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A characterization for a graphic sequence to be potentially C_r-graphic

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Science china Mathematics 2010年第11期53卷 2893-2905页

作者： YIN JianHua Department of Mathematics, College of Information Science and Technology, Hainan university, Haikou 5702.8, china 1. Department of Mathematics College of Information Science and Technology Hainan University Haikou 570228 China

Let r 3, n r and π = (d1, d2. . . . , dn) be a graphic sequence. If there exists a simple graph G on n vertices having degree sequence π such that G contains Cr (a cycle of length r) as a subgraph, then π is said to be potentially Cr-graphic. Li and Yin (2.04) posed the following problem: characterize π = (d1, d2. . . . , dn) such that π is potentially Cr-graphic for r 3 and n r. Rao and Rao (1972. and Kundu (1973) answered this problem for the case of n = r. In this paper, this problem is solved completely.

关键词： graph cycle degree sequence

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Simulation of gravity wave instability and the formation of large winds and shears in the mesosphere and lower thermosphere

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Simulation of gravity wave instability and the formation of ...

第十四届全国日地空间物理学术研讨会

作者： Xiao Liu1, 2.Jiyao Xu1 Han -Li Liu3 Wei Yuan1 (1 State Key Laboratory of Space Weather, Center for Space Science and Applied research, Chinese Academy of Sciences, Beijing, china, 100190) (2.College of Mathematics and Information Science, Henan Normal {2., Xinxiang, china) (3 High Altitude Observatory, national Center for Atmospheric research, Boulder, Colorado, USA)

Large winds and wind shears in the mesosphere and lower thermosphere （MLT） region have been observed for decades and by various techniques （1）. It is necessary to investigate the causes of the large winds and wind shears （2.. A high resolution parallel numerical model is developed to simulate the propagation of gravity waves （GWs） in a compressible atmosphere. The winds and wind shears are determined by the wave perturbation, the mean flow change induced by wave breaking and/or dissipation, as well as the vertical scale of the waves. In particular, the accelerated mean winds in the direction of the GWs horizontal phase velocity decrease the GWs vertical wavelength, and increase the large wind shears. As a result, the positive feedback between GWs momentum deposition, mean wind acceleration, and the decreasing vertical wavelength induces the large wind shears in the MLT region. The comparative studies show that background temperature and the height of mesopause can affect the time and height of GWs breaking, the accelerated mean winds and total wind shears. In addition, decreasing diffusion in the numerical simulations generally increases the magnitude of mean winds and total wind shears. When GWs with different wavelengths propagate in the tidal background with different initial tidal phases, their interactions result in a strong correlation between the initial tidal phase and the large wind shears and may be responsible for the local time dependence of the occurrence of the large wind shears observed by Yue et al.（3）. Moreover, the tidal modulation effect decreases （but does not disappear） with the increasing vertical wavelength of GWs. In addition, large wind shears occur at two heights separated approximately by the vertical wavelength of the tide and just below the maximum of positive tidal wind shear for GWs with vertical wavelengths longer than 10 km.

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The Chinese Renminbi:In Transition to a Managed Float

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World Economy & china 2000年第3期8卷 3-15页

作者： Fred Hu Ph.D.(Professor and Director,national Center for Economic research, Tsinghua {2.)

china is likely to introduce greater flexibility in its nompinal exchange rate from 2.00 *** main rationale behind such a policy shift would the need to better handle shocks to china'sbalance of payments, particularly after china' entry to the World Trade Organization (WTO)The policy shift would be timed to coincide with Asia 's recovery becoming more entrenched. Themove toward greater flexibility is unlikely to be preceded, or accompanied by uncontrolled, substantial renminbi weakening or persistently high volatility over an extended *** will be an orderly exit from the current de facto peg, and a smooth transition to a managed *** policy shift should not entail a dislodging of the Hong Kong dollar peg. The impact oon the rest of Asia should also be relatively muted.

关键词： World In MIT IMF

维普期刊数据库

An overview of computational photography

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Science china(Information Sciences) 2012年第6期55卷 1229-1248页

作者： SUO JinLi,JI XiangYang & DAI QiongHai Department of Automation,Tsinghua university,Beijing 100084,china 1. Department of Automation Tsinghua University Beijing 100084 China

Computational photography is an emerging multidisciplinary *** the last two decades,it has integrated studies across computer vision,computer graphics,signal processing,applied optics and related *** are exploring new ways to break through the limitations of traditional digital imaging for the benefit of photographers,vision and graphics researchers,and image processing *** to much effort in various associated fields,the large variety of issues related to these new methods of photography are described and discussed extensively in this *** give the reader the full picture of the voluminous literature related to computational photography,this paper briefly reviews the wide range of topics in this new field,covering a number of different aspects,including:(i) the various elements of computational imaging systems and new sampling and reconstruction mechanisms;(ii) the different image properties which benefit from computational photography,*** of field,dynamic range;and(iii) the sampling subspaces of visual scenes in the real *** on this systematic review of the previous and ongoing work in this field,we also discuss some open issues and potential new directions in computational *** paper aims to help the reader get to know this new field,including its history,ultimate goals,hot topics,research methodologies,and future directions,and thus build a foundation for further research and related developments.

关键词： computational photography computational imaging plenoptic function light field

A verifiable low-level concurrent programming model based on colored Petri nets

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Science china(Information Sciences) 2011年第10期54卷 2013-2027页

作者： WANG ShengYuan & DONG Yuan Department of Computer Science and Technology,Tsinghua university,Beijing 100084,china 1. Department of Computer Science and Technology Tsinghua University Beijing 100084 China

Concurrent programs written in a machine-level language are being used in many areas,but the verification of such programs brings various new challenges to the programming language *** of existing contributions on verifying the safety properties of concurrent programs are for high-level languages,specifications,or calculi in the *** to the lack of abstraction at a low level,additional work is needed to extend these methods to machine-level *** paper describes an approach to integrate Petri nets into low-level concurrent programs to form a new programming model (abstract machine).A program in the programming model is a restricted version of colored Petri net,with transitions colored by assembly codes for machine-level threads,and places colored by shared data consisting of memory locations or *** analysis and verification approaches for usual Petri nets can be applied indirectly for such a low-level concurrent program.

