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2,397 Matching Results
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A Hypothetical Burning-Velocity Formula for Very Lean Hydrogen-Air Mixtures
Very lean hydrogen-air mixtures experience strong diffusive-thermal types of cellular instabilities that tend to increase the laminar burning velocity above the value that applies to steady, planar laminar flames that are homogeneous in transverse directions. Flame balls constitute an extreme limit of evolution of cellular flames. To account qualitatively for the ultimate effect of diffusive-thermal instability, a model is proposed in which the flame is a steadily propagating, planar, hexagonal, close-packed array of flame balls, each burning as if it were an isolated, stationary, ideal flame ball in an infinite, quiescent atmosphere. An expression for the laminar burning velocity is derived from this model, which theoretically may provide an upper limit for the experimental burning velocity.
Date:
June 30, 2008
Creator:
Williams, Forman; Williams, Forman A & Grcar, Joseph F
Object Type:
Article
System:
The UNT Digital Library
Identifying Fracture Types and Relative Ages Using Fluid Inclusion Stratigraphy
Enhanced Geothermal Systems (EGS) are designed to recover heat from the subsurface by mechanically creating fractures in subsurface rocks. Understanding the life cycle of a fracture in a geothermal system is fundamental to the development of techniques for creating fractures. Recognizing the stage of a fracture, whether it is currently open and transmitting fluids; if it recently has closed; or if it is an ancient fracture would assist in targeting areas for further fracture stimulation. Identifying dense fracture areas as well as large open fractures from small fracture systems will also assist in fracture stimulation selection. Geothermal systems are constantly generating fractures, and fluids and gases passing through rocks in these systems leave small fluid and gas samples trapped in healed microfractures. Fluid inclusions trapped in minerals as the fractures heal are characteristic of the fluids that formed them, and this signature can be seen in fluid inclusion gas analysis. Our hypothesis is that fractures over their life cycle have different chemical signatures that we can see in fluid inclusion gas analysis and by using the new method of fluid inclusion stratigraphy (FIS) the different stages of fractures, along with an estimate of fracture size can be identified during the …
Date:
June 30, 2008
Creator:
Dilley, Lorie M.; Norman, David & Owens, Lara
Object Type:
Report
System:
The UNT Digital Library
Imaging Reservoir Quality: Seismic Signatures of Geologic Processes
Lithofacies successions from diverse depositional environments show distinctive patterns in various rock-physics planes (velocity-porosity, velocity-density and porosity-clay). Four clear examples of decameter-scale lithofacies sequences are documented in this study: (1) Micocene fluvial deposits show an inverted-V pattern indicative of dispersed fabric, (2) a fining-upward sequence of mud-rich deep deposits shows a linear trend associated with laminated sand-clay mixtures, (3) sand-rich deposits show a pattern resulting from the scarcity of mixed lithofacies, and (4) a coarsening-upward sequence shows evidence of both dispersed and horizontally laminated mixed lithofacies, with predominating dispersed mixtures generated by bioturbation. It was observed that carbonate-cemented sandstones are extremely heterogeneous in the project deep-water study area. Those from the base of incisions are usually associated with lower shaliness, lower porosity and higher P-impedance, while from the top of flooding surfaces exhibit higher shaliness, higher porosity and lower P-impedance. One rock physics model that captures the observed impedance-porosity trend is the 'stiff-sand model'. For this model, the high-porosity end-member is unconsolidated sand whose initial porosity is a function of sorting and shaliness, while the low-porosity end-member is solid mineral. These two end points are joined with a Hashin-Shtrikman equation. A systematic variation of quartz:clay ratio from proximal to distal …
Date:
June 30, 2008
Creator:
Stanford University. Department of Geophysics.
Object Type:
Report
System:
The UNT Digital Library
Improved Membrane Materials for PEM Fuel Cell Application
The overall goal of this project is to collect and integrate critical structure/property information in order to develop methods that lead to significant improvements in the durability and performance of polymer electrolyte membrane fuel cell (PEMFC) materials. This project is focused on the fundamental improvement of PEMFC membrane materials with respect to chemical, mechanical and morphological durability as well as the development of new inorganically-modified membranes.
