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The invasion of multi-core and multi-processor platforms on all aspects of computing makes shared memory parallel programming mainstream. Yet, the fundamental problems of exploiting parallelism efficiently and correctly have not been fully addressed. Moreover, the execution model of these platforms (notably the relaxed memory models they implement) introduces new challenges to static and dynamic program analysis. In this work we address 1) the optimization of pessimistic implementations of critical sections and 2) the dynamic information flow analysis for parallel executions of multi-threaded programs. Critical sections are excerpts of code that must appear as executed atomically. Their pessimistic implementation reposes on synchronization mechanisms, such as mutexes, and consists into obtaining and releasing them at the beginning and end of the critical section respectively. We present a general algorithm for the acquisition/release of synchronization mechanisms and define on top of it several policies aiming to reduce contention by minimizing the possession time of synchronization mechanisms. We demonstrate the correctness of these policies (i.e. they preserve atomicity and guarantee deadlock freedom) and evaluate them experimentally. The second issue tackled is dynamic information flow analysis of parallel executions. Precisely tracking information flow of a parallel execution is infeasible due to non-deterministic accesses to shared memory. Most existing solutions that address this problem enforce a serial execution of the target application. This allows to obtain an explicit serialization of memory accesses but incurs both an execution-time overhead and eliminates the effects of relaxed memory models. In contrast, the technique we propose allows to predict the plausible serializations of a parallel execution with respect to the memory model. We applied this approach in the context of taint analysis , a dynamic information flow analysis widely used in vulnerability detection. To improve precision of taint analysis we further take into account the semantics of synchronization mechanisms such as mutexes, which restricts the predicted serializations accordingly. The solutions proposed have been implemented in proof of concept tools which allowed their evaluation on some hand-crafted examples. ; L'utilisation massive des plateformes multi-cœurs et multi-processeurs a pour effet de favoriser la programmation parallèle à mémoire partagée. Néanmoins, exploiter efficacement et de manière correcte le parallélisme sur ces plateformes reste un problème de recherche ouvert. De plus, leur modèle d'exécution sous-jacent, et notamment les modèles de mémoire "relâchés", posent de nouveaux défis pour les outils d'analyse statiques et dynamiques. Dans cette thèse nous abordons deux aspects importants dans le cadre de la programmation sur plateformes multi-cœurs et multi-processeurs: l'optimisation de sections critiques implémentées selon l'approche pessimiste, et l'analyse dynamique de flots d'informations. Les sections critiques définissent un ensemble d'accès mémoire qui doivent être exécutées de façon atomique. Leur implémentation pessimiste repose sur l'acquisition et le relâchement de mécanismes de synchronisation, tels que les verrous, en début et en fin de sections critiques. Nous présentons un algorithme générique pour l'acquisition/relâchement des mécanismes de synchronisation, et nous définissons sur cet algorithme un ensemble de politiques particulier ayant pour objectif d'augmenter le parallélisme en réduisant le temps de possession des verrous par les différentes threads. Nous montrons alors la correction de ces politiques (respect de l'atomicité et absence de blocages), et nous validons expérimentalement leur intérêt. Le deuxième point abordé est l'analyse dynamique de flot d'information pour des exécutions parallèles. Dans ce type d'analyse, l'enjeu est de définir précisément l'ordre dans lequel les accès à des mémoires partagées peuvent avoir lieu à l'exécution. La plupart des travaux existant sur ce thème se basent sur une exécution sérialisée du programme cible. Ceci permet d'obtenir une sérialisation explicite des accès mémoire mais entraîne un surcoût en temps d'exécution et ignore l'effet des modèles mémoire relâchées. A contrario, la technique que nous proposons permet de prédire l'ensemble des sérialisations possibles vis-a-vis de ce modèle mémoire à partir d'une seule exécution parallèle ("runtime prediction"). Nous avons développé cette approche dans le cadre de l'analyse de teinte, qui est largement utilisée en détection de vulnérabilités. Pour améliorer la précision de cette analyse nous prenons également en compte la sémantique des primitives de synchronisation qui réduisent le nombre de sérialisations valides. Les travaux proposé ont été implémentés dans des outils prototype qui ont permit leur évaluation sur des exemples représentatifs.

