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Study Of Algebraic Reynolds Stress Models For The Computation Of Secondary Motion In Channels, Tomas Chylek

Mechanical & Aerospace Engineering Theses & Dissertations

A three-dimensional computer code for solving Reynolds equations of turbulent flow at high Reynolds numbers in generalized curvilinear coordinates is used to study the engineering applications of several variants of linear and nonlinear second moment algebraic Reynolds stress models based on pressure-strain correlation of Launder, Recce and Rodi (1975) and Speziale, Sarkar and Gatski (1991). A new form of algebraic Reynolds stress equation in generalized curvilinear coordinates is derived based on simplification of Reynolds stress transport equations. Two implicit and two explicit implementations are explored in three different geometries of straight channel flows. The predictions of secondary motion driven by …

Three-Dimensional Transport Simulations Of The Dispersal Of Volcanic Aerosol From Mount Pinatubo, T. Duncan A. Fairlie

Mechanical & Aerospace Engineering Theses & Dissertations

A global finite-difference model that simulates the large-scale dynamics of the Earth's stratosphere and mesosphere is combined with a global spectral transport model to investigate aspects of the initial dispersal of the volcanic aerosol plume from the Mount Pinatubo eruption in 1991. Results of the modelling study are found to compare well with observations of the volcanic plume made from satellite instruments. Dynamical quantities, diagnosed from the simulated fields are used to provide insight into the evolution of the volcanic plume. Lagrangian trajectory analysis is used to help assess the performance of the Eulerian transport model and to highlight small-scale …

The Isolation And Identification Of Polyphenolics From Grape Seeds And Their Activity Towards Specific Cell Lines, Joseph A. Reddy

Chemistry & Biochemistry Theses & Dissertations

Grape seed extract is being marketed in France for cardiovascular use and skin care. The active constituents of both these drugs are certain polyphenols called procyanidins. A similar seed extract has now been obtained from Virginia Chardonnay grape seeds. Ten of the major components in this extract have been isolated in their pure form by the semi-preparative HPLC separation on a YMC ODS-AQ (Octadecylsilane-AQ) column. The ODS-Aq column has been shown to have a better resolving capacity compared to the Spherisorb ODS (Octadecylsilane) column previously described in the literature. This has been attributed to the ODSAQ support which has both …

Phytoplankton Assemblages Associated With A Bloom Of Ptychodiscus Brevis Off The North Carolina Coast, Traycie Lea West

Biological Sciences Theses & Dissertations

A bloom of the dinoflagellate Ptychodiscus brevis occurred off the North Carolina coast in late 1987, and samples were forwarded by NOAA to the Old Dominion University Phytoplankton Laboratory for total phytoplankton analysis. Six sampling stations were chosen to represent different bloom scenarios and these six were clustered into three site groups based on the concentrations of statistically significant taxa. Abundances of phytoplankton taxonomic groups over time were examined in relation to P. brevis concentrations to identify any general tendencies. These results indicated the total phytoplankton concentration, and most taxonomic groups, increased at all three site groups regardless of the …

Absorption Imaging Studies On Intrinsic Gaas, John Samuel Kenney

Electrical & Computer Engineering Theses & Dissertations

A diagnostic technique has been developed which allows recording of the temporal and spatial development of electric field structures in GaAs photoconductive switches. The optical method is based on the Franz-Keldysh effect. Measurements were performed with a Nd:YAG activation laser and a GaAs laser diode as the probe laser. At low applied voltages a 100 atm wide region of high electric field is seen at the cathode only. With increasing voltage strong domain like structures emerge at the anode also. A calibration measurement shows that the electric fields in these domains are well above 50 kV/cm. At a threshold voltage, …

Towards A Universal Nuclear Nonproliferation Treaty, T. P. Radhakrishnan

Graduate Program in International Studies Theses & Dissertations

The 1968 Treaty on the Nonproliferation of Nuclear Weapons (NPT) came into force in 1970 and expires in 1995. In 1995 an extension conference has to be convened to decide whether the treaty continues in force indefinitely or will be extended for an additional period or periods.

The treaty, cosponsored by the us, the USSR, and the UK, has 155 signatories, but a few countries like Israel, India and Pakistan have refused to be bound by it. They have done so mainly on the formal grounds that the treaty is structurally discriminatory between nuclear and nonnuclear weapons states.

