Rozprawy doktorskie na temat „Compression de modèle”
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 50 najlepszych rozpraw doktorskich naukowych na temat „Compression de modèle”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.
Pedroso, Meloni Luis Geraldo. "Compression spectrale du signal vocal par modification du modèle autorégressif". Nancy 1, 1985. http://www.theses.fr/1985NAN10275.
Pełny tekst źródłaSalazar, Betancourt Luis Fernando. "Modélisation de la compression de SMCs haute-performance". Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM079.
Pełny tekst źródłaThis work deals with the numerical simulation and modeling of thermomechanical analysis of fiber reinforcedcomposites materials. Specifically for SMC (Sheet Molding Compound) materials that are used in compression molding processes to build automotive high performance parts. The work is divided into fourchapters, firstly describing a fully coupled thermo-mechanical model for standard SMC materials and for innovative SMC with high fiber concentration (> 25% in volume). The SMC is treated as an incompressible mixtureof fibers and paste complemented by a compressible porosity phase. Its anisotropy is modeled by means of structural tensors. Kinetic of reaction and consolidation of the part is also modeled and studied. Mechanicaland thermal experimental data recorded on samples of SMC materials are compared to the model and numerical solution provided in this work. A numerical framework, we use the immersed boundary method and the level set method. We describe the compression molding process by proposing an unified anisotropic compressible resolution able to describe the transition between compressible/ incompressible of SMC materials under deformation. We are able to describe the mechanical response of the SMC and to predict locally the consolidation (curing) of thepart throughout the thermal cycle
Ngadi, Abderrazzaq. "Fluctuations de forces dans le processus de compression d'un milieu granulaire modèle". Paris 6, 1999. http://www.theses.fr/1999PA066670.
Pełny tekst źródłaCaillaud, Florian. "Compression progressive de maillages surfaciques texturés". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI004/document.
Pełny tekst źródłaSince several years, 3D models become more and more detailed. This increases substantially the amount of data needed to describe them. However, in the same time, a rising number of applications are constrained in memory and/or in speed (mobile device visualization, video games, etc.). These difficulties are even more visible within a Web context. This situation can lead to incompatibilities, latency in transmission or rendering, which is generally an issue. The progressive compression of these models is a possible solution. The goal is to compress the information (geometry, connectivity and associated attributes) in order to allow a progressive reconstruction of the mesh. Contrary to a single-rate compression, progressive compression quickly proposes a faithful draft of the 3D model and, then, refines it until the complete mesh is recovered. This allows a better comfort for the user and a real adaptation of the rendered element number in adequacy with the terminal device properties. The existing approaches for progressive compression mainly focus on triangular 2- manifold meshes. Very few methods are able to compress progressively non-manifold surface meshes and, to our knowledge, none can deal with every surface meshes (i.e. nomanifold and polygonal), in a generic way. So as to suppress these limitations, we present a new generic progressive method allowing the compression of polygonal non-manifold surface meshes. Moreover, our approach takes care of the texture attribute, possibly associated to these meshes, by handling properly potential texture seams. For that purpose, we progressively decimate the mesh using a new generic simplification operator. This decimation is driven by a local metric which aims to preserve both the geometry and the texture parametrisation. During the simplification, we progressively encode the necessary information for the reconstruction. In order to improve the compression rate, we propose several entropy reduction mechanisms, as well as geometry based prediction strategies for the connectivity and UV coordinates encoding. Finally, the texture map is progressively compressed then multiplexed with mesh data. This multiplexing is achieved using a perceptual metric to provide the best rate-distortion ratio as possible during the decompression
Mira, Anna. "Modèle biomécanique du sein pour l’évaluation de la compression et de la perception d’inconfort en mammographie". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAS009/document.
Pełny tekst źródłaBackground: Mammography is a specific type of breast imaging that uses low-dose X-rays to detect breast cancer at early stage. During the exam, the women breast is compressed between two plates in order to even out the breast thickness and to spread out the soft tissues. This compression improves the exam quality but can also be a source of discomfort. Though mammography is the most effective breast cancer screening method, the discomfort perceived during the exam might deter women from getting the test. Therefore, an alternative breast compression technique considering the patient comfort in addition to an improved clinical image quality is of large interest.Methods: In this work, a simulation environment allowing the evaluation of different breast compression techniques was put forward. The compression quality was characterized in terms of patient comfort, image quality and average glandular dose. To estimate the breast deformation under compression, a subject-specific finite element biomechanical model was developed. The model was calibrated and evaluated using MR images in three different breast configurations (supine, prone and supine tilted). On the other hand, image quality was assessed by using an already validated simulation framework. This framework was largely used to mimic image acquisitions in mammography.Findings: The capability of our breast biomechanical model to reproduce the real breast deformations was evaluated. To this end, the geometry estimates of the three breast configurations were computed using Neo-Hookean material models. The subject specific mechanical properties of each breast's structures were assessed, such as the best estimates of the supine and prone configurations were obtained. The Hausdorff distances between the estimated and the measured geometries were equal to 2.17 mm and 1.72 mm respectively. Then, the model was evaluated using a supine tilted configuration; with a Hausdorff distance of 6.14 mm was obtained in that case. However, we have showed that the Neo-Hookean strain energy function cannot totally describe the rich mechanical behavior of breast soft tissues. Therefore, alternative material models based on the Gent strain energy function were proposed. The latter assumption reduced the maximal error in supine tilted breast configuration by about 10 mm.The coupling between the simulations of the breast mechanics and the X-ray simulations allowed us to run two preliminary studies. In the first study, the differences between standard rigid and flex compression paddles were assessed. According to the performed simulations, using the flex paddle for breast compression may improve the patient comfort without affecting the image quality and the delivered average glandular dose.In the second study, the impact of breast positioning on the general compression mechanics was described. Our simulations confirm that positioning the paddle closer to the chest wall is suspected to increase the patient discomfort. Indeed, based on the estimated data, for the same breast thickness under compression, the force applied to the breast may increase by 150%.Conclusion: The good results we get for the estimation of breast deformation under gravity, as well as the conforming results on breast compression quality with the already published clinical statements, have shown the feasibility of such studies by the means of a simulation framework
Deschênes, Jean-Daniel. "Modélisation interactive : amélioration du processus de reconstruction d'un modèle 3D par la compression temps réel". Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25372/25372.pdf.
