Tesis sobre el tema "Distribution des temps de relaxation"
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El, Bassiri Fatima-Ezzahra. "Étude de la réaction de réduction de l'oxygène : application de la spectroscopie d'impédance à un système innovant dérivé de Ca3Co4O9+δ". Electronic Thesis or Diss., Centrale Lille Institut, 2024. http://www.theses.fr/2024CLIL0003.
Texto completoIn the context of energy transition towards carbon neutrality by 2050, Solid Oxide Fuel Cells (SOFCs) and Solid Oxide Electrolysis Cells (SOECs) offer real potential for use via hydrogen as an energy carrier. The aim of this thesis is to understand the electrochemical processes in these systems, with a view to improving their performance and durability. The technique chosen is impedance spectroscopy to study the oxygen reduction reaction. This is a complex reaction involving several stages: diffusion of molecular oxygen, dissociation of molecular oxygen at the electrode surface, diffusion of oxygen or partially ionized atoms at the solid surface or their incorporation into the solid, charge transfer, diffusion of ions into the solid, etc. Whereas gaseous diffusion is a slow process, ionic diffusion in solids is rapid. The detailed study of impedance spectra measured on symmetrical cells enables us to define the steps that limit the reaction and identify the directions to take to optimize the systems. This requires the measurement of reliable data. The Kramers-Krönig test is used to check the quality of the data. From these data, it is possible to calculate the distribution function of the relaxation times characteristic of the phenomena involved within the cell, but as the number of data is finite, solving the equation associated with this function is not straightforward. The aim of this thesis was first to define a methodology for the rigorous processing of impedance spectra measured on symmetrical cells consisting of a gadolinium-doped ceria electrolyte on which a model electrode based on Ca3Co4O9+δ, an innovative electrode material studied for several years at UCCS, has been deposited. Unlike state-of-the-art materials, calcium cobaltites have the advantage of not containing rare earths and, above all, of presenting an expansion coefficient of the same order of magnitude as that of the electrolytes used for these applications, giving rise to the hope of increased durability. Initially used as a model electrode, the substitution of strontium for calcium in this compound and its use as a composite with ceria enabled the specific features required for the application to be achieved: a specific surface resistance of less than or equal to 0.15 Ω.cm² at 700°C. The study was then extended to the characterization of complete cells. This thesis was funded by the Hauts de France Region and Centrale Lille. Part of the work was carried out as part of the MODTESTER project, a BPI-funded Eurostars Eureka project led by Fiaxell, a Swiss SME, and as part of the European NOUVEAU project, which focuses on the search for new, sustainable and reusable electrode and interconnector materials for high-temperature water electrolysis
Gex, Vincent. "Suivi in situ de la genèse des matériaux par relaxométrie RMN : application aux catalyseurs". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00829405.
Texto completoJaffel, Hamouda. "Caractérisation multi-échelles de matériaux poreux en évolution : cas du plâtre". Phd thesis, Ecole Polytechnique X, 2006. http://tel.archives-ouvertes.fr/tel-00122888.
Texto completoFaloss, Mohammed. "Mesure polarimetrique du temps de relaxation transversal en resonance magnetique". Clermont-Ferrand 2, 1986. http://www.theses.fr/1986CLF2S864.
Texto completoFaloss, Mohammed. "Mesure polarimétique du temps de relaxation transversal en résonance magnétique". Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375974612.
Texto completoVincendon, Marc. "Introduction de la relaxation dans la théorie de la fonctionnelle de la densité dépendant du temps". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30253/document.
