涡轮叶栅气热耦合数值模拟

本文建立了透平机械叶栅流场与叶片温度场的气热耦合计算模型,编制了三维非正交曲线坐标系下的温度场求解程序,计算了实心及空心叶片的温度场分布。介绍了区域分解方法在耦合计算及并行计算中的应用,以矩形区域温度场求解程序为例研究了程序的并行化,最后进仃了叶栅流场计算与叶片导热计算程序的分区耦合计算。     

Characterization of the barrier parameter of homogeneous convex cones

We characterize the smallest (best) barrier parameter of self-concordant barriers for homogeneous convex cones. In particular, we prove that this parameter is the same as the rank of the cone which is the number of steps in a recursive construction of the cone (Siegel domain construction). We also provide lower bounds on the barrier parameter in terms of the Carathéodory number of the cone. The bounds are tight for homogeneous self-dual cones. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.Research supported in part by an operating grant from NSERC of Canada.Research supported in part by the National Science Foundation under grant DMS-9306318.     

Observation of sequential excited-to-excited states resonant tunneling in weakly coupled superlattices with wide quantum wells

The sequential excited-to-excited state resonant tunneling effect was observed in weakly coupled long-period superlattices resulting in additional negative differential conductivity resonances in multistable current–voltage characteristics. The results obtained show the evidence of the highly nonequilibrium distribution of carriers over subbands with energies below the optical phonon energy in superlattices. A new type of electric field domains, due to resonant tunneling between excited subbands in adjacent wells, is considered, and experimental evidencies of such a domain's existence are given.     

Imaging a reflecting plate located in scattering media using optical frequency domain reflectometry

A new imaging system based on optical frequency domain reflectometry is presented. The intensity-integration effect of the charge coupled device camera to be used acts effectively as a low pass filter for the intensity fluctuation and the 2nd order moment of the detected signals is proportional to a low beat frequency component of the interference signal. Consequently, two-dimensionally imaging of the reflectance of a selective plane located in scattering media is demonstrated.     

Thickness dependence of magnetic domain formation in La0.6Sr0.4MnO3 epitaxial thin films studied by XMCD-PEEM

We have used photoelectron emission microscopy (PEEM) and X-ray magnetic circular dichroism (XMCD) to study the effect of thin film thickness on the magnetic domain formation in La_0.6Sr_0.4MnO₃ samples that were epitaxially grown on stepped SrTiO₃ (0 0 1) substrates. The magnetic image exhibited a stripe structure elongated along the step direction, irrespective of film thickness, suggesting that uniaxial magnetic anisotropy induced by step-and-terrace structures plays an important role in the magnetic domain formation. Additional domains evolved gradually with increasing film thickness. In these domains, the direction of magnetization differed from the step direction due to biaxial magneto-crystalline anisotropy. The evolution of additional magnetic domains with increasing film thickness implies that a competition exists between the two anisotropies in LSMO films.     

Attractors of Weakly Asymptotically Compact Set-Valued Dynamical Systems

The existence of weak attractors is established for set-valued dynamical systems which are weakly asymptotically compact and weakly dissipative. Here weak properties mean with respect to at least one trajectory for each initial value. A condition ensuring the uniqueness of such weak attractors is given. The results are illustrated with an application involving a partial differential inclusion in bounded and unbounded domains. Mathematics Subject Classifications (2000) 34D45, 37B25, 37B75, 58C06.     

紫外激光诱导近化学计量比钽酸锂晶体铁电畴反转

对紫外激光诱导近化学计量比钽酸锂晶体铁电畴反转进行了实验研究。波长为351 nm的连续紫外激光被聚焦在近化学计量比钽酸锂晶体的-z表面,同时沿与晶体自发极化相反的方向施加均匀外电场。实验证实紫外激光辐照可以有效地降低晶体畴反转所需的矫顽电场,采用数字全息干涉测量技术检测证实在激光辐照区域实现局域畴反转。研究表明采用紫外激光诱导可以实现对近化学计量比钽酸锂晶体铁电畴反转的局域控制。提出了物理机理的理论分析,认为外电场和激光辐照场的共同作用在晶体内部产生高浓度、大尺寸的缺陷结构,缺陷一定程度上降低畴体成核和畴壁运动所需要克服的退极化能和畴壁能,实现激光诱导畴反转。     

凸域内定长线段运动测度公式的另一种表达式

本文研究了凸域内定长线段的运动测度.利用广义支持函数及径向函数的概念,获得了运动测度公式的另一种表达式,并改进了已有文献中的相关结果.     

Invariant Integrals for the Equilibrium Problem for a Plate with a Crack

We consider the equilibrium problem for a plate with a crack. The equilibrium of a plate is described by the biharmonic equation. Stress free boundary conditions are given on the crack faces. We introduce a perturbation of the domain in order to obtain an invariant Cherepanov–Rice-type integral which gives the energy release rate upon the quasistatic growth of a crack. We obtain a formula for the derivative of the energy functional with respect to the perturbation parameter which is useful in forecasting the development of a crack (for example, in study of local stability of a crack). The derivative of the energy functional is representable as an invariant integral along a sufficiently smooth closed contour. We construct some invariant integrals for the particular perturbations of a domain: translation of the whole cut and local translation along the cut.     

Domain Structures in Minerals

Domain structures in mineral crystals could be categorized into three groups and several subgroups within each group, based on characteristics of domain structures and mechanisms causing domain structures: (ⅰ) domain structures constituted by domains with the same (or identical) crystal structure and chemical composition, including anti-phase domain structures, twinning domain structures, inversion domain structures, and translationtwinning domain structures; (ⅱ) domain structures constituted by two or more than two kinds of domains with the same chemical composition but different crystal structures; and (ⅲ) domain structures constituted by two kinds of compositional and structural different domains, including exsolution-induced and polysomatic reaction-induced domain structures. Different types of domain structures may display different phenomena in their TEM images and SAED patterns, due to different crystallographic characteristics of different domain structures. The domain structures in minerals