Improving the Material Response for Slow Heat of Energetic Materials (open access)

Improving the Material Response for Slow Heat of Energetic Materials

The goal of modern high explosive slow heat cookoff modeling is to understand the level of mechanical violence. This requires understanding the coupled thermal-mechanical-chemical system that such an environment creates. Recent advances have improved our ability to predict the time to event, and we have been making progress on predicting the mechanical response. By adding surface tension to the product gas pores in the high explosive, we have been able to reduce the current model's tendency to overpressurize confinement vessels. We describe the model and demonstrate how it affects a LX-10 STEX experiment. Issues associated with current product gas equations of state are described and examined.
Date: March 8, 2010
Creator: Nichols, A. L.
Object Type: Article
System: The UNT Digital Library
Electronic Spectroscopy & Dynamics (open access)

Electronic Spectroscopy & Dynamics

The Gordon Research Conference (GRC) on Electronic Spectroscopy and Dynamics was held at Colby College, Waterville, NH from 07/19/2009 thru 07/24/2009. The Conference was well-attended with participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. The GRC on Electronic Spectroscopy & Dynamics showcases some of the most recent experimental and theoretical developments in electronic spectroscopy that probes the structure and dynamics of isolated molecules, molecules embedded in clusters and condensed phases, and bulk materials. Electronic spectroscopy is an important tool in many fields of research, and this GRC brings together experts having diverse backgrounds in physics, chemistry, biophysics, and materials science, making the meeting an excellent opportunity for the interdisciplinary exchange of ideas and techniques. Topics covered in this GRC include high-resolution spectroscopy, biological molecules in the gas phase, electronic structure theory for excited states, multi-chromophore and single-molecule spectroscopies, and excited state dynamics in chemical and biological systems.
Date: June 8, 2010
Creator: Mark Maroncelli, Nancy Ryan Gray
Object Type: Report
System: The UNT Digital Library
Using wesBench to Study the Rendering Performance of Graphics Processing Units (open access)

Using wesBench to Study the Rendering Performance of Graphics Processing Units

Graphics operations consist of two broad operations. The first, which we refer to here as vertex operations, consists of transformation, lighting, primitive assembly, and so forth. The second, which we refer to as pixel or fragment operations, consist of rasterization, texturing, scissoring, blending, and fill. Overall GPU rendering performance is a function of throughput of both these interdependent stages: if one stage is slower than the other, the faster stage will be forced to run more slowly and overall rendering performance will be adversely affected. This relationship is commutative: if the later stage has a greater workload than the earlier stage, the earlier stage will be forced to 'slow down.' For example, a large triangle that covers many screen pixels will incur a very small amount of work in the vertex stage while at the same time incurring a relatively large amount of work in the fragment stage. Rendering performance of a scene consisting of many large-area triangles will be limited by throughput of the fragment stage, which will have relatively more work than the vertex stage. There are two main objectives for this document. First, we introduce a new graphics benchmark, wesBench, which is useful for measuring performance of …
Date: January 8, 2010
Creator: Bethel, Edward W
Object Type: Report
System: The UNT Digital Library
Neutronics Design of a Thorium-Fueled Fission Blanket for LIFE (Laser Inertial Fusion-based Energy) (open access)

Neutronics Design of a Thorium-Fueled Fission Blanket for LIFE (Laser Inertial Fusion-based Energy)

The Laser Inertial Fusion-based Energy (LIFE) project at LLNL includes development of hybrid fusion-fission systems for energy generation. These hybrid LIFE engines use high-energy neutrons from laser-based inertial confinement fusion to drive a subcritical blanket of fission fuel that surrounds the fusion chamber. The fission blanket contains TRISO fuel particles packed into pebbles in a flowing bed geometry cooled by a molten salt (flibe). LIFE engines using a thorium fuel cycle provide potential improvements in overall fuel cycle performance and resource utilization compared to using depleted uranium (DU) and may minimize waste repository and proliferation concerns. A preliminary engine design with an initial loading of 40 metric tons of thorium can maintain a power level of 2000 MW{sub th} for about 55 years, at which point the fuel reaches an average burnup level of about 75% FIMA. Acceptable performance was achieved without using any zero-flux environment 'cooling periods' to allow {sup 233}Pa to decay to {sup 233}U; thorium undergoes constant irradiation in this LIFE engine design to minimize proliferation risks and fuel inventory. Vast reductions in end-of-life (EOL) transuranic (TRU) inventories compared to those produced by a similar uranium system suggest reduced proliferation risks. Decay heat generation in discharge fuel …
Date: March 8, 2010
Creator: Powers, J.; Abbott, R.; Fratoni, M.; Kramer, K.; Latkowski, J.; Seifried, J. et al.
Object Type: Article
System: The UNT Digital Library
Alternative Neutron Detection Testing Summary (open access)

