Table of Content

31 March 2000, Volume 18 Issue 1

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Articles

A New Approach for Determining Magnetic Field and Eddy Current in Nonlinear Ferromagnetic Materials

XING Ling-ling, XI Bao-feng, SHENG Jian-ni

2000, 18(1):  1-5. 

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A new approach based on operator decomposition method has been developed to solve nonlinear Helmholtz equation.The approach is applied to compute the magnetic field and eddy current in nonlinear ferromagnetic materials and it provides an analytical solution.It is found that the method converges rapidly and is efficient for determining magnetic filed and eddy current in two-dimension nonlinear ferromagnetic materials.In addition,the new appoach may be used to solve three dimensional even multidimensional problems.

Quasi-monotone Decomposition of Boolean Functions on B₂

CHENG Li, LIU Yong-cai

2000, 18(1):  6-11. 

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In this paper, quasi-monotone decomposition of Boolean functions on B 2 is discussed systematically. The quasi-monotone decomposition tree is used to define the general form of quasi-monotone decomposition. It gives great flexibility in its application. Several practical quasimonotone decomposition approaches for boolean operators ⊚,⊕, ∪ and ° are given. Then the above results are extended to the general form of quasi-monotone decomposition. In conclusion, we give the necessary and sufficient condition under which a boolean function can be decomposed into k monotonous boolean functions.

Research on the Method of Accurate Relief Grinding for Making Gear Hobs

SUN Yu-wen, WANG Xiao-ming, CAO Li-xin, LIU Jian

2000, 18(1):  12-15. 

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Based on the acentric relief principle, a new method of accurate relief grinding is presented for making Archimedes hobs. The result of our calculation testifies its feasibility. This provides reliable theoretical bases for the manufacture of hobs with high precision. The method can also be used in other types of hobs.

Study on the Making Electret Radiation Dosimeter and Measuring Dose

XU Jia-yun, LIN Li-bin, YAN Mei-qiong, ZHANG Yi-yun

2000, 18(1):  16-19. 

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In this paper, the application of the electret (made by corona -charging) in γ radiation dose measurement is described. The description focuses on the setup for forming electret by corona -charging and the designing and making of the electret dose measuring setup. Working principle of the dose measuring setup and its structure and special features are also described, with emphasis on the importance of these features to the accurate measurement of radiation dose. The experimental results of the electret charge stability and of the radiation dose measurement are given. These results indicate that both the electret and the setup are suitable for radiation dose measurement.

Application of Genetic Algorithm and FD-MEI Method to Electromagnetic Imaging

QIAN Zu-ping, HONG Wei

2000, 18(1):  20-23. 

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In this paper, the forward scattering problem is analyzed by using the FD-MEI (finite difference measured equation of invariance) method. The far fields are then obtained by the equivalence principle and the asymptotic expression of Green's function. The objective function is constructed in terms of the maximum of difference between the computed scattering fields and the measured fields, and scattering cylinder is reconstructed through optimization of objective function with the genetic algorithm. Some numerical results of the reconstruction are presented.

Study on BP Algorithm of Single Parameter Quick Search and Its Application

CHEN Xiao-dong, FENG Ying-jun

2000, 18(1):  24-26. 

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Single parameter quick search method, an improved BP algorithm based on single parameter coordinate -rotated method, is presented in this paper. Compared with other BP algorithms, it not only has a definite orientation in optimization and little time-consuming in computation, but also makes the convergent speed of the BP network very fast. Simulation results show that the new BP algorithm has strong robustness.

Research on One-dimensional Superlattice Structure of In_1-xAl_xAs/GaAs by X-ray Diffraction and Raman Scattering

YANG Chuan-zheng

2000, 18(1):  27-31. 

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One-dimensional superlattice structure of In_1-x Al_xAs/GaAs has been comparatively researched by X-ray diffraction method from synchrotron radiation and CuKα radiation. The superlattice structural period Λ,and refraction index n are calculated from low angle X-ray diffraction data. The superlattice structural parameters have been determined from high angle X-ray diffraction data. The results from two X-ray sources have been compared and discussed. Raman scattering spectrum of this one-dimensional superlattice has been interpreted and 275cm^-1 peak which is absent in Ga_1-x Al_xAs/GaAs system has been found.

