Table of Content

31 December 2000, Volume 18 Issue 4

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Articles

Reconstructive Method of Microscopic Elasticity Images of Vascular Tissues Based on Intravascular Ultrasound

LI Yang-mei, WAN Ming-xi

2000, 18(4):  283-288. 

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A static pressure was applied in the artery. The displacement and strain distributions of artery wall tissue were estimated using high frequency intravascular ultrasound imaging and two-dimensional motion estimation. The authors obtained "real" elasticity distribution images of different strain vascular tissues for the first time in the world by the reconstructive methods proposed in this paper. When arteries are in the small strain condition, the regions and boundaries of clear elasticity distribution variation are roughly identified. The vascular tissue elasticity distributions are reconstructed by using stress equlibrium equations. When arteries are in the large strain and nonlinear condition, the Newton-Raphson method is used to minimizes the least square error between experimentally estimated and theoretically predicted displacement fields so as to reconstruct elasticity distribution. The vitro experimental results of porcine artery demonstrates that the linear and nonlinear elasticity reconstructive methods are reasonable. The artifacts in the strain imaging can be reduced. Experimental research of vascular mechanics can be advanced to 2D or 3D sub-millimeter microstructure levels. These studies are of great importance in fundamental research of vascular mechanics and in the monitoring and evaluation of PTCA process.

A New Adaptive Chaotic Digital Encoder

ZHANG Jin-gang, DAI Xu-chu, XU Pei-xia

2000, 18(4):  289-293. 

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A new adaptive chaotic digital encoder is proposed. The parameters of the chaotic digital encoder can be adjusted adaptively. Compared with Frey's adaptive chaotic encoder, it possesses more complexity and much better correlation properties.

Construction of Authentication Codes with Arbitration from Pseudo-symplectic Geometry

MA Wen-ping, WANG Xin-mei

2000, 18(4):  294-297. 

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A construction of authentication codes with arbitration form pseudo-symplectic geometry is given, the parameters are computed. Assuming that the probability distribution of source state and encoding rules are uniform, the probabilities of successful attacks are also computed.

Wideband CDMA Wireless Multimedia Multiple Access Techniques Research and Implementation

QIU Ling, ZHU Jin-kang

2000, 18(4):  298-302. 

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In this paper, we present the result of our researches on the wideband code division multiple access (W-CDMA) multimedia wireless access techniques. This includes to propose W-CDMA modulation scheme of variable transmission rate, partial-balance power control algorithm, and wireless access method of variable access rate. Based on the proposed W-CDMA multimedia wireless multiple access techniques, an experimental system which consists of a base station and multimedia terminals is also developed. The system realizes the wireless communication of voice with 8kbps transmission rate and data with 144kbps transmission rate.

The Research on the Application of Wireless Spread Spectrum Modem

HUANG Qian, CHEN Hui-min

2000, 18(4):  303-308. 

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In this paper, a wireless spread spectrum modern designed by a programmable digit spread spectrum processing module is introduced. The hardware system of this modem is first presented. Next, the setting method for the spread spectrum processing module, the key to the realization of this modem, is discussed in detail. The experimental results of this system are given at the end of the paper.

A New Topology of Zero-IF Receiver

XU Jian, SUN Da-you

2000, 18(4):  309-312. 

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With increasing demand for mobile wireless receivers of low power and high integration, the zero-IF receiver demonstrates a greater advantage than the conventional superheterodyne receivers. The normal zero-IF topology with the single quadrature channels is very sensitive to the phase-error of the phase-shift network of LO. It decreases the image-reject ratio (IRR) and limits the applications of this structure. This paper presents a new topology called double-quadrature zero-IF topology, which is insensitive to the phase-error of the phase-shift network of LO and greatly increases the performance of the zero-IF receiver.

Carrier Recovery Based on Correlation Technique

ZHENG Jie, HU Ai-qun

2000, 18(4):  313-316. 

