WiMAX技术与Wi-Fi技术的对比分析

论述了近年来发展迅速的WiMAX和Wi-Fi两种无线网络技术,在对WiMAX技术和WLAN技术介绍的同时,重点从覆盖范围、传输速率、移动性和安全性上对WiMAX技术和Wi-Fi技术进行对比分析,使大家对WiMAX技术和Wi-Fi技术有一个更加深入清醒的认识。     

无线接入技术WiMAX研究

本文探讨了WiMAX技术,对WiMAX网络结构进行了分析研究,在此基础上,指出了WiMAX发展前景。     

WiMAX技术特点及网络规划

本文综述了WiMAX的技术特点,在此基础上对WiMAX的网络规划的具体步骤进行了探讨与阐述.     

浅谈移动通信新技术——WiMAX

文章分析了WiMAX技术及其优势,根据WiMAX本身的特点分析了WiMAX在无线通信领域的应用前景。     

浅谈WiMAX技术及其在广电宽带数据网中应用

无线通信的应用在宽带网络的发展进程中起到了决定性的作用.基于IEEE802.16标准的WiMAX技术是一种宽带无线接入技术.文章介绍了WiMAX技术的基表概念、组网方式、频率使用、技术特点,叙述了WiMAX技术应用于广电宽带数据网络的可行性.     

WiMAX的发展及其关键技术概述

WiMAX技术作为一种新型的无线宽带接入技术,受到广泛关注,主要介绍了IEEES02．16协议和WiMAX的关键技术,并分析了WiMAX与Wi—Fi技术的差异。     

浅谈WiMAX无线接入技术

IEEE 802工作组制定了WiMAX(World Interoperability for Microwave Access,全球微波接入互操作性)技术规范.WiMAX的出现大大的加快了宽带移动化的进程,满足了宽带用户对宽带移动化的需求.首先分析了WiMAX的产生背景,其次介绍了WiMAX的基本概念和无线接入技术,包括OOFDM调制技术、自适应天线系统技术等,最后对WiMAX无线接入技术的应用作了展望.     

PMC-Sierr新款器件采用无线数字预失真技术

PMC-Sierra公司日前宣布，其PM7800 PALADIN 10和PM7815 PALADIN 15器件成功地进行了演示，完全符合严格的美国联邦通信委员会（FCC）针对WiMAX的04-258要求。这些器件采用了PMC—Sierra工业标准无线数字预失真（DPD）技术及高频混合信号设计能力，可使产品满足新兴的WiMAX无线标准。     

瞄准印度WiMAX市场，Aperto在班加罗尔设开发中心

提供WiMAX基站和用户设备的Aperto Networks公司日前宣布，将在印度班加罗尔（Bangalore）设立一家开发中心，以加速通过WiMAX论坛认证的和WiMAX级产品开发。     

WiMAX技术特点和应用前景分析

WiMAX技术具有传输距离远、传输速率高、容量大、信道宽度灵活、安全性高等特点。随着该技术被ITU批准为入第三代移动通信技术的最新标准,“无线城域网”的概念已经进入了“滨海新区信息化发展合作协议”。作者首先对IEEE802．16标准的内部结构进行介绍,又对利用该技术的组网方式进行了分析,最后得出WiMAX技术的应用在我国信息化的过程中具有良好的发展前景。     

Students' Reactions to the Introduction of Videoconferencing for Classroom Instruction

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.     

Cooler temperatures inductive to locust outbreaks

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.     

Exploring Multiplexity: Social Network Structures in a Computer-Supported Distance Learning Class

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.     

The Role of Intermediating Institutions in the Diffusion of Electronic Data Interchange (EDI): How Industry Associations Intervened in Denmark, Finland, and Hong Kong

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.     

Low doses of a red wine ingredient figh diabetes in mice

Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.     

How Electronic Publishers are Protecting Against Piracy: Doubts About Technical Systems of Protection

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.     

Rough Justice: A Statistical Assessment of ICANN's Uniform Dispute Resolution Policy

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.     

Prevalence of soft neurological signs in Chinese people

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.     

Monoculture Rubber Plantations Have Negative Ef ects on Controlling Splash Erosion

<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence     

Chinese Scientists Use Earth Observation Technologies to Study and Protect Wild Camels

<正>Chinese scientists plan to apply Earth Observation technologies to protect the critically endangered wild camels(Camelus ferus).With the help of remote sensing,satellite positioning,geographical information system and wireless sensors networks,they will be able to access the distribution and population of the wild camels and protect their habitats.The project will be carried out by the International Research Center for Wild Camel Conservation,which was jointly established earlier this year by the Institute of Remote Sensing and Digital Earth(RADI)of the Chinese