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An improved Neutrino Oscillations Analysis of the MiniBooNE Data
We calculate the exclusion region in the parameter space of {nu}{sub {mu}} {yields} {nu}{sub e} oscillations of the LSND type using a combined fit to the reconstructed energy distributions of neutrino candidate samples from the MiniBooNE data obtained with two different particle identification methods. The two {nu}{sub e} candidate samples are included together with a high statistics sample of {nu}{sub {mu}} events in the definition of a {chi}{sup 2} statistic which includes the correlations between the energy intervals of all three samples and handles the event overlap between the {nu}{sub e} samples. The {nu}{sub {mu}} sample is introduced to constrain the effect of systematic uncertainties. This analysis increases the exclusion limit in the region {Delta}m{sup 2} {approx}< 1eV{sup 2} when compared with the result previously published by the collaboration, which used a different technique.
Date:
January 1, 2008
Creator:
Aguilar-Arevalo, Alexis Armando
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Recombination Lifetimes Using the RCPCD Technique: Comparison with Other Methods
The theory and operation of the resonance-coupled photoconductive decay (RCPCD) technique is described. Examples are presented of data measured on a wide variety of sample types. The RCPCD technique has been applied to a variety of wafer and thin-film materials. Using this technique, we can measure recombination lifetime over at least three decades of injection level. We can also measure relative values of minority-carrier mobility and diffusion length. By scanning the excitation wavelength, we can measure spectral response and photoconductive excitation spectra. Deep-level impurities have been detected by several variations of RCPCD.
Date:
January 1, 2005
Creator:
Ahrenkiel, R. K.; Johnston, S. W. & Dashdorj, J.
Object Type:
Article
System:
The UNT Digital Library
Towards enhancing Sandia's capabilities in multiscale materials modeling and simulation.
We report our conclusions in support of the FY 2003 Science and Technology Milestone ST03-3.5. The goal of the milestone was to develop a research plan for expanding Sandia's capabilities in materials modeling and simulation. From inquiries and discussion with technical staff during FY 2003 we conclude that it is premature to formulate the envisioned coordinated research plan. The more appropriate goal is to develop a set of computational tools for making scale transitions and accumulate experience with applying these tools to real test cases so as to enable us to attack each new problem with higher confidence of success.
Date:
January 1, 2004
Creator:
Aidun, John Bahram; Fang, Huei Eliot; Barbour, John Charles; Westrich, Henry Roger & Chen, Er-Ping
Object Type:
Report
System:
The UNT Digital Library
Procedure for measuring the solar reflectance of flat or curved roofing assemblies
None
Date:
January 1, 2008
Creator:
Akbari, Hashem; Akbari, Hashem; Levinson, Ronnen & Stern, Stephanie
Object Type:
Article
System:
The UNT Digital Library
An inter-realm, cyber-security infrastructure for virtual supercomputing
Virtual supercomputing, (ise ., high-performance grid computing), is poised to revolutionize the way we think about and use computing. However, the security of the links interconnecting the nodes within such an environment will be its Achilles heel, particularly when secure communication is required to tunnel through heterogeneous domains. In this paper we examine existing security mechanisms, show their inadequacy, and design a comprehensive cybersecurity infrastructure that meets the security requirements of virtual supercomputing. Keywords Security, virtual supercomputing, grid computing, high-performance computing, GSS-API, SSL, IPsec, component-based software, dynamic reconfiguration.
Date:
January 1, 2001
Creator:
Al-Muhtadi, J. (Jalal); Feng, W. C. (Wu-Chun) & Fisk, M. E. (Mike E. )
Object Type:
Article
System:
The UNT Digital Library
Quantification of ammonia binding sites in Davison (Type 3A) zeolite desiccant : a solid-state Nitrogen-15 MAS NMR spectroscopy investigation.
The quantitative analysis of ammonia binding sites in the Davison (Type 3A) zeolite desiccant using solid-state {sup 15}N MAS NMR spectroscopy is reported. By utilizing 15N enriched ammonia ({sup 15}NH{sub 3}) gas, the different adsorption/binding sites within the zeolite were investigated as a function of NH{sub 3} loading. Using {sup 15}N MAS NMR multiple sites were resolved that have distinct cross-polarization dynamics and chemical shift behavior. These differences in the {sup 15}N NMR were used to characterize the adsorption environments in both the pure 3A zeolite and the silicone-molded forms of the desiccant.
