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25 May 2012, Volume 29 Issue 3 Previous Issue    Next Issue

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K2_SPH Method and Simulation of 2D Breaking Waves ZHENG Xing, MA Qingwei, DUAN Wenyang 2012, 29(3): 317-325.  Abstract ( )   PDF (1367KB) ( )   We introduce several improvements on key numerical techniques,especially for free surface identification and solid boundary handling method.They make K2_SPH simulating breaking waves successfully.It includes running-up,over-turning and breaking processes.Numerical test of violent tank sloshing shows that K2_SPH method is more accurate and reliable than traditional smoothed particle hydrodynamics(SPH) method for wave profile and pressure distribution.

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Training Algorithms for EGO Method and Applications DENG Feng, QIN Ning, WU Yizhao 2012, 29(3): 326-332.  Abstract ( )   PDF (1722KB) ( )   Three kinds of training algorithms for efficient global optimization(EGO) method are investigated.A kind of training algorithm based on low-discrepancy sequences is proposed to reduce randomness of EGO method.Performance of EGO method depends on a good training algorithm.Since training problems in EGO are non-convex and non-smooth,meta-heuristic algorithms,random algorithm and low-discrepancy sequences are chosen to address five benchmark optimization problems and two aerodynamic shape optimization problems.In these problems,differential evolution algorithm was found the best in meta-heuristic algorithms.Training algorithm based on low-discrepancy sequences can effectively reduce randomness of EGO method and Faure sequence has the best performance.

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A Fast Node Placement Method with Bubble Simulation QI Nan, NIE Yufeng, ZHANG Weiwei 2012, 29(3): 333-339.  Abstract ( )   PDF (1273KB) ( )   Node placement method with bubble simulation can generate high-qualify node sets in complex domains.However,its efficiency needs to be increased.Several modifications were done to reduce the cost of simulation.Firstly,let viscosity coefficient c gradually increases instead of being taken as a constant.It speeds up convergency.Moreover,at the end of each round simulation,in which bubbles additions or deletions are operated,c is assigned to a small value in order to ensure quality of bubble distribution.Secondly,as solving ordinary differential equations that control movement of bubbles,a low order numerical algorithm is chosen.Finally,sort process of overlapping rate of bubbles is removed.It is replaced by setting only threshold for bubbles additions and deletions.Numerial examples show that computing cost decreases by approximately 40% and average quality of Delaunay triangulation corresponding to node set is over 0.9.It shows that the algorithms are efficient and generate node sets with high-quality.

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Modeling and Numerical Simulation of Gas/drop Flows XUE Shesheng, SUN Shunkai, LI Yan 2012, 29(3): 340-346.  Abstract ( )   PDF (306KB) ( )   To investigate mechanism of TUDOG(transeverse uniform singlet oxygen generator),a chemical reaction model is made to describe physical and chemical performances of Cl2/He mixed gases transversely traveling into a falling BHP(KOH,H2O2,H2O)drop field.Numerical computation is carried out.In two-phase flows,exchange of mass and momentum between two phases is considered.One set of 2-D gas-phase flow equations are solved with SIMPLEC scheme.Simulation results agree well with experiments provided in references.It is found that chlorine utility and singlet oxygen yield decreases with increase of gaseous inflow speed,and increases with speed of falling drops.Absorb and utility of chlorine mainly takes place in reactive region upstream.

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Conservative Non-equlibrium Extrapolation Boundary Condition in Lattice Boltzmann Method ZHAI Xujun, ZHAO Kai 2012, 29(3): 347-353.  Abstract ( )   PDF (838KB) ( )   Removing mass leakage in non-equilibrium extrapolation method,a mass conservative boundary condition is proposed with improving non-equilibrium extrapolation method based on conservation of mass.Mass conservation of a system is ensured by defining an artificial density at solid boundary.Precision and stability of the new boundary condition are validated by simulating three classical flows (Poiseuille,Couette and Womersley).

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Mathematical Simulation on Induced Polarization of Reservoir Rock in Time Domain GUAN Jiteng, YU Hua, WANG Qian, FAN Yehuo, CHENG Yuanyuan 2012, 29(3): 354-360.  Abstract ( )   PDF (375KB) ( )   Based on a microscope capillary model,a mathematical model for induced polarization of reservoir rock is obtained.Influences of concentration difference polarization and electric double-layer deformation on induced polarizability are studied numerically.It shows that induced polarization is governed by ion concentration difference polarization in capillary.Electric double-layer deformation has greater influence on total polarizability.Speed of charging and discharging in induced polarization depends mainly on cation exchange capacity and pore structure of rock.

