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Estudo do processo de filtragem de rejeito grosso de flotação de nióbio para disposição em pilhas.
No full textPrograma de Pós-Graduação em Engenharia de Materiais. Departamento de Engenharia Metalúrgica, Escola de Minas, Universidade Federal de Ouro Preto.Uma nova estrutura de disposição de rejeitos denominada EDR9 (Estrutura de Disposição de
Rejeitos 9) está sendo desenvolvida na Companhia Brasileira de Metalurgia e Mineração
(CBMM) para garantir a continuidade operacional do complexo industrial de Araxá. Esse
projeto contempla a maximização do desaguamento dos rejeitos de acordo com as tecnologias
disponíveis e aplicáveis às características dos rejeitos gerados e as condições climáticas da
região de implantação do empreendimento. Neste sentido, o presente estudo teve como objetivo
compreender o processo de filtragem de rejeitos grossos de flotação de nióbio, a fim de
contribuir para futuras pesquisas sobre o empilhamento desses rejeitos. Os objetivos específicos
incluem a investigação do espessamento e filtragem dos rejeitos, a análise das variáveis que
influenciam esses processos e o impacto dos auxiliares químicos na formação e desaguamento
das tortas. Além disso, buscou-se caracterizar o rejeito grosso de flotação de nióbio, estabelecer
um procedimento padrão de filtragem, em escala de bancada, avaliar o desempenho de
diferentes meios filtrantes e a performance de diferentes dosagens de reagentes auxiliares de
filtragem, com aplicação do tecido filtrante que apresentou a melhor eficiência. Através de
ensaios Leaf Test, foram definidos experimentalmente, os tempos de formação e secagem da
torta, e realizadas medições de umidade das tortas, da taxa unitária de filtragem e do percentual
de sólidos no filtrado; para avaliar o desempenho de diferentes meios filtrantes e dosagens de
reagentes químicos, para assegurar que as tortas atinjam umidade adequada para empilhamento.
Foi definido experimentalmente o tempo de formação da torta em 13 segundos e 40 segundos
para a secagem com base na espessura de torta e umidade adequada ao empilhamento de
rejeitos. Na utilização dos tecidos filtrantes avaliados nesse trabalho, não houve grande
mudança na umidade da torta, uma vez que todos apresentaram performance bem semelhante.
No entanto, observou-se maior influência na clarificação do filtrado e na taxa unitária de
filtragem. O tecido 03-1001-K 050 de poliamida, monofilamentar, com tessitura sarja,
possibilitou a produção da torta com 11,7% de umidade, o filtrado mais limpo com 0,26% de
sólidos e TUF de 1.544,22kg/h/m2. Quanto à adição dos reagentes auxiliares de filtragem, foi
constatada a possibilidade da adequação do desempenho das instalações industriais, como a
necessidade de aumentar a taxa de produção ou reduzir a umidade da torta. O reagente
coagulante Magnafloc 1587, em baixa dosagem, apresentou notoriedade, com aumento na taxa
unitária de filtragem de 1544,22kg/h/m2 para 1736,36kg/h/m2 e ligeira redução da umidade da
torta de 11,70% para 11,53%. Os resultados indicam que a aplicação de filtragem a vácuo para
o rejeito grosso de nióbio deve gerar uma torta com umidade adequada para ser empilhada.A new tailings disposal structure, named EDR9 (Tailings Disposal Structure 9), is being
developed at the Companhia Brasileira de Metalurgia e Mineração (CBMM) to ensure the
operational continuity of the Araxá industrial complex. This project aims to maximise the
dewatering of tailings using the available and applicable technologies suited to the
characteristics of the generated tailings and the climatic conditions of the region where the
project is being implemented. In this context, the present study aimed to understand the
filtration process of coarse niobium flotation tailings to contribute to future research on the
stacking of these tailings. The specific objectives include investigating the thickening and
filtration of the tailings, analysing the variables that influence these processes, and the impact
of chemical aids on the formation and dewatering of the cakes. Additionally, the study sought
to characterise the coarse niobium flotation tailings, establish a standard bench-scale filtration
procedure, evaluate the performance of different filtering media, and the performance of
different dosages of filtration auxiliary reagents, applying the filtering fabric that showed the
best efficiency. Through Leaf Test trials, the formation and drying times of the cake were
experimentally defined, and measurements of the cake moisture, unit filtration rate, and the
percentage of solids in the filtrate were carried out to evaluate the performance of different
filtering media and chemical reagent dosages to ensure that the cakes reach adequate moisture
for stacking. The formation time of the cake was experimentally defined as 13 seconds and 40
seconds for drying, based on the cake thickness and adequate moisture for tailings stacking. In
the use of the filtering fabrics evaluated in this work, there was no significant change in the
cake moisture, as all showed very similar performance. However, greater influence was
observed in the clarification of the filtrate and the unit filtration rate. The 03-1001-K 050
polyamide, monofilament, twill weave fabric enabled the production of the cake with 11.7%
moisture, the cleanest filtrate with 0.26% solids, and a unit filtration rate (UFR) of 1,544.22
kg/h/m2. Regarding the addition of filtration auxiliary reagents, it was found that the
performance of industrial installations could be adjusted, such as the need to increase the
production rate or reduce the cake moisture. The coagulant reagent Magnafloc 1587, at a low
dosage, showed prominence, with an increase in the unit filtration rate from 1,544.22 kg/h/m2
to 1,736.36 kg/h/m2 and a slight reduction in the cake moisture from 11.70% to 11.53%. The
results indicate that the application of vacuum filtration for coarse niobium tailings should
generate a cake with adequate moisture for stacking
Análise da percepção do uso de cigarros eletrônicos no Brasil por meio de comentários no YouTube.
