Journal of Electrical and Computer Engineering The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . 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. Forest Fire Smoke Video Detection Using Spatiotemporal and Dynamic Texture Features Thu, 02 Jul 2015 11:32:12 +0000 Smoke detection is a very key part of fire recognition in a forest fire surveillance video since the smoke produced by forest fires is visible much before the flames. The performance of smoke video detection algorithm is often influenced by some smoke-like objects such as heavy fog. This paper presents a novel forest fire smoke video detection based on spatiotemporal features and dynamic texture features. At first, Kalman filtering is used to segment candidate smoke regions. Then, candidate smoke region is divided into small blocks. Spatiotemporal energy feature of each block is extracted by computing the energy features of its 8-neighboring blocks in the current frame and its two adjacent frames. Flutter direction angle is computed by analyzing the centroid motion of the segmented regions in one candidate smoke video clip. Local Binary Motion Pattern (LBMP) is used to define dynamic texture features of smoke videos. Finally, smoke video is recognized by Adaboost algorithm. The experimental results show that the proposed method can effectively detect smoke image recorded from different scenes. Yaqin Zhao, Zhong Zhou, and Mingming Xu Copyright © 2015 Yaqin Zhao et al. All rights reserved. Time-Frequency Feature Extraction of HRRP Using AGR and NMF for SAR ATR Mon, 29 Jun 2015 10:36:04 +0000 A new approach to classify synthetic aperture radar (SAR) targets based on high range resolution profiles (HRRPs) is presented. Features from each of the target HRRPs are extracted via the nonnegative matrix factorization (NMF) algorithm in time-frequency domain represented by adaptive Gaussian representation (AGR). Firstly, SAR target images have been converted into HRRPs. And the time-frequency matrix for each of HRRPs is obtained by using AGR. Secondly, the time-frequency feature vectors are extracted from the time-frequency matrix utilizing NMF. Finally, hidden Markov models (HMMs) are employed to characterize the time-frequency feature vectors corresponding to one target and are used to being the recognizer. To demonstrate the performance of the proposed approach, experiments are performed in the 10-target MSTAR public dataset. The results support the effectiveness of the proposed technique for SAR automatic target recognition (ATR). Xinzheng Zhang, Zhouyong Liu, Shujun Liu, and Guojun Li Copyright © 2015 Xinzheng Zhang et al. All rights reserved. A Zero-Watermarking Scheme for Vector Map Based on Feature Vertex Distance Ratio Wed, 17 Jun 2015 12:46:49 +0000 With the rapid development of GIS and computer techniques, vector map data has been widely used in many fields. Since the production of map data is very costly, illegal copying will result in huge loss for data owners. In order to protect the copyright of vector data, digital watermarking has been employed in recent years. In this paper, a zero-watermarking scheme for vector map data is proposed. In the proposed scheme, FVDR (feature vertex distance ratio) is constructed based on the feature vertices of objects. The feature data, FVDR, is combined with watermark to generate the zero-watermark. Due to the specially designed cover data, the proposed scheme is robust to geometrical attacks, vertex attacks, and object attacks. The results of extensive experiments also demonstrate the robustness of the proposed scheme. Yuwei Peng and Mingliang Yue Copyright © 2015 Yuwei Peng and Mingliang Yue. All rights reserved. Wavelet Domain Multidictionary Learning for Single Image Super-Resolution Mon, 15 Jun 2015 06:53:59 +0000 Image super-resolution (SR) aims at recovering the high-frequency (HF) details of a high-resolution (HR) image according to the given low-resolution (LR) image and some priors about natural images. Learning the relationship of the LR image and its corresponding HF details to guide the reconstruction of the HR image is needed. In order to alleviate the uncertainty in HF detail prediction, the HR and LR images are usually decomposed into 4 subbands after 1-level discrete wavelet transformation (DWT), including an approximation subband and three detail subbands. From our observation, we found the approximation subbands of the HR image and the corresponding bicubic interpolated image are very similar but the respective detail subbands are different. Therefore, an algorithm to learn 4 coupled principal component analysis (PCA) dictionaries to describe the relationship between the approximation subband and the detail subbands is proposed in this paper. Comparisons with various state-of-the-art methods by experiments showed that our proposed algorithm is superior to some related works. Xiaomin Wu, Jiulun Fan, Jian Xu, and Yanzi Wang Copyright © 2015 Xiaomin Wu et al. All rights reserved. Unsupervised Classification Method for Polarimetric Synthetic Aperture Radar Imagery Based on Yamaguchi Four-Component Decomposition Model Wed, 03 Jun 2015 06:16:51 +0000 For improving the accuracy of unsupervised