关键词： low-level concurrent programs colored Petri nets abstract machine verification

Molecular and quantum mechanical studies on the monomer recognition of a highly-regular β-helical antifreeze protein

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Science china Chemistry 2004年第1期47卷 34-40页

作者： YANG Zuoyin, JIA Zongchao, LIU Ruozhuang & CHEN GuangjuDepartment of Chemistry, Beijing Normal university, Beijing 100875, china Faculty of Science, Beijing university of Chemical Technology, Beijing 10002., china Department of Biochemistry, Queen’s university, Kingston, Ontario K7L 3N6, Canada 1. Department of Chemistry Beijing Normal University 100875 Beijing China 2. Faculty of Science Beijing University of Chemical Technology 100029 Beijing China 3. Department of Biochemistry Queen? University K7L 3N6 Kingston Ontario Canada

The possible interaction models for an antifreeze protein from Tenebrio molitar (TmAFP) have been systematically studied using the methods of molecular mechanics, molecular dynamics and quantum chemistry. It is hoped that these approaches would provide insights into the nature of interaction between protein monomers through sampling a number of interaction possibilities and evaluating their interaction energies between two monomers in the course of recognition. The results derived from the molecular mechanics indicate that monomer? β-sheets would be involved in interaction area and the side chains on two p-faces can match each other at the two-dimensional level. The results from molecular mechanics and ONIOM methods show that the strongest interaction energy could be gained through the formation of H-bonds when the twoβ-sheets are involved in the interaction model. Furthermore, the calculation of DFT and analysis of van der Waals bond charge density confirm further that recognition between the two TCTs mainly depends on inter-molecular hydroxyls. Therefore, our results demonstrate that during the course of interaction the most favorable association of TmAFPs is via their β-sheets.

关键词： antifreeze protein, recognition, dynamics simulation, molecular mechanics, quantum chemistry.

维普期刊数据库

A Theory for Mixed Vortex Rossby- Gravity Waves in Tropical Cyclones

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A Theory for Mixed Vortex Rossby- Gravity Waves in Tropical ...

第七次全国动力气象学术会议

作者： Han-Cheng Lu~1,Wei Zhong~1,and Da-Lin Zhang~2.1 Institute of Meteorology,PLA university of Science and Technology,nanjing 2.1101 2.Department of Atmospheric and Oceanic Science,university of Maryland,College Park,Maryland 2.742

＜正＞Previou;studies have developed theories of vortex-Rossby waves（VRW）and inertial gravity waves（IGWs）to explain the propagation of spiral rainbands and the development of dynamical instability in tropical cyclones（TCs）.In the present work, a theory for azimuthally propagating mixed vortex-Rossby-inertial-gravity waves

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The Absolute and Convective Secondary Instabilities in the Conduction Regime

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communications in Nonlinear Science and Numerical Simulation 1999年第1期4卷 34-38页

作者： Jianjun TAO and Dachun YAN (Dept. of Mechanics & Engineering Sciences,Peking university, Beijing 100871, china) Dept. of Mechanics & Engineering Sciences Peking University Beijing 100871 China

Convective and absolute instabilities in the conduction regime of a vertical heated slot are investigated. It is found that in a large range of Prandtl number (0 12. a secondary instability appears with stationary mo... 详细信息

Convective and absolute instabilities in the conduction regime of a vertical heated slot are investigated. It is found that in a large range of Prandtl number (0 2.00) different instability mode has different characteristics: the stationary mode is absolute instability while the traveling wave mode is convective instability. When Pr > 12. a secondary instability appears with stationary mode, and it is proven that even at large Prandtl numbers the stationary mode still exists.

关键词： absolute instability convective instability conduction regime

Effects of the grain size distribution on the temperature-dependent magnetic susceptibility of magnetite nanopartieles

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Effects of the grain size distribution on the temperature-de...

中国科学院地质与地球物理研究所第十届(2.10年度)学术年会

作者： ZHAO XiangYu~(1,2. & LIU QingSong~(1*) 1 Paleomagnetism and Geochronology Laboratory(SKL-LE),Institute of Geology and Geophysics,Chinese Academy of Sciences, Beijing 10002.,china 2.Graduate university of Chinese Academy of Sciences,Beijing 100049,china

Magnetite is an important magnetic remanence carrier in natural samples and therefore is of great interest in paleo-,rock-,and environmental *** magnetic properties of magnetite depend on many factors,e.g.,concentration and grain size distribution(GSD).In this study,we theoretically investigated the temperature-dependent susceptibility(TDS)of magnetite nanoparticles with a lognormal *** show that the TDS is affected highly by the GSD mainly in three ***, the unblocking process becomes smoother with the increase of distribution width,characterizing as a wider Hopkinson peak on the TDS ***,the blocking temperature increases with the increase of the median diameter or/and the distribution ***,the maximum susceptibility decreases with the increase of distribution width,and has a logarithmic function relation with the standard deviation of the *** a case study,this model was further applied to the thermal products of the Chinese loess/paleosol samples to determine the granulometry of newly-formed magnetite upon heating based on TDS *** results demonstrate the fidelity and feasibility of this method to determine the GSD of nano-sized magnetic particles.

关键词： Neel theory temperature dependence of susceptibility grain size distribution