Papers

De acordo com o Decreto-Lei nº 93/90 relativamente à delimitação da Reserva Ecológica Nacional (REN), onde se incluem as áreas de infiltração máxima, estas são definidas como "áreas em que, devido à natureza do solo e do substrato geológico e ainda às condições de morfologia do terreno, a infiltração das águas apresenta condições favoráveis, contribuindo assim para a alimentação de lençóis freáticos". A partir deste conceito procurou-se desenvolver uma metodologia que permitisse a definição destas zonas. A metodologia proposta baseia-se na informação cartográfica existente sobre solos, uso do solo, topografia e geologia/hidrogeologia. Esta informação cartográfica permite derivar valores de parâmetros que condicionam o processo de infiltração: o tipo de solo, a quantidade máxima de água utilizável para a evapotranspiração e o declive da superfície topográfica. Considera-se ainda um factor geológico, relacionado com a fracturação ou a carsificação. Definem-se as áreas de infiltração máxima escolhendo os locais onde os parâmetros assumem determinados valores. Para permitir uma mais fácil verificação das áreas mais e menos favoráveis à infiltração, desenvolveu-se o índice de facilidade de infiltração (IFI) que se baseia no somatório dos valores assumidos por cada um dos parâmetros. Os dois procedimentos foram aplicados para definir as áreas de infiltração máxima em dois casos de estudo: o sistema aquífero da Mexilhoeira Grande (Algarve) e a área do concelho de Montemor-o-Novo incluída na carta nº 446 à escala 1:25 000.

LE PONT DU 25 AVRIL A LISBONNE A ETE MODIFIE RECEMMENT POUR POUVOIR ACCUEILLIR UNE CIRCULATION FERROVIAIRE A L’INTERIEUR DE SON CAISSON EN TREILLIS AINSI QU’UNE EXTENSION DU NOMBRE DE VOIES DE CIRCULATION AU NIVEAU DE LA PARTIE SUPERIEURE. SI LE PROJET INITIAL AVAIT DEJA TENU COMPTE DE CETTE EVOLUTION POTENTIELLE, IL A FALLU RENFORCER L’OUVRAGE POUR L’ADAPTER AUX NOUVELLES ACTIONS QU’IL DOIT MAINTENANT SUPPORTER.

A high-resolution finite element model of barotropic tides in the Iberian Atlantic shelf is presented. The model accurately reproduces available tidal data, with average amplitude discrepancies at twelve Atlantic stations below 3% and 15% for semi-diurnal and diurnal tides, respectively. The accuracy of the model simulations is also supported by a qualitative comparison with velocity data. Model results are then used to examine the generation of shelf waves by diurnal tides off the western Portuguese coast. Shelf waves in this area are responsible for large diurnal currents, which can exceed semi-diurnal currents by an order of magnitude. Numerical experiments show that these shelf waves can be generated by obstacles perpendicular to the coastline, and are enhanced in the presence of wide and shallow shelves and steep continental slopes. In the Portuguese coast, the Tagus plateau is responsible for most of the shelf wave generation.

Ten numerical schemes to reduce spurious oscillations in transport simulations were implemented and tested in an Eulerian-Lagrangian control volume finite element model. The schemes included both new and existing Flux Corrected Transport (FCT) algorithms and non-linear filters. The ability of the methods to eliminate numerical oscillations while preserving mass and minimizing the introduction of numerical diffusion was compared in 2D tests of varying complexity. The application of local mass correction algorithms was shown to be vital to avoid the introduction of mass errors by FCT. While none of the methods emerged as optimal for all cases, a new FCT method with a local mass correction scheme and a non-linear filter can be recommended as the best approaches in general. The method of choice depends on the problem being solved, in particular on the concentration gradients and on the grid resolution.

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This set of articles describes the behaviour of formulated polyvinylchorides in various conditions of photoageing, including exposition in artificial and in natural conditions. In this article, the modification of the infrared and UVvisible spectra of PVC films irradiated with a xenon light are reported

One major problem encountered with polymeric materials is their sensitivity to outdoors weathering. Exposure to outdoors conditions leads to a degradation of the use properties of the material. This set of articles describes a comparison of the behavior of several stabilised polyvinylchlorides exposed to various conditions of ageing including light and temperature. The first article focusses on the effect of thermal ageing on the infrared and UV-visible characteristics of the selected samples.