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25 November 2010, Volume 27 Issue 6 Previous Issue    Next Issue

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A Summarization on Monte Carlo Simulation in Particle Transport DENG Li, LI Gang 2010, 27(6): 791-798.  Abstract ( )   PDF (475KB) ( )   Development of Monte Carlo method is over sixty years.It is widely used in nuclear science and other relative fields.It has superpower capability in simulating various complicated geometry.With precision point-wise cross-section,it can simulate various particle transport problems,such as neutron,photon,electron,α particle and proton etc.With rapid development of computers and large scale parallel computation,Monte Carlo method is a first tool for simulating particle transport problems.

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Calculation of CFBR-Ⅱ's Multiplication-reactivity Conversion Factor YIN Yanpeng, ZHENG Chun, HUANG Po 2010, 27(6): 799-804.  Abstract ( )   PDF (286KB) ( )   Multiplication-reactivity conversion factor is a key parameter in CFBR-Ⅱ to get reactivity at subcriticality by neutron source multiplication method.It was measured in many experiments,but the results were different.In order to explain this,we derive an expression of multiplication-reactivity conversion factor with transport equation.Aimed at CFBR-Ⅱ,multiplication-reactivity conversion factor in different reactivity states are calculated with Monte Carlo Method.It is concluded that multiplication-reactivity conversion factor is determined by delayed neutron fraction,importance ratio of external neutron source and fission neutron source,neutron leakage probability ratio of multiplication system and substitute system,detector efficiency ratio of multiplication system and substitute system.Multiplication-reactivity conversion factor varies with CFBR-Ⅱ's reactivity.

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Mixed Monte Carlo Simulation of Electron Backscattering from Solids ZHUO Jun, HUANG Liuxing, NIU Shengli, ZHU Jinhui 2010, 27(6): 805-810.  Abstract ( )   PDF (291KB) ( )   A mixed Monte Carlo algorithm for transport with electrons of energy from 50 eV to 1 GeV is described which combines detailed simulation and condensed simulation.Through adjusting scattering angle and energy loss factors,times of single collisions are decided.In the process,single collisions are simulated with detailed method,and multiple scatterings among single collisions are simulated with condensed method.Results and efficiency of calculation affected by factors mentioned above are discussed.Backscattering on solids induced by incident electrons is simulated.Calculated backscattering coefficients and energy distribution agree with theoretical and experimental results well.

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Elastic Scattering of Low-energy Electrons in Liquid Water TAN Zhenyu, ZHANG Liming, GAO Hongxia 2010, 27(6): 811-815.  Abstract ( )   PDF (227KB) ( )   With a combination of mean cross section and Mott model,differential cross section,total cross section and angular distribution of electron elastic scattering in liquid water with energy below 10 keV are calculated and systematically compared with those of Rutherford model and experiment.Elastic scattering of low-energy electrons in liquid water is simulated.The method is reliable and can be applied conveniently to the simulation of track structure of low-energy electrons in liquid water.

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Monte Carlo Study on Point Spread Function of a Granular Phosphor Screen PENG Xianke, XU Haibo 2010, 27(6): 816-822.  Abstract ( )   PDF (359KB) ( )   Light absorption and scatteing coefficients of phosphor grain with different sizes and packing densities are computed with Mie theory.Optical photons in a granular phosphor screen are modeled by simulating scattering and absorption events of individual optical photons by Monte Carlo method (MC).Depth-dependent optical collection efficiencies are obtained.Using MCNP,distribution of energy deposition of 6 MeV mono-energetic X-ray in tungsten and phosphor screen is modeled.The point spread function of screen is given as a convolution of energy deposition kernel and optical kernel.Granular screens of smaller grain and higher packing density exhibit better spatial resolution in megavoltage radiography.

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Monte Carlo Method in B-spline Seperating Signals WANG Chang, HUANG Hanyan, WU Fuqiang 2010, 27(6): 823-828.  Abstract ( )   PDF (284KB) ( )   To represent a ballistic trajectory with B-spline,Monte Carlo method is used in the simulation of B-spline separating signals method.A suggestion is given on how to add external knots to the internal knots sequence.Consistency of B-spline approximation space is discussed to demonstrate the relevant theorem.Further more,B-spline separating signals method is validated by a comparison with Monte Carlo simulation.It decides efficiently exact knots sequence needed to represent a ballistic trajectory.With the knots sequence,the parameters to be estimated is greatly eliminated.

