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A review of the properties of Nb3Sn and their variation with A15composition, morphology and strain state
None
Date:
November 10, 2006
Creator:
Godeke, Arno
Object Type:
Article
System:
The UNT Digital Library
An Incompressible Navier-Stokes with Particles Algorithm andParallel Implementation
We present a variation of an adaptive projection method forcomputing solutions to the incompressible Navier-Stokes equations withsuspended particles. To compute the divergence-free component of themomentum forcing due to the particle drag, we employ an approach whichexploits the locality and smoothness of the Laplacian of the projectionoperator applied to the discretized particle drag force. We presentconvergence and performance results to demonstrate the effectiveness ofthis approach.
Date:
November 28, 2006
Creator:
Martin, Daniel F.; Colella, Phillip & Keen, Noel D.
Object Type:
Article
System:
The UNT Digital Library
Chemical reaction rates using the semiclassical Van-Vleck initialvalue representation
A semiclassical IVR formulation using the Van-Vleck propagator has been used to calculate the flux correlation function and thereby reaction rate constants. This Van-Vleck formulation of the flux-flux correlation function is computationally as simple as the classical Wigner model. However unlike the latter, it has the ability to capture quantum interference/coherence effects. Classical trajectories are evolved starting from the dividing surface that separates reactants and products, and are evolved negatively in time. This formulation has been tested on model problems ranging from the Eckart barrier, double well to the collinear H + H{sub 2}.
Date:
November 29, 2006
Creator:
Venkataraman, Charulatha & Miller, William H.
Object Type:
Article
System:
The UNT Digital Library
HINS R&D Collaboration on Electron Cloud Effects: Midyea rReport
We present a report on ongoing activities on electron-cloud R&D for the MI upgrade. These results update and extend those presented in Refs. 1, 2. In this report we have significantly expanded the parameter range explored in bunch intensity Nb, RMS bunch length {sigma}{sub z} and peak secondary emission yield (SEY) {delta}{sub max}, but we have constrained our simulations to a field-free region. We describe the threshold behaviors in all of the above three parameters. For {delta}{sub max} {ge} 1.5 we find that, even for N{sub b} = 1 x 10{sup 11}, the electron cloud density, when averaged over the entire chamber, exceeds the beam neutralization level, but remains significantly below the local neutralization level (ie., when the electron density is computed in the neighborhood of the beam). This 'excess' of electrons is accounted for by narrow regions of high concentration of electrons very close to the chamber surface, especially at the top and bottom of the chamber, akin to virtual cathodes. These virtual cathodes are kept in equilibrium, on average, by a competition between space-charge forces (including their images) and secondary emission, a mechanism that shares some features with the space-charge saturation of the current in a diode at …
Date:
November 7, 2006
Creator:
Furman, M. A.; Sonnad, K. & Vay, J. L.
Object Type:
Report
System:
The UNT Digital Library
Material Removal and Specific Energy in the Dynamic Scratching of Gamma Titanium Aluminides
Mechanical responses of three gamma titanium aluminides (TiAls) (denoted as Alloy A, Alloy B and Alloy C) subjected to dynamic scratching were studied by using a single-grit pendulum (rotating) scratch tester. The maximum depth of groove was {approx} 0.07 mm, and the scratch velocity was {approx} 1.0 m/s. Normal and tangential forces were monitored. The material removal mechanisms were examined using a scanning electron microscope (SEM) and the scratches were measured by using a laser profilometer. The mechanical properties of the tested TiAls were characterized by the instantaneous specific energy, scratch resistance and scratch hardness as related to the groove depth. Extensive thermal softening was observed in the dynamic scratch test of the TiAls, which facilitated both the detachment of developing chips and pile-up of material on side ridges. Sizable fractures were observed in the transverse direction in the tested TiAls; these fractures tended to participate in the chip formation, depending on the microstructure of the TiAl and the size of the scratch groove. Specific energy and scratch hardness are depth-dependent to various degrees for the TiAls tested. The material removal might be subjected to different mechanisms, but the overall material response can be effectively characterized by the HEM (Hwang, …
Date:
November 30, 2006
Creator:
Wang, H.; Lin, H. T. & Wereszczak, A. A.
