A balancing domain decomposition method by constraints for advection-diffusion problems (open access)

A balancing domain decomposition method by constraints for advection-diffusion problems

The balancing domain decomposition methods by constraints are extended to solving nonsymmetric, positive definite linear systems resulting from the finite element discretization of advection-diffusion equations. A pre-conditioned GMRES iteration is used to solve a Schur complement system of equations for the subdomain interface variables. In the preconditioning step of each iteration, a partially sub-assembled finite element problem is solved. A convergence rate estimate for the GMRES iteration is established, under the condition that the diameters of subdomains are small enough. It is independent of the number of subdomains and grows only slowly with the subdomain problem size. Numerical experiments for several two-dimensional advection-diffusion problems illustrate the fast convergence of the proposed algorithm.
Date: December 10, 2008
Creator: Tu, Xuemin & Li, Jing
Object Type: Article
System: The UNT Digital Library
Band Structure Asymmetry of Bilayer Graphene Revealed by Infrared Spectroscopy (open access)

Band Structure Asymmetry of Bilayer Graphene Revealed by Infrared Spectroscopy

We report on infrared spectroscopy of bilayer graphene integrated in gated structures. We observe a significant asymmetry in the optical conductivity upon electrostatic doping of electrons and holes. We show that this finding arises from a marked asymmetry between the valence and conduction bands, which is mainly due to the inequivalence of the two sublattices within the graphene layer and the next-nearest-neighbor interlayer coupling. From the conductivity data, the energy difference of the two sublattices and the interlayer coupling energy are directly determined.
Date: December 10, 2008
Creator: Li, Z. Q.; Henriksen, E. A.; Jiang, Z.; Hao, Zhao; Martin, Michael C.; Kim, P. et al.
Object Type: Article
System: The UNT Digital Library
BDDC for nonsymmetric positive definite and symmetric indefinite problems (open access)

BDDC for nonsymmetric positive definite and symmetric indefinite problems

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 only slightly on the subdomain problem size. Numerical experiments for several two-dimensional examples illustrate the fast convergence of the proposed algorithms.
Date: December 10, 2008
Creator: Tu, Xuemin & Li, Jing
Object Type: Article
System: The UNT Digital Library
China-U.S. Trade Issues (open access)

China-U.S. Trade Issues

This report mainly focuses on China-U.S. Trade Issues. China-U.S. ties have been substantially expanded over the past three decades. U.S imports from China have risen much more rapidly than the U.S exports to China.
Date: December 10, 2008
Creator: Morrison, Wayne M.
Object Type: Report
System: The UNT Digital Library
Complexation of Lanthanides with Nitrate at Variable Temperatures: Thermodynamics and Coordination Modes (open access)

Complexation of Lanthanides with Nitrate at Variable Temperatures: Thermodynamics and Coordination Modes

Complexation of neodymium(III) with nitrate was studied at variable temperatures (25, 40, 55 and 70 C) by spectrophotometry and microcalorimetry. The NdNO{sub 3}{sup 2+} complex is weak and becomes slightly stronger as the temperature is increased. The enthalpy of complexation at 25 C was determined by microcalorimetry to be small and positive, (1.5 {+-} 0.2) kJ {center_dot} mol{sup -1}, in good agreement with the trend of the stability constant at variable temperatures. Luminescence emission spectra and lifetime of Eu(III) in nitrate solutions suggest that inner-sphere and bidentate complexes form between trivalent lanthanides (Nd{sup 3+} and Eu{sup 3+}) and nitrate in aqueous solutions. Specific Ion Interaction approach (SIT) was used to obtain the stability constants of NdNO{sub 3}{sup 2+} at infinite dilution and variable temperatures.
Date: December 10, 2008
Creator: Rao, Linfeng & Tian, Guoxin
Object Type: Article
System: The UNT Digital Library
Convergence analysis of a balalncing domain decomposition method for solving interior Helmholtz equations (open access)

Convergence analysis of a balalncing domain decomposition method for solving interior Helmholtz equations

