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Articles 31 - 52 of 52
Full-Text Articles in Physical Sciences and Mathematics
Radiative Width Of K*(892) From Lattice Quantum Chromodynamics, Archana Radhakrishnan
Radiative Width Of K*(892) From Lattice Quantum Chromodynamics, Archana Radhakrishnan
Dissertations, Theses, and Masters Projects
In this dissertation, we use lattice quantum chromodynamics to explore the radiative transitions of πK to K, to calculate the radiative width of the resonant K*(892) which appears in the P-wave πK → γK transition amplitude. The matrix elements are extracted from three-point functions calculated in a finite-volume discretized lattice with a pion mass of 284 MeV. The finite-volume amplitudes, which are constrained over a large number of πK energy points and four-momentum transfers, are mapped to the infinite volume transition amplitude by using the Lellouch-Lüscher formalism. The radiative width is determined to be …
Exploring The Effects Of Microplastics On Marine Biota, Meredith Evans Seeley
Exploring The Effects Of Microplastics On Marine Biota, Meredith Evans Seeley
Dissertations, Theses, and Masters Projects
There is mounting evidence that microplastics are a persistent and increasing hazard for aquatic organisms. The effects of microplastics on organisms and ecosystems are complex, however, and may be linked to a wide variety of particle characteristics including size, shape, polymer, additive chemistry, and degree of weathering. Assessing risk is complicated by the fact that many known effects of microplastics are sublethal, and that plastics have been postulated to interact with other stressors, such as pathogens. The work presented here expands our understanding of these complex effects. First, the impacts of microplastics on sedimentary microbial ecosystems and biogeochemical carbon and …
Roles Of Hydrodynamics And Topographies On The Transport Of Dissolved Material, Particulates, And Harmful Algae In Chesapeake Bay, Jilian Xiong
Dissertations, Theses, and Masters Projects
Estuaries are highly productive and characterized by complex shoreline geometry and topography. Multiple materials produced within or transported into estuaries include non-living dissolved/particulate materials and living organisms. Estuarine circulation determines material transport and distributions, which further impact estuarine ecosystem to support abundant fauna/flora and their vulnerability to escalated anthropogenic inputs. Short-term material transport process in Chesapeake Bay (CB) has been studied for years, yet its long-term characteristics and the transport of materials with settling and biological behaviors that interact with physical transport have not been fully studied. This study aims to understand the transport of non-living and non-motile dissolved/particulate materials, …
Barrier-Island Dynamics: Transgression, Regression, And State Changes, Justin Lee Shawler
Barrier-Island Dynamics: Transgression, Regression, And State Changes, Justin Lee Shawler
Dissertations, Theses, and Masters Projects
Barrier islands provide critical habitat for shorebirds and buffer backbarrier and inland coastal habitats and communities from the direct effects of storms and wave energy. Yet, barrier systems are under threat from these very same processes. In particular, whereas long-term barrier behavior and landward migration rate is directly related to the rate of sea-level rise, decadal to centennial barrier-island dynamics are more complicated, and often highly localized. Barrier-island dynamics—including state changes between seaward growth and landward migration—are driven by a complex interplay of forcings and interactions, including changes in longshore and cross-shore sediment fluxes, underlying geology and slope, barrier-marsh and …
Data-Driven Approaches For Water Quality Modeling In Coastal Systems, Xin Yu
Data-Driven Approaches For Water Quality Modeling In Coastal Systems, Xin Yu
Dissertations, Theses, and Masters Projects
Water quality in coastal waters is of great socio-economic concern. Anthropogenic activities along the coast have led to an increasing number of impaired waterbodies and degraded ecosystems. To manage water quality issues, accurately modeling the coastal water quality is vitally important. One traditional way to model water quality is using numerical models. Despite great advances in hydrodynamic modeling over the past few decades, water quality simulation is still challenging as the performance of water quality model depends on how well the complex biogeochemical processes are parameterized. While numerical models are the dominant tool for water quality modeling, there are increasing …
The Role Of Zooplankton Community Composition In Fecal Pellet Carbon Production In The York River Estuary, Chesapeake Bay, Kristen Nicole Sharpe
The Role Of Zooplankton Community Composition In Fecal Pellet Carbon Production In The York River Estuary, Chesapeake Bay, Kristen Nicole Sharpe
Dissertations, Theses, and Masters Projects
