氧化物阴极的多次曝大气应用

本文从氧化物阴极的工作机理出发，分析了氧化物阴极在使用时出现的异常现象和消除办法。讨论了如何正确的使用氧化物阴极，延长其使用寿命。根据动态发射中心理论提出了在动态真空系统中工作的电子枪多次曝露大气使用的方法，使在动态真空系统应用中阴极的使用寿命大大地延长。     

电子探针及镀膜仪故障三例与镀膜仪样品架的设计

各种大型精密的电子显微镜，都有一个真空系统，主要给仪器的电子枪和镜筒部分提供一个高真空的空间，使电子枪发射的电子束在经过镜筒时不受气体分子的干扰，有利于形成高质量的电子显微图像，有利于进行高质量的微区成份分析。真空系统在使用过程中，由于有机械部分、电子测量与控制部分、冷却水循环部分，因此故障率较高。为了与同行相互交流经验，现将JCXA-733电子探针及JEE-4X真空镀膜仪的真空部分的三例故障分析和排除方法介绍如下。     

毫米波带状注电子枪的设计方法

利用理论分析和仿真模拟相结合的方法对带状电子注的产生进行了系统的研究,并提出了一种带状注电子枪的设计方法.首先通过理论分析,提出了一种计算带状注电子枪结构参数的迭代算法,即根据注电压、注电流、电子注注腰处半厚度、阴极半厚度和阴极宽度,计算出带状注电子枪的阴极柱面半径、阴阳极间距、阳极柱面半径和射程等主要参数;在此基础上,通过仿真模拟,为毫米波真空电子器件设计了一种带状注电子枪.     

电极零件的卷边与极间高压击穿

电子束管是电真空器件的一种,它通常由抽成真空的玻壳及封入其中的电子枪构成。作为管芯的电子枪是电子束管的心脏,无论是那种类型的电子束管都缺少不了电子枪。电子枪是由阴极发射透镜、预聚焦透镜、主聚焦透镜、偏转棱镜等一系列电子透镜依次组合装配而成的电子光学系统。轴对称静电式电子透镜,均是由馈以不同直流电压的圆筒型电极零件按不同间隙装架而成。除掉阴极、调制极外,各个     

微电真空折叠波导行波管放大器的电子枪设计

研制工作于太赫兹波段的微电真空折叠波导行波管(FWG-TWT)放大器,需要设计束流集中且发射度小、结构紧凑的热阴极电子枪.本文首先依据典型皮尔斯电子枪的设计理论,通过编程计算初步选定了热阴极电子枪的基本结构参数,然后利用模拟工具对电子枪的结构参数模型进行了初步的仿真优化.针对工作频率为0.22 THz的微型折叠波导行波...     

W波段带状注电子枪的仿真研究

随着电真空器件向更高频段的发展,传统电真空器件的发展受到了限制,而带状电子注器件相对于传统的电真空器件有很多优点,有很好的发展前景,对该种器件来说重要的一点就是如何产生带状电子注.本文对传统的轴对称收敛型皮尔斯电子枪进行变形,设计了一种用于W波段的带状注电子枪,进行了理论分析,推导出计算公式,然后用3D电磁仿真软件CST进行了仿真计算,并对电子枪结构进行调整优化,得到了符合预期要求的高质量电子注.     

高亮度细束可拆卸电子枪

研制一种高亮度细束可拆卸电子枪。电子束工作电压10kV,总束流100300A。在采用直径20m的圆形或2020m2的方形物孔限制光阑时,通过物孔光阑的束流是12A,束角为510-3。对电子枪的结构作了介绍,对阴极灯丝、阳极头、物孔光阑等的制造和组装也作了说明。枪外径特别小,只有17mm,可用于大屏幕油膜光阀、热塑记录等需要动态真空系统的场合。     

