Etude expérimentale du ruissellement sur des sols à végétation contrastée du Mont Lozère

Les conditions d'apparition du ruissellement de surface, et les valeurs limites que peut atteindre l'infiltration sont étudiés expérimentalement par simulation de pluie sur des sols à végétation contrastée du Mont Lozère (Sud du Massif Central, France), développés sur arène granitique peu profonde. Les résultats mettent en évidence la forte capacité d'infiltration du milieu naturel, mais aussi la grande variabilité spatiale de cette capacité d'infiltration, pour aboutir à un schéma de fonctionnement dans lequel, si la circulation hypodermique, à la limite de la roche saine, demeure le processus essentiel de transfert de l'eau entre son point de chute et le cours d'eau, le ruissellement sur les versants n'est pas exclu et peut jouer un rôle important dans la formation des crues. Par ailleurs il semblerait qu'une pelouse en bon état, couvrant parfaitement le sol, présente une aussi bonne protection contre le ruissellement et l'érosion que les litières forestières testées. (Résumé d'auteur

Au/TiO2(110) interfacial reconstruction stability from ab initio

We determine the stability and properties of interfaces of low-index Au surfaces adhered to TiO2(110), using density functional theory energy density calculations. We consider Au(100) and Au(111) epitaxies on rutile TiO2(110) surface, as observed in experiments. For each epitaxy, we consider several different interfaces: Au(111)//TiO2(110) and Au(100)//TiO2(110), with and without bridging oxygen, Au(111) on 1x2 added-row TiO2(110) reconstruction, and Au(111) on a proposed 1x2 TiO reconstruction. The density functional theory energy density method computes the energy changes on each of the atoms while forming the interface, and evaluates the work of adhesion to determine the equilibrium interfacial structure.Comment: 20 pages, 11 figure

Gas Sensing Materials Based on TiO2 Thin Films

Ti O 2 thin films were prepared by spray pyrolysis using a solution of titanium tetrachloride and ethyl alcohol. The deposition was performed onto different substrates (silicon, quartz, glass) maintained at the same temperature, 270 ° C . After annealing, a predominant rutile structure is obtained for films deposited onto silicon and quartz substrates, as revealed by x-ray diffraction patterns. The Ti O 2 films were exposed to different gases, at different temperatures, in order to evaluate their gas sensitivity. The optimum operating temperatures, showing the highest gas sensitivity, were determined for some gases (acetone, ethanol, methane, and liquefied petroleum gas)

Measuring Market Liquidity Risk - Which Model Works Best?

Market liquidity risk, the difficulty or cost of trading assets in crises, has been recognized as an important factor in risk management. Literature has already proposed several models to include liquidity risk in the standard Value-at-Risk framework. While theoretical comparisons between those models have been conducted, their empirical performance has never been benchmarked. This paper performs comparative back-tests of daily risk forecasts for a large selection of traceable liquidity risk models. In a 5.5 year stock sample we show which model provides most accurate results and provide detailed recommendations which model is most suitable in a specific situation

Rainwater Infiltration Rate and Groundwater Sustainable Management in the Dakar Region

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 6 (2004): S. Dasylva, C. Cosandey, D. Orange, and S. Sambou. Rainwater Infiltration Rate and Groundwater Sustainable Management in the Dakar Region. (October 2004)