No full textThe rise of video platforms such as YouTube has revolutionized information sharing and influenced social habits and product consumption. At the same time, the diverse global regulatory landscape and ongoing studies on the health effects of e-cigarettes have led to intense and controversial debates. Amidst this, the production of content about e-cigarettes on the internet is rapidly increasing, particularly on YouTube, one of the most popular video platforms globally and the most popular in Brazil. Despite the growing body of research focused on understanding online interactions with ecigarettes, there is a lack of comprehensive and detailed temporal analyses that capture the dynamics of the debate and people’s stance towards these products, especially in the Brazilian context. To address this gap, our study aims to investigate the popularity and acceptance of e-cigarettes in Brazil by analyzing YouTube videos and their associated comments. We collected an extensive dataset of videos, channels, comments and their metadata from 2018 to 2023. Our methodology involved analyzing production and engagement metrics, and developing a deep learning-based stance detection model to estimate people’s stance (approval or disapproval) based on comments and quantify the temporal dynamics of these attitudes over the years. Our findings reveal a significant increase in content production and user engagement, indicating a growing public interest, with a notable increase in approving comments on the product. This study fills previous research gaps by offering a comprehensive and pioneering overview of e-cigarette use and public perception in Brazil, emphasizing the need for a more informed discussion among society and regulatory bodies
Evaluation of compressive strength of manganese oxidized ore briquettes : effects of compaction pressure, curing time, and percentage of binder.
No full textAgglomeration is a common process to safely recycle wastes from the mining and metallurgical sectors. In this process, the mineralogical and chemical characteristics of manganese ores exert a significant influence on the reduction reactions within the electric furnace. Therefore, a systematic work has been done to evaluate the compressive strength of briquettes composed of manganese oxidized ore fines, ferromanganese dust, charcoal fines, and three different binders, bentonite, pregelatinized starch, and slaked lime + molasses. A response surface methodology was used to evaluate the effects of compaction pressure, curing time, and % binder, whose response was measured in terms of compressive strength. The results were assessed by Analysis of Variance and a regression model was generated. The study showed that briquettes with bentonite demonstrated an optimized compressive strength of 2.54 MPa with a compaction pressure of 52.5 MPa, 11 days of curing time, and 11.5% bentonite content. Briquettes with slaked lime + molasses achieved a compressive strength of 3.70 MPa with a compaction pressure of 62.12 MPa, a curing time of 24 days, and an addition of 16.2% slaked lime + molasses. For briquettes produced with pre-gelatinized starch, the design of the proposed variables resulted in a lack of fit to the model. Optimization studies revealed that briquettes made with bentonite and slaked lime + molasses are viable alternatives to replace oxidized lump ore in electric furnaces
Not reconciled : form and representation on Joaquim Pedro de Andrade's Os Inconfidentes.
