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In this article we describe a retrieval schema which goes beyond the classical information retrieval keyword hypothesis and takes into account also linguistic variation. Guided by the failures and successes of other state-of-the-art approaches, as well as our own experience with the Irena system, our approach is based on phrases and incorporates linguistic resources and processors. In this respect, we introduce the phrase retrieval hypothesis to replace the keyword retrieval hypothesis. We suggest a representation of phrases suitable for indexing, and an architecture for such a retrieval system. Syntactical normalization is introduced to improve retrieval effectiveness. Morphological and lexico-semantical normalizations are adjusted to fit in this model.  相似文献   

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This award recognizes years of research by the laureates using elusive neutrinos to probe the internal workings of the sun. Bahcall and Davis identified an apparently fundamental problem: the fusion reactions that generate the sun's power deep in its core appeared to generate fewer neutrinos than expected. The number of neutrinos detected by Davis was only about a third the number calculated by Bahcall. Koshiba developed a new type of detector that not only confirmed the deficit but also showed that the neutrinos counted by Davis actually come from the Sun. Together the work of these three scientists prepared the way for the resolution of the puzzle, the discovery of a new property of neutrinos called “neutrino oscillations”. On the way from the sun, some neutrinos change identity and become nearly invisible in the detectors. This insight promises to open up new vistas in the fundamental physics of elementary particles.  相似文献   

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