Les oscillations de neutrinos occupent la majeure partie des expériences s'intéressant à cette particule. Ce mécanisme utilise le fait que les neutrinos soient massifs pour permettre de passer d'un état de saveur à un autre. L'expérience OPERA commencera à prendre des données au printemps 2006. Son but est de prouver sans ambiguïté ce mécanisme en observant l'apparition de neutrinos tauïques dans le faisceau CNGS composé de neutrinos muoniques. Cette thèse présente une description des faisceaux de neutrinos, en s'appuyant sur le faisceau CNGS, tiré du CERN vers le laboratoire italien du Gran Sasso. Le flux de ces neutrinos est recalculé, et des simulations sont menées pour étudier les défauts d'alignement des éléments de la ligne de faisceau. Le détecteur OPERA est composé de briques faites d'un empilement de plaques de plomb et de films d'émulsion photographique, de deux trajectrographes et de deux spectromètres. La haute résolution en position des émulsions (<1 mu m) permet d'identifier les tau crées par l'interaction par courant chargé des neutrinos tauïques. La localisation des briques touchées par un neutrino est faite à l'aide d'un réseau de scintillateurs. La reconstruction des traces dans ces scintillateurs, ainsi que dans les spectromètres, fait partie des travaux présentés dans cette thèse. Un algorithme d'identification des muons a également été développé dans cette thèse. Il permet une réduction d'un facteur 20 du bruit de fond charmé. Le futur de la physique des oscillations de neutrinos passe par la construction de faisceaux de neutrinos de plus en plus intenses, pour arriver à mesurer les derniers paramètres inconnus (theta13 et deltaCP). Le projet de faisceau du CERN vers le tunnel de Fréjus est revisité dans la dernière partie de cette thèse. Une optimisation complète de la ligne de faisceau est proposée, et permet d'atteindre une sensibilité de theta13 de l'ordre du degré.

L'enthousiasme de la communauté scientifique pour l'étude des oscillations<br />de neutrinos n'a d'égal que les masses de leurs détecteurs. L'expérience<br />MINOS détermine et compare les spectres proches et lointains des neutrinos<br />muoniques du faisceau NuMI, afin de mesurer deux paramètres d'oscillation:<br />$\Delta m_{23}^2$ et $sin^2(2\theta_{23})$. Les spectres sont obtenus par<br />l'analyse des interactions par courant chargés dont la difficulté réside<br />dans l'identification des produits des interactions (e.g. muons). Une<br />méthode alternative permettant d'identifier les traces de muons courbées par<br />le champ magnétique des détecteurs, ainsi que de déterminer leurs énergies<br />est présentée dans ce manuscrit. La sensibilité des détecteurs est optimale<br />pour les interactions quasi-élastiques dont une méthode de sélection est<br />proposée, afin d'étudier leur oscillation. Bien que réduisant la<br />statistique, une telle étude introduit moins d'erreur systématique,<br />constituant la méthode idéale à long terme.

L'expérience T2K, construite au Japon, est une expérience d'oscillations de neutrinos à base longue. Dans cette expérience, les paramètres décrivant ce phénomène quantique, et plus particulièrement l'angle de mélange theta13, sont mesurés en utilisant un faisceau de neutrinos muoniques produit par un accélérateur de particules. Dans cette thèse, des résultats obtenus à partir des données prises pendant la première année de fonctionnement de l'expérience sont présentés. Après avoir présenté la théorie de l'oscillation quantique des neutrinos, et l'expérience en elle-même, nous nous concentrons sur le détecteur proche sur axe de T2K, INGRID. Nous présentons les études de calibration de ce détecteur, qui ont permis de montrer qu'il fonctionnait correctement, et de façon stable dans le temps. Nous présentons ensuite les mesures réalisées sur le faisceau de neutrinos, pour déterminer sa direction et sa forme dans le plan transverse. Le second objet de cette thèse est un nouveau détecteur, le Module Proton, qui fut la première modification ajoutée au détecteur INGRID. Ce nouveau module a vocation à étudier plus précisément les interactions quasi élastiques se produisant sur l'axe du faisceau. Nous présentons les motivations physiques ainsi que les études de conception qui ont mené à sa construction. Dans la dernière partie de cette thèse, nous présentons les premiers résultats obtenus à partir de données prises par ce module, qui donnent une idée des possibilités offertes par ce nouveau détecteur pour étudier le faisceau de neutrinos de l'expérience T2K.

