Engineering Commons^™

The Extraction Of Type Ii Collagen And The Electrospinning Of Nano-Fibrous Scaffolds, Danielle Careen Knapp

Theses and Dissertations

Articular cartilage lining joints, such as in the knee, functions to reduce friction and absorb shock. Collagen type II is the largest constituent in the extracellular matrix of articular cartilage and its restoration is of the highest interest to tissue engineers. Cartilage has little ability to naturally regenerate due to the absence of vascularity and the inability of the chondrocytes to proliferate at a high rate. It would be ideal to create a mimicking extracellular matrix/scaffold from type II collagen that could possibly be used to replace damaged articular cartilage that has the same function and morphology. Three different groups …

Synthesis And Characterization Of Methylene Bis (P-Cyclohexyl Isocyanate)-Poly (Tetramethyl Oxide) Based Polyurethane Elastomers, Kennard Marcellus Brunson

Theses and Dissertations

This research concerns the development and characterization of methylene bis (p-cyclohexyl isocyanate/butanediol) (HMDI/BD) based polyurethanes used in connection with surface-active anti-microbial polyurethanes. Previously studied polyurethanes having an isophorone diisocyanate/butanediol (IPDI/BD) hard block contaminated water during dynamic contact angle (DCA) analyses. This contamination by unknown species confounds results from biocidal studies and jeopardizes the use of the polyurethane as a matrix polyurethane. By contrast, polyurethanes with methylene bis (p-cyclohexyl isocyanate)/butanediol hard block showed no contamination during DCA analysis. For this reason, further study of HMDI/BD/PTMO polyurethanes was conducted. HMDI/BD polyurethanes were synthesized with 15-50wt% hard block and a soft block of …

Electromechanical Characterization Of Poly(Dimethyl Siloxane) Based Electroactive Polymers, Wrutu Deepak Parulkar

Theses and Dissertations

The main objectives of this thesis are 1) to evaluate the effect of cross-linking polar cyano phenyl (CN) groups on poly (dimethyl siloxane) (PDMS) and 2) to characterize the electromechanical properties of the resulting CN-PDMS blend as an electroactive actuator. Materials responding to an external stimulus are referred to as electroactive materials. There are several phenomena, which govern the mechanism in these materials, such as piezoelectricity, Maxwell's effect, ferroelectricity, electrostriction to name a few. These electroactive materials can be employed in several applications such as biomedical devices, robots, MEMs, aerospace vehicles, where the application is governed by the specific mechanism. …

Investigation Of Surface States And Device Surface Charging In Nitride Materials Using Scanning Kelvin Probe Microscopy, Mohammed Shahriar Sabuktagin

Theses and Dissertations

In this work Scanning Kelvin Probe Microscopy (SKPM) was used to characterize surface states and device surface charging in nitride materials. Samples grown by Molecular Beam Epitaxy (MBE), Metal Organic Chemical Vapor Deposition (MOCVD) and Hydride Vapor Phase Epitaxy (HVPE) typically show a high surface band bending of about 1 eV. In an n-type sample with 3X1017 cm-3 carrier concentration, 1 eV upward band bending corresponds to 1.7X1012 cm-2 trapped charge density in the surface states. Under continuous ultraviolet (UV) illumination up to 0.6 eV surface photo voltage effect could be observed in some samples, which further indicates that surface …

Real Time Frequency Analysis Of Signals From Lasso Catheter For Radiofrequency Ablation During Atrial Fibrillation, Prashant Yadav

Theses and Dissertations

Real time spectrum analysis of signals obtained through lasso catheter during radiofrequency ablation of pulmonary vein was performed to determine the channel with dominant frequency. Threshold algorithm was used for signals which could be classified as type I and type II AF. Type III AF Signals which were highly fractionated or differentiated were evaluated for frequency content by performing Fast Fourier Transform. Data from Seven patients was collected and an episode of 180 ± 40 seconds was recorded and analyzed for each pulmonary vein that showed electrical activation. Frequency spectra for one second segment of signal for each channel were …

Joint Center Movement Analysis And 3d Motion Modeling Of Upper Arm - Comparison Of Several Algorithms With The Visual 3-D Program, Leena Joseph

