3D-Simulation Studies of SNS Ring Doublet Magnets (open access)

3D-Simulation Studies of SNS Ring Doublet Magnets

The accumulator ring of the Spallation Neutron Source (SNS) at ORNL employs in its straight sections closely packed quadrupole doublemagnets with large aperture of R=15.1 cm an relatively short iron-to-iron distance of 51.4 cm. These quads have much extended fringe field, and magnetic interferences among them in the doublet assemblies is not avoidable. Though each magnet in the assemblies has been individually mapped to high accuracy of lower than 0.01 percent level, the experimental data including the magnetic interference effect will not be available. We have performed 3D computing simulations on a quadrupole doublet model in order to assess the degree of the interference and to obtain relevant data for the SNS commissioning and operation.
Date: May 5, 2005
Creator: Wang, J. G.; N., Tsoupas & Venturini, M.
Object Type: Article
System: The UNT Digital Library
Suppression of Large Edge Localized Modes with Edge Resonant Magnetic Fields in High Confinement DIII-D Plasmas (open access)

Suppression of Large Edge Localized Modes with Edge Resonant Magnetic Fields in High Confinement DIII-D Plasmas

None
Date: May 5, 2005
Creator: Evans, T. E.; Moyer, R. A.; Watkins, J. G.; Osborne, T. H.; Thomas, P. R.; Becoulet, M. et al.
Object Type: Article
System: The UNT Digital Library
Emerging Energy-Efficient Technologies for Industry (open access)

Emerging Energy-Efficient Technologies for Industry

U.S. industry consumes approximately 37 percent of thenation's energy to produce 24 percent of the nation's GDP. Increasingly,society is confronted with the challenge of moving toward a cleaner, moresustainable path of production and consumption, while increasing globalcompetitiveness. Technology is essential in achieving these challenges.We report on a recent analysis of emerging energy-efficient technologiesfor industry, focusing on over 50 selected technologies. The technologiesare characterized with respect to energy efficiency, economics andenvironmental performance. This paper provides an overview of theresults, demonstrating that we are not running out of technologies toimprove energy efficiency, economic and environmental performance, andneither will we in the future. The study shows that many of thetechnologies have important non-energy benefits, ranging from reducedenvironmental impact to improved productivity, and reduced capital costscompared to current technologies.
Date: May 5, 2005
Creator: Worrell, Ernst; Martin, Nathan; Price, Lynn; Ruth, Michael; Elliot, Neal; Shipley, Anna et al.
Object Type: Report
System: The UNT Digital Library
Supersymmetry Parameter Analysis: SPA Convention and Project (open access)

Supersymmetry Parameter Analysis: SPA Convention and Project

High-precision analyses of supersymmetry parameters aim atreconstructing the fundamental supersymmetric theory and its breakingmechanism. A well defined theoretical framework is needed whenhigher-order corrections are included. We propose such a scheme,Supersymmetry Parameter Analysis SPA, based on a consistent set ofconventions and input parameters. A repository for computer programs isprovided which connect parameters in different schemes and relate theLagrangian parameters to physical observables at LHC and high energy e+e-linear collider experiments, i.e., masses, mixings, decay widths andproduction cross sections for supersymmetric particles. In addition,programs for calculating high-precision low energy observables, thedensity of cold dark matter (CDM) in the universe as well as the crosssections for CDM search experiments are included. The SPA scheme stillrequires extended efforts on both the theoretical and experimental sidebefore data can be evaluated in the future at the level of the desiredprecision. We take here an initial step of testing the SPA scheme byapplying the techniques involved to a specific supersymmetry referencepoint.
Date: May 5, 2005
Creator: Hinchliffe, I. & al., et
Object Type: Article
System: The UNT Digital Library
Experimental Signatures of Homoclinic Tangles in Poloidally Diverted Tokamaks (open access)

Experimental Signatures of Homoclinic Tangles in Poloidally Diverted Tokamaks

None
Date: May 5, 2005
Creator: Evans, T E; Roeder, R W; Carter, J A; Rapoport, B I; Fenstermacher, M E & Lasnier, C J
Object Type: Article
System: The UNT Digital Library
Variability of Ocean Heat Uptake: Reconciling Observations and Models (open access)

