Teses / dissertações sobre o tema "Approche à interface diffuse"
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Ait-Ali, Takfarines. "Modélisation de la cavitation par une approche à interface diffuse avec prise en compte de la tension de surface". Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0024/document.
Texto completo da fonteCavitation is the transformation of a liquid into vapor which is caused by a pressure drop below the vapor saturation pressure. This phenomenon usually occurs in turbine engines that interact with liquids like: hydraulic pumps, injectors, inductors or boat propellers. View its negative effects: noise, vibrations, damage to the metal and decreased performance, it should be included in the design of turbomachinery The main objective of this thesis is to model this phenomenon so as to reproduce the nucleation, convection and the implosion of cavitation bubbles. We rely on a diffuse interface model (the homogeneous equilibrium model) on which we graft a surface tension model based on compressible Navier Stokes & Korteweg equations. We study the influence of surface tension on the bubble collapse. We used a finite volume approach whose spatial discretization is made by moving least squared method. Coupled with a Riemann solver called SLAU, the numerical model can go further difficulties related to the nature of the cavitation phenomenon which is mainly the strong gradients that remain through the liquid-vapor interface. Another issue addressed in this thesis is the determination of a numerical capillary coefficient which corresponds to a real surface tension in function of the thickness of the artificially extended interface for a given mesh
Diedhiou, Moussa Mory. "Approche mixte interface nette-diffuse pour les problèmes d'intrusion saline en sous-sol : modélisation, analyse mathématique et illustrations numériques". Thesis, La Rochelle, 2015. http://www.theses.fr/2015LAROS023/document.
Texto completo da fonteThe context of the subject is the management of aquifers, in especially the control of their operations and their possible pollution. A critical case is the saltwater intrusion problem in costal aquifers. The goal is to obtain efficient and accurate models to simulate the displacement of fresh and salt water fronts in coastal aquifer for the optimal exploitation of groundwater. More generally, the work applies for miscible and stratified displacements in slightly deformable porous media. In this work we propose an original model mixing abrupt interfaces/diffuse interfaces approaches. The advantage is to adopt the (numerical) simplicity of a sharp interface approach, and to take into account the existence of diffuse interfaces. The model is based on the conservation laws written in the saltwater zone and in the freshwater zone, these two free boundary problems being coupled through an intermediate phase field model. An upscaling procedure let us reduce the problem to a two-dimensional setting. The theoretical analysis of the new model is performed. We also present numerical simulations comparing our 2D model with the classical 3D model for miscible displacement in a confined aquifer. Physical predictions from our new model are also given for an unconfined setting
Kirov, Nikolay. "Simulation numérique de l’écoulement air-huile dans une enceinte moteur". Electronic Thesis or Diss., Toulouse, ISAE, 2024. http://www.theses.fr/2024ESAE0015.
Texto completo da fonteThe current trend towards more powerful and fuel-efficient aircraft engines produces the need for bearings, capable of transferring higher mechanical loads between rotating and stationary machine components, at extreme temperatures and higher engine speeds. The bearings demand lubrication oil at all times in order to reduce friction, dissipate heat, drive tiny debris away and therefore ensure the mechanical integrity of the engine.The resulting oil mass flow rates within the engine are significant and thus the lubricant must be continuously recycled via an oil recirculation system. As a result, the bearings are encompassed within oil sumps, consisting of chambers, seals and the bearings themselves. The bearing chambers are essentially sealed chambers adjacent to, or sometimes enclosing the bearings, whereby the ejected oil is channeled into after lubrication. They are typically sealed with pressurised air on the opposite side, which is passed through a labyrinth seal in order to provide flow obstruction. Typically, a vent port opening is included on the top for the air to escape, and a scavenge port opening is located near the bottom to lead the oil to the oil scavenge pumps back to the reservoir.While still contained within the bearing chamber, the oil and the air form a complex two-phase flow, whereby centrifugal effects, aerodynamic shear and gravity forces cause the majority of the oil to disperse within the bearing chamber and accumulate as film on its outer stationary walls. Heat transfer from these walls to the pre-cooled oil takes place, therefore giving it an important secondary function - to absorb some of the heat and therefore cool the bearing chamber enclosure. It is important, however, that the oil from the bearings is collected and returned to the reservoir before reaching temperatures that are too high, in order to avoid coking or even worse - ignition, that can start a fire within the bearing chamber. The complex two-phase flow physics lead to an optimisation problem which can only be tackled via numerical simulations.To date, a considerable amount of uncertainty remains concerning the most optimal computational modelling practice for the accurate, reliable and cost-efficient simulation of bearing chambers across different operating conditions. The objective of this thesis, is therefore to test several computational modelling approaches for the simulation of a simplified bearing chamber test rig, hereby named ELUBSYS, for which some experimental measurements are available that can be used to provide means of validation of the said approaches. These are, namely, an interfacial multi-fluid diffuse-interface approach, an Eulerian Integral Thin Film (EITF) approach, a two-way coupled Discrete Parcel Method approach, and, lastly, an EITF-DPM coupled approach. During all of these investigations, new knowledge has been gained for the flow field characteristics, influencing parameters and overall predictory performance, as compared to the experimental data for two bearing chamber configurations under a variety of oil mass flow rates and shaft rotational speeds.The cost-efficient coupled EITF-DPM methodology proposed within this thesis was found to obtain good accuracy for the film thickness distribution measurements for a variety of operating conditions
Cordesse, Pierre. "Contribution to the study of combustion instabilities in cryotechnic rocket engines : coupling diffuse interface models with kinetic-based moment methods for primary atomization simulations". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASC016.
