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Literatura académica sobre el tema "Transport entropique"
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Artículos de revistas sobre el tema "Transport entropique"
Granja, Lourdes Z. y Félix Mora-Camino. "Modèles entropiques multimodaux de prévision de flux de transport". RAIRO - Operations Research 19, n.º 2 (1985): 143–58. http://dx.doi.org/10.1051/ro/1985190201431.
Texto completoPicard, Guy, Sang Nguyen y Marc Gaudry. "Fret: a multiregional freight flow mode for Canada". Les Cahiers Scientifiques du Transport - Scientific Papers in Transportation 17-18 | 1988 (30 de junio de 1988). http://dx.doi.org/10.46298/cst.11860.
Texto completoTesis sobre el tema "Transport entropique"
Baradat, Aymeric. "Transport optimal incompressible : dépendance aux données et régularisation entropique". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX016/document.
Texto completoThis thesis focuses on Incompressible Optimal Transport, a minimization problem introduced by Brenier in the late 80's, aiming at describing the evolution of an incompressible and inviscid fluid in a Lagrangian way , i.e. by prescribing the state of the fluid at the initial and final times and by minimizing some functional among the set of admissible dynamics. This text is divided into two parts.In the first part, we study the dependence of this optimization problem with respect to the data. More precisely, we analyse the dependence of the pressure field, the Lagrange multiplier corresponding to the incompressibility constraint, with respect to the endpoint conditions, described by a probability measure γ determining the state of the fluid at the initial and final times. We show in Chapter 2 by purely variational methods that the gradient of the pressure field, as an element of a space that is close to the dual of C^1, is a Hölder continuous function of γ for the Monge-Kantorovic distance. On the other hand, we prove in Chapter 4 that for all r>1 the pressure field, as an element of L^r_t L^1_x, cannot be a Lipschitz continuous function of γ for the Monge-Kantorovic distance. This last statement is linked to an ill-posedness result proved in Chapter 3 for the so-called kinetic Euler equation, a kinetic PDE interpreted as the optimality equation of the Incompressible Optimal Transport problem.In the second part, we are interested in the entropic regularization of the Incompressible Optimal Transport problem: the so-called Brödinger problem, introduced by Arnaudon, Cruzeiro, Léonard and Zambrini in 2017. On the one hand, we prove in Chapter 5 that similarly to what happens in the Incompressible Optimal Transport case, to a solution always corresponds a scalar pressure field acting as the Lagrange multiplier for the incompressibility constraint. On the other hand, we prove in Chapter 6 that when the diffusivity coefficient tends to zero, the Brödinger problem converges towards the Incompressible Optimal Transport problem in the sense of Gamma-convergence, and with convergence of the pressure fields. The results of Chapter 6 come from a joint work with L. Monsaingeon
Thurin, Gauthier. "Quantiles multivariés et transport optimal régularisé". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0262.
Texto completoThis thesis is concerned with the study of the Monge-Kantorovich quantile function. We first address the crucial question of its estimation, which amounts to solve an optimal transport problem. In particular, we try to take advantage of the knowledge of the reference distribution, that represents additional information compared with the usual algorithms, and which allows us to parameterize the transport potentials by their Fourier series. Doing so, entropic regularization provides two advantages: to build an efficient and convergent algorithm for solving the semi-dual version of our problem, and to obtain a smooth and monotonic empirical quantile function. These considerations are then extended to the study of spherical data, by replacing the Fourier series with spherical harmonics, and by generalizing the entropic map to this non-Euclidean setting. The second main purpose of this thesis is to define new notions of multivariate superquantiles and expected shortfalls, to complement the information provided by the quantiles. These functions characterize the law of a random vector, as well as convergence in distribution under certain assumptions, and have direct applications in multivariate risk analysis, to extend the traditional risk measures of Value-at-Risk and Conditional-Value-at-Risk
Caron, Jérôme. "Etude et validation clinique d'un modèle aux moments entropique pour le transport de particules énergétiques : application aux faisceaux d'électrons pour la radiothérapie externe". Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0452/document.
