Physical Sciences and Mathematics Commons^™

All Minimal Prime Extensions Of Hereditary Classes Of Graphs, Vassilis Giakoumakis, Stephan Olariu

Computer Science Faculty Publications

The substitution composition of two disjoint graphs G₁ and G₂ is obtained by first removing a vertex x from G₂ and then making every vertex in G₁ adjacent to all neighbours of x in G₂. Let F be a family of graphs defined by a set Z* of forbidden configurations. Giakoumakis [V. Giakoumakis, On the closure of graphs under substitution, Discrete Mathematics 177 (1997) 83–97] proved that F∗, the closure under substitution of F, can be characterized by a set Z∗ of forbidden configurations — the minimal prime extensions of Z. He also …

How Much Preservation Do I Get If I Do Absolutely Nothing? Using The Web Infrastructure For Digital Preservation, Martin Klein, Frank Mccown, Joan A. Smith, Michael Nelson

Computer Science Faculty Publications

To date, most of the focus regarding digital preservation has been on removing copies of the resources to be preserved from the “living web” and placing them in an archive for controlled curation. Once inside an archive, the resources are subject to careful processes of refreshing (making additional copies to new media) and migrating (conversion to new formats and applications). For small numbers of resources of known value, this is a practical and worthwhile approach to digital preservation. However, due to the infrastructure costs (storage, networks, machines) and more importantly the human management costs, this approach is unsuitable for web …

Brass: A Queueing Manager For Warrick, Frank Mccown, Amine Benjelloun, Michael L. Nelson

Computer Science Faculty Publications

When an individual loses their website and a backup can-not be found, they can download and run Warrick, a web-repository crawler which will recover their lost website by crawling the holdings of the Internet Archive and several search engine caches. Running Warrick locally requires some technical know-how, so we have created an on-line queueing system called Brass which simplifies the task of recovering lost websites. We discuss the technical aspects of recon-structing websites and the implementation of Brass. Our newly developed system allows anyone to recover a lost web-site with a few mouse clicks and allows us to track which …

Clarifications Of Rule 2 In Teaching Geometric Dimensioning And Tolerancing, Cheng Lin, Alok Verma

Engineering Technology Faculty Publications

Geometric dimensioning and tolerancing is a symbolic language used on engineering drawings and computer generated three-dimensional solid models for explicitly describing nominal geometry and its allowable variation. Application cases using the concept of Rule 2 in the Geometric Dimensioning and Tolerancing (GD&T) are presented. The rule affects all fourteen geometric characteristics. Depending on the nature and location where each feature control frame is specified, interpretation on the applicability of Rule 2 is quite inconsistent. This paper focuses on identifying the characteristics of a feature control frame to remove this inconsistency. A table is created to clarify the confusions for students …

Microscopic-Macroscopic Simulations Of Rigid-Rod Polymer Hydrodynamics: Heterogeneity And Rheochaos, M. Gregory Forest, Ruhai Zhou, Qi Wang

Mathematics & Statistics Faculty Publications

Rheochaos is a remarkable phenomenon of nematic (rigid-rod) polymers in steady shear, with sustained chaotic fluctuations of the orientational distribution of the rod ensemble. For monodomain dynamics, imposing spatial homogeneity and linear shear, rheochaos is a hallmark prediction of the Doi-Hess theory [M. Doi, J. Polym. Sci. Polym. Phys. Ed., 19 (1981), pp. 229-243; M. Doi and S. F. Edwards, The Theory of Polymer Dynamics, Oxford University Press, London, New York, 1986; S. Hess, Z. Naturforsch., 31 (1976), pp. 1034-1037. The model behavior is robust, captured by second-moment tensor approximations G. Rienäcker, M. Kröger, and S. Hess, Phys. Rev. …

Validating Pareto Optimal Operation Parameters Of Polyp Detection Algorithms For Ct Colonography, Jiang Li, Adam Huang, Nicholas Petrick, Jianhua Yao, Ronald M. Summers, Maryellen L. Giger (Ed.), Nico Karssemeijer (Ed.)

