CDRsp - Artigos em revistas internacionais
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- Toward Integrative Biomechanical Models of Osteochondral Tissues: A Multilayered PerspectivePublication . Filipe Ramos Cardoso da Silva, Bruna; Marco Domingos; Amado, Sandra; Dias, Juliana; Pascoal-Faria, Paula; Ana C. Maurício; Alves, NunoUnderstanding the complex mechanical behavior of osteochondral tissues in silico is essential for improving experimental models and advancing research in joint health and degeneration. This review provides a comprehensive analysis of the constitutive models currently used to represent the different layers of the osteochondral region, from articular cartilage to subchondral bone, including intermediate regions such as the tidemark and the calcified cartilage layer. Each layer exhibits unique structural and mechanical properties, necessitating a layer-specific modeling approach. Through critical comparison of existing mathematical models, the viscoelastic model is suggested as a pragmatic starting point for modeling articular cartilage zones, the tidemark, and the calcified cartilage layer, as it captures essential time-dependent behaviors such as creep and stress relaxation while ensuring computational efficiency for initial coupling studies. On the other hand, a linear elastic model was identified as an optimal starting point for both the subchondral bone plate and the subchondral trabecular bone, reflecting their dense and stiff nature, and providing a coherent framework for early-stage multilayer integration. This layered modeling approach enables the development of physiologically coherent and computationally efficient representations of osteochondral region modeling. Furthermore, by establishing a layer-specific modeling approach, this review paves the way for modular in silico simulations through the coupling of computational models. Such an integrative framework supports scaffold design, in vitro experimentation, preclinical validation, and the mechanobiological exploration of osteochondral degeneration and repair. These efforts are essential for deepening our understanding of tissue responses under both physiological and pathological conditions. Ultimately, this work provides a robust theoretical foundation for future in silico and in vitro studies aimed at advancing osteochondral tissue regeneration strategies.
- Stakeholder Differences in Valued Hotel Green PracticesPublication . Julião, Jorge; Monteiro, Inês; Gaspar, Marcelo; Trindade, Maria AliceThis paper aims to compare the perceptions of hotel customers and hotel staff regarding the value of green hotel attributes. By examining both stakeholder groups, the study addresses a gap in sustainable hospitality research, which largely overlooks employee perspectives in favour of customer preferences. An exploratory, cross-sectional survey was conducted using structured questionnaires, administered to hotel guests (n = 307) and hotel staff (n = 89) in Porto, Portugal. Respondents rated 15 green hotel attributes using a five-point Likert scale. Demographic data were also collected to analyse perceptual differences across gender, age, income, and education. The results revealed that both customers and staff exhibited environmental awareness, though their prioritisation of specific green practices differed. Customers tended to value visible environmental measures, such as recycling bins, energy-saving light bulbs, and renewable energy signage, while staff placed greater emphasis on operational sustainability aspects, including low-flow plumbing fixtures, refillable soap dispensers, and durable goods used in service areas. These differences reflect the stakeholders’ distinct roles and experiences within the hotel ecosystem. This study enriches the discourse on sustainable hospitality by providing a dual-stakeholder analysis of green hotel attributes using a shared evaluative framework. The findings offer practical insights for hotel managers aligning sustainability strategies with the expectations of both guests and employees, supporting more effective and inclusive green implementation in the lodging sector.
- Comparative Analysis of Pressure Platform and Insole Devices for Plantar Pressure AssessmentPublication . Amaro, Catarina M.; Paulino, Maria F.; Valvez, Sara; Roseiro, Luis; Castro, Maria António; Amaro, Ana M.Foot plantar pressure refers to the pressure or force that the foot generates in contact with the ground, varying across different regions of the foot. This parameter is essential in static and dynamic analyses to access accurate diagnoses, study the human body biomechanics, create functional footwear designs, aid in rehabilitation and physiotherapy, and prevent injuries in athletes during sports practice. This study presents an experimental comparison between two different plantar pressure measurement devices, Pedar® (sensorized insoles) and Physiosensing® (pressure platform). The devices were selected based on their capacity to measure contact area and peak pressure points. Results showed that Physiosensing® provided a more uniform measurement of the contact area, proving its efficiency for weight distribution and stability analysis applications, particularly in posture assessment and balance studies. The Pedar® system showed higher capacity in peak pressure point detection. Therefore, the insole system is more suitable for applications requiring precise high-pressure zone localization. Comparative analysis highlights the strengths and limitations of each device and offers insights regarding its optimal usage in clinical, sports, and research settings.
- Reconstructing Classical Algebras via Ternary OperationsPublication . Pereira Fatelo, Jorge; Martins-Ferreira, NelsonAlthough algebraic structures are frequently analyzed using unary and binary operations, they can also be effectively defined and unified using ternary operations. In this context, we introduce structures that contain two constants and a ternary operation. We demonstrate that these structures are isomorphic to various significant algebraic systems, including Boolean algebras, de Morgan algebras, MV-algebras, and (near-)rings of characteristic two. Our work highlights the versatility of ternary operations in describing and connecting diverse algebraic structures.
- Tribological behavior of Ti6Al4V cellular structures produced by Selective Laser MeltingPublication . Bartolomeu, F.; Sampaio, M; Carvalho, O.; Pinto, E.; Alves, N.; Gomes, J. R.; Silva, F. S.; Miranda, G.Additive manufacturing (AM) technologies enable the fabrication of innovative structures with complex geometries not easily manufactured by traditional processes. Regarding metallic cellular structures with tailored/customized mechanical and wear performance aiming to biomedical applications, Selective Laser Melting (SLM) is a remarkable solution for their production. Focusing on prosthesis and implants, in addition to a suitable Young's modulus it is important to assess the friction response and wear resistance of these cellular structures in a natural environment. In this sense, five cellular Ti6Al4V structures with different open-cell sizes (100–500 μm) were designed and produced by SLM. These structures were tribologicaly tested against alumina using a reciprocating sliding ball-on-plate tribometer. Samples were submerged in Phosphate Buffered Saline (PBS) fluid at 37 °C, in order to mimic in some extent the human body environment. The results showed that friction and wear performance of Ti6Al4V cellular structures is influenced by the structure open-cell size. The higher wear resistance was obtained for structures with 100 μm designed open-cell size due to the higher apparent area of contact to support tribological loading.
