Digital Commons Network^™

Development Of A Perturbation Generator For Vortex Stability Studies, John Edward Riester Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

Theory predicts vortex instability when subjected to certain types of disturbances. It was desired to build a device which could introduce controlled velocity perturbations into a trailing line vortex in order to study the effects on stability. A perturbation generator has been designed and manufactured which can be attached to the center-body of an airfoil type vortex generator. Details of design tests and manufacturing of the perturbation generator are presented. The device produced controlled perturbations with frequencies in excess of 250 Hz. Preliminary testing and evaluation of the perturbation generator performance was conducted in a 4 inch cylindrical pipe. Observations …

Assessment Of Lipid Extraction From Human Bone On Subsequent Demineralization, Jaeeun Lee

Biological Sciences Theses & Dissertations

The purpose of this study was to assess the effectiveness of various solvents m removal of lipids from human bone, and to determine the effects of lipid extraction on subsequent acid solubilization of the mineral components of bone. Specifically, the following processing steps were studied; 1) ground human bone was de fatted in various ethanol / water mixtures, and / or chloroform / methanol ( 2: 1, v:v ), 2) ground human bone which had lipids extracted ( in absolute ethanol ) and bone which had not had lipids extracted were demineralized using vanous concentrations of hydrochloric acid to assess …

The Hydrogeology And Leachate Generation Of An Alum Sludge Lagoon Chesapeake Virginia, Charles M. Darling

OES Theses and Dissertations

In 1986 the City of Chesapeake, Virginia began to dig shallow ponds ("lagoons") to contain alum sludge, a waste generated by the City from the process of treating potable water. Borings at the disposal site reveal that the near-surface geologic units include a thin mud-rich facies which overlies a thick sandy facies, both of which are in the Lynnhaven Member of the Tabb Formation. At 7 meters depth, a clay-rich facies of the Yorktown Formation (Morgarts Beach Member?) underlies the sandy water table aquifer. Water levels from twenty observation wells and two monitoring wells installed into the water table aquifer …

Effects Of Quantum Noise On A Two-Level System In A Single-Mode Cavity, Linda L. Vahala

Electrical & Computer Engineering Faculty Publications

The effects of quantum noise on a two-level system in the bad-cavity regime are considered perturbatively in the form of closure at the pair-correlation level. It is found that pair-correlation effects can reduce the level of semiclassical chaos. However, under the rotating-wave approximation (RWA), quantum noise can lead to chaos if there is an initial population inversion, while the full RWA Hamiltonian system remains integrable.

The Study Of Oxygen Transport Through Polycrystalline, Single Crystal And Alloyed Silver, Dongchuan Wu

Physics Theses & Dissertations

The permeation of oxygen through large grain polycrystalline silver, through the (110), (111) and (100) single crystals of silver and through Ag0.05Zr alloy have been studied over the temperature range of 400 - 800 °C. In addition, studies were also conducted using glow discharge dissociation of the supply side ( upstream ) molecular oxygen in order to examine whether normal dissociative adsorption is a limiting step in the overall transport process.

The permeability of oxygen through polycrystalline silver was found to be quite linear and quite repeatable. The diffusivity measurements were found to exhibit two distinct linear regions, one above …

Microwell Based Solid Phase Competitive Enzyme Immunoassay For Estradiol And Estriol, Jeng-Ting Yang

Chemistry & Biochemistry Theses & Dissertations

A sensitive and simple microwell based competition enzyme immunoassay for the quantitative determination of estradiol (E₂) and estriol (E₃) was developed. Nicrowells coated with antibody were incubated with antigen followed by adding horseradish peroxidase (HRPO) conjugate. The assay, which can be performed within two hours at room temperature, involved simultaneous incubation of E₂ - or E₃-HRPO conjugate and serum sample in polystyrene microwells coated with anti- E₂ or anti-E₃ gamma globulin fraction.

