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1-D Equilibrium Discrete Diffusion Monte Carlo
We present a new hybrid Monte Carlo method for 1-D equilibrium diffusion problems in which the radiation field coexists with matter in local thermodynamic equilibrium. This method, the Equilibrium Discrete Diffusion Monte Carlo (EqDDMC) method, combines Monte Carlo particles with spatially discrete diffusion solutions. We verify the EqDDMC method with computational results from three slab problems. The EqDDMC method represents an incremental step toward applying this hybrid methodology to non-equilibrium diffusion, where it could be simultaneously coupled to Monte Carlo transport.
Date:
August 2000
Creator:
Evans, T. M.; Urbatsch, T. J. & Lichtenstein, H.
Object Type:
Article
System:
The UNT Digital Library
1999 Gordon Research Conference on Atmospheric Chemistry
The Gordon Research Conference (GRC) on Atmospheric Chemistry was held at Salve Regina University in Newport, Rhode Island, June 13-18, 1999. The conference was well attended with 151 participants. The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both US and foreign scientists, senior researchers, young investigators, and students.
Date:
August 1, 2000
Creator:
Storm, C.
Object Type:
Article
System:
The UNT Digital Library
AIR DISPERSION MODELING AT THE WASTE ISOLATION PILOT PLANT
One concern at the Waste Isolation Pilot Plant (WIPP) is the amount of alpha-emitting radionuclides or hazardous chemicals that can become airborne at the facility and reach the Exclusive Use Area boundary as the result of a release from the Waste Handling Building (WHB) or from the underground during waste emplacement operations. The WIPP Safety Analysis Report (SAR), WIPP RCRA Permit, and WIPP Emergency Preparedness Hazards Assessments include air dispersion calculations to address this issue. Meteorological conditions at the WIPP facility will dictate direction, speed, and dilution of a contaminant plume of respirable material due to chronic releases or during an accident. Due to the paucity of meteorological information at the WIPP site prior to September 1996, the Department of Energy (DOE) reports had to rely largely on unqualified climatic data from the site and neighboring Carlsbad, which is situated approximately 40 km (26 miles) to the west of the site. This report examines the validity of the DOE air dispersion calculations using new meteorological data measured and collected at the WIPP site since September 1996. The air dispersion calculations in this report include both chronic and acute releases. Chronic release calculations were conducted with the EPA-approved code, CAP88PC and …
Date:
August 1, 2000
Creator:
Rucker, D. F.
Object Type:
Report
System:
The UNT Digital Library
Algorithmic Strategies in Combinatorial Chemistry
Combinatorial Chemistry is a powerful new technology in drug design and molecular recognition. It is a wet-laboratory methodology aimed at ``massively parallel'' screening of chemical compounds for the discovery of compounds that have a certain biological activity. The power of the method comes from the interaction between experimental design and computational modeling. Principles of ``rational'' drug design are used in the construction of combinatorial libraries to speed up the discovery of lead compounds with the desired biological activity. This paper presents algorithms, software development and computational complexity analysis for problems arising in the design of combinatorial libraries for drug discovery. The authors provide exact polynomial time algorithms and intractability results for several Inverse Problems-formulated as (chemical) graph reconstruction problems-related to the design of combinatorial libraries. These are the first rigorous algorithmic results in the literature. The authors also present results provided by the combinatorial chemistry software package OCOTILLO for combinatorial peptide design using real data libraries. The package provides exact solutions for general inverse problems based on shortest-path topological indices. The results are superior both in accuracy and computing time to the best software reports published in the literature. For 5-peptoid design, the computation is rigorously reduced to an exhaustive …
Date:
August 1, 2000
Creator:
Goldman, Deborah; Istrail, Sorin; Lancia, Giuseppe; Piccolboni, Antonio & Walenz, Brian
Object Type:
Article
System:
The UNT Digital Library
The Aluminum-Free P-n-P InGaAsN Double Heterojunction Bipolar Transistors
The authors have demonstrated an aluminum-free P-n-P GaAs/InGaAsN/GaAs double heterojunction bipolar transistor (DHBT). The device has a low turn-on voltage (V{sub ON}) that is 0.27 V lower than in a comparable P-n-p AlGaAs/GaAs HBT. The device shows near-ideal D. C. characteristics with a current gain ({beta}) greater than 45. The high-speed performance of the device are comparable to a similar P-n-p AlGaAs/GaAs HBT, with f{sub T} and f{sub MAX} values of 12 GHz and 10 GHz, respectively. This device is very suitable for low-power complementary HBT circuit applications, while the aluminum-free emitter structure eliminates issues typically associated with AlGaAs.