Variability of Ocean Heat Uptake: Reconciling Observations and Models

This study examines the temporal variability of ocean heat uptake in observations and in climate models. Previous work suggests that coupled Atmosphere-Ocean General Circulation Models (A-OGCMs) may have underestimated the observed natural variability of ocean heat content, particularly on decadal and longer timescales. To address this issue, we rely on observed estimates of heat content from the 2004 World Ocean Atlas (WOA-2004) compiled by Levitus et al. (2005). Given information about the distribution of observations in WOA-2004, we evaluate the effects of sparse observational coverage and the infilling that Levitus et al. use to produce the spatially-complete temperature fields required to compute heat content variations. We first show that in ocean basins with limited observational coverage, there are important differences between ocean temperature variability estimated from observed and infilled portions of the basin. We then employ data from control simulations performed with eight different A-OGCMs as a test-bed for studying the effects of sparse, space- and time-varying observational coverage. Subsampling model data with actual observational coverage has a large impact on the inferred temperature variability in the top 300 and 3000 meters of the ocean. This arises from changes in both sampling depth and in the geographical areas sampled. Our …
Date: May 5, 2005
Creator: AchutaRao, K. M.; Santer, B. D.; Gleckler, P. J.; Taylor, K.; Pierce, D.; Barnett, T. et al.
Object Type: Article
System: The UNT Digital Library
The Power of a Good Idea: Quantitative Modeling of the Spread of Ideas from Epidemiological Models (open access)

The Power of a Good Idea: Quantitative Modeling of the Spread of Ideas from Epidemiological Models

The population dynamics underlying the diffusion of ideas hold many qualitative similarities to those involved in the spread of infections. In spite of much suggestive evidence this analogy is hardly ever quantified in useful ways. The standard benefit of modeling epidemics is the ability to estimate quantitatively population average parameters, such as interpersonal contact rates, incubation times, duration of infectious periods, etc. In most cases such quantities generalize naturally to the spread of ideas and provide a simple means of quantifying sociological and behavioral patterns. Here we apply several paradigmatic models of epidemics to empirical data on the advent and spread of Feynman diagrams through the theoretical physics communities of the USA, Japan, and the USSR in the period immediately after World War II. This test case has the advantage of having been studied historically in great detail, which allows validation of our results. We estimate the effectiveness of adoption of the idea in the three communities and find values for parameters reflecting both intentional social organization and long lifetimes for the idea. These features are probably general characteristics of the spread of ideas, but not of common epidemics.
Date: May 5, 2005
Creator: Bettencourt, L. M. A.; Cintron-Arias, A.; Kaiser, D. I. & Castillo-Chavez, C.
Object Type: Report
System: The UNT Digital Library

Why Evolutionary Biology and Genome Sciences Need Each Other

None
Date: May 5, 2005
Creator: Boore, Jeffrey
Object Type: Presentation
System: The UNT Digital Library
Improved Processes to Remove Naphthenic Acids (open access)

Improved Processes to Remove Naphthenic Acids

In the second year of this project, we continued our effort to develop low temperature decarboxylation catalysts and investigate the behavior of these catalysts at different reaction conditions. We conducted a large number of dynamic measurements with crude oil and model compounds to obtain the information at different reaction stages, which was scheduled as the Task2 in our work plan. We developed a novel adsorption method to remove naphthenic acid from crude oil using naturally occurring materials such as clays. Our results show promise as an industrial application. The theoretical modeling proposed several possible reaction pathways and predicted the reactivity depending on the catalysts employed. From all of these studies, we obtained more comprehensive understanding about catalytic decarboxylation and oil upgrading based on the naphthenic acid removal concept.
Date: May 5, 2005
Creator: Zhang, Aihua; Ma, Qisheng; Wang, Kangshi; Goddard, William A. & Tang, Yongchun
Object Type: Report
System: The UNT Digital Library
A texture-based framework for improving CFD data visualization in a virtual environment (open access)

A texture-based framework for improving CFD data visualization in a virtual environment

