200 research outputs found
Elicitation and structuration of knowledge related to Additive Manufacturing
No full textCe travail contribue à proposer des méthodes et outils de gestion des connaissances (Knowledge Management) propres au domaine de la Fabrication Additive (FA). Le modèle KAM(Knowledge Aided Manufacturing) permet de représenter visuellement les états et actions en lien avec les activités spécifiques à la Fabrication Additive. Il inclut plusieurs types d’objets de connaissance dont le niveau de maturité dépend du degré de certitude ou conviction des experts FA interrogés individuellement et/ou collectivement.Plusieurs techniques et outils d’élicitation personnalisés sont testés puis éprouvés auprès de chercheurs et d’experts industriels impliqués dans la fabrication EBM. L’analyse en termes de connaissances procédurales et déclaratives qui en résulte permet une classification puis une structuration dans le KAM. Ceci nous amène à construire une ontologie sous forme de graphe conceptuel dont la dynamique varie en fonction de contraintes contextuelles (influences, règles d’état, lois) imposées par l’état du monde et de règles d’action dictées par le processus de FA à suivre.Ces éléments de connaissance ont pour but d’aider un utilisateur de FAAO (Fabrication Additive Assistée par Ordinateur) à : mieux appréhender le monde de la FA et en apprendre les principaux concepts ; simuler des actions et en évaluer les impacts en termes de valeur QCT (Qualité, Coût, Temps); décider et agir en conséquence avant de lancer une fabrication.Additive Manufacturing (AM) has enabled the building of parts with new shapes and geometrical features. As this technology modifies the practices, new knowledge is required for designing and manufacturing properly. To help experts create and share this knowledge through formalization, this research work focuses on knowledge elicitation, analysis and structuring. After defining knowledge concepts we present the SoA in knowledge elicitation and classification. Three case studies present different approaches to capture AM knowledge. The first one points out the assets and limits of three individual elicitation techniques. The second one describes tools and techniques to elicit and structure knowledge about support structures for EBM parts. The last one proposes a method to model AM process rules in relation with EBM technology. As a conclusion, we provide some propositions and recommendations for a better elicitation and formalization of AM knowledge
Systèmes et procédés pour la détermination de structures de support en fabrication additive
No full textA new method with ultrasonic mechanism for efficient depowdering of parts produced by electron beam melting
No full textInternational audienceAmong metallic additive manufacturing technologies, electron beam melting (EBM) requires a specific operation called depowdering once a part is built. With the help of a powder recovery system (PRS), this process consists in blowing titanium powder onto a “cake” of a manufactured part in order to separate sintered but not melted powder from the part itself. However, the depowdering of some geometries can in fact become difficult, even impossible, due to the part shape. This article aims at proposing an ultrasonic depowdering mechanism that allows to improve and to quantify the depowdering capabilities of the PRS system currently used. Experimentations are led onto geometries that include canals. A “depowderable depth”/diameter criterion is then applied for comparing the depowdering capacity of the proposed system with the traditional one. First results show that the quantity of powder removed onto samples is highly enhanced with an ultrasonic process. This outcome creates opportunities since additional tests could be implemented onto more complex shapes such as, for instance, parts with internal complex shapes
Proteomic analysis of inflammatory protein expression patterns in cell culture and transgenic animal models for Alzheimer's disease
No full textDementia is a syndrome characterized by failure of recent memory and other cognitive functions that is usually insidious in onset but steadily progresses with age. Alzheimer’s disease (AD) is the most common form of senile dementia. It is neuropathologically characterized by extracellular and perivascular aggregation of amyloid β (Aβ) peptide, by the generation of intracellular neurofibrillary tangles due to a hyperphosphorylation of tau protein and by an increased rate of neuronal degeneration. The degenerative process starts 20-30 years before the clinical onset of the disease. Clinical diagnosis of AD is difficult but possible, but can only be confirmed by biopsy or autopsy. At present, no biological marker exists for early diagnosis of AD during life. Therefore, identification of biomarkers for AD would be of great value for clinical diagnosis of incipient AD. Recent studies have proven the involvement of inflammatory processes in the neurodegenerative events in AD. Inflammation may not be the first event in the progression of the disease, but it involves activation of glia cells including microglia and astrocytes and subsequent release of proinflammatory mediators. Cytokines released such as IL-1, TNF-α and IL-6 are the main proinflammatory cytokines that can modulate inflammatory responses as well as glial proliferation and activation. Oxidative stress triggered by inflammatory processes causes changes in proteins such as tyrosine nitration or lipid peroxidation. Aβ deposits, tau hyperphosphorylation, inflammation and oxidative stress may finally lead to changes in synaptic connectivity and efficacy including perturbation of long-term potentiation (LTP), important in the formation of memory. Proteomic technology used in these studies is a recent technology which is a two step process: separation of proteins and their subsequent analysis by mass spectrometry. Moreover, this technology can provide new information concerning the expression level, post-translational modification of specific proteins as well as their conformational changes during disease progression. In our study, this technology was modified and improved, e.g by the miniaturization of the complete process. Proteomic technology was also used in parallel with other methods such as chromatography in order to increase the sensitivity of detection by mass spectrometry.