The biological pump is a critical component of carbon transformation in aquatic ecosystems, but the role that zooplankton play in carbon production and vertical export is rarely studied in estuaries. Zooplankton produce carbon-rich fecal pellets which sink to depth and can fuel benthic community metabolism. The body size and taxonomic structure of the zooplankton community varies on interannual, seasonal, and diel time scales, and can lead to varying carbon production and export rates. We quantified fecal pellet carbon (FPC) production by the whole mesozooplankton community (> 200 µm) in the York River, a sub-estuary of Chesapeake Bay. Biomass and taxonomic …
Flexible And Robust Iterative Methods For The Partial Singular Value Decomposition, Steven Goldenberg
Flexible And Robust Iterative Methods For The Partial Singular Value Decomposition, Steven Goldenberg
Dissertations, Theses, and Masters Projects
The Singular Value Decomposition (SVD) is one of the most fundamental matrix factorizations in linear algebra. As a generalization of the eigenvalue decomposition, the SVD is essential for a wide variety of fields including statistics, signal and image processing, chemistry, quantum physics and even weather prediction. The methods for numerically computing the SVD mostly fall under three main categories: direct, iterative, and streaming. Direct methods focus on solving the SVD in its entirety, making them suitable for smaller dense matrices where the computation cost is tractable. On the other end of the spectrum, streaming methods were created to provide an …
Practical Gpgpu Application Resilience Estimation And Fortification, Lishan Yang
Practical Gpgpu Application Resilience Estimation And Fortification, Lishan Yang
Dissertations, Theses, and Masters Projects
Graphics Processing Units (GPUs) are becoming a de facto solution for accelerating a wide range of applications but remain susceptible to transient hardware faults (soft errors) that can easily compromise application output. One of the major challenges in the domain of GPU reliability is to accurately measure general purpose GPU (GPGPU) application resilience to transient faults. This challenge stems from the fact that a typical GPGPU application spawns a huge number of threads and then utilizes a large amount of potentially unreliable compute and memory resources available on the GPUs. As the number of possible fault locations can be in …
Quantum Sensing For Low-Light Imaging, Savannah Cuozzo
Quantum Sensing For Low-Light Imaging, Savannah Cuozzo
Dissertations, Theses, and Masters Projects
In high-precision optical measurements, noise due to quantum fluctuations in the amplitude and phase of the probing field becomes the limiting factor in detection sensitivity. While this quantum noise is fundamental and not a result of detection, it is possible to engineer a quantum state that has reduced noise in either amplitude or phase (at the cost of increasing noise in the other) called a quadrature-squeezed state. In this dissertation, we study the use of quadrature-squeezed vacuum states for low-light imaging and develop a quantum detection method to measure the spatial dependence of the quantum noise using a camera instead …
Electronic Transport In Topological Superconducting Heterostructures, Joseph Jude Cuozzo
Electronic Transport In Topological Superconducting Heterostructures, Joseph Jude Cuozzo
Dissertations, Theses, and Masters Projects
In this dissertation, we study Andreev transport and Josephson effects in topological superconducting heterostructures. We study consider two platforms: quantum Hall-superconductor (QH-SC) heterostructures and Josephson junctions. In the first platform, we study QH graphene-SC systems with a focus on the influence symmetry-breaking effects have on Andreev transport. In graphene, valley and spin degeneracy lead to an approximate SU(4) symmetry that is reflected in the approximate 4-fold degeneracy of graphene's Landau levels (LL). We develop an effective low-energy description of Andreev edge states that takes into account the correction to the drift velocity of the QH-SC edge modes due to SU(4) …
Diel, Seasonal, And Interannual Changes In Coastal Antarctic Zooplankton Community Composition And Trophic Ecology, John A. Conroy
Diel, Seasonal, And Interannual Changes In Coastal Antarctic Zooplankton Community Composition And Trophic Ecology, John A. Conroy
Dissertations, Theses, and Masters Projects
Throughout the ocean, zooplankton transfer energy from primary producers to higher predators and transport carbon from surface waters to depth. The efficiency of these processes depends in part upon the taxonomic composition and trophic ecology of the zooplankton community. Zooplankton species abundance and distribution shifted over recent decades along the West Antarctic Peninsula during a period of rapid regional warming and sea-ice decline. Although conducted within the context of long-term change, this dissertation research focuses on zooplankton dynamics at finer temporal scales that have received less attention. I analyzed depth-stratified net samples to investigate zooplankton diel vertical migration during Antarctic …
