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Searches for standard model Higgs at the Tevatron (open access)

Searches for standard model Higgs at the Tevatron

A summary of the latest results of Standard Model Higgs boson searches from CDF and D0 presented at the DIS 2007 conference is reported in this paper. All analyses presented use 1 fb{sup -1} of Tevatron data. The strategy of the different analyses is determined by the Higgs production mechanism and decay channel.
Date: April 1, 2007
Creator: Vilar Cortabitarte, Rocio & /Cantabria U., Santander
Object Type: Article
System: The UNT Digital Library
Annual Technical Progress Report of Radioisotope Power System Materials Production and Technology Program Tasks for October 1, 2005 Through September 30, 2006 (open access)

Annual Technical Progress Report of Radioisotope Power System Materials Production and Technology Program Tasks for October 1, 2005 Through September 30, 2006

The Office of Space and Defense Power Systems of the Department of Energy (DOE) provides Radioisotope Power Systems (RPS) for applications where conventional power systems are not feasible. For example, radioisotope thermoelectric generators were supplied by the DOE to the National Aeronautics and Space Administration for deep space missions including the Cassini Mission launched in October of 1997 to study the planet Saturn. For the Cassini Mission, ORNL produced carbon-bonded carbon fiber (CBCF) insulator sets, iridium alloy blanks and foil, and clad vent sets (CVS) used in the generators. The Oak Ridge National Laboratory (ORNL) has been involved in developing materials and technology and producing components for the DOE for more than three decades. This report reflects program guidance from the Office of Space and Defense Power Systems for fiscal year (FY) 2006. Production activities for prime quality (prime) CBCF insulator sets, iridium alloy blanks and foil, and CVS are summarized in this report. Technology activities are also reported that were conducted to improve the manufacturing processes, characterize materials, or to develop information for new radioisotope power systems.
Date: April 1, 2007
Creator: King, James F.
Object Type: Report
System: The UNT Digital Library
A Time-Slotted On-Demand Routing Protocol for Mobile Ad Hoc Unmanned Vehicle Systems (open access)

A Time-Slotted On-Demand Routing Protocol for Mobile Ad Hoc Unmanned Vehicle Systems

The popularity of UAVs has increased dramatically because of their successful deployment in military operations, their ability to preserve human life, and the continual improvements in wireless communication that serves to increase their capabilities. We believe the usefulness of UAVs would be dramatically increased if formation flight were added to the list of capabilities. Currently, sustained formation flight with a cluster of UAVs has only been achieved with two nodes by the Multi-UAV Testbed at the Massachusetts Institute of Technology. (Park, 2004) Formation flight is a complex operation requiring the ability to adjust the flight patterns on the fly and correct for wind gusts, terrain, and differences in node equipment. All of which increases the amount of inner node communication. Since one of the problems with MANET communication is network congestion, we believe a first step towards formation flight can be made through improved inner node communication. We have investigated current communication routing protocols and developed an altered hybrid routing protocol in order to provide communication with less network congestion.
Date: April 1, 2007
Creator: Forsmann, Hope; Hiromoto, Robert & Svoboda, John
Object Type: Article
System: The UNT Digital Library
High Performance Piezoelectric Actuated Gimbal (HIERAX) (open access)

High Performance Piezoelectric Actuated Gimbal (HIERAX)

This paper presents a 3-axis gimbal whose three rotational axes are actuated by a novel drive system: linear piezoelectric motors whose linear output is converted to rotation by using drive disks. Advantages of this technology are: fast response, high accelerations, dither-free actuation and backlash-free positioning. The gimbal was developed to house a laser range finder for the purpose of tracking and guiding unmanned aerial vehicles during landing maneuvers. The tilt axis was built and the test results indicate excellent performance that meets design specifications.
Date: April 1, 2007
Creator: Tschaggeny, Charles; Jones, Warren & Bamberg, Eberhard
Object Type: Article
System: The UNT Digital Library
Selective enrichment of a methanol-utilizing consortium using pulp & paper mill waste streams (open access)

Selective enrichment of a methanol-utilizing consortium using pulp & paper mill waste streams

