Digital Commons Network^™

Alignment Dynamics Of Slow Light Diffusion In Ultracold Atomic 85Rb, S. Balik, R. G. Olave, C. I. Sukenik, M. D. Havey, V. M. Datsyuk, I. M. Sokolov, D. V. Kupriyanov

Physics Faculty Publications

A combined experimental and theoretical investigation of time- and alignment-dependent propagation of light in an ultracold atomic gas of atomic ⁸⁵Rb is reported. Coherences among the scattering amplitudes for light scattering off excited hyperfine levels produce strong variations of the light polarization in the vicinity of atomic resonance. Measurements are in excellent agreement with Monte Carlo simulations of the multiple scattering process.

Section Abstracts: Education, Virginia Journal Of Science

Virginia Journal of Science

Abstracts of the Education Section for the 83rd Annual Virginia Academy of Science Meeting, May 19-20, at James Madison University, Harrisonburg, Virginia.

Assessment Of Human Health Risks From Chemically Contaminated Lake Fishes In Greece, Eugene G. Maurakis, David V. Grimes, Dimitra Bobori, Rob Hale, Jennifer Jones

Virginia Journal of Science

Objectives were to conduct screening level surveys of locally consumed fish tissues in vicinities of two lakes (Kastoria and Pamvotis) in Greece to determine the presence of halogenated organic compounds and determine carcinogenic and non-carcinogenic human health risks associated with the consumption of sampled fish tissues. Results estimate the Incremental Lifetime Cancer Risks (ILCR) and Hazard Index (HI) values for the two local populations using site-specific population data. These results were compared to analyses conducted using U.S. Environmental Protection Agency default values in an effort to determine the applicability of USEPA default values to assessments of risks in non U.S. …

Ozone Concentration In An Atmospheric Pressure Air Plasma Jet, Srinivas Reddy Suddala

Electrical & Computer Engineering Theses & Dissertations

A stable micro-plasma jet in air was generated from a direct current discharge between two molybdenum electrodes (0.25 mm thick) that were separated by an alumina insulator of the same thickness. The after-glow plasma jet was generated by blowing air through the space between the electrodes. A change from laminar to turbulent flow was observed at a gas flow rate of 140 ml/min. The length of the plasma jet increased with flow rate in the laminar mode to approximately 15 mm and decreased in the turbulent mode.

Increasing the gas flow rate up to 200 ml/min at a constant discharge …

Natural And Synthetic Viniferins Associated With The Grapevine Disease Young Vine Decline, David Michael Mcginnis

Chemistry & Biochemistry Theses & Dissertations

Grapevine disease has been thc subject of intense research amongst viticulturists over the last few decades, especially during the 1990's. There has been discoveries that suggest grapevine disease is commonly caused by fungal pathogens. One of the most common fungi that the vine may become infected by is known as Botrytis cinerea. B. cinerea is capable of attacking the grapevine which in turn will lead to bunch rot in the grape clusters. This disease has been researched in great detail during the past several years and is one of only few microorganisms that have actually been identified. Phaeoacremrmium chnlmydospnrum …

Complexity Measure Of A Product Or Process By Application Of Fuzzy Multi-Attribute Utility Theory, Shrikant Chandrakant Nagpure

Mechanical & Aerospace Engineering Theses & Dissertations

During the early phases of design, the development cost of complex products or systems is very difficult to obtain because of the uncertainties related to their work breakdown structures and the wide choice of manufacturing technologies with no historical data specific to these products. This thesis presents a method to derive a complexity index to capture the non-additive property and inherent uncertainty, i.e. fuzziness, of the technologies that could be used for complex objects. This complexity index can then be used as a cost index for comparing various candidate manufacturing processes.

