Dissertations / Theses on the topic 'Limite à faible dispersion'
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Mésognon-Gireau, Benoît. "Limites singulières en faible amplitude pour l'équation des vagues." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066467/document.
In this thesis, we study the behavior of the solutions of the Water-Waves equations in the rigid lid regime as the amplitude of the waves goes to zero. More precisely, the Water-Waves equations investigate the dynamic of a free surface fluid, bounded from below by a fixed bottom. The equations depends on many physical parameters, as the ratio epsilon between the wave amplitude and the deepness of the water. The rigid lid model consists in scaling the time by an epsilon factor and taking the limit epsilon goes to zero, simulating a situation where the amplitude of the waves goes to zero. The mathematical study of this limit correspond to a singular perturbation problem of a dispersive equation. In this thesis, we first use classical tools of hyperbolics equations to prove a long time existence result for the Water-Waves equations. We then prove a dispersion result for these equations, using stationary phase methods and Paley-Littlewood decomposition. We then combine these results to highlight the lack of compactness in the weak (but non strong) convergence of the solutions of the Water-Waves equations as the amplitude goes to zero
Badreddine, Rana. "On a DNLS equation related to the Calogero-Sutherland-Moser Hamiltonian system." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASM008.
This thesis is devoted to a PDE obtained by A. Abanov et al (J. Phys. A, 2009) from the hydrodynamic limit of the Calogero-Sutherland Hamiltonian system. A nonlinear integrable Schrödinger-type equation on the Hardy space is obtained and has a Lax pair structure on the line and on the circle. The goal of this thesis is to establish, by using the integrability structure of this PDE, some global well-posedness results on the circle, extending down to the critical regularity space. Secondly, we investigate the existence of particular solutions. Thus, we characterize the traveling waves and finite gap potentials of this equation on the circle. Thirdly, we study the zero-dispersion (or semiclassical) limit of this equation on the line and characterize its solutions using an explicit formula
Personne, Arnaud. "Dynamique du modèle de Moran en environnement aléatoire." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC102.
In some ecosystems and more particularly in virgin tropical forests, different species having the same ecological requirements coexist in the same environment. For example, some forests have over a hundred different tree species on one hectare. To explain this incrediblediversity, scientists have built models in which the community composition isonly due to the stochastic dispersion of individuals.The mathematical model studied in this thesis follows this line. It was suggested by Mr. Kalyuzhni in an article where he justifies its relevance. It is known as the Moran model in random environment. It is therefore a question of studying a birth and death process taking into account the environmental stochasticity (climates, diseases, etc.) To study this dynamic, we use an approximation by a diffusion, on the classical scale where the acceleration in time is given by the square of the population size, moreover selective advantage and immigration are inversely proportional to thethis size. The selective advantage varies randomly and is modeled by a Markov jump process. We study the convergence in law of the processes sequence and give a quantitative estimate of the error made for a given population. We are then interested in the moments estimation of the population frequencies, motivated in particular by biodiversity indices such as the Simpson's index andbased on the approximations obtained before.In the case of a non-zero selection, the stochastic differential equation governing a moment appeals to the higher order moment. To overcome this difficulty, we create a closure method to reduce the study of the first moments to a finite system of differential equations. We give an estimation of the error made by neglecting the terms of higher degrees. Finally, in the case of two species and with constant coefficients, we give an estimate of the convergence speed of the diffusion towards the stationary measure. In a second time, we are interested in a time scale proportional to the size of the population. This leads to a convergence of the process law towards a deterministic limitcharacterized by an ordinary differential equation. The selection coefficient evolving randomly, still following a Markov jump process, this process is a PDMP.We then study the persistence of the different species and the potential coexistencethanks the persistence theory, developed by Benaïm and Schreiber. In this part, we are particularly interested in the case where all the species persist. With only two environments: we show that two species can persist but not three. With more environments,the explicit classification stay an open problem but an example of persistence with three speciesand three environments is given
Golliard, Joachim. "Bruit de cavités résonantes excitées par un écoulement turbulent à faible nombre de Mach." Poitiers, 2002. http://www.theses.fr/2002POIT2283.
The subject of this study is the noise generated by a turbulent boundary layer flow grazing on the opening of a Helmholtz-resonator like cavity. A prediction model is developed, based upon the passive response of the cavity to an excitation located at its opening. The excitation is computed from the wall-pressure fluctuations within the turbulent boundary layer. The acoustic response of the cavity is computed with the transfer matrix method. The impedance of the opening submitted to a grazing flow is an important parameter which required an experimental study. An empirical law extracted from this experimental study is proposed. The prediction model is validated by an experimental study. The influence of the flow characteristics on the spectra of generated noise inside the cavity and on the occurrence and frequency of tones is well predicted by the model
Wintenberger, Olivier. "Utilisation des notions de dépendance faible en statistique." Phd thesis, Université Panthéon-Sorbonne - Paris I, 2007. http://tel.archives-ouvertes.fr/tel-00160702.
Ouro, Koura Baba-Issa. "Pompabilité des bétons autoplaçants à faible teneur en liant : Étude des mécanismes de formation de la couche limite." Thesis, CY Cergy Paris Université, 2020. http://www.theses.fr/2020CYUN1058.
The increase in the use of Self-consolidating concrete (SCC) raises the problem of their environmental impact, justifying the recent interest in the development of SCC with low binder content (eco-SCC). On the other hand, in most of concrete applications, the casting of SCC is conducted by pumping process due to its numerous advantages, including the ease to transport the material into the casting zones that are barely accessible. The pumpability of SCC depends on the ability of the material to form lubrication layer (LL) as well as its properties. Despite the numerous advances in this domain, predict the pumpability of concrete remains a real challenge. In fact, this requires besides the rheology of the concrete, a good control of the rheological properties and the thickness of LL this concrete could form. However, it is very difficult to identify the LL material during the pumping process. Moreover, the mechanisms of its formation still are less well understood. This limit the determination of LL characteristics and their variations.This project aims firstly to develop an effective approach to proportion SCC with normal and low binder content. Secondly, the study aims to develop an approach to determine the rheological properties of LL. Finally, the project deal with the study of the potential mechanisms involved in the formation of the LL and determine the main parameters controlling these mechanisms. In this project, SCC is considered as a diphasic suspension of coarser particles (> 1.25 mm) in a fluid matrix of fine mortar (< 1.25 mm). A new approach based on the coupled effect of the characteristics of both suspending (fine mortar) and suspended (coarse aggregate) phases was proposed to proportion SCC. Furthermore, new methodology was established to evaluate the rheological properties of the LL, simulated as a diphasic suspension of fine sand (< 1.25 mm) and cement paste. The results showed the significant effect of the volumetric content and packing density of fine sand, as well as cement paste rheology on the visco-elastoplastic characteristics of the lubrication layer. The main mechanisms of LL formation, namely dynamic segregation and Reynolds dilatancy were investigated through a new segregation index and a new established test of Reynolds dilatancy. Other phenomena such as blocking that can occur during the pumping process and influence the formation of LL are evaluated through new proposed test.The proposed optimization approach allows to determine the required characteristics of granular skeleton and fine mortar mixture to obtain SCC with the desired flowability and mechanical performances. The adopted diphasic approach of SCC mixture allowed a better comprehension of the mechanisms of LL formation. The results showed low dynamic segregation of eco-SCC compared to normal SCC. On the other hand, the normal and eco-SCC exhibited comparable Reynolds dilatancy of around 1 % of the initial volume of the mixture. The relative packing density of coarse aggregate was found to govern the mechanism of LL formation. In order to facilitate the selection of the optimal mixture of aggregate for better pumpability, attempt was made to determine the morphological characteristics of aggregate that control their packing density. Then empirical models were established to predict all the phenomena involved in LL formation based on morphological aggregate morphological characteristics and fine mortar mixture properties. Based on the results of this project, different normal and eco-SCC mixtures were recommended regarding their flow performances
Grégori, Fabienne. "Plasticité de l'alliage γ-TiAl : rôle des dislocations ordinaires et superdislocations dans l'anomalie de limite d'élasticité." Paris 6, 1999. http://www.theses.fr/1999PA066568.
