Effects of non-abrupt interface on waveguide properties of sitle/Si MQW photodetector

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InGaAs/GaAs和InGaAs/AlGaAs应变层量子阱中的子带驰豫过程

利用时间分辨光谱技术,在11～90K温度范围研究了不同阱宽的InGaAs/GaAs和InGaAs/AlGaAs应变层量子阱子带弛豫过程,讨论了这两种量子阱材料中不同散射机制的作用。

Mode theory and analysis of planar array waveguides

Bloch modes can be excited in planar array due to its periodic lateral refractive index. The power coupled into each eigenmode of the array waveguides is calculated through the overlap integrals of the input field with the eigenmode fields of the coupled infinite array waveguides projected onto the x-axis. Low losses can be obtained if the transition from the array to the free propagation region is adiabatic. Due to the finite resolution of lithographic process the gap between the waveguides will stop abruptly, however, when the waveguides come into too close together. Calculation results show that losses will occur at this discontinuity, which are dependent on the ratio of the gap between the waveguides and grating pitch and on the confinement of field in the array waveguides. Tapered waveguides and low index contrast between the core and cladding layers can lower the transmitted losses.

The content calculation of hexagonal phase inclusions in cubic GaN films on GaAs(001) substrates grown by metalorganic chemical vapor deposition

Cubic GaN(c-GaN) films are grown on GaAs(001) substrates by metalorganic chemical vapor deposition (MOCVD). Two GaN samples were grown with different buffer layer, the deposition time of each was 1 and 3 min, respectively. 4-circle X-ray double crystal diffraction (XRDCD) was used to study the secondary crystallographic phases presented in the c-GaN films. The phase composition of the epilayers was determined by X-ray reciprocal space mapping. The intensities of the c-GaN(002) and h-GaN(10 (1) over bar 1) planes detected in the mapping were investigated by omega scans. The content of the hexagonal phase inclusions in the c-GaN films was calculated to about 1.6 and 7.9%, respectively. The thicker buffer layer is not preferable for growing high quality pure c-GaN films. (C) 2000 Elsevier Science S.A. All rights reserved.

Formation and magnetic properties of Fe16N2 films prepared by ion-beam-assisted deposition

Fe-N films containing the Fe16N2 phase were prepared in a high-vacuum system of ion-beam-assisted deposition (IBAD). The composition and structure of the films were analysed by Auger electron spectroscopy (AES) and X-ray diffraction (XRD), respectively. Magnetic properties of the films were measured by a vibrating sample magnetometer (VSM). The phase composition of Fe-N films depend sensitively on the N/Fe atomic arrival ratio and the deposition temperature. An Fe16N2 film was deposited successfully on a GaAs (1 0 0) substrate by IBAD at a N/Fe atomic arrival ratio of 0.12. The gram-saturation magnetic moment of the Fe16N2 film obtained is 237 emu/g at room temperature, the possible cause has been analysed and discussed. Hysteresis loops of Fe16N2 have been measured, the coercive force H-c is about 120 Oe, which is much larger than the value for Fe, this means the Fe16N2 sample exhibits a large uniaxial magnetocrystalline anisotropy. (C) 1998 Elsevier Science B.V. All rights reserved.

一种面向OSGi的构件化软件再工程方法

面向服务的构件模型可以解决当前大型软件系统难于管理、维护困难和缺乏动态性等问题,而OSGi框架为基于构件系统的服务化开发提供了有力支持.把OSGi作为基础框架对遗留软件系统进行再工程,设计了OSGi化软件的总体框架,提出了软件系统构件化方法,并针对再工程过程中普遍存在的问题给出了相应的解决方案.最后,通过对Web容器再工程的实例研究,验证了面向OSGi的构件化软件再工程方法的有效性.

长白山北坡水甲虫的生物多样性研究

长白山地区为保护较为完善的原始森林区，物种丰富，因此被选为论文的研究区域.这里地处温带，气候寒冷，水甲虫种类分布有着一定的独特性.该项研究通过对不同海拔高度的不同水体中水甲虫的采样，研究了长白山北坡水甲虫的种类、生物多样性及其颁与环境因子的相关性.通过调查和研究，发现长白山水甲虫已记录的种类共有8科37属67种，其中占种群优势的是龙虱科和水龟虫科.同时，通过对文献的系统研究，发现中国有已记录的水甲虫共21科141属916种，比原记录601种（杨集昆，1994）多215种.在对长白山北坡水甲虫区系研究的同时，对生物多样性指数进行了分析，结果表明长白山北坡的水甲虫生物多样性各项指标均显示出该地区水甲虫物种较为丰富，物种均匀度高.在研究水甲虫的分布与环境因子的关系时发现，不同水体中环境因子对水甲虫分布的影响不同，活水水体中起主要作用的因子是植被密度和水流速度，静水水体中起主要作用的因子是海拔和腐殖化程度.

杂谷脑流域景观格局优化配置研究

景观格局优化理论、方法和技术的研究是景观生态学的一个热点问题，同时也是一个难点。本文以眠江上游典型研究区-杂谷脑流域为研究对象，利用遥感和GIS技术分析该流域从1974年到2000年景观格局的时空变化，并分析了对该流域生态安全存在威胁的主要因素；以空间模拟技术和线性规划为基础建模，从理论和方法上探讨景观格局优化配置问题，以期为该区域的农林复合景观系统的生态安全和可持续发展找出切实可行的格局优化模式；并提出生态敏感度概念，为景观管理优先级提供依据。本文的主要结论如下：（l）杂谷脑流域作为长江上游重要的森林资源输出地，从1974年到2000年景观变化得出，有林地面积减少13％；灌木林地面积增加37％；相应的水源涵养能力下降，土壤侵蚀量增加7.8％；（2）杂谷脑流域陡坡耕作严重，分布在20°-45°坡度上的耕地占耕地总面积的78．2％；干旱河谷分布范围扩大，面积从1974年的217.99km2增加到2000年的237．38kmZ对生态安全造成威胁；（3）产业结构以资源密集型产业和重污染工业为主，结构不合理，第一产业比例大，农民人均纯收入远低于同期全国平均水平，教育水平比较低，这些问题会对杂谷脑流域生态安全产生负向影响；（4）以减少土壤侵蚀为依据，通过空间建模和线性规划方法优化设计杂谷脑流域景观格局，优化结果显示土壤侵蚀量比2000年减少2.35*106吨／年，土壤保持能力与1974年相近，水源涵养能力增强；（5）景观管理对于区域安全必不可少，针对该流域现存问题，建议以提高科学技术水平，调整产业结构和资源利用方式，提高教育水平为突破口。