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458 Matching Results
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Government Activities to Protect the Electric Grid
This report provides a description of initiatives within the Federal Energy Regulatory Commission and the Departments of Energy, Homeland Security, and Defense to protect the physical transmission infrastructure.
Date:
October 20, 2004
Creator:
Abel, Amy
Object Type:
Report
System:
The UNT Digital Library
Government Activities to Protect the Electric Grid
This report provides a description of initiatives within the Federal Energy Regulatory Commission and the Departments of Energy, Homeland Security, and Defense to protect the physical transmission infrastructure.
Date:
December 20, 2004
Creator:
Abel, Amy
Object Type:
Report
System:
The UNT Digital Library
Spatial Analysis of Emissions Sources for HCCI Combustion at Low Loads Using a Multi-Zone Model
We have conducted a detailed numerical analysis of HCCI engine operation at low loads to investigate the sources of HC and CO emissions and the associated combustion inefficiencies. Engine performance and emissions are evaluated as fueling is reduced from typical HCCI conditions, with an equivalence ratio f = 0.26 to very low loads (f = 0.04). Calculations are conducted using a segregated multi-zone methodology and a detailed chemical kinetic mechanism for iso-octane with 859 chemical species. The computational results agree very well with recent experimental results. Pressure traces, heat release rates, burn duration, combustion efficiency and emissions of hydrocarbon, oxygenated hydrocarbon, and carbon monoxide are generally well predicted for the whole range of equivalence ratios. The computational model also shows where the pollutants originate within the combustion chamber, thereby explaining the changes in the HC and CO emissions as a function of equivalence ratio. The results of this paper contribute to the understanding of the high emission behavior of HCCI engines at low equivalence ratios and are important for characterizing this previously little explored, yet important range of operation.
Date:
February 20, 2004
Creator:
Aceves, S. M.; Flowers, D. L.; Espinosa-Loza, F.; Martinez-Frias, J.; Dec, J. E.; Sjoberg, M. et al.
Object Type:
Article
System:
The UNT Digital Library
The Impact of humidity above stratiform clouds on indirect aerosol climate forcing
Some of the global warming effect of anthropogenic greenhouse gases is offset by increased solar reflection from clouds with smaller droplets that form on increased numbers of cloud condensation nuclei in polluted air. The global magnitude of the resulting indirect aerosol climate forcing is estimated to be comparable (and opposed) to the anthropogenic carbon dioxide forcing, but estimates are highly uncertain because of complexities in characterizing the physical process that determine global aerosol and cloud populations and their interactions. Beyond reflecting sunlight more effectively, smaller droplets are less efficient at producing precipitation, and decreased precipitation is expected to result in increased cloud water and cloud cover, further increasing the indirect forcing. Yet polluted marine boundary-layer clouds are not generally observed to hold more water. Here we use model simulations of stratocumulus clouds to show that suppression of precipitation from increased droplet concentrations leads to increased cloud water only when sufficient precipitation reaches the surface, a condition favored when the overlying air is moist. Otherwise, aerosol induced suppression of precipitation enhances entrainment of overlying dry air, thereby reducing cloud water and diminishing the indirect climate forcing.
Date:
December 20, 2004
Creator:
Ackerman, A. S.; Kirkpatrick, M. P.; Stevens, D. E. & Toon, O. B.
Object Type:
Article
System:
The UNT Digital Library
Search for b0(s) --> mu+ mu- and b0(d) --> mu+ mu- decays in p anti-p collisions at s**(1/2) = 1.96 tev
The authors report on a search for B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -} and B{sub d}{sup 0} {yields} {mu}{sup +}{mu}{sup -} decays in p{bar p} collisions at {radical}s = 1.96 TeV using 171 pb{sup -1} of data collected by the CDF II experiment at the Fermilab Tevatron Collider. The decay rates of these rare processes are sensitive to contributions from physics beyond the Standard Model. One event survives all the selection requirements, consistent with the background expectation. They derive branching ratio limits of {Beta}(B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -}) < 5.8 x 10{sup -7} and {Beta}(B{sub d}{sup 0} {yields} {mu}{sup +}{mu}{sup -}) < 1.5 x 10{sup -7} at 90% confidence level.
