Digital Commons Network^™

Generating Series For Interconnected Nonlinear Systems And The Formal Laplace-Borel Transform, Yaqin Li

Electrical & Computer Engineering Theses & Dissertations

Formal power series methods provide effective tools for nonlinear system analysis. For a broad range of analytic nonlinear systems, their input-output mapping can be described by a Fliess operator associated with a formal power series. In this dissertation, the inter connection of two Fliess operators is characterized by the generating series of the composite system. In addition, the formal Laplace-Borel transform of a Fliess operator is defined and its fundamental properties are presented. The formal Laplace-Borel transform produces an elegant description of system interconnections in a purely algebraic context.

Specifically, four basic interconnections of Fliess operators are addressed: the parallel, …

Scaling And Characterization Of Direct Current Glow Discharge Plasma In Atmospheric Air, Abdel-Aleam Hefney Mohamed

Electrical & Computer Engineering Theses & Dissertations

A microhollow cathode discharge was used as a plasma cathode to sustain a stable direct current glow discharge in atmospheric pressure air. The volumetric scale of glow discharge increased from the millimeter to the centimeter range by extending the plasma in lateral and axial directions. In the axial direction, the length of the glow discharge column was varied from 1 mm to 2 cm, with the sustaining voltage increasing linearly with the glow discharge column length. Extension in the lateral direction was obtained by operating discharges in parallel. The glow discharge plasma of the parallel discharge columns was found to …

Speaker Normalization For Improved Automatic Speech Recognition For Digital Libraries, Wei Wang

Electrical & Computer Engineering Theses & Dissertations

The context of this thesis work is the improvement of automatic speech recognition (ASR) for use with digital libraries. First, commonly used multimedia file formats and codecs are surveyed with the objective of identifying those formats that preserve speech quality while keeping file sizes compact. The main contribution of the work is a new technique for speaker adaptation based on frequency scale modifications. The frequency scale is modified using a minimum mean square error matching of a spectral template for each speaker to a "typical speaker" spectral template. Each spectral template is computed from the average amplitude-normalized spectra of several …

Microdischarge Arrays, Wenhui Shi

Electrical & Computer Engineering Theses & Dissertations

Microhollow cathode discharges (MHCDs) are DC or pulsed gas discharges between two electrodes, separated by a dielectric, and containing a concentric hole. The diameter of the hole, in this hollow cathode configuration, is in the hundred-micrometer range. MHCDs satisfy the two conditions necessary for an efficient excimer radiation sources: (1) high energy electrons which are required to provide a high concentration of excited or ionized rare gas atoms; (2) high pressure operation which favors excimer formation (a three-body process). Flat panel excimer sources require parallel operation of MHCDs. Based on the current-voltage characteristics of MHCD discharges, which have positive slopes …

A Value Focused Thinking Model For The Development And Selection Of Electrical Energy Source Alternatives At Military Installations, Gregory T. Schanding

Theses and Dissertations

Electrical power on military installations is vital for mission accomplishment. Most installations obtain electrical power from a local commercial utility. Although commercial power service has a very low interruption rate, the threat of a sustained power outage resulting from a terrorist act or a natural disaster is of concern. The military should posture itself to prevent such power outages and prepare to mitigate the adverse effects associated with the loss of power. This thesis presents a Value Focused Thinking approach to the development of a decision analysis model to assist a decision maker at a military installation in the generation …

Vector Dissipativity Theory For Large-Scale Impulsive Dynamical Systems, Wassim H. Haddad, Vijaysekhar Chellaboina, Qing Hui, Sergey Nersesov

Department of Electrical and Computer Engineering: Faculty Publications

Modern complex large-scale impulsive systems involvemultiplemodes of operation placing stringent demands on controller analysis of increasing complexity. In analyzing these large-scale systems, it is often desirable to treat the overall impulsive system as a collection of interconnected impulsive subsystems. Solution properties of the large-scale impulsive system are then deduced from the solution properties of the individual impulsive subsystems and the nature of the impulsive system interconnections. In this paper, we develop vector dissipativity theory for large-scale impulsive dynamical systems. Specifically, using vector storage functions and vector hybrid supply rates, dissipativity properties of the composite large-scale impulsive systems are shown to …