Pełny tekst źródłaKouyoumdjian, Pascal. "Mise au point d’un modèle de compression médullaire chez la souris : étude comportementale et histopathologique". Montpellier 2, 2009. http://www.theses.fr/2009MON20017.
Pełny tekst źródłaDespite considerable efforts over the last two decades there is so far no efficient therapeutic approach in spinal cord injuries (SCI). This may be attributable, at least in part, to difficulties encountered for elaborating predictive and accurate experimental animal models of this pathology. Previous studies have identified two relevant conditions of such model. First, the comparison of data arising from rat models by developing mice models that permits to have access to a large repertory of transgenic models, thus allowing to probe precise pathophysiological hypotheses. Second, the exploration of the consequences of each mechanism of the spinal trauma requires modeling the different etiologic aspects of the injury (i. E. Ischemia, mechanic contusion and compression). In order to fulfill these two conditions we have devised a new model of compression injury of the mouse spinal cord using a thread-driven olive-shaped compressive device. We havecharacterized early motor, sensory and histological outcomes using three olive diameters anddifferent compression duration. We show a gradual and reproducible functional severity thatcorrelates with lesion extension. To further substantiate the characterization of this model, wedispensed a non-competitive NMDA antagonist and demonstrated the involvement ofexcitotoxicity in this model. We thus demonstrate that spinal olive-compression injury in the mouse is a reproducible, well-characterized and predictable model to analyse early event following SCI. The nonmagnetic and remote controlled design of this model will allow further real-time MRI studies that will give insights in the characterization of spatial and temporal evolution of SCI. Moreover it paves the way toward in vivo studies of functional and histological outcomes following SCI in genetically engineered animals
Abou, Rached Ghady. "Experimental and numerical study of a cooled compression by oil injection in a screw compressor". Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM057.
Pełny tekst źródłaThis thesis’ objective is designing a dedicated oil injection system in order to achieve a cooled compression solution for compressors using R-134a, a relatively low pressure refrigerant. Bi fluid atomizers are identified as a technology capable of generating fine droplets of oil suitable with the pressure regime of R-134a. An experimental study was carried out to characterize this family of injectors in terms of particle sizes and mass flow rates. Correlations were suggested in order to determine these magnitudes as a function of pressure conditions at the outlet of the injector. A complete injection system is then designed and built for a commercial R134a screw compressor water chiller, where the injection conditions were varied systematically. A 1D model was also developed taking into consideration the whole compressor. It is divided into three main parts: Pre compression, compression and post compression zones. The model parameters were fitted using the experimental results. A parametric study was conducted to determine an optimal functioning point with best results and best operating conditions. The main result of this thesis is an innovative design with high energy performance and moderate cost of a compression cooling system dedicated for a screw compressor. The experimental study validated an increase of COP of 3% and a maximal temperature discharge reduction of 7°C. The model predicts up to 20% of COP improvement if certain operating conditions are met
Cavaro-Ménard, Christine. "Compression d'images basée sur un modèle contour-texture : adaptation d'un système de codage aux images biomédicales". Tours, 1991. http://www.theses.fr/1991TOUR3308.
Pełny tekst źródłaSaidou, Adamou. "Étude du comportement en compression-cisaillement d'isolateurs sismiques en caoutchouc". Mémoire, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/6209.
Pełny tekst źródłaStopin, Alexandre. "Détermination de modèle de vitesse anisotrope par tomographie de réflexion des modes de compression et de cisaillement". Université Louis Pasteur (Strasbourg) (1971-2008), 2001. http://www.theses.fr/2001STR13203.
Pełny tekst źródłaMarc, Daniel. "Étude expérimentale de la compression d'un écoulement de rouleau : situation modèle de l'aérodynamique interne des moteurs à pistons". Toulouse, INPT, 1998. http://www.theses.fr/1998INPT013H.
Pełny tekst źródłaTobbi, Hany. "Comportement en compression de colonnes en béton renforcées d'armatures en PRF". Thèse, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/6144.
Pełny tekst źródłaPeng, Kun. "Compression et vérification de visages pour les cartes d'identité à puce". Caen, 2009. http://www.theses.fr/2009CAEN2060.
Pełny tekst źródłaSmart identification cards will undoubtedly replace the current paper-based ones and become the next generation of identification cards. This Ph. D. Thesis presents and proposes a smart identification card system using facial biometric information for identity authentification on following a strategy containing three security levels: manual verification offline, manual verification online and automatic verification. The principal task of manual face verification online is to find out a compact and secure way to stock a photograph of the identification card holder into the chip on the smart card. We bring out an idea based on decomposing the face image into two parts which are stocked into the card and the database of system respectively. An algorithm based on Singular Value Decomposition of 2D matrix is proposed to realize this idea. The work on automatic face verification faces mainly to establish a reliable face verification algorithm adapting to the context. A novel face verification scheme based on class-specific face models is proposed in this thesis. And the technique Active Appearance Model (AAM) is applied for face modeling and representation. To improve the performance of the system, we developed an algorithm of eye position detection, which can offer a better initialization for AAM matching, and a technique of virtual faces generation, which can enrich the variety of class-specific AAM models. In the sight of the performance evaluation of the proposed method, the database XM2VTS and the accompanied protocol, Lausanne Protocol, are selected to make the experiments
Dubuis, Laura. "Biomécanique des tissus mous de la jambe humaine sous compression élastique". Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2011. http://tel.archives-ouvertes.fr/tel-00716423.
Pełny tekst źródłaTabouillot, Pascal. "Caractérisation rhéologique des pâtes biscuitières en compression uniaxiale : Impact industriel de la méthode". Compiègne, 1993. http://www.theses.fr/1993COMP647S.
