Table of Content

30 July 2007, Volume 25 Issue 4

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Articles

Sub-band Stereo Acoustic Echo Cancellation Using Human Auditory

QIAO Jie;ZHAO Li;ZOU Cai-rong

2007, 25(4):  331-331 . 

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In this paper, a sub-band stereo acoustic echo cancellation using human auditory characteristics is proposed. This method can converge to “true” echo path more quickly than traditional methods. The length of adaptive filters is shortened, and processing complexity reduced by using sub-band decomposition. Based on the sub-band decomposition, correlation of input signals can be reduced by using human auditory characteristics. Thus, the adaptive filters converge faster. Simulation results show validity of the proposed method.

Multi-level Decoding of DP-HARQ Proticol with LDPC Coding and Performance Evaluation

WANG Fang;CHENG Shi-xin;CHEN Ming;WANG Hai-feng

2007, 25(4):  337-337 . 

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A novel decoding algorithm, multi-level decoding, for data puncturing type-II hybrid-ARQ protocol is proposed in this paper. Compared to the conventional two-level decoding, the proposed algorithm makes full use of error-correcting capability of each punctured codeword to improve the system performance. Performance evaluation for the multi-level decoding algorithm with density evolution is made. Analysis and numerical simulation results show that, if a proper puncturing rate is chosen, the multi-level decoding algorithm can improve the throughput performance by a few tenths of a decibel at lower SNR.

Steganography in Color Images Using a Binary Image Data Hiding Scheme

LIU Chun-qing;LIANG Guang-lan;WANG Shuo-zhong;ZHANG Xin-peng

2007, 25(4):  342-342 . 

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A new method for hiding secret information in color images is proposed, in which bit planes are treated as binary images. A set of rules is used to check boundary pixels in the bit planes for data embedding eligibility. These rules can ensure correct extraction of the secret data from the stego-image without any other additional information. A key is introduced in identifying the eligible embedding positions to enhance security. Experiments show that, at an embedding rate of 1.5 bits per color pixel, the stego-images have no perceptual and histogram abnormality with PSNR values greater than 40 dB, and can resist several effective methods for steganalytical detection, achieving a good trade-off between security and embedding capacity.

CDMA Sequences with Optimal Correlation and Large Linear Span

HUANG Ze-Ming;LI Chao;

2007, 25(4):  348-348 . 

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The Hellseth-Gong(HG) sequence is a kind of CDMA sequences used in wireless communication systems with ideal autocorrelation. For an odd prime p and integers n,m,d satisfying n=2(2d+1)m , using the theory of quadratic forms and properties of trace transform over finite field, a new unbalanced p -ray CDMA sequence family with large family size and optimal correlation property is constructed based on HG sequences.which means the family has optimal correlation in terms of Welch’s lower bound.Similarly,for an even number n=2(2d+1)m , using the trace transform,a family of balanced p -ray CDMA sequences with large family size has the property of optimal correlation,which is constructed from the unbalanced p-ray CDMA sequence family.It is shown that the two CDMA sequence families have large period and linear span,and are sutable for transmission in wireless communication systems.

Compensation of Range Walking of Space-Based Surveillance Radar

WANG Hai-tao;ZHU Gen-cai;BEN De;PAN Ming-hai;CHANG Jian-ping;WANG Li-sen

2007, 25(4):  354-354 . 

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To derive clutter cancellation, high-resolution angle estimation and wide-area surveillance, space-based radar (SBR) uses a signal processing system of 3-channel DPCA/monopulse. The radar's motion and earth rotation generate a Doppler frequency component in the clutter return form any point on the earth — range walking. We discuss range walking based on the SBR-earth geometry, and show that range walking together with range foldover significantly degrade the clutter suppression performance of the DPCA algorithms. Effects of range walking are eliminated with appropriate inverse compensation during coherent processing interval, and with linear interpolations during non-coherent interval. Effect of range foldover is eliminated using waveform diversity.

Parameters' Impact on Performance of Antenna in Planar Microstrip Spiral ICP Source

ZHOU Bei;LIAO Bin;ZHU Shou-zheng

2007, 25(4):  359-359 . 

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In this paper, theoretical analysis of inductivity-coupled microwave plasma source (ICP) is presented. According to its equivalent circuit, a planar microstrip spiral antenna with resonant frequency at 2.45GHz is designed. The antenna is simulated and optimized based on modeling, and the loss reduction method is proposed. The dimensions of coil are found to be the key factors having significant impact on resonance frequency and quality factor. Theoretical foundation is obtained for further research on low power planar spiral inductively-coupled microwave plasma source.

Reducing Edge Effect of EMD with Second Generation Wavelet Denoising

ZENG Feng;WEN Chenglin

2007, 25(4):  365-365 . 

