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>Semi-open street roofs protect pedestrians from strong sunshine and heavy rains. >But they may affect airflows and ventilation in urban canopy layers (UCL).> Age of air & flow rates are analyzed under wind directions of 0 o ,15 o ,30 o , 45 o .>Walls fully or partly covering street roofs at z=H get the worst UCL ventilation.> Semi-open street roofs at z=1.2H,1.1H get good ventilation and are realistic designs.

The chemical composition and architecture of catalytic layers significantly affect the performance of membrane electrode assemblies in proton exchange membrane fuel cells. In this work, a novel catalytic layer with hierarchical proton transport pathways has been designed by simultaneously employing Nafion nanofibers and Nafion ionomers. A H2/O2 fuel cell based on the hierarchical catalytic layer shows an increase of 32.3% on power output in comparison with the conventional fuel cell at 70 °C and 100% relative humidity. That is attributed to unique roles of Nafion nanofibers in the hierarchical catalytic layer. First, the addition of Nafion nanofibers significantly increases the proton conductivity of the catalytic layer up to 8.3 × 10–1 S cm–1 at 70 °C and 100% relative humidity, which is 15.7 times higher than that of the catalytic layer where the Nafion nanofibers are replaced by the same content of Nafion ionomers. That is confirmed by the accumulated proton transportation of a single Nafion nanofiber in the Nafion-nanofiber-based catalytic layer by a simulated model. Second, the porosity of the catalytic layer is increased due to the introduction of a Nafion nanofiber, leading to enhancement of mass transfer. Third, the Pt/C nanoparticles are homogeneously anchored on the surface of the Nafion nanofibers, which improves the electrochemical surface area and the utilization of the Pt catalyst.

DC electrodeposition of iron-rich terbium alloys on copper electrodes has been achieved using aqueous citrate solutions. Experiments were carried out in a Hull cell to examine the influence of a wide current density range on the composition and thickness of Fe-Tb alloys. Bright, gray, thin Fe-Tb alloy films were obtained with low current efficiencies. Energy dispersive spectroscopic analysis indicated that Na, S, and O impurities were incorporated in the film. The experimental results demonstrated, for the first time, that Fe promoted terbium electrodeposition. Thus, the alloy codeposition mechanism was classified as the induced type. © 2000 The Electrochemical Society. S1099-0062(00)04-110-9. All rights reserved. Electrodeposited terbium alloys are of interest for their potential use as thin film magnetostrictive, smart materials with applications for remote sensing and actuating. Bulk Terfenol, TbFe 2 , and Terfenol-D, Tb 0.3 Dy 0.7 Fe 1.9 , exhibit giant magnetostriction at room temperature with yield displacements on the order of 1000 ppm under modest magnetic fields (~1 kOe). 1,2 These materials are currently manufactured by bulk metallurgical processes 3,4 and thin film deposits have been realized using vapor deposition techniques. [5][6][7][8][9] To our knowledge there is only one report of Fe-Tb alloy electrodeposition from an aqueous solution. Lim et al. 10 investigated the electrodeposition of Fe-Tb-O films from a tartrate electrolyte with ac currents and measured their magnetic properties. This paper reports our recent findings on the dc electrodeposition of Fe-Tb alloys from a citrate electrolyte. The qualitative features of the electrodeposition mechanism are addressed.The challenge in electrodepositing rare earth metals stems from their electronegative oxidation-reduction potentials (e.g., Tb +3 + 3e -} Tb; -2.28 V). 11 Such a negative potential can limit electrodeposition from aqueous solutions, because water decomposes at a much higher potential (e.g., 2H 2 O + 4e -} 2 OH -+ H 2 ; -0.828 V). 11 Either complexing agents must be used to move the reduction potentials to a more favorable region in an aqueous solution or a different electrolyte can be employed (e.g., organic or fused salt). In the literature, both methods have been reported for a variety of rare earth elemental and alloy electrodepositions.Aqueous electrolytes have been used for the reduction of Sm, 12 La, 13 Dy-Ba-Cu, 14 and Nd 2 CuO 4 . 15 Lokhande and Jundhale 12 investigated the electrodeposition of elemental samarium films from aqueous acidic and alkaline baths with tartaric acid. The deposition potentials were found to be substrate and complexing agent dependent. Lokhande et al. 13 also reported the electrodeposition of lanthanum from aqueous solutions on different substrates. Sodium citrate was found to be a suitable complexing agent for lanthanum deposition. Concerning alloy rare earth deposits, Pawar and Pendse 14 carried out Dy-Ba-Cu electrodeposition from an aqueous bath. They obtained Dy-Ba-Cu alloys with thicknesses of 3-...

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