• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 22
  • 11
  • 4
  • 1
  • 1
  • Tagged with
  • 45
  • 45
  • 21
  • 13
  • 11
  • 10
  • 8
  • 8
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • 6
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

A Michelson-Morley test of Lorentz invariance using a rotating optical cavity

Herrmann, Sven 07 March 2008 (has links)
Diese Arbeit präsentiert ein modernes Michelson-Morley Experiment, welches genauere Grenzwerte für Testparameter liefert, die eine Verletzung der Lorentzinvarianz modellieren. Die Messung setzt einen oberen Grenzwert für eine Anisotropie der Lichtgeschwindigkeit im Bereich von dc/c ~10^-16. Das Experiment vergleicht die Frequenzen zweier optischer Hoch-Finesse Resonatoren, wobei einer dieser Resonatoren kontinuierlich auf einem Drehtisch rotiert. Um die Eigenfrequenzen der Resonatoren abzufragen, werden die Frequenzen zweier Nd:YAG-Laser auf die Resonatoren stabilisiert. Die relative Frequenzstabilität auf der Zeitskala einer Tischdrehung (~45s) liegt bei ~1x10^-14, limitiert durch das thermische Rauschen der Resonatorspiegel. Die Messung erstreckt sich über einen Zeitraum von einem Jahr, wobei mehr als 10^5 Tischumdrehungen eingehen. Ausführlich werden die systematischen Effekte und ihre Unterdrückung auf Signalamplituden unter 1 Hz dargestellt. Im Vergleich zu vorhergehenden Messungen konnten diese systematischen Effekte um einen Faktor 10 bis 100 reduziert werden. Zwei verschiedene Testtheorien wurden herangezogen, um ein Signal für eine Anisotropie der Lichtgeschwindigkeit als Folge einer Verletzung der Lorentzinvarianz zu modellieren: eine die Lorentzinvarianz verletzende Erweiterung des Standardmodells und die Testtheorie von Robertson, Mansouri und Sexl. Es wird eine Analyse der Daten im Rahmen beider Testtheorien präsentiert, und Grenzwerte auf die relevanten Parameter werden bestimmt. Diese Grenzwerte schränken eine Anisotropie der Lichtgeschwindigkeit im Bereich von 10^-16 ein, d.h. etwa 10 mal genauer als die Ergebnisse vorangegangener Messungen. Schließlich wird ein Ausblick auf einen verbesserten Aufbau gegeben, welcher neue Resonatoren zum Einsatz bringt, und es werden erste verbesserte Resultate präsentiert. Damit steht der Weg offen für eine Langzeit-Messung, welche die Grenze für eine Anisotropie der Lichtgeschwindigkeit bis in den Bereich von dc/c~10^-17 drücken wird. / This thesis presents a modern Michelson-Morley experiment, which provides improved limits on test parameters that model a violation of Lorentz invariance in electrodynamics. The measurement sets an upper limit on an anisotropy of the speed of light at a level of dc/c~10^-16. The experiment compares the resonance frequencies of two optical high-finesse cavities, one of them continuously rotating on a turntable. To read out their resonance frequencies, two Nd:YAG lasers are frequency-stabilized to these cavities. On the timescale of a turntable rotation (~45s), a relative frequency stability of ~1x10^-14 is achieved, limited by thermal noise of the cavity mirrors. The measurement extends over one year and includes ~10^5 rotations. The systematic effects compromising the measurement are described in detail, together with the measures that have been taken to suppress systematic effects below 1 Hz. This is a reduction by a factor of up to 100 as compared to preceding experiments. Two different test theories are applied to derive a signal for an anisotropy of the speed of light as a consequence of a violation of Lorentz invariance: a Lorentz violating extension of the standard model and the test theory by Robertson, Mansouri and Sexl. An analysis of the data within these two test models is presented, and limits on the relevant test parameters are deduced. These limits restrict an anisotropy of the speed of light at a level of 10^-16, which is a factor of ten more stringent as compared to results of previous such measurements. Finally, an outlook on an improved setup with new cavities and and first results from this setup are presented. This setup should allow for another order of magnitude improvement of the experiment''s sensitivity within a following long-term measurement aiming for the dc/c ~10^-17 level of accuracy.
22