In the field of computational fluid dynamics (CFD) accurate representations of fluid phenomena can be simulated hut require large amounts of data to represent the flow domain. Most datasets generated from a CFD simulation can be coarse, {approx}10,000 nodes or cells, or very fine with node counts on the order of 1,000,000. A typical dataset solution can also contain multiple solutions for each node, pertaining to various properties of the flow at a particular node. Scalar properties such as density, temperature, pressure, and velocity magnitude are properties that are typically calculated and stored in a dataset solution. Solutions are not limited to just scalar properties. Vector quantities, such as velocity, are also often calculated and stored for a CFD simulation. Accessing all of this data efficiently during runtime is a key problem for visualization in an interactive application. Understanding simulation solutions requires a post-processing tool to convert the data into something more meaningful. Ideally, the application would present an interactive visual representation of the numerical data for any dataset that was simulated while maintaining the accuracy of the calculated solution. Most CFD applications currently sacrifice interactivity for accuracy, yielding highly detailed flow descriptions hut limiting interaction for investigating the field.
Date: May 5, 2005
Creator: Bivins, Gerrick O'Ron
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Empirical Study of Ne in H-Mode Pedestal in DIII-D (open access)

Empirical Study of Ne in H-Mode Pedestal in DIII-D

There is compelling empirical [1] and theoretical [2] evidence that the global confinement of H-mode discharges increases as the pedestal pressure or temperature increases. Therefore, confidence in the performance of future machines requires an ability to predict the pedestal conditions in those machines. At this time, both the theoretical and empirical understanding of transport in the pedestal are incomplete and are inadequate to predict pedestal conditions in present or future machines. Recent empirical results might be evidence of a fundamental relation between the electron temperature T{sub e} and electron density n{sub e} profiles in the pedestal. A data set from the ASDEX-Upgrade tokamak has shown that {eta}{sub e}, the ratio between the scale lengths of the n{sub e} and T{sub e} profiles, exhibits a value of about 2 throughout the pedestal, despite a large range of the actual density and temperature values [3]. Data from the DIII-D tokamak show that over a wide range of pedestal density, the width of the steep gradient region for the T{sub e} profile is about 1-2 times the corresponding width for the n{sub e} profile, where both widths are measured from the plasma edge [4]. Thus, the barrier in the density might form a …
Date: May 5, 2005
Creator: . Groebner, R. J.; Osborne, T. H.; Fenstermacher, M. E.; Leonard, A. W.; Mahdavi, M. A.; Snyder, P. B. et al.
Object Type: Article
System: The UNT Digital Library
Edge Currents and Stability in DIII-D (open access)

Edge Currents and Stability in DIII-D

Understanding the stability physics of the H-mode pedestal in tokamak devices requires an accurate measurement of plasma current in the pedestal region with good spatial resolution. Theoretically, the high pressure gradients achieved in the edge of H-mode plasmas should lead to generation of a significant edge current density peak through bootstrap and Pfirsh-Schlueter effects. This edge current is important for the achievement of second stability in the context of coupled magneto hydrodynamic (MHD) modes which are both pressure (ballooning) and current (peeling) driven [1]. Many aspects of edge localized mode (ELM) behavior can be accounted for in terms of an edge current density peak, with the identification of Type 1 ELMs as intermediate-n toroidal mode number MHD modes being a natural feature of this model [2]. The development of a edge localized instabilities in tokamak experiments code (ELITE) based on this model allows one to efficiently calculate the stability and growth of the relevant modes for a broad range of plasma parameters [3,4] and thus provides a framework for understanding the limits on pedestal height. This however requires an accurate assessment of the edge current. While estimates of j{sub edge} can be made based on specific bootstrap models, their validity …
Date: May 5, 2005
Creator: Thomas, D. M.; Fenstermacher, M. E.; Finkenthal, D. K.; Groebner, R. J.; Lao, L. L.; Leonard, A. W. et al.
Object Type: Article
System: The UNT Digital Library
Advanced Electric and Magnetic Material Models for FDTD Electromagnetic Codes (open access)

