17,337 research outputs found

    The use of learning management platforms in school context - a national study

    Get PDF
    This report results from a national study carried out under the Project “Educational application of learning management platforms”, supported and funded by the Computers, Networks, and Internet in Schools department of the Portuguese Ministry of Education- General Directorate for Innovation and Educational Development. This report has been developed by the ICT Competence Centre of the Faculty of Sciences- University of Lisbon, during the school year 2007/2008

    Combining exclusive semi-leptonic and hadronic B decays to measure |V_ub|

    Get PDF
    The Cabibbo-Kobayashi-Maskawa matrix element |V_ub| can be extracted from the rate for the semi-leptonic decay B -> pi + l + antineutrino_l, with little theoretical uncertainty, provided the hadronic form factor for the B -> pi transition can be measured from some other B decay. In here, we suggest using the decay B -> pi J\psi. This is a color suppressed decay, and it cannot be properly described within the usual factorization approximation; we use instead a simple and very general phenomenological model for the b d J\psi vertex. In order to relate the hadronic form factors in the B -> pi J\psi and B -> pi + l + antineutrino_l decays, we use form factor relations that hold for heavy-to-light transitions at large recoil.Comment: Latex, 7 pages, no figure

    Exact Nonequilibrium Work Generating Function for a Small Classical System

    Full text link
    We obtain the exact nonequilibrium work generating function (NEWGF), for a small system consisting of a massive Brownian particle connected to internal and external springs. The external work is provided to the system for a finite time interval. The Jarzynski equality (JE), obtained in this case directly from the NEWGF, is shown to be valid for the present model, in an exact way regardless of the rate of external work

    Structural and optical properties of europium doped zirconia single crystals fibers grown by laser floating zone

    Get PDF
    Yttria stabilized zirconia single crystal fibers doped with europium ions were developed envisaging optical applications. The laser floating zone technique was used in order to grow millimetric high quality single crystal fibers. The as-grown fibers are completely transparent and inclusion free, exhibiting a cubic structure. Under ultraviolet (UV) excitation, a broad emission band appears at 551 nm. The europium doped fibers are translucent with a tetragonal structure and exhibit an intense red emission at room temperature under UV excitation. The fingerprint transition lines between the 5D0 and 7FJ(0–4) multiplets of the Eu3+ ions are observed with the main emission line at ∼ 606 nm due to 5D0→7F2 transition. Photoluminescence excitation and wavelength dependent the photoluminescence spectra confirm the existence of different Eu3+ optical centers. © 2011 American Institute of PhysicsFCT-PTDC/CTM/66195/2006FCT-SFRH/BD/45774/200

    Solução analítica para placas piezoeléctricas

    Get PDF
    Neste trabalho apresenta-se um processo de solução analítica para placas rectangulares contendo lâminas de materiais compósitos, piezoeléctricos e piezomagnéticos. Mostram-se resultados para um laminado espesso actuado mecanicamente e electricamente, comparando uma situação sem a presença de defeitos estruturais com o caso em que existe uma delaminagem total ao longo de uma interface
    corecore