Alternative Neutron Detection Testing Summary

Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. Most currently deployed radiation portal monitors (RPMs) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large area neutron detector. This type of neutron detector is used in the TSA and other RPMs installed in international locations and in the Ludlum and Science Applications International Corporation RPMs deployed primarily for domestic applications. There is a declining supply of 3He in the world and, thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He in RPMs. These technologies are: 1) Boron trifluoride-filled proportional counters, 2) Boron-lined proportional counters, 3) Lithium-loaded glass fibers, and 4) Coated wavelength-shifting plastic fibers. Reported here is a summary of the testing carried out at Pacific Northwest National Laboratory on these technologies to date, as well as measurements on 3He tubes at various …
Date: April 8, 2010
Creator: Kouzes, Richard T.; Ely, James H.; Erikson, Luke E.; Kernan, Warnick J.; Lintereur, Azaree T.; Siciliano, Edward R. et al.
Object Type: Report
System: The UNT Digital Library
A Survey of the U.S. ESCO Industry: Market Growth and Development from 2008 to 2011 (open access)

A Survey of the U.S. ESCO Industry: Market Growth and Development from 2008 to 2011

In this study, LBNL analyzes the current size of the Energy Service Company (ESCO) industry, industry growth projections to 2011, and market trends in order to provide policymakers with a more indepth understanding of energy efficiency activity among private sector firms. We draw heavily on information from interviews with ESCOs conducted from October 2009 to February 2010 and from our review of publicly available financial information regarding individual ESCOs. A significant ramp-up in energy efficiency activities is occurring at the local, state, and federal level. These activities include the establishment in {approx}18 states of statewide energy savings goals to be obtained from adoption of an Energy Efficiency Resource Standard (EERS), legislative or state regulatory directives to obtain all cost-effective demand-side resources (Barbose et al 2009), and a significant increase in federal funding for energy efficiency programs as part of the American Recovery and Reinvestment Act (ARRA). As part of this increased focus on energy efficiency, policymakers are evaluating the role of private sector companies, including ESCOs, in delivering cost-effective energy savings to end-users. The U.S. ESCO industry has long been recognized for its role in successfully delivering comprehensive energy projects in the public sector. This study analyzes the current size …
Date: June 8, 2010
Creator: Satchwell, Andrew; Goldman, Charles; Larsen, Peter; Gilligan, Donald & Singer, Terry
Object Type: Report
System: The UNT Digital Library
Recommended Changes to Specifications for Demand Controlled Ventilation in California's Title 24 Building Energy Efficiency Standards (open access)

Recommended Changes to Specifications for Demand Controlled Ventilation in California's Title 24 Building Energy Efficiency Standards

In demand-controlled ventilation (DCV), rates of outdoor air ventilation are automatically modulated as occupant density varies. The objective is to keep ventilation rates at or above design specifications and code requirements and also to save energy by avoiding excessive ventilation rates. DCV is most often used in spaces with highly variable and sometime dense occupancy. In almost all cases, carbon dioxide (CO{sub 2}) sensors installed in buildings provide the signal to the ventilation rate control system. People produce and exhale CO{sub 2} as a consequence of their normal metabolic processes; thus, the concentrations of CO{sub 2} inside occupied buildings are higher than the concentrations of CO{sub 2} in the outdoor air. The magnitude of the indoor-outdoor CO{sub 2} concentration difference decreases as the building's ventilation rate per person increases. The difference between the indoor and outdoor CO{sub 2} concentration is also a proxy for the indoor concentrations of other occupant-generated bioeffluents, such as body odors. Reviews of the research literature on DCV indicate a significant potential for energy savings, particularly in buildings or spaces with a high and variable occupancy. Based on modeling, cooling energy savings from applications of DCV are as high as 20%. With support from the California …
Date: April 8, 2010
Creator: Fisk, William J.; Sullivan, Douglas P. & Faulkner, David
Object Type: Report
System: The UNT Digital Library
RADBALL TECHNOLOGY TESTING IN THE SAVANNAH RIVER SITE HEALTH PHYSICS INSTRUMENT CALIBRATION LABORATORY (open access)

