数字无线本地环路和系统

本文对数字无线本地环路进行系统的介绍，着重研究和讲话了ＤＷＬＬ的体系结构及关键技术，为开发和利用数字无线本地环路提供一种借鉴和参考。     

无线本地环路（WLL）技术及发展趋势

本文介绍无线本地环路（ＷＬＬ）系统的基本结构及其相关技术，指出无线本地环路ＷＬＬ的优势和关键技术，并就ＷＬＬ的现状和发展趋势作出分析。     

采用CDMA及V5接口技术的WLL系统

文章分析了无线本地环路（ ＷＬＬ） 的优势及所采用的技术，介绍了采用ＣＤＭＡ 及Ｖ５ 接口技术的ＷＬＬ 系统。     

对利用PHS技术实现微小区无线接入系统的探讨

本文介绍了无线本地环路（ＷＬＬ）的发展，并着重分析了一种典型的微小区无线本地环路系统－美国ＵＴＳｔａｒｃｏｍ的ＡＩＲＳＴＡＲ－ＷＬＬ的结构、功能特点及应用。     

中兴ZXDWLL系统

我国地域辽阔、地形复杂，人口众多，将电话业务延伸到边远地区，扩大电话覆盖面，已经成为各地电信规划的重要课题。中兴通讯为了满足市场需求，适应社会发展趋势，推出基于ＣＤＭＡ技术的ＺＸＤＷＬＬ数字无线本地环路系统，为未来个人无线通信奠定了基础，为实现“村...     

PHS-WLL无线接入系统简介

和有线本地环路相比，无线本地环路（ＷＬＬ－ＷｉｒｅｌｅｓｓＬｏｃａｌＬｏｏｐ）由于具有安装容易，维护方便等优点而应用得越来越多。ＷＬＬ有多种技术解决方案，其中ＰＨＳＷＬＬ是造价较低，性能较好的方案之一。１ＰＨＳ与ＰＨＳＷＬＬ的技术特点ＰＨＳ（Ｐｅ...     

“空中之星”无线本地环路

“空中之星”无线本地环路美国ＵＴ斯达康的ＡｉｒＳｔａｒ“空中之星”ＷＬＬ系统是当前各种ＷＬＬ系统产品中的佼佼者．它是ＵＴ斯达康的ＡＮ２０００综合接入网系统与ＰＨＳ技术集成的无线本地接入网系统．ＡＮ２０００与中央交换局连接，主要担任数字复用、光纤传输、...     

WLL的市场前景

ＷＬＬ的市场前景无线本地环路系统近几年来受到了发展中国家和发达国家的共同重视，很快得到市场的普遍欢迎。ＡＴ＆Ｔ分司预计，无线本地环路产品市场总值到１９９８年会超过８０亿美元。据北方电讯分司估计，在亚太地区，至少会有１５％新用户采用ＷＬＬ。由此可见，Ｗ...     

无线本地环路的研究与应用

无线本地环路（ＷＬＬ）技术发展迅猛。本文在介绍ＷＬＬ系统结构的基础上，着重对其技术类型和业务应用进行了探讨，并就我国发展ＷＬＬ技术的有关问题提出了建议。     

数字无线本地环路

简要介绍了无线本地环路的基本概念，采用的数字技术，ＴＤＭＡ和ＣＤＭＡ无线本地环路系统的结构，并指出无线本地环路在减少成本，灵活入网，扩展网络等许多方面的优势，对几种无线本地环路的容量作了比较，对无线本地环路的前景作了展望。     

胆小管超微细胞酶学研究

以电镜细胞化学的方法,观察了小鼠胆小管酶的分布。观察的12种酶中,NDPase和G6Pase三种酶分布于胆小管微绒毛;AlPase、Na~+-K~+ATPase、Mg~(++)-ATPase、Ca~(++)-ATPase、CMPase、ACase和5＇-Nase等7种酶分布于胆小管微绒毛,也分布于肝细胞邻接面细胞膜和Disse间隙微绒毛;ACPase、细胞色素氧化酶以及线粒体ATPase不分布胆小管微绒毛,也不分布Disse间隙微绒毛和肝细胞膜。据信,胆小管微绒毛上的酶参与胆汁成份的转运,提供转运所需能量以及还可能与某些代谢过程有关。本实验中磷酸水解酶类使用的铈基法及亚铁氰化钾半还原的锇酸后固定法,效果优于铅法。     