Texto completoIn radiotherapy field, dose deposition simulations in patients are performed on Treatment Planning Systems (TPS) equipped with specific algorithms that differ in the way they model the physical interaction processes of electrons and photons. Although those clinical TPS are fast, they show significant discrepancies in the neighbooring of inhomogeneous tissues. My work consisted in validating for clinical electron beams an entropic moments based algorithm called M1. Develelopped in CELIA for warm and dense plasma simulations, M1 relies on the the resolution of the linearized Boltzmann kinetic equation for particles transport according to a moments decomposition. M1 equations system requires a closure based on H-Theorem (entropy maximisation). M1 dose deposition maps of 9 and 20 MeV electron beams simulations were compared to those extracted from reference codes simulations : clinical macro Monte-Carlo (eMC) and full Monte-carlo (GEANT4-MCNPX) codes and from experimental data as well. The different test cases consisted in homogeneous et complex inhomogeneous fantoms with bone and lung inserts. We found that M1 model provided a dose deposition accuracy better than some Pencil Beam Kernel algorithm and close of those furnished by clinical macro and academic full Monte-carlo codes, even in the worst inhomogeneous cases. Time calculation performances were also investigated and found better than the Monte-Carlo codes
Mallet, Jessy. "Contribution à la modélisation et à la simulation numérique multi-échelle du transport cinétique électronique dans un plasma chaud". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14584/document.
Texto completoIn plasma physics, the transport of electrons can be described from a kinetic point of view or from an hydrodynamical point of view.Classically in kinetic theory, a Fokker-Planck equation coupled with Maxwell equations is used to describe the evolution of electrons in a collisional plasma. More precisely the solution of the kinetic equations is a non-negative distribution function f specifying the density of particles as a function of velocity of particles, the time and the position in space. In order to approximate the solution of such problems, many computational methods have been developed. Here, a deterministic method is proposed in a planar geometry. This method is based on different high order numerical schemes. Each deterministic scheme used presents many fundamental properties such as conservation of flux particles, preservation of positivity of the distribution function and conservation of energy. However the kinetic computation of this accurate method is too expensive to be used in practical computation especially in multi-dimensional space.To reduce the computational time, the plasma can be described by an hydrodynamic model. However for the new high energy target drivers, the kinetic effects are too important to neglect them and replace kinetic calculus by usual macroscopic Euler models.That is why an alternative approach is proposed by considering an intermediate description between the fluid and the kinetic level. To describe the transport of electrons, the new reduced kinetic model M1 proposed is based on a moment approach for Maxwell-Fokker-Planck equations. This moment model uses integration of the electron distribution function on the propagating direction and retains only the energy of particles as kinetic variable. The velocity variable is written in spherical coordinates and the model is written by considering the system of moments with respect to the angular variable. The closure of the moments system is obtained under the assumption that the distribution function is a minimum entropy function. This model is proved to satisfy fundamental properties such as the non-negativity of the distribution function, conservation laws for collision operators and entropy dissipation. Moreover an entropic discretization in the velocity variable is proposed on the semi-discrete model. Moreover the M1 model can be generalized to the MN model by considering N given moments. The N-moments model obtained also preserves fundamental properties such as conservation laws and entropy dissipation. The associated semi-discrete scheme is shown to preserve the conservation properties and entropy decay
Jimenez, Julien. "Modèles non linéaires de transport dans un milieu poreux hétérogène". Phd thesis, Université de Pau et des Pays de l'Adour, 2007. http://tel.archives-ouvertes.fr/tel-00204610.
Texto completoEn premier lieu nous considérons un problème couplé hyperbolique/hyperbolique. Sous une condition de non dégénérescence du flux, nous avons obtenu un résultat d'existence et d'unicité d'une solution faible entropique d'abord en dimension 1 d'espace puis en dimension quelconque. La preuve de l'unicité est basée sur la méthode de dédoublement des variables due à S.N. Kruzkov puis sur un raisonnement presque partout à l'interface. Dans le cas particulier de la dimension 1 l'existence s'obtient par une régularisation adéquate du coefficient discontinu dans le terme de convection alors que nous utilisons la méthode de viscosité artificielle dans le cas général.
En second lieu nous traitons le cas de termes de convection qui apparaissent dans l'ingénierie pétrolière pour lesquels la condition de non dégénérescence de la non linéarité n'est pas vérifiée. Nous ne pouvons donc pas adapter les méthodes précédemment utilisées. Nous nous sommes donc intéressés à un problème couplé perturbé où sur l'un des deux ouverts un terme de diffusion est ajouté. Sous l'hypothèse que les caractéristiques provenant de la zone hyperbolique sont sortantes à l'interface, l'unicité d'une solution faible entropique est établie. La méthode de viscosité artificielle et la notion de processus entropique nous permettent de prouver le résultat d'existence .
