Distortion of optical feedback signals in microchip Nd:YAG lasers subjected to external multi-beam interference feedback

This paper proposes a theoretical analysis for the characteristics of an external cavity Nd:YAG laser with feedback of multiple-beam interference, which is induced by the multi-reentrance of the light from the external Fabry--Perot cavity. The theoretical model considers the multiple beam interference of the external Fabry--Perot cavity. It is found that the optical feedback signals are distorted to pulse waveforms instead of the sinusoidal ones in conventional feedback. The experimental results are in good agreement with the theoretical analysis. The obtained theoretical and experimental results can advance the development of a laser feedback interferometer.     

Influence of AlN buffer layer thickness on structural properties of GaN epilayer grown on Si (111) substrate with AlGaN interlayer

We present the growth of GaN epilayer on Si (111) substrate with a single AlGaN interlayer sandwiched between the GaN epilayer and AlN buffer layer by using the metalorganic chemical vapour deposition. The influence of the AlN buffer layer thickness on structural properties of the GaN epilayer has been investigated by scanning electron microscopy, atomic force microscopy, optical microscopy and high-resolution x-ray diffraction. It is found that an AlN buffer layer with the appropriate thickness plays an important role in increasing compressive strain and improving crystal quality during the growth of AlGaN interlayer, which can introduce a more compressive strain into the subsequent grown GaN layer, and reduce the crack density and threading dislocation density in GaN film.     

Microstructure and strain films using in-plane grazing analysis of GaN epitaxial incidence x-ray diffraction

This paper investigates the major structural parameters, such as crystal quality and strain state of （001）-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in-plane grazing incidence x-ray diffraction technique. The results are analysed and compared with a complementary out-of-plane x- ray diffraction technique. The twist of the GaN mosaic structure is determined through the direct grazing incidence t of （100） reflection which agrees well with the result obtained by extrapolation method. The method for directly determining the in-plane lattice parameters of the GaN layers is also presented. Combined with the biaxial strain model, it derives the lattice parameters corresponding to fully relaxed GaN films. The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established, reaching to a maximum level of-0.89 GPa.     

从劲舞风波看韩国公司的合纵连横计

最近几个月,无论是九城还是久游网,为了一个<劲舞团>,都多少有点闹心.九城是得而复失,原本一个借"机"下蛋的好买卖,最终竹篮打水一场空,成了镜花水月.久游网是失而复得,本来归属权很明了的一个游戏就因此变得多少有点悬念.而就在这失而复得的空档中,久游网暂停了上市日本的计划,闹出了和韩国T3公司之间所谓的账务纠纷,闹得沸沸扬扬.虽然它一再澄清,但名誉有些受损,经济受困.尽管最后总算拿回了失去的东西,也将恢复在日本的上市计划,但中间的一番波折已经让久游网承受了太多压力和冲击.     

基于虚拟分割机制的多服务交换路由器的研究

本文提出了一处基于虚拟分割机制的可编程多服务器由器实现结构：PVSMR，并对它的三个层面的主要构成及其关键技术进行了深入研究。PVSMR基于一种有效而灵活的资源虚拟分割算法，它能够提供与多类应用相适应的、灵活的报文处理和转发控制能力。     

阿尔泰山地啮齿动物的地带性分布及其价值的探讨

阿尔泰山位于我国新疆北部,最北端跨入北纬49°,整个山体呈西北——东南走向,山势缓坦,森林茂密。在海拔4374米的奎屯峰及其周围还保留有发育完整的现代冰川,3000米以上各地段多为高山寒漠冰碛砾石,永久冰雪复盖带并不多见。该山位于亚洲腹地北沿,受中亚干热气流和大西洋寒冷气流双重影响,夏季潮湿多雨,冬季寒冷多雪,年降水量达300—600毫升,无霜期100天左右.     

中国鸟类的两个新纪录

新中国成立后,钱燕文等(1963)、陈服官等(1980)、向礼陔(1980)等曾先后报导过分布于新疆的若干鸟类新纪录.近来,我们在整理新疆大学生物系所收藏的鸟类标本中,又发现两种鸟类为我国首次纪录,现报导如下;     

多源异构土地基础数据一体化管理检索方法研究

为了从多源异构的复杂土地基础数据中快速准确地提取用户所需信息,提出了基于元数据的一体化管理检索方法.在元数据信息提取、元数据加权索引、实体同义词扩展检索3个环节中,结合土地领域专业知识和用户实际需求,设计和开发了共享元数据表结构、加权元数据中字段相对重要性和信息熵因子,构建地名实体和专题数据层实体同义词库,并集成到包括中文分词、实体识别、同义词扩展、索引检索和相似度计算的一体化管理检索框架中,解决了多源异构土地基础数据统一管理和精确检索的问题.实践表明,该方法较传统的通用信息检索方法具有更好的适用性和更高的准确率.