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  • Uma Introdução à Filosofia da Matemática
    Publication . Castro, Eduardo Jorge de Sousa
    Este livro é um manual para um primeiro curso de Filosofia da Matemática. Pode ser usado ao nível de uma graduação ou de uma pós -graduação, de Filosofia ou de Matemática. Restantes académicos e investigadores, bem como professores do ensino não -universitário, podem também encontrar aqui uma referência e uma orientação para o seu trabalho e investigação. O livro apenas pressupõe conhecimentos de matemática e de filosofia, de nível pré -universitário.
    2025-02Book Open access Show more
  • “Não quero morrer a ensinar”: Perspetivas de envelhecimento de pessoas LGBTQ+ com mais de 50 anos em Portugal
    Publication . Taborda, Catarina Marques; Augusto, Amélia Maria Cavaca
    Não obstante a sua jovem democracia, Portugal tem subido no ranking de legislação igualitária, no contexto europeu. Apesar disso, são ainda várias as formas de discriminação presentes nas vidas de pessoas LGBTQ+ com mais de 50 anos, que conviveram com o período da criminalização, invisibilização e patologização da sua existência. Esta discriminação, enraizada nas normas sociais que indicam a cis heteronormatividade como o caminho a seguir, impacta a saúde e bem-estar de pessoas LGBTQ+ idosas, que, por vezes, são levadas a “regressar ao armário” para receber cuidados na velhice. Ainda assim, não existem em Portugal respostas sociais dirigidas à população idosa LGBTQ+. Esta dissertação procura conhecer as perspetivas de envelhecimento de pessoas LGBTQ+ com mais de 50 anos em Portugal, enquanto explora os seus processos de autodescoberta, o experienciar de discriminação, a sua relação com os serviços de saúde, as suas redes de cuidados, assim como a sua relação com o movimento associativo LGBTQ+ português. A pesquisa segue uma abordagem qualitativa, com recurso a entrevistas semiestruturadas, que permitem valorizar a subjetividade das suas vivências e o seu conhecimento, em profundidade. Foram realizadas dez entrevistas, com pessoas LGBTQ+ entre os 51 e os 70 anos de idade, cujo conteúdo transcrito foi posteriormente submetido a uma análise categorial. A presente investigação permitiu conhecer os receios e as necessidades sentidas por pessoas LGBTQ+ com mais de 50 anos em relação ao seu processo de envelhecimento. São apontadas divergências com o atual movimento associativo LGBTQ+ português, assim como mudanças na prestação de cuidados de saúde a pessoas LGBTQ+ na velhice. E ainda, são desenhadas alternativas aos espaços de cuidados tradicionais existentes em Portugal para pessoas idosas, e nomeadas as condições que as mesmas devem ter para garantir a sua qualidade de vida.
    2025-02-04Master thesis Open access Show more
  • Splashing correlation for single droplets impacting liquid films under non-isothermal conditions
    Publication . Rodrigues, Daniel de Almeida Vasconcelos ; Barata, Jorge Manuel Martins ; Silva, André Resende Rodrigues da
    The droplet impact phenomenon onto liquid films is predominant in a variety of modern industrial applications, including internal combustion engines and cooling of electronic devices. These are characterised by heat and mass transfer processes, such as evaporation, condensation and boiling. However, studies regarding droplets and liquid films under non-isothermal conditions are scarce in the literature and do not explore temperature-dependent phenomena. Due to this, the main objective of this work is to evaluate the influence of temperature on the splashing occurrence of single droplets impinging onto liquid films under the presence of a heat flux. The crown evolution is evaluated qualitatively to provide insight regarding breakup mechanisms. Water, n-heptane and n-decane are the fluids considered for the current study, as these provide a wide range of thermophysical properties and saturation temperatures. The splashing dynamics are evaluated by varying the droplet impact velocity and dimensionless temperature of the liquid film. Qualitative results show that an increase in the liquid film temperature leads to the transition from spreading to splashing, which is less evident for fuels in comparison with water. For water and n-heptane, the formation of cusps on the crown rim is promoted, which is associated with ligament breakup. For n-decane, the crown rims are relatively homogeneous in terms of shape and size, whereas the atomisation process varies a function of the liquid film temperature. Visually, the secondary droplets exhibit a greater size in comparison with lower temperatures. Transitional regimes display some irregularities, such as splashing suppression/reduction, which require further attention. In terms of splashing correlation, the authors propose to develop a non-splash/splash boundary for both iso- and non-isothermal conditions. Results show that the splashing threshold is dependent on the thermophysical properties and the dimensionless temperature of the liquid film.
