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Graph based multilevel algorithms for preconditioning finite element problems (open access)

Graph based multilevel algorithms for preconditioning finite element problems

This paper discusses: (1) A general block-factorization (matrix) form of multilevel preconditioners; algebraic methods; (2) Selecting parameters based on the matrix topology; graph based algorithms; (3) Examples of coarsening; (4) Numerical experiments.
Date: March 24, 2000
Creator: Vassilevski, P S
System: The UNT Digital Library
Nonlinear self-duality in even dimensions (open access)

Nonlinear self-duality in even dimensions

We show that the Born-Infeld theory with n complex abelian gauge fields written in an auxiliary field formulation has a U(n, n) duality group. We conjecture the form of the Lagrangian obtained by eliminating the auxiliary fields and then introduce a new reality structure leading to a Born-Infeld theory with n real gauge fields and an Sp(2n, IR) duality symmetry. The real and complex constructions are extended to arbitrary even dimensions. The maximal noncompact duality group is U(n, n) for complex fields. For real fields the duality group is Sp(2n, IR) if half of the dimension of space-time is even and O(n, n) if it is odd. We also discuss duality under the maximal compact subgroup, which is the self-duality group of the theory obtained by fixing the expectation value of a scalar field. Supersymmetric versions of self-dual theories in four dimensions are also discussed.
Date: March 24, 2000
Creator: Aschieri, Paolo; Brace, Daniel; Morariu, Bogdan & Zumino, Bruno
System: The UNT Digital Library
Integration of Multiple Contractors with Performance Type of Contracts (open access)

Integration of Multiple Contractors with Performance Type of Contracts

The management practices, procedures, and processes that are suited to managing Management and Operation (M&O) type of contracts at Department of Energy (DOE) sites, which were cost reimbursement with award fee, are not well suited to managing contracts where fee is determined by performance metrics. Thus a different style of management, requiring substantial revamping of the management process, is needed. This shift in philosophy also requires a dramatic shift in culture. This paper will describe how these changes are being managed at the River Protection Project (RPP), located at the DOE's Hanford Site in Washington State, one of DOE's largest and highest risk environmental clean-up project.
Date: September 24, 2000
Creator: BURDGE, L.F.
System: The UNT Digital Library
Potential Vulnerability Issues for Drum-Type Packages (open access)

Potential Vulnerability Issues for Drum-Type Packages

Type B and Type A fissile drum packages are required to undergo a series of tests that simulate both normal conditions of transport (NCT) and hypothetical accident conditions (HAC) as specified in 10 CFR Part 71. In particular for HAC, it must be demonstrated that the package can withstand a 30 ft. drop in the most unfavorable orientation without damage that would compromise its ability to survive a subsequent regulatory fire test. Historically, it has usually been assumed that the most unfavorable orientations are those that allow the maximum amount of available kinetic energy to be used for package deformation. Therefore, drop test orientations have been mostly limited to Top-Down, Bottom-Down, Side, and C.G. Over Top-Corner. (Where C.G. refers to the center of gravity of the package.) Here, it is shown that shallow angle top impact, where a portion of the translational kinetic energy of the package is transformed into rotational kinetic energy at impact, may also be a likely orientation that will lead to failure of drum packages that use bolted ring closures.
Date: May 24, 2000
Creator: Hagler, L. B.; Sheaffer, M. K.; Anderson, B. L.; Hafner, R. S. & Witte, M. C.
System: The UNT Digital Library
Modeling Collapse Chimney and Spall Zone Settlement as a Source of Post-Shot Subsidence Detected by Synthetic Aperture Radar Interferometry (open access)

Modeling Collapse Chimney and Spall Zone Settlement as a Source of Post-Shot Subsidence Detected by Synthetic Aperture Radar Interferometry

Ground surface subsidence resulting from the March 1992 JUNCTION underground nuclear test at the Nevada Test Site (NTS) imaged by satellite synthetic aperture radar interferometry (InSAR) wholly occurred during a period of several months after the shot (Vincent et al., 1999) and after the main cavity collapse event. A significant portion of the subsidence associated with the small (less than 20 kt) GALENA and DIVIDER tests probably also occurred after the shots, although the deformation detected in these cases contains additional contributions from coseismic processes, since the radar scenes used to construct the deformation interferogram bracketed these two later events, The dimensions of the seas of subsidence resulting from all three events are too large to be solely accounted for by processes confined to the damage zone in the vicinity of the shot point or the collapse chimney. Rather, the subsidence closely corresponds to the span dimensions predicted by Patton's (1990) empirical relationship between spall radius and yield. This suggests that gravitational settlement of damaged rock within the spall zone is an important source of post-shot subsidence, in addition to settlement of the rubble within the collapse chimney. These observations illustrate the potential power of InSAR as a tool for …
Date: July 24, 2000
Creator: Foxwall, W.
System: The UNT Digital Library
Office of River Protection: Simplifying Project management tools (open access)

