Digital Commons Network^™

Numerical Modeling Of Gas Flows In Micronozzles, Orner San

Mechanical & Aerospace Engineering Theses & Dissertations

Since many microfluidic devices are operated in the continuum-transition regimes, the understanding of heat transfer behavior and fluid flow characteristics in this regime becomes important. The conventional Navier-Stokes model may become less accurate because of its first order constitutive relations. A direct simulation Monte Carlo method can be considered a more accurate numerical simulation for higher Knudsen numbers. However, the large number of required simulated molecules can easily make it prohibitively expensive in terms of computational time. Therefore, the Burnett equations, with their higher order constitutive relations for viscous stress and heat fluxes, are used in modeling flow characteristics in …

Simulations Of Intracellular Calcium Release In Response To High-Intensity, Ultrashort Electric Pulse, Anh Nguyen

Electrical & Computer Engineering Theses & Dissertations

Calcium modulation is an important signaling process and could even contribute to cell apoptosis through ionic-induced perturbations in trans-membrane potential at the mitochondria. In this research, the numerical study constitutes a first step in quantitatively probing the time- and spatially-dependent modulation of calcium dynamics through the application of external electrical fields. The research uses both widely accepted deterministic continuum and discrete stochastic intracellular calcium models coupling with external electric field, with a focus on high-intensity ultrashort pulse electrical field.

For deterministic continuum intracellular calcium models with electric field assisted, numerical simulations for electrically induced, intra-cellular calcium-release from the endoplasmic reticulum …

The A-B Signal Detection Theory Model, Ernesto A. Bustamante

Psychology Theses & Dissertations

The purpose of this research was threefold: (1) Present the a-b SDT model as an alternative framework to overcome the limitations of the underlying SDT model and the traditional measures of sensitivity and criterion setting, (2) Provide empirical support to validate the adequacy of the a-b SDT model, and (3) Conduct a Monte Carlo Study to compare and contrast the strengths and weaknesses of both the traditional and the a-b SDT models across the full spectrum of response values with the goal of providing researchers and practitioners with recommendations regarding the adequacy of each model. The results from this research …

Linear And Nonlinear Responses Of Isotropic Beams Under Concentrated Random Loads Unsynchronized In Time, Ravi Putrevu

Mechanical & Aerospace Engineering Theses & Dissertations

Large-amplitude random response of slender isotropic beams is studied using finite element analysis. The random load is assumed to be a stationary ergodic random Gaussian excitation with white noise characteristics. The loading is considered for three cases, namely synchronized, anti-synchronized, and unsynchronized in time. The linear response of beams is studied for the simply-supported and clamped-simply support conditions at the two ends. The non-linear response is, however, limited only to the simply-supported condition. There are no analytical solutions to the linear and non-linear responses of beams under concentrated random loads unsynchronized in time. The deflections due to unsynchronized loads are …

Condensed And Expanded Sections In The Lower Mesaverde Clastic Wedge, Campanian Of Wyoming: Evidence For Tectonic Rectification Of Sea Level, Matthew W. Botzler

OES Theses and Dissertations

The stratigraphy of the Cretaceous Western Interior basin indicates that sea level oscillated during the late Cretaceous. The oscillations were polyharmonic, with periods ranging from millions of years to hundred thousands and ten thousands of years. However, there is disagreement over the extent to which sea level change was global in nature and the extent to which it was driven by local uplift or subsidence (tectonism). In orogenic regions where subsidence, sediment supply, and eustatic variation are all affecting sea level, comparisons of high and low frequency cycles can help to sort out forcing mechanisms. Low frequency eustatic sea level …

On The Use Of Quasi-Newton Methods For The Minimization Of Convex Quadratic Splines, William Howard Thomas Ii

Mathematics & Statistics Theses & Dissertations

In reformulating a strictly convex quadratic program with simple bound constraints as the unconstrained minimization of a strictly convex quadratic spline, established algorithms can be implemented with relaxed differentiability conditions. In this work, the positive definite secant update method of Broyden, Fletcher, Goldfarb, and Shanno (BFGS) is investigated as a tool to solve the unconstrained minimization problem. It is shown that there is a linear convergence rate and, for nondegenerate problems, the process terminates in a finite number of iterations. Numerical examples are provided.

