Tesis sobre el tema "Variation géométrique"
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Mille, Tiphaine. "Sources de variation intra-populationnelle de la morphologie des otolithes : asymétrie directionnelle et régime alimentaire". Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10200/document.
Texto completoOtoliths are calcified structures located in Osteichthyes’ inner ear that are involved in audition and balance. Their morphology is used as an indicator of various ecological processes or properties. This application requires identifying the endogenous and exogenous factors that act simultaneously as sources of shape variation. This thesis aims at detecting and quantifying the relative contributions of directional asymmetry and diet to otolith shape variation at the intra-population level. Directional asymmetry between left and right otoliths was found in flat-fishes, the blind-side otolith being always longer and larger, whereas it was negligible in round-fishes. However, asymmetry amplitude never exceeded 18%, which suggests evolutionary canalization of otolith shape symmetry. A correlation between global diet and otolith was detected in 4 species studied in situ. Diet composition contributed more than food amount to morphological variation and affected otolith shape both globally and locally. An experimental study on sea bass (Dicentrarchus larbrax) showed that diet composition in terms of essential polyunsaturated fatty acids at larval stage affects otolith morphogenesis during juvenile stage without impacting on individuals’ somatic growth. This result suggests a direct effect of diet on otolith shape and not an indirect one through the somatic-otolith growth relationship. This effect disappeared at later stages, morphogenetic trajectories converging back to a similar shape, which suggests ontogenetic canalization of otolith shape
Restrepo, García Carlos Andrés. "Intégration du comportement mécanique des éléments non idéaux en analyse de tolérances par des polyèdres prismatiques". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0263.
Texto completoThe architectures of new products are more complex nowadays due to the need of the marketfor customized and optimized products, the technological advancements in manufacturingmachines and inspection devices, and the extensive use of data in the product’s modelingand simulation. The evolution of manufacturing processes and the advanced measurementcapabilities in response to the market needs do not translate immediately into more accurateproducts. Actually, there is a limited consideration of geometric defects and variability inthe design process, this is partially due to the limitations of the mathematical models andtheir underlying hypothesis. The first contribution of this work is on the characterizationof the geometric variability in tolerancing. The first part of this work concerns the shaperepresentation models and specifically the adoption of the skin model shapes paradigm inthe tolerance management context using the polyhedral-based method. The skin modelinstances are more representative of individual real parts than the traditional CAD models.To simulate more realistic behavior of assemblies, the second part presents a novel approachfor simulation of rigid contact using polyhedra is presented. The approach integrates the loadboundary conditions that allow the contact between matting features by enriching the defintion of a prismatic polyhedron operand for contact simulation. With this enriched approachan objective quantification of the impact of disregarding form defects for a given mechanismcan be computed given a loading condition. An approach for simulating features potentiallyin contact by taking into account the local deformations of potentially contacting parts hasalso been developed for the polyhedral method in tolerancing. Finally, the algorithms for thecontact simulation and the generator of realistic shape representatives were implemented inan open source CAD compatible software
Galland, Manon. "Le premier peuplement des Amériques : application de la morphométrie géométrique 3D à la variation crânienne actuelle et fossile". Paris, Muséum national d'histoire naturelle, 2013. http://www.theses.fr/2013MNHN0022.
Texto completoThe arrival of modern humans in the New World remains subject to numerous research issues regarding the origin, timing, possible route(s) taken, as well as the number of migration waves that contributed to the biological diversity of Native Americans. At the core of this debate lie geographic and diachronic patterns of cranial variation and their interpretation as either supporting (i) two migration waves, (ii) a single wave followed by local diversification and/or recurrent gene flow. This study applies 3D geometric morphometrics and a population genetics framework to a large sample consisting of 89 fossils and 889 modern human specimens from the Americas, Asia, Australo-Melanesia and Polynesia. Several approaches have been taken: (i) We analyzed cranial and neurocranial shape and the influence of chrono-geographic, environmental, climatic and linguistic parameters; (ii) we investigated the use of sliding semilandmarks to study within- and between-population differences; (iii) we tested hypotheses about the peopling by defining specific models and by statistically assessing how well they fit our data, while accounting for various microevolutionary processes. Our results demonstrate significant cranial variability both in time and space, and they show that most of this variance can be explained through regional factors rather than resulting from chronological or environmental factors. Our morphometric data best fit single major wave scenario, followed by local microevolutionary processes, notably in Baja California. Our results can also be seen as in support of recurrent gene flow in subarctic regions, as well as a late arrival in the extreme northern part of the continent, but they also confirm that the populations of this region have been greatly impacted by adaption to a cold climate
Souquet, Louise. "Etude des patrons de variation intraspécifique et de covariation chez les éléments conodontes". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEN083/document.
Texto completoEvolution is the result of two main factors: the environment and the development. In this context, untangling the impact of these two forces on the morphological evolution of a structure is of major importance. To do so, studying evolution in deep time is useful, as it is the only way to observe the mechanisms in action over a long time interval and the responses to major environmental variations. In this thesis, we aim to better understand the evolution of a fossil species: the conodont. These marine jawless vertebrates possess a feeding apparatus composed of mineralized structures comparable to teeth, called conodont elements. Their high evolutionary rate, their long and sub-continuous fossil record, and their large populations made them a relevant model to conduct evolutionary studies in deep time. In the literature, only a few studies attempt to quantify the shape of conodont elements, and never in a developmental framework. With the discovery of new exceptionally preserved fossils, and the establishment of a methodology to quantify the patterns of morphological variation and covariations in these elements, the morphological evolution of conodont elements have been studied from different angles. We have established the existence of covariations between some morphological characters, illustrating the constraints on possible morphologies. Some constraints are considered developmental, while others are potentially mechanical. Evolutionary directions are highlighted, channelled by developmental constraints. At the inter-genera scale, we demonstrated a relationship between environmental changes (especially temperature variations) and these evolutionary directions. The results revealed a combined effect of the developmental forces (that constrain the initial possible morphologies) and the evolutionary forces (selecting the fittest morphologies depending on conditions) in the conodont elements evolution. We proposed heterochrony as underlying mechanism for these patterns, potentially driven by oceanic temperature. Shape quantification is also used in an attempt to clarify the neogondolellids taxonomy of the early Triassic. This work demonstrates the conodont's potential as model organism to study evolution in deep time
Albessard, Lou. "Co-variation morphologique du crâne et de l'endocrâne au cours de l'évolution du genre Homo". Thesis, Paris, Muséum national d'histoire naturelle, 2018. http://www.theses.fr/2018MNHN0024.
