三维泡泡布点方法及网格生成

本文研究如何在三维区域上生成高质量的节点集并基于节点集进行网格生成．根据区域边界的几何描述和理想间隔控制函数,先后对曲面及区域内部用泡泡布点法进行节点布置．节点布置结束后,对区域边界的节点集运用高质量点集的局部网格生成算法(BLMG)进行网格剖分,对区域内部的点集直接进行Delaunay三角剖分．通过计算节点集生成Delaunay网格单元的质量来评价区域节点集的质量．泡泡均匀分布与非均匀分布的算例均表明,该算法生成的节点具有较高的质量并且在泡泡非均匀分布时具有很好的渐进性．     

Manufacturing process problem analysis using monte carlo simulation

The Monte Carlo simulation technique is already well known and used to analyse complex problems. In this paper we present its use to determine the impact of a manufacturing process problem on output quality. During production start-up on an automated manufacturing line a process problem escaped detection for a short period. There was the need to know its impact on output quality in order to provide an appropriate corrective action strategy for the products already in the warehouse and ready for shipment to selected users.     

SIMULATE Program: a gamma ray spectroscopy tool

A software package which simulates the virtual creation of gamma ray spectra emitted from a combination of radioactive sources, as seen by a semiconductor or scintillation detector, is presented . It partially utilizes Monte Carlo techniques based on the physics of gamma ray spectroscopy. In addition, certain algorithms are used to compensate for the premature termination of the fate of the detected photons of any particular energy.     

基于蒙特卡洛方法的触发器聚类布局算法

针对触发器聚类的布局问题,提出了一种基于蒙特卡洛方法的触发器聚类布局算法。该方法的核心思想为设计合理的评分函数,并通过蒙特卡洛方法模拟触发器聚类在版图上的随机游走过程,获取样本,再通过评分函数评价样本质量,逐步地在可行域中搜索最优解。实验结果表明,相较于现有的方法,该方法在总线长与时序性能两方面,分别得到平均约9%与17%的改善与提升。此外,该方法具有较强的健壮性,适用于复杂度较高或者版图利用率较高的设计,并能够快速收敛,以较小的时间代价完成优化。     

用MC仿真计算不确定度

介绍MC仿真的基础,将它用于不确定度的分布传播,并作了扩展不确定度的算法验证.     

Population balance modelling of bubbling fluidized beds. II. Axially dispersed dense phase

The population balance model of Sweet, Gustafson and Ramkrishna for a steady state gas-solid fluidized bed reactor is extended in this work to include axial mixing in the dense phase. A trivariate population balance equation for the bubble phase, and an axial dispersion equation for the dense phase are solved simultaneously by combining a Monte Carlo simulation technique with the method of successive approximations. Conversion for a first-order reaction is analysed in terms of five dimensionless groups including: a coalescence parameter controlling the extent of coalescence, a Peclet number measuring the amount of mixing in the dense phase, a Damkohler number which relates the dispersive mixing time in the dense phase to the reaction time, a dimensionless group representing the ratio of the dispersive mixing time to the time scale of mass transfer, and a dimensionless reaction rate constant. The computations show that coalescence can significantly affect reactor conversion. It appears that the effect of mixing is less significant particularly at higher reaction rates. Comparison of these results with those obtained earlier in which the dense phase was assumed to be perfectly mixed shows that higher conversions could be obtained in the latter case for sufficiently fast reactions while the opposite is true for slow reactions. This paper is dedicated to Dr L K Doraiswamy on his sixtieth birthday.     

A spectral representation based model for Monte Carlo simulation

A new model is proposed for generating samples of real-valued stationary Gaussian processes. The model is based on the spectral representation theorem stating that a weakly stationary process can be viewed as a superposition of harmonics with random properties. The classical use of this theorem for Monte Carlo simulation is based on models consisting of a superposition of harmonics with fixed frequencies but random amplitude and phase. The resulting samples have the same period depending on the discretization of the frequency band. In contrast, the proposed model consists of a superposition of harmonics with random amplitude, phase, and frequency so that different samples have different periods depending on the particular sample values of the harmonic frequencies.

A band limited Gaussian white noise process is used to illustrate the proposed Monte Carlo simulation algorithm and demonstrate that the estimates of the covariance function based on the samples of the proposed model are not periodic.     

Optimizing the design of a moderator-based neutron detector for a flat response curve in the 2–14 MeV energy range

The efficiency of a neutron detector with boron trifluoride proportional tubes embedded in a polyethylene moderator was simulated with a Monte Carlo program. A moderator structure where the detector had uniform sensitivity for neutrons from 2 to 14 MeV was determined by simulation. A counter was built based on the simulation results. The counter's efficiencies were calibrated with an Am–Be source and an accelerator that served as a D–D and D–T neutron source. Experimental neutron efficiencies of these sources are approximately uniform. The simulated model was validated by the consistent results between the calculated and experimental data.     

