Free-Space Optical (FSO) communication through the terrestrial atmospheric channel offers many benefits in the wireless communications arena, like power efficiency; suitability for secure communications; absence of electromagnetic interference; and potentially very high bandwidth. An optical beam propagating through the atmosphere is subject to optical turbulence. Optical turbulence is a random process that distorts the intensity and phase structure of a propagating optical beam and induces a varying signal at the receiver of an FSO communication link. This phenomenon (usually referred to as scintillation) degrades the performance of the FSO link by increasing the probability of error. In this dissertation we seek to characterize the effects of the scintillation-induced power fluctuations by determining the channel capacity of the optical link using numerical methods. We find that capacity decreases monotonically with increasing turbulence strength in weak turbulence conditions, but it is non-monotonic in strong turbulence conditions. We show that low-density parity-check (LDPC) codes provide strong error control capabilities in this channel if a perfect interleaver is used. Multiple transmit optical beams can be used to reduce scintillation. We characterize the spatial correlation of the atmospheric optical channel and determine a scintillation model for the multiple-beam scheme. With this model we can predict the effective reduction in scintillation as a function of the system design parameters. A Multi-channel FSO communications system based on orbital angular momentum (OAM)-carrying beams is studied. We analyze the effects of turbulence on the system and find that turbulence induces attenuation and crosstalk among OAM channels. Based on a model in which the constituent channels are binary symmetric and crosstalk is a Gaussian noise source, we find optimal sets of OAM states at each turbulence condition studied, and determine the aggregate capacity of the multi-channel system at those conditions. At very high data rates the FSO channel shows inter-symbol interference (ISI). We address the problem of joint sequence detection in ISI channels and decoding of LDPC codes. We derive the belief propagation equations that allow the simultaneous detection and decoding of a LDPC codeword in a ISI channel.

Magistrantūros teorinėje dalyje nagrinėjamas žmogaus gyvenimas kosmose ir kosminių aparatų dizaino kriterijai. Pirmoje dalyje susipažįstama su istoriniu kosminio skrydžio kontekstu, apžvelgiamos komercinių kosminių skrydžių realijos ir perspektyvos, pažymima dizaino svarba kosmoso turizmui. Taip pat apžvelgiama kosminių aparatų tipologija, siekiant atrasti optimaliausią dizaino objektą tolesniam tyrimui. Antroje dalyje apžvelgiami unikalūs kosminėje erdvėje žmogų veikiantys faktoriai ir jų pasekmės. Trečioje dalyje analizuojama turistinės orbitinės stoties struktūra. Remiantis realiais analogais, įvardijamos nesvarumo būklėje kylančios probleminės situacijos bei galimi jų sprendimai. Funkcinės analizės būdu suformuojamos gairės magistrantūros projektiniam darbui. / Human process of living in space and spacecraft design requirements are examined in this Master’s thesis. In part one we take a look at the historical background of space exploration, the current state and future prospects of commercial spaceflight. The importance of design in space tourism industry is stressed. Also, the classification of human spacecraft is summarized in order to select the optimal subject for the subsequent analysis. In part two we review the unique conditions and human factors in an orbital spaceflight situation. In part three, orbital space-tourism station structure is analyzed. Based on real-life analogues, we indicate problematic situations caused by weightlessness, and ponder upon possible solutions. By the means of functional analysis, guidelines are formed for the Master’s design project.

Final accepted manuscripts of parts 4 and 5 from Roadmap on Structured Light, authored by Masud Mansuripur, College of Optical Sciences, The University of Arizona.

Context: Slivan (2002) determined spin state of ten asteroids in the Koronis family. Surprisingly, all four asteroids with prograde sense of rotation were shown to have spin axes nearly parallel in the inertial space. All asteroids with retrograde sense of rotation had large obliquities and rotation periods either short or long. It was shown that Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect can explain all these peculiar facts. In particular, it drives spin axes of the prograde rotators to be captured in a secular spin-orbital resonance known as Cassini state 2. Vokrouhlický et al. (2002) dubbed these configurations "Slivan states". Aims: A question arises whether Slivan states could exist also in other regions of the main asteroid belt, in particular its inner part, where observations are most easily obtained. Here, however, dynamical difficulties arise due to convergence of the proper frequency s and the planetary frequency s6. We investigate possibilities of a long-term stable capture in the Slivan state in the inner part of the main belt. Method: We used SWIFT integrator to determine orbital evolution of selected asteroids in the inner part of the main belt. In the case of 20 Massalia, we observed the asteroid in 2011, and used these new data to help better solve the rotation state using the...

