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Projeto e construção de bancada para ensaios de filtração de gases a alta pressão
(Universidade Federal de São Carlos, 2009-03-30) Ricco Junior, Edison; Aguiar, Mônica Lopes; https://lattes.cnpq.br/0431688649128529; https://lattes.cnpq.br/9890679530471543
With the industrial expansion and the increase of vehicles assembled daily, there was an increase in the use of natural gas as combustible. Beyond the cheaper the level of emission of pollutants by burning natural gas as fuel it is lower than all the fuels used until today. The increasing consumption of natural gas and the severity of the legislation in respect to the environment caused a greater search for knowledge of the behavior of various filter media that could be used in high pressure filtration. In face of this situation, it was projected and developed an equipment capable to support high pressures during the filtration of gases. During the tests, some changes in this project were needed, with the objective of obtaining the most suitable configuration for the accomplishment of the experiments. To verify the operation of this equipment there was a preliminary investigation, not only of cellulose filter media, that sufficiently are used in this type of filtration but also, the polyester treated and metallic, which could be reused to avoid the accumulation of residues with its discard. The tests were conducted with pressures ranging from 98 to 900 KPa and fair flow from 0.00028 to 0.0019 m3 / s , to determine the coefficient of permeability. To verify the formation of filter cake and efficiency of the filter media, it was made tests from 500 KPa and 0.0016 m3 / s using phosphate rock as particulate material. At the end of this study, it was verified that the permeability coefficients darciana and non-darciana ( 1 k and 2 k ) increased with increasing pressure of the system. The curves of pressure versus velocity showed linear behavior, showing that the viscous forces was predominant in relation to the inertial forces. The cellulose filter media, when subjected to pressure of 5 bar, showed the greatest loss, lower efficiency and lower permeability. The filter media made of polyester and metal showed loss of load and efficiency quite similar, but the fabric has a permeability a slightly smaller than the metallic one. Three filter media showed similar fractional efficiency for collecting particles larger than 15 μm (~ 90%), but for particles smaller than 0.5 μm, the cellulose filter media, was shown to be less efficient than the other studies in this project, because of its high back pressure and lower permeability. This shows that despite the cellulosic filter has a relatively cheaper cost for the filtration of gas, this gives a performance below the metalic filter media polyester treated and the last two the most suitable for filtration at high pressure. It was chosen the filter media of cellulose paper, which was showed the lowest performance for the assays with pressure variaty. It was submitted to pressures of 1, 3 and 7 bar. When analyzing the fractional efficiency, we find out that the higher the pressure, the smaller the efficiency of the filter media.
Diagrama de fases magnéticas e transição de fase quântica em ligas de Cr-Ti
(Universidade Federal de São Carlos, 2009-03-30) Varella, André Luiz Soares; Oliveira, Adilson Jesus Aparecido de; https://lattes.cnpq.br/4640148190073166; https://lattes.cnpq.br/4475272608314836
In this work we present the results of characterization of Cr-Ti alloys with small quantities of Ti. The samples were prepared in a melting arc furnace, using hight purity Cr and Ti. The magnetic phase diagram was determined from critical temperatures obtained by eletrical resistivity and DC magnetic susceptibility measurements, delimiting the boundaries between the transverse and longitudinal SDW (Spin Density Wave) and paramagnetic phases. We have observed that the Band Rigid Model is valid only for concentrations below 1.5%Ti. Above this concentration, a possible structural phase transition explain the disappearance of antiferromagnetic phase. From the observation of anomalies in resistivity ratio, magnetic susceptibilty and Hall effect measurements at low temperature, we have concluded that the system exhibits a quantum critical point in 1.2%Ti.
Interação da matéria de vórtices com estruturas de defeitos em filmes de Nb
(Universidade Federal de São Carlos, 2009-03-30) Kapp, Juliana Sens Nunes; Ortiz, Wilson Aires; https://lattes.cnpq.br/0241177338066307; https://lattes.cnpq.br/9813454606298337
In this work we have studied the Vortex Matter dynamics in Nb superconducting films with different arrays of columnar defects. For that we studied the order-disorder line H (T) OD , where the melting of the vortex lattice occurs. The H (T) OD frontier was determined through the imaginary component " of the susceptibility in T measurements, whose peak temperature T Hp is associated with a maximum in energy dissipation, due to the viscous movement of vortices, which signals the beginning of a nonlinear regime. For this study we modified the pinning force efficiency in Nb samples using three different approaches: varying the technique employed to fabricate the defects, using large-value excitation fields and modifying the angle between the columnar defects in the sample and the applied magnetic field. As the pinning efficiency decreases, two regimes in the melting line become detectable, distinguished form each other by the appearance of a kink in a characteristic temperature k T . For temperatures lower than k T , pinning is significantly more efficient, and the H (T) OD line can be adjusted with a power-law; at higher temperatures, depinning is favored by thermal excitation, and the transition line is adjusted by a Bose-glass model for columnar defect systems. In this work we also studied both regimes with these theoretical models, previously available in the literature. For this we built the H T diagram with the irreversibility line irr H , upper critical field C2 H , and the order-disorder line H (T) OD , studying the dependence of the solid-liquid transition with the excitation field, frequency and angle of the applied magnetic field. We compared the pinning forces acting on different samples and applied a universal scaling approach to our experimental data points, proving the adequacy of the model to our results.
Estudo cinético da produção de ácido clavulânico e cefamicina C por Streptomyces clavuligerus
(Universidade Federal de São Carlos, 2009-03-30) Oliveira, Liliane Maciel de; Hokka, Carlos Osamu; https://lattes.cnpq.br/7409321531977750
Clavulanic acid and cephamycin C are ϐ-lactam compounds, an important group of drugs used in the treatment of several bacterial diseases, and are simultaneously produced by the bacteria Streptomyces clavuligerus. Similarly to any secondary metabolite, the production of these compounds can be controlled by the intracellular concentration of precursors and cofactors, and their availability to be used in the secondary metabolism depends directly on the nutritional composition changes in the culture media. Based on these facts, the aim of this work was to evaluate the effect of some carbon and nitrogen sources on clavulanic acid (CA) and cephamycin C (CefC) production by S. clavuligerus, and to propose a kinetic model able to represent the influence of these compounds on the behavior of this bioprocess. The fermentation runs were carried out in shakers, using synthetic media, combining glycerol, maltose, asparagine, proline, glutamic acid and ornithine. The results showed that both carbon and nitrogen sources were limitants. The fermentations with media containing maltose gave the highest CA and CefC productions, but the bacterial growth was lower. On the other hand, the fermentations with the media containing glycerol gave a higher bacterial growth and lower production, except for the fermentation using the media composed by glycerol, proline and ornithine, that gave the lowest growth and CA production, and there was no CefC production. The aditition of glutamic acid in the medium containing maltose and asparagine, and the aditition of more asparagine in this same medium favored the bacterial growth, but have no effect on production. The glutamic acid effect on the growth was more intense than that of asparagine. Based on the obtained results, a kinetic model describing the growth, CA and CefC production was proposed. The adjustment of the model to the experimental data was made in six different fermentations. The model had a good adjustment to four of all the media tested, and was able to represent the bioprocess within the conditions studied in this work.