Physical Sciences and Mathematics Commons^™

Mat Movement In Coastal Louisiana Marshes: Effect Of Salinity And Inundation On Vegetation And Nutrient Levels, Christopher Martin Swarzenski

Biological Sciences Theses & Dissertations

The present research compared and contrasted the physical structure of floating and rooted marshes, their differing responses to open-water salinities and inundation, as well as the nutrient distribution in the porewaters and sediment. The effects of the physical differences in the two marsh types on the ocurrence of the dominant emergent vegetation was discussed.

The main difference in physical structure of the two marsh types was the presence of a mineral, non-buoyant layer at 25-45 cm depth in the rooted marsh, which could serve as an anchor for the overlying highly organic mat layer found in both marsh types. Porewater …

Visual Graphic Knowledge Management Methodology, Jih-Shih Hsu

Computer Science Theses & Dissertations

As computer technology evolves, graphic workstations are becoming more popular. They support more friendly user interfaces than do conventional terminals. The better user interfaces require more effort to develop. Therefore, many user interface (UI) design systems have been developed to facilitate the creation of modern user interfaces, but not very successfully. Many of them either provide limited features or are difficult to use. Besides, these UI design systems are actually like black boxes to their users because the underlying technology is opaque; their users cannot learn how to utilize the underlying window systems through user interface design sessions. In a …

Investigation Of Alignment Dynamics In Mg-Ne And Mg-Ar Two-Photon Fractional Collisions, David Allen Olsgaard

Physics Theses & Dissertations

A new technique is used to observe the dynamics of electronic alignment in a dissociating collision complex. The technique requires the absorption of two optical photons during a single binary collision. Two exciting light fields are tuned into the wings of the 3s¹s₀-3p₁ and 3p¹p₁-5s¹s₀ resonances of Mg where strong collisions with rare gas atoms induce transitions between corresponding molecular states. The alignment produced in the intermediate state by the first excitation is probed by the second laser as a function of relative linear laser polarization and laser …

Direct Measurement Of The Van Der Waals Interaction Between An Atom And Its Images In A Micron-Sized Cavity, V. Sandoghdar, C. I. Sukenik, E. A. Hinds, S. Haroche

Physics Faculty Publications

The authors have measured by laser spectroscopy the energy of interaction between a sodium atom and its images in the walls of a micron-sized cavity. This cavity-QED study is the first direct quantitative test of the Lennard-Jones van der Waals interaction as a function of controlled atom-surface separation and mean-square electric dipole moment.

Single Object Detection Using Multiple Sensors With Unknown Noise Distributions, Shaofen Chen

Computer Science Theses & Dissertations

We consider the design of an object classification system that identifies single objects using a system of sensors; each sensor outputs a random vector, according to an unknown (noise) probability distribution, in response to a sensed object. We consider a special class of systems, called the linearly separable systems, where the error-free sensor outputs corresponding to distinct objects can be mapped into disjoint intervals on real line. Given a set of sensor outputs corresponding to known objects, we show that a detection rule α_emp that approaches the correct rule with a high probability can be computed. We show …

The Growth And Bioenergetics Of Callinectes Sapidus Larvae And The Effects Of Diet Quality On Larval Physiology, James J. Pletl

OES Theses and Dissertations

Food quality, especially ω3 polyunsaturated fatty acids (PUFA), can affect the physiology and metabolic efficiency of larvae of the blue crab, Callinectes sapidus. These affects may correlate with success in development and juvenile recruitment.