Texto completo da fonteGatekeepers to the open space, launchers are subject to intense and competitive enhancements, through experimental and numerical test campaigns. Predictive numerical simulations have become mandatory to increase our understanding of the physics. Adjustable, they provide early-stage optimization processes, in particular of the combustion chamber, to guaranty safety and maximize efficiency. One of the major physical phenomenon involved in the combustion of the fuel and oxidizer is the jet atomization, which pilotes both the droplet distributions and the potential high-frequency instabilities in subcritical conditions. It encompasses a large sprectrum of two-phase flow topologies, from separated phases to disperse phase, with a mixed region where the small scale physics and topology of the flow are very complex. Reduced-order models are good candidates to perform predictive but low CPU demanding simulations on industrial configurations but have only been able so far to capture large scale dynamics and have to be coupled to disperse phase models through adjustable and weakly reliable parameters in order to predict spray formation. Improving the hierarchy of reduced order models in order to better describe both the mixed region and the disperse region requires a series of building blocks at the heart of the present work and give on to complex problems in the mathematical analysis and physical modelling of these systems of PDE as well as their numerical discretization and implementation in CFD codes for industrial uses. Thanks to the extension of the theory on supplementary conservative equations to system of non-conservation laws and the formalism of the multi-fluid thermodynamics accounting for non-ideal effects, we give some new leads to define a strictly convex mixture entropy consistent with the system of equations and the pressure laws, which would allow to recover the entropic symmetrization of two-phase flow models, prove their hyperbolicity and obtain generalized source terms. Furthermore, we have departed from a geometric approach of the interface and proposed a multi-scale rendering of the interface to describe multi-fluid flow with complex interface dynamics. The Stationary Action Principle has returned a single velocity two-phase flow model coupling large and small scales of the flow. We then have developed a splitting strategy based on a Finite Volume discretization and have implemented the new model in the industrial CFD software CEDRE of ONERA to proceed to a numerical verification. Finally, we have constituted and investigated a first building block of a hierarchy of test-cases designed to be amenable to DNS while close enough to industrial configurations in order to assess the simulation results of the new model but also to any up-coming models
Villanueva, Walter. "Diffuse-Interface Simulations of Capillary Phenomena". Doctoral thesis, Stockholm : Kungl. tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4402.
Texto completo da fonteSchaubeck, Stefan [Verfasser], e Helmut [Akademischer Betreuer] Abels. "Sharp interface limits for diffuse interface models / Stefan Schaubeck. Betreuer: Helmut Abels". Regensburg : Universitätsbibliothek Regensburg, 2013. http://d-nb.info/1047236966/34.
Texto completo da fonteMarth, Wieland. "Hydrodynamic Diffuse Interface Models for Cell Morphology and Motility". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-204651.
Texto completo da fonteDiese Dissertation beschäftigt sich mit mathematischen Modellen zur Beschreibung von Gleichgewichts- und dynamischen Zuständen von verallgemeinerten biologischen Zellen. Die Zellen werden dabei als thermodynamisches System aufgefasst, bei dem Strömungseffekte innerhalb und außerhalb der Zelle zusammen mit einem Helfrich-Modell für Zellmembranen kombiniert werden. Schließlich werden durch einen Energie-Variations-Ansatz die Evolutionsgleichungen für die Zelle hergeleitet. Es ergeben sie dabei Mehrphasen-Systeme, die Strömungseffekte mit einem freien Randwertproblem, das zusätzlich physikalischen Einflüssen wie Biegung und Oberflächenspannung unterliegt, vereinen. Um solche Probleme effizient zu lösen, wird in dieser Arbeit die Diffuse-Interface-Methode verwendet. Ein Vorteil dieser Methode ist, dass es sehr einfach möglich ist, Modelle, die verschiedenste Prozesse beschreiben, miteinander zu vereinen. Dies erlaubt es, komplexe biologische Phänomene, wie zum Beispiel Zellmotilität oder auch die kollektive Bewegung von Zellen, zu beschreiben. In den Modellen für Zellmotilität wird ein biologisches Netzwerk-Modell für GTPasen oder auch ein Active-Polar-Gel-Modell, das die Aktinfilamente im Inneren der Zellen als Flüssigkristall auffasst, mit dem Multi-Phasen-Modell kombiniert. Beide Modelle erlauben es, komplexe Vorgänge bei der selbst hervorgerufenen Bewegung von Zellen, wie das Vorantreiben der Zellmembran durch Aktinpolymerisierung oder auch die Kontraktionsbewegung des Zellkörpers durch kontraktile Spannungen innerhalb des Zytoskelets der Zelle, zu verstehen. Weiterhin ist die kollektive Bewegung von vielen Zellen von großem Interesse, da sich hier viele nichtlineare Phänomene zeigen. Um das Diffuse-Interface-Modell für