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science China(Technological sciences) 2005年第Z1期48卷 1-17页

作者： LI Shihai1, LIAN Zhenzhong1,2 & J. G. Wang3.1. institute of Mechanics, Chinese Academy of sciences, Beijing 100080, China 2. Graduate School, Chinese Academy of sciences, Beijing 100060, China {3., national university of singapore, singapore 119260 institute of Mechanics Chinese Academy of Sciences Beijing 100080 China Graduate School Chinese Academy of Sciences Beijing 100060 China tropical marine science {3. National University of Singapore Singapore 119260 Singapore

This paper studies the stability of jointed rock slopes by using our improved three-dimensional discrete element methods (DEM) and physical modeling. Results show that the DEM can simulate all failure modes of rock slopes with different joint configurations. The stress in each rock block is not homogeneous and blocks rotate in failure development. Failure modes depend on the configuration of joints. Toppling failure is observed for the slope with straight joints and sliding failure is observed for the slope with staged joints. The DEM results are also compared with those of limit equilibrium method (LEM). Without considering the joints in rock masses, the LEM predicts much higher factor of safety than physical modeling and DEM. The failure mode and factor of safety predicted by the DEM are in good agreement with laboratory tests for any jointed rock slope.

关键词： rock masses, slope stability, DEM simulation, block size effect, joints configuration effect, limit equilibrium method.

Experimental and discrete element numerical analysis of side slope instability induced by fissure water underlying impervious bed

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science China(Technological sciences) 2005年第Z1期48卷 65-80页

作者： LIU Bingshan1, LI Shihai1, ZHANG Lei1,2 & WANG Jianguo3.. institute of Mechanics, Chinese Academy of sciences, Beijing 100080, China 2. Graduate School, Chinese Academy of sciences, Beijing 100060, China {3., national university of singapore, 10 Kent Ridge Crescent, singapore 119260 institute of Mechanics Chinese Academy of Sciences Beijing 100080 China Graduate School Chinese Academy of Sciences Beijing 100060 China tropical marine science {3. National University of Singapore 10 Kent Ridge Crescent Singapore 119260 Singapore

When the sliding mass contains impervious bed, rainfall can infiltrate into mountain via crevices and form higher artesian aquifer at impervious bed inferior. This will decrease slip resistance and increase sliding forces of the sliding mass, thus lowering the safety factor, and inducing landslide disasters. In this paper, a landslide experimental apparatus is designed for experimental studies on the mechanism of this type of landslides. Meanwhile, the non-dimensional parameters in the model experiment are taken into account using dimensional analysis. The experimental results show that (1) the ratio of the cleft water pressure to the overlying pressure is a crucial parameter affecting the stability of the slope; (2) when the shut-in pressure reaches 80% of the normal component of the pressure on the slip surface made up of rock and soil, landslide will occur; (3. the whole slope will start to slide when the shut-in pressure is equal to the normal component of the pressure formed by the overlying rock and soil on the upper 3.% area. In this article, a discrete element method simulation is used to investigate the influence of cleft water pressure and shearing strength on the landslide stability. It can be concluded that the critical value of Ccr, ?cr, which determines the slide mass stability, increases with the increase of the water pressure; if the water pressure reaches a high level, the stability of the slide mass depends mainly on C, while the influence of ? becomes smaller than C.

关键词： impervious bed, rainfall infiltration, pore water pressure, landslide experiment, displacement monitor, discrete element method.

Stochastic structural model of rock and soil aggregates by continuum-based discrete element method

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science China(Technological sciences) 2005年第Z1期48卷 95-106页

作者： WANG Yuannian1, ZHAO Manhong1, LI Shihai1 & J.G. Wang21. institute of Mechanics, Chinese Academy of sciences, Beijing 100080, China 2. tropical {3. science institute, national university of singapore, 10 Kent Ridge Crescent, singapore 119260 institute of Mechanics Chinese Academy of Sciences Beijing China Tröpical marine science institute National University of Singapore Singapore

This paper first presents a stochastic structural model to describe the random geometrical features of rock and soil aggregates. The stochastic structural model uses mixture ratio, rock size and rock shape to construct the microstructures of aggregates, and introduces two types of structural elements (block element and jointed element) and three types of material elements (rock element, soil element, and weaker jointed element) for this microstructure. Then, continuum-based discrete element method is used to study the deformation and failure mechanism of rock and soil aggregate through a series of loading tests. It is found that the stress-strain curve of rock and soil aggregates is nonlinear, and the failure is usually initialized from weaker jointed elements. Finally, some factors such as mixture ratio, rock size and rock shape are studied in detail. The numerical results are in good agreement with in situ test. Therefore, current model is effective for simulating the mechanical behaviors of rock and soil aggregates.

