BESⅡ上光子探测效率的研究

利用J/ψ→ρπ衰变道,对BESⅡ上BSC对于光子的探测效率做了细致的研究.结果表明在从探测器光子能量阈值直到BES上可产生的最大光子能量范围内,用目前的Monte Carlo可以在1%—3%的精度下模拟光子的探测效率.并且对Monte Carlo在探测效率上与数据的差别进行了详细研究.同时用质心系能量s=3.770GeV处的e+e–→γe+e–数据检验了高能区MonteCarlo和数据的探测效率都达到100%,并且在1%精度下是一致的     

Investigation of the local structure variance of water molecules in laser-induced thermal desorption process

This paper presents the use of molecular dynamics simulation in the study of laser-induced thermal desorption (LITD) of water molecules adjacent to a laser-heated Au substrate. The local structure of the water molecules is investigated by considering the densities of the oxygen and hydrogen atoms, the average number of neighbors, n_NN, and the average number of H-bonds, n_HB. At an equilibrium temperature of 300 K, the simulation results show that three adsorption water layers are formed in the immediate vicinity of the Au surface, and that each four-fold hollow site on the uppermost Au(0 0 1) surface is occupied by a single water molecule. Following laser-induced heating of the Au substrate with a sub-picosecond laser pulse of 350 fs, the substrate temperature increases to 1000 K. This causes a gradual heating of the adjacent water film, which is accompanied by a decrease in the values of n_NN and n_HB. Hence, it can be concluded that an increase in the water film temperature destroys the hydrogen-bonding network throughout the water film. Although the maximum local temperature of the water film occurs in the region immediately adjacent to the Au substrate, it is determined that the attractive energy between the Au atoms and the water molecules in this region causes the water molecules to aggregate together to form three-dimensional water clusters. Furthermore, this energy prevents the hydrogen bonds in this region from breaking apart as violently as those within the phase explosion region. Finally, it is observed that the phase explosion phenomenon occurs in the region of the water film where the values of n_NN and n_HB are at a minimum.     

光学综合孔径望远镜成像分析及计算机仿真

阐述了光学综合孔径(OSA)望远镜成像原理以及综合孔径望远镜的几种实现形式；采用快速傅里叶变换(FFT)算法得到了任意子孔径综合模式下的点扩展函数(PSF)和光学传递函数(OTF)分布；从子孔径结构排列、共相位、图像恢复几个方面论述了光学综合孔径的成像特征。初步分析了稀疏率、填充因子、“实际截止频率”等因素对光学综合孔径望远镜成像的影响。分析和仿真结果表明：光学综合孔径通过相干成像不但可以突破传统单孔径系统的口径局限获得极高的成像分辨率，而且对于实现空间光学遥感系统轻量化和模块化都具有重要意义。     

阻滞增长模型支持下对益虫和害虫数量关系及农药影响的分析

研究了在自然状态和喷洒农药情况下益虫和害虫数量的发展趋势.基于logistic模型并加以改进建模,通过分析微分方程平衡点的稳定性,分别得出了自然状态下益虫和害虫的数量发展规律.在此基础上,进而建立了农药影响的模型并进行了计算机仿真,仿真结果证明了新模型的合理性和适用性,解决了Lotka—Volterra模型存在的问题.另外,该仿真程序本身可以作为应用程序用于实际的农田管理.     

基态非简并聚合物中的极化子和双极化子的动力学(Ⅰ)--弱电场下研究

文中模拟了在基态非简并聚合物中的极化子和双极化子在弱电场中的运动,研究了在不同简并参数的系统中极化子和双极化子的动力学稳定性,发现在同一个系统中,双极化子比极化子的运动速度慢,晶格振荡小; 在简并参数大的系统中,极化子和双极化子的运动速度都变慢.极化子和双极化子在弱电场下都存在饱和速度,达到饱和速度后, 电场的能量发生了转换.     

数字波束形成算法仿真实现

从讨论波束形成方法在声系统中的主要作用和主要形成过程入手，介绍几种具体实现波束形成的算法。主要讨论一种能够降低硬件要求的波束形成算法——正交波束形成算法。此种方法不但适用于声系统，对于其他检测系统也有一定的实际意义。给出几种主要波束形成算法的Matlab仿真实现程序，将按照此类方法仿真所得到的波束形成指向性图与理论指向性图比较，两者非常类似。     

半导体超晶格属性的高分辨率X射线衍射研究

详细阐述了低维半导体材料的X射线衍射的动力学理论和运动学理论从高木陶平(T-T)方程出发,基于波动光学原理,推导出任意结构的多层膜的X射线衍射振幅的递推关系式并编写X射线衍射的程序,分别用动力学和运动学衍射理论模型模拟了20层GaAlAs/GaAs超晶格的X射线衍射结果,得到超晶格样品的结构参量.     

计算物理前沿及其与计算技术的交叉

计算物理学是随着计算技术发展而形成的一门新兴的交叉学科。它是用现代计算技术武装起来的“实验的”理论物理学和“虚拟的”实验物理学。文章回顾了计算物理的发展历史，介绍了计算物理研究状况和前沿问题，并展望了新世纪计算物理面临的挑战。     

Monte-Carlo study of correlations in quantum spin chains at non-zero temperature

Antiferromagnetic Heisenberg spin chains with various spin values (S=1/2,1,3/2,2,5/2) are studied numerically with the quantum Monte-Carlo method. Effective spin S chains are realized by ferromagnetically coupling n=2S antiferromagnetic spin chains with S=1/2. The temperature dependence of the uniform susceptibility, the staggered susceptibility, and the static structure factor peak intensity are computed down to very low temperatures, . The correlation length at each temperature is deduced from numerical measurements of the instantaneous spin-spin correlation function. At high temperatures, very good agreement with exact results for the classical spin chain is obtained independent of the value of S. For the S=2 chain which has a gap , the correlation length and the uniform susceptibility in the temperature range are well predicted by the semi-classical theory of Damle and Sachdev. Received: 23 December 1997 / Revised and Accepted: 11 March 1998     

Analysis and design of mechanical crack arrestors for gas pipeline

Mechanical arrestors are frequently used in gas transmission pipelines to prevent the possibility of long running cracks. These arrestors have the effect of reducing the pipe from opening as the crack passes. This decreases the available crack driving force and, as a result, crack arrest may take place. This essentially is a second line of defence against catastrophic failure in the event crack initiation cannot always be prevented. A novel analyzing method presented in this paper has been developed to investigate the suitability of these crack arrestors. This is based on a fluid/structure/fracture interaction package, PFRAC. A dynamic finite element approach has been developed for a three dimension curved beam with initial plane curvature, which has been implemented in PFRAC to simulate the behaviour of the arrestor. The contact conditions between the pipe wall and the arrestor, along with the various computational procedures, are described. Several numerical results for a cracked pipe with arrestors are presented and compared with those for pipes without arrestors.