Texto completoSpecies of the genus Homo display cranial and endocranial morphological variations, with complex interactions between these two elements. Generally speaking, throughout the evolution of this taxon the neurocranium becomes increasingly important by comparison with the facial skeleton, due to a marked cerebral expansion. The modalities of this expansion differ accross species and occur at least partly through species-specific morphological processes. Apart from the increase in cerebral volume, the endocast bears the traces of neuroanatomical reorganisations. These two factors – volume and organisation – as well as various morpho-functional constraints on the external face of the cranium, may result in a variety of morphological and spacial relationships between the neurocranium and the endocranium. It is therefore important to document these relations in order to better apprehend the variability and the evolutionary mechanisms behind the morphologies of the different Homo species.This doctoral thesis explores the joint morphological variations of the neurocranium and endocast in the genus Homo and within Homo sapiens through multiple approaches. We offer a contribution to this topic based on shape analyses of virtual crania and endocasts, using geometric morphometrics and an innovative technique of surface deformations. We analysed morphological data from extant populations in order to clarify the nature of the relationship between the neurocranium and the endocast in Homo sapiens. One of the lines of evidence investigated is the correspondence between neurocranial and endocranial (and therefore cerebral) gross asymmetries. Our results show that the patterns of bilateral asymmetries of the neurocranium are identical to those of the endocranium. There is a close correspondance between the morphologies of the endocranial and cranial vaults, despite the neurocranium not displaying the full extent of cerebral asymmetries on its external vault. Correlations between asymmetry and factors including sex, endocranial volume and importance of the bony superstructures were also tested. Co-variation patterns between neurocranial and endocranial morphologies in the genus Homo were analysed. Our results highlight elements of co-variation between the neuro and endocranium which are shared accross the genus Homo, and others which are species-specific. While the cranial vault closely follows endocranial morphology, interaction patterns between the endo and neurocranium in the occipito-cerebellar area appear more variable and linked to the overall degree of globularisation of the brain and neurocranium. These results highlight some of the interactions between cerebral reorganisations and cranial morphology in Homo species, and underline the importance of crossing data and methods in order to interpret the fossil record
Labourie, Camille. "Limites d'ensembles quasiminimaux et existence d'ensembles minimaux sous contraintes topologiques". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS008.
Texto completoIn the nineteenth century, Joseph Plateau described the geometrical disposition of soap films. Their shape is explained by their tendency to minimize their area to a reach an equilibrium. Mathematicians have abstracted the concept of "surface with minimal area spanning a boundary" and have named the corresponding minimization problem, "Plateau problem". It has different formulations corresponding to as many ways of defining the class of "surfaces spanning a given boundary" and the "area" to minimize. In this thesis, we generalize to quasiminimizing sequences, the weak limit of minimizing sequences introduced by De Lellis, De Philippis, De Rosa, Ghiraldin and Maggi. We show that a weak limit of quasiminimal sets is quasiminimal. This result is analogous to the limiting theorem of David for the local Hausdorff convergence. Our proof is inspired by David's one while being simpler. We deduce a direct method to prove existence of solutions to various Plateau problem, even with a free boundary. We apply it then to two variants of the Reifenberg problem (fixed or free boundary) for all coefficient groups. Furthermore, we propose a structure to build Federer-Fleming projections as well as a new estimate on the choice of projection centers
Fraimout, Antoine. "Evolution de la variation génétique et phénotypique au cours d'une invasion : le cas de Drosophila suzukii". Thesis, Paris, Muséum national d'histoire naturelle, 2016. http://www.theses.fr/2016MNHN0019.
Texto completoBiological invasions are a component of global change and have dramatic effects on ecosystems, agrosystems and human health. Nonetheless, these peculiar biological processes offer a great opportunity for the study of rapid phenotypic and genetic evolution, at an ecological timescale. Biological invasions often involve environmental and demographic constraints on populations, as well as strong effects of selection and drift. However, these species are among the most successful colonialists in nature, and their ability to respond to these constraints is remarkable. The evolutionary and adaptive potential of invasive populations have been proposed as facilitating factors of the success of invasions. Processes of genetic (i.e. changes in allele frequencies) and plastic (i.e. adjustment to environmental fluctuation through phenotypic plasticity) involved in the success of biological invasions are at the center of modern evolutionary biology. Here, we use the recent spread of the spotted-wing Drosophila suzukii to study the underlying mechanisms of response to selection potentially involved in the success of this global invasion. Analyzing patterns of neutral genetic variation allowed us to decipher the complex history of this worldwide invasion, and subsequently evaluate phenotypic divergence and evolution of quantitative genetic variation among ancestral and derived populations. We thus estimated the effects of selection and drift throughout this invasion and discuss their importance regarding the evolution of wing shape in this species. Finally, experimental protocols on the analysis of phenotypic plasticity as well as Species Distribution Modeling methods allowed us to discuss the influence of environmental fluctuations on the success of this invasion
Ressayre, Nicolas. "Variations de quotients géométriques et applications". Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10184.