eine Zelle auf die Beschreibung mehrerer Zellen zu übertragen, werden mehrere Phasenfelder eingeführt, die die Zellen jeweils kennzeichnen. Schließlich werden die Zellen durch ein lokales Abstoßungspotential gekoppelt. Das Modell wird angewendet, um White blood cell margination, das die Annäherung von Leukozyten an die Blutgefäßwand bezeichnet, zu verstehen. Dieser Prozess wird dabei bestimmt durch den komplexen Zusammenhang zwischen Kollisionen, den jeweiligen mechanischen Eigenschaften der Zellen, sowie deren Auftriebskraft innerhalb der Adern. Die Simulationen zeigen, dass diese Annäherung sich in bestimmten Gebieten des kardiovaskulären Systems stark vermindert, in denen die Blutströmung das Stokes-Regime verlässt. Schließlich wird das Active-Polar-Gel-Modell mit dem Modell für die kollektive Bewegung vom Zellen kombiniert. Dies macht es möglich, die kollektive Bewegung der Zellen und den Einfluss von Hydrodynamik auf diese Bewegung zu untersuchen. Es zeigt sich dabei, dass der Zustand der kollektiven gerichteten Bewegung sich spontan aus der Neuausrichtung der jeweiligen Zellen durch inelastische Kollisionen ergibt. Obwohl die Hydrodynamik einen großen Einfluss auf solche Systeme hat, deuten die Simulationen nicht daraufhin, dass Hydrodynamik die kollektive Bewegung vollständig unterdrückt. Weiterhin wird in dieser Arbeit gezeigt, wie die stark gekoppelten Systeme numerisch gelöst werden können mit Hilfe der Finiten-Elemente-Methode und wie die Effizienz der Methode gesteigert werden kann durch die Anwendung von Operator-Splitting-Techniken und Problemparallelisierung mittels OPENMP
Dunbar, Oliver. "A diffuse interface model of surfactants in multi-phase flow". Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/99133/.
Texto completo da fonteLam, Kei Fong. "Diffuse interface models of soluble surfactants in two-phase fluid flows". Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/62686/.
Texto completo da fonteAland, Sebastian, Sabine Egerer, John Lowengrub e Axel Voigt. "Diffuse interface models of locally inextensible vesicles in a viscous fluid". Elsevier, 2014. https://htw-dresden.qucosa.de/id/qucosa%3A32307.
Texto completo da fonteMoser, Maximilian Jörg Josef [Verfasser], e Helmut [Akademischer Betreuer] Abels. "Sharp Interface Limits for Diffuse Interface Models with Contact Angle / Maximilian Jörg Josef Moser ; Betreuer: Helmut Abels". Regensburg : Universitätsbibliothek Regensburg, 2021. http://d-nb.info/1225935733/34.
Texto completo da fonteMehrabian, Hadi. "Simulation of selected interfacial dynamic problems using Cahn-Hilliard diffuse-interface method". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46267.
Texto completo da fonteŘehoř, Martin [Verfasser], e Peter [Akademischer Betreuer] Bastian. "Diffuse interface models in theory of interacting continua / Martin Řehoř ; Betreuer: Peter Bastian". Heidelberg : Universitätsbibliothek Heidelberg, 2018. http://d-nb.info/1177149982/34.
Texto completo da fonteMohaghegh, Fazlolah. "A parallelized diffuse interface solver with applications to meso scale simulation of suspensions". Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5971.
Texto completo da fonteZhou, Chunfeng. "Simulations of interfacial dynamics of complex fluids using diffuse interface method with adaptive meshing". Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/1062.
Texto completo da fonteAhmad, Noor Atinah. "Phase-field model of rapid solidification of a binary alloy". Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242477.
Texto completo da fontePelletier, Milan. "Diffuse interface models and adapted numerical schemes for the simulation of subcritical to supercritical flows". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC059/document.
Texto completo da fonteIn various industrial combustion devices, such as liquid rocket engines at ignition or Diesel engines during the compression stage, the operating point varies over a wide range of pressures. These pressure variations can lead to a change of thermodynamic regime when the critical pressure is exceeded, switching from two-phase injection to transcritical injection. This change modifies the topology of the flow and the mixing, thereby impacting the flame dynamics. The objective of the present Ph.D thesis is to develop an original methodology able to address both subcritical and supercritical flows within the same solver. To achieve this, an extension of the real gas solver AVBP-RG to subcritical two-phase flows is provided, based on diffuse interface models. The required developments for the integration of such models into the finite-element framework of the solver are provided. Multidimensional numerical simulations are led in order to confront the model with experimental data, with which good agreement is observed. These results offer encouraging perspectives regarding further enhancements of the model and applications to complex industrial cases
Kahle, Christian [Verfasser], e Michael [Akademischer Betreuer] Hinze. "Simulation and Control of Two-Phase Flow Using Diffuse Interface Models / Christian Kahle. Betreuer: Michael Hinze". Hamburg : Staats- und Universitätsbibliothek Hamburg, 2015. http://d-nb.info/1065805586/34.