应用Monte Carlo算法研究大分子蠕动阻力的影响因素

采用一种基于高分子Monte Carlo模拟算法分析分子蠕动阻力的软件,借助于二维空间中的8配位点键长涨落的格子链模型,对不同温度、分子量、共混小分子时的大分子蠕动行为进行了模拟分析,考察了温度、分子长、共混小分子等因素对蠕动阻力的影响,得到了随着温度增加、分子长减小和共混浓度增加,大分子蠕动阻力减小的结果,这与传统经验理论相符合。这些结果为选择大分子量添加剂黄原胶作为抗结块剂,以及选择β-环糊抑制玻璃化转变等提供了理论依据。     

晶粒生长的蒙特卡罗模拟研究进展

概述了经典的晶粒生长蒙特卡罗(MC)模型并指出了其存在的缺陷,总结了近几年国内外研究者对经典MC模型的改进算法,综述了MC方法模拟晶粒生长的应用研究,指出了目前研究中存在的问题,并展望了今后的主要研究方向.     

Optimization of piezoelectric sensor location for delamination detection in composite laminates

The optimal placement of sensors is a critical issue in detecting damage in laminated composite structures. The aim is to use a minimum number of sensors, placed at the correct locations, so that the voltage signals received from the sensor set can be used to detect both the presence and the extent of damage. In this study, an optimization procedure is developed to detect arbitrarily located discrete delamination in composite plates using distributed piezoelectric sensors. The probability of damage distribution in the plate is determined using a statistical model. A genetic algorithm (GA) is used to detect the number and location of the sensors. The analysis uses a Monte Carlo method to generate the initial population. The simulation and signal processing is performed using a finite element procedure based on the refined layer-wise theory, which is capable of modelling ply-level stresses, and seeded delaminations are modelled with Heaviside step functions. A two-way electromechanical coupled field formulation is used to describe the induced strain. The objective function is a damage index which compares the voltage signals from a healthy (no delamination) and a statistically determined delaminated model. The voltage signals are affected by the local changes in the strain induced by the presence of delamination. The optimization solutions are verified by numerical simulation as well as with experiments conducted using customized piezoelectric sensors and a laser scanning vibrometer. The results presented show that the optimum sensor pattern is capable of detecting discrete seeded delaminations in moderately thick composite plates.     

Computer simulation of the effect of post annealing parameters on the microstructure inhomogeneity of the non-uniformly deformed copper

A computer simulation on the basis of the Finite Element Method and Monte Carlo Model is developed to simulate the microstructure of the non-uniformly deformed copper workpiece after annealing. Using the computer simulation, the effects of annealing time and temperature on the microstructure inhomogeneity of the workpiece are simulated and investigated quantitatively, by defining an Inhomogeneity Factor, to design an annealing program for reducing the microstructure inhomogeneity. The results show that with increasing the parameters of annealing time and temperature, the inhomogeneity is decreased when one of the parameters is constant. Also, at high annealing temperature, the annealing time changes the inhomogeneity slowly compared with which occurs at low annealing temperature. The simulation results agree well with the experimental values.     

中和室脉冲进气的蒙特卡罗模拟及实验验证

对于中和室内的脉冲气体，用蒙特卡罗方法模拟了气体压力沿轴向的分布。并用模拟进气系统和气压瞬时测量系统，对模拟结果进行了验证。得到与模拟结果较为一致的曲线，从而为注入器真空系统的设计提供了可靠的依据。并通过实验结果，给出了气体靶厚的建立时间约为６０ｍｓ。     

Three-Dimensional Model of the Spectral Emissivity of Light- Scattering Exhaust Plumes

A three-dimensional model of radiation of rocket exhaust plumes is given, which is based on the Monte Carlo simulation method. Two problems associated with the determination of spectral directional radiation of rocket exhaust plumes are treated, namely, the self-radiation of multiple plumes and the scattering of solar radiation incident on a single or multiple plume at an arbitrary angle by the condensed phase of the combustion products. The suggested model enables one to calculate the spectral emissivity with averaging of the rotational structure of molecular emission spectrum by diatomic and triatomic molecules of combustion products in the spectral range from 0.1 to 10 m. The results are given of calculations of the spectral and integral emissivity of light-scattering rocket exhaust plumes of various configurations, containing Al₂O₃ particles with an average radius of 2 m, in the infrared spectral region of 2-5 m.     

Monte Carlo simulation analysis of the effects of different system performance levels on the importance of multi-state components

In the present paper, we consider some frequently used importance measures, in their generalized form proposed by the authors for application to multi-state systems constituted by multi-state components. To catch the dynamics of multi-state systems, Monte Carlo simulation has been utilized. A simulation approach has been presented which allows estimating of all the importance measures of the components at a given performance level in a single simulation, provided that the components are independent. The effects of different performance demands made on the system on the importance of its multi-state components have been examined with respect to a simple multi-state series–parallel system. The results have shown that a performance level of a component may be more critical for the achievement of a system performance and less critical for another.     

磁性多层膜系统自旋重取向行为的Monte Carlo模拟

依据Heisenberg模型,利用Monte　Carlo方法模拟了磁性多层膜系统的自旋重取向行为,研究了各向异性、偶极相互作用以及外磁场对系统自旋取向的影响。通过模拟计算,获得了系统组态、磁分量等随偶极相互作用、外加磁场和温度的变化规律,重点研究了磁性多层膜系统在外磁场作用下的磁滞现象。     

Monte Carlo模拟薄膜生长的研究

阐述了Monte Carlo方法在薄膜生长中的应用和最新进展;简要论述了Monte Carlo算法的类型及各自的特点;结合MonteCarlo方法的特点,提出了模拟薄膜生长的模型以及处理方法.同时,归纳出MonteCarlo模拟薄膜生长需要解决的主要问题.