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Automatic Simulation of the Chemical Langevin Equation

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Applied Mathematics 2013年第1期4卷 235-241页

作者： Silvana Ilie Monjur Morshed Department of Mathematics Ryerson University Toronto Canada

Biochemical systems have important practical applications, in particular to understanding critical intra-cellular processes. Often biochemical kinetic models represent cellular processes as systems of chemical reactions, traditionally modeled by the deterministic reaction rate equations. In the cellular environment, many biological processes are inherently stochastic. The stochastic fluctuations due to the presence of some low molecular populations may have a great impact on the biochemical system behavior. Then, stochastic models are required for an accurate description of the system dynamics. An important stochastic model of biochemical kinetics is the Chemical Langevin Equation. In this work, we provide a numerical method for approximating the solution of the Chemical Langevin Equation, namely the derivative-free Milstein scheme. The method is compared with the widely used strategy for this class of problems, the Milstein method. As opposed to the Milstein scheme, the proposed strategy has the advantage that it does not require the calculation of exact derivatives, while having the same strong order of accuracy as the Milstein scheme. Therefore it may be used for an automatic simulation of the numerical solution of the Chemical Langevin Equation. The tests on several models of practical interest show that our method performs very well.

关键词： Stochastic Biochemical Kinetics Chemical Langevin Equation Derivative-Free Milstein Method

General Laser Intensity Langevin Equation in a Single-Mode Laser Model

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Chinese Physics Letters 2001年第3期18卷 370-372页

作者：柯圣志曹力吴大进姚凯伦 State Key Laboratory of Laser Technology Huazhong University of Science and TechnologyWuhan 430074 CCAST(World Laboratory) P.O.Box 8730Beijing 100080 Department of Physics Huazhong University of Science and TechnologyWuhan 430074

A two-dimensional single-mode laser model with cross-correlations between the real and imaginary parts of the quantum noise as well as the pump noise is investigated.The general closed form of the laser intensity Langevin equation(GILE)is obtained under a stable locked phase resulting from the cross-correlationλ_(q) between the real and imaginary parts of the quantum noise.Because of the presence of a new term containingλ_(q),we can unify the two opposite intensity Langevin equations which correspond to the two special cases for|λ_(q)|→0 and|λ_(q)|→1 in the GILE.It is expected that the transient and stationary properties of the laser model can be changed qualitatively whenλ_(q) varies.

关键词： pump Langevin quantum

Discrete-Time Langevin Motion in a Gibbs Potential

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Applied Mathematics 2012年第12期3卷 2032-2037页

作者： Reza Rastegar Alexander Roitershtein Vadim Roytershteyn Jiyeon Suh Department of Electrical and Computer Engineering University of California San Diego San Diego USA Department of Mathematics Grand Valley State University Allendale USA Department of Mathematics Iowa State University Ames USA

We consider a multivariate Langevin equation in discrete time, driven by a force induced by certain Gibbs’states. The main goal of the paper is to study the asymptotic behavior of a random walk with stationary increments (which are interpreted as discrete-time speed terms) satisfying the Langevin equation. We observe that (stable) functional limit theorems and laws of iterated logarithm for regular random walks with i.i.d. heavy-tailed increments can be carried over to the motion of the Langevin particle.

关键词： Langevin Equation Dynamics of a Moving Particle Multivariate Regular Variation Chains with Complete Connections

A simulation method of combinding boundary element method with generalized Langevin dynamics

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Chinese Science Bulletin 2000年第24期45卷 2227-2231页

作者： CHEN Weizu LU Benzhuo WANG Cunxin Center tor Biomedical Engineering Beijing Polytechnic UniversityBeijing 100022China School of Life Science University of Science and Technology of ChinaHefei 230026China

A new simulation approach to incorporate hydration force into generalized Langevin dynamics (GLD) is developed in this note. The hydration force determined by the boundary element method (BEM) is taken into account as the mean force terms of solvent including Coulombic interactions with the induced surface charge and the surface pressure of solvent. The exponential model is taken for the friction kernel. A simulation study has been performed on the cyclic undecapeptide cyclosporin A (CPA). The results obtained from the new method (GLDBEM) have been analyzed and compared with that obtained from the molecular dynamics (MD) simulation and the conventional stochastic dynamics (SD) simulation. We have found that the results obtained from GLDBEM show the obvious improvement over the SD simulation technique in the study of molecular structure and dynamic properties.