Texto completoLang, Iris. "Variabilité génétique et phénotypique de deux espèces invasives : patrons, déterminants et implications pour le fonctionnement des écosystèmes dulçaquicoles". Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30216.
Texto completoIntraspecific variability is now recognized for its importance on ecosystem functioning. In the context of biological invasions, which can strongly impact ecological processes, it is of high importance to understand the determinants and the patterns of genetic and phenotypic variability to fully apprehend the consequences of invasive individuals on recipient ecosystems. We demonstrated a high variability among and within populations of two crayfish species, Procambarus clarkii and Faxonius limosus, with distinct life-history traits and colonization histories in a narrow-invaded area. We highlighted that colonization history and environmental conditions were the main drivers of the contrasting patterns of genetic and phenotypic variability between the two species. Genetic analyses provided a great inference of local invasion pathways for P. clarkii, which had a great genetic variability, compared to F. limosus for which the local invasion pathways were more cryptic. We found that neutral and adaptive processes shaped the phenotypic variability of the two species in differing proportions. Then, we demonstrated the existence of a stable resource polymorphism along the benthic littoral-pelagic axis within populations of P. clarkii, suggesting that invaders could have contrasting impacts on ecosystem functioning between littoral and pelagic trophic chains. Finally, in an experiment context using a multi-traits approach, we demonstrated that the structure of trait covariations differed between species in a sympatric population, suggesting that P. clarkii impacts would be more predictable than F. limosus, and that P. clarkii could affect a higher range of ecological processes or impact the ecosystem functioning with a greater intensity than F. limosus. Overall, our findings stress the need to integrate intraspecific variability in the context of biological invasions to better understand their impacts on ecosystem functioning
Elharfaoui, Echarif. "La convergence faible des U-statistiques multivariées pour des processus non stationnaires dépendants". Toulouse 3, 2003. http://www.theses.fr/2003TOU30144.
Texto completoFoare, Marion. "Analyse d'images par des méthodes variationnelles et géométriques". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAM043/document.
Texto completoIn this work, we study both theoretical and numerical aspects of an anisotropic Mumford-Shah problem for image restoration and segmentation. The Mumford-Shah functional allows to both reconstruct a degraded image and extract the contours of the region of interest. Numerically, we use the Amborsio-Tortorelli approximation to approach a minimizer of the Mumford-Shah functional. It Gamma-converges to the Mumford-Shah functional and allows also to extract the contours. However, the minimization of the Ambrosio-Tortorelli functional using standard discretization schemes such as finite differences or finite elements leads to difficulties. We thus present two new discrete formulations of the Ambrosio-Tortorelli functional using the framework of discrete calculus. We use these approaches for image restoration and for the reconstruction of normal vector field and feature extraction on digital data. We finally study another similar shape optimization problem with Robin boundary conditions. We first prove existence and partial regularity of solutions and then construct and demonstrate the Gamma-convergence of two approximations. Numerical analysis shows once again the difficulties dealing with Gamma-convergent approximations
Lévesque, Sylvain. "Modélisation des variations dimensionnelles et géométriques d'une structure soudée dans le cas d'une structure d'autocar". Mémoire, École de technologie supérieure, 2009. http://espace.etsmtl.ca/992/1/L%C3%89VESQUE_Sylvain.pdf.
Texto completoMarguet, Benoît. "Contribution à l'analyse des variations géométriques dans les ensembles structuraux en aéronautique : démarche et outils". Cachan, Ecole normale supérieure, 2001. http://www.theses.fr/2001DENS0022.
Texto completo"The subject of this thesis is the management of the geometrical variations for aircraft assemblies. More particularly the goal of this document is to show the feasibility of an integrated method to select the optimal solutions minimizing the impact of the geometrical variations on the product. This global method of assembly improvement is based on a selection of product's Key Characteristics and an analysis of assembly sequences. This method is based on a set of analysis tools. Among these tools, functional analysis allows to the designer to define the expected functional product requirements and to decompose them inside the product tree. A qualitative tolerance analysis is alos proposed. The goal of this analysis is to eliminate quickly all the bad solutions. At least a quantitative tolerance analysis allows to identify and to validate among the remaining solutions, one or several solutions for the studied criterion. This method and the proposed analysis are illustrated by a case study resulting from the aircraft industry. This illustration allows to show in what the proposed method allows to study and evaluate a complex problem based on geometrical variations criteria"
Baraket, Sami. "Quelques résultats sur des équations aux dérivées partielles non linéaires provenant de problèmes géométriques". Cachan, Ecole normale supérieure, 1994. http://www.theses.fr/1994DENS0012.
Texto completoBalacheff, Florent. "Inégalités isopérimétriques sur les graphes et applications en géométrie différentielle". Montpellier 2, 2005. https://tel.archives-ouvertes.fr/tel-00010580.
Texto completoArambourou, Hélène. "Stress toxique et variations de forme chez "Chironomus riparius" (insecte, diptère)". Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0104/document.
