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High Energy Coupled Nucleon Tranpsort In One Dimension, Stanley L. Lamkin

Physics Theses & Dissertations

The problem of energetic nucleon transport through extended bulk matter is considered in the context of the 'straight ahead' approximation. The applicable form of the Boltzmann transport equation is derived and solved in one dimension. The production term for secondary generation nucleons due to nuclear fragmentation includes 'coupling' of the flux to other types of nucleon projectiles. A physically motivated perturbation series approach is developed to enhance solution convergence. The Boltzmann operator is inverted and the flux is computed using a numerical marching scheme. The secondary production integrals are optimized for second order accuracy using a set of analytical benchmarks. …

Three-Dimensional Aerodynamic Shape Optimization Using Discrete Sensitivity Analysis, Gregory Wayne Burgreen

Mechanical & Aerospace Engineering Theses & Dissertations

An aerodynamic shape optimization procedure based on discrete sensitivity analysis is extended to treat three-dimensional geometries. The function of sensitivity analysis is to directly couple computational fluid dynamics (CFD) with numerical optimization techniques, which facilitates the construction of efficient direct-design methods. The development of a practical three-dimensional design procedures entails many challenges, such as: (1) the demand for significant efficiency improvements over current design methods; (2) a general and flexible three-dimensional surface representation; and (3) the efficient solution of very large systems of linear algebraic equations. It is demonstrated that each of these challenges is overcome by: (1) employing fully …

Iodate Transformation By Marine Phytoplankton, Ajcharaporn Udomkit

OES Theses and Dissertations

The speciation and distribution of iodine in the oceans are partly under biological control. Phytoplankton are suspected to mediate the transformation of iodate to iodide via reduction by the enzyme nitrate reductase. However, there has been no direct evidence to support this hypothesis.

The influence of phytoplankton on the speciation of iodine was examined with emphasis on the transformation of iodate to iodide. Six cultures of marine phytoplankton: Skeletonema costatum, Dunaliella tertiolecta, Amphidinium carterae, Tetraselmis levis, Emiliania huxleyi, and Synechococcus sp. , have been examined for their ability to take up and reduce iodate under a reduced nitrate environment. In …

The Contribution Of Selected Cognitive And Noncognitive Variables To The Academic Success Of Medical Technology Students, Mildred Keels Fuller

Health Services Research Dissertations

The research problem for this study assessed the relationship of cognitive and noncognitive variables to the academic success of African-American versus Caucasian medical technology students attending traditionally black institutions versus majority institutions. Academic success was defined as cumulative grade point average, cumulative clinical practica grades, and graduation status. The cognitive variable was the preclinical cumulative grade point average, and the noncognitive variables were the noncognitive subscale scores.

Seventy-five senior medical technology students provided demographic data, and completed the Noncognitive Questionnaire (Tracey & Sedlacek, 1984) that assessed eight noncognitive dimensions: positive self-concept; realistic self-appraisal: understands and deals with racism; prefers long-range …

Optimal Active And Passive Control Design For A Slewing Piezoelectric Laminate Beam, Travis V. Dubois

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis presents the development and experimental verification of a distributed parameter model for a slewing beam system with piezoelectric actuators and sensors. Also presented is the development of an optimal active control synergism which employs IMSC, (Independent Modal Space Control) and an optimally designed, viscoelastic damping treatment. The beam is pinned at the proximal end and patches of thin piezoelectric laminates are attached to its surface. Formulation is general enough to allow the patches to be located anywhere on the beam's surface. A viscoelastic material with a constraining layer covers the rest of the beam. The differential equation of …

A Direct Numerical Simulation Of Vortex Breakdown Induced Tail Buffet, Steven James Massey

Mechanical & Aerospace Engineering Theses & Dissertations

A simulation of tail buffet is presented for a delta wing-vertical tail configuration. Flow conditions are chosen such that the wing primary-vortex cores experience vortex breakdown and the resulting turbulent wake flow impinges on the vertical tail. The dimensions and material properties of the vertical tail are chosen such that the deflections are large enough to insure interaction with the flow, and the natural frequencies are high enough to facilitate a practical computational solution. This multidisciplinary problem is solved sequentially for the fiuid flow, the elastic deformations and the grid displacements. The fluid flow is simulated by time accurately solving …

Transverse Stress Effects For Laminated Composite Beams In Bending, Christine Chatterton Schleicher

Mechanical & Aerospace Engineering Theses & Dissertations

A higher-order theory and an associated finite element formulation are developed for analysis of laminated planar beams in bending. The higher-order theory incorporates both transverse normal stress and transverse shear stress, and is developed using two approaches. The first approach is based on assuming the transverse normal strain distribution to be a cubic function through the beam thickness, while the second approach is based on assuming the transverse normal stress distribution to be a cubic function through the beam thickness. In both approaches, the transverse shear strain distribution is assumed to be a quadratic function through the beam thickness. Theoretical …

