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25 January 2010, Volume 27 Issue 1 Previous Issue    Next Issue

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Parallel Domain Decomposition for Neutron Transport Equations with 2-D Cylindrical Geometry WEI Junxia, YANG Shulin, FU Lianxiang 2010, 27(1): 1-7.  Abstract ( )   PDF (448KB) ( )   We analyze domain decomposition and priority queuing algorithms for neutron transport equations with 2-D cylindrical geometry. A domain decomposition method based on the lowest surface-to-volume aspect and a corresponding priority queuing algorithm are proposed.Numerical experiments indicate that the method exhibits perfect speedup with hundreds of processors on parallel computers with high network latency.

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A One-dimensional Numerical Study on Early Fireball in Strong Explosion TIAN Zhou, QIAO Dengjiang, GUO Yonghui 2010, 27(1): 8-14.  Abstract ( )   PDF (402KB) ( )   One-dimensional radiation hydrodynamics equations with spherical symmetry are used to study early development of fireball front and case shocks in strong explosion.Numerical method for radiation transport equations is established.The calculation results agree well with Brode's.Early formation of fireball front and case shocks in strong explosion at different yield,density in explosion zone and altitude are simulated numerically.Calculation results are analyzed.

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Monte Carlo Simulation on Equivalent of Nuclear Explosion Using X-ray Imaging LIU Zhiliang, MAO Yongze 2010, 27(1): 15-22.  Abstract ( )   PDF (307KB) ( )   Using X-ray imaging to deduce equivalent of nuclear explosion is preliminarily discussed.A characterized ring pinhole geometry model is established.MCNP4C is used.The source area,determinaton of Ec,influence of ring width,equivalent temperature and incident angle of X-rays are simulated.It is poined out that the source area should be selected as S0=6.25πcm2 and Ec=2×10-8 MeV.Energy response and angle response should be considered.Characterized ring pinhole models at equivalent temperatures 1.4 keV and 3.8 keV and at incident angles 0,1,2,3,4,5,6 degree are simulated.

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Lattice Boltzmann Method with Tree-structured Mesh and Treatment of Curved Boundaries CHEN Yu, XIA Zhenhua, CAI Qingdong 2010, 27(1): 23-30.  Abstract ( )   PDF (680KB) ( )   Lattice Boltzmann method(LBM) and back and forth error compensation and correction(BFECC) skill are combined together for two-dimensional incompressible flows with quad-tree mesh.The scheme is equivalent to conventional LBM. Results for flows in two-dimensional cavity and around a cylinder demonstrate the scheme.

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Lattice Boltzmann Simulation of Two Liquid Droplets Impacting on a Liquid Film ZHOU Yi, GUO Jiahong, CHEN Hongxun 2010, 27(1): 31-37.  Abstract ( )   PDF (501KB) ( )   With single-phase free surface Boltzmann method for flow field,free-surface condition and surface tension approach,we investigate process of two droplets impacting on a liquid film and two droplets with vertical interval successively impacting on a liquid film.Numerical result indicates that vertical distance between two droplets has influence on liquid film.Shape of liquid film changes greatly with intervals between droplets.Numerical result is in accordance with experiment qualitatively.

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A Two-phase Turbulence PDF Model with Expanding Dimension Method of Colored Noise and Simulation of Wall-jet-flows LI Zhaoxiang, XU Jiangrong, YANG Zhonghua 2010, 27(1): 38-44.  Abstract ( )   PDF (440KB) ( )   With Langevin equation of particle motion,PDF equations in two levels are obtained in which the fluid fluctuation velocity is expanded in dimension and one-dimensional colored noise is transformed into two-dimensional white noise.They are two-phase PDF transport equation of turbulence and particle-phase PDF transport equation.With particle motion equations and assumption of Gaussian distribution,a closure problem of PDF equation is solved and a second-order-moment model is obtained.It is simplified into an algebra stress model [ASM].A finite analytic numerical method for convective diffusion equation is applied to solve the two-order moment model of two-phase flows.A wall-jet-flow loaded with solid particles is studied in the ASM by finite analytic numerical method.Numerical results are compared with experimental results.

