Browsing by Issue Date, starting with "2022-09"
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- A Miguel Torga: ‘Sagração’ de São Leonardo de Galafura, em Sol MaiorPublication . Rosa, José Maria SilvaBreve testemunho de deambulação outonal pelo «pagus» de um "Douro desconhecido", em homenagem a Miguel Torga, e memória de outros percursos durienses, por entre vinhas, o solo e o Céu.
- O ‘Projecto para uma Ética Mundial’ e 0 'caminho das pedras' daquilo que nos separa: Da universalidade dos princípios (H. Küng) à hospitalidade das convicções (P. Ricoeur)Publication . Rosa, José Maria SilvaRelativamente a problemática do diálogo intercultural e religioso, apresentam-se duas perspetivas diferentes. Hans Küng, teólogo alemão, parte da ideia central de que não haverá paz no mundo enquanto as religiões não fizerem as pazes entre si, defendendo um projeto de ética mundial, de inspiração kantiana, uma vez que há valores universais e princípios comuns a todas as religiões. Frente a esta proposta de encontrar denominadores comuns, o filosofo francês Paul Ricoeur propõe uma via diferente. Começar não por aquilo que nos une, mas precisamente por aquilo que nos divide, pelo "caminho das pedras". E atender as razoes e as condições concretas histórico-geográficas dos conflitos religiosos, e de outros que destes decorrem, para aí, adentro da hospitalidade das convicções presente nas diferentes tradições religiosas, iniciar o lento trabalho de cura das memorias feridas em direção ao fundo místico e não dito presente em todas as religiões.
- Introdução: in Diálogo Intercultural e ReligiosoPublication . Rosa, José Maria SilvaO ramalhete de textos, de fotos e de sentidos - multiplos «logoi» - que compõem o presente livro, não obstante terem como tema e objeto de estudo precisamente «O Diálogo Intercultural e Religioso» e, por isso, se situarem de certo modo num nível superior de analise, não escapam sem mais para o plano puramente teórico. Radicam ao invés num espaço e num tempo concretos, a partir de uma oportunidade e de um determinado contexto que os fez nascer: diálogos havidos no Convento de Balsamão, em Chacim, Macedo de Cavaleiros, em outubro de 2021, à semelhança do que se costuma fazer todos os anos. São vozes e olhares plurais, cruzados, de variegada proveniência, situando-se alguns a meio caminho entre 0 ensaio geral e o estudo de caso.
- Roda de bicicleta a rodar na horizontal e na verticalPublication . Reis, António; Rocha, José Ferreira da; Gameiro, Atilio; Carvalho, José Pacheco De; Barata, Rui Eugénio da SilvaEste trabalho mostra a roda de bicicleta, a rodar na horizontal como um pião e a rodar na vertical, pendurada na extremidade do eixo. Esta experiência tem sido usada em eventos científico œ pedagógicos, desde os antigos dias da UBI até agora. É a conservação do momento angular, que tem módulo, direcção e sentido, que mantém, por algum tempo, a roda a rodar na horizontal e também a rodar na vertical, sem tombar (Fig.1a,b). No caso horizontal, com a roda parada, quando o centro de gravidade da roda começa a cair fora da base de sustentação, ela tomba. Contudo, se estiver a rodar, ela tem momento angular, que tende a conservar-se, mantendo a roda na horizontal. No caso vertical, com a roda parada, o peso da roda aplica um torque em relação ao ponto de amarração da corda, que a faz tombar. Porém, se estiver a rodar, ela tem momento angular, que tende a conservar-se, mantendo a roda na vertical, embora com movimento de precessão. Este é tanto maior quanto maior for o torque.
- Exploring the effects of interchange rotations on high-intensity activities of elite futsal playersPublication . Ribeiro, João Nuno; Gonçalves, Bruno; Illa, Jordi; Couceiro, Micael; Sampaio, Jaime; Travassos, BrunoThe literature lacks an understanding of the physical demands of team sports with unlimited substitutions (player interchange rotations). Because of this characteristic of the game, it is necessary to analyze the physical requirements through player rotation rather than analyzing global averages. The objective of this research is to investigate the relationship between high-intensity activities (HIA; sum of accelerations, decelerations, and high-speed running actions) performed per interchange rotations and match time variables (playtime, rest time, and work–rest ratio) in elite futsal players. A retrospective observational design was used. Twelve matches from an elite male team competing in the Premier Spanish Futsal League were analyzed using a local positioning system, yielding a total sample of 17 players. The number of HIA performed per interchange rotation varies between players and allows the identification of three distinct activity profiles—lower HIA (10 HIA), medium HIA (28 HIA), and higher HIA (38 HIA). Furthermore, these profiles were found to be stable alongside the existing interchange rotations throughout the match. Playtime (F = 40.9, p < .001) and work–rest ratio (F = 15.6, p < .001) are the time variables that best differentiate match activity profiles. Players with more playing time (4.6 ± 1.0 min) and a work–rest ratio equal to or greater than 1 (1.1 ± 0.6 a.u.) have a greater ability to repeat HIA per rotation.
