Stephen is a researcher, mainly in the area of numerical methods; their implementation in software, their application in engineering and science and their analysis. He has a particular interest in the boundary element method (BEM), its application in acoustics (Helmholtz equation) and to the fundamental Laplace equation. Stephen has also published papers on inverse diffusion (backward heat conduction problem) and on the finite-difference time-domain method (FDTD) in electromagnetics.