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1.
Equations for the calculation of radiant power F through two apertures in series are well known. A characteristic of these formulae is that they give F as a small difference between two large terms. Evidently, the flux through the apertures must decrease as the spacing between them increases; and for large spacing, the inverse-square relation must hold. Instead of exhibiting this behaviour in an obvious manner, however, the traditional equations give the specious impression of an increase in F with increase in spacing. The paper develops an approximate formulae that applies to apertures in the shape of any regular polygon and that shows clearly how the inverse square relation is approached for large separation. 相似文献
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Based on quantitative data from the Norwegian Statistisk Sentralbyrå (Statistics Norway) study of Mosjon, Friluftsliv og Kulturaktiviteter, this paper explores trends in Norwegians' participation in sports, with a focus on young people. Norway boasts particularly high levels of sports participation as well as sports club membership and young Norwegians are the quintessential sporting omnivores. Among other things, the Statistics Norway study reveals substantial increases in participation (among young people and females especially) during the period 1997–2007, a shift in the peak of participation to the late teenage years, a relatively high level of lifelong participants, a re-bound effect in the post-child rearing years and a growth in lifestyle sports. Young Norwegians grow up in a socio-economic context of relative equality between the sexes and high standards of living. An abundance of natural and artificial outdoor and indoor sporting facilities alongside a well-established voluntary sports club sector and an elementary school system that emphasizes physical exercise and recreation, as well as high levels of parental involvement, add to the favourable socio-economic conditions to create seemingly optimal circumstances for sports participation. All these reinforce the sporting and physical recreation cultures deeply embedded in Norwegian society and embodied by the very many middle-class parents in a country which, for the time being at least, remains relatively young in demographic terms. In terms of lessons to be learned for policy towards sports and physical education beyond Norway, there may be grounds for some optimism around parental involvement in children's sport as well as the potential appeal of lifestyle sports. That said, it is likely to be the greater socio-economic equalities in Scandinavian countries such as Norway that make them unrealistic benchmarks for sports participation elsewhere. 相似文献
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This paper completes our treatment of radiant flux through pairs of apertures. In Part II, we obtained approximate equations for rectangular apertures in parallel planes, with the restriction that two apertures be identical and that one be directly above the other. Here we generalize to the case of any apertures that fit into a rectangular grid. The idea for this generalization originated with Ondracek but it is here expressed in matrix notation, which allows coefficients Fij to be obtained rather simply. 相似文献
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