Prieur, Clémentine. "Dépendance faible: estimation et théorèmes limite.Application à l'étude statistique de certains systèmes dynamiques." Habilitation à diriger des recherches, Université Paul Sabatier - Toulouse III, 2006. http://tel.archives-ouvertes.fr/tel-00133468.
non -mélangeantes au sens de Rosenblatt (1956). La notion de mélange classique est affaiblie
afin d'établir des inégalités ainsi que des théorèmes limite pour différentes classes de processus
comme par exemple certains systèmes dynamiques, des chaînes de Markov non irréductibles,
ou encore des fonctions de processus linéaires non mélangeants. Les résultats obtenus sont
ensuite appliqués au domaine de la statistique non paramétrique.
Deux autres thématiques sont abordées dans ce manuscrit : d'une part l'étude de principes
de grandes déviations (notamment pour le processus de records généralisés), et d'autre part
l'estimation adaptative de fonctionnelles linéaires.
Coste, Nicolas. "Contribution à l'étude de la dispersion des contre-mesures dans la couche de surface marine." Aix-Marseille 2, 2000. http://www.theses.fr/2000AIX22069.
Latron, Mathilde. "Adaptation, régression et expansion en limite d’aire de répartition." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R025/document.
Ongoing global changes may lead to shifts in the geographical range of biological species. Adaptive evolution and phenotypic plasticity will determine these shifts. The demography of the species and their dispersal capacities will also determine their ability to colonize newly favourable habitats. When geographical distributions are shifting, one can expect a variation in life history traits across the geographic range. Indeed, survival, reproduction and dispersal capacity will determine the success or failure of population establishment and persistence. These traits are thus theoretically expected to be maximized on colonization fronts because low recruitment rates, mate limitation and inbreeding depression, among other factors, can lead to population decline, local extinction, or colonization failure. On colonization fronts, we therefore expect to observe an increase in dispersal capacities and self-fertilization rate, advanced phenology, and higher fertility compared to populations located in the central part of the range. On retraction fronts, mate limitation can also drive selection for increased self-fertilization, and worsening habitat conditions can lead to higher investment in survival as compared to central populations. Understanding the evolution of life history traits in relation to species range dynamics is therefore essential to better understand the future evolution of biodiversity in the Anthropocene. In this context, spatial variations of life history traits were characterized for four plant species that show expansion or retraction fronts in northern France: Miner’ lettuce (Claytonia perfoliata), Danish scurvygrass (Cochlearia danica), Rock samphire (Crithmum maritimum) and Dune pansy (Viola tricolor subsp. curtisii). Variations of life history traits were surveyed from the core to the edge of their geographic ranges by using phenotypic measurements in the natural environment and in the common garden and by analysing the spatial genetic structure for a subset of two species. The geographical range dynamics of these focal species were explained by species-specific factors in interaction with their respective environment. Miner’s lettuce and Danish scurvygrass, both expanding in northern France, showed high propagule pressure on their colonization fronts: while Miner’s lettuce exhibited a higher germination rate at the edge of its range, marginal populations of Danish scurvygrass showed an increase in dispersal capacities. Rock samphire, which is expanding northwards, showed no variation in its life history traits along its geographical range. All populations may show a high capacity for successful colonization and analyses of spatial genetic structure indicated large amount of gene flow among populations via long-distance dispersal events of diaspores. Lastly, the retracting populations of Dune pansy showed an increase in selfing rate that may provide some reproductive assurance. However, their lower reproductive output could threaten their long-term persistence. Altogether, while each species shows variations in life history traits consistent with theoretical predictions, trait variations appeared to be idiosyncratic. This suggested that no common evolutionary syndrome occurred in expanding or receding range edges and that species' responses mostly depend on their specific biology. These results have therefore important implications relevant to conservation biology and to forecasting of geographical range shifts under rapidly changing environments
Latron, Mathilde. "Adaptation, régression et expansion en limite d’aire de répartition." Electronic Thesis or Diss., Université de Lille (2018-2021), 2019. http://www.theses.fr/2019LILUR025.
Ongoing global changes may lead to shifts in the geographical range of biological species. Adaptive evolution and phenotypic plasticity will determine these shifts. The demography of the species and their dispersal capacities will also determine their ability to colonize newly favourable habitats. When geographical distributions are shifting, one can expect a variation in life history traits across the geographic range. Indeed, survival, reproduction and dispersal capacity will determine the success or failure of population establishment and persistence. These traits are thus theoretically expected to be maximized on colonization fronts because low recruitment rates, mate limitation and inbreeding depression, among other factors, can lead to population decline, local extinction, or colonization failure. On colonization fronts, we therefore expect to observe an increase in dispersal capacities and self-fertilization rate, advanced phenology, and higher fertility compared to populations located in the central part of the range. On retraction fronts, mate limitation can also drive selection for increased self-fertilization, and worsening habitat conditions can lead to higher investment in survival as compared to central populations. Understanding the evolution of life history traits in relation to species range dynamics is therefore essential to better understand the future evolution of biodiversity in the Anthropocene. In this context, spatial variations of life history traits were characterized for four plant species that show expansion or retraction fronts in northern France: Miner’ lettuce (Claytonia perfoliata), Danish scurvygrass (Cochlearia danica), Rock samphire (Crithmum maritimum) and Dune pansy (Viola tricolor subsp. curtisii). Variations of life history traits were surveyed from the core to the edge of their geographic ranges by using phenotypic measurements in the natural environment and in the common garden and by analysing the spatial genetic structure for a subset of two species. The geographical range dynamics of these focal species were explained by species-specific factors in interaction with their respective environment. Miner’s lettuce and Danish scurvygrass, both expanding in northern France, showed high propagule pressure on their colonization fronts: while Miner’s lettuce exhibited a higher germination rate at the edge of its range, marginal populations of Danish scurvygrass showed an increase in dispersal capacities. Rock samphire, which is expanding northwards, showed no variation in its life history traits along its geographical range. All populations may show a high capacity for successful colonization and analyses of spatial genetic structure indicated large amount of gene flow among populations via long-distance dispersal events of diaspores. Lastly, the retracting populations of Dune pansy showed an increase in selfing rate that may provide some reproductive assurance. However, their lower reproductive output could threaten their long-term persistence. Altogether, while each species shows variations in life history traits consistent with theoretical predictions, trait variations appeared to be idiosyncratic. This suggested that no common evolutionary syndrome occurred in expanding or receding range edges and that species' responses mostly depend on their specific biology. These results have therefore important implications relevant to conservation biology and to forecasting of geographical range shifts under rapidly changing environments
Bihhadi, Abdelkader. "Etude de la propagation acoustique dans les conduits et les silencieux en écoulements non isothermes par une méthode de différences finies et enveloppe d'onde." Poitiers CEAT, 1995. http://www.theses.fr/1995POIT2285.
