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Articles 5521 - 5550 of 5948
Full-Text Articles in Physical Sciences and Mathematics
Estimates Of Spawning Stock Size Of Blue Crab, Callinectes Sapidus, In Chesapeake Bay, 1986-1987, Cynthia M. Jones, John R. Mcconaugha, Patrick J. Geer, Michael H. Prager
Estimates Of Spawning Stock Size Of Blue Crab, Callinectes Sapidus, In Chesapeake Bay, 1986-1987, Cynthia M. Jones, John R. Mcconaugha, Patrick J. Geer, Michael H. Prager
OES Faculty Publications
The 1986 spawning stock exhibited a single abundance peak, increasing from 1.0×105 individuals in early July to 9.3×106 in late July, maintaining high levels throughout the summer, and declining in the fall to 7.4×105 individuals. The 1987 spawning stock showed 2 peaks of abundance. The population reached the lesser peak, 1.0×106 individuals, in late July; the greater peak, 1.5×106, in late August. By late September, the population had declined to 6.5×105 individuals. The peak abundance of the 1987 female spawning stock was only 16% as great as the peak abundance in 1986; the 1987 spawning stock size in 1986. Variability …
Fecundity Of Blue Crab, Callinectes Sapidus, In Chesapeake Bay: Biological, Statistical And Management Considerations, Michael H. Prager, John R. Mcconaugha, Cynthia M. Jones, Patrick J. Geer
Fecundity Of Blue Crab, Callinectes Sapidus, In Chesapeake Bay: Biological, Statistical And Management Considerations, Michael H. Prager, John R. Mcconaugha, Cynthia M. Jones, Patrick J. Geer
OES Faculty Publications
Ovigerous blue crabs were collected from the mouth of Chesapeake Bay during the 1986 and 1987 spawning seasons. Mean carapace width was 14.7 cm; mean fecundity was 3.2×106 eggs. Fecundity was significantly related to carapace width, and did not vary significantly with developmental stage of the eggs. Mean fecundities were 2.6×106 eggs in 1986, and 4.0×106 eggs in 1987. An additive model with year and size effects described the observed fecundities reasonably well, was compact, and was easier to interpret than a multiplicative model. To fit a more general model without year effects, the authors took the mean of 1986 …
A Model Of Dc Glow Discharges With Abnormal Cathode Fall, Karl H. Schoenbach, Hao Chen, G. Schaefer
A Model Of Dc Glow Discharges With Abnormal Cathode Fall, Karl H. Schoenbach, Hao Chen, G. Schaefer
Bioelectrics Publications
A model for an abnormal glow discharge, including a self‐consistent analysis of the cathode fall, was developed. It combines microscopic particle simulation by means of Monte Carlo methods with a fluid model of the gas discharge. The model allows calculations of the steady‐state electrical field distribution, the charged‐particle densities, and the current densities along the axis of the discharge. The model was used to simulate a glow discharge in 80% He and 20% SF6 at a pressure of 8 Torr with a current density of 1 A/cm2. The computed discharge voltage agrees well with measured values. The …
A Characterization Of The Solution Of A Fredholm Integral Equation With L∞ Forcing Term, Hideaki Kaneko, Richard Noren, Yuesheng Xu
A Characterization Of The Solution Of A Fredholm Integral Equation With L∞ Forcing Term, Hideaki Kaneko, Richard Noren, Yuesheng Xu
Mathematics & Statistics Faculty Publications
In this paper we investigate the regularity properties of the Fredholm equation (Formula Presented) . The kernel is the product of the smooth function k and the singular function gα (Formula Presented). The forcing function f is in L∞. We obtain a decomposition of the solution as the sum of two functions—one with a discontinuity reflecting that of the forcing function—and the other a regular function. Our results extend those of C. Schneider [6], who assumes a condition that is stronger than f ∈ C[a, b] ∩ Cm(a,b) (for some integer m). © 1990 …
The Effects Of Variable Parameters On The Behavior Of Initial Wind Waves, Glen Harvey Wheless
The Effects Of Variable Parameters On The Behavior Of Initial Wind Waves, Glen Harvey Wheless
OES Theses and Dissertations
The generation mechanism of short wind waves is generally thought to be a viscous instability at the air-sea interface. The short, regular waves arising from a sudden wind on a still water surface have a dispersion relation which is characteristic of gravity-capillary waves. The effects of variable surface tension, viscosity and shear flow parameters on the behavior of these waves were studied.
