ESTG - Artigos em revistas internacionais
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- Fatigue behaviour in hybrid hollow microspheres/fibre reinforced compositesPublication . Ferreira, J. A. M.; Salviano, K.; Costa, J. D.; Capela, C.This article presents the results of a current study concerning the influence of the addition of short fibres on the fatigue behaviour of syntactic foams. The material was obtained by vacuum-assisted resin transfer moulding adding hollow glass microspheres to an epoxy resin acting as binding matrix. Specimens with microsphere contents up to 50% and fibre reinforcement up to 1.2% in volume were tested at three-point bending at room temperature. Foams show significantly lower static and fatigue strength than an epoxy matrix. A significant decrease in the absolute strength with filler increase was observed, and even specific strength decreases for low filler contents and is nearly constant for the higher filler contents. Fatigue strength also decreases with the increase in filler content. The addition of glass fibre reinforcement produces only a slight improvement in flexure strength, while the addition of carbon fibres promotes an important improvement; a hybrid composite containing 0.9% carbon fibre is about 30% stronger than unreinforced foams. An improvement in fatigue strength more than 30% was obtained by the addition of small percentages of glass or carbon fibre.
- Correlations between VIMS and RADAR data over the surface of Titan: Implications for Titan’s surface propertiesPublication . Tosi, F.; Orosei, R.; Seu, R.; Coradini, A.; Lunine, J. I.; Filacchione, G.; Gavrishin, A. I.; Capaccioni, F.; Cerroni, P.; Adriani, A.; Moriconi, M. L.; Negrão, A.; Flamini, E.; Brown, R. H.; Wye, L. C.; Janssen, M.; West, R. D.; Barnes, J. W.; Wall, S. D.; Clark, R. N.; Cruikshank, D. P.; McCord, T. B.; Nicholson, P. D.; Soderblom, J. M.We apply a multivariate statistical method to Titan data acquired by different instruments onboard the Cassini spacecraft. We have searched through Cassini/VIMS hyperspectral cubes, selecting those data with convenient viewing geometry and that overlap with Cassini/RADAR scatterometry footprints with a comparable spatial resolution. We look for correlations between the infrared and microwave ranges the two instruments cover. Where found, the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for incidence angle, and the calibrated antenna temperature measured along with the scatterometry echoes, are combined with the infrared reflectances, with estimated errors, to produce an aggregate data set, that we process using a multivariate classification method to identify homogeneous taxonomic units in the multivariate space of the samples.In medium resolution data (from 20 to 100. km/pixel), sampling relatively large portions of the satellite's surface, we find regional geophysical units matching both the major dark and bright features seen in the optical mosaic. Given the VIMS cubes and RADAR scatterometer passes considered in this work, the largest homogeneous type is associated with the dark equatorial basins, showing similar characteristics as each other on the basis of all the considered parameters.On the other hand, the major bright features seen in these data generally do not show the same characteristics as each other. Xanadu, the largest continental feature, is as bright as the other equatorial bright features, while showing the highest backscattering coefficient of the entire satellite. Tsegihi is very bright at 5 μm but it shows a low backscattering coefficient, so it could have a low roughness on a regional scale and/or a different composition. Another well-defined region, located southwest of Xanadu beyond the Tui Regio, seems to be detached from the surrounding terrains, being bright at 2.69, 2.78 and 5 μm but having a low radar brightness. In this way, other units can be found that show correlations or anti-correlations between the scatterometric response and the spectrophotometric behavior, not evident from the optical remote sensing data.
- Artificial Intelligence-Driven User Interaction with Smart Homes: Architecture Proposal and Case StudyPublication . Lemos, João; Ramos, João; Gomes, Mário; Coelho, PauloThe evolution of Smart Grids enabled the deployment of intelligent and decentralized energy management solutions at the residential level. This work presents a comprehensive Smart Home architecture that integrates real-time energy monitoring, appliance-level consumption analysis, and environmental data acquisition using smart metering technologies and distributed IoT sensors. All collected data are structured into a scalable infrastructure that supports advanced Artificial Intelligence (AI) methods, including Large Language Models (LLMs) and machine learning, enabling predictive analysis, personalized energy recommendations, and natural language interaction. Proposed architecture is experimentally validated through a case study on a domestic refrigerator. Two series of tests were conducted. In the first phase, extreme usage scenarios were evaluated: one with intensive usage and another with highly restricted usage. In the second phase, normal usage scenarios were tested without AI feedback and with AI recommendations following them whenever possible. Under the extreme scenarios, AI-assisted interaction resulted in a reduction in daily energy consumption of about 81.4%. In the normal usage scenarios, AI assistance resulted in a reduction of around 13.6%. These results confirm that integrating AI-driven behavioral optimization within Smart Home environments significantly improves energy efficiency, reduces electrical stress, and promotes more sustainable energy usage.
