Attractors for a Three-Dimensional Thermo-Mechanical Model of Shape Memory Alloys

Abstract In this note, we consider a Frémond model of shape memory alloys. Let us imagine a piece of a shape memory alloy which is fixed on one part of its boundary, and assume that forcing terms, e.g., heat sources and external stress on the remaining part of its boundary, converge to some time-independent functions, in appropriate senses, as time goes to infinity. Under the above assumption, we shall discuss the asymptotic stability for the dynamical system from the viewpoint of the global attractor. More precisely, we generalize the paper [12] dealing with the one-dimensional case. First, we show the existence of the global attractor for the limiting autonomous dynamical system; then we characterize the asymptotic stability for the non-autonomous case by the limiting global attractor. * Project supported by the MIUR-COFIN 2004 research program on “Mathematical Modelling and Analysis of Free Boundary Problems”.     

雷达尾涡对垂尾气动性能的影响

基于雷达-垂尾简化模型,通过数值模拟来分析雷达尾涡效应对垂尾气动性能的影响机理,探讨了不同安装角以及几何外形变化对雷达尾涡效应的影响.结果表明:在一定范围内加长雷达法向直径可使月牙状三维涡的三维性减弱,从而减弱雷达尾涡效应,但当雷达侧面母线倾斜时反而增强雷达尾涡效应.     

基于遗传算法的升力体外形优化设计

升力体由于低热流率再入物理特性和高效的内部容积利用率，是高超声速飞行器气动外形的一种典型布局.文章对升力体飞行器进行参数化数值建模，并提取其表征外形的参数作为设计变量，综合考虑飞行器再入过程中的气动力、气动热、容积利用率及稳定性等性能指标.运用多目标混合遗传算法对升力体进行了多变量、多约束下的气动外形优化设计，获得了再入飞行器外形的最优Pareto解.数值模拟结果表明，典型状态下最优Pareto解与CFD结果相差12%，验证了优化结果的准确性.      

“组装法”证明对称不等式

随着科技的进步,如今大型桥梁、地铁等都是采用分段施工、整体合拢的“组装”建造模式.其实,在解决数学问题时,尤其是证明那些外形结构相似的对称(或对称轮换)不等式,也可以借鉴上述模式:先精心分割成对称的局部,紧盯整体的目标和方向,最后有机融合于一体,我们把这种方法称为“组装法”.1.几个案例     

飞艇外型设计中曲线参数化方法的比较

采用合适的参数化方法快速准确地描述优化前后的几何结构是形状和气动性能优化问题的前提.目前常用的曲线参数化基本方法有三种:Bezier,B-spline和NURBS曲线.参数化曲线拟合的关键是从已知形状反求控制点的信息,本文综合对比了三种不同参数化方法关于飞艇外形拟合性能的差异.结果表明,与其它两种曲线参数化方法相比,N...     

Determining Nuclear Form factor for Detection of Dark Matter in Relativistic Mean Field Theory

In this work, we derive the nuclear form factor for the spin-independent collision between the WIMPs and nucleus in terms of the relativistic mean field (RMF) theory. Comparison with the traditional form factors which are commonly used in literature is given and it is found that our results are slightly above that of the 2PF model by 4% to 8%, but deviate from the Helm form factor by 15% to 25% for the whole recoil energy spectrum of 0 ∽ 100keV. Moreover, taking Xe and Ge as examples, we show the dependenceof the form factor on the recoil energy.     

Bichromatic Coherent Population Trapping Under Hanle Configuration

We report the observation of bichromatic coherent population trapping under the transition ^87 RbFg = 1 → Fc = 0 with two linearly polarized laser beams by means of a Hanle effect configuration. The mechanism behind this effect is identified, and numerical solutions for the pump rates equations are presented.     

高升力外形下机翼的位流计算

本文采用第二代低阶面元法给出了一种高升力外形外机翼位流计算方法。     

高速列车外形的气动性能数值计算和头部外形的改进

运用流体力学数值计算软件CFX对我国200km／h电动旅客列车的空气动力性能进行了数值模拟计算，针对列车气动外形存在的问题，对列车头部外形进行了改进，并提出了三种列车头部外形改进方案且对其进行了数值模拟研究。计算结果表明，方案三优于其它两种方案，且较改进前列车的空气动力性能有了较大改善。     

机械补偿式三组元连续变焦光学系统设计方法(3)

介绍了机械补偿式三组元连续变焦光学系统的基本工作原理以及光学设计方法的全过程.其中包括变焦和补偿方案的选择、高斯光学各组元焦距分配,外形尺寸计算、初级像差平衡、PW求解、初始结构参数确定、系统实际像差自动平衡,直到凸轮曲线优化设计等.以图形和公式说理,以具体0CAD通用自动设计软件为工具,全面介绍三组元连续变焦系统的设计方法及过程.