检索结果-南通市图书馆

Global Existence,Uniqueness and Pathwise Property of Solutions to a Stochastic Rssler-Lorentz System

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Annals of Mathematics,Series B 2015年第1期36卷 105-124页

作者： Song JIANG Junping YIN Institute of Applied Physics and computational Mathematics Beijing center for Mathematics and Information Interdisciplinary Sciences

The authors integrate two well-known systems, the Rssler and Lorentz systems,to introduce a new chaotic system, called the Lorentz-Rssler system. Then, taking into account the effect of environmental noise, the authors incorporate white noise in both Rssler and Lorentz systems to have a corresponding stochastic system. By deriving the uniform a priori estimates for an approximate system and then taking them to the limit,the authors prove the global existence, uniqueness and the pathwise property of solutions to the Lorentz-Rssler system. Moreover, the authors carried out a number of numerical experiments, and the numerical results demonstrate their theoretic analysis and show some new qualitative properties of solutions which reveal that the Lorentz-Ro¨ssler system could be used to design more complex and more secure nonlinear hop-frequence time series.

关键词： Stochastic differential equations Rossler-Lorentz systems Existence Pathwise property

Review of the current status of fast ignition research atthe IAPCM

在线全文

学校读者我要写书评

暂无评论

High Power Laser Science and Engineering 2014年第1期2卷 4-12页

作者： Hong-bo Cai Si-zhong Wu Jun-feng Wu Mo Chen Hua Zhang Min-qing He Li-hua Cao Cang-tao Zhou Shao-ping Zhu Xian-tu He Institute of Applied Physics and computational Mathematics center for Applied Physics and Technology Peking University

We review the present status and future prospects of fast ignition(FI) research of the theoretical group at the IAPCM(Institute of Applied Physics and computational Mathematics, Beijing) as a part of the inertial confinement fusion project. Since the approval of the FI project at the IAPCM, we have devoted our efforts to improving the integrated codes for FI and designing advanced targets together with the experimental group. Recent FI experiments [K. U. Akli et al., Phys. Rev. E 86, 065402(2012)] showed that the petawatt laser beam energy was not efficiently converted into the compressed core because of the beam divergence of relativistic electron beams. The coupling efficiency can be improved in three ways:(1) using a cone–wire-in-shell advanced target to enhance the transport efficiency,(2) using external magnetic fields to collimate fast electrons, and(3) reducing the prepulse level of the petawatt laser beam. The integrated codes for FI, named ICFI, including a radiation hydrodynamic code, a particle-in-cell(PIC) simulation code,and a hybrid fluid–PIC code, have been developed to design this advanced target at the IAPCM. The Shenguang-II upgraded laser facility has been constructed for FI research; it consists of eight beams(in total 24 kJ/3ω, 3 ns) for implosion compression, and a heating laser beam(0.5–1 kJ, 3–5 ps) for generating the relativistic electron beam. A fully integrated FI experiment is scheduled for the 2014 project.

关键词： fast ignition integrated simulation codes

Performance improvement of optimization solutions by POD-based data mining

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2019年第4期32卷 826-838页

作者： Yanhui DUAN Wenhua WU Peihong ZHANG Fulin TONG Zhaolin FAN Guiyu ZHOU Jiaqi LUO computational Aerodynamics Institute China Aerodynamics Research and Development Center School of Aeronautics and Astronautics Zhejiang University

The performance of an optimized aerodynamic shape is further improved by a second-step optimization using the design knowledge discovered by a data mining technique based on Proper Orthogonal Decomposition(POD) in the present study. Data generated in the first-step optimization by using evolution algorithms is saved as the source data, among which the superior data with improved objectives and maintained constraints is chosen. Only the geometry components of the superior data are picked out and used for constructing the snapshots of POD. Geometry characteristics of the superior data illustrated by POD bases are the design knowledge, by which the second-step optimization can be rapidly achieved. The optimization methods are demonstrated by redesigning a transonic compressor rotor blade, NASA Rotor 37, in the study to maximize the peak adiabatic efficiency, while maintaining the total pressure ratio and mass flow ***, the blade is redesigned by using a particle swarm optimization method, and the adiabatic efficiency is increased by 1.29%. Then, the second-step optimization is performed by using the design knowledge, and a 0.25% gain on the adiabatic efficiency is obtained. The results are presented and addressed in detail, demonstrating that geometry variations significantly change the pattern and strength of the shock wave in the blade passage. The former reduces the separation loss,while the latter reduces the shock loss, and both favor an increase of the adiabatic efficiency.

关键词： Aerodynamic shape optimization computational fluid dynamics Data mining Particle swarm optimization Proper Orthogonal Decomposition Transonic flow Turbomachinery

Electron impact excitation of helium atom

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2015年第8期24卷 271-278页

作者：韩小英曾德灵高翔李家明 Institute of Applied Physics and computational Mathematics Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics and Astronomy Shanghai Jiao Tong University Beijing computational Science Research center Department of Physics and center for Atomic and Molecular Nanosciences Tsinghua University Collaborative Innovation center of Quantum Matter

A method to deal with the electron impact excitation cross sections of an atom from low to high incident energies are presented. This method combines the partial wave method and the first Born approximation(FBA), i.e., replacing the several lowest partial wave cross sections of the total cross sections within FBA by the corresponding exact partial wave cross sections. A new set of codes are developed to calculate the FBA partial wave cross sections. Using this method,the convergent e–He collision cross sections of optical-forbidden and optical-allowed transitions at low to high incident energies are obtained. The calculation results demonstrate the validity and efficiency of the method.

