Ciências e Tecnologia | Artigos em revistas internacionais / Papers in international journals
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Browsing Ciências e Tecnologia | Artigos em revistas internacionais / Papers in international journals 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.
- 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.
- 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.
- A matheuristic for the resource-constrained project scheduling problemPublication . Vanhoucke, Mario; Coelho, JoséThis paper presents a matheuristic solution algorithm to solve the well-known resource-constrained project scheduling problem (RCPSP). The problem makes use of a restricted neighbourhood method using an activity selection and a search space restriction module and implements them as two alternative search algorithms. The first algorithm makes use of the best-performing components of the branch-and-bound procedures from the literature, and embeds them into a greedy neighbourhood search. The second matheuristic implements the exact branch-and-bound procedures into a known and well-performing meta-heuristic search algorithm. Computational experiments have been carried out on seven different datasets consisting of 10,000+ project instances. Experiments reveal that the choice of exact algorithm is key in finding high-quality solutions, and illustrate that the trade-off between selecting an activity set size and search space restriction depends on the specific implementation. The computational tests demonstrate that the matheuristic discovered 24 new best known solutions that could not be found by either a meta-heuristic or an exact method individually. Moreover, a new benchmark dataset has been proposed that can be used to develop new matheuristic search procedures to solve the problem consisting of 461 instances from the literature.
- Micro-oxygenation level as a key to explain the variation in the colour and chemical composition of wine spirits aged with chestnut wood stavesPublication . Canas, Sara; Anjos, Ofélia; Caldeira, Ilda; Fernandes, Tiago; Santos, Nádia; Lourenço, Sílvia; Soares, Joana Granja; Fargeton, Laurent; Boissier, Benjamin; Catarino, SofiaChemistry and to select the most suitable technological option towards quality and sustainability. Following two articles on the same trial, this work focused on colour, total phenolic index (TPI) and basic chemical characteristics of a wine spirit aged in 50 L demijohns with chestnut wood staves together with three micro-oxygenation (MOX) levels. Chromatic characteristics and TPI were monitored over time (8–365 days) while sensory colour, alcoholic strength, acidity, pH and dry extract were assessed at the end of ageing. Results showed that stronger oxygenation promoted significantly faster colour evolution (lower lightness, higher chroma, red, yellow and brown hues) and higher TPI than mild and intermediate oxygenation until 60 days, probably by favouring the leaching of outer wood layers and extraction/degradation of tannins. No significant differences were found between these ageing modalities at 365 days. Outcomes suggest that the stronger MOX is the most suitable modality in terms of quality and sustainability. Significant differences between wine spirits resulting from MOX and control modality (slower colour evolution, lower TPI and dry extract) confirms the oxygen pivotal role in wine spirit’s ageing, particularly in the colour evolution.
- New resource-constrained project scheduling instances for testing (meta-)heuristic scheduling algorithmsPublication . Coelho, José; Vanhoucke, MarioThe resource-constrained project scheduling problem (RCPSP) is a well-known scheduling problem that has attracted attention since several decades. Despite the rapid progress of exact and (meta-)heuristic procedures, the problem can still not be solved to optimality for many problem instances of relatively small size. Due to the known complexity, many researchers have proposed fast and efficient meta-heuristic solution procedures that can solve the problem to near optimality. Despite the excellent results obtained in the last decades, little is known why some heuristics perform better than others. However, if researchers better understood why some meta-heuristic procedures generate good solutions for some project instances while still falling short for others, this could lead to insights to improve these meta-heuristics, ultimately leading to stronger algorithms and better overall solution quality. In this study, a new hardness indicator is proposed to measure the difficulty of providing near-optimal solutions for meta-heuristic procedures. The new indicator is based on a new concept that uses the 𝜎 distance metric to describe the solution space of the problem instance, and relies on current knowledge for lower and upper bound calculations for problem instances from five known datasets in the literature. This new indicator, which will be called the 𝜎𝐷 indicator, will be used not only to measure the hardness of existing project datasets, but also to generate a new benchmark dataset that can be used for future research purposes. The new dataset contains project instances with different values for the 𝜎𝐷 indicator, and it will be shown that the value of the 𝜎 distance metric actually describes the difficulty of the project instances through two fast and efficient meta-heuristic procedures from the literature.
- On the summary measures for the resource-constrained project scheduling problemPublication . Van Eynde, Rob; Vanhoucke, Mario; Coelho, JoséThe resource-constrained project scheduling problem is a widely studied problem in the literature. The goal is to construct a schedule for a set of activities, such that precedence and resource constraints are respected and that an objective function is optimized. In project scheduling literature, summary measures are often used as a tool to evaluate the performance of algorithms and to analyze instances and datasets. They can be classified in two groups, network measures describe the precedence constraints of a project, while resource measures focus on the resource constraints of the instance. In this manuscript we make an exhaustive evaluation of the summary measures for project scheduling. We provide an overview of the most prevalent measures and also introduce some new ones. For our tests we combine different datasets from the literature and generate a new set with diverse characteristics. We evaluate the performance of the summary measures on three dimensions: consistency, instance complexity and algorithm selection. We conclude by providing an overview of which measures are best suited for each of the three investigated dimensions.
- PLS-R calibration models for wine spirit volatile phenols prediction by near-infrared spectroscopyPublication . Anjos, Ofélia; Caldeira, Ilda; Fernandes, Tiago; Pedro, Soraia; Vitória, Cláudia; Alves, Sheila Cristina Oliveira; Catarino, Sofia; Canas, SaraNear-infrared spectroscopic (NIR) technique was used, for the first time, to predict volatile phenols content, namely guaiacol, 4-methyl-guaiacol, eugenol, syringol, 4-methyl-syringol and 4-allyl-syringol, of aged wine spirits (AWS). This study aimed to develop calibration models for the volatile phenol’s quantification in AWS, by NIR, faster and without sample preparation. Partial least square regression (PLS-R) models were developed with NIR spectra in the near-IR region (12,500–4000 cm−1) and those obtained from GC-FID quantification after liquid-liquid extraction. In the PLS-R developed method, cross-validation with 50% of the samples along a validation test set with 50% of the remaining samples. The final calibration was performed with 100% of the data. PLS-R models with a good accuracy were obtained for guaiacol (r2 = 96.34; RPD = 5.23), 4-methyl-guaiacol (r2 = 96.1; RPD = 5.07), eugenol (r2 = 96.06; RPD = 5.04), syringol (r2 = 97.32; RPD = 6.11), 4-methyl-syringol (r2 = 95.79; RPD = 4.88) and 4-allyl-syringol (r2 = 95.97; RPD = 4.98). These results reveal that NIR is a valuable technique for the quality control of wine spirits and to predict the volatile phenols content, which contributes to the sensory quality of the spirit beverages.