Engineering Commons^™

Ensemble Of Classifiers Based Data Fusion Of Eeg And Mri For Diagnosis Of Neurodegenerative Disorders, Tejash Patel

Theses and Dissertations

The prevalence of Alzheimer's disease (AD), Parkinson's disease (PD), and mild cognitive impairment (MCI) are rising at an alarming rate as the average age of the population increases, especially in developing nations. The efficacy of the new medical treatments critically depends on the ability to diagnose these diseases at the earliest stages. To facilitate the availability of early diagnosis in community hospitals, an accurate, inexpensive, and noninvasive diagnostic tool must be made available. As biomarkers, the event related potentials (ERP) of the electroencephalogram (EEG) - which has previously shown promise in automated diagnosis - in addition to volumetric magnetic resonance …

Data Fusion Based Optimal Eeg Electrode Selection For Early Diagnosis Of Alzheimer's Disease, Brian Balut

Theses and Dissertations

As medicinal and technological advances lengthen the average human life span, diseases affecting the elderly such as Alzheimer's disease and Parkinson's disease are seeing increasingly growing numbers, especially in developed countries. As a result, the necessity for an accurate, inexpensive, noninvasive means of diagnosis becomes particularly important, since such a method is not readily available to the general population. One biomarker that has recently showed promise is the analysis of the electroencephalogram (EEG).

Over the course of two studies, more than 130 subjects have been recruited providing information from 16-19 EEG electrodes for each subject. These signals have been decomposed …

Exploration Of Multiple Pathways For The Development Of Immersive Virtual Reality Environments, Kevin Laurence Garrison

Theses and Dissertations

The focus of this thesis is the study and recommendation of optimal techniques for developing immersive virtual environments for generic applications. The overarching objective is to ensure that virtual environments can be created and deployed, rapidly and accurately, using commercial off-the-shelf software. Specific subjective and objective criteria have been employed to determine trade-offs between multiple pathways for designing such environments and specific recommendations are made for the applicability of each. The efficacy of the techniques developed as part of this research work has been demonstrated by applying them to three widely differing areas - visualizing arbitrary 2D surface data, synthesis …

Use Of Linear Predictive Features And Pattern Recognition Techniques To Develop A Vector Quantization Based Blind Snr Estimation System, Russell Paul Ondusko Iii

Theses and Dissertations

Signal-to-noise ratio is defined as the ratio of a given transmitted signal to the background noise of the transmission medium. Signal-to-noise ratio (SNR) is a common concept found in all forms of electrical communications. The easiest way to measure the signal-to-noise ratio is through intrusive means in which a corrupt signal is compared to its original signal. This technique is inefficient and impractical because it requires the original signal and can only be used to theoretically test the noise properties of a channel rather than estimate the SNR of a communicated signal. Characteristics of speech signals can be used to …

Quad General Tree Drawing Algorithm And General Trees Characterization: Towards An Environment For The Experimental Study On General Tree Drawing Algorithms, Chu Yao

Theses and Dissertations

Information visualization produces (interactive) visual representations of abstract data to reinforce human cognition and perception; thus enabling the viewer to gain knowledge about the internal structure of the data and causal relationships in it. The visualization of information hierarchies is concerned with the presentation of abstract hierarchical information about relationships between various entities. It has many applications in diverse domains such as software engineering, information systems, biology, and chemistry. Information hierarchies are typically modeled by an abstract tree, where vertices are entities and edges represent relationships between entities. The aim of visualizing tree drawings is to automatically produce drawings of …

Integrated Approach To Airborne Laser Communication, James A. Louthain

Theses and Dissertations

Lasers offer tremendous advantages over RF communication systems in bandwidth and security, due to their ultra-high frequency and narrow spatial beamwidth. Atmospheric turbulence causes severe received power variations and high bit error rates (BERs) in airborne laser communication. Airborne optical communication systems require special considerations in size, complexity, power, and weight. Conventional adaptive optics systems correct for the phase only and cannot correct for strong scintillation, but here the two transmission paths are separated sufficiently so that the strong scintillation is \averaged out" by incoherently summing up the two beams in the receiver. This requisite separation distance is derived for …

