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25 September 2014, Volume 31 Issue 5 Previous Issue    Next Issue

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Transport Synthetic Acceleration Methods for Multi-group Radiative Transfer Calculations LI Shuanggui, YANG Rong, HANG Xudeng 2014, 31(5): 505-513.  Abstract ( )   PDF (1837KB) ( )   Convergence of source iteration is analyzed for multi-group radiative transfer calculations. A two-level nesting transport acceleration method is developed. Numerical results show speedup factors of the scheme are higher than that of GTA method. The scheme is feasible for non-rectangle grid calculations of 2D problems with large discontinuities of material properties.

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Low-pass Filter Boundary Condition for Atomic-based Finite Element Method REN Guowu, TANG Tiegang, LI Qingzhong 2014, 31(5): 514-522.  Abstract ( )   PDF (2181KB) ( )   An atomic-based finite element method is developed,spanning from atomic scale to macroscopic one. With theoretical deduction dispersion relation and dynamic scattering behavior are calculated. For spurious reflection caused by non-uniform grid,lowpass filter boundary condition is designed to effectively eliminate the reflection of high-frequency phonons,while keeping low-frequency ones transparent. These schemes are demonstrated with numerically calculating reflection and transmission coefficients in onedimensional modeling.

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DEM Study on Hot Spots Formation of Heterogeneous Explosives Under Shock Loading LIU Chao, SHI Yina, LIANG Xianhong 2014, 31(5): 523-530.  Abstract ( )   PDF (6920KB) ( )   Mesoscale responses of plastic boned explosives (PBX) and grannular HMX under shock loading were investigated with discrete element method(DEM). It shows that for shocked grannular HMX temperature and pressure in grain boundary are much higher than those of inner HMX crystals. In the case of shocked PBX high temperature and pressure regions are mostly located in binder and near parts. Comparisons show that temperature and pressure in grain boundary are effectively reduced by binder.

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Numerical Study of Thermochemical Nonequilibrium Nozzle Flow in State-to-State Model XU Dan, ZENG Ming, ZHANG Wei, LIU Jun 2014, 31(5): 531-538.  Abstract ( )   PDF (2685KB) ( )   A state-to-state model is used to simulate thermochemical nonequilibrium nozzle flow of N2/N mixture. Quasi-onedimensional nozzle flow at reservoir temperature from 3 000 K to 8 000 K and pressure from 1 atm to 10 atm is simulated numerically to obtain flow properties,especially detail vibrational population distribution. Evolution of macro- and micro-properties of nonequilbrium flow during expanding is analyzed. Rationality of two-temperature or multi-temperature approach is investigated for recombination dominating flows.

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High Resolution Entropy Consistent Schemes for Hyperbolic Conservation Laws REN Jiong, FENG Jianhu, LIU Youqiong, LIANG Nan 2014, 31(5): 539-551.  Abstract ( )   PDF (3147KB) ( )   To improve accuracy of entropy consistent schemes,we proposed high resolution entropy consistent schemes by inserting a new flux limiter into entropy consistent schemes. It uses limiter mechanism to construct high resolution schemes. In constructing high resolution entropy consistent schemes of Euler equations,we improve resolution of contact discontinuity by adjusting parameters of corresponding entropy consistent schemes. Several numerical experiments illustrate robustness and essentially non-oscillations of the schemes.

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Numerical Simulation of Nonlinear Flow in Heterogeneous and Low-permeability Reservoirs YAO Jun, HUANG Tao, HUANG Zhaoqin 2014, 31(5): 552-558.  Abstract ( )   PDF (3141KB) ( )   A numerical method is developed to model nonlinear flow in heterogeneous and low-permeability reservoirs. In order to obtain pressure gradient of each gridcells precisely,we introduced two sets of physical quantities,cell face pressures and surface efflux for each gridcell. Principle of the method is elaborated based on single-phase fluid flow problem. Several numerical examples are presented to demonstrate efficiency and applicability of the scheme.

