Thèses sur le sujet « Propriétés radiatives et effectives »
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Guerra, Timothée. « Interaction lumière-matière dans des suspensions de nanoparticules : homogénéisation et conception de nouvelles propriétés optiques ». Electronic Thesis or Diss., Orléans, 2024. http://www.theses.fr/2024ORLE1005.
Texte intégralDisordered media composed of nanoparticles are of great importance in many applications, particularly those related to energy efficiency such as radiative cooling. Understanding the light-matter interaction is therefore essential, but highly complex. Indeed, these studies often involve solving Maxwell's equations in systems made up of thousands of particles, to take account of scattering and interference phenomena. In order to reduce the ensuing numerical burden, this thesis focuses on 2D systems, with some discussion of 3D systems. In this context, the first part of this manuscript focuses on the concept of homogenization for particle systems that are small relative to the radiation wavelength and may exhibit resonances. This study highlights exotic behaviours that allow us to discuss, among other things, the link between homogenization and coherent and incoherent parts of the scattered field.The second part is dedicated to optimizing the absorption of radiation in subwavelength plates made of nanoparticles. It is shown that the use of resonant particles only results in absorption up to 70%. However, combining them with purely scattering particles results in near-perfect absorption (∼95%), through an effect similar to critical coupling. Finally, a detailed study of the mechanisms governing absorption gain in 2D has enabled them to be reproduced in 3D systems
Szczap, Frédéric. « Etude des effets des heterogeneites des nuages sur leurs proprietes radiatives effectives et leurs parametrisations ». Clermont-Ferrand 2, 2000. http://www.theses.fr/2000CLF22188.
Texte intégralDeville, Pascal. « Modélisation et simulation des propriétés radiatives des sources lumineuses ». Nancy 1, 1996. http://www.theses.fr/1996NAN10004.
Texte intégralThe physical precision of simulations which permit the realistic visualization of a given geometric environnement depends on two factors: the precision of the physical model which describes the radiative properties of light sources (emittance) and surface (reflectance) of this environnement, and the precision of light propagation calculations between these surfaces. The work of my thesis presented here consists of defining a model for light source which permits the simulation of complex lighting system. This model takes into account any arbitrary type of spectral distributions (continuous or non-continuous) and spatial distributions (uniform or non-uniform). - In image synthesis technology today, the spectral characteristics of light sources are still often modelized in the RGB colorimetric system. This colorimetric system does not allow us to obtain precise simulations from given spectral data because it depends on display device. Methods have been recently developed to sample the wavelength domain and calculate the light propagation from this set of samplesj which however, do not permit the treatment of complex spectral characteristics. To solve this problem, we have proposed a method based upon preliminary analyse of spectrums utilized. This method removed certain constraints imposed by actual methods. -To take into account the spatial energy distribution of light sources in the illumination calculations, classical methods assume that the distributions are uniform. This simplification is unjust since artificial sources never have a uniform spatial energy distribution. To simulate this type of light sources, models based upon gonio-photometric diagram provided by the manufacturers of lighting systems have been developed. However, these methods introduce an important error in the surface illumination calculation when sources are dose to the surface. This is why we have proposed a new method founded upon a precise geometric modelization of a light fixture (lamp, reflector, lens) and consider the source like a sub-domain of this environnement which emits energy by an intermediate interface zone. Inside this sub-domain, the spatial energy distribution is calculated on the interface zone by using a projection method. The two methods (spatial and spectral distributions) actually proposed in this thesis have been experimented and will be transferred into the industrial domain further developement
Cazier, Dorothée. « Modélisation et simulation des propriétés radiatives des surfaces : implantation et expérimentation ». Nancy 1, 1996. http://www.theses.fr/1996NAN10116.
Texte intégralIn the light transfer equation, we have to take into account the physical features of the material reflection. This have led many researchers to elaborate various models. These models are more or less physically valid; they are also more or less easy to use. In fact, on one hand they have to be processed by an algorithm of global lighting transfer between all surfaces of the geometrical environment to be simulated, and in the other hand they have to permit to determine parameters for the complex photometrical behavior of these surfaces. Our study concerns the modelisation of the radiative properties of surfaces. We focus more precisely on the properties measurement for real cases of surfaces, by taking into account these properties in the illumination simulation process and on the experimentation of a number of models, in the perspective of lighting engineering applications
Chepfer, Hélène. « Etude théorique et expérimentale des propriétés optiques et radiatives des cirrus ». Lille 1, 1997. http://www.theses.fr/1997LIL10079.
Texte intégralLa comparaison des différentes mesures avec les modeles montre que les données de polarisation (POLDER et lidar) sont très discriminantes pour la microphysique (forme, taille, orientation des cristaux), et que la combinaison de différentes mesures permet de réduire le nombre de modèles susceptibles de les expliquer. Une étude de sensibilité du forçage radiatif met en évidence l'impact important de l'orientation préférentielle des cristaux de glace dans le cirrus
Brogniez, Gérard. « Contribution à l'étude des propriétés optiques et radiatives des cirrus ». Lille 1, 1992. http://www.theses.fr/1992LIL10116.
Texte intégralJulien, Vieaud. « Propriétés optiques effectives de films composites de polymère et de nanoparticules d'or ». Phd thesis, Université Sciences et Technologies - Bordeaux I, 2011. http://tel.archives-ouvertes.fr/tel-00676817.
