21 resultados para Solution of mathematical problems

em QUB Research Portal - Research Directory and Institutional Repository for Queen's University Belfast


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This article is a response to an article by Ray Mackay (1996) which constitutes an attack on stylistic analysis in general, and the writings of the above authors and Ron Carter in particular. Mackay's article (in Language and Communication) accuses stylistics of 'scientificness' and claims that its attempt to provide objective analyses of literary texts is futile.1 We suggest that Mackay has misrepresented what stylisticians have said about objectivity, and that his understanding of objectivity, science and the nature of text-interpretative argument is seriously flawed.

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In the presence of inhomogeneities, defects and currents, the equations describing a Bose-condensed ensemble of alkali atoms have to be solved numerically. By combining both linear and nonlinear equations within a Discrete Variable Representation framework, we describe a computational scheme for the solution of the coupled Bogoliubov-de Gennes (BdG) and nonlinear Schrodinger (NLS) equations for fields in a 3D spheroidal potential. We use the method to calculate the collective excitation spectrum and quasiparticle mode densities for excitations of a Bose condensed gas in a spheroidal trap. The method is compared against finite-difference and spectral methods, and we find the DVR computational scheme to be superior in accuracy and efficiency for the cases we consider. (C) 2004 Elsevier B.V. All rights reserved.

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We present a study on the effect of the alkyl chain length of the imidazolium ring in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [C1CnIm][NTf2] (n = 2 to 10), on the mixing properties of (ionic liquid + alcohol) mixtures (enthalpy and volume). We have measured small excess molar volumes with highly asymmetric curves as a function of mole fraction composition (S-shape) with more negative values in the alcohol-rich regions. The excess molar volumes increase with the increase of the alkyl-chain length of the imidazolium cation of the ionic liquid. The values of the partial molar excess enthalpy and the enthalpy of mixing are positive and, for the case of methanol, do not vary monotonously with the length of the alkyl side-chain of the cation on the ionic liquid – increasing from n = 2 to 6 and then decreasing from n = 8. This non-monotonous variation is explained by a more favourable interaction of methanol with the cation head group of the ionic liquid for alkyl chains longer than eight carbon atoms. It is also observed that the mixing is less favourable for the smaller alcohols, the enthalpy of mixing decreasing to less positive values as the alkyl chain of the alcohol increases. Based on the data from this work and on the knowledge of the vapour pressure of {[C1CnIm][NTf2] + alcohol} binary mixtures at T = 298 K reported in the literature, the excess Gibbs free energy, excess enthalpy and excess entropy could be then calculated and it was observed that these mixtures behave like the ones constituted by a non-associating and a non-polar component, with its solution behaviour being determined by the enthalpy.

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This paper addresses the analytical solution of the mixed-mode bending (MMB) problem. The first published solutions used a load separation in pure mode I and mode II and were applied for a crack length less than the beam half-span, a <= L. In later publications, the same mode separation was used in deriving the analytical solution for crack lengths bigger than the beam half-span, a > L. In this paper it is shown that this mode separation is not valid when a > L and in some cases may lead to very erroneous results. The correct mode separation and the corresponding analytical solutions, when a > L, are presented. Results, of force vs. displacement and force vs. crack length graphs, obtained using the existing formulation and the corrected formulation are compared. A finite element solution, which does not use mode separation, is also presented

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In this article, using Ireland where debt issues are of particular salience, as a test case, we seek to locate over-indebtedness and the severity of debt problems in the context of the broader economic circumstances of households. In doing so, we first identify an economically vulnerable segment of households and then explore the debt experience of vulnerable and non-vulnerable households. Our analysis reveals a striking contrast between the debt experiences of less than one in five households defined as economically vulnerable and all others. Financial exclusion, relating to access to a bank account and a credit card, was found to increase debt levels. However, such effects were modest. The impact of economic vulnerability seems to be largely a consequence of its relationship to a wide
range of socio-economic attributes and circumstances. The manner in which a potential debt crisis
unfolds will be shaped by the broader socio-economic structuring of life-chances. Any attempt to
respond to such problems by concentrating on financial exclusion or household behaviour or, indeed,
triggering factors without taking the wider social structuring of economic vulnerability is likely to be
both seriously misguided and largely ineffective.

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This article reconstructs British constitutional policy in Northern Ireland after power-sharing collapsed in May 1974. Over the following two years, the British government publicly emphasised that Northern Ireland would decide its own future, but ministers secretly considered a range of options including withdrawal, integration and Dominion status. These discussions have been fundamentally misunderstood by previous authors, and this article shows that Harold Wilson did not seriously advocate withdrawal nor was policy as inconsistent as argued elsewhere. An historical approach, drawing from recently released archival material, shows that consociationalists such as Brendan O'Leary and Michael Kerr have neglected the proper context of government policy because of their commitment to a particular form of government, failing to recognise the constraints under which ministers operated. The British government remained committed to an internal devolved settlement including both communities but was unable to impose one.