Dissertationen zum Thema „Propagation de propriétés“
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Riou, Jean-Félix. „Etude des propriétés de propagation d'un laser à atomes“. Paris 11, 2006. https://pastel.archives-ouvertes.fr/tel-00138450.
Der volle Inhalt der QuelleThis thesis presents various experimental and theoretical aspects concerning a specific system of atom optics: the atom laser. In our experiment, this one results from a Bose-Einstein condensate of rubidium 87 and we thus initially detail the various cooling techniques used to obtain this coherent atomic source in a hybrid ferromagnetic trap. The atom lasers we produce are extracted from the condensed cloud by radiofrequency, and propagate vertically under the effect of gravity. One specificity of our setup lies in the strong magnetic confinement used, which results in non negligible collisional interactions between the laser and the condensed source. We show that this has an influence, not only on the atom laser coupling dynamics, but also on its propagation. We indeed observe a transverse structure containing caustics on the laser beam. By using methods initially developed for photonic optics (eikonal approximation, Fresnel-Kirchhoff integral, ABCD matrices), we calculate the atom laser wavefunction. Moreover, we characterize the matter wave propagation in the paraxial regime by using the beam quality factor M2. We finally report the realization of an atom laser, guided by a horizontal optical potential, which enables us to cancel the acceleration due to gravity in such way, that the De Broglie wavelength remains constant throughout propagation
Baste, Stéphane. „Propagation des ondes élastiques dans les composites carbone 3D“. Bordeaux 1, 1985. http://www.theses.fr/1985BOR10626.
Der volle Inhalt der QuelleMetayer, Cyrille. „Etude de la structuration de suspensions colloïdales sous l'effet d'un champ électrique ou magnétique“. Nice, 2004. http://www.theses.fr/2004NICE4106.
Der volle Inhalt der QuelleWe studied the structure obtained by application of an electric or a magnetic field on suspensions constituted of submicronic particles. This reversible aggregation results from the polarization of the particles and thus depends on contrast of the permittivity or permeability between the suspending liquid and the particles. The formed structure will depend on the value of l, the ratio between dipolar and thermal energies. If l is higher than one, the dipolar force dominates, the particles form fibrils parallel to the field. This change of structure results in an evolution of the angular distribution of the light scattered by the suspension. By means of these characteristics, it is possible to determine the distribution of sizes of the chains and the distance between particles inside chains simultaneously. By introducing a repulsive force, estimated from the evolution of the distance versus the electric field, we obtain a good agreement between the theoretical and experimental sizes at high frequency. On the other hand at low frequency, they differ from several orders of magnitude. The structures formation kinetic is experimentally slower than that predicted b theory. The other part of this thesis concerns the study of phase separation of a magnetorheological suspension (transition from chains to columns). The theoretical model where the distance between the particles is an adjustable parameter allows to predict accurately the critical values of the concentration and of the parameter l. However the shapes of the experimental and theoretical phase diagrams are rather different
Przybilla, Frédéric. „Aspects fondamentaux de la transmission exaltée de la lumière à travers des ouvertures sub-longueurs d'onde“. Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/public/theses_doctorat/2008/PRZYBILLA_Frederic_2008.pdf.
Der volle Inhalt der QuelleAbi, rizk Lara. „Ondes progressives et propriétés de propagation pour un problème d’épidémiologie évolutive non-local“. Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0244.
Der volle Inhalt der QuelleIn this thesis we study the existence of a travelling wave solutions for an integro-differential system of equations from evolutionary epidemiology. We use ideas from dynamical system ideas theory coupled with estimates of the asymptotic behaviour of profiles. We prove that the wave solutions have a rather simple structure. This analysis allows us to reduce the infinite dimensional travelling wave profile system of equations to a four dimensional ODE system. The latter is used to prove the existence of travelling wave solutions for any wave speed larger than a minimal wave speed c?, provided that the epidemic threshold R0, which is expressed as a function of the principal eigenvalue of a certain integral operator, is strictly greater than 1. This same threshold condition is also used to prove that any travelling wave connects two determined stationary states. In the second part, we study the propagation properties of the solutions for the same spatially distributed system of equations, when the initial density of infected plants is a compactly supported function with the space variable x. When R0 > 1, we prove that spreading occurs with a definite spreading speed that coincides with the minimal speed c? of the travelling wave solutions discussed in the first part. Moreover, the solution of the Cauchy problem asymptotically converges to some specific function for which the moving frame variable x and the phenotype one y are separated
Li, Xiang-Yu. „Propagation des ondes acoustiques dans les milieux hétérogènes“. Paris 6, 2010. http://www.theses.fr/2010PA066641.
Der volle Inhalt der QuelleMassaneda-Clares, Josep M. „Utilisation des techniques d'optique guidée pour les mesures d'indice et d'épaisseur de couches minces uniques ou prises dans un empilement“. Aix-Marseille 3, 1997. http://www.theses.fr/1997AIX30082.
Der volle Inhalt der QuelleDE, POLLIER CLAUDE. „Theorie de biot et prediction des proprietes acoustiques des materiaux poreux : propagation dans les milieux acoustiques desordonnes“. Le Mans, 1989. http://www.theses.fr/1989LEMA1001.