A numerical hydrodynamic stability analysis of a coupled laminar shear flow was accomplished by integrating a transformed version of the Orr-Sommerfeld equation, subject to the boundary conditions at a two-fluid interface. Unbounded growth problems usually encountered in a …
Middle Eocene Foraminifera From The Piney Point Formation Of The Virginia And Maryland Coastal Plain, Megan S. Jones
Middle Eocene Foraminifera From The Piney Point Formation Of The Virginia And Maryland Coastal Plain, Megan S. Jones
OES Theses and Dissertations
This study examines the foraminiferal fauna, both benthic and planktonic, of the outcropping (45 samples) and subsurface (31 samples) middle Eocene Piney Point Formation in Virginia and Maryland. The primary objective of this study is to further refine the depositional history of the Salisbury Embayment which is represented by the middle Eocene Piney Point Formation. Ninety-six species of benthic and planktonic foraminifera were identified in this study. Of these, several are characteristic of the middle Eocene: Asterigerina texana, Hanzawaia danvillensis, Ceratobulimina exima, Cibicides westi, Chiloguembelitria columbiana, C. stavensis, Testacarinata inconspicua and Pseudohastigerina wilcoxensislmicra. While these were relatively abundant, diagnostic middle …
Efficient Schemes To Evaluate Transaction Performance In Distributed Database Systems, R. Mukkamala, S. C. Bruell
Efficient Schemes To Evaluate Transaction Performance In Distributed Database Systems, R. Mukkamala, S. C. Bruell
Computer Science Faculty Publications
Database designers and researchers often need efficient schemes to evaluate transaction performance. In this paper, we chose two important performance measures: the average number of nodes accessed and the average number of data items accessed per node by a transaction in a distributed database system. We derive analytical expressions to evaluate these metrics. For general applicability, we consider partially replicated distributed database systems. Our first set of analytic results are closed-form expressions for these two measures. These are based on some fairly restrictive simplifying assumptions. When these assumptions are relaxed, no closed-form expressions exist for these averages. Hence, we develop …
Wings And Perfect Graphs, Stephan Olariu
Wings And Perfect Graphs, Stephan Olariu
Computer Science Faculty Publications
An edge uv of a graph G is called a wing if there exists a chordless path with vertices u, v, x, y and edges uv, vx, xy. The wing-graph W(G) of a graph G is a graph having the same vertex set as G; uv is an edge in W(G) if and only if uv is a wing in G. A graph G is saturated if G is isomorphic to W(G). A star-cutset in a graph G is a non-empty set of …
Construction Of The Best Monotone Approximation On Lp [0, 1], J. J. Swetits, S. E. Weinstein
Construction Of The Best Monotone Approximation On Lp [0, 1], J. J. Swetits, S. E. Weinstein
Mathematics & Statistics Faculty Publications
(First paragraph) For 1 ≤ p < ∞, let Lp, denote the Banach space of pth power Lebesgue integrable functions on [0, l] ∥ƒ∥p = (∫¹₀∣ƒ∣ p)1/p Let Mp denote the set of nondecreasing functions in Lp. For l < p < ∞ , each ƒ∊Lp has a unique best approximation from Mp, while, for p = 1, existence of a best approximation from M1 follows from Proposition 4 of [6].
Measurement Of Magnetic Fluctuations By O-X Mode Conversion, L. L. Vahala, G. Vahala, N. Bretz
Measurement Of Magnetic Fluctuations By O-X Mode Conversion, L. L. Vahala, G. Vahala, N. Bretz
Electrical & Computer Engineering Faculty Publications
The possibility of measuring magnetic fluctuations in a fusion plasma is considered by examining the O→X mode conversion. Under certain conditions and with good angular resolution, this mode conversion can be attributed to the presence of magnetic fluctuations even though the level of these fluctuations is much lower than that of density fluctuations. Some nonideal effects such as mode polarization mismatch at the plasma edge are also discussed.
