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In dit bachelorverslag wordt de verspreiding van een griepepidemie in Nederland gemodelleerd. Ten eerste worden enkele wiskundige modellen opgesteld, waarbij het ene model een verbetering is van het vorige. Deze modellen leveren beginwaarde problemen op die numeriek worden opgelost. Hierbij wordt gebruik gemaakt van enkele bekende numerieke tijdsintegraties. Vervolgens brengen we de verspreiding van een griepepidemie in Nederland in kaart en aan de hand hiervan wordt nagegaan of de oplossing goed overeenkomt met de realiteit. Tenslotte wordt nog een praktische toepassing bekeken, zoals een manier om een griepepidemie tegen te gaan.
This thesis discusses the use of fast and robust solution methods for advection-dominated advection-diffusion-reaction equations coming from water quality problems. Therefore we look at fluxlimiters by the FCT method in combination with the local-theta approach to increase both the accuracy and the efficiency. The discretized equations (by the FVM method) are solved by means of iterative methods.
O presente artigo vai debruçar‑se sobre a História da Amadora enquanto localidade e a sua evolução sócio demográfica até se tornar cidade, bem como acerca do tipo de população que aí se instalou, principalmente a partir dos anos 50. Apresenta‑se uma história de vida de uma família de um bairro degradado. Caracteriza‑se através de dois testemunhos de Assistentes Sociais da vivência dos cabo‑verdianos noutro bairro degradado. Por último descreve‑se o que deu origem à exclusão social de uma franja da população e uma conclusão sobre o Concelho.
A micromechanical model is presented for predicting the longitudinal tensile strength of polymer matrix composites. The model assumes strength is determined by fibre breaks within a representative volume element (RVE). Its length is equal to the so-called ineffective length, associated with the stress transfer to a broken fibre. An elastic-plastic stress transfer model is used to determine the ineffective length, while fibre strength is described by a Weibull distribution. The longitudinal tensile strength is then obtained by solving numerically an equation for the maximum load supported by the RVE. A closed-form expression was also obtained by neglecting elastic stress transfer and the contribution of broken fibres. The closed-form solution was found to be in very good agreement with the base model. In spite of the high level of uncer...
This paper presents a new approach to the prediction of the layer longitudinal compression strength of continuous fibre polymer matrix composites. It is known that failure is caused by fibre microbuckling and that the initial fibre waviness and the matrix non-linear behaviour play a major role. A previous model compared very well with experimental results, but required a relatively complex numerical solution procedure. In the present model, the compression strength is obtained by solving a fourth-order polynomial equation. Although based on several simplifying assumptions, the model is in good agreement with the numerical model predictions and with experimental data. Further model simplifications lead to a closed-form expression that seems to be valid for carbon and boron fibre composites.
The determination of the lamina longitudinal compression strength remains an unsolved problem. Non-valid failure modes are commonly observed in compression tests of unidirectional specimens. Micromechanical modelling has also proven to be a difficult task. It is believed that failure is initiated by fibre microbuckling, and that non-linear matrix behaviour and fibre misalignments play a major role. The main obstacles are thus the non-linear nature of the phenomenon and the scarcity of material data. Here 2D and 3D Finite Element models are presented. The Finite Element Method can easily deal with non-linear problems. The models are computationally inexpensive and can be easily implemented on a commercial code. A sensitivity analysis was performed using realistic input data. The model predictions are well above the unreliable experi...
A micromechanical model was developed for the prediction of the longitudinal tensile strength of polymer matrix composites. The model considers successive fibre breaks within an infinitely wide Li-long representative volume element (RVE), Li being the so-called ineffective length. An elastic-plastic stress transfer model is used to define Li and fibre strength is described by a Weibull distribution. The composite strength is obtained by solving numerically an equation for the maximum RVE stress. A simplified closed-form solution derived proved to be in very good agreement with the base formulation. Although there is still significant uncertainty over model input data, predictions agreed well with experimental strengths of carbon fibre composites.
A new test was developed for measuring the mixed mode I + III interlaminar fracture toughness. The specimen adopted was an 8-point bending plate (8PBP) with a cross-ply lay-up and a mid-thickness edge pre-delamination at the standard 0/0 interface. Finite element analyses (FEA) showed that a wide range of mode mix ratios can be achieved by varying the load point displacements imposed. However, the need of FEA based experimental data reduction and of a relatively complicated fixture are important drawbacks of test developed. Nevertheless, results for carbon/epoxy laminates showed a realistic evolution of initiation Gc values with the GIII/G mode mix ratio.
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