud environment, we proposed a user utility oriented queuing model for task scheduling. Firstly, we modeled task scheduling in cloud environment as an //1 queuing system. Secondly, we classified the utility into time utility and cost utility and built a linear programming model to maximize total utility for both of them. Finally, we proposed a utility oriented algorithm to maximize the total utility. Massive experiments validate the effectiveness of our proposed model. Zhe Zhang and Ying Li Copyright © 2015 Zhe Zhang and Ying Li. All rights reserved. A Genetic Algorithm Based Minimal Maximal Load Tree Routing Algorithm in Wireless Sensor Networks Sun, 08 Nov 2015 13:33:16 +0000 The key issue of static routing algorithms is how to construct an energy efficient routing tree that is utilized during the whole network duration in order to extend network lifetime. In this paper, we have illuminated that, in applications that define network lifetime as the time when the first sensor dies, the optimal routing tree should be the routing tree with minimal maximal load of all sensors and named such trees the Minimal Maximal Load Tree (MMLT). Since the procedure of constructing a routing tree is complex and the number of possible routing trees in a network is very huge, we have proposed a genetic algorithm (GA) based algorithm to obtain approximate Minimal Maximal Load Tree (MMLT). Each individual corresponds to a routing tree, and the fitness function is defined as the maximal load of all sensors in accordance with the routing tree that the individual corresponds to. Thus, approximate MMLT is obtained and network lifetime is extended. Simulation results show that our proposed algorithm notably extends network lifetime. Zhi Huang Copyright © 2015 Zhi Huang. All rights reserved. Compressed Sensing MRI Reconstruction Algorithm Based on Contourlet Transform and Alternating Direction Method Wed, 04 Nov 2015 11:45:25 +0000 Compressed sensing (CS) based methods have recently been used to reconstruct magnetic resonance (MR) images from undersampled measurements, which is known as CS-MRI. In traditional CS-MRI, wavelet transform can hardly capture the information of image curves and edges. In this paper, we present a new CS-MRI reconstruction algorithm based on contourlet transform and alternating direction method (ADM). The MR images are firstly represented by contourlet transform, which can describe the images’ curves and edges fully and accurately. Then the MR images are reconstructed by ADM, which is an effective CS reconstruction method. Numerical results validate the superior performance of the proposed algorithm in terms of reconstruction accuracy and computation time. Zhenyu Hu, Qiuye Wang, Congcong Ming, Lai Wang, Yuanqing Hu, and Jian Zou Copyright © 2015 Zhenyu Hu et al. All rights reserved. The Routing Algorithm Based on Fuzzy Logic Applied to the Individual Physiological Monitoring Wearable Wireless Sensor Network Mon, 02 Nov 2015 08:57:17 +0000 In recent years, the research of individual wearable physiological monitoring wireless sensor network is in the primary stage. The monitor of physiology and geographical position used in wearable wireless sensor network requires performances such as real time, reliability, and energy balance. According to these requirements, this paper introduces a design of individual wearable wireless sensor network monitoring system; what is more important, based on this background, this paper improves the classical Collection Tree Protocol and puts forward the improved routing protocol F-CTP based on the fuzzy logic routing algorithm. Simulation results illustrate that, with the F-CTP protocol, the sensor node can transmit data to the sink node in real time with higher reliability and the energy of the nodes consumes balance. The sensor node can make full use of network resources reasonably and prolong the network life. Jie Jiang, Yun Liu, Fuxing Song, Ronghao Du, and Mengsen Huang Copyright © 2015 Jie Jiang et al. All rights reserved. Regression Cloud Models and Their Applications in Energy Consumption of Data Center Mon, 19 Oct 2015 13:29:02 +0000 As cloud data center consumes more and more energy, both researchers and engineers aim to minimize energy consumption while keeping its services available. A good energy model can reflect the relationships between running tasks and the energy consumed by hardware and can be further used to schedule tasks for saving energy. In this paper, we analyzed linear and nonlinear regression energy model based on performance counters and system utilization and proposed a support vector regression energy model. For performance counters, we