多束部分相干光通过强湍流对光强闪烁的影响

在Rytov方差的基础上,利用Andrews的唯像闪烁模型,推导出部分相干光通过强大气湍流后其对数光强起伏方差的公式,并用此公式对部分相干光通过强湍流后给光强闪烁造成的影响进行了仿真。其结果表明,当光源的相干性变差,即变为部分相干光后,对数光强起伏方差变小;当采用多束部分相干光时,接收面上光强起伏方差得到明显改善,而且光束越多,改善越明显。     

物体面形对结构光场的空间调制：计算机模拟

提出一个实现三维面形对结构光场的空间调制的计算机仿真系统。重点讨论仿真系统的基本原理、投影光场与观察光场和三维面形的几何关系、该系统的实现方案。本文还给出了在一定系统参数条件下，几种特殊三维面形对空间结构光场调制的实验结果。     

薄膜生长的计算机模拟

薄膜技术在现代科技领域中有着广泛的应用。人们对薄膜的生长过程通过理论和实验进行了深入的研究，其中计算机模拟是重要的方法，本文概述了对薄膜生长过程的实验观察结果及其理论分析，主要讨论了薄膜生长的计算机模拟中经常采用的方法-蒙特卡罗法和分子动力学方法、描述衬底上成膜粒子运动的一些模型以及在计算机模拟中需注意的一些问题，其中主要包括粒子间的相互作用，入射粒子的能量和粒子上的衬底上的扩散运动。     

计算机模拟建模

通过在数学建模教学实践中编写的两个典型案例的建模和利用MATLAB软件求解，具体展示了对连续系统计算机模拟的建模步骤和方法。     

水声信号的计算机模拟

介绍了典型情况下的海洋环境噪声,混响、目标辐射噪声、回波等声信号模型、给出了表达式以及所建声信号模型的计算机模拟结果。模拟结果与理论值符合良好。     

冷风型空调器的计算机模拟

用步进计算法建立了冷风型空调器的系统模拟模型，模型中考虑了毛细管内亚稳态液体区的存在，以及翅片形状、管排管因素对换热的影响。空调顺运行工况的模拟计算结果与实测数据是吻合的，证明本模型和算法可靠。利用此模型对空调器性能随蒸发器、冷凝器迎面风速的变化情况作了预测，结果合理。     

磁控过程的计算机模拟

本文基于蒙特卡罗方法,并结合SRIM软件,编制程序跟踪模拟了磁控溅射各物理过程的粒子状态.以铝靶材为例,得到了粒子在磁控溅射各物理过程的状态分布,讨论了工作参数对薄膜沉积过程的影响.模拟结果表明:溅射原子的能量主要分布在20 eV以下,当原子沉积到基片表面时,其能量主要分布在15 eV以下,但有两个分布峰值,两个分布峰值对应着快慢两种不同形式的沉积过程.原子沉积到基片 表面的位置大致服从正态分布,气压p和靶基距离d影响正态分布的方差,也即影响沉积原子在基片表 面分布的均匀性.功率与沉积速度呈良好的线性关系,在工作气压为1 Pa,靶基距离为60mm的条件下,当入射粒子的能量为250 eV时,模拟得到的功率效率最大.     

基于LabVIEW的纳米颗粒动态散射光模拟

采用实验室虚拟仪器工程平台LabVIEW实现了纳米颗粒动态光散射信号的计算机模拟。用G语言(图形语言)设计了信号模拟的框图程序,给出了5nm, 15 nm两种粒径颗粒的模拟动态散射光信号及自相关函数。对模拟信号的粒度分析表明,这两种模拟信号产生的测量偏差分别为0.4nm和-0.6nm。     

Computer simulation studies of Ar clusters

Results of the solid-liquid transition of Ar₁₃ cluster in a spherically symmetric external potential have been presented. The transition temperature is observed to show an elevation with pressure. The broadening of the heat capacity peaks indicate the transition becoming more diffused with pressure. The icosahedral structure of the cluster remains unaltered under pressure. Ar₅₅ cluster has also been studied by similar approach. A possible connection between glass transition phenomenon and melting of clusters under pressure has been examined. Communication no. 1413 from Solid State and Structural Chemistry Unit.     