Larvae were exposed to two diets differing quantitatively in ω3 PUFA and respiration, excretion, growth, and feeding rates were measured for each larval stage and the megalopal stage. The energy partitioned to molts and specific dynamic action was also measured. T

he ω3 PUFA enriched diet resulted in a lower respiration rate when compared to the unsupplemented diet, but there was little differences in excretion …

Relation Of Groundwater Fluoride Concentrations To Sediment Mineralogy, Potomac Formation (Cretaceous), Southeastern Virginia, Paul Anthony Maciuika

OES Theses and Dissertations

Thirty-seven Early cretaceous sediment samples of the Potomac Formation were obtained from four cores to determine if fluoride bearing minerals are responsible for elevated fluoride concentrations in Potomac Formation groundwaters of southeastern Virginia. Investigative methods included total sediment fluoride and particle size analysis, semiquantitative mineralogical analysis (achieved by X-Ray Diffraction) and statistical methods (cluster, canonical and regression analysis). The sediments showed wide variation in textures, ranging from clean sands and gravels to silty clays. Sediment mineralogies were dependent on the prevailing size fraction, with quartz and feldspar dominating the sand and silt fractions, muscovite primarily being found in the silt …

Biodegradation Of Crude Oil By Marine Higher Fungi, Brian J. Dyer

Biological Sciences Theses & Dissertations

Four experiments were performed to determine the ability of marine higher fungi to grow in and degrade crude oil. Eight species, previously determined to be hydrocarbonoclastic, were grown in artificial sea water medium (ASM) and southern Louisiana crude oil. The dry mycelial weights were measured and consumption of crude oil was measured gravimetrically. The two species with the best growth, Corollospora maritima and Zalerion maritimum, were grown in ASM containing crude oil spiked with three known hydrocarbons. To this was added glucose (0.15%) and incubated 49 days to test for possible cometabolism of hydrocarbons. Hydrocarbons remaining in the growth …

Hierarchical Flux-Based Thermal-Structural Finite Element Analysis Method, Sandra P. Polesky

Mechanical & Aerospace Engineering Theses & Dissertations

A hierarchical flux-based finite element method is developed for both one- and two-dimensional thermal-structural analyses. Derivation of the finite element equations is presented. The resulting finite element matrices associated with the flux-based formulation are evaluated in closed-form. The hierarchical finite elements include additional degrees of freedom in the approximation of the element variable distributions by the use of nodeless variables. The nodeless variables offer increased solution accuracy without the need for defining actual nodes and rediscretizing the finite element model. Thermal and structural responses obtained using the hierarchical flux-based method are compared with results obtained from a conventional linear finite …

Formant Estimation From Dctc's Using A Feedforward Neural Network, Shubhangi U. Kelkar

Electrical & Computer Engineering Theses & Dissertations

Formants are the natural frequencies of the human vocal tract. Existing methods for estimating formants from speech signals are computationally complex and subject to errors for certain type of speech sounds. This thesis describes a method for estimating vowel formant frequencies from Discrete Cosine Transform Coefficients (DCTC's), a form of cepstral coefficients, using a feedforward neural network with back-propagation training. Experimental results are based on a large multispeaker data base. The results are obtained for both a linear transformation and a feedforward neural network with a nonlinear hidden layer. In general, the neural network transformation is superior to the linear …

Evaluation Of Late Mesozoic And Cenozoic Tectonism: Atlantic Inner Coastal Plain Margin Near Richmond, Virginia, Andrew A. Gremos

OES Theses and Dissertations

A combined geologic, geophysical, and geomorphic analysis of the Virginia Inner Coastal Plain margin near Richmond was conducted to investigate the presence of basement structures and to evaluate their influence on the overlying sedimentary package and present-day landscape. Basement structures identified included north-northeast and northwest oriented faults that appear to bound and transect a north-northeast trending early Mesozoic basin or basins and other pre-existing zones of weakness. Observed offsets are propagated upward through the pre-Miocene strata in the form of reverse faults and flexuring. Fracture sets measured in the Petersburg Granite and overlying Coastal Plain units, stream drainage lines, and …

Factors Affecting The Kinetics Of Light Intensity Adaptation In Marine Phytoplankton, Chunzhi Guo

OES Theses and Dissertations

It has been suggested that the recent light history of phytoplankton and the kinetics of photoadaptation can be used to provide information about the vertical mixing processes in the upper mixed layer. To be useful as a parameter in a model of photoadaptation and vertical mixing, the response of a photoadaptive variable to changes in growth irradiance must be monotonic, significant, and comparable in time rate scale to mixing processes. Previous studies of photoadaptation kinetics have focused on the response of phytoplankton to changes in light intensity under continuous illumination. This dissertation attempts to elucidate the effects of light:dark cycle, …

