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Articles 1 - 30 of 43
Full-Text Articles in Physical Sciences and Mathematics
In-Situ Frequency-Dependent Electromagnetic Sensing For Monitoring Physical And Chemical Attributes During Chemical Processing, Jeffrey David Rogozinski
In-Situ Frequency-Dependent Electromagnetic Sensing For Monitoring Physical And Chemical Attributes During Chemical Processing, Jeffrey David Rogozinski
Dissertations, Theses, and Masters Projects
The objective of this research was to develop an in-situ sensing technique that monitors the molecular-level response of ions and dipoles to an applied electric field in order to characterize the changes in state of a polymer resin during chemical processing. This technique needs to be capable of monitoring the reaction progress not only in the laboratory setting but also in-situ in the processing tool or reaction environment. Frequency Dependent Electromagnetic Sensing (FDEMS) was selected for this task.;This dissertation investigates the applicability of FDEMS to monitoring two types of processing methods: reactive and batch reactor. The reactive processing system examined …
The Use Of Long-Lived Tracer Observations To Examine Transport Characteristics In The Lower Stratosphere, Gretchen Scott Lingenfelser
The Use Of Long-Lived Tracer Observations To Examine Transport Characteristics In The Lower Stratosphere, Gretchen Scott Lingenfelser
Dissertations, Theses, and Masters Projects
No abstract provided.
Bioremediation Of Tributyltin Contaminated Sediment Using Spartina Alterniflora In A Created Tidal Wetland, Britt-Anne Anderson
Bioremediation Of Tributyltin Contaminated Sediment Using Spartina Alterniflora In A Created Tidal Wetland, Britt-Anne Anderson
Dissertations, Theses, and Masters Projects
No abstract provided.
Population Dynamics Of The Smooth Dogfish, Mustelus Canis, In The Northwest Atlantic, Christina L. Conrath
Population Dynamics Of The Smooth Dogfish, Mustelus Canis, In The Northwest Atlantic, Christina L. Conrath
Dissertations, Theses, and Masters Projects
No abstract provided.
Organic Matter Composition Of Sediments And The History Of Eutrophication And Anoxia In The Mesohaline Chesapeake Bay, Andrew R. Zimmerman
Organic Matter Composition Of Sediments And The History Of Eutrophication And Anoxia In The Mesohaline Chesapeake Bay, Andrew R. Zimmerman
Dissertations, Theses, and Masters Projects
To evaluate the effects of anthropogenic alteration of the Chesapeake Bay (CB) watershed since European settlement, the historical progression of eutrophication and anoxia in the mesohaline region of CB was reconstructed. Lipid biomarker and carbon and nitrogen stable isotopic and elemental composition of CB surficial sediments were examined seasonally in order to identify the present sources of organic matter to CB sediments and the processes controlling their distribution. Temporal variability in surficial sediment composition could be linked to seasonal changes in phytoplankton community composition and biomass while spatial variation was dominated by the delivery of alloclithonous versus autochthonous sources of …
The Human Factor In Size Selectivity In The Sea Scallop, Placopecten Magellanicus Fishery, Arman O. Kaltayev
The Human Factor In Size Selectivity In The Sea Scallop, Placopecten Magellanicus Fishery, Arman O. Kaltayev
Dissertations, Theses, and Masters Projects
No abstract provided.
