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- Percursos profissionais e de vida dos licenciados da UAbPublication . Abrantes, Pedro; Carvalho, Alda; Silva, Ana Paula; Bäckström, Bárbara; Seabra, Filipa; Falé, Isabel; Jacquinet, Marc; Ramos, Maria do Rosário; Magano, OlgaO presente relatório apresenta os primeiros resultados da 4.ª edição do questionário aos licenciados da Universidade Aberta, aplicado em 2023 e referente à coorte que concluiu este grau de ensino entre 2019 e 2021. Todos os graduados de licenciaturas na instituição foram convidados a responder, num total de 1310 diplomados, distribuídos por 12 ofertas formativas, tendo-se obtido 490 respostas, o que corresponde a uma taxa de resposta de 35,9%. Relativamente ao perfil sociodemográfico, constatamos uma ligeira prevalência do sexo feminino (53%), que se acentua nas faixas etárias mais jovens, ainda que seja muito variável entre cursos. A idade desta população é muito heterogénea, embora exista alguma concentração numa fase intermédia da vida ativa, com ingresso na licenciatura na faixa dos 35-45 e conclusão entre os 40 e os 50 anos. A larga maioria residia em Portugal (93%), com alguma concentração na Área Metropolitana de Lisboa (38%), ainda que existam contingentes significativos em todas as regiões do território nacional. Entre os restantes (em parte, provenientes de Portugal), destacam-se a Suíça, o Reino Unido, o Luxemburgo e Angola como países de residência. Em termos educativos, 77% apresentavam o ensino secundário com habilitação literária, enquanto 12% possuíam já um título de ensino superior (maioritariamente de outra instituição). Uma proporção considerável (36%) já havia frequentado o ensino superior sem ter obtido qualquer grau.
- Experiências e trajetórias dos mestres e doutores da Universidade Aberta (2011- 2020)Publication . Abrantes, Pedro; Carvalho, Alda; Silva, Ana Paula; Bäckström, Bárbara; Seabra, Filipa; Falé, Isabel; Jacquinet, Marc; Ramos, Maria do Rosário; Magano, OlgaO presente relatório apresenta os primeiros resultados do inquérito aos mestres e doutorados da Universidade Aberta, com base no questionário aplicado entre março e abril de 2023, abrangendo os diplomados do 2.º e 3.º ciclos, entre 2011 e 2020. Foram obtidas 431 respostas, de um universo de 1375 graduados, o que corresponde a 31% dos mestres e 44% dos doutorados. Desta forma, o Observatório dos Percursos Profissionais e de Vida dos Diplomados da Universidade Aberta alarga o seu campo de análise, até ao momento centrado nas experiências e trajetórias dos licenciados da instituição, acompanhando também a estratégia da instituição para ampliar e consolidar a sua oferta pedagógica ao nível dos mestrados e doutoramentos.
- Projetos e necessidades de formação dos licenciados da Universidade AbertaPublication . Ramos, Maria do Rosário; Abrantes, Pedro; Carvalho, Alda; Novo, Ana; Silva, Ana Paula; Bäckström, Bárbara; Jacquinet, Marc; Almeida, Ana Patrícia da Silva ; Magano, Olga
- Variability on functionally graded plates’ deflection due to uncertainty on carbon nanotubes’ propertiesPublication . Carvalho, Alda; Martins, Ana; Mota, Ana; Loja, AméliaCarbon nanotubes are widely used as material reinforcement in diverse fields of engineering. Being that their contribution is significant to improving the mean properties of the resulting materials, it is important to assess the influence of the variability on carbon nanotubes’ material and geometrical properties to structures’ responses. This work considers functionally graded plates constituted by an aluminum continuous phase reinforced with single-walled or multi-walled carbon. The nanotubes' weight fraction evolution through the thickness is responsible for the plates’ functional gradient. The plates’ samples are simulated considering that only the nanotubes’ material and geometrical characteristics are affected by uncertainty. The results obtained from the multiple regression models developed allow us to conclude that the length of the nanotubes has no impact on the maximum transverse displacement of the plates in opposition to the carbon nanotubes’ weight fraction evolution, their internal and external diameters, and the Young’s modulus. The multiple regression models developed can be used as alternative prediction tools within the domain of the study.
