Engineering Commons^™

Development Of An Efficient Ti:Sapphire Laser Transmitter For Atmospheric Ozone Lidar Measurements, Khaled A. Elsayed

Electrical & Computer Engineering Theses & Dissertations

The impetus of this work was to develop an all solid-state Ti:sapphire laser transmitter to replace the current dye lasers that could provide a potentially compact, robust, and highly reliable laser transmitter for differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 nm and 900 nm, with M² of 1.3, have been experimentally demonstrated and compared to model results. The Ti:sapphire lasers have shown the required output beam quality at maximum output pulse energy, 115 mJ at 867 nm and …

Excimer Emission From Pulsed Microhollow Cathode Discharges, Mohamed Moselhy

Electrical & Computer Engineering Theses & Dissertations

Microhollow cathode discharges (MHCDs) are direct current, high-pressure, non-equilibrium gas discharges. Direct current MHCDs in xenon and argon have shown to emit excimer radiation at 172 and 127 nm, respectively. Internal efficiency of excimer emission in DC MHCD was measured to be 6–9% in xenon, and 1–6%, depending on the gas flow rate in argon. This high efficiency is due to the high rate of rare gas excitation by electrons accelerated in the cathode fall and to subsequent three-body collisions in the high-pressure gas. The excimer power scales linearly with current; however, due to the increasing size of the source …

Study Of Non-Equilibrium Electron Dynamics In Metals, Wael Mohamed Gomaa Ibrahim

Electrical & Computer Engineering Theses & Dissertations

Thermal phenomena, such as heat propagation, lattice melting, and ablation, are the result of energy deposition in metals. A fundamental understanding of the electron dynamics leading to these thermal phenomena would benefit many laser applications, such as laser deposition of thin films and laser processing.

In this work, thin metal films were prepared using the resistive heating evaporation technique. High dynamic range autocorrelators were constructed to characterize the different laser systems used in this study. The nonequilibrium electron dynamics in single layer gold films, multi-layer gold-vanadium, and gold-titanium films were studied. The time evolution of the electron temperature was monitored …

Robust Face Representation And Recognition Under Low Resolution And Difficult Lighting Conditions, Mohammad Moinul Islam

Electrical & Computer Engineering Theses & Dissertations

This dissertation focuses on different aspects of face image analysis for accurate face recognition under low resolution and poor lighting conditions. A novel resolution enhancement technique is proposed for enhancing a low resolution face image into a high resolution image for better visualization and improved feature extraction, especially in a video surveillance environment. This method performs kernel regression and component feature learning in local neighborhood of the face images. It uses directional Fourier phase feature component to adaptively lean the regression kernel based on local covariance to estimate the high resolution image. For each patch in the neighborhood, four directional …

A Formal Object Model For Layered Networks To Support Verification And Simulation, Rasha M. B. E. Morsi

Electrical & Computer Engineering Theses & Dissertations

This work presents an abstract formal model of the interconnection structure of the Open Systems Interconnection Reference Model (OSI-RM) developed using Object-Oriented modeling principles permitting it to serve as a re-usable platform in supporting the development of simulations and formal methods applied to layered network protocols. A simulation of the object model using MODSIM III was developed and Prototype Verification System (PVS) was used to show the applicability of the object model to formal methods by formally specifying and verifying a Global Systems for Mobile communications (GSM) protocol. This application has proved to be successful in two aspects. The first …