磁控溅射靶材刻蚀特性的模拟研究

靶材刻蚀特性是研究磁控溅射靶材利用率、薄膜生长速度和薄膜质量的关键因素.本文用有限元 分析软件ANSYS模拟了磁控溅射放电空间的磁场分布,用粒子模拟软件OOPIC Pro(object oriented particle in cell)模拟了放电过程,最后用SRIM(stopping and range of ions in matter)模拟了靶材的溅射特性,得到了靶材的刻蚀形貌和刻蚀速度,并讨论了不同工作气压和不同阴极电压对靶材刻蚀的影响.模拟结果表明:靶材刻蚀形貌与磁场分布有关,磁通密度越强,对应的靶材位置刻蚀越深;靶材的刻蚀速度随阴极电压的增大而增大,而当工作气压增大时,靶材的刻蚀速度先增大后趋向平衡,当工作气压超过一定的值时,刻蚀速度随气压的增大开始减小.模拟结果与实验观测进行了比较,二者符合较好.     

Computer simulation of amorphization phenomena in metals under irradiation

In this paper, we use a simplified model to simulate the amorphization phenomenon in metals under irradiation. The model has few parameters but can reflect the essential characteristics of the processes. Our simulation results show that the relaxation of collision cascades forms small crystal grains and the amorphization phenomenon is a result of total overlap of different grains, which depends on the irradiation temperature.     

Computer simulation of pressure sintering

The densification process during pressure sintering has been analyzed using finite element analysis. This analysis uses an iterative solution algorithm. With this the densification process in complex geometries with complex boundary conditions can be analyzed and this technique is particularly suited for tackling material nonlinearity. Evolution of dense structures with gradual closure of pores is described for two typical geometries.     

卤化银感光过程的计算机模拟

本文以光电子动力学理论为基础,采用成核生长理论模型(Nucleation&GrowthModel)和蒙特卡罗方法(Monte-CarloMethod),模拟光电子的产生、传播、衰减、直到实现潜影中心为止的感光过程.在讨论成核生长模型的基础上,把卤化银材料的感光过程分为五个阶段进行模拟,并对各个阶段的模拟算法进行了较详细的论述.     

Computer simulation of dislocation-carbon interaction in nickel

An atomistic computer model based on a rigid boundary method has been developed to estimate the interaction energy between a single edge dislocation and an impurity carbon interstitial in nickel. The simulation was carried out using the static relaxation technique on a total of 600 atoms, using an appropriate host-host pair potential. The impurity-host potential has been chosen to be a cubic function in this calculation. In the absence of the dislocation the dipole tensor for the octahedral site is seen to be spherical. Two impurity positions, one above and one below the slip plane were investigated. The carbon-dislocation interaction energies obtained were 1·4 eV and 0·7 eV respectively for the two impurity positions. The dipole tensor for the impurity in the presence of the dislocation was found to be non-diagonal.     

Two-faceted mirror for active integration of coherent high-power laser beams

A new integration method suited for spatially coherent high-power laser beams is demonstrated. The integrator system is based on a mirror with two facets, one of which can vibrate under the action of a piezoelectric translator. After reflection in the faceted mirror, the beam intensity distribution is modified to obtain greater uniformity. However, because of the coherence of the reflected beamlets, this distribution is affected by an interference pattern. The active integration consists of a periodic displacement of the moving facet that causes the interference pattern to vibrate, and its contribution to the intensity profile therefore averages out (fringe visibility within a 5% range). The combination of a faceted mirror and a simple imaging system results in an intensity profile with good uniformity over large spot sizes. Both simulated and experimental results are presented, the latter showing that a final uniformity within a 10% range can be achieved and it is limited mainly by diffraction at the edges of the facets.     

不同强度分布激光水平传输稳态热晕效应的数值模拟

采用数值模拟的方法,以高斯光束、平顶光束、有中心遮拦的平顶光束为例,研究了激光在均匀大气传输过程中产生的稳态热晕效应。详细分析了发射功率、传输距离、光束直径、横向风速四种参数对热晕效应的影响,得到了以上三种光束的斯特列尔比和峰值偏移量随广义热畸变参数N的变化关系。数值仿真结果表明,在其他参数一致的情况下,发射功率越大、传输距离越长,热晕效应越强;而光束直径和横向风速的增加会减小热晕效应;不同激光强度分布对热晕效应的影响不同。在同样广义热畸变参数N的条件下,高斯光束的热晕效应最严重,平顶光束次之,空心光束的热晕效应最小。