Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2003. / Bibliogr.: f. [98]-105. Document électronique également accessible en format PDF. CaQCU

La détection d'agents biologiques dans l'air ambiant est devenue un enjeu majeur notamment en environnement hospitalier et dans la protection contre le bioterrorisme. Dans ce contexte, la miniaturisation des dispositifs d'analyse permet d'envisager leur utilisation directement sur la zone d'étude. Afin d'obtenir un échantillon concentré et représentatif, la filtration de l'air reste cependant un point délicat. Parmi les différents principes exploitables pour la collecte de particules aéroportées, l'emploi des forces électriques semble être prometteur pour améliorer les performances des dispositifs qui se trouvent généralement fondés sur des forces inertielles. Dans cette étude, une modélisation fine des collecteurs électrostatiques a été conduite pour une géométrie fil / cylindre. Elle décrit tout d'abord les champs hydrodynamiques d'un écoulement charriant des inclusions dans lequel est imposée une décharge couronne. Une injection éventuelle de vapeur dans la chambre de collecte a nécessité ensuite la détermination des champs de température et concentration de la vapeur. Une analyse dimensionnelle inspectionnelle a montré que ces champs possèdent deux termes de couplage fort dont on a justifié l'omission dans cette étude ; les phénomènes physiques mis en jeu ont alors pu être classés selon une cascade d'influences non réciproques et la résolution numérique du modèle s'en est trouvée facilitée. Quatre configurations d'écoulement différentes, caractérisées par des recirculations d'origine électro hydrodynamiques, ont été identifiées et leurs impacts sur les rendements de collecte quantifiés. De plus, une procédure de dimensionnement des filtres électrostatiques fondée sur un nombre de Deutsch représentatif des rendements a été mise en place. Son exploitation a montré l'intérêt de la mise en parallèle de petits collecteurs pour filtrer des débits d'air importants. Cette étude s'est achevée par l'analyse des effets engendrés par l'injection de vapeur dans la chambre de collecte. Elle a jeté les bases d'une explication pour l'augmentation des rendements de collecte résultant de cette injection. / Detection of airborne biological agents has become a major challenge especially in hospitals and the protection against bioterrorism. In this context, the miniaturization of analytical devices allows to consider their direct use in the field. To obtain a representative and concentrated sample, air filtration remains a delicate point. Among the various principles used to collect airborne particles, the use of electrical forces seems to be promising to improve performance beyond these of devices that are based on inertial forces.In this study, a detailed model of electrostatic collectors was developed in the wire/cylinder geometry. It first describes the hydrodynamic flow fields carring inclusions in which a corona discharge is imposed. Afterwards, the possible injection of steam into the collection chamber required the determination of the temperature and vapor concentration fields. An inspectionnal dimensional analysis justified the omission of two strong coupling terms. Therefore, in this study, the involved physical phenomena could be classified according to a non-reciprocal influences cascade and the numerical model is become simpler. Four different flow patterns, characterized by their electrohydrodynamic secondary flows, were identified and their impact on the collection efficiencies was quantified. In addition a design procedure of electrostatic filters, based on a representative efficiency Deutsch number, has been developed. This procedure shows the interest of parallelizing small collectors to filter important airflows. This study was completed by the analysis of the effects of steam into the collection chamber. It provides the basis for an explanation of the collection efficiencies increase related to this injection.

