503 research outputs found

    Salty ice and the dilemma of ocean exoplanet habitability

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    Habitability of exoplanet's deepest oceans could be limited by the presence of high-pressure ices at their base. New work demonstrates that efficient chemical transport within deep planetary ice mantles is possible through significant salt incorporation within the high-pressure ice

    Les recherches experimentales au centre de Geomorphologie du CNRS a Caen

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    Le Centre de Géomorphologie a été construit à Caen en 1964 par le Centre National de la Recherche Scientifique (CNRS). Depuis 10 ans qu'il est en fonctionnement, quelques modifications ont été apportées à l'organigramme, mais le buts définis lors de sa création demeurent les mêmes: (...

    Les mines de fer de Schefferville

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    The iron mines of Schefferville, at a latitude of 55° N., are the first mines exploited in one of the best provided iron ore regions in the World ; the geosynclinal of Labrador. Their distance from the sea (360 miles to the estuary of the St. Lawrence) is compensated for by the richness of the ore deposits : abundant reserves, high percentage yield, and the quality of the mineral.The ore is mined in open pits ; the main difficulty is the harshness of the climate, which necessitates the interruption of operations from the end of November to the middle of April. The deposits are found in a subarctic taiga zone. It has been necessary to bring in all the workers ; mostly French Canadians, but also some foreigners. All tools and provisions have to be transported a great distance. The ore production is increasing rapidly : 2.25 million tons in 1954, 6 million tons in 1955, and 12 million tons in 1956. It will reach 20 million tons within the next few years. The ore is transported entirely by the railroad specially built to the port of Sept-Iles, from which it reaches, either by the sea route or by the St. Lawrence, the iron-smelting region of the north-eastern United States, where the principal outlets of the Iron Ore Co. of Canada are found. The port of Sept-Iles, which had a population of 5,573 in 1956, compared to that of 1,866 in 1951, could very possibly see its importance increase when the completion of the St. Lawrence Seaway will allow prairies grain, and possibly Pennsylvania coal, to serve as return freight for the iron ore. Close to the mines, Schefferville already has 3,500 inhabitants and has become the largest town in Labrador. Besides its purely mining junctions there are others, in particular that of a supply centre and of a transportation terminus. Its population is becoming progressively more stable and of a more balanced composition. The camp of the first prospectors is thus transformed into a permanently populated centre, of which the legal existence was recognized on the first of August, 1955

    Essai d’une définition de régions géopédologiques

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    The Hierarchical Agglomerative Clustering with Gower index: a methodology for automatic design of OLAP cube in ecological data processing context

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    International audienceThe OLAP systems can be an improvement for ecological studies. In fact, ecology studies, follows and analyzes phenomenon across space and time and according to several parameters. OLAP systems can provide to ecologists browsing in a large dataset. One focus of the current research on OLAP system is the automatic design of OLAP cubes and of data warehouse schemas. This kind of works makes accessible OLAP technology to non information technology experts. But to be efficient, the automatic OLAP building must take into account various cases. Moreover the OLAP technology is based on the concept of hierarchy. Thereby the hierarchical clustering methods are often used by OLAP system designer. In this article, we propose using hierarchical agglomerative clustering with a metric that comes from ecological studies (the Gower similarity index) to build automatically hierarchical dimensions in an OLAP cube. With this similarity index we can perform a hierarchical clustering on heterogeneous datasets that contains qualitative and quantitative variables. We offer a prototypical automatic system which builds dimension for an OLAP cube and we measure the performances of this system according to the number of clustered individuals and according to the number of variables used for clustering. Thanks to these measures we can offer an approximation of performances with a large dataset. Thereby the Gower index in a hierarchical agglomerative clustering permits the management of heterogeneous dataset with missing values in a context of automatic building of OLAP cube. With this methodology, we can build new dimensions based on hierarchies in the data, which are not evident. The data mining methods can complete the expert knowledge during the design of an OLAP cube, because these methods can explain the inherent structure of the data

    Une nouvelle approche mixte d'enrichissement de dimensions dans un schéma multidimensionnel en constellation Application à la biodiversité des oiseaux