Explicit And Iterative Lqg Controller Design, Min-Hung Hsiao

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation presents two new LQG controller designs, namely, explicit and iterative designs. For the explicit design, the explicit solutions to the corresponding Riccati equations of controller design for large structures with collocated rate sensors and actuators are derived. Numerically solving the Riccati equations for state feedback and state estimation is no longer required. Since the number of design parameters for either state feedback or state estimation equals the number of controlled modes, the performance of each mode can be easily adjusted. NASA's Spacecraft COntrol Laboratory Experiment (SCOLE) configuration is used to demonstrate the effectiveness of the explicit design.

For …

Unsteady Flow Simulations About Moving Boundary Configurations Using Dynamic Domain Decomposition Techniques, Guan-Wei Yen

Mechanical & Aerospace Engineering Theses & Dissertations

A computational method is developed to solve the coupled governing equations of an unsteady flowfield and those of rigid-body dynamics in six degrees-of-freedom (6-DOF). This method is capable of simulating the unsteady flowfields around multiple component configurations with at least one of the components in relative motion with respect to the others. Two of the important phenomena that such analyses can help us to understand are the unsteady aerodynamic interference and the boundary-induced component of such a flowfield. By hybridizing two dynamic domain decomposition techniques, the grid generation task is simplified, the computer memory requirement is reduced, and the governing …

On The Low-Frequency Current And Temperature Fluctuations Along The Shelf Break In The South Atlantic Bight, Sunny Yu Wu

OES Theses and Dissertations

Current and temperature data collected along the shelf edge in the South Atlantic Bight were analyzed using a spectral analysis technique. The power spectra of both alongshore currents and temperatures (upon removal of seasonal trends) in the mid- to lower water column suggest a significant energy peak at 28 days. The spatial characteristics of the fluctuations around this period band were determined using the frequency domain empirical orthogonal function (EOF) analysis applied to the concurrent current and temperature records. Consistent results were obtained from the upstream side of the Charleston Bump. Around the 28-day period, temperature seems to have little …

Flow Simulations About Steady-Complex And Unsteady Moving Configurations Using Structured-Overlapped And Unstructured Grids, James Charles Newman Iii

Mechanical & Aerospace Engineering Theses & Dissertations

The limiting factor in simulating flows past realistic configurations of interest has been the discretization of the physical domain on which the governing equations of fluid flow may be solved. In an attempt to circumvent this problem, many Computational Fluid Dynamic (CFD) methodologies that are based on different grid generation and domain decomposition techniques have been developed. However, due to the costs involved and expertise required, very few comparative studies between these methods have been performed. In the present work, the two CFD methodologies which show the most promise for treating complex three-dimensional configurations as well as unsteady moving boundary …

Implementation Of A Multiblock Sensitivity Analysis Method In Numerical Aerodynamic Shape Optimization, James Matthew Lacasse

Mechanical & Aerospace Engineering Theses & Dissertations

A multiblock sensitivity analysis method is applied in a numerical aerodynamic shape optimization technique. The Sensitivity Analysis Domain Decomposition (SADD) scheme which is implemented in this study was developed to reduce the computer memory requirements resulting from the aerodynamic sensitivity analysis equations, Discrete sensitivity analysis offers the ability to compute quasi-analytical derivatives in a more efficient manner than traditional finite-difference methods, which tend to be computationally expensive and prone to inaccuracies.

The direct optimization procedure couples CFD analysis based on the two-dimensional thin-layer Navier-Stokes equations with a gradient-based numerical optimization technique. The linking mechanism is the sensitivity equation derived from …

The Vital Life: D.H. Lawrence's Response To A Dehumanized World, Rebecca Recce White

English Theses & Dissertations

As D.H. Lawrence experienced World War I and the Industrial Revolution, he recognized the inner spirits of men and women being valued less in the midst of war and industrialism. Lawrence's novels, short stories, and other works dramatize this dehumanizing process. Of his novels, five will be examined in this study: Sons and Lovers, The Rainbow, Women in Love, The Plumed Serpent, and Lady Chatterley's Lover. Pivotal relationships between men and women are outlined by Lawrence to illustrate the ways in which they either reflect or challenge society.