Advanced Electric and Magnetic Material Models for FDTD Electromagnetic Codes

The modeling of dielectric and magnetic materials in the time domain is required for pulse power applications, pulsed induction accelerators, and advanced transmission lines. For example, most induction accelerator modules require the use of magnetic materials to provide adequate Volt-sec during the acceleration pulse. These models require hysteresis and saturation to simulate the saturation wavefront in a multipulse environment. In high voltage transmission line applications such as shock or soliton lines the dielectric is operating in a highly nonlinear regime, which require nonlinear models. Simple 1-D models are developed for fast parameterization of transmission line structures. In the case of nonlinear dielectrics, a simple analytic model describing the permittivity in terms of electric field is used in a 3-D finite difference time domain code (FDTD). In the case of magnetic materials, both rate independent and rate dependent Hodgdon magnetic material models have been implemented into 3-D FDTD codes and 1-D codes.
Date: May 5, 2005
Creator: Poole, B. R.; Nelson, S. D. & Langdon, S.
Object Type: Article
System: The UNT Digital Library
Assessment of Raman Spectroscopy as a Silicone Pad Production Diagnostic (open access)

Assessment of Raman Spectroscopy as a Silicone Pad Production Diagnostic

Silicone pressure pads are currently deployed in the W80. The mechanical properties of these pads are largely based on the degree of crosslinking between the polymer components that comprise the raw gumstock from which they are formed. Therefore, it is desirable for purposes of both production and systematic study of these materials to have a rapid, reliable means of assaying the extent of crosslinking. The present report describes the evaluation of Raman spectroscopy in this capacity.
Date: May 5, 2005
Creator: Saab, A P; Balazs, G B & Maxwell, R S
Object Type: Report
System: The UNT Digital Library
Notes on the Measurement of pH Values (open access)

Notes on the Measurement of pH Values

The original definition of pH is: pH = -log a{sub H}. Where a{sub H} is the (relative) hydrogen ion activity. However, a single ion activity cannot be measured. Activities of individual ionic species are necessarily conventional. The pH number, of course, has in itself little absolute significance. As the negative of the logarithm of a product of a concentration (c or m) and an activity coefficient (y or {gamma}), it acquires its magnitude from the numerical scale adopted for the latter. Experimental pH measurements are nonetheless widely applied to the determination of thermodynamic equilibrium data such as pK values, on the assumption that they represent -log a{sub H} (or paH). The single ion activity coefficient approaches unity as the ionic strength goes to zero, so that activity becomes m or c and paH becomes pmH or pcH. pH is therefore defined operationally in terms of the operation or method used to measure it, that is, by means of a cell called an operational cell. The cell is standardized by solutions of assigned pH value (Reference Value pH Standard, Primary pH Standards and Operational Standards). Such standard reference solutions are buffer solutions whose pH values are assigned from measurements on cells …
Date: May 5, 2005
Creator: Carranza, R M & Rebak, R B
Object Type: Report
System: The UNT Digital Library
ELECTROMAGNETIC SIMULATIONS OF DIELECTRIC WALL ACCELERATOR STRUCTURES FOR ELECTRON BEAM ACCELERATION (open access)

ELECTROMAGNETIC SIMULATIONS OF DIELECTRIC WALL ACCELERATOR STRUCTURES FOR ELECTRON BEAM ACCELERATION

Dielectric Wall Accelerator (DWA) technology incorporates the energy storage mechanism, the switching mechanism, and the acceleration mechanism for electron beams. Electromagnetic simulations of DWA structures includes these effects and also details of the switch configuration and how that switch time affects the electric field pulse which accelerates the particle beam. DWA structures include both bi-linear and bi-spiral configurations with field gradients on the order of 20MV/m and the simulations include the effects of the beampipe, the beampipe walls, the DWA High Gradient Insulator (HGI) insulating stack, wakefield impedance calculations, and test particle trajectories with low emittance gain. Design trade-offs include the transmission line impedance (typically a few ohms), equilibration ring optimization, driving switch inductances, and layer-to-layer coupling effects and the associated affect on the acceleration pulse's peak value.
Date: May 5, 2005
Creator: Nelson, S D & Poole, B R
Object Type: Article
System: The UNT Digital Library
Recovery of the orbital parameters and pulse evolution of V0332+53 during a huge outburst (open access)

Recovery of the orbital parameters and pulse evolution of V0332+53 during a huge outburst

