Evidence and modeling of mechanoluminescence in a transparent glass particulate composite

International audienceMechanoluminescence (ML) of a transparent alkali-phosphate glass composite with SrAl2O4:Eu, Dy particles is reported. Uniaxial compression experiments show the linear dependence of the mechanoluminescence intensity with the mechanical power. A theoretical model, based on the physics of delayed processes (in analogy of viscoelasticity), is proposed. This model accurately predicts the ML intensity changes induced by a complex mechanical loading and provides a convincing description of the mechanoluminescence response

A relationship between non-exponential stress relaxation and delayed elasticity in the viscoelastic process in amorphous solids: Illustration on a chalcogenide glass

International audienceInorganic glasses are viscoelastic materials since they exhibit, below as well as above their glass transition temperature, a viscoelas-tic deformation under stress, which can be decomposed into a sum of an elastic part, an inelastic (or viscous) part and a delayed elastic part. The delayed elastic part is responsible for the non-linear primary creep stage observed during creep tests. During a stress relaxation test, the strain, imposed, is initially fully elastic, but is transformed, as the stress relaxes, into an inelastic and a delayed elastic strains. For linear viscoelastic materials, if the stress relaxation function can be fitted by a stretched exponential function, the evolution of each part of the strain can be predicted using the Boltzmann superposition principle. We develop here the equations of these evolutions, and we illustrate their accuracy by comparing them with experimental evolutions measured on GeSe 9 glass fibers. We illustrate also, by simple equations, the relationship between any kind of relaxation function based on additive contribution of different relaxation processes and the delayed elastic contribution to stress relaxation: the delayed elasticity is directly correlated to the dispersion of relaxations times of the processes involved during relaxation

Vérification de la sûreté des systèmes hybrides (calcul d atteignabilité par abstractions linéaires)

Dans cette thèse, nous proposons des techniques algorithmiques de vérification formelle de propriétés pour des systèmes dynamiques hybrides (continus/discrets). Ces techniques de vérification se basent sur le calcul de l espace atteignable à partir d une région initiale pour déterminer si l intersection de cet espace avec le domaine à éviter est bien vide. Notre méthode consiste à partitionner l espace d état du système complexe en régions et à approximer pour chacune de ces régions la dynamique du système étudié par une dynamique plus simple. Nous présentons des extensions à une proposition précédente afin de prendre en compte des incertitudes dans les dynamiques affines. Dans un premier temps cette incertitude est considérée comme invariante. Dans un second temps nous la considérons variante. Cette deuxième extension permet de considérer l atteignabilité des systèmes non-linéaires.This thesis offers a practical framework for the formal verification properties of hybrid dynamic systems. In other words, the reachable space from an initial set of states is computed, and this space is then checked for intersection with the set to be of undesirable states. Our method computes an over approximation of the reachable space. This method is based on a partition of the continuous state space and on an abstraction of the continuous dynamics in each cell by a simpler one. We present an extension to uncertain systems of an approach which computes the reachable space of autonomous hybrid affine systems. Two cases are distinguished in order to analyze the reachability of these systems. One concerns fixed uncertainties in time and the other time dependant uncertainties variables. An extension of the approach offered for the uncertain hybrid affine systems is then developed to take into account non-linear dynamics.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Commande générique d ouvrants pilotés Automobiles garantissant la sécurité utilisateur

Nous assistons depuis plusieurs années à une multiplication des ouvrants pilotés dans le domaine Automobile. En effet, les constructeurs sont sans cesse dans l obligation d innover pour rester attractifs et différenciants pour le client. Il faut alors assurer un fonctionnement sûr et robuste du système d ouvrant piloté automatisé. Dès lors, il devient nécessaire de concevoir des méthodes de détection d obstacle génériques, pour garantir la sécurité de l utilisateur. Deux approches distinctes sont proposées en fonction de la qualité de la mesure. Dans un premier cas, la formalisation des incertitudes de la mesure est développée pour assurer une détection rapide, robuste, et au paramétrage simplifié, malgré le peu d informations disponibles. Dans un second cas, des synthèses innovantes d observateurs d effort extérieur sur l ouvrant sont proposées, à l aide du modèle physique du système. Ces deux approches sont validées sur des applications représentatives, en simulation et sur moyens d essais.We have been witnessing for several years an increase of opening parts in Automotive. Indeed, car manufacturers must continuously innovate to keep their models attractive and differentiating for the customer. Secure and robust opening part system must be ensured. Therefore, it becomes necessary to develop generic methods of obstacle detection to ensure user s safety. Two differents approaches are proposed based on measurement quality. In one case, the formalization of measurement uncertainty is developed to guaranty early and robust detection, with simplified tuning, despite the limited information available. In a second case, innovative observers syntheses for opening part external effort are proposed, based on physical models of the system. Both approaches are validated on representative applications by simulation and test facilities.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Modélisation comportementale des composants et des applications de contrôle-commande IEC 61499

Les applications de commande présentent un caractère distribué qui s'accompagne de forts besoins de sûreté et de validation. La norme IEC 61499 définit un modèle de composants logiciels sous la forme de blocs fonctionnels. Si l'utilisation de tels blocs fonctionnels permet de répondre aux exigences de modularité et de réutilisation, elle pose des problèmes de validation du comportement des applications, auxquels le test seul ne peut pas apporter toutes les solutions. Nous proposons dans ce travail une modélisation formelle du comportement des blocs fonctionnels et de leurs interactions sous la forme d'un réseau d'automates temporisés. La construction du modèle de l'application se fait par la composition des modèles associés aux blocs fonctionnels élémentaires en cohérence avec la démarche de construction de l'application elle-même. Afin de limiter la complexité des modèles élémentaires, en cohérence avec le modèle d'exécution, ceux-ci sont basés sur le concept de réactions aux événements extérieurs. Le développement d'un outil de traduction automatique et son application à la validation d'un exemple permettent de valider ces concepts de modélisation.RENNES1-BU Sciences Philo (352382102) / SudocCACHAN-ENS (940162301) / SudocSudocFranceF

