Weak selection and stability of localized distributions in Ostwald ripening

We support and generalize a weak selection rule predicted recently for the self-similar asymptotics of the distribution function (DF) in the zero-volume-fraction limit of Ostwald ripening (OR). An asymptotic perturbation theory is developed that, when combined with an exact invariance property of the system, yields the selection rule, predicts a power-law convergence towards the selected self-similar DF and agrees well with our numerical simulations for the interface- and diffusion-controlled OR.Comment: 4 pages, 2 figures, submitted to PR

The electrorheological effect in static squeeze-flow

The static behaviour of an Electrorheological (ER) fluid in squeeze-flow is investigated both theoretically and experimentally for three types of loading condition namely single and superimposed loading when the fluid in energised by a constant potential, and superimposed loading when the fluid in energised by a constant field. From the experimental work an empirical equation for yield stress as a function of field is derived and there are found to be two values of the exponent in squeeze mode depending on the type of loading. The exponent obtained under single loading is consistent with that commonly quoted for ER fluids in shear mode while the exponent obtained under superimposed loading upon application of a constant potential is seen to be much larger. The theoretical analysis was successfully applied to modelling an ER fluid in static squeeze-flow. Comparison of theoretical and experimental results shows good agreement between them. The distributions of the electric field strength and field lines are investigated for parallel circular electrodes and whilst the value of the field is almost uniform in the middle regions of the inter-electrode space, there is an extremely high field existing around the edges of the space. The existence of this non-uniform edge field causes a back pressure which inhibits the radial movement of the fluid from the space between the electrodes

FIELD EVAPORATION OF IRON AND NIOBIUM IN NEON AND HYDROGEN

Field evaporation of iron and niobium in neon and in hydrogen was examined between 20 K and 200 K with an FIM. From the temperature dependence of the evaporation field and the field dependence of the evaporation rate, the activation energy for the evaporation was estimated and the effect of hydrogen was discussed

Role of Bi, Sb and in in microstructure formation and properties of Sn-0.7Cu-0.05Ni-X BGA interconnections

The Sn-0.7Cu-0.05Ni solder composition was first introduced in 1999 as a Pb-free interconnection material for the electronics industry and quickly earned widespread popularity as a cost-effective alternative to the Ag-containing solders then being widely promoted as the best way of meeting the requirement of the impending EU RoHS regulations. Recently there has been ongoing industrial interest in the development of next-generation Pb-free and Ag-free electronic solder alloys with enhanced reliability in a wider range of applications. In the search for improved reliability, first generation Pb-free solders are being modified with alloying additions, such as Bi, Sb and In to improve their performance in harsh environments. The present investigation explores microstructures formed in Sn-0.7Cu-0.05Ni-X/Cu solder joints (where X = 0-5wt%Bi, Sb, In or combinations thereof) and explores the correlation between the resulting solder joint microstructures and their mechanical response during shear impact testing