Table of Content

31 December 2001, Volume 19 Issue 4

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Articles

Distribution of Space Charges and Analysis of Trap Levels in Cross-linked Polyethylene

LI Ji-xiao, ZHANG Ye-wen, ZHENG Fei-hu, WU Chang-shun, XIA Zhong-fu

2001, 19(4):  283-287. 

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The formation and evaluation of space charge in cross-linked polyethylene have been studied by using Piezo-PWP and TSD methods. There is a large difference between two TSD curves, but little difference between two PWP curves. The results indicate that deeper understanding and more details can be gained by using both methods. Space charges in XLPE might be due to the injection charges, the impurity ions and the orientation of small molecules dipoles, which seems to be the major cause. The capture of electrons by traps can broaden the peak of TSD. The traps are related with the small molecules in XLPE.

An Intermittent Linear Feedback Method for Controlling Henon-like Attractor

LI Guo-hui, ZHOU Shi-ping, XU De-ming, LAI Jian-wen

2001, 19(4):  288-290. 

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In this paper, a method based on intermittent linear feedback to control Henon-like attractor is proposed. The technique consists of autonomous and controlling phases. The different stable periodic orbits are obtained by adjusting the feedback coefficients and the time duration, which the control phase occupies. As an example, we get the expected conclusion by numerically simulating the Henon-like attractor with unidentical feedback coefficients. The results from the computer simulation show that the proposed scheme can switch effectively the system to the desired periodic orbits.

Determinations of Mean Charge Depth and Charge Density in Electret Based on Silicon Substrate

ZHANG Xiao-qing, XIA Zhong-fu, ZHANG Ye-wen, LIU Xiang-huai

2001, 19(4):  291-294. 

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In this paper, a method for determining the mean charge depth and equivalent surface charge density in an electret-semiconductor system is presented. It consists of two nondestructive measurements. Firstly, the surface potential at the electret-air interface is measured by the compensation method. Secondly, using a contacting front electrode, a metal insulator semiconductor structure (MIS) is formed, on which C-V measurement is carried out. The mean charge depth and the charge density can be calculated. The method was applied to the electret double layers of Si₃N₄/SiO₂ based on silicon substrate. It was found that the annealing temperature influences the mean charge depth markedly. The mean charge depth of the sample positively charged at room temperature shifted to the interface of Si₃N₄ and SiO₂ from the free surface after annealed at 400℃ for 20 minutes.

A Study on the Optimization of the Effective Heating Field in Hyperthermia Based on Genetic Algorithms

CHENG Xiao-man, WAN Bai-kun, ZHU Xin, ZHANG Li-xin, LIN Shi-yin, WANG Wei

2001, 19(4):  295-298. 

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An inverse optimization method, applied in hyperthermia to search for the ideal heating physical configurations in the expected temperature distribution of heat-field, is proposed. First, in order to realize the target temperature distribution of tumor tissues and avoid the over-heating of healthy tissues, an objective function and some related weight coefficients are introduced. Next, based on the 2-D finite element method(FEM) and the solutions of Laplace and Pennes' bio-heat transfer equations, the genetic algorithm(GA) recursively modifies the heating conditions to minimize the objective function, that is, the difference between the calculated temperature distribution and the expected one, satisfactory simulation results are demonstrated in 3-aplicator RF-capacitive hyperthermia of a simplified non-homogeneous human model obtained from a X-CT human slice. This technology of target heat-field temperature control is believed to have an important practical value in the design of hyperthermia devices and clinical applications.

The Application of Float-encoding Genetic Algorithm to System Identification

SHEN Chun-hua, LU Jing, XU Bo-ling

2001, 19(4):  299-302. 

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In this paper, a new approach to identify ARMA model under noisy background is real-ized by using float-encoding genetic algorithms. With the aid of this method, unbiased parameters estimates of the system can be obtained when the output is corrupted by noise unrelated with the input signals. The effectiveness of the approach is testified by several simulations and the results show that it is more effective than least-square method. And it has been successfully applied in the measurement of the low-frequency characteristic parameters of a vented-box loudspeaker system.

Design of the Output Feedback Passive Controllers for Time-delay Systems

LI Zhi-hu, SHAO Hui-he

2001, 19(4):  303-307. 

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This paper focuses on the problem of output feedback passive control for a class of linear time-delay systems. By using Lyapunov stability theory and linear matrix inequality (LMI) approach, sufficient conditions are given for the existence of static or dynamic output feedback controllers which render the closed-loop system to be quadratically stable and strictly passive. The design of the two control laws is transformed into finding a feasible solution of LMIs.

