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Hydrogen Storage Properties of the Tetrahydrofuran Treated Magnesium
The electronic structure, crystalline feature and morphology of the tetrahydrofuran (THF) treated magnesium, along with its hydriding and dehydriding properties have been investigated. The THF treated magnesium absorbs 6.3 wt per cent hydrogen at 723K and 3.5 MPa. After hydrogenation, in addition to the expected MgH2, a new less-stable hydride phase appears at 673K, but not at a lower temperature. Desorption produces 5.5 wt per cent hydrogen at 723K against a back pressure of 1.3 Pa after 20 cycles of hydriding-dehydriding. The THF treatment improves the kinetics of hydrogen absorption and desorption significantly. From 723K to 623K, the THF treated Mg demonstrates acceptable reaction rates. XPS studies show that tetrahydrofuran treatment causes the electronic energy state of the magnesium surface atoms to change, but the XRD studies show the crystal structure remains unchanged. Metallographic observation of the bulk hydrides of THF treated magnesium reveal they are poly-crystalline wi th the wide-spreading slip bands and twins within the crystals, indicating the phase transformation upon hydriding causes serious stress and distortion. It appears this microstructural deformation explains the much higher energy requirements (higher pressure and temperature) for magnesium hydrogenation than the simple lattice expansion that accompany hydrogen uptake for LaNi5 and FeTi.
Date:
May 25, 2004
Creator:
AU, MING
Object Type:
Article
System:
The UNT Digital Library
Exotic physics: search for scalar leptoquark pairs decaying to nu nu-bar qq-bar in p anti-p collisions at s**(1/2) = 1.96 tev
We report on a search for the pair production of scalar leptoquarks, LQ, using 191 pb{sup -1} of proton-antiproton collision data recorded by the CDF experiment during Run II of the Tevatron. The leptoquarks are sought via their decay into a neutrino and quark yielding missing transverse energy and several jets of large transverse energy. No evidence for leptoquark production is observed, and limits are set on {sigma}(p{bar p} {yields} LQ{ovr OQ}X {yields} v{bar v}q{bar q}X). Using a next-to-leading order theoretical prediction of the cross section for scalar leptoquark production, we exclude first-generation leptoquarks in the mass interval 78 to 117 GeV/c{sup 2} at the 95% confidence level for BR(LQ {yields} vq) = 100%.
Date:
October 25, 2004
Creator:
Acosta, D.
Object Type:
Report
System:
The UNT Digital Library
Radiation dose measurements of the insertion devices using radiachromic film dosimeters.
The Advanced Photon Source (APS) uses Nd-Fe-B permanent magnets in the insertion devices to produce x-rays for scientific research [1,2]. Earlier investigations have exhibited varying degrees of demagnetization of these magnets [3] due to irradiation from electron beams [4,5,6], {sup 60}Co {gamma}-rays [5], and high-energy neutrons [7,8]. Radiation-induced demagnetization has been observed in the APS insertion devices [9] and was first measured in December of 2001. Partial demagnetization has also been observed in insertion devices at the European Synchrotron Radiation Facility (ESRF) [4,6], where Nd-Fe-B permanent magnets are also used. Growing concern for the lifetime of APS insertion devices, as well as the permanent magnets that will be used in next-generation, high-power light sources, like the FEL [10,11], resulted from the partial demagnetization observations made at both facilities. This concern in relation to radiation-induced demagnetization spurred a long-term project to measure and analyze the absorbed doses received by the APS insertion devices. The project required a reliable photon high-dose dosimetry technique capable of measuring absorbed doses greater than 10{sup 6} rad, which was not readily available at the APS. Through a collaboration with the National Institute of Standards and Technology (NIST), one such technique using radiachromic films was considered, tested, …
Date:
May 25, 2004
Creator:
Alderman, J.; Semones, E. & Job, P. K.
Object Type:
Report
System:
The UNT Digital Library
Timpson & Tenaha News (Timpson, Tex.), Vol. 19, No. 13, Ed. 1 Thursday, March 25, 2004
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
March 25, 2004
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Timpson & Tenaha News (Timpson, Tex.), Vol. 19, No. 46, Ed. 1 Thursday, November 25, 2004
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
November 25, 2004
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Oral History Interview with Douglas R. Crawford, February 25, 2004
Access:
Use of this item is restricted to the UNT Community
Interview with Air Force veteran Douglas R. "Roy" Crawford. The interview includes Crawford's personal experiences about early family life, joining the U.S. Army Air Forces, training as a bulldozer operator, removing radioactive debris from Hiroshima, training as a radar operator at Edwards Air Force Base, California, and working as the radar tracker when Major Chuck Yeager broke the sound barrier in the Bell X-1 on October 19, 1947. Additionally, Crawford talks about his assignments to Clark Air Force Base, Philippines, and Korea, as a forward air observer, his role as an airborne radar operator during the Bay of Pigs invasion and the Cuban Missile Crisis, his various activities with the NASA Space Program, and clandestine missions with the CIA and Air America over Cambodia during the Vietnam War.
