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| 1 | Entransy dissipation minimization for liquid-solid phase change processes显示文摘The liquid-solid phase change process of a simple one-dimensional slab is studied in this paper.By taking entransy dissipation minimization as optimization objective,the optimal external reservoir temperature profiles are derived by using optimal control theory under the condition of a fixed freezing or melting time.The entransy dissipation corresponding to the optimal heat exchange strategies of minimum entransy dissipation is 8/9 of that corresponding to constant reservoir temperature operations,which is independent of all system parameters.The obtained results for entransy dissipation minimization are also compared with those obtained for the optimal heat exchange strategies of minimum entropy generation and constant reservoir temperature operations by numerical examples.The obtained results can provide some theoretical guidelines for the choice of optimal cooling or heating strategy in practical liquid-solid phase change processes. | XIA ShaoJun,CHEN LinGen & SUN FengRui Postgraduate School,Naval University of Engineering,Wuhan 430033,China | 2010 | Science China(Technological Sciences)2010，53，4： | 41 |
| 2 | Numerical simulation of mechanisms of deformation,failure and energy dissipation in porous rock media subjected to wave stresses显示文摘The pore characteristics,mineral compositions,physical and mechanical properties of the subarkose sandstones were acquired by means of CT scan,X-ray diffraction and physical tests.A few physical models possessing the same pore characteristics and matrix properties but different porosities compared to the natural sandstones were developed.The 3D finite element models of the rock media with varied porosities were established based on the CT image processing of the physical models and the MIMICS software platform.The failure processes of the porous rock media loaded by the split Hopkinson pressure bar(SHPB) were simulated by satisfying the elastic wave propagation theory.The dynamic responses,stress transition,deformation and failure mechanisms of the porous rock media subjected to the wave stresses were analyzed.It is shown that an explicit and quantitative analysis of the stress,strain and deformation and failure mechanisms of porous rocks under the wave stresses can be achieved by using the developed 3D finite element models.With applied wave stresses of certain amplitude and velocity,no evident pore deformation was observed for the rock media with a porosity less than 15%.The deformation is dominantly the combination of microplasticity(shear strain),cracking(tensile strain) of matrix and coalescence of the cracked regions around pores.Shear stresses lead to microplasticity,while tensile stresses result in cracking of the matrix.Cracking and coalescence of the matrix elements in the neighborhood of pores resulted from the high transverse tensile stress or tensile strain which exceeded the threshold values.The simulation results of stress wave propagation,deformation and failure mechanisms and energy dissipation in porous rock media were in good agreement with the physical tests.The present study provides a reference for analyzing the intrinsic mechanisms of the complex dynamic response,stress transit mode,deformation and failure mechanisms and the disaster mechanisms of rock media. | JU Yang1,2,WANG HuiJie1,YANG YongMing1,HU QinAng3 & PENG RuiDong1 1 State Key Laboratory of Coal Resources and Safe Mining,Beijing Key Laboratory of Fracture and Damage Mechanics of Rock and Concrete,China University of Mining and Technology,Beijing 100083,China 2 Department of Mechanical and Manufacturing Engineering,University of Calgary,Calgary,Alberta,T2N 1N4,Canada 3 School of Environment and Civil Engineering,College of Engineering,Oklahoma State University,Stillwater,OK 74078,USA | 2010 | Science China(Technological Sciences)2010，53，4： | 32 |
| 3 | Numerical modeling of concrete hydraulic fracturing with extended finite element method显示文摘The extended finite element method (XFEM) is a new numerical method for modeling discontinuity. Research about numerical modeling for concrete hydraulic fracturing by XFEM is explored. By building the virtual work principle of the fracture problem considering water pressure on the crack surface, the governing equations of XFEM for hydraulic fracture modeling are derived. Implementation of the XFEM for hydraulic fracturing is presented. Finally, the method is verified by two examples and the advan- tages of the XFEM for hydraulic fracturing analysis are displayed. | REN QingWen DONG YuWen YU TianTang | 2009 | Science China(Technological Sciences)2009，52，3： | 29 |
