Table of Content

30 September 1997, Volume 15 Issue 3

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Articles

A NOVEL METHOD FOR MICROWAVE IMAGLNG OF TWO-DIMENSIONAL TARGETS

QING ANYONG, LI JING, REN LANG

1997, 15(3):  253-258. 

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The microwave imaging of two dimensional targets is discussed in this paper.By volume equivalence principle, a system of integral equations is obtained. They link the media's permittivity and conductivity with scattering field and total field. Then, the inversion equation is obtained after taking variation on these integral equations. Some properties including the converging speed, inversion accuracy and its ability to inverse complex targets are investigated. The effect of random noise is also discussed in this pa-per.

SSAR MODEL IDENTIFICATION BY SIMULATED ANNEALING

ZHU XIANGYANG, ZHONG BINGLIN, YANG SHUZI

1997, 15(3):  259-264. 

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This paper deals with identification of subset autoregressive time series model. The motivation of this paper is to solve the problem of "combinational explosion" which results from determination of the optimal subset of regression terms. By using simulated annealing, an approach for optimizing the subset is introduced for this pur-pose.
The proposed algorithm is applied for modeling and prediction of monthly death rate in the population. The results show the effectiveness of the method,

ANALYSIS OF MILLIMETER-WAVE MULTILAYER MICROSTRIP LINES WITH SPECTRAL-DOMAIN GREEN'S FUNCTIONS

LING FENG, FANG DAGANG

1997, 15(3):  265-271. 

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This paper presents the general and concise expressions of spectral-domain electric and magnetic Green's functions for multilayer media derived by using spectral -domain immittance approach-Because the determination of the spectral-domain Green's functions is accomplished by the investigation of voltages and currents on the equivalent circuits, which correspond to electric and magnetic current sources respec-tively, the derivation procedure is easy to follow. Finally, the above Green's functions are applied to millimeter wave multilayer microstrip lines. The dispersion characteristics and the effects of physical parameters on the effective dielectric constant and characteris-tic impedance are investigated.

GIANT MAGNETORESISTANCES OF MAGNETIC GRANULAR FILMS WITH SMALL AND LARGE GRAINS

TANG DUOQIANG, YANG XINE, ZHANG DAIZHONG

1997, 15(3):  272-278. 

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We have calculated the scattering cross sections of the magnetic granular films with small grains, each of which contains atom number n<12, and large grains (n>>12) by Born approximation. Besides, we derived the formulas of the giant magne-toresistances(GMR) of the films. The results show that for small grains the GMRincreases with the atom number n. At a scale n₀, the GMR has the maximum value. For n>n₀, GNR decreases with the number n. The results also show that GMR increases dis-tinctly with the roughness of the surface of the grains and it comes from the spin-depen-dent scattering between conduction electrons and magnetic grains. With our model, the calculation results are in agreement with the experiments reported.

THE PHOTON ABSORPTION COEFFICIENT OF (HgCd) Te DETECTORS AND ITS EFFECT ON THE FRANZ-KELDYSH SHIFT OF CUTOFF WAVELENGTH

YE YUTANG, LI JlAXU, HONG YONGHE, LI ZHONGDONG, YE JING, SHU HAIHONG, LI ZHENGDONG

1997, 15(3):  279-284. 

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The width of the depletion region d and the photon absorption coefficient a of the pn⁺ junction (HgCd) Te detectors are calculated. The equation about the relation among a, d and the effetive Franz-Keldysh shift △λ_ce is derived. And an interpretation of tremendous difference between △λ_cm and △λ_ce presented.

ELECTROCHROMIC PROPERTIES OF V₂O₅ THIN FILMS

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

1997, 15(3):  285-290. 

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Electrochromic and electrochemical properties of V₂O₅ thin films prepared by evaporation followed by annealing posttreatment are studied. Lithium is inserted elec-trochemically from an electrolyte so that Li_xV₂O₅ (O<x<0. 35) is formed. The XRD analyses show that V₂O₅ thin films are cornposed of amorphous (postannealed at tempe-rature <500℃) and microcrystalline (postannealed at 500℃) structures, respectively.The formation mechanism of redox current peaks, the evolution of Li_xV₂O₅ structures and the relation between the evolution and optical properties during Li intercalation are analyzed. Electrochromic coefficient of cathodic and anodic electrochromic V₂O₅ thin films have been calculated.

