DSpace Communidade:

Aquisição e validação de sinal de ruído eletroquímico

2022-02-17T00:00:00Z

Título: Aquisição e validação de sinal de ruído eletroquímico Abstract: 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. Tipo: Dissertação

Sobre o teorema de Kruskal de que todo tensor 3 × 3 × 3 tem posto no máximo 5

2025-12-19T00:00:00Z

Título: Sobre o teorema de Kruskal de que todo tensor 3 × 3 × 3 tem posto no máximo 5 Abstract: The main objective of this dissertation is the study of the article written by M. Bremner and Jiaxiong Hu “On Kruskal’s theorem that every 3×3×3 array has rank at most 5”, where the objective is to show that the rank of every tensor 3×3×3 is at most 5, a case previously studied by Kruskal. To achieve this, we will start with basic definitions and concepts of linear and multilinear algebra, we will continue with tensors and their rank, showing properties necessary for the development of the subject. We will come to the specific study of the tensors 2×2×2 and an algorithm to find their rank, at the end we will study the tensors 3×3×2 and 3×3×3 showing results and examples about them to reach the demonstration of the main theorem with everything that is necessary to understand it. Tipo: Dissertação

Avaliação do potencial de produção de água para reúso em estação de tratamento de águas residuárias de pequeno porte

2025-10-23T00:00:00Z

Título: Avaliação do potencial de produção de água para reúso em estação de tratamento de águas residuárias de pequeno porte Abstract: Water reuse emerges as a sustainable and strategic solution in the face of increasing water-stress events. In Brazil, although this practice remains underexplored, several sanitation utilities have adopted the principles of circular economy, progressively adjusting their processes to enable the valorization of by-products generated in wastewater treatment plants (WWTPs). In 2020, the State Water Resources Council of Minas Gerais (CERH-MG) issued Normative Resolution No. 65, establishing criteria and quality standards for non-potable water reuse in four modalities Urban, Environmental, Agricultural, and Industrial thus providing a regulatory stimulus for the implementation of this practice within the state. However, few applied studies have assessed its actual feasibility in small-scale plants. The present study aimed to evaluate the potential for non-potable water reuse in a small-scale WWTP. The case study was the Pirajuba WWTP, a secondary-level treatment facility comprising upflow anaerobic sludge blanket (UASB) reactors followed by overland flow application, a treatment configuration characteristic of low-population-density municipalities. The objective was to validate reuse potential to meet the non-potable demand of a municipal tree nursery and an ecological park. The methodology included the characterization of the study area and treatment units, along with the quantitative and qualitative assessment of both user demand and treated effluent, considering the environmental reuse quality standards defined by DN 65 (CERH-MG, 2020). Effluent characterization revealed the need for operational adjustments to ensure compliance with the intended reuse category. Accordingly, an investigative study was conducted that led to the modification of the overland operation regime, shifting from parallel to in-series configuration. The in-series operation fulfilled environmental reuse requirements, presenting a median pH of 7.9, viable helminth eggs < 1 egg·L⁻¹, and a median Escherichia coli reduction of 1.69 log (97.8% removal efficiency); the final median concentration of 6.8 × 10³ remained far below the maximum permissible limit of 1 × 10⁶, as stipulated by DN CERH-MG No. 65/2020.It is concluded that the in-series operation of overland flow application proved to be an effective strategy for enhancing treated effluent quality, validating the proposed non-potable reuse in the environmental modality and reinforcing the potential of small-scale WWTPs as viable producers of reuse water. Tipo: Dissertação

Nióbio como aditivo metálico na hidrólise de ligas de alumínio para a geração de hidrogênio verde

2025-10-22T00:00:00Z

Título: Nióbio como aditivo metálico na hidrólise de ligas de alumínio para a geração de hidrogênio verde Abstract: The hydrolysis route of aluminum alloys has been gaining prominence for producing green hydrogen in a clean, simple, and in situ manner, reducing costs associated with transportation and storage. However, this route still requires research aimed at improving the reaction yield. In this context, the addition of various metallic additives to aluminum through high-energy milling has been studied. Although it has theoretical potential, the use of niobium as an additive does not have extensive literature on this topic. With a focus on understanding the role of this additive, this study produced Al-Nb samples with compositions of 80, 85, 90, and 95% aluminum, respectively. The use of niobium as an additive in combination with bismuth was also evaluated, given the widespread use of bismuth in the literature, and for comparative purposes, pure aluminum milled for 7 hours was also assessed. With the exception of pure aluminum, the samples were milled for 15 and 21 hours at 300 rpm with a ball-to-powder mass ratio of 1:30. The morphology of the samples, as well as the distribution of the additives, were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and particle size analysis. The hydrolysis reaction was conducted in an aqueous medium containing 0.5 mol·L⁻¹ NaOH at 30 °C. The incorporation of niobium into aluminum promoted an increase in the reaction yield, with the 95 wt.% Al-5 wt.% Nb mixture achieving 90% yield in the hydrogen production reaction. This effect was attributed to structural defects introduced into the aluminum particles during milling, along with the additive. The hydrogen production rate was also evaluated, reaching a maximum value of 116.8 ml/min in the sample containing bismuth. This result was influenced by particle size, as well as by the anodic activation effect caused by the difference in reduction potential of the additives relative to aluminum. The study demonstrated the potential of niobium and its combined use with bismuth, providing initial data for further research on the topic. Tipo: Dissertação