Solution to Problem 11275 (open access)

Solution to Problem 11275

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Date: February 28, 2007
Creator: Bailey, David H. & Borwein, Jonathan M.
System: The UNT Digital Library
Subtask 3.12 - Oxygen-Fired CFBC (open access)

Subtask 3.12 - Oxygen-Fired CFBC

Traditionally, air is used as the source of oxygen for firing a combustion system. A fully oxygen-fired circulating fluidized-bed combustion (CFBC) system would result in the production of a flue gas stream consisting of mostly carbon dioxide and water. The concentrated carbon dioxide stream would be available for sequestering or other purposes. Temperatures in an oxygen-blown CFBC system would be controlled by a combination of flue gas recycle, solids recirculation, and by appropriately sizing and locating the amount of heat-transfer surface required. Flue gas recycle provides the additional gas required for adequate fluidization and circulation of solids replacing the nitrogen that would be present in an air-blown system. The amount of flue gas recycle will determine how much of the remaining heat from the coal combustion will have to be removed. If the amount of flue gas recycle required by increasing solids recirculation and oxygen staging is limited, introducing the pure oxygen at multiple locations in the combustor to result in a more even temperature profile should result in a more compact system, thus reducing initial capital costs for construction. The overall efficiency of the process should be greater than that of an air-blown system since less fuel is required …
Date: February 28, 2007
Creator: Hajicek, Douglas; Musich, Mark & Henderson, Ann
System: The UNT Digital Library
Evaluation of Juvenile Salmonid Outmigration and Survival in the Lower Umatilla River Basin, Annual Report 2003-2006. (open access)

Evaluation of Juvenile Salmonid Outmigration and Survival in the Lower Umatilla River Basin, Annual Report 2003-2006.

This report summarizes activities conducted by the Oregon Department of Fish and Wildlife's Juvenile Outmigration and Survival M&E project in the Umatilla River subbasin between 2004-2006. Information is used to make informed decisions on hatchery effectiveness, natural production success, passage improvement and flow enhancement strategies. Data collected includes annual estimates of smolt abundance, migration timing, and survival, life history characteristics and productivity status and trends for spring and fall Chinook salmon, coho salmon and summer steelhead. Productivity data provided is the key subbasin scale measure of the effectiveness of salmon and steelhead restoration actions in the Umatilla River. Information is also used for regional planning and recovery efforts of Mid-Columbia River (MCR) ESA-listed summer steelhead. Monitoring is conducted via smolt trapping and PIT-tag interrogation at Three Mile Falls Dam. The Umatilla Juvenile Outmigration and Survival Project was established in 1994 to evaluate the success of management actions and fisheries restoration efforts in the Umatilla River Basin. Project objectives for the 2004-2006 period were to: (1) operate the PIT tag detection system at Three Mile Falls Dam (TMFD), (2) enhance provisional PIT-tag interrogation equipment at the east bank adult fish ladder, (3) monitor the migration timing, abundance and survival of naturally-produced …
Date: February 1, 2007
Creator: White, Tara
System: The UNT Digital Library
Arrow Lakes Reservoir Fertilization Experiment, Technical Report 1999-2004. (open access)

Arrow Lakes Reservoir Fertilization Experiment, Technical Report 1999-2004.

The Arrow Lakes food web has been influenced by several anthropogenic stressors during the past 45 years. These include the introduction of mysid shrimp (Mysis relicta) in 1968 and 1974 and the construction of large hydroelectric impoundments in 1969, 1973 and 1983. The construction of the impoundments affected the fish stocks in Upper and Lower Arrow lakes in several ways. The construction of Hugh Keenleyside Dam (1969) resulted in flooding that eliminated an estimated 30% of the available kokanee spawning habitat in Lower Arrow tributaries and at least 20% of spawning habitat in Upper Arrow tributaries. The Mica Dam (1973) contributed to water level fluctuations and blocked upstream migration of all fish species including kokanee. The Revelstoke Dam (1983) flooded 150 km of the mainstem Columbia River and 80 km of tributary streams which were used by kokanee, bull trout, rainbow trout and other species. The construction of upstream dams also resulted in nutrient retention which ultimately reduced reservoir productivity. In Arrow Lakes Reservoir (ALR), nutrients settled out in the Revelstoke and Mica reservoirs, resulting in decreased productivity, a process known as oligotrophication. Kokanee are typically the first species to respond to oligotrophication resulting from aging impoundments. To address the …
Date: February 1, 2007
Creator: Schindler, E.
System: The UNT Digital Library
HANFORD DST THERMAL & SEISMIC PROJECT DYTRAN ANALYSIS OF SEISMICALLY INDUCED FLUID STRUCTURE INTERACTION IN A HANFORD DOUBLE SHELL PRIMARY TANK (open access)

