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International MultiConference of Engineers and Computer Scientists, IMECS 2014

作者： Chankong, Kittiphong Intiyot, Boonyarit Sinapiromsaran, Krung Applied Mathematics and Computational Science Program Department of Mathematics and Computer Science Faculty of Science Chulalongkorn University Bangkok Thailand

ISBN: (纸本)9789881925336

The simplex algorithm is a widely used method for solving a linear programming problem (LP) which is first presented by George B. Dantzig. One of the important steps of the simplex algorithm is applying an appropriate pivot rule, the rule to select the entering variable. An effective pivot rule can lead to the optimal solution of LP with the small number of iterations. In a minimization problem, Dantzig's pivot rule selects an entering variable corresponding to the most negative reduced cost. The concept is to have the maximum improvement in the objective value per unit step of the entering variable. However, in some problems, Dantzig's rule may visit a large number of extreme points before reaching the optimal solution. In this paper, we propose a pivot rule that could reduce the number of such iterations over the Dantzig's pivot rule. The idea is to have the maximum improvement in the objective value function by trying to block a leaving variable that makes a little change in the objective function value as much as possible. Then we test and compare the efficacy of this rule with Dantzig' original rule.

关键词： Linear programming

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Pressure dependence of the structure and electronic properties of Sr3Ir2O7

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Physical Review B 2016年第17期93卷 174118-174118页

作者： C. Donnerer Z. Feng J. G. Vale S. N. Andreev I. V. Solovyev E. C. Hunter M. Hanfland R. S. Perry H. M. Rønnow M. I. McMahon V. V. Mazurenko D. F. McMorrow London Centre for Nanotechnology University College London London WC1H 0AH United Kingdom Laboratory for Quantum Magnetism Ecole Polytechnique Federal de Lausanne 1015 Lausanne Switzerland Theoretical Physics and Applied Mathematics Department Ural Federal University 620002 Ekaterinburg Russia Computational Materials Science Unit National Institute for Materials Science 1-1 Namiki Tsukuba Ibaraki 305-0044 Japan SUPA School of Physics and Astronomy and Centre for Science at Extreme Conditions The University of Edinburgh Mayfield Road Edinburgh EH9 3JZ United Kingdom European Synchrotron Radiation Facility CS 40220 38043 Grenoble Cedex 9 France Research Complex at Harwell Didcot Oxon OX11 0FA United Kingdom

We study the structural evolution of Sr3Ir2O7 as a function of pressure using x-ray diffraction. At a pressure of 54 GPa at room temperature, we observe a first-order structural phase transition, associated with a change from tetragonal to monoclinic symmetry and accompanied by a 4% volume collapse. Rietveld refinement of the high-pressure phase reveals a novel modification of the Ruddlesden-Popper structure, which adopts an altered stacking sequence of the perovskite bilayers. As the positions of the oxygen atoms could not be reliably refined from the data, we use density functional theory (local-density approximation+U+spin orbit) to optimize the crystal structure and to elucidate the electronic and magnetic properties of Sr3Ir2O7 at high pressure. In the low-pressure tetragonal phase, we find that the in-plane rotation of the IrO6 octahedra increases with pressure. The calculations further indicate that a bandwidth-driven insulator-metal transition occurs at ∼20 GPa, along with a quenching of the magnetic moment. In the high-pressure monoclinic phase, structural optimization resulted in complex tilting and rotation of the oxygen octahedra and strongly overlapping t2g and eg bands. The t2g bandwidth renders both the spin-orbit coupling and electronic correlations ineffectual in opening an electronic gap, resulting in a robust metallic state for the high-pressure phase of Sr3Ir2O7.

关键词： Metal-insulator transition Pressure effects Structural properties Oxides Perovskites Pressure techniques X-ray diffraction

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Incompressible Magnetohydrodynamic Kelvin-Helmholtz Instability with Continuous Profiles

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Chinese physics Letters 2014年第3期31卷 23-26页

作者： ZHAO Kai-Ge WANG Li-Feng YE Wen-Hua WU Jun-Feng LI Ying-Jun State Key Laboratory for Ceomechanics and Deep Underground Engineering China University of Mining and Technology Beijing 100083 Institute of Applied Physics and Computational Mathematics Beijing 100094 HEDPS Center for Applied Physics and Technology Peking University Beijing 100871 Department of Physic Zhejiang University Hangzhou 310027

Effects of a continuous magnetic field in the direction of streaming on the incompressible Kelvin–Helmholtz instability （KHI） are investigated by solving the linear ideal magnetohydrodynamic equations. It is found that the frequency of the KHI is not influenced by the magnetic field. The magnetic field strength effect decreases the linear growth of the KHI, while the magnetic field gradient scale length effect increases its linear growth. The KHI can even be completely suppressed when the magnetic field is strong enough. The linear growth rate approaches a maximum when the magnetic field gradient scale length is large enough.