In this paper, we presented a unified and comprehensive model of behavior of shape memory materials and energy criterion for calculating the fatigue of structures operating in pseudo elastic. The model and the test is validated by comparing their predictions with experimental results. Our model has the following advantages: - It is complete, that is to say, it can simulate all the main phenomena behavior characteristics MMF. The simulation uses the same law of behavior and the same set of complementary legislation, which gives it a unified character; - Parameters are easy to identify; - The agreement of predictions with available experimental results is satisfactory; - Given the inclusion of non-proportional loadings, it is possible to perform calculations of structures subjected to loads MMF complex; - The cyclic loading are taken into account. It is therefore possible to determine the steady state of a structure subjected to cyclic phase change in repeated pseudoelastic. In particular, the model calculates the energy dissipated per cycle stabilized at any point of the structure and the energy criterion can then be used to estimate its lifetime. Our work paves the way for a more detailed modeling of the behavior of MMF, which can take into account some often neglected effects, such as formation of R phase, the occurrence of internal loops related expenses partial discharges in pseudoelastic and the asymmetry of behavior in tension and compression. We believe, moreover, it is possible to describe the dynamics MMF through an extension of this model. Experimentally, it would be interesting to apply new technologies to the study of shape memory materials. In this context, infrared thermography seems appropriate to characterize the location of the phase change at certain structures other techniques such as laser material interaction, promise a better description of the kinetics of martensitic transformation. In addition, the problem of fatigue MMF should be further researched. In the short term it is necessary to ...

In this paper, we presented a unified and comprehensive model of behavior of shape memory materials and energy criterion for calculating the fatigue of structures operating in pseudo elastic. The model and the test is validated by comparing their predictions with experimental results. Our model has the following advantages: - It is complete, that is to say, it can simulate all the main phenomena behavior characteristics MMF. The simulation uses the same law of behavior and the same set of complementary legislation, which gives it a unified character; - Parameters are easy to identify; - The agreement of predictions with available experimental results is satisfactory; - Given the inclusion of non-proportional loadings, it is possible to perform calculations of structures subjected to loads MMF complex; - The cyclic loading are taken into account. It is therefore possible to determine the steady state of a structure subjected to cyclic phase change in repeated pseudoelastic. In particular, the model calculates the energy dissipated per cycle stabilized at any point of the structure and the energy criterion can then be used to estimate its lifetime. Our work paves the way for a more detailed modeling of the behavior of MMF, which can take into account some often neglected effects, such as formation of R phase, the occurrence of internal loops related expenses partial discharges in pseudoelastic and the asymmetry of behavior in tension and compression. We believe, moreover, it is possible to describe the dynamics MMF through an extension of this model. Experimentally, it would be interesting to apply new technologies to the study of shape memory materials. In this context, infrared thermography seems appropriate to characterize the location of the phase change at certain structures other techniques such as laser material interaction, promise a better description of the kinetics of martensitic transformation. In addition, the problem of fatigue MMF should be further researched. In the short term it is necessary to ...

The arrival of Napoleonic troops in Italy in 1796 shapes the way in which Italian people design change in politics. First of all, the article seeks to demonstrate how the revolution drill brought by the French armies is described as an intimate and deep regeneration of Italian society. In the new republican regimes, citizens are supposed to live political life as a religious or emotional experience. In the 19th century, while contact with the ideas and men of the French Revolution was one of the main ingredients of the cultural origins of Risorgimento, Italian patriots did not dwell on the memory of the revolutionary decade. Rather, they pose an intellectual and political challenge to the French revolutionary model, seeking to distinguish their activism for Italian unification from the memory of 1789. The miners and democrats that make up the Italian nationalist movement take part with the same zeal, although their aims remain very different. ; Varia ; The arrival of Napoleonic troops in Italy in 1796 shapes the way in which Italian people design change in politics. First of all, the article seeks to demonstrate how the revolution drill brought by the French armies is described as an intimate and deep regeneration of Italian society. In the new republican regimes, citizens are supposed to live political life as a religious or emotional experience. In the 19th century, while contact with the ideas and men of the French Revolution was one of the main ingredients of the cultural origins of Risorgimento, Italian patriots did not dwell on the memory of the revolutionary decade. Rather, they pose an intellectual and political challenge to the French revolutionary model, seeking to distinguish their activism for Italian unification from the memory of 1789. The miners and democrats that make up the Italian nationalist movement take part with the same zeal, although their aims remain very different. ; International audience The arrival of Napoleonic troops in Italy shape the way Italians imagine political change. This ...

