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Oxidation of alloys targeted for advanced steam turbines

Description: Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of alloys for use in USC systems, with emphasis placed on applications in high- and intermediate-pressure turbines.
Date: March 12, 2006
Creator: Holcomb, G. R.; Covino, B. S., Jr.; Bullard, S. J.; Ziomek-Moroz, M. & Alman, D. E.
Partner: UNT Libraries Government Documents Department
open access

Mechanical and charge transport properties of alkanethiol self-assembled monolayers on Au (111) surface: The Role of Molecular Tilt

Description: The relationship between charge transport and mechanical properties of alkanethiol self-assembled monolayers (SAM) on Au(111) films has been investigated using an atomic force microscope with a conductive tip. Molecular tilts induced by the pressure applied by the tip cause stepwise increases in film conductivity. A decay constant {beta} = 0.57 {+-} 0.03 {angstrom}{sup -1} was found for the current passing through the film as a function of tip-substrate separation due to this molecular tilt. Th… more
Date: November 12, 2007
Creator: Mulleregan, Alice; Qi, Yabing; Ratera, Imma; Park, Jeong Y.; Ashby, Paul D.; Quek, Su Ying et al.
Partner: UNT Libraries Government Documents Department
open access

Compact Proton Accelerator for Cancer Therapy

Description: An investigation is being made into the feasibility of making a compact proton dielectric wall (DWA) accelerator for medical radiation treatment based on the high gradient insulation (HGI) technology. A small plasma device is used for the proton source. Using only electric focusing fields for transporting and focusing the beam on the patient, the compact DWA proton accelerator m system can deliver wide and independent variable ranges of beam currents, energies and spot sizes.
Date: June 12, 2007
Creator: Chen, Y. & Paul, A. C.
Partner: UNT Libraries Government Documents Department
open access

TRITIUM EFFECTS ON DYNAMIC MECHANICAL PROPERTIES OF POLYMERIC MATERIALS

Description: Dynamic mechanical analysis has been used to characterize the effects of tritium gas (initially 1 atm. pressure, ambient temperature) exposure over times up to 2.3 years on several thermoplastics-ultrahigh molecular weight polyethylene (UHMW-PE), polytetrafluoroethylene (PTFE), and Vespel{reg_sign} polyimide, and on several formulations of elastomers based on ethylene propylene diene monomer (EPDM). Tritium exposure stiffened the elastic modulus of UHMW-PE up to about 1 year and then softened i… more
Date: November 12, 2008
Creator: Clark, E
Partner: UNT Libraries Government Documents Department
open access

Void Coalescence Processes Quantified Through Atomistic and Multiscale Simulation

Description: Simulation of ductile fracture at the atomic scale reveals many aspects of the fracture process including specific mechanisms associated with void nucleation and growth as a precursor to fracture and the plastic deformation of the material surrounding the voids and cracks. Recently we have studied void coalescence in ductile metals using large-scale atomistic and continuum simulations. Here we review that work and present some related investigations. The atomistic simulations involve three-dime… more
Date: January 12, 2007
Creator: Rudd, R E; Seppala, E T; Dupuy, L M & Belak, J
Partner: UNT Libraries Government Documents Department
open access

Convergence Analysis of a Domain Decomposition Paradigm

Description: We describe a domain decomposition algorithm for use in several variants of the parallel adaptive meshing paradigm of Bank and Holst. This algorithm has low communication, makes extensive use of existing sequential solvers, and exploits in several important ways data generated as part of the adaptive meshing paradigm. We show that for an idealized version of the algorithm, the rate of convergence is independent of both the global problem size N and the number of subdomains p used in the domain … more
Date: June 12, 2006
Creator: Bank, R E & Vassilevski, P S
Partner: UNT Libraries Government Documents Department
open access

Communication Requirements and Interconnect Optimization forHigh-End Scientific Applications

Description: The path towards realizing peta-scale computing isincreasingly dependent on building supercomputers with unprecedentednumbers of processors. To prevent the interconnect from dominating theoverall cost of these ultra-scale systems, there is a critical need forhigh-performance network solutions whose costs scale linearly with systemsize. This work makes several unique contributions towards attaining thatgoal. First, we conduct one of the broadest studies to date of high-endapplication communicati… more
Date: November 12, 2007
Creator: Kamil, Shoaib; Oliker, Leonid; Pinar, Ali & Shalf, John
Partner: UNT Libraries Government Documents Department
open access

