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BDDC for nonsymmetric positive definite and symmetric indefinite problems

Description: The balancing domain decomposition methods by constraints are extended to solving both nonsymmetric, positive definite and symmetric, indefinite linear systems. In both cases, certain nonstandard primal constraints are included in the coarse problems of BDDC algorithms to accelerate the convergence. Under the assumption that the subdomain size is small enough, a convergence rate estimate for the GMRES iteration is established that the rate is independent of the number of subdomains and depends … more
Date: December 10, 2008
Creator: Tu, Xuemin & Li, Jing
Partner: UNT Libraries Government Documents Department
open access

Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Horizontal Window Frames with Internal Cavities

Description: This paper assesses the accuracy of the simplified frame cavity conduction/convection and radiation models presented in ISO 15099 and used in software for rating and labeling window products. Temperatures and U-factors for typical horizontal window frames with internal cavities are compared; results from Computational Fluid Dynamics (CFD) simulations with detailed radiation modeling are used as a reference. Four different frames were studied. Two were made of polyvinyl chloride (PVC) and two of… more
Date: December 1, 2008
Creator: Gustavsen, Arlid; Kohler, Christian; Dalehaug, Arvid & Arasteh, Dariush
Partner: UNT Libraries Government Documents Department
open access

STATUS OF CHEMICAL CLEANING OF WASTE TANKS AT THE SAVANNAH RIVER SITE F TANK FARM CLOSURE PROJECT - 9114

Description: Chemical Cleaning is currently in progress for Tanks 5 and 6 at the Savannah River Site. The Chemical Cleaning process is being utilized to remove the residual waste heel remaining after completion of Mechanical Sludge Removal. This work is required to prepare the tanks for closure. Tanks 5 and 6 are 1950s vintage carbon steel waste tanks that do not meet current containment standards. These tanks are 22.9 meters (75 feet) in diameter, 7.5 meters (24.5 feet) in height, and have a capacity of 2.… more
Date: December 31, 2008
Creator: Thaxton, D; Geoff Clendenen, G; Willie Gordon, W; Samuel Fink, S & Michael Poirier, M
Partner: UNT Libraries Government Documents Department
open access

The Sloan Bright Arcs Survey : Six Strongly Lensed Galaxies at z=0.4-1.4

Description: We present new results of our program to systematically search for strongly lensed galaxies in the Sloan Digital Sky Survey (SDSS) imaging data. In this study six strong lens systems are presented which we have confirmed with followup spectroscopy and imaging using the 3.5m telescope at the Apache Point Observatory. Preliminary mass models indicate that the lenses are group-scale systems with velocity dispersions ranging from 466?878 km s{sup -1} at z = 0.17-0.45 which are strongly lensing sour… more
Date: December 1, 2008
Creator: Kubo, Jeffrey M.; Allam, Sahar S.; Annis, James; Buckley-Geer, Elizabeth J.; Diehl, H. Thomas; Kubik, Donna et al.
Partner: UNT Libraries Government Documents Department
open access

Measurements and Modeling of Coherent Synchrotron Radiation and its Impact on the LCLS Electron Beam

Description: In order to reach the high peak current required for an x-ray free electron laser, two separate magnetic dipole chicanes are used in the Linac Coherent Light Source (LCLS) accelerator to compress the electron bunch length in stages. In these bunch compressors, coherent synchrotron radiation (CSR) can be emitted either by a short electron bunch or by any longitudinal density modulation that may be on the bunch. In this paper, we report detailed measurements of the CSR-induced energy loss and tra… more
Date: December 18, 2008
Creator: Bane, K. L. F.; Decker, F. J.; Ding, Y.; Dowell, D.; Emma, P.; Frisch, J. et al.
Partner: UNT Libraries Government Documents Department
open access

Practical error estimates for Reynolds' lubrication approximation and its higher order corrections

Description: Reynolds lubrication approximation is used extensively to study flows between moving machine parts, in narrow channels, and in thin films. The solution of Reynolds equation may be thought of as the zeroth order term in an expansion of the solution of the Stokes equations in powers of the aspect ratio {var_epsilon} of the domain. In this paper, we show how to compute the terms in this expansion to arbitrary order on a two-dimensional, x-periodic domain and derive rigorous, a-priori error bounds … more
Date: December 10, 2008
Creator: Wilkening, Jon
Partner: UNT Libraries Government Documents Department
open access

Lattice QCD workflows

Description: This paper discusses the application of existing workflow management systems to a real world science application (LQCD). Typical workflows and execution environment used in production are described. Requirements for the LQCD production system are discussed. The workflow management systems Askalon and Swift were tested by implementing the LQCD workflows and evaluated against the requirements. We report our findings and future work.
Date: December 1, 2008
Creator: Piccoli, Luciano; Kowalkowski, James B.; Simone, James N.; Sun, Xian-He; Jin, Hui; Holmgren, Donald J. et al.
Partner: UNT Libraries Government Documents Department
open access

