https://repositorio.unifei.edu.br/jspui/handle/123456789/55 Mon, 14 Sep 2026 11:29:22 GMT 2026-09-14T11:29:22Z 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 Thu, 17 Feb 2022 00:00:00 GMT https://repositorio.unifei.edu.br/jspui/handle/123456789/3173 2022-02-17T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4471 Estudo numérico de vibrações induzidas por interferência de esteira e efeito de rugosidade no arranjo de dois cilindros alinhados A purely Lagrangian Discrete Vortex Method (DVM) with a roughness model is employed to numerically simulate the two-dimensional, incompressible, unsteady flow around two tandem circular cylinders of equal diameter immersed in an incident flow. The downstream cylinder is located in the wake interference region of the upstream one for streamwise center-to-center distance between two cylinders of L=5D (D is the cylinder diameter). The streamwise spacing ratio L/D=5 is greater than the critical spacing L/D=4, the latter characterizes the known bistable flow for two immovable cylinders, where two values of drag coefficient are identified for two different flow patterns; namely, reattachment-flow and jump-flow regimes for the downstream cylinder. In this work, the downstream cylinder is forced to vibrate transversely in the wake of another fixed tandem cylinder aiming to investigate a regime of Wake-Induced Vibration (WIV) at Re=6.5 x 104. The literature has reported that WIV is a phenomenon resulting from the interaction between the incoming wake and the downstream flexible structure, in which the downstream cylinder vibrates significantly over a wide range of reduced velocities and, additionally, the cross-flow fluid force is not in phase with the body’s motion. The non-dimensionalized vibration amplitude is fixed at A/D=0.15 and the reduced velocity is adopted as VR=5. The phenomenon of WIV appears combined with a resonant regime, in which the downstream cylinder vibrates at the resonant velocity similar to the Vortex-Induced Vibration (VIV) of a single cylinder. For the streamwise spacing ratio of L/D=5, the individual resonant regime is captured for both smooth surfaces. The main contribution of the present research is to show that the variation of downstream cylinder roughness desynchronizes the VIV and WIV regimes, and also promotes transition between them. Dissertação Mon, 06 Jul 2026 00:00:00 GMT https://repositorio.unifei.edu.br/jspui/handle/123456789/4471 2026-07-06T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4470 Framework metodológico de modelagem e simulação híbrida com aprendizagem por reforço aplicado à racionalização de pontos de ônibus The rationalization of bus stops represents a major challenge in urban public transportation planning, with direct implications for population accessibility, system operational efficiency, and travel quality. Despite advances in urban computing, there remains a lack of methodological frameworks capable of integrating Agent-Based Simulation (ABS), Discrete-Event Simulation (DES), and Reinforcement Learning (RL) in a structured and synergistic manner to support the rationalization of public transportation infrastructure. To address this conceptual and methodological gap, this dissertation aims to develop a Hybrid Modeling and Simulation (HMS) methodological framework to support the rationalization of urban public transportation bus stop locations by integrating ABS, DES, and RL based on measures of accessibility and system usage. The methodological approach comprised a Systematic Literature Review (SLR) conducted according to the PRISMA protocol, the theoretical formulation of the framework, and its computational implementation in the AnyLogic platform, using a georeferenced case study of the municipality of Passos, Minas Gerais, Brazil, for validation. The computational model integrated a spatially distributed synthetic population, origin–destination (OD) matrices, a georeferenced road network obtained from OpenStreetMap, urban Points of Interest (POIs), and the behavioral and operational processes of the public transportation system. Agent behavioral parameters were calibrated and statistically validated against real boarding and electronic ticketing data. During the rationalization stage, a tabular Q-Learning algorithm employing an ε-greedy policy was implemented, in which the reward function combined variations in the global accessibility indicator with variations in the number of public transportation users. In an experiment configured with 10 episodes and 2,000 training steps per episode, the model identified alternative spatial configurations for the bus stop network, producing an improvement of approximately 8% in the global accessibility indicator and an increase of more than 10% in the number of public transportation users compared with the calibrated and validated baseline scenario. These improvements were achieved exclusively by modifying bus stop locations while keeping routes, itineraries, and all other operational characteristics of the system unchanged. The resulting locations were interpreted as candidate solutions and subsequently subjected to physical and topological feasibility assessments. The results demonstrate the methodological feasibility and practical applicability of the proposed framework as an evidence-based decision-support tool for urban transportation planning. Scientifically, this dissertation contributes by proposing a systematic, replicable, and adaptable methodological framework that expands the possibilities for integrating hybrid simulation, reinforcement learning, and spatial analysis to support the rationalization of urban public transportation. Tese Wed, 26 Aug 2026 00:00:00 GMT https://repositorio.unifei.edu.br/jspui/handle/123456789/4470 2026-08-26T00:00:00Z 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 Mon, 29 Jun 2026 00:00:00 GMT https://repositorio.unifei.edu.br/jspui/handle/123456789/4469 2026-06-29T00:00:00Z