gave a general linear regression framework and compared three linear regression models. For system utilization, we compared our support vector regression model with linear regression and three nonlinear regression models. The experiments show that linear regression model is good enough to model performance counters, nonlinear regression is better than linear regression model for modeling system utilization, and support vector regression model is better than polynomial and exponential regression models. Yanshuang Zhou, Na Li, Hong Li, and Yongqiang Zhang Copyright © 2015 Yanshuang Zhou et al. All rights reserved. Optimal Contract Design for Cooperative Relay Incentive Mechanism under Moral Hazard Mon, 19 Oct 2015 12:47:17 +0000 Cooperative relay can effectively improve spectrum efficiency by exploiting the spatial diversity in the wireless networks. However, wireless nodes may acquire different network information with various users’ location and mobility, channels’ conditions, and other factors, which results in asymmetric information between the source and the relay nodes (RNs). In this paper, the relay incentive mechanism between relay nodes and the source is investigated under the asymmetric information. By modelling multiuser cooperative relay as a labour market, a contract model with moral hazard for relay incentive is proposed. To effectively incentivize the potential RNs to participate in cooperative relay, the optimization problems are formulated to maximize the source’s utility while meeting the feasible conditions under both symmetric and asymmetric information scenarios. Numerical simulation results demonstrate the effectiveness of the proposed contract design scheme for cooperative relay. Nan Zhao, Minghu Wu, Wei Xiong, and Cong Liu Copyright © 2015 Nan Zhao et al. All rights reserved. New Method of Image Background Suppression Based on Soft Morphology and Retinex Theory Sun, 18 Oct 2015 09:02:42 +0000 A new river flow measurement method based on graphic process has been proposed recently, which gets the velocity in optical imaging modality through measuring the continuous displacement of floating debris, then reconstructs a two-dimensional river surface velocity field by using the velocity of floating debris, and computes the section flow at last. However, the surface optical images have not only lights of target information, but also surface optical noise. It is difficult for reliable and stable continuous displacement detection of complex small observation target, which occupies only a small number of pixels comparing to a large field imaging area and has complex optical reflection properties. To solve this problem, this paper presents a background suppression method based on soft morphology and Retinex theory. Soft morphology is firstly used for the opening operation of the image, and then Retinex theory is used for optimal estimation of image incident component to suppress background of image. Finally, the simulations show that our method is superior to gray morphology and soft morphology on the performance of targets enhancement, noise filtering, and background suppression, and it has better background and targets discrimination quality subjective evaluation and higher signal-to-clutter ratio. Lili Zhang, Tanghuai Fan, Xin Wang, Cheng Kong, and Xijun Yan Copyright © 2015 Lili Zhang et al. All rights reserved. Crowd Motion Analysis Based on Social Force Graph with Streak Flow Attribute Thu, 15 Oct 2015 09:31:58 +0000 Over the past decades, crowd management has attracted a great deal of attention in the area of video surveillance. Among various tasks of video surveillance analysis, crowd motion analysis is the basis of numerous subsequent applications of surveillance video. In this paper, a novel social force graph with streak flow attribute is proposed to capture the global spatiotemporal changes and the local motion of crowd video. Crowd motion analysis is hereby implemented based on the characteristics of social force graph. First, the streak flow of crowd sequence is extracted to represent the global crowd motion; after that, spatiotemporal analogous patches are obtained based on the crowd visual features. A weighted social force graph is then constructed based on multiple social properties of crowd video. The graph is segmented into particle groups to represent the similar motion patterns of crowd video. A codebook is then constructed by clustering all local particle groups, and consequently crowd abnormal behaviors are detected by using the Latent Dirichlet Allocation model. Extensive experiments on challenging datasets show that the proposed method achieves