浅析网格技术在现代远程课程中的应用

现代远程教学是对正规教育的有益补充，将网格技术运用到远程教学中，将推动教育信息化的发展。本文介绍了网格技术的概念和特征，分析了网格技术在现代远程教学中的应用，并概述了基于网格技术的远程教学系统模型的构成。     

远程教学中动画技术的应用研究

远程教学作为未来教育的一种发展趋势,受到了国内外教育工作者的关注.而教学课件呈现质量的好坏与动画技术息息相关.本文介绍了远程教学的发展现状及意义,探讨了远程教学中的动画技术,并分析了Flash动画技术在远程教学应用中的特点.     

创建现代远程教学系统的探索与实践

基于卫星通信技术、互联网技术和流媒体技术创建的新型远程教学系统,为构建终身学习提供了有力支持。人们在创建远程教学系统时,都希望实现为学习者提供在任何时间、任何地点自主学习的环境,能最大限度地满足各类人员的学习需求,并保证良好的学习效果。远程教学中信息传送系统能否为传送教学信息提供强有力的、可靠的支持,这是决定远程教学效果的关键环节之一。本文对构建现代远程教学系统进行了探讨,并结合自行研发的清华大学远程教学播出系统,阐述了播出系统的构成及技术特点。     

电子学太赫兹技术研究概述

太赫兹技术是交叉前沿技术,本文首先介绍了太赫兹及电子学太赫兹技术基本概念,然后介绍了国内外电子学太赫兹器件的现状和应用情况,重点介绍了电子学太赫兹技术在通信及雷达方面的应用现状。最后给出了电子学太赫兹应用研究的具体内容及发展方向。     

个性化远程教学系统中决策树方法的应用研究

现代远程教学是随着计算机网络技术和多媒体技术的发展而产生的一种新型的教学形式。因材施教,个性化教学一直是远程教学服务系统追求的目标,如何从大量堆积的学习者信息中发现有价值的规律,实现远程教学系统的个性化教学,已经成为教育研究者一个亟待解决的课题。探讨了如何将数据挖掘技术中的决策树方法应用于远程教学系统中来为学习者进行分类,以实现针对不同学生的个性化教学。     

分布式远程教学平台在中外合作教学中的应用探究

教育国际化是当今世界教育发展的潮流,中外合作教学已成为教育国际化的一种模式。分布式远程教学平台软件是合作模式实现的技术基础。本文研究了远程教学信息发布与管理,给出了一个完整的基于教学的远程教学平台的结构和系统整体设计思想,为资源的有效共享提供技术解决方案。     

基于流媒体技术的远程教学系统设计

远程教学系统是基于Internet网和现代计算机技术、与教学理论相结合、为教学系统的远程教学过程提供服务的软件系统.系统运用面向对象的设计思想,采用UML语言抽象对象,完成了一个远程教学系统的设计.     

视频会议技术和虚拟现实技术在远程教学系统中的应用

远程教学是在开放式教育网络基础上构建的学习系统。本文对现阶段远程视频会议技术及其在远程教学系统中的应用进行分析,并对虚拟现实技术进行讨论,从而得出远程教学的新模式。视频会议技术可将音视频数据在多个终端设备间进行实时传输,达到即时通信的效果;虚拟现实技术可构建物体及其运动的三维信息,同时嵌入文本、图像等二维信息,使用户置身于三维环境中,给人以真实感受。本文认为将视频会议技术与虚拟现实技术结合,将产生新模式,能满足师生对远程教学的高需求,提高教学质量,实现更理想的远程教学系统。     

异构网络的多终端教学方案设计与实现

基于三网融合实验室网络环境,应用H.264编码与P2P技术,设计了异构网络的视频监控与远程教学方案,实现了智能手机、计算机、平板、电视屏实时监控或者远程教学.重点介绍了网络摄像机在实验室网络上的组建方案与网络技术在此方案中的应用.方案中体现了现代网络技术在视频监控、远程教学和高校信息化建设中取得的显著效果.     

优化计算机网络远程教学的多媒体环境设计

计算机网络技术的不断发展为教育教学带来了广阔的发展空间。在远程教学方面，应用计算机网络技术已经成为主流。然而，由于网络传输的特殊性，远程教学中容易遇到一些问题，如视频卡顿、声音不清晰、数据传输不稳定等。为解决这些问题，需要对远程教学的多媒体环境进行设计和优化。随着数字化和网络化时代的到来，计算机网络技术已成为教育教学的重要工具。文中从多媒体环境设计的角度出发，探讨了如何优化计算机网络远程教学，以达到更好的教育效果，提升用户体验。     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

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.     

