Physical Sciences and Mathematics Commons^™

Analysis Of (Iso)Surface Reconstructions: Quantitative Metrics And Methods, Tracey Allen Beauchat

Dissertations, Theses, and Masters Projects

Due to sampling processes volumetric data is inherently discrete and most often knowledge of the underlying continuous model is not available. Surface rendering techniques attempt to reconstruct the continuous model, using isosurfaces, from the discrete data. Therefore, it natural to ask how accurate the reconstructed isosurfaces are with respect to the underlying continuous model. A reconstructed isosurface may look impressive when rendered ("photorealism"), but how well does it reflect reality ("physical realism")?;The users of volume visualization packages must be aware of the short-comings of the algorithms used to produce the images so that they may properly interpret, and interact with, …

Surface Reflection Hyperthermal Neutral Stream Source, Christopher A. Nichols

Dissertations, Theses, and Masters Projects

A novel source of hyperthermal (1-30 eV) reactive neutrals based on the surface-reflection-neutralization technique is described. This source is potentially capable of minimizing the charge-induced damage associated with plasma based semiconductor processing steps. The goal of this thesis is to investigate the issues involved in scale-up of this technology for processing of 8{dollar}\sp{lcub}\prime\prime{rcub}{dollar} diameter wafers used today in the semiconductor industry. This includes modeling the plasma ion source and trajectory simulations of the reflected neutral flux. A prototype source was constructed for experimental verification of the plasma model.;An inductively coupled plasma (ICP) source is used to provide a source of …

A Grammar-Based Technique For Genetic Search And Optimization, Clayton Matthew Johnson

Dissertations, Theses, and Masters Projects

The genetic algorithm (GA) is a robust search technique which has been theoretically and empirically proven to provide efficient search for a variety of problems. Due largely to the semantic and expressive limitations of adopting a bitstring representation, however, the traditional GA has not found wide acceptance in the Artificial Intelligence community. In addition, binary chromosones can unevenly weight genetic search, reduce the effectiveness of recombination operators, make it difficult to solve problems whose solution schemata are of high order and defining length, and hinder new schema discovery in cases where chromosome-wide changes are required.;The research presented in this dissertation …

The Meteorological Effects Of The Kuwait Oil Fires, Patrick Kevin Dowling

Dissertations, Theses, and Masters Projects

No abstract provided.

Synthesis And Characterization Of Cyclic Arylene Ether Oligomers, David Lewis Eldridge

Dissertations, Theses, and Masters Projects

No abstract provided.

Low-Valent Metal Complexes As Reductive Coupling Agents For Smoke Suppression In Poly(Vinyl Chloride), Panagiotis Ioannou Kourtesis

Dissertations, Theses, and Masters Projects

No abstract provided.

Spectroscopic Characterization Of Hg(Ii) Coordination Complexes, Sharon Rosemary Fitzhenry

Dissertations, Theses, and Masters Projects

No abstract provided.

Synthesis And Characterization Of Poly(Carborane-Sulfone), Beth Le Ogura

Dissertations, Theses, and Masters Projects

No abstract provided.

Characterizing The Degradation Of Nylon-11 And Pvdf In A Flexible Oil Pipe And Cure Monitoring Of Chemflake Vinylester, John Chen Yang

Dissertations, Theses, and Masters Projects

No abstract provided.

Fate And Transport Processes For Polycyclic Aromatic Hydrocarbons In The Surface Microlayer Of Southern Chesapeake Bay, Kewen Liu

Dissertations, Theses, and Masters Projects

Surface microlayer (SM) samples were collected with a rotating cylinder sampler from the York and Elizabeth River estuaries of southern Chesapeake Bay every other month from May 1994 through June 1995. Total suspended particle concentration (TSP) concentrations in the SM were found to be up to 1000 times higher than in the corresponding subsurface water, and to be exponentially associated with the wind speed at sampling. A relatively larger POC/TN ratio in the Elizabeth River SM compared with that in the York River SM was also observed. No seasonal trends were noticed in the SM characteristics; however, TSP, POC, and …

User's Manual For The Environmental Fluid Dynamics Computer Code, John M. Hamrick

Reports

No abstract provided.

Status Of The Major Oyster Diseases In Virginia 1995 A Summary Of The Annual Monitoring Program, Lisa M. Ragone Calvo, Eugene M. Burreson

Reports

No abstract provided.

Analysis Of Temporal And Spatial Variations In Vegetation Communities For The Buxton Woods Region Of Cape Hatteras National Seashore, Marcia Berman, Gene Silberhorn, Carl Hershner

Reports

Residential development and growth along private lands bordering the southern portion of Cape Hatteras may be increasing at a rate inconsistent with the current water supply and demand. In the late 1960's and again in the late 1970's a series of wells were drilled to supply area residences and businesses with potable water from the local shallow water aquifer. Today, additional wells are being considered to serve the expanding community of Buxton Woods.