preferable results in the application of crowd motion segmentation and abnormal behavior detection. Shaonian Huang, Dongjun Huang, and Mansoor Ahmed Khuhro Copyright © 2015 Shaonian Huang et al. All rights reserved. Modeling and Fault Diagnosis of Interturn Short Circuit for Five-Phase Permanent Magnet Synchronous Motor Wed, 07 Oct 2015 13:36:27 +0000 Taking advantage of the high reliability, multiphase permanent magnet synchronous motors (PMSMs), such as five-phase PMSM and six-phase PMSM, are widely used in fault-tolerant control applications. And one of the important fault-tolerant control problems is fault diagnosis. In most existing literatures, the fault diagnosis problem focuses on the three-phase PMSM. In this paper, compared to the most existing fault diagnosis approaches, a fault diagnosis method for Interturn short circuit (ITSC) fault of five-phase PMSM based on the trust region algorithm is presented. This paper has two contributions. (1) Analyzing the physical parameters of the motor, such as resistances and inductances, a novel mathematic model for ITSC fault of five-phase PMSM is established. (2) Introducing an object function related to the Interturn short circuit ratio, the fault parameters identification problem is reformulated as the extreme seeking problem. A trust region algorithm based parameter estimation method is proposed for tracking the actual Interturn short circuit ratio. The simulation and experimental results have validated the effectiveness of the proposed parameter estimation method. Jian-wei Yang, Man-feng Dou, and Zhi-yong Dai Copyright © 2015 Jian-wei Yang et al. All rights reserved. A Secure Privacy-Preserving Data Aggregation Model in Wearable Wireless Sensor Networks Wed, 07 Oct 2015 09:59:17 +0000 With the rapid development and widespread use of wearable wireless sensors, data aggregation technique becomes one of the most important research areas. However, the sensitive data collected by sensor nodes may be leaked at the intermediate aggregator nodes. So, privacy preservation is becoming an increasingly important issue in security data aggregation. In this paper, we propose a security privacy-preserving data aggregation model, which adopts a mixed data aggregation structure. Data integrity is verified both at cluster head and at base station. Some nodes adopt slicing technology to avoid the leak of data at the cluster head in inner-cluster. Furthermore, a mechanism is given to locate the compromised nodes. The analysis shows that the model is robust to many attacks and has a lower communication overhead. Changlun Zhang, Chao Li, and Jian Zhang Copyright © 2015 Changlun Zhang et al. All rights reserved. Priority Control Strategy of VSC-MTDC System for Integrating Wind Power Sun, 04 Oct 2015 09:03:51 +0000 For the obvious advantages in integrating wind power, multiterminal HVDC transmission system (VSC-MTDC) is widely used. The priority control strategy is proposed in this paper considering the penetration rate of wind power for the AC grid. The strategy aims to solve the problems of power allocation and DC voltage control of the DC system. The main advantage of this strategy is that the demands for wind power of different areas can be satisfied and a power reference for the wind power trade can also be provided when wind farms transmit active power to several AC grids through the DC network. The objective is that power is well distributed according to the output power of wind farm with the demand of AC system and satisfactory control performance of DC voltage is obtained. Wen-ning Yan, Ke-jun Li, Zhuo-di Wang, Xin-han Meng, and Jianguo Zhao Copyright © 2015 Wen-ning Yan et al. All rights reserved. Investigating a Mobility-Aware QoS Model for Multimedia Streaming Rate Adaptation Thu, 01 Oct 2015 09:44:31 +0000 Supporting high quality multimedia streaming on wireless devices poses several challenges compared to wired networks due to the high variance in network performance encountered in the mobile environment. Although rate adaptation is commonly used in multimedia applications to compensate for fluctuations in network performance, it is a reactive mechanism which is not aware of the frequently changing connectivity that may occur on mobile devices. This paper proposed a performance evaluation model for multimedia streaming applications that is aware of user mobility and network performance. We presented an example of mathematical solution to the model and demonstrated the functionality using common mobility and connectivity examples that may be found in an urban environment. The proposed model is evaluated based on this functionality and how it may be