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Tracer Transport in Intraformational Water Channeling Reservoir LI Junjian, JIANG Hanqiao, LIU Tongjing 2010, 27(1): 45-50.  Abstract ( )   PDF (361KB) ( )   We establish a 2D diffusion mathematic model considering transverse diffusion and feature of channeling reservoir.With Laplace transform an analytical model is solved.A solution with small slug is found.With general-purpose finite element software in a geometrical model numerical solution is solved.2D concentration profile is ploted.It is shown that larger Peclet number leads to higher peak concentration and later break through time.With combination of analytic solution and numerical solution,it is helpful in understanding the essential of mass transfer diffusion.

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Supersonic Flow Characteristics of Dispenser with Opened Cabin TAO Ruyi, JIANG Kun, ZHAO Runxiang, WANG Hao 2010, 27(1): 51-58.  Abstract ( )   PDF (846KB) ( )   Supersonic flow characteristics of a dispenser with oponed cabin are numerically simulated with Reynolds-averaged Navier-Stokes equations.Computations are well consistent with experimental results.Flow characteristics are simulated well with S-A turbulent model and splitting scheme AUSM+.If attack angle is not zero,reverse flow is found at backward-facing step of head.Vortices are developed between adjacent submunitions.Several extremes of surface circumferential pressure are shown,and shell tail wave is not symmetric.The principle of flow field is revealed.Vital reference is provided for submunition initial conditions.

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Aerothermodynamics of Hypersonic Small Nose Cone with Local Rarefied Gas Effects WANG Zhihui, BAO Lin 2010, 27(1): 59-64.  Abstract ( )   PDF (511KB) ( )   A small nose sphere-cone is taken as vehicles leading-edge,and kinetic-theory based DSMC method is used to simulate aerothermal environment of hypersonic sphere-cone with different nose radii.Stagnation point heat fluxes calculated by DSMC are compared with that by Fay-Riddell formulae and other theories.Aerothermodynamic characteristics of hypersonic small nose cone with local rarefied gas effect are studied.It is found that the modified Cheng's parameter is a credible criterion in predicting rarefied gas effects at stagnation point of sharp leading-edges.

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Aero-optical Effects in Compressible Mixing Layers SHI Ketian, MA Handong 2010, 27(1): 65-72.  Abstract ( )   PDF (612KB) ( )   A method is established to calculate aero-optical effects.It is valid for nonuniform flow fields.A three-dimensional spatially developing mixing layer is simulated by large eddy simulation(LES).Favre-filtered Navier-Stocks equation is discretized with a high order compact difference scheme.Transition from laminar to turbulence is simulated successfully.And it is compared with that of direct numerical simulation.Aero-optical effects caused by mixing layer is calculated to study relation between flow field and imaging distortion.It shows that imaging distortion is the severest at transition region.

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Direct Domain Decomposition Method for Bistatic Scattering from 3-D Rough Surfaces LIU Peng 2010, 27(1): 73-81.  Abstract ( )   PDF (552KB) ( )   A direct domain decomposition method(DDM) is developed to simulate bistatic scattering from a 3-D random rough surface.Coupling boundary conditions on interface between adjacent subdomains are derived as iterative Robin boundary condition(IRBC) is used as a truncation boundary in a finite element method(FEM).The final coupling matrix is obtained by an inward-looking approach.A diagonal reordering of subdomains is adopted to reduce the matrix band width.Most time consuming of IRBC computation is on large scale planar fictitious boundary above the rough surface,where the field integral equation is written in 2-D convolution form and calculated efficiently by fast Fourier transform(FFT).Our codes are examined by FEM without DDM and FEM with perfectly matched layers.