Office of River Protection: Simplifying Project management tools

The primary approach to the effort was to form a multi-organizational team comprised of federal and contractor staff to develop and implement the necessary tools and systems to manage the project. In late 1999 the DOE Manager of the Office of River Protection formed the Project Integration Office to achieve the objective of managing the efforts as a single project. The first major task, and the foundation upon which to base the development of all other tools, was the establishment of a single baseline of activities. However, defining a single scope schedule and cost was a difficult matter indeed. Work scopes were available throughout the project, but the level of detail and the integration of the activities existed primarily between working groups and individuals and not on a project-wide basis. This creates a situation where technical needs, logic flaws, resource balancing, and other similar integration needs are not elevated for management attention and resolution. It should be noted that probably 90% of the interface issues were known and being addressed. The key is simplifying the process and providing tangible assurance that the other 10% does not contain issues that can delay the project. Fortunately all of the contractors employed a …
Date: September 24, 2000
Creator: TAYLOR, D.G.
System: The UNT Digital Library
Low-Spin Collective Excitations in Deformed Nuclei: When is a B a B Vibration? (open access)

Low-Spin Collective Excitations in Deformed Nuclei: When is a B a B Vibration?

The 0{sub 2}{sup +} level in deformed nuclei has historically been given the label {beta}, even though its properties vary drastically from one nucleus to another. By reviewing models from where the original term {beta} vibration arose, and appealing to microscopic calculations, guidelines are proposed for the properties of a true {beta} vibration. An examination of available data, including B(E2) values, {rho}{sup 2}(E0) values, and single- and two-nucleon-transfer populations, shows that very few 0{sub 2}{sup +} levels satisfy the criteria for a {beta} vibration. It is suggested that pairing excitations may be playing a dominant role.
Date: February 24, 2000
Creator: Garrett, P.E.
System: The UNT Digital Library
Elliptic Solvers with Adaptive Mesh Refinement on Complex Geometries (open access)

Elliptic Solvers with Adaptive Mesh Refinement on Complex Geometries

Adaptive Mesh Refinement (AMR) is a numerical technique for locally tailoring the resolution computational grids. Multilevel algorithms for solving elliptic problems on adaptive grids include the Fast Adaptive Composite grid method (FAC) and its parallel variants (AFAC and AFACx). Theory that confirms the independence of the convergence rates of FAC and AFAC on the number of refinement levels exists under certain ellipticity and approximation property conditions. Similar theory needs to be developed for AFACx. The effectiveness of multigrid-based elliptic solvers such as FAC, AFAC, and AFACx on adaptively refined overlapping grids is not clearly understood. Finally, a non-trivial eye model problem will be solved by combining the power of using overlapping grids for complex moving geometries, AMR, and multilevel elliptic solvers.
Date: July 24, 2000
Creator: Phillip, B.
System: The UNT Digital Library
["Behind the Scenes at a Bush 'Sensitivity Session'" article, April 24, 2000] (open access)

["Behind the Scenes at a Bush 'Sensitivity Session'" article, April 24, 2000]

An article, written by Steve Gunderson for Newsweek, about a meeting between Presidential candidate George W. Bush and gay and lesbian Republicans. The piece focuses on an exchange between Gunderson and Bush specifically and Bush's response to the event as a whole.
Date: April 24, 2000
Creator: Gunderson, Steve
System: The UNT Digital Library
Measurement of sin2{Beta} From J/{Psi} K{Sub S} Decays (open access)

Measurement of sin2{Beta} From J/{Psi} K{Sub S} Decays

The CP-violating parameter sin 2{beta} is directly measured using 110 pb{sup {minus}1} of data accumulated with the CDF detector at the Fermilab {anti p}p Tevatron collider operating at {radical}s = 1.8 TeV. The signal consists of 395 {+-} 31 B{sub d}{sup 0} {r{underscore}arrow} J/{psi} K{sub s} events. Three tagging methods are used to identify the type of B meson at production (B{sub d}{sup 0} or {anti B}{sub d}{sup 0}). From the CP asymmetry, sin 2{beta} is measured to be 0.79 {sub {minus}0.44}{sup +0.41}, consistent with Standard Model predictions. Sin 2{beta} is in the interval 0 {lt} sin2{beta} {lt} 1 at the 93% confidence level.
Date: January 24, 2000
Creator: Blocker, C. A.
System: The UNT Digital Library
Review of cathodic arc deposition technology at the start of the new millennium (open access)