Observations of the surface of the Sun reveal multi-scaled, mixed magnetic features that carpet the entire solar surface. Not surprisingly, the global magnetic fields extrapolated from these observations are highly complex. This thesis explores the topology of the Sun's global coronal magnetic fields. The magnetic skeleton of a magnetic field provides us with a way of examining the magnetic field and quantifying its complexity. Using specialised codes to find the magnetic skeletons which were written during the course of this work, we first examine potential field extrapolations of the global solar coronal magnetic field determined from observed synoptic magnetograms from the Heliospheric Magnetic Imager on the Solar Dynamics Observatory. The resolution of the PFSS models is found to be very important for discovering the true nature of the global magnetic skeleton. By increasing the maximum number of harmonics used in the potential field extrapolations and, therefore, the grid resolution, 60 times more null points may be found in the coronal magnetic field. These high resolution fields also have a large global separator network which connects the coronal magnetic field over large distances and involves between 40 % and 60 % of all the null points in the solar atmosphere. This global separator network exists at both solar minimum and solar maximum and has separators that reach high into the solar atmosphere (> 1R☉) even though they connect null points close to the solar surface. These potential field extrapolations are then compared with magnetohydrostatic (MHS) extrapolations of the coronal magnetic field which also provide us with information about the plasma in the corona. With a small component of electric current density in the direction perpendicular to the radial direction, these MHS fields are found to have a plasma beta and pressure typical of the corona. As this small component of electric current density grows, the heliospheric current sheet is warped significantly and the magnetic field, plasma beta and pressure become unphysical. Torsional spine reconnection is also studied local to a single null point. First using a dynamical relaxation of a spiral null point under non-resistive magnetohydrodynamics (MHD) to a MHS equilibrium is form in which a current layer has built up around the spine lines. Then the reconnection under resistive MHD in this current sheet is studied. The current about the spine lines is dissipated and the magnetic energy is mainly converted into heat directly as the field lines untwist about the spine line.

Cette thèse porte sur la simulation tridimensionnelle (3D) des décharges couronnes à l'aide du calcul haute performance. Lorsqu'on applique une impulsion de haute tension entre une pointe et un plan, les lignes de champ électrique fortement resserrées autour de la pointe induisent la propagation simultanée de plusieurs streamers et la formation d'une décharge couronne de structure arborescente. Dans ces conditions, seule une simulation électro-hydrodynamique 3D est apte à reproduire cette structure et fournir les ordres de grandeur de l'énergie déposée et de la concentration des espèces créées durant la phase de décharge. Cependant, cette simulation 3D est très consommatrice en temps et mémoire de calcul et n'est désormais accessible que grâce à l'accroissement permanent de la puissance des ordinateurs dédié au calcul haute performance. Dans le cadre d'une simulation électro-hydrodynamique 3D, une attention particulière doit être prise concernant l'efficacité des solveurs à résoudre les équations elliptiques 3D car leur contribution en termes de temps de calcul peut dépasser 80% du temps global de la simulation. Ainsi, une partie de manuscrit est consacrée aux tests de performances de méthodes de résolution d'équations elliptiques directes ou itératives telle que SOR R&B, BiCGSTAB et MUMPS, en utilisant le calcul massivement parallèle et les librairies MPI. Les calculs sont réalisés sur le supercalculateur EOS du réseau CALMIP, avec un nombre de cœurs de calcul allant jusqu'à 1800, et un nombre de mailles atteignant 8003 (soit plus 1/2 Milliard de mailles). Les tests de performances sont réalisés en statique sur le calcul du potentiel géométrique et en dynamique en propageant une densité de charge d'espace analytique caractéristique des streamers. Pour réaliser une simulation complète 3D de la décharge il faut également intégrer au programme un algorithme capable de résoudre les équations de transport de particule chargée à fort gradients de densité caractéristiques aux streamers. Dans ce manuscrit, l'algorithme MUSCL est testé dans différentes conditions de propagation d'un cube de densité (à vitesse homogène ou non homogène spatialement) afin d'optimiser le transport des densités d'espèces chargées impliquées. Le code 3D, conçu pour résoudre le modèle électro- hydrodynamique complet de la décharge (couplant les équations de transport, de Poisson et de cinétique réactionnelle) est ensuite validé par la confrontation des résultats 3D et 2D dans une condition de simulation présentant une symétrie de révolution autour de l'axe de propagation d'un streamer. Enfin, les premiers résultats des simulations 3D de la phase décharge avec la propagation d'un ou plusieurs streamers asymétriques sont présentés et analysés. Ces simulations permettent de suivre la structure arborescente de la décharge lorsqu'on applique une tension pulsée entre une pointe et un plan. L'initiation de la structure arborescente est étudiée en fonction de la position de spots plasmas et de leur influence sur l'amorçage des streamers. / This work is devoted to the three dimensional (3D) simulation of streamer corona discharges in air at atmospheric pressure using high-performance parallel computing. When a pulsed high-voltage is applied between a tip and a plane in air, the strong electric field lines constricted around the tip induce the simultaneous propagation of several streamers leading to a corona discharge with a tree structure. Only a true 3D electro-hydrodynamics simulation is able to reproduce this branching and to provide the orders of magnitude of the local deposited energy and the concentration of the species created during the discharge phase. However, such a 3D simulation which requires large computational memory and huge time calculation is nowadays accessible only when performed with massively parallel computation. In the field of 3D electro-hydrodynamics simulations, a special attention must be paid to the efficiency of solvers in solving 3D elliptic equations because their contribution can exceed 80% of the global computation time. Therefore, a specific chapter is devoted to test the performance of iterative and direct methods (such as SOR R&B, BiCGSTAB and MUMPS) in solving elliptic equations, using the massively parallel computation and the MPI library. The calculations are performed on the supercomputer EOS of the CALMIP network, with a number of computing cores and meshes increasing up to respectively 1800 and 8003 (i.e. more than 1/2 Billion meshes). The performances are compared for the calculation of the geometric potential and in a dynamic simulation conditions consisting in the propagation of an analytical space charge density characteristic of the streamers. To perform a complete 3D simulation of the streamer discharge, must also involve a robust algorithm able to solve the coupled conservation equations of the charged particle density with very sharp gradients characteristic of the streamers. In this manuscript, the MUSCL algorithm is tested under different propagation conditions of a cubic density (with uniform or non-uniform velocity field). The 3D code, designed to solve the complete electro-hydrodynamics model of the discharge (coupling the conservation equations, the Poisson equation and the chemical kinetics) is validated by comparing the 3D and 2D results in a simulation conditions presenting a rotational symmetry around the propagation axis of a mono-filamentary streamer. Finally, the first results of the 3D simulations of the discharge phase with the propagation of one or several asymmetric streamers are presented and analyzed. These simulations allow to follow the tree structure of a corona discharge when a pulsed voltage is applied between a tip and a plane. The ignition of the tree structure is studied as a function of the initial position of the plasma spots.

