Modelling of streaky structures and turbulent-spot generation process in wing boundary layer at high free-stream turbulence

Results of an experimental study of turbulent breakdown in gradient boundary layer at high freestream turbulence are reported. For the first time it is shown that, like the flat-plate boundary layer, the wing boundary layer at high freestream turbulence is modulated with streaky structures. One of possible mechanisms underlying the generation of turbulence spots in wing boundary layer is modelled assuming the interaction of streaky structures with high-frequency waves. Qualitative and quantitative data concerning the evolution of streaky structures in swqpt-wing boundary layer and in swept-wing boundary layer are presented. Certain differences between the evolution of streaky structures in wing boundary layer and in flat-plate boundary layer are revealed. This work was supported by the President of the Russian Federation (Grants NSh-454.2008.1, MK- 101.2007.1), by the Russian Foundation for Basic Research (Grant No. 05-01-00034), by the Ministry of Education and Science of the Russian Federation (Grant No. RNP 2.1.2.3370), and by the Russian Government (State Contract No. 02.513.12.0043).     

退火对非故意掺杂4H-SiC外延材料386 nm和388 nm发射峰的影响

10 K条件下,采用光致发光(PL)技术研究了不同退火处理后非故意掺杂4H-SiC外延材料的低温PL特性.结果发现,在370—400 nm范围内出现了三个发射峰,能量较高的峰约为3.26 eV,与4H-SiC材料的室温禁带宽度相当.波长约为386 nm和388 nm的两个发射峰分别位于~3.21 eV和~3.19 eV,与材料中的N杂质有关.当退火时间为30 min时,随退火温度的升高,386 nm和388 nm两个发射峰的PL强度先增加后减小,且退火温度为1573 K时,两个发射峰的PL强度均达到最大. 关键词： 光致发光 退火处理 能级 4H-SiC     

船用超声液位传感器的分析与设计

介绍了一种船用某型超声液位传感器的基本结构和工作原理。在对脉冲式超声探头的轴向声压分布特点及其声透射强度分析研究的基础上,给出了该传感器的超声信号发射端与接收端之间距离d和压电晶片保护膜的壁厚δ值的确定方法。最后设计了一套超声液位传感器性能测试实验平台,对上述理论研究结论进行了实验验证。     

模糊(Fuzzy)映象的广义补余问题*

本文引入一类关于模糊(Fuzzy)映象的新的广义补余问题,构造出一类新的迭代算法.我们讨论这类广义补余问题解的存在性及迭代序列的收敛性.     

Pseudo-monotone complementarity problems in Hilbert space

In this paper, some existence results for a nonlinear complementarity problem involving a pseudo-monotone mapping over an arbitrary closed convex cone in a real Hilbert space are established. In particular, some known existence results for a nonlinear complementarity problem in a finite-dimensional Hilbert space are generalized to an infinite-dimensional real Hilbert space. Applications to a class of nonlinear complementarity problems and the study of the post-critical equilibrium state of a thin elastic plate subjected to unilateral conditions are given.This research was partially supported by the National Science Foundation Grant DMS-89-13089, Department of Energy Grant DE-FG03-87-ER-25028, and Office of Naval Research Grant N00014-89-J-1659. The authors would like to express their sincere thanks to Professor S. Schaible, School of Administration, University of California, Riverside, for his helpful suggestions and comments. They also thank the referees for their comments and suggestions that improved this paper substantially.     

A note on a characterization of P-matrices

In this note we show that the characterization results for P-matrices due to K.G. Murty and A. Tamir which state that a given square matrixM of ordern is a P-matrix if and only if the linear complementarity problem (q, M) has a unique solution for allq in a specified finite subset of ⁿ depending onM are incorrect whenn > 3.Research supported by Dr. K.S. Krishnan (DAE) fellowship for research in Mathematics and Computer Science, Bombay, India.     

Local convergence of quasi-Newton methods for B-differentiable equations

We study local convergence of quasi-Newton methods for solving systems of nonlinear equations defined by B-differentiable functions. We extend the classical linear and superlinear convergence results for general quasi-Newton methods as well as for Broyden's method. We also show how Broyden's method may be applied to nonlinear complementarity problems and illustrate its computational performance on two small examples.