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1 .Introduction Underwater acoustic (UWA) communicationis a fast developingfield,and its applicationis notlimitedto military affairs ,but is also extendinginto commercial fields .Catipovic (1990) ,Stojanovic(1996) and Kilfoyle and Baggeroer (2000) pointed… 相似文献
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Management of sediment in river basins and waterways has been an important issue for water managers throughout history. The changing nature of sediment issues has meant that water managers today face many complex technical and environmental challenges in relation to sediment management. UNESCO's International Hydrological Programme(IHP) launched the International Sediment Initiative(ISI) in 2002.ISI aims to further advance sustainable sediment management on a global scale. This is achieved through the delivery of a decision support framework for sediment management that provides guidance on legislative and institutional solutions, applicable across a range of socio-economic and physiographic settings in the context of global change. ISI mobilizes international experience on sediment problems and their management through the compilation of a series of case studies representative of a broad range of physiographic and socio-economic conditions, which are made available as guidance for policy makers dealing with water and river basin management. Case studies prepared to date include the basins of the Nile, Mississippi, Rhine, Volga, Yellow, and Haihe and Liaohe rivers. Available in full from the ISI website,these detailed case studies are briefly introduced in this review articles. 相似文献
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对 ISI数据库的编辑、出版情况作了简要介绍。从基本期刊标准、编辑内容、国际性和引文分析等方面 ,详细说明了 ISI选择期刊的步骤。针对我国期刊的现状 ,提出了相应的提高期刊质量 ,争取加入 ISI数据库的应对措施。 相似文献
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单频网中所有基站以相同的时频资源发送相同信号,对于单频网内某一用户,来自不同基站信号的传输时延不同,可能会出现符号间干扰。因此LTE设计了较长的循环前缀保证用户能够有效合并来自不同基站的信号。但是,当单频网区域过大时,部分基站的传输时延会超过循环前缀长度,产生符号间干扰,导致单频网性能下降。提出基于最大传输时延差或有效基站比例的单频网拆分算法,将区域过大的单频网拆分成多个子单频网,减少单频网内的符号间干扰,实现单频网数目和多播性能之间的合理折衷,以少量单频网数目为代价,提高单频网的覆盖率和吞吐量。仿真结果显示新的拆分算法在满足多播业务覆盖率的同时大大提高了系统吞吐量,验证了单频网拆分算法的有效性。 相似文献
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Oliver T. Coomes Tim Moore Jaclyn Paterson Sébastien Breau Nancy A. Ross Nigel Roulet 《The Professional geographer》2013,65(3):433-450
A common problem faced by geography departments, particularly during times of fiscal compression and mounting pressure for accountability, is how to compare themselves and their faculty with others. The recent revolution in bibliometrics provides a growing volume of data that can be used in benchmarking exercises. In this article, we assess the production and citation of journal articles and books by tenure-track and tenured faculty in selected U.S. and Canadian geography departments (n = 17) according to a set of readily derived and transparent performance indicators derived from publicly available data. Scopus was used to assess article production and citation; Google Scholar was used for book citation. Results point to significant heterogeneity in department characteristics, productivity, and citation of published work. The number of publications, citations, and h-Index scores among scholars in the sample (n = 369) is related strongly to academic age and subfield of enquiry (i.e., physical or human geography) but not—despite apparently marked differences in output and citations—to gender. 相似文献
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