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A Coupling Flow Model of Finite-conductivity Fractured Directional Well JIA Pin, CHENG Linsong, HUANG Shijun, FANG Sidong 2014, 31(5): 559-566.  Abstract ( )   PDF (2146KB) ( )   Considering artificial fracture,inclined wellbore and formation coupling flow,flow to directional well is divided into three parts： Flow from reservoir to fracture,flow in fracutre and variable mass flow in production pipe. Principles of potential superposition and mirror reflection as well as the concept of infinitesimal line congruence are used to model flow from reservoir to fracture and potential distribution in reservoir. By discreting fracuture to 2D grid,boundary theory is used to couple flow dynamics in fracture with variable mass flow in inclined pipe. A comprehensive coupling model for finite-conductivity fractured directional well is shown.Iteration method is used to solve the model. A practical case shows that for vertical fracutre result of coupling model agrees with that of Prats method. Fracture conductivity and inclined angle have great effects on productivity and pressure.

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Monte Carlo Calculation of Stable Productivity of Fractured Directional Wells in Natural Fracture Reservoirs ZHANG Jin, HUANG Shijun, CHENG Linsong 2014, 31(5): 567-572.  Abstract ( )   PDF (3034KB) ( )   We focus on anisotropic reservoir with natural fractures,and simulate distribution of natural fracture with Monte Carlo. It characterizes natural fracture parameters from the perspective of statistics. Coupled natural and artificial fractures are considered as independent sources. A formula of steady production is derived according to potential superposition principle. It shows that Monte Carlo simulations of natural fractures reflect trends of productivity from a statistical point of view. It analyzes quickly steady productivity of fractured directional well.

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A Calculation Method for Temperature and Pressure Distribution in Water Production Gas Wellbores LI Bo, NING Bo, SU Haiyang, LIU Hong, WEI Yunsheng 2014, 31(5): 573-580.  Abstract ( )   PDF (1231KB) ( )   Based on drift model which copes with gas-liquid phase slippage and non-uniform distribution along section of wellbore,a coupled temperature-pressure prediction model was established for varied angle gas wellbores considering momentum conservation,conservation of energy and wellbore heat transmission. The model was validated with 15 tested gas wells. The calculation showed satisfying results with average absolute error of 3. 6% which meets engineering requirements.

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Numerical Study of an 8×8 Optical Cross Connector Based on CDT and Self-trapping LI Liping, WANG Bo, TANG Hailing, LUO Xiaobing 2014, 31(5): 581-586.  Abstract ( )   PDF (2367KB) ( )   Based on a method combining coherent destruction of tunneling( CDT) theory and self-trapping effect,a scheme realized all-optical transform. In scalar field and paraxial approximation,and by using tight binding approximation,we derived coupled mode equations of optical signal propagation in periodic modulated optical fibers. Considering coupling effect of adjacent fibers,we realized all-optical transform function numerically and conditions required were obtained. With introduction of tunable filter at output side,broadcast transmitting,optical transformation and drop/on functions are realized with an 8×8 optical cross connector,which can be extended to N×N optical cross connector. It can be used to solve problems of signals delay and capacity requirements in WDM optical networks.

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Simulation on 2-2 Type PMNT/NFO Composite Magnetoelectric Effect YANG Huanyin, FAN Dongmei, GUO Hongli 2014, 31(5): 587-592.  Abstract ( )   PDF (1709KB) ( )   In an elastic mechanics model,a magnetoelectric composites constitutive equation was established. Longitudinal and transverse ME voltage coefficient formulas of double-layer and three-layer composited thin films of 2-2 type in non-ideal condition were deduced with ferroelectric and magnetic constitutive equation. Composite ME voltage coefficient of ferromagnetic phase material nickel ferrite (NFO) and ferroelectric phase material lead magnesium niobate-lead titanate (PMNT) are studied. Relations between ME voltage coefficient and PMNT volume fraction,interface coupling parameters,two phase volume ratio and total number of layers are analyzed. It shows that performance of two phase material,appropriate volume fraction,coupling coefficient and total layer number are key to ME voltage coefficient.