Reasoning By Analogy In A Multi-Level System Architecture For The Design Of Mechanisms, Ghassan F. Issa

Computer Science Theses & Dissertations

Since the first attempts to integrate AI technology and engineering design nearly two decades ago, few expert systems have been shown to demonstrate sufficient reasoning capabilities to solve real-world design problems. The complex nature of design, the lack of understanding of the design process, and the limitations of current expert system technology have all been shown to have adverse effects on the maturity of this research area. Therefore, our direction in this research concentrates on understanding the design process, investigating a novel area of research focusing on creative design, and incorporating the results into a system model feasible for production …

Search For The Mössbauer Effect In 109ag, Shokrollah Rezaie-Serej

Physics Theses & Dissertations

The 88-keV first-excited nuclear state in ¹⁰⁹Ag has a mean lifetime of 57.1 sec and a corresponding natural linewidth of 1.15 x 10^-17 eV which is nearly six orders of magnitude narrower than the width for the 93-keV 13.2-μsec state in ⁶⁷Zn. The 93-keV transition in ⁶⁷Zn has the narrowest linewidth for which the Mossbauer effect has been observed. The 88-keV transition in ¹⁰⁹Ag is obviously a very difficult case for the observation of the Mossbauer effect and provides a stringent test for exploring the practical limits of inhomogeneous line broadening in real single …

Some Solutions To A Lens Model With Applications To Warm-Core Eddies, Juping Liu

OES Theses and Dissertations

A model of lens-shaped anticyclonic eddies based on nonlinear shallow water equations is developed. The model is a three-layer fluid and allows for one asymmetric mode as well as specified environmental flows. The solution scheme is a polynomial expansion of the field variables. When inserted into the hydrographic equations, the expansion yields eight first-order differential equations for the time dependent amplitudes. This system of ordinary differential equations is numerically tractable. As long as the initial values meet the requirement of elliptical structure and the prescribed external force is tolerable for the initial values, the numerical solutions are stable. Numerical solutions …

Ring Dynamics In The Western Gulf Of Mexico, Adolphe W. Indest

OES Theses and Dissertations

The interaction of a recently-formed Loop Current ring and a fossil ring is studied using observations and a two-layered eddy-resolving general circulation model of the Gulf of Mexico. This interaction is investigated by following the evolution of volume, energy, potential vorticity, angular momentum and enstrophy within a model ring as it moves westward and encounters a fossil ring along the continental slope of the Gulf of Mexico. By comparing the model results with drifter and hydrographic data several new insights into ring/ring and ring/slope interactions are seen. A Loop Current ring may merge with a fossil ring along the slope. …

Monitoring Computer Systems: An Intelligent Approach, Myron Zhihong Xu

Computer Science Theses & Dissertations

Monitoring modern computer systems is increasingly difficult due to their peculiar characteristics. To cope with this situation, the dissertation develops an approach to intelligent monitoring. The resulting model consists of three major designs: representing targets, controlling data collection, and autonomously refining monitoring performance. The model explores a more declarative object-oriented model by introducing virtual objects to dynamically compose abstract representations, while it treats conventional hard-wired hierarchies and predefined object classes as primitive structures. Taking the representational framework as a reasoning bed, the design for controlling mechanisms adopts default reasoning backed up with ordered constraints, so that the amount of data …

Density Effect In Cu K-Shell Ionization By 5.1-Gev Electrons, W. E. Meyerhof, D. G. Jensen, D. M. Kawall, S. E. Kuhn, D. W. Spooner, Z. E. Meziani, D.. N. Faust

Physics Faculty Publications

We have made an absolute measurement of the Cu K-shell impact ionization cross section by 5.1-GeV electrons, which demonstrates directly a density effect predicted by Fermi in 1940. By determining the ratio of the K x-ray yield from a thin front and back layer of the target by a novel grazing emission method, we have verified the effect of transition radiation on the x-ray production, suggested by Sorensen and reported by Bak et al.

