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Articles 151 - 180 of 1876
Full-Text Articles in Physical Sciences and Mathematics
Exploring Heterogeneous Architectures With Tools And Applications, Du Shen
Exploring Heterogeneous Architectures With Tools And Applications, Du Shen
Dissertations, Theses, and Masters Projects
Heterogeneous architectures have become popular due to programming flexibility and energy efficiency. Heterogeneous architectures include GPU accelerators, and memory subsystems consisting fast and slow components. Achieving high performance for programs running on heterogeneous architectures requires sophisticated tools and applications. They either lack hardware support for fast memory component, or provide complex programming model, which puts extra burdens on compilers and programmers. However, existing tools either rely on simulators or lack support across different GPU architectures, runtime or driver versions. Thus, they only provide insufficient insights. In the first project, we develop DataPlacer, a profiling tool to provide guidance for data …
Filling In The Gaps: Applications Of Deep Learning, Satellite Imagery, And High Performance Computing For The Estimation And Distribution Of Geospatial Data, Seth Goodman
Dissertations, Theses, and Masters Projects
Many regions around the world suffer from a lack of authoritatively-collected data on factors critical to understanding human well-being. This challenges our ability to understand the progress society is making towards reducing poverty, improving lifespans, or otherwise improving livelihoods. A growing body of research is exploring how deep learning algorithms can be used to produce novel estimates of sparse development data, and how access to such data can impact development efforts. This dissertation contributes to this literature in three parts. First, using Landsat 8 satellite imagery and data from the Armed Conflict Location & Event Data Project, convolutional neural networks …
Reducing Avian Collisions With Human-Made Structures: A Sensory Ecology Approach To Open-Air Settings, Timothy James Boycott
Reducing Avian Collisions With Human-Made Structures: A Sensory Ecology Approach To Open-Air Settings, Timothy James Boycott
Dissertations, Theses, and Masters Projects
Billions of birds fatally collide with human-made structures each year. These mortalities have impacts on species of conservation concern and potentially on avian populations as a whole. This source of human-wildlife conflict also places economic and operational constraints on various human industries. Furthermore, with continued increases in urbanization, the rate and extent of collisions continues to increase. Efforts to reduce collisions have largely centered on making structures more visible to birds but have been met with limited success. Currently, there is a call for solutions to be tailored to both the environmental context of hazardous structures and to the sensory …
Development Of Quantum Information Tools Based On Multi-Photon Raman Processes In Rb Vapor, Nikunjkumar Prajapati
Development Of Quantum Information Tools Based On Multi-Photon Raman Processes In Rb Vapor, Nikunjkumar Prajapati
Dissertations, Theses, and Masters Projects
Multi-photon nonlinear processes in atoms have served as important tools for quantum metrology, quantum communications, and quantum sensing. In this thesis, we experimentally address the interplay of various multi-photon Raman processes in hot Rb vapor, with the four-wave mixing (FWM) process being a central theme. FWM is the nonlinear response of a medium to a strong optical pump field inelastically scattering off atomic resonances and resulting in the generation of additional photons in different modes. FWM is a detrimental, but inherent part of electromagnetically induced transparency (EIT) and Raman based quantum memories. However, we were able to weaken the four-photon …
Impacts Of Fertilization On Salt Marsh Resilience: Altered By Location-Specific Drivers, Kenneth Michael Czapla
Impacts Of Fertilization On Salt Marsh Resilience: Altered By Location-Specific Drivers, Kenneth Michael Czapla
Dissertations, Theses, and Masters Projects
Salt marshes provide valuable ecosystem services to human society, but are currently under threat from accelerating sea level rise and nutrient enrichment. Carbon (C) and mineral accumulation allow salt marshes to maintain elevation above sea level and survive. Anthropogenic nitrogen (N) loading is increasing in many salt marshes, causing negative impacts on marsh resilience such as increased decomposition and decreased below-ground production. However, increasing N may also have simultaneous positive effects such as increased primary production and above-ground biomass, surface sediment accretion, and denitrification rates, which remove excess N from coastal waters. Many studies have been conducted to determine the …