Object Type:
Report
System:
The UNT Digital Library
Jet Energy Scale Studies and the Search for the Standard Model Higgs Boson in the Channel ZH -> nu anti-nu b anti-b at D�
The D0 experiment is based at the Tevatron, which is currently the world's highest-energy accelerator. The detector comprises three major subsystems: the tracking system, the calorimeter and the muon detector. Jets, seen in the calorimeter, are the most common product of the proton-proton interactions at 2TeV. This thesis is divided into two parts. The first part focuses on jets and describes the derivation of a jet energy scale using p{bar p} {yields} (Z + jets) events as a cross-check of the official D0 jet energy scale (Versions 4.2 and 5.1) which is derived using p{bar p} {yields} {gamma} + jets events. Closure tests were also carried out on the jet energy calibration as a further verification. Jets from b-quarks are commonly produced at D0, readily identified and are a useful physics tool. These require a special correction in the case where the b-jet decays via a muon and a neutrino. Thus a semileptonic correction was also derived as an addition to the standard energy correction for jets. The search for the Higgs boson is one of the largest physics programs at D0. The second part of this thesis describes a search for the Standard Model Higgs boson in the ZH …
Date:
November 1, 2006
Creator:
Lobo, Lydia Mary Isis
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Corrosion Performance of Ferritic Steel for SOFC Interconnect Applications
Ferritic stainless steels have been identified as potential candidates for interconnects in planar-type solid oxide fuel cells (SOFC) operating below 800ºC. Crofer 22 APU was selected for this study. It was studied under simulated SOFC-interconnect dual environment conditions with humidified air on one side of the sample and humidified hydrogen on the other side at 750ºC. The surfaces of the oxidized samples were studied by scanning electron microscopy (SEM) equipped with microanalytical capabilities. X-ray diffraction (XRD) analysis was also used in this study.
Date:
November 1, 2006
Creator:
Ziomek-Moroz, M.; Holcomb, G. R.; Covino, B. S., Jr.; Bullard, S. J.; Jablonski, P. D. & Alman, D. E.
Object Type:
Article
System:
The UNT Digital Library
Evidence for Merging or Disruption of Red Galaxies from the Evolution of Their Clustering
The formation and evolution of massive red galaxies form a crucial test of theories of galaxy formation based on hierarchical assembly. In this Letter we use observations of the clustering of luminous red galaxies from the Boötes field and N-body simulations to argue that about of the most luminous satellite galaxies appear to undergo merging or disruption within massive halos between and 0.5.
Date:
November 29, 2006
Creator:
White, Martin; White, Martin; Zheng, Zheng; Brown, Michael J. I.; Dey, Arjun & Jannuzi, Buell T.
Object Type:
Article
System:
The UNT Digital Library
Benchmark of the IMPACT Code for High Intensity Beam DynamicsSimulation
The IMPACT (Integrated Map and Particle Accelerator Tracking) code was first developed under Computational Grand Challenge project in the mid 1990s [1]. It started as a three-dimensional (3D) data parallel particle-in-cell (PIC) code written in High Performance Fortran. The code used a split-operator based method to solve the Hamiltonian equations of motion. It contained linear transfer maps for drifts, quadrupole magnets and rf cavities. The space-charge forces were calculated using an FFT-based method with 3D open boundary conditions and longitudinal periodic boundary conditions. This code was completely rewritten in the late 1990s based on a message passing parallel programming paradigm using Fortran 90 and MPI following an object-oriented software design. This improved the code's scalability on large parallel computer systems and also gave the code better software maintainability and extensibility [2]. In the following years, under the SciDAC-1 accelerator project, the code was extended to include more accelerating and focusing elements such as DTL, CCL, superconducting linac, solenoid, dipole, multipoles, and others. Besides the original split-operator based integrator, a direct integration of Lorentz equations of motion using a leap-frog algorithm was also added to the IMPACT code to handle arbitrary external nonlinear fields. This integrator can read in 3D electromagnetic …
Date:
November 16, 2006
Creator:
Qiang, J. & Ryne, R.D.
