检索结果-南通市图书馆

Entropy number and non-linear approximations on multivariate Besov space by manifolds of finite pseudo-dimension

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural science:materials International 2006年第3期16卷 260-265页

作者： LONG Jingfan and FANG Gensun (School of Mathematical sciences, beijing normal university,{2., china department of Computer science, Information Technology Institute, beijing 100101, china) [a]School of Mathematical sciences Beijing Normal University Beijing China [b]department of Computer science Information Technology Institute Beijing China

We determine the asymptotic order of entropy number and optimal non -linear approximations of anisotropic periodic Besov class of Bpθr(Td') (1≤p≤∞,1≤0≤∞) by manifolds of finite pseudo-dimension in the metric Lq... 详细信息

关键词： Pseudo-dimension anisotropic Besov class of functions entropy number nonlinear width.

Structure and kinematic analysis of a novel 2.DOF translational parallel robot

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural science:materials International 2007年第10期17卷 1213-1219页

作者： Chen Tao1, Wu Chao2.and Liu Xinjun2.1. School of Application science and Technology, Harbin university of science and Technology, Harbin 150080, china 2. department of Precision Instruments, Tsinghua university, beijing 100084, china) School of Application science and Technology Harbin University of Science and Technology Harbin 150080 China department of Precision Instruments Tsinghua University Beijing 100084 China

This paper addresses the analysis of a novel parallel robot with 2.translational degrees of freedom (DOFs). The robot can position a rigid body in a plane with constant orientation. The kinematic structure of the robot is first described in detail. Some kinematic problems, such as the inverse and forward kinematics, velocity, and singularity are then analyzed. The working and assembly modes are discussed. Since it is the most important index to design a robot, the workspace of the robot is studied systematically in this paper. Based on the analysis of reachable workspace and singularity, a kind of workspace concept characterizing the region that the end-effector of the robot can reach in practice is defined. The results of this paper will be very useful for the design and application of the robot.

关键词： parallel robot degree of freedom kinematics workspace.

Flooding 1990s along the Yangtze River, has it concern of global warming?

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 Geographical sciences 2001年第1期11卷 43-52页

作者： GONG Dao-yi1, ZHU Jin-hong2. WANG Shao-wu2.(1. Key Laboratory of Environmental Change and Natural Disaster, Institute of Resources science, beijing normal university,{2., china 2. department of Geophysics, Peking university, beijing 100871, Key Laboratory of Environmental Change and Natural Disaster Institute of Resources Science Beijing Normal University Beijing China department of Geophysics Peking University Beijing China

There were a series of severe floods along the middle to lower reaches of the Yangtze River (Changjiang River) in china during the 1990s. The extensive summer (June, July and August) precipitation is mostly responsible for the flooding. The summer rainfall in the 1980s and the 1990s is much higher than that in the previous 3 decades. The means for 1990–1999 is +87.62.mm above normal, marked the 1990s the wettest decade since the 1950s. Six stations with a time span of 1880–1999 are selected to establish century-long rainfall series. This series also shows that the 1990s is the wettest decade during the last 12. years. In the wettest 12.years, four occurred in the 1990s (1991, 1996, 1998 and 1999). Both global and china’s temperature show there is a relative lower air temperature during the 1960–1970s, and a rapid warming in the 1980–1990s. Comparisons of rainfall between 1960–1979 and 1980–1999 show there are dramatic changes. In the cold period 1960–1979, the summer rainfall along the Yangtze River is 3.8 % to 4.7 % below the normal, during the warm period 1980–1999, over 8.4 % to 18.2.% of summer rainfall occurs. Over the whole eastern china, the summer rainfall shows opposite spatial patterns from the 1960–1970s to 1980–1990s. The consistent trend toward more rainfall with global warming is also presented by the greenhouse scenario modeling. A millennial Drought/flood Index for the middle to lower reaches of the Yangtze River showed that although the surplus summer rainfall in the 1990s is the severest during the past 150 years, it is not outstanding in the context of past millennium. Power spectra of the Drought/flood Index show significant interdecadal periods at 33.3 and 11.8 years. Thus, both the natural interdecadal variations and the global warming may play important roles in the frequent floods witnessed during the last two decades.