- Fur Farming: EU Citizens’ StancePublication . Mata, Fernando; Baptista, Nuno; Jesus, Meirielly; Santos, JoanaDespite its economic profitability, fur farming in Europe, responsible for half of global production, faces a growing ethical backlash. Animal welfare concerns, particularly regarding mink, foxes, and raccoon dogs kept in restrictive cages, have intensified due to advocacy, scientific reviews, and COVID-19 outbreaks. In response, several EU nations have implemented bans or stricter regulations. However, limited research exists on EU public opinion. This study analyses data from Eurobarometer 533 (March 2023), surveying 26,368 citizens across 27 EU countries, to assess attitudes toward fur farming. Respondents selected from three policy preferences: a full ban, EU-wide regulation, or acceptance of current practices. Multinomial logistic regression and chi-square tests revealed significant socio-demographic and ideological influences. Older individuals were more supportive of current practices (p = 0.001), while higher education levels correlated with support for a ban or stricter regulation (p = 0.003). Income positively influenced support for regulation (p = 0.002), and women (p = 0.008), urban residents (p = 0.001), and those with regular animal contact (p = 0.007) were more likely to support reform. Right-leaning respondents (p = 0.012) and residents of countries without fur farming bans (p < 0.001) were less supportive. These findings suggest that values, demographics, and national legislation significantly shape public opinion. Aligning policy with evolving societal values requires integrated legislative reform, public engagement, and equitable transition strategies to ensure meaningful and sustainable improvements in animal welfare across the EU.
- Micro Computed Tomography Detects Changes in Liver Density in Control and in Prediabetes RatsPublication . Fonseca, A. R.; Franco, M. C.; Sacramento, J.; Melo, B.; Conde, S.V.; Guarino, M. P.Fatty liver disease is an early event in the development of insulin resistance that predicts the presence and progression of the metabolic syndrome. In humans, fatty liver diagnosis is usually performed by imaging techniques based on ultrasound, computed tomography and magnetic resonance. Rodent models are often used in metabolic research allowing access to tissue biopsies however, studies describing ex vivo computed tomography of biological samples are scarce. X-ray Micro Computed Tomography (Micro-CT) is an imaging technique that reveals the internal structure of materials in great detail, also allowing a quantitative analysis of properties such as density measured as arbitrary Hounsfield Units (HU). Herein, we tested the hypothesis that Micro CT detects changes in liver tomographic density induced by metabolic diseases and its reversal upon therapeutic surgical intervention. Two groups of male Wistar rats were used: a group submitted to a hypercaloric diet for 14 weeks to induce prediabetes and the control group submitted to a standard diet). The animals were randomly submitted to a surgical treatment and maintained on their respective diets after the procedure for 11 more weeks. Liver and adipose tissues samples were excised and samples were scanned using a compact X-ray micro-CT scanner. The projection images obtained were analyzed and reconstructed and values of HU density were calculated after calibration for all samples. Results showed that liver density was lower in prediabetes rats (74.8±5.87 HU) than in control animals (97.2±6.3 HU), p<0.05. Liver density was not affected by surgical treatment in control animals however, in prediabetes animals, the surgical therapy restored liver density to control values. Visceral fat density was significantly lower than hepatic density, as expected and was affected, neither by the disease condition nor by the surgical treatment. We concluded that micro-CT detects metabolic disease-induced changes in liver density, but not in visceral adipose tissue density in biopsy samples ex vivo. Changes in hepatic density, assessed by micro-CT, correlate with disease state and with therapeutic interventions.
- “Not Even Hell Must Look like This”—Print Media Narratives about the October 2017 Wildfires in Portuguese Public-Managed ForestsPublication . Figueiredo, Elisabete; Ribeiro, Cristina; Fernandes, Maria EduardaThe unprecedented wildfires of 2017 in Portugal, particularly affecting the Centre Region, resulted in more than 100 deaths and numerous other dramatic socioeconomic and environmental impacts. Due to the unparalleled magnitude of these events, the extent of the burned area, and the catastrophic consequences, forest and fire management were placed at the center stage of public and political concerns, receiving wide mass media attention and amplification likely to shape public opinion and influence policy decisions. Through a quasi-qualitative content analysis approach, this article focuses on the media narratives conveyed by the news issued over two years (N = 1056) by eight newspapers of different periodicities and geographical scopes regarding the wildfires of October 2017 in the Matas do Litoral—coastal public-managed forest areas located in the Centre Region of Portugal. The analysis focuses on three main dimensions: the agents and actors mentioned and their power-related positions, the geographical coverage of the newspapers, and the relevance ascribed to emotions and feelings in the media narratives about the wildfires. The results demonstrate the relevance attributed in media narratives to the views of institutional agents and the negligence of local people’s voices. When particularly highlighting the material impacts of the wildfires, media narratives tended to focus less on people’s emotions and other non-tangible issues. The variation in these narratives according to the geographical scope of the newspapers and the publication time of the news strongly points out the need to address the heterogeneous character of the media coverage of wildfires.
