Influence du vieillissement marin sur l'endommagement en sollicitation hors plan de bordé de bateau de course = Influence of sea water aging on damage development in racing boat hull under inplane shear loading.

National audienceNous avons étudié l'influence du vieillissement en eau de mer d'échantillons de stratifiés carbone/époxy provenant de la structure de voilier de course. D'abord, afin d'établir une référence pour la suite de l'étude, les cinétiques de prise de masse d'eau ont été déterminées à 5 températures (4°, 20°, 40°, 60°,80°C), ainsi que l'influence de l'immersion sur les propriétés mécaniques et sur l'endommagement. Ensuite différents domaines ont été étudiés : l'incidence de la protection de type peinture et enduit sur la prise de masse, l'évolution des propriétés mécaniques et l'endommagement de plaques issues de la même structure a été étudiée. Nous avons montré que la peinture époxy utilisée pour le revêtement des voiliers présentait des propriétés barrières retardant la diffusion de l'eau et la diminution des propriétés mécaniques. L'influence du nombre de couche de peinture n'est pas négligeable, allant même à légèrement modifier l'endommagement. En complément, une peinture anticorrosion couvrant les quilles des monocoques fut testée, on note que la diminution de propriété ne suit pas la prise de masse. Par ailleurs, des plaques protégées par un enduit ont également été vieillies et analysées

Multi-scale analysis of hypochlorite induced PES/PVP ultrafiltration membranes degradation

In drinking water production plants, the use of oxidants such as sodium hypochlorite during in-place cleanings may impair the membrane integrity and radically impact the ultrafiltration process efficiency, leading to potential contamination of the permeate water with pathogens. This study investigates the effects of hypochlorite exposure on the properties of a commercially available UF hollow fiber. Mechanical performances and water permeability appeared to be greatly affected by the contact with hypochlorite. Monitoring them olecular changes by X-rayphoto electron spectroscopy (XPS), attenuated total reflectance infraredspectroscopy (ATR-IR), size exclusion chromatography (SEC) and VITA-mode atomic forcemicroscopy (VITA-AFM) revealed high stability of the main polymer constituting the membrane (i.e. polyethersulfone (PES)) and very high reactivity of the additive (i.e. poly (N-vinyl pyrrolidone (PVP)) towards immersion in aqueous sodium hypochlorite solution with maximal reaction rate for neutral to slightly basic pH. Correlation of those results unexpectedly leads to the conclusion that the over all membrane properties changes are governed by the additive fate

Machine Learning Potential for Modelling H2_2 Adsorption/Diffusion in MOF with Open Metal Sites

Metal-organic frameworks (MOFs) incorporating open metal sites (OMS) have been identified as promising sorbents for many societally relevant-adsorption applications including CO$_2$ capture, natural gas purification and H$_2$ storage. It is critical to derive generic interatomic potential to achieve accurate and effective evaluation of MOFs for H$_2$ adsorption. On this path, as a proof-of-concept, the Al-soc-MOF containing Al-OMS, previously envisaged as a potential candidate for H$_2$ adsorption, was selected and a machine learning potential (MLP) was derived from a dataset initially generated by ab-initio molecular dynamics (AIMD) simulations. This MLP was further implemented in MD simulations to explore the binding modes of H$_2$ as well as its temperature dependence distribution in the MOFs pores from 10K to 90K. MLP-Grand Canonical Monte Carlo (GCMC) simulations were further performed to predict the H$_2$ sorption isotherm of Al-soc-MOF at 77K that was further confirmed by gravimetric sorption measurements. As a further step, MLP-based MD simulations were conducted to anticipate the kinetics of H$_2$ in this MOF. This work delivers the first MLP able to describe accurately the interactions between the challenging H$_2$ guest molecule and MOFs containing OMS. This innovative strategy applied to one of the most complex molecules owing to its highly polarizable nature alongside its quantum-mechanical effects that are only accurately described by quantum calculations, paves the way towards a more systematic accurate and efficient in silico assessment of the MOFs containing OMS for H$_2$ adsorption and beyond to the low-pressure capture/sensing of diverse molecules.Comment: 11 pages, 4 figure

A kinetic model for predicting the oxidative degradation of additive free polyethylene in bleach desinfected water

