SIAM Workshop on Combinatorial Scientific Computing February 27-28, 2004 San Francisco, CA (open access)

SIAM Workshop on Combinatorial Scientific Computing February 27-28, 2004 San Francisco, CA

None
Date: October 4, 2004
Creator: /a, n
Object Type: Report
System: The UNT Digital Library
Minijet Deformation and Charge-independent Two-particleCorrelations on Momentum Subspace (eta,phi) In Au-Au Collisions atsqrt(sNN) = 130 GeV (open access)

Minijet Deformation and Charge-independent Two-particleCorrelations on Momentum Subspace (eta,phi) In Au-Au Collisions atsqrt(sNN) = 130 GeV

We present first measurements of charge-independent correlations on momentum-space difference variables {eta}{sub 1}-{eta}{sub 2} (pseudorapidity) and {phi}{sub 1}-{phi}{sub 2} (azimuth) for charged primary hadrons with transverse momentum within 0.15 {le} p{sub t} {le} 2 GeV/c and |{eta}| {le} 1.3 from Au-Au collisions at {radical}s{sub NN} = 130 GeV. We observe strong charge-independent correlations associated with minijets and elliptic flow. The width of the minijet peak on {eta}{sub 1}-{eta}{sub 2} increases by a factor 2.3 from peripheral to central collisions, suggesting strong coupling of partons to a longitudinally-expanding colored medium. New methods of jet analysis introduced here reveal nonperturbative medium effects in heavy ion collisions.
Date: November 4, 2004
Creator: Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D.; Arkhipkin, D. et al.
Object Type: Article
System: The UNT Digital Library
Heat Pump Water Heater Technology: Experiences of Residential Consumers and Utilities (open access)

Heat Pump Water Heater Technology: Experiences of Residential Consumers and Utilities

This paper presents a case study of the residential heat pump water heater (HPWH) market. Its principal purpose is to evaluate the extent to which the HPWH will penetrate the residential market sector, given current market trends, producer and consumer attributes, and technical parameters. The report's secondary purpose is to gather background information leading to a generic framework for conducting market analyses of technologies. This framework can be used to compare readiness and to factor attributes of market demand back into product design. This study is a rapid prototype analysis rather than a detailed case analysis. For this reason, primary data collection was limited and reliance on secondary sources was extensive. Despite having met its technical goals and having been on the market for twenty years, the HPWH has had virtually no impact on contributing to the nation's water heating. In some cases, HPWH reliability and quality control are well below market expectations, and early units developed a reputation for unreliability, especially when measured against conventional water heaters. In addition to reliability problems, first costs of HPWH units can be three to five times higher than conventional units. Without a solid, well-managed business plan, most consumers will not be drawn …
Date: August 4, 2004
Creator: Ashdown, BG
Object Type: Report
System: The UNT Digital Library
Atmospheric Radiation Measurement Program Facilities Newsletter, February 2004. (open access)

Atmospheric Radiation Measurement Program Facilities Newsletter, February 2004.

Monthly newsletter discussing news and activities related to the Atmospheric Radiation Measurement Program, articles about weather and atmospheric phenomena, and other related topics.
Date: March 4, 2004
Creator: Atmospheric Radiation Measurement Program (U.S.)
Object Type: Journal/Magazine/Newsletter
System: The UNT Digital Library
Demonstration of an Instrument for On-Line Measuring of the Alpha Radiation (open access)

Demonstration of an Instrument for On-Line Measuring of the Alpha Radiation

The Salt Waste Processing Facility and the Actinide Removal Process at the Savannah River Site will remove alpha emitting radioisotopes from High Level Waste to meet regulatory disposal requirements. The removal occurs prior to removal of the radioactive cesium. Both facility designs currently include verification measurement using conventional wet chemistry approaches remote from the operation. Use of an on-line monitor for this purpose offers the opportunity to shorten process cycle time and thereby increase facility throughput. Personnel from Pacific Northwest National Laboratory designed, built, and functionally tested an on-line monitor, which is capable of measuring the residual transuranic concentrations in processed high-level wastes with a detection limit of 370 Bq/mL (10 nCi/mL) in less than six hours. Personnel from Savannah River National Laboratory assisted in the design and tested the equipment using actual waste. The monitor measures the neutrons produced by the transuranics in the presence of gamma-ray fields up to 1 Sv/h (100 R/h). The optimum design derives in part from Monte Carlo modeling tempered with practical engineering and cost considerations. We demonstrated operation of the monitor in a cell utilizing an actual sample of high-level waste. Results of that demonstration are given, and suggestions for improvements in the …
Date: August 4, 2004
Creator: BARNES, MARKJ.
Object Type: Report
System: The UNT Digital Library
High-speed horizontal-path atmospheric turbulence correction using a large actuator-number MEMS spatial light modulator in an interferometric phase conjugation engine (open access)

