1,633 research outputs found

    SOM-based Data Analysis of Speculative Attacks' Real Effects

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    In some cases, currency crises are followed by strong recessions (e.g., recent Asian and Argentinean crises), but in other cases they are not. This paper uses Self-Organizing Maps (SOM) to search for meaningful associations between speculative attacks' real effects and 28 variables that characterize the economic, financial, legal, and socio-political structure of the country at the onset of the attack. SOM is a neural network-based generalization of Principal Component Analysis (PCA) that provides an efficient non-linear projection of the multidimensional data space on a curved surface. This paper finds a strong association of speculative attacks' real effects with fundamentals and the banking sector structureexploratory data analysis, self-organizing maps, neural networks, speculative attacks' real effects

    The Catalan Parliament (2). Structure and Functions

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    Le Parlement catalan (2). Structure et fonctions

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    The Catalan Parliament (I). A historical report

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    Optimal control of fed-batch processes with particle swarm optimization

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    Optimal control problems appear in several engineering fields. These problems are often described by sets of nonlinear differential and algebraic equations, usually subject to constraints in the state and control variables. Some bioprocess optimal control problems are revisited and a numerical approach to its solution is introduced. The numerical procedure used to solve the problems takes advantage of the well know modeling AMPL language, providing an external dynamic library that solve the nonlinear differential equations. The optimal control problem as generally presented belongs to the class of semi-infinite programming (SIP) problems. A transformation of the SIP problem results in a nonlinear optimization problem (NLP) that can be address by off-the-shelf optimization software. The NLP formulation results in nondifferentiable optimization problems were the global solution is mostly desirable. We apply a particle swarm optimization strategy implemented in the MLOCPSOA [13] solver. Particle swarm optimization (PSO) is a stochastic technique that mimics the social behavior of a swarm

    An application of semi-infinite programming to air pollution control

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    Environment issues are more then ever important in a modern society. Complying with stricter legal thresholds on pollution emissions raises an important economic issue. This talk presents some ideas in the use of optimization tools to help in the planning and control of non mobile pollution sources. We assume a Gaussian plume model where a plume rise and weather stabilities classes are considered. Three main semi-infinite programming formulations are described and numerical results are shown

    Optimização e controlo da poluição atmosférica

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    Alguns problemas de controlo da poluição atmosférica podem ser formulados como problemas de programação semi-infinita (PSI). Estas formulações, das quais descrevemos três abordagens, permitem que as instalações fabris cumpram a legislação da poluição atmosférica enquanto que o impacto económico é minimizado. As mesmas ferramentas da programação matemática podem também ser usadas pelas autoridades competentes no sentido de verificar que os limites impostos por lei são cumpridos, através do planeamento da localização dos postos de amostragem/controlo. A primeira das formulações consiste em optimizar um determinado objectivo enquanto que o nível de poluição atmosférica é mantido abaixo de um valor de referência. A segunda consiste no cálculo da poluição atmosférica máxima atingida numa determinada região e a terceira considera um problemas de redução da poluição. Estas formulações permitem obter os melhores parâmetros de controlo e as posições onde os valores máximos da poluição são atingidos, posições essas que correspondem ao melhor posicionamento dos postos de amostragem/controlo. As abordagens propostas são ilustradas com quatro problemas académicos. As ferramentas actualmente existentes apoiam a PSI desde a modelação do problema até à sua resolução. A linguagem de modelação (SIP)AMPL foi usada para codificar os problemas propostos e o solver NSIPS foi empregue na resolução dos mesmos

    Semi-infinite air pollution control problems

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    Semi-infinite programming (SIP) problems arise in many engineering areas. Robot trajectory planning and optimal signal sets are two fine examples. Air pollution abatement problems, which are linear SIP problems, were proposed in the seventies by Gustafson and Kortanek [Analytical properties of some multiple-source urban diffusion models, Environment and Planning 4, pp. 31- 41, 1972]. Recent available tools for non-linear SIP allow the formulation of more general air control problems, namely the optimum stack design. In the air control SIP problem an objective function is to be optimised (minimum stack height or minimum cleaning costs), where the air pollution, at ground level, is kept bellow a given threshold. A Gaussian model is used to provide estimates of air pollution in a region where mean weather conditions are assumed. In this talk, we present three formulated air pollution control problems coded in the (SIP)AMPL modelling language and numerical results obtained with the discretization method of the NSIPS solver

    Texture of Two Vanishing Subtraces in Neutrino Mass Matrix and Current Experimental Tests

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    We present a full phenomenological and analytical study for the neutrino mass matrix characterized by two vanishing 2×22\times2 subtraces. We update one past result in light of the recent experimental data. Out of the fifteen possible textures, we find seven cases can accommodate the experimental data instead of eight ones in the past study. We also introduce few symmetry realizations for viable and nonviable textures based on non-abelian (A4A_4 or S4S_4) flavor symmetry within type II seesaw scenario.Comment: pdflatex, 57 pages, 10 tables, 9 figures, version to appear in PR
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