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铁路机车移频信号的载波频率及调制频率承载了重要信息,因此对机车信号检测的准确性至关重要。文中对自相关解调方法进行了实际应用验证,通过验证与分析知道,该自相关解调方法在铁路机车信号检测上有一定的应用价值,特别是对调制频率的检测。针对该算法的不足,在保证时效的情况下,本文对载波频率的检测方法进行了研究,提出了一种载频频率检测的方法,为铁路机车信号检测提供参考依据。 相似文献
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铁路轨道电路信号是相位连续的键控移频信号,传递自动闭塞区间列车轨道占用信息,实现机车和地面设备间的通信。研究轨道电路信号参数的测试,实现信号的高精度解调势在必行。利用LabVIEW编程语言,结合EMD算法完成信号解调的软件设计。经过Matlab数据仿真表明,软件满足了键控移频信号的高精度解调和信号检测的需要。 相似文献
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孟宪章 《内蒙古科技与经济》2003,(11):84-84
1 问题的提出机车信号设备是用于机车驾驶室内 ,自动反映地面信号运行条件 ,指示司机运行的信号 ,是具有保证行车安全 ,提高运输效率的机车三大件重要技术设备之一。如果机车信号在运行时出现掉码、串码或接收不到码 ,都将影响到机车的正常运行 ,严重威胁铁路运输安全。2 故障现象分析及解决办法机车信号掉码主要表现为机车信号在移频区段内接收码的过程中出现 :绿码—无码—绿码或红黄码—无码—红黄码 ,此种情况一般表现在 :2 .1 地面移频发送设备的发送功率不够。正常情况下 ZP.HFJ— D型带载发送电压为 1 90伏～ 2 30伏间 ,有的发… 相似文献
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通过对铁路调度信号的自动控制和通信系统设计,实现对列车运行系统通信性能的改善。传统的铁路调度信号通信控制方法采用单频包络瞬时值统计的通信信号最佳冲击脉冲响应匹配方法进行通信控制算法设计,当列车运行区间为随机分布式,通信性能不好。提出一种基于线性反馈匹配滤波的铁路调度信号通信控制算法。进行铁路调度通信信号和铁路无线通信信道模型构建,信号分离的同时采用线性反馈匹配滤波技术实现支路信号同相相加,设计线性反馈滤波器,进行通信干扰抑制,实现基于线性反馈匹配滤波的铁路调度信号通信控制算法改进。研究表明,该算法能克服常规控制模型在铁路机车到达阶段不具有鲁棒性的弱点,非稳定阶段前比传统方法更平滑,在铁路调度信号通信中,具有较小的误码率,展示了较好的通信性能和控制性能。 相似文献
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铁路运输行车的实践表明,机车信号、地面信号、低频信息三者之间保持正确的显示关系,对于保障行车安全的可靠性至关重要。随着列车速度的加快,机车信号系统提高运输效率、保证行车安全程度的效果尤显突出,对机车信号工作的正确性、可靠性要求也越来越高。本文以朔黄线UM71自动闭塞区段为例,对机车信号的显示与地面固定信号、移频轨道电路低频信息的关系进行了详细的阐述,对确保机车信号系统工作正确性及现场设备维修养护具有积极的指导意义。 相似文献
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基于测宽法原理对轨道移频信号进行检测,通过测量波形零点间的波形宽度进而求出移频信号的一系列周期,分析这些周期从而可以得出移频信号的上边频、下边频、中心频率以及低频.同时对原有算法进行相应的更改,提高了其抗干扰能力以及精确度,并使用Matlab对改进后的算法进行仿真,验证了其可行性.此方法简单易行,具有很高的工程实用价值. 相似文献
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传统的滤波方法不能满足测量公路平整度的精度要求。为此,提出一种新的用于公路平整度测量的滤波算法。利用伪距和多普勒频移建立乘性噪声测量模型,利用二阶马尔卡夫对模型进行变换,在运用卡尔曼算法进行滤波,消除测量中的伪距和多普勒频移干扰误差,完成优化测量。结果表明,利用该算法能够有效消除GPS信道中的乘性噪声,实现了对公路平整度的精确测量。 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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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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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
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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
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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
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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