Unravelling The Aggregation Of Eosin Y Photosensitisers For Solar Energy Conversion, Huw Richards
Unravelling The Aggregation Of Eosin Y Photosensitisers For Solar Energy Conversion, Huw Richards
Dissertations, Theses, and Masters Projects
The impact of molecular aggregation on the photophysics of eosin y adsorbed to TiO2 was investigated using diffuse reflectance spectroscopy, steady-state fluorescence and time correlated single photon counting (TCSPC) measurements. Deconvolution of the diffuse reflectance spectra of eosin y on TiO2 revealed the formation of H-aggregates, with the extent of H-aggregation increasing with increasing dye-loading concentration. The resultant bathochromic shift from the monomer diffuse reflectance maximum is due to Charge-transfermediated H-aggregates The fluorescent maximum also shifts with increasing dye loading concentration starting at 537.5 nm at a dye loading concentration of 7.5x10-7 M and shifting to 585 …
Single Image Direct-Global Illumination Separation, Zhaoliang Duan
Single Image Direct-Global Illumination Separation, Zhaoliang Duan
Dissertations, Theses, and Masters Projects
Global light transport, including diffuse interreflections, caustic, refractions and subsurface scattering, is important to achieve photorealistic rendering. However rendering these phenomena is very time-consuming. Furthermore, many inverse rendering methods’ accuracy in computer graphics and computer vision is adversely affected by the presence of global light transport. Therefore, separating direct-global light transport components is necessary to help in designing new rendering methods and in improving the accuracy of many image inverse methods. Prior work on separating direct and global light transport from photographs either requires expensive hardware, requires multiple photographs of the scene, or fails to accurately recover high frequency details. …
Impacts Of Physical Transport On Estuarine Phytoplankton Dynamics And Harmful Algal Blooms, Qubin Qin
Impacts Of Physical Transport On Estuarine Phytoplankton Dynamics And Harmful Algal Blooms, Qubin Qin
Dissertations, Theses, and Masters Projects
The spatial and temporal variability of phytoplankton biomass in estuaries is determined by both local processes and transport processes. Local processes include biological processes (e.g., photosynthesis, respiration/excretion, and grazing) and settling, whereas transport processes include advective and diffusive transports. Transport processes have been demonstrated to regulate phytoplankton dynamics significantly by distributing both phytoplankton and other dissolved and particulate substances (e.g., nutrients, salts, sediments, and chromophoric dissolved organic matter). Yet, these transport properties lack a framework that unifies the pieced description of their various effects, and quantification of their importance under various environmental conditions. This dissertation highlights the role of horizontal …
Seasonal Variability Of The Co2-System Throughout The Chesapeake Bay Mainstem, Jaclyn Rain Friedman
Seasonal Variability Of The Co2-System Throughout The Chesapeake Bay Mainstem, Jaclyn Rain Friedman
Dissertations, Theses, and Masters Projects
Declining water quality, in addition to hypoxia and eutrophication, may have a significant impact on the seasonality of biogeochemical parameters throughout the mainstem of the Chesapeake Bay. The carbonate (CO2) system in the Chesapeake Bay experiences seasonal and spatial complexities and is influenced by both natural and anthropogenic variability. Although site-specific studies investigating CO2-system variability exist within the Chesapeake Bay, few studies have investigated the seasonality of the CO2-system throughout the entire mainstem. Additionally, recent comprehensive studies investigating over 50 estuaries along the East Coast of the United States suggest that estuarine systems are heterotrophic and act as sources of …
Gpgpu Reliability Analysis: From Applications To Large Scale Systems, Bin Nie
Gpgpu Reliability Analysis: From Applications To Large Scale Systems, Bin Nie
Dissertations, Theses, and Masters Projects
Over the past decade, GPUs have become an integral part of mainstream high-performance computing (HPC) facilities. Since applications running on HPC systems are usually long-running, any error or failure could result in significant loss in scientific productivity and system resources. Even worse, since HPC systems face severe resilience challenges as progressing towards exascale computing, it is imperative to develop a better understanding of the reliability of GPUs. This dissertation fills this gap by providing an understanding of the effects of soft errors on the entire system and on specific applications. To understand system-level reliability, a large-scale study on GPU soft …