Simplicial matter in discrete and quantum spacetimes

Unknown Date (has links)
A discrete formalism for General Relativity was introduced in 1961 by Tulio Regge in the form of a piecewise-linear manifold as an approximation to (pseudo-)Riemannian manifolds. This formalism, known as Regge Calculus, has primarily been used to study vacuum spacetimes as both an approximation for classical General Relativity and as a framework for quantum gravity. However, there has been no consistent effort to include arbitrary non-gravitational sources into Regge Calculus or examine the structural details of how this is done. This manuscript explores the underlying framework of Regge Calculus in an effort elucidate the structural properties of the lattice geometry most useful for incorporating particles and fields. Correspondingly, we first derive the contracted Bianchi identity as a guide towards understanding how particles and fields can be coupled to the lattice so as to automatically ensure conservation of source. In doing so, we derive a Kirchhoff-like conservation principle that identifies the flow of energy and momentum as a flux through the circumcentric dual boundaries. This circuit construction arises naturally from the topological structure suggested by the contracted Bianchi identity. Using the results of the contracted Bianchi identity we explore the generic properties of the local topology in Regge Calculus for arbitrary triangulations and suggest a first-principles definition that is consistent with the inclusion of source. This prescription for extending vacuum Regge Calculus is sufficiently general to be applicable to other approaches to discrete quantum gravity. We discuss how these findings bear on a quantized theory of gravity in which the coupling to source provides a physical interpretation for the approximate invariance principles of the discrete theory. / by Jonathan Ryan McDonald. / Vita. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.
23

The dynamical approach to relativity as a form of regularity relationalism

Stevens, Syman January 2014 (has links)
This thesis investigates the interplay between explanatory issues in special relativity and the theory's metaphysical foundations. Special attention is given to the 'dynamical approach' to relativity, promoted primarily by Harvey Brown and collaborators, according to which the symmetries of dynamical laws are explanatory of relativistic effects, inertial motion, and even the Minkowskian geometrical structure of a specially relativistic world. The thesis begins with a review of Einstein's 1905 introduction to special relativity, after which brief historical introductions are given for the standard 'geometrical' approach to relativity and the unorthodox 'dynamical' approach. After a critical review of recent literature on the topic, the dynamical approach is shown to be in need of a metaphysical package that would undergird the explanatory claims mentioned above. It is argued that the dynamical approach is best understood as a form of relationalism - in particular, as a relativistic form of 'regularity relationalism', promoted recently by Nick Huggett. According to this view, some portion of a world's geometrical structure actually supervenes upon the symmetries of the best-system dynamical laws for a material ontology endowed with a primitive sub-metrical structure. To explore the plausibility of this construal of the dynamical approach, a case study is carried out on solutions to the Klein-Gordon equation. Examples are found for which the field values, when purged of all spatiotemporal structure but their induced topology, are still arguably best-systematized by the Klein-Gordon equation itself. This bolsters the plausibility of the claim that some system of field values, endowed with mere sub-metrical structure, might have as its best-systems dynamical laws a (set of) Lorentz-covariant equation(s), on which Minkowski geometrical structure would supervene. The upshot is that the dynamical approach to special relativity can be defended as what might be called an ontologically and ideologically relationalist approach to Minkowski spacetime structure. The chapters refer regularly to three appendices, which include a brief introduction to topological and differentiable spaces.
24

A construção de uma Unidade de Ensino Potencialmente Significativa (UEPS) para ensinar relatividade utilizando animações e o game A slower speed of light / Building up a teaching and learning sequence (tls) to teach special relativity using animations and the game a slower speed of light

