Structural schemes for one dimension stationary equations

In this paper, we propose a new paradigm for finite differences numerical methods, based on compact schemes to provide high order accurate approximations of a smooth solution. The method involves its derivatives approximations at the grid points and the construction of structural equations deriving from the kernels of a matrix that gathers the variables belonging to a small stencil. Numerical schemes involve combinations of physical equations and the structural relations. We have analysed the spectral resolution of the most common structural equations and performed numerical tests to address both the stability and accuracy issues for popular linear and non-linear problems. Several benchmarks are presented that ensure that the developed technology can cope with several problems that may involve non-linearity.S. Clain acknowledges the financial support by Portuguese Funds through Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/00324/2020. R. M. S. Pereira acknowledges the financial support by Portuguese Funds through Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020. P. A. Pereira acknowledges the financial support by Portuguese Funds through Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/00013/2020. Diogo Lopes acknowledges the financial support by national funds (PIDDAC), through the FCT – Fundação para a Ciência e a Tecnologia and FCT/MCTES under the scope of the projects UIDB/05549/2020 and UIDP/05549/2020. S. Clain and R. M.Pereira acknowledge the financial support by FEDER – Fundo Europeu de Desenvolvimento Regional, through COMPETE 2020 – Programa Operacional Fatores de Competitividade, and the National Funds through FCT, project N◦. POCI-01-0145-FEDER-028118

Friction surfacing of aluminium alloys

Dissertação para a obtenção do grau de Mestre em Engenharia MecânicaFriction surfacing is a solid state joining process that has attracted much interest in the past decades. This technology allows joining dissimilar metallic materials while avoiding the brittle intermetallic formations, involving temperatures bellow melting point and producing like forged metal structures. Much research using different steels has been made but the same does not happen with aluminium alloys, specially using different aluminium alloys. Friction surface coatings using consumable rods of AA6082-T6 were produced on AA2024-T3 plates using a wide range of parameters. Coatings were examined to assure the best set of parameters according to the physical properties, such as: bonding width and thickness. Coatings were characterized metallurgical and mechanically. Besides metallurgical techniques, hardness, tensile, bending and wear tests were carried out. From this study, it was shown that high rotation speeds reduce the coating thickness and improve bonding to the substrate, while the applied load is the key parameter to obtain a good bonding width. Travel speed controls the deposition rate and the coating thickness. For the tested parameters a fine grain structure was obtained. The coatings have similar properties to the as-received rods but with higher ultimate tensile strength (UTS), elongation and wear resistance. Finally, an assessment of power and material consumption was performed revealing that Friction Surfacing is quite competitive when compared to other surface coating technologies

Artroplastia Total do Joelho Dolorosa

A Artroplastia Total do Joelho (ATJ) tem vindo a assumir-se como a opção cirúrgica mais frequente no tratamento de doentes com alterações degenerativas da articulação do joelho devido aos ótimos resultados funcionais e melhoria da dor. No entanto, a percentagem de doentes com sintomas dolorosos após a realização deste procedimento atinge em algumas estatísticas publicadas valores significativos que oscilam entre os 10 e os 20%. Em alguns casos a dor não é facilmente explicável, representando um desafio para o cirurgião. Os autores relatam o caso de uma doente de 71 anos submetida a ATJ primária, no contexto de patologia degenerativa idiopática associado a desvio axial em varum. A dor localizava-se na face anteroexterna do joelho ao nível da interlinha articular e tiveram início no pós-operatório de forma gradual, associadas ao aumento da mobilidade. Devido à presença de um sintoma associado a atividade mecânica, foram colocadas várias hipóteses, entre as quais a possibilidade de conflito com resquício intra-articulares do compartimento externo do joelho. A doente foi submetida a artroscopia da articulação do joelho que revelou a existência de um fragmento meniscal que provocava conflito entre o côndilo externo do componente artroplástico femoral e o polietileno no movimento de extensão máxima do joelho. Procedeu-se a remoção artroscópica do fragmento com melhoria sintomática completa. Os autores pretendem com este caso evidenciar a importância da investigação diagnóstica para o tratamento da dor inexplicável na ATJ, e o valor terapêutico da artroscopia nos casos de provável conflito