Loeck, Jaqueline Fischer. "Modelo operacional para dispersão de poluentes na camada limite atmosférica com contornos parcialmente reflexivos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/183286.
The present work proposes a new model for pollutant dispersion in the atmosphere, this model was idealized in the dissertation work of the author and continued its development in this research. The model is based on the semi-analytic solution of the advectiondiffusion equation for continuous emission, with resolution through the method of separation of variables and the Fourier transform. The boundary conditions are treated as infinite reflections of the pollutant in the soil and at the top of the atmospheric boundary layer. These reflections are used in a partial way in the attempt to consider phenomena of dispersion that can not be explained in the deterministic model, so that the boundaries can be understood as stochastic, that is, one can interpret the boundaries as a sampling of a distribution. In addition, an optimization is performed in the partially reflective boundaries, with the purpose of developing an optimization methodology and determining the optimal values for the partial reflection. The results obtained were firstly compared with the experiments of Copenhagen and Hanford. Subsequently, the model was compared with concentration data collected at a cellulose production plant. The dispersion of pollutants emitted by a thermoelectric plant in Brazil was also simulated, which is part of the research and technological development program of the electric energy sector of the National Electric Energy Agency (ANEEL).
Grazzini, Fabienne. "Étude expérimentale de la dispersion de polluants en présence d'obstacles." Toulouse, INPT, 1999. http://www.theses.fr/1999INPT001H.
Gisch, Debora Lidia. "Simulação da dispersão de poluentes na camada limite planetária : um modelo determinístico-estocástico." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/182254.
Environmental issues have been at the center of discussions in the last few decades. Atmospheric pollution, caused by post-industrial revolution, has increased the necessity to describe, using mathematical models, this phenomenon. With this knowledge is possible to propose solutions mitigating the pollution and collateral damages caused in the environment. The pollutant dispersion modeled by analytical solutions, from advection-diffusion equations, offers a knowledge about each component that constructs the equation, a characteristic that does not exist in other approaches, such as numerical. However it was unable to describe properties that refer to turbulence, coherent structures, caused by nonlinear components suppressed by constructing the model governing equations. This work studied a way to recover characteristics associated with turbulence through a fundamental component in coherent structures, the phase. This is included in the model which describes manifestations of turbulence in the dispersion process through the presence of small-scale concentration fluctuations in the sesquilinear model, which is deterministicstochastic. In the course of this work there is a study through variations of parameters to understand the phase effects in the model. It was also applied to Copenhagen experiment and to two real scenarios with the intention of understanding the model regarding micrometeorological variables as well as improving it to simulate the pollutant dispersion from sources in a realistic way.
Souidi, Kaïes. "Effet de la configuration des agitateurs dans une colonne à faible entrefer mécaniquement agitée sur la dispersion du gaz en foisonnement : approches expérimentale et numérique." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2012. http://tel.archives-ouvertes.fr/tel-00836761.
Boyer, Patrick. "Contribution à l'étude de la dispersion des polluants dans les basses couches de l'atmostphère en situations stables et par vent faible." Aix-Marseille 2, 1995. http://www.theses.fr/1995AIX22102.
Hug, Gilles. "Étude par microscopie électronique en faisceau faible de la dissociation des dislocations dans TiAl : relation avec le comportement plastique." Paris 11, 1988. http://www.theses.fr/1988PA112095.
TiA1 is fcc-related metal alloy, ordered under in the L10 structure. It shows an anomalous dependence of the flow stress with temperature, with a peak at about 600°C, that originales from processes intrinsic to dislocations. A weak-beam dark-field transmission electron microscopestudy has been carried out in order to characterize the dislocations together with their fine structure as a function of the deformation temperature. The nature of the Burgers vectors encoutered in TiA1 depends upon the temperature of the deformation test. Namely, in so far as the Burgers of superdislocations are concerned, four domains approximately centered on the following temperatures have been found:- room temperature, l/2<110], 1/2<112] and <011],- 600CC l/2<110] and <011],-800"C 1/2<110] and 1/2<1 12],-1000"C 1/2<110], <001] and 1/2<112]. Both the change in Burgers vector and the flow stress anomaly result from modifications of the fine structure of the <011] superdislocation. Its fine structure is basically threefold with two planar defects generated, viz. A superlattice intrinsic stacking fault (SISF) and an antiphase boundary (APB). It assumes a transition from a configuration fully glissile in {111} after room temperature deformation, to a sessile Jock at 600CC, with the APB now in the cube plane whereas the SISF still belong to the octahedral plane. This glissile-sessile core transition explains the flow stress anomal y that appears as the consequence of the loss of mobility of the supcrdislocations. Regarding the change in Burgers vectors, it is shown thal the sessile nature of dislocations after deformation at 600CC prevents the decomposition reaction, that yields the formation of 1/2<112) superdislocations, from occuring. At high temperature, 800°C, the above <011] locks are unstable, again, decomposition into 1/2<112] may occur the flow stress drops. At higher temperatures, 1000°C the{110) slip planes become operative and the shortest Burgers vectors (<001]) are activated
Filho, Edson Pereira Marques. ""Investigação da camada limite planetária convectiva com modelo LES aplicado à dispersão de poluentes"." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/14/14133/tde-20082004-134629/.
This work describes the spatial and temporal evolution of the dispersion of an inert and passive pollutant in a highly convective planetary boundary layer (PBL) simulated by LES model. The LES model used here was developed by Moeng (1984) and modified by Sullivan et al. (1994). The quasi-stationary state is verified by total turbulent kinetic energy (TKE) integrated in the PBL. The vertical profiles of the first, second and third order statistical moments, agreed with the predictions of the mixed layer similarity theory available in the literature. The TKE equation terms are balance and TKE pressure-transport is a source in the near to the surface. The spatial spectra show a inertial subrange proportional k^(-5/3), were isotropy relations are reproduced for vertical velocity. The Kolmogorov constant estimated is 0,52. The equivalent results are obtained for temporal wind velocity spectra. The wind velocity spectra show very well defined production region, allowing to estimate the spectral peak wavelength and characteristic length. In the spatial spectra cases, the horizontal velocity peak wavelengths are approximately constants and equal to 1.3 zi. The values obtained from temporal spectra are 1.5 larger. The same factor is found for temporal and spatial estimates. These results confirm the restrictions to the Taylors hypothesis applications in highly convective PBL. The concentration of pollutant released from a continuous area source located near to the surface, representing CO emissions in São Paulo city, is strongly dependent on the intensity of the entrainment at the top of PBL. The eulerian and lagrangian approaches are equally capable to describe the dispersion of continuous elevated point source located in PBL, reproducing the plume behaviour for convective conditions, when associated to LES model. This agreement indicates that LES model can be used as a tool to validated operational dispersion models.