Texte intégralVieaud, Julien. « Propriétés optiques effectives de films composites de polymère et de nanoparticules d’or ». Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14349/document.
Texte intégralBy spectroscopic ellipsometry, we study the optical properties in the range of UV-Visible-Infrared of composites films made of polymer and gold nanoparticles. We study the relation between these measurement and the structure of the nanocomposites, that we study by atomic force microscopy in particular. We distinguish the analysis of thicks films (tridimensionals) and thins (quasi-bidimensionals). In both of case, we confronte these experimentals results to the theoric models of effectives medium derivated for Maxwell-Garnett in particular
Lallich, Sylvain. « Détermination expérimentale et modélisation des propriétés radiatives de matrices nanoporeuses de silice ». Phd thesis, INSA de Lyon, 2009. http://tel.archives-ouvertes.fr/tel-00397453.
Texte intégralChartier, Céline. « Propriétés physiques et radiatives du luminophore vert SrGa2S4 : eu2+ en couche mince ». Paris 6, 2003. http://www.theses.fr/2003PA066417.
Texte intégralJarrah, Walid. « Calcul de structures atomiques et des propriétés radiatives des plasmas de fusion ». Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS543/document.
Texte intégralThe radiative properties are of utmost importance when studying astrophysical and ICF plasmas, particularly in non local thermodynamic equilibrium conditions. This is the reason why we have developed a collisional-radiative model that enables us to calculate the radiative properties of plasmas under any temperature and density conditions. We developed and implemented new Gaunt factors to the CR model. These factors greatly improve the precision when calculating the cross sections of the microscopic processes. These cross sections are required to calculate the populations of the atomic levels. We obtained these new factors by using the distorted-wave and generalized line strength methods of the Flexible Atomic Code (FAC).In order to validate our new-developed CR model, we compared our results to those of Hill and Rose, of a plasma composed of carbon and 5% silicon, in LTE and NLTE conditions. We obtained satisfactory results in both conditions. We also compared our results to the experimental transmission measured by Xiong et al., of a pure silicon plasma, with Te = 72 eV et Ne = 1.3 x 10²¹ cm⁻³. Again, we obtained results that are in good agreement with the measured spectrum. However, we noticed some discrepancies in the line shift of some lines, and some missing transitions. This can be explained by the absence of certain electronic configurations in the calculation of the atomic structure with the Cowan atomic code.We also explored the absorption of a plasma composed of carbon and 5% germanium with a restricted number of electronic configurations. We investigated the effect of configuration interaction and the effect of the radiative field. We also developed new laws that predict the Planck and Rosseland mean opacities very quickly. For the time being, these laws work for carbon, silicon and germanium, with Te between 250 and 350 eV, and Ne between entre 2 et 8x10²³ cm⁻³
Deron, Christine. « Rayonnement thermique des plasmas d'air et d'argon : modélisation des propriétés radiatives et étude expérimentale ». Châtenay-Malabry, Ecole centrale de Paris, 2003. http://www.theses.fr/2003ECAP0942.
Texte intégralAn exhaustive spectroscopical database which takes into account all the radiative processes in an air plasma between 300 and 25000K was previously built ; it required calculation of internal partition function and concentrations of the main species contributing to radiative processes at thermal local equilibrium (TLE) in an air plasma which are presented here. The previously database is then used to develop some radiative transfer models such as net emission coefficient approach, averaged absorption coefficient mixed with escape factors model, mxiture absorption distribution function of fictitious gases, from 300 to 25000 K. These models are tested on an elementary geometry with different temperature profiles. Besides, to validate the database, an experimental set-up has been built (MAECKER ARC). Some post-processing techniques are developped to caracterize the plasma produced in emission. Measurements are made on argon and argon-hydrogen plasmas. Theoritical spectra between 300 and 1000 nm are simulated at TLE; the comparison between these spectra and the experimental ones leads to very good agreements
Ehrhardt, Kevin. « Mesures, modélisations et simulations numériques des propriétés optiques effectives de métamatériaux auto-assemblés ». Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0309/document.
Texte intégralThis PhD work was dedicated to the experimental, theoretical and numerical studyof the optical properties of self-assembled metamaterials made of gold nanoparticles, operatingat visible frequencies. We were interested in three different structure types and analyzed theiroptical properties experimentally by spectroscopic ellipsometry.We studied the effect of a high index substrate proximity on the plasmonic response of goldnanoparticles, both experimentally and numerically, on nanoparticle monolayers deposited ontopolyelectrolytes multilayers. We discuss an enhancement effect of the nanoparticle absorptioncross-section for small distances to the substrate. Dense polymer/gold nanoparticles compositefilms were shown to have tunable optical properties depending on their gold filling fractionand to behave, at high filling fraction, like a dielectric or a metal depending on the frequencyrange. We developed a phenomenological model, adapted to a large number of cases, whichsuccessfully describes the films optical properties. Finally, lamellar films made of block copolymersand gold nanoparticles were studied. We have shown how to access, for certain structuralconditions, the extraction and the modelisation of the effective permittivity anisotropy, affectedby the resonance of the nanoparticles
Qiao, Jianghao. « Modélisation des propriétés thermomécaniques effectives de dépôts élaborés par projection thermique ». Phd thesis, Université de Technologie de Belfort-Montbeliard, 2012. http://tel.archives-ouvertes.fr/tel-00879252.
