826 resultados para 230119 Systems Theory and Control


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Forecasting, for obvious reasons, often become the most important goal to be achieved. For spatially extended systems (e.g. atmospheric system) where the local nonlinearities lead to the most unpredictable chaotic evolution, it is highly desirable to have a simple diagnostic tool to identify regions of predictable behaviour. In this paper, we discuss the use of the bred vector (BV) dimension, a recently introduced statistics, to identify the regimes where a finite time forecast is feasible. Using the tools from dynamical systems theory and Bayesian modelling, we show the finite time predictability in two-dimensional coupled map lattices in the regions of low BV dimension. © Indian Academy of Sciences.

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This paper presents the analysis, design, simulation, and experimental results for a high frequency high Power-Factor (PF) AC (Alternate Current) voltage regulator, using a Sepic converter as power stage. The control technique employed to impose a sinusoidal input current waveform, with low Total Harmonic Distortion (THD), is the sinusoidal variable hysteresis control. The control technique was implemented in a FPGA (Field Programmable Gate Array) device, using a Hardware Description Language (VHDL). Through the use of the proposed control technique, the AC voltage regulator performs active power-factor correction, and low THD in the input current, for linear and non-linear loads, satisfying the requirements of the EEC61000-3-2 standards. Experimental results from an example prototype, designed for 300W of nominal output power, 50kHz (switching frequency), and 127Vrms of nominal input and output voltages, are presented in order to validate the proposed AC regulator. © 2005 IEEE.

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It is possible to show that there are three independent families of models describing a massive spin-2 particle via a rank-2 tensor. One of them contains the massive Fierz-Pauli model, the only case described by a symmetric tensor. The three families have different local symmetries in the massless limit and can not be interconnected by any local field redefinition. We show here, however, that they can be related with the help of a decoupled and nondynamic (spectator) field. The spectator field may be either an antisymmetric tensor B μν=-Bνμ, a vector Aμ or a scalar field φ, corresponding to each of the three families. The addition of the extra field allows us to formulate master actions which interpolate between the symmetric Fierz-Pauli theory and the other models. We argue that massive gravity models based on the Fierz-Pauli theory are not expected to be equivalent to possible local self-interacting theories built up on top of the two new families of massive spin-2 models. The approach used here may be useful to investigate dual (nonsymmetric) formulations of higher-spin particles. © 2013 American Physical Society.

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Contiene antecedentes, asistencia y organización de los trabajos y resumen de las presentaciones de la reunión que tuvo como objetivo analizar los aspectos jurídicos, institucionales, económicos y tecnológicos de la política de descontaminación ambiental. Incluye lista de documentos presentados y de participantes.

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Although public transport has undergone a series of changes over the last few decades, fares are still strongly affecting the budget of low-income families. This is despite the fact that, with very few exceptions, public transport fares are one of the few prices still fixed by the government authorities. The introduction of integrated networks made up of trunk lines and feeder services is not guaranteed to reduce the cost for users. It would be possible to reduce fares if free transport provided by the authorities to various groups of citizens were financed by the authorities themselves, and not by other groups of passengers.

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The notions of inclusion and exclusion have a long tradition in sociology, but have gained significant currency more recently in public policy analysis. However, a certain conceptual inflexibility arises when the distinction is applied to complex social situations. This article examines the main approaches to inclusion/exclusion in the sociological tradition, systems theory and the theory of new inequalities. On this basis, five interrelated situations of inclusion and exclusion are constructed: self-inclusion/self-exclusion, inclusion by risk/exclusion by danger, compensatory inclusion, inclusion in exclusion and sub-inclusion. They are illustrated with specific examples to refine an analytical approach to problems of inclusion and exclusion, with a view to contributing to sociological analysis and to assessing the consequences of public and private decisions.

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The aim of this study was to analyze the prevalence of hypertension and control practices among the elderly. The survey analyzed data from 872 elderly people in São Paulo, Brazil, through a cluster sampling, stratified according to education and income. A Poisson multiple regression model checked for the existence of factors associated with hypertension. The prevalence of self-reported hypertension among the elderly was 46.9%. Variables associated with hypertension were self-rated health, alcohol consumption, gender, and hospitalization in the last year, regardless of age. The three most common measures taken to control hypertension, but only rarely, are oral medication, routine salt-free diet and physical activity. Lifestyle and socioeconomic status did not affect the practice of control, but knowledge about the importance of physical activity was higher among those older people with higher education and greater income. The research suggests that health policies that focus on primary care to encourage lifestyle changes among the elderly are necessary.