Sousa Jr. J.B.M.,Federal University of Ouro Preto
Computers and Structures | Year: 2013
Multilayered beams are an association of beams of different materials and cross sections, usually linked together by some mechanical connection. In some cases this connection cannot provide enough stiffness to prevent the displacement between the components, leading to partial interaction or interlayer slip. Most of the work on partially connected composite beams is restricted to the case of two members, but in many practical applications several layers are present. The objective of this paper is to present a new finite element formulation for the numerical analysis of partially connected multilayered composite beams, based on the analytical solution of the differential equations of the problem. The proposed element enables the simulation of multilayered beams according to Euler and Timoshenko beam theories, and generalizes the two-layer case. Numerical examples are presented to assess the precision and robustness of the proposed numerical scheme compared to exact solutions and other FE formulations. © 2013 Elsevier Ltd. All rights reserved.
Rodrigues da Cunha L.,Federal University of Ouro Preto
Gut microbes | Year: 2012
The potential health benefits of probiotic bacteria have led to the isolation of new microbial strains for incorporation into food products. However, newly isolated candidate probiotic organisms do not automatically share the "generally recognized as safe" (GRAS) status of traditional lactic acid bacteria (LAB). Before their introduction into food products, the safety of new isolates has to be evaluated. The objective of this study was to characterize LAB isolates from the stool of a newborn infant, and evaluate their safety and probiotic potential, in vitro. Thirty colonies were identified as Lactobacillus gasseri through sequencing of 16S rDNA. Pulsed Field Gel Electrophoresis using restriction enzymes SmaI and Apa I revealed that 29 of the L. gasseri were nearly identical, however one isolate exhibited a distinctive DNA fingerprint. All 30 L. gasseri were evaluated for resistance to antibiotics, bile tolerance, hemolytic activity and antagonism toward selected pathogens. All 30 strains harbored three plasmids, with one strain that showed strong tolerance to 0.5% of bile and harbored a unique fourth plasmid encoding a putative multidrug resistance transporter protein (LmrB). No hemolytic activity or antagonism, beyond acid inhibition was observed. Three selected strains UFVCC1083, 1091 and 1112 showed strong resistance to simulated small intestinal and gastric juices and adhered in vitro to mucin and two intestinal epithelial cell lines, Caco-2 and HT-29. This study identified and characterized recently isolated L. gasseri strains from faeces of a breast fed infant as potential probiotic candidates for use in the human milk banks in Brazil.
Rocha R.,Federal University of Ouro Preto
Renewable Energy | Year: 2011
This paper presents a sensorless control for a variable speed wind turbine (WT) operating at partial load in order to eliminate the direct measurement of the wind speed. In this proposal, the estimated aerodynamic torque is used to determine the optimal reference of the speed control for maximum energy conversion. The maximization of the efficiency on energy conversion and the minimization of detrimental dynamical loads are control trade-offs considered in the design of an optimal discrete-time feedback LQG/LTR controller for the Wind Energy Conversion System (WECS), which is based on the optimization of a quadratic cost function. The performance of the proposed control when the WT is submitted to a gust or step variation on wind speed is evaluated from computational simulations. It is also presented some proposals for sensorless control of the electrical generator. © 2010 Elsevier Ltd.
Cariglia M.,Federal University of Ouro Preto
Reviews of Modern Physics | Year: 2014
This article reviews the role of hidden symmetries of dynamics in the study of physical systems, from the basic concepts of symmetries in phase space to the forefront of current research. Such symmetries emerge naturally in the description of physical systems as varied as nonrelativistic, relativistic, with or without gravity, classical or quantum, and are related to the existence of conserved quantities of the dynamics and integrability. In recent years their study has grown intensively, due to the discovery of nontrivial examples that apply to different types of theories and different numbers of dimensions. Applications encompass the study of integrable systems such as spinning tops, the Calogero model, systems described by the Lax equation, the physics of higher-dimensional black holes, the Dirac equation, and supergravity with and without fluxes, providing a tool to probe the dynamics of nonlinear systems. © 2014 American Physical Society.
Cariglia M.,Federal University of Ouro Preto
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012
The Eisenhart-Duval lift allows embedding nonrelativistic theories into a Lorentzian geometrical setting. In this paper we study the lift from the point of view of the Dirac equation and its hidden symmetries. We show that dimensional reduction of the Dirac equation for the Eisenhart-Duval metric in general gives rise to the nonrelativistic Lévy-Leblond equation in lower dimension. We study in detail in which specific cases the lower dimensional limit is given by the Dirac equation, with scalar and vector flux, and the relation between lift, reduction, and the hidden symmetries of the Dirac equation. While there is a precise correspondence in the case of the lower dimensional massive Dirac equation with no flux, we find that for generic fluxes it is not possible to lift or reduce all solutions and hidden symmetries. As a by-product of this analysis, we construct new Lorentzian metrics with special tensors by lifting Killing-Yano and closed conformal Killing-Yano tensors and describe the general conformal Killing-Yano tensor of the Eisenhart-Duval lift metrics in terms of lower dimensional forms. Last, we show how, by dimensionally reducing the higher dimensional operators of the massless Dirac equation that are associated with shared hidden symmetries, it is possible to recover hidden symmetry operators for the Dirac equation with flux. © 2012 American Physical Society.