The high mass X-ray binary (HMXB) V0332+53 became active at the end of 2004, with the outburst being monitored by RXTE and INTEGRAL at hard X-rays. Here, the orbital parameters are measured with the hard X-ray data through the fitting of the Doppler-shifted spin periods. The derived orbital period and the eccentricity are consistent with those reported by Stella et al. (1985) from earlier EXOSAT observations, whereas the projected semimajor axis and the periastron longitude are found to differ, from 48 {+-} 4 to 86{sub -10}{sup +6} lt-s and from 313{sup o} {+-} 10 to 282{sup o} {+-} 14, respectively. This would indicate an angular speed of {ge} 1.6 {sup o} {+-} 0.9 yr{sup -1} for the orbit over the past 20 years. The periastron passage time, TJD 13367 {+-} 1, is just around the time when the intensity reached the maximum and, an orbital period earlier is the time when the outburst occurred. This correlation resembles the behavior of a Type I outburst. During the outburst the source spun up with {dot P}{sub spin} = 8.01{sub -1.14}{sup 1.00} x 10{sup -6} s day{sup -1}. The evolution of the pulse profile is highly intensity dependent. The separation of the double …
Date: May 5, 2005
Creator: Zhang, S.; Qu, J. L.; Song, L. M. & Torres, D. F.
Object Type: Article
System: The UNT Digital Library
Time-of-flight flow imaging using NMR remote detection (open access)

Time-of-flight flow imaging using NMR remote detection

A time-of-flight imaging technique is introduced to visualize fluid flow and dispersion through porous media using NMR. As the fluid flows through a sample, the nuclear spin magnetization is modulated by RF pulses and magnetic field gradients to encode the spatial coordinates of the fluid. When the fluid leaves the sample, its magnetization is recorded by a second RF coil. This scheme not only facilitates a time-dependent imaging of fluid flow, it also allows a separate optimization of encoding and detection subsystems to enhance overall sensitivity. The technique is demonstrated by imaging gas flow through a porous rock.
Date: May 5, 2005
Creator: Granwehr, Josef; Harel, Elad; Han, Song-I; Garcia, Sandra; Pines,Alex; Sen, Pabitra N. et al.
Object Type: Article
System: The UNT Digital Library
Edge Localized Mode Control with an Edge Resonant Magnetic Perturbation (open access)

Edge Localized Mode Control with an Edge Resonant Magnetic Perturbation

None
Date: May 5, 2005
Creator: Moyer, R. A.; Evans, T. E.; Osborne, T. H.; Thomas, P. R.; Becoulet, M.; Harris, J. et al.
Object Type: Article
System: The UNT Digital Library
Characterization of Tank 23H Supernate Per Saltstone Waste Acceptance Criteria Analysis Requirements -2005 (open access)

Characterization of Tank 23H Supernate Per Saltstone Waste Acceptance Criteria Analysis Requirements -2005

Variable depth Tank 23H samples (22-inch sample [HTF-014] and 185-inch sample [HTF-013]) were pulled from Tank 23H in February, 2005 for characterization. The characterization of the Tank 23H low activity waste is part of the overall liquid waste processing activities. This characterization examined the species identified in the Saltstone Waste Acceptance Criteria (WAC) for the transfer of waste into the Salt-Feed Tank (SFT). The samples were delivered to the Savannah River National Laboratory (SRNL) and analyzed. Apart from radium-226 with an average measured detection limit of < 2.64E+03 pCi/mL, which is about the same order of magnitude as the WAC limit (< 8.73E+03 pCi/mL), none of the species analyzed was found to approach the limits provided in the Saltstone WAC. The concentration of most of the species analyzed for the Tank 23H samples were 2-5 orders of magnitude lower than the WAC limits. The achievable detection limits for a number of the analytes were several orders of magnitude lower than the WAC limits, but one or two orders of magnitude higher than the requested detection limits. Analytes which fell into this category included plutonium-241, europium-154/155, antimony-125, tin-126, ruthenium/rhodium-106, selenium-79, nickel-59/63, ammonium ion, copper, total nickel, manganese and total organic carbon.
Date: May 5, 2005
Creator: Oji, L
Object Type: Report
System: The UNT Digital Library
Microstructure evolution of tin under electromigration studied bysynchrotron X-Ray micro-diffraction (open access)

Microstructure evolution of tin under electromigration studied bysynchrotron X-Ray micro-diffraction

