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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 200433, China 2 Department of Statistics and Applied Probability, National University of singapore, singapore 117546, singapore 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

Decay of geometry for unimodal maps:The C^2 case

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Chinese Science Bulletin 2009年第11期54卷 1859-1862页

作者： SHEN WeiXiao1,2 1 Department of Mathematics, University of Science and Technology of China, Hefei 230026, China 2 Department of Mathematics, National University of singapore, singapore 117543, singapore Department of Mathematics University of Science and Technology of China Hefei 230026 China Department of Mathematics National University of Singapore Singapore 117543 Singapore

We prove that a C2 unimodal interval map with critical order not greater than 2 has the decay of geometry property, by showing that all the cross-ratio estimates needed in the previous proof for the C3 case remain true.

关键词：衰变几何图案件几何性质比率估计证明

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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, singapore 2 State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, 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

Revisit of Sheppard corrections in linear regression

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Science China Mathematics 2010年第6期53卷 1435-1451页

作者： LIU TianQing1,ZHANG BaoXue1,HU GuoRong1 & BAI ZhiDong1,2,1Key Laboratory for Applied Statistics of MOE and School of Mathematics and Statistics,Northeast Normal University,Changchun 130024,China 2Department of Statistics and Applied Probability,National University of singapore,singapore 117543,singapore 1. Key Laboratory for Applied Statistics of MOE and School of Mathematics and Statistics Northeast Normal University Changchun 130024 China2. Department of Statistics and Applied Probability National University of Singapore Singapore 117543 Singapore

Dempster and Rubin(D&R) in their JRSSB paper considered the statistical error caused by data rounding in a linear regression model and compared the Sheppard correction,BRB correction and the ordinary LSE by *** asymptotic results when the rounding scale tends to 0 were also *** a previous research,we found that the ordinary sample variance of rounded data from normal populations is always inconsistent while the sample mean of rounded data is consistent if and only if the true mean is a multiple of the half rounding *** the light of these results,in this paper we further investigate the rounding errors in linear *** notice that these results form the basic reasons that the Sheppard corrections perform better than other methods in D&R examples and their conclusion in general cases is *** in which the Sheppard correction works worse than the BRB correction are also ***,we propose a new approach to estimate the parameters,called "two-stage estimator",and establish the consistency and asymptotic normality of the new estimators.

关键词： asymptotic normality consistency linear regression model rounded data two-stage estimates

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 Marine Science Institute, National University of singapore, 10 Kent Ridge Crescent, singapore 119260 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.

Wave mechanics in quantum phase space: hydrogen atom

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Progress in Natural Science:Materials International 2007年第2期17卷 144-149页

作者： LU Jun ( Department of Foundational Science, Beijing Union University, Beijing 100101, China Department of Computational Science, National University of singapore, singapore 117543, singapore) [a]Department of Foundational Science Beijing Union University Beijing China [b]Department of Computational Science National University of singapore Singapore Singapore

The rigorous solutions of the stationary Schrodinger equation for hydrogen atom are solved with the wave-mechanics method within the framework of the quantum phase-space representation established by Torres-Vega and Frederick. The "Fourier-like" projection transformations of wave function from the phase space to position and momentum spaces are extended to three-dimensional systems. The eigenfunctions in general position and momentum spaces could be obtained through the transformations from eigenfunction in the phase space.

关键词： quantum phase space hydrogen atom projection transformation.

Effect of rock mass structure and block size on the slope stability——Physical modeling and discrete element simulation

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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. Tropical Marine Science Institute, National University of singapore, singapore 119260 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.

Characteristics of In_(0.52)Al_(0.48)As Grown on InP(100) Substrates by Molecular Beam Epitaxy: Growth Optimisation and Effects of Si Doping

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Journal of Materials Science & Technology 1997年第2期13卷 91-98页

作者： S.F.Yoon(School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyng Avenue,singapore 639798, Rep. of singapore) School of Electrical and Electronic Engineering Nanyang Technological University Nanyang Avenue Singapore 639798 Singapore

Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at a wide range of substrate tempreatures (470~550℃) and at different Si doping levels has been carried out. Low temperature photoluminescence (PL) and double-axis X-ray diffraction (XRD) analyses shaw a strong dependence of the PL and XRD linewidths, XRD intensity ratio (Lepi/Isub), and lattice-mismatch on the substrate temperature. The X-ray diffraction peaks of samples grown at law temperatures show a composition of smaller peaks, indicating the presence of disorder due to alloy clustering. Raman scattering measurements of the same samples show an additional higher energy mode at 273 cm-1 in addition to the InAs-like and AlAs-like longitudinal-optic (LO) phonon modes. Samples doped with Si show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping levels due to a possible reduction in the donor binding energy. Supported be observations of a reduction in both the AlAs-like and InAs-like LO phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased, the PL intensity also shows in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.

关键词： As Grown on InP Characteristics of In Growth Optimisation and Effects of Si Doping Substrates by Molecular Beam Epitaxy InP Al Si

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 Jianguo31. Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China 2. Graduate School, Chinese Academy of Sciences, Beijing 100060, China 3. Tropical Marine Science Institute, National University of singapore, 10 Kent Ridge Crescent, singapore 119260 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 30% 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.