Texto completo da fonteKahle, Christian Verfasser], e Michael [Akademischer Betreuer] [Hinze. "Simulation and Control of Two-Phase Flow Using Diffuse Interface Models / Christian Kahle. Betreuer: Michael Hinze". Hamburg : Staats- und Universitätsbibliothek Hamburg, 2015. http://nbn-resolving.de/urn:nbn:de:gbv:18-71295.
Texto completo da fonteDussault, David (David Michael) 1975. "A diffuse interface model of transport limited electrochemistry in two-phase fluid systems with application to steelmaking". Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/89341.
Texto completo da fonteGouin-Vallerand, Charles. "Une approche autonome pour la gestion logicielle des espaces intelligents". Phd thesis, Institut National des Télécommunications, 2011. http://tel.archives-ouvertes.fr/tel-00681885.
Texto completo da fonteBurley, Adam Craig. "Toward a Fundamental Understanding of Bubble Nucleation in Polymer Foaming". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338220471.
Texto completo da fonteKlingbeil, Fabian [Verfasser], e Günther [Akademischer Betreuer] Grün. "On the numerics of diffuse-interface models for two-phase flow with species transport / Fabian Klingbeil. Gutachter: Günther Grün". Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2014. http://d-nb.info/1075477581/34.
Texto completo da fonteWeber, Josef Thomas [Verfasser], e Helmut [Akademischer Betreuer] Abels. "Analysis of diffuse interface models for two-phase flows with and without surfactants / Josef Thomas Weber. Betreuer: Helmut Abels". Regensburg : Universitätsbibliothek Regensburg, 2016. http://d-nb.info/1111883769/34.
Texto completo da fontePuszka, Agathe. "Tomographie optique diffuse : une approche résolue en temps pour les mesures en réflectance à courtes distances entre sources et détecteurs". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENY051/document.
Texto completo da fonteDiffuse optical tomography (DOT) is an emerging medical imaging technique using near-infrared light to probe biological tissues. This technique can retrieve three-dimensional maps of absorption and scattering coefficients inside organs from non-invasive measurements. With a multispectral approach, the spatial distribution of endogenous chromophores (hemoglobin, water) can even be obtained. For some clinical applications, it is desirable to carry out the measurements for DOT with a compact probe including all sources and detectors. However, the depth sensitivity is a real challenge in this configuration. We propose to tackle this challenge by using time-resolved measurements. A time-resolved approach is developed to perform DOT with reflectance measurements at short source-detector separation. This approach involves methodological aspects including the processing of time-resolved signals by DOT algorithms based on the Mellin-Laplace transform. Then, this approach consists in optimizing the detection chain on two aspects for enhancing the detection and localization of absorption contrast in depth in diffusive media. First, the impact of the temporal response of the detector is studied with commercially available single-photon detectors (classical and hybrid photomultipliers). Second, the enhancements in probed depth permitted with fast-gated single-photon avalanche diodes are explored in a joint work with the Politecnico di Milano. To finish, a study is carried out to illustrate the performance of the proposed approach with respect to spatial resolution in depth for different configurations of sources and detectors in the optical probe. Probes with a width limited to a few centimeters open the gate to multiple clinical interests. They could access intern organs like the prostate or facilitate the measurements on extern organs like the breast or the brain
Gaillard, Pierre. "Interfaces diffuses et flammes transcritiques LOX/H2". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066510/document.
Texto completo da fonteIn cryogenic engines, the propellants are refrigerated and stored liquid in order to limit the dimension of the tanks. They are pressurized by turbopumps before their injection in the combustion chamber. To increase the efficiency of the engines, the chamber pressure is increased and can be above the critical pressure of the propellants. This combustion regime is called transcritical. It exhibits some properties of diphasic injection with a high density core jet but does not have a phenomenon of atomization. The study of the oxygen transition from dense to light has been the main objectives of this thesis. In supercritical regime, the width of this transition decreases with the pressure till it reaches the critical pressure where it becomes infinitely thin. The lack of discretization in the zone of strong gradients leads to numerical instabilities. This situation is analog from a numerical point of view to a liquid-vapor interface. Thus, in this thesis we have extented the diffuse interface methods to the supercritical regime. The second gradient method introduced by van der Waals has allowed the simulation of subcritical and supercritical flames. The multifluid approach has been implemented in the solver CEDRE for the computation of a large eddy simulation of the experimental bench MASCOTTE in supercritcal conditions
LOYON, JEAN-FRANCOIS. "La lissencephalie isolee classique : approche histopathogenique et vision actuelle d'une dysplasie corticale diffuse rare a partir de deux cas". Dijon, 1994. http://www.theses.fr/1994DIJOM009.
Texto completo da fonteBagnoli, Annalisa. "Diffuse interface models for tumour growth within a non-isothermal Cahn-Hilliard theory for phase separation: thermodynamics, chemotaxis and stability". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14120/.