Macros are written in Microsoft Excel to establish a …

Validation Of Finite Element Beam Models, Pavan R. Madhineni

Mechanical & Aerospace Engineering Theses & Dissertations

Finite Element (FE) methods these days are becoming very popular to predict the responses of structures in industries, such as the aerospace and automobile industries. When there is a new design or modification of an existing design, the product must be tested to fulfill the criterion projected by the industry or external agencies before it can be launched. The product must be checked for each and every aspect, and every minute detail of each of the external forces. Hence, it becomes very important to carry out the model validation on the product.

This thesis describes validation of finite element (FE) …

Shape And Size Sensitivity Analysis Of Geometrically Nonlinear Laminated Composite Plates, Nitin R. Mane

Mechanical & Aerospace Engineering Theses & Dissertations

Since major applications of composite laminates involve large deformation, the nonlinear strain-displacement relation in the Von Karman sense has been incorporated here with the first order shear deformation to study bending analysis of composite laminated panels. The finite element model constructed here is an extension of the MIN3 element which is a displacement based element developed by Hughes and Tessler. The element avoids shear locking in the thin bending regime and achieves computational efficiency. The resultant nonlinear matrix equation is solved for analysis of composite panels by using the Newton-Raphson iterative method. Based upon the nonlinear matrix equation, the shape …

Gauss-Hermite Integration For Reliability Calculation And Sensitivity Analysis, Nilesh K. Borade

Mechanical & Aerospace Engineering Theses & Dissertations

In the real world, many applications are subjected to uncertainty. A simple illustration would be a structure like a bridge where magnitude and the speed of the loads acting on it are continuously changing. Therefore it becomes essential to study this stochastic or random nature. The thrust of this research is to develop an efficient reliability and sensitivity technique based on stochastic response surfaces (polynomial chaos expansions) constructed using Gauss-Hermite integration. The focus is on calculating the uncertainty propagation using less number of function evaluations since the stochastic response surface needs to be reconstructed at each design cycle. Using the …

Contemporary-Classical Sequential Loop Design With Parameter Uncertainty, Donghyuk Jeong

Mechanical & Aerospace Engineering Theses & Dissertations

Standard sequential loop closure design based on Evans root migration concepts is a well accepted, insightful and effective technique for meeting nominal performance objectives and traditional gain-phase stability margin requirements. Unfortunately, assessment of closed-loop variations resulting from parameter error is a post-process, implying an undesirable design-assess-redesign procedure is necessary if variations are found unacceptable. Further, the modem parameter uncertainty assessment framework is often inconsistent, both quantitatively and qualitatively, with the redesign task. Specifically, the parameter uncertainty assessment variables are not readily apparent in the sequential loop design framework, and these variables provide little guidance for the redesign strategy. Therefore, enhancing …

Characterization Of Pfiesteria Ichthyocidal Activity, Andrew S. Gordon, Harold G. Marshall, Sandra E. Shumway, Kathryn J. Coyne, Alan J. Lewitus, Michael A. Mallin, Parke A. Rublee

Biological Sciences Faculty Publications

Letter to the Editor regarding article: Drgon, T., et al. 2005. Characterization of ichthyocidal activity of Pfiesteria piscicida: Dependence on the dinospore cell density. Appl. Environ. Microbiol. 71:519–529

Circulation, Vol. 12, No. 2, Center For Coastal Physical Oceanography, Old Dominion University, Marjorie Friedrichs

CCPO Circulation

Fall 2005 issue of CCPO Circulation featuring article "The Regional Ecosystem Modeling Testbed Project" by Dr. Marjorie Friedrichs

Numerical Integration Strategy For Generating Root Migration Diagrams, Deepak H. Panduranga

Mechanical & Aerospace Engineering Theses & Dissertations

Evans root locus is a graphical method for analyzing or designing the stability and performance of a single channel closed-loop system. The method consists of plotting the locus of closed-loop characteristic equation roots in the complex plane as the loop gain parameter is varied over a wide range of values. Several methods for plotting the root locus graph exist and can be mainly classified into two types: analytical methods and numerical methods. The most common numerical method is based on polynomial factoring or root solving. A less common, alternative method for generating the root locus graph is based on numerical …

