Transfer function-noise modeling and spatial interpolation to evaluate the risk of extreme (shallow) water-table levels in the Brazilian Cerrados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Analysis of the effects of damping in the models validation

The search for better performance in the structural systems has been taken to more refined models, involving the analysis of a growing number of details, which should be correctly formulated aiming at defining a representative model of the real system. Representative models demand a great detailing of the project and search for new techniques of evaluation and analysis. Model updating is one of this technologies, it can be used to improve the predictive capabilities of computer-based models. This paper presents a FRF-based finite element model updating procedure whose the updating variables are physical parameters of the model. It includes the damping effects in the updating procedure assuming proportional and non proportional damping mechanism. The updating parameters are defined at an element level or macro regions of the model. So, the parameters are adjusted locally, facilitating the physical interpretation of the adjusting of the model. Different tests for simulated and experimental data are discussed aiming at evaluating the characteristics and potentialities of the methodology.

Effects of two chronic stress models on ligature-induced periodontitis in Wistar rats

Objectives: The present study aims at comparing the effects of physical and variable chronic stress on ligature-induced periodontitis in rats.Design: Forty-eight adult Wistar rats were randomly assigned to four groups (n = 12): physical stress, variable stress, positive control and negative control. The models of physical stress were immobilization and immobilization associated with exposure to cold. The models of variable stress were exposure to intermittent light, 24 h isolation, oral cavity examination, crowded environment, smell of blood and noise. After 10 days of physical or variable stress animals underwent experimental induction of periodontal disease in one oral side. Positive control also underwent experimental induction of periodontal disease on the 10th day. Negative control did not receive any type of intervention. At the end of the experimental period (60 days), all animals were euthanized. After routine laboratory processing, images of the histological sections were digitised and submitted to histometric measurement using two parameters: histologic attachment loss and bone loss.Results: Histological attachment loss and bone loss were greater (p < 0.05) in the physical stress group than in the other groups (variable stress, positive and negative control groups). on the non-periodontitis side, these same histological parameters did not significantly differ amongst groups.Conclusions: Physical stress negatively modulated the response pattern to experimentally induced periodontitis in rats. (C) 2011 Elsevier Ltd. All rights reserved.

Numerical study of the Ginzburg-Landau-Langevin equation: coherent structures and noise perturbation theory

Pós-graduação em Física - IFT

Dynamic analysis for different finite element models of beams with viscoelastic damping layer

Many new viscoelastic materials have been developed recently to help improve noise and vibration levels in mechanical structures for applications in automobile and aeronautical industry. The viscoelastic layer treatment applied to solid metal structures modifies two main properties which are related to the mass distribution and the damping mechanism. The other property controlling the dynamics of a mechanical system is the stiffness that does not change much with the viscoelastic material. The model of such system is usually complex, because the viscoelastic material can exhibit nonlinear behavior, in contrast with the many available tools for linear dynamics. In this work, the dynamic behavior of sandwich beam is modeled by finite element method using different element types which are then compared with experimental results developed in the laboratory for various beams with different viscoelastic layer materials. The finite element model is them updated to help understand the effects in the damping for various natural frequencies and the trade-off between attenuation and the mass add to the structure.