共查询到20条相似文献，搜索用时 140 毫秒
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传统的自动化大棚温度监测方法采用基于ZigBee的无线组网方法,基于中心唤醒中断机制,辅助以温度传感采集,通过自动标签识别与随机自组网方法,实时监测大棚温度,此方法在大面积监测时需要布设许多节点,且远距组网通信质量不佳。提出一种基于双随机寻址RFID组网分割的大棚温度监测方法,对系统所有RFID节点采用地址编码方式进行排布,通过双随机寻址方式对节点进行精确定位,采用临界决策树组网分割方法将系统节点划分为多个单元,并基于单元合成矢量与系统采集节点进行数据传输,提高传输信号质量。采用远距离温度监测进行测试,结果显示在远距监测时,该方法效果明显优于传统组网方法,对于大面积大棚温度监测具有较好的应用性能。 相似文献
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无线门卫汽车身份识别系统采用有源RFID技术,实现快速准确的汽车身份识别。同其它RFID系统一样,本系统的实现重点也在于RFID防碰撞算法的实现。在此首先简单介绍了几种通信系统中常用的防碰撞算法,然后根据RFID系统的特殊性,总结了RFID系统经常使用的防碰撞算法的实现方法,最后提出了本系统防碰撞算法的实现过程。 相似文献
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传统定时车流调度模型,主要采用周期性边界条件,其对于车流量密度较大情况下,不同车速车辆急停状态下交叉路口车流无法进行准确控制。考虑不同急停车辆速度的条件下,提出了一种主动式交叉路口车流引导的调度模型,分析不同车速急停状态下的交叉路口车流引导过程,不同车速急停车辆与交叉路口构建通信机制,依据"时间片"调度方法,将交叉路口分配给对应的通行车辆。采用开放边界条件,基于不同车速急停状态下的交叉路口车流引导过程,融入车辆急停概率,通过数值模拟,实现交叉路口车流的有效调度。实验结果表明,相比传统定时调度模型,具有较低的平均等待时间。 相似文献
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在蜂窝移动通信网络中,多阵元天线系统的BPSK调制码元分布优化问题决定了码间干扰抑制性能和信道优化。提出一种基于S变换和模拟退火算法的多阵元天线系统BPSK调制码元优化分布设计算法,建立多阵元天线系统的信道模型,并进行BPSK调制码元帧格式设计,采用S变换的高斯窗函数进行能量聚集,改变移动通信信道中的时变、空变及多径效应,提高了信道传输性能。仿真实验表明,采用该算法进行蜂窝移动通信网络的天线系统设计,能有效抑制干扰,优化天线阵列分布,提高接收阵元信道冲激响应增益,改善提高通信质量。 相似文献
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在射频识别系统中,存在阅读器与多个标签同时通信的碰撞问题,多标签识别的防碰撞算法是解决数据冲突的关键。本文分析了RFID多标签防碰撞原理,在此基础上提出了一些提高RFID多标签防碰撞效率的解决方法。 相似文献
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提出一种改进的RFID标签防碰撞算法,将RFID算法进行改善,建立新型RFID射频识别技术模块,提高RFID系统的识别效率,通过识别数据进行系统扫描核实,结合碰撞数据模块进行对应搜索,该技术与互联网、通讯等技术相结合,可实现大面积范围内的防碰撞问题,完成在全网络系统建立数据集的核查提取信息的过程。仿真实验表明,一种改进的RFID标签防碰撞算法实现了RFID自动识别技术,具有体积小、容量大、寿命长、可重复使用等特点,随着RFID射频识别技术的不断发展,其应用领域正日益扩大,具有广泛的应用前景,为用户提供了完整的RFID射频识别系统,优化利用了RFID资源,提高了射频识别技术,为RFID标签防碰撞技术的改革和发展提供了帮助。 相似文献
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文章根据自主设计的一种高速公路汽车防碰撞预警系统,车载装置检测车辆运行状况,判断车辆运行是否异常或有故障,自动或手动发送信息预警,高速公路路边装置接收车载装置的信息,根据信息类型向该车辆行驶方向后面的路边装置发送信息,后面的路边装置将车辆前方的交通异常状况发送给车载装置。文章中构建Zigbee无线网络,设计无线通信协议,规范了车载装置与路边装置,路边装置相互之间,车载装置与入口测试启动装置,出口关闭装置,通信频率设置的通信协议,给出了程序流程图,经过测试满足高速公路汽车防碰撞预警系统的应用要求。 相似文献
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在RFID系统数据通信的过程中,数据传输的完整性和正确性是保证整个识别系统数据通信性能的关键技术。系统数据传输的完整性和正确性的降低主要有两个方面的原因,即外界的各种干扰及多个标签和多个阅读器同时占用信道发送数据产生碰撞。可以通过数据校验的方法解决外界对RFID通信过程的干扰;而防碰撞算法可以解决标签和阅读器的碰撞。 相似文献
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A research 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 in red wine-can improve the sensitivity of mice to the hormone insulin according to a report in the October issue of Cell Metabolism.…… 《中国科学院院刊(英文版)》2008,22(1):14-15
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. 相似文献
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《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
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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
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《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
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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
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Active biological molecules functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery disease diagnosis therapy new nanodevice construction.…… 《中国科学院院刊(英文版)》2008,22(1):22-22
Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction. 相似文献
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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
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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
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Leah A. Lievrouw 《The Information Society》2000,16(2):155-159
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment. 相似文献
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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