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Browsing Ciências e Tecnologia / Sciences and Technology by Sustainable Development Goals (SDG) "12:Produção e Consumo Sustentáveis"
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- Automated design of priority rules for resource-constrained project scheduling problem using surrogate-assisted genetic programmingPublication . Luo, Jingyu; Vanhoucke, Mario; Coelho, JoséIn the past few years, the genetic programming approach (GP) has been successfully used by researchers to design priority rules for the resource-constrained project scheduling problem (RCPSP) thanks to its high generalization ability and superior performance. However, one of the main drawbacks of the GP is that the fitness evaluation in the training process often requires a very high computational effort. In order to reduce the runtime of the training process, this research proposed four different surrogate models for the RCPSP. The experiment results have verified the effectiveness and the performance of the proposed surrogate models. It is shown that they achieve similar performance as the original model with the same number of evaluations and better performance with the same runtime. We have also tested the performance of one of our surrogate models with seven different population sizes to show that the selected surrogate model achieves similar performance for each population size as the original model, even when the searching space is sufficiently explored. Furthermore, we have investigated the accuracy of our proposed surrogate models and the size of the rules they designed. The result reveals that all the proposed surrogate models have high accuracy, and sometimes the rules found by them have a smaller size compared with the original model.
- Behaviour of low molecular weight compounds, iron and copper of wine spirit aged with chestnut staves under different levels of micro-oxygenationPublication . Canas, Sara; Danalache, Florina; Anjos, Ofélia; Fernandes, Tiago; Caldeira, Ilda; Santos, Nádia; Fargeton, Laurent; Boissier, Benjamin; Catarino, SofiaAlternative technologies for a more sustainable wine spirits’ ageing have been studied but a lack of knowledge on the effect of oxygenation level remains. This work examined the behaviour of low molecular weight compounds, iron and copper of a wine spirit aged in 50 L demijohns with chestnut wood staves combined with three levels of micro-oxygenation or nitrogen. Compounds and mineral elements were quantified by HPLC and FAAS, respectively, in samples collected at 8, 21, 60, 180, 270 and 365 days of ageing. Results showed that most of the compounds underwent significant changes in their content over time and behave differently depending on the wine spirit’s oxygenation level: higher contents of gallic acid, syringic acid and vanillin were associated with lower micro-oxygenation level while higher contents of ellagic acid, syringaldehyde, coniferaldehyde and sinapaldehyde resulted from higher one; lowest contents of these compounds were found in the nitrogen modality. Weak correlation between copper and the studied compounds was evidenced whereas closer relationship between iron, vanillin, gallic, syringic and ellagic acids at end of ageing was observed. This study provides innovative information on the role of oxygen in wine spirit’s ageing, and on chestnut wood effect on wine spirit’s mineral composition.
- Context-aware mobile applications in Fog Infrastructure: a literature reviewPublication . Barros, Celestino Lopes de; Rocio, Vitor; Sousa, André; Paredes, HugoToday’s cloud computing techniques are becoming unsustainable for real time applications as very low latency is required with billions of connected devices. New paradigms are arising; the one that offers an integrated solution for extending cloud resources to the edge of the network and addresses current cloud issues is Fog Computing. Performing Fog Computing brings a set of challenges such as: provisioning edge nodes to perform task volumes downloaded from the Cloud; placing task volumes on edge nodes; resource management on edge nodes; need for a new programming model; programming, resource management, data consistency service discovery challenges; privacy and security and improving the quality of service (QoS) and user experience (QoE). This paper aims at introducing the Fog Computing concept and it presents a literature review on the way it is applied: context-sensitive applications and context-sensitive mobile service platforms. The result of the study is presented as the current research challenges for context aware mobile applications in Fog Computing infrastructure.