Riboldi, Bruno Marconi 21 December 2015 (has links)
Submitted by Livia Mello (liviacmello@yahoo.com.br) on 2016-10-06T20:18:19Z No. of bitstreams: 1 DissBMR.pdf: 4436976 bytes, checksum: 6798de1dc9fbb33dbd67f393ab12e887 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T19:20:22Z (GMT) No. of bitstreams: 1 DissBMR.pdf: 4436976 bytes, checksum: 6798de1dc9fbb33dbd67f393ab12e887 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T19:20:28Z (GMT) No. of bitstreams: 1 DissBMR.pdf: 4436976 bytes, checksum: 6798de1dc9fbb33dbd67f393ab12e887 (MD5) / Made available in DSpace on 2016-10-20T19:20:35Z (GMT). No. of bitstreams: 1 DissBMR.pdf: 4436976 bytes, checksum: 6798de1dc9fbb33dbd67f393ab12e887 (MD5) Previous issue date: 2015-12-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / This present work aims to build a Teaching and Learning Sequence (TLS) proposed by Marco. A. Moreira , based on David Ausubel's Meaningful Learning Theory. The TLS aims to lead to a meaningful conceptual learning of Einstein's Special Relativity theory by suppressing the excessive calculus involving it. One of its greatest achievements is the use of the educational game - a slower speed of light and animations. The topics of the unit content are time dilation, length contraction, invariance of the speed of light, the relativity of simultaneity, spotlight effect and Terrell effect. The TLS was able to promote differentiated classes, providing evidences of conceptual evolution - stimulating and making it possible the teaching of modern and contemporary physics at this level. The TLS developed for this study was applied in two classes in a State high school in Itapira - SP and the results were analyzed so that the teaching unit efficiency could be evaluated. At the end of this work an instructional product, which is the TLS itself, is presented. / O presente trabalho tem como objetivo construir e aplicar uma Unidade de Ensino Potencialmente Significativa (UEPS), baseada na teoria da Aprendizagem Significativa de David Ausubel e proposta por Marco A. Moreira. A UEPS visa facilitar a aprendizagem significativa da teoria da Relatividade Restrita e suprimir o excesso de matematização que envolve a tal teoria. Um dos diferenciais desta UEPS é o uso do game educativo A slower speed of light e animações. Os temas abordados na unidade de ensino são a dilatação temporal, a contração do comprimento, a invariância da velocidade da luz, a simultaneidade de eventos relativísticos, o efeito holofote e o efeito Terrell. A UEPS construída foi capaz de permitir aulas diferenciadas, fornecendo evidências de uma evolução conceitual por parte dos alunos, viabilizando e incentivando o ensino da física moderna e contemporânea neste nível de ensino. A UEPS desenvolvida neste trabalho foi aplicada em duas salas de uma escola pública de Itapira – SP, sendo que os resultados foram analisados para que se pudesse avaliar a eficácia da unidade de ensino. Ao final do trabalho é apresentado o produto educacional que consiste na UEPS para o ensino da teoria da Relatividade Restrita.
25

Geometria de Weyl e A teoria gravitacional de Nordström

Almeida, Tony Silva 20 August 2010 (has links)
Made available in DSpace on 2015-05-14T12:14:07Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 649165 bytes, checksum: 4b61e26e50f256db343ba95b4cf95a8b (MD5) Previous issue date: 2010-08-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this disssertation we are concerned with Nordström s scalar gravity theory, one of the first attempts to formulate a relativistic theory of gravitation. We start be describing the theory in its original formulation given by Nordström. We then proceed to show how Nordström s approach is equivalent to a metric theory of gravity which regards gravity as a manifestation of spacetime curvature, a result first obtained by Einstein and Fokker in 1914. We exlore this formal equivalence between the two approaches to derive Nordström s predictions of some observed phenomena, such as Mercury s perihelium and the time delay of the light. finally we consider a third approach which makes use of Weyl geometry through its concept of gauge transformations. We then show that one can regard both Nordström s and Einstein-Fokker s framework as equivalent to a theory formulated to a theory formulated in minkowski spacetime in which the gravitational field is encoded in a non-trivial affine connection. / Nesse dissertação descrevemos a teoria da gravitação escalar de Norsdtröm em diferentes formalismos. Iniciamos tratando esta teoria em sua formulação original, que ficou conhecida por manter a estrutura geométrica da relatividade especial. A seguir revisamos a formulação métrica da teoria de Nordström, devido à Einstein e Fokker, que descreve a gravitação como manifestação da curvatura do espaço-tempo. Nessa formulação, descrevemos as predições da teoria de Nordström para alguns efeitos gravitacionais observados, tais como o movimento do periélio de Mercúrio e o atraso gravitacional da luz. Finalmente introduzimos a geometria de Weyl juntamente com o conceito das transformações de calibre para fazer a transição da formulação métrica em Einstein-Fokker (referencial de Riemann) para o espaço-tempo de Minkowski (referencial de Weyl), onde o campo gravitacional fica codificado pela conexão afim de Weyl. Mostramos também que a estrutura geodésica nessas três formulações é idêntica.
26