Texte intégralQiAO, Jianghao. « Modélisation des propriétés thermomécaniques effectives de dépôts élaborés par projection thermique ». Thesis, Belfort-Montbéliard, 2012. http://www.theses.fr/2012BELF0186/document.
Texte intégralIn the present study, the thermal conductivity and elastic modulus of thermal spray YPSZcoatings were predicted by 2D and 3D finite differences and finite elements numericalmodeling based on cross-sectional images.The influence of the image resolution, size and threshold on the predicted properties of thecoating was studied. Moreover, the effects of the numerical method and of the boundarycondition were investigated. In particular, the quantification of the Knudsen effect(rarefaction effect) on the heat transfer through a porous structure was realized by numericalmodeling in combination with image analysis. The predicted thermal conductivities obtainedby 3D modeling were found to be higher than those obtained by 2D modeling, and in betteragreement with the measured results. A 2D/3D correlation was sucessfully found for themodeling of thermal conductivity: this correlation allows predicting 3D computed valuesfrom 2D ones
Hervo, Maxime. « Etude des propriétés optiques et radiatives des aérosols en atmosphère réelle : Impact de l'hygroscopicité ». Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2013. http://tel.archives-ouvertes.fr/tel-00866936.
Texte intégralBanner, Didier. « Propriétés radiatives des verres et des fontes de silicates : modélisation des transferts de chaleur ». Châtenay-Malabry, Ecole centrale de Paris, 1990. http://www.theses.fr/1990ECAP0156.
Texte intégralMondet, Guillaume. « Propriétés radiatives des plasmas de fusion. Emissivité et opacité dans des structures atomiques complexes ». Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00946767.
Texte intégralMichel, Florent. « Relations entre structure et propriétés radiatives de verres et de liquides d'oxydes en conditions in-situ ». Paris 6, 2013. http://www.theses.fr/2013PA066571.
Texte intégralThe radiative properties of the liquids used to produce glass and glass fibers may represent economic and environmental interests. The objective of this thesis is to connect the optical absorption properties at high-temperature to the liquid/glass structure. We are dealing firstly with alkali boro-silicates, corresponding to glass fibers, to understand the role of boron at high temperatures. We then examine the role of iron in soda-lime/alumino-silicate matrices. Those matrices correspond to sheet glass and fiberglass, respectively. For the borosilicate liquid, the three-fold coordinated boron proportion increases by 40 \% when the temperature increases from 25 °C to 1200 °C. As the trigonal boron absorbs infrared at 10 µm, it improves the absorption of radiated energy by a heated building. A rapid quench of the liquid would maximize the insulation properties of the fiber. X-ray absorption spectroscopy shows that iron has low coordination number in the glass but also in the liquid. For UV/VIS/NIR spectroscopic properties with temperature, we see systematic evolution of the spectrum for the both compositions. For the soda-lime glass, strong changes of the UV/Vis/NIR spectrum can be observed with temperature. Up to 1400 °C, the transmittance of the glass batch is improved. The UV-VIS-NIR results obtained in situ at high temperature allow a better understanding of the radiative transfer in the batch within the furnace. We have evidenced a different behavior for the two matrices, which could allow a better control of the radiative transfer efficiency
Noel, Vincent. « Etude des propriétés optiques et radiatives des cirrus par télédetection active : apport des observations polarisées ». Phd thesis, Université Paris-Diderot - Paris VII, 2002. http://tel.archives-ouvertes.fr/tel-00006430.
Texte intégralNoël, Vincent. « Étude des propriétés optiques et radiatives des cirrus par télédétection active : apport des observations polarisées ». Paris 7, 2002. http://www.theses.fr/2002PA077133.
Texte intégralLefevre, Tony. « Etude des propriétés radiatives d'un plasma d'hélium hors équilibre : expériences et simulations avec le code SOPHIA ». Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4776/document.
Texte intégralThe experimental study of the radiative properties of plasmas of helium out of equilibrium can be achieved by emission spectroscopy, a non-invasive diagnostic which does not affect the system. In this thesis, this diagnostic was used on plasmas created in discharge tubes and in the linear magnetized machine MISTRAL. The experimental data were compared with theoretical results coming from the atomic physics code SOPHIA (collisional-radiative model). The discharge tubes are characterized by electron temperatures of the order of the electron volt and electron densities in the range of 10 12 cm-3. The first part of the results of this thesis has shown that under these conditions, the CCC model (Convergent Close Coupling) reproduces in the best way the atomic dynamics of such a system. The second part of the results reveals the spectroscopic signatures (line intensities ratios and radial studies), in the machine MISTRAL, the presence of ionizing energetic electrons and the diffusion of charged particles through a magnetic field
Zerhouni, Othmane. « Etude des propriétés élastiques effectives de matériaux poreux à microstructure aléatoire : Impression 3D, caractérisation, expérimentale et numérique ». Thesis, Institut polytechnique de Paris, 2019. http://www.theses.fr/2019IPPAX008.
