This study evaluates the feasibility of reusing lightweight solar sails in order to transport 1.69 * 10^6 sunshades, made out of occulting membranes with free-standing SiO2 nanotube films, to the adjusted sun-Earth Lagrange point, L1'. The purpose of the study was therefore to evaluate if this method is sufficient enough to lower Earth's average surface temperature by 1 degree C within a reasonable time frame, due to the rapid climate change, and compare the total launch mass to previously proposed methods. Two mission times of 10 years and 15 years were used, and three different starting altitudes, the GEO, MEO and LEO orbits, were investigated. The results showed that the method in this study was feasible for all combinations of starting altitudes and mission times. The solution where the mission time was set to 15 years and where the starting altitude was set to the GEO orbit, resulted in a launch mass of 11\% of the mass of the previously proposed solution. Furthermore, the investigation showed that high altitude starting orbits and long mission times resulted in a lower launch mass. However, in order to fulfill the goal of reducing the average temperature by 1 degree C in a reasonable time frame, the mission time cannot be too long. Finally, the results and calculations in this study are partially based on assumptions and simplifications, and therefore the results should be considered as approximations and not exact analytical solutions.

No description available.

No description available.

No description available.

No description available.

Este trabalho buscou verificar se as tecnologias da informação e comunicação podem ser utilizadas como meios potencialmente significativos para se efetivar a aprendizagem significativa de conceitos introdutórios de Física sobre ondas sonoras. Para alcançar este objetivo foi elaborado um material educacional, sob a forma de um ambiente virtual, em que os conceitos físicos a serem aprendidos foram problematizados na forma de desafios. Estes desafios foram desenvolvidos tendo como base a teoria da aprendizagem significativa de Ausubel. A metodologia que orientou a realização desta pesquisa foi o delineamento experimental com grupo de controle e só pós-teste. A pesquisa foi realizada com alunos do ensino médio de uma escola pública estadual de Mato Grosso do Sul, localizada na cidade de Campo Grande. Os dados obtidos foram analisados segundo a teoria da aprendizagem significativa e a epistemologia de Bachelard. As análises revelaram a existência de obstáculos epistemológicos que prejudicaram a aprendizagem de alguns dos conceitos físicos problematizados nos desafios. Além dos aspectos cognitivos, observou-se que o ambiente virtual e a forma de utilização adotada favoreceram a motivação e a satisfação dos alunos para aprender Física e também atenderam às expectativas deles. A pesquisa permitiu verificar que as tecnologias da informação e comunicação são recursos educacionais que facilitam a aprendizagem significativa de conceitos introdutórios sobre ondas sonoras. A partir destes resultados não se pretende, entretanto, advogar a favor do computador como uma estratégia ou mesmo um recurso que possa substituir as aulas expositivas e presenciais. O que se pretende é: evidenciar que o computador - quando devidamente utilizado, pode favorecer a construção do conhecimento pelo aluno; e que, desta maneira deve ser considerado como mais um recurso a ser utilizado pelo professor para favorecer a aprendizagem de seus alunos. This work tried to verify if the information and communication technologies can be used like potential and significant ways to accomplish learning physics basic concepts about sound waves. To get to this objective, I had developed an educational material on form of a virtual environment, in which physics concepts to be learnt were showed like gages. These gages were developed using Ausubel's significant learning theory. The methodology which oriented the realization of this research was the experimental delineation, with control group and post test. This research was realized with medium-level students from a public school of Campo Grande, in the State of Mato Grosso do Sul, Brazil. The data that has been got were analised according as the significant learning theory and Bachelard's epistemology. The analysis showed the existence of epistemology obstacles, which damaged the learning of some physics concepts showed in the gages. Beyond the cognition aspects, the motivation and satisfaction were analysed, and the results sugested that the virtual environment and the way of use adopted helped the student's motivation and answered their expectatives. This research showed that information and communication technologies are educational resources which help people to learn basic concepts of sound waves. Although the good results, nobody pretends to defend the computer as a strategy or a resource that can substitute the expository and presential lessons. The objective is to evidence that the computer - when correctly used, can help the knowledge construction by the student; and in this way it has to be considered as an one more resource to be used by teachers to help the learning of their students. / This work tried to verify if the information and communication technologies can be used like potential and significant ways to accomplish learning physics basic concepts about sound waves.