Theses and Dissertations

600 out of every 100,000 people in the United States today suffer from some form of cerebellar disease that causes major abnormalities in the equilibrium and aligned, coordinated movement of the body. Hence it becomes essential to diagnose the extent of the movement and gait disorder and provide required therapy to the patients. Various developments have been made in the designing and application of interactive software system for body positioning. Object oriented design techniques are used in the field of software engineering for interactive geometric representation of system behavior. Motion analysis of the upper and lower extremities of the body …

A Study On The Nature Of Anomalous Current Conduction In Gallium Nitride, Joshua K. Spradlin

Theses and Dissertations

Current leakage in GaN thin films limits reliable device fabrication. A variety of Ga and N rich MBE GaN thin films grown by Rf, NH3, and Rf+ NH3, are examined with electrical measurements on NiIAu Schottky diodes and CAFM. Current-voltage (IV) mechanisms will identify conduction mechanisms on diodes, and CAFM measurements will investigate the microstructure of conduction in GaN thin films. With CAFM, enhanced conduction has been shown to decorate some extended defects and surface features, while CAFM spectroscopy on a MODFET structure indicates a correlation between extended defects and field conduction behavior at room temperature. A remedy for poor …

Myocardial Perfusion Imaging With Rb-82 Pet, George Nittil Francis

Theses and Dissertations

Myocardial perfusion imaging (MPI) is an effective technique used to study the left ventricular ejection function (LVEF), myocardial perfusion, wall motion, and wall thickening. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are two modalities that can be used to quantify the left global and regional perfusion at rest and stress. While PET and SPECT rely on similar principles to produce images, important differences in instrumentation and experimental applications are dictated by inherent differences in their respective physics of radioactive decay. With a sensitivity > 90% in combination with a high specificity, PET is today the best available …

Reentrainment Of Submicron Solid Particles, Ramin Mortazavi

Theses and Dissertations

In this work, an experimental method is developed to study the effects of particle size, flow rate, pulsation, particle/substrate material, and temperature on the short-term reentrainment of submicron particles. The particles tested are in the size range of 10-900 nm and are deposited by wetting the inside of capillary tubes with a liquid suspension. The tubes are then dried in a desiccator. The particles are reentrained under turbulent dry air flow conditions and a condensation particle counter is used to measure the number of entrained particles.There has been very limited work done with nanoscale particles in general and no previous …

Characterization Of Fluoropolymer Powders Made By Supercritical Assisted Mixing With Crystalline Additives, Ntoh Atem-Tambe

Theses and Dissertations

This research project investigates a new technique to efficiently mix crystalline solid additives with polymers by gentle ball milling with steel balls in the presence of carbon dioxide (C02) at 17 to 30°C and 1300 to 2500 psig. As the ball milling system is agitated, the steel balls transfer mechanical energy to the fluoropolymer and additive thereby converting them to powders. C02 is added into the chamber to expand the polymer and make it amenable to impregnation by the additive. At the end of the mixing process, a free flowing powder is produced consisting of the additive coated with fluoropolymer. …

Characterization Of Electrosprayed Poly(Vinylidene Fluoride)/Cnt Nanocomposite, Ihab Maher Abdelsayed

Theses and Dissertations

PVDF, Poly(vinylidene fluoride), is a polymer that has been studied for over four decades due to its good electromechanical properties, stability, and durability in various environments. Currently, PVDF is the only commercially available piezoelectric polymer. PVDF is a polymorph, which indicates the presence of several crystalline phases such as α, β, γ, and δ-phase. Oriented β-phase PVDF exhibits ferroelectric properties and displays the largest piezoelectricity amongst the four phases, which makes it the most desirable phase. Preparing oriented β-phase PVDF is a multi-step process, which is cost intensive, due to the time, labor and energy utilized. The main goal of …

Analysis And Shape Modeling Of Thin Piezoelectric Actuators, Makram Mouhli

Theses and Dissertations

The field of smart materials is an increasingly growing area of research. In aerodynamics applications especially, transducers have to fulfill a series of requirements such as light weight, size, energy consumption, robustness and durability. Piezoelectric transducers, devices which transform an electrical signal into motion, fulfill many of these requirements. Specifically, piezoelectric composites are of interest due to their added toughness and ease of integration into a structure. Resulting composites have a characteristic initial curvature with accompanying residual stresses that are responsible for enhanced performance, relative to flat actuators, when the active material is energized. A number of transducer designs based …