Learning Code Transformations Via Neural Machine Translation, Michele Tufano
Learning Code Transformations Via Neural Machine Translation, Michele Tufano
Dissertations, Theses, and Masters Projects
Source code evolves – inevitably – to remain useful, secure, correct, readable, and efficient. Developers perform software evolution and maintenance activities by transforming existing source code via corrective, adaptive, perfective, and preventive changes. These code changes are usually managed and stored by a variety of tools and infrastructures such as version control, issue trackers, and code review systems. Software Evolution and Maintenance researchers have been mining these code archives in order to distill useful insights on the nature of such developers’ activities. One of the long-lasting goal of Software Engineering research is to better support and automate different types of …
Topics In Proton Structure: Bsm Answers To Its Radius Puzzle And Lattice Subtleties Within Its Momentum Distribution, Michael Chaim Freid
Topics In Proton Structure: Bsm Answers To Its Radius Puzzle And Lattice Subtleties Within Its Momentum Distribution, Michael Chaim Freid
Dissertations, Theses, and Masters Projects
This thesis covers two subjects, briefly outlined below, of hadronic physics. The proton radius puzzle and the muon anomalous magnetic moment discrepancy point to possible signs of lepton-universality violation. We introduce the context and background necessary to understand these two problems. And we analyze two suitable beyond-the-standard-model solutions, one vector-based and one scalar-based, which simultaneously solves both issues. Furthermore, we demonstrate that the parameter space of the respective solutions can be chosen so as to not be completely forbidden by considered experimental constraints. Specifically, we show that certain violations, analyzed by other authors in the context of similar solutions to …
Evolution Of The Genome-Wide Distribution Of Genes And Transposons, Ronald Dutilh Smith
Evolution Of The Genome-Wide Distribution Of Genes And Transposons, Ronald Dutilh Smith
Dissertations, Theses, and Masters Projects
Genomes exhibit a striking amount of complexity across a broad range of scales. This includes variation in the spatial distribution of features such as genes and transposable elements (TEs), which is observed both between species and among individuals in natural and artificial populations. Additionally, all eukaryotes studied to date have had gene duplications occur in their evolutionary history. In this dissertation, we develop a statistical method for analyzing relative changes in the expression of duplicated genes. We show that this method performs better than could otherwise be achieved using traditional methods of differential gene expression analysis. We apply this method …
Scattering A Bose-Einstein Condensate Off A Modulated Barrier, Andrew James Pyle
Scattering A Bose-Einstein Condensate Off A Modulated Barrier, Andrew James Pyle
Dissertations, Theses, and Masters Projects
A quantum pump is a device that transports particles through a circuit with localized time-varying potentials, and without the need for an external applied voltage or chemical potential. Quantum pumping was originally proposed in the context of electron transport in nanowires, but has proven difficult to implement. The ultracold atom approach represents a possible route around the current experimental bottleneck. We present an experiment to study 1D quantum mechanical scattering by an amplitude-modulated barrier. This experiment represents a first step toward implementing a quantum pump for ultracold atoms based on two such barriers modulated out of phase with one another. …
Complex Mixtures: Identifying And Characterizing Secondary Organic Aerosols, Emma Quinn Walhout
Complex Mixtures: Identifying And Characterizing Secondary Organic Aerosols, Emma Quinn Walhout
Dissertations, Theses, and Masters Projects
Complex organic mixtures in the environment can contain hundreds to thousands of different organic molecules, and their composition and reactivity can have important environmental implications. In addition to gases, the atmosphere is made of a variety of small liquids and solids called aerosols. These aerosols have large impacts on human health, climate, and atmospheric chemical reactions. Here, secondary organic aerosol (SOA) from the ozonolysis of α-pinene is characterized. The atmospheric lifetime of SOA is very uncertain, but recent laboratory and modeling studies have demonstrated that photolysis is potentially an important process for organic mass loss from aerosol particles.1-5 Photolysis modifies …