Energetic Protons And Deuterons Emitted Following Μ⁻ Capture By ³He Nuclei, W. J. Cummings, G. E. Dodge, S. S. Hanna, B. H. King, S. E. Kuhn, Y. M. Shin, R. Helmer, R. B. Schubank, N. R. Stevenson, U. Wienands, Y. K. Lee, G. R. Mason, B. E. King, K. S. Chung, J. M. Lee, D. P. Rosenzweig

Physics Faculty Publications

Spectra of energetic protons and deuterons emitted following negative muon capture from rest in ³He have been measured for the first time. Significant capture strength is observed at high energy transfers (mμ- E_v >60 MeV) for the two-body and three-body breakup channels, indicative of the importance of nucleon-nucleon correlations and meson exchange currents in the capture process. A simple plane wave impulse approximation calculation reproduces the proton spectrum reasonably well, but underpredicts the deuteron rate at the highest energies by a large factor.

A Tree Representation For P4-Sparse Graphs, B. Jamison, Stephan Olariu

Computer Science Faculty Publications

A graph G is P₄-sparse if no set of five vertices in G induces more than one chordless path of length three. P₄-sparse graphs generalize both the class of cographs and the class of P₄-reducible graphs. We give several characterizations for P₄-sparse graphs and show that they can be constructed from single-vertex graphs by a finite sequence of operations. Our characterization implies that the P₄-sparse graphs admit a tree representation unique up to isomorphism. Furthermore, this tree representation can be obtained in polynomial time.

On Sources In Comparability Graphs, With Applications, Stephan Olariu

Computer Science Faculty Publications

We characterize sources in comparability graphs and show that our result provides a unifying look at two recent results about interval graphs.

A Charming Class Of Perfectly Orderable Graphs, Chinh T. Hoang, Frederic Maffray, Stephan Olariu, Myriam Preissmann

Computer Science Faculty Publications

We investigate the following conjecture of Vašek Chvátal: any weakly triangulated graph containing no induced path on five vertices is perfectly orderable. In the process we define a new polynomially recognizable class of perfectly orderable graphs called charming. We show that every weakly triangulated graph not containing as an induced subgraph a path on five vertices or the complement of a path on six vertices is charming.

The Morphology Of Convex Polygons, Stephan Olariu

Computer Science Faculty Publications

A simple polygon P is said to be unimodal if for every vertex of P, the Euclidian distance function to the other vertices of P is unimodal. The study of unimodal polygons has emerged as a fruitful area of computational and discrete geometry. We study unimodality properties of a number of special convex polygons from the morphological point of view. In particular, we establish a hierarchy among three classes of convex polygons in terms of their unimodality properties.

Distribution Of Foraminifera And Pollen In Coastal Depositional Environments Of The Southern Delmarva Peninsula, Virginia, U.S.A., Han Jun Woo

OES Theses and Dissertations

The coastal zone of the southern Delmarva Peninsula exhibits a wide variety of barrier island system subenvironments. This study investigates whether 20 a priori subenvironments can be distinguished from each other on the basis of abiotic environmental variables, pollen assemblages, living foraminiferal populations, and total (living plus dead) foraminiferal assemblages.

The physical data collected from the coastal zone were subjected to canonical variate analysis which discriminated 83% of the stations in 19 groups. These groups were clustered into two internally overlapping sets which represented the inside and outside of the inlet.

Twenty-two pollen types were found in low-energy marsh and …

High Performance Issues In Image Processing And Computer Vision, Jingyuan Zhang

Computer Science Theses & Dissertations

Typical image processing and computer vision tasks found in industrial, medical, and military applications require real-time solutions. These requirements have motivated the design of many parallel architectures and algorithms. Recently, a new architecture called the reconfigurable mesh has been proposed. This thesis addresses a number of problems in image processing and computer vision on reconfigurable meshes.

