Table of Content

30 June 1999, Volume 17 Issue 2

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Articles

A New Method for the Determination of Path Interval in Five-Axis NC Machining of Free Form Surfaces

ZHOU YANHONG, ZHOU JI

1999, 17(2):  127-133. 

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In this paper, a rigorous expression for calculating the path interval, which is based on analyzing the enveloping movement of cutters is obtained and is fit for five-axis NC machining of free form surfaces with general torus cutters. The practical algorithm and measures for improving the calculating efficiency are given. The factors that influence the path interval in five-axis surface machining are discussed, and the approaches to optimizing the tool path are also explored.

Numerical Simulation Method for Electrical Heating Reservoir to Enhance Heavy Oil Recovery

WANG YUDOU, GUAN JITENG, WANG DIANSHENG

1999, 17(2):  134-141. 

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According to the mechanisms of electrical heating heavy oil reservoir, the mathematical models and discrete models of current field, pressure field and temperature field are developed; The algorithm of these models are discussed and the computational software is tailored; The results of numerical calculation are given; The results show electrical heating is an effective method for heavy oil recovery.

Mean Field Equations for High Density Situation of Fukui-Ishibashi Traffic Flow Models

WANG BINGHONG, WANG LEI, HUI PAKMING, HUI PAKMING

1999, 17(2):  142-147. 

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In this paper, Fukui Ishibashi one dimensional traffic flow cellular automaton model for high speed vehicles (v_max=M>1) with stochastic delay is studied from the point of view of inter-car spacings. Starting from the basic equation describing the time evolution of the number of empty sites in front of each car, the concepts of inter-car spacing longer (shorter) than M are defined, the occurrence probabilities of longer spacing and shorter spacing are calculated respectively. For the situation of high density (d ≥ 1/M), it is proved that the inter-car spacing longer than M will be shorten, any initial configuration will approach to the steady state for which all the inter-car spacing belong to shorter type. Hence it is proved strictly that for general Fukui -Ishibashi traffic flow model with stochastic delay, when the car density is high, the fundamental diagram for the traffic flow asymptotic steady state does not change as the delay probability.

Context -Sensitive Automatic Chinese Word Segmentation and Lexical Preprocessing

HUANG HEYAN, LI YUSHENG

1999, 17(2):  148-155. 

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In this paper, a context -sensitive automatic Chinese word segmentation and lexical preprocessing for Chinese-English machine translation system is proposed. This algorithm incorporates with improved MM matching and rule based context -sensitive ambiguity resolution by taking advantage of large amount of syntax, semantic and common sense knowledge in the lexicon of MT system. Its accurate rate reaches up to 99%. On the same time, in this algorithm, some lexical phonomena, such as reduplication word, function word, etc. are also processed, so as to deduce the amont of words in lexicon entry, and facilitate the parsing of a Chinese sentence.

An Information Theory Based Method for Blind Separation of Sources

LIU JU, LU ZIYI, HE ZHENYA, MEI LIANGMO

1999, 17(2):  156-162. 

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Based on the assumption of statistics independent, we proposed an mutual information minimizing object function where Edgeworth expansion is used. This function can be explained clearly and its minimization would make the outputs independent. Computer simulation shows the validity of proposed method.

A Normalized Fast Blind Adaptive Beamforming Algorithm

HE ZHENYA, CHEN YUXIN

1999, 17(2):  163-168. 

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LS SCORE is an adaptive beamforming algorithm with the array manifold unknown. However, its slow convergence speed is often unable to meet the requirements for use. A new algorithm having fast tracking ability and permitting large dynamic input range is present in this paper. The experiment results have shown that this algorithm has better performance than LS SCORE.

Electromagnetic Scattering From Two-Dimensional Electrically Large Multi-Conducting Bodies

CHEN XIAOGUANG, JIN YAQIU

1999, 17(2):  169-176. 

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Numerical simulation of electromagnetic scattering from electrically large multiconducting bodies has been implemented by using the exact fast multipole method (FMM). Scattering cross sections of four clustered, conducting cylinders and the distribution of electricity on the surfaces are calculated by the FMM. The calculation speed of FMM is much superior to the conventional MOM's. The functional dependence of RCS and surface current distribution upon the distance between the cylinders, and other parameters are numerically discussed.

