Principais Coleções do Repositório
Submissões Recentes
Computational tool to evaluate the efficency of hydrogen in internal combustion engines
(Universidade Federal de Lavras, 2025-03-20) Rincon, Alvaro Ferney Algarra; Alvarez, Carlos Eduardo Castilla; Ensinas, Adriano Viana; Rodriguez, Christian Jeremi Coronado
Behavioral studies on the efficiency of a hydrogen engine are important, as they are part of a global initiative to decarbonize the automotive sector, and this technological route for the use of hydrogen is promising within recent energy transition studies. In this sense, the exploration of new technological development routes around production, commercialization and use of hydrogen for the state of Minas Gerais and for Brazil has been proposed through various government initiatives in recent years. For this reason, this work has developed a computational tool based on a zero-dimensional mathematical model capable of predicting the efficiency of a spark ignition engine when using hydrogen as fuel. The simplicity of the model offers a quick view of the operation and thermodynamics of the engine, which reduces computational effort and produces results that represent the real behavior of hydrogen combustion. This focus helps in the study of combustion and in making decisions about the economic viability of using hydrogen in internal combustion engines. To do this, the compression, combustion and expansion processes in the Otto cycle were mathematically modeled to represent the combustion behavior of the air-hydrogen blend inside the engine cylinder, using code written in MATLAB. The mathematical model was validated with experimental data taken from the research engine bench and those reported in the literature in relation to the pressure curve for the different engines and operating conditions evaluated, and the efficiency produced by the engine under these conditions was estimated. A graphical interface was generated in AppDesigner for the computational tool, making it easier for the user to develop the behavioral and operational study of a hydrogen engine. The results obtained with the computational tool show that the estimated pressure and efficiency values are in good agreement with those found in the literature in all the cases evaluated. The maximum error when comparing the pressure curve was 1.32% for an engine with a speed of 3300 RPM. In addition, the minimum fit of the mathematical model to the experimental data was 86%, which represents a good alternative for estimating the thermal efficiency value.
O tratamento dado à leitura de textos digitais nos cadernos MAPA voltados ao ensino médio em tempo integral em Minas Gerais
(Universidade Federal de Lavras, 2026-03-11) Silva, Raquel Candida Torres; Ferreira, Helena Maria; Cabral, Giovanna Rodrigues; Vieira, Daniela da Silva
Considering the need to expand the effectiveness of teaching proposals related to the context of Full-Time Upper Secondary Education (EMTI), this study has as its main objective to critically analyze the approach to the reading of multisemiotic texts in the MAPA Booklets in the light of the guidelines of the BNCC and multiliteracies theories and, thus, to understand the potential of this proposal for the holistic education of Upper Secondary students in the public school system of Minas Gerais. To structure the research proposal, a bibliographical study and a documentary study were carried out. The bibliographical research consists of a discussion about concepts of reading, multiliteracies, and the specificities of reading in digital contexts. The documentary research consists of an analysis of the planning proposed in the MAPA Booklets – Pedagogical Support Material for Learning (2024), developed by the State Department of Education of Minas Gerais and aimed at public-school Upper Secondary students as an alternative to complement the teaching and learning process. For this purpose, three editions were selected, and the sections devoted to the teaching of Portuguese language were analyzed. Within the scope of the bibliographical research, a discussion is carried out on the characteristics of the meme genre and its contributions to the teaching of reading. In the documentary part, an analysis is proposed of how the meme genre is treated in the teaching sequences (SD) designed for EMTI. The research undertaken made it possible to verify that the MAPA Booklets are aligned with the assumptions of multiliteracies and multimodality, since competencies, knowledge objects, and skills are articulated with the dimensions of cultural diversity and semiotic multiplicity. However, the proposed activities lack a more indepth exploration of these dimensions. Considering the relevance of reading multisemiotic texts, of problematizing social issues, and of the ethical treatment of information, an educational product was proposed that focuses on the reading of the meme genre, in the form of a didactic sequence. This didactic sequence sought to present a proposal for working with the meme genre from a multimodal perspective. In this way, the study carried out can contribute to the construction of a theoretical framework for work with the reading of multisemiotic texts, especially with regard to the use of memes in the classroom.