Sub-Circuit Selection And Replacement Algorithms Modeled As Term Rewriting Systems, Eric D. Simonaire

Theses and Dissertations

Intent protection is a model of software obfuscation which, among other criteria, prevents an adversary from understanding the program’s function for use with contextual information. Relating this framework for obfuscation to malware detection, if a malware detector can perfectly normalize a program P and any obfuscation (variant) of the program O(P), the program is not intent protected. The problem of intent protection on programs can also be modeled as intent protection on combinational logic circuits. If a malware detector can perfectly normalize a circuit C and any obfuscation (variant) O(C) of the circuit, the circuit is not intent protected. In …

Limitations Of A True Random Number Generator In A Field Programmable Gate Array, Jennifer L. Brady

Theses and Dissertations

Random number generators are used in many areas of engineering, computer science, most notably in simulations and cryptographic applications. There are true random number generators (TRNG) and pseudo random number generators (PRNG). Only a true random number generator is secure because the output bits are non-repeating and nonreproducible. As society has become more dependent on electronic technology the need for true random number generators has increased due to processes that require encryption in everyday use. A fast true random number generator on a field programmable gate array presents digital designers with the ability to have the generator on chip. Since …

Surface Relief D-Fiber Bragg Gratings For Sensing Applications, Tyson Lee Lowder

Theses and Dissertations

This dissertation presents the novel creation of a surface relief fiber Bragg grating on the flat surface of a D-shaped optical fiber. In order to produce an efficient surface relief grating the grating must be etched into the surface of the glass fiber close to the core. A short etch that removes the cladding above the core is performed in order to decrease the core-to-flat distance and allow the light to interact with the grating on the flat surface. Due to the unique D-shape of the optical fiber the mechanical integrity of the fiber remains high even after the fabrication …

Spin Transport Studies In Nanoscale Spin Valves And Magnetic Tunnel Junctions, Sridhar Patibandla

Theses and Dissertations

Spintronics or electronics that utilizes the spin degree of freedom of a single charge carrier (or an ensemble of charge carriers) to store, process, sense or communicate data and information is a rapidly burgeoning field in electronics. In spintronic devices, information is encoded in the spin polarization of a single carrier (or multiple carriers) and the spin(s) of these carrier(s) are manipulated for device operation. This strategy could lead to devices with low power consumption. This dissertation investigates spin transport in one dimensional and two dimensional semiconductors, with a view to applications in spintronic devices.

A Detailed Look At The Omega-K Algorithm For Processing Synthetic Aperture Radar Data, Matthew A. Tolman

Theses and Dissertations

In this thesis, the Omega-k algorithm used for processing stripmap synthetic aperture radar (SAR) data is explored in detail. While the original Omega-k algorithm does not achieve the same SNR as a matched filter, a modification is presented which enables the algorithm to nearly achieve that SNR. It is shown that the focused point spread function obtained when the Omega-k algorithm is used differs in important ways from the output of a modified version of the matched filter. Spread out sidelobes and a stretched mainlobe are observed when the data is processed by the Omega-k algorithm. These differences may increase …

Range Precision Of Ladar Systems, Steven E. Johnson

Theses and Dissertations

A key application of Laser Detection and Ranging (LADAR) systems is measurement of range to a target. Many modern LADAR systems are capable of transmitting laser pulses that are less than a few nanoseconds in duration. These short-duration pulses provide excellent range precision. However, randomness in the detected laser signals places limits on the precision. The goal of this dissertation is to quantify the range precision limits of LADAR systems. The randomness in the time between photon arrivals, which is called shot noise, is discussed in depth. System-dependent noise sources such as dark current and detector gain variation are considered. …