Pełny tekst źródłaThe objective of the work was to develop a simple and reproductible physical measuring method to determine the technological properties of cookie dough. A rheometer was constructed which allows the application of various types of one dimensional deformation, e. G. : (I) different compression/relaxation velocities, (II) sinusoidal deformations, (III) compression-relaxation cycles. Rheological measurements of dough samples by compression at constant velocity were analysed using the upper convected Maxwell model, giving the sample's viscosity and relaxation time. The deformation mechanism and in particular the effect of lubrification is studied using image analysis. Hence the experimental conditions for which the new method is valid were determined. The effects of the various dough ingredients on the rheological behaviour are quantified by a statistical study ; based on varying the dough's composition. Finally industrial use of the developed methodology has shown the validity of our approach ; the behaviour of a dough based on a different type of flour, could be effectively predicted
Mahmoudian, Bigdoli Navid. "Compression for interactive communications of visual contents". Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S072.
Pełny tekst źródłaInteractive images and videos have received increasing attention due to the interesting features they provide. With these contents, users can navigate within the content and explore the scene from the viewpoint they desire. The characteristics of these media make their compression very challenging. On the one hand, the data is captured in high resolution (very large) to experience a real sense of immersion. On the other hand, the user requests a small portion of the content during navigation. This requires two characteristics: efficient compression of data by exploiting redundancies within the content (to lower the storage cost), and random access ability to extract part of the compressed stream requested by the user (to lower the transmission rate). Classical compression schemes can not handle random accessibility because they use a fixed pre-defined order of sources to capture redundancies. The purpose of this thesis is to provide new tools for interactive compression schemes of images. For that, as the first contribution, we propose an evaluation framework by which we can compare different image/video interactive compression schemes. Moreover, former theoretical studies show that random accessibility can be achieved using incremental codes with the same transmission cost as non-interactive schemes and with reasonable storage overhead. Our second contribution is to build a generic coding scheme that can deal with various interactive media. Using this generic coder, we then propose compression tools for 360-degree images and 3D model texture maps with random access ability to extract the requested part. We also propose new representations for these modalities. Finally, we study the effect of model selection on the compression rates of these interactive coders
Vauzelle, Rodolphe. "Un modèle de diffraction en 3D dans le premier ellipsoi͏̈de de Fresnel". Poitiers, 1994. http://www.theses.fr/1994POIT2255.
Pełny tekst źródłaDupray, Fabrice. "Comportement du béton sous fort confinement : étude en compression et en extension triaxiales à l'échelle mésoscopique". Phd thesis, Grenoble 1, 2008. http://www.theses.fr/2008GRE10266.
Pełny tekst źródłaThis Ph. D. Thesis aims at characterising and modeling the mechanical behaviour of concrete under high confinement at the mesoscopic scale. This scale corresponds to that of the large aggregates and the cementitious matrix. The more general scope of this study is the understanding of concrete behaviour under dynamic loading. A dynamic impact can generate mean pressures around 1GPa. But the characterisation of a material response, in an homogeneous state of stress, can only be achieved through quasi-static tests. The experimentations led in 3S-R Laboratory have underlined the importance of the aggregates in the triaxial response of concrete. Modeling concrete at the mesoscopic level, as a composite of an aggregates phase and a mortar phase, permits a representation of the aggregates effect. An experimental study of the behaviour of mortar phase is performed. Usual tests and hydrostatic and triaxial high confinement tests are realised. The parameters of a constitutive model that couples plasticity with a damage law are identified from these tests. This model is able to reproduce the nonlinear compaction of mortar, the damage behaviour under uniaxial tension or compression, and plasticity under high confinement. The biphasic model uses the finite element method with a cubic and regular mesh. A Monte-Carlo method is used to place quasi-spherical aggregates that respect the given granulometry of a reference concrete. Each element is identified by belonging either to the mortar or to the aggregate phase. Numerical simulations are compared with the experimental tests on this concrete. The parameters for these simulations are only identified on the mortar. The simulations reproduce the different phases observed in hydrostatic compression. The evolution of axial moduli under growing confinement is shown, as is the good reproduction of the limit-states experimentally observed under high confinement. The fracture aspect of numerical simulations is comparable with that of experimental tests. The triaxial extension loading shows the limits of this numerical model
Odent, Thierry. "Création d’un modèle animal original de scoliose et caractérisation en trois dimensions des déformations : étude de la perméabilité macroscopique des plateaux vertébraux dans un modèle de compression asymétrique". Lyon 1, 2008. http://www.theses.fr/2008LYO10178.
Pełny tekst źródłaScolisis is mainly an human spinal deformity which appears during growth and is characterized by a progressive structural deformity of the spine, the thorax and the pelvis. An original animal model based on the animal growth using an original device was developed in pigs. Using a three dimensional reconstruction of the spine, we demonstrated that deformity approximates children scoliosis deformity. The deformity consequences on the cartilage end plate (macroscopic permeability changes) and on bone vertebral micro-architecture (micro-CT parameters changes) were analysed to improve the knowledge on disc and vertebrae behaviour in deformity process and to develop new approaches of treatment in children
Sambe, Alioune Nar. "Développement d’un modèle de simulation 3D d’impact de vagues en zones côtières et offshores". Thesis, Toulon, 2011. http://www.theses.fr/2011TOUL0012/document.
