Physical Sciences and Mathematics Commons^™

Crab Crossing Schemes And Studies For Electron Ion Collider, S. Ahmed, Y. Derbenev, V. Morozov, A. Castilla, Geoffrey A. Krafft, B. Yunn, Subashini U. De Silva, Jean R. Delayen

Physics Faculty Publications

This report shows our progress in crab crossing consideration for future electron-ion collider envisioned at JLab. In this design phase, we are evaluating two crabbing schemes viz., the deflecting and dispersive. The mathematical formulations and lattice design for these schemes are discussed in this paper. Numerical simulations involving particle tracking through a realistic deflecting RF cavity and optics illustrate the desired crab tilt of 25 mrad for 1.35 MV. Evolution of beam propagation are shown which provides the physical insight of the crabbing phenomenon.

Design Of Low-Frequency Superconducting Spoke Cavities For High-Velocity Applications, Jean R. Delayen, C. S. Hopper, R. G. Olave

Physics Faculty Publications

Superconducting single- and multi-spoke cavities have been designed to-date for particle velocities from β~0.15 to β~0.65. Superconducting spoke cavities may also be of interest for higher-velocity, low-frequency applications, either for hadrons or electrons. We present the design of 325 and 352 MHz spoke cavities optimized for β=0.8 and β=1.

Design Of Superconducting Multi-Spoke Cavities For High Velocity Applications, C. S. Hopper, Jean R. Delayen

Physics Faculty Publications

Superconducting spoke cavities have been designed and tested for particle velocities up to β₀ ~ 0.6 and are currently being designed for velocities up to β₀ = 1. We present the electromagnetic designs for two-spoke cavities operating at 325 MHz for β₀ = 0.82 and β₀ = 1.

Conceptual Design Of A Polarized Medium Energy Electron-Ion Collider At Jlab, S. Ahmed, A. Bogacz, Ya. Derbenev, A. Hutton, Geoffrey Krafft, R. Li, V. Morozov, F. Pilat, R. Rimmer, Y. Roblin, T. Satogata, M. Spata, B. Terzić, M. Tiefenback, H. Wang, B. Yunn, Y. Zhang, P. Chetsov, Jean R. Delayen, Subashini Desilva, Hisham Sayed, V. Dudnikov, R. Johnson, F. Marhauser, M. Sullivan, S. Manikonda, P. N. Ostroumov, S. Abeyratne, B. Erdelyi, Y. Kim, A. Kondratenko

Physics Faculty Publications

A medium energy electron-ion collider is envisioned as the primary future of the JLab nuclear science program beyond the 12 GeV upgraded CEBAF. The present conceptual design selects a ring-ring collider option, covers a CM energy range up to 65 GeV for collisions of polarized electrons with polarized light ions or unpolarized light to heavy ions, and reaches a luminosity at above 10³⁴ cm^-2s^-1 per detector over multiple interaction points. This paper presents a brief description of the current conceptual design of the accelerator.

Do We Need M&S Science?, Jose J. Padilla, Saikou Y. Diallo, Andreas Tolk

VMASC Publications

No abstract provided.

Uniform L1 Behavior Of A Time Discretization Method For A Volterra Integrodifferential Equation With Convex Kernel; Stability, Charles B. Harris, Richard D. Noren

Mathematics & Statistics Faculty Publications

We study stability of a numerical method in which the backward Euler method is combined with order one convolution quadrature for approximating the integral term of the linear Volterra integrodifferential equation u'(t) + ∫0 β (t - s)Au(s) ds = 0, t ≥ 0, u(0) = u0, which arises in the theory of linear viscoelasticity. Here A is a positive self-adjoint densely defined linear operator in a real Hilbert space, and β (t) is locally integrable, nonnegative, nonincreasing, convex, and -β'(t) is convex. We establish stability of the method under these hypotheses on β(t). Thus, …

Weighted Scores Method For Regression Models With Dependent Data, Aristidis K. Nikoloulopoulos, Harry Joe, N. Rao Chaganty

Mathematics & Statistics Faculty Publications

There are copula-based statistical models in the literature for regression with dependent data such as clustered and longitudinal overdispersed counts, for which parameter estimation and inference are straightforward. For situations where the main interest is in the regression and other univariate parameters and not the dependence, we propose a "weighted scores method", which is based on weighting score functions of the univariate margins. The weight matrices are obtained initially fitting a discretized multivariate normal distribution, which admits a wide range of dependence. The general methodology is applied to negative binomial regression models. Asymptotic and small-sample efficiency calculations show that our …

