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Minas Gerais, Brazil

Santos M.N.,Federal University of Ouro Preto | Rocha P.A.S.,Federal University of Sao Joao del Rei | da Silva A.R.D.,Programa de Pos graduacao em | da Mota Silveira R.A.,Programa de Pos graduacao em
Revista Escola de Minas

In this work, a hybrid finite element that incorporates in its formulation the second-order effect, material yielding and connection flexibility effects are presented to study the behavior of plane steel frames. In fact, it is the classic beam-column finite element that presents, at its ends, pairs of springs arranged in sequence. One of the springs is represented in the mathematical formulation of this element by the parameter Sc, which defines the joint stiffness of the members; the other spring, whose rigidity is simulated by the parameter Ss, evaluates the plastification of the cross section. The element stiffness matrix incorporates these three mentioned nonlinear effects. Therefore, the aim of this work is to investigate the computer efficiency of this hybrid finite element in the isolated and combined simulation of these nonlinear effects. Initially, equilibrium and stability of classic structural problems with high nonlinear behavior and critical points in the equilibrium paths are studied. Semi-rigid structural systems with initial geometric imperfections are also evaluated. Later, the hybrid element is tested in the inelastic analysis of plane steel frames based on refined plastic-hinge method. Through these examples, it was possible to validate and verify the use of the proposed hybrid finite element in the numerical modeling of various nonlinear structural problems in civil engineering. Source

Thome R.G.,Federal University of Minas Gerais | Domingos F.F.T.,Federal University of Minas Gerais | Santos H.B,Federal University of Sao Joao del Rei | Martinelli P.M.,Federal University of Minas Gerais | And 3 more authors.
Tissue and Cell

Aiming to better understand folliculogenesis, this study evaluated cell death and proliferation of ovarian cells, besides cathepsin-D expression in Prochilodus argenteus captured in two sites of the São Francisco River downstream from the Três Marias Dam, Brazil. In the site immediately following the Dam (S1), low levels of dissolved oxygen were registered in the rainy period. The water temperature was higher in the São Francisco River immediately after the confluence with the Abaeté River (S2), regardless of the period. In S1, the ovaries showed smaller oocytes, high caspase-3 enzymatic activity and apoptosis, lower cells in proliferation and GSI, as well as a lesser quantity of cathepsin-D when compared to females captured from S2. Regarding relative frequency of ovarian structures, in the dry period, only oogonia and perinucleolar oocytes were found in fish ovaries from both sites. On the other hand, in the rainy period, the relative frequency of oogonia and perinucleolar oocytes decreased and the vitellogenic oocytes increased in S2. Postovulatory follicles were observed only in S2, whereas atretic follicles occurred at a higher frequency in S1. Our results showed that apoptosis, cell proliferation and cathepsina-D evaluation can be used as biomarkers of environmental impact. © 2011 Elsevier Ltd. Source

Barros J.D.,Programa de Pos graduacao em | De Oliveira Junior J.J.,Federal University of Rio Grande do Norte | Da Silva S.G.,Programa de Pos graduacao em | De Farias R.F.,Campus Universitario
Journal of Microwaves and Optoelectronics

In this work, the electrical signals obtained by application of microwaves in chemical and bone tissues are analyzed and classified using techniques of signal processing and pattern recognition. For this, Wavelet Transform is applied as a method to extract relevant features of signal and KNN is used as a classification technique. The results showed that microwave signals can be analyzed using Wavelet Transform, which can be used to reconstruct the signals with minimal error rate and KNN showed satisfactory results. © 2011 SBMO/SBMag. Source

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