Comparação do controle do inversor trifásico conectado à rede com filtro LCL considerando o amortecimento passivo e ativo

Distributed generation systems must fulfill standards specifications of current harmonics injected to the grid. In order to satisfy these grid requirements, passive filters are connected between inverter and grid. This work compares the characteristic response of the traditional inductive (L) filter with the inductive-capacitive-inductive (LCL) filter. It is shown that increasing the inductance L leads to a good ripple current suppression around the inverter switching frequency. The LCL filter provides better harmonic attenuation and reduces the filter size. The main drawback is the LCL filter impedance, which is characterized by a typical resonance peak, which must be damped to avoid instability. Passive or active techniques can be used to damp the LCL resonance. To address this issue, this dissertation presents a comparison of current control for PV grid-tied inverters with L filter and LCL filter and also discuss the use of active and passive damping for different regions of resonance frequency. From the mathematical models, a design methodology of the controllers was developed and the dynamic behavior of the system operating in closed loop was investigated. To validate the studies developed during this work, experimental results are presented using a three-phase 5kW experimental platform. The main components and their functions are discussed in this work. Experimental results are given to support the theoretical analysis and to illustrate the performance of grid-connected PV inverter system. It is shown that the resonant frequency of the system, and sampling frequency can be associated in order to calculate a critical frequency, below which is essential to perform the damping of the LCL filter. Also, the experimental results show that the active buffer per virtual resistor, although with a simple development, is effective to damp the resonance of the LCL filter and allow the system to operate stable within predetermined parameters.

A Parentalidade tardia : Os pais, os filhos e o amanhã

Dissertação de Mestrado apresentada no Instituto Superior de Psicologia Aplicada para obtenção de grau de Mestre na especialidade de Psicologia Clínica

Cuidador informal de idosos: efeitos sociais e familiares decorrentes do cuidar, uma revisão da literatura

Introdução - O papel dos cuidadores informais junto de pessoas idosas tem vindo a ser considerado pertinente na medida em que proporciona estabilidade e melhor qualidade de vida à pessoa idosa. É uma tarefa praticada na grande maioria por mulheres, originando efeitos sociais e familiares que modificam as relações entre familiares e até entre a rede de amigos. Objetivo - Identificar os efeitos sociais e familiares decorrentes do cuidar de idosos. Método – Trata-se de uma revisão da literatura com busca nas bases de dados eletrónicas: Repositório Científico de acesso aberto de Portugal (RCCAP) e Scielo. Foram selecionados artigos publicados entre os anos 2008 e 2015, a partir da questão de investigação: “Quais os efeitos sociais e familiares decorrentes do cuidar de idosos ”. Resultados - Após análise dos estudos selecionados verificou-se que os cuidadores são predominantemente do sexo feminino, nomeadamente esposa, filha ou neta da pessoa idosa. Apurou-se que existem alterações nas relações sociais e familiares devido ao excesso de tarefas que o cuidar exige. Identificaram-se o impacto financeiro, ausência de apoios sociais e familiares, impactos sociais, sobrecarga física e emocional, impactos na saúde, impacto profissional, a falta ou escassa formação/ preparação para exercer a função de cuidador, a falta ou diminuição do tempo para o casamento e para os filhos, a diminuição do tempo de lazer o que origina o isolamento social, o afastamento da rede de amigos e por último as alterações familiares como efeitos decorrentes do cuidar de idosos. Conclusão - conclui-se que apesar das dificuldades da prática de cuidar, os familiares sentem-se realizados por ser possível proporcionar um final de vida digno ao seu familiar, contudo seria pertinente a existência de formações e o desenvolvimento de estratégias que auxiliem o cuidador informal na execução das suas tarefas.

O compromisso de casar e o desejo de amar : experimentos existenciais entre jovens abastados na cidade de Nova Délhi

Tese (doutorado)—Universidade de Brasília, Instituto de Ciências Sociais, Departamento de Antropologia, Programa de Pós-graduação em Antropologia Social, 2015.