THE DISCRETE ACTIVATION ENERGY DENSITY DISTRIBUTION AND THERMALLY STIMULATED DEPOLARIZATION CURRENT OF DIPOLES IN POLAR DIELECTRIC

LIU FUDE, LING ZHIYUAN, XIONG MAOREN

1997, 15(3):  291-298. 

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Having regard to the physical process of thermally stimulated depolariza-tion of the dipoles with a single activation energy, this paper obtaimed the thermally stimulated depolarization current (TSDC) of multi-or continous distribution activation energy dipoles. Numerical calculation results show that if the activation energy differ-ence between dipoles is less than 2kT, the dipoles can be considered to be existing in theform of continuous activation energy distribution, and if larger than 2kT, to be in the form of discrete distribution. Further work on transcendental fimction in TSDC equation has provided a method for directly calculating activation energy from the TSDC of dipoles, which is consistent with the exact numerical calculation results.

AN IMPROVED METHOD ON TIME-DOMAIN BORN ITERATION

YU WENHUA, PENG ZHONHQIU, LI SHIZHI

1997, 15(3):  299-304. 

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In this paper, we presnet a new method for improving Born iterative method——the frequency coniensation technique. The frequency compensation technique is used to solve nonlinear inverse scattering problem for two-dimensional lossless dielectric inho-mogeneity using time-domain data. We use the transmitting boundary condition and the superabsorption technique in FDTD to reduce the error of scattering fields.

MEASURING OF NONLINEAR OPTLCAL COEFFICIENT OF ORGANIC THIN FILMS DOPED WITH PUSH-PULL AZOBENZENES BY Z-SCAN TECHNIQUE

JIA ZHENHONG, LI QU, ZHOU JUN, CHEN YIXIN, ZHANG XIANGYANG

1997, 15(3):  305-309. 

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With Z-scan technique, we have measured nonlinear optical coefficient of organic thin films doped with push-pull azobenzene compounds, Experimental analysis shows that nonlinear refractive index is caused by π-electrons effect.

PATH PLANNING OF REALTIME OBSTACLE AVOIDANCE FOR MOBILE ROBOT CAPABLE OF MOVING ON THE VERTICAL WALL SURFACE

TAN SHILI, GONG ZHENBANG, WAN DEJUN

1997, 15(3):  310-314. 

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The purpose of this paper is to develop a realtime path planning algorithm used for the mobile robot capable of moving on the vertical wall surface. Artificial po-tential approach is used to avoid the random obstacles in the local range. Based on this algorithm, a closed-loop control between robot system and environment around robot system can be constructed to yield the optimal realtime path, so that the stability of robot system and its adaption to the environment are enhanced.

SOFTWARE FOR SIMULATION OF SEMICONDUCTOR DEVICE FOR LOW TEMPERATURE:SE-PISCES

WANG MINGWANG, WEI TONGLI, LI YAO, XIAO ZHIXIONG

1997, 15(3):  315-324. 

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Based on the software for simulation of semiconductor device PISCES, a software for simulation of semiconductor device for low temperature SE-PISCES was develpoed, by modifying model equations and adding parameter models for low temperature. The steady property, the transient property and AC small signal analysis of diode at low temperature were simulated and compared with the simulation resluts at 300K.

AN ITERATIVE ALGORITHM fOR DAMPED, WEOGETED SEISMIC TOMOGRAPHY AND ITS APPLICATION TO ENGINEERING

SONG LINPING, LIU HAOWU, SHA CHUN, SONH ZHENGZONG

1997, 15(3):  325-334. 

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Thls paper presents a new conjugate gradient type algorithm to solve the damped, weighted least-squares problem for seismic tonlography. Combining the natural weight and a priori constralnt, the numerical tests with Gaussian noisy data are performed. The results show that the method is superior to the conventional least squares method. Finally, the method has been applied to Tongzhilin (Sichuan, China) Hydro-electric Power cross-well data, and the reconstructed velocity image agrees well with the geological conclusion.

THE THEORETICAL RESEARCH ON A BASIC CHARGED GAS-SOLID FLOW AROUND A CYLINDER

YAO DAKANG, LUO TIQIAN

1997, 15(3):  335-342. 

