Browsing by Issue Date, starting with "2024-05-13"
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- An Additive Manufacturing Suitable Methodology for Topology Optimization of Bolted Structural Joints with Cover-plates in Compliance with Structural EurocodesPublication . Ribeiro, Tiago Pinto; Bernardo, Luís Filipe AlmeidaThe current design of steel connections does not meet the possibilities offered for its fabrication by novel Additive Manufacturing (AM) techniques, both due to calculation methods insufficiency and standards limitations. This leads to building structures that are heavier, less economical, and less sustainable than our industrial capacity allows. While AM has been employed for rapid prototyping mostly in automotive, materials design, medical devices and aerospace industries through the past twenty years and Topology Optimization (TO) has gained momentum since the 1990s, the fact is that the lack of a comprehensive set of boundaries and methodology has limited its use to product development, rather than widespread, scalable, safe and standardised use in construction. Currently, while we already have good software for TO, which can assist in developing structural solutions whose added value justifies its production with AM enterprises, there is not a strong link between optimisation, mass fabrication and safety checking. We design to optimise weight, strength, and stiffness, not fully facilitate fabrication, comply with codes or use the best options given by AM. The lack of methodologies and guidelines prevents civil and structural engineering from embracing TO and AM. To address the meagre use of TO in the civil engineering industry, this research programme allowed to develop a methodology which accounts for i) the TO capabilities and software, ii) AM fabrication practical requirements and problems, iii) code requirements, iv) structural safety and performance goals to enable and foster the TO and AM to structural steel joints. Specifically, this was focused on bolted joints with cover plates in steel beams, designed to the current European standards, as joints are essential in steel structures, contributing up to 25% of the global weight and concentrating the complexity in design and, therefore, the industry’s added value. The novel code-compliant methodology was proposed, validated with non-linear Finite Element Analyses (NLFEA) and applied to several parts of a typical bolted joint. Through the research programme, successive methodology developments were made to account for different loading and buckling phenomena. For the cover flange plate under tension, it has been found that a 50% volume reduction is possible by employing linear elastic TO and establishing the non-exceedance of the steel ultimate stress as a criterion. NLFEA showed that if the original joint capacity is to be maintained, the maximum optimisation threshold reduces only 45% of the initial volume. For the cover-plate under compression, the initial volume can be decreased by up to 40% while maintaining the connection’s original capacity and that a 30% volume decrease may be achieved while maintaining the original plate capacity. In both cases, the plate’s ultimate deformation capacity was enhanced. Furthermore, for web plates subjected to shear forces, results show that reducing up to 87.5% of the plate’s initial volume is possible while keeping the connection’s original capacity. Also, it has been found that the initial volume can be reduced up to 20% without affecting the original plate capacity and up to 60% while ensuring that the ultimate plastic displacement is larger than that of the original plate. Further developments allowed employing state-of-the-art optimisation techniques, namely the Non-penalisation Smooth-Edged Material Distribution for Optimising Topology (np-SEMDOT) algorithm and assess both the added value and practicality of using it in the proposed code-compliant methodology, instead of broad-use software packages. Ultimately, laboratory testing was endeavoured to evaluate the numerical investigation results, allowing the validation of the former. Two critical conclusions that emerged from this work are that linear elastic TO could not meet the safety needs and that the introduced validation stage with NLFEA is an essential step, highlighting the novelty and significance of the proposed method. Topologically optimised solutions showed a significant volume and cost reduction, meaningfully contributing to the steel construction decarbonisation goals and leading to joints with more ductile behaviour.