Searching for a new identity, the founders of the American Republic started ont by identifying with Rome and its heroes such as Cincinnatus, Brutus and Publicola. But the Roman model, rediscovered by reading Montesquieu, was problematic : the Republic was possible only on a small territory. Some critics of the 1787 federal constitution, e.g. Brutus, seized upon Montesquieu's arguments to discredit the work of the Philadelphia constituents, who reacted by literally turning Montesquieu upside down. The Republic, they claimed, was concevable only on a large territory, within a federal framework. The return to Antiquity advocated by the anti-federalists was absurd and dangerous, especially as the ancient city knew nothing of the great founding principle of the American Republic : the representative regime. That is probably why the ideologue Destutt de Tracy, Montesquieu's toughest critic and the impassioned defender of the "refusal of Rome ", was elevated to the rank of America's "philosopher " by Jefferson, his translater and admirer. ; A la recherche d'une identité nouvelle, les fondateurs de la République américaine n'hésitèrent pas, dans un premier temps, à s'identifier à Rome et à ses héros, tels Cincinnatus, Brutus, et Publicola. Mais le modèle romain, redécouvert à la lecture de Montesquieu, était problématique : la République n'était possible que sur un petit territoire. Des critiques de la Constitution fédérale de 1787, comme Brutus, s'emparèrent des arguments de Montesquieu pour discréditer l'œuvre des constituants de Philadelphie. Ces derniers réagirent en mettant littéralement Montesquieu la tête à l'envers. La République, prétendirent-ils, n'était concevable que sur un grand territoire, dans un cadre fédéral. Le retour à l'antique prôné par les antifédéralistes était absurde et dangereux, d'autant plus que la cité antique ignorait tout du grand principe fondateur de la République américaine : le régime représentatif. C'est sans doute pourquoi l'idéologue Destutt de Tracy, le plus sévère des critiques de ...

Searching for a new identity, the founders of the American Republic started ont by identifying with Rome and its heroes such as Cincinnatus, Brutus and Publicola. But the Roman model, rediscovered by reading Montesquieu, was problematic : the Republic was possible only on a small territory. Some critics of the 1787 federal constitution, e.g. Brutus, seized upon Montesquieu's arguments to discredit the work of the Philadelphia constituents, who reacted by literally turning Montesquieu upside down. The Republic, they claimed, was concevable only on a large territory, within a federal framework. The return to Antiquity advocated by the anti-federalists was absurd and dangerous, especially as the ancient city knew nothing of the great founding principle of the American Republic : the representative regime. That is probably why the ideologue Destutt de Tracy, Montesquieu's toughest critic and the impassioned defender of the "refusal of Rome ", was elevated to the rank of America's "philosopher " by Jefferson, his translater and admirer. ; A la recherche d'une identité nouvelle, les fondateurs de la République américaine n'hésitèrent pas, dans un premier temps, à s'identifier à Rome et à ses héros, tels Cincinnatus, Brutus, et Publicola. Mais le modèle romain, redécouvert à la lecture de Montesquieu, était problématique : la République n'était possible que sur un petit territoire. Des critiques de la Constitution fédérale de 1787, comme Brutus, s'emparèrent des arguments de Montesquieu pour discréditer l'œuvre des constituants de Philadelphie. Ces derniers réagirent en mettant littéralement Montesquieu la tête à l'envers. La République, prétendirent-ils, n'était concevable que sur un grand territoire, dans un cadre fédéral. Le retour à l'antique prôné par les antifédéralistes était absurde et dangereux, d'autant plus que la cité antique ignorait tout du grand principe fondateur de la République américaine : le régime représentatif. C'est sans doute pourquoi l'idéologue Destutt de Tracy, le plus sévère des critiques de Montesquieu et l'avocat passionné du « refus de Rome », est érigé au rang de « philosophe » de l'Amérique par Jefferson, son traducteur et admirateur.

