The nonlinear solvers in numerical solution of water flow in variably saturated soils are prone to convergence difficulties. Many aspects can give rise to such difficulties, like very dry initial conditions, a steep pressure gradient and great variation of hydraulic conductivity occur across the wetting front during the infiltration of water.  So, the averaging method applied to compute hydraul...

ii ACKNOWLEDGMENTS In order to complete this study, a substantial amount of background theory beyond the traditional Medical Physics curriculum was necessary. I am grateful to Dr. Kenneth Hogstrom for providing additional instruction in these areas and recognize that I am fortunate to have learned this material from a prominent expert in this field. I also owe a large debt of gratitude to my ve...

Background: Dose calculation algorithms play a very important role in predicting the explicit dose distribution. We evaluated the percent depth dose (PDD), lateral depth dose profile, and surface dose volume histogram in inhomogeneous media using calculation algorithms and inhomogeneity correction methods. Materials and Methods: The homogeneous and inhomogeneous virtual slab phantoms used in th...