Gamma globulin was isolated from whole anti-serum by DEAE-cellulose chromatography. A carbodiimide coupling method was utilized to prepare the …

Development Of A Solid Phase Enzyme Immunoassay For Total Serum Testosterone, Li Li

Chemistry & Biochemistry Theses & Dissertations

An enzyme-labeled immunoassay of sufficient range and sensitivity was developed for serum testosterone determination. In this method, the testosterone in the serum sample and testosterone-HRPO conjugate compete with each other for the limited antibody binding sites on the anti-testosterone gamma globulin coated microwell. The assay can be performed in only 2.5 hours.

The gamma globulin fraction was isolated from the anti-testosterone whole serum by DEAE-cellulose column chromatography. Testosterone-peroxidase conjugate was prepared by a carbodiimide coupling method. The interference which arises from the binding of testosterone to steroid hormone binding protein was eliminated by the addition of 17 beta-estradiol. All assay …

A Mathematical Model Of The Dynamics Of An Optically Pumped Codoped Solid State Laser System, Thomas G. Wangler

Mathematics & Statistics Theses & Dissertations

This is a study of a mathematical model for the dynamics of an optically pumped codoped solid state laser system. The model comprises five first order, nonlinear, coupled, ordinary differential equations which describe the temporal evolution of the dopant electron populations in the laser crystal as well as the photon density in the laser cavity. The analysis of the model is conducted in three parts.

First, a detailed explanation of the modeling process is given and the full set of rate equations is obtained. The model is then simplified and certain qualitative properties of the solution are obtained.

In the …

Grid Generation And Flow Computation About A Martian Entry Vehicle, John Edward Stewart

Mechanical & Aerospace Engineering Theses & Dissertations

A number of vehicles are currently being proposed for a manned mission to Mars. One of these vehicles has a modified blunt-nosed cone configuration. Experimental results have been obtained for this vehicle in 1968. These results show lift-over-drag ratios comparable to those needed for Mars entry. Computations are performed here to verify the earlier results and to further describe the flight characteristics of this vehicle.

An analytical method is used to define the surface of this vehicle. A single-block volume grid is generated around the vehicle using an algebraic Two-Boundary Grid Generation algorithm (TBGG) and transfinite interpolation. Euler solutions are …

Seasonal And Diel Patterns Of Abundance And Productivity Of Phototrophic Picoplankton In The Lower Chesapeake Bay, Lewis Francis Affronti Jr.

Biological Sciences Theses & Dissertations

This study was performed to evaluate phototrophic pico-plankton (0.2 to 2.0 μm) dynamics within the lower Chesapeake Bay. A 15 month study of phototrophic picoplankton abundance and productivity was made from June 1988 to October 1989. Annual picoplankton abundance using epifluorescence microscopy ranged from 7.26 x 10⁶ cells/1 in the winter to 9.28 x 10⁸ cells/1 during late summer.

In situ incubations of natural picoplankton populations over the 15 month study were used to test the applicability of the frequency of dividing cells technique in estimating phototrophic picoplankton growth rates. The regression equation o fμ = 2.37 x …

Metal Mobilization From A Near-Shore Lake Sediment Under Simulated Acidic Groundwater Inputs, Raveendra V. Ika

OES Theses and Dissertations

Simulation of acidic groundwater passing through lake sediments was conducted under controlled conditions in a laboratory. Three sediment cores collected intact from the near-shore region of an acidic lake were subjected to simulated groundwater inputs of initially identical chemistry for a seven day period. Following this period water being used in the simulation for two of the sediment cores was acidified by hydrochloric acid (HC1) addition to examine the ability of these sediments to neutralize acidic groundwater with varying H⁺ concentration.

Simulated acidic water passing through the sediment cores mobilized significant amounts of metals. The sediment acted as a …

Phytoplankton In Lake Drummond And Two Drainage Ditches In The Great Dismal Swamp, Virginia, Christine Gregory Phillips

Biological Sciences Theses & Dissertations

A twelve month study was conducted on the phytoplankton of Lake Drummond and Washington and Jericho Ditches from December 1988 to November 1989. Surface water samples were collected for nutrient and chlorophyll analysis from June 1989 to November 1989. The dominant phytoplankton component was the pico-nanoplankton (< 3 micron) category. A total of 57 species were identified from Lake Drummond, 51 species from Washington Ditch, and 31 species from the Jericho Ditch. Three major phytoplankton groups were identified at these sites: bacillariophyceans, cyanophyceans and cryptophyceans. The dominant species was the diatom Asterionella formosa. Nutrient and chlorophyll concentrations increased from summer to fall. Based on nutrient and chlorophyll g concentrations and species diversity indices, Lake Drummond is classified as eutrophic.

