986 resultados para Eragrostis plana Nees
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Mode of access: Internet.
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Mode of access: Internet.
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CCBE S. XVI,
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Originally published in 1829.
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Includes index.
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In a scenario of increasing competitiveness of the global industrial sector and with a consumer market increasingly demanding, there is an increased demand for new materials and, consequently, possibilities to explore new research and technological advances towards the development of new manufacturing methods or the improvement of existing technologies. In the case of cast irons, new grades of them have been developed so that their mechanical properties have been improved, making them more competitive with steel, expanding the applications and thus represents great economic gain for metallurgy and manufacturing sectors. This increases the interest and creates new opportunities to study these materials and identify how they respond in terms of the surface integrity, tool wear, cutting forces, among others, when machined by grinding operation. In this context, due to the lack of results from grinding of cast irons and studies comparing grindability among several grades of cast irons found in the literature, this work aims to generate scientific and technological contribution to the metallurgical and metal working sector through roughness results (Ra and Rz parameters) and evaluation and analysis of the subsurface integrity of three cast iron grades (gray, compacted graphite and nodular). The machining trials were performed on a surface grinding machine with silicon carbide grinding wheel at different cutting conditions. The input variables were the radial depth of cut (15 and 30 μm), worktable speed, vw (5 and 10 m/min) and the abrasive grain size of the grinding wheel. The results showed that surface roughness increased with the radial depth of cut for all materials tested; and the lowest values were obtained for gray cast iron. Also, roughness was sensitive to variation of worktable speed and the lowest values were obtained after machining with vw = 5 m/min. With respect to the abrasive grain size, as it decreased the roughness values increased to gray and nodular cast iron grades. Furthermore, grinding burns marks were observed on the surfaces of nodular cast iron and compacted graphite iron grades after grinding the smallest grain size, contrary to what is usually reported in literature. However, no evidence of severe thermal damages below the machined surfaces of all cast iron grades was observed after analyzing the results of hardness and the SEM micrograph images.
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Trabajo de suficiencia profesional
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This study will introduce a brief history of the Geometry development, focused in the appearing of the organization in the logical deductive structure achieved by Euclid. Following will be discussed the situation of the learning and teaching of geometry topics since antiquity until the present day, where we will notice that it does not happen with the logical-deductive perspective. After this contextualization, we will propose the realization of a geometry workshop for students of the sixth grade of elementary school, focusing to the development of logical-deductive reasoning. Applied to workshop, changes were observed in the organization of thought of the participating students in the research, furthering the understanding of the concepts and properties of flat euclidean geometry.
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Dissertação (mestrado)—Universidade de Brasília, Faculdade UnB Gama, Programa de Pós-graduação em Integridade de Materiais da Engenharia, 2015.
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El presente trabajo titulado Guía Didáctica de Geometría Plana en las Unidades Didácticas de: Triángulos y Cuadriláteros para los estudiantes de la Carrera de Matemáticas y Física de la Universidad de Cuenca ha sido diseñado para fortalecer el proceso de enseñanza-aprendizaje en el primer ciclo de la carrera con el objetivo de facilitar la comprensión de la asignatura al momento de relacionar la teoría con la práctica. En el primer capítulo se da a conocer de manera general los antecedentes históricos de la Geometría Plana, la importancia de aplicar corrientes pedagógicas innovadoras como la del Constructivismo y la aplicación de la teoría del aprendizaje significativo en la educación actual, las dificultadesen el aprendizaje de la Geometría Plana,el valor de utilizar recursosdidácticos en el aulade clase y la importancia de las guías didácticas para el aprendizaje. En el segundo capítulo se desarrolla el diagnóstico de la propuesta mediante la aplicación de una encuesta, la misma que evidencia las razonespor las cuales los estudiantes de la Carrera de Matemáticas y Física presentan un bajo rendimientoen la asignatura de Geometría Plana, además de la factibilidad del uso de una guía didáctica como complemento en el proceso de enseñanza-aprendizaje. Finalmente, el tercer capítulo está compuesto por once prácticas en los temas de triángulos y cuadriláteros, las mismas que están elaboradas de una manera secuencial, de modo que guíen al estudiante y reten su intelecto mediante actividades dinámicas con el apoyo de la manipulación de material didáctico.