Review of cathodic arc deposition technology at the start of the new millennium

The vacuum cathodic arc has been known to provide a means of producing coatings since the second half of the 19th century. This makes it one of the oldest known means for making coatings in a vacuum. In the last century it has been recognized that the copious quantities of ions produced by the process offers certain advantages in terms of coating properties. Specifically, ions can be steered and/or accelerated toward the parts to be coated. This, in turn, can provide enhanced adhesion, film density, and composition stoichiometry in the case of compound coatings. The ions generated by the cathodic arc have high ''natural'' kinetic energy values in the range 20-200 eV, leading to enhanced surface mobility during the deposition process and even ion subplantation. In many cases, dense coatings are achieved even when non-normal arrival angles are involved. The ion energy can further manipulated by the plasma immersion biasing technique. The issue of macroparticle contamination has been addressed by a variety of novel plasma filters. In spite of all of these advantages, this deposition technique has not been widely adopted in the western nations for commercial coating except in the case of enhancing the performance of cutting tools. The …
Date: February 24, 2000
Creator: Sanders, D. M. & Anders, A.
System: The UNT Digital Library
Angular Sensitivity of Gated Micro-Channel Plate Framing Cameras (open access)

Angular Sensitivity of Gated Micro-Channel Plate Framing Cameras

Gated, microchannel-plate-based (MCP) framing cameras have been deployed worldwide for 0.2 - 9 keV x-ray imaging and spectroscopy of transient plasma phenomena. For a variety of spectroscopic and imaging applications, the angular sensitivity of MCPs must be known for correctly interpreting the data. We present systematic measurements of angular sensitivity at discrete relevant photon energies and arbitrary MCP gain. The results can been accurately predicted by using a simple 2D approximation to the 3D MCP geometry and by averaging over all possible photon ray paths.
Date: July 24, 2000
Creator: Landen, O L; Lobban, A; Tutt, T; Bell, P M; Costa, R & Ze, F
System: The UNT Digital Library
Dynamic Software Testing of MPI Applications with Umpire (open access)

Dynamic Software Testing of MPI Applications with Umpire

As evidenced by the popularity of MPI (Message Passing Interface), message passing is an effective programming technique for managing coarse-grained concurrency on distributed computers. Unfortunately, debugging message-passing applications can be difficult. Software complexity, data races, and scheduling dependencies can make programming errors challenging to locate with manual, interactive debugging techniques. This article describes Umpire, a new tool for detecting programming errors at runtime in message passing applications. Umpire monitors the MPI operations of an application by interposing itself between the application and the MPI runtime system using the MPI profiling layer. It, then, checks its MPI behavior for specific errors. The initial collection of programming errors includes deadlock detection, mismatched collective operations, and resource exhaustion. They present an evaluation that demonstrates the effectiveness of this approach.
Date: July 24, 2000
Creator: Vetter, J & de Supinski, B
System: The UNT Digital Library
Defects at the carbon terminated SiC (001) surface (open access)

Defects at the carbon terminated SiC (001) surface

We present first principle molecular dynamics simulations for selected point defects on the (001) stoichiometric carbon terminated surface of cubic Silicon Carbide. In particular we investigated missing units and coordination defects. The results of our calculations are compared with recent experiments, in particular we discuss simulated STM images, which are in good agreement with measured ones.
Date: July 24, 2000
Creator: Catellani, A & Galli, G
System: The UNT Digital Library
Real-time control system for adaptive resonator (open access)

Real-time control system for adaptive resonator

Sustained operation of high average power solid-state lasers currently requires an adaptive resonator to produce the optimal beam quality. We describe the architecture of a real-time adaptive control system for correcting intra-cavity aberrations in a heat capacity laser. Image data collected from a wavefront sensor are processed and used to control phase with a high-spatial-resolution deformable mirror. Our controller takes advantage of recent developments in low-cost, high-performance processor technology. A desktop-based computational engine and object-oriented software architecture replaces the high-cost rack-mount embedded computers of previous systems.
Date: July 24, 2000
Creator: Flath, L.; An, J.; Brase, J.; Hurd, R.; Kartz, M.; Sawvel, R. et al.
System: The UNT Digital Library
Cookoff response of PBXN-109: material characterization and ALE3D model (open access)

