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Full relativistic calculations of energy levels and oscillator strengths up to autoionization region of atomic fluorine

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Journal of physics: Conference Series 2012年第2期388卷

作者： Qing Bo Gao Xiang Yan Jun Li Jiaming Department of Physics and Center for Atomic and Molecular Nanosciences Tsinghua University Beijing 100084 China Key Laboratory for Laser Plasmas and Department of Physics Shanghai Jiao Tong University Shanghai 200240 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China

Based on a well optimized quasi-complete basis sets, full relativistic calculations have been performed on the energy levels of 2p4ns, np, nd (n=3, 4) states of atomic fluorine up to higher than the first ionization potential corresponding to F+ (3P2). In addition, the oscillator strengths for transitions from 2p4(1D)4s 2D and 2p4(1S)3s 2S to 2p5 2P3/2 are given.

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Study on the measurement of the deformation of solid material in infrared radiation imaging

Study on the measurement of the deformation of solid materia...

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International Conference on Electronics and Optoelectronics

作者： Cheng, Tao Teng, Ai-Ping Wang, Fang Zhang, Guang-Cai Zhang, Yong-Jun State Key Laboratory for Geo-Mechanics and Deep Underground Engineering China University of Mining and Technology Beijing China Beijing China Institute of Applied Physics and Computational Mathematics China Academy of Engineering Physics Beijing China Department of Mathematics-Physics Qingdao Technological University Shandong China

ISBN: (纸本)9781612842738

Based on the thermodynamics and plastoelasticity, mechanics of the infrared radiation of solid material was investigated and theoretical explanation was given. The constitutive relation between temperature and principal strains was obtained. According to the theory we simulated the infrared radiation temperature field of the solid material subjected to external loading. Calculation results were in good agreement with experimental results, which verifying the validity of the theory and the feasibility of the measurement of deformation using infrared radiation imaging. © 2011 IEEE.

关键词： Temperature

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Nucleation-Initiated Solidification of Thin Si Films

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MRS Online Proceedings Library 2011年第1期979卷 1-6页

作者： S. Hazair P. C. van der Wilt Y. Deng U. J. Chung A. B. Limanov James S. Im Program of Materials Science Department of Applied Physics and Applied Mathematics Columbia University New York USA

Thin Si films on SiO2 that are completely melted by pulsed laser irradiation cool rapidly and eventually solidify via nucleation and growth of solids. It has been observed that a variety of solidified microstructures can be obtained, depending primarily (but not exclusively) on the degree of supercooling achieved prior to the onset of nucleation. This paper focuses on investigating one particular and unusual polycrystalline microstructure that consists of “flowerlike” grains, the interiors of which can be described as being made up of two distinct regions: (1) an extremely defective core region consisting of fine-grained material, and (2) an outer region consisting of relatively defect-free crystal “petals” that radiate outwards. After considering the microstructural details and experimental behavior of the microstructure, we have formulated a growth-based physical model to account for the formation of the microstructure. The model is found to be also capable of accounting for other complex and unusual microstructures obtained via nucleation and growth in the complete melting regime.

关键词： Si nucleation & growth thin film

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Densest local sphere-packing diversity. II. Application to three dimensions

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Physical Review E 2011年第1期83卷 011304-011304页

作者： Adam B. Hopkins Frank H. Stillinger Salvatore Torquato Department of Chemistry and Department of Physics Princeton Center for Theoretical Science Princeton Institute for the Science and Technology of Materials Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA

The densest local packings of N three-dimensional identical nonoverlapping spheres within a radius Rmin(N) of a fixed central sphere of the same size are obtained for selected values of N up to N=1054. In the predecessor to this paper [A. B. Hopkins, F. H. Stillinger, and S. Torquato, Phys. Rev. E 81, 041305 (2010)], we described our method for finding the putative densest packings of N spheres in d-dimensional Euclidean space Rd and presented those packings in R2 for values of N up to N=348. Here we analyze the properties and characteristics of the densest local packings in R3 and employ knowledge of the Rmin(N), using methods applicable in any d, to construct both a realizability condition for pair correlation functions of sphere packings and an upper bound on the maximal density of infinite sphere packings. In R3, we find wide variability in the densest local packings, including a multitude of packing symmetries such as perfect tetrahedral and imperfect icosahedral symmetry. We compare the densest local packings of N spheres near a central sphere to minimal-energy configurations of N+1 points interacting with short-range repulsive and long-range attractive pair potentials, e.g., 12–6 Lennard-Jones, and find that they are in general completely different, a result that has possible implications for nucleation theory. We also compare the densest local packings to finite subsets of stacking variants of the densest infinite packings in R3 (the Barlow packings) and find that the densest local packings are almost always most similar as measured by a similarity metric, to the subsets of Barlow packings with the smallest number of coordination shells measured about a single central sphere, e.g., a subset of the fcc Barlow packing. Additionally, we observe that the densest local packings are dominated by the dense arrangement of spheres with centers at distance Rmin(N). In particular, we find two “maracas” packings at N=77 and N=93, each consisting of a few unjammed sphere

