Physical Sciences and Mathematics Commons^™

The Distribution Of Airborne Coal Dust In Soil Profiles Of Norfolk, Va And Its Implication For Arsenic Loading To These Soils, William Joseph Bounds

OES Theses and Dissertations

Norfolk, Virginia is home to the Northern Hemisphere's largest coal terminal the Lamberts Point Docks. The coal loading process of this terminal creates large amounts of coal dust, which subsequently is distributed throughout the local region by atmospheric transport and deposition. While the coal dust itself poses only minor health hazards, certain trace elements within the coal, particularly arsenic, may pose environmental as well as significant health hazards. Within coal, arsenic occurs primarily in the mineral pyrite. As pyrite in the coal dust is subsequently oxidized via exposure to the atmosphere and/or meteoric water, arsenic may be released to the …

Hydrographic Variability On Decadal And Interdecadal Scales In The Northern Gulf Of Alaska, Nandita Sarkar

OES Theses and Dissertations

The mixed layer depth (MLD) in the North Pacific is important to vertical mixing and hence the flux nutrients into the euphotic zone. A time series of hydrographic measurements, tem perature and salinity versus depth, at a coastal site in the northern Gulf of Alaska is used to determine the seasonal and interannual variations in the MLD. Data from this station called GAK 1 (59°50.7‘X. 149C28.0'\V) in 203 m of water begin in 1974 and end in 1998. The MLD changes seasonally from about 50 m in summer to more than 130 m in winter. These changes are in response …

Dynamical Sedimentary Models Of Shallow Marine Environments, Yong Zhang

OES Theses and Dissertations

This treatise represents a contribution of quantitative, dynamical sedimentary modeling to the analytical understanding of sedimentary processes in shallow marine environments. The dynamical sedimentary models in this treatise numerically simulate the sedimentary processes from an event time scale, based on the fundamental physics of sediment dynamics in coastal and shelf depositional environments, to a longer, facies time scale. The simulated geologic processes serve to the illustrate shoreface equilibrium profile, shelf storm bed generation, and the shelf sedimentary facies system.

This treatise presents a nearshore profile evolution model for the abandoned Huanghe Delta, a two-dimensional storm deposition model, and a sedimentary …

Transverse Variability Of The Flow And Density In Inlets Of Southern Chile, Mario Arturo Cáceres Muñoz

OES Theses and Dissertations

Measurements of velocity and density profiles were made to describe the flow transverse structure in three inlets of southern Chile. The inlets show marked differences in their transverse dynamics in response to external forcing. In Aysen Fjord (45.2°S) the mean flow showed a three layer structure that was consistent with up-fjord wind-induced exchange, while in Chacao Channel (41.8°S), the mean flow exhibited predominantly a lateral structure that featured sharp velocity shears. In both cases, a bank in the center of the sections seemed to play an important role in shaping the mean flows. In Ventisquero Sound (44.4°S), the presence of …

Trichodesmium Spp.: Numerical Studies Of Resource Competition, Carbohydrate Ballasting, And Remote-Sensing Reflectance, Tonya Denise Clayton

OES Theses and Dissertations

In recent years, a new appreciation for the role of diazotrophy in the oceans has emerged. This dissertation reports on three modeling studies designed to investigate ecological processes associated with Trichodesmium spp., the most conspicuous marine diazotroph: (1) characterization of a generalized model Trichodesmium and issues of macronutrient resource competition; (2) carbohydrate ballasting by Trchodesmium and implications for the formation of surface accumulations; and (3) the vertical distribution of Trichodesmium and implications for detection from space.

