Browsing by Issue Date, starting with "2011-11"
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- Os guias da montanha e sua contribuição para a sustentabilidade do territórioPublication . Carvalho, Mário João Paulo de Jesus; Ezequiel, GraçaA actividade turística é não só uma estratégia que contraria a rotina como também se assume como fonte de energia para situações de desgaste físico e mental do quotidiano. As viagens turísticas não só respondem às expectativas dos turistas que procuram lugares e experiências como contribuem para o desenvolvimento endógeno e competitivo dos destinos. A sustentabilidade desses espaços torna-se, pois, dependente de acções equilibradas, protagonizadas pelos diferentes agentes do fenómeno turístico. A redescoberta das potencialidades lúdicas e desportivas associadas à montanha impulsionam significativamente a atractividade turística daqueles espaços o que por outro lado significa a necessidade de se criar um modelo de desenvolvimento equilibrado e sustentado. Sem estratégias de auto-regulação e manutenção do equilíbrio ecológico os ambientes de montanha degradar-se-ão perdendo os valores diferenciadores que, em primeiro lugar, atraíram para aí o turismo. Por outro lado o aumento do número de clientes, mais exigentes, legitima a apropriação de novos lugares e a oferta de profissionais qualificados. Por acção dos guias de turismo, os visitantes podem assim desfrutar dos destinos numa perspectiva cultural, ambiental e social. A montanha do Pico, ponto mais alto de Portugal localizado na ilha do Pico - Açores, é um destino de montanha cuja forma dominante de visitação - ascensão ao Pico Pequeno - implica o acompanhamento de um Guia de Montanha. Os Guias de Montanha, responsáveis pela segurança dos visitantes na visita à montanha, têm que estar devidamente credenciados pelo Secretaria do Ambiente. A vulnerabilidade da Montanha do Pico acrescida da pressão exercida pelos visitantes faz do trabalho dos Guias de Montanha do Pico uma variável de excepcional importância para a sustentabilidade do território. Torna-se assim crucial conhecer a importância dos Guias de Montanha enquanto elementos interventivos no modelo onde a satisfação dos visitantes e o reforço da imagem do destino são prioridades. Nesse sentido levou-se a efeito um estudo relativamente à importância dos Guias de Montanha face à sustentabilidade do território. Para tal procedeu-se a uma revisão de literatura sobre o turismo de montanha, sustentabilidade dos territórios e turismo natureza. Com a aplicação das entrevistas semi-estruturadas aos Guias de Montanha do Pico processou-se uma análise qualitativa da oferta dos serviços prestados pelos Guias. Da aplicação das entrevistas concluiu-se que a actividade dos Guias de Montanha assume importante papel para a aquisição de competitividade e sustentabilidade dos territórios na Montanha do Pico - Açores.
- Inversion of the noisy Radon transform on SO(3) by Gabor frames and sparse recovery principlesPublication . Cerejeiras, Paula; Ferreira, Milton; Kaehler, Uwe; Teschke, GerdThe inversion of the one-dimensional Radon transform on the rotation group SO(3) is an ill-posed inverse problem that can be applied to X-ray tomography with polycrystalline materials. This paper is concerned with the development of a method to stably approximate the inverse of the noisy Radon transform on SO(3). The proposed approach is composed by basic building blocks of the coorbit theory on homogeneous spaces, Gabor frame constructions and variational principles for sparse recovery. The performance of the finally obtained iterative approximation is studied through several experiments.
- Comparative structural response of two steel bridges constructed 100 years apartPublication . Varum, Humberto; Sousa, Romain; Delgado, Walter; Fernandes, Catarina; Costa, Aníbal; Jara, José; Jara, Manuel; Álvarez, JesúsThis paper presents a comparative numerical analysis of the structural behaviour and seismic performance of two existing steel bridges, the Infiernillo II Bridge and the Pinhão Bridge, one located in Mexico and the other located in Portugal. The two bridges have similar general geometrical characteristics, but their construction is separated by one hundred years. 3D structural models of both bridges were developed and analyzed for various load cases and several seismic conditions. The results of the comparative analysis between the two bridges are presented in terms of natural frequencies and corresponding vibration modes, maximum stresses in the structural elements and maximum displacements. The study aimed at determining the influence of one century period in material properties, transverse sections and expected behaviour of two quite similar bridges. In addition, the influence of the bearing conditions in the global response of the Pinhão Bridge was evaluated.