关键词： electron impact excitation cross section first Born approximation partial wave method

Successive Picket Drive for Mitigating the Ablative Richtmyer–Meshkov Instability

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2019年第2期36卷 28-31页

作者： Meng Li Wen-Hua Ye Institute of Applied Physics and computational Mathematics center for Applied Physics and Technology HEDPS Peking University

The ablative Richtmyer–Meshkov instability(ARMI) is crucial to the successful ignition implosion of the inertial confinement fusion(ICF) because of its action as the seed of the Rayleigh–Taylor instability. In usual ICF implosions, the first shock driven by various foots of the pulses plays a central role in the ARMI growth. We propose a new scheme for refraining from ARMI with a pulse of successive pickets. With the successive-picket pulse design, a rippled capsule surface is compressed by three successive shocks with sequentially strengthening intensities and ablated stabilization, and the ablative Richtmyer–Meshkov growth is mitigated quite *** numerical simulations and theoretical analyses identify the validity of this scheme.

关键词： RMI ICF Successive Picket Drive for Mitigating the Ablative Richtmyer Meshkov Instability

Constructing reduced model for complex physical systems via interpolation and neural networks

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2021年第3期30卷 78-87页

作者： Xuefang Lai Xiaolong Wang Yufeng Nie Research center for computational Science School of Mathematics and StatisticsNorthwestern Polytechnical UniversityXi’an 710129China

The work studies model reduction method for nonlinear systems based on proper orthogonal decomposition (POD)and discrete empirical interpolation method (DEIM). Instead of using the classical DEIM to directly approximate thenonlinear term of a system, our approach extracts the main part of the nonlinear term with a linear approximation beforeapproximating the residual with the DEIM. We construct the linear term by Taylor series expansion and dynamic modedecomposition (DMD), respectively, so as to obtain a more accurate reconstruction of the nonlinear term. In addition, anovel error prediction model is devised for the POD-DEIM reduced systems by employing neural networks with the aid oferror data. The error model is cheaply computable and can be adopted as a remedy model to enhance the reduction ***, numerical experiments are performed on two nonlinear problems to show the performance of the proposed method.

关键词： model reduction discrete empirical interpolation method dynamic mode decomposition neural networks

Marine Metagenome as A Resource for Novel Enzymes

在线全文

学校读者我要写书评

暂无评论

Genomics, Proteomics & Bioinformatics 2015年第5期13卷 290-295页

作者： Amani D.Alma'abadi Takashi Gojobori Katsuhiko Mineta computational Bioscience Research center (CBRC) King Abdullah University of Science and Technology (KAUST)

More than 99% of identified prokaryotes, including many from the marine environment, cannot be cultured in the laboratory. This lack of capability restricts our knowledge of microbial genetics and community ecology. Metagenomics, the culture-independent cloning of environmental DNAs that are isolated directly from an environmental sample, has already provided a wealth of information about the uncultured microbial world. It has also facilitated the discovery of novel bio- catalysts by allowing researchers to probe directly into a huge diversity of enzymes within natural microbial communities. Recent advances in these studies have led to a great interest in recruiting microbial enzymes for the development of environmentally-friendly industry. Although the metage- nomics approach has many limitations, it is expected to provide not only scientific insights but also economic benefits, especially in industry. This review highlights the importance of metagenomics in mining microbial lipases, as an example, by using high-throughput techniques. In addition, we dis- cuss challenges in the metagenomics as an important part of bioinformatics analysis in big data.

关键词： Microbial diversity Culture-independent studies Catalysis Lipase Biotechnology

Genome-Wide Analysis of Epigenetic Modifications

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2010年第1期25卷 35-41页

作者：梁守丹 Department of Bioinformatics and computational Biology The University of Texas M.D. Anderson Cancer Center Houston

In plants and animals, gene expression can be altered by changes that do not alter the sequence of nucleotides in DNA but rather modify the chemical structure of either the DNA or the histones that interact with the DNA. These so-called epigenetic modifications are not transient, but persist through cell divisions. Rapidly advancing technologies, such as next-generation DNA sequencing, have dramatically increased our ability to survey epigenetic markers throughout an entire genome. These techniques are revealing in great detail that the many forms and stages of cancer are characterized by a massive number of epigenetic changes. Interpreting such epigenetic marks in cell differentiation and in carcinogenesis is computationally challenging. We review several examples of epigenetic data analysis and discuss the need for computational methods that will enable us to learn from the data the relationships between different kinds of histone modifications and DNA methylation.

关键词： epigenetics non-coding DNA DNA methylations histone modifications

Controlling Chaos Using Modified Lyapunov Exponents

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 1993年第6期10卷 321-324页

作者： TAN Yi HE Xiantu CHEN Shigang center for Nonlinear Studies Institute of Applied Physics and Computational MathematicsBeijing 100088

We suggested a method using a small perturbation to modify Lyapunov exponents of the unstable periodic orbit for controlling *** benefit of this control scheme is studied and the effect of noise is *** on these studie... 详细信息

关键词： chaos. Lyapunov Chaos