Texto completoThis thesis presents works in 5 areas where we aim at improving or extending toward dissipative cases the TDLDA (Time Dependent Local Density Approximation) method. - The propagation in a natural basis allows first to formalize technics which are a prerequisite to the operation of methods accounting for collisions. - The SIC (Self Interaction Correction) method improves the efficiency of the full Self Interaction Correction. It allows to use efficiently this method in complex conditions such as mixed systems of metallic and covalent molecules. - The TDCDFT (Time Dependent Current and Density Functional Theory) allows to consider some time delay effects by introducing a functional of time and current. It was extended to a 3 dimensional case on little atoms and clusters. The results confirm the damping already evidenced in previous works, but TDCDFT does not predict correctly the non-linear dependence of the damping versus the excitation energy. - The TDHF((Stochastic Time-Dependent Hartree Fock) method introduces correlation by a method of stochastics jumps, in separate time-histories. This method has been modified (Average Stochastic TDHF) to use only one mean field, the jumps are then accounted for by transition probabilities, which allow to modify the occupation numbers. In this form it can work only in a closed box. We show here its extension to an open calculation space. - The RTA (Relaxation Time Approximation) was developed in a 2 dimension model. We show here the extension of this method to 3 dimensions. The amplitude of the numerical method leads to the introduction of new optimization methods. But the results do confirm the tendencies observed in the 2 dimensional case. This method also allows calculation on new molecules
OIKRIM, SAID. "Determination polarimetrique du temps de relaxation transversale en resonance electrique electronique". Clermont-Ferrand 2, 1989. http://www.theses.fr/1989CLF21171.
Texto completoBaral, Paul. "Caractérisation mécanique des phénomènes dépendants du temps par nanoindentation instrumentée en température". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC038/document.
Texto completoThis manuscript presents a study on the mechanical properties’ characterization of time dependent phenomena using instrumented nanoindentation at different temperatures.This research subject treats the development of methods dealing with the adaptation of classical indentation methodologies to high temperature characterizations. Bringing a better understanding of time and temperature dependent phenomena at a local scale is the first aim of the methods developed. The second objective is to compare materials behaviors measured at micro and macro-scale.The proposed methods are based on indentation relaxation tests. Their development and applications to polymers and metals characterization are studied analytically and experimentally. The analytical study shows that the indentation relaxation test is equivalent to the uniaxial one. This study also highlights the great influence of loading kinetics on the measured relaxation behavior.The proposed experimental study in temperature permits the extraction of the strain rate sensitivity and the activation energy of the viscous phenomena. However, thermal drift limits the characterization duration – i.e. the maximum experimental time remains limited to a couple of minutes. Another experimental study configuration, at room temperature, opens the way to longer test durations. It is based on the equivalence of contact area and stiffness for a homogeneous material. With this configuration, we successfully hold the contact area constant for 10 hours without any evidences of drift.Eventually, the high temperature nanoindentation application to in situ microstructural changes characterization of an aluminum alloy is studied. Measurements and limitations are carefully discussed for a better understanding of the studied phenomenon. The results show that the recrystallization kinetics can be successfully described with reduced test duration and samples’ set
Dias, Claude. "Le temps et les contrats de distribution commerciale". Versailles-St Quentin en Yvelines, 2010. http://www.theses.fr/2010VERS001S.
Texto completoThis thesis, which is entitled "the times and the contracts of distribution", tries to show the close link between the concept of time and the various contracts of distribution. The occurrences of time are numerous during the contract of distribution’s life, which remains a successive contract. Time can be seen as a common denominator of many litigations which the subject has recently known and continues to know nowadays. Time is also the reason of various and characteristics contracts’ study. This study proposes to highlight the interaction between the times and the contracts of distribution
Nicot, Benjamin. "Détermination de la viscosité des pétroles bruts lourds par relaxation RMN". Paris 6, 2007. http://www.theses.fr/2007PA066639.
Texto completoPetroleum exploration and production has a tremendous need of understanding the underground reservoir rock and saturating uids characteristics. NMR relaxation times (T1, T2) measurements is a powerful technique to provide informations such as porosity, permeability, and oil viscosity (in the range 1-10000cP). With increasing energy demand, heavy crude oil (>10000cP) are now produced, using complex Enhanced Oil Recovery (EOR) techniques which require a good estimation of the oil viscosity in the reservoir. In this work, we study in details the reasons why the correlations available in the literature fail to estimate heavy crude oil viscosity. We identify several key parameters in the NMR-viscosity correlation. The e ect of molecular weight is studied on a polymer system. The e ect of inter proton distance is discussed and the presence of paramagnetic species is investigated. Besides, the problem of short relaxation time detection is studied in details and, coupled with a distribution of correlation times, lead to the proposition of a methodology to build NMR-viscosity correlations. These correlations have been tested on experimental data from this work and the literature, and provide better viscosity prediction for heavy oils than the correlations from the literature
Swaminathan, Bhargav Prasanna. "Gestion prévisionnelle des réseaux actifs de distribution - relaxation convexe sous incertitude". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT039/document.