Jobic, Yann. "Numerical approach by kinetic methods of transport phenomena in heterogeneous media". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4723/document.
Texto completoA novel kinetic scheme satisfying an entropy condition is developed, tested and implemented for the simulation of practical problems. The construction of this new entropic scheme is presented. A classical hyperbolic system is approximated by a discrete velocity vector kinetic scheme (with the simplified BGK collisional operator), but applied to an inviscid compressible gas dynamics system with a small Mach number parameter, according to the approach of Carfora and Natalini (2008). The numerical viscosity is controlled, and tends to the physical viscosity of the Navier-Stokes system. The proposed numerical scheme is analyzed and formulated as an explicit finite volume flux vector splitting (FVS) scheme that is very easy to implement. It is close in spirit to Lattice Boltzmann schemes, but it has the advantage to satisfy a discrete entropy inequality under a CFL condition and a subcharacteristic stability condition involving a cell Reynolds number. The new scheme is proved to be second-order accurate in space. We show the efficiency of the method in terms of accuracy and robustness on a variety of classical benchmark tests. Some physical problems have been studied in order to show the usefulness of both schemes. The LB code was successfully used to determine the longitudinal dispersion of metallic foams, with the use of a novel indicator. The entropic code was used to determine the permeability tensor of various porous media, from the Fontainebleau sandstone (low porosity) to a redwood tree sample (high porosity). These results are pretty accurate. Finally, the entropic framework is applied to the advection-diffusion equation as a passive scalar
Nenna, Luca. "Numerical Methods for Multi-Marginal Optimal Transportation". Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLED017/document.
Texto completoIn this thesis we aim at giving a general numerical framework to approximate solutions to optimal transport (OT) problems. The general idea is to introduce an entropic regularization of the initialproblems. The regularized problem corresponds to the minimization of a relative entropy with respect a given reference measure. Indeed, this is equivalent to find the projection of the joint coupling with respect the Kullback-Leibler divergence. This allows us to make use the Bregman/Dykstra’s algorithm and solve several variational problems related to OT. We are especially interested in solving multi-marginal optimal transport problems (MMOT) arising in Physics such as in Fluid Dynamics (e.g. incompressible Euler equations à la Brenier) and in Quantum Physics (e.g. Density Functional Theory). In these cases we show that the entropic regularization plays a more important role than a simple numerical stabilization. Moreover, we also give some important results concerning existence and characterization of optimal transport maps (e.g. fractal maps) for MMOT
Osenciat, Nicolas. "Propriétés de transport dans les oxydes à haute entropie". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF005.
Texto completoThe aim of this thesis is to assess the potential of a new material for solid-state electrolyte applications in all-solid-state batteries and/or micro-batteries. This new compound, which exhibits remarkable Li+ and Na+ ionic conductivity, belongs to a new class of oxides, recently discovered by Rost et al. (Nature Communication, 2015). This new family is formed through configuration entropy stabilisation, at high temperature, into a simple single phase, from a complex mixture of binary oxides (in our case NaCl-Rocksalt structure). We have studied the charge compensation mechanisms involved in the synthesis of the (MgCoNiCuZn)1−xLixO series and the influence of their composition on their ionic conductivity properties. We have attempted to densify these compounds at low temperature using the original Cold Sintering Process, without succeeding in obtaining defect-free ceramics. Finally, we have also developed and described the crystallographic structure and the electrochemical behaviour of a new anode material (possibly compatible with these entropy-stabilised oxides), the Li2(Mg,Co,Ni,Cu,Zn)Ti3O8 multicationic lithium titanate
Burada, Poornachandra Sekhar. "Entropic transport in confined media". kostenfrei, 2008. http://d-nb.info/991298292/34.
Texto completoMa, Ta-Yu. "Modèle dynamique de transport basé sur les activités". Marne-la-vallée, ENPC, 2007. https://pastel.archives-ouvertes.fr/pastel-00003309.
Texto completoLibros sobre el tema "Transport entropique"
1973-, Villani Cédric y Centre Émile Borel, eds. Entropy methods for the Boltzmann equation: Lectures from a special semester at the Centre Émile Borel, Institut H. Poincaré, Paris, 2001. Berlin: Springer, 2008.
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