Data Structures For The Analysis Of Large Structured Markov Models, Andrew S. Miner
Data Structures For The Analysis Of Large Structured Markov Models, Andrew S. Miner
Dissertations, Theses, and Masters Projects
High-level modeling formalisms are increasingly popular tools for studying complex systems. Given a high-level model, we can automatically verify certain system properties or compute performance measures about the system. In the general case, measures must be computed using discrete-event simulations. In certain cases, exact numerical analysis is possible by constructing and analyzing the underlying stochastic process of the system, which is a continuous-time Markov chain (CTMC) in our case. Unfortunately, the number of states in the underlying CTMC can be extremely large, even if the high-level model is "small". In this thesis, we develop data structures and techniques that can …
Theoretical And Experimental Study Of Generation Mechanisms For Laser Ultrasound In Woven Graphite /Epoxy Composites With Translaminar Stitching, Adam D. Friedman
Theoretical And Experimental Study Of Generation Mechanisms For Laser Ultrasound In Woven Graphite /Epoxy Composites With Translaminar Stitching, Adam D. Friedman
Dissertations, Theses, and Masters Projects
The aerospace industry is beginning to use advanced composite materials for primary load bearing structures and their failure mechanisms must be better understood to predict their behavior in service. The Combined Loads Tests (COLTS) facility is being constructed at the NASA Langley Research Center to characterize these failure mechanisms. Laser based ultrasonic NDE can monitor the samples during dynamic loading without interfering with the structural tests. However, the constraints of implementing laser ultrasound in a structures laboratory reduces the efficiency of the technique. The system has to be "eye-safe" because many people will be present during the structural tests. Consequently, …
The Absorption Spectrum Of The Hydrogen Atom In Crossed Electric And Magnetic Fields, Dongmei Wang
The Absorption Spectrum Of The Hydrogen Atom In Crossed Electric And Magnetic Fields, Dongmei Wang
Dissertations, Theses, and Masters Projects
This dissertation reports the theoretical interpretation of the measured absorption spectrum of hydrogen atoms in crossed electric and magnetic fields. Closed-orbit theory is modified from two-dimensions to three-dimensions to interpret the large scale structure in the absorption spectrum. A new computational method---a Chirped-Fourier-Transform---is developed to extract the closed orbits from an energy spectrum. A quantitative model is provided to calculate the continuum absorption. We prove that the observed continuum absorption is proportional to the flux of electrons along trajectories which escape within a short time. Einstein-Brillouin-Keller (EBK) quantization theory is applied to obtain an approximate energy spectrum. Our results prove …
Assessment Of Spawning And Nursery Habitat Suitability For American Shad (Alosa Sapidissima) In The Mattaponi And Pamunkey Rivers, Donna Marie Bilkovic
Assessment Of Spawning And Nursery Habitat Suitability For American Shad (Alosa Sapidissima) In The Mattaponi And Pamunkey Rivers, Donna Marie Bilkovic
Dissertations, Theses, and Masters Projects
Delineation of essential fish habitat is particularly difficult for migratory fish which utilize large expanses of habitat throughout their life history. This study's main objective was the development and evaluation of habitat assessment tools for the early life stages of American shad (Alosa sapidissima) in two coastal plain rivers. to accomplish this, shad spawning and larval nursery habitats were delineated in the Mattaponi and Pamunkey rivers using presence of eggs and larvae (1997--1999) as evidence of habitat use. A watershed habitat assessment protocol was developed and used to rate habitat based on hydrographic, physical habitat, shoreline and land use parameters. …
Osteology, Phylogeny, And Biogeography Of The Marine Fish Family Ephippidae (Perciformes, Acanthuroidei), With Comments On Sister Group Relationships, Martin Ray Cavalluzzi