Efficient utilization of carbon inputs is critical to the economic viability of the current forest products sector. Input carbon losses occur in various locations within a pulp mill, including losses as volatile organics and wastewater . Opportunities exist to capture this carbon in the form of value-added products such as biodegradable polymers. Waste activated sludge from a pulp mill wastewater facility was enriched for 80 days for a methanol-utilizing consortium with the goal of using this consortium to produce biopolymers from methanol-rich pulp mill waste streams. Five enrichment conditions were utilized: three high-methanol streams from the kraft mill foul condensate system, one methanol-amended stream from the mill wastewater plant, and one methanol-only enrichment. Enrichment reactors were operated aerobically in sequencing batch mode at neutral pH and 25°C with a hydraulic residence time and a solids retention time of four days. Non-enriched waste activated sludge did not consume methanol or reduce chemical oxygen demand. With enrichment, however, the chemical oxygen demand reduction over 24 hour feed/decant cycles ranged from 79 to 89 %, and methanol concentrations dropped below method detection limits. Neither the non-enriched waste activated sludge nor any of the enrichment cultures accumulated polyhydroxyalkanoates (PHAs) under conditions of nitrogen sufficiency. …
Date: April 1, 2007
Creator: Mockos, Gregory R.; Smith, William A.; Loge, Frank J. & Thompson, David N.
Object Type: Article
System: The UNT Digital Library
CMS DAQ event builder based on Gigabit Ethernet (open access)

CMS DAQ event builder based on Gigabit Ethernet

The CMS Data Acquisition System is designed to build and filter events originating from 476 detector data sources at a maximum trigger rate of 100 KHz. Different architectures and switch technologies have been evaluated to accomplish this purpose. Events will be built in two stages: the first stage will be a set of event builders called FED Builders. These will be based on Myrinet technology and will pre-assemble groups of about 8 data sources. The second stage will be a set of event builders called Readout Builders. These will perform the building of full events. A single Readout Builder will build events from 72 sources of 16 KB fragments at a rate of 12.5 KHz. In this paper we present the design of a Readout Builder based on TCP/IP over Gigabit Ethernet and the optimization that was required to achieve the design throughput. This optimization includes architecture of the Readout Builder, the setup of TCP/IP, and hardware selection.
Date: April 1, 2007
Creator: Bauer, G.; Boyer, V.; Branson, J.; Brett, A.; Cano, E.; Carboni, A. et al.
Object Type: Article
System: The UNT Digital Library
Macroscopic Modeling of Polymer-Electrolyte Membranes (open access)

Macroscopic Modeling of Polymer-Electrolyte Membranes

In this chapter, the various approaches for the macroscopic modeling of transport phenomena in polymer-electrolyte membranes are discussed. This includes general background and modeling methodologies, as well as exploration of the governing equations and some membrane-related topic of interest.
Date: April 1, 2007
Creator: Weber, A.Z. & Newman, J.
Object Type: Book
System: The UNT Digital Library
Structure, Magnetism, and Transport of CuCr2Se4 Thin Films (open access)

Structure, Magnetism, and Transport of CuCr2Se4 Thin Films

We report the successful growth of highly spin-polarized chalcogenide thin films of CuCr{sub 2}Se{sub 4}, which are promising candidates for spin-based electronic applications. We also present electronic structure calculations for CuCr{sub 2}Se{sub 4} that, together with magnetic and transport data, imply that the stoichiometric compound is a metallic ferromagnet with a relatively low density of hole-like carriers at the Fermi energy. These calculations also predict that a deficiency of Se will deplete the minority density of states at the Fermi energy perhaps leading to a half-metal. We have successfully grown thin films of CuCr{sub 2}Se{sub 4} by pulsed laser deposition on isostructural MgAl{sub 2}O{sub 4} substrates followed by an anneal in a Se-rich environment. X-ray diffraction confirms the structure of CuCr{sub 2}Se{sub 4} on MgAl{sub 2}O{sub 4} substrates as well as a secondary phase of Cr{sub 2}Se{sub 3}. X-ray absorption spectroscopy indicates that the chemical structure at the surface of the films is similar to that of bulk CuCr{sub 2}Se{sub 4} single crystals. Magnetization measurements indicate that these films saturate with a magnetic moment close to 5 {micro}{sub B} per formula unit and a T{sub c} above 400 K. X-ray magnetic circular dichroism shows that the magnetism persists to the …
Date: April 1, 2007
Creator: Bettinger, J. S.; Chopdekar, R. V.; Liberati, M.; Neulinger, J. R.; Chshiev, M.; Takamura, Y. et al.
Object Type: Article
System: The UNT Digital Library
6th Annual Systems Biology Symposium: Systems Biology and the Environment (open access)