Date:
August 1, 2000
Creator:
Chang, Ping-Chih; Li, N. Y.; Baca, Albert G.; Monier, C.; Laroche, J. R.; Hou, H. Q. et al.
Object Type:
Article
System:
The UNT Digital Library
Americium Separations From Nitric Acid Process Effluent Streams
The aging of the US nuclear stockpile presents a number of challenges, including the ever-increasing radioactivity of plutonium residues from {sup 241}Am. Minimization of this weak gamma-emitter in process and waste solutions is desirable to reduce both worker exposure and the effects of radiolysis on the final waste product. Removal of americium from plutonium nitric acid processing effluents, however, is complicated by the presence of large.quantities of competing metals, particularly Fe and Al, and-strongly oxidizing acidic solutions. The reprocessing operation offers several points at which americium removal maybe attempted, and we are evaluating two classes of materials targeted at different steps in the process. Extraction chromatography resin materials loaded with three different alkylcarbamoyl phosphinates and phosphine oxides were accessed for Am removal efficiency and Am/Fe selectivity from 1-7 molar nitric acid solutions. Commercial and experimental mono- and bifunctional anion-exchange resins were evaluated for total alpha-activity removal from post-evaporator solutions whose composition, relative to the original nitric acid effluent, is reduced in acid and greatly increased in total salt content. With both classes of materials, americium/total alpha emission removal is sufficient to meet regulatory requirements even under sub-optimal conditions. Batch distribution coefficients, column performance data, and the effects of Fe-masking agents …
Date:
August 1, 2000
Creator:
Barr, M. & Jarvinen, G.
Object Type:
Article
System:
The UNT Digital Library
Analysis and databasing software for integrated tomographic gamma scanner (TGS) and passive-active neutron (PAN) assay systems
None
Date:
August 1, 2000
Creator:
Estep, R.; Melton, S. & Buenafe, C.
Object Type:
Article
System:
The UNT Digital Library
Analysis of Fragmentation and Resulting Shrapnel Penetration of Naturally Fragmenting Cylindrical Bombs
Fragmentation of exploding cylinders and penetration mechanics of surrounding vessel walls were examined and a qualitative understanding was achieved. This understanding provided a basis for making simplifying approximations and assumptions that aided in creating a shrapnel penetration model. Several mathematical models were discussed, and results from 6 cylinder tests were analyzed in order to select a model that best represented the data. It was determined that the overall best mathematical model to predict shrapnel penetration uses the modified Gurney equation to calculate fragment velocity, the Mott equation to calculate largest fragment weight, and the Christman/Gehring equation to calculate penetration depth.
Date:
August 1, 2000
Creator:
Gardner, S. E.
Object Type:
Report
System:
The UNT Digital Library
Analysis of longitudinal bunching in an FEL driven two-beam accelerator
Recent experiments have explored the use of a free-electron laser (FEL) as a buncher for a microwave two-beam accelerator, and the subsequent driving of a standing-wave rf output cavity. Here the authors present a deeper analysis of the longitudinal dynamics of the electron bunches as they are transported from the end of the FEL and through the output cavity. In particular, the authors examine the effect of the transport region and cavity aperture to filter the bunched portion of the beam.
Date:
August 1, 2000
Creator:
Lidia, S.; Gardelle, J.; Lefevre, T.; Donohue, J.T.; Gouard, P.; Rullier, J.L. et al.
Object Type:
Article
System:
The UNT Digital Library
An Analysis of the Impact of Sport Utility Vehicles in the United States
It may be labeled sport utility vehicle, SUV, sport-ute, suburban assault vehicle, or a friend of OPEC (Organization for Petroleum Exporting Countries). It has been the subject of comics, the object of high-finance marketing ploys, and the theme of Dateline. Whatever the label or the occasion, this vehicle is in great demand. The popularity of sport utility vehicles (SUVs) has increased dramatically since the late 1970s, and SUVs are currently the fastest growing segment of the motor vehicle industry. Hoping to gain market share due to the popularity of the expanding SUV market, more and more manufacturers are adding SUVs to their vehicle lineup. One purpose of this study is to analyze the world of the SUV to determine why this vehicle has seen such a rapid increase in popularity. Another purpose is to examine the impact of SUVs on energy consumption, emissions, and highway safety.
Date:
August 1, 2000
Creator:
Davis, S. C. & Truett, L. F.
