Kontext: Die Sonnenkorona wird seit 1932 mit Koronographen beobachtet. Nur wenige Jahre später war klar, dass die Korona viel heißer ist als die sichtbare Sonnenoberfläche; seit dem ist der Mechanismus der koronalen Heizung ungeklärt. Viele Mechanismen wurden vorgeschlagen, die genügend Energie zur Basis der Korona liefern, es hat sich aber kein vollständig selbstkonsitentes Bild des Energietransports und der koronalen Dissipation etabliert. Ziele: Wir möchten ein selbstkosistentes Modell aufstellen, welches Bewegungen auf der Sonnenoberfläche enthält, welche das Magnetfeld verbiegen und verflechten, wodurch in der Korona Ströme induziert und Ohm’sch dissipiert werden. Die Modellbeschreibung soll durch den Vergleich von synthetischen mit realen Beobachtungen untermauert werden. Methoden: Wir treiben das 3D MHD Model mit beobachteten photosphärischen Magnetfeldern und Horizontalbewegungen an. Durch Wärmeleitung entlang des Feldes sowie Strahlungsverluste wird die koronale Energiebilanz realistisch. Wir synthetisieren Spektren in verschiedenen Emissionslinien mit einer Atom-Datenbank und der berechneten koronalen Plasmatemperatur sowie -dichte. Diese vergleichen wir mit entsprechenden Beobachtungen der Korona über der aktiven Region, mit der wir die Simulation antreiben. Wir vergleichen extrahierte Modell-Feldlinien mit empirischen und theoretischen Skalengesetzen, die die koronale Heizung entlang von Bögen voraussagen. Resultate: Im Modell bilden sich heiße koronale Bögen mit Temperaturen deutlich über 1 MK. Ihre 3D-Struktur entspricht den beobachteten koronalen Bögen; Doppler-Karten lassen auf ähnliche Plasmaströmungen entlang der Bögen schließen. An die Modell-Daten passen wir ein Skalengesetz an, welches von der Bogenlänge und der magnetischen Flussdichte an den Fußpunkten abhängt. Schlussfolgerungen: Aus der substanziellen Übereinstimmung zwischen Modell und Beobachtung schließen wir, dass das Modell eine genügende Beschreibung der Heizung und Wärmeleitung entlang von koronalen Bögen darstellt, um die Beobachtungen zu erklären.

Studies of resonant magnetic perturbations (RMP) have been an active topic in the tokamak research. The RMP technique involves the use of magnetic perturbations generated by external coils installed on a tokamak device. The resonant interaction between the plasma and RMP has favorable effects on magnetohydrodynamic (MHD) stability and other plasma parameters in tokamaks. The RMP experiments are carried out in the Saskatchewan Torus-Modified (STOR-M) tokamak using (l = 2, n = 1) helical coils carrying a static current pulse. The effect of RMP on the (m = 2, n = 1) magnetic islands is examined during ohmic discharges with high MHD activities. The amplitude and frequency of (2, 1) Mirnov fluctuations are significantly reduced after application of RMP. A phase of improved plasma confinement, characterized by a reduction in the H_alpha emission level and an increase in the soft x-ray (SXR) emission, is induced after application of RMP. It is also observed using the ion Doppler spectroscopy (IDS) that RMP can strongly affect the plasma rotation in STOR-M. It is found that during the RMP pulse, the toroidal velocity of C_III impurities (located at the plasma edge) increases in the co-current direction. However, the toroidal velocities of O_V and C_VI impurities (located near the plasma core) change direction from counter-current to co-current. The reduction of the toroidal flow velocity is accompanied by a reduction of the MHD frequency. It is also found that radial profiles of ion saturation current and floating potential in the edge region can be modified by RMP. An increase in the pedestal plasma density and a more negative electric field are observed at the plasma edge region during the RMP pulse. An internal probe array is assembled and installed in STOR-M to study the RMP penetration and the plasma response to RMP.

