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25 January 2017, Volume 34 Issue 1 Previous Issue    Next Issue

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Analysis of Impact Load on Elastic Plate in Underwater Explosions with Modified Ghost Fluid Method XU Liang, FENG Chengliang, LIU Tiegang 2017, 34(1): 1-9.  Abstract ( )   HTML ( )   PDF (3373KB) ( )   Effects of thickness and density of plate on impact load and cavitation evolution in non-contact underwater explosions are investigated.A modified ghost fluid method developed recently is extended to treat nonlinear interaction between compressible flow and elastic plate.With assumption that fracture of a plate does not occur, it discloses that relatively small thickness or density of plate weakens impact of blast wave on structure.Impact load tends to result of rigid wall boundary nonlinearly with increase of thickness or density.Furthermore, smaller thickness or density causes cavitation to occur earlier and creates a larger cavitation region.It delays and weakens secondary impact on structure induced by cavitation collapse as well.

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Numerical Integrations Over Arbitrary Domains and Arbitrary Surfaces on Block-Structured Adaptive Meshes XU Jianjun, SHI Weidong, LI Xingwei, SHU Shi 2017, 34(1): 10-18.  Abstract ( )   HTML ( )   PDF (2311KB) ( )   We study numerical integration over arbitrary interface and arbitrary domain on block-structured adaptive mesh.Arbitrary interface and arbitrary domain are described by a level set function.We first describe numerical methods on uniform Cartesian grid.Then we extend the methods to block-structured adaptive mesh.Numerical calculations demonstrate that adaptive mesh methods are second-order accurate.Compared with uniform mesh methods, the adaptive mesh methods reduce needs on computer storage significantly.

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Solving Diffusion Equation on Three-Dimensional Non-Conformal Mesh GUO Shaodong, ZHANG Mingyu, ZHOU Haibing, XIONG Jun, ZHANG Shudao 2017, 34(1): 19-28.  Abstract ( )   HTML ( )   PDF (2167KB) ( )   Sub-division method based on support operator is used to solve diffusion equation with three-dimensional non-conformal mesh and non-planar mesh.Numerical experiments show that the method is second-order accurate on general non-conformal mesh.For curved-face mesh and non-planar-face mesh, the method is more accurate than traditional plane-approximation method.For non-conformal orthogonal mesh, the method can obtain accurate solutions of linear problems.

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A Study of Optimal and Adaptive Rule of Smooth Length in SPH Kernel Function ZHAO Yazhou, MA Zhibo 2017, 34(1): 29-38.  Abstract ( )   HTML ( )   PDF (2002KB) ( )   Based on wavelet analysis theory and reproducing kernel function, a multiscale diagnostic tool for meshfree method SPH is developed.Multi-scale reproducing kernel function make it possible to separate numerical computation response at different scales.Frequency characteristics of computational domain at different position is depicted by dynamic retractable window function, which constructs "adaptive mesh" in mesh method for meshfree system to carry multi-resolution analysis at different position of flow field.With wavelet decomposition algorithm in multi-scale diagnostic tool, a kernel smoothing length optimal selection rule is developed on the basis of estimated energy error ratio of SPH kernel function in frequency domain.Finally, for shock/rarefaction wave coexistence in compressible flow field and defects of traditional method, we construct a numerical method to avoid "tailing" phenomenon.

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Lattice Boltzmann Simulation of Mixed Convection in an Enclosure Filled with Porous Medium WANG Tingting, GAO Qiang, CHEN Jian, XU Hongtao, YANG Mo 2017, 34(1): 39-46.  Abstract ( )   HTML ( )   PDF (3388KB) ( )   Lattice Boltzmann method is adopted to investigate mixed convection in an enclosure filled with porous medium.A heated cylinder (D/L=0.4) is located at center of the enclosure with high temperature.Inlet flow with low temperature is located at lower-left wall of the enclosure and exit is at upper-left wall.Other walls are assumed adiabatic.Influences of Richardson number Ri and Darcy number Da on average Nusselt number Nu around heated cylinder are investigated while Prandtl and Grashof numbers are kept at 0.71 and 1.4×104, respectively.It indicates that Nu decreases with increasing Ri.Influence of Richardson number on Nu is significant as Darcy number is great.At 10-5≤Da≤10-2, Nu increases with increasing Darcy number as forced convection dominates flow (Ri≤0.1).As natural convection dominates flow (Ri=10), Nu is not sensitive to Darcy number.