Persistence And Extinction Dynamics In Reaction-Diffusion-Advection Stream Population Model With Allee Effect Growth, Yan Wang
Dissertations, Theses, and Masters Projects
The question how aquatic populations persist in rivers when individuals are constantly lost due to downstream drift has been termed the ``drift paradox." Reaction-diffusion-advection models have been used to describe the spatial-temporal dynamics of stream population and they provide some qualitative explanations to the paradox. Here random undirected movement of individuals in the environment is described by passive diffusion, and an advective term is used to describe the directed movement in a river caused by the flow. In this work, the effect of spatially varying Allee effect growth rate on the dynamics of reaction-diffusion-advection models for the stream population is …
Electronic Properties Of Two-Dimensional Van Der Waals Systems, Yohanes Satrio Gani
Electronic Properties Of Two-Dimensional Van Der Waals Systems, Yohanes Satrio Gani
Dissertations, Theses, and Masters Projects
In this dissertation we study the electronic structure of van der Waals systems. A van der Waals systems is a heterostructure in which the different constituents are held together by van der Waals forces. We study two different types of van der Waals systems: van der Waals systems formed by graphene and a monolayer of NbSe2, van der Waals systems obtained by placing graphene nanoribbons on a two-dimensional crystal. For the first type of systems we build a continuous low-energy effective model that takes into account the presence of a twist angle between graphene and NbSe2, and of spin-orbit coupling …
Optimization Approaches For Open-Locating Dominating Sets, Daniel Blair Sweigart
Optimization Approaches For Open-Locating Dominating Sets, Daniel Blair Sweigart
Dissertations, Theses, and Masters Projects
An Open Locating-Dominating Set (OLD set) is a subset of vertices in a graph such that every vertex in the graph has a neighbor in the OLD set and every vertex has a unique set of neighbors in the OLD set. This can also represent where sensors, capable of detecting an event occurrence at an adjacent vertex, could be placed such that one could always identify the location of an event by the specific vertices that indicated an event occurred in their neighborhood. By the open neighborhood construct, which differentiates OLD sets from identifying codes, a vertex is not able …
Investigation Of Pattern Formation In Marine Environments Through Mathematical Modeling And Analysis Of Remotely Sensed Data, Sofya Zaytseva
Investigation Of Pattern Formation In Marine Environments Through Mathematical Modeling And Analysis Of Remotely Sensed Data, Sofya Zaytseva
Dissertations, Theses, and Masters Projects
Pattern formation in ecological systems refers to a nonuniform distribution of animal and plant species across a landscape. Pattern formation can be observed in many aquatic and terrestrial systems and can provide important insights into their dynamics and ability to cope with environmental changes. In this dissertation, we focus on pattern formation in tidal marshes and oyster reefs, two important habitats that provide a number of essential ecosystem services. Both of these systems have also experienced dramatic losses, prompting much research to investigate their dynamics as and viable restoration and management strategies. The first part of this dissertation focuses on …
Applying The Concept Of Thresholds In Ecotoxicology With Focus On The Joint Effects Of Habitat Fragmentation And Contamination, Marcos Krull
Applying The Concept Of Thresholds In Ecotoxicology With Focus On The Joint Effects Of Habitat Fragmentation And Contamination, Marcos Krull
Dissertations, Theses, and Masters Projects
A threshold can be defined as the point where small changes in an environmental driver produce an abrupt change within a biological system. These changes can occur at different levels of organization, from organisms to ecosystems. Although thresholds seem to be receiving more attention by ecotoxicologist, not much is known about how contaminants cause or affect thresholds at the landscape level, such as habitat fragmentation thresholds. Habitat fragmentation thresholds can occur due to rapid changes in the landscape structure after a certain amount of habitat is lost, which can cause abrupt effects on the movement of organisms, population abundance and …
Improving Wifi Sensing And Networking With Channel State Information, Yongsen Ma
