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Articles 511 - 540 of 1876
Full-Text Articles in Physical Sciences and Mathematics
First-Principles Calculations Of Nuclear Magnetic Resonance Chemical Shielding Tensors In Complex Ferroelectric Perovskites, Daniel Lawrence Pechkis
First-Principles Calculations Of Nuclear Magnetic Resonance Chemical Shielding Tensors In Complex Ferroelectric Perovskites, Daniel Lawrence Pechkis
Dissertations, Theses, and Masters Projects
Nuclear magnetic resonance (NMR) spectroscopy is one of the most important experimental probes of local atomistic structure, chemical ordering, and dynamics. Recently, NMR has increasingly been used to study complex ferroelectric perovskite alloys, where spectra can be difficult to interpret. First-principles calculations of NMR spectra can greatly assist in this task. In this work, oxygen, titanium, and niobium NMR chemical shielding tensors, s&d4; , were calculated with first-principles methods for ferroelectric transition metal prototypical ABO3 perovskites [SrTiO3, BaTiO 3, PbTiO3 and PbZrO3] and A(B,B')O3 perovskite alloys Pb(Zr1/2Ti1/2)O3 (PZT) and Pb(Mg1/3Nb2/3)O3 (PMN). The principal findings are 1) a large anisotropy between …
The Influence Of Golf Course Landscapes On The Occupancy And Reproductive Success Of Eastern Bluebirds, Marie Louise Pitts
The Influence Of Golf Course Landscapes On The Occupancy And Reproductive Success Of Eastern Bluebirds, Marie Louise Pitts
Dissertations, Theses, and Masters Projects
No abstract provided.
Treatment Of Synchronizations In Compiling Fine-Grained Spmd-Threaded Programs For Cpu, Ziyu Guo
Treatment Of Synchronizations In Compiling Fine-Grained Spmd-Threaded Programs For Cpu, Ziyu Guo
Dissertations, Theses, and Masters Projects
No abstract provided.
The Total Synthesis Of The Lolium Alkaloids, Michael Todd Hovey
The Total Synthesis Of The Lolium Alkaloids, Michael Todd Hovey
Dissertations, Theses, and Masters Projects
No abstract provided.
Search For Effects Beyond The Born Approximation In Polarization Transfer Observables In Ep Elastic Scattering, Mehdi Meziane
Search For Effects Beyond The Born Approximation In Polarization Transfer Observables In Ep Elastic Scattering, Mehdi Meziane
Dissertations, Theses, and Masters Projects
Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, GE/GM, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange (TPEX) contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, this thesis reports measurements, of the GEp2gamma experiment, of polarization transfer observables in the elastic H ( e&ar;,e' p&ar; ) reaction for three different beam energies at a fixed squared momentum transfer Q² = 2.5 GeV², spanning a wide range …
An Interoperable And Secure Architecture For Internet-Scale Decentralized Personal Communication, David Alan Bryan
An Interoperable And Secure Architecture For Internet-Scale Decentralized Personal Communication, David Alan Bryan
Dissertations, Theses, and Masters Projects
Interpersonal network communications, including Voice over IP (VoIP) and Instant Messaging (IM), are increasingly popular communications tools. However, systems to date have generally adopted a client-server model, requiring complex centralized infrastructure, or have not adhered to any VoIP or IM standard. Many deployment scenarios either require no central equipment, or due to unique properties of the deployment, are limited or rendered unattractive by central servers. to address these scenarios, we present a solution based on the Session Initiation Protocol (SIP) standard, utilizing a decentralized Peer-to-Peer (P2P) mechanism to distribute data. Our new approach, P2PSIP, enables users to communicate with minimal …
The Life History Of Longnose Gar, Lepisosteus Osseus, An Apex Predator In The Tidal Waters Of Virginia, Patrick E. Mcgrath
The Life History Of Longnose Gar, Lepisosteus Osseus, An Apex Predator In The Tidal Waters Of Virginia, Patrick E. Mcgrath
Dissertations, Theses, and Masters Projects
Longnose gar (Lepisosteus osseus) inhabit all of the major tributaries of Chesapeake Bay in Virginia, extending from fresh to estuarine waters. Literature concerning longnose gar from tidal environments is limited and this is study concerns important aspects of the life history (e.g., growth, reproduction, dimorphism, movements, and diet). Age, growth, and reproduction are important life history aspects for understanding the biology of fishes and may be affected by the environment in which an individual lives. This study found no differences in the age, growth, and fecundity parameters between longnose gar from tidal portions of Chesapeake Bay tributaries and previous studies …
