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17,865 Matching Results
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USING BLOCKS OF SKEWERS FOR FASTER COMPUTATION OF PIXEL PURITY INDEX
The pixel purity index (PPI) algorithm proposed by Boardman, et al.1 identifies potential endmember pixels in multispectral imagery. The algorithm generates a large number of skewers (unit vectors in random directions), and then computes the dot product of each skewer with each pixel. The PPI is incremented for those pixels associated with the extreme values of the dot products. A small number of pixels (a subset of those with the largest PPI values) are selected as pure and the rest of the pixels in the image are expressed as linear mixtures of these pure endmembers. This provides a convenient and physically-motivated decomposition of the image in terms of a relatively few components. We report on a variant of the PPI algorithm in which blocks of B skewers are considered at a time. From the computation of B dot products, one can produce a much larger set of derived dot products that are associated with skewers that are linear combinations of the original B skewers. Since the derived dot products involve only scalar operations, instead of full vector dot products, they can be very cheaply computed. We will also discuss a hardware implementation on a field programmable gate array (FPGA) processor …
Date:
October 1, 2000
Creator:
Theiler, James; Lavenier, Dominique D.; Harvey, Neal R.; Perkins, Simon J. & Szymanski, John J.
Object Type:
Article
System:
The UNT Digital Library
Vaporization of Elemental Mercury from Pools of Molten Lead at Low Concentrations
Should coolant accidentally be lost to the APT (Accelerator Production of Tritium) blanket and target, and the decay heat in the target be deposited in the surrounding blanket by thermal radiation, temperatures in the blanket modules could exceed structural limits and cause a physical collapse of the blanket modules into a non-coolable geometry. Such a sequence of unmitigated events could result in some melting of the APT blanket and create the potential for the release of mercury into the target-blanket cavity air space. Experiments were conducted which simulate such hypothetical accident conditions in order to measure the rate of vaporization of elemental mercury from pools of molten lead to quantify the possible severe accident source term for the APT blanket region. Molten pools of from 0.01% to 0.10% mercury in lead were prepared under inert conditions. Experiments were conducted, which varied in duration from several hours to as long as a month, to measure the mercury vaporization from the lead pools. The melt pools and gas atmospheres were held fixed at 340 C during the tests. Parameters which were varied in the tests included the mercury concentration, gas flow rate over the melt and agitation of the melt, gas atmosphere …
Date:
October 1, 2000
Creator:
Greene, G. A. & Finfrock, C. C.
Object Type:
Report
System:
The UNT Digital Library
Vaporization of Tungsten-Metal in Steam at High Temperatures
The vaporization of tungsten from the APT spallation target dominates the radiological source term for unmitigated target overheating accidents. Chemical reactions of tungsten with steam which persist to tungsten temperatures as low as 800 C result in the formation of a hydrated tungsten-oxide which has a high vapor pressure and is readily convected in a flowing atmosphere. This low-temperature vaporization reaction essentially removes the oxide film that forms on the tungsten-metal surface as soon as it forms, leaving behind a fresh metallic surface for continued oxidation and vaporization. Experiments were conducted to measure the oxidative vaporization rates of tungsten in steam as part of the effort to quantify the MT radiological source term for severe target accidents. Tests were conducted with tungsten rods (1/8 inch diameter, six inches long) heated to temperatures from approximately 700 C to 1350 C in flowing steam which was superheated to 140 C. A total of 19 experiments was conducted. Fifteen tests were conducted by RF induction heating of single tungsten rods held vertical in a quartz glass retort. Four tests were conducted in a vertically-mounted tube furnace for the low temperature range of the test series. The aerosol which was generated and transported downstream …
Date:
October 1, 2000
Creator:
Greene, G. A. & Finfrock, C. C.
Object Type:
Report
System:
The UNT Digital Library
Waste Volume Reduction Using Surface Characterization and Decontamination By Laser Ablation
The U.S. Department of Energy's nuclear complex, a nation-wide system of facilities for research and production of nuclear materials and weapons, contains large amounts of radioactively contaminated concrete[1]. This material must be disposed of prior to the decommissioning of the various sites. Often the radioactive contaminants in concrete occupy only the surface and near-surface ({approx}3-6 mm deep) regions of the material. Since many of the structures such as walls and floors are 30 cm or more thick, it makes environmental and economic sense to try to remove and store only the thin contaminated layer rather than to treat the entire structure as waste. Current mechanical removal methods, known as scabbling, are slow and labor intensive, suffer from dust control problems, and expose workers to radiation fields. Improved removal methods are thus in demand[2-5]. Prior to decontamination, the surface must be characterized to determine the types and amounts of contaminants present i n order to decide on an appropriate cleaning strategy. Contamination occurs via exposure to air and water-borne radionuclides and by neutron activation. The radionuclides of greatest concern are (in order of abundance) [1]: 137Cs & 134Cs, 238U, 60Co, and 90Sr, followed by 3H, radioactive iodine, and a variety of …
Date:
October 1, 2000
Creator:
Pellin, Michael J.; Savina, Michael R.; Reed, Claude B.; Zhiyue, Xu & Yong, Wang
Object Type:
Report
System:
The UNT Digital Library
[Wheeler Avenue Baptist Church Bulletin: October 1, 2000]
Church bulletin listing the order of worship for the 7:30 and 11:00 Sunday morning services at the Wheeler Avenue Baptist Church, as well as various notes about upcoming events, congregational news, and other information of relevance to church members.
Date:
October 1, 2000
Creator:
Wheeler Avenue Baptist Church (Houston, Tex.)
Object Type:
Pamphlet
System:
The Portal to Texas History
[Wine country tour resources]
Resource list for an article about Hill Country wineries that was published in the October 2000 issue of Texas Highways magazine.
Date:
2000-10~
Creator:
Mallory, Randy
Object Type:
Text
System:
The UNT Digital Library
Wine Country Weekend
Text about Hill Country wineries and other related attractions that was published in the 'When..." section of an October 2000 Texas Highways magazine article.
Date:
2000-10~
Creator:
Mallory, Randy
Object Type:
Text
System:
The UNT Digital Library
Winning, October 2000
Pamphlet containing information about Texas Lottery winners, scratch-off prizes, new games, and more.
Date:
October 2000
Creator:
Texas Lottery Commission
Object Type:
Journal/Magazine/Newsletter
System:
The Portal to Texas History
Zirconia-Based Mixed Potential CO/HC Sensors with LaMnO3 and Th-doped YSZ Electrodes
Abstract: We have investigated the performance of dual metal oxide electrode mixed potential sensors in an engine-out, dynamometer environment. Sensors were fabricated by sputtering thin films of LaMnO{sub 3} and Tb-doped YSZ onto YSZ electrolyte. Au gauze held onto the metal oxide thin films with Au ink was used for current collection. The exhaust gas from a 4.8L, V8 engine operated in open loop, steady-state mode around stoichiometry at 1500 RPM and 50 Nm. The sensor showed a stable EMF response (with no hysteresis) to varying concentrations of total exhaust gas HC content. The sensor response was measured at 620 and 670 C and shows temperature behavior characteristic of mixed potential-type sensors. The results of these engine-dynamometer tests are encouraging; however, the limitations associated with Au current collection present the biggest impediment to automotive use.
Date:
October 1, 2000
Creator:
Brosha, Eric L.; Mukundan, Rangachary; Brown, David R.; Garzon, Fernando H.; Visser, J. H.; Thompson, David J. et al.
Object Type:
Article
System:
The UNT Digital Library