The Method of Transformed Field Expansions (TFE) has been demonstrated to be a robust and highly accurate numerical scheme for simulating solutions of boundary value and free boundary problems from the sciences and engineering. As a Boundary Perturbation Method it builds highly accurate solutions based upon exact solutions in a simple, canonical, geometry and corrects these via Taylor series to...

Gate degradation in high electron mobility transistors (HEMTs) under OFF-state stress results from the high electric field near the gate edge. We investigate the evolution of this field over time in AlGaN/ GaN HEMTs upon OFF-state stress using a combination of electroluminescence (EL) microscopy and spectroscopy. EL analysis suggests that the electric field at the sites of generated surface def...

We investigate the applicability of a high-order Spectral Element Method (SEM) to density based topology optimization unsteady flows in two dimensions. Direct Numerical Simulations (DNS) are conducted relying on Brinkman penalization describe presence solid within domain. The procedure uses adjoint-variable method compute gradients and checkpointing strategy reduce storage requirements. A nonli...

The SEMum model of Lekic and Romanowicz (2011) (SEMum v.1) was the first global VS model obtained using spectral-element forward modeling (SEM: Komatitsch and Vilotte, 1998), and exhibits impressive amplitudes of heterogeneity in the upper 200km of the mantle compared to previous global models. Among other measures to make SEM-based modeling tractable, SEMum v.1 was developed using an homogeniz...

A spectral element method together with a surface integral equation as the radiation boundary condition is used to simulate the scattering properties of periodic subwavelength slits. The surface integral equation utilizes the periodic Green’s function in the wave number space and is solved by the method of moments, while the interior inhomogeneous medium is modeled by the spectral element metho...