| 4 | Development of Finite Element Limiting Analysis Method and Its Applications in Geotechnical Engineering显示文摘The Finite Element Limiting Analysis Method(LELAM) has the advantage of combining a numerical analysis method with traditional limiting equilibrium methods.It is particularly applicable to the analysis and design of geotechnical engineering.In the early 20th century,FELAM has been developed vigorously in domestic geotechnical engineering over international common finite element procedures.It has made great achievements in basic theory research and computational precision,thus broadening the application fields in practical projects.In order to gradually make innovations in geotechnical design methods,some of our research results are presented,mainly including geotechnical safety factor definitions,the principles for use of the method concerned,the overall failure criterion,the deduction and selection of the yield criterion,and the measurement to improve the computational precision,etc..The application field has been broadened from two-dimensional to three-dimensional,from soil slope to jointed rock slope and foundation,from stable seepage to non-stable seepage,from slope and foundation to tunnel.This method has also been used in search of many hidden sliding surfaces of complex landslides,conducting the structural support design considering the interaction between the soil and the structure,and computing simulation foundation bearing plates load tests,etc.. | Zheng Yingren1,Deng Chujian1,Zhao Shangyi1,Tang Xiangsong1,Liu Mingwei1,Zhang Liming2(1 Department of Civil Engineering,Logistical Engineering University,Chongqing 400041,China 2 Department of Science and Information Engineering,Qingdao Technological University,Qingdao 266033,China) | 2007 | 工程科学(英文版)2007，5，3： | 27 |
| 5 | 深度包检测中一种高效的正则表达式压缩算法显示文摘提出一种基于确定的有穷状态自动机(deterministic finite automaton,简称DFA)的正则表达式压缩算法.首先,定义了膨胀率DR(distending rate)来描述正则表达式的膨胀特性.然后基于DR提出一种分片的算法RECCADR(regular expressions cut and combine algorithm based on DR),有效地选择出导致DFA状态膨胀的片段并隔离,降低了单个正则表达式存储需求.同时,基于正则表达式的组合关系提出一种选择性分群算法REGADR(regular expressions group algorithm based on DR),在可以接受的存储需求总量下,通过选择性分群大幅度减少了状态机的个数,有效地降低了匹配算法的复杂性. | 徐乾 鄂跃鹏 葛敬国 钱华林 | 2009 | 软件学报2009，20，8： | 28 |
| 6 | Numerical analysis of application for induction caving roof显示文摘New method for handling roof of the base successive mining is proposed, which is induction caving in the roof. The key is that it is made certain to the station of the space-time in the induction caving roof, as the stress is released with the mining process. And applying the catastrophe theory, the influencing factors of induction caving roof are studied in the emptied areas, such as the mechanical property of the surrounding rock, the area of the gob,the scope and dimension of tensile stress. The results show that the key factor is the area of the gob to the method of the induction caving roof. Then according to the geology and the ore characteristic, the three dimension FEM mechanical model is built in Tongkeng Mine, the laws of the tensile stress are analyzed to the space and the time in the roof with the mining, then it is rational design to the mine step and time of the handing the roof. | HU Jian-hua ZHOU Ke-ping LI Xi-bing YANG Nian-ge SU Jia-hong | 2005 | Journal of Central South University of Technology2005，12，z1： | 22 |
| 7 | Optimal configuration for a finite high-temperature source heat engine cycle with the complex heat transfer law显示文摘The optimal configuration of a heat engine operating between a finite high-temperature source and an infinite low-temperature reservoir is derived by using finite time thermodynamics based on a complex heat transfer law,including Newtonian heat transfer law,linear phenomenological heat transfer law,radiative heat transfer law,Dulong-Petit heat transfer law,generalized convective heat transfer law and generalized radiative heat transfer law,q ∝(△T n). In the engine model the only irreversibility of finite rate heat transfer is considered. The optimal relation between the power output and efficiency of the heat engine is also derived by using an equivalent temperature of the hot reservoir. The obtained results include those obtained in recent literature and can provide some theoretical guidance for the designs of practical engines. | LI Jun CHEN LinGen SUN FengRui | 2009 | Science China(Physics,Mechanics & Astronomy)2009，52，4： | 22 |