The main objective of this thesis is to develop a comprehensive model with the capability of modeling both a high Reynolds number and high magnetic Reynolds number turbulent flow for application to supersonic combustor. The development of this model can be divided into three categories: one, the development of a self-consistent MHD numerical model capable of modeling magnetic turbulence in high magnetic Reynolds number applications. Second, the development of a gas discharge model which models the interaction of externally applied fields in conductive medium. Third, the development of models necessary for studying supersonic combustion applications with plasma-assistance such the extension of chemical kinetics models to extremely high temperature and non-equilibrium phenomenon.

No description available.

La plupart des objets astrophysiques, comme les planètes ou les étoiles, produisent leur proprechamp magnétique à partir d’une forte agitation d’un fluide conducteur d’électricité comme un métalen fusion ou un plasma ionique. Un champ magnétique de grande échelle est alors crée lorsqueles mouvements de ce fluide génèrent des courants induits suffisamment intenses pour compenserla dissipation Ohmique du système. Ceci est vrai pour des dynamiques à haut nombre de Reynoldsmagnétique Rm = UL/h (U et L sont la vitesse et la longueur caractéristique du système et h la diffusivitémagnétique). Il est connu, que l’écoulement moyen d’un fluide en rotation peut produire unchamp magnétique de grande échelle en cisaillant les lignes d’un champ magnétique déjà présentdans le système. Il s’agit de l’effet Omega. Cependant, un tel processus d’induction ne permet pasd’obtenir une dynamo qui s’auto-entretienne, celle-ci a donc besoin d’un mécanisme d’inductionsupplémentaire pour exister. Ainsi, on fait souvent appelle aux mouvements turbulents de petiteséchelles pour fournir l’ingrédient manquant à l’effet dynamo.Les contributions des fluctuations turbulentes au champ magnétique moyen font l’objet d’une étudeapprofondie dans notre expérience de Couette sphérique soumise à un fort champ magnétique.Notre dispositif expérimental, appelé Derviche Tourneur Sodium (DTS), est une expérience en sodiumliquide conçue pour explorer le régime magnétostrophique du noyau terrestre où les forcesde Coriolis et de Lorentz sont à l’équilibre.De nombreuses mesures sont réalisées au sein de notre expérience et nous obtenons par méthodeinverse des profils radiaux de la force électromotrice moyenne, exprimée en terme d’effets alpha etbeta, et des cartes de l’écoulement moyen pour des Reynolds magnétique allant Rm = 30 à 100. Il résultede ces inversions que les fluctuations turbulentes de l’écoulement peuvent être modélisées parune forte contribution à la diffusivité magnétique, négative dans la région interne et positive prés dela sphère externe. Une simulation numérique directe de l’expérience appuie également ce résultat.La réduction de la diffusivité magnétique effective par les mouvements de petites échelles impliqueque la turbulence peut aider à l’auto-génération d’un champ magnétique de grande échelle. De cepoint de vue la turbulence est un ingrédient favorisant l’effet dynamo. / Earth, Sun and many other astrophysical bodies produce their own magnetic field by dynamoaction, where induction of magnetic field by fluid motion overcomes the Joule dissipation when themagnetic Reynolds number Rm = UL/h is large enough (U and L are characteristic velocity andlength-scale and h the magnetic diffusivity). Large scale motion of a conducting medium shearingpre-existing magnetic field lines is a well known process to produce large scale magnetic field by omega-effect. However, such a process cannot sustain a self-excited dynamo and small-scaleturbulent motions are usually invoked as the appropriate mechanism to dynamo action.The contribution of turbulent fluctuations to the induction of mean magnetic field is investigated inour liquid sodium spherical Couette experiment, with an imposed magnetic field. Our experimentaldevice, named Derviche Tourneur Sodium (DTS), has been designed to explore the magnetostrophicregime of the Earth outer core where Coriolis and Lorentz forces are in balance.Many measurements are used through an inversion technique to obtain radial profiles of the meanelectromotrice force, expended interns of alpha and beta effects, together with the mean flow atmagnetic Reynolds number Rm = 30 up to 100. It appears that the small scale turbulent fluctuationscan be modeled as a strong contribution to the magnetic diffusivity which is negative in the interiorregion and positive close to the outer shell. Direct numerical simulations of our experiment supportthese results. The lowering of the effective magnetic diffusivity by small scale fluctuations impliesthat turbulence can actually help to achieve self-generation of large scale magnetic fields.