检索结果-南通市图书馆

An efficient algorithm for finding the largest chain graph according to a given chain graph

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2005年第11期48卷 1517-1530页

作者： LIU Baijun,ZHENG Zhongguo & ZHAO Hui School of Mathematical Sciences, peking university, beijing 100871, china department of Statistics, Central china Normal university, Wuhan 4.0079, china 1. School of Mathematical Sciences Peking University 100871 Beijing China 2. department of Statistics Central China Normal University 430079 Wuhan China

Chain graph (CG) is a general model of graphical Markov models. Some different chain graphs may describe the same conditional independence structure, then we say that these CGs are Markov equivalent. In 1990 Frydenberg showed that every class of Markov equivalent CGs has a CG which is called the largest chain graph with the greatest number of lines. This paper presents an efficient algorithm for finding the largest chain graph of the corresponding Markov equivalent class of a given CG. The computational complexity of the algorithm is O(n3). It is more efficient than the complexity O(n!) of the present algorithms. Also a more intuitive graphical characterization of the largest chain graph is provided based on the algorithm in this paper.

关键词： graphical Markov model,chain graph,largest chain graph,protected arrows,efficient algorithm

Commutant of Analytic Toeplitz Operators on the Bergman Space

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2010年第12期26卷 2255-2258页

作者： Jia Yi JIANG Di Sheng XU department of Mathematics, peking university, beijing 100871, P.R. china department of Mathematics Peking University Beijing P. R. China

In this paper, we characterize the commutant of Toeplitz operators on weighted Bergman space with symbol polynomial by using algebraic curves theory.

关键词： Toeplitz operator commutant Bergman space algebraic curves

Design of a new dynamical core for global atmospheric models based on some efficient numerical methods

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2004年第z1期47卷 4-21页

作者： WANG Bin, WAN Hui, Jl Zhongzhen, ZHANG Xin, YU Rucong, YU Yongqiang & LIU HongtaoState Key Laboratory of Numerical Modeling for atmospheric Sciences and Geophysical Fluid Dynamics, Institute of atmospheric Physics, Chinese Academy of Sciences, beijing 100029, china {4. of Computational Mathematics, Academy of Mathematics and System Sciences, peking university, beijing 100871, china Chinese Acad Sci Inst Atmospher Phys State Key Lab Numer Modeling Atmospher Sci & Geop Beijing 100029 Peoples R China peking Univ Acad Math & Syst Sci Dept Computat Math Beijing 100871 Peoples R China

A careful study on the integral properties of the primitive hydrostatic balance equations for baroclinic atmosphere is carried out, and a new scheme todesign the global adiabatic model of atmospheric dynamics ispresented. This scheme includes a method of weighted equal-areamesh and a fully discrete finite difference method with quadraticand linear conservations for solving the primitive equationsystem. Using this scheme, we established a new dynamical corewith adjustable high resolution acceptable to the availablecomputer capability, which can be very stable without anyfiltering and smoothing. Especially, some important integralproperties are kept unchanged, such as the anti-symmetries of thehorizontal advection operators and the vertical convectionoperator, the mass conservation, the effective energy conservationunder the standard stratification approximation, and so on. Somenumerical tests on the new dynamical core, respectively regardingits global conservations and its integrated performances inclimatic modeling, incorporated with the physical packagesfrom the Community atmospheric Model Version 2 (CAM2) of NationalCenter for atmospheric Research (NCAR), are included.

关键词： dynamical core, equal-area mesh, anti-symmetry, effective energy conservation.

When Closed Graph Manifolds are Finitely Covered by Surface Bundles Over S^1

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 1999年第1期15卷 11-20页

作者： Yan Wang Fengchun Yudepartment of Mathematics,peking university,beijing {4. P.R.china department of Mathematics Peking University Beijing P. R. China

The problem of deciding whether a graph manifold is finitely covered by a surface bundle over the circle is discussed in this paper.A necessary and sufficient condition in term of the solutions of a certain matrix equation is obtained,as well as a necessary condition which is easy to compute. Our results sharpen and extend the earlier results of ***,***,and ***-F. Yu in this topic.

