Electrical and Computer Engineering Commons^™

Temperature Dependence Of Step Density On Vicinal Pb(111), Z. H. Zhang, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The temperature dependence of step density on the vicinal Pb(111) surface is investigated using reflection high-energy electron diffraction. When the temperature is increased from 323 to 590 K. the average terrace width and the average string length at the step edge decrease from 85±25 to 37±16 Å and from 220±33 to 25±8 Å, respectively. Thermal step collapse on the Pb(111) surface near its bulk melting temperature is not observed. Above 530±7 K, the change in the string length at the step edge with temperature becomes small, and the intensity of the (00) beam is significantly decreased. We conclude that partial …

Femtosecond Photoemission Study Of Ultrafast Electron Dynamics In Single-Crystal Au(111) Films, J. Cao, Y. Gao, H. E. Elsayed-Ali, R. J. D. Miller, D. A. Mantell

Electrical & Computer Engineering Faculty Publications

The energy-dependent relaxation of photoexcited electrons has been measured by time-resolved two-photon photoemission spectroscopy on single-crystal Au(111) films with thickness ranging from 150 to 3000 Å. It is found that the energy-dependent relaxation does not show any significant thickness dependence, which indicates that electron transport is a much slower dynamical process in the near-surface region than expected from bulk properties. Furthermore, lifetimes of the photoexcited electrons can be fitted well by the Fermi-liquid theory with a scaling factor plus an effective upper lifetime. This observation enables separation of electron-electron scattering, and to a lesser extent electron-phonon scattering, processes from electron-transport …

Thermodynamic Modeling And Analysis Of Human Stress Responses, Satish C. Boregowda

Mechanical & Aerospace Engineering Theses & Dissertations

A novel approach based on the second law of thermodynamics is developed to investigate the psychophysiology and quantify human stress level. Two types of stresses (thermal and mental) are examined. A Unified Stress Response Theory (USRT) is developed under the new proposed field of study called Engineering Psychophysiology. The USRT is used to investigate both thermal and mental stresses from a holistic (human body as a whole) and thermodynamic viewpoint. The original concepts and definitions are established as postulates which form the basis for thermodynamic approach to quantify human stress level. An Objective Thermal Stress Index (OTSI) is developed by …

Surface Morphology Of Laser-Superheated Pb(111) And Pb(100), Z. H. Zhang, Bo Lin, X. L. Zeng, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The surface step density on the vicinal Pb(111) and the surface vacancy density on Pb(100) after laser superheating and melting are investigated using reflection high-energy electron diffraction. With ∼100-ps laser pulses, Pb(111) surface superheating does not significantly change the density of the steps and step-edge roughness. However, after laser surface melting, the average terrace width and the string length at the step edge become as large as those at room temperature. The average terrace width at 573 K changes from 38±15 to 64±19 Å after laser surface melting, while the average string length at the step edge changes from 90±14 …

Determination Of Head Kinematics From Impact Acceleration Test Data Using Neural Networks, Edit J. Kaminsky, Anwer Bashi

Electrical Engineering Faculty Publications

This paper presents a study of feed-forward neural network (NN) systems developed to determine the head kinematics of subjects who are exposed to impact accelerations. The neural networks process accelerometer data collected during short-duration impact acceleration tests conducted at the National Biodynamcis Laboratory of the University of New Orleans. During an impact acceleration experiment, the subject sits on the sled chair and a piston gives impetus to the sled to travel down a track. Head data is gathered by an array of nine accelerometers. Two more accelerometers are mounted on the sled.

The neural processing systems produce the history of …

An Approach To Exact Modeling Of The Pwm Switch, Anas N. Al-Rabadi

Dissertations and Theses

Large number of small-signal models of de-to-de power converters exists already. These models usually use two techniques. The first is the averaging technique, such as: volt-second and current-second balance, state space averaging, and the averaged modeling approach. The other technique focuses on the exact modeling approach, such as: the application of time varying systems theory to linearize networks. One of the methodologies to apply the above techniques, is to view the three-terminal systems as a two-port network.

The aim of the work presented in this thesis is to develop a new approach, by the application of the two-port network methodology …