The effect of superplasticizers on the workability and compressive strength of concrete made with fine recycled concrete aggregates

The reuse of structural concrete elements to produce new concrete aggregates is accepted as an alternative to dumping them and is favourable to the sustainability of natural reserves. Even though the construction sector is familiar with the use of coarse recycled concrete aggregates, the recycled concrete fines are classified as less noble resources. This research sets out to limit the disadvantages associated with the performance of concrete containing fine recycled concrete aggregates through the use of superplasticisers. Two types of latest generation superplasticisers were used that differ in terms of water reduction capacity and robustness, and the workability, density and compressive strength of each of the compositions analysed were then compared: a reference concrete, with no plasticisers, and concrete mixes with the superplasticisers. For each concrete family mixes with 0%, 10%, 30%, 50% and 100% replacement ratios of fine natural aggregates (FNA) by fine recycled concrete aggregates (FRA) were analysed. Concrete with incorporation of recycled aggregates was found to have poorer relative performance. The mechanical performance of concrete with recycled aggregates and superplasticisers was generally superior to that of the reference concrete with no admixtures and of conventional concrete with lower performance superplasticisers

Avaliação das consequências de galgamento sobre estruturas portuárias: caso de estudo da praia da Vitória, Açores

Dissertação para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização em HidráulicaA presente dissertação, inserida na área de especialização de hidráulica de engenharia civil, procura avaliar o risco de galgamento sobre estruturas portuárias. Devido à ocorrência de galgamentos, há necessidade em garantir a segurança de bens, pessoas, equipamentos, estruturas e atividades junto a elas desenvolvidas e, ainda, em precaver gastos a nível económico. Nesse sentido, recorre-se neste trabalho a previsões da agitação marítima em águas profundas fornecidas pelo modelo WAM que, acoplado aos modelos SWAN e DREAMS, permite a caracterização do estado de agitação do mar junto à estrutura portuária. Posteriormente, aplica-se a ferramenta neuronal NN_OVERTOPPING2 que fornece os caudais médios galgados nas estruturas. Seguidamente, recorre-se a três metodologias distintas para avaliar as consequências do galgamento: uma metodologia simples, Analytic Hierarchy Process (AHP) e Analytic Network Process (ANP). As metodologias multicritério AHP e ANP tornam-se mais vantajosas em relação à metodologia simples, na medida em que permitem análises espaciais definindo o risco a que cada área está sujeita. Estas melhorias sustentam uma avaliação do risco mais fiável, o que é fundamental para o apoio à tomada de decisão e numa gestão eficaz das zonas costeiras e portuárias. Por fim, aplica-se o procedimento descrito ao porto da Praia da Vitória (Açores, Portugal).Abstract: This dissertation, developed within the hydraulics branch of civil engineering, aims at contributing to the assessment of the risk associated to the wave overtopping of port structures. Due to the occurrence of overtopping, there is a requirement to ensure the safety of goods, people, equipment, structures and activities developed in their surroundings and, still, avoid economic spending. Therefore, the study uses forecast wave conditions in deep water, provided by the WAMmodel, which coupled to SWAN and DREAMS models, allows to characterize the sea state near the port structure. Subsequently, the NN_OVERTOPPING2 artificial neuronal tool is applied, which provides the mean flow overtopping discharge over the structures. Finally, three different methodologies to assess the consequences of wave overtopping are used: a simple methodology, the Analytic Hierarchy Process (AHP) and the Analytic Network Process (ANP). The multi-criteria AHP and ANP methodologies are more advantageous in comparison with the simplistic methodology, since they allow spatial analysis and definition of the risk that each area is subject to. These improvements support a more reliable risk assessment, which is essential in the decision-making process and in a effective management of coastal and port areas. The procedure in this study is applied in the port of Praia da Vitória (Azores, Portugal).N/

Modelamento de motor de indução : uma contribuição ao estudo de chaveamento das correntes de rotor de motor de indução de rotor enrolado

Orientador : Yaro Burian JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de CampinasResumo: Dadas as dificuldades apresentadas pelos modelos matemáticos mais comuns de motor de indução desenvolveu-se, a partir das transformações de Park, Blondel e Kron, um modelo adequado para simulação de motor de indução de rotor enrolado quando submetido a chaveamento das correntes de rotor. O presente trabalho procurou, didaticamente, na medida do possível, desenvolver alguns modelos de motor em questao, modificando-os gradati vamente, ate chegar ao seu objetivo finalMestradoMestre em Ciência

Control Of Wound-rotor Induction Machine

The main goal of this paper is to present a new torque and speed control method of the wound rotor induction machine (WRIM) through the control of the voltage applied to the rotor winding. The method is based on the rotor voltage orientation with respect to current using a converter cascade and a PI controller. It is shown by simulation using Pspice that the best way to comply with the control specifications is to maintain rotor voltage lagging rotor current.19710

Direct power control for switched reluctance: generator in wind energy

This paper proposes a direct power control for switched reluctance generator for wind energy systems directly connected to electric system, microgrid or system isolated. The controller process the power error directly and manipulates the turn-off angle of the converte in order to the generator power reach the reference.Simulations results are presented to validate the controller operation131123128FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2012/04872-0; 2012/08911-

A simplified method for determining the high frequency induction motor equivalent electrical circuit parameters to be used in EMI effect

The aim of this paper is to present a simple method for determining the high frequency parameters of a three-phase induction motor to be used in studies involving variable speed drives with PWM three-phase inverters, in which it is necessary to check the effects caused to the motor by the electromagnetic interference, (EMI) in the differential mode, as well as in the common mode. The motor parameters determination is generally performed in adequate laboratories using accurate instruments, such as very expensive RLC bridges. The method proposed here consists in the identification of the motor equivalent electrical circuit parameters in rated frequency and in high frequency through characteristic tests in the laboratory, together with the use of characteristic equations and curves, shown in the references to be mentioned for determining the motor high frequency parasite capacitances and also through system simulations using dedicated software, like Pspice, determining the characteristic waveforms involved in the differential and common mode phenomena, comparing and validating the procedure through published papers [01]