Date:
February 25, 2004
Creator:
Alexander, William J. & Crawford, Douglas R., 1929-
Object Type:
Book
System:
The UNT Digital Library
Reactive Multiphase Behavior of CO2 in Saline Aquifers Beneath the Colorado Plateau
Field and laboratory investigations of naturally occurring CO{sub 2}-reservoirs are being conducted to determine the characteristics of potential seal and reservoir units and the extent of the interactions that occur between the host rocks and the CO{sub 2} charged fluids. Efforts have focused on the Farnham Dome field, located in central Utah, the Springerville-St. Johns field in Arizona and New Mexico, and most recently, the Crystal Geyser-Salt Wash graben areas with their CO{sub 2}-charged geysers and springs in central Utah. At both the Springerville-St. Johns field and the central Utah CO{sub 2} spring area, there is evidence of extensive travertine deposits that document release of CO{sub 2} to the atmosphere. At Farnham Dome, calcite debris fields appear to be remnants of vein calcite and an earlier period of fluid leakage. The main achievements during this quarter are (1): preparation for a soil gas flux survey in October at the Crystal Geyser --Little Grand Wash fault zone, and the Salt Wash graben; (2) submission of an abstract to the upcoming Measurement, Monitoring and Verification session at the Fall AGU meeting; (3) submission of an invited abstract to the Gordon Conference on Hydrocarbon Resources; and (4) receipt of initial radiocarbon dates of …
Date:
October 25, 2004
Creator:
Allis, R. G.; Moore, J. & White, S.
Object Type:
Report
System:
The UNT Digital Library
Altus Times (Altus, Okla.), Vol. 105, No. 268, Ed. 1 Sunday, January 25, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
January 25, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 105, No. 295, Ed. 1 Wednesday, February 25, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
February 25, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 105, No. 320, Ed. 1 Thursday, March 25, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
March 25, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 21, Ed. 1 Sunday, April 25, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
April 25, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 47, Ed. 1 Tuesday, May 25, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
May 25, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 74, Ed. 1 Friday, June 25, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
June 25, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 99, Ed. 1 Sunday, July 25, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
July 25, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 125, Ed. 1 Wednesday, August 25, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
August 25, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 177, Ed. 1 Monday, October 25, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
October 25, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Altus Times (Altus, Okla.), Vol. 106, No. 197, Ed. 1 Thursday, November 25, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
November 25, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The CDF Run IIb Silicon Detector
Fermilab plans to deliver 5-15 fb{sup -1} of integrated luminosity to the CDF and D0 experiments. The current inner silicon detectors at CDF (SVXIIa and L00) will not tolerate the radiation dose associated with high luminosity running and will need to be replaced. A new readout chip (SVX4) has been designed in radiation-hard 0.25 {micro}m CMOS technology. Single sided sensors are arranged in a compact structure, called a stave, with integrated readout and cooling systems. This paper describes the general design of the Run IIb system, testing results of prototype electrical components (staves), and prototype silicon sensor performance before and after irradiation.
Date:
February 25, 2004
Creator:
Aoki, M.; Bacchetta, N. & al., S. Behari et
Object Type:
Article
System:
The UNT Digital Library
Compatible Spatial Discretizations for Partial Differential Equations
From May 11--15, 2004, the Institute for Mathematics and its Applications held a hot topics workshop on Compatible Spatial Discretizations for Partial Differential Equations. The numerical solution of partial differential equations (PDE) is a fundamental task in science and engineering. The goal of the workshop was to bring together a spectrum of scientists at the forefront of the research in the numerical solution of PDEs to discuss compatible spatial discretizations. We define compatible spatial discretizations as those that inherit or mimic fundamental properties of the PDE such as topology, conservation, symmetries, and positivity structures and maximum principles. A wide variety of discretization methods applied across a wide range of scientific and engineering applications have been designed to or found to inherit or mimic intrinsic spatial structure and reproduce fundamental properties of the solution of the continuous PDE model at the finite dimensional level. A profusion of such methods and concepts relevant to understanding them have been developed and explored: mixed finite element methods, mimetic finite differences, support operator methods, control volume methods, discrete differential forms, Whitney forms, conservative differencing, discrete Hodge operators, discrete Helmholtz decomposition, finite integration techniques, staggered grid and dual grid methods, etc. This workshop seeks to foster …
Date:
November 25, 2004
Creator:
Arnold, Douglas, N.