Object Type:
Article
System:
The UNT Digital Library
SYNTHESIS OF METAL HYDRIDES BY MECHANICAL ALLOYING IN AN ATTRITOR MILL: FY06 STATUS REPORT
Hydridable metal alloys are used at the Savannah River Site to process tritium. The goal of this work was to develop a mechanical alloying process as a low-cost option to produce these alloys on-site. High-speed milling at elevated temperatures has the potential to significantly reduce the time and cost of the mechanical alloying process. It was demonstrated that elemental metal powders can be alloyed in an attritor mill under argon. In order to form LaNi{sub 4.25}Al{sub 0.75} from elemental metals it was found that lanthanum and nickel must be alloyed prior to adding aluminum. It was also demonstrated that metal powders could be alloyed in the high-speed attritor with the temperature in the mill equilibrating at {approx}220 C. Optimization of the process parameters will require additional testing.
Date:
November 30, 2006
Creator:
Fox, K
Object Type:
Report
System:
The UNT Digital Library
Electronic Excitations and Metal-Insulator Transition inPoly(3-hexylthiophene) Organic Field-Effect Transistors
We carry out a comprehensive theoretical and experimentalstudy of charge injection in poly(3-hexylthiophene) (P3HT) to determinethe most likely scenario for metal-insulator transition in this system.Wecalculate the optical-absorption frequencies corresponding to a polaronand a bipolaron lattice in P3HT. We also analyze the electronicexcitations for three possible scenarios under which a first- or asecond-order metal-insulator transition can occur in doped P3HT. Thesetheoretical scenarios are compared with data from infrared absorptionspectroscopy on P3HT thin-film field-effect transistors (FETs). Ourmeasurements and theoretical predictions suggest that charge-inducedlocalized states in P3HT FETs are bipolarons and that the highest dopinglevel achieved in our experiments approaches that required for afirst-order metal-insulator transition.
Date:
November 7, 2006
Creator:
Sai, N.; Li, Z.Q.; Martin, M.C.; Basov, D.N. & Di Ventra, M.
Object Type:
Article
System:
The UNT Digital Library
Material Removal and Specific Energy in the Dynamic Scratching of Gamma Titanium Aluminides
Mechanical responses of three gamma titanium aluminides (TiAls) (denoted as Alloy A, Alloy B and Alloy C) subjected to dynamic scratching were studied by using a single-grit pendulum (rotating) scratch tester. The maximum depth of groove was ~ 0.07 mm, and the scratch velocity used was ~ 1.0 m/s. Normal and tangential forces were monitored. The material removal mechanisms were examined using a scanning electron microscope (SEM) and the scratches were measured by using a laser profilometer. The mechanical properties of the tested TiAls were characterized by the instantaneous specific energy, scratch resistance and scratch hardness as related to the depth of groove. Extensive thermal softening was observed in the dynamic scratch of the tested TiAls, which facilitated both the detachments of developing chips and the pile-ups of materials on side ridges. Sizable fractures were observed in the transverse direction on the tested TiAls; these fractures tended to participate in the chip formation, depending on the microstructure of the TiAl and the size of the scratch groove. Specific energy and scratch hardness are depth-dependent to various degrees for the tested TiAls. The materiel removal might be subjected to different mechanisms, but the overall response of materials can be effectively characterized …
Date:
November 1, 2006
Creator:
Wang, Hong; Lin, Hua-Tay & Wereszczak, Andrew A.