Transmission Strategies For Wireless Multi-User, Multiple-Input, Multiple-Output Communication Channels, Quentin H. Spencer

Theses and Dissertations

Multiple-Input, Multiple-Output (MIMO) processing techniques for wireless communication are of interest for next-generation systems because of their potential to dramatically improve capacity in some propagation environments. When used in applications such as wireless LAN and cellular telephony, the MIMO processing methods must be adapted for the situation where a base station is communicating with many users simultaneously. This dissertation focuses on the downlink of such a channel, where the base station and all of the users have antenna arrays. If the transmitter has advance knowledge of the users' channel transfer functions, it can use that information to minimize the interuser …

Analysis And Design Of Low-Jitter Oscillators, Justin Jennings Fitzpatrick

Theses and Dissertations

This thesis presents an examination of the jitter performance of different oscillator types in the presence of flicker noise, white noise and power supply noise. Key results are achieved using time domain simulations to determine cycle jitter of several different oscillator architectures, semiconductor processes and component features. In the end, a design procedure is developed for creating a low-jitter oscillator in a TSMC .25mm CMOS semiconductor process.

Autonomous Landing Of A Rotary Unmanned Aerial Vehicle In A Non-Cooperative Environment Using Machine Vision, Joshua Martin Hintze

Theses and Dissertations

Landing an Unmanned Aerial Vehicle (UAV) is a non-trivial problem. Removing the ability to cooperate with the landing site further increases the complexity. This thesis develops a multi-stage process that allows a UAV to locate the safest landing site, and then land without a georeference. Machine vision is the vehicle sensor used to locate potential landing hazards and generate an estimated UAV position. A description of the algorithms, along with validation results, are presented. The thesis shows that software-simulated landing performs adequately, and that future hardware integration looks promising.

Design Of A High Speed Mixed Signal Cmos Mutliplying Circuit, David Ray Bartholomew

Theses and Dissertations

This thesis presents the design of a mixed-signal CMOS multiplier implemented with short-channel PMOS transistors. The multiplier presented here forms the product of a differential input voltage and a five-bit digital code. A TSMC 0.18 µm MOSFET model is used to simulate the circuit in Cadence Design Systems. The research presented in this thesis reveals a configuration that allows the multiplier to run at a speed of 8.2 GHz with end-point nonlinearity less than 5%. The high speed and low nonlinearity make this circuit ideal for applications such as filtering and digital to analog conversion.

A Linear Subspace Approach To Burst Communication Signal Processing, Daniel E. Gisselquist

Theses and Dissertations

This dissertation focuses on the topic of burst signal communications in a high interference environment. It derives new signal processing algorithms from a mathematical linear subspace approach instead of the common stationary or cyclostationary approach. The research developed new algorithms that have well-known optimality criteria associated with them. The investigation demonstrated a unique class of multisensor filters having a lower mean square error than all other known filters, a maximum likelihood time difference of arrival estimator that outperformed previously optimal estimators, and a signal presence detector having a selectivity unparalleled in burst interference environments. It was further shown that these …

Simulating A Chromotomographic Sensor For Hyperspectral Imaging In The Infrared, Anthony J. Dearinger

Theses and Dissertations

Hyperspectral imaging systems passively sense radiant electromagnetic energy from a remote scene to form a three dimension profile of the remote scene. The data contained in this profile describes real images of the remote scene for a certain number of spectral wavelength bands across a finite spectral range of electromagnetic radiation. Typical grating type hyperspectral imaging systems collect spectral electromagnetic radiation in the visible and near infrared spectral range, by incrementally scanning across the spatial extent of the remote scene. The legacy of low optical throughput because of the optical scanning techniques employed in these systems means adapting these systems …

Evaluating The Navigation Potential Of The National Television System Committee Broadcast Signal, Ryan J. Eggert