High-speed horizontal-path atmospheric turbulence correction using a large actuator-number MEMS spatial light modulator in an interferometric phase conjugation engine

Atmospheric propagation results for a high-speed, large-actuator-number, adaptive optics system are presented. The system uses a MEMS-based spatial light modulator correction device with 1024 actuators. Tests over a 1.35 km path achieved correction speeds in excess of 800 Hz and Strehl ratios close to 0.5. The wave-front sensor was based on a quadrature interferometer that directly measures phase. This technique does not require global wave-front reconstruction, making it relatively insensitive to scintillation and phase residues. The results demonstrate the potential of large actuator number MEMS-based spatial light modulators to replace conventional deformable mirrors.
Date: March 4, 2004
Creator: Baker, K.; Stappaerts, E.; Gavel, D.; Wilks, S.; Tucker, J.; Silva, D. et al.
Object Type: Article
System: The UNT Digital Library
Results of Groundwater Modeling for Tritium Tracking at the Hanford Site 200 Area State-Approved Land Disposal Site--2004 (open access)

Results of Groundwater Modeling for Tritium Tracking at the Hanford Site 200 Area State-Approved Land Disposal Site--2004

The model results presented in this report incorporates the reported data through June 2004 and then uses the updated discharge and tritium inventory values through 2034 based on more current information . Simulation results show that the tritium concentration in the aquifer reaching 1.6 million pCi/L in 1996 After that time, predicted concentration levels at the water table were variable ranging from just over 1 million to several hundred thousand pCi/L and on a downward trend by the year 2004, These simulated results generally reflect the changes in simulated monthly effluent discharges and tritium inventories discharged to the aquifer in the model analysis. These results are also generally consistent with tritium concentration levels and trends that have been observed in well 699-48-77A, the well south of the SALDS facility that is the first well impacted by SALDS operations. Given the differences between the smaller actual facility discharges and those projected in previous modeling, the updated 2004 model was generally consistent with previous estimates made with the 1997 model with regard to plume behavior. Concentrations for the updated model did not reach levels projected in 1997 and the plume did not extend as far out as was estimated in previous modeling. …
Date: October 4, 2004
Creator: Barnett, D BRENT.; Bergeron, Marcel P. & Freeman, Eugene J.
Object Type: Report
System: The UNT Digital Library
Highly charged ion research at the Livermore electron beam ion traps (open access)

Highly charged ion research at the Livermore electron beam ion traps

Spectroscopy performed with the three Livermore electron beam ion traps is reviewed, which is continuing and complementing the innumerable contributions to atomic physics provided over the years by heavy-ion accelerators. Numerous spectrometers were developed that cover the spectral bands from the visible to the hard x ray region. These enabled exhaustive line surveys useful for x-ray astrophysics and for systematic studies along iso-electronic sequences, such as the 4s-4p, 3s-3p, and 2s-2p transitions in ions of the Cu-I, Na-I, and Li-I sequences useful for studying QED and correlation effects as well as for precise determinations of atomic-nuclear interactions. They also enabled measurements of radiative transition probabilities of very long-lived (milli- and microseconds) and very short-live (femtosecond) levels. Because line excitation processes can be controlled by choice of the electron beam energy, the observed line intensities are used to infer cross sections for electron-impact excitation, dielectronic recombination, resonance excitation, and innershell ionization. These capabilities have recently been expanded to simulate x-ray emission from comets by charge exchange. Specific contributions to basic atomic physics, nuclear physics, and high-temperature diagnostics are illustrated.
Date: January 4, 2004
Creator: Beiersdorfer, P
Object Type: Article
System: The UNT Digital Library
Estimates of U.S. Commercial Building Electricity Intensity Trends: Issues Related to End-Use and Supply Surveys (open access)