Cookoff response of PBXN-109: material characterization and ALE3D model

Materials properties measurements are made for the RDX-based explosive, PBXN-109, and an initial ALE3D model for cookoff is discussed. A significant effort is underway in the U.S. Navy and Department of Energy (DOE) laboratories to understand the thermal explosion behavior of this material. Benchmark cookoff experiments are being performed by the U.S. Navy to validate DOE materials models and computer codes. The ALE3D computer code can model the coupled thermal, mechanical, and chemical behavior of heating and ignition in cookoff tests. In order to provide a predictive capability, materials characterization measurements are being performed to specify parameters in these models. We report on progress in the development of these ALE3D materials models and present measurements as a function of temperature for thermal expansion, heat capacity, shear modulus, bulk modulus, and One-Dimensional-Time-to-Explosion (ODTX).
Date: October 24, 2000
Creator: McClelland, M A; Tran, T D; Cunningham, B J; Weese, R K & Maienschein, J L
System: The UNT Digital Library
Optical studies of the {beta}{double_prime}-(ET){sub 2}SF{sub 5}RSO{sub 3} R = CH{sub 2}CF{sub 2}, CHFCF{sub 2} and CHF system: Chemical tuning of the counterion (open access)

Optical studies of the {beta}{double_prime}-(ET){sub 2}SF{sub 5}RSO{sub 3} R = CH{sub 2}CF{sub 2}, CHFCF{sub 2} and CHF system: Chemical tuning of the counterion

The authors compare the polarized optical spectra of the organic metal {beta}{double_prime}-(ET){sub 2}SF{sub 5}CHFSO{sub 3} and the {beta}{double_prime}-ET{sub 2}SF{sub 5}CHFCF{sub 2}SO{sub 3} metal/insulator material with those of the first fully organic superconductor {beta}{double_prime}-ET{sub 2}SF{sub 5}CH{sub 2}SO{sub 3}. The small chemical modification of the counterion has a dramatic effect on the spectral and charge transport properties of these materials, and they discuss their electronic structure in terms of band structure, many-body effects, and disorder. Based on structural differences in the anion pocket of the three salts, they conclude that the unusual electronic excitations observed in the {beta}{double_prime}-(ET){sub 2}SF{sub 5}CHFCF{sub 2}SO{sub 3} metal/insulator material are caused by disorder-related localization.
Date: July 24, 2000
Creator: Olejniczak, I.; Jones, B. R.; Dong, J.; Pigos, J. M.; Zhu, Z.; Garlach, A. D. et al.
System: The UNT Digital Library
On the distinction between large deformation and large distortion for anisotropic materials (open access)

On the distinction between large deformation and large distortion for anisotropic materials

A motion involves large distortion if the ratios of principal stretches differ significantly from unity. A motion involves large deformation if the deformation gradient tensor is significantly different from the identity. Unfortunately, rigid rotation fits the definition of large deformation, and models that claim to be valid for large deformation are often inadequate for large distortion. An exact solution for the stress in an idealized fiber-reinforced composite is used to show that conventional large deformation representations for transverse isotropy give errant results. Possible alternative approaches are discussed.
Date: February 24, 2000
Creator: BRANNON,REBECCA M.
System: The UNT Digital Library
A high-precision cryogenically-cooled crystal monochromator for the APS diagnostics beamline (open access)

A high-precision cryogenically-cooled crystal monochromator for the APS diagnostics beamline

A high-precision cryogenically-cooled crystal monochromator has been developed for the APS diagnostics beamline. The design permits simultaneous measurements of the particle beam size and divergence. It provides for a large rotation angle, {minus}15{degree} to 180{degree}, with a resolution of 0.0005{degree}. The roll angle of the crystal can be adjusted by up to {+-}3{degree} with a resolution of 0.0001{degree}. A vertical translational stage, with a stroke of {+-}25 mm and resolution of 8 {micro}m, is provided to enable using different parts of the same crystal or to retract the crystal from the beam path. The modular design will allow optimization of cooling schemes to minimize thermal distortions of the crystal under high heat loads.
Date: July 24, 2000
Creator: Rotela, E.; Yang, B.; Sharma, S. & Barcikowski, A.
System: The UNT Digital Library
Liquid fuel reformer development: Autothermal reforming of Diesel fuel (open access)

