Browsing by Issue Date, starting with "2005"
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- Penha: Retrospectiva Iconográfica da Sacralização da MontanhaPublication . Barroso, Paulo M.Com o presente texto pretende-se caracterizar a sacralização do espaço montanhoso como processo ao qual corresponde uma tipologia em que predominam dois factores, um físico e outro psicológico: o primeiro é designado "factor geográfico", porque acentua a heterogeneidade do espaço, diferenciado-o entre "sagrado" e "profano"; o segundo, "factor mitológico", porque forma e conserva a matriz espiritual. Atendemos ao caso da Montanha da Penha, no concelho de Guimarães, como forma típica de ocupação religiosa do espaço.
- Manipulação de efluentes de bovinicultura: Pré-tratamento e aplicação ao soloPublication . Pereira, J.As crescentes preocupações ambientais para a redução das perdas de azoto em explorações de bovinicultura leiteira impõem o desenvolvimento de métodos de manipulação dos efluentes produzidos. Nesta Dissertação apresenta-se uma revisão bibliográfica sobre os principais processos de tratamento e valorização de efluentes de bovinicultura e um trabalho experimental que teve como objectivos avaliar a utilização dos floculantes PAM e bentonite na remoção de sólidos e nutrientes da fracção líquida do chorume, comparar as emissões de N2O e degradação do N orgânico a partir de chorumes com e sem pré-tratamento após incorporação em solos agrícolas. Após separação mecânica do chorume, foram adicionados à fracção líquida obtida os floculantes PAM e bentonite. A PAM apresentou maior capacidade de remoção de azoto, fósforo e matéria seca na fracção sobrenadante obtida. Também se realizou um ensaio de incubação durante 94 dias, no qual foram medidas as emissões de N2O e o teor de N mineral. Os tratamentos incorporados a solos foram: chorume bruto, fracções sólida e líquida, fracções sedimentada e sobrenadante com PAM. Os processos de pré-tratamento que conduziram à redução das emissões gasosas, relativamente ao chorume bruto, foram: fracção sólida (-25,6%), fracção líquida (-5,1%) e fracção sobrenadante com PAM (-10,3%).
- Stress analysis of lap joints involving natural fibre reinforced interface layersPublication . Ferreira, J.A.M.; Silva, H.; Costa, J.D.M.; Richardson, M. O. WThis paper is concerned with a fatigue study of composite adhesive lap joints. The tests were carried out on specimen joints manufactured using different stacking sequences: solely bi-directional woven E-glass fibres and polypropylene composites; and hybrid stacked composites. The main objective of the work was to improve the fatigue strength using hybrid fibre composites with a polypropylene/hemp natural fibre layer adjacent to the bond interface which was expected to produce more uniform stresses in transient regions. The adhesive used was a Bostik 7452 (Rubber and Plastics Grade) ethyl cyanoacrylate type. The results are presented in the form of curves of stress amplitude versus number of cycles to failure. The failure mechanisms (together with peak stresses in the regions adjacent to the bond obtained by finite elements analysis and experimental values of interlaminar toughness) are discussed in order to explain the lower fatigue strength in hybrid stacked joints than in the original thermoplastic composite joints (contrary what was expected) and the decrease with the natural fibre content. q 2004 Elsevier Ltd. All rights reserved.
- Technological improvement of Portuguese eucalypt and pine woods by heat treatmentPublication . Esteves, BrunoHeat treatments for technological improvement of wood were made in the presence of air using Eucalyptus globulus. The heat treatment was made using an oven during 2 to 24 h and temperatures of 170 ºC, to 200 ºC. Mass losses increased with treatment time and temperature. Anti Shrinking Efficiency (ASE) between treated and untreated samples was calculated at 35%, 65% and 85% relative humidity for radial and tangential directions. Bending strength and MOE were also determined. Equilibrium moisture content of heat-treated wood decreased by 67%. 87%Radial ASE35% for Tangential ASE35% was usually higher than radial. ASE65% and ASE85% showed behaviour similar to ASE35% but smaller. All ASE values increased with temperature and treatment time. Bending strength and MOE decreased with mass loss.
- Modelos Preditivos para Ventilação NaturalPublication . Pinto, Manuel; Silva, Fernando; Freitas, VascoA noção de desenvolvimento implica necessariamente a melhoria das condições de vida das populações, ou seja, conforto entendido em sentido lato incluindo, por exemplo, a Qualidade do Ar Interior. O recurso a sistemas AVAC para garantir as condições de conforto tem algumas desvantagens, nomeadamente o recurso a energias primárias finitas. Está hoje generalizada a ideia de que a Energia e o Ambiente são bens que têm de ser geridos e utilizados com os cuidados devidos ao que é finito. No sentido de incrementar o recurso a energias renováveis, infinitas por definição e não poluentes, apresentam-se no presente artigo modelos preditivos para ventilação natural que recorrem a duas fontes: as diferenças de temperatura exterior-interior e o vento. Estes modelos podem ser usados na fase de concepção arquitectónica para prever as renovações horárias devido à existência de aberturas na envolvente de edifícios, por exemplo em edifícios de serviços ou comerciais.
