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24 June 1984, Volume 1 Issue 1    Next Issue

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DEVELOPING THE COMPUTATIONAL PHYSICS TO SERVE THE “FOUR MODERNIZATION” CHIN YUAN-SHUN 1984, 1(1): 1-7.  Abstract ( )   PDF (593KB) ( )

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INVESTIGATION OF POPULATION INVERSIONS BY AVERAGE ATOM MODEL PENG HUI-MIN, QIU YU-BO, CHENG YIN 1984, 1(1): 8-20.  Abstract ( )   PDF (691KB) ( )   In this paper, the rate equetions of average atom model and hydrogen-like ions are discussed. At very high ionization they are equivalent. The emphasis is put on the investigation of using average atom model to calculate population inversions. Stripping the inner electrons with X-ray and recombining them to outer shell by three-body recombination, we can obtain the population inversions. Some conditions and results are given.

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REFLECTION OF UNSTEADY BLAST WAVE COMPUTED BY SECOND ORDER ACCURATE MUSCL SCHEME ZHOU NING 1984, 1(1): 21-30.  Abstract ( )   PDF (634KB) ( )   The MUSCL developed by Van Leer is aimed to eliminate or diminish the overshoot usually unavoidable for second ovder shock capturing schemes.It gives narrow transition zone for discontinuities. We tested this scheme by the Riemann problem and by a more complicated problem baring known highly accurate result. Both boundary condition and high temperature singularity should be treated properly. Some knowledge about the adjectable constant used in the monotone algorithm have been accumulated. Besides, a main formula in Van Leer's paper is corrected, the stability condition is refined.

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THE APPLICATION OF MONTE CARLO METHOD TO STUDY THE PROPERTIES OF THE GROUND STATE OF THE FOUR NUCLEON SYSTEM JIN XING-NAN, ZHANG XIAO-ZE 1984, 1(1): 31-39.  Abstract ( )   PDF (467KB) ( )   The Monte Carlo Method has been applied to study the properties of the ground state of the four nucleon system. The wave function of the nucleon is assumed to contain the Jastrow factor, which Is due to the correlation of the other nucleons in the system. The variational constants of the wave function have been calculated by Zabolitzky and Kalos.Jn this article, we have used the wave function quoted above to calculate the binding energy of the system, its root mean square radius, the density distribution of the nucleon and the form factor.The result of our calculation indicates that the Monte Carlo Method can be used to study the properties of the ground state of the nuclear system. It requires to do further work to ensure that this method can be used to study other properties of the nucleus such as the properties of the excited states, the nuclear transitions, etc.

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A BOUNDARY ELEMENT METHOD FOR SOLVING THE FREE BOUNDARY PROBLEMS OF NON-UNIFORM MEDIA ZHENG JIA-DONG 1984, 1(1): 40-46.  Abstract ( )   PDF (416KB) ( )   In this paper we discuss the boundary element method for solving the free boundary problems of non-uniform media. A boundary integral equation with integral kernals of weak singularity is presented with its application to the seepage tree boundary problem in which the eartbdams are piece-wise homogeneous.

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APPLICATION OF DIRECT METHOD TO THE SOLUTION OF FREE BOUNDARY PLASMA EQUILIBRIUM EQUATION LONG YONG-XING, SHI BING-REN 1984, 1(1): 47-53.  Abstract ( )   PDF (391KB) ( )   Numerical method for solving the free boundary plasma equilibrium equation (a nonlinear partial differential equation of elliptic type) during the evolution of the external maintaining, field is presented. The direct method is employed to solve the corresponding set of difference equation and compared with the over relaxation method.It is shown that the direct method can give better computation precision and can save considerable computer time.

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CALCULATION OF DOSE DISTRIBUTION IN THE INTRACAVITAL RADIOTHERAPY OF CARCINOMA OF UTERINE CERVIX BY MONTE CARLO METHOD MIAO QUAN-SHENG, SU BING-HUA, WANG JIANG-MING, SHI BING-ZHANG, JANG JI, XU KAI-YE, JIANG SHU-QUAN 1984, 1(1): 54-64.  Abstract ( )   PDF (629KB) ( )   In this study, Monte Carlo method is applied to evaluate dose distribution in radiotherapy.This method has following advantages:1.Overcoming some defects in other methods, the method can guarantee the accuracy.2.Considering the real composition of tissue and the geometric shape of the organ, the calculation has higher accuracy.3.The method is easy to use and popularize in clinic.By use of this method the internal and external radiation dose can be coordinaed each other more accurately and better, so that the 5 years survival rate may be increased.The treatment result is improved.The principle of the new method can be popularized to other hospitals or radiation centers for routin radiotherapy and after-loading system in carcinoma of uterine cervix.