Date:
June 30, 2008
Creator:
Mauritz, Kenneth A. & Moore, Robert B.
Object Type:
Report
System:
The UNT Digital Library
Improved Neutron Scintillators Based on Nanomaterials
The development work conducted in this SBIR has so far not supported the premise that using nano-particles in LiFZnS:Ag foils improves their transparency to 420 (or other frequency) light. This conclusion is based solely on the light absorption properties of LiFZnS foils fabricated from nano- and from micro-particles. Furthermore, even for the case of the Gd{sub 2}O{sub 3} foils, the transmission of 420 nm light gained by using nano-particles all but disappears as the foil thickness is increased beyond about 0.2 mm, a practical scintillator thickness. This was not immediately apparent from the preliminary study since no foils thicker than about 0.04 mm were produced. Initially it was believed that the failure to see an improvement by using nano-particles for the LiFZnS foils was caused by the clumping of the particles in Toluene due to the polarity of the ZnS particles. However, we found, much to our surprise, that nano-particle ZnS alone in polystyrene, and in Epoxy, had worse light transmission properties than the micro-particle foils for equivalent thickness and density foils. The neutron detection measurements, while disappointing, are attributable to our inability to procure or fabricate Bulk Doped ZnS nanoparticles. The cause for the failure of nano-particles to improve …
Date:
June 30, 2008
Creator:
Dennis Friesel, PhD
Object Type:
Report
System:
The UNT Digital Library
Innovative Seals for Solid Oxide Fuel Cells (SOFC)
A functioning SOFC requires different type of seals such as metal-metal, metal-ceramic, and ceramic-ceramic. These seals must function at high temperatures between 600--900{sup o}C and in oxidizing and reducing environments of the fuels and air. Among the different type of seals, the metal-metal seals can be readily fabricated using metal joining, soldering, and brazing techniques. However, the metal-ceramic and ceramic-ceramic seals require significant research and development because the brittle nature of ceramics/glasses can lead to fracture and loss of seal integrity and functionality. Consequently, any seals involving ceramics/glasses require a significant attention and technology development for reliable SOFC operation. This final report is prepared to describe the progress made in the program on the needs, approaches, and performance of high temperature seals for SOFC. In particular, a new concept of self-healing glass seals is pursued for making seals between metal-ceramic material combinations, including some with a significant expansion mismatch.
Date:
June 30, 2008
Creator:
Singh, Raj
Object Type:
Report
System:
The UNT Digital Library
Intermediate Temperature Solid Oxide Fuel Cell Development
Solid oxide fuel cells (SOFCs) are high efficiency energy conversion devices. Present materials set, using yttria stabilized zirconia (YSZ) electrolyte, limit the cell operating temperatures to 800 C or higher. It has become increasingly evident however that lowering the operating temperature would provide a more expeditious route to commercialization. The advantages of intermediate temperature (600 to 800 C) operation are related to both economic and materials issues. Lower operating temperature allows the use of low cost materials for the balance of plant and limits degradation arising from materials interactions. When the SOFC operating temperature is in the range of 600 to 700 C, it is also possible to partially reform hydrocarbon fuels within the stack providing additional system cost savings by reducing the air preheat heat-exchanger and blower size. The promise of Sr and Mg doped lanthanum gallate (LSGM) electrolyte materials, based on their high ionic conductivity and oxygen transference number at the intermediate temperature is well recognized. The focus of the present project was two-fold: (a) Identify a cell fabrication technique to achieve the benefits of lanthanum gallate material, and (b) Investigate alternative cathode materials that demonstrate low cathode polarization losses at the intermediate temperature. A porous matrix supported, …
Date:
June 30, 2008
Creator:
Elangovan, S.; Barnett, Scott & Haile, Sossina
Object Type:
Report
System:
The UNT Digital Library
Intermixing and chemical structure at the interface between n-GaN and V-based contacts
The interface between n-type GaN and V-based contacts was characterized by soft x-ray spectroscopy. We have investigated the chemical interface structure before and after a rapid thermal annealing (RTA) step, which is crucial for the formation of an Ohmic contact. X-ray photoelectron and x-ray excited Auger electron spectra suggestthat RTA induces an accumulation of metallic Ga at the surface. Using x-ray emission spectroscopy, we find that the probed nitrogen atoms are in a VN-like environment, indicating that vanadium interacts with nitrogen atoms from the GaN to form VN.
