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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 1.92.0 Chinese Acad Sci Inst Mech Beijing 100080 Peoples R China Chinese Acad Sci Grad Sch Beijing 100060 Peoples R China Natl Univ singapore Trop Marine Sci Inst 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 1.92.0 Chinese Acad Sci Inst Mech Beijing 100080 Peoples R China Chinese Acad Sci Grad Sch Beijing 100060 Peoples R China Natl Univ singapore Trop Marine Sci Inst 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 1.92.0 1. institute of Mechanics Chinese Academy of Sciences 100080 Beijing China 2. Tr?pical marine science institute National University of Singapore 10 Kent Ridge Crescent 119260 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. 1. institute of Accounting and Finance Shanghai University of Finance and Economics Shanghai 200433 China2. Department of Statistics and Applied Probability National University of Singapore Singapore 117546 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 1.92.0, {3. 2 State Key Laboratory of Freshwater Ecology and Biotechnology, institute of Hydrobiology, Chinese Academy of sciences, Wuhan 43.072, China 1. Department of Biological sciences National University of Singapore Singapore 119260 Singapore2. State Key Laboratory of Freshwater Ecology and Biotechnology Institute of Hydrobiology Chinese Academy of Sciences Wuhan 430072 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

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

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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

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 ...

Preparation of grain size controlled boron-doped diamond thin films and their applications in selective detection of glucose in basic solutions

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, 1.92.0 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.

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science China Chemistry 2010年第6期53卷 1378-1384页

作者： ZHAO JianWen1,2,WANG JinLiang3.ZHI JinFang3.& ZHANG ZhiMing4 1College of Chemistry and Chemical Engineering,Jishou university,Jishou 416000,China 2Schools of Materials science and Engineering,Nanyang Technological university,63.798,{3. 3.aboratory of Organic Optoelectronic Functional Materials and Molecular Engineering,Technical institute of Physics and Chemistry & Graduate university of Chinese Academy of sciences,Beijing 100080,China 4Research institute of Micro-Nano science and Technology,Shanghai Jiao Tong university,Shanghai 20003.,China 1. College of Chemistry and Chemical Engineering Jishou University Jishou 416000 China2. Schools of Materials Science and Engineering Nanyang Technological University 639798 Singapore Singapore3. Laboratory of Organic Optoelectronic Functional Materials and Molecular Engineering Technical Institute of Physics and Chemistry & Graduate University of Chinese Academy of Sciences Beijing 100080 China4. Research Institute of Micro-Nano Science and Technology Shanghai Jiao Tong University Shanghai 200030 China

Boron-doped diamond (BDD) thin films with different crystal grain sizes were prepared by controlling the reacting gas pressure using hot filament chemical vapor deposition (HFCVD).The morphologies and structures of the prepared diamond thin films were characterized by scanning electron microscopy (SEM) and Raman *** electrochemical responses of K4Fe(CN)6 on different BDD electrodes were *** results suggested that electron transfer was faster at the boron-doped nanocrystalline diamond (BDND) thin film electrodes in comparison with that at other BDD thin film *** prepared BDD thin film electrodes without any modification were used to directly detect glucose in the basic *** results showed that the as-prepared BDD thin film electrodes exhibited good selectivity for detecting glucose in the presence of ascorbic acid (AA) and uric acid (UA).The higher sensitivity was observed on the BDND thin film grown on the boron-doped microcrystalline diamond (BDMD) thin film surface,and the linear response range,sensitivity and the low detection limit were 0.25–10 mM,189.1 μA mmol-1 cm-2 and 25 μM (S/N=3. for glucose in the presence of AA and UA,respectively.

关键词： diamond thin films electrochemical properties selective glucose detection

Field measurement and analysis of turbulence coherence for Typhoon Nuri at Macao Friendship Bridge

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science China(Technological sciences) 2010年第10期53卷 2647-2657页

作者： SONG LiLi1, PANG JiaBin2, JIANG ChengLin3. HUANG HaoHui3.& QIN Peng3.1 Guangzhou institute of tropical and marine Meteorology, CMA, Guangzhou 510080, China 2 Tongji {3., Shanghai 200092, China 3.Guangdong Climate Centre, Guangzhou 510080, China 1. Guangzhou institute of tropical and marine Meteorology CMA Guangzhou 510080 China2. Tongji University Shanghai 200092 China3. Guangdong Climate Centre Guangzhou 510080 China

For the purpose of investigating the turbulent and spatial coherent characteristics of strong wind during typhoon landing period,two 3.dimensional ultrasonic anemometer stations were set up 3. m horizontally apart on the Macao Friendship Bridge to caputure the turbulent wind velocities of Typhoon Nuri. Based on the reliable and representative field measured data,the mean wind speed and direction,turbulence intensity,turbulence integral scale,turbulence power spectra,spatial correlation coefficient and coherence function were statistically evaluated. The field measurement analysis have presented the following results: 1) Two anemometer stations provided consistent results. The mean wind speed variation in time domain presented typical M-shape curves. The strong wind (10-minute mean wind speed higher than 8th grade in Beaufort wind scale) direction changed in a big range up to 122-degrees-angle,indicating the field measurements scoped over the typhoon landing period. 2) The ratio of the longitudinal,lateral and vertical turbulence intensities of the strong wind in the typhoon eye wall region was 1:0.96:0.3.. Compared with the code defined ratio 1:0.88:0.5,the lateral component was larger and the vertical component was smaller. 3. The value of integral scale increased when the eye wall of Typhoon Nuri passed over the field measurement site. Before the center of Typhoon Nuri arrived,the integral scale of the strong typhoon wind was about twice compared with that for the non-typhoon wind. 4) The spatial correlation of the turbulent wind,coherence function curve and the decay factor had significant differences at different times during the typhoon process. In the eye wall of the typhoon,the horizontal spatial correlation was relatively strong and horizontally spatial correlation spectrum decayed slower with frequency increase. The minimum regressed coefficient C in coherence function model was 4.67,which is lower than the code defined low limit. The maximum decay factor w

关键词： typhoon field measurement and analysis turbulence characteristics coherence spectral function

Local Existence for Inhomogeneous Schrdinger Flow into Kihler Manifolds

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Acta Mathematica Sinica,English Series 2000年第3期16卷 487-504页

作者： Peter Y.H.Pang Hongyu WangDepartment of Mathematics,national university of singapore,2 {3. Drive 2,Republic of singapore 117543.oude Wang institute of Mathematics,Academy of Mathematics and System {3.s,Academia Sinica,Beijing,100080,P.R.China

In this paper we show that there exists a unique local smooth solution for the Cauchy problem of the inhomogeneous Schrdinger flow for maps from a compact Riemannian manifold M with dim(M)≤3.into a compact Khler mani... 详细信息

关键词： Inhomogeneous Schrdinger flow Khler manifold Local existence