Across-Scale Energy Transfer In The Southern Ocean, Laur Ferris
Across-Scale Energy Transfer In The Southern Ocean, Laur Ferris
Dissertations, Theses, and Masters Projects
Numerous physics are responsible for forward energy cascade at oceanic fronts but their roles are not fully clear. This dissertation investigates wind-sheared turbulence in the ocean surface boundary layer (OSBL), internal wave interactions in the ocean interior, and instability-driven turbulence in energetic jets; with attention paid to the parameterizations used to quantify them. At the OSBL, meteorological forcing injects turbulent kinetic energy (TKE), mixing the upper ocean and rapidly transforming its density structure. In the absence of direct observations or capability to resolve sub-grid scale turbulence in ocean models, the community relies on boundary layer scalings (BLS) of shear and …
Investigation Of Stripes, Spin Density Waves And Superconductivity In The Ground State Of The Two-Dimensional Hubbard Model, Hao Xu
Dissertations, Theses, and Masters Projects
The Hubbard model is a "paradigmatic" model in the realm of condensed matter physics. Recently a work with various state-or-art methods established the ground state stripe order near 1/8 doping and strong on-site interaction. Therefore, in this thesis, we determine the spin and charge order of ground state of 2D doped Hubbard model in its simplest form (with only on site repulsion and nearest-neighbor hoping) with various doping and small to medium interaction. At half-filling, the ground state is known to be an antiferromagnetic Mott insulator. Doping Mott insulators is believed to be relevant to the superconductivity observed in cuprates. …
Feedbacks Among Benthic Metabolism, Nitrogen Cycling, And Intense Phytoplankton Blooms In The York River Estuary, Michelle H. Woods
Feedbacks Among Benthic Metabolism, Nitrogen Cycling, And Intense Phytoplankton Blooms In The York River Estuary, Michelle H. Woods
Dissertations, Theses, and Masters Projects
Benthic-pelagic coupling is defined as the deposition of organic matter from the water column to the sediments, and the subsequent remineralization of this organic matter and release of inorganic nutrients back to the water column. This process plays an important role in determining the magnitude of benthic net community production (NCP), a metric that reflects the balance between gross primary production and respiration. Environmental factors, such as the presence or absence of intense phytoplankton blooms can influence the direction and magnitude of benthic-pelagic coupling and determine if benthic NCP is net autotrophic or heterotrophic. The objective this thesis was to …
Importance Of Muddy Bed Aggregate Processes In Cohesive Sediment Dynamics Associated With Sediment Management Projects, David Perkey
Importance Of Muddy Bed Aggregate Processes In Cohesive Sediment Dynamics Associated With Sediment Management Projects, David Perkey
Dissertations, Theses, and Masters Projects
The erosion and transport processes of fine sediment is largely impacted by the aggregation state. Understanding fine sediment transport processes is a key component to managing the nation’s navigation channels, ports, and reservoirs. To improve its ability to apply management strategies related to fine sediments, the USACE has undertaken research that focusses on the aggregation state of fine sediment. Of particular interest is the ability to expand the use of fine-grained sediment in projects that seek to beneficially use dredge material. In this study, a newly developed camera system was used to evaluate the aggregation state of eroded sediment from …
The Fate And Transport Of Nitrogen In Subterranean Estuaries, Stephanie J. Wilson
The Fate And Transport Of Nitrogen In Subterranean Estuaries, Stephanie J. Wilson
Dissertations, Theses, and Masters Projects
The subterranean estuary (STE) is a subsurface ecosystem where fresh groundwater mixes with intruding, recirculated seawater at the coastline. Despite being present globally, STEs and their potential impacts as hotspots for biogeochemical processing, or as a source of nutrients to coastal systems, are not well understood. STEs have been recognized as highly reactive zones for biogeochemical reactions, which influence the fate and transport of nutrients, organic matter, and trace metals discharged to the coastal ocean. Biogeochemical processing of nitrogen (N) in STEs influences N in submarine groundwater discharge (SGD) including its availability for use by primary producers and cascading eutrophication. …
Enabling Practical Evaluation Of Privacy Of Commodity-Iot, Sunil Manandhar
Enabling Practical Evaluation Of Privacy Of Commodity-Iot, Sunil Manandhar
Dissertations, Theses, and Masters Projects
There has been a massive shift towards the use of IoT products in recent years. While companies have come a long way in making these devices and services easily accessible to the consumers, very little is known about the privacy issues pertaining to these devices. In this dissertation, we focus on evaluating privacy pertaining to commodity-IoT devices by studying device usage behavior of consumers and privacy disclosure practices of IoT vendors. Our analyses consider deep intricacies tied to commodity-IoT domain, revealing insightful findings that help with building automated tools for a large scale analysis. We first present the design and …