- Experimental assessment of strengthening strategy to improve the masonry infills out-of-plane behaviour through textile reinforced mortarPublication . Furtado, André; Melo, José; Arêde, António; Varum, Humberto; Rodrigues, HugoThroughout the last years, the study of the masonry infill walls out-of-plane behavior is being observed by the scientific community with special attention, mainly due to damages observed during post-earthquake scenarios, where several number of damages and out-of-plane collapses of infill panels were found. Different causes are pointed to justify the seismic vulnerability of these type of elements, most of all related to deficient construction practices, which are nowadays still applicable Based on this motivation, two experimental quasi-static, full-scale, out-ofplane tests were carried out on RC frames that were built and infilled with a thin masonry wall made up of horizontal hollow clay bricks. The first specimen is representative of the enclosure of a typical existing RC building in the Southern countries in its "as-built" condition. The second specimen was strengthened with textile-reinforced mortar using glass fiber mesh. Both specimens were subjected to semi-cyclic (loading-unloading-reloading) history of imposed displacements by means of small pneumatic jacks through a uniform distributed load. Experimental results will be presented and detailed in terms of out-of-plane force-displacement responses and damage evolution. In the end, the results of the tests are compared to assess the effectiveness of the strengthening technique.
- The X++2X→X2++X reaction rate constant for Ar, Kr and Xe, at 300 KPublication . Neves, P. N. B.; Conde, C. A. N.; Távora, L. M. N.The X++2X → X+2X- reaction rate constants were measured for Ar, Kr and Xe, at 300 K, using a new experimental technique. The results for Ar, kAr=(1.2 ± 0.2) × 10 -31 cm6 Kr, kKr=(2.1 ± 0.9) × 10-31 cm and Xe, kxe=(1.48 ± 0.18) x 10 -31 cm6S-1 are discussed and compared with those of other authors using different techniques.
- Recognition of human activity based on sparse data collected from smartphone sensorsPublication . Gordalina, Goncalo; Correia, Pedro; Pires, Gabriel; Oliveira, Luis; Figueiredo, Maria João; Martinho, Ricardo; Rijo, Rui, Rui Pedro Charters Lopes; Assunção, Pedro; Seco, Maria Alexandra Abreu Henriques; Fonseca-Pinto, RuiThis paper proposes a method of human activity monitoring based on the regular use of sparse acceleration data and GPS positioning collected during smartphone daily utilization. The application addresses, in particular, the elderly population with regular activity patterns associated with daily routines. The approach is based on the clustering of acceleration and GPS data to characterize the user’s pattern activity and localization for a given period. The current activity pattern is compared to the one obtained by the learned data patterns, generating alarms of abnormal activity and unusual location. The obtained results allow to consider that the usage of the proposed method in real environments can be beneficial for activity monitoring without using complex sensor networks.
- Response of fabric insert injection overmolding PP based composites subjected to single and muti-impactPublication . Ferreira, José; Febra, Tiago; Costa, José; Capela, CarlosThis paper presents the results of a current study on the development and impact response of composite plates manufactured by injection overmolding on the two sides of a single reinforcement fibre mat. The injection polymer is a talc-filled polypropylene, nowadays used for structural purposes. Three configurations with different insert fibre mats were used: Kevlar, biaxial and multiaxial glass fibre mats. The parameters studied were the fibre mat type and the impact energy. For single impact tests, it was concluded that the highest impact energy required to achieve impactor perforation is obtained with Kevlar insert, while the highest percentage of energy recovered is achieved with biaxial glass fibre netting. Kevlar insert also allows for the maximum impact stiffness. For the multi-impact tests, the recovered energy and the dynamic stiffness show the same tendencies of the single impact tests. On low energy impacts, the effect of the insert fibre and of the previous impact are quite reduced, while for impact energies above 6J, previous impacts reduce significantly the recovered energy and the impact energy for which the perforation was achieved.