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本文针对"最后一公里"技术,综合分析ADSL、光纤、无源光网络、无线等常用的几种接入方式,从组网建设、应用技术、网络特点等几个方面进行比较,最后根据接入特点、市场特点和用户需求等,提出"最后一公里"接入建议. 相似文献
2.
吉比特无源光网络GPON技术广泛应用于高校校园网,本文着重从GPON下行帧结构、GPON上行帧结构及GPON的特点对GPON系统的工作原理进行了一些研究和探讨。 相似文献
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有线电视网的发展方向是提供全业务的宽带信息网,即是一个能够容纳各种形式的信息,在统一的管理平台下,实现音频、视频、数据信号的传输和管理,提供各种宽带应用和传统业务的、真正实现宽带窄带一体化、有源无源一体化、传输接入一体化的综合业务网络。我国已提出2015年将关闭模拟电视,全部实现电视数字化,但在中小城市的推广却十分不顺利,数字电视用户增长十分缓慢。本文通过对有线电视网络两种双向接入技术进行对照分析,为中小城市有线电视双向化改造方案选择提供一定参考。 相似文献
4.
随着光纤接入成本逐渐下降、技术快速发展,光纤接入业务需求逐渐增加。针对目前用户光纤接入的各种应用方案进行分析探讨,为用户选择光纤接入业务和运营商网络规划建设提供参考。 相似文献
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宽带接入作为用户和骨干网络之间的最后一公里的连接,有许多成熟的技术可供选择.本文从目前我国主流部署应用的角度出发,分别选取了xDSL数字用户环路、xPON无源光网络、MSTP多业务传送平台三种技术进行简单介绍,提出了自己的看法和建议,了解具有一定的参考价值. 相似文献
6.
随着互联网的迅猛发展,新业务层出不穷,人们对接入带宽的需求越来越高,而宽带光纤接入技术的快速发展,为实施接入网络的转型升级,加速FTTx建设奠定了基础。作为移动运营商,为克服城区铜缆资源缺乏的不足,积极采用新的光纤接入技术,为用户提供高带宽、多业务的综合接入能力,是适应业务发展需求,应对市场环境变化,促进网络转型的重要举措之一。本文主要结合当前宽带光纤接入技术和业务需求,对移动运营商PON技术的应用和网络建设进行了探讨。 相似文献
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EPON(以太网无源光网络)是一种新型的光纤接入技术,其采用点到多点的拓扑结构、无源光传输方式,在以太网基础上承载多业务。EPON网络相对其他光纤接入网来说具有较高性价比,技术比较成熟,能够为终端用户提供可靠的数据、语音和视频业务。本文在描述了EPON网络结构和原理的基础上,探讨了将EPON技术应用于烟草工业企业的视频监控系统中的实践,提出了一种系统结构,为烟草工业企业的安防系统以及生产监控系统建设提出新的思路和建议。 相似文献
9.
NGN是下一代网络的缩写,是基于IP分组网络,它具有许多区别于传统网络的特点,逐渐把语音变成IP包,大大扩展丁媒体范围：分层的体系结构,使网络的控制、承载和业务分离,方便用户终端在任何时间、任何地点、采用任何方式接入网络享受NGN网络所带来的各种新业务;开放的接口,使得现有的网络能够融合到NGN网络,方便用户接入;控制和业务核心为软交换,扩展了业务空间;综合语音、数据和多媒体业务,满足用户多样化的需求;能够快速的引进和推出新业务,实现业务的差异化。 相似文献
10.
姚辉 《中外科技政策与管理》2011,(7):17-22
从回顾计算机网络产生、发展的历程入手,伴之以不同发展阶段网络与终端用户、业务之间的互动,导引出云计算的特性与网络之间的关系。分析了云接入网络的优势：自由移动、接入可控;云接入网关的特性：业务识别分级、按需管控;云智能管道的长项：按级服务、按需组网;数据中心网络的特质：高速无阻塞、网络虚拟化;云网络管控的便捷：用户业务端到端按需监管。进而得出云计算的发展将直接依托智能管道化的网络最终通过“云”提供服务,必将给现有的网络基础设施带来变革,也对网络的监管提出了新的挑战。 相似文献
11.
《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
12.
Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
13.
《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
14.
A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
15.
Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
16.
Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
17.
Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献
18.
Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
19.
Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献
20.
Prof. SUN Changpu from the CAS Institute of Theoretical Physics coworkers from University of Basel in Switzerland have worked out a way - at least in theory - to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams is similar to the famous Stern-Gerlach effect whereby a beam of atoms passing through a magnetic field is split in two according to the atoms' spin states 《中国科学院院刊(英文版)》2008,22(1):23-23
Prof. SUN Changpu from the CAS Institute of Theoretical Physics and coworkers from University of Basel in Switzerland have worked out a way --at least in theory --to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams and is similar to the famous Stern-Gerlach effect, whereby a beam of atoms passing through a magnetic field is split in two according to the atoms＇ spin states （Phys. Rev. Lett. 99 130403）. 相似文献