等温圆柱型空腔表面辐射传递方向分布特性

用蒙特卡罗法计算了圆柱型空腔底面与管内壁面单元之间的辐射传递系数,研究了底面为黑体表面、管内壁面为等温灰体、漫发射、漫反射时,管内壁发射率、管长与半径比的变化对管口表面定向发射率的影响,结果表明:管长与半径比增加,管口表面定向发射率极值点向小角度的天顶角方向移动,管长与半径比超过30,管口表面最大定向发射率对应天顶角<2°;管内壁发射率为变量时,距离管出口1倍管内直径处的发射率对管口表面最大定向发射率的影响较大;管内壁的发射率越小,管口表面定向辐射集中特性越好.     

等温方型通道方向辐射特性

为了比较辐射通道几何形状变化对通道出口逸出辐射能的方向分布特性的影响,本文采用蒙特卡罗法,研究了等温方管、等温方管空腔两种方形通道的方向辐射特性,计算并分析了相关参数如管内壁发射率、管长与当量直径比变化对通道出口表面方向辐射系数的影响.结果表明:经方管、方管空腔辐射通道出口处的辐射加热比经圆管、圆管空腔的定向集中辐射加热特性更好.该计算结果为定向辐射器辐射通道几何结构选取提供参考.     

偏置电场对THz辐射强度影响的蒙特卡罗模拟

采用系综蒙特卡罗方法对光生载流子在偏置电场作用下的输运过程进行模拟,从微观角度研究偏置电场对连续太赫兹辐射强度的影响.模拟结果表明,由于空间电荷电场屏蔽效应以及散射等因素的影响,太赫兹辐射强度先是随偏置电场的增强而上升,当达到峰值后逐渐趋于饱和.虽然降低温度使粒子发生散射的几率降低,但同时也减小粒子的初始能量,故低偏置电场时低温下连续太赫兹辐射功率比常温下小,而当偏置电场超过某一阈值时,降低温度能够提高连续太赫兹辐射功率.     

辐射离散坐标法在柱形炉膛中的辐射传热计算

利用离散坐标法对圆柱形炉膛辐射传热进行了计算,结果与计算精确的区域法的计算结果符合较好;同时又利用离散坐标法和热流法对旋流燃烧室温度场进行比较计算,结果表明：离散坐标法计算结果与文献中实验结果符合较好;离散坐标法具有较好计算精度,可应用旋流燃烧辐射计算中.     

Numerical simulation of bistatic scattering from fractal rough surface in the finite element method

By using the Monte Carlo method and numerical finite element approach, bistatic scattering from the fractal and Gaussian rough surfaces is studied. The difference between these two surfaces and their functional dependence on the surface parameters are discussed. Angular variation of bistatic scattering from the fractal surface is very significant, even for fairly smooth surface, whilst scattering from the Gaussian rough surface tends to the specular reflection. The slope of angular variation is linearly related with the fractal dimension. If an electrically-large target is placed over the rough surface, the fractal dimension inverted from bistatic scattering would be reduced. As the surfaces become very rough, scattering from different fractal and Gaussian surfaces would be not identified.     

岩体结构面模拟方法探析

结合盐津桥水库右岸岩体结构面的实际情况,综合考虑结构面的几何特征和力学特征,针对不同类型的结构面,先运用蒙特卡洛（Monte-Carlo）方法获得随机结构面的几何参数,再利用有限元软件ANSYS对确定性结构面进行数值模拟,以获得有效的结构面模拟方法。此方法有效地解决了难以对数量多、尺寸小的随机节理进行逐条模拟的问题,又从变形和强度的弱化方面把节理考虑进去,与现实情况近似,是一种行之有效的方法。     

反向蒙特卡罗法模拟参与性介质中热辐射传递

为解决传统蒙特卡罗法结果收敛时间长的问题,当仅需要了解某个指定位置和方向的信息时,提出了反向蒙特卡罗法替代方法．该反向运算法则与传统的蒙特卡罗法类似,除了能束射线反向跟踪外．能束的传播是从探测位置到参与性介质中,而不是从像传统的蒙特卡罗法从源到探测位置处．利用反向蒙特卡罗法模拟计算一维和二维的热辐射传递问题,并且与相关文献进行比较,结果吻合较好．     

W型火焰煤粉锅炉炉内传热过程的三维数值模拟

本文研究了Ｗ型火焰煤粉锅炉炉内传热过程的数值模拟计算方法．用蒙特卡洛法计算辐射换热，用差分法计算对流换热及导热．利用这一方法计算了３００ＭＷＷ型火焰锅炉炉内的温度分布，取得了比较满意的结果．另外，本文还对有关蒙特卡洛法的几个问题进行了研究．     

XY模型中涡旋数密度的Monte Carlo模拟

应用蒙特卡罗方法,系统地研究了铁磁XY模型中涡旋数密度随时间的弛豫过程,仔细分析了序参数和涡旋数密度的临界标度行为。自由涡旋数密度存在幂次律行为,但需要引入修正。测量得到静态临界指数η,与理论得到的结果相符合。     

Two-flux method for radiation heat transfer in anisotropic gas-particles media

1 Introduction Two-flux method is considered as a simple model and can be used to predict heatflux in 1-D radiative heat transfer. In the original two-flux method[1,2], the radiation fieldwas assumed to be isotropic. But for gas-particles mixture in combustion environments,the scatterings of particles are usually anisotropic, and the original two-flux methodgives critical errors when ignoring this anisotropy. It is desirable to have a two-flux ra-diative transfer model to be applied rega…     

Verification of topological relationship in 2-D grain growth process by simulation

Behaviors of the quasi-steady state grain size distribution and the corresponding topological relationship were investigated using the Potts Monte Carlo method to simulate the normal grain growth process. The observed quasi-steady state grain size distribution can be well fit by the Weibull function rather than the Hillert distribution. It is also found that the grain size and average number of grain sides are not linearly related. The reason that the quasi-steady state grain size distribution deviates from the Hillert distribution may contribute to the nonlinearity of the relation of the average number of grain sides with the grain size. The results also exhibit the reasonability of the relationship deduced by Mullins between the grain size distribution and the average number of grain sides.     

