281 resultados para eletrônicos


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Pós-graduação em Desenvolvimento Humano e Tecnologias - IBRC

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Pós-graduação em Química - IQ

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fuel cells powered directly with ethanol (Direct Ethanol Fuel Cell-DEFC) are very attractive for the possibility of using a renewable fuel in the generation of clean energy. However, it is still necessary to deepen the understanding of catalytic processes and their dependence on the catalytic properties. This work proposes to study the catalytic activity of ethanol oxidation in an alkaline medium of Pd nanoparticles supported in carbon oxide hybrids using various transition metal oxides (MoO3, TiO2, WO3 and ZrO2). The materials prepared were characterized by techniques such as X-ray diffraction, transmission electron microscopy (TEM) and X-ray dispersive spectroscopy (EDX) to verify the structure, the distribution of particles in the supports and the presence of Pd on particles oxide. Experiments of X-rays absorption spectroscopy were carried out using soft X-rays (SXS) to evaluate the changes in the electronic properties of the Pd particles caused by interactions with different oxides. Measurements of cyclic voltammetry and potential sweeps of adsorbed CO oxidation allowed evaluating general aspects of the catalysts' electrochemical behavior and determining the electrochemically active area thereof. The catalytic performances of ethanol oxidation in alkaline medium were evaluated by electrochemical techniques (potential scan and chronoamperometry), and showed an improvement in activity with the addition of oxides in material containing only carbon, which was most pronounced for the catalyst containing TiO2. This improvement was predominantly associated with the electronic effects caused by the interaction of Pd on the support, causing a vacancy in the 4d band of Pd which, in turn, produces variations in adsorption energies of the species...

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This study analyses the quotations from a specific Facebook page called Brasileiríssimos, which presents itself as a project aiming to publicize and value the Brazilian culture. For this analysis one can observe the use of concepts of traditional quotations, to highlight, when comparing to these formats, the different ways of quoting that can be found on this means of communication: Facebook. The research aims to reflect about how the image of the page is built from the dialogue between the I and the other. More specifically, we look at the dialogue of the author of the page with the quoted text and the reader. In order to analyze that, concepts of quotation from authors belonging to Bakhtin's Circle are going to be used, amongst others. These concepts constitute the analysis criteria of the quoted texts, especially on how the quotation is made. The chosen methodological approach is a qualitative analysis from the quotations made on Facebook, as well as texts that help to visualize the dialogue between the traditional forms of quotation and the forms found on the abovementioned page. On the proposed dialogue about the concepts of quotation it is possible to notice the production of meaning caused by the way in which the quotation is made, by how the author of the page inserts herself in relation to the quoted text and, finally, by the relation of the text with the reader. Because this research bases itself on the dialogical discourse analysis, it be turned to the concept of dialogism, analyzing discourses in contact. Departing from there, one of the main goals is to understand which discourses dialogue when the production of the quotation and in what manner the quotation is made on the chosen means of communication

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Ceramic powders based on Zn3Ga2Ge2O10: Cr3+ X% (X = 0.0; 0.5; 0.75; 1.0) were synthesized by solid-state reaction method. The gallium-zinc germanate doped with chromium presents an interesting property of phosphorescence, that means, it is capable of emitting light when excited by a source of radiation, and such emission remains for some time after stopping the source. For this reason, these materials can be widely applied in night-vision surveillance, (through the use of solar energy, for example), electronic devices screen, emergency routes signals, control panels indicators in dark environments, etc. In this job were considered different amounts of dopant in order to perform a comparison of structural and photoluminescent properties. For that, some analyses were performed on samples, such as XRD, FT-Raman, SEM, UV-vis and photoluminescence measurements (PL). Such analysis allowed to infer that the presence of chromium results in no phase transformation, so that the four compositions have the same set of phases: cubic, rhombohedral and hexagonal. Although the structure was not changed, chromium influences other properties / characteristics of these materials. Examples are: increase of band-gap, decrease of average particle size, small changes in binding energy checked by Raman and especially the increase of photoluminescent property. The chromium ions have great ease in replacing gallium ions in octahedral sites, resulting in emission of light with a wavelength of about 700 nm (infrared region), which is justified by the spin-forbidden 2E 4A2 transition. In other words, chromium is a favorable luminescent center, acting as a trap in the crystal structure, since it imprisons the excitation energy easily and releases it gradually, allowing the phosphorescence. It was observed that the composition ... (Complete abastract click electronic access below)

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In order to diversify the global and national energy matrix and reduce harmful impacts on the environment caused by the emission of polluting gases into the atmosphere, the use of clean and renewable energy sources is presented as a good alternative. This work discusses the use of photovoltaic solar energy, a source that presents such characteristics. The photovoltaic system under study is the type distributed connected to the grid, in the residential segment. It is informed of its use in the global and national levels. They are also present their characteristics, electrical and electronic circuits that make up the equipment required for its operation and the design of a system to be installed in a residence

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Pós-graduação em Psicologia - FCLAS

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Pós-graduação em Geografia - IGCE