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An Artificial Viscosity in Lagrangian Hydrodynamics Method ZHOU Haibing, XIONG Jun, LIU Wentao, ZHANG Shudao 2010, 27(6): 829-832.  Abstract ( )   PDF (250KB) ( )   An artificial viscosity is presented for Lagrangian hydrodynamics method.The formulation is based on artificial viscosity first presented by Lew.It contains a limiter switching off viscosity for shockless compression.The artificial viscosity reduces dependence of solution on relation of grid to flow structure.The eigenvalue viscosity limiter controls magnitude of the artificial viscosity.By the limiter it is able to distinguish between adiabatic compression and shock compression.The formulation is applicable to any dimensions and to logically rectangular or unstructured grids.

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Coupling Eulerian Multi-material Hydrodynamic and Lagrangian Structure Dynamic Method for Numerical Simulation of Fluid-structure Interaction PU Xifeng, WANG Zhongqi, BAI Chunhua, ZHOU Gang 2010, 27(6): 833-839.  Abstract ( )   PDF (440KB) ( )   A coupling method is developed to describe field-structure interaction.Eulerian multi-material hydrodynamic code is used to simulate fluid field.Lagrangian hydrodynamic finite element code is used to calculate response of structures.Coupling technology is made to merge these two codes.Technology to speed calculation and to avoid mismatch of fluid structure meshs and structure meshs are given.Dynamic response and shock wave propagation within an explosion containment vessel are simulated.Fluid-structure coupling algorithm is used for analyzing coupling of explosion field and structures.It indicates that the method has the ability of simulating fluidstructures interation.

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Numerical Study on Underwater Contact Explosion of Ships YAO Xiongliang, YANG Wenshan, CHU Wenhua, MING Furen 2010, 27(6): 840-846.  Abstract ( )   PDF (871KB) ( )   Considering material strength of the outside plate of a ship,a numerical model of underwater contact explosion is built based on SPH method.Mixed density and generalized smooth length are put forward to overcome calculation breakdown in numerical simulations.Underwater contact explosion of ships is simulated,and calculation results agree well with shock wave theory and contact explosion tests.It shows that a circular extrusion crevasse,whose size is close to the thickness of the explosive,forms on the steel structure in contact explosion.As regularizing thickness of the steel plate and the explosive reaches 1.8,only plastic deformation occurs on the plate.Reflection coefficient of the steel,which equals about 1.2,and approximate deformation formulas are obtaind.

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Size Distribution of Initial Liquid Drops During Aerosol Explosive Dispersal Process SHI Yina, HONG Tao, QIN Chengsen 2010, 27(6): 847-853.  Abstract ( )   PDF (376KB) ( )   Theoretical study and numerical simulations are made on size distribution characteristic of initial liquid drops during aerosol explosive dispersal process.With thermodynamic consistent concept,the maximization of entropy generation in the initial breakup process,constraint equations of the problem are derived,and probability distribution function of initial drop size is obtained.Numerical predictions are in agreement with air-blast annular nozzle experimental data and Samirant experimental data.

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Optimization of COIL with Jet in Supersonic Section Based on Mixing Process LV Junming, HU Zongmin, JIANG Zonglin, WANG Qiang 2010, 27(6): 854-860.  Abstract ( )   PDF (344KB) ( )   Three-dimensional algorithms solving laminar Navier-Stokes equations coupled with chemical reaction and transportation equations are developed.Detailed flow field and distribution of yield,dissociation and pumping rates and small signal gain are obtained which cannot easily be got in experiments.The reason that experimental results are not as good as that in theories is analyzed.Furthermore,a better way to operate the system is suggested.It is shown that the mixing and chemical process in a nozzle of limited length is not complete due to the high speed in supersonic mixing zone and low mixing efficiency.Higher iodine concentration for speeding up chemical reaction causes insufficient of singlet oxygen,so as an unreasonable gain.A primary flow without buffer gas is claimed necessary and essential to reduce flow velocity and assure mixing process and chemical reaction accomplished before arriving the cavity.With an appropriate flow rate ratio,a small signal gain can reach 1.3% cm-1.

