Rozprawy doktorskie na temat „Régime propagatif”
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Lalloz, Samy. "De la diffusion à la propagation d'ondes en magnétohydrodynamique bas-Rm : études théorique et expérimentale". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALI020.
Pełny tekst źródłaThe thesis aims to clarify the conditions for Alfvén waves to propagate in a closed liquid metal domain. A first part of the research work presented is dedicated to a linear study of Alfvén waves in the low-Rm approximation and under the inertia-less limit. The second part is the experimental investigation of an electrically-induced oscillating flow subjected to an axial, static and uniform magnetic field and confined between two electrically insulating and no-slip horizontal walls.The theoretical study is itself split into two sub-parts. The first one aims to discuss the dispersion relation which contains the Alfvén wave dynamics. It presents the consequences of (mechanical and magnetic) gradients perpendicular to the imposed magnetic field. As such transverse gradients tend to impede the wave propagation. In the second sub-part an axisymmetric vortex confined between to electrically insulated and no-slip horizontal walls is magnetically forced at a given frequency. This forcing is radially dependent so as to study the impact of transverse gradients on the flow dynamics. A semi-analytical investigation of the flow dynamics is again carried out in the low-Rm approximation and under the inertia-less limit. This investigation is performed by varying the forcing frequency and the magnetic field intensity. This brings to emphasize two very distinct regimes for the oscillating vortex:- an oscillating-diffusive regime governed by the competition between pseudo-diffusive effects of the Lorentz force and the unsteady term of the momentum- a truly propagative regime, obtained for higher forcing frequencies, found definitelygoverned by Alfvén waves.The study also highlights how the propagative regime can be affected by transverse gradients. In addition to over-damping the waves, transverse gradients are found to modify the natural frequencies for which wave resonance peaks result from the superimposition of incident and reflected waves in the container.Beside this theoretical work, a setup has been designed in order to experimentally investigate the dynamics of oscillating flows under a strong magnetic field (up to 10T). A flow was forced in a cuboid vessel 15 cm x 15 cm x 10 cm by means of AC currents injected through a cartesian grid of four electrodes located at the bottom plate. Using instrumentation based on the measurement of local electric potential differences at the top and bottom horizontal (Hartmann) plates, we validate model's prediction. More precisely, a propagative dynamics in the presence of transverse gradients is recovered. The oscillating-diffusive regime is also recovered from experiments performed at small enough forcing frequency.In addition to results obtained at the forcing frequency, a first insight of signals obtained at other frequencies is shown. Frequency peaks obtained, eg the harmonics of the forcing frequency, are demonstrated not to be explained by a linear approach. We suggest that Alfvén wave non-linear interactions are a good candidate to explain these peaks. A preliminary study further shows that peaks at the first harmonic are likely to be Alfvén waves
Elaloufi, Rachid. "Propagation du rayonnement en milieu diffusant : étude de la transition entre régime balistique et régime diffusif et des fluctuations temporelles d'intensité". Châtenay-Malabry, Ecole centrale de Paris, 2003. http://www.theses.fr/2003ECAP0890.
Pełny tekst źródłaLeconte, Marc. "Propagation de front de réaction sous écoulement". Paris 7, 2004. http://www.theses.fr/2004PA077113.
Pełny tekst źródłaHiez, Brigitte. "Propagation en régime ductile de fissures amorcées dans des conditions de chargement hors normes". Paris 6, 1986. http://www.theses.fr/1986PA066509.
Pełny tekst źródłaBerriri, Kamel. "Approche analytique et numérique pour l'aéroacoustique en régime transitoire par le modèle de Galbrun". Phd thesis, Paris 9, 2006. http://pastel.archives-ouvertes.fr/pastel-00002485.
Pełny tekst źródłaMesgouez, Arnaud. "Etude numérique de la propagation des ondes mécaniques dans un milieu poreux en régime impulsionnel". Phd thesis, Université d'Avignon, 2005. http://tel.archives-ouvertes.fr/tel-00110663.
Pełny tekst źródłaUne approche par éléments finis est proposée dans le cadre de la théorie générale de Biot. Les caractéristiques de l'outil numérique développé sont précisées. En particulier, la structure orientée objet donne un code compact et souple. Un travail
semi-analytique, préalablement effectué, s'intéresse aux phénomènes de dispersion, d'atténuation et à la détermination des vitesses de propagation des différentes ondes.
Une modélisation bidimensionnelle permet d'obtenir les déplacements temporels des phases solide et fluide en surface et en profondeur d'un sol poreux semi-infini. Une étude paramétrique des couplages mécaniques est effectuée. La seconde onde de compression est mise en évidence. Une première approche de sols hétérogènes ou partiellement saturés est en outre proposée.
L'étude de problèmes tridimensionnels est ensuite envisagée. La taille numérique importante de cette problématique nécessite alors la parallélisation du code de calcul. Des essais sur différents supercalculateurs sont réalisés pour mesurer la performance du
calcul parallèle et conduisent à des résultats tridimensionnels.
Foulon, Michel-François. "Métamatériaux térahertz en régime linéaire et non linéaire". Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10121/document.