基于GNSS_CN高速公路自动收费系统的研究与设计

本文独创性的提出将多卫星定位系统融合来提高定位精度,并采用高可靠、高精度的定位应用于高速公路等收费系统中,实现了基于GNSS/CN高速公路收费车载单元的研究与设计.介绍了车载单元工作原理,以及硬件和软件系统的设计方案,通过硬件和软件设计与调试,相比原有单一卫星定位系统,在多卫星定位系统融合的基础上,实现了更高精度的定位.车载单元利用GPS或/和BD等系统获取车辆的位置、速度等信息,通过蜂窝网络和控制中心进行通信,将位置、速度等信息发送到控制收费中心,可在控制收费中心和车载单元上进行地图匹配,动态显示车辆位置、速度以及收费等信息.该成果已成功试运行.     

铁路机车设备检修管理信息化系统的研究

随着国家轨道交通事业的迅速发展,铁路维修业务不断增多,铁路物资积累日趋丰富,鉴于自身发展的需求,文章提出在检修流程、任务派发、人员管理、物资使用、维修管理、物品存放、安全监测、循环利用等环节,都需要采用更加现代化的管理模式。通过对机车设备检修流程信息化的实现,进行检修产品全生命周期的管理,以及检修产品故障原因的总结和分析,提高检修管理和实施的效率,最终形成一个安全、稳定、高效、协同的精细化管理模式。     

基于微件的井位部署论证系统实现

针对勘探、油藏井位部署过程中涉及的地理位置、勘探开发历程、油藏地质特征、产能状况等重要环节,对油田各级地质构造、三级储量、沉积相、井位等勘探开发图形对象叠加地形地貌在平面上进行多尺度、多层系的图形展示,并结合地质信息服务和企业数据服务,实现了探区内地震资料处理、解释一体化查询展示、已探邻井相关资料一体化研究、正钻井生产状况实时查询、区块内岩性、物性统计分析、油气储量分布情况展示、井位的在线编辑及成果标注等功能,有效支撑井位部署过程中的各种数据查询、在线踏勘、井位编辑,统计分析以及成果展示,从而提高油田井位部署的效率及水平。     

基于属性密码体制的区块链安全技术研究进展

区块链是一种集合了分布式存储、点对点传输、共识机制、密码学算法和智能合约等关键技术的分布式账本,具有去中心化、不可篡改、透明化等特性.近年来区块链技术的安全性问题逐渐显露,阻碍了区块链应用的发展.本文介绍了区块链的基本概念与安全模型,分析了区块链的安全性问题;然后,基于属性密码体制,从访问控制、密钥管理、数据隐私保护这三个方面分析了区块链安全技术的各类研究,论述了主要的解决方案的特点;最后,总结了基于属性密码体制的区块链安全技术研究进展,并对未来的研究工作进行了讨论.     

Survey on data security and privacy-preserving for the research of edge computing

With the rapid development and extensive application of the Internet of things (IoT),big data and 5G network architecture,the massive data generated by the edge equipment of the network and the real-time service requirements are far beyond the capacity if the traditional cloud computing.To solve such dilemma,the edge computing which deploys the cloud services in the edge network has envisioned to be the dominant cloud service paradigm in the era of IoT.Meanwhile,the unique features of edge computing,such as content perception,real-time computing,parallel processing and etc.,has also introduced new security problems especially the data security and privacy issues.Firstly,the background and challenges of data security and privacy-preserving in edge computing were described,and then the research architecture of data security and privacy-preserving was presented.Secondly,the key technologies of data security,access control,identity authentication and privacy-preserving were summarized.Thirdly,the recent research advancements on the data security and privacy issues that may be applied to edge computing were described in detail.Finally,some potential research points of edge computing data security and privacy-preserving were given,and the direction of future research work was pointed out.     

SEM在半导体工艺研究中的应用实例

根据半导体工艺的需要,介绍了利用SEM分析工艺问题的方法。主要包括样品的解理、缀饰及为提高导电性所采用的镀膜方法比对,其中高效、准确的解理定位是重要前提。三个典型案例中,埋层漂移是在问题刚显露时就得到及时分析、彻底解决;而MEMS器件悬臂梁断裂翘曲及减少鸟嘴工艺,则是在研制开发新工艺过程之初,就列为"定点清除"的主要问题。上述问题是发生在科研生产中的实例,且均已在工艺规范层面定型。在形成成品之前,特别是工艺设计及加工制造阶段的失效分析及可靠性研究,能够在隐患转变为大面积工艺问题及后期性能参数问题之前,就能够提早定位并彻底解决,更为今后产品大规模量产及产品升级换代提供客观准确的科学依据。SEM是其中的重要技术手段,尤其在线检测分析更是物尽其用。     