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Two-dimensional Numerical Simulation of Radiation Hydrodynamics in Underground Strong Explosions TIAN Zhou, GUO Yonghui, QIAO Dengjiang 2012, 29(3): 361-368.  Abstract ( )   PDF (1791KB) ( )   For evaluating damage of strong explosion,boundary conditions of coupled Eulerian-Lagrangian calculation are used.Energy accumulation due to radiative transfer is considered.Coupled methods of two-dimensional numerical simulation with cylinder symmetry are established,which calculate simultaneously equations of radiation hydrodynamics and hydro-elasto-plastic.Full physical processes of underground strong explosion are presented.They are propagation of radiation front in detonating room,transmitting of radiative energy to wall of detonating room,inward expanding of detonating room wall,propagation of shock wave in rock,compressing of high-pressure in detonating to room wall and outward expanding like waves of detonating room wall.

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Rayleigh Quotient Iteration Algorithm for Source Inversion in Neutron Transport Problem MEI Liquan, FANG Ye, YUAN Changqi 2012, 29(3): 369-374.  Abstract ( )   PDF (279KB) ( )   With spherical harmonic function expansion and finite difference discretization,an inversion problem of neutron transport equation is turned to solving effective multiplication factor related to eigenvalue problem.According to characteristics of the matrix,Gerschgorin disk theorem is applied to initial value selection without any physical experience.Rayleigh quotient iteration algorithm is used in solving effective multiplication factor.Third order convergence is achieved without a specific initial value.

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Numerical Solution of Full Wave Equation for Fast Wave Current Drive in Tokamak LIU Yan, GONG Xueyu, YANG Lei, PENG Xiaowei, YIN Lan 2012, 29(3): 375-382.  Abstract ( )   PDF (380KB) ( )   A full wave numerical method is developed for fast wave current drive in tokamak plasmas,in which finite Larmor radius effects and parallel dispersion are taken into account.A physical model with full wave are developed.Electric field distribution in radial is obtained.It shows that fast wave can propagate to central plasma;Mode conversion happened near central plasmas;Fast wave can drive current in centre to improve balance current profile;Parallel electric is weaker than that in vertical direction.The current is droven by Landau damping and transit-time magnetic pumping.

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Development of Photoemission Module and Simulation of Linear Induction Accelerator Injector YANG Changhong, MENG Lin, ZHANG Kaizhi, LIU Dagang, LIAO Shuqing, DAI Zhiyong 2012, 29(3): 383-388.  Abstract ( )   PDF (1210KB) ( )   We study photocathode of linear induction accelerator.A photoemission model was implemented which takes into account details such as photocathode material and laser source.A relationship between photocathode and macro particle initial condition is established.We achieved this model in LIAPIC code.A photocathode injector model was set up to simulate photoemission.At last,the model is verified.Simulation results are concordant with experiment.

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Effect of Two Strip Antenna Distance on Plasma Coupling Characteristics DU Dan, GONG Xueyu, CAO Jinjia, WANG Zhenhua, ZHENG Pingwei, YANG Wenchao 2012, 29(3): 389-393.  Abstract ( )   PDF (1168KB) ( )   With a hypothesis that energy is completely absorbed by plasma in a plasma slab model and a three-dimensional antenna model,we numerically stimulate coupling of two strip antennas with plasma in ion cyclotron resonance heating.Antenna radiation power and power density distribution absorbed by plasma at different antenna distances are calculated.Through analyzing we draw a conclusion: For two strip antennas feed in phase at certain experimental parameters,the shorter the antenna distance is,the better ion cyclotron resonance heating is.

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Compressive Sensing for Solution of Electromagnetic Scattering over Wide Angles DU Hongmei, CHEN Mingsheng, WU Xianliang, CAO Xinyuan 2012, 29(3): 394-398.  Abstract ( )   PDF (273KB) ( )   Based on a fact that impedance matrix in the method of moments(MoM) is independent of incident angles,a compressive sensing(CS) technique is introduced in constructing an incident source,in which much information about incident angle is included.Under the incident source,measurement of induced currents can be obtained with MoM.With orthogonal matching pursuit(OMP) technique,induced currents are reconstructed with few measurements.Compared with conventional MoM,high accuracy numerical results are obtained while computational time is reduced to one third.Computational complexity of wide angle electromagnetic scattering is reduced greatly.

