This Thesis is concerned with three particular aspects of extended cosmic strings and domain walls in cosmology: their dynamics, gravitation and interaction with a black hole. In Chapter 3, we study the dynamics of an abelian-Higgs cosmic string. We find its equations of motion from an effective action and compare, for three test trajectories, the resulting motion with that observed in the Nambu-Gotō approximation. We also present a general argument showing that the corrected motion of any string is generically antirigid. We pursue the investigation of the dynamics of topological defects in Chapter 5, where we find (from integrability conditions rather than an effective action) the effective equations governing the motion of a gravitating curved domain wall. In Chapter 4 we investigate the spacetime of a gravitating domain wall in a theory with a general potential V(ɸ). We show that, depending on the gravitational coupling e of the scalar ɸ, all nontrivial solutions fall into two categories interpretable as describing respectively domain wall and false vacuum-de Sitter solutions. Wall solutions cannot exist beyond a value (^4)(_3)ɛmax, and vacuum-de Sitter solutions are unstable to decaying into wall solutions below ɛmax at ɛmax we observe a phase transition between the two types of solution. We finally specialize for the Goldstone and sine-Gordon potentials. In Chapter 6 we consider a Nielsen-Olesen vortex whose axis passes through the centre of an extremal Reissner-Nordstr0m black hole. We examine in particular the existence of piercing and expelled solutions (where the string respectively does and does not penetrate the black hole's horizon) and determine that while thin strings penetrate the horizon — and therefore can be genuinely called hair — thick strings are expelled; the two kinds of solution are separated by a phase transition.

O objetivo deste trabalho é desenvolver um sistema de controle capaz de realizar o apontamento automático de uma antena parabólica de forma mais precisa e com menor tempo de apontamento quando comparado ao apontamento manual. A antena parabólica em estudo consta de uma parábola metálica de 1.60 m de diâmetro, base de sustentação em ferro, dois conjuntos de engrenagens e dois motores elétricos para realização dos movimentos. Os parâmetros físicos do sistema mecânico, tais como massa, volume e inércia, puderam ser facilmente obtidos a partir de uma modelagem tridimensional em um software de plataforma CAD. Para a modelagem dinâmica do sistema utilizou-se a similaridade do sistema físico em estudo com um manipulador de cadeia aberta de dois graus de liberdade o que permitiu que se aplicassem conceitos referentes a cinemática e modelagem de manipuladores robóticos. Através da notação de Denavit-Hartenberg a cinemática direta da antena com dois graus de liberdade foi obtida com sucesso. As equações dinâmicas que descrevem o movimento do sistema foram levantadas através de um modelador automático implementado em um software de manipulação simbólica. Para tanto foi desenvolvido um algoritmo que descreve os passos necessários para obtenção das equações de movimento de um manipulador robótico em cadeia aberta, a partir da formulação Lagrangeana. Um sistema de controle adaptativo por modelo de referência foi projetado e implementado considerando as incertezas do modelo oriundas de imperfeições contidas na modelagem tridimensional realizada. Os resultados obtidos por simulação do sistema de controle adaptativo se mostraram satisfatórios e os índices de desempenho esperados para um perfeito apontamento foram alcançados. / The objective of this work is to develop a control system capable of performing the automatic maneuver of a satellite dish more accurately with less time maneuvering when compared to manual maneuver. The dish consists of a study on metal parabola 1.60 m in diameter, base of support in iron, two sets of gears and two electric motors to perform the movements. The physical parameters of the mechanical system, such as mass, volume and inertia could be easily obtained from a three-dimensional modeling in a CAD software platform. For modeling the system dynamics we used the similarity of the physical system under study with an open chain manipulator of two degrees of freedom that allowed it to apply concepts related to kinematics and modeling of robotic manipulators. Through the Denavit-Hartenberg notation of the direct kinematics of the antenna with two degrees of freedom was successfully obtained. The dynamic equations describing the motion of the system were raised through an automatic model implemented in symbolic manipulation software. To that end, an algorithm that describes the steps necessary to obtain the equations of motion of a robotic manipulator in open chain, from the Lagrangian method, was developed. A model reference adaptive control system was designed and implemented considering the uncertainties of the model arising from imperfections within the three-dimensional modeling. The results obtained by simulation of the system of closed loop control were satisfactory as well as the high rates of the perfect maneuver have been achieved.

