Engineering Commons^™

Enhanced Sensing Performance Of Novel Nanostructured Zno Gas Sensors In Ethanol Vapor Concentration Detection Applications, Pengtao Lin

Electrical & Computer Engineering Theses & Dissertations

Sensors are devices which have been commonly used to measure the functional dependence and the variability of physical parameters like temperature, pressure, pH, voltage, current, concentration, and others. Among the numerous kinds of sensors in different areas, gas sensors have been widely used and investigated for gas monitoring. Gas sensors are of crucial importance for the detection of hazardous atmospheres, because toxic gases are frequently odorless, colorless, invisible, rapidly evaporating, and flammable, and would otherwise go unnoticed. Gas sensors have been used in a variety of applications among others for the detection of specific gas species and the detection of …

A Laser Ion Source For Thin Film Deposition: Characterization Of Source And Growth Conditions, Md Mahmudur Rahman

Electrical & Computer Engineering Theses & Dissertations

Multicharged aluminum and carbon ions are generated by a laser-arc ion source. The design, construction, and testing of a compact laser ion source is demonstrated where the laser plasma is amplified by a high voltage spark-discharge. Optical emission and ion time-of-flight are measured for a spark-coupled laser aluminum plasma. A Q-switched Nd:YAG laser (wavelength λ = 1064 nm, pulse width τ ~7 ns, pulse energy E_p ≤ 260 mJ, intensity I ≤ 15 × 10⁹ W/cm²) generates the Al plasma, while a synchronized spark-discharge enhances the ion flux and charge state. Time-integrated, spatially resolved optical spectra …

A Multi-Agent Systems Approach For Analysis Of Stepping Stone Attacks, Marco Antonio Gamarra

Electrical & Computer Engineering Theses & Dissertations

Stepping stone attacks are one of the most sophisticated cyber-attacks, in which attackers make a chain of compromised hosts to reach a victim target. In this Dissertation, an analytic model with Multi-Agent systems approach has been proposed to analyze the propagation of stepping stones attacks in dynamic vulnerability graphs. Because the vulnerability configuration in a network is inherently dynamic, in this Dissertation a biased min-consensus technique for dynamic graphs with fixed and switching topology is proposed as a distributed technique to calculate the most vulnerable path for stepping stones attacks in dynamic vulnerability graphs. We use min-plus algebra to analyze …

Demonstration Of Visible And Near Infrared Raman Spectrometers And Improved Matched Filter Model For Analysis Of Combined Raman Signals, Alexander Matthew Atkinson

Electrical & Computer Engineering Theses & Dissertations

Raman spectroscopy is a powerful analysis technique that has found applications in fields such as analytical chemistry, planetary sciences, and medical diagnostics. Recent studies have shown that analysis of Raman spectral profiles can be greatly assisted by use of computational models with achievements including high accuracy pure sample classification with imbalanced data sets and detection of ideal sample deviations for pharmaceutical quality control. The adoption of automated methods is a necessary step in streamlining the analysis process as Raman hardware becomes more advanced. Due to limits in the architectures of current machine learning based Raman classification models, transfer from pure …

Laser-Spark Multicharged Ion Implantation System ‒ Application In Ion Implantation And Neural Deposition Of Carbon In Nickel (111), Oguzhan Balki

Electrical & Computer Engineering Theses & Dissertations

Carbon ions generated by ablation of a carbon target using an Nd:YAG laser pulse (wavelength λ = 1064 nm, pulse width τ = 7 ns, and laser fluence of 10-110 J/cm²) are characterized. Time-of-flight analyzer, a three-mesh retarding field analyzer, and an electrostatic ion energy analyzer are used to study the charge and energy of carbon ions generated by laser ablation. The dependencies of the ion signal on the laser fluence, laser focal point position relative to target surface, and the acceleration voltage are described. Up to C⁴⁺ are observed. When no acceleration voltage is applied between …

Pulse Power Effects On Transient Plasma Ignition For Combustion, David Wayne Alderman Ii

Electrical & Computer Engineering Theses & Dissertations

Transient plasma ignition (TPI) uses highly non-equilibrium plasmas, driven by less than 100 nanosecond, high-voltage pulses, to initiate combustion. The effects of pulse repetition frequency (PRF) and ultrashort nanosecond rise times on TPI are investigated in this work using lean, stoichiometric, and rich air-fuel mixtures at atmospheric pressure. Experimental data show the transient plasmas driven by ultrashort rise time, high voltage pulses at high PRF’s enhance the combustion of lean or stoichiometric air-methane mixtures in a static chamber. In particular, increasing PRF enhances the combustion performance by means of reduced delay times independent of the equivalence ratio of the air-fuel …

A Design Of Inductive Coupling Wireless Power Transfer System For Electric Vehicle Applications, Sarika Reddy Daida

Electrical & Computer Engineering Theses & Dissertations

This research focuses on the study of using an inductive-coupled Wireless Power Transfer (WPT) system for electric vehicle charging applications in Medium Voltage DC (MVDC) power networks. Implementing WPT in Electric Vehicles (EVs) can provide a convenient alternative charging option, versus static charging in a station that would take hours. Also, it can prevent the potential of electrocution hazards that might occur due to the usage of physical medium like wires in EV charging. Even though inductive coupling has been applied in some applications of WPT, it is still not efficient enough to transfer high power at the kilowatts level …

