Computational Engineering Commons^™

Three-Dimensional Calculation Of Contaminant Transport In Groundwater At A Dover Afb Site, Tariq O. Hashim

Theses and Dissertations

Macroscale rate-limited sorption modeling was tested using a production transport code, the GMS/FEMWATER ground-water modeling package. The code (Version 1.1 of FEMWATER. dated 1 August 1995) was applied to a 3D conceptual model developed from a field site at Dover AFB, DE. A simulation was performed of a 200 hour contaminant injection pulse followed by clean water flushing. A moment analysis performed on the resulting breakthrough curve validated code self-consistency. Another injection pulse simulation showed that retardation temporally delays the breakthrough peak. Transport simulations of pulsed clean water pumping of the test cell with a prescribed initial contaminant distribution demonstrated …

Computer Simulations Of Electromigration Based On A Molecular Dynamics Approach, John Stephen Peake

Electrical & Computer Engineering Theses & Dissertations

Most research on electromigration has centered around macroscopic simulations of electromigration where a value for the diffusion coefficient was assumed to be spatially uniform throughout the material. The research in this thesis goes a step further and, through microscopic molecular dynamics computer simulations, calculates and updates the atomic drift velocity and atomic position as a function of time to analyze how various defects within the conductor affect these quantities. The simulations are carried out with defects in the form of dislocation half-planes placed in different locations within the simulation space. The atomic drift velocity and position changes derived from these …

Two Dimensional, Time Dependent Modeling And Simulation Of Semi-Insulating Gaas High-Power Photoconductive Switches, Prakasit Kayasit

Electrical & Computer Engineering Theses & Dissertations

The current-voltage (I-V) characteristics and photoconductive behavior of semi-insulating GaAs (SI GaAs) high-power switches have been investigated by using a two-dimensional, time dependent, drift diffusion transport model. The dc current-voltage behavior as predicted by the results of this model was compared with available experimental data to evaluate the accuracy and validity of the model. The results show very good agreement, Next, research was carried out to investigate the behavior of the switches under high-field operation.

Simulations at high voltages emphasize on the two following processes: (a) The mechanism of impact ionization and the effect of this mechanism on device stability …