- From Knowledge to Action: How Portuguese Higher Education Students Engage with Circular Economy PrinciplesPublication . Pardal, Ana; Moreira, Anabela; Galacho, Cristina; Mateus, Dina; Viegas, Laura; Gaspar, Marcelo; Teixeira, Margarida Ribau; Manteigas, Vitor; Dinis, Maria Alzira PimentaThis study investigates the perceptions and practices of Portuguese higher education students regarding the circular economy (CE), emphasising their knowledge, attitudes, and behaviours toward sustainable resource management. Carried out by the Working Group on Circular Economy and Waste Management of the Portuguese Sustainable Campus Network (RCS), the research used an online survey targeting students from 20 higher education institutions (HEIs), resulting in 400 responses. The findings indicate that while students generally hold positive views of the CE, their understanding of its practical applications, such as waste reduction and resource efficiency, remains limited. Only a small proportion of students reported exposure to CE-related topics in their curriculum, revealing a gap in academic integration. This study also identifies significant demographic variations in CE awareness and practices, influenced by factors such as age, field of study, and employment status. These insights underscore the need for HEIs to strengthen CE education and actively involve students in hands-on sustainability initiatives, fostering a generation equipped to drive the transition toward a circular economy.
- Design of a Video Otoscope Prototype with an Integrated Scanner for Hearing Aid Direct Digital Manufacturing: A Preliminary StudyPublication . Ganhão, Francisco; Santos, António Carvalho; Silva, Carla; Monteiro de Moura, Carla SofiaIn the current landscape of hearing rehabilitation, ear mold manufacturing typically involves the injection of silicone into the external ear canal (EEC) of each patient. This invasive procedure poses several risks, including the potential for silicone residue retention and tympanic membrane perforation, which may necessitate surgical intervention. To mitigate these risks, we present the design of a video otoscope that integrates a scanner capable of capturing high-precision, real-time images of the EEC’s geometry. The developed device allows (i) the generation of a 3D CAD model leading to the direct, quick, and low-cost production of customized hearing aids using 3D printing and (ii) the establishment of medical protocols for carrying out diagnoses and monitoring of hearing pathology evolution using methodologies based on Artificial Intelligence. Furthermore, the use of customized hearing aids that allow the application of Rhythmic Auditory Stimulation (RAS) and music therapy enhances audiology as an alternative and innovative way to treat cognitive and degenerative diseases, as well as pathological disorders.
- Development of composite anion-exchange membranes using poly(vinyl alcohol) and silica precursor for pervaporation separation of water–isopropanol mixturesPublication . Premakshi, H. G.; Kariduraganavar, M. Y.; Mitchell, GeoffreyComposite anion-exchange membranes were prepared using sol-gel techniques with poly(vinyl alcohol) (PVA) and anion-exchange silica precursor (AESP). Ammonium functionality was created on the AESP through a ring opening reaction between 2-(3-aminoethylamino)propyltrimethoxysilane and glycidyltrimethylammonium chloride under mild heating conditions. The resulting membranes were subjected to physico-chemical investigations using various techniques. The pervaporation performance of the membranes was systematically investigated based on the effects of feed composition and the mass% of AESP. Among the membranes studied, the membranes containing 4 mass% of AESP exhibited the highest separation factor of 2,991 with a flux of 10.76 × 10-2 kg/m2h at 30 °C for 10 mass% of water in the feed. The trade-off phenomenon which exists between the flux and the separation factors was overcome by the incorporation of AESP in PVA matrix. We find that the overlap between the total flux and flux of water, suggests that these membranes could be used effectively to break the azeotropic point of water-isopropanol mixtures. From the temperature dependent diffusion and permeation values, the Arrhenius activation parameters were estimated. The Ep and ED values ranged between 18.36 and 7.94, and 18.68 and 8.09 kJ/mol, respectively. The negative heat of sorption ( Hs) values was obtained for all the membranes, indicating that Langmuir’s mode of sorption is predominant in the transport process.
- Effect of the mean stress on the fatigue behaviour of single lap jointsPublication . Pereira, António; Reis, P. N. B.; Ferreira, J. A. M.Steel is the most important construction material for the mass production of engineered structures, especially in the transport industry. On the other hand, adhesive joints are typically used to join load-bearing components. Therefore, this work intends to investigate the stress ratio effects on the fatigue behaviour of adhesively bonded steel lap joints. S–N diagrams of fatigue tests, under constant amplitude loading, were obtained for stress ratios ranging between 0.05 and 0.7. It was observed that the fatigue life of the adhesive joints has very little dependence on the stress amplitude, indicating that only the maximum stress is important. The combination of a linear equation with a quadratic equation seems to be the best formulation to fit the experimental results. Finally, the Palmgren–Miner’s Law is accurate enough to predict the fatigue design for sequential block loadings.
- On Algebraic and More General Categories Whose Split Epimorphisms Have Underlying Product ProjectionsPublication . Gray, J. R. A.; Martins-Ferreira, NelsonWe characterize those varieties of universal algebras where every split epimorphism considered as a map of sets is a product projection. In addition we obtain new characterizations of semi-abelian, protomodular, unital and subtractive varieties as well as varieties of right Ω-loops and biternary systems.