Texte intégralThis thesis deals with the 3D-printing, numerical simulation and experimental testing of porous materials with random isotropic microstructures. In particular, we attempt to assess by means of well-chosen examples the effect of partial statistical descriptors (i.e., porous volume fraction or porosity, two-point correlation functions and chord-length distribution) upon the linear effective elastic response of random porous materials and propose (nearly) optimal microstructures by direct comparison with available theoretical mathematical bounds. To achieve this, in the first part of this work, we design ab initio porous materials comprising single-size (i.e. monodisperse) and multiple-size (polydisperse) spherical and ellipsoidal non-overlapping voids. The microstructures are generated using a random sequential adsorption (RSA) algorithm that allows to reach very high porosities (e.g. greater than 80%). The created microstructures are then numerically simulated using finite element (FE) and Fast Fourier Tranform (FFT) methods to obtain representative isotropic volume elements in terms of both periodic and kinematic boundary conditions. This then allows for the 3D-printing of the porous microstructures in appropriately designed dog-bone specimens. An experimental setup for uniaxial tension loading conditions is then developed and the 3D-printed porous specimens are tested to retrieve their purely linear elastic properties. This process allows, for the first time experimentally, to show that such polydisperse (multiscale) microstructures can lead to nearly optimal effective elastic properties when compared with the theoretical Hashin-Shtrikman upper bounds for a very large range of porosities spanning values between 0-82%. To understand further the underlying mechanisms that lead to such a nearly optimal response, we assess the influence of several statistical descriptors (such as the one- and two-point correlation functions, the chord-length distribution function) of the microstructure upon the effective elastic properties of the porous material. We first investigate the ability of the two-point correlation function to predict accurately the effective response of random porous materials by choosing two different types of microstructures, which have exactly the same first (i.e., porosity) and second-order statistics. The first type consists of non-overlapping spherical and ellipsoidal pores generated by the RSA process. The second type, which uses the thresholded Gaussian Random Field (GRF) method, is directly reconstructed by matching the one- and two-point correlation functions from the corresponding RSA microstructure. The FFT-simulated effective elastic properties of these two microstructures reveal very significant differences that are in the order of 100% in the computed bulk and shear moduli. This analysis by example directly implies that the two-point statistics can be highly insufficient to predict the effective elastic properties of random porous materials. We seek to rationalize further this observation by introducing controlled connectivity in the original non-overlapping RSA microstructures. The computed effective elastic properties of these microstructures show that the pore connectivity does not change neither the two-point correlation functions nor the chord-length distribution but leads to a significant decrease in the effective elastic properties. In order to quantify better the differences between those three microstructures, we analyze the link between the local geometry of the porous phase and the corresponding computed elastic fields by computing the first (average) and second moments of the elastic strain fluctuations. This last analysis suggests that partial statistical information of the microstructure (without any input from the corresponding elasticity problem) might be highly insufficient even for the qualitative analysis of a porous material and by extension of any random composite material
Rozanski, Adrian. « Sur la représentativité, la taille minimale du VER et les propriétés effectives de transport des matériaux composites aléatoires ». Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10137/document.
Texte intégralThe thesis focuses on random composites and some specific features such as: the minimum size of a representative volume element (RVE) and the determination of effective transport properties. The main objective is to formulate a computationally efficient method which would allow for quick determination of effective properties. The effective properties of transport are considered. It is shown that this class of properties can be estimated either by performing calculations over one large sample or by averaging over a sufficient number of smaller microstructure realizations. However, for a given type of microstructure; the size of such smaller realizations can not be smaller than some critical minimum size. It is shown that this critical size of RVE is strongly affected by several parameters. These are: microstructure type, volume fractions of constituents, contrast in mechanical properties of composite phases, number of performed realizations as well as a desired accuracy. Furthermore, two separate types of representativity are introduced: geometrical representativity and representativity with respect to overall transport properties. Therefore, two distinct criteria for the minimum size of RVE are formulated based on the properties of the two-point correlation function. Comparing to other methods proposed in wide literature, the criterion formulated in the thesis gives an advantage: the condition proposed includes microstructure morphology. Therefore, in order to determine the minimum size of RVE none numerical calculations like those of FE are necessary. A validation of proposed methodology is performed on several examples of 2D microstructures
Reine, Bénédicte. « Étude et simulation de la conductivité thermique de matériaux composites à matrice organique chargée et renforcée de fibres de carbone PITCH ». Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2540/.
Texte intégralThis thesis was a part of our on-going research in the frame of the THEOREM project leaded by THALES Systèmes Aéroportés. This project was a collaborative work between industrial and academic partners. The purpose was to develop a hybrid composite material made of a polymeric matrix filled with micro and nanoparticles and reinforced with PITCH carbon fibres. The ultimate material should exhibit high thermal conductivity like aluminum (~ 300 W/m/K). Two main lines are developed: one line on doped matrix and another one on reinforcements. On the matrix line numerical models of random dispersion of fillers in a predefined R. V. E. Were developed to obtain homogenized properties of the doped matrix. On the reinforcement line the influence of different fibre architectures on heat flux in the three directions of space was highlighted. Effective properties of the ultimate composite were numerically deduced from the gathering of those two lines. Different numerical models were correlated with different experimental measurements
Tinel, Claire. « Restitution des propriétés microphysiques et radiatives des nuages froids et mixtes à partir des données du système RALI (RAdar-LIdar) ». Phd thesis, Université Paris-Diderot - Paris VII, 2002. http://tel.archives-ouvertes.fr/tel-00004241.
Texte intégralBaumann, Xavier. « Étude de la composition chimique et des propriétés thermodynamiques et radiatives d'un plasma de SF6-C2F4 en condition de déséquilibre thermique ». Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30032.