6th Annual Systems Biology Symposium: Systems Biology and the Environment

Systems biology recognizes the complex multi-scale organization of biological systems, from molecules to ecosystems. The International Symposium on Systems Biology is an annual two-day event gathering the most influential researchers transforming biology into an integrative discipline investigating complex systems. In recognition of the fundamental similarity between the scientific problems addressed in environmental science and systems biology studies at the molecular, cellular, and organismal levels, the 2007 Symposium featured global leaders in “Systems Biology and the Environment.” The objective of the 2007 “Systems Biology and the Environment” International Symposium was to stimulate interdisciplinary thinking and research that spans systems biology and environmental science. This Symposium was well aligned with the DOE’s Genomics:GTL program efforts to achieve scientific objectives for each of the three DOE missions: • Develop biofuels as a major secure energy source for this century, • Develop biological solutions for intractable environmental problems, and • Understand biosystems’ climate impacts and assess sequestration strategies Our scientific program highlighted world-class research exemplifying these priorities. The Symposium featured 45 minute lectures from 12 researchers including: Penny/Sallie Chisholm of MIT gave the keynote address “Tiny Cells, Global Impact: What Prochlorococcus Can Teach Us About Systems Biology”, plus Jim Fredrickson of PNNL, Nitin Baliga …
Date: April 1, 2007
Creator: Galitski, Timothy, P.
Object Type: Article
System: The UNT Digital Library
The Complete Genome Sequence of Bacillus thuringiensis AlHakam (open access)

The Complete Genome Sequence of Bacillus thuringiensis AlHakam

Bacillus thuringiensis is an insect pathogen that is widelyused as a biopesticide (3). Here we report the finished, annotated genomesequence of B. thuringiensis Al Hakam, which was collected in Iraq by theUnited Nations Special Commission (2).
Date: April 1, 2007
Creator: Challacombe, Jean F.; Altherr, Michael R.; Xie, Gary; Bhotika, Smriti S.; Brown, Nancy; Bruce, David et al.
Object Type: Article
System: The UNT Digital Library
Laboratory Directed Research and Development Program FY 2006 Annual Report (open access)

Laboratory Directed Research and Development Program FY 2006 Annual Report

The Oak Ridge National Laboratory (ORNL) Laboratory Directed Research and Development (LDRD) Program reports its status to the US Departmental of Energy (DOE) in March of each year. The program operates under the authority of DOE Order 413.2B, 'Laboratory Directed Research and Development' (April 19, 2006), which establishes DOE's requirements for the program while providing the Laboratory Director broad flexibility for program implementation. LDRD funds are obtained through a charge to all Laboratory programs. This report includes summaries all ORNL LDRD research activities supported during FY 2006. The associated FY 2006 ORNL LDRD Self-Assessment (ORNL/PPA-2007/2) provides financial data about the FY 2006 projects and an internal evaluation of the program's management process.
Date: April 1, 2007
Creator: Sjoreen, Terrence P
Object Type: Report
System: The UNT Digital Library
Exploring the Variable Sky with the Sloan Digital Sky Survey (open access)

Exploring the Variable Sky with the Sloan Digital Sky Survey

We quantify the variability of faint unresolved optical sources using a catalog based on multiple SDSS imaging observations. The catalog covers SDSS Stripe 82, which lies along the celestial equator in the Southern Galactic Hemisphere (22h 24m < {alpha}{sub J2000} < 04h 08m, -1.27{sup o} < {delta}{sub J2000} < +1.27{sup o}, {approx} 290 deg{sup 2}), and contains 58 million photometric observations in the SDSS ugriz system for 1.4 million unresolved sources that were observed at least 4 times in each of the gri bands (with a median of 10 observations obtained over {approx}5 years). In each photometric bandpass we compute various low-order lightcurve statistics such as root-mean-square scatter (rms), {chi}{sup 2} per degree of freedom, skewness, minimum and maximum magnitude, and use them to select and study variable sources. We find that 2% of unresolved optical sources brighter than g = 20.5 appear variable at the 0.05 mag level (rms) simultaneously in the g and r bands. The majority (2/3) of these variable sources are low-redshift (< 2) quasars, although they represent only 2% of all sources in the adopted flux-limited sample. We find that at least 90% of quasars are variable at the 0.03 mag level (rms) and confirm …
Date: April 1, 2007
Creator: Sesar, Branimir; Ivezic, Zeljko; Lupton, Robert; Juric, Mario; Gunn, James; Knapp, Gillian et al.
Object Type: Article
System: The UNT Digital Library
Mercury Emission Control Technologies for PPL Montana-Colstrip Testing (open access)