Texto completoUsing traditional and geometric morphometrics, we analysed morphological variations of the mentum and the wings in Chironomus riparius (Insecta, Diptera) exposed to toxic stress. To understand both the causes and mechanisms involved in phenotypic changes, we studied: (1) the relationship between toxic stress, cellular response and shape variations, (2) the pattern of shape variations according to the type of stress: single vs toxic mixture, (3) the evolution of shape variations after metamorphosis and the transmission of the morphological defects to the next generation. To achieve this, Chironomus riparius larvae were exposed during their entire larval life cycle, first to sediment spiked with lead (from 3 to 500 mg/kg dry weight) or 4-NP (from 0 to 200 mg/kg dry weight), second to two sediments sampled in the wild. The first of the latter was characterized by light urban pollution and the other by heavy urban and industrial pollution. We measured the effects of lead on three biochemical markers (energy reserve content, concentrations of metallothionein and cellular damages). Furthermore, for all the bioassays, we assessed shape variations (phenodeviations, fluctuating asymmetry and mean shape changes) of the mentum, a mouthpart structure of the chironomid larvae. For both the sediments sampled in the wild, we also assessed the shape changes of imago wings and the shape changes of the mentum affecting the next generation. At the station where the sediment was characterized by light urban pollution, we also measured morphological variations of the mentum in the Chironomid population belonging to the genus Chironomus. Despite the adverse effects of lead observed at the biochemical level, only slight effects were observed in the mentum shape. Similarly, 4-NP exposure did not induce strong phenotypic defects. On the contrary, mentum deformities increased in Chironomid larvae exposed to slightly contaminated sediment sampled in the wild. This might have been due to the exposure to the toxic mixture. In the heavily contaminated sediment, the low levels of both deformities and fluctuating asymmetry observed might have been the result of selection acting during early developmental stages. This hypothesis could thus explain the increase of developmental instability observed in the next generation placed in a control sediment. In the imago from exposed larvae, no increases in fluctuating wing asymmetry were detected. We observed that the level of morphological variations observed in natural population was similar to that detected in the laboratory in our stock culture reared in the sediment from this station. These results underlined the weak response of the shape biomarkers studied to toxic stress, whether related to multiple toxic exposure or not. Moreover, they highlighted the importance of genetics in shape changes. Consequently, the use of these ontogenic biomarkers as indicators of toxic stress in Chironomus riparius seems to be of limited interest
Le, Luyer Mona. "Évolution dentaire dans les populations humaines de la fin du Pléistocène et du début de l’Holocène (19000 – 5500 cal. BP) : une approche intégrée des structures externe et interne des couronnes pour le Bassin aquitain et ses marges". Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0003/document.
Texto completoSince the Late Pleistocene, a reduction in size and a morphological simplification of human teeth have been observed and arguably linked to cultural and environmental changes. Following new discoveries along with the revision of key archaeological contexts, a re-assessment of the nature of crown variations on more than 1900 teeth is proposed for 176 Late Paleolithic, Mesolithic and Early Neolithic individuals from the Aquitaine Basin and its margins. In particular, a non-invasive assessment of internal tooth structure variability (enamel thickness, dental tissue proportions, enamel-dentine junction morphology) has been performed using 3D imaging methods (microtomography) and geometric morphometrics in order to characterize and interpret dental evolution from a whole crown perspective. Results from the morphometric analyses show a discontinuity between Late Pleistocene and Early Holocene populations. External dimensions, enamel thicknesses and tissue proportions are reduced in Mesolithic individuals compared to those of the Late Paleolithic, while major differences are observed in occlusal wear patterns and enamel distribution between Mesolithic and Early Neolithic samples. These data suggest that environmentally-driven modifications during the Early Holocene had a major impact on dental reduction in human populations and that Neolithic cultural changes had mostly affected enamel distribution. Finally, a correlation between occlusal wear pattern and enamel thickness distribution is observed and associated with dietary changes. In particular, enamel thickness may have rapidly evolved as a selective response to functional changes in masticatory biomechanics
Goldman, Dorian. "Formation de motifs dans une énergie de Cahn-Hilliard non locale". Paris 6, 2013. http://www.theses.fr/2013PA066349.
Texto completoWe study the asymptotic behavior of a non-local Cahn-Hilliard energy, often referred to as the Ohta-Kawasakienergy in the context of di-block copolymer melts. In that model, twophases appear, and they interact via a non-local Coulombic type energy. We focus onthe regime where one of the phases has very small volume fraction, thus creating``droplets" of that phase in a sea of the other phase. We computethe Gamma-limit of the leading order energy and yield averaged information foralmost minimizers, namely that the density of the minority phase forms droplets which are almost spherical, with the same radii, and areuniformly distributed throughout the domain. We then derive a next order Gamma-limit energy which determines the geometricarrangement of the droplets. Without thus appealing at all to the Euler-Lagrange equation, we establish here for allconfigurations which have ``almost minimal energy," the asymptotic roundness andradius of the droplets, and the fact that they asymptoticallyshrink to points whose arrangement should minimize this energy, insome averaged sense; this leads to expecting to see triangular lattices ofdroplets. In addition, we prove that the density of droplets of a priori non-minimizing stationarypoints of the energy is also aysmptotically uniform even in dimensions \geq 2. We also study a non-local isoperimetric problem in \mathbb{R}^2 We showthat the connected critical points are determined by perimeter alone, under mild assumptions on theboundary, in the small energy/mass regime. These results differ from the recent results ofJulin and Muratov-Knupfer in that they concerngeneral critical points rather than global minimizers to the energy, making it a non-local extensionof the well known fact by Alexandrov that the only compact, connected, constant curvature curve in the planeis the circle. Our method demonstrates that notonly does the perimeter dominate the non-locality when minimizing this energy, but alsothat the change in perimeter slaves to the change of the non-local term in this scaling regime
Ridwan, Ahmad. "Réponses comportementales aux variations de facteurs faunistiques du milieu chez une araignée à toile géométrique zygiellax-notata (clerck) (araneae, araneidae)". Nancy 1, 1993. http://www.theses.fr/1993NAN10231.
Texto completoRouger, Nicolas. "Sensibilité de la convection naturelle en cavité différentiellement chaufféé à des variations de paramètres géométriques, thermiques et massiques". Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aéronautique, 2009. http://www.theses.fr/2009ESMA0004.
