Monte-Carlo Simulation of Multiple-Molecular-Motor Transport

Multimotor transport is studied by Monte-Carlo simulation with consideration of motor detachment from the filament. Our work shows, in the case of low load, the velocity of multi-motor system can decrease or increase with increasing motor numbers depending on the single motor force-velocity curve.The stall force and run-length reduced greatly compared to other models.Especially in the case of low ATP concentrations, the stall force of multi motortransport even smaller than the single motor's stall force.     

EAST托卡马克杂质输运蒙特卡洛模拟

介绍DIVIMP程序的基本思想和采用的物理模型,研究EAST托卡马克欧姆放电条件下碳杂质的产生与输运.模拟结果与实验测量具有较好的一致性,说明将该程序应用于EAST装置中杂质输运模拟的合理性.并利用DIVIMP程序预测EAST在8MW加热功率条件下钨杂质的输运特性.     

微通道板电子输运特性的仿真研究

对微通道板(Micro-Channel Plate,MCP)的电子输运特性进行仿真研究.利用数值方法分析微光像增强器电子光学系统,得到电场分布.通过电场分布追踪MCP电子运动轨迹,确定电子在荧光屏像面上的落点分布.据此研究MCP电子输运,分析斜切角、通道直径及两端电压对电子输运、像增强器调制传递函数(Modulation Transfer Function,MTF)及分辨率的影响.结果显示,当MCP斜切角为14°、通道直径为5.0μm、两端电压为900 V时,MCP具有良好的电子输运特性,像增强器MTF特性好,分辨率高.     

Simulation of Kelvin-Helmholtz Instability with Flux-Corrected Transport Method

The sixth-order accurate phase error flux-corrected transport numerical algorithm is introduced, and used to simulate Kelvin-Helmholtz instability. Linear growth rates of the simulation agree with the linear theories of Kelvin Helmholtz instability. It indicates the validity and accuracy of this simulation method. The method also has good capturing ability of the instability interface deformation.     

Simulation Study of the Electron and Hole Transport in a CNTFET

In this work we have investigated electron and hole transport through zig zag carbon nanotubes by solving Boltzmann Transport Equation(BTE).We find that the mobility of electrons is rather greater than holes.Carbo nanotubes with longer diameter can carry higher current.Normally,transport of electrons(or holes) is dominated by scattering events,which relax the carrier momentum in an effort to bring the conducting material to equilibrium.     

三维混合沙输运数值模拟

采用计算流体力学和颗粒离散元耦合的方法模拟了三维混合沙输运过程。采用体平均的Navier-stokes方程来描述气相运动,考虑了气相和颗粒相的相互作用。颗粒运动通过求解牛顿运动方程来求解,采用硬球模型描述颗粒和颗粒及颗粒和壁面的碰撞。本模型中,颗粒运动是三维的而气相运动是二维的。计算结果表明:总输沙率沿高度方向在大于2cm以上按照指数衰减,在2 cm以下则偏大;各粒径颗粒具有不同的输沙率分布,粗粒径颗粒按指数规律衰减,其它粒径颗粒输沙率随高度先指数增加后减少;各粒径颗粒平均水平速度随高度对数函数增加且同高度时随粒径增大而减小,1 cm高度以下则相反;沙粒平均粒径沿高度线性递减,2 cm以下粒径偏大。     

单级跨声速压气机旋转失速模拟方法

为了研究多排跨声轴流压气机旋转失速先兆的表现形式与失速演化规律,基于自主研发的CFD软件AS-PAC,通过发展动态重叠网格技术,流量出口边界条件以及节流阀边界条件,对单级跨声速压气机NASA Stage 35由近失速状态到完全失速状态的过程进行了模拟.结果表明,发展的数值模拟方法能准确地模拟多排压气机的旋转失速发展过程...     

分子间相互作用对硫醇分子膜电输运性质的影响

利用密度泛函理论和弹性散射格林函数方法,对硫醇分子膜的电学特性进行模拟.计算结果表明,由于分子间的相互作用,导致分子膜的导电能力比单分子提高2~3个数量级.分子结的导电能力随着压力增加而增加,电极距离的变化使分子与电极以及分子间的耦合增强、分子结的链内隧穿和链间隧穿几率增大,导致电流增加.     