What are …

Robust Control Of Nonlinear Multibody Flexible Space Structures, Atul G. Kelkar

Mechanical & Aerospace Engineering Theses & Dissertations

A generic nonlinear math model of a multibody flexible system is developed. Asymptotic stability of such systems using dissipative compensators is established. It is proved that, under certain conditions, this class of systems exhibit global asymptotic stability under dissipative compensation. The dissipative compensators considered are static as well as dynamic dissipative compensators. The stability proofs are based on passivity approaches, Lyapunov methods, as well as a key property of such systems, i.e., skew-symmetricity of certain matrix. The importance of the stability results obtained is that the stability is robust to parametric uncertainties and modeling errors.

For static dissipative compensators, it …

Lithofacies Of The Pliocene-Pleistocene Lucayan Limestone, Great Abaco Island, Little Bahama Bank, Mary K. Mullen

OES Theses and Dissertations

Petrographic and sedimentologic analyses of eleven shallow subsurface cores (3 to 19 meters in length) from the Lucayan Limestone where it occurs along northeastern Great Abaco Island (little Bahama Bank) are used to delineate five carbonate lithofacies. The most prevalent lithofacies is a mottled, nonskeletal, peloidal packstone to grainstone. Other lithofacies include a rudstone, a laminated nonskeletal grainstone, a crossbedded grainstone and a mudstone-wackestone.

Cementation varies from poor to very well cemented core intervals. Cements observed included equant granular, equant blocky, drusy, meniscus, and needle fiber "whisker" cements. These cements reflect a variety of diagenetic environments such as the vadose, …

Fast Fourier Transforms On Distributed Memory Parallel Machines, Anshu Dubey

Computer Science Theses & Dissertations

One issue which is central in developing a general purpose subroutine on a distributed memory parallel machine is the data distribution. It is possible that users would like to use the subroutine with different data distributions. Thus there is a need to design algorithms on distributed memory parallel machines which can support a variety of data distributions. In this dissertation we have addressed the problem of developing such algorithms to compute the Discrete Fourier Transform (DFT) of real and complex data. The implementations given in this dissertation work for a class of data distributions commonly encountered in scientific applications, known …

The Biogeochemistry Of Hydrogen Sulfide In The Open Ocean, Joël Radford-Knoery

OES Theses and Dissertations

Hydrogen sulfide is a poorly quantified component of the global sulfur cycle. In seawater, its dissolved species (dissolved sulfide) can react with trace metals to form dissolved complexes and insoluble compounds. Therefore, the study of dissolved° sulfide in the open ocean can yield a better understanding of the biogeochemical cycles of sulfur and trace metals.

The biogeochemical cycling of dissolved sulfide was examined using specially developed sampling and analytical methods. In the western North Atlantic and central Equatorial Pacific Oceans, total dissolved sulfide concentrations ranged from /L; they were highest, in the mixed layer and decreased with depth. The depth …

A Follow-Up Study Investigating The Relationships Between Holland's Personality Types And Selected Career Choice Variables, Kennard S. Brackney Sr.

Theses and Dissertations in Urban Services - Urban Education

This follow-up study utilized John L. Holland's theory of vocational personalities and work environments to examine the relationship between students personality types and their career choices. The study sought to determine whether data collected using Holland's Self-Directed Search (SDS) was a valid predictor of (1) career goal, (2) eventual choice of college major, (3) persistence to graduation, (4) occupation (type of job held at the time the data was collected), and (5) level of satisfaction with occupation (job) at the time data was gathered.

The stratified random sample for the study was composed of 180 subjects drawn from a population …

Attributions For Change In Attitude Among Urban Elementary Parochial School Teachers Toward Children Who Speak Nonstandard English, Charles A. Saglio Jr.

Theses and Dissertations in Urban Services - Urban Education

A comparatively large number of African American children fail in urban schools. Hundreds of research studies concerning interpersonal expectations suggest a link between teacher expectancies and pupil performance. Researchers have found that teachers expect less of students who speak nonstandard English. Attempts to modify teachers' culturo-linguistic attitudes and expectations have been unsuccessful. While teachers' beliefs, theories, and attitudes change over time as a function of teaching experience, the mechanisms for change are unclear.