Cette thèse est consacrée aux phénomènes paramétriques optiques dans les microcavités de semiconducteurs structurées. Les non-linéarités des excitons des puits quantiques, associées au confinement optique, permettent d'observer des processus paramétriques sous excitation résonnante. Dans le régime d'oscillation, un couple de faisceaux est généré, dont les corrélations d'intensité sont potentiellement quantiques. Dans les cavités planaires, les conditions d'oscillation (angle de pompage, couplage fort) sont restrictives, et les corrélations sont limitées par le déséquilibre en intensité des faisceaux produits. Nous étudions deux approches de structuration pour lever ces restrictions. Dans la première, des microcavités sont gravées en fils. Le confinement latéral fait apparaître une collection de modes. Nous montrons dans ces fils l'existence de l'oscillation paramétrique dégénérée en énergie et mesurons les corrélations d'intensité des faisceaux générés. Les observations sont confrontées quantitativement à un modèle de polaritons en interaction. Dans la seconde approche, nous étudions des microcavités couplées. Les modes sont délocalisés sur les multiples cavités. Nous présentons l'oscillation paramétrique à basse température. Puis nous analysons un échantillon conçu pour la génération paramétrique à température ambiante. L'étude spectrale valide un modèle de système à 2 niveaux, utilisé pour prévoir les conditions d'observation du régime d'oscillation. Enfin, nous présentons une étude en polarisation de la génération paramétrique. Nous mesurons, sur une large gamme de paramètres, le rapport des potentiels d'interaction entre excitons qui conservent ou non la polarisation.

<p>In this thesis we have studied speciation in three butterfly genera <i>Polygonia</i> (Nymphalidae, Nymphalini), <i>Pararge </i>(Nymphalidae, Satyrinae) and <i>Celastrina</i> (Lycaenidae: Polyommatinae). In the first paper a dated phylogeny, based on molecular data, of <i>Polygonia</i> was constructed. We found strong conflict between the nDNA and mtDNA datasets. Possibly this can be explained by ancestral and recent hybridizations between contemporary taxa. The results point to the importance in using different markers when we try to resolve evolution of taxa. In the second paper a sister group comparison was made in order to discover whether host plant range has had an effect on species diversity in <i>Polygonia</i>. Our result indicated higher diversification rates in clades which included species with larvae feeding on different, or additional, plants compared to the ”urticalean rosids” specialists. In the third paper our focus was on the colonization abilities in polyphagous butterflies. The haplotype structures of the mtDNA <i>cytochromeoxidase I</i> (COI) within the Nearctic species of <i>Celastrina</i> as well as within<i> P. c-album</i> and <i>P. faunus</i> were analysed in a network. We found little variation in <i>Celastrina</i> and <i>P. c-album.</i> This results imply that the genera have expanded recently and rapidly. There are indications of differentiation in COI in <i>Celastrina</i> and, possibly, host plant use is involved. However, in <i>P.</i> <i>faunus</i> we found structure among the haplotypes. We believe that several different haplotypes of this species have been preserved during glaciations in the Nearctic. In the fourth paper the evolution of the grassfeeding <i>Pararge</i> was analysed. The phylogeny was based on the mtDNA COI and the nDNA <i>wingless</i> (wgl) and times of divergences were calculated. We found a deep divergence between the European and Moroccan populations of <i>P. aegeria</i> which indicates the importance of the Mediterranean as a barrier for gene flow. </p>

<p>In this thesis, a computer program that in a simple way can calculate the performance of control loops at the refinery Preemraff Lysekil has been created. The computer program has been adapted to the environment at Preemraff Lysekil. Theories for evaluation has been studied in aspect of reliability and of automatic implementation. The evaluation has been carried out from data collected directly from control loops at the refinery and from simulated control loops with implemented errors. </p><p>Among the studied methods are Harris index and Stattin´s oscillation index. According to the literature the Harris index is the most used for measure of control performance, but the results show that it does not work as a single measure at Preemraff Lysekil. However Stattin´s oscillation index works well and can be used for detection of oscillations. Statistic measures like variance, IAE, ISE and a method based on histogram are also studied. All the statistical measures are simple to implement and are rather accurate. Several tests on control loops has been carried out and it has been shown that it ís enough to use the method based on histograms and Stattins oscillation index to get a good picture of the performace of the control loops at Preemraff Lysekil. </p><p>The work has resulted in a MATLAB tool that evaluates the control loops and can be run at any time. The tool first calculates Stattin´s oscillation index. The loops that are oscillating are marked. In the next step, the method based on histograms is used and a list with the worst performing loops at the top is created.</p>

Limit Cycle Oscillation is a type of aircraft wing structural vibration caused by the non-linearity of the system. The objective of this thesis is to provide a numerical study of this aeroelastic behavior. A CFD solver is used to simulate airfoils displaying such an aeroelastic behavior under certain airflow conditions. Two types of airfoils are used for this numerical study, including the NACA64a010 airfoil, and the supercritical NLR 7301 airfoil. The CFD simulation of limit cycle oscillation (LCO) can be obtained by using published flow and structural parameters. Final results from the CFD solver capture LCO, as well as flutter, behaviors for both wings. These CFD results can be obtained by using two different solution schemes, including the Roe and Zha scheme. The pressure coefficient and skin friction coefficient distributions are computed using the CFD results for LCO and flutter simulations of these two airfoils, and they provide a physical understanding of these aeroelastic behaviors.