Du composant à l automate hybride pour la modélisation et la simulation des systèmes en commutation (application à l électronique de puissance)

Les avancées des dernières décennies dans le domaine de l électronique ont permis l intégration plus facile des dispositifs de commande à base de convertisseur sur un plus grandnombre d application, des plus simples, tel que les sources d alimentation des PCs, la téléphonie mobile, l alimentation des moteurs à courant continu, au plus complexes, tel que les technologies aérospatiales, les appareils à utilisation médicales, les TGVs, etc. Afin de mieux prendre en compte la complexité de tels systèmes, dans les dix dernières années, le paradigme des systèmes hybrides a été appliqué pour la résolution des problèmes rencontrés dans ce domaine. Dans ce contexte, l objectif de la thèse est de proposer une démarche compositionnelle systématique qui associant un nouveau modèle logique pour les conditions de commutation des interrupteurs en complément de leur aspect énergétique permet d obtenir un modèle complètement explicite. Cette approche doit permettre un traitement unitaire dans les phases de modélisation et de simulation de tous les convertisseurs utilisés dans les applications.The goal of this thesis is to provide a systematic method that finds an explicit model for electronic power converters in the context of hybrid dynamical systems. This study has been triggered by the wide integration of these devices in control in a large area of applications (e.g. the power supplies for PCs, mobile phones and DC motors, medical use equipment, TGVs, aeronautics, etc.) and the latest interest from the control engineering community in addressing this kind of problems from the hybrid systems point of view. In order to achieve the objective, the present work integrates in a compositional approach previous results issued from energy based formalisms like the bond graphs with a new switch model that enhances the logical commutation conditions. The proposed method provides a generic solution for the modelling and the simulation phases of electronic power converters, from simple ones, as the buck , the boost , the buckboost , to more complex resonant converters, one such converter issued from medical imaging being used as a case study.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Detection and Mitigation of Corrupted Information in Distributed Model Predictive Control Based on Resource Allocation

International audienceIn distributed predictive control structures, communication among agents is required to achieve a consensus and approach an optimal global behavior. Such negotiation mechanisms are sensitive to attacks on these exchanges. This paper proposes a monitoring scheme that detects and mitigates these attacks’ effects in a resource allocation framework. The performance of the proposed method is illustrated through simulations of the temperature control of multiple rooms under power scarcity

Tombes et ensembles funéraires d’époque romaine en Pays de la Loire

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Nesting and fate of transplanted stem cells in hypoxic/ischemic injured tissues: The role of HIF1α /sirtuins and downstream molecular interactions

International audienceOxidative stress (OS) plays a pivotal role in diabetes mellitus (DM) onset, progression, and chronic complications. Hyperglycemia-induced reactive oxygen species (ROS) have been shown to reduce insulin secretion from pancreatic β-cells, to impair insulin sensitivity and signaling in insulin-responsive tissues, and to alter endothelial cells function in both type 1 and type 2 DM. As a powerful antioxidant without side effects, astaxanthin (ASX), a xanthophyll carotenoid, has been suggested to contribute to the prevention and treatment of DM-associated pathologies. ASX reduces inflammation, OS, and apoptosis by regulating different OS pathways though the exact mechanism remains elusive. Based on several studies conducted on type 1 and type 2 DM animal models, orally or parenterally administrated ASX improves insulin resistance and insulin secretion; reduces hyperglycemia; and exerts protective effects against retinopathy, nephropathy, and neuropathy. However, more experimental support is needed to define conditions for its use. Moreover, its efficacy in diabetic patients is poorly explored. In the present review, we aimed to identify the up-to-date biological effects and underlying mechanisms of ASX on the ROS-induced DM-associated metabolic disorders and subsequent complications. The development of an in-depth research to better understand the biological mechanisms involved and to identify the most effective ASX dosage and route of administration is deemed necessary

Impact of Astaxanthin on Diabetes Pathogenesis and Chronic Complications.

International audienceOxidative stress (OS) plays a pivotal role in diabetes mellitus (DM) onset, progression, and chronic complications. Hyperglycemia-induced reactive oxygen species (ROS) have been shown to reduce insulin secretion from pancreatic β-cells, to impair insulin sensitivity and signaling in insulin-responsive tissues, and to alter endothelial cells function in both type 1 and type 2 DM. As a powerful antioxidant without side effects, astaxanthin (ASX), a xanthophyll carotenoid, has been suggested to contribute to the prevention and treatment of DM-associated pathologies. ASX reduces inflammation, OS, and apoptosis by regulating different OS pathways though the exact mechanism remains elusive. Based on several studies conducted on type 1 and type 2 DM animal models, orally or parenterally administrated ASX improves insulin resistance and insulin secretion; reduces hyperglycemia; and exerts protective effects against retinopathy, nephropathy, and neuropathy. However, more experimental support is needed to define conditions for its use. Moreover, its efficacy in diabetic patients is poorly explored. In the present review, we aimed to identify the up-to-date biological effects and underlying mechanisms of ASX on the ROS-induced DM-associated metabolic disorders and subsequent complications. The development of an in-depth research to better understand the biological mechanisms involved and to identify the most effective ASX dosage and route of administration is deemed necessary