Browsing by Issue Date, starting with "2010-09"
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- A comunicação ao serviço da 'qualidade' : uma meta-ideiaPublication . Faria, SusanaO reforço e a diversificação do investimento na comunicação por parte das instituições educativas serão discutidos neste artigo como uma das consequências da nova gestão pública. Tendo em vista a ‘qualidade’ e a ‘eficácia’ das suas prestações, as escolas têm procurado tornar-se mais dialogantes, assumindo a aposta na comunicação organizacional como parte integrante de uma estratégia empreendedora, que lhes tem vindo a conferir uma nova identidade colectiva, unificada em torno dos valores neo-liberais. Não obstante, os sistemas de comunicação criados são mais complexos do que se poderia supor. Revelando a influência de pressões híbridas, estes sistemas transformaram-se num contexto mediador da mudança, embutido em novas concepções de escola e nos novos mandatos para a educação (assim legitimados interna e externamente), surgindo, ao mesmo tempo, como o locus de produção de novas identidades. Tal acontece porque a comunicação Parece constituir o ponto de convergência entre as diferentes políticas educativas e as práticas localmente adoptadas na sequência de um processo de interpretação criativa das diferentes pressões. É este o sentido com que afirmamos que a comunicação se constitui numa meta-ideia ao serviço da ‘qualidade’, ainda que, como argumenta Stensaker (2004) esta possa ser perspectivada a partir do ideal burocrático da organização (como sinónimo de eficiência administrativa), do ideal profissional (centrada no processo de ensino-aprendizagem) ou do ideal empreendedor (valorizando a capacidade de resposta às solicitações do mercado). Os dados empíricos que sustentaram o nosso estudo, recolhidos no âmbito de um projecto de doutoramento, resultaram da observação do quotidiano de um agrupamento de escolas do ensino básico e dos testemunhos recolhidos, ao longo de três anos, na respectiva comunidade educativa. Os resultados obtidos apontam para a centralidade dos processos de comunicação na transformação induzida pela nova gestão pública e para o desenvolvimento de uma matriz discursiva bilinguista, que procura harmonizar os imperativos de ‘mercado’ com o discurso pedagógico e com modelos burocrático-profissionais de organização.
- A performance na abordagem RBV: estudo das publicações do JIBSPublication . Reis, Nuno; Ferreira, Manuel Portugal; Santos, João CarvalhoA medição de performance é uma questão que não reúne consenso, apesar de amplamente estudada. Mesmo numa área restrita da investigação em gestão como os negócios internacionais, diversas medidas de performance são utilizadas. Neste artigo, recorremos aos artigos publicados no Journal of International Business Studies no período entre 2000 e 2009 que utilizam a perspectiva RBV. Com base nos artigos identificados, procurámos identificar qual o tipo de medida de performance mais utilizado nos negócios internacionais, sob a perspectiva RBV.
- Singing voice resynthesis using vocal sound librariesPublication . Fonseca, Nuno; Ferreira, AníbalAlthough resynthesis may seem a simple analysis/synthesis process, it is a quite complex task, even more when it comes to recreating a singing voice. This paper presents a system whose goal is to start with an original audio stream of someone singing and recreate the same performance (melody, phonetics, dynam-ics) using an internal vocal sound library (choir or solo voice). By extracting dynamics and pitch information, and looking for phonetic similarities between the original audio frames and the frames of the sound library, a completely new audio stream is created. The obtained audio results, although not perfect (mainly due to the existence of audio artifacts), show that this technologi-cal approach may become an extremely powerful audio tool.
- A comparison of the vibration characteristics of a rotating machine with a linear and a keyed shaftPublication . Oliveira, F.; Pelaez, G.; Donsion, M. P.This paper presents some results of an ongoing work aimed at studying a number of characteristics of rotating machines and how they are influenced by both constructive features and the way they are driven. The following will present the main results obtained when a simple one-stage inertia turbomachine is built with a linear, cylindrical shaft or, instead, with a shaft that has a small slot such as those used in many mechanical couplings. Experimental results will show some significant differences in the behavior of the machine, both in terms of the orbit and in the resonance frequencies, as well as in the phase and amplitude of mechanical vibrations.
- Stereo vision in blind navigation assistancePublication . Fernandes, H.; Costa, P.; Filipe, V.; Hadjileontiadis, L.; Barroso, J.Visual impairment and blindness caused by infectious diseases has been greatly reduced, but increasing numbers of people are at risk of age-related visual impairment. Visual information is the basis for most navigational tasks, so visually impaired individuals are at disadvantage because appropriate information about the surrounding environment is not available. With the recent advances in inclusive technology it is possible to extend the support given to people with visual impairment during their mobility. In this context we propose a system, named SmartVision, whose global objective is to give blind users the ability to move around in unfamiliar environments, whether indoor or outdoor, through a user friendly interface. This paper is focused mainly in the development of the computer vision module of the SmartVision system.