Date:
June 30, 2008
Creator:
Pookpanratana, S.; France, R.; Bar, M.; Weinhardt, L.; Fuchs, O.; Blum, M. et al.
Object Type:
Article
System:
The UNT Digital Library
Investigation of Pressurized Entrained-Flow Kraft Black Liquor Gasification in an Industrially Relevant Environment
The University of Utah's project 'Investigation of Pressurized Entrained-Flow Kraft Black Liquor Gasification in an Industrially Relevant Environment' (U.S. DOE Cooperative Agreement DE-FC26-04NT42261) was a response to U.S. DOE/NETL solicitation DE-PS36-04GO94002, 'Biomass Research and Development Initiative' Topical Area 4-Kraft Black Liquor Gasification. The project began September 30, 2004. The objective of the project was to improve the understanding of black liquor conversion in high pressure, high temperature reactors that gasify liquor through partial oxidation with either air or oxygen. The physical and chemical characteristics of both the gas and condensed phase were to be studied over the entire range of liquor conversion, and the rates and mechanisms of processes responsible for converting the liquor to its final smelt and syngas products were to be investigated. This would be accomplished by combining fundamental, lab-scale experiments with measurements taken using a new semi-pilot scale pressurized entrained-flow gasifier. As a result of insufficient availability of funds and changes in priority within the Office of Biomass Programs of the U.S. Department of Energy, the research program was terminated in its second year. In total, only half of the budgeted funding was made available for the program, and most of this was used during the …
Date:
June 30, 2008
Creator:
Whitty, Kevin
Object Type:
Report
System:
The UNT Digital Library
Legal Challenge to the FCC’s Media Ownership Rules: An Overview of Prometheus Radio v. FCC
This report provides an overview of the Commission's 2002 Biennial Review from which the 2003 rules originated and the Prometheus case.
Date:
June 30, 2008
Creator:
Ruane, Kathleen Ann
Object Type:
Report
System:
The UNT Digital Library
Livestock Feed Costs: Concerns and Options
Sharply higher feed costs, fueled by competing use demands for corn and soybeans and by rising energy prices, are affecting the beef, pork, dairy, and poultry industries. In contrast, wholesales prices for most animal products have held steady. Some analysts argue that current public policies, including financial incentives that divert corn from feed uses into ethanol production, have exacerbated if not caused these higher costs. Other factors include crop production declines due to weather, and higher global demand for consumption. Proposed options aimed at easing the impacts of higher feed costs include changes in ethanol incentives, use of conservation land for forage use, and direct aid to producers.
Date:
June 30, 2008
Creator:
Becker, Geoffrey S.
Object Type:
Report
System:
The UNT Digital Library
Long-Term Care Insurance: Oversight of Rate Setting and Claims Settlement Practices
A letter report issued by the Government Accountability Office with an abstract that begins "As the baby boom generation ages, the demand for long-term care services, which include nursing home care, is likely to grow and could strain state and federal resources. The increased use of long-term care insurance (LTCI) may be a way of reducing the share of long-term care paid by state and federal governments. Oversight of LTCI is primarily the responsibility of states, but over the past 12 years, there have been federal efforts to increase the use of LTCI while also ensuring that consumers purchasing LTCI are adequately protected. Despite this oversight, concerns have been raised about both premium increases and denials of claims that may leave consumers without LTCI coverage when they begin needing care. GAO was asked to review the consumer protection standards governing LTCI policies and how those standards are being enforced. Specifically, GAO examined oversight of the LTCI industry's (1) rate setting practices and (2) claims settlement practices. GAO reviewed information from the National Association of Insurance Commissioners (NAIC) on all states' rate setting standards. GAO also completed 10 state case studies on oversight of rate setting and claims settlement practices, which …
Date:
June 30, 2008
Creator:
United States. Government Accountability Office.
