6,231 research outputs found

    I wouldn’t mind moving actually: exploring student mobility in Northern Ireland

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    WOS:000288508300006 (NÂș de Acesso Web of Science)This article examines orientations towards future geographical mobility amongst young people in Northern Ireland presently studying at third level educational institutions. Following contextualisation of youth mobility as pertaining to students in this region, the results of recent quantitative and qualitative research are discussed. Over half of these young people, 55 per cent, see themselves living outside Northern Ireland at some point in the future. Furthermore, in response to a number of statements on family relationships, peer associations and community attachments, young people with mobility intentions are found to be more likely to have families who support migration intentions. These potentially mobile young people also tend to have peers and siblings with prior experience of geographical mobility and show signs of being less deeply attached to their local communities and/or local identities. A number of qualitative case studies further illustrate the diversity of mobility orientations within the sample, ranging from those positively predisposed towards migration to those more averse to such movement

    Life cycle analysis of steel railway bridges

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    This paper focuses on the growth of cracks that arise from natural corrosion in steel bridges. It is shown that these two effects of corrosion and stress, need to be simultaneously analysed. A methodology used to compute the growth of such cracks in bridge steels is presented. A better understanding of the remaining life of steel bridges would help establish an assessment procedure and guide engineers when deciding between reinforcement and replacement

    First-order thermal correction to the quadratic response tensor and rate for second harmonic plasma emission

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    Three-wave interactions in plasmas are described, in the framework of kinetic theory, by the quadratic response tensor (QRT). The cold-plasma QRT is a common approximation for interactions between three fast waves. Here, the first-order thermal correction (FOTC) to the cold-plasma QRT is derived for interactions between three fast waves in a warm unmagnetized collisionless plasma, whose particles have an arbitrary isotropic distribution function. The FOTC to the cold-plasma QRT is shown to depend on the second moment of the distribution function, the phase speeds of the waves, and the interaction geometry. Previous calculations of the rate for second harmonic plasma emission (via Langmuir-wave coalescence) assume the cold-plasma QRT. The FOTC to the cold-plasma QRT is used here to calculate the FOTC to the second harmonic emission rate, and its importance is assessed in various physical situations. The FOTC significantly increases the rate when the ratio of the Langmuir phase speed to the electron thermal speed is less than about 3.Comment: 11 pages, 2 figures, submitted to Physics of Plasma

    Numerical simulation of unconstrained cyclotron resonant maser emission

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    When a mainly rectilinear electron beam is subject to significant magnetic compression, conservation of magnetic moment results in the formation of a horseshoe shaped velocity distribution. It has been shown that such a distribution is unstable to cyclotron emission and may be responsible for the generation of Auroral Kilometric Radiation (AKR) an intense rf emission sourced at high altitudes in the terrestrial auroral magnetosphere. PiC code simulations have been undertaken to investigate the dynamics of the cyclotron emission process in the absence of cavity boundaries with particular consideration of the spatial growth rate, spectral output and rf conversion efficiency. Computations reveal that a well-defined cyclotron emission process occurs albeit with a low spatial growth rate compared to waveguide bounded simulations. The rf output is near perpendicular to the electron beam with a slight backward-wave character reflected in the spectral output with a well defined peak at 2.68GHz, just below the relativistic electron cyclotron frequency. The corresponding rf conversion efficiency of 1.1% is comparable to waveguide bounded simulations and consistent with the predictions of kinetic theory that suggest efficient, spectrally well defined radiation emission can be obtained from an electron horseshoe distribution in the absence of radiation boundaries.Publisher PD
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