Coronae, stephanai e diademata sono gli attributi più evidenti nella ritrattistica femminile di età imperiale e si configurano non solo come gioielli, ma anche come veicolo di informazioni. Obiettivo del presente lavoro è dimostrare come tali manufatti siano significativi indizi del rango e della posizione delle donne della famiglia imperiale, poiché legati al titolo di Augusta e alla legittimazione del potere grazie al ruolo delle donne come madri. Attraverso lo studio di un campione di ritratti pertinenti alla statuaria, alla glittica e alla numismatica, si propone una tipologia degli attributi e si affronta la loro analisi in relazione ai singoli soggetti, alle diverse dinastie e ai contesti in cui sono utilizzati. La ricerca ha sviluppo diacronico e copre il periodo compreso fra Livia ed Elia Ariadne. / Coronae, stephanai and diademata are the clearest feautures in Roman female portraiture and they emerge not only as jewels, but also as a way to convey information. Aim of this work is to demonstrate how these artifacts are substantial clues to understand roles and positions of the female part of Roman Imperial families, since they are connected to the title of Augusta and to the dynastic legitimacy, thanks to female role as mothers of emperors. A catalogue of portraits from statuary, glyptic and numismatic leads to a tipology of these objects and to their analysis regarding single persons, dynasties and backgrounds. The study goes from Livia to Aelia Ariadne.

My diploma thesis is focused on the use of numerical computer codes for simulation in plasma astrophysics. They will learn the basic characteristics of the Sun, a closer focus on the solar corona and the solar corona heating problem. The following section is devoted to simulation software in plasma astrophysics, their installing and displaying the results using the visualization software. In the conclusion is demonstrated using this software on a model example and a simulation that performs simulation of impulsively generated waves in solar coronal loops.

En este artículo se busca esclarecer el significado de la institución de la disolución parlamentaria. En primer término, se revisan sus orígenes y los usos que se dio a esta institución en Inglaterra. En segundo lugar, se explica que la disolución parlamentaria es una institución perteneciente al ordenamiento constitucional de un país, y que sirve para viabilizar su funcionamiento pero no para destruir ese ordenamiento mediante un golpe de Estado. Finalmente, se examina cómo fue regulada en el Perú la disolución parlamentaria en la Constitución de 1979, y cómo se encuentra regulada actualmente en la Constitución de 1993 vigente en nuestro país.