Der volle Inhalt der QuelleParenthoine, Denis. „Influence des propriétés de céramiques piezoélectriques sur des mesures ultrasonores non-linéaires“. Thesis, Tours, 2008. http://www.theses.fr/2008TOUR3111/document.
Der volle Inhalt der QuelleDuring the detection of nonlinear phenomena in solids, under the non-destructive evaluation by ultrasound, nonlinearities of piezoelectric ceramics might introduce parasitic effects that could disrupt the measurements. The objective here is to characterize the nonlinear properties of these ceramics and predict their influence on the propagation of ultrasonic waves. A method to characterize nonlinear properties based on the analysis of the generation of second harmonic on a piezoelectric resonator is developed here. It is shown that the analysis of the distortions for a wide range of excitation frequencies, allow to distinguish different sources of nonlinearity. Thereafter, the influence of an acoustic load on the nonlinear behaviour of vibration is studied. Finally, the previous results are used to predict the influence of non-linearity of piezoelectric ceramic on the propagation of acoustic waves in an environment outside
VOLIOTIS, VASSILIKI. „Etude des transitions optiques dans des puits quantiques et des super-reseaux gaas/alas en propagation guidee“. Paris 7, 1994. http://www.theses.fr/1994PA077106.
Der volle Inhalt der QuelleTa, Quang Anh. „Modélisation des propriétés mécaniques anisotropes aléatoires et impacts sur la propagation des ondes élastiques“. Phd thesis, Ecole Centrale Paris, 2011. http://tel.archives-ouvertes.fr/tel-00589052.
Der volle Inhalt der QuelleTa, Quang Anh. „Modélisation des propriétés mécaniques anisotropes aléatoires et impacts sur la propagation des ondes élastiques“. Electronic Thesis or Diss., Châtenay-Malabry, Ecole centrale de Paris, 2011. http://www.theses.fr/2011ECAP0006.
Der volle Inhalt der QuelleThe aim of this thesis is to take into account the heterogeneity, the anisotropy and the uncertainties within 3D numerical simulation of elastic waves propagation. Firstly, the elasticity tensor field is modeled by means of a stochastic tensor-valued field. Its construction is generalized from the model of Soize [2008]. Hence, our model preserves principle properties of the former : a small set of parameters controlling the whole dispersion and the characteristic size of spatial variability, a local behavior being a priori arbitrary anisotropic (triclinic anisotropy) andothers essential mathematical properties. Moreover, a new parameter is added in order to impose a desired anisotropy mean level. Secondly, we carry out adaptations of an existing spectral finite elements-based elastic waves simulation software, namely the SPEC3D parallel computing code. On the one hand a sample generator of the elasticity random field model is implemented and on the other hand anisotropic material behavior is introduced in the elastodynamic solver. Finally, numerical parametric studies are performed using SPEC3D highlighting influences of heterogeneity and anisotropy on elastic waves behavior. In particular, it is observed that the characteristic time beyond which a multiple scattering pattern can be approximated by a diffusion regime directly depends on the correlation length of elasticity tensor field model. This time is detected by an energy equipartition between rotational and irrotational movements
Johnson, Philippe. „Propagation des fissures en fatigue par chocs : développement d'une méthodologie et étude experimentale“. Vandoeuvre-les-Nancy, INPL, 1989. http://www.theses.fr/1989NAN10415.
Der volle Inhalt der QuelleLoukou, Kouassi. „Etude expérimentale des caractéristiques acoustiques et thermophysiques de bétons de terre stabilisée au ciment“. Lyon 1, 1994. http://www.theses.fr/1994LYO10069.
Der volle Inhalt der QuelleLiu, Xu. „Mesures de déflexion photothermique pour l'étude de la propagation guidée dans les couches minces : étude théorique et expérimentale de l'atténuation“. Aix-Marseille 3, 1990. http://www.theses.fr/1990AIX30024.
Der volle Inhalt der QuelleReungoat, David. „Analyse de la température à l'interface d'une garniture mécanique par mesure par thermographie infrarouge“. Poitiers, 1994. http://www.theses.fr/1994POIT2355.
Der volle Inhalt der QuellePrat, Jérome. „Mesure des propriétés optiques de milieux diffusants stratifiés par l'analyse de la rétrodiffusion d'impulsions infrarouges sub-picosecondes“. Paris 13, 2002. http://www.theses.fr/2002PA132012.
Der volle Inhalt der QuelleAhmiedi, El Hadj. „Etude de la propagation des fissures en milieu viscoélastique : applications aux enrobés bitumeux“. Limoges, 1994. http://www.theses.fr/1994LIMO0035.
Der volle Inhalt der QuelleIftimovici, Andrei. „Etude des propriétés de propagation pour des systèmes quantiques du type N-corps à noyaux durs“. Paris 7, 1994. http://www.theses.fr/1994PA077043.
Der volle Inhalt der QuelleMollenhauer, Ralf. „Etude de la propagation guidée dans les multicouches optiques : mesures d'atténuation et localisation des pertes dans l'empilement“. Aix-Marseille 3, 1994. http://www.theses.fr/1994AIX30013.
Der volle Inhalt der QuelleKamoun, Fathallah Ines. „Etude de quelques propriétés des équations aux dérivées partielles : propagation des singularités, identification du potentiel et stabilisation“. Versailles-St Quentin en Yvelines, 2009. http://www.theses.fr/2009VERS0036.