Influence Of Copper Doping On The Performance Of Optically Controlled Gaas Switches, St. T. Ko, V. K. Lakdawala, K. H. Schoenbach, M. S. Mazzola
Influence Of Copper Doping On The Performance Of Optically Controlled Gaas Switches, St. T. Ko, V. K. Lakdawala, K. H. Schoenbach, M. S. Mazzola
Electrical & Computer Engineering Faculty Publications
The influence of the copper concentration in silicon-doped gallium arsenide on the photoionization and photoquenching of charge carriers was studied both experimentally and theoretically. The studies indicate that the compensation ratio (NCu/NSi) is an important parameter for the GaAs:Si:Cu switch systems with regard to the turn-on and turn-off performance. The optimum copper concentration for the use of GaAs:Si:Cu as an optically controlled closing and opening switch is determined.
Application Of The Results Of Carbon Pellet Modeling To The Problem Of Plasma Penetration, L. L. Vahala, A. G. El Cashlan, G. A. Gerdin, P. B. Parks
Application Of The Results Of Carbon Pellet Modeling To The Problem Of Plasma Penetration, L. L. Vahala, A. G. El Cashlan, G. A. Gerdin, P. B. Parks
Electrical & Computer Engineering Faculty Publications
The assumptions of the evaporation model for low-Z pellets interacting with magnetic fusion plasmas developed by Parks are tested. These assumptions are that the vapor density profile in the region adjacent to the pellet surface falls off with radial distance as r-α , where 5 <α<6, and that the ionization time for the transition between charge states זf (i.e., for r < ~3 sonic radii). The first assumption is tested by solving a two-parameter eigenvalue problem for the evaporation cloud in the region interior to the sonic radius; the results are found to be consistent with the low-Z evaporation model. The second assumption, that זzi «זf, is tested at the sonic radius using the results from atomic physics and the low-Z evaporation model. It is found that indeed זzi «זf for plasmas with parameters close to thermonuclear conditions (e.g. CIT), but not for those of smaller Tokamaks such as …6,>
A Generalization Of Linear Multistep Methods, Leon Arriola
A Generalization Of Linear Multistep Methods, Leon Arriola
Mathematics & Statistics Theses & Dissertations
A generalization of the methods that are currently available to solve systems of ordinary differential equations is made. This generalization is made by constructing linear multistep methods from an arbitrary set of monotone interpolating and approximating functions. Local truncation error estimates as well as stability analysis is given. Specifically, the class of linear multistep methods of the Adams and BDF type are discussed.
An Extension Of Essentially Non-Oscillatory Shock-Capturing Schemes To Multi-Dimensional Systems Of Conservation Laws, Jay Casper
Mathematics & Statistics Theses & Dissertations
In recent years, a class of numerical schemes for solving hyperbolic partial differential equations has been developed which generalizes the first-order method of Godunov to arbitrary order of accuracy. High-order accuracy is obtained, wherever the solution is smooth, by an essentially non-oscillatory (ENO) piecewise polynomial reconstruction procedure, which yields high-order pointwise information from the cell averages of the solution at a given point in time. When applied to piecewise smooth initial data, this reconstruction enables a flux computation that provides a time update of the solution which is of high-order accuracy, wherever the function is smooth, and avoids a Gibbs …
Performance Improvements For Fddi And Csma/Cd Protocols, David Earl Game
Performance Improvements For Fddi And Csma/Cd Protocols, David Earl Game
Computer Science Theses & Dissertations
The High-Performance Computing Initiative from the White House Office of Science and Technology Policy has defined 20 major challenges in science and engineering which are dependent on the solutions to a number of high-performance computing problems. One of the major areas of focus of this initiative is the development of gigabit rate networks to be used in environments such as the space station or a National Research and Educational Network (NREN).
