Browsing by Author "Correia, A."
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- Rheological Behaviour of PP Nanocomposites by Extrusion ProcessPublication . Almeida, F. De; Silva, E. Costa e; Correia, A.; Silva, F.J.G.The effect of organophilic clay (C15A) in PP compatibilized polymer (PP/PP-g-MA) through rheological experimental results is presented. This study focusses on the description of the rheological behaviour of the organophilic layers along the screws of a twin screw extruder by melting process, varying the screw profile as well as the processing conditions, namely screw speed, temperature and feed rate. Different levels of dispersion were found along the screws for all conditions and positions analyzed by rheology. The qualitative analysis of the images obtained by transmission electron microscopy, reinforced the results. Furthermore, the effects of the processing conditions on dispersion of C15A layers along the screw profile are analyzed using multiple linear regression techniques. The results show statistically significant differences of all rheology measures for all the processing conditions and positions along the extruder.
- Scrap production of extruded aluminum alloys by direct extrusionPublication . Ferrás, A.F.; Almeida, F. De; Silva, E. Costa e; Correia, A.; Silva, F.J.G.The growing globalization of the different types of market requires that companies invest, in a recurrent way, to optimize and improve all the processes inherent to their activities. Aluminium extrusion is the main industrial process used to create profiles of a fixed cross-section. This process requires appropriate processing parameters to be used, in order to produce diverse profiles and high-quality products. The company’s ability to adapt and improve the productive process are differentiating factors against the competition. Thus, understand the main operations and dynamics of the companies is crucial. This work presents an empirical study concerning the extrusion process of a Portuguese company in the aluminium sector. By analysing a real data base provided by the company, the main objective is to model the aluminium extrusion process. Taking into account the variables that most influence the extrusion of different profiles, the aim is to minimize the production of scrap. First, by studying the literature in the subject, the variables that most contribute to scrap production were identified. Since the database provided by the company did not present all the variables described in literature, proxy variables were considered. Next, a multivariate linear regression model for explaining the amount of scrap taking as explanatory the identified variables was estimated. With this analysis, it was possible to identify levels of significance of the variables under study, and therefore understand how each of the variables contributes to the increase or decrease of the amount of scrap on the production of aluminium profiles. The results show that variables concerning with extrusion temperature, time, speed, pressure and die geometry are crucial to improve and control the scrap production. The obtained model will be improved, in future work, by including further variables of the extrusion process. Furthermore, factor analysis and GHML methodologies will also be considered for explaining the production of scrap and therefore improve the production process.
- Uma tarefa diferente de OTD para o 1º ciclo do ensino básicoPublication . Couto, A.; Correia, A.; Graciano, A.; Nunes, C.; Monteiro, S.; Maia-Lima, C.Este estudo debruça-se sobre a abordagem da temática da Organização e Tratamento de Dados (OTD) no 1º Ciclo do Ensino Básico, procurando dar a conhecer aspetos relevantes e mostrar uma possibilidade de trabalhar este conteúdo de modo a proporcionar, aos alunos, uma aprendizagem com significado. A tarefa implementada desenvolveu-se numa turma do 3º ano, utilizando-se para tal uma estratégia de ensino e de aprendizagem exploratória, proporcionando-se um trabalho de construção por parte do aluno para a construção do seu próprio conhecimento. Depois da descrição da tarefa implementada apresentaram-se os resultados, analisaram-se os erros e as dificuldades mais comuns na temática mencionada. Com a análise de todo o trabalho desenvolvido verificou-se que uma das maiores dificuldades residiu na representação gráfica dos dados, que pode ter na sua origem um desconhecimento sobre os aspetos importantes que estão subjacentes a esta forma de apresentar os dados. Porém, as fases anteriores à construção foram por norma bem-sucedidas pelos alunos.