The impact of breeding Yellow-Legged Gulls on vegetation cover and plant composition of Grey Dune habitats

The establishment of large populations of yellow-legged gull Larus michahellis in coastal and urban areas can lead to strong changes in vegetation cover and composition through creating physical disturbance in the vegetation and impacting the soil quality through defecation. In this study, we evaluated the effects of breeding yellow-legged gull populations on tall and short vegetation cover and plant species composition in old (occupied for 13 years) and new (occupied for 3 years) colony sites in grey dunes of the Algarve, southern Portugal. In each site, sampling plots were used to measure the percentage of vegetation cover in areas with and without breeding gulls. In the old colony site, the cover by tall vegetation was substantially reduced and the cover by short vegetation substantially increased in the areas where gulls are breeding in comparison with the adjacent areas. In the new colony sites, there were only minor differences. The increase in cover of short vegetation in the breeding area of the old colony site was mostly by nitrophilous species (Paronychia argentea and Malcolmia littorea) and should be explained by the decrease in vegetation cover of tall plant species and by feces deposition. Tall and slow-growing species Suaeda maritima and Helichrysum italicum covers were negatively affected. Our results showed that yellow-legged gulls affected vegetation cover and composition of grey dunes after 3 years of consecutive breeding, and this should be considered in the management of these habitats where breeding yellow-legged gulls are increasing.info:eu-repo/semantics/publishedVersio

Multivariable optimization process of heterotrophic growth of Chlorella vulgaris

Microalgae have received increasing attention as one of the most promising feedstocks in the development of new healthier food products and different strategies have been attempted to improve their growth. However, the high production costs and low productivities, commonly associated with photoautotrophic growths, are still a big challenge. In this study, a two-step optimization strategy was carried out in order to maximize the biomass production of a Chlorella vulgaris strain used at industrial scale under heterotrophic conditions. From a total of 24 independent variables, which were studied simultaneously, 10 have presented a positive effect over Xmax, while the remaining have shown to be negative. The amount of (NH4)2SO4 (6.3 g L1), MgSO4·7H2O (0.7 g L1), and C6H12O6 (50% w/v) in the culture medium has revealed to be the only factors with a significant impact on biomass concentration, with optimum values of 25.5, 64.6, and 75 ml.L1, respectively. The optimized medium resulted in an improvement of the Xmax by 99.6% when compared to the growth medium applied at industrial scale, proving the success of this strategy. Additionally, the carbohydrates production was enhanced by 48.0%.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and by LABBELS – Associate Laboratory in Biotechnology, Bioengineering and Microelectromechanical Systems, LA/P/0029/2020. This work was funded by NORTE2020 Funds through the SUPPORT SYSTEM FOR SCIENTIFIC AND TECHNOLOGICAL RESEARCH - "STRUCTURED R & D & I PROJECTS" - HORIZON EUROPE under the project NORTE-01-0145-FEDER-000070. This research work was supported by ALGAVALOR - Lisboa-01-0247-FEDER-035234, supported by Operational Programme for Competitiveness and Internationalization (COMPETE2020), by Lisbon Portugal Regional Operational Programme (Lisboa 2020) and by Algarve Regional Operational Programme (Algarve 2020) under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). Filipe Maciel and Leandro Madureira acknowledge the FCT for their fellowships (SFRH/BD/133005/2017 and SFRH/BD/151474/2021, respectively).info:eu-repo/semantics/publishedVersio

Influence of service temperature on shear creep behaviour of a rigid low-density closed-cell PIR foam