Spatio-temporal dynamics of microplastic contamination in tropical freshwater fish
(Universidade Federal de Lavras, 2026-03-05) Moreira, Marina Ferreira; Pompeu, Paulo dos Santos; Leal, Cecília Gontijo; Vieira, Larissa Fonseca Andrade; Hallwass, Gustavo; Leitão, Rafael Pereira; Sampaio, Francisco Alexandre Costa
Plastic production and consumption have increased steadily over recent decades, contributing to the accumulation of debris in the environment, among which microplastics are now widely detected. Although research on microplastic contamination has expanded rapidly, freshwater ecosystems, particularly in tropical regions, remain comparatively understudied, and long-term perspectives are still rare. This thesis advances the understanding of microplastic contamination in tropical freshwater environments by addressing spatial and temporal dimensions. First, a literature review synthesizes the current state of research on microplastics in tropical freshwaters, identifying major advances and gaps across regions, ecosystems, and organism groups. Second, microplastic ingestion by fish is evaluated across different freshwater environments within a river basin, including lotic and lentic ecosystems, highlighting the role of hydrological context and the complexity of contamination patterns. Finally, long-term trends in microplastic ingestion by fish are assessed over a 24-year period across regions with contrasting land-use contexts, representing the first analysis of this kind for tropical freshwater fish. Overall, the results show that lentic environments can act as important accumulation zones, exposing organisms to higher contamination levels, and that temporal trends in fish contamination are not uniform but depend on regional environmental context. In addition, water turbidity influences microplastic ingestion in visual foragers. This thesis also highlights the importance of long-term ecological monitoring and biological archives as essential tools for reconstructing past contamination and advancing knowledge on plastic pollution.
Dendroclimatologia de Cedrela fissilis, no semiárido Mineiro
(Universidade Federal de Lavras, 2026-02-12) Azevedo, Sérgio Abílio; Barbosa, Ana Carolina Maioli Campos; Santos, Rubens Manoel Dos; Quintilhan, Manolo Trindade; Pereira, Gabriel de Assis
Our understanding of the effects of climate change on the growth dynamics of tree species in tropical forests remains incomplete, particularly in regions with marked seasonal climate patterns. The aim of this study was to identify growth patterns over time, detect signs of extreme weather events in tree-ring chronologies, and assess the influence of climate change on the radial growth of the species. The study was conducted in the ecotone between the Cerrado and Caatinga biomes, in the semi-arid region of Minas Gerais, in the municipality of Januária (Peruaçu Caves National Park), where 40 trees of the species Cedrela fissilis were sampled, which were subsequently taken to the Dendrochronology Laboratory at UFLA, where laboratory procedures were carried out to obtain information relevant to the study. Using the COFECHA software and the ARSTAN program, the quality of the dendrochronological series dating and the establishment of chronologies were assessed, respectively. Finally, the analysis and processing of spatial and dendrometric data were carried out using R software (v. 4.5.2) within the RStudio environment. Subsequently, climatic and hydrological data (temperature, precipitation, river flow and drought indices over time) were used, obtained from official sources and stations closest to the sampling areas, such as WorldClim, ANA, INMET and CRU. Principal component regression was applied to reconstruct past climate, calibrating the treering data against seasonal climate observations. The results of this study demonstrate a strong correlation between the tree-ring series (0.719), and when correlated with average monthly precipitation, showed a moderate positive correlation (r ≈ 0.3–0.4), and a negative correlation with average annual temperature (r ≈ –0.26). The results suggest that the secondary growth of the tree species Cedrela fissilis responds to interannual climatic variations at a regional level. These results demonstrate the importance of incorporating dendroclimatic studies in order to obtain insights into the current state of forests in the face of climate change, and the responses of tree species in the study region to environmental stimuli within these ecosystems.
Saberes científicos sobre o queijo Canastra: da pesquisa à comunidade
(2025) Olímpio, Hellen Barros Ferreira; Silva, Júlia Pereira de Bessa; Silva, Julia Aparecida Rodrigues; Rodrigues, Jéssica Ferreira