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Structure Effects in Angle-Resolved High-Order Above-Threshold Ionization of Molecules

Physical Review Letters 2010年第20期104卷 203001-203001页

作者： H. Kang W. Quan Y. Wang Z. Lin M. Wu H. Liu X. Liu B. B. Wang H. J. Liu Y. Q. Gu X. Y. Jia J. Liu J. Chen Y. Cheng State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences Wuhan 430071 China Graduate School of Chinese Academy of Sciences Beijing 100080 China Laboratory of Optical Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China Fusion Research Center Chinese Academy of Engineering Physics P. O. Box 919-18 Mianyang Sichuan Province China Center for Applied Physics and Technology Peking University Beijing 100084 China Institute of Applied Physics and Computational Mathematics P. O. Box 8009 Beijing 100088 China State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences P.O. Box 800-211 Shanghai 201800 China

We present energy-resolved angular distributions of photoelectrons generated in above-threshold ionization (ATI) of nonaligned diatomic molecules N2 and O2 in high-intensity short laser pulses, with emphasis on the most energetic part of the spectra. The angular distribution for photoelectrons with energy of 10Up (Up: ponderomotive energy), i.e., the plateau cutoff in ATI spectra, is found to be broader in O2 than in N2. Resorting to the analyses from both an S-matrix theory and an intuitive semiclassical model, we attribute the observation to the effect of the ground state molecular orbital structure on high-energy electron emission in strong-field molecular ionization.

关键词： Photoelectrons

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Coarse-Grained Langevin Approximations and Spatiotemporal Acceleration for Kinetic Monte Carlo Simulations of Diffusion of Interacting Particles

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Chinese Annals of mathematics,Series B 2009年第6期30卷 653-682页

作者： Sasanka ARE Markos A. KATSOULAKIS Anders SZEPESSY Department of Mathematics and Statistics University of MassachusettsAmherstMA 01003-9305USA Department of Applied Mathematics University of Crete and Foundation of Research and TechnologyHellasHeraklion 71405Greece Matematiska Institutionen Kungliga Tekniska Hgskolan (Royal Institute of Technology)SE-100 44 StockholmSweden

Kinetic Monte Carlo methods provide a powerful computational tool for the simulation of microscopic processes such as the diffusion of interacting particles on a surface, at a detailed atomistic level. However such algorithms are typically computationatly expensive and are restricted to fairly small spatiotemporal scales. One approach towards overcoming this problem was the development of coarse-grained Monte Carlo algorithms. In recent literature, these methods were shown to be capable of efficiently describing much larger length scales while still incorporating information on microscopic interactions and fluctuations. In this paper, a coarse-grained Langevin system of stochastic differential equations as approximations of diffusion of interacting particles is derived, based on these earlier coarse-grained models. The authors demonstrate the asymptotic equivalence of transient and long time behavior of the Langevin approximation and the underlying microscopic process, using asymptotics methods such as large deviations for interacting particles systems, and furthermore, present corresponding numerical simulations, comparing statistical quantities like mean paths, auto correlations and power spectra of the microscopic and the approximating Langevin processes. Finally, it is shown that the Langevin approximations presented here are much more computationally efficient than conventional Kinetic Monte Carlo methods, since in addition to the reduction in the number of spatial degrees of freedom in coarse-grained Monte Carlo methods, the Langevin system of stochastic differential equations allows for multiple particle moves in a single timestep.

关键词： Kinetic Monte Carlo methods Diffusion Fluctuations

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Atmospheric observation data de-noising based on a new wavelet threshold function

Atmospheric observation data de-noising based on a new wavel...

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2009 International Conference on computational Intelligence and Software Engineering, CiSE 2009

作者： Guo, Xiaochao Xu, Lisheng Chrysoulakis, Nektarios Ding, Jilie Deng, Xiaobo Wu, Tao Satellite Remote Sensing and Space Sciences Research Lab. College of Atmospheric Soundings Chengdu University of Information Technology Chengdu Sichuan 610225 China Foundation for Research and Technology - Hellas Institute of Applied and Computational Mathematics Vassilika Vouton P.O. Box 1358 71110 Heraklion Crete Greece

ISBN: (纸本)9781424445073

Atmospheric observation data are unavoidable mixed with noise and the performance of the data processing system will degrade remarkably. Wavelet threshold de-noising techniques is an important method to reduce noise in signal process. In this paper a new wavelet threshold function is proposed for removing noise in signal, which is based on the conventional soft and hard threshold functions. Both quantities of signal to noise radio (SNR) and mean square error (MSE) are introduced to judge the de-noising effectiveness. Some precipitable water (PW) time series data are processed by combined use of the new threshold function with Kolmogorov entropy and neural network prediction which are used to judge the de-noising effectiveness. The study results show that the new threshold function proposed can overcome the shortcoming of the conventional soft and hard threshold functions to a certain degree and is efficient for signal de-noising. ©2009 IEEE.

