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数字参考咨询的“本地”问题研究——温州大学图书馆案例分析 被引量:3
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作者 杨凌云 詹德优 《大学图书馆学报》 CSSCI 北大核心 2007年第6期70-75,共6页
数字参考咨询的本地问题指需要提供本地知识或检索本地资源才能解答的咨询问题。文章通过对温州大学图书馆数字参考咨询问题的案例分析,找出本地问题在咨询总量中所占比重与产生原因。认为咨询馆员利用本地知识解答咨询问题的形式固然... 数字参考咨询的本地问题指需要提供本地知识或检索本地资源才能解答的咨询问题。文章通过对温州大学图书馆数字参考咨询问题的案例分析,找出本地问题在咨询总量中所占比重与产生原因。认为咨询馆员利用本地知识解答咨询问题的形式固然不容忽视,但在理想的网页设计前提下,如果拥有必要的本地信息、清晰的网络导航和专业的检索系统,许多本地问题是可由合作咨询组织加盟成员馆进行异地回复的。 展开更多
关键词 数字参考咨询 本地问题 合作机制
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A Preliminary Application of the Differential Evolution Algorithm to Calculate the CNOP 被引量:4
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作者 SUN Guo-Dong MU Mu 《Atmospheric and Oceanic Science Letters》 2009年第6期381-385,共5页
A projected skill is adopted by use of the differential evolution (DE) algorithm to calculate a conditional nonlinear optimal perturbation (CNOP). The CNOP is the maximal value of a constrained optimization problem wi... A projected skill is adopted by use of the differential evolution (DE) algorithm to calculate a conditional nonlinear optimal perturbation (CNOP). The CNOP is the maximal value of a constrained optimization problem with a constraint condition, such as a ball constraint. The success of the DE algorithm lies in its ability to handle a non-differentiable and nonlinear cost function. In this study, the DE algorithm and the traditional optimization algorithms used to obtain the CNOPs are compared by analyzing a theoretical grassland ecosystem model and a dynamic global vegetation model. This study shows that the CNOPs generated by the DE algorithm are similar to those by the sequential quadratic programming (SQP) algorithm and the spectral projected gradients (SPG2) algorithm. If the cost function is non-differentiable, the CNOPs could also be caught with the DE algorithm. The numerical results suggest the DE algorithm can be employed to calculate the CNOP, especially when the cost function is non-differentiable. 展开更多
关键词 differential evolution algorithm conditional nonlinear optimal perturbation non-differentiable
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An Range-free Localization Scheme for Large Scale Underwater Wireless Sensor Networks 被引量:2
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作者 周异 顾宝军 +2 位作者 陈凯 陈剑波 管海兵 《Journal of Shanghai Jiaotong university(Science)》 EI 2009年第5期562-568,共7页
In this paper, we study an area localization problem in large scale underwater wireless sensor networks (UWSNs). The limited bandwidth, the severely impaired channel and the cost of underwater equipment all make the... In this paper, we study an area localization problem in large scale underwater wireless sensor networks (UWSNs). The limited bandwidth, the severely impaired channel and the cost of underwater equipment all make the underwater localization problem very challenging. Exact localization is very difficult for UWSNs in deep underwater environment. We propose a range free method based on mobile detachable elevator transceiver (DET) and 3D multi-power area localization scheme (3D-MALS) to address the challenging problem. In the proposed scheme, the ideas of 2D multi-power area localization scheme (2D-ALS) and utilizing DET are used to achieve the simplicity, location accuracy, scalability and low cost performances. The DET can rise and get down to broadcast its position. And it is assumed that all the underwater nodes underwater have pressure sensors and know their z coordinates. We evaluate the performances of 2D-ALS and our proposed 3D-MALS schemes under both ideal and non-ideal channel propagation conditions, in terms of localization error and localization ratio. The simulation results show that our proposed scheme is much more efficient than the 2D-ALS. 展开更多
关键词 underwater sensor networks LOCALIZATION MULTI-POWER mobile beacons range free
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