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430 Matching Results
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Annealing as grown large volume CZT single crystals increased spectral resolution
The spectroscopic performance of current large-volume Cadmium 10% Zinc Telluride, Cd{sub 0.9}Zn{sub 0.1}Te, (CZT) detectors is impaired by cumulative effect of tellurium precipitates (secondary phases) presented in CZT single-crystal grown by low-pressure Bridgman techniques(1). This statistical effect may limit the energy resolution of large-volume CZT detectors (typically 2-5% at 662 keV for 12-mm thick devices). The stochastic nature of the interaction prevents the use of any electronic or digital charge correction techniques without a significant reduction in the detector efficiency. This volume constraint hampers the utility of CZT since the detectors are inefficient at detecting photons >1MeV and/or in low fluency situations. During the project, seven runs CZT ingots have been grown, in these ingots the indium dopant concentrations have been changed in the range between 0.5ppm to 6ppm. The I-R mapping imaging method has been employed to study the Te-precipitates. The Teprecipitates in as-grown CZT wafers, and after annealing wafers have been systematically studied by using I-R mapping system (home installed, resolution of 1.5 {micro}m). We employed our I-R standard annealing CZT (Zn=4%) procedure or two-steps annealing into radiation CZT (Zn=10%), we achieved the 'non'-Te precipitates (size < 1 {micro}m) CZT n+-type with resistivity > 10{sup 9-10} {Omega}-cm. We …
Date:
March 19, 2008
Creator:
Li, Dr. Longxia
Object Type:
Report
System:
The UNT Digital Library
Structural characterization of terrestrial microbial Mn oxides from Pinal Creek, AZ
The microbial catalysis of Mn(II) oxidation is believed to be a dominant source of abundant sorption- and redox-active Mn oxides in marine, freshwater, and subsurface aquatic environments. In spite of their importance, environmental oxides of known biogenic origin have generally not been characterized in detail from a structural perspective. Hyporheic zone Mn oxide grain coatings at Pinal Creek, Arizona, a metals-contaminated stream, have been identified as being dominantly microbial in origin and are well studied from bulk chemistry and contaminant hydrology perspectives. This site thus presents an excellent opportunity to study the structures of terrestrial microbial Mn oxides in detail. XRD and EXAFS measurements performed in this study indicate that the hydrated Pinal Creek Mn oxide grain coatings are layer-type Mn oxides with dominantly hexagonal or pseudo-hexagonal layer symmetry. XRD and TEM measurements suggest the oxides to be nanoparticulate plates with average dimensions on the order of 11 nm thick x 35 nm diameter, but with individual particles exhibiting thickness as small as a single layer and sheets as wide as 500 nm. The hydrated oxides exhibit a 10-A basal-plane spacing and turbostratic disorder. EXAFS analyses suggest the oxides contain layer Mn(IV) site vacancy defects, and layer Mn(III) is inferred …
Date:
March 19, 2008
Creator:
Bargar, John; Fuller, Christopher; Marcus, Matthew A.; Brearley, Adrian J.; Perez De la Rosa, M.; Webb, Samuel M. et al.
Object Type:
Article
System:
The UNT Digital Library
The Davis-Bacon Act: Issues and Legislation During the 108th Congress
This report discusses the debate surrounding the Davis-Bacon Act (1931, as amended), which requires, among other things, that not less than the locally-prevailing wage be paid to workers employed in federal contract construction. Through recent decades, the Act has become a continuing source of contention, particularly regarding its impacts, whether it should be modified, strengthened, or repealed, and if it is being administered effectively.
Date:
March 19, 2004
Creator:
Whittaker, William G.