Object Type:
Report
System:
The UNT Digital Library
Application of the SmartSampling Methodology to the Evaluation of Contaminated Landscape Soils at Brookhaven National Laboratory
Portions of the SmartSampling{trademark} analysis methodology have been applied to the evaluation of radioactive contaminated landscape soils at Brookhaven National Laboratory. Specifically, the spatial, volumetric distribution of cesium-137 ({sup 137}Cs) contamination within Area of Concern 16E-1 has been modeled probabilistically using a geostatistical methodology, with the purpose of identifying the likelihood of successfully reducing, with respect to a pre-existing, baseline remediation plan, the volume of soil that must be disposed of offsite during clean-up. The principal objective of the analysis was to evaluate the likelihood of successful deployment of the Segmented Gate System (SGS), a novel remediation approach that emphasizes real-time separation of clean from contaminated materials during remediation operations. One primary requirement for successful application of the segmented gate technology investigated is that a variety of contaminant levels exist at the deployment site, which would enable to the SGS to discriminate material above and below a specified remediation threshold value. The results of this analysis indicate that there is potential for significant volume reduction with respect to the baseline remediation plan at a threshold excavation level of 23 pCi/g {sup 137}Cs. A reduction of approximately 50%, from a baseline volume of approximately 1,064.7 yd{sup 3} to less than 550 …
Date:
August 1, 2000
Creator:
RAUTMAN,CHRISTOPHER A.
Object Type:
Report
System:
The UNT Digital Library
Ash Deposit Formation and Deposit Properties. A Comprehensive Summary of Research Conducted at Sandia's Combustion Research Facility
This report summarizes experimental and theoretical work performed at Sandia's Combustion Research Facility over the past eight years on the fate of inorganic material during coal combustion. This work has been done under four broad categories: coal characterization, fly ash formation, ash deposition, and deposit property development. The objective was to provide sufficient understanding of these four areas to be able to predict coal behavior in current and advanced conversion systems. This work has led to new characterization techniques for fuels that provide, for the first time, systematic and species specific information regarding the inorganic material. The transformations of inorganic material during combustion can be described in terms of the net effects of the transformations of these individual species. Deposit formation mechanisms provide a framework for predicting deposition rates for abroad range of particle sizes. Predictions based on these rates many times are quite accurate although there are important exceptions. A rigorous framework for evaluating deposit has been established. Substantial data have been obtained with which to exercise this framework, but this portion of the work is less mature than is any other. Accurate prediction of deposit properties as functions of fuel properties, boiler design, and boiler operating conditions represents …
Date:
August 1, 2000
Creator:
Baxter, Larry L.
Object Type:
Report
System:
The UNT Digital Library
Assessing Housing Markets for Seniors
A short report on housing market research and needs for seniors.
Date:
August 2000
Creator:
Cowley, Jennifer S. & Witherspoon, John R.
Object Type:
Report
System:
The Portal to Texas History
Association of ventilation with health and other responses in commercial and institutional buildings
The paper presents a summary of a review [1] of current literature on the associations of ventilation rates in non-residential and non-industrial buildings (primarily offices) with health and other human outcomes. Twenty studies, with close to 30,000 subjects, investigated the association of ventilation rates with human responses. (Twenty one studies investigating the association of carbon dioxide with human responses, although included in the previous review, are not summarized here.) Almost all studies including ventilation rates below 10 Ls{sup -1} per person found these ventilation rates to be associated in all building types with statistically significant worsening in one or more health or perceived air quality outcomes. Some studies comparing only ventilation rates above 10 Ls{sup -1} per person determined that increases in ventilation rate above 10 Ls{sup -1} per person, up to approximately 20 Ls{sup -1} per person, were associated with further significant decreases in the prevalence of SBS symptoms or with further significant improvements in perceived air quality. The studies reported relative risks of 1.5-2 for respiratory illnesses and 1.1-6 for sick building syndrome symptoms for low compared to high ventilation rates.
Date:
August 1, 2000
Creator:
Seppanen, Olli; Fisk, William J. & Mendell, Mark J.
Object Type:
Article
System:
The UNT Digital Library
ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN
Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg-rich lamellar-hydroxide based minerals (e.g., brucite and serpentine) offer a class of widely available, low-cost materials, with intriguing mineral carbonation potential. Carbonation of such materials inherently involves dehydroxylation, which can disrupt the material down to the atomic level. As such, controlled dehydroxylation before and/or during carbonation may provide an important parameter for enhancing carbonation reaction processes. Mg(OH){sub 2} was chosen as the model material for investigating lamellar hydroxide mineral dehydroxylation/carbonation mechanisms due to (i) its structural and chemical simplicity, (ii) interest in Mg(OH){sub 2} gas-solid carbonation as a potentially cost-effective CO{sub 2} mineral sequestration process component, and (iii) its structural and chemical similarity to other lamellar-hydroxide-based minerals (e.g., serpentine-based minerals) whose carbonation reaction processes are being explored due to their low-cost CO{sub 2} sequestration potential. Fundamental understanding of the mechanisms that govern dehydroxylation/carbonation processes is essential for cost optimization of any lamellar-hydroxide-based …
Date:
August 1, 2000
Creator:
McKelvy, M.J.; Sharma, R.; Chizmeshya, A.V.G.; Bearat, H. & Carpenter, R.W.