Combustion instability is a problem that has plagued the development of rocket-propelled devices since their conception. It is characterized by the occurrence of high-frequency nonlinear gas oscillations inside the combustion chamber. This phenomenon degrades system performance and can result in damage to both structure and instrumentation. The goal of this dissertation is to clarify the role of unsteady combustion in the combustor instability problem by providing the first quantified estimates of its effect upon the stability of liquid rocket engines. The combination of this research with a new system energy balance method, accounting for all dynamic interactions within a system, allows for the isolation of combustion effects for this study. These effects are quantified through use of classical linear stability analysis to calculate the unsteady combustion heat release growth rate. Since combustion modeling can become very involved, including the mixing process and multiple reactions concerned, for this initial evaluation the model is limited to a one-dimensional flame analysis for a one-step premixed chemical reaction. Using classical analysis of oscillatory burning, the governing combustion equations are expanded into sets of steady and unsteady equations adapted for premixed liquid rockets. From this expansion process, the first real treatment of the effects of unsteady combustion in a rocket system is presented, and the first quantified values of the unsteady heat release in a rocket system are computed. Finally, the corresponding linear heat release growth rate for the system is then calculated for the first quantified effects of unsteady combustion on the overall system stability. The mechanism of unsteady combustion is shown to behave as a driving mechanism, serving as one of the more important stability mechanisms comparable to the magnitude of the nozzle damping mechanism. This analysis confirms that unsteady combustion is an important stability mechanism that warrants further investigation. This study also creates a firm foundation upon which to extend the analysis of this important mechanism to fully understand all of its effects within a rocket system.

The author examines nonlinear aeroelastic responses of air vehicle systems. Herein, the governing equations for a cantilevered configuration are developed and the methods of analysis are explored. Based on the developed nonlinear bending-bending-torsion equations, internal resonance, which is possible in future air vehicles, and the possible cause of limit cycle oscillations of aircraft wings with stores are investigated. The nonlinear equations have three types of nonlinearities caused by wing flexibility, store geometry and aerodynamic stall, and retain up to third-order nonlinear terms. The internal resonance conditions are examined by the Method of Multiple Scales and demonstrated by time simulations. The effect of velocity change for various physical parameters and stiffness ratio is investigated through bifurcation diagrams derived from Poinar´e maps. The dominant factor causing limit cycle oscillations is the stiffness ratio between in-plane and out-of-plane motion.

In this work we consider the overhead power transmission lines (OHL). Their specifics are related to the presence of cables (conductors) whose length between supporting towers may extend to dozens of thousand meters. The OHL components are exposed to a combination of natural actions wind, rain, ice / snow / frost deposits. Compared to other structural parts, conductors have the highest flexibility and very low structural self-damping (of the order of 0.1 % of critical damping or lower, depending on frequencies). They are among structural elements the most sensitive to these actions. Since early fifties the increased energy demand gave a rise to large construction of high-voltage and extra-high-voltage overhead lines equipped with bundled electrical conductors. For such arrangements there was noticed a kind of wind-induced oscillations originated by a zone of disturbed and retarded air flow (wake), that the cables located upwind(windward) cast onto the downwind (leeward) ones. The effect of this phenomenon called Wake-Induced Oscillations (WIO) resulted in fatigue damages of conductors, failures of insulator strings and cable suspension hardware and fatigue failures of spacers. There have been identified analogues to transmission lines WIO in other regular structures subjectto the cross-flow of viscous fluids (air, gas, water etc.): heat exchanger tubes, clusters of fuel rods of nnuclear reactors, groups of chimneys, buildings. Early works in this field relate to the aerodynamics of tandem and staggered twin struts to support the wings of biplanes and published by Pannell, Griffits and Coales in 1915. Other cable structures like suspenders in suspension bridges or stays in cable-stayed bridges may be also subject to wake-induced oscillations. In each of these cases, conditions of oscillations occurrence and structural response depend on cables specific mass and stiffness, kind of fixation, dimension scale versus fluid viscosity and velocity (Reynolds number) etc. The cables separation plays important role, as there are different kinds of wake interference especially when the cables are closely spaced. A number of research projects were entertained to study the wake-induced oscillations of different structures, which brought to development of analytical and experimental models and methods of protection against this phenomenon. A particular solution to overhead lines was found by unevenly distributing the spacers along the line span. To achieve that, no unique approach exists; virtually each grid company, or manufacturer of spacers proceeds with its own method. It may rely on different basis, either field experience or analytical study or a mixture of them. And, despite advances in numerical modelling of latest decades, few publications uncover phenomenological side of WIO. The issues of modelling WIO in a view of helping to develop methods for protection of line against WIO are a main subject of this work. Original advances studied in this thesis include: - Current state-of-the art for analytical calculation of WIO, including the loads in the wake - Overview of classic theory of wake-induced flutter and its evaluation from the standpoint of modern numerical tools for analytical applications (e.g., Matlab) - Nonlinear Finite-Element Modelling of WIO using classic theory of wake-induced flutter, study of its domains of application, advantages and limitations, including validation upon field experiments - Foundation of basic methodology for optimal placement of spacers over the bundle conductor span