- Strength and Power Performance Changes During an In-Season Resistance Training Program in Elite Futsal Players: A Case StudyPublication . Marques, Diogo Luís; Ribeiro, João Nuno; Sousa, António Carlos; Travassos, Bruno; Marques, Mário CardosoIn this study, we aimed to analyze (i) the strength and power changes after resistance training (RT) in elite futsal players, and (ii) the associations between the session rate of perceived exertion (sRPE) and perceived total quality recovery (TQR), and the sRPE and TQR with the volume load of the RT program. Ten elite futsal players (24.8 ± 5.4 years; 76.2 ± 7.1 kg; 1.77 ± 0.05 m) performed an in-season 8-week RT program twice per week. RT consisted of 2-3 sets x 3-6 reps at 45-65% of one-repetition maximum (1RM) with maximal velocities in the full squat and complementary exercises with the same volume. We assessed the TQR before every session, while the sRPE was calculated after each RT session. One week before and after the intervention, we measured the countermovement jump (CMJ) height, isometric hip adduction strength (IHAS), 1RM, and peak power (PP) in the full squat progressive loading test. After the 8-week training program, there was a significant improvement in most outcomes, yet the gains (%Δ) remained below the minimal detectable change (MDC), except for IHAS (CMJ: p < 0.05, %Δ = 6.7, MDC% = 7.2; IHAS: p < 0.001, %Δ = 19.1, MDC% = 14.6; 1RM: p > 0.05, %Δ = 9.2, MDC% = 21.5; PP: p < 0.05; %Δ = 14.4, MDC% = 22.4). We also found a significant negative correlation between TQR and the sRPE (r = -0.45, p < 0.001). Our data suggest that RT based on low-volume and low-to-moderate loads may not produce a sufficient stimulus to induce meaningful dynamic strength and power gains in elite futsal players, although it improves isometric strength. Furthermore, monitoring TQR before sessions may show coaches how the elite futsal player will perceive the session's intensity.
- Survey on 5G Second Phase RAN Architectures and Functional SplitsPublication . Bahram, Khan; Nidhi, Nidhi; OdetAlla, Hatem; Flizikowski, Adam; Mihovska, Albena Dimitrova; Wagen, Jean-Frédéric; Velez, FernandoThe Radio Access Network (RAN) architecture evolves with different generations of mobile communication technologies and forms an indispensable component of the mobile network architecture. The main component of the RAN infrastructure is the base station, which includes a Radio Frequency unit and a baseband unit. The RAN is a collection of base stations connected to the core network to provide coverage through one or more radio access technologies. The advancement towards cloud native networks has led to centralizing the baseband processing of radio signals. There is a trade-off between the advantages of RAN centralization (energy efficiency, power cost reduction, and the cost of the fronthaul) and the complexity of carrying traffic between the data processing unit and distributed antennas. 5G networks hold high potential for adopting the centralized architecture to reduce maintenance costs while reducing deployment costs and improving resilience, reliability, and coordination. Incorporating the concept of virtualization and centralized RAN architecture enables to meet the overall requirements for both the customer and Mobile Network Operator. Functional splitting is one of the key enablers for 5G networks. It supports Centralized RAN, virtualized Radio Access Network, and the recent Open Radio Access Networks. This survey provides a comprehensive tutorial on the paradigms of the RAN architecture evolution, its key features, and implementation challenges. It provides a thorough review of the 3rd Generation Partnership Project functional splitting complemented by associated challenges and potential solutions. The survey also presents an overview of the fronthaul and its requirements and possible solutions for implementation, algorithms, and required tools whilst providing a vision of the evaluation beyond 5G second phase.