Texto completoPower systems are faced by the rising shares of distributed renewable energy sources (DRES) and the deregulation of the electricity system. Distribution networks and their operators (DSO) are particularly at the front-line. The passive operational practives of many DSOs today have to evolve to overcome these challenges. Active Distribution Networks (ADN), and Active Network Management (ANM) have been touted as a potential solution. In this context, DSOs will streamline investment and operational decisions, creating a cost-effective framework of operations. They will evolve and take up new roles and optimally use flexibility to perform, for example, short-term op- erational planning of their networks. However, the development of such methods poses particular challenges. They are related to the presence of discrete elements (OLTCs and reconfiguration), the use of exogenous (external) flexibilities in these networks, the non-linear nature of optimal power flow (OPF) calculations, and uncertainties present in forecasts. The work leading to this thesis deals with and overcomes these challenges. First, a short-term economic analysis is done to ascertain the utilisation costs of flexibilities. This provides a common reference for different flexibilities. Then, exact linear flexibility models are developed using mathematical reformulation techniques. The OPF equations in operational planning are then convexified using reformulation techniques as well. The mixed-integer convex optimisation model thus developed, called the novel OP formulation, is exact and can guarantee globally optimal solutions. Simulations on two test networks allow us to evaluate the performance of this formulation. The uncertainty in DRES forecasts is then handled via three different formulations developed in this thesis. The best performing formulations under uncertainty are determined via comparison framework developed to test their performance
Tsemekhman, Vadim. "Charge relaxation, current distribution, and breakdown of the quantum Hall effect /". Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9739.
Texto completoZinsou, Paul Komlan. "Amélioration d'un spectromètre de mesure des temps de relaxation courts. Application aux matériaux vitreux". Toulouse 3, 1996. http://www.theses.fr/1996TOU30050.
Texto completoKASSAB, GHAZI. "Etude des milieux poreux par rmn : instrumentation specifique et etude des temps de relaxation". Paris 6, 1992. http://www.theses.fr/1992PA066524.
Texto completoYu, Wing-chi Gigi. "The effect of practice distribution on the training of laryngeal muscle relaxation". Click to view the E-thesis via HKU Scholors Hub, 2005. http://lookup.lib.hku.hk/lookup/bib/B3827940X.
Texto completo"A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, June 30, 2005." Also available in print.
El, Hajj Christian. "Estimation et classification des temps de relaxation multi-exponentiels en IRM. Application aux tissus végétaux". Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0066.
Texto completoAcquired relaxation data in magnetic resonance imaging makes it possible to conduct fine analysis of tissues composition. Conventionally, the analysis is realized by adopting a mono-exponential model at each voxel of the image, yet, a multi-exponential decay model may provide richer information. However, obtaining and interpreting multi-exponential relaxation time maps at the whole image level, from magnitude MRI images, requires solving a large scale inverse problem. This thesis work proposes algorithms for multiexponential relaxation times and their associated intensities maps reconstruction. These algorithms are based on the maximum-likelihood estimator under the hypothesis of a Rician noise distribution, case of magnitude images, and a spatial regularization favoring the regularity of the maps. The resulting large-scale optimization problem is solved using an iterative descent approach by majorization-minimization coupled with a Levenberg-Marquardt algorithm with step search. Finally, we propose a method for image composition characterization from the estimated parameters using classification algorithms. The developed algorithms in this thesis are applied to vegetal tissue analysis
MATOS, GOMES MARIA JESUS. "Etude des temps de relaxation et des constantes de diffusion de quasi-particules dans cucl". Université Louis Pasteur (Strasbourg) (1971-2008), 1990. http://www.theses.fr/1990STR13096.
Texto completoPolski, Michel. "Structure temporelle des industries : le cas de la distribution". Université Louis Pasteur (Strasbourg) (1971-2008), 1999. http://www.theses.fr/1999STR1EC06.