A variant of balancing domain decomposition method by constraints (BDDC) is proposed for solving a class of indefinite system of linear equations, which arises from the finite element discretization of the Helmholtz equation of time-harmonic wave propagation in a bounded interior domain. The proposed BDDC algorithm is closely related to the dual-primal finite element tearing and interconnecting algorithm for solving Helmholtz equations (FETI-DPH). Under the condition that the diameters of the subdomains are small enough, the rate of convergence is established which depends polylogarithmically on the dimension of the individual subdomain problems and which improves with the decrease of the subdomain diameters. These results are supported by numerical experiments of solving a Helmholtz equation on a two-dimensional square domain.
Date: December 10, 2008
Creator: Li,Jing & Tu, Xuemin
Object Type: Article
System: The UNT Digital Library
Couse/Tenmile Creeks Watershed Project Implementation : 2007 Conservtion Projects. [2007 Habitat Projects Completed]. (open access)

Couse/Tenmile Creeks Watershed Project Implementation : 2007 Conservtion Projects. [2007 Habitat Projects Completed].

The Asotin County Conservation District (ACCD) is the primary entity coordinating habitat projects on private lands within Asotin County watersheds. The Tenmile Creek watershed is a 42 square mile tributary to the Snake River, located between Asotin Creek and the Grande Ronde River. Couse Creek watershed is a 24 square mile tributary to the Snake River, located between Tenmile Creek and the Grande Ronde River. Both watersheds are almost exclusively under private ownership. The Washington Department of Fish and Wildlife has documented wild steelhead and rainbow/redband trout spawning and rearing in Tenmile Creek and Couse Creek. The project also provides Best Management Practice (BMP) implementation throughout Asotin County, but the primary focus is for the Couse and Tenmile Creek watersheds. The ACCD has been working with landowners, Bonneville Power Administration (BPA), Washington State Conservation Commission (WCC), Natural Resource Conservation Service (NRCS), Farm Service Agency (FSA), Salmon Recovery Funding Board (SRFB), Washington Department of Fish and Wildlife (WDFW), U.S. Forest Service, Pomeroy Ranger District (USFS), Nez Perce Tribe (NPT), Washington Department of Ecology (DOE), National Marine Fisheries Service (NOAA Fisheries), and U.S. Fish and Wildlife Service (USFWS) to address habitat projects in Asotin County. The Asotin Subbasin Plan identified priority areas …
Date: December 10, 2008
Creator: District, Asotin County Conservation
Object Type: Report
System: The UNT Digital Library
Development of ZnO:Ga as an Ultrafast Scintillator (open access)

Development of ZnO:Ga as an Ultrafast Scintillator

We report on several methods for synthesizing the ultra-fast scintillator ZnO(Ga), and measurements of the resulting products. This material has characteristics that make it an excellent alpha detector for tagging the time and direction of individual neutrons produced by t-d and d-d neutron generators (associated particle imaging). The intensity and decay time are strongly dependent on the method used for dopant incorporation. We compare samples made by diffusion of Ga metal to samples made by solid state reaction between ZnO and Ga2O3 followed by reduction in hydrogen. The latter is much more successful and has a pure, strong near-band-edge fluorescence and an ultra-fast decay time of the x-ray-excited luminescence. The luminescence increases dramatically as the temperature is reduced to 10K. We also present results of an alternate low-temperature synthesis that produces luminescent particles with a more uniform size distribution. We examine possible mechanisms for the bright near-band-edge scintillation and favor the explanation that it is due to the recombination of Ga3+ donor electrons with ionization holes trapped on H+ ion acceptors.
Date: December 10, 2008
Creator: Bourret-Courchesne, E. D.; Derenzo, S. E. & Weber, M. J.
Object Type: Article
System: The UNT Digital Library
Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology (open access)

Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology

Shock and thermal metamorphism of meteorites from differentiated bodies such as the Moon and Mars have the potential to disturb chronometric information contained in these meteorites. In order to understand the impact-related mechanisms and extent of disturbance to isochrons, we undertook experiments to shock and heat samples of 10017, a 3.6 billion year old lunar basalt. One sub-sample was shocked to 55 GPa, a second subsample was heated to 1000 C for one week, and a third sub-sample was maintained as a control sample. Of the isotope systems analyzed, the Sm-Nd system was the least disturbed by shock or heat, followed by the Rb-Sr system. Ages represented by the {sup 238}U-{sup 206}Pb isotope system were degraded by shock and destroyed with heating. In no case did either shock or heating alone result in rotated or reset isochrons that represent a spurious age. In some cases the true crystallization age of the sample was preserved, and in other cases age information was degraded or destroyed. Although our results show that neither shock nor thermal metamorphism alone can account for the discordant ages represented by different isotope systems in martian meteorites, we postulate that shock metamorphism may render a meteorite more susceptible …
Date: December 10, 2008
Creator: Gaffney, Amy M.; Borg, Lars E. & Asmerom, Yemane
Object Type: Article
System: The UNT Digital Library
Freedom of Speech and Press: Exceptions to the First Amendment (open access)