- Influence of Dimensionless Temperature on Droplet Impact onto Heated Liquid Films for Subcooled Boiling RegimesPublication . Vasconcelos, Daniel; Silva, A. R. R.; Barata, Jorge M MHeat and mass transfer mechanisms related to multiphase flows occur in several applications such as spray cooling, quenching, internal combustion engines and plasma spraying. These mechanisms have become increasingly important due to the need of achieving higher heat rate coefficients associated with phase-change processes, such as evaporation and condensation. Specifically, the phenomenon of droplet impact onto non-heated liquid films has been extensively researched, both experimentally and numerically. However, the influence of temperature on droplet impact and liquid film stability has been overlooked in the literature, which is a focal point in understanding interfacial phenomena. The main objective of this work is to experimentally study droplet impact onto heated liquid films. Therefore, an experimental facility was designed for this purpose. A borosilicate glass surface is used to contain the liquid film. This surface is placed above an aluminium block with four embedded cartridge heaters of 250W each, heating the liquid film by conduction. Immersion type-k thermocouples are employed for liquid film temperature measurements. Liquid film evaporation rates are calculated in order to ensure the liquid film thickness prior to the droplet impact. Water and n-decane are the fluids adopted due to their differences in thermophysical properties and saturation temperature. The impact conditions are 100 < W e < 300, 0.5 < h* < 1.5, and a dimensionless temperature of θ < 0.6. Qualitative analysis is performed regarding crater and central jet evolution, and quantitative data regarding evaporation rate and central jet height are measured. The dimensionless temperature affects the droplet impact phenomena, creating recirculation zones near the crater and the impact surface, and affecting the crater formation. The central jet height increases with increasing values of θ for h* = 1.0 and h* = 1.5, whereas for h* = 0.5, the measurements do not follow a similar tendency. The emerging time of the central jet is delayed for higher values of θ, meaning that future studies regarding crater evolution should be considered. The dimensionless temperature also promotes central jet breakup, as well increasing the number of secondary droplets originated from the breakup.
- Influence of Vapour Bubbles Size and Spacing on Droplet Impact Outcomes under Subcooled Boiling RegimesPublication . Vasconcelos, Daniel; Silva, A. R. R.; Barata, Jorge M MMultiphase flows are characterised as heterogeneous mixtures of two or more phases, such as gas-liquid or solid-liquid. These are extremely complex due to the underlying dynamics that may occur, which include interfacial phenomena, such as boiling and evaporation, and interactions between phases. Specifically, droplet impact onto heated wetted surfaces has been overlooked in the literature, which involves heat and mass transfer mechanisms related to sensible heating, condensation and evaporation. The droplet impact phenomenon occurs in several industrial applications, such as internal combustion engines, electronics cooling devices, heat exchangers, among others. In numerical terms, improving efficiency and reliability of simulations is of interest to understand the behaviour of mathematical models for complex physical systems. The main objective of this work is to numerically simulate droplet impact onto a heated liquid film in the presence of vapour bubbles in a 2D-axisymmetric assumption. The numerical model solves the incompressible mass, momentum and energy equations coupled with the VOF method and height functions for accurately capturing the interface. Phase-change processes such as evaporation and condensation are neglected for the current simulations. Water and n-decane are the fluids adopted for the simulation. The impact conditions are D0 = 3.0 mm, h* = 0.5, and U0 = 3.0 m/s. Different vapour bubble sizes, (Dv), and spacings, (xv), are studied to evaluate the vapour bubble phenomena and crown geometrical parameters. An initial vapour bubble is positioned on the axis of symmetry, xs = 0, and, therefore, in the droplet trajectory. Results indicate that vapour bubbles have a lower influence on crown diameter, and a higher influence on crown height. Increasing the size of vapour bubbles leads to a decrease in both crown diameter and height, whereas an increase in the vapour bubbles spacing causes an increase in the crown height and diameter. The initial vapour bubble positioning in relation to the axis of symmetry is a factor that should also be considered in future studies.
- The Impact of High Particles Concentration in a Biofuel Droplet CombustionPublication . Mendes, Tomás S. M.; Ferrão, Inês; Mendes, Miguel; Moita, A. S.; Silva, A. R. R.Aviation is one of the largest transportation sectors and is operated on fossil fuels, being responsible for about 2% of global CO2 emissions. In order to reduce the environmental impact, biofuels emerged as a promising solution. Additionally, a possible approach to improve the performance of biofuels is to add nanoparticles, leading to the concept of nanofuel. The present work evaluates the nanofuel droplet combustion of a biofuel containing high aluminum particle concentrations. To enhance the nanofuel stability, a preliminary study focusing on the addition of a surfactant was mandatory. Particle size of 40 nm and three particle concentrations from 1.0 to 4.0 wt.% were considered. The results show that the oleic acid effectively improves the stability, and no visible oxidation of the nanoparticles was reported. Regarding the single droplet combustion, the observations show that the addition of nanoparticles promotes micro-explosions, contrary to the combustion of pure biofuel, and increases the overall droplet burning rate.
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