Computational Analysis And Validation Of The Hans Head And Neck Support, Kapil Tyagi

Mechanical & Aerospace Engineering Theses & Dissertations

One of the major causes of racing fatalities is basilar skull fracture from excessive head motions and neck loading in a frontal impact. There are many head/neck restraints available in the market but HANS head and neck support has proved to be the most efficient one in sled testing. This paper evaluates and compares the performance of the HANS device in MAthematical DYnamic MOdel (MADYMO) software with the sled testing. The tests were conducted for the frontal impact motions, with a crash pulse of 45 G's.

The goal of the tests was to evaluate the performance of HANS without the …

Fourier Transform Analysis Of Terahertz Radiation, Chikaodira N. Okpo

Electrical & Computer Engineering Theses & Dissertations

Advances in terahertz radiation (T-rays) technology have great promise in various technological areas ranging from medical technology, imaging technology and accelerator technology. At Thomas Jefferson Laboratory, the Free Electron Laser division (FEL) produces very powerful beam of laser light by accelerating electrons in bunches along a beamline. This laser light absorbs and releases energy at various wavelengths. The new FEL upgrade led to the production of very bright terahertz (THz) radiation with an average power of 1 00watts which is about 100,000 times brighter than those produced elsewhere. These T-rays have very significant applications in the Laboratory. The most significant …

An Analysis Of A Finite Element Human Brain In Low Speed Rear Impact Automobile Collision Comparison, Model Development And Study Using Tno Rear Impact Dummy, Mangesh S. Kadam

Mechanical & Aerospace Engineering Theses & Dissertations

According to the National Safety Council, rear-end collisions are the most common types of collisions with approximately two and a half million cases reported every year. Crash tests indicate a change of vehicle velocity of 4km/h (2.5 mph) may produce occupant symptoms. Vehicle damage may not occur until 14-15km/h (8.7 mph) (Davis CG, 1998). Occupants, in rear-end vehicle impacts sustain a motion associated with whiplash, where the head snaps backwards quickly, resulting in linear and/or angular acceleration forces acting on the brain. This angular motion tends to subject the brain to shear deformations from rapid rotation. This study is a …

Sonic Boom Prediction Using Euler/Full Potential Methodology, Isik Ali Ozcer

Mechanical & Aerospace Engineering Theses & Dissertations

Sonic Booms of two different bodies, a double cone configuration and a modified F-SE aircraft, are predicted using Euler solvers for the near field, and a Full Potential Propagation method for the far field. The problem is considered inviscid since viscous effects in high Reynolds number flows are negligible in Sonic Boom propagation. To enhance the accuracy of the predictions, elaborate shock fitting and grid adaptation routines are developed that can handle complicated shock topologies. The far field propagation code using the full potential equation is the first three-dimensional computational fluid dynamics code in literature that can march the solution …

New Methodology For Robust Control System Design And Analysis For Single Parameter Uncertain Systems, Charles J. Player

Mechanical & Aerospace Engineering Theses & Dissertations

Due to the conservative nature of the standard singular value robustness tests there is ambiguity in the results that they provide. The tests only establish a sufficient condition and therefore provide little insight to the stability robustness of a system that fails the test. However, for a single parameter uncertain system that is modeled using structured uncertainty, an Evans root locus can be derived that shows how system closed-loop poles change with the magnitude of the single parameter uncertainty. This technique provides clear stability robustness insight. Further, another Evans root locus can be derived that shows how system closed-loop zeros …

Development And Application Of A Gg-Irms Reductive Pyrolysis Reactor Interface For The Δ34S Determination Of Sulfur In Individual Organic Compounds, N. Deborah Hewlett