Mercury Emission Control Technologies for PPL Montana-Colstrip Testing

The Energy & Environmental Research Center (EERC) was asked by PPL Montana LLC (PPL) to provide assistance and develop an approach to identify cost-effective options for mercury control at its coal-fired power plants. The work conducted focused on baseline mercury level and speciation measurement, short-term parametric testing, and week long testing of mercury control technology at Colstrip Unit 3. Three techniques and various combinations of these techniques were identified as viable options for mercury control. The options included oxidizing agents or sorbent enhancement additives (SEAs) such as chlorine-based SEA1 and an EERC proprietary SEA2 with and without activated carbon injection. Baseline mercury emissions from Colstrip Unit 3 are comparatively low relative to other Powder River Basin (PRB) coal-fired systems and were found to range from 5 to 6.5 g/Nm3 (2.9 to 3.8 lb/TBtu), with a rough value of approximately 80% being elemental upstream of the scrubber and higher than 95% being elemental at the outlet. Levels in the stack were also greater than 95% elemental. Baseline mercury removal across the scrubber is fairly variable but generally tends to be about 5% to 10%. Parametric results of carbon injection alone yielded minimal reduction in Hg emissions. SEA1 injection resulted in 20% …
Date: April 1, 2007
Creator: Kay, John P.; Jones, Michael L. & Benson, Steven A.
Object Type: Report
System: The UNT Digital Library
Climate Change and the Long-Term Evolution of the U.S. Buildings Sector (open access)

Climate Change and the Long-Term Evolution of the U.S. Buildings Sector

This paper discusses a new U.S. building module in the MiniCAM integrated assessment model, and it presents a scenario based on that module.
Date: April 1, 2007
Creator: Rong, Fang; Clarke, Leon E. & Smith, Steven J.
Object Type: Report
System: The UNT Digital Library
Current Comparison of Advanced Nuclear Fuel Cycles (open access)

Current Comparison of Advanced Nuclear Fuel Cycles

This paper compares potential nuclear fuel cycle strategies – once-through, recycling in thermal reactors, sustained recycle with a mix of thermal and fast reactors, and sustained recycle with fast reactors. Initiation of recycle starts the draw-down of weapons-usable material and starts accruing improvements for geologic repositories and energy sustainability. It reduces the motivation to search for potential second geologic repository sites. Recycle in thermal-spectru
Date: April 1, 2007
Creator: Piet, Steven; Bjornard, Trond; Dixon, Brent; Hill, Robert; Matthern, Gretchen & Shropshire, David
Object Type: Article
System: The UNT Digital Library
Exploring Shared Memory Protocols in FLASH (open access)

Exploring Shared Memory Protocols in FLASH

ABSTRACT The goal of this project was to improve the performance of large scientific and engineering applications through collaborative hardware and software mechanisms to manage the memory hierarchy of non-uniform memory access time (NUMA) shared-memory machines, as well as their component individual processors. In spite of the programming advantages of shared-memory platforms, obtaining good performance for large scientific and engineering applications on such machines can be challenging. Because communication between processors is managed implicitly by the hardware, rather than expressed by the programmer, application performance may suffer from unintended communication – communication that the programmer did not consider when developing his/her application. In this project, we developed and evaluated a collection of hardware, compiler, languages and performance monitoring tools to obtain high performance on scientific and engineering applications on NUMA platforms by managing communication through alternative coherence mechanisms. Alternative coherence mechanisms have often been discussed as a means for reducing unintended communication, although architecture implementations of such mechanisms are quite rare. This report describes an actual implementation of a set of coherence protocols that support coherent, non-coherent and write-update accesses for a CC-NUMA shared-memory architecture, the Stanford FLASH machine. Such an approach has the advantages of using alternative coherence only …
Date: April 1, 2007
Creator: Horowitz, Mark; Kunz, Robert; Hall, Mary; Lucas, Robert & Chame, Jacqueline
Object Type: Report
System: The UNT Digital Library
SUBCONTRACT REPORT-Power Module Investigationfor High Temperature (175-200 degrees C) Automotive Application (open access)

SUBCONTRACT REPORT-Power Module Investigationfor High Temperature (175-200 degrees C) Automotive Application

None
Date: April 1, 2007
Creator: Marlino, Laura D & McCluskey, Dr. F. Patrick
Object Type: Report
System: The UNT Digital Library
Soil Management Plan For The Potable Water System Upgrades Project (open access)

