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| 1 | Fuzzy interface treatment in Eulerian method显示文摘In this paper, we incorporate fuzzy mathematics approach into the Eulerian method to simulate three dimensional multi-material interfaces. In particular, we propose a fuzzy interface treatment for describing interfaces, designing transport plans, and computing transport quantities. Using a set of three-dimensional inviscid isothermal elastic-plastic hydrodynamic equations, we simulate shaped charge jet in different filled dynamite structures. Strain and stress have been under consideration in simulations. Numerical results demonstrate that the fuzzy interface treatment is correct and efficient for three-dimensional multi-material problems. | NING Jianguo1 & CHEN Longwei1,2 1. National Key Laboratory of Protection and Control of Explosive Disaster, Beijing Institute of Technology, Beijing 100081, China 2. The Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming 650093, China Correspondence should be addressed to Ning Jianguo | 2004 | Science China(Technological Sciences)2004，47，5： | 40 |
| 2 | Improvement of tree-like network constructal method for heat conduction optimization显示文摘The analysis of the “tree-like network” construct method has been repeated. The high effective conduction channel distribution has been optimized again, without the premise that the new order assembly construct must be assembled by the optimized last order construct. It is proved that the “tree-like network” construct method is faultiness. A more optimal construct is obtained, and when the thermal conductivity and the proportion of the two heat conduction materials are constant, the limit of the minimum heat resistance is derived. All these conclusions can be used to guide the engineering application. | WU Wenjun CHEN Lingen SUN Fengrui | 2006 | Science China(Technological Sciences)2006，49，3： | 25 |
| 3 | Concatenating construction of the multisymplectic schemes for 2+1-dimensional sine-Gordon equation显示文摘In this paper, taking the 2+1-dimensional sine-Gordon equation as an example, we present the concatenating method to construct the multisymplectic schemes. The method is to discretizee independently the PDEs in different directions with symplectic schemes, so that the multisymplectic schemes can be constructed by concatenating those symplectic schemes. By this method, we can construct multisymplectic schemes, including some widely used schemes with an accuracy of any order. The numerical simulation on the collisions of solitons are also proposed to illustrate the efficiency of the multisymplectic schemes. | WANG Yushun, WANG Bin & QIN MengzhaoLASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China School of Mathematics and Computer Science, Nanjing Normal University, Nanjing 210097, China School of Mathematics and System Science, Chinese Academy of Sciences, Beijing 100080, China | 2004 | Science China Mathematics2004，47，1： | 17 |
| 4 | A complex variable meshless method for fracture problems显示文摘Based on the moving least-square (MLS) approximation, the complex variable moving least-square approximation (CVMLS) is discussed in this paper. The complex variable moving least-square approximation cannot form ill-conditioned equations, and has greater precision and computational efficiency. Using the analytical solution near the tip of a crack, the trial functions in the complex variable moving least-square approxi- mation are extended, and the corresponding approximation function is obtained. And from the minimum potential energy principle, a complex variable meshless method for fracture problems is presented, and the formulae of the complex variable meshless method are obtained. The complex variable meshless method in this paper has greater precision and computational efficiency than the conventional meshless method. Some examples are given. | CHENG Yumin1 & LI Jiuhong2 1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072, China 2. Department of Building Engineering, Xi’an University of Technology, Xi’an 710048, China | 2006 | Science China(Physics,Mechanics & Astronomy)2006，49，1： | 15 |
| 5 | Geometrically constrained isogeometric parameterizedlevel-set based topology optimization via trimmed elements显示文摘In this paper, an approach based on the fastpoint-in-polygon (PIP) algorithm and trimmed elements isproposed for isogeometric topology optimization (TO)with arbitrary geometric constraints. The isogeometricparameterized level-set-based TO method, which directlyuses the non-uniform rational basis splines (NURBS) forboth level set function (LSF) parameterization andobjective function calculation, provides higher accuracyand efficiency than previous methods. The integration oftrimmed elements is completed by the efficient quadraturerole that can design the quadrature points and weights forarbitrary geometric shape. Numerical examples demon-strate the efficiency and flexibility of the method. | Yingjun WANG David J. BENSON | 2016 | Frontiers of Mechanical Engineering2016，11，4： | 13 |