HANFORD DST THERMAL & SEISMIC PROJECT DYTRAN ANALYSIS OF SEISMICALLY INDUCED FLUID STRUCTURE INTERACTION IN A HANFORD DOUBLE SHELL PRIMARY TANK

Revision 0A of this document contains new Appendices C and D. Appendix C contains a re-analysis of the rigid and flexible tanks at the 460 in. liquid level and was motivated by recommendations from a Project Review held on March 20-21, 2006 (Rinker et al Appendix E of RPP-RPT-28968 Rev 1). Appendix D contains the benchmark solutions in support of the analyses in Appendix C.
Date: February 14, 2007
Creator: Mackey, T. C.; Rinker, M. W. & Abatt, F. G.
System: The UNT Digital Library
HANFORD DOUBLE SHELL TANK (DST) THERMAL & SEISMIC PROJECT INCREASED LIQUID LEVEL ANALYSIS FOR 241-AP TANK FARMS (open access)

HANFORD DOUBLE SHELL TANK (DST) THERMAL & SEISMIC PROJECT INCREASED LIQUID LEVEL ANALYSIS FOR 241-AP TANK FARMS

The overall scope of the project is to complete an up-to-date comprehensive analysis of record of the SDT System at Hanford. The "Double-Shell Tank (DST) Integrity Project - DST Thermal and Seismic Project" is in support of Tri-Party Agreement Milestone M-48-14.
Date: February 16, 2007
Creator: Mackey, T. C.; Deibler, J. E.; Johnson, K. I.; Pilli, S. P.; Karri, N. K.; Rinker, M. W. et al.
System: The UNT Digital Library
Arrow Lakes Reservoir Fertilization Experiment; Years 4 and 5, Technical Report 2002-2003. (open access)

Arrow Lakes Reservoir Fertilization Experiment; Years 4 and 5, Technical Report 2002-2003.

This report presents the fourth and fifth year (2002 and 2003, respectively) of a five-year fertilization experiment on the Arrow Lakes Reservoir. The goal of the experiment was to increase kokanee populations impacted from hydroelectric development on the Arrow Lakes Reservoir. The impacts resulted in declining stocks of kokanee, a native land-locked sockeye salmon (Oncorhynchus nerka), a key species of the ecosystem. Arrow Lakes Reservoir, located in southeastern British Columbia, has undergone experimental fertilization since 1999. It is modeled after the successful Kootenay Lake fertilization experiment. The amount of fertilizer added in 2002 and 2003 was similar to the previous three years. Phosphorus loading from fertilizer was 52.8 metric tons and nitrogen loading from fertilizer was 268 metric tons. As in previous years, fertilizer additions occurred between the end of April and the beginning of September. Surface temperatures were generally warmer in 2003 than in 2002 in the Arrow Lakes Reservoir from May to September. Local tributary flows to Arrow Lakes Reservoir in 2002 and 2003 were generally less than average, however not as low as had occurred in 2001. Water chemistry parameters in select rivers and streams were similar to previous years results, except for dissolved inorganic nitrogen (DIN) …
Date: February 1, 2007
Creator: Schindler, E.
System: The UNT Digital Library
ACRF Instrumentation Status: New, Current, and Future February 2007 (open access)

ACRF Instrumentation Status: New, Current, and Future February 2007

The purpose of this report is to provide a concise but comprehensive overview of Atmospheric Radiation Measurement Program Climate Research Facility instrumentation status. The report is divided into four sections: (1) new instrumentation in the process of being acquired and deployed, (2) existing instrumentation and progress on improvements or upgrades, (3) proposed future instrumentation, and (4) Small Business Innovation Research instrument development
Date: February 1, 2007
Creator: Liljegren, J. C.
System: The UNT Digital Library
The RadAssessor manual (open access)