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FDTD Investigation on Electromagnetic Scattering of 1D Band-limited Weierstrass Fractal Layered Land Surface and a Conducting Column with Rectangular Cross-section ZHU Xiaomin, REN Xincheng, GUO Lixin 2012, 29(3): 399-405.  Abstract ( )   PDF (862KB) ( )   Composite electromagnetic scattering of 1D band-limited Weierstrass fractal layered rough land surface and a conducting column with rectangular cross-section is studied with FDTD.Composite scattering coefficient with varying scattering angle is obtained based on bistatic scattering coefficient.Influence of root-mean-square of height fluctuation,dimension of fractal,parameters of the middle layer medium,lower medium and conducting column with rectangular cross-section on composite scattering coefficient is discussed.

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Fast Computation of Wide-band RCS for Objects with AWE Technique and Equivalent Dipole-moment Method YANG Shuaishuai, SUN Yufa 2012, 29(3): 406-410.  Abstract ( )   PDF (241KB) ( )   Asymptotic waveform evaluation(AWE) technique in conjunction with equivalent dipole-moment(EDM) method is applied to obtain radar cross section(RCS) of an arbitrarily shaped three-dimensional(3-D) perfect electric conductor(PEC) over a frequency band.EDM method is used to achieve fast filling of impedance matrix and more derivative matrices.Inner and outer iterative near field preconditioning technique is used to solve matrix equation.Wide-band radar cross section is achieved by using AWE technique.Numerical results show that the computational efficiency is improved significantly with ensuring accuracy.

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Computation Method for Temperature Field of Mass Concrete Containing Cooling Water Pipes CHEN Guorong, XU Wentao, YANG Yun, LI Kai 2012, 29(3): 411-416.  Abstract ( )   PDF (316KB) ( )   We present a method for numerical simulation of temperature field of mass concrete with cooling pipes.Cooling pipes are put in conventional concrete element.Contact surface of concrete and cooling pipes is considered as thermal surface in boundary conditions of control equation.And energy dissipating through cooling pipe walls in concrete is brought into conventional functional.A governing equation of finite element method is established for concrete containing cooling pipes with variational principle.A finite element simulation program for three-dimensional transient temperature field is designed.In the program,topology information of cooling pipe mesh can be completed automatically.Cooling pipes can cross concrete elements anywhere which does not increase difficulty of mesh generation.Numerical examples show that the method accurately simulates cooling of concrete.

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Temperature Distribution Within a Hollow Cylinder in Outer Space: A Study with View Factors to Trace Reflected Energy LUO Jianfeng, ZHANG Hailiang, YIN Hongwei, WANG Xiaofeng 2012, 29(3): 417-425.  Abstract ( )   PDF (1354KB) ( )   With view factors to trace reflected energy for radiative factors,effect of thermal control coating on temperature distribution in a hollow cylinder in outer space under solar incidence is studied.A finite difference method is used to discrete three-dimensional steady energy equation in circular cylindrical coordinates.Radiation-conduction boundary condition is used.Patankar linearization method is used to linearize boundary condition and iteration method is used to solve the nominal linearized equations.Temperature distribution within a hollow cylinder is obtained.Emitting properties of thermal control coatings are approximately expressed by a series of rectangular spectral bands.The methods can be extended to solve precisely temperature distribution within apparatus of spacecraft in outer space.

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Aberration Correction of Single Aspheric Lens with Particle Swarm Algorithm QIN Hua, WAN Yunfang, ZHANG Weiyuan, SONG Yansong 2012, 29(3): 426-432.  Abstract ( )   PDF (1276KB) ( )   Automatic design and analysis of a single aspheric lens using particle swarm algorithm is presented.Particle swarm algorithm is applied to aberration correction of a single aspheric lens to meet requirements of spherical aberration.A mathematical model is constructed.And a program code is developed.Merit functions in an optical system are employed as fitness functions,which combined coefficients of a higher degree polynomial equation,a reciprocal of radius of curvature,a conic constant,thicknesses among lens surfaces and refractive indices regarding an optical system.Automatic correction of spherical aberration is performed with the function.An example shows that PSO as a tool for spherical aberration correction of a single aspheric lens is simple and effective.