Breakdown Characteristics Study on an 18 Cell X-band Structure

Description: A CLIC designed 18 cells, low group velocity (2.4% to 1.0% c), X-band (11.4 GHz) accelerator structure (denoted T18) was designed at CERN, its cells were built at KEK, and it was assembled and tested at SLAC. An interesting feature of this structure is that the gradient in the last cell is about 50% higher than that in the first cell. This structure has been RF conditioned at SLAC NLCTA for about 1400 hours where it incurred about 2200 breakdowns. This paper presents the characteristics of thes… more
Date: November 12, 2008
Creator: Wang, Faya
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

Aligned vertical fractures, HTI reservoir symmetry, and Thomsenseismic anisotropy parameters for polar media

Description: Sayers and Kachanov (1991) defined crack-influence parameters that are shown to be directly related to Thomsen (1986) weak-anisotropy seismic parameters for fractured reservoirs when the crack/fracture density is small enough. These results are then applied to the problem of seismic wave propagation in polar (i.e., non-isotropic) reservoirs having HTI seismic wave symmetry due to the presence of aligned vertical fractures and resulting in azimuthal seismic wave symmetry at the earth's surface. … more
Date: December 12, 2007
Creator: Berryman, James G.
Partner: UNT Libraries Government Documents Department
open access

Precise predictions for B -> Xs l+ l- in the large q2 region

Description: The inclusive B -> Xs l+ l- decay rate in the large q2 region (q2> m_psi'2) receives significant nonperturbative corrections. The resulting uncertainties can be drastically reduced by normalizing the rate to the B -> Xu l nu rate with the same q2 cut, which allows for much improved tests of short distance physics. We calculate this ratio, including the order 1/m_b3 nonperturbative corrections and the analytically known NNLO perturbative corrections. Since in the large q2 region an … more
Date: July 12, 2007
Creator: Ligeti, Zoltan; Ligeti, Zoltan & Tackmann, Frank J.
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

TOUGH+/GasH20 study of the effects of a heat source buried in theMartian permafrost

Description: We use TOUGH+/GasH2O to study the effects of a heat sourceburied in the Martian permafrost to evaluate the possibility ofestablishing a wet zone of liquid water, in which terrestrialmicroorganisms could survive and multiply. Analysis of the problemindicates that (1) only a limited permafrost volume (not exceeding 0.35 min radius) is affected, (2) a "wet" zone with limited amounts of liquidwater de-velops (not exceeding 8 and 0.7 kg for a 250 W and a 62.5 Wsource, respectively), (3) the wet zone… more
Date: May 12, 2006
Creator: Moridis, George J. & Pruess, Karsten
Partner: UNT Libraries Government Documents Department
open access

Improved Technology To Prevent Nuclear Proliferation And Counter Nuclear Terrorism

Description: As the world moves into the 21st century, the possibility of greater reliance on nuclear energy will impose additional technical requirements to prevent proliferation. In addition to proliferation resistant reactors, a careful examination of the various possible fuel cycles from cradle to grave will provide additional technical and nonproliferation challenges in the areas of conversion, enrichment, transportation, recycling and waste disposal. Radiation detection technology and information mana… more
Date: June 12, 2006
Creator: Richardson, J; Yuldashev, B; Labov, S & Knapp, R
Partner: UNT Libraries Government Documents Department
open access

Rare B Decays at Babar

Description: The author presents some of the most recent BABAR measurements for rare B decays. These include rate asymmetries in the B decays to K{sup (*)}l{sup +}l{sup -} and K{sup +}{pi}{sup -} and branching fractions in the B decays to l{sup +}{nu}{sub l}, K{sub 1}(1270){sup +}{pi}{sup -} and K{sub 1}(1400){sup +}{pi}{sup -}. The author also reports a search for the B{sup +} decay to K{sub S}{sup 0}K{sub S}{sup 0}{pi}{sup +}.
Date: January 12, 2009
Creator: Palombo, Fernando & Collaboration, for the BABAR
Partner: UNT Libraries Government Documents Department
open access

Toward Production From Gas Hydrates: Current Status, Assessment of Resources, and Simulation-Based Evaluationof Technology and Potential

Description: Gas hydrates are a vast energy resource with global distribution in the permafrost and in the oceans. Even if conservative estimates are considered and only a small fraction is recoverable, the sheer size of the resource is so large that it demands evaluation as a potential energy source. In this review paper, we discuss the distribution of natural gas hydrate accumulations, the status of the primary international R&D programs, and the remaining science and technological challenges facing c… more
Date: February 12, 2008
Creator: Reagan, Matthew; Moridis, George J.; Collett, Timothy; Boswell, Ray; Kurihara, M.; Reagan, Matthew T. et al.
Partner: UNT Libraries Government Documents Department
open access