SUSY Without Prejudice at Linear Colliders

Description: We explore the physics of the general CP-conserving MSSM with Minimal Flavor Violation, the pMSSM. The 19 soft SUSY breaking parameters are chosen so to satisfy all existing experimental and theoretical constraints assuming that the WIMP is the lightest neutralino. We scan this parameter space twice using both flat and log priors and compare the results which yield similar conclusions. Constraints from both LEP and the Tevatron play an important role in obtaining our final model samples. Implic… more
Date: December 11, 2008
Creator: Rizzo, Thomas G.
Partner: UNT Libraries Government Documents Department
open access

Head-Tail Modes for Strong Space Charge

Description: Head-tail modes are described here for the space charge tune shift significantly exceeding the synchrotron tune. General equation for the modes is derived. Spatial shapes of the modes, their frequencies, and coherent growth rates are explored. The Landau damping rates are also found. Suppression of the transverse mode coupling instability by the space charge is explained.
Date: December 1, 2008
Creator: Burov, Alexey
Partner: UNT Libraries Government Documents Department
open access

Non-Standard Physics in Leptonic and Semileptonic Decays of Charmed Mesons

Description: Recent measurements of the branching fraction for D{sub s} {yields} {ell}v disagree with the Standard Model expectation, which relies on calculations of f{sub D{sub s}} from lattice QCD. This paper uses recent preliminary measurements from CLEO and a new preliminary lattice-QCD result from this conference to update the significance of the discrepancy. The 'f{sub D{sub s}} puzzle' stands now at 3.5{sigma}, with {sigma} predominantly from the statistical uncertainty of the experiments. New physic… more
Date: December 1, 2008
Creator: Kronfeld, Andreas S.
Partner: UNT Libraries Government Documents Department
open access

RADIATION EFFECTS ON EPOXY/CARBON FIBER COMPOSITE

Description: The Department of Energy Savannah River Site vitrifies nuclear waste incident to defense programs through its Defense Waste Processing Facility (DWPF). The piping in the DWPF seal pot jumper configuration must withstand the stresses during an unlikely but potential deflagration event, and maintain its safety function for a 20-year service life. Carbon fiber-reinforced epoxy composites (CFR) were proposed for protection and reinforcement of piping during such an event. The proposed CFR materials… more
Date: December 12, 2008
Creator: Hoffman, E & Eric Skidmore, E
Partner: UNT Libraries Government Documents Department
open access

Reaction chemistry and ligand exchange at cadmium selenide nanocrystal surfaces

Description: Chemical modification of nanocrystal surfaces is fundamentally important to their assembly, their implementation in biology and medicine, and greatly impacts their electrical and optical properties. However, it remains a major challenge owing to a lack of analytical tools to directly determine nanoparticle surface structure. Early nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) studies of CdSe nanocrystals prepared in tri-n-octylphosphine oxide (1) and tri-n-octylpho… more
Date: December 2, 2008
Creator: Owen, Jonathan; Park, Jungwon; Trudeau, Paul-Emile & Alivisatos, A. Paul
Partner: UNT Libraries Government Documents Department
open access

QCD Evolution of the Transverse Momentum Dependent Correlations

Description: We study the QCD evolution for the twist-three quark-gluon correlation functions associated with the transverse momentum odd quark distributions. Different from that for the leading twist quark distributions, these evolution equations involve more general twist-three functions beyond the correlation functions themselves. They provide important information on nucleon structure, and can be studied in the semi-inclusive hadron production in deep inelastic scattering and Drell-Yan lepton pair produ… more
Date: December 10, 2008
Creator: Zhou, Jian; Liang, Zuo-Tang & Yuan, Feng
Partner: UNT Libraries Government Documents Department
open access

Index Theorem for Topological Excitations on R^3 \times S^1 and Chern-Simons Theory

Description: We derive an index theorem for the Dirac operator in the background of various topological excitations on an R{sup 3} x S{sup 1} geometry. The index theorem provides more refined data than the APS index for an instanton on R{sup 4} and reproduces it in decompactification limit. In the R{sup 3} limit, it reduces to the Callias index theorem. The index is expressed in terms of topological charge and the {eta}-invariant associated with the boundary Dirac operator. Neither topological charge nor {e… more
Date: December 12, 2008
Creator: Poppitz, Erich & Unsal, Mithat
Partner: UNT Libraries Government Documents Department
open access

Global paths of time-periodic solutions of the Benjamin-Ono equation connecting arbitrary traveling waves

Description: We classify all bifurcations from traveling waves to non-trivial time-periodic solutions of the Benjamin-Ono equation that are predicted by linearization. We use a spectrally accurate numerical continuation method to study several paths of non-trivial solutions beyond the realm of linear theory. These paths are found to either re-connect with a different traveling wave or to blow up. In the latter case, as the bifurcation parameter approaches a critical value, the amplitude of the initial condi… more
Date: December 11, 2008
Creator: Ambrose, David M. & Wilkening, Jon
Partner: UNT Libraries Government Documents Department
open access

Local Two-Photon Couplings and the J=0 Fixed Pole in Real and Virtual Compton Scattering