车辆状态信息显示处理系统的研究与设计

介绍了基于CAN总线的车辆状态信息显示处理系统,分析了CAN.总线的特点及在汽车中使用CAN总线的优点,并给出了其在国内外汽车中的应用现状.首重介绍了系统的总体设计方案,系统的主节点、固定节点及活动节点的硬件组成和工作原理,以及大屏幕液晶显示器的特点及其在系统中的应用.     

单相无刷直流电机的设计分析与建模仿真

文中针对单相无刷直流电机结构设计及驱动方式展开研究,推导出电机理想工况下的基本方程,根据工程实际需求并结合无刷直流电机的设计原则确定该电机的设计方案。利用设计方案设计一台额定功率38 W,额定转速750 rpm的单相无刷直流电机,并分析了渐变气隙对电机起动性能和齿槽转矩的影响,确定了最优气隙长度。通过对比单极性绕组和双极性绕组形式的优缺点确定绕组形式,结合传统电机设计公式确定绕组匝数。文中利用有限元法初步验证了设计方案的合理性。根据电机动态数学模型在Simulink环境中搭建了电机系统的模型,仿真得到电机的转速、转矩变化曲线,结果与理论分析吻合良好,验证了电机设计方案的合理性和电机模型的有效性。     

位屏蔽多叉树搜索射频识别防碰撞算法

针对RFID树型防碰撞算法中时隙数多、数据通行量大等问题,提出了一种改进的多叉树防碰撞算法,阅读器准确检测碰撞位并向标签反馈碰撞位信息,标签对阅读器已知的ID位进行屏蔽,把ID号转换成连续碰撞的序列号.阅读器利用屏蔽位信息和标签返回的碰撞位编码信息,对标签进行分层分类搜索.通过对标签ID进行屏蔽,阅读器和标签间仅发送对方不知道的碰撞位信息.该算法减少了碰撞时隙和识别时隙,避免了空闲时隙,减少了阅读器和标签间的数据通信量.理论分析和仿真结果表明,该算法减少了系统的时隙总数和数据通信量,提高了阅读器的识别效率.     

Metadata Design for Reconfigurable Protocol Stacks in Systems Beyond 3G

Global consensus on the next generation of wireless mobile communications, broadly termed “beyond 3G”, sketches a heterogeneous infrastructure comprising different wireless systems in a complementary manner and vested with reconfiguration capabilities, which support a flexible and dynamic adaptation of the wireless network and its spectrum resources to meet the ever-changing service requirements. For ubiquitous reconfiguration to become a practical capability of mobile communication systems, it is necessary to establish a global architecture for modeling, expressing, and circulating essential metadata related to reconfiguration, including reconfigurable device capabilities and semantic properties of protocol stacks. We outline the relevant standardization initiatives in the mobile domain, summarize existing work in reconfiguration-supporting architectures, and identify key shortcomings that may hinder the advent of ubiquitously reconfigurable systems. Further on, we point out some major limitations of current metadata standards in the mobile domain for the representation of capability information pertaining to reconfigurable protocol stacks. Next, we identify essential metadata classes in support of reconfigurable communication systems, introducing an associated object-oriented UML model. We elaborate on the design rationale of the UML model, presenting and discussing the alternative metadata representation standards and suitable encoding formats. Finally, we demonstrate the suitability of our UML model by applying our reconfiguration-supporting vocabulary in the cases of a standardized protocol stack of 3G mobile devices and stationary 3G cellular network elements. Vangelis Gazis received his B.Sc. and M.Sc. (Communication Networking) degrees from the Department of Informatics & Telecommunications of the University of Athens, Greece, in 1995, and 1998, respectively. He also received an M.B.A. degree from the Athens University of Economics and Business in 2001. Since 1996 until, he has been with the research staff of the Communication Networks Laboratory (CNL) of the University of Athens. He has participated in national and European research projects (MOBIVAS, ANWIRE) of the IST framework programme. He specializes in reconfigurable mobile systems and networks for beyond 3G, metadata and ontology languages, reflective and component middleware, adaptable services and open API frameworks for telecommunications. He is currently a Ph.D. candidate in the Department of Informatics & Telecommunications of the University of Athens. Nancy Alonistioti holds a B.Sc. degree and a Ph.D. degree in informatics and telecommunications from the University of Athens. Presently, she is a senior researcher in the Department of Informatics and Telecommunications of the University of Athens. In the past, she has held a research position with the Institute of Informatics and Telecommunications of NCSR “Demokritos” in the areas of protocol and service design and testing, mobile systems (UMTS), open architectures, and software defined radio systems and networks. Her current research interests are in reconfigurable mobile systems and networks beyond 3G, and adaptable services, pervasive computing and context awareness. She has participated in several national and European R&D projects, and has been the technical manager of the IST-MOBIVAS and IST-ANWIRE projects, which have had a focus on reconfigurable mobile systems, networks an respective service provision. She is currently a member of the management team and workpackage leader in the FP6 IST-E2R project on reconfigurability; she also serves as technical manager for the University of Athens in the FP6 IST-LIAISON project, which focuses on location based services in working environments. Dr Alonistioti is co-editor and co-author of the book entitled “Software defined radio, Architectures, Systems and Functions”, published by John Wiley in May 2003. She has authored over 55 publications in the area of mobile communications and reconfigurable systems and networks. Lazaros Merakos received the Diploma in electrical and mechanical engineering from the National Technical University of Athens, 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 the Electrical Engineering and Computer Science Department, University of Connecticut, Storrs. From 1986 to 1994, he was on the faculty of the Electrical and Computer Engineering Department, Northeastern University, Boston, MA. During the period 1993D1994, he served as Director of the Communications and Digital Processing Research Center, 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. 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 and Services (ACTS) and Information Society Technologies (IST) programs funded by the European Union (projects RAINBOW, Magic WAND, WINE, MOBIVAS, POLOS, ANWIRE, E2R, LIAISON). His research interests are in the design and performance analysis of communication networks, and wireless/mobile communication systems and services. He has authored more than 190 papers in the above areas. Dr. Merakos 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.     

