Table of Content

10 March 2003, Volume 21 Issue 1

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Articles

Automatic Recognition Algorithm of the Upper Sideband and the Lower Sideband SSB Signals by Using the Adaptive Threshold

FANG Xiao-qing, JI Yong, XU Pei-xia

2003, 21(1):  1-4. 

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Based on the statistical characterisitic of speech spectrum, a new algorithm which can distinguish LSB or USB cases of speech from SSB signals without any prior information is presented here. It is simple and very suitable for DSP's real-time implementation, and the adaptive threshold increases the algorithm's robustness. The simulation results show that this algorithm gives good performance even under the conditions of low SNR values.

An Investigation of the Modeling for a Parallel Directional Coupler Based on the 3D-GM-BPM

XIAO Jin-biao, SUN Xiao-han, CAI Chun, ZHANG Xi-fei, ZHUJian-bin, ZHANG Ming-de, DING Dong

2003, 21(1):  5-8. 

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A three-dimensional beam propagation method based on the Galerkin method (3D-GM-BPM) is proposed for directly modeling a parallel directional coupler based on optical rib waveguides. The computational efficiency is raised due to the small matrix derived from this method, which is reduced to solver a first-order normal differential equation system. A tangent-type function is applied to map the infinite region into closed region. As a result, the artificial boundary condition is eliminated.

A Novel Low Complexity Receiver in the Low Spreading Factor for the CDMA System

ZENG Rong, ZHAO Chun-ming

2003, 21(1):  9-12. 

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In the CDMA system, the inter-path interference (IPI) becomes very serious when the spreading factor is low. In order to decrease IPI, a low complexity receiver structure in the low spreading factor for the CDMA system which combines the conventional Rake with chip equalizer is proposed. Computer simulation shows that the Equalizer-Rake receiver performs better than Rake and chip equalizer with equal complexity.

Performance of Nonuniform 16-DAPSK Modu-lation with Punctured Convolutional Coding on Radio Broadcasting Channels

SAYHOOD Khalid Hassan, WU Le-nan

2003, 21(1):  13-19. 

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Simple closed-form expressions for the probability of error for nonuniform 16-differential amplitude phase-shift-key (DAPSK) signaling over an additive white Gaussian noise (AWGN) and Rayleigh fading channels are presented. The performance of nonuniform 16-DAPSK with punctured convolutional coding is presented. The results show that the coding can be used with nonuniform 16-DAPSK modulation to transmit additional message in radio broadcasting systems with little degradation to the basic message.

The New Reliability Design Theory of Multiple Failure Modes for Machine Elements

XU Hong-wei, YU Tian-xiang, ZHANG Xuan-sheng, ZHANG Zu-ming

2003, 21(1):  20-24. 

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The new reliability design theory of multiple failure modes for machine elements is presented. The reliability design computing method of multiple failure modes for machine elements is developed, and the Ditlevsen theory is used to prove the new theory. Finally, an example is given to show how the new theory is used.

The Grey Optimum Model for the Test of the Fineness of Ramie Fiber and Its Error Analysis

LI Xiao-feng, LUO You-xin

2003, 21(1):  25-29. 

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The grey modeling method has been developed according to the theory of the grey system and is used for correlation analysis of experimental data. Compared with the method of data regression, the grey model analysis (GMA) enjoys an obvious advantage. It can enhance the reliability of prediction in particular, in the testing of samples of small size. In this paper, the grey GM (1,2) model and grey optimum GM^* (1,2) model for the testing and analysis of the fineness of ramie fiber are described. Correlation analysis is then performed to predict the relationship between the data Tex (sample Y) and the data projection breadth (sample X). The error is evaluated and proves acceptable. The model for testing the fineness of ramie fiber established on it provides a concise and scientific method for technical control of production, quality inspection and supervision.

A Genetic Algorithm for QoS Multicast Routing with Imprecise State Information

CHEN Ping, DONG Tian-lin

2003, 21(1):  30-35. 

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Most of the known QoS multicast routing algorithms are based on accurate network state information available, however, we cannot obtain accurate information in fact. So the problem is how to construct multicast routing trees with QoS requirements satisfied when the information available for making such routing decisions is inaccurate. This paper presents a new heuristic genetic algorithm ISIMR-GA for solving the problem. Based on PC-ISI algorithm which is a kind of unicast routing algorithm used in inaccurate information networks environment. the ISIMR-GA can improve the searching ability and quicken the convergent speed by selecting initial population and using a series of heuristic genetic operations. Moreover, the simulation results demonstrate that the algorithm performs very well.

Recognition of the Scanning Style of the Radar Antenna Using Immune Neural Networks

TANG Bin, HU Guang-rui

2003, 21(1):  36-38. 

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The scanning style of the radar antenna varies with the working state. The correct recognition of radar scanning style is important in deciding its threatening degree to our side. It is also an important means to recognize the types and working styles of radar. We uses the radial basis function (RBF) network based on immune evolutionary algorithm to recognize the scanning style of the radar antenna. Computer simulation shows that for simple radar scanning styles, the recognition rate of immune RBF network has reached 99. 13% when SNR is 4dB. The training period of the network has only 99 steps, which proves its excellent performance.