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-02-15T11:38:42Z No. of bitstreams: 1 PedroRicardoVasconcelosDeMoraesJunior_DISSERT.pdf: 2981903 bytes, checksum: d8c6074e1bcaf9fefb3aac688a2d7012 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-02-16T13:03:43Z (GMT) No. of bitstreams: 1 PedroRicardoVasconcelosDeMoraesJunior_DISSERT.pdf: 2981903 bytes, checksum: d8c6074e1bcaf9fefb3aac688a2d7012 (MD5) / Made available in DSpace on 2018-02-16T13:03:43Z (GMT). No. of bitstreams: 1 PedroRicardoVasconcelosDeMoraesJunior_DISSERT.pdf: 2981903 bytes, checksum: d8c6074e1bcaf9fefb3aac688a2d7012 (MD5) Previous issue date: 2017-04-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Nos ?ltimos anos os estudos sobre sistemas complexos vem ganhando for?a e ferramentas para poder simul?-lo e verificar seu comportamento estatisticamente. Grande parte disso se deve a muitos sistemas que passaram a se comportar de forma n?o-linear e dissipativo. Para esses casos, as geometrias convencionais como a euclidiana, n?o ? poss?vel para a proeza de explica-lo, com isso a geometria dos fractais surgiu como alternativa importante para o trato deste meio, sendo leis de escalas (pot?ncia) se aplicando muito bem para esse sistema sendo exemplificado em forma de s?ries temporais e superf?cies (geometrias bidimensionais e tridimensionais). Assim, uma variedade de m?todos foi contabilizada para esse tratamento, entre eles est?o a an?lise via expoente de Hurst e an?lise multifractal. Nosso trabalho tem como objetivo propor um novo m?todo para analisar multifractalmente imagens bidimensionais, sendo essas imagens advindas de simula??es de nuvens do meio interestelar. Primeiro passo foi gerar 12 simula??es MHD em que se diferenciavam a partir de valores de press?o e campo magn?tico, depois gerada a imagem em 2D que ? aplicado sobre elas o m?todo de tratamento multifractal MFDMA. Com a aplica??o deste m?todo ? poss?vel avaliar as imagens atrav?s de um quadro contendo os expoentes de an?lise multifractal, sendo poss?vel avaliar o comportamento de escala nas imagens e verificar o grau de complexidade, e ainda descobrir quais as fontes causadoras da multifractalidade, usando dois m?todos de an?lise multifractal que s?o embaralhamento dos dados da imagem original e substitui??o dos dados originas a partir da transformada de Fourier. Os resultados mostraram que para todas as imagens o m?todo de embaralhamento consegue destruir a fonte de multifractalidade da imagem original e ainda se comportar como um monofractal, enquanto o outro m?todo ? ineficaz, concluindo que os fatores n?o -lineares n?o est?o inclu?dos dentre as fontes e indicando como fonte de multifractalidade as correla??es de longo alcance. Outro resultado importante ? a rela??o do grau de multifractalidade ?h com a press?o. / In recent years studies on complex systems have been gaining strength and tools to be able to simulate and verify their behavior statistically.Much of this is due to many systems that have come to behave in a nonlinear and dissipative way.For these cases conventional geometries such as Euclidean is not possible for the prowess of explaining it, with this the geometry of the fractals emerged as an important alternative for the treatment of this medium,being laws of scales (power) applying very well for this system being exemplified in the form of time series and surfaces (two-dimensional and three-dimensional geometries).Thus a variety of methods were counted for this treatment, among them are the analysis via exponent of Hurst and multifractal analysis.Our work aims to propose a new method to analyze two-dimensional images multifractally, being these images coming from clouds simulations of the interstellar medium.First step was to generate 12 MHD simulations in which they differed from values of pressure and magnetic field, then generated the 2D image that is applied on them the multifractal MFDMA treatment method.With the application of this method it is possible to evaluate the images through a frame containing the exponents of multifractal analysis, being possible to evaluate the scale behavior in the images and verify the degree of complexity, and to find out which sources cause multifractality,using two methods of multifractal analysis that are shuffling the original image data and replacing the original data from the Fourier transform.The results show that for all images the shuffling method can destroy the multifractal source of the original image and still behave like a monofractal,While the other method is ineffective, concluding that nonlinear factors are not included among the sources and indicating as a source of multifractality the long-range correlations. Other important results are the relation of degree of multifractity ?h with pressure, sonic number of Mach and number of Alfv?n.