used to enhance application performance. Fragkiskos Sardis, Glenford Mapp, Jonathan Loo, Mahdi Aiash, and Alexey Vinel Copyright © 2015 Fragkiskos Sardis et al. All rights reserved. Cloud Platform Based on Mobile Internet Service Opportunistic Drive and Application Aware Data Mining Thu, 01 Oct 2015 06:46:08 +0000 Because the static cloud platform cannot satisfy the diversity of mobile Internet service and inefficient data mining problems, we presented a reliable and efficient data mining cloud platform construction scheme based on the mobile Internet service opportunistic driving and application perception. In this scheme, first of all data selection mechanism was established based on mobile Internet service opportunistic drive. Secondly, through the cloud platform different cloud and channel aware, nonlinear mapping from the service to a data set of proposed perceptual model is applied. Finally, on the basis of the driving characteristics and extraction of perceptual features, the cloud platform would be constructed through the service opportunities of mobile Internet applications, which could provide robust and efficient data mining services. The experimental results show that the proposed mechanism, compared to the cloud platform based on distributed data mining, has obvious advantages in system running time, memory usage, and data clustering required time, as well as average clustering quality. Ge Zhou Copyright © 2015 Ge Zhou. All rights reserved. Applying Pulse Width Modulation in Body Coupled Communication Thu, 01 Oct 2015 06:45:12 +0000 We study the application of Pulse Width Modulation (PWM) technique in Body Coupled Communication. The term Body Coupled Communication is used in order to specify that the human body or a part of it, such as an arm, is used as a path that transfers digital information. The digital information is either generated due to coupling of the body, for example, in medical equipment as a result of a measurement, or generated by external circuitry attached somewhere onto the body and is transferred to a terminal by touching it. In this paper, the latter case will be described, where, for illustration purposes, the touch of the human hand on a doorknob triggers the unlocking mechanism. Miltiadis Moralis-Pegios, Pelagia Alexandridou, and Christos Koukourlis Copyright © 2015 Miltiadis Moralis-Pegios et al. All rights reserved. QoE Guarantee Scheme Based on Cooperative Cognitive Cloud and Opportunistic Weight Particle Swarm Wed, 30 Sep 2015 14:03:45 +0000 It is well known that the Internet application of cloud services may be affected by the inefficiency of cloud computing and inaccurate evaluation of quality of experience (QoE) seriously. In our paper, based on construction algorithms of cooperative cognitive cloud platform and optimization algorithm of opportunities weight particle swarm clustering, the QoE guarantee mechanism was proposed. The mechanism, through the sending users of requests and the cognitive neighbor users’ cooperation, combined the cooperation of subcloud platforms and constructed the optimal cloud platform with the different service. At the same time, the particle swarm optimization algorithm could be enhanced dynamically according to all kinds of opportunity request weight, which could optimize the cooperative cognitive cloud platform. Finally, the QoE guarantee scheme was proposed with the opportunity weight particle swarm optimization algorithm and collaborative cognitive cloud platform. The experimental results show that the proposed mechanism compared is superior to the QoE guarantee scheme based on cooperative cloud and QoE guarantee scheme based on particle swarm optimization, compared with optimization fitness and high cloud computing service execution efficiency and high throughput performance advantages. Weihang Shi Copyright © 2015 Weihang Shi. All rights reserved. Design and Analysis of a Low Cost Wave Generator Based on Direct Digital Synthesis Thu, 17 Sep 2015 14:19:08 +0000 Signal generators are widely used in experimental courses of universities. However, most of the commercial tests signal generators are expensive and bulky. In addition, a majority of them are in a fixed working mode with many little-used signals. In order to improve this situation, a small sized and highly accurate economic signal generator based on DDS technology has been developed, which is capable of providing wave signals commonly used in experiments. Firstly, it is introduced the basic principles of DDS and is determined the overall scheme of the signal generator. Then, it proposes a design of the hardware, which include power supply module, display