Alternative Schemes for Dynamic Secure VPN Deployment in UMTS

Three alternative schemes for secure Virtual Private Network (VPN) deployment over the Universal Mobile Telecommunication System (UMTS) are proposed and analyzed. The proposed schemes enable a mobile node to voluntarily establish an IPsec-based secure channel to a private network. The alternative schemes differ in the location where the IPsec functionality is placed within the UMTS network architecture (mobile node, access network, and UMTS network border), depending on the employed security model, and whether data in transit are ever in clear-text, or available to be tapped by outsiders. The provided levels of privacy in the deployed VPN schemes, as well as the employed authentication models are examined. An analysis in terms of cost, complexity, and performance overhead that each method imposes to the underlying network architecture, as well as to the mobile devices is presented. The level of system reliability and scalability in granting security services is presented. The VPN management, usability, and trusted relations, as well as their behavior when a mobile user moves are analyzed. The use of special applications that require access to encapsulated data traffic is explored. Finally, an overall comparison of the proposed schemes from the security and operation point of view summarizes their relative performance. Christos Xenakis received his B.Sc. degree in computer science in 1993 and his M.Sc. degree in telecommunication and computer networks in 1996, both from the Department of Informatics and Telecommunications, University of Athens, Greece. In 2004 he received his Ph.D. from the University of Athens (Department of Informatics and Telecommunications). From 1998–2000 was with the Greek telecoms system development firm Teletel S.A., where was involved in the design and development of advanced telecommunications subsystems for ISDN, ATM, GSM, and GPRS. Since 1996 he has been a member of the Communication Networks Laboratory of the University of Athens. He has participated in numerous projects realized in the context of EU Programs (ACTS, ESPRIT, IST). His research interests are in the field of mobile/wireless networks, security and distributed network management. He is the author of over 15 papers in the above areas. Lazaros Merakos received the Diploma in electrical and mechanical engineering from the National Technical University of Athens, Greece, in 1978, and the M.S. and Ph.D. degrees in electrical engineering from the State University of New York, Buffalo, in 1981 and 1984, respectively. From 1983 to 1986, he was on the faculty of Electrical Engineering and Computer Science at the University of Connecticut, Storrs. From 1986 to 1994 he was on the faculty of the Electrical and Computer Engineering Department at Northeastern University, Boston, MA. During the period 1993–1994 he served as Director of the Communications and Digital Processing Research Center at Northeastern University. During the summers of 1990 and 1991, he was a Visiting Scientist at the IBM T. J. Watson Research Center, Yorktown Heights, NY. In 1994, he joined the faculty of the University of Athens, Athens, Greece, where he is presently a Professor in the Department of Informatics and Telecommunications, and Director of the Communication Networks Laboratory (UoA-CNL) and the Networks Operations and Management Center. His research interests are in the design and performance analysis of broadband networks, and wireless/mobile communication systems and services. He has authored more than 150 papers in the above areas. Since 1995, he is leading the research activities of UoA-CNL in the area of mobile communications, in the framework of the Advanced Communication Technologies & Services (ACTS) and Information Society Technologies (IST) programmes funded by the European Union (projects RAINBOW, Magic WAND, WINE, MOBIVAS, POLOS, ANWIRE). He is chairman of the board of the Greek Universities Network, the Greek Schools Network, and member of the board of the Greek Research Network. In 1994, he received the Guanella Award for the Best Paper presented at the International Zurich Seminar on Mobile Communications.     

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。     

化合物半导体器件与电路的研究进展

介绍了GaAs,InP和GaN等几种重要化合物半导体电子器件的特点、应用和发展前景。回顾了GaAs,InP和GaN材料的材料特性及其器件发展历程与现状。分别讨论了GaAs基HEMT由PHEMT渐变为MHEMT结构和性能的变化,GaAs基HBT在不同电路应用中器件的特性,InP基HEMT与HBT的器件结构及工作特性,GaN基HEMT与HBT的器件特性参数。总体而言,化合物半导体器件与电路在高功率和高频电子器件方面发展较快,GaAs,InP和GaN材料所制得的各种器件电路工作在不同的频率波段,其在相关领域发展潜力巨大。