Salizzoni, Pietro. "Mass and momentum transfer in the urban boundary layer." Ecully, Ecole centrale de Lyon, 2006. http://www.theses.fr/2006ECDL0015.
Gamel, Hervé. "Caractérisation expérimentale de l'écoulement et de la dispersion autour d'un obstacle bidimensionnel." Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0002/document.
In the last decades, there has been an increasing use of Computational Fluid Dynamics (CFD)simulations to evaluate the impact of atmospheric pollutants dispersion in within industrial and urban sites. Given the high geometrical complexity of these sites, these simulations are mainly performed adopting a Reynolds Averaged Navier-Stokes (RANS) approach and using k−e closure models. As is well known from previous studies, RANS k−e simulations are affected by some limitations that prevent them correctly reproducing the dynamics of the flow and the pollutant dispersion in complex geometrical configurations. The aim of the PhD is to provide a detailed experimental characterization of the flow and the turbulent dispersion around an idealized two-dimensional obstacle placed within a boundary layer flow. This is subsequently used to analyse the reliability of RANS closure models as predictive tools for the atmospheric dispersion of airborne pollutants. Initially we focus on the flow dynamics of a boundary layer flow developing over a rough wall and in the wake of a 2D obstacle. The velocity field is investigated experimentally by means of different measurement techniques, namely Hot Wire Anemometry (HWA), Laser Doppler Anemometry (LDA) and Stereo-Particle Imagery Velocimetry (PIV). A particular attention was devoted to the estimate of the turbulent viscosity nt as well as of the terms composing the turbulent kinetic energy budget (TKE), including its rate of dissipation e which was determined adopting different approaches. These measurements allowed us to analyse the accuracy of the parameterizations included in a standard k−e closure model. Our analysis show that a value of the coefficient Cμ = 0.09 leads to significant overestimation of nt in a boundary layer flow. Conversely, adopting Cμ = 0.09 provides a good agreement between modeled and direct estimates of nt in the wake of the obstacle. As a second step, we studied the dispersion of a passive scalar emitted by a ground level line source. To that purpose we measured the first four order moments of the concentration probability density function by mean of a flame ionization detector (FID). Furthermore, the coupling of the FID system with the LDA or HWA system allowed us to directly measure the turbulent mass transfer, i.e. the correlation between velocity and concentration fluctuations. The combination of these two techniques was carefully analyzed, in order to quantify eventual mutual disturbances of one measurement technique on the other. The measurements of the velocity/concentration correlations allowed us to determine experimentally the turbulent diffusivity Dt and the turbulent Schmidt number Sct , and therefore to test the accuracy of different closure models of the advection-distribution equation. Our results show that the value of the turbulent Schmidt number is approximately equal to 0.7 in most of the domain, except in the recirculation zone on the wake of the obstacle. Experimental data provide also a complete description of the spatial distribution of the concentration variance, and of the term composing its budget (with a focus on its dissipation). As for the velocity field, we test the reliability of different closure model proposed in the literature of the turbulent mass transfer terms, enlightening the shortcomings of simple gradient-law closer models
Saint-Etienne, Eric. "Nouvelle filière technologique de circuits micro-ondes coplanaires à faibles pertes et à faible dispersion sur membrane composite d'oxyde et de nitrure de silicium." Phd thesis, Université Paul Sabatier - Toulouse III, 1998. http://tel.archives-ouvertes.fr/tel-00141275.
SAINT, ETIENNE ERIC. "Nouvelle filiere technologique de circuits micro-ondes coplanaires a faibles pertes et a faible dispersion sur membrane composite d'oxyde et de nitrure de silicium." Toulouse 3, 1998. http://www.theses.fr/1998TOU30231.
Tignat-Perrier, Romie. "Facteurs de structuration des communautés microbiennes de la couche limite atmosphérique." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAU034.
Up to 106 microbial cells per cubic meter are found in suspension in the planetary boundary layer, the lowest part of the atmosphere. Direct influences of the planetary boundary layer on humans, crops and diverse ecosystems like soils and oceans make the full understanding of its composition, both chemical and microbiological, of utmost importance. While microbial communities of the planetary boundary layer vary significantly at different temporal and spatial scales, they remain largely unexplored. The main goal of this thesis was to understand how airborne microbial communities are structured in the troposphere with special emphasis on the planetary boundary layer and to identify their main controlling factors. We investigated both the taxonomic and functional composition of airborne microbial communities in the dry phase (i.e. not cloud-associated) over time at nine different geographical sites around the world using high throughput sequencing technologies.Our investigation that focused on microbial taxonomy showed that local landscapes were the main contributors to the global distribution of airborne microbial communities despite the potential occurrence of long-range transport of airborne microorganisms. We also observed that meteorology and the diversity of the surrounding landscapes played major roles in the temporal variation of the microbial community structure in the planetary boundary layer. We further explored the temporal variation of airborne microbial communities at a continental and mountainous site in France (1465 m above sea level) over a full-year. This study demonstrated the importance of the surface conditions (i.e. vegetation, snow cover etc.) of the surrounding landscapes on the taxonomic composition of airborne microorganisms. The seasonal changes in agricultural and vegetated areas, which represented a significant part of the site’s surrounding landscape, were correlated to the shifts in the taxonomic composition of airborne microbial communities during the year. Finally, we investigated the functional composition of microbial communities of the planetary boundary layer to identify whether the physical and chemical conditions of the atmosphere played a role in selection or microbial adaptation of airborne microorganisms. The comparative metagenomic analysis did not show a specific atmospheric signature in the functional potential of airborne microbial communities. To the contrary, their functional composition was mainly correlated to the underlying ecosystems. However, we also showed that fungi were more dominant relatively to bacteria in air as compared to other (planetary bound) ecosystems. This result suggested a selective process for fungi during aerosolization and/or aerial transport and that fungi might likely survive aerosolization and/or aerial transport better than bacteria due to their innate resistance to stressful physical conditions (i.e. UV radiation, desiccation etc.). Our results provide a clearer understanding of the factors (i.e. surrounding landscapes, distant sources, local meteorology, and stressful physical atmospheric conditions) that control the distribution of microbial communities in the atmospheric boundary layer. Our investigations provide a basis for further studies on the prediction and even control of airborne microbial communities that would be of interest for public health and agriculture
Alves, Claudia Marins. "Stochastic models for the treatment of dispersion in the atmosphere." Laboratório Nacional de Computação Científica, 2006. http://www.lncc.br/tdmc/tde_busca/arquivo.php?codArquivo=135.