module, keyboard module, waveform generating module based on DDS chip, and the minimum system module based on C8051F010. The signal generator was designed to output sine and square waveforms, and the other achieved performances included the frequency range 0.1 Hz–12.5 MHz, the frequency resolution 0.05 Hz–0.1 Hz, the output amplitude 1.0–4.5 V, the frequency accuracy % and %, and the signal distortion % and %. Jian Qi, Qun Sun, Xiaoliang Wu, Chong Wang, and Linlin Chen Copyright © 2015 Jian Qi et al. All rights reserved. An Advanced Partial Discharge Recognition Strategy of Power Cable Sun, 13 Sep 2015 12:05:27 +0000 Detection and localization of partial discharge are very important in condition monitoring of power cables, so it is necessary to build an accurate recognizer to recognize the discharge types. In this paper, firstly, a power cable model based on FDTD simulation is built to get the typical discharge signals as training samples. Secondly, because the extraction of discharge signal features is crucial, fractal characteristics of the training samples are extracted and inputted into the recognizer. To make the results more accurate, multi-SVM recognizer made up of six Support Vector Machines (SVM) is proposed in this paper. The result of the multi-SVM recognizer is determined by the vote of the six SVM. Finally, the BP neural networks and ELM are compared with multi-SVM. The accuracy comparison shows that the multi-SVM recognizer has the best accuracy and stability, and it can recognize the discharge type efficiently. Xiaotian Bi, Ang Ren, Simeng Li, Mingming Han, and Qingquan Li Copyright © 2015 Xiaotian Bi et al. All rights reserved. High Dynamic Optimized Carrier Loop Improvement for Tracking Doppler Rates Tue, 08 Sep 2015 16:04:25 +0000 Mathematical analysis and optimization of a carrier tracking loop are presented. Due to fast changing of the carrier frequency in some satellite systems, such as Low Earth Orbit (LEO) or Global Positioning System (GPS), or some planes like Unmanned Aerial Vehicles (UAVs), high dynamic tracking loops play a very important role. In this paper an optimized tracking loop consisting of a third-order Phase Locked Loop (PLL) assisted by a second-order Frequency Locked Loop (FLL) for UAVs is proposed and discussed. Based on this structure an optimal loop has been designed. The main advantages of this approach are the reduction of the computation complexity and smaller phase error. The paper shows the simulation results, comparing them with a previous work. Amirhossein Fereidountabar, Gian Carlo Cardarilli, and Marco Re Copyright © 2015 Amirhossein Fereidountabar et al. All rights reserved. Impact of Interface Traps on Direct and Alternating Current in Tunneling Field-Effect Transistors Thu, 03 Sep 2015 11:53:09 +0000 We demonstrate the impact of semiconductor/oxide interface traps (ITs) on the DC and AC characteristics of tunnel field-effect transistors (TFETs). Using the Sentaurus simulation tools, we show the impacts of trap density distribution and trap type on the n-type double gate- (DG-) TFET. The results show that the donor-type and acceptor-type ITs have the great influence on DC characteristic at midgap. Donor-like and acceptor-like ITs have different mechanism of the turn-on characteristics. The flat band shift changes obviously and differently in the AC analysis, which results in contrast of peak shift of Miller capacitor for n-type TFETs with donor-like and acceptor-like ITs. Zhi Jiang, Yiqi Zhuang, Cong Li, Ping Wang, and Yuqi Liu Copyright © 2015 Zhi Jiang et al. All rights reserved. A Formal Verification Methodology for DDD Mode Pacemaker Control Programs Tue, 01 Sep 2015 08:54:06 +0000 Pacemakers are safety-critical devices whose faulty behaviors can cause harm or even death. Often these faulty behaviors are caused due to bugs in programs used for digital control of pacemakers. We present a formal verification methodology that can be used to check the correctness of object code programs that implement the safety-critical control functions of DDD mode pacemakers. Our methodology is based on the theory of Well-Founded Equivalence Bisimulation (WEB) refinement, where both formal specifications and implementation are treated as transition systems. We develop a simple and general formal specification for DDD mode pacemakers. We also develop correctness proof obligations that can be applied to validate object code programs used for pacemaker control. Using our methodology, we were able to verify a control program with millions of transitions against the simple specification with only 10 transitions. Our method also found several bugs during