Texto completoNatural convection in cavity is a chaotic phenomenon, so the influence of different parameters on the flow and the heat transfer is essential to know. This thesis presents three experimental complementary studies of natural convection in differentially heated cavity. The first part studied the influence of the changes in the CO2 rate in the enclosure air on the natural convection flow, characterized by a Rayleigh number of 1. 5×10^9 (for pure air). The CO2 rate has almost no influence on the natural convection flow, whether on the thermal stratification in the heart of the cavity or on the mass flow rate circulating in the boundary layers. Likewise, when a lintel is stuck at the ceiling of this same cavity, the mass flow rate does not change despite the pressure loss doubling. The main flow follows the walls without distinguishable separation. The lintel introduces, only locally, 3-D secondary flows more important, especially in the angles. An experimental study for a Rayleigh number close to 10^11, realized in a large differentially heated cavity (4m high), has enabled to quantify the essential natural convection parameters characterizing dynamics and thermics in an unusual geometric configuration. This experiment has enabled to expand nearly 4 decades of Rayleigh number variation in differentially heated cavities, the only evolution law of the Reynolds number, based on the circulating flow rate, according to Rayleigh number exponent 1/3
Caux, Mickael. "Méthodologie de maîtrise des variations géométriques des produits en conception, fabrication et contrôle dans le contexte de l'usine numérique". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2012. http://tel.archives-ouvertes.fr/tel-00777192.
Texto completoCostadoat, Renaud. "Contribution à la recherche de spécifications pour la gestion des variations géométriques au plus tôt dans le cycle de conception". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2010. http://tel.archives-ouvertes.fr/tel-00566221.
Texto completoDaniel, Jérémy. "Variations de structures de Hodge lacées et fibrés harmoniques". Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC175.
Texto completoTwo Hodge-theoretic independent problems are discussed in this thesis. In the first chapter, we introduce an object that generalizes a Hodge structure: a loop Hodge structure. We prove that the datum of a variation of loop Hodge structures is equivalent to the datura of a harmonic bundle, so that one can study harmonic bundles using classical tools of Hodge theory, especially the existence of a period map. In the second chapter, we consider the problem of defining harmonic forms computing the characteristic cohomology of a manifold endowed with an exterior differential system. This is motivated by the example of the period domains, where the exterior differential system is induced by the horizontal distribution
Louet, Jean. "Problèmes de transport optimal avec pénalisation en gradient". Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01070163.
Texto completoImsatfia, Moheddine. "Géométrie de Cartan fondée sur la notion d'aire et application du problème d'équivalence". Phd thesis, Université Paris-Diderot - Paris VII, 2012. http://tel.archives-ouvertes.fr/tel-00850134.
Texto completoBrisson, Jade y Jade Brisson. "Problèmes isopérimétriques et isospectralité pour le problème de Steklov". Master's thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/37633.
Texto completoEn géométrie spectrale, on s’intéresse aux liens entre le spectre d’une variété riemannienne et sa géométrie. On recherche notamment des bornes supérieures et inférieures pour les va-leurs propres qui font intervenir des quantités géométriques, comme l’aire et le périmètre. On se questionne aussi sur l’isospectralité : Quelles sont les variétés riemanniennes non iso-métriques qui possèdent le même spectre ? Au cours des dernières années, le problème de Steklov, problème introduit au tout début du 20e siècle en mécanique des fluides, a suscité l’intérêt de plusieurs mathématiciens. Le but de ce mémoire est de donner une banque de variétés riemanniennes Steklov-isospectrales. On y présente aussi une preuve d’une borne supérieure pour la première valeur propre de Steklov pour un domaine borné du plan, sans hypothèse sur sa connexité.
In spectral geometry, we are interested in the links between the spectrum of a Riemannian manifold and its geometry. We are looking for geometric upper and lower bounds for the eigenvalues. These bounds are geometric, for they involve geometric quantities such as area and perimeter. Isospectrality is also a subject of interest in spectral geometry: What are thenon isometric Riemannian manifolds that share the same spectrum? In the last few years, the Steklov problem, introduced in the beginning of the 20th century in fluid mechanics, raised the interest of many mathematicians. In this memoir, we present a bank of Steklov-isospectral Riemannian manifolds. We also give a proof of an upper bound for the first Steklov eigenvalue for a bounded domain of the plane without any connectedness assumption.
In spectral geometry, we are interested in the links between the spectrum of a Riemannian manifold and its geometry. We are looking for geometric upper and lower bounds for the eigenvalues. These bounds are geometric, for they involve geometric quantities such as area and perimeter. Isospectrality is also a subject of interest in spectral geometry: What are thenon isometric Riemannian manifolds that share the same spectrum? In the last few years, the Steklov problem, introduced in the beginning of the 20th century in fluid mechanics, raised the interest of many mathematicians. In this memoir, we present a bank of Steklov-isospectral Riemannian manifolds. We also give a proof of an upper bound for the first Steklov eigenvalue for a bounded domain of the plane without any connectedness assumption.
Allaud, Emmanuel. "Variations de structures de Hodge et systèmes différentiels extérieurs". Toulouse 3, 2002. http://www.theses.fr/2002TOU30123.
Texto completoSeppecher, Laurent. "Modélisation de l'imagerie biomédicale hybride par perturbations mécaniques". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-01021279.
Texto completoPegon, Paul. "Transport branché et structures fractales". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS444/document.
Texto completoThis thesis is devoted to the study of branched transport, related variational problems and fractal structures that are likely to arise. The branched transport problem consists in connecting two measures of same mass through a network minimizing a certain cost, which in our study will be proportional to mLα in order to move a mass m over a distance L. Several continuous models have been proposed to formulate this problem, and we focus on the two main static models : the Lagrangian and the Eulerian ones, with an emphasis on the first one. After setting properly the bases for these models, we establish rigorously their equivalence using a Smirnov decomposition of vector measures whose divergence is a measure. Secondly, we study a shape optimization problem related to branched transport which consists in finding the sets of unit volume which are closest to the origin in the sense of branched transport. We prove existence of a solution, described as a sublevel set of the landscape function, now standard in branched transport. The Hölder regularity of the landscape function, obtained here without a priori hypotheses on the considered solution, allows us to obtain an upper bound on the Minkowski dimension of its boundary, which is non-integer and which we conjecture to be its exact dimension. Numerical simulations, based on a variational approximation a la Modica-Mortola of the branched transport functional, have been made to support this conjecture. The last part of the thesis focuses on the landscape function, which is essential to the study of variational problems involving branched transport as it appears as a first variation of the irrigation cost. The goal is to extend its definition and fundamental properties to the case of an extended source, which we achieve in the case of networks with finite root systems, for instance if the measures have disjoint supports. We give a satisfying definition of the landscape function in that case, which satisfies the first variation property and we prove its Hölder regularity under reasonable assumptions on the measures we want to connect
Fougeron, Charles. "Exposants de Lyapunov et variations de structures de Hodge". Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC160/document.