关键词： potential of mean force of solvent boundary element method friction memory function generalized Langevin dynamics.

Determination of The Frequency Parameters of Langevin Type Piezoelectric Transducers in Paucity of Data

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Determination of The Frequency Parameters of Langevin Type P...

Motile parameters of cell migration in anisotropic environment derived by speed power spectrum fitting with double exponential decay

第二届全国压电和声波理论及器件技术研讨会

作者： Yeong-Chin Chen Department of Electronics Engineering and Computer Science Tung-Fang Institute of TechnologyTaiwanR.O.C.

In underwater environment acoustical waves can transmit a longer range away from the transmitter than electromagnetic waves do.Underwater acoustical transducer is utilized as the physical element for sound wave transmitting and receiving.By transmitting a sound wave from the transducers, the surface or underwater objects ranging several miles away from the transducers can be located by detected the reflected sound wave from the objects itself.So far,the Langevin type piezoelectric transducer is still the best candidate as acoustical telemetry transmitters.Since the operating frequency of the transducer determines the distance that the sound wave could travel,it is important to measure it. However,it takes a long time to simulate and measure the transducer’s resonance frequency in the laboratory experiments.Some methods are proposed to calculate and prediction the frequency instead of experiments,but they caused more or less accuracy errors.In the meantime,the Mega-fuzzification is a machine learning method that aims at increasing the prediction accuracy in the paucity of data.This study develops a prediction system using Mega-fuzzification to determine the frequency of the Langevin type piezoelectric transducer.The results indicate that the proposed system gets the prediction error less than other methods.

关键词： Acoustical Langevin Piezoelectric transducer Mega-fuzzification Machine learning Artificial intelligence

来源： cnki会议评论

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Frontiers of physics 2020年第1期15卷 51-61页

作者：刘艳平李翔屈静高学娟何情祖刘雳宇刘如川帅建伟 Department of Physics Xiamen UniversityXiamen 361005China State Key Laboratory of Cellular Stress Biology.Innovation Center for Cell Signaling Network.Xiamen University Xiamen 361102China College of Physics Chongqing UniversityChongqing 401331China National Institute for Big Data in Healthcare at Xiamen University Xiamen 361102China

Cell migration through anisotropic microenvironment is critical to a wide variety of physiological and pathological processes.However,adequate analytical tools to derive motile parameters to characterize the anisotropic migration are lacking.Here,we proposed a method to obtain the four motile parameters of migration cells based on the anisotropic persistent random walk model which is described by two persistence times and two migration speeds at perpendicular directions.The key process is to calculate the velocity power spectra of cell migration along intrinsically perpendicular directions respectively,then to apply maximum likelihood estimation to derive the motile parameters from the power spectra fitting with double exponential decay.The simulation results show that the averaged persistence times and the corrected migration speeds can be good estimations for motile parameters of cell migration.

关键词： cell migration heterogeneity power spectrum random walk Langevin equation

Fractional Langevin Equation in Quantum Systems with Memory Effect

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Applied Mathematics 2014年第12期5卷 1741-1749页

作者： Jing-Nuo Wu Hsin-Chien Huang Szu-Cheng Cheng Wen-Feng Hsieh Department of Optoelectric Physics Chinese Culture University Taiwan Department of Photonics and Institute of Electro-Optical Engineering Taiwan

In this paper, we introduce the fractional generalized Langevin equation (FGLE) in quantum systems with memory effect. For a particular form of memory kernel that characterizes the quantum system, we obtain the analytical solution of the FGLE in terms of the two-parameter Mittag-Leffler function. Based on this solution, we study the time evolution of this system including the qubit excited-state energy, polarization and von Neumann entropy. Memory effect of this system is observed directly through the trapping states of these dynamics.

