8,026 research outputs found

    CGE: da divulgação à investigação

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    A divulgação da ciência e da tecnologia aparece como uma área fundamental na sociedade actual. Isto não será de estranhar pois os tremendos desafios que se colocam ao futuro de um planeta que a cada 12 a 13 anos tem mais mil milhões de habitantes e onde o consumo aumenta de uma forma exponencial, levanta problemas que eventualmente só o conhecimento científico poderá resolver; é importante que as opções que venham a ser tomadas possam ser compreendidas pela generalidade das pessoas, pois são justamente elas que irão ser mais afectadas por essas decisões. Ciente das responsabilidades sociais que lhe cabe enquanto instituição produtora de saber, desde sempre tem sido estratégia do CGE um forte empenhamento nas actividades de divulgação científica e tecnológica. A par do compromisso com a investigação e sua apresentação à comunidade científica, sem dúvida o primeiro factor de prestígio para qualquer grupo de investigação, acresce a responsabilidade de zelar pela qualidade com que a ciência chega ao grande público. Nesse âmbito o CGE mantém, desde a sua formação, uma dinâmica de incentivo, apoio e valorização a todas as iniciativas de divulgação científica, em particular na área das Ciências da Terra. Este trabalho continuado levou a que o CGE se destaque no panorama nacional, tendo o seu nome ligado a algumas das actividades mais importantes de divulgação que têm sido realizadas em Portugal nos últimos dez anos

    Fractional Hamiltonian analysis of higher order derivatives systems

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    The fractional Hamiltonian analysis of 1+1 dimensional field theory is investigated and the fractional Ostrogradski's formulation is obtained. The fractional path integral of both simple harmonic oscillator with an acceleration-squares part and a damped oscillator are analyzed. The classical results are obtained when fractional derivatives are replaced with the integer order derivatives.Comment: 13 page

    Lagrangian formulation of classical fields within Riemann-Liouville fractional derivatives

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    The classical fields with fractional derivatives are investigated by using the fractional Lagrangian formulation.The fractional Euler-Lagrange equations were obtained and two examples were studied.Comment: 9 page

    Fractional Dirac Bracket and Quantization for Constrained Systems

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    So far, it is not well known how to deal with dissipative systems. There are many paths of investigation in the literature and none of them present a systematic and general procedure to tackle the problem. On the other hand, it is well known that the fractional formalism is a powerful alternative when treating dissipative problems. In this paper we propose a detailed way of attacking the issue using fractional calculus to construct an extension of the Dirac brackets in order to carry out the quantization of nonconservative theories through the standard canonical way. We believe that using the extended Dirac bracket definition it will be possible to analyze more deeply gauge theories starting with second-class systems.Comment: Revtex 4.1. 9 pages, two-column. Final version to appear in Physical Review

    Mode identification in the high-amplitude {\delta} Scuti star V2367 Cyg

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    We report on a multi-site photometric campaign on the high-amplitude δ\delta Scuti star V2367 Cyg in order to determine the pulsation modes. We also used high-dispersion spectroscopy to estimate the stellar parameters and projected rotational velocity. Time series multicolour photometry was obtained during a 98-d interval from five different sites. These data were used together with model atmospheres and non-adiabatic pulsation models to identify the spherical harmonic degree of the three independent frequencies of highest amplitude as well as the first two harmonics of the dominant mode. This was accomplished by matching the observed relative light amplitudes and phases in different wavebands with those computed by the models. In general, our results support the assumed mode identifications in a previous analysis of Kepler data.Comment: 9 pages, 5 figures, 4 tables. Accepted for publication in MNRA
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