Liquid fuel reformer development: Autothermal reforming of Diesel fuel

Argonne National Laboratory is developing a process to convert hydrocarbon fuels to clean hydrogen feeds for a polymer electrolyte fuel cell. The process incorporates an autothermal reforming catalyst that can process hydrocarbon feeds at lower temperatures than existing commercial catalysts. The authors have tested the catalyst with three diesel-type fuels: hexadecane, certified low-sulfur grade 1 diesel, and a standard grade 2 diesel. Hexadecane yielded products containing 60% hydrogen on a dry, nitrogen-free basis at 850 C, while maximum hydrogen product yields for the two diesel fuels were near 50%. Residual products in all cases included CO, CO{sub 2}, ethane, and methane. Further studies with grade 1 diesel showed improved conversion as the water:fuel ratio was increased from 1 to 2 at 850 C. Soot formation was reduced when the oxygen:carbon ratio was maintained at 1 at 850 C. There were no significant changes in hydrogen yield as the space velocity and the oxygen:fuel ratio were varied. Tests with a microchannel monolithic catalyst yielded similar or improved hydrogen levels at higher space velocities than with extruded pellets in a packed bed.
Date: July 24, 2000
Creator: Pereira, C.; Bae, J-M.; Ahmed, S. & Krumpelt, M.
System: The UNT Digital Library
Unique Rock-n-Roll Dynamic Appearance of a Ge-Si Ad-Dimer on Si(001) (open access)

Unique Rock-n-Roll Dynamic Appearance of a Ge-Si Ad-Dimer on Si(001)

The authors carry out a comparative study of the energetic and dynamics of Si-Si, Ge-Ge, and Ge-Si ad-dimers on top of a dimer row in the Si(001) surface, using first-principles calculations. The dynamic appearance of a Ge-Si dimer is distinctively different from that of a Si-Si or Ge-Ge dimer, providing a unique way for its identification by scanning tunneling microscopy (STM). Its rocking motion, observed in STM, actually reflects a 180{degree} rotation of the dimer, involving a piecewise-rotation mechanism. The calculated energy barrier of 0.74 eV is in good agreement with the experimental value of 0.82 eV.
Date: July 24, 2000
Creator: Lu, Zhong-Yi; Liu, Feng; Wang, Cai-Zhuang; Qin, X. R.; Swartzentruber, Brian S.; Lagally, M. G. et al.
System: The UNT Digital Library
Design and performance of nitride-based ultraviolet (UV) LEDs (open access)

Design and performance of nitride-based ultraviolet (UV) LEDs

The authors overview several of the challenges in achieving high efficiency nitride-based UV (< 400 nm) LEDs. The issue of optical efficiency is presented through temperature-dependent photoluminescence studies of various UV active regions. These studies demonstrate enhanced optical efficiencies for active regions with In-containing alloys (InGaN, AlInGaN). The authors compare the performance of two distinct UV LED structures. GaN/AlGaN quantum well LEDs with {lambda} < 360 nm emission have demonstrated output powers > 0.1 mW, but present designs suffer from internal absorption effects. InGaN/AlInGaN quantum well LEDs with 370 nm < {lambda} < 390 nm emission and > 1 mW output power are also presented.
Date: April 24, 2000
Creator: Crawford, Mary H. & Han, Jung
System: The UNT Digital Library
Physics beyond the standard model (open access)

Physics beyond the standard model

The author briefly summarizes the prospects for extending the understanding of physics beyond the standard model within the next five years. He interprets ``beyond the standard model'' to mean the physics of electroweak symmetry breaking, including the standard model Higgs boson. The nature of this TeV-scale new physics is perhaps the most crucial question facing high-energy physics, but one should recall (neutrino oscillations) that there is ample evidence for interesting physics in the flavour section too. In the next five years, before the LHC starts operations, the facilities available will be LEP2, HERA and the Fermilab Tevatron. He devotes a bit more time to the Tevatron as it is a new initiative for United Kingdom institutions. The Tevatron schedule now calls for data taking in Run II, using two upgraded detectors, to begin on March 1, 2001, with 2 fb{sup {minus}1} accumulated in the first two years. A nine-month shutdown will follow, to allow new silicon detector layers to be installed, and then running will resume with a goal of accumulating 15 fb{sup {minus}1} (or more) by 2006.
Date: January 24, 2000
Creator: Womersley, J.
System: The UNT Digital Library
Hydrodynamic modeling of tissue ablation with a free-electron laser (open access)

Hydrodynamic modeling of tissue ablation with a free-electron laser

None
Date: February 24, 2000
Creator: London, R A; Uhlhorn, S R; Makarewicz, A J & Jansen, E D
System: The UNT Digital Library