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Adopting the particle-cloud model, this paper discusses the steady motion of a charged solid-phase in a gas-phase flow-field around a cylinder with a uniform flow at infinitude and in an electrostatic field around the cylindrical conductor with a uniform electric field intensity at infinitude. The most important result is that the smaller the solid-phase particle diameter the weaker the effect of charging on the solid-phase motion.

ANALYSING THE CONDUCTANCE CHARACTERISTICS OF PE THIN FILMS BY MEANS OF NONLINEAR REGRESSION

WU ZONGHAN, SHEN CAIKANG, HU YAOQING, ZHOU YUXIANG, SUN RIJUN

1997, 15(3):  343-347. 

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In this paper, we have analysed the measured data of conductance characte ristics of PE thin films by means of nonlinear regression and obtained three relative models. An analysation of these models has made it possible for us to obtain the physical meanings of relative items and physical natures of ohmic conducting, space -charge limited current, tunnel current and their mutual interactions.

ARTIFICIAL NEURAL NETWORKS AS APPLIED TO DIAGNOSIS OF LUNG CANCER

LI ZHILIANG, ZENG G M, HU F, MATSUMOTO S, WU X P, MURAMATSU Y, LI MENGLONG, GAO YUEPING

1997, 15(3):  348-352. 

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Artificial neural networks has been applied to biomedical engineering and life science. In this paper, a modified backpropagation algorithm (MBP) is developed for di-agnosis of lung cancer.This algorithm gives quite high correct recognition rate with its mean being 84. 5per cent.

ANALYTICAL PREDICTION OF SPADE DRILLING PROCESS Part 1 Basic Spade Drilling Model

SHEN QIAN, LIU WEICHENG, LI DACHAO, WANG MIN

1997, 15(3):  353-361. 

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The paper proposes first the spade drilling process in which the cutting action of lips is modelled as oblique machining process with inclination angle, rake angle and the cutting velocity varying along the edges. Then, a model for calculating the cutting power along the lips in spade drilling of ductile metals is described in detail. The model enables to predict the chip flow angle, which is based on the principle that the material removal in cutting process flows up along the direction of minimal cutting power consumption. The calculated and experimental results are well consistent.

ANALYSIS OF REFRIGERATING CAPACITY OF BINARY CRYOGENIC MIXTURES CONTAINLNG NITROGEN AND ALKANES

XU MINGYAO, HE YALING, CHEN ZHONGQI

1997, 15(3):  362-364. 

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The PR equation is used to calculate the refrigerating capacity of binary cryogenic mixtures containing nitrogen and alkanes. The effects of inlet pressure, standard boiling point and composition on the isothermal Joule-Thomoson effect when using these mixtures are also revealed. The refrigerating capacity will be increased by using binary cryogenic mixtures in a Joule-Thomoson cryocooler. And also, the inlet pressure will be decreased at the same refrigerating capacity.

FREQUENCY DOMAIN ANALYSIS OF NONLINEAR INTERMODULATION DISTORTION IN ACTIVE FILTERS

ZENG XUEGANG

1997, 15(3):  365-369. 

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The frequency-domain intermodulation balance method is presented for nonlinear intermodulation distortion prediction in active filters. As an example, a second-order bandpass filter with two-tone input is analyzed and measured. This technique and the time domain spectral balance are compared with respect to accuracy and computational efficiency.

THE WAVE-LIKE PHENOMENA RESEARCH FOR ENERGY FLOW IN REMOTE FIELD EDDY CURRENTS

CHEN MEIJUAN, ZHAO YANG, SHI DANING, QU MINGXING

1997, 15(3):  370-374. 

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The remote field eddy current (RFEC) technique is a new powerful tool for pipe inspection. ln this paper the diffusive energy flow of RFEC has been systematically analyzed with finite element method upon electromagnetic theory. Results show that it has wave-like phenomena for diffusive energy flow of RFEC in both quasistatic and translent excltion.

MICROWAVE ACTIVE FLOATING INDUCTOR

WEI DONGBEI

1997, 15(3):  375-378. 

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Microwave active inductor^[1,2] could be realized in general by a capacitor-loa ded two port active inverter network. This kind of inductor has its one end connected to ground. Active floating inductor can be designed theoretically by two inverters and a parallel capacitor inserted between them, but it isn't useful in practice due to its complex configuration and its relatively large size. In this paper a simple method of the design of actice floating inductor which is based on the active grounded inductor is proposed. This method may be of importance in synthesizing microwave monolithic integrated circuits (MMIC).