Optical matching layer structures in evanescent coupling photodiodes at a wavelength of 1.55 mu m: physics, design and simulation

We have studied the optical matching layers (OMLs) and external quantum efficiency in the evanescent coupling photodiodes (ECPDs) integrating a diluted waveguide as a fibre-to-waveguide coupler, by using the semi-vectorial beam propagation method (BPM). The physical basis of OML has been identified, thereby a general designing rule of OML is developed in such a kind of photodiode. In addition, the external quantum efficiency and the polarization sensitivity versus the absorption and coupling length are analysed. With an optical matching layer, the absorption medium with a length of 30 mu m could absorb 90% of the incident light at 1.55 mu m wavelength, thus the total absorption increases more than 7 times over that of the photodiode without any optical matching layer.

1.55-mu m Ridge DFB laser and electroabsorption modulator integrated with buried-ridge-stripe dual-waveguide spot-size converter output

A 1.55-mu m ridge distributed feedback laser and electroabsorption modulator monolithically integrated with a buried-ridge-stripe dual-waveguide spot-size converter (SSC) at the output port for low-loss coupling to a cleaved single-mode optical fiber was fabricated by means of selective area growth, quantum-well intermixing, and dual-core technologies. These devices exhibit threshold current of 28 mA, 3-dB modulation bandwidth of 12.0 GHz, modulator extinction ratios of 25.0-dB dc. The output beam divergence angles of the SSC in the horizontal and vertical directions are as small as 8.0 degrees x 12.6 degrees, respectively, resulting in 3.2-dB coupling loss with a cleaved single-mode optical fiber.

The chemistry of alpha-oxo ketene cyclic dithioacetal .36. Studies on silica G catalyzed decomposition of adducts of beta,beta-1,3-propylenedithio-alpha,beta-unsaturated arylketones with grignard reagents

beta, beta-1, 3-Piopylenedithio-alpha, beta-unsaturated arylketones 2 via chemoselective 1,2-addition with allyl or benzyl Grignard reagents afforded the corresponding carbinols 3 and 4. Catalysed by silica gel, the carbinols 3 and 4 were converted to the beta,gamma-unsaturated arylketones 5, 6. The mechanism and reaction condition were discussed.

α-羰基烯酮环二硫代缩醛化学(XXXVI)──β,β-1,3-亚丙二流基-α,β-不饱和芳酮与Grignard试剂加成物的硅胶催化分解反应

以β，β-1，3-亚丙二硫基-α，β-不饱和芳酮2与烯丙基或等基Grfenard试剂可选择性地进行1，2-加成得醇3、4，在硅胶G的催化下，醇3、4可分解生成β，γ-不饱和芳酮5、6．并对该分解反应的机制进行了初步探讨.

21世纪初的力学发展趋势

回顾力学发展史，阐明在科技发展过程中力学对于认识自然规律和解决工程技术问题中的地位和作用；提出在固体力学、流体力学、一般力学以及有关力学的若干交叉学科领域中的一些重要研究课题；展望２１世纪（特别是２１世纪前期）的力学发展趋势．

建立在野外地质调查基础上的高速滑坡灰色分析

本文针对各种大型工程论证和设计需要,提出了建立在野外地质调查基础上的高速滑坡灰色分析方法。应用该方法,可在收集滑坡方量、地形、环境等八个因素的基础上,准确预测工程区滑坡灾害性。文中将此方法应用于三峡工程,收到了令人满意的效果。

复合材料离心机转子动力学分析中的几个问题

<正> 前言 应用离心机分离铀是目前技术先进国家都在使用的方法,由于离心机分离功的大小随线速度的增加而大大增加,所以,尽力提高线速度是离心机转子设计中追求的主要目标。鉴于复合材料具有较高的比强度和比刚度,而且材料的力学性能可根据实际需要进行调整,从而使它成为制造离心机转子的理想材料。在这个基础上,对转子的结构形式、所选材料的种类和结构的铺层设计等方面提出了一系列要求,这些要求都与转子的动力分析有密切关系,亦即关系到复合材料转子的振动和稳定。关于普通材料转子的动力分析问题,已有相当成熟的研究结果,仅在80—82年,就有近200篇文章和报告从不同角度讨论了转子的稳定问题;但是由于复合材料离心机转子在结构形式、运行状态与构造材料方面所具有的特殊性,我们必须着重研究以下问题。

基于偏析线的圆棒颈缩分析

本文基于拉伸圆棒颈缩后纵剖面上形成的偏析线(腐蚀后可见)提出了建立颈部最小截面上的应变场的方法。利用试验得到的有关数据,并借助于塑性全量理论及逐步插值积分法得到颈缩后材料的及最小截面上的应力场。计算结果反映了宏观断裂过程中微观结构变化所导致的应变“软化”现象。电镜观察表明:曲线上的极值点所对应的颈缩状态正反映了微结构中的次级空洞大量形成的阶段,紧随而来的是宏观断裂的到来,因此是一个与材料临界断裂有着密切关系的一个量。

激波管中强激波的前驱真空紫外辐射

在Φ800毫米的低密度激波管的中轴上用钼靶探测入射强激波前发射的真空紫外光子,研究了以下三个问题。(1)研究了真空紫外光子的通量密度随波前距离的关系,建立了一个考虑到有限的激波发射层尺度和波前气体吸收的模型,得到了与实测前驱辐射一致的结果。(2)研究了氩气中强激波真空紫外辐射的激发机制,指出它属于非平衡共振激发辐射,其激发截面系数S~

Triple-region structure for turbulent-flow in a square duct - a finite-element approach

The Reynolds-averaged Navier-Stokes equations for describing the turbulent flow in a straight square duct are formulated with two different turbulence models. The governing equations are then expanded as a multi-deck structure in a plane perpendicular to the streamwise direction, with each deck characterized by its dominant physical forces as commonly carried out in analytical work using triple-deck expansion. The resulting equations are numerically integrated using higher polynomial (H-P) finite element technique for each cross-sectional plane to be followed by finite difference representation in the streamwise direction until a fully developed state is reached. The computed results using the two different turbulence models show fair agreement with each other, and concur with the vast body of available experimental data. There is also general agreement between our results and the recent numerical works anisotropic k-epsilon turbulence model.

复合材料薄壁梁力学特性分析

综述了人们在建立研究复合材料薄壁梁力学特性的非线性梁理论及分析结构剖面特性，确立结构算子参数等方面所做的工作以及这些研究工作的特点。同时，介绍了近年来各国学者在复合材料薄壁梁力学特性研究上的进展。