Texto completoFlandrin, Patrick. "Représentations temps-fréquence des signaux non-stationnaires". Grenoble INPG, 1987. http://www.theses.fr/1987INPG0048.
Texto completoBALME, THIBAUT. "Interet biologique et medical de la resonance magnetique du sodium-23 : revue bibliographique et mesures de temps de relaxation". Lyon 1, 1989. http://www.theses.fr/1989LYO1M080.
Texto completoRaisuddin, K. B. M. "Relaxation methods for simulating large power systems". Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182457060.
Texto completoXu, Bo. "Proton NMR relaxation investigations of particle exfoliation and distribution in polymer/clay nanocomposites". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42936.
Texto completoLopes, Quintas Christian Louis. "Système ultra précis de distribution du temps dans le domaine de la picoseconde". Paris, CNAM, 2001. http://www.theses.fr/2001CNAM0387.
Texto completoTanonkou, Guy Aimé. "Une approche par relaxation lagrangienne pour l'optimisation d'un réseau de distribution : modèles stochastiques et fiables". Metz, 2007. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2007/Tanonkou.Guy_Aime.SMZ0708.pdf.
Texto completoThis thesis deals with the development of models and heuristic algorithms for stochastic distribution network design problems. In the first part, the core decision problem lies in optimally designing a distribution network by finding the optimal distribution centers (DCs) location and the best supplier that would replenish the DCs. The first objective of this project is to join strategics decisions (location of DCs and supplier selection) and operational decision (inventory) in the same optimization model. The goal is to minimize the total fixed location cost, transportation cost, working-inventory cost. The problem is difficult to solve since it integrates all these decisions at the same time with non linear cost function to optimize. We provide an efficient technique which reduces system complexity. The second part of this thesis deals with the design of a distribution network where decisions must be made in the presence of uncertainty. Once the facilities have been constructed in the network, one or more of them may from time to time become unavailable because of some risks. To cope with this uncertain environment, we develop strategic decisions that take into account possible scenarios and strategies need to react when risk events occur. A two-period stochastic programming model is proposed. The goal is to minimize the total first stage cost plus the expected value of the random second stage cost taken trough all scenarios. As solution technique, we propose a Monte Carlo optimization approach combining the sample average approximation scheme and an efficient heuristic based on Lagrangian relaxation to generate efficient solutions and determine tight lower bounds
Tanonkou, Guy Aimé Xie Xiaolan Benyoucef Lyes. "Une approche par relaxation lagrangienne pour l'optimisation d'un réseau de distribution modèles stochastiques et fiables /". [S.l.] : [s.n.], 2007. ftp://ftp.scd.univ-metz.fr/pub/Theses/2007/Tanonkou.Guy_Aime.SMZ0708.pdf.
Texto completoLerbet, François. "Processus cohérents et temps de relaxation dans des verres magnétiques à très basse température : étude par acoustique propagative". Paris 11, 1987. http://www.theses.fr/1987PA112026.
Texto completoWe study the acoustical properties of amorphous magnetic insulators for varying concentration of magnetic impurities between 10,1 % at. And 1,5 % at. . We use a method of propagating wave between 10 MHz and 1000 MHz at very low temperature (from 10 mK up to 10 K) and for magnetic fields up to 60 kOe. With the choice of Ho3+ ions as magnetic impurities, we have been able to point out low energies activated movements of magnetic entities (V 5 K) which are not related at the spin glass transition. The study of tunnelling states in these glasses shows that their classical description in the insulators is no more valid here and that we must take into account the "direct" interaction between tunnelling states and magnetic impurities
FAYE, ANDRE. "Relaxation collisionnelle de l'etat b 3 g de n 2. Etude par spectroscopie de fourier resolue en temps". Paris 11, 2000. http://www.theses.fr/2000PA112298.
Texto completoVinée, Philippe. "Temps de relaxation par RMN du proton et biomécanique de la paroi vasculaire humaine : étude expérimentale in vitro". Université Louis Pasteur (Strasbourg) (1971-2008), 1991. http://www.theses.fr/1991STR1M022.
Texto completoLerbet, François. "Processus cohérents et temps de relaxation dans des verres magnétiques à très basse température étude par acoustique propagative /". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37607302k.