Texto completo da fonteMarth, Wieland [Verfasser], Axel [Akademischer Betreuer] [Gutachter] Voigt e James J. [Gutachter] Feng. "Hydrodynamic Diffuse Interface Models for Cell Morphology and Motility / Wieland Marth. Betreuer: Axel Voigt. Gutachter: Axel Voigt ; James J. Feng". Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://d-nb.info/1105876799/34.
Texto completo da fonteCardon, Clément. "Modélisation de la diffusion multi-composants dans un bain de corium diphasique oxyde-métal par une méthode d'interface diffuse". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX096/document.
Texto completo da fonteThis Ph.D. topic is focused on the modelling of stratification kinetics for an oxide-metal corium pool (U-O-Zr-steel system) in terms of multicomponent and multiphase diffusion. This work is part of a larger research effort for the development of a detailed corium pool modelling based on a CFD approach (“Computational Fluid Dynamics”) for thermal-hydraulics. The overall goal is to improve the understanding of the involved phenomena and obtain closure laws for integral macroscopic models.The phase-field method coupled with an energy functional using the CALPHAD method appears to be relevant for this purpose.In a first part, this works has been focused on the U-O binary system. We have developed a diffuse interface model (based on a Cahn-Hilliard equation) in order to describe the diffusion process in this system. This model has been coupled with a CALPHAD thermodynamic database and its parameterization has been developed with, in particular, an upscaling procedure related to the interface thickness.Then, within the framework of a modelling for the U-O-Zr ternary system, we have proposed a generalization of the diffuse interface model through an assumption of local equilibrium for redox mechanisms. A particular attention was paid to the model analysis by 1D numerical simulations with a special focus on the steady state composition profiles.Finally we have applied this model to the U-O-Zr-Fe system. For that purpose, we have considered a configuration close to small-scale experimental tests dedicated to the study of oxide-metal corium pool stratification
Gouin-Vallerand, Charles. "Une approche autonome pour la gestion logicielle des espaces intelligents". Electronic Thesis or Diss., Evry, Institut national des télécommunications, 2011. http://www.theses.fr/2011TELE0016.
Texto completo da fonteSince two decades, the developments in the information technologies have changed the computer science paradigms. The arrival of new approaches such as the pervasive computing create new technologies, which improved the quality of the interactions with the I.T. systems, However, the broad utilization of the pervasive computing and the development of smart spaces are facing several challenges. The large number of hardware and software components and their heterogeneous natures, contributes to the complexity of deploying and managing these environments, resulting in high costs. This thesis contributes to the software management of the smart spaces by reducing the complexity of the management tasks. Our proposal consists of an autonomic approach to software management based on the autonomic pervasive computing. As part of this work, we propose a solution using the environment’s contextual information to determine the software distribution among the environment’s devices, which best fits the needs of the software, environments and the interaction modalities and preferences of the environment’s users. The proposed solution was implemented and evaluated using a series of tests and software organization scenarios
Maison, Philippe. "Un modèle hydrologique de suivi de la pollution diffuse en bassin versant : approche mécaniste simplifiée de la zone non saturée". Toulouse, INPT, 2000. http://www.theses.fr/2000INPT009H.
Texto completo da fonteDompoint, Déborah. "Etude de la transition 3C-6H au sein de monocristaux de 3C-SiC : approche par diffusion diffuse des rayons X". Limoges, 2012. https://aurore.unilim.fr/theses/nxfile/default/cf59fed3-d819-4786-845a-7d226069ad8a/blobholder:0/2012LIMO4035.pdf.
Texto completo da fonteThis work deals with the study of the 3C-6H polytypic transition in 3C-SiC single crystals. We used high-resolution X-ray diffraction and reciprocal space mapping. The analysis of the diffuse scattering intensity distribution along selected directions, for single crystals annealed in various conditions, allows to obtain qualitative and quantitative informations regarding the transition. Firstly, we used an analytical approach to study the transition. The simulation of the diffuse scattering with two analytical models allow to determine the transformation mechanism which has been further confirmed by complementary TEM (Transmission electron microscopy) observations. The transition kinetics obtained allow to conclude that the transition involves two different mechanisms. Secondly, a Monte-Carlo approach has been used so as to overcome the limitations of the analytical study. The simulation of the experimental diffraction profiles for different configurations allow us to conclude that the transition involves the ordering of double and triple stacking faults. Finally, the stacking faults organization has been rationalized by energy calculations of crystals within an ANNNI interaction scheme
Anoun, Houda. "Approche logique des grammaires pour les langues naturelles". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2007. http://tel.archives-ouvertes.fr/tel-00414778.
Texto completo da fonteJacquot, Francis. "Contributions expérimentale et théorique à une nouvelle approche de la mouillabilité". Vandoeuvre-les-Nancy, INPL, 1998. http://www.theses.fr/1998INPL056N.
Texto completo da fonteSaeedi, Navid. "Une approche très efficace pour l'analyse du délaminage des plaques stratifiées infiniment longues". Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST1160/document.
