Optimal attitude corrections for cylindrical spacecraft

A first order analytical model for optimal small amplitude attitude maneuvers of spacecraft with cylindrical symmetry in an elliptical orbits is presented. The optimization problem is formulated as a Mayer problem with the control torques provided by a power limited propulsion system. The state is defined by Seffet-Andoyer's variables and the control by the components of the propulsive torques. The Pontryagin Maximum Principle is applied to the problem and the optimal torques are given explicitly in Serret-Andoyer's variables and their adjoints. For small amplitude attitude maneuvers, the optimal Hamiltonian function is linearized around a reference attitude. A complete first order analytical solution is obtained by simple quadrature and is expressed through a linear algebraic system involving the initial values of the adjoint variables. A numerical solution is obtained by taking the Euler angles formulation of the problem, solving the two-point boundary problem through the shooting method, and, then, determining the Serret-Andoyer variables through Serret-Andoyer transformation. Numerical results show that the first order solution provides a good approximation to the optimal control law and also that is possible to establish an optimal control law for the artificial satellite's attitude. (C) 2003 COSPAR. Published by Elsevier B.V. Ltd. All rights reserved.

Boundary crisis and transient in a dissipative relativistic standard map

Some dynamical properties for a problem concerning the acceleration of particles in a wave packet are studied. The model is described in terms of a two-dimensional nonlinear map obtained from a Hamiltonian which describes the motion of a relativistic standard map. The phase space is mixed in the sense that there are regular and chaotic regions coexisting. When dissipation is introduced, the property of area preservation is broken and attractors emerge. We have shown that a tiny increase of the dissipation causes a change in the phase space. A chaotic attractor as well as its basin of attraction are destroyed thereby leading the system to experience a boundary crisis. We have characterized such a boundary crisis via a collision of the chaotic attractor with the stable manifold of a saddle fixed point. Once the chaotic attractor is destroyed, a chaotic transient described by a power law with exponent 1 is observed. (C) 2011 Elsevier B.V. All rights reserved.

A produção de conhecimento e verdade no contemporâneo

O presente artigo procura refletir sobre a produção de conhecimento e verdade no contemporâneo articuladas com o conceito de biopoder e a imersão do sujeito na construção desse conhecimento. Mediante tais reflexões, chega-se à conclusão que as ciências humanas precisam rever o lugar cômodo do cientificismo acadêmico para repensar e relativizar a verdade visando a transformação das práticas sociais objetivantes e historicamente construídas para uma outra forma de conhecimento capaz de questionar as instâncias instituídas nos campos do saber e do poder a fim de propor novos paradigmas científicos e uma subjetividade mais autêntica e com novas significações

Travestilidades nômades: a explosão dos binarismos e a emergência queering

Apresentamos neste artigo algumas problematizações a respeito da expressão travesti, que, não se apoiando em um modelo único de referência sexual e de gênero para sua efetivação, nos permitiria falar em processos de 'travestilização'. Esses processos se constituem através de dispositivos em que lineamentos duros, flexíveis e de fuga participam da criação de seus corpos, desejos e prazeres, transitando entre efeitos-consequências de discursos normativos e singularizadores. Sua circulação no mundo coloca em xeque as matrizes binárias heteronormativas do sistema sexo/gênero/desejo, que se desmancham diante de modos de subjetivação orientados por potências subversivas criadoras de novos campos possíveis de existencialização. Nessa perspectiva, queremos mostrar que as expressões sexuais e de gêneros das travestis formulam novas questões a respeito dos modelos identitários vigentes, demonstrando que a coerência e a inteligibilidade impostas pelos códigos heteronormativos precisam ser urgentemente revistas, de modo a questionar a respeito da ordem social que apresenta o gênero associado ao sexo reprodutivo, para ressignificar as expressões sexuais, gendradas e subjetivas, em sua processualidade histórica que explode os binarismos, despreza os universais e desmancha o absolutismo da ideia de verdade, enraizados nos sistemas binários de pensamentos sedentários, fechados, universais e a-históricos.

Relation between quality and rheological properties of lactic beverages

The physicochemical (pH, fat and total solids content), sensory (appearance, consistency and taste), and rheological characteristics of five different commercial brands of lactic beverages were determined. Rheological measurements were obtained at 5 degreesC and 25 degreesC using a Brookfield rheometer. The experimental data were described by the power law and Herschel-Bulkley models. The ANOVA of the results were conducted using an incomplete block design, and using Tukey test. Samples showed a significant difference (P less than or equal to 0.05%) for fat content and pH. There was a significant difference in total solids content only among Nestle (A), Batavo (C), and Parmalat (D) samples. Sensory evaluation showed more global acceptability for Nestle; however, Nestle and Vigor (E) lactic beverages obtained better results for appearance than for consistency and taste. Batavo obtained the best score for taste. All test samples exhibited non-Newtonian behavior, with thixotropy. Upward curves showed pseudoplastic behavior, while downward curves showed dilatant behavior with the exception of the Nestle sample, at 25 degreesC. Lactic beverages from all brands analyzed showed similar rheological behavior. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Rheological properties and fluid dynamics of egg yolk