Fault Detection Filter Design for a Class of Linear Time-invariable Systems

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

2001, 19(4):  308-312. 

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A new full order detection filter for a class of time-invariable systems is proposed. It obtains a detection filter for the original system by augmenting the original system and designing a new one. This filter can asymptotically detect m (can be increased to n) faults that occur simultaneously with the initial state estimations error. The relation between the detection threshold, designing parameters and the performance of the filter is analysed. The rules for the choice of the parameters and threshold in the design procedure are also given. The simulation result indicates that this detection filter has good detection capability.

Sampled-data Iterative Learning Control with an Exponential Convergence Rate for Time-delay Systems

FANG Zhong, CHEN Peng-nian, HAN Zheng-zhi

2001, 19(4):  313-316. 

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A sampled-data iterative learning algorithm is proposed for a class of continuous time systems with state delay. Sufficient conditions for exponential convergence of the algorithm are presented and proven by the induction. Exponential convergence is achieved not only at every sampling instant but the entire time span.

Nonredundant Error Correction Differential Demodulation Combined with Soft-decision Decoding

GUO Dao-sheng, ZHANG Bang-ning, GAN Zhong-min, YANG Xi-gen, LIU Ai-jun

2001, 19(4):  317-321. 

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The paper proposes the application of nonredundant error-correction in differential demodulation combined with soft-decision decoding. According to the hard-decision information of nonredundant error-correction, the soft output of conventional differential demodulation is weighted. Thus nonredundant error-correction can be used in a system in which the differential demodulation is combined with soft-decision decoding. The algorithm improves the performance of system. Computer simulation shows that the improved performance of the proposed algorithm is superior to the conventional differential demodulation combined with soft-decision decoding by 1.4dB at a BER of 10^-5 in AWGN channel. In Rician channel there is the same notable performance improvements. It enables nonredundant error-correction to be used in the system of differential demodulation combined with soft-decision decoding which is widely used in satellite communication system. The system's capacity and communication quality is notably improved.

The Study of Real-time Data Transfer Method in Fiber-optic Industry Network

HUANG Hai-feng, SUN Xiao-han, ZHANG Ming-de, DING Dong

2001, 19(4):  322-326. 

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Multimedia fiber optic industrial network (FIN) based on fast ethernet includes several types of data, such as alert data, control data and multimedia video signals, and each station of the industrial network must meet the demand of real-time transferring. This paper offers a hybrid mode transfer scheme based on the network application layer. According to the non-preemptive M/M/1 queuing model, waiting-time and system task number are used as parameters. A multi-task queuing model with the priority mode in the industrial network is established. The transferring mechanism and realizing method of priority transfer protocol (PTP) are founded and discussed. Lastly, the performance parameters and running results of the hybrid model are analyzed in different environments.

A Combined Synchronization Method for OFDM System

SHU Feng, LIU Yi-feng, LUO Ling, WU Le-nan

2001, 19(4):  327-332. 

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In this paper, a combined synchronization method for OFDM system is proposed. It provides good synchronization for frame, symbol, and carrier. Theoretical analysis is made for the above method. In the case of multipath fading channel, the simulation result shows that the method provides not only accurate carrier synchronization but also high-resolution symbol synchronization. Consequently, intersymbol interference (ISI) and interchannel interference (ICI) from symbol timing error and frequency offset are effectively reduced.

An Approach for Multiple-view Data Capture by a Single-view 3D Camera Using a Simple Revolve Device

HENG Wei

2001, 19(4):  333-336. 

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An approach is proposed for multiple-view 3D capturing by a single-view 3D camera using a simple revolve device. In this article we discuss the structure of a multiple-view 3D camera based on our method, the configure calibration for the revolve device and the alignment of the object surface 3D data captured from different views directly through space coordinate transformation. We have also demonstrated the space coordinate transformation function with regards to the revolve angle. The alignment error caused by the revolve device is analyzed, and an example is given and discussed. The multiple-view 3D camera based on our method will have many advantages:simple system, no additional operation and special requirement when capturing, computable alignment precision, automatic and rapid capturing and alignment processing.

Expanding the Capacities of WDM Star Networks by Reusing Wavelengths

GAN Chao-qin, ZHANG Ming-de, SUN Xiao-han

2001, 19(4):  337-341. 

