Effect of hole drilling at the overlap on the strength of single-lap joints

Bonded unions are gaining importance in many fields of manufacturing owing to a significant number of advantages to the traditional fastening, riveting, bolting and welding techniques. Between the available bonding configurations, the single-lap joint is the most commonly used and studied by the scientific community due to its simplicity, although it endures significant bending due to the non-collinear load path, which negatively affects its load bearing capabilities. The use of material or geometric changes in single-lap joints is widely documented in the literature to reduce this handicap, acting by reduction of peel and shear peak stresses at the damage initiation sites in structures or alterations of the failure mechanism emerging from local modifications. In this work, the effect of hole drilling at the overlap on the strength of single-lap joints was analyzed experimentally with two main purposes: (1) to check whether or not the anchorage effect of the adhesive within the holes is more preponderant than the stress concentrations near the holes, arising from the sharp edges, and modification of the joints straining behaviour (strength improvement or reduction, respectively) and (2) picturing a real scenario on which the components to be bonded are modified by some external factor (e.g. retrofitting of decaying/old-fashioned fastened unions). Tests were made with two adhesives (a brittle and a ductile one) varying the adherend thickness and the number, layout and diameter of the holes. Experimental testing showed that the joints strength never increases from the un-modified condition, showing a varying degree of weakening, depending on the selected adhesive and hole drilling configuration

Electrospray Deposition of PEDOT:PSS on Carbon Yarn Electrodes for Solid-State Flexible Supercapacitors

Funding Information: This work was financed by national funds from FCT─Fundação para a Ciência e a Tecnologia, I.P., in the scope of the All-FIBRE project with the reference PTDC/CTM-CTM/1571/2020, and the projects LA/P/0037/2020, UIDP/50025/2020, and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling, and Nanofabrication─i3N. This work was also supported by ERC-CoG-2014, CapTherPV, 647596. The authors would like to thank Professor Daniela Gomes from CENIMAT for the SEM images. Publisher Copyright: © 2023 The Authors. Published by American Chemical Society.The increasing demand for flexible electronic devices has risen due to the high interest in electronic textiles (e-textiles). Consequently, the urge to power e-textiles has sparked enormous interest in flexible energy storage devices. One-dimensional (1D) configuration supercapacitors are the most promising technology for textile applications, but often their production involves complex synthesis techniques and expensive materials. This work unveils the use of the novel electrospray deposition (ESD) technique for the deposition of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). This deposition methodology on conductive carbon yarns creates flexible electrodes with a high surface area. The deposition conditions of PEDOT:PSS were optimized, and their influence on the electrochemical performance of a 1D symmetric supercapacitor with a cellulose-based gel as an electrolyte and a separator was evaluated. The tests herein reported show that these capacitors exhibited a high specific capacitance of 72 mF g-1, an excellent cyclability of more than 85% capacitance retention after 1500 cycles, and an outstanding capability of bending.publishersversionpublishe

Tensile behaviour of single and double-strap repairs on aluminium structures

In this work, an experimental study was performed on the influence of plug filling, loading rate and temperature on the tensile strength of single-strap (SS) and double-strap (DS) repairs on aluminium structures. The experimental programme includes repairs with different values of overlap length (LO=10, 20 and 30 mm), and with and without plug filling. The influence of the testing speed on the repairs strength is also addressed (considering 0.5, 5 and 25 mm/min). Accounting for the temperature effects, tests were carried out at room temperature, 50ºC and 80ºC. This will permit a comparative evaluation of the adhesive tested below and above the Glass Transition Temperature (Tg), established by the manufacturer at 67ºC. The global tendencies of the test results concerning the plug filling and overlap length analyses are interpreted from the fracture modes and typical stress distributions for bonded repairs. According to the results obtained from this work, design guidelines for repairing aluminium structures were recommended

Effect of plug-filling, Testing velocity and temperature on the tensile strength of strap repairs on aluminium structures