| 8 | Analysis of extrapolation cascadic multigrid method(EXCMG)显示文摘Based on an asymptotic expansion of finite element,a new extrapolation formula and extrapolation cascadic multigrid method(EXCMG)are proposed,in which the new extrapolation and quadratic interpolation are used to provide a better initial value on refined grid.In the case of triple grids,the error of the new initial value is analyzed in detail.A larger scale computation is completed in PC. | CHEN ChuanMiao HU HongLing XIE ZiQing LI ChenLiang | 2008 | Science China Mathematics2008，51，8： | 23 |
| 9 | Forming limits under multi-index constraints in NC bending of aluminum alloy thin-walled tubes with large diameters显示文摘With increasing diameters of aluminum alloy thin-walled tubes (AATTs), the tube forming limits, i.e. the minimum bending factors, and their predictions under multi-index constraints including wrinkling, thinning and flattening have been being a key problem to be urgently solved for improving tube forming potential in numerical control (NC) bending processes of AATTs with large diameters. Thus in this paper, a search algorithm of the forming limits is put forward based on a 3D elastic-plastic finite element (FE) model and a wrinkling energy prediction model for the bending processes under axial compression loading (ACL) or not. This algorithm enables to be considered the effects of process parameter combinations including die, friction parameters on the multi-indices. Based on this algorithm, the forming limits of the different size tubes are obtained, and the roles of the process parameter combinations in enabling the limit bending processes are also revealed. The followings are found: the first, within the appropriate ranges of friction and clearances between the different dies and the tubes enabling the bending processes with smaller bending factors, the ACL enables the tube limit bending processes after a decrease of the mandrel ball thickness and diameters; then, without considering the effects of the tube geometry sizes on the tube constitutive equations, the forming limits will be decided by the limit thinning values for the tubes with diameters smaller than 80 mm, while the wrinkling for the tubes with diameters no less than 80 mm. The forming limits obtained from this algorithm are smaller than the analytical results, and reduced by 57.39%; the last, the roles of the process parameter combinations in enabling the limit bending processes are verified by experimental results. | YAN Jing, YANG He, ZHAN Mei & LI Heng College of Materials Science and Engineering, State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China | 2010 | Science China(Technological Sciences)2010，53，2： | 21 |
| 10 | 伪双曲型积分-微分方程的H^1-Galerkin混合元法误差估计显示文摘1引言考虑如下一类具有Lipschitz连续边界(?)Ω的凸有界区域Ω上的伪双曲型积分微分方程其中Ω(?)Rd,(d=1,2,3)J=(0,T],对于固定的T,0 | 刘洋 李宏 何斯日古楞 | 2010 | 高等学校计算数学学报2010，32，1： | 21 |
| 11 | Pure quantitative characterization of finite projective special unitary groups显示文摘We prove that each projective special unitary group G can be characterized using; only the set of element orders of G and the order of G. | 曹洪平 施武杰 | 2002 | Science China Mathematics2002，45，6： | 20 |
| 12 | Finite difference scheme based on proper orthogonal decomposition for the nonstationary Navier-Stokes equations显示文摘The proper orthogonal decomposition(POD)and the singular value decomposition(SVD) are used to study the finite difference scheme(FDS)for the nonstationary Navier-Stokes equations. Ensembles of data are compiled from the transient solutions computed from the discrete equation system derived from the FDS for the nonstationary Navier-Stokes equations.The optimal orthogonal bases are reconstructed by the elements of the ensemble with POD and SVD.Combining the above procedures with a Galerkin projection approach yields a new optimizing FDS model with lower dimensions and a high accuracy for the nonstationary Navier-Stokes equations.The errors between POD approximate solutions and FDS solutions are analyzed.It is shown by considering the results obtained for numerical simulations of cavity flows that the error between POD approximate solution and FDS solution is consistent with theoretical results.Moreover,it is also shown that this validates the feasibility and efficiency of POD method. | Zhen-dong LUO Rui-wen WANG Jiang ZHU | 2007 | Science China Mathematics2007，50，8： | 20 |
