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分析了数字视频的特点和优势,阐述了基于内容的视频检索的迫切性和重要性。比较分析了4个典型检索系统,归纳了其系统结构、功能和应用领域等,指出存在的主要问题,并提出了解决方案。分析了研究的热点和方向。 相似文献
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为解决当前知识管理系统中检索时存在大量无关知识等问题,提出了一种新的企业网络知识管理系统,该系统成功引入了本体的概念和Agent技术,实现时采用了面向对象的方法。文中给出了系统的框架结构,研究了其实现的关键技术——本体的建立、知识的获取和存储、知识的检索。最后设计了一个实验系统,给出了OWL源码描述的本体实例。实验证明,本体的引入增强了知识管理的语义性和智能性,提高了信息检索的查全率和查准率。 相似文献
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本文分析和研究了Linux系统在实时性方面存在的问题,并分析了实时系统的原理,以及提出了实时Linux系统的系统结构和应用程序的结构。 相似文献
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简要介绍了互联网组管理协议(Internet Group Management Protocol,IGMP)和协议无关组播的稀疏模式(Protocol Independent Multicast-Dense Mode,PIM-SM)协议的基本原理。结合移动无线自组网的需求和VxWorks 6.9操作系统的特点,对IGMP协议和PIM-SM协议进行了适配和改进。首先,给出了IGMP协议的查询器选举和Query消息的接收者的改进方法;其次,扩展了PIM-SM协议在单接口和路由表项不写入内核等情况下的应用场景,设计了一套多任务处理方案,通过轮询实现了内核信令的触发(如“IGMPMSG_NOCACHE”类型的信令)和组播数据转发调度的功能;最后,通过搭建两对“主机-电台”的实测环境,实现了消息交互功能,验证了该方案的可行性。 相似文献
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对精确制导武器的各种精确制导模式进行了比较。指出了各种制导模式存在的缺陷和局限性,提出了影响精确制导武器发展的关键技术,并分析了几种关键技术的研究方向和进展情况。为国内精确制导武器的研究和发展提供了一定的参考价值和使用价值。 相似文献
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Graphene, a two‐dimensional, single‐atom‐thick carbon crystal arranged in a honeycomb lattice, shows extraordinary electronic, mechanical, thermal, optical, and optoelectronic properties, and has great potential in next‐generation electronics, optics, and optoelectronics. Graphene and graphene‐based nanomaterials have witnessed a very fast development of both fundamental and practical aspects in optics and optoelectronics since 2008. In this Feature Article, the synthesis techniques and main electronic and optical properties of graphene‐based nanomaterials are introduced with a comprehensive view. Recent progress of graphene‐based nanomaterials in optical and optoelectronic applications is then reviewed, including transparent conductive electrodes, photodetectors and phototransistors, photovoltaics and light emitting devices, saturable absorbers for ultrafast lasers, and biological and photocatalytic applications. In the final section, perspectives are given and future challenges in optical and optoelectronic applications of graphene‐based nanomaterials are addressed. 相似文献
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现代通信网络应能满足各种通信业务和通信容量日益发展的需求,实现话音、数据、视频、IP等业务的一体化综合交换和传输。在比较TDM、IP和ATM三种协议的基础上,提出"采用内置RPR和MPLS功能的MSTP平台"建设光纤综合通信网络平台的实现方法。MSTP采用SDH的数据帧结构,保持了SDH标准光接口、灵活分插低速信号、自愈环保护和功能强大的网管等优点,可对TDM、IP和ATM协议进行优化传输。 相似文献
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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. 相似文献
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Sudhir Dixit 《Wireless Personal Communications》2006,38(1):55-65
As the convergence in digital industry takes shape, the digital networks, both wireline and wireless, are also converging to offer seamless services and enhanced experience to the user. With the arrival of the mobile Internet the mobility is also moving into new areas, e.g., imaging, games, video, multimedia, and across different types of networks. In this paper we explore why, what, and how of the network convergence, and identify how the industry viewpoints align and differ. We also identify the key barriers to achieving true network convergence. We then discuss the role of the Internet Protocol (IP) as the common thread that enables network convergence, and the key industry and standards initiatives to actually provide solutions and the equipment to implement a cost-efficient and high performance converged network.