Texto completo da fonteThe analysis of local phenomena such as free-edge effects and delamination in multilayered structures requires the accurate theories which can provide a good description of the local response. Since the three-dimensional approaches are generally very expensive in computational time and memory, the layerwise two-dimensional approaches are widely used. In this Ph.D. thesis, a stress layerwise model, called LS1, is applied to the multi-delamination problem in longitudinally invariant multilayered plates. The invariance in the longitudinal direction allows us to solve the problem analytically. At first, we propose an analytical method for the analysis of multi-delaminated multilayered plates subjected to the uniaxial traction. The free-edge interlaminaire stress singularities and the mode III delamination onset are investigated. A refined model, called Refined LS1, is proposed in order to improve the approximations in singularity zones such as free edges and crack tips. The results of the refined model are validated by comparing them with those obtained by a three-dimensional finite element model. Afterwards, the proposed analytical approach is extended to the cylindrical bending of the multilayered plates. The propagation of delamination in modes I and II is studied and the approximations of the LS1 model are validated. At last, we generalize the proposed analytical method to take into account all invariant loads in the longitudinal direction. The final approach allows us to analyze the rectangular multilayered plates subjected to invariant loads on the top and bottom surfaces, imposed displacements or forces at the lateral edges, and also four types of loading at the longitudinal ends: uniaxial traction, out-of-plane bending, torsion and in-plane bending. The analytical solution of the LS1 model is obtained for a laminated plate subjected to all the loads mentioned above. The approach is validated by comparison with the three-dimensional finite element method for various types of loading
Benhalima, Djamel-Eddine. "Contribution à la conception d'un système d'analyse expérimentale SICOPE fondée sur une approche orientée-objet : Application à la communication graphique". Valenciennes, 1995. https://ged.uphf.fr/nuxeo/site/esupversions/3eea74bf-26cc-473d-9ec6-11405b54fb6c.
Texto completo da fonteAptel, Jean-Denis. "Cinetiques d'adsorption des proteines a une interface solide/liquide : mise au point d'une nouvelle approche experimentale". Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13069.
Texto completo da fonteAptel, Jean-Denis. "Cinétiques d'adsorption des protéines à une interface solide/liquide mise au point d'une nouvelle approche expérimentale /". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37602280w.
Texto completo da fonteQuiviger, Audrey. "Ultrasons diffus pour la caractérisation d'une fissure dans le béton. : approche linéaire et non linéaire". Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4067/document.
Texto completo da fonteThe various processes of deterioration of the building structures lead to a micro and macro-cracking of the concrete. Consequently, the mechanical properties of the structure are reduced and, eventually, the building is no longer airtight. It is therefore necessary to supply information regarding the presence and size of cracks to carry out the necessary repairs and keep the integrity of the structure. First, the control of concrete as well as the morphology of the actual crack are presented. The notion of contacts between its lips is introduced to define the problem of its characterization. The bibliography shows that the standard acoustic methods are not adapted for characterizing of a crack in concrete. Two tracks are then identified: the diffuse ultrasound and the nonlinear acoustics. Subsequently, we present the characterization of the crack by analyzing the transport of the energy with a diffusion equation. The associated parameters (diffusivity and dissipation) are experimentally determined on test tubes cracked at different depths. We introduce and define the arrival time of the maximum energy (ATME), which turns out to be the most sensitive parameter to the open part of a crack. Its evolution with regard to the measurement uncertainties does not allow a full characterization of the closed part. A digital modeling in finite differences is performed. It highlights the role of the contacts within the closed part of the crack and confirms the experimental observations. Then, we present the nonlinear acoustics and the associated methods applied to concrete
Ammar, Kais. "Modélisation et simulation du couplage changement de phases-mécanique par la méthode des champs de phases". Phd thesis, École Nationale Supérieure des Mines de Paris, 2010. http://tel.archives-ouvertes.fr/tel-00508677.
Texto completo da fonteBensah, Yaw D. "Interfacial Solid-Liquid Diffuseness and Instability by the Maximum Entropy Production Rate (MEPR) Postulate". University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439310971.
Texto completo da fonteTrontin, Pierre. "Développement d'une approche de type LES pour la simulation d'écoulements diphasiques avec interface : application à l'atomisation primaire". Phd thesis, Ecole nationale superieure de l'aeronautique et de l'espace, 2009. http://tel.archives-ouvertes.fr/tel-00499373.
Texto completo da fonteMunteanu, Dana. "Une approche hypertexte pour la formation en automatique : activités guidées et explication". Grenoble INPG, 1998. http://www.theses.fr/1998INPG0064.
Texto completo da fonteQuint, Vincent. "Une approche de l'édition structurée des documents". Phd thesis, Grenoble 1, 1987. http://tel.archives-ouvertes.fr/tel-00010612.
Texto completo da fontel'organisation logique des composants du document. A partir de ce principe, on propose un méta-modèle
qui permet la description des structures logiques de toutes sortes de documents et de différents types
d'objets fréquents dans les documents : formules mathématiques, tableaux, schémas, etc... on associe aux
structures logiques des règles de présentation qui déterminent l'aspect graphique de leurs composants.