The strategy here is to use existing network designs as building blocks for achieving higher rates, with the ultimate goal being a gigabit rate network. Two strategies which contribute …
Lithofacies Of The Pliocene Yorktown Formation In The Vicinity Of Kingsmill On The James River, Virginia, Michael David Lawless
Lithofacies Of The Pliocene Yorktown Formation In The Vicinity Of Kingsmill On The James River, Virginia, Michael David Lawless
OES Theses and Dissertations
The Yorktown Formation beds which crop out along the James River in southeastern Virginia near Kingsmill and Carter's Grove are lithologically described in order to compare them with the "typical" Yorktown beds upriver in the area of Fort Boykins, Rushmere, and Cobham Wharf. Thirty-four stratigraphic sections are constructed of the bluffs along the river. The Yorktown beds in the area of Kingsmill and Cobham Wharf are divided into ten lithofacies: the silty sand facies (B), the Chesapecten facies (C), the Glycymeris facies (D), the Chama facies (E), the glauconitic biofragmental sand facies (F), the laminated silty clay facies (G), the …
Nonlinear Solutions To A Two-Layer Quasi-Geostrophic Model Of The Gulf Stream, Eiichi Oka
Nonlinear Solutions To A Two-Layer Quasi-Geostrophic Model Of The Gulf Stream, Eiichi Oka
OES Theses and Dissertations
The Gulf Stream shows a large meander off Cape Hatteras. This is driven by an energy conversion process known as baroclinic instability and observations suggest that nonlinearity is an important part in this process. In order to understand the fundamental role of nonlinearity in baroclinic instability, an inviscid 2-layer quasi-geostrophic model is studied.
The linear solution is obtained by methods of normal mode and Fourier-Laplace transforms. It is found that the set corresponding to the continuous spectrum is null and the set corresponding to the discrete spectrum is complete.
The nonlinear solution is expanded in terms of the complete set …
Identification And Quantitation Of Volatile Amines In Marine Sediments, Chuen Mei Huang
Identification And Quantitation Of Volatile Amines In Marine Sediments, Chuen Mei Huang
Chemistry & Biochemistry Theses & Dissertations
Pore waters which were taken from sediments of the Chesapeake Bay were analyzed to determine the presence of volatile amines. A purge-and-trap technique was used to concentrate the amines. Then, following derivatization with heptaflourobutyric anhydride, the HFBA-amines were analyzed by gas chromatography with electron capture detection and with mass spectrometric detection. One secondary amine, diethylamine with a concentration of 0.3-0.6 uM, was found in a total of three pore water samples from cores collected on two different dates. A primary amine, sec-butylamine with a concentration of O. 05 AIM, was also found in one of these same samples. Another primary …
A Geophysical Study Of The Easternmost Piedmont: Brunswick County, Virginia, Mark A. Corbin
A Geophysical Study Of The Easternmost Piedmont: Brunswick County, Virginia, Mark A. Corbin
OES Theses and Dissertations
Gravity and magnetic models indicate that a steeply dipping, mylonitic shear zone recognized by reconnaissance mapping in the easternmost Piedmont of Brunswick County, Virginia is a listric fault. A pronounced 3 to 5 mgal Bouguer anomaly high is associated with the fault zone. A band of N10° trending aeromagnetic anomalies delineate the areal extent of the fault zone. The fault zone flattens eastward over a short distance to a depth of 15 kms where it joins a near horizontal surface that cuts across the region. This surface is herein interpreted to be a decollement. The fault zone of this study …
Optical Machine Recognition Of Lower-Case Greek Characters Of Any Size, Ivan X. D. D'Cunha
Optical Machine Recognition Of Lower-Case Greek Characters Of Any Size, Ivan X. D. D'Cunha
Electrical & Computer Engineering Theses & Dissertations
An algorithm utilizing a syntactic approach and a criterion based on normalized moments is defined for the reliable, automatic, machine recognition of handwritten and printed Greek characters of any size and font. In this approach a binary image of the character in question is obtained initially; its skeleton is then produced by utilizing a standard thinning algorithm. The classification process then incorporates the topological features of the characters such as existence of closed curves, number of intersections, number and location of free ends, axial symmetry, and the criteria derived from normalized moments to uniquely identify each pattern. Experiments conducted demonstrated …
The Geomorphology And Surficial Geology Of The West Flank Of The Blue Ridge, Sherando Area, Virginia, Derek Weston Ryter
The Geomorphology And Surficial Geology Of The West Flank Of The Blue Ridge, Sherando Area, Virginia, Derek Weston Ryter
OES Theses and Dissertations
The west flank of the Blue Ridge near Sherando, Virginia (Augusta County) consists of many landforms including talus slopes, bedrock cliffs, boulder streams, colluvial slopes, residual knobs, and debris fans. The purpose of this study is to describe the geomorphic history of the area by understanding the spatial and temporal relationships between landforms on the hillslopes.