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Parallel-Program Development and Experiment of Regional Atmospheric Model Based on JASMIN Framework XU Youping, CHENG Yufeng, WANG Bin, GUO Hong, PU Ye, CHENG Rui 2017, 34(1): 47-60.  Abstract ( )   HTML ( )   PDF (4731KB) ( )   Meso-scale heavy rain numerical model was studied.Regional atmospheric model parallel program with high hierarchy and modularity was built based on parallel applications infrastructure.With simulation of typical weather event, correctness, improvement of parallel performance and high-resolution simulation are tested.The new parallel model kept well prediction performance of original model and improved parallel performance and extendibility.The model simulated better with higher resolution.

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An Isogeometric Boundary Element Method for 3D Helmholtz Problems WANG Xianhui, QIAO Hui, ZHANG Xiaoming, GU Jinliang 2017, 34(1): 61-66.  Abstract ( )   HTML ( )   PDF (2234KB) ( )   An isogeometric analysis based on a kind of local bivariate B-spline function and Burton-Miller method is introduced in boundary element method (BEM) for 3D Helmholtz problems.The method avoid efficiently computation of singular and nearly singular integrals aroud singular point of parametric surface.Numerical examples show that the algorithm has good performance in accuracy, efficiency and convergence.The algorithm performs isogeometric BEM (IBEM) with traditional global B-spline shape functions on CPU time and accuracy.The method has potential in engineering applications.

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Pseudo-Random Numbers for Identical Results on Varying Numbers of Processors in Domain Decomposed Particle Monte Carlo Simulations LI Gang, ZHANG Baoyin, DENG Li, SHANGGUAN Danhua, LI Rui, MA Yan, FU Yuanguang, HU Xiaoli 2017, 34(1): 67-72.  Abstract ( )   HTML ( )   PDF (1448KB) ( )   Detailed modeling and massive tallying of nuclear reactors lead to memory overload for a single core processor.It could not be calculated by Monte Carlo particle transport with particle parallelism only.Domain decomposition is one of solutions.Domain decomposition needs to interchange particles between processors, so that inherit technique of pseudo-random number could not make identical results between serial and parallel.Two techniques of pseudo-random number are described to obtain identical results on different numbers of domains in a Monte Carlo particle simulation code.

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Optimization Design of Radiation Shielding Materials for 235U Fission Source in Reactor YANG Shiyan, HE Manli, JIANG Danfeng, WANG Guohui, YUAN Chao, DAI Yaodong 2017, 34(1): 73-81.  Abstract ( )   HTML ( )   PDF (3677KB) ( )   With 235U fission source in thermal neutron reactor as radiation source, MCNP code is employed to simulate energy spectrum and to study shielding protect.It shows that for prompt neutron, emitting by 235U fission source, with energy more than 3 MeV, heavy metals materials have better shielding effect.However, light hydrogen materials performance better for neutrons with energy below 1MeV.For compounds-W/LiH, W/B4C and TiH2/W, shielding effect is best as weight ratios are W:LiH=19:1, W:B4C=9:1, W:TiH2=3:1.GA combined with MCNP code is employed to search optimized design of compounds, W/TiH2/B4C, TiH2/Cu/Gd and TiH2/B4C/Gd, respectively.Weight fractions are calculated as shielding effect performance is best.Exponential decay relations between dose equivalent rate (10-11Sv·h-1) in tissues caused by neutron and gamma rays penetrating materials and thickness of materials can be expressed as 1.071exp (-0.187 8x), 1.077exp (-0.166 2x) and 1.608exp (-0.171 9x), respectively, where x is thickness of material in cm.

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A Modified Confocal Microwave Imaging Method for Detection of Breast Cancer LIU Guangdong 2017, 34(1): 82-88.  Abstract ( )   HTML ( )   PDF (1505KB) ( )   Algorithms are tentatively modified by adding refraction effect due to inhomogeneous media.Robust Capon beam-forming (RCB) algorithm is used for confocal procession.A frequently-used three-dimensional (3-D) hemispherical breast model is selected.Electrical parameters of breast tissues are modeled by a multi-pole Cole-Cole model in order to consider frequency-dependent property.Finite-difference time-domain (FDTD) method is used to simulate wave propagation in breast with illumination of an ultra-wide band (UWB) plane wave source.In a numerical application, two spherical 3 mm-radius tumors are added into breast to test performance of original CMI method and modified version.It shows that there is improvement on computational precision with slight increase in computational complexity.