Estimates of U.S. Commercial Building Electricity Intensity Trends: Issues Related to End-Use and Supply Surveys

This report examines measurement issues related to the amount of electricity used by the commercial sector in the U.S. and the implications for historical trends of commercial building electricity intensity (kWh/sq. ft. of floor space). The report compares two (Energy Information Administration) sources of data related to commercial buildings: the Commercial Building Energy Consumption Survey (CBECS) and the reporting by utilities of sales to commercial customers (survey Form-861). Over past two decades these sources suggest significantly different trend rates of growth of electricity intensity, with the supply (utility)-based estimate growing much faster than that based only upon the CBECS. The report undertakes various data adjustments in an attempt to rationalize the differences between these two sources. These adjustments deal with: 1) periodic reclassifications of industrial vs. commercial electricity usage at the state level and 2) the amount of electricity used by non-enclosed equipment (non-building use) that is classified as commercial electricity sales. In part, after applying these adjustments, there is a good correspondence between the two sources over the the past four CBECS (beginning with 1992). However, as yet, there is no satisfactory explanation of the differences between the two sources for longer periods that include the 1980s.
Date: September 4, 2004
Creator: Belzer, David B.
Object Type: Report
System: The UNT Digital Library
Spatially Continuous Mixed P2-P1 Solutions for Planar Geometry (open access)

Spatially Continuous Mixed P2-P1 Solutions for Planar Geometry

Even-order Legendre polynomial (P{sub N}) expansion approximations of the neutron transport equation have historically seen only limited practical application. Research in the last decade has resolved one of the historical theoretical objections to the use of even-order PN approximations in planar geometry, namely the ambiguity in the prescription of boundary conditions as a result of an odd number of unknowns. This research also demonstrated the P{sub 2} approximation to be more accurate than the P{sub 1} approximation in planar geometry away from boundary layers and material interfaces. Neither the P{sub 1} nor the P{sub 2} approximation is convincingly more accurate near material interfaces. This progress motivated the reexamination of the multidimensional simplified P{sub 2} (SP{sub 2}) approximation, the development of P{sub 2} approximations for planar geometry stochastic transport problems, and the examination of the P{sub 2} and SP{sub 2} approximations as a synthetic acceleration technique for the discrete ordinates equations. The major remaining objection to even-order PN approximations is that the scalar flux distributions obtained using these approximations can exhibit large spatial discontinuities at material interfaces and source discontinuities. In contrast, the odd-order PN approximations typically utilized give spatially continuous scalar flux distributions at these locations. In this paper, we …
Date: June 4, 2004
Creator: Brantley, P S
Object Type: Article
System: The UNT Digital Library
Standard Design Certification with Prototype Testing (open access)

Standard Design Certification with Prototype Testing

Standard design certification has been used over the past 20 years to develop NRC approval of Advanced Light Water Reactor (ALWR) designs. The standard design approval approach is intended to remove much of the uncertainty in the regulatory schedule prior to commitment of major funds to construction. The value of the approach has not been tested in the US but it has supported construction of ABWRs in Japan and Taiwan. Application of the approach to other types of advanced reactors may be possible but is not clear how this might be accomplished in the case of reactors with little or no operating experience. This paper discusses an approach that was proposed by General Electric over 15 years ago and its possible application to GEN-IV reactors.
Date: February 4, 2004
Creator: Brown, N W
Object Type: Article
System: The UNT Digital Library
Automated whole-genome multiple alignment of rat, mouse, and human (open access)