可输入气体及加热样品的高分辨原位电子显微镜及其应用

在材料科学和工业生产中,气态-固态相互作用是材料合成及处理过程中的基本环节之一,很多研究诸如纳米材料的生长、纳米材料对生态环境及生物组织的影响、催化剂的制备和催化过程,以及微量气体探测等都离不开对气态-固态反应的深入了解.随着纳米时代的来临,对气态-固态作用机制的研究也随之进入了原子分辨率的水平.所以样品室能够接受气体和根据需要对样品进行加热,并具备原子分辨率成像能力的透射电子显微镜就变得非常重要.本文旨在介绍应用日立300 kV H-9500型高分辨透射电子显微镜对不同材料进行原位电子显微术观察的技术,目的是研究固体材料与气体相互作用而产生的原子水平上的结构变化.日立H-9500型电镜具有较为独特的真空系统设计.一台高速涡轮分子真空泵与样品室连接使得气体可以不断被注入样品室又不断被快速抽出.在样品室的上方加装有一个小孔光阑,其作用是让电子束正常通过但大幅减少样品室中的气体向高真空的电子枪区域的扩散.在电子枪的下方设有一个真空测量装置,当从样品室泄漏过来的气体过多时,电子枪下方的一个阀门会自动关闭从而保护电子枪不被损坏.这台电镜既可以作为普通电镜用于结构研究和成分分析,需要时又可以用日立公司的'气体-加热样品台'将气体注入电镜样品室和对样品加热进行动态结构变化的高分辨研究.用这种电镜可以研究半导体材料、催化剂颗粒、纳米碳管、以及陶瓷材料.本文对部分研究结果进行了简略的介绍.     

栅控电子枪设计的新理论

本文介绍近年来在高功率真空电子器件中广泛应用的栅控电子枪的设计新理论,即电子注成形系统与周期永磁聚焦之间的耦合问题和得到的一系列简单关系式。文中还阐述了周期聚焦行波管中电子注成形、传输和收集系统的发散率及其增长理论,这一理论为栅控电子枪、周期永磁聚焦和收集极系统提供了新的设计准则。     

DXB2－12型透射电镜部分故障的维修

ＤＸＢ２－１２型透射电镜部分故障的维修杨煜升，候燕平，牛吉山（山西农业大学电镜室，山西太谷０３０８０１）本文介绍我室ＤＸＢ２－１２型透射电镜发生在电子枪灯丝电源、电子枪栅偏压、镜筒与照相机高真空等方面的故障及排除方法。一、电子枪灯丝电源故障故障现象；...     

Progress in ZnO materials and devices

ZnO is a wide-band-gap semiconductor material that is now being developed for many applications, including ultraviolet (UV) light-emitting diodes, UV photodetectors, transparent thin-film transistors, and gas sensors. It can be grown as boules, as thin films, or as nanostructures of many types and shapes. However, as with any useful semiconductor material, its electrical and optical properties are controlled by impurities and defects. Here, we consider various important donor-type impurities, such as H, Al, Ga, and In, and acceptor-type impurities, such as N, P, As, and Sb. We also examine the effects of a few common point defects, including Zn interstitials, Zn vacancies, O vacancies, and complexes of each. The main experimental techniques of interest here include temperature-dependent Hall-effect and low-temperature photoluminescence measurements, because they alone can provide donor and acceptor concentrations and donor energies. The important topic of p-type ZnO is also considered in some detail.     

植物园

植物园（含树木园）以科学研究、保护、展示和教育为目的,收集保存活植物并保有其档案记录。其主要任务是迁地保护植物多样性、实现其资源的可持续利用,开展相应的植物展示、科普教育和科学研究。全世界现有约2 000个各种类型的植物园和树木园,保存了80 000种植物,包括许多珍稀、濒危的植物种类。中国的植物园目前已达约160个,在植物引种、驯化、开发利用、保护方面取得了巨大成绩,在科普教育、旅游服务方面的重要性得到承认。植物园工作者在相关研究领域取得了理论和技术的创新成果,在管理、政策、培训和植物记录系统计算机化方面也在和世界接轨。面临生物多样性保护与可持续发展的挑战和机遇,我们期待中国的植物园在建园、植物收集保存、科普旅游、能力建设、科学研究等领域取得更大成绩,更好地满足经济和社会发展、环境和资源保护利用的需求,与世界植物园同步前进。     

Design of Stimuli-Responsive Peptides and Proteins

Stimuli-responsive peptides and proteins are an exciting class of smart biomaterials for various applications and have received significant attention over the past decades. A wide variety of stimuli such as temperature, pH, ions, enzymes, magnetic field, redox, etc., are explored. This article provides a review of five intensively studied types of stimuli-responsive peptides and proteins, their design principles and applications, including temperature-, pH-, light-, metal ion-, and enzyme-responsive with an emphasis on the key design concepts and switch function. Moreover, typical examples of their applications are discussed to provide a better understanding of the design concept and underlying methodology. This review will facilitate and inspire future innovation toward new peptide- and protein-based materials and their diverse applications.     

