Engineering Commons^™

Experiments On Melting Around An Isothermal Horizontal Cylinder Under Computer Control, Timothy Moore Rothgeb

Mechanical & Aerospace Engineering Theses & Dissertations

The melting of a solid around an isothermal horizontal cylinder is a physical phenomenon which must be understood when attempting to design a latent heat storage system. The desire to design such a system is the motivating factor in this research. To gain this understanding of the fundamental melting processes several experiments were designed, and two sets of Stefan and Rayleigh number experiments were undertaken. Experiments were also performed to determine the properties of the paraffin that was used in these investigations. During the investigations of the melting processes, the temperature was measured at several locations throughout the liquid and …

Design Of Efficient Algorithms Through Minimization Of Data Transfers, Yong Mo Chong

Electrical & Computer Engineering Theses & Dissertations

This thesis explores the time optimal implementation of computational graphs on a finite register machine. The implementation fully exploits the machine architecture, especially, the number of registers. The derived algorithms allow one to obtain time efficient implementations of a given graph in machines with a known number of registers.

These optimization procedures are applied to digital signal processing graphs. It is shown that the regular structure of these graphs allows one to identify computational kernels which, when used repeatedly, can cover the entire graph. The l- and r-register implementations of Hadamard and Fast Fourier Transforms using various computational kernels are …

Design Of Efficient Algorithms Through Minimization Of Data Transfers, Yong Mo Chong

Electrical & Computer Engineering Theses & Dissertations

This thesis explores the time optimal implementation of computational graphs on a finite register machine. The implementation fully exploits the machine architecture, especially, the number of registers. The derived algorithms allow one to obtain time efficient implementations of a given graph in machines with a known number of registers.

These optimization procedures are applied to digital signal processing graphs. It is shown that the regular structure of these graphs allows one to identify computational kernels which, when used repeatedly, can cover the entire graph, The l- and r-register implementations of Hadamard and Fast Fourier Transforms using various computational kernels are …

Circuit Analysis Of A Gas Flow Switch, Teri Marie Owens

Electrical & Computer Engineering Theses & Dissertations

The circuit analysis of a gas flow switch is presented. The objective of the analysis is to model the switching process during spark gap breakdown. This information is useful in understanding switch operation and identifying ways to improve switch performance.

A lumped circuit model is used to describe a gas flow switch during the switching process. Certain circuit element values are determined experimentally through static tests. Other component values, including a time-varying switch resistance and inductance, are estimated from current measurements. In particular, unknown constants in expressions for gap resistance and inductance are determined using an iterative parameter estimation technique. …

Experiments Conducted On The Electron Beam Produced By A Dense Plasma Focus, Mark Steven Pronko

Electrical & Computer Engineering Theses & Dissertations

An experimental investigation was conducted using a 34-kJ Dense Plasma Focus (DPF) in which the possible enhancement of the electron beam was addressed. Electron beams ejected from the DPF have been observed to exceed 30 kA with pulse durations of a few nanoseconds. Enhancement was considered to be either an increase in the probability that the peak beam current exceeded some lower limit, or an increase in the mean energy of the beam electrons. The investigation was divided into two parts, each addressing one of the aspects of enhancement.

In the first part of the investigation, an axial magnetic field …

On The Space Shuttle Wing Thermal-Structural Analysis, Kumar Krishna Tamma

Mechanical & Aerospace Engineering Theses & Dissertations

A finite element approach for efficient thermal-structural analysis of structures with thermal protection systems (TPS) is described. The approach is applied to Space Shuttle wing structure configurations subjected to reentry heating. New two and three-dimensional finite elements are developed to model heat transfer in the TPS and supporting structure. A typical TPS/Structural element predicts transient nonlinear temperature variations through the TPS thickness and detailed structural temperatures at the TPS/Structure interface. The accuracy of the TPS/Structure approach in two and three-dimensions is evaluated by comparisons with the conventional approach for various configurations of the wing structure. The results indicate that the …

Stability Analysis Of Closed Surge Tanks By Phase-Plane Method, Mostafa A. Sabbah

Civil & Environmental Engineering Theses & Dissertations

The governing equations describing water level oscillations in a closed surge tank with compressed air at the top of the tank are a set of nonlinear ordinary differential equations if the hydraulic system is analyzed as a lumped system. These oscillations are stable or unstable depending on the parameters of the plant and the type and magnitude of the disturbance.

The present available stability criterion has been developed by linearizing the governing equations and is, therefore, valid only for small disturbances.

In the research reported herein, the governing equations are normalized to reduce the number of parameters from nine to …