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25 November 2017, Volume 34 Issue 6 Previous Issue    Next Issue

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DG Method for Compressible Gas-Solid Two-phase Flow DUAN Maochang, YU Xijun, CHEN Dawei, HUANG Chaobao, AN Na 2017, 34(6): 631-640.  DOI: 10.19596/j.cnki.1001-246x.7568 Abstract ( )   HTML ( )   PDF (3021KB) ( )   We present DG method for solving two-way coupling compressible gas-solid two-phase flow. Equations of both phases are discreted simultaneously, including convection term and source term. Splitting technique to discretize governing equations separately is avoided. Numerical flux of both phases is based on approximate Riemann solver. Dusty-gas shock tube problem with particles in low pressure section is simulated. Comparisons of equilibrium flow and frozen flow are made. Influence of particles in gas and interaction rules between two phases in relaxation zone behind shock are studied. It found that mass ratio of particles determines last equilibrium state and particles diameter determines transition process of two-phase flow from nonequilibrium to equilibrium flow. Namely, different diameter particles correspond to different relaxation time and distance. It shows that the numerical method proposed is reliable. It lays a foundation for more complicated gas-solid two-phase flow problems.

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Numerical Simulation of Typical Free Surface Flow with SPH-ALE SHANGGUAN Zining, ZHOU Xiuli, SONG Xin, CHEN Qian 2017, 34(6): 641-650.  DOI: 10.19596/j.cnki.1001-246x.7551 Abstract ( )   HTML ( )   PDF (7120KB) ( )   We present simulation of two typical free surface flows using Smoothed Particle Hydrodynamics-Arbitrary Lagrangian Eulerian(SPH-ALE) method basd on Rimann-solver. A first order kernel correction pressure integral method is presented, which was used to estimate pressure of boundary by integrating water particles within the kernel radius influence. Distribution of pressure field and evolution of free surface are given, and compared with experimental data and numerical solutions. It shows that SPH-ALE method is more accurate and reliable than traditional SPH in pressure calculation of flow field. It has a higher precision in solving strong nonlinear free surface flows.

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An Efficient Parallel Direct Method for Turbulent Thermal Convection BAO Yun, YE Mengxiang, LUO Jiahui 2017, 34(6): 651-656.  Abstract ( )   HTML ( )   PDF (1692KB) ( )   A parallel direct methods of DNS (PDM-DNS) for two-dimensional turbulent thermal convection was created with PDD algorithm for Poisson equation direct solving. DNS calculations of turbulent convection with high Ra were completed on "Tianhe-2" supercomputer, in which iteration time steps are over one hundred million. Effect of calculations is surprised. A calculation scale, which was difficult to achieve a year before, is realized. It shows that turbulent convection flow with different high Ra number are completely different. This work provides a valuable method for massively parallel computing and numerical simulation of turbulent convection with high Ra number.

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Two-level Subgrid Stabilized Methods for Navier-Stokes Equations at High Reynolds Numbers YANG Xiaocheng, SHANG Yueqiang 2017, 34(6): 657-665.  DOI: 10.19596/j.cnki.1001-246x.7569 Abstract ( )   HTML ( )   PDF (3237KB) ( )   Based on two-grid discretizations,three two-level subgrid stabilized finite element algorithms for stationary Navier-Stokes equations at high Reynolds numbers are proposed and compared. Basic idea of the algorithms is to solve a fully nonlinear Navier-Stokes problem with a subgrid stabilization term on a coarse grid,and then solve a subgrid stabilized linear fine grid problem based on one step of Newton,Oseen or Stokes iterations for Navier-Stokes equations.It shows that with suitable stabilization parameters and coarse and fine grid sizes,those algorithms yield an optimal convergence rate. Finally, numerial results are given to show efficiency of the algorithms.