Freedom of Speech and Press: Exceptions to the First Amendment

This report provides an overview of the major exceptions to the First Amendment.
Date: December 10, 2008
Creator: Cohen, Henry
Object Type: Report
System: The UNT Digital Library
Georgia (Republic): Recent Developments and U.S. Interests (open access)

Georgia (Republic): Recent Developments and U.S. Interests

This report discusses the information related to recent developments and U.S interests in Georgia.
Date: December 10, 2008
Creator: Nichol, Jim
Object Type: Report
System: The UNT Digital Library
Horse Slaughter Prevention Bills and Issues (open access)

Horse Slaughter Prevention Bills and Issues

This report focuses on horse slaughter prevention bills and issues, and how they are implemented or enforced.
Date: December 10, 2008
Creator: Becker, Geoffrey S.
Object Type: Report
System: The UNT Digital Library
Humane Treatment of Farm Animals: Overview and Issues (open access)

Humane Treatment of Farm Animals: Overview and Issues

None
Date: December 10, 2008
Creator: Becker, Geoffrey S.
Object Type: Report
System: The UNT Digital Library
Immigration Legislation and Issues in the 110th Congress (open access)

Immigration Legislation and Issues in the 110th Congress

This report discusses immigration-related issues that have seen legislative action or are of significant congressional interest.
Date: December 10, 2008
Creator: Bruno, Andorra
Object Type: Report
System: The UNT Digital Library
Inf-sup estimates for the Stokes problem in a periodic channel (open access)

Inf-sup estimates for the Stokes problem in a periodic channel

We derive estimates of the Babuska-Brezzi inf-sup constant {beta} for two-dimensional incompressible flow in a periodic channel with one flat boundary and the other given by a periodic, Lipschitz continuous function h. If h is a constant function (so the domain is rectangular), we show that periodicity in one direction but not the other leads to an interesting connection between {beta} and the unitary operator mapping the Fourier sine coefficients of a function to its Fourier cosine coefficients. We exploit this connection to determine the dependence of {beta} on the aspect ratio of the rectangle. We then show how to transfer this result to the case that h is C{sup 1,1} or even C{sup 0,1} by a change of variables. We avoid non-constructive theorems of functional analysis in order to explicitly exhibit the dependence of {beta} on features of the geometry such as the aspect ratio, the maximum slope, and the minimum gap thickness (if h passes near the substrate). We give an example to show that our estimates are optimal in their dependence on the minimum gap thickness in the C{sup 1,1} case, and nearly optimal in the Lipschitz case.
Date: December 10, 2008
Creator: Wilkening, Jon
Object Type: Article
System: The UNT Digital Library
Iraq: Oil and Gas Legislation, Revenue Sharing, and U.S. Policy (open access)

Iraq: Oil and Gas Legislation, Revenue Sharing, and U.S. Policy

This report reviews proposed legislation and contracts, analyzes the positions of various Iraqi political actors, and discusses potential implications for U.S. foreign policy goals in Iraq.
Date: December 10, 2008
Creator: Blanchard, Christopher M.
Object Type: Report
System: The UNT Digital Library
Israel and the Palestinians: Prospects for a Two-State Solution (open access)

Israel and the Palestinians: Prospects for a Two-State Solution

None
Date: December 10, 2008
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Measurements of NaI(Tl) electron response: comparison of different samples (open access)

