Browsing by Issue Date, starting with "2018-05"
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- Evaluation of Focus Metrics in Extended Depth-of-field ReconstructionPublication . Filipe, Jose N.; Távora, Luis M.N.; Assunção, Pedro A. A.; Fonseca-Pinto, Rui; Faria, Sérgio M. M. deThe performance of focus metrics in the evaluation of refocused images from light fields is investigated in this paper. To this aim, the paper presents a comprehensive study on the performance of a large set of different focus metrics (34 in total) in the evaluation of patch-based extended depth-of-field reconstructed images (e.g., all-in-focus). The new findings of this work demonstrate that optimal reconstruction of extended depth-of-field images, from light fields captured with focused plenoptic cameras, is not consistent with the focus level figures computed by available focus metrics. The results show that a higher focus level, as given by such computational methods, does not actually correspond to better all-in-focus images, thus indicating that currently available focus metrics are not suitable for evaluating the quality of extended depth-of-field reconstruction. The results obtained through subjective evaluation confirm that objective focus metrics fail to indicate the best focused images. Finally, the paper presents recommendations to adapt existing metrics to extended depth-of-field reconstruction in plenoptic imaging.
- Large scale additive manufacturing of eco-compositesPublication . Horta, João; Simões, Fábio; Mateus, ArturThe evolution of additive manufacturing processes is enabling the production of parts with improved dimensional accuracy, mechanical, physical and chemical properties [1]. New materials also contribute to this trend, and in this scope, eco-composites, materials with environmental and ecological advantages, which include natural polymers, have been acquiring increased relevance [2]. The purpose of this study is to develop composite material parts manufactured from recycled thermoplastics and natural fibres, in this case, wood residues. Additive manufacturing (fused deposition modelling) will be accomplished using a robot combined with extrusion unit. The objective is to access the influence of the main manufacturing parameters, such as temperature, distance between layers or deposition speed, on the final part characteristics, especially dimensional accuracy. Reverse engineering and several material analysis techniques will be employed to achieve this goal.
- O conhecimento matemático de futuros professores no início da sua formação: o caso da organização e tratamento de dadosPublication . Tavares, Dina; Pinto, Hélia Gonçalves; Menino, Hugo Lopes; Rodrigues, Marina; Rainho, NunoNeste artigo apresentamos parte dos resultados de um estudo que procura compreender o conhecimento matemático dos estudantes da Licenciatura em Educação Básica da Escola Superior de Educação e Ciências Sociais (ESECS) do Instituto Politécnico de Leiria (IPL), no que respeita aos 4 grandes temas matemáticos, nomeadamente números e operações, geometria e medida, organização e tratamento de dados e álgebra. Em particular, apresentamos os resultados relativos à caraterização do conhecimento acerca do tema organização e tratamento de dados dos estudantes, no momento do seu ingresso na licenciatura. Os resultados encontrados nesta fase inicial da investigação apesar de evidenciarem alguma facilidade dos estudantes no uso e interpretação de algumas representações como o gráfico de barras e o gráfico circular, mostram maiores dificuldades ao nível de outras representações como o diagrama de Carrol ou a tabela de frequências. Ao nível das medidas de localização os estudantes evidenciam maiores dificuldades no cálculo e interpretação da mediana. Adicionalmente, as maiores lacunas surgem ao nível do sentido crítico relativamente à informação, às representações e às medidas. São ainda visíveis alguns conhecimentos elementares da noção clássica de probabilidade.
- First and second fundamental solutions of the time-fractional telegraph equation with Laplace or Dirac operatorsPublication . Ferreira, Milton; Rodrigues, Manuela M.; Vieira, NelsonIn this work we obtain the first and second fundamental solutions (FS) of the multidimensional time-fractional equation with Laplace or Dirac operators, where the two time-fractional derivatives of orders α ∈]0, 1] and β ∈]1, 2] are in the Caputo sense. We obtain representations of the FS in terms of Hankel transform, double Mellin- Barnes integrals, and H-functions of two variables. As an application, the FS are used to solve Cauchy problems of Laplace and Dirac type.
- The influence of corporate social responsibility associations on consumers’ perceptions towards global brandsPublication . Crespo, Cátia Fernandes; Inacio, NicoleThe key research question in this study concerns the effect of global brands corporate social responsibility (CSR) associations on corporate ability (CA) associations and consumer-company identification and their ultimate impact on brand loyalty. The study tests the hypotheses using Structural Equation Modelling (SEM) in the software PLS (Partial Least Squares) with a data-set composed of survey data from 344 consumers. One important finding is the empirical validation of the relationship between two important types of corporate associations (CSR and CA). CSR associations are a relevant precursor of CA associations and consumer-company identification, demonstrating that consumers’ perceptions regarding CSR can influence both the formation of other corporate associations and the construction of an emotional link and sense of attachment established with the brand. The findings also evidence that CSR associations lead to consumers’ brand loyalty mediated by CA associations and consumer-company identification. This research contributes to social identity theory by demonstrating that CSR is a mechanism that deepens the consumers’ strength of identification with the organization reinforcing brand loyalty through both CA associations and consumer-company identification. Another important finding of this research is the empirical validation of the impact of consumer psychological features on the construction of CA associations as result of CSR associations. Customers highly supportive of CSR are more prone to build favorable CA associations. The study finds evidence that CSR associations are essential for managing and for the differentiation of global brands.
