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25 January 2001, Volume 18 Issue 1 Previous Issue    Next Issue

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THE NUMERICAL MODELING OF ERBIUM-DOPED SUPERFLUORESCENT FIBER SOURCE SHEN Lin-fang, CHEN Deng-peng, QIAN Jing-ren 2001, 18(1): 1-6.  Abstract ( )   PDF (218KB) ( )   Based on the principie of shooting method, an effective approach to the soiution of nonlinear eguations with boundary problem is proposed for modeling the Er-doped superfluorescent fiber sources (SFSs).The characteristics of SFS in doubie-pass backward configuration have been analyzed theoretically and well explained physically for the first time.

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PLUME CONTAMINATION COMPUTATION OF REMAINDER-PROPELLANT FOR LAUNCH VEHICLE CHENG Xiao-li, MAO Ming-fang, YAN Xi-qin 2001, 18(1): 7-9.  Abstract ( )   PDF (107KB) ( )   The physical processes of remainder-propellant exhausting from the tank of the third stage rocket after the separation of SatelliteRocket for a CZ-4B launch vehicle are analyzed by the vacuum technigue.The probable contamination for FY-1 satellite and SJ-5 carrier satellite from the exhausting propellant are computed.The paper discribes the basic assumptions, physical modeI and numerical method.The maximum contamination accumulated on the satellite and auxiliary satellite during the propellant exhausting process has been reasonably analyzed and obtained.

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NUMERICAL STUDY ON A MOVING SHOCK DIFFRACTED OVER THE CYLINDER/SQUARE COLUMN IN HYDROGEN AIR MIXTURE YUE Peng-tao, XU Sheng-li, ZHANG Peng 2001, 18(1): 10-16.  Abstract ( )   PDF (200KB) ( )   Upwind TVD scheme is used to solve laminar, 2D fully N-S equations.A shock diffracted by a cylinder or square cylinder along hydrogen air interface, and mixing enhancement in a shear flow are numerically studied.The results indicate that the shock travels faster in hydrogen.An adjustable shock and a swirling ovrtex appear in the shear region.After the swirling vortex impacts the cylinders, a reflected shock is formed, and hydrogen diffuses downstream in the region near cylinder walls.Contact surfaces are deformed and another vortex is generated.The distribution of hydrogen shows that the mixing is enhanced effectively by inserting cylinders along the interface, expecially for a square cylinder.The transition from RR to MR can be found for shocks traveling both in air and in hydrogen for a cylinder.Two Mach stems will transmit each other at the downstream.But in the case of a square column, the shock is almost not affected along the lower wall but Mach reflection takes place along the upper wall, then a diffracted shock and a Mach stem transmit each other finally.For both cases, the detached shock occurs on the right of cylinders.Similar shock structures arise, and contributions of cylinder shape are eventually forgotten.

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SEVERAL PROBLEMS IN CONSERVATIVE REMAPPING CAI Qing-dong, SHUI Hong-shou, FU Shang-wu 2001, 18(1): 17-22.  Abstract ( )   PDF (180KB) ( )   The strict explanation about conservation on discrect sitiuation is given at first.Then the dilemma among different conservative variables are discussed,and a least squart method is presented to solve it.Some easily confused concepts about conservation are analysed in detail.

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A COMPUTATIONAL SCHEME OF DIFFERENT MEDIUM INTERFACES IN THE NUMERICAL SIMULATION OF FLOW INTERFACIAL INSTABILITY YU Xi-jun, YOU Ying-jiu 2001, 18(1): 23-26.  Abstract ( )   PDF (134KB) ( )   In the numerical simulation of the interfacial instability, the schemes in [1,4~8] were limited probiems in one medium with different densities or two media with homologous adiabatic exponent.If the schemes are used in computing the disturbance of different medium interfaces with homologous adiabatic exponent, the physical guantities on interfaces may give rise to nonphysical oscillation.To overcome the problem, this paper introduces the front tracking scheme [2] into the Level Set method, name y the contact discontinuous boundary conditions are coercively added on interfaces so that the nonphysical oscillation is avoided.The evolution of Rayleigh-Taylor instability is examined by the three-dimensional TVD/AC program under the single wave.The disturbed figures with time are given.

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NUMERICAL SIMULATIONS OF RICHTMYER-MESHKOV INSTABILITY YAN Chang-lin, SUN De-jun, YIN Xie-yuan, TONG Bing-gang 2001, 18(1): 27-32.  Abstract ( )   PDF (199KB) ( )   An approach combining the adaptive unstructured grids and the high order Godunov type scheme based on the finite volume method is applied to simulate the evolution of the interface between two layers of fluid with different densities.The research focuses on Richtmyer Meshkov instability and baroclinic effect in the evolution of the interface.The perturbation growth rates of the interface are also presented.

