Browsing by Issue Date, starting with "2012-07"
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- A numerical analysis of generalized Boussinesq-type equation using continuos/discontinuous FEMPublication . Lopes, Nuno David; Pereira, P. J. S.; Trabucho, L.An improved class of Boussinesq systems of an arbitrary order using a wave surface elevation and velocity potential formulation is derived. Dissipative effects and wave generation due to a time-dependent varying seabed are included. Thus, high-order source functions are considered. For the reduction of the system order and maintenance of some dispersive characteristics of the higher-order models, an extra O(mu 2n+2) term (n ??? N) is included in the velocity potential expansion. We introduce a nonlocal continuous/discontinuous Galerkin FEM with inner penalty terms to calculate the numerical solutions of the improved fourth-order models. The discretization of the spatial variables is made using continuous P2 Lagrange elements. A predictor-corrector scheme with an initialization given by an explicit RungeKutta method is also used for the time-variable integration. Moreover, a CFL-type condition is deduced for the linear problem with a constant bathymetry. To demonstrate the applicability of the model, we considered several test cases. Improved stability is achieved.
- Anti-Corrosion performance of a new silane coating for corrosion protection of AZ31 Magnesium alloy in Hank’s solutionPublication . Zomorodian, A.; Brusciotti, F.; Fernandes, A.; Carmezim, M. J.; Silva, Maria Teresa Oliveira de Moura e; Fernandes, J. C. S.; Montemor, M. F.Mg alloys can be used as bioresorsable metallic implants. However, the high corrosion rate of magnesium alloys has limited their biomedical applications. Although Mg ions are essential to the human body, an excess may cause undesirable health effects. Therefore, surface treatments are required to enhance the corrosion resistance of magnesium parts, decreasing its rate to biocompatible levels and allowing its safe application as bioresorbable metallic implants. The application of biocompatible silane coatings is envisaged as a suitable strategy for retarding the corrosion process of magnesium alloys. In the current work, a new glycidoxypropyltrimethoxysilane (GPTMS) based coating was tested on AZ31 magnesium substrates subjected to different surface conditioning procedures before coating deposition. The surface conditioning included a short etching with hydrofluoric acid (HF) or a dc polarisation in alkaline electrolyte. The silane coated samples were immersed in Hank's solution and the protective performance of the coating was studied through electrochemical impedance spectroscopy (EIS). The EIS data was treated by new equivalent circuit models and the results revealed that the surface conditioning process plays a key role in the effectiveness of the silane coating. The HF treated samples led to the highest impedance values and delayed the coating degradation, compared to the mechanically polished samples or to those submitted to dc polarisation.
- On the analysis of compensation correctnessPublication . Vaz, Cátia; Ferreira, CarlaOne fundamental idea of service-oriented computing is that applications should be developed by composing already available services. Due to the long running nature of service interactions, a main challenge in service composition is ensuring correctness of transaction recovery. In this paper, we use a process calculus suitable for modelling long running transactions with a recovery mechanism based on compensations. Within this setting, we discuss and formally state correctness criteria for compensable processes compositions, assuming that each process is correct with respect to transaction recovery. Under our theory, we formally interpret self-healing compositions, that can detect and recover from faults, as correct compositions of compensable processes. Moreover, we develop an automated verification approach and we apply it to an illustrative case study.
- O processo de desenvolvimento profissional visto pelos professores mentoresPublication . Roldão, Maria do Céu; Leite, TeresaNeste artigo apresentam-se e discutem-se os resultados da análise de 74 reflexões realizadas pelos mentores relativamente à oficina de formação em que participaram. Os resultados permitem concluir que os professores mentores consideraram que a formação contribuiu para o seu desenvolvimento profissional e, através deles, para o desenvolvimento profissional dos professores em período probatório que supervisionavam. No entanto, os professores mentores referem-se consideravelmente menos ao contributo da formação para o desenvolvimento organizacional das escolas e preveem escassas repercussões a esse nível. Quanto ao processo de formação, consideram-no útil e de qualidade, valorizando essencialmente os documentos trabalhados nas sessões e as estratégias utilizadas. - Abstract In this paper we present and discuss the results of 74 reflections made by mentors regarding the training workshops in which they took part. The results show that teachers mentors consider that the training contributed to their professional development and, through them, to the professional development of teachers who they supervised during the probation period. However teachers mentors refer considerably less to the contribution of training towards the organizational development of schools and foresee little impact at this level. Asfor the training process, they consider it useful and of quality, valuing mainly the documents worked on during sessions and the strategies used. - Resumen En este artículo se presentan los resultados del análisis realizado sobre 74 reflexiones hechas por los mentores sobre el taller de formación en el que participaron. Los resultados concluyen que los profesores mentores consideraron que la formación contribuyó para su desarrollo profesional, y a través de ello, para el desarrollo profesional de los profesores en periodo probatorio que supervisaban. Los profesores mentores se refieren poco a la contribución de la formación para el desarrollo organizacional de las escuelas y consideran que habrá escasa repercusión a ese nivel. En cuanto al proceso de formación, lo consideran útil y de calidad, valorando esencialmente los documentos elaborados en las sesiones y las estrategias utilizadas.