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This paper presents a new method for carrier recovery in a direct sequence (DS) code division multi-access (CDMA) receiver. The data demodulation scheme used is multiple phase shift keying (MPSK). The proposed scheme employs two balanced X-correlators to form a frequency discriminator. Theoretical analysis indicates that the proposed method has a tracking range that doubles the symbol rate, and the tracking range is independent of the keying phase number of the MPSK modulation.

The Transmission and Reception of SCA Radio Paging

WU Jian-hui, SHI Long-xing, SUN Da-you

2000, 18(4):  317-321. 

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In this paper, the mechanism of transmission of SCA radio paging is discussed. The way for radio reception of SCA radio paging is researched. The new topology for the single chip radio reception of SCA is presented, and it is simulated and proved by using MATLAB.

Theoretical Analysis of Adaptive Notch and Its Application in Receiving Relay Protection Signals

ZHOU Yi-qing, HU Ai-qun

2000, 18(4):  322-326. 

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The adaptive notch's performance is analyzed when it is used in a real system. It is discovered that there are several elements that effect its performance and the performance will be much better if the input signals are frequency down-converted and processed in low frequency. A low-frequency plan based on this result is presented. The comparison between the low-frequency and high-frequency plan is made by computer simulations and hardware experiments. It is shown that the low-frequency plan has a much better performance than the high-frequency plan:the speed request for iC chips can be lowered, the range of input signal's amplitude is 25 times larger and the tracking range of signal's frequency is larger than the high-frequency plan, too.

An Efficient Interval-valued Fuzzy Reasoning Approach

LI Fan, XU Zhang-yan

2000, 18(4):  327-330. 

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Based on the interval-valued fuzzy set theory, a reasoning method for a interval-valued fuzzy production rules based on interval-valued fuzzy set is proposed. In order to use the new rule for reasoning, a interval-valued fuzzy matching function, by which whether the antecedent of interval-valued fuzzy production rule matches the fact can be judged, is given. Finally, the process of inexact reasoning is illustrated with an example.

An Improved Love Equation of Electron Energy Loss

TAN Zhen-yu, HE Yan-cai

2000, 18(4):  331-334. 

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An improved Love equation (ML equation) of electron energy loss is presented. It not only retains love equation's analytical characteristic of deriving Bethe path by integration, but can also better describe the energy loss of electron in low energy region. With ML equation, the stopping power and range for electron in Al, Ag, An are calculated and compared with those from Love equation. By using Monte Carlo method and based on Mott cross section for elastic scattering of electron and ML or Love equation for energy loss of electron respectively, the scattering process of low energy electrons with energy E ≤ 5keV in solids is simulated. The calculated electron backscattering coefficients shows that the calculated results based on the ML equation are in agreement with experiments.

Parameter Decision Making in Adaptive Markov Decision Process with Finite Planning Horizon

LI Jiang-hong, HAN Zheng-zhi

2000, 18(4):  335-339. 

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An algorithm is proposed for adaptive MDP with finite planning horizon by reason of the fact that all current algorithms only consider adaptive MDP with infinite planning horizon. Bayes principle is applied to learn an unknown system; and for every decision the probability that the actual decision equals the optimal decision is maximized. Simulation results demonstrate the validity of the new algorithm.

A Robust Control Approach Using Model State Feedback

JI Qin-nan, WENG Zheng-xin

2000, 18(4):  340-344. 

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This paper proposes a robust control approach which uses state feedback of a model similar to a plant to improve the performance of the system. It also utilizes the sign feedback of the output error between the plant and the model and the sign inner model to enhance the system's robustness while various uncertainties exist. Theoretical analysis and simulations show its strong robustness both in stability and performances.

The Stabilization of a Class of Uncertain Nonlinear Systems Which Can Be Transformed into Lurie's Direct Forms

SHI Xiao-ping, MA Ke-mao, WANG Zi-cai

2000, 18(4):  345-347. 

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Using the exact linearization method of affine nonlinear systems, a class of nonlinear systems with uncertain executors are transformed into Lurie's direct systems and therefore the stabilization problem of the original systems is solved.