非均匀大气中γ射线输运的蒙特卡罗模拟方法

γ射线在高空大气中的输运问题常采用蒙特卡罗方法进行模拟,但由于大气是非均匀连续介质,通常需要根据高度上的密度变化将大气进行分层处理.高空大气密度变化非常剧烈,精细的分层会带来很大的计算量.针对非均匀连续介质中的粒子输运问题,利用质量距离抽样方法代替传统的步长抽样方法,提出一种可直接模拟粒子在非均匀连续介质中输运的蒙特卡罗方法,实现γ射线在非均匀大气中输运的蒙特卡罗模拟,并与MCNP程序的计算结果进行比较,结果符合较好.     

氮等离子体枪中电子输运行为的蒙特卡罗模拟

采用蒙特卡罗模拟,对氮等离子体枪的两个环形电极间的氮气辉光放电过程中电子的输运过程进行研究.计算在不同平均电场与粒子数密度的比值(E/N)下,电子与氮分子发生不同碰撞的概率、出射电子的平均能量、方向角分布和电子的能量分布.结果表明,电子能量近似服从玻尔兹曼分布.随着E/N的升高,电子平均能量升高,发生激发、离化、电离和离化电离碰撞的概率增大;非均匀分布的电场使分子获得更高的离化率,同时显著增强出射电子的能量.模拟结果为等离子体应用设计提供了参考依据.     

蒙特卡洛模拟中伪随机数的STTDMR检验

伪随机数发生器(PNG)是蒙特卡洛法概率模拟中的基本工具,但它也成为影响蒙特卡洛法精确度的最大误差源.提出了一种检验方法——二维介质辐射对称性检验法STTDMR,它可在不同条件下对各种伪随机数程序进行无限制的检验,在更精细的层次上区分伪随机数发生器的优劣.STTDMR不仅可检验伪随机数的特性,还可检验概率模型是否正确.利用STTDMR分析了多种典型的伪随机数产生法,获得一个性能上较优越的组合伪随机数ZH产生程序.     

超薄膜生长的Monte-Carlo研究

利用MonteCarlo(MC)模型研究了薄膜生长的初始阶段岛的形貌和岛的尺寸与基底温度之间的关系.模型中考虑了原子沉积、吸附原子扩散和蒸发等过程,与以前模型不同的是我们用Morse势计算粒子之间的相互作用,并详细考虑了临近和次临近原子的影响.结果表明,随基底温度的升高,岛的形貌经历了一个从分形生长到凝聚生长的变化过程.进一步研究表明,岛的形貌与基底的形貌之间的关系随着基底温度的升高有很大的变化,基底温度低时,岛的形状与基底形貌无关,高温时岛具有与基底形貌相似的结构.这些结果与实验结果一致.为了进一步说明 关键词：     

粒子输运蒙特卡罗模拟现状概述

蒙特卡罗(MC)方法发展已有60多年历史,广泛应用于核科学及相关领域.MC方法超强的几何处理能力,使用精密的连续点截面参数,能够模拟各种复杂几何系统内的中子、光子、电子、α粒子、质子及其耦合输运问题.随着计算机的快速发展,通过大规模并行计算,MC方法及程序已成为模拟各种粒子输运问题的首选工具.     

Simulation of kinetic processes by the Monte-Carlo method

Statistical simulation of kinetic processes involving the interaction between different particle species is carried out by a Monte-Carlo method which differs from the classical application of this method by omitting calculations of the trajectories and mean free paths. Data on the latter quantities are included in the experimentally determined cross sections and rate constants used in the simulation. This qualitatively changes the computational procedure, simplifying and accelerating it. Data are provided on the simulation of a second-order sequential process and on the synthesis and dissociation of carbon dioxide, and they are compared to the known experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 55–60, October, 1973.     