Soil Management Plan For The Potable Water System Upgrades Project

This plan describes and applies to the handling and management of soils excavated in support of the Y-12 Potable Water Systems Upgrades (PWSU) Project. The plan is specific to the PWSU Project and is intended as a working document that provides guidance consistent with the 'Soil Management Plan for the Oak Ridge Y-12 National Security Complex' (Y/SUB/92-28B99923C-Y05) and the 'Record of Decision for Phase II Interim Remedial Actions for Contaminated Soils and Scrapyard in Upper East Fork Popular Creek, Oak Ridge, Tennessee' (DOE/OR/01-2229&D2). The purpose of this plan is to prevent and/or limit the spread of contamination when moving soil within the Y-12 complex. The major feature of the soil management plan is the decision tree. The intent of the decision tree is to provide step-by-step guidance for the handling and management of soil from excavation of soil through final disposition. The decision tree provides a framework of decisions and actions to facilitate Y-12 or subcontractor decisions on the reuse of excavated soil on site and whether excavated soil can be reused on site or managed as waste. Soil characterization results from soil sampling in support of the project are also presented.
Date: April 1, 2007
Creator: Field, S. M.
Object Type: Report
System: The UNT Digital Library
Biocompatible Silver-containing a-C:H and a-C coatings: AComparative Study (open access)

Biocompatible Silver-containing a-C:H and a-C coatings: AComparative Study

Hydrogenated diamond-like-carbon (a-C:H) and hydrogen-free amorphous carbon (a-C) coatings are known to be biocompatible and have good chemical inertness. For this reason, both of these materials are strong candidates to be used as a matrix that embeds metallic elements with antimicrobial effect. In this comparative study, we have incorporated silver into diamond-like carbon (DLC) coatings by plasma based ion implantation and deposition (PBII&D) using methane (CH4) plasma and simultaneously depositing Ag from a pulsed cathodic arc source. In addition, we have grown amorphous carbon - silver composite coatings using a dual-cathode pulsed filtered cathodic-arc (FCA) source. The silver atomic content of the deposited samples was analyzed using glow discharge optical spectroscopy (GDOES). In both cases, the arc pulse frequency of the silver cathode was adjusted in order to obtain samples with approximately 5 at.% of Ag. Surface hardness of the deposited films was analyzed using the nanoindentation technique. Cell viability for both a-C:H/Ag and a-C:/Ag samples deposited on 24-well tissue culture plates has been evaluated.
Date: April 1, 2007
Creator: Endrino, Jose Luis; Allen, Matthew; Escobar Galindo, Ramon; Zhang, Hanshen; Anders, Andre & Albella, Jose Maria
Object Type: Article
System: The UNT Digital Library
Evidence for electroweak top quark production in proton-antiproton collisions at s**(1/2) = 1.96 TeV (open access)

Evidence for electroweak top quark production in proton-antiproton collisions at s**(1/2) = 1.96 TeV

We present the first evidence for electroweak single top quark production using nearly 1 fb{sup -1} of Tevatron Run II data at {radical}s = 1.96 TeV. We select single-top-like data events in the lepton+jets decay channel and separate them from backgrounds using the matrix element analysis method. This technique uses leading order matrix elements to compute an event probability for both signal and background hypotheses. Using the expected signal acceptance, background, and observed data we measure the single top quark cross section: {sigma}(p{bar p} {yields} tb + tqb + X) = 4.6{sub -1.5}{sup +}1.8 pb. The probability for the background to have fluctuated up to give at least the cross section measured in this analysis is 0.21%, which corresponds to a Gaussian equivalent significance of 2.9{sigma}.
Date: April 1, 2007
Creator: Gadfort, Thomas & /Washington U., Seattle
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Measurements of Ammonia at Blodgett Forest (open access)

Measurements of Ammonia at Blodgett Forest

Ammonia is a reactive trace gas that is emitted in large quantities by animal agriculture and other sources in California, which subsequently forms aerosol particulate matter, potentially affecting visibility, climate, and human health. We performed initial measurements of NH{sub 3} at the Blodgett Forest Research Station (BFRS) during a 3 week study in June, 2006. The site is used for ongoing air quality research and is a relatively low-background site in the foothills of the Sierra Nevada. Measured NH{sub 3} mixing ratios were quite low (< 1 to {approx}2 ppb), contrasting with typical conditions in many parts of the Central Valley. Eddy covariance measurements showed NH{sub 3} fluxes that scaled with measured NH{sub 3} mixing ratio and calculated aerodynamic deposition velocity, suggesting dry deposition is a significant loss mechanism for atmospheric NH{sub 3} at BFRS. A simple model of NH{sub 3} transport to the site supports the hypothesis that NH{sub 3} is transported from the Valley to BFRS, but deposits on vegetation during the summer. Further work is necessary to determine whether the results obtained in this study can be generalized to other seasons.
Date: April 1, 2007
Creator: Fischer, Marc L. & Littlejohn, David
Object Type: Report
System: The UNT Digital Library
Effects of Extreme Sleep Deprivation on Human Performance (open access)

