http://repositorio.ufc.br/handle/riufc/16297 2026-04-18T00:21:48Z 2026-04-18T00:21:48Z Sousa, Laise Lima de Carvalho Oliveira, Suzana Matos França de Vidal, Creto Augusto Cavalcante Neto, Joaquim Bento http://repositorio.ufc.br/handle/riufc/48390 2019-12-11T19:33:58Z 2019-01-01T00:00:00Z

Título: A one-dimensional least-square-consistent displacement-based meshless local Petrov-Galerkin method Autor(es): Sousa, Laise Lima de Carvalho; Oliveira, Suzana Matos França de; Vidal, Creto Augusto; Cavalcante Neto, Joaquim Bento Abstract: In recent years, the Meshless Local Petrov-Galerkin (MLPG) Method has attracted the attention of many researchers in solving several types of boundary value problems. This method is based on a local weak form, evaluated in local subdomains and does not require any mesh, either in the construction of the test and shape functions or in the integration process. However, the shape functions used in MLPG have complicated forms, which makes their computation and their derivative’s computation costly. In this work, using the Moving Least Square (MLS) Method, we dissociate the point where the approximating polynomial’s coefficients are optimized, from the points where its derivatives are computed. We argue that this approach not only is consistent with the underlying approximation hypothesis, but also makes computation of derivatives simpler. We apply our approach to a two-point boundary value problem, and perform several tests to support our claim. The results show that the proposed model is efficient, achieves good precision, and is attractive to be applied to other higher-dimension problems. Tipo: Relatório

2019-01-01T00:00:00Z Rocha, Geriane Macedo Gonçalves, Gisele Maria Campos Ramos, Kennedy da Silva Cota, Tiany Guedes Lima, Rosa Malena Fernandes http://repositorio.ufc.br/handle/riufc/45369 2021-05-14T11:58:54Z 2019-01-01T00:00:00Z

Título: Caracterização física, química e mineralógica de uma amostra de minério de ferro de brucutu Autor(es): Rocha, Geriane Macedo; Gonçalves, Gisele Maria Campos; Ramos, Kennedy da Silva; Cota, Tiany Guedes; Lima, Rosa Malena Fernandes Abstract: The characterization of an ore allows the predictability of its behavior in relation to the concentration methods. Only size and chemical analyses are not always sufficient, and the recognition of mineral species, their proportions, grain form, and liberability are also fundamental. In this work the physical, chemical and mineralogical characteristics of an iron ore from Brucutu mine in Quadrilátero Ferrífero is presented. Particle size analyses were carried out by sieve and laser granulometer, chemistry by X-ray fluorescence and mineralogical by optical microscopy and X-ray diffraction. Based on the results obtained, the ore was classified as friable, with an overall Fe content of 42.9% and SiO2 of 36.1%. The iron minerals identified were hematite and goethite, and the main gangue mineral was quartz. In the fraction +1.0 mm the quartz occurs mainly in mixed particles with the hematite and goethite grains. Below this size, the same occurs as free particles. Above 0.15 mm the hematite is predominantly porous, and below 0.15 mm granular. Goethite is associated with granular hematite in all size distribution.Keywords: Characterization; Iron ore; Mineral processing. Tipo: Artigo de Periódico

2019-01-01T00:00:00Z Lima, Sandro V. Oliveira, Helinando Melo, Celso http://repositorio.ufc.br/handle/riufc/45358 2022-04-29T19:51:42Z 2016-11-07T00:00:00Z

Título: Monitoramento de impedância elétrica de desdobramento de proteínas Autor(es): Lima, Sandro V.; Oliveira, Helinando; Melo, Celso Abstract: We have applied electrical impedance spectroscopy (EIS) to investigate how the dielectric characteristics of protein aqueous solutions respond to varying amounts of a co-dissolved surfactant. Using bovine serum albumin (BSA) as our model system, we followed the conformational changes of the protein molecules that result from the progressive increment in the concentration of either ionic (sodium dodecyl sulfate – SDS, and dodecyltrimethylammonium bromide – DTAB) or non-ionic (Triton X-100) surfactants, and modeled the corresponding electrical response through a modified Randles circuit. From the dielectric data, we selected the behavior of the passive layer resistance (RPL) as a convenient parameter to map the conformational changes in the BSA molecules. The profile of the dielectric response of the BSA–surfactant solutions as a function of the amount of the added surfactant allows the identification of different ranges of the detergent relative concentration that can be associated to each one of the successive regimes of the surfactant–protein interaction. These results were similar to those obtained from a standard Stern–Volmer analysis of the fluorescence emission of the protein chain, with a better agreement occurring in the case of the non-ionic surfactant. We propose this novel EIS approach as a convenient alternative methodology to follow conformational changes of weakly fluorescent proteins. Tipo: Artigo de Periódico

2016-11-07T00:00:00Z Ramos, Kennedy da Silva http://repositorio.ufc.br/handle/riufc/45002 2019-08-21T20:43:04Z 2018-01-01T00:00:00Z

Título: Flotação de metafosforito silicatado de Lagamar/MG Autor(es): Ramos, Kennedy da Silva Abstract: The concentration via froth flotation of the metaphosphorite ore, mined at Lagamar/MG, requires careful studies considering that it consists of a complex material from the bottom of the pit. The present bench scale flotation study aimed at investigating the effects of reagents (depressant/dispersant, collector and booster) and pH capable to adequate the concentrate to the targets of P2O5 26% grade and 80% recovery. As preliminary steps, the ore was characterized and dispersion degree determinations were conducted. The P2O5 bearing mineral is fluorapatite and the silicatic gangue contains predominantly quartz, kaolinite, and mica. The natural slimes fraction, material passing 0,038 mm, represents 49% in weight. The silicates are finely disseminated in the apatite grains impairing the concentration due to the lack of liberation. The isoelectric point of the fluorapatite was determined at pH = 2.27. The dispersion degrees of quartz and apatite were low in the presence of sodium metasilicate and sodium tripolyphosphate. In the exploratory step, consisting of rougher flotation at pH = 9, reagents used in direct flotation were sodium oleate as collector and sodium metasilicate as depressant and those employed in reverse flotation were dodecyl amine chloride as collector and sodium tripolyphosphate as depressant, soluble starch and sodium carbonate as depressants. The affinity of the sodium oleate collector with apatite was satisfactory and dodecylamine chloride was selective regarding silicates but the required dosage was high. Concerning the reverse flotation, the decreasing sequence of apatite depression was achieved with sodium carbonate, starch, and sodium tripoliphosphate. Nevertheless, the last acted as gangue depressant, negatively affecting the concentrate grade and recovery. The next stages were planned according to the factorial design of experiments method: (1st) direct flotation (collector sodium oleate, depressant sodium metasilicate); (2nd) direct flotation (same reagents of 1st stage plus booster: emulsion of fuel oil and ethoxylated nonyilphenol); (3rd) reverse flotation (collector dodecylamine chloride, depressant sodium tripolyphosphate); (4th) reverse flotation same reagents of (3rd) stage plus booster: emulsion of fuel oil and ethoxylated nonyilphenol). The performance of the sodium oleate collector used in the rougher flotation was better than that of the dodecylamine chloride employed in the cleaner flotation. The target parameters for the concentrate were achieved with sodium metasilicate as depressant. On the other hand, results obtained with sodium tripolyphosphate were not satisfactory. The emulsion was effective only when added in conjunction with sodium oleate, condition under which the target parameters for the concentrate were achieved and leading to decrease in collector consumption. Tipo: Dissertação

2018-01-01T00:00:00Z