Incorporating Industry Based Dredge Surveys Into The Assessment Of Sea Scallops, Placopecten Magellanicus, David B. Rudders
Incorporating Industry Based Dredge Surveys Into The Assessment Of Sea Scallops, Placopecten Magellanicus, David B. Rudders
Dissertations, Theses, and Masters Projects
Cooperative research utilizing industry vessels represents a viable approach to acquire the data necessary to meet the increasing needs associated with the modern management of marine resources. This dissertation addresses a variety of topics associated with the integration of commercial vessels into the stock assessment of the sea scallop, Placopecten magellanicus. In this study we evaluate the efficacy of utilizing industry vessels with respect to topics that range from rotational closed area survey design, sampling gear evaluation as well as an experiment that broadens the scale of the traditional use of industry vessels in this fishery and provides data to …
The Role Of Copepods And Heterotrophic Dinoflagellates In The Production Of Dissolved Organic Matter And Inorganic Nutrients, Grace Kathleen Saba
The Role Of Copepods And Heterotrophic Dinoflagellates In The Production Of Dissolved Organic Matter And Inorganic Nutrients, Grace Kathleen Saba
Dissertations, Theses, and Masters Projects
Zooplankton play a key role in the cycling of dissolved organic matter (DOM) and inorganic nutrients. The factors that affect these processes, however, are not fully understood. I measured the effects of various diets on DOM and inorganic nutrient production by the copepod Acartia tonsa and the heterotrophic dinoflagellate Oxyrrhis marina, and explored the mechanisms of nutrient release from copepods. Copepods feeding on a mixed diet, the preferred diet of most copepods, had significantly lower dissolved organic carbon (DOC), ammonium (NH4+), and total dissolved nitrogen (TDN) release rates compared to feeding on a carnivorous or herbivorous diet. Thus, copepod feeding …
Accounting For Undesirable Outputs In Productivity Measurements: Application To The California-Oregon Drift Gillnet Fishery, Tara L. Scott
Accounting For Undesirable Outputs In Productivity Measurements: Application To The California-Oregon Drift Gillnet Fishery, Tara L. Scott
Dissertations, Theses, and Masters Projects
Many production activities typically produce undesirable outputs, e.g., the production of the pollutant sulfur dioxide in the generation of electricity. Traditional economic metrics may overstate the efficiency and productivity of these production activities by failing to account for the undesirable outputs. These omissions can lead to conclusions that are biased against resource conservation and protection. Many fisheries capture their target species concomitantly with undesirable outputs such as bycatch of juvenile fish, marine mammals, sea birds, and sea turtles. One such fishery is the California-Oregon (CA/OR) drift gillnet fishery (DGNF), which incidentally takes protected species, such as sea turtles and marine …
Towards Secure Message Systems, Mengjun Xie
Towards Secure Message Systems, Mengjun Xie
Dissertations, Theses, and Masters Projects
Message systems, which transfer information from sender to recipient via communication networks, are indispensable to our modern society. The enormous user base of message systems and their critical role in information delivery make it the top priority to secure message systems. This dissertation focuses on securing the two most representative and dominant messages systems---e-mail and instant messaging (IM)---from two complementary aspects: defending against unwanted messages and ensuring reliable delivery of wanted messages.;To curtail unwanted messages and protect e-mail and instant messaging users, this dissertation proposes two mechanisms DBSpam and HoneyIM, which can effectively thwart e-mail spam laundering and foil malicious …
Hadron Structure From Holographic Qcd, Zainul Abidin
Hadron Structure From Holographic Qcd, Zainul Abidin
Dissertations, Theses, and Masters Projects