Pełny tekst źródłaArtificial materials so called «metamaterials» are studied theoretically and characterized at few hundred of GigaHetrz frequencies. Frequencial and temporal (electro-optic) methods are used to prove their left handed behaviour. For this study, two approaches have been considered : - the first one is based on the fabrication of micro-resonators and metallic wires arrays aiming at operating at 100 GHz. An experimental evidence of a left handed dispersion branch is then made from vectorial analysis. - the second approach takes profit of phase advance effects that can be obtained from a transmission line periodically loaded with a series capacitance and a parallel inductance. The specificity of this study is a coherent time domain approach that allows us to directly visualize a phase advance and the corresponding left handed behaviour. Those results are confirmed by the calculations of Fourier transforms up to 1 TeraHertz. Non linear properties of those circuits are then studied by introducing a non linearity by the mean of a Heterostructure Barrier Varactor component. The extension of this study to the non linear regime is treated via the dynamic characterization of this component. Finally, two types of non linear regimes are studied for a left handed transmission line loaded with HBV diodes with respectively harmonic generation and parametric amplification
Fauqueux, Sandrine. "Eléments finis mixtes spectraux et couches absorbantes parfaitement adaptées pour la propagation d'ondes élastiques en régime transitoire". Phd thesis, Paris 9, 2003. http://tel.archives-ouvertes.fr/tel-00007445.
Pełny tekst źródłaAyrault, Christophe. "Influence de la pression statique sur la caractérisation ultrasonore de matériaux poreux : étude du régime de faible diffusion". Le Mans, 1999. http://www.theses.fr/1999LEMAA005.
Pełny tekst źródłaHashmi, Faheel. "Effets de propagation dans des systèmes atomiques en régime d'impulsions longues et courtes: Contrôle de la réponse optique". Phd thesis, Université Paul Sabatier - Toulouse III, 2009. http://tel.archives-ouvertes.fr/tel-00361143.
Pełny tekst źródłaHashmi, Faheel-Ather. "Effets de propagation dans des systèmes atomiques en régime d'impulsions longues et courtes : contrôle de la réponse optique". Toulouse 3, 2009. http://thesesups.ups-tlse.fr/650/.
Pełny tekst źródłaThis thesis deals with the study of propagation effects experienced by weak light pulses as they propagate in atomic media driven by strong pulses. We explore both the ultra-short and long pulse regime and investigate the phenomena that arise at these different time scales. In the short pulse regime, a strongly driven two level atomic system presents transient light shifts, and non-adiabatic transitions occur between these adiabatic levels. We have studied a method to probe these light shifts in real time by propagating a weak probe through the medium. The light shifts enrich the spectrum of the probe and the probe gets shaped as a result. In this way a strongly driven two-level system can act as an active pulse shaper, and can introduce oscillations in the temporal profile of an ultra-short pulse at a time scale shorter than the pulse duration. We also show that by driving the system with two time delayed non-resonant strong fields, the non-adiabatic effects can be rendered phase dependent. This gives very sensitive phase control of the excited state population and can be used to formulate new techniques in interferometry. In the long pulse regime we present a new method of slowing light that can be realized in a double two-level system interacting with two orthogonally polarized light pulses that propagate along different axis. Spatio-temporal dependence of the total polarization induces a grating in the ground Zeeman coherence. .
Saracco, Ginette. "Propagation acoustique en régime harmonique et transitoire à travers un milieu inhomogène : méthodes asymptotiques et transformation en ondelettes". Aix-Marseille 2, 1989. https://tel.archives-ouvertes.fr/tel-00178676.
Pełny tekst źródłaPannier, Philippe. "Optimisation de méthodes de formulations intégrales pour l'analyse électromagnétique, en régime force, de discontinuités entre lignes de propagation multimodale". Lille 1, 1997. http://www.theses.fr/1997LIL10228.
Pełny tekst źródłaDesprés, Bruno. "Méthodes de décomposition de domaine pour la propagation d'ondes en régime harmonique. Le théorème de Borg pour l'équation de Hill vectorielle". Paris 9, 1991. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=1991PA090032.
Pełny tekst źródłaFuchs, Julien. "Interaction laser-plasma en régime relativiste dans le contexte de l'allumeur rapide. Propagation dans les plasmas sous-critiques et sur-critiques". Paris 11, 1998. http://www.theses.fr/1998PA112169.
Pełny tekst źródłaMessager, Alexandre. "Étude de l'amorçage et de la propagation de fissures de fatigue internes courtes en régime gigacyclique dans un alliage d'aluminium de fonderie". Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAE032.