Study on Characteristics of SINR Polarization Filter in the Partially Polarized Case

WANG XUESONG, XIAO SHUNPING, CHEN ZHIJIE, ZHUANG ZHAOWEN

1999, 17(2):  177-182. 

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In this paper,polarization characteristics of SINR filter are studied in the most general partially polarized case.Emphatically,the band characteristics of filter are discussed while formulae of filter's band and its area are derived.A novel methodology to solve the optimal filter's parameters is presented by taking advantage of the analysis of band characteristics,by which the analytic expression of optimal filter's parameters can be derived directly.

A Novel Method for Microwave Imaging of Two Dimensional Electromagnetic Target in Half Space

QING ANYONG, LI JING, REN LANG, ZHONG SHUNSHI

1999, 17(2):  183-188. 

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A novel method for microwave imaging of two-dimensional lossless electromagnetic target which buried in half space using time-domain scattering data is presented in this paper.It is an iterative method derived volume equivalence principle,variation principle,Fourier transform.We name it as time-domain variational iterative method(TVIM).In each iteration,both the direct and inverse problems are solved once.The direct problem is solved by finite-difference time-domain(FDTD) method and the inverse problem is solved iteratively.Some Typical numerical results are given to show its inversion performance such as converging property,ability to invert arbitrary targets,tolerance of random noise et al.Comparision with our former method is also done.Those factors which make TVIM performs better are investigated.

A Study of Parallel Corner-Fed Square Microstrip Antenna

GAO SHICHANG, ZHONG SHUNSHI

1999, 17(2):  189-193. 

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The parallel corner-fed square microstrip antenna is studied. A method of analysis of input impedance properties is developed, and the closed-form expressions are derived. The Multiport network model, the cavity theory, the segmentation technique and the desegmentation technique are combined in the present approach. The characteristics of parallel corner-fed structure are fully included in the method. For antenna design, more accurate results can be conveniently obtained from it than those from the cavity theory. The experimental results validate the theory.

Free Space Mode Approximation for Radiation Modes of a Slab Waveguide and Its Application

WANG ZIHUA, LI MINGSHENG

1999, 17(2):  194-198. 

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Taking the symmetric slab waveguide as an example,we show that radiation modes of a weakly guiding planar optical waveguide can be approximated by the free space modes,their field expression and normalization constants are simple and understandable physically and can be obtained directly without any calculation.By applying this approximation,the far field and radiation loss calculations caused by random wall imperfections have been significantly simplified.

On The Equivalence of Green Functions to Integral Transform Technique for the Problem of Heat Conduction

HU HANPING, GE XINSHI, CHENG SHUXIA

1999, 17(2):  199-205. 

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A new method of solving Green function for the problem of heat conduction is presented and a general purpose Green function representative by which the equivalence of Green functions to integral transform technique can be proved.

The Optimal Performance of a Stirling Heat Engine

SU GUOZHEN, YAN ZIJUN

1999, 17(2):  206-210. 

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The optimal performance of a Stirling heat engine with heat resistance, heat leak and regeneration loss is studied. The fundamental optimal relation is deduced, and the influences of various irreversible factors on the performance of the heat engine are discussed. The conclusions obtained here may provide some new theoretical guides to the optimal design of Stirling heat engines.

A Circuit Test Generation Method Based on Optimization

PAN ZHONGLIANG, ZHANG GUANGZHAO, CHEN GUANGJU

1999, 17(2):  211-215. 

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Test pattern generation for integrated circuits is an important and complex problem. An optimization method of test pattern generation for digital circuits is proposed in this paper. In the method, a characteristic function for each basic gate circuit and the constrained network for the circuit under test (CUT) are defined, the test patterns for a fault can be obtained by means of a simulated annealing algorithm. A new algorithm, namely annealing descent algorithm(SDA), is presented, which enhance the performance of conventional simulated annealing method, and accelerate the test generation process further.

Control Method of Robot Position and Posture Based Genetic Algorithms

CAI JINDA, LI HAOLIN

1999, 17(2):  216-220. 

