Jurnal Edukasi
Not a member yet
4879 research outputs found
Sort by
Pressure Control of Cuprophilic Interactions in a Luminescent Mechanochromic Copper Cluster
No full textInternational audienceFor the development of applications based on mechanochromic luminescent materials, acomprehensive study of the mechanism responsible for the emission changes is required. We report thestudy of a mechanochromic copper iodide cluster under hydrostatic pressure, which allows control ofcrystal packing via modification of the intermolecular interactions. In situ single-crystal powder X-raydiffraction analysis and emission measurements under pressure permit one to establish a directcorrelation between the molecular structure and luminescence properties and, in particular, todemonstrate that cuprophilic interactions are responsible for the stimuli-responsive luminescenceproperties of such multinuclear coordination compounds
Electronic properties of CVD Graphene capped with p and n-type doped amorphous silicon
No full textInternational audienc
SiGe Low Temperature Epitaxy by PECVD on III-V MOVPE Grown Material for High Efficiency Tandem Solar Cell Applications
No full textInternational audienc
Investigation of Photovoltaic Properties of Single Core–Shell GaN/InGaN Wires
No full textInternational audienc
The Computability Path Ordering
No full textInternational audienceThis paper aims at carrying out termination proofs for simply typed higher-order calculi automatically by using ordering comparisons. To this end, we introduce the computability path ordering (CPO), a recursive relation on terms obtained by lifting a precedence on function symbols. A first version, core CPO, is essentially obtained from the higher-order recursive path ordering (HORPO) by eliminating type checks from some recursive calls and by incorporating the treatment of bound variables as in the so-called computability closure. The well-foundedness proof shows that core CPO captures the essence of computability arguments à la Tait and Girard, therefore explaining its name. We further show that no more type check can be eliminated from its recursive calls without loosing well-foundedness, but one for which we found no counterexample yet. Two extensions of core CPO are then introduced which allow one to consider: the first, higher-order inductive types; the second, a precedence in which some function symbols are smaller than application and abstraction
THÈSE Caractérisation Expérimentale, Modélisation et Simulation des Elastomères Magnéto-Rhéologiques
No full textIn this thesis, we study a class of active materials named Magneto-Rheological Elastomers (MREs) with a main focus on their coupled magneto-mechanical response up to large strains and up to high magnetic fields. With the purpose of achieving a coupled characterization of MREs behavior for the design of haptic interface devices, this work encompasses experimental, theoretical and numerical developments.The first part of this work is dedicated to aspects pertaining to sample fabrication. Isotropic and magnetic field-cured MREs, composed of soft silicone rubber and micrometric carbonyl iron powder, are manufactured using a reliable and repeatable process. A special sample geometry is designed in order to obtain both homogeneous mechanical and magnetic fields during the coupled-field characterization. The interfacial adhesion between the iron fillers and the silicone matrix in MREs submitted to large deformations is investigated and a critical strain threshold is identified beyond which a primer treatment of the particles is needed to prevent debonding between the particles and the matrix.The second part of this thesis focuses on the coupled magneto-mechanical characterization of MREs and involves both theoretical and experimental developments. Based on the general theoretical framework for transversely isotropic magneto-elastic continua proposed by Kankanala, Danas and Triantafyllidis [Kan04, Dan12, Dan14], the coupled magneto-mechanical constitutive laws for both isotropic and anisotropic MREs are used to determine experimentally the corresponding constitutive model’s material parameters. The actual characterization of MREs is conducted thanks to a specially designed and novel experimental setup allowing tensile tests up to large strains and under high magnetic fields. The experimental data thus obtained provide the constitutive models for the isotropic and anisotropic MREs needed as input for the subsequent numerical simulations.The third part of this work pertains to the experiments, modeling and numerical calculations for boundary value problems corresponding to the design of a haptic interface prototype. A coupled variational formulation for a non-uniform applied magnetic field, using displacement, magnetic vector potential and magnetization as independent variables, is proposed and subsequently applied to the solution of the boundary value problem of an MRE layer subjected to the spatially localized magnetic field produced by an electromagnetic coil. The axisymmetric problem is solved numerically using finite element analysis. The device has been built and experimental results are compared to numerical simulations, thus providing a benchmark for the validation of the axisymmetric simulations as well as a proof of concept for the design of haptic interface applications.Cette thèse porte sur une classe de matériaux actifs nommés Elastomères Magnéto-Rhéologiques (EMR) et en particulier sur leur réponse magnéto-mécanique en grandes déformations et en présence de champs magnétiques élevés. Dans l'objectif d'aboutir à une caractérisation couplée du comportement des EMR pour permettre le design d'interfaces haptiques, ce travail comporte des développements expérimentaux, théoriques et numériques.La première partie de ce travail s'intéresse aux aspects liés à la fabrication des échantillons. Des