Object Type:
Report
System:
The UNT Digital Library
An Audit Report on Compliance with Revised Historically Underutilized Business Requirements
Report of the Texas State Auditor's Office related to 18 entities in the process of implementing or that have already basic elements of the revised Historically Underutilized Business (HUB) rules.
Date:
August 2000
Creator:
Texas. Office of the State Auditor.
Object Type:
Report
System:
The Portal to Texas History
An Audit Report on Formula Funding Reporting for 35 State Universities
Report of the Texas State Auditor's Office related to determining whether select universities are in compliance with the Coordinating Board Rules and Regulations, Article III of the General Appropriations Act, and provisions of the Texas Education Code for the purpose of receiving formula funded state appropriations.
Date:
August 2000
Creator:
Texas. Office of the State Auditor.
Object Type:
Report
System:
The Portal to Texas History
An Audit Report on Groundwater Conservation Districts: Phase One
Report of the Texas State Auditor's Office related to determining whether the nine groundwater districts reviewed are operational, based on their activities under their unique management plans, and whether the districts comply with certain statutory requirements established in Texas Water Code for groundwater districts.
Date:
August 2000
Creator:
Texas. Office of the State Auditor.
Object Type:
Report
System:
The Portal to Texas History
An Audit Report on the Contracting Practices of the Texas Life, Accident, Health, and Hospital Service Insurance Guaranty Association
Report of the Texas State Auditor's Office related to determining if the Texas Life, Accident, Health, and Hospital Service Insurance Guaranty Association's (Association) contracting and oversight practices are sufficient to ensure that contractors are fairly and objectively selected and that the Association receives the best value; and whether the Department of Insurance (Department) provides sufficient supervision of the Association's operations.
Date:
August 2000
Creator:
Texas. Office of the State Auditor.
Object Type:
Report
System:
The Portal to Texas History
An Audit Report on the Department of Protective and Regulatory Services' Administration of Foster Care Contracts
Report of the Texas State Auditor's Office related to evaluating the Department of Protective and Regulatory Services' contract administration for the various types of contracts associated with children in foster care.
Date:
August 2000
Creator:
Texas. Office of the State Auditor.
Object Type:
Report
System:
The Portal to Texas History
An Audit Report on the Texas Department of Economic Development's Contracting Practices for the Smart Jobs Program
Report of the Texas State Auditor's Office related to determining the extent of potential fraud, waste, and/or abuse in the Smart Jobs program by focusing on how many employees were actually trained and how many new jobs were actually created through the use of the Smart Jobs funds.
Date:
August 2000
Creator:
Texas. Office of the State Auditor.
Object Type:
Report
System:
The Portal to Texas History
BALLOON-BASED HIGH-TIME RESOLUTION MEASUREMENTS OF X-RAY EMISSIONS FROM LIGHTNING
This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project consisted of a series of balloon flights to collect high-time-resolution x-ray and electric-field-change measurements in thunderstorms in order to validate the existence of the runaway air-breakdown mechanism during lightning and/or sprite production. The runaway air-breakdown mechanism is currently the leading theory to account for unexplained balloon and aircraft-based measurements of x-ray enhancements associated with sprites. Balloon-borne gamma-ray and electric-field-change instruments were launched into a daytime summer thunderstorm. A greater than three-fold increase in the gamma-ray flux was observed as the balloon descended through a thunderstorm anvil where a strong electric field was present. These observations suggest that gamma-ray production in thunderstorms may not be as uncommon as previously believed.
Date:
August 1, 2000
Creator:
EACK, K.; SUSZCYNSKY, D. & AL, ET
Object Type:
Report
System:
The UNT Digital Library
BEAM DIAGNOSTICS INSTRUMENTATION FOR A 6.7-MEV PROTON BEAM HALO EXPERIMENT
None
Date:
August 1, 2000
Creator:
GILPATRICK, J. & AL, ET
Object Type:
Article
System:
The UNT Digital Library
Beam emittance measurements for the low-energy demonstration accelerator (LEDA) radio-frequency quadrupole (RFQ)
None
Date:
August 1, 2000
Creator:
Schulze, M.
Object Type:
Article
System:
The UNT Digital Library