检索结果-南通市图书馆

Basin filling algorithm for the circular packing problem with equilibrium behavioral constraints

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(information Sciences) 2010年第5期53卷 885-895页

作者： LIU JingFa1& LI Gang2.1school of Computer and Software, nanjing {2. of information Science & technology, nanjing 2.0044, china 2.0} of mathematics and physics, nanjing {2. of information Science & technology, nanjing 2.0044, china school of Computer and Software Nanjing University of Information Science & Technology Nanjing China school of mathematics and {2. Nanjing University of Information Science & Technology Nanjing China

With the background of the satellite module layout design, the circular packing problem with equilibrium behavioral constraints is a layout optimization problem and NP-hard problem in math. For lack of a powerful optimization method, this problem is hard to solve. The energy landscape paving (ELP) method is a class of stochastic global optimization algorithms based on the Monte Carlo sampling. Based on the quasiphysical strategy and the penalty function method, the problem is converted into an unconstrained optimization problem. Here by combining the improved ELP method, the gradient method based on local search and the heuristic configuration update mechanism, a new global search algorithm, basin filling algorithm, is put forward. The numerical results show that the proposed algorithm is effective to solving the circular packing problem with equilibrium behavioral constraints, and is easy to be popularized to other layout optimization problems.

关键词： equilibrium behavioral constraints packing problem layout optimization

Characteristics of fMRI BOLD signal and its neurophysiological mechanism

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6期17卷 630-638页

作者： Zhao Xiaohu1,2. Wu Yigen3 and Guo Shengli3(1. College of Life Sciences, Zhejiang university, Hangzhou 310058, china 2. Imaging Department of Tongji Hospital of Tongji university, Shanghai 2.0065, china 3. College of mathematics and physics, nanjing university of information Science and technology, nanjing 2.0044, china) College of Life Sciences Zhejiang University Hangzhou 310058 China Imaging Department Tongji Hospital Tongji University Shanghai 200065 China College of mathematics and physics Nanjing University of Information Science and Technology Nanjing 210044 China

The functional magnetic resonance imaging (fMRI) based on blood oxygen level dependent (BOLD) contrast has emerged as one of the most potent noninvasive tools for mapping brain function and has been widely used to explore physiological, pathological changes and mental activity in the brain. Exploring the nature and property of BOLD signal has recently attracted more attentions. Despite that great progress has been made in investigation of the characteristics and neurophysiological basis, the exact nature of BOLD signal remains unclear. In this paper we discuss the characteristics of BOLD signals, the nonlinear BOLD response to external stimuli and the relation between BOLD signals and neural electrophysiological recordings. Furthermore, we develop our new opinions regarding nonlinear BOLD response and make some perspectives on future study.

关键词： functional magnetic resonance imaging blood oxygen level dependent nonlinear response neural electrophysiological activity.

Numerical simulation of Meiyu front and the diagnosis of moist vorticity vector

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11期17卷 1341-1347页

作者： Ping Fan1,2.and Luo Zhexian2.1. Institute of Atmospheric physics, Chinese Academy of Sciences, Beijing 10002., china 2. {2. university of information Sciences & technology, nanjing 2.0044, china) Institute of Atmospheric physics Chinese Acad. of Sci. Beijing 100029 China nanjing university of {2. Sciences and technology Nanjing 210044 China

Moist vorticity vector is introduced to study the development and evolution of mesoscale convective vortex (MCV) in the Meiyu front precipitation with the Advanced Regional Predication System (ARPS). In this study, the heavy rainfall is simulated to investigate the genesis, development and dissipation of middle scale convective vortex, which occurred from 0000 UTC 3 July to 12.0 UTC 5 July over the Jianghuai River valley. Moist vorticity vector (MVV) has zonal, radial and vertical components in its 3D spatial distribution. The simulation shows that the vertical component of moist vorticity vector well demonstrates the spatial distribution characteristics of middle scale convective vortex, especially in the process of Meiyu front precipitation. Diagnosis upon zonal, radial averaged and mass-integrated quantities of MVV shows that its vertical component and the surface precipitating ratio are in phase with a correlation coefficient of 0.68, indicating that the vertical component of MVV is closely associated with the Meiyu front precipitation. In addition, the tendency of the vertical component of MVV is mainly determined by the interaction between the vorticity and the zonal and radial gradient of condensational or depositional heating.

