Projecto e construção de uma máquina para estampagem incremental

Mestrado em Engenharia MecânicaSingle Point Incremental Forming is a recent technology that is currently under development. Its applicability is diverse because it allows the attainment of functional parts in sheet metal without great costs. Due to this characteristic, areas such as biomechanics, rapid prototyping and products of customizable features make this process a target of interest. Unfortunately, the means of obtaining parts using single point incremental forming are limited. Usually, CNC machining centers are utilized but due to their cutting-type characteristics, the implementation of the Single Point Incremental Forming is limited and inefficient. Also, the market supply of dedicated machinery requires high investments, thus becoming an unattractive solution. A major obstacle to the application of this technique focuses on the superior time of forming especially when compared to conventional forming techniques. Another disadvantage of this process is the low dimensional accuracy, however, with the development of numerical studies and correction algorithms this problem tends to be minimized. This work aims to complete the project of a single point incremental forming machine that began in previous years. This project has the objective of overcoming the limitations of the current incremental forming machines, but not ignoring the economic factor. Also, this project aims to enlarge the horizons for future research and development of the process, not only improving the machine but also developing and understanding the forming mechanism and the consequent effects of improved material formability.A estampagem incremental é um processo recente que está em desenvolvimento. A sua aplicabilidade é variada pois permite a obtenção de peças funcionais em chapa metálica sem grandes custos associados. Devido a esta característica, áreas como a biomecânica, prototipagem rápida e produtos de características personalizáveis fazem deste processo um alvo de interesse. Infelizmente, os meios de obtenção de peças usando estampagem incremental por ponto único são limitados. Normalmente faz-se uso de centros de maquinagem CNC adaptados, que devido às suas características próprias de corte por arranque de apara, tornam a aplicação da estampagem incremental limitada e ineficiente. Além disso, a oferta de mercado em maquinaria com características dedicadas ao uso de estampagem incremental requerem elevados investimentos, tornando-se assim uma solução pouco atractiva. Um dos principais obstáculos à aplicação desta técnica centra-se no tempo de conformação elevado, principalmente quando comparado com técnicas de estampagem convencionais. Outra desvantagem deste processo é a baixa precisão dimensional, que todavia com o avanço dos estudos numéricos e com o desenvolvimento de algoritmos de correcção tende a ser minimizado. Neste trabalho pretende-se concluir o projecto de uma máquina para realização de estampagem incremental por ponto único que teve início em anos anteriores. Este projecto tem por objectivo a obtenção de uma máquina que ultrapasse as limitações das máquinas actuais, mas não desconsiderando o factor económico. Além disso este projecto visa ampliar os horizontes para futuras pesquisas e desenvolvimento do processo, tanto na melhoria da máquina, mas também no desenvolvimento e na compreensão do mecanismo de deformação existente e aumento associado da formabilidade material

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally

The surgical safety checklist and patient outcomes after surgery: a prospective observational cohort study, systematic review and meta-analysis

© 2017 British Journal of Anaesthesia Background: The surgical safety checklist is widely used to improve the quality of perioperative care. However, clinicians continue to debate the clinical effectiveness of this tool. Methods: Prospective analysis of data from the International Surgical Outcomes Study (ISOS), an international observational study of elective in-patient surgery, accompanied by a systematic review and meta-analysis of published literature. The exposure was surgical safety checklist use. The primary outcome was in-hospital mortality and the secondary outcome was postoperative complications. In the ISOS cohort, a multivariable multi-level generalized linear model was used to test associations. To further contextualise these findings, we included the results from the ISOS cohort in a meta-analysis. Results are reported as odds ratios (OR) with 95% confidence intervals. Results: We included 44 814 patients from 497 hospitals in 27 countries in the ISOS analysis. There were 40 245 (89.8%) patients exposed to the checklist, whilst 7508 (16.8%) sustained ≥1 postoperative complications and 207 (0.5%) died before hospital discharge. Checklist exposure was associated with reduced mortality [odds ratio (OR) 0.49 (0.32–0.77); P\u3c0.01], but no difference in complication rates [OR 1.02 (0.88–1.19); P=0.75]. In a systematic review, we screened 3732 records and identified 11 eligible studies of 453 292 patients including the ISOS cohort. Checklist exposure was associated with both reduced postoperative mortality [OR 0.75 (0.62–0.92); P\u3c0.01; I2=87%] and reduced complication rates [OR 0.73 (0.61–0.88); P\u3c0.01; I2=89%). Conclusions: Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine

Critical care admission following elective surgery was not associated with survival benefit: prospective analysis of data from 27 countries

This was an investigator initiated study funded by Nestle Health Sciences through an unrestricted research grant, and by a National Institute for Health Research (UK) Professorship held by RP. The study was sponsored by Queen Mary University of London