902 resultados para Triangular arrangements


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The ferromagnetic and antiferromagnetic Ising model on a two dimensional inhomogeneous lattice characterized by two exchange constants (J1 and J2) is investigated. The lattice allows, in a continuous manner, the interpolation between the uniforme square (J2 = 0) and triangular (J2 = J1) lattices. By performing Monte Carlo simulation using the sequential Metropolis algorithm, we calculate the magnetization and the magnetic susceptibility on lattices of differents sizes. Applying the finite size scaling method through a data colappse, we obtained the critical temperatures as well as the critical exponents of the model for several values of the parameter α = J2 J1 in the [0, 1] range. The ferromagnetic case shows a linear increasing behavior of the critical temperature Tc for increasing values of α. Inwhich concerns the antiferromagnetic system, we observe a linear (decreasing) behavior of Tc, only for small values of α; in the range [0.6, 1], where frustrations effects are more pronunciated, the critical temperature Tc decays more quickly, possibly in a non-linear way, to the limiting value Tc = 0, cor-responding to the homogeneous fully frustrated antiferromagnetic triangular case.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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An analytical approach based on the generalized integral transform technique is presented, for the solution of laminar forced convection within the thermal entry region of ducts with arbitrarily shaped cross-sections. The analysis is illustrated through consideration of a right triangular duct subjected to constant wall temperature boundary condition. Critical comparisons are made with results available in the literature, from direct numerical approaches. Numerical results for dimensionless average temperature and Nusselt numbers are presented for different apex angles.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Background: Rapid demographic ageing will soon lead to large increases in the numbers of persons with dementia in developing countries. This study is the first comprehensive assessment of care arrangements for people with dementia in those regions. Methods: A descriptive and comparative study of dementia care; caregiver characteristics, the nature of care provided, and the practical, psychological (Zarit Burden Interview, General Health Questionnaire) and economic impact upon the caregiver in 24 centres in India, China and South East Asia, Latin America and the Caribbean and Africa. Results: We interviewed 706 persons with dementia, and their caregivers. Most caregivers were women, living with the person with dementia in extended family households. One-quarter to one-half of households included a child. Larger households were associated with lower caregiver strain, where the caregiver was co-resident. However, despite the traditional apparatus of family care, levels of caregiver strain were at least as high as in the developed world. Many had cutback on work to care and faced the additional expense of paid carers and health services. Families from the poorest countries were particularly likely to have used expensive private medical services, and to be spending more than 10% of the per capita GNP on health care. Conclusions: Older people in developing countries are indivisible from their younger family members. The high levels of family strain identified in this study feed into the cycle of disadvantage and should thus be a concern for policymakers in the developing world. Copyright © 2004 John Wiley & Sons, Ltd.

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This paper presents models that can be used in the design of microstrip antennas for mobile communications. The antennas can be triangular or rectangular. The presented models are compared with deterministic and empirical models based on artificial neural networks (ANN) presented in the literature. The models are based on Perceptron Multilayer (PML) and Radial Basis Function (RBF) ANN. RBF based models presented the best results. Also, the models can be embedded in CAD systems, in order to design microstrip antennas for mobile communications.

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Includes bibliography

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Includes bibliography

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)