the verification process. Sana Shuja, Sudarshan K. Srinivasan, Shaista Jabeen, and Dharmakeerthi Nawarathna Copyright © 2015 Sana Shuja et al. All rights reserved. A Bit String Content Aware Chunking Strategy for Reduced CPU Energy on Cloud Storage Mon, 17 Aug 2015 13:47:00 +0000 In order to achieve energy saving and reduce the total cost of ownership, green storage has become the first priority for data center. Detecting and deleting the redundant data are the key factors to the reduction of the energy consumption of CPU, while high performance stable chunking strategy provides the groundwork for detecting redundant data. The existing chunking algorithm greatly reduces the system performance when confronted with big data and it wastes a lot of energy. Factors affecting the chunking performance are analyzed and discussed in the paper and a new fingerprint signature calculation is implemented. Furthermore, a Bit String Content Aware Chunking Strategy (BCCS) is put forward. This strategy reduces the cost of signature computation in chunking process to improve the system performance and cuts down the energy consumption of the cloud storage data center. On the basis of relevant test scenarios and test data of this paper, the advantages of the chunking strategy are verified. Bin Zhou, ShuDao Zhang, Ying Zhang, and JiaHao Tan Copyright © 2015 Bin Zhou et al. All rights reserved. Micro-Doppler Ambiguity Resolution Based on Short-Time Compressed Sensing Mon, 17 Aug 2015 11:45:16 +0000 When using a long range radar (LRR) to track a target with micromotion, the micro-Doppler embodied in the radar echoes may suffer from ambiguity problem. In this paper, we propose a novel method based on compressed sensing (CS) to solve micro-Doppler ambiguity. According to the RIP requirement, a sparse probing pulse train with its transmitting time random is designed. After matched filtering, the slow-time echo signals of the micromotion target can be viewed as randomly sparse sampling of Doppler spectrum. Select several successive pulses to form a short-time window and the CS sensing matrix can be built according to the time stamps of these pulses. Then performing Orthogonal Matching Pursuit (OMP), the unambiguous micro-Doppler spectrum can be obtained. The proposed algorithm is verified using the echo signals generated according to the theoretical model and the signals with micro-Doppler signature produced using the commercial electromagnetic simulation software FEKO. Jing-bo Zhuang, Zhen-miao Deng, Yi-shan Ye, Yi-xiong Zhang, and Yan-yong Chen Copyright © 2015 Jing-bo Zhuang et al. All rights reserved. Applying Partial Power-Gating to Direction-Sliced Network-on-Chip Sun, 16 Aug 2015 12:05:46 +0000 Network-on-Chip (NoC) is one of critical communication architectures for future many-core systems. As technology is continually scaling down, on-chip network meets the increasing leakage power crisis. As a leakage power mitigation technique, power-gating can be utilized in on-chip network to solve the crisis. However, the network performance is severely affected by the disconnection in the conventional power-gated NoC. In this paper, we propose a novel partial power-gating approach to improve the performance in the power-gated NoC. The approach mainly involves a direction-slicing scheme, an improved routing algorithm, and a deadlock recovery mechanism. In the synthetic traffic simulation, the proposed design shows favorable power-efficiency at low-load range and achieves better performance than the conventional power-gated one. For the application trace simulation, the design in the mesh/torus network consumes 15.2%/18.9% more power on average, whereas it can averagely obtain 45.0%/28.7% performance improvement compared with the conventional power-gated design. On balance, the proposed design with partial power-gating has a better tradeoff between performance and power-efficiency. Feng Wang, Xiantuo Tang, and Zuocheng Xing Copyright © 2015 Feng Wang et al. All rights reserved. A Robust Watermarking Scheme Based on Maximum Wavelet Coefficient Modification and Optimal Threshold Technique Sun, 09 Aug 2015 10:45:37 +0000 Digital watermarking has received extensive attention as a new method for copyright protection. This paper proposes a robust watermarking algorithm based on maximum wavelet coefficient modification and optimal threshold technique. The medium wavelet coefficients are randomly permutated according to a secret key and divided into subgroups. We modify the maximum wavelet in each subgroup according to the embedded watermark bits, which can effectively resist attacks. During the extraction process, an optimal