- Context-aware task scheduling slgorithm for the Fog paradigm: a model proposalPublication . Barros, Celestino Lopes de; Rocio, Vitor; Sousa, André; Paredes, Hugo; Teixeira, OlavoTask scheduling in fog paradigm is very complex and, in the literature, according to the author’s knowledge there are still few studies. In the cloud architecture, it is widely studied, and, in much research, it is approached from the perspective of service providers. Trying to bring innovative contributions in these areas, in this paper, we propose a solution to the context-aware task-scheduling problem for fog paradigm. In our proposal, different context parameters are normalized through Min-Max normalization, requisition priorities are defined through the application of the Multiple Linear Regression (MLR) technique and scheduling is performed using Multi-Objective Non-Linear Programming Optimization (MONLIP) technique. The results obtained from simulations in the iFogSim toolkit, show that our proposal performs better compared to the non-context-aware proposals.
- Di-Alkyl adipates as new phase change material for low temperature energy storagePublication . Sequeira, Maria Carolina; Nogueira, Bernardo A.; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João M. N. A.; Fausto, RuiThis work is a contribution to the thermal characterization of a selected binary system of two di-n-alkyl adipates that can be used as phase change material for thermal energy storage at low temperatures. The construction of the solid–liquid phase diagram using differential scanning calorimetry (DSC), complemented with Raman Spectroscopy studies for the system composed by diethyl and dibutyl adipates is presented. The solidus and liquidus equilibrium temperatures were determined by DSC for the pure components and 30 binary mixtures at selected molar compositions were used to construct the corresponding solid–liquid phase diagram. The binary system of diethyl and dibutyl adipates presents eutectic behaviour at low temperatures. The eutectic temperature was found at 240.46 K, and the eutectic composition was determined to occur at the molar fraction xdibutyl = 0.46. Additionally, the system shows a polymorphic transition, characteristic of dibutyl adipate, occurring at ca. 238 K, confirmed by optical microscopy. To the best of our knowledge, no reference to the phase diagram of the present system could be found in the literature. Raman spectroscopy was essential to complement the construction of the phase equilibrium diagram, enabling the identification of the solid and liquid phases of the system. Finally, the liquidus curve of the phase diagram was also successfully predicted using a suitable fitting equation, being the root mean square deviation of the data from the correlation equal to 0.54 K. In addition, this fitting operation enabled a correct prediction of the eutectic composition of the system.
- Energia nuclear em Portugal: não, obrigado?Publication . Pires, Maria Eliana Santos; Sousa, NunoAs alterações climáticas, marcadamente visíveis, principais responsáveis pela degradação do nosso planeta, são um facto inegável. Largamente impulsionadas pelo boom energético, assente na queima desenfreada de combustíveis fósseis, desde meados do século passado e que se perspetiva cada vez mais acelerado. A premência da mudança de paradigma reúne consenso mundial. Portugal ao apostar nas energias renováveis trilha caminho tentando alcançar a neutralidade carbónica. Pese embora o esforço, as intermitências climatéricas, assoladas de elevada imprevisibilidade, comprometem, claramente este objetivo. Sendo, por isso, desejável e necessário adotar um mix energético que colmate as crescentes necessidades energéticas, onde a energia nuclear, preterida em Portugal, poderá assumir papel fundamental, contribuindo, na atualidade, com uma décima parte da energia elétrica produzida a nível mundial. Neste trabalho, após breve enquadramento teórico da energia nuclear, aplicou-se uma metodologia que visa perceber a atitude face ao nuclear de uma amostra populacional específica, nomeadamente os estudantes da Licenciatura em Ciências do Ambiente (LCA) da Universidade Aberta. Para tal, aplicou-se um questionário global, exceto no reporte à unidade curricular Novas Energias da LCA, onde o assunto foi debatido com alguma profundidade, lecionada aos participantes. No entanto, o reduzido âmbito populacional traduziu-se numa pequena quantidade de dados coletados, repercutindo-se numa dificuldade na identificação de tendências com validade estatística. A análise foi efetuada com o recurso, maioritariamente, às técnicas de regressão. Foi possível identificar, apenas, oito tendências com significado estatístico. Contudo, fica preparado um questionário que possa ser traduzido, futuramente, para toda a população portuguesa.