Object Type:
Report
System:
The UNT Digital Library
The Hierarchical Build-Up of Massive Galaxies And the Intracluster Light Since z=1
We use a set of simulation-based models for the dissipationless evolution of galaxies since z = 1 to constrain the fate of accreted satellites embedded in dark matter subhalos. These models assign stellar mass to dark matter halos at z = 1 by relating the observed galaxy stellar mass function (GSMF) to the halo+subhalo mass function monotonically. The evolution of the stellar mass content is then followed using halo merger trees extracted from N-body simulations. Our models are differentiated only in the fate assigned to satellite galaxies once subhalos, within which satellites are embedded, disrupt. These models are confronted with the observed evolution in the massive end of the GSMF, the z {approx} 0 brightest cluster galaxy (BCG)-cluster mass relation, and the combined BCG and intracluster light (ICL) luminosity distribution--all observables expected to evolve approximately dissipationlessly since z = 1. The combined observational constraints favor a model in which the vast majority ({approx}> 80%) of satellite stars from disrupted subhalos go into the ICL (operationally defined here as light below a surface brightness cut of {mu}{sub i} {approx} 23mag arcsec{sup -2}). Conversely, models that leave behind a significant population of satellite galaxies once the subhalo has disrupted are strongly disfavored, …
Date:
March 19, 2007
Creator:
Conroy, Charlie; Wechsler, Risa H. & Kravtsov, Andrey V.
Object Type:
Article
System:
The UNT Digital Library
Development of a Simple Radioactive marker System to Reduce Positioning Errors in Radiation Treatment
The objective of this research is to implement an inexpensive, quick and simple monitor that provides an accurate indication of proper patient position during the treatment of cancer by external beam X-ray radiation and also checks for any significant changes in patient anatomy. It is believed that this system will significantly reduce the treatment margin, provide an additional, independent quality assurance check of positioning accuracy prior to all treatments and reduce the probability of misadministration of therapeutic dose.
Date:
March 19, 2007
Creator:
Miller, William H. & Palta, Dr. Jatinder
Object Type:
Report
System:
The UNT Digital Library
Early Computing and Its Impact on Lawrence Livermore National Laboratory
None
Date:
March 19, 2007
Creator:
Lokke, W.
Object Type:
Report
System:
The UNT Digital Library
A Symposium in Honor of William A. Lester, Jr. on His 70thBirthday
None
Date:
March 19, 2007
Creator:
Lester, William A., Jr.
Object Type:
Article
System:
The UNT Digital Library
Applications of Cfd Method to Gas Mixing Analysis in a Large-Scaled Tank
The computational fluid dynamics (CFD) modeling technique was applied to the estimation of maximum benzene concentration for the vapor space inside a large-scaled and high-level radioactive waste tank at Savannah River site (SRS). The objective of the work was to perform the calculations for the benzene mixing behavior in the vapor space of Tank 48 and its impact on the local concentration of benzene. The calculations were used to evaluate the degree to which purge air mixes with benzene evolving from the liquid surface and its ability to prevent an unacceptable concentration of benzene from forming. The analysis was focused on changing the tank operating conditions to establish internal recirculation and changing the benzene evolution rate from the liquid surface. The model used a three-dimensional momentum coupled with multi-species transport. The calculations included potential operating conditions for air inlet and exhaust flows, recirculation flow rate, and benzene evolution rate with prototypic tank geometry. The flow conditions are assumed to be fully turbulent since Reynolds numbers for typical operating conditions are in the range of 20,000 to 70,000 based on the inlet conditions of the air purge system. A standard two-equation turbulence model was used. The modeling results for the typical …
Date:
March 19, 2007
Creator:
Lee, S. & Richard Dimenna, R.