关键词： summer rainfall Yangtze River global warming interdecadal variation

Anomalous magnetotransport in LaMn_(1-x)Te_xO_3

在线全文

学校读者我要写书评

暂无评论

science china(Physics,Mechanics & Astronomy) 2009年第7期52卷 987-992页

作者： TAN GuoTai1,2. CHEN ZhengHao3 & ZHANG XiaoZhong4,5 1 Key Laboratory of Beam Technology & materials Modification of the Ministry of Education, Institute of Low Energy Nuclear Physics, beijing normal university,{2., china 2.beijing Radiation Center,{2., china 3 Laboratory of Optical Physics, Institute of Physics, Chinese Academy of sciences, beijing 100080, china 4 Key Laboratory of Advanced materials of the Ministry of Education, department of materials science and Engineering, Tsinghua university, beijing 100084, china 5 beijing National Center for Electron Microscopy, Tsinghua university, beijing 100084, china 1. Key Laboratory of Beam Technology & materials Modification of the Ministry of Education Institute of Low Energy Nuclear Physics Beijing Normal University Beijing 100875 China 2. beijing Radiation Center Beijing 100875 China 3. Laboratory of Optical Physics Institute of Physics Chinese Academy of Sciences Beijing 100080 China 4. Key Laboratory of Advanced materials of the Ministry of Education Department of Materials Science and Engineering Tsinghua University Beijing 100084 China 5. beijing National Center for Electron Microscopy Tsinghua University Beijing 100084 China

The LaMn1-xTexO3+δ (x=0.1, 0.2. 0.3) were synthesized using solid-state reaction method for the first time. X-ray photoemission spectrum (XPS) shows that in the samples the Te ions have a valence of Te4+, and Mn3+ ions are partly converted into Mn2. and Mn4+ due to the excess oxygen and Te doping. The magnetotransport associated with Mn2., Mn3+ and Mn4+ was investigated. The experimental results show that the samples are insulator at 0 T when the amount of Mn3+ is much larger or less than the sum of Mn2. and Mn4+; by contrast, the samples display metal to insulator transition with increasing temperature when the amount of Mn3+ is close to the sum of Mn2. and Mn4+. These anomalous magnetotransport behaviors were analyzed in the frame of the double-exchange (DE) mechanism.

关键词： colossal magnetoresistance La-Te-Mn-O magnetotransport

Recent progress on the structure of Ser/Thr protein phosphatases

在线全文

学校读者我要写书评

暂无评论

science china(Life sciences) 2008年第6期51卷 487-494页

作者： WANG BaiJing1,2. ZHANG Peng1 & WEI Qun1 1 department of Biochemistry and Molecular Biology, beijing normal university, {2. Key Laboratory, beijing 100875, china 2.School of Life science, Changchun normal university, Changchun 130032. china 1. department of Biochemistry and Molecular Biology Beijing Normal University Beijing Key Laboratory Beijing 100875 China 2. School of Life science Changchun Normal University Changchun 130032 China

PP1, PP2. and PP2., belonging to the PPP family of Ser/Thr protein phosphatases, participate in regulating many important physiological processes, such as cell cycle control, regulation of cell growth and division regulation, etc. The sequence homology between them is relatively high, and ter- tiary structure is conserved. Because of the complexity of the structure of PP2. and the diversity of its regulatory subunits, its structure is less well known than those of PP1 and PP2.. The PP2. holoen- zyme consists of a heterodimeric core enzyme, comprising a scaffolding subunit and a catalytic sub- unit, as well as a variable regulatory subunit. In this study, the subunit compositions, similarities and differences between the Ser/Thr protein phsphatases structures are summarized.