- The Role of Innate Lymphoid Cells in Food AllergyPublication . Naia, Catarina Isabel Carvalho; Ibáñez, Carlos Lozoya; Fonseca, Ana Mafalda LoureiroFood allergy is a disorder caused by an exacerbated immunologic reaction, which occurs in response to specific allergenic substances, present in certain foods, such as tree nuts, milk, fish, and shellfish. It is estimated to affect around 1-20% of the European population, with its prevalence varying according to the diagnostic methodology used. Moreover, in the last years, systematic reviews have indicated an increasing prevalence, which suggests an important public health problem. Clinical manifestations of food allergy are wide-ranging and can affect the dermatologic, respiratory, cardiovascular, and neurological systems. The intensity of the symptoms is highly variable, ranging from mild reactions to severe and potentially fatal reactions, such as anaphylaxis. Innate lymphoid cells are immune cells that differ from T and B lymphocytes mainly for not possessing receptor-specific antigens on their surface. Type 2 innate lymphoid cells respond to previously activated cells, releasing cytokines that promote inflammation and the development of allergic symptoms. Eosinophilic Esophagitis is a disorder characterized by chronic inflammation of the esophageal mucosa, with a predominantly eosinophilic infiltrate. 70% of the patients diagnosed with Eosinophilic Esophagitis have a previous history of food allergy. In these patients, the number of Innate Lymphoid Cells is increased in the esophageal mucosa, suggesting that these cells, by promoting inflammation, can also promote the development of Eosinophilic Esophagitis. In conclusion, this review aims to clarify and detail the functions of Innate Lymphoid Cells which, through the production of cytokines and interactions with other immune cells, may contribute to the pathophysiology of food allergy and influence its possible treatments.
- Análise custo-benefício da técnica de “Wide Awake Local Anesthesia No Tourniquet”: Uma Revisão SistemáticaPublication . Vaz, Filipa Daniela Canteiro; Lopes, Cláudia Manuela Silva Santos; Saraiva, Maria do Rosário CapeloIntrodução: A técnica de anestesia “Wide Awake Local Anesthesia No Tourniquet” WALANT em cirurgia da mão destaca-se pela vantagem de ser administrada sem a necessidade de sedação e sem o uso de um garrote. Permite ao doente permanecer acordado e mobilizar os dedos durante a operação. Estudos recentes destacam a sua segurança, satisfação do doente e revelam benefícios económicos consideráveis. Esta revisão visa explorar se a técnica anestésica WALANT em cirurgias da mão é uma abordagem com custobenefício em comparação com outras técnicas. Métodos: Foi realizada uma revisão sistemática da literatura sobre as vantagens económicas da técnica de WALANT na cirurgia da mão, tendo como base as Guidelines PRISMA 2020.Foram utilizadas as bases de dados PubMed/MEDLINE, Science Direct, Scopus e Web of Science, com a equação (“walant” OR ”wide awake” OR “no tourniquet” OR “local anestesia” OR “tumescent anestesia”) AND (“cost” OR “economic”) . Foram selecionados os artigos que apresentavam uma análise comparativa entre WALANT e outras técnicas anestésicas para procedimentos cirúrgicos da mão em adultos e que abordavam os respetivos custos. Excluíram-se os estudos que não especificavam o tipo de anestesia local, que não utilizavam WALANT e que não apresentavam valores concretos dos gastos. O principal objetivo foi a avaliação do custo-benefício da técnica de WALANT e os objetivos secundários incluíram o tempo associado a cada procedimento e a produção de resíduos hospitalares. Resultados: No total, foram encontrados 3417 artigos nas quatro das bases de dados e selecionados 22. Entre as condições patológicas, 13 artigos abordam a Síndrome do Túnel do Carpo, oito o dedo em gatilho, quatro a doença de Dupuytren, quatro procedimentos ósseos, três a síndrome de De Quervain e dois a excisão de quistos sinoviais. Quanto à variável custo-benefício, 20 artigos demonstraram diferenças estatisticamente significativas entre WALANT e outras técnicas anestésicas. Relativamente ao tempo, há evidências de uma redução significativa do tempo total no bloco operatório com WALANT. Está associada a menos tempo na unidade de cuidados pós anestésicos e a menos tempo de turnover entre doentes. No que diz respeito aos resíduos, também permite uma redução significativa da sua produção. Conclusão: Os resultados desta revisão indicam que a técnica WALANT demonstra vantagens económicas, pode contribuir para otimizar recursos e reduzir listas de espera, alinhando-se com o crescente interesse dos sistemas de saúde em fornecer cuidados de alto valor. No entanto, persistem desafios na superação da resistência à sua adoção, e destacase a necessidade de estudos mais detalhados e uniformização de ferramentas de avaliação em Portugal.