Osteology, Phylogeny, And Biogeography Of The Marine Fish Family Ephippidae (Perciformes, Acanthuroidei), With Comments On Sister Group Relationships, Martin Ray Cavalluzzi
Dissertations, Theses, and Masters Projects
The marine fish family Ephippidae comprises eight genera and 15 species of extant fishes. Spadefishes or batfishes inhabit nearshore tropical to temperate waters. They are almost circumglobal in distribution, with the highest diversity in the Indo-west Pacific and the lowest diversity in the east Pacific and west Atlantic. Fifty-nine potentially informative morphological characters, 10 outgroup taxa, and eight ingroup taxa (i.e., genera) were used to explore sister group hypotheses to the Ephippidae, as well as generate a phylogeny of the Ephippidae. Seven constraint tree analyses were utilized to examine various sister group hypotheses based on previous morphological and molecular analyses …
Application Of Genetic Markers To Provide Species Identification And Define Stock Structure: Analyses Of Selected Marine Fishes Of The Mid -Atlantic Bight, Jan F. Cordes
Dissertations, Theses, and Masters Projects
Molecular markers and techniques were employed to develop a genetic key for the forensic identification of 16 species of Chesapeake Bay sportfishes and to investigate the stock structure of one of those species, the weakfish Cynoscion regalis. Regions within the ATP synthetase 6 (ATPase 6), Cytochrome b , cytochrome c oxidase I, NADH dehydrogenase 4 (ND4), and 12S/16S ribosomal RNA mitochondrial genes were amplified using the polymerase chain reaction (PCR) and digested with a bank of restriction endonucleases to find a genetic marker that exhibited complete interspecific differentiation and low intraspecific variation. Complete separation of all sixteen species was accomplished …
Synoptic Scale Climatic Forcing Of Multispecies Fish Recruitment Patterns In Chesapeake Bay, Robert J. Wood
Synoptic Scale Climatic Forcing Of Multispecies Fish Recruitment Patterns In Chesapeake Bay, Robert J. Wood
Dissertations, Theses, and Masters Projects
Five fishery independent data sets were used to investigate multispecies fish recruitment patterns in Chesapeake Bay (1966--1997). Despite differences in sampling gear, sampled habitat, collection methods, and sampling sites, the strongest multispecies recruitment patterns within each data set (revealed by separate principal components analyses) depict a negative relationship between recruitment of spring spawning anadromous fishes and fall-winter continental shelf spawning species. This pattern dominates both low and high frequency components of the multispecies data. Because these two species groups utilize freshwater and oligohaline reaches of the Bay and its tributaries as springtime nursery areas, this Chesapeake Bay Anadromous-Shelf Spawner (CBASS) …
Across-Shelf Sediment Transport Modeling And Its Application To Storms At Duck, North Carolina, Guan-Hong. Lee
Across-Shelf Sediment Transport Modeling And Its Application To Storms At Duck, North Carolina, Guan-Hong. Lee
Dissertations, Theses, and Masters Projects
To understand the morphodynamics of the inner shelf, a benthic boundary layer tripod supporting 6 point-measuring current meters, an acoustic Doppler current profiler, and three near-bed profiling acoustic backscatter sensors documented storm and swell conditions during October, 1996, at a depth 13 in on the inner shelf off Duck, North Carolina. The relationship between eddy viscosity and eddy diffusivity during storm and swell conditions was examined using data collected in October 1996 on the inner shelf off Duck, NC. Sediment suspension models, including Rouse-type diffusion models, combined advection and diffusion models, and a Rouse model with a thickened wave boundary …
Carbon Dynamics In A Tidal Freshwater Marsh, Scott C. Neubauer
Carbon Dynamics In A Tidal Freshwater Marsh, Scott C. Neubauer
Dissertations, Theses, and Masters Projects
The sources and fates of carbon in a tidal freshwater marsh (Sweet Hall marsh; Pamunkey River, Virginia) were determined to understand the role that these marshes play with respect to estuarine carbon cycling. A carbon gas flux model, based on measured carbon dioxide and methane fluxes, was developed to calculate annual rates of macrophyte and microalgal photosynthesis and community and belowground respiration. Because carbon fluxes out of marsh sediments may underestimate true belowground respiration if sediment-produced gases are transported through plant tissues, gross nitrogen mineralization was used as a proxy for belowground carbon respiration. Annual community respiration exceeded gross photosynthesis, …
