1,720,976 research outputs found
Una strategia di Text Mining basata su regole di associazione
No full textQuesto lavoro propone una strategia per affrontare l'analisi di corpora di grandi dimensioni che presentino una strutturazione interna, con il duplice vantaggio, da un lato, di un notevole risparmio del peso computazionale dell'analisi e, dall'altro, di introdurre elementi relativi al contesto in cui le singole parole sono utilizzate. La strategia si avvale di un modesto intervento preliminare da parte di esperti al fine di pervenire, grazie all'utilizzo di metodi statistici di segmentazione, alla categorizzazione del testo e alla costruzione, sulla base di un training set, di regole di associazione, Queste regole, applicate all'intero corpus, consentono si sottoporre ad analisi soltanto i frammenti individuati come di interesse diretto per gli obiettivi conoscitivi perseguit
A text mining strategy based on local contexts of words
No full textAim of the paper is to propose a Text Mining strategy based on statistical tools, which make more efficient the extraction of information buried in massive quantities of documents. Usually, in Text Mining procedures (such as in textual data analyses) we deal with a corpus consisting of a set of documents. In order to build the data structure to be processed, each document is encoded in a document vector, according to the bag-of-words model, which associates words and their frequencies for the given document. Documents are considered as a whole. The proposed mining strategy identifies interesting sentences in the corpus we deal with, where to concentrate the knowledge extraction. The sentence interest will depend on the researcher’s objective. The proposed procedure is useful when we are interested in local contexts for words. Prior information, i.e. expert knowledge, is included, as an input for the procedure, but differently to content analysis, the key-word system is automatically built. The strategy can be applied in any case we can introduce information for partitioning documents in lower order grammatical units (e.g. sentences, but also paragraphs, etc.). The mining procedure consists in two steps: first of all the Text Categorisation, i.e. the recognition of the interesting sentences, by means of a statistical segmentation procedure, and then the knowledge extraction from the identified sub-texts. The procedure first step produces association rules useful in filtering e-mail, chat, or Web access, too. The paper aims at contributing to the day-by-day wider literature on Text Mining, devoted to go beyond the "bag-of-words" model of structuring the data set in document vectors, enhancing the role of a statistical perspective. An application on Italian on-line job offers ends the paper, showing the effectiveness of the proposal
The Ideal Candidate. Analysis of Professional Competences through Text Mining of Job Offers
No full textContributions of Textual Data Analysis to Text Retrieval
No full textAim of this paper is to show how Textual Data Analysis techniques, namely correspondence analysis, in its symmetrical and non-symmetrical version, can improve performance of the LSI retrieval method. Moreover an approach to text retrieval with external information based on PLS regression is introduced
Il testamento di Nino Visconti giudice di Gallura (26 luglio 1296)
No full textNino Visconti, the Pisan king of the little Sardinian Kingdom of Gallura, shared for a few mounths (between 1287 and 1288) the rule of Pisa with the famous Count Ugolino, and was equally encountered by Dante in his Comedy. Nino made his will on 1296, July 26. At this time, he was attempting to defend his Kingdom against Mariano, king of Arborea, who had allied himself with the Commune of Pisa. The paper aims to clarify the last years of Nino’s life and his final decision to make a desperate effort to save his political position in Sardinia
Effects of ocean acidification on skeletal characteristics of a temperate coral at a CO2 vent system
No full textOcean Acidification (OA) is predicted to have profound impacts on marine ecosystems because carbonate ions are an essential substrate for the biomineralization of shells and skeletons of calcifying marine organisms, from phytoplankton and corals to fishes1,2,3. Volcanic CO2 vent systems, where seawater is naturally acidified, offer a unique opportunity to investigate the response of benthic organisms and habitats to OA. The Ischia Island (Tyrrhenian Sea, Italy) offers a natural laboratory for OA studies, allowing us to investigate how a suite of habitats and species responds to acidification. A. calycularis is a Mediterranean endemic azooxanthellate coral. It is long-lived species and commonly found in dim light shallow rocky habitats of the south-western Mediterranean Sea4. It broods its larvae5 and thus has relatively low dispersal capacities and high potential for local adaptation. This coral is reported as vulnerable in the IUCN red list6. There is one population of A. calycularis that naturally occurs in a semi-submersed cave (Grotta del Mago) affected by CO2 venting, where is highly abundant (70% cover at 1 m depth). Here, we assess population structure and the skeletal characteristics of A. calycularis originating from different sites (naturally acidified and ambient pH sites) along the coast of Ischia Island . We hypothesize that the population thriving under naturally acidified conditions shows higher population dynamics and differences in biomineralization process than the populations studied from other reference sites with ambient pH.Colonies in the Grotta del Mago have encrusting morphology, with smaller size and consequent, lower weight and lower number of polyps compared to conspecifics from sites at normal pH conditions. With increasing acidification (lower pH), the skeletal porosity decreased while the bulk and micro- density increased. Given the reduced calcification rate that may be expected in acidified waters, the observed increase in skeletal density may be counterbalanced by a strong decrease in linear extension rate
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