Pełny tekst źródłaThe aim of the thesis is thus to improve the field validity for the CFD(Computational Fluid Dynamics) code for waves modelling, by integrating new numerical methods more efficient. The project should eventually lead to make a powerful simulation tool that can be used for forecasting the impact of waves in coastal areas and offshore. It is therefore completely in line with PRINCIPIA development activities in hydrodynamic with the aim of strengthening its position and support its growth. In this paper, we first focus on the specific problem of numerical diffusion for the convection equation that models the two fluid interface discontinuities. Interface compression methods allowing limiting the interface diffusion problem are presented. The main advantages of these compression methods are that they keep properly the interface and minimize the spurious free surface diffusion which may be beneficial in case of strongly nonlinear motion of the free surface. Moreover, they are easy to implement for problems in two or three dimensions. In the other hand, an improvement of the solver is presented; it concerns the development and validation of the Adams-Bashforth multi-scale time integration method which adjusts the time step depending on the local size cell. The advantage of this method is that it significantly reduces the computation time when small cells are mixed with large cells in the mesh domain. Each cell is assigned with a level of CFL only based on a geometric criterion. The improved model is validated. It is confronted with experimental results of 2D solitary wave breaking on a sloping bottom and the 3D dam break problem over a rectangular obstacle. In both cases, a very satisfactory agreement is found, with a better interface definition with the sharpening method and a significant gain in CPU time with Adams-Bashforth multi-scale time integration method
Aregabi, Nidal. "Comportement en compression centrée des poteaux en béton à hautes performances (BHP) renforcés de fibres synthétiques". Mémoire, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11575.
Pełny tekst źródłaGuérin, Michaël. "Diagramme d'interaction des charges combinées flexion-compression des colonnes carrées en béton armé de PRFV". Thèse, Université de Sherbrooke, 2018. http://hdl.handle.net/11143/11792.
Pełny tekst źródłaKochrad, Nidal. "Modèle de performance système du cycle thermodynamique récupéré opérant avec une turbine en céramique renversée". Mémoire, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/9904.
Pełny tekst źródłaFernández, Sabido Silvia Fidelina. "Applications exploratoires des modèles de spins au traitement automatique de la langue". Thesis, Nancy 1, 2009. http://www.theses.fr/2009NAN10055/document.
Pełny tekst źródłaIn this thesis we explored the ability of magnetic models of statistical physics to extract the essential information contained in texts. Documents are represented as sets of interacting magnetic units, the intensity of such interactions are measured and they are used to calculate quantities that are evidence of the importance of information scope. We propose two new methods. Firstly, we studied a spin model which allowed us to introduce the textual energy. This quantity was used as an indicator of information relevance. Several adaptations were necessary to adapt the energy calculation to a wide range of tasks such as summarisation, information retrieval, document classification and thematic segmentation. Furthermore, and even exploratory, we propose a second algorithm that defines a grammatical coupling between types of terms to retain the important terms and produce contractions. In this way, the compression of a sentence is the ground state of the chain of terms. As this compression is not necessarily good, it was interesting produce variants by thermal fluctuations. We have done simulations Metropolis Monte-Carlo with the aim of finding the ground state of this system that is analogous to spin glass
Dupray, Fabrice. "Comportement du béton sous fort confinement : Étude en compression et en extension triaxiales à l'échelle mésoscopique". Phd thesis, Université Joseph Fourier (Grenoble), 2008. http://tel.archives-ouvertes.fr/tel-00365786.
Pełny tekst źródłaMammeri, Abdelhamid. "Compression et transmission d'images avec énergie minimale application aux capteurs sans fil". Thèse, Université de Sherbrooke, 2010. http://hdl.handle.net/11143/5800.
Pełny tekst źródłaAgostini, Marie Andrée. "New Trends in High Definition Video Compression - Application to Multiple Description Coding". Phd thesis, Université de Nice Sophia-Antipolis, 2009. http://tel.archives-ouvertes.fr/tel-00451684.
Pełny tekst źródłaSambe, Alioune Nar. "Développement d’un modèle de simulation 3D d’impact de vagues en zones côtières et offshores". Electronic Thesis or Diss., Toulon, 2011. http://www.theses.fr/2011TOUL0012.
Pełny tekst źródłaThe aim of the thesis is thus to improve the field validity for the CFD(Computational Fluid Dynamics) code for waves modelling, by integrating new numerical methods more efficient. The project should eventually lead to make a powerful simulation tool that can be used for forecasting the impact of waves in coastal areas and offshore. It is therefore completely in line with PRINCIPIA development activities in hydrodynamic with the aim of strengthening its position and support its growth. In this paper, we first focus on the specific problem of numerical diffusion for the convection equation that models the two fluid interface discontinuities. Interface compression methods allowing limiting the interface diffusion problem are presented. The main advantages of these compression methods are that they keep properly the interface and minimize the spurious free surface diffusion which may be beneficial in case of strongly nonlinear motion of the free surface. Moreover, they are easy to implement for problems in two or three dimensions. In the other hand, an improvement of the solver is presented; it concerns the development and validation of the Adams-Bashforth multi-scale time integration method which adjusts the time step depending on the local size cell. The advantage of this method is that it significantly reduces the computation time when small cells are mixed with large cells in the mesh domain. Each cell is assigned with a level of CFL only based on a geometric criterion. The improved model is validated. It is confronted with experimental results of 2D solitary wave breaking on a sloping bottom and the 3D dam break problem over a rectangular obstacle. In both cases, a very satisfactory agreement is found, with a better interface definition with the sharpening method and a significant gain in CPU time with Adams-Bashforth multi-scale time integration method
Derrien, Olivier. "Optimisation de la quantification par modèles statistiques dans le MPEG advanced audio coder (AAC) : application à la spatialisation d'un signal comprimé en environnement MPEG-4". Paris, ENST, 2002. http://www.theses.fr/2002ENST0030.
Pełny tekst źródłaToussaint, Pascal. "Application et modélisation du principe de la précontrainte sur des assemblages de structure bois". Thesis, Nancy 1, 2010. http://www.theses.fr/2010NAN10014/document.
Pełny tekst źródłaIn a pre-stressed fastener, forces are transmitted between two elements by friction which is made possible by the application of transversal compression forces. The aim of this work was to apply this principle to timber fasteners. Thanks to former results, a preliminary experimental study was done on stubbles of bamboo. This “grass” has a higher transversal compression resistance than wood. In order to transpose the principle of pre-stress from bamboo to timber, it was necessary to increase the compression resistance of timber. The idea proposed here is the densification of wood by localised cold compression beyond its elastic limit. Picea abies was characterized in transversal compression beyond its elastic limit. This analysis gave stress-strain curves which depend on the density of the wood. The influence of the densification on the resistance in longitudinal tension was also measured. This resistance is constant and then it decreases rapidly from a critical densification rate function of the density of the wood. The pre-stress of the tested timber and bamboo fasteners was modelled by a finite elements model. The anisotropy of the materials was taken into account by the superposition of a crushable foam model (non linear behaviour in transversal direction) and beams (longitudinal direction). This structural mesoscopic model allowed simulating the densification, the loading and unloading of the fasteners until their failure which lead to an optimization of the connectors
Stasiak, Marta. "Compression uniaxiale d'un matériau granulaire fragile très compressible - une étude par éléments discrets 3D". Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI041/document.
