977 resultados para perturbações periódicas


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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This work aimed to point out the major changes in post-graduation and their implications on professor's well-being. For this proposal, exploratory research was carried out using books and periodicals, indexed in SciELO and Web of Science. We tried to emphasize research published in the last decade. The subject is difficult to bound, as the definition of quality of life itself depends on geographical and cultural aspects. Thus, the main aspects that surround this controversial issue were selected, with no claim to exhaust it. It is pretty clean that university managers believe that the university must meet the productivist requirements. Therefore, university and undergraduate, which in the recent past were spaces of thinking, became a series production space. In this scenario it is not enough pure research and long-term, but the rapid and direct research. Also, some studies already show the relationship between the work of public universities and health issues. It is believed that the deleterious relationship between the productivist pressure and the teacher's quality of life will be quite evident in a near future

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Oeceoclades aculate (Lindl.) Lindl., an invasive orchid, was analyzed as to its reproductive phenology and spatial distribution, correlation between abundance of mature and immature individuals, and verifying these with microclimate patterns in the Cerrado (savanna-like vegetation) of Mogi Guacu, Sao Paulo State, Brazil. For the reproductive phenology 100 plants were followed and the distribution pattern was identified by the Morisita Index (MI) and the Variance Ratio/Average (R) in 20 plots of 20x10m, reduced to 10x10m afterwards. The phenology presented seasonality, with flowering from November to February, fructification from February to June, and dehiscence from June to July. Mature and immature individuals aggregated and correlated to each other, indicating dependence between the ontogenetic stages. The luminosity was the preponderant microclimatic factor in the allocation of plants. Seasonal climatic changes and intensity of anthropogenic disturbances seem to be more important for the establishment of the species than microclimate.

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Consider a finite body of mass m (C1) with moments of inertia A, B and C. This body orbits another one of mass much larger M (C2), which at first will be taken as a point, even if it is not completely spherical. The body C1, when orbit C2, performs a translational motion near a Keplerian. It will not be a Keplerian due to external disturbances. We will use two axes systems: fixed in the center of mass of C1 and other inertial. The C1 attitude, that is, the dynamic rotation of this body is know if we know how to situate mobile system according to inertial axes system. The strong influence exerted by C2 on C1, which is a flattened body, generates torques on C1, what affects its dynamics of rotation. We will obtain the mathematical formulation of this problem assuming C1 as a planet and C2 as the sun. Also applies to case of satellite and planet. In the case of Mercury-Sun system, the disturbing potential that governs rotation dynamics, for theoretical studies, necessarily have to be developed by powers of the eccentricity. As is known, such expansions are delicate because of the convergence issue. Thus, we intend to make a development until the third order (superior orders are not always achievable because of the volume of terms generated in cases of first-order resonances). By defining a modern set of canonical variables (Andoyer), we will assemble a disturbed Hamiltonian problem. The Andoyer's Variables allow to define averages, which enable us to discard short-term effects. Our results for the resonant angle variation of Mercury are in full agreement with those obtained by D'Hoedt & Lemaître (2004) and Rambaux & Bois (2004)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Saúde Coletiva - FMB

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Pós-graduação em Agronomia (Irrigação e Drenagem) - FCA

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Pós-graduação em Física - FEG

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Neste trabalho, foi estudado o modelo matemático oscilatório proposto por Daugulis et al. (1997) referente a um processo contínuo de fermentação alcoólica, de modo a compreender sua estrutura, variáveis, fenômenos e hipóteses postuladas. O estudo foi realizado de modo a compreender como os mecanismos de inibição por produto e substrato, e como os mecanismos adaptativos do microrganismo são levados em consideração pelo modelo, resultando no comportamento oscilatório desejado. Por fim, foram realizadas simulações com perturbações do tipo degrau na taxa de diluição e na concentração de substrato na alimentação, de modo a extrapolar o comportamento do modelo.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The dynamics of the rotation of a satellite is an old and classical problem, specially in the Euler formalism. However, with these variables, even in torque free motion problem, the integrability of the system is far from trivial, mainly when the three moments of the inertia are not equal. Another disadvantage occurs when the inclinations between some plans are null or close to zero, so the nodes become undetermined. In this work, we propose the use of modern Andoyer's variables. These are a set of canonical variables and therefore some significant advantages can be obtained when dealing with perturbation methods. On other the hand, the integrability of the torque free motion becomes very clear, as the system is reduced to a problem of one degree of freedom. The elimination of the singularities mentioned above, can be solved very easily, with Pincaré-type variables. In this work we give the background concepts of the Andoyer's variables and the disturbing potential is obtained for the rotational dynamics of a satellite perturbed by a planet. In the case when A = B (moments of inertia) and due to the current variables, the averaged system is trivially obtained through very simple integrations

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)