Orientador: João Sinezio de Carvalho Campos / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-10T13:40:00Z (GMT). No. of bitstreams: 1 Giordano_JoaoBatista_D.pdf: 4390680 bytes, checksum: 205aa7153da8e4745f9366e58adcb8cf (MD5) Previous issue date: 2007 / Resumo: Dentre as técnicas de modificação de superfícies aplicadas na indústria para melhorar adesão, o tratamento por descarga corona é amplamente utilizado. Durante o tratamento por descarga coro na, espécies ativas são geradas, as quais podem reagir com a superfície do polímero ocasionando quebra de cadeias e formação de radicais, criando assim grupos polares na superfície e conseqüentemente, aumentando a sua energia superficial e propriedade de adesão. Neste trabalho utilizaram-se tecidos de poliéster e de algodão. Nos processos convencionais de preparação de tecidos são usados agentes químicos que agridem os efluentes têxteis, assim a descarga corona propõe-se como tratamento prévio do material sem ação de tais agentes, sendo tratamento único e apenas físico. Os objetivos deste trabalho são: 1. Tratar com descarga corona tecidos de poliéster e tecidos de algodão (engomado, lavado e desengomado); 2. Verificar hidrofilidade e absorção de corantes em tecidos de algodão tratados com descarga corona; 3. Verificar propriedades mecânicas em tecidos tratados com descarga corona. 4. Verificar a adesão de pigmentos em de tecidos de poliéster tratados com corona. Tecidos foram submetidos à descarga: corona variando-se o tempo exposição e altura entre os eletrodos, em seguida foi realizada testes de hídrofilidade, absorção de corante tipo reativo, adesão de pigmentos, solidez a lavagem e ensaios de resistência à tração e alongamento. Foi utilizada a técnica de microscopia óptica, ensaio de hidrofilidade para caracterizar os efeitos causados. Os resultados mostram que: houve aumento da hidrofilidade do tecido de algodão que de 50% em amostra sem tratamento passou até a 280% com o tratamento, observou-se também que com te~pos de 1 mino já ocorrem modificações nos tecidos quanto a hidrofilidade e absorção de corantes; houve aumento da absorção de corante nas regiões tratadas principalmente em processos contínuos de tingimento; ocorreu boa aderência de pigmentos em tecidos de poliéster tratados; não ocorrem alteração das propriedades mecânicas (resistência a tração e alongamento) nas amostras tratadas. / Abstract: Amongst the techniques of modification of surfaces applied in the industry to improve adhesion, the treatment for discharge corona widely is used. During the treatment for discharge corona, active species are generated, which can consequently react with the surface of polymer causing chain in addition and formation of radicals, thus creating polar groups in the surface and, increasing its superficial energy and property of adhesion. In this work they had been used weaveed of polyester and cotton. In the conventional processes of fabric preparation they are used chemical agents whom the effluent textile attack, thus the discharge corona is considered as previous treatment of the material without action of such agents, being treatment only e only physicist. The objectives of this work are: 1.To deal with discharge corona weaveed to polyester and fabrics cotton (starchy, washed and dissolved the gum); 2. To verify water absorption and absorption of corantes in fabrics of cotton treated with discharge corona; to 3.Verificar mechanical properties in fabrics dealt with discharge corona. 4. To verify the pigment adhesion in of treated polyester fabrics with corona. Fabrics had been submitted to the discharge corona varying the time exposition and height between the electrodes and, after that water absorption tests had been carried through, absorption of corante reactive type, pigment adhesion, solidity the laudering and assays of tensile strenght and allonge. The technique of optic microscopy was used, assay of water absorption to characterize the caused effect. The results show that: it had increase of the hidrofilidade of the cotton fabric that of 50% in sample without treatment passed until 280% with the treatment, was 9.lso observed that with times of 1 min. already the water absorption and absorption of corantes occur modifications in fabrics how much; it had increase of the absorption of corante in the regions treated mainly in continuous processes of dyeing good pigment tack occurred in treat polyester fabrics; they do not occur alteration of the mechanical properties (resistance the traction and allonge) in the treated samples. / Doutorado / Ciencia e Tecnologia de Materiais / Doutor em Engenharia Química

