Detection of incoherent broadband terahertz light using antenna-coupled high-electron-mobility field-effect transistors

The sensitivity of direct terahertz detectors based on self-mixing of terahertz electromagnetic wave in field-effect transistors is being improved with noise-equivalent power close to that of Schottky-barrier-diode detectors. Here we report such detectors based on AlGaN/GaN two-dimensional electron gas at 77~K are able to sense broadband and incoherent terahertz radiation. The measured photocurrent as a function of the gate voltage agrees well with the self-mixing model and the spectral response is mainly determined by the antenna. A Fourier-transform spectrometer equipped with detectors designed for 340, 650 and 900~GHz bands allows for terahertz spectroscopy in a frequency range from 0.1 to 2.0~THz. The 900~GHz detector at 77~K offers an optical sensitivity about $1~\mathrm{pW/\sqrt{Hz}}$ being comparable to a commercial silicon bolometer at 4.2~K. By further improving the sensitivity, room-temperature detectors would find applications in active/passive terahertz imaging and terahertz spectroscopy.Comment: 4.5 pages, 5 figure

Study on Corrosion Inhibitors for Reinforcing Steel and Electrochemical Chloride Extraction Applied to Reinforced Concrete Structures

钢筋腐蚀而导致钢筋混凝土结构的过早失效是当今世界日益突出和普遍关注的灾害。Cl-侵蚀是导致混凝土中钢筋腐蚀的首要因素，研究混凝土中钢筋的腐蚀与防护已成为一项迫切任务。本工作针对实际需要，研究钢筋的腐蚀机理，探索钢筋的缓蚀剂保护方法和钢筋混凝土结构电化学除氯技术，对保护钢筋具有重要的实用价值和学术意义。主要研究内容和结果如下：1.探明若干缓蚀剂对钢筋的缓蚀作用，发现D－葡萄糖酸钠具有良好缓蚀效果应用交流阻抗测试等电化学技术，检测了苯甲酸钠、β－甘油磷酸钠、乙醇胺和D－葡萄糖酸钠在含NaCl的模拟混凝土孔隙液中对钢筋的缓蚀作用。结果表明，缓蚀剂的浓度为0.1mol·L-1时，苯甲酸钠和β...Abstract Reinforcing steel corrosion is the major cause of premature degradation of concrete structures and has been a serious and significant problem in modern society. Cl- ingress is the main cause of reinforcing steel corrosion. It is very significant to study the corrosion and protection of reinforcing steel in chloride-contaminated concrete. The aim of this work is to study the corrosion me...学位：理学硕士院系专业：化学化工学院化学系_物理化学(含化学物理)学号：20042511

Asymmetric Information and Venture Capitalist Certification:An Empirical Evidence from SME Board IPOs

作为支撑高科技产业发展、推动产业升级的一种新兴的金融创新模式，风险投资能否有效地提高经营业绩、提升企业价值显得尤为重要。而对于如何衡量风险投资对企业产生的积极影响，较多的文献通过实证研究其所支持企业的IPO特征或经营表现，以此验证风险投资对企业是否存在明显的认证效应，即风险投资是否扮演了积极投资者的角色，通过全程参与企业管理、战略规划等过程最终对企业IPO产生了实质性的影响，进而以此作为风险投资降低企业与外界的信息不对称程度，提升企业价值的有力佐证。 循着这个思路，国外许多学者的研究均以企业IPO作为分析视角，得出的研究结论表明，风险投资在企业IPO中的认证功能较为明显，向外界传达了反映企业...As a totally new investment mode, Venture Capital have affected enormously the High-Tech industry which is also upgraded by VC. According to this, whether VC can add value to the enterprises or not, has become especially important to those enterprises who are invested by VCs. To test VC’s positive effect on the enterprises, the existing studies always do empirical research on the characteristics o...学位：经济学硕士院系专业：经济学院金融系_投资学学号：1562007115143

A wide-area distributed cluster

中文摘要: 本文研究了广域网分布式集群的设计。与LVS 相比,这种集群的结构虽然复杂,但是能够克服传统集群的局限性,提供质量好,容量大,性价比高的解决方案。根据一种称之为CG 树的分布式集群的抽象模型,作者设计了自己CG 树算法。这种方案能有效的减少网络节点之间的通信开销,并能在集群系统出现故障时自动进行调整,保证了高可用性。模拟实验结果表明,该系统具有很好的性能。英文摘要：The paper studies the designs of wide-area distributed cluster. Although these kinds of cluster have more complex structure,they can overcome limitations of traditional cluster and provide resolutions with good quality, large capacity and high performance compared to LVS. Base on a model of distributed cluster, named CG tree, the author design his algorithms to manipulate CG trees. The scheme can efficiently reduce the cost of intercommunication between different networks, and can automatically adjust tree to ensure high availability when cluster faults occur. The result of simulated experiments indicates that the system has quite good performance.基金项目: 国家重点基础研究发展计划(973 计划) 项目(No.2007CB311005);国家863 计划项目(2006AA01Z129);福建省自然科学基金计划资助项目(A0710020);厦门大学985 二期信息创新平台项

Effect of ZnO on Cu/ZnO/Al_2O_3 catalysts for methanol synthesis

[中文文摘]用高速碰撞共沉淀法制备m(CuO) /m(ZnO) /m(Al2 O3 )比分别为 60 /3 0 /1 0和 3 0 /60 /1 0的 1 #和 2 #催化剂 ,结果表明高ZnO的 2 #催化剂活性较好 ,分散度较大。XPS测试表明 2 #催化剂表面ZnO吸附的中间体 (CHx 或CHxO)较多且表面的Cu+1浓度较高 ,从而促进CO加氢合成甲醇的活性。[英文文摘]Cu/ZnO/Al_2O_3 catalysts with ratios of 60/30/10 and 30/60/10 have been prepared by high speed collision coprecipitation method. The performance of the catalyst with the higher ZnO content shows the higher activity in methanol synthesis. The characterization results indicated that the catalyst with the higher ZnO content has higher dispersion. On the surface of the higher ZnO content catalyst, there was more Cu+1 and more intermediate (CH_x and CH_xO) adsorpted. It is beneficial for the CO hydrogenating to produce methanol

我国企业环境报告:现状、需求与未来

经济快速发展带来了环境污染和生态失衡的负面影响 ,如何解决经济发展与环境保护的矛盾 ,促进社会经济的可持续发展 ,已成为世界各国共同关注的问题 ,环保运动、绿色浪潮席卷全球 ,并渗透到各行各业。会计学界在环境信息 ,特别是环境会计信息披露方面发挥了其应有的作用。本文通过问卷调查 ,就我国企业环境报告的现状和需求情况进行了实证分析 ,在此基础上 ,尝试构建一个符合我国社会主义市场经济条件下可持续发展战略要求的企业环境报告框架

海峡论坛·海峡两岸传统武术交流大赛的思考

运用文献资料、问卷调查、专家访谈、数理统计及逻辑分析法,通过对"海峡论坛.海峡两岸传统武术交流大赛"的调查分析以及对闽台武术近年来交流发展的现状进行调研。结果表明:其功能和影响远远超出武术的范围,不仅加深了两岸民众的情感,也推动了两岸武术文化的发展;是闽台武术进一步交流发展的重要途径,也还有更大的发展空间

浅析巨灾期权在我国的运用

我国是一个自然灾害多发的国家,巨大自然灾害的破坏力不言而喻,多年来我国也一直在寻找着有效的解决办法。本文从目前我国巨灾风险的现状出发,以巨灾期权为例剖析了我国应如何应对巨灾风险,并相应提出了建议及对策