Texto completoThis thesis is organized around two main themes : on one hand (chapter 1 to 3) we study the Lyapunov exponents associated to a flat bundle on a complex curve, their application to wind-tree models and links with variation of Hodge structures on the bundle endowed with them. On the other hand (chapter 4 and 5) we introduce dilatation surfaces, and study their symmetries and dynamics.In chapter 1, a result binds diffusion rates of wind-tree models and a Lyapunov exponent of some affine invariant spaces in strata of quadratic differentials. This theorem enables us to compute numerically these diffusion rates for a large familly of models and hence to observe the influence of the shape of the obstacles on the speed of the flow. Chapter 2 is devoted to the proof of a conjecture on Lyapunov exponents behaviour for strata of a given genus and large number of poles when the number of zeros is bounded. It confirms an intuition explained in the previous chapter that diffusion rate on periodic wind-tree models with obstacles with a large number of angles is close to zero. At last, in chapter 3, we consider Lyapunov exponents in the more general setting of flat bundles endowed with a variation of Hodge structure on the sphere minus three points. This example coming from hypergeometric equations mimics the structure of a Hodge bundle on a moduli space parametrized by the sphere. We investigate the relation between these exponents and algebraic numbers like parabolic degrees of holomorphic subbundles.In chapter 4 we consider Veech groups of dilatation surfaces and give a complete topological classification of them. We also convey our intuition of this object and claim a conjecture on the existence of cylinders on each surface. In chapter 5 we describe the dynamics of a genus 2 example in every directions. We show the existence and genericity of directions corresponding to cylinders and we describe an infinite set of directions for which the geodesic flow accumulates on a Cantor set
Bayen, Térence. "Optimisation de formes dans la classe des corps de largeur constante et des rotors". Paris 6, 2007. http://www.theses.fr/2007PA066010.
Texto completoLabbi, Mohammed Larbi. "Courbure riemannienne: variations sur différentes notions de positivité". Habilitation à diriger des recherches, Université Montpellier II - Sciences et Techniques du Languedoc, 2006. http://tel.archives-ouvertes.fr/tel-00267987.
Texto completojusqu'à l'intégrand de Gauss-Bonnet.
Les $(p,q)$-courbures que nous dégageons englobent toutes ces notions. On examine ensuite le terme en courbure de la formule classique de Weitzenböck. On étudie aussi les propriétés de positivité de la $p$-courbure, la seconde courbure de Gauss-Bonnet-Weyl, la courbure d'Einstein et de la courbure isotrope.
Vathanakhool, Khoollapath. "Estimation de la sécurité des poteaux en béton armé : compte tenu des variations aléatoires de leurs caractéristiques géométriques et mécaniques le long de leur ligne moyenne". Toulouse, INSA, 1987. http://www.theses.fr/1987ISAT0015.
Texto completoLenglet, Christophe. "Geometric and variational methods for diffusion tensor MRI processing". Nice, 2006. http://www.theses.fr/2006NICE4083.
Texto completoThis thesis deals with the development of new processing tools for Diffusion Tensor Magnetic Resonance Imaging (DT-MRI). This recent MRI technique is of utmost importance to acquire a better understanding of the brain mechanisms and to improve the diagnosis of neurological disorders. We introduce new algorithms relying on Riemannian geometry, partial differential equations and front propagation techniques. The first part of this work is theoretical. After a few reminders about the human nervous system, MRI and differential geometry, we study the space of multivariate normal distributions. The introduction of a Riemannian structure on that space allows us to define statistics and intrinsic numerical schemes that will constitute the core of the algorithms proposed in the second part. The properties of that space are important for DT-MRI since diffusion tensors are the covariance matrices of normal laws modeling the diffusion of water molecules at each voxel of the acquired volume. The second part of this thesis is methodological. We start with the introduction of original approaches for the estimation and regularization of DT-MRI. We then show how to evaluate the degree of connectivity between cortical areas. Next, we introduce a statistical surface evolution framework for the segmentation of those images. Finally, we propose a non-rigid registration method. The last part of this thesis is dedicated to the application of our tools to two important neuroscience problems: the analysis of the connections between the cerebral cortex and the basal ganglia, implicated in motor tasks, and the study of the anatomo-functional network of the human visual cortex
Loison, Arthur. "Unified two-scale Eulerian multi-fluid modeling of separated and dispersed two-phase flows". Electronic Thesis or Diss., Institut polytechnique de Paris, 2024. http://www.theses.fr/2024IPPAX009.