Classroom Manipulative To Engage Students In Mathematical Modeling Of Disease Spread: 1 + 1 = Achoo!, H. Gaff, M. Lyons, G. Watson

Biological Sciences Faculty Publications

Infectious diseases ranging from the common cold to cholera affect our society physically, emotionally, ecologically, and economically. Yet despite their importance and impact, there remains a lack of effective teaching materials for epidemiology and disease ecology in K-12, undergraduate, and graduate curricula [2]. To address this deficit, we've developed a classroom lesson with three instructional goals: (1) Familiarize students on basic concepts of infectious disease ecology; (2) Introduce students to a classic compartmental model and its applications in epidemiology; (3) Demonstrate the application and importance of mathematical modeling as a tool in biology. The instructional strategy uses a game-based mathematical …

Estimating The Reproductive Numbers For The 2008-2009 Cholera Outbreaks In Zimbabwe, Zindoga Mukandavire, Shu Liao, Jin Wang, Holly Gaff, David L. Smith, J. Glenn Morris Jr.

Biological Sciences Faculty Publications

Cholera remains an important global cause of morbidity and mortality, capable of causing periodic epidemic disease. Beginning in August 2008, a major cholera epidemic occurred in Zimbabwe, with 98,585 reported cases and 4,287 deaths. The dynamics of such outbreaks, particularly in nonestuarine regions, are not well understood. We explored the utility of mathematical models in understanding transmission dynamics of cholera and in assessing the magnitude of interventions necessary to control epidemic disease. Weekly data on reported cholera cases were obtained from the Zimbabwe Ministry of Health and Child Welfare (MoHCW) for the period from November 13, 2008 to July 31, …

Improving Simulations Of The Upper Ocean By Inclusion Of Surface Waves In The Mellor-Yamada Turbulence Scheme, Chuan Jiang Huang, Fangli Qiao, Zhenya Song, Tal Ezer

CCPO Publications

The Mellor-Yamada turbulence closure scheme, used in many ocean circulation models, is often blamed for overly high simulated surface temperature and overly low simulated subsurface temperature in summer due to insufficient vertical mixing. Surface waves can enhance turbulence kinetic energy and mixing of the upper ocean via wave breaking and nonbreaking-wave-turbulence interaction. The influences of wave breaking and wave-turbulence interaction on the Mellor-Yamada scheme and upper ocean thermal structure are examined and compared with each other using one-dimensional and three-dimensional ocean circulation models. Model results show that the wave-turbulence interaction can effectively amend the problem of insufficient mixing in the …

The Us Southern Ocean Global Ocean Ecosystems Dynamics Program, Eileen E. Hofmann, John M. Klinck, Dan P. Costa, Kendra L. Daly, Joseph J. Torres

CCPO Publications

The article presents information on the U.S. Southern Ocean Global Ocean Ecosystem Dynamics program (US SO GLOBEC). It was aimed at understanding the environmental and biological factors that contribute to enhanced Antarctic krill growth, reproduction, recruitment and survivorship, as well as the interactions between Antarctic krill and its predators and competitors. The highlights of US SO GLOBEC research are also discussed.

Draft Genome Sequence Of Strain Himb100, A Cultured Representative Of The Sar116 Clade Of Marine Alphaproteobacteria, Jana Grote, Cansu Bayindirli, Kristin Bergauer, Paula C. De Moraes, Huan Chen, Lindsay D'Ambrosio, Bethany Edwards, Beatriz Fernandez-Gomez, Mariam Hamisi, Dan Nguyen, Yoshimi M. Rii, Emily Saeck, Charles Schutte, Brittany Widner

OES Faculty Publications

Strain HIMB100 is a planktonic marine bacterium in the class Alphaproteobacteria. This strain is of interest because it is one of the first known isolates from a globally ubiquitous clade of marine bacteria known as SAR116 within the family Rhodospirillaceae. Here we describe preliminary features of the organism, together with the draft genome sequence and annotation. This is the second genome sequence of a member of the SAR116 clade. The 2,458,945 bp genome contains 2,334 protein-coding and 42 RNA gene

Meridional Shifts In The Marine Itcz And The Tropical Hydrologic Cycle Over The Last Three Glacial Cycles, Matthew W. Schmidt, Howard J. Spero

