Showing papers by "Simon Brown published in 2010"

Coefficient of restitution for bouncing nanoparticles

Abstract: We demonstrate the measurement of the coefficient of restitution, $e$, for nanoparticles, through observations of the final distribution of bismuth particles that have bounced within silicon V-grooves. The experiments, taken together with complementary molecular-dynamics simulations, show that $e$ is generally smaller for liquid than for solid nanoparticles, and that macroscopic theories underestimate the velocity dependence of $e$. Hence, while nanoparticles are harder than bulk materials, once they have begun to yield the rate of increase of the inelastic deformation is greater.

Synchrotron x-ray diffraction measurements of strain in metallic nanoparticles with oxide shells.

Abstract: We describe synchrotron x-ray diffraction measurements of strain in Cu and Pd metal nanoparticles (1.7?40?nm diameter) both with an air-formed oxide shell and after reduction of the oxide by treatment in a hydrogen-containing atmosphere. Oxide removal is evident from x-ray diffraction (for Cu) and x-ray absorption spectroscopy (for Pd). A simple model that uses bulk elastic properties is applied to each system. In the Pd case the model predictions agree well with the experiment. For Cu the observed strains are much smaller than predicted. This discrepancy is attributed to (a) the presence of multiple grains within the Cu particles and (b) the incoherency of the oxide with the metal core.

Oblique Impacts and Rebounds of Lennard-Jones Clusters on Solid Surfaces

Abstract: We report on molecular dynamics simulations of oblique impacts of Lennard-Jones clusters with a weakly attractive solid surface. We confirm that the probability of adhesion to the substrate by the cluster is largely determined by the normal velocity of the cluster. We also analyze the dependence of the angle of reflection on the impact velocity, showing that it can be understood in terms of the velocity dependence of Newton’s normal and tangential coefficients of restitution. In particular, we find that the tangential coefficient of restitution remains close to one, depending only weakly on the impact velocity, so that the angle of reflection is principally determined by the magnitude of the normal coefficient of restitution, which has a much stronger dependence on velocity. This strong velocity dependence means that at high velocities relatively small angles of reflection can occur.

UK Climate Change Projections Report

Abstract: The UK Climate Projections (UKCP09) provide projections of climate change for the UK, giving greater spatial and temporal detail, and more information on uncertainty, than previous UK climate scenarios. This report is designed for those who wish to find out more about the purpose and design of the UKCP09 methodology for producing the probabilistic projections of climate change, and is drafted to suit a range of levels of expertise. It shows some examples of projections; the full set of results is available through the User Interface and the pre-prepared maps and graphs, with key findings presented in the Briefing Report.

Electrical signature of nanoscale coalescence in a percolating Bi nanocluster film

Abstract: We explore changes in the electrical conductance of a percolating Bi nanocluster film due to coalescence. A power law increase in conductance is observed immediately after deposition and we show this corresponds to power law changes in the radius of the necks between clusters. The power-law exponent $(\ensuremath{\lesssim}0.04)$ is much smaller than expected from classical models of microparticle coalescence. Atomistic kinetic Monte Carlo simulations reveal similar behavior during a late stage of coalescence where faceting near the necks slows the effects of surface diffusion.

Major Tribunal Decisions in 2009

Abstract: The year 2009 has seen significant change in Australian industrial relations, in particular, the repeal of the Workplace Relations Act 1996 and its replacement with Labor’s Fair Work Act 2009. From 1 July 2009, a new industrial tribunal, Fair Work Australia, replaced the Australian Industrial Relations Commission. The decisions issued by Fair Work Australia (FWA) since 1 July 2009 have put the provisions of the Fair Work Act into practice and perspective. This article focuses on those decisions which have dealt with enterprise bargaining and the agreement-making process under the Fair Work Act. Those cases demonstrate that the new agreement-making process is procedurally complex, and that FWA lacks discretion to approve enterprise agreements notwithstanding some procedural irregularity. FWA’s lack of discretion in determining whether an enterprise agreement has been ‘genuinely agreed to’ is inconsistent with the discretion reposed in FWA in other matters, including in determining whether an applicant for ...