No full textLeitura de uma das mais elusivas obras-primas do cinema brasileiro moderno, esse ensaio analisa os impasses de representação em Os inconfidentes(1972), de Joaquim Pedro de Andrade, tendo como pontos de partida, de um lado, as tensões criadas entre o vasto arsenal de dispositivos formais que o filme mobiliza – ope rando quase como um modelo reduzido de toda a história do cinema, de Griffith a Godard, de Eisenstein a Rosselini –,e de outro, as hesitações em torno da construção da personagem de Tiradentes, cujo status heroico é ao mesmo tempo celebrado e desfigurado pela mise-en-scène de Joaquim Pedro. Discutir o complexo choque de significados que essa aposta deflagra, explorando algumas das implicações estéticas e políticas desse jogo de báscula, é o principal propósito deste artigo.A reading of one of the most elusive masterpieces of modern brazilian cinema, this essay analyses the dead-ends of representation on Joaquim Pedro de Andrade’s Osinconfidentes (1972), taking as points of depar ture, on the one hand, the tensions among the vast arsenal of formal devices mobilized by the film, working as a sort of reduced model of the whole history of Cinema, from Griffith to Godard, from Eisenstein to Rosselini, and, on the other, the hesitations concerning the view of Tiradentes as a heroe, a status which is, in equal measure, celebrated and disfigured by the mise-en-scène. To discuss the complex clash of meanings that this bet enacts, by exploring some of the formal and political implications of the narrative indecisions, is the main purpose of this article
A faster and more accessible method for the analysis of acephate and methamidophos in water samples by LC-MS/MS.
No full textPesticide pollution on environmental matrices has attracted increasing attention worldwide. Pesticide runoff from agricultural crops into surface waters may impact ecosystems and human health through drinking water consumption in pesticidepolluted areas. This study aims to develop and validate a simpler, faster, and more accessible methodology for the analysis of organophosphate pesticides, such as acephate and methamidophos, using HPLC-ESI-MS (QqQ). Acephate and methamidophos are two of the most common and efficient systemic pesticides in the organophosphate family, known for their high effectiveness against insects and pests. Firstly, different extractions were tested: liquid-liquid extraction (LLE), lowtemperature partitioning extraction (LTPE) and solid-phase extraction (SPE) with a usual and accessible cartridge, C18. LLE and LTPE showed low sensitivities, probably because acephate and methamidophos are extremely hydrophilic compounds, like many organophosphorus pesticides. Thus, they have low interaction with the extractor solvent, resulting in low extraction rates. SPE with C18 cartridge led to the best extraction of acephate and methamidophos in water matrices and was chosen for the validated process. The selected method ensured acceptable recoveries, within the same range found in the scientific literature (9–49%) and within relative standard deviations below 20%. However, future efforts regarding other types of cartridges are encouraged. The limit of detection (LOD) and limit of quantification (LOQ) of the analytical method were 0.2 μg/L and 0.5 μg/L for acephate and methamidophos, values lower than those reported in the scientific literature. The developed method was used to quantify the levels of such organophosphate pesticides in samples from Brazilian surface water and none of the target pesticides were detected in these aquatic matrices
Os tapetes devocionais como representação visual do patrimônio cultural imaterial da Semana Santa de Ouro Preto, Minas Gerais.
No full textPrograma de Pós-Graduação em Turismo e Patrimônio. Departamento de Turismo, Escola de Direito, Turismo e Museologia, Universidade Federal de Ouro Preto.A confecção dos tapetes devocionais da Semana Santa de Ouro Preto é uma
tradição religiosa que remonta ao século XVIII e se destaca como patrimônio
cultural, unindo história, cultura e arte durante a Procissão da Ressurreição. Neste
sentido, a pesquisa apresenta a convergência de determinados aspectos sobre os
tapetes como patrimônio cultural imaterial que se permeiam em um processo que
envolve algumas implicações. Como objetivo principal, a pesquisa propõe analisar
os tapetes devocionais da Semana Santa enquanto elementos estéticos, simbólicos
e sua representação visual com ênfase nos materiais e processos produtivos. A
metodologia aplicada consistiu em uma abordagem descritiva e qualitativa, com
enfoque na pesquisa etnográfica e observação participante. Inicialmente, foi
realizada uma revisão de literatura abrangente nas áreas de patrimônio cultural
imaterial, representação visual, tradição, memória, identidade e turismo religioso. A
pesquisa de campo foi conduzida por meio da aplicação de 85 questionários mistos
não probabilísticos aos moradores da cidade, registro fotográfico e entrevista. Ao
analisar como a população da cidade atribui significados aos tapetes confeccionados
para a Procissão da Ressurreição, ápice da celebração, surgiu como principal
problema, o seguinte questionamento: como conciliar a tradição religiosa da
confecção dos tapetes devocionais em Ouro Preto com a valorização do patrimônio
cultural e o potencial turístico da cidade? As respostas dos questionários evidenciam
a importância dos tapetes como um aparato valioso para a compreensão das
representações visuais ligadas aos seus elementos estéticos e simbólicos, para a
construção de narrativas que destacam o seu valor religioso, histórico, patrimonial e
turístico, e como elemento da manifestação da identidade dos ouropretanos,
fortalecendo a memória coletiva entre os diferentes sujeitos que nela participam.
