An overview on a nonideal system with three and a half degrees of freedom

The present paper studies a system comprised of two blocks connected by springs and dampers, and a DC motor with limited power supply fixed on a block, characterizing a non-ideal problem. This DC motor exciting the system causes interactions between the motor and the structure supporting it. Because of that, the non-ideal mathematical formulation of the problem has one and a half extra degree of freedom than the ideal one. A suitable choice of physical parameters leads to internal resonance conditions, that is, its natural frequencies are multiple of each other, by a known integer quantity. The purpose here is to study the dynamic behavior of the system using an analytical method based on perturbation techniques. The literature shows that the averaging method is the more flexible method concerning non-ideal problems. Summarizing, an steady state solution in amplitude and phase coordinates was obtained with averaging method showing the dependence of the structure amplitudes with the rotation frequency of the motor. Moreover, this solution shows that on of the amplitude coordinates has influence in the determination of the stationary rotation frequency. The analytical solution obtained shows the presence of the rotation frequency in expressions representing the oscillations of the structure, and the presence of amplitude coordinates in expressions describing the dynamic motion of the DC motor. These characteristics show the influence not only of the motor on structure but also of the response of the structure on dynamical behavior of the motor. Copyright © 2005 by ASME.

On the dynamic behaviour of a nonlinear system weakly connected to a linear single degree-of-freedom system

This paper discusses the dynamic behaviour of a nonlinear two degree-of-freedom system consisting of a harmonically excited linear oscillator weakly connected to a nonlinear attachment that behaves as a hardening Duffing oscillator. A system which behaves in this way could be a shaker (linear system) driving a nonlinear isolator. The mass of the nonlinear system is taken to be much less than that in the linear system and thus the nonlinear system has little effect on the dynamics of the linear system. Of particular interest is the situation when the linear natural frequency of the nonlinear system is less than the natural frequency of the linear system such that the frequency response curve of the nonlinear system bends to higher frequencies and thus interacts with the resonance frequency of the linear system. It is shown that for some values of the system parameters a complicated frequency response curve for the nonlinear system can occur; closed detached curves can appear as a part of the overall amplitude-frequency response. The reason why these detached curves appear is presented and approximate analytical expressions for the jump-up and jump-down frequencies of the system under investigation are given.

Comments on the paper presented by professor Christian Morrisson: The redistributive consequence of public choices according to the development of economies""

Includes bibliography

A estética da recepção contribuindo para o ensino de literatura-infantil: uma experiência com o conto A pequena vendedora de fósforos, de Hans Christian Andersen (1805-1875)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

O patinho feio e O rouxinol e o imperador da China, de Hans Christian Andersen: a literatura infantil em uma 4ª série do ensino fundamental em Presidente Prudente

Pós-graduação em Educação - FCT

The fifth freedom and the Southern Cone: a new perspective

An ECLAC document to be published in the near future examines a subject that has become a frequent topic of discussion in recent years, particularly in the Southern Cone of Latin America (Argentina, Bolivia, Brazil, Chile, Paraguay, Peru and Uruguay), where the greatest volume of land transport in South America is concentrated. Against a background of economic liberalization and integration in the region, and at a time when the development of regional transport infrastructures is growing in importance, the ECLAC Transport Unit analyses the Southern Cone Agreement on International Land Transport (Valparaíso, 1989) in an effort to give it fresh relevance and to determine whether its provisions can cope with the new challenges thrown up by more open international transport markets and management.

A contribuição do pensamento de Emmanuel Mounier para uma reflexão ético-cristã-personalista da pessoa na contemporaneidade

A presente tese explicita a proposta da filosofia social, política, cristã e ética de Emmanuel Mounier, a partir de sua antropologia filosófica, cujo fundamento é a pessoa concebida não somente em sua pessoalidade, vocação essencial de sua existência, mas, sobretudo, na sua dimensão comunitária, social/ política e transcendental e na compreensão da pessoa como um ser-com-o-outro, chegando-se à idéia de comunidade como a estrutura social que melhor permite ao homem realizar sua natureza relacional. Com esses pressupostos discuto suas principais idéias, articulando éom autores que influenciaram e fundamentaram sua filosófica como Paul Louis Landsberg, Gabriel Marcel, Max Scheler, Paul Ricoeur, indo também ao encontro de Buber no que se referem alguns conceitos discutidos por ele e que guardam grandes aproximações com o pensamento de Mounier. Os elementos essenciais da idéia de Mounier são a existência incorporada e encarnada no mundo, a comunicação, a vocação e a liberdade. Logo, o modelo político que melhor poderia favorecer esse tipo de comunidade é a sua proposta de um projeto personalista, cuja estrutura social, política e econômica tivesse como primazia a pessoa, acima das instituições ou processo político e econômico, a qual está sedimentada no ser comunitário. O caminho para se chegar a esse modelo seria uma revolução permanente, sobretudo, uma revolução espiritual, fruto de uma descentralização social e econômica que reestruturaria toda a sociedade.

Control of Limit Cycle Oscillation in a Three Degrees of Freedom Airfoil Section Using Fuzzy Takagi-Sugeno Modeling

This work presents a strategy to control nonlinear responses of aeroelastic systems with control surface freeplay. The proposed methodology is developed for the three degrees of freedom typical section airfoil considering aerodynamic forces from Theodorsen's theory. The mathematical model is written in the state space representation using rational function approximation to write the aerodynamic forces in time domain. The control system is designed using the fuzzy Takagi-Sugeno modeling to compute a feedback control gain. It useds Lyapunov's stability function and linear matrix inequalities (LMIs) to solve a convex optimization problem. Time simulations with different initial conditions are performed using a modified Runge-Kutta algorithm to compare the system with and without control forces. It is shown that this approach can compute linear control gain able to stabilize aeroelastic systems with discontinuous nonlinearities.

A recepção do mito de Heráclio por Gautier d’Arras

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Um percurso teórico-metodológico para leitura de “O isqueiro mágico” e “A rainha da neve”, de Hans Christian Andersen (1805-1875)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nonlinear dynamical analysis of an aeroelastic system with multi-segmented moment in the pitch degree-of-freedom

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)