    2025-02-07Journal article Open access Show more
  • Analysis of the influence of the tip clearance on the performance of transonic compressors
    Publication . Lopes, Diogo Marques; Brojo, Francisco Miguel Ribeiro Proença
    In aviation, compressor efficiency is essential for reducing operating costs and improving engine performance. More efficient compressors consume less fuel, which reduces airlines' expenses. It is with this goal in mind that this study was carried out, focusing on the analysis of a transonic compressor. This study explores the performance of the NASA Rotor 67 axial compressor in two configurations: with and without tip clearance. Computational fluid dynamics simulations were carried out to evaluate the effects of tip clearance on the flow characteristics and overall efficiency of the compressor. Tip clearance refers to the small gap between the blade tips of a rotor and the surrounding casing in turbomachinery. This gap is necessary and intentionally designed to allow for thermal expansion, mechanical tolerances, and structural deformation during operation to ensure that the blades do not come into direct contact with the casing. In this study, Ansys CFX software was used as a tool to analyze the aerodynamic performance of the transonic compressor under steady-state conditions, and the model used for the simulations was the SST k-? turbulence model. Ansys CFX makes it possible to accurately simulate the complex flow phenomena present in turbomachinery, including the effects of compressibility. The analysis focused on critical performance metrics such as pressure ratio and efficiency, comparing the two models to understand the impact of the gap on flow characteristics. Contours of the relative Mach number and pressure distributions were used to study the flow behavior in different sections of the rotor, highlighting the main differences between the two cases. The results showed that the absence of spacing improves performance, achieving higher pressure ratios and more uniform flow patterns near the blade tips, where the irregularities induced by spacing were mitigated. This was expected, as tip clearance is associated with leaked losses, which can reduce overall efficiency.
    2025-02-10Master thesis Open access Show more
  • New delivery systems based on gellan gum nanoparticles for Parkinson Diseases Therapeutics
    Publication . Rodrigues, Madalena Filipa Geada; Passarinha, Luís António Paulino; Sousa, Ângela Maria Almeida de; Cristóvão, Ana Clara Braz
    Globally, there are up to 10 million people diagnosed with Parkinson's Disease, a chronic neurodegenerative disorder without a cure. Physiologically, it is characterized by the progressive loss of dopaminergic neurons in the substantia nigra. Clinically, patients with this disease reveal several motor symptoms, such as tremors, tension, and postural instability, and non-motors, such as depression and anxiety. To date, the most effective drug combination used in the treatment of Parkinson's disease is the administration of levodopa (L-Dopa) combined with catechol-O-methyltransferase (COMT) inhibitors and monoamine oxidase inhibitors to restore dopaminergic brain levels. However, the commercially available inhibitors have low capabilities to cross the blood-brain barrier and, thus, low bioavailability in the brain. Also, the prolonged use of these drugs is associated with high hepatotoxicity, which currently limits their use. Therefore, the discovery of molecules with the potential to inhibit the COMT and the development of new delivery systems for these drugs are crucial elements to improve the effectiveness of existing therapies. Using polymeric nanoparticles as antiparkinsonian drug carriers presents numerous advantages considering the current therapies. These nanosystems can cross biological barriers due to their chemical properties and small size. Furthermore, they can achieve the therapeutic target more efficiently, increasing the bioavailability of the drug in restricted environments, such as the brain. Also, the application of polysaccharides in developing this type of delivery system presents advantages such as lower economic costs and better biocompatibility and biodegradability compared to oral and intravenous therapies. The discovery of the molecules 3,4-dihydroxy-5-nitrobenzonitrile (ZINC035) and 2- bromo-3,4-dihydroxy-S-nitrobenzaldehyde (ZINC496) as new COMT inhibitors, combined with the potential of nanoparticles based on natural polymers, such as gellan and chitosan, as drug delivery systems, have proven to be the impulse for this work. In the first part of this work, an analytical method using High-Performance Liquid Chromatography (HPLC) was developed to detect and quantify these new inhibitors in brain tissue samples from adult Wistar rats. In this study, the biological samples were spiked with each inhibitor and, subsequently, analyzed using two different types of detection, in which electrochemical detection (HPLC-ECD) was more effective for biological matrices than diode-array detection (HPLC-DAD). Additionally, a study was realized using different mobile phases, varying