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Nowadays, railway electrification is the most efficient way to power the trains. However, power quality (PQ) phenomena toward public power systems (PPSs) have always a main concern to the railway operators, especially when the single-phase traction power system is interconnected to the three-phase PPS. The last decades have witnessed an on-going evolution of PQ improvement and traction power supply systems, contributing to diminish the negative impacts of AC railway networks on PQ of the three-phase PPS. In this context, this paper presents a global overview of the PQ phenomena in AC railway electrification, as well as the impacts of the potential hazards on the safe operation of electrified railways. The paper also reviews PQ improvement methods from the early use of AC railway electrification until the emergence of the new power electronics devices in railways industry.

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A three‐dimensional isothermal model of a high temperature polymer membrane fuel cell equipped with polybenzimidazole membrane is described. All major transport phenomena were taken into account except the species crossover through the membrane. The cathode catalyst layer was treated as spherical catalyst agglomerates with porous inter‐agglomerate spaces. The inter‐agglomerate spaces were filled with a mixture of electrolyte (hot phosphoric acid) and polytetrafluoroethylene (PTFE). This approach proved to be an essential requirement for accurate simulation. In this particular paper, the influence of different flow field designs and dimensions on performance was intensely study. Traditional configurations were tested (straight, serpentine, pin‐in, and interdigitated), and new designs were proposed. With these new designs, we tried to maximize performance by providing homogeneous reactants distribution over the active area keeping low‐pressure drop and relatively high velocity. The dimension and position of the inlet and outlet manifolds were also analyzed. From the obtained results a massive influence of the manifolds position and dimension on performance was observed. This fact can provide important guidelines for future bipolar plates optimization.

A one-dimensional model of a high temperature polymer electrolyte membrane fuel cell using polybenzimidazole (PBI) membranes is described. The model considers mass transport through a thin film electrolyte covering the catalyst particles as well as through the porous media. The incorporation of a thin film model describing reactant gas mass transport through electrolyte covering the electrocatalyst is shown to be an essential requirement for accurate simulation. The catalyst interface is represented using a macrohomogeneous model. The influence of carbon monoxide, carbon dioxide, and methane, which would be present in a reformate gas, is considered in terms of the effect on the anode polarisation/kinetics behaviour. The model simulates the influence of operating conditions, cell parameters, and fuel gas compositions on the cell voltage current density characteristics. The model gives good predictions of the effect of oxygen and air pressures on cell behaviour and correctly simulates the mass transport behaviour of the cell. The model with reformate gas shows that additional voltage losses associated with CO poisoning can lead to loss in voltage of tens of mV and thus reduction in power.

ResumoO envelhecimento é caracterizado por degeneração da função neuromuscular traduzida por diminuição da força muscular, do equilíbrio e da coordenação. Este estudo visou avaliar os efeitos de programas de exercícios resistidos, de equilíbrio e de alongamentos sobre a mobilidade funcional em idosas com baixa massa óssea. 36 voluntárias foram aleatorizadas em dois grupos: G1 [n=18; 69,4 ± 6,8 anos] e G2 [n=18; 69,4 ± 5,7 anos] e avaliadas através do Teste Sentar-levantar com 5 repetições (STS-5), Teste de Caminhada de seis metros (SMW) e Teste de Alcance funcional (FRT). O programa de exercício foi aplicado durante 4 meses, 2 vezes por semana, com treinamento de força muscular e mobilidade funcional para G1, e alongamentos e palestras informativas para G2. Após a intervenção os indivíduos de ambos os grupos diminuíram o tempo de realização do STS-5 (G1= 12,6±3,5 vs. 8,4±1,3 s, p=0,01; G2= 12,2±2,6 vs. 8,1±1,3 s, p= 0,00), bem como do SMW (G1= 4,4±1,2 vs. 3,9±0,8 s, p=0,014; G2= 4,2±0,5 vs. 3,6±0,4s, p= 0,000), enquanto se evidenciou aumento do alcance no FRT (G1=26,4±4,9 vs. 31,6±5,0 cm, p= 0,001; G2= 24,6±4,8 vs. 30,3±4,3 cm, p=0,001). Os nossos resultados permitem concluir que foram encontradas melhoras em ambos os grupos estudados e que os exercícios físicos propostos são capazes de trazer benefícios para idosas com baixa massa óssea, através de melhora na sua mobilidade funcional. Palavras-chaveIdoso; Exercício; Osteoporose; Acidentes por Quedas; Treinamento de Resistência; Equilíbrio Postural. G1 [n=18; 69.4 ± 6.8 years] e G2 [n=18; 69.4 ± 5.7 years] which were evaluated using the , Six metre walk test (SMW) and Functional Reach Test (FRT). The exercise program was applied for 4 months, two times per week, with muscle strength and functional mobility training for G1, and stretching and informative lectures for G2. After the intervention, individuals from both groups decreased their time of performance in p=0.01; G2= 12.2±2.6 vs. 8.1±1.3 s, p= 0.00), as well as in SMW (G1= 4.4±1.2 vs. 3.9±0.8 s, p=0.014; G2= 4.2±0.5 vs. 3.6±0.4 s, p= 0,000), while an increase in the reach of FRT was evident (G1 = 26.4±4.9 vs. 31.6±5.0 cm, p= 0.001; G2 = 24.6±4.8 vs. 30.3±4.3 cm, p=0.001). The results indicate that improvements were found in both studied groups and that the proposed exercise programs are able to provide benefits for elderly with low bone mass, throughout the improvement in their functional mobility. Abstract Aging is characterized by neuromuscular function degeneration reflected on a decrease of muscle strength, balance and coordination. This study aimed to evaluate the effects of resistance, balance and stretching exercise programs on functional mobility in community-dwelling elderly with low bone mass. 36 volunteers were randomized into two groups:

This paper presents a comparison between different possibilities for the vehicle-to-vehicle (V2V) power transfer between two electric vehicles (EVs). The traditional V2V operation mode is performed through a common energy aggregator, such as the electrical power grid, consisting of a combination of the vehicle-to-grid (V2G) and grid-to-vehicle (G2V) operation modes. The traditional V2V power transfer is based on four power conversions, since each on-board EV battery charger is comprised by two power converters (dc-dc and dc-ac). In this context, this paper proposes new perspectives for the V2V power transfer, both in ac and dc, focusing in the V2V power transfer using dc power (dcV2V). The proposed methods discard the need for an energy aggregator connection, being possible to directly connect two EVs, charging one EV from the other. Furthermore, the proposed dcV2V method allows the reduction of four power conversions to a single one, allowing to increase the overall efficiency of the power transfer between EVs, An efficiency-based evaluation of the different V2V methods is performed, supporting the benefits of dcV2V.