- A Time Domain Channel Estimation Scheme for Equalize-and-Forward Relay-Assisted SystemsPublication . Neves, D.; Ribeiro, C.; Silva, A.; Gameiro, A.In this paper we propose a scheme with a dedicated relay node for an OFDM-based system. We consider an antenna array at the base station and a single antenna at both the user terminal and the relay node. The relay-assisted protocol considered is equalize-and-forward. The proposed scheme requires the computation of parameters which depend on unknown variables at the destination and we show that under some assumptions the scheme is suitable to provide all those requirements. Also, we show that since the pilots at the relay node are properly designed the TD-MMSE estimator can still provide the required channel estimate. The system performance is evaluated by considering a typical pedestrian scenario based on WiMAX specification. The results show that the degradation in the estimator performance is negligible.
- Intra-prediction for color image coding using YUV correlationPublication . Lucas, Luís F.R.; Rodrigues, Nuno M. M.; Faria, Sérgio M. M. de; Silva, Eduardo A. B. da; Carvalho, Murilo B. de; Silva, Vitor M. M. daIn this paper we present a new algorithm for chroma prediction in YUV images, based on inter component correlation. Despite the YUV color space transformation for inter component decorrelation, some dependency still exists between the Y, U and V chroma components. This dependency has been previously used to predict the chrominance data from the reconstructed luminance. In this paper we show that a chrominance component can be more efficiently predicted by using the reconstructed data from both the luminance and the remaining chrominance signal. The proposed chroma prediction is implemented and tested using the Multidimensional Multiscale Parser (MMP) image encoding algorithm. It is shown that the new color prediction mode outperforms the originally proposed prediction methods. Furthermore, by using the new color prediction scheme, MMP is consistently better than the state-of-the-art H.264/AVC for coding both for the luminance and the chrominance image components.
- Comparison of Methods for Texture Assessment of Concrete SurfacesPublication . Santos, Pedro Miguel Duarte; Júlio, Eduardo Nuno Brito SantosThe bond strength of the interface between concrete layers cast at different times is important to ensure the monolithic behavior of reinforced concrete (RC) composite members. The roughness of the substrate surface has a significant influence in this scope. Current design codes use a qualitative approach based on visual inspection to assess roughness. This procedure is highly dependent on the designer and, therefore, can lead to inaccurate results. Previous studies conducted by the authors proved that it is possible to use a quantitative criterion to classify roughness. This paper describes an experimental study conducted to compare four roughness quantification methods: the processing of the digital image (PDI) and the two-dimensional (2D) laser roughness analyzer (2D-LRA) methods, both developed by the authors; an upgrade of these, using a three-dimensional (3D) laser scanner; and the sand patch test (SPT), a simple and widespread method. The 2D-LRA proved to be the best from the four methods considered because it gives a quantitative assessment of the roughness with adequate accuracy, is nondestructive, easy and fast to use, and is cost effective.
- A multi-objective genetic algorithm applied to autonomous underwater vehicles for sewage outfall plume dispersion observationsPublication . Moura, Ana; Rijo, Rui; Silva, Pedro; Crespo, SidónioThis work presents a multi-objective genetic algorithm to solve route planning problem for multiple autonomous underwater vehicles (AUVs) for interdisciplinary coastal research. AUVs are mobile unmanned platforms that carry their own energy and are able to move themselves in the water without intervention from an external operator. Using AUVs one can provide high-quality measurements of physical properties of effluent plumes in a very effective manner under real oceanic conditions. The AUV's route planning problem is a combinatorial optimization problem, where the vehicles must travel through a three-dimensional irregular space with all dimensions known. Therefore, minimization of the total travel distance while considering the maximum number of water samples is the main objective. Besides the AUV kinematics restrictions other considerations must be taken into account to the problem, like the ocean currents. The practical applications of this approach are the environmental monitoring missions which typically require the sampling of a volume of water with non-trivial geometry for which parallel line sweeping might be a costly solution. Some real-life test problems and related solutions are presented.
- Power converter fault diagnosis in SRM drives based on the DC Bus current analysisPublication . Gameiro, Natália S.; Cardoso, A. J. MarquesThis paper presents a new fault diagnostic technique applied to switched reluctance motor (SRM) drives. A fault is detected when the measured amplitude of the DC bus current differs from its expected amplitude, assuming normal operating conditions. The information about phase currents amplitudes and the control states of all power switches permit to easily estimate the amplitude of the power converter supply current, since an asymmetric bridge converter is used. Open-and short-circuit fault occurrences in the converter power switches are presented. The proposed technique can early detect these fault occurrences and can also, in almost situations, identify not only the affected motor phase but also the faulty element. A short-circuit fault in a converter power switch of a SRM drive does not necessarily causes a short-circuit in the DC bus, unlike to what happens in many other converter-fed electrical machine drives. On the other hand, although a converter power switch open-circuit fault can be easily detected by the observation of the phase currents, the identification of the faulty element becomes impossible to achieve, if only phase currents are measured. This information is of paramount importance in the development of fault tolerant power converters.