Magnetic resonance properties of metal-containing nanosystems

Roukala, J. (Juho) 03 October 2016 (has links)
Abstract This thesis presents computational first-principles investigations of nuclear magnetic resonance (NMR) parameters in metal-containing nanosystems. Special attention is paid to the relativistic effects observed in the vicinity of heavy elements. Small transition metal complexes are used to assess the feasibility of a quasirelativistic density functional theory (DFT) approach for calculating nuclear magnetic shielding tensors of increasingly heavy metal nuclei, followed by applications of the concept to larger systems. Nuclear magnetic shielding constants, shielding anisotropies, and chemical shifts with respect to metal ions are calculated in dimethyl and water complexes of the group-12 transition metals 67Zn, 111/113Cd, and 199/201Hg, using Hartree–Fock and DFT methods with relativistic corrections from the Breit–Pauli Perturbation Theory (BPPT). Four-component relativistic Dirac–Hartree–Fock and correlated, nonrelativistic ab initio calculations are used to benchmark the BPPT and DFT methods, respectively. The DFT/BPPT approach, combined with Monte Carlo simulations at finite temperatures, is subsequently used to calculate the chemical shift of a guest 129Xe inside a tetrahedral, iron-based cage. Complementing experiments, the encapsulation of xenon is verified, and empirically elusive details are revealed about the guest dynamics. Finally, the full shielding tensors of 31P and 195Pt and the indirect spin–spin coupling constants between the two nuclei are studied in five crystalline platinum(II) dialkyldithiophosphato complexes, concentrating on the solid-state chemical shift anisotropy and asymmetry parameters of phosphorus and platinum. The NMR parameters are calculated using DFT and the two-component zerothorder regular approximation (ZORA) for relativistic effects, combining molecular and solid-state models to incorporate indispensable contributions due to spin–orbit and crystal lattice corrections for the shielding tensors. Four-component matrix-Dirac–Kohn–Sham shielding calculations are used to benchmark the ZORA method. Qualitative, in cases nearly quantitative agreement is obtained with experiments, allowing the validation of the X-ray structures of the complexes, as well as a deeper analysis of the differences between them, including the major contributions to the NMR parameters. The results presented here demonstrate that computational NMR, a branch of relativistic quantum chemistry, is applicable and useful in studying nanoscale systems containing heavy elements, such as transition metals. Approximations are necessary to enable the treatment of large and complex targets, but sufficient accuracy is achieved for supplementing experiments with reliable and useful data that provides additional insight and analysis possibilities.
27

Espaces virtuels pour l’éducation et l’illustration scientifiques : contribution à l’appréhension de la Théorie de la Relativité Restreinte par la réalité virtuelle / Virtual spaces for scientific exploration and education : contribution to the apprehension of the Theory of Special Relativity through virtual reality