Texte intégralTo transport the electrical current on large distances, we have to use high voltage to minimize the energy losses. However, if an electrical fault occurs in the distribution network, we should be able to turn off the electrical current. For this purpose, we use specific devices: the high voltage circuit breakers that should to shut off the electrical arc formed when the electrical contacts are separated. To design and to upgrade the high voltage circuit breakers, the manufacturers are increasingly using numerical modelisations that simulate the electrical arc and the plasma behaviors. Nevertheless, the physics phenomena in the plasma are complex. To describe them, a specific expertise, available in the public research laboratories, is necessary. This thesis is in a partnership between the Siemens company and the AEPPT group in LAPLACE to create a databank to study the extinction phase of electrical arc. This data bank includes thermodynamic and radiative properties of plasma. The transport coefficients have been studied in another thesis conducted in parallel by G. Vanhulle. The calculation of these properties is relatively well known if the plasma is in local thermodynamic equilibrium. But, during the extinction of arc, the free electrons and the heavy particles (molecules, atoms and ions) are not necessary in thermal equilibrium and are describe by different temperatures (the plasma is referred to as 2T plasma). The originality of this thesis is in the extension of the calculation of properties for a SF_6-C_2 F_4 plasma out of thermal equilibrium. First, we discuss the calculation of internal temperatures of heavy particles (excitation temperatures of electronic, vibrational and rotational levels). Then, we report the calculation of partition functions that are essential to get the others properties. To get the 2T chemical composition of the plasma, we developed an approach based on a set of balance equations. In this method, the physical approximations are limited but it is not adapted for the massive calculation of a databank. Therefore, we opted for a method based on two multi-temperature laws of mass action. With the chemical compositions, we calculated the thermodynamic and radiative properties. The thermodynamic properties (mass density, enthalpy and heat capacity) are described and the results are discussed. The radiative properties are complex. We describe in details the radiative processes and the broadening phenomena of atomic lines to get the emission and absorption coefficients. Finally, we discuss the transfer of radiation across the plasma. We show our results resulting of the net emission coefficient method to get the divergence of radiation flux used in magneto-hydrodynamic model
Bensmina, Halima. « Calcul numérique à partir de la géométrie et des propriétés microscopiques de grandeurs effectives d'un milieu poreux : tortuosité, perméabilité, dispersion ». Besançon, 2002. http://www.theses.fr/2002BESA2006.
Texte intégralHleli, Ali. « Étude de la cinétique chimique et des propriétés radiatives d'un plasma d'arc dédié à la synthèse de nanoparticules de carbone ». Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30075.
Texte intégralThe electric arc process or the quasi-thermal plasma is one of the most used to produce nanomaterials. The study of the physicochemical phenomena underlaying arcs can be achieved by means of collisional-radiative models to thoroughly describe the chemical composition with the use of the particles number conservation law in the plasma. This method allows a straightforward calculation of thermal properties. These models provide a realistic description of the arc-induced chemistry and allow better understanding of the deviations from local thermodynamic equilibrium. It is in this context that the present work is clearly situated, relating to develop multi-temperature numerical tools able to predict, the chemical composition of Ar-He-N2 mixtures in the presence of carbon, nickel and yttrium removal from electrodes, experimentally used for carbon nanotubes synthesis, and determine the radiative proprieties such as the emission spectra of the C2 Swan and the CN Violet systems frequently observed in nitrogen and carbon containing mixtures and useful for arc characterization and diagnostics : the determination of the rotational and the vibrational temperatures
Couillard-Labonnote, Laurent. « Etude des propriétés optiques et radiatives des cirrus à l'aide de modèles microphysiques élaborés : analyse de mesures in situ (Néphélomètre) et satellitaire (POLDER) ». Lille 1, 2001. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2001/50376-2001-147.pdf.
Texte intégralN'Guessan, Yao. « Contribution à l'étude des propriétés radiatives des matériaux opaques et semi-transparents, à température ambiante, par une méthode radiométrique en régime modulé ». Paris 12, 1996. http://www.theses.fr/1996PA120026.
Texte intégralPorcherot, Quentin. « Un modèle hybride pour le calcul de propriétés radiatives des plasmas chauds combinant niveaux, configurations et supraconfigurations à l'équilibre thermodynamique local ». Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00694714.
Texte intégralPapazzoni, Mathieu. « Caractérisation des propriétés microphysiques et radiatives des nuages de glaces dans la Mousson d'Afrique de l'Ouest à partir de données aéroportées et satellite (AMMA) ». Versailles-St Quentin en Yvelines, 2010. http://www.theses.fr/2010VERS0049.
Texte intégralTo improve our knowledge of cloud processes is crucial to reduce errors due to the representation of clouds in current climate predictions and for numerical weather prediction. That is why the complex contribution of ice clouds to the water and radiative budgets needs to be clarified. In this framework this work strives to characterize ice cloud properties in the West-African monsoon system at different scales. In the first part a local study is carried out with data from the airborne cloud radar RASTA. Dynamical properties are obtained with a method specifically developed for this instrument. The contrast between land and ocean is also investigated with this data. The second part exploits a regional view of the phenomenon. Annual and monthly climatologies are developed with satellite data from CloudSat and CALIPSO in order to characterize the statistical properties of ice clouds and the dominant microphysical processes as a function of height. The characterization of the spatio-temporal variability of these ice cloud properties and of the frequency of occurrence of multilayer situations completes this work
Bécu, Laurianne Guilaine. « Modélisation des propriétés optiques et radiatives des cirrus dans l'infrarouge : validation à l'aide des mesures effectuées lors de l'expéience FRENCH/DIRAC 2001 ». Lille 1, 2003. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2003/50376-2003-213-214.pdf.