Techniques For Accelerating Large-Scale Automata Processing, Hongyuan Liu
Techniques For Accelerating Large-Scale Automata Processing, Hongyuan Liu
Dissertations, Theses, and Masters Projects
The big-data era has brought new challenges to computer architectures due to the large-scale computation and data. Moreover, this problem becomes critical in several domains where the computation is also irregular, among which we focus on automata processing in this dissertation. Automata are widely used in applications from different domains such as network intrusion detection, machine learning, and parsing. Large-scale automata processing is challenging for traditional von Neumann architectures. To this end, many accelerator prototypes have been proposed. Micron's Automata Processor (AP) is an example. However, as a spatial architecture, it is unable to handle large automata programs without repeated …
Toward A Comprehensive Water Quality Model For The Chesapeake Bay Using Unstructured Grids, Xun Cai
Toward A Comprehensive Water Quality Model For The Chesapeake Bay Using Unstructured Grids, Xun Cai
Dissertations, Theses, and Masters Projects
Chesapeake Bay is one of the most productive ecosystems on the US east coast which supports various living resources and habitat, and therefore has significant impacts on human beings and ecosystem health. Developing the capability of accurately simulating the water quality condition in the Chesapeake Bay, such as seasonal hypoxia, phytoplankton production, and nutrient dynamics, helps to better understand the interactions of hydrodynamical and biochemical processes, and more importantly, to predict conditions under changing climate and human intervention. Currently, most Chesapeake Bay models use structured grids that lack the flexibility for local refinements to fit complex geometry over both large …
Communication And Computation Efficient Deep Learning, Zeyi Tao
Communication And Computation Efficient Deep Learning, Zeyi Tao
Dissertations, Theses, and Masters Projects
Recent advances in Artificial Intelligence (AI) are characterized by ever-increasing datasets and rapid growth of model complexity. Many modern machine learning models, especially deep neural networks (DNNs), cannot be efficiently carried out by a single machine. Hence, distributed optimization and inference have been widely adopted to tackle large-scale machine learning problems. Meanwhile, quantum computers that process computational tasks exponentially faster than classical machines offer an alternative solution for resource-intensive deep learning. However, there are two obstacles that hinder us from building large-scale DNNs on the distributed systems and quantum computers. First, when distributed systems scale to many nodes, the training …
Environmental Justice In The Elizabeth River Watershed: Exploring The Utility Of Environmental Justice Screening Tools, Julianna M. Ramirez
Environmental Justice In The Elizabeth River Watershed: Exploring The Utility Of Environmental Justice Screening Tools, Julianna M. Ramirez
Dissertations, Theses, and Masters Projects
The Environmental Justice (EJ) movement has long highlighted the disproportionate exposure to environmental hazards experienced by Black, Indigenous, People of Color (BIPOC) and low-income communities across the country. Environmental practitioners have recently focused on utilizing EJ screening tools, which combine environmental and social data to visualize vulnerable communities, to begin to address environmental injustice rampant in BIPOC and low-income communities. This project explores EJ theoretical frameworks and the historical context of social oppression and environmental pollution in the Elizabeth River watershed (ERW) of Virginia to: 1) understand the social, political, and economic context behind environmental injustice; and 2) generate goals …
Exploring Multi-Level Parallelism For Graph-Based Applications Via Algorithm And System Co-Design, Zhen Peng
Exploring Multi-Level Parallelism For Graph-Based Applications Via Algorithm And System Co-Design, Zhen Peng
Dissertations, Theses, and Masters Projects
Graph processing is at the heart of many modern applications where graphs are used as the basic data structure to represent the entities of interest and the relationships between them. Improving the performance of graph-based applications, especially using parallelism techniques, has drawn significant interest both in academia and industry. On the one hand, modern CPU architectures are able to provide massive computational power by using sophisticated memory hierarchy and multi-level parallelism, including thread-level parallelism, data-level parallelism, etc. On the other hand, graph processing workloads are notoriously challenging for achieving high performance due to their irregular computation pattern and unpredictable control …