Obstacles and levers related to implementing and sustaining innovative pedagogical teachings to meet the needs of primary care and support workers and patients. Descriptive qualitative research

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Contribution to a comprehensive selection of surface treatments: the case of aluminium foundry devices.

Sélectionner des traitements de surface pour l’industrie nécessite de prendre en compte :les propriétés à conférer au substrat, la nature et la géométrie de celui-ci et les caractéristiques du milieu extérieur. Certaines combinaisons de ces paramètres rendent difficile la sélection d’un traitement unique, d’où le recours à des multitraitements de surface. Dès lors, se posent les questions suivantes :<p>- Utiliser des multitraitements de surface peut se faire en scindant les différentes requêtes en sous-ensembles, de manière à ce que chaque traitement réponde à l’un d’eux. Dans quel ordre ces requêtes doivent-elles être introduites par rapport au substrat ?<p>- Comment sélectionner les traitements de surface répondant à chaque requête individuelle ?<p>- Comment classer des multitraitements en termes d’adéquation au problème posé ?<p>Dans ce travail, les première et troisième questions sont abordées, en explorant les requêtes concernant habituellement les dispositifs de moulage de l’aluminium :<p>- Résistance aux contraintes d’origine thermique.<p>- Résistance à la corrosion par les métaux fondus.<p>- Résistance au frottement.<p>L’analyse de la bibliographie relative aux traitements de surface utilisés dans ces systèmes a été analysée et des « architectures »-types ont été identifiées (chapitre 3). On prévoit, par exemple, un traitement conférant la résistance à la fatigue superficielle, ainsi qu’un revêtement étanche et résistant à l’aluminium fondu. Une barrière thermique est parfois préconisée.<p>Pour chacune des architectures, des traitements de surface individuels peuvent être sélectionnés. Un « facteur de performance » permettant de classer les solutions par rapport au problème de la fatigue thermique a été construit (chapitre 4) et discuté dans deux situations :<p>- Lorsqu’un revêtement est présent, et que les contraintes d’origine thermique (différence de dilatation thermique couche-substrat) menacent de le rompre lors de l’immersion dans un milieu corrosif à haute température. Des essais de corrosion dans de l’aluminium fondu ont été réalisés sur un acier revêtu par du nitrure de chrome dopé à l’aluminium, synthétisé par déposition physique en phase vapeur (chapitre 5 – collaboration :Inasmet).<p>- Lorsque des variations thermiques rapides menacent de rompre le substrat et la (les) couches. Des essais de fatigue thermique ont été réalisés sur de l’acier à outils pour travail à chaud non traité, boruré ou recouvert d’un multitraitements (zircone yttriée / NiCrAlY / boruration / acier). Le revêtement en zircone yttriée a été obtenu par projection par plasma. L’essai de fatigue thermique a été modélisé et le facteur de performance, discuté (chapitre 6).<p>Au chapitre 7, les architectures-types ont été introduites dans une méthodologie de sélection des multi-traitements de surface, qui a été appliquée dans deux cas :<p>- Celui des moules de fonderie, devant résister à la fatigue thermique et à la corrosion par l’aluminium fondu. Le facteur de performance a été extrapolé à d’autres situations qu’aux chapitres 5 et 6. Les solutions habituellement proposées pour résoudre ce problème sont retrouvées.<p>- Celui de deux pièces en acier frottant l’une contre l’autre en présence d’aluminium fondu.<p><p>To select surface treatments, one must account for the required functional properties, the substrate features and the solicitations the substrate must endure. Certain combinations of these parameters make it difficult to select a single surface treatment, a reason why several successive treatments are preferred. To select them, one needs to determine:<p>- How to divide the several requests into groups and how to stack up these groups from the substrate to the outer surface, so that each treatment deals with one specific group of requests/properties.<p>- How to select individual layers for each group of properties.<p>- How to rank the multi-treatments in terms of relevance for a given application.<p>In this work, one tries to answer the first and the third questions, by studying the case of aluminium foundry, in which the industrial devices frequently face the following solicitations:<p>- Thermal stress (thermal fatigue, thermal expansion mismatch).<p>- Presence of corrosive molten metal.<p>- Sliding wear.<p>In the literature, several “standard” architectures are proposed (chapter 3), like a diffusion layer reducing superficial fatigue plus a corrosion barrier layer. A thermal barrier coating is also sometimes proposed.<p>For each of these architectures, one can select individual treatments. To rank them, one devised a “performance index” for thermal stress (chap.4), which is discussed for two cases:<p>- For large differences between layer and substrate thermal expansion coefficients, when both are put into contact with a high temperature corrosive medium, the layer may be damaged. One discusses this case by examining the corrosion caused by molten aluminium for a steel substrate coated by anticorrosive chromium nitride doped with aluminium. The layer is produced by physical vapour deposition (chap. 5 – cooperation: Inasmet).<p>- Repeated fast surface temperature transients can also damage the substrate and/or the layer by thermal fatigue. One conducted thermal fatigue tests with samples of hot work tool steel, respectively untreated, simply borided and protected by a multilayer. In the last case, top coat is yttria stabilised zirconia, followed by a nickel superalloy and then a borided layer (undercoat). One synthesized the zirconia coating by plasma spray and one modelled the thermal fatigue (chap. 6).<p>In chap. 7, architectures from chap. 2 are introduced in a multi-treatment selection routine, which is applied in two cases:<p>- Foundry moulds for molten aluminium, withstanding both thermal fatigue and corrosion. The devised performance index is extrapolated beyond the tests of chap. 5 and 6 to treatments for this industrial application, thereby quantifying their respective merits.<p>- A foundry device exposed to molten metal and sliding wear.<p><p>Doctorat en Sciences de l'ingénieurinfo:eu-repo/semantics/nonPublishe

