新型分布反馈式气体激光器

本文论述了三种分布反馈(DFB)式气体激光器的理论及其首次实现的情况,这三种气体激光器是线性DFB激光器、螺旋DFB激光器和与二阶DFB效应相关的切向入射光栅式激光器。这些新型激光器是分别把线性周期金属波导、螺旋型金属波导以及带光栅的楔形金属波导应用到496μm光泵远红外CH_3F激光器上而实现的。螺旋DFB结构在激光研究上是一个新的概念,它引起人们的兴趣不仅在微波技术方面,同样在染料激光器和胆甾醇液晶的研究方面。DFB气体激光器未来研究的一个目标是实现10μm波长的CO_2 DFB激光器,它将具有很优异的特性和应用价值。     

抗蚀剂组合法制造DFB激光器λ／4相移光栅

本文介绍用正、负光致抗蚀剂组合的方法,制造用于DFB激光器λ/4相移光栅的原理及工艺,并给出了研究结果和质量评价。光栅周期为4600A,相移转换区小于3μm。     

混合光栅型的三段式自脉动DFB激光器

制作了1.55μm InGaAsP-InP三段式混合光栅型DFB激光器.观察到了20GHz左右的自脉动信号.讨论了自脉动的产生机制,并且对调相区所起的作用进行了研究.     

混合光栅型的三段式自脉动DFB激光器

制作了1.55μm InGaAsP-InP三段式混合光栅型DFB激光器.观察到了20GHz左右的自脉动信号.讨论了自脉动的产生机制,并且对调相区所起的作用进行了研究.     

纳米压印制作半导体激光器的分布反馈光栅

分布反馈(DFB)光栅的制作是半导体激光器芯片的关键工艺,通过纳米压印技术在InP基片表面涂覆的光刻胶上压印出DFB光栅图形,并分别通过湿法腐蚀和干法刻蚀技术将光栅图形转移到InP基片上。所制作的DFB光栅周期为240nm(对应于1 550nm波长的DFB激光器),光栅中间具有λ/4相移结构。采用纳米压印技术制作的DFB光栅相对于通常双光束干涉法制作的光栅具有更好的均匀性以及更低的线条粗糙度,而且解决了双光束干涉法无法制作非均匀光栅的技术难题。相对于电子束直写光刻法,采用纳米压印技术制作DFB光栅具有快速与低成本的优势。采用纳米压印技术在InP基片上成功制作具有相移结构的DFB光栅,为进一步进行低成本高性能的半导体激光器芯片的制作奠定了良好基础。     

取样光栅DFB激光器

制作了取样光栅DFB激光器,比较研究了三种取样光栅的制备工艺,测试得到的取样光栅DFB激光器梳装光谱和理论计算大致吻合.     

取样光栅DFB激光器

制作了取样光栅DFB激光器，比较研究了三种取样光栅的制备工艺，测试得到的取样光栅DFB激光器梳装光谱和理论计算大致吻合.     

取样光栅DFB激光器

制作了取样光栅DFB激光器,比较研究了三种取样光栅的制备工艺,测试得到的取样光栅DFB激光器梳装光谱和理论计算大致吻合.     

电子束光刻制备1.5μm 波长的一级DFB激光器

英国 STC 及卡文迪斯实验室报导了采用高压电子束曝光、化学蚀刻配合 LPE 及 MOCVD外延技术,制备1.5μm InGaAsP 一级光栅的分布反馈(DFB)半导体激光器。该激光器采用一级分布反馈光栅,比起一般用的高阶光栅有较好的耦合效率及性能。一般的 DFB 激光器是采用全息曝光的方法制备光刻胶的周期光栅的,但由它得到的光栅     

非统一多量子阱波长可选DFB激光器

报道了一种单片集成的串联DFB激光器芯片,在合适工作条件下,可以在疏波分复用(CWDM)的两个信道波长激射。芯片通过非统一多量子阱有源区拓宽材料增益谱,给DFB激光器的纯折射率光栅引入弱增益耦合,提高DFB激光器的动态单模特性。芯片采用普通DFB激光器的制备工艺制备,工艺简单成本低,重复性高。测试结果表明,芯片能够在1.51μm和1.53μm两个波长激射,出光功率均能达到6mW以上,边模抑制比均达到40dB。     

无人作战模拟仿真中的VV＆A

根据无人作战模拟研究、开发过程中分队级作战单位建模与仿真环节上所存在的VV&A问题,从军事建模的过程与军事工程技术的角度出发,将一般仿真过程中的VV&A技术与军事作战模拟的特点以及无人作战模拟的特殊性三者有机的结合在一起,深入的探讨了在无人作战模拟仿真过程中VV&A问题的解决办法以及实现过程。通过对无人作战模拟仿真中VV&A的研究与解决,为今后的作战模拟,特别是无人作战模拟中如何解决建模及仿真过程中所存在的类似问题提出了一套系统的、科学的实现办法,具有一定的理论及实践意义。对于我军无人作战研究的深入开展以及跨越式发展具有一定的参考价值。     

