Reversible Hamiltonian Liapunov center theorem

We study the existence of periodic solutions in the neighbourhood of symmetric (partially) elliptic equilibria in purely reversible Hamiltonian vector fields. These are Hamiltonian vector fields with an involutory reversing symmetry R. We contrast the cases where R acts symplectically and anti-symplectically. In case R acts anti-symplectically, generically purely imaginary eigenvalues are isolated, and the equilibrium is contained in a local two-dimensional invariant manifold containing symmetric periodic solutions encircling the equilibrium point. In case R acts symplectically, generically purely imaginary eigenvalues are doubly degenerate, and the equilibrium is contained in two two-dimensional invariant manifolds containing nonsymmetric periodic solutions encircling the equilibrium point. In addition, there exists a three-dimensional invariant surface containing a two-parameter family of symmetric periodic solutions.

A procedure to estimate parameters of a line segment taking into account its representation through π circuits: Theoretical development

The objective of this paper is to show an alternative methodology to estimate per unit length parameters of a line segment of a transmission line. With this methodology the line segment parameters can be obtained starting from the phase currents and voltages in receiving and sending end of the line segment. If the line segment is represented as being one or more π circuits whose frequency dependent parameters are considered lumped, its impedance and admittance can be easily expressed as functions of the currents and voltages at the sending and receiving end. Because we are supposing that voltages and currents at the sending and receiving end of the line segment (in frequency domain) are known, it is possible to obtains its impedance and admittance and consequently its per unit length longitudinal and transversal parameters. The procedure will be applied to estimate the longitudinal and transversal parameters of a small segment of a single-phase line that is already built. © 2006 IEEE.

The effect of chloride ions and A. ferrooxidans on the oxidative dissolution of the chalcopyrite evaluated by electrochemical noise analysis (ENA)

It is believed that the dissolution of chalcopyrite (CuFeS2) in acid medium can be accelerated by the addition of Cl- ions, which modify the electrochemical reactions in the leaching system. Electrochemical noise analysis (ENA) was utilized to evaluate the effect of the Cl- ions and Acidithiobacillus ferrooxidans on the oxidative dissolution of a CPE-chalcopyrite (carbon paste electrode modified with chalcopyrite) in acid medium. The emphasis was on the analysis of the admittance plots (Ac) calculated by ENA. In general, a stable passive behavior was observed, mainly during the initial stages of CPE-chalcopyrite immersion, characterized by a low passive current and a low dispersion of the Ac plots, mainly after bacteria addition. This can be explained by the adhesion of bacterial cells on the CPE-chalcopyrite surface acting as a physical barrier. The greater dispersions in the Ac plots occurred immediately after the Cl- ions addition, in the absence of bacteria characterizing an active-state. In the presence of bacteria the addition of Clions only produced some effect after some time due to the barrier effect caused by bacteria adhesion. © (2009) Trans Tech Publications.

Representaciones imaginarias de la interacción y violencia en la escuela

School violence research (sociopaedagogical and psychosocial perspectives) has not appropiately taken into account interpersonal and imaginary elements that may be extremely relevant for the understanding of this phenomena. This article analizes the imaginaries that articulates the violence of youth groups in a context of interpersonal relationships in the institutional space of a Rio Claro (Brazil) secondary school. The results are based on the analysis of four youth groups discourses, gathered in succesive group interviews, as well as the drawings made and pictures taken on their respective schools. They show a strong imaginary of generalized violence, in and out the school, with a representation of the school as unfair and aggressor and the students, aggressors themselves, as humiliated and undervalued.

A set of linear equations to calculate the steady-state operation of an electrical distribution system

In this paper, the calculation of the steady-state operation of a radial/meshed electrical distribution system (EDS) through solving a system of linear equations (non-iterative load flow) is presented. The constant power type demand of the EDS is modeled through linear approximations in terms of real and imaginary parts of the voltage taking into account the typical operating conditions of the EDS's. To illustrate the use of the proposed set of linear equations, a linear model for the optimal power flow with distributed generator is presented. Results using some test and real systems show the excellent performance of the proposed methodology when is compared with conventional methods. © 2011 IEEE.

A mixed-integer LP model for the reconfiguration of radial electric distribution systems considering distributed generation

The problem of reconfiguration of distribution systems considering the presence of distributed generation is modeled as a mixed-integer linear programming (MILP) problem in this paper. The demands of the electric distribution system are modeled through linear approximations in terms of real and imaginary parts of the voltage, taking into account typical operating conditions of the electric distribution system. The use of an MILP formulation has the following benefits: (a) a robust mathematical model that is equivalent to the mixed-integer non-linear programming model; (b) an efficient computational behavior with exiting MILP solvers; and (c) guarantees convergence to optimality using classical optimization techniques. Results from one test system and two real systems show the excellent performance of the proposed methodology compared with conventional methods. © 2012 Published by Elsevier B.V. All rights reserved.

O processo de individualização do sujeito no discurso publicitário

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise discursiva de dicionários de língua portuguesa

Pós-graduação em Estudos Linguísticos - IBILCE

Letramento digital e letramento escolar: uma abordagem linguística da prática de escrita em blogs

Pós-graduação em Estudos Linguísticos - IBILCE

A realidade-ficção do discurso televisivo

Pós-graduação em Estudos Linguísticos - IBILCE

O doente imaginário, de Molière, encenado pelo Teatro do Ornitorrinco (1989)

Pós-graduação em Artes - IA

Vibrações: a arte/educação nas práticas e no discurso em saúde mental

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

O brinquedo do parque: um conceito lúdico como arte do reaproveitamento

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Flicts, livro de artista

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Tàpies e seus corpos: um olhar sexuado

Pós-graduação em Artes - IA