Dessa forma, conclui-se que a tradição dos tapetes devocionais por meio da
representação visual se constitui em uma rica manifestação cultural que integra
estética, simbolismo e narrativas no seu entendimento como patrimônio cultural
imaterial.The making of sawdust carpets for Holy Week in Ouro Preto is a religious tradition
that dates back to the 18th century and stands out as cultural heritage, uniting
history, culture and art during the Resurrection Procession. In this sense, the
research presents the convergence of certain aspects about sawdust carpets as
intangible cultural heritage that permeate each other in a process that involves some
implications. As a main objective, the research proposes to analyze the sawdust
carpets of Holy Week as aesthetic and symbolic elements and their visual
representation with an emphasis on materials and productive processes. The
methodology applied consisted of a descriptive and qualitative approach, focusing on
ethnographic research and participant observation. Initially, a comprehensive
literature review was carried out in the areas of intangible cultural heritage, visual
representation, tradition, memory, identity and religious tourism. The field research
was conducted through the application of 85 non-probabilistic mixed questionnaires
to the city's residents, photographic records and interviews. When analyzing how the
city's population attributes meanings to the sawdust carpets made for the
Resurrection Procession, the culmination of the celebration, it emerged as the main
problem, the following question: how to reconcile the religious tradition of making
sawdust carpets in Ouro Preto with the appreciation of the city's cultural heritage and
tourist potential? The answers to the questionnaires highlight the importance of
carpets as a valuable device for understanding visual representations linked to their
aesthetic and symbolic elements, for the construction of narratives that show their
religious, historical, heritage and tourist value, and as an element of manifestation of
the identity of yours residents, strengthening the collective memory among the
different subjects who participate in it. Thus, it is concluded that the tradition of
sawdust carpets through visual representation constitutes a rich cultural
manifestation that integrates aesthetics, symbolism and narratives in its
understanding as intangible cultural heritage
Devops and CI/CD pipeline : exploring the IoT-related projects landscape.
No full textPrograma de Pós-Graduação em Ciência da Computação. Departamento de Ciência da Computação, Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto.The evolution of Internet of Things (IoT) systems has brought challenges to software engineering, such as continuously delivering reliable software and hardware components, forming and maintaining multidisciplinary teams, implementing best practices for firmware and hardware development, and deploying and updating soft- ware on IoT embedded components. These challenges can be addressed by applying agile development techniques and automating the continuous integration and de- livery pipeline (CI/CD pipeline). However, using these practices for IoT-related projects presents significant obstacles. Some of them are the resistance of teams to initiate development techniques that are not common to their areas and build- ing and maintaining informative documentation on pipeline automation. Given this scenario, this research aims to investigate the challenges and propose approaches to continuously develop, maintain, and deliver reliable software for IoT-related projects. To achieve this goal, we adopted a methodological approach composed of a System- atic Literature Review, an Exploratory Study, a Software Repository Mining Study, and a Quasi-Experiment. Our contributions include identifying challenges when im- plementing the CI/CD pipeline in IoT-related projects, addressing knowledge gaps, and providing practical guidance for practitioners and researchers. The results high- light the need to adapt software engineering practices to meet the specific demands of these projects and the importance of prior knowledge of continuous integration and delivery for their successful implementation. This research provides a solid foun- dation for advancing software development for IoT-related projects, contributing to quality and agility in this ever-evolving field.A evolução dos sistemas de Internet das Coisas (IoT) trouxe desafios para a engenharia de software. Como entregar componentes de software e hardware confiáveis, formar e manter equipes multidisciplinares, implementar boas práticas para o desenvolvimento de firmware e hardware e implantar e atualizar software em componentes embarcados IoT. Esses desafios podem ser abordados aplicando técnicas de desenvolvimento ágil e automatizando o pipeline de integração e entrega contínua (pipeline CI/CD). No entanto, usar essas práticas para projetos relacionados à IoT apresenta obstáculos significativos. Alguns deles são a resistência das equipes em iniciar técnicas de desenvolvimento que não são comuns às suas áreas e construir e manter documentação informativa sobre automação do pipeline. Dado esse cenário, esta pesquisa investiga os desafios e propõe abordagens para desenvolver, manter e entregar continuamente software confiável para projetos relacionados à IoT. Para atingir esse objetivo, adotamos uma abordagem metodológica composta por uma Revisão Sistemática de Literatura, um Estudo Exploratório, um Estudo de Mineração de Repositório de Software e um Quasi-Experimento. Nossas contribuições incluem a identificação de desafios ao implementar o pipeline CI/CD em projetos relacionados à IoT, abordando lacunas de conhecimento e fornecendo orientação prática para profissionais e pesquisadores. Os resultados destacam a necessidade de adaptar práticas de engenharia de software para atender às demandas específicas desses projetos e a importância do conhecimento prévio de integração e entrega contínua para sua implementação bem-sucedida. Esta pesquisa fornece uma base sólida para o avanço do desenvolvimento de projetos relacionados à IoT, contribuindo para a qualidade e agilidade neste campo em constante evolução
Two sides of the same coin : a study on developers' perception of defects.