Pełny tekst źródłaCasting allows the mass production of parts with complex geometry at a low cost. However, defectsinherent to the manufacturing process (pores, shrinkages, etc.) are natural stress concentrators and act as amajor cause of fatigue crack initiation. The defect position from the part surface influences its harmfulnessand the fatigue strength of the component. Initiation and propagation mechanisms of internal fatiguecracks are currently less studied than those emanating from surface defects. The purpose of this work is tocharacterize short internal fatigue crack initiation and propagation mechanisms and kinetics in the A357-T6 cast aluminium alloy. An experimental testing device allowing the observation of internal fatigue crackinitiation and propagation by in-situ synchrotron tomography and infrared thermography was developed.The propagation kinetics of internal cracks were quantif ied through tomographic data processing. Stressintensity factor ranges were calculated by f inite element analysis along the crack fronts assuminghomogeneous material. In addition, the microstructure of the specimens was characterized by diffractioncontrast tomography (DCT) which allowed polycrystalline aggregates simulation in order to betterunderstand the interactions between cracks and microstructure. Finally, thanks to f inite elementthermomechanical simulations, the surface temperature increases of the specimens, measured by infraredthermography, were correlated to the 3D evolution of the crack fronts observed by tomography
Barthélémy, Alain. "Propagation cohérente d'impulsions dans les fibres optiques : Etude de régimes solitons en présence de non-linéarité de Kerr". Limoges, 1986. http://www.theses.fr/1986LIMO0002.
Pełny tekst źródłaViard, Nicolas. "Contribution expérimentale à l'étude de la diffusion multiple des ultrasons en régimes de propagation linéaire et non linéaire". Phd thesis, Université Paris-Diderot - Paris VII, 2014. http://pastel.archives-ouvertes.fr/pastel-00955942.
Pełny tekst źródłaKarakaş, Çağil. "Propagation et évolution structurale de la faille Nord Anatolienne dans la région de Marmara". Paris, Institut de physique du globe, 2013. http://www.theses.fr/2013GLOB0003.
Pełny tekst źródłaBillard, Franck. "Métrologie de l'indice non-linéaire dans les verres en régime nanoseconde, picoseconde et sub-picoseconde". Phd thesis, Aix-Marseille 3, 2005. http://tel.archives-ouvertes.fr/tel-00011812.
Pełny tekst źródłaNous avons développé un modèle numérique permettant d'étudier le signal. Nous montrons que le profil spatial du faisceau avait une grande importance sur la mesure. Ensuite la réalisation expérimentale des bancs comprenant tous les moyens de caractérisation nécessaires à une mesure absolue est détaillée.
Enfin, une étude de l'indice de réfraction non-linéaire de la silice est entreprise pour différents régimes temporels. Une grande dépendance avec la durée des impulsions et l'absence d'effets thermiques sont constatées ainsi qu'une contribution non négligeable de l'électrostriction en nanoseconde.
Kha, Kim Quoc Nguyen. "Contribution à la modélisation et à la simulation numérique de la combustion turbulente pré-mélangée dans des régimes d'interaction chimie-turbulence extrêmes : Prise en compte des écarts à l'hypothèse de flamme mince". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2016. http://www.theses.fr/2016ESMA0018/document.
Pełny tekst źródłaThe present study is devoted to the modeling of turbulent reactive flows. In a first step of the analysis, one-dimensional flames are considered to scrutinize analytically and numerically the characteristics of the propagating flame front. Then, we introduce a new definition for the flamelet thickness that may differ from the laminar flame thickness. Accordingly a generalized and consistent form of the presumed probability density function(PDF) is proposed. The parameters of this PDF depend on the ratio of the Kolmo-gorov length scale to laminar flame thickness. The corresponding developments can be associated with a boundary layer description applied to the turbulent flame in which the thicknesses of the different sub-layers are determined from the sole knowledge of the turbulent Reynolds number Re and Karlovitz number Ka. This description leads to amodeling proposal (i) for the mean reaction rate as well as (ii) for the turbulent scalar flux. The values of all chemical characteristics are calculated from one-dimensional flame susing either the MathematicaTM software or detailed chemical kinetics computations.Numerical simulations are finally performed with the CFD code Code-Saturne and the model is validated through comparisons with reference experimental configurations :turbulent V-shaped flames and impinging flames. Satisfactory results are obtained for these two distinct configurations
Diaz, Julien. "Approches analytiques et numériques de problèmes de transmission en propagation d'ondes en régime transitoire : application au couplage fluide-structure et aux méthodes de couches parfaitement adaptées". Phd thesis, Paris 6, 2005. http://tel.archives-ouvertes.fr/tel-00008708.
Pełny tekst źródłaRagoubi, Refka. "Filtrage anisotrope robuste régi par propagation de fronts : vers une segmentation automatique de volumes IRM". Télécom Bretagne, 2013. http://www.telecom-bretagne.eu/publications/publication.php?idpublication=14132.