Texte intégralLE, 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.
Texte intégralChelin, Pascale. « Étude des propriétés radiatives de la vapeur d'eau à haute température et haute pression par diagnostic optique de la combustion H2/02/N2 ». Paris 10, 2003. http://www.theses.fr/2003PA100022.
Texte intégralThis dissertation concerns the study of the rovibrational spectrum of water vapour in hydrogen flames for high temperature (T>2000 K) thermodynamic conditions and for pressures between 2 and 40 bar. The water molecule was selected as a probe species to retrieve the distributions of temperature and concentration in hot gases, for example the exhaust gases of a ramjet. We have designed and used as a test bed a combustion chamber (deflagration tube) in order to experimentally validate the current spectroscopic parameters of H2O at high pressure and temperature. The experimental set-up consists of a grating spectrometer and a CCD camera. The instrument has been precisely calibrated both spectrally by its apparatus function and radiometrically using a variable temperature blackbody. A time dependent numerical model has been developed, which simulates reliably the pressure profiles of the hydrogen-air flame after initiation of the combustion process. We have introduced the profiles of temperature and of H2O concentration simulated by this combustion code into a line-by-line radiative transfer model. Then, we have calculated the water vapour spectra in the 10332-10496 cm-1 spectral region, at the end of the combustion process (one way propagation of the flame within the tube). After spectral fitting of some of the spectroscopic parameters a good agreement between calculated and experimental spectra is obtained
Laroche, Marine. « Rôle des ondes de surface dans la modification des propriétés radiatives de matériaux microstructurés : application à la conception de sources infrarouges et à l'effet thermophotovoltaïque ». Phd thesis, Ecole Centrale Paris, 2005. http://tel.archives-ouvertes.fr/tel-00011615.
Texte intégralLa 1ère partie de cette thèse est consacrée au phénomène d'émission thermique cohérente et amplifiée par plasmon-polaritons de surface. Nous avons tout d'abord conçu et réalisé une source thermique de tungstène avec une directivité exceptionnelle dans le proche infrarouge. Nous avons ensuite étudié le refroidissement radiatif du silicium dopé grâce à l'amplification d'émission thermique par plasmons de surface. Nous avons comparé les performances de ces sources cohérentes avec celles d'un système anti-réfléchissant : l'écran de Salisbury.
Dans la 2ème partie, nous étudions l'impact du transfert radiatif en champ proche sur la conversion thermophotovoltaïque (TPV). L'excitation d'ondes de surface sur la source éclairant la cellule TPV engendre un transfert radiatif amplifié et quasi-monochromatique. Nous présentons un modèle quantitatif permettant de calculer le photocourant et le rendement. Nous montrons que l'on peut obtenir une augmentation significative de la puissance électrique extraite et du rendement d'un dispositif TPV éclairé en champ proche.
La 3ème partie porte sur les propriétés radiatives des cristaux photoniques induites par ondes de surface. Deux phénomènes connus en plasmonique ont pu être obtenus : la transmission résonante à travers un film opaque et l'émission thermique cohérente. Un avantage des cristaux photoniques est la possibilité de modifier la fréquence d'excitation des ondes de surface en faisant varier les paramètres du cristal.
Pierrot, Laurent. « Développement, étude critique et validation de modèles, de propriétés radiatives infrarouges de CO2 et H2O à haute température : applications au calcul des transferts dans des chambres aéronautiques et à la télédétection ». Châtenay-Malabry, Ecole centrale de Paris, 1997. http://www.theses.fr/1997ECAP0512.
Texte intégralFlih, Sid Ali. « Etude des profils de la raie Hα et de raies atomiques et ioniques de gaz rares émises par des plasmas denses et froids créés dans des tubes à éclairs à remplissage variable (Kr - H2, Ar - H2) ». Paris 6, 2003. http://www.theses.fr/2003PA066528.
Texte intégralDepraz, Sebastien. « Etude expérimentale et modélisation des propriétés radiatives des mélanges gazeux de type CO2-N2 à très haute température en vue de l'application aux rentrées atmosphériques martiennes ». Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2011. http://www.theses.fr/2011ECAP0051/document.
