排序方式： 共有28条查询结果，搜索用时 165 毫秒
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Tuomo Korenius Jorma Laurikkala Martti Juhola Kalervo Järvelin 《Information Retrieval》2006,9(1):33-53
Search facilitated with agglomerative hierarchical clustering methods was studied in a collection of Finnish newspaper articles
(N = 53,893). To allow quick experiments, clustering was applied to a sample (N = 5,000) that was reduced with principal components analysis. The dendrograms were heuristically cut to find an optimal partition,
whose clusters were compared with each of the 30 queries to retrieve the best-matching cluster. The four-level relevance assessment
was collapsed into a binary one by (A) considering all the relevant and (B) only the highly relevant documents relevant, respectively.
Single linkage (SL) was the worst method. It created many tiny clusters, and, consequently, searches enabled with it had high
precision and low recall. The complete linkage (CL), average linkage (AL), and Ward's methods (WM) returned reasonably-sized
clusters typically of 18–32 documents. Their recall (A: 27–52%, B: 50–82%) and precision (A: 83–90%, B: 18–21%) was higher
than and comparable to those of the SL clusters, respectively. The AL and WM clustering had 1–8% better effectiveness than
nearest neighbor searching (NN), and SL and CL were 1–9% less efficient that NN. However, the differences were statistically
insignificant. When evaluated with the liberal assessment A, the results suggest that the AL and WM clustering offer better
retrieval ability than NN. Assessment B renders the AL and WM clustering better than NN, when recall is considered more important
than precision. The results imply that collections in the highly inflectional and agglutinative languages, such as Finnish,
may be clustered as the collections in English, provided that documents are appropriately preprocessed. 相似文献
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The effects of query structures and query expansion (QE) on retrieval performance were tested with a best match retrieval system (InQuery1). Query structure means the use of operators to express the relations between search keys. Six different structures were tested, representing strong structures (e.g., queries with facets or concepts identified) and weak structures (no concepts identified, a query is a bag of search keys). QE was based on concepts, which were first selected from a searching thesaurus, and then expanded by semantic relationships given in the thesaurus. The expansion levels were (a) no expansion, (b) a synonym expansion, (c) a narrower concept expansion, (d) an associative concept expansion, and (e) a cumulative expansion of all other expansions. With weak structures and Boolean structured queries, QE was not very effective. The best performance was achieved with a combination of a facet structure, where search keys within a facet were treated as instances of one search key (the SYN operator), and the largest expansion. 相似文献
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Kalervo N. Gulson 《Globalisation, Societies & Education》2007,5(2):219-237
This paper attempts to make sense of a public–private partnership in London’s East End. I am interested in how policy directions, in terms of cultural practices, may operate as links between transnational corporations and education provision, and, additionally, how concepts of space and place provide possibilities for different understandings of educational policy change in local instances. I examine the philanthropic practices of a corporation and the practices of schools receiving this philanthropy, and suggest that these are practices of ‘everyday globalisation’ occurring as part of a specific policy direction, Excellence in Cities. 相似文献
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Focused web crawling in the acquisition of comparable corpora 总被引：2，自引：0，他引：2
Tuomas Talvensaari Ari Pirkola Kalervo Järvelin Martti Juhola Jorma Laurikkala 《Information Retrieval》2008,11(5):427-445
Cross-Language Information Retrieval (CLIR) resources, such as dictionaries and parallel corpora, are scarce for special domains.
Obtaining comparable corpora automatically for such domains could be an answer to this problem. The Web, with its vast volumes
of data, offers a natural source for this. We experimented with focused crawling as a means to acquire comparable corpora
in the genomics domain. The acquired corpora were used to statistically translate domain-specific words. The same words were
also translated using a high-quality, but non-genomics-related parallel corpus, which fared considerably worse. We also evaluated
our system with standard information retrieval (IR) experiments, combining statistical translation using the Web corpora with
dictionary-based translation. The results showed improvement over pure dictionary-based translation. Therefore, mining the
Web for comparable corpora seems promising. 相似文献
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Kalervo N Gulson 《教育政策杂志》2013,28(2):141-158
Little attention has been paid to the relationship between policy and space in the sociology of education. This paper analyses the relationships between educational policy change, in the form of the Excellence in cities policy initiative, and urban change in inner London. I propose, and apply, a framework for a spatialised policy analysis explicitly linking space and policy. I suggest that the intersections of policy, schools, place and space provide new opportunities to explore the interconnection of educational policy change and urban change. I argue that relationships between physical locations and students are significant enabling and disabling factors in neo‐liberal educational policy‐making. These relationships form what I term the educational renovation of identity. 相似文献
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Word form normalization through lemmatization or stemming is a standard procedure in information retrieval because morphological variation needs to be accounted for and several languages are morphologically non-trivial. Lemmatization is effective but often requires expensive resources. Stemming is also effective in most contexts, generally almost as good as lemmatization and typically much less expensive; besides it also has a query expansion effect. However, in both approaches the idea is to turn many inflectional word forms to a single lemma or stem both in the database index and in queries. This means extra effort in creating database indexes. In this paper we take an opposite approach: we leave the database index un-normalized and enrich the queries to cover for surface form variation of keywords. A potential penalty of the approach would be long queries and slow processing. However, we show that it only matters to cover a negligible number of possible surface forms even in morphologically complex languages to arrive at a performance that is almost as good as that delivered by stemming or lemmatization. Moreover, we show that, at least for typical test collections, it only matters to cover nouns and adjectives in queries. Furthermore, we show that our findings are particularly good for short queries that resemble normal searches of web users. Our approach is called FCG (for Frequent Case (form) Generation). It can be relatively easily implemented for Latin/Greek/Cyrillic alphabet languages by examining their (typically very skewed) nominal form statistics in a small text sample and by creating surface form generators for the 3–9 most frequent forms. We demonstrate the potential of our FCG approach for several languages of varying morphological complexity: Swedish, German, Russian, and Finnish in well-known test collections. Applications include in particular Web IR in languages poor in morphological resources. 相似文献
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Turid Hedlund Eija Airio Heikki Keskustalo Raija Lehtokangas Ari Pirkola Kalervo Järvelin 《Information Retrieval》2004,7(1-2):99-119
In this study the basic framework and performance analysis results are presented for the three year long development process of the dictionary-based UTACLIR system. The tests expand from bilingual CLIR for three language pairs Swedish, Finnish and German to English, to six language pairs, from English to French, German, Spanish, Italian, Dutch and Finnish, and from bilingual to multilingual. In addition, transitive translation tests are reported. The development process of the UTACLIR query translation system will be regarded from the point of view of a learning process. The contribution of the individual components, the effectiveness of compound handling, proper name matching and structuring of queries are analyzed. The results and the fault analysis have been valuable in the development process. Overall the results indicate that the process is robust and can be extended to other languages. The individual effects of the different components are in general positive. However, performance also depends on the topic set and the number of compounds and proper names in the topic, and to some extent on the source and target language. The dictionaries used affect the performance significantly. 相似文献
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