- Physical layer aware network architecture for the future internetPublication . Cardoso, Filipe D.; Correia, Luís M.; Petteri Mannersalo; Frantti, Tapio; Serrador, António; Nunzi, Giorgio; Genay, Naveena; Le Rouzic, EstherIn this article, physical layer awareness in access, core, and metro networks is addressed, and a Physical Layer Aware Network Architecture Framework for the Future Internet is presented and discussed, as proposed within the framework of the European ICT Project 4WARD. Current limitations and shortcomings of the Internet architecture are driving research trends at a global scale toward a novel, secure, and flexible architecture. This Future Internet architecture must allow for the co-existence and cooperation of multiple networks on common platforms, through the virtualization of network resources. Possible solutions embrace a full range of technologies, from fiber backbones to wireless access networks. The virtualization of physical networking resources will enhance the possibility of handling different profiles, while providing the impression of mutual isolation. This abstraction strategy implies the use of well elaborated mechanisms in order to deal with channel impairments and requirements, in both wireless (access) and optical (core) environments.
- Robust design and statistical process control in a collaborative environmentPublication . Navas, Helena V. G.; Requeijo, José; Abreu, AntónioNowadays, enterprises in global markets have to achieve high levels of performance and competitiveness to stay “alive". In order to be competitive enterprises must develop capabilities that will enable them to respond quickly to market needs. According to several authors and as frequently mentioned by reports from practical case studies, one of the most relevant sources of competitive advantage is the involvement of enterprises in collaborative networks. However, in spite of this assumption, it is also frequently mentioned that the lack of operational tools tailored to collaborative networks is not available yet and might be an obstacle for a wider acceptance of this paradigm. In this context, the collaborative networks need new statistical tools, new approaches and concepts of quality improvement. Starting with a brief discussion about the nature and the role of some tools in order to support the development of robust design, this paper introduces some discussion about the application advantages of product design in a collaborative environment as a contribution to a future identification of methodologies, approaches that are suitable for collaborative contexts.
- Determination of airborne nanoparticles from welding operationsPublication . Gomes, João Pereira; Albuquerque, Paula Cristina; Miranda, Rosa M.; Vieira, Maria TeresaThe aim of this study is to assess the levels of airborne ultrafine particles emitted in welding processes (tungsten inert gas [TIG], metal active gas [MAG] of carbon steel, and friction stir welding [FSW] of aluminum) in terms of deposited area in pulmonary alveolar tract using a nanoparticle surface area monitor (NSAM) analyzer. The obtained results showed the dependence of process parameters on emitted ultrafine particles and demonstrated the presence of ultrafine particles compared to background levels. Data indicated that the process that resulted in the lowest levels of alveolar deposited surface area (ADSA) was FSW, followed by TIG and MAG. However, all tested processes resulted in significant concentrations of ultrafine particles being deposited in humans lungs of exposed workers.
- Effects of lower limb strengthening on balance and function in persons who suffered a strokePublication . Fernandes, Beatriz; Batista, Filomena; Evangelista, I.; Ferreira, M. J.; Prates, L.; Sérgio, J. SilveiraIntroduction - Cerebrovascular diseases, and among them, cerebral vascular accidents, are one of the main causes of morbidity and disability at European Union countries. Clinical framework resulting from these diseases include important limitations in functional ability of the these patients Postural control dysfunctions are one of the most common and devastating consequences of a stroke interfering with function and autonomy and affecting different aspects of people’s life and contributing to decrease quality of life. Neurological physiotherapy plays a central role in the recovery of movement and posture, however it is necessary to study the efficacy of techniques that physiotherapists use to treat these problems. Objectives - The aim of this study was to investigate the effects of a physiotherapy intervention program, based on oriented tasks and strengthening of the affected lower limb, on balance and functionality of individuals who have suffered a stroke. In addition our study aimed to investigate the effect of strength training of the affected lower limb on muscle tone.
- Grip strength: are dinamometers equivalent? JAMAR vs E-LinkPublication . Tomás, Maria Teresa; Fernandes, BeatrizLevels of risk for future disability can be assessed with grip strength. This assessment is of fundamental importance for establishing prevention strategies. It also allows verifying relationships with functional capacity of individuals. Most studies on grip strength use the JAMAR Hydraulic dynamometer that provides the value of isometric force obtained during the performance of grip movement and is considered the “gold standard” for measurement of grip strength. However, there are different dynamometers available commercially, such as portable computerized dynamometer E-Link (Biometrics), which provides the value of maximum force (peak force) in addition to other variables as the rate of fatigue for hand strength, among others. Of our knowledge, there are no studies that allow us to accept or not and compare values obtained with both devices and perhaps use them interchangeably. The aim of this study was to evaluate the absolute agreement between the measurements of grip strength (peak force or maximum force in kg) obtained from two different devices (portable dynamometers): a computerized (E-Link, Biometrics) and one hydraulic (JAMAR).
- Processo de internalização das actividades de MPS de via/geotecnia do centro de manutenção de LisboaPublication . Palma, Pedro Serra de Sousa; Cruz, António Artur Sequeira da; Morais, Victor Manuel MendesVerificando-se nos últimos anos um aumento gradual das exigências referentes ao serviço ferroviário, as condições de tráfego das composições têm também aumentado, a fim de preencher os requisitos exigidos. A velocidade, a tonelagem ou a frequência das composições são características que condicionam a periodicidade e o modo como é efectuada a manutenção das infraestruturas ferroviárias. Actualmente, após anos de grande investimento na construção de infraestruturas ferroviárias, novas problemáticas emergem, nomeadamente na gestão e conservação destas mesmas infraestruturas. Como resposta a estas problemáticas, têm sido equacionadas e colocadas em prática diferentes estratégias de manutenção das infraestruturas ferroviárias. É nesta óptica que se insere este trabalho, tentando, de um modo objectivo, comparar modelos alternativos aos que hoje estão implementados. Procurou-se analisar, sempre de um modo crítico, as diversas possibilidades equacionadas de forma a promover a discussão sobre a sustentabilidade do meio de transporte ferroviário.