- Endoscopy - Brief historical survey, developments and therapeuticsPublication . Libório, Ana; Couto, Sylvie; Cunha, António; Coelho, PauloRapid increase of elder population and the appearance of more diseases needs the creation of new medical devices, as minimal invasive as possible. Nowadays, the endoscopic capsule allows good image and much less stress and pain to the patient than traditional endoscopic catheters. The endoscopy to become as developed as today had many improvements. We present on this paper a brief survey of the historical background of equipment developments, some of the most commonly used endoscopic procedures, their drawbacks and virtues.
- On using crowdsourcing and active learning to improve classification performancePublication . Costa, Joana; Silva, Catarina; Antunes, Mário; Ribeiro, BernardeteCrowdsourcing is an emergent trend for general-purpose classification problem solving. Over the past decade, this notion has been embodied by enlisting a crowd of humans to help solve problems. There are a growing number of real-world problems that take advantage of this technique, such as Wikipedia, Linux or Amazon Mechanical Turk. In this paper, we evaluate its suitability for classification, namely if it can outperform state-of-the-art models by combining it with active learning techniques. We propose two approaches based on crowdsourcing and active learning and empirically evaluate the performance of a baseline Support Vector Machine when active learning examples are chosen and made available for classification to a crowd in a web-based scenario. The proposed crowdsourcing active learning approach was tested with Jester data set, a text humour classification benchmark, resulting in promising improvements over baseline results.
- Estimation of dielectric concrete properties from power measurements at 18.7 and 60 GHzPublication . Feitor, Bruno; Caldeirinha, Rafael; Fernandes, Telmo, Telmo Rui Carvalhinho Cunha, Telmo R.; Ferreira, David; Leonor, NunoIn this paper, microwave and millimetre wave reflection coefficient measurements at 18.7 and 60 GHz are presented for a group of concrete slabs, in which only the thickness of the gravel present inside is varied. An empirical reflection coefficient value is determined using both reflected and LOS power measurements. A concrete slab with no gravel is used as a reference. The measurement results show the dependence of the reflection coefficient with the thickness of the gravel inside the slab. The measurement results allow for the appropriate extraction of dielectric properties of the materials under study.
- A finite element analysis of the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in tDCSPublication . Pascoal-Faria, Paula; Hallett, Mark; Miranda, Pedro CavaleiroWe investigated the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in transcranial direct current stimulation (tDCS). For this purpose, we used the finite element method to compute the distribution of the current density in a four-layered spherical head model using various electrode montages, corresponding to a range of electrode sizes and inter-electrode distances. We found that smaller electrodes required slightly less current to achieve a constant value of the current density at a reference point on the brain surface located directly under the electrode center. Under these conditions, smaller electrodes also produced a more focal current density distribution in the brain, i.e. the magnitude of the current density fell more rapidly with distance from the reference point. The combination of two electrodes with different areas produced an asymmetric current distribution that could lead to more effective and localized neural modulation under the smaller electrode than under the larger one. Focality improved rapidly with decreasing electrode size when the larger electrode sizes were considered but the improvement was less marked for the smaller electrode sizes. Also, focality was not affected significantly by inter-electrode distance unless two large electrodes were placed close together. Increasing the inter-electrode distance resulted in decreased shunting of the current through the scalp and the cerebrospinal fluid, and decreasing electrode area resulted in increased current density on the scalp under the edges of the electrode. Our calculations suggest that when working with conventional electrodes (25–35 cm2), one of the electrodes should be placed just ‘behind’ the target relative to the other electrode, for maximum current density on the target. Also electrodes with areas in the range 3.5–12 cm2 may provide a better compromise between focality and current density in the scalp than the traditional electrodes. Finally, the use of multiple small return electrodes may be more efficient than the use of a single large return electrode.