Theses and Dissertations

The accuracy and worldwide availability of the Global Positioning System (GPS) make it the dominant system for navigation and precise positioning. Unfortunately, many situations arise in which GPS may not be adequate, e.g., urban navigation. This research evaluates the navigation potential of the National Television System Committee (NTSC) broadcast signal using a time-difference-of-arrival (TDOA) algorithm. TDOA measurements are made using NTSC broadcast signals collected from low and high multipath environments. These measurements are then used to evaluate the severity and dynamic effects of NTSC broadcast multipath signals. Three data reduction algorithms were developed--one that modifies the classical cross-correlation TDOA approach, …

Deviation Of Time-Resolved Luminescence Dynamics In Mwir Semiconductor Materials From Carrier Recombination Theory Predictions, Peter M. Johnson

Theses and Dissertations

Time resolved luminescence spectroscopy was used to characterize luminescence decay curves for a bulk InAs sample and an InAsSb type-I quantum-well sample over the first 3ns following excitation. The luminescence decay curves were then converted to carrier densities and used to find recombination coefficients that provided the least-squared-error solution of the rate equation describing carrier recombination. Recombination coefficients describing Shockley Read-Hall (A_SRH) radiative (B_rad) and Auger (C_Aug) recombination were determined at two different temperatures and four excitation powers, then analyzed for consistency and physical significance. For all of the resulting least …

Multiple Access Interference Characterization For Direct-Sequence Spread-Spectrum Communications Using Chip Waveform Shaping, Matthew G. Glen

Theses and Dissertations

This research characterizes MAI effects on DS/SSMA system performance through simulation in Matlab , and explores the impact of multiple access code selection, chip waveform shaping, and multiple access code length on BER for both synchronous and asynchronous multiple access networks. In addition, the simulated DS/SSMA model permits rapid research into the effects of additional factors on BER. Prior to experimental testing, model validation is conducted through single user trials and by comparison with existing research for similar system designs. For synchronous and asynchronous networks, Gold coding improves BER by 7.5 and 4.0 dB, respectively, relative to aperiodic random spreading …

An Analysis Of Electromagnetic Interference (Emi) Of Ultra Wideband(Uwb) And Ieee 802.11a Wireless Local Area Network (Wlan) Employing Orthogonal Frequency Division Multiplexing (Ofdm), Juan Lopez Jr.

Theses and Dissertations

Military communications require the rapid deployment of mobile, high-bandwidth systems. These systems must provide anytime, anywhere capabilities with minimal interference to existing military, private, and commercial communications. Ultra Wideband (UWB) technology is being advanced as the next generation radio technology and has the potential to revolutionize indoor wireless communications. The ability of UWB to mitigate multipath fading, provide high-throughput data rates (e.g., greater than 100 Mbps), provide excellent signal penetration (e.g., through walls), and low implementation costs makes it an ideal technology for a wide range of private and public sector applications. Preliminary UWB studies conducted by The Institute for …

Implementation Issues Of Real-Time Trajectory Generation On Small Uavs, Derek B. Kingston

Theses and Dissertations

The transition from a mathematical algorithm to a physical hardware implementation is non-trivial. This thesis discusses the issues involved in the transition from the theory of real-time trajectory generation all the way through a hardware experiment. Documentation of the validation process as well as modifications to the existing theory as a result of hardware testing are treated at length. The results of hardware experimentation show that trajectory generation can be done in real-time in a manner facilitating coordination of multiple small UAVs.

Discovering The Merit Of The Wavelet Transform For Object Classification, Matthew D. Eyster

Theses and Dissertations

Vision is the primary sense by which most biological systems collect information about their environment. Computer vision is a branch of artificial intelligence concerned with endowing machines with the ability to understand images. Object recognition is a key part of machine vision with far reaching benefits ranging from target recognition, surveillance systems, to automation systems. Extraction of salient features from an image is one of the key steps in object recognition. Typically, geometric primitives are extracted from an image using local analysis. However, the wavelet transform provides a global approach with good locality. Additionally, the directional and multiresolution properties may …