- A genetic algorithm for the resource-constrained project scheduling problem with alternative subgraphs using a boolean satisfiability solverPublication . Servranckx, Tom; Coelho, José; Vanhoucke, MarioThis study evaluates a new solution approach for the Resource-Constrained Project Scheduling with Alternative Subgraphs (RCPSP-AS) in case that complex relations (i.e. nested and linked alternatives) are considered. In the RCPSP-AS, the project activity structure is extended with alternative activity sequences. This implies that only a subset of all activities should be scheduled, which corresponds with a set of activities in the project network that model an alternative execution mode for a work package. Since only the selected activities should be scheduled, the RCPSP-AS comes down to a traditional RCPSP problem when the selection subproblem is solved. It is known that the RCPSP and, hence, its extension to the RCPSP-AS is NP-hard. Since similar scheduling and selection subproblems have already been successfully solved by satisfiability (SAT) solvers in the existing literature, we aim to test the performance of a GA-SAT approach that is derived from the literature and adjusted to be able to deal with the problem-specific constraints of the RCPSP-AS. Computational results on small and large-scale instances (both artificial and empirical) show that the algorithm can compete with existing metaheuristic algorithms from the literature. Also, the performance is compared with an exact mathematical solver and learning behaviour is observed and analysed. This research again validates the broad applicability of SAT solvers as well as the need to search for better and more suited algorithms for the RCPSP-AS and its extensions.
- Influence of the storage in bottle on the antioxidant activities and related chemical characteristics of wine spirits aged with chestnut staves and micro-oxygenationPublication . Alves, Sheila Cristina Oliveira; Lourenço, Sílvia; Anjos, Ofélia; Fernandes, Tiago; Caldeira, Ilda; Catarino, Sofia; Canas, SaraDifferent ageing technology of wine spirits (WSs) has been investigated, but little has been published on the chemical evolution of aged WS during storage in bottle. The purpose of this study was to examine how 12 months of storage in bottle affected the evolution of antioxidant activity (DPPH, FRAP and ABTS assays), total phenolic index (TPI) and low molecular weight (LMW) compounds content of the WSs aged through alternative technology using three micro-oxygenation levels (MOX) and nitrogen control (N). Results revealed the ability of phenolic compounds from aged WSs to scavenge free radicals during storage in bottle. Among the in vitro antioxidant-activity methods, FRAP assay was the more effective to differentiate WSs according to the ageing technology. Concerning the overall influence of storage in bottle on antioxidant activity, and TPI and LMW compounds content, the higher results were obtained for the MOX modalities (O15, O30 and O60), which showed a similar evolution. In summary, this study provides innovative information, demonstrating that the differences between the aged WSs imparted throughout the ageing process (resulting from different MOX levels) were mostly retained, and only slight modifications during storage in bottle were found.
- Introdução à programação: apresentação da unidade curricularPublication . Coelho, JoséIntroduz-se a unidade curricular de Introdução à Programação da Universidade Aberta. Mostra-se uma visão geral da matéria com a informação da ficha da unidade curricular pública. Aborda-se a metodologia de estudo proposta, e descreve-se como é realizada a avaliação. Detalha-se o plano de trabalho com todas as atividades previstas, e mostram-se os espaços online disponíveis. Termina-se com estatísticas da atividade letiva e resultados dos anos letivos anteriores.
- Introdução à programação: ciclosPublication . Coelho, JoséIntroduz-se o conceito de ciclo na programação, o que é e porque é necessário. Mostra-se como criar um ciclo na linguagem C, sendo ainda demonstrados os ciclos dentro de ciclos. Realçam-se os erros de qualidade que se podem cometer por desconhecimento deste conceito, e resolve-se uma atividade formativa de pré-programação. No final apresentam-se os exercícios do módulo 1, que devem ser resolvidos de modo a consolidar a matéria antes de avançar para o próximo módulo.