Improving Wifi Sensing And Networking With Channel State Information, Yongsen Ma
Dissertations, Theses, and Masters Projects
In recent years, WiFi has a very rapid growth due to its high throughput, high efficiency, and low costs. Multiple-Input Multiple-Output (MIMO) and Orthogonal Frequency-Division Multiplexing (OFDM) are two key technologies for providing high throughput and efficiency for WiFi systems. MIMO-OFDM provides Channel State Information (CSI) which represents the amplitude attenuation and phase shift of each transmit-receiver antenna pair of each carrier frequency. CSI helps WiFi achieve high throughput to meet the growing demands of wireless data traffic. CSI captures how wireless signals travel through the surrounding environment, so it can also be used for wireless sensing purposes. This dissertation …
Human Dimensions Of A Participatory, Collaborative Modeling Process - Oysterfutures, Taylor Dawn Goelz
Human Dimensions Of A Participatory, Collaborative Modeling Process - Oysterfutures, Taylor Dawn Goelz
Dissertations, Theses, and Masters Projects
Participatory, collaborative modeling processes represent a unique decision-making technique within natural resources management that allows for the combination of stakeholder involvement with the analytical and predictive power of scientific models. The continued use of participatory modeling within decision-making processes depends in part upon the willingness of stakeholders to participate. Continued participation of stakeholders is key to the persistence and overall success of these processes, and yet limited information exists concerning the impacts of these processes on participants. The consideration of human dimensions advances our understanding of the design and function of participatory modeling processes, including their ability to create consensus …
Partitioning Of Hydrophobic Organic Contaminants And Microbial Communities On Microplastics, Kelley Ann Uhlig
Partitioning Of Hydrophobic Organic Contaminants And Microbial Communities On Microplastics, Kelley Ann Uhlig
Dissertations, Theses, and Masters Projects
Microplastic contamination of aquatic environments has only recently caught the attention of scientists, regulators and the public. Microplastics are typically more recalcitrant than naturally occurring polymers and so have the potential to cause a range of issues, including increased exposure of marine life to chemical contaminants sorbed to or leached from microplastics, negative impacts due to ingestion of microplastics by biota, and the potential to carry and transport pathogenic and invasive species long distances. Bio-based, bio-degradable polymers have begun to gain market share as an alternative to traditional petrochemical-based plastics, but not much is known about their impacts in marine …
Extraction And Parametrization Of Isobaric Trinucleon Elastic Cross Sections And Form Factors, Scott Kevin Barcus
Extraction And Parametrization Of Isobaric Trinucleon Elastic Cross Sections And Form Factors, Scott Kevin Barcus
Dissertations, Theses, and Masters Projects
By mining data from Jefferson Lab Hall A experiment E08-014 a new measurement of the 3He elastic cross section at Q^2 ≈ 34 fm^−2 was extracted from a large quasielastic background. This new data point falls approximately halfway between the first and second diffractive minima of the 3He form factors. When combined with recent high Q^2 3He elastic cross section measurements from JLab this new point improves our knowledge of the cross section and form factors at large momentum transfers. The new high Q^2 data motivate a reanalysis of the 3He elastic cross section world data and promise an improved …
Computational Graphics And Statistical Analysis: Mixed Type Random Variables, Confidence Regions, And Golden Quantile Rank Sets, Christopher Weld
Computational Graphics And Statistical Analysis: Mixed Type Random Variables, Confidence Regions, And Golden Quantile Rank Sets, Christopher Weld
Dissertations, Theses, and Masters Projects
This dissertation has three principle areas of research: mixed type random variables, confidence regions, and golden quantile rank sets. While each offers a specific focus, some common themes persist; broadly stated, there are three. First, computational graphics play a critical role. Second, software development facilitates implementation and accessibility. Third, statistical analysis---often attributable to the aforementioned automation---provides valuable insights and applications. Each of the principle research areas are briefly summarized next. Mixed type random variables are a hybrid of continuous and discrete random variables, having components of both continuous probability density and discrete probability mass. This dissertation illustrates the challenges inherent …