RADBALL TECHNOLOGY TESTING IN THE SAVANNAH RIVER SITE HEALTH PHYSICS INSTRUMENT CALIBRATION LABORATORY

The United Kingdom's National Nuclear Laboratory (NNL) has developed a radiation-mapping device that can locate and quantify radioactive hazards within contaminated areas of the nuclear industry. The device, known as RadBall{trademark}, consists of a colander-like outer collimator that houses a radiation-sensitive polymer sphere. The collimator has over two hundred small holes; thus, specific areas of the polymer sphere are exposed to radiation becoming increasingly more opaque in proportion to the absorbed dose. The polymer sphere is imaged in an optical-CT scanner that produces a high resolution 3D map of optical attenuation coefficients. Subsequent analysis of the optical attenuation data provides information on the spatial distribution of sources in a given area forming a 3D characterization of the area of interest. The RadBallTM technology has been deployed in a number of technology trials in nuclear waste reprocessing plants at Sellafield in the United Kingdom and facilities of the Savannah River National Laboratory (SRNL). This paper summarizes the tests completed at SRNL Health Physics Instrument Calibration Laboratory (HPICL).
Date: July 8, 2010
Creator: Farfan, E.
Object Type: Article
System: The UNT Digital Library
MCNPX Simulation Study of STRAW Neutron Detectors (open access)

MCNPX Simulation Study of STRAW Neutron Detectors

A novel prototype fission meter is being designed at National Security Technologies, LLC, using a thin uniform coating (only 1 micron thick) of {sup 10}B as a neutron converter inside a large array of thin (4 mm diameter) copper tubes. The copper tubes are only 2 mils thick, and each holds the stretched anode wire under tension and high voltage. The tubes are filled with proportional counter gas (a mixture of 90%/10% of Ar/CO{sub 2}). The tubes operate in proportional counter mode and attract mobile charged particles ({alpha}'s) created in the nuclear interaction {sup 10}B(n, {sup 4}He){sup 7}Li. However, a single tube has about 1/7th the sensitivity of a {sup 3}He tube. Modeling is required to determine if enough such tubes could be placed in a neutron detection assembly of the current size to give comparable sensitivity to {sup 3}He. Detectors lined with {sup 10}B lie between {sup 3}He and {sup 10}BF{sub 3} proportional counters and fission chambers in terms of neutron detection efficiency and gamma ray insensitivity. The mean free path of thermal neutrons in {sup 10}B is about 18 {micro}m. It takes about 60 {micro}m of {sup 10}B layer to completely stop thermal neutrons, but the energetic {alpha}-particles …
Date: January 8, 2010
Creator: Sanjoy Mukhopadhyay, Richard Maurer, Stephen Mitchell
Object Type: Article
System: The UNT Digital Library
CERTS Microgrid Laboratory Test Bed (open access)

CERTS Microgrid Laboratory Test Bed

The objective of the CERTS Microgrid Test Bed project was to enhance the ease of integrating energy sources into a microgrid. The project accomplished this objective by developing and demonstrating three advanced techniques, collectively referred to as the CERTS Microgrid concept, that significantly reduce the level of custom field engineering needed to operate microgrids consisting of generating sources less than 100kW. The techniques comprising the CERTS Microgrid concept are: 1 a method for effecting automatic and seamless transitions between grid-connected and islanded modes of operation, islanding the microgrid's load from a disturbance, thereby maintaining a higher level of service, without impacting the integrity of the utility's electrical power grid; 2 an approach to electrical protection within a limited source microgrid that does not depend on high fault currents; and 3 a method for microgrid control that achieves voltage and frequency stability under islanded conditions without requiring high-speed communications between sources.
Date: June 8, 2010
Creator: ETO, J.; LASSETER, R.; SCHENKMAN, B.; STEVENS, J.; KLAPP, D.; VOLKOMMER, H. et al.
Object Type: Article
System: The UNT Digital Library
Evidence for plasma phase transition in high pressure hydrogen from ab-initio simulations (open access)