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A new algorithm for control of position and posture of robot is presented in this paper, which based on genetic algorithm. According to problems of control of position and posture of robot, the methods to improve parameter search procedures are discussed as well. Finally, the method is validated by simulation experiments.

Electrochromic Characteristics of Electron-Beam Evaporated Nickel Oxide Films

WU YONGGANG, WU GUANGMING, NI XINGYUAN, ZHOU ZHEN, ZHANG HUIQING, WU XIANG

1999, 17(2):  221-226. 

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In this paper, nickel oxide films are deposited by rapid electron-beam evaporating NiO powder pellet in the presence of a selected oxygen pressure. The deposited films show superior electrochromic properties without activation process, transmittance variation of 23.4%~92.0% at 550nm can be achieved at the second cycle of cyclic voltammetry between -0.6 and +0.8V. In the initial dozens of cycles, the transmittance of the colored state is lowered gradually, but the transmittance of the bleached state retains the same as the original state. The anodic and cathodic current increase, while the cathodic current peak shifts to lower potentials with the cycling. The maximum transmittance variation reachs 20.5%~77.4%in the photopic vision spectra and 27.2%~69.1% in the solar spectra when the cycling reachs stable. Switching times for coloration and bleaching are 15s and 7s respectively.

Time Series Forecasting Based Neural Networks and Its Application

CHEN XIYUAN, CHENG QIMING, WAN DEJUN, YU YONG

1999, 17(2):  227-231. 

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This paper proposes the modeling and forecasting method by neural networks for marine strapdown gyro which based on time series analysis, and makes research for random drift rate of gyro applied for strapdown attitude systems.

Study on Plasma Diagnostics of Double -Glow Plasma Surface Alloying Technique

LI CHENGMING, XU ZHONG, TIAN LINHAI, WANG JIANMING, SU YONGAN, XIE XISHAN, DONG JIANXIN

1999, 17(2):  232-236. 

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Langmuir probe technique is used for the plasma diagnostics of double glow plasma surface alloying technique. It has been shown that the plasma potential and the electron temperature decrease and the plasma density increase, with the rise of the gas pressure and the source electrode voltage and substrate cathode voltage. Under suitable processes condition, the unequal potential hollow cathode effect is produced between the source electrode and substrate cathode. The plasma density is increased apparently from 10¹⁰ to 10¹² cm^-3.

Temperature Rising Behavior of Sr-Ni-La Composite Oxide in Microwave Field

BI XIANJUN, DUAN AIHONG, WANG ZHEN, HONG PINJIE, DAI SHUSHAN

1999, 17(2):  237-240. 

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In this paper, a series of Sr-Ni-La composite oxides are prepared by dipping, and the influences of composition preparing condition of catalyst and anode current on the temperature rising under microwave irradiation are studied. The results show that all oxides could rise temperature, moreover the preparing conditions and the current have effects on the temperature rising.

Topography of Defects in PrP₅O₁₄ Crystals by X Ray Diffraction

LIU XILING, GUAN WENLI, ZHANG JIE, XU ZHONGBIN

1999, 17(2):  241-244. 

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The defects in PrP₅O₁₄ crystals have been studied first by means of X-ray topography. It is found that the main defects are ferroelastic domains, antiphase domains, growth layers, growth sectors and dislocations. Their forming reasons are analysed and the way of improving the quality of crystals has been discussed.

Solid Phase Synthesis of Nanophase MnO 2 Powders and Its Electrochemical Properties

LI JUAN, LI QINGWEN, XIA XI, CAO YALI

1999, 17(2):  245-249. 

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In this paper,MnO 2 nanophase powders are successfully prepared by the redox reaction in solid state. Their morphology,particle size, thermal stability and electrochemical properties are characterized and discussed by x ray diffraction (XRD), TEM,TG/DTA, CV,and constant current discharge.

Exact Solutions of the Fisher-Type Equation with Variable Coefficient

GU YUAN, GU YI

1999, 17(2):  250-252. 

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The paper describes the Fisher -type equation with variable coefficient by similarity reduction method and a direct method, and constructs its exact solutions that contain solitary wave solutions.