The chemical interactions between additive free PE and bleach were investigated by FTIR spectrophotometry and viscosimetry in molten state after immersion (for a maximum duration of one hundred days) in bleach solutions maintained at a temperature of 60 °C, a free chlorine concentration of 100 ppm, and a pH = 4, 5 or 7. It was found that the polymer undergoes a severe oxidation from the earliest days of exposure in a superficial layer of about 50–100 μm thick, almost independent of the pH value. In this layer, oxidation leads to the formation and accumulation of various carbonyl products (mostly ketones and carboxylic acids) but also, after about 2–3 weeks of exposure, to a dramatic decrease in the average molar mass due to the large predominance of chain scissions over crosslinking. It was also found that the oxidation rate is maximum at pH = 5, and of the same order of magnitude at pH = 4 and 7. Based on the equilibrium diagram giving access to the relative predominance of the three main chemical species as a function of the pH value of the bleach solution, it was assumed that oxidation is initiated by radical species coming firstly from hypochlorous acid (ClOH) and secondarily from chlorine (Cl2), given that hypochlorite ions (ClO−) are totally insoluble into the PE matrix. In addition, for explaining the surprisingly large value of the oxidized layer thickness despite the high reactivity of the involved radicals, it was assumed that ClOH and Cl2 do not decompose into radicals in the water phase, but migrate deeply into the PE matrix prior to dissociating into Cl and HO radicals and then, initiating a radical chain oxidation. The validity of the kinetic model derived from this scenario was successfully checked by comparing the numerical simulations with all the experimental data collected in this study. This model predicts the general trends of the oxidation kinetics and its dependence on the pH value, but also gives access to the transport properties of the chlorinated disinfectants and their radical species, and the rate constants of the radical attack

Bob Meets Sam

Transcription de la rencontre autour de la venue de Robert Wilson au Théâtre Garonne (Toulouse) le 21 février 2015. L’échange autour de la mise en scène par Wilson de La Dernière Bande fut organisé par le laboratoire CAS (Cultures Anglo-Saxonne) de Toulouse Jean-Jaurès (sur l’initiative d’Emeline Jouve) et le Théâtre Garonne (sur l’initiative de Stéphane Boitel) et réunissait trois intervenants en les personnes de Romain Fohr (discutant), Charles Chemin et Frédéric Maurin.Transcription of the round-table on Robert Wilson’s work at Théâtre Garonne (Toulouse) on February, 21th 2015. The discussion with Romain Fohr, Charles Chemin, Frédéric Maurin and the audience about Wilson’s staging of Krapp’s Last Tape was set up by the research group on the English-speaking world (CAS) of Toulouse Jean-Jaurès University and the Théâtre Garonne

Bob Meets Sam

Transcription de la rencontre autour de la venue de Robert Wilson au Théâtre Garonne (Toulouse) le 21 février 2015. L’échange autour de la mise en scène par Wilson de La Dernière Bande fut organisé par le laboratoire CAS (Cultures Anglo-Saxonne) de Toulouse Jean-Jaurès (sur l’initiative d’Emeline Jouve) et le Théâtre Garonne (sur l’initiative de Stéphane Boitel) et réunissait trois intervenants en les personnes de Romain Fohr (discutant), Charles Chemin et Frédéric Maurin.Transcription of the round-table on Robert Wilson’s work at Théâtre Garonne (Toulouse) on February, 21th 2015. The discussion with Romain Fohr, Charles Chemin, Frédéric Maurin and the audience about Wilson’s staging of Krapp’s Last Tape was set up by the research group on the English-speaking world (CAS) of Toulouse Jean-Jaurès University and the Théâtre Garonne

The Astropy Problem

The Astropy Project (http://astropy.org) is, in its own words, "a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages." For five years this project has been managed, written, and operated as a grassroots, self-organized, almost entirely volunteer effort while the software is used by the majority of the astronomical community. Despite this, the project has always been and remains to this day effectively unfunded. Further, contributors receive little or no formal recognition for creating and supporting what is now critical software. This paper explores the problem in detail, outlines possible solutions to correct this, and presents a few suggestions on how to address the sustainability of general purpose astronomical software

Plant based resins for fibre composites

Epoxidized vegetable oils were obtained by epoxidation of plant oils, such as canola, soybean or linseed. These epoxidized oils could be used, after curing with suitable amines, to prepare rubbery materials, which are proposed as a replacement of the commercially produced CTBN-style resins. Incorporation of such resins to commercial epoxy systems gives an increased toughness, similar to the CTBN additives, but at much lowers cost. The paper discusses the preparation of the epoxidized oils, their characteristics and use in preparation of the vegetable rubber resins. Results of DMA and other tests are discussed. The authors have demonstrated that vegetable oils can be used to partially replace petrochemically derived materials. While exceeding or maintaining the sought-after properties (stiffness, toughness), such systems use renewable raw materials and are therefore environmentally more sound than systems which use only petrochemically derived components

Restaurations postérieures en méthode directe : les nouvelles résines composites peuvent-elles , en 2010 supplanter l'amalgame?

REIMS-BU Santé (514542104) / SudocSudocFranceF