On montre l'intérêt de cette approche en présentant deux systèmes interactifs construits sur ce modèle :
l'éditeur de formules mathématiques Edimath et l'éditeur de documents Grif. La présentation de ces systèmes
s'appuie sur un état de l'art de la typographie informatique.
Bacha, Firas. "Une approche MDA pour l'intégration de la personnalisation du contenu dans la conception et la génération des applications interactives". Phd thesis, Université de Valenciennes et du Hainaut-Cambresis, 2013. http://tel.archives-ouvertes.fr/tel-00874766.
Texto completo da fonteGacias, Bernat. "Une approche interdisciplinaire pour l'ordonnancement des transports". Phd thesis, Université Paul Sabatier - Toulouse III, 2010. http://tel.archives-ouvertes.fr/tel-00554205.
Texto completo da fonteDelwaulle, Céline. "Etude de la dissolution du dioxyde d’uranium en milieu nitrique : une nouvelle approche visant à la compréhension des mécanismes interfaciaux". Thesis, Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL078N/document.
Texto completo da fonteThe reprocessing of irradiated nuclear fuel passes through a stage of separation of uranium, plutonium and fission products by dissolution in nitric acid. To be able to optimize the process regardless of the fuel used, it is necessary to understand physical and chemical phenomena, kinetics and hydrodynamic parameters involved in the process, to allow its modelling and to be able to forecast behaviours during the operation. The state of the art can only provide limited guidance because it is based on macroscopic studies in reactors of hundreds of millilitres. The conclusions that can be drawn are therefore subject to the overlay of microscopic phenomena related to the complexity of the nitric mid, and to the composition and nature of the solid to dissolve that are generally poorly defined. It is therefore necessary to use another approach which is to separate and analyze the various processes involved. A model implementing a coupling between hydrodynamics and kinetics involved in the dissolution of a solid in the presence of autocatalytic species is then proposed. This model was used to highlight the need for observations of the concentrations of the species at the level of the reactive interface. A miniaturized reactor was designed, and experiments were conducted on copper beads, simulating the fuel, and provided initial observations of gas bubbles formed during dissolution. A novel method for monitoring pH in-situ at the level of the interface has been developed: a fluorescent marker enabled to visualize in-situ acidity and pH mapping during dissolution, and a direct visualization of the transfer process with diffusion layers. This method could be transposed in the nuclear area on uranium dioxide and has led to the understanding and modelling of the process of dissolution in nitric environment
Hérisson, Joan. "Représentation spatiale et exploration virtuelle des génomes : une approche globale pour l'analyse des éléments architecturaux des séquences". Paris 11, 2004. http://www.theses.fr/2004PA112147.
Texto completo da fonteDNA sequences are often represented by a succession of four nucleotides: A, C, G and T. Even if this representation allows to study the linguistics and syntax of DNA sequences, it remains textual, local and monodimensional and does not provide any visual, local nor spatial information. However, DNA is a three-dimensional structure forming a double helix which can bend and create long distance interactions. The aim of this thesis is to propose a new approach of the genomic sequences in order to enrich classic analyses with three-dimensonal criteria. The modelling of these 3D DNA sequences is based on a biophysical model of spatial conformation of DNA. Such a representation raises problematics both in computer science - concerning Virtual Reality for scene management, interaction, data representation and associated algorithms - and in Bioinformatics of genomes. These different aspects, which form the pluridisciplinary nature of this thesis, have been treated through the software program tool ADN-Viewer that I have developed. Two directions have been taken during this work and should endure after this thesis. The first one is to come close as much as possible to the DNA biological reality. Our work represents a very first step in this sense and has to be enriched by new criteria of spatial conformation and by the integration of biological partners of DNA. The second direction is to exploit the three-dimensional structure of DNA as a representation among others to explore, treat and analyze the biological content of sequences
Remigi, Alberto. "Modélisation numérique d'un injecteur aéromécanique : de l'écoulement interne au spray dispersé". Thesis, Normandie, 2021. http://www.theses.fr/2021NORMR012.