Data servers are at the heart of information systems (IS) architecture. They consequently must be made of efficient resource management mechanisms and their resource management policies have to be adapted to the behavioral features of the IS. Unfortunately, it is not possible to build an universal data server that would fit any IS requirements. Actually, ISs differ significantly according to the data they manage, the nature of the applied treatments, guaranteed properties of execution, underlying hardware features, etc. Hence, any IS integrates its own data server with specific resource management policies. The drawbacks of such an approach are however far from being negligible. First, re-implementing elementary resource management mechanisms is not profitable. Second, because of the rigidity of their architecture, those IS are poorly reactive to (qualitative or quantitative) changes of information, treatments or hardware. Finally, the opaqueness of such systems makes them difficult to coexist on a same platform. In this thesis, we show that there is no ideal memory management policy. Rather than trying to provide an ideal server, we wish to define a framework that eases the design of adaptable data servers. We focus on the management of the memory of data servers deployed on clusters of workstations. We propose the ADAMS memory support based on an hierarchical management model and event-based communication model. This support eases the integration of different types of memory management policies by distinguishing their respective responsibilities but without doing any hypothesis on their inter-dependencies. We explain how we integrate ADAMS to the persistent and adaptable distributed shared memory provided by the Arias system. ADAMS extends the features of Arias so as to take into account the specific requirements of data servers and by reducing the granularity of adaptability. We illustrate through an example how the resulting support makes possible the design of data servers that can be dynamically adapted. ; Du fait qu'il constitue un passage obligé du flux d'information, un serveur de données joue un rôle central dans l'architecture d'un système d'information (SI). Il doit en conséquence implanter des mécanismes de gestion de ressources efficaces et des politiques de gestion adaptées aux caractéristiques comportementales du SI. Il n'est malheureusement pas possible d'offrir un serveur de données universel capable de répondre aux exigences de tous les SI. Ceux-ci diffèrent en effet significativement par le type des informations qu'ils traitent, la nature des traitements effectués, les propriétés de traitement qu'ils garantissent, les caractéristiques du matériel sous-jacent, etc. De ce fait, chaque système d'information intègre son ou ses propres serveurs de données implantant des politiques de gestion figées. Les inconvénients d'une telle approche sont loin d'être négligeables. Tout d'abord, la ré-implantation de mécanismes élémentaires de gestion de ressources augmente le coût de conception. Ensuite, la rigidité comportementale réduit considérablement la réactivité à l'évolution tant en qualité qu'en quantité des informations, traitements et ressources matérielles. Enfin, l'opacité des tels systèmes rend difficile leur coexistence sur une même plate-forme. Cette thèse montre qu'il n'existe pas de politique de gestion de la mémoire idéale. Plutôt que d'essayer d'offrir un serveur idéal, elle tente de définir une infrastructure permettant de concevoir des serveurs de données adaptés et évolutifs. Elle adresse plus particulièrement le problème de la gestion de la mémoire physique et se place dans le contexte des grappes de machines. Elle propose le support mémoire adaptable ADAMS basé sur un modèle de gestion hiérarchique et un modèle de communication par événements. Ce support facilite l'intégration de différents types de politiques tout en séparant bien leurs rôles respectifs sans faire d'hypothèse sur leur inter-dépendances. Une intégration d'ADAMS à la mémoire virtuelle répartie permanente et adaptable du système Arias est ensuite exposée. ADAMS étend les caractéristiques de ce système afin de prendre en compte les besoins particulier de gestion des serveurs de données tout en réduisant le grain d'adaptabilité. Nous illustrons à travers un exemple comment le support résultant permet d'implanter un serveur de données dont les politiques de gestion peuvent être adaptées dynamiquement.

