共查询到20条相似文献，搜索用时 625 毫秒
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林杰 《福建广播电视大学学报》1997,(3)
求矩阵特征值和特征向量问题的传统方法是先求解矩阵的特征多项式方程,以求得特征值,然后对每一个特征值解一个齐次线性方程组以求得对应的特征向量。但是,我们注意到对于特征值的存在性按此方法无法得到一个较简捷的判别法。本文给出一种求二阶方阵的特征值与特征向量的简便方法,它是通过解一个不同于特征多项式的与矩阵有关的方程,并给出矩阵特征值存在性的判别方法。由此为导出求三阶以上矩阵的特征值、特征向量及特征值的存在性起抛砖引玉作用。设: 相似文献
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选择包括基础、应用和技术领域12个学科领域进行实证研究,对数据集构建过程和基本原则进行详细描述,重点阐述将文章、作者和引文归属到一级学科的原因,并对引文类共现矩阵作重点讨论。最后获得各领域的数据表格和结果,为下一步进行指标计算、分析和研究学科交叉现象做足准备。 相似文献
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以矩阵理论作为研究的切入点,将经典向量空间模型中常用的向量和集合以矩阵的形式加以重构,并认为基于向量内积法的相似性计算与相应矩阵的乘法运算等价。结合稀疏矩阵和数据稀疏的定义,分析VSM信息检索背景下数据稀疏产生的原因;同时,讨论三种情形下数据稀疏对相似性计算的共同影响--部分毫无意义的时间复杂度。最后,给出规避数据稀疏问题的三层策略:文本级策略、文本集级策略和矩阵级策略。 相似文献
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为了创建中国期刊的名优品牌 ,促进我国期刊业更加健康、迅速地发展 ,国家新闻出版总署最近组建了中国期刊方阵。“方阵”从全国870 0多种期刊中遴选出 130 0余种优秀期刊组成。《中国图书馆学报》因刊物质量高、专业学术影响大而入选中国期刊方阵。《中国图书馆学报》将再接再厉 ,不断提高质量和学术水平 ,为发展我国图书情报事业做出更大的贡献《中国图书馆学报》入选中国期刊方阵@徐苇 相似文献
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Web表格信息抽取研究综述 总被引：4，自引：0，他引：4
介绍Web表格的特点与结构、Web表格信息抽取及其过程,分析Web表格信息抽取的4个关键技术：Web表格定位、Web表格结构识别、Web表格内容整合和抽取结果表示,以及Web表格信息抽取的应用。最后指出目前国内外该项研究的不足之处及未来发展方向。 相似文献
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医学期刊表格的编辑加工 总被引：8，自引：2，他引：6
医学期刊表格分量大,编辑尤其要重视表格的编辑加工.做好表格的编辑加工,关键是要处理好表格与文字、图示之间的关系,以及表格内各部分间的关系. 相似文献
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科学计量学的发展与布局：1978-2008 总被引：1，自引：0，他引：1
陈云伟 《现代图书情报技术》2010,26(1):71-76
采用科学计量学的方法,基于Scientometrics期刊,对其收录的1978－2008年的 2 461篇论文进行科学计量分析,研究世界科学计量学的国家、机构和主题布局。通过时间序列趋势图、列表和矩阵图等手段描述科学计量学的国家布局,分析论文数在20篇以上的机构分布情况,利用关键词分析科学计量学研究的主题分布,主要分析工具包括TDA和 Excel。 相似文献
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Gaurav Pandey Zhaochun Ren Shuaiqiang Wang Jari Veijalainen Maarten de Rijke 《Information Retrieval》2018,21(6):481-506
We address the feature extraction problem for document ranking in information retrieval. We then propose LifeRank, a Linear feature extraction algorithm for Ranking. In LifeRank, we regard each document collection for ranking as a matrix, referred to as the original matrix. We try to optimize a transformation matrix, so that a new matrix (dataset) can be generated as the product of the original matrix and a transformation matrix. The transformation matrix projects high-dimensional document vectors into lower dimensions. Theoretically, there could be very large transformation matrices, each leading to a new generated matrix. In LifeRank, we produce a transformation matrix so that the generated new matrix can match the learning to rank problem. Extensive experiments on benchmark datasets show the performance gains of LifeRank in comparison with state-of-the-art feature selection algorithms. 相似文献
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为了促进我国医学期刊编辑、作者及审稿专家对图表著作权问题的重视,通过调查医学期刊对论文中图表的合理使用和授权许可使用规定的现状,发现医学期刊存在对图表的著作权意识较薄弱,稿约和著作权协议中相关规定和要求表述不完善及不规范等现象。提出了医学期刊出版单位应提倡和尊重图表原创性,要求作者使用他人已发表的图表必须获得著作权许可,明确图表二次使用的合法使用范围,从而提高著作权意识,促进期刊论文图表的著作权保护。 相似文献
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Sumiko Asai 《Journal of Media Economics》2013,26(2):97-113
This article explores the hit chart period of Japanese popular music between January and March in 1990 and in 2004, using the survival model, and examines the factors involved in producing a hit. First, the results showed that fame of the artist, ties with other media, and compilation albums featuring several artists prolonged the hits chart period. Second, the music's survival period on the charts was shorter in 2004 than in 1990. This means that more titles appeared on the charts in 2004. 相似文献