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Structural,Electronic and Thermodynamic Properties of Tetragonal,Monoclinic and Orthorhombic Ge3N4 YAO Xiaoling, CHEN Dong 2017, 34(1): 89-98.  Abstract ( )   HTML ( )   PDF (3005KB) ( )   We calcuate lattice constants, volumes, elastic moduli, Vickers hardnesses and density of states of the tetragonal, monoclinic and orthorhombic Ge3N4.Fundamental properties obtained are compared with experimental data and other theoretical results, which shows good agreement.Negative formation enthalpy, linear relation between lattice deformation and pressure, and volume show that three phases retain stabilities in a pressure range of 0~20 GPa.Density of states show that Ge3N4 are semiconductors with strong s-p hybridizations.All polymorphs are brittle materials but anisotropic.Several thermodynamic properties are investigated with quasi-harmonic approach considering lattice vibrations and anharmonic effects.Helmholz free energy and internal energy show strong dependences on pressure.Interesting features are seen in heat capacity of the novel Ge3N4 nitrides, especially at high temperatures.

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Effect of Cu and Non-metal Double Acceptor Impurity Level Cooperative Action on Optical Properties of Anatase TiO2 CHEN Xiaoyu, FENG Qing, ZHOU Qing 2017, 34(1): 99-108.  Abstract ( )   HTML ( )   PDF (4182KB) ( )   With first-principles plane-wave ultrasoft pseudopotential method based on density functional theory (DFT), we studied acceptor level characreristics of anatase titanium dioxide doped and co-doped with 3d metal impurities Cu and non-metallic impurities C, N and F.It shows that Cu-N co-doping system and Cu, N single-doped system are better for visible light.Cu-N co-doping system, compared with Cu, N single-doped system, has a smaller band gap and greater density distribution on shallow acceptor level.It also shows that Cu-N co-doping system has highest absorption and reflectivity.Therefore, this system is the best for visible light.Cu and N acceptor level cooperative action results in the best visible light effect.

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Numerical Simulation on Optical Cross Section of Complex Targets YUE Yufang, ZHANG Feizhou, ZOU Kai, CHEN Tianjiang, ZHANG Jianzhu, XIE Xiaogang, AN Jianzhu 2017, 34(1): 109-118.  Abstract ( )   HTML ( )   PDF (1737KB) ( )   Numerical simulation on optical cross section (OCS) of complex targets is shown.An adaptive Z buffer method is discussed.Optical hidden facets are processed precisely and subtracted from integral OCS.Optical scattering characteristics described by bidirectional reflectance distribution function (BRDF) are used in numerical simulation.For surface pleats of space targets with grass-like optical scattering characteristics, normal vector model of pleat and scattering model are analyzed.An analysis for OCS experimental evaluation is given.OCS for a downsizing space target with different azimuth and zenith angle attitudes are achieved.Simulation parameters for downsizing target are calibrated with experimental results.Simulation images and trendlines are coherent with experiment results roughly, which indicates that the method describes OCS at a certain extent.

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Effect of Femtosecond Laser Parameters on State Populations of Nonadiabatic Coupling Molecules GUO Wei, BAI Jing, LI Yuehua 2017, 34(1): 119-125.  Abstract ( )   HTML ( )   PDF (2499KB) ( )   Influence of pulse width, laser wavelength and laser intensity on state populations of a NaI molecule driven by a pump-probe pulse was studied via time-dependent wave packet approach.Wave packet moves periodically with roundtrip time 1 000 fs.Wave packet bifurcates in crossing region firstly at delay time 200 fs, which affects state populations.Excitation probability increases and dissociation probability decreases with increasing pulse width.Excitation probability approaches the maximum at resonance pump wavelength 318 nm.Dissociation probability decreases with increasing pump wavelength.As pump intensity increases, excitation probability increases while dissociation probability does not change.Probe wavelength and probe intensity do not affect state populations.Wave packet motion and selective distribution of state populations can be achieved by adjusting laser parameters.It provides bases for realizing light manipulation of molecules experimentally.