The aim of this thesis is to model and to evaluate load transferring algorithms in parallel and/or distributed systems. After a synthesis of the different possible approaches of this load transfer and the main problems one gets both to install and to evaluate them with quantitative analysis, we study some models based on a Markovian evolution of the map of the total load of the whole set of processors. The performance indexes under consideration , in order to compare the values with and without transfer, are the memory saturation, the throughput, the workload and the mean response time. In the first two models, only two sites can transfer tasks on each other, but the communication and the transfer delays are taken into account. Critical values about accuracy or not of the transfer are obtained. When the communication and the transfer delays are negligible in front of the computation delays, two models are studied. The first one allows to evaluate a global load balancing algorithm for any number of sites fully connected, with finite memory capacity. This study yields the asymptotic behavior of massively parallel systems and upperbounds of some benefits that one can expect from a real transfer are derived. The second one takes into account the architecture of the net and the algorithm assumes that transfers occur between neighboring processors as soon as the load difference between them exceeds one. In the case of infinite lattice the model is proved to be ergodic and to converge exponentially fast to its equilibrium. Experimental results for different types of architectures are presented and compared to the solution of the mean field equations, that turn out in most cases to give fairly good approximation to the quantities of practical interest. Incidences of this politic of transfer on the values of the performance indexes are presented. ; Cette thèse porte sur la modélisation et l'evaluation d'algorithmes de transfert de charge dans des systèmes parallèles et/ou distribués. Après une synthèse des différentes ...

Shape memory alloys (SMA) undergo a solid-solid phase transformation called martensitic transformation, involving a "high temperature" phase, austenite, and a "low temperature" phase, martensite. The crystalline microstructure of the alloy alters mechanisms of transformations, and its pseudo-elastic behavior. The reduction of the grains to nanometric size shows new and unknown thermal and mechanical characteristics. Knowledge of thermomechanical behavior is however essential for the validation of multiaxial models to democratize the use of these materials. This work presents the development of innovative biaxial dynamic tests for the study of the pseudo-elastic mechanical behavior of a nickel titanium under biaxial dynamic compression. A single projectile, launched on a complex system of 45 ^ { circ} triangles, bars and transmitters, creates a biaxial solicitation of the sample. This mechanism ensures that the loads are synchronized along the two axes. Thanks to its architecture, the system makes possible many cases of multiaxial dynamic stress, unexplored until now. The forces and displacements across the sample are calculated independently, along both axes, from strain gauges glued on bars. The use of a thermal and optical camera allows strain and heating sources fields to be identified. The stress field is estimated by combining the information from the strain gauges placed on the bars and a finite element analysis of the specimen. The deformation appears homogeneous in the biaxial loading region of interest where a significant rise in temperature due to the phase change latent heat is observed. On the other hand the dynamic testing allows an equivalent dynamic stress/strain curve under biaxial and quasi-adiabatic conditions to be plotted. Experiments are finally compared to the results of finite difference axisymmetric model where the constitutive law is given by a fully coupled stochastic multiscale model. ; La microstructure cristalline de l'alliage joue un rôle vis-à-vis des mécanismes de transformations, ...

National audience Alvin Roth and Lloyd Shapley received in 2012 the Royal Bank of Sweden Prize for Economics in memory of Alfred Nobel, for their work on the centralised organisation of certain economic markets, which depend on the matching of agents of two distinct types (e.g. pupils and schools). Shapley is the co-author, together with David Gale, of the founding article of the domain, proposing an algorithm to achieve stable matching. Roth led the restructuring of the procedure for assigning in-house staff to hospitals in the United States and the design of a market for the transplantation of kidneys. After reporting on these contributions, we also discuss Shapley's decisive role in theory of games. ; Alvin Roth and Lloyd Shapley have received in 2012 the Sveriges Riksbank prize in economic sciences in memory of Alfred Nobel, for their work on the centralized organization of some economic markets, which rely on the matching of agents of two different types (students and schools, for instance). Shapley is the co-author, with David Gale, of the seminal paper of the area, which proposes an algorithm to reach a stable matching. Roth directed the reform of the entry level labor market for American physicians (the National Resident Matching Program) and the design of a market for kidney transplants. After having surveyed these contributions, we also give an account of Shapley's leading role in game theory. ; National audience Alvin Roth and Lloyd Shapley received in 2012 the Royal Bank of Sweden Prize for Economics in memory of Alfred Nobel, for their work on the centralised organisation of certain economic markets, which depend on the matching of agents of two distinct types (e.g. pupils and schools). Shapley is the co-author, together with David Gale, of the founding article of the domain, proposing an algorithm to achieve stable matching. Roth led the restructuring of the procedure for assigning in-house staff to hospitals in the United States and the design of a market for the transplantation of kidneys. After ...