Texto completoSingh, Manish K. "Optimal Operation of Water and Power Distribution Networks". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/86860.
Texto completoMaster of Science
The advent of smart cities has promoted research towards interdependent operation of utilities such as water and power systems. While power system analysis is significantly developed due to decades of focused research, water networks have been relying on relatively less sophisticated tools. In this context, this thesis develops Advanced efficient computational tools for the analysis and optimization for water distribution networks. Given the consumer demands, an optimal water flow (OWF) problem for minimizing the pump operation cost is formulated. Developing a rigorous analytical framework, the proposed formulation provides significant computational improvements without compromising on the accuracy. Explicit network conditions are provided that guarantee the optimality and feasibility of the obtained OWF solution. The developed formulation is next used to solve two practical problems: the water flow problem, that solves the complex physical equations yielding nodal pressures and pipeline flows given the demands/injections; and an OWF problem that finds the best operational strategy for water utilities during power outages. The latter helps the water utility to maximize their service time during power outages, and helps power utilities better plan their restoration strategy. While the increased instrumentation and automation has enabled power utilities to better manage restoration during outages, finding an optimal strategy remains a difficult problem. The operational and coordination requirements for the upcoming distributed resources and microgrids further complicate the problem. This thesis develops a computationally fast and reasonably accurate power distribution restoration scheme enabling optimal coordination of different generators with optimal islanding. Numerical tests are conducted on benchmark water and power networks to corroborate the claims of the developed formulations.
Ji, Ming Chao. "Molecular relaxation dynamics of Anthracene cations studied in an electrostatic storage ring". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10051.
Texto completoThe polycyclic aromatic hydrocarbon (PAH) molecules have been considered as possible carrier of the unidentified infrared emission bands from the interstellar medium (ISM) for about thirty years. The cooling dynamics of the PAH molecules which is essential to estimate their photostability and therefore their lifetime and size distributions in the ISM, has attracted numerous theoretical and experimental studies. In recent years, electrostatic storage devices (ESD) became powerful tool to investigate the cooling regime of molecules and clusters in a large time range from microseconds to seconds. Generally speaking, the decay of the emitted neutral yields due to dissociation of molecular cations or electron detachment of anions in such experiments carries information on the internal energy of the stored molecular ions. In this thesis work, the cooling regimes of anthracene cations are studied by following the time evolution of the internal energy distribution (IED) of the stored anthracene cations. A spontaneous neutral yield curve obtained from the stored molecular ions as a function of the storage time shows three distinguishable regions. The three regions indicate different cooling regimes at corresponding storage time range, i.e., the dissociation mechanism of the molecule dominates at storage time t < 1 ms, quenching of the dissociation by radiative cooling processes occurs during 1 < t < 3 ms and radiative cooling governs at t > 3 ms
Mechti, Redouane. "Contribution à la résolution des problèmes de tournées de véhicules avec fenêtres de temps et composition de flotte". Versailles-St Quentin en Yvelines, 1999. http://www.theses.fr/1999VERS0023.
Texto completoEmerit, Valérie. "Etude quantitative des images en imagerie de résonance magnétique nucléaire : détermination rapide in vivo des temps de relaxation tissulaires". Toulouse 3, 1997. http://www.theses.fr/1997TOU30094.
Texto completoJohnson, Alan M. "Relaxation of Vibrationally Excited Trifluorobenzene and Tetrafluorobenzene by Collisions with Carbon Dioxide". BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2177.
Texto completoSuas-David, Nicolas. "Jets hypersoniques sondés par temps de déclin d’une cavité optique : application à l’astrophysique de laboratoire". Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S009/document.