Pełny tekst źródłaThe reliable and accurate segmentation of anatomical volumes (normal or pathological) from imaging systems remains an important goal in the medical information processing because it is the first step in the chain of analysis leading to perform diagnosis to the study of internal structures morphology, for detection and quantification of lesions. Segmentation is a difficult step, especially for MRI images, for which it is primarily performed manually when there are high precision constraints. In this context, the objective of this PhD is the filtering of MRI bony joint of the human body, to achieve efficient and accurate segmentation. The first contribution is the development of a robust iterative 3D anisotropic filtering. This method can diffuse the voxels intensity according to their belonging to two populations: high diffusion for voxels located inside homogeneous regions in order to reduce noise while preventing the diffusion through the transition areas (surfaces). A rigorous comparison of several stopping functions was performed to insert the most relevant one in the iterative model. The threshold parameter splitting these two populations was estimated in an original and effective way in relation to the state of the art. The original diffusion scheme was confronted to the front propagation methods. The identification of these two models, currently separated in the literature, helped to merging the two approaches into a comprehensive anisotropic diffusion scheme governed by a front propagation. This formulation has helped offset the disadvantages of each approach namely i) the difficulty of stopping the iterative diffusion scheme, ii) the difficulty of implementing the level-sets approach facing to prohibitive calculation times. The proposed iterative scheme combines four terms related to diffusion, contrast, initial data, and to the local geometry. In particular, we have shown the importance of the ''geometrical term'' which fixes the problem of the edges discontinuities after filtering. Applications of MRI data of shoulder joints, hip and knee are presented in the testing and validation chapter. The results are given using two evaluation functions concerning edges and regions. These functions demonstrate robustness and accuracy of proposed model in removing noise and preserving edges
Olivier, Côme. "Contributions à l’étude des générateurs d'ondes thermoacoustiques : contrôle actif des auto-oscillations et propagation non linéaire". Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1023/document.
Pełny tekst źródłaThermoacoustic engines are heat engines in which a fluid in a porous media submitted to temperature gradient undergoesa thermodynamic cycle performing acoustic work. The design and optimization of such engine usually makes use of the linear theory of thermoacoustics. Though it is sufficient to describe the onset conditions of the instability, this theory fails to predict accurately the operating conditions of engines. Indeed, nonlinear effects develop due to high acoustic levels, which tend to perturb the temperature distribution in the thermoacoustic core and take it away from the ideal distribution for which the engine as been optimized.The work presented in this manuscript is devoted to a technique of control of the acoustic field distribution in the engine, in order to optimize the thermoacoustic interaction though nonlinear effects distort the temperature distribution. An auxiliary acoustic source added to the engine, powered by a feedback loop allows to control the efficiency of thermoacoustic conversion. Experimental results are presented, showing complex behavior such as oscillation death or hysteretic behavior of thresholds.A low order model of the engine under the influence of the feedback loop is presented, giving an insight of the physical phenomena at stake in this control. It is based on a lumped element electro-acoustic analogy, coupled with a discretization of the heat transfer description.A complementary study of the nonlinear propagation is presented for simple configurations of thermoacoustic prime movers. The condition leading to shock-wave formation are sought thanks to a numerical model, adapted to selfsustainedoscillations from a previous model of weakly nonlinear guided propagation
Mrozowski, Nicolas. "Mécanismes de propagation de fissure dans un superalliage base nickel polycristallin en régime d’interaction fatigue-fluage-oxydation-vieillissement métallurgique Aging of γ′ precipitates at 750°C in the nickel-based superalloy AD730TM: a thermally or thermo-mechanically controlled process?" Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0010.
Pełny tekst źródłaThe 750°C crack propagation behavior in the polycristalline nickel-base superalloy AD730TM is studied. This study falls within the overall objectives of optimizing the “microstructure – mechanical properties” relations in nickel-base superalloys used for example in turbine disks. The deceleration of the crack propagation with the increase in ΔK value is specifically at the core of the PhD thesis work. Via a crack propagation test campaign, this phenomenon is systematically identified when dwell-fatigue loading are performed. The influence of the thermomechanical history of the material in investigated by varying several experimental parameters such as the initial microstructural state (γ’ precipitates), the initial value of ΔK, the environment or the dwell durations. The origin of the deceleration phenomenon is therefore shown to be linked with combined and protective effects of stress relaxation, oxide growth and metallurgical aging at the crack tip. To improve the understanding of the crack propagation results, complementary analysis of the 750°C γ’ precipitates aging is performed. One of the main outcomes is that aging kinetics (γ’ growth, carbide precipitation) are enhanced thanks to a cyclic loading. Besides, the more the microstructure is aged, the higher the stress relaxation rate at 750°C
Latorre, Diana. "Imagerie sismique du milieu de propagation à partir des ondes directes et converties : application à la région d'Aigion (Golfe de Corinthe, Grèce)". Phd thesis, Université de Nice Sophia-Antipolis, 2004. http://tel.archives-ouvertes.fr/tel-00653801.
Pełny tekst źródłaPeynaud, Emilie. "Rayonnement sonore dans un écoulement subsonique complexe en régime harmonique : analyse et simulation numérique du couplage entre les phénomènes acoustiques et hydrodynamiques". Thesis, Toulouse, INSA, 2013. http://www.theses.fr/2013ISAT0019/document.