Automated whole-genome multiple alignment of rat, mouse, and human

We have built a whole genome multiple alignment of the three currently available mammalian genomes using a fully automated pipeline which combines the local/global approach of the Berkeley Genome Pipeline and the LAGAN program. The strategy is based on progressive alignment, and consists of two main steps: (1) alignment of the mouse and rat genomes; and (2) alignment of human to either the mouse-rat alignments from step 1, or the remaining unaligned mouse and rat sequences. The resulting alignments demonstrate high sensitivity, with 87% of all human gene-coding areas aligned in both mouse and rat. The specificity is also high: <7% of the rat contigs are aligned to multiple places in human and 97% of all alignments with human sequence > 100kb agree with a three-way synteny map built independently using predicted exons in the three genomes. At the nucleotide level <1% of the rat nucleotides are mapped to multiple places in the human sequence in the alignment; and 96.5% of human nucleotides within all alignments agree with the synteny map. The alignments are publicly available online, with visualization through the novel Multi-VISTA browser that we also present.
Date: July 4, 2004
Creator: Brudno, Michael; Poliakov, Alexander; Salamov, Asaf; Cooper, Gregory M.; Sidow, Arend; Rubin, Edward M. et al.
Object Type: Article
System: The UNT Digital Library
The Global Genome Question: Microbes as the Key to Understanding Evolution and Ecology (open access)

The Global Genome Question: Microbes as the Key to Understanding Evolution and Ecology

A colloquium was convened in Longboat Key, Florida, in October 2002, by the American Academy of Microbiology to discuss the role of genomic techniques in microbiology research. Research professionals from both academia and industry met to discuss the current state of knowledge in microbial genomics. Unanswered questions that should drive future studies, technical challenges for applying genomics in microbial systems, and infrastructure and educational needs were discussed. Particular attention was focused on the great potential of genomic approaches to advance our understanding of microbial communities and ecosystems. Recommendations for activities that might promote and accelerate microbial genome science were identified and discussed. Microbiology has always advanced in tandem with new technologies. Beginning with the first observations of microscopic organisms with early microscopes in the 17th century, the tools and methods for studying microbes have continually evolved. Slowly at first, and now with startling speed, scientists have developed increasingly complex and informative tools for analyzing the functions, interactions, and diversity of microorganisms. Today, genomic technologies are revolutionizing microbiology. Genomics employs all or part of the genome to answer questions about an organism and represents a generic tool that can be used to dissect any or all living cells. In this report, …
Date: April 4, 2004
Creator: Buckley, Merry R.
Object Type: Article
System: The UNT Digital Library
Investigation of Microwave Transitions and Nonlinear Magneto-Optical Rotation in Anti-Relaxation-Coated Cells (open access)

Investigation of Microwave Transitions and Nonlinear Magneto-Optical Rotation in Anti-Relaxation-Coated Cells

Using laser optical pumping, widths and frequency shifts are determined for microwave transitions between the components of the ground-state hyperfine structure for {sup 85}Rb and {sup 87}Rb atoms contained in vapor cells with alkane anti-relaxation coatings. The results are compared with data on Zeeman relaxation obtained in nonlinear magneto-optical rotation (NMOR) experiments, a comparison important for quantitative understanding of spin-relaxation mechanisms in coated cells. By comparing cells manufactured over a forty-year period we demonstrate the long-term stability of coated cells, which may be useful for atomic clocks and magnetometers.
Date: June 4, 2004
Creator: Budker, D.; Hollberg, L.; Kimball, D. F.; Kitching, J.; Pustelny, S.; Robinson, H. G. et al.
Object Type: Article
System: The UNT Digital Library
Identification of Minerals and Meteoritic Materials via Raman Techniques After Capture in Hypervelocity Impacts on Aerogel (open access)

Identification of Minerals and Meteoritic Materials via Raman Techniques After Capture in Hypervelocity Impacts on Aerogel

For this study, an extensive suite of mineral particles analogous to components of cosmic dust were tested to determine if their Raman signatures can be recognized after hypervelocity capture in aerogel. The mineral particles were mainly of greater than 20 micrometers in size and were accelerated onto the silica aerogel by light gas gun shots. It was found that all the individual minerals captured in aerogel could be subsequently identified using Raman (or fluorescent) spectra. The beam spot size used for the laser illumination was of the order of 5 micrometers, and in some cases the captured particles were of a similar small size. In some samples fired into aerogel there was observed a shift in the wavenumbers of some of the Raman bands, a result of the trapped particles being at quite high temperatures due to heating by the laser. Temperatures of samples under laser illumination were estimated from the relative intensities of Stokes and anti-Stokes Raman bands, or, in the case of ruby particles, from the wavenumber of fluorescence bands excited by the laser. It was found that the temperature of particles in aerogel varied greatly, dependent upon laser power and the nature of the particle. In the …
Date: October 4, 2004
Creator: Burchell, M. J.; Mann, J.; Creighton, J. A.; Kearsley, A. T.; Graham, G. A.; Esposito, A. P. et al.
Object Type: Article
System: The UNT Digital Library
Restoring Sustainable Forests on Appalachian Mined Lands for Wood Products, Renewable Energy, Carbon Sequestration, and Other Ecosystems Services Quarterly Report (open access)