| 13 | Optimal performance of a generalized irreversible four-reservoir isothermal chemical potential transformer显示文摘A new cyclic model of a four-reservoir isothermal chemical potential transformer with irreversible mass transfer, mass leakage and internal dissipation is put forward in this paper. The optimal relation be-tween the coefficient of performance (COP) and the rate of energy pumping of the generalized irre-versible four-reservoir isothermal chemical potential transformer has been derived by using finite-time thermodynamics or thermodynamic optimization. The maximum COP and the corresponding rate of energy pumping, as well as the maximum rate of energy pumping and the corresponding COP, have been obtained. Moreover, the influences of the irreversibility on the optimal performance of the iso-thermal chemical potential transformer have been revealed. It was found that the mass leakage affects the optimal performance both qualitatively and quantitatively, while the internal dissipation affects the optimal performance quantitatively. The results obtained herein can provide some new theoretical guidelines for the optimal design and development of a class of isothermal chemical potential trans-formers, such as mass exchangers, electrochemical, photochemical and solid state devices, fuel pumps, etc. | XIA Dan CHEN LinGen SUN FengRui | 2008 | Science China Chemistry2008，51，10： | 20 |
| 14 | Three-dimensional Finite Element Analysis of the Mechanical Properties of Helical Thread Connection显示文摘Conventional analytical and numerical methods for the mechanical properties of helical threads are relied on many assumptions and approximations and thus hardly yield satisfied results. A parameterized 3D finite element model of bolted joints with real helical thread geometry is established and meshed with refined hexahedral elements. The Von Mises plasticity criterion, kinematic hardening rule of materials and interfacial contacts are employed to make it possible for the suggested model be able to approach real assembly conditions. Then, the mechanical properties of bolted joints with different thread pitches, thread numbers and modular ratios are investigated, including the contact pressure distribution at joint interfaces, the axial load distribution and stress concentration in screw threads during the loading and unloading process. Simulation results indicate that the load distribution in screw threads produced by the suggested model agrees well the results from CHEN's photoelastic tests. In addition, an interesting phenomenon is found that tightening the bolt with a large preload first and then adjusting the clamping force by unloading can make the load distribution more uniform and reduce the maximum residual equivalent stress in thread roots by up to 40%. This research provides a simple and practical approach to constructing the 3D finite element model and predicting the mechanical properties of helical thread connection. | YANG Guoqing HONG Jun ZHU Linbo LI Baotong XIONG Meihua WANG Fei | 2013 | Chinese Journal of Mechanical Engineering2013，26，3： | 19 |
| 15 | Finite difference method and analysis for three-dimensional semiconductor device of heat conduction显示文摘The mathematical model of the three-dimensional semiconductor devices of heat conduction is described by a system of four quasilinear partial differential equations for initial boundary value problem. One equation in elliptic form is for the electric potential; two equations of convection-dominated diffusion type are for the electron and hole concentration; and one heat conduction equation is for temperature. Characteristic finite difference schemes for two kinds of boundary value problems are put forward. By using the thick and thin grids to form a complete set and treating the product threefold-quadratic interpolation, variable time step method with the boundary condition, calculus of variations and the theory of prior estimates and techniques, the optimal error estimates in L2 norm are derived in the approximate solutions. | 袁益让 | 1996 | Science China Mathematics1996，39，11： | 19 |