The rheological behavior of egg yolk was studied at a range of temperatures (277-333 K) using a concentric cylinder viscometer. Rheological behavior was pseudoplastic and flow curves fitted by the power law model. The consistency and behavior indexes, dependent on temperature, were expressed by an Arrhenius-type equation. The rheological parameters, together with experimental values of pressure loss in tube flow were used to calculate friction factors. The good agreement between predicted and observed values confirmed the reliability of the equations proposed for describing the flow behavior of the egg yolk. (c) 2005 Published by Elsevier Ltd.

O encabecamento das armaduras urbanas nacionais: uma revisão

Starting from Jefferson's 'law of the primate city' and Zipf's 'rank-size rule', examines the question of the heading of national urban systems, seeking to stretch the analysis as far as possible in space and time. Thus, 131 countries were included in the study, most of them also viewed from the evolutive side. It was found that there is a main tendency for urban systems to evolve to the primate leadership, maintained by Jefferson as the normal pattern. Among the various factors that act in this direction, the attraction exercised by political power located in the capital cities is dominant.-English summary

Experimental model of pulmonary carcinogenesis in Wistar rats

Purpose: To elaborate an experimental model of pulmonary carcinogenesis in Wistar rats. Methods: Male Rattus norvegicus albinus, Wistar lineage was carried through an intra-pulmonary instillation of the Benzo[a]pyrene (B[a]P) dilution in alcohol 70%, a polycyclic aromatic hydrocarbon widely known by its power of tumoral induction. Three experimental groups had been formed with 08 animals each: Control Group (Alcohol 70%); B[a]P Group 10 mg/kg; e B[a]P Group 20mg/ kg, submitted to euthanasia 08, 10, 12 and 14 weeks after the experimental procedure. The pulmonary sections had been colored by hematoxilin-eosin (HE) and submitted to the morphometrical analysis to describe the tissue alterations. Results: The presence of diffuse inflammatory alterations was observed in all groups, however, at the analysis of the pulmonary tissue of the experimental groups, it had been observed hyperplasic alterations (BALT hyperplasia), and in one of the animals of the experimental group 20mg/kg (12 weeks), it was noticed the presence of cellular epithelial tracheal pleomorphism, suggesting the adenocarcinoma formation in situ. Conclusion: The main secondary alterations to the intra-pulmonary instillation of B[a]P in Wistar rats were: cellular proliferation, inflammatory alterations of several degrees and nodular lymphoid hyperplasias. The association of an activator agent of the pulmonary metabolic reply is necessary to establish the ideal reply-dose to the development of the lung cancer.

Fast non-technical losses identification through Optimum-Path Forest

Fraud detection in energy systems by illegal consumers is the most actively pursued study in non-technical losses by electric power companies. Commonly used supervised pattern recognition techniques, such as Artificial Neural Networks and Support Vector Machines have been applied for automatic commercial frauds identification, however they suffer from slow convergence and high computational burden. We introduced here the Optimum-Path Forest classifier for a fast non-technical losses recognition, which has been demonstrated to be superior than neural networks and similar to Support Vector Machines, but much faster. Comparisons among these classifiers are also presented. © 2009 IEEE.

Some dynamical properties of a classical dissipative bouncing ball model with two nonlinearities

Some dynamical properties for a bouncing ball model are studied. We show that when dissipation is introduced the structure of the phase space is changed and attractors appear. Increasing the amount of dissipation, the edges of the basins of attraction of an attracting fixed point touch the chaotic attractor. Consequently the chaotic attractor and its basin of attraction are destroyed given place to a transient described by a power law with exponent -2. The parameter-space is also studied and we show that it presents a rich structure with infinite self-similar structures of shrimp-shape. © 2013 Elsevier B.V. All rights reserved.

Desenvolvimento de ferramentas computacionais inteligentes para identificação de perdas comerciais em sistemas de energia

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo comparativo de medição de força de corte no processo de retificação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Disciplinamento corporal: as relações de poder nas práticas escolares cotidianas

Pós-graduação em Educação - FFC

Reflorestamento ciliar à margem do Reservatório da Hidrelétrica de Ilha Solteira em diferentes modelos de plantio

Pós-graduação em Agronomia - FEIS

Efeito do tratamento a plasma do politetrafluoroetileno (PTFE) nas suas propriedades eletrostáticas e superficiais

Pós-graduação em Ciência e Tecnologia de Materiais - FC