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    31 December 1997, Volume 15 Issue 4
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    Articles
    RESEARCH AND APPLICATION OF MATHEMATICAL MODEL FOR HOT FORMING STRESS-STRAIN CURVE
    XU YONG SHUN, LIU JIANTAO, NIE MING, LI ZHIGANG, RUAN XUEYU
    1997, 15(4):  379-384. 
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    Two types of mathematical models for hot forming stress-strain curve in metal are analysed in this paper. Through a detailed investigation on hot forming processing, a new model for true stress-strain curve, quite suitable for engingeering application, is put forward:σ=Aεaεbexp[-(cT+dε)], It provides a useful referential foundation for realizing the controlled forging technology in steel.
    A NEW METHOD FOR SOLVING ELECTROMAGNETIC EIGENVALUE PROBLEMS
    ZHU ZHENHAI, HONG WEI, JI HAO
    1997, 15(4):  385-393. 
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    By adding a known source function to the right-hand side and giving the unknown eigenvalue a trial value, the homogeneous Helmholtz equation that models the eigenvalue problems is turned into an inhomogeneous Helmholtz equation that models the deterministic problems. When the trial value approaches one of the correct eigenvalues, the norm of the solution of the deterministic equation will approach infinite. Taking this as a criterion, an eigenvalue problem can be turned into a deterministic problem. The most attractive feature of this method is that it can solve the non-standard eigenvalue sparse matrix equation by using the methods for the deterministic sparse matrix equation.
    DETECTION OF TWO-DIMENSIONAL OBJECTS IN HALF SPACE
    QING ANYONG, LI JING, REN LANG
    1997, 15(4):  394-401. 
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    The detection of shallow two-dimensional objects in layered media by using time domain scattering data is considered in this paper. A volumn integral equation which relates the scattering fields in time domain with the permittivity of the objects is obtained by volumn equivalence principle. The equation is transfered into frequency domain and the inversion equation is obtained after discretion. With our iterative method both forward and inverse problems are solved in each iteration. The forward problem is solved by using finite-difference time-domian method. The inverse problem is carried out by using a pseudoinverse technique. The Green function excited by line current source is derived by using plane wave expansion method. Several examples are given to show the ability of this metohd to invert arbitrarily shaped objects.
    THE SCATTERING OF A CYLINDER COVERED WITH A LOSSY DIELECTRIC LAYER
    YAN JlNKUI, XU CHANGLONG, XU DEMING
    1997, 15(4):  402-407. 
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    The expressions of the scattered field of a dielectric-covered conductor cylinder are derived by using the eigenfuction method. When the electric dimension of the cylinder is large and the thickness of the dielectric layer is small, a simple form of surface impedance of the cylinder is obtained. The distribution of total field and the total RCS per length are analyzed.
    ASYMMETRIC ETCHED OPTICAL FIBER SENSOR ARRAY AND ITS NEURAL NETWORK PROCESSING
    REN XUE BING, YANG JIAN LIANG, HUANG DE XIU
    1997, 15(4):  408-412. 
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    A new fiber optic sensor array which is made of asymmetiric periodically etched multimode optical fiber is described. It may be applied to detect structure state such as strain and stress, or damage assessment in smart material and structures. The method, model of array sensing signal processing in artificial neural network are decribed, and the simulation results of BP network are also given.
    REMOTE SENSING OF THE TEMPERATURE OF THE EXPOSED REGION IN LASER ASSISTED DIFFUSION
    LI ZHONGDONG, YE YUTANG, HONG YONGHE, YE JING, LI JIAXU
    1997, 15(4):  413-417. 
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    The determination of the temperature distribution in the exposed region is something difficult since the size of the exposed region in laser assisted diffusion is only of the order 10 microns. Remote sensing of the temperature of the extrasmall areas in that exposed region is reported. The theoretical principle, experimental set-up and the experimental results are presented, and especially, the callibration of the temperature sensing system is discussed in detail.
    REALIZATION OF SOME NON-LINEAR PERMUTATIONS WITH ITS DIFFERENTIAL DISTRIBUTIONS
    GU DAWU, XIAO GUOZHEN
    1997, 15(4):  418-423. 
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    The exponential functions over a finite field, which are chosen as some nonlinear permutations, are illustrated in details. Two new principles of designing S-boxes are proposed. Series of cryptographic parameters are calculated with characteristics of equivalent I/O differential distribution. And an assumption is put forward.
    THE RESEARCH OF InGaAs MSM-PD SCHOTTKY BARRIER ENHANCEMENT LAYER
    ZHU HONGWEI, SHI CHANGXIN, CHEN YIXIN
    1997, 15(4):  424-428. 