Modelos Lagrangianos estocásticos constituem ferramenta muito utilizada no estudo da dispersão de substâncias passivas na Camada Limite Atmosférica. Sua aplicação consiste em calcular a trajetória de milhares de partículas, que simulam numericamente a dispersão de uma substância em suspensão na atmosfera. Nesta tese, são apresentados e discutidos os conceitos básicos relacionados à Modelagem Lagrangiana Estocástica de Partículas, bem como suas principais características e sua implementação computacional, para o estudo da dispersão de partículas na atmosfera. Numa experimentação computacional, comparam-se os resultados obtidos com dados observacionais provenientes do experimento TRACT, realizado na Europa em 1992. Os dados de entrada necessários ao modelo de dispersão são extraídos de simulações do modelo de previsão numérica do tempo RAMS. A dispersão sobre o Estado do Rio de Janeiro é também testada em um segundo experimento.
Dhahri, Ameur. "Contributions aux approches hamiltonienne et markovienne des systèmes quantiques ouverts." Phd thesis, Université Claude Bernard - Lyon I, 2007. http://tel.archives-ouvertes.fr/tel-00174273.
Pour décrire cette interaction, les physiciens et les mathématiciens utilisent souvent deux approches: l'approche markovienne et l'approche hamiltonienne.
Nous comparons systématiquement les approches hamiltonienne et markovienne dans les cas des modèles de spin-boson et de Pauli-Fierz. Ensuite, nous présentons un modèle lindbladien pour une chaîne de N spins couplée à des bains thermiques. Puis, nous étudions le lien entre les interactions quantiques répétées et la limite de densité faible. Finalement, nous étudions les propriétés des équations d'évolutions discrètes associées aux modèles d'interactions répétées, qui sont dirigées par des bruits discrets classiques.
Rouzès, Maxime. "Etude expérimentale de l'hydrodynamique d'un écoulement turbulent à surface libre sur fond rugueux à faible submersion." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/14164/1/rouzes.pdf.
Krone, Ralf. "Sismique onde S en faible profondeur d'eau : propriétés de cisaillement des sédiments marins superficiels par inversion simultanée de la dispersion des ondes de love de scholte." Brest, 1997. http://www.theses.fr/1997BRES2005.
Giraudo, Davide. "Théorèmes limites de la théorie des probabilités dans les systèmes dynamiques." Rouen, 2015. http://www.theses.fr/2015ROUES056.
This thesis is devoted to limit theorems for strictly stationary sequences and random fields. We concentrate essentially on the central limit theorem and its invariance principle. First, we show with the help of a counter-example that for a strictly stationary absolutely regular sequence, the central limit theorem may hold but not the invariance principle. We also show that the central limit theorem does not take place for partial sums of a Hilbert space valued, strictly stationary and absolutely regular sequence, even if we assume that the normalized partial sums form a uniformly integrable family. Second, we investigate the Holderian invariance principle. We treat the case of tau-dependent (Dedecker, Prieur, 2005) and rho-mixing strictly stationary sequences. We provide a sufficient condition on the law of a strictly stationary martingale difference sequence and the quadratic variance which guarantee the invariance principle in a Hölder space. We construct a counter-example which shows its sharpness. We derive conditions in the spirit of Hannan (1979), and Maxwell and Woodroofe (2000) by a martingale approximation. We then discuss the martingale/coboundary decomposition. In dimension one, we provide sharp integrability conditions on the transfer function and the coboundary for which the later does not spoil the invariance principle, the law of the iterated logarithm or the strong law of large numbers if these theorems take place for the martingale involved in the decomposition. We also provide a sufficient condition for an orthomartingale/coboundary decomposition for strictly stationary random fields. Lastly, we establish tails inequalities for orthomartingale and Bernoulli random fields. We prove an invariance principle in Hölder spaces for these random fields using such inequalities
Baili, Ghaya. "Contribution à la réduction du bruit d'intensité relatif des lasers à semiconducteurs pour des applications aux radars." Paris 11, 2008. http://www.theses.fr/2008PA112362.
The objective of the following thesis is to study two original techniques aiming at reducing the Relative Intensity Noise (RIN) of semiconductor lasers used in optical links for transmission of radar signals. Within the first technique, a dispersion compensating fiber exhibiting low losses is used to study the phase to amplitude noise and amplitude to phase noise conversion mechanisms with a very good signal-to-noise ratio over à 20 GHz bandwidth. The second technique consists in increasing the photon lifetime well above the carrier lifetime in order to eliminate adiabatically the carrier population effects, leading to a relaxation oscillation free class-A laser operation. Two laser architectures have been proposed, theoretically analyzed and experimentally validated. The first configuration is based on a semiconductor optical amplifier in a long fibred cavity. The second one uses a ½-VCSEL in a high-Q external cavity. For both configurations, we demonstrated that class-A laser operation leads to a shot-noise-limited RIN (at -155 dB/Hz for 1 mA detected) over a frequency bandwidth from 100 MHz to 18 GHz
Sadek, Radi. "Modélisation de l'écoulement atmosphérique à l'échelle hectométrique." Thesis, Ecully, Ecole centrale de Lyon, 2013. http://www.theses.fr/2013ECDL0011/document.
Many practical and industrial applications, such as the study of atmospheric dispersion of pollutants, air quality,micro-meteorology in complex terrain and wind assessment, require accurate prediction of the atmospheric flow at a so-called local scale (approximately 10 km horizontally). Therefore, the main objective in this thesis is to propose a chain of methodologies capable of simulating the atmospheric flow at this scale, with a horizontal hectometric spatial resolution. First of all, we were interested in modeling of turbulence in the atmospheric boundary layer (ABL). In addition to the largely used RANS k−ε model, we considered the use of the RANS Ri j− ε model as a way of simulating turbulence anisotropy.We were able to verify the necessity of using the Duynkerke (1988) constants in order to achieve atmospheric levels of turbulence with the k− ε model. In a similar way, we also developed a new set of atmospheric constants for the Ri j− ε model. Finally, we proposed a theoretical model capable of reproducing the main characteristics of a turbulent flow for any given sampling duration, thus allowing a more continuous approach between « standard » and « atmospheric » constants for turbulence models. Also, in this thesis, we developed the « CFD 1D-3D » modeling approach. It is based on the use of a 1D CFD model as a way of providing vertical profiles of meteorological data for boundary conditions of a 3D CFD code, used in complex terrain. This 1D model was developed as a part of the thesis, along with k− ε and Ri j − ε turbulence models. It was validated by being compared with empirical and theoretical results. The comparisons showed very encouraging results concerning the ability of this model in simulating ABL in the presence of a flat terrain. In addition, the « CFD 1D- 3D » methodology was assessed by comparison with wind tunnel measurements in the presence of complex terrain, which showed very satisfactory resultst. These comparisons also validated the newly developed set of constants for the Ri j− ε model. Finally, we studied the use of partially converged CFD as a way of reducing the CPU time of CFD simulations for operational purposes. We therefore demonstrated that we can achieve a low error solution (< 10% error compared with the converged solution), with a CPU time of about 5%−10% of the time required to achieve convergence. This result was very interesting because the methodology significantly reduces the computational time while maintaining a low error as compared to the overall uncertainty of the CFD approach
Lesouëf, Dorothée. "Étude numérique des circulations locales à la Réunion : application à la dispersion de polluants." Phd thesis, Université de la Réunion, 2010. http://tel.archives-ouvertes.fr/tel-00633096.