| 16 | 大型工艺往复压缩机系统振动分析显示文摘对大型工艺往复式压缩机系统出现振动异常现象的原因进行分析,计算了不平衡力/力矩,在扰力矩计算的基础上对压缩机基础振动状况进行了分析;建立了压缩机-驱动电机轴系模型并进行了有限元模态分析,得到了轴系振动前六阶振型与相应频率;建立了气流脉动与管道系统振动分析的有限元模型,进行了有限元分析计算,得到了管路系统的固有频率和相关研究节点的振幅。分析计算结果表明:由扰力矩引起的机身振动在允许范围内;管路系统的流固耦合振动是导致压缩机系统发生振动故障的主要原因。通过调整压缩机运行转速,改变了激振力频率;提出了管路系统优化方案,优化后的管路系统的固有频率显著提高,能有效避开激振力频率,明显降低管路系统的振幅,其最大振幅降至165μm,满足API618标准要求。 | 唐斌 刘广彬 许海平 杨启超 王乐 赵远扬 李连生 | 2014 | 中国机械工程2014，25，7： | 18 |
| 17 | The optimal path of piston motion for Otto cycle with linear phenomenological heat transfer law显示文摘An Otto cycle engine with internal and external irreversibilities of friction and heat leakage, in which the heat transfer between the working fluid and the environment obeys linear phenomenological heat transfer law [q ∝△(T -1)], is studied in this paper. The optimal piston motion trajectory for maximizing the work output per cycle is derived for the fixed total cycle time and fuel consumed per cycle. Optimal control theory is applied to determine the optimal piston trajectories for the cases of with and without piston acceleration constraint on each stroke and the optimal distribution of the total cycle time among the strokes. The optimal piston motion with acceleration constraint for each stroke consists of three segments, including initial maximum acceleration and final maximum deceleration boundary segments, respectively. Numerical examples for optimal configuration are provided, and the obtained results are compared with those obtained with Newton’s heat transfer law [q ∝△(T )]. The results also show that optimizing the piston motion can improve power and efficiency of the engine by more than 9%. This is primarily due to the decrease in heat leakage loss on the initial portion of the power stroke. | XIA ShaoJun CHEN LinGen SUN FengRui | 2009 | Science China(Physics,Mechanics & Astronomy)2009，52，5： | 18 |
| 18 | CASCADIC MULTIGRID FOR PARABOLIC PROBLEMSCASCADIC MULTIGRID FOR PARABOLIC PROBLEM显示文摘In this paper, we develop the cascadic multigrid method for parabolic problems. The optimal convergence accuracy and computation complexity are obtained. | Zhong-ci Shi, Xue-jun Xu (State Key Laboratory of Scientific and Engineering Computing, Institute of Computational Mathematics, Chinese Academy of Sciences, Beijing 100080, China) | 2000 | Journal of Computational Mathematics2000，18，5： | 18 |
| 19 | The minimum heat consumption for heat-driven binary separation processes with linear phenomenological heat transfer law显示文摘The optimal performance of heat-driven binary separation processes with linear phenomenological heat transfer law(q∝△(T-1)) is analyzed by taking the processes as heat engines which work between high-and low-temperature reservoirs and produce enthalpy and energy flows out of the system,and the temperatures of the heat reservoirs are assumed to be time-and space-variables.A numerical method is employed to solve convex optimization problem and Lagrangian function is employed to solve the average optimal control problem.The dimensionless entropy production rate coefficient and dimensionless enthalpy flow rate coefficient are adopted to indicate the major influence factors on the performance of the separation process,such as the properties of different materials and various separation requirements for the separation process.The dimensionless minimum average entropy production rate and dimensionless minimum average heat consumption of the heat-driven binary separation processes are obtained.The obtained results are compared with those obtained with the Newtonian heat transfer law(q∝△(T)). | SHU LiWei CHEN LinGen SUN FengRui | 2009 | Science China Chemistry2009，52，8： | 17 |
| 20 | Finite element formulation based on proper orthogonal decomposition for parabolic equations显示文摘A proper orthogonal decomposition (POD) method is applied to a usual finite element (FE) formulation for parabolic equations so that it is reduced into a POD FE formulation with lower dimensions and enough high accuracy. The errors between the reduced POD FE solution and the usual FE solution are analyzed. It is shown by numerical examples that the results of numerical computations are consistent with theoretical conclusions. Moreover, it is also shown that this validates the feasibility and efficiency of POD method. | LUO ZhenDong CHEN Jing SUN Ping YANG XiaoZhong | 2009 | Science China Mathematics2009，52，3： | 16 |
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