Estudos de Durabilidade Frente ao Ataque Ácido de Compósitos Portland-Polímero para Cimentação de Poços de Petróleo

Portland-polymers composites are promising candidates to be used as cementing material in Northeastern oil wells of Brazil containing heavy oils submitted to steam injection. In this way, it is necessary to evaluate its degradation in the commonly acidizind agents. In addition, to identify how aggressive are the different hostile environments it is an important contribution on the decision of the acidic systems to be used in. It was investigated the performance of the Portland-polymer composites using powdered polyurethane, aqueous polyurethane, rubber tire residues and a biopolymer, those were reinforced with polished carbon steel SAE 1045 to make the electrochemical measurements. HCl 15,0 %, HCl 6,0 % + HF 1,5 % (soft mud acid), HCl 12,0 % + HF 3,0 % (regular mud acid) and HAc 10 % + HF 1,5 % were used as degrading environment and electrolytes. The more aggressive acid solution to the plain Portland hardened cement paste was the regular mud acid, that showed loss of weight around 23.0 %, followed by the soft mud acid, the showed 11.0 %, 15.0 % HCl with 7,0 % and, at last the 10.0 % HAc plus HF 1.5 % with just 1.0 %. The powdered polyurethane-composite and the aqueous polyurethane one showed larger durability, with reduction around 87.0 % on the loss of weight in regular mud acid. The acid attack is superficial and it occurs as an action layer, where the degraded layer is responsible for the decrease on the kinetic of the degrading process. This behavior can be seen mainly on the Portland- aqueous polyurethane composite, because the degraded layer is impregnated with chemically modified polymer. The fact of the acid attack does not have influence on the compressive strength or fratography of the samples, in a general way, confirms that theory. The mechanism of the efficiency of the Portland-polymers composites subjected to acid attack is due to decreased porosity and permeability related with the plain Portland paste, minor quantity of Ca+2, element preferentially leached to the acidic solution, wave effect and to substitute part of the degrading bulk for the polymeric one. The electrolyte HAc 10 % + HF 1,5 % was the least aggressive one to the external corrosion of the casing, showing open circuit potentials around +250 mV compared to -130 mV to the simulated pore solution to the first 24 hours immersion. This behavior has been performed for two months at least. Similar corrosion rates were showed between both of the electrolytes, around 0.01 μA.cm-2. Total impedance values, insipient arcs and big polarization resistance capacitive arcs on the Nyquist plots, indicating passivity process, confirm its efficiency. In this way, Portlandpolymers composites are possible solutions to be succeed applied to oilwell cementing concomitant submitted to steam injection and acidizing operation and the HAc 10,0 % + HF 1,5 % is the less aggressive solution to the external corrosion of the casing

Determinação eletroanalítica de ácido salicílico em produto dermatológico com eletrodos de nanotubos de carbono e nanopartículas de óxido de ferro

Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Tecnologias Química e Biológica, 2016.

Obtenção de polímeros de LCC para aplicação como antioxidante de biodiesel de soja

Biodiesel is a fuel obtained from vegetable oils, such as soy, castorbean, among others. The monoester of fatty acid of these oils have chains with mono, di and tri double connections. The presence of these insaturations are susceptible to oxidization. Antioxidants are substances able to prevent oxidization from oils, fats, fat foods, as well as esters of Alquila( biodiesel). The objective of this work is to summarize a new antioxidant from the Cashew Nut Shell Liquid (CNSL) using the electrolysis technique. A current of 2 amperes was used in a single cell of only one group and two eletrodos of stainless steel 304 in a solution of methanol, together with the eletrolits: acetic acid, sodium chloride and sodium hydroxide, for two hours of agitation. The electrolysis products are characterized by the techniques of cromatography in a thin layer, spectroscopy of infrared and gravimetric analysis. The material was submitted to tests of oxidative stability made by the techniques of spectropy of impendancy and Rancimat (EN 14112). The analyses of characterization suggest that the polimerization of the electrolytic material ocurred. The application results of these materials as antioxidants of soy biodiesel showed that the order of the oxidative stability was obtained by both techniques used