Der volle Inhalt der QuelleThis thesis consists of three parts. The purpose, of the first part, is to define a general geometry of the analytic wavefront set, in order to study the microlocal singularity of solutions to the Schrödinger equation with high power. In the second part, we study, in dimension n> or =3, the inverse problem of determining the potential q of the Schrödinger equation from infinity measurements on any open subset of the boundary. Provided that q is known in a neighborhood of the boundary, we prove the logarithmic stability estimate. The last part is devoted to the study of a coupled system consisting in a wave and heat equations coupled through transmission condition along a steady interface. This system is a linearized model for fluid-structure interaction introduced by Rauch, Zhang and Zuazua for a simple transmission condition and by Zhang and Zuazua for a natural transmission condition. Using an abstract Theorem of Burq and a new Carleman estimate shown near the interface, we complete the results obtained by Zhang and Zuazua and by Duyckaerts. We show, without any geometric restriction, a logarithmic decay result
Aït, Alaïwa Abdelghafour. „Etude des propriétés de transfert et de la propagation de coulis de ciment dans les milieux granulaires“. Nantes, 2007. http://www.theses.fr/2007NANT2145.
Der volle Inhalt der QuelleThis research work deals with the study of the cement grout transfer properties and the cement grout propagation in the injected soils. First, we develop an experimental device which is able to inject under water saturation conditions laboratory soil columns. We study the flow and the transport of these complex fluids in granular soils. This device allows highlighting particle filtration phenomenon which occurs in porous media. Then, we examine the influence of the main parameters (grout rheology, injection pressure, injection flow rate, injection distance, porosity, permeability) during the injection. Moreover, we add image processing techniques to this apparatus in order to characterize the hydrodynamic behaviour of the injected soil when the cement grout propagates in the soil samples. Then, we analyze the retained cement particles repartition using gammadensimetry. After the cast, we estimate the efficiency of the process by gas permeability measurements. We realize a micro structural analysis of these injected soils by means of SEM and MIP. Besides, we show a correlation between the permeability evolution and the modification of this porous medium due to injection process. We adapt the Katz-Thompson approach to estimate the permeability evolution using MIP tests. Finally, we improve the model initially developed in the laboratory adding another permeability equation of state which better considers the filtration phenomenon
Seetharamdoo, Divitha. „Étude des métamatériaux à indice de réfraction négatif : paramètres effectifs et applications antennaires potentielles“. Rennes 1, 2006. http://www.theses.fr/2006REN1S013.
Der volle Inhalt der QuelleKamara, Souleymane. „Étude des propriétés ferromagnétiques de structures à base de Ga1-xMnxAs dédiées à l'électronique de spin“. Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20217.
Der volle Inhalt der QuelleAt the same time semiconductor and ferromagnetic, the Ga1-xMnxAs offers interesting potentialities for spintronic. This double property is due to the exchange interaction between localized spin of Mn atoms and the spin charge carrier. The work presented in this thesis is centred on the magnetization control of these magnetic structures. A comparative and detailed experimental study of the magnetic anisotropy is carried out on two series of samples. An analysis method based on the free energy density study of the observed systems was also been developed to confront the results with theoretical predictions. The Hall effect and SQUID measurements on the structures with planar magnetization allowed us to bring to light two types of anisotropy: a cubic anisotropy for T < TC / 2 with a magnetization reversal by jumps of 90 ° and an uniaxial anisotropy for temperatures TC / 2 < T < TC with a reversal of magnetization in 180°. The structure with perpendicular magnetization present a magnetization switch at 180° for all temperatures T < TC. Consequently in these compounds, the magnetic anisotropy is strongly uniaxiale. Lastly this study deals the magnetic domains structures and the determination of domain wall propagation velocity. The results reveal an anisotropic domain wall propagation along crystallographic axes <110> with two distinct velocity regimes, including one strongly controlled by structural defects
Turatsinze, Anaclet. „Caractérisation microstructurale de la fissuration des bétons et mortiers en mode I de propagation“. Toulouse 3, 1992. http://www.theses.fr/1992TOU30185.
Der volle Inhalt der QuelleFasquel, Sophie. „Propriétés optiques de structures guidantes en cristal photonique“. Lille 1, 2005. https://ori-nuxeo.univ-lille1.fr/nuxeo/site/esupversions/e2f8fa6b-4758-4782-808c-b7155b110a74.
Der volle Inhalt der QuelleGaubert, Jean-François. „Applications thermodynamiques de la propagation d'ondes ultrasonores, sous pression élevée, dans des mélanges gazeux et liquides en relation avec les fluides d'origine pétrolière“. Pau, 1995. http://www.theses.fr/1995PAUU3018.
Der volle Inhalt der QuelleMassala, Gaston. „Propagation et propriétés électriques des streamers positifs à grande distance dans l'huile minérale sous très haute tension impulsionnelle“. Grenoble INPG, 1997. http://www.theses.fr/1997INPG0112.