Improved LUT Technique for HPA Nonlinear Pre-Distortion in OFDM Systems

In this paper, we focus on the Look-up Table (LUT) technique for the compensation of HPA nonlinear distortion. An improved LUT method is proposed with better performance compared with conventional LUT technique in terms of convergence speeds, BER and total degradation (TD). It can get over 8 dB gain in out-of-band spectrum re-growth suppression and about 0.3 dB BER performance gain than conventional LUT technique with the same iteration times. Also, we propose an actual application of HPA with pre-distorter in OFDM transmitter. Ai Bo was born in Shannxi Province in China on February 7, 1974. He received a BSc. Degree from Engineering Institute of Armed Police Force in 1997, a Master and Dr. degree from Xidian University in 2002 and 2004 in China respectively, and now working as a post dr. in Dept. of E&E, state of key lab. on microwave and digital communications in Tsinghua University in China. He has once participated in the key research project on HDTV in TEEG (Team of Engineering Expert Group) of China. He is an editorial committee member of journal of “Computer Simulations”, “Information and Electronic Engineering”, an IEEE member and a senior member of Electronics Institute of China (CIE). He has published over 60 scientific papers in his research area till now. His current interests are the research and applications of OFDM techniques with emphasis on synchronization and HPA linearization techniques. Yang Zhi-Xing graduated from Tsinghua University, P.R. China in 1970. He is now a Professor and Deputy Director of State Key Lab. on Microwave and Digital Communication at the Department of Electronic Engineering and the Director of the DTV R&D Center in Tsinghua University. As a DTV technical expert for the Chinese government, Professor Yang has also been a member of the DTV standardization Committee of China and a leader of the DTV Standardization Harmonizing Group in Ministry of Information Industry of China. His major research interests include broadband information transmission technologies and DTV broadcasting systems. Pan Chang-Yong received the B.S. and M.S. degrees from the Department of Electronic Engineering in Tsinghua University, P.R. China, in 1996 and 1999, respectively. He is now an associate professor in the Department of Electronic Engineering and a member of the DTV R&D Center in Tsinghua University. His research interests are in the areas of broadband wireless transmission systems and satellite communications. Zhang Tao-Tao was born in Shandong Province in China in 1982, he received BSc. degree from Tsinghua University in 2004 and now pursing his Master degree in Dept. of E&E, state of key lab. on microwave and digital communications in Tsinghua University in China. His research interests is the power amplifier linearization techniques. Wang Yong was born in Shannxi Province in China in 1976. He received a BSc., a Master and a Dr. Degree from Xidian University in China in 1997, 2002 and 2005, respectively, and now is an associate professor in Xidian University. He has once participated in the key research project on HDTV in TEEG (Team of Engineering Expert Group) in China and is an IEEE Member. His interests are broadband multimedia communications. Ge Jian-Hua was born in September, 1961 in JiangSu Province in China. He received the B.Sc., Master and Ph.D. degree from Xidian University in 1982, 1985 and 1989, respectively. He is now the professor in both Xidian University in Xi’an and Shanghai Jiaotong University in Shanghai. He is the senior member of Chinese Electronics Institute. He has won lots of scientific and technical prizes in China and published many papers. His interests are transmission communications and web security.     

Inventive payoff from R&D in Japanese industry: convergencewith the West

An attempt is made to determine if investment in R&D and the hiring of college-educated employees result in a higher rate of inventions. The relationship between the input of R&D and inventive output is studied in two samples of Japanese factories, 34 in 1982 and 44 in 1970. These results are compared with findings in a parallel American study. The correlations between R&D and inventive output are similar in Japan and America in the 1980s, despite some differences in the management of innovation in the two nations. Moreover, the most Westernized subsample of Japanese firms in the 1970s had correlations between R&D and invention similar to those observed in the American study. Thus, it is concluded that some degree of convergence may be taking place in R&D management strategies in the two nations     

东海有机碳存量估算

海洋有机碳存量估算对研究碳循环过程和预估气候变化趋势有重要的作用。海洋有机碳存量可以通过遥感反射率、水体光学特性等参数反演得到。根据东海水域的水体特性,对比了多种有机碳反演算法,并结合东海有机碳垂直分布情况,得到一套完整的东海有机碳存量估算模型。利用2010年MODIS提供的遥感反射率数据和Argo提供的温盐数据,对中国东海区域的有机碳储量分季节进行计算分析。结果表明东海全水柱有机碳储量在1.530×1014 g到2.125×1014 g之间,真光层有机碳储量在4.119×1013 g到7.980×1013 g之间。全水柱有机碳储量整体呈现冬季高、春季低的特点,真光层有机碳储量整体呈现夏季高、冬季低的特点。从2006年至2015年,有机碳存量呈波动上升趋势。对东海有机碳存量进行了较为准确的估算,为今后我国海洋碳储量的评估提供了可供参考的思路。     

微视频在高校计算机操作性课程中的应用探究

微视频在学校各类教育中应用越来越普遍.依据微视频的教学特点,针对高校计算机操作性课程中存在的问题,本研究依据ADDIE模型和ARCS动机理论,探索构建微视频在高校计算机操作性课程中的教学应用模型,通过教学案例展示微视频在课堂应用中教与学的过程,利用微视频提高课堂教学质量.     