| 6 | A transient energy function for power systems including the induction motor model显示文摘A construction method for power system transient energy function is studied in the paper, which is simple and universal, and can unify the forms of some current en- ergy functions. A transient energy function including the induction motor model is derived using the method. The unintegrable term is dealt with to get an approxi- mate energy function. Simulations in a 3-bus system and in the WSCC 4-generator system verify the validity of the proposed energy function. The function can be applied to direct transient stability analysis of multi-machine large power systems and provides a tool for analysis of the interaction between the generator angle stability and the load voltage stability. | MIN Yong CHEN Lei | 2007 | Science China(Technological Sciences)2007，50，5： | 12 |
| 7 | An unconstrained optimization method using nonmonotone second order Goldstein's line search显示文摘In this paper, an unconstrained optimization method using the nonmonotone second order Goldstein's line search is proposed. By using the negative curvature information from the Hessian,the sequence generated is shown to converge to a stationary point with the second order optimality conditions. Numerical tests on a set of standard test problems confirm the efficiency of our new method. | Wen-yu SUN~(1+) Qun-yan ZHOU~(1,2) ~1 School of Mathematics and Computer Science,Nanjing Normal University,Nanjing 210097,China ~2 Department of Basic Courses,Jiangsu Teachers University of Technology,Changzhou 213001,China | 2007 | Science China Mathematics2007，50，10： | 12 |
| 8 | Two-scale analysis method for predicting heat transfer performance of composite materials with random grain distribution显示文摘A two-scale analysis (TSA) method for predicting the heat transfer performance of composite materials with the random distribution of same-scale grains is presented. First the representation of the materials with the random distribution is briefly described. Then the two-scale analysis formulation of heat transfer behavior of the materials with random grain distribution of small periodicity is formally derived by means of construction way for each cell. Finally the numerical result on the heat transfer parameters of composite materials is shown. The numerical result shows that TSA is effective to predict the heat transfer performance of composite materials with random grain distribution. | LI Youyun CUI Junzhi | 2004 | Science China Mathematics2004，47，z1： | 12 |
| 9 | Boundary element-free method for elastodynamics显示文摘The moving least-square approximation is discussed first. Sometimes the method can form an ill-conditioned equation system, and thus the solution cannot be obtained correctly. A Hilbert space is presented on which an orthogonal function system mixed a weight function is defined. Next the improved moving least-square approximation is discussed in detail. The improved method has higher computational efficiency and precision than the old method, and cannot form an ill-conditioned equation system. A boundary element-free method (BEFM) for elastodynamics problems is presented by combining the boundary integral equation method for elastodynamics and the improved moving least-square approximation. The boundary element-free method is a meshless method of boundary integral equation and is a direct numerical method compared with others, in which the basic unknowns are the real solutions of the nodal variables and the boundary conditions can be applied easily. The boundary element-free method has a higher computational efficiency and precision. In addition, the numerical procedure of the boundary element-free method for elastodynamics problems is presented in this paper. Finally, some numerical examples are given. | CHENG Yumin1 & PENG Miaojuan2 1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072, China 2. Department of Civil Engineering, Shanghai University, Shanghai 200072, China | 2005 | Science China(Physics,Mechanics & Astronomy)2005，48，6： | 12 |
| 10 | Accurate studies on dissociation energies of diatomic molecules显示文摘The molecular dissociation energies of some electronic states of hydride and N2 molecules were studied using a parameter-free analytical formula suggested in this study and the algebraic method (AM) proposed recently. The results show that the accurate AM dissociation energies DeAM agree excellently with experimental dissociation energies Deexpt, and that the dissociation energy of an electronic state such as the 23Δg state of 7Li2 whose experimental value is not available can be predicted using the new formula. | SUN WeiGuo1, FAN QunChao1 & REN WeiYi1,2 1 Institute of Physics, Sichuan University, Chengdu 610065, China 2 Institute of Theoretical Physics, Xihua Normal University, Nanchong 637002, China | 2007 | Science China(Physics,Mechanics & Astronomy)2007，50，5： | 10 |
| 11 | An adaptive trust region method and its convergence显示文摘In this paper, a new trust region subproblem is proposed. The trust radius in the new subproblem adjusts itself adaptively. As a result, an adaptive trust region method is constructed based on the new trust region subproblem. The local and global convergence results of the adaptive trust region method are proved.Numerical results indicate that the new method is very efficient. | 章祥荪 张菊亮 廖立志 | 2002 | Science China Mathematics2002，45，5： | 9 |