Hypothesis-free learning is increasingly popular given the large amounts of data becoming available. Structure learning, a hypothesis-free approach, of graphical models is a field of growing interest due to the power of such models and lack of domain knowledge when applied on complex real-world data. State-of-the-art techniques improve on scalability of structure learning, which is often characterized by a large problem space. Nonetheless, these techniques still suffer computational bottlenecks that are yet to be approached. In this work, we focus on two popular models: dynamical linear systems and Markov random fields. For each case, we investigate major computational bottlenecks of baseline learning techniques. Next, we propose two frameworks that provide higher scalability using appropriate problem reformulation and efficient structure based heuristics. We perform experiments on synthetic and real data to validate our theoretical analysis. Current results show that we obtain a quality similar to expensive baseline techniques but with higher scalability. / Master of Science / Structure learning of graphical models is the process of understanding the interactions and influence between the variables of a given system. A few examples of such systems are road traffic systems, stock markets, and social networks. Learning the structure uncovers the invisible inter-variables relationships that govern their evolution. This process is key to qualitative analysis and forecasting. A classic approach to obtain the structure is through domain experts. For example, a financial expert could draw a graphical structure that encodes the relationships between different software companies based on his knowledge in the field. However, the absence of domain experts in the case of complex and heterogeneous systems has been a great motivation for the field of data driven, hypothesis free structure learning. Current techniques produce good results but unfortunately require a high computational cost and are often slow to execute. In this work, we focus on two popular graphical models that require computationally expensive structure learning methods. We first propose theoretical analysis of the high computational cost of current techniques. Next, we propose a novel approach for each model. Our proposed methods perform structure learning faster than baseline methods and provide a higher scalability to systems of large number of variables and large datasets as shown in our theoretical analysis and experimental results.

The solution u=u(t)=u(t,λ) of (E) u′(t)+λ∫₀^tu(t-τ)(d+a(τ))dτ=0, u(0)=1, t ≥ 0, λ ≥ 1 where d ≥ 0, a is nonnegative, nonincreasing, convex and ∞ ≥ a(0+) > a(∞) = 0 is studied. In particular the question asked is: When is (F) ∫₀^∞_{λ ≥ 1}^sup|u′′(t, λ)/λ|dt < ∞? We obtain two necessary conditions for (F). For (F) to hold, it is necessary that (-lnt)a(τ)∈L¹(0,1) and lim sup _τ→∞ (τθ(τ))²/φ(τ) <∞ where â(τ)=∫₀^∞e^-iτta(t)dt=φ(τ)-iτθ(τ) (φ,θ both real). We obtain sufficient conditions for (F) to hold which involve φ and θ (See Theorem 7). Then we look for direct conditions on a which imply (F). with the addition assumption -a′ is convex, we prove that (F) holds provided any one of the following hold: (i) a(0+)<∞, (ii) 0<lim inf _τ→∞ τ∫₀^1/τsa(s)ds / ∫₀^1/τ-sa′(s)ds ≤ lim sup _τ→∞ τ∫₀^1/τsa(s)ds / ∫₀^1/τ-sa′(s)ds < ∞, (iii) lim _τ→∞ τ∫₀^1/τsa(s)ds / ∫₀^1/τa(s)ds = 0, (iv) lim _τ→∞ ∫₀^1/τ-sa′(s)ds / ∫₀^1/τa(s)ds = 0, a²(t)/-a′(t) is increasing for small t and a²(t) / -ta′(t)∈L¹(0,∈) for some ∈>0, (v) lim _τ→∞ ∫₀^1/τ-sa′(s)ds / ∫₀^1/τa(s)ds = 0 and τ(∫₀^1/τ a(s)ds)³ / ∫₀^1/τ-sa′(s)ds ≤ M < ∞ for δ ≤ τ < ∞ (some δ > 0). Thus (F) holds for wide classes of examples. In particular, (F) holds when d+a(t) = t^-p, 0 < p < 1; a(t)+d = -lnt (small t); a(t)+d = t⁻¹(-lnt)^-q, q > 2 (small t). / Ph. D. / incomplete_metadata

