Propagation and radiation characteristics of the circular electric, circular magnetic and hybrid waveguide modes

The field distributions and propagation constants of the circular electric, circular magnetic and hybrid modes of oversized waveguides are expressed, taking the effects of walls into account. These effects are described by wall functions which depend on surface impedances of the wall, and are determined for different types of guides. The near and far field patterns are derived in the case of real wall functions. It is shown that, for very oversized waveguides, the terms containing wall functions can be ignored in the calculations, and it results that the expressions of fields and propagation constants become independent of the types of waveguides. An application to corrugated waveguides for Electron Cyclotron Resonance Heating experiments shows the variations of the radiation characteristics versus geometric parameters of the corrugations and determines the ranges of interest for these parameters.     

介质复盖对圆形微带天线性能的影响

基于汉克尔变换域分析，对具有一层介质复盖的圆形微带天线进行了严格的全波分析．利用伽略金法推导出对于未知电流展开系数的齐次矩阵方程，通过数值解求得谐振频率和电流展开系数及远场辐射方向图．文中给出了无介质复盖与介质复盖层厚度为不同数值时，圆形微带天线谐振频率和辐射方向图的数值结果，并与实验数值吻合得很好．     

环形光斑激光束在非线性克尔介质中的分束现象

对于非线性克尔介质中的环形斑调制光束,通过数值求解非线性Schrdinger方程,发现当入射光强度超过一定值时,光束在传输过程中发生分束现象.对光分束的阈值、光分束与环半径及半宽度的关系、分束光的特点,以及自聚焦焦点上光强度的横向分布与光分束之间的关系进行了详细的讨论 关键词： 环形光斑 克尔介质 非线性传输 光分束     

Heme CD as a probe for monitoring local structural changes in hemeproteins: Alkaline transition in hemeproteins

Structural change due to acid-alkaline transition in hemeproteins were monitored by circular dichroism measurements in the Soret region. It was observed that in cytochrome c and horseradish peroxidase, alkaline transition results in a large change in the heme CD due to significant conformational change in the heme cavity region. In metmyoglobin a simple protolytic mechanism associated with alkaline transition involves very small conformational changes.     

数值模拟圆柱绕流旋涡运动及尾流不稳定性分析

1引言流体绕过圆柱所产生的非定常旋涡运动以及由此引起的流动不稳定性在理论和实践上都具有重要的意义。数值模拟圆柱绕流旋涡产生及演化过程，探讨圆柱尾流涡街产生的机制，控制尾迹不同速度型以抑制涡街的产生，避免涡激振动在工程上造成破坏作用具有重大实际意义。为使问题简化，本文以二维圆柱绕流作为研究对象。该流动涉及到非定常分离，旋涡的形成、运动及发展，流动不稳定性质改变等许多未完全解决的问题。B。had等山对圆柱突然起动问题作了一系列实验研究。文献门对二维圆柱绕流问题作了系统数值研究。本文采用文献门提出的差分格…     

An analysis of axisymmetric buckling and growth of circular-shaped delamination

The buckling and post-buckling of clamped circular plate subjected to distributed radial compressed load is presented by using the high-order perturbation analysis and shooting method. The sixth-order solution shows good agreement with the FEM results in [11]. The results in this paper are applied to investigate the buckling and growth of pressed thin film delamination in the film/substrate system. Under a certain residual pressure in the thin film, two characteristic blister radiiR _c andR _g, the critical radius and growing radius respectively, are obtained. The numerical result shows that the growth criterion of delamination in [9,10] is not perfect. In variant residual stress or interface toughness, the conditions of no growth, stable growth and unstable growth of the delamination are obtained by comparing the driving force at the interface crack tip with the interface toughness.This project is supported by National Natural Science Foundation of China.     

Low energy excitations of a quasi-2D Bose-Einstein condensate

Starting from the Gross-Pitaevskii energy functional of the 3D Bose-Einstein Condensate, we derive approximately the energy functional and the effective coupling constant of the quasi-2D condensate. The evolution of the quasi-2D condensate wave function is studied by a variational method. Low energy excitation spectra for both positive and negative scattering lengths are analyzed. The condition of collapse instability of a quasi-2D Bose gas with attractive particle interaction is also proposed. Received 31 October 2001 / Received in final form 1st March 2002 Published online 28 June 2002     

受圆形表面单面约束的点锚固圆环热屈曲分析

应用Ｗ．Ｔ．Ｋｏｉｔｅｒ的初始后屈曲理论，研究了受圆形混凝土表面单面约束的点锚固圆环的热屈曲问题，根据混凝土容器壁的几何约束条件，假设了圆环的合理屈曲模状，得出了圆环在两锚固点之间发生屈曲的临界温度，并研究了其后屈曲性态和缺陷敏感性。结果表明，临界点和后屈曲路径的平衡均为稳定的，圆环对于与屈曲模态形状相同的缺陷是不敏感的。     

中细柔性圆环壳整体弯曲的一般解及在波纹管计算中的应用（I）—基本方程和一般解

讨论了圆环壳在横向载荷作用下的整体弯曲问题，提出了中细柔性圆环壳的概念、基本方程和一般解。本文称粗细比（子午线曲率半径与子午线曲率中心到回转轴的距离之比）小于1／3的圆环壳为中细圆环壳；方程的推导基于E.L.Axelrad的柔性壳理论；所得的解含有处理边界问题所必须的积分常数并且在全域内处处收敛；本解能方便地用于有关波纹管的计算。全文共分4个部分：（I）基本方程和一般妥；（Ⅱ）Ω型波纹管的计算；（Ⅲ）C型波纹管的计算；（Ⅳ）U型波纹管的计算。     

Electromagnetic beam wave scattering by arbitrary cross-sectional conducting cylinder using N circular cylindrical models

Rigorous expression of the electromagnetic beam wave scattering by N circular cylindrical models is described. To check this method, comparison between exact solution and this model composed of N=24 circular cylinders is presented for a single circular conducting cylinder. Numerical results of conducting square cylinder has been also checked with well-known result (B.E.M).