A Robust Method of Real-Time Motion Estimation in Model-Based Image Coding

LI Zhong-ke, YANG Xiao-hui, WU Le-nan

2003, 21(1):  39-43. 

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In this paper, the nature of the PLS algorithm is analyzed. To overcome its disadvantages, a modified PLS algorithm is proposed. Experimental results are presented to provide synthetic data and real image sequences. Compared with PLS and EKF algorithm, the modified algorithm can estimate motion more accurately in real-time.

Joint Estimation of PN Code Delay and Multipath Using the Unscented Filter

XUE Wen-hu, CAN Zhong-min

2003, 21(1):  44-48. 

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In this paper the problem of joint estimation of PN code delay and multipath channel coefficients is considered. We present an estimator based on the unscented filter (UF) for the joint estimation of delay and multipath, and obtain the simulation results of the estimator. Next the mean square error (MSE) of the UF estimator is compared with both the MSE provided by EKF and the Cramer-Rao lower bound. The results show that the UF performs better than the EKF in multipath channels.

A New Scheme for Adjusting the Estimated Average Length of Channel

MA Zhang-yong, ZHAO Chun-ming, YOU Xiao-hu

2003, 21(1):  49-52. 

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The author proposes that the channel coefficient of the effective arriving path can be estimated with the Rake coherent receiver. By calculating the level cross rate (LCR) of the envelope, the Doppler-shift is estimated. The observation length is then adjusted dynamically with the help of the connection between the Doppler-shift and the optimal observation length, enabling the whole receiver to obtain better performance in variant velocities.

A Study on Mine Detection and Identification Through Pattern Recognition with the Help of Multi-Features

WANG Qun, NI Hong-wei, XU Yi-gang

2003, 21(1):  53-58. 

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Based on the analysis of the echo from buried objects, a novel method of locating buried mines using pattern recognition is recommended. The process comprises pre-processing stage, feature-extraction stage, feature reduction and a neural network classification stage. A PNN neural network is employed to identify the objects by training it to recognize the features extracted from time domain and frequency domain, wavelet domain as well as Welch power spectral density estimation of signal segments reflected from various types of buried targets. The data concerning mines and some other objects which are like mines in shape and size are compared and tested with the network, and the results indicate that the neural network using multi-feature can improve mine detection greatly.

A Correlation Analysis of Time-Variable Sequence Variable-Memory

LU Shu-wang, LIU Chuan-dong

2003, 21(1):  59-62. 

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The probability model of a class of combined pseudo -random sequence variable memory is suggested and analyzed, of which the main characteristic is given. The information leak caused by time-variable function while the output sequence is turning into the input sequence is analyzed. The quasi -like sequence method by which the output sequence constructs the input sequence of variable-memory threshold is suggested in this paper.

Restrictions on a Realizable Gait of a Biped Robot Climbing Upstairs

KE Xian-xin, GONG Zhen-bang, WU Jia-qi

2003, 21(1):  63-67. 

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The gait of a biped robot climbing stairs consists of foot trajectory and hip trajectory. Through analyzing the dynamical restrictions on stable walking and the geometry restrictions on the gait of a robot climbing stairs, the restrictions on a realizable gait of a robot climbing stairs were obtained. The simulations of climbing upstairs gait were presented.

The Application of the FEM Technology on the Deformation Analysis of the Thin-Wall Workpieces Milling in Aerospace Industries

WU Kai, HE Ning, JIANG Cheng-yu, HE Lei, ZHANG Ping, GONG Hui-min, CHEN Xue-mei

2003, 21(1):  68-71. 

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Thin-wall structure workpieces are often used in aerospace industries. They are easy to deform in the process of machining and the deformation affects the dimension precision of the workpieces. This paper proposed a systematic method to ensure the dimension precision of the thin-wall workpieces in end milling. By using the mechanistic model developed by the author and the ANSYS FEM software, machining errors have been computed, and the results fit in with the actual machining process.

Fatigue Analysis for the High-Speed Elastic Transporting Manipulator under Impact Condition

WANG Guo-qing, LIU Hong-zhao

2003, 21(1):  72-76. 

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To analyze the aeronautic high-speed elastic transporting maniplator fatigue in the experiment, this paper firstly takes account of the external oblique impact and inner contact resulting from a joint with clearance. Nonlinear spring and damper formulations are adopted to model the resulting reaction force between contact objects, then based on the finite element method, a dynamic model is established. By means of numerical simulations, the stress chart of dangerous sectional and fatigue life are investigated. The value of the fatigue life caculated is in accord with the experiment result.

Robust Fault Diagnosis for Nonlinear Systems Based on Least Squares Estimation

CHEN Yu-dong, WENG Zheng-xin, SHI Song-jiao

2003, 21(1):  77-83. 