关键词： Signal denoising

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The velocity effect on GEDEM measurements

The velocity effect on GEDEM measurements

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1st International Workshop on Mobilizing Health Information to Support Healthcare-Related Knowledge Work, MobiHealthInf 2009 In Conjunction with BIOSTEC 2009

作者： Papadakis, Nikos Tzagarakis, George Kampams, N. Savakis, K. Katonis, P. Stergiopoulos, K. Christakis, D.G. TEI of Crete Biomechcanics Laboratory School of Mechanical Engineering TEI of Crete Estavromenos Greece Department of Orthopaedics University of Crete School of Medicine University Hospital of Heraklion Crete Greece Foundation of Research and Technology Hellas Institute of Applied and Computational Mathematics PO Box 1385 71110 Heraklion Crete Greece

ISBN: (纸本)9789898111784

Gait Evaluation Differential Entropy Measure (GEDEM) [1] is a new quantitative approach to evaluating the condition of a subject by monitoring the acceleration [2][3]. The approach is capable to identify medical conditions [2, 3] and is also not dependent on age, weight, height or BMI. The initial studies [4][5][6] required the walking on the ground along a straight line for 20-30 seconds. Due to the promising results of the method, work is currently carried out on a treadmill. The treadmill alleviates the constraint of long corridors, and additionally offers better control on the gait velocity, minimum deviation in the coronal plane, and less variability in the GEDEM values [7, 8]. This work investigates the relationship between the gait velocity and the GEDEM. The gait velocity is a measurement parameter that influences the gait acceleration spectrum and therefore it is expected to influence GEDEM values.

关键词： Velocity

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Atmospheric Observation Data De-Noising Based on a New Wavelet Threshold Function

Atmospheric Observation Data De-Noising Based on a New Wavel...

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International Conference on computational Intelligence and Software Engineering (CiSE)

作者： Xiaochao Guo Lisheng Xu Nektarios Chrysoulakis Jilie Ding Xiaobo Deng Tao Wu Satellite Remote Sensing & Space Sciences Research Laboratory College of Atmospheric Soundings Chengdu University of Information and Technology Chengdu Sichuan China Institute of Applied and Computational Mathematics Vassilika Vouton Foundation for Research and Technology Hellas Crete Greece

关键词： Atmospheric waves Noise reduction Data processing Degradation Signal processing Signal to noise ratio Mean square error methods Entropy Neural networks Signal denoising

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Collimation of relativistic laser-generated high energy electron beams via double cone target in fast ignition scheme

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Journal of Physics: Conference Series 2010年第2期244卷

作者： Hong-bo Cai Kunioki Mima Tomoyuki Jozaki Hideo Nagatomo Atsushi Sunahara Wei-min Zhou Rodney J Mason Institute of Applied Physics and Computational Mathematics PO Box 8009 Beijing 100088 China Institute of Laser Engineering Osaka University 2-6 Yamadaoka Suita Osaka 565-0871 Japan The Graduate School for the Creation of New Photonics Industries 1955-1 Kurematsu Nishiku Hamamatsu Sizuoka 431-1202 Japan Institute for Laser Technology 2-6 Yamadaoka Suita Osaka 565-0871 Japan Laser Fusion Research Center China Academy of Engineering Physics Mianyang Sichuan 621900 China Research Applications Corporation Los Alamos New Mexico 87544 USA

The success of fast ignitor scheme will ultimately relies on the efficient generation and propagation of enormous number of high-energy charged particles. Particle-in-cell simulations aimed at improving the coupling efficiency of input laser energy deposited to a compressed core by using a double cone are described. Quasistatic magnetic fields generated at the vacuum layer inside the double cones are found to play an important role in confining the high energy electrons. The double cones result in the confinement and focusing of about 15% of the input energy for deposition in the compressed core.

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Radiative heating of plastic-tamped aluminum foil by x rays from a foam-buffered hohlraum

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Physical Review E 2009年第1期79卷 016401-016401页

作者： Jiyan Zhang Jiamin Yang Yan Xu Guohong Yang Yaonan Ding Jun Yan Jianmin Yuan Yongkun Ding Zhijian Zheng Yang Zhao Zhimin Hu Research Center of Laser Fusion P. O. Box 919-986 Mianyang 621900 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China National University of Defense Technology of China Changsha 410073 China

The time dependence of the x-ray absorption of aluminum samples heated with intense radiation sources from a foam-buffered gold hohlraum has been studied in this work. Hydrodynamic simulations were used to illustrate the plasma conditions in the plastic-tamped aluminum foils contained in this type of hohlraum. Experiments were conducted to measure the K-shell x-ray absorption spectra of the aluminum sample. With densities taken from the hydrodynamic simulations, electron temperatures were then inferred by fitting the measured absorption spectra with detailed-term-accounting calculations. The inferred temperatures have a maximum of about 93eV and were found to agree within 25% with the simulated results at times after 1ns, indicating that the use of foam shields, together with a compact cavity, has created a clean and high-temperature radiation source preferable to opacity measurements.