低温液体流动沸腾数值计算中的动量模拟

采用双流体模型计算了液氮在垂直管内的过冷流动沸腾过程,着重考察了相间动量传输模型对数值预测结果准确性的影响。研究表明,相间非曳力,尤其是壁面润湿力对于数值预测的准确性有着决定性的作用。此外,正确地估计沸腾系统中气泡的平均直径对于两相流传输特性的准确预测也有着十分重要的作用。     

Quantum Transport of Particles and Entropy

A unified view on macroscopic thermodynamics and quantum transport is presented. Thermodynamic processes with an exchange of energy between two systems necessarily involve the flow of other balancable quantities. These flows are first analyzed using a simple drift-diffusion model, which includes the thermoelectric effects, and connects the various transport coefficients to certain thermodynamic susceptibilities and a diffusion coefficient. In the second part of the paper, the connection between macroscopic thermodynamics and quantum statistics is discussed. It is proposed to employ not particles, but elementary Fermi- or Bose-systems as the elementary building blocks of ideal quantum gases. In this way, the transport not only of particles but also of entropy can be derived in a concise way, and is illustrated both for ballistic quantum wires, and for diffusive conductors. In particular, the quantum interference of entropy flow is in close correspondence to that of electric current.     

X光导管传输特性的蒙特卡罗模拟

 X光在导管中的传输性能是设计X光透镜的基础。在研究X光导管传输理论基础上，建立了X光在导管中传输的射线跟踪方法，编制了蒙特卡罗模拟计算程序。对具体的模型，计算给出了导管的传输效率随X光源与导管入口面的距离、导管直径和曲率半径的变化关系。模拟表明：直圆柱导管的传输效率随导管直径增大而减小，随Ｘ光源所在平面与导管入口面之间的距离增大而增大；弯曲圆柱导管的传输效率随其曲率半径的增大而增大，当曲率半径趋向无穷大时，X光在弯圆柱导管的传输效率趋向于直圆柱导管的传输效率。利用编制程序计算得到的传输效率与实验结果符合较好。     

冷中子三轴谱仪屏蔽体的蒙特卡罗模拟

冷中子三轴谱仪( CTAS ) 的屏蔽体对于保障工作人员安全、降低散射大厅本底及提高信噪比具有重要的意义。采用蒙特卡罗程序MCNP5 对谱仪各部分屏蔽体进行了计算,并结合Mcstas 程序确定了CTAS 入口处的中子源,大大提高了计算效率。经过模拟计算和优化表明:单色器后端使用厚350mm、密度4.6 g/cm3 的重混凝土,衔接屏蔽体使用厚300 mm、密度3.6 g/cm3的重混凝土,生物屏蔽采用厚150 mm、密度3.6 g/cm3 的重混凝土可保证屏蔽体外表面的剂量率满足散射大厅的剂量要求。The shielding of Cold neutron Triple-Axis Spectrometer( CTAS ) is important for radiation safety of workers, and reduce the background of scattering hall as well as enhancing the ratio of signal-to-noise. In this study,Monte-Carlo simulation was performed to conduct the calculation on the shielding of CTAS. To increase the calculation efficiency, neutron source was obtained by using Mcstas code. The results indicate that, in the case of heavy concrete ( density 4.6 g/cm3 ) with thickness of 350 mm for the shielding behind the monochromater, and heavy concrete ( density 3.6 g/cm3 ) with thickness of 300 mm for the other monochromater shielding, as well as the heavy concrete ( density 3.6 g/cm3 ) with thickness of 150 mm for biological shielding, the dose rate outside shielding may meet the requirement of national standard of China.     

纳米SiO2材料声子热输运的格子玻尔兹曼法模拟

根据德拜物理模型,采用格子玻尔兹曼方法（LBM）对纳米二氧化硅薄膜内的声子热输运特性进行了模拟分析,得到了薄膜内的温度响应特性;在此基础上,分析了其法向有效导热系数。计算结果表明,当努森数大于0．01时,薄膜边界处出现温度跳跃,呈现出明显的微纳米尺度传热特性;当薄膜厚度小于20nm时,减小厚度可使其有效导热系数迅速降低...