Beyond The Standard Model: Flavor Symmetry, Nonperturbative Unification, Quantum Gravity, And Dark Matter, Shikha Chaurasia
Beyond The Standard Model: Flavor Symmetry, Nonperturbative Unification, Quantum Gravity, And Dark Matter, Shikha Chaurasia
Dissertations, Theses, and Masters Projects
Despite the vast success of the Standard Model of particle physics, it is no secret that is also has its shortcomings, thus providing incentive to look beyond the Standard Model for solutions. In this thesis we focus in particular on a model of horizontal flavor symmetry, unification via a universal Landau pole, emergent gravity, and dark matter. First we explain the observed hierarchies in the elementary fermion mass spectrum via a model based on the double tetrahedral group, the smallest discrete subgroup of SU(2), while relaxing previous assumptions of supersymmetry. A sequential symmetry breaking process results in a hierarchy in …
Investigating The Molecular Choreography Of Atmospherically Relevant Molecules: A Dynamics Study, Kenneth Jacob Blackshaw
Investigating The Molecular Choreography Of Atmospherically Relevant Molecules: A Dynamics Study, Kenneth Jacob Blackshaw
Dissertations, Theses, and Masters Projects
Investigating and understanding the chemistry of the atmosphere has historically been an important research topic. This importance has only strengthened in the recent decades as technological advancements have drastically increased anthropogenic emissions of hydrocarbons and nitroaromatic compounds. Indeed, we are in an era of unprecedented change of the chemical composition of the troposphere and never before has an in-depth understanding of atmospheric chemical properties been more sought-after. This study seeks to fill that need by probing the molecular dynamics of atmospherically relevant molecules through the use of velocity map imaging (VMI). In particular, we utilize VMI to study the photolysis …
Research On Efficiency And Security For Emerging Distributed Applications, Zijiang Hao
Research On Efficiency And Security For Emerging Distributed Applications, Zijiang Hao
Dissertations, Theses, and Masters Projects
Distributed computing has never stopped its advancement since the early years of computer systems. In recent years, edge computing has emerged as an extension of cloud computing. The main idea of edge computing is to provide hardware resources in proximity to the end devices, thereby offering low network latency and high network bandwidth. However, as an emerging distributed computing paradigm, edge computing currently lacks effective system support. To this end, this dissertation studies the ways of building system support for edge computing. We first study how to support the existing, non-edge-computing applications in edge computing environments. This research leads to …
Controlling Infectious Disease: Prevention And Intervention Through Multiscale Models, Adrienna N. Bingham
Controlling Infectious Disease: Prevention And Intervention Through Multiscale Models, Adrienna N. Bingham
Dissertations, Theses, and Masters Projects
Controlling infectious disease spread and preventing disease onset are ongoing challenges, especially in the presence of newly emerging diseases. While vaccines have successfully eradicated smallpox and reduced occurrence of many diseases, there still exists challenges such as fear of vaccination, the cost and difficulty of transporting vaccines, and the ability of attenuated viruses to evolve, leading to instances such as vaccine derived poliovirus. Antibiotic resistance due to mistreatment of antibiotics and quickly evolving bacteria contributes to the difficulty of eradicating diseases such as tuberculosis. Additionally, bacteria and fungi are able to produce an extracellular matrix in biofilms that protects them …
On Enhancing Security Of Password-Based Authentication, Yue Li
On Enhancing Security Of Password-Based Authentication, Yue Li
Dissertations, Theses, and Masters Projects
Password has been the dominant authentication scheme for more than 30 years, and it will not be easily replaced in the foreseeable future. However, password authentication has long been plagued by the dilemma between security and usability, mainly due to human memory limitations. For example, a user often chooses an easy-to-guess (weak) password since it is easier to remember. The ever increasing number of online accounts per user even exacerbates this problem. In this dissertation, we present four research projects that focus on the security of password authentication and its ecosystem. First, we observe that personal information plays a very …