Modeling Habitat And Environmental Factors Affecting Mosquito Abundance In Chesapeake, Virginia, Alan Scott Bellows

Biological Sciences Theses & Dissertations

The models I present in this dissertation were designed to enable mosquito control agencies in the mid-Atlantic region that oversee large jurisdictions to rapidly track the spatial and temporal distributions of mosquito species, especially those species known to be vectors of eastern equine encephalitis and West Nile virus. I was able to keep these models streamlined, user-friendly, and not cost-prohibitive using empirically based digital data to analyze mosquito-abundance patterns in real landscapes.

This research is presented in three major chapters: (II) a series of semi-static habitat suitability indices (HSI) grounded on well-documented associations between mosquito abundance and environmental variables, (III) …

Mixed Layer Dynamics Along The Seward Line In The Northern Gulf Of Alaska, Nandita Sarkar

OES Theses and Dissertations

The northern Gulf of Alaska marine ecosystem is very productive with a "nutrient paradox". Primary producers require light and nutrients for photosynthesis. A primary source of nutrients is the deep ocean, while light is available in a relatively shallow layer in the upper ocean. In most productive parts of the world oceans, nutrients are brought to surface waters by upwelling. However, in the northern Gulf of Alaska, the winds are generally downwelling inducing and the mechanism(s) by which nutrients are brought to the euphotic zone are not known. One mechanism that might bring nutrients into the euphotic zone is the …

Shaken Baby Syndrome: Retinal Hemorrhaging. A Biomechanical Approach To Understanding The Mechanism Of Causation, Steven Alex Hans

Mechanical & Aerospace Engineering Theses & Dissertations

Shaken Baby Syndrome (SBS) is a form of abuse where typically an infant, age six months or less, is held and shaken. There may or may not be direct impact associated with this action. Further, there is very little agreement on the actual mechanism of SBS. Clinical studies are limited in showing the exact mechanism of injury and only offer postulations and qualitative descriptions. SBS has received much attention in the media, has resulted in a great deal of litigation and can be the source of unfounded accusations. Therefore, it is necessary to try to quantify the forces that may …

A General Engineering Technology Program In Motorsports Technology, Gary Crossman, Anthony Dean

Engineering Technology Faculty Publications

Southside Virginia, in particular the cities of Danville, Martinsville and the surrounding area, is the home of Virginia International Raceway and a rapidly growing motorsports industry. There is a strong need for educational opportunities to support manufacturing and related industries in this region. In the early 2000’s Patrick Henry Community College in Martinsville established an associate of applied science degree in Motorsports Technology to help meet the need for technical support personnel. As the industry has grown it has become evident that engineers and technologists are needed at the baccalaureate and masters levels. Old Dominion University (ODU), located in Norfolk, …

Factors Affecting Website Reconstruction From The Web Infrastructure, Frank Mccown, Norou Diawara, Michael L. Nelson

Computer Science Faculty Publications

When a website is suddenly lost without a backup, it may be reconstituted by probing web archives and search engine caches for missing content. In this paper we describe an experiment where we crawled and reconstructed 300 randomly selected websites on a weekly basis for 14 weeks. The reconstructions were performed using our web-repository crawler named Warrick which recovers missing resources from the Web Infrastructure (WI), the collective preservation effort of web archives and search engine caches. We examine several characteristics of the websites over time including birth rate, decay and age of resources. We evaluate the reconstructions when compared …

The Open Archives Initiative, Michael L. Nelson

Computer Science Presentations

PDF of a powerpoint presentation from the Open Archives Initiative DRIADE ( Digital Repository of Information and Data for Evolution) Workshop, Durham, North Carolina, May 16-17, 2007. Also available on Slideshare.

