检索结果-内蒙古大学图书馆

Erratum: “Effect of dimensionality on the continuum percolation of overlapping hyperspheres and hypercubes. II. Simulation results and analyses” [J. Chem. Phys. 137, 074106 (2012)]

引用

The Journal of Chemical Physics 2014年第15期141卷

作者： S. Torquato Y. Jiao 1Department of Chemistry Department of Physics Princeton Center for Theoretical Science and Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA 2Princeton Institute for the Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA

In Table I and the caption of Fig. 8 of Ref. 1, the numerical value of the percolation threshold ηc of three-dimensional overlapping spheres as determined via t

关键词：

来源：评论

学校读者我要写书评

暂无评论

Current-driven homogenization and effective medium parameters for finite samples

引用

Physical Review B 2013年第12期88卷 125131-125131页

作者： Vadim A. Markel Igor Tsukerman Departments of Radiology and Bioengineering and the Graduate Group in Applied Mathematics and Computational Science University of Pennsylvania Philadelphia Pennsylvania 19104 USA Department of Electrical and Computer Engineering The University of Akron Ohio 44325-3904 USA

Reflection and refraction of electromagnetic waves by artificial periodic composites (metamaterials) can be accurately modeled by an effective medium theory only if the boundary of the medium is explicitly taken into account and the two effective parameters of the medium (the index of refraction and the impedance) are correctly determined. Theories that consider infinite periodic composites do not satisfy the above condition. As a result, they can not model reflection and transmission by finite samples with the desired accuracy and are not useful for design of metamaterial-based devices. As an instructive case in point, we consider the “current-driven” homogenization theory, which has recently gained popularity. We apply this theory to the case of one-dimensional periodic medium wherein both exact and homogenization results can be obtained analytically in closed form. We show that, beyond the well-understood zero-cell limit, the current-driven homogenization result is inconsistent with the exact reflection and transmission characteristics of the slab.

关键词： ELECTROMAGNETISM MAGNETIC fields METAMATERIALS MAGNETOELECTRIC effect REFRACTION (Optics)

来源：评论

学校读者我要写书评

暂无评论

Angular-Momentum-Dependent Orbital-Free Density Functional Theory

引用

Physical Review Letters 2013年第6期111卷 066402-066402页

作者： Youqi Ke Florian Libisch Junchao Xia Lin-Wang Wang Emily A. Carter Department of Mechanical and Aerospace Engineering Program in Applied and Computational Mathematics and Andlinger Center for Energy and the Environment Princeton University Princeton New Jersey 08544 USA Material Science Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA

Orbital-free (OF) density functional theory (DFT) directly solves for the electron density rather than the wave function of many electron systems, greatly simplifying and enabling large scale first principles simulations. However, the required approximate noninteracting kinetic energy density functionals and local electron-ion pseudopotentials severely restrict the general applicability of conventional OFDFT. Here, we present a new generation of OFDFT called angular-momentum-dependent (AMD)-OFDFT to harness the accuracy of Kohn-Sham DFT and the simplicity of OFDFT. The angular momenta of electrons are explicitly introduced within atom-centered spheres so that the important ionic core region can be accurately described. In addition to conventional OF total energy functionals, we introduce a crucial nonlocal energy term with a set of AMD energies to correct errors due to the kinetic energy density functional and the local pseudopotential. We find that our AMD-OFDFT formalism offers substantial improvements over conventional OFDFT, as we show for various properties of the transition metal titanium.

关键词： DENSITY functional theory ELECTRON density KINETIC energy PSEUDOPOTENTIAL method TRANSITION metal compounds ELECTRON-ion collisions

来源：评论

学校读者我要写书评

暂无评论

Collimation of Energetic Electrons from a Laser-Target Interaction by a Magnetized Target Back Plasma Preformed by a Long-Pulse Laser

引用

Physical Review Letters 2014年第21期112卷 215003-215003页

作者： H. B. Zhuo Z. L. Chen Z. M. Sheng M. Chen T. Yabuuchi M. Tampo M. Y. Yu X. H. Yang C. T. Zhou K. A. Tanaka J. Zhang R. Kodama College of Science National University of Defense Technology Changsha 410073 People’s Republic of China Graduate School of Engineering Osaka University 2-1 Yamada-oka Suita Osaka 565-0871 Japan MOE Key Laboratory for Laser Plasmas and Department of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 People’s Republic of China Department of Physics SUPA University of Strathclyde Glasgow G4 0NG United Kingdom Institute of Laser Engineering Osaka University 2-6 Yamada-oka Suita Osaka 565-0871 Japan Institute for Fusion Theory and Simulation and Department of Physics Zhejiang University Hangzhou 310027 People’s Republic of China Institute for Theoretical Physics I Ruhr University Bochum D-44780 Germany Institute of Applied Physics and Computational Mathematics Beijing 100094 People’s Republic of China

It is demonstrated experimentally and by numerical simulations that the presence of a long-pulse-laser-created back plasma on the target backside can focus the relativistic electrons produced by short-pulse laser interaction with the front of a solid target. Comparing this to that without the back plasma, the number density of the fast electrons is increased by one order of magnitude, and their divergence angle is reduced fivefold. The effect is attributed to the absence of the backside sheath electric field and the collimation effect of the megagauss self-generated baroclinic magnetic field there. Such an acceleration scheme can be useful to applications requiring high-energy and charge-density electron bunches, such as fast ignition in inertial fusion.