The aim of this thesis is to model and to evaluate load transferring algorithms in parallel and/or distributed systems. After a synthesis of the different possible approaches of this load transfer and the main problems one gets both to install and to evaluate them with quantitative analysis, we study some models based on a Markovian evolution of the map of the total load of the whole set of processors. The performance indexes under consideration , in order to compare the values with and without transfer, are the memory saturation, the throughput, the workload and the mean response time. In the first two models, only two sites can transfer tasks on each other, but the communication and the transfer delays are taken into account. Critical values about accuracy or not of the transfer are obtained. When the communication and the transfer delays are negligible in front of the computation delays, two models are studied. The first one allows to evaluate a global load balancing algorithm for any number of sites fully connected, with finite memory capacity. This study yields the asymptotic behavior of massively parallel systems and upperbounds of some benefits that one can expect from a real transfer are derived. The second one takes into account the architecture of the net and the algorithm assumes that transfers occur between neighboring processors as soon as the load difference between them exceeds one. In the case of infinite lattice the model is proved to be ergodic and to converge exponentially fast to its equilibrium. Experimental results for different types of architectures are presented and compared to the solution of the mean field equations, that turn out in most cases to give fairly good approximation to the quantities of practical interest. Incidences of this politic of transfer on the values of the performance indexes are presented. ; Cette thèse porte sur la modélisation et l'evaluation d'algorithmes de transfert de charge dans des systèmes parallèles et/ou distribués. Après une synthèse des différentes approches possibles du transfert de charge et des problèmes rencontres pour leurs mises en oeuvre et leurs évaluations quantitatives, nous développons plusieurs modèles basés sur une évolution markovienne de la configuration des charges de l'ensemble des processeurs. Les indices de performance étudiés afin de comparer les valeurs obtenues avec transfert et sans transfert sont la saturation mémoire, le débit du système, la charge de travail et le temps de réponse moyen. Dans les deux premiers modèles seuls deux sites se transfèrent des tâches, mais les temps de communication et de transfert sont modélisés. Des valeurs critiques concernant la pertinence ou non du transfert sont obtenues. Lorsque les temps de communication et de transfert sont négligés devant les temps de calculs, deux modèles sont étudies. Le premier permet d'évaluer un algorithme d'équilibrage de charge pour un nombre quelconque de sites homogènes totalement connectés, de capacité mémoire finie. Cette étude permet de prévoir le comportement de systèmes massivement parallèles et des bornes supérieures de bénéfices que l'on peut attendre d'un réel transfert sont explicitées. Le deuxième prend en compte l'architecture du réseau et l'algorithme induit un transfert dés que la différence de charge entre deux sites voisins excède un. Dans le cas de réseaux infinis dont la topologie est régulière, ce modèle est ergodique et converge à vitesse exponentielle vers son régime stationnaire. Des résultats de simulations sont présentés pour différentes architectures et comparés aux solutions des équations de champ moyen, qui donnent de très bonnes approximations dans la plupart des cas pour les quantités d'intérêt pratique. Enfin, l'incidence sur la valeur des indices de performance est étudiée et interprétée.

Shape memory alloys (SMA) undergo a solid-solid phase transformation called martensitic transformation, involving a "high temperature" phase, austenite, and a "low temperature" phase, martensite. The crystalline microstructure of the alloy alters mechanisms of transformations, and its pseudo-elastic behavior. The reduction of the grains to nanometric size shows new and unknown thermal and mechanical characteristics. Knowledge of thermomechanical behavior is however essential for the validation of multiaxial models to democratize the use of these materials. This work presents the development of innovative biaxial dynamic tests for the study of the pseudo-elastic mechanical behavior of a nickel titanium under biaxial dynamic compression. A single projectile, launched on a complex system of 45 ^ { circ} triangles, bars and transmitters, creates a biaxial solicitation of the sample. This mechanism ensures that the loads are synchronized along the two axes. Thanks to its architecture, the system makes possible many cases of multiaxial dynamic stress, unexplored until now. The forces and displacements across the sample are calculated independently, along both axes, from strain gauges glued on bars. The use of a thermal and optical camera allows strain and heating sources fields to be