Application Research of Neural Networks Based on Image Splitting in Two Phase Electrical Capacitance Tomography

XIAO Hua, HE Hui-ling, CHEN Xiao-lan, BAO Zong-ti

2000, 18(1):  32-34. 

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A neural network based on image splitting method for electrical capacitance tomography is proposed in this paper. A neural network model for image reconstruction and its realization are studied. Experimental results illustrate that the method is effective and accurate for image reconstruction.

Stabilization of a Class of Nonlinear Systems with Uncertainty Both in Their Executors and in Their Models

SHI Xiao-ping, ZHANG Wei-ping, WANG Zi-cai

2000, 18(1):  35-38. 

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By applying the exact linearization method, this paper studies the stabilization problem of a class of nonlinear systems with uncertainty both in their executors and in their models. First, the original affine nonlinear system is transformed into Lurie's indirect system with uncertain parameter, Lurie's method is then used to deal with the stabilization problem. In this paper, Lurie's theory is made available in case of nonlinearity and uncertainty of parameters.

Newly Near Shannon Limit Codes: Parallel Concatenated Extended Hamming Codes

CAO Jia-lin, DENG Jia-mei, MA Shi-wei

2000, 18(1):  39-41. 

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This paper designs a new class of codes:parallel concatenated extended Hammin codes using a combination of multi-dimensional parallel concatenation and extension techniques. The encoder is built using a parallel concatenation of multiple extended Hamming codes. The decoder uses the iterative decoding of the maximum a posterior algorithm based on the trellis technique, discussed in the paper.

Process Semantics of Composition Nets

JIANG Chang-jun, ZHU Ming-fa, LI Guo-jie

2000, 18(1):  42-46. 

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In this paper, we study the process properties of Petri net synchronous composition nets and share composition nets. The projection of process semantics on the subsystems and its modelling characteristic on sequence semantics are discussed respectively. A group of the formulas of semantics relations are thus obtained. They will be used in the analysis and verification of concurrent systems.

Research on Gauss Devolution of Raman Spectrum of Diamond Like Carbon Thin Film

ZHU Ji-jun, LU Zu-hong, ZHONG Xin, ZUO Dun-wen, WANG Min

2000, 18(1):  47-50. 

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The diamond-like carbonfilm is achieved by filtered cathode arc deposition. The results of Raman spectrum tests show that this kind of diamond-like carbon film is a typical nonhydrogen diamond-like carbon film. The Gauss devolution algorithm is studied in this paper and the results show:the position of D line and G line increase with the increasing of applied voltage. The intensity ratio of I_d/I_g has the highest value on the bias voltage of -100V.

A Study of the Field Conjugation Method for Direct Synthesis of Two-frequency Phased-array Ultrasound Hyperthermia

LU Ming-zhu, WAN Ming-xi

2000, 18(1):  51-54. 

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In order to tailor the ultrasound distributions to deep and sized tumors, a new method of two-frequency signals simultaneously driving phased-array elements is firstly proposed in this paper. Two requirements should be met in method of field conjugation with direct synthesis; One is the use of the pseudo -inverse method to compute element amplitude and phase driving distributions as a constraint condition; the other is the objective function to concentrate the energy to the sites. The paper also illustrates the field patterns of two frequencies driving to the rectangular sources.

A Study on the Gd₂O₃-MgF₂ Film by Positron Annihilation Life Spectroscopy

GUAN Yue-ying, SHI Zi-kang

2000, 18(1):  55-57. 

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In this paper,the quality of Gd₂O₃-MgF₂ film on thin quartz slice is determined by positron annihilation life spectroscopy. It illuminates the relationship between positron annihilation parameters and film structure.

A Study of the Dynamic Interfacial Tension of Crude Oil/Brine Interface

PU Bing-yin, CHEN Dong-hao

2000, 18(1):  58-63. 