Texto completoA huge quantity of infrared spectra is collected by terrestrial and space telescopes from cool astrophysical objects (500-3000 K) like exoplanet (hot Jupiter) and brown dwarf atmospheres or circumstellar envelop of AGB stars. The main purpose of this thesis connected to experimental astrophysics is to provide high temperature data of key molecules by reproducing in the laboratory some aspects of such environments. A new setup built in Rennes couples a High Enthalpy Source to a highly sensitive Cavity Ring-Down Spectrometer. The gas studied, heated in the reservoir up to 2000 K, is expanded in a vacuum chamber through a circular nozzle and the resulting hypersonic jet can be probed at any location. Computational flow dynamics (CFD) calculations associated to a modeling of the infrared absorption lead to synthetic lines which are in very good agreement with the observed spectra. These numerical data were used to attribute the unusual double peak line shapes to the particular flow structure of axisymmetric hypersonic jets. Strong out-of-equilibrium conditions were evidenced in the isentropic core of the expansion. High vibrational temperature (1350 K) and rotational temperature lower than 10 K were recorded inside a jet of CO seeded in Ar. This degrees-of-freedom decoupling greatly simplifies the rotational structure of the recorded infrared spectra and unveils the presence of hot bands stemming from highly excited vibrational states which are significantly populated at high temperature. Our approach is therefore well suited for the study of rotationally cold hot bands of polyatomic molecules which are virtually missing in spectroscopic databases. A complementary approach consists in probing the shock layer formed upstream of an obstacle set perpendicularly to the hypersonic flow axis. Rotational temperature raises abruptly downstream the shock, revealing transitions associated with high J quantum numbers. These two methods were successfully applied to methane which plays an important role in numerous astrophysical environments. In addition to the acquisition of infrared spectroscopic data, the relaxation of internal degrees-of-freedom of CO seeded in different carrier gases (Ar and He) was studied by following the evolution of rotational and vibrational temperatures along the flow, in the isentropic core as well as in the peripheral viscous layers. These temperatures were compared to excitation temperatures calculated by an ab initio method in order to validate collision rates. These data will feed databases needed for the development of radiative transfer codes with a view to a better modeling of spectra observed from "hot" astrophysical environments
Jalocha, Dimitri. "Modélisation du comportement viscoélastique d'un élastomère fortement chargé sous sollicitations multiaxiales". Palaiseau, Ecole polytechnique, 2015. https://theses.hal.science/tel-01219041/document.
Texto completoLegault, Jean-François. "Étude par photoluminescence résolue en temps des mécanismes de relaxation inter-sous-bandes dans des structures à puits quantiques multiples". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0018/MQ56930.pdf.
Texto completoGillardin, Jean-Claude. "Réalisation d'un spectromètre de résonance magnétique nucléaire à impulsions pour la mesure des temps de relaxation dans les solides moléculaires". Mulhouse, 1986. http://www.theses.fr/1986MULH0007.
Texto completoLegault, Jean-François. "Étude par photoluminescence résolue en temps des mécanismes de relaxation inter-sous-bandes dans des structures à puits quantiques multiples". Sherbrooke : Université de Sherbrooke, 1998.
Buscar texto completoLi, Qingwei. "Decision Support Models for Design of Fortified Distribution Networks". Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3206.
Texto completoPaillard, Mathieu. "Dynamique de relaxation de spin dans les boîtes quantiques auto-organisées InAs/GaAs". Toulouse, INSA, 2001. http://www.theses.fr/2001ISAT0011.
Texto completoWe have investigated the carrier dynamics in self-organized InAs/GaAs quantum dots structures by time-resolved photoluminescence. By performing a strict resonant excitation of the quantum dot ground state, we have directly measured the exciton radiative recombination time. At low temperature, we observe strictly no decay of both the linear and the circular luminescence polarization. This demonstrates that neither the electron, nor the hole spin relax on the exciton lifetime scale (2̃,5 ns). These experiments allow also to probe the exciton fine structure without resolving it spectrally. After optical orientation of carrier photogenerated under non resonant excitation, an unexpected increase of the quantum dot excited state luminescence polarization is observed. This effect is interpreted in terms of Pauli blocking which prevent the relaxation of an electron in the quantum dot ground state already occupied by another electron with the same spin orientation. We have developed a simple theoretical model, based on the Master Equation of Microstates, which qualitatively describes the experimental results
Azzimani, Abderrachid. "Etude de la transition vitreuse de la m-toluidine par spectroscopie résolue dans le temps". Paris 6, 2006. http://www.theses.fr/2006PA066004.
