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Table of Content

    30 March 2010, Volume 28 Issue 2
    Communication Engineering
    Recognition of Communication Signals in Noise with Alpha Stable Distribution
    YANG Wei-chao, ZHAO Chun-hui, CHENG Bao-zhi
    2010, 28(2):  111-114. 
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    Alpha stable distribution is a limiting distribution that maintains the generating mechanism and spreading condition of natural noise. We study the fractal box dimension characteristics of alpha stable distribution and show that, in theory, the fractal box dimension is insensitive to alpha stable distribution with a characteristic index between 1 and 2. We select the fractal box dimensions of signal phase as the recognition characteristic parameter to complete signal recognition. Theoretical study and numerical simulation show that the method has good robustness in background noise with alpha stable distribution.

    Sliding Mode Adaptive Synchronization Control of Hyperchaotic System and Its Application in Secure Communication
    MEI Rong,WU Qing-xian, JIANG Chang-sheng
    2010, 28(2):  115-122. 
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    Due to their intrinsic randomness, sensitivity to initial values and broadband spectrum, chaotic systems have been used to implement secure communication. To improve security and enhance anti-interference ability, a four-dimensional hyperchaotic system with unknown parameter is designed based on the classical Lorenz chaotic system. A single signal control is proposed based on sliding mode adaptive control to synchronize hyperchaotic systems with the same structure. When synchronization is achieved, the hidden signal can be restored effectively at the receiving end. Numeric simulation shows effectiveness of the proposed technique.

    Wireless Handoff Scheme in IEEE802.11 MAC Layer for High-Speed Mobile Communications
    ZHAO Li-fang, CHEN Bing
    2010, 28(2):  123-128. 
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    Mobile station performs a handoff when it moves out of the range of one access point and tries to connect to the next. The delay and lost packets caused by the handoff process affect the network quality of service. Taking subway wireless communication system as an application scenario, the number of channels used is reduced, which decreases the scan delay effectively. An algorithm called Layer2-Buff is proposed to solve the problem of lost packets, which sets up buffers for STA, and used to save data that cannot be sent successfully. Test results show that Layer2-Buff reduces the packet loss rate to zero in an automatic train control system, and extra delay to the network is tolerable. This algorithm has been applied to a pre-research project of subway signal systems.

    Signal and Information Processing
    Performance of Online Blind Separation of Dynamically Segmented Mixed Acoustic Signal for CVR
    YANG Lin, WANG Cong-qing, ZHANG Hong-zhan
    2010, 28(2):  129-135. 
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    Considering the existence of slight time-varying characteristics and a large number of near-zero signal values, we propose an online blind separation algorithm based on signal sample dynamic segmentation. The online algorithm of independent component analysis (ICA) is used to achieve dynamic segmentation. The FastICA algorithm is executed until converging to an optimal solution. To obtain better performance, weights of the rows in the separation matrix are adjusted. Simulation results show excellent performance of the proposed algorithm, indicating that the algorithm can effectively separate mixed acoustic signals recorded by CVR.

    Detection and Compensation of Shadows in High Resolution Remote Sensing Images Using PCA
    2010, 28(2):  136-141. 
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    From the shadow region properties, a new algorithm of shadow detection and compensation based on principal component analysis (PCA) is proposed for high resolution remote sensing images. The ratio between the original blue band and the first principal component is computed. Shadow and non-shadow regions are segmented using the histogram-thresholding method. A morphological algorithm is used to produce an accurate shadow mask, and a dilation operation is performed to find the surrounding homogeneous region of a shadow. Each shadow region is matched to its adjacent homogeneous region to achieve shadow compensation. Finally,image smoothing and inverse PCA transformation are performed on the compensated image. Experimental results show that the algorithm is effective.

    Audio Tampering Detection Based on Band-Partitioning Spectral Smoothness
    DING Qi, PING Xi-jian
    2010, 28(2):  142-146. 
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    To detect resampling in audio tampering, a new spectral measure, band-partitioning spectral smoothness (BPSS), is proposed to measure the degree of spectral fluctuation. Based on the analysis to spectral characteristics of non-interpolated and interpolated audio signals, a comprehensive strategy to detect audio interpolation and stitching with BPSS is presented. Experiment results show that, by using the proposed method, it can be correctly determined whether the audio signals are interpolated or stitched. Furthermore, the original sampling rates of the interpolated signals can be estimated with high accuracy. Low computational complexity enables this method to be useful in real time audio tampering detection.

