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Rozprawy doktorskie na temat "Plasmas (gaz ionisés) – Turbulence – Mesure"
Vermare, Laure. "Mesures de l'activité magnétohydrodynamique et de la micro-turbulence par réflectométrie à balayage". Aix-Marseille 1, 2005. http://www.theses.fr/2005AIX11014.
Pełny tekst źródłaMoreau, Philippe. "Développement d'un réflectomètre micro-onde hétérodyne à balayage ultra rapide : étude de l'influence de la turbulence du plasma sur la mesure des profils de densité électronique". Aix-Marseille 1, 1997. http://www.theses.fr/1997AIX11019.
Pełny tekst źródłaScipioni, Angel. "Contribution à la théorie des ondelettes : application à la turbulence des plasmas de bord de Tokamak et à la mesure dimensionnelle de cibles". Electronic Thesis or Diss., Nancy 1, 2010. http://www.theses.fr/2010NAN10125.
Pełny tekst źródłaThe necessary scale-based representation of the world leads us to explain why the wavelet theory is the best suited formalism. Its performances are compared to other tools: R/S analysis and empirical modal decomposition method (EMD). The great diversity of analyzing bases of wavelet theory leads us to propose a morphological approach of the analysis. The study is organized into three parts. The first chapter is dedicated to the constituent elements of wavelet theory. Then we will show the surprising link existing between recurrence concept and scale analysis (Daubechies polynomials) by using Pascal's triangle. A general analytical expression of Daubechies' filter coefficients is then proposed from the polynomial roots. The second chapter is the first application domain. It involves edge plasmas of tokamak fusion reactors. We will describe how, for the first time on experimental signals, the Hurst coefficient has been measured by a wavelet-based estimator. We will detail from fbm-like processes (fractional Brownian motion), how we have established an original model perfectly reproducing fBm and fGn joint statistics that characterizes magnetized plasmas. Finally, we will point out the reasons that show the lack of link between high values of the Hurst coefficient and possible long correlations. The third chapter is dedicated to the second application domain which is relative to the backscattered echo analysis of an immersed target insonified by an ultrasonic plane wave. We will explain how a morphological approach associated to a scale analysis can extract the diameter information
Scipioni, Angel. "Contribution à la théorie des ondelettes : application à la turbulence des plasmas de bord de Tokamak et à la mesure dimensionnelle de cibles". Thesis, Nancy 1, 2010. http://www.theses.fr/2010NAN10125.
Pełny tekst źródłaThe necessary scale-based representation of the world leads us to explain why the wavelet theory is the best suited formalism. Its performances are compared to other tools: R/S analysis and empirical modal decomposition method (EMD). The great diversity of analyzing bases of wavelet theory leads us to propose a morphological approach of the analysis. The study is organized into three parts. The first chapter is dedicated to the constituent elements of wavelet theory. Then we will show the surprising link existing between recurrence concept and scale analysis (Daubechies polynomials) by using Pascal's triangle. A general analytical expression of Daubechies' filter coefficients is then proposed from the polynomial roots. The second chapter is the first application domain. It involves edge plasmas of tokamak fusion reactors. We will describe how, for the first time on experimental signals, the Hurst coefficient has been measured by a wavelet-based estimator. We will detail from fbm-like processes (fractional Brownian motion), how we have established an original model perfectly reproducing fBm and fGn joint statistics that characterizes magnetized plasmas. Finally, we will point out the reasons that show the lack of link between high values of the Hurst coefficient and possible long correlations. The third chapter is dedicated to the second application domain which is relative to the backscattered echo analysis of an immersed target insonified by an ultrasonic plane wave. We will explain how a morphological approach associated to a scale analysis can extract the diameter information
De, Dominici Gregory. "Understand and predict the power threshold leading to reduced turbulent transport at the edge of tokamak plasma". Electronic Thesis or Diss., Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0320.