Texto completoSoufi, Mohamed Manil. "Dynamique de la relation dipolaire à la transition vitreuse dans les matériaux polymères par réponses transitoires des courants de dépolarisation thermostimulés". Rouen, 2011. http://www.theses.fr/2011ROUES007.
Texto completoThe study of relaxation phenomena plays an important part in the field of polymer research. Several analysis techniques are used for these studies, among which is the Thermo stimulated depolarization current TSDC spectroscopy. This method is very sensitive and its data are typically obtained by two protocols leading to well-know spectra, complex spectra and elementary spectra. The work of this thesis is divided into several separate but complementary. Initially, we proposed a new protocol on TSDC based on a modification of the experimental algorithm. This protocol allowed us to replace a single point at a given temperature by a significant amount of points expressing the dynamics of relaxation. To establish the parameters of this protocol, we conducted a design experiments on PET samples that we took as a reference. Then, we set up a new timing analysis method based on mathematical optimization Simplex-DLTS and our results have shown that the most suitable model was the two-relaxation time t1 and t2 (sum of twot exponential). We applied this new method for the study of different polymers: PETG, PLLA and the PC where for each of its polymers, the method revealed the existence of two relaxation times. With the Simplex-CDTS, we have demonstrated the principle of dynamic heterogeneity of polymers. We also studied by this method, the effect of ageing and that of crystallization. Simplex-CDTS method also has to be a good alternative technique for the study of relaxation at the glass transition temperature and can easily replace the use and crossing of data obtained by applying three different techniques
Muggli, Mark W. "Physical Aging and Characterization of Engineering Thermoplastics and Thermoplastic Modified Epoxies". Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/40509.
Texto completoPh. D.
Oehlmann, Harald. "Analyse temps-fréquence de signaux vibratoires de boites de vitesses". Nancy 1, 1996. http://docnum.univ-lorraine.fr/public/SCD_T_1996_0216_OEHLMANN.pdf.
Texto completoZaripov, Marat Madridovitch. "Contribution au développement d'un spectromètre de mesure des temps de relaxation en R. P. E. Application à l'analyse de polymères dopés". Toulouse 3, 1997. http://www.theses.fr/1997TOU30083.
Texto completoMiot, Elisabeth. "Etude expérimentale par imagerie isotopique et IRM quantitative des lésions cérébrales post-radiques : dépendance vis-à-vis de la dose et contrôle histopathologique". Tours, 1994. http://www.theses.fr/1994TOUR3312.
Texto completoZebrowska, Grazyna. "Application a la radiodosimetrie physico-chimique ou biologique des relaxations spin-reseau et spin-spin en rmn du proton (doctorat : genie biologique et medical)". Rennes 1, 1999. http://www.theses.fr/1999REN1B042.
Texto completoBras, Frédéric. "Dynamique des polarons dans les boîtes quantiques InAs/GaAs". Paris 6, 2006. http://www.theses.fr/2006PA066524.
Texto completoMoutault, Sébastien. "Définition et implémentation d'un modèle causal d'exécution temps-réel distribuée". Phd thesis, Paris, ENMP, 2011. https://pastel.hal.science/pastel-00667238.
Texto completoThis work is part of the AROS project. Its goal is to define a fast prototyping tool for dynamic and distributed real-time applications, mostly for automotive industry and robotic. Two distinct methods are normally used to develop distributed real-time applications. The first one -the time triggered approach- is based on worst execution time analysis, whereby time sharing for the various tasks of an application is statically defined. This approach offers considerable safety but the time analysis is sometimes difficult to process. The second one -the priority scheduling approach- is based on ascribing a priority level to each task, which will then allow the system to define an execution order, based on the events is has received. This second approach is more flexible and easier to implement but is less safe and cannot ensure that the application behaves predictably. The structure of the AROS applications being dynamic, the time-triggered approach is irrelevant as it requires a static analysis that cannot be conducted. The priority scheduling approach is also irrelevant because of the non predictable behaviour. We propose an approach based on causal events scheduling inspired by distributed event simulators scheduling techniques. While comparatively easy to use for application designers, this new approach produces applications with a perfectly predictable behaviour. Two main obstacles must be overcome: the real time synchronisation of the execution engine and compliance with real-time constraints