Digital Commons Network^™

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 …

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 …

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 …

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 …

Investigation Of The Performance Of Flexible Pavement Systems Under Moving Loads Using Finite Element Analyses, Dona Jacqueline Johnson

Theses and Dissertations

The introduction of larger and heavier aircraft with more complex wheel configurations is making the current design methods inadequate for airfield pavements. In addition, airport pavements experience significant wander. However, the effect of wander on airport pavement performance has not been evaluated. In previous studies, the stress interactions between each tire of a triple-dual-tandem (TDT) axle used on B-777 and A380 aircraft cannot be captured using a two-dimensional model. In addition, many of these studies have assumed a linear-elastic material behavior of the pavement layers.

The purpose of this study is to conduct a three-dimensional finite element analysis to quantify …

Attitude Estimation And Maneuvering For Autonomous Obstacle Avoidance By Miniature Air Vehicles, James K. Hall

Theses and Dissertations

Utilizing the Euler-Rodrigues symmetric parameters (attitude quaternion) to describe vehicle orientation, we develop a multiplicative, nonlinear (extended) variation of the Kalman filter (MEKF) to fuse data from low-cost sensors. The sensor suite is comprised of gyroscopes, accelerometers, and a GPS receiver. In contrast to the common approach of using the complete vehicle attitude as the quantities to be estimated, our filter states consist of the three components of an attitude error vector. In parallel with the time update of the attitude error estimate, we utilize the gyroscope measurements for the time propagation of the attitude quaternion. The accelerometer and the …

Flexible Screw Design For Bone Implant Application, Seule Kabir

Theses and Dissertations

Disruption of the scapholunate ligament can result in significant immediate and long-term disability. Of the available current acute and subacute treatment strategies for this disorder, the use of a solid screw to stabilize the scapholunate relationship has been proposed. However, subsequent carpal bone loss is an inherent risk to this technique. The goal of this study was to design a flexible orthopedic screw that can be placed between the scaphoid and lunate to restore more normal biomechanics without the risk of osteolysis. Several ideas were generated during the course of the study to create a moveable section in a bone …

Characterization Of The Thermal Transport Through A Temporally-Varying Ash Layer, Darron Palmer Cundick

Theses and Dissertations

Ash deposits in commercial coal-fired boilers frequently pose serious maintenance challenges and decrease thermal efficiency. A better understanding of fundamental thermal transport properties in ash deposits can help mitigate their negative effects. In order to characterize the thermal properties of boiler-side deposits, this work presents a thermal transport model and in-situ measurements of effective thermal conductivity in coal ash deposits. A simple model of the thermal transport through an ash deposit, with and with out slagging, was developed. The model approximates the deposit by dividing it into four regimes: particulate, sintered, solidified slag, and molten slag. The development of this …

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 …

Development Of An Inexpensive, Haptic Graphical Display Device, David Burch

Theses and Dissertations

A finger-worn haptic device capable of rendering 2-D graphics through vibrotactile feedback is presented. The device development is presented from its initial stages of being a stylus design using a photo-interrupter optical sensor and pager-motor actuator to a small case worn on the finger using a RGB color sensor and a piezoelectric actuator. Testing of the latest prototype design shows that it has a spatial sensitivity (<2mm) comparable to natural touch (~1mm) and can be used to output a variety of vibrotactile textures. The design can be expanded for a multiple finger, independent device, while remaining affordable (<$100) and highly portable (<500g).

Nondestructive Evaluation Of Aircraft Composites Using Terahertz Time Domain Spectroscopy, Christopher D. Stoik

Theses and Dissertations

Terahertz (THz) time domain spectroscopy (TDS) was assessed as a nondestructive evaluation technique for aircraft composites. Material properties of glass fiber composite were measured using both transmission and reflection configuration. The interaction of THz with a glass fiber composite was then analyzed, including the effects of scattering, absorption, and the index of refraction, as well as effective medium approximations. THz TDS, in both transmission and reflection configuration, was used to study composite damage, including voids, delaminations, mechanical damage, and heat damage. Measurement of the material properties on samples with localized heat damage showed that burning did not change the refractive …

Dynamic Supersonic Base Store Ejection Simulation Using Beggar, Michael D. Johnson

Theses and Dissertations

Static and dynamic conditions throughout various aft supersonic store separation events are examined using the Beggar Computational Fluid Dynamics (CFD) code from Air Force SEEK Eagle Office at Eglin Air Force Base, FL. An 8.9 deg half angle sphere cone is used for the carrier vehicle with an identically shaped store stowed within a hollow compartment in the aft section of the carrier body. Dynamic store separation simulations are implemented at a free-stream Mach of 2.9 with a Reynolds number of Re = 6.9 x 10⁶/m referenced against carrier base diameter. Analysis covers multiple dynamic separation events along …

Investigation Of Heterogeneity Of Fsw Inconel 718 Coupled With Welding Thermal Cycle, Dong Fang Huang