关键词： CDEM, rock and soil aggregate, mixture ratio.

Saddlepoint approximations for studentized compound Poisson sums with no moment conditions in audit sampling

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science China Mathematics 2010年第12期53卷 3131-3138页

作者： ZHOU GuoLiang 1 & ZHOU Wang 2, 1 institute of Accounting and Finance, Shanghai university of Finance and Economics, Shanghai 20043., China 2 Department of Statistics and Applied Probability, national university of singapore, {3. 117546, {3. institute of Accounting and Finance Shanghai University of Finance and Economics Shanghai China Department of Statistics and Applied Probability National University of Singapore Singapore Singapore

Saddlepoint approximations for the studentized compound Poisson sums with no moment conditions in audit sampling are derived. This result not only provides a very accurate approximation for studentized compound Poisson sums, but also can be applied much more widely in statistical inference of the error amount in an audit population of accounts to check the validity of financial statements of a firm. Some numerical illustrations and comparison with the normal approximation method are presented.

关键词： saddlepoint approximation Laplace approximation self-normalized compound Poisson sum stu- dentized compound Poisson sum

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Fish germ cells

science China(Life sciences) 2010年第4期53卷 435-446页

作者： XU HongYan1, LI MingYou1, GUI JianFang2 & HONG YunHan1,2 1Department of Biological sciences, national university of singapore, singapore 119260, {3. 2 State Key Laboratory of Freshwater Ecology and Biotechnology, institute of Hydrobiology, Chinese Academy of sciences, Wuhan 43.072, China Department of Biological sciences National University of Singapore Singapore Singapore State Key Laboratory of Freshwater Ecology and Biotechnology Institute of Hydrobiology Chinese Academy of Sciences Wuhan China

Fish, like many other animals, have two major cell lineages, namely the germline and soma. The germ-soma separation is one of the earliest events of embryonic development. Germ cells can be specifically labeled and isolated for culture and transplan-tation, providing tools for reproduction of endangered species in close relatives, such as surrogate production of trout in salmon. Haploid cell cultures, such as medaka haploid embryonic stem cells have recently been obtained, which are capable of mimicking sperm to produce fertile offspring, upon nuclear being directly transferred into normal eggs. Such fish originated from a mosaic oocyte that had a haploid meiotic nucleus and a transplanted haploid mitotic cell culture nucleus. The first semi-cloned fish is Holly. Here we review the current status and future directions of understanding and manipulating fish germ cells in basic research and reproductive technology.

关键词： fish germ cell germ plasm reproduction reproductive technology semi-cloning

A Computational Model for Simulation of Fractured Materials Using Continuum-Based Discrete Element Method(CDEM)

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A Computational Model for Simulation of Fractured Materials ...

Temperature dependence of circular DNA topological states and a solution to a single molecular experiment problem

The Sixth World Congress on Computational Mechanics in Conjunction with the Second Asian-Pacific Congress on Computational Mechanics

作者： Manhong Zhao, Shihai Li, Yuannian Wang', J. G. Wang institute of Mechanics, Chinese Academy of science, Beijing 10080, China tropical {3. science institute, national university of singapore, 119260 singapore

Based on the continuum-based discrete element method (CDEM), this paper presents a computational' model to simulate fractured materials. The relationship of macroscopic failure of material and internal rupture strain strength is exploited. First, the CDEM treats the 8-node solid isoparametric element in FEM as a fundamental system composed of 8 particles and interconnecting springs. A complete process from continuum to discontinuum under loading can be simulated by CDEM. Second, a spring changes its properties if this spring is intersected by a fracture: 1, the shear and tension forces are equal to zero on fracture plane when the spring in normal direction of the fracture plane is in tension. 2, When the spring is in compression, the normal force in the fracture plane is the projection of spring force in normal direction, and the shear force in the fracture plane is the one in tangential direction. When the normal and shear forces satisfy the Mohr-Coulomb failure criterion, the spring fails and the spring stiffness should be revalued. Third, the stress to strain curve for fractured samples are tested under tension and compression. It is found that the material performs linear elasticity when fracture density is small and external load is low. However, nonlinearity occurs with the larger load. Furthermore, the 'hardening' and 'softening' property of fractured material is simulated under displacement loading test.