Electrical & Computer Engineering Faculty Publications

We evaluated a Pareto front-based multi-objective evolutionary algorithm for optimizing our CT colonography (CTC) computer-aided detection (CAD) system. The system identifies colonic polyps based on curvature and volumetric based features, where a set of thresholds for these features was optimized by the evolutionary algorithm. We utilized a two-fold cross-validation (CV) method to test if the optimized thresholds can be generalized to new data sets. We performed the CV method on 133 patients; each patient had a prone and a supine scan. There were 103 colonoscopically confirmed polyps resulting in 188 positive detections in CTC reading from either the prone or …

Formation Of In- (2×1) And In Islands On Si (100) - (2×1) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The growth of indium on a vicinal Si (100) - (2×1) surface at room temperature by femtosecond pulsed laser deposition (fsPLD) was investigated by in situ reflection high-energy electron diffraction (RHEED). Recovery of the RHEED intensity was observed between laser pulses and when the growth was terminated. The surface diffusion coefficient of deposited In on initial two-dimensional (2D) In- (2×1) layer was determined. As growth proceeds, three-dimensional In islands grew on the 2D In- (2×1) layer. The RHEED specular profile was analyzed during film growth, while the grown In islands were examined by ex situ atomic force microscopy. The full …

Exploration Of Computational Methods For Classification Of Movement Intention During Human Voluntary Movement From Single Trial Eeg, Ou Bai, Peter Lin, Sherry Vorbach, Jiang Li, Steve Furlani, Mark Hallett

Electrical & Computer Engineering Faculty Publications

Objective: To explore effective combinations of computational methods for the prediction of movement intention preceding the production of self-paced right and left hand movements from single trial scalp electroencephalogram (EEG).

Methods: Twelve naïve subjects performed self-paced movements consisting of three key strokes with either hand. EEG was recorded from 128 channels. The exploration was performed offline on single trial EEG data. We proposed that a successful computational procedure for classification would consist of spatial filtering, temporal filtering, feature selection, and pattern classification. A systematic investigation was performed with combinations of spatial filtering using principal component analysis (PCA), independent component analysis …

Using Pareto Fronts To Evaluate Polyp Detection Algorithms For Ct Colonography, Adam Huang, Jiang Li, Ronald M. Summers, Nicholas Petrick, Amy K. Hara

Electrical & Computer Engineering Faculty Publications

We evaluate and improve an existing curvature-based region growing algorithm for colonic polyp detection for our CT colonography (CTC) computer-aided detection (CAD) system by using Pareto fronts. The performance of a polyp detection algorithm involves two conflicting objectives, minimizing both false negative (FN) and false positive (FP) detection rates. This problem does not produce a single optimal solution but a set of solutions known as a Pareto front. Any solution in a Pareto front can only outperform other solutions in one of the two competing objectives. Using evolutionary algorithms to find the Pareto fronts for multi-objective optimization problems has been …

Entopic Lattice Boltzmann Representations Required To Recover Navier Stokes Flows, Brian Keating, George Vahala, Jeffrey Yepez, Min Soe, Linda L. Vahala

Electrical & Computer Engineering Faculty Publications

There are two disparate formulations of the entropic lattice Boltzmann scheme: one of these theories revolves around the analog of the discrete Boltzmann H function of standard extensive statistical mechanics, while the other revolves around the nonextensive Tsallis entropy. It is shown here that it is the nonenforcement of the pressure tensor moment constraints that lead to extremizations of entropy resulting in Tsallis-like forms. However, with the imposition of the pressure tensor moment constraint, as is fundamentally necessary for the recovery of the Navier-Stokes equations, it is proved that the entropy function must be of the discrete Boltzmann form. Three-dimensional …

Simulations Of Phytoplankton Species And Carbon Production In The Equatorial Pacific Ocean 2. Effects Of Physical And Biogeochemical Processes, Baris Salihoglu, Eileen E. Hofmann