Júnior, Rosiberto Salustiano da Silva. "Sensibilidade na estimativa da concentração de poluentes fotoquímicos com a aplicação de diferentes parametrizações de camada limite planetária utilizando o modelo de qualidade do ar WRF/Chem." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/14/14133/tde-23012010-102058/.
This work evaluated the parameterizations´ sensibility of the Planetary Boundary Layer (PBL) in the simulation of photochemical pollutants above the Metropolitan Region of São Paulo, by using the Weather Research and Forecasting (WRF) non-hydrostatic mesoscale model, with the coupling of chemical modules (WRF/Chem). In order to analyze the accuracy of the results obtained with the model, there will be used the measurements made by the automatic air quality stations from CETESB on surface, and the validation of the O3 vertical profile, will be based on ozonesoundings experiments conducted during the period of the study. The motivation for this study was the great difficulty in representing the PBLs structure specially during the night, witch is an new utilization of an on-line model to simulate the chemical composition of the atmosphere of the MASP, and finally, to analyze the impact of the coupling with the Urban Canopy Model (UCM). The study area is the Metropolitan Region of São Paulo and surroundings, and the period was between 10/28 11/01/2006. The annual variations of the air temperature, wind speed and solar radiation for 2006, showed that the month of October was marked by wide availability of solar radiation, high values of air temperature and intense winds. The simulations with idealized cases showed that the PBLs order of height based on the numerical scheme is YSU, MYJ, BOULAC and UCM, which influences directly the dispersion of pollutants with lower concentrations of the CO for YSU and higher for UCM respectively, and for the concentrations of the O3, the scheme YSU shows lower concentrations but unlike the CO, the other schemes are equal. However, for the simulations of real cases, the results showed a good correlation between simulated and observed for the surface concentrations of the O3 and CO, and a great difficulty of the model on the vertical profiles representation of the concentration of O3, when the 2.1 version of the WRF/Chem model is used. This problem was partially solved (can be better improved) when used with the latest version, as version 3, and coupled with the Urban Canopy Model. The experiments performed to estimate the impact of the land use type on the variation of the PBL height and consequent relationship with the chemical composition of the atmosphere, showed that the PBL height is higher on the urban areas compared to rural areas, thus influencing effectively in the dispersal of pollutants, and a lower PBL height was associated with higher concentrations due to lower dispersion of pollutants. This work has demonstrated the transport of pollutants between the metropolitan regions of São Paulo - Campinas and São Paulo - Sorocaba, due to topography that acts targeting the wind in the direction of Campinas. The proximity of emission sources has been important for the level of concentration of O3, as it moves away from sources of emissions both vertically and horizontally increases its concentration. Due the proximity with the Atlantic Ocean, the formation of Sea Breeze helps dispersion of pollutants emitted and formed in the MASP.
Bernardos, Barreda Luis Francisco. "Modélisation de la transition vers la turbulence d'une couche limite décollée Algebraic Nonlocal Transition Modeling of Laminar Separation Bubbles Using k−ω Turbulence Models Prediction of Separation-Induced Transition on the SD7003 Airfoil Using Algebraic Transition Triggering." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS184.
The objective of this thesis was to propose new models that improve the precision of RANS predictions of LSB. Firstly, high-fidelity numerical data was analyzed in order to understand the precision defects of existing models. From this analysis, two main defects were identified: existing models do not produce turbulence at a sufficient rate in the transitional region, and they generally lack diffusion right downstream of the LSB. Secondly, a set of models were proposed that correct the defects. The new approach, named laminar separation transition triggering (LSTT), allow several existing RANS models for enhanced production of turbulence in the transitional region, which improves the precision of the prediction of the LSB topology and the overall flowfield. Lastly, a large assessment of LSTT models was undertaken using different airfoils of drones, wind turbines, tubojet engines and helicopters. In general, it was found that LSTT models improve the precision of the RANS predictions of LSB and can be used to predict the influence on angle-of-attack, Reynolds number and turbulence intensity
Bahlali, Meïssam. "Adaptation de la modélisation hybride eulérienne/lagrangienne stochastique de Code_Saturne à la dispersion atmosphérique de polluants à l’échelle micro-météorologique et comparaison à la méthode eulérienne." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1047/document.
This Ph.D. thesis is part of a project that aims at modeling pollutant atmospheric dispersion with the Computational Fluid Dynamics code Code_Saturne. The objective is to simulate atmospheric dispersion of pollutants in a complex environment, that is to say around power plants, industrial sites or in urban areas. In this context, the focus is on modeling the dispersion at micro-scale, that is for distances of the order of a few meters to a few kilometers and corresponding to time scales of the order of a few tens of seconds to a few tens of minutes: this is also called the near field area. The approach followed in this thesis follows a hybrid Eulerian/Lagrangian formulation, where the mean dynamical fields relative to the carrier fluid (pressure, velocity, temperature, turbulence) are calculated through an Eulerian approach and are then provided to the Lagrangian solver. This type of formulation is commonly used in the atmospheric literature for its numerical efficiency. The Lagrangian stochastic model considered in our work is the Simplified Langevin Model (SLM), developed by Pope (1985,2000). This model belongs to the methods commonly referred to as PDF (Probability Density Function) methods, and, to our knowledge, has not been used before in the context of atmospheric dispersion. First, we show that the SLM meets the so-called well-mixed criterion (Thomson, 1987). This criterion, essential for any Lagrangian stochastic model to be regarded as acceptable, corresponds to the fact that if particles are initially uniformly distributed in an incompressible fluid, then they must remain so. We check the good respect of the well-mixed criterion for three cases of inhomogeneous turbulence representative of a wide range of practical applications: a mixing layer, an infinite plane channel, and an atmospheric-like case involving an obstacle within a neutral boundary layer. We show that the good respect of the well-mixed criterion lies simply in the good introduction of the pressure gradient term as the mean drift term in the Langevin model (Pope, 1987; Minier et al., 2014; Bahlali et al., 2018c). Also, we discuss the importance of consistency between Eulerian and Lagrangian fields in the framework of such Eulerian/Lagrangian hybrid formulations. Then, we validate the model in the case of continuous point source pollutant dispersion, under uniform wind and homogeneous turbulence. In these conditions, there is an analytical solution allowing a precise verification. We observe that in this case, the Lagrangian model discriminates well the two different near- and far-field diffusion regimes, which is not the case for an Eulerian model based on the eddy-viscosity hypothesis (Bahlali et al., 2018b).Finally, we work on the validation of the model on several experimental campaigns in real atmosphere, taking into account atmospheric thermal stratification and the presence of buildings. The first experimental program considered in our work has been conducted on the `SIRTA' site (Site Instrumental de Recherche par Télédétection Atmosphérique), in the southern suburb of Paris, and involves a stably stratified surface layer. The second campaign studied is the MUST (Mock Urban Setting Test) experiment. Conducted in the United States, in Utah's desert, this experiment aims at representing an idealized city, through several ranges of containers. Two cases are simulated and analyzed, respectively corresponding to neutral and stable atmospheric stratifications (Bahlali et al., 2018a)
Tounsi, Bouchaïb. "Etude par microscopie en faisceau faible de la dissociation des dislocations dans Ni(3)Si : relation avec le comportement plastique." Poitiers, 1988. http://www.theses.fr/1988POIT2338.