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    International audienceLes entrepôts de données (DW) et les systèmes OLAP sont des technologies d'analyse en ligne pour de grands volumes de données, basés sur les be-soins des utilisateurs. Leur succès dépend essentiellement de la phase de conception où les exigences fonctionnelles sont confrontées aux sources de données (méthodologie de conception mixte). Cependant, les méthodes de conception existantes semblent parfois inefficaces, lorsque les décideurs définissent des exi-gences fonctionnelles qui ne peuvent être déduites à partir des sources de don-nées (approche centrée sur les données), ou lorsque le décideur n'a pas intégré tous ces besoins durant la phase de conception (approche centrée sur l'utilisa-teur). Cet article propose une nouvelle méthodologie mixte d'enrichissement de schémas en constellation, où l'approche classique de conception est améliorée grâce à la fouille de données dans le but de créer de nouvelles hiérarchies au sein d'une dimension. Un prototype associé est également présenté

    Solvothermal Synthesis of Oxamate-Based Helicate: Temperature Dependence of the Hydrogen Bond Structuring in the Solid

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    International audienceSolvothermal synthesis has been successfully tested as a new synthetic method towards the formation of oxamate-based coordination compounds. The reaction of 1,3-benzenedioxamic acid (H4mpba) with divalent metal ions has afforded the dinuclear compounds TBA2[Co2(H2mpba)3].2DMF.5H2O (1a), (HNEt3)2[Co2(H2mpba)3].6DMF.5H2O (1b), TBA2[Ni2(H2mpba)3].2DMF.2.5H2O (2) and (HNEt3)2[Co2(H2mpba)3] (3). Although the 3:2 ligand to metal ratio is known for the (mpba) 4-ligand under bench conditions these complexes are the first examples of oxamate-based helicate. Furthermore, crystalographic studies show a temperature-dependent hydrogen bond structuring that leads to racemic or chiral hexagonal 3D networks

    3D image acquisition system based on shape from focus technique

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    agent Agrosup Dijon de l'UMREcolDurGEAPSIThis paper describes the design of a 3D image acquisition system dedicated to natural complex scenes composed of randomly distributed objects with spatial discontinuities. In agronomic sciences, the 3D acquisition of natural scene is difficult due to the complex nature of the scenes. Our system is based on the Shape from Focus technique initially used in the microscopic domain. We propose to adapt this technique to the macroscopic domain and we detail the system as well as the image processing used to perform such technique. The Shape from Focus technique is a monocular and passive 3D acquisition method that resolves the occlusion problem affecting the multi-cameras systems. Indeed, this problem occurs frequently in natural complex scenes like agronomic scenes. The depth information is obtained by acting on optical parameters and mainly the depth of field. A focus measure is applied on a 2D image stack previously acquired by the system. When this focus measure is performed, we can create the depth map of the scene

    Enrichissement de schéma multidimensionnel en constellation grâce à la Classification Ascendante Hiérarchique

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    National audienceLes hiérarchies sont des structures cruciales dans un entrepôt de don-nées puisqu'elles permettent l'agrégation de mesures dans le but de proposer une vue analytique plus ou moins globale sur les données entreposées, selon le niveau hiérarchique auquel on se place. Cependant, peu de travaux s'intéressent à la construction de hiérarchies, via un algorithme de fouille de données, pre-nant en compte le contexte multidimensionnel de la dimension concernée. Dans cet article, nous proposons donc un algorithme, implémenté sur une architecture ROLAP, permettant d'enrichir une dimension avec des données factuelles

    Effect of oxidoreduction potential and of gas bubbling on rheological properties and microstructure of acid skim milk gels acidified with glucono-delta-lactone

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    Milk oxidoreduction potential was modified using gases during the production of a model dairy product and its effect on gel setting was studied. Acidification by glucono-δ-lactone was used to examine the physicochemistry of gelation and to avoid variations due to microorganisms sensitive to oxidoreduction potential.Four conditions of oxidoreduction potential were appliedto milk: milk was gassed with air, nongassed, gassed with N2, or gassed with N2H2. The rheologicalproperties and microstructure of these gels were determined using viscoelasticimetry, measurement of whey separation, and confocal laser scanning microscopy. It appeared that a reducing environment led to less-aggregated proteins within the matrix and consequently decreased whey separation significantly. The use of gas to modify oxidoreduction potential is a possible way to improve the quality of dairy products
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