Evidence for plasma phase transition in high pressure hydrogen from ab-initio simulations

We have performed a detailed study of molecular dissociation in liquid hydrogen using both Born-Oppenheimer molecular dynamics with Density Functional Theory and Coupled Electron-Ion Monte Carlo simulations. We observe a range of densities where (dP/d{rho}){sub T} = 0 that coincides with sharp discontinuities in the electronic conductivity, which is clear evidence of the plasma phase transition for temperatures 600K {le} T {le} 1500K. Both levels of theory exhibit the transition, although Quantum Monte Carlo predicts higher transition pressures. Based on the temperature dependence of the discontinuity in the electronic conductivity, we estimate the critical point of the transition at temperatures slightly below 2000 K. We examine the influence of proton zero point motion by using Path Integral Molecular Dynamics with Density Functional Theory; the main effect is to shift the transition to lower pressures. Furthermore, we calculate the melting curve of molecular hydrogen up to pressures of 200 GPa, finding a reentrant melting line in good agreement with previous calculations. The melting line crosses the metalization line at 700 K and 220 GPa using density functional energetics and at 550 K and 290 GPa using Quantum Monte Carlo energetics.
Date: February 8, 2010
Creator: Morales, M; Pierleoni, C; Schwegler, E & Ceperley, D
Object Type: Article
System: The UNT Digital Library
Radballtechnology Testing and MCNP Modeling of the Tungsten Collimator (open access)

Radballtechnology Testing and MCNP Modeling of the Tungsten Collimator

The United Kingdom's National Nuclear Laboratory (NNL) has developed a remote, non-electrical, radiation-mapping device known as RadBall{trademark}, which can locate and quantify radioactive hazards within contaminated areas of the nuclear industry. RadBall{trademark} consists of a colander-like outer shell that houses a radiation-sensitive polymer sphere. The outer shell works to collimate radiation sources and those areas of the polymer sphere that are exposed react, becoming increasingly more opaque, in proportion to the absorbed dose. The polymer sphere is imaged in an optical-CT scanner, which produces a high resolution 3D map of optical attenuation coefficients. Subsequent analysis of the optical attenuation matrix provides information on the spatial distribution of sources in a given area forming a 3D characterization of the area of interest. RadBall{trademark} has no power requirements and can be positioned in tight or hard-to reach locations. The RadBall{trademark} technology has been deployed in a number of technology trials in nuclear waste reprocessing plants at Sellafield in the United Kingdom and facilities of the Savannah River National Laboratory (SRNL). This study focuses on the RadBall{trademark} testing and modeling accomplished at SRNL.
Date: July 8, 2010
Creator: Farfan, E.
Object Type: Article
System: The UNT Digital Library
Novel Anionic Clay Adsorbents for Boiler-Blow-Down Waters Reclaim and Reuse (open access)

Novel Anionic Clay Adsorbents for Boiler-Blow-Down Waters Reclaim and Reuse

Arsenic (As) and Selenium (Se) are found in water in the form of oxyanions. Relatively high concentrations of As and Se have been reported both in power plant discharges, as well as, in fresh water supplies. The International Agency for Research on Cancer currently classifies As as a group 1 chemical, that is considered to be carcinogenic to humans. In Phase I of this project we studied the adsorption of As and Se by uncalcined and calcined layered double hydroxide (LDH). The focus of the present work is a systematic study of the adsorption of As and Se by conditioned LDH adsorbents. Conditioning the adsorbent significantly reduced the Mg and Al dissolution observed with uncalcined and calcined LDH. The adsorption rates and isotherms have been investigated in batch experiments using particles of four different particle size ranges. As(V) adsorption is shown to follow a Sips-type adsorption isotherm. The As(V) adsorption rate on conditioned LDH increases with decreasing adsorbent particle size; the adsorption capacity, on the other hand, is independent of the particle size. A homogeneous surface diffusion model (HSDM) and a bi-disperse pore model (BPM) - the latter viewing the LDH particles as assemblages of microparticles and taking into account …
Date: January 8, 2010
Creator: Sahimi, Muhammad & Tsotsis, Theodore
Object Type: Report
System: The UNT Digital Library
Strain induced electronic structure changes in magnetic transition metal oxides thin films (open access)