identified. The stress field is estimated by combining the information from the strain gauges placed on the bars and a finite element analysis of the specimen. The deformation appears homogeneous in the biaxial loading region of interest where a significant rise in temperature due to the phase change latent heat is observed. On the other hand the dynamic testing allows an equivalent dynamic stress/strain curve under biaxial and quasi-adiabatic conditions to be plotted. Experiments are finally compared to the results of finite difference axisymmetric model where the constitutive law is given by a fully coupled stochastic multiscale model. ; La microstructure cristalline de l'alliage joue un rôle vis-à-vis des mécanismes de transformations, et de son comportement pseudo-élastique. La réduction des grains vers une taille nanométrique offre notamment des caractéristiques thermiques et mécaniques bien différentes et peu connues. La démocratisation de l'utilisation de ces matériaux passe par la validation de modèles complets et donc par la connaissance du comportement thermomécanique multiaxial dynamique. Ce travail propose la mise en place d'essais dynamiques biaxiaux innovants pour l'étude du comportement mécanique pseudo-élastique d'un nickel titane sous compression dynamique biaxiale. Un seul et unique projectile, lancé sur un système complexe de triangles à 45^{circ}, barres et renvois d'angles, permet de solliciter l'échantillon de manière biaxiale. Le mécanisme permet notamment d'assurer la synchronisation des chargements selon les deux axes. Grâce à son architecture, le banc d'essais rend possibles des cas de sollicitations dynamiques multiaxiales inexplorés jusqu'à présent. Le grand nombre de points de mesure par jauges de déformations collées sur les barres permet de calculer les efforts et déplacements aux limites de l'échantillon et ce indépendamment suivant les deux axes de sollicitation. L'utilisation d'une caméra thermique et d'une caméra optique permet d'identifier les champs de déformations et de sources de chaleur. Le champ de contrainte est estimé en combinant les informations des jauges de déformations et une analyse par éléments finis de l'échantillon. La déformation apparaît homogène dans la région de chargement biaxiale, où une augmentation significative de la température due à la chaleur latente de changement de phase est observée. Les essais dynamiques permettent d'autre part d'établir une courbe contrainte / déformation dynamique équivalente dans des conditions biaxiales et quasi-adiabatiques. Les expériences sont finalement comparées aux résultats du modèle axisymétrique en différences finies où la loi de comportement est donnée par un modèle multi-échelle stochastique entièrement couplé.

Shape memory alloys (SMA) undergo a solid-solid phase transformation called martensitic transformation, involving a "high temperature" phase, austenite, and a "low temperature" phase, martensite. The crystalline microstructure of the alloy alters mechanisms of transformations, and its pseudo-elastic behavior. The reduction of the grains to nanometric size shows new and unknown thermal and mechanical characteristics. Knowledge of thermomechanical behavior is however essential for the validation of multiaxial models to democratize the use of these materials. This work presents the development of innovative biaxial dynamic tests for the study of the pseudo-elastic mechanical behavior of a nickel titanium under biaxial dynamic compression. A single projectile, launched on a complex system of 45 ^ { circ} triangles, bars and transmitters, creates a biaxial solicitation of the sample. This mechanism ensures that the loads are synchronized along the two axes. Thanks to its architecture, the system makes possible many cases of multiaxial dynamic stress, unexplored until now. The forces and displacements across the sample are calculated independently, along both axes, from strain gauges glued on bars. The use of a thermal and optical camera allows strain and heating sources fields to be identified. The stress field is estimated by combining the information from the strain gauges placed on the bars and a finite element analysis of the specimen. The deformation appears homogeneous in the biaxial loading region of interest where a significant rise in temperature due to the phase change latent heat is observed. On the other hand the dynamic testing allows an equivalent dynamic stress/strain curve under biaxial and quasi-adiabatic conditions to be plotted. Experiments are finally compared to the results of finite difference axisymmetric model where the constitutive law is given by a fully coupled stochastic multiscale model. ; La microstructure cristalline de l'alliage joue un rôle vis-à-vis des mécanismes de transformations, et de son comportement pseudo-élastique. La réduction des grains vers une taille nanométrique offre notamment des caractéristiques thermiques et mécaniques bien différentes et peu connues. La démocratisation de l'utilisation de ces matériaux passe par la validation de modèles complets et donc par la connaissance du comportement thermomécanique