Sudhir Dixit joined Nokia Research Center in 1996, where he is currently a Research Fellow and works on next generation wireless networks. From 1996 to 2003 he was a Senior Research Manager, focusing on IP/ATM, wireless, content networks, and optical networks. Prior to that he worked at NYNEX Science & Technology (now Verizon), GTE (now Verizon), Codex Motorola, Wang, Harris, and STL (now Nortel Europe Labs). He has published or presented over 150 papers, published three books, and holds 14 patents. He is on the Editorial Board of the IEEE Communications Magazine, Springer's Wireless Personal Communications Journal, and KIC's Journal of Communications and Networks. He received a B.E. degree from MANIT, Bhopal, India, an M.E. degree from BITS, Pilani, India, a Ph.D. degree from the University of Strathclyde, Glasgow, Scotland, and an M.B.A. degree from Florida Institute of Technology, Melbourne. He is a Fellow of IEE (UK) and IETE (India). He represents Nokia on the Steering Board of the Wireless World Research Forum, and is also Chair of the SIG on Self-Organization of Wireless World Systems. 相似文献
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组呼通信在指挥调度中有着重要作用,而在一些地面没有基站的地方,就无法正常使用。卫星通信具有无视地形,通信范围广,不易受陆地灾害影响,易于建设等优点。把卫星通信和组呼通信结合在一起的卫星组呼通信技术兼顾两者的优点,能更好的发挥指挥调度这一作用。当前卫星组呼通信采用固定频率方式,组呼成员在一个频率下进行通信,这种方式实用性不好。本文研究的是移动卫星组呼,在GMR-1系统的基础上研究了卫星组呼通信中MAC层的功能,提出了MAC-Ready-Gcc、MAC-Dedicated-Gcc这两个为了支持组呼的状态,并针对在MAC层发生的PTT竞争提出了一种回退策略。 相似文献
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The tremendous momentum toward building a mobile wireless Internet using the Internet Protocol (IP) has thrust many challenges upon the technology developers and the operators. These challenges encompass the 2.5G, 3G, and future solutions and standards. Some of the key issues deal with supporting IP traffic across different wireless and MAC protocols, end-to-end QoS and mobility, traffic engineering and scalability, protection/restoration, operations and management, authentication/privacy/security, billing, and content and context aware networking. This article addresses the drivers, the issues, and solutions (wherever possible) in the above areas, and concludes with a summarization of the challenges that lie ahead. 相似文献
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Towards Mobile Ubiquitous Service Environment 总被引:2,自引:0,他引:2
JI Yang Zhang Ping Hu Zheng Wang Xu Li Yinong Tang Xiaosheng 《Wireless Personal Communications》2006,38(1):67-78
In this article we present a perspective on future vision of mobile communications and services which is referred to as Mobile Ubiquitous Service Environment (MUSE). Based on analysis of wireless communications and services, we exploit a conceptual model for MUSE via a top-down approach. The conceptual model consists of three major elements: Terminal Service Environment (TSE), Network Service Environment (NSE) and User Identity (UID). The concept of Always the Best Experience (ABE) is addressed as the hinge in design and development such that the user-centric services could be provided automatically and intelligently in the future diverse wireless world Based on these, we further discuss the issues on design and implementation of architecture of future wireless communication system. Requirements for architecture brought by the new features of MUSE are listed. Moreover, we also address several tradeoffs that should be taken into consideration in design. Finally, the deployment challenges for MUSE, such as reflectiveness of system, security and privacy, as well as peer-to-peer AAA are predicted.Ji Yang received PhD degree on Circuit and System, Bachelor degree on Telecommunication Engineering from Beijing University of Posts and Telecommunications (BUPT) in 2002 and 1993 respectively. Currently, he is an associate professor of BUPT, chief technical supervisor of Wireless Technology Innovation Institute, and vice manager of MTlab of Sino-Germany Software Institute. He leads the research on service and application in Future Forum in China. He also made much contribution to the China Communication Standardization Association (CCSA), including the vision of future Mobile Ubiquitous Service Environment, architecture of future B3G mobile terminal, etc. His research interests include architecture design for mobile ubiquitous networks, theory of self-organization, etc.Zhang Ping is now the professor of Beijing University of Posts and Telecommunications and director of Wireless Technology Innovation (WTI) Institute, BUPT. He has also served on the senior member of C3G Group, China MOST 863 future mobile communication FuTURE project, vice-chairman of China FuTURE Forum, and member of Vision Committee of