O problema de reconstrucão digital de imagens (Image Inpainting) possui diversas abordagens para sua resolução. Uma possibilidade consiste na sua modelagem como um problema de otimizacão contínua (lasso). Na presente dissertacão aplica-se o método do gradiente espectral projetado a esse problema. Desenvolve-se inteiramente a modelagem do problema assim como a implementacão computacional do método de otimização que o resolve. Resultados computacionais demonstram a qualidade do método para um conjunto de imagens digitais / The image inpainting problem has several resolution approaches. One possibility consists in its modeling as a continuous optimization problem. In the present dissertation we apply the spectral projected gradient method to this problem. We develop the whole modeling of the problem as well as the computational implementation of the optimization method to solve it. Computational results show the quality of the method for a set of digital images

Papilomavírus humanos (HPVs) são vírus de DNA que infectam células epiteliais, podendo ser responsáveis pelo aparecimento de lesões benignas e malignas. Dentre os mais de 120 tipos identificados, o HPV -16 constitui o principal agente etiológico do câncer cervical, que é uma das maiores causas de morte por câncer em mulheres no mundo. Sendo assim, infecções associadas ao HPV devem ser prevenidas por vacinas indutoras de resposta imune vírus-específicas. A proteína L1 do capsídio viral é capaz de arranjar-se em partículas morfologicamente e antigenicamente semelhantes ao vírus, denominadas \"virus-like particles\" (VLPs), que induzem altos títulos de anticorpos neutralizantes. Neste trabalho, foram clonados os genes L1 selvagem e otimizado de HPV -16 em vetores de expressão de leveduras metilotróficas como Hansenula polymorpha e Pichia pastoris. Foi observada uma expressão consistente da proteína recombinante apenas em P. pastoris, com o gene L1 otimizado. Foram realizadas diversas tentativas de purificação da proteína heteróloga, empregando técnicas de cromatografia e ultracentrifugação em gradiente descontínuo de sacarose. A correta montagem das VLPs foi confirmada por microscopia eletrônica. Problemas de agregação, heterogeneidade e adsorção a superfícies apresentados pela proteína L1 foram resolvidos após utilização de surfactante não-iônico e de um procedimento de desmontagem e remontagem das partículas, gerando preparações mais homogêneas. Ensaios de hemaglutinação e inibição da hemaglutinação comprovaram a apresentação de epítopos conformacionais na superfície das VLPs. Este trabalho demonstrou pela primeira vez a expressão da proteína L1 de HPV -16 em P. pastoris, visando ao desenvolvimento de uma vacina profilática de baixo custo para o sistema público de saúde. / Human papillomaviruses (HPVs) are DNA viruses that infect epithelial cells and can cause both benign and malignant lesions. From over 120 types catalogued so far, HPV-16 is the main etiologic agent of cervical cancer, which is the one of the most common causes of cancer deaths among women worldwide. Thus, HPV -associated infections might be prevented by vaccine inducing virus-specific immune responses. The L1 major capsid protein can self assemble into virus-like particles (VLPs), which are morphologically and antigenically indistinguishable from native viruses and induce high titers of neutralizing antibodies. In this work, we have cloned wild-type and codon-optimized L1 genes from HPV-16 in expression vectors of the methylotrophic yeasts Hansenula polymorpha and Pichia pastoris. Consistent L1 expression was only observed in P. pastoris transformed with the construction containing the codon-optimized gene. Many attempts to purify the heterologous protein were made, including chromatography and ultracentrifugation in sucrose density gradients. The correct assembly of VLPs was confirmed by electron microscopy. Some problems presented by recombinant L1 like aggregation, surface adsorption and heterogeneity were solved by using non-ionic surfactants and a procedure of disassembly and reassembly of the particles. Hemagglutination and hemagglutination inhibition assays corroborated the display of surface conformational epitopes by VLPs. This work showed for the first time the expression of the HPV-16 L1 protein in P. pastoris, aiming the development of a prophylactic vaccine free of charge for the public health system in Brazil.