This report focuses on the utilisation of flight mechanics in the context of aircraftconceptual design to assess stability, control, and motion characteristics. The pri-mary objective is to acquire the equations of motion and implement longitudinalstability and control criteria using Pacelab Aircraft Preliminary Design 8.1, a com-mercial software tool. The equations and criteria employed in this study are derivedfrom an extensive review of relevant literature.By incorporating a dedicated Flight Mechanics chapter within the software, it be-comes possible to evaluate aircraft concepts under varying conditions. To ensureaccuracy and validity, DATCOM+ and OpenVSP were employed for testing andverification purposes.The key aspects covered in this report include flight mechanics, its implementationin Pacelab APD 8.1, determination of aerodynamic derivatives, formulation of equa-tions of motion, and their application to the B747 aircraft model. The emphasis liesin assessing longitudinal stability and control, including specific characteristics suchas the phugoid and short period modes.This report provides valuable insights into the integration of flight mechanics withinthe Pacelab APD 8.1 software for aircraft conceptual design. The results contributeto a better understanding of stability and control parameters and their impact onaircraft performance.

This thesis aims to explore if multibody simulations is a suitable method to investigate vibrations in the steering system of trucks. Vibrations in the steering system and subsequently in the steering wheel is a common issue that automotive manufacturers face. The vibration levels in the steering wheel are in some countries regulated and some vibration phenomena can even cause issues with the handling properties of the whole vehicle. Therefore being able to predict and reduce these with the help of multibody simulations would be of great value. The thesis does this by comparing the simulations to measurements. It investigates what parts can be approximated as rigid, what the effects different numerical solvers have and compares different driving scenarios. This can however be quite challenging, one reason being that the differential equations arising when performing multibody simulations of trucks are very stiff. The numerical challenges of this must be overcome while still keeping the resolution of the accelerations in the solution high enough to still be representative of reality. The thesis also explains how to mathematically model a physical system such that the numerical analysis of it can be efficient. The results show that the success of multibody simulations is very dependent on the test case. However, they also show that together with physical measurements multibody simulations can be a powerful complementary tool. The thesis also presents improvements that could be made to the model as well as certain key areas that need to be studied more in order to align the multibody simulations results with measurements. The multibody simulations software used to perform the calculations and the modelling in the report is Adams developed by Hexagon AB. / Den här rapporten syftar till att ge inblick i om flerkroppssimuleringar kan vara ett användbart verktyg för att undersöka styrsystemsvibrationer i lastbilar. Dessa vibrationer är orsaken till en mängd styrningsproblem samt att rattvibrationer har lagkrav att inte vara för stora. Att kunna förutspå och efterlikna dessa vibrationer med flerkroppssimulering skulle därmed vara till stor fördel. Detta undersöks genom att jämföra simuleringarna med mätdata. Det undersöks vilken påverkan stelkroppsapproximationer av vissa komponenter har, påverkan av olika numeriska integrationmetoder samt steglängder och även olika körningslastfall. Att genomföra flerkroppssimuleringar av lastbilar är dock inte alltid helt enkelt, på grund av differentialekvationernas styva karaktär uppstår ofta konvergensproblem. Ska man sedan använda resultaten för att undersöka styrsystemsvibrationer måste man överkomma dessa konvergensproblem men bibehålla en tillräckligt fin upplösning av resultatet för att resultatet fortfarande ska vara representativt av den fysiska lastbilens dynamiska egenskaper. Rapporten beskriver även hur man kan gå tillväga för att matematiskt modellera ett fysisk system så att det effektivt går att utföra dynamisk analys av det. Resultaten visar att flerkroppssimulering kan vara väldigt beroende på vad körfallet är, med vissa körfall där simuleringar och mätningar stämmer väl överens och andra där detta inte är fallet. På grund av detta kan det vara otillräckligt att endast använda flerkroppssimulering för att utvärdera styrsystemsvibrationer, men resultaten visar att tillsammans med mätdata kan flerkroppssimulering vara ett kraftfullt komplement. I rapporten presenteras även exempel av viktiga komponenter att ta hänsyn till för att bättre kunna simulera styrsystemsvibrationer samt områden där mer forskning har potential att förbättra flerkroppssimuleringar i hänsyn till styrsystemsvibrationer. Mjukvaran som används för att utföra flerkroppssimulering är Adams som utvecklas av Hexagon AB.

No description available.