from 9 to 18% (v/v) of the organic compound (acetonitrile) to optimize the experimental procedure time. The results obtained using an HPLC-ECD analysis system interestingly showed that the molecules under study have interaction capabilities with brain tissues, and due to their similarity with commercial inhibitors, their potential use in Parkinson's therapies has been proven. In the progress of this work, a new polymeric delivery system has been developed to improve metabolism and absorption, increasing their chemical stability, decreasing their susceptibility to enzymatic degradation, and improving bioavailability of the commercial drugs. This delivery system results from the complexation of two natural polymers with opposite charges, the gellan gum (GG) and the chitosan (CH). These polymeric complexes were formulated, testing different conditions, varying the molecular weight of chitosan (5 kDa and low molecular weight) and the ratio and concentration of the polymers (0.05-1 mg/mL). After optimization, the GG/CH systems were prepared with the inclusion of the selected COMT inhibitor (ZINC035) or L-Dopa. In order to obtain the encapsulation efficiency of the nanoparticles, a purification system was developed, testing three different methodologies (centrifugation, filtration and molecular exclusion chromatography) and varying some conditions, such as centrifugation speeds (8000- 12500 rpm), the size of filter pore (0.22 and 0.45 µm) and the elution buffers (sodium acetate, sodium chloride and phosphate-buffered saline). The best GG/CH delivery system had a size of 238.52 nm; a polydispersity index (PDI) value of 0.449 and a zeta potential (ZP) of +30.2 mV. Also, GG/CH nanoparticles loaded with ZINC035 showed a mean size of 163.5 nm; a PDI of 0.355; a zeta potential of +20.6 mV and an encapsulation efficiency of 67.04%, which are stable up to 48h after formulation. Finally, the L-Dopa-loaded delivery systems achieved a size of 177.01 nm, a PDI of 0.392, and an encapsulation efficiency of approximately 26%. Overall, the HPLC system with electrochemical detection developed in this work is an effective and innovative methodology for studying COMT inhibitors in biological tissues. Furthermore, nanoparticulate polymeric systems have unique properties that can be used according to the desired intranasal delivery application and will certainly present advantages over conventional therapies.
    2025-02-12Master thesis Embargoed access Show more
  • Transcranial magnetic stimulation in behavioral addiction in the digital era: a systematic review
    Publication . Almeida, Inês Roseta Duarte de; Pinto, Nuno Filipe Cardoso; Patto, Maria da Assunção Morais e Cunha Vaz
    Background The rapid evolution of digital technologies and widespread internet use in daily life have led to the emergence of behavioral addictions, such as gambling disorder (GD), internet gaming disorder (IGD), and internet addiction disorder (IAD). These conditions pose complex challenges for treatment, with conventional interventions, such as psychological and pharmacological interventions, often proving insufficient. Transcranial magnetic stimulation (TMS) has been proposed as a promising approach for treating these addictions. Aims To clarify the evidence available around the use of TMS in patients with GD (internetassociated), IGD, or IAD. Specifically, to evaluate changes in frequency and extent of the addictive behavior, craving, relapse rate, and assessment of psychosocial or other functioning domains after the intervention. Methods A comprehensive search strategy was employed across multiple bibliographic databases, including PubMed/MEDLINE, Embase, Scopus, and Web of Science. The search spanned from the inception of the databases to the search date, with no language restrictions, and required full-length articles. Additionally, Grey Literature sources such as Google Scholar were searched to identify supplementary qualifying studies, and citation searching was conducted to locate additional relevant articles. Results The search yielded 460 records, with no relevant records found in Grey Literature. After removing duplicates, 244 records remained. Screening based on eligibility criteria narrowed the focus to 15 potentially relevant articles, leading to a full-text examination. Citation searching added three more studies. Ultimately, only four articles met the criteria for inclusion in this systematic review. Of these, two involved patients diagnosed with IGD and two were related to IAD. The findings generally suggest a decrease in the severity of symptoms related to internet gaming addiction, impulsivity, cravings, anxiety and depression symptoms after the use of rTMS in the left DLPFC. Similarly, in the case of IAD, a reduction in symptom severity and cravings was observed. Conclusion Despite the promising results of using high-frequency TMS on the left-DLPFC (dorsolateral prefrontal cortex), current research on the feasibility of TMS in addressing GD, IGD and IAD is minimal. Further intervention studies are needed to fully understand the potential of TMS in ameliorating these digital dependencies.
