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25 June 1996, Volume 13 Issue 2 Previous Issue    Next Issue

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ANALYSIS OF THE α PARTICLE TRANSPORT IN TOKAMAKS BY THE TWO-DIMENSIONAL TIME-DEPENDENT FOKKER-PLANCK EQUATION Wang Shaojie, Qiu Lijian 1996, 13(2): 129-135.  Abstract ( )   PDF (433KB) ( )   For different definitions of the distribution function,there are different forms of Fokker-Planck equation to describe the energetic charged particles transport in plasma.The different forms of Fokker-Planck eqation have been compared and evaluated from the viewpoint of numerical calculation,and it is indicated that the Fokker-Planck collision term can be interpreted as the convection diffusion term in the velocity space.Based upon this,a code,CAPT,has been made to solve the two-dimensional (space and velocity) time-dependent Fokker-Planck equation by difference method,and it is applied to study the alpha particles transport problem.The loss of alpha particles has been calculated for a typical Tokamak D-T fusion reactor,and the core alpha particles distribution and the lost alpha particles velocity distribution have also been shown.

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THEORETICAL STUDIES ON THE VALENCE-BAND OFFSETS AT Si/Ge HETEROJUNCTIONS Wang Renzhi, Zheng Yongmei, Kea Snhuang, Huang Meiehun, Zhu Zizhong 1996, 13(2): 136-140.  Abstract ( )   PDF (372KB) ( )   Based on an ab initio pseudopotentials band structure method,a theoretical approach of tak-ing the average-band energy as a energy reference is suggested to determine the valence-band offsets at Si/Ge heterojunctions under three different strain conditions:using Si as a substrate,using Ge as a substrate and Si-layer,Ge-layer deforming freely.The results are 0.731eV,0.243eV and 0.521eV respectively,in good agreement with relevant experimental values.

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INVERSTIGATION ON THE NUMERICAL SIMULATION OF THE FEL——SPECTRAL METHODS SOLVING LIGHT FIELD EQUATION Zhang Zhichou, Yao Jun 1996, 13(2): 141-146.  Abstract ( )   PDF (327KB) ( )   This paper is concerned with the method,which approaches to analytical solution of the light field equation with the Gauss-Hermite mode in three-dimension free space.The number of modes needed for calculating has been eatimated.The method has the following advantages:(1)Simulation electron number is reduced by about two orders of magnitude in comparison with DM methed;(2)Electron equations and G-H modes can be computed parallely.

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PLASMA-SCREENING EFFECTS ON ELASTIC COLLISIONS IN HOT DENSE PLASMAS Yuan Jiankui, Sun Yongsheng, Zheng Shaotang 1996, 13(2): 147-151.  Abstract ( )   PDF (388KB) ( )   An average-atom(AA) model is employed to calculate differential cross sections for the elastic scattering of electrons from argon and iron plasmas.The results are in good agreement with other theoretical calculations and available experimental data in the low temperature and density limit.Numerical simulations show that the effect from temperature is more complicated than that from density,and differential cross sections change greatly with the condition of the plasma.

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ON RESEARCHING OF THE INTEGRALS J(n,X) WITH SERIO USLY OSCILLATORY WAVEFUNCTIONS IN ATOMIC PHYSICS(Ⅱ) Chen Guoxin, Fang Quanyu, Shen Zhijun 1996, 13(2): 153-158.  Abstract ( )   PDF (350KB) ( )   Following the preceding paper(Ref.[I]),an improved method is presented for calculating the integrals in electron-atom colllisions by transforming the integration contours into complex plane.This method can calculate the integrals accurately not only for cases like Ref[I],but also for the case of"nearly degenerate"which cannot be calculated by methods given in Ref[I].The caleulational accuracies have been compared and checked to be very high.

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NUMERICAL METHOD OF SIMULATING LOW HYBRID WAVE CURRENT DRIVE He Qibing, Tang Yu, Mu Zongze 1996, 13(2): 159-166.  Abstract ( )   PDF (440KB) ( )   Numerical method of the steady-state Fokker-planck equation is discussed.The numerical results are obtained by linear combination method and single step method based on Gauss node collection. Ratio frequency(RF) current density and power density of the steady state low hybrid wave(LHW) current drive are calculated numerically.

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CALCULATING APPROACH FOR PULSED PROMPT γ-RAY PROPAGATION IN ATMOSPHERE Wang Yaocai 1996, 13(2): 167-172.  Abstract ( )   PDF (394KB) ( )   The weveform distortion of γ-ray pulses propagating in the atmosphers is dealt with in terms of the combination of Monte-Carlo method and the fold integration method.Mathematical expressions are given for the propagation function of γ-ray with any energy spectrum distributions in the atmosphere and the fold integration calculation of γ-ray pulse waveforms at detection points.The effects of γ-ray propagating on the waveforms have been calculated for some typical pulse waveforms.Discussion covers the treatment to decrease or avoid waveform distortion.