CCPO Publications

A one-dimensional multi-component lower trophic level ecosystem model that includes detailed algal physiology is used to investigate the response of phytoplankton community and carbon production and export to variations in physical and biochemical processes in the Cold Tongue region of the equatorial Pacific Ocean at ON, 140W. Results show that high-frequency variability in vertical advection and temperature is an important mechanism driving the carbon export. Filtering out low frequency physical forcing results in a 30% increase in primary production and dominance of high-light adapted Prochlorococcus and autotrophic eukaryotes. Sensitivity studies show that iron availability is the primary control on carbon …

Assessment Of Skill And Portability In Regional Marine Biogeochemical Models: Role Of Multiple Planktonic Groups, Marjorie A. M. Friedrichs, Jeffery A. Dusenberry, Laurence A. Anderson, Robert A. Armstrong, Fei Chai, James R. Christian, Scott C. Doney, John Dunne, Masahiko Fujii, Jerry D. Wiggert

CCPO Publications

[1] Application of biogeochemical models to the study of marine ecosystems is pervasive, yet objective quantification of these models' performance is rare. Here, 12 lower trophic level models of varying complexity are objectively assessed in two distinct regions (equatorial Pacific and Arabian Sea). Each model was run within an identical one-dimensional physical framework. A consistent variational adjoint implementation assimilating chlorophyll-a, nitrate, export, and primary productivity was applied and the same metrics were used to assess model skill. Experiments were performed in which data were assimilated from each site individually and from both sites simultaneously. A cross-validation experiment was also conducted …

Scaling Tests Of The Cross Section For Deeply Virtual Compton Scattering, C. Muñpz Camacho, A. Camsonne, M. Mazouz, C. Ferdi, G. Gavalian, E. Kuchina, M. Amaryan, K. A. Aniol, M. Beaumel, H. Benaoum, D. Hayes, C. E. Hyde-Wright, H. Ibrahim, P. E. Ulmer, L. B. Weinstein

Physics Faculty Publications

We present the first measurements of the ep → epγ cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region. The Q² dependence (from 1.5 to 2.3 GeV²) of the helicity-dependent cross section indicates the twist-2 dominance of DVCS, proving that generalized parton distributions (GPDs) are accessible to experiment at moderate Q². The helicity-independent cross section is also measured at Q²=2.3 GeV². We present the first model-independent measurement of linear combinations of GPDs and GPD integrals up to the twist-3 approximation.

A Simplified Model For Growth Factor Induced Healing Of Wounds, F. J. Vermolen, E. Van Baaren, J. A. Adam

Mathematics & Statistics Faculty Publications

A mathematical model is developed for the rate of healing of a circular or elliptic wound. In this paper the regeneration, decay and transport of a generic 'growth factor', which induces the healing of the wound, is taken into account. Further, an equation of motion is derived for radial healing of a circular wound. The expressions for the equation of motion and the distribution of the growth factor are related in such a way that no healing occurs if the growth factor concentration at the wound edge is below a threshold value. In this paper we investigate the influence of …

Minutes: Council Meeting

Virginia Journal of Science

Minutes of the VAS Council meeting Friday May 26, 2006, 8 - 9:40 AM, at Skelton Conference Center Inn, Virginia Tech, Blacksburg VA. Minutes were edited for publication.

2004 Jeffress Research Grant Awards

Virginia Journal of Science

List of winners of the 2004 Jeffress Research Grant Awards.

Exchange Hydrodynamics Between A Subestuary And Its Adjacent Estuary, Diego A. Narváez

OES Theses and Dissertations

Four oceanographic surveys and two periods of moored data were analyzed to describe the subtidal exchange hydrodynamics between a subestuary (Nansemond River) and its adjacent estuary (James River) in the lower Chesapeake Bay. The surveys were carried out during two semidiurnal periods (~25 hrs), which included two spring and two neap tides. Velocity profiles and hydrographic data were recorded over an area ~4 km long and ~1 km wide allowing a spatial resolution rarely obtained with observational data. The results obtained in the surveys were extended with instruments deployed at the entrance to the subestuary during winter and summer time …

Fault Modeling In Wireless Sensor Networks, Ahmed A. Elmiligui

Electrical & Computer Engineering Theses & Dissertations

A large amount of research has been done in the area of wireless sensor networks (WSN), but not much work has been done in modeling the fault tolerance and reliability of these networks. In this thesis, the fault tolerance of a WSN to node failures is studied and an analytical reliability model of the network is derived. A valid reliability model of a network could reveal an estimate of the network's performance before it is deployed.