Doat, Tony 20 September 2012 (has links)
La Théorie de la Relativité (TRR), est une théorie particulièrement contre-intuitive dont les implications sont inaccessibles à l'expérience sensible humaine ; ce qui pose un certain nombre de difficultés de compréhension aux étudiants. Cependant, la Réalité Virtuelle (RV) offre une approche intéressante en permettant à un utilisateur d'être immergé et d'interagir dans un monde virtuel où la vitesse de la lumière est ramenée à 1 m/s. Les phénomènes relativistes deviennent ainsi directement accessibles par ses sens. Cette caractéristique, point départ de nos travaux, permet alors d’appréhender les phénomènes relativistes par une expérience « par la pratique ». L'enjeu de notre travail porte plus précisément sur la définition de moyens et de méthodes intégrés dans une plate-forme immersive permettant d'appréhender les phénomènes relativistes. Dans ce contexte, nous proposons, tout d’abord, des méthodes novatrices pour simuler les phénomènes relativistes sur un nombre quelconque d'objets en mouvement arbitraire et tenant compte de la dynamique relativiste des objets dans la scène, notamment durant leurs interactions. Nous nous focalisons sur les effets qui déforment les objets vus par l'observateur, à savoir le délai de propagation des photons, la relativité des longueurs et l'effet d'aberration. Nous définissons ensuite des méthodes pour intégrer une simulation relativiste dans un environnement immersif basé intrinsèquement sur un monde newtonien. Nous proposons également une plate-forme expérimentale dans laquelle sont intégrées des méthodes d'interaction utilisées pour mettre en scène un « jeu sérieux », ici un billard relativiste. Enfin, nous démontrons la portée de notre outil expérimental par deux voies : l'une concerne l'utilisation de l'application dans des évaluations de didactique et l'autre concerne un exemple d'extension de l'outil pour mettre en lumière un autre aspect de la Physique relativiste : la relation entre vitesse et énergie. / The Theory of Special Relativity (TSR) is a particularly counterintuitive theory. Its implications are, by nature, out of reach by human experience. Therefore we cannot perceive its effects directly, thus raising problems of comprehension for the students confronted to it. However, Virtual Reality (VR) enables us to overcome this limitation by immersing a user into a world where the velocity of light is reduced to 1 m/s. As a result, the relativistic phenomena become directly perceivable through our senses. This possibility, which is the cornerstone of our work, brings a unique way to apprehend the relativistic phenomenon trough a "hands-on" experiment.In this context, we propose, first, innovative methods to include relativistic effects in simulation containing any number of objects moving in an arbitrary direction and velocity and taking into account the relativistic dynamics of the objects, including object-to-object interaction. We focused on the relativistic phenomenon involved in the deformation of objects: the delay of propagation of the photons from the light source to the observer, as well as the relativity of length and the aberration of light. We describe, second, methods to integrate the simulation techniques, previously introduced, into an immersive environment intrinsically based on Newtonian physics. We also provide interaction methods and a concrete application in a serious game framework: a relativistic carom billiard. Finally, we demonstrate the possibilities of our platform are demonstrated in two ways: one tackles usage in the context of learning evaluation and the other is an extension of the tool to access new pieces of information relevant to TSR, such as the force profile used to launch an object with a relativistic velocity.
28

Prediction of NMR J-coupling in condensed matter

Green, Timothy Frederick Goldie January 2014 (has links)
Nuclear magnetic resonance (NMR) is a popular spectroscopic method and has widespread use in many fields. Recent developments in solid-state NMR have increased interest in experiment and, alongside simultaneous developments in computational theory, have led to the field dubbed 'NMR crystallography.' This is a suite of methodologies, complementing the capabilities of other crystallographic methods in the determination of atomic structure, especially when large crystals cannot be made and when exploring materials with phenomena such as compositional, positional and dynamic disorder. NMR J-coupling is the indirect coupling between nuclear spins, which, when measured, can reveal a wealth of information about structure and bonding. This thesis develops and applies the method of Joyce for the prediction of NMR J-coupling in condensed matter systems using plane-wave pseudopotential density-functional theory, an important requirement for efficient treatment of finite and infinite periodic systems. It describes the first-ever method for the use of ultrasoft pseudopotentials and inclusion of special relativistic effects in J-coupling prediction, allowing for the treatment of a wider range of materials systems and overall greater user friendliness, thus making the method more accessible and attractive to the wider scientific community.
29