Preparação e caracterização de filmes cerâmicos para cátodos de células a combustível de óxido sólido

Alternative and clean energy generation research has been intensified in last decades. Among the alternatives, fuel cells are one of the most important. There are different types of fuel cells, among which stands out intermediate temperature solid oxide fuel cell (IT-SOFC) matter of the present work. For application as cathode on this type of devices, the ceramic Ba0.5Sr0.5C0.8Fe0.2O3-δ doped with rare earth ions (Nd, Sm) have been quite promising because they show good ionic conductivity and operate at relatively low temperatures (500 - 800°C). In this work, Ba0.5Sr0.5Co0.8Fe0.2O3-δ, (BaSr)0.5Sm0.5Co0.8Fe0.2O3-δ and (BaSr)0.5Nd0.5C0.8Fe0.2O3-δ were obtained by modified Pechini method, making use of gelatin as polymerizing agent. The powders were characterized by X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR) and Scanning Electron Microscopy (SEM). The perovskite phase was observed in all X-ray patterns for the materials Ba0.5Sr0.5C0.8Fe0.2O3-δ doped with rare earth ions (Nd, Sm). The SEM images showed that the materials have a characteristics porous, with very uniform pore distribution, which are favorable for application as cathodes. Subsequently, screen-printed assymmetrical cells were studied by impedance spectroscopy, to assess the kinetics of the cathode for the reduction reaction of oxygen. The best resistance to the specific area was found for the cathode BSSCF sintered at 1050 °C for 4 hours with around 0.15 Ω.cm2 at 750 °C as well as cathodes BSNCF and BSCF obtained resistances specific area of 0.2 and 0.73 Ω.cm2, respectively, for the same conditions. The polarization curves showed similar behavior to the best cathodes BSSCF and BSNCF, such combination of properties indicates that the film potentially depict good performance as IT-SOFC cathodes

Efeito da Gália como aditivo de sinterização em eletrólitos cerâmicos à base de céria sintetizados pelo método de complexação de cátions

Fuel cells are considered one of the most promising ways of converting electrical energy due to its high yield and by using hydrogen (as fuel) which is considered one of the most important source of clean energy for the future. Rare earths doped ceria has been widely investigated as an alternative material for the electrolyte of solid oxide fuel cells (SOFCs) due to its high ionic conductivity at low operating temperatures compared with the traditional electrolytes based on stabilized zirconia. This work investigates the effect of gallium oxide (Gallia) as a sintering aid in Eu doped ceria ceramic electrolytes since this effect has already been investigated for Gd, Sm and Y doped ceria electrolytes. The desired goal with the use of a sintering aid is to reduce the sintering temperature aiming to produce dense ceramics. In this study we investigated the effects on densification, microstructure and ionic conduction caused by different molar fraction of the dopants europium (10, 15 and 20%) and gallium oxide (0.3, 0.6 and 0.9%) in samples sintered at 1300, 1350 and 1450 0 C. Samaria (10 and 20%) doped ceria samples sintered between 1350 and 1450 °C were used as reference. Samples were synthesized using the cation complexation method. The ceramics powders were characterized by XRF, XRD and SEM, while the sintered samples were investigated by its relative density, SEM and impedance spectroscopy. It was showed that gallia contents up to 0.6% act as excellent sintering aids in Eu doped ceria. Above this aid content, gallia addition does not promote significant increase in density of the ceramics. In Ga free samples the larger densification were accomplished with Eu 15% molar, effect expressed in the microstructure with higher grain growth although reduced and surrounded by many open pores. Relative densities greater than 95 % were obtained by sintering between 1300 and 1350 °C against the usual range 1500 - 1600 0 C. Samples containing 10% of Sm and 0.9% of Ga reached 96% of theoretical density by sintering at 1350 0 C for 3h, a gain compared to 97% achieved with 20% of Sm and 1% of Ga co-doped cerias sintered at 1450 0 C for 24 h as described in the literature. It is found that the addition of gallia in the Eu doped ceria has a positive effect on the grain conductivity and a negative one in the grain boundary conductivity resulting in a small decrease in the total conductivity which will not compromise its application as sintering aids in ceria based electrolytes. Typical total conductivity values at 600 and 700 °C, around 10 and 30 mS.cm -1 respectively were reached in this study. Samples with 15% of Eu and 0.9 % of Ga sintered at 1300 and 1350 °C showed relative densities greater than 96% and total conductivity (measured at 700 °C) between 20 and 33 mS.cm -1 . The simultaneous sintering of the electrolyte with the anode is one of the goals of research in materials for SOFCs. The results obtained in this study suggest that dense Eu and Ga co-doped ceria electrolytes with good ionic conductivity can be sintered simultaneously with the anode at temperatures below 1350 °C, the usual temperature for firing porous anode materials

