148,961 research outputs found

    Overcoming the barriers to walking for children

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    This paper is an output from the project CAPABLE (Children?s Activities,Perceptions and Behaviour in the Local Environment) being carried out at UCL,jointly between the Centre for Transport Studies, the Department of Psychology, theBartlett School of Planning and the Centre for Advanced Spatial Analysis. The overallaim of the project, which runs from 1 August 2004 to 31 July 2006, is to examine theinteraction between children and the local environment, including identifying howchildren use open space and streets, and why they go to some places but not others.This paper draws on results from questionnaires completed by children about theextent to which they are allowed out unaccompanied by an adult. The surveys werecarried out in four schools, two in Hertfordshire, the area immediately north ofLondon, and two in the London Borough of Lewisham. The purpose is to establish theextent to which the children are allowed by their parents to go out unaccompanied byadults. The issues covered include whether the children go out walking or cyclingwithout an adult, whether they are allowed out alone to visit friends houses, go outafter dark or to cross main roads. The results are considered in terms of the children?sage and gender, and in terms of the households? car ownership level and the strengthof its local social networks. It is found that more of the children in Hertfordshire areallowed out alone, despite the fact that the factors that seem to correlate with beingallowed out unaccompanied are stronger in Lewisham. It is concluded that this maywell be due to environmental factors, real and perceived

    Penrose Diagram for a Transient Black Hole

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    A Penrose diagram is constructed for a spatially coherent black hole that smoothly begins an accretion, then excretes symmetrically as measured by a distant observer, with the initial and final states described by a metric of Minkowski form. Coordinate curves on the diagram are computationally derived. Causal relationships between space-time regions are briefly discussed. The life cycle of the black hole demonstrably leaves asymptotic observers in an unaltered Minkowski space-time of uniform conformal scale.Comment: 14 pages, 9 figures, spelling correction

    Fundamental frequency height as a resource for the management of overlap in talk-in-interaction.

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    Overlapping talk is common in talk-in-interaction. Much of the previous research on this topic agrees that speaker overlaps can be either turn competitive or noncompetitive. An investigation of the differences in prosodic design between these two classes of overlaps can offer insight into how speakers use and orient to prosody as a resource for turn competition. In this paper, we investigate the role of fundamental frequency (F0) as a resource for turn competition in overlapping speech. Our methodological approach combines detailed conversation analysis of overlap instances with acoustic measurements of F0 in the overlapping sequence and in its local context. The analyses are based on a collection of overlap instances drawn from the ICSI Meeting corpus. We found that overlappers mark an overlapping incoming as competitive by raising F0 above their norm for turn beginnings, and retaining this higher F0 until the point of overlap resolution. Overlappees may respond to these competitive incomings by returning competition, in which case they raise their F0 too. Our results thus provide instrumental support for earlier claims made on impressionistic evidence, namely that participants in talk-in-interaction systematically manipulate F0 height when competing for the turn

    Field Quantization, Photons and Non-Hermitean Modes

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    Field quantization in three dimensional unstable optical systems is treated by expanding the vector potential in terms of non-Hermitean (Fox-Li) modes in both the cavity and external regions. The cavity non-Hermitean modes (NHM) are treated using the paraxial and monochromaticity approximations. The NHM bi-orthogonality relationships are used in a standard canonical quantization procedure based on introducing generalised coordinates and momenta for the electromagnetic (EM) field. The quantum EM field is equivalent to a set of quantum harmonic oscillators (QHO), associated with either the cavity or the external region NHM. This confirms the validity of the photon model in unstable optical systems, though the annihilation and creation operators for each QHO are not Hermitean adjoints. The quantum Hamiltonian for the EM field is the sum of non-commuting cavity and external region contributions, each of which is sum of independent QHO Hamiltonians for each NHM, but the external field Hamiltonian also includes a coupling term responsible for external NHM photon exchange processes. Cavity energy gain and loss processes is associated with the non-commutativity of cavity and external region operators, given in terms of surface integrals involving cavity and external region NHM functions on the cavity-external region boundary. The spontaneous decay of a two-level atom inside an unstable cavity is treated using the essential states approach and the rotating wave approximation. Atomic transitions leading to cavity NHM photon absorption have a different coupling constant to those leading to photon emission, a feature resulting from the use of NHM functions. Under certain conditions the decay rate is enhanced by the Petermann factor.Comment: 38 pages, tex, 2 figures, ps. General expression for decay rate added. To be published in Journal of Modern Optic

    A latitudinal survey of hydroxyl airglow emissions Final report, 1 Apr. 1969 - 31 Mar. 1970

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    Airborne photometer instrumentation and measurement data on high latitude hydroxyl airglow emissio

    Attitudes in Physics Education: An Alternative Approach to Teaching Physics to Non-Science College Students

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    In this article, we present an alternative way of teaching conceptual physics for non-science majors by depicting the role of physics in today\u27s technology. The goal of this approach is to increase in the minds of non-science students the acceptance of physics as a useful component in general education, and as a major tool in comprehending the present-day technological world experienced by students outside the classroom
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