| 12 | The upwind finite difference fractional steps method for combinatorial system of dynamics of fluids in porous media and its application显示文摘For combinatorial system of multilayer dynamics of fluids in porous media, the second order and first order upwind finite difference fractional steps schemes applicable to parallel arithmetic are put forward and two-dimensional and three-dimensional schemes are used to form a complete set. Some techniques,such as implicit-explicit difference scheme, calculus of variations, multiplicative commutation rule of difference operators, decomposition of high order difference operators and prior estimates, are adopted. Optimal order estimates in L2 norm are derived to determine the error in the second order approximate solution. This method has already been applied to the numerical simulation of migration-accumulation of oil resources. | 袁益让 | 2002 | Science China Mathematics2002，45，5： | 9 |
| 13 | Eddy flux corrections for CO_2 exchange in broad-leaved Korean pine mixed forest of Changbai Mountains显示文摘Based on analysis of mechanisms causing energy no-closure and nocturnal low fluxes issues for CO2 exchange studies by eddy covariance method, corrections were done with the raw data sets obtained from Changbai Mountains forest flux site, to evaluate the impacts of sonic anemometer tilt, frequency response limitations and advection on estimation of CO2 exchange, respectively. The results show that the planar fit coordinate transforming method is superior to the streamline coordinate transforming method in tilt correction. The latter could cause a systematical underestimation of eddy fluxes relating with the angle of sensor and terrain tilt. The underestimation of CO2 and energy fluxes for frequency response limitations average 3.0% and 2.0% during daytime, respectively, which increase by 9.0% and 5.5% during nighttime, respectively. The corrections of frequency response limitations are closely related to atmospheric stability. The advection loss of CO2 fluxes is dominated by nocturnal vertical advection, which is at least 18% when the horizontal advection is neglected. It is suggested that more work be done to understand the characteristics of horizontal advection and turbulent eddies under a complexcircumstance. | WU Jiabing, GUAN Dexin, SUN Xiaomin, YU Guirui, ZHAO Xiaosong, HAN Shijie & JIN Changjie Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China Graduate school of the Chinese Academy of Sciences, Beijing 100093, China Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China | 2005 | Science China Earth Sciences2005，48，z1： | 8 |
| 14 | Response simulation and theoretical calibration of a dual- induction resistivity LWD tool显示文摘In this paper, responses of a new dual-induction resistivity logging-while-drilling (LWD) tool in 3D inhomogeneous formation models are simulated by the vectorfinite element method (VFEM), the influences of the borehole, invaded zone, surroundingstrata, and tool eccentricity are analyzed, and calibration loop parameters and calibrationcoefficients of the LWD tool are discussed. The results show that the tool has a greater depthof investigation than that of the existing electromagnetic propagation LWD tools and is moresensitive to azimuthal conductivity. Both deep and medium induction responses have linearrelationships with the formation conductivity, considering optimal calibration loop parametersand calibration coefficients. Due to the different depths of investigation and resolution, deepinduction and medium induction are affected differently by the formation model parameters,thereby having different correction factors. The simulation results can provide theoreticalreferences for the research and interpretation of the dual-induction resistivity LWD tools. | 许巍 柯式镇 李安宗 陈鹏 朱军 张维 | 2014 | Applied Geophysics2014，11，1： | 8 |
| 15 | New direction of computational fluid dynamics and its applications in industry显示文摘For the past ten years there has been much progress in computational fluid dy- namics (CFD), among which the formation and development of the lattice Boltz- mann method (LBM) are an important new direction. We give a review on the main aspect and the latest development of this method in this article, and at the same time we also discuss the related development of scientific software and its impact on the real-world applications in industry. | CHEN YaoSong1, SHAN XiaoWen2 & CHEN HuDong2 1 Department of Mechanics, Peking University, Beijing 100871, China 2 Exa Corporation, Burlington, MA 01803 USA | 2007 | Science China(Technological Sciences)2007，50，5： | 8 |
| 16 | Convergence rates to nonlinear diffusion waves for weak entropy solutions to p-system with damping显示文摘This paper studies the asymptotic behavior ofweak entropy solutions to the Cauchy problem of the so-called p-system with damping. The convergence rates to nonlinear diffusion waves for weak entropy solutions are obtained in L∞-norm or L2-norm. These convergence rates are the same to the decay rates of smooth solution obtained by Nishihara. They are proved by using the vanishing viscosity method and the elementary L2-energy method. | 朱长江 | 2003 | Science China Mathematics2003，46，4： | 8 |
| 17 | Monotone method for initial value problem for fractional diffusion equation显示文摘Using the method of upper and lower solutions and its associated monotone iterative, consider the existence and uniqueness of solution of an initial value problem for the nonlinear fractional diffusion equation. | ZHANG Shuqin | 2006 | Science China Mathematics2006，49，9： | 7 |