Lawrence gives the readers a view of the modern age torn apart …

Dynamic Task Scheduling For The Atamm Multicomputer Operating System Using Embedded Firmware On Microcontrollers, Sudhir Sastry

Electrical & Computer Engineering Theses & Dissertations

A dynamic task scheduling strategy for the distributed processing of large grain dataflow algorithms using embedded firmware on an ATAMM testbed consisting of interconnected microcontrollers is presented in this thesis. The ODU/NASA developed Algorithm to Architecture Mapping Model, ATAMM, uses marked graph models to specify data and control flow for the execution of iterative, deterministic large grain dataflow algorithms in a multicomputing environment. The testbed consists of a bank of four 68HC11 microcontrollers that communicate over a token bus. The token bus arbitration scheme used is contention free and well suited for real-time computing applications. The execution of data flow …

Optimization Of Electron-Beam Activated Gaas Switches, Raymond Jack Allen Iii

Electrical & Computer Engineering Theses & Dissertations

The use of electron induced luminescence (cathodoluminescence) in gallium arsenide offers the possibility to modulate the conductance of the material on a timescale of nanoseconds and with a pulse rate of MHz, through modulation of an electron-beam current. This ionization mechanism allows the utilization of semi-insulating GaAs in fast, high power closing and opening switches. The efficiency of the switches is determined by the hold-off voltage of the GaAs switches, and by the conversion efficiency of electron energy into (useful) photon energy. Studies of the dark-current and the electron-beam induced conductance in semi-insulating GaAs have been performed in order to …

Diamond Thin Film Sensors For Hypersonic Flow Studies, Bhaskar Kumar Bulusu

Electrical & Computer Engineering Theses & Dissertations

Conventional metal film sensors can measure flow instabilities of the order of 60 kHz. The turbulence fluctuations in the hypersonic regime are of the order of 200- 400 kHz. To measure these fluctuations, sensors with an enhanced frequency response are required. Therefore, it is required to identify the parameters to enhance the frequency response. These include parameters such as the temperature sensitivity, the resistivity, the thermal conductivity, the diffusivity, specific heat capacity and the geometric size and shape of the film and the substrate. A selection of materials was then carried out to maximize the frequency response. Diamond was identified …

Derivative Absorption Spectroscopy With Tunable Laser Diodes, Andrew D. Jackson

Electrical & Computer Engineering Theses & Dissertations

Derivative Absorption Spectroscopy using tunable diode lasers provides a non­ intrusive, sensitive, and convenient method for monitoring gaseous characteristics such as concentration, temperature, and flow velocity. In addition, the specie type can be identified, and if the equation of state is known, pressure may be deduced.

This technique was used on molecular oxygen, in which the rovibronic transitions of the A-band ( b ¹ ∑_g ⁺ ← X ³ ∑g ^- ; v^II = O, v^I = O) were probed. Phase sensitive detection with a lock-in amplifier provides the flexibility to examine lineshape derivatives; several such derivative …

Circulation, Winter 1994, Center For Coastal Physical Oceanography, Old Dominion University

CCPO Circulation

Winter 1994 issue of CCPO Circulation featuring article "Hydrographic Observations in the Chesapeake Bay Mouth"

Some Triple Sine Series, G. Kerr, G. Melrose, J. Tweed

Mathematics & Statistics Faculty Publications

Two types of triple sine series are investigated. They are reduced to singular integral equations with kernels involving elliptic functions. Closed form solutions are obtained.

Characterization Of The Local Lipschitz Constant, M. W. Bartelt, J. J. Swetits

Mathematics & Statistics Faculty Publications

A characterization, using polynomials introduced by A. V. Kolushov, is given for the local Lipschitz constant for the best approximation operator in Chebyshev approximation from a Haar set. The characterization is then used to study the existence of uniform local Lipschitz constants.

The Oceanographer's Toolkit: Oceanatlas And Atlast, Larry P. Atkinson

CCPO Publications

Most of us spend a great deal of time looking at data, visualizing it in our mind, and interpreting it for others. I am sure we all have also often realized how much time we spend on the unproductive part of these tasks. How often have you said, “I could have done this faster by hand!” I looked at two free software packages, OceanAtlas (OA) and Atlast, with success, but I wondered what longtime users thought of them. OceanAtlas is for the Mac and Atlast for the PC. Both have extensive data visualization capability and both come with large datasets: …

Modeling Oyster Populations. Iv. Rates Of Mortality, Population Crashes, And Management, E. N. Powell, J. M. Klinck, E. E. Hofmann, S. M. Ray

CCPO Publications

A time-dependent energy-flow model was used to examine how mortality affects oyster populations over the latitudinal gradient from Galveston Bay, Texas, to Chesapeake Bay, Virginia. Simulations using different mortality rates showed that mortality is required for market-site oysters to be a component of the population's size-frequency distribution; otherwise a population of stunted individuals results. As mortality extends into the juvenile sizes, the population's size frequency shifts toward the larger sizes. In many cases adults increase despite a decrease in overall population abundance. Simulations, in which the timing of mortality varied, showed that oyster populations are more susceptible to population declines …