Date:
January 1, 2004
Creator:
Alam, Todd Michael; Holland, Gregory P. & Cherry, Brian Ray
Object Type:
Report
System:
The UNT Digital Library
Reconstructing cosmological matter perturbations using standard candles and rulers
For a large class of dark energy (DE) models, for which the effective gravitational constant is a constant and there is no direct exchange of energy between DE and dark matter (DM), knowledge of the expansion history suffices to reconstruct the growth factor of linearized density perturbations in the non-relativistic matter component on scales much smaller than the Hubble distance. In this paper, we develop a non-parametric method for extracting information about the perturbative growth factor from data pertaining to the luminosity or angular size distances. A comparison of the reconstructed density contrast with observations of large-scale structure and gravitational lensing can help distinguish DE models such as the cosmological constant and quintessence from models based on modified gravity theories as well as models in which DE and DM are either unified or interact directly. We show that for current supernovae (SNe) data, the linear growth factor at z = 0.3 can be constrained to 5% and the linear growth rate to 6%. With future SNe data, such as expected from the Joint Dark Energy Mission, we may be able to constrain the growth factor to 2%-3% and the growth rate to 3%-4% at z = 0.3 with this unbiased, …
Date:
January 1, 2008
Creator:
Alam, Ujjaini; Sahni, Varun & Starobinsky, Alexei A
Object Type:
Article
System:
The UNT Digital Library
Multi-Ton Argon and Xenon
None
Date:
January 1, 2009
Creator:
Alarcon, Ricardo; Balascuta, Septimiu; U., /Arizona State; Alton, Drew; College, /Augustana; Aprile, Elena et al.
Object Type:
Report
System:
The UNT Digital Library
GW correlation effects on plutonium quasiparticle energies: changes in crystal-field splitting
We present results for the electronic structure of plutonium by using a recently developed quasiparticle self-consistent GW method (QSGW). We consider a paramagnetic solution without spin-orbit interaction as a function of volume for the face-centered cubic (fcc) unit cell. We span unit-cell volumes ranging from 10% greater than the equilibrium volume of the 8 phase to 90 % of the equivalent for the a phase of Pu. The self-consistent GW quasiparticle energies are compared to those obtained within the Local Density Approximation (LDA). The goal of the calculations is to understand systematic trends in the effects of electronic correlations on the quasiparticle energy bands of Pu as a function of the localization of the J orbitals. We show that correlation effects narrow the f bands in two significantly different ways. Besides the expected narrowing of individual f bands (flatter dispersion), we find that an even more significant effect on the f bands is a decrease in the crystal-field splitting of the different bands
Date:
January 1, 2009
Creator:
Albers, Robert C; Chantis, Athanasios N; Svane, Axel & Christensen, Niels E
Object Type:
Article
System:
The UNT Digital Library
Improved Intrinsic Stability of CdTe Polycrystalline Thin Film Devices
A systems-driven approach linking upstream solar cell device fabrication history with downstream performance and stability has been applied to CdS/CdTe small-area device research. The best resulting initial performance (using thinner CdS, thicker CdTe, no oxygen during VCC, and the use of NP etch) was shown to simultaneously correlate with poor stability. Increasing the CdS layer thickness significantly improved stability at only a slight decrease in overall performance. It was also determined that cell perimeter effects can accelerate degradation in these devices. A ''margined'' contact significantly reduces the contribution of edge shunting to degradation, and thus yields a more accurate determination of the intrinsic stability. Pspice discrete element models demonstrate how spatially localized defects can effectively dominate degradation. Mitigation of extrinsic shunting improved stabilized efficiency degradation levels (SEDL) to near 20% in 100 C tests. Further process optimization to reduce intrinsic effects improved SEDL to better than 10% at the same stress temperatures and times.
Date:
January 1, 2005
Creator:
Albin, D.; Berniard, T.; McMahon, T.; Noufi, R. & Demtsu, S.