关键词： Fractional Generalized Langevin Equation Memory Effect Mittag-Leffler Function Memory Kernel Trapping States Polarization von Neumann Entropy

Structural and Magnetic Properties of Nanocomposite Nd Fe BPrepared by Rapid Thermal Processing

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Engineering 2020年第2期6卷 132-140页

作者： Jinbo Yang Jingzhi Han Haidong Tian Liang Zha Xiongzuo Zhang Chol Song Kim Dong Liang Wenyun Yang Shunquan Liu Changsheng Wang State Key Laboratory for Artificial Microstructure and Mesoscopic Physics School of PhysicsPeking UniversityBeijing 100871China Collaborative Innovation Center of Quantum Matter School of PhysicsPeking UniversityBeijing 100871China Beijing Key Laboratory for Magnetoelectric Materials and Devices Collegue of EngineeringPeking UniversityBeijing 100871China

Nanoscale permanent magnetic materials,which possess excellent magnetic and mechanical properties,thermal stability,and corrosion resistance,have become a research hotspot for permanent magnets.In reality,however,the obtained maximum energy product,(BH)max,is not satisfactory in comparison with the theory limit,especially for exchange-coupled nanocomposite magnets.The construction of an ideal microstructure still remains a challenge in the synthesis and preparation of nanoscale permanent magnets.This work reported the impact of rapid thermal process(RTP)with electron-beam heating on the microstructures of Nd12.5-xFe80.8+xB6.2Nb0.2Ga0.3(x=0,2.5)nanocomposites.It was found that the crystallization time was greatly reduced,from 15 min under the conventional annealing conditions to 0.1 s under the RTP.For Nd2Fe14B single-phase materials,the crystallization temperature of the RTP ribbons decreased by about 248 C compared with that of the ribbons produced by the conventional annealing method.A synergetic crystallization of the Nd2Fe14B and a-Fe phases was observed under the RTP,which restrained not only the shape,size distribution,and compositions of the hard and the soft phases,but also the interface between them.This modification effect became more obvious as the fraction of Fe increased.Due to the improvement in the uniformity of the Nd2Fe14B and a-Fe phases,and their grain size distribution,better magnetic properties were achieved using RTP in comparison with the conventional annealing method.

关键词： Nanocomposites Electron-beam heating Landau model and Langevin dynamics simulation Synergetic crystallization

Bulk moduli of two-dimensional Yukawa solids and liquids obtained from periodic compressions

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Plasma Science and Technology 2023年第3期25卷 15-20页

作者：卢少瑜黄栋 A SHAHZAD 冯岩 Institute of Plasma Physics and Technology School of Physical Science and TechnologySoochow UniversitySuzhou 215006Peopleʼs Republic of China Department of Physics Government College University Faisalabad(GCUF)Allama Iqbal RoadFaisalabad 38040Pakistan National Laboratory of Solid State Microstructures Nanjing UniversityNanjing 210093Peopleʼs Republic of China

Langevin dynamical simulations are performed to determine the bulk modulus in twodimensional(2D) dusty plasmas from uniform periodic radial compressions. The bulk modulus is calculated directly from its physical definition of the ratio of the internal pressure/stress to the volume strain. Under various conditions, the bulk moduli obtained agree with the previous theoretical derivations from completely different approaches. It is found that the bulk moduli of2D Yukawa solids and liquids are almost independent of the system temperature and the external compressional frequency.

关键词： bulk modulus dusty plasma simulation Langevin complex plasma Yukawa systems