Symbolically Aided Model Development For An Induction Machine In Virtual Test Bed, Wenzhong Gao, Eugene V. Slovodnik, Roger A. Dougal

Faculty Publications

A new phase-domain induction machine model for use in power system dynamic simulation is developed with the aid of a symbolic tool. The symbolic tool can automatically construct a time-domain power system component model in the resistive companion form (RCF) that is widely used in time-domain simulators. The automatic differentiation technique (aDT) is utilized within the context of a symbolic modeling language, and the tool has been implemented for the virtual test bed (VTB) simulation environment. The new induction machine model was used to study start-up transients of an induction motor. The new model was verified by comparing the simulation …

Swarming Reconnaissance Using Unmanned Aerial Vehicles In A Parallel Discrete Event Simulation, Joshua J. Corner

Theses and Dissertations

Current military affairs indicate that future military warfare requires safer, more accurate, and more fault-tolerant weapons systems. Unmanned Aerial Vehicles (UAV) are one answer to this military requirement. Technology in the UAV arena is moving toward smaller and more capable systems and is becoming available at a fraction of the cost. Exploiting the advances in these miniaturized flying vehicles is the aim of this research. How are the UAVs employed for the future military? The concept of operations for a micro-UAV system is adopted from nature from the appearance of flocking birds, movement of a school of fish, and swarming …

Optimization Of Heterogeneous Uav Communications Using The Multiobjective Quadratic Assignment Problem, Mark P. Kleeman

Theses and Dissertations

The Air Force has placed a high priority on developing new and innovative ways to use Unmanned Aerial Vehicles (UAVs). The Defense Advanced Research Projects Agency (DARPA) currently funds many projects that deal with the advancement of UAV research. The ultimate goal of the Air Force is to use UAVs in operations that are highly dangerous to pilots, mainly the suppression of enemy air defenses (SEAD). With this goal in mind, formation structuring of autonomous or semi-autonomous UAVs is of future importance. This particular research investigates the optimization of heterogeneous UAV multi-channel communications in formation. The problem maps to the …

Swarm Based Implementation Of A Virtual Distributed Database System In A Sensor Network, Wen C. Lee

Theses and Dissertations

The deployment of unmanned aerial vehicles (UAVs) in recent military operations has had success in carrying out surveillance and combat missions in sensitive areas. An area of intense research on UAVs has been on controlling a group of small-sized UAVs to carry out reconnaissance missions normally undertaken by large UAVs such as Predator or Global Hawk. A control strategy for coordinating the UAV movements of such a group of UAVs adopts the bio-inspired swarm model to produce autonomous group behavior. This research proposes establishing a distributed database system on a group of swarming UAVs, providing for data storage during a …

Atmospheric Simulation Using A Liquid Crystal Wavefront Controlling Device, Matthew R. Brooks

Theses and Dissertations

Test and evaluation of laser warning devices is important due to the increased use of laser devices in aerial applications. In this thesis, an atmospheric aberrating system is developed to enable in-lab testing of laser warning devices. This system employs laser light at 632.8nm from a Helium-Neon source and a spatial light modulator (SLM) to cause phase changes using a birefringent liquid crystal material. Before the system can be used, the SLM phase response must be quantified to ensure proper manipulation of index of refraction. Additionally, diffraction from the SLM and real-world system scaling are addressed. Once completed, the atmospheric …

Forward Looking Radar: Interference Modelling, Characterization, And Suppression, James T. Caldwell

Theses and Dissertations

This research characterizes forward looking radar performance while noting differences with traditionally examined sidelooking radar. The target detection problem for forward looking radar is extremely difficult due to the severe, heterogeneous and range dependent ground clutter. Consequently, forward looking radar detection represents an important but overlooked topic because of the increased difficulty compared to sidelooking radar. This void must be filled since most fighter aircraft use forward looking radar, making this topic intensely interesting to the Air Force. After characterizing forward looking radar performance, basic radar concepts along with advanced adaptive interference suppression techniques improve the output Signal-to-Interference-plus-Noise Ratio (SINR) …