    2025-02-12Master thesis Embargoed access Show more
  • Characterization of Elite Rink Hockey Players, Match and Training Demands
    Publication . Ferraz, António Leopoldo Lopes; Travassos, Bruno Filipe Rama; Santos, João Alberto Valente dos; Mendes, Pedro Alexandre Duarte
    This work aimed to provide valuable insights into the characteristics of players, training, and game demands in rink hockey, applying the knowledge developed towards a more suitable method for monitoring training and competition to enhance player performance. To achieve this, six studies were conducted with specific objectives: (1) to understand the evolutionary trends in the characterization of players and game performance in men's rink hockey; (2) to characterize the body composition and grip strength of elite male rink hockey players and establish the relationship between ethnicity in body composition and grip strength; (3) to understand the applicability of monitoring systems for physical performance analysis in team sports over the last decade in order to develop knowledge for load monitoring in rink hockey; (4) to understand the dynamics of external and internal load throughout the 2-week training period and competition week of a rink hockey International Championship; (5) to propose a new approach to characterize and classify the physiological and biomechanical specificity of training tasks in relation to elite competition - a quadrant-based classification system; (6) to apply the quadrant-based classification system to characterize and classify load demands, considering the physiological and biomechanical requirements of training and games according to positional dimensions. Overall, the results obtained in the six studies of this thesis promoted a proposal for practical applicability from player profiling to training and game monitoring. Study 1 revealed that the literature on rink hockey is scarce and generally presents a holistic approach to physiological and functional demands, cardiorespiratory adaptations, training characteristics, anthropometry, body composition, conditional profile, game characterization, and injuries in rink hockey. However, most studies are conducted on young athletes, with few studies on elite athletes. Thus, it was essential to conduct research toward characterizing elite athletes and the physical demands of training and competition. Study 2 described that given the characteristics of the sport and its neuromuscular adaptation, elite rink hockey players show a specific anthropometric profile considering percentile values of fat and characteristic grip strength for this sport, with ethnicity, right thigh circumference, and right calf circumference being the variables that best describe fat percentile, while age, distal circumference of the right thigh, and ethnicity better describe grip strength. Considering that monitoring through positional analysis technology in rink hockey is almost non-existent, Study 3 sought to understand how research using indoor positioning systems could contribute to a better understanding of the demands of rink hockey. It was found that most studies have focused on performance analysis, load management, injury development process, and nutrition. Still, in Study 3, it was proposed that integrated analysis of kinematic and mechanical variables should be studied alongside their correlation or association with internal load variables to understand athletes' performance improvement strategies better. In this logic, Study 4 observed in a preparation for an international competition that training demands do not match those of the competition. High-intensity impacts followed by decelerations characterize the metrics that most impact athletes' subjective perception of effort during competition, which are underexplored during training, particularly high-intensity impacts. Therefore, in Studies 5 and 6, a proposal was developed to characterize physiological and biomechanical demands in training and competition situations, providing coaching staff with a methodological tool to optimize microcycle planning. In Study 5, it was found that no exercise category analysed has the physiological and biomechanical demands of the game. While the game is characterized by high physiological and biomechanical demands, most exercises have low physiological and biomechanical demands, except for exercises performed in midcourt and full court, which have high physiological and medium biomechanical demands. Still, in Study 5, no category of exercises with simultaneous high biomechanical and low physiological demands was found. Finally, in study 6, a misalignment between the specific demands of different positions was observed when comparing the game with the training sessions of the microcycle. That is, although the game is characterized by high physiological and biomechanical efforts, advanced players tend to achieve a lower physiological and biomechanical profile than defender-midfielder players. These differences are not considered throughout the microcycle. Finally, this approach used in Studies 5 and 6 allows us to assume that the integrated variables that best characterize the physiological demands in rink hockey are average heart rate, maximum heart rate, and distances skated at high intensity. In turn, those that best integrate biomechanical demands are high-intensity impacts, decelerations, and accelerations. In summary, the results suggest that training does not meet the demands of the game, compromising athletes' appropriate response capacity, particularly considering the game's biomechanical demands. This is because there is a failure to replicate these demands in training in terms of training structure and player individualization, mainly due to the absence of exercises that promote high-intensity impacts associated with decelerations and accelerations. The quadrant-based classification system proposal presented in studies 5 and 6 offers coaching staff a methodology to analyse and adjust training structure and player specificity, thus promoting an environment that better replicates competition demands.