Modeling Oyster Populations Ii. Adult Size And Reproductive Effort, E. E. Hofmann, J. M. Klinck, E. N. Powell, S. Boyles, M. Ellis

CCPO Publications

A time-dependent model of energy flow in post-settlement oyster populations is used to examine the factors that influence adult size and reproductive effort in a particular habitat, Galveston Bay, Texas, and in habitats that extend from Laguna Madre, Texas to Chesapeake Bay. The simulated populations show that adult size and reproductive effort are determined by the allocation of net production to somatic or reproductive tissue development and the rate of food acquisition, both of which are temperature dependent. For similar food conditions, increased temperature reduces the allocation of net production to somatic tissue and increases the rate of food acquisition. …

Continuous Assimilation Of Geosat Altimeter Data Into A Three-Dimensional Primitive Equation Gulf Stream Model, Tal Ezer, George L. Mellor

CCPO Publications

A three-dimensional data assimilation scheme is described and tested, using the Geosat altimeter data and a high-resolution, primitive equation, numerical ocean model of the Gulf Stream region. The assimilation scheme is based on an optimal interpolation approach in which data along satellite tracks are continuously interpolated horizontally and vertically into the model grid and assimilated with the model prognostic fields. Preprocessed correlations between surface elevation anomalies and subsurface temperature and salinity anomalies are used to project surface information into the deep ocean; model and data error estimates are used to optimize the assimilation. Analysis fields derived from the Navy's Optimum …

The Pressure Gradient Conundrum Of Sigma Coordinate Ocean Models, George L. Mellor, Tal Ezer, Lie-Yauw Oey

CCPO Publications

It is shown that the differencing scheme cited here, though conventional, is not hydrostatically inconsistent; the sigma coordinate, pressure gradient error decreases with the square of the vertical and horizontal grid size. Furthermore, it is shown that the pressure gradient error is advectively eliminated after a long time integration. At the other extreme, it is shown that diagnostic calculations of the North Atlantic Ocean using rather coarse resolution, and where the temperature and salinity and the pressure gradient error are held constant, do not exhibit significant differences when compared to a calculation where horizontal pressure gradients are computed on z-level …

Prediction Of The Stochastic Behavior Of Nonlinear Systems By Deterministic Models As A Classical Time-Passage Probabilistic Problem, L. M. Ivanov, A. D. Kirwan Jr., O. V. Melnichenko

CCPO Publications

Assuming that the behaviour of a nonlinear stochastic system can be described by a Markovian diffusion approximation and that the evolution equations can be reduced to a system of ordinary differential equations, a method for the calculation of prediction time is developed. In this approach, the prediction time depends upon the accuracy of prediction, the intensity of turbulence, the accuracy of the initial conditions, the physics contained in the mathematical model, the measurement errors, and the number of prediction variables. A numerical application to zonal channel flow illustrates the theory. Some possible generalizations of the theory are also discussed.

Surface Flow Structure Of The Gulf Stream From Composite Imagery And Satellite-Tracked Drifters, C. P. Mullen, A. D. Kirwan Jr.

CCPO Publications

A unique set of coutemporaneous satellite-tracked drifters and five-day composite Advanced Very High Resolution Radionmeter (AVHRR) satellite imagery of the North Atlantic has been analyzed to examine the surface flow structure of the Gulf Stream. The study region was divided into two sections, greater than 37 degrees N and less than 37 degrees N, in order to answer the question of geographic variability. Fractal and spectral analyses methods were applied to the data. Fractal analysis of the Lagrangian trajectories showed a fractal dimension of 1.21 +/- 0.02 with a scaling range of 83 - 343 km. The fractal dimension of …

A Study To Determine The Effects Of An Interactive Audio/Video Classroom On Retention Test Performance, Timothy R. Barry

OTS Master's Level Projects & Papers

The objectives of this study were established to determine: 1. If traditional lecture was replaced by a computer driven interactive AV teaching format in a technical training environment, would "retention test" scores improve? 2. Will retention test scores improve after only one week-long class using an interactive AV classroom?

The Considerations For Planning Marketing Education Courses In Virginia, Stephanie Gilmore

OTS Master's Level Projects & Papers

The following questions need to be answered in order to solve the research problem: 1. Should business and marketing teachers collaborate to design an entrepreneurship course? 2. Should entrepreneurship be taught as a separate course in the marketing department? 3. Should Principles of Marketing be offered as a year-long course instead of a semester course? 4. Should students studying under the cooperative method of instruction complete basic employability skills?

Female Enrollment In Technology Education In Virginia During The 1993/1994 School Year, J. Scott Christman

OTS Master's Level Projects & Papers

The problem of the study was to determine if a significant difference exists between male and female enrollment in the approved technology education courses offered as electives in Virginia for the 1993/1994 school year.