Brief overview of CMCs engine components experiments coupled with representative sub-element tests

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aIOLi : gestion des Entrées/Sorties Parallèles dans les grappes SMP

Un grand nombre d'applications scientifiques (biologie, climatologie, ...) utilisent et génèrent des quantités de données qui ne cessent de croître en plus de modes d'accès parallèles qui leur sont particuliers. Aux problématiques " out-of-core " ou " parallel I/O " longuement abordées dans un contexte d'accès local, viennent s'ajouter les onsidérations et les contraintes imposées par un environnement distribué comme l'est une grappe. Plusieurs approches ont été proposées à la communauté scientifique dans le but d'améliorer les performances lors d'accès parallèles à des fichiers distants (systèmes de fichiers ou encore librairies d'entrées/sorties spécialisées). Toutefois, ces solutions intègrent des API plus ou moins lourdes mais surtout spécifiques qui nécessitent une connaissance exacte de chaque subtilité interne au modèle. Ce papier présente la solution " aIOLi " : une librairie transparente et efficace pour les accès parallèles aux fichiers au sein d'une grappe SMP. En intervenant au niveau des points de concentration, aIOLI exploite des algorithmes d'Entrées/Sorties parallèles sans pour autant faire appel à des mécanismes de synchronisations inter-processus et en s'appuyant simplement sur les interfaces standard de la librairie C (open/lseek/read/write/close). Les performances obtenues avec notre prototype atteignent les limites du système de stockage distant

Excitons in InGaAs Quantum Dots without Electron Wetting Layer States

The Stranski-Krastanov (SK) growth-mode facilitates the self-assembly of quantum dots (QDs) using lattice-mismatched semiconductors, for instance InAs and GaAs. SK QDs are defect-free and can be embedded in heterostructures and nano-engineered devices. InAs QDs are excellent photon emitters: QD-excitons, electron-hole bound pairs, are exploited as emitters of high quality single photons for quantum communication. One significant drawback of the SK-mode is the wetting layer (WL). The WL results in a continuum rather close in energy to the QD-confined-states. The WL-states lead to unwanted scattering and dephasing processes of QD-excitons. Here, we report that a slight modification to the SK-growth-protocol of InAs on GaAs -- we add a monolayer of AlAs following InAs QD formation -- results in a radical change to the QD-excitons. Extensive characterisation demonstrates that this additional layer eliminates the WL-continuum for electrons enabling the creation of highly charged excitons where up to six electrons occupy the same QD. Single QDs grown with this protocol exhibit optical linewidths matching those of the very best SK QDs making them an attractive alternative to standard InGaAs QDs

Holographie électronique en champ sombre (une technique fiable pour mesurer des déformations dans les dispositifs de la microélectronique)