Texte intégralModeling of the radiation of CO2 above 2000 K remains a challenge for the prediction of radiative transfer at high temperatures, especially for the design of thermal protection of space vehicles entering the Martian atmosphere. The challenge for both the creation of databases that the development of models to perform calculations coupled between Aerothermodynamics and radiative transfer. Several spectroscopic databases have been developed in recent decades. Simulations of CO2-N2 mixtures at equilibrium showed that the IR emission of CO2 is important, if not predominant, up to 4000 K. But the experimental data to verify their accuracy at high temperature are few and limited to the low spectral resolution, at lower temperatures, or involve significant uncertainties. The main objective of this work is to provide experimental data at medium or high spectral resolution and high temperature in order to verify the accuracy of the theoretical foundations developed. The gas mixture at high temperature we measure the emission spectra is achieved through a microwave discharge through a stream of pure CO2. The temperatures reached (about 6000 K), the mixture is in local thermodynamic equilibrium (LTE) and mainly contains the following species: CO2, CO, O2 and O. The measurement of the spectra is carried out using a Fourier transform spectrometer in the infrared. The harmonic emission bands of CO in the region 3800-4400 cm-1 power allows accurate determination of the radial temperature field in the plasma. The theoretical CO2 emissions, both in emission coefficient or radiance integrated on an optical path, in the regions of 2.7 and 4.3 _m _m, is then calculated from the spectroscopic database and compared measures. The databases are based spectroscopic studied CDSD-4000 and recently published EM2C-1994 which is older. The results show that the latter is sufficient for combustion in conventional applications, typically requiring low spectral resolutions and temperatures below 2500 K, for which it was originally developed. However, based CDSD-4000 is generally in good agreement with experimental data, especially in the wings of bands indicating reliability for applications at very high temperatures. Although comparisons have revealed that the line positions for high energy transitions are unclear in this basis, the high degree of overlap of the lines in the regions 2.7 and 4.3 _m _m should greatly reduce the impact of this imprecision in practice. The other objective of this work concerns the difficulty of coupling between the calculations of radiative transfer and aerothermodynamics. Indeed, calculations of radiative transfer iv involving polyatomic molecules must take into account a large number of rovibronic transitions. Therefore, an approximate model of radiative properties (Statistics narrowband model) was developed and its accuracy has been studied for electronic systems optically thick carbon diatomic molecules encountered in problems of Martian atmospheric reentry. These systems are CO 4th positive, C2 Swan and CN violet. Various conditions to the non-LTE and LTE, and various mixtures have been studied for different regimes of line broadening. Comparisons with calculations "line by line" showed excellent agreement. The model parameters were tabulated in terms of two temperatures, Tg (vibrational temperature) and Tr (rotational temperature)
Depraz, Sébastien. « Etude expérimentale et modélisation des propriétés radiatives des mélanges gazeux de type CO2-N2 à très haute température en vue de l'application aux rentrées atmosphériques martiennes ». Phd thesis, Ecole Centrale Paris, 2011. http://tel.archives-ouvertes.fr/tel-00697001.
Texte intégralDahi, Ghiles. « Etude expérimentale et modélisation par approche radiative d'un photoréacteur pour la production d'hydrogène ». Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22782/document.
Texte intégralTo address the energy challenge of the 21 st century, a solution is the development of solar processes for the production of energy vectors by artificial photosynthesis, in particular photocatalytic synthesis of solar fuels. However high kinetic and thermodynamic performances for these processes must be reached, this requires the development of tools for optimal design, including predictive knowledge models addressing radiative transfer that is the controlling physical process at different scales. A predictive multi-scale model has therefore been developed, implemented and validated on a simple reaction for hydrogen photo-production from CdS particle slurry. On the basis of their characteristics (size, shape, etc.) and their optical properties, the radiative properties of the particles, namely absorption and scattering cross sections and phase function, were calculated using the Lorenz-Mie theory and validated by measurements of transmittances on a high accuracy optical bench. These parameters were then used as input parameters to solve rigorously the radiative transfer equation with the Monte Carlo method. The agreement between predicted and experimental transmittance, taking into account light scattering by hydrogen bubbles, is good in the absorbed spectral band. In parallel, the use of complete experimental bench centered on a small photoreactor, where incident flux densities have been validated by actinometry, yielded high accuracy hydrogen photo-production results. A first and original model of thermokinetic coupling was then formulated and validated after identification of a single lumped parameter whose reification will be approached later and used predictively with success. This work opens up a large number of research prospects because it makes possible to transpose the predictive chain to artificial photosynthesis. This work provides also guidance on the kinetic and thermodynamic optimization of photo-processes producing solar fuels
Le, Coroller Hervé. « Effet de la conductivité thermique sur la structure des ondes de choc radiatives : étude de la pulsation de deux étoiles super-géantes froides HD 56126 et HD 179821 ». Aix-Marseille 1, 2002. http://www.theses.fr/2002AIX11028.
Texte intégralSourdeval, Odran. « Étude des propriétés optiques et radiatives des nuages de type cirrus déduites de la synergie des mesures de rayonnement passif et actif : application dans le contexte de l’A-Train et des futures missions spatiales ». Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10137/document.
Texte intégralCirrus are cloud types that are recognized to have a strong but still poorly understood impact on the Earth-atmosphere radiation balance. Recently, the A-Train satellite constellation has efficiently contributed to the study of these clouds, due to a multitude of instruments in perfect synergism. In this PhD research, several A-Train instruments have been used to study the optical and radiative properties of cirrus. Firstly, with the help of the data from two airborne campaigns, we have performed a validation of the measurements from the Infrared Imaging Radiometer (IIR) onboard CALIPSO. We have observed strong similarities between the airborne and space borne radiometric measurements, which allows validating the latter. A second study presents an algorithm developed in order to perform retrievals of the optical thickness of cirrus and the effective size of their ice crystals using IIR measurements. We demonstrate that these retrievals are perfectly coherent with in situ measurements and operational products of IIR. It is nevertheless observed that better constraints on the properties of liquid water clouds underneath cirrus layers could significantly improve the retrievals. Therefore, a third study presents a modification of this algorithm, allowing us to simultaneously retrieve the properties of one cirrus layer and two layers of liquid water clouds underneath. This ‘multi-layer’ algorithm is applied to a large amount of cases in order to assess its effectiveness. Comparisons with several operational products indicate a good coherence of our retrievals
Hannachi, Riadh. « Etude expérimentale et propriétés radiatives d'un plasma thermique induit par impact laser à la surface de milieux aqueux eau-chlorure de calcium/chlorure de magnésium/chlorure de sodium ». Toulouse 3, 2007. http://thesesups.ups-tlse.fr/89/.
