37 resultados para Packing dimension


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Worldwide, science education reform movements are stressing the need to promote ‘scienti?c literacy’ among young people. Increasingly, this is taken to include empowering students to engage critically with science-related news reporting. Despite this requirement now featuring in statutory curricula throughout the UK, there has, to date, been a dearth of research-informed advice to assist science teachers as they identify appropriate instructional objectives in this regard and design relevant learning activities through which these might be achieved. In this study, prominent science communication
scholars, science journalists, science educators and media educators were interviewed to determine what knowledge, skills and habits of mind they judged valuable for individuals reading science-related news stories. Teachers of science and of English from nine secondary schools in Northern Ireland addressed the same issue. A striking – and signi?cant – ?nding of the study was the very substantial number of statements of knowledge, skill and disposition o?ered by participants that relate to ‘media awareness’, an issue largely overlooked in the science education literature. The school-focused phase of the research suggests that cross-curricular approaches involving teachers of science collaborating with those of English/media education or media studies may best serve to address this important curricular goal.

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Near-infrared diffuse tomography was used in order to observe dynamic behaviour of flowing gases by measuring the 3D distributions of composition and temperature in a weakly scattering packed bed reactor, subject to wall effects and non-isothermal conditions. The technique was applied to the vapour phase hydrogen isotopic exchange reaction in a hydrophobic packing of low aspect ratio made of platinum on styrene divinyl benzene sulphonate copolymer resin. The results of tomography revealed uneven temperature and composition maps of water and deuterated water vapours in the core-packed bed and in the vicinity of the wall owing to flow maldistribution. The dynamic lag between the near-wall water vapour and deuterated water vapour compositions were observed suggesting that the convective transfer which was significant near the wall at the start, owing to high porosity, was also effective at large conversions.

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Over the past few years, attention to the role of state-wide political parties in multi-level polities has increased in recognition of their linkage function between levels of government, as these parties compete in both state-wide and regional elections across their countries. This article presents a coding scheme designed to describe the relationship between central and regional levels of state-wide parties. It evaluates the involvement of the regional branches in central decision-making and their degree of autonomy in the management of regional party affairs. This coding scheme is applied to state-wide parties in Spain (the socialist PSOE and the conservative Partido Popular) and in the UK (Labour, the Conservatives and the Liberal Democrats). It is an additional tool with which to analyse party organization and it facilitates the comparison of parties across regions and in different countries.

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The study of interrelationships between soil structure and its functional properties is complicated by the fact that the quantitative description of soil structure is challenging. Soil scientists have tackled this challenge by taking advantage of approaches such as fractal geometry, which describes soil architectural complexity through a scaling exponent (D) relating mass and numbers of particles/aggregates to particle/aggregate size. Typically, soil biologists use empirical indices such as mean weight diameters (MWD) and percent of water stable aggregates (WSA), or the entire size distribution, and they have successfully related these indices to key soil features such as C and N dynamics and biological promoters of soil structure. Here, we focused on D, WSA and MWD and we tested whether: D estimated by the exponent of the power law of number-size distributions is a good and consistent correlate of MWD and WSA; D carries information that differs from MWD and WSA; the fraction of variation in D that is uncorrelated with MWD and WSA is related to soil chemical and biological properties that are thought to establish interdependence with soil structure (e.g., organic C, N, arbuscular mycorrhizal fungi). We analysed observational data from a broad scale field study and results from a greenhouse experiment where arbuscular mycorrhizal fungi (AMF) and collembola altered soil structure. We were able to develop empirical models that account for a highly significant and large portion of the correlation observed between WSA and MWD but we did not uncover the mechanisms that underlie this correlation. We conclude that most of the covariance between D and soil biotic (AMF, plant roots) and abiotic (C. N) properties can be accounted for by WSA and MWD. This result implies that the ecological effects of the fragmentation properties described by D and generally discussed under the framework of fractal models can be interpreted under the intuitive perspective of simpler indices and we suggest that the biotic components mostly impacted the largest size fractions, which dominate MWD, WSA and the scaling exponent ruling number-size distributions. (C) 2010 Elsevier Ltd. All rights reserved.

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This paper presents a 3D simulation system which is employed in order to predict cutting forces and tool deflection during end-milling operation. In order to verify the accuracy of 3D simulation, results (cutting forces and tool deflection) were compared with those based on the theoretical relationships, in terms of agreement with experiments. The results obtained indicate that the simulation is capable of predicting the cutting forces and tool deflection.

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The building sector is widely recognized as having a major impact on sustainable development. Both in developed and developing countries, sustainability in buildings approaches are growing. Laterite dimension stone (LDS) is a building material that was traditionally used in sub-Saharan Africa, but its technical features still need to be assessed. This article presents some results of a study focused on the characterization of LDS exploited in Burkina Faso for building purposes. The measured average thermal conductivity is 0.51  W/mK, which increases with water content and evolves with the specific gravity and with porosity. Rock mineral phases (quartz, goethite, hematite, magnetite) are cemented by kaolinite. The porosity of the material is high (30%), with macropores visible on the surface and found in the rock inner structure as well. Results from the hygrothermal monitoring of a pilot building are also presented.