The AdS/CFT correspondence relates a strongly coupled gauge theory in four dimensional space-time with a weakly coupled gravity theory in five dimensional space-time. This correspondence provides a way to access the strongly coupled regime of a gauge theory via a perturbative approach in its gravity dual theory. In this dissertation, the gravity dual of Quantum Chromodynamics (QCD) is discussed. The so-called bottom-up approach (AdS/QCD) successfully reproduces the low energy observables at 10-20% accuracy.;An AdS/QCD model with two flavors of quarks is considered, assuming isospin symmetry. Pions and rho mesons masses and decay constants are obtained. We calculate the stress tensor, …
Observations Of Storm Morphodynamics Using Coastal Lidar And Radar Imaging System (Claris): Importance Of Wave Refraction And Dissipation Over Complex Surf-Zone Morphology At A Shoreline Erosional Hotspot, Katherine L. Brodie
Dissertations, Theses, and Masters Projects
Elevated water levels and large waves during storms cause beach erosion, overwash, and coastal flooding, particularly along barrier island coastlines. While predictions of storm tracks have greatly improved over the last decade, predictions of maximum water levels and variations in the extent of damage along a coastline need improvement. In particular, physics based models still cannot explain why some regions along a relatively straight coastline may experience significant erosion and overwash during a storm, while nearby locations remain seemingly unchanged. Correct predictions of both the timing of erosion and variations in the magnitude of erosion along the coast will be …
Processing And Conversion Of Algae To Bioethanol, Sara Katherine Kampfe
Processing And Conversion Of Algae To Bioethanol, Sara Katherine Kampfe
Dissertations, Theses, and Masters Projects
No abstract provided.
Extra Dimensions And Electroweak Symmetry Breaking, Jong Anly Tan
Extra Dimensions And Electroweak Symmetry Breaking, Jong Anly Tan
Dissertations, Theses, and Masters Projects
In anticipation of the Large Hadron Collider (LHC) which is currently scheduled to start operating in September 2009, Particle physicists have developed various models to predict phenomena that may be observed in the LHC data. One of the ideas that have been developed is warped extra dimensions. The S parameter, one of the electroweak precision observables is predicted by experiments to be less than about 0.1. However, most of the models that try to explain the electroweak symmetry breaking without a Higgs Boson have a large S parameter > 0.2.;We study the possibility of reducing the S parameter in a wared …
Building Efficient Wireless Infrastructures For Pervasive Computing Environments, Bo Sheng
Building Efficient Wireless Infrastructures For Pervasive Computing Environments, Bo Sheng
Dissertations, Theses, and Masters Projects
Pervasive computing is an emerging concept that thoroughly brings computing devices and the consequent technology into people's daily life and activities. Most of these computing devices are very small, sometimes even "invisible", and often embedded into the objects surrounding people. In addition, these devices usually are not isolated, but networked with each other through wireless channels so that people can easily control and access them. In the architecture of pervasive computing systems, these small and networked computing devices form a wireless infrastructure layer to support various functionalities in the upper application layer.;In practical applications, the wireless infrastructure often plays a …
Applications Of Pattern Classification To Time-Domain Signals, Crystal Ann Bertoncini
Applications Of Pattern Classification To Time-Domain Signals, Crystal Ann Bertoncini
Dissertations, Theses, and Masters Projects
Many different kinds of physics are used in sensors that produce time-domain signals, such as ultrasonics, acoustics, seismology, and electromagnetics. The waveforms generated by these sensors are used to measure events or detect flaws in applications ranging from industrial to medical and defense-related domains. Interpreting the signals is challenging because of the complicated physics of the interaction of the fields with the materials and structures under study. often the method of interpreting the signal varies by the application, but automatic detection of events in signals is always useful in order to attain results quickly with less human error. One method …
A Measurement Of The Neutron Electric Form Factor At Very Large Momentum Transfer Using Polarized Electrons Scattering From A Polarized Helium-3 Target, Aidan Michael Kelleher
A Measurement Of The Neutron Electric Form Factor At Very Large Momentum Transfer Using Polarized Electrons Scattering From A Polarized Helium-3 Target, Aidan Michael Kelleher
Dissertations, Theses, and Masters Projects