Texto completoLiquid-gas two-phase flows are present in numerous industrial applications such as aerospace propulsion, nuclear hydraulics or bubble column reactors in the chemical industry.The simulation of such flows is of primary interest for their understanding and optimization.However, the dynamics of the interface separating the gas from the liquid can present a multiscale dynamics and thus makes simulations of industrial processes computationally too expensive.Some modelling efforts have been conducted on the development of cheaper multi-fluid models adapted to particular interface dynamics regime, e.g. in the separated regime where the fluids are separated by a single smooth surface or in the disperse regime where there are inclusions of one fluid carried by the other.Attempts of coupling between these models have showed some progress to simulate multiscale flows like atomization, but usually have physical or mathematical drawbacks.This thesis then pursues the goal of proposing a unified two-scale modelling framework with appropriate numerical methods adapted to this multiscale interface dynamics which goes from a separated to a disperse regime.The main contributions related to this modelling effort are :1- The combination of compressible multi-fluid models of the literature adapted to either the separated or the disperse regime into a unified two-scale multi-fluid model relying on Hamilton’s Stationary Action Principle;2- The local coupling of the models with an inter-scale mass transfer both regularizing the large-scale inter face and modelling mixed regime phenomena such as in primary break-up;3- Enhancing the small-scale models for the disperse regimes by adding the dynamics of geometrical quantities for oscillating droplets and pulsating bubbles, built as moments of a kinetic description.From the numerical perspective, finite-volume schemes and relaxation methods are used to solve the system of conservative laws of the models.Eventually, simulations with the open-source finite solver Josiepy demonstrates the regularization properties of the model on a set of well-chosen numerical setups leading to multi-scale interface dynamics
Lasseur, Eric. "La Craie du Bassin de Paris (Cénomanien-Campanien, Crétacé supérieur). Sédimentologie de faciès, stratigraphie séquentielle et géométrie 3D". Phd thesis, Université Rennes 1, 2007. http://tel.archives-ouvertes.fr/tel-00350422.
Texto completoBriançon, Tanguy. "Problème de régularité en optimisation de formes". Rennes 1, 2002. http://www.theses.fr/2002REN10047.
Texto completoVasilyev, Ioann. "On the existence for the Plateau problem in finite dimensional Banach spaces". Thesis, Sorbonne Paris Cité, 2018. https://theses.md.univ-paris-diderot.fr/VASILYEV_Ioann_2018.pdf.
Texto completoIn this work we study existence of minimisers for the Plateau problem in case of finite dimensional Banach spaces. We work in the context of polyhedral and rectifiable G chains. We start with improving one theorem by Busemann, which states that each hyperplane in a finite dimensional Banach space admits area non-increasing projections (which by the way we call good projections). Namely, we prove that these projections do not increase Hausdorff measure of arbitrary (n - 1) rectifiable subsets. We use this property in order to show that those good projections do not increase the mass (the one relative to th Hausdorff measure) of (n - 1) rectifiable G chains. From here we derive the lower semi-continuity of the mass on the space of rectifiable G chains (via using the strong approximation theorem). This in turn gives us the desired existence result. Furthermore, we were able to prove that in the problem stated above there always exists a solution with the support inside of the convex hull of the boundary data.Along with the “classical" proof discussed above we have also established another proof of the existence of mass-minimizing (n - 1) rectifiable G chains in finite dimensional Banach spaces. Namely, we have proved that for rectifiable subsets of finite dimensional Banach spaces the Hausdorff and the Gross measures coincide. Since those Gross measures are lower semicontinuous, this provides us with an alternative proof of the existence.We apply one theorem of Burago and Ivanov in our proof of the corresponding triangle inequality for the polyhedral 2-cycles. Finally, we show the existence of mass minimizing 2 rectifiable G chains in finite dimensional Banach spaces
Imsatfia, Moheddine. "Géométrie de Cartan fondée sur la notion d'aire et application du problème d'équivalence". Phd thesis, Paris 7, 2012. http://www.theses.fr/2012PA077187.
Texto completoThe main objective of this thesis is to present a geometry given by Cartan in 1933. The Finsler Geometry has many analogies with this theory. We studied the outline of this geometry. The starting point of Cartan is similar to that which leads to the Finsler geometry, is to imagine the space to be made of "contact elements", an element being given by a point M in a manifold of dimension n and an oriented hyperplan passing through this point in the tangent space. Thus we have defined Cartan's geometry based on the concept of area. In a first step, I was interested in the notion of orthogonality in this geometry. Cartan's method to state the equivalence problem is a crucial tool. After, we applied this method to Monge-Ampere equations (elliptic case). Hence following the work of R. Bryant, P. Griffiths and D. Grossman in order to clarify the strategy of Caran. However, many points have to be explored in order to have a clear dictionary between a modern language as the one used by Bryant, Griffiths and Grossman and that of Cartan
Lemenant, Antoine. "SUR LA REGULARITE DES MINIMISEURS DE MUMFORD-SHAH EN DIMENSION 3 ET SUPERIEURE". Phd thesis, Université Paris Sud - Paris XI, 2008. http://tel.archives-ouvertes.fr/tel-00288822.
Texto completoBabadjian, Jean-François. "Méthodes variationnelles pour l'étude de milieux dissipatifs : applications en rupture, endommagement et plasticité". Habilitation à diriger des recherches, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00804504.
Texto completoDos, Santos Lourenço João. "Les causes des variations du taux d’évolution moléculaire entre lignées". Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20084/document.
Texto completoThe main objective of the present thesis is to elucidate the causes of variations in rates of molecular evolution among lineages, and in particular, to understand how factors connected to mutation, selection and genetic drift can influence these variations
Galindo, Patricio A. "Image matching for 3D reconstruction using complementary optical and geometric information". Electronic Thesis or Diss., Université de Lorraine, 2015. http://www.theses.fr/2015LORR0007.
Texto completoAbstractImage matching is a central research topic in computer vision which has been mainly focused on optical aspects. The aim of the work presented herein consists in the direct use of geometry to complement optical information in the tasks of 2D matching. First, we focus on global methods based on the calculus of variations. In such methods occlusions and sharp features raise difficult challenges. In these scenarios only the contribution of the regularizer accounts for results. Based on a geometric characterization of this behaviour, we formulate a variational matching method that steers grid lines away from problematic regions. While variational methods provide well behaved results, local methods based on match propagation provide results that adapt closely to varying 3D structures although choppy in nature. Therefore, we present a novel method to propagate matches using local information about surface regularity correcting 3D positions along with corresponding 2D matchings
Guézou, Marc. "Etude et développement d'un système expert de génération de paramètres de soudage, et d'obtention des lois de variation de ces paramètres en fonction de la géométrie d'accostage des tôles, pour le soudage à l'arc robotisé". Paris 6, 1995. http://www.theses.fr/1995PA066099.