基于SAT的ARX不可能差分和零相关区分器的自动化搜索

ARX（Addition，Rotation，Xor）算法基于模整数加，异或加和循环移位三种运算，便于软硬件的快速实现.不可能差分分析和零相关分析是攻击ARX的有效方法，攻击的关键是搜索更长轮数、更多数量的不可能差分和零相关区分器.目前很多的搜索方法都没有充分考虑非线性组件的性质，往往不能搜索得到更好、更准确的区分器.本文提出了基于SAT（Satisfiability）的ARX不可能差分和零相关区分器的自动化搜索算法.通过分析ARX算法组件的性质，特别是常规模加和密钥模加这两种非线性运算差分和线性传播的特性，给出了高效简单的SAT约束式.在此基础上，建立SAT模型进行区分器的搜索.作为应用，本文首次给出了Chaskey算法13条4轮不可能差分和1条4轮零相关区分器；首次给出了SPECK32算法10条6轮零相关区分器和SPECK48算法15条6轮零相关区分器；在较短的时间内，给出了HIGHT算法17轮的不可能差分和零相关区分器.与现有结果相比，无论是区分器的条数，还是搜索区分器的时间均有明显的提升.此外，通过重新封装求解器STP的输出接口，建立了自动化的SAT\\SMT分析模型，能够给出ARX算法在特殊输入输出差分和掩码集合下，不可能差分和零相关区分器轮数的上界.     

Job schedulers for Big data processing in Hadoop environment: testing real-life schedulers using benchmark programs

At present, big data is very popular, because it has proved to be much successful in many fields such as social media, E-commerce transactions, etc. Big data describes the tools and technologies needed to capture, manage, store, distribute, and analyze petabyte or larger-sized datasets having different structures with high speed. Big data can be structured, unstructured, or semi structured. Hadoop is an open source framework that is used to process large amounts of data in an inexpensive and efficient way, and job scheduling is a key factor for achieving high performance in big data processing. This paper gives an overview of big data and highlights the problems and challenges in big data. It then highlights Hadoop Distributed File System (HDFS), Hadoop MapReduce, and various parameters that affect the performance of job scheduling algorithms in big data such as Job Tracker, Task Tracker, Name Node, Data Node, etc. The primary purpose of this paper is to present a comparative study of job scheduling algorithms along with their experimental results in Hadoop environment. In addition, this paper describes the advantages, disadvantages, features, and drawbacks of various Hadoop job schedulers such as FIFO, Fair, capacity, Deadline Constraints, Delay, LATE, Resource Aware, etc, and provides a comparative study among these schedulers.     

VoIP技术--语音和数据的集成

介绍了VoIP(Voice over IP)的基本组成构件即网关(Gateway)、网守(Gatekeeper)的概念和用途。讲述了语音在IP网上传输的基本原理，语音和数据、数据和IP包之间的转换和传送过程。在H．323协议栈的基础上详细讲述了H．248，H．225，H．245等通信协议和语音编码G．729，G．23l，G．7ll等协议。最后对VoIP的语音服务质量作了较为详细的阐述。     

A Progress Report on Metal–Sulfur Batteries

Nonaqueous conversion‐reaction sulfur chemistry has been attracting increasing attention over the past decade for the development of next‐generation lithium‐based batteries. Li–S batteries are currently approaching a nexus stage from lab‐scale experiments to possible pragmatic applications. Inspired by the success of Li–S chemistry, other metal–sulfur batteries with a variety of metallic anodes, such as sodium, potassium, magnesium, calcium, and aluminum, have also started to attract attention. In comparison to lithium, Na, Mg, Al, K, and Ca are naturally more abundant and affordable. The Na‐S, Mg‐S, Al‐S, K‐S, and Ca‐S battery systems provide a great potential for improving the volumetric energy density of sulfur‐based batteries. The multivalent metal‐sulfur systems, Mg‐S, Al‐S, and Ca‐S, offer better safety features as well. However, the research and development on Na‐S, Mg‐S, Al‐S, K‐S, and Ca‐S batteries is far behind the Li–S system due to many critical challenges. In this progress report, the fundamental principles of various metal–sulfur chemistries are first presented and compared. Then, the historical progress, recent advances, and key challenges of the Li–S, Na‐S, Mg‐S, Al‐S, K‐S, and Ca‐S systems are summarized and discussed. Finally, future efforts and directions for both the fundamental and practical research are prospected.     