Pełny tekst źródłaThis thesis deals with the numerical simulation of time harmonic acoustic propagation in an arbitrary mean flow in an unbounded domain. Our approach is based on an equation equivalent to the linearized Euler equations called the Galbrun equation. It is derived from a mixed Eulerian-Lagrangian formulation and results in a single equation whose only unknown is the perturbation of the Lagrangian displacement. A direct solution using finite elements is unstable but this difficulty can be overcome by using an augmented equation which is constructed by adding a new unknown, the vorticity, defined as the curl of the displacement. This leads to a set of equations coupling a wave like equation with a time harmonic transport equation which allows the use of perfectly matched layers (PML) at artificial boundaries to bound the computational domain. The first part of the thesis is a study of the time harmonic transport equation and its approximation by means of a discontinuous Galerkin scheme, the difficulties coming from the oscillating behaviour of its solutions. Once these difficulties have been overcome, it is possible to deal with the resolution of the acoustic propagation problem. The approximation method is based on a mixed continuous-Galerkin and discontinuous-Galerkin finite element scheme. The well-posedness of both the continuous and discrete problems is established and the convergence of the approximation under some mean flow conditions is proved. Finally a numerical implementation is achieved and numerical results are given which confirm the validity of the method and also show that it is relevant in complex cases, even for unstable flows
Virot, Florent. "Contribution à l'étude expérimentale et numérique du régime hélicoïdal de détonation dans les systèmes H2, CH4, C2H6–O2 dilués ou non par N2 ou Ar". Phd thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aéronautique, 2009. http://tel.archives-ouvertes.fr/tel-00443884.
Pełny tekst źródłaAlbert, Marie. "Prévention du phénomène de nucléation et de la propagation des tauopathies par immunothérapie passive utilisant un anticorps ciblant une région centrale de la protéine tau". Thesis, Lille 2, 2018. http://www.theses.fr/2018LIL2S030/document.
Pełny tekst źródłaIn tauopathies, such as Alzheimer's disease, tau protein becomes abnormally hyperphosphorylated which leads to its accumulation and intracellular aggregation. This process gradually leads to neuronal loss and cognitive decline. Anti-tau immunotherapy is increasingly considered as a potential treatment to block tauopathies’s progression.UCB BioPharma recently showed that antibody D, targeting an epitope in the central region of tau (aa 235-250), is able to block, in vitro, the intracellular seeding of tau proteins induced by PHFs purified from the brain of Alzheimer's patients. The antibody A, same isotype and associated with similar binding properties but recognizing the N-terminal region of tau (aa 15 to 24) is not able to prevent tau seeding in this cell based assay. This observation underlines the importance of the targeted epitope on tau protein in order to neutralize pathological species contained in Alzheimer's brains (Courade et al., 2018).In order to study the properties of antibody D in vivo, we developed two murine models of tauopathies. First, a seeding model based on a unilateral injection of Alzheimer's brain homogenate into the hippocampus of young Tg30tau mice. Secondly, a spreading model to study the propagation of pathological tau seeds, based on unilateral hippocampal injection of P301L-K18 fibrils in hTauP301L transgenic mice. Tauopathies induced in these models were quantified in the ipsi and contralateral hippocampus in the presence of immunotherapeutic treatments with anti-tau antibodies (D, A) or a negative control antibody. Quantification of hyperphosphorylated and aggregated tau was performed by immunohistochemical or biochemical analyses.In the seeding model, antibody D significantly reduces the appearance of hyperphosphorylated and aggregated tau both in the ipsi and contralateral CA1 regions of hippocampus. In contrast, antibody A is not able to prevent the appearance of pathological tau in this model. In the spreading model, immunotherapeutic treatments with antibody D significantly reduces the spread of pathological tau seeds in the contralateral hippocampus.From these two murine models of tauopathies, we confirmed in vivo the ability of antibody D to neutralize the pathological tau species contained in an Alzheimer's brains homogenate and demonstrated its capacity to reduce the intercellular propagation of tauopathies. In the seeding model, antibody A wasn’t able to affect the onset of tauopathy. These results confirm those described by UCB BioPharma based on their in vitro aggregation assay and confirm the importance of the targeted epitope in order to effectively prevent the development of tauopathies in vivo
Navas, Nunez Rafael. "Modélisation hydrologique distribuée des crues en région Cévennes-Vivarais : impact des incertitudes liées à l'estimation des précipitations et à la paramétrisation du modèle". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAU025/document.