The first study focuses on issues of nitrogen and phosphorus competition and ecosystem structure. It utilizes a simple ecosystem model that includes dissolved nitrogen …

Measurement Of The Gπnn(T) Form Factor, Kelly Gene Vansyoc

Physics Theses & Dissertations

Cross sections were measured for the reaction ¹H(e, e′π+) n at the energy W = 1.95 GeV and momentum transfer Q² = 0.6 (GeV/c)². At this W and Q², the longitudinal cross section is dominated by t-channel production, giving a unique opportunity to examine the strong coupling form factor gπNN(t). The measured cross sections were separated using a method similar to a Rosenbluth separation. For the extraction of gπNN(t), the Actor and Körner model [42] and a parameterization of the MAID2000 …

A Software Reliability Model Combining Representative And Directed Testing, Brian Michael Mitchell

Computer Science Theses & Dissertations

Traditionally, software reliability models have required that failure data be gathered using only representative testing methods. Over time, however, representative testing becomes inherently less effective as a means of improving the actual quality of the software under test. Additionally, the use of failure data based on observations made during representative testing has been criticized because of the statistical noise inherent in this type of data. In this dissertation, a testing method is proposed to make reliability testing more efficient and accurate. Representative testing is used early, when the rate of fault revelation is high. Directed testing is used later in …

The Implications Of The Target-Area Hypothesis On The Population Dynamics Of The Spotted Spiny Lobster, Panulirus Guttatus, Denice N. Robertson

Biological Sciences Theses & Dissertations

The target-area hypothesis, based on the theory of island biogeography, predicts that larger islands are more effective at intercepting passive immigrants. Most marine invertebrates have meroplanktonic larvae and open population dynamics, so immigration to populations in isolated benthic habitats is primarily by pelagic larval recruits. Thus, recruitment to isolated habitat “islands” may be more continuous and predictable on large islands than on small ones. Consequently, populations on large islands should not only be larger than those on small islands, but should also have more evenly distributed size structures. These differences in size structure among populations in isolated habitats of differing …

Effects Of Human Disturbances On The Behavior Of Dabbling Ducks, Melissa Lynn Pease

Biological Sciences Theses & Dissertations

Disturbance of wintering and migrating birds by human activities can cause birds to expend energy in avoidance of humans and reduces the time available for resting and feeding at a time in the annual cycle when fat deposition and energy conservation are important. Also, human disturbances can effectively cause habitat loss by displacing birds from feeding or resting habitat. Managers of natural resources are increasingly faced with decisions about the types and amounts of public use that should be allowed without lowering the value of the resource for wildlife. In order for managers to make decisions about how to minimize …

Morphostatic Long-Term Hypsometric Analysis Of Coastal Bay Environments: Hog Island Bay, Virginia, Kathleen Marie Overman

OES Theses and Dissertations

Sea level has been rising at a variable rate since the end of the last glaciation approximately 18,000 years ago. As the transgressing sea inundates the shore areas a series of landform state changes occur in coastal regions. One such change of state in a coastal paleo-river channel is from an estuary into a coastal lagoon. At large temporal intervals (thousands of years) the hypsometry of a coastal lagoon varies as a result of sea level rise due to these changes of state. Using a morphostatic technique, the time period in which an estuary transforms into a coastal lagoon can …

Coherent Differential Absorption Lidar For Combined Measurement Of Wind And Trace Atmospheric Gases, Grady James Koch

Electrical & Computer Engineering Theses & Dissertations

A lidar system was developed for making combined range-resolved measurements of wind speed and direction, water vapor concentration, and carbon dioxide concentration in the atmosphere. This lidar combines the coherent Doppler technique for wind detection and the differential absorption lidar (DIAL) technique to provide a multifunctional capability. DIAL and coherent lidars have traditionally been thought of and implemented as separate instruments, but the research reported here has shown a demonstration of combining the coherent and DIAL techniques into a single instrument using solid-state lasers. The lasers used are of Ho:Tm:YLF, which operates at a wavelength of 2 μm. This wavelength …

A Comparison Of Phytoplankton Communities In Lake Prince And The Western Branch Reservoir, Suffolk, Virginia, Cara Marie Muscio

Biological Sciences Theses & Dissertations

Lake Prince and the Western Branch Reservoir are two eutrophic bodies of water located in Suffolk, Virginia. Lake Prince and its two small tributaries join the Western branch via a constructed spillway. This lake system is a source of water for the surrounding municipalities, and a recreational area for community citizens. In the past, these bodies of water had repeated incidents of low oxygen and nuisance algal blooms, particularly cyanobacteria species. As a result aerators have been installed in the main body of both Lake Prince and the Western Branch Reservoir. In addition, a pipeline has been installed from North …

External Memory Algorithms For Factoring Sparse Matrices, Florin Dobrian

Computer Science Theses & Dissertations

We consider the factorization of sparse symmetric matrices in the context of a two-layer storage system: disk/core. When the core is sufficiently large the factorization can be performed in-core. In this case we must read the input, compute, and write the output, in this sequence. On the other hand, when the core is not large enough, the factorization becomes out-of-core, which means that data movement and computation must be interleaved.