Object Type:
Article
System:
The UNT Digital Library
Processing Effects on Junction Interdiffusion in CdS/CdTe Polycrystalline Devices
The performance of CdS/CdTe solar cells is strongly impacted by the process used to grow the CdS layer. CdS films grown by chemical-bath deposition (CBD) exhibit lower sublimation (CSS).
Date:
January 1, 2000
Creator:
Albin, D.; Yan, Y.; King, D.; Moutinho, H.; Jones, K.; Matson, R. et al.
Object Type:
Article
System:
The UNT Digital Library
A Parallel Multigrid Method for Neutronics Applications
The multigrid method has been shown to be the most effective general method for solving the multi-dimensional diffusion equation encountered in neutronics. This being the method of choice, we develop a strategy for implementing the multigrid method on computers of massively parallel architecture. This leads us to strategies for parallelizing the relaxation, contraction (interpolation), and prolongation operators involved in the method. We then compare the efficiency of our parallel multigrid with other parallel methods for solving the diffusion equation on selected problems encountered in reactor physics.
Date:
January 1, 2001
Creator:
Alcouffe, Raymond E.
Object Type:
Article
System:
The UNT Digital Library
Configuration Manual Polarized Proton Collider at RHIC
In this report we present our design to accelerate and store polarized protons in RHIC, with the level of polarization, luminosity, and control of systematic errors required by the approved RHIC spin physics program. We provide an overview of the physics to be studied using RHIC with polarized proton beams, and a brief description of the accelerator systems required for the project.
Date:
January 1, 2006
Creator:
Alekseev, I.; Allgower, C.; Bai, M.; Batygin, Y.; Bozano, L.; Brown, K. et al.
Object Type:
Report
System:
The UNT Digital Library
Grain refinement in beryllium by equal channel angular extrusion.
Ultrafine-grained Be is the material of choice for fabrication of the NIF target capsules. One method of producing ultrafine grains in metals is by imposing very large strains. Equal channel angular extrusion (ECAE) has been used to achieve these high strains. Previous work has shown that powder-source Be can be successfully processed by ECAE. Pure Be and Be-0.9 at% Cu alleys have been arc melted and cast into billets 5 mm in diameter by 30 mm in length. These billets were enclosed in cans fabricated from commercial purity Ni, with an electron-beam welded end plug. These cans were extruded at 425C in ECAE tooling with a 120' angle between the inlet and outlet channels. The billets were extruded up to 4 times. The microstructures of the powdersource Be and the arc-melted Be and Be-0.9 at% Cu materials will be presented, and the effects of the ECAE processing on the grain size will be discussed.
Date:
January 1, 2003
Creator:
Alexander, D. J. (David J.); Mauro, M. E. (Michael Ernest); Cooley, J. C. (Jason C.) & Dauelsberg, L. B. (Lawrence B.)
Object Type:
Article
System:
The UNT Digital Library
Algorithm refinement for stochastic partial differential equations.
A hybrid particle/continuum algorithm is formulated for Fickian diffusion in the fluctuating hydrodynamic limit. The particles are taken as independent random walkers; the fluctuating diffusion equation is solved by finite differences with deterministic and white-noise fluxes. At the interface between the particle and continuum computations the coupling is by flux matching, giving exact mass conservation. This methodology is an extension of Adaptive Mesh and Algorithm Refinement to stochastic partial differential equations. A variety of numerical experiments were performed for both steady and time-dependent scenarios. In all cases the mean and variance of density are captured correctly by the stochastic hybrid algorithm. For a non-stochastic version (i.e., using only deterministic continuum fluxes) the mean density is correct, but the variance is reduced except within the particle region, far from the interface. Extensions of the methodology to fluid mechanics applications are discussed.
Date:
January 1, 2001
Creator:
Alexander, F. J. (Francis J.); Garcia, Alejandro L., & Tartakovsky, D. M. (Daniel M.)