- Policy recommendations for improving academic achievement among IPLeiria student-workersPublication . Lopes, Ana Sofia; Carreira, PedroIn Portugal, student-workers represent 8.5% of higher-education students and observe higher dropout rates, partially because of a higher education system that is more fitted to the traditional students. Using an extensive longitudinal database with original information on individual, degree and employment characteristics of 1566 undergraduate studentworkers from IPLeiria, we determine the factors that drive the dropout and graduation risks of adult workers in higher education. We concluded that academic failure explains only a fraction of dropout behaviour among adult student-workers. Indeed, academic achievement is also affected by school-residence distance, financial difficulties, marital status, motivation, field of study, academic integration and professional background. We found that men are more likely to drop out and more influenced by employment variables (self-employment, job qualification and job-degree relation) while, for women, marriage (associated with household responsibilities) seems to increase the risk of dropout. Some policy recommendations are suggested for the higher education system to adapt better to the particular characteristics of adult workers, namely by: adjusting the schedule and composition of classes; appreciating the curriculum and orienting candidates, stopouts and poor performance students; providing scholarships; distributing the vacancies across admission regimes; and introducing shorter/simplified versions of the degrees.
- Development of a mixed-meal that impacts carotid-body mediated cardiorespiratory and metabolic parameters - a pilot studyPublication . Frazão, Ana; Costa, Andreia; Teixeira, Bárbara; Santo, Marisa; Brito, Gabriel; Lages, Marlene; Lopes, Nuno Vieira; Fonseca-Pinto, Rui; Pereira, Cidália; Guarino, Maria PedroThe carotid bodies (CB) have been recently implicated in the genesis of metabolic diseases in animal models. The CBs respond to circulating insulin to increase heart rate, respiratory rate and blood glucose levels. In humans, this mechanism is not well characterized.
- CBmeter- a new medical device for early screening of metabolic diseasesPublication . Guarino, Maria Pedro; Brito, Gabriel; Lages, Marlene; Fonseca-Pinto, Rui; Lopes, Nuno VieiraType 2 diabetes mellitus (T2DM) is a highly prevalent disease worldwide which is asymptomatic in about 44% of patients being critical to search for new ways of early diagnosis. Recent studies have demonstrated that the etiology of this disease may be associated with alterations in the function of the carotid body (CB), a chemosensor organ located within the bifurcation of the carotid artery. In animal models of metabolic syndrome it was observed that the CBs are overactivated, underlying diseases such as obesity, hypertension and T2DM. This discovery provided a new paradigm in the neuroendocrinology field, suggesting that diagnostic function of the CBs has predictive value for the development of metabolic diseases. Despite this fact, it is not common in clinical practice to look at the CBs as organs associated with endocrine dysfunction and we believe this is probably due to the nonexistence of a user-friendly, portable medical device that diagnosis the function of the CBs.
- Introducing flow architecture in the design and optimization of mold inserts cooling systemsPublication . Clemente, Miguel R.; Panão, Miguel R. OliveiraMold cooling is a critical phase of the molding cycle, comprising more than half of its total time. It affects the final quality of the plastic part and production rate. Therefore, the cooling channel system design is essential to achieve better control over the cycle time. Despite the improvements of conformal cooling, the flow configuration is still absent from cooling optimization criteria. In this work, using the constructal principle, we introduce in these criteria the flow systems svelteness as a global geometric design parameter expressing its architecture. In the configuration explored for cooling small-scale mold inserts, the flow enters through a primary channel and returns through secondary channels, equally spaced, similar to an umbrella shape. The evolution of flow configuration toward minimizing the flow resistance (local pressure losses) points to an architecture with smaller secondary channels and larger return angles. Depending on thermal requirements, it is possible to define optimal regions of interest presenting the cooling systems designer with an appropriate optional range.
- Effect of the alien invasive bivalve Corbicula fluminea on the nutrient dynamics under climate change scenariosPublication . Coelho, J. P.; Lillebø, A. I.; Crespo, D.; Leston, Sara; Dolbeth, M.The main aim of this study was to evaluate the impact of the alien invasive bivalve Corbicula fluminea (Müller, 1774) in the nutrient dynamics of temperate estuarine systems (oligohaline areas) under climate change scenarios. The scenarios simulated shifts in climatic conditions, following salinity (0 or 5) and temperature (24 or 30 °C) changes, usual during drought and heat wave events. The effect of the individual size/age (different size classes with fixed biomass) and density (various densities of <1 cm clams) on the bioturbation-associated nutrient dynamics were also evaluated under an 18-day laboratory experimental setup. Results highlight the significant effect of C. fluminea on the ecosystem nutrient dynamics, enhancing the efflux of both phosphate and dissolved inorganic nitrogen (DIN) from the sediments to the water column. Both drought and heat wave events will have an impact on the DIN dynamics within C. fluminea colonized systems, favouring a higher NH4-N efflux. The population structure of C. fluminea will have a decisive role on the impact of the species, with stronger nutrient effluxes associated with a predominantly juvenile population structure.