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A Comparative Study on Dispersions of Rectangle-shaped Microshield Lines Loaded with Right-handed Materials and Left-handed Materials SUN Hai 2014, 31(5): 593-601.  Abstract ( )   PDF (2854KB) ( )   Edge-based finite element method is introduced to study dispersions of six types of rectangle-shaped microshield lines loaded with right-handed materials and left-handed materials. They are rectangle-shaped microshield lines with symmetrical single signal line,with asymmetrical single signal line,with symmetrical dual signal lines,with asymmetrical dual signal lines of position,with asymmetrical dual signal lines of width and with asymmetrical dual signal lines of height. Dispersions of microshield lines with changed dielectric constant of dielectric substrate are discussed. Numerical results are helpful in design of microwave components that use rectangle-shaped microshield lines and left-handed materials.

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Collision Dynamics of Hydroxyl and Proton at 15eV ZHU Yun, ZHANG Xiumei, WANG Zhiping 2014, 31(5): 602-608.  Abstract ( )   PDF (1877KB) ( )   Under the frame of time-dependent density functional theory( TDDFT) and molecular dynamics,we studied microscopic electronic-ionic association dynamics in collision between hydroxyl and proton which moves toward molecular axis of hydroxyl with 15 eV initial kinetic energy. Energies of projectile and target,electron and vibration excitations of target and real time distribution of electron density are identified. It is found that proton captures electrons of hydroxyl in collision and it rebounds from the target with loss of 26.7% of initial kinetic energy. While the kinetic energy of hydroxyl increases and hydroxyl moves toward to numerical boundary accompanied with stretch oscillation. Hydroxyl loses 1% electrons and exists as neutral and ＋1 valence forms with 93% and 7%probabilities respectively.

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Computational and Experimental Study on Mechanical Behavior of V-Ta Alloys CHEN Jinfan, LUO Chao, AO Bingyun, PENG Lixia, SHI Jie 2014, 31(5): 609-616.  Abstract ( )   PDF (1401KB) ( )   First-principles calculations on mechanical behavior of V-Ta( Ta=0 to~20 wt. %) alloys are performed. Calculated Young's modulus,shear modulus,Cauchy pressure and bulk modulus/shear modulus indicate that as content of Ta is around 10 wt. %,V-Ta alloy shows good mechanical properties with large strength and good ductility. To examine calculation predictions,binary V-Ta alloys including V-10 wt. % Ta,V-15 wt. % Ta,V-20 wt. % Ta were processed and tested at room temperature. Computational results agree with experiment well. It indicates that the approach is a promising way for alloy design.

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First-principles Study of Optical and Electronic Properties of Ag Doped AlN Semiconductors DENG Junquan, WU Zhimin, WANG Ailing, ZHAO Ruoyu, HU Aiyuan 2014, 31(5): 617-624.  Abstract ( )   PDF (2195KB) ( )   Geometrical structure of Ag doped 32-atom super-cell of AlN was optimized with first principle density functional theory based on full potential linearized augumented plane wave method. Electronic structures,magnetic and optical properties were calculated and discussed in detail. It shows that Ag doping makes Ag4 d electrons hybrid with its nearest neighbor N2 p electrons,which introduces impurity bands to form acceptor energy level and realizes p-type doping. The system enhances its conductivity and shows metallic and weak magnetism. Its net magnetic moment is 1.38 μв. Mulliken charge population of N-Ag bonds through Ag doping is small and bonds show strong ionic bonding properties. Imaginary part of dielectric function and optical absorption spectrum of the doping system show a new peak in low energy region. Complex refractive index function changes in low energy region. And absorption edge extends to low energy. Doping system enhances long-wave absorption and energy loss decreases obviously.

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Simulation on Control of Spiral Wave by Two-stage Pulse Force YANG Cuiyun, LIU Haiying, TANG Guoning 2014, 31(5): 625-630.  Abstract ( )   PDF (1809KB) ( )   Modified Bär model is used to study suppression of spiral wave. Methods of suppressing spiral wave by two-stage pulse force control are proposed. In the first stage,fast variable of the model is acted by a positive rectangular pulse force. In the second stage,direction of force is changed to the opposite or the force is acted on the slow variable. It shows that two-stage pulse control method is more efficient than one-stage method,and magnitude of the force is 38%~55% of the latter. It suggests that two-stage method of control of spiral wave can improve defibrillation efficiency.