Boulder streams (maximum 30 m wide, 400 m long, 6.1 m thick) exhibit a gently dipping imbricated fabric and basal shear stresses of 0.1 to 0.4 bars.
Debris fans in Group L (lower) and Group U (upper) are distinguished by topographic position, degree of …
Simultaneous Determination Of 3-Methoxy-4-Hydroxyphenyl-Glycol, Homovanillic Acid, And 5-Hydroxyindoleacetic Acid In Plasma By High Performance Liquid Chromatography, Yung-Te Tseng
Chemistry & Biochemistry Theses & Dissertations
A rapid, reliable, and sensitive method for simultaneous determination of 3-methoxy-4-hydroxyphenylglycol (MHPG), Homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5- HIAA) in plasma is described. The method is based on high performance liquid chromatography with electrochemical detection. Samples were filtered with Amicon Centrifree micropartition systems and extracted with organic solvent before chromatography. Chromatographic separation of sample components was achieved isocratically in a C18 reverse-phase column. Quantitation was performed by measuring the peak height ratios of the sample components to an internal standard. Analytical recoveries ranged from 50.78 (SD 4.2%) to 67.94 (SD 3.28). Within-run coefficient of variations (CVs) ranged from 3.78 …
The Temporal And Spatial Distribution Of Blue Crab Larvae On The Mid-Atlantic Bight Adjacent To The Chesapeake Bay, 1982-1983, Lyle Michael Varnell
The Temporal And Spatial Distribution Of Blue Crab Larvae On The Mid-Atlantic Bight Adjacent To The Chesapeake Bay, 1982-1983, Lyle Michael Varnell
OES Theses and Dissertations
Recruitment processes are important information for the management of commercially and recreationally exploited marine species. Recruitment processes of the Chesapeake Bay's most important commercial and recreational species, the blue crab, are unknown, due in part to the lack of knowledge of the processes directly preceeding recruitment.
The present study was undertaken to investigate and explain the movement and developmental patterns of blue crab larvae while offshore. Interannual and intraseasonal variations of these patterns were also examined.
Sampling occurred from May to November during 1982 and 1983. Larvae were collected at three depths (neuston layer (upper 10 cm), one meter and …
Nuclear Fragmentation Energy And Momentum Transfer Distributions In Relativistic Heavy-Ion Collisions, Ferdous Khan
Nuclear Fragmentation Energy And Momentum Transfer Distributions In Relativistic Heavy-Ion Collisions, Ferdous Khan
Physics Theses & Dissertations
An optical model description of energy and momentum transfer in relativistic heavy-ion collisions, based upon composite particle multiple scattering theory, is presented. Transverse and longitudinal momentum transfers to the projectile are shown to arise from the real and absorptive part of the optical potential, respectively. Comparisons of fragment momentum distribution observables with experiments are made and trends outlined based on our knowledge of the underlying nucleon-nucleon interaction. Corrections to the above calculations are discussed. Finally, use of the model as a tool for estimating collision impact parameters is indicated.
