Effect of Particle Morphology on the Ripening of Supported Pt Nanoparticles

To improve the understanding of sintering in diesel and lean-burn engine exhaust aftertreatment catalysts, we examined oxygen-induced sintering in a model catalyst consisting of Pt nanoparticles supported on a planar, amorphous Al2O3 substrate. After ageing at increasing temperatures, transmission electron microscopy analysis reveals that highly monodisperse ensembles of nanoparticles transformed into ensembles with bimodal and subsequently Lifshitz-Slyozov-Wagner particle size distributions. Moreover, scanning transmission electron microscopy and atomic force microscopy analysis suggest that the Pt nanoparticles have size-dependent morphologies after sintering in oxidizing environment. The evolution of the particle sizes is described by a simple kinetic model for ripening and the size-dependent particle morphology is proposed as an explanation for the observed bimodal particle size distribution shapes

Three-dimensional steep wave impact on a vertical cylinder

In the present study we investigate the 3-D hydrodynamic slamming problem on a vertical cylinder due to the impact of a steep wave that is moving with a steady velocity. The linear theory of the velocity potential is employed by assuming inviscid, incompressible fluid and irrotational flow. As the problem is set in 3-D space, the employment of the Wagner condition is essential. The set of equations we pose, is presented as a mixed boundary value problem for Laplace's equation in 3-D. Apart from the mixed-type of boundary conditions, the problem is complicated by considering that the region of wetted surface of the cylinder is a set whose boundary depends on the vertical coordinate on the cylinder up to the free-surface. We make some simple assumptions at the start but otherwise we proceed analytically. We find closed-form relations for the hydrodynamic variables, namely the time dependent potential, the pressure impulse, the shape of the wave front (from the contact point to beyond the cylinder) and the slamming force

Violent breaking wave impacts. Part 3. Effects of scale and aeration

AbstractThe effects of scale and aeration on violent breaking wave impacts with trapped and entrained air are investigated both analytically and numerically. By dimensional analysis we show that the impact pressures for Froude scaled conditions prior to the impact depend on the scale and aeration level. The Bagnold–Mitsuyasu scaling law for the compression of an air pocket by a piston of incompressible water is rederived and generalised to 3D air pockets of arbitrary shape. Numerical results for wall pressure, force and impulse are then presented for a flip-through impact, a low-aeration impact and a high-aeration impact, for nine scales and five levels of initial aeration. Two of these impact types trap a pocket of air at the wall. Among the findings of the paper is that for fixed initial aeration, impact pressures from the flip-through impact broadly follow Froude scaling. This is also the case for the two impact types with trapped air pockets for impact pressures below 318 kPa, while impact pressures above this value broadly follow the Bagnold–Mitsuyasu scaling law with full-scale pressures greater than those predicted by the Froude law. For all impact types, the effect of aeration is found to reduce the maximum impact pressure, maximum force and impulse. Good agreement with the asymptotic model of Peregrine &amp; Thais (J. Fluid Mech., vol. 325, 1996, pp. 377–397) is found for the flip-through impact pressure and a fair agreement is found for the low- and high-aeration impacts. Based on the numerical results, a modified scaling curve that combines Froude scaling and the Bagnold–Mitsuyasu law is suggested. The practical implications of the findings are discussed and attention is drawn to the limitations of physical model tests.</jats:p

ISAFRUIT - Increasing fruit consumption through a trans-disciplinary approach delivering high quality produce from environmentally friendly, sustainable production methods T5.4.1.1

An Integrated European Project, focussing on increasing fruit consumption at the European level, lasting 54 months, starting on Jan. 1st, 2006. This is a 21 million plus project, receiving 13.8 million euro from the EU. The project comprises 8 Pillars: Pillar 1: Consumer preferences (Coordinator: K. Zimmermann) Pillar 2: Human Health studies (Coordinator: L. Dragsted) Pillar 3: Fruit Processing (Coordinator: W. Plocharski) Pillar 4: Post-harvest (Coordinator: A. van Schaick) Pillar 5: Pre-harvest fruit quality (Coordinator: L. Bertschinger) Pillar 6: Genetics of fruit quality (Coordinator: Y. Lespinasse) Pillar 7: ISAFRUIT Knowledge management (Coordinator: L. Corelli Grappadelli Pillar 8: ISAFRUIT Management (Coordinator: O. Callesen