A wireless sensor network was modeled as a k-out-of-n system and a generic fault tolerant framework for the network in terms of node losses …

Fault Arrangements And Their Effect On The Performance Of Wireless Sensor Networks, Dwayne Sayone Blai

Electrical & Computer Engineering Theses & Dissertations

Wireless sensor networks face many reliability challenges. The networks are deployed in open, hostile environments, making them easily susceptible to network failure. As a result, there are countless faults that can occur in sensor networks, from component failure to outside attacks. Outside attacks take place when an adversary gains control over a node or set of nodes in the network. Outside attackers can destroy a network in numerous ways such as random attacks, clustering attacks, search-based attacks, etc. The method and strategy used in each of these attacks directly affects the network's reliability. Understanding how these adversaries are positioned is …

Characterization Of Β-Lactam Resistant Pandemic Serotypes Of Vibrio Cholerae Isolated From Ships' Ballast Tanks And Coastal Waters, Amanda Lynn Goodrich

OES Theses and Dissertations

Vibrio cholerae serotypes 01 and 0139 are responsible for world-wide epidemics of cholera. These pandemic causing strains must possess genes that encode for the cholera toxin (CTX) and toxin co-regulated pili (TCP) in order to infect their hosts. In this study, 284 isolates of Vibrio cholerae from ballast and coastal waters were serotyped, with 11 % testing positive for serotype 01 and 21 % testing positive for serotype 0139. PCR assays were used to detect the presence of ctxA and tcpA genes in all positive isolates, none of which contained ctxA while 2% of the isolates contained tcpA. The 01 …

Continuously Stratified Flow Dynamics Over A Hollow, David Salas-Monreal

OES Theses and Dissertations

Acoustic Doppler current profiles (ADCP) and density profiles were measured over three lower Chesapeake Bay bathymetric depressions (hollows) in order to determine the effects of a hollow on a continuously stratified flow. Measurements showed an acceleration of the near-bottom flow as it moved toward the deepest part of the hollows, in contrast to the deceleration expected from two-dimensional Bernoulli-type dynamics. The acceleration was attributed to lateral water intrusions that were most apparent during floods. The presence of lateral water intrusions was corroborated by observations in a transverse section that crossed the deepest part of the hollows. The observed deceleration of …

An Operational Model For Mobile Sensor Cloud Management, Indrajeet Kalyankar

Electrical & Computer Engineering Theses & Dissertations

Mobile sensors provide a safe, cost effective method for gathering information in hazardous environments. When the hazardous environment is either unexplored, such as the surface of Mars, or unanticipated, such as the result of chemical contamination, it is desirable for a system to gather information with a minimal amount of outside control (localization, decision control, etc.) and prepositioned sensors. If one takes a look at the number of the sensors deployed on a scale, at the lower end is the sole, multipurpose sensor unit. The upper end deals with hordes of inexpensive, expendable sensors. In the middle, a cluster of …

Tidally Induced Variability At The Chesapeake Bay Entrance, María Andrea Piñones

OES Theses and Dissertations

Time series of current velocity from 6 stations at the Chesapeake Bay entrance were used to study the variability of tidal currents. Particular emphasis was placed on the semidiurnal tidal currents, which explains ~ 70% of the variability of tidal currents. Four different deployments that spanned more than one year showed that the vertical structure of the semidiurnal tidal currents vary seasonally in response to changes in water column stratification. Under destratified conditions favored by wind forcing, the semidiurnal tidal currents rotated cyclonically throughout the water column, thus emulating a Kelvin wave. In contrast, during stratified conditions the tidal currents …

Efficient Unbiased Estimating Equations For Analyzing Structured Correlation Matrices, Yihao Deng