threshold value calculated by iterative computation is used to extract the watermark from the watermarked image under different attacks, without using the original image or watermark. Numerous experiments are conducted to evaluate the watermarking performance. Experimental results demonstrate the superiority of our scheme on robustness against content-preserving operations and incidental distortions such as JPEG compression, Gaussian noise, median filter, resizing, cropping, and sharpening. Chunlei Li, Xiaowei Song, Zhoufeng Liu, Aihua Zhang, and Ruimin Yang Copyright © 2015 Chunlei Li et al. All rights reserved. An Approach to Generate Spatial Voronoi Treemaps for Points, Lines, and Polygons Wed, 29 Jul 2015 06:39:19 +0000 As a space-filling method, Voronoi Treemaps are used for showcasing hierarchies. Previously presented algorithms are limited to visualize nonspatial data. The approach of spatial Voronoi Treemaps is proposed in this paper to eliminate these problems by enabling the subdivisions for points, lines, and polygons with spatial coordinates and references. The digital distance transformation is recursively used to generate nested raster Voronoi polygons while the raster to vector conversion is used to create a vector-based Treemap visualization in a GIS (geographic information system) environment. The objective is to establish a spatial data model to better visualize and understand the hierarchies in the geographic field. Song Tian, Ximin Cui, and Yu Gong Copyright © 2015 Song Tian et al. All rights reserved. Design of Wireless Automatic Synchronization for the Low-Frequency Coded Ground Penetrating Radar Mon, 27 Jul 2015 05:55:11 +0000 Low-frequency coded ground penetrating radar (GPR) with a pair of wire dipole antennas has some advantages for deep detection. Due to the large distance between the two antennas, the synchronization design is a major challenge of implementing the GPR system. This paper proposes a simple and stable wireless automatic synchronization method based on our developed GPR system, which does not need any synchronization chips or modules and reduces the cost of the hardware system. The transmitter omits the synchronization preamble and pseudorandom binary sequence (PRBS) at an appropriate time interval, while receiver automatically estimates the synchronization time and receives the returned signal from the underground targets. All the processes are performed in a single FPGA. The performance of the proposed synchronization method is validated with experiment. Zhenghuan Xia, Qunying Zhang, Shengbo Ye, Zhiwu Xu, Jie Chen, Guangyou Fang, and Hejun Yin Copyright © 2015 Zhenghuan Xia et al. All rights reserved. Novel Chaos Secure Communication System Based on Walsh Code Thu, 09 Jul 2015 09:51:12 +0000 A multiuser communication scheme which is a hybrid of Walsh code with DCSK and CDSK is proposed to improve low data transmission rate of Differential Chaos Shift Keying (DCSK), poor bit error ratio (BER) performance of Correlation Delay Shift Keying (CDSK), and disadvantage of orthogonality in traditional multiuser DCSK. It not only overcomes the disadvantages of DCSK and CDSK, but also has better performance than CDSK and higher transmission data rate than DCSK. It has been proved that the novel multiuser CDSK-DCSK has better properties than traditional Multiple Input Multiple Output-Differential Chaos Shift Keying (MIMO-DCSK) and Modified-Differential Chaos Shift Keying (M-DCSK). Also the multiuser interference is greatly suppressed due to the orthogonality of Walsh code. Gang Zhang, Niting Cui, and Tianqi Zhang Copyright © 2015 Gang Zhang et al. All rights reserved. Human Activity Recognition Based on the Hierarchical Feature Selection and Classification Framework Tue, 07 Jul 2015 11:56:22 +0000 Human activity recognition via triaxial accelerometers can provide valuable information for evaluating functional abilities. In this paper, we present an accelerometer sensor-based approach for human activity recognition. Our proposed recognition method used a hierarchical scheme, where the recognition of ten activity classes was divided into five distinct classification problems. Every classifier used the Least Squares Support Vector Machine (LS-SVM) and Naive Bayes (NB) algorithm to distinguish different activity classes. The activity class was recognized based on the mean, variance, entropy of magnitude, and angle of triaxial accelerometer signal features. Our proposed activity recognition method recognized ten activities with an average accuracy of 95.6% using only a single triaxial accelerometer. Yuhuang Zheng Copyright © 2015 Yuhuang Zheng. All rights reserved.