Pełny tekst źródłaIt is known that having a precipitation observation system at high space - time resolution is crucial to obtain good results in rainfall - runoff modeling. Radar is a tool that offers quantitative precipitation estimates with very good resolution. When it is merged with a rain gauge network the advantages of both systems are achieved. However, radars estimates have different uncertainties than those obtained with the rain gauge. In the modeling process, uncertainty of precipitation interacts with uncertainty of the hydrological model. The objective of this work is: To study methods used to quantify the uncertainty in radar – raingauge merge precipitation estimation and uncertainty in hydrological modeling, in order to develop a methodology for the analysis of their individual contributions in the uncertainty of rainfall - runoff estimation.The work is divided in two parts, the first one evaluates: How the uncertainty of radar precipitation estimation can be quantified? To address the question, the geostatistical approach by Kriging with External Drift (KED) and Stochastic Generation of Precipitation was used, which allows to model the spatio - temporal structure of errors. The method was applied in the Cévennes - Vivarais region (France), where there is a very rich observation system. The second part explains: How can it be quantified the uncertainty of the hydrological simulation coming from the radar precipitation estimates and hydrological modeling process? In this point, the hydrological mesoscale computation tool was developed; it is distributed hydrological software in time continuous, within the basis of the Curve Number and the Unit Hydrograph. It was applied in 20 spatio-temporal resolutions ranging from 10 to 300 km2 and 1 to 6 hours in the Ardèche (~ 1971 km2) and the Gardon (1810 km2) basins. After a sensitivity analysis, the model was simplified with 4 parameters and the uncertainty of the chain of process was analyzed: 1) Precipitation estimation; 2) Hydrological modeling; and 3) Rainfall - runoff estimation, by using the coefficient of variation of the simulated flow.It has been shown that KED is a method that provides the standard deviation of the precipitation estimation, which can be transformed into a stochastic estimation of the local error. In the chain of processes: 1) Uncertainty in precipitation estimation increases with decreasing spatio-temporal scale, and its effect is attenuated by hydrological modeling, probably due by storage and transport properties of the basin; 2) The uncertainty of hydrological modeling depends on the simplification of hydrological processes and not on the surface of the basin; 3) Uncertainty in rainfall - runoff treatment is the result of the amplified combination of precipitation and hydrologic modeling uncertainties
Wang, Shengrui. "Réseaux multicouches de neurones artificiels : algorithmes d'apprentissage, implantations sur hypercube : applications". Phd thesis, Grenoble INPG, 1989. http://tel.archives-ouvertes.fr/tel-00335818.
Pełny tekst źródłaLorival, Jean-Etienne. "Descritption d'un modèle analytique pour la détermination des caractéristiques d'une tension de bruit dans un réseau d'interconnexions". Montpellier 2, 2008. http://www.theses.fr/2008MON20073.
Pełny tekst źródłaAdvancements in the field of VLSI have lead to more compact digital circuits with higher clock rates. Yet, they become more sensitive to noise, especially when those ones are generated by interconnection lines networks when lines are submitted to diaphonic or coupling phenomena; resulting then in the apparition of propagation delays through the lines or noise voltages known as crosstalk. In order to quantify, limit or suppress those coupling effects, integrated circuits designers try to propose interconnection lines model more and more precise at the condition they could be easily incorporated in simulation tools. In this context, to evaluate noise voltages characteristics, an analytical interconnection lines model is proposed in this manuscript. It is based on the quasi-TEM propagation modes existing in an interconnect network and also on a correlation method allowing a description of the network with 1st and 2nd order filters
Hally, Alan. "Prévisibilité des épisodes méditerranéens de précipitations intenses : propagation des incertitudes liées aux paramétrisations de la microphysique des nuages et de la turbulence". Phd thesis, Toulouse 3, 2013. http://thesesups.ups-tlse.fr/3241/.
Pełny tekst źródłaThe north-western Mediterranean region is susceptible to heavy precipitation events (HPEs) between the months of September and November with south-eastern France being one of the areas most affected. Numerical forecasting of such events has drastically improved in recent years. However, because of the complex and multiscale interactions taking place in deep convective cloud systems, model errors remain, especially in the representation of the physical processes. In particular, the cloud physics and turbulence parameterisations rely upon unavoidable simplifications and assumptions which clearly limit the potential accuracy of deterministic forecasts in capturing extreme weather events. To represent the uncertainties associated with these parameterisations, a probabilistic methodology using ensemble prediction systems (EPSs) was proposed. Perturbations were introduced upon the time tendencies of the warm and cold microphysical and turbulence processes, as well as the adjustable parameters of the microphysical parameterisations. This approach was tested and assessed upon two idealised convective events with the aim of uncovering the processes which induced the greatest dispersion in the surface rainfall. Following these tests, ensembles were constructed for seven real world events which occurred over south-eastern France in the autumns of 2010, 2011 and 2012. Simultaneously perturbing the time tendencies of the warm and cold microphysical and turbulence processes was shown to produce the greatest degree of dispersion in the rainfall pattern with the level of that dispersion depending upon the nature of the precipitating event. The dispersion is gen- erally more important when the incident flow is weak to moderate and precipitation is observed on the plains. For certain events, the level of dispersion introduced by perturbations upon the physical processes is similar to that generated by perturbing the initial and boundary conditions. It is concluded that, even though the impact of perturbing the physical parameterisations is moderate, it is sufficiently important to warrant an inclusion of such perturbations in an operational EPS
Hally, Alan. "Prévisibilité des épisodes méditerranéens de précipitations intenses : Propagation des incertitudes liées aux paramétrisations de la microphysique des nuages et de la turbulence". Phd thesis, Université Paul Sabatier - Toulouse III, 2013. http://tel.archives-ouvertes.fr/tel-00939287.
Pełny tekst źródłaCheron, Elie. "Guides d'ondes et transport dans les milieux désordonnés : effets de la symétrie et de la localisation". Thesis, Le Mans, 2019. http://www.theses.fr/2019LEMA1017.
