24 resultados para mechanical contact


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3rd Historic Mortars Conference, 11-14 September 2013, Glasgow, Scotland

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In the context of this dissertation several studies were developed resulting in submission and publication “Evaluation of mechanical soft-abrasive blasting and chemical cleaning methods on alkyd-paint graffiti made on calcareous stones” to Journal of Cultural Heritage. (http://dx.doi.org/10.101 /j.culher.2014.10.004)

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Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Mestrado Integrado em Engenharia Química e Bioquímica

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The industrialization of traditional processes relies on the scientific ability to understand the empirical evidence associated with traditional knowledge. Cork manufacturing includes one operation known as stabilization, where humid cork slabs are extensively colonized by fungi. The implications of fungal growth on the chemical quality of cork through the analysis of putative fungal metabolites have already been investigated. However, the effect of fungal growth on the mechanical properties of cork remains unexplored. This study investigated the effect of cork colonization on the integrity of the cork cell walls and their mechanical performance. Fungal colonization of cork by Chrysonilia sitophila, Mucor plumbeus Penicillium glabrum, P. olsonii, and Trichoderma longibrachiatum was investigated by microscopy. Growth occurred primarily on the surface of the cork pieces, but mycelium extended deeper into the cork layers, mostly via lenticular channels and by hyphal penetration of the cork cell wall. In this first report on cork decay in which specific correlation between fungal colonization and mechanical proprieties of the cork has been investigated, all colonizing fungi except C. sitophila, reduced cork strength, markedly altering its viscoelastic behaviour and reducing its Young’s modulus.

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Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do Grau de Mestre em Engenharia Biomédica

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Mestrado integrado em Engenharia Química e Bioquímica

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A thesis submitted in fulfilment of the requirements for the Degree of Doctor of Philosophy in Sanitary Engineering in the Faculty of Sciences and Technology of the New University of Lisbon

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This study focus on the probabilistic modelling of mechanical properties of prestressing strands based on data collected from tensile tests carried out in Laboratório Nacional de Engenharia Civil (LNEC), Portugal, for certification purposes, and covers a period of about 9 years of production. The strands studied were produced by six manufacturers from four countries, namely Portugal, Spain, Italy and Thailand. Variability of the most important mechanicalproperties is examined and the results are compared with the recommendations of the ProbabilisticModel Code, as well as the Eurocodes and earlier studies. The obtained results show a very low variability which, of course, benefits structural safety. Based on those results, probabilistic modelsfor the most important mechanical properties of prestressing strands are proposed.

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Dissertação para obtenção do Grau de Mestre em Engenharia de Materiais

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Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

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Intern.Conference AZULEJAR, Univ. Aveiro, 10-12 October 2012

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Construction and Building Materials 51 (2014) 287–294

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A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

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Considering the fundamental importance of preserving the built heritage and of ensuring the good performance achieved by incorporating ceramic particles in lime mortars in ancient times, it is important to study solutions that use materials the available today, in order to produce mortars intended to repair and replace the old ones. Solutions incorporating industrial ceramic waste might be profitable for several reasons, namely for economic, environmental and technical aspects. In this paper, seven ceramic waste products collected from ceramics factories are characterized. Their mineralogy, dimensional features and pozzolanicity were determined. Three of these products, with different particle size fractions (obtained directly from milling, dust only and fragment fractions only), were selected, incorporated into air lime mortars, and their mechanical strength was determined. In the present work, evidence of mechanical efficiency, when common sand or air lime were partially replaced by ceramic wastes, was made clear, drawing attention to the sustainability of this type of mortars, hence, encouraging further research.

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Cryogen-free superconducting magnet systems have become popular during the last two decades for the simple reason that with the use of liquid helium is rather cumbersome and is a scarce resource. Some available CFMS uses a mechanical cryocooler as cold source of the superconductor magnet. However, the cooling of the sample holder is still made through an open circuit of helium. A thermal management of a completely cryogen-free system is possible to be implemented by using a controlled gas gap heat switch (GGHS) between the cryocooler and the variable temperature insert (VTI). This way it would eliminate the helium open circuit. Heat switches are devices that allow to toggle between two distinct thermal states (ON and OFF state). Several cryogenic applications need good thermal contact and a good thermal insulation at different stages of operation. A versatile GGHS was designed and built with a 100 mm gap and tested with helium as exchange gas. An analytic thermal model was developed and a good agreement with the experimental data was obtained. The device was tested on a crycooler at 4 to 80 K ranges. A 285 mW/K thermal conductance was measured at ON state and 0.09 mW/K at OFF. 3000 ON/OFF thermal conductance ratio was obtained at 4 K with helium.