At the same time, the National Park Service maintains a series of ditches for both mosquito and flood control management. A large ditch which trends approximately northeast/southwest …

Preliminary Evaluation Of Water Quality In Tidal Creeks Of Virginia's Eastern Shore In Relation To Vegetable Cultivation, Mark W. Luckenbach, Morris H. Roberts Jr., Keith Boyd

Reports

In response to concerns raised about the impacts of vegetable cultivation using plastic ground covers on water quality, we have initiated a broad-scale, systematic study of water quality in seaside tidal creeks of Virginia' s Eastern Shore. Our objective was to determine if acute toxicity associated with heavy metals or pesticides was more prevalent in tidal creeks with drainage areas which include this agricultural practice than in those which do not. Though such correlations do not confirm cause and effect, they may serve as the basis for future, more targeted investigations and for some immediate changes in land management practices …

Effects Of Sand-Mining On Benthic Communities And Resource Value : Thimble Shoal, Lower Chesapeake Bay, Linda C. Schaffner, Michele A. Horvath, Carl H. Hobbs Iii

Reports

In August 1990 the City of Hampton placed approximately 276,000 cubic yards of sand from a designated borrow site on Thimble Shoal onto Buck:roe Beach for beach restoration. The Buck:roe reserve identified by Kimball et al. (1989) contains large quantities of beach quality material and is located less then 2.5 km offshore of Buck:roe Beach. In early 1989 a small section (330 m by 240 m) located in 5 m of water was delineated and permitted for dredging. This project represents the first instance of permitted, sand-mining activities for beach nourishment in the lower bay. Although the impacts of the …

Investigation Of Isolated Sand Shoals On The Inner Shelf Of Virginia Relative To The Potential For Aggregate Mining : Report On Task 4, Possible Physical Impact Of Dredging At Sandbridge Shoal Of The 1993-1995 U. S. Minerals Management Service - Commonwealth Of Virginia Cooperative Project, Jerome P.-Y. Maa

Reports

The Virginia Institute of Marine Science, together with other state agencies, has a continuing interest in preserving the coastline of Virginia, particularly, the Atlantic coastline in the vicinity of the resort city of Virginia Beach. Because a well maintained beach can serve several purposes, e.g., (1) providing public recreational areas, (2) protecting valuable properties that are located near coastline, and (3) reducing the rate of land loss, a great deal of efforts has been devoted to understand the processes that affect the change of shoreline. Among several erosion forces, waves are especially important elements as they can alter the shoreline …

Distribution Of Submerged Aquatic Vegetation In The Chesapeake Bay And Tributaries And Chincoteague Bay - 1994, R J. Orth, Judith F. Nowak, Gary F. Anderson, David J. Wilcox, Jennifer R. Whiting, Leah S. Nagy

Reports

No abstract provided.

Water!, Kirk J. Havens, Virginia Institute Of Marine Science, Wetlands Program

Reports

No abstract provided.

The Magnitude And Persistence Of Soil No, N2o, Ch4, And Co, Fluxes From Burned Tropical Savanna In Brazil, M Poth, Iris C. Anderson, Et Al

VIMS Articles

Among all global ecosystems, tropical savannas are the most severely and extensively affected by anthropogenic burning. Frequency of fire in cerrado,a type of tropical savanna covering 25% of Brazil, is 2 to 4 years. In 1992 we measured soil fluxes of NO, N2O, CH4, and CO2 from cerrado sites that had been burned within the previous 2 days, 30 days, 1 year, and from a control site last burned in 1976. NO and N2O fluxes responded dramatically to fire with the highest fluxes observed from newly burned soils after addition of water. Emissions of N-trace gases after burning were of …

Recurrences Associated With A Classical Orbit In The Node Of A Quantum Wave Function, John A. Shaw, John B. Delos, Michael Courtney, Daniel Kleppner

Arts & Sciences Articles

Absorption spectra of atoms in magnetic fields reveal recurrences: manifestations of classical orbits (or quantum wave packets) that go out from the atom and later return. A formula from closed-orbit theory asserts that if the orbit lies on a node of the outgoing wave function, then the strength of the recurrence is zero. New quantum calculations, however, show that the recurrence strength is nonzero, though small. We derive a semiclassical formula for the recurrence strength associated with a classical orbit at a node of the quantum wave function. This formula is compared to the quantum mechanical calculation. Compared to …

Organization Of Sequences Of Bifurcations Of Periodic Orbits, D. A. Sadovskii, J. A. Shaw, John B. Delos

Arts & Sciences Articles

Numerical calculations have shown that bifurcations of periodic orbits of Hamiltonian systems often occur in organized groups. Normal-form theory provides an explanation.

Public Beach Assessment Report Huntington Park, Anderson Park, And King-Lincoln Park City Of Newport News, Virginia, Donna A. Milligan, C. Scott Hardaway Jr., George R. Thomas

Reports

The City of Newport News has three public beaches within its limits: Huntington Park beach, Anderson Park beach, and King-Lincoln Park beach. Each beach and its associated park has undergone or is undergoing improvements. The purpose of this report is to assess the rates and patterns of beach change at these three public beaches. Field survey data, aerial photos, wave hindcasting data, and computer modelling were utilized for this report. The computer model used was RCPWAVE, a wave hydrodynamic model developed by the Corps of Engineers.