Observations of terrestrial exoplanets provide a unique statistical set that may improve our knowl- edge of their formation, structure as well as internal and orbital evolution. Close-in extrasolar planets are subjected to strong stellar tides, resulting in an extensive dissipation of mechanical energy (tidal heating), long-term orbital evolution and evolution of the rotational frequency. For the exoplanets on eccentric orbits, the traditional tidal theories predict locking into pseudo-synchronous spin states, for which the rotational frequency is slightly higher than the orbital frequency. Such predictions are, how- ever, in contradiction with the observations of moons in the Solar system, and are a consequence of simplified rheological assumptions. Here, we focus on a numerical approach to the tidal evolution of planetary orbit and rotation in a single-planet system, assuming a Maxwell viscoelastic rheology. We find equillibrium spin states, including the spin-orbit resonances, and discuss their connection with the minima of tidal heating. Locking into a spin-orbit resonance results in an irregular insolation pattern and an unequal surface temperature distribution, affecting the internal dynamics of the planet. The second part of the thesis therefore deals with the evaluation of the surface temperature and...

La majeure partie de cette thèse concerne l’étude de la susceptibilité diamagnétique en champ magnétique nul d’un gaz d’électrons de Bloch à température et densité fixées dans la limite de sfaibles températures. Pour les électrons libres (i.e. en l’absence de potentiel périodique), la susceptibilité diamagnétique a été calculée par L. Landau en 1930 ; le résultat est connu sous le nom de formule de Landau. Quant au cas des électrons de Bloch, E.R. Peierls montra en 1933 que dans l’approximation des électrons fortement liés, la formule pour la susceptibilité diamagnétique reste la même en remplaçant la masse de l’électron par sa ”masse effective” ; ce résultat est connu sous le nom de formule de Landau-Peierls. Depuis, de nombreuses tentatives pour clarifier les hypothèses de validité de la formule de Landau-Peierls ont vu le jour. Le résultat principal de cette thèse établit rigoureusement qu’à température nulle, lorsque la densité d’électrons tend vers zéro, la contribution dominante à la susceptibilité diamagnétique est donné par la formule de Landau-Peierls avecla masse effective de la plus petite bande d’énergie de Bloch. / The main part of this thesis deals with the zero-field diamagnetic susceptibility of a Blochelectrons gas at fixed temperature and fixed density in the limit of low temperatures. For a freeelectrons gas (that is when the periodic potential is zero), the steady diamagnetic susceptibilityhas been computed by L. Landau in 1930 ; the result is known as Landau formula. As for the Blochelectrons, E.R. Peierls in 1933 showed that under the tight-binding approximation, the formula forthe diamagnetic susceptibility remains the same but with the mass of the electron replaced by its”effective mass” ; this result is known as the Landau-Peierls formula. Since, there were very manyattempts in order to clarify the assumptions of validity of the Landau-Peierls formula. The mainresult of this thesis establishes rigorously that at zero temperature, as the density of electrons tendsto zero, the leading contribution of the diamagnetic susceptibility is given by the Landau-Peierlsformula with the effective mass of the lowest Bloch energy band.

We investigate two medium-facilitated interactions between properties of light upon propagation through optical fiber. The first is interaction between the spin and intrinsic orbital angular momentum in a linear optical medium. This interaction gives rise to fine structure in the longitudinal momenta of fiber modes and manifests in rotational beating effects. We probe those beating effects experimentally in cutback experiments, where small segments are cut from the output of a fiber to probe the evolution of both output polarization and spatial orientation, and find agreement between theoretical predictions and measured behavior. The second is nonlinear optical interaction due to cross- and self-phase modulation between the complex-valued temporal amplitude profile of pump pulses and the amplitude profiles of generated signal and idler pulses in optical fiber photon-pair sources utilizing the four-wave mixing process named modulation instability. We develop a model including the effects of these nonlinear phase modulations (NPM) describing the time-domain wave function of the output biphoton in the low-gain regime. Assuming Gaussian temporal amplitude profiles for the pump pulse, we numerically simulate the structure of the biphoton wave function, in symmetric and asymmetric group velocity matching configurations. Comparing the overlap of the joint temporal amplitudes with and without NPM indicates how good of an approximation neglecting NPM is, and we investigate the effects of NPM on the Schmidt modes. We find that effects of NPM are small on temporally separable sources utilizing symmetric group velocity matching, but appreciably change the state of temporally entangled sources with the same group velocity matching scheme. For sources designed to produce entangled biphotons, our simulations suggest that NPM increases the Schmidt number, which may increase entanglement resource availability with utilization of a phase-sensitive detection scheme. We find that NPM effects on temporally separable sources designed with asymmetric group velocity matching produce non-negligible changes in the state structure. The purity is unaffected at perfect asymmetric group velocity matching, but if the pump is detuned from the correct wavelength, the purity degrades. The largest changes to the state due to NPM occur in long fibers with long pulse durations and low repetition rates.