An experimental campaign was carried out to assess shear creep behaviour of a rigid low-density closed-cell polyisocyanurate (PIR) foam. Two service temperature values were considered, 20 ºC and 30 ºC, and the applied stresses ranged between 20% and 60% of the corresponding shear strength. The results showed that a stress amplitude of 30% was enough to cause nonlinear creep response. Furthermore, creep deformations were slightly smaller in the tests at 30 ºC, a fact that matched the viscoelastic response of the PIR foam obtained from DMA testing. Finally, creep prediction curves were calibrated through an analytical approach based on the Findley’s power law.This work is part of the research project “EasyFloor – Development of composite sandwich panels for rehabilitation of floor buildings”, involving the company ALTO – Perfis Pultrudidos, Lda., CERis/Instituto Superior Técnico and ISISE/University of Minho, supported by FEDER funds through the Operational Program for Operational Program for Competitiveness and Internationalization (POCI) and the Portuguese National Innovation Agency (ANI) - project no. 3480 (POCI-01-0247-FEDER-003480). The second author acknowledge the grant SFRH/BSAB/150266/2019 provided by FCT, financed by European Social Fund and by national funds through the FCT/MCTES. Acknowledgments are extended to LEST – Laboratório de Estruturas for their material support. The contribution of the Department of Mechanical Engineering of the University of Minho is also gratefully acknowledged in the person of Engineer Pedro Ribeiro. Lastly, the authors would like to thank SIKA Company for suppling the adhesive

Characterisation and Evaluation of the Mechanical Behaviour of Endodontic-grade NiTi Wires

With the introduction of new materials and advances in medical science, the endodontic files have changed since the early days of root canal treatments. In the late days, we have seen an increasing use of Nickel-Titanium (NiTi) alloys, to the detriment of more conventional alloys. At body temperature, NiTi alloys present a superelastic behaviour, which allows to be more effective in the removal of the tooth pulp tissue, and in the protection of the tooth structure. Anyhow, these NiTi instruments will eventually fracture, usually without any visual signal of degradation. Thus, there is a need of studying these alloys, as they present a high hysteresis cycle and non-linearities in the Elastic domain. Currently, there is no international standard to test NiTi endodontic files, so various authors have attempted to design systems that can test them under fatigue loads, usually based on empirical setups. Following a systematic approach, this work presents the results of rotary fatigue tests for two Alfa Aesar® Nitinol wires with different diameters (0.58mm and 0.25mm).The formulation is presented, where the material strength reduction can be quantified from the determination of the strain and the number of cycles until failure, as well numerical FEM simulation to verify the analytical model predictions

Decision support visualization approach in textile manufacturing a case study from operational control in textile industry

Decision support visualization tools provide insights for solving problems by displaying data in an interactive, graphical format. Such tools can be effective for supporting decision-makers in finding new opportunities and in measuring decision outcomes. In this study, was used a visualization tool capable of handling multivariate time series for studying a problem of operational control in a textile manufacturing plant; the main goal was to identify sources of inefficiency in the daily production data of three machines. A concise rule-based model of the inefficiency measures (i.e. quantitative measures were transformed into categorical variables) was developed and then performed an in-depth visual analysis using a particular technique, the categorical time series plots stacked vertically. With this approach were identified a wide array of production inefficiency patterns, which were difficult to identify using standard quantitative reporting - temporal pattern of best and worst performing machines - and critically, along with most important sources of inefficiency and some interactions between them were revealed. The case study underlying this work was further contextualized within the state of the art, and demonstrates the effectiveness of adequate visual analysis as a decision support tool for operational control in manufacturing.This study was partially conducted at the Psychology Research Centre (UID/PSI/01662/2013), University of Minho, and supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Science, Technology and Higher Education through national funds and co-financed by FEDER through COMPETE2020 under the PT2020 Partnership Agreement (POCI-010145-FEDER-007653). This work was also supported by the following grants: FCT project PTDC/MHC/PCN/1530; FEDER Funds through the "Programa Operacional Factores de Competitividade - COMPETE" program and by National Funds through FCT "Fundacao para a Ciencia e a Tecnologia" under the project: FCOMP-010124-FEDER-PEst-OE/EEI/UI0760/2011, PEst-OE/EEI/UI0760/2014, PEst2015-2020 and UID/CEC/00319/2019