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Analytical Study of Hypersinglar Integral Equations with Constant Element for 2D Helmholtz Problems WANG Xianhui, ZHENG Xingshuai, QIAO Hui, ZHANG Xiaoming 2017, 34(6): 666-672.  Abstract ( )   HTML ( )   PDF (1301KB) ( )   Burton-Miller method, a complex linear combination of conventional boundary element method (CBIE) and hypersinglar boundary element method (HBIE), is widely used to deal with exterior acoustic problems. The difficult in implementing Burton-Miller method is computing strongly singular integrals (2D problems). Although, many weakly singular/regularization methods have been presented to evaluate these integrals, these methods are still difficult or extremely time consuming. In this paper, analytical integration of strongly singular boundary integral equations discretized with constant element for 2D Helmholtz problems is presented. All singular and strongly singular integrals are analytically evaluated in finite part sense as constant elements are applied to discretize boundary. Contour integral is used for singular and strongly integrals. Validity of formulas is demonstrated with numerical examples.

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Extended Newmark-FDTD Method for Analysis of Electromagnetic Characteristics of Complex Dispersive Media ZHANG Yuqiang 2017, 34(6): 673-678.  DOI: 10.19596/j.cnki.1001-246x.7547 Abstract ( )   HTML ( )   PDF (1498KB) ( )   A finite-difference time-domain (FDTD) method combined with Newmark algorithm in finite-element method for analysis of electromagnetic characteristics in dispersive media, named as extended Newmark-FDTD method, is presented. In the method, a unified time-domain updated formula can be applied to typical kind of dispersive model, i.e., Debye, Drude and Lorentz medium, and to novel dispersive models, i.e., modified Lorentz, quadratic complex rational function model and hybrid dispersive model as well, which has higher accuracy and better stability than traditional center difference scheme. Finally, validity of the algorithm is verified by several examples.

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Mechanism of Acetylenic-Keton Intramolecular Cyclization Reaction Catalyzed by AuCl3 LI Anjun, ZHU Yuanqiang, SU Hong, YANG Zehong 2017, 34(6): 679-684.  Abstract ( )   HTML ( )   PDF (2518KB) ( )   Density functional theory with B3LYP functionals was used to study generating phenanthrene derivatives mechanism of acetylenic-keton intramolecular cyclization reaction catalyzed by AuCl3. It shows that the reaction can occur through [2+2] and [2+6] reaction pathways with and without AuCl3 catalyst. Without catalyst, energy barrier of rate determining step of [2+2] pathway is lower than that of [2+6] pathway by 32.01 kJ·mol-1. Reaction mainly occurs through [2+2] pathway. With AuCl3 catalyst, dominent reaction pathway is still [2+2] pathway with an energy barrier of rate determining step of 137.05 kJ·mol-1. Energy barrier of rate determining step of four-membered ring pathway with AuCl3 catalyst is 102.72 kJ·mol-1 lower than that of reaction without catalyst. This difference indicates that AuCl3 is an efficient catalyst which can raise reaction rate and moderate reaction condition.

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Study of Chemical Reactivity of Doped Carbon Nanotubes by Simple Hückel Molecular Orbital Calculations with Matlab Programming YANG Longfei, ZHANG Yexin, DU Shiyu 2017, 34(6): 685-696.  DOI: 10.19596/j.cnki.1001-246x.7546 Abstract ( )   HTML ( )   PDF (5257KB) ( )   A Matlab program was self-developed for simple Hückel molecular orbital calculations, with which carbon nanotubes of CNT(5,5) doped with vacancy, Stone-Wales defect, N and B atoms were analyzed. Calculated π-electron density and frontier molecular orbitals (HOMO and LUMO) provide a basis to study chemical reactivity of CNTs. Homogenous distributions of π-electron, HOMO and LUMO are broken by dopants with different electronic character. Furthermore, dopants and/or nearby carbon atoms contribute more in HOMO or LUMO, behaving nucleophile or electrophile in different reactions, respectively. Calculated HOMO-LUMO gaps reflect electrical conductivity of doped CNTs well. Calculated results are in agreement with experimental and theoretical results reported elsewhere.