关键词： moist vorticity vector mesoscale convective vortex Meiyu front precipitation

A relative local variational principle for topological pressure

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 2010年第6期53卷 1491-1506页

作者： MA XianFeng1,CHEN ErCai2.3,& ZHANG AiHua2.4 1Department of mathematics,East china {2. of Science and technology,Shanghai 2.02.7,china 2.5} of mathematics and Computer Science,nanjing Normal {2.,nanjing 2.0097,china 3Center of Nonlinear Science,nanjing {2.,nanjing 2.0093,china 4College of mathematics and physics,nanjing {2. of Posts and Telecommunications,nanjing 2.0046,china Department of mathematics East China University of Science and Technology Shanghai China school of mathematics and Computer Science Nanjing Normal University Nanjing China Center of Nonlinear Science Nanjing University Nanjing China College of mathematics and physics Nanjing University of Posts and Telecommunications Nanjing China

We define the relative local topological pressure for any given factor map and open cover,and prove the relative local variational principle of this *** precisely,for a given factor map π:(X,T)→(Y,S) between two topological dynamical systems,an open cover U of X,a continuous,real-valued function f on X and an S-invariant measure ν on Y,we show that the corresponding relative local pressure P(T,f,U,y) satisfies sup μ∈M(X,T){ hμ(T,U|Y)+∫X f(x)dμ(x) :πμ=ν}=∫Y P(T,f,U,y)dν(y),where M(X,T) denotes the family of all T-invariant measures on ***,the supremum can be attained by a T-invariant measure.

关键词： pressure conditional entropy relative local variational principle

维普期刊数据库

Travelling wave solutions of a generalized Camassa-Holm-Degasperis-Procesi equation

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 555-572页

作者： DENG ShengFu1, GUO BoLing2.& WANG TingChun2.3 1Department of mathematics, Zhanjiang Normal university, Zhanjiang 52.048, {2. 2.nstitute of Applied physics and Computational mathematics, Beijing 100088, {2. 3 College of Math and physics, nanjing university of information Science and technology, nanjing 2.0044, {2. Department of mathematics Zhanjiang Normal University Zhanjiang China Institute of Applied physics and Computational mathematics Beijing China College of Math and physics Nanjing University of Information Science and Technology Nanjing China

The travelling wave solutions of a generalized Camassa-Holm-Degasperis-Procesi equation ut-uxxt + (1 + b)umux = buxuxx + uuxxx are considered where b > 1 and m are positive integers. The qualitative analysis methods of planar autonomous systems yield its phase portraits. Its soliton wave solutions, kink or antikink wave solutions, peakon wave solutions, compacton wave solutions, periodic wave solutions and periodic cusp wave solutions are obtained. Some numerical simulations of these solutions are also given.

关键词： homoclinic orbits heteroclinic orbits peakon wave solutions compacton wave solutions periodic cusp wave solutions

维普期刊数据库

Two possible mechanisms for vortex self-organization

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2006年第2期49卷 202-211页

作者： LUO Zhexian2. ZHOU Xiuji1 & GAO Shouting3 1. Chinese Academy of Meteorological Sciences, Beijing 100081, china 2. Department of Space information Science, {2. university of information Science and technology, nanjing 2.0044, china 3. Institute of Atmospheric physics, Chinese Academy of Sciences, Beijing 10002., china Department of Environmental Science Nanjing University of Information Science and Technology Nanjing China Chinese Academy of Meteorological Sciences Beijing China Institute of Atmospheric physics Chinese Academy of Sciences Beijing China

The vortex self-organization is investigated in this paper by four groups of numerical experiments within the framework of quasi-geostrophic model, and based on the experimental results two types of possible mechanisms for vortex self-organization are suggested. The meso-scale to-pography may enable separated vortices to merge into a larger scale vortex; and the interaction of meso-γ and meso-β scale systems may make separated vortices to self organize a typhoon-like vor-tex circulation.

关键词： vortex, self-organization, meso-scale topography, interaction of different scales.