Statistical Methods For Polarimetric Imagery, Daniel A. Lemaster

Theses and Dissertations

Estimation theory is applied to a physical model of incoherent polarized light to address problems in polarimetric image registration, restoration, and analysis for electro-optical imaging systems. In the image registration case, the Cramer-Rao lower bound on unbiased joint estimates of the registration parameters and the underlying scene is derived, simplified using matrix methods, and used to explain the behavior of multi-channel linear polarimetric imagers. In the image restoration case, a polarimetric maximum likelihood blind deconvolution algorithm is derived and tested using laboratory and simulated imagery. Finally, a principal components analysis is derived for polarization imaging systems. This analysis expands upon …

Fiber Bragg Grating (Fbg) Based Chemical Sensor, Gopakumar Sethuraman

Theses and Dissertations

In this work, reagentless fiber optic-based chemical sensors for water quality testing were fabricated by coating fiber Bragg gratings with the glassy polymer cellulose acetate. With this polymeric matrix capable of localizing or concentrating chemical constituents within its structure, immersion of the coated grating in various chemical solutions causes the rigid polymer to expand and mechanically strain the glass fiber. The corresponding changes in the periodicity of the grating subsequently result in altered Bragg-reflected responses. A high-resolution tunable fiber ring laser interrogator is used to obtain room temperature reflectance spectrograms from two fiber gratings at 1550 nm and 1540 nm …

Planning Continuous Curvature Paths Using Constructive Polylines, Joshua H. Henrie

Theses and Dissertations

Previous methods for planning clothoid based continuous curvature paths aim at minimizing path length. However, minimal length paths are not always smooth, natural, and drivable. A method of generating clothoid-based trajectories is discussed using constructive polylines. The goal of the motion planner is to create a path for a large car-like vehicle in human driving environments. Thus, the trajectories generated by the motion planner must be smooth, drivable, and natural such that the vehicle can follow the planned path on human roadways. Several examples are shown of trajectories developed for a DARPA Urban Challenge vehicle and a method of testing …

Nineteen-Element Phased-Array Feed Development And Analysis On Effects Of Focal Plane Offset And Beam Steering On Sensitivity, Jacob S. Waldron

Theses and Dissertations

Presented herein is the design and construction process in the expansion of BYU's seven-element experimental platform to a nineteen-element platform for phased array feed experiments. The nineteen-element system was deployed at the National Radio Astronomy Observatory (NRAO) in Green Bank West Virginia for use on the Green Bank 20-Meter Telescope. Numerical simulations were performed to determine how sensitivity was affected by electronic beam steering and offset of the phased array feed (PAF) relative to the focal plane of the reflector. These simulated results were then compared to experimental data.

Compact Trench-Based Silicon-On-Insulator Rib Waveguide 90-Degree And 105-Degree Bend And Splitter Design, Jiguo Song

Theses and Dissertations

This thesis presents a theoretical and numerical investigation of silicon-on-insulator trench based passive optical components, bend and splitter, respectively. Compact 90 degree and 105 degree bend and splitter are designed with high index-contrast rib waveguide at wavelength 1550nm and serve as building blocks of splitting network in micro-cantilever biosensing application. The main characteristic of trench based bend and splitter structures is their miniature size and their low radiation loss due to the strong light confinement in high index-contrast systems. Thus large scale, high density optical integrated splitting network becomes possible with the associated advantages of compactness. With FDTD simulation, we …

Inverse Scattering Image Quality With Noisy Forward Data, Thomas J. Sorensen

Theses and Dissertations

Image quality metrics for several inverse scattering methods and algorithms are presented. Analytical estimates and numerical simulations provide a basis for poor image quality diagnostics. The limitations and noise behavior of reconstructed images are explored analytically and empirically using a contrast ratio. Theoretical contrast ratio estimates using the canonical PEC circular cylinder are derived. Empirical studies are conducted to confirm theoretical estimates and to provide examples of image quality vs SNR for more complex scatterer profiles. Regularized sampling is shown to be more noise sensitive than tomographic reconstructive methods.