Object Type:
Report
System:
The UNT Digital Library
Microhole Coiled Tubing Bottom Hole Assemblies
The original objective of the project, to deliver an integrated 3 1/8-inch diameter Measurement While Drilling (MWD) and Logging While Drilling (LWD) system for drilling small boreholes using coiled tubing drilling, has been achieved. Two prototype systems have been assembled and tested in the lab. One of the systems has been successfully tested downhole in a conventional rotary drilling environment. Development of the 3 1/8-inch system has also lead to development and commercialization of a slightly larger 3.5-inch diameter system. We are presently filling customer orders for the 3.5-inch system while continuing with commercialization of the 3 1/8-inch system. The equipment developed by this project will be offered for sale to multiple service providers around the world, enabling the more rapid expansion of both coiled tubing drilling and conventional small diameter drilling. The project was based on the reuse of existing technology whenever possible in order to minimize development costs, time, and risks. The project was begun initially by Ultima Labs, at the time a small company ({approx}12 employees) which had successfully developed a number of products for larger oil well service companies. In September, 2006, approximately 20 months after inception of the project, Ultima Labs was acquired by Sondex …
Date:
June 30, 2008
Creator:
Macune, Don
Object Type:
Report
System:
The UNT Digital Library
A Modular Building Controls Virtual Test Bed for the Integrations of Heterogeneous Systems
This paper describes the Building Controls Virtual Test Bed (BCVTB) that is currently under development at Lawrence Berkeley National Laboratory. An earlier prototype linked EnergyPlus with controls hardware through embedded SPARK models and demonstrated its value in more cost-effective envelope design and improved controls sequences for the San Francisco Federal Building. The BCVTB presented here is a more modular design based on a middleware that we built using Ptolemy II, a modular software environment for design and analysis of heterogeneous systems. Ptolemy II provides a graphical model building environment, synchronizes the exchanged data and visualizes the system evolution during run-time. Our additions to Ptolemy II allow users to couple to Ptolemy II a prototype version of EnergyPlus,MATLAB/Simulink or other simulation programs for data exchange during run-time. In future work we will also implement a BACnet interface that allows coupling BACnet compliant building automation systems to Ptolemy II. We will present the architecture of the BCVTB and explain how users can add their own simulation programs to the BCVTB. We will then present an example application in which the building envelope and the HVAC system was simulated in EnergyPlus, the supervisory control logic was simulated in MATLAB/Simulink and Ptolemy II was …
Date:
June 30, 2008
Creator:
Wetter, Michael; Wetter, Michael & Haves, Philip
Object Type:
Article
System:
The UNT Digital Library
Nanotechnology: Small Matters
The primary objective of this project was to engage members of the public in an active and balanced deliberative discussion about the social, ethical, legal, environmental, and policy issues arising from nanotechnologies. A second but equally important objective was to interest members of the public in learning more about science and technology and nanotechnology specifically by understanding how it will affect their lives. The objectives were met through a series of electronic and face-to-face citizen forums conducted in conjunction with three Fred Friendly Seminars being taped on the University of California, Berkeley campus in partnership with Lawrence Hall of Science (this forum was conducted in partnership with the St. Louis Science Center); the Boston Museum of Science in Boston, MA; and the State Museum of South Carolina in Columbia, South Carolina. The topical area for each forum paralleled the content of the Fred Friendly Seminars series being taped at each location, but specific topics/issues were drawn from the concerns and interests of the communities. The three topical areas included Environmental Impact (St. Louis), Privacy vs. Security (Boston), and Health and Enhancement (Columbia). The PI and project leader worked with the local science centers to identify stakeholder groups, such as academic, …
Date:
June 30, 2008
Creator:
Needham, Cynthia
Object Type:
Text
System:
The UNT Digital Library
The National Bio- and Agro-Defense Facility: Issues for Congress
This report outlines current progress towards establishment of the National Bio- and Agro-Defense Facility (NBAF), presents current and projected funding levels and timelines, and describes policy issues of potential interest to Congress, such as agency coordination, possession of viruses, construction timelines, disposition of PIADC, and community safety concerns.
