Multi-scale modeling of the mechanical behavior of polymer-based materials

Polymers have become the reference material for high reliability and performance applications. In this work, a multi-scale approach is proposed to investigate the mechanical properties of polymeric based material under strain. To achieve a better understanding of phenomena occurring at the smaller scales, a coupling of a Finite Element Method (FEM) and Molecular Dynamics (MD) modeling in an iterative procedure was employed, enabling the prediction of the macroscopic constitutive response. As the mechanical response can be related to the local microstructure, which in turn depends on the nano-scale structure, the previous described multi-scale method computes the stress-strain relationship at every analysis point of the macro-structure by detailed modeling of the underlying micro- and meso-scale deformation phenomena. The proposed multi-scale approach can enable prediction of properties at the macroscale while taking into consideration phenomena that occur at the mesoscale, thus offering an increased potential accuracy compared to traditional methods.

Coupling Mechanical and Electrical Behavior in the Multi-scale Simulation of Polymer-based CNT Nanocomposites

A numeric model has been proposed to investigate the mechanical and electrical properties of a polymeric/carbon nanotube (CNT) composite material subjected to a deformation force. The reinforcing phase affects the behavior of the polymeric matrix and depends on the nanofiber aspect ratio and preferential orientation. The simulations show that the mechanical behavior of a computer generated material (CGM) depends on fiber length and initial orientation in the polymeric matrix. It is also shown how the conductivity of the polymer/CNT composite can be calculated for each time step of applied stress, effectively providing the ability to simulate and predict strain-dependent electrical behavior of CNT nanocomposites.

Measuring fund performance using multi-factor models: evidence for the Portuguese market

This paper examines the performance of Portuguese equity funds investing in the domestic and in the European Union market, using several unconditional and conditional multi-factor models. In terms of overall performance, we find that National funds are neutral performers, while European Union funds under-perform the market significantly. These results do not seem to be a consequence of management fees. Overall, our findings are supportive of the robustness of conditional multi-factor models. In fact, Portuguese equity funds seem to be relatively more exposed to smallcaps and more value-oriented. Also, they present strong evidence of time-varying betas and, in the case of the European Union funds, of time-varying alphas too. Finally, in terms of market timing, our tests suggest that mutual fund managers in our sample do not exhibit any market timing abilities. Nevertheless, we find some evidence of timevarying conditional market timing abilities but only at the individual fund level.

O Papel do Agente de Execução na Fase da Penhora-Determinação dos Bens a Penhorar

A penhora é, no contexto actual de crise económica, uma realidade frequente, sendo o ato executivo por excelência no âmbito das execuções para o pagamento de quantia certa, que consiste na apreensão de bens, num desapossamento de bens do devedor, com vista á satisfação do credito adequando. Previamente á realização á realização deste ato processual, terão de ser determinados os bens que do mesmo serão objecto, devendo ser consideradas as limitações legais e, eventualmente, convencionais. Os poderes de indicação dos bens a penhorar sofreram alterações desde o Código de Processo Civil de 1939 ate ao actualmente em vigor, que tem a redacção do DL nº 226/2008, de 20 de novembro, tendo sido atribuído ao Agente de Execução, com a reforma de 2003, o poder de determinar os bens a penhorar.O objectivo principal desta dissertação é, precisamente determinar qual o papel do Agente de Execução na fase da penhora, em especial na determinação dos bens a penhorar, com analise de todos os aspectos relacionados, e aferir a interpretação e aplicação do regime em vigor por aqueles que lidam diariamente com os processos executivos. Para o efeito, alem da analise teórica da matéria, foi realizado um estudo empírico, mediante a aplicação e tratamento de um inquérito por questionário ministrado a todos os Agentes de Execução a exercer funções nas comarcas abrangidas pelo Conselho Regional do Norte da Câmara dos Solicitadores. Genericamente, no presente estudo, concluímos que apesar da atribuição ao Agente de Execução do poder de determinar quais os bens que ira penhorar, esse poder esta vinculado, designadamente por critérios e imperativos legais. E o Agente de Execução deve, ainda, ter em consideração a vontade manifestada pelo exequente, o que, como resulta do estudo empírico realizado, é, na pratica, frequente. Paralelamente e de forma a garantir a legalidade da penhora determinada pelo gente de Execução, ao juiz de execução é atribuída competência para controlada este seu poder.

Predicting the mechanical behavior of amorphous polymeric materials under strain through multi-scale simulation

Polymeric materials have become the reference material for high reliability and performance applications. However, their performance in service conditions is difficult to predict, due in large part to their inherent complex morphology, which leads to non-linear and anisotropic behavior, highly dependent on the thermomechanical environment under which it is processed. In this work, a multiscale approach is proposed to investigate the mechanical properties of polymeric-based material under strain. To achieve a better understanding of phenomena occurring at the smaller scales, the coupling of a finite element method (FEM) and molecular dynamics (MD) modeling, in an iterative procedure, was employed, enabling the prediction of the macroscopic constitutive response. As the mechanical response can be related to the local microstructure, which in turn depends on the nano-scale structure, this multiscale approach computes the stress-strain relationship at every analysis point of the macro-structure by detailed modeling of the underlying micro- and meso-scale deformation phenomena. The proposed multiscale approach can enable prediction of properties at the macroscale while taking into consideration phenomena that occur at the mesoscale, thus offering an increased potential accuracy compared to traditional methods.

Multi-centre validation of an automatic algorithm for fast 4D myocardial segmentation in cine CMR datasets

Quantitative analysis of cine cardiac magnetic resonance (CMR) images for the assessment of global left ventricular morphology and function remains a routine task in clinical cardiology practice. To date, this process requires user interaction and therefore prolongs the examination (i.e. cost) and introduces observer variability. In this study, we sought to validate the feasibility, accuracy, and time efficiency of a novel framework for automatic quantification of left ventricular global function in a clinical setting.