Front Matter

Front Matte

Front Matter

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Front Matter

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Ce que nous dit l'étude d'une recherche de Kepler de l'influence d'une relation singulière aux objets naturalisés

International audienceLa question des articulations entre histoire, épistémologie et didactique est suffisamment riche pour être source inépuisable de réflexion. Nous souhaitons proposer ici une approche qui étudie l'activité du savant cherchant et les liens potentiels avec des situations didactiques où la recherche de problème est centrale. Nous explicitons dans un premier temps comment une vision philosophique, mettant en avant l'agir en mathématique, peut légitimer l'étude de l'activité du chercheur jusque dans sa relation aux objets familiers. Cette approche nous amène ensuite à étudier, à titre d'exemple générique, la relation aux objets de Kepler à la découverte des pavages archimédiens du plan. Nous présentons pour finir des retombées de l'enquête historique et épistémologique sur un travail d'ingénierie qui étudie la construction de situations lors desquelles les élèves peuvent, dans des allers-retours entre objets familiers et objet nouveau, élaborer de nouveaux savoirs

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Front Matte

Can we improve the identification of cold homes for targeted home energy-efficiency improvements?

Objective: To investigate the extent to which homes with low indoor-temperatures can be identified from dwelling and household characteristics.Design: Analysis of data from a national survey of dwellings, occupied by low-income households, scheduled for home energy-efficiency improvements. Setting: Five urban areas of England: Birmingham, Liverpool, Manchester, Newcastle and Southampton.Methods: Half-hourly living-room temperatures were recorded for two to four weeks in dwellings over the winter periods November to April 2001-2002 and 2002-2003. Regression of indoor on outdoor temperatures was used to identify cold-homes in which standardized daytime living-room and/ or nighttime bedroom-temperatures were < 16 degrees C (when the outdoor temperature was 5 degrees C). Tabulation and logistic regression were used to examine the extent to which these cold-homes can be identified from dwelling and household characteristics.Results: Overall, 21.0% of dwellings had standardized daytime living-room temperatures < 16 degrees C and 46.4% had standardized nighttime bedroom-temperatures below the same temperature. Standardized indoor-temperatures were influenced by a wide range of household and dwelling characteristics, but most strongly by the energy efficiency (SAP) rating and by standardized heating costs. However, even using these variables, along with other dwelling and household characteristics in a multi-variable prediction model, it would be necessary to target more than half of all dwellings in our sample to ensure at least 80% sensitivity for identifying dwellings with cold living-room temperatures. An even higher proportion would have to be targeted to ensure 80% sensitivity for identifying dwellings with cold-bedroom temperatures.Conclusion: Property and household characteristics provide only limited potential for identifying dwellings where winter indoor temperatures are likely to be low, presumably because of the multiple influences on home heating, including personal choice and behaviour. This suggests that the highly selective targeting of energy-efficiency programmes is difficult to achieve if the primary aim is to identify dwellings with cold-indoor-temperatures. (c) 2006 Published by Elsevier Ltd

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Newsletter providing "a lighter, human interest side of the news" from the Boston University Medical Campus

Statistical properties of single-file diffusion front

Statistical properties of the front of a semi-infinite system of single-file diffusion (one dimensional system where particles cannot pass each other, but in-between collisions each one independently follow diffusive motion) are investigated. Exact as well as asymptotic results are provided for the probability density function of (a) the front-position, (b) the maximum of the front-positions, and (c) the first-passage time to a given position. The asymptotic laws for the front-position and the maximum front-position are found to be governed by the Fisher-Tippett-Gumbel extreme value statistics. The asymptotic properties of the first-passage time is dominated by a stretched-exponential tail in the distribution. The farness of the front with the rest of the system is investigated by considering (i) the gap from the front to the closest particle, and (ii) the density profile with respect to the front-position, and analytical results are provided for late time behaviors.Comment: 4 revtex page