Effects Of Polychlorinated Biphenyl Exposure On Development And Sexual Differentiation In Ranid Tadpoles, Mary J. Rybitski
Effects Of Polychlorinated Biphenyl Exposure On Development And Sexual Differentiation In Ranid Tadpoles, Mary J. Rybitski
Dissertations, Theses, and Masters Projects
The effects of AroclorRTM1242 exposure on developing amphibians were examined by exposing southern leopard frogs, Rana sphenocephala, to a contaminated diet throughout the larval period. Treatment groups consisted of an untreated control, a solvent control, 17beta-estradiol, and three PCB doses (10, 100, and 1000 mug/g). PCB accumulation and biotransformation were examined. Effects of PCB exposure on metamorphosis and sexual differentiation were assessed. PCB accumulation was not statistically different between the egg masses. Levels of PCBs in the tissues differed in a dose related manner. Within treatments, body weight appeared to be the major factor correlated with PCB concentration. Congener patterns …
Ecological Interactions Between Benthic Oyster Reef Fishes And Oysters, Juliana Maria Harding
Ecological Interactions Between Benthic Oyster Reef Fishes And Oysters, Juliana Maria Harding
Dissertations, Theses, and Masters Projects
Restoration of oyster reef structures rehabilitates habitats and the multi-level ecological communities built on eastern oysters (Crassostrea virginica), the keystone species. Quantitative descriptions of ecological interactions within a habitat are required to delineate essential fish habitats for management and protection. Parallel development of primary (oysters) and secondary trophic levels (benthic fishes) offer an ecological metric of restoration progress over time. The interaction between larval oysters and larval fishes (e.g., Gobiosoma bosc, Chasmodes bosquianus) is quantitatively examined. Oyster settlement estimates for Palace Bar reef, Piankatank River, Virginia are of the same order of magnitude as field densities of recently settled oysters. …
Photosynthetic Response And Nutrient Uptake Dynamics Of Phytoplankton In The Ross Sea, Antarctica, Christina Marie Van Hilst
Photosynthetic Response And Nutrient Uptake Dynamics Of Phytoplankton In The Ross Sea, Antarctica, Christina Marie Van Hilst
Dissertations, Theses, and Masters Projects
No abstract provided.
The Habitat Utilization Of Juvenile Hawksbill Sea Turtles (Eretmochelys Imbricata) At Buck Island Reef National Monument, St Croix, U.S Virgin Islands, Roy A. Pemberton
The Habitat Utilization Of Juvenile Hawksbill Sea Turtles (Eretmochelys Imbricata) At Buck Island Reef National Monument, St Croix, U.S Virgin Islands, Roy A. Pemberton
Dissertations, Theses, and Masters Projects
No abstract provided.
A Framework For Construction And Analysis Of Juvenile Abundance Indices For American Shad (Alosa Sapidissima) In The York River, Virginia, Mary Lynn Aiken
A Framework For Construction And Analysis Of Juvenile Abundance Indices For American Shad (Alosa Sapidissima) In The York River, Virginia, Mary Lynn Aiken
Dissertations, Theses, and Masters Projects
No abstract provided.
Efficiency Of Pound-Net Cull Panels: A Comparison Of Size Selectivity And Relative Release For Weakfish (Cynoscion Regalis) And Summer Flounder (Paralichthys Dentatus), Christian Harding Hager
Efficiency Of Pound-Net Cull Panels: A Comparison Of Size Selectivity And Relative Release For Weakfish (Cynoscion Regalis) And Summer Flounder (Paralichthys Dentatus), Christian Harding Hager
Dissertations, Theses, and Masters Projects
No abstract provided.
Microgeographic Population Genetic Structure Of The Mummichog (Fundulus Heteroclitus L) Inhabiting An Industrialized Waterway, Luis Felipe Arzayus
Microgeographic Population Genetic Structure Of The Mummichog (Fundulus Heteroclitus L) Inhabiting An Industrialized Waterway, Luis Felipe Arzayus
Dissertations, Theses, and Masters Projects
No abstract provided.