This study aimed:
1) To establish that cytokine treatment of human microglia cells is an efficient method to
study certain aspects of AD pathogenesis. For this analysis, a map of protein expression
in normal and in treated microglia cells was made.
2) To map protein expression in APP/PS2 transgenic mice, a model for human AD, in
order to compare human AD brain with murine models.
3) To identify highly nitrated proteins in brains of transgenic animals. Several proteins
were found to be modified after injury.
4) To provide evidence for instability of synapses in AD brains. To start with this study,
the technologies used to map mouse brain cytosolic proteins were improved.
5) To isolate synaptosomal membranes from the whole brain and to analyse it by massspectrometry.
For mapping synaptic membrane protein expression in controls or
transgenic mouse models, the technology was miniaturizated and optimized. This study is
still in progress
Proposition of a model to determine the process parameters for manufacturing thick parts with WAAM technology
No full textABSTRACTWire Arc Additive Manufacturing (WAAM) is a metallic additive manufacturing process based on the fusion of metallic wires using an electric arc as a heat source. The challenge associated with WAAM is heat management and understanding bead geometry. All of the process variables, such as travel speed (TS), wire feed speed (WFS), idle time, combine to produce the geometry of the deposited bead that results in the desired component shape. Therefore, determining a method for selecting a good combination of process parameters is critical to obtain a high-quality part. This article presents a study on how to control the WAAM process to produce a thick part of aluminium alloys. An experimental design is determined to study the influence between various process parameters such as WFS, TS, the layer height, or the length of the bead. Different samples are made using a Yaskawa robot, and the classic CMT (Cold Metal Transfer) mode as a manufacturing method. A new manufacturing method is then proposed by adding an important step in the process parameters determination. The results indicate that the length of the bead has a significant impact on the torch speed of the process
Retraction Note to: Omega-3 fatty acid levels in red blood cell membranes and physical decline over 3 years: longitudinal data from the MAPT study
No full textInternational audienceThe Editors-in-Chief have retracted this articlebecause it contains text in the introduction and dis-cussion sections that overlaps with a previous pub-lished article by a different author group [1]. BertrandFougere, Christelle Cantet, Gaelle Soriano, SophieGuyonnet, Philipe De Souto Barreto, Matteo Cesari,Sandrine Andrieu and Bruno Vellas agree with thisretraction. Bertrand Fougere agrees with this retrac-tion on behalf of the MAPT Study Group. SabineGossier has not responded to correspondence fromthe publisher about this retraction
Proposition d'intégration d'un outil d'aide à la décision dans les méthodologies multicritères de conception de produit
No full textInternational audienceLa conception de produits est un processus complexe nécessitant l'analyse de multiples paramètres. Cette complexité s'accentue dans les contextes collaboratifs, lorsque des parties prenantes aux objectifs divergents doivent concilier leurs perspectives. Bien que les méthodes d'analyse décisionnelle multicritère (MCDA) soient couramment employées pour comparer des solutions candidates selon plusieurs critères d'évaluation, elles peinent parfois à intégrer la subjectivité des décideurs et conduisent à des recommandations éloignées des attentes réelles.Plutôt que d'automatiser entièrement la prise de décision, il est proposé de redonner la main au décideur tout en l'accompagnant avec un outil adapté. Cet article étudie l'intégration d'un outil de représentation graphique dynamique, le Parallel Coordinate Plot (PCP), au sein des méthodes MCDA traditionnelles. L'utilisation de cet outil est proposée en substitution des calculs algorithmiques dans les étapes d'intégration des préférences des décideurs et de sélection d'une solution optimale. Contrairement aux méthodes classiques, cette approche favorise une approche interactive où les parties prenantes peuvent filtrer, ajuster et négocier les solutions en fonction de leurs priorités. La question de recherche traitée dans l'article la suivante : Comment intégrer cet outil de représentation dynamique au sein des méthodologies de décision