This study has attempted to uncover events to which teachers attribute a change in their culturo-linguistic attitudes. Once causal conditions for change have been identified, then those …

An Analysis Of The Response Of A Buckled Beam With Fixed Ends To An Harmonic Base Excitation Using The Finite Element Method, Peter John O'Donoghue

Mechanical & Aerospace Engineering Theses & Dissertations

A finite element formulation is developed to analyze the large deflection vibration of a buckled isotropic beam. The beam is buckled mechanically by an applied end displacement, and the dynamic loading is derived from the forced periodic base motion. The principle of virtual work is used to derive the system equations of motion. A Newton-Raphson iteration routine modified for the case of an applied end displacement is used with the incremental equations of motion to determine static deflection. The 0l time numerical integration algorithm is applied to the system of equations of motion in physical coordinates to determine dynamic response …

Time-Optimal Algorithms On Meshes With Multiple Broadcasting, Dharmavani Bhagavathi

Computer Science Theses & Dissertations

The mesh-connected computer architecture has emerged as a natural choice for solving a large number of computational tasks in image processing, computational geometry, and computer vision. However, due to its large communication diameter, the mesh tends to be slow when it comes to handling data transfer operations over long distances. In an attempt to overcome this problem, mesh-connected computers have recently been augmented by the addition of various types of bus systems. One such system known as the mesh with multiple broadcasting involves enhancing the mesh architecture by the addition of row and column buses. The mesh with multiple broadcasting …

Recent Benthic Foraminifera, Petrology, And Implications For Recent Transport In Wilmington And South Heyes Submarine Canyons, U.S. Atlantic Continental Margin, Jason James Lundquist

OES Theses and Dissertations

Two hundred and forty-six species of benthic foraminifera have been recognized in fourteen short cores (≤ 24cm) taken from within the Wilmington and South Heyes submarine canyons along the slope and rise of the United States Atlantic Continental Margin. Of these one hundred and forty-five species were identified to the species level, thirty were closely related to known species, sixty-six could not be assigned specific names, and five species were of uncertain generic placement. The petrologic character of the sediments was determined for each of the seventy-eight micropaleontogical samples.

Cluster analysis of benthic foraminiferal data identified twelve groups which, together …

Paleocene To Miocene Foraminifera From A Well Near Gloucester, Virginia, Nelson Stanley Ford

OES Theses and Dissertations

Lithologic analysis of twenty-one core samples from a well near Gloucester, Virginia, when compared to published descriptions of formations occurring in the study area, indicates the presence of five formations. From oldest to youngest these units are the Aquia (late Paleocene), Nanjemoy (early Eocene), Chickahominy (late Eocene), Old Church (late Oligocene and early Miocene), and Eastover (late Miocene) formations. Comparison of the stratigraphic ranges of key planktic and benthic foraminifera from each of the core samples shows chronological agreement with previously published ages for each of these formations.

Paleoenvironmental analysis of each of the formations in the well is based …

Effects Of Radiative Interactions In Molecular Gases Under Local And Nonlocal Thermodynamic Equilibrium Conditions, Manoj Kumar Jha

Mechanical & Aerospace Engineering Theses & Dissertations

Basic formulations, analyses, and numerical procedures are presented to investigate radiative heat interactions in diatomic and polyatomic gases under local and nonlocal thermodynamic equilibrium conditions. Essential governing equations are presented for both gray and nongray gases. Information is provided on absorption models, relaxation times, and transfer equations. Radiative flux equations are developed which are applicable under local and nonlocal thermodynamic equilibrium conditions.

The problem is solved for fully developed laminar incompressible flows between two parallel plates under the boundary condition of a uniform surface heat flux. For specific applications, three diatomic and three polyatomic gases are considered. The results are …

Paleobathymetric Interpretation Of Pleistocene Sediments In The South Padre Island Area, Northwestern Gulf Of Mexico, Using Benthic Foraminiferal Morphology, Karen Ianthe Kruebbe-Belwood

OES Theses and Dissertations

This study tested the validity of using intraspecific variation in benthic foraminifera as a means for determining Pleistocene paleobathymetry. Canonical variate analysis was used as a means for determining visually undetectable but statistically significant differences in the morphology of selected species. Two species, Cassidulina subglobosa and Uvigerina peregrina, were collected from Pleistocene well cuttings from the northwest Gulf of Mexico. The canonical analysis involved comparing the intraspecific variation of these Pleistocene species to their counterparts occurring in the modern Gulf of Mexico, where intraspecific variation was previously analyzed and found to be sufficient to allow detection of bathymetric differences …