Restoring Sustainable Forests on Appalachian Mined Lands for Wood Products, Renewable Energy, Carbon Sequestration, and Other Ecosystems Services Quarterly Report

The overall purpose of this project is to evaluate the biological and economic feasibility of restoring high-quality forests on mined land, and to measure carbon sequestration and wood production benefits that would be achieved from forest restoration procedures. We are currently estimating the acreage of lands in VA, WV, KY, OH, and PA mined under SMCRA and reclaimed to non-forested post-mining land uses that are not currently under active management, and therefore can be considered as available for carbon sequestration. To determine actual sequestration under different forest management scenarios, a field study was installed as a 3 x 3 factorial in a random complete block design with three replications at each of three locations, Ohio, West Virginia, and Virginia. The treatments included three forest types (white pine, hybrid poplar, mixed hardwood) and three silvicultural regimes (competition control, competition control plus tillage, competition control plus tillage plus fertilization). Each individual treatment plot is 0.5 acres. Each block of nine plots requires 4.5 acres, and the complete installation at each site requires 13.5 acres. The plots at all three locations have been installed and the plot corners marked with PVC stakes. GPS coordinates of each plot have been collected. Soil samples were …
Date: August 4, 2004
Creator: Burger, J.; Galbraith, J.; Fox, T.; Amacher, G.; Sullivan, J. & Zipper, C.
Object Type: Report
System: The UNT Digital Library
Restoring Sustainable Forests on Appalachian Mined Lands for Wood Products, Renewable Energy, Carbon Sequestration, and Other Ecosystems Services Quarterly Report (open access)

Restoring Sustainable Forests on Appalachian Mined Lands for Wood Products, Renewable Energy, Carbon Sequestration, and Other Ecosystems Services Quarterly Report

The overall purpose of this project is to evaluate the biological and economic feasibility of restoring high-quality forests on mined land, and to measure carbon sequestration and wood production benefits that would be achieved from forest restoration procedures. In this quarterly report, we present a preliminary comparison of the carbon sequestration potential of forests growing on 14 mined sites in a seven-state region in the Midwestern and Eastern Coalfields. Carbon contents of these forests were compared to adjacent forests on non-mined land. The study was installed as a 3 x 3 factorial in a random complete block design with three replications at each location. The treatments include three forest types (white pine, hybrid poplar, mixed hardwood) and three silvicultural regimes (competition control, competition control plus tillage, competition control plus tillage plus fertilization). Each individual treatment plot is 0.5 acres. Each block of nine plots requires 4.5 acres, and the complete installation at each site requires 13.5 acres. The plots at all three locations have been installed and the plot corners marked with PVC stakes. GPS coordinates of each plot have been collected. Soil samples were collected from each plot to characterize the sites prior to treatment. Analysis of soil samples …
Date: June 4, 2004
Creator: Burger, J.; Galbraith, J.; Fox, T.; Amacher, G.; Sullivan, J. & Zipper, C.
Object Type: Report
System: The UNT Digital Library
Field Test Program for Long-Term Operation of a COHPAC System for Removing Mercury from Coal-Fired Flue Gas (open access)

Field Test Program for Long-Term Operation of a COHPAC System for Removing Mercury from Coal-Fired Flue Gas

