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Evolution in morphological, optical, and electronic properties of ZnO:Al thin films undergoing a laser annealing and etching process
No full textInternational audienc
Fatigue design of railway wheels: a probabilistic approach
No full textInternational audienceThis paper deals with a method to evaluate and optimize the design of railway wheels subjected to multiparameter variable fatigue loading. The fatigue loads are statistically evaluated from in-service measurements. Representative realistic loading paths are built from the knowledge of the influence of various factors (such as train speed and track curvature). Using these paths, the method combines finite element computations and the fatigue equivalence method for damage evaluation in the structure. An extension of the Dang Van fatigue criterion in the high-cycle fatigue finite life domain associated with a damage accumulation law is adopted. The probability of failure of the structure is directly obtained from the interference between a local fatigue equivalent stress and fatigue strength distributions (based on the stress-strength interference approach). The result is useful for the optimization during the design stage or the validation of the fatigue strength of structures
Study of filamentation threshold in zinc selenide
No full textInternational audienceThe possibility of creating filaments with laser wavelengths ranging from 800 nm to 2.4 µm was investigated using an OPA laser system. Zinc Selenide's (ZnSe) unique characteristics – small band gap 2.67 gZnSe E e V = and positive dispersion for this wavelength range – are well suited for filamentation study where multi-photon absorption can be achieved with two to six photons
Technological prototype of a silicon-tungsten imaging electromagnetic calorimeter
No full textInternational audienceHighly granular calorimeters and particle flow algorithms are essential tools for achieving an excellent jet energy resolution. This is a key asset for precision physics at future high energy particle colliders aiming at precise physics measurements. The PFA concept is best supported by a silicon tungsten electromagnetic calorimeter. The R&D as carried out by the CALICE collaboration has shown the feasibility of a fine-grained pixelization while assuring high operation stability. Our concept has been selected to compete for the upgrade of the CMS ECAL. The latest version of our detector concept, featuring 1024 channels on 4 dm2 board will be presented including technological choices for an application on an ILC. First thoughts for the CMS ECAL upgrade will be discussed
On the efficiency of energy harvesting using vortex-induced vibrations of cables
No full textInternational audienceMany technologies based on fluid–structure interaction mechanisms are being developed to harvest energy from geophysical flows. The velocity of such flows is low, and so is their energy density. Large systems are therefore required to extract a significant amount of energy. The question of the efficiency of energy harvesting using vortex-induced vibrations (VIV) of cables is addressed in this paper, through two reference configurations: (i) a long tensioned cable with periodically-distributed harvesters and (ii) a hanging cable with a single harvester at its upper extremity. After validation against either direct numerical simulations or experiments, an appropriate reduced-order wake-oscillator model is used to perform parametric studies of the impact of the harvesting parameters on the efficiency. For both configurations, an optimal set of parameters is identified and it is shown that the maximum efficiency is close to the value reached with an elastically mounted rigid cylinder. The variability of the efficiency is studied in light of the fundamental properties of each configuration, i.e. body flexibility and gravity-induced spatial variation of the tension. In the periodically-distributed harvester configuration, it is found that the standing-wave nature of the vibration and structural mode selection plays a central role in energy extraction. In contrast, the efficiency of the hanging cable is essentially driven by the occurrence of traveling wave vibrations
Modeling of the Martian Water Cycle with an Improved Representation of Water Ice Clouds
No full textThe Martian water cycle has been studied for a long time thanks to remote observations and the use of GCMs (Global Climate Model). Thanks to GCMs, the comprehension of the water cycle has been improved, revealing for instance the impor- tance of clouds in the global water transport [5] with implications for atmospheric dynamics, paleo- climates. From that perspective, the modeling of the Martian water cycle by the LMD (Laboratoire de Météorologie Dynamique) Mars GCM has been im- proved by implementing significant processes, such as radiatively active water ice clouds and a micro- physical scheme described in [4], including pro- cesses such as nucleation, growth of ice particles, sedimentation, coalescence and scavenging of dust nuclei