classification based on scattering models, the four-component Yamaguchi model is introduced, which is an improved version of the best-known three-component Freeman model. Therewith, the four-component model is combined with the Wishart distance model. The new proposed algorithm of clustering is rolled out thereafter and the procedure of this new method is listed. In experiments, seven areas of various homogeneities are singled out from the Flevoland sample image in AIRSAR dataset. Qualitative and quantitative experiments are performed for a comparative study. It can be easily seen that the resolution and details are remarkably upgraded by the new proposed method. The accuracy of classification in homogeneous areas has also increased significantly by adopting the new iterative algorithm. Sheng Sun, Renfeng Liu, and Wen Wen Copyright © 2015 Sheng Sun et al. All rights reserved. Drive Current Enhancement in TFET by Dual Source Region Sun, 24 May 2015 13:38:06 +0000 This paper presents tunneling field-effect transistor (TFET) with dual source regions. It explores the physics of drive current enhancement. The novel approach of dual source provides an effective technique for enhancing the drive current. It is found that this structure can offer four tunneling junctions by increasing a source region. Meanwhile, the dual source structure does not influence the excellent features of threshold slope (SS) of TFET. The number of the electrons and holes would be doubled by going through the tunneling junctions on the original basis. The overlap length of gate-source is also studied. The dependence of gate-drain capacitance and gate-source capacitance on gate-to-source voltage and drain-to-source voltage was further investigated. There are simulation setups and methodology used for the dual source TFET (DS-TFET) assessment, including delay time, total energy per operation, and energy-delay product. It is confirmed that the proposed TFET has strong potentials for VLSI. Zhi Jiang, Yiqi Zhuang, Cong Li, Ping Wang, and Yuqi Liu Copyright © 2015 Zhi Jiang et al. All rights reserved. Doppler Ambiguity Resolution Based on Random Sparse Probing Pulses Mon, 11 May 2015 12:30:26 +0000 A novel method for solving Doppler ambiguous problem based on compressed sensing (CS) theory is proposed in this paper. A pulse train with the random and sparse transmitting time is transmitted. The received signals after matched filtering can be viewed as randomly sparse sampling from the traditional fixed-pulse repetition frequency (PRF) echo signals. The whole target echo could be reconstructed via CS recovery algorithms. Through refining the sensing matrix, which is equivalent to increase the sampling frequency of target characteristic, the Doppler unambiguous range is enlarged. In particular, Complex Approximate Message Passing (CAMP) algorithm is developed to estimate the unambiguity Doppler frequency. Cramer-Rao lower bound expressions are derived for the frequency. Numerical simulations validate the effectiveness of the proposed method. Finally, compared with traditional methods, the proposed method only requires transmitting a few sparse probing pulses to achieve a larger Doppler frequency unambiguous range and can also reduce the consumption of the radar time resources. Yunjian Zhang, Zhenmiao Deng, Jianghong Shi, Linmei Ye, Maozhong Fu, and Chen Zhao Copyright © 2015 Yunjian Zhang et al. All rights reserved. An Extraction Method of Weak Low-Frequency Magnetic Communication Signals Based on Multisensor Sun, 10 May 2015 06:11:53 +0000 It is a technical challenge to effectively remove the influence of magnetic noise from the vicinity of the receiving sensors on low-frequency magnetic communication. The traditional denoising methods are difficult to extract high-quality original signals under the condition of low SNR (the signal-to-noise ratio). In this paper, we analyze the numerical characteristics of the low-frequency magnetic field and propose the algorithms of the fast optimization of blind source separation (FOBSS) and the frequency-domain correlation extraction (FDCE). FOBSS is based on blind source separation (BSS). Signal extraction of low SNR can be implemented through FOBSS and FDCE. This signal extraction method is verified in multiple field experiments which can remove the magnetic noise by about 25 dB or more. Chao Huang, Xin Xu, Dunge Liu, Wanhua Zhu, Xiaojuan Zhang, and Guangyou Fang Copyright © 2015 Chao Huang et al. All rights reserved. Robust Recursive Algorithm under Uncertainties via Worst-Case SINR Maximization Wed, 06 May 2015 09:56:47 +0000 The performance of traditional constrained-LMS (CLMS) algorithm is known to degrade seriously in the presence of small training data size and mismatches between the assumed array response and the true array response. In this paper, we develop a robust constrained-LMS (RCLMS) algorithm based on worst-case SINR maximization. Our algorithm belongs to the class of diagonal loading techniques, in which the diagonal loading factor is obtained in a simple form and it decreases the computation cost. The updated weight vector is derived by the descent gradient method and Lagrange multiplier method. It