The Sensitivity Of The Southwest Monsoon Phytoplankton Bloom To Variations In Aeolian Iron Deposition Over The Arabian Sea, Jerry D. Wiggert, Raghu G. Murtugudde

CCPO Publications

[1] A coupled, 3-D biophysical ocean general circulation model is used to investigate how aeolian iron deposition affects the Arabian Sea ecosystem. Two separate aeolian iron deposition fields, derived from the GISS and GOCART atmospheric transport models, have been applied as surface boundary conditions. The model results exhibit widespread biogeochemical sensitivity to the choice of deposition field. With GOCART deposition, SW Monsoon phytoplankton blooms in the western and central Arabian Sea are enhanced and exhibit greater realism. The central Arabian Sea bloom is supported by supplemental input of horizontally advected iron from a pool that undergoes a yearlong progression that …

Trees On K-12 School Campuses In Virginia, Jeffrey L. Kirwan, P. Eric Wiseman, John R. Seiler

Virginia Journal of Science

Trees and saplings growing on K-12 school campuses were investigated in 105 school districts across Virginia. There were 2812 trees (>12.5 cm stem diameter at 1.4 m above ground level) inventoried across all campuses. The mean and median campus tree population was 27 and 18, respectively. Loblolly pine (Pinus taeda L.) was the most abundant species, accounting for 11% of all inventoried trees. Red maple (Acer rubrum L.) was the most frequently inventoried species, present on 44% of the campuses. Sapling (trees with 2.5-12.5 cm stem diameter at 1.4 m above ground level) populations were similar …

An Isotropic Metric, Joseph D. Rudmin

Virginia Journal of Science

An isotropic metric for a black hole and a better vacuum condition \nabla^2 V_G =0 are presented which yield distinct terms for the energy densities of ordinary matter and gravitational fields in the Einstein tensor (G^44 =-g^2 (2\nabla^2 V_G +(\nabla V_G)^2)). This model resolves an inconsistency between electromagnetism and gravity in the calculation of field energy. Resolution of this inconsistency suggests a slight modification of the Einstein equation to gG^\mu\nu = 8\pi G T^\mu\nu.

High Resolution Dune Complex Mapping For The Monitoring Of Coastal Landform Change, First Landing State Park, Virginia, George M. Mcleod, Joe Daigneau, James Collins, Norma Swan, Thomas R. Allen

Virginia Journal of Science

First Landing State Park is located on the southern shore of the mouth of the Chesapeake Bay. The park contains a prograding shoreline and dune complex that has been steadily growing northward. Accurate three dimensional mapping of the resident coastal dune features is challenging due to the dynamic nature of the dunescape. Precise mapping within First Landing was accomplished through careful planning, employ of advanced Global Positioning System (GPS) technology, and intensive data analysis. Mapping ensued during a period of optimal satellite signal availability and strength. Data points were collected at manual intervals with a Leica GS50+ GPS receiver, utilizing …

Translating Ecocriticism: Dialoguing With Michel Serres, Stephanie Posthumus

Reconstruction: Studies in Contemporary Culture

Since its humble beginnings in the Western United States, ecocriticism has grown under the banner of the Association for the Study of Literature and the Environment into an organization of over 1000 members with international affiliates in Australia-New Zealand, Canada, Europe, India, Japan, Koria and the UK. At first sight, it would seem that ecocriticism has achieved global status. But as Ursula Heise remarks in her assessment of ecocriticism, this process of globalisation has been mainly a process of becoming known internationally. In truth, ecocriticism has remained strongly rooted in Anglophone literary studies even as it has been exported to …

Jeffress Research Grant - 2005

Virginia Journal of Science

Seven-page list of winners of the Jeffress Research Grant Awards for 2005.

Jeffress Research Grant Awards - 2006

Virginia Journal of Science

List of winners of the Jeffress Research Grant Awards for 2006.