Two-dimension Multiple Indexes Method of Rubber Dispersion

WANG Ming-lan

2000, 18(4):  348-352. 

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Model identification of rubber dispersion is a project that will improve the quality of rubber and reduce losses in the form of rejects with high-tech means. The new technique badly needed by the rubber industry will reach the world advanced level and product remarkable economic benefit. It will greatly improve the micro-graphic method which is being used now.#br#The author of this paper has achieved the following results:(1) the colorful patterns of carbon particles dispersed in rubber can be shown clearly on the screen of computer and the quantitative norm that reasonably describes the dispersion of carbon particles can be obtained; (2) the author is able to determine the stability of classified objects and put forward the two-dimension multiple indexes method. The carbon dispersion degree will be automatically judged by computer. Up to now, no similar technology has been in existence in this country.

A Study on the High Field Conduction of LDPE After Being Aged by Electrical Stress

YIN Yi, SUN Jing, TU De-min

2000, 18(4):  353-358. 

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The space charge distributions of low-density polyethylene under different dc electrical stresses are measured with the pulsed electro-acoustic (PEA) method. The high field conduction of low-density polyethylene thin films (with and without the voltage stabilizer) after being aged at different times are measured and the energy level distributions of traps in the samples are calculated by the space-charge-limited-current (SCLC) theory. In addition, the high field conduction of polyethylene at different temperatures is measured. It is shown by test results that the voltage stabilizer can effectively reduce the producing of deep traps in the samples during the electrical aging process. Therefore adding the stabilizer will reduce the energy of hot electrons caused by recombination or trapping of charge carriers and lengthen the lifetime of the samples.

Numerical Simulation of PSA Process for Nitrogen Production from Air

LU Hong, LI Cheng-yue

2000, 18(4):  359-364. 

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The PSA cycling process for nitrogen production,based on the difference in adsorption kinetics of oxygen and nitrogen on a commercial carbon molecular sieve, is systematically studied. Some results of developing models and algorithms are reported in this paper. A linear driving force model (LDF) of mass transfer is introduced into the mathematical model of the cycling process and an iteration algorithm combined with an orthogonal collocation method for solving PDEs is developed. Computation shows the high efficiency and stability of the algorithm. With this model, the performance of a pilot plant packed with 15Kg of carbon molecular sieve, BF-CMS, is simulated and predicted under different operation conditions. This paper also discusses the effects of thermodynamic and kinetic parameters on the unit performance.

Research on (Pb_1-xSr_x)TiO₃ Infrared Sensitive Ferroelectric Ceramics

WANG Mao-xiang, SUN Tong, SUN Ping

2000, 18(4):  365-367. 

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Through varying the component proportion of the Pb/Sr and doping 0. 25wt% MnO₂, a series of (Pb_1-xSr_x) TiO₃ infrared sensitive ferroelectric ceramic material was prepared. In this paper, the temperature, frequency, pyroelectric properties of these materials were studied. Results showed that the Curie temperature To would shift lineally with the Pb/Sr ratio. And the increase of 1% mol ratio Pb would raise Curie temperature by about 5℃. With the increase of working frequency, the dielectric constant ε of these materials showed a decrease, but the Curie temperature T_c and the temperature coefficient remained basically the same. The spontaneous polarization intensity of these materials decreased with the rise of the ambient temperature. The pyroelectric coefficient was in the order of 10^-3C/(m²·K).

A Study on the Microstructure and Properties of Fe-Al Alloy TIG Weld Joint

DING Cheng-gang, CHEN Chun-huan, CONG Gou-zhi, YIN Yan-sheng, BAO Zhi-chen

2000, 18(4):  368-370. 

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The microstructure of weld metal was studied by means of XRD, SAED and EDS. High-temperature oxidation-resistance test and tensile test of joint were carried out. The results are as follows:the weld metal is Fe₃Al. The tensile strength of the weld joint is inferior to that of the base metal, and the location of rupture is in the overheated zone. The oxidation-resistance property (900℃) of the base metal is superior to that of the weld metal.