demonstrates that our proposed recursive algorithm provides excellent robustness against signal steering vector mismatches and the small training data size and, has fast convergence rate, and makes the mean output array signal-to-interference-plus-noise ratio (SINR) consistently close to the optimal one. Some simulation results are presented to compare the performance of our robust algorithm with the traditional CLMS algorithm. Xin Song, Feng Wang, Jinkuan Wang, and Jingguo Ren Copyright © 2015 Xin Song et al. All rights reserved. Climate Characteristics of High-Temperature and Muggy Days in the Beijing-Tianjin-Hebei Region in the Recent 30 Years Wed, 29 Apr 2015 06:23:14 +0000 The climate characteristics of high-temperature (37°C and above) and muggy days in the Beijing-Tianjin-Hebei region over the past 30 years from 1981 to 2010 are analyzed. The results are summarized as follows. During this period, the years with the most number of high-temperature days are 1997–2005 and 2009 in the Beijing-Tianjin-Hebei region, while high-temperature extremes appear in 1999, 2000, 2002, 2009, and 2010. This disparity between the years with high-temperature extremes and the years with the most number of high-temperature days is located primarily in the central and southern cities of the Beijing-Tianjin-Hebei region. High-temperature extremes in the southern cities appear in June and July, while high-temperature extremes in the other cities appear in July. The years with the most number of muggy days are 1994, 1997, 1998, 2000, and 2010 in the Beijing-Tianjin-Hebei region, but the years with the extreme muggy conditions appear in 1981, 2002, 2005, and 2010. The most number of muggy days are in July, and the muggy days in July and August account for about 90% of the entire summer. Over the 30-year period, no apparent changes are observed in the number of days with precipitation and the annual precipitation amount. Guohua Zhang, Jian Guan, Jingyi Ai, Jiangtao Zhang, and Xiaoqing Jin Copyright © 2015 Guohua Zhang et al. All rights reserved. Performance Analysis of Multiscale Entropy for the Assessment of ECG Signal Quality Mon, 27 Apr 2015 09:09:45 +0000 This study explored the performance of multiscale entropy (MSE) for the assessment of mobile ECG signal quality, aiming to provide a reasonable application guideline. Firstly, the MSE for the typical noises, that is, high frequency (HF) noise, low frequency (LF) noise, and power-line (PL) noise, was analyzed. The sensitivity of MSE to the signal to noise ratio (SNR) of the synthetic artificial ECG plus different noises was further investigated. The results showed that the MSE values could reflect content level of various noises contained in the ECG signals. For the synthetic ECG plus LF noise, the MSE was sensitive to SNR within higher range of scale factor. However, for the synthetic ECG plus HF noise, the MSE was sensitive to SNR within lower range of scale factor. Thus, a recommended scale factor range within 5 to 10 was given. Finally, the results were verified on the real ECG signals, which were derived from MIT-BIH Arrhythmia Database and Noise Stress Test Database. In all, MSE could effectively assess the noise level on the real ECG signals, and this study provided a valuable reference for applying MSE method to the practical signal quality assessment of mobile ECG. Yatao Zhang, Shoushui Wei, Yutao Long, and Chengyu Liu Copyright © 2015 Yatao Zhang et al. All rights reserved. Time-Frequency Analysis of Clinical Percussion Signals Using Matrix Pencil Method Thu, 16 Apr 2015 15:47:07 +0000 This paper discusses time-frequency analysis of clinical percussion signals produced by tapping over human chest or abdomen with a neurological hammer and recorded with an air microphone. The analysis of short, highly damped percussion signals using conventional time-frequency distributions (TFDs) meets certain difficulties, such as poor time-frequency localization, cross terms, and masking of the lower energy features by the higher energy ones. The above shortcomings lead to inaccurate and ambiguous representation of the signal behavior in the time-frequency plane. This work describes an attempt to construct a TF representation specifically tailored to clinical percussion signals to achieve better resolution of individual components corresponding to physical oscillation modes. Matrix Pencil Method (MPM) is used to decompose the signal into a set of exponentially damped sinusoids, which are then plotted in the time-frequency plane. Such representation provides better visualization of the signal structure than the commonly used frequency-amplitude plots and facilitates tracking subtle changes in the signal for diagnostic purposes. The performance of our approach has been verified on both ideal and real percussion signals. The MPM-based time-frequency analysis appears to be a better choice for clinical percussion signals than conventional TFDs, while its ability to visualize damping has immediate practical applications. Moinuddin Bhuiyan, Eugene V. Malyarenko, Mircea A. Pantea, Dante Capaldi, Alfred E. Baylor, and Roman Gr. Maev Copyright © 2015 Moinuddin Bhuiyan et al. All rights reserved.