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A fault diagnosis approach based on least squares estimation(FDBLSE) for a class of nonlinear systems is proposed in this paper. It first constructs a state estimator for the systems to be diagnosed so that the dynamic relationship between state estimation error and faults is obtained, it then identifies the faults using least squares estimation method based on the obtained dynamic relationship. The fault identification error and the robustness, sensitivity to faults and the detection time of the fault diagnosis are analyzed. A deep-going comparison between the approach proposed in this paper and the fault diagnosis approach based on the learning method is also given. FDBLSE approach can not only identify faults, but also give the upper limit of the identification error. It highlights short identification-time and high accuracy of fault identification. The simulation indicates the effectiveness of the approach proposed in this paper.

A Study on the Mixed Design of Active Control of Frame Structures

ZHOU Xing-de, WANG Feng-quan, HAN Xiao-lin

2003, 21(1):  84-87. 

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In order to reduce control energy needed for active vibration control of frame structures, a mixed design which combines structural design with controller design is considered. The original structures are redesigned to diminish control energy without affecting the basic performance and control effect of frame structures. Using systemic stability, controllability and other factors as restrictive conditions, a random structural dimension and material constant are chosen to acquire control energy through system reduction and controller design. And an improved genetic algorithm is used to search for optimal control energy. Finally, a numerical example is provided to show the effectiveness of the method.

A Random Simulation Model in Porous Media

ZHANG Dong-hui, JIN Feng, SHI Ming-heng, YANG Hao

2003, 21(1):  88-92. 

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The dispersion process in porous media is analysed and simulated by use of the random simulation method in this paper. Anomalous dispersion and the preferential path for dispersion flow are found near a percolation threshold caused by random pore removal or blockage. The calculated results show that the longitudinal dispersivity is greater when it is near a percolation threshold than in Euclidean space.

A Study on the Design of Extra-Long Measuring Bars

NIE Heng-jing, DENG Shan-xi, LIU Wen-wen

2003, 21(1):  93-95. 

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A study on the performance of an extra-long measuring bar used for non-contact measurement of inner diameter and geometrical form in a long tube is reported in this paper. A method of pre-bending the measuring bar for compensating its elastic deflection is proposed. Thus, a straight measuring bar can be used to carry a sensor for accurate and steady data acquisition. Secondly, to avoid or reduce the effect of environmental vibration, the natural frequencies of measuring bar with two kinds of loads are analyzed, and a suggestion to reduce that effect is given in this paper. The research results are of universal significance for the design of various extra-long measuring bars.

Research on the Teeth Profile Error of Grinding Teeth

TAO Xiao-jie

2003, 21(1):  96-98. 

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The technological parameters are one of the key factors that cause the teeth profile error. The paper analyses the causes that lead to the teeth profile error when grinding teeth using a machine equipped with the coned shape grinding wheel is used. The relation formula between the teeth profile error and the parameters of technology was obtained after experiments and the main factors that affect the error were found. It is very important for us to reduce the profile error and increase gear precision.

Some Sufficient Conditions for Hamilton Graph and a Conjeture

ZHAO Ke-wen, WU Yan

2003, 21(1):  99-102. 

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In this paper, let u, v, w be arbitrary vertices in simple graph of order n-G=(V,E) satisfing wu ∈V(G),d(u,v)=d(v,w)=2, with|N(u) ∪N(v)|+d(w) ≥ n, then G is Hamilto-nian. The result is better than those of other authors.

Fast Calculation of the Electromagnetic Scattering Directional Characteristics of Frequency Selective Surfaces

TONG Chuang-ming, YUAN Nai-chang, FU Yun-qi, ZHANG Guo-hua

2003, 21(1):  103-106. 

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The method of moments (MOM) in conjunction with the asymptotic waveform evaluation (AWE) technique is applied to calculate the electromagnetic scattering directional characteristics of one-dimensional frequency selective surfaces (FSS). The electric field integral equation (EFIE) of FSS irradiated by the electromagnetic (EM) wave is firstly changed into the matrix equations of the induced currents using MOM, and the matrix equations of an angular derivative (MEAD) can be then obtained from the matrix equations. In the AWE technique, the induced currents of angular derivative at a given angle within an angular are first obtained to find MEAD. The induced currents at any angle within the angle can be then obtained from the induced currents of an angular derivative at given angle via the Pade approximation. According to the induced currents and the Floquet harmonic of the spectral domain, the EM scattering directional characteristics can be calculated. It was observed that the results of AWE can exactly approximate those of MOM that sweeps frequency at a certain interval, and AWE technique can result in considerable CPU time saving.

Effects of Thermal Cycles on the Properties of CuZnAl Shape Memory Alloys

SI Nai-chao, LIU Hai-xia, QI Long-biao

2003, 21(1):  107-110. 

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The effects of thermal cycles on the properties of CuZnAl shape memory alloys under different heating temperatures, pre-deformations ε and amounts of complex rare earth mixture added were researched with electronic microscopes. The results indicate that thermal cycles can increase the transformation temperature M_s of the alloys by 5-6℃. Increasing the pre-deforma-tion ε will decrease the necessary cycle times for stable two-way-shape memory property. However the shape recovery rate of the alloys will decrease when the pre-deformation exceeds 3.6%. The shape memory property of the alloys will change insignificantly if the amount of rare earth added is less than 0.10%. But the alloys without rare earth will have worse shape memory property after thermal cycles reach 1800 times.