O objetivo do presente estudo foi avaliar a resposta tecidual e clínica a um implante orbitário de polimetilmetacrilato (PMMA), oco e multiperfurado em sua porção posterior em modelo animal de evisceração. Dezesseis coelhos da raça Nova Zelândia foram submetidos à evisceração do globo ocular direito. Todos receberam implante de polimetilmetacrilato de 12 mm de diâmetro multiperfurado em sua semiesfera posterior. O estudo foi dividido em avaliação clínica e histopatológica. A avaliação clínica foi diária até 14 dias pós-evisceração e, a cada sete dias, até completar 180 dias. Os animais foram divididos em grupos de quatro animais e cada um foi submetido à exenteração com 07, 30, 90 e 180 dias e depois à eutanásia. A análise histopatológica teve por fim caracterizar o padrão inflamatório, a estrutura do colágeno e o grau de neovascularização. Para isso, além da tradicional coloração pela hematoxilina-eosina (HE), utilizou-se o corante Picrosirius Red (PSR) e imunohistoquímica com o marcador CD34. Não houve sinais de infecção, exposição ou extrusão do implante em nenhum animal durante o estudo. Já no sétimo dia, o tecido neoformado migrou para dentro do implante formando uma rede fibrovascular através dos canais posteriores. A resposta inflamatória diminuiu ao longo do tempo avaliado e não foram encontradas células gigantes multinucleadas. O implante analisado é biocompatível, inerte e sua estrutura permite a sua integração aos tecidos orbitários pelo crescimento fibrovascular. / The objective of the present study was to evaluate the tissue and clinical response to a hollow and multiperforated polymethylmethacrylate (PMMA) orbital implant in its posterior portion in an evisceration animal model. Sixteen New Zealand rabbits were submitted to evisceration of the right eyeball. All animals were implanted with 12 mm diameter of PMMA multiperforated in their posterior hemisphere. The study was divided into clinical and histopathological evaluation. The clinical evaluation was daily during the 14 days after evisceration, and every seven days until completing 180 days. The animals were divided into groups of four animals and each was exenterated at 07, 30, 90 and 180 days and then at euthanasia. Histopathological analysis was aimed at characterizing the inflammatory pattern, the collagen structure and the degree of neovascularization. For this, in addition to the traditional hematoxylin-eosin staining (HE), we used the Picrosirius Red dye (PSR) and immunohistochemistry with the CD34 marker. There were no signs of infection, exposure or extrusion of the implant in any animal during the study. On the seventh day, the newly formed tissue migrated into the implant, forming a fibrovascular network through the posterior channels. The inflammatory response decreased over time and no multinucleated giant cells were found. The implant analyzed is biocompatible, inert and its structure allows its integration into the orbital tissues by fibrovascular growth.

Esta tese apresenta o desenvolvimento de métodos numéricos diretos e indiretos para otimização de trajetórias e determinação de controle ótimo baseados na teoria da variação segunda. São desenvolvidos os métodos do gradiente combinado e da variação segunda, também conhecido como método dos extremais vizinhos. O primeiro é um método direto, resultante da utilização do método do gradiente - descida mais rápida - e do método do gradiente em segunda ordem. O segundo é um método indireto que resolve o problema de valor de contorno em dois pontos associado ao problema de controle ótimo. Visando mostrar a eficiência e aplicabilidade dos métodos, são resolvidos, primeiramente, problemas clássicos em teoria do controle ótimo como: problema de Zermelo e problema da brachistócrona. Em seguida, os métodos são aplicados a problemas de trajetórias espaciais envolvendo transferências entre órbitas circulares e de pequenas excentricidades. São analisadas diversas variações de raios e diferentes tempos finais. Os resultados também são comparados com os obtidos por uma teoria linear.

Neste trabalho é mostrado um quadro geral de possibilidades de movimento num plano representativo para o espaço de fase quadrimensional associado ao problema restrito de três corpos médio plano, na vizinhança da ressonância 3:1. Isto é obtido através de sucessivas intersecções de trajetórias com o referido plano sobre várias curvas de energia constante. As trajetórias não caóticas estão relacionadas a pontos que podem ser considerados fixos no plano representativo. A interpretação destes pontos é feita a partir de secções de Poincaré representadas em termos de excentricidade e longitude do perihélio, cujas trajetórias correspondem a libração internas ou externas e circulações com relação ao referido ângulo. A identificação de asteróides reais sobre o plano representativo é realizada e mostra que estes estão sempre localizados em regiões de curvas invariantes. Além disto, é apresentado um modelo qualitativo integrável usando parte do hamiltoniano mádio elíptico, que embora não seja suficiente para descrever a dinâmica da ressonânica 3:1, constitui uma generalização do modelo circular plano.