OES Faculty Publications

Paleoproxy studies show a strong correlation between tropical climate and high-latitude temperature variability recorded in the Greenland ice cores over the last glacial cycle. In particular, abrupt cooling events in the Greenland Ice Sheet Project II δ¹⁸O ice record appear synchronous with a southward migration of the Intertropical Convergence Zone (ITCZ) in the Atlantic, a weakening of the Indian and East Asian monsoon systems, and a strengthening of the South American monsoon system. Because this high-to-low-latitude climate teleconnection significantly alters the tropical hydrologic cycle around the globe, it plays a critical role in regulating global climate on glacial-interglacial …

Lithospheric Control On The Spatial Pattern Of Azores Hotspot Seafloor Anomalies: Constraints From A Model Of Plume-Triple Junction Interaction, Jennifer E. Georgen

OES Faculty Publications

The Azores hotspot is located near a plate boundary triple junction (TJ) consisting of the Terceira Rift (TER) and two branches of the Mid-Atlantic Ridge (MAR). The seafloor expression of the Azores hotspot has a complex spatial pattern. Latitudinal anomalies in seafloor depth and other data along the MAR extend farther to the south of the inferred location of the mantle heterogeneity than to the north. Longitudinal anomalies span a greater distance to the east of the MAR (along the TER) than to the west. A finite element model is used to investigate how the divergence of three plates away …

Cascading Migrations And Implications For Vertical Fluxes In Pelagic Ecosystems, Stephen M. Bollens, Gretchen Rollwagen-Bollens, Joel A. Quenette, Alexander B. Bochdansky

OES Faculty Publications

Diel vertical migration is widespread across diverse taxa in the world's lakes and seas, yet its biogeochemical consequences are still poorly understood. The biologically mediated vertical flux of material in the ocean (also known as the "biological pump") is a matter of major interest and concern, as it is thought to play an important role in regulating ocean carbon storage, and by extension, the global carbon cycle. Recent studies spanning multiple trophic levels from fish to dinoflagellates have led us to a concept of coupled vertical migrations that we refer to as "cascading migrations". That is, migrations that …

Executable Architecture Research At Old Dominion University, Andreas Tolk, Johnny J. Garcia, Edwin A. Shuman

Computational Modeling & Simulation Engineering Faculty Publications

Executable Architectures allow the evaluation of system architectures not only regarding their static, but also their dynamic behavior. However, the systems engineering community do not agree on a common formal specification of executable architectures. To close this gap and identify necessary elements of an executable architecture, a modeling language, and a modeling formalism is topic of ongoing PhD research. In addition, systems are generally defined and applied in an operational context to provide capabilities and enable missions. To maximize the benefits of executable architectures, a second PhD effort introduces the idea of creating an executable context in addition to the …

Florida Straits Deglacial Temperature And Salinity Change: Implications For Tropical Hydrologic Cycle Variability During The Younger Dryas, Matthew W. Schmidt, Jean Lynch-Stieglitz

OES Faculty Publications

The prevailing paradigm of abrupt climate change holds that rapid shifts associated with the most extreme climate swings of the last glacial cycle were forced by changes in the strength and northward extension of Atlantic Meridional Overturning Circulation (AMOC), resulting in an abrupt reorganization of atmospheric circulation patterns with global teleconnections. To determine the timing of tropical Atlantic atmospheric circulation changes over the past 21 ka BP, we reconstruct high resolution sea surface temperature and δ¹⁸O_SW (a proxy for surface salinity) records based on Mg/Ca ratios and oxygen isotope measurements in the planktonic foraminifera Globigerinoides ruber from …

Parallel-Sparse Symmetrical/Unsymmetrical Finite Element Domain Decomposition Solver With Multi-Point Constraints For Structural/Acoustic Analysis, Siroj Tungkahotara, Willie R. Watson, Duc T. Nguyen, Subramaniam D. Rajan

Civil & Environmental Engineering Faculty Publications

Details of parallel-sparse Domain Decomposition (DD) with multi-point constraints (MPC) formulation are explained. Major computational components of the DD formulation are identified. Critical roles of parallel (direct) sparse and iterative solvers with MPC are discussed within the framework of DD formulation. Both symmetrical and unsymmetrical system of simultaneous linear equations (SLE) can be handled by the developed DD formulation. For symmetrical SLE, option for imposing MPC equations is also provided.

