Acompanhamento da construção e remodelação da estação fluvial do Terreiro do Paço

O trabalho que se segue reporta as actividades resultantes da experiência em obra ao serviço da firma Interpaço A.C.E., durante um período de quatro meses. A esta empresa foi adjudicada a seguinte empreitada: “Execução dos Toscos, Acabamentos, Baixa Tensão, Telecomunicações e AVAC do Novo Terminal Fluvial, No Interface do Terreiro do Paço sito em Lisboa”. O objectivo principal foi o de adquirir conhecimentos nas várias áreas de execução de uma obra desta natureza: Área de Projecto, Produção, Preparação, Técnico/Comercial e Orçamentação. Adquiriram-se igualmente conhecimentos na área de gestão de consórcios e das subempreitadas, como seja a interacção e coordenação entre os diversos departamentos e organismos que integram o mesmo. O estágio consistiu principalmente no acompanhamento do Director de Obra nos vários processos de construção, na verificação da conformidade da execução destes processos, de acordo com planeamento efectuado, na verificação do registo de recepção dos diversos materiais, no contacto com os diversos intervenientes no processo construtivo e na elaboração de detalhes construtivos. Foram obtidas diversas competências nas seguintes áreas: Projecto, onde se ganharam noções básicas da leitura e interpretação deste, complementando-o com as informações fornecidas pelo caderno de encargos e memória descritiva; Encomenda e Recepção de Materiais, onde se adquiriu um conhecimento relevante do mercado disponível, tendo em conta igualmente futuros empreendimentos; Elaboração de Autos, onde se compreenderam as relações entre a Empresa Construtora, Subempreiteiros e Dono de Obra; Trabalhos de Preparação, onde se percebeu a importância de planear com antecedência todos os passos da execução dos trabalhos.

Comparing a current-carrying circular wire with polygons of equal perimeter: Magnetic field versus magnetic flux

We compare the magnetic field at the centre and the self-magnetic flux through a current-carrying circular loop, with those obtained for current-carrying polygons with the same perimeter. As the magnetic field diverges at the position of the wires, we compare the self-fluxes utilizing several regularization procedures. The calculation is best performed utilizing the vector potential, thus highlighting its usefulness in practical applications. Our analysis answers some of the intuition challenges students face when they encounter a related simple textbook example. These results can be applied directly to the determination of mutual inductances in a variety of situations.

Influence of growth temperature and carrier flux on the structure and transport properties of highly oriented CrO2 on Al2O3 (0001)

In this work we report on the structure and magnetic and electrical transport properties of CrO2 films deposited onto (0001) sapphire by atmospheric pressure (AP)CVD from a CrO3 precursor. Films are grown within a broad range of deposition temperatures, from 320 to 410 degrees C, and oxygen carrier gas flow rates of 50-500 seem, showing that it is viable to grow highly oriented a-axis CrO2 films at temperatures as low as 330 degrees C i.e., 60-70 degrees C lower than is reported in published data for the same chemical system. Depending on the experimental conditions, growth kinetic regimes dominated either by surface reaction or by mass-transport mechanisms are identified. The growth of a Cr2O3 interfacial layer as an intrinsic feature of the deposition process is studied and discussed. Films synthesized at 330 degrees C keep the same high quality magnetic and transport properties as those deposited at higher temperatures.

Severity and exposure associated with tsunami actions in urban waterfronts: the case of Lisbon, Portugal

The Tagus estuary is bordered by the largest metropolitan area in Portugal, the Lisbon capital city council. It has suffered the impact of several major tsunamis in the past, as shown by a recent revision of the catalogue of tsunamis that struck the Portuguese coast over the past two millennia. Hence, the exposure of populations and infrastructure established along the riverfront comprises a critical concern for the civil protection services. The main objectives of this work are to determine critical inundation areas in Lisbon and to quantify the associated severity through a simple index derived from the local maximum of momentum flux per unit mass and width. The employed methodology is based on the mathematical modelling of a tsunami propagating along the estuary, resembling the one occurred on the 1 November of 1755 that followed the 8.5 M-w Great Lisbon Earthquake. The employed simulation tool was STAV-2D, a shallow-flow solver coupled with conservation equations for fine solid phases, and now featuring the novelty of discrete Lagrangian tracking of large debris. Different sets of initial conditions were studied, combining distinct tidal, atmospheric and fluvial scenarios, so that the civil protection services were provided with comprehensive information to devise public warning and alert systems and post-event mitigation intervention. For the most severe scenario, the obtained results have shown a maximum inundation extent of 1.29 km at the AlcA cent ntara valley and water depths reaching nearly 10 m across Lisbon's riverfront.

Magnetic flux density distribution in the air gap of a ferromagnetic core with superconducting blocks: three-dimensional analysis and experimental NMR results

The design of magnetic cores can be carried out by taking into account the optimization of different parameters in accordance with the application requirements. Considering the specifications of the fast field cycling nuclear magnetic resonance (FFC-NMR) technique, the magnetic flux density distribution, at the sample insertion volume, is one of the core parameters that needs to be evaluated. Recently, it has been shown that the FFC-NMR magnets can be built on the basis of solenoid coils with ferromagnetic cores. Since this type of apparatus requires magnets with high magnetic flux density uniformity, a new type of magnet using a ferromagnetic core, copper coils, and superconducting blocks was designed with improved magnetic flux density distribution. In this paper, the designing aspects of the magnet are described and discussed with emphasis on the improvement of the magnetic flux density homogeneity (Delta B/B-0) in the air gap. The magnetic flux density distribution is analyzed based on 3-D simulations and NMR experimental results.