EMR isotropes et structurés par l'application d'un champ magnétique pendant la fabrication, composés d'une matrice de silicone mou et de particules de fer doux micrométriques, sont fabriqués de façon précise et répétable. Un échantillon dédié est également développé afin d'obtenir simultanément des champs mécaniques et magnétiques homogènes dans celui-ci lors de la caractérisation couplée. La question de l'adhésion interfaciale entre les particules de fer doux et la matrice de silicone est également étudiée pour des EMR soumis à de grandes déformations et un seuil de déformation critique est identifié, au-delà duquel un traitement chimique des particules devient nécessaire pour éviter la décohésion entre les particules et la matrice.La seconde partie de cette thèse couvre la caractérisation magnéto-mécanique couplée des EMR et comporte des développement numériques et expérimentaux. S'appuyant sur le cadre théorique général des solides magnéto-élastiques continus isotropes transverses proposé par Kankanala, Danas and Triantafyllidis [Kan04, Dan12, Dan14], les lois de comportement magnéto-mécaniques couplées pour des EMR isotropes et anisotropes sont utilisées pour obtenir expérimentalement les jeux de paramètres matériaux du modèle de comportement correspondant. La caractérisation expérimentale est réalisée grâce à un dispositif dédié et original permettant de mener des essais de traction uniaxiale en grandes déformations et sous champs magnétiques élevés. Les données expérimentales ainsi obtenues fournissent les modèles de comportement des EMR isotropes et anisotropes nécessaires pour pouvoir mener ensuite des simulations numériques.La troisième partie de ce travail concerne les expériences, la modélisation et les simulations numériques de problèmes aux limites correspondant au design d'un prototype d'interface haptique. Une formulation variationnelle couplée pour un champ magnétique non uniforme, utilisant le déplacement, le vecteur potentiel magnétique et la magnétisation comme variables indépendantes, est proposée et appliquée pour obtenir la solution d'un problème aux limites pour une couche d'EMR soumise à un champ localisé produit par une bobine électromagnétique. Le problème axisymétrique est résolu par éléments finis. Un prototype d'interface haptique a été développé et les résultats expérimentaux sont comparés aux simulations numériques, servant ainsi à la fois de validation expérimentale pour les simulations éléments finis axisymétriques mais aussi de preuve de concept pour l'application technologique correspondante
Tissue tomographic phase image contrast improvement with adaptive optics
No full textInternational audienc
Quantitative phase imaging with a 3D resolution equivalent to fluorescence: application to label-free biological tissue reconstruction
No full textInternational audienc
In situ monitoring of the deformation mechanisms in titanium with different oxygen contents.
No full textInternational audienceThe deformation mechanisms of two titanium batches with different oxygen contents were monitored during tensile tests performed along the rolling and transverse directions under an optical or scanning electron microscope, after EBSD mappings of grain orientations. Whereas the contribution of mechanical twinning was very limited, grain boundary sliding, sometimes leading to intergranular decohesion, as well as kink bands formation were observed. Based on the identification of the primary slip traces in a significant number of grains, the critical resolved shear stresses (CRSSs) for prismatic, basal and pi1 were estimated. Transmission electron microscopy was used to identify unambiguously dislocations of pi1 systems and to estimate the corresponding CRSS. The difference in oxygen content between T40 and T60 was found to modify the magnitude of the CRSSs, but to leave their relative values nearly unchanged. The evolutions in the work hardening rate were correlated with the active deformation mechanisms
Size of wildfires in the Euro-Mediterranean region: observations and theoretical analysis
No full textInternational audienceMODIS (Moderate Resolution Imaging Spectroradiometer) satellite observations of fire size and ERA-Interim meteorological reanalysis are used to derive a relationship between burnt area and wind speed over the Mediterranean region and Eastern Europe. The largest wildfire size does not show a strong response with respect to wind speed in Eastern Europe. In the Mediterranean, as intuitively expected, the burnt area associated with the largest wildfires is an increasing function of wind speed for moderate temperature anomalies. In situations of severe heatwaves, the relationship between burnt area and wind speed displays a bimodal shape. Burnt areas are large for low 10 m wind speed (lower than 2 m s−1), decrease for moderate wind speed values (lower than 5 m s−1 and larger than 2 m s−1) and increase again for high wind speed (higher than 5 m s−1). To explain such behavior we use a stochastic model of fire propagation, known as a probabilistic cellular automata. This model uses a probabilistic local rule to derive the total burnt area. The observed relationship between burnt area and wind speed can be interpreted in terms of percolation threshold above which the propagation in the model is infinite, which mainly depends on local terrain slope and vegetation state (type, density, fuel moisture). In Eastern Europe, the percolation threshold is never exceeded for observed wind speeds. In the Mediterranean Basin we see two behaviors. During moderately hot weather, the percolation threshold is passed when the wind grows strong. On the other hand, in situations of severe Mediterranean heatwaves, moderate wind speed values impair the propagation of the wildfire against the wind and do not sufficiently accelerate the forward propagation to allow a growth of wildfire size