Now showing items 1-10 of 451
Performance analysis of parallel I/O models for external mergesort
Since the I/O subsystem is the bottleneck in external mergesort, I/O parallelism can result in substantial performance improvements. Concurrency can be introduced by overlapping I/O requests at different disks, and the average service time can be reduced by reading several blocks on each I/O operation. However, a RAM-based cache is required to support ...
The wavelet transforms and time-scale analysis of signals
Orthonormal wavelet bases provide an alternative technique for the analysis of non-stationary signals. Unlike the Gabor representation, the basis functions in the wavelet representation all have the same band width on a logarithmic scale. This thesis develops a general framework for the time-scale analysis of signals. In this context, the ON wavelets ...
Traveltime solution for the two dimensional Eikonal equation in an arbitrarily complex slowness field via first or second order conservative upwind difference formulations
The determination of first-arrival seismic traveltimes radiating outward from a point-source in an arbitrary slowness field plays an important role in methods which require knowledge of curved wavefronts in a complex domain. Adaptations of the 1st order upwind finite difference Godunov and 2nd MUSCL schemes are presented which model the two dimensional ...
The use of optimization techniques in the solution of partial differential equations from science and engineering
Optimal Control of systems governed by Partial Differential Equations is an applications-driven area of mathematics involving the formulation and solution of minimization problems. Given a physical phenomenon described by a differential equation, the Optimal Control Problem (OCP) seeks to force state variables to behave in a particular, desired way. ...
Using complexity bounds to study positive Heegaard diagrams of genus two
The complexity of a Heegaard splitting is the minimal intersection number of two essential simple closed curves which bound disks on either side of the splitting. In order to study the complexity of a splitting, we discuss symmetries and other properties of positive genus two Heegaard diagrams. The complementary regions in such a diagram are either ...
Fuchsian groups and polygonal billiards
Let P be a simple, closed polygon in the plane, all interior angles of which are rational multiples of $\pi$. We consider the possible paths of a point, rebounding in the interior of P with constant speed and elastic reflections. Such a dynamical system is known as "billiards in P". By means of a well-known construction, "billiard" trajectories in ...
Stabilized finite element solution of optimal control problems in computational fluid dynamics
This thesis discusses the solution of optimal flow control problems, with an emphasis on solving optimal design problems involving blood as the fluid. The discretization of the governing equations of fluid flow is accomplished using stabilized finite element formulations. Although frequently and successfully applied, these methods depend on significant ...
Weak approximation for degree 2del Pezzo surfaces at places of bad reduction
This thesis addresses weak approximation for certain degree 2 del Pezzo surfaces defined over the function field of a curve. We study the rational connectivity of the smooth locus of singular reductions of the surfaces to find prescribed sections through these fibers.
Nonlinear multicriteria optimization and robust optimality
This dissertation attempts to address two important problems in systems engineering, namely, multicriteria optimization and robustness optimization. In fields ranging from engineering to the social sciences designers are very often required to make decisions that attempt to optimize several criteria or objectives at once. Mathematically this amounts ...
Optimization for parameter estimation with application to transmission electron microscopy
We consider a parameter estimation problem for an important model in structural molecular biology. We propose two new mathematical formulations for the problem as constrained nonlinear least-squares problems, develop a numerical algorithm for solving this problem using interior-point methodology, and prove the convergence results for nonlinear ...