In the Shadow of Power

Pedro Feytor Pinto headed the Department of Information Services (SEIT) in the government of Marcello Caetano who replaced Antonio Oliveira Salazar in 1968 as the head of the Portuguese government. Feytor Pinto has just released a book entitled Na Sombra do Poder (In the Shadow of Power)[Lisboa, D. Quixote, 2011, pp. 402]. Not wishing to classify it as history or memoirs, yet hoping that historians may find it useful, the author chooses to narrate events as he experienced them from his vantage point in the shadow of Power, during the years ending with the Carnation Revolt of 25 April 1974, which put an end to half a century of dictatorship, known as Estado Novo.

Metaphors of opulence and power in the life of Thomas Wolsey, the King’s Cardinal

This essay approaches the display of power and rulership both through the art of writing and the art of painting by focusing on George Cavendish's biographical account of Thomas Wolsey.

Diversidade ética e exclusão social no processo da consolidação da unidade nacional : o caso dos vendedores e vendedoras informais do Mercado de Estrela Vermelha : cidade de Maputo

O presente trabalho, estuda as relações sociais e interculturais dos vendedores informais do mercado de Estrela Vermelha- cidade de Maputo. Analisa os fatores que afetam a unidade nacional, entendida como o sentido de pertença a uma identidade e a um destino comuns. Há duas teses que explicam a crise da unidade nacional. A primeira argumenta que o que coloca em causa a unidade nacional é a pretensão de se querer construir uma nação cívica, excluindo e até mesmo hostilizando as identidades étnicas vistas como fator de divisão e de conflitos. Propõe por isso, o reconhecimento e a inclusão dos diferentes grupos étnicos no poder (Magode, 1996; Cahen, 1996; Lundin, 1996). Na segunda, argumenta-se que as etnias perderam a sua relevância em virtude das transformações sociopolíticas e económicas havidas no país (Castiano, 2010), ou como outros defendem, que objetivamente elas não existem, se não apenas como reflexo dos conflitos pelo acesso aos recursos e poder (Serra, 1996). Sendo assim, o obstáculo da unidade nacional são as desigualdades económicas e não as diferenças étnicas. Mediante o trabalho de observação, que incluiu entrevistas, conversas, descrição e fotografias, como técnicas de recolha de dados, combinado com a pesquisa documental, este trabalho argumenta que, existe no mercado uma convivência multicultural, mas regista-se ainda défice nas relações interculturais. Os vendedores do Sul, consideram-se culturalmente superiores em relação aos seus colegas do norte do Save. Tal como outras pessoas da região sul, estes vendedores tratam os seus colegas pelo termo xingondo, que além da simples identificação, é usado para desqualificar os seus colegas do norte. Assim, o silêncio em relação ao etnocentrismo das pessoas do sul, a timidez que ainda se verifica em relação ao uso oficial das línguas moçambicanas, que são o meio de comunicação mais usado, bem como a incipiente provisão dos direitos da cidadania, constituem os principais obstáculos à unidade nacional. O estudo termina propondo a operacionalização do conceito da unidade nacional, tendo em conta, por um lado o respeito pelas diferenças culturais e a promoção do diálogo intercultural e por outro, o combate contra as diferenças abismais entre ricos e pobres.

A hybrid PSO-ANFIS approach for short-term wind power prediction 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. Wind power prediction plays a key role in tackling these challenges. The contribution of this paper is to propose a new hybrid approach, combining particle swarm optimization and adaptive-network-based fuzzy inference system, for short-term wind power prediction in Portugal. Significant improvements regarding forecasting accuracy are attainable using the proposed approach, in comparison with the results obtained with five other approaches.

Electromagnetic transients analysis of lightning overvoltages on wind power plants

As wind power generation undergoes rapid growth, lightning and overvoltage incidents involving wind power plants have come to be regarded as a serious problem. Firstly, lightning location systems are discussed, as well as important parameters regarding lightning protection. Also, this paper presents a case study, based on a wind turbine with an interconnecting transformer, for the study of adequate lightning and overvoltage protection measures. The electromagnetic transients circuit under study is described, and computational results are presented.

Direct Power Control of Matrix Converter Based Unified Power Flow Controllers

This paper presents the Direct Power Control of Three-Phase Matrix Converters (DPC-MC) operating as Unified Power Flow Controllers (UPFC). Since matrix converters allow direct AC/AC power conversion without intermediate energy storage link, the resulting UPFC has reduced volume and cost, together with higher reliability. Theoretical principles of DPC-MC method are established based on an UPFC model, together with a new direct power control approach based on sliding mode control techniques. As a result, active and reactive power can be directly controlled by selection of an appropriate switching state of matrix converter. This new direct power control approach associated to matrix converters technology guarantees decoupled active and reactive power control, zero error tracking, fast response times and timely control actions. Simulation results show good performance of the proposed system.

