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The transport of thermal energy in thermodynamics is described as the product of entropy flow and of the absolute temperature, in analogy to the volume flow and pressure in oil hydraulics and to electric charge flow (= current) and voltage in electronics. Bond graphs are shown to be especially suitable to describe the splitting of applied thermal energy into internal energy and external mechanical work. Transformers and the 0- and 1-junctions of Paynter can illustrate various entropy flow processes, including Carnot engines and heat exchangers. Entropy flow in heat conduction is distinguished from entropy convection, or transport by moving mass, where the entropy/temperature characteristic or equation of state is important. Irreversibilities are represented by impedance transformers reducing temperature and increasing entropy flow but conserving power. 相似文献
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This article estimates the effects of school expenditure on school performance at Key Stage 4 in England, over the period 2003–07 during which real per pupil expenditure increased rapidly. It adds to previous investigations by using dynamic panel analysis to: exploit time series data on individual schools that only recently has become available; adjust for the potential endogeneity not only of expenditure but also of other determinants of performance; and differentiate the short‐run and the (higher) long‐run attainment effects of spending changes. Consistent with other recent work, the article reports a generally significant but small effect of expenditure on school performance, but it also finds that the effect varies between specialist and non‐specialist schools, with the effect on the latter being larger. Further, the article identifies significant dynamics in the school improvement process, quantifies the long‐run effect of expenditure changes, suggests that spending effects increase with socio‐economic disadvantage, and quantifies absence effects. 相似文献
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In this paper, we lay out a relational approach for indexing and retrieving photographs from a collection. The increase of digital image acquisition devices, combined with the growth of the World Wide Web, requires the development of information retrieval (IR) models and systems that provide fast access to images searched by users in databases. The aim of our work is to develop an IR model suited to images, integrating rich semantics for representing this visual data and user queries, which can also be applied to large corpora. 相似文献
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This article highlights the birth and current benefits of a partnership between Keene State College and Keene Public Library. It is a smaller one-on-one partnership that represents a rarer model than that of consortia and joint-use library partnerships. The authors offer additional ideas for partnering with local community groups in order to strengthen the town/gown relationship. 相似文献
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