The RadAssessor manual

THIS manual will describe the functions and capabilities that are available from the RadAssessor database and will demonstrate how to retrieve and view its information. You’ll learn how to start the database application, how to log in, how to use the common commands, and how to use the online help if you have a question or need extra guidance. RadAssessor can be viewed from any standard web browser. Therefore, you will not need to install any special software before using RadAssessor.
Date: February 1, 2007
Creator: Seitz, Sharon L.
System: The UNT Digital Library
Nanostructured Catalyst Systems for Fuel Cells: Synthesis and Characterization of Low Platinum Content Electrocatalysts for O{sub 2} Reduction (open access)

Nanostructured Catalyst Systems for Fuel Cells: Synthesis and Characterization of Low Platinum Content Electrocatalysts for O{sub 2} Reduction

The objective of this project is to synthesize and characterize new O{sub 2} reduction catalysts with enhanced activity and ultra low Pt loading, and to test them in membrane electrode assemblies (MEAs) to determine their performance under fuel cell cathode operating conditions.
Date: February 1, 2007
Creator: Adzic, Radoslav
System: The UNT Digital Library
Monitoring and Evaluation; Statistical Support for Life-cycle Studies, Annual Report 2006. (open access)

Monitoring and Evaluation; Statistical Support for Life-cycle Studies, Annual Report 2006.

This report summarizes the statistical analysis and consulting activities performed under Contract No. 00025093, Project No. 199105100, funded by Bonneville Power Administration (BPA) during 2006. These efforts are focused on providing real-time predictions of outmigration timing, assessment of life-history performance measures, evaluation of status and trends in recovery, and guidance on the design and analysis of Columbia Basin fish and wildlife studies monitoring and evaluation studies. The overall objective of the project is to provide BPA and the rest of the fisheries community with statistical guidance on design, analysis, and interpretation of monitoring data, which will lead to improved monitoring and evaluation of salmonid mitigation programs in the Columbia/Snake River Basin. This overall goal is being accomplished by making fisheries data readily available for public scrutiny, providing statistical guidance on the design and analyses of studies by hands-on support and written documents, and providing real-time analyses of tagging results during the smolt outmigration for review by decision makers. For over a decade, this project has been providing in-season projections of smolt outmigration timing to assist in spill management. As many as 52 different fish stocks at 10 different hydroprojects are tracked in real-time to predict the 'percent of run to …
Date: February 1, 2007
Creator: Skalski, John
System: The UNT Digital Library
Kootenay Lake Fertilization Experiment; Years 11 and 12, Technical Report 2002-2003. (open access)

Kootenay Lake Fertilization Experiment; Years 11 and 12, Technical Report 2002-2003.

This report examines the results from the eleventh and twelfth years (2002 and 2003) of the Kootenay Lake fertilization experiment. Experimental fertilization has occurred with an adaptive management approach since 1992 in order to restore productivity lost as a result of upstream dams. One of the main objectives of the experiment is to restore kokanee (Oncorhynchus nerka) populations, which are a main food source for Gerrard rainbow trout (Oncorhynchus mykiss). Kootenay Lake is located between the Selkirk and Purcell mountains in southeastern British Columbia. It has an area of 395 km2, a maximum depth of 150 m, a mean depth of 94 m, and a water renewal time of approximately two years. The quantity of agricultural grade liquid fertilizer (10-34-0, ammonium polyphosphate and 28-0-0, urea ammonium nitrate) added to Kootenay Lake in 2002 and 2003 was similar to that added from 1992 to 1996. After four years of decreased fertilizer loading (1997 to 2000), results indicated that kokanee populations had declined, and the decision was made to increase the loads again in 2001. The total load of fertilizer in 2002 was 47.1 tonnes of phosphorus and 206.7 tonnes of nitrogen. The total fertilizer load in 2003 was 47.1 tonnes of …
Date: February 1, 2007
Creator: Schindler, E.
System: The UNT Digital Library
Final Report for DOE Support of 5th the International Workshop on Oxide Surfaces (IWOX-V) (open access)

Final Report for DOE Support of 5th the International Workshop on Oxide Surfaces (IWOX-V)