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An Integrated High-throughput Computational Material Platform YANG Xiaoyu, WANG Juan, REN Jie, SONG Jianlong, WANG Zongguo, ZENG Zhi, ZHANG Xiaoli, HUANG Sunchao, ZHANG Ping, LIN Haiqing 2017, 34(6): 697-704.  Abstract ( )   HTML ( )   PDF (2633KB) ( )   The core philosophy of Material Genome Initiative is transition of way of new material design from traditional "try-and-error" approach to in-silico material design approach where intensive computing and material informatics are employed. It aims to effectively speed up discovery, development, production and deployment of new material two times faster as it is now. It means a culture shift of new material discovery:simulation and prediction first, followed by experiment. An integrated computational material platform that can facilitate high-throughput quantum mechanical simulations and manage simulation lifecycle data is therefore vital. This paper depicts a high throughput computational material platform and software framework, namely, MatCloud, which effectively integrates individual quantum mechanical simulation tasks, data extraction and data storage into an automatic flow in an end-to-end manner without direct human control. Especially, core data curation activities are also integrated into this flow rather than happening at post-simulation stage separately. MatCloud is demonstrated in an example of disorder binary alloy design to be valid and effective.

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First-Principles Study on Dehydrogenation Ability of MgH2 Hydrogen Storage Materials with Component Element Substitution MA Hongji, ZHANG Guoying, FANG Geliang 2017, 34(6): 705-712.  Abstract ( )   HTML ( )   PDF (3088KB) ( )   Pseudopotential plane-wave method based on density functional theory was used to study influences of metal elements substitution on dehydrogenation of MgH2. It shows that width of band gap and impurity energy levels are key factors. Impurity energy levels introduced by Fe, V, Nb, Ti are in the middle of energy gap, while those introduced by La are in the bottom of conduction band. Energy gap becomes narrower. The weakest Mg-H bond breaks easier, which is helpful to MgH2 dehydrogenation. Covalent bonds formed between Nb, Fe, Ti, V, La and neighboring hydrogen lead to metal hydrides formation, which plays a catalytic role to dehydrogenation of MgH2. Electrostatic forces between Mg1 and surround hydrogens are no longer symmetrical duo to doping. H with weaker force to Mg releases easier, which improves dehydrogenation properties of MgH2.

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Effects of Zinc Vacancies on Electronic Structure of Al-P Co-doped ZnO:First-principles Calculations LI Leilei, LI Weixue, DAI Jianfeng, WANG Qing 2017, 34(6): 713-721.  Abstract ( )   HTML ( )   PDF (4331KB) ( )   With pseudo-potential plane-wave based on density functional theory (DFT), effects of zinc vacancies on ZnO lattice parameters and electronic structure of Al-P co-doped were studied. Formation energy, density of states are analysed. It shows that AlZn-PZn has the lowest formation energy and presents n-type in the process of co-doping. Presence of zinc vacancies make cell volume decrease, and lattice constant c increase and decreases as concentration of zinc vacancies increase. According to formation energy of co-doping, formation of zinc vacancies system is more stable than AlZn-PO. System with Al and P ratio of 1:2 co-doping can reduce formation energy and become more stable. With comparisons of band structure of VZn and 2VZn, it is found that band gap increased with zinc vacancies increasing, which makes p-type ZnO more obvious and enhances conductivity of AlZn-2PZn co-doping systems. However, for AlZn-2PZn co-doping of 2VZn, it shows great superiority of p-type. According to state density analysis, AlZn-2PZn of 2VZn makes the state density more diffuse, and go through the Fermi level, which leads to formation of obvious p-type. As a result, better p-type ZnO can be obtained by controlling Al/P in proportion of 1:2 co-doing with zinc vacancy to 2VZn.