Pełny tekst źródłaThis thesis focuses on the wave propagation in disordered waveguides. First, we introduce the basic tools and concepts in order to present the different transport regimes and phenomena related to coherent effects (such as universal conductance fluctuations, enhanced backscattering or Anderson's localization). Beside the remarkable phenomena associated to diffuse transport, the coherent effects are also noticeable when the spatial distribution of the scatterers displays symmetries. The second part is dedicated to the observation of a significant and broadband enhancement in transmission through opaque barriers. The sensitivity of this phenomenon to symmetry defects is discussed in Chapter 4. Limitations due to absorption, which are always present in an experimental context, and localization are also inspected. The fourth chapter focuses on one of the signatures of the localization regime: the propagation within these insulating media is insensitive to the source. We present some special cases in which this property is broken. Finally, several preliminary studies related to other propagation phenomena in complex media are discussed as perspectives for this work
Simon, Damien. "Survie et généalogies dans quelques modèles de dynamique des populations". Phd thesis, Université Paris-Diderot - Paris VII, 2008. http://tel.archives-ouvertes.fr/tel-00286612.
Pełny tekst źródłaLa première partie étudie l'évolution de marches aléatoires avec branchements unidimensionnelles en présence d'un seuil de survie qui croît linéairement au cours du temps. En reliant les propriétés de ces marches aléatoires à une équation de propagation de fronts, nous étudions la transition vers l'extinction de ces marches lorsque la vitesse du seuil croît et obtenons les comportements critiques de la probabilité de survie. Nous construisons également un processus biaisé décrivant une population de telles marches conditionnée sur sa taille à un instant final. Cette construction permet d'étudier le régime quasi-stationnaire près de la vitesse critique. Enfin, nous présentons un modèle exactement soluble sur lequel plusieurs conjectures peuvent être vérifiées.
Dans une seconde partie, nous étudions des populations de taille constante du point de vue des généalogies et des temps de coalescence. Nous expliquons dans quelle mesure certains modèles d'évolution avec sélection se rapprochent des modèles de polymères dirigés et montrons plusieurs résultats numériques qui mettent en évidence l'existence de classes d'universalité dans les généalogies. En absence de sélection, nous étudions la dynamique des temps de coalescence et de l'âge de l'ancêtre commun d'une population, ainsi que les corrélations de ce dernier avec la diversité génétique dans un cas simple.
Lorival, Jean-Etienne. "Description d'un modèle analytique pour la détermination des caractéristiques d'une tension de bruit dans un réseau d'interconnexions". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2008. http://tel.archives-ouvertes.fr/tel-00331748.
Pełny tekst źródłaMarty, Renaud. "PREVISION HYDROLOGIQUE D'ENSEMBLE ADAPTEE AUX BASSINS A CRUE RAPIDE. Elaboration de prévisions probabilistes de précipitations à 12 et 24 h. Désagrégation horaire conditionnelle pour la modélisation hydrologique. Application à des bassins de la région Cévennes Vivarais". Phd thesis, Université de Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00480713.
Pełny tekst źródłaNirrengarten, Michael. "Modes de déformation et implications cinématiques des marges hyper-étirées : les exemples du sud de l'Atlantique Nord". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAH014/document.
Pełny tekst źródłaDeformation modes of magma-poor hyper-extended rift systems evolve through time and space. Hence the observed structures and architectures vary along a depth section as well as on a map. This study aims to characterize the deformation modes of hyper-extended systems and their propagation using the examples of the southern North Atlantic. The architecture of the continental crust termination has been compared to the critical Coulomb wedge theory because it has a wedge shape, the final deformation is brittle/frictional and this wedge is gliding over a basal detachment. This theory highlights the distinct behavior of the two conjugate margins. Moreover it constrains crustal architecture of the continental crust termination, integrates continentward dipping faults and explains the formation of extensional allochthons in a sequential faulting model. The integration of deformation modes in an evolving 3D model necessitates a reliable kinematic context, which is not the case for the opening of the southern North Atlantic Ocean. This is linked to the interpretation of the J-magnetic anomaly as an oceanic isochron. Re-investigations of this anomaly revealed its polygenic and polyphased formation, which is inconsistent for an oceanic isochrons or a domain boundary making it unusable for plate reconstruction. The evolution of rift deformation has been analyzed with a new plate reconstruction of the southern North Atlantic. It appears that the continental crust deformation is segmented whereas oceanic crust propagates in a V-shape. The approach developed in this thesis also asks new geodynamical questions on the influence of inheritance and the effect of triple junction
Ben, Gdara Sarra. "Etude des déclenchements intempestifs des produits différentiels". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT032.