The 5th International Workshop on Oxide Surfaces (IWOX-V) was held at Granlibakken Conference center in Lake Tahoe, CA, January 7-12. The total attendance was ~90. The breakdown of attendees by country is as follows: USA 41 Germany 18 Japan 7 UK 5 Italy 5 France 4 Austria 3 Denmark 3 Cech. Repub. 1 Ireland 1 New Zealand 1 India 1 The technical program included oral sessions on the electronic and magnetic properties of oxide surfaces, surface and interface structure, advances in theory, surface defects, thin film oxides on metals and on oxides, thin film metals on oxides, surface photochemistry, surface reactivity, and interactions with water. Two evening poster sessions had similar themes. As in previous years, the program stimulated significant interest and discussion among the attendees. The local expenses (food and lodging, $918 per person) for eight foreign invited speakers were covered by BES funds. In addition, partial reimbursement for travel ($328 per person) was supported by BES funds for two more foreign invited speakers.
Date: February 2, 2007
Creator: Campbell, Charles T.
System: The UNT Digital Library
Modeling the Oil Transition: A Summary of the Proceedings of the DOE/EPA Workshop on the Economic and Environmental Implications of Global Energy Transitions (open access)

Modeling the Oil Transition: A Summary of the Proceedings of the DOE/EPA Workshop on the Economic and Environmental Implications of Global Energy Transitions

The global energy system faces sweeping changes in the next few decades, with potentially critical implications for the global economy and the global environment. It is important that global institutions have the tools necessary to predict, analyze and plan for such massive change. This report summarizes the proceedings of an international workshop concerning methods of forecasting, analyzing, and planning for global energy transitions and their economic and environmental consequences. A specific case, it focused on the transition from conventional to unconventional oil and other energy sources likely to result from a peak in non-OPEC and/or global production of conventional oil. Leading energy models from around the world in government, academia and the private sector met, reviewed the state-of-the-art of global energy modeling and evaluated its ability to analyze and predict large-scale energy transitions.
Date: February 1, 2007
Creator: Greene, David L.
System: The UNT Digital Library
Design and Analysis of Salmonid Tagging Studies in the Columbia Basin, Volume XXI; A Summary of Methods for Conducting Salmonid Fry Mark-Recapture Studies for Estimating Survival in Tributaries, Technical Report 2005-2006. (open access)

Design and Analysis of Salmonid Tagging Studies in the Columbia Basin, Volume XXI; A Summary of Methods for Conducting Salmonid Fry Mark-Recapture Studies for Estimating Survival in Tributaries, Technical Report 2005-2006.

Productivity and early fry survival can have a major influence on the dynamics of fish stocks. To investigate the early life history of fish, numerous methods have been developed or adapted to these much smaller fish. Some of the marking techniques provide individual identification; many others, only class identification. Some of the tagging techniques require destructive sampling to identify a mark; other methods permit benign examination and rerelease of captured fish. Sixteen alternative release-recapture designs for conducting fry survival investigations were examined. Eleven approaches were found capable of estimating survival parameters; five were not. Of those methods capable of estimating fry survival, five required unique marks, four required batch-specific marks, and two approaches required remarking and rereleasing captured fry. No approach based on a simple batch mark was capable of statistically estimating survival.
Date: February 1, 2007
Creator: Skalski, John
System: The UNT Digital Library
Restoring Anadromous Fish Habitat in the Lapwai Creek Watershed, Technical Report 2003-2006. (open access)

Restoring Anadromous Fish Habitat in the Lapwai Creek Watershed, Technical Report 2003-2006.

The Restoring Anadromous Fish Habitat in the Lapwai Creek Watershed is a multi-phase project to enhance steelhead trout in the Lapwai Creek watershed by improving salmonid spawning and rearing habitat. Habitat is limited by extreme high runoff events, low summer flows, high water temperatures, poor instream cover, spawning gravel siltation, and sediment, nutrient and bacteria loading. Funded by the Bonneville Power Administration (BPA) as part of the Northwest Power Planning Council's Fish and Wildlife Program, the project assists in mitigating damage to steelhead runs caused by the Columbia River hydroelectric dams. The project is sponsored by the Nez Perce Soil and Water Conservation District (District). Target fish species include steelhead trout (Oncorhynchus mykiss). Steelhead trout within the Snake River Basin were listed in 1997 as threatened under the Endangered Species Act. Accomplishments for the contract period December 1, 2003 through February 28, 2004 include; seven grade stabilization structures, 0.67 acres of wetland plantings, ten acres tree planting, 500 linear feet streambank erosion control, two acres grass seeding, and 120 acres weed control.
Date: February 1, 2007
Creator: Rasmussen, Lynn
System: The UNT Digital Library
Magnetic Profiles in Ferromagnetic/Superconducting Superlattices. (open access)

Magnetic Profiles in Ferromagnetic/Superconducting Superlattices.