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The traditional empirical mode decomposition (EMD) usually uses cubic spline interpolation to fit the upper and lower envelopes of the signal, leading to ill behavior on edges and therefore degrading the signal processing quality. We resolve the edge problem of EMD by using the second-generation wavelet denoise technique. Compared with the first generation wavelets, the second generation has lower computational complexity and less memory requirement. Numerical experiments show that the second-generation wavelet denoising can effectively reduce the edge effect with fewer decomposition layers, making EMD more practical.

Registration of Computer Temographic Images in Preoperation Planning

TANG Hui;LUO Li-Min;DILLENSEGER Jean-Louis

2007, 25(4):  370-370 . 

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Fusion of CT urography images is necessary in kidney preoperative planning system. A kidney-centered registration is the first step in the fusion. In this paper, several steps were taken to achieve this goal. Semi-automatic segmentation based on DDCM model was first performed to segment the kidney contours from CT slices. A binary kidney volume was obtained by contours reconstruction. The binary volume was then intersected with the original gray volume after 3D dilated. Finally, rigid registration between the kidney gray volumes was accomplished. The effect of initial parameters during registration was analyzed. Characteristics of geometric moments were applied to initialize parameters in order to avoid local extrema. Experimental results show that the proposed method can realize a kidney-centered registration between CT acquisitions, and the precision and speed can meet practical requirements.

Attitude Control of Micro-satellite with Active Magnetic Control

LIU Hai-ying;WANG Hui-nan;CHENG Yue-hua

2007, 25(4):  377-377 . 

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Different from the normal sequence consisting of attitude detumble, acquisition, and wheel speed-up, a method of attitude acquisition and stabilization for magnetic controlled micro-satellite is proposed, which uses B-dot controller, momentum wheel acceleration for detumble and active magnetic controller, and constant wheel. A limiting attitude feedback controller is designed for attitude capture and stabilization, and a LQG controller for attitude stabilization. Simulation is carried out using magnetic determination and control at different time. Measurement error, disturber moment and different bias momentum are considered. The result indicates that the method makes the control process simple and convenient, and can reduce initial control time with high control time with high control precision and robustness in stabilization.

Multi-Model Switching Control for Nonlinear Systems Based on Local T-S Models

QIAN Cheng-shan;WU Qing-xian;JIANG Chang-sheng;WANG Yan-qing

2007, 25(4):  382-382 . 

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We Propose a multi-model switching control for nonlinear systems based on local T-S (Takagi-Sugeno) models, which divides the input space into multiple regions with T-S models and controls in every region. This method improves precision as the fuzzy domain decreases under a constant fuzzy rule. The approach and control of the entire nonlinear system is established by the multiple-model switching control. Effectiveness of the proposed method is demonstrated with simulation results.

Distributed Control of Formation Maneuvers Based on Virtual Structures

HE Zhen;LU Yu-ping;LIU Yan-bin

2007, 25(4):  387-387 . 

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A distributed formation control approach to formation maneuvers is presented. Based on virtual structures, formation feedback is incorporated in the formation control scheme, which increases the robustness of the formation. The decentralized controllers are designed to communicate and cooperate with their neighbours, which keep the formation during the whole process of formation maneuvers. Convergence of the system is proved theoretically. Simulation results of multiple robot system with actuator saturation show effectiveness of the proposed control strategies.

Multi-Object Optimization Design of PID Controllers Based on Particle Swarm Algorithms

ZHANG Xing-hua;ZHOU Liu-xi

2007, 25(4):  392-392 . 

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A parameter tuning method for PID controllers based on particle swarm optimization with a constriction factor is proposed. A fitness function containing terms of overshoot, rise time and steady-state error of the system is defined. These terms are properly weighted. The particle swarm optimization algorithm is used in the multi-object optimization of PID controllers so that automatic tuning of the PID parameters can be achieved. The overall performance of the PID controllers using the proposed method is better than that by using conventional methods.

Optimal Inspection Model Using Delay-Time Concept

CAI Jing;ZUO Hong-fu;Wang Hua-wei

2007, 25(4):  397-397 . 

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For systems in which symptoms of failure is delayed and the possible failure can only be detected through inspection, replacement probability and expected lifespan are analyzed by considering imperfection of the inspection in normal state, imminent failure state and failed state, respectively. An optimal inspection model is proposed to minimize the total mean maintenance cost. Influence of system failure rate, maintenance cost and imperfect inspection on the optimal inspection interval is illustrated with a practical example, showing effectiveness of the modele.

Multi-criteria Decision Making Based on Variable Weights and k-Additive Fuzzy Measures

ZHANG Ling;ZHOU De-qun;ZHANG Jia-chun

2007, 25(4):  402-402 . 

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As k-additive fuzzy measures are flexible, the importance of decision-making criteria and their coalitions are modelled by k-additive fuzzy measures for the multi-criteria decision-making (MCDM) problems with interaction. The axiomatic system of variable weight and local state variable weight are introduced based on the k-additive fuzzy measures and the existing theories of variable weight. Determination of k-additive fuzzy measures for criteria and their coalitions are discussed based on Marichal entropy. Synthetical values of alternatives are calculated by fuzzy integrals. Finally, an example of selecting the succeed resource for coal enterprice is given to show that the theory and the method are reasonable and feasible.