An Artificial Neural Approach To The Decomposition Problem, Chandrashekar L. Masti

Electrical & Computer Engineering Theses & Dissertations

The goal of this thesis is to develop an artificial neural approach toward addressing the intractability involved with the decomposition problem. The search for the lattice of substitution property (s. p.) partitions essential to decompositions is cast into the framework of constraint satisfaction. An artificial neural network is developed to provide solutions by performing optimization of a mathematically derived objective function over the problem space. The issue of transitivity is verified to belong to a class of problems beyond the scope of solvability for conventional quadratic-order constraint satisfaction neural networks. A theorem is stated and proved establishing that third-order correlations …

Visual Speech Training Aid For The Deaf, Subhashri Venkat

Electrical & Computer Engineering Theses & Dissertations

A computer-based vowel articulation training aid has been developed. A "continuous" acoustic-phonetic transformation is performed to map speech parameters to a lower dimensionality display space. There are two possible approaches to this transformation problem. The transformation could be either linear or a combination nonlinear/linear. The nonlinear transformation is performed using a multi-layered feedforward neural network with linear output layers. Speech parameters are extracted either from an analog filter bank arrangement (band energies) or by a digital signal processing procedure (Discrete Cosine Transform Coefficients). The speech parameters obtained from both methods correspond to the spectral envelope of the speech signals. The …

The Role Of Longshore Sediment Transport In The Loss Of Fill Material From An Estuarine Groin System, R. Neville Reynolds

OES Theses and Dissertations

The influence of shoreline structures on longshore sediment transport and the evolution of a stable beach planform was investigated at Willoughby Spit, Virginia following the placement of 410,590 cubic meters of beach fill within a groin system. Shoreline changes and wave conditions in a single groin compartment, and the growth rate of a downdrift terminal spit were monitored during 1985 and 1986. Short term fluctuations in the shoreline position within the groin compartment suggested an episodic westerly movement of sediment through the groin system. Primary sediment moving events were associated with northerly winds which produced waves up to 50 cm …

Encoding Phonetic Knowledge For Use In Hidden Markov Models Of Speech Recognition, Danming Qian

Electrical & Computer Engineering Theses & Dissertations

Hidden Markov models (HMM's) have achieved considerable success for isolated-word speaker-independent automatic speech recognition. However, the performance of an HMM algorithm is limited by its inability to discriminate between similar sounding words. The problem arises because all differences between speech patterns are treated as equally important. Thus the algorithm is particularly susceptible to confusions caused by phonetically-irrelevant differences. This thesis presents two types of preprocessing schemes as candidates for improving HMM performance. The aim is to maximize the differences between phonologically-distinct speech sounds while minimizing the effect of variations in phonologically-equivalent speech sounds. The preprocessors presented are a discrete cosine …

Finite Element Formulation And Numerical Simulation Of The Large Deflection Random Vibration Of Laminated Composite Plates, Jay Howard Robinson

Mechanical & Aerospace Engineering Theses & Dissertations

A theoretical large deflection finite element formulation is developed for the purpose of simulating the random vibration of thin generally laminated composite plates. The random acoustic load is taken to be stationary and Gaussian with zero mean and uniform magnitude and phase over the surface of the plate. In­ plane inertia terms are included in the formulation however rotary inertia terms are assumed negligible.