Petrology Of A Large Granophyre-Rich Mesozoic Diabase Dike Near Farmville, Virginia, Philip Thomas Rogan

OES Theses and Dissertations

Up to 37% granophyre occurs in the center of a 150m-wide Mesozoic diabase dike near Farmville, Virginia. The exceptional abundance of granophyre compared with other Mesozoic diabase dikes suggests unusual petrogenetic processes are involved in formation of the dike. Petrographic analyses show that granophyre increases from 5-10% near the flanks of the dike to a maximum of 37% in the core of the dike, and that granophyre distribution is approximately symmetrical about the center of the dike. Major and trace element concentrations parallel variations in the modal abundance of granophyre, with SiO₂ , Na₂O and K_{2 …}

Analysis Of Pultrusion Processing For Long Fiber Reinforced Thermoplastic Composite System, Wen Tso

Mechanical & Aerospace Engineering Theses & Dissertations

Pultrusion is one of the composite processing technology, commonly recognized as a simple and cost-effective means for the manufacturing of fiber-reinforced, resin matrix composite parts with different regular geometries. Previously, because the majority of the pultruded composite parts were made of thermosetting resin matrix, emphasis of the analysis on the process has been on the conservation of energy from various sources, such as heat conduction and the curing kinetics of the resin system. Analysis on the flow aspect of the process was almost absent in the literature for thermosetting process. With the increasing uses of thermoplastic materials, it is desirable …

Robot Force Velocity Control Using Expert System For Control Mode Changes, William R. Doggett

Electrical & Computer Engineering Theses & Dissertations

The most important property of an automated mechanical system is reliable execution of a specified task. Automated mechanical systems work best in precisely structured environments where all operations are repeatable. Typically, these systems are difficult to modify and expensive to install. Sensors can be used to detect disturbances, thus reducing hardware cost by offsetting the need for precise rigid construction components. Sensors, however, increase the complexity and cost of the control software. Efficient methods of reacting to sensor information during automated system operation are required to reduce software complexity and expense.

This thesis analyzes a robotic construction task and describes …

The Effects Of Electron Radiation On The Glass Transition Temperature Of A Polyetherimide, Kristen Tulloch Kern

Physics Theses & Dissertations

The effects of electron radiation on a polyetherimide (PEI), Ultem*, were investigated. In particular, the changes in the glass transition temperature (T_g) with absorbed radiation dose were studied. The polymer was exposed to mono-energetic beams of 100-keV electrons and 1.0-MeV electrons for doses up to 100 megagray (MGy). Dosimetry for the exposures was based on Monte-Carlo simulations of the transfer of energy from an energetic electron to the polymer and on comparison to Nylon standards. Dynamic mechanical analysis was used to determine the (T_g) for non-exposed PEI and the changes in (T_g) resulting from …

The Influence Of Reynolds Number And Atmospheric Effects On Aircraft Wake Vortices Near The Ground, Zhongquan Charlie Zheng

Mechanical & Aerospace Engineering Theses & Dissertations

Aircraft wakes represent potential hazards which can control aircraft spacing and thus limit airport capacity. Wake vortex trajectories and strengths are altered radically by interactions with the ground plane and by atmospheric conditions. This work has been concerned with developing more accurate numerical predictions. A two-dimensional, unsteady numerical-theoretical study is presented which has included viscous effects, the influence of stratification, crosswind and turbulence on vortex behavior near the ground plane, using a vorticity-streamfunction formulation.

A two-parameter perturbation procedure has been developed which uses analytic solutions for the initial flow field to accommodate the ground effect region in the numerical simulation. …

A Meta-Analysis Of The Relative Effectiveness Of Two Cooperative Learning Models In Increasing Mathematics Achievement, Frances Burton Spuler

Theses and Dissertations in Urban Services - Urban Education

The meta-analysis compares two popular cooperative learning models, Student-Teams-Achievement Divisions (STAD) and Teams-Games-Tournaments (TGT), for their relative effectiveness in increasing mathematics achievement of K-12 students. The findings of the available research were integrated to determine both the magnitude and the direction of the effects of the cooperative learning models and effect sizes were calculated. More studies comparing the TGT cooperative learning model with a traditional learning model (81% of the studies) resulted in statistically significant higher gains in mathematics achievement than studies comparing the STAD model with a traditional learning model (51% of the studies). Other measures of relative effectiveness …