Reding, Lucas. "Contributions au théorème central limite et à l'estimation non paramétrique pour les champs de variables aléatoires dépendantes." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR049.
This thesis deals with the central limit theorem for dependent random fields and its applications to nonparametric statistics. In the first part, we establish some quenched central limit theorems for random fields satisfying a projective condition à la Hannan (1973). Functional versions of these theorems are also considered. In the second part, we prove the asymptotic normality of kernel density and regression estimators for strongly mixing random fields in the sense of Rosenblatt (1956) and for weakly dependent random fields in the sense of Wu (2005). First, we establish the result for the kernel regression estimator introduced by Elizbar Nadaraya (1964) and Geoffrey Watson (1964). Then, we extend these results to a large class of recursive estimators defined by Peter Hall and Prakash Patil (1994)
Nironi, Chiara. "Concentration fluctuations of a passive scalar in a turbulent boundary layer." Phd thesis, Ecole Centrale de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00964852.
Karam, Hugo Abi. ""Estudo do Jato de Baixos Níveis de Iperó e das Implicações no Transporte de Poluentes no Estado de São Paulo"." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/14/14133/tde-29052003-161622/.
ABSTRACT This work investigates the nocturnal Low-Level Jet (LLJ) in Iperó, Brazil, and its role in the pollutant dispersion on the State of São Paulo (SP). Data of four field campaigns in Iperó-SP was used in this investigation. A mesoscale and non-hydrostatic TVM model is also used to simulate the 3D structure of the LLJ, which is a dynamic response to topography and land use. The observational results indicate that the LLJ is frequently found during clear air nights, with a maximum between 8 and 10 m s1, located around 350 m above surface. The LLJ in Iperó is characterized by a directional wind shear, with SE winds near surface and ENE near to the maximum. They occur during the winter and summer, and can modify the diurnal cycle of the mean wind in the first 100 m in the Iperó area. The LLJ are responsible by the nocturnal maximum (21:00 LT) in the mean wind in Iperó. The numerical results indicate the Iperó LLJ is a result of four factors: (1) anabatic circulation in São Paulo sector of the Paraná River Basin; (2) inertial oscillation; (3) nocturnal katabatic circulation and (4) sea breeze. These factors, together, sustain a LLJ with jet core intensity between 5 and 10 m/s, located between 100 and 400 m above surface during the major of nighttime period. The simulated LLJ numerically is found in the west sector in the convergence zone of the anabatic and sea breeze circulations. This convergence flow area appears during the daytime above the more elevated areas in the State of São Paulo, i.e., along mountains aligned parallel to coastline (Serra do Mar and Cantareira). The effects of the LLJ in a pollutant transport were investigated using a Lagrangian Particle Dispersion model coupled to the mesoscale model TVM. The results show that the LLJ increases the horizontal dispersion of the particles released near surface in Iperó and is able to transport the pollutant up to 250 km downwind the source.
Buske, Daniela. "Solução GILTT bidimensional em geometria cartesiana : simulação da dispersão de poluentes na atmosfera." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/13448.
In the present thesis it is presented a new analytical solution for the transient two- dimensional advection-diffusion equation to simulate the pollutant dispersion in atmosphere. For that, the advection-diffusion equation is solved combining the Laplace transform and the GILTT (Generalized Integral Laplace Transform Technique) techniques. The turbulence closure for Fickian and non-Fickian cases is considered. It is investigated the problem of modeling the pollutant dispersion in strong and weak winds considering, for the case of low wind conditions, the longitudinal diffusion in the advection-diffusion equation. Moreover, it was considered in the model the vertical velocity and its influence was evaluated considering velocities field constant and also generated by means of LES (Large Eddy Simulation), to simulate a more realistic turbulent boundary layer. The results attained by this methodology are validated with experimental results available in literature.
Markeviciute, Jurgita. "Résultats asymptotiques sur des processus quasi non stationnaires." Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10066/document.
We study some Hölderian functional central limit theorems for the polygonal partial sum processes built on a first order nearly nonstationary autoregressive process yn,k = φn yn,k−1 + εk and its least squares residuals εk with φn converging to 1 and i.i.d. centered square-integrable innovations. In the case where φn = exp( γn /n) with a negative constant γ, we prove that the limiting process depends on Ornstein-Uhlenbeck one. In the case where φn = 1 − γn /n, with γn tending to infinity slower than n, the convergence to Brownian motion is established in Hölder space in terms of the rate of γn and the integrability of the εk’s. As a statistical application of these results, we investigate some epidemic change in the innovations of the first order nearly nonstationary autoregressive process AR(1). Two types of models are considered. For 0 ≤ α < 1, we build the α-Hölderian uniform increments statistics based on the observations and on the least squares residuals to detect the short epidemic change in the process under consideration. Under the assumptions for innovations we find the limit of the statistics under null hypothesis, some conditions of consistency and we perform a test power analysis. We also discuss the interplay between the various parameters to detect the shortest epidemics
Schuch, Daniel Andrade, and Daniel Andrade Schuch. "Simulação de dispersão de poluentes na atmosfera pela técnica de transformada integral para uma fonte arbitrária." Universidade Federal de Pelotas, 2011. http://repositorio.ufpel.edu.br/handle/ri/2208.
The present work shows an analytical solution for the two-dimensional advectiondiffusion equation applied to the dispersion of pollutants released in the Atmospheric Boundary layer. The problem is solved by the combination of the Laplace Transform and GILTT (Generalized Integral Laplace Transform Technique) techniques. This solution has no limitations regarding the turbulent diffusion coefficients and wind profile depending on the height. An arbitrary source is added to the advectiondiffusion equation to model the process of first order chemical reactions. The concentration fields obtained computationally are compared with experimental data available in the literature.
Esta dissertação apresenta uma solução analítica para a equação de advecçãodifusão bidimensional aplicada a dispersão de poluentes lançados na Camada Limite Atmosférica (CLA). A resolução do problema será com o uso das técnicas da Transformada de Laplace e GILTT (Generalized Integral Laplace Transform Technique). Esta solução é válida para qualquer coeficiente de difusão turbulenta e perfil de vento dependentes da altura. Um termo fonte arbitrário é adicionado à equação de advecção-difusão para modelar o processo de reação química de primeira ordem. Os campos de concentração obtidos computacionalmente são comparados com dados experimentais e da literatura.