维普期刊数据库

MMSE relay precoding schemes based on quantization error compensation for multi-relay system

在线全文

学校读者我要写书评

暂无评论

Science china(information Sciences) 2010年第12期53卷 2548-2556页

作者： LI Ting 1,2.& YANG LuXi 2.1 College of Communication and information Engineering,nanjing {2. of Posts and Telecommunications,nanjing 2.0003,china 2.school of information Science and Engineering,Southeast {2.,nanjing 2.0096,china College of Communication and information Engineering Nanjing University of Posts and Telecommunications Nanjing China school of information Science and Engineering Southeast University Nanjing China

In order to deal with the performance degradation resulting from the quantization error,this paper introduces the statistics of Grassmannian codebook's quantization error into relay precoding design for multirelay *** on the two-step MMSE optimization algorithm for relay precoding and receiver equalizing with full feedback under QoS requirements,we first propose a limited feedback two-step MMSE optimization scheme for relay precoding and receiver equalizing with quantization error compensation,and then we propose a limited feedback joint MMSE optimization scheme for relay precoding and receiver equalizing with quantization error compensation subject to a global power constraint at the output of *** results show that the proposed joint MMSE optimization scheme with quantization error compensation has a much lower bit-error rate than the two-step MMSE optimization scheme with quantization error compensation and the joint MMSE optimization scheme without quantization error compensation.

关键词： multi-relay precoding limited feedback minimum mean square error

Three-dimensional investigation of velocity skin effect in U-shaped solid armature

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 2008年第12期18卷 1565-1569页

作者： Xin Li~a Chunsheng Weng~b a school of Power Engineering,nanjing {2. of Science and technology,nanjing 2.0094,china b National Key Laboratory of Transient physics,nanjing {2. of Science and technology,nanjing 2.0094,china school of Power Engineering Nanjing University of Science and Technology Nanjing 210094 China National Key Laboratory of Transient physics Nanjing University of Science and Technology Nanjing 210094 China

A three-dimensional transient computational model is applied to investigate the velocity skin effect (VSE) in a U-shaped solid arma- *** this model,current and heat transport in the armature can be evaluated *** results show a local concentration of current and joule heating at the interface,and significant damage occurs at the edges of the *** is also observed that there is significant enhanced heating at sharp comers because of the armature *** three-dimensional model can efficiently capture the salient features of the physical phenomena at the rail-armature interface,and contribute to the development of the armature design.

关键词： Electromagnetic launch Railgun U-shaped armature Velocity skin effect Erosion

Seasonal variation of global stratosphere-troposphere mass exchange

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12期17卷 1466-1475页

作者： Guo Dong1,2. Lu Daren2.and Sun Zhaobo1(1. Institute of Atmospheric Sciences, nanjing university of {2. Science and technology, nanjing 2.0044, china 2. LAGEO, Institute of Atmospheric physics, Chinese Academy of Sciences, Beijing 10002., china) Institute of Atmospheric Sciences Nanjing University of Information Science and Technology Nanjing 210044 China LAGEO Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

By Wei formula in pressure coordinate, the stratosphere-troposphere mass exchange (STME) is diagnosed globally for 44 years from 1958 to 2.01 using the European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis datasets. Regions of mass flux into the stratosphere are found over Indonesia, bay of Bangladesh and the mid-west coast of South Africa. Compensating mass outflow from the stratosphere appears mainly over mid-latitudes near large-scale troughs. Upward and downward transport of mass at the middle and high latitudes accompany with each other. Mass flux into troposphere is stronger in autumn and winter than in spring and summer. Strong downward mass flux into the troposphere occurs in eastern Asia the whole year with nearly stable sites. Although the area of eastern Asia accounts for only 5.6% of that of the northern hemisphere (NH), its net mass exchange reaches 15.83% of that of the NH, which means that research on STME of eastern Asia is greatly important to that of the NH and even the global areas. Air across the tropopause enters more from stratosphere to troposphere than that from troposphere to stratosphere, which is possibly related with systematic bias of the assimilated datasets and with persistent rise of the tropopause height. Contributions of the mass exchange and the mass flux exchange in the NH and southern hemisphere (SH) on their latitudes increase from equator to pole, with larger contributions in the NH. Mass exchange and mass flux exchange per areas at high latitudes are larger than that at low latitudes, which means greater mass exchange efficiency at high latitudes.

关键词： stratosphere troposphere mass exchange seasonal variation.