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Drop volume method was used to measure the dynamic interfacial tension at the crude oil/brine interface. Experiments were performed with the existence of a nonionic demulsifier in water or crude oil under different concentrations and at three operation temperatures.
The result shows that (1) natural surfactants in crude oil were adsorbed slowly to the interface; (2) the fast build -up of demulsifiers present in crude oil at the interface was observed and they had advantage in the competition; (3) the concentration and operation temperature of demulsifier played an important role in affecting the dynamic interfacial tension data. Our investigation shows the ways to optimize the demulsification conditions and understand the demulsification mechanism.

A Dictionary Approach for Fault Location of Sub-Circuits in Cascade Linear Circuits

LI Feng, DENG Tie-jun, HE Xiu-fen

2000, 18(1):  64-67. 

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In this paper,a dictionary approach for fault location in cascade linear circuits is presented. The approach can locate any sub -circuits which have any faults (soft or hard, one or more than one). Because "cascade" is the universal joint way among sub-circuits of linear circuits, the approach is practical and usefull.

The Determination of Trellis Complexity of Linear Constant Weight Codes

YUE Dian-wu, JIANG Ling-yun, DUAN Bing-juan

2000, 18(1):  68-71. 

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In this paper, the trellis complexity of linear constant weight codes is considered. The trellis complexity of linear constant weight codes is determined with the help of the knowledge of dimension/length profiles and generalized Hamming weights, which improves the related result given by Y. Berger and Y. Be'ery in 1993.

True RMS AC/DC Conversion Based on the Log and Anti-log Electronic Circuits

NIE Kai-bao, CHEN Di, CHEN Zhi-jian

2000, 18(1):  72-75. 

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This paper discusses the high accuracy true RMS AC/DC conversion using log and anti log algorithm. On the basis of theoretical analysis, basic conversion formula is derived and then is used to analyze how to realize high accuracy AC/DC conversion. Finally, an actual conversion system with super-β and difference-matched transistors is implemented and tested. Results show that the new method is capable of realizing a high accuracy AC/DC conversion for measurement of true RMS value.

Directional Orthonormal Wavelet Bases and Direction Detection of Signals

WANG Qiao, WU Le-nan

2000, 18(1):  76-79. 

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The directional orthonormal wavelet bases are constructed and the corresponding fast algorithm is also provided, by which the directional characterizations of the signal can be extracted efficiently.

A New Approach of Speech Recognition Based on Second-Order Difference Cochlear Model

YU Xiao-qing, WAN Wang-gen, TAO An, YUAN Jing-xian

2000, 18(1):  80-84. 

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In this paper, the second -order difference cochlear model is used to extract the speech parameters. A kind of speech recognition front-end parameters based on auditory spectrum is obtained. A new "amplitude sum multiplied by frequency difference" distance measure is proposed according to the feature of speech parameters. The recognition algorithm is an improved DTW algorithm that sets two free frames in the beginning of speech segments and has the trace slope between 1/2 and 2. Under the recognition condition of small vocabulary or digits vocabulary and speaker independence, computer simulation shows that the algorithm attains an recognition accuracy of at least 98 percent, and it has the quite good robustness as well.

Reverse Solution Principle of Curved-profile Worms and Its Utilization

SHI Zhao-yao, XIE Hua-kun, FEI Ye-tai

2000, 18(1):  85-88. 

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Based on the general equation of curved profile worms, the reverse solution principle of parameters of these worms is introduced. Emphases are made on measuring worm profile and analyzing measured data in the case of no specifications of worms. Meanwhile, example of reverse solution of ZC worm is presented. Practice indicates that the principle and method are effective.

Study on Ternary-tree Algorithms of Packet Conflict Resolution for Random Access Channels

ZHAO Dong-feng, ZONG Rong

2000, 18(1):  89-91. 

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This paper presents a new ternary-tree algorithm of packet conflict resolution to analyze random access channels. The mean times of packet conflict resolution are explicitly obtained. The analytic formulae of the throughputs for dynamic and static algorithms are provided.

Study of Bit Allocation for DMT-HDSL System

WANG Jia-mei, ZHOU zhu

2000, 18(1):  92-94. 

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Bit allocation for DMT-HDSL system is presented. Through computer simulation, the results of performance analyses are given.