Electrocatalytic activity of IrO2-RuO2 supported on Sb-doped SnO2 nanoparticles

Electrocatalytic IrO₂-RuO₂ supported on Sb-doped SnO₂ (ATO) nanoparticles is very active towards the oxygen evolution reaction. The IrO₂-RuO₂ material is XRD amorphous and exists as clusters on the surface of the ATO. Systematic changes to the surface chemical composition of the ATO as a function of the IrO₂:RuO₂ ratio suggests an interaction between the IrO₂-RuO₂ and ATO. Cyclic voltammetry indicates that the electrochemically active surface area of IrO₂-RuO₂ clusters is maximised when the composition is 75 mol% IrO₂-25 mol% RuO₂. Decreasing the loading of IrO₂-RuO₂ on ATO reduces the electrochemically active surface area, although there is evidence to support a decrease in the clusters size with decreased loading. Tafel slope analysis shows that if the clusters are too small, the kinetics of the oxygen evolution reaction are reduced. Overall, clusters of IrO₂-RuO₂ on ATO have similar or better performance for the oxygen evolution reaction than many previously reported materials, despite the low quantity of noble metals used in the electrocatalysts. This suggests that these oxides may be of economic advantage if used as PEM water electrolysis anodes.     

Wind tunnel blockage corrections: Review and application to Savonius vertical-axis wind turbines

An investigation into wake and solid blockage effects of vertical axis wind turbines (VAWTs) in closed test-section wind tunnel testing is described. Static wall pressures have been used to derive velocity increments along wind tunnel test section which in turn are applied to provide evidence of wake interference characteristics of rotating bodies interacting within this spatially restricted domain. Vertical-axis wind turbines present a unique aerodynamic obstruction in wind tunnel testing, whose blockage effects have not yet extensively investigated. The flowfield surrounding these wind turbines is asymmetric, periodic, unsteady, separated and highly turbulent. Static pressure measurements are taken along a test-section sidewall to provide a pressure signature of the test models under varying rotor tip-speed ratios (freestream conditions and model RPMs). Wake characteristics and VAWT performance produced by the same vertical-axis wind turbine concept tested at different physical scales and in two different wind tunnels are investigated in an attempt to provide some guidance on the scaling of the combined effects on blockage. This investigation provides evidence of the effects of large wall interactions and wake propagation caused by these models at well below generally accepted standard blockage figures.     

Solubilisation of nickel from powders at near-neutral pH and the role of oxide layers

Dissolution rates of nickel powder in pH 5 acetate buffers were observed to be an effective indicator of the thickness of the oxide layer on the surface of the nickel particle. Tests on powders pre-cleaned with acid or pre-oxidized in air demonstrated this dependence. The saturation level of nickel in the solution is not greatly affected by the initial state of the powder. Effects of additive solutes are most pronounced during short-term dissolution tests. Among such solutes, reduced sulphur and selenium species, phosphate, fluoride, oxalate, and permanganate cause the largest increases in dissolution rate, while hexacyanoferrate, arsenite, periodate, chromate, vanadate, molybdate, iodate, and tungstate suppress the dissolution.     

On the relationship between recognition speed and accuracy for words rehearsed via rote versus elaborative rehearsal.

Tacit within both lay and cognitive conceptualizations of learning is the notion that those conditions of learning that foster "good" retention do so by increasing both the probability and the speed of access to the relevant information. In 3 experiments, time pressure during recognition is shown to decrease accessibility more for words learned via elaborative rehearsal than for words learned via rote rehearsal, despite the fact that elaborative rehearsal is a more efficacious learning strategy as measured by the probability of access. In Experiment 1, participants learned each word using both types of rehearsal, and the results show that access to the products of elaborative rehearsal is more compromised by time pressure than is access to the products of rote rehearsal. The results of Experiment 2, in which each word was learned via either pure rote or pure elaborative rehearsal, exhibit the same pattern. Experiment 3, in which the authors used the response-signal procedure, provides evidence that this difference in accessibility owes not to differences in the rate of access to the 2 types of traces, but rather to the higher asymptotic level of stored information for words learned via elaborative rehearsal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)