    2025-02-18Doctoral thesis Open access Show more
  • Bug Taxonomy Classification Using Machine Learning Algorithms
    Publication . Caldeira, Beatriz Isabel Trocas; Pombo, Nuno Gonçalo Coelho Costa
    Bugs are a natural occurrence in the realm of software development. As society increasingly relies on software, the frequency of these occurrences has naturally increased as well, potentially leading to catastrophic consequences for products or businesses. To monitor and manage the bug resolution process, various bug tracking systems have been developed. These platforms enable teams responsible for bug analysis to view identified bugs, track the most common issues, and monitor their resolution status. However, the challenge lies in analyzing each of these reports. In large-scale products, hundreds of reports can be submitted daily through these platforms, whether by other developers, pen testers, or end users. End users, due to their likely lack of knowledge about software, system architecture, or other inherent processes, may submit incorrect or unclear reports. Addressing the need for developers to manually analyze and classify each of these reports (a complex and time-consuming task) through automation is an idea that has been explored by various researchers. This research aims to develop a comprehensive and detailed classification schema that can provide additional, automated information to report analysts, thereby facilitating part of their analysis process. To achieve this, the proposed solution is based on leveraging the high performance and capabilities of the BERT model, a model rooted on Transformer architecture, to classify these reports as accurately as possible, based on the textual descriptions within each report. A dataset was created following this schema, designed through a divideand-conquer approach, and multiple models were trained on each category. The results indicate that BERT can form the basis of a robust solution for this purpose, even when provided with a small amount of labeled data as input and despite the need for some refinement in the training process. The best results were obtained when both the title and the description were used together as input data for the model, with one model achieving an overall accuracy of 75%, and the lowest accuracy being 54.6%.
    2025-02-19Master thesis Open access Show more
  • Deep Learning-Based Software Defect Prediction via Semantic Key Features of Source Code, Handling Imbalanced Datasets
    Publication . Andrade, Hiro Gaspar Inglês de; Pombo, Nuno Gonçalo Coelho Costa; Pais, Sebastião Augusto Rodrigues Figueiredo
    This work is part of the master’s thesis in Computer Engineering at the University of Beira Interior. It addresses themes related to software defect prediction, known as SDP, with the main objective of developing a predictive model using contextual features generated through deep learning models. To achieve the defined goals, five fundamental steps were followed: data preprocessing, mapping and embedding of tokens, extraction of contextual information, handling of datasets with class imbalance, and building the machine learning model for defect prediction. The dataset used was PROMISE, which encompasses software projects developed in Java, with multiple versions for each one. The experiments were conducted individually for each version, using static and contextual features generated through LSTM networks. The models were evaluated based on AUC, Accuracy, MCC, Recall, and Precision metrics. In general, it was observed that the use of contextual features resulted in significantly better performance. Among the models tested, Logistic Regression proved to be the most effective, demonstrating the best predictive capability. However, when combining different versions of the projects, a drop in performance was recorded, with the MCC showing low values, especially in the case of Naive Bayes, which in some scenarios even presented negative values. This phenomenon can be explained by factors such as concept drift (the change in data behavior over time) and overfitting (when the model fits excessively to the training data, compromising its ability to generalize), issues that have not been deeply addressed but are considered for future work.
    2025-02-19Master thesis Embargoed access Show more
  • Thrust force assessment of a MFC-actuated tail-like robotic fish using Unsteady Panel Method
    Publication . Silva, Maíra Martins da ; Camacho, Emanuel António Rodrigues ; Silva, André Resende Rodrigues da ; Marques, Flávio D.
    Fish-like robots are used in various fields, such as environmental monitoring and underwater exploration. These devices are designed to emulate the motion of a real fish. They can have flexible bodies to mimic body/caudal-based locomotion patterns or fins to mimic median/paired fin-based locomotion patterns. Standard propulsion methods include oscillating fins, flapping tails, and body undulations. This work investigates a robotic fish with a flexible tail actuated by a Macro-Fiber Composite (MFC) pair in a bi-morph configuration. This device is designed to mimic body/caudal-based locomotion patterns; therefore, it should present propulsion capabilities due to its body undulations. These propulsion capabilities are assessed using the Unsteady Panel Method for different sinusoidal inputs. This method requires the device’s kinematics, which is derived using an analytical model based on the Euler–Bernoulli beam theory, considering the electro-mechanical coupling of the actuators. The mean thrust force derived using the Unsteady Panel Method is compared with the actual mean thrust acquired during an experimental campaign. The experimental and numerical results indicated that higher thrust forces can be achieved when the device is excited in its second resonance frequency. These results are in line with Lighthill’s findings.
    2025-02-22Journal article Embargoed access Show more