Effects of Extreme Sleep Deprivation on Human Performance

Sleep is a fundamental recuperative process for the nervous system. Disruption of this homeostatic drive can lead to severe impairments of the operator’s ability to perceive, recognize, and respond to emergencies and/or unanticipated events, putting the operator at risk. Therefore, establishing a comprehensive understanding of how sleep deprivation influences human performance is essential in order to counter fatigue or to develop mitigation strategies. The goal of the present study was to examine the psychological effects of prolonged sleep deprivation (approx. 75 hrs) over a four-day span on a general aviation pilot flying a fixed-based flight simulator. During the study, a series of tasks were employed every four hours in order to examine the pilot’s perceptual and higher level cognitive abilities. Overall, results suggest that the majority of cognitive and perceptual degradation occurs between 30-40 hours into the flight. Limitations and future research directions are also discussed.
Date: April 1, 2007
Creator: Tran, Tuan; Raddatz, Kimberly R.; Cady, Elizabeth T.; Amstutz, Bradford; Elgin, Pete D.; Vowels, Christopher et al.
Object Type: Article
System: The UNT Digital Library
Aria 1.5 : user manual. (open access)

Aria 1.5 : user manual.

Aria is a Galerkin finite element based program for solving coupled-physics problems described by systems of PDEs and is capable of solving nonlinear, implicit, transient and direct-to-steady state problems in two and three dimensions on parallel architectures. The suite of physics currently supported by Aria includes the incompressible Navier-Stokes equations, energy transport equation, species transport equations, nonlinear elastic solid mechanics, and electrostatics as well as generalized scalar, vector and tensor transport equations. Additionally, Aria includes support for arbitrary Lagrangian-Eulerian (ALE) and level set based free and moving boundary tracking. Coupled physics problems are solved in several ways including fully-coupled Newton's method with analytic or numerical sensitivities, fully-coupled Newton-Krylov methods, fully-coupled Picard's method, and a loosely-coupled nonlinear iteration about subsets of the system that are solved using combinations of the aforementioned methods. Error estimation, uniform and dynamic h-adaptivity and dynamic load balancing are some of Aria's more advanced capabilities. Aria is based on the Sierra Framework.
Date: April 1, 2007
Creator: Hopkins, Matthew Morgan; Moffat, Harry K.; Noble, David R.; Notz, Patrick K. & Subia, Samuel Ramirez
Object Type: Report
System: The UNT Digital Library
A taxonomy and comparison of parallel block multi-level preconditioners for the incompressible Navier-Stokes equations. (open access)

A taxonomy and comparison of parallel block multi-level preconditioners for the incompressible Navier-Stokes equations.

In recent years, considerable effort has been placed on developing efficient and robust solution algorithms for the incompressible Navier-Stokes equations based on preconditioned Krylov methods. These include physics-based methods, such as SIMPLE, and purely algebraic preconditioners based on the approximation of the Schur complement. All these techniques can be represented as approximate block factorization (ABF) type preconditioners. The goal is to decompose the application of the preconditioner into simplified sub-systems in which scalable multi-level type solvers can be applied. In this paper we develop a taxonomy of these ideas based on an adaptation of a generalized approximate factorization of the Navier-Stokes system first presented in [25]. This taxonomy illuminates the similarities and differences among these preconditioners and the central role played by efficient approximation of certain Schur complement operators. We then present a parallel computational study that examines the performance of these methods and compares them to an additive Schwarz domain decomposition (DD) algorithm. Results are presented for two and three-dimensional steady state problems for enclosed domains and inflow/outflow systems on both structured and unstructured meshes. The numerical experiments are performed using MPSalsa, a stabilized finite element code.
Date: April 1, 2007
Creator: Shadid, John Nicolas (Sandia National Laboratories, Albuquerque, NM); Elman, Howard (University of Maryland, College Park, MD); Shuttleworth, Robert R. (University of Maryland, College Park, MD); Howle, Victoria E. & Tuminaro, Raymond Stephen
Object Type: Report
System: The UNT Digital Library