Object Type:
Article
System:
The UNT Digital Library
First-principles studies of H2S adsorption and dissociation on metal surfaces
Exposure of Pd-based hydrogen purification membranes to H,S. a common contaminant in coal gasification streams, can cause membrane performance to deteriorate, either by deactivating surface sites required for dissociative H, adsorption or by forming a low-permeability sulfide scale. In this work. the composition, structure, and catalytic activity of Pd4S, a surface scale commonly observed in Pd-membrane separation of hydrogen from sulfur-containing gas streams, were examined using a combination of experimental characterization and density functional theory (DFT) calculations. A Pd,S sample was prepared by exposing a 100 f1m Pd foil to H2S at 908 K. Both X-ray photoemission depth profiling and low energy ion scattering spectroscopic (LEISS) analysis reveal slight sulfur-enrichment of the top surface of the sample. This view is consistent with the predictions of DFT atomistic thermodynamic calculations. which identified S-terminated Pd,S surfaces as energetically favored over corresponding Pd-terminated surfaces. Activation barriers for H2 dissociation on the Pd,S surfaces were calculated. Although barriers are higher than on Pd(lll). transition state theory analysis identified reaction pathways on the S-terminated surfaces for which hydrogen dissociation rates are high enough to sustain the separation process at conditions relevant to gasification applications
Date:
January 1, 2008
Creator:
Alfonso, D.R.
Object Type:
Article
System:
The UNT Digital Library
Extension of the Inverse Adding-Doubling Method to the Measurement of Wavelength-Dependent Absorption and Scattering Coefficients of Biological Samples
Light interaction with biological tissue can be described using three parameters: the scattering and absorption coeffi cients (μs and μa), as well as the anisotropy (g) which describes the directional dependence of the scattered photons. Accurately determining these optical properties for different tissue types at specifi c wavelengths simultaneously would be benefi cial for a variety of different biomedical applications. The goal of this project was to take a user defi ned g-value and determine the remaining two parameters for a specifi ed wavelength range. A fully automated computer program and process was developed to collect data for all wavelengths in a timely and accurate manner. LabVIEW® was used to write programs to automate raw intensity data collection from a spectrometer equipped integrating sphere, conversion of the data into a format for analysis via Scott Prahl’s Inverse Adding-Doubling (IAD) C code execution, and fi nally computation of the optical properties based on the output from the IAD code. To allow data to be passed effi ciently between LabVIEW® and C code program modules, the two were combined into a single program (OPT 3.1). OPT 3.1 was tested using tissue mimicking phantoms. Determination of the absorption and scattering coeffi cients showed …
Date:
January 1, 2008
Creator:
Allegood, M.S. & Baba, J.S.
Object Type:
Article
System:
The UNT Digital Library
Dependence of the Characteristics of Mo Films on Sputter Conditions
The residual stress, resistance, orientation, and microstructure of sputtered Mo films were studied as a function of varied-deposition power and pressure.
Date:
January 1, 2000
Creator:
Alleman, J. L.; Althani, H.; Noufi, R.; Moutinho, H.; Al-Jassim, M. M. & Hasoon, F.
Object Type:
Article
System:
The UNT Digital Library
Analysis of Coconut-Derived Biodiesel and Conventional Diesel Fuel Samples from the Philippines: Task 2 Final Report
NREL tested Philippines coconut biodiesel samples of neat and blended fuels. Results show that the current fuel quality standards were met with very few exceptions. Additional testing is recommended.
Date:
January 1, 2006
Creator:
Alleman, T. L. & McCormick, R. L.
Object Type:
Report
System:
The UNT Digital Library
Experimental study of proton beam halo in mismatched beams
We report measurements of transverse beam-halo formation in mismatched proton beams in a 52-quadrupole FODO-transport channel following the 6.7 MeV RFQ at the Low-Energy Demonstration Accelerator (LEDA) at Los Alamos. Beam profiles in both transverse planes were measured using a new diagnostic device that consists of a movable carbon filament for measurement of the beam core, and scraper plates for measurement of the outer part of the distributions. The initial results indicate a surprisingly strong growth rate of the rms emittance even for the modest space-charge tune depressions of the experiment. Our results are consistent with the complete transfer of free energy of the mismatched beams into emittance growth within 10 envelope oscillations for both the breathing and the quadrupole modes.
Date:
January 1, 2002
Creator:
Allen, C. K. (Christopher K.); Chan, K. D. (Kwok-Chi D.); Colestock, P. L. (Patrick L.),; Garnett, R. W. (Robert W.); Gilpatrick, J. D. (John Douglas); Qiang, J. (Ji) et al.
