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Interações discursivas, práticas e movimentos epistêmicos no ensino de relatividade restrita
(Universidade Federal de São Carlos, 2020-08-10) Neves, Jefferson Adriano; Pierson, Alice Helena Campos; https://lattes.cnpq.br/3749421379531019; https://lattes.cnpq.br/6323444324286748
In this work, we analyze and comprehend the discursive interactions that emerge in the classroom during the realization of a teaching sequence on the concepts of space and time according to the Theory of Special Relativity, and identify the epistemic practices mobilized by students and the role of the teacher in this process, in order to answer the following research problems: Introductory classes in Theory of Special Relativity designed to encourage discursive interactions support the development of which epistemic practices? What discursive and epistemic actions of the teacher support or not the development of such practices? What discursive and epistemic actions of the teacher support or not the development of such practices? Epistemic practices are those that are socially organized, standardized and performed in an interactive way, in which the members of a community propose, justify, evaluate and legitimize knowledge. In the field of science education, several authors argue that learning science is related to learning scientific and epistemic practices. The designed sequence for this research context was performed with students who were studying in the first semester of the Physics Degree course in 2018. The investigation took place in the classroom space, with all activities recorded in audio and video, and described in the form of a field diary. The written activities that were written by the students were also part of the process. With the collected material, we organized seven teaching episodes that were transcribed and analyzed using the Argumentative Processes and Products and Practices and Epistemic Movements. In order to investigate Epistemic Practices, we proposed a set of practices specifically related to Modern and Contemporary Physics. The proposed instrument is composed of 13 practices organized in the social instances of Sense Production, Communication and Knowledge Assessment. In the analysis, we identified the student involvement in nine epistemic practices. This process had a high degree of inference and the context was essential in distinguishing between practices. Another fundamental element in carrying out the sequence was the teacher and his actions throughout the episodes, which were modified according to the problem situation or due to the pedagogical objectives. In the discursive interactions, present in the episodes, we reconstructed 17 arguments that were influenced, to a greater or lesser degree, by the teacher's actions.
Investigação do comportamento mecânico de scaffolds utilizados no tratamento de fraturas ósseas
(Universidade Federal de São Carlos, 2020-08-10) Liu, James; Malavolta, Alexandre Tácito; https://lattes.cnpq.br/8477313173581967; https://lattes.cnpq.br/8182373031517663
Scaffolds are implants used to accelerate the bone regeneration process of fractured bones. These components, developed in a research area called Bone Tissue Engineering, are designed to mimic human bone both in its composition and mechanical properties and are composed of biocompatible and biodegradable materials that have a manipulable shape whose function is to assist the regeneration of the desired site providing a temporary structure that facilitates cell union, proliferation and differentiation at the region and subsequently is absorbed and eliminated by the body after bone regeneration at the site. This study used the finite element method to investigate the mechanical behavior of scaffolds and the objective of the work was to compare the numerical results with the experimental data and to evaluate and determine the stiffness of the modeled scaffold configurations. It was concluded that of the two configurations composed of the same material, one having an organizational structure composed of cylinders and the other with hexagons, the latter exhibited a superiority in relation to rigidity and weight. However, the mechanical properties of the scaffolds proved to be inferior to those considered ideal in the literature, showing that the pure material studied is not the most suitable, but a composite. The need to refine the model was also seen, as a significant error was observed between the simulations and the real experiment, in addition to studying other types of loads to obtain a better understanding of the material's behavior. Despite this, it was possible to conclude that the finite element method is a tool that helps to understand complex problems with the ability to reduce time and cost in analysis, resulting in more efficient and less invasive medical procedures and treatments, providing a higher quality of life for the patient.
Caracterização microestrutural e mecânica da liga Ti-35Nb-7Zr-5Ta produzida por fusão seletiva à laser
(Universidade Federal de São Carlos, 2020-08-10) Batalha, Weverson Capute; Gargarella, Piter; https://lattes.cnpq.br/4641435644243916; Kiminami, Claudio Shyinti; https://lattes.cnpq.br/5443002033733395; https://lattes.cnpq.br/3930761900295202
Selective Laser Melting (SLM) is an additive manufacturing technique that consists of a layer-by-layer fusion of a powder bed by scanning a laser enabling the production of full density parts accordingly to a 3D CAD model with complex geometry. Biocompatible beta-TiNb alloys have been specially considered as promising to replace the more conventional Ni-Ti and Ti-6Al-4V alloys to be used in prostheses because their low Young’s modulus and their excellent biocompatibility. In this study, the main objective is to investigate and compare the microstructure and mechanical properties of a beta Ti-35Nb-7Zr-5Ta (TNZT) alloy processed by SLM using three different scanning strategies: unidirectional (Y); bi-directional, 79° rotating between layers (R79°); and checkboard (CHB). We produced samples in a SLM Realizer 50 with a laser power of 129W, scanning speed of 0,57 m/s, layer thickness of 40μm, in argon atmosphere, using those three different strategies. We analyzed these samples in terms of density and porosity using Archimedes’ principle and micro X-ray computerized tomography. Moreover, we characterized the samples by X-ray diffraction, optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron backscattered diffraction, and compression and microhardness tests. All samples presented columnar dendritic and equiaxial grains of beta Ti phase, preferably oriented in the building direction. The oxygen percentage increased in relation to the starting powder, indicating oxygen absorption during the process. The samples showed greater than 99.5% relative density with pores of different shapes, sizes and distribution among the strategies. The EBSD showed samples with different textures. The samples showed high ductility under compression, without premature failure. The yield limit ranged between σ = 436 and 466 MPa and elastic modulus between E = 47 and 50 GPa. The Vickers microhardness values kept constant along the building direction (190 HV) for both samples.