检索结果-南通市图书馆

Mean field study of a propagation-turnover lattice model for the dynamics of histone marking

在线全文

学校读者我要写书评

暂无评论

science China(Physics,Mechanics & Astronomy) 2017年第2期60卷 49-63页

作者： Fan Yao FangTing Li TieJun Li lmam and school of mathematical sciences Peking University Beijing 100871 China Schooi of Physics Peking University Beijing 100871 China center for Quantitative Biology Peking University Beijing 100871 China

We present a mean field study of a propagation-tumover lattice model, which was proposed by Hodges and Crabtree [Proc. Nat. Acad. Sci. 109, 13296 （2012）] for understanding how posttranslational histone marks modulate gene expression in mammalian ceils. The kinetics of the lattice model consists of nucleation, propagation and turnover mechanisms, and exhibits second-order phase transition for the histone marking domain. We showed rigorously that the dynamics essentially depends on a non-dimensional parameter k = k＋/k-, the ratio between the propagation and turnover rates, which has been observed in the simulations. We then studied the lowest order mean field approximation, and observed the phase transition with an analytically obtained critical parameter. The boundary layer analysis was utilized to investigate the structure of the decay profile of the mark density. We also studied the higher order mean field approximation to achieve sharper estimate of the critical transition parameter and more detailed features. The comparison between the simulation and theoretical results shows the validity of our theory.

关键词： histone marking contact process mean field approximation boundary layer analysis

An Alternative Derivation for Bronnikov's Reconstruction Algorithm in X-ray Phase Contrast Tomography

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Biomedical Engineering(English Edition) 2015年第2期24卷 80-84页

作者： ZHOU Yu ZHOU Tie JIANG Ming lmam School of Mathematical Sciences Peking University

In this article, we present an alternative derivation for Bronnikov's reconstruction algorithm in X-ray phase contrast tomography with holographic measurements. A two-step method was used in the alternative derivation. The phase shift induced by the object was obtained by Fourier transform and the real part of the complex refractive index of the object was retrieved by applying the conventional filtered backprojection method. The alternative derivation provides an easier way to understand the reconstruction formula.

关键词： phase contrast tomography Fourier transform filtered backprojection

Implementing optimized pairings with elliptic nets

在线全文

学校读者我要写书评

暂无评论

science China(Information sciences) 2014年第5期57卷 137-146页

作者： TANG ChunMing NI DongMei XU MaoZhi GUO BaoAn QI YanFeng school of Mathematics and Information China West Normal University lmam Chinese Ministry of Education Peking University school of mathematical sciences Peking University

In this paper,we use elliptic nets to implement the optimized Ate pairings and optimal pairings on the Barreto-Naehrig curves with embedding degree *** order to do the arithmetic of elliptic curves over finite fields with elliptic nets,we first give some basic properties of elliptic nets associated to elliptic curves over finite fields and the expression of Miller function in terms of elliptic *** we give formulae to compute some optimized pairings with elliptic nets,which is a new method to implement *** method with elliptic nets has time complexity comparable to Miller’s algorithm and it can be optimized.

关键词： elliptic curves elliptic nets pairings Miller’s algorithm pairing-based cryptography

A Cubic H3-Nonconforming Finite Element

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Communications on Applied Mathematics and Computation 2019年第1期1卷 81-100页

作者： Jun Hu Shangyou Zhang lmam and school of mathematical sciences Peking UniversityBeijing 100871.China Department of mathematical sciences University of DelawareNewarkDE 19716USA

The lowest degree of polynomial for a finite element to solve a 2^th-order elliptic equation is *** Morley element is such a finite element,of polynomial degree 2,for solving a fourth-order biharmonic *** design a cubic H3-nonconforming macro-element on two-dimensional triangular grids,solving a sixth-order tri-harmonic *** also write down explicitly the 12 basis functions on each macro-element.A convergence theory is established and verified by numerical tests.

关键词： Nonconforming macro-element Minimum element Tri-harmonic equation

Numerical comparison of three stochastic methods for nonlinear PN junction problems

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Mathematics in China 2014年第3期9卷 659-698页

作者： Wenqi YAO Tiao LU school of mathematical sciences Peking University Beijing 100871 China HEDPS CAPT and LMAM Peking University Beijing 100871 China

We apply the Monte Carlo, stochastic Galerkin, and stochastic collocation methods to solving the drift-diffusion equations coupled with the Poisson equation arising in semiconductor devices with random rough surfaces. Instead of dividing the rough surface into slices, we use stochastic mapping to transform the original deterministic equations in a random domain into stochastic equations in the corresponding deterministic domain. A finite element discretization with the help of AFEPack is applied to the physical space, and the equations obtained are solved by the approximate Newton iterative method. Comparison of the three stochastic methods through numerical experiment on different PN junctions are given. The numerical results show that, for such a complicated nonlinear problem, the stochastic Galerkin method has no obvious advantages on efficiency except accuracy over the other two methods, and the stochastic collocation method combines the accuracy of the stochastic Galerkin method and the easy implementation of the Monte Carlo method.