Chemistry & Biochemistry Theses & Dissertations

The incorporation of sulfur into sedimentary organic matter is an important aspect of organic carbon preservation. A better understanding of the sulfur cycle and the formation of organo-sulfur compounds are necessary if we are to better understand the interaction of biogeochemical cycles of C, N, O, H. and S. Currently, the determination of ³⁴S/³²S in organic matter is limited to bulk organic samples. The sulfur isotopic analysis of individual organo-sulfur compounds within the sediments should allow for a more complete understanding of the sulfur cycle and the processes which lead to sulfur incorporation into organic matter. This …

Benthic Biological Monitoring Program Of The Elizabeth River Watershed (2004), Daniel M. Dauer

Elizabeth River Reports

Executive Summary

Macrobenthic communities of the Elizabeth River watershed have been quantitatively sampled since summer 1999. This report presents the data from the sixth year of sampling in 2004. The three objectives of the Benthic Biological Monitoring Program of the Elizabeth River watershed are: (1) To characterize the health of the tidal waters of the Elizabeth River watershed as indicated by the structure of the benthic communities. ( 2) To conduct trend analyses on long-term data at 14 fixed-point stations to relate temporal trends in the benthic communities to changes in water and/or sediment quality. Trend analyses will be updated …

Phytoplankton Development Within Tidal Freshwater Regions Of Two Virginia Rivers, Harold G. Marshall, Lubomira Burchardt

Virginia Journal of Science

Phytoplankton composition and the range of seasonal patterns of abundance are presented for the tidal freshwater regions in two Virginia rivers based on data accumulated monthly from 1986 through 1999. Diatoms dominated the flora during spring, summer, and fall, whereas, other taxonomic categories were more representative when the river flow rates decreased, allowing for a more stable water system and increased residency time within this tidal region during summer and early fall. This summer/fall period was associated with increased water temperatures, higher productivity rates and chlorophyll levels, increased total phytoplankton abundance and species diversity. The major components of the summer …

Investigation Of The Superconducting Properties Of Niobium Radio-Frequency Cavities, Gianluigi Ciovati

Physics Theses & Dissertations

Radio-frequency (rf) superconducting cavities are widely used to increase the energy of a charged particle beam in particle accelerators. The maximum gradients of cavities made of bulk niobium have constantly improved over the last ten years and they are approaching the theoretical limit of the material. Nevertheless, rf tests of niobium cavities are still showing some "anomalous" losses (so-called "Q-drop"), characterized by a marked increase of the surface resistance at high rf fields, in absence of field emission. A low temperature "in-situ" baking under ultra-high vacuum has been successfully applied by several laboratories to reduce those losses and …

Loss, Attachment, And Place: A Case Study Of Grand Isle, Louisiana, David Burley, Pam Jenkins, Joanne Darlington, Brian Azcona

Reconstruction: Studies in Contemporary Culture

This study examines how residents of a Louisiana barrier island think about place in light of slow and rapid onset of coastal land loss. The island community has always faced change due to hurricanes, development, and erosion. Today the island, as well as the region, is faced with great environmental change due to coastal land loss. This paper uses a phenomenological approach to examine how change, caused by a range of environmental factors, is transmitted and understood by residents of Grand Isle, Louisiana. Residents convey a heightened awareness of place attachment, communicated through elements of fragility and uniqueness, that we …

Nurturing Sense Of Place Through The Literature Of The Bioregion, Patrick Howard

Reconstruction: Studies in Contemporary Culture

This paper explores the possibility that a participatory engagement with the literature of the bioregion, in this case the North Atlantic coast, may work against the life alienating tendencies of our modern culture, to reaffirm and renew our children’s consciousness of and sensitivity for their place in a larger Earth community. We are in need of another way of knowing our place, a way to activate and reactivate the complex articulations and relations of things. Through the literature of the bioregion and a bodily, imaginative and participatory engagement with the other-than-human, children can return to the conditions of human embeddedness …

Mobility-Pattern Based Localization Update Algorithm For Mobile Wireless Sensor Networks, Mohammad Yacoub Al-Laho