In this work, an experimental study was performed on the influence of plug-filling, loading rate and temperature on the tensile strength of single-strap (SS) and double-strap (DS) repairs on aluminium structures. Whilst the main purpose of this work was to evaluate the feasibility of plug-filling for the strength improvement of these repairs, a parallel study was carried out to assess the sensitivity of the adhesive to external features that can affect the repairs performance, such as the rate of loading and environmental temperature. The experimental programme included repairs with different values of overlap length (L O = 10, 20 and 30 mm), and with and without plug-filling, whose results were interpreted in light of experimental evidence of the fracture modes and typical stress distributions for bonded repairs. The influence of the testing speed on the repairs strength was also addressed (considering 0.5, 5 and 25 mm/min). Accounting for the temperature effects, tests were carried out at room temperature (≈23°C), 50 and 80°C. This permitted a comparative evaluation of the adhesive tested below and above the glass transition temperature (T g), established by the manufacturer as 67°C. The combined influence of these two parameters on the repairs strength was also analysed. According to the results obtained from this work, design guidelines for repairing aluminium structures wer

Permeation of model membranes by Peptaibolin mimetics bearing different α,α-dialkylglycines

Comunicação oral OC19 no XV EPI- Iberian Peptide Meeting, Porto, Portugal, 10-12 Fevereiro 2016.It is reported the membrane permeation studies of a model peptide, Peptaibolin (Ac-Leu-Aib-Leu-Aib-Phol), which is the shortest member of the peptaibols family, and several mimetics incorporating unnatural α,α- dialkylglycines (Deg, Dpg, Ac6c) at the native Aib positions. The model membranes were based on small unilamellar vesicles composed of phosphatidylcholines (egg lecithin, DPPC), phosphatidylglycerols (DPPG, DOPG) and cholesterol, at different compositions and ratios, containing a fluorescent probe encapsulated in their aqueous interior, in order to monitor the permeation process by fluorescence spectroscopy. The obtained results revealed a correlation between the length and bulk of the side chain of the unnatural α,α-dialkylglycines and the ability of the corresponding peptide to permeate the model membranes.The authors acknowledge Fundação para a Ciência e a Tecnologia (Portugal) and FEDER-COMPETE-QREN-EU for financial support through projects PTDC/QUIBIQ/118389/2010 (FCOMP-01-0124-FEDER-020906), PEst-C/QUI/UI0686/2013 (F-COMP-01- 0124-FEDER-037302), and PEst-C/FIS/UI0607/2013 (F-COMP-01-0124-FEDER-022711).info:eu-repo/semantics/publishedVersio

Membrane active peptides with unnatural amino acids: permeation studies in model membranes

Comunicação em painel P60 no 2nd Symposium on Medicinal Chemistry, Braga, Portugal, 8 Maio 2015It is reported the membrane permeation studies of Peptaibolin and several mimetics incorporating unnatural α,α-dialkylglycines (Deg, Dpg, Ac6c) with model membranes (egg phosphatidylcholine/cholesterol, in different ratios). The permeation activity was monitored by fluorescence spectroscopy, following release of an encapsulated fluorescent probe (6-carboxyfluorescein). The obtained results revealed a correlation between the length and bulk of the side chain of the unnatural α,α-dialkylglycines and the ability of the corresponding peptide to permeate the model membranes.Fundação para a Ciência e Tecnologia(Portugal) and FEDER-COMPETE for financial support through project PTDC/QUI-BIQ/118389/2010 (FCOMP- 01-0124-FEDER-020906) and PEst-C/QUI/UI0686/2013 (F-COMP-01-0124-FEDER-037302). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased with fund s from FCT and FEDERinfo:eu-repo/semantics/publishedVersio

Effects of grazing pressure on activity and richness of bats in a Portuguese silvo-pastoral system