Durieu, Olivier. "Comportements asymptotiques des processus stationnaires et des processus empiriques dans des systèmes dynamiques." Phd thesis, Rouen, 2008. http://www.theses.fr/2008ROUES022.
The aim of this thesis is the study of limit theorems for stationary sequences of random variables (in particular, from dynamical system). We concentrate on two results which are important by their applications in statistics. We first study the asymptotique behavior of sums of random variables, precisely the central limit theorem and its invariance principles. We also consider the invariance principle of empirical processes. For the Donsker's weak invariance principle, many results can be obtained by martingale approximations and more generaly by projective criteria. We compare four of these criteria and we show that they are independent of each other. These criteria are the martingale-coboundary decomposition (Gordin, 1969), the Hannan condition (1979), the Dedecker and Rio criterion (2000) and the Maxwell-Woodroofe condition (2000). Concerning the asympotic behavior of empirical processes, we establish an invariance principle in the case of toral automorphisms. This permits to generalize the known hyperbolic case and to find a first result for a partially hyperbolic transformation. We also propose a new approach, based on operator techniques, for establishing an invariance principle. This technique is well adapted to cases when we only have good properties for a class of functions not containing the indicators. In particular, this is the case for some dynamical systems for which the transfer operator admits a spectral gap. At the end, following a question by Burton and Denker (1987), we are interested in the class of processes for which the central limit theorem holds. To refer to the empirical processes case, we study in particular the sequences of partial sums of iterates of indicator functions
El-Dakkak, Omar. "Décompositions de Hoeffding pour des suites échangeables : asymptotiques pour la mesure empirique séquentielle." Paris 6, 2007. http://www.theses.fr/2007PA066536.
Gomez, Garcia José Gregorio. "Théorèmes limites pour des fonctionnelles de clusters d'extrêmes et applications." Thesis, Cergy-Pontoise, 2017. http://www.theses.fr/2017CERG0916/document.
This thesis deals mainly with limit theorems for empirical processes of extreme cluster functionals of weakly dependent random fields and sequences. Limit theorems for empirical processes of extreme cluster functionals of stationnary time series are given by Drees & Rootzén [2010] under absolute regularity (or "ß-mixing") conditions. However, these dependence conditions of mixing type are very restrictive: on the one hand, they are best suited for models in finance and history, and on the other hand, they are difficult to verify. Generally, for other models common in applications, the mixing conditions are not satisfied. In contrast, weak dependence conditions, as defined by Doukhan & Louhichi [1999] and Dedecker & Prieur [2004a], are dependence conditions which generalises the notions of mixing and association. These are easier to verify and applicable to a wide list of models. More precisely, under weak conditions, all the causal or non-causal processes are weakly dependent: Gaussian, associated, linear, ARCH(∞), bilinear and Volterra processes are some included in this list. Under these conveniences, we expand some of the limit theorems of Drees & Rootzén [2010] to weakly dependent processes. These latter results are used in order to show the convergence in distribution of the extremogram estimator of Davis & Mikosch [2009] and the functional estimator of the extremal index introduced by Drees [2011] under weak dependence. We prove an extreme value theorem for weakly dependent stationary random fields and we propose, under the same conditions, a domain of attraction criteria of a law of extremes. The document ends with limit theorems for the empirical process of extreme cluster functionals of stationary weakly dependent random fields, deriving also the convergence in distribution of the estimator of an extremogram for stationary weakly dependent space-time processes
Cajgfinger, Thomas. "Étude théorique et expérimentale du suivi de particules uniques en conditions extrêmes : imagerie aux photons uniques." Phd thesis, Université Claude Bernard - Lyon I, 2012. http://tel.archives-ouvertes.fr/tel-00770124.
Durieu, Olivier. "Comportements Asymptotiques des Processus Stationnaires et des Processus Empiriques dans des Systèmes Dynamiques." Phd thesis, Université de Rouen, 2008. http://tel.archives-ouvertes.fr/tel-00346539.
Dans le cadre du principe d'invariance faible de Donsker, plusieurs résultats s'obtiennent au travers d'approximations par des martingales et plus généralement par des critères projectifs. Nous comparons quatre de ces critères et montrons leur indépendance mutuelle. Les critères étudiés sont la décomposition martingale-cobord (Gordin, 1969), la condition de Hannan (1979), le critère de Dedecker et Rio (2000) et
la condition de Maxwell et Woodroofe (2000).
En ce qui concerne le comportement asymptotique des processus empiriques, nous établissons un principe d'invariance dans le cas des automorphismes du tore. Cela permet de sortir du cadre hyperbolique connu et d'obtenir un premier résultat pour une transformation partiellement hyperbolique.
Nous proposons également une nouvelle approche, basée sur des méthodes d'opérateurs, permettant d'établir un principe d'invariance empirique. Cette méthode s'applique en particulier aux cas où l'on a de bonnes propriétés pour une classe de fonctions ne contenant pas les fonctions indicatrices. C'est en particulier le cas de certains systèmes dynamiques dont l'opérateur de transfert admet un trou spectral.
En dernier lieu, suivant une question de Burton et Denker (1987), nous nous intéressons à la classe des processus pour lesquels le théorème limite central a lieu. En référence au cadre des processus empiriques, nous étudions en particulier les suites de sommes partielles des itérées d'une fonction indicatrice.
Stefanello, Michel Baptistella. "Desenvolvimento de um modelo lagrangiano para estimar a dispersão de escalares passivos em condições de meandro do vento horizontal." Universidade Federal de Santa Maria, 2017. http://repositorio.ufsm.br/handle/1/12408.
Descrever os efeitos provocados pelo meandro do vento na dispersão de escalares é uma tarefa desafiadora, uma vez que este tipo de escoamento representa um estado físico caracterizado por múltiplas escalas. Neste trabalho, deriva-se um modelo estocátisco Lagrangiano para descrever a dispersão de escalares, na camada limite planetária, durante o fenômeno de meandro do vento horizontal. O modelo é derivado a partir da linearização da equação de Langevin e emprega uma forma funcional heurística, que representa as funções de autocorrelação do meandro. As novas soluções, que descrevem as componentes longitudinais e laterais do vento, foram empregadas para simular dois experimentos de dispersão de contaminantes em condições de vento fraco, INEL (USA) e GRAZ (Áustria). Os resultados das comparações indicam que o novo modelo pode ser usado para reproduzir as concentrações observadas de contaminantes e, portanto descreve de forma satisfatória a difusão reforçada provocada pelo meandro do vento.
Boillot, Benjamin. "Contribution à l'étude des écoulements turbulents en convection mixte." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10062.
Dupont, Sylvain. "Modélisation de la micrométéorologie à l'échelle de paysages complexes." Habilitation à diriger des recherches, Université Paul Sabatier - Toulouse III, 2009. http://tel.archives-ouvertes.fr/tel-00443770.