关键词： Ser/Thr phosphatases subunit composition similarities and differences crystal structure

OPTIMIZATION OF ADAPTIVE DIRECT METHOD FOR APPROXIMATE SOLUTION OF INTEGRAL EQUATIONS OF SEVERAL VARIABLES

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Scientia 2004年第2期24卷 228-234页

作者：马万房艮孙 departmentofMathematics BeijingNormalUniversityBeijing100875China

This paper determines the exact error order on optimization of adaptive direct methods of approximate solution of the class of Fredholm integral equations of the second kind with kernel belonging to the anisotropic So... 详细信息

关键词： Integral equations direct methods anisotropic sobolev classes

Weighted estimates for the multilinear singular integral operators with non-smooth kernels

在线全文

学校读者我要写书评

暂无评论

science china Mathematics 2011年第3期54卷 587-602页

作者： HU GuoEn1 & LU ShanZhen2.1department of Applied Mathematics, Zhengzhou Information science and Technology Institute, Zhengzhou 450002.{2. 2.0} of Mathematics, beijing normal university, beijing 100875,{2. 1. department of Applied Mathematics Zhengzhou Information Science and Technology Institute Zhengzhou 450002 China2. Department of Mathematics Beijing Normal University Beijing 100875 China

In this paper, by sharp function estimates and certain weak type endpoint estimates, the authors establish some weighted norm inequalities with Ap weights for the multilinear singular integral operators with non-smoot... 详细信息

关键词： approximation to the identity weighted norm inequality singular integral operator non-smooth kernel Calderón-Zygmund decomposition

Estimating surface evapotranspiration using combined MODIS and CBERS-02.data

在线全文

学校读者我要写书评

暂无评论

science china(Technological sciences) 2005年第S2期48卷 145-160页

作者： XIN Xiaozhou1,2. LIU Qinhuo1, TANG Yong1,3, TIAN Guoliang1, GU Xingfa1, LI Xiaowen1,2. ZHENG Hongsheng4 & CHEN Jiayi4 1. State Key Laboratory of Remote Sensing science, Institute of Remote Sensing Applications, Chinese Academy of sciences, {2. 100101, china 2. Research Center for Remote Sensing and GIS, department of Geography, beijing normal university, beijing 100875, china 3. Graduate university of Chinese Academy of sciences, {2. 100039, china 4. department of Atmospheric Physics, Peking university, {2. 100871, china 1. State Key Laboratory of Remote Sensing science Institute of Remote Sensing Applications Chinese Academy of Sciences 100101 Beijing China2. Research Center for Remote Sensing and GIS Department of Geography Beijing Normal University 100875 Beijing China3. Graduate University of Chinese Academy of Sciences 100039 Beijing China4. Department of Atmospheric Physics Peking University 100871 Beijing China

Spatial scale error is one of the most serious problems in the estimates of land surface heat fluxes of sensible and latent from satellite-borne data such as MODIS 1km resolution reflectance and emissive data. One of the feasible and economic ways to decrease the spatial scale error is to use high resolution land use class data together with the MODIS data. CBERS-02.data were used to produce land use class of Baiyangdian area, Hebei Province, china in the autumn of 2.04. The area ratio of each class in MODIS pixel was calculated, and used to derive the heat fluxes of the mixed pixel. The results showed that the estimated heat fluxes of soil, sensible and latent have been changed remarkably after using the high resolution land class data. It could be concluded from the comparison between simulated and ground-measured fluxes as well as the theoretical analysis that high resolution land class data are useful to diminishing the scale error of heat fluxes estimated from low resolution satellite data.

关键词： surface evapotranspiration spatial scale error MODIS CBERS land class.

Sufficient and Necessary Conditions for Stochastic Comparability of Jump Processes

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2000年第1期16卷 99-102页

作者： Yuhui Zhang department of Mathematics,beijing {2. university,beijing 100875,P.R.china department of Mathematics Beijing Normal University Beijing 100875 P.R. China

This note is devoted to the study of the stochastic comparability of jump *** the basis of[2.and[3],it is proved that two jump processes are stochastically comparable if and only if their q-pairs are ***,the result co... 详细信息

关键词： Stochastically comparable Totally stable Conservative Uniqueness