Texte intégralThis thesis is part of a project concerning the development of a process which enables the detection of pollutants in water using a laser ablation device. The impact of a laser beam on a material allows to vaporize it and to generate a plasma. The elementary composition of the sample is obtained by the spectroscopic analysis of the ionized gas. This method, applicable to any kind of materials (solid, liquid, gaseous, insulating or conductive) is known as LIBS (Laser induced Breakdown Spectroscopy). A Nd: Yag laser (lambda = 532 nm, pulse duration 4ns, deposited energy 30 mJ, frequency 5 Hz) is used to generate a plasma on the surface of liquid targets containing weak proportions of alkaline salts (5. 10-4 to 2 mol/liter of CaCl2, MgCl2 and NaCl). This work allowed to test the sensibility of the process and to define the detection limits of the species Ca, Mg and Na acting as impurities. Various optical emission spectroscopy diagnosis techniques based upon the assumption of local thermodynamic equilibrium (LTE) are used to characterize the plasma plume in its extinction phase (temperature and species densities). The second part of this thesis is dedicated to the development of calculation codes enabling the determination of the chemical equilibrium composition and radiative properties: the mean absorption coefficients k\lambda (m-1) by frequency bands and the net emission coefficient epsilon\N (W. M-3. Sr-1). .
Parveaud, Claude-Eric. « Propriétés radiatives des couronnes de Noyers (Juglans nigra x J. regia) et croissance des pousses annuelles - Influence de la géométrie du feuillage, de la position des pousses et de leur climat radiatif ». Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2006. http://tel.archives-ouvertes.fr/tel-00087909.
Texte intégralBastardis, Roland. « Dérivations et extractions de hamiltoniens modèles pour l'étude de composés à propriétés électroniques remarquables ». Toulouse 3, 2007. http://thesesups.ups-tlse.fr/82/.
Texte intégralThe goal of this thesis is to identify the microscopic mechanisms responsible for the macroscopic of molecular and crystalline magnetic compounds. A first part is devoted to the explicitly correlated ab initio methods allowing the study of such compounds. We propose an original method to introduce the dynamical polarization effects though a series of constrained SCF calculations. Then we show how the embedded cluster method combined with the effective Hamiltonian theory makes possible the rational and controlled extraction of model Hamiltonians likely to reproduce the macroscopic properties. We are interested in the isotropic deviations from Heisenberg behavior and propose a new Hamiltonian including a three-body operator susceptible to change the collective properties. The following chapter compares the capabilities of the double exchange, Heisenberg and Hubbard Hamiltonians to reproduce the chemical physics of doped-manganites. It is shown that the physics of a Hubbard Hamiltonian is contained in the simpler double exchange and Heisenberg Hamiltonians, in the case of a Mn dimer bridged by an oxygen, and that the energy expressions obtained from these last two Hamiltonians are analytically identical. Finally, we show that only a double exchange Hamiltonian, taking account both non-Hund state effects and a Heisenberg antiferromagnetic contribution, accurately describes the microscopic physics of these compounds
Hartmann, Jean-Michel. « Etude de l'absorption infra-rouge par des mélanges gazeux H2O-CO2-CO-Air à température élevee : modélisation, pour l'ingenieur, des propriétés radiatives : approches théorique et expérimentale de l'élargissement par collisions de raies de H2O et CO ». Châtenay-Malabry, Ecole centrale de Paris, 1986. http://www.theses.fr/1986ECAP0013.
Texte intégralLorrette, Christophe. « Outils de caractérisation thermophysique et modèles numériques pour les composites thermostructuraux à haute température ». Phd thesis, Université Sciences et Technologies - Bordeaux I, 2007. http://tel.archives-ouvertes.fr/tel-00410254.
Texte intégralCalonne, Neige. « Physique des métamorphoses de la neige sèche : de la microstructure aux propriétés macroscopiques ». Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI047/document.
Texte intégralThe main objective of the thesis is to improve our knowledge about dry snow metamorphismand its physical description, at the microscopic (ice grains and pores) andmacroscopic (snow layer) scales. First, the homogenization method of multiple scaleexpansions is applied for the first time to the physics involved in dry snow metamorphism.This way, we present the equivalent macroscopic descriptions of heat and vaportransfers derived from the physical description at micro-scale. We consider at the grainscale diffusion, conduction, and forced convection, coupled to phase changes (sublimationand deposition). Second, the effective properties of transport arising in the macroscopicdescriptions (effective thermal conductivity, effective coefficient of vapor diffusion, andintrinsic permeability) are estimated from 3D images of snow spanning the whole range ofdensity and snow types. Finally, the monitoring of metamorphism with time is considered.The relationship between the microstructure and the effective properties of a snow layerare investigated during temperature gradient metamorphism using 3D images. We presentthen a new cryogenic cell that we developed to monitor the grain to grain evolution of asnow sample by time-lapse tomography during the metamorphism, and which operates atroom temperature