Elasto-Plastic Analysis Of Buried Pipelines Subjected To The Large Fault Movement, Luo-Jia Wang

Civil & Environmental Engineering Theses & Dissertations

The responses of buried pipelines subjected to a large fault movement are examined based upon a new non-linear cantilever beam analogy. This analogy assumes that the pipeline in the large deformation zone behaves like a cantilever beam subjected to a transversely concentrated shear at the inflection point and a uniformly distributed soil pressure along the entire span. Tangent modulus approach is adopted to analyze the coupled axial force-bending moment interaction effect on pipeline deformation in the inelastic range. Parametric studies of both tensile and compressive responses of buried pipeline to various fault movements, crossing angles, buried depths, pipe diameters and …

Statistical Variations In Beach Parameter Change Rates For Walled And Non-Walled Profiles At Sandbridge, Virginia, Douglas Allen Bellomo

Civil & Environmental Engineering Theses & Dissertations

The interaction of seawalls {bulkheads) and beaches is a highly controversial subject today. In many locations all over the United States, seawalls have been both praised and ridiculed. It is well documented that Sandbridge, Virginia is, and has been, experiencing shoreline recession. Many believe however, that the recent construction of the seawalls has worsened this existing situation.

Fortunately, historical maps, and beach profiles are available to help determine if this is truly the case. The following defines several visible beach parameters, and describes how these parameters were calculated from two different data sources. Several methods and statistical techniques are then …

Chlorination Products Of Glycylphenylalanine In Model Solutions And A Wastewater, Daniel J. Keefe

Chemistry & Biochemistry Theses & Dissertations

Model solutions of the dipeptide glycylphenylalanine were chlorinated to five different chlorine-to-amino nitrogen (Cl/N) mole ratios and analyzed after 30 min by high performance liquid chromatography. At mole ratios of ≤ 1, N-chloroglycylphenylalanine (I) appeared to be the only major product. At a mole ratio ≤ 2, N, N-dichloroglycylphenylalanine (II) was the only product. Compound II decomposes in model solutions (t_1/2= 6.4 hr) at pH 7.0 to form a compound tentatively identified as an H-chloroaldimine (III). Compound III in turn decomposes (t_1/2= 36 hr) in model solutions at pH 7. o to (IV) . From ^{13 …}

A Study Of The Interface Between A Turbulent Boundary Layer And The Irrotational Free Stream, Shih-Chao Lin

Mechanical & Aerospace Engineering Theses & Dissertations

A mathematical model has been developed to simulate the events which occur at the interface between a turbulent boundary layer and the irrotational free stream. By assuming the streamwise velocity component of this interface to be constant and that the interface is uncontorted initially, the solution to the equations of motion is used to derive the position functions of a point element on the interface. This analysis is restricted to a fully developed incompressible turbulent boundary layer with zero pressure gradient. Vertical velocity disturbances which are periodic in the spanwise direction and restricted to small streamwise domains are assumed.

The …

Recognition Of Quadric Surfaces From Range Data: An Analytical Approach, Ivan X. D. D'Cunha

Electrical & Computer Engineering Theses & Dissertations

In this dissertation, a new technique based on analytic geometry for the recognition and description of three-dimensional quadric surfaces from range images is presented. Beginning with the explicit representation of quadrics, a set of ten coefficients are determined for various three-dimensional surfaces. For each quadric surface, a unique set of two-dimensional curves which serve as a feature set is obtained from the various angles at which the object is intersected with a plane. Based on a discriminant method, each of the curves is classified as a parabola, circle, ellipse, hyperbola, or a line. Each quadric surface is shown to be …

A Performance Prediction Model For A Fault-Tolerant Computer During Recovery And Restoration, Rodrigo A. Obando

Electrical & Computer Engineering Theses & Dissertations

The modeling and design of a fault-tolerant multiprocessor system is addressed in this dissertation. In particular, the behavior of the system during recovery and restoration after a fault has occurred is investigated. Given that a multicomputer system is designed using the Algorithm to Architecture To Mapping Model (ATAMM) model, and that a fault (death of a computing resource) occurs during its normal steady-state operation, a model is presented as a viable research tool for predicting the performance bounds of the system during its recovery and restoration phases. Furthermore, the bounds of the performance behavior of the system during this transient …