Under constant current electromigration, white tin(?-Sn)exhibited a resistance drop of up to 10 percent. It has a body centertetragonal (BCT) structure, and the resistivity along the aand b axes is35 percent smaller than that along the c axis.Microstructure evolutionunder electromigration could be responsible for the resistance drop.Synchrotron radiation white beam x-ray microdiffraction was used to studythis evolution. Both stress and grain orientation was studied.Grain-by-grain analysis was obtained from the diffracted Laue patternsabout the changes of grain orientation during electromigration testing inex-situ and in-situ samples. We observed that high resistance grainsreorient with respect to the neighboring low resistance grains, mostlikely by grain rotation of the latter. A different mechanism ofmicrostructure evolution under electromigration from the normal graingrowth is proposed and discussed.
Date: May 5, 2005
Creator: Wu, Albert T.; Lloyd, J.R.; Tamura, N. & Tu, K.-N.
Object Type: Article
System: The UNT Digital Library
Nanotube-based gas sensors - role of structural defects (open access)

Nanotube-based gas sensors - role of structural defects

Existing theoretical literature suggests that defect-free, pristine carbon nanotubes (CNTs) interact weakly with many gas molecules like H{sub 2}O, CO, NH{sub 3}, H{sub 2}, and so on. The case of NH{sub 3} is particularly intriguing because this is in disagreement with experimentally observed changes in electrical conductance of CNTs upon exposure to these gases. In order to explain such discrepancy, we have carried out Density Functional Theory (DFT) investigations of the role of common atomistic defects in CNT (Stone-Wales, monovacancy, and interstitial) on the chemisorption of NH{sub 3}. Computed binding energies, charge transfer, dissociation barriers, and vibrational modes are compared with existing experimental results on electrical conductance, thermal desorption and infrared spectroscopy.
Date: May 5, 2005
Creator: Andzelm, J; Govind, N & Maiti, A
Object Type: Article
System: The UNT Digital Library
Final Report: Understanding the Chemistry of the Actinides in High Level Waste Tank Systems: The Impact of Temperature on Hydrolysis and Complexation with Organics (open access)

Final Report: Understanding the Chemistry of the Actinides in High Level Waste Tank Systems: The Impact of Temperature on Hydrolysis and Complexation with Organics

The solubility of CeO2 and ThO2 in aqueous NaNO3 solutions was studied as a function of pH and ionic strength, and the concentration of the organic ligands: citrate, EDTA, and oxalate. The main findings of the study are that these organic ligands increase the solubility of CeO2 markedly via the formation of complexes. On the other hand, the solubility of ThO2 was not affected by the presence of these ligands at levels of several hundred micromolar. These results have implications for the behavior of Pu(IV), for which Ce(IV) and Th(IV) are analogues.
Date: May 5, 2005
Creator: Wood, Scott A.
Object Type: Report
System: The UNT Digital Library
Estimation of field-scale soil hydraulic and dielectric parametersthrough joint inversion of GPR and hydrological data (open access)

Estimation of field-scale soil hydraulic and dielectric parametersthrough joint inversion of GPR and hydrological data

A method is described for jointly using time-lapse multiple-offset cross-borehole ground-penetrating radar (GPR) travel time measurements and hydrological measurements to estimate field-scale soil hydraulic parameters and parameters of the petrophysical function, which relates soil porosity and water saturation to the effective dielectric constant. We build upon previous work to take advantage of a wide range of GPR data acquisition configurations and to accommodate uncertainty in the petrophysical function. Within the context of water injection experiments in the vadose zone, we test our inversion methodology with synthetic examples and apply it to field data. The synthetic examples show that while realistic errors in the petrophysical function cause substantial errors in the soil hydraulic parameter estimates,simultaneously estimating petrophysical parameters allows for these errors to be minimized. Additionally, we observe in some cases that inaccuracy in the GPR simulator causes systematic error in simulated travel times, making necessary the simultaneous estimation of a correction parameter. We also apply the method to a three-dimensional field setting using time-lapse GPR and neutron probe (NP) data sets collected during an infiltration experiment at the U.S. Department of Energy (DOE) Hanford site in Washington. We find that inclusion of GPR data in the inversion procedure allows for …
Date: May 5, 2005
Creator: Kowalsky, Michael B.; Finsterle, Stefan; Peterson, John; Hubbard,Susan; Rubin, Yoram; Majer, Ernest et al.
Object Type: Article
System: The UNT Digital Library