Modelação da furação de laminados por elementos finitos

Furação de estruturas em compósitos de matriz poliméricaO recurso ao Método de Elementos Finitos (MEF) para a simulação e estudo da maquinagem tem vindo a merecer um interesse crescente. Neste trabalho comparam-se os resultados experimentais obtidos usando diferentes brocas helicoidais com uma simulação numérica da furação usando elementos sólidos tridimensionais do software ABAQUS® Explicit. Os resultados obtidos mostram a aplicabilidade do modelo, nomeadamente no que respeita à variação do principal parâmetro de corte no processo de furação – o avanço – e da geometria da ferramenta. O desenvolvimento das forças axiais durante a furação está directamente relacionado com a selecção dos parâmetros de corte e geometria de ferramenta e contribui para a existência de danos na placa. Assim, a minimização destas forças permite reduzir o risco de delaminação. Os resultados relativos à força para o início da delaminação são comparados com modelos analíticos já conhecidos. Os resultados numéricos apresentam uma concordância apreciável com os obtidos experimentalmente

Direct estimations of linear and non-linear functionals of a quantum state

We present a simple quantum network, based on the controlled-SWAP gate, that can extract certain properties of quantum states without recourse to quantum tomography. It can be used used as a basic building block for direct quantum estimations of both linear and non-linear functionals of any density operator. The network has many potential applications ranging from purity tests and eigenvalue estimations to direct characterization of some properties of quantum channels. Experimental realizations of the proposed network are within the reach of quantum technology that is currently being developed.Comment: This paper supersedes the paper quant-ph/0112073, titled "Universal Quantum Estimator". We emphasise the estimation of linear and non-linear functionals of a quantum stat

Fracture toughness determination of adhesive and co-cured joints in natural fibre composites

Adhesive bonding has become more efficient in the last few decades due to the adhesives developments, granting higher strength and ductility. On the other hand, natural fibre composites have recently gained interest due to the low cost and density. It is therefore essential to predict the fracture behavior of joints between these materials, to assess the feasibility of joining or repairing with adhesives. In this work, the tensile fracture toughness (Gc n) of adhesive joints between natural fibre composites is studied, by bonding with a ductile adhesive and co-curing. Conventional methods to obtain Gc n are used for the co-cured specimens, while for the adhesive within the bonded joint, the J-integral is considered. For the J-integral calculation, an optical measurement method is developed for the evaluation of the crack tip opening and adherends rotation at the crack tip during the test, supported by a Matlab sub-routine for the automated extraction of these quantities. As output of this work, an optical method that allows an easier and quicker extraction of the parameters to obtain Gc n than the available methods is proposed (by the J-integral technique), and the fracture behaviour in tension of bonded and co-cured joints in jute-reinforced natural fibre composites is also provided for the subsequent strength prediction. Additionally, for the adhesively- bonded joints, the tensile cohesive law of the adhesive is derived by the direct method

Modelação por elementos finitos do processo de furação em laminados de carbono/epóxido

Neste trabalho apresentam-se os resultados obtidos em simulações numéricas dafuração de laminados de carbono/epóxido usando elementos sólidos tridimensionais dosoftware ABAQUS® Explicit. O início e propagação do dano são simulados recorrendo ainstruções específicas do programa, bem como a remoção dos elementos ao longo doprocesso. Os resultados obtidos numericamente são comparados com resultadosexperimentais obtidos previamente pelos autores. Verifica-se uma boa concordância entre osresultados numéricos e os experimentais, confirmando a validade do modelo proposto

Fast 3D reconstruction of the spine by non-expert users using a statistical articulated model

Three-dimensional spine reconstruction methods currently used to study scoliosis require manual identification of several anatomical features, which is time-consuming, costly and error-prone

Microtiming patterns and interactions with musical properties in Samba music

In this study, we focus on the interaction between microtiming patterns and several musical properties: intensity, meter and spectral characteristics. The data-set of 106 musical audio excerpts is processed by means of an auditory model and then divided into several spectral regions and metric levels. The resulting segments are described in terms of their musical properties, over which patterns of peak positions and their intensities are sought. A clustering algorithm is used to systematize the process of pattern detection. The results confirm previously reported anticipations of the third and fourth semiquavers in a beat. We also argue that these patterns of microtiming deviations interact with different profiles of intensities that change according to the metrical structure and spectral characteristics. In particular, we suggest two new findings: (i) a small delay of microtiming positions at the lower end of the spectrum on the first semiquaver of each beat and (ii) systematic forms of accelerando and ritardando at a microtiming level covering two-beat and four-beat phrases. The results demonstrate the importance of multidimensional interactions with timing aspects of music. However, more research is needed in order to find proper representations for rhythm and microtiming aspects in such contexts

SORPTION OF S-TRIAZINES IN BRAZILIAN RAINFOREST SOILS

This research was conducted to evaluate the sorption of Ametryn, Atrazine, Simazine, Prometrine and Metamitron to soils from "Mata Atlântica" at Ubatuba region (Atlantic rainforest soils), employing the batch equilibrium approach. The herbicides were weakly retained in soils with low soil organic matter (SOM) content and thus presenting high potential to water contamination. All herbicides have shown high Koc at Typic Humaquepts soil, the higher in SOM content. The sorption isotherms for the herbicides at Typic Humaquepts soil suggested specific interactions between herbicides and SOM probably with partial protonation of herbicides followed by ion-exchange processes and/or hydrogen bonding formation of hydroxyl groups on the SOM surface.Esta pesquisa foi conduzida para avaliar a sorção de ametrina, atrazina, simazina, prometrina e metamitron em solos de Mata Atlântica na região de Ubatuba, empregando-se o método em batelada. Os herbicidas foram fracamente retidos em solos com baixo teor de matéria orgânica (MO) e, portanto, apresentaram elevado potencial de contaminação da água. Todos os herbicidas mostraram alto valor de Koc em solos da classe Gleissolo Melânico Distrófico, que contém o teor mais elevado de MO. As isotermas de sorção dos herbicidas no Gleissolo Melânico Distrófico sugerem interações específicas entre os herbicidas e a MO, provavelmente com protonação parcial dos herbicidas seguida por processos de troca-iônica e/ou formação de pontes de hidrogênio dos grupos hidroxila sobre a superfície da MO