multiaxial dynamique. Ce travail propose la mise en place d'essais dynamiques biaxiaux innovants pour l'étude du comportement mécanique pseudo-élastique d'un nickel titane sous compression dynamique biaxiale. Un seul et unique projectile, lancé sur un système complexe de triangles à 45^{circ}, barres et renvois d'angles, permet de solliciter l'échantillon de manière biaxiale. Le mécanisme permet notamment d'assurer la synchronisation des chargements selon les deux axes. Grâce à son architecture, le banc d'essais rend possibles des cas de sollicitations dynamiques multiaxiales inexplorés jusqu'à présent. Le grand nombre de points de mesure par jauges de déformations collées sur les barres permet de calculer les efforts et déplacements aux limites de l'échantillon et ce indépendamment suivant les deux axes de sollicitation. L'utilisation d'une caméra thermique et d'une caméra optique permet d'identifier les champs de déformations et de sources de chaleur. Le champ de contrainte est estimé en combinant les informations des jauges de déformations et une analyse par éléments finis de l'échantillon. La déformation apparaît homogène dans la région de chargement biaxiale, où une augmentation significative de la température due à la chaleur latente de changement de phase est observée. Les essais dynamiques permettent d'autre part d'établir une courbe contrainte / déformation dynamique équivalente dans des conditions biaxiales et quasi-adiabatiques. Les expériences sont finalement comparées aux résultats du modèle axisymétrique en différences finies où la loi de comportement est donnée par un modèle multi-échelle stochastique entièrement couplé.

Notre étude du concept de taux naturel de chômage a comme objectif une réflexion sur le concept et sa possible utilisation comme indicateur de politique économique. Après la réflexion faite sur le concept (I), nous présentons les principaux modèles théoriques qui déterminent le taux (II). Au-delà des problèmes soulevés par l'estimation économétrique, nous proposons, pour l'économie portugaise, une étude fondée sur des séries trimestrielles (III). Finalement nous concluons (IV). ; This paper presents some of the conclusions reached by us in the framework of a broader research on the Natural Rate of Unemployment (NRU). Our main aim is to ascertain the NRH properties as an economic indicator, placing special emphasis on the Portuguese economy. First we review the concept of NRU. Secondly we compare the two most important types of NRU models: the Phillips model, updated by Gordon's "triangle" model (1997) and Layard, Nickell and Jackman's model (1991) updated by Blanchard's version (1999). The economic and social factors leading to the existence of a short or medium-run varying NRU (NAIRU) or to the non-existence of a long-run NRU (NAIRU) are emphasised. Thirdly, some of the major difficulties concerning the econometric analysis of the NRU are pointed out. Fourthly, with a non-linear version of Elmeskov method we obtain a very stable and predictable series of the NRU dependent on cyclical and trend output. The AIC criterion leads to a long memory model. A near-VECM model produces impulse responses that confirm our previous results of hysteresis in unemployment rate. Finally we conclude.

International audience ; More than forty years have passed since the military coup of the 11th of September 1973, which overthrew the Government of Popular Unity headed by Salvador Allende and incarnating at that point of the Cold War the only hope of an alternative socialist model capable of spreading throughout the world. If 2013 marked an important moment of commemoration of the coup, notably in France, this article proposes an analysis of the effects of that event on the family memories of Chilean exiles and the retornados (literally "the returned") who predominately lived in France. In other words, this article addresses the issues of inheritance and construction of the self in the framework of a specific sociological case: exile and its corollary of return, alongside experiences of forced migration marked by political engagements with the left of the political spectrum and extreme violence, which has traumatized at least two generations. ; Plus de quarante années ont passé depuis le coup d'État militaire du 11 septembre 1973 qui renversa le gouvernement d'Unité Populaire, présidé par Salvador Allende, incarnant à ce moment de la guerre froide l'espoir d'un modèle d'alternative socialiste susceptible de se propager dans le monde. Si l'année 2013 a été l'occasion d'importantes commémorations de l'événement, en particulier en France, il s'agira ici d'analyser les effets de ce dernier sur les mémoires familiales d'exilés et retornados (littéralement retournés) chiliens, ayant vécu principalement en France. Autrement dit, il sera question d'héritage et de construction de soi, à partir d'un cas sociologique spécifique : l'exil et son corollaire le retour, expériences migratoires forcées marquées par des engagements politiques sur la gauche de l'échiquier politique et par la violence extrême, traumatisant au moins deux générations.