Influence de l'état mécanique d'un alliage réfractaire sur sa réactivité à haute température

The aim of this work is the reactivity of a ferritic alloy studied considering both chemical and mechanical evolutions versus time between 800 and 1300°C in air. A singular strength behaviour is showed at 900°C in isothermal conditions whereas an accelerated oxidation is visible at the same temperature. The evolution of the Young's modulus and thermal expansion studies explained these anomalies with carbides precipitation

Laissons les acteurs formaliser les jeux - A propos de l'utilisation de jeux de rôle peu formalisés avec des agriculteurs marocains

A Role Playing Game was developed to prepare farmers for the technical, financial and organisational design of these collective irrigation projects within a larger support package which included individual and collective surveys, information meetings and farmer-to-farmer visits. It was decided to focus the scope of the tool on facilitating the design process. This is why it was decided to adopt a tool with a low degree of formalisation. After a short outline of the context of tool application and its resulting functions and objectives , the article will provide the reasons for this decision that were exchanged during the discussion about the tool's design. They can be found, above all, in the support for stakeholders' knowledge formalisation. The tool itself did not have to endow with a lot of information, but was intended to generate discussion in order to highlight the need for defining management rules and to help farmers formulate these rules. The article then will present a short outline of the resulting design of the tool. Since the Role Playing Game was used for process facilitation in the context of the research project AquaStress, its application is first examined regarding its contribution to the proces

Supporting the Shift from State Water to Community Water: Lessons from a Social Learning Approach to Designing Joint Irrigation Projects in Morocco

This paper focuses on the evaluation of a participatory approach aimed at supporting groups of small-scale farmers in the design of joint drip irrigation projects. Our idea was to create a sustainable social learning environment in which they could acquire adaptive knowledge about new irrigation technology and about designing and managing a joint irrigation project while at the same time improving their negotiation capacities. We developed a framework to evaluate the process as well as the outputs and outcomes of the use of our approach with four groups of smallholder farmers in the Tadla irrigation scheme in Morocco. Our findings showed that the learning environment made it possible to compensate for the knowledge differential among stakeholders and to co-produce knowledge that can be mobilized by small-scale farmers to help them make better informed decisions when choosing whether or not to engage in a joint irrigation project and when developing and implementing such a project. We expect that this will ultimately contribute to supporting the shift from state water to community water through a shared understanding of the technical, economic, and social issues and options related to the management of irrigation wate

Accompagner la transformation de l'eau de l'Etat à l'eau communautaire : leçons tirées d'une démarche d'apprentissage social lors de la co-conception de périmètres collectifs d'irrigation

International audienceThis paper focuses on the evaluation of a participatory approach aimed at supporting groups of small-scale farmers in the design of joint drip irrigation projects. Our idea was to create a sustainable social learning environment in which they could acquire adaptive knowledge about new irrigation technology and about designing and managing a joint irrigation project while at the same time improving their negotiation capacities. We developed a framework to evaluate the process as well as the outputs and outcomes of the use of our approach with four groups of smallholder farmers in the Tadla irrigation scheme in Morocco. Our findings showed that the learning environment made it possible to compensate for the knowledge differential among stakeholders and to co-produce knowledge that can be mobilized by smallscale farmers to help them make better informed decisions when choosing whether or not to engage in a joint irrigation project and when developing and implementing such a project. We expect that this will ultimately contribute to supporting the shift from state water to community water through a shared understanding of the technical, economic, and social issues and options related to the management of irrigation water

Influence of the chemical composition and the fabrication process on the behaviour of high temperature oxidation of Fe-Cr-Al alloys

The oxidation behaviour of four industrial Fe-Cr-Al alloys was studied. Two of them were Fe-Cr-Al alloys fabricated either by melting or by powder metallurgy. The two other ones were Fe-Cr-Al-Y alloys either produced by melting or by mechanical alloying. On these alloys, we determined oxidation kinetics and observed the morphology of the oxide layer after isothermal and cyclic exposures from 1000°C up to 1300°C. The beneficial effect of yttrium on the adherence of oxide layers was confirmed. The powder metallurgy fabrication route does not improve the oxidation resistance of yttrium-free alloys. On the other hand, the association of the powder metallurgy and the addition of yttrium allow the manufacturing of alloys which present an excellent behaviour to high temperature oxidation

Optical Investigation of Ignition Timing and Equivalence Ratio in Dual-Fuel CNG/Diesel Combustion

International audienc

How to test and evaluate

International audienceAs defined in chapters 2 and 3, participatory approaches can be used to identify water stress-related problems and project goals in order to mitigate the problems. This chapter takes the process further by looking at the participatory testing and evaluation at two levels: mitigation options and specific measures (as specified in Chapter 5). These measures are defined as the different alternatives which are studied when an option is applied. For instance, when applying an option which targets the improvement of irrigation efficiency, the different measures studied could then be: changes toward alternative irrigation technologies, changes in irrigation practices, etc

67P/Churyumov–Gerasimenko’s dust activity from pre- to post-perihelion as detected by Rosetta/GIADA

We characterized the 67P/Churyumov–Gerasimenko’s dust activity, by analysing individual dust particle velocity and momentum measurements of Grain Impact Analyser and Dust Accumulator (GIADA), the dust detector onboard the ESA/Rosetta spacecraft, collecting dust from tens to hundreds of kilometres from the nucleus. Specifically, we developed a procedure to trace back the motion of dust particles down to the nucleus, identifying the surface’s region ejecting each dust particle. This procedure has been developed and validated for the first part of the mission by Longobardo et al. and was extended to the entire GIADA data set in this work. The results based on this technique allowed us to investigate the link between the dust porosity (fluffy/compact) and the morphology of the ejecting surface (rough/smooth). We found that fluffy and compact particles, despite the lack of correlation in their coma spatial distribution (at large nucleocentric distances) induced by their different velocities, have common ejection regions. In particular, the correlation between the distributions of fluffy and compact particles is maintained up to an altitude of about 10 km. Fluffy particles are more abundant in rough terrains. This could be the result of past cometary activity that resurfaced the smooth terrains and/or of the comet formation process that stored the fluffy particles inside the voids between the pebbles. The variation of fluffy particle concentration between rough and smooth terrains agrees with predictions of comet formation models. Finally, no correlation between dust distribution on the nucleus and surface thermal properties was found