Pełny tekst źródłaA model based on a model which natively contained turbulence and turbulence driven flow. It has been improved to include the diamagnetic effects, the magnetic fluctuations, and in this work, we study the parametric dependencies of the observed L-H transition power threshold with respect to the ion mass. By including the diamagnetic effects in our model, we allow the competition between the drift waves and the interchange instabilities. This competition is here studied using fixed gradient simulation. We show in this work that the diamagnetic effects are stabilizing for a resistivity close to experimental conditions. Electromagnetic effects lead to more unstable modes at realistic resistivities. Moreover, a quasilinear estimation of the turbulent flux is able to qualitatively grasp the competition between the drift waves and the interchange and the behaviour of the nonlinear electrostatic turbulent flux with resistivity and plasma beta. Another parametric dependency of the turbulence is studied, by changing the mass of the isotope. This is known as the isotope effect. We show here that the turbulence is reduced when the ion mass is increased. Finally, the characteristic times of the turbulence are studied.Magnetic fluctuations have a dramatic effect on correlation times of the turbulence, by drastically reducing them. Accounting for these results, we present in this work the auto-generation of a transport barrier with electromagnetic simulations of edge turbulence, when the heat power is higher than a threshold, using flux-driven simulations. We have then changed the isotope, and correspondingly to experiments, the power threshold is lower for higher isotope mass
Fleurence, Emmanuel. "Descriptions fluide et cinétique d'une turbulence d'interchange dans un plasma magnétisé". Nancy 1, 2005. http://docnum.univ-lorraine.fr/public/SCD_T_2005_0141_FLEURENCE.pdf.
Pełny tekst źródłaThe kinetic and fluid descriptions of the interchange instability are compared in the linear and non-linear regimes. The prediction of the turbulent transport in tokamaks is the general framework. The kinetic model is two dimensional in space, and one dimensional in energy. The fluid analogue retains the dynamics of both density and pressure. The closure, which acts on the heat flux, is collisional. The fluid system is shown to be equivalent to two Vlasov-type equations for two distinct monokinetic distribution functions. This allows one to use the same numerical tool to run non-linear simulations in kinetic and fluid. For similar linear characteristics, the level of heat turbulent transport is larger in fluid than in kinetics, by orders of magnitudes. Zonal flows do not explain the whole discrepancy. As a matter of fact, the distribution function departs significantly from a maxwellian, so that the adopted closure is failing. An alternative collisionless closure is proposed. It aims at fitting the quasi-linear entropy production rates. In this case, the kinetic and fluid linear properties can be made similar
Futatani, Shimpei. "Etude du transport turbulent des impuretés dans les plasmas de tokamak". Aix-Marseille 1, 2009. http://www.theses.fr/2009AIX11056.
Pełny tekst źródłaThe aim of this thesis is to understand impurity transport dynamics in the magnetically confined fusion plasmas. This includes the influence of the turbulent field which induces an anomalous transport in the plasma. Furthermore, this work demonstrates remarkable aspects for impurity transport in two different instabilities: ``ion temperature gradient (ITG) and trapped electron mode (TEM)''. It is shown that in presence of an internal transport barrier (ITB) created by a reversed magnetic shear configuration, one can obtain the reversal of impurity pinch velocity which can change from inward direction to outward direction. This scenario is favourable for expelling impurities from the central region and decontaminating the core plasma. The mechanism of pinch reversal is attributed to a change of direction of the curvature pinch and to a modification of the dominant underlying instability caused by a change of the gradient of the ion temperature which is a consequence of the ITB formation
Zekri, Stéphane. "Approche hamiltonienne de la turbulence faible de Langmuir". Aix-Marseille 1, 1993. http://www.theses.fr/1993AIX11022.
Pełny tekst źródłaBrun, Cédric. "Propriétés statistiques des modes de Fourier en turbulence dévéloppée". Nice, 2001. http://www.theses.fr/2001NICE5597.