关键词： Surface bundle Covering Graph manifolds

Application of Fast Radical Rearrangement in the Mechanistic Investigation of Intramolecular C-H Insertion by Rh(Ⅱ)-Mediated Carbenoids

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 1998年第8期9卷 701-704页

作者： Jian Bo WANG Feng Ting LIANG(department of Chemistry, peking university, beijing 100871) department of Chemistry Peking University Beijing 100871 China

In order to investigate the reaction mechanism of intramolecular C-H insertion by Rh(II)-mediated carbenoids with trans-(2-phenylcyclopropyl) carbinal radical as the mechanistic probe, diazo compounds 2-(2-phenylcyclopropyl)ethyl diazoacetoacetate 8a and methyl 2-diazo-3oxo-6-(2-phenylcyclopropyl) hexanoate 8b have been synthesized. Preliminary investigation of the intramolecular C-H insertion with Rh2(OAc)4.as catalyst supports a concerted insertion process.

关键词： Rh(Ⅱ)-mediated carbenoids intramolecular C-H insertion mechanism

SUPERCONDUCTIVITY IN La1.85Sr0.15Cu1-xZnxO4

在线全文

学校读者我要写书评

暂无评论

低温物理学报 1993年第6期15卷 425-426页

作者： Fusui LiuPhysics department, peking university, beijing, 100871 北京大学北京

Based on the multiple exchange-mediated interaction mechanism of high- Tc superconductivity and the Abrikosov-Gorkov theory of magnetic impurity superconductors, this paper quantitatively explains the Zn-substitution ... 详细信息

关键词： Zn SUPERCONDUCTIVITY IN La x)ZnxO4 Cu Sr

Flux of dimethylsulfide in the Jiaozhou Bay,china

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 1997年第1期9卷 80-85页

作者： Hu Min Tang Xiaoyan Center of Environmental Sciences,peking university,beijing 100871,{4.Li Jinlong Yu Zhongju department of Technical Physics,peking university,beijing 100871,{4. Center of Environmental Sciences Peking University Beijing 100871 China department of Technical Physics Peking University Beijing 100871 China

Seasonal measurements of dimethylsulfide(DMS)in surface waters were carried out during 1993-1994.in the Jiaozhou Bay.A seasonal variation is observed for DMS concentrations in seawater,ranging from 0.6 to 8.97 nmol S/L with the highest values in spring.A factor of 4.was measured for DMS concentrations with mean concentrations of 5.85 nmol S/L or 6.58 nmol S/L in spring and 1.4.nmol S/L in winter.A sea-to-air flux of DMS also showed a seasonal variation.

关键词： dimethyl sulfide flux seawater atmosphere.

Oblique Derivative Problems for NonlinearEquations of Mixed Type in General Domains

在线全文

学校读者我要写书评

暂无评论

Communications in Nonlinear Science and Numerical Simulation 1998年第3期3卷 148-151页

作者： Guochun WEN and Maoying TAIN(department of Mathematics, peking university, beijing 100871, china)e-mail: wengc@*** department of Mathematics Peking University Beijing 100871 China

The paper deals with oblique derivative boundary value problem for secondorder nonlinear equations of mixed (elliptic-hyperbolic ) type in general domains. By usingthe method of complex analysis, the uniqueness and ex... 详细信息

关键词： oblique derivative problems nonlinear equations of mixed type general domains

On the Markov equivalence of maximal ancestral graphs

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china Mathematics 2005年第4期48卷 548-562页

作者： ZHAO Hui, ZHENG Zhongguo & LIU Baijun School of Mathematical Sciences, peking university, beijing 100871, china department of Statistics, Central china Normal university, Wuhan 4.0079, china 1. School of Mathematical Sciences Peking University 100871 Beijing China

Necessary and sufficient conditions for a maximal ancestral graph (MAnG)to be Markov equivalent to another MAnG and to a DAG are provided respectively. Also a polynomial-time algorithm for converting a MAnG into its e... 详细信息

关键词： maximal ancestral graph, Markov equivalence, minimal collider path, m-separation.