Der volle Inhalt der QuelleThe aim of this work is to study the propagation of the "streamers" and their electrical properties in mineral oil at long distances under pulsed voltage (up to 480 kV) under various voltage conditions (from the minimum propagation voltage to the high overvoltages), inter-electrode distance (2. 5 to 35 cm), electrode geometry (plane-to-plane, semi-uniform, planar sphere) of solid insulators. This work makes a contribution on the characterization of the breakdown phenomena and the mechanisms involved in the positive streamers. For voltages below the breakdown voltage, stopping, transition to breakdown and conductivity of the streamers are described. In particular, it has been shown that the streamer is conductive only during a total re-ignition of its main branch. In the presence of overvoltages, the existence of an acceleration voltage correlated with the appearance of the fast streamers is highlighted. Three different propagation modes are identified and characterized: 2nd mode (2 to 4 km / s), 3rd mode (10 to 20 km / s) and 4th mode (> 100 km / s). A correlation between the shape, speed and load of the streamers was highlighted and the voltage drop in the streamer was determined. Calculations of the charge and field on the plane electrode carried out by the Load Simulation Method (CSM), considering different macroscopic models in the presence of a voltage drop, have led to the conclusion that the streamers are comparable to objects conductors of simple shape (cylinder or sphere). A qualitative correlation between the macroscopic field at the end of the streamers calculated by CSM, and the speed was obtained. E there exists a critical field = 400 kV / cm, beyond which the streamers are always fast (> 10 km / s). This work proposes two complementary mechanisms allowing to explain the constancy of the speed of the positive streamers in the mineral oil: the effect of the voltage drop and / or the electrostatic effect due to the branching of the streamers. It has been shown that the overall shape of the streamers determines the field at their end and hence the propagation modes. This has been verified by studying the influence of electrode geometry (shielding effect), insulating solids (positional effect) and the nature of the liquid (additive effect)
Baume, Olivier. „Approche géostatistique de l'influence des paramètres physiques sur la propagation acoustique à grande distance“. Le Mans, 2006. http://cyberdoc.univ-lemans.fr/theses/2006/2006LEMA1019.pdf.
Der volle Inhalt der QuelleIn non-urban zones, the long range sound propagation for road or industrial sources is highly dependent on the boundary conditions (ground characteristics) and on the stability conditions of the surface boundary layer of the atmosphere. Therefore the characterization of the sound propagation conditions are meant to include the micrometeorological information. Besides, the relation between propagation conditions and the acoustic level is statistically uncertain. The purpose of the thesis is to bring new ideas and methods on the problem of time and space estimation of the acoustic field an its related parameters of influence within the geostatistical framework. First, acoustic time series are analysed. The experimental variogram of the series gives an image of the autocorrelation, the shape of which we try to explain with the corresponding micrometeorological conditions. The second part of the work is focused on both time and space evolution of the ground properties of an average field. The ground specifie air flow resistivity is the main parameter of the study. An ordinary Kriging technique is used for mapping. Conditional simulations are also obtained and can be utilized in future studies as input data in complex numerical models. Third, when considering the acoustic field as a stochastic field, it is possible to analyse in situ data. We develop a method of space estimation of the sound level using geostatistical tools combining both a simple physical model and a random model of the fluctuations
Baron, Cécile. „Le développement en série de Peano du matricant pour l'étude de la propagation des ondes élastiques en milieux à propriétés continûment variables“. Bordeaux 1, 2005. http://www.theses.fr/2005BOR13036.
Der volle Inhalt der QuelleLi, Hui. „Bubbles propagation in undoped and Titanium (Ti3+)-doped sapphire crystals grown by Czochralski (Cz) technique“. Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10327/document.
Der volle Inhalt der QuelleIn spite of the chemical simplicity, the congruent melt behaviour and it’s performed mechanical and optical properties sapphire single crystals contain bubbles defects also known as micro-voids. Whatever the growth technology, the grown crystals are characterized by the presence of micro and macro bubbles which affect the optical and mechanical quality of the crystal limiting their application. They degrade the optical properties and the laser efficiency by reduction of the transparency; they also induce surface defects during substrate polishing process. In order to improve the crystal quality, it is important to eliminate bubbles defects and know the reason of their formation, the causes of their propagation, their incorporation and their distribution in the crystal. We have studied bubbles distribution and their size in undoped and Ti-doped sapphire crystals grown by Czochralski (Cz) technique. The collected experimental data made it possible to know the effect of several growth parameters on the distribution, the density and the size of the bubbles. The bubbles propagation and distribution in the crystal are not influenced by the seed type. If the pulling rate increases, the diameter of bubbles decreases and their density increases. The bubbles formed in sapphire crystal are influenced by the starting charge material. Using sapphire crackle as starting charge could be a good way to minimise bubbles creation and limited their propagation. The obtained results in the frame of this thesis describe the whole phenomena involved during bubbles incorporation in undoped and Ti-doped sapphire crystals
Pedraza, Alvaro. „Propriétés thermomécaniques d’enrobés multi-recyclés“. Thesis, Lyon, 2018. http://www.theses.fr/2018LYSET001/document.
