共查询到20条相似文献，搜索用时 62 毫秒
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《科技通报》2016,(8)
扩频通信中,由于扩频码序列所占的带宽度远大于所传信息的最小带宽,引起码间干扰和信道失衡,通过对扩频通信的信道均衡设计,降低扩频通信的误码率。传统方法采用子信道载波干扰抑制的扩频通信信道均衡算法,通过扩频码控制子信道载波线性调频变化,实现码间干扰抑制,但该算法会引起时分复用系统之间的相位畸变,信道均衡效果不好。提出一种基于多径分量重组的扩频通信信道均衡算法。先构建了扩频通信的信道模型,分析了扩频通信信道的时变特性,采用多径分量重组实现码间干扰抑制,结合多阵元被动时间反转镜技术实现扩频通信的信道均衡。仿真结果表明,采用该算法进行扩频通信信道均衡和码间干扰抑制,降低通信误码率,改善通信质量,提高了扩频通信系统的稳定性和可靠性。 相似文献
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可见光通信中LED失真负信号消波抑制算法 总被引：1，自引：0，他引：1
在可见光通信中采用正交频分复用进行低通信道调制而产生强烈的LED非线性失真。传统的抑制该类失真的方法采用单极性单周补偿控制算法进行LED失真抑制,当载波幅值出现负信号失真时,无法实现失真动态补偿。提出一种基于翻转正交频分复用(Flip-OFDM)的负信号消波LED失真抑制算法,通过翻转正交频分复用实现负信号消波抑制,保证LED工作在准线性安全区域。实验表明,该算法能得到平稳的CCDF均衡,失真误差得到及时动态补偿,误比特率较低,在光通信系统设计中有较好应用价值。 相似文献
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研究了幅度受限环境下MIMO（Multiple-Input Multiple-Output）系统的功率分配策略,提出了一种适用于该环境的功率分配算法。该算法充分考虑了功放特性,能够抑制限幅引起的非线性失真,更加合理地分配资源。仿真结果也表明,在幅度受限环境下,信号功率接近限幅门限时,传统的注水算法性能会有明显的恶化,而新算法能够保持最优性能。 相似文献
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高斯噪声产生于图像采集、成像和传输的各个部分,由于其对于图像时域和频域的全局覆盖作用,难以进行有效抑制.低信噪比图像在雷达、遥感、医学成像等领域有着广泛应用,本文提出一种基于图像功率谱的非线性模值滤波算法(Nonliear Module Filter,NMF),图像功率谱用模值作为非线性滤波的阅值,在保留信息比例高的系数基础上滤除包含高噪声比例的系数,从而达到提高信噪比抑制高斯噪声的目的. 相似文献
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提出了一种降低峰均功率比(PAPR)的新的融合方法,利用在发射端使经过部分传输序列(PTS)算法处理的OFDM信号再通过一种新颖的限幅滤波装置来降低PAPR. 相似文献
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针对TDCS系统中基函数峰均比过大的问题,分析变换域通信系统影响已调信号PAPR的因素;引用正交频分复用系统中PAPR抑制的技术思路,提出了适用于TDCS系统的基于限幅法的PAPR抑制算法,并论证了该算法的有效性。理论分析和仿真结果表明:基于限幅法的TDCS中PAPR抑制算法具有较好的抑制性能,对系统误码率影响不大。 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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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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《中国科学院院刊(英文版)》2014,(3)
<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 相似文献
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Chinese Scientists Use Earth Observation Technologies to Study and Protect Wild Camels 总被引：1，自引：0，他引：1
《中国科学院院刊(英文版)》2014,(3):267-268
<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 相似文献
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WANG Sijia 《中国科学院院刊(英文版)》2014,(2):192-194
<正>The Paul Gerson Unna Research Group on Dermatogenomics was founded in October 2012 at the Partner Institute for Computational Biology.The ultimate goal of the group is to understand the biology of skin and skin appendages. 相似文献