关键词： DENSITY functionals SPHERES MATHEMATICAL models EUCLIDEAN metric CORRELATION (Statistics) SYMMETRY

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Large plastic deflection of fully clamped beam subjected to impact load

Large plastic deflection of fully clamped beam subjected to ...

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作者： Chen, F.L. Yu, T.X. Institute of Applied Physics and Computational Mathematics PO Box 8009-11 Beijing 100088 China Department of Mechanical Engineering Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong

By taking into account plastic dissipation by the axial (membrane) force induced by large deflection, a modifying factor is introduced into the bending-only formulation (valid for small deflection) to construct the equations of motion for the large deflection where both bending moment and axial force are of importance. A complete theoretical solution is undertaken to trace the entire response history (including the transient phase) of a fully clamped beam subjected to impact load and a favourable succinct solution is obtained. In comparison with the small deflection solution, the axial force induced by large deflection is found to substantially decrease the final deflection of structures. This solution provides reliable prediction for deflections up to some 10 times the beam thickness. © W. S. Maney & Son Ltd. 2011.

关键词： Equations of motion

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Sequential Lateral Solidification of Ultra-Thin a-Si Films

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MRS Online Proceedings Library 2011年第1期621卷 991-996页

作者： Hans S. Cho Dongbyum Kim Alexander B. Limanov Mark A. Crowder James S. Im Program in Materials Science and Engineering Department of Applied Physics and Applied Mathematics School of Engineering and Applied Science Columbia University New York USA

This paper demonstrates that Sequential Lateral Solidification (SLS) of Si can be carried out on films as thin as–and potentially much thinner than–250 Å. When compared to thicker Si films, however, the SLS-processed ultra-thin films contain more twins, and successful processing requires irradiation within a narrower laser energy density range and a smaller per-pulse translation distance. The physical interpretation of these findings is formulated by analyzing the details of the microstructures observed in single-pulse-irradiation-induced Controlled Super-Lateral Growth (C-SLG) experiments. SEM and TEM analyses reveal complicated microstructural details that we interpret as originating from breakdown of epitaxial growth during lateral solidification, an effect that is detrimental to the SLS process. Based on considerations of far-from- equilibrium solidification behavior of Si, it is argued that undercooling of the solidification interface below a threshold value at which solidification no longer proceeds epitaxially–arising from reduction in interfacial recalescence during lateral solidification of ultra-thin Si films, relative to that of thicker films–is responsible for the breakdown. Based on this model, we discuss how external parameters may be adjusted so as to permit optimal crystallization of ultra-thin Si films using SLS.

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Fast wavelet-based single-particle reconstruction in Cryo-EM

Fast wavelet-based single-particle reconstruction in Cryo-EM

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IEEE International Symposium on Biomedical Imaging

作者： Cédric Vonesch Lanhui Wang Yoel Shkolnisky Amit Singer Program in Applied and Computational Mathematics Princeton University Princeton NJ USA Department of Applied Mathematics Tel-Aviv University Tel-Aviv Israel

This paper presents a novel algorithm for the 3D tomographic inversion problem that arises in single-particle electron cryomicroscopy (Cryo-EM). It is based on two key components: 1) a variational formulation that promotes sparsity in the wavelet domain and 2) the Toeplitz structure of the combined projection/back-projection operator. The first idea has proven to be very effective for the recovery of piecewise-smooth signals, which is confirmed by our numerical experiments. The second idea allows for a computationally efficient implementation of the reconstruction procedure, using only one circulant convolution per iteration.

