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Hermano C.L.,Federal University of Campina Grande | Lima A.M.N.,Federal University of Campina Grande | Almeida L.A.L.,Federal University of ABC | Ferreira C.L.,Instituto Militar Of Engineering Ime | Neff H.,Federal University of Campina Grande
Conference Record - IEEE Instrumentation and Measurement Technology Conference | Year: 2014

The pronounced variation of the optical reflectance R of nanometer thin VO2 films with temperature T at the phase transition recently has triggered interest in the development of compact thermo-optical sensors that utilize optical fiber technology. Its immunity against electromagnetic interference effects makes this approach suited for an optical detection of local areas with increased temperature, i.e. so called hot spots, inside of high power transformers. Optical reflectance of thin VO2-films as function of T throughout the hysteretic phase transition is reported in this work. A modified version of the Preisach hysteresis model is utilized, and combined with experimental optical data. Suited VO2 film thickness values and wavelengths range for optimum sensor operation can be extracted. The achievable temperature range, as confirmed by experimental observations, is consistent with requirements that apply for power transformers of the first group, according to NBR 5416 (ABNT). © 2014 IEEE. Source

De Moraes I.G.,Federal University of Minas Gerais | Silva A.O.,Federal University of Minas Gerais | Martinez M.A.G.,Federal University of Minas Gerais | Giraldi M.T.M.R.,Instituto Militar Of Engineering Ime
Progress in Electromagnetics Research Symposium | Year: 2015

Nonorthogonal coupled mode theory is used to analyze the impact of iron nano-inclusion in the TE mode coupling between two integrated optical waveguides structures. In the first case, the nano-inclusion fractions are included in an identical manner in both waveguides, and in the second the nano-inclusion are added only in one of the waveguides. The structures beating lengths strongly depends on the inclusion filling factor and the thickness of the cladding layer. They reduce with increasing inclusion-filling factors, reaching a 70% and a 56% reduction with respect to the lossless case, for the identical and non-identical cases, respectively. Cladding thickness increases the beating length reducing the structure total power as filling factor increases, for the identical case, and depicting a inflection point for the non-identical case where the total power increases. Source

Rangel I.R.,Federal University of Fluminense | Rangel I.R.,Instituto Militar Of Engineering Ime | Thompson R.L.,Federal University of Fluminense | Pereira R.G.,Federal University of Fluminense | De Abreu F.L.B.,National Institute of Metrology of Brazil
Journal of the Brazilian Society of Mechanical Sciences and Engineering | Year: 2012

Enhanced oil recovery methods are becoming an important source of oil production of wells that have already been explored and, by these methods, of increase of the total volume of oil extracted. An important example is the injection of polymeric solutions after the injected water has reached the breakthrough point. In the present work an experimental apparatus was built in order to test the ability of enhanced oil recovery of polymeric solutions, composed by Xanthan Gum (XG) dissolved in distilled water. This apparatus consists of an idealized porous media made with small spheres inserted in a cylindrical cell and then filled with oil with the same viscosity as the petroleum found in Campos Basin (Rio de Janeiro, Brazil). As displacing fluid, we tested polymeric solutions of different concentrations of Xanthan Gum and these non-Newtonian fluids were characterized using a rotational rheometer. The resulting characterization has shown that increasing the concentration, not only the level of viscosity, but also the elasticity of the fluid increases. The shear-thinning behavior of the solution can be well captured by a power-law model. For higher concentrations the shear-thinning feature of the Xanthan Gum solution is more pronounced. We conducted an experimental procedure to mimic enhanced oil recovery process by first injecting water until the breakthrough point. Increasing the polymer concentration, the extra amount of oil recovered also increase. Theoretical and heuristic analyses show that in the shear dominated regions, the Xanthan Gum polymeric solutions do not increase pore efficiency, but increase sweep efficiency, while the extensional character of the polymeric solution seems to indicate that in extensional dominated regions the polymeric solutions play an important role on the oil recovery efficiency from both perspectives: pore and sweep efficiencies. Copyright © 2012 by ABCM. Source

Loureiro F.A.M.,Federal University of Rio de Janeiro | De Marins E.S.,Federal University of Rio de Janeiro | Dos Anjos G.D.C.,Federal University of Rio de Janeiro | Rocco A.M.,Federal University of Rio de Janeiro | Pereira R.P.,Instituto Militar Of Engineering Ime
Polimeros | Year: 2014

The optimization of fuel cell materials, particularly polymer membranes, for PEMFC has driven the development of methods and alternatives to achieve systems with more adequate properties to this application. The sulfonation of poly(styrene-co-allyl alcohol) (PSAA), using sulfonating agent:styrene ratios of 2:1, 1:1, 1:2, 1:4, 1:6, 1:8 and 1:10, was previously performed to obtain proton conductive polymer membranes. Most of those membranes exhibited solubility in water with increasing temperature and showed conductivity of approximately 10-5 S cm-1. In order to optimize the PSAA properties, especially decreasing its solubility, semi-IPN (SIPN) membranes are proposed in the present study. These membranes were obtained from the diglycidyl ether of bisphenol A (DGEBA), curing reactions in presence of DDS (4,4-diaminodiphenyl sulfone) and PSAA. Different DGEBA/PSAA weight ratios were employed, varying the PSAA concentration between 9 and 50% and keeping the mass ratio of DGEBA:DDS as 1:1. The samples were characterized by FTIR and by electrochemical impedance spectroscopy. Unperturbed bands of PSAA were observed in the FTIR spectra of membranes, suggesting that chemical integrity of the polymer is maintained during the synthesis. In particular, bands involving C-C stretching (1450 cm-1), C=C (aromatic, ∼ 3030 cm-1) and C-H (2818 and 2928 cm-1) were observed, unchanged after the synthesis. The disappearance or reduction of the intensity of the band at 916 cm-1, attributed to the DGEBA epoxy ring, is evidenced for all samples, indicating the epoxy ring opening and the DGEBA crosslinking. Conductivity of H3PO4 doped membranes increases with temperature, reaching 10-4 S cm-1. Source

Vermelho A.B.,Federal University of Rio de Janeiro | Nogueira de Melo A.C.,Federal University of Rio de Janeiro | Soares R.A.,Federal University of Rio de Janeiro | Alviano D.S.,Federal University of Rio de Janeiro | And 9 more authors.
Open Parasitology Journal | Year: 2010

Peptidases are a group of enzymes which have a catalytic function that is to hydrolyze peptide bonds of proteins. The enzymes that hydrolyze peptide bonds at the amino- or carboxy- terminus are classified as exopeptidases, and those that cleave peptide bonds inside the polypeptide are endopeptidases. Endopeptidases, such as cysteine-, metalo-, serine-and threonine peptidases as well as some exopeptidases, have been characterized in Trypanosoma cruzi. Understanding the pathogenesis of T. cruzi requires the identification of functional properties of those peptidases, as they are implied in virulence, are important for host-parasite interactions and are critical for successful survival in their hosts. Here we examine the main T. cruzi peptidases, focusing on their biological roles, especially concerning the parasite-mammalian host relations. © Vermelho et al. Source

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