9,740 research outputs found

    Sport as a privilege in Spain

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    The reduction of Physical Education hours in the Spanish curriculum originates from a false premise: families are already aware of the importance of physical activity, and attempt to compensate for the lack of it at school with an extra schedule. It seems then, that there is an assumption that classes that are available after school are only related to physical activity: this is not the case. Furthermore, only those families that are fully aware of the consequences of their children’s inactivity, and who can (and want to) invest in those extra classes and engage in some kind of physical activity after school. But the reality is that Physical activity only is important for some families

    Inconsistencies in the application of harmonic analysis to pulsating stars

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    Using ultra-precise data from space instrumentation we found that the underlying functions of stellar light curves from some AF pul- sating stars are non-analytic, and consequently their Fourier expansion is not guaranteed. This result demonstrates that periodograms do not provide a mathematically consistent estimator of the frequency content for this kind of variable stars. More importantly, this constitutes the first counterexample against the current paradigm which considers that any physical process is described by a contin- uous (band-limited) function that is infinitely differentiable.Comment: 9 pages, 8 figure

    Analysis of debris from APG-3, the simulated destruct system test of a full-scale Rover/NERVA reactor

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    Analysis of debris from simulated destruction system test of full scale Rover/NERVA reacto

    Statistical Mechanics of finite arrays of coupled bistable elements

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    We discuss the equilibrium of a single collective variable characterizing a finite set of coupled, noisy, bistable systems as the noise strength, the size and the coupling parameter are varied. We identify distinct regions in parameter space. The results obtained in prior works in the asymptotic infinite size limit are significantly different from the finite size results. A procedure to construct approximate 1-dimensional Langevin equation is adopted. This equation provides a useful tool to understand the collective behavior even in the presence of an external driving force

    Impact of gaps in the asteroseismic characterization of pulsating stars. I. On the efficiency of pre-whitening

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    It is known that the observed distribution of frequencies in CoRoT and Kepler {\delta} Scuti stars has no parallelism with any theoretical model. Pre-whitening is a widespread technique in the analysis of time series with gaps from pulsating stars located in the classical instability strip such as {\delta} Scuti stars. However, some studies have pointed out that this technique might introduce biases in the results of the frequency analysis. This work aims at studying the biases that can result from pre-whitening in asteroseismology. The results will depend on the intrinsic range and distribution of frequencies of the stars. The periodic nature of the gaps in CoRoT observations, just in the range of the pulsational frequency content of the {\delta} Scuti stars, is shown to be crucial to determine their oscillation frequencies, the first step to perform asteroseismolgy of these objects. Hence, here we focus on the impact of pre-whitening on the asteroseismic characterization of {\delta} Scuti stars. We select a sample of 15 {\delta} Scuti stars observed by the CoRoT satellite, for which ultra-high quality photometric data have been obtained by its seismic channel. In order to study the impact on the asteroseismic characterization of {\delta} Scuti stars we perform the pre-whitening procedure on three datasets: gapped data, linearly interpolated data, and ARMA interpolated data. The different results obtained show that at least in some cases pre-whitening is not an efficient procedure for the deconvolution of the spectral window. therefore, in order to reduce the effect of the spectral window to the minimum it is necessary to interpolate with an algorithm that is aimed to preserve the original frequency content, and not only to perform a pre-whitening of the data.Comment: 27 pages, 47 figures Tables and typos fixe

    Adhesively-bonded GFRP-glass sandwich components for structurally efficient glazing applications

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    Composite sandwich structures made of thick glass face sheets adhesively-bonded to glass fibre-reinforced polymer (GFRP) core profiles have the potential to outperform existing non-composite glazing configurations but their feasibility has yet to be investigated and there are no analytical models that describe their structural response. This paper presents the new analytical models for predicting deflections and strains in adhesively-bonded GFRP-glass sandwich beams. The new analytical models successfully account for: the shear deformations of the core and adhesive layers; the local bending of the constituent parts about their centroidal axes; and the global bending of the sandwich component as a whole. The deflections and strains predicted by analytical models are validated by finite element simulations and compared with the results of destructive tests performed on adhesively-bonded GFRP-glass beams in a four-point bending configuration. The analytical models were also evaluated for alternative GFRP-glass configurations tested by others. The GFRP-glass beams specially assembled in this study confirm the physical feasibility of constructing these proposed components.The authors would like to thank the Engineering and Physical Sciences Research Council – United Kingdom for the financial support of the project
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