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SPECIAL TREATMENTS IN TWO-DIMENSIONAL MAGNETOHYDRODYNAMIC CALCULATION OF THE DENSE PLASMA FOCUS SHI JANG-JUN, DONG WEI-SHEN, LIU GUI-XIAN, XIE MING-SHU, LIU ZI-WEI 1984, 1(1): 65-75.  Abstract ( )   PDF (653KB) ( )   Two-dimensional magnetohydrodynamic behaviour of the plasma in co-axis of the plasma focus eguipment is studied in this paper. The two-step Lax-Wendroff scheme is applied to Eulerian cells of (r-z) plane in axial deuices. Applied special treatments are as follows. The complex diffusion terms have been treated by the forward time-defference method; The ion-electron equipartition terms are solved by a implicit iteration; The hapidus three-order smooth technics is used in all MHD equations; The mixed schame of Lax and Leapfrog schemes is used in the density equation and the momentum equation to eliminate the nonliear instabilities; The magneticfield of low-density region is treated as vacuum magnetic field, so that the calculations of magnetic field and fluids are decoupled,and the severe restriction in choosing the timestep is avoided.Each time-step of calculation takes 39 sec.on a DJS-8 (320), and approximately 370 timesteps are needed altogether. The steady dynamic structure is calculated.

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ALTERNATING DIRECTION PARTIAL IMPLICIT AND COMPLETE IMPLICIT METHODS FOR SOLVING STREAMFUNCTION OF NAVIER-STOKES EQUATIONS XU DA-PENG 1984, 1(1): 76-83.  Abstract ( )   PDF (436KB) ( )   Alternating direction partial implicit and alternating direction complete implicit methods for solving Navier-Stokes equations formulated by stream-function are presented. The two-dimensional cavity flow is calculated as a test problem and the results are discu ssed and compared.

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THE TRIANGULAR MESH-DISCONTINUOUS FINITE ELEMENT METHOD FOR THE TWO-DIMENSIONAL TRANSPORT PROBLEM DU MING-SHENG, FENG TIE-KAI, PU LIAN-XIANG, CAO CHANG-SHU, LIU YU-LAN 1984, 1(1): 84-100.  Abstract ( )   PDF (824KB) ( )   A discontinuous finite element numerical method for treating transient or steady neutron ransport problem with 2-D Cylindrical symmetry is presented.We use central difference of Crank-Nicholson type for time variable, while the discritization in phase space is shown in fig.1 for a special case.In geometrical space triangular mesh is used, which can be generated automatically in our program.Numerical analysis starts from an aprioestimate of a normal.From which uniqueness and stability follow.Satisfactory numerical tests are shown including comparison with an exact solution as well as with results obtained using DSN method.

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A FAST SAMPLING METHOD FOR MONTE CARLO SIMULATIONS OF LATTICE GAUGE FIELD THEORIES DONG SHAO-JING 1984, 1(1): 101-107.  Abstract ( )   PDF (412KB) ( )   A fast sampling method which can afford saving much computer time was suggested.We studied the behaviour of this method near the critical points for Z2 and SU(3) gauge groups.It is found that this method will lose his effect when passes through the first order phase transition points.This character will be used to find the first order transition according to some program.

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FILTRATE WAVE EFFECT OF THE PERIODICAL SMOOTHING IN PHASE SPACE IN THE PLASMA PARTICLE SIMULATION LIU CHENG-HAI, XU LIN-BAO 1984, 1(1): 108-113.  Abstract ( )   PDF (337KB) ( )   The noise-restraining mechanism due to introducing periodical smoothing in phase space in the particle simulation is analyzed. We introduce a concept of filtrate effect of the smoothing and give a analytical expression for filtrate wave coefficent that is dependent on wavelength.The results obtained show that the smoothing restrain is mainly for short wave noises and no energy transfer happens in wavenumber space.

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MONTE CARLO METHOD ON SIMULTANEOUSLY MEASURING COMPOSITION AND THICKNESS OF FILMS IN MICRO-DOMAIN HE YAN-CAI 1984, 1(1): 114-117.  Abstract ( )   PDF (247KB) ( )   The method proposed in reference[3] has been developed to e-nable measurement of compositions and thicknesses of films in micro-domain at the same time by Monte Carlo simulation.

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NUMERICAL SIMULATION ON NON-LINEAR ELASTIC VIBRATION YAN PAN-CHI, QU XIAO-GANG, ZHAO YAN-HUI 1984, 1(1): 118-121.  Abstract ( )   PDF (222KB) ( )   In this paper we studied the non-linear elastic vibration of straight thin beam by numerical method and discoverd a kind of BEAT-phenomena. Some numerical results are given.