Pełny tekst źródłaThe Residual Current Device (RCD) must ensure the continuity of service which means that no default other than those that can put the user at risk should make the product trigger, to avoid any inconvenience (freezer not supplied) or a financial loss (non-operation of a photovoltaic). The measurement function is made up of:- A torus for measuring the residual current, it naturally carries the sum of currents entering and exiting the installation- A plate shaping (filtering)- An actuator, the polarized relay which sets the threshold of the device (through its power of initiation) and provides mechanical energy to turn off power supply.These false triggering are caused by defaults initiated among the measurement chain. We can cite three main reasons:- Residual current too high (over-voltages on electrical network by common mode)- Radiated Magnetic Fields (current through the primary circuit of the torus)- Balancing the torus (differential mode) (current through the primary circuit of the torus)As the atmospheric over-voltages are considered to be the most critical disturbances, they will appear as the principal subject of this thesis. The main issue is the behavior of the RCD facing a lightning stroke. So, a well understanding of the manner that it will respond in such situations is necessary. The objectives of this study are to:- Establish a temporal model of lightning stroke- Highlight the different working phases in front of a lightning stroke- Establish a RCD's behavioral model adapted to every phase- Highlight the causes of unwanted triggers- Propose solutions enabling our products to not trigger by default and so improve the reliability of their functioning- Reduce customer returns
Sanchez-Palencia, Laurent. "ETUDE THEORIQUE DE LA DYNAMIQUE NON LINEAIRE D'ATOMES FROIDS DANS UN RESEAU OPTIQUE DISSIPATIF : TRANSPORT SPONTANE ET TRANSPORT STIMULE". Phd thesis, Ecole Polytechnique X, 2003. http://tel.archives-ouvertes.fr/tel-00003425.
Pełny tekst źródłaNous distinguons deux classes d'atomes, respectivement piégés et non-piégés dans les puits de potentiel, aux comportements très différents. Cette distinction permet de comprendre précisément le comportement des distributions de vitesse ainsi que les propriétés du transport spontané (diffusion spatiale) dans un domaine de paramètres allant du régime sautant au régime oscillant.
Des phénomènes de transport stimulés sont étudiés dans le régime intermédiaire entre les régimes sautant et oscillant où les temps typiques du mouvement hamiltonien et des phénomènes dissipatifs sont comparables. Nous caractérisons les modes de propagation Brillouin ainsi que leurs mécanismes d'excitation. Nous montrons que ceux-ci donnent lieu au phénomène de résonance stochastique qui correspond à la synchronisation du mouvement hamiltonien et des processus dissipatifs. Nous étudions enfin un rochet atomique temporel correspondant à un mouvement dirigé induit par la brisure de la symétrie temporelle.
Saracco, Ginette. "Propagation acoustique en régime harmonique & transitoire a travers un milieu inhomogène: Méthodes asymptotiques & Transformation en ondelettes". Phd thesis, 1989. http://tel.archives-ouvertes.fr/tel-00178676.
Pełny tekst źródłaDans un premier temps, nous avons traité le cas s'une source ponctuelle monochromatique à l'aide de méthodes asymptotiques, de façon à vérifier l'existence physique de cette contribution. Dans le cas du dioptre plan air-eau, nous avons pu séparer expérimentalement la contribution latérale de la contribution géométrique, et mettre en évidence le comportement et les propriétés de celles-ci. Le champ réfracté total fait alors apparaître des zones d'interférences en parfait accord avec l'étude théorique et numérique. La contribution latérale présentant un caractère "dispersif", montre l'intérêt dans le cas du régime transitoire, d'utiliser une méthode de type temps-échelle.
La fonction de Green peut être décomposée de façon naturelle en trois contributions analogues à celles du régime harmonique. La transformée en ondelettes permet alors de calculer de façon exacte ces différentes contributions et d'en étudier leur comportement. L'orginalité des résultats obtenus est la mise en évidence à certaines échelles, de phénomènes transitoires très brefs (échos) qui permettent d'engager une discussion nouvelle de ce type de problème. Une expérimentation combinée à une analyse temps-échelle (ondelettes) a confirmé ces observations.
Par analogie à la formule de reconstitution simple de la transformée en ondelettes inverse, nous avons pu élaborer, pour de grandes distances radiales, une formule de reconstruction de la dépendance temporelle du signal-source (problème inverse) à partir de la mesure de la pression transmise (jouant le rôle de "pseudo-coefficients d'ondelettes") sur les profondeurs.
Enfin, l'application de cette transformation à un problème de rétrodiffusion acoustique par des coques sphériques élastiques (interface fluide/solide) a montré qu'il est possible d'accéder à certaines caractéristiques physiques de la cible.
Lee, Dong-Hyun. "Difference target propagation". Thèse, 2018. http://hdl.handle.net/1866/21284.
Pełny tekst źródłaRAGOUBI, HOR Refka. "Filtrage anisotrope robuste régi par propagation de fronts : vers une segmentation automatique de volumes IRM". Phd thesis, 2013. http://tel.archives-ouvertes.fr/tel-00956465.
Pełny tekst źródłaOlivier, Thomas. "Contribution à la métrologie de l'indice de réfraction et de l'absorption non-linéaires en régime nanoseconde : amélioration de la méthode de Z-scan et simulations numériques". Phd thesis, 2004. http://tel.archives-ouvertes.fr/tel-00009261.
Pełny tekst źródłaProulx, Louis-Xavier. "Étude numérique et asymptotique d'une approche couplée pour la simulation de la propagation de feux de forêt avec l'effet du vent en terrain complexe". Thèse, 2016. http://hdl.handle.net/1866/20586.
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