Large-scale (up to 25 million unknowns involving complex numbers) structural and acoustic Finite Element (FE) analysis are used to evaluate the parallel computational performance of the proposed DD implementation using …

Anaerobic Oxidation Of Methane And The Stoichiometry Of Remineralization Processes In Continental Margin Sediments, David J. Burdige, Tomoko Kamada

OES Faculty Publications

In many coastal and continental margin sediments, pore-water property-property plots yield values of r_c:s, the stoichiometric ratio of dissolved inorganic carbon (DIC) produced to sulfate reduced, that are lower than the commonly assumed value of 2. Remineralization of organic matter more reduced than CH₂O can cause such observations, as can DIC loss due to authigenic carbonate precipitation. However, through studies of Santa Monica Basin sediments, we have observed that these observations could also be related to the occurrence of anaerobic oxidation of methane (AOM) in sediments. Specifically, using a reactive transport sediment model, we have shown …

Fossil And Contemporary Aerosol Particulate Organic Carbon In The Eastern United States: Implications For Deposition And Inputs To Watersheds, Andrew S. Wozniak, James E. Bauer, Rebecca M. Dickhut

Chemistry & Biochemistry Faculty Publications

Atmospheric particulate matter samples were collected from mid-Atlantic and northeastern U. S. (Virginia and New York, respectively) sites to assess the fossil versus contemporary sources contributing to aerosol organic carbon (OC) and the implications for its deposition to watersheds. Mean particulate matter total OC (TOC) deposition rates (wet + dry deposition) were calculated to be 1.6 and 2.4 mg C m^-2 d^-1 for the Virginia and New York sites, respectively. Wet deposition of particulate TOC was determined to be the dominant depositional mode, accounting for >65% (Virginia) and >80% (New York) of total aerosol TOC deposition. Isotopic mass …

Behavior Constrains The Dispersal Of Long-Lived Spiny Lobster Larvae, Mark J. Butler Iv, Claire B. Paris, Jason S. Goldstein, Hirokazu Matsuda, Robert K. Cowen

Biological Sciences Faculty Publications

Behavior such as ontogenetic vertical migration (OVM) limits the transport of marine larvae with short pelagic larval durations (PLDs), but its effect on the supposed long-distance dispersal of larvae with long PLDs is unknown. We conducted laboratory tests of ontogenetic change in larval phototaxis and examined size-specific patterns of larval distribution in the plankton to characterize OVM in the Caribbean spiny lobster Panulirus argus during its long (6 mo) PLD. We then used a coupled biophysical model to explore the consequences of OVM and hydrodynamics on larval P. argus dispersal in the Caribbean Sea. Larvae reared in the laboratory were …

Evaluating Methods For Optimizing Classification Success From Otolith Tracers For Spotted Seatrout (Cynoscion Nebulosus) In The Chesapeake Bay, Stacy Kavita Beharry

OES Theses and Dissertations

Identifying the natal sources of fish is an important step in understanding its population dynamics. Adult recruits are often sourced from multiple nursery areas, with good quality locations contributing disproportionately more fish to the adult stock. Because population persistence is strongly influenced by nursery habitat, methods that correctly identify the source of recruits are necessary for effective management. Within the last decade, otolith chemistry signatures have been increasingly used as a natural marker to delineate fish from a mixture of nursery sources. Despite the widespread use of otolith trace element and stable isotope ratios as habitat markers, the statistical approaches …

Elementary Teachers' Views Of Environmental Education, Rose M. Hotchkiss

Teaching & Learning Theses & Dissertations

The purpose of this research is to examine teachers' views of environmental education (EE) at the elementary level. The study addresses teachers' attitudes toward the EE at the elementary school level and their self-efficacy in teaching EE.

The study's sample consisted of 201 randomly selected kindergarten through fifth grade United States public school teachers. The participants completed an on-line survey with eight percent of the respondents participating in follow up interviews. The questionnaire measured two constructs; Teachers Attitudes Toward EE and Teacher Efficacy in EE. Teachers Attitudes Toward EE had 3 subscales; Advocacy for EE, Stewardship in EE, …

Understanding The Elements Of Executable Architectures Through A Multi-Dimensional Analysis Framework, Edwin A. Shuman Iv

Computational Modeling & Simulation Engineering Theses & Dissertations

The objective of this dissertation study is to conduct a holistic investigation into the elements of executable architectures. Current research in the field of Executable Architectures has provided valuable solution-specific demonstrations and has also shown the value derived from such an endeavor. However, a common theory underlying their applications has been missing.