Date:
June 30, 2008
Creator:
Shea, Dana A.; Monke, Jim & Gottron, Frank
Object Type:
Report
System:
The UNT Digital Library
A New Type of Steady and Stable, Laminar, Premixed Flame in Ultra-Lean, Hydrogen-Air Combustion
Ultra-lean, hydrogen-air mixtures are found to support another kind of laminar flame that is steady and stable beside flat flames and flame balls. Direct numerical simulations are performed of flames that develop into steadily and stably propagating cells. These cells were the original meaning of the word"flamelet'' when they were observed in lean flammability studies conducted early in the development of combustion science. Several aspects of these two-dimensional flame cells are identified and are contrasted with the properties of one-dimensional flame balls and flat flames. Although lean hydrogen-air flames are subject to thermo-diffusive effects, in this case the result is to stabilize the flame rather than to render it unstable. The flame cells may be useful as basic components of engineering models for premixed combustion when the other types of idealized flames are inapplicable.
Date:
June 30, 2008
Creator:
Grcar, Joseph F. & Grcar, Joseph F
Object Type:
Article
System:
The UNT Digital Library
NEXT GENERATION NEUTRON SCINTILLATORS BASED ON SEMICONDUCTOR NANOSTRUCTURES
The results reported here successfully demonstrate the technical feasibility of ZnS QDs/{sup 6}LiF/polymer composites as thermal neutron scintillators. PartTec has obtained stable ZnS QDs with a quantum yield of 17% induced by UV light, and light pulse decay lifetimes of 10-30 ns induced by both UV and neutrons. These lifetime values are much shorter than those of commercial ZnS microparticle and {sup 6}Li-glass scintillators. Clear pulse height peaks induced by neutron irradiation were seen for PartTec's ZnS nanocomposites. By adjusting the concentrations, particle size and degree of dispersion of ZnS QD/{sup 6}LiF in a PVA matrix, the light absorption and light yield of films at 420-440 nm can be optimized. PartTec's novel scintillators will replace traditional {sup 6}Li-glass and ZnS/{sup 6}LiF:Ag scintillators if the PL quantum yield can be improved above 30%, and/or increase the transparency of present nanoscintillators. Time and resources inhibited PartTec's total success in Phase I. For example, bulk doping preparations of ZnS QDs with Ag{sup +}, Eu{sup 3+} or Ce{sup 3+} QDs was impractical given those constraints, nor did they permit PartTec to measure systematically the change of PL decay lifetimes in different samples. PartTec will pursue these studies in the current proposal, as well as …
Date:
June 30, 2008
Creator:
Wang, Cai-Lin
Object Type:
Report
System:
The UNT Digital Library
Nuclear Reactor Power Monitoring Using Silicon Carbide Semiconductor Radiation Detectors
Define Generation IV Reactor Power Monitoring Requirements.
Date:
June 30, 2008
Creator:
Blue, Thomas & Miller, Don
Object Type:
Report
System:
The UNT Digital Library
Nuclear Safety: NRC's Oversight of Fire Protection at U.S. Commercial Nuclear Reactor Units Could Be Strengthened
A letter report issued by the Government Accountability Office with an abstract that begins "After a 1975 fire at the Browns Ferry nuclear plant in Alabama threatened the unit's ability to shut down safely, the Nuclear Regulatory Commission (NRC) issued prescriptive fire safety rules for commercial nuclear units. However, nuclear units with different designs and different ages have had difficulty meeting these rules and have sought exemptions to them. In 2004, NRC began to encourage the nation's 104 nuclear units to transition to a less prescriptive, risk-informed approach that will analyze the fire risks of individual nuclear units. GAO was asked to examine (1) the number and causes of fire incidents at nuclear units since 1995, (2) compliance with NRC fire safety regulations, and (3) the transition to the new approach. GAO visited 10 of the 65 nuclear sites nationwide, reviewed NRC reports and related documentation about fire events at nuclear units, and interviewed NRC and industry officials to examine compliance with existing fire protection rules and the transition to the new approach."
Date:
June 30, 2008
Creator:
United States. Government Accountability Office.