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Effect of Uniaxial Strain on Electronic Structure and Optical Properties of InN WEN Shumin, YAO Shiwei, ZHAO Chunwang, WANG Xijun, HOU Qingyu 2017, 34(6): 722-730.  DOI: 10.19596/j.cnki.1001-246x.7557 Abstract ( )   HTML ( )   PDF (5966KB) ( )   Effect of uniaxial strain on electronic structure and optical properties of zinc-blende structure of InN was investigated using first-principles based on density functional theory. It shows that both tensile and compressive strains make band gap of indium nitride decrease linearly. With increase of tensile strain, decrease amount of band gap increases; But with increase of compressive strain, decrease amount of band gap decreases. Between 4 eV and 12 eV, both tensile and compressive strains make absorption spectra of indium nitride red-shift. With increase of tensile strain, decrease amount of absorption spectra increases. But with increase of compressive strain, decrease amount of absorption spectra decreases. In same range of energy, refractive index and reflectivity of indium nitride increase with increase of tensile strain. But refractive index and reflectivity decrease with increase of compressive strain. As tensile strain is applied, peak value of energy loss increases. As compressive strain is applied, peak value of energy loss decreases. Electrical structure and optical properties of indium nitride can be controlled effectively by uniaxial strain.

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A Controllable Electrostatic Well for Cold Polar Molecules in Weak Field Seeking State on a Chip LI Shengqiang 2017, 34(6): 731-739.  DOI: 10.19596/j.cnki.1001-246x.7556 Abstract ( )   HTML ( )   PDF (3990KB) ( )   A novel electrostatic surface trap for cold polar molecules with an insulator-embedded charged ring and six charged spherical electrodes together with a bias electric field is proposed. Distributions of electric field in loading and trapping are calculated. Distance between trap center and chip surface are controlled conveniently with bias electric field and voltage applied to the ring electrode. For ND3 molecular beam centered at ~15 m·s-1, a loading efficiency as high as 70% is obtained. Corresponding temperature of trapped molecules is about 45 mK. As bias electric field is continued to increase, the single well splits into two identical ones. If voltages applied to spherical electrodes are changed in the meanwhile, two different wells are generated. Number ratio of molecules trapped in two wells can be adjusted. Dynamic processes of loading, trapping and splitting were simulated with classical Monte Carlo simulations.

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Lunar Geophysical Parameter Inversion with Admixed Particle Swarm Optimization ADPSO ZHONG Zhen 2017, 34(6): 740-746.  Abstract ( )   HTML ( )   PDF (2259KB) ( )   Ordinary particle swarm optimization PSO fails frequently in estimation of low sensitivity selenophysics parameters. With an adaptive inertia weight and a mutation factor, an admixed particle swarm optimization ADPSO is proposed. It is found that misfit is not reduced as increasing number of particles and probability of mutation. For four-parameter inversion, the best-fitting parameters can be estimated as considering about 400 particles and a low probability (<0.03) of mutation. With employment of gravity filed model GL0990d and altimeter data from LRO, we apply the method into selenophysical parameter inversion on southern highland of the moon. It shows a best-fit between modeled admittance spectral and observed values. Small residual of gravity anomaly verifies success of parameter inversion and validity of the method. The approach can be used in selenophysics research and could provide a reference for large-scale estimation of parameters.

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Coexisting Attractors and Hopf Bifurcation in Floating Memristors Based Chaotic Circuit WANG Wei, ZENG Yicheng, CHEN Zheng, SUN Ruiting 2017, 34(6): 747-756.  DOI: 10.19596/j.cnki.1001-246x.7563 Abstract ( )   HTML ( )   PDF (6135KB) ( )   We propose a novel floating memristor chaotic circuit with serial connection between a charge-controlled memristor and an inductor.Basic dynamic properties of the system are investigated with conventional dynamic analysis method. It shows that the system produces a pair of "heart" type attractors about origin symmetry. Simulation results indicate that strange attractors like bow tie type are observed as voltage and electricity signal in observing chaotic attractors are generalized to power and energy signal. Hopf bifurcation behavior is analyzed and verified by numerical simulation. It shows that the system can produce two bifurcation behaviors by adjusting parameters. They are Hopf bifurcation and anti-period doubling bifurcation. Remarkable feature of the citcuit is that it adopts a floating memristor, and with different initial state it generates nonlinear phenomena including coexisting chaotic and coexisting chaotic-periodic attractors.