Existence of Solitary Wave Solution to a Nonlinear Traving Wave Equation

XIA Liang-Juan;DING Dan-ping

2007, 25(4):  407-407 . 

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Non-linear traveling wave equation is studied,and a kind of effective methods for solitary waves solution to a non-linear traveling wave equation is presented,which is a generalized form of Kdv equation and Mkdv equation.We use the relation between homoclinic orbit and solitary waves of planar autonomous ,and study the homoclinic orbits of autonomous system with various parameters using the bifurcation theory of dynamical systems and an analytical method.Existence of solitary waves of the nonlinear traving wave equation is investigated.

Optimal Configuration of Ambient Vibration Sensors Based on Structural Modeling for Long Cable-Stayed Bridge

SUN Zheng-hua;LI Zhao-xia;CHAN Hung-tian;HAN Xiao-lin

2007, 25(4):  411-411 . 

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This paper studies the finite element (FE) modeling oriented to structural health monitoring (SHM) of long cable-stayed bridge and the optimal sensor configuration based on the structural dynamic response. Firstly, the FE oriented SHM of Runyang Cable-Stayed Bridge (RYCB) is developed using ANSYS. Model analysis of RYCB is carried out using the developed FE model. Taking the non-diagonal elements of the MAC matrix as target function, and increasing or decreasing the number of degree of freedom (DOF), the optimal sensor placement of the bridge is obtained by minimizing the target function. Validation of the sensor placement is checked with the results obtained from the ambient vibration test of RYCB. It is shown that the sensor placement obtained from the measured data of RYCB is coincident with the result calculated from the FE model. The sensor placement obtained from the FE model of RYCB is valid from the experimental point of view.

Local Stability Analysis for Optimal Performance of an Irreversible Carnot Heat Engine

NIE Wen-jie;HE Ji-zhou;ZHOU Feng

2007, 25(4):  418-418 . 

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Local stability of an irreversible Carnot heat engine at the maximum power output and the optimum ecological function has been studied based on the optimal performance parameters of the heat engine based on the Newton transfer heat law and using the local stability analysis. Expressions of relaxation time describing stability are derived. Relationship between relaxation time and heat-transfer coefficient ratio a/b, heat capacity C, total heat exchange area F, temperatures of heat reservoirs TH and TL, and heat leak are found. The characteristics of local stability at two steady states are compared. It is concluded that the optimal performance and local stability of the system should be considered simultaneously both in design and application.

Improved Antenna Design Based on Aesthetics in Electromagnetic Engineering

WANG Wei;ZHONG Shun-Shi LIANG Xian-Ling

2007, 25(4):  424-424 . 

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Electromagnetic problems are analyzed based on symmetrical aesthetics. A common characteristic, i.e., a concise symmetrical beauty in EM theory and EM engineering is summarized. Eexamples show that the symmetry derived from the nature can help design antennas.

Variable Step-Size Affine Projection with Robust Estimators for Adaptive Signal Processing

JIA Chong;GUO Ming-xi;ZHANG Xiong-wei

2007, 25(4):  428-428 . 

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We propose a variable step-size affine projection algorithm (APA) with robust-M estimators. The step-size is controlled with an exponential function, based on a criterion of optimal variable step-size performance. The robust-M estimators are applied to the variable step-size APA algorithm using the equivalent error with tri-weights. Theoretical analyses and numerical results show that the proposed algorithm performs well with a low misadjustment error rate and is robust against outliers.

DC-DC Converter with PWM/PFM Automatic Switching

CHANG Chang-yuan;YAO Jin－nan;TAN Chun-ling;ZOU Yi-zhao;SHI Long-xin

2007, 25(4):  433-433 . 

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We present an efficient CMOS DC-DC converter with automatic PWM/PFM switching, which can automatically switch between pulse width modulation (PWM) and pulse frequency modulation (PFM) modes according to the load variation. An expression of the load current at the threshold of automatic switching is derived. A simulated system works properly, achieving automatic PWM/PFM switching and high efficiency over a wide ranged of varied load.


Analyzing Monitoring Efficiency of Sucker-Rod Pumping Unit with Empirical Mode Decomposition

YUAN Da-ning;ZHANG Hai-feng;LIU Hong-zhao;RAO Jian-hua

2007, 25(4):  437-437 . 

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In evaluating the sucker-rod pumping performance of an oil well, the measured signal is inevitably contaminated by instrument errors and disturbances of various environment effects. As a result, the system efficiency obtained from the original monitoring signal cannot be used directly for analyzing the system efficiency. To deal with this problem, comparison is made between the empirical mode decomposition (EMD) and the wavelet method in terms of signal trend extraction. The EMD method has been found to be better, and used in analyzing the monitoring signal of sucker-rod pumping unit. The variation trend of system efficiency of the oil well is obtained. Numerical simulations show that EMD is an accurate, simple, and efficient method for extracting trend of monitoring signal of the oil well.