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Catalisadores de CuO/CeO2 promovidos com Au e Pt - estudo do impacto da interface e das propriedades eletrônicas do Cu no desempenho catalítico na reação de CO-PROX
(Universidade Federal de São Carlos, 2020-05-06) Cruz, Aline Rodrigues Miranda; Gomes, Janaina Fernandes; https://lattes.cnpq.br/6718634914051168; Assaf, José Mansur; https://lattes.cnpq.br/9563312407691130; https://lattes.cnpq.br/2338318076586637
The copper-ceria system has been extensively investigated to be used as a catalyst in the preferential oxidation of CO reaction (CO-PROX), aiming the purification of H2 streams from reformed fuels, due to its oxygen storage capacity and redox properties. However, many aspects of these catalysts must be better understood, such as the impact of successive redox cycles on the copper-ceria interaction, the role played by copper species in the CO-PROX reaction mechanism and the effect of adding noble metals to CuO/CeO2 catalysts in the properties and performance in the reaction. These issues were addressed in this thesis. CuO/CeO2 catalysts with 1 to 3% of copper promoted or not with Au and Pt were synthesized by different methods, characterized by physical-chemical techniques, and applied in the PROX reaction. The results showed that the stability of the CuO/CeO2 interface, submitted to successive redox cycles, is important to the CO-PROX reaction and that this stability depends on the employed synthesis method. For co-precipitated materials, it was verified that the CO-PROX reaction is impacted by the nature of the Cu species, which may vary with the reaction temperature, depending on the amount of metal in the material. From these results, it was proposed a new PROX reaction mechanism for these materials. In addition, our results indicated that the materials synthesized by impregnation and co-precipitation follow different preferential pathways in the PROX reaction. After understanding these aspects, the effect of adding Au and Pt to Cu/ceria catalysts was evaluated. The increase in gold content from 0% to 0.75% worsened the performance in the CO-PROX reaction, which may be associated with the gold particle size, higher than 10 nm, and the possible blocking of Cu sites by deposition of Au, resulting in less interaction between Au-Cu-Ce. The promotion of the CuO/CeO2 catalyst with platinum also did not bring benefits in the ideal CO-PROX reaction, which can be explained by the stability of the Pt0-CO bond up to 120 ºC during the reaction. On the other hand, with the addition of CO2 and water in the reaction stream, i.e. under real CO-PROX conditions, the PtCu bimetallic material showed a promising result up to 120 ºC, with greater resistance to the presence of these reactants. Therefore, this thesis provides a new perspective on the redox property, on the CO-PROX reaction mechanism and on the addition of noble metals on CuO/CeO2 catalysts, based on consistent results of in situ and ex situ characterizations.
Modelagem de pilares-parede de concreto armado: estudo paramétrico visando recomendações para o projeto estrutural
(Universidade Federal de São Carlos, 2020-05-06) Silva, Leonardo Martins e; Carvalho, Roberto Chust; https://lattes.cnpq.br/3633394168236221; Christoforo, André Luis; https://lattes.cnpq.br/7623383075429186; https://lattes.cnpq.br/3643832044819726
Reinforced concrete shear walls, or structural walls, can be a challenge during structural design, due to the non-linear behavior of the materials associated with a geometry of complex analysis. The structural design standard recommends considering displacements caused by the shear force and nonlinear behavior of reinforced concrete in the structural analysis of walls. Considering the difficulties inherent to this simulation, this work contributes to the structural analysis of these elements, providing answers for the structural consideration of such behavior. Therefore, it is opportune to use simulations with shell and solid finite elements to represent observed complex effects, such as the interaction between axial and tangential forces. The Opensees and ABAQUS® softwares are used, since they already integrate the necessary packages. The experimental comparison is used to make the calibration representative. The tests described in the literature on slender structural walls are considered here, in which the shear force is relevant, but the behavior is still governed by bending. The experiments are mostly cyclical, while the modeling is monotonic; therefor, a simplification is used to compare them using the backbone curve. The calibration suggests values for the CDP (Concrete Damaged Plasticity) constitutive model, calibrated to mainly simulate the ductility, since the initial rise curve is insensitive to the values adopted according to the results observed here. The expressions are obtained for yield lateral strength, peak lateral strength, stiffness in service, yield displacement and maximum displacement using linear regression. The displacement expressions have a weak coefficient of determination and the other variables expressions have large. The secant stiffness obtained agrees reasonably with the ACI 318 standard, however the stiffness still depends on reinforcement ratio used.
Representação colaborativa de dados científicos: estudo na rede de repositórios de dados científicos do estado de São Paulo
(Universidade Federal de São Carlos, 2020-05-06) Viana, Joyce Mirella dos Anjos; Dal'Evedove, Paula Regina; https://lattes.cnpq.br/1170937498266968; https://lattes.cnpq.br/5238461044667684
Big Data has caused transformations in various sectors of society and has demanded new approaches for studies in Information Science. These transformations also imply the emergence of new forms of scientific communication, intensifying the demand for scientific data, with the collaborative representation of information being a contemporary alternative to the problems arising from the advancement of digital technologies. In this perspective, it was questioned how the scientific data repositories act as collaborative information systems through the active participation of users or groups of people in the organization and treatment of scientific records from research activities. In order to contribute to the issue, we investigated the practices of organization and treatment of information in scientific data repositories, in order to contribute with subsidies for the collaborative representation of scientific records from research activities, through the following specific objectives: a) conceptualize the collaborative representation of information in the studies of Information Science and its potential in times of Big Data; b) explore the guidelines and practices adopted for the organization and treatment of scientific data within the scope of the Network of Scientific Data Repositories of the State of São Paulo; and to present and reflect the possibilities of collaborative representation of scientific data in the Network of Scientific Data Repositories of the State of São Paulo, in all its dimensions and perspectives. To this end, exploratory and descriptive research was conducted through the collection of data of a bibliographic order and by survey, with the investigative scope of the specialized literature on Information Science and the digital repositories belonging to the network. Although some theoretical indications in the scientific literature point to Folksonomy as a possible strategy for the organization and treatment of information in the context of Big Data, it was found that there is no such practice in the data repositories that integrate the network, even though the system has possible technological infrastructure for tagging. It is concluded that Information Science needs to investigate and incorporate, in its professional practices, viable parameters for the organization and recovery of informational resources implied by Big Data.