关键词： MAGNETIC fields RESEARCH MAGNETOHYDRODYNAMICS MAGNETIC confinement MAGNETISM physics research

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Probing dynamic information and spatial structure of Rydberg wave packets by harmonic spectra in a few-cycle laser pulse

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Physical Review A 2015年第4期91卷 043403-043403页

作者： Jigen Chen Yujun Yang Jing Chen Bingbing Wang Department of Physics and Materials Engineering Taizhou University Taizhou 318000 China Institute of Atomic and Molecular Physics Jilin University Changchun 130012 China Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy Jilin University Changchun 130012 China Key Laboratory of High Energy Density Physics Simulation CAPT Peking University Beijing 100084 China Institute of Applied Physics and Computational Mathematics Post Office Box 8009 Beijing 100088 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China

We demonstrate that the dynamic information and the spatial structure of a Rydberg wave packet formed by two neighboring Rydberg states can be simultaneously probed by harmonic spectra in a few-cycle laser pulse, where the Rydberg wave packet is produced by a pump laser field. By controlling the time delay of the pump-probe laser pulses, the harmonic spectra present a periodic variation, which directly illustrates the electron oscillation between the two neighboring Rydberg states. Specifically, by taking advantage of the periodic variation of the harmonic efficiency and the dip structure in the spectrum, one can detect the spatial characteristics and the dynamic information of the initial Rydberg wave packet.

关键词： RYDBERG states HARMONICS (Electric waves) WAVE packets LASER pulses PICOSECOND pulses ATTOSECOND pulses

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Vanishing capillarity limit of the compressible fluid models of korteweg type to the navier-stokes equations

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SIAM Journal on Mathematical Analysis 2014年第2期46卷 1633-1650页

作者： Bian, Dongfen Yao, Lei Zhu, Changjiang Institute of Applied Physics and Computational Mathematics Beijing 100088 China Center for Nonlinear Studies Department of Mathematics Northwest University Xi'an 710127 China School of Mathematics and Statistics Central China Normal University Wuhan 430079 China

In this paper, we consider the three-dimensional isentropic compressible fluid models of Korteweg type, called the compressible Navier-Stokes-Korteweg system. We mainly present the vanishing capillarity limit of the smooth solution to the initial value problem. Precisely, we first establish the uniform estimates of the global smooth solution with respect to the capillary coefficient κ. Then by the Lions-Aubin lemma, we show that the unique smooth solution of the three-dimensional Navier-Stokes-Korteweg system converges globally in time to the smooth solution of the three-dimensional Navier-Stokes system as κ tends to zero. Also, we give the convergence rate estimates for any given positive time. © 2014 Society for Industrial and applied mathematics.

关键词： Capillarity

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Effective Potentials and Morphological Transitions for Binary Black Hole Spin Precession

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Physical Review Letters 2015年第8期114卷 081103-081103页

作者： Michael Kesden Davide Gerosa Richard O’Shaughnessy Emanuele Berti Ulrich Sperhake Department of Physics The University of Texas at Dallas Richardson Texas 75080 USA Department of Applied Mathematics and Theoretical Physics Centre for Mathematical Sciences University of Cambridge Wilberforce Road Cambridge CB3 0WA United Kingdom Center for Computational Relativity and Gravitation Rochester Institute of Technology Rochester New York 14623 USA Department of Physics and Astronomy The University of Mississippi University Mississippi 38677 USA California Institute of Technology Pasadena California 91125 USA

We derive an effective potential for binary black hole (BBH) spin precession at second post-Newtonian order. This effective potential allows us to solve the orbit-averaged spin-precession equations analytically for arbitrary mass ratios and spins. These solutions are quasiperiodic functions of time: after a fixed period, the BBH spins return to their initial relative orientations and jointly precess about the total angular momentum by a fixed angle. Using these solutions, we classify BBH spin precession into three distinct morphologies between which BBHs can transition during their inspiral. We also derive a precession-averaged evolution equation for the total angular momentum that can be integrated on the radiation-reaction time and identify a new class of spin-orbit resonances that can tilt the direction of the total angular momentum during the inspiral. Our new results will help efforts to model and interpret gravitational waves from generic BBH mergers and predict the distributions of final spins and gravitational recoils.