We first show that a number of low-level descriptors of a digitized image such as the perimeter, area, histogram and median row can be reduced to computing the sum of all the integers in a matrix, which in turn can be reduced to computing …

Diapycnal Mixing And Mass Transfer In Western Boundary Currents, Jose Luis Pelegri Llopart

OES Theses and Dissertations

The distribution of nutrient flux in five sections across the Gulf Stream (from the Florida Straits of 35°W) is characterized by an intense core, centered at the depth of the 26.8 σ_t isopycnal surface. This 'Nutrient Stream' transports nutrients of O(10³ kmol s^-1} of nitrate and proportional amounts of other nutrients. Water mass and nutrient balances of nine isopycnal layers reveal significant diapycnal mixing between upper-thermocline and surface waters in the sector of the Stream between the Florida Straits and the Mid-Atlantic Bight. A two-box model of the nutrient-depleted surface layers (σ_t < 26.8) and the nutrient-rich thermocline layers (26.8< σ_t < 27.5) shows upward one-way transfer and two-way exchange, both at a a rate at about 1.m²s …

Smimd - A Synchronous Multiple Instruction Multiple Data Computer Architecture, Cathy C. Roberts

Computer Science Theses & Dissertations

This thesis assesses the feasibility of utilizing a hypercube interconnect topology to link a heterogeneous processor array in a very long instruction word (VLIW) computer architecture. The research focused upon the selection of a suitable arrangement of processors for the computer and the subsequent demonstration of the architecture's capability to handle simple loop iterations. Previous attempts at VLIW computer design are summarized, the new SMIMD architecture is presented, and suggestions for future research are given. The thesis concludes with results of the initial performance evaluations of the architecture design.

A Numerical Study Of The Variability And The Separation Of The Gulf Stream, Induced By Surface Atmospheric Forcing And Lateral Boundary Flows, Tal Ezer, George L. Mellor

CCPO Publications

A primitive equation model is used to study the effects of surface and lateral forcing on the variability and the climatology of the Gulf Stream system. The model is an eddy-resolving, coastal ocean model that includes thermohaline dynamics and a second-order turbulence closure scheme to provide vertical mixing. The surface forcing consists of wind stress and heat fluxes obtained from the Comprehensive Ocean-Atmosphere Data Set (COADS). Sensitivity studies are performed by driving the model with different forcing (e.g., annual versus zero surface forcing or monthly versus annual forcing). The model climatology, obtained from a five-year simulation of each case, is …

Effects Of Wind, Density, And Bathymetry On A One-Layer Southern Ocean Model, John M. Klinck

CCPO Publications

Steady solutions from a one-layer, wind-driven, primitive equation model are analyzed to determine the importance of wind forcing, pressure gradient force due to the climatological density distribution and bottom form drag on circulation in the Southern Ocean. Five simulations are discussed: three wind-forced simulations, with differing bathymetry (flat bottom, 15% bathymetry, and full bathymetry), one case with full bathymetry forced with the density-induced pressure force, and one case with full bathymetry forced by both wind and density-induced pressure gradients. The simulations presented here confirm the previous speculation (Munk and Palmen, 1951) that form drag is effective in balancing the driving …

Molecular And Physiological Responses Of Diatoms To Variable Levels Of Irradiance And Nitrogen Availability: Growth Of Skeletonema Costatum In Simulated Upwelling Conditions, G. Jason Smith, Richard C. Zimmerman, Randall S. Alberte

OES Faculty Publications

Molecular mechanisms that drive metabolic acclimation to environmental shifts have been poorly characterized in phytoplankton. In this laboratory study. the response of light- and N-limited Skeletonema costatum cells to an increase in light and NO₃ availability was examined. C assimilation was depressed relative to N assimilation early in enrichment, and the photosynthetic quotient (O₂: CO₂) increased, consistent with the shunting of reducing equivalents from CO₂ fixation to NO₃- reduction. The concomitant increase in dark respiration was consistent with the increased energetic demand associated with macromolecular synthesis. The accelerations of N-specific rates of …