Les contraintes font maintenant partie des boosters de la microélectronique au même titre que le SOI (silicium sur isolant) ou le couple grille métallique / diélectrique haute permittivité. Appliquer une contrainte au niveau du canal des transistors MOSFETs (transistors à effet de champ à structure métal-oxyde-semiconducteur) permet d'augmenter de façon significative la mobilité des porteurs de charge. Il y a par conséquent un besoin de caractériser les déformations induites par ces contraintes à l'échelle nanométrique. L'holographie électronique en champ sombre est une technique de MET (Microscopie Électronique en Transmission) inventée en 2008 qui permet d'effectuer des cartographies quantitatives de déformation avec une résolution spatiale nanométrique et un champ de vue micrométrique. Dans cette thèse, la technique a été développée sur le microscope Titan du CEA. Différentes expériences ont été réalisées afin d'optimiser la préparation d'échantillon, les conditions d'illumination, d'acquisition et de reconstruction des hologrammes. La sensibilité et la justesse de mesure de la technique ont été évaluées en caractérisant des couches minces épitaxiées de Si_{1-x}Ge_{x}/Si et en effectuant des comparaisons avec des simulations mécaniques par éléments finis. Par la suite, la technique a été appliquée à la caractérisation de réseaux recuits de SiGe(C)/Si utilisés dans la conception de nouveaux transistors multi-canaux ou multi-fils. L'influence des phénomènes de relaxation, tels que l'interdiffusion du Ge et la formation des clusters de b-SiC a été étudiée. Enfin, l'holographie en champ sombre a été appliquée sur des transistors pMOS placés en déformation uniaxiale par des films stresseurs de SiN et des sources/drains de SiGe. Les mesures ont notamment permis de vérifier l'additivité des deux procédés de déformation.Strain engineering is now considered as one of the most important boosters of microelectronics among other technologies such as SOI (Silicon On Insulator) and high- metal gates. By applying a stress in the channel of MOSFET (Metal Oxyde Semiconductor Field Effect Transistor) devices, the charge carriers mobility can be significantly increased. Consequently, there is now a need for a strain metrology at the nanometer scale. Dark-field electron holography is a TEM (Transmission Electron Microscopy) technique invented in 2008 that allows to map strain with micrometer field-of-view and nanometer spatial resolution. In this thesis, the technique was developed on the CEA Titan microscope. First, different developements were carried out concerning the sample preparation, the illumination/acquisition conditions and the reconstruction of the holograms. The sensitivity and the accuracy of the technique were evaluated through the characterization of Si_{1-x}Ge_{x} layers epitaxied on Si and by comparing the results with mechanical finite element simulations. Then, the technique was applied to the study of annealed SiGe(C)/Si superlattices that are used in the construction of new 3D architectures such as multichannel or multiwires transistors. The influence of the different relaxation mechanisms on the strain especially Ge interdiffusion and b-SiC clusters formation was investigated. Finally, dark-field electron holography was applied to the characterization of uniaxially strained pMOS transistors by SiN liners and recessed SiGe sources and drains. The measurements allowed to confirm the strain additivity of the two processes.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

A Phase Field Approach to Limited-angle Tomographic Reconstruction

The tomography of an object with limited angle can be addressed through Iterative Reconstruction Reprojection (IRR) procedure, wherein a standard reconstruction procedure is used together with a “filtering” of the image at each iteration. It is here proposed to use as a filter a phase-field—or Cahn-Hilliard—regularization interlaced with a filtered back-projection reconstruction. This reconstruction procedure is tested on a cone-beam tomography of a 3D woven ceramic composite material, and is shown to retrieve a reconstructed volume with very low artifacts in spite of a large missing angle interval (up to 28%)

J Synchrotron Rad

A high-temperature multi-axial test is carried out to characterize the thermo-mechanical behaviour of a 3D-woven SiC/SiC composite aeronautical part under loads representative of operating conditions. The sample is L-shaped and cut out from the part. It is subjected to severe thermal gradients and a superimposed mechanical load that progressively increases up to the first damage. The sample shape and its associated microstructure, the heterogeneity of the stress field and the limited accessibility to regions susceptible to damage require non-contact imaging modalities. An in situ experiment, conducted with a dedicated testing machine at the SOLEIL synchrotron facility, provides the sample microstructure from computed micro-tomographic imaging and thermal loads from infrared thermography. Experimental constraints lead to non-ideal acquisition conditions for both measurement modalities. This article details the procedure of correcting artefacts to use the volumes for quantitative exploitation (i.e. full-field measurement, model validation and identification). After proper processing, despite its complexity, the in situ experiment provides high-quality data about a part under realistic operating conditions. The influence of the mesostructure on fracture phenomena can be inferred from the tomography in the damaged state. Experiments show that the localization of damage initiation is driven by the geometry, while the woven structure moderates the crack propagation. This study widens the scope of in situ thermo-mechanical experiments to more complex loading states, closer to in-service conditions

Combining Ontology Alignment with Model Driven Engineering Techniques for Home Devices Interoperability

International audienceUbiquitous Systems are expected in the near future to have much more impact on our daily tasks thanks to advances in embedded systems, "Plug-n-Play" protocols and software architectures. Such protocols target home devices and enables automatic discovery and interaction among them. Consequently, smart applications are shaping the home into a smart one by orchestrating devices in an elegant manner. Currently, several protocols coexist in smart homes but interactions between devices cannot be put into action unless devices are supporting the same protocol. Furthermore, smart applications must know in advance names of services and devices to interact with them. However, such names are semantically equivalent but syntactically different needing translation mechanisms. In order to reduce human efforts for achieving interoperability, we introduce an approach combining ontology alignment techniques with those of Model Driven Engineering domain to reach a dynamic service adaptation