关键词： COMPUTER simulation LASER pulses ELECTRONS PLASMA acceleration ACCELERATION (Mechanics)

来源：评论

学校读者我要写书评

暂无评论

Quasienergy resonance in a dynamic Wannier-Stark ladder

引用

Physical Review B 2013年第20期87卷 205305-205305页

作者： Yuya Nemoto Ken-ichi Hino Nobuya Maeshima Doctoral Program in Frontier Science Graduate School of Pure and Applied Sciences University of Tsukuba Tsukuba Ibaraki 305-8573 Japan Division of Materials Science Faculty of Pure and Applied Sciences University of Tsukuba Tsukuba 305-8573 Japan Center for Computational Sciences University of Tsukuba Tsukuba 305-8577 Japan

We examine a continuum effect of a dynamic Wannier-Stark ladder (DWSL) driven by a cw laser—with Fac and ω as amplitude and frequency, respectively—by means of an excess density of states (DOS), ρ(ex)(E), closely related to the more familiar DOS and proportional to the lifetime of a resonance state. It is mathematically shown that ρ(ex)(E) is governed by three different physical mechanisms: the single-channel resonance mechanism, the multichannel nonresonance mechanism, and the multichannel resonance mechanism. The last mechanism becomes more important with the increase in Fac. The effect of the interchannel interaction is maximized when the ratio of a Bloch frequency to ω, represented as η, equals unity. In the actual calculations based on the R-matrix Floquet theory, it is revealed that, in a large-Fac region, ρ(ex)(E) for η=1 shows a complicated spectral structure composed of a couple of newly growing peaks, in contrast to ρ(ex)(E) for η=3 which just shows a monotonic change of a single spectral peak. It is speculated that the pronounced feature of the former spectra is attributed to the Fano-like multichannel resonance mechanism, whereas the feature of the latter case is attributed to the multichannel nonresonance mechanism.

关键词： WANNIER-stark effect DENSITY of states RESONANCE R-matrices FLOQUET theory

来源：评论

学校读者我要写书评

暂无评论

AMUSE: Empowering Users for Cost-Aware Offloading with Throughput-Delay Tradeoffs

AMUSE: Empowering Users for Cost-Aware Offloading with Throu...

引用

IEEE INFOCOM Conference

作者： Youngbin Im Carlee Joe-Wong Sangtae Ha Soumya Sen Ted "Taekyoung" Kwon Mung Chiang School of Computer Science and Engineering Seoul National University Seoul Korea Program in Applied and Computational Mathematics Princeton University Princeton NJ USA Department of Electrical Engineering Princeton University Princeton NJ USA

ISBN: (纸本)9781467359443

Mobile users face a tradeoff between cost, through-put, and delay in making their offloading decisions. To navigate this tradeoff, we propose AMUSE (Adaptive bandwidth Management through USer-Empowerment), a practical, cost-aware WiFi offloading system that takes into account a user's throughput-delay tradeoffs and cellular budget constraint. Based on predicted future usage and WiFi availability, AMUSE decides which applications to offload to what times of the day. To practically enforce the assigned rate of each TCP application, we introduce a receiver-side TCP bandwidth control algorithm that adjusts the rate by controlling the TCP advertisement window from the user side. We implement AMUSE on Windows 7 tablets and evaluate its effectiveness with 3G and WiFi usage data obtained from a trial with 25 mobile users. Our results show that AMUSE improves user utility.

关键词： tradeoffs UNLOADING Wi-Fi third generation rate control

来源：评论

学校读者我要写书评

暂无评论

Laser-induced Fano resonance in semiconductor superlattice

引用

AIP Conference Proceedings 2013年第1期1566卷 514-515页

作者： N. Maeshima K. Yamada K. Hino Center for Computational Sciences University of Tsukuba Tsukuba 305-8577 Japan and Division of Materials Science University of Tsukuba Tsukuba 305-8573 Japan Doctoral Program in Materials Science Graduate School of Pure and Applied Sciences University of Tsukuba Tsukuba 305-8573 Japan Division of Materials Science University of Tsukuba Tsukuba 305-8573 Japan and Center for Computational Sciences University of Tsukuba Tsukuba 305-8577 Japan

We study excitonic Floquet states in semiconductor superlattices driven by a monochromatic laser. Optical absorption spectra are calculated by using the R-matrix propagation method, and the obtained results show the excitonic Fano resonance structure induced by the laser field. Further, physical quantities related to this resonance, such as an asymmetry parameter and a resonance width, show clear dependence on laser strength.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Nearly hyperuniform network models of amorphous silicon