In recent years, multi-core graphics processing units (GPUs) have been increasingly used by researchers for other purposes than rendering graphics. This thesis presents the implementation of GPU computing for real-time control of plasma instabilities known as resistive wall modes at the EXTRAP T2R fusion plasma device. A NVIDIA GPU is installed in the device plasma control system. Using the CUDA parallel computing platform, PID and LQG control algorithms are developed for the GPU. It is shown that computation times decrease with up to 80 % for the LQG algorithm and 33 % for the PID algorithm if computations in the control system are shifted from the central processing unit (CPU) to the GPU. The gains of GPU utilization are limited by latencies introduced by the CPU-GPU interaction. To better exploit the potential of the GPU, a zero-copy method is proposed, in which the GPU is allowed to perform read and write operations on CPU memory.

This thesis is an account of various phenomena caused by the interaction of the motion of electrically conducting fluids with magnetic fields. Such phenomena, the study of which is usually known as Magnetohydrodynamics (MHD), occur on a galactic, planetary or laboratory length scale; however in this thesis we concentrate on those phenomena which can be reproduced in the laboratory. In chapter 2 we study the laminar flow of uniformly conducting, incompressible fluids in rectangular ducts under the action of transverse magnetic fields. We begin by proving that when the duct has a constant cross-section the solution is unique and then analyse theoretically some of the curious effects on the flow of the duct's walls being electrically conducting. We find close agreement between the results of these theories and the experiments of Alty (1966) and Baylis (1966). We then analyse the flow in ducts with varying cross-sections. In chapter 3 we analyse some of the curious flows and current streamline patterns produced by placing electrodes on the non-conducting walls of a container, filled with a conducting fluid, and passing electric currents between the electrodes in the presence of a strong magnetic field. In chapter 4 we analyse some of the theoretical limitations on the use of Pitot tubes and electric potential (e.p.) probes in MHD flows, and provide some estimates of the errors to be expected. In chapter 5 we analyse the stability of parallel flows in parallel magnetic fields and also some aspects of the stability of the flows analysed in chapters 2 and 3. In chapters 6, 7 and 8 we describe our experimental apparatus, the experiments to investigate directly some of the flows analysed theoretically in chapters 2 and 3 by means of Pitot and e.p. probes, and experiments to measure the MHD errors inherent in the use of these probes. We concluded that the curious phenomena predicted actually exist. We also learnt much about the use of Pitot and e.p. probes, especially as some of the experimental results were as predicted in chapter 4.

Masters thesis creates project of public transport in Česká Třebová. Confronts the current situation in the city with its needs and taking account of the planned solution to the traffic situation creates new and better project.

This This Master´s Thesis deals with the problems of the integrated transport system in the South Bohemian Region. After the explanation of the concept the integrated transport system follows the specification of the transport systems, the transport divisions and short introduction with the legislative framework. Further in my Master´s thesis I describe two chosen efficient and sophisticated integrated transport systems in the Czech Republic. Next part of this work deals with the current traffic situation in the South Bohemian Region. It follows the prices comparison for the tickets in the local transport and analysis the connection in chosen towns in the South Bohemian Region. The aim of this work is to make a suggestion of the integrated transport system, chose the model, tariffs and prices for the tickets. In the last part of this work I pay attention to the detected weaknesses and I suggest their possible solution.