关键词： Stochastic partial differential equation stochastic Galerkin method stochastic collocation method Monte Carlo method

Population Size Estimation with Covariate Values Missing Non-ignorable

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2016年第3期32卷 659-668页

作者： Li-ping LIU Zhi-chao GUO Xiao-gang DUAN lmam and CSS School of Mathematical Sciences Peking University Beijing 100871 China Beijing Normal University Beijing 100875 China

The main purpose of this paper is using capture-recapture data to estimate the population size when some covariate values are missing, possibly non-ignorable. Conditional likelihood method is adopted, with a sub-model describing various missing mechanisms. The derived estimate is proved to be asymptotically normal, and simulation studies via a version of EM algorithm show that it is approximately unbiased. The proposed method is applied to a real example, and the result is compared with previous ones.

关键词： capture-recapture conditional likelihood EM algorithm missing non-ignorable

A family of mixed finite elements for the biharmonic equations on triangular and tetrahedral grids

在线全文

学校读者我要写书评

暂无评论

science China Mathematics 2021年第12期64卷 2793-2816页

作者： Jun Hu Rui Ma Min Zhang lmam and school of mathematical sciences Peking UniversityBeijing 100871China Fakultat fur Mathematik Universitat Duisburg-EssenEssen 45127Germany Beijing Computational science Research center Beijing 100193China

This paper introduces a new family of mixed finite elements for solving a mixed formulation of the biharmonic equations in two and three *** symmetric stress σ=−∇^(2)u is sought in the Sobolev space H(divdiv,Ω;S)simultaneously with the displacement u in L^(2)(Ω).By stemming from the structure of H(div,Ω;S)conforming elements for the linear elasticity problems proposed by Hu and Zhang(2014),the H(divdiv,Ω;S)conforming finite element spaces are constructed by imposing the normal continuity of divσ on the H(div,Ω;S)conforming spaces of P_(k) symmetric *** inheritance makes the basis functions easy to *** discrete spaces for u are composed of the piecewise P_(k−2) polynomials without requiring any *** mixed finite elements are inf-sup stable on both triangular and tetrahedral grids for k≥3,and the optimal order of convergence is ***,the superconvergence and the postprocessing results are *** numerical experiments are provided to demonstrate the theoretical analysis.

关键词： biharmonic equation symmetric stress tensor conforming finite element mixed finite element method

A Moving Mesh Method for the Euler Flow Calculations Using a Directional Monitor Function

在线全文

学校读者我要写书评

暂无评论

Communications in Computational Physics 2006年第4期1卷 656-676页

作者： Hua-Zhong Tang lmam School of Mathematical SciencesPeking UniversityBeijing 100871P.R.China

This paper is concerned with the adaptive grid method for computations of the Euler equations in fluid *** new feature of the present moving mesh algorithm is the use of a dimensional-splitting type monitor function,which is to increase grid concentration in regions containing shock waves and contact discontinuities or their *** two–dimensional flow problems are computed to demonstrate the effectiveness of the present adaptive grid algorithm.

关键词： Euler equations adaptive grid method finite volume method monitor function

GVW ALGORITHM OVER PRINCIPAL IDEAL DOMAINS

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems science & Complexity 2013年第4期26卷 619-633页

作者： LI Dongmei LIU Jinwang LIU Weijun ZHENG Licui Department of Mathematics and Computing sciences Hunan University of Science and Technology Xiangtan 411201 China Department of mathematical and statistical Central South University Changsha 410083 China. Department of Mathematics and Computing sciences Hunan University of Science and Technology Xiangtan 411201 China. school of mathematical and statistical Central South University Changsha 410083 China.

GVW algorithm was given by Gao, Wang, and Volny in computing a Grobuer bases for ideal in a polynomial ring, which is much faster and more simple than F5. In this paper, the authors generalize GVW algorithm and presen... 详细信息

关键词： Buchberger's algorithm F5 algorithm Grobner basis GVW algorithm principal ideal domain.