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CREATION AND APPLICATION OF A KIND OF NONLINEAR FILTERS ZHENG Xiao-shi, ZHU Ben-ren 2001, 18(1): 33-36.  Abstract ( )   PDF (153KB) ( )   Some nonlinear differential operators and their discrete schemes are considered.The discrete schemes can be used as nonlinear filters in the field of Signal and Image Processing.They possess some interesting features while the linear filters do not.

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DISPERSION ANALYSIS OF CYLINDRICAL LOVE WAVES AND NUMERICAL CALCULATION OF SH WAVES FIELD YAO Gui-jin, WANG Ke-xie, MA Jun, WU Xian-yun 2001, 18(1): 37-42.  Abstract ( )   PDF (192KB) ( )   SH wave field excited by circumferential shear source in cylindrically double layered media is theoretically analysed.Dispersion equation of cylindrical Love waves (guide waves) has been derived.Both existence condition and existence range of cylindrical Love waves are discussed.Dispersion and excitation of cylindrical Love waves are investigated by numerical calculation.It is discovered that the lowest order cylindrical Love waves have cut off frequency,which differs from Love waves in half space with horizontally double layered elastic media.The asymptotic expression of dispersion equation of cylindrical Love waves as well radius r1→∞ consistently tends to the dispersion equation in the horizontal half space case,and cut off frequency tends to zero.The transient full waveform calculation is also calculated and illustrated, showing that realizing direct shear wave logs through exciting SH wave would be a more forthright way.

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EVOLUTIONARY SOLUTION ON OUTFIELD CHARACTERISTIC OF H- AND He XU Jing-wen, LIU Lian-jun, MAO You-dong, ZHAO Li, LI Yuan-xiang 2001, 18(1): 43-46.  Abstract ( )   PDF (129KB) ( )   Considering the robustness and commonness, it uses the evolutionary algorithm to calculate the characteristic of H- and He in outfield.The calculation for ground state energy of H- and He can be converted to a problem of function optimization.At first the MCI method is adopted to deal with state wave functions of H- and He, then the evolutionary algorithm calculates their ground state energies.Results show that it can obtain much more accurate results, and compared with other algorithms, it's more efficient.

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COMPUTATION OF MAGNETOTELLURIC RESPONSE IN THE 2-D INHOMOGENEOUS MEDIA WANG Gong-li, ZHANG Geng-ji 2001, 18(1): 47-51.  Abstract ( )   PDF (167KB) ( )   In the 2-D inhomogeneous media, the magnetotelluric problem can be taken as one on propagation of electromagnetic wave in the dissipitive open waveguide, and is attacked with the numerical modematching method (NMM).First, the problem domain is sectioned into several subdomains, in each of which the resistivity changes only along the horizontal direction.Then the governing equation is separated into two differential equations.One equation relates to z variable and has analytical solution, while the other relating to y variable is computed with numerical method.The electromagnetic fields between different subdomains are related through the continuous conditions of the electromagnetic field.While the dimension of the problem is reduced to one, the demand for the computer resources decreases apparently and the speed increases substantially.In order to further improve the efficiency of the algorithm, the Hermite basis functions and the inhomogeneous elements are used in Ex problem, and the modified Hermite basis functions are used in Hx problem.Comparison with the finite element method (FEM) shows that NMM is at least ten times faster than FEM.

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STUDY ON NONLINEAR WATER RESOURCE TIME-DELAY CONTROL MODELS JI Guo-jun, SONG Wen-zhong, DAI Xian-zhong 2001, 18(1): 52-56.  Abstract ( )   PDF (147KB) ( )   Water resource systems can be regard as a complicated large system composed of the natural subsystems and the artificial subsystems.It takes the designed constructed water resource engineering as a controller installed on natural systems, and accounts for time delay factors.The nonlinear water resource time delay control mathematical mode is first set up by considering that the systems are composed of river basin、lakes and diversion works.Stability,optimal control and suboptimal control of the model are discussed.The computational algorithms and results by analysis are provided.

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AIR-SEA STOCHASTIC CLIMATIC MODEL A D ITS APPLICATION FENG Gou-lin, CAO Yong-zhong, CAO Hong-xing 2001, 18(1): 57-63.  Abstract ( )   PDF (223KB) ( )   The effects of stochastic forcing on air-sea interaction, energy baiance ciimate modei is considered.The noniinear source is dynamicai heat transport.The roie to coupiing different temporai and spatiai scaies of the atmosphere is examined.A stochastic dynamicai modei of air-sea interaction is derived via the Fokker-Pianck eguation (FPE).The FPE from statisticai mechanics is used to obtain a time evoiution of the probabiiity density function and the ciimatic potentiai function.The matrix-continued fraction method (MCFM) is appiied to get the soiution with which effect of greenhouse gases was caicuiated.As a resuit, sea surface temperature rises by 1.2 K,meanwhiie the basic period is about 3~4 years and becomes ionger on doubiing CO2.

