Jurnal Edukasi
Not a member yet
4879 research outputs found
Sort by
Large size crystalline vs. co-sintered ceramic Yb 3+ :YAG disk performance in diode pumped amplifiers
No full textInternational audienceA comprehensive experimental benchmarking of Yb3+:YAG crystalline and co-sintered ceramic disks of similar thickness and doping level is presented in the context of high average power laser amplifier operation. Comparison is performed considering gain, depolarization and wave front deformation quantitative measurements and analysis
On topological and geometric configurations
No full textInternational audienceAn configuration is a set of points and lines such that each point lies on lines while each line contains points. The configuration is geometric, topological, or combinatorial depending on whether lines are considered to be straight lines, pseudolines, or just combinatorial lines. The existence and enumeration of configurations for a given has been subject to active research. A current front of research concerns geometric configurations: it is now known that geometric configurations exist for all , apart from sporadic exceptional cases. In this paper, we settle by computational techniques the first open case of configurations: we obtain all topological configurations among which none are geometrically realizable
Bacillus subtilis Bacteria generate an Internal Mechanical Force within a Biofilm
No full textInternational audienc
Modelling complex high speed multimaterial evolutions using a single mesh multivelocity strategy
No full textInternational audienceIn the present paper, we propose another space discretization of the kinematic constraint for a single grid multi velocity formulation leading to a better approximation of the interface physics. The paper is organized as follows. In the next section, we will briefly review the problem to solve and the single mesh multi-velocity discretization strategy. In Section 3, we will then introduce our new cell-based discretization of the normal velocity continuity constraint on the interface, develop the proper velocity enrichment, and analyse its stability. A generic time discretization is next introduced in Section 4 and adapted to the specific space discretization proposed herein. The proposed methodology is finally validated on a few numerical examples
L'équation de Landau-Lifshitz-Gilbert stochastique avec bruit gaussien
No full text This thesis is devoted to the influence of a noise term in the stochastic Landau-Lifshitz-Gilbert Equation (SLLG).It is a nonlinear stochastic partial differential equation with a non-convex constraint on the modulus of the solutions.First, we study in chapter 1 the question of local solvability.Using classical properties of stochastic integration with Banach space-valued processes, we propose a mild formulation, and give the existence and uniqueness of a local solution in any dimension, for a Gaussian noise, regular in space. Secondly, we focus on the specific study of SLLG in a two-dimensional space domain.Chapter 2 deals with the existence of a strong solution, in the probabilistic sense. Using the energy formula, we give a method to obtain uniquely a global solution in time.Chapter 3 gives uniqueness of weak solutions, provided that the energy satisfies a super-martingale property. This is the stochastic counterpart of a known deterministic result giving the uniqueness of weak solutions, knowing that the energy decreases.Chapter 4 gives the existence, in the so-called ``overdamped case'', of solutions that blow-up in finite time. We prove that, unlike the deterministic case, a singularity may appear with positive probability, regardless of the initial data chosen.Then we return to the case of general dimension of space, providing in chapter 5 a new time semi-discrete scheme for SLLG. This chapter is based on an article in collaboration with F. Alouges and A. De Bouard. We show the convergence in law of a projection-type scheme for SLLG, which has the advantage of respecting exactly the local constraint on the magnitude. This scheme treats the case of a rather general noise term regularized in space but infinite-dimensional.In Chapter 6, we show how to implement it with a finite element dicretization in space, and we give a practical method for approaching a regular noise in this framework. We also evidence numerical blow-up of the solutions, despite the presence of a gyromagnetic term, and of a more general noise than that of Chapter 4.Cette thèse porte sur l'influence d'un bruit Gaussien dans l'équation de Landau-Lifshitz-Gilbert Stochastique (SLLG).Il s'agit d'une équation aux dérivées partielles stochastique, non linéaire, avec une contrainte non convexe sur le module des solutions.Le chapitre 1 se consacre tout d'abord à la solvabilité locale de SLLG.Utilisant les propriétés classiques de l'intégration stochastique dans un espace de Banach, nous proposons une formulation mild,et donnons l'existence et l'unicité d'une solution locale en dimension quelconque, pour un bruit Gaussien régulier en espace, dans le cas sur-amorti.Dans un second temps, nous effectuons une étude spécifique de la dimension deux d'espace.Le chapitre 2 porte sur l'existence de solutions fortes au sens probabiliste pour SLLG en 2D. En se basant sur la formule de l'énergie,nous donnons une méthode permettant d'obtenir une solution globale en temps, de manière unique.Le chapitre 3 s'intéresse à l'unicité des solutions faibles en 2D. Un résultat déterministe donnait l'unicité sachant en supposant l'énergie décroît au cours du temps, hypothèse impossible dans le cas bruité. Nous montrons néanmoins l'unicité des solutions faibles vérifiant une propriété de sur-martingale sur la fonctionnelle d'énergie.Le chapitre 4 donne l'existence, sous l'hypothèse de sur-amortissement, de solutions explosives en temps fini.Nous expliquons que contrairement au cas déterministe, une singularité peut apparaître avec probabilité positive, quelle que soit la donnée initiale choisie.Nous revenons ensuite au cas d'une dimension d'espace quelconque, proposant dans le chapitre 5 un nouveau schéma numérique semi-discrétisé en temps. Ce chapitre est basé sur un article en collaboration avec F. Alouges et A. De Bouard. Nous montrons la convergence en loi d'un schéma de projection pour SLLG, qui a l'avantage de respecter de manière exacte la contrainte sur le module des solutions. Ce schéma traite le cas d'un terme de bruit assez général, régularisé en espace mais de dimension infinie.Nous montrons ensuite comment l'implémenter dans le chapitre 6, à l'aide d'éléments finis, et nous donnons une méthode pratique pour approcher un bruit régulier dans ce cadre. Nous mettons également en évidence le phénomène d'explosion, observé numériquement malgré la présence d'une terme gyromagnétique, et d'un bruit plus général qu'au chapitre 4.