Electrical & Computer Engineering Theses & Dissertations

In mobile wireless sensor networks, sensors move in the monitored area at any direction and speed. Unlike many other networking hosts, sensor nodes do not have global addresses. They are often identified by using a location-based addressing scheme. Therefore, it is important to have the knowledge of the sensor location indicating where the data came from. In this thesis, three localization update algorithms were designed, Specifically, a sensor movement is divided into three states: Pause, Linear, and Random. Each state adopts different localization update algorithm. Since complex movement involves different mobility patterns, a state transition model is developed to …

Principal Component Regression For Construction Of Wing Weight Estimation Models, Humberto Rocha

Mathematics & Statistics Theses & Dissertations

The multivariate data fitting problem occurs frequently in many branches of science and engineering. It is very easy to fit a data set exactly by a mathematical model no matter how the data points are distributed. But building a response by using a limited number of poorly distributed data points is very unreliable, yet necessary in conceptual design process. This thesis documents the lessons learned from fitting the wing weight data of 41 subsonic transports by three types of interpolation methods---least polynomial interpolation, radial basis function interpolation, and Kriging interpolation. The objective of this thesis is to develop an automatic …

Investigation And Applications Of Latin Hypercube Sampling Methods, Prashant K. Patel

Mechanical & Aerospace Engineering Theses & Dissertations

The Latin hypercube sampling method, sometimes called the stratified sampling method, is a commonly used variance reduction method. Recently, the optimal Latin hypercube sampling method (OLH) and the modified optimal Latin hypercube sampling method (MOLH) are introduced in the literature, which use the genetic algorithm to adjust the distance between sampled points.

This paper will compare the basic Latin hypercube, the optimal Latin hypercube and the modified optimal Latin hypercube methods for generating the sample points for statistical application and curve fitting, in te1ms of accuracy and efficiency. Analytical and structural examples are used in this thesis to facilitate the …

Fine-Tuning Of Mass-Spring Model Properties For Simulating Realistic Soft Body Deformation, Sylva A. Girtelschmid

Computational Modeling & Simulation Engineering Theses & Dissertations

Obtaining a well behaved soft-tissue model is one of the most challenging and important tasks in the development of surgical simulation systems. Achieving both accurate and real-time deformation response from a soft-tissue model becomes more difficult as the complexity of the represented anatomy and the degree of deformation increases. One common approach to modeling deformable objects is the Mass-Spring (MS) system method. Mass-Spring systems are attractive to real-time applications due to their relatively low computational requirement and ease of implementation. However, their parameter determination is typically done manually, which becomes tedious when accurate approximation to real-world objects is desired. This …

Interannual Variation Of Stratification In Lower Chesapeake Bay, Christopher S. Katzenmiller

OES Theses and Dissertations

Stratification in the water column can prove to be an important indicator to the state of the water column and ecosystem. The focus of this research is to evaluate trends in stratification in the Lower Chesapeake Bay. Detailed analysis was performed on a 14 year data set to study interannual variation in the region of study. Potential energy anomaly was used to quantify stratification. Potential energy anomaly is the amount of energy required to mix a water column. It is determined from the vertical density structure of density. Potential energy anomaly is the departure of potential energy from climate conditions. …

Computational Sensing And Closed-Loop Active Flow Control Of Airfoil At Post-Stall Conditions, Volkan Kamaci

Mechanical & Aerospace Engineering Theses & Dissertations

Flow separation over lifting aerodynamic components, such as airfoils and wings, occurs during stall conditions which are caused by adverse changes (i.e. high angle of attack, inflow conditions, etc.) in the operating conditions of aerodynamic components. During stall conditions, the flow over airfoil loses its momentum, creating high pressure zones on the upper surface of the airfoil and even a small increase in pressure causes the fluid particles to stop and separate to a low pressure zone. In order to eliminate the flow separation, the low momentum flow should be removed in order to maintain the high momentum and low …