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LIMIT-CYCLE-LIKE OSCILLATION CAUSED BY WAVELENGTH STABILIZATION FEEDBACK IN A FREE-ELECTRON LASER WANG Zun-wei, SHU Xiao-jian 2001, 18(1): 64-66.  Abstract ( )   PDF (113KB) ( )   A new kind of osciiiations caused by waveiength stabiiization feedback ioop is investigated.The resuits of 1D numericai simuiations confirm the moduiations of the eiectron energy and FEL power, and the caicuiated moduiation freguency and depth are in good agreement with the experiments.It is found that the freguency creep caused by superradiance usuaiiy resuits in this kind of iimit-cycie-iike osciiiations.

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MOLECULAR DYNAMICS SIMULATIONS OF SOLIDIFICATION OF LIQUID Ni3Al GU Ting-kun, QI Yuan-hua, QIN Jing-yu 2001, 18(1): 67-71.  Abstract ( )   PDF (173KB) ( )   By means of molecular dynamics simulation technique, the rapid solidification processes of Ni3Al are studied with many body potential as atomic interaction.The orientation order parameters and pair analysis technique are used to reveal the structural features, The calculated results indicate that the cooling rate is very important for the liquid Ni3Al solidifies.

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NUMERICAL SIMULATION OF COMET HALE-BOPP'S SPIRAL JET STRUCTURE WANG Yu, ZHOU Hong-nan 2001, 18(1): 72-74.  Abstract ( )   PDF (109KB) ( )   Based on the observational data of comet Hale Bopp's spiral jet structure obtained in Shanghai Astronomical Observatory from March to May 1997,the formation of the spiral jet structure is simulated by using Monte Carlo method.A basic model is proposed and the effect of different parameters is discussed.The numerical results reproduce the observed jet morphology Satisfactorily.

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THE STUDY OF SOLUTIONS FOR DIFFERENCE SYSTEM OF 2-D HEAT CONDUCTION COUPLED THREE-TEMPERATURE DUAN Qing-sheng, YUAN Guo-xing 2001, 18(1): 75-81.  Abstract ( )   PDF (179KB) ( )   In view of the special needs for systems of difference equations of 2-D heat conduction coupled three temperature,the block G-S algorithm and the ICCG algorithm are presented and compared.Numerical results show that the ICCG algorithm is thousands times faster than the block G-S algorithm.Furthermore,in 2-D numerical simulation of laser hohlraum target coupling,the ICCG algorithm will raise greatly computational efficiency if it can realize vectorzation operation.

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SIMULATION OF AZIMUTHAL RESISTIVITY IMAGER BY THE 3D FINITE-ELEMENT METHOD(FEM) YANG Wei 2001, 18(1): 82-86.  Abstract ( )   PDF (156KB) ( )   For the interpretation of Azimuthal Resistivity Imager (ARI) in quantity,a modeling code using finite element method (FEM) is developed to simulate ARI responses in three dimensional inhomogeneous formation models.The code has been benchmarked against analytical solutions and 2D finite difference method (FDM) for subsets of the 3D geometry.The differences between the present results and two others are within 5%.The code has been also used to research some typical formation models in 3D environments.The results show it can provide support for the interpretation of ARI in quantity.

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NUMERICAL PARALLEL COMPUTING OF MICRO A E PULSE COUPLING INTO NARRO SLOTS LIU Jie, CHI Li-hua, HU Qing-feng 2001, 18(1): 87-90.  Abstract ( )   PDF (116KB) ( )   The finite-difference time-domain (FDTD) algorithm is employed to simulate microwave pulse coupling into narrow slots which have depths much narrower than on FDTD cell.It analyzes the parallelism of FDTD algorithm and presents a parallel algorithm of simulation.In order to reduce the communication time, it also uses the message fusion and the lap of computation and communication.In addition it analyzs the complex of the parallel algorithm and gives some results on the Alpha workstation.

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MONTE CARLO SIMULATION OF POINT SPREAD FUNCTION OF INTENSIFYING SCREENS WANG Yi, WANG Jing-jin, WANG Kui-lu, LIU Guo-zhi, DU Hong-liang 2001, 18(1): 91-96.  Abstract ( )   PDF (179KB) ( )   A general Monte Carlo program has been developed to study the performance of the X-ray intensifying screens and imaging systems.The program contains three major parts, each of which describes one of the interaction steps occuring in the system:the absorption and scattering of X-rays, the diffusion of generated electrons, and the diffusion of light photons.Through comprehensive verification, it shows that the simulation methods for all physical processes are correct and the results obtained are credible.For a kind of Gd2O2S:Tb intensifying screen, several characteristic parameters such as the number of collected light photons, light collection efficiency and PSF depending on the incident X-ray energy are calculated.These basic physical quantities are useful for the prediction of the information transfer properties of a phosphor layer.