Cross Range Smear Characterization In Xpatch Isar Images, Peter E. Muend

Theses and Dissertations

This thesis investigates a cross range smear phenomenon seen in far field, frequency domain Xpatch calculations. The phenomenon is very subtle, manifesting itself in 2-D ISAR images as a low-level scatterer response smeared in the cross range direction. This cross range smear occurs only using complex target models with certain characteristics. It is also a mathematical construct, not occurring in physical SAR systems. Using a carefully constructed scattering target set, Xpatch-generated ISAR images are used to characterize cross range smear in terms of its input parameters. The characterization is done as a DOE-based polynomial approximation to the observed smear levels. …

Characterization Of The Target-Mount Interaction In Radar Cross Section Measurement Calibrations, Donald W. Powers

Theses and Dissertations

Radar Cross Section (RCS) measurements are quintessential in understanding target scattering phenomenon. The reduced RCS of modern weapons systems stresses the capability of current RCS measurement ranges. A limiting factor that has recently become more significant is the electromagnetic coupling between a test target and the mounting hardware used to support it and control its orientation during the RCS measurement. Equally important is the electromagnetic coupling between the RCS calibration artifact and its mount, which provides an opportunity to explore the coupling phenomena without delving into operationally sensitive areas. The primary research goal was to characterize the interaction between a …

Enhancing The Instantaneous Dynamic Range Of Electronic Warfare Receivers Using Statistical Signal Processing, Bryan E. Smith

Theses and Dissertations

Accurately processing multiple, time-coincident signals presents a challenge to Electronic Warfare (EW) receivers, especially if the signals are close in frequency and/or mismatched in amplitude. The metric that quantifies an EW receiver's ability to measure time-coincident signals is the Instantaneous Dynamic Range (IDR), defined for a given frequency estimation accuracy, a given frequency separation and a given SNR as the maximum signal amplitude ratio that can be accommodated. Using a two sinusoid time-series model, this thesis analyzes IDR for ideal intercept and parametric digital EW receivers. In general, the number of signals contained in the EW receiver measurement interval is …

Stepped Waveguide Electromagnetic Material Characterization Technique, Sean P. Dorey

Theses and Dissertations

Electromagnetic material characterization is the process of determining the complex permittivity and permeability of a material. A new waveguide material measurement technique is developed to reduce test sample size requirements for low-frequency applications. Specifically, a waveguide sample holder having a reduced aperture is utilized to decrease the time and cost spent producing large precision test samples. This type of sample holder causes a disruption in the waveguide-wall surface currents that results in the excitation of higher-order modes. This thesis will demonstrate how these higher-order modes can be accommodated using a modal-analysis technique, thus resulting in the ability to measure smaller …

Estimative Current Mode Control Technique For Dc-Dc Converters Operating In Discontinuous Conduction Mode, Mehdi Ferdowsi, Ali Emadi

Electrical and Computer Engineering Faculty Research & Creative Works

A new control technique for DC-DC converters is introduced and applied to a boost converter operating in discontinuous conduction mode (DCM). In contrast to conventional control methods, the principal idea of the proposed control scheme is to obtain samples of the required signals and estimate the required switch-on time. The proposed technique is applicable to any converter operating in DCM, including power factor correctors (PFC), however, this letter mainly focuses on boost topology. In this letter, the main mathematical concept of a new control algorithm is introduced, as well as the robustness investigation of the proposed method with simulation and …

Intelligent Control Schemes For A Static Compensator Connected To A Power Network, Salman Mohagheghi, Ganesh K. Venayagamoorthy, Ronald G. Harley

Electrical and Computer Engineering Faculty Research & Creative Works

Two intelligent controllers are designed for a static compensator (STATCOM) connected to a single machine infinite bus power system (SMIB): a novel nonlinear adaptive controller using artificial neural networks based on the indirect adaptive control technique and a Takagi-Sugeno type fuzzy controller. Both schemes provide nonlinear adaptive control with better performance compared to the conventional PI controllers. Simulation results are presented to compare the performances of these controllers with that of the conventional PI controllers.