We identify two major out-of-core factorization scenarios: read-once/write-once (R1/W1) and read-many/write-many (RM/WM). The former requires minimum traffic, exactly as much as the in-core factorization: reading the input and writing the …

Tidal And Subtidal Lateral Structures Of Density And Velocity In The Chesapeake Bay Entrance, Austreberto Cristobal Reyes-Hernandez

OES Theses and Dissertations

Hydrographic and velocity data collected along the Chesapeake Bay Entrance during seven 25-hours cruises centered around neap or spring tides, were used to assess the fortnightly variability in the transverse structure of the tidal and subtidal density and velocity fields. Amplitude and phase of the semidiurnal and diurnal harmonics reflected the influence of bathymetry, buoyancy conditions and fortnightly variability. Tidal amplitudes were almost twice as large in springs than in neaps. Both Chesapeake and North Channels had similar along-channel amplitudes, which suggested a higher vertically integrated mixing energy in North Channel. Tidal velocity convergences were more intense for springs than …

Coastal Ocean Morphodynamics And The Resulting Erosion And Deposition: An Analytical Approach, Shejun Fan

OES Theses and Dissertations

Coastal ocean morphodynamics is the study of the morphological change of the coastal ocean system. Environmental conditions, such as climatic and geological controls, are exogenous inputs of the system, which are responsible for geographic variation among coastal oceans. In the coastal ocean system, coastal morphological changes are the results of a series of morphodynamical processes. In this treatise, quantitative, dynamical sedimentary models are developed to provide an analytical understanding of morphodynamical processes in coastal ocean environments. These dynamical sedimentary models numerically simulate the sedimentary processes over a range of time scales from an event time scale, based on the fundamental …

Perceptual Cues And Subjective Organization In A Virtual Information Workspace, Todd M. Eischeid

Psychology Theses & Dissertations

The key to effectively using the immense body of data on the Internet is an efficient method of organizing relevant information. Researchers and designers are beginning to promote the advantages of three-dimensional (3D) models of information storage and retrieval; however, the potential benefits of perceptual depth cues have not been systematically studied.

The present study used a computer task to examine the effectiveness of three types of virtual desktops. A two-dimensional (2D) virtual desktop display, lacking in the cues that give the illusion of depth, was compared to two different 3D virtual desktops, both of which used perceptual cues to …

Mathematical Models Of Quiescent Solar Prominences, Iain Mckaig

Mathematics & Statistics Theses & Dissertations

Magnetic fields in the solar atmosphere suspend and insulate dense regions of cool plasma known as prominences. The convection zone may be the mechanism that both generates and expels this magnetic flux through the photosphere in order to make these formations possible. The connection is examined here by modeling the convection zone as both one-dimensional, then more realistically, two-dimensional.

First a Dirichlet problem on a semi-infinite strip is solved using conformal mapping and the method of images. The base of the strip represents the photosphere where a current distribution can be given as a boundary condition, and the strip extends …

New Sequential And Scalable Parallel Algorithms For Incomplete Factor Preconditioning, David A. Hysom

Computer Science Theses & Dissertations

The solution of large, sparse, linear systems of equations Ax = b is an important kernel, and the dominant term with regard to execution time, in many applications in scientific computing. The large size of the systems of equations being solved currently (millions of unknowns and equations) requires iterative solvers on parallel computers. Preconditioning, which is the process of translating a linear system into a related system that is easier to solve, is widely used to reduce solution time and is sometimes required to ensure convergence. Level-based preconditioning (ILU(ℓ)) has long been used in serial contexts and is widely recognized …