Daubechies And Quadratic B-Spline Wavelets For Automated Early Diagnosis Of Alzheimer's Disease, Genevieve Jacques

Theses and Dissertations

Alzheimer's disease is a neurological disorder characterized by nerve degeneration and neuronal death. The diagnosis of Alzheimer's disease at an early stage is a major concern due to the lack of a standard and effective diagnosis procedure available to community healthcare providers, as well as the increasing numbers of the elderly population affected. Clinical evaluation, the standard AD diagnostic procedure conducted at major university hospitals and research clinics, achieves, on average, a positive predictive value of 93%, with a sensitivity of 83%, specificity of 55% and an overall accuracy of 75%. An effective and objective tool for early diagnosis of …

Vlsi Implementation Of An Efficient Method For The Computation Of Line Spectral Frequencies, David L. Reynolds

Theses and Dissertations

In speech coding applications using linear predictive techniques, the computation of line spectral frequencies (LSFs) from the predictor coefficients is an extremely computationally intensive task. The unique properties of the symmetric and antisymmetric polynomial roots limit the region which must be searched, however it is still necessary to perform a root-finding algorithm on a high-order polynomial.

Certain algorithms have been developed to reduce the complexity of the root finding exercise. One such algorithm, developed by Ramachandran and Kabal, takes advantage of certain properties of the symmetric and antisymmetric polynomials to map the upper portion of the unit circle onto the …

Three-Dimensional Shape Characterization For Particle Aggregates Using Multiple Projective Representations, Jonathan Paul Corriveau

Theses and Dissertations

Shape descriptors are used extensively in computer vision/automated recognition applications such as fingerprint matching, robotics, character recognition, etc. The conventional two-dimensional shape descriptors used in these applications do not readily lend themselves to compact representations in three dimensions. The situation is even more challenging when one attempts to numerically describe the three-dimensional shapes of a mixture of objects such as in an aggregate mix.

The goal of this study is the design, development and validation of automated image processing algorithms that can estimate three-dimensional shape-descriptors for particle aggregates. The thesis demonstrates that a single set of numbers representing a composite …

An Investigation Of Multi-Dimensional Evolutionary Algorithms For Virtual Reality Scenario Development, Scott Papson

Theses and Dissertations

Virtual reality (VR) has emerged as a powerful visualization tool for design, simulation, and analysis in modem complex industrial systems. The primary motivation for this thesis is to develop a framework for the effective use of VR in design-simulation-analysis cycles, particularly in situations involving large, complex, multi-dimensional data-sets. This thesis develops a framework that is intended to support not only the integration of such data for visual, interactive, and immersive displays, but also provides a method for performing risk analysis. Previously "static" VR environments are enhanced with time-evolutionary capabilities. Four candidate algorithms are evaluated for this purpose – deterministic modeling, …

Heterogeneous Multi-Sensor Data Fusion Using Geometric Transformations And Parzen Windows For The Nondestructive Evaluation Of Gas Transmission Pipelines, Joseph Anthony Oagaro

Theses and Dissertations

The natural gas transmission pipeline network in the United States is a key component of the nation's energy supply infrastructure and extends for over 280,000 miles and has an average age of over 60 years. The integrity of the pipeline is maintained by periodic inline inspections using magnetic or ultrasonic pigs. Defect characterization algorithms developed using current pigging data are hampered by the fact that single inspection techniques (either magnetic or ultrasonic) do not yield sufficient information for accurately and repeatably characterizing defects. This thesis demonstrates that defect characterization algorithms using multiple inspection techniques can accomplish this task. In particular, …

New Product Launch Decisions Under Competition And Uncertainty: A Real Options And Game-Theoretic Approach To New Product Development, James O. Ostler

Theses and Dissertations

New product development is central to many firms' future success. Not only as a means to continue to maintain their piece of the market, but product development can also be a strategic means for a company to diversify, and/or alter focus to adapt to changing market conditions.