    Red Tide MODIS Monitoring Based on Multi-oceanic Parameters
    XUE Cun-jin, DONG Qing
    2010, 28(2):  147-151. 
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    Taking into account the drawbacks in the red tide extraction from single oceanic parameter, this paper presents a new red tide monitoring technique using multiple oceanic parameters. The method focuses on the sea surface temperature and chlorophyll-a concentration retrieved from MODIS imagery. In combination with suspended sediment concentration and sea water abnormalities, we have designed the discrimination rules, which take full advantages of each oceanic parameter to extract red tides, and avoid missing and erroneous information obtained based on a single parameter. MODIS imageries acquired on May 30 and June 11, 2004, covering the Bohai Sea, are taken as an example to show validity and feasibility of the proposed method.

    Acoustic Model of Noise Prediction and Algorithm for Capacitor Tower in DC Converter Station
    WEI Hao-zheng, LI Zhi-yuan, LI Xiao-lin, HUANG Ying, RUAN Xue-yun
    2010, 28(2):  152-157. 
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    According to the noise property of capacitor tower in DC converter station, we compare the algorithms for vertical linear acoustic sources, and propose an improved method of optimal division of vertical linear acoustic sources alone. The method chooses a proper value of the division length by comparison. An algorithm is developed  based on the proposed method, giving better accuracy of noise attenuation prediction of capacitor tower and more reasonable results than a commercial software product.

    Demodulation of Touch Trigger Probe Based on FBG with Experimental Study
    DING Bang-zhou, FEI Ye-tai, FAN Zhe-guang
    2010, 28(2):  158-162. 
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    The touch trigger probe based on fiber Bragg gratings is a newly developed probe. With a sensing element used in a three-dimensional probe, sensor signal demodulation is a key technique. By means of the dual-frequency laser interferometer and nano-level stage, the sampling probe is tested using a self-demodulation approach based on the functional relations between optical power and wavelength shift. Resolution of more than 100 nm can be achieved from the analysis of experimental data on a developed probe. Furthermore, experiments verify that application of FBG sensors in a three-dimensional probe is feasible.

    Video Restoration Using Exemplar-Based Inpainting
    GU Yi, HAN Jun
    2010, 28(2):  163-169. 
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     This paper applies exemplar-based image inpainting to video restoration, and improves the repairing method by using time correlation characteristic of video sequences. The new method of video damage restoration can repair damages which are difficult to be detected in videos. Experiments show that, comparing with exemplar-based image inpainting, the method is more efficient in video restoration, can avoid filling errors and error spread, and has better efficiency.

    Electronic Engineering
    Calculation of 2D Site Percolation Parameters of Electrical Conductivity Using Renormalization Group Method
    HE Chao, Lü Xu-liang, GAO Fu-yin JIA Qi
    2010, 28(2):  170-174. 
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    The renormalization group method is an effective way to calculate percolation parameters of conducting polymer composites. Percolation parameters of the 8-neighbor rule and the 4-neighbor rule are calculated by renormalization group in different correlation dimensions. The results show that more accurate parameters can be obtained by raising the value of correlation dimension M. The fractal dimension of infinite percolation cluster is reduced because of the increase of critical exponent. The 8-neighbor rule is to some degree more appropriate to demonstrate the percolation model of electrical conductivity because its percolation threshold is close to the experimental results.

    Computer Science and Applications
    Energy-Oriented Dynamic SPM Allocation Based on Time-Slotted Cache Conflict Graph
    WANG Huan, LING Ming, ZHANG Yang, MEI Chen
    2010, 28(2):  175-181. 
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    In this paper, an allocation strategy is proposed to optimize energy of memory system. A timeslotted cache conflict graph is proposed to model the behavior of data cache conflict. An integer nonlinear programming (INP) is implemented, which can avoid time-consuming linearization process, to select the most profitable data pages and employ a virtual memory system to remap those data pages that can cause severe cache conflict within a time slot, to the on-chip scratchpad memory (SPM). To minimize the swapping overhead of dynamic SPM allocation, we introduce a novel SPM controller with a tightly coupled DMA to issue the swapping operations without CPU intervention. The proposed method can optimize all data segments including global data, heap and stack data in general, and reduce the total energy consumption by 24.83% on average without any performance degradation.

