Letteratura scientifica selezionata sul tema "Gaz polyatomiques"
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Articoli di riviste sul tema "Gaz polyatomiques"
Aufrère, Loı̈c, e J. Gilbert Méolans. "Fonction de distribution pour les gaz polyatomiques dans la couche de Knudsen. Solution approchée de l'équation de Boltzmann". Comptes Rendus de l'Académie des Sciences - Series IIB - Mechanics 329, n. 2 (febbraio 2001): 117–23. http://dx.doi.org/10.1016/s1620-7742(01)01304-6.
Testo completoDesvillettes, Laurent. "Sur un modèle de type Borgnakke—Larsen conduisant à des lois d'énergie non linéaires en température pour les gaz parfaits polyatomiques". Annales de la faculté des sciences de Toulouse Mathématiques 6, n. 2 (1997): 257–62. http://dx.doi.org/10.5802/afst.864.
Testo completoMéolans, J. Gilbert, e Loı̈c Aufrère. "Interaction d'un gaz polyatomique avec une paroi : expression du noyau". Comptes Rendus de l'Académie des Sciences - Series IIB - Mechanics 329, n. 3 (marzo 2001): 201–5. http://dx.doi.org/10.1016/s1620-7742(01)01318-6.
Testo completoTesi sul tema "Gaz polyatomiques"
Dion, François. "Dynamique de systèmes polyatomiques et polyélectroniques en champ laser intense". Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/30325.
Testo completoThis thesis deals with the dynamics of molecules in intense laser fields in the quasi-static picture. Two types of dynamics are considered, namely the dynamics of nuclear motions, i.e. vibrations and molecular dissociations, in the first part of the thesis, and the dynamics of electronic motions, excitations and ionization of a N-electron molecule, in the second part. In the first part, we will be concerned particularly about a vibrational trapping mechanism called Dynamical Dissociation Quenching (DDQ), applicable in the quasi-static regime, and two objectives in this respect are set: The generalization of the concept for strong-field induced dynamical structural changes to polyatomic molecules, and the search for optimal conditions for the control of the molecule/field synchronization that underlies the DDQ effect. To this end, new parameters are explored, among them is a laser frequency chirp, and a set of parameters defining a proper pump-probe setting and deduced from properties of the mean trajectory of the field-free vibrational wavepacket. In the second part of the thesis, a methodology recently developed for the computation of multiconfigruation wavefunctions describing a N-electron system interacting with an ulrashort, intense laser pulse, is used to describe the dynamics of electronic excitations and ionization of the linear molecule CO2 in an intense Infra-red laser pulse. Emphasis is placed on manyelectron, many-orbital effects on momentum (velocity) distributions of the photoelectron, and more specifically, on the Laser-Induced Electron Diffraction (LIED) spectra, as well as on their robustness under molecule/field misalignment.
Bekstein, Alexandre. "Données de base des ions polyatomiques dans les gaz d'échappement : modélisation et validation expérimentale". Toulouse 3, 2009. http://thesesups.ups-tlse.fr/596/.
Testo completoThese research works are devoted to the numerical and experimental determination of polyatomic ions swarm data in flue gases. Then, we used the data to simulate non-thermal discharges at atmospheric pressure and to show the role of polyatomic ions in the physics of the discharge. In this work, we calculated the transport coefficients (reduced mobility, diffusion coefficients, reaction rates, etc) of the polyatomic ions N4+, O4+ et N2O2+ in N2, O2 and dry air, and of H3O+, H5O2+ et H7O3+ in N2. The model used to determine the swarm data consists, on the one hand, on the JWKB approximation and an interaction potential and, on the other hand, on an optimised Monte Carlo code that calculates the transport coefficients from a set of collision cross sections. Moreover, by using the pulsed Townsend experiment, we measured the transport coefficients of ions and/or electrons in various gases (CO2, O2, N2/O2 et N2/O2/CO2). Then, we measured the transport coefficients of the polyatomic ion O4- in O2 and N2/O2 that we completed numerically in N2, O2 and dry air. Finally, non-thermal discharge simulations in dry air were done to determine the role of the polyatomic ions N4+, O4+ et N2O2+. Results show the great influence of these ions on the chemistry of the discharge while they affect poorly its dynamics. It is then obvious that in the frame of the application to non-pollution reactors, the polyatomic ions must be considered for their role in the chemical kinetics of the non-pollution process
Pavić, Milana. "Mathematical modelling and analysis of polyatomic gases and mixtures in the context of kinetic theory of gases and fluid mechanics". Thesis, Cachan, Ecole normale supérieure, 2014. http://www.theses.fr/2014DENS0033/document.
Testo completoConsidering polyatomic gases, we first propose two independent hierarchies of the moment equations, which allow to obtain conservation laws for mass density, momentum and total energy of a gas. Such hierarchies are usually truncated at some order. A method which provides an appropriate solution to the closure problem is the maximization of entropy method. We formulate a variational problem and explore in detail the physical case of 14 moments. We study mixtures of polyatomic gases in which the distribution function of each species converges towards a Maxwellian distribution function, each with its own bulk velocity and temperature. Balance laws for mass density, momentum and energy can be obtained. In particular, the phenomenological coefficients of extended thermodynamics can be determined from the source terms. Regarding mixtures of monatomic gases, we discuss the diffusion asymptotics of the Boltzmann equations. The Hilbert expansion yields two equations. The first equation allows to state that the mixture is close to equilibrium. The second equation is a linear functional equation in the velocity variable. We prove the existence of a solution to this equation. On the one hand, when molecular masses are equal, the techniques introduced by Grad can be used. On the other hand, we propose a new approach, which only holds when molecular masses are different
Levi, Di Leon Rémi. "Etude théorique et expérimentale de l'absorption par CO2 et H2O dans le domaine infrarouge à température élevée". Châtenay-Malabry, Ecole centrale de Paris, 1986. http://www.theses.fr/1986ECAP0026.