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A STUDY OF THE SDKZ-MODEL AND ITS STABILITY OF THE SOLUTION Wang Xiangsan 1996, 13(2): 173-180.  Abstract ( )   PDF (497KB) ( )   A synthetic model of three dimensional-multilevel two dimensional diffusion is presented based on physical analysis for river current characters and boundary conditions of strong mixing seaward firth with warm sewage pollutional sources.Numerical simulation for realistic velocity and temperature fields of seaward firth shows that this model has a satisfied precision.

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CALCULATION OF ABEL INVERSE TRANSFORMATION COEFFIC-IENTS IN ANY EQUIDISTANT DISCRETIZATION Pu Xiaoyun, Xiong Ye, Lin Lizhong, Zhang Zhongming 1996, 13(2): 181-189.  Abstract ( )   PDF (463KB) ( )   The transformation coefficients of Abel inverse transformation in any equidistant discretization are calculated with the method of third-degree polynomial.They can be applied to transforming the observed transverse radiance into the corrosbonding radial distribution for optical thin plasma with cylindrical symmetry.The calculated result shows that this method reaches high accuracy.

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COMPUTER SIMULATION AND CURVE FITTING FOR MEASUREMENT OF TINY PARTICLE GROUP SIZE DISTRIBUTION BY LASER DIFFRACTION Ying Xuantong 1996, 13(2): 190-194.  Abstract ( )   PDF (335KB) ( )   The principle and mathematical model of laser diffraction of tiny particle group are introduced.The corresponding computer simulation and curve fitting for measurement of tiny particle group size distribution are reported.

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A MONTE-CARLO METHOD FOR SIMULATING A NUCLEAR LOCKING TOOL Jin Changqiu, Huang Zhengfeng 1996, 13(2): 195-200.  Abstract ( )   PDF (524KB) ( )   Monte-Carlo method for simulationg the responses of a dual-space neutron porosity oil well-logging tool is developed and presented.For practical computations,the specific Monte-Carlo code introduced here uses implicit capture、weight and energy cut off、geometric splitting and Russian roulette and directional biasing techniques as primary variance reduction methods.Some of the techniques have been improved partly.Numerical tests of practical examples are discussed and analyzed,which confirmed the effectiveness of these techniques.

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IMPROVED CHARACTERISTIC FINITE ELEMENT METHOD IN SOLVING HIGHLY NONLINEAR SEA WATER INTRUSION PROBLEM Wu Jichun, Xue Yuqun, Xie Chunhong, Zhang Zhihui 1996, 13(2): 201-206.  Abstract ( )   PDF (375KB) ( )   In order to surmount the difficulty of numerical dispersion and numerical oscillation an improved characteristic finite element method is presented to solve the highly nonlinear sea water intrusion problem.The solved three-dimensional mathematical model,which regards exchanging cations Na+ and Ca2+ as simulation factor,takes account of cation exchange reaction between water and rock.The simulated results are satisfactory by comparison with the field data,and show that this model can be applied to predict the movement and evolution of exchanging cations during sea water intrusion.

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BOUNDARY ELEMENT METHOD FOR BENDING PLATES ON ELASTIC FOUNDATIONS AND THE IDENTIFICATION OF PHYSICAL PARAMETERS Zheng Xiaoping, Wang Shangwen, Yu Long 1996, 13(2): 207-212.  Abstract ( )   PDF (357KB) ( )   The fundamental solution for the bending of thin plates on elastic foundations is derived by Hankel transformation.This solution in an unified form includes all three different kinds of foundation models,which are treated separately in existing literature.For the generalized boundary value problem a complete set of boundary integral equations and relevant numerical scheme are established.By combining the boundary element method with the optimization technique a procedure is also presented for identifying mechanical parameters,in which the displacements of plate at several points are measured by JGPD instru-ment.The effectiveness of the proposed method in illustrated by two typical examples with practical appli-cations.

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EXCITATION CROSS SECTIONS AND RATE COEFFICIENTS OF Mn22+ Zhang Xianzhong, Zhou Zhongyuan, Pan Shoufu, Sun Jiazhong 1996, 13(2): 213-216.  Abstract ( )   PDF (271KB) ( )   By using Coulomb-Born-exchange approximation and Zscaled hydrogenic approximation the excitation cross sections and rate coefficients between fine-structure levels of Mn22+ in water window are calculated.In order to take the correlation effects and relativistic effects into account more effectively, the effective nuclear charges are modified in the computation.