Object Type:
Report
System:
The UNT Digital Library
Analysis of Order Formation in Block Copolymer Thin Films UsingResonant Soft X-Ray Scattering
The lateral order of poly(styrene-block-isoprene) copolymer(PS-b-PI) thin films is characterized by the emerging technique ofresonant soft X-ray scattering (RSOXS) at the carbon K edge and comparedto ordering in bulk samples of the same materials measured usingconventional small-angle X-ray scattering. We show resonance using theoryand experiment that the loss of scattering intensity expected with adecrease in sample volume in the case of thin films can be overcome bytuning X-rays to the pi* resonance of PS or PI. Using RSOXS, we study themicrophase ordering of cylinder- and phere-forming PS-b-PI thin films andcompare these results to position space data obtained by atomic forcemicroscopy. Our ability to examine large sample areas (~;9000 mu m2) byRSOXS enables unambiguous identification of the lateral lattice structurein the thin films. In the case of the sphere-forming copolymer thin film,where the spheres are hexagonally arranged, the average sphere-to-spherespacing is between the bulk (body-centered cubic) nearest neighbor andbulk unit cell spacings. In the case of the cylinder-forming copolymerthin film, the cylinder-to-cylinder spacing is within experimental errorof that obtained in the bulk.
Date:
November 27, 2006
Creator:
Virgili, Justin M.; Tao, Yuefei; Kortright, Jeffrey B.; Balsara,Nitash P. & Segalman, Rachel A.
Object Type:
Article
System:
The UNT Digital Library
Telomere dysfunction and cell survival: roles for distinctTIN2-containing complexes
Telomeres are maintained by three DNA binding proteins, TRF1, TRF2 and POT1, and several associated factors. One factor, TIN2, binds TRF1 and TRF2 directly and POT1 indirectly. These and two other proteins form a soluble complex that may be the core telomere-maintenance complex. It is not clear whether subcomplexes exist or function in vivo. Here, we provide evidence for two TIN2 subcomplexes with distinct functions in human cells. TIN2 ablation by RNA interference caused telomere uncapping and p53-independent cell death in all cells tested. However, we isolated two TIN2 complexes from cell lysates, each selectively sensitive to a TIN2 mutant (TIN2-13, TIN2-15C). In cells with wild-type p53 function, TIN2-15C was more potent than TIN2-13 in causing telomere uncapping and eventual growth arrest. In cells lacking p53 function, TIN215C more than TIN2-13 caused genomic instability and cell death. Thus, TIN2 subcomplexes likely have distinct functions in telomere maintenance, and may provide selective targets for eliminating cells with mutant p53.
Date:
November 7, 2006
Creator:
Kim, Sahn-Ho; Davalos, Albert R.; Heo, Seok-Jin; Rodier, Francis; Beausejour, Christian; Kaminker, Patrick et al.
Object Type:
Article
System:
The UNT Digital Library
Ion Deflection for Final Optics In Laser Inertial Fusion Power Plants
Left unprotected, both transmissive and reflective final optics in a laser inertial fusion power plant would quickly fail from melting, pulsed thermal stresses, or degradation of optical properties as a result of ion implantation. One potential option for mitigating this threat is to magnetically deflect the ions such that they are directed into a robust energy dump. In this paper we detail integrated studies that have been carried out to asses the viability of this approach for protecting final optics.
Date:
November 17, 2006
Creator:
Abbott, R P & Latkowski, J F
Object Type:
Article
System:
The UNT Digital Library
Lifetime Assessments of Weapon Organics and Polymers FY05 Annual Report
Non-nuclear organics, while not yet regarded to be at risk, figure in a large percentage of Significant Findings Investigations. Further, early application of advanced lifetime, compatibility, and base-lining assessments for LEP replacement materials and emerging materials for the Reliable Replacement Warhead (RRW) provides data for rational material choices. This task is currently assessing the chemical and mechanical characteristics of a variety of weapon organics prioritized by the risk-consequence of material aging. The majority of effort to date has been dedicated to silicone elastomer components known to lose their load resistance with age, with additional effort dedicated to urethane adhesives. This fiscal year, we have focused on initial aging studies of UNI620-3, a candidate replacement material for DC745U, and Adiprene (LW520). Aging studies of S5455, originally scheduled for testing in FY05, were postponed until FY07. We have initiated aging studies on these materials by employing accelerated aging tests with exposure to Co-60 {gamma}-radiation and elevated temperatures and studying their mechanical properties using a variety of analytical tools including nuclear magnetic resonance (NMR), dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC). Additionally, we have investigated aging signatures present in parts returned from surveillance as well as initiated long and short term …
Date:
November 1, 2006
Creator:
Chinn, S.; Maxwell, R.; Sawvel, A.; Madabhushi, R.; Dinh, L.; Solyom, D. et al.
