Indexation et interrogation de pages web décomposées en blocs visuels

Cette thèse porte sur l'indexation et l'interrogation de pages Web. Dans ce cadre, nous proposons un nouveau modèle : BlockWeb, qui s'appuie sur une décomposition de pages Web en une hiérarchie de blocs visuels. Ce modèle prend en compte, l'importance visuelle de chaque bloc et la perméabilité des blocs au contenu de leurs blocs voisins dans la page. Les avantages de cette décomposition sont multiples en terme d'indexation et d'interrogation. Elle permet notamment d'effectuer une interrogation à une granularité plus fine que la page : les blocs les plus similaires à une requête peuvent être renvoyés à la place de la page complète. Une page est représentée sous forme d'un graphe acyclique orienté dont chaque nœud est associé à un bloc et étiqueté par l'importance de ce bloc et chaque arc est étiqueté la perméabilité du bloc cible au bloc source. Afin de construire ce graphe à partir de la représentation en arbre de blocs d'une page, nous proposons un nouveau langage : XIML (acronyme de XML Indexing Management Language), qui est un langage de règles à la façon de XSLT. Nous avons expérimenté notre modèle sur deux applications distinctes : la recherche du meilleur point d'entrée sur un corpus d'articles de journaux électroniques et l'indexation et la recherche d'images sur un corpus de la campagne d'ImagEval 2006. Nous en présentons les résultats.This thesis is about indexing and querying Web pages. We propose a new model called BlockWeb, based on the decomposition of Web pages into a hierarchy of visual blocks. This model takes in account the visual importance of each block as well as the permeability of block's content to their neighbor blocks on the page. Splitting up a page into blocks has several advantages in terms of indexing and querying. It allows to query the system with a finer granularity than the whole page: the most similar blocks to the query can be returned instead of the whole page. A page is modeled as a directed acyclic graph, the IP graph, where each node is associated with a block and is labeled by the coefficient of importance of this block and each arc is labeled by the coefficient of permeability of the target node content to the source node content. In order to build this graph from the bloc tree representation of a page, we propose a new language : XIML (acronym for XML Indexing Management Language), a rule based language like XSLT. The model has been assessed on two distinct dataset: finding the best entry point in a dataset of electronic newspaper articles, and images indexing and querying in a dataset drawn from web pages of the ImagEval 2006 campaign. We present the results of these experiments.AIX-MARSEILLE3-Bib. élec. (130559903) / SudocSudocFranceF

Across-arc geochemical variations in the Southern Volcanic Zone, Chile (34.5- 38.0°S): Constraints on Mantle Wedge and Input Compositions

Crustal assimilation (e.g. Hildreth and Moorbath, 1988) and/or subduction erosion (e.g. Stern, 1991; Kay et al., 2005) are believed to control the geochemical variations along the northern portion of the Chilean Southern Volcanic Zone. In order to evaluate these hypotheses, we present a comprehensive geochemical data set (major and trace elements and O-Sr-Nd-Hf-Pb isotopes) from Holocene primarily olivine-bearing volcanic rocks across the arc between 34.5-38.0°S, including volcanic front centers from Tinguiririca to Callaqui, the rear arc centers of Infernillo Volcanic Field, Laguna del Maule and Copahue, and extending 300 km into the backarc. We also present an equivalent data set for Chile Trench sediments outboard of this profile. The volcanic arc (including volcanic front and rear arc) samples primarily range from basalt to andesite/trachyandesite, whereas the backarc rocks are low-silica alkali basalts and trachybasalts. All samples show some characteristic subduction zone trace element enrichments and depletions, but the backarc samples show the least. Backarc basalts have higher Ce/Pb, Nb/U, Nb/Zr, and Ta/Hf, and lower Ba/Nb and Ba/La, consistent with less of a slab-derived component in the backarc and, consequently, lower degrees of mantle melting. The mantle-like δ18O in olivine and plagioclase phenocrysts (volcanic arc = 4.9-5.6 and backarc = 5.0-5.4 per mil) and lack of correlation between δ18O and indices of differentiation and other isotope ratios, argue against significant crustal assimilation. Volcanic arc and backarc samples almost completely overlap in Sr and Nd isotopic composition. High precision (double-spike) Pb isotope ratios are tightly correlated, precluding significant assimilation of older sialic crust but indicating mixing between a South Atlantic Mid Ocean-Ridge Basalt (MORB) source and a slab component derived from subducted sediments and altered oceanic crust. Hf-Nd isotope ratios define separate linear arrays for the volcanic arc and backarc, neither of which trend toward subducting sediment, possibly reflecting a primarily asthenospheric mantle array for the volcanic arc and involvement of enriched Proterozoic lithospheric mantle in the backarc. We propose a quantitative mixing model between a mixed-source, slab-derived melt and a heterogeneous mantle beneath the volcanic arc. The model is consistent with local geodynamic parameters, assuming water-saturated conditions within the slab

Geochemical variations in the Central Southern Volcanic Zone, Chile (38-43°S): The role of fluids in generating arc magmas