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An Optimization for Eigenvalue Problems with Multiple Reciprocity Boundary Element Method LI Jisan, WANG Yong, LIU Wenxin 2012, 29(3): 433-438.  Abstract ( )   PDF (272KB) ( )   A boundary element method (BEM) based on multiple reciprocity method(MRM) is employed to solve eigenvalue and eigenfrequency of a two-dimensional linear acoustic cavity.By direct searching of the zero-points of determination of a matrix,we determine eigenfrequency of the system.An effective estimation for the first wave-number was suggested based on the principle of wave propagation.Estimation efficiency of several models is calculated.We evaluated fundamental solution's order and found that more than seven reciprocity are needed.Numerical results agree well with analysis and other literature.Estimation for the first wave-number is effective and correct.

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A Scalable Parallel Algorithm for Three-dimensional Semiconductor Device Simulation CHENG Jie, ZHANG Linbo 2012, 29(3): 439-448.  Abstract ( )   PDF (2294KB) ( )   A scalable parallel algorithm for three-dimensional semiconductor device simulation on unstructured tetrahedral meshes using drift-diffusion model is proposed,which is characterized by finite volume discretization,fully coupled Newton iterations for discretized nonlinear equations,and GMRES iterations using algebraic multigrid(AMG) preconditioner for linear equations in Newton iterations.The algorithm was implemented using a parallel adaptive finite element toolbox PHG.Large scale parallel numerical experiments with several problems,including PN diode and MOSFET,were carried out.In numerical simulations the largest mesh size are 500 million elements and the largest number of MPI processes used are 1 024.It shows that the proposed algorithm is efficient,robust and highly scalable.

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Exchange-coupling Effect in Anisotropy of Nano-meter Permanent Materials SUN Yan 2012, 29(3): 449-452.  Abstract ( )   PDF (220KB) ( )   Exchange-coupling effect in anisotropy constant of nano-meter magnetic materials is investigated.An equation was put forward for anisotropy at grain boundaries.Due to exchange-coupling between magnetically soft and hard grains,anisotropy of hard grain is decreased while that of soft grain is enhanced.The average anisotropy of soft-hard grains,increases rapidly,reaches a maximum and then decreases slowly.It is consistent with related experimental and theoretic results.Calculated average anisotropy of hard grains is consistent with experiment.

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Theoretical Study on Structure and Stability of PtIrn0,± (n=1~5) Clusters GUO Wenlu, RAO Qian, ZHANG Xiurong 2012, 29(3): 453-458.  Abstract ( )   PDF (381KB) ( )   Possible geometrical configurations of PtIrn0,± (n=1~5) clusters are optimized with density functional theory(b3lyp) at lanl2dz level.For ground state structures of PtIrn0,± (n=1~5) clusters,stability is calculated and analyzed.It shows that there are many isomerides in PtIrn0,± (n=1~5) clusters.Clusters with less atoms are two-dimensional graphic structures,while clusters with more atoms are three-dimensional graphic structures.With increase of atoms,thermodynamics stability of clusters is better.And stability of PtIr3+ cluster is the best.Compared with pure iridium clusters,it is easier for PtIrn(n=1~5) clusters to get an electron,Nonmetallicity of PtIrn(n=1~5) clusters is stronger.iridium atoms play a dominant action in stability of PtIrn0,± (n=1~5) clusters.

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Adaptive Hybrid Genetic Algorithm for Atomic Clusters XING Xiaoning, JING Xili, MA Yiheng, WANG Quanzhi, XU Yaoyun 2012, 29(3): 459-465.  Abstract ( )   PDF (331KB) ( )   We develop an optimization method for stable geometries of atomic clusters.It combines adaptive genetic algorithm,which has the ability of global optimization,with a local optimization method proposed in this paper which is based on the Newton method.Geometry optimization of carbon clusters is used to test the method.Compared with adaptive genetic algorithm,it is found that the new local optimization method can find local extremum effectively.Compared with hybrid genetic algorithm,it shows that the method can jump out of local extremes.The method presents good stability in four optimizations of C12.

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Quantum Analysis of BCS-BEC Crossover in Feshbach Resonances LI Jing, LIU Bin 2012, 29(3): 466-474.  Abstract ( )   PDF (478KB) ( )   We consider a many-particle model which concludes interaction of molecular BEC,and gave a semi-analytical method to calculate conversion efficiency of Fermion atom pairs convert to Boson molecules.The method used mainly independent crossing approximation.With mean-field theory we get an equation for conversione efficiency.Calculating results are supported by numerical simulation and experiment of 6Li by Hulet group in 2003.