Higher order numerical methods for singular perturbation problems

Philosophiae Doctor - PhDIn recent years, there has been a great interest towards the higher order numerical methods for singularly perturbed problems. As compared to their lower order counterparts, they provide better accuracy with fewer mesh points. Construction and/or implementation of direct higher order methods is usually very complicated. Thus a natural choice is to use some convergence acceleration techniques, e.g., Richardson extrapolation, defect correction, etc. In this thesis, we will consider various classes of problems described by singularly perturbed ordinary and partial differential equations. For these problems, we design some novel numerical methods and attempt to increase their accuracy as well as the order of convergence. We also do the same for existing numerical methods in some instances. We find that, even though the Richardson extrapolation technique always improves the accuracy, it does not perform equally well when applied to different methods for certain classes of problems. Moreover, while in some cases it improves the order of convergence, in other cases it does not. These issues are discussed in this thesis for linear and nonlinear singularly perturbed ODEs as well as PDEs. Extrapolation techniques are analyzed thoroughly in all the cases, whereas the limitations of the defect correction approach for certain problems is indicated at the end of the thesis.South Afric

Transport modelling in the Cape Town Metropolitan Area

MSc (Mathematics and Applied Mathematics)The use of MEPLAN by the Metropolitan Transport Planning Branch of the Cape Town City Council since 1984 was not successful due to apartheid anomalies. EMME/2 was then introduced in 1991 in replacement of MEPLAN. In this thesis we first introduce some aspects of transport modelling. Secondly we summarize the above-mentioned models before we undertake their comparative study in a post-apartheid situation. A mathematical proof of why MEPLAN was discarded is provided. The strengths and weaknesses of both MEPLAN and EMME/2 are recorded.South Afric