The dynamics of the solar corona are dominated by the magnetic field which creates its structure. The magnetic field in most of the corona is ‘frozen’ to the plasma very effectively. The exception is in small localised regions of intense current concentrations where the magnetic field can slip through the plasma and a restructuring of the magnetic field can occur. This process is known as magnetic reconnection and is believed to be responsible for a wide variety of phenomena in the corona, from the rapid energy release of solar flares to the heating of the high-temperature corona. The coronal field itself is three-dimensional (3D), but much of our understanding of reconnection has been developed through two-dimensional (2D) models. This thesis describes several models for fully 3D reconnection, with both kinematic and fully dynamic models presented. The reconnective behaviour is shown to be fundamentally different in many respects from the 2D case. In addition a numerical experiment is described which examines the reconnection process in coronal magnetic flux tubes whose photospheric footpoints are spun, one type of motion observed to occur on the Sun. The large-scale coronal field itself is thought to be generated by a magnetohydrodynamic dynamo operating in the solar interior. Although the dynamo effect itself is not usually associated with reconnection, since the essential element of the problem is to account for the presence of large-scale fields, reconnection is essential for the restructuring of the amplified small-scale flux. Here we examine some simple models of the solar-dynamo process, taking advantage of their simplicity to make a full exploration of their behaviour in a variety of parameter regimes. A wide variety of dynamic behaviour is found in each of the models, including aperiodic modulation of cyclic solutions and intermittency that strongly resembles the historic record of solar magnetic activity.

L'allumage par choc est une approche récente à la fusion par confinement inertiel où les phases de compression et d'allumage par un choc fort sont séparées. Ce schéma est prometteur dans la mesure où il peut générer des gains élevés et être testée sur des installations laser existantes. Par ailleurs, il nécessite des vitesses d'implosions plus faibles permettant ainsi de comprimer une plus grande quantité de combustible et limitant l'impact des instabilités hydrodynamiques. Malgré tout, la physique liée à cette approche reste très largement inconnue surtout du point de vue expérimental. En effet, même si la phase de compression est dans un régime dit collisionnel bien connu (I<1014W=cm2), l'allumage fait intervenir un spike d'une intensité supérieure à 1015W=cm2, régime très fortement non-linéaire où apparaissent des instabilités paramétriques. Ces instabilités peuvent diminuer l'absorption et générer des électrons suprathermiques pouvant préchauffer le coeur de la cible et donc empêcher son allumage. Un deuxième problème est la possibilité de générer un choc fort en présence d'un plasma de couronne qui pourrait, entrer autre, détériorer le couplage laser-cible. Néanmoins, des considérations théoriques tendent à montrer que si on génère des électrons chauds modérément énergétiques (<100keV), non seulement ils ne sont pas dangereux vis-à-vis du préchauffage mais, en plus, ils peuvent améliorer le couplage en déposant leur énergie dans le front de choc et amplifier sa pression. Le travail réalisé dans cette thèse consiste à tester la possibilité de générer un choc fort dans les conditions de l'allumage par choc i.e. en présence d'un plasma de couronne mais aussi d'étudier l'effet des électrons chauds sur le choc en quantifiant leur énergie et leur abondance. / Shock ignition is a novel approach for inertial confinement fusion where the compression and the ignition phases by a strong shock are separated. The scheme is promising to the extent that it can generate very high gains and can be tested on already existing lasers systems. In addition, this concept requires lower implosion velocities that allows for compressing more massive targets which limits the impact of hydrodynamic instabilities. However, the physic issues related to shock ignition are still largely unexplored especially experimentally. Indeed, even if the compression phase takes place in the well-known collisional regime (I<1014W=cm2), ignition requires a spike which intensity exceeds 1015W=cm2.This regime is strongly non-linear with the onset of parametric instabilities. These instabilities may decrease the absorption and can also generate suprathermal electrons that can preheat the central part of the fuel and make the compression less efficient. Another key issue is the capability of launching a strong shock in presence of a plasma corona which can deteriorate the laser-target coupling and produce lamentation. Nevertheless, theoretical considerations tend to show that if the energy of fast electrons is moderate (<100keV), they could improve the coupling, deposit their energy in the shock front and hence amplify it. The work presented in this thesis consists in testing these two issues : launching a strong shock in the conditions corresponding to shock ignition i.e. in presence of a plasma corona and study the effect of hot electrons on the shock strength by measuring their energy and their quantity.