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    It is shown in this paper that the dark current of InGaAs MSM photodetectors can be greatly reduced with the structure of p-InGaAs Schottky barrier enhanccmcnt layer. Theoretical explanation is given and the lowest dark currents with the order of 10-11 A are obtained in our experiments.
    EFFECTS OF DISPLACED P-N JUNCTION OF HBT
    ZHANG YUMING, ZHANG YIMEN, LUO JINSHENG
    1997, 15(4):  429-435. 
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    The Hydrodynamic Transport Model is used to simulate the effects of displacemeilt of PN junctions of HBT. The electric characteristics are shown to be drastically altered due to changes in the potential profiles and in recombination in both neutral base and space-charge region of the emitter. The effects of a small displacement of the PN junctions from emitter-base are examined and results for current gains and cutoff frequencies are given.

    PREPARATION, MICROSTRUCTURE, STATIC AND DYNAMIC MAGNETIC PROPERTIES OF ULTRA-FINE METALLIC AND BIMETALLIC ALLOY POWDERS
    YANG SHIQING, WANG HAOCAI, ZHANG WANLI, HE SHIGUANG
    1997, 15(4):  436-439. 
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    The polyxol method is used to prepare the fine metallic and bimetallic alloy powders. XRD and TEM analysis show that the fine Co and Ni metallic powders have a fcc structure and CoxNi1-x. powder has a solid solution or a mixed fcc phase, and all of these powders have a nearly spherical shape with grain size being about 50nm. The specific saturation magnetisation σs increases (from σs=18.8 to 128. 8 Am2/kg) and the coercivity Hc decreases (from Hc=14000 to 7520 A/m) as the mole fraction of cobalt x varies from 0 to 1. The HP8510B is used to measure the dynamic permeability of metalepoxy resin composite material within the frequency range of 8. 20~12. 40 GHz. The dependence of static and dynamic magnetic properties upon mole fraction x is also discussed.
    A STUDY ON ADMITTANCE SPECTROSCOPY OF ZnO VARISTOR CERAMICS
    FU GANG, CHEN HUAN, CHEN ZHIXIONG
    1997, 15(4):  440-445. 
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    Kinds and causes of deep electron traps in the depletion region of ZnO varistors and effects of some additives on the traps have been studied by using admittance spectroscopy method. The results show that some additives such as Ba have a restraint effect on the formation of intrinsic defect Zni2+. The detection of Zni2+ depends not only on the defect density, but also on the measurement temperature. Besides the normal conductance peaks 1 and 2, that are considered to associate with the intrinsic defects Vo+ and Zni2+, peak 3 has been observed at lowwtemperature (about -170℃) and the corresponding trapping level is Et=0. 163eV, the capture cross section is σn=7.71×10-12cm2 and the room temperature (300K) thermal emission time constant is τ=1. 11×10-6μs.The conductance peak might be caused by extrinsic defects resulting from the interaction between grain boundary and the additives.
    GENERAL ECOLOGICAL FIGURE OF MERIT FOR THERMODYNAMIC CYCLES AND ITS APPLICATION
    CHEN TIANZE, YAN ZIJUN
    1997, 15(4):  446-452. 
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    It is pointed out that the main purpose of introducing the ecological figure of merit of a thermodynamic cycle is to make the best compromise between the rate of function and its dissipation of the cycle. Thus, the ecological figure of merit of a thermodynamic cycle should be based on the general ecological criterion function, while that based on the objective function of exergy analysis is not applicable in many cases. The significance and application of the ecological figure of merit are also discussed.
    THERMODYNAMICS OF MECHANICAL ALLOYED Fe-Ni
    ZHANG TONGJUN, YANG JUNYOU, ZHANG JIE, CUI KUN
    1997, 15(4):  453-458. 
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    Fe60Ni40 powders were prepared by mechanical alloying (MA) in a planetary ball milling in argon atmorsphere. XRD analysis pointed out that the Fe-Ni MA powders consist of α (bcc) and γ (fcc) noncrystalline supersaturated solid solutions. And the two phases transformed each other during milling. In initial stage, the a phase was dominant, then it decomposed and transformed into γ phase gradually during milling. Some structure parameters of the MA powders, such as lattice parameter, grain size and lattice strain and so on, were determined by analysing the XRD patterns. A thermodynamic model of MA of Fe-Ni system was developed based on Miedema semi-experimental theory to explain the phases transformation of Fe-Ni system during milling. The thermodynamic analysis showed that there is no chemical driving force to form amorphous alloy. And what type solution or solutions presented in the MA powders during milling was controlled by structural contribution of the forming enthalpy of the alloy. All of the results are agreed with the experiments.