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THEORETICAL STUDY OF RADIATIVE ABLATION OF AI FOIL DRIVEN BY X-RAY PRODUCED IN CYLINDRICAL HOHLRAUM ON SHENGUANG-Ⅰ LASER FACILITY Zeng Xiancai, Li Yunsheng, Chang Tieqiang 1996, 13(2): 217-222.  Abstract ( )   PDF (411KB) ( )   The physical processes of radiative ablation and burn-through of Al foil are theoretically studied using the time-dependent radiation temperature curve inside the cylindrical hohlraum measured on Shenguang-Ⅰ facility.Some scaling laws and numerical simulation results are simultaneously presented.

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MONTE CARLO METHOD FOR SOLVING EQUATIONS OF CHEMICAL REACTION DYNAMICS IN THE PROCESS OF NOX/SO2 REMOVAL Gong Ye, Sun Jizhong, Wang Rongyi 1996, 13(2): 223-226.  Abstract ( )   PDF (251KB) ( )   Monte Carlo method will be applied to solve chemical reaction equations in the process of NOX/SO2 removal.The results are highly satistactory and show that this method is extremely effective

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MO METHODS STUDY OF H ABSTRACTION FROM HYDROGENETED DIAMOND(111) SURFACE BY GAS HYDROGEN ATOM Rong Chuiqing, Li Yanxin, Ding Peizhu 1996, 13(2): 227-231.  Abstract ( )   PDF (435KB) ( )   The value of potential barrier of H abstraction from hydrogeneted diamond (111) surface is critical to understand nucleation and growth dynamics of diamond film under the condition of Chemical Vapor Deposition.The previous theoretical works on the value are far from accord based upon different MO methods.On use of a series of cluster models and some kinds of MO methods the potential barrier is systematically studied here.After determinating the MNDO approach reliability for this problem,the corrected theoretical value is given as well.

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THEORETICAL RESEARCH ON OPTICAL AND MAGNETIC PROPERTIES OF Ni(mpz)4Cl2 COMPOUND Yang Fuxing, Yan Zhanxian, Zhou Xiaoqing, Li Cuilian 1996, 13(2): 232-236.  Abstract ( )   PDF (332KB) ( )   By means of a complete configuration mixing unified crystal field theory for d8(D4h*),the optical spectra,the ground state ZFS,EPS parameters,the ground state paramagnetic susceptibility and the magnetization of the Ni(mpz)4Cl2 compounds are analysed and calculated systematically.Numerical results agree well with the experimental data,so a complete and reasonable explanation is provicled for the magnetic of Ni(mpz)4Cl2 compounds.

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A SEMI-ANALYTICAL METHOD BASED ON CONVOLUTIONTYPE VARIATIONAL PRINCIPLE TO SOLVE THE TRANSIENT HEAT TRANSFER PROBLEMS Peng Jianshe, Zhang Jingyu,. Yang Jie 1996, 13(2): 237-242.  Abstract ( )   PDF (372KB) ( )   The Semi-analytical method is derived based on convolution-type varicational principles to solve the 2-D transient heat transfer problems,which takes finite element discretization in space domain and analytic function in time domain.

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DETERMINATION OF THE BOND LENGTH OF DIATOMIC MOLECULE BY USING NEURAL NETWORK APPROACH He liming, Chen Kongchang 1996, 13(2): 243-248.  Abstract ( )   PDF (367KB) ( )   By using the back-propagation (BP) model of neural network,the bond length of diatomic molecule is determinated.Slater atomic radius,Pauling electronegativity,major group and cycle numbers of the periodic table,etc.,are used as features.The calculated and predicted results of neural network appear to be better than those of reported calculations.

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A NUMERIAL COMPUTATION OF SUPERSONIC DIFFRACTION Xu Guorong 1996, 13(2): 249-252.  Abstract ( )   PDF (527KB) ( )   High resolution physical phenomenons for shock wave.Rarefaction waves and their interaction are obtained by first order accurate Friedrichs-Lax finite difference approximating to equation system in consenation law in stremline cooordinate.

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FINITE ELEMENT METHOD FOR CYLINDRICAL WAVE SCATTERING FROM IRREGULAR OBJECTS Yang Jisheng, Gu Jinqi, Xu Lijun, Yang Guang, Liu Yizu 1996, 13(2): 253-256.  Abstract ( )   PDF (467KB) ( )   Based on finite element and artificial transmitting boundary method, the cylindrical wave scattering by infinite circular cylinder is computed and compared with analytical solution. Then other problems on scattering induced by irregular objects are also solved on use of the same method, whose superiority and efficiency have been indicated by numerical examples.