Avaliação da espécie vegetal Croton cajucara Benth como inibidor de biocorrosão em aço carbono Aisi 1020

Actually in the oil industry biotechnological approaches represent a challenge. In that, attention to metal structures affected by electrochemical corrosive processes, as well as by the interference of microorganisms (biocorrosion) which affect the kinetics of the environment / metal interface. Regarding to economical and environmental impacts reduction let to the use of natural products as an alternative to toxic synthetic inhibitors. This study aims the employment of green chemistry by evaluating the stem bark extracts (EHC, hydroalcoholic extract) and leaves (ECF, chloroform extract) of plant species Croton cajucara Benth as a corrosion inhibitor. In addition the effectiveness of corrosion inhibition of bioactive trans-clerodane dehydrocrotonin (DCTN) isolated from the stem bark of this Croton was also evaluated. For this purpose, carbon steel AISI 1020 was immersed in saline media (3,5 % NaCl) in the presence and absence of a microorganism recovered from a pipeline oil sample. Corrosion inhibition efficiency and its mechanisms were investigated by linear sweep voltammetry and electrochemical impedance. Culture-dependent and molecular biology techniques were used to characterize and identify bacterial species present in oil samples. The tested natural products EHC, ECF and DCTN (DMSO as solvent) in abiotic environment presented respectively, corrosion inhibition efficiencies of 57.6% (500 ppm), 86.1% (500 ppm) and 54.5% (62.5 ppm). Adsorption phenomena showed that EHC best fit Frumkin isotherm and ECF to Temkin isotherm. EHC extract (250 ppm) dissolved in a polar microemulsion system (MES-EHC) showed significant maximum inhibition efficiency (93.8%) fitting Langmuir isotherm. In the presence of the isolated Pseudomonas sp, EHC and ECF were able to form eco-compatible organic films with anti-corrosive properties