- O Risco de Incêndio no Distrito de Viseu. Uma visão integrada das estruturas existentesPublication . Viana, Helder; Amaral, Nuno; Ladeira, Rui
- Evaluation of isoprene degradation in the detailed tropospheric chemical mechanism, MCM v3, using environmental chamber dataPublication . Pinho, P.G.; Pio, C.A.; Jenkin, M.E.The isoprene degradation mechanism included in version 3 of the Master Chemical Mechanism (MCM v3) has been evaluated and refined, using the Statewide Air Pollution Research Center (SAPRC) environmental chamber datasets on the photo-oxidation of isoprene and its degradation products, methacrolein (MACR) and methylvinyl ketone (MVK). Prior to this, the MCM v3 butane degradation chemistry was also evaluated using chamber data on the photo-oxidation of butane, and its degradation products, methylethyl ketone (MEK), acetaldehyde (CH3CHO) and formaldehyde (HCHO), in conjunction with an initial evaluation of the chamber-dependent auxiliary mechanisms for the series of relevant chambers. The MCM v3 mechanisms for both isoprene and butane generally performed well and were found to provide an acceptable reaction framework for describing the NOx-photo-oxidation experiments on the above systems, although a number of parameter modifications and refinements were identified which resulted in an improved performance. All these relate to the magnitude of sources of free radicals from organic chemical process, such as carbonyl photolysis rates and the yields of radicals from the reactions of O3 with unsaturated oxygenates, and specific recommendations are made for refinements. In addition to this, it was necessary to include a representation of the reactions of O(3P) with isoprene, MACR and MVK (which were not previously treated in MCM v3), and conclusions are drawn concerning the required extent of free radical formation from these reactions. Throughout the study, the performance of MCM v3 was also compared with that of the SAPRC-99 mechanism, which was developed and optimized in conjunction with the chamber datasets.
- Drying kinetics of some varieties of pears produced in Portugal.Publication . Guiné, RaquelIn this study, the solar drying behaviour of two varieties of pears produced in Portugal was investigated. To accomplish this, pears of the varieties Rocha and Rosa were dried whole, after peeling, by direct sun exposure, and measurements of their moisture content were conducted along the process. The experimental data was later used to test different empirical kinetic models, namely a cubic and an exponential decay function to fit the batch drying data and a first order kinetics and the Page equation to fit the drying rate data. From the present work was possible to conclude that the two varieties of pears studied show a similar drying behaviour and that the drying curves are better described by the exponential rather than the cubic function. As to the drying rate curves, the fits obtained with the Page equation are the ones which better represent the process over the entire time range.
- A Utilização de Calculadoras Financeiras no Ensino do Cálculo Financeiro. Uma Aplicação Prática, o "Leasing"Publication . Matias, Rogério; Silva, IlídioA resolução de problemas de Cálculo Financeiro envolve, por vezes, cálculos matemáticos demorados e trabalhosos. A utilização de calculadoras financeiras pode, assim, desempenhar um importante papel neste contexto, na medida em que permite poupar tempo e trabalho na resolução de tais problemas. Sabe-se que muitos docentes não são favoráveis à utilização de calculadoras financeiras no ensino desta disciplina. Pela nossa parte, assumimos uma posição contrária, entendendo que, mais do que simplesmente autorizar o seu uso, devemos incentivá-lo. Neste artigo expomos a nossa posição sobre este assunto, referimos sucintamente os princípios básicos de funcionamento das calculadoras financeiras e recorremos a um exemplo concreto (operação de “leasing”) que julgamos interessante, porque ilustra não só a rapidez e a comodidade de cálculo conseguidas, mas também a necessidade de dominar solidamente os conceitos teóricos por forma a tirar partido das capacidades específicas das calculadoras financeiras.
- Improvements on the traditional method used to produce dried pears in portugal.Publication . Guiné, Raquel; Barroca, Maria João; Pinto, António; Gonçalves, Fernando; Salomé, Cristina; Monteiro, Vera; Ferreira, DulcineiaIn Portugal dried pears are produced from pears of the variety identified as S. Bartolomeu by a traditional open-air solar drying process, that includes the following steps: 1 – skin removing; 2 – a first drying stage in which the pears are exposed to the sun for 5 to 8 days; 3 – a barrelling process in which the pears are covered and left at shadow to increase elasticity; 4 – a pressing operation where the pears change their characteristics from round shape to a flattened one; 5 – a second drying stage, also at the sun, but for only 2 to 3 more days. Although it is a much appreciated food product its production is very small due to the complexity and slowness of the processing method, to the intensive handwork and space requirements and to the shortcomings associated to the natural open-air sun drying. In fact, this process greatly depends on atmospheric conditions, with the variations in temperature influencing quite significantly the drying rates and the rain or night moist delaying or stopping the process, or even rotten the fruits. Moreover, the process is not very hygienic, and during the drying the pears are exposed to dust and can be attacked by ants, rats, bacteria and fungi, and therefore reliable quality standards are difficult to meet. It is important to adapt the traditional drying process, making it a profitable and competitive production method, offering the consumer products of unquestionable quality. To achieve these goals a solar stove was used for the drying, and 4 varieties of pears were tested in order to find alternatives to the traditional variety. The pears of the varieties Amêndoa, Amorim, Carapinheira Branca and S. Bartolomeu (this one is the traditional) were peeled and dried in a solar stove, following the steps of the traditional method, and their water content was evaluated throughout the drying process. The temperature and relative humidity inside the stove were measured hourly. The nutritional value of the pears was evaluated before and after drying for the 4 varieties, as well as their microbial charge. It was possible to conclude from the present work that the use of the solar stove allowed the obtaining of conditions very favourable to drying, with periods of very high temperatures and very low relative humidities, and also enabling to proceed with drying even when the outside conditions would not allow it. It was also concluded that the four varieties have a very similar kinetic behaviour and that the use of the stove did not influence the nutritional value of the pears.