Testo completoBorsoni, Thomas. "Contributions autour de l'équation de Boltzmann et certaines de ses variantes". Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS099.
Testo completoWe study some variants of the Boltzmann equation, the latter describing, via a classical approach, single and monatomic rarefied gases at the mesoscopic scale. First, we propose a general framework for Boltzmann modelling of polyatomic gases, encompassing a wide class of pre-existing models and allowing to build new ones. Primarily presented for a single gas, the framework is then extended to mixtures, within which we allow binary chemical reactions. Second, we focus on a singular type of polyatomic gas, the molecules of which undergo resonant collisions, and prove a compactness property of the linearized operator related to this model. In order to make the latter resonant framework more flexible, we then propose a Boltzmann formalism with quasi-resonant collisions, study its key properties and conduct numerical experiences to support our understanding of them. Third, we turn our attention towards a Boltzmann equation which includes Pauli's exclusion principle, notably used in the study of electron distributions in semi-conductors. We develop a method that allows to transfer some functional inequalities, related to entropy, which are known in the classical case, to this quantum case. As a consequence, we use these new inequalities to obtain an explicit rate of relaxation to equilibrium for solutions to the homogeneous Boltzmann-Fermi-Dirac equation with cut-off hard potentials
Billoux, Tommy. "Élaboration d'une base de données radiatives pour des plasmas de type CwHxOyNz et application au transfert radiatif pour des mélanges air, CO2 et CO-H2". Toulouse 3, 2013. http://thesesups.ups-tlse.fr/2254/.
Testo completoThe calculation of the radiative properties of plasma requires the elaboration of a spectroscopic database. The objective of this thesis consists on one hand, to establish a spectroscopic database for various molecular plasmas and on the other hand, to use partially this database for the calculation of terms of radiative power in thermal plasmas created by electric arcs. These calculations concern plasmas containing elements C, H, O and N, covering a wide variety of applications relative to CO2 mixtures (high voltage circuit breakers, atmospheric re-entry), air at various pressures (plasma torches), CO/H2 mixtures (creation of synthesis gas by the gasification of biomass). An additional, but important objective of our work was to develop a tool necessary for the experimental characterization of plasmas, by comparison of the observations with the theoretical spectra calculated with our algorithm, to estimate or validate the deduced temperature and densities. We have elaborated an algorithm allowing the calculation of the emission and absorption spectra under the assumption of local thermodynamic equilibrium (LTE) for various mixtures of CwHxOyNz. The database was extended to a wide range of temperatures (300-30kK) and pressures (1bar-100 bar) to investigate numerous applications. We took into account using a "line by line" method the whole radiative phenomena involved in a plasma to treat accurately the lines and the continuum. The calculation of the line and continuum spectra was developed using previous works developed in the team. The atomic lines were calculated using the energy levels oscillator strengths extracted from the literature concerning 22276 lines (C, C+, C2+, C3+, N, N+, N2+, N3+, O, O+, O2+, O3+, H). The atomic continuum was calculated by analytical formulae describing the bound-free (photodetachment, photoionization) and free-free (Bremsstrahlung) transition. The molecular continuum was modeled from experimental cross-sections of photodissociation and photoionization extracted from literature. The most important contribution of this work concerned the calculation of molecular spectra. We took into account 46 electronic systems for the 12 diatomic molecules : OH, CH, CH+, H2, CO, CO+, C2, O2, NO, CN, N2, N2+. The diatomic molecular spectra were calculated by means of spectroscopic constants based on the resolution of the molecular Hamiltonians. We have developed a method for the calculation of the transition probabilities in the case of hydrogen molecules to take into account the rotational dependence of the transition probabilities. Our results were systematically compared with the literature. Finally 18 polyatomic molecules (including CO2 and H2O) were described by using some free access databases. Physical modeling of industrial processes concerning electric arcs requires som approximated procedures to solve the radiative transfer equation such as the Net Emission Coefficient or the mean absorption coefficient approximation. We present the results obtained for air, CO2 and CO/H2 mixtures at various pressures and proportions in the case of the approximation of the net emission coefficient. Finally, we propose a qualitative study of the influence of the molecular radiation by means of a simplified one-dimensional model of the radiative transfer for various configurations of plasma. If the temperature in the hot regions exceeds 10 000K, the molecular influence on the radiative transfer is rather low. However, for colder plasmas at the boundary between thermal plasmas and combustion, the presence of molecules is essential and we highlighted their low-temperature important influence through the infrared brilliance
Benseddik, Mohammed. "Etude de la dynamique d'un mélange de gaz monoatomique-polyatomique de massses très différentes : cas du SF6-He". Bordeaux 1, 1988. http://www.theses.fr/1988BOR10634.
Testo completoBenseddik, Mohammed. "Etude de la dynamique d'un mélange de gaz monoatomique-polyatomique de masses très différentes cas du SF-He /". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376029699.
Testo completo