- An application of time series clustering using a combined distancePublication . Martins, Ana; Vaz, Daniel; Silva, Tiago; Cardoso, Margarida; Carvalho, Alda; Loja, AméliaClustering time series aims at uncovering diverse longitudinal patterns. In this study we analyse time series of various parameters collected atop wind turbines in a wind farm in Portugal. Considering wind data in clustering may reveal differences in operation between neighbouring turbines, due to their position relative to one another and to terrain features. In this work, we use an approach to wind speed time series clustering based on a convex combination of distance measures between time series. For visualizing the resulting groups, we propose a graphical representation, Distance Matrix, which is quite more informative than the classical Multidimensional Scaling (MDS) map. This representation allows for quick comparisons between pairs of turbines for (dis)similarities. Our approach provides distinct insights regarding the differences between time series, emphasizing differences in values (Euclidean distance), trends (Pearson-based distance), and cyclical behaviours (Euclidean distance between periodograms and/or autocorrelation structures). In most cases, we found two groups, which were not always coincident with the geographical groups, but the proposed approach could also find the rationale behind the clusters that were formed. The results obtained may help identifying undesirable aerodynamic loads that the blades of a particular wind turbine may be subjected to, thereby shortening its time in-service.
- Analysis of thoracic aortic aneurysm CTA scans using spatial statisticsPublication . Rodriguez, Katalina; Carvalho, Alda; Valente, Rodrigo; Xavier, José; Tomás, AntónioThis study leverages spatial statistics to analyze the spatial distribution of the aorta, aiming to better understand the biomechanical behavior of Ascending Thoracic Aortic Aneurysms (ATAA) and its impact on clinical outcomes. CTA angiography was performed on 87 ATAA patients. Experimental variograms were computed for various variables, such as maximum diameter, from which key parameters of interest were extracted. These parameters were then analyzed over time to assess temporal patterns. The goal of this analysis was to identify whether similar patterns or behaviors emerge in features from CTA scans of patients with aneurysms of similar sizes, ultimately aiming to statistically validate the quality of the CTA scans.
- Sidewalks of Lisbon and AzoresPublication . Carvalho, Alda; Santos, Carlos; Silva, Jorge; Teixeira, Ricardo; Fong, ChamberlainPart of the beauty of Lisbon and Azores lies under the feet of anyone who walks in the streets. Given their highly symmetrical nature, Portuguese sidewalk drawings are ideal to be analyzed geometrically. Furthermore, these drawings provide opportunities for promoting mathematical concepts through exhibitions, card decks, and other forms of dissemination.
- Clinical prediction and spatial statistical analysis of ascending thoracic aortic aneurysm structurePublication . Rodriguez, Katalina; Carvalho, Alda; Valente, Rodrigo; Xavier, José; Tomás, AntónioThis study presents an analysis of data from patients with ascending thoracic aortic aneurysms (ATAAs). Two databases of 87 patients were available: one containing clinical variables and the other consisting of measurements of the maximum diameter taken along the ascending aorta. For the clinical database, both a supervised and an unsupervised learning method were applied to explore patterns within the data. On the other hand, for the ascending aorta dataset, experimental variograms were calculated, from which key parameters of interest were extracted. These parameters were then analyzed over time to assess temporal patterns. This analysis aimed to assess the emergence of similar patterns or behaviour in patients with aneurysms of comparable sizes. Based on the analyses conducted, the clinical variables with the greatest importance in surgical decision-making were identified, while the spatial statistical analysis revealed patterns that may be related to elasticity, stiffness, or deformations of the aorta
- Some notes on disjunctive short sum: polychromatic nimPublication . Carvalho, Alda; Santos, Carlos Pereira dospolychromatic nim is a version of the classic game nim, played with colored stones, in which each pile has stones of a single color, and the player who successfully extinguishes a color wins the game. This game is closely related to the concept of short rule, the ending condition that states that a disjunctive sum ends as soon as any one of the components ends. Here, we discuss that rule, namely when applied to impartial games, and prove that the Grundy-values of polychromatic nim present an arithmetic-periodic behavior.
- Clustering of wind speed time series as a tool for wind farm diagnosisPublication . Martins, Ana; Vaz, Daniel; Silva, Tiago; Cardoso, Margarida; Carvalho, AldaIn several industrial fields, environmental and operational data are acquired with numerous purposes, potentially generating a huge quantity of data containing valuable information for management actions. This work proposes a methodology for clustering time series based on the K-medoids algorithm using a convex combination of different time series correlation metrics, the COMB distance. The multidimensional scaling procedure is used to enhance the visualization of the clustering results, and a matrix plot display is proposed as an efficient visualization tool to interpret the COMB distance components. This is a general-purpose methodology that is intended to ease time series interpretation; however, due to the relevance of the field, this study explores the clustering of time series judiciously collected from data of a wind farm located on a complex terrain. Using the COMB distance for wind speed time bands, clustering exposes operational similarities and dissimilarities among neighboring turbines which are influenced by the turbines’ relative positions and terrain features and regarding the direction of oncoming wind. In a significant number of cases, clustering does not coincide with the natural geographic grouping of the turbines. A novel representation of the contributing distances—the COMB distance matrix plot—provides a quick way to compare pairs of time bands (turbines) regarding various features.