Strain induced electronic structure changes in magnetic transition metal oxides thin films

We show that the angular dependence of x-ray magnetic circular dichroism (XMCD) is strongly sensitive to strain-induced electronic structure changes in magnetic transition metal oxides. We observe a pronounced dependence of the XMCD spectral shape on the experimental geometry as well as nonvanishing XMCD with distinct spectral features in transverse geometry in compressively strained MnCr{sub 2}O{sub 4} films. The angular dependent XMCD can be described as a sum over an isotropic and anisotropic contribution, the latter linearly proportional to the axial distortion due to strain. The XMCD spectra are well reproduced by atomic multiplet calculations.
Date: July 8, 2010
Creator: van der Laan, G.; Chopdekar, R.V.; Suzuki, Y. & Arenholz, E.
Object Type: Article
System: The UNT Digital Library
Time-Temperature-Transformation  (TTT) Diagrams for Future Waste Compositions (open access)

Time-Temperature-Transformation (TTT) Diagrams for Future Waste Compositions

As a part of the Waste Acceptance Product Specifications (WAPS) for Vitrified High-Level Waste Forms defined by the Department of Energy - Office of Environmental Management, the waste form stability must be determined for each of the projected high-level waste (HLW) types at the Savannah River Site (SRS). Specifically, WAPS 1.4.1 requires the glass transition temperature (T{sub g}) to be defined and time-temperature-transformation (TTT) diagrams to be developed. The T{sub g} of a glass is an indicator of the approximate temperature where the supercooled liquid converts to a solid on cooling or conversely, where the solid begins to behave as a viscoelastic solid on heating. A TTT diagram identifies the crystalline phases that can form as a function of time and temperature for a given waste type or more specifically, the borosilicate glass waste form. In order to assess durability, the Product Consistency Test (PCT) was used and the durability results compared to the Environmental Assessment (EA) glass. The measurement of glass transition temperature and the development of TTT diagrams have already been performed for the seven Defense Waste Processing Facility (DWPF) projected compositions as defined in the Waste Form Compliance Plan (WCP) and in SRNL-STI-2009-00025. Additional phase transformation information …
Date: July 8, 2010
Creator: Billings, A. & Edwards, T.
Object Type: Report
System: The UNT Digital Library
Fermi level stabilization energy in cadmium oxide (open access)

Fermi level stabilization energy in cadmium oxide

We have studied the effects of high concentrations of native point defects on the electrical and optical properties of CdO. The defects were introduced by irradiation with high energy He+, Ne+, Ar+ and C+ ions. Increasing the irradiation damage with particles heavier than He+ increases the electron concentration until a saturation level of 5x1020 cm-3 is reached. In contrast, due to the ionic character and hence strong dynamic annealing of CdO, irradiation with much lighter He+ stabilizes the electron concentration at a much lower level of 1.7x1020 cm-3. A large shift of the optical absorption edge with increasing electron concentration in irradiated samples is explained by the Burstein-Moss shift corrected for electron-electron and electron-ion interactions. The saturation of the electron concentration and the optical absorption edge energy are consistent with a defect induced stabilization of the Fermi energy at 1 eV above the conduction band edge. The result is in a good agreement with previously determined Fermi level pinning energies on CdO surfaces. The results indicate that CdO shares many similarities with InN, as both materials exhibit extremely large electron affinities and an unprecedented propensity for n-type conductivity.
Date: April 8, 2010
Creator: Speaks, D. T.; Mayer, M. A.; Yu, K. M.; Mao, S. S.; Haller, E. E. & Walukiewicz, W.
Object Type: Article
System: The UNT Digital Library
National Atmospheric Release Advisory Center (NARAC) Capabilities for Homeland Security (open access)

National Atmospheric Release Advisory Center (NARAC) Capabilities for Homeland Security

