Finite size effects in a model for plasticity of amorphous composites

We discuss the plastic behavior of an amorphous matrix reinforced by hard particles. A mesoscopic depinning-like model accounting for Eshelby elastic interactions is implemented. Only the effect of a plastic disorder is considered. Numerical results show a complex size-dependence of the effective flow stress of the amorphous composite. In particular the departure from the mixing law shows opposite trends associated to the competing effects of the matrix and the reinforcing particles respectively. The reinforcing mechanisms and their effects on localization are discussed. Plastic strain is shown to gradually concentrate on the weakest band of the system. This correlation of the plastic behavior with the material structure is used to design a simple analytical model. The latter nicely captures reinforcement size effects in $-(\log N/N)^{1/2}$ observed numerically. Predictions of the effective flow stress accounting for further logarithmic corrections show a very good agreement with numerical results.Comment: 18 pages, 19 figure

Modélisation multi-modèle incertaine du trafic routier et suivi robuste de profils optimaux aux entrées des voies périurbaines

Ce document synthétise mes travaux de thèse de doctorat en Automatique Productiqueà Grenoble INP (Institut National Polytechnique), thèse préparée au sein dudépartement automatique du laboratoire GIPSA-lab (Grenoble Image Parole Signal etAutomatique). Ce travail s inscrit dans le cadre du contrôle local et de la supervisiondes systèmes de trafic routier. Les principales contributions portent sur la modélisation,la supervision et la commande locale des systèmes de trafic routier.La contribution apportée à la modélisation du trafic est l ajout d un modèle d incertitudesur le modèle CTM (Cell Transmission Model [Daganzo, 1994]). Ce nouveaumodèle permet de prendre en compte les incertitudes sur différents paramètres dumodèle pour in-fine proposer de nouvelles stratégies de commandes commutées robustes.Outre cette approche de modélisation, nous proposons un niveau de supervisionpermettant d une part d estimer en temps réel le mode de fonctionnement et d autrepart de détecter, localiser et estimer certaines fautes sur le système. L estimation dynamiquede mode de fonctionnement nous permet de connaître l état de congestion (ou denon-congestion) de l aménagement routier considéré. Nous sommes en mesure de détecterdes fautes telles que des chutes de vitesse ou des chutes de capacité survenant sur la route.Enfin, nous proposons deux lois de commandes locales basées sur la théorie dessystèmes à commutations. Ainsi, le schéma de contrôle s adaptera dynamiquementaux changements de propriétés du système. Ces lois de commande ont pour objet des insérer dans un schéma de régulation hiérarchique.This document synthesizes my Phd thesis work in Automatic Control in Grenoble-INP. This thesis has been prepared in the automatic control department of thelaboratory GIPSA-lab. This work is situated in the area of traffic systems control andsupervision. Our contributions are about modeling, supervision and local traffic control.The CTM traffic model has been extended with a model of uncertainties. Thisnews model allows us to take into account the uncertain parameters of the model, topropose new robust switched control law.In addition to this modeling approach, we propose some developments on supervisionof trafic systems. On one hand, we can estimate the operating mode of thesystem in real time and on the other hand to estimate some faults on the system. Thedynamical estimation of the operating mode allows us to know the state of congestion(or non congestion) of the road. We are able to estimate faults such as speed fall andcapacities drop that may appear.Finally, we propose two control laws based on switching systems control. The developedcontrollers adapt their geometry to the properties of the system. The purposeof these controllers is to be inserted in a hierarchic control scheme.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Empreintes isotopiques des interactions eau-roche : de l'échelle du bassin versant à celle du minéral

Géochimi

Géochimie isotopique du bore (érosion continentale)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

30. Comment les eaux acquièrent-elles leur composition chimique ?

L’eau de pluie interagit avec les roches qu’elle rencontre par l’intermédiaire de réactions chimiques qui libèrent en solution les éléments les plus solubles et recombinent sur place les éléments insolubles pour former de nouveaux minéraux. Il s’agit du processus d’altération chimique des roches. À l’échelle des temps géologiques, ces interactions à petite échelle entre les molécules d’eau et les éléments chimiques contenus dans les roches s’opposent à la tectonique des plaques en détruisant ..

On the Connected Spanning Cubic Subgraph Problem

International audienc

Multi-Objective optimization: Comparison of methods for the p-median problem

International audienc

A comparative study of the dissolution mechanisms of amorphous and crystalline feldspars at acidic pH conditions

International audienceAbstract The dissolution of amorphous and crystalline oligoclase, a Na-feldspar with traces of Ca and K, was investigated at 90 °C and acidic pH of 1.5 and 3 to unravel the impact of long- and short-range orders on silicate dissolution mechanisms. Experiments were conducted in solutions spiked with 29 SiO 2 (aq) and saturated with respect to SiO 2 (am). Through morphology, structural, and composition characterizations, we showed that on the amorphous samples (glass samples), the altered layer was mostly formed by leaching, while a combination of both interfacial precipitation and leaching explains the layers formed on the crystalline sample. As expected, the altered layer was thicker at the most acidic pH and it became passivating on crystalline sample at pH 3. The alteration was faster on amorphous oligoclase than on its crystalline equivalent due to the more open structure of the glass. The preferential release of Al was suggested to play a key role, by weakening the silicate network of both substrates. Finally, in this study, a large overestimation of the global alteration of the materials was noticed based on the solution analyses. Discrepancies with solid analyses were attributed to an underestimation (≥2-fold factor) of the total reactive surface area