Performance Of Cognitive Radio Networks With Unknown Dynamic Primary User Signals, Sara L. Macdonald

Electrical & Computer Engineering Theses & Dissertations

The current static assignment of RF spectrum in the United States and other parts of the world has led to a large portion of the RF spectrum to be geographically and temporally underutilized. While the amount of RF spectrum is finite, the demand for spectrum continues to increase making it necessary to increase utilization of many bands. Several innovative methods for allowing licensed primary users (PUs) to share spectrum with unlicensed secondary users (SUs) have being proposed. Of these methods Cognitive Radio (CR) has emerged as a promising technology that enables SUs to dynamically access spectrum after first sensing the …

Radio Frequency Toolbox For Drone Detection And Classification, Abdulkabir Bello

Electrical & Computer Engineering Theses & Dissertations

The continuous development of inexpensive embedded sensors has led to the rapid proliferation of new civilian use of unmanned aerial vehicle (UAVs) or drones. It is now easier for civilians to own drones as the cost falls. As we all know drones have a variety of important applications and can also be used for negative effects too. These drones can pose a threat to the security of the population either civilian, organization or industry. There is a need for Radio Frequency Signal Classification (RF-Class) toolbox which can monitor, detect, and classify RF signals from drone communication system. The ability to …

Mimo Radar Waveform Design And Sparse Reconstruction For Extended Target Detection In Clutter, Christopher Alan Rogers

Electrical & Computer Engineering Theses & Dissertations

This dissertation explores the detection and false alarm rate performance of a novel transmit-waveform and receiver filter design algorithm as part of a larger Compressed Sensing (CS) based Multiple Input Multiple Output (MIMO) bistatic radar system amidst clutter. Transmit-waveforms and receiver filters were jointly designed using an algorithm that minimizes the mutual coherence of the combined transmit-waveform, target frequency response, and receiver filter matrix product as a design criterion. This work considered the Probability of Detection (P _D) and Probability of False Alarm (P _FA) curves relative to a detection threshold, τ _th, Receiver Operating Characteristic (ROC), …

Design, Implementation, And Analysis Of Electrical System Architecture For Cubesat To Ground Communications, Anthony G. Cappiello

Electrical & Computer Engineering Theses & Dissertations

CubeSats facilitate a low barrier to entry in University and Industrial space research. With the rapid, low-cost development of CubeSats, the need for a reliable and ro- bust communications subsystem becomes evident to ensure mission accomplishment. With the advent of Software Defined Radio, Old Dominion University is compelled to upgrade the rigid Legacy Hardware systems in place with inexpensive and flexible Software Defined Radio Solutions. Currently, Old Dominion University is on the cusp of conducting its first space science mission as a member organization of the Virginia Space Grant Consortium Cubesat Constellation and is manifest for launch on April 17, …

Solid State Polyaniline Supercapacitors Based On Electrodes Fabricated With Electropolymerization, Jonathan R. Blincoe

Electrical & Computer Engineering Theses & Dissertations

Supercapacitors are energy storage devices with the potential to overshadow lithium-ion batteries in the energy storage sector. Generally supercapacitors store less energy than a lithium-ion battery, but make up for it with much higher power densities that allow supercapacitors to charge and discharge quickly. This can be through the formation of an electric double layer or faradaic phenomenon between the electrode and electrolyte. The energy storage mechanism relies heavily on the electrode material and the ions contained within the electrolyte. In this research, polyaniline was used as an active material to prepare supercapacitors. Polyaniline is a conductive polymer that is …

Effect Of Grain Size And Interface Engineering On The Photovoltaic Performance And Stability Of Perovskite Solar Cells, Abdullah Al Mamun

Electrical & Computer Engineering Theses & Dissertations

Organic-inorganic halide perovskite solar cells (PSCs) have grown rapidly in recent years due to their outstanding optoelectronic properties, high efficiency, and low-cost. However, this emerging solar cell technology is experiencing some challenges such as defects, hysteresis, and long-term stability, which need to be addressed in order to make it commercially available. This dissertation aims to assist in overcoming some of the barriers and is therefore important to the field of perovskite solar cells.

Initially, this dissertation focuses on investigating the role of grain interiors (GIs) and grain boundaries (GBs) of perovskite film using chemically, spatially, and temporally resolved measurements at …

On Analytic Nonlinear Input-Output Systems: Expanded Global Convergence And System Interconnections, Irina M. Winter Arboleda

Electrical & Computer Engineering Theses & Dissertations

Functional series representations of nonlinear systems first appeared in engineering in the early 1950’s. One common representation of a nonlinear input-output system are Chen-Fliess series or Fliess operators. Such operators are described by functional series indexed by words over a noncommutative alphabet. They can be viewed as a noncommutative generalization of a Taylor series. A Fliess operator is said to be globally convergent when its radius of convergence is infinite, in other words, when there is no a priori upper bound on both the L1-norm of an admissible input and the length of time over which the corresponding output is …