| 18 | Stochastic modelling of soil moisture dynamics in a grassland of Qilian Mountain at point scale显示文摘Stochastic modeling of soil moisture dynamics is crucial to the quantitative understanding of plant responses to water stresses,hydrological control of nutrient cycling processes,water competition among plants,and some other ecological dynamics,and thus has become a hotspot in ecohydrology at present.In this paper,we based on the continuously monitored data of soil moisture during 2002―2005 and daily precipitation date of 1992―2006,and tried to make a probabilistic analysis of soil moisture dynamics at point scale in a grassland of Qilian Mountain by integrating the stochastic model improved by Laio and the Monte Carlo method.The results show that the inter-annual variations for the soil moisture patterns at different depths are very significant,and that the coefficient of variance(CV) of surface soil moisture(20 cm) is almost continually kept at about 0.23 whether in the rich or poor rainy years.Interestingly,it has been found that the maximal CV of soil moisture has not always appeared at the surface layer.Comparison of the analytically derived soil moisture probability density function(PDF) with the statistical distribution of the observed soil moisture data suggests that the stochastic model can reasonably describe and predict the soil moisture dynamics of the grassland in Qilian Mountain at point scale.By extracting the statistical information of the historical precipitation data in 1994―2006,and inputting them into the stochastic model,we analytically derived the long-term soil moisture PDF without considering the inter-annual climate fluctuations,and then numerically derived the one when considering the inter-annual fluctuation effects in combination with a Monte-Carlo procedure.It was found that,though the peak position of the probability density distribution significantly moved towards drought when considering the disturbance forces,and its width was narrowed,accordingly its peak value was increased,no significant bimodality was observed in the soil moisture dynamics under the given intensity of random fluctuation disturbance. | LIU Hu,ZHAO WenZhi HE ZhiBin & ZHANG LiJie Linze Inland River Basin Research Station,Chinese Ecosystem Research Network Laboratory of Watershed Hydrology and Ecol-ogy,Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences,Lanzhou 730000,China | 2007 | Science China Earth Sciences2007，50，12： | 7 |
| 19 | Large range step method for acoustic waveguide with two layer media显示文摘A numerical method is developed for solving the two-dimensional Helmholtz equation in a two-layer region bounded by a flat top, a flat bottom and a curved interface. A better local orthogonal transformation is used to flatten the curved interface of the waveguide. The one-way re-formulation based on the Dirichlet-to-Neumann (DtN) map is then used to reduce the boundary value problem to an initial value problem. Numerical implemetation of the resulting operator Riccati equation uses a large range step method for discretizing the range variable and a truncated local eigenfunction expansion for approximating the operators. This method is particularly useful for solving long range wave propagation problems in slowly varying waveguides. | ZHU Jianxin and LU Yayan(1. Department of Mathematics, Zhejiang University, Hangzhou 310027, China 2. Department of Mathematics, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China) | 2002 | Progress in Natural Science:Materials International2002，12，11： | 7 |
| 20 | Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation显示文摘The gas-kinetic unified algorithm using Boltzmann model equation have been extended and developed to solve the micro-scale gas flows in Poiseuille-like micro-channels from Micro-Electro-Mechanical Systems (MEMS). The numerical modeling of the gas kinetic boundary conditions suitable for micro-scale gas flows is presented. To test the present method, the classical Couette flows with various Knudsen numbers, the gas flows from short microchannels like plane Poiseuille and the pressure-driven gas flows in two-dimensional short microchannels have been simulated and compared with the approximate solutions of the Boltzmann equation, the related DSMC results, the modified N-S solutions with slip-flow boundary theory, the gas-kinetic BGK-Burnett solutions and the experimental data. The comparisons show that the present gas-kinetic numerical algorithm using the mesoscopic Boltzmann simplified velocity distribution function equation can effectively simulate and reveal the gas flows in microchannels. The numerical experience indicates that this method may be a powerful tool in the numerical simulation of micro-scale gas flows from MEMS. | LI Zhihui1,2, ZHANG Hanxin1 & FU Song2 ⒈ National Laboratory for CFD, Hypervelocity Aerodynamics Institute,China Aerodynamics Research and Development Center,Mianyang 621000,China 2.Department of Engineering Mechanics,Tsinghua University,Beijing 100084,China | 2005 | Science China(Physics,Mechanics & Astronomy)2005，48，4： | 6 |
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