Disorder and size effects on Kondo interactions and magnetic correlations in CePt2 nanoscrystals

Description: The evolution of the Kondo effect and magnetic correlations with size reduction in CePt{sub 2} nanoparticles (3.1-26 nm) is studied by analysis of the temperature-dependent specific heat and magnetic susceptibility. The antiferromagnetic correlations diminish with size reduction. The Kondo effect predominates at small particle size with trivalent, small Kondo temperature (T{sub K}) magnetic regions coexisting with strongly mixed valent, large T{sub K} nonmagnetic regions. We discuss the role of… more
Date: December 12, 2006
Creator: Chen, Y. Y.; Huang, P. H.; Ou, M. N.; Wang, C. R.; Yao, Y. D.; Lee, T. K. et al.
Partner: UNT Libraries Government Documents Department
open access

Performance of a 1.3 GHZ Normal-Conducting 5-Cell Standing-Wave Cavity

Description: A 5-cell, normal-conducting, 1.3 GHz, standing-wave (SW) cavity was built as a prototype capture accelerator for the ILC positron source. Although the ILC uses predominantly superconducting cavities, the capture cavity location in both a high radiation environment and a solenoidal magnetic field requires it to be normal conducting. With the relatively high duty ILC beam pulses (1 msec at 5 Hz) and the high gradient required for efficient positron capture (15 MV/m), achieving adequate cavity coo… more
Date: November 12, 2008
Creator: Wang, Faya; Adolphsen, Chris & Wang, Juwen
Partner: UNT Libraries Government Documents Department
open access

Ferromagnetism and suppression of metallic clusters in Fe implanted ZnO -- a phenomenon related to defects?

Description: We investigated ZnO(0001) single crystals annealed in high vacuum with respect to their magnetic properties and cluster formation tendency after implant-doping with Fe. While metallic Fe cluster formation is suppressed, no evidence for the relevance of the Fe magnetic moment to the observed ferromagnetism was found. The latter along with the cluster suppression is discussed with respect to defects in the ZnO host matrix, since the crystalline quality of the substrates was lowered due to the pre… more
Date: March 12, 2008
Creator: Arenholz, Elke; Zhou, S.; Potzger, K.; Talut, G.; Reuther, H.; Kuepper, K. et al.
Partner: UNT Libraries Government Documents Department
open access

Search for lepton flavor violating decays tau to l \omega (l = e, mu)

Description: A search for lepton flavor violating decays of a {tau} to a lighter-mass charged lepton and an {omega} vector meson is performed using 384.1 fb{sup -1} of e{sup +}e{sup -} annihilation data collected with the BABAR detector at the Stanford Linear Accelerator Center PEP-II storage ring. No signal is found, and the upper limits on the branching ratios are determined to be {beta}({tau}{sup {+-}} {yields} e{sup {+-}}{omega}) < 1.1 x 10{sup -7} and {beta}({tau}{sup {+-}} {yields} {mu}{sup {+-}}{o… more
Date: November 12, 2007
Creator: Collaboration, The BABAR & Aubert, B.
Partner: UNT Libraries Government Documents Department
open access

Effects of d-electrons in pseudopotential screened-exchange density functional calculations

Description: We report a theoretical study on the role of shallow d states in the screened-exchange local density approximation (sX-LDA) band structure of binary semiconductor systems.We found that inaccurate pseudo-wavefunctions can lead to 1) an overestimation of the screened-exchange interaction betweenthe localized d states and the delocalized higher energy s and p states and 2) an underestimation of the screened-exchange interaction between the d states. The resulting sX-LDA band structures have substa… more
Date: September 12, 2007
Creator: Lee, Byounghak; Canning, Andrew & Wang, Lin-Wang
Partner: UNT Libraries Government Documents Department
open access

ATLAS Inner Detector Event Data Model

Description: The data model for event reconstruction (EDM) in the Inner Detector of the ATLAS experiment is presented. Different data classes represent evolving stages in the reconstruction data flow, and specific derived classes exist for the sub-detectors. The Inner Detector EDM also extends the data model for common tracking in ATLAS and is integrated into the modular design of the ATLAS high-level trigger and off-line software.
Date: December 12, 2007
Creator: ATLAS; Akesson, F.; Costa, M. J.; Dobos, D.; Elsing, M.; Fleischmann, S. et al.
Partner: UNT Libraries Government Documents Department
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