Object Type:
Report
System:
The UNT Digital Library
Nuclear Waste: DOE Lacks Critical Information Needed to Assess Its Tank Management Strategy at Hanford
A letter report issued by the Government Accountability Office with an abstract that begins "The Department of Energy (DOE) manages more than 56 million gallons of radioactive and hazardous waste stored in 149 single-shell and 28 double-shell underground tanks at its Hanford Site in Washington State. Many of these aging tanks have already leaked waste into the soil. Meanwhile, DOE's planned process for emptying the tanks and treating the waste--mixing it with molten glass and solidifying it in canisters for storage--has experienced delays, lengthening the time the tanks will store waste and intensifying concerns about the tanks' viability during a long cleanup process. This report addresses (1) the condition, contents, and long-term viability of Hanford's underground tanks; (2) DOE's strategy for managing the tanks; and (3) the extent to which DOE has weighed the risks and benefits of its tank management strategy against the growing costs of that strategy. GAO analyzed numerous studies and reports on the tanks and interviewed DOE officials and other experts on relevant issues."
Date:
June 30, 2008
Creator:
United States. Government Accountability Office.
Object Type:
Report
System:
The UNT Digital Library
Operations Plan for Support Network Development
This report describes the operational processes and strategies that are building a support network for the National Security Technology Incubator (NSTI) program. The NSTI program currently is under development as part of the National Security Preparedness Project (NSPP), funded by Department of Energy (DOE)/National Nuclear Security Administration (NNSA) Grant No. DE FG52-07NA28084. Although the NSTI program offers a wide array of in-house business services, there are a certain number of services that will be provided by entities outside of Arrowhead Center. This report identifies the steps needed to develop an appropriate support network. The Arrowhead Center is working with external service providers and key stakeholders to establish feasible referral and implementation mechanics offering NSTI program participants the most comprehensive incubation services possible.
Date:
June 30, 2008
Creator:
unknown
Object Type:
Text
System:
The UNT Digital Library
PKU-RBRC Workshop on Transverse Spin
Understanding the structure of the nucleon is a fundamental question in subatomic physics, and it has been under intensive investigation for the last several years. Modern research focuses in particular on the spin structure of the nucleon. Experimental and theoretical investigations worldwide over the last few decades have established that, contrary to nave quark model expectations, quarks carry only about 30% of the totd spin of the proton. The origin of the remaining spin is the key question in current hadronic physics and also the major driving forces for the current and future experiments, such as RHIC and CEBAF in US, JPARC in Japan, COMPASS at CERN in Europe, FAIR at GSI in Germany. Among these studies, the transverse-spin physics develops actively and rapidly in the last few years. Recent studies reveal that transverse-spin physics is closely related to many fundamental properties of the QCD dynamics such as the factorization, the non-trivial universality of the parton distribution and fragmentation functions. It was very timely to bring together the theorists and experimentalists in this field at this workshop to review and discuss the latest developments and future perspective in hadronic spin physics. This workshop was very success iu many aspects. First …
Date:
June 30, 2008
Creator:
Avakian,H.; Bunce, G. & Yuan, F.
Object Type:
Article
System:
The UNT Digital Library
Prediction of atmospheric δ13CO2 using fossil plant tissues. Reviews of Geophysics, 46/2006RG0002.(view/download pdf)
To summarize the content: we presented the results of laboratory experiments designed to quantify the relationship between plant tissue δ13C and δ13CO2 values under varying environmental conditions, including differential pCO2 ranging from 1 to 3 times today’s levels. As predicted, plants grown under elevated pCO2 showed increased average biomass compared to controls grown at the same temperature. Across a very large range in δ13Ca (≈ 24 ‰) and pCO2 (≈ 740 ppmv) we observed a consistent correlation between δ13Ca and δ13Cp (p<0.001). We show an average isotopic depletion of −25.4 ‰ for above-ground tissue and −23.2 ‰ for below-ground tissue of Raphanus sativus L. relative to the composition of the atmosphere under which it formed. For both above- and below-ground tissue, grown at both ~23 ˚C and ~29 ˚C, correlation was strong and significant (r2 ≥ 0.98, p<0.001); variation in pCO2 level had little or no effect on this relationship.
Date:
June 30, 2008
Creator:
A.H. Jahren, N.C. Arens and S.A. Harbeson
Object Type:
Report
System:
The UNT Digital Library