The integration routine is derived from a set of unified single step algorithms, using a weighted satisfaction of the equilibrium equation. The algorithm is second order accurate and unconditionally stable for particular values of its free …

Navier-Stokes Simulations Of Flows About Complex Configurations Using Domain Decomposition Techniques, Kamran Fouladi-Semnani

Mechanical & Aerospace Engineering Theses & Dissertations

An algorithm is developed to obtain numerical simulations of flows about complex configurations composed of multiple and nonsimilar components with arbitrary geometries. The algorithm uses a hybridization of the domain decomposition techniques for grid generation and to reduce the computer memory requirement. Three dimensional, Reynolds-averaged, unsteady, compressible, and complete Navier-Stokes equations are solved on each of the subdomains by a fully-vectorized, finite-volume, upwind-biased, approximately-factored, and multigrid method. The effect of Reynolds stresses is incorporated through an algebraic turbulence model with several modifications for interference flows. The present algorithm combines the advantages of an efficient, geometrically conservative, minimally and automatically dissipative …

The Fokker-Planck And Related Equations In Theoretical Population Dynamics, George Derise

Mathematics & Statistics Theses & Dissertations

The population growth of a single species is modeled by a differential equation with initial condition(s) so that the number of organisms in the population is derived using some mechanism of growth, i.e. a growth rate function. However, such deterministic models are often highly unrealistic in population dynamics because population growth is basically a random event. There are a large number of chance factors influencing growth that might not be taken into account by deterministic models. The effect of other species (for example, in the chance meeting of a predator), population fluctuations due to weather changes that would alter food …

Use Of A Generalized Set Of Variables In Fluid Flow Calculations, Pawel Chwalowski

Mechanical & Aerospace Engineering Theses & Dissertations

In fluid flow calculations, a set of generalized field variables is used to replace the more conventional choice of either the conserved variables, or the primitive variables. This generalized set of variables represents an infinite number of possible choices for the specific set of field variables. For algorithms of both the implicit and explicit type, the resulting effect of a change in field variables on a steady-state flow solution is in general relatively small. However, for implicit algorithms, a consistent linearization with respect to the new variables results in dramatic changes in the overall matrix conditioning of the linear systems …

A Potentiometric Gaseous Hydrogen Sensor, Anne Guillory

Chemistry & Biochemistry Theses & Dissertations

The development of a potentiometric gaseous hydrogen sensor using a 75% palladium - 25% silver alloy as a selectively hydrogen permeable electrode is described. The sensor showed some promise when used with a molten base electrolyte. Other electrolytes are investigated at ambient and higher temperatures. Various cell designs including a platinum/silver-silver chloride sensor with a gel electrolyte are discussed.

A Numerical Study Of The Interaction Between A Deep Cold Jet And The Bottom Boundary Layer Of The Ocean, Tal Ezer, Georges L. Weatherly

CCPO Publications

Abstract A two-dimensional (x-z) primitive equation model is used to study the interaction between a deep cold jet on a sloping bottom and the bottom boundary layer (BBL) of the deep ocean. Two closure schemes are used: a standard second order turbulence closure (SOTC) scheme (the level 2 1/2 model of Mellor and Yamada), and a new eddy viscosity closure scheme (K-model). The latter is a computationally simple model that produces very similar eddy viscosity and velocity fields as the more complicated SOTC-model while saving about 20% of the computational time. The results of the numerical simulations compare favorably to …

A Root Finding Algorithm For Parallel Architecture Machines, Stuti Moitra

Computer Science Theses & Dissertations

In this thesis a parallel algorithm for determining the zeros of any given analytic function is described. Parallelism is achieved by modifying the traditional bisection algorithm for architecture machines.

Given any user supplied function f(X), continuous on the interval A_o ≤ x ≤ B₀, and the tolerance of accuracy an algorithm of determining up to ten roots, with error of approximation less than or equal to tolerance, on parallel systems like Distributed Array Processor (OAP) and N-cube is considered.

A variation of the bisection method has been adapted for this purpose. At each level of iteration a …

Effects Of An Urban Alternative High School Dropout Prevention And Rehabilitation Program On The Attendance, Attitude And Academic Achievement Of At-Risk Students, Margaret Shearin Bell

Theses and Dissertations in Urban Services - Urban Education

The purpose of this study was to determine the effects of a dropout prevention program on at-risk high school students who returned to their home schools. The study was conducted in Newport News, Virginia at four high schools and an alternative school site, housing the dropout program. The subjects were divided into two independent treatment groups: Group One (N = 30) who participated in the program in the fall semester of 1988 and returned to their home schools in the spring semester of 1989, and Group Two (N = 21) who participated in the program in the spring semester of …

Stability Of A Viscoelastic Burgers Flow, D. Glenn Lasseigne, W. E. Olmstead

Mathematics & Statistics Faculty Publications

The system of equations proposed by Burgers to model turbulent flow in a channel is extended to include viscoelastic affects. The stability and bifurcation properties are examined in the neighborhood of the critical Reynolds number. For highly elastic fluids, the bifurcated state is periodic with a shift in frequency.