Knowledge of the electric and magnetic elastic form factors of the nucleon is essential for an understanding of nucleon structure. of the form factors, the electric form factor of the neutron has been measured over the smallest range in Q2 and with the lowest precision. Jefferson Lab experiment 02-013 used a novel new polarized 3He target to nearly double the range of momentum transfer in which the neutron form factor has been studied and to measure it with much higher precision. Polarized electrons were scattered off this target, and both the scattered electron and neutron were detected. GEn was measured …
The Logarithmic Method And The Solution To The Tp2-Completion Problem, Shahla Nasserasr
The Logarithmic Method And The Solution To The Tp2-Completion Problem, Shahla Nasserasr
Dissertations, Theses, and Masters Projects
A matrix is called TP2 if all 1-by-1 and 2-by-2 minors are positive. A partial matrix is one with some of its entries specified, while the remaining, unspecified, entries are free to be chosen. A TP2-completion, of a partial matrix T , is a choice of values for the unspecified entries of T so that the resulting matrix is TP2. The TP2-completion problem asks which partial matrices have a TP2-completion. A complete solution is given here. It is shown that the Bruhat partial order on permutations is the inverse of a certain natural partial order induced by TP2 matrices and …
Supporting Feature-Level Software Maintenance, Meghan Kathleen Revelle
Supporting Feature-Level Software Maintenance, Meghan Kathleen Revelle
Dissertations, Theses, and Masters Projects
Software maintenance is the process of modifying a software system to fix defects, improve performance, add new functionality, or adapt the system to a new environment. A maintenance task is often initiated by a bug report or a request for new functionality. Bug reports typically describe problems with incorrect behaviors or functionalities. These behaviors or functionalities are known as features. Even in very well-designed systems, the source code that implements features is often not completely modularized. The delocalized nature of features makes maintaining them challenging. Since maintenance tasks are expressed in terms of features, the goal of this dissertation is …
Secure And Efficient Data Extraction For Ubiquitous Computing Applications, Chiu Chiang Tan
Secure And Efficient Data Extraction For Ubiquitous Computing Applications, Chiu Chiang Tan
Dissertations, Theses, and Masters Projects
Ubiquitous computing creates a world where computers have blended seamlessly into our physical environment. In this world, a "computer" is no longer a monitor-and-keyboard setup, but everyday objects such as our clothing and furniture. Unlike current computer systems, most ubiquitous computing systems are built using small, embedded devices with limited computational, storage and communication abilities. A common requirement for many ubiquitous computing applications is to utilize the data from these small devices to perform more complex tasks. For critical applications such as healthcare or medical related applications, there is a need to ensure that only authorized users have timely access …
Comparison Of Full-Wave And Ray-Tracing Analysis Of Mode Conversion In Plasmas, Yanli Xiao
Comparison Of Full-Wave And Ray-Tracing Analysis Of Mode Conversion In Plasmas, Yanli Xiao
Dissertations, Theses, and Masters Projects
This dissertation reports on the first direct comparison between the results of ray-based and full-wave calculations for mode conversion in plasma. This study was motivated by the modular method originally developed by Ye and Kaufman to treat a magnetosonic wave crossing a cold minority-ion gyroresonance layer. We start with the cold plasma fluid model and introduce a system of evolution equations for electrons and two ion species: deuterium and hydrogen. We first study this system of equations for uniform plasma by Fourier methods, which gives the dispersion relations. We discuss how the traditional approach---which eliminates all other dynamical variables in …
Spatial And Temporal Patterns In Erosional And Depositional Processes: Physical And Biological Controls In The York River, Chesapeake Bay, Virginia, Cielomar Rodríguez-Calderon
Spatial And Temporal Patterns In Erosional And Depositional Processes: Physical And Biological Controls In The York River, Chesapeake Bay, Virginia, Cielomar Rodríguez-Calderon
Dissertations, Theses, and Masters Projects
No abstract provided.