Mission Concept for a Satellite Mission to Test Special Relativity

Anadol, Volkan January 2016 (has links)
In 1905 Albert Einstein developed the theory of Special Relativity. This theory describes the relation between space and time and revolutionized the understanding of the universe. While the concept is generally accepted new experimental setups are constantly being developed to challenge the theory, but so far no contradictions have been found. One of the postulates Einsteins theory of Relativity is based on states that the speed of light in vacuum is the highest possible velocity. Furthermore, it is demanded that the speed of light is independent of any chosen frame of reference. If an experiment would find a contradiction of these demands, the theory as such would have to be revised. To challenge the constancy of the speed of light the socalled Kennedy Thorndike experiment has been developed. A possible setup to conduct a Kennedy Thorndike experiment consists of comparing two independent clocks. Likewise experiments have been executed in laboratory environments. Within the scope of this work, the orbital requirements for the first space-based Kennedy Thorndike experiment called BOOST will be investigated.BOOST consists of an iodine clock, which serves as a time reference, and an optical cavity, which serves as a length reference. The mechanisms of the two clocks are different and can therefore be employed to investigate possible deviations in the speed of light. While similar experiments have been performed on Earth, space offers many advantages for the setup. First, one orbit takes roughly 90 min for a satellite based experiment. In comparison with the 24 h duration on Earth it is obvious that a space-based experiment offers higher statistics. Additionally the optical clock stability has to be kept for shorter periods, increasing the sensitivity. Third, the velocity of the experimental setup is larger. This results in an increased experiment accuracy since any deviation in the speed of light would increase with increasing orbital velocity. A satellite planted in a Low Earth Orbit (LEO) travels with a velocity of roughly 7 km/s. Establishing an Earth-bound experiment that travels with a constant velocity of that order is impossible. Finally, space offers a very quiet environment where no disturbances, such as vibrations, act upon the experiment, which is practically unavoidable in a laboratory environment. This thesis includes two main chapters. The chapter titled "Mission Level" exploits orbital candidates. Here, possible orbits are explained in detail and the associated advantages and problems are investigated. It also contains a discussion about ground visibility and downlink feasibility for each option. Finally, a nominal mission scenario is sketched. The other chapter is called "Sub-Systems". Within this chapter the subsystems of the spacecraft are examined. To examine the possible orbits it is necessary to define criteria according to which the quality of the orbits can be determined. The first criterion reflects upon the scientific outcome of the mission. This is mainly governed by the achievable velocity and the orbital geometry. The second criterion discriminates according to the mission costs. These include the launch, orbital injection, de-orbiting, satellite development, and orbital maintenance. The final criteria defines the requirements in terms of mission feasibility and risks, e.g. radiation. The criteria definition is followed by explaining the mission objectives and requirements. Each requirement is then discussed in terms of feasibility. The most important parameters, such as altitude, inclination, and the right ascension of the ascending node (RAAN), are discussed for each orbital option and an optimal range is picked. The optimal altitude depends on several factors, such as the decay rate, radiation concerns, experimental contributions, and eclipse duration. For the presented mission an altitude of 600 km seems to be the best fit. Alongside the optimal altitude possible de-orbiting scenarios are investigated. It is concluded that de-orbiting of the satellite is possible without any further external influence. Thus, no additional thrusters are required to de-orbit the satellite. The de-orbiting scenario has been simulated with systems tool kit (STK). From the simulation it can be concluded, that the satellite can be deorbited within 25 years. This estimation meets the requirements set for the mission. Another very important parameter is the accumulative eclipse duration per year for a given orbit. For this calculation it is necessary to know the relative positions and motion of the Earth and the Sun. From this the eclipse duration per orbit for different altitudes is gained. Ground visibilities for orbital options are examined for two possible ground stations. The theory is based on the geometrical relation between the satellite and the ground stations. The results are in an agreement with the related STK simulations. Finally, both ground stations are found adequate to maintain the necessary contact between the satellite and the ground station. In the trade-off section, orbit candidates are examined in more detail. Results from the previous sections with some additional issues such as the experiment sensitivities, radiation concern and thermal stability are discussed to conclude which candidate is the best for the mission. As a result of the trade-off, two scenarios are explained in the "Nominal Mission Scenario" section which covers a baseline scenario and a secondary scenario. After selecting a baseline orbit, two sub-systems of the satellite are examined. In the section of "Attitude Control System (ACS)" where the question of "Which attitude control method is more suitable for the mission?" is tried to be answered. A trade-off among two common control methods those are 3-axis stabilization and spin stabilization is made. For making the trade-off possible external disturbances in space are estimated for two imaginary satellite bodies. Then, it is concluded that by a spin stabilization method maintaining the attitude is not feasible. Thus, the ACS should be built on the method of 3-axis stabilization. As the second sub-system the possible power system of the satellite is examined. The total size and the weight of the solar arrays are estimated for two different power loads. Then, the battery capacity which will be sufficient for the power system budget is estimated together with the total mass of the batteries. In the last section, a conclusion of the thesis work is made and the possible future works for the BOOST mission are stated.
30