Uma caracterização dos imigrantes no distrito de Évora

Uma vez que existe uma grande necessidade de se obter um maior conhecimento das comunidades imigrantes residentes no Distrito, este trabalho tem como principal objectivo caracterizar a população de imigrantes comunitários residentes no distrito de Évora. Em particular, procuramos analisar os casamentos realizados não só entre os não nacionais e portugueses, bem como entre os nãos nacionais entre si. Consideramos os 354 imigrantes que constituem os imigrantes comunitários inscritos legalmente nos Serviços Estrangeiros e Fronteiras de Évora entre 2006 a 2009. Por outro lado, analisamos, para o mesmo período, os casamentos dos imigrantes que casaram com os portugueses num total de 165 indivíduos. Começamos por levar a efeito uma investigação básica de tipo descritivo para uma caracterização dos imigrantes relativamente a diferentes variáveis e investigamos algumas associações entre elas via tabelas de contingência. Refira-se que a maioria dos imigrantes é do sexo feminino, sendo a nacionalidade mais representativa a brasileira. Com base no modelo de regressão de Cox identificamos factores de risco e diferentes perfis associados à rotura do casamento. Mostramos que há evidência estatística para considerar que um menor nível de escolaridade, o pertencer a um país da União Europeia e o ter entrado à procura de trabalho são níveis de factores que aumentam o risco de rotura do casamento. Analisam-se, ainda, de uma forma crítica, a abordagem paramétrica, procurando modelar os dados através dos modelos Exponencial, Weibull, Lognormal e Log-logístico. ABSTRACT: There is a need to obtain a greater understanding of immigrant communities in the district; this work has as main objective to characterize the population of immigrant community residing in the district of Évora. ln particular, we analyze not only marriages between Portuguese and non-nationals, as well as among non-nationals among themselves. We consider the 354 immigrants who are legally registered immigrants in the Community Service of Foreigners and Frontiers of Évora, from 2006 to 2009. Moreover, we analyze, for the same period, the marriages of immigrants who intermarried with the Portuguese for a total of 165 individuals. We start by carrying out a basic descriptive research in order to characterize the immigrants in relation to several variables and investigated some associations between them by contingency tables. It should be noted that most immigrants are women, and the more representative the Brazilian nationality. Based on the Cox regression model, were possible to identify risk factors and identify profiles of high and low risk associated with the rupture of the marriage. We show that there is statistical evidence to conclude that a less educated levels, belonging to a country inside the European Union and have gone looking for work are factors that increase the risk of rupture of the marriage. The parametric approach is analyzed also, in a critical way, seeking to model the data using exponential, Weibull, Lognormal and Log-logistic.

Sobre a separação de facto como fundamento do divórcio, e algo mais

Este Capítulo analisa a política legislativa relativa separação de facto como fundamento do divórcio, desde 1910 até à actualidade, e os problemas jurídicos inerentes, salientando a importância das contribuições doutrinárias do Senhor Professor Doutor Francisco Manuel Pereira Coelho no tocante ao assunto, mas sem prejuízo das referências pertinentes a outros autores relevantes e à jurisprudência atinente à matéria. Também dá conta dos dados estatísticos relativos a divórcios e separações de pessoas e bens que se afiguram relevantes para se compreender a relevância estatística do referido fundamento.

A Natalidade e a Fecundidade em Portugal

Para melhor compreendermos a situação de fecundidade em Portugal no início do século XXI, precisamos analisar a evolução das últimas décadas, na medida em que o comportamento passado condiciona o observado no momento actual. Nos últimos 30 a 40 anos, registaram-se enormes alterações nos padrões de fecundidade por idades. Nos anos 60 e 70, o modelo alterou-se, na medida em que as mulheres passaram a ter filhos mais cedo, isto é, a fecundidade elevou-se abaixo dos 28 anos (principalmente, entre os 23 e os 26) e a fecundidade tardia (a partir dos 32 anos) reduziu-se bastante. Até ao início dos anos 80, a contracepção foi utilizada maioritariamente no interior do casamento, por mulheres com idade acima dos 30 anos, após terem atingido o número desejado de filhos. Nos anos 80, o modelo voltou a alterar-se. O número de filhos por mulher desceu para valores abaixo de 2. Na década seguinte, última do século XX, a tendência acentuou-se: o número de filhos manteve-se baixo, e continuou a adiar-se, para idades cada vez mais tardias, o momento do nascimento (valores mais elevados entre os 28 e os 30 anos). Registou-se um elevado nível de contracepção, em mulheres jovens com idades até aos 28 anos; contracepção eficaz e generalizada, antes do casamento, precedendo o nascimento do primeiro filho. A partir de 2000 até 2009, o número de nascimentos diminuiu ainda mais e o adiamento não parou de aumentar. Todavia, começou a assistir-se a uma recuperação muito ténue no número de nascimentos em idades mais tardias, entre os 33 e os 42 anos (valores mais elevados registados em mães com 29, 30 e 31 anos). Como resultado de um comportamento de declínio ao longo de décadas, agravado por um quadro recente onde as mulheres não pararam de adiar a idade da maternidade, Portugal converteu-se num dos países da Europa e do Mundo com mais baixos níveis de fecundidade.