近独立子系系统的统计规律(四)——巨正则分布函数

根据吉布斯系综理论导出了由任意数目刚性粒子构成的力学系统的巨正则分布函数、化学势及粒子数和能量涨落公式.并介绍了刚球模型下,对二维和三维近独立子系系统巨正则分布的计算机模拟,结果与理论完全一致.     

后体参数对运输机后体阻力的影响

出于实际使用需求的考虑,运输机后体通常设计成上翘收缩的外形.这种外形会引起机身尾部出现比较强的负压区,使得飞机阻力大大增加.因此,通过运输机后体外形优化设计进行减阻是运输机减阻研究中重要的内容.选用典型上翘后体运输机的单独机身外形模型,采用外式张线天平测力和CFD数值模拟相结合的方法,分别研究了后体收缩比和后体上翘角两个主要的后体几何参数对阻力系数的影响.研究结果表明:阻力系数随后体收缩比的增大而增大,后体上翘角对阻力系数的影响与迎角相关;收缩比和上翘角对摩擦阻力系数影响较小,阻力系数的变化主要来源于收缩比和上翘角对压差阻力系数的影响;外式张线天平可以测量出后体参数变化引起的微小阻力差量,因此可以用于开展后体试验研究.     

铁路车辆/轨道耦合系统在竖向冲击载荷作用下动态响应的计算机模拟研究

车辆与轨道的动态相互作用,是铁路轮轨接触式运输系统中最基本的问题之一,它直接制约着铁路运营速度的提高和运载重量的增加,也影响着铁路安全运行.本文采用有限元方法,对我国C61型运煤货车,按照车辆/轨道系统的实际几何形状、材料性质和边界条件建立了包括车辆和轨道系统的有限元模型,应用大型非线性动力分析程序LS-DYNA3D来模拟车辆通过轨道错牙接头时的轮/轨动态响应过程.计算结果表明车轮和轨道之间的竖向动态接触力大约是静轮载的2倍,与已有的现场试验结果基本吻合.因此应用有限元方法研究车辆/轨道耦合系统是可行和可靠的.     

内爆法制备双金属管复合参数的计算机辅助设计

根据爆炸复合窗口理论和内爆轰作用下管的飞行姿态计算公式,编制计算机程序来确定双金属管内爆复合的工艺参数,使得复合参数的选取大为简化。结果表明,该方法可以用于指导内爆法制备双金属管复合工艺参数的选择。     

面向先进光源的硅像素传感器保护环结构仿真研究

硅像素传感器上的保护环结构有利于提高传感器的耐高电压性能,为评估保护环结构对硅像素传感器的保护效果,仿真分析了三种保护环结构。通过计算机辅助设计技术对三种保护环结构进行二维建模,利用TACD内置的电学模型对三种保护环结构的I-V特性进行了仿真。研究结果表明,电流收集环会提高像素的耐高电压性能,同时不等间距保护环、保护环的内外等距离Al悬挂以及多个保护环结构有利于进一步提高传感器的击穿电压。     

田口方法和双重曲面响应(DRSM)法

田口参数设计在理论界遭到较多批评 ,也提出一些替代方法。双曲面响应 ( DRSM)法是结合田口参数设计的思想和统计回归模型发展起来的。本文通过正交旋转设计和计算机模拟噪声因子变化来提高双曲面响应法的精度并对两种方法应用结果进行比较 ,说明田口参数设计仍具有实践和方法论的启发意义     

Recent advances of variational model in medical imaging and applications to computer aided surgery

In this paper, we review some mathematical models in medical image processing. Due to the superiority in modeling and computation, variational methods have been proven to be powerful techniques, which have been extremely popular and dramatically improved in the past two decades. On one hand, many models have been proposed for nearly all kinds of applications. On the other hand, a lot of models can be globally optimized and also many computation tools have been introduced. Under the variational framework, we focus on two basic problems in medical imaging: image restoration and segmentation, which are core components for kinds of specific tasks. For image restoration, we discuss some models on both additive and multiplicative noises. For image segmentation, we review some models on both whole image segmentation and specific target delineation, with the later being a key step in computer aided surgery. Additionally, we present some models on liver delineation and give their applications to living donor liver transplantation.     

光学传递函数测定计算机仿真实验系统

在５８６微机上的Ｗｉｎ ９５／ＮＴ操作系统环境下实现了光学系统传递函数测定的仿真实验,克服了因缺少光学传递函数测定仪而无法开设实验的困难。本文阐述了光学传递函数测定实验计算机仿真系统的实验原理与步骤,以及软件结构与特点。     

Synthesis of Heterocyclic Ring Systems for Heat-Resistant Plastics from Polyisocyanates

Investigations on space flight and rockets carried out in particular in the United States have aroused great interest in plastics with enhanced thermal stability. It has become possible to pass far beyond the expected limits of thermal stability with organic plastics, and to synthesize plastics and polymers that can be used at temperatures between about 200 and about 500 °C, a range that formerly appeared to be the exclusive province of inorganic materials.     

Møller-Plesset (MP2) perturbation theory for large molecules

Summary A novel formulation of MP2 theory is presented which starts from the Laplace transform MP2 ansatz, and subsequently moves from a molecular orbital (MO) representation to an atomic orbital (AO) representation. Consequently, the new formulation is denoted AO-MP2. As in traditional MP2 approaches electron repulsion integrals still need to be transformed. Strict bounds on the individual MP2 energy contribution of each intermediate four-index quantity allow to screen off numerically insignificant integrals with a single threshold parameter. Implicit in our formulation is a bound to two-particle density matrix elements. For small molecules the computational cost for AO-MP2 calculations is about a factor of 100 higher than for traditional MO-based approaches, but due to screening the computational effort in larger systems will only grow with the fourth power of the size of the system (or less) as is demonstrated both in theory and in application. MP2 calculations on (non-metallic) crystalline systems seem to be a feasible extension of the Laplace transform approach. In large molecules the AO-MP2 ansatz allows massively parallel MP2 calculations without input/output of four-index quantities provided that each processor has in-core memory for a limited number of two-index quantities. Energy gradient formulas for the AO-MP2 approach are derived.Dedicated to Prof. W. Kutzelnigg whose books on theoretical chemistry aroused my interest in this field