    Improved Ant Colony Optimization Algorithm for Job Shop Scheduling Problem
    ZHANG Zhi-qiang, ZHANG Jing, ZHANG Xiang, LI Shu-juan
    2010, 28(2):  182-188. 
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    An improved ant colony optimization algorithm for job shop scheduling problems is proposed in this paper. The tabu list which can generate active schedule is designed. The traditional ant colony optimization algorithm is hen simplified, and a new priority rule proposed to serve as heuristic information. A local search procedure based on the neighborhood structure of job shop scheduling problem is introduced to improve convergence and solution quality of the proposed algorithm. Experiments show effectiveness of the proposed algorithm.

    Control and System
    Design of Dynamic Output Feedback Controller for Lurie Networked Control Systems
    JIANG Bing, ZHANG Chong-wei
    2010, 28(2):  189-196. 
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    Taking into consideration network-induced delay, data packet dropout and data packet disorder, the Lurie networked control system is modeled as a multiple delay Lurie system. A delay-dependent stability condition is established via free weighting matrices. Based on an equation constraint, it is transformed into a solvability problem described by linear matrix inequality. The dynamic output feedback control law is then presented. Two numerical examples show feasibility and effectiveness of the design method.

    Optimal Control of Structure Seismic Response Using Linear Quadratic Performance Function and Iterative Learning
    WANG Jian-guo, WANG Quan, ZHANG Ming-xiang
    2010, 28(2):  197-202. 
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    By combining linear quadratic optimal control and iterative learning control (ILC), a new hybrid control strategy named linear quadratic optimal iterative learning control is obtained. The optimal control force is determined according to quadratic performance function minimization in the process of ILC to reduce the earthquake displacement response of engineering structures. Effectiveness of the control is studied. The model of a typical seismically excited building in the second generation benchmark vibration control for buildings is studied using the new hybrid control strategy to calculate seismic displacement response of the building. Simulation results show that the new control strategy can effectively control earthquake displacement response with improved effectiveness.

    Adaptive Pinning Synchronization for Complex Network Coupled with the Outputs
    FAN Chun-xia, JIANG Guo-ping
    2010, 28(2):  203-208. 
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    An adaptive pinning control method is proposed for synchronization of a complex network coupled with output. Unlike existing synchrnization methods, output of a complex network is used to construct synchronization controllers, and the synchronization-controller gains are adapted according to synchronization errors, and only part of nodes need to be controlled in the complex network. Furthermore, synchronization criteria are achieved for a complex network on the basis of the Lyapunov stability theory. Numerical simulations are carried out for a small-world network and a scale-free network, the results showing effectiveness of the proposed scheme for synchronization of complex network.

    Satellite Formation Fly Control Based on Atmospheric Drag
    CHEN Zhi-ming, WANG Hui-nan, LIU Hai-ying
    2010, 28(2):  209-215. 
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    A new control method is described using atmospheric drag. It was based on the traditional control method of  satellite formation flying. Besides, the system configuration and control law are given. With drag panels, fuel is no longer a limitation to the satellite service life. This method is useful both in attitude control and formation control problems. It can reduce system complexity and enhance function density, and therefore has a good application prospect. Simulation results show that the method is effective in terms of the expected control efficiency.

    Control of Ascending Flight of Reusable Launch Vehicles
    HE Cheng-long, CHEN Xin, WU Liao-ni
    2010, 28(2):  216-220. 
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    As the initial flight phase of reusable launch vehicle (RLV), the ascending phase has its special characteristics, that is, fast changes during flight in the gravity center, the atmospheric density and the motion state. The control law should suit the fine stability and maneuverability in the whole flight envelope to make analysis easy. The entire flight is divided into four phases in this paper: drop, ignition, powered climb and unpowered climb. Different control strategies are used according to the characteristic of each phase. Trajectory linearization control (TLC) is involved for advanced nonlinear tracking and robust control, and the forward control and feedback control law are designed. Nonlinear simulation shows that the control scheme satisfies the ascent control requirements.