World Wireless Research Forum(WWRF), he was vice chair of WWRF in 2005. He is also invited as the consultants for many domestic and oversea communication companies. He is very active on the international research activity on Beyond 3G area. He also participated in several European projects such as E2R and MOCCA. Until now, he has published 6 books, around 400 publications in journals and conferences in the area of telecommunications. His main research interests are theory and applications in wireless communication area. He was awarded by government, city of Beijing and Ministry of Information Industry several times for his great contribution to the industry and research activity in China.Hu Zheng is a PH.D candidate in mobile communications engineering in Wireless Technology Innovation Institute (WTI) at Beijing University of Posts and Telecommunications (BUPT). He received B.S degree from Nanjing University of Posts and Telecommunications in 2002, majoring in computer communications engineering. He currently works on serivce aspects of mobile ubiquitous communication system with focus on design and performance evaluation of interaction protocols and services in self-organized service environment.Wang Xu received the B.Tech. degree in electronic engineering from Beijing Polytechnic University (now named as Beijing University of Technology), Beijing, China, in 2002. Now he is working for his Ph.D. degree in Wireless Technology Innovation (WTI) Institute, Beijing University of Posts and Telecommunications (BUPT). His current interests include wireless communications in personal area, ad hoc networks and peer-to-peer system.Li Yinong received the BS degree major in Telecommunication Engineering in 1993 from Beijing University of Posts and Telecommunications, the MS degree and PhD degree major in Telecommunication and Electronic System in 1995 and 2003 from the Beijing University of Posts and Telecommunications. He is currently a lecture of STE (School of Telecommunication Engineering) of BUPT. His main research interests include service modeling, service composition approach, and intelligent service. In BUPT, he has given several lectures to both graduate and undergraduate students such as Information Theory, Speech Recognition, Pattern Recognition and Artificial Intelligence. 相似文献
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Yijie Hu Zehong Chen Hao Zhuo Linxin Zhong Xinwen Peng Run‐Cang Sun 《Advanced functional materials》2019,29(44)
3D monoliths have undergone great progress in the past decades in scientific and engineering fields. Especially, compressible and elastic 3D monoliths (CEMs) hold great promise in a series of applications, such as pressure/strain sensing, energy storage, oil/water separation, and thermal insulation, attributed to their unique mechanical properties and multifunctionality (e.g., conductivity, thermal stability, and high adsorption capacity). Recently, plenty of advanced CEMs have been developed from 1D and 2D building blocks, polymers, and biomass via various methods. Herein, the latest progress in controllable design and preparation of advanced CEMs, which mainly refer to aerogels, sponges, and foams, are reviewed in terms of their structural units and applications. The relationship between structure and mechanical performances of CEMs is discussed. Moreover, their applications in sensing, energy storage and conversion, water treatment, fire‐resistance, and electromagnetic interface shielding are presented. Finally, the challenges and future opportunities of CEMs are also discussed. 相似文献
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This paper investigated the impacts of self-esteem and empathy on cyber bullies, victims and bystanders. Additionally, it also examined their impacts on emotional responses experienced, and actions taken by the perpetrators, victims and bystanders. Self-administered surveys were used to gather data from a large sample of 1263 young adults, mostly university students in Malaysia (Mage?=?20.9?years; SD?=?1.22). The Rosenberg Self-Esteem Scale and Toronto Empathy Scale were used to measure self-esteem and empathy, respectively. Binary logistic regressions revealed no significant impacts of self-esteem and empathy on the participants, regardless of their roles. However, self-esteem was found to have significant relationships with victims’ feeling angry and reporting a cyberbullying incident. As for bystanders, self-esteem also had significant relationships with feeling angry, sad, victim-pity and defending the victims. Empathy had no significant relationships with any of the actions and emotional responses for bullies, victims and bystanders. 相似文献