Habitat Complexity And Habitat Function Of Native (Crassostrea Virginica) And Non-Native (C. Ariakensis) Oysters In The Chesapeake Bay Region, Heather D. Harwell
Habitat Complexity And Habitat Function Of Native (Crassostrea Virginica) And Non-Native (C. Ariakensis) Oysters In The Chesapeake Bay Region, Heather D. Harwell
Dissertations, Theses, and Masters Projects
Complex oyster reefs created by the Eastern oyster, Crassostrea virginica, though once prominent features of the Chesapeake Bay region, have become relatively scarce in comparison to historic descriptions. This decline, caused by a combination of overfishing, disease, habitat destruction and pollution, this decline continues despite substantial restoration efforts that have spanned decades. In response to this decline, the states of Virginia and Maryland considered the intentional introduction of the non-native Suminoe oyster, C. ariakensis. Previous studies questioned the reef-building capability of this Crassostrea species, which may affect its habitat function. Through a combination of field and mesocosm studies, I examined …
Estimating Detection Probabilities In Beach Seine Surveys For Estuarine Fishes, Branson D. Williams
Estimating Detection Probabilities In Beach Seine Surveys For Estuarine Fishes, Branson D. Williams
Dissertations, Theses, and Masters Projects
Detectability, the probability that a species is encountered if it inhabits a site, is often overlooked in fisheries research despite its potential to obscure habitat use inferences. Detectability can be estimated using models that also provide an estimate of occupancy (Ψ), the probability that a species inhabits a site. I used these models to estimate both probabilities, and to examine factors affecting detectability and occupancy for three fishes in Chesapeake Bay tributaries: young-of-the-year striped bass (Morone saxatilis), yearling Atlantic croaker (Micropogonias undulatus), and spottail shiner (Notropis hudsonius). Occupancy models were fitted to data from a seine survey conducted during summer, …
Modeling Shoreline Change And Resulting Wetland Response Due To Erosion And Sea-Level Rise: A Case Study In Dorchester County, Maryland, Mirtha Karinna Nunez
Modeling Shoreline Change And Resulting Wetland Response Due To Erosion And Sea-Level Rise: A Case Study In Dorchester County, Maryland, Mirtha Karinna Nunez
Dissertations, Theses, and Masters Projects
The present study was focused on developing a shoreline change forecast and wetland response model for Dorchester County, MD, to evaluate the vulnerability of wetlands to shoreline erosion and inundation due to relative sea level rise. The model considers the following forces involved in wetland stability and sustainability: inundation (as a function of topography and sea-level rise), shoreline erosion, vertical accretion and horizontal migration. To predict the long-term risk to nearshore wetlands and the potential habitat zone for wetlands in the next 50 years, shoreline change due to inundation and erosion/accretion was assessed within the frameworks of two-dimensional and three-dimensional …
The Effect Of Salinity On Experimental Hematodinium Sp Infections In The Blue Crab, Callinectes Sapidus, Anna Huntley Coffey
The Effect Of Salinity On Experimental Hematodinium Sp Infections In The Blue Crab, Callinectes Sapidus, Anna Huntley Coffey
Dissertations, Theses, and Masters Projects
No abstract provided.
Quantifying The Ecosystem Role Of A Suspension And A Facultative Deposit Feeding Bivalve In The New River Estuary, Nc: With Responses To Changes In Nutrient And Sediment Inputs, Heather Marie Wiseman
Quantifying The Ecosystem Role Of A Suspension And A Facultative Deposit Feeding Bivalve In The New River Estuary, Nc: With Responses To Changes In Nutrient And Sediment Inputs, Heather Marie Wiseman
Dissertations, Theses, and Masters Projects
No abstract provided.
Partial Year Tagging Models: Accounting For Changing Tag Visibility And Delayed Mixing, Lynn Waterhouse
Partial Year Tagging Models: Accounting For Changing Tag Visibility And Delayed Mixing, Lynn Waterhouse
Dissertations, Theses, and Masters Projects
No abstract provided.
Exploring The Potential For Bay Scallop Restoration In The Lynnhaven River Sub-Estuary Of Chesapeake Bay, Ana Liza Hernandez Cordero
Exploring The Potential For Bay Scallop Restoration In The Lynnhaven River Sub-Estuary Of Chesapeake Bay, Ana Liza Hernandez Cordero
Dissertations, Theses, and Masters Projects
No abstract provided.