关键词：

来源： cnki会议评论

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生物物理学报 2009年第S1期25卷 296-297页

作者： Yanhui Liu1, Hu Chen2, Lin Hu1, Zhong-Can Ou-Yang3. and Jie Yan2 1.Guizhou university, College of science, Guiyang, 550025 2.national university of singapore, Department of Physics, science Drive 3. singapore, 117542 3.The institute of Theoretical Physics, Chinese Academy of sciences, Beijing, China, 100080

Circular double stranded DNA has different topological states which are defined by their linking numbers. Equilibrium distribution of linking numbers can be obtained by closing

关键词： DNA Temperature dependence of circular DNA topological states and a solution to a single molecular experiment problem

Study on optimization of agent initial positions in land combat simulation

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Progress in Natural science:Materials International 2004年第3期 65-69页

作者： WU Chunguo 1,2 , LIANG Yanchun* 1, 2 , LEE Heow Pueh 2, LU Chun 2 and YANG Xiaowei 3.4 (1. College of Computer science and Technology, Key Laboratory of Symbol Computation and Knowledge Engineering of the Ministry of Education, Jilin university, Changchun 13.012, China 2. institute of High Performance Computing, {3. 117528, {3. 3. Department of Applied Mathematics, South China university of Technology, Guangzhou 510640, China 4. Centre for ACES, Department of Mechanical Engineering, national university of singapore, 119260, {3.) CollegeofComputerscienceandTechnology KeyLaboratoryofSymbolComputationandKnowledgeEngineeringoftheMinistryofEducationJilinUniversityChangchun130012China InstitiuteofHighPerformanceComputing Singapore117528Singapore DepartmentofAppliedMathematics SouthChinaUniversityofTechnologyGuangzhou510640China

The use of computational intelligence based techniques in the optimization of agent initial positions in land combat simulations is studied. A novel method for the reduction of support vectors in the support vector machine (SVM) is presented. The optimization on the width of the Gaussian kernel function and the combination of the SVM with the radial basis function neural network are performed in the proposed method. Simulation results show that the proposed method can improve the running efficiency drastically compared with that using the traditional SVM with the same precision. We also summarize and present some experiences and trends in the study on the optimization problem in land combat simulation.

关键词： multi agent support vector machine radial basis function genetic algorithm regression.

An Integration Framework for Digital Progressive Die Design and Manufacturing

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武汉理工大学学报 2006年第S1期28卷 55-61页

作者： A. Y. C. Nee Department of Mechanical Engineering National University of Singapore10 Kent Ridge CrescentSingapore 119260

This paper reports an effort to develop an intelligent integration framework for digital progressive die design and manufacturing. Both data-and process-centric integration functions are provided by the framework as if a special ight-weight PDM/PLM (Product Data Management/Product Lifecycle Management) and WM (Workflow Management) system is embedded in the integrated engineering environment. A flexible integration approach based on the CAD (Computer-Aided Design) framework tenet is employed to rapidly build up the system while the intrinsic characteristics of the process are comprehensively taken into account. Introduction of this integration framework would greatly improve the dynamic performance of the overall progressive die design and manufacturing process.

关键词： progressive die digital manufacturing product data integration process integration integration frame

Soil Erosion Changes over the Past Five Decades in the Red Soil Region of Southern China

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Journal of Mountain science 2010年第1期7卷 92-99页

作者： LIANG Yin LI Decheng LU Xixi YANG Xuan PAN Xianzhang MU Huan SHI Deming ZHANG Bin institute oj: Soil science Chinese Academy of Sciences Nanjing 210008 China Department of Geography National University of Singapore Singapore 119260 Key Laboratory of Soil Environment and Pollution Remediation Institute of Soil Science Chinese Academy of Sciences. Nanjing 210008 China

This paper reports the dynamic changes of soil and water loss in the red soil region of Southern China since the 1950s. The red soil region covers eight provinces: Jiangxi, Zhejiang, Fujian, Anhui, Hubei, Hunan, Guangdong and Hainan. From the 1950s to 1986, the annual rate of soil erosion increased by 3.4%. From 1986 to 1996 and from 1996 to 2000, the annual rates of soil erosion decreased by 2.0% and 0.3.%, respectively. Field surveys showed that from 2000 to 2005, the area of soil and water loss decreased annually by 1.2%. This decrease was a result of large-scale erosion control activities across China. Although the eroded soil has been restored, the restoration process is very slow and full restoration will take a long time. Our report suggests that controlling soil and water loss is a challenging task, and additional measures must be taken to effectively control the soil erosion in the red soil region.

关键词： red soil region soil and water loss dynamic change remote sensing field samplingsurvey