The Department of Energy's National Atmospheric Release Advisory Center (NARAC) provides critical information during hazardous airborne releases as part of an integrated national preparedness and response strategy. Located at Lawrence Livermore National Laboratory, NARAC provides 24/7 tools and expert services to map the spread of hazardous material accidentally or intentionally released into the atmosphere. NARAC graphical products show affected areas and populations, potential casualties, and health effect or protective action guideline levels. LLNL experts produce quality-assured analyses based on field data to assist decision makers and responders. NARAC staff and collaborators conduct research and development into new science, tools, capabilities, and technologies in strategically important areas related to airborne transport and fate modeling and emergency response. This paper provides a brief overview of some of NARAC's activities, capabilities, and research and development.
Date: March 8, 2010
Creator: Sugiyama, G; Nasstrom, J; Baskett, R & Simpson, M
Object Type: Article
System: The UNT Digital Library
Development of an Atomic Force Microscope (open access)

Development of an Atomic Force Microscope

None
Date: February 8, 2010
Creator: Obrebski, J W; Buice, E S & Munnig Schmidt, R H
Object Type: Article
System: The UNT Digital Library
CERTS Microgrid Laboratory Test Bed (open access)

CERTS Microgrid Laboratory Test Bed

CERTS Microgrid concept captures the emerging potential of distributed generation using a system approach. CERTS views generation and associated loads as a subsystem or a 'microgrid'. The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system can disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. CERTS Microgrid concepts were demonstrated at a full-scale test bed built near Columbus, Ohio and operated by American Electric Power. The testing fully confirmed earlier research that had been conducted initially through analytical simulations, then through laboratory emulations, and finally through factory acceptance testing of individual microgrid components. The islanding and resynchronization method met all Institute of Electrical and Electronics Engineers Standard 1547 and power quality requirements. The electrical protection system was able to distinguish between normal and faulted operation. The controls were found to be robust under all conditions, including difficult motor starts and high impedance faults.
Date: June 8, 2010
Creator: Lasseter, R. H.; Eto, J. H.; Schenkman, B.; Stevens, J.; Volkmmer, H.; Klapp, D. et al.
Object Type: Article
System: The UNT Digital Library
Coupling Visualization and Data Analysis for Knowledge Discovery from Multi-dimensional Scientific Data (open access)

Coupling Visualization and Data Analysis for Knowledge Discovery from Multi-dimensional Scientific Data

Knowledge discovery from large and complex scientific data is a challenging task. With the ability to measure and simulate more processes at increasingly finer spatial and temporal scales, the growing number of data dimensions and data objects presents tremendous challenges for effective data analysis and data exploration methods and tools. The combination and close integration of methods from scientific visualization, information visualization, automated data analysis, and other enabling technologies"such as efficient data management" supports knowledge discovery from multi-dimensional scientific data. This paper surveys two distinct applications in developmental biology and accelerator physics, illustrating the effectiveness of the described approach.
Date: June 8, 2010
Creator: Rubel, Oliver; Ahern, Sean; Bethel, E. Wes; Biggin, Mark D.; Childs, Hank; Cormier-Michel, Estelle et al.
Object Type: Article
System: The UNT Digital Library
GLYCOLIC ACID PHYSICAL PROPERTIES, IMPURITIES, AND RADIATION EFFECTS ASSESSMENT (open access)

GLYCOLIC ACID PHYSICAL PROPERTIES, IMPURITIES, AND RADIATION EFFECTS ASSESSMENT

The DWPF is pursuing alternative reductants/flowsheets to increase attainment to meet closure commitment dates. In fiscal year 2009, SRNL evaluated several options and recommended the further assessment of the nitric/formic/glycolic acid flowsheet. SRNL is currently performing testing with this flowsheet to support the DWPF down-select of alternate reductants. As part of the evaluation, SRNL was requested to determine the physical properties of formic and glycolic acid blends. Blends of formic acid in glycolic acid were prepared and their physical properties tested. Increasing amounts of glycolic acid led to increases in blend density, viscosity and surface tension as compared to the 90 wt% formic acid that is currently used at DWPF. These increases are small, however, and are not expected to present any difficulties in terms of processing. The effect of sulfur impurities in technical grade glycolic acid was studied for its impact on DWPF glass quality. While the glycolic acid specification allows for more sulfate than the current formic acid specification, the ultimate impact is expected to be on the order of 0.03 wt% sulfur in glass. Note that lower sulfur content glycolic acid could likely be procured at some increased cost if deemed necessary. A paper study on the …
Date: June 8, 2010
Creator: Pickenheim, B. & Bibler, N.
Object Type: Report
System: The UNT Digital Library
Gasdynamic Model of Turbulent Combustion in TNT Explosions (open access)

