Science & Mathematics

Parce qu'un concert de protestations (P-A. Buvet et J -H.Lim 1996) et une litanie de réclamations (P-A. Buvet 1993, table C16) sont classés parmi les déterminants nominaux métaphoriques, nous voudrions interroger par les critères avancés dans les travaux substantiels de (M. Gross 1985 ; P-A. Buvet 2001 ; X. Blanco 1998 ; 2002), quelques syntagmes à référence musicale dont le classement nous pose problèmes : un chœur de mécontents/ un coro di proteste, etc. L'approche comparée (ici italien/français) porte, on le verra, aux mêmes conclusions que celles de Blanco (2002) et Mirto et Necker (2007).

The performance of bifunctional hybrid catalysts based on phosphotungstic acid (H3PW12O40, HPW) supported on TiO2 combined with a Cu-ZnO(Al) catalyst in the direct synthesis of dimethyl ether (DME) from syngas has been investigated. In this work, different types of TiO2 were used as a support to study the effect of changes in the structure of the TiO2 support on the acidity and dispersion of HPW. Various TiO2 supports with different structural and surface characteristics have been studied and the results indicate that: (i) the crystallinity and crystallite size of the primary particles of the HPW units depend on the TiO2 support; (ii) the pore size distribution of the TiO2 support affects the surface segregation of the heteropolyacids; and (iii) changes in the supported HPW acid catalysts do not significantly alter the crystal structure of the CuO and ZnO phases after contact with CZA in bifunctional catalysts. The activity results indicate that the variation in the intrinsic activity of the Cu-ZnOx centers in the bifunctional catalysts for direct DME synthesis is minimal due to the limited alteration of the crystal structure of the centers.

There is a growing need for systems that allow to monitor continuously the health condition of patients with chronic diseases, while allowing these patients to live their daily life as usual, at home as well as out of home. Developing such systems is now feasible based on currently available wireless transmission technologies and off-the-shelf wearable sensors, but most of the applications developed so far fall into the quantified-self movement, and can hardly be used for medical monitoring. This paper presents a general architecture for mobile bio-physical monitoring, covering all stages of data acquisition, transmission, and processing. This architecture has been designed so as to meet the expectations of the medical field (especially regarding confidentiality and dependability), while remaining open and flexible (i.e., new types of sensors or data processing algorithms can be incorporated as and when needed).

Mission archéologique au Jebel Druze. Plaque de verre (13x18)

Mobility, social interactions, and other human characteristics shall support Future Mobile Networks in routine prediction and resource management. This work investigates human-aware metrics supporting services or protocols leveraging opportunistic communication. These metrics represent different types of knowledge extracted from people routine present in their movements. Because of the strong routine component of human mobility, such metrics capture different but recurrent behaviors on wireless encounters between mobile users. We report the experience through a case study with a real-world dataset along with results from trace and metrics analysis. The results show heterogeneity in metric coefficients and contact occurrence and duration in different periods of the day, highlighting the need for characterising traces before their use.

Carte du Ceriscope Pauvreté

The double manganite CaCu3Mn4O12 doped with 119Sn atoms (∼1 at.% with respect to manganese atoms) was studied by use of Mössbauer spectroscopy. Formally tetravalent Sn4+ ions substitute for isovalent manganese ions in the octahedral (Mn4+O6) polyhedra. The covalency effects on the magnetic interactions like superexchange in Cu2+-O-Mn4+ and Mn4+-O-Mn4+ bonds and supertransferred hyperfine interactions of the 119Sn probe atoms in the manganite structure are discussed. Using a semiquantitative nearest-neighbor cluster model relating the hyperfine magnetic field on the 119Sn nuclei (HSn = 105 kOe at T = 77 K) to covalency parameters and angle characterizing the Sn-O-M (M = Cu, Mn) bonds, it has been shown how such an analysis of supertransferred hyperfine interactions of tin probe ions can get fruitful information about strength and sign of the superexchange interactions between Mn4+ and Cu2+ magnetic ions. A consistent description of the results in the framework of the Weiss molecular field model considering the specific local environment of tin atoms has made it possible to estimate exchange integrals: JCuMn = −51.1 ± 0.3 K and JMnMn = −0.6 ± 0.2 K.

Les composants magnétiques sont des constituants essentiels des convertisseurs électroniques de puissance en termes de volume et de coût, en particulier dans les alimentations à découpage. Pour cette raison, il est intéressant de développer des méthodes et des outils logiciels pour optimiser la conception de dispositif magnétiques en relation avec les paramètres de conversion. Concevoir et optimiser un composant magnétique suppose de définir parfaitement les contraintes induites par les spécifications, de choisir des conducteurs, isolants et circuits magnétiques, tant sur le plan des matériaux que des géométries, de calculer finement les pertes dans ces différentes parties et enfin, de disposer de modèles thermiques permettant de conduire le design en considérant la contrainte majeure que constituent les températures de fonctionnement des différentes parties du composant. L'objectif de cette thèse est de jeter les bases d'un outil générique d'aide à la conception optimale de composants magnétiques en s'appuyant sur des modélisations analytiques et numériques.

Deux systèmes de tomographie à fils ont été utilisés pour étudier la maldistribution du liquide dans un réacteur à lit fixe arrosé en écoulement à co-courant descendant de gaz et de liquide (RCLFA). La technique, qui se base sur celle utilisée par Prasser et coll. (1998) dans les colonnes à bulles, utilise deux faisceaux de fils horizontaux placés à une profondeur donnée pour détecter la présence d'un liquide conducteur entre eux. En occupant seulement 6,5% de la surface passante du réacteur, le système de tomographie à fils permet l'estimation de la rétention liquide sur un plan transversal de la colonne avec une résolution spatiale de 313 pixels. Cet article présente quelques exemples de mesures faites avec ce système à l'intérieur d'un lit fixe en utilisant différents types de distributeurs. Les résultats sont satisfaisants et font de la tomographie à fils une technique prometteuse pour l'étude de la maldistribution du liquide dans un lit fixe de particules non poreuses.

The objective of this paper is to give an overview of the synthesis, properties of different organoclays, including organo-montmorillonite, organo-sepiolite and organo-palygorskite, and their use as rheological additives in oil-based drilling fluids. The researches performed until the present moment are described and summarized. A significant amount of work had been done in this area, including the rheological behavior at normal and high temperature, the structure changes of organoclays in oil-based system, thermal stability and the rheological mechanisms. The role of layered and fibrous organoclays in oil-based drilling fluids in the enhancement of the rheological properties and thermal stability is deeply reviewed.