Detection Of Outliers And Influential Observations In Regression Models, Anwar M. Hossain
Detection Of Outliers And Influential Observations In Regression Models, Anwar M. Hossain
Mathematics & Statistics Theses & Dissertations
Observations arising from a linear regression model, lead one to believe that a particular observation or a set of observations are aberrant from the rest of the data. These may arise in several ways: for example, from incorrect or faulty measurements or by gross errors in either response or explanatory variables. Sometimes the model may inadequately describe the systematic structure of the data, or the data may be better analyzed in another scale. When diagnostics indicate the presence of anomalous data, then either these data are indeed unusual and hence helpful, or contaminated and, therefore, in need of modifications or …
Mathematical Models Of Prevascular Tumor Growth By Diffusion, Sophia A. Maggelakis
Mathematical Models Of Prevascular Tumor Growth By Diffusion, Sophia A. Maggelakis
Mathematics & Statistics Theses & Dissertations
A study of several complementary mathematical models that describe the early, prevascular stages of solid tumor growth by diffusion under various simplifying assumptions is presented. The advantage of these models is that their degree of complexity is relatively low, which ensures fairly straightforward comparisons with experimental or clinical data (as it becomes available), yet they are mathematically sophisticated enough to capture the main biological phenomena of interest.
The tumor growth and cell proliferation rate are assumed to depend on the local concentrations of nutrients and inhibitory factors. The effects of geometry and spatially non-uniform inhibitor production and non-uniform nutrient consumption …
Best Approximation With Geometric Constraints, Yuesheng Xu
Best Approximation With Geometric Constraints, Yuesheng Xu
Mathematics & Statistics Theses & Dissertations
This is a study of best approximation with certain geometric constraints. Two major problem areas are considered: best Lp approximation to a function in Lp (0,1) by convex functions, (m, n)-convex functions, (m, n)-convex functions and (m, n)-convex splines, for 1 < p < ∞ , and best uniform approximation to a continuous function by convex functions, quasi-convex functions and piecewise monotone functions.
The Remipedia (Crustacea): A Study Of Their Reproduction And Ecology, Jill Yager
The Remipedia (Crustacea): A Study Of Their Reproduction And Ecology, Jill Yager
Biological Sciences Theses & Dissertations
Remipedes are an unusual group of troglobitic crustaceans that live exclusively in anchialine caves. Since their discovery in 1979, nine species have been described, seven of which are found in caves in the West Indies, one from the Yucatan peninsula of Mexico and one from the Canary Islands. Most of what is known about these animals has come mainly from taxonomic descriptions. Little has been published about their reproductive biology or ecology. The objectives of this dissertation were to investigate the reproductive biology and ecology of the remipedes inhabiting Sagittarius Cave on Grand Bahama Island, Bahamas.
Sagittarius Cave was chosen …
Mounting Sex Pheromone: A Novel Pheromone Responsible For Mate Recognition In The Ixodidae, Jgc Hamilton
Mounting Sex Pheromone: A Novel Pheromone Responsible For Mate Recognition In The Ixodidae, Jgc Hamilton
Theses and Dissertations in Biomedical Sciences
Cholesterol oleate was demonstrated to be the cuticular contact sex pheromone of Dermacentor variabilis. This pheromone which has been termed the Mounting Sex Pheromone (MSP) was also demonstrated to be present on the surface of D. andersoni, Amblyomma maculatum and A. americanum. This contact sex pheromone enables males excited and attracted by 2,6-dichlorophenol to identify the female as a potential mating partner. The MSP is the second in the series of three sex pheromones guiding the hierarchy of behavioral responses which constitute tick courtship behavior. Tests with D. variabilis and D. andersoni showed that this pheromone …
Picoplankton/Phytoplankton Dynamics In Hampton Roads, Virginia, Leslie E. Dorworth
Picoplankton/Phytoplankton Dynamics In Hampton Roads, Virginia, Leslie E. Dorworth
OES Theses and Dissertations
The biomass distribution of the three main size components of the phytoplankton (net, nano, and picoplankton) was examined in the lower Chesapeake Bay. Work was done at two stations during the spring and neap tidal cycles when freshwater flow into the bay was at its seasonal minimum and maximum. Emphasis was placed on how the picoplankton ( < 2.0 μm, > 0.2 μm) reacted during the sampling period.
Picoplankton made up approximately 13% of the total biomass, during the observed time period, at the more oceanic station. The picoplankton fraction contributed up to 16% of the total biomass at the estuarine station. From this …