A systematic analysis of printed circuit boards bending during in-circuit tests

When performing In-Circuit Tests (ICTs) of Printed Circuit Boards (PCBs), there are certain phenomena related with strain analysis that must be known in order to obtain stronger and more accurate testing results. During testing, PCBs are often subjected to mechanical bending efforts that induce excessive strain. This study focuses on the building of a Finite Elements Analysis (FEA) methodology that prevents excessive bending strain in critical points of a PCB during an ICT. To validate this methodology, a set of experimental tests, matched with a set of FEA, were carried out. Thus, companies, before the development of an ICT machine (fixture), will be able to use this FEA methodology to predict whether the maximum strain of a PCB under study, when subjected to its ICT, will damage it, thus reducing unnecessary production costs. A guideline was thus designed to enable the creation of the most representative Finite Elements Model (FEM) for any PCB, based on its amount and direction of copper traces.This work is co-funded by the European Regional Development Fund (ERDF) through the North Regional Operational Program (NORTE 2020) of the Portugal 2020 Program (Project No. 43922, with acronym “iFixturing”; Funding Reference NORTE-01-0247-FEDER-043922)

A hybrid cementitious based-G/CFRP sandwich panel: concept, design and initial outcomes

Nowadays, the advantages of using fibre-reinforced polymers (FRP) in Civil Engineering structures are very well-known. In comparison to other materials, the FRPs show high strength-to-weight and stiffness-to-weight ratios, as well as high corrosion resistance [1]. Moreover, they can be easily moulded into complex shapes during the manufacturing process. Due to the slenderness of the cross section components and systems [2], and their significant initial cost [3], the FRPs are typically used along with other materials in composite structural elements. In the recent years, the FRPs have been increasingly used in composite sandwich panels designed for the building and housing industry [4]. However, in terms of flooring solutions, the sandwich panels still reveal some limitations for the most typical values of spans and loads in buildings [5]. In order to overcome the aforementioned drawbacks, the EasyFloor project was launched to develop enhanced composite sandwich panels for rehabilitation of floors in buildings. One of the important innovations included in the project relies on the use of both glass and carbon fibre roving (G/CFRP). This hybrid solution aims at improving significantly both the strength and stiffness. Furthermore, the top face of the panel is made of steel fibre reinforced self-compacting micro concrete (SFRSCMC), instead of the usual FRP compressive face, aiming to overcome face wrinkling issues. Additionally, this solution can provide higher ductility, fire endurance and impact resistance [6]. Furthermore, polycianurate (PIR) closed-cell foam is used as core material of the panel. Proper adhesion between G/CFRP and SFRSCMC is developed in order to obtain the full bending capacity of the composite solution. Finally, the FRP component is produced by pultrusion, taking all the advantages of this manufacturing process. The final proposal for the hybrid sandwich panel was obtained through the use of genetic algorithms in the design, which consisted in optimizing the geometric and the mechanical properties of the panel, taking into account the following features: (i) structural and energy efficiency; (ii) durability, versatility of use, ease of handling, quick assembly and production; (iii) low maintenance needs and aesthetics. The present work describes the design solution that resulted from the optimization procedure and subsequently presents initial experimental results regarding the mechanical characterization of the different materials, as well as the FRP/SFRSCMC interface. The experimental program comprised: (i) tensile and flexural tests on both the bottom and external ribs of the C/GFRP laminate skins; (ii) tensile, compressive and direct shear tests on both foam core materials (PIR); (iii) compressive and flexural tests on the SFRSCMC top face, and; (iv) pull-off tests for the characterization of the connection between the SFRSCMC and FRP using different types of adhesives.This work is part of the research project “EasyFloor – Development of composite sandwich panels for rehabilitation of floor buildings”, involving the company ALTO – Perfis Pultrudidos, Lda., CERis/Instituto Superior Técnico and ISISE/University of Minho, supported by FEDER funds through the Operational Program for Operational Program for Competitiveness and Internationalization (POCI) and the Portuguese National Innovation Agency (ANI) - project no. 3480 (POCI-01-0247-FEDER-003480). The authors would like to thanks the following companies for suppling the adhesives: KERAKOLL, MAPEI and SIKADUR.info:eu-repo/semantics/publishedVersio