No full textSoftware defect prediction is a subject of study involving the interplay of software engineering and machine learning. The current literature proposed numerous machine learning models to predict software defects from software data, such as commits and code metrics. Further, the most recent literature employs explainability techniques to understand why machine learning models made such predictions (i.e., predicting the likelihood of a defect). As a result, developers are expected to rea- son on the software features that may relate to defects in the source code. However, little is known about the developers' perception of these machine learning models and their explanations. To explore this issue, we focus on a survey with experienced developers to understand how they evaluate each quality attribute for the defect prediction. We chose the developers based on their contributions at GitHub, where they contributed to at least 10 repositories in the past 2 years. The results show that developers tend to evaluate code complexity as the most important quality attribute to avoid defects compared with the other target attributes such as source code size, coupling, and documentation. At the end, a thematic analysis reveals that developers evaluate testing the code as a relevant aspect not covered by the static software fea- tures. We conclude that, qualitatively, there exists a misalignment between devel- opers' perceptions and the outputs of machine learning models. For instance, while machine learning models assign high importance to documentation, developers often overlook documentation and prioritize assessing the complexity of the code instead
Considerations on theatre antropology in Brazil.
No full textO artigo aborda os conceitos de Antropologia Teatral e Teatro Eurasiano em relação à construção da identidade artística e profissional do ator e da atriz no Brasil: sua pertinência, sua utilidade e suas implicações éticas, antropológicas e culturais, por meio de contextualização histórica e análise conceitual. O artigo é um dos resultados da pesquisa “Arquivo da Memória Intercultural das Artes da Cena no Brasil”, financiado pela FAPEMIG.The article addresses the concepts of Theatre Anthropology and Eurasian Theatre in relation to the construction of the artistic and professional identity of actors and actresses in Brazil: it's relevance, it's usefulness and it's ethical, anthropological and cultural implications, through historical contextualization and conceptual analysis. The article is one of the results of the research “Archive of Intercultural Memory of the Performative Arts in Brazil”, sponsored by FAPEMIG
Microstructural evolution and mechanical behavior of pearlitic steel under multi-directional forging.
No full textThe mechanical behavior and the microstructural evolution of a pearlitic SAE 1080 steel were analyzed along 12 Multi-Directional Forging (MDF) cycles at room temperature and strain amplitude Δε ≈ 0.30 (MDF0.30). The resulting cumulative strain flow curve is typical of metals undergoing extensive dynamic recovery, displaying appreciable work hardening up to a strain εt ≈ 0.9, followed by a very low work hardening, where flow stress rises from ≈1400 MPa to ≈1510 MPa. Similarly, the microhardness raises up to a total cumulative strain εt ≈ 1.8 and seems to stabilize for further straining, reaching ~3626 MPa after εt ≈ 10.8. Conversely, yield strength initially rises and then falls remarkably after εt > 5.4. This behavior is related with directional cross effects that favor dynamic recovery as the total applied strain increases. These results differ remarkably from those con- nected to a monotonic deformation process such as axisymmetric drawing. In addition, directional cross effects decrease the material yield stress as the total applied strain increases. Microstructural results revealed that MDF0.30 leads to increasing shearing, bending and fragmentation of the cementite lamellae into particles <50 nm in diameter dispersed in the ferritic matrix as the total imposed strain rises. As a consequence, only limited alignment and changes in the cementite interlamellar spacing are observed, up to a total applied strain ≈10.8. It is considered that the work hardening of pearlitic steel deformed through MDF0.30 is dominated by the dynamic recovery of the interlamellar ferrite and a limited contribution from the cementite. Such results have never been reported in the literature and are of practical importance, since extensive cold working of eutectoid steel through MDF can be performed with standard presses and large specimens