Grain size distribution and topology in 3D grain growth simulation with large-scale Monte Carlo method

Three-dimensional normal grain growth was appropriately simulated using a Potts model Monte Carlo algorithm. The quasi-stationary grain size distribution obtained from simulation agreed well with the experimental result of pure iron. The Weibull function with a parameter β=2.77 and the Yu-Liu function with a parameter ν =2.71 fit the quasi-stationary grain size distribution well. The grain volume distribution is a function that decreased exponentially with increasing grain volume. The distribution of bounda...     

Geometry model construction in infrared image theory simulation of buildings

Geometric model construction is the basis of infrared image theory simulation. Taking the construction of the geometric model of one building in Harbin as an example, this paper analyzes the theoretical groundings of simplification and principles of geometric model construction of buildings. It then discusses some particular treatment methods in calculating the radiation transfer coefficient in geometric model construction using the Monte Carlo Method.     

A new hybrid method——combined heat flux method with Monte-Carlo method to analyze thermal radiation

A new hybrid method, Monte-Carlo-Heat-Flux （MCHF） method, was presented to analyze the radiative heat transfer of participating medium in a three-dimensional rectangular enclosure using combined the Monte-Carlo method with the heat flux method. Its accuracy and reliability was proved by comparing the computational results with exact results from classical ＂Zone Method＂.     

热加工材料动态再结晶介观组织模拟模型的研究进展

通过计算机模拟技术可以有效模拟金属材料热变形过程中动态再结晶组织的演化过程, 从而达到预测材料性能的目的。介绍了目前材料动态再结晶过程介观组织模拟的两种模型--元胞自动机(cellular automaton, CA)模型和蒙特卡洛(monte carlo, MC)模型的模拟技术及其研究进展, 重点分析了现有动态再结晶介观组织MC模型存在的问题并且提出了解决思路。     

Preparation and Monte Carlo Simulation of La0.67Ca0.33MnO3/Cr2O3 Composites

The （ 1 - x ） La0.67Ca0.33MnO3 （ LCMO ） ＋ x Cr2O3 composites were synthesized by a new liquid phase method. The XRD and SEM meusurements reveal that few Cr2O3 were soluble in the LCMO structure and the lattice constant of LCMO almost did not change, while most Cr2O3 were distributed at the grain boundaries or on surfaces of the LCMO grains. In resistivity versus temperature meusurements, a metal-insalator transition was observed when x 〈 0.20. The resistivity increases and the metal-insalator transition temperature deereases with the increasing content of Cr2O3 . A random resistor network （RRN） model was used to simulate the transport property of the mixture samples. The simulation results agree with the experimental observations. The results show that the method is reasonable for understanding the electronic transport of the composites of the manganite.     

New method for wave radiation and propagation in anisotropic stratified media

A matrix-exponent method is proposed to treat wave radiation and propagation in aniotropic stratified media. By using matrix-exponent formulations, the present method is elegant for expressions and reliable for computations. As an example, the method is used to calculate the ELF excitation of the Earth-ionosphere waveguide by an equivalent dipole resulting from heating the lower ionosphere with modulated HF waves.     

一类机会约束规划的回溯逼近求解法

研究了一类机会约束随机规划的近似求解问题,提出了基于蒙特卡罗随机模拟的回溯逼近求解算法,该方法通过在迭代过程中逐步增加抽样次数和精确求解确定性数学规划,最终得到机会约束规划的最优解。文中讨论了最优解的计算方法及算法迭代终止条件。最后,通过算例验证了该方法的有效性。     

圆柱状空腔辐射能的方向性与传热效率

为分析空腔出口辐射能定向集中加热特性与传热效率数值,利用有限差分法求解圆管壁与管内冷却空气温度场,其中辐射换热量利用蒙特卡罗法中的辐射交换因子计算．圆管壁为漫发射、漫反射镜反射混合分布,管底部为假想的圆形黑体辐射器．引入有效方向发射率等参数来描述管口辐射能的方向分布特性,并计算了相关参数如管壁发射率、镜漫反射分布、管长与半径比变化时有效方向发射率的数值．计算结果表明：管内壁发射率以及管长与半径比较大时,管口辐射能向小角度天顶角方向集中,但传热效率较低;镜漫反射的比例相同时,比全管长漫反射时传热效率提高约1～2倍．     

Monte Carlo simulations of dense gas flow and heat transfer in micro- and nano-channels

The flow and heat transfer in micro/nano electro-mechanical-systems (MEMS/ NEMS) is an important theoretical problem, which drives or restricts the further de- velopment of MEMS/NEMS. Now this kind of studies are of hot activity[1,2]. Due to the small characteristic length, the gas in micro- and nano-channels shows different features from the one in flow and heat transfer at macroscale. Generally, the mean free path of gas, even under common temperature and pressure, could be comparable…