Optically Powered Logic Transistor, Hanho Cho

Theses and Dissertations

This thesis presents the modeling and fabrication of a new solid-state device meant to be used for digital logic circuits. Most current logic circuits are based on MOSFETs. The new logic device uses some of the same operating principles, but also relies on optical illumination to provide input power. In order to obtain the desired current-voltage behavior of the new device, the Silvaco (Atlas) device simulation was used to give some insight into the correct doping levels in the semiconductor and device geometries. Prototypes were fabricated on p-type silicon wafers using CMOS fabrication processes including oxide growth, photolithography, precise plasma …

Characterization Of A Phased Array Feed Model, David A. Jones

Theses and Dissertations

Creating accurate software based models of phased array feeds (PAFs) is one of many steps to successfully integrating PAFs with current and future radio telescopes, which is a goal of many groups around the globe. This thesis characterizes the latest models of a 19 element hexagonal PAF of dipoles used by the BYU radio astronomy research group and presents comparisons of these models with experimental data obtained using a prototype array. Experiments were performed at the NRAO site in Green Bank, West Virginia, and utilized the outdoor antenna test range and 20 meter radio telescope. Accurate modeling of the PAF …

A Wide Area Bipolar Cascade Resonant Cavity Light Emitting Diode For A Hybrid Range-Intensity, Reginald J. Turner

Theses and Dissertations

This dissertation focused on the development of an illuminator for the HRIS. This illuminator enables faster image rendering and reduces the potential of errors in return signal data, that could be generated from extremely rough terrain. Four major achievements resulted from this work, which advance the field of 3-D image acquisition. The first is that the TJ is an effective current spreading layer for LEDs with mesa width up to 140 micrometers and current densities of approximately 1 x 10⁶ Amp/square centimeter. The TJ allows fabrication of an efficient illuminator, with required geometry for the HRIS to operate as …

Material Perturbations To Enhance Performance Of The Theile Half-Width Leaky Mode Antenna, Jason A. Girard

Theses and Dissertations

Microstrip traveling-wave antennas, often referred to as leaky-wave antennas, have been shown to radiate when the dominant or fundamental mode is suppressed and the first higher-order mode is excited. One such microstrip variation is the Thiele Half-Width (THW) antenna, which operates from 5.9 - 8.2 GHz for this research. Increasing the bandwidth over which the THW antenna radiates is desired, as is a fundamental understanding of the propagation characteristics over this region. This dissertation seeks to vary or perturb the material and physical properties of the THW antenna, including strip-width variations and modifications of the substrate layer, to achieve these …

A Surveillance System To Create And Distribute Geo-Referenced Mosaics Using Suav Video, Evan D. Andersen

Theses and Dissertations

Small Unmanned Aerial Vehicles (SUAVs) are an attractive choice for many surveillance tasks. However, video from an SUAV can be difficult to use in its raw form. In addition, the limitations inherent in the SUAV platform inhibit the distribution of video to remote users. To solve the problems with using SUAV video, we propose a system to automatically create geo-referenced mosiacs of video frames. We also present three novel techniques we have developed to improve ortho-rectification and geo-location accuracy of the mosaics. The most successful of these techniques is able to reduce geo-location error by a factor of 15 with …

The Effect Of Radiation On The Electrical Properties Of Aluminum Gallium Nitride/Gallium Nitride Heterostructures, John W. Mcclory

Theses and Dissertations

AlGaN/GaN Heterojunction Field Effect Transistors (HFETs) were irradiated at low temperature and the temperature dependent changes to drain current, gate current, capacitance, and transconductance were measured. The results were compared to the charge control model of the drain current and trap-assisted tunneling model of the gate current to determine the source of the radiation-induced changes. AlGaN/GaN HFETs demonstrated threshold voltage shifts and drain current changes after irradiation. After electron and neutron irradiation applied at ~80 K, measurement of the drain current at this temperature showed an increase that saturated after 10¹³ electrons/cm² or 10¹⁰ neutrons/cm² due …