Predictors Of Student Success In An Entry-Level Baccalaureate Dental Hygiene Program, Mohammad J. Alzahrani, Evelyn M. Thomson, Deborah Blythe Bauman

Dental Hygiene Faculty Publications

PURPOSE: The purpose of this study was to measure the utility of various predictors used by the Old Dominion University Gene W. Hirschfeld School of Dental Hygiene baccalaureate degree dental hygiene program in selecting dental hygiene students who are most likely to graduate and be successful in passing the National Board Dental Hygiene Examination (NBDHE). The following factors were examined: grade point average (GPA); science GPA; final grade in various prerequisite courses; final grade in first-year dental hygiene courses; academic setting where prerequisite courses were completed; multiple attempts to achieve a passing course grade; and admissions criteria points (ACP).

METHODS: …

Molecular Dynamics Simulations To Probe Effects Of Ultra-Short, Very-High Voltage Pulses On Cells, Viswanadham Sridhara

Electrical & Computer Engineering Theses & Dissertations

The use of very high electric fields (∼ 100kV/cm or higher) with pulse durations in the nanosecond range (Ultra-short) has been a very recent development in bioelectrics. Traditionally, the electric field effects have mostly been confined to: (a) low field, long-duration pulses, and (b) focused mainly on electroporation studies. Thus, aspects such as possible field-induced DNA damage, calcium release, alterations in neuro-transmitters, or voltage-gating have generally been overlooked.

Ultra-short, high-field pulses open the way to targeted and deliberate apoptotic cell killing (e.g., of tumor cells). Though experimental data is very useful, it usually yields information on macroscopic variables that is …

The Computation Of Exact Green's Functions In Acoustic Analogy By A Spectral Collocation Boundary Element Method, Andrea D. Jones

Mathematics & Statistics Theses & Dissertations

Aircraft airframe noise pollution resulting from the take-off and landing of airplanes is a growing concern. Because of advances in numerical analysis and computer technology, most of the current noise prediction methods are computationally efficient. However, the ability to effectively apply an approach to complex airframe geometries continues to challenge researchers. The objective of this research is to develop and analyze a robust noise prediction method for dealing with geometrical modifications. This new approach for determining sound pressure involves computing exact, or tailored, Green's functions for use in acoustic analogy. The effects of sound propagation and scattering by solid surfaces …

Canonical Correlation And Correspondence Analysis Of Longitudinal Data, Jayesh Srivastava

Mathematics & Statistics Theses & Dissertations

Assessing the relationship between two sets of multivariate vectors is an important problem in statistics. Canonical correlation coefficients are used to study these relationships. Canonical correlation analysis (CCA) is a general multivariate method that is mainly used to study relationships when both sets of variables are quantitative. When the variables are qualitative (categorical), a technique called correspondence analysis (CA) is used. Canonical correspondence analysis (CCPA) is used to deal with the case when one set of variables is categorical and the other set is quantitative. By exploiting the interrelationships between these three techniques we first provide a theoretical basis for …

Vital Tooth Whitening Effects On Oral Health-Related Quality Of Life In Older Adults, Ann Michelle Poindexter

Dental Hygiene Theses & Dissertations

This study determined if vital tooth whitening affects oral health-related quality of life (OHRQOL) in adults ≥50-years old, and if tooth whitening promotes individuals to seek regular professional dental care and participation in social activities. Using a two-group, single blind, randomized, pre-test-post-test design, 62 participants were enrolled. The experimental group used a whitening product twice daily for three weeks, while the control group used no whitening products. Tooth color satisfaction was assessed using the Tooth Color Satisfaction Scale and was correlated with overall oral health-related quality of life. The Oral Health Impact Profile (OHIP), used as the pre-test …

Uncertainty Assessment In High-Risk Environments Using Probability, Evidence Theory And Expert Judgment Elicitation, Stella Barberis Bondi

Engineering Management & Systems Engineering Theses & Dissertations

The level of uncertainty in advanced system design is assessed by comparing the results of expert judgment elicitation to probability and evidence theory. This research shows how one type of monotone measure, namely Dempster-Shafer Theory of Evidence can expand the framework of uncertainty to provide decision makers a more robust solution space. The issues imbedded in this research are focused on how the relevant predictive uncertainty produced by similar action is measured.