We present new Sr-Nd-Pb-Hf-O isotope data from the volcanic arc (VA, volcanic front and rear arc) in Chile and the backarc (BA) in Argentina of the Central Southern Volcanic Zone in Chile (CSVZ; 38-43°S). Compared to the Transitional (T) SVZ (34.5-38°S; Jacques et al., 2013), the CSVZ VA has erupted greater volumes over shorter time intervals (Völker et al., 2011) and produced more tholeiitic melts. Although the CSVZ VA monogenetic cones are similar to the TSVZ VA samples, the CSVZ VA stratovolcanoes have higher ratios of highly fluid-mobile to less fluid-mobile trace elements (e.g. U/Th, Pb/Ce, Ba/Nb) and lower more- to less-incompatible fluid-immobile element ratios (e.g. La/Yb, La/Sm, Th/Yb, Nb/Yb), consistent with an overall higher fluid flux and greater degree of flux melting beneath the CSVZ stratovolcanoes compared to the CSVZ monogenetic centers and the TSVZ VA. The CSVZ monogenetic centers overlap the TSVZ in Sr and Nd isotopes, but the stratovolcanoes are shifted to higher Sr and/or Nd isotope ratios. The Pb isotopic composition of the CSVZ overlaps the TSVZ, which is clearly dominated by the composition of the trench sediments, but the CSVZ monogenetic samples extend to less radiogenic Pb isotope ratios. δ18Omelt from the CSVZ stratovolcano samples are below the MORB range, whereas the CSVZ monogenetic and the TSVZ samples fall within and slightly above the MORB range. The Nd and Hf isotopic ratios of the CSVZ VA extend to more radiogenic compositions than found in the TSVZ VA, indicating a greater contribution from a more depleted source. These correlations are interpreted to reflect derivation of fluids from hydrothermally altered oceanic crust and/or serpentinized upper mantle of the subducting plate. CSVZ BA basalts largely overlap TSVZ BA basalts, displaying less or no subduction influence compared to the VA, but some CSVZ BA basalts tap more enriched mantle, possibly subcontinental lithosphere, with distinctively lower Nd and Hf and elevated 207Pb/204Pb and 208Pb/204Pb isotope ratios

The role of changing geodynamics in the progressive contamination of Late Cretaceous to Late Miocene arc magmas in the southern Central Andes

The tectonic and geodynamic setting of the southern Central Andean convergent margin changed significantly between the Late Cretaceous and the Late Miocene, influencing magmatic activity and its geochemical composition. Here we investigate how these changes, which include changing slab-dip angle and convergence angles and rates, have influenced the contamination of the arc magmas with crustal material. Whole rock geochemical data for a suite of Late Cretaceous to Late Miocene arc rocks from the Pampean flat-slab segment (29–31 °S) of the southern Central Andes is presented alongside petrographic observations and high resolution age dating. In-situ U–Pb dating of magmatic zircon, combined with Ar–Ar dating of plagioclase, has led to an improved regional stratigraphy and provides an accurate temporal constraint for the geochemical data. A generally higher content of incompatible trace elements (e.g. Nb/Zr ratios from 0.019 to 0.083 and Nb/Yb from 1.5 to 16.4) is observed between the Late Cretaceous (~ 72 Ma), when the southern Central Andean margin is suggested to have been in extension, and the Miocene when the thickness of the continental crust increased and the angle of the subducting Nazca plate shallowed. Trace and rare earth element compositions obtained for the Late Cretaceous to Late Eocene arc magmatic rocks from the Principal Cordillera of Chile, combined with a lack of zircon inheritance, suggest limited assimilation of the overlying continental crust by arc magmas derived from the mantle wedge. A general increase in incompatible, fluid-mobile/immobile (e.g., Ba/Nb) and fluid-immobile/immobile (e.g., Nb/Zr) trace element ratios is attributed to the influence of the subducting slab on the melt source region and/or the influx of asthenospheric mantle. The Late Oligocene (~ 26 Ma) to Early Miocene (~ 17 Ma), and Late Miocene (~ 6 Ma) arc magmatic rocks present in the Frontal Cordillera show evidence for the bulk assimilation of the Permian–Triassic (P–T) basement, both on the basis of their trace and rare earth element compositions and the presence of P–T inherited zircon cores. Crustal reworking is also identified in the Argentinean Precordillera; Late Miocene (12–9 Ma) arc magmatic rocks display distinct trace element signatures (specifically low Th, U and REE concentrations) and contain inherited zircon cores with Proterozoic and P–T ages, suggesting the assimilation of both the P–T basement and a Grenville-aged basement. We conclude that changing geodynamics play an important role in determining the geochemical evolution of magmatic rocks at convergent margins and should be given due consideration when evaluating the petrogenesis of arc magmas.</p

Ingénierie des systèmes d'information, numéro spécial Bases de données avancées pour XML et le Web

National audienceno abstrac

Information, Interaction, Intelligence. Actes des 2e Assises nationales du GdR I3

National audienceno abstrac

Le langage fonctionnel de programmation pour bases de donnees GRIFFON

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 84241 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Ingénierie des systèmes d'information, numéro spécial Systèmes d'information avancés

National audienceno abstrac

Approche extraction de connaissance de l'analyse de données astronomiques (application à l'identification croisée multi-[lambda])

TOULON-BU Centrale (830622101) / SudocAIX-MARSEILLE1.OAMP.Le Verrier (130552205) / SudocSudocFranceF