Pełny tekst źródłaThis thesis deals with the intermittency in fully developed turbulence. In a first part, we study the statistical properties of Fourier modes in a turbulent flow. These quantities are often evoked to describe turbulence. Recent experimental studies demonstrated that the Fourier modes of vorticity and temperature are only weakly intermittent in the inertial range of scales. We confirm these results by measurements done in direct numerical simulations. Our work proposes an explanation of the observed effects and some more general remarks. The second part of this work is devoted to the intermittency of a passive scalar. We use an approach based on the evolution equations through scales of the density probability function of the passive scalar increments. These equations are derived from first principles, under different hypothesis of isotropy ; the closure problem is reduced to the determination of some conditional averages. We carry out a study by means of direct numerical simulations in order to provide the data needed to validate this approach. This work demonstrates the influence of the large scales in the inertial statistical properties of the mixing
Tretinnikov, Pavel. "New developments on the interpretative model of ITER diagnostics using microwaves". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0027.
Pełny tekst źródłaThe turbulence in thermonuclear fusion plasma can lead to increase of the plasma transport coefficient that enhances the particles and energy losses therefore deteriorates the plasma confinement. That is why measurements of the plasma turbulence is important for description of the plasma transport processes. Microwave plasma diagnostics is an efficient kind of the active plasma diagnostics to characterize the turbulence. Their principles are based on the collection of information integrated over the probed plasma volume, and printed on the reflected or scattered waves reaching the detector, for which interpretative models are required to extract the turbulence properties. The radial correlation reflectometry (RCR) and the Doppler reflectometry are widely used technics that provide information on plasma turbulence characteristics. The Collective Thomson Scattering (CTS) is a valuable microwave diagnostic that can give the information about such plasma parameters as the bulk ion temperature, bulk ion composition, the fast particles (alpha particles or ions of a heating beam) velocity distribution. The knowledge of the alpha particle velocity distribution is especially interesting and important to evaluate the ITER performance where the energy amplification of plasma heating power Q is expected to achieve the value about 10. The actual data analysis of the microwave diagnostics, or interpretations of a measured signal is fulfilled assuming a smooth Gaussian probing beam. It was demonstrated that the microwave beams can be significantly distorted due to the edge plasma turbulence, that may lead to misleading interpretations of the diagnostic signal, based on the microwaves, so the diagnostics interpretative models should be analyzed taken into account to the probing beam distortion. The improvement of the microwave diagnostics interpretative models is the main object of the study presented in this thesis.The aim of this PhD work is to include these missing effects in an interpretative model for CTS using X-mode probing beam
Książki na temat "Plasmas (gaz ionisés) – Turbulence – Mesure"
Yoshizawa, Akira. Plasma and fluid turbulence: Theory and modelling. Bristol: Institute of Physics Pub., 2003.
Znajdź pełny tekst źródłaOraevsky, V. N. Non-Linear Instabilities in Plasmas and Hydrodynamics. CRC Press LLC, 2017.
Znajdź pełny tekst źródłaItoh, K., 吉澤 徴 i S. I. Itoh. Plasma and Fluid Turbulence. Taylor & Francis Group, 2010.
Znajdź pełny tekst źródłaYoshizawa, A., K. Itoh i S. I. Itoh. Plasma and Fluid Turbulence. Taylor & Francis Group, 2019.
Znajdź pełny tekst źródłaItoh, K., 吉澤 徴 i S. I. Itoh. Plasma and Fluid Turbulence: Theory and Modelling. Taylor & Francis Group, 2002.
Znajdź pełny tekst źródłaItoh, K., 吉澤 徴 i S. I. Itoh. Plasma and Fluid Turbulence: Theory and Modelling. Taylor & Francis Group, 2002.
Znajdź pełny tekst źródłaItoh, K., 吉澤 徴 i S. I. Itoh. Plasma and Fluid Turbulence: Theory and Modelling. Taylor & Francis Group, 2002.
Znajdź pełny tekst źródłaItoh, K., 吉澤 徴 i S. I. Itoh. Plasma and Fluid Turbulence: Theory and Modelling. Taylor & Francis Group, 2002.
Znajdź pełny tekst źródłaItoh, K., 吉澤 徴 i S. I. Itoh. Plasma and Fluid Turbulence: Theory and Modelling (Series in Plasma Physics). Taylor & Francis, 2002.
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