With the Nation's coal-burning utilities facing the possibility of tighter controls on mercury pollutants, the U.S. Department of Energy is funding projects that could offer power plant operators better ways to reduce these emissions at much lower costs. Sorbent injection technology represents one of the simplest and most mature approaches to controlling mercury emissions from coal-fired boilers. It involves injecting a solid material such as powdered activated carbon into the flue gas. The gas-phase mercury in the flue gas contacts the sorbent and attaches to its surface. The sorbent with the mercury attached is then collected by the existing particle control device along with the other solid material, primarily fly ash. During 2001, ADA Environmental Solutions (ADA-ES) conducted a full-scale demonstration of sorbent-based mercury control technology at the Alabama Power E.C. Gaston Station (Wilsonville, Alabama). This unit burns a low-sulfur bituminous coal and uses a hot-side electrostatic precipitator (ESP) in combination with a Compact Hybrid Particulate Collector (COHPAC{reg_sign}) baghouse to collect fly ash. The majority of the fly ash is collected in the ESP with the residual being collected in the COHPAC{reg_sign} baghouse. Activated carbon was injected between the ESP and COHPAC{reg_sign} units to collect the mercury. Short-term mercury removal …
Date: June 4, 2004
Creator: Bustard, Jean; Lindsey, Charles; Brignac, Paul; Starns, Travis; Sjostrom, Sharon; Taylor, Trent et al.
Object Type: Report
System: The UNT Digital Library
BIG SKY CARBON SEQUESTRATION PARTNERSHIP (open access)

BIG SKY CARBON SEQUESTRATION PARTNERSHIP

The Big Sky Partnership, led by Montana State University, is comprised of research institutions, public entities and private sectors organizations, and the Confederated Salish and Kootenai Tribes and the Nez Perce Tribe. Efforts during the first performance period fall into four areas: evaluation of sources and carbon sequestration sinks; development of GIS-based reporting framework; designing an integrated suite of monitoring, measuring, and verification technologies; and initiating a comprehensive education and outreach program. At the first Partnership meeting the groundwork was put in place to provide an assessment of capture and storage capabilities for CO{sub 2} utilizing the resources found in the Partnership region (both geological and terrestrial sinks), that would complement the ongoing DOE research. The region has a diverse array of geological formations that could provide storage options for carbon in one or more of its three states. Likewise, initial estimates of terrestrial sinks indicate a vast potential for increasing and maintaining soil C on forested, agricultural, and reclaimed lands. Both options include the potential for offsetting economic benefits to industry and society. Complementary to the efforts on evaluation of sources and sinks is the development of the Big Sky Partnership Carbon Cyberinfrastructure (BSP-CC) and a GIS Road Map …
Date: January 4, 2004
Creator: Capalbo, Susan M.
Object Type: Report
System: The UNT Digital Library
Controls of Net Ecosystem Exchange at an Old Field, a Pine Plantation, and a Hardwood Forest under Identical Climatic and Edaphic Conditions-Isotopic Studies (open access)

Controls of Net Ecosystem Exchange at an Old Field, a Pine Plantation, and a Hardwood Forest under Identical Climatic and Edaphic Conditions-Isotopic Studies

During the past year we have submitted two manuscripts. 1. Mortazavi, B., J. Chanton, J.L. Prater, A.C. Oishi, R. Oren and G. Katul. Temporal variability in 13C of respired CO2 in a pine and a hardwood forest subject to similar climatic conditions (in Press). Oecologia 2. Mortazavi, B. and J. P. Chanton. Use of Keeling plots for determining sources of dissolved organic carbon in nearshore and open ocean systems (Published in Limnology and Oceanography (2004) Vol 49 pages 102-108). 3. Mortazavi, B., J. L. Prater, and J. P. Chanton (2004). A field-based method for simultaneous measurements of the 18O and 13C of soil CO2 efflux. Biogeosciences Vol 1:1-16 Most recent products delivered: Mortazavi, B. and J. P. Chanton. Abiotic and biotic controls on the 13C of respired CO2 in the southeastern US forest mosaics and a new technique for measuring the of soil CO2 efflux. Joint Biosphere Stable Isotope Network (US) and Stable Isotopes in Biosphere Atmosphere Exchange (EU) 2004 Meeting, Interlaken, Switzerland, March 31-April 4, 2004. Mortazavi, B., J. Chanton, J.L. Prater, A.C. Oishi, R. Oren and G. Katul. Temporal variability in 13C of respired CO2 in a pine and a hardwood forest subject to similar climatic conditions. American …
Date: November 4, 2004
Creator: Chanton, J. P. & Mortazavi, B.
Object Type: Report
System: The UNT Digital Library
Further Evaluation of an Urban Canopy Parameterization using VTMX and Urban 2000 Data (open access)

