Browsing by Author "Gomes, Elsa"
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- Computer-supported Techniques to Increase Students Engagement in ProgrammingPublication . Tavares, Paula Correia; Henriques, Pedro Rangel; Gomes, ElsaOne of the main reasons that justify the student’s failure in (introductory) programming courses is the lack of motivation that impacts on the knowledge acquisition process, affecting learning results. As soon as students face the difficulties concerning the development of algorithms or the coding in a programming language, they give up and do not try harder to solve other problems; they think it is a demanding activity and feel frustrated. In this paper we describe in detail an experiment conducted to verify the effectiveness, in terms of the increase in motivation and in knowledge acquisition, of combining program Animation tools with the immediate feedback provided by Automatic Evaluations Systems.
- Drop distribution determination in a liquid-liquid dispersion by image processingPublication . Brás, Luís M.R.; Gomes, Elsa; Ribeiro, Margarida; Guimarães, M.M.L.This paper presents the implementation of an algorithm for automatic identification of drops with different sizes in of a These image frames were obtained at our Laboratory, using a nonintrusive process, with a digital video camera, a microscope, and an illumination setup from a dispersion of toluene in water within a transparent mixing vessel. In this implementation, we propose a two-phase approach, using a Hough transform that automatically identifies drops in images of the chemical process. This work is a promising starting point for the possibility of performing an automatic drop classification with good results. Our for the analysis and interpretation of digitized images will be used for the calculation of particle size and shape distributions for modelling liquid-liquid systems.
- Multi-criteria design optimization study of solvent extraction in mixer–settler unitsPublication . Pinto, Gilberto; Gomes, Elsa; Durão, F. O.; Madureira, C. M. N.; Guimarães, M. M. B. L.; Morais, S.Solvent extraction is considered as a multi-criteria optimization problem, since several chemical species with similar extraction kinetic properties are frequently present in the aqueous phase and the selective extraction is not practicable. This optimization, applied to mixer–settler units, considers the best parameters and operating conditions, as well as the best structure or process flow-sheet. Global process optimization is performed for a specific flow-sheet and a comparison of Pareto curves for different flow-sheets is made. The positive weight sum approach linked to the sequential quadratic programming method is used to obtain the Pareto set. In all investigated structures, recovery increases with hold-up, residence time and agitation speed, while the purity has an opposite behaviour. For the same treatment capacity, counter-current arrangements are shown to promote recovery without significant impairment in purity. Recycling the aqueous phase is shown to be irrelevant, but organic recycling with as many stages as economically feasible clearly improves the design criteria and reduces the most efficient organic flow-rate.