In-Plane Epitaxial Growth of Silicon Nanowires and Junction Formation on Si(100) Substrates
No full textInternational audienceGrowing self-assembled silicon nanowires (SiNWs) into precise locations represents a critical capability to scale up SiNW-based functionalities. We here report a novel epitaxy growth phenomenon and strategy to fabricate orderly arrays of self-aligned in-plane SiNWs on Si(100) substrates following exactly the underlying crystallographic orientations. We observe also a rich set of distinctive growth dynamics/modes that lead to remarkably different morphologies of epitaxially grown SiNWs/or grains under variant growth balance conditions. High-resolution transmission electron microscopy cross-section analysis confirms a coherent epitaxy (or partial epitaxy) interface between the in-plane SiNWs and the Si(100) substrate, while conductive atomic force microscopy characterization reveals that electrically rectifying p-n junctions are formed between the p-type doped in-plane SiNWs and the n-type c-Si(100) substrate. This in-plane epitaxy growth could provide an effective means to define nanoscale junction and doping profiles, providing a basis for exploring novel nanoelectronics
Types intersections non-idempotents pour raffiner la normalisation forte avec des informations quantitatives
No full textWe study systems of non-idempotent intersection types for different variants of the lambda-calculus and we discuss properties and applications. Besides the pure lambda-calculus itself, the variants are a λ-calculus with explicit substitutions and a lambda-calculus with constructors, matching and a fixpoint operator. The typing systems we introduce for these calculi all characterize strongly normalising terms. But we also show that, by dropping idempotency of intersections, typing a term provides quantitative information about it: a trivial measure on its typing tree gives a boundon the size of the longest beta-reduction sequence from this term to its normal form. We explore how to refine this approach to obtain finer results: some of the typing systems, under certain conditions, even provide the exact measure of this longestbeta-reduction sequence, and the type of a term gives information on the normal form of this term. Moreover, by using filters, these typing systems can be used to define a denotational semantics.Nous étudions des systèmes de typage avec des types intersections non-idempotents pour des variantes du lambda-calcul et nous discutons de leurs propriétés et de leurs applications. Outre le lambda-calcul lui-même, les variantes sont un lambda-calcul avec des substitutions explicites et un lambda-calcul avec des constructeurs, du filtrage et un opérateur de point fixe. Les sytèmes de typage que l'on présente caractérisent les termes fortement normalisables. Mais nous montrons également qu'un jugement de typage d'un terme donne des informations quantitatives : une mesure triviale sur l'arbre de typage d'unlambda-terme quelconque donne une borne sur la taille de la plus longue séquence de beta-reductions depuis ce lambda-terme jusqu'à sa forme normale. Nous raffinons cette approche pour obtenir un résultat plus précis: certains systèmes de typages, sous certaines conditions, donnent même une mesure exacte de cette plus longue séquence de beta-reductions, et le type du terme donne des informations sur la forme normale de ce terme. De plus, en utilisant des filtres, ces systèmes de typage peuvent être utilisés pour définir une sémantique dénotationnelle
Convergent Routes to Substituted Naphthylamides
No full textInternational audiencePractical, convergent routes to variously substituted 1- and 2-naphthylamides have been developed. They exploit the ability of xanthates to undergo both intermolecular radical additions to vinyl pivalate and intramolecular radical cyclisations to aromatic rings. In the case of 1-naphthylamides, the existence of an intramolecular hydrogen bond was used to facilitate the cyclisation step
Adaptive density estimation in deconvolution problems with unknown error distribution
No full textInternational audienceA density deconvolution problem with unknown distribution of the errors is considered. To make the target density identifiable, one has to assume that some additional information on the noise is available. We consider two different models: the framework where some additional sample of the pure noise is available, as well as the repeated observation model, where the contaminated random variable of interest can be observed repeatedly. We introduce kernel estimators and present upper risk bounds. The focus of this work lies on the optimal data driven choice of the smoothing parameter using a penalization strategy