Mathematics & Statistics Theses & Dissertations

Analysis of dependent continuous and discrete data has become an active area of research. For normal data, correlations fully quantify the dependence. And historically, maximum likelihood method has been very successful to estimate the correlations and unbiased estimating equation approach has become a popular alternative when there may be a departure from normality. In this thesis we show that the optimal unbiased estimating equation coincides with the likelihood equations for normal data. We then introduce a general class of weighted unbiased estimating equations to estimate parameters in a structured correlation matrix. We derive expressions for asymptotic covariance of the estimates, …

Investigation Of Ultracold Rubidium Atoms In A Pulsed Far Off Resonance Trap, Minarni Minarni

Physics Theses & Dissertations

This dissertation reports on the design, construction, and investigation of a pulsed optical dipole force trap which uses laser light to confine ultracold rubidium (Rb) atoms. Because the laser frequency is detuned far from the atomic resonance frequency, the optical dipole force trap is also called a "far-off-resonance trap" (FORT). The use of pulsed laser light to create an optical trap may find application in expanding the number of atomic species which can be confined. The experiments reported here are principally aimed, however, at understanding the physics of pulsed FORT dynamics in anticipation of using the free electron laser (FEL) …

Estimating Familial Correlations Using A Kotz Type Density, Amal Helu

Mathematics & Statistics Theses & Dissertations

Two useful familial correlations often used to study the resemblance between the family members are the sib-sib correlation (ρ_ss) and the mom-sib or parent-sib correlation (ρ_ps). Since their introduction early in the last century by Galton, Fisher and others, many improved estimators of these correlations have been suggested in the literature. Several moment based estimators as well as the maximum likelihood estimators under the assumption of multivariate normality have been extensively studied and compared by various authors. However, the performance of these estimators when the data are not from multivariate normal distribution is poor. In this …

Circulation, Vol. 13, No. 2, Center For Coastal Physical Oceanography, Old Dominion University, Michael Ott

CCPO Circulation

Summer 2006 issue of CCPO Circulation featuring article "Chesapeake Bay Mouth Monitoring Program" by Dr. Michael Ott

Marine And Freshwater Cyanophages In A Laurentian Great Lake: Evidence From Infectivity Assays And Molecular Analyses Of G20 Genes, Steven W. Wilhelm, Matthew J. Carberry, Melanie L. Eldridge, Leo Poorvin, Matthew A. Saxton, Martina A. Doblin

OES Faculty Publications

While it is well established that viruses play an important role in the structure of marine microbial food webs, few studies have directly addressed their role in large lake systems. As part of an ongoing study of the microbial ecology of Lake Erie, we have examined the distribution and diversity of viruses in this system. One surprising result has been the pervasive distribution of cyanophages that infect the marine cyanobacterial isolate Synechococcus sp. strain WH7803. Viruses that lytically infect this cyanobacterium were identified throughout the western basin of Lake Erie, as well as in locations within the central and eastern …

Dimensionality Reduction Using Non-Linear Principal Components Analysis, Tara Singh

Electrical & Computer Engineering Theses & Dissertations

Advances in data collection and storage capabilities during the past decades have led to an information overload in most sciences. Traditional statistical methods break down partly because of the increase in the number of observations, but mostly because of the increase in the number of variables associated with each observation. While certain methods can construct predictive models with high accuracy from high-dimensional data, it is still of interest in many applications to reduce the dimension of the original data prior to any modeling of the data. Patterns in the data can be hard to find in data of high dimensionality, …

An Adaptive Algorithm To Identify Ambiguous Prostate Capsule Boundary Lines For Three-Dimensional Reconstruction And Quantitation, Rania Yousry Hussein

Electrical & Computer Engineering Theses & Dissertations

Currently there are few parameters that are used to compare the efficiency of different methods of cancerous prostate surgical removal. An accurate assessment of the percentage and depth of extra-capsular soft tissue removed with the prostate by the various surgical techniques can help surgeons determine the appropriateness of surgical approaches. Additionally, an objective assessment can allow a particular surgeon to compare individual performance against a standard. In order to facilitate 3D reconstruction and objective analysis and thus provide more accurate quantitation results when analyzing specimens, it is essential to automatically identify the capsule line that separates the prostate gland tissue …