Este estudo teve como objetivo avaliar os impactos das aulas remotas no ensino e aprendizado de discentes do curso de Licenciatura em Ciências - Biologia e Química, do Instituto de Educação, Agricultura e Ambiente (IEAA), da Universidade Federal do Amazonas (UFAM). O método para a coleta dos dados foi através de um questionário semiestruturado com questões abertas e fechadas destinado aos alunos matriculados a partir do 8º período, assumindo uma abordagem de cunho qualitativo. Os resultados apontaram que 82,8% dos participantes consideram que a proposta de ensino, embora seja boa como uma medida paliativa para sanar lacunas ocasionadas pela suspensão das aulas presenciais, ocasionará interferência no aprendizado por não comtemplar todas as áreas de ensino. Ao considerar os resultados das análises se percebe que ainda deve-se pensar em ações que possam ampliar esse novo modelo de ensino para que possa minimizar as perdas no ensino e aprendizado da comunidade acadêmica.
The mineral diesel oil sold in Brazil, due to environmental reasons; presents sulfur concentration of 10 ppm, which causes a deficiency of lubricity, since sulfur is one of the chemical species that gives a good lubricating characteristic. Poor lubricity affects performance and causes failure of engine parts. This study aimed to evaluate the use of glycerin as an antiwear additive by means of tribological tests of the mineral diesel S10 B7 and 10 formulations of diesel based fuels, micro emulsified with 0% (distilled water), 7.5% and 15% of glycerin solution. The formulations were subjected to lubricity tests on HFRR (Hight Frequency Reciprocating Rig) under hydrodynamic lubrication conditions, according to the ASTM D-6079 standard. The results showed that the increased concentration of glycerin added to diesel S10 B7 contributes to improved lubricity and wear reduction.
The new generation of cutting fluids should have some characteristics, such as low toxicity and biodegradability. A bio-cutting fluid emulsion are an excellent option because they present those properties, as well as good mechanical performance. The present study aims to investigate the lubricity of O/W emulsions (cutting fluid emulsion), varying the concentration of anionic surfactant (1%, 2.5% and 5%) and epoxidized oil (5%, 10%, 15%, 20% e 25%). A sunflower oil was chemically modified by epoxidation reaction, then its viscosity, iodine and oxirane index, density, and acidity were characterized. The performances of the emulsions were evaluated using a tribometer HFRR (High Frequency Reciprocating Rig), under hydrodynamic lubrication conditions. The ball wear scars were analyzed using an optical microscopy. The results showed that a low concentration of surfactant promote friction and wear reduction. Based on the tribological performance, the emulsions with 5% and 10% of epoxidized oil are more suitable.
Este trabalho objetiva investigar as motivações que contribuíram para o ingresso e a permanência dos alunos em cursos de licenciaturas duplas e específicas, na perspectiva de indicar potencialidades e fragilidades na formação inicial e formativa do professor. A metodologia adotou abordagens qualitativa e quantitativa com o intuito de responder as indagações propostas neste trabalho, com aplicação de um questionário semiaberto e uso da escala de Likert. Para análise dos dados foram utilizados os programas Excel e SPSS (Statistical Package for Social Sciences). Os resultados mostraram que, independentemente da licenciatura em que ingressaram, a permanência dos alunos no curso depende de fatores sociais e econômicos, como o local em que estes residem e as dificuldades de conciliação trabalho-estudo, além de fatores institucionais, como apoio pedagógico e oferta de atividades complementares, e o papel decisivo do exemplo dos professores do curso para consolidar a escolha pela carreira docente por parte dos licenciandos.
The development of new environmentally-friendly cutting fluids is an important technological advancement. The aim of this study was to assess the tribological behavior of microemulsions (W/O) developed with epoxidized soybean oil and nonionic surfactants with different degrees of ethoxylation (NP4EO, NP6EO and NP9.5EO). The tribological performance of the microemulsion systems was assessed in a High Frequency Reciprocating Rig (HFRR) tribometer. Microemulsions showed Newtonian fluid behavior, with viscosities compatible with conventional cutting fluids. In addition, contact angle values above 90º indicate spherical-shaped drops on the surface on which they are deposited, due to their hydrophobic nature. The microemulsions formulated using surfactants with lower ethoxylation numbers and 20% concentration exhibited greater stability, lower viscosity and better friction reduction during tribological contact between surfaces, given that the average wear scar diameter was 118 µm with smooth surfaces exhibiting slight slippage wear caused by abrasion, as identified by SEM/EDS analyses.
The future lubricants must be more environmentally adapted, with a higher level of performance lower total life cycle, cost than currently used lubricants. Environmental friendly, the biodegradable alternatives are available for a large variety of mineral oil based lubricants. Vegetable oils are the major source of these base fluids, although they have lower thermal and oxidation stability and even worse low-temperature behavior than mineral oil. These physical and chemical properties can be improved by chemical modification. The aim of this study was to evaluate physicochemical properties and film formation from modified vegetable oils. The vegetable oil was chemically modified by epoxidation reaction with acetic and formic acid using sunflower oils. Viscosity, iodine value, density, acidity value and thermal stability were determined for epoxidized oils. The film formation was analyzed using a HFRR tribometer. The results showed that epoxidized vegetable oils had excellent properties to be used as lubricant, and their tribological performance is higher than mineral oil.
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