Interpretando a relatividade especial: discutindo o debate realismo e antirrealismo científicos no ensino de ciências / Interpreting the Special Relativity: Discussing Scientific Realism Antirealism Debate in the Science Teaching

Moreira, André Batista Noronha 20 February 2014 (has links)
Neste trabalho investigamos, teoricamente e empiricamente, quais são os possíveis aspectos da natureza da ciência, relacionados ao debate realismo e antirrealismo científicos, que emergem da história e filosofia da teoria da relatividade especial e têm potencial para promover debates no ensino de física. Para tal, primeiramente reconhecemos a importância da aproximação histórico-filosófica ao ensino de ciências, assim como a relevância dos aspectos consensuais e não consensuais da natureza da ciência. Argumentamos, em especial, que estes aspectos controversos e não consensuais podem trazer uma visão ainda mais rica e realista da ciência. Fazemos uma exposição sintética sobre algumas das principais características do debate realismo e antirrealismo científicos, suas principais vertentes, categorias e argumentos correntes. Fazemos também um estudo teórico histórico e filosófico sobre a teoria da relatividade, no qual enfatizamos a capacidade do formalismo matemático da teoria ser filosoficamente interpretável. Quatro interpretações históricas da teoria, a de Lorentz (1904), a de Einstein (1905), a de Poincaré (1906) e a de Minkowski (1907) são discutidas e caracterizadas com base no estudo sobre o debate realismo e antirrealismo científicos. Descrevemos em seguida uma pesquisa de campo realizada no primeiro semestre de 2013 aplicada a estudantes de física, de licenciatura e bacharelado, da Universidade de São Paulo. Seus objetivos foram investigar as concepções filosóficas dos estudantes sobre o debate realismo e antirrealismo científicos no contexto da teoria da relatividade especial e mostrar como ele pode trazer ricas discussões no ensino de ciências . A pesquisa foi dividida em três etapas: aplicação de questionário específico sobre o tema filosófico; análise de resenhas entregues pelos estudantes, e; realização de grupo focal. O resultado da análise e triangulação dos dados sugere que o debate mostra-se, também entre os estudantes, de uma forma não consensual e filosoficamente rica. / In this work we investigate theoretically and empirically some possible aspects of the nature of science, related to scientific realism and anti-realism debate emerging from the history and philosophy of the special theory of relativity which can potentially encourage related discussions in physics education. For such, first we acknowledge the importance of historical-philosophical approach to teaching science, as well the educational relevance of the consensual and nonconsensual aspects of nature of science. We argue, particularly, that these controversial and non-consensual aspects can provide an even richer and more realistic view of science. We make a summary of some of the main features of scientific realism and anti-realism debate, its main categories and current arguments. We also make a historical and philosophical theoretical study on the special theory of relativity, wherein we emphasize the capacity of its mathematical formalism be philosophically interpretable. Four historical interpretations of the theory, Lorentz\'s (1904), Einstein\'s (1905), Poincaré\'s (1906) Minkowski\'s (1907), are discussed and characterized based on earlier study on scientific realism and anti-realism debate. We report then a field research conducted in the first semester of 2013 applied to undergraduated physics students at the University of São Paulo. Its objectives went to investigate the philosophical conceptions of students about scientific realism and anti-realism debate under the special theory of relativity and its subjects, and to show how rich can it be for science education. This research was divided into three stages: the application of a specific questionnaire on the philosophical subject; the analysis of papers submitted by students, and; the performing of a focus group. The outcome of data triangulation suggests that the debate reveals itself also among students, in a non-consensual and philosophically rich way.

Page generated in 0.0874 seconds