Texto completo da fonteThe more stringent regulation about aeronautical engines emission posed by ICAO requires always more predictive design tools. The droplets diameter distribution produced during the atomization process is a key parameter in order to predict the pollutant emission released during the combustion process. Thus the study of the atomization phenomenon with itsmulti-scale nature is a relevant and an important challenge. For this reason the objective of this work are: first to review the existent models in the literature to understand their key features in order to define a classification that gives guidelines on the modeling choices; second to apply industrial oriented approaches on an aeronautical configuration, in order to propose an improvement of the available design tools. A systematic classification of the models is done with respect to the length-scale considered to represent the interface characteristics. From this point of view, it is possible to distinguish two kinds of approaches: the separated phases representation and the mixed phases representation. The diffuse interface approaches belongs on the second category together with many other approaches, compressible and incompressible, that share the same characteristic: they considers a mixture that contains both phases. An air-assisted liquid sheet configuration has been built to test different models in order to define a metric of comparison. Two different models using the sharp interface approach (ARCHER and InterFoam ), two models using the diffuse interface approach (CEDRE and ELSA ) and an hybrid model (ICMelsa ) have been considered on this test case. A comparison on two parts, based on statistical quantities, has been proposed. A fist part called "classical study", compare the first order statistics showing that all approaches lead to very similar results, as soon as certain level of mesh resolution is achieved. At the contrary the second order statics present noticeable differences. These results motivate a second part called "phase analysis" to study the link between the small scale representation of the interface and the second-order statics. In particular, the phase marker variance and the associated segregation level are found to be sensible indicators of the interface description. A 1D signal analysis shows that they can be used to detect any departure from the separated phases representation.Then the importance of the phase indicator variance is demonstrated on other second-order statistics: Reynolds stress components and turbulent liquid flux. Thus, second-order statistics are partly described with direct mixed phases representations and require complementary model to be fully recovered. A first attempt, based on a linear approach, is proposed to model the level of segregation of mixed phases representation. It is based on the filtering of a fully segregated signal at a given scale. In a second part of this thesis, an industrial test case (a pressure swirling injector) proposed by SAFRAN Aircraft Engines is studied. Three industrial oriented models, among those studied in the first part, have been applied to simulate this injector flow (InterFoam , ELSA , ICMelsa). Their present numerical approaches are able to work with complex geometries, with a computational effort representative of the industrial current standards. The results of the three models (liquid film thickness, breakup length and Sauter Mean Diameter) have been compared with respect to the available experimental data. Eventually, a proposal to improve the ICMelsa model multi-scale have been successfully tested on the liquid sheet configuration and implemented to further improve the results of the SAFRAN Aircraft Engines industrial case. These results have shown that we are very close to predict the characteristics of a spray produced by a real aeronautical injection system
Le normative più rigorose sulle emissioni dei motori aeronautici poste dall’ICAO, richiedono strumenti di progettazione sempre più predittivi. La distribuzione dei diametri delle droplets prodotte durante il processo di atomizzazione è un parametro chiave per predire l’emissione di inquinanti rilasciati durante il processo di combustione. Lo studio del fenomeno di atomizzazione con la sua natura multi scala diventa una sfida rilevante. Per questo motivo, gli obiettivi di questo lavoro sono: in primo luogo una revisione dei modelli esistenti in letteratura per comprenderne le caratteristiche chiave al fine di definire una classificazione che dia delle linee guida sulle scelte di modellistica; in secondo luogo applicare approcci orientati all’industria ad una configurazione aeronautica, al fine di proporre un miglioramento degli strumenti di progettazione disponibili al giorno d’oggi. Nella prima parte del PhD proponiamo una classificazione sistematica dei modelli rispetto alla scala di lunghezza considerata per rappresentare l’interfaccia. Da questo punto di vista, è possibile distinguere due tipi di approccio: una rappresentazione a fasi separate e una rappresentazione delle fasi miste. Gli approcci a interfaccia diffusa appartengono alla seconda categoria insieme a molti altri approcci (che ricorrano ad un approccio comprimibile o incomprimibile) che condividono la stessa caratteristica: considerano una miscela che contiene entrambe le fasi. È stata realizzata una configurazione air-assisted liquid sheet per testare diversi modelli al fine di definire una metrica di confronto. In questo caso per i test sono stati considerati due diversi modelli che utilizzano l’approccio sharp interface (ARCHER e InterFoam ), due modelli che utilizzano l’approccio a interfaccia diffusa (CEDRE e ELSA ) e un modello ibrido (ICMelsa ). È stato proposto un confronto su due parti, basato su statistiche di diversa natura. Una prima parte chiamata "studio classico", confronta le statistiche del primo ordine, le quali mostrano che tutti gli approcci portano a risultati molto simili non appena viene raggiunto un certo livello di risoluzione della mesh. Al contrario, le statistiche di secondo ordine presentano notevoli differenze. Questi risultati motivano una seconda parte dello studio, chiamata "analisi di fase" sviluppata per studiare il legame tra le piccole scale dell’interfaccia e le statiche di secondo ordine. In particolare, la varianza del marker di fase e il livello di segregazione associato si trovano ad essere indicatori sensibili alla descrizione dell’interfaccia. Un’analisi di un segnale 1D mostra che questi due indicatori possono essere utilizzati per rilevare qualsiasi deviazione dalla rappresentazione a fasi separate. successivamente l’importanza della varianza del marker di fase è dimostrata su altre statistiche di secondo ordine: componenti del tensore degli sforzi di Reynolds e flusso liquido turbolento. Pertanto, le statistiche di secondo ordine che sono descritte con una rappresentazione a fasi miste richiedono un modello complementare per essere completamente recuperate. Un primo tentativo, basato su un approccio lineare, è proposto per modellare il livello di segregazione della rappresentazione a fasi miste. Si basa sul filtraggio di un segnale completamente separato su una data scala. In una seconda parte della tesi viene studiato un caso industriale (un iniettore di tipo swirling) proposto dall’azienda SAFRAN Aircraft Engines . Per simulare il flusso prodotto da questo iniettore sono stati applicati tre modelli (con un approccio industriale) tra quelli studiati nella prima parte (InterFoam , ELSA , ICMelsa )