Most of the research in new product development has been on how to do it cheaper and faster than the next guy. However, early commercialization does not guarantee a position of strength in the market. Failures of EMI in CT scanners and Xerox in personal computers illustrate that being first to market does …

Dynamic Stability And Handling Qualities Of Small Unmanned-Aerial-Vehicles Unmanned-Aerial-Vehicles, Tyler Michael Foster

Theses and Dissertations

General aircraft dynamic stability theory was used to predict the natural frequencies, damping ratios and time constants of the dynamic modes for three specific small UAVs with wingspans on the scale from 0.6 meters to 1.2 meters. Using USAF DatCom methods, a spreadsheet program for predicting the dynamic stability and handling qualities of small UAVs was created for use in the design stage of new small UAV concept development. This program was verified by inputting data for a Cessna-182, and by then comparing the program output with that of a similar program developed by DAR Corporation. Predictions with acceptable errors …

A Finite Element Simulation Of Temperature And Material Flow In Fricton Stir Welding, Mark J. Lasley

Theses and Dissertations

The purpose of this research was to use the Transvalor S.A. product, Forge3, to develop a finite element simulation of the friction stir welding process that improves the predictability of temperature evolution and material flow within the plunge portion of the process. Previous modeling created more heating within the billet than experimental results, probably due to the simplification of the simulation with adiabatic boundary conditions. More realistic tooling temperatures were included in this model as these affect heat evolution which is a determining factor in microcrystalline growth. These results were validated by experimental efforts using a billet and tooling instrumented …

Byu Micro-Sar: A Very Small, Low-Power Lfm-Cw Synthetic Aperture Radar, Michael Israel Duersch

Theses and Dissertations

Brigham Young University has developed a low-cost, light-weight, and low power consumption SAR for flight on a small unmanned aerial vehicle (UAV) at low altitudes. This micro-SAR, or uSAR, consumes only 18 watts of power, ideal for application on a small UAV. To meet these constraints, a linear frequency modulation-continuous wave (LFM-CW) transmit signal is utilized. Use of an LFM-CW signal introduces some differences from the typical strip map SAR processing model that must be addressed in signal processing algorithms. This thesis presents a derivation of the LFM-CW signal model and the associated image processing algorithms used for the uSAR …

A Method For Winding Advanced Composites Of Unconventional Shapes Using Continuous And Aligned Fibers, Abraham K. Allen

Theses and Dissertations

Advanced composites are extremely strong, rigid, and light, even when compared with advanced metals. Advanced composites are replacing high-tech metals as the material of choice for aerospace engineering. However, the processes used to manufacture advanced composites generally lose some of the properties of the materials by their process limitations.

One process that keeps the theoretically awesome qualities of the composite materials in tact is filament winding. Filament wound parts are used as rocket shells, bicycle frame tubes, drive shafts, pressure vessels, etc. Filament winding is an automated process and makes reliable parts to close tolerances. If a straight tube were …

Wind Tunnel Investigation Of The Static Stability And Control Effectiveness Of A Rotary Tail In A Portable Uav, Jose R. Rivera Parga

Theses and Dissertations

The Air Force Research Lab, Munitions Directorate, Flight Vehicles Integration Branch (AFRL/MNAV) developed a man-portable, carbon-fiber matrix UAV with a flexible rectangular wing of 24" span and 6" chord, 18.2" length. There is a need for the development of smaller and lighter UAV's to perform certain missions. The objective of this experimental study was to determine the behavior and the aerodynamic characteristics of rotary tails. The bird-inspired rotary tail mechanism studied enabled control of two degrees of freedom and was configured to provide elevator deflection and rotation. Its effects on the static stability and control effectiveness were measured using the …

Ultra Wide Band Signal Modeling For Radar Receiver Characterization, Robert J. Backscheider

Theses and Dissertations

Results for modeling, simulation, and analysis of interference effects that modern wideband signals have on existing narrowband radar system performance are presented. In particular, radar detection performance is characterized using a basic radar receiver model and operational parameters consistent with those of the ARSR-4 air route surveillance radar. Two modern wideband signals (interferers) are addressed in this work, including the GPS military signal (M-Code signal) and a direct sequence ultra wideband (DS-UWB) waveform meeting outdoor emission restrictions imposed by the Federal Communications Commission (FCC). Interference effects are characterized for an unmodulated sinusoidal pulse as well as linear frequency modulated (LFM) …