Date:
March 20, 2004
Creator:
Acosta, D.
Object Type:
Report
System:
The UNT Digital Library
Design, Construction, and Operation of a Laboratory Scale Reactorfor the Production of High-Purity, Isotopically Enriched Bulksilicon
The design and operation of a recirculating flow reactor designed to convert isotopically enriched silane to polycrystalline Si with high efficiency and chemical purity is described. The starting material is SiF{sub 4}, which is enriched in the desired isotope by a centrifuge method and subsequently converted to silane. In the reactor, the silane is decomposed to silicon on the surface of a graphite starter rod (3 mm diameter) heated to 700-750 C. Flow and gas composition (0.3-0.5% silane in hydrogen) are chosen to minimize the generation of particles by homogeneous nucleation of silane and to attain uniform deposition along the length of the rod. Growth rates are 5 {micro}m/min, and the conversion efficiency is greater than 95%. A typical run produces 35 gm of polycrystalline Si deposited along a 150 mm length of the rod. After removal of the starter rod, dislocation-free single crystals are formed by the floating zone method. Crystals enriched in all 3 stable isotopes of Si have been made: {sup 28}Si (99.92%), {sup 29}Si (91.37%), and {sup 30}Si (88.25%). Concentrations of electrically active impurities (P and B) are as low as mid-10{sup 13} cm{sup -3}. Concentrations of C and O lie below 10{sup 16} and 10{sup …
Date:
December 20, 2004
Creator:
Ager, J. W., III; Beeman, J. W.; Hansen, W. L. & Haller, E. E.
Object Type:
Report
System:
The UNT Digital Library
Small Column Ion Exchange Analysis for Removal of Cesium from SRS Low Curie Salt Solutions Using Crystalline Silicotitanate (CST) Resin
Savannah River Technology Center (SRTC) researchers modeled ion exchange removal of cesium from dissolved salt waste solutions. The results assist in evaluating proposed configurations for an ion exchange process to remove residual cesium from low curie waste streams. A process for polishing (i.e., removing small amounts) of cesium may prove useful should supernate draining fail to meet the Low Curie Salt (LCS) target limit of 0.1 Ci of Cs-137 per gallon of salt solution. Cesium loading isotherms and column breakthrough curves for Low Curie dissolved salt solutions were computed to provide performance predictions for various column designs.
Date:
April 20, 2004
Creator:
Aleman, Sebastian E. & Hamm, L. L.
Object Type:
Report
System:
The UNT Digital Library
Timpson & Tenaha News (Timpson, Tex.), Vol. 19, No. 21, Ed. 1 Thursday, May 20, 2004
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
May 20, 2004
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Guide to Individuals Seated on the Senate Dais
This report briefly discusses where various individuals are seated in the Senate chamber.
Date:
October 20, 2004
Creator:
Amer, Mildred
Object Type:
Report
System:
The UNT Digital Library
Membership of the 109th Congress: A Profile
None
Date:
December 20, 2004
Creator:
Amer, Mildred L.