The interplay between ferromagnetism and superconductivity has been of longstanding fundamental research interest to scientists, as the competition between these generally mutually exclusive types of long-range order gives rise to a rich variety of physical phenomena. A method of studying these exciting effects is by investigating artificially layered systems, i.e. alternating deposition of superconducting and ferromagnetic thin films on a substrate, which enables a straight-forward combination of the two types of long-range order and allows the study of how they compete at the interface over nanometer length scales. While originally studies focused on low temperature superconductors interchanged with metallic ferromagnets, in recent years the scope has broadened to include superlattices of high T{sub c} superconductors and colossal magnetoresistance oxides. Creating films where both the superconducting as well as the ferromagnetic layers are complex oxide materials with similar crystal structures (Figure 1), allows the creation of epitaxial superlattices, with potentially atomically flat and ordered interfaces.
Date: February 28, 2007
Creator: te Velthuis, S. G. E.; Hoffmann, A.; Santamaria, J.; Division, Materials Science & Madrid, Univ. Complutense de
System: The UNT Digital Library
Final Work Plan: Investigation of Potential Contamination at the Former USDA Facility in Powhattan, Kansas. (open access)

Final Work Plan: Investigation of Potential Contamination at the Former USDA Facility in Powhattan, Kansas.

This Work Plan outlines the scope of work to be conducted to investigate the subsurface contaminant conditions at the property formerly leased by the Commodity Credit Corporation (CCC) in Powhattan, Kansas (Figure 1.1). Data obtained during this event will be used to (1) evaluate potential contaminant source areas on the property; (2) determine the vertical and horizontal extent of potential contamination; and (3) provide recommendations for future action, with the ultimate goal of assigning this site No Further Action status. The planned investigation includes groundwater monitoring requested by the Kansas Department of Health and Environment (KDHE), in accordance with Section V of the Intergovernmental Agreement between the KDHE and the Farm Service Agency of the U.S. Department of Agriculture (USDA). The work is being performed on behalf of the CCC/USDA by the Environmental Science Division of Argonne National Laboratory. A nonprofit, multidisciplinary research center operated by the University of Chicago for the U.S. Department of Energy, Argonne provides technical assistance to the CCC/USDA with environmental site characterization and remediation at former CCC/USDA grain storage facilities. Argonne issued a Master Work Plan (Argonne 2002) that has been approved by the KDHE. The Master Work Plan describes the general scope of all …
Date: February 2, 2007
Creator: LaFreniere, L. M.
System: The UNT Digital Library
Research and Development of an Integral Separator for a Centrifugal Gas Processing Facility (open access)

Research and Development of an Integral Separator for a Centrifugal Gas Processing Facility

A COMPACT GAS PROCESSING DEVICE WAS INVESTIGATED TO INCREASE GAS PRODUCTION FROM REMOTE, PREVIOUSLY UN-ECONOMIC RESOURCES. THE UNIT WAS TESTED ON AIR AND WATER AND WITH NATURAL GAS AND LIQUID. RESULTS ARE REPORTED WITH RECOMMENDATIONS FOR FUTURE WORK.
Date: February 27, 2007
Creator: Hays, Lance
System: The UNT Digital Library
Test Report on ISR Double-Loop, Spray-Cooled Inverter (open access)