Object Type:
Report
System:
The UNT Digital Library
A Review of Stress and Strain Effects on Bi-2212
None
Date:
November 6, 2006
Creator:
Godeke, Arno
Object Type:
Article
System:
The UNT Digital Library
Cleanup Verification Package for the 118-F-7, 100-F Miscellaneous Hardware Storage Vault
This cleanup verification package documents completion of remedial action for the 118-F-7, 100-F Miscellaneous Hardware Storage Vault. The site consisted of an inactive solid waste storage vault used for temporary storage of slightly contaminated reactor parts that could be recovered and reused for the 100-F Area reactor operations.
Date:
November 2, 2006
Creator:
Appel, M. J.
Object Type:
Report
System:
The UNT Digital Library
Revealing Charge Density Wave Formation in the LaTe2 System byAngle Resolved Photoemission Spectroscopy
We present the first direct study of charge density wave(CDW) formation in quasi-2D single layer LaTe2 using high-resolutionangle resolved photoemission spectroscopy (ARPES) and low energy electrondiffraction (LEED). CDW formation is driven by Fermi surface (FS)nesting, however characterized by a surprisingly smaller gap (~;50 meV)than seen in the double layer RTe3 compounds, extending over the entireFS. This establishes LaTe2 as the first reported semiconducting 2D CDWsystem where the CDW phase is FS nesting driven. In addition, the layerdependence of this phase in the tellurides and the possible transitionfrom a stripe to a checkerboard phase is discussed.
Date:
November 15, 2006
Creator:
Garcia, D. R.; Gweon, G.-H.; Zhou, S. Y.; Graf, J.; Jozwiak, C. M.; Jung, M. H. et al.
Object Type:
Article
System:
The UNT Digital Library
Comparison of kinetic and equilibrium reaction models insimulating gas hydrate behavior in porous media
In this study we compare the use of kinetic and equilibriumreaction models in the simulation of gas (methane) hydrate behavior inporous media. Our objective is to evaluate through numerical simulationthe importance of employing kinetic versus equilibrium reaction modelsfor predicting the response of hydrate-bearing systems to externalstimuli, such as changes in pressure and temperature. Specifically, we(1) analyze and compare the responses simulated using both reactionmodels for natural gas production from hydrates in various settings andfor the case of depressurization in a hydrate-bearing core duringextraction; and (2) examine the sensitivity to factors such as initialhydrate saturation, hydrate reaction surface area, and numericaldiscretization. We find that for large-scale systems undergoing thermalstimulation and depressurization, the calculated responses for bothreaction models are remarkably similar, though some differences areobserved at early times. However, for modeling short-term processes, suchas the rapid recovery of a hydrate-bearing core, kinetic limitations canbe important, and neglecting them may lead to significantunder-prediction of recoverable hydrate. The use of the equilibriumreaction model often appears to be justified and preferred for simulatingthe behavior of gas hydrates, given that the computational demands forthe kinetic reaction model far exceed those for the equilibrium reactionmodel.
Date:
November 29, 2006
Creator:
Kowalsky, Michael B. & Moridis, George J.