网络空间威胁狩猎的研究综述

近年来,随着网络的普及和信息化水平的不断提高,越来越多的公司把重要信息和机密文件存储在连接着网络的计算机上。但是,由于网络攻击的手段层出不穷,威胁狩猎的思想和理念孕育而生并且逐渐成熟。由此,首先对网络空间威胁的定义和攻击流程模型进行介绍,再阐述了威胁狩猎的定义和核心技术,然后描述了威胁狩猎使用的工具;最后,概括总结现有的主流威胁狩猎的框架,比较各个框架的优缺点,并阐明了下一步的发展方向。     

5G传输网络承载方案分析

5G时代3类典型场景的业务需求对承载网络在容量、时延和组网灵活性方面提出了更高的要求,同时针对无线网和核心网架构的变化提出了网络切片、增强路由转发功能等要求。首先分析5G的承载需求,重点考虑5G的3类典型业务场景、无线和核心网的架构变化;然后结合现网100GE PTN的实际应用情况,重点围绕容量、时延等维度完成需求与网络现状的对标;最后提出了网络回传、机房配套的演进方案。     

Instantaneous envelope and phase extraction from real signals: Theory,implementation, and an application to EEG analysis

This paper presents a unified treatment of various important signal processing techniques for the extraction of the instantaneous envelope and phase of a real signal. These techniques include Complex Demodulation, Hilbert Transformation, In-Phase and In-Quadrature Filtering, Phase-Locked Loop Demodulation, and Peak Amplitude and Zero-Crossing Detection. The salient points in the mathematical theory and implementation of these techniques are outlined, as well as their interrelationships via the theory of analytic signals. The advantages and limitations of each of these techniques are elaborated upon, and Complex Demodulation is shown to be the most effective and flexible method from an implementation point of view. The relation of the above techniques to Fourier spectrum analysis is elucidated, and an example is presented of applying Complex Demodulation for the quantification of time nonstationarities in the electrographic morphology of an EEG waveform.     

网元性能及业务数据特征精准分析方法

传统的网络性能分析以及业务数据分析,都是通过网管KPI 确定的,网络指标出现异常则需要根据优化人员经验进行问题定位。对问题定位的效率取决于技术人员的水平,同时网络业务数据特征的分析粒度也很粗,不能精细化、全面化、多样化地分析用户特征。随着统一DPI系统的引入,展示了用户会话过程中涉及的最细粒度的业务状态以及网络信道质量。为了更加准确地反映小区网络质量和用户真实业务体验,所研究的网元性能及业务数据分析方法采用数据切片和关联的方式,更加精细化地将体现网络质量的控制面信令XDR（X data recording,呼叫数据记录的扩展）数据和用户面业务XDR数据关联在一起分析。实现分应用、分业务拓展的用户感知分析,明确质差用户或场景等情况下XDR的数据特征,从而提升网络优化效率、提高用户感知。