Current Measurements In The York River Near The Coleman Bridge, John M. Brubaker

Reports

In support of Tidewater Construction Corporation's project to widen the George P. Coleman Bridge, current measurements were conducted in the York River between Gloucester Point and Yorktown, Virginia, along both sides of the bridge. The objective was to sample the currents at approximately 10 feet below the water surface during maximum ebb and flood flow, at enough locations to resolve cross-river variations in the flow field. This objective was well satisfied with multiple surveys conducted during ebb, slack, and flood phases of the tidal flow, each survey providing current data at multiple depths. Significant cross-river variability was documented.

The Virginia Wetlands Report Vol. 10, No. 2, Virginia Institute Of Marine Science

Virginia Wetlands Reports

• Prothonotary Warbler. Julie G. Bradshaw
• Spanish Mackerel. Lyle Varnell
• Sixth Annual Virginia GIS Conference. Marcia Berman
• Washington and Wetlands: Where Do Things Stand? Wetlands and People. Pam Mason
• VIMS and DEQ Water Division Complete Joint Study of Nontidal Wetland Scientific Advisory Needs. Lyle Varnell and Thomas Barnard
• What are nonvegetated wetlands and why are they valuable?

Status Of The Major Oyster Diseases In Virginia 1994 A Summary Of The Annual Monitoring Program, Lisa M. Ragone Calvo, Eugene M. Burreson

Reports

No abstract provided.

Closed Orbit Bifurcations In Continuum Stark Spectra, Michael Courtney, Hong Jiao, Neal Spellmeyer, Daniel Kleppner, J. Gao, John B. Delos

Arts & Sciences Articles

We report an experimental and theoretical study of the effect of bifurcations of closed classical orbits in continuum Stark spectra. Our findings provide a natural way to understand how the spectrum evolves from a simple sinusoidal modulation at positive energy to a quasidiscrete spectrum below the classical ionization limit. The experiment employs scaled-energy spectroscopy of lithium. The results provide the first experimental confirmation of a formulation of closed-orbit theory that provides a quantitative description of the behavior of the spectrum at a bifurcation.

Ecotourism: Tripping With Mother Nature, Jill Barnard, Virginia Institute Of Marine Science, Wetlands Program

Reports

No abstract provided.

Semiclassical Treatment Of A Half-Cycle Pulse Acting On A One-Dimensional Rydberg Atom, C. D. Schwieters, John B. Delos

Arts & Sciences Articles

The final-state distribution of hydrogen, acted upon by a 1/2-cycle pulse, has been calculated semiclassically for a proposed one-dimensional experiment. This work was motivated by the recent experimental realization of half-cycle pulses by Jones, You, and Bucksbaum [Phys. Rev. Lett. 70, 1236 (1993)] in which preliminary studies of ionization and state redistribution for hydrogenlike atoms were carried out. To simplify the situation theoretically, an experiment is proposed in which an additional weak static electric field is imposed and approximately one-dimensional states are selected. Within this one-dimensional approximation the transition probability to various n states (n is the principal …

Half-Cycle Pulse Acting On A One-Dimensional Rydberg Atom: Semiclassical Transition Amplitudes In Action And Angle Variables, C. D. Schwieters, John B. Delos

Arts & Sciences Articles

In this paper we derive the expression for the transition coefficient used in the preceding paper [C. D. Schwieters and J. B. Delos, Phys. Rev. A 51, 1023 (1995)] for principal-quantum-number transitions in one-dimensional hydrogen caused by half-cycle pulses. We briefly review the methods of Miller [Adv. Chem. Phys. 25, 69 (1974)] and Marcus [Chem. Phys. Lett. 7, 525 (1970); J. Chem. Phys. 54, 3965 (1971)], and then derive the result using the methods of Maslov and Fedoriuk [Semi-Classical Approximation in Quantum Mechanics, (Reidel, Dordrecht, 1981)]. Also, we examine the approximate reduction of hydrogen …

The Virginia Wetlands Report Vol. 10, No. 1, Virginia Institute Of Marine Science

Virginia Wetlands Reports

• Louisiana Waterthrush. Julie G. Bradshaw
• American Eel. Lyle Varnell
• Comprehensive Coastal Inventory Develops New Tidal Wetlands Inventories. Marcia Berman
• Earthwatchers Witness Change in the Chesapeake. Jill Barnard
• Corrotoman River Nature Trail. Pam Mason
• Monkey Bottom Wetland Walkway: A Walk on the Wild Side. Jill Barnard
• Gapped Breakwaters. Walter I. Priest, III
• Why is riprap preferred over bulkheads?
• How do marsh grasses act to stabilize shorelines?