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Temperature Simulation of Supersonic & Hypersonic Kinetic Energy Projectiles CHEN Xinhong, ZHOU Zhichao, ZHAO Runxiang, XU Houqian 2010, 27(6): 861-868.  Abstract ( )   PDF (408KB) ( )   A method with CFD technology is used for accurate prediction of temperature field of supersonic and hypersonic kinetic energy projectiles.It includes equilibrium flow governing equations and difference scheme,equilibrium flow Jacobian matrixs and equilibrium gas state equations.A real gas equilibrium air model is used to calculate temperature in vector flux split in a difference scheme.Thermal environment for typical high-speed kinetic energy projectile is validated.Rationality of the method is considered.Temperature field of a designed hypersonic kinetic energy projectile is simulated.Reliable numerical data for projectile aerodynamic design and aerodynamic heat protection are provided.

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Acoustic Characteristics of Axisymmetric Periodic Groove Structures YAN Xianghong, SU Yuanda, SUN Jianmeng, ZHUANG Chunxi, ZHANG Meiling 2010, 27(6): 869-876.  Abstract ( )   PDF (647KB) ( )   A sound isolator with axisymmetric periodic groove structures is given for eliminating drill collar wave.Sound isolation effect with different groove's depth (H),length,number,section shape and thickness of the drill collar is studied.With rectangle section shape,decreasing thickness of the drill collar and increasing H,isolation effect of the acoustic isolator can be increased.It can get a maximum of 36 dB sound attenuation which meets requirement of the sound isolator in LWD.

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SARC-FDTD Method for Electromagnetic Scattering by an Object Coated with Plasma ZHANG Yuqiang, GE Debiao 2010, 27(6): 877-882.  Abstract ( )   PDF (200KB) ( )   A novel finite-difference time-domain(FDTD) method combined with semi-analytical recursive convolution (SARC) algorithm in digital signal processing(DSP) techniques is presented to analyze electromagnetic scattering by dispersive media.Absolute stability,high accuracy,less storage and high effectiveness are retained while a unified update formulation is possessed.It can be applied to analysis of general dispersive media provided that the poles and corresponding coefficients in dispersive medium are given.Finally,the proposed SARC-FDTD approach is validated.RCS of an object coated with plasma are calculated.

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Numerical Study of Negative Ion Effect on Plasma Sheath GONG Ye, DUAN Ping, ZHANG Jianhong, ZOU Xiu, LIU Jinyuan, LIU Yue 2010, 27(6): 883-890.  Abstract ( )   PDF (328KB) ( )   A model of sheath formation on a planar electrode in strongly electronegative plasmas is presented.The plasma sheath is studied by using a set of hydrodynamic equations.Spatial potential,net space charge distributions and sheath width as functions of distance are obtained.It shows that in a strongly electronegative sheath a presheath between bulk plasma and sheath hardly exist,and electrons,negative and positive ions in the sheath form a pure positive ion sheath near boundary of electrode.Density of net space charge has a sharp peak near the sheath edge.Compared with an electropositive sheath,it is found that the width of strongly electronegative sheath is much narrower,and the spatial potential within the sheath falls much faster.

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Precision Control in Transfer Matrix Method for Laser Mode-fields LING Dongxiong, ZHANG Shaoqiang, WANG Hongcheng, ZHANG Mei 2010, 27(6): 891-897.  Abstract ( )   PDF (580KB) ( )   A transfer matrix method is discussed,and precision of the method is controlled.It is shown that the transfer matrix method and the intergral iterative method show same results for a general confocal resonator.Convergence problem of the intergral iterative method can be solved and laser resonators can be analyzed by the transfer matrix mothod with reasonable control of calculation precision.

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Molecular Dynamics Simulation of Tension Deformation in Monocrystalline β-SiC Bulk ZONG Liang, XU Xiaojing, ZHOU Hai 2010, 27(6): 898-904.  Abstract ( )   PDF (907KB) ( )   Tension simulations of[001]monocrystalline face-centered cubic SiC(β-SiC) and C-doped β-SiC bulks are performed with molecular dynamics method to investigate intrinsic deformation mechanisms and mechanical behaviors of β-SiC under strain rates of 5×108/s,1×109/s,1×1010/s.It is found that Si-C sp3 and C-C sp3 bonds respectively transform to Si-C sp2 and C-C sp2 bonds as soon as the strains reach certain critical values.As certain amounts of sp2 bonds are formed,instable fractures emerge in β-SiC.Since C-C sp2 bonds are formed earlier than Si-C sp2 bonds,the doping of C elements leads to the decrease of strength,Young's modulus and tension fracture strain of β-SiC.In addition,it is found that the strain rates have effects on tensile-strength,but not on Young's modulus.