Test Report on ISR Double-Loop, Spray-Cooled Inverter

The Isothermal Systems Research, Inc. (ISR) double-loop, two-phase spray cooling system was designed to use 85 C transmission oil to cool a heat exchanger via a second cooling loop. The heat exchanger condenses the working fluid vapor back to liquid inside a sealed enclosure to allow for continuous spray cooling of electronics. In the ORNL tests, 85 C water/ethylene/glycol (WEG), which has better thermal properties than transmission oil, was substituted for the transmission oil. Because the ISR spray-cooling system requires a second cooling loop, the final inverter might be inherently larger than inverters that do not require a second-loop cooling system. The ISR test setup did not include a dc bus capacitor. Because the insulated gate bipolar transistor (IGBT) conduction test indicated that the ISR test setup could not be properly loaded thermally, no switching tests were conducted. Therefore it was not necessary to attach external capacitors outside the test setup. During load situations not exceeding 400A, the WEG inlet temperature was higher than the WEG outlet temperature. This meant that the 85 C WEG heat exchanger was not cooling the inverter and became a thermal load to the inverter. Only when the load was higher than 400A with a …
Date: February 1, 2007
Creator: Hsu, John S; Coomer, Chester; Campbell, Steven L; Wiles, Randy H; Lowe, Kirk T & McFee, Marshall T
System: The UNT Digital Library
Phosphor-Free Solid State Light Sources (open access)

Phosphor-Free Solid State Light Sources

The objective of this work was to demonstrate a light emitting diode that emitted white light without the aid of a phosphor. The device was based on the combination of a nitride LED and a fluorescing ZnO substrate. The early portion of the work focused on the growth of ZnO in undoped and doped form. The doped ZnO was successfully engineered to emit light at specific wavelengths by incorporating various dopants into the crystalline lattice. Thereafter, the focus of the work shifted to the epitaxial growth of nitride structures on ZnO. Initially, the epitaxy was accomplished with molecular beam epitaxy (MBE). Later in the program, metallorganic chemical vapor deposition (MOCVD) was successfully used to grow nitrides on ZnO. By combining the characteristics of the doped ZnO substrate with epitaxially grown nitride LED structures, a phosphor-free white light emitting diode was successfully demonstrated and characterized.
Date: February 28, 2007
Creator: Nause, Jeff E; Ferguson, Ian & Doolittle, Alan
System: The UNT Digital Library
Sampling and Analysis Instruction for Evaluation of Residual Chromium Contamination in the Subsurface Soil at 100-C-7 (open access)

Sampling and Analysis Instruction for Evaluation of Residual Chromium Contamination in the Subsurface Soil at 100-C-7

This sampling and analysis instruction (SAI) provides the requirements for sample collection and laboratory analysis to evaluate the extent of hexavalent chromium contamination present in the soil below the 100-C-7 and 100-C-7:1 remedial action waste site excavations.
Date: February 15, 2007
Creator: Thompson, W. S.
System: The UNT Digital Library
Chunking of Large Multidimensional Arrays (open access)

Chunking of Large Multidimensional Arrays

Data intensive scientific computations as well on-lineanalytical processing applications as are done on very large datasetsthat are modeled as k-dimensional arrays. The storage organization ofsuch arrays on disks is done by partitioning the large global array intofixed size hyper-rectangular sub-arrays called chunks or tiles that formthe units of data transfer between disk and memory. Typical queriesinvolve the retrieval of sub-arrays in a manner that accesses all chunksthat overlap the query results. An important metric of the storageefficiency is the expected number of chunks retrieved over all suchqueries. The question that immediately arises is "what shapes of arraychunks give the minimum expected number of chunks over a query workload?"In this paper we develop two probabilistic mathematical models of theproblem and provide exact solutions using steepest descent and geometricprogramming methods. Experimental results, using synthetic workloads onreal life data sets, show that our chunking is much more efficient thanthe existing approximate solutions.
Date: February 28, 2007
Creator: Rotem, Doron; Otoo, Ekow J. & Seshadri, Sridhar
System: The UNT Digital Library
Submittal of Final Post-Closure Inspection Letter Report for Corrective Action Unit 91: Area 3 U-3fi Injection Well, 2006 (open access)

Submittal of Final Post-Closure Inspection Letter Report for Corrective Action Unit 91: Area 3 U-3fi Injection Well, 2006

This letter serves as the post-closure monitoring letter report for the above Corrective Action Unit (CAU) for calendar year 2006. CAU 91 is inspected every six months. The first inspection was conducted on March 23, 2006, and the second inspection was conducted on September 19, 2006. All access roads, fences, gates, and signs were in excellent condition. No settling, cracking, or erosion was observed on the cover, and the use restriction had been maintained. No issues were identified, and no corrective actions were needed. The post-closure inspection checklists for CAU 91 are attached. Photographs and fields notes taken during site inspections are maintained in the project files.
Date: February 5, 2007
Creator: National Security Technologies, LLC
System: The UNT Digital Library