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An overlay-type rheological model is presented, which is used to introduce viscosity in inviscid elasto-plastic material laws with softening, in order to reduce the mesh-dependency of Finite Element solutions. This model is intended to be an alternative to the well-known visco-plastic formulations of Perzyna and Duvaut-Lions. A time integration algorithm for the visco-elastic model component is presented, being demonstrated in the paper, that it is unconditionally stable and oscillation-free. The algorithm is tested in a problem with slip driven softening (von Mises material) and in a problem with decohesion driven softening (Cam-Clay model). Figures showing the capability of the algorithm to regularize the solution are presented. Copyright © 2004 John Wiley & Sons, Ltd.
In this paper it is intended to verify the capacity of regularization of the numerical solution of an elasto-plastic problem with linear strain softening. The finite element method with a displacement approach is used. Drucker-Prager yield criteria is considered. The radial return method is used for the integration of the elasto-plastic constitutive relations. An elastovisco- plastic scheme is used to regularize the numerical solution. Two constitutive laws have been developed and implemented in a FE-program, the first represent the radial return method applied to Drucker-Prager yield criteria and the second is a time integration procedure for the Maxwell visco-elastic model. Attention is paid to finite deformations. An associative plastic flow is considered in the Drucker-Prager elasto-plastic model. The algorithms are tested in two p...
This article presents some applications of time-series procedures to solve two typical problems that arise when analyzing demographic information in developing countries: (1) unavailability of annual time series of population growth rates (PGRs) and their corresponding population time series and (2) inappropriately defined population growth goals in official population programs. These problems are considered as situations that require combining information of population time series. Firstly, we suggest the use of temporal disaggregation techniques to combine census data with vital statistics information in order to estimate annual PGRs. Secondly, we apply multiple restricted forecasting to combine the official targets on future PGRs with the disaggregated series. Then, we propose a mechanism to evaluate the compatibility of the demogra...
4º Congresso de Argamassas de Construção da APFAC. Coimbra, U.Coimbra, APFAC/ITeCons, 29-30 Março 2012
Pseudoxantoma elástico é uma doença genética rara que se caracteriza pela progressiva calcificação e fragmentação das fibras elásticas da pele, retina e sistema cardiovascular. Os pacientes apresentam lesões cutâneas típicas e as manifestações extracutâneas aparecem posteriormente. O diagnóstico baseia-se na clínica, histologia e genética. Os autores apresentam o caso de um rapaz de 8 anos que refere aparecimento de pápulas alaranjadas, confluindo em placas de consistência elástica, de limites imprecisos, inicialmente limitadas à região cervical e estendendo-se posteriormente às regiões axilares. Realizou biopsia de pele que confirmou a suspeita clínica de pseudoxantoma elástico. Efectuou estudo analítico, electrocardiograma, ecocardiograma, eco-Doppler das carótidas e aorto-ilíacas, retinograma e potenciais evocados visuais que foram ...
RESUMO Introdução: A osteogenesis imperfecta (OI) é uma doença genética rara, devida a alterações estruturais ou quantitativas do colagénio tipo 1. A classificação em tipos tem sofrido alterações recentes. O espectro clínico é variado, desde formas ligeiras (OI tipo I) ou moderadas (OI tipo IV-VII), até formas muito graves (OI tipo II-III). Caso Clínico: É apresentado o caso de um recém-nascido do sexo masculino, fruto de uma primeira gestação, mal vigiada, com o diagnóstico de OI, com manifestações pré-natais (encurtamento dos membros inferiores e desmineralização da calote craniana na ecografia das 34 semanas). No exame objetivo, apresentava atividade espontânea diminuída, crânio grande com fontanelas alargadas e comunicantes, calote craniana fina e depressível, facies peculiar com nariz em sela, palato em ogiva, escleróticas brancas...
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