Percorrer por autor "Silva, Tiago"
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- Adaptive empirical distributions in the framework of inverse problemsPublication . Silva, Tiago; Loja, Amélia; Carvalho, Alda; Maia, Nuno. M.; Barbosa, JoaquimThis article presents an innovative framework regarding an inverse problem. One presents the extension of a global optimization algorithm to estimate not only an optimal set of modeling parameters, but also their optimal distributions. Regarding its characteristics, differential evolution algorithm is used to demonstrate this extension, although other population-based algorithms may be considered. The adaptive empirical distributions algorithm is here introduced for the same purpose. Both schemes rely on the minimization of the dissimilarity between the empirical cumulative distribution functions of two data sets, using a goodness-of-fit test to evaluate their resemblance.
- Assessing the influence of material and geometrical uncertainty on the mechanical behavior of functionally graded material platesPublication . Carvalho, Alda; Silva, Tiago; Loja, Amélia; Damásio, Fábio RaimundoComposite materials possessing a functional gradient are becoming strong candidates to enhance the performance of structures when severe operating conditions are a reality. These types of conditions may, for example, range from situations where a high thermal gradient is present to others where it is imperative to minimize abrupt stresses transitions between material interfaces. The manufacturing achievement of the gradients determined for a specific application may in practice face some limitations, which can be due, among other factors, to technological process constraints, eventual operating condition deterioration of production stages, or to nonconforming raw materials. Regardless of the origin of such limitations, the reality is that the uncertainty is always present to some extent; this is clearly reflected in the scattering of material and geometrical properties of these composites. The understanding that deterministic analyses are not enough to provide a complete prediction of the composite structures’ behavior emphasizes the crucial need to identify the effects that the variability in material and geometrical parameters will produce in the structural response.With the presentwork, one intends to study the influence of this variability in the static and free vibrations behavior of functionally graded plates. It is also an objective of this study to use regression models to predict these responses and to characterize the contribution of each model parameter to the explanation of the response variability. To this purpose, a set of numerical results is presented and discussed.
- Thickness profile of the ganglion cell complex and choroid in patients with persistent diabetic macular edemaPublication . Condelipes, Ana; Correia, Daniela; Fernandes, Inês; Silva, Tiago; Correia, Eduardo; Pereira, Bruno; Camacho, PedroPurpose: Approximately 40% of patients with diabetic macular edema (DME) do not respond optimally to first-line treatment with intravitreal injections of anti-vascular endothelial growth factor (VEGF). Evidence suggests that additional vascular and neurodegenerative mechanisms may be involved. This study aimed to characterise the thickness of the Ganglion Cell Complex (GCC) and investigate the Choroidal Vascularity Index (CVI) in patients with different patterns of therapeutic response to AVEGF DME. Methods: This cross-sectional study included 27 diabetic patients divided into three groups based on their response to AVEGF therapy: a control group, a responder DME group, and a persistent DME group. The study's approach to vascular and neurodegenerative imaging biomarkers involved three steps: (1) Automatic quantification of GCC thickness, with manual correction when necessary; (2) Semi-automatic measurement of choroidal thickness; and (3) Analysis of choroidal area and choroidal luminal area using ImageJ software to calculate the CVI. Results: In the overall characterization of the sample, a significant difference was observed only in the Best Corrected Visual Acuity (BCVA). There was a significant difference in Average Retinal Thickness (1 mm, 3 mm, and 6 mm) between the 3 groups and in GCC thickness at 1 mm. BCVA was negatively correlated with mean retinal thickness, while CVI showed a potential positive correlation with BCVA. Conclusions: While demographic and general clinical characteristics showed minimal differences across the groups, important differences in GCC and choroidal characteristics were observed. GCC (1 mm) may be interesting to explore in predicting visual outcomes after treatment, and CVI may impact visual gain.