multicritères dans le cadre de la conception de produit ?Pour répondre à cette problématique, une méthodologie en quatre phases est proposée : (1) formalisation du problème, (2) phase de créativité pour enrichir l'espace de solutions, (3) construction et représentation du modèle via le PCP, et (4) négociation et prise de décision collaborative.Un cas d'application est étudié dans un contexte collaboratif de reconception d'une pièce électromécanique. La représentation graphique du système a permis de faire émerger de nouveaux paramètres d'entrée et d'améliorer la compréhension du problème. Les experts ont ensuite pu identifier visuellement des compromis, ajuster leurs priorités et aboutir à un consensus. Cette approche répond aux limites des méthodes MCDA en réduisant l'effet boîte noire et la charge computationnelle liés au processus de décision, en permettant l'utilisation de grandeurs qualitatives et en proposant un support de négociation du poids des critères.Plusieurs perspectives de recherche ont été identifiées : l'intégration du PCP au sein des environnements de conception assistée par ordinateur (CAO), et l'optimisation des interactions entre les utilisateurs et le PCP en exploitant des technologies émergentes (comme la réalité augmentée ou l'intelligence artificielle)
A model for Manufacturing Large Parts with WAAM Technology
No full textInternational audienceWire Arc Additive Manufacturing (WAAM) is a metallic additive manufacturing process based on the fusion of metallic wire using an electric arc as a heat source. The challenge associated with WAAM is heat management and understanding bead geometry. The printing process involves high temperatures, which results in the build-up of residual stresses can often cause deformations in a component. All of the process variables, such as torch speed (TS), wire feed speed (WFS), idle time, combine to produce the geometry of the deposit bead that results in the desired component shape. So, determining a method for choosing a good combined parameter process is very important to obtain a high-quality part. This article presents a study on how to use the WAAM process to produce a complexity part of aluminium alloys. The step of the determination process parameter is concentrated to develop in this study. An experimental design is determined to study the influence between the process parameters, for example, WFS, TS, high layer, length of bead. Different samples are made using the Yaskawa robot, using the classic CMT (Cold Metal Transfer) as a manufacturing method, using zigzag filling as a manufacturing strategy with the same WFS and same idle times and different TS, different bead lengths. A new manufacturing method using the zigzag filling strategy is proposed by adding an important step in determining the process parameters. The results indicate that the length of the bead has a significant impact on another parameter of the process
Les femmes, le genre et les sexualités dans le Maghreb colonial (1830-1962)
No full textDans cet article, Christelle Taraud revient sur trente ans d’histoire des femmes, du genre et des sexualités au Maghreb à l’époque coloniale (1830-1962). Mettant l’accent sur l’apport fondamental des gender, subaltern & colonial studies, l’article vise aussi à faire un bilan critique des avancées, et au contraire des absences et résistances dans un champ qui, au moins depuis les années 1970, est en voie de constitution. Au cœur de l’article, cinq grandes thématiques – colonisation, peuplement et femmes européennes ; femmes européennes et femmes « indigènes » : une rencontre coloniale ? ; l’orientalisme recontextualisé ; sexualités en situation coloniale ; et femmes, hommes et guerre en contexte colonial – permettent d’avoir une vision claire, quoique non exhaustive, de la production historiographique des années 1980-2010.The article examines thirty years in the history of women, gender and sexualities in colonial Maghreb (1830-1962). The author emphasizes the essential contribution of gender and subaltern & colonial studies, while also offering a critical review of the advances, as well as the silences and resistances within the field. Five themes structure the analysis of the historiographic production between 1980 and the present – colonization, settlement and European women ; relationships between European women and indigenous women ; recontexualised orientalism ; sexualities in a colonial context ; women, men and war in colonial situations
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