Der volle Inhalt der QuelleReuse of Reclaimed Asphalt Pavement (RAP) is considered as one of the main solutions to cope with the objectives of worldwide sustainable development. In this way, the reuse of RAP in bituminous mixtures has been matter of study in previous papers (Chen et al., 2009; Kaur et al., 2013; Mogawer et al., 2012; Ru-bio et al., 2012; Sias Daniel et al., 2013; Valdés et al., 2011) and had concluded be economically profitable as well as had demonstrated the durability of the tested materials. Nowadays, new topics overcome dealing with how increase the RAP content and how many times RAP could be recycled. In France, a collaborative research and development project called “Multi-recycling of warm foam bitu-minous mixtures” (MURE) have brought together all the stakeholders involved in road construction. The pro-gram has run since March 2014. The scientific part of MURE project is IMPROVMURE project (Innovation for Materials and Processes for Improving the Multi-Recycling of Mixes). The overall budget of the project were €4.7M, €2.3M of which been provided by the ANR (National Re-search Agency) in the framework of the IMPROVMURE project, which has gotten under way in March 2014 and its main goal of characterizing the remobilization of the binder from recycled materials was the evalua-tion of the durability of mixes with the addition of binder. Thus, one objective of this project is to determine the thermomechanical properties of multi-recycled bi-tuminous mixtures, so in the context of this goal the current study was made. Likewise this investigation was a collaboration between the Tribology and System Dynamics Laboratory (LTDS) of the University of Lyon/ENTPE (“Ecole Nationale des Travaux Publics de l’Etat” ) and the French company EIFFAGE Infra-structures. For this study 15 types of bituminous mixtures were tested, the bituminous mixtures were produced in the laboratory and construction site, also two different techniques were studied for mixtures elaboration: hot and warm using foamed bitumen in both cases, the RAP content on these were 0%, 40%, 70% and even close to 100% produced after several recycling operations (up to 3 cycles). All bituminous mixtures have 3 invariants: the first is the same aggregate grading curves (except the bituminous mixture with 100% of RAP). The second one is the total binder content (5.4% in total weight). The last is classified as BBSG-03 0/10 bitu- 15 minous mixture, as is specified in the European standards for classification of bituminous mixtures (NF EN 13108-1 - 2007). Three domains of behaviour were studied: Linear Viscoelastic behaviour (LVE), cracking behaviour at low temperature and the fracture behaviour at low temperature. The LVE was studied considering complex modulus tests on bituminous mixtures and were performed in tension/compression on cylindrical samples, thus LVE behaviour was then modelled with 2S2P1D rheological model, developed at Uni. of Lyon / ENTPE, for the other hand cracking behaviour at low temperature was studied considering Thermal Stress Restrained Specimen Tests (TSRST), and finally fracture behaviour at low temperature was studied with the crack propagation tests as a monotonic loading
Brunet, Thomas. „Étude de milieux granulaires secs et mouillés à l'aide des ondes ultrasonores“. Marne-la-Vallée, 2006. https://tel.archives-ouvertes.fr/tel-00129738v2.
Der volle Inhalt der QuelleThis work deals with the sound propagation in a stressed dense granular medium. Elastic waves offer a non invasive method for probing the structure, the viscoelastic properties and non linear behaviours of force networks in the material. First of all, we briefly describe some results about small-amplitude ultrasound propagation in granular materials (effective coherent modes, multiply scattered waves). After then, we show how to infer elastic modulii and characterize the internal dissipation by using coherent waves and multiply scattered waves, respectively. By studying the influence of small amount of added liquid in the medium (< 0,1%) or the surface state of beads, on the viscoelastic properties of dry and wet granular media, we are able to identify two different origins of dissipation : frictionnal and viscous mechanisms. Finally, we study the non linear behaviour of large-amplitude sound propagation in a granular medium. More precisely, we characterize experimentally the reversible hertzian non linear elasticity of the granular medium via harmonic generation. And then we discuss an original experimental finding which concerns irreversible interaction process between elastic waves and granular medium. The underlying physics is related to the Mindlin hysteretic non linearity which causes a softening of the elastic modulus of granular medium accompagnied by micro-rearrangements at the grain asperity scale
Tran, Duy Chau. „Propriétés diélectriques de liquides isolants d'origine végétale pour applications en haute tension“. Grenoble 1, 2009. http://www.theses.fr/2009GRE10017.
Der volle Inhalt der QuelleFor the environmental, economic or technical reasons, oils based on natural esters were used to replace mineral oil in electrical equipments in low and medium voltage. This work consists on characterization of a mixture (RS50) of low viscosity natural esters based on rapeseed oil for applications in high voltage transformers. The influence of humidity, temperature, particle content and thermal aging on its dielectric properties such as permittivity, conductivity, losses and electrical strength was highlighted. The RS50 has a high-water solubility, its conductivity, permittivity and losses are both higher than those of mineral oil but these differences are reduced in aged oils. Its electrical strength is similar to mineral oil even after aging. However, an analysis more precise of prebreak down and breakdown phenomena in specific configurations have shown that natural esters are less favorable for high voltage applications than mineral oil. In parallel, a methodological study was carried out. Advantage of using the frequency spectroscopy measuring method for the characterization of insulating liquids is highlighted. The validity of conditions for the dielectric strength measurement in the liquid insulation, which is traditionally imposed following the standards, was also discussed
Ponnelle, Sylvain. „Propagation des fissures par fatigue a haute temperature dans l'Inconel 718 : effets de microstructure et de chargements complexes“. Paris, ENMP, 2001. http://www.theses.fr/2001ENMP1003.