Object Type:
Report
System:
The UNT Digital Library
Altus Times (Altus, Okla.), Vol. 105, No. 264, Ed. 1 Tuesday, January 20, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
January 20, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 105, No. 291, Ed. 1 Friday, February 20, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
February 20, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 17, Ed. 1 Tuesday, April 20, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
April 20, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 43, Ed. 1 Thursday, May 20, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
May 20, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 69, Ed. 1 Sunday, June 20, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
June 20, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 95, Ed. 1 Tuesday, July 20, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
July 20, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 121, Ed. 1 Friday, August 20, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
August 20, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 147, Ed. 1 Monday, September 20, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
September 20, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 173, Ed. 1 Wednesday, October 20, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
October 20, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 218, Ed. 1 Monday, December 20, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
December 20, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
European Views and Policies Toward the Middle East
None
Date:
January 20, 2004
Creator:
Archick, Kristin
Object Type:
Report
System:
The UNT Digital Library
Aspects of the SrO-CuO-TiO2 Ternary System Related to the Deposition of SrTiO3 and Copper-Doped SrTiO3 Thin-Film Buffer Layers
YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) coated conductors are promising materials for large-scale superconductivity applications. One version of a YBCO coated conductor is based on ion beam assisted deposition (IBAD) of magnesium oxide (MgO) onto polycrystalline metal substrates. SrTiO{sub 3} (STO) is often deposited by physical vapor deposition (PVD) methods as a buffer layer between the YBCO and IBAD MgO due to its chemical stability and lattice mismatch of only {approx}1.5% with YBCO. In this work, some aspects of the stability of STO with respect to copper (Cu) and chemical solution deposition of STO on IBAD MgO templates were examined. Solubility limits of Cu in STO were established by processing Cu-doped STO powders by conventional bulk preparation techniques. The maximum solubility of Cu in STO was {approx}1% as determined by transmission electron microscopy (TEM) and Rietveld refinements of x-ray diffraction (XRD) data. XRD analysis, performed in collaboration with NIST, on powder compositions on the STO/SrCuO{sub 2} tie line did not identify any ternary phases. SrCu{sub 0.10}Ti{sub 0.90}O{sub y} buffer layers were prepared by pulsed laser deposition (PLD) and CSD on IBAD MgO flexible metallic textured tapes. TEM analysis of a {approx}100 nm thick SrCu{sub 0.10}Ti{sub 0.90}O{sub y} buffer layer deposited by …
Date:
December 20, 2004
Creator:
Ayala, A.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
ASSESSMENT OF GENOTOXIC ACTIVITY OF PETROLEUM HYDROCARBON-BIOREMEDIATED SOIL
The relationship between toxicity and soil contamination must be understood to develop reliable indicators of environmental restoration for bioremediation. Two bacterial rapid bioassays: SOS chromotest and umu-test with and without metabolic activation (S-9 mixture) were used to evaluate genotoxicity of petroleum hydrocarbon-contaminated soil following bioremediation treatment. The soil was taken from an engineered biopile at the Czor Polish oil refinery. The bioremediation process in the biopile lasted 4 years, and the toxicity measurements were done after this treatment. Carcinogens detected in the soil, polyaromatic hydrocarbons (PAHs), were reduced to low concentrations (2 mg/kg dry wt) by the bioremediation process. Genotoxicity was not observed for soils tested with and without metabolic activation by a liver homogenate (S-9 mixture). However, umu-test was more sensitive than SOS-chromotest in the analysis of petroleum hydrocarbon-bioremediated soil. Analytical results of soil used in the bioassays confirmed that the bioremediation process reduced 81 percent of the petroleum hydrocarbons including PAHs. We conclude that the combined test systems employed in this study are useful tools for the genotoxic examination of remediated petroleum hydrocarbon-contaminated soil.
Date:
October 20, 2004
Creator:
BRIGMON, ROBIN
Object Type:
Report
System:
The UNT Digital Library
High Efficiency Amorphous and Microcrystalline Silicon Based Double-Junction Solar Cells made with Very-High-Frequency Glow Discharge
We have achieved a total-area initial efficiency of 11.47% (active-area efficiency of 12.33%) on a-Si:H/μc-Si:H double-junction structure, where the intrinsic layer bottom cell was made in 50 minutes. On another device in which the bottom cell was made in 30 min, we achieved initial total-area efficiency of 10.58% (active-efficiency of 11.35%). We have shown that the phenomenon of ambient degradation of both μc-Si:H single-junction and a-Si:H/μc-Si:H double-junction cells can be attributed to impurity diffusion after deposition. Optimization of the plasma parameters led to alleviation of the ambient degradation. Appropriate current matching between the top and bottom component cells has resulted in a stable total-area efficiency of 9.7% (active-area efficiency of 10.42%) on an a-Si:H/μc-Si:H double-junction solar cell in which the deposition time for the μc-Si:H intrinsic layer deposition was of 30 min.
Date:
October 20, 2004
Creator:
Banerjee, Arindam
Object Type:
Report
System:
The UNT Digital Library