A Secure And Efficient Communications Architecture For Global Information Grid Users Via Cooperating Space Assets, Victor P. Hubenko

Theses and Dissertations

With the Information Age in full and rapid development, users expect to have global, seamless, ubiquitous, secure, and efficient communications capable of providing access to real-time applications and collaboration. The United States Department of Defense’s (DoD) Network-Centric Enterprise Services initiative, along with the notion of pushing the “power to the edge,” aims to provide end-users with maximum situational awareness, a comprehensive view of the battlespace, all within a secure networking environment. Building from previous AFIT research efforts, this research developed a novel security framework architecture to address the lack of efficient and scalable secure multicasting in the low earth orbit …

Statistical Methods For Image Registration And Denoising, Matthew D. Sambora

Theses and Dissertations

This dissertation describes research into image processing techniques that enhance military operational and support activities. The research extends existing work on image registration by introducing a novel method that exploits local correlations to improve the performance of projection-based image registration algorithms. The dissertation also extends the bounds on image registration performance for both projection-based and full-frame image registration algorithms and extends the Barankin bound from the one-dimensional case to the problem of two-dimensional image registration. It is demonstrated that in some instances, the Cramer-Rao lower bound is an overly-optimistic predictor of image registration performance and that under some conditions, the …

Monitoring The Antarctic Ice Sheet From Space, Benjamin Rule Lambert

Theses and Dissertations

The Antarctic ice sheet is a geophysically - and in an age of growing concern about global warming, geopolitically - important portion of Earth. The composition and dynamics of the Antarctic ice sheet influence global climate patterns, global sea level and the planet's radiation budget. Recent evidence also suggests that the long term stability of portions of the ice sheet may be in jeopardy. In this thesis I use data from three Ku-band space-borne scatterometers to monitor changes in the backscatter signature of the Antarctic ice sheet from 1978 through 2007. Significant changes in backscatter, which result from geophysical changes …

Performance Analysis Of Effective Range And Orientation Of Uhf Passive Rfid, Paul N. Roque

Theses and Dissertations

The purpose of this research is to characterize the performance of UHF passive RFID tags. Factors of importance are the impact of tag orientation and distance from the RFID reader. Within this study, a comprehensive literature review of RFID technology is presented as well as the methodology used for the research. Furthermore, an analysis of RFID tag experiments is discussed and the results reviewed. To accomplish this task, two main objectives have been established as goals for the study. The first objective is to determine an optimum tag orientation within the RFID reader’s normal read range. Once the optimum tag …

Stabilization And Control Of A Quad-Rotor Micro-Uav Using Vision Sensors, Spencer G. Fowers

Theses and Dissertations

Quad-rotor micro-UAVs have become an important tool in the field of indoor UAV research. Indoor flight poses problems not experienced in outdoor applications. The ability to be location- and movement-aware is paramount because of the close proximity of obstacles (walls, doorways, desks). The Helio-copter, an indoor quad-rotor platform that utilizes a compact FPGA board called Helios has been developed in the Robotic Vision Lab at Brigham Young University. Helios allows researchers to perform on-board vision processing and feature tracking without the aid of a ground station or wireless transmission. Using this on-board feature tracking system a drift stabilization control system …

Real-Time Implementation Of Vision Algorithm For Control, Stabilization, And Target Tracking For A Hovering Micro-Uav, Beau J. Tippetts

Theses and Dissertations

A lightweight, powerful, yet efficient quad-rotor platform was designed and constructed to obtain experimental results of completely autonomous control of a hovering micro-UAV using a complete on-board vision system. The on-board vision and control system is composed of a Helios FPGA board, an Autonomous Vehicle Toolkit daughterboard, and a Kestrel Autopilot. The resulting platform is referred to as the Helio-copter. An efficient algorithm to detect, correlate, and track features in a scene and estimate attitude information was implemented with a combination of hardware and software on the FPGA, and real-time performance was obtained. The algorithms implemented include a Harris feature …