A direct formulation of electromagnetic scattering based only on scalar Helmholtz equations is given. The solution, expressed as coupled non-singular boundary integral equations for the field components, provides the benefits of the reduction of dimensionality. For perfect conductors, consideration of induced surface current densities, central to standard methods, is not required. This approach has utility in high aspect ratio electromagnetic problems, surface plasmon spectra and dis- persion force calculations of complex nano structures as near and far field values are given with equal precision. Extension to dielectric scatterers and elastic wave propagation in solids is immediate.
J. Oshitani, S. Hahashi, D. Y. C. Chan
Order from Chaos: Dynamics of density segregation in continuously aerated granular systems
Physical Review Letters [Submitted 6 Feb 2017]. pdf, supp
Under continual disturbance such as vibration, tumbling, flow or aeration, granular or powder systems can display solid or fluid like behavior. Using a well-mixed system of same size (0.2 mm) non-cohesive glass beads and iron powder, we show that gentle aeration can completely segregate the components thereby reducing the entropy of mixing to create near total order from an initially chaotic mixture. We quantify the time dependence of the segregation process and identify two dynamic pathways that dominate depending on the intensity of the aeration. Such findings can facilitate the search for energy efficient methods to process granular systems in pharmaceutical, mining and waste recovery industries.
E. Klaseboer, Q. Sun, D. Y. C. Chan
A field only integral equation method for time domain scattering of electromagnetic pulses
Applied Optics [306002 Submitted 30 Aug 2017]. pdf
A combination of a non-singular boundary integral method to solve directly for the electromagnetic field components in the frequency domain and Fourier transform is used to describe the space-time behavior in electromagnetic problems. The approach is stable for wavelengths both small and large relative to characteristic length scales. Amplitudes and phases of field values can be obtained accurately on or near material boundaries. Local field enhancement due to multiple scattering is quantified.