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In order to expand the capacities of WDM star networks and free them from the restriction caused by the limited number of wavelengths, a scheme of reusing wavelengths is proposed in this paper. According to the scheme, not only can the number of nodes be doubled, but also all the data wavelengths can be reused in the network and the throughput of the network doubled. With the same number of nodes, the delay of the network can be greatly reduced and the properties of the network effectively improved. Besides, through the network structure proposed is simple, and the scheme can be easy implemented in practice. In this paper, the network structure is introduced first. Next, the properties of reusing wavelengths in the network are analyzed. The required gain and output power of optical amplifier in the network are computed, Finally, the maximum number of available wavelengths and the maximum number of supportable nodes in the network are also computed.

A Study of the Improvement in the Method for Synthesizing Alkye Polyglucosides and Its Application

GU Xu-peng, CHEN Tong-yun

2001, 19(4):  342-344. 

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In this article, we synthesise dodecyl-polyglucosides by using a complex catalyst and through the direct reaction of glucose and laurel alcohol and optimize the technological datum. The proper reaction conditions:reaction pressure 4.05kPa, reaction temperature 120℃, mole ratio of laurel alcohol and glucose 5:1, mass ratio of complex catalyst and glueos 0.008:1, are obtained. There is further discussion on the active mechanism and application properties of the APG.

Numerical Simulation of Rapid Transient Mass Transfer

HUAI Xiu-lan, LIU Deng-ying, MENG Qun

2001, 19(4):  345-348. 

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The numerical simulation of rapid transient mass transfer is made. The influence of mass relaxation time, mass disturbance concentration and disturbance manner etc on the process of rapid transient mass transfer are studied. The results indicate that mass relaxation time has important influence on the mass transfer process. Mass disturbance concentration and manner also have some effect on it.

Research on Relaxation Phenomena of Heat and Mass Coupling in Wet Porous Media

WANG Xin, SHI Ming-heng, YU Wei-ping

2001, 19(4):  349-352. 

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With the first boundary condition of one-dimensional porous media in view, this paper seeks to solve the general differential equations of heat and mass transfer under the condition of highly intense and rapid drying by taking into account of both non-Fourier effect and non-Fick effect at the same time. The coupling phenomena between non-Fourier heat transfer and non-Fick mass transfer in wet porous media is also investigated. Thus it helps to establish the theoretical basis for correct confirmation and control of temperature field and moisture field in wet porous media.

A Study on the Artificial Neural Network Model of the Solidified Grain Size of Al^- alloy

ZI Bing-tao, YAO Ke-fu, CUI Jian-zhong, BA Qi-xian

2001, 19(4):  353-356. 

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A BP algorithmic model was established for the artificial neural network of the grain size of Al-alloy's solidification structure under the action of strong pulse electromagnetic field. The simulating results were in agreement with the experimental results. It was shown that this BP algorithmic model of artificial neural network could be used to control the parameters and predict the solidified grain size under the action of strong pulse electromagnetic field. It provides us with an easy and practical method and means for optimizing experimental design.

Research on the Deformation and the Energy Absorption of Cellular Aluminum Under Compression

WU Zhao-jin, HE De-ping

2001, 19(4):  357-361. 

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The characteristics of cellular aluminum specimen under compression were investigated, and the effects of porosity and pore-diameter on energy absorption of cellular aluminum were revealed. Finally, a comprehensive method for justifying the energy absorption of cellular aluminum with different porosity and pore-diameters was proposed.

System Identification for the Active Network of a Thermoacoustic Regenerator

WU Feng, GUO Fang-zhong, LI Duan-yong

2001, 19(4):  362-364. 

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An active thermoacoustic network model of the regenerator has been established. The H matrix is identified by making the capillary number as an identification parameter.

Development of an Electronically Controlled VE Distributor Injection Pump

WEN Ren-lin, GU Zhi-hua, ZHANG Yi, ZONG Zhi-bin

2001, 19(4):  365-368. 

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Using electronic control to lower fuel exhaustion and emission is one of the problems to be dealt with in the development of the engine and the fuel injection system. The special feature of the construction, the working mode and the control principle of a new electronically controlled VE distributor pump are set forth in this paper. The new electronically controlled VE pump and a mechanical VE pump are respectively used in the engine JX493Q1. Experimental results show that the electronically controlled VE pump has an advantage over the mechanical VE pump both in power and economic performance. Viewed from its full-load-speed characteristic, the engine is more adaptable to load change when equipped with the electronically controlled VE pump than with the mechanical VE pump.

Research Notes

TEM Observation of the Abnormal Behavior of Nanometer Metal Powder and Nanometer Copper Powder

SHENG Ke-ping

2001, 19(4):  369-370. 

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Observing Cu, Al, Ni metal powder with an electron microscope, we discoveried that copper powder's melting point is much lower than the melting point of aluminum powder etc. When its size is reduced to nanometer scale. This characteristic will have great value in practical application.