Quantitative Approaches to the Protection of Private Information: State of the Art and Some Open Challenges
No full textInternational audienc
A single-column model intercomparison on the stratocumulus representation in present-day and future climate
No full textInternational audienceSix Single-Column Model (SCM) versions of climate models are evaluated on the basis of their representation of the dependence of the stratocumulus-topped boundary layer regime on the free tropo-spheric thermodynamic conditions. The study includes two idealized experiments corresponding to the present-day and future climate conditions in order to estimate the low-cloud feedback. Large-Eddy Simulation (LES) results are used as a benchmark and GCM outputs are included to assess whether the SCM results are representative of their 3-D counterparts. The SCMs present a variety of dependencies of the cloud regime on the free tropospheric conditions but, at the same time, several common biases. For all the SCMs the stratocumulus-topped boundary layer is too shallow, too cool, and too moist as compared to the LES results. Moreover, they present a lack of clouds and liquid water and an excess of precipitation. The disagreement among SCMs is even more distinct for the response to a climate perturbation. Even though the overall feedback is positive for all the models, in line with the LES results, the SCMs show a rather noisy behavior, which depends irregularly on the free tropospheric conditions. Finally, the comparison with the host GCM outputs demonstrates that the considered approach is promising but needs to be further generalized for the SCMs to fully capture the behavior of their 3-D counterparts
The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6): simulation design and preliminary results
No full textInternational audienceWe present a suite of new climate model experiment designs for the Geoengineering Model Intercompari-son Project (GeoMIP). This set of experiments, named Ge-oMIP6 (to be consistent with the Coupled Model Intercom-parison Project Phase 6), builds on the previous GeoMIP project simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more longwave radiation to escape to space. We discuss experiment designs, as well as the rationale for those designs, showing preliminary results from individual models when available. We also introduce a new feature, called the GeoMIP Testbed, which provides a platform for simulations that will be performed with a few models and subsequently assessed to determine whether the proposed experiment designs will be adopted as core (Tier 1) GeoMIP experiments. This is meant to encourage various stakeholders to propose new targeted experiments that address their key open science questions, with the goal of making GeoMIP more relevant to a broader set of communities
Constructing elastic distinguishability metrics for location privacy
No full textInternational audienceWith the increasing popularity of hand-held devices, location-based applications and services have access to accurate and real-time location information, raising serious privacy concerns for their users. The recently introduced notion of geo-indistinguishability tries to address this problem by adapting the well-known concept of differential privacy to the area of location-based systems. Although geo-indistinguishability presents various appealing aspects, it has the problem of treating space in a uniform way, imposing the addition of the same amount of noise everywhere on the map. In this paper we propose a novel elastic distinguishability metric that warps the geometrical distance, capturing the different degrees of density of each area. As a consequence, the obtained mechanism adapts the level of noise while achieving the same degree of privacy everywhere. We also show how such an elastic metric can easily incorporate the concept of a "geographic fence" that is commonly employed to protect the highly recurrent locations of a user, such as his home or work. We perform an extensive evaluation of our technique by building an elastic metric for Paris' wide metropolitan area, using semantic information from the OpenStreetMap database. We compare the resulting mechanism against the Planar Laplace mechanism satisfying standard geo-indistinguishability, using two real-world datasets from the Gowalla and Brightkite location-based social networks. The results show that the elastic mechanism adapts well to the semantics of each area, adjusting the noise as we move outside the city center, hence offering better overall privacy
Revealing transversity GPDs through the photoproduction of a photon and a rho meson
No full text6 pages, 3 figures. Contribution to the proceedings of the 6th International Conference on Physics Opportunities at an Electron-Ion Collider (POETIC6), September 7-11, 2015, Palaiseau, France.International audiencePhotoproduction of a pair of particles with large invariant mass is a natural extension of collinear QCD factorization theorems which have been much studied for deeply virtual Compton scattering and deeply virtual meson production. We discuss the production of a photon and a meson, where the wide angle Compton scattering on a meson subprocess factorizes from generalized parton distribution. We calculate at dominant twist and leading order in alpha_s, the production cross-section of a transversely polarized rho meson which is sensitive to chiral-odd GPDs, and show that it may be measurable in near future JLab experiments