Texto completoPant, Dibakar Raj. "Line element and variational methods for color difference metrics". Phd thesis, Université Jean Monnet - Saint-Etienne, 2012. http://tel.archives-ouvertes.fr/tel-00981484.
Texto completoSpinaci, Marco. "Déformations des applications harmoniques tordues". Phd thesis, Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00877310.
Texto completoDelyon, Alexandre. "Shape Optimisation Problems Around the Geometry of Branchiopod Eggs". Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0123.
Texto completoIn this thesis we are interested in a problem of mathematics applied to biology. The aim is to explain the shape of the eggs of Eulimnadia, a small animal belonging to the class Branchiopods}, and more precisely the Limnadiidae. Indeed, according to the theory of evolution it is reasonable to think that the shape of living beings or objects derived from living beings is optimized to ensure the survival and expansion of the species in question. To do this we have opted for the inverse modeling method. The latter consists in proposing a biological explanation for the shape of the eggs, then modeling it in the form of a mathematical problem, and more precisely a shape optimisation problem which we try to solve and finally compare the shape obtained to the real one. We have studied two models, one leading to geometry and packing problems, the other to shape optimisation problems in linear elasticity. After the resolution of the first modeling problem, another mathematical question naturally arose to us, and we managed to solve it, resulting in the complete Blaschke-Santalò (A,D,r) diagram. In other words we can answer the following question: given three positive numbers A,D, and r, and it is possible to find a convex set of the plane whose area is equal to A, diameter equal to D, and radius of the inscribed circle equal to r
Galindo, Patricio A. "Image matching for 3D reconstruction using complementary optical and geometric information". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0007/document.
Texto completoAbstractImage matching is a central research topic in computer vision which has been mainly focused on optical aspects. The aim of the work presented herein consists in the direct use of geometry to complement optical information in the tasks of 2D matching. First, we focus on global methods based on the calculus of variations. In such methods occlusions and sharp features raise difficult challenges. In these scenarios only the contribution of the regularizer accounts for results. Based on a geometric characterization of this behaviour, we formulate a variational matching method that steers grid lines away from problematic regions. While variational methods provide well behaved results, local methods based on match propagation provide results that adapt closely to varying 3D structures although choppy in nature. Therefore, we present a novel method to propagate matches using local information about surface regularity correcting 3D positions along with corresponding 2D matchings
Ouni, Marwa. "Problèmes inverses en mécanique des fluides résolus par des stratégies de jeux". Thesis, Université Côte d'Azur, 2021. http://theses.univ-cotedazur.fr/2021COAZ4021.
Texto completoThis thesis aims to study the ability of theoretic game approaches to deal with ill-posed problems. The first part of the thesis is dedicated to the Stokes system’s linear problem, with the goal of detecting unknown geometric inclusions or pointwise sources in a stationary viscous fluid, using a single compatible pair of Dirichlet and Neumann data, available only on a partially accessible part of the boundary. Inverse geometric-or-source identification for the Cauchy-Stokes problem is severely ill-posed (in the sense of Hadamard) for both the inclusions or sources and the missing data reconstructions, and designing stable and efficient algorithms is challenging. To solve the joint completion/detection problem, we reformulate it as a three players Nash game. The two first players aim at recovering the missing data (Dirichlet and Neumann conditions prescribed over the inaccessible boundary), while the third player seeks to identify the shape and locations of the inclusions (in Chapter 2) or determine the source term (in Chapter 3). We then introduce new algorithms dedicated to the Nash equilibria, which is expected to approximate the original coupled problems’ solutions. We present different numerical experiments to illustrate the efficiency and robustness of our 3- player Nash game strategy. The extension of this work to another situation, such as identifying small objects, has been carried out (in Chapter 4). The second purpose of this thesis is to extend those results to the case of quasi-Newtonian fluid flow whose viscosity is assumed to be a nonlinear function that varies upon the imposed rate of deformation. The considered problem then is a nonlinear Cauchy type because of the non-linearity of the viscosity function. Two different iterative procedures, control-type and Nash game algorithms, are considered to solve it. From a computational point of view, the non-linearity needs some particular algorithms. We propose a novel one-shot algorithm to solve the nonlinear state equations during a recovery process, representing a different idea to treat the nonlinear Cauchy problems. Some numerical experiments are provided to demonstrate our algorithm’s efficiency in the noise-free and noisy data cases. A comparison between the one-shot scheme and the fixed-point method was performed. Finally, we introduce an algorithm to jointly recover the missing boundary data and the location and shape of the inclusions for nonlinear Stokes models based on the Game-Theoretic approach
Poineau, Jérôme. "Espaces de Berkovich sur Z". Phd thesis, Université Rennes 1, 2007. http://tel.archives-ouvertes.fr/tel-00193626.
Texto completoLa majeure partie de notre travail est consacrée à la droite analytique. Elle jouit de propriétés semblables à celles des espaces analytiques complexes d'un point de vue topologique, mais également algébrique, son faisceau structural étant cohérent. En outre, en termes cohomologiques, ses disques se comportent comme des espaces de Stein.
Pour finir, nous exposons quelques applications des résultats géométriques énoncés auparavant. Nous obtenons ainsi quelques propriétés de classes de fonctions particulières, telles les fonctions holomorphes sur un disque contenu dans C et dont le développement en un point est à coefficients entiers.