Further Evaluation of an Urban Canopy Parameterization using VTMX and Urban 2000 Data

Almost two-thirds of the U.S. population live in urbanized areas occupying less than 2% of the landmass. Similar statistics of urbanization exists in other parts of the world. With the rapid growth of the world population, urbanization appears to be an important issue on environmental and health aspects. As a result, the interaction between the urban region and atmospheric processes becomes a very complex problem. Further understanding of this interaction via the surface and/or atmosphere is of importance to improve the weather forecast, and to minimize the loss caused by the weather-related events, or even by the chemical-biological threat. To this end, Brown and Willaims, (1998) first developed an urban canopy scheme to parameterize the urban infrastructure effect. This parameterization accounts for the effects of drag, turbulent production, radiation balance, and anthropogenic and rooftop heating. Further modification was made and tested in our recent sensitivity study for an idealized case using a mesoscale model. Results indicated that the addition of the rooftop surface energy equation enables this parameterization to more realistically simulate the urban infrastructure impact (Chin et al., 2000). To further improve the representation of the urban effect in the mesoscale model, the USGS land-use data with different resolutions …
Date: June 4, 2004
Creator: Chin, H S & Leach, M J
Object Type: Article
System: The UNT Digital Library
Simulating Electron Cloud Effects in Heavy-Ion Beams (open access)

Simulating Electron Cloud Effects in Heavy-Ion Beams

Stray electrons can be introduced in heavy ion fusion accelerators as a result of ionization of ambient gas or gas released from walls due to halo-ion impact, or as a result of secondary-electron emission. We summarize here results from several studies of electron-cloud accumulation and effects: (1) Calculation of the electron cloud produced by electron desorption from computed beam ion loss; the importance of ion scattering is shown; (2) Simulation of the effect of specified electron cloud distributions on ion beam dynamics. We find electron cloud variations that are resonant with the breathing mode of the beam have the biggest impact on the beam (larger than other resonant and random variations), and that the ion beam is surprisingly robust, with an electron density several percent of the beam density required to produce significant beam degradation in a 200-quadrupole system. We identify a possible instability associated with desorption and resonance with the breathing mode. (3) Preliminary investigations of a long-timestep algorithm for electron dynamics in arbitrary magnetic fields.
Date: August 4, 2004
Creator: Cohen, R. H.; Friedman, A.; Lund, S. W.; Molvik, A. W.; Azevedo, T.; Vay, J. L. et al.
Object Type: Article
System: The UNT Digital Library
Simulating Electron Cloud Effects in Heavy-Ion Beams (open access)

Simulating Electron Cloud Effects in Heavy-Ion Beams

None
Date: June 4, 2004
Creator: Cohen, R; Friedman, A; Lund, S; Molvik, A; Azevedo, T; Vay, J et al.
Object Type: Article
System: The UNT Digital Library
Analysis of Boron Dilution Transients in PWRS. (open access)

Analysis of Boron Dilution Transients in PWRS.

A study has been carried out with PARCS/RELAP5 to understand the consequences of hypothetical boron dilution events in pressurized water reactors. The scenarios of concern start with a small-break loss-of-coolant accident. If the event leads to boiling in the core and then the loss of natural circulation, a boron-free condensate can accumulate in the cold leg. The dilution event happens when natural circulation is re-established or a reactor coolant pump (RCP) is restarted in violation of operating procedures. This event is of particular concern in B&W reactors with a lowered-loop design and is a Generic Safety Issue for the U.S. Nuclear Regulatory Commission. The results of calculations with the reestablishment of natural circulation show that there is no unacceptable fuel damage. This is determined by calculating the maximum fuel pellet enthalpy, based on the three-dimensional model, and comparing it with the criterion for damage. The calculation is based on a model of a B&W reactor at beginning of the fuel cycle. If an RCP is restarted, unacceptable fuel damage may be possible in plants with sufficiently large volumes of boron-free condensate in the cold leg.
Date: February 4, 2004
Creator: Diamond, David J.; Bromley, Blair P. & Aronson, Arnold L.
Object Type: Article
System: The UNT Digital Library