Risk Aversion in a Mixed-Integer Nonlinear Approach to Support Decision-Making for a Hydro Power Producer

In this paper, a mixed-integer nonlinear approach is proposed to support decision-making for a hydro power producer, considering a head-dependent hydro chain. The aim is to maximize the profit of the hydro power producer from selling energy into the electric market. As a new contribution to earlier studies, a risk aversion criterion is taken into account, as well as head-dependency. The volatility of the expected profit is limited through the conditional value-at-risk (CVaR). The proposed approach has been applied successfully to solve a case study based on one of the main Portuguese cascaded hydro systems.

Stability Condition Based Sliding Mode Modulators for Multilevel Power Converters

Sliding mode controllers for power converters usually employ hysteresis comparators to directly generate the power semiconductors switching states. This paper presents a new sliding mode modulator based on the direct implementation of the sliding mode stability condition, which for multilevel power converters shows advantages, as branch equalized switching frequencies and less distortion on the ac currents when operating near the rated converter power. The new sliding mode multilevel modulator is used to control a three-phase multilevel converter, operated as a reactive power compensator (STATCOM), implementing the stability condition in a digital signal processing system. The performance of this new sliding mode modulator is compared with a multilevel modulator based on hysteresis comparators. Simulation and experimental results are presented in order to highlight the system operation and control robustness.

Modeling, control and simulation of full-power converter wind turbines equipped with permanent magnet synchronous generator

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.

A Pitch Control Malfunction Analysis for Wind Turbines with Permanent Magnet Synchronous Generator and Full-power Converters: Proportional Integral Versus Fractional-order Controllers

A transient analysis for two full-power converter wind turbines equipped with a permanent magnet synchronous generator is studied in this article, taking into consideration, as a new contribution to earlier studies, a pitch control malfunction. The two full-power converters considered are, respectively, a two-level and a multi-level converter. Moreover, a novel control strategy based on fractional-order controllers for wind turbines is studied. Simulation results are presented; conclusions are in favor of the novel control strategy, improving the quality of the energy injected into the electric grid.

Pressão, memorização e eficácia publicitária. Para além da repetição: a criatividade como factor potencial de eficácia da comunicação publicitária

Este artigo analisa a questão da eficácia publicitária num contexto de saturação. O reconhecimento da marca ou a recordação da publicidade associada à marca serão sempre, pelo menos, objectivos secundários de uma qualquer campanha publicitária. A eficácia surge assim associada inegavelmente à capacidade de memorização por parte do público-alvo das campanhas. Assim, parece consensual que as bases da eficácia publicitária são a memorização e a frequência publicitária no seu conjunto. Os modelos quantitativos existentes baseados em extensas bases de dados utilizados para estimar os resultados de eficácia utilizam sobretudo a relação cobertura/repetição, mas não chegam para saber qual a real eficácia do anúncio face aos objectivos junto de um determinado target. É possível aumentar a eficácia, através da criatividade, sem aumentar a pressão publicitária. Num contexto de saturação publicitária, o aumento da pressão publicitária não resultará certamente em maior eficácia. A resposta passará pelo poder da criatividade, desde logo nas estratégias do marketing e da comunicação, mas também das próprias mensagens publicitárias e na criatividade ao nível da utilização dos meios, sejam eles mais ou menos tradicionais.

An artificial neural network approach for short-term wind power forecasting in Portugal

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.

Fractional-order control and simulation of wind energy systems with PMSG/full-power converter topology

This paper presents a new integrated model for the simulation of wind energy systems. The proposed model is more realistic and accurate, considering a variable-speed wind turbine, two-mass rotor, permanent magnet synchronous generator (PMSG), different power converter topologies, and filters. Additionally, a new control strategy is proposed for the variable-speed operation of wind turbines with PMSG/full-power converter topology, based on fractional-order controllers. Comprehensive simulation studies are carried out with matrix and multilevel power converter topologies, in order to adequately assert the system performance in what regards the quality of the energy injected into the electric grid. Finally, conclusions are duly drawn.

A simulation study on the abatement of CO2 emissions by de-absorption with monoethanolamine

Because of the adverse effect of CO2 from fossil fuel combustion on the earth's ecosystems, the most cost-effective method for CO2 capture is an important area of research. The predominant process for CO2 capture currently employed by industry is chemical absorption in amine solutions. A dynamic model for the de-absorption process was developed with monoethanolamine (MEA) solution. Henry's law was used for modelling the vapour phase equilibrium of the CO2, and fugacity ratios calculated by the Peng-Robinson equation of state (EOS) were used for H2O, MEA, N-2 and O-2. Chemical reactions between CO2 and MEA were included in the model along with the enhancement factor for chemical absorption. Liquid and vapour energy balances were developed to calculate the liquid and vapour temperature, respectively.

Power Electronics Didactic Modules for Direct Current Machine Control

Several didactic modules for an electric machinery laboratory are presented. The modules are dedicated for DC machinery control and get their characteristic curves. The didactic modules have a front panel with power and signal connectors and can be configurable for any DC motor type. The three-phase bridge inverter proposed is one of the most popular topologies and is commercially available in power package modules. The control techniques and power drives were designed to satisfy static and dynamic performance of DC machines. Each power section is internally self-protected against misconnections and short-circuits. Isolated output signals of current and voltage measurements are also provided, adding versatility for use either in didactic or research applications. The implementation of such modules allowed experimental confirmation of the expected performance.