Non-Cooperative Detection Of Ultra Wideband Signals, Brett D. Gronholz

Theses and Dissertations

Techniques for the non-cooperative (non-matched filter) detection of impulse-like ultra wideband signals using channelized receiver architectures are developed and evaluated. Each technique considered is modeled and simulations conducted to characterize detection performance, the results of which are compared with the detection performance of three receivers: the matched filter receiver, which provides optimum detection performance in AWGN; the radiometer, or energy detector; and the multi-aperture cross correlation receiver. It is shown that a channelized receiver (with no downconversion) can provide approximately 2.5 dB improvement over the radiometer when performing detection using the temporal-temporal matrix (TTM). The TTM processing technique provides the …

Effects Of Variable Contact Load On Fretting Fatigue Behavior Of Shot-Peened And Un-Peened Titanium Alloy, Chia-Hawa Lee

Theses and Dissertations

Fretting fatigue occurs between two components in contact under relative motion and reduces fatigue life when compared with plain fatigue. Shot-peening, on the other hand, is the most commonly used cold working process to improve material fatigue resistance in aeronautical industries. Nearly all work accomplished to date has assumed a constant contact load while investigating fretting fatigue. The primary goal of this study was to explore fretting fatigue behavior under constant and variable contact load configurations using both shot-peened and un-peened specimens made up of Ti-6Al-4V alloy. Contact loads were applied with four different frequencies. Applied axial loads were also …

Consistency Results For The Roc Curves Of Fused Classifiers, Kristopher S. Bjerkaas

Theses and Dissertations

The U.S. Air Force is researching the fusion of multiple classifiers. Given a finite collection of classifiers to be fused, one seeks a new classifier with improved performance. An established performance quantifier is the Receiver Operating Characteristic (ROC) curve, which allows one to view the probability of detection versus the probability of false alarm in one graph. Previous research shows that one does not have to perform tests to determine the ROC curve of this new fused classifier. If the ROC curve for each individual classifier has been determined, then formulas for the ROC curve of the fused classifier exist …

Trade Space Analysis Of Antenna Array Architecture Using System Modeling Tools, Eugene Johnson

Theses and Dissertations

This trade study has two objectives. The first provides a trade space analysis of differing array architectures and associated radio frequency components using system-modeling tools. The second objective develops system modeling tools aiding similar analysis by other users. These objectives were accomplished by evaluating a selected group of output parameters to include overall system cost, mass, and power consumption, as well as the minimum detectable input level, system spurious free dynamic range, and selected beam spoilage parameters caused by the use of discrete phase shifters. A fixed number of designs were evaluated using simulation. The evaluation process examined input parameter …

Understanding And Improving Moment Method Scattering Solutions, Clayton Paul Davis

Theses and Dissertations

The accuracy of moment method solutions to electromagnetic scattering problems has been studied by many researchers. Error bounds for the moment method have been obtained in terms of Sobolev norms of the current solution. Motivated by the historical origins of Sobolev spaces as energy spaces, it is shown that the Sobolev norm used in these bounds is equivalent to the forward scattering amplitude, for the case of 2D scattering from a PEC circular cylinder. A slightly weaker relationship is obtained for 3D scattering from a PEC sphere. These results provide a physical meaning for abstract solution error bounds in terms …

Design Of Cmos Four-Quadrant Gilbert Cell Multiplier Circuits In Weak And Moderate Inversion, Craig Timothy Remund

Theses and Dissertations

This thesis presents four-quadrant CMOS current-mode multiplier architectures based on the bipolar Gilbert cell multiplier architecture. Multipliers are designed using the CMOS subthreshold region to take advantage of the subthreshold exponential I-V relationship that closely matches bipolar modeling. It is discovered that biasing to remove drift current components and to address higher order effects such as ideality factor mismatch, threshold mismatch, body effect, and short channel effects, is important to provide a linear multiplier. It is also shown that distortion caused by device size mismatch and offset input currents can be used to cancel the distortion introduced by drift currents …