We study point particles to illustrate the various symmetries such as the Poincaré group and its non-relativistic version. In order to find the Noether charges and the Noether currents, which are conserved under physical symmetries, we study Noether’s theorem. We describe the Pauli-Lubanski spin vector, which is invariant under the Poincaré group and describes the spin of a particle in field theory. By promoting the Pauli-Lubanski spin vector to an operator in the quantized theory we will see that it describes the spin of a particle. Moreover, we find an action for a smooth spinning bosonic particle by compactifying one string dimension together with one embedding dimension. As with the Pauli-Lubanski spin vector, we need to quantize this action to confirm that it is the action for a smooth spinning particle. / Vi studerar punktpartiklar för att illustrera olika symemtrier som t.ex. Poincaré gruppen och dess icke-relativistiska version. För att hitta de Noether laddningar och Noether strömmar, vilka är bevarade under symmetrier, studerar vi Noether’s sats. Vi beskriver Pauli-Lubanksi spin vektorn, vilken har en invarians under Poincaré gruppen och beskriver spin hos en partikel i fältteori. Genom att låta Pauli-Lubanski spin vektorn agera på ett tillstånd i kvantfältteori ser vi att den beskriver spin hos en partikel. Dessutom finner vi en verkan för en spinnande partikel genom att kompaktifiera en bosonisk sträng dimension tillsammans med en inbäddad dimension. Som med Pauli-Lubanski spin vektorn, kvantiserar vi denna verkan för att bekräfta att det är en verkan för en spinnande partikel.

Les transferts d'électron sont au cœur de nombreux processus d'intérêts chimiques, biologiques ou photochimiques comme, par exemple, dans la technologie du photovoltaïque ou la photosynthèse où ils ne sont que rarement isolés. Par ailleurs, des résultats expérimentaux tendent à montrer que les phénomènes quantiques, notamment les superpositions d'états ou cohérences, peuvent se maintenir sur l'échelle de temps du transfert d'électron même en présence d'un environnement. Dans ce travail, le transfert d'électron est étudié dans trois types de systèmes moléculaires. Le premier est un transfert intermoléculaire dans une hétérojonction oligothiophène-fullerène modélisant une interface de séparation de charge pour de futures cellules photovoltaïques organiques. Le second est un transfert intramoléculaire dans des composés organiques à valence mixte où l'on étudie l'effet d'un pont avec une chaîne croissante de n-paraphénylènes dans des polymères aromatiques avec des sites donneur-accepteur (1,4-diméthoxy-3-méthylphénylènes). Le troisième est le transfert intermoléculaire dans une chaîne de tryptophanes dans une chromoprotéine cryptochrome. Dans tous ces cas, une attention particulière est portée à une modélisation réaliste. Dans ce contexte, il est crucial de faire une partition judicieuse entre l'ensemble des degrés de liberté et de décrire proprement l'interaction entre ceux impliqués dans le transfert et ceux qualifiés d'environnement. A cette fin, un hamiltonien décrivant un système électronique donneur-accepteur couplé à un bain d'oscillateurs harmoniques a été paramétré en utilisant notamment la méthode de la DFT contrainte (cDFT). Le bain d'oscillateurs a été décrit par une analyse en modes normaux ou via la fluctuation de l'écart énergétique obtenue par des calculs de type QM/MM. Les systèmes étudiés présentent tous des environnements fortement couplés et structurés nécessitant d'explorer des stratégies peu conventionnelles. Dans un modèle d'environnement formé d'un nombre fini d'oscillateurs traités explicitement, le traitement dynamique nécessite d'utiliser des méthodes multidimensionnelles telles que la méthode multi-couches multiconfigurationnelle de produits de Hartree dépendant du temps (ML-MCTDH). Dans l'approche de dynamique dissipative où le bain intervient seulement par ses propriétés statistiques il est alors nécessaire de se tourner vers une méthode non perturbative telle que les matrices hiérarchiques. A côté de ces approches exactes, une autre stratégie consiste à effectuer une transformation de coordonnées afin de définir une coordonnée collective incluse avec le système électronique qui est elle-même couplée à un bain secondaire. La propagation dynamique peut alors être effectuée par une équation-maîtresse approchée s'appuyant sur la théorie de perturbation. Comme principaux résultats, nous analysons en détail le domaine de validité des différentes méthodes utilisées puis expliquons le comportement dynamique des différents cas amenant à une délocalisation facile ou à un piégeage de la charge. Par là même, nous montrons que la méthodologie proposée, appliquée à des systèmes-modèles dans ce travail, est bien adaptée pour l'analyse de l'influence mutuelle entre le transfert de charge et les déformations nucléaires, une situation prototypique pour de nombreux processus importants dans les systèmes chimiques et biologiques. / Electron transfer reactions are at stake in several chemical, biological or photochemical processes of great interest as, for instance, photovoltaic technology or photosynthesis where they are rarely isolated. Furthermore, experimental results show that quantum phenomena, notably superpositions of states or coherences, can persist on the time scale of the electron transfer even in the presence of an environment. In this work, electron transfer is studied in three types of molecular systems. The first one is an intermolecular transfer in an oligothiophene-fullerene heterojonction modelling a charge separation interface for future organic photovoltaic devices. The second one is an intramolecular transfer in mixed-valence organic compounds where the bridge effect of an increasing n-paraphenylens chain is studied on aromatic polymers with donor-acceptor sites (1-4,dimethoxy-3-methylphenylens). The third one is an intermolecular transfer in a tryptophan chain of a cryptochrome chromoprotein. In all these cases, a special attention is given to realistic modelling. In this context, it is crucial to define carefully the partition between the degrees of freedom, in particular amongst those implied in the transfer and those qualified to be part of an environment. To this end, a Hamiltonian describing a donor-acceptor electronic system coupled to a bath of harmonic oscillators is parameterized using the constrained DFT method (cDFT). The oscillators' bath is described by a normal mode analysis or via the electronic gap fluctuation obtained by QM/MM calculations. The systems under study turn out to be strongly coupled, and structured which requires to explore non-conventional strategies. In a model environment constituted of a finite number of oscillators treated explicitly, the dynamics is performed by multidimensional quantum propagation methods such as the multi-layer multiconfigurational time-dependent Hartree method (ML-MCTDH). In the dissipative approach, where the bath acts only by its statistical properties, it is mandatory to turn to non-perturbative methods such as the hierarchical equations of motion approach. Apart from these exact approaches, an alternative strategy consists in carrying out a change of coordinates in order to define a collective bath mode included in the electronic system, which itself is coupled to a secondary bath. The dynamical propagation can then be done by an approximated quantum master equation using perturbation theory. As main results, we show in detail the domain of validity of the different methods presented and explain the dynamical behaviour of the different cases leading to an easy delocalization or a trapping of the charge. Hence, we show that the methodology applied in model systems are well suited for the analysis of the mutual interplay between the charge transfer and nuclear deformations, a prototypical situation in many important chemical and biological processes.