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Multifractal Analysis Method Based on Several Scale-free Zones CHEN Yiwang, XU Xin, FU Qiang 2010, 27(6): 905-911.  Abstract ( )   PDF (382KB) ( )   Formation of multifractal structure is simulated.Through a contrastive analysis on analytic,multifractal spectrum of structure and calculated multifractal spectrum with partition function,it is found that multifractal spectrum can describe structure growth pattern in a certain scale-free zone.It is found that all structure scale-free zones exhibit value of research.Since traditional multifractal analysis method can not make full use of the data in a structure,we propose a new method to calculate multifractal spectrum based on several scale-free zones.

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Analytical Solution of Forward Problem for Magnetic Induction Tomography in a Multi-layer Sphere Brain Model HE Wei, LI Qian, XU Zheng, ZHU Jinhua, HE Yangguang, WANG Lei 2010, 27(6): 912-918.  Abstract ( )   PDF (353KB) ( )   A 4-layer sphere model of human head is built for the forward problem of magnetic induction tomography.The layers represent the brain,the CFS,the skull,and the scalp respectively.Taking vector magnetic potential as a variable,Helmholtz equation in a spherical coordinates is constructed as a control equation of the forward problem.A variables separation method is used to solve the equations with boundary and interface conditions.Distribution of the magnetic vector potential and eddy current in the model are obtained.Equi-potential lines of the eddy current are given.Influence of frequency and magnitude of the exciting current on the induced voltage is analyzed.The algorithm is validated by solving a forward problem of magnetic induction tomography.It can be used as a fast algorithm to generate sensitivity matrix in an inverse problem.

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Numerical Simulation of Stochastic Ginzburg-Landau Equation WANG Tingchun, GUO Boling 2010, 27(6): 919-926.  Abstract ( )   PDF (744KB) ( )   Stochastic Ginzburg-Landau equation is numerically studied.A nonlinear difference scheme and a linearized scheme which avoid iteration in implementation are constructed.Numerical solutions of both deterministic equation and stochastic equation show accuracy and efficiency of the difference schemes.Numerical experiments with different noise amplitudes are presented and different types of behaviors are described.

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Dynamical Analysis and Circuit Implementation of an Autonomous Chaotic System WANG Mengjiao, ZENG Yicheng, XU Maolin 2010, 27(6): 927-932.  Abstract ( )   PDF (271KB) ( )   We study a three-dimensional quadratic autonomous chaotic system.Basic dynamic characteristics are analyzed via theoretical analysis and numerical simulation.Lyapunov exponent spectrum,Lyapunov dimension as well as bifurcation diagram are calculated.An electronic circuit is designed to realize the chaotic system.Relationships between system parameters and circuit parameters are built.The circuit is simulated using Pspice.Simulation results confirm the analysis.The system discussed is different from Lorenz system,Rössler system,Chen system and Lü system.The chaotic circuit is simple and practical.

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Control and Synchronization of Chaotic Systems with Synergy of Bacterial Foraging and Differential Evolution Algorithm JIANG Fei, LIU Sanyang, ZHANG Jianke, GAO Weifeng 2010, 27(6): 933-939.  Abstract ( )   PDF (324KB) ( )   Control and synchronization of chaotic systems are studied.They are transformed into numerical optimization problems.A novel hybridization of differential evolution(DE) and bacterial foraging algorithm(BFOA),called CDEM algorithm,is proposed.The algorithm incorporates an adaptive chemotactic step from the BFOA into DE,which improves convergence of the classical DE.It introduces mutation operation of genetic algorithm for enhancing population diversity.Finally,CDEM algorithm is used to chaotic system control and synchronization.Numerical simulations based on Hénon Map demonstrate effectiveness and stability of the algorithm.Effects of parameters are investigated as well.

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Dynamical Character of an Improved Time-delayed Dual Model for Internet Congestion Control LIU Yuliang, ZHANG Hua, ZHU Jie 2010, 27(6): 940-946.  Abstract ( )   PDF (256KB) ( )   An improved time-delayed dual model for internet congestion control is investigated.Normal form theory,center manifold theorem and Hopf bifurcation theory are used for analysis.Bifurcation and stability analysis are mainly decided by communication time delay.As the delay passes through a critical value,Hopf bifurcation forms,which leads to a large oscillation of link price function.In addition,bifurcation direction and bifurcation periodic solution are derived,which provide model design with theoretical foundations.This work is summarized as two theorems verified by numerical simulations.