A strategy for the selection of multiple materials and processes fulfilling inherently incompatible functions: The case of successive surface treatments

Multiple surface treatment technologies are used as an example of: (i) simultaneous selection of materials and processes; (ii) selection of multiple materials each of which fulfills different functions; and (iii) selection of materials with incompatibility issues. A questionnaire-based screening algorithm uses a small surface treatment database mostly filled in with Booleans to address these issues. It relies on the fact that functions can be brought by the first treatment, the latest treatment, all treatments or at least one treatment, like for corrosion resistance. Functions are associated with attributes and combinations of treatments are suggested. The system is illustrated for four examples (automobile corrosion protection, electronic packaging, aluminum die casting and wear protection of gears) and successfully proposes candidates from literature as well as alternatives. It can be used as an exchange tool between the users and the providers of surface treatments, as a marketing tool for a specific family of processes or as a complement to industrial drawing software.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

How to minimise thermal fatigue in surface multi-treatments and coatings?

A tool is developed to rank surface treated materials with respect to thermal fatigue. It comprises a modelling of the temperature profile in the component and an adaptation of the Coffin-Manson model for surface treatments fatigue. It is used as a performance index and discussed onto several surface treatments and multi-treatments relevant for the protection of steel in aluminium foundry moulds, exposed to thermal fatigue, with some insight in the effect of surface treatments processes on the final result. The model reproduces the well-known capability of duplex PVD nitride onto nitriding to withstand thermal fatigue. Using thermal barrier coatings may also be relevant, but the internal stress must be sufficiently compressive to be resistant to the studied thermal cycles. © 2012 Elsevier B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Accounting for surface treatments in life-cycle assessments

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A comparative assessment of WEEE collection in an urban and rural context: Case study on desktop computers in Belgium

In order to comply with the targeted collection rates set by new European waste management regulations, a better knowledge of Waste Electrical and Electronic Equipment (WEEE) collection flows is needed. This paper highlights the importance of considering the regional spatial context to develop an appropriate waste collection strategy. Through material flow analysis, we compare the collection flows of end-of-life desktop computers in two neighbouring regions and link the differences of collection rates with spatial ones. The Brussels Capital Region (BCR), an urban area, and the Walloon Region (WR), a mixed urban-rural area with a predominance of rural areas, are chosen as case studies. The quantities and collection flows of end-of-life desktop computers are estimated by combining statistics and reporting data. Globally, in the WR, 70.99% of end-of-life desktop computers are collected in accordance with the WEEE Directive while only 32.98% are in the BCR. This difference may be related to spatial context. For instance, the high population density increases the built-up areas and limits space for waste collection infrastructures. As a consequence, in the BCR, only 22.29% of end-of-life desktop computers from households are captured by compliant collection channels against 84.80% in the WR. The collection from businesses still needs to be developed in both regions but also suffers from this lack of infrastructures. While the reliability assessment of our estimates emphasizes a lack of data regarding non-compliant collection channels, our results underline the need to take into account the regional spatial context in setting up the collection of WEEE.SCOPUS: ar.jDecretOANoAutActifinfo:eu-repo/semantics/publishe

Recovery of metals from waste 1st generation photovoltaic panels: leaching behaviours in H2SO4, H2SO4 with H2O2 and HNO3

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Récents progrès en traitements de surface destinés aux dispositifs de fonderie de l’aluminium, y compris les multicouches

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Issues and limitation of recycling: The case of gallium

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