https://repositorio.unifei.edu.br/jspui/handle/123456789/87 2026-08-28T07:56:19Z https://repositorio.unifei.edu.br/jspui/handle/123456789/3173 Aquisição e validação de sinal de ruído eletroquímico Corrosion is a global problem, which implies costs in industrialized countries of up to 4.5% of GDP, with either economic, but also social and environmental impacts. In the case of Brazil, the waste of water supply networks due to leaks loss is quite significant and much of it is caused by network degradation, indicating that corrosion control should be promoted whenever possible. This study proposes a corrosion monitoring system, in system subject to the use of inhibitor, with the approach of passive technique for monitoring corrosion by electrochemical noise (EN), in which the classification of events in a corrosion sensor by EN is part of methodological study for structural integrity (or “health”) monitoring system (SHM). Due to very dynamic and stochastic nature of the signal, this study and analysis of EN measurements (ENM) considers numerical and graphic characteristics of two corrosion systems both in saline aqueous solution: carbon steel and stainless steel. These experiments are repeated for accumulating data, which allow the generation of several graphs in time and frequency domains, from which at least one characteristic is extracted, which has a good correlation with data from corrosion processes. Then, based on a supervised machine learning system, the training data allows the model to be calibrated. From the test data, the correctness rate of the model above 50% is verified. Dissertação 2022-02-17T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4469 Avaliação de parâmetros associados ao envelhecimento de para-raios submetidos a descargas de corrente Surge arresters are protective devices installed throughout power systems to limit overvoltages caused by lightning impulses, switching operations, and network faults. However, these devices are subject to degradation processes that may compromise their performance, lead to failure, and affect system reliability. In this context, it is essential to investigate the mechanisms associated with surge arrester aging and to identify the most sensitive parameters for monitoring their operational condition. For this purpose, an aging procedure based on current impulse stresses was applied to three groups of surge arresters from different manufacturers, each group consisting of three 15 kV samples. Throughout the aging process, the devices were evaluated through leakage current and partial discharge measurements. At the end of the aging procedure, microstructural analyses were performed on both new and aged samples to investigate the effects of degradation. The results indicated that leakage current-derived parameters exhibited the highest sensitivity for monitoring surge arrester aging, with dissipated power and third-order harmonics standing out as the most representative indicators. Partial discharge activity was detected only in a subset of the samples and during the final stages of the degradation process. Furthermore, samples exhibiting partial discharge activity also showed changes in the final leakage current measurements. Microstructural analyses confirmed the degradation evidence observed in the electrical tests. Therefore, it was concluded that the combined application of the employed techniques was effective for assessing the aging of distribution surge arresters, with leakage current-derived parameters emerging as the most promising indicators for monitoring the degradation of these devices. Dissertação 2026-06-29T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4468 Electric motor fault detection under nonstationary operation using koopman operator spectral analysis. Accurate motor fault detection and flow rate estimation in industrial centrifugal pumps is essential for diagnostics, performance monitoring, and process optimization, yet traditional frequency-domain techniques such as Motor Current Signature Analysis (MCSA) often rely on fixed spectral bands and assume stationarity, making them less effective under variable-speed operation, changing loading conditions, and multiphase flow environments. This work introduces a Koopman-theoretic framework for motor fault and flow-rate classification based on Hankel-embedded Higher-Order Dynamic Mode Decomposition (HODMD), enabling extraction of physically interpretable spectral-dynamical features from multichannel current, voltage, and vibration measurements. The proposed pipeline computes Koopman eigenvalues, modal energies, growth rates, temporal coherence, and spectral entropy to construct a compact descriptor of pump electromechanical behaviour, which is subsequently evaluated through supervised and unsupervised learning pipelines incorporating SMOTE balancing, nonlinear UMAP projection, and extensive hyperparameter optimization via TPESearchCV. Using 2 laboratory datasets, the first consisting of 106 signals describing 4 motor faulty operation states with different input frequencies, its results were as high as 96.8% cross validation accuracy and 80.7% balanced test accuracy. The second dataset consists of 1304 signals spanning multiple rotational speeds, heterogeneous fluid compositions, and 11 unbalanced flow-rate range classes, the system achieves up to 97.8% cross-validation balanced accuracy and up to 92.6% balanced test accuracy while revealing coherent manifold structure aligned with physical flow-rate regimes. Although overlapping operating states and speed-dependent spectral shifts introduce classification challenges, the results demonstrate that Koopman spectral feature captures the essential dynamic structure of the pump more effectively than traditional Fourier-based approaches, highlighting their potential for robust, reliable, and generalizable monitoring and diagnostics of industrial pumping systems. Dissertação 2026-07-08T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4466 A educação ambiental no processo de construção da profissionalidade docente de licenciandos em ciências biológicas In view of the urgent need to discuss socio-environmental issues in times of environmental collapse, this study investigates the process of constructing the professional identity of future Biology teachers enrolled in an Environmental Education course. From this context, the following research question emerged: which dimensions of teacher professionality are highlighted and/or developed by Biology undergraduate students when they are placed in situations in which they need to think about and develop Environmental Education projects? To answer this question, the general objective of this study is to identify and analyze the possibilities that a course exclusively focused on Environmental Education themes offers for the construction of teacher professionality. More specifically, the study aims to: understand the process of constructing teacher professionality among undergraduate students in a Biological Sciences teacher education program enrolled in a mandatory Environmental Education course; identify which dimensions of teacher professionality emerge from this educational process; and analyze which dimensions of teacher professionality are expressed by Biology undergraduate students in their discourse about future Environmental Education teaching practices. This research is qualitative in nature and characterized as a field study. The following procedures were used for data collection: participant observation in a mandatory Environmental Education course, questionnaires, and semi-structured interviews with students participating in the course. For data analysis, Content Analysis with a focus on thematic analysis was chosen due to its ability to organize and interpret qualitative data. The results highlight the contributions of Environmental Education to the initial teacher education process, making it possible to observe different relationships between Environmental Education and the construction of different aspects of teacher professionality, analyzed through four categories: moral obligation, which encompasses the teacher’s commitment to students’ education beyond the curricular dimension; commitment to the community, derived from the relationships established with the social community in which teachers carry out their practice and from the political aspects involving teaching work; professional competence, related to teachers’ practices, activities, and knowledge; and, finally, the construction of teacher professional identity. Dissertação 2026-04-02T00:00:00Z