Pełny tekst źródłaThe National Agency for Radioactive Waste Management (FR Andra) in France suggested a new way to design a tunnel lining, especially, beneficial in the case of very deep tunnels. To avoid very thick tunnel segments, they propose to integrate a layer of granular material on the extrados of the thinner lining. This approach takes the advantages of the compressible capacity of the crushable particles and the load transfer in the granular material. A tunnel segment with such design is called a Mono-block Compressible Arch-segment VMC (Andra’s & CMC’s pending patent) and is an innovative new type of tunnel linings.This PhD dissertation is dedicated to the creation of a numerical model capable of reproducing the mechanical behaviour of this compressible granular layer using 3D Discrete Element Method (DEM). The granular packing is made of the brittle hollow coarse-size cylindrical particles, called shells. Each shell is a 2 cm long tube with a diameter of 2 cm. Its small thickness makes the cylindrical shell mainly made of void surrounded by a thin layer of clay. In the model, a breakable cluster (shell) is generated using sphero-polyhedral elongated clumps. These clumps, called sectors, are glued together using two adhesive contact force laws. If the combination of the normal and tangential contact forces exceeds a suitable failure criterion, a de-clustering of the shell (breakage) occurs. The DEM tool Rockable devel- oped for this research can operate on such crushable particles. The mechanical properties of the shell model, composed of 12 to 24 sectors, are adjusted in the case of a uniaxial (vertical) radial compres- sion of shells. The preceding grain-scale experiments on the true shells made of baked clay serve as a reference. We determine the true range of the failure tensile load and its statistical Weibull distribu- tion. The user-specified parameters is then successfully validated in the case of radial compression of a horizontally constrained shell.Firstly, the macroscopic study of shell assemblies focuses on the experimental characterisation of the samples with a control of the initial state variables like a number density and a spatial arrangement of shells (shells orientations). 3D reconstruction from X-ray tomographies of the original coated shells samples extracted from the extrados of a tunnel segment help us to characterise the anisotropy of the shells orientation. This is a piece of valuable information to the generation the numerical samples of shells with relevant initial features. Secondly, a series of DEM oedometric tests on ⟨1 000 : 2 000⟩ shells is simulated. A parametric study successfully leads to the understanding of each internal state variable role. A well-chosen set of initial variables with properly adapted DEM parameters give the relevant predictive simulations for a final comparison with the experimental oedometer tests. Thanks to a discrete insight into the micromechanics, the evolutions of the breakage level, the orientation anisotropy and the local stresses exerted on the shells (and/or the fragments) are quantified during the compression. The breakage of the shells result in high compressibility of the material. Therefore, the mechanical response is seen as a consequence of the breakage evolution. Finally, an analytical model is suggested in order to predict the Stress↔Void ratio relationship knowing the initial state of the sample and the tensile strength of the constituents: the shells
Méchin, Pierre-Yves. "Contribution à l’étude de la résistance à la compression de stratifiés composites à fibres de carbone haut module : cas de chargements statiques et cycliques". Thesis, Lorient, 2017. http://www.theses.fr/2017LORIS434.
Pełny tekst źródłaThis PhD dissertation is a contribution to the modelling of Carbon-Fiber-Epoxy-Polymer laminates, undergoing specifically compression loadings, according to components. The aim is to build a design tool for composites structures taking into account this compression specificity for dimensioning racing yachts parts (masts, daggerboards, foils), which is the expertise of HDS/GSea-Design, the company associated to this work. Emphasis was put on the influence of linear or non-linear properties of each phase by varying the type of fibre (from high stiffness to high strength) and the type of matrix (from brittle to ductile). The effect of a mechanical loading, static, constant (creep, relaxation) or variable (fatigue) on durability is studied and a numerical model for predicting the residual strength is proposed. The first part of this work deals with the mechanisms involved in compressive strength. An analytical model is used for an experimental validation. It considers a contribution linked to the micro-buckling of the fibre as contained by the shear behaviour of the matrix (Budiansky et Fleck [1993]). It considers also a contribution of the deformation gradient induced for instance in a bending loading (Gardin et al. [2002]). To validate this model, an experimental campaign was conducted on six different epoxy matrices (from brittle to ductile) on identical monolithic stackings processed in autoclave. The results allowed the validation of the model capability to predict the influence of the matrix stiffness on the compressive strength of unidirectional laminas. Taking into account the matrix behaviour validates the micro-buckling contribution. Regarding the deformation gradient contribution, it is validated through a comparison using additional experimental results on sandwich samples in bending. The latter samples were specifically designed to favour a pure compression fracture (without any deformation gradient). The second part examines durability in compression. Another experimental campaign with fatigue tests was conducted with four points bending tests on the same sandwich samples. Experiments were carried out at 10 Hz and different load ratios were used to study their influence on the compressive residual strength. A numerical model involving different scales (laminate, laminas, fibres and matrix) is developed in parallel (Huang et al. [2012a]), based on the degradation and the plasticity of the matrix. The assumption of thermo-rheological simplicity of the matrix is made to build master curves from dedicated experiments (creep, relaxation). We then use the residual properties (stiffness, strength) of the ply to estimate a damage level. This latter parameter is used to modify the elastic stiffness of the matrix with a linear law. A Miner-type cumulative law is used in fatigue to take into account the different possible loadings. A micro-mechanical solver is developed to extract the non-linear shear behaviour of the ply accounting for this degradation. This behaviour is described by a Ramberg-Osgood law used in the analytical model described in the first part of this work. The joint contributions of these two parts allowed us to program a numerical tool for predicting the residual strength of plies undergoing a biaxial in- plane loading, being monotonous, constant or with a variable amplitude, with emphasis on the particular case of compression loading
Devillard, Julie. "Lien entre microstructure et résistance à la compression du gypse moussé". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI043.