Object Type:
Article
System:
The UNT Digital Library
The Molecular Basis for Metabolic and Energetic Diversity
We have used experimental and computational analysis of R. sphaeroides photosynthesis and other gene expression networks (Kaplan, Gomelsky, Donohue) (3-9, 12, 13, 15-18, 20). We have identified many new candidate photosynthesis genes with expression patterns that varied as a function of light intensity. Results from these experiments suggest there are many more light-regulated aspects of the photosynthetic lifestyle of this bacterium than previously appreciated. Ongoing genetic analysis confirms that mutations in some of these newly-identified photosynthesis block the ability of cells to use solar energy in the laboratory. We also carried out transcriptome and computational analysis of individual R. sphaeroides regulons. This identified additional genes that are directly regulated by individual transcription factors and refined the consensus sequence for master regulators of photosystem development. We also showed that PpsR indirectly regulates genes that do not contain the PpsR-binding sites, e.g. puf and puhA operons. This suggests that PpsR plays a more global role as a regulator of photosystem development than what was assumed before. A similar computational and microarray analysis of PrrA target genes has identified many new candidate promoters that are controlled by this master regulator of photosynthesis. We have begun bioinformatic, genetic and biochemical experiments aimed at elucidating …
Date:
March 19, 2007
Creator:
Timothy Donohue, PI
Object Type:
Report
System:
The UNT Digital Library
CHEMICAL STORAGE: MYTHS VERSUS REALITY
A large number of resources explaining proper chemical storage are available. These resources include books, databases/tables, and articles that explain various aspects of chemical storage including compatible chemical storage, signage, and regulatory requirements. Another source is the chemical manufacturer or distributor who provides storage information in the form of icons or color coding schemes on container labels. Despite the availability of these resources, chemical accidents stemming from improper storage, according to recent reports (1) (2), make up almost 25% of all chemical accidents. This relatively high percentage of chemical storage accidents suggests that these publications and color coding schemes although helpful, still provide incomplete information that may not completely mitigate storage risks. This manuscript will explore some ways published storage information may be incomplete, examine the associated risks, and suggest methods to help further eliminate chemical storage risks.
Date:
March 19, 2007
Creator:
Simmons, F
Object Type:
Article
System:
The UNT Digital Library
Friction Factor Measurements in an Equally Spaced Triangular Tube Array
Friction factor data for adiabatic cross-flow of water in a staggered tube array was obtained over a Reynolds number range (based on hydraulic diameter and gap velocity) of about 10,000 to 250,000. The tubes were 12.7mm (0.5 inch) outer diameter, in a uniformly spaced triangular arrangement with a pitch-to-diameter ratio of 1.5. The friction factor was compared to several literature correlations, and was found to be best matched by the Idelchik correlation. Other correlations were found to vary significantly from the test data. Based on the test data, a new correlation is proposed for this tube bundle geometry which covers the entire Reynolds number range tested.
Date:
March 19, 2007
Creator:
Vassallo P, Symolon P
Object Type:
Report
System:
The UNT Digital Library
Studies of Hydrogen Getter Material Self-decomposition and Reaction Capacity
Diacetylene based hydrogen getters are examined in order to gauge their self decomposition products, as well as to determine possible origins for observed losses in origins getter capacity. Simple long term (several months) thermal aging tests were conducted, with periodic solid solid-phase micro micro-extraction (SPME) sampling followed by GC/MS analysis. The results suggest that bis(diphenylethynyl) benzene tends to decompose to give phenyl contaminants more readily than diphenylbutadiyne. Transmission electron microscopy (TEM) and electron diffraction studies of the palladium catalyst following varying extents of reaction with hydrogen show that there is no change to the catalyst particles, indicating that any change in capacity originates from other causes. These causes are suggested by Sievert's-type experiments on the reaction of the getter with a low pressure (about 10 Torr) hydrogen atmosphere. The reaction data indicate that the getter capacity depends on the pressure of hydrogen to which the material is exposed, and also its thermal history.
Date:
March 19, 2007
Creator:
Saab, A P & Dinh, L N
Object Type:
Report
System:
The UNT Digital Library
Tandem Filter Development for Thermophotovoltaic Energy Conversion from January 2003 to February 2006
The intent of this report is to summarize the tandem filter development for spectral control of thermophotovoltaic energy conversion from January 2003 to the termination of the program in February 2006 and to closeout tandem filter development in order to capture the knowledge gained from the development effort. Over the last three years, the goals of the tandem filter development have been the following: (1) Study the limits of the design of the interference optical coatings component of a tandem filter in order to develop higher performance designs; (2) Enhance the fabrication process of the optical interference coatings to increase the fidelity with the intended design and allow more complex, higher performing designs; (3) Support TPV module testing by providing tandem filters and assembly assistance; (4) Identify and develop materials for optical interference coatings that are stable at higher temperatures than current materials; and (5) Improve the understanding of the directional and spectral reflectance and transmittance characterization of the completed tandem filters to insure the veracity of the characterization data and to provide useful feedback to the tandem filter development process. This development effort has been a collaboration between KAPL and its contracted development partner, Rugate Technologies Inc.