Theses and Dissertations

In order to develop a better understanding of the property, microstructure evolution and thermal history of FSW Inconel 718's, the strain, strain rate and thermal cycles need to be determined. In order to estimate the strain field of a deformed body, a displacement function needs to be determined. A 3D deformation model was developed to determine the displacement coefficients. A rectangular box created in this model deforms following a linear displacement function. Three orthogonal planes cut this deformed box, which leads to three deformed planes. The shape parameters (L, H, θ¹ and θ²) on the three orthogonal planes can be …

Flexible Twist For Pitch Control In A High Altitude Long Endurance Aircraft With Nonlinear Response, Vanessa L. Bond

Theses and Dissertations

Information dominance is the key motivator for employing high-altitude long-endurance (HALE) aircraft to provide continuous coverage in the theaters of operation. A joined-wing configuration of such a craft gives the advantage of a platform for higher resolution sensors. Design challenges emerge with structural flexibility that arise from a long-endurance aircraft design. The goal was to demonstrate that scaling the nonlinear response of a full-scale finite element model of a high-altitude long-endurance (HALE) aircraft was possible if the model was aeroelastically and "nonlinearly" scaled. A straight-forward method of scaling the first three natural vibration frequencies and mode shapes, and the first …

Warm Hydroforming Characteristics Of Stainless Steel Sheet Metals, Eren Billur

Theses and Dissertations

For numerical modeling and predictive analysis of warm hydroforming, better understanding of material properties (i.e. Flow curves) is required at elevated temperatures and high strains. Hydraulic bulge testing is a suitable method to obtain this information. However, analysis of the test data is not standardized as there are numerous approaches developed and adopted throughout the years. In this study, first, different approaches for hydraulic bulge analysis were compared with stepwise experiments to determine the best combination of approaches in obtaining accurate flow curves at different temperatures and strain rates. Then, three different grades of stainless steels (AISI 201, 301 and …

The Effect Of Liquid Hot Filling Temperature On Blow-Molded Hdpe Bottle Properties, Benjamin S. Hudson

Theses and Dissertations

The occurrence of deformation in plastic bottles is a common problem in the bottling industry where bottles are blow molded, hot filled at high temperatures and sealed. Plastics have unique properties that make it difficult to predict when and why such changes may occur. The root cause of such deformation is unknown by many bottle producers and recent attempts have been made to minimize the occurrence of such defects. The purpose of this research is to determine which variables involved in the bottle production process influence bottle shape. Earlier variables that were tested included both blow molding resin and total …

Assessing Water Quality Modeling In Subtropical Regions Based On A Case Study Of The Aguamilpa Reservoir, Oliver Obregon

Theses and Dissertations

The shortage of water in Mexico has made public and private institutions look at reservoirs as an alternative solution for present and future water supply. However, eighty percent of the existing reservoirs in Mexico are contaminated at some level, many severely. Water quality models are water-management tools used to diagnose water quality problems and the impact of various environmental conditions. They can be effective in assessing various measures of remediation leading to improved water quality. In most of the cases such water quality models have been successfully applied in reservoirs located in temperate climates. However, the use of water quality …

Multidimensional Modeling Of Solid Propellant Burning Rates And Aluminum Agglomeration And One-Dimensional Modeling Of Rdx/Gap And Ap/Htpb, Matthew Wilder Tanner

Theses and Dissertations

This document details original numerical studies performed by the author pertaining to solid propellant combustion. Detailed kinetic mechanisms have been utilized to model the combustion of the pseudo-propellants RDX/GAP and AP/HTPB. A particle packing model and a diffusion flame model have been utilized to develop a burning rate and an aluminum agglomeration model. The numerical model for RDX/GAP combustion utilizes a "universal" gas-phase kinetic mechanism previously applied to combustion models of several monopropellants and pseudo-propellants. The kinetic mechanism consists of 83 species and 530 reactions. Numerical results using this mechanism provide excellent agreement with RDX and GAP burning rate data, …

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 …

Theoretical Determination Of Subcritical Sequent Depths For Complete And Incomplete Hydraulic Jumps In Closed Conduits Of Any Shape, Nathan John Lowe

Theses and Dissertations

In order to predict hydraulic jump characteristics for channel design, the jump height may be determined by calculating the subcritical sequent depth from momentum theory. In closed conduits, however, outlet submergence may fill the conduit entirely before the expected sequent depth is reached. This is called an incomplete or pressure jump (as opposed to a complete or free-surface jump), because pressure flow conditions prevail downstream. Since the momentum equation involves terms for the top width, area, and centroid of flow, the subcritical sequent depth is a function of the conduit shape in addition to the upstream depth and Froude number. …

Optimal Re-Entry Trajectory Terminal State Due To Variations In Waypoint Locations, William J. Karasz

