La Tour-Blanche – Grotte de Jovelle

Identifiant de l'opération archéologique : 025473 Date de l'opération : 2008 (PT) État des lieux historique et archéologique I) Contexte Récemment acquise par le département de la Dordogne (2006) et vierge de toute étude scientifique approfondie, la cavité ornée de Jovelle est constituée d’une unique galerie se développant sur une trentaine de mètres selon un axe nord-ouest - sud-est, au dépend d’une assise de calcaire attribuable au Turonien moyen c3b..

Approche économique de la reproduction chez la Blonde d’Aquitaine

L’objectif de ce travail était de quantifier l’impact économique associé à des mauvais résultats de reproduction, en particulier lors de dégradation de l’intervalle vêlage-vêlage. Un modèle économique expérimental a été crée et calibré dans le système d’élevage de la race Blonde d’Aquitaine dans le sud ouest de la France. Le coût d’un jour supplémentaire d’IVV diminue avec l’IVV, ces résultats s’opposent aux résultats en système laitiers. Un éleveur peut gagner de 5,3€ à 22,5€ par vache et par an en réduisant l’IVV de 400 jours à 380 jours et de 4,8€ à 20,3€ en réduisant l’IVV de 420 jours à 400 jours, le gain varie selon l’âge au premier vêlage (compris entre 24 mois et 48 mois) et selon l’âge moyen de réforme (compris entre 6 ans et 11 ans). Réduire l’IVV d’un élevage est d’autant plus difficile que celui-ci est performant (valeur d’IVV déjà faible). Ainsi cet outil peut être utilisé directement en élevage pour décider de la conduite à tenir la plus adaptée pour améliorer les performances de reproduction (et donc le gain), il est applicable à chaque élevage aux caractéristiques d’un système Blonde d’Aquitaine dans la région du sud ouest de la France

Propriétés rhéologiques du beurre d'arachides

Forces agissant sur les particules d'une suspension -- Modèles rhéologiques -- Effet des propriétés des particules -- Phénomènes propres aux suspensions -- Suspensions concentrées dans le domaine alimentaire -- Rhéomètres et géométries employés -- Tests rhéologiques menés -- Analyse morphologique et caractérisatin des suspensions -- Expériences en régime transitoire et permanent -- Glissement : mise en évidence expérimentale -- Caractérisation du glissement -- Prévention du glissement -- Expériences réalisées en régime transitoire -- Résultats pour le type "crémeux" -- Résultats pour le type "100% arachides" -- Propriétés en mode oscillatoire -- Mise en évidence de phénomènes temporels -- Recherche de zone linéaire -- Étude des courbes obtenues lors de balayages en déformation -- Balayage en fréquence -- Effet du stabilisant et du sel sur la rhéologie du produit

Effects of oxygen depletion on soot production, emission and radiative heat transfer in opposed-flow flame spreading over insulated wire in microgravity

This paper investigates experimentally and numerically pressure effects on soot production and radiative heat transfer in non-buoyant opposed-flow flames spreading over wires coated by Low Density PolyEthylene (LPDE). Experiments, conducted in parabolic flights, consider pressure levels ranging from 50.7 kPa to 121.6 kPa and an oxidizer flowing parallel to the wire's axis at a velocity of 150 mm/s and composed of 20% O2/80% N2 in volume. The numerical model includes a detailed chemistry, a two-equation smoke-point based soot production model, a radiation model coupling the Full-Spectrum correlated-k method with the finite volume method and a simple degradation model for LDPE. An analysis of the experimental data shows that the spread rate, the pyrolysis mass flow rate, and the residence time for soot formation are independent of pressure whereas the soot formation rate is third-order in pressure. The model reproduces quantitatively the effects of pressure on soot production and captures the transition from non-smoking to smoking flames. The radiant fraction increases with pressure because of an enhancement in soot radiation whereas the contribution of radiating gases remains approximately constant over the range of pressures considered. In addition, gas radiation dominates at pressure lower than 75 kPa whereas soot radiation prevails at higher-pressure levels. Consistently with the data obtained at normal gravity, the smoke-point transition is found to occur for a radiant fraction of about 0.3 and the soot oxidation freezing temperature is estimated in the range 1350-1450K. Eventually, whatever the pressure considered, the surface re-radiation from the wire is higher than the incident radiative flux from the flame to the surface along the entire wire. This shows that radiative heat transfer contributes negatively to the heating of the unburnt LDPE and to the heat balance along the pyrolysing surface

Wideband measurements and analysis of propagation losses within a building

International audienceA simplified setup using an HP network analyzer to perform path loss measurements for the indoor radio channel in the 0.8 - 1 GHz band is described. In order to analyse the frequency selectivity of the channel, two new postprocessing data methods are proposed. A comparison with anotherpublished method is also presented

Effect of Ambient Pressure on the Extinction Limit for Opposed Flame Spread over an Electrical Wire in Microgravity

Parabolic flight experiments were carried out to investigate the effect of ambient pressure on the extinction limit for opposed flame spread over an electric wire insulation in microgravity. Low-density polyethylene insulated Nickel-Chrome wires with inner core diameter of 0.50 mm and insulation thickness of 0.30 mm were examined for ambient pressures ranging from 50 kPa to 140 kPa for an external opposed flow of 10 cm/s. The experiments showed that the limiting volumetric oxygen concentration (LOC) increased as the total ambient pressure decreased. This LOC trend can be explained by radiation loss from wire surface. The radiation loss increased as the ambient pressure decreased & ndash; a result that can be explained by the increase in preheat length with decreasing ambient pressure. Moreover, when the data was plotted in a partial pressure vs. total pressure space, it became evident that the limiting oxygen partial pressure (LOPP) decreased with decreasing total ambient pressure. This LOPP trend can be explained by the fact that the flame temperature increased as the ambient pressure decreased under constant oxygen partial pressure. In current fire safety design for spacecraft, tentative oxygen concentration criteria in spacecraft suggested by NASA is assumed as 30% of oxygen concentration, and this value is assumed independent of ambient pressure. However, the present result implies that consideration of the effect of ambient pressure on the flammability limit is necessary, especially with respect to the possibility of an extension of the allowable atmosphere condition for spacecraft cabin in the low pressure region

Time delay measurements in the frequency domain for indoor radio propagation

International audienceMeasurement results of average time delay and RMS delay spread are reported. A statistic of RMS delay spread is presented. A linear regression analysis between the above delay times and the T-R separation is also described. Using a method to discard the location with the maximum absolute error, this regression analysis allows us to obtain a minimum mean square error (MMSE) line with more important correlaton coefficient and more reduced mean syuare error