关键词： BINARY black holes PRECESSION ANGULAR momentum (Nuclear physics) GRAVITATIONAL waves SPIN-orbit resonance

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Tunable heat conduction through coupled Fermi-Pasta-Ulam chains

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Physical Review E 2015年第1期91卷 012136-012136页

作者： Ruixia Su Zongqiang Yuan Jun Wang Zhigang Zheng Department of Physics and the Beijing-Hong Kong-Singapore Joint Centre for Nonlinear and Complex Systems (Beijing) Beijing Normal University Beijing 100875 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Key Laboratory of Enhanced Heat Transfer and Energy Conservation Ministry of Education College of Environmental and Energy Engineering Beijing University of Technology Beijing 100124 China

We conduct a study on heat conduction through coupled Fermi-Pasta-Ulam (FPU) chains by using classical molecular dynamics simulations. Our attention is dedicated to showing how the phonon transport is affected by the interchain coupling. It has been well accepted that the heat conduction could be impeded by the interchain interaction due to the interface phonon scattering. However, recent theoretical and experimental studies suggest that the thermal conductivity of nanoscale materials can be counterintuitively enhanced by the interaction with the substrate. In the present paper, by consecutively varying the interchain coupling intensity, we observed both enhancement and suppression of thermal transport through the coupled FPU chains. For weak interchain couplings, it is found that the heat flux increases with the coupling intensity, whereas in the case of strong interchain couplings, the energy transport is found to be suppressed by the interchain interaction. Based on the phonon spectral energy density method, we attribute the enhancement of the energy transport to the excited phonon modes (in addition to the intrinsic phonon modes), while the upward shift of the high-frequency phonon branch and the interface phonon-phonon scattering account for the suppressed heat conduction.

关键词： HEAT conduction MOLECULAR dynamics PHONONS -- Scattering SUBSTRATES (Biochemistry) HEAT flux

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Forced axial segregation in axially inhomogeneous rotating systems

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Physical Review E 2015年第2期92卷 022202-022202页

作者： S. González C. R. K. Windows-Yule S. Luding D. J. Parker A. R. Thornton Multi-Scale Mechanics Department of Mechanical Engineering MESA+ University of Twente P.O. Box 217 7500 AE Enschede The Netherlands School of Physics and Astronomy University of Birmingham United Kingdom B15 2TT Mathematics of Computational Science Department of Applied Mathematics MESA+ University of Twente P.O. Box 217 7500 AE Enschede The Netherlands

Controlling segregation is both a practical and a theoretical challenge. Using a novel drum design comprising concave and convex geometry, we explore, through the application of both discrete particle simulations and positron emission particle tracking, a means by which radial size segregation may be used to drive axial segregation, resulting in an order of magnitude increase in the rate of separation. The inhomogeneous drum geometry explored also allows the direction of axial segregation within a binary granular bed to be controlled, with a stable, two-band segregation pattern being reliably and reproducibly imposed on the bed for a variety of differing system parameters. This strong banding is observed to persist even in systems that are highly constrained in the axial direction, where such segregation would not normally occur. These findings, and the explanations provided of their underlying mechanisms, could lead to radical new designs for a broad range of particle processing applications but also may potentially prove useful for medical and microflow applications.

关键词： AXIAL loads SEGREGATION (Metallurgy) POSITRON emission EMISSION tomography GRANULAR materials

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Covalency effects reflected in the magnetic form factor of low-dimensional cuprates

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Physical Review B 2015年第24期92卷 245113-245113页

作者： V. V. Mazurenko I. V. Solovyev A. A. Tsirlin Theoretical Physics and Applied Mathematics Department Ural Federal University 620002 Ekaterinburg Russia Computational Materials Science Unit National Institute for Materials Science 1-1 Namiki Tsukuba Ibaraki 305-0044 Japan National Institute of Chemical Physics and Biophysics 12618 Tallinn Estonia Experimental Physics VI Center for Electronic Correlations and Magnetism Institute of Physics University of Augsburg 86135 Augsburg Germany

We analyze the magnetic form factor of Cu2+ in low-dimensional quantum magnets by taking the metal-ligand hybridization into account explicitly. In this analysis, we use the form of magnetic Wannier orbitals, derived from first-principles calculations, and identify contributions of different atomic sites. We demonstrate that covalency of metal-ligand interactions has a strong effect on the magnetic form factor and must be taken into account in the evaluation of magnetic neutron scattering. The use of covalent form factors facilitates quantitative description of inelastic neutron-scattering data for BaCuSi2O6 that would not be possible when ionic form factors are used. We also propose easy-to-use approximations of the partial orbital contributions to the magnetic form factor in order to give microscopic explanation for the results obtained in previous first-principles studies.

关键词： CUPRATES MAGNETIC forming DIMENSIONAL analysis COPPER ions NUMERICAL calculations BARIUM compounds

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R-matrix calculations of the photoionization cross sections of Ti2+

R-matrix calculations of the photoionization cross sections ...

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第十八届全国原子与分子物理学术会议

作者： Jun-Wen Gao Xiao-Ying Han Jian-Guo Wang Jia-Ming Li Collaborative Innovation Center of Quantum Matter Beijing100084China Department of Physics and Center for Atomic and Molecular Nanosciences Tsinghua UniversityBeijing100084China Key Laboratory for Laser Plasmas(Ministry of Education)and Department of Physics and Astronomy Shanghai Jiao Tong UniversityShanghai200240China Institute of Applied Physics and Computational Mathematics Beijing100088China

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