An Investigation of MIMO Performance in the Indoor Ricean Environment

In this paper, we investigate the Multiple-Input Multiple-Output (MIMO) channel capacity in indoor Ricean channels based on MIMO channel measurements at 2.45 GHz. The measured data is analysed using a super resolution parameter estimation algorithm. Our results demonstrate that the line-of-sight (LOS) component in a Ricean scenario influences indoor MIMO performance through increased spatial correlation between array elements. We found that indoor channels with higher values of Ricean K factor have smaller numbers of effective multipath components and increased spatial correlation. Measurement results also showed that, the effect of varying antenna height on indoor MIMO capacity is also due to the spatial correlation of multipath propagation and has a close relationship with the separation between the transmitter and receiver. Zhongwei Tang is currently with the Wireless Technologies Laboratory at CSIRO. He was with Microwave and Wireless Technology Research Laboratory (MWTRL), Information and Communication Group, Faculty of Engineering of the University of Technology Sydney, Australia, where he pursued his Ph.D. Degree. His current research interests include RF propagation, MIMO Space-Time channel measurements, characterization and channel modelling, smart antennas, MIMO systems and array signal processing. Ananda S. Mohan is currently a member of the Faculty of Engineering, University of Technology, Sydney (UTS), Australia where he leads research on antennas, microwaves, wave propagation, and wireless technology. He received a Ph.D. degree in electrical communication engineering from the Indian Institute of Technology, Kharagpur, India and was a Scientist and Senior Scientist at the Research and Training Unit for Navigational Electronics, Hyderabad, India. At UTS, he directed the Sydney microwave design resource centre and was the associate program leader of the co-operative research centre for satellite systems. He currently directs the microwave and wireless technology research laboratory and a core member of the university research centre on health technologies. His current teaching and research interests include wireless mobile communications, microwaves and antennas, smart antennas and applications of microwave and wireless technology in medicine and has obtained many competitive research grants in these areas. Dr. Mohan was a co-recipient of the Priestly memorial award from the Institute of Radio and Electronic Engineers (IREE), Australia. He was a member of the organizing and technical Program Committees of the IEEE Globecom'98, APMC 2000, and International Symposium on Wireless Systems and Networks, 2003 and IASTED International Conference on Antennas, Radar, and Wave Propagation, for 2004 and 2005.     

支持冗余和兼容设计的智能建筑综合管理系统

为推动城市智能建筑管理新技术的开发和应用,针对工程实际问题,提出了一种支持冗余和兼容设计的城市智能建筑综合管理系统的设计方案.系统设计内容包括为楼宇控制、照明控制和停车引导控制设计的同一架构的CPU模块及软件、通信网关模块及软件、集中控制模块及软件、I/O模块及软件、无线模块、超声波检测模块及内部总线等,并阐述和分析了总线冗余、设备兼容性和集成监控软件等系统关键技术.系统具有先进的分布式系统、开放的网络化通信和标准化程序设计等多项新特性,可以显著提升大型城市建筑的智能化和节能管理水平.     

智能语音操控在广电端到端的系统设计及应用

在数字化中国的大背景下,在公司个人宽带与互动电视在线交费用户均突破300万户的情况下,为解决我们的用户总找不到自己喜欢看的节目,记不住频道名称和喜欢的节目,提升公司竞争力。通过对前端的点播系统、AAA系统、EPG系统、PORTAL系统、ISMP系统、媒资系统、机顶盒终端的功能进行剥离、整合和详细设计,最后完成终端用户语音操控电视直播、点播、时移、回看、页面操控、系统设置,并支持普通话和四川话方言的目的。达到提升用户体验,增加公司竞争力,促进业务的发展。系统试运行后,用户体验效果得到很大提升,完全达到预期设计目的。