856 resultados para Almeida Garrett, João Baptista da Silva Leitão de Almeida Garrett, Visconde de, 1799-1854.


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Relatório da prática de ensino supervisionada, Mestrado em Ensino de Filosofia, Universidade de Lisboa, 2011

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O presente volume de estudos em homenagem ao Professor Hélio Osvaldo Alves é composto por duas partes. A primeira, com o título de ‘Testemunhos’, reúne as palavras com que amigos, colegas e discípulos recordaram a pessoa de Hélio Alves. A segunda parte, ‘Comunicações’, inclui os textos de carácter científico apresentados e debatidos no colóquio, realizado em Novembro de 2003. ‘O lago de todos os recursos’ é uma expressão que o Professor Hélio tomou de empréstimo a E. P. Thompson, e adaptou, para baptizar um dos seus estudos sobre a ideia de Cultura. Escolhemos esse título para o colóquio que deu origem a este volume por ele sugerir as infinitas possibilidades de estudo e análise que se contêm na palavra Cultura, bem como a diversidade de escolhas e aproximações que os estudos de Cultura proporcionam.

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Trabalho de projeto de mestrado, Ciências da Educação (Formação de Adultos), Universidade de Lisboa, Instituto de Educação, 2013

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Tese de doutoramento, História (Arte Património e Restauro), Universidade de Lisboa, Faculdade de Letras, 2014

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Tese de doutoramento, Ciências Biomédicas (Ciências Biopatológicas), Universidade de Lisboa, Faculdade de Medicina, 2014

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Tese de doutoramento, Belas-Artes (Design de Equipamento), Universidade de Lisboa, Faculdade de Belas-Artes, 2015

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Tese de doutoramento, Antropologia (Antropologia do Parentesco e do Género), Universidade de Lisboa, Instituto de Ciências Sociais, 2015

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Tese de doutoramento, História (Arte, Património e Restauro), Universidade de Lisboa, Faculdade de Letras, 2016

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In this paper, the development of bidding strategies is investigated for a wind farm owner. The optimization model is characterized by making the analysis of scenarios. The proposed approach allows evaluating alternative production strategies in order to submit bids to the electricity market with the goal of maximizing profits. The problem is formulated as a linear programming problem. An application to a case study is presented

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In this paper, two wind turbines equipped with a permanent magnet synchronous generator (PMSG) and respectively with a two-level or a multilevel converter are simulated in order to access the malfunction transient performance. Three different drive train mass models, respectively, one, two and three mass models, are considered in order to model the bending flexibility of the blades. Moreover, a fractional-order control strategy is studied comparatively to a classical integer-order control strategy. Computer simulations are carried out, and conclusions about the total harmonic distortion (THD) of the electric current injected into the electric grid are in favor of the fractional-order control strategy.

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This paper presents an artificial neural network approach for short-term wind power forecasting in Portugal. The increased integration of wind power into the electric grid, as nowadays occurs in Portugal, poses new challenges due to its intermittency and volatility. Hence, good forecasting tools play a key role in tackling these challenges. The accuracy of the wind power forecasting attained with the proposed approach is evaluated against persistence and ARIMA approaches, reporting the numerical results from a real-world case study.

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In this paper, a stochastic programming approach is proposed for trading wind energy in a market environment under uncertainty. Uncertainty in the energy market prices is the main cause of high volatility of profits achieved by power producers. The volatile and intermittent nature of wind energy represents another source of uncertainty. Hence, each uncertain parameter is modeled by scenarios, where each scenario represents a plausible realization of the uncertain parameters with an associated occurrence probability. Also, an appropriate risk measurement is considered. The proposed approach is applied on a realistic case study, based on a wind farm in Portugal. Finally, conclusions are duly drawn. (C) 2011 Elsevier Ltd. All rights reserved.

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The increased integration of wind power into the electric grid, as nowadays occurs in Portugal, poses new challenges due to its intermittency and volatility. Hence, good forecasting tools play a key role in tackling these challenges. In this paper, an adaptive neuro-fuzzy inference approach is proposed for short-term wind power forecasting. Results from a real-world case study are presented. A thorough comparison is carried out, taking into account the results obtained with other approaches. Numerical results are presented and conclusions are duly drawn. (C) 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

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Power converters play a vital role in the integration of wind power into the electrical grid. Variable-speed wind turbine generator systems have a considerable interest of application for grid connection at constant frequency. In this paper, comprehensive simulation studies are carried out with three power converter topologies: matrix, two-level and multilevel. A fractional-order control strategy is studied for the variable-speed operation of wind turbine generator systems. The studies are in order to compare power converter topologies and control strategies. The studies reveal that the multilevel converter and the proposed fractional-order control strategy enable an improvement in the power quality, in comparison with the other power converters using a classical integer-order control strategy. (C) 2010 Elsevier Ltd. All rights reserved.

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As wind power generation undergoes rapid growth, new technical challenges emerge: dynamic stability and power quality. The influence of wind speed disturbances and a pitch control malfunction on the quality of the energy injected into the electric grid is studied for variable-speed wind turbines with different power-electronic converter topologies. Additionally, a new control strategy is proposed for the variable-speed operation of wind turbines with permanent magnet synchronous generators. The performance of disturbance attenuation and system robustness is ascertained. Simulation results are presented and conclusions are duly drawn. (C) 2010 Elsevier Ltd. All rights reserved.