Description: The local coupling of two photons to the fundamental quark currents of a hadron gives an energy-independent contribution to the Compton amplitude proportional to the charge squared of the struck quark, a contribution which has no analog in hadron scattering reactions. We show that this local contribution has a real phase and is universal, giving the same contribution for real or virtual Compton scattering for any photon virtuality and skewness at fixed momentum transfer squared t. The t-depende… more
Date: December 5, 2008
Creator: Brodsky, Stanley J.; Llanes-Estrada, Felipe J. & Szczepaniak, Adam P.
Partner: UNT Libraries Government Documents Department
open access

Mesoscopic structure conditions the emergence of cooperation on social networks

Description: We study the evolutionary Prisoner's Dilemma on two social networks substrates obtained from actual relational data. We find very different cooperation levels on each of them that cannot be easily understood in terms of global statistical properties of both networks. We claim that the result can be understood at the mesoscopic scale, by studying the community structure of the networks. We explain the dependence of the cooperation level on the temptation parameter in terms of the internal struct… more
Date: December 1, 2008
Creator: Lozano, S.; Arenas, A. & Sanchez, A.
Partner: UNT Libraries Government Documents Department
open access

HYDROGEN EFFECTS ON STRAIN-INDUCED MARTENSITE FORMATION IN TYPE 304L STAINLESS STEEL

Description: Unstable austenitic stainless steels undergo a strain-induced martensite transformation. The effect of hydrogen on this transformation is not well understood. Some researchers believe that hydrogen makes the transformation to martensite more difficult because hydrogen is an austenite stabilizer. Others believe that hydrogen has little or no effect at all on the transformation and claim that the transformation is simply a function of strain and temperature. Still other researchers believe that h… more
Date: December 11, 2008
Creator: Morgan, M & Ps Lam, P
Partner: UNT Libraries Government Documents Department
open access

KPiX, An Array of Self Triggered Charge Sensitive Cells Generating Digital Time and Amplitude Information

Description: The Silicon Detector proposed for the International Linear Collider (ILC) requires electronic read-out that can be tightly coupled to the silicon detectors envisioned for the tracker and the electromagnetic calorimeter. The KPiX is a 1024-channel read-out chip that bump-bonds to the detector and communicates through a few digital signals, power, and detector bias. The KPiX front-end is a low-noise dual-range charge-amplifier with a dynamic range of 17 bit, achieved by autonomous switching of th… more
Date: December 11, 2008
Creator: Freytag, D.; Herbst, R.; /SLAC; Brau, J.; U., /Oregon; Breidenbach, M. et al.
Partner: UNT Libraries Government Documents Department
open access

Ion Partitioning at the liquid/vapor interface of a multi-component alkali halidesolution: A model for aqueous sea salt aerosols

Description: The chemistry of Br species associated with sea salt ice and aerosols has been implicated in the episodes of ozone depletion reported at Arctic sunrise. However, Br{sup -} is only a minor component in sea salt, which has a Br{sup -}/Cl{sup -} molar ratio of {approx}0.0015. Sea salt is a complex mixture of many different species, with NaCl as the primary component. In recent years experimental and theoretical studies have reported enhancement of the large, more polarizable halide ion at the liqu… more
Date: December 22, 2008
Creator: Ghosal, Sutapa; Brown, Matthew A.; Bluhm, Hendrik; Krisch, Maria J.; Salmeron, Miquel; Jungwirth, Pavel et al.
Partner: UNT Libraries Government Documents Department
open access

Light-Front Holography and Novel Effects in QCD

Description: The correspondence between theories in anti-de Sitter space and conformal field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. We identify the AdS coordinate z with an invariant light-front coordin… more
Date: December 18, 2008
Creator: Brodsky, Stanley J. & de Teramond, Guy F.
Partner: UNT Libraries Government Documents Department
open access

Probing the spin polarization of current by soft x-ray imaging of current-induced magnetic vortex dynamics

Description: Time-resolved soft X-ray transmission microscopy is applied to image the current-induced resonant dynamics of the magnetic vortex core realized in a micron-sized Permalloy disk. The high spatial resolution better than 25 nm enables us to observe the resonant motion of the vortex core. The result also provides the spin polarization of the current to be 0.67 {+-} 0.16 for Permalloy by fitting the experimental results with an analytical model in the framework of the spin-transfer torque.
Date: December 9, 2008
Creator: Kasai, Shinya; Fischer, Peter; Im, Mi-Young; Yamada, Keisuke; Nakatani, Yoshinobu; Kobayashi, Kensuke et al.
Partner: UNT Libraries Government Documents Department
open access

Search For the Lepton-Flavor Violating Decays Y(3S)->e tau and Y(3S)->mu tau

Description: Charged lepton-flavor violating processes are extremely rare in the Standard Model, but they are predicted to occur in several beyond-the-Standard Model theories, including Supersymmetry or models with leptoquarks or compositeness. We present a search for such processes in a sample of 117 x 10{sup 6} {Upsilon}(3S) decays recorded with the BABAR detector. We place upper limits on the branching fractions BF({Upsilon}(3S) {yields} e{sup {+-}}{tau}{sup {-+}}) < 5.0 x 10{sup -6} and BF({Upsilon}(… more
Date: December 11, 2008
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department
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