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Stability and Numerical Dispersion of High Order Symplectic Schemes HUANG Zhixiang, SHA Wei, WU Xianliang, CHEN Mingsheng, KUANG Xiaojing 2010, 27(1): 82-88.  Abstract ( )   PDF (277KB) ( )   Euler-Hamilton equations are provided using Hamiltonian function of Maxwell's equations.High order symplectic schemes of three-dimensional time-domain Maxwell's equations are constructed with symplectic integrator technique combined with high order staggered difference.The method is used to analyzing stability and numerical dispersion of high order time-domain methods and symplectic schemes with matrix analysis and tensor product.It confirms accuracy of the scheme and super ability compared with other time-domain methods.

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A Combined Field Integral Equation for Electromagnetic Scattering of Homogeneous Dielectric Objects Above Half-space HU Yunqin, AN Ning, DING Dazhi, CHEN Rushan 2010, 27(1): 89-94.  Abstract ( )   PDF (285KB) ( )   Electromagnetic scattering of arbitrarily shaped 3-D homogenous dielectric objects located above a lossy half space is investigated.With spatial domain half-space Green's functions surface integral equations are studied to reduce iterations and to enhance efficiency of the method of moment(MoM).An integral equation called JMCFIE is extended to half-space to realize accurate and fast solution.This formulation leads to a well-conditioned matrix equation with RWG basis functions and Galerkin's method.Numerical results demonstrate accuracy and efficiency of the proposed method.

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Multilevel Fast Multipole Algorithm for EM Scattering of Conducting Objects Above Lossy Half-space FAN Zhenhong, LIU Jingquan, HU Yunqin, CHEN Rushan 2010, 27(1): 95-100.  Abstract ( )   PDF (381KB) ( )   Electromagnetic scattering of conducting targets located above lossy half-space is analyzed with multilevel fast multipole algorithm (MLFMA).In order to expand half space Green's functions with addition theorem,a high order approximation method is proposed for evaluation of reflection term of half-space Green's functions with far interactions.A careful investigation is presented to confirm accuracy of the Green's function analysis.Accuracy and efficiency of the proposed method is examined by several numerical applications.It demonstrates that the proposed method has merit of low memory requirement and simple operation.

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Electromagnetic Scattering of Complex Medium by FETI SHENG Yijun, ZHU Jian, FAN Zhenhong, CHEN Rushan 2010, 27(1): 101-106.  Abstract ( )   PDF (298KB) ( )   Finite element tearing and interconnecting method(FETI) is used in analyzing electromagnetic scattering of complex medium.It decomposes computational space and complex medium.With reasonable operations of algebra,a 3D problem is changed to a 2D problem.It reduces computational complexity.By using Krylov solver,computation of reverse matrix is avoid in the equation about interface system.Numerical results show that the method is accurate and efficient for electromagnetic scattering of complex medium.

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Analytical Solution of Forward Problem in Brain Electrical Impedance Tomography XU Zheng, HE Wei, HE Chuanhong, ZHANG Zhanlong 2010, 27(1): 107-114.  Abstract ( )   PDF (366KB) ( )   A 4-layer sphere model of human head is built.Layers from outside to inside represent scalp,skull,CFS and brain,respectively.The point current source placed on the outmost layer is regarded as boundary condition.A method of separation of variables is used to solve the equations.Potential distributions with different injecting angles are shown.We simulate conductivity distribution of brain tissue, and plot real and imaginary potentials at nine points on the outmost layer.As conductivity of brain tissue changes,the real potentials vary greatly than the imaginary parts.Frequency characteristic is simulated,and the result shows that the imaginary potentials on the outmost layer is influenced mostly by frequency.These can be used in analyzing head EIT problems and improving the Back-projection Algorithm.

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Inversion of Electrical Logging by Newton-SVD with Stochastic Particle Swarm LI Zhiqiang, FAN Yiren, DENG Shaogui, CHEN Hua 2010, 27(1): 115-120.  Abstract ( )   PDF (309KB) ( )   We propose a method to invert two parameters(virgin zone resistivity,invaded zone) of dual lateral logging which is based on Newton-SVD of particle swarm.Reasonable initial values are selected by random particle swarm method.Newton-SVD is applied to invert dual lateral logging data.It improves stability and reliability of logging inversion greatly,and offers a radical way for setting initial values of inversion.Ideal model with noise and practical logging data are compared.It shows that the method eliminates effects of complex logging environments effectively and offer true formation parameters.