Theses and Dissertations

The Air Force's Prompt Global Reach concept describes the desire to have a capability to reach any target within a 9000 nautical mile radius within two hours of launch. To meet this objective, much effort is being devoted to hypersonics and re-entry vehicles. Given the limited maneuverability of hypersonic vehicles, computational modeling is used to generate trajectories before launch to strike intended targets. In addition to endpoint (target) constraints, additional waypoints may constrain the trajectory. This research finds the optimal trajectory which satisfies the endpoint and waypoint constraints, and then investigates where else the vehicle can go while still meeting …

Design And Testing Of A Pumpless Microelectromechanical System Nanoinjector, Quentin Theodore Aten

Theses and Dissertations

A deeper understanding of human development and disease is made possible partly through the study of genetically modified model organisms, such as the common mouse (Mus musculus). By genetically modifying such model organisms, scientists can activate, deactivate, or highlight particular characteristics. A genetically modified animal is generated by adding exogenous (foreign) genetic material to one or more embryonic cells at their earliest stages of development. Frequently, this exogenous genetic material consists of specially engineered DNA, which is introduced into a fertilized egg cell (zygote). When successfully introduced into the zygote, the exogenous DNA will be incorporated into the …

Product Family Design Using Smart Pareto Filters, Jonathan D. Yearsley

Theses and Dissertations

Product families are frequently used to provide consumers with a variety of appealing products and to help maintain reasonably low production costs for manufacturers. Three common objectives in the design of product families are used to balance the interests of both consumers and manufacturers. These objectives are to maximize (i) product performance, (ii) product distinctiveness as perceived by the consumer, and (iii) product commonality as seen by the manufacturer. In this thesis, three methods are introduced that use multiobjective optimization and Smart Pareto filtering to satisfy the three objectives of product family design. The methods are progressive in nature and …

Ecad To Mcad Interoperability For Automated Enclosure Design, Adam C. Wilcox

Theses and Dissertations

Enclosure design is the process of creating a package that will support and protect enclosed circuitry. Electronic enclosures are used in almost all industries, such as aerospace, automotive, naval, computer, toy, etc. Many designers use computer aided design (CAD) packages to aid them in creating these enclosures. Enclosure creation involves a working knowledge of the physics behind electrical and mechanical systems. Each of these engineering disciplines has separate CAD packages with their own set of rules, programming language, and interfaces. This creates a barrier for communication flow between electrical CAD (ECAD) and mechanical CAD (MCAD). The purpose of this thesis …

Synthesis And Characterization Of Novel Temperature-Responsive Dendritic Peg-Pdlla Star Polymers For Drug Delivery, Arunvel Kailasan

Theses and Dissertations

This study describes a novel thermoresponsive dendritic polyethylene glycol-poly(D, L-lactide) (PEG-PDLLA) core-shell nanoparticle with potential for drug delivery and controlled release. A series of dendritic PEG-PDLLA nanoparticles were synthesized through conjugation of PEG to Starburst™ polyamidoamine (PAMAM) dendrimer G3.0 and subsequent ring-opening polymerization of DLLA, in which PEG chain length (i.e., MW=1500, 6000 or 12000 Dalton) was varied; however, the feeding molar ratio of DLLA monomers to the overall PEG repeat units on the dendrimer surface was kept at 1:1. Linear PEG-PDLLA copolymers were also syntheiszed under the same condition and used as control. According to our results, dendritic PEG-PDLLA …

Design Of A Three-Passage Low Reynolds Number Turbine Cascade With Periodic Flow Conditions, Daniel R. Rogers

Theses and Dissertations

A numerical method for modeling a low Reynolds number turbine blade, the L1M, is presented along with the pitfalls encountered. A laminar solution was confirmed to not accurately predict the flow features known in low Reynolds number turbine blade flow. Three fully turbulent models were then used to try to predict the separation and reattachment of the flow. These models were also found to be insufficient for transitioning flows. A domain was created to manually trip the laminar flow to turbulent flow using a predictive turbulence transition model. The trip in the domain introduced an instability in the flow field …

Crashes In The Vicinity Of Major Crossroads, Charles G. Allen

Theses and Dissertations

Major crossroads are designed to facilitate the conflicting movements of numerous vehicles in a manner that is both safe and efficient. Accesses located within the functional areas of major crossroads add complication to intersection activity due to additional conflicts arising from ingressing and egressing movements at the accesses. In this research, the impact of accesses on crashes within major crossroad functional areas was analyzed. Specifically, the effects of access spacing within functional areas and access setback from intersections were addressed. In order to conduct the analysis, the functional areas of 159 signalized major arterial crossroads across the state of Utah …

Foundational Data Repository For Numeric Engine Validation, Jason Michael Hollingsworth

Theses and Dissertations

Many different numeric models have been created to address a variety of hydraulic and hydrologic engineering applications. Each utilizes formulations and numeric methods to represent processes such as contaminant transport, coastal circulation, and watershed runoff. Although one process may be adequately represented by a model, this does not guarantee that another process will be represented even if that process is similar. For example, a model that computes subcritical flow does not necessarily compute supercritical flow. Selecting an appropriate numeric model for a situation is a prerequisite to obtaining accurate results. Current policies and resources do not provide adequate guidance in …