Biology Of The Spotted Seatrout, Cynoscion Nebulosus, In The Chesapeake Bay Region, Thomas F. Ihde
Biology Of The Spotted Seatrout, Cynoscion Nebulosus, In The Chesapeake Bay Region, Thomas F. Ihde
Dissertations, Theses, and Masters Projects
No abstract provided.
Sand- And Clay-Size Mineralogy Of The Ganges And Brahmaputra Rivers: Records Of River Switching And Late-Quaternary Climate Change, David Carlson Heroy
Sand- And Clay-Size Mineralogy Of The Ganges And Brahmaputra Rivers: Records Of River Switching And Late-Quaternary Climate Change, David Carlson Heroy
Dissertations, Theses, and Masters Projects
No abstract provided.
Seasonal Residence, Movement, And Activity Patterns Of Adult Tautog, Tautoga Onitis, In Lower Chesapeake Bay, Michael D. Arendt
Seasonal Residence, Movement, And Activity Patterns Of Adult Tautog, Tautoga Onitis, In Lower Chesapeake Bay, Michael D. Arendt
Dissertations, Theses, and Masters Projects
No abstract provided.
Characterization Of Iron-Bearing Solids Used By Naturally-Occurring Microbes In The Anaerobic Degradation Of Hydrocarbons, David C. Powell
Characterization Of Iron-Bearing Solids Used By Naturally-Occurring Microbes In The Anaerobic Degradation Of Hydrocarbons, David C. Powell
Dissertations, Theses, and Masters Projects
No abstract provided.
Maturation And Repeat Spawning By American Shad In The York River, Virginia, Kristin L. Maki
Maturation And Repeat Spawning By American Shad In The York River, Virginia, Kristin L. Maki
Dissertations, Theses, and Masters Projects
No abstract provided.
Structural Instabilities In Strontium Titanate From First-Principles Calculations, Christopher A. Lasota
Structural Instabilities In Strontium Titanate From First-Principles Calculations, Christopher A. Lasota
Dissertations, Theses, and Masters Projects
For some time now, first-principles calculation methods have proven to be an effective tool for investigating the physics of condensed matter systems. The additional use of density functional theory (DFT) and the local density approximation (LDA) has permitted even complex materials to be studied on desktop workstations with remarkable success. The incorporation of linear response theory into these methods has extended their power, allowing investigation of important dynamical properties.;Contained within the following pages are the results of a first-principles study of SrTiO3. This transition metal oxide is often grouped with ferroelectric materials, due to its similar composition and perovskite structure. …
Routing And Wavelength Assignment In Wdm Optical Networks, Guangzhi Li
Routing And Wavelength Assignment In Wdm Optical Networks, Guangzhi Li
Dissertations, Theses, and Masters Projects
In this thesis, we focus on the routing and wavelength assignment problems in WDM all-optical networks. Since the general problem is difficult (NP-complete), we classify the problem into several models with different formulations. Our objectives are to analyze some subclasses of routing and wavelength assignment problems; to understand their special properties; to estimate algorithm bounds and performance; and, to design efficient heuristic algorithms. These goals are important because results that follow can help engineers design efficient network topologies and protocols, and eventually provide end-users with cost-effective high bandwidth.;We first study the off-line wavelength assignment problem in single fiber ring and …
An Interactive Simulation Environment For End-To-End Digital Imaging System Design And Fidelity Analysis, Moira Joyce Turner
An Interactive Simulation Environment For End-To-End Digital Imaging System Design And Fidelity Analysis, Moira Joyce Turner
Dissertations, Theses, and Masters Projects
The detailed specification, implementation, and documentation of an interactive software environment based on a continuous/discrete/continuous imaging system model is presented. The purpose of the interactive environment is to support the design and performance analysis of end-to-end digital imaging systems. Development of the environment is based on the objectives of acceptable response time, large sampling grid capability, good graphical user interface design, independence from proprietary applications and portability among UNIX workstations. While one-dimensional variations of interactive design environments have been developed by the commercial active filter design community, there is little or no evidence that the increased complexity associated with the …