Browsing by Author "Loja, M. A. R."
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- Bat-inspired optimization of multilayered adaptive structuresPublication . Costa, D. M. S.; Loja, M. A. R.Adaptive structures constituted by composites and smart materials is a remarkable engineering combination that join together the already known composites’ advantages and the possibility of actively control the mechanical response of a structure. These versatile structures are able to react and interact with their surrounding environments, continuously, to accomplish specific objectives. In this work, the main objective is to study, model and predict the mechanical behaviour of adaptive structures by programming the finite element method and optimization algorithms based on micro-bats’ echolocation capacity. An integrated symbolic-numerical-graphical package devoted to the analysis of plate/beam-type structures and its meta-heuristic optimization is implemented, with capabilities of simulating active multilayered structures, constituted by a variable number of different material models. Graded mixtures of piezoelectric particles and non-active materials are also modelled along the structures’ length direction. A set of illustrative case studies are performed, for different types of structures and materials and the results obtained are discussed and conclusions are drawn.
- Developments on finite element methods for medical image supported diagnosticsPublication . Almeida, Ana; Barbosa, J. I.; Carvalho, A.; Loja, M. A. R.; Portal, R.; Rodrigues, J. A.; Vieira, LinaVariational image-processing models offer high-quality processing capabilities for imaging. They have been widely developed and used in the last two decades, enriching the fields of mathematics as well as information science. Mathematically, several tools are needed: energy optimization, regularization, partial differential equations, level set functions, and numerical algorithms. For this work we consider a second-order variational model for solving medical image problems. The aim is to obtain as far as possible fine features of the initial image and identify medical pathologies. The approach consists of constructing a regularized functional and to locally analyse the obtained solution. Some parameters selection is performed at the discrete level in the framework of the finite element method. We present several numerical simulations to test the efficiency of the proposed approach.
- Radiotherapy-customized head immobilization masks: from modeling and analysis to 3D printingPublication . Loja, M. A. R.; Craveiro, D. S.; Vieira, Lina; Sousa, Eva; Rodrigues, J. A.; Portal, R. J.Immobilization devices may be a valuable aid to ensure the improved effectiveness of radiotherapy treatments were constraining the movements of specific anatomical segments is crucial. This need is also present in other situations, specifically when the superposition of various medical images is required for fine identification and characterization of some pathologies. Because of their structural characteristics, existing head immobilization systems may be claustrophobic and very uncomfortable for patients, during both the modeling and usage stages. Because of this, it is important to minimize all the discomforts related to the mask to alleviate patients’ distress and to simultaneously guarantee and maximize the restraint effectiveness of the mask. In the present work, various head immobilization mask models are proposed based on geometrical information extracted from computerized tomography images and from 3D laser scanning point clouds. These models also consider the corresponding connection to a radiotherapy table, as this connection is easily altered to accommodate various manufacturers’ solutions. A set of materials used in the radiotherapy field is considered to allow the assessment of the stiffness and strength of the masks when submitted to typical loadings.