引用

Physical Review B 2013年第24期87卷 245204-245204页

作者： Miroslav Hejna Paul J. Steinhardt Salvatore Torquato Department of Physics Princeton University Princeton New Jersey 08544 USA Princeton Center for Theoretical Science Princeton University Princeton New Jersey 08544 USA Department of Chemistry Princeton Institute for the Science and Technology of Materials and Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA

We introduce the concept of nearly hyperuniform network (NHN) structures as alternatives to the conventional continuous random network (CRN) models for amorphous tetrahedrally coordinated solids, such as amorphous silicon (a-Si). A hyperuniform solid has a structure factor S(k) that approaches zero as the wavenumber k→0. We define a NHN as an amorphous network whose structure factor S(k→0) is smaller than the liquid value at the melting temperature. Using a novel implementation of the Stillinger-Weber potential for the interatomic interactions, we show that the energy landscape for a spectrum of NHNs includes a sequence of local minima with an increasing degree of hyperuniformity [smaller S(k→0)] that is significantly below the frozen-liquid value and that correlates with other measurable features in S(k) at intermediate and large k and with the width of the electronic band gap.

关键词： SPECTRUM analysis AMORPHOUS silicon WAVENUMBER INTERATOMIC angles ELECTRONIC band structure

来源：评论

学校读者我要写书评

暂无评论

Efficient linear programming algorithm to generate the densest lattice sphere packings

引用

Physical Review E 2013年第6期87卷 063303-063303页

作者： Étienne Marcotte Salvatore Torquato Department of Physics Princeton University Princeton New Jersey 08544 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA Princeton Institute of the Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA

Finding the densest sphere packing in d-dimensional Euclidean space Rd is an outstanding fundamental problem with relevance in many fields, including the ground states of molecular systems, colloidal crystal structures, coding theory, discrete geometry, number theory, and biological systems. Numerically generating the densest sphere packings becomes very challenging in high dimensions due to an exponentially increasing number of possible sphere contacts and sphere configurations, even for the restricted problem of finding the densest lattice sphere packings. In this paper we apply the Torquato-Jiao packing algorithm, which is a method based on solving a sequence of linear programs, to robustly reproduce the densest known lattice sphere packings for dimensions 2 through 19. We show that the TJ algorithm is appreciably more efficient at solving these problems than previously published methods. Indeed, in some dimensions, the former procedure can be as much as three orders of magnitude faster at finding the optimal solutions than earlier ones. We also study the suboptimal local density-maxima solutions (inherent structures or “extreme” lattices) to gain insight about the nature of the topography of the “density” landscape.

关键词： LINEAR programming BIOLOGICAL systems COLLOIDAL crystals CODING theory DISCRETE geometry NUMBER theory

来源：评论

学校读者我要写书评

暂无评论

Novel linear algebraic theory and one-hundred-million-atom quantum material simulations on the K computer 1

Novel linear algebraic theory and one-hundred-million-atom q...

引用

1st International Workshop on computational science and Engineering, IWCSE 2013

作者： Hoshi, Takeo Sogabe, Tomohiro Miyata, Takafumi Lee, Dongjin Zhang, Shao-Liang Imachi, Hiroto Kawai, Yoshifumi Akiyama, Yohei Yamazaki, Keita Yokoyama, Seiya Department of Applied Mathematics and Physics Tottori University Koyama Minami Tottori680-8550 Japan 5 Sanbancho Chiyoda-ku Tokyo102-0075 Japan Graduate School of Information Science and Technology Aichi Prefectural University 1522-3 Ibaragabasama Kumabari Nagakute-cho Aichi-gun Aichi480-1198 Japan Department of Computational Science and Engineering Nagoya University Furo-cho Chikusa-ku Nagoya464-8603 Japan Center for Research and Development of Higher Education University of Tokyo Bunkyo-ku Tokyo113-8656 Japan

The present paper gives a review of our recent progress and latest results for novel linear-algebraic algorithms and its application to large-scale quantum material simulations or electronic structure calculations. The algorithms are Krylov-subspace (iterative) solvers for generalized shifted linear equations, in the form of (zS-H)x = b, in stead of conventional generalized eigen-value equation. The method was implemented in our order-N calculation code ELSES (http://***/) with modelled systems based on ab initio calculations. The code realized one-hundred-million-atom, or 100-nm-scale, quantum material simulations on the K computer in a high parallel efficiency with up to all the built-in processor cores. The present paper also explains several methodological aspects, such as use of XML files and 'novice' mode for general users. A sparse matrix data library in our real problems (http://***/matrix/) was prepared. Internal eigen-value problem is discussed as a general need from the quantum material simulation. The present study is a interdisciplinary one and is sometimes called 'Application-Algorithm-Architecture co-design'. The co-design will play a crucial role in exa-scale scientific computations. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.

关键词： Iterative methods

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：