Measurements of NaI(Tl) electron response: comparison of different samples

This paper measures the sample to sample variation in the light yield proportionality of NaI(Tl), and so explores whether this is an invariant characteristic of the material or whether it depends on the chemical and physical properties of the tested samples. We report on the electron response of nine crystals of NaI(Tl), differing in shape, volume, age, manufacturer and quality. The proportionality has been measured at the SLYNCI facility in the energy range between 3.5 to 460 keV. We observe that while samples produced by the same manufacturer at approximately the same time have virtually identical electron response curves, there are significant sample to sample variations among crystals produced by different manufacturers or at different times. In an effort to correlate changes in the electron response with details of the scintillation mechanism, we characterized other scintillation properties, including the gamma response and the x-ray excited emission spectra and decay times, for the nine crystals. While sample to sample differences in these crystals were observed, we have been unable to identify the underlying fundamental mechanisms that are responsible for these differences.
Date: December 10, 2008
Creator: Hull, Giulia; Choong, Woon-Seng; Moses, William W.; Bizarri, Gregory; Valentine, John D.; Payne, Stephen A. et al.
Object Type: Article
System: The UNT Digital Library
Microwave Plasma Chemical Vapor Deposition of Carbon Coatings on LiNi1/3Co1/3Mn1/3O2 for Li-Ion Battery Composite Cathodes (open access)

Microwave Plasma Chemical Vapor Deposition of Carbon Coatings on LiNi1/3Co1/3Mn1/3O2 for Li-Ion Battery Composite Cathodes

In this paper, we report results of a novel synthesis method of thin film conductive carbon coatings on LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} cathode active material powders for lithium-ion batteries. Thin layers of graphitic carbon were produced from a solid organic precursor, anthracene, by a one-step microwave plasma chemical vapor deposition (MPCVD) method. The structure and morphology of the carbon coatings were examined using SEM, TEM, and Raman spectroscopy. The composite LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} electrodes were electrochemically tested in lithium half coin cells. The composite cathodes made of the carbon-coated LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} powder showed superior electrochemical performance and increased capacity compared to standard composite LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} electrodes.
Date: December 10, 2008
Creator: Doeff, Marek M.; Kostecki, Robert M.; Marcinek, Marek L. & Wilcox, James W.
Object Type: Article
System: The UNT Digital Library
Obscenity, Child Pornography, and Indecency: Recent Developments and Pending Issues (open access)

Obscenity, Child Pornography, and Indecency: Recent Developments and Pending Issues

None
Date: December 10, 2008
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Practical error estimates for Reynolds' lubrication approximation and its higher order corrections (open access)

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

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 for the difference between the exact solution and the truncated expansion solution. Unlike previous studies of this sort, the constants in our error bounds are either independent of the function h(x) describing the geometry, or depend on h and its derivatives in an explicit, intuitive way. Specifically, if the expansion is truncated at order 2k, the error is O({var_epsilon}{sup 2k+2}) and h enters into the error bound only through its first and third inverse moments {integral}{sub 0}{sup 1} h(x){sup -m} dx, m = 1,3 and via the max norms {parallel} 1/{ell}! h{sup {ell}-1}{partial_derivative}{sub x}{sup {ell}}h{parallel}{sub {infinity}}, 1 {le} {ell} {le} 2k + 2. We validate our estimates by comparing with finite element solutions and present numerical evidence that suggests …
Date: December 10, 2008
Creator: Wilkening, Jon
Object Type: Article
System: The UNT Digital Library
QCD Evolution of the Transverse Momentum Dependent Correlations (open access)

QCD Evolution of the Transverse Momentum Dependent Correlations

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 production in pp scattering process.
Date: December 10, 2008
Creator: Zhou, Jian; Liang, Zuo-Tang & Yuan, Feng
Object Type: Article
System: The UNT Digital Library
Questions About the $700 Billion Emergency Economic Stabilization Funds (open access)

Questions About the $700 Billion Emergency Economic Stabilization Funds

December report of the U.S. Congressional Oversight Panel describing their activities and findings regarding the U.S. Treasury's strategy in combating the ongoing financial crisis
Date: December 10, 2008
Creator: United States. Congressional Oversight Panel.
Object Type: Report
System: The UNT Digital Library
Recent Development in Proton Spin Physics (open access)

Recent Development in Proton Spin Physics

In the naive model of the proton, its 1/2 spin is carried by its quark constituents. However, experiments over the last several decades have shown that the quark spin only contribute a small portion of the proton spin. In this talk, I will present recent developments exploring this proton spin puzzle, and focus on the progress made in the last few years on the longitudinal spin physics, the generalized parton distribution physics, and the transverse spin physics.
Date: December 10, 2008
Creator: Yuan, Feng
Object Type: Article
System: The UNT Digital Library