    ANALYTICAL PREDICTION OF SPADE DRILLING PROCESS PART 2 DRILLING FORCES WITH ARBITRARY DRILL POINT ANGLE
    SHEN QIAN, LI DACHAO, LIU WEICHENG, ZHOU CHANGXIU, WANG MIN
    1997, 15(4):  459-468. 
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    In this paper, the spade drill point geometric parameters are analyzed in detail. The cutting lips were modeled in the previous part of this study, and are extended to accounting for the dynamic effects of cutting and feed velocities. The models for calculating main cutting edge torque and thrust force in spade drilling are deduced. The force components.obtained from the models are integrated along the lips. These models can be applied to the spade drills with arbitrary drill point angle. Predicted torque and thrust force for the cutting lips are agreed well with the experimental data from spade drilling tests.
    THERMOCHEMICAL STUDY OF MITOCHONDRIA ⅡTHERMOCHEMICAL STUDY OF THE ACTIVITY OF MITOCHONDRIAL METABOLISM
    LIU YI, FENG YING, XIE CHANGLI, ZHOU PEIJIANG, QU SONGSHENG, ZHU YINGGUO, ZHOU HANTAO
    1997, 15(4):  469-473. 
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    The metabolic thermogenesis curves of the metabolism of the mitochondria isolated from rice have been determined by using an LKB2277 Bioactivity Monitor. The thermodynamics and kinetics of the rice mitochondrial metabolism out of the cell have been studied. The metabolic thermogenesis curves of the rice mitochondria appeared four different phases. If the rice mitochondria have been laid up for different time, the metabolic thermogenesis curves and the kinetic behaviours of the rice mitochondria are different. Some thermodynamic values and kinetic paramters, as well as some new experimental thermokinetic equations in the activity increasing phase of the rice mitochondria,have been calculated and established.
    MODELLING OF THE TIDAL MODEL SYSTEM AND ADAPTIVE CONTROL
    ZHANG CHENGHUI, WANG HUAYI, ZHANG TIANDE
    1997, 15(4):  474-481. 
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    In order to improve the dynamic feature and static accuracy of tidal model system, it is necessary to obtain an accurate dynamic model and select a rational control strategy. In this paper, the modelling and adaptive control for tidal model system are studied in detail with the water level and water flow being controlled variables. The weighting minimum variance self-tuning regulator is designed to obtain a high accuracy control for the tidal model system. A new parameter estimation method is used to increase the accuracy. The adoption of "fogetting factor" in the method can avoid the data saturation and improve the robustness. Both simulations and application have proved that the new control strategy is sucessful.
    THE EXPRESSION OF KNOWLEDGE AND ORGANIZATION OF KNOWLEDGE BASE IN GEOGRAPHICAL EXPERT SYSTEM
    FU WEI
    1997, 15(4):  482-489. 
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    This paper presents basic approaches and principles for how to express knowledge and to organize the knowledge base in Geographical Expert System(GES),and taking Water and Soil Conservation Expert System (WSCES) as an example, the author expounds the methods of classification and gradation for Water and Soil Conservation Expert Knowledge (WSCEK), and discusses the basic rules of knowledge expression in the WSCES and the organization patterns of expert knowledge in the knowledge base. In the mechanism of knowledge capture the system provides the mutual interface for taking supplemental edit of knowledge as a primary and understanding of natural language as a complement between man and system. Therefore, the input process of expert knowledge is simplified greatly, and working efficiency of thesystem is promoted to a high degree.
    ROBUST DESIGN A NEW METHOD TO MINIMIZE||A+BK||F
    XU XUPING, ZHOU QIANG, SHI SONGJIAO, DU XIUHUA
    1997, 15(4):  490-493. 
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    A new robust design method is discussed in this paper. The main idea of this method is to use the addition of the pole differences and robustness measurement as a destination for optimization. It provides a quick and efficient optimizatoin method suitable for engineering.#br#Frobenius norm of the closed-loop matrix A+BK is used here as a robustness index. This index is minimized by Powell method, thus to make the lower bound of a robustness measurement maximized.
    A STUDY OF THE PREPARATION OF MONODISPERSED SPINDLE HEMATITE
    WEI YU, HE HUILAN, ZHENG XUEZHONG, LIU XIAOLIN
    1997, 15(4):  494-498. 
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    The spindle monodispersed hematite particles were prepared by forced hy drolysis in boiling refluex state from Fe(NO3)3 solution for 70h. The influcence of modifers and their concentration on the size and morphology of the particles were studied.The morphology and composition were characterized by TEM and XRD. The mechanism of formation of spindle α-Fe2O3 was discussed.
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Bimonthly, Founded in 1983
Editor-in-Chief:Wang Tingyun
ISSN 0255-8297
CN 31-1404/N