Object Type:
Article
System:
The UNT Digital Library
Characterization of the proton beam at the output of the 6.7MeV LEDA RFQ.
The present configuration of the Low-Energy Demonstration Accelerator (LEDA) consists of a 75-keV proton injector, a 6.7-MeV 350-MHz cw radio-frequency quadrupole (RFQ) with associated high-power and lowlevel rf systems, a 52-magnet periodic lattice followed by a short high-energy beam transport (HEBT) and highpower (670-kW cw) beam stop. The rms beam emittance was measured prior to the installation of the 52-magnet lattice, based on wire-scanner measurements of the beam profile at a single location in the HEBT. New measurements with additional diagnostic hardware have been performed to determine the rms transverse beam properties of the beam at the output of the 6.7-MeV LEDA RFQ. The 52-magnet periodic lattice also includes ten beam position monitors (BPMs) evenly spaced in pairs of two. The BPMs provide a measure of the bunched beam current that exhibits nulls at different locations in the lattice. Model predictions of the locations of the nulls and the strength of the bunched beam current are made to determine what information this data can provide regarding the longitudinal beam emittance.
Date:
January 1, 2001
Creator:
Allen, C. K. (Christopher K.); Colestock, P. L. (Patrick L.),; Gilpatrick, J. D. (John Douglas); Lysenko, W. P. (Walter P.); Rybarcyk, L. J. (Lawrence J.); Schneider, J. D. (J. David) et al.
Object Type:
Article
System:
The UNT Digital Library
Summary report : direct approaches for recycling carbon dioxide into synthetic fuel.
The consumption of petroleum by the transportation sector in the United States is roughly equivalent to petroleum imports into the country, which have totaled over 12 million barrels a day every year since 2004. This reliance on foreign oil is a strategic vulnerability for the economy and national security. Further, the effect of unmitigated CO{sub 2} releases on the global climate is a growing concern both here and abroad. Independence from problematic oil producers can be achieved to a great degree through the utilization of non-conventional hydrocarbon resources such as coal, oil-shale and tarsands. However, tapping into and converting these resources into liquid fuels exacerbates green house gas (GHG) emissions as they are carbon rich, but hydrogen deficient. Revolutionary thinking about energy and fuels must be adopted. We must recognize that hydrocarbon fuels are ideal energy carriers, but not primary energy sources. The energy stored in a chemical fuel is released for utilization by oxidation. In the case of hydrogen fuel the chemical product is water; in the case of a hydrocarbon fuel, water and carbon dioxide are produced. The hydrogen economy envisions a cycle in which H{sub 2}O is re-energized by splitting water into H{sub 2} and O{sub 2}, …
Date:
January 1, 2009
Creator:
Allendorf, Mark D. (Sandia National Laboratories, Livermore, CA); Ambrosini, Andrea; Diver, Richard B., Jr.; Siegel, Nathan Phillip; Miller, James Edward; Gelbard, Fred et al.
Object Type:
Report
System:
The UNT Digital Library
Relative {sup 235}U(n,{gamma}) and (n,f) cross sections from {sup 235}U(d,p{gamma}) and (d,pf)
The internal surrogate ratio method allows for the determination of an unknown cross section, such as (n,{gamma}), relative to a better-known cross section, such as (n,f), by measuring the relative exit-channel probabilities of a surrogate reaction that proceeds through the same compound nucleus. The validity of the internal surrogate ratio method is tested by comparing the relative gamma and fission exit-channel probabilities of a {sup 236}U* compound nucleus, formed in the {sup 235}U(d,p) reaction, to the known {sup 235}U(n,{gamma}) and (n,f) cross sections. A model-independent method for measuring the gamma-channel yield is presented and used.
Date:
January 1, 2009
Creator:
Allmond, J. M.; Bernstein, L. A.; Beausang, C. W.; Phair, L.; Bleuel, D. L.; Burke, J. T. et al.
Object Type:
Article
System:
The UNT Digital Library
THE NEED FOR IMAGE PROCESSING IN INFRARED CAMERA DESIGN
None
Date:
January 1, 2000
Creator:
Allred, L.G. & Jones, M.H.
Object Type:
Article
System:
The UNT Digital Library