Date:
March 19, 2007
Creator:
PM, Fourspring
Object Type:
Report
System:
The UNT Digital Library
The Wylie News (Wylie, Tex.), Vol. 55, No. 43, Ed. 1 Wednesday, March 19, 2003
Weekly newspaper from Wylie, Texas that includes local, state and national news along with advertising.
Date:
March 19, 2003
Creator:
Engbrock, Chad B.
Object Type:
Newspaper
System:
The Portal to Texas History
Interim Letter Report - Verification Survey of Partial Grids H19, J21, J22, X20, and X21 at the David Witherspoon, Inc. 1630 Site, Knoxville Tennessee
Conduct verification surveys of available grids at the David Witherspoon Incorporated 1630 Site (DWI 1630) in Knoxville, Tennessee. The IVT conducted verification activities of partial grids H19, J21, J22, X20, and X21.
Date:
March 19, 2008
Creator:
Weaver, P. C.
Object Type:
Report
System:
The UNT Digital Library
Rains County Leader (Emory, Tex.), Vol. 114, No. 40, Ed. 1 Tuesday, March 19, 2002
Weekly newspaper from Emory, Texas that includes local, state, and national news along with advertising.
Date:
March 19, 2002
Creator:
Hill, Earl Clyde, Jr.
Object Type:
Newspaper
System:
The Portal to Texas History
[News Clip: Gorilla Latest 2]
Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story.
Date:
March 19, 2004
Creator:
NBC 5 (Television station : Fort Worth, Tex.)
Object Type:
Video
System:
The UNT Digital Library
[News Clip: Gorilla Latest]
Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story.
Date:
March 19, 2004
Creator:
NBC 5 (Television station : Fort Worth, Tex.)
Object Type:
Video
System:
The UNT Digital Library
Seminole Sentinel (Seminole, Tex.), Vol. 97, No. 46, Ed. 1 Sunday, March 19, 2006
Semiweekly newspaper from Seminole, Texas that includes local, state, and national news along with extensive advertising.
Date:
March 19, 2006
Creator:
Wright, Dustin
Object Type:
Newspaper
System:
The Portal to Texas History
[News Clip: Fort Hood Deploy 01]
Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story.
Date:
March 19, 2003
Creator:
NBC 5 (Television station : Fort Worth, Tex.)
Object Type:
Video
System:
The UNT Digital Library
[News Clip: Fort Hood Deploy 02]
Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story.
Date:
March 19, 2003
Creator:
NBC 5 (Television station : Fort Worth, Tex.)
Object Type:
Video
System:
The UNT Digital Library
Timpson & Tenaha News (Timpson, Tex.), Vol. 27, No. 11, Ed. 1 Thursday, March 19, 2009
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
March 19, 2009
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
The Clifton Record (Clifton, Tex.), Vol. 113, No. 12, Ed. 1 Wednesday, March 19, 2008
Weekly newspaper from Clifton, Texas that includes local, state, and national news along with advertising.
Date:
March 19, 2008
Creator:
Smith, W. Leon
Object Type:
Newspaper
System:
The Portal to Texas History
The Clifton Record (Clifton, Tex.), Vol. 108, No. 23, Ed. 1 Wednesday, March 19, 2003
Semi-weekly newspaper from Clifton, Texas that includes local, state, and national news along with advertising.
Date:
March 19, 2003
Creator:
Smith, W. Leon
Object Type:
Newspaper
System:
The Portal to Texas History