Pełny tekst źródłaThis study focuses on the microstructural and mechanical characterization of foamed gypsum, the core material of lightweight gypsum boards, with a high (75%) multi-scale porosity. The objective of this work is to determine the influence of the microstructure of foamed gypsum on the hardness measured in spherical indentation and to analyze the damage mechanisms for different microstructures. Spherical indentation tests were conducted on samples showing variations in microstructural features of foamed gypsum. The results of these tests show that density has a first-order influence on hardness and that the dispersion of hardness measurements in spherical indentation can be related to heterogeneity in macroporosity. In situ indentation tests were also carried out, with X-ray tomography and digital volume correlation (DVC) analysis, in order to accurately study the damage mechanisms. Two different modes of damage were determined according to the densities considered (variable macropore fraction). The results of these tests were used to feed an analytical model, based on an energy criterion that links the indentation force to the damaged area under the indenter. This provides the prediction of the indentation force-displacement curve specific to a microstructure with a scan of the initial microstructure as the only input data. Numerical modelling was also carried out using the finite element method with consideration of the actual microstructure, at two scales. The densified areas were properly predicted by different behaviour models based on plasticity criteria
KIM, Geun-Beom. "Recherche des sélectrons, neutralinos et squarks dans le cadre du modèle GMSB avec le détecteur CMS. Etude de la compression sans pertes de données provenant du calorimètre électromagnétique". Phd thesis, Université Louis Pasteur - Strasbourg I, 2001. http://tel.archives-ouvertes.fr/tel-00001120.
Pełny tekst źródłaBelloulata, Kamel. "Compression d'images par fractale : études sur la mesure et le domaine de recherche de l'autosimilarité (spatial ou transforme) et sur l'accélération de la génération du modèle fractal". Lyon, INSA, 1998. http://www.theses.fr/1998ISAL0013.
Pełny tekst źródłaThe goal of this work is to develop an optimize method to the image compression based on fractal theory. The fractal coding is based on the detection, the measure and a coding of the self-similarity presented in the natural pictures. It is well known that the quality of decoded images depends directly on the efficiency of the measurement of the self-similarity between objects of the original image. We present two coding schemes based on L͚ and Lα metrics. The performance of these schemes is compared with various standard images in terms •of PPSNR and maximum local distortion. Concerning the hybrid schemes, we propose a new image compression scheme based on fractal coding of the coefficients of a wavelet transform, in order to take into account the advantages of the two theories (wavelet and fractal) and the self-similarity observed in each sub band. Concerning the acceleration of the fractal coding, a new approach using a hybrid fractal/QV / sub band coding scheme is developed and compared. This approach uses a fast non-iterative algorithm for black clustering in order to code a wavelet • transform coefficients. Our fast non-iterative algorithm is compared with other algorithm in terms of rate improvement obtained
Kim, Geun-Beom. "Recherche des sélectrons, neutralinos et squarks dans le cadre du modèle GMSB avec le détecteur CMS : étude de la compression sans pertes de données provenant du calorimètre électromagnétique". Université Louis Pasteur (Strasbourg) (1971-2008), 2001. http://www.theses.fr/2001STR13102.
Pełny tekst źródłaHoxha, Dashnor. "Modélisation de l'endommagement des massifs rocheux". Vandoeuvre-les-Nancy, INPL, 1998. http://www.theses.fr/1998INPL087N.
Pełny tekst źródłaMercier, Charlotte. "Développement d’un modèle de stabilité des barres à section tubulaire comprimées fléchies sensibles aux effets du second ordre". Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0113/document.
Pełny tekst źródłaThis thesis is part of an effort to improve knowledge of the instabilities of beam-columns sensitive to second-order effects. The works deal with the means to take into account the initial imperfections in the structural analysis and to adapt the current verification criteria for tubular section structures, such as scaffold structures. The existing formulations, proposed in the literature and calculation codes, are often based on hypotheses, and thus lead to inconsistencies between, on the one hand, the verification criteria in section, and on the other hand, the verification criteria in instability. The developed approach takes into account the interaction between section resistance and instability phenomena, and includes the influence of initial imperfections (initial defect of aplomb, lack of straightness, residual stresses). As far as possible, these effects will be decoupled. As such, a method has been developed to allow the definition of initial imperfections of a structure, to be as accurate as possible. This method, based on the definition of a single imperfection, identical in appearance to the shape of the predominant critical buckling mode, is a precise, fully defined method to take into account the geometric characteristics, intrinsic mechanical characteristics, limits and the form of loading, in the definition of the initial imperfections of a structure. A test campaign was carried out in collaboration with the French Syndicate of Scaffolding, Formwork and Shoring (SFECE), aiming to analyze the experimental behavior of buckling of cold-formed tubular sections. Nine buckling tests on scaffold ladders, from various European suppliers, have been carried out. A statistical study of the experimental results has made it possible to highlight that the imperfection factor currently defined for the cold-formed tubular sections is far too penalizing for the sections used in the field of scaffolds. In order to respond to the problem, new instability criteria have also been established using a similar approach to that of Ayrton-Perry. These new criteria make it possible to free ourselves from the modeling of initial imperfections while offering a safe and accurate estimate of the stress factor of a structure. A comparative study was conducted in order to ensure the safety of the proposed formulations as regards the section verification criteria of the NF EN 1993-1-1 current standard
Vanhove, Guillaume. "Oxydation, co-oxydation et auto-inflammation à basses températures d'alcènes et aromatiques types : étude expérimentale des interactions au sein d'un carburant-modèle". Lille 1, 2004. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2004/50376-2004-213-214.pdf.