Background High Nature Value Farmlands (HNVF) harbor species dependent upon habitats maintained by low-intensity farming. Among HNVF, the montado (dehesa in Spain) is a multifunctional system declining due to droughts, pathogens, and increasing grazing pressure. Specifically, grazing pressure leads to compact soils and hinders natural tree regeneration. Regrettably, there is a dearth of information supporting management decisions on the side-effects of high grazing pressure on HNVF-dwelling biodiversity. In particular, little is known about the impact of grazing pressure on bats, a group of species of special conservation concern that may provide key ecosystem services such as biological pest control. Purpose We investigated patterns of activity levels and community composition of insectivorous bats to test the hypothesis that there is a significant relationship between the level of livestock grazing pressure within montado HNVF parcels and patterns of insectivorous bats’ presence and activity. Our specific aims were to (i) assess separately the effects of grazing pressure on bat activity and species composition, (ii) test the predictive significance of key covariates (e.g., insect availability). Methods We conducted this study in 2014 in the Natura 2000 network site “Monfurado”, southern Portugal. This site is specifically acknowledged for its well-preserved montados providing feeding areas for bat species. We quantified acoustically bat flight activity and species richness in farm parcels dominated by cork oak trees. Per parcel, we selected two separate locations (high vs. low grazing pressure) based on landowners’ interviews and grazing pressure indicators, totaling 42 sampling locations. We then used linear mixed-effects modeling to evaluate the effects of grazing pressure and covariates on activity and species richness. Results Bat activity and bat species richness peaked at low grazing pressure locations. Bat activity also increased with tree cover and in locations where livestock grazing signs were old or absent. Conversely, bat activity at low grazing pressure locations decreased with distance to the nearest standing water body. Discussion Our study clearly demonstrated that locations maintained under high grazing pressure within HNVF can have negative consequences for bats, which are acknowledged as good bioindicators of habitat quality. In order to promote better habitat for bats, practitioners should avoid favoring grazing-prone areas (e.g., rotating the location of livestock feeders, drinkers, and gates) across montado HNVF. Broadly, ecosystem services provided by bats for HNVF must be enhanced through sustainability oriented agro-environment schemes under the Economic Community Rural Development Program, including the reduction of stocking density

Is Students’ Satisfaction in Electrical Engineering Courses Influenced by Gender?

Electrical/Electronic Engineering courses are often regarded as male courses. In this paper it is presented a study conducted in two Portuguese and two Brazilian high education institutions (six courses) where the goal was to analyze if gender affects students’ perceptions and satisfaction regarding Electrical/Electronic Engineering courses. The analysis was based on 654 questionnaires rating 44 items (among the six groups: Teacher Involvement Perception, Student Interest, Student-Teacher interaction, Course organization and functioning, Infrastructures, and Overall satisfaction). The investigation was performed by year, from the first to the third year (1st cycle) and considering the six programs. Based on students’ perceptions, some items showed differences that were significant, namely the ones regarding how teachers and students interact and how teachers challenge students.N/

How do students perceive their Learning Assessment?

The present work was developed considering the learning assessment vector and linking it to students’ general satisfaction with the engineering course. The key findings show a positive association between students’ general satisfaction and the learning assessment, specifically with the assessment methodologies effectiveness regarding the different subjects taught. Globally,studentsconsidered the assessment methodologies effective and appropriate to the different subjects taught however, they do not feel encouraged to be part of the process of monitoring his/her performance, and to thetime allocated to the assessment testsas it wasnot considered appropriateto the volume of subjects taught.The authors would like to express their acknowledgments to all students who accepted to collaborate in this study. The authors also thank the Research Centre CIETI and FCT, for all the support provided in the scope of the projects COMPETE: POCI-01-0145-FEDER-007043, UID/CEC/00319-2019 and UID-EQU-04730-2013.N/

Antimicrobial activity and bioactive compounds of portuguese wild edible mushrooms methanolic extracts

The antimicrobial properties of phenolic extracts of Portuguese wild edible mushroom species (Lactarius deliciosus, Sarcodon imbricatus and Tricholoma portentosum) against pathogens were investigated. The minimal inhibitory concentrations (MICs) were evaluated for the entire mushroom, the cap and the stipe, separately; the portion of the mushroom used proved to be influenced in the results obtained, which are directly correlated with the content of total phenols and flavonoids in the extracts. The growth of Grampositive bacteria (Bacillus cereus, B. subtilis,) was well inhibited by these mushrooms, while Escherichia coli (Gramnegative bacteria) was resistant. The study on the antifungal effect of these mushrooms revealed that Candida albicans and Cryptococcus neoformans were differently inhibited for the mushrooms used