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Medical Subject Headings and medical terminology: an analysis of terminology used in hospital charts
Terminology used by health professionals in everyday written discourse was compared with terminology in a standardized medical vocabulary, the Medical Subject Headings (MeSH). Fifty written hospital charts were selected at random and analyzed by a computer program that identified MeSH terms in the charts. The charts were analyzed against two related MeSH vocabularies--one containing MeSH terms and one containing both MeSH terms and backwards cross-reference terms. When small words such as articles and prepositions were disregarded, approximately 50% of the words in a medical chart were found to be MeSH-related terminology. In addition, about 40% of MeSH-related words in the charts were either MeSH terms or backwards cross-reference terms. 相似文献
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Web search algorithms that rank Web pages by examining the link structure of the Web are attractive from both theoretical and practical aspects. Todays prevailing link-based ranking algorithms rank Web pages by using the dominant eigenvector of certain matrices—like the co-citation matrix or variations thereof. Recent analyses of ranking algorithms have focused attention on the case where the corresponding matrices are irreducible, thus avoiding singularities of reducible matrices. Consequently, rank analysis has been concentrated on authority connected graphs, which are graphs whose co-citation matrix is irreducible (after deleting zero rows and columns). Such graphs conceptually correspond to thematically related collections, in which most pages pertain to a single, dominant topic of interest.A link-based search algorithm A is rank-stable if minor changes in the link structure of the input graph, which is usually a subgraph of the Web, do not affect the ranking it produces; algorithms A,B are rank-similar if they produce similar rankings. These concepts were introduced and studied recently for various existing search algorithms.This paper studies the rank-stability and rank-similarity of three link-based ranking algorithms—PageRank, HITS and SALSA—in authority connected graphs. For this class of graphs, we show that neither HITS nor PageRank is rank stable. We then show that HITS and PageRank are not rank similar on this class, nor is any of them rank similar to SALSA.This research was supported by the Fund for the Promotion of Research at the Technion, and by the Barnard Elkin Chair in Computer Science. 相似文献
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《Journal of Informetrics》2007,1(1):59-67
Statistical distributions in the production of information are most often studied in the framework of Lotkaian informetrics. In this paper, we recall some results of basic theory of Lotkaian informetrics, then we transpose methods (Theorem 1) applied to Lotkaian distributions by Leo Egghe (Theorem 2) to the exponential distributions (Theorem 3, Theorem 4). We give examples and compare the results (Theorem 5). Finally, we propose to widen the problem using the concept of exponential informetric process (Theorem 6). 相似文献
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矩阵思考法及其在图书情报工作中的应用 总被引：5，自引：2，他引：3
介绍矩阵思考法及操作要点,论述以矩阵思考法为基础而发展演化的目标因素分析法、一对关联法及其在图书情报机构的管理、决策和服务中的应用。 相似文献