This dissertation develops and explores a method for holistically developing an Executable Architecture Specification (EAS), i.e., a meta-model containing both semantic and syntactic information, using a conceptual framework for guiding data coding, analysis, and validation. Utilization of this method resulted in the description of the elements of executable …

Balloon Borne Mars Research Platforms, Sean Michael Hancock

Mechanical & Aerospace Engineering Theses & Dissertations

Aerial platforms can fill a measurement gap between orbiters and rovers, providing planetary scale high resolution in situ measurements, access to scientifically interesting terrain that is either inaccessible or hazardous to rovers, and serve as a planet-wide delivery platforms to deploy surface probes and rovers to areas inaccessible given existing entry, descent, and landing systems. A permanent robotic outpost on the Martian surface can utilize locally-derived hydrogen as a lifting gas for balloon systems deployed from Mars. That approach can simplify the inflation and launch of aerial vehicles while allowing for a long duration deployment campaign that is not constrained …

Photoproduction Of The Φ(1020) Meson In Neutral Decay Mode Γp → Φp → K(S)K(L)P, Heghine Seraydaryan

Physics Theses & Dissertations

The Φ(1020) meson photoproduction cross sections in the neutral decay mode Φ → K_SK_L are measured for the first time. This work presents measurements of differential cross sections, dσ/dt, dσ/d cos θ^Φ_c.m.; Φ decay angular distributions, W(cos θ) and W(Φ), and spin-density matrix elements, ρ⁰, in the Helicity and Gottfried-Jackson frames, in the energy range 1.6 GeV < E_γ < 2.6 GeV. We analyzed the photoproduction data of the g11a experiment collected on an LH2 target using the CLAS detectector at Hall B, TJNAF. The measured cross sections show some differences from the charged decay mode Φ → K⁺ K⁻.

Modeling And Analysis Of Repeated Ordinal Data Using Copula Based Likelihoods And Estimating Equation Methods, Raghavendra Rao Kurada

Mathematics & Statistics Theses & Dissertations

Repeated or longitudinal ordinal data occur in many fields such as biology, epidemiology, and finance. These data normally are analyzed using both likelihood and non-likelihood methods. The first part of this dissertation discusses the multivariate ordered probit model which is a likelihood method based on latent variables. We show that this latent variable model belong to a very general class of Copula models. We use the copula representation for the multivariate ordered probit model to obtain maximum likelihood estimates of the parameters. We apply the methodology in the analysis of real life data examples.

Though likelihood methods are preferable, there …

The Doubly Inflated Poisson And Related Regression Models, Manasi Sheth-Chandra

Mathematics & Statistics Theses & Dissertations

Most real life count data consists of some values that are more frequent than allowed by the common parametric families of distributions. For data consisting of only excess zeros, in a seminal paper Lambert (1992) introduced Zero-Inflated Poisson (ZIP) model, which is a mixture model that accounts for the inflated zeros. In this thesis, two Doubly Inflated Poisson (DIP) probability models, DIP (p, λ) and DIP ( p1, p2, λ), are discussed for situations where there is another inflated value k > 0 besides the inflated zeros. The distributional properties such as identifiability, moments, and conditional probabilities …

Marine Buoy Detection Using Circular Hough Transform, Loc Tran, Justin Selfridge, Gene Hou, Jiang Li

Electrical & Computer Engineering Faculty Publications

A low cost method for buoy detection in maritime settings is presented using inexpensive digital cameras. In this method, the circular Hough transform is applied to an edge image to circular objects in the image. The center of these circles will signify the locations of each buoy. The known color information of the buoys is also used to enhance the performance by removing false detections. The algorithm is compared to an approach that locates buoys purely on color information. In order to validate the method, we test the approach synthetically and also with real images captured from a small surface …

Electronically Enhanced Surface Diffusion During Ge Growth On Si(100), Ali Orguz Er, Hani E. Elsayed-Ali

Physics Faculty Publications

The effect of nanosecond pulsed laser excitation on surface diffusion during the growth of Ge on Si(100) at 250 °C was studied. In situ reflection high-energy electron diffraction was used to measure the surface diffusion coefficient while ex situ atomic force microscopy was used to probe the structure and morphology of the grown quantum dots. The results show that laser excitation of the substrate increases the surface diffusion during the growth of Ge on Si(100), changes the growth morphology, improves the crystalline structure of the grown quantum dots, and decreases their size distribution. A purely electronic mechanism of enhanced surface …