Pełny tekst źródłaUne étude comparative détaillée de la réactivité de trois isomères de position: les 1-, 2-, et 3-hexènes a été réalisée entre 600 et 900 K, 5 et 25 bar. Des chemins réactionnels spécifiques de la double liaison sont mis en jeu, et les trois h'exènes présentent chacun un poids différents des réactivités'de la chaîne alkyle et de la double liaison. Dans les mêmes conditions de température et de pression, les aromatiques et les alcènes sont moins réactifs que les alcanes, mais on a montré qu'ils sont susceptibles d'être oxydés plus rapidement lorsqu'ils se trouvent mélangés à un alcane. Trois mélanges binaires ont été étudiés: Un mélange toluène/iso-octane, un mélange 1-hexène/iso-octane, et un mélange 1-hexène/toluène. A partir de la mesure des délais d'autoinflammation et des produits d'oxydation intermédiaires des deux composés impliqués dans les mélanges, il est apparu que deux types d'interactions existent entre les mécanismes d'oxydation, soit par le pool de petits radicaux créé par le composé le plus réactif, soit par la recombinaison de radicaux hydrocarbonés originaires des deux partenaires. Les données collectées dans le cas des hydrocarbures purs ou en mélange binaire ont été utilisées afin d'interpréter les résultats obtenus avec un carburant-modèle représentatif de la composition des carburants commerciaux pour moteur à allumage commandé et composé d'iso-octane, de 1-hexène et de toluène
Fernandez, Sabido Silvia. "Applications exploratoires des modèles de spins au Traitement Automatique de la Langue". Phd thesis, Université Henri Poincaré - Nancy I, 2009. http://tel.archives-ouvertes.fr/tel-00412369.
Pełny tekst źródłaBoulegane, Dihia. "Machine learning algorithms for dynamic Internet of Things". Electronic Thesis or Diss., Institut polytechnique de Paris, 2021. http://www.theses.fr/2021IPPAT048.
Pełny tekst źródłaWith the rapid growth of Internet-of-Things (IoT) devices and sensors, sources that are continuously releasing and curating vast amount of data at high pace in the form of stream. The ubiquitous data streams are essential for data driven decisionmaking in different business sectors using Artificial Intelligence (AI) and Machine Learning (ML) techniques in order to extract valuable knowledge and turn it to appropriate actions. Besides, the data being collected is often associated with a temporal indicator, referred to as temporal data stream that is a potentially infinite sequence of observations captured over time at regular intervals, but not necessarily. Forecasting is a challenging tasks in the field of AI and aims at understanding the process generating the observations over time based on past data in order to accurately predict future behavior. Stream Learning is the emerging research field which focuses on learning from infinite and evolving data streams. The thesis tackles dynamic model combination that achieves competitive results despite their high computational costs in terms of memory and time. We study several approaches to estimate the predictive performance of individual forecasting models according to the data and contribute by introducing novel windowing and meta-learning based methods to cope with evolving data streams. Subsequently, we propose different selection methods that aim at constituting a committee of accurate and diverse models. The predictions of these models are then weighted and aggregated. The second part addresses model compression that aims at building a single model to mimic the behavior of a highly performing and complex ensemble while reducing its complexity. Finally, we present the first streaming competition ”Real-time Machine Learning Competition on Data Streams”, at the IEEE Big Data 2019 conference, using the new SCALAR platform
Bettadahalli, Channakeshava Anil. "Non-Local Modeling of the Compressive Strength of Composite Structures". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0018.
Pełny tekst źródłaThe compressive failure of long carbon fiber composites is due to complex mechanisms. The knowledge of these mechanisms is important for the design of composite structures because the compressive strength and stiffness of laminates are assumed less than their tensile strength. Further, compressive failure is a mechanism of non-local ruin that depends on the composite structure (layer thickness, load gradient) which makes it a peculiarity. The mechanism has been described and modelled in the literature with suitable numerical tools and experiments that accounted for this effect. There are many articles in the literature regarding the modelling of composites compressive behavior, particularly the microbuckling phenomenon / local instability. But only a few researchers modelled the mechanism at the structural/mesoscopic scale. For example, Drapier et al., [D3] proposed a 2D homogenized model, which takes into account fiber initial alignment defects, matrix plasticity and structural parameters. The model is successful in predicting the elastic microbuckling modes and to predict the failure. But the model is built for 2D unidirectional laminates and assumes microbuckling is periodic in the fiber direction, just one gradient in the thickness direction is taken into account and the influence of the misalignment is not completely described [D4]. Therefore, to extend the developments of these works ([D1],[D3],[G1],[G4]), new non-local finite element models are developed: one with using ABAQUS® in-built structural elements, named Beam Non-Local (BNL) model and the other with User Element (UEL) subroutine of ABAQUS®, named Homogenized Non-Local Model (HOMNL), implemented in the user element (NL U32), which can be applied with the aim to predict the compressive strength of unidirectional plies/laminates and also for woven composites (2D and 3D). Both the non-linear geometrical and material effects are taken into account in this model. With the BNL model, it is possible to capture the mechanism in 2D and 3D space for laminates of unidirectional composites. Results of the bibliography have been confirmed and new results are presented, for example, the elastic mode in 3D or the mechanism under bending. The width and angle of the kink band are determined by this model. In the framework of more general, the validation of the NL U32 element has been performed with respect to ABAQUS® classical elements for both linear and non-linear (geometry and material) cases. The classical (elastic and plastic) and non-local material properties (elastic) are identified by comparison to the responses of a Representative Volume Element (RVE) of full heterogenous microstructures. Some results have been validated with the bibliography. The developed non-local user element (NL U32) is 2D in this thesis and it can be extended easily to a 3D case, which remains one of the future perspectives.In this work, ABAQUS® v2017, DAKOTA v6.10.0, PARAVIEW v5.8.0 are the softwares used and FORTRAN, Python are the programming languages used
Moustacas, Hélène. "Modélisation et simulation du comportement de mèches de fibres de carbone à l'échelle mésoscopique pour l'analyse du comportement de préformes tissées interlock". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC062.
