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7 Janeiro 2020, 12:37 - Jorge Manuel Fontes Coelho

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Seminário

Prof. Jose Herskovits Norman


OptimizE - Engineering Optimization Lab 

Mechanical Engineering Program

COPPE

Federal University of Rio de Janeiro


12 de Fevereiro de 2020, 11:00, Sala de Reuniões DEM


A Feasible Direction Interior Point Method for Generalized Nash Equilibrium Problem


José Herskovits (COPPE/UFRJ), Carolina Effio (COPPE/UFRJ)

Jean Roche (Universite de Lorraine, France)


ABSTRACT

We present a new feasible direction interior-point algorithm for the calculation of the normalized solution of the Generalized Nash Equilibrium Problem (GNEP), with shared constraints. The GNEP is a game where each player is associated with an optimization problem, constrained or not, such that the objective function and the feasible set of each player depend on their own variables as well as of the strategies of the other players. The numerical method presented in this paper is a feasible direction Newton-type method employed to solve the concatenated Karush-Kuhn-Tucker (KKT) conditions. Given an initial point at the interior of the feasible region for each player, the present algorithm generates a feasible sequence converging to the normalized solution of the GNEP. This sequence is descent with respect to a potential function for each player. We prove the global convergence of the algorithm. The presented approach was already employed on a collection of test problems and the results suggest that our method is strong and efficient.

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No dia 19 de Fevereiro, às 13:30, na anfiteatro FA1, terá lugar a conclusão da apresentação dos resultados da sessão de brainstorming que decorreu no dia do DEM.

No dia 4 de Março, à mesma hora e no mesmo local, o Prof. Jão Miguel Sousa irá apresentar um seminário intitulado "Intelligent Systems in Mechanical Engineering"

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Informamos que o Prof. Mário Costa foi nomeado Fellow do Instituto de Combustão (The Combustion Institute). 

O DEM felicita o Prof. Mário Costa por esta distinção, que atesta a qualidade científica do trabalho por ele desenvolvido nesta área.

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O Prof. João Melo Sousa foi nomeado representante nacional no Scientific Advisory Committee do von Kármán Institute for Fluid Dynamics, no quadro da participação nacional nas actividades da NATO-STO. 

O DEM felicita o Prof. João Melo Sousa pela nomeação para este prestigiante cargo.

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O próximo seminário do DEM terá  lugar na 4ª feira, 15 de janeiro, às 13:30, no anfiteatro VA5. Este seminário é organizado em conjunto com o IDMEC.

Orador: Prof. Nuno Silvestre

Título "GRAPHENE_ING: Cracking, Buckling, Wrinkling".

Resumo: Graphene is a planar nanomaterial under current and intensive research because of its excellent mechanical, thermal, optical and electrical properties. The use of graphene in nanocomposites and technological nano-devices makes it always loaded under a given stress state, either tensile or compressive. In case of tension, the hexagonal latticed structure of graphene gets extremely stiff but the breakage of the first C-C atomic bond leads to the onset of crack and its evolution, which depends on the tensile loading direction (either armchair or zigzag). Despite being extremely stiff in its plane, the atomic structure of graphene sheets is very prone to out-of-plane deformations, which may occur when the sheet is being compressed. Buckling phenomena of graphene sheets also decreases their load carrying capacity and may limit their application in some technological nano-devices. However, it is also seen that the capacity of graphene sheets to sustain compressive loads depends much on the loading direction (either armchair or zigzag). Sometimes, because of their low out-of-plane stiffness, graphene sheets are attached to elastic substrates in order to increase their stiffness. However, the sheet may also wrinkle if the substrate shortens. This wrinkling phenomenon, which induces the formation of many wrinkles, may also affect the intended purpose of the graphene sheet. The main objective of this lecture is to show how these three types of failure (cracking, buckling, wrinkling) affect the mechanical behaviour of graphene, namely its anisotropy, nonlinearity, stiffness, strength and toughness. For this purpose, molecular dynamics models were developed and controlled simulations were carried out. Some remarkable differences between the behaviour of graphene at nanoscale and their continuum counterparts (at macroscale) are highlighted. Finally, some relevant conclusions about the graphene anisotropy and nonlinearity are also drawn.