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Fast Acoustic Far-field Inverse of Three-dimensional Scattering Objects in an Ocean Waveguide PAN Wenfeng, ZONG Zhixiong, YOU Yunxiang, MIAO Guoping 2010, 27(1): 121-130.  Abstract ( )   PDF (830KB) ( )   We study an inverse problem of reconstructing a 3D object in an ocean waveguide from far-field measurements of scattered field.An indicator sampling method for fast imaging of scattering object is presented.The method does not depend on any acoustic and geometric properties of the scattering object.It is valid for obtaining good imaging of location and shape of the scattering object,even as far-field data are measured in a limited aperture and corrupted by noise.Generally,multiple scattering between object and waveguide boundaries has positive influence on reconstruction of the scattering object.

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Defect Mode and Reforming of Oblique Incidence Elastic Waves in Phononic Crystal LIU Qineng 2010, 27(1): 131-136.  Abstract ( )   PDF (285KB) ( )   Transfer matrix and transmission coefficients in doping phononic crystal are obtained.Transmission coefficient of elastic waves in doping phononic crystal is calculated.With oblique incidence transversal wave, defect mode of transversal wave decreases with increase of incident angle.Transformation of transversal wave toward longitudinal wave increases with increase of incident angle.With oblique incidence longitudinal wave,defect mode of longitudinal wave decreases with increase of incident angle.Transformation of longitudinal wave toward transversal wave increases with increase of incident angle.

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Antiferromagnetic Magnetization and Exchange Anisotropy in Ferromagnetic/Antiferromagnetic/Ferromagnetic Trilayers WANG Yeli, MA Yingying, XU Xiaoyong, HU Jingguo 2010, 27(1): 137-142.  Abstract ( )   PDF (351KB) ( )   Phases of antiferromagnetic magnetization and exchange bias and coercivity in ferromagnetic/antiferromagnetic/ferromagnetic(FM/AF/FM) trilayers with interface quadratic and biquadratic exchange coupling are studied comprehensively.Three possible cases are found,namely reversible recovering case,irreversible continuously-reversing case and irreversible discontinuously-reversing case. Realization of the cases strongly depends on pinned-MFM interface quadratic exchange coupling J1,free-MFM interface quadratic exchange coupling J2 and biquadratic coupling J'2.In the reversible recovering,the exchange coupling results in an exchange bias,and there is no exchange bias in other cases.It provides possible explanation for both hysteresis energy loss and perpendicular coupling at the interface.

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Magnetic Properties and Controllable Vortex Circulation of Asymmetric Co Nanorings:Monte Carlo Simulation LIN Zhiqin, YE Qingying, ZHONG Kehua, HUANG Zhigao 2010, 27(1): 143-149.  Abstract ( )   PDF (314KB) ( )   With Monte Carlo simulation,we study magnetic properties and controllable vortex circulation of asymmetric Co nanorings.Simulated results indicate that magnetic field direction has great effect on magnetic states and magnetization process of asymmetric Co nanorings.It is found that direction of the magnetic-moment circulation in asymmetric nanorings can be controlled by gradient of the domain-wall energy along the circumference in cooperation with an external magnetic field.It is found that size effect is obvious on stability of vortex-type state and magnetization process of asymmetric nanorings.

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Molecular Dynamics Simulation of Contact Force Between Sample and AFM Tip TIAN Wenchao, CHEN Guimin, LIU Huanling 2010, 27(1): 150-156.  Abstract ( )   PDF (549KB) ( )   Contact between tip of atomic force microscope(AFM) and tested sample surface is simulated using molecular dynamics (MD).Relationship between contact force and gap is analyzed.Surface pressure distribution is discussed.Phenomena of "jump-to-contact" and "neck-separation" are observed.Hysteresis between contact process and separate process is obtained.Relationship of surface distortion radius with contact force and gap is also discussed.Only atomic layer close to contact area affects the contact force.Surface atoms close to the contact are pressed and those far from the contact are pulled.