Der volle Inhalt der QuelleFayolle, Caroline. „Influence de la dispersion de la silice sur les propriétés viscoélastiques et mécaniques des élastomères renforcés“. Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10059/document.
Der volle Inhalt der QuelleFilled elastomers are used in tread tires. It has been demonstrated that most of rolling resistance of tires is due to filled elastomer energy dissipation. In that way, understanding viscoelastic properties of these materials is a key point. Then, filled elastomer behavior at high deformations may be involved in ultimate properties of tire application such as fatigue crack propagation and wear. The aim of this work is to study the impact of silica dispersion on viscoelastic and mechanical properties of filled elastomers. First, levers impacting silica dispersion are evaluated. Dispersion of fillers can be considered as a competition between fillers cohesion forces and applied forces to the system to break them, these parameters have been studied methodically. Finally, the impact of silica-matrix interactions is studied, changing silica surface treatments or elastomer natures. The quantity of interactions possible per polymer chain between the silica and the elastomer may play a role in silica dispersion. Secondly, the impact of silica dispersion on viscoelastic and mechanical properties is discussed. It is shown than increasing silica dispersion leads to a decrease of linear elastic modulus and an increase of reinforcement in tensile at high deformations. Finally, regarding ultimate properties, our experimental device on the selected formulations has not shown any impact of silica dispersion on fatigue crack propagation. Nevertheless, we observe a better wear resistance with increasing dispersion, despite the lower materials hardness
Latef, Kaddour. „Contribution à la propagation des ondes et aux transferts thermiques dans les matériaux multicouches et aux modélisations des échanges thermiques“. Lille 1, 1991. http://www.theses.fr/1991LIL10110.
Der volle Inhalt der QuelleMangeas, Morgan. „Propriétés statistiques des modèles paramétriques non-linéaires de prévisions de séries temporelles : application aux réseaux de neurones à propagation directe“. Paris 1, 1996. http://www.theses.fr/1996PA010076.
Der volle Inhalt der QuelleFohr, François. „Application des propriétés de la propagation acoustique guidée avec écoulement à la mesure de la vitesse de débit dans une conduite“. Poitiers, 1996. http://www.theses.fr/1996POIT2315.
Der volle Inhalt der QuelleBuirette, Christophe. „Étude des mécanismes de propagation de fissure dans un alliage de titane TA6V soudé par faisceau d'électrons“. Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0103/document.
Der volle Inhalt der QuelleIn the aeronautic industry, the reduction of the « buy-to-fly » ration for structural parts has become a major issue. The goal is to develop planes, at a reduced material cost, requiring less fuel with an extended range and higher load capacity. This research study has been designed with the Airbus Company in order to contribute to solve this industrial problem. In particular, the development of the electron beam welding process of the β annealed titanium alloy Ti-6Al-4V should concurrence the usual forging/pressing processes of structural parts. However, welding of Ti-6Al-4V, despite a stress relieving heat treatment, lead to a microstructural heterogeneity between the welded zone and the base metal and, as a consequence, to an heterogeneity of the mechanical properties. In comparison to the crack propagation resistance of the base metal, the one measured fusion zone is weaker and is associated to the presence of very thin α platelets. This mechanical properties gradient remains acceptable for the industrial purpose, nevertheless, in order to extend the use of the electron beam welding process to other structural parts, a Post-Welding Heat Treatment (PWHT) is considered. The aim is to achieve, in the entire welded plate, a better compromise between the crack propagation resistance and the static properties. In this PhD work, fusion lines were performed by the Airbus company on two rolled plates of biphasic α+β Ti-6Al-4V presenting either a lamellar microstructure (also called β annealed) or an equiaxe microstructure (also called α-β annealed). Characterizations of the microstructures involved as well as the mechanical properties helped to understand the failure mechanisms of the welded alloy. The analysis of the different test revealed, thanks to the observation of the crack propagation path on the Charpy specimens, that the very thin α platelets in the fusion zone do not act as a strong barrier against the crack propagation. On the contrary, in the case of the β annealed base metal, the α platelets are thick enough (1µm) to be an obstacle and to slow down the crack. In this case, the crack undergoes many deviations at the α/β interfaces, generating a very long and tortuous crack path. In order to improve the mechanical properties of the fusion zone, it seems appropriate to apply a PWHT, which will transform the microstructure and increase the thickness of the α platelets in the fusion zone. This PWHT consists mainly in a treatment in the β field followed by a controlled cooling rate. However, even if the PWHT applied on the β annealed and welded material lead to a thickening of the α platelets and improve the crack propagation resistance in the fusion zone, a strong enlargement of the prior β grain in the base metal is responsible of low tensile properties. That is why, a PWHT applied on the α-β annealed material is considered in order to homogenize simultaneously the microstructure in both fusion zone and base metal and improve the mechanical in the entire welded plate. Results obtained from the Charpy tests underline that the PWHT applied on the α-β annealed and welded material lead to homogeneous fracture energies in the plate, and to an higher fracture energy after PWHT than the one in the fusion zone of the β annealed material, which fulfill the initial industrial goal. An important anisotropy of the mechanical properties as well as important fluctuations of these properties in t he thickness of the plates has also been observed. The EBSD analyses of the crystallographic microtexture revealed the presence of numerous macrozones responsible of the heterogeneities observed for both microstructures
Ranier, Marc. „Déflexion photothermique et propagation guidée dans les structures planaires multicouches. Etude théorique et expérimentale du coéfficient d'atténuation“. Aix-Marseille 3, 1994. http://www.theses.fr/1994AIX30073.