Object Type:
Article
System:
The UNT Digital Library
Downhole Fluid Analyzer Development
A novel fiber optic downhole fluid analyzer has been developed for operation in production wells. This device will allow real-time determination of the oil, gas and water fractions of fluids from different zones in a multizone or multilateral completion environment. The device uses near infrared spectroscopy and induced fluorescence measurement to unambiguously determine the oil, water and gas concentrations at all but the highest water cuts. The only downhole components of the system are the fiber optic cable and windows. All of the active components--light sources, sensors, detection electronics and software--will be located at the surface, and will be able to operate multiple downhole probes. Laboratory testing has demonstrated that the sensor can accurately determine oil, water and gas fractions with a less than 5 percent standard error. Once installed in an intelligent completion, this sensor will give the operating company timely information about the fluids arising from various zones or multilaterals in a complex completion pattern, allowing informed decisions to be made on controlling production. The research and development tasks are discussed along with a market analysis.
Date:
November 28, 2006
Creator:
Turner, Bill
Object Type:
Report
System:
The UNT Digital Library
A Simplistic View of Hadron Calorimetry
All too often we rely on Monte Carlo simulations withoutworrying too much about basic physics. It is possible to start with avery simple calorimeter (a big cylinder) and learn the functional form ofpi e by aninduction argument. Monte Carlo simulations provide sanitychecks and constants. A power-law functional form describes test beamresults surprisingly well. The prediction that calorimeters responddifferently to protons and pions of the same energy was unexpected. Theeffect was later demonstrated by the CMS forward calorimeter group, usingthe most noncompensating calorimeter ever built. Calorimeter resolutionis dominated by fluctuations in piz production and the energy deposit byneutrons. The DREAM collaboration has recently used a dual readoutcalorimeter to eliminate the first of these. Ultimate resolution dependson measuring neutrons on an event-by-event basis as well.
Date:
November 16, 2006
Creator:
Groom, Donald E.
Object Type:
Article
System:
The UNT Digital Library
K-alpha conversion efficiency measurments for x-ray scattering in inertial confinement fusion plasmas
The conversion efficiency of ultra short-pulse laser radiation to K-{alpha} x-rays has been measured for various chlorine-containing targets to be used as x-ray scattering probes of dense plasmas. The spectral and temporal properties of these sources will allow spectrally-resolved x-ray scattering probing with picosecond temporal resolution required for measuring the plasma conditions in inertial confinement fusion experiments. Simulations of x-ray scattering spectra from these plasmas show that fuel capsule density, capsule ablator density, and shock timing information may be inferred.
Date:
November 21, 2006
Creator:
Kritcher, A L; Neumayer, P; Urry, M K; Robey, H; Niemann, C; Landen, O L et al.
Object Type:
Article
System:
The UNT Digital Library
FutureGen: Stepping-Stone to Sustainable Fossil-Fuel Power Generation
This presentation will highlight the U.S. Department of Energy's FutureGen Initiative. The nearly $1 billion government-industry project is a stepping-stone toward future coal-fired power plants that will produce hydrogen and electricity with zero-emissions, including carbon dioxide. The 275-megawatt FutureGen plant will initiate operations around 2012 and employ advanced coal gasification technology integrated with combined cycle electricity generation, hydrogen production, and carbon capture and sequestration. The initiative is a response to a presidential directive to develop a hydrogen economy by drawing upon the best scientific research to address the issue of global climate change. The FutureGen plant will be based on cutting-edge power generation technology as well as advanced carbon capture and sequestration systems. The centerpiece of the project will be coal gasification technology that can eliminate common air pollutants such as sulfur dioxide and nitrogen oxides and convert them to useable by-products. Gasification will convert coal into a highly enriched hydrogen gas, which can be burned much more cleanly than directly burning the coal itself. Alternatively, the hydrogen can be used in a fuel cell to produce ultra-clean electricity, or fed to a refinery to help upgrade petroleum products. Carbon sequestration will also be a key feature that will set …
Date:
November 1, 2006
Creator:
Zitney, S. E.
Object Type:
Article
System:
The UNT Digital Library