Recherche d'images en mobilité - Le système IOTA-EyeSnap

National audienceCet article décrit le système IOTA-EyeSnap, un système de recherche d'images mobile appliqué à la recherche de photographies de peintures dans le cadre du projet CLICIDE. Ce système repose sur un enchaînement d'approches probabilistes : la première à base de modèle de langue sur des graphes représentant les images, et la seconde à base de modèles bayésiens. Nous détaillons les contraintes et les choix réalisés. Ils sont adaptés à la mobilité dans un cadre muséal. Les différents outils permettant une évaluation a priori et a posteriori sont présentés, et les résultats expérimentaux sont décrits et analysés

Designing indoor tangible games based on fuzzy localisation

International audienceWe present in this paper the development of an easy-to-adapt architecture for radio based, indoor geolocation; and the new opportunities it brings for game design. The weak precision of such systems, usually regarded as a problem, is considered here as a source of innovation for the design of pervasive games

Physical ageing of spreading droplets in a viscous ambient phase

Nanoscale topographic features of solid surfaces can induce complex metastable behavior in colloidal and multiphase systems. Recent studies on single microparticle adsorption at liquid interfaces have reported a crossover from fast capillary driven dynamics to extremely slow kinetic regimes that can require up to several hours or days to attain thermodynamic equilibrium. The observed kinetic regime resembling physical ageing in glassy materials has been attributed to unobserved surface features with dimensions on the order of a few nanometers. In this work, we study the spontaneous spreading of water droplets immersed in oil and report an unexpectedly slow kinetic regime not described by previous spreading models. We can quantitatively describe the observed regime crossover and spreading rate in the late kinetic regime with an analytical model considering the presence of periodic metastable states induced by nanoscale topographic features (characteristic area ~4 nm^2, height ~1 nm) observed via atomic force microscopy. The analytical model proposed in this work reveals that certain combinations of droplet volume and nanoscale topographic parameters can significantly hinder or promote wetting processes such as spreading, wicking, and imbibition

Fabricación industrial de arcilla expandida

Not availableLa construcción da cada vez más importancia a los hormigones preparados con áridos ligeros. De hecho, estos materiales permiten, suponiéndoles unas resistencias mecánicas suficientes, sustituir los elementos del hormigón pesado por otros que, a igualdad de espesor, proporcionan un aislamiento térmico muy superior. Ciertos áridos ligeros se encuentran en estado natural (piedra pómez) o son subproductos industriales (escorias). Pero cada día se fabrica una proporción mayor de materiales ligeros industrialmente, entre ellos: la arcilla expandida

Use of a porous membrane for gas bubble removal in microfluidic channels: physical mechanisms and design criteria

We demonstrate and explain a simple and efficient way to remove gas bubbles from liquid-filled microchannels, by integrating a hydrophobic porous membrane on top of the microchannel. A prototype chip is manufactured in hard, transparent polymer with the ability to completely filter gas plugs out of a segmented flow at rates up to 7.4 microliter/s per mm2 of membrane area. The device involves a bubble generation section and a gas removal section. In the bubble generation section, a T-junction is used to generate a train of gas plugs into a water stream. These gas plugs are then transported towards the gas removal section, where they slide along a hydrophobic membrane until complete removal. The system has been successfully modeled and four necessary operating criteria have been determined to achieve a complete separation of the gas from the liquid. The first criterion is that the bubble length needs to be larger than the channel diameter. The second criterion is that the gas plug should stay on the membrane for a time sufficient to transport all the gas through the membrane. The third criterion is that the gas plug travel speed should be lower than a critical value: otherwise a stable liquid film between the bubble and the membrane prevents mass transfer. The fourth criterion is that the pressure difference across the membrane should not be larger than the Laplace pressure to prevent water from leaking through the membrane