Der volle Inhalt der QuelleAlam, MB Mahbub. „Acoustic wave propagation through a random dispersion of solid particles in a viscous fluid“. Thesis, Normandie, 2019. http://www.theses.fr/2019NORMLH15/document.
Der volle Inhalt der QuelleA random dispersion of identical elastic solid particles in a viscous fluid is considered and effective properties, appropriate to the propagation through the medium of an ultrasonic compressional wave of large wavelength compared to the radius of the particles, is investigated.The scattering coefficients of a single spherical particle in a viscous medium are investigated for all combinations of incident and scattered wave types for use in multiple scattering models. Approximate formulae are obtained for the coefficients at n’th partial wave order in the Rayleigh limit. For spherical particles, a core-shell self-consistent model is used, in which the medium is modelled by an elastic core of the same material and radius as the particles, surrounded by a shell of the host fluid, and placed in the effective medium. The radius of the shell is such that the ratio of the core/shell volume is equal to the particle concentration. The dynamic properties of the effective medium are sought by minimising the scattering of the shell for different incident compressional partial wave orders (n).The effective bulk modulus is found from the monopole mode n=0 and the effective mass density from the dipole mode n=1. When compared to Ament’s formula based on local force balance at the particles (assumed rigid), the effective mass density obtained from the core-shell model shows a frequency-dependent effect of concentration similar to that observed in multiple scattering models and experimentally. Ament’s method is then applied to obtain the effective mass density in case of aligned rigid spheroids
Xie, Jilong. „Etude de la fatigue et de la rupture des assemblages collés composite-élastomère“. Châtenay-Malabry, Ecole centrale de Paris, 1995. http://www.theses.fr/1995ECAP0390.
Der volle Inhalt der QuelleFarcy, Alexis. „Optimisation des performances électriques appliquée aux interconnexions des circuits intégrés en présence de variabilité“. Chambéry, 2009. http://www.theses.fr/2009CHAMS040.
Der volle Inhalt der QuelleThe contribution of interconnects to overal1 integrated circuit performance is increasing as lines and vias dimensions scale down. Designers' work is now impacted by technological constraints such as Cu resistivity increase or process variability, which affect electrical properties of interconnects. The development of innovative processes and materials in a limited time frame to ensure economical viability of each new generation is absolutely mandatory. This study aims at developing a methodology to predict the real impact of technological solutions on interconnect propagation performance in order to identify the most suitable solutions. After a review of the main innovations under development, the methodology proposed to predict the dependence of signal transmission on technological stack properties and process variability is presented. This approach is then applied to the case of the 32 nm technological node. The experimental results obtained based on the analysis of real circuits to define realistic simulation conditions lead to the extraction of analytic models suitable for statistical analysis. An optimisation of interconnect technological stack is then performed taking into account process variability to identify the most promising technological solutions to reach the required electrical specifications
Nordmann, Samuel. „Équations de réaction-diffusion, propriétés qualitatives et dynamique des populations“. Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS278.
Der volle Inhalt der QuelleWe are interested in some problems arising in reaction-diffusion equations and their application to population dynamics. The first part deals with stable stationary solutions of reaction-diffusion equations. More precisely, our aim is to understand the influence of the geometry of the domain on the existence of stable non-constant solutions, called patterns. We establish a criterion for the non-existence of patterns in general domains. In the second part, we address a Hamilton-Jacobi model for Darwin's theory of evolution. This models features a concentration phenomenon, that is, the solution converges to a Dirac mass when a rescaling parameters goes to 0. We study the case of a population structured by age and phenotype, subject to competition between individuals. In a second step, we add the effect of mutations. We also consider a model which features a phenomenon of evolutionary rescue, in which the population can have cyclic dynamics. The third part is devoted to the study of systems of reaction-diffusion equations. Our framework encompasses the epidemiological SI model, and extends some results to a broader class. Finally, we propose a model to account for the dynamics of riots and social unrest
Chkeir, Aly. „Modélisation de la propagation de l'activité électrique utérine avec des approches mathématiques et expérimentales“. Compiègne, 2011. http://www.theses.fr/2011COMP1938.
Der volle Inhalt der QuelleAs part the development of a physical model for generating the surface uterine electromyogram, also called the Electrohysterogram (EHG), recorded by electrodes placed on the abdominal wall, this thesis focuses on modeling the electrical propagation in the uterine muscle. The pattern of cellular activity has been developed. The spread or propagation will first be addressed by a surface modeling 2D and 3D surface (surface reproducing a uterine volume), to finally reach a 3D solid modeling, from a realistic structure ot the uterine muscle. The uterine structure will be extracted from MRI images of pregnant uterus. Experimental measurements of the spread of fragments of uterus (rats and monkeys) will be conducted in order to provide realistic data of the local velocity across the tissue. The propagation of the EHG on the surface of the abdomen will be generated for comparison with model data, on a global scale of the organ, through collaboration with the University of Reykjavik (Iceland)
Baron, Cécile. „Le Développement en Série de Peano du Matricant Pour l'Etude de la Propagation des Ondes Elastiques en Milieux à Propriétés Continûment Variables“. Phd thesis, Université Sciences et Technologies - Bordeaux I, 2005. http://tel.archives-ouvertes.fr/tel-00113951.