This methodology uses the established approach from traditional probability theory and Dempster-Shafer evidence theory to combine two classes of uncertainty, aleatory and epistemic. Probability theory provides the mathematical …

A Risk- And Fuzzy Set-Based Methodology For Advanced Concept Technology Demonstration Military Utility Assessment Design, Thomas James Meyers

Engineering Management & Systems Engineering Theses & Dissertations

The U.S. Department of Defense Advanced Concept Technology Demonstration (ACTD) and derivative, rapid acquisition programs offer timely solutions to critical military needs by assessing the utility of technologies mature enough to be fielded without application of traditional, defense system development processes. Military utility assessments (MUA) are ACTDs' most critical features, but the lack of a standard for identifying assessment criteria tailored to specific demonstrations risks poorly informed acquisition decisions and the military operations those decisions are intended to support.

The purpose of this research was to develop and deploy a methodology for identifying measures of effectiveness integral to advanced concept …

What Should Be In A Human Behavior Representation Federation Object Model For High Level Architecture, Gurkan Haznedaroglu

Electrical & Computer Engineering Theses & Dissertations

Modeling and Simulation (M&S) can assist in evaluating scenarios and enhancing the performance of operational systems. Fully integrated use of MBS can enable the evaluation of the effectiveness of proposed equipment or software in realistic simulated environments and can provide an assessment of the impacts of specific equipment or capabilities on battle outcomes. Every level, from strategic planners, technology experts, operations research analysts, weapons systems designers and users, testers, maintainers, and cost analysts, has to be interactively involved to maximize the benefits of this approach. Human behavior is a very important part of the M&S process. Especially in constructive simulations, …

A Resolution Enhancement Technique In Digital Images, Mehmet R. Ormanoglu

Electrical & Computer Engineering Theses & Dissertations

Image enhancement is the processing of images to increase their usefulness. The image enhancement methods and objectives vary with the application. When images are enhanced for human viewers, as in television, the objective is mostly to improve perceptual aspects: image quality, intelligibility, or visual appearance. The aim of this research work is to make the processed image better in the visual sense than the unprocessed image. An image can often be enhanced by modifying its contrast or dynamic range, increasing the sharpness of edges, reducing the noise, or reducing the blurring. The most commonly used contrast enhancement technique is histogram …

Simulation And Modeling Of Nerve Impulse Propagation And Its Blockage By External Electrical Stimulation, Nidhi Nahar

Electrical & Computer Engineering Theses & Dissertations

The electric nature of biological tissues permits the transmission of signals for information and for control and is, therefore, of vital importance for life. The latest scientific achievements and nanoscale probing techniques now allow scientists to research at the subcellular level by measuring the electric current flows through a single ion channel of the cell membrane with the patch-clamp method. With the latter approach, the effects of electrical stimulation can be quantified, understood, and applied to molecular biology and the development of medical diagnostic and therapeutic methods.

In this thesis, the Hodgkin-Huxley approach for unmyelinated fibers, coupled with a transmission …

Long-Range Target Classification In A Cluttered Environment Using Multi-Sensor Image Sequences, Cenk Yaman

Electrical & Computer Engineering Theses & Dissertations

Accurate identification of unknown contacts is crucial in military intelligence. Automated systems which quickly and accurately determine the identity of a contact could be a benefit in backing up electronic signal identification methods such as Identification Friend and Foe (IFF) systems. Radio Detection and Ranging (RADAR) images are often undesirable in military applications since they reveal the location of the imaging system. So we explore the use of visible and infrared images of which are generally more consistent than RADAR images and for which it is easy to compensate for environmental effects. Recent advances in visible and IR imaging technology …