关键词： aluminium foils hydrodynamics plasma diagnostics plasma heating plasma thermodynamics X-ray absorption ABSORPTION-MEASUREMENTS OPACITY MEASUREMENTS PLASMA HOT IRON

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Progress of opacity experiment on the shengguang ii laser facility

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Journal of Physics: Conference Series 2009年第1期163卷

作者： Yang, Jiamin Zhang, Jiyan Xu, Yan Yuan, Jianmin Yan, Jun Ding, Yaonan Zhao, Yang Jin, Fengtao Hu, Zhimin Yang, Guohong Zhang, Baohan Research Center of Laser Fusion China Academy of Engineering Physics Mianyang SICHUAN 621900 PO Box 919-986 China Beijing Institute of Applied Physics and Computational Mathematics Beijing 10088 China Department of Applied Physics National University of Defense Technology Changsha 410073 China

In recent years, a series of opacity diagnostics have been developed at the research Center of Laser Fusion in China. Two types of cavities (a conical cavity called a type I target, and a cylindrical cavity with foam baffles called a type II target) were designed to convert the eight-beam laser into x-ray radiation to efficiently heat the sample and to prevent the sample from irradiation of the reflected laser and plasmas on the Shengguang II laser facility. Typical opacity experiments have been carried out using the two target designs, respectively. The results show that a sample temperature of about 95 eV has been reached using the type II target which is the highest obtained on the high power laser facility. © 2009 IOP Publishing Ltd.

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Ab initio study of the phase stability in paramagnetic duplex steel alloys

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Physical Review B 2009年第2期79卷 024108-024108页

作者： H. Pitkänen M. Alatalo A. Puisto M. Ropo K. Kokko M. P. J. Punkkinen P. Olsson B. Johansson S. Hertzman L. Vitos Department of Mathematics and Physics Lappeenranta University of Technology P.O. Box 20 FIN-53851 Lappeenranta Finland Department of Applied Physics Helsinki University of Technology P.O. Box 1100 FI-02015 HUT Espoo Finland Department of Physics and Astronomy University of Turku FIN-20014 Turku Finland Department of Information Technology Åbo Akademi Fin-20500 Turku Finland Department of Materials Science and Engineering Applied Materials Physics Royal Institute of Technology Stockholm SE-100 44 Sweden Department of Materials and Mechanics of Components EDF R&D F-77250 Moret-sur-Loing France Department of Physics and Materials Science Division for Materials Theory Uppsala University SE-75121 Uppsala Sweden Department of Materials Science and Engineering Outokumpu Stainless Research Foundation Royal Institute of Technology Stockholm SE-100 44 Sweden Research Institute for Solid State Physics and Optics P.O. Box 49 Budapest H-1525 Hungary

Duplex stainless steels have many superior properties compared to conventional steels, this being mainly due to their microstructure containing approximately equal amount of ferrite and austenite phases formed by iron, chromium (or Cr equivalent), and nickel (or Ni equivalent). Using computational methods based on first-principles theories, the phase stability of paramagnetic Fe1−c−nCrcNin alloys (0.12≤c≤0.32 and 0.04≤n≤0.32) at high temperatures (≳1000 K) is addressed. It is shown that the stabilization of the ferrite-austenite two-phase field in duplex steels is a result of complex interplay of several competing phenomena. Taking into account only the formation energies yields a complete phase separation, strongly overestimating the two-phase region. The formation energies are calculated to be lower for the austenite than for the ferrite, meaning that the configurational entropy has a more significant impact on the stability field of the austenitic phase. The magnetic and vibrational free energies have opposite effects on the phase stability. Namely, the magnetic entropy favors the ferrite phase, whereas the vibrational free energy stabilizes the austenite phase. Combining the formation energies with the magnetic, vibrational, and configurational free energies, a region of coexistence between the two phases is obtained, in line with former thermodynamic assessments as well as with experimental observations.

关键词： ab initio calculations free energy magnetic transitions paramagnetic materials phase diagrams steel

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Adiabatic Rosen-Zener interferometry with ultracold atoms

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Physical Review A 2009年第1期80卷 013619-013619页

作者： Li-Bin Fu De-Fa Ye Chaohong Lee Weiping Zhang Jie Liu Center for Applied Physics and Technology Peking University Beijing 100084 People’s Republic of China Institute of Applied Physics and Computational Mathematics Beijing 100088 People’s Republic of China Nonlinear Physics Center and ARC Center of Excellence for Quantum-Atom Optics Research School of Physical Sciences and Engineering Australian National University Canberra Australian Capital Territory 0200 Australia Department of Physics State Key Laboratory of Precision Spectroscopy East China Normal University Shanghai 200062 People’s Republic of China College of Physics and Information Engineering Hebei Normal University Shijiazhuang 050016 People’s Republic of China

We propose a time-domain “interferometer” based on double-well ultracold atoms through a so-called adiabatic Rosen-Zener process, that is, the barrier between two wells is ramped down slowly, held for a while, and then ramped back. After the adiabatic Rosen-Zener process, we count the particle population in each well. We find that the final occupation probability shows nice interference fringes. The fringe pattern is sensitive to the initial state as well as the intrinsic parameters of the system such as interatomic interaction or energy bias between two wells. The underlying mechanism is revealed and possible applications are discussed.

关键词： Interferometry

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