中国地区云量和云光学厚度的分布与变化趋势

利用最新的1983~2009年国际卫星云气候计划（ISCCP） D2月平均资料集,得到了中国地区总云量、低云量、中云量、高云量与云光学厚度的分布与变化趋势,结果表明：中国总云量和中云量呈现南多北少的分布,青藏高原地区高云量较大而低云量很小;总云量和中云量在东部呈增加趋势,西部呈减小趋势,低云量和高云量在大部分地区呈减小趋势。从不同季节来看,春季和秋季北方总云量增加,西部总云量减小;夏季大部分地区总云量增加,冬季大部分地区总云量减少。云的光学厚度呈现南多北少的分布,且在大部分地区呈增加趋势。同时利用中分辨率成像光谱仪（MODIS）资料分析了2001~2013年间中国不同污染地区总云量与云光学厚度的分布及变化趋势的异同,结果表明：中国不同污染地区云量与云光学厚度呈现不同的分布和变化规律。     

狭叶柴胡根发育过程中柴胡皂苷积累的超微细胞化学研究

用醋酸铅溶液对狭叶柴胡（Bupleurum scorzonerifolium Willd.）根内的药用成分柴胡皂苷进行细胞化学定位,在透射电镜下探讨不同发育时期根的结构特征与柴胡皂苷积累的关系。结果表明：狭叶柴胡根的初生结构和次生结构类似一般双子叶植物。在根的初生分生组织中表皮原及皮层原均有皂苷的分布。在根的初生结构中,柴胡皂苷分布于表皮、皮层、中柱鞘、初生韧皮部及原生木质部的薄壁组织细胞内,其中中柱鞘和韧皮部是主要的分布部位。在根的次生结构中,柴胡皂苷主要分布于中柱鞘和次生韧皮部薄壁组织细胞内,在次生木质部及形成层中也有少量分布。高尔基体可能与皂苷的合成有关,且胞间连丝参与皂苷的运输。柴胡皂苷在幼嫩结构中的含量高于次生结构,但其总含量低于次生结构。     

虚拟现实技术在高校计算机教学中的应用

虚拟现实技术是一种模拟现实环境的计算机技术，近年来其在教学中得到了广泛应用。在高校计算机教学中应用虚拟现实技术，不仅可以节约教学成本，还能满足学生的差异化需求。高校计算机教学涉及的内容专业性强，且较为抽象，传统教学存在情境单一、互动不足、方法僵化等问题。虚拟现实技术的应用推动了高校计算机教学的创新，丰富了教学手段，对推动高校计算机教学的发展具有重要意义。文中分析了虚拟现实技术的特点，并探究了虚拟现实技术在高校计算机教学中的应用。     

Noise in solid-state devices and lasers

A survey is given of the most important noise problems in solid-state devices. Section II discusses shot noise in metal-semiconductor diodes, p-n junctions, and transistors at low injection; noise due to recombination and generation in the junction space-charge region; high-level injection effects; noise in photodiodes, avalanche diodes, and diode particle detectors, and shot noise in the leakage currents in field-effect transistors (FETs). Section III discusses thermal noise and induced gate noise in FETs; generation-recombination noise in FETs and transistors at low temperatures; noise due to recombination centers in the space-charge region(s) of FETs, and noise in space-charge-limited solid-state diodes. Section IV attempts to give a unified account of 1/f noise in solid-state devices in terms of the fluctuating occupancy of traps in the surface oxide; discusses the kinetics of these traps; applies this to flicker noise in junction diodes, transistors, and FETs, and briefly discusses flicker noise in Gunn diodes and burst noise in junction diodes and transistors. Section V discusses shot noise in the light emission of luminescent diodes and lasers, and noise in optical heterodyning. Section VI discusses circuit applications. It deals with the noise figure of negative conductance amplifiers (tunnel diodes and parametric amplifiers), and of FET, transistor, and mixer circuits. In the latter discussion capacitive up-converters, and diode, FET, and transistor mixers are dealt with.     

Errors due to spatial discretization and numerical precision in thefinite-element method

The effects of the spatial discretization and the numerical precision on a plane wave propagating through a finite-element mesh are investigated in this work. The spatial discretization results in dispersion in the amplitude and the phase of the wave and in a non-uniform rate of convergence within an element. The finite precision in the calculations used in a finite-element code results in degraded accuracy. These errors are investigated as a function of the node density, the order of the elements, and the precision of the calculations used in the finite element code. The errors for first- through eighth-order elements are investigated both analytically and numerically