关键词： Image reconstruction Signal to noise ratio Three dimensional displays Fourier transforms Kernel Tomography

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Plasmoid Ejection and Secondary Current Sheet Generation from Magnetic Reconnection in Laser-Plasma Interaction

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Physical Review Letters 2012年第21期108卷 215001-215001页

作者： Quan-Li Dong (董全力) Shou-Jun Wang (王首钧) Quan-Ming Lu (陆全明) Can Huang (黄灿) Da-Wei Yuan (袁大伟) Xun Liu (刘勋) Xiao-Xuan Lin (林晓宣) Yu-Tong Li (李玉同) Hui-Gang Wei (魏会冈) Jia-Yong Zhong (仲佳勇) Jian-Rong Shi (施建荣) Shao-En Jiang (江少恩) Yong-Kun Ding (丁永坤) Bo-Bin Jiang (蒋柏彬) Kai Du (杜凯) Xian-Tu He (贺贤土) M. Y. Yu (郁明阳) C. S. Liu (刘全生) Shui Wang (王水) Yong-Jian Tang (唐永健) Jian-Qiang Zhu (朱健强) Gang Zhao (赵刚) Zheng-Ming Sheng (盛政明) Jie Zhang (张杰) Beijing National Laboratory of Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100080 China CAS Key Laboratory of Basic Plasma Physics University of Science and Technology of China Hefei Anhui 230026 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Research Center for Laser Fusion China Academy of Engineering Physics Mianyang 621900 China Institute of Applied Physics and Computational Mathematics Beijing 100094 China Institute for Fusion Theory and Simulation Physics Department Zhejiang University Hangzhou 310027 China Institute for Theoretical Physics I Ruhr University D-44780 Bochum Germany Department of Physics University of Maryland College Park Maryland 20742 USA National Laboratory on High Power Lasers and Physics Shanghai 201800 China Key Laboratory for Laser Plasmas (MoE) and Department of Physics Shanghai Jiao Tong University Shanghai 200240 China

Reconnection of the self-generated magnetic fields in laser-plasma interaction was first investigated experimentally by Nilson et al. [Phys. Rev. Lett. 97, 255001 (2006)] by shining two laser pulses a distance apart on a solid target layer. An elongated current sheet (CS) was observed in the plasma between the two laser spots. In order to more closely model magnetotail reconnection, here two side-by-side thin target layers, instead of a single one, are used. It is found that at one end of the elongated CS a fanlike electron outflow region including three well-collimated electron jets appears. The (>1 MeV) tail of the jet energy distribution exhibits a power-law scaling. The enhanced electron acceleration is attributed to the intense inductive electric field in the narrow electron dominated reconnection region, as well as additional acceleration as they are trapped inside the rapidly moving plasmoid formed in and ejected from the CS. The ejection also induces a secondary CS.

关键词： SPHEROMAKS LASER-plasma interactions MAGNETIC fields MAGNETOTAILS PARTICLE acceleration MATHEMATICAL models physics experiments ELECTRONS

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Strong and weak divergence in finite time of Euler's method for stochastic differential equations with non-globally Lipschitz continuous coefficients

Strong and weak divergence in finite time of Euler's method ...

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作者： Hutzenthaler, Martin Jentzen, Arnulf Kloeden, Peter E. LMU Biozentrum Department Biologie II University of Munich 82152 Planegg-Martinsried Germany Program in Applied and Computational Mathematics Princeton University Princeton NJ 08544-1000 United States Institute for Mathematics Goethe University Frankfurt am Main 60054 Frankfurt am Main Germany

The stochastic Euler scheme is known to converge to the exact solution of a stochastic differential equation (SDE) with globally Lipschitz continuous drift and diffusion coefficients. Recent results extend this convergence to coefficients that grow, at most, linearly. For superlinearly growing coefficients, finite-time convergence in the strong mean-square sense remains. In this article, we answer this question to the negative and prove, for a large class of SDEs with non-globally Lipschitz continuous coefficients, that Euler's approximation converges neither in the strong mean-square sense nor in the numerically weak sense to the exact solution at a finite time point. Even worse, the difference of the exact solution and of the numerical approximation at a finite time point diverges to infinity in the strong mean-square sense and in the numerically weak sense. © 2010 The Royal Society.

关键词： Stochastic systems

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Second-order time evolution scheme for time-dependent neutron transport equation

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World Academy of Science, Engineering and Technology 2011年 77卷 752-757页

作者： Hong, Zhenying Yuan, Guangwei Fu, Xuedong Yang, Shulin Institute of Applied Physics and Computational Mathematics Department 6 NO.2. Fenghaodong Road Haidian District Beijing 100094 China

In this paper, the typical exponential method, diamond difference and modified time discrete scheme is researched for self adaptive time step. The second-order time evolution scheme is applied to time-dependent spherical neutron transport equation by discrete ordinates method. The numerical results show that second-order time evolution scheme associated exponential method has some good properties. The time differential curve about neutron current is more smooth than that of exponential method and diamond difference and modified time discrete scheme.

关键词： Diamonds

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