Gasdynamic Model of Turbulent Combustion in TNT Explosions

A model is proposed to simulate turbulent combustion in confined TNT explosions. It is based on: (i) the multi-component gasdynamic conservation laws, (ii) a fast-chemistry model for TNT-air combustion, (iii) a thermodynamic model for frozen reactants and equilibrium products, (iv) a high-order Godunov scheme providing a non-diffusive solution of the governing equations, and (v) an ILES approach whereby adaptive mesh refinement is used to capture the energy bearing scales of the turbulence on the grid. Three-dimensional numerical simulations of explosion fields from 1.5-g PETN/TNT charges were performed. Explosions in six different chambers were studied: three calorimeters (volumes of 6.6-l, 21.2-l and 40.5-l with L/D = 1), and three tunnels (L/D = 3.8, 4.65 and 12.5 with volumes of 6.3-l) - to investigate the influence of chamber volume and geometry on the combustion process. Predicted pressures histories were quite similar to measured pressure histories for all cases studied. Experimentally, mass fraction of products, Y{sub p}{sup exp}, reached a peak value of 88% at an excess air ratio of twice stoichiometric, and then decayed with increasing air dilution; mass fractions Y{sub p}{sup calc} computed from the numerical simulations followed similar trends. Based on this agreement, we conclude that the dominant effect that …
Date: January 8, 2010
Creator: Kuhl, A L; Bell, J B & Beckner, V E
Object Type: Article
System: The UNT Digital Library
Final Scientific Report, New Proton Conductive Composite Materials for PEM Fuel Cells (open access)

Final Scientific Report, New Proton Conductive Composite Materials for PEM Fuel Cells

This project covered one of the main challenges in present-day PEM fuel cell technology: to design a membrane capable of maintaining high conductivity and mechanical integrity when temperature is elevated and water vapor pressure is severely reduced. The DOE conductivity milestone of 0.1 S cm-1 at 120 degrees C and 50 % relative humidity (RH) for designed membranes addressed the target for the project. Our approach presumed to develop a composite membrane with hydrophilic proton-conductive inorganic material and the proton conductive polymeric matrix that is able to “bridge” the conduction paths in the membrane. The unique aspect of our approach was the use of highly functionalized inorganic additives to benefit from their water retention properties and high conductivity as well. A promising result turns out that highly hydrophilic phosphorsilicate gels added in Nafion matrix improved PEM fuel cell performance by over 50% compared with bare Nafion membrane at 120 degrees C and 50 % RH. This achievement realizes that the fuel cell operating pressure can be kept low, which would make the PEM fuel cell much more cost efficient and adaptable to practical operating conditions and facilitate its faster commercialization particularly in automotive and stationary applications.
Date: November 8, 2010
Creator: Lvov, Serguei
Object Type: Report
System: The UNT Digital Library
Contained Modes In Mirrors With Sheared Rotation (open access)

Contained Modes In Mirrors With Sheared Rotation

In mirrors with E × B rotation, a fixed azimuthal perturbation in the lab frame can appear as a wave in the rotating frame. If the rotation frequency varies with radius, the plasma-frame wave frequency will also vary radially due to the Doppler shift. A wave that propagates in the high rotation plasma region might therefore be evanescent at the plasma edge. This can lead to radially localized Alfven eigenmodes with high azimuthal mode numbers. Contained Alfven modes are found both for peaked and non-peaked rotation profiles. These modes might be useful for alpha channeling or ion heating, as the high azimuthal wave number allows the plasma wave frequency in the rotating frame to exceed the ion cyclotron frequency. __________________________________________________
Date: October 8, 2010
Creator: Fetterman, Abraham J.
Object Type: Report
System: The UNT Digital Library