Nonproportionally Loaded Steel Beam-Columns And Flexibly-Connected Nonsway Frames, Siva Prasad Darbhamulla

Civil & Environmental Engineering Theses & Dissertations

A theoretical study of the inelastic stability of nonproportionally loaded steel beam-columns and flexibly-connected frames is conducted. Specifically, solution techniques are formulated to predict the nonlinear behavior of cross sections, spatial beam-columns, and nonsway plane frames under the combined influence of imperfections, flexible connections, and nonproportional loads. A set of new inelastic slope-deflection equations for imperfect members are derived and their use illustrated through in-depth studies of flexibly-connected portal and two-bay two-story frames. These equations are derived from a system of nonlinear ordinary differential equations. The member studies are carried out using a second-order finite-difference solution to a set of …

Survey Of Virginia Dental Practices To Determine Compliance With The Standards Of Risk Management Theory, Joanne Schade Boyce

Dental Hygiene Theses & Dissertations

The purpose of this survey was to determine selected areas of risk in dental practices within the Commonwealth of Virginia. A self-designed, 51 item questionnaire was sent to a random sample of 300 Virginia dentists to examine their risk management procedures in: (1) the medical record and related documentation, (2) infection control, (3) identification and classification of periodontally involved patients, (4) obtaining informed consent, and (5) emergency protocols. Data from 62% of the dentists were analyzed via the chi-square goodness of fit test, frequency and percentage of responses. Results suggest that Virginia dental practitioners are practicing some of the recommended …

The Truncated Cauchy Distribution: Estimation Of Parameters And Application To Stock Returns, Paul G. Staneski

Mathematics & Statistics Theses & Dissertations

The problem addressed in this dissertation is the existence and estimation of the parameters of a truncated Cauchy distribution. It is known that when a number of distributions with infinite support are truncated to a finite interval that the maximum likelihood estimator of the scale parameter fails to exist with positive probability. In particular, necessary and sufficient conditions which give rise to instances of non-existence have been found for the exponential (Deemer and Votaw (1955)), gamma (Broeder (1955), Hegde and Dahiya (1989)), Weibull (Mittal and Dahiya (1989)) and normal distribution (Barndorff-Nielsen (1978), Mittal and Dahiya (1987), Hegde and Dahiya (1989)). …

Knowing God In William Blake: A Study To Find Meaning In His Work Through Plato, Swedenborg, And Mystical Tradition, David B. Gabel

Institute for the Humanities Theses

This project takes a look into the philosophical and theological sources found in the work of William Blake as they culminate in his epic poem Jerusalem. This study includes an examination of the philosophies of Plato and Emanuel Swedenborg, the mystical pathway, the Jewish mystical tradition known as Kabbalah, and finally an examination of the works of Blake himself. We work from a three-fold premise: 1) that mystical experience occurs, 2) that archetypes exist in the collective unconscious, and 3) that these archetypes can be known through intuition and mystical experience. The focus is on those elements which are characteristic …

A Pulse Gas Chromatographic Method For Determining The Dispersion And Surface Area Of Co Oxidation Catalysts, Susan Kay Ohorodnik

Chemistry & Biochemistry Theses & Dissertations

Catalysts composed of platinum and/or palladium on tin(IV) oxide supports with or without silica gel have been developed for the recombination of carbon monoxide and oxygen to form carbon dioxide for use in carbon dioxide lasers. A pulse gas chromatographic method has been developed to measure the chemisorption properties of the catalysts. From the chemisorption measurements, the active surface area and dispersion of the catalysts have been determined.