Der volle Inhalt der QuelleLe schéma classique de résolution des équations d'ondes en milieux à hétérogénéité unidirectionnelle repose sur un modèle multicouche, la stratification du milieu étudié pouvant être naturelle, les propriétés sont des fonctions constantes par morceaux, ou artificielle, les propriétés sont des fonctions continues que l'on discrétise. Cette approche est alors connue sous le nom de méthode de Thomson-Haskell. Dans le cas des milieux continûment variables, on calcule une solution exacte à un problème approché ce qui suscite de nombreuses interrogations quant à la précision et à la validité des solutions obtenues.
Dans ce travail, le problème est abordé sous un angle différent offrant ainsi de nouvelles perspectives d'approche des milieux hétérogènes. Afin de conserver l'authenticité du problème, nous proposons d'utiliser une méthode basée sur le développement en série de Peano du matricant, forme explicite de la solution analytique exacte des équations d'onde mises sous la forme d'un système différentiel ordinaire du premier ordre à coefficients non constants, pour des profils quelconques de propriétés. Les développements asymptotiques et numériques de cette écriture appliquée à des problèmes de conditions aux limites ont fourni une méthode robuste pour l'analyse des phénomènes acoustiques (courbes de dispersion, spectre fréquentiel du coefficient de réflexion etc.). Des résultats prometteurs quant à la détection du caractère hétérogène et à la quantification de certains paramètres caractéristiques de l'hétérogénéité ont été obtenus.
Zhang, Wencong. „Recherche numérique et expérimentale sur les propriétés de décharge et les caractéristiques de propagation électromagnétique dans les torches à plasma micro-ondes“. Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0050.
Der volle Inhalt der QuelleThis work aims to better understand the discharges in the microwave plasma torches, by investigating the microwave propagation characteristics and the discharge properties in the microwave plasma torches based on rectangular waveguide under different operational conditions.First, the electromagnetic mode of the microwave in the discharge tube and their existence conditions have been theoretically studied and numerically validated by the full-wave analysis, with the assumption of constant plasma properties, when the discharge occurs. Secondly, based on our assumption that the microwave plasma torch will become a waveguide-coaxial mode convertor when the discharge occurs, experiments are carried out to investigate the effects of the glass tube on the efficiency of power coupling from the input microwave to the discharge in a microwave plasma torch under different input powers, pressures and gas inflow rates in order to explore the possibility to improve the microwave coupling efficiency. Thirdly, a twodimensional fluid model is proposed to simulate the argon discharges in the microwave plasma torch under atmospheric pressure, by making use of approximation of the ambipolar diffusion and axisymmetric distribution of microwave field in the discharge tube. With this simplified model, the mechanism of the plasma column length change under different microwave powers and gas inflow rates, as well as the mechanism of the glass tube overheating problem have been numerically investigated. Finally, a three-dimensional model is further proposed to investigate the discharges in the microwave plasma torches. The argon discharges under atmospheric pressure in two types of microwave plasma torches with different glass tubes has been modelled and compared to the two-dimensional simulation. It is shown that the discharge tube with metallic enclosure in the microwave plasma torches is able to become a two-conductor-like coaxial waveguide, when the discharge properties meet some requirements. With this waveguide structure transition, the cylindrical discharge tube allows the input microwave to enter the discharge tube and propagate along the plasma column towards both ends of the glass tube without the limitation of cut-off frequency. These conclusions may help to better understand the discharge properties and microwave propagation characteristics in the microwave plasma torches and contribute to the optimization of current microwave plasma torches or the design of new types of microwave plasma torches
Casset, Fabrice. „Caractérisation par acoustique picoseconde des propriétés mécaniques du PZT déposé en couches minces pour des applications MEMS“. Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10040/document.
Der volle Inhalt der QuelleMEMS components are today an economic reality and are already used in many mass market applications. These devices can use a piezoelectric actuation, in particular based on thin-film PZT due to its high piezoelectric coefficient. To perform predictive design of high performances components based on PZT actuators, mechanical properties of the PZT are required. We used the picosecond ultrasonic technique which probes thin layers with high frequency acoustics waves generated by ultra-short laser pulses. It allows the transposition of the sonar principle at nanometric scale. During this PhD, we studied thin-film PZT using picosecond ultrasonics. We extracted both Young’s modulus and Poisson ratio without an approximation of one or the other. We also studied wall domain relaxation using picosecond ultrasonic measurement at various frequencies. Using PZT mechanical properties obtained from picosecond ultrasonics, we extracted the PZT piezoelectric coefficient, from the comparison between PZT-based cantilever measurement and numerical modeling. Finally, we applied these data for the design of haptic plates using thin-film PZT actuators. The good agreement between haptic plate measurements and modelization proves all the benefit of picosecond ultrasonics for MEMS design
LE, GALL JANIG. „Etude expérimentale et théorique de la propagation d'ondes de surfaces sur un réseau : application à la modification des propriétés radiatives infrarouges de matériaux“. Châtenay-Malabry, Ecole centrale de Paris, 1996. http://www.theses.fr/1996ECAP0450.
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