Pełny tekst źródłaThe increasing use of 3D interlock woven preforms for the manufacturing of composite parts in aircraft industry createsnew requirements for modelling and simulation to optimize these structures. In order to simulate the mechanicalbehaviour of 3D interlock woven preforms for fan blades, this work is aimed at developing a model at mesoscopic scaleable to represent the behaviour of carbon fibre tows, specially when submitted to transverse compression. In order tounderstand the mechanisms involved in this kind of loading, simulations have been performed at the scale of theirelementary components, using a macro-filament model. A higher order beam model, based on a polynomial expansion to anyorder with respect to transverse coordinates, has been proposed. A new approach for detecting and modelling frictionalcontact interactions between higher order beams with highly deformable cross-sections has been developed. Finally, ahybrid rheological model, suited to the higher order beam model, in the form of a combination of various elementaryhyperelastic models (transversely isotropic Saint-Venant, 2D neo-hookean and exponential), has been proposed to fit themechanical response identified under transverse compression tests
Brault, Patrice. "Estimation de mouvement et segmentation d'image". Paris 11, 2005. https://tel.archives-ouvertes.fr/tel-00011310.
Pełny tekst źródłaThe first part of this thesis presents a new vision of the motion estimation (ME) in video sequences. We investigate motion estimation with redundant wavelet families tuned to different kind of transformations and, in particular, to speed. Today video compression standards are supposed to realize the compression in an object-based approach, but still compute raw motion vectors on “blocks”. We thus implemented these wavelet families because 1) they are built to perform motion parameter quantization on several kinds of motions (rotation, speed, acceleration) and 2) based on the motion parameters, we can propose an approach of the ME through the identification of the objects trajectories. The global approach is then closer to a contextual compression, based on the understanding of the scene. The second part introduces two new developments on unsupervised segmentation in a Bayesian approach. 1) we reduce the computation time of a sequence through an iterative implementation of the segmentation. We show an application with the ME of a segmented region. 2) We reduce the segmentation time by making the projection of the image in the wavelet domain. These two developments are based on a Potts-Markov modelling (PMRF) for the labels of the pixels and of the wavelet coefficients. They use a Markov Chain Monte Carlo iterative algorithm with a Gibbs sampler. We also develop a Potts model in the wavelet domain to tune it to the specific orientations of the wavelet subbands
Nastar, Chahab. "Modèles physiques déformables et modes vibratoires pour l'analyse du mouvement non-rigide dans les images multidimensionnelles". Phd thesis, Ecole Nationale des Ponts et Chaussées, 1994. http://pastel.archives-ouvertes.fr/pastel-00569475.
Pełny tekst źródłaGautier, Josselin. "Un modèle d'attention visuelle dynamique pour conditions 2D et 3D ; codage de cartes de profondeur et synthèse basée inpainting pour les vidéos multi-vues". Phd thesis, Université Rennes 1, 2012. http://tel.archives-ouvertes.fr/tel-00758112.
Pełny tekst źródłaThoral, Claudia. "Développement galénique de probiotiques conditionnés sous forme comprimés". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA114827.
Pełny tekst źródłaOne of the main issues in the development of biological products, such as probiotics, is the impact of the manufacturing process on the strain of interest. Maintaining therapeutic activity is of great interest for the expected beneficial effect and work has even optimized the properties of the Lcr35® strain through the manufacturing process. Therefore, all process stages leading to the final product are steps that can alter the characteristics of the bacterial strain.Compression is recognized in some publications as being a step which eliminates bacterial contaminations present for example in the excipients. For the development of new probiotic products, compression has also been described as negative for bacterial viability. These data are therefore a negative a priori on development of probiotic products in the tablet form. Conversely, this dosage form is known to improve the half-Life of products and improve the stability of bacteria in gastric environment. However, no comprehensive study of the properties of a probiotic strain after compression was done. Nevertheless, to establish a marketing authorization, all the properties of the strain must be checked on the final product.This work has proposed a review of the main properties of the Lcr35® strain after compression. First of all, the initial loss of viability as a function of compression pressure was studied experimentally and was modeled by a first order law. It allows us to anticipate the loss of viability of a strain depending on the formulation and compression conditions. Furthermore, the genetic profile and the profile of gene expression have not been changed due to the compression step. We also noticed that the inhibition properties of the pathogen C. albicans growth and acid resistance of the strain are maintained. Resistance to gastric pH is also enhanced by a phenomenon of mechanical protection against the environment.According to the data of stability under ICH conditions, the viability of the compressed Lcr35® strain is not affected by the compression. Stability data have therefore been modeled by the Arrhenius equation to obtain a reliable model for predicting the stability data from accelerated conditions (40°C). In a QbD approach to pharmaceutical development, these data serve as a basis of comparison for the characterization of developing formulations where parameters such as the culture environment, the drying method, the strain or the galenic form can be changed. This global characterization of Lcr35® strain after compression has set aside the negative a priori against the compression of bacteria. This work helped to understand, characterize and model aspects linked to probiotics compression. They are an essential prerequisite for the development of a new probiotic product in the form of a tablet. Following a further development step, they also helped to lead to the first product in the tablet form, marketed by the company Probionov : Gynophilus® LP (vaginal administration). These compression data considerably broaden the field of development of probiotics. Indeed, this form is a considerable advantage in terms of stability but more importantly, the tablet form involves many development opportunities: gastro-Resistant, effervescent, multi-Layered tablets, etc. Through this technology, a more targeted administration of the strain such as up to the colon may be considered to maximize the therapeutic benefit of the probiotic strains. The ultimate goal is to be able to decrease the dosage of treatment while improving observance of the treatment and the patient comfort
Picard, Mathieu. "Dynamique des gaz et combustion du Rim-Rotor Rotary Ramjet Engine (R4E)". Mémoire, Université de Sherbrooke, 2011. http://savoirs.usherbrooke.ca/handle/11143/1607.
Pełny tekst źródłaAzzouz, Kamel. "Etude d'un système frigorifique domestique à haute inertie thermique avec matériau à changement de phase". Paris 6, 2008. http://www.theses.fr/2008PA066007.
Pełny tekst źródła