This diploma thesis deals with the design of an inclined three-sided vibrating screen, which is designed for sorting bulk aggregates. The aim of the diploma thesis is primarily to make a construction design with a specific comparison of various design solutions, considering the calculated operating parameters. In the construction design, is used not only the experience of the manufacturer of this type of machine, but also recommendations based on the manu-facturers of screens component. The design also includes a comparison of two types of flex-ible mounting, which is one of the basic structural units of the entire vibrating screen. The thesis is conceived from the basics, with emphasis on the simplicity and functionality of the device.

Nedávné studie předpovídají nárůst pasažérů využívajících leteckou dopravu. Tento trend bude vyžadovat zavedení nových leteckých linek, důsledkem čeho bude zhuštěn letový provoz s dopadem hlavně na nápor letišť v metropolitních oblastech. Automatizovaně řízení pojíždení letounu umožní menší rozestupy mezi jednotlivými linkami a zvýšení příletové a odletové kapacity letišť. Tato práce se zabývá návrhem modelu pohybu dopravního letounu po zemi s ohledem na různé provozní podmínky jako např.: stav povrchu vzletové a přistávací dráhy za různého počasí a lišící se provozní parametry letounu (tlak v pneumatikách, zatížení podvozků a pod.). Validace modelu byla založena na sledování poloměru zatáčky pro různe uhly natočení přední podvozkové nohy. Výsledky simulace byly validovany vzhledem k analytickému modelu Ackermanovy geometrie a na specifikační dokument od Boeingu určený pro plánovaní pohybu letounu na letišti. Výsledky prokázaly přesnost modelu a potvrdily jeho možné nasazení pro simulace v reálnem čase.

The aim of the presented thesis is to create a compact publication which deals with properties, solution and examination of behavior of dynamical systems as models of mechanical structures. The opening portion of the theoretical part leads the reader through the subject of description of dynamical systems, offers solution methods and investigates solution stability. As the introduction proceeds, possible forms of structure loading, damping and response are presented. Following chapters discuss extensively the possible approaches to system behavior observation and identification of nonlinear and chaotic phenomena. The attention is also paid to displaying methods and color spaces as these are essential for the examination of complex and sensitive systems. The theoretical part of the thesis ends with an introduction to fractal geometry. As the theoretical background is laid down, the thesis proceeds with an application of the knowledge and shows the approach to numerical simulation and study of models of real structures. First, the reader is introduced to the single pendulum model, as the simplest model to exhibit chaotic behavior. The following double pendulum model shows the obstacles of observing systems with more state variables. The models of free rod and cantilever serve as examples of real structure models with many degrees of freedom. These models show even more that a definite or at least sufficiently relevant monitoring of behavior of such deterministic systems is a challenging task which requires sophisticated approach.