Federal University of Ouro Preto

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Ouro Preto, Brazil

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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.


Cariglia M.,Federal University of Ouro Preto
Annals of Physics | Year: 2015

We describe natural Hamiltonian systems using projective geometry. The null lift procedure endows the tangent bundle with a projective structure where the null Hamiltonian is identified with a projective conic and induces a Weyl geometry. Projective transformations generate a set of known and new dualities between Hamiltonian systems, as for example the phenomenon of coupling-constant metamorphosis. We conclude outlining how this construction can be extended to the quantum case for Eisenhart-Duval lifts. © 2015 Elsevier Inc.


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.


Gomes C.J.S.,Federal University of Ouro Preto
Journal of Structural Geology | Year: 2013

To broaden the availability of granular materials that are suitable for the analog modeling of upper crustal deformation, we investigated the mechanical behaviors of pure quartz sand and two sand mixtures (quartz sand-powdered barite and quartz sand mica crystals) using ring-shear tests and simple convergent sandbox experiments. The ring-shear test results indicate that the three materials have similar peak friction angles (between 39.25° and 36.02°), but the magnitude of the shear strain and the shear strength required to cause their failure are different. The differences between the analog models are identified by distinct fault kinematics and different grain flows, which are primarily related to differences in the plastic elasto-frictional rheology. We conclude that the use of the quartz-mica mixture, which showed the strongest distributed (plastic) deformation, can improve analog models where different materials are required to simulate crystalline basement (sand) and supracrustal rocks (sand mica mixture). This is a common situation in extension and inversion tectonics, such as, for example, in inversion tectonics, when a granitic basement block acts as a buttress. © 2012 Elsevier Ltd.


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.


The present invention relates to the development of two types of polymer nanocapsules to encapsulate cloxacillin benzathine, an antimicrobial drug. More specifically, this invention relates to a new form of treatment for mastitis in dairy cattle. Two nanocapsule formulations have been developed and can be used to encapsulate various drugs, besides cloxacillin benzathine, providing a new therapy for mastitis in cows, avoiding the inconvenience of the use of high doses of drugs used in conventional formulations, thus contributing to an improvement in milk quality.


The present invention relates to the development of two types of polymer nanocapsules to encapsulate cloxacillin benzathine, an antimicrobial drug. More specifically, this invention relates to a new form of treatment for mastitis in dairy cattle. Two nanocapsule formulations have been developed and can be used to encapsulate various drugs, besides cloxacillin benzathine, providing a new therapy for mastitis in cows, avoiding the inconvenience of the use of high doses of drugs used in conventional formualtions, thus contributing to an improvement in milk quality.


News Article | February 22, 2017
Site: www.eurekalert.org

Dive bombing a much larger bird isn't just a courageous act by often smaller bird species to keep predators at bay. It also gives male birds the chance to show off their physical qualities in order to impress females. This is according to a study in Springer's journal Behavioral Ecology and Sociobiology on predator mobbing behavior of birds where potential prey approach and harass would-be predators such as owls. The study was led by Filipe Cunha of the University of Zurich in Switzerland and the Federal University of Ouro Preto in Brazil. In birds, mobbing behavior includes calls, aerial swoops and even physical attacks. For a long time, researchers believed that this behavior mainly served as protection against predators, since most predators move away in response to mobbing. As an added bonus, mobbing might give males the chance to advertise who has the best physical qualities, in an effort to impress potential mating partners. To investigate this further, Cunha and his fellow researchers studied what happened when replicas of two types of owls of similar size were presented to a bird community in south-eastern Brazil. The models were of a pygmy owl that regularly eats birds, and of a less threatening burrowing owl. The researchers measured the size of the mob that then assembled, the intensity by which individual members participated in the mock attacks, and whether things changed if females from the same species were present. While 79 different bird species were seen to mob the models, data from only 19 sexually dimorphic species were included in the current study. In these species, males and females are easily distinguished from one another in the field. These experiments showed that the mobbing was more intense when the less-threatening burrowing owl model was put out. This is in line with other findings that birds know whether there is a high or low risk associated with certain predators or behavior. In most cases, the mobs were made up of males. The group size did not influence the intensity by which males participated in these anti-predatory activities. Males in the 19 species were, however, definitely more likely to up their game when more females from their own species were around. Cunha explains, "Females may use these mobbing events to assess a male's quality, for example their motor skills which allow them to escape from an attacking predator. This characteristic may provide clues about how well a male will be able to defend a nest or to forage." The findings highlight the importance of sexual selection and help to better understand the evolution of anti-predatory behavior. Moreover, they show that mobbing not only has a predator deterrence function. "Recent studies showed that predator mobbing has other important social functions, such as to teach younger birds to distinguish friend from foe," says Michael Griesser, co-author of the study. Reference: Cunha, F.C.R. et al. (2017). The presence of conspecific females influences male-mobbing behavior, Behavioral Ecology and Sociobiology. DOI 10.1007/s00265-017-2267-7


News Article | February 22, 2017
Site: phys.org

Dive bombing a much larger bird isn't just a courageous act by often smaller bird species to keep predators at bay. It also gives male birds the chance to show off their physical qualities in order to impress females. This is according to a study in Springer's journal Behavioral Ecology and Sociobiology on predator mobbing behavior of birds where potential prey approach and harass would-be predators such as owls. The study was led by Filipe Cunha of the University of Zurich in Switzerland and the Federal University of Ouro Preto in Brazil. In birds, mobbing behavior includes calls, aerial swoops and even physical attacks. For a long time, researchers believed that this behavior mainly served as protection against predators, since most predators move away in response to mobbing. As an added bonus, mobbing might give males the chance to advertise who has the best physical qualities, in an effort to impress potential mating partners. To investigate this further, Cunha and his fellow researchers studied what happened when replicas of two types of owls of similar size were presented to a bird community in south-eastern Brazil. The models were of a pygmy owl that regularly eats birds, and of a less threatening burrowing owl. The researchers measured the size of the mob that then assembled, the intensity by which individual members participated in the mock attacks, and whether things changed if females from the same species were present. While 79 different bird species were seen to mob the models, data from only 19 sexually dimorphic species were included in the current study. In these species, males and females are easily distinguished from one another in the field. These experiments showed that the mobbing was more intense when the less-threatening burrowing owl model was put out. This is in line with other findings that birds know whether there is a high or low risk associated with certain predators or behavior. In most cases, the mobs were made up of males. The group size did not influence the intensity by which males participated in these anti-predatory activities. Males in the 19 species were, however, definitely more likely to up their game when more females from their own species were around. Cunha explains, "Females may use these mobbing events to assess a male's quality, for example their motor skills which allow them to escape from an attacking predator. This characteristic may provide clues about how well a male will be able to defend a nest or to forage." The findings highlight the importance of sexual selection and help to better understand the evolution of anti-predatory behavior. Moreover, they show that mobbing not only has a predator deterrence function. "Recent studies showed that predator mobbing has other important social functions, such as to teach younger birds to distinguish friend from foe," says Michael Griesser, co-author of the study. Explore further: Eat, escape, love: the price of looking sexy More information: Filipe Cristovão Ribeiro da Cunha et al, The presence of conspecific females influences male-mobbing behavior, Behavioral Ecology and Sociobiology (2017). DOI: 10.1007/s00265-017-2267-7

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