Object Type:
Report
System:
The UNT Digital Library
[Letter to Hilton Americus Houston]
Letter from Shannon Bailey and Al Daniels to the GM of the Hilton Americus hotel in Houston about the staff of the hotel's excellence, with attached business card.
Date:
June 25, 2004
Creator:
Bailey, Shannon; Daniels, Al
Object Type:
Letter
System:
The UNT Digital Library
[Letter to Hilton Americus Houston]
Unsigned copy of a letter from Shannon Bailey and Al Daniels to the general manager of the Houston Hilton Americus hotel commending their staff for their work.
Date:
June 25, 2004
Creator:
Bailey, Shannon; Daniels, Al
Object Type:
Letter
System:
The UNT Digital Library
Large-Actuator-Number Horizontal Path Correction of Atmospheric Turbulence utilizing an Interferometric Phase Conjugate Engine
An adaptive optical system used to correct horizontal beam propagation paths has been demonstrated. This system utilizes an interferometric wave-front sensor and a large-actuator-number MEMS-based spatial light modulator to correct the aberrations incurred by the beam after propagation along the path. Horizontal path correction presents a severe challenge to adaptive optics systems due to the short atmospheric transverse coherence length and the high degree of scintillation incurred by laser propagation along these paths. Unlike wave-front sensors that detect phase gradients, however, the interferometric wave-front sensor measures the wrapped phase directly. Because the system operates with nearly monochromatic light and uses a segmented spatial light modulator, it does not require that the phase be unwrapped to provide a correction and it also does not require a global reconstruction of the wave-front to determine the phase as required by gradient detecting wave-front sensors. As a result, issues with branch points are eliminated. Because the atmospheric probe beam is mixed with a large amplitude reference beam, it can be made to operate in a photon noise limited regime making its performance relatively unaffected by scintillation. The MEMS-based spatial light modulator in the system contains 1024 pixels and is controlled to speeds in excess …
Date:
August 25, 2004
Creator:
Baker, K. L.; Stappaerts, E. A.; Gavel, D.; Tucker, J.; Silva, D. A.; Wilks, S. C. et al.
Object Type:
Article
System:
The UNT Digital Library
Final Progress Report: Direct Experiments on the Ocean Disposal of Fossil Fuel CO2.
OAK-B135 This report summarizes activities and results of investigations of the potential environmental consequences of direct injection of carbon dioxide into the deep-sea as a carbon sequestration method. Results of field experiments using small scale in situ releases of liquid CO2 are described in detail. The major conclusions of these experiments are that mortality rates of deep sea biota will vary depending on the concentrations of CO2 in deep ocean waters that result from a carbon sequestration project. Large changes in seawater acidity and carbon dioxide content near CO2 release sites will likely cause significant harm to deep-sea marine life. Smaller changes in seawater chemistry at greater distances from release sites will be less harmful, but may result in significant ecosystem changes.
Date:
May 25, 2004
Creator:
Barry, James P. & Brewer, Peter G.
Object Type:
Report
System:
The UNT Digital Library
Synthesis of High Surface Area Alumina Aerogels without the Use of Alkoxide Precursors
Alumina aerogels were prepared through the addition of propylene oxide to aqueous or ethanolic solutions of hydrated aluminum salts, AlCl{sub 3} {center_dot} 6H{sub 2}O or Al(NO{sub 3}){sub 3} {center_dot} 9H{sub 2}O, followed by drying with supercritical CO{sub 2}. This technique affords low-density (60-130 kg/m{sup 3}), high surface area (600-700 m{sup 2}/g) alumina aerogel monoliths without the use of alkoxide precursors. The dried alumina aerogels were characterized using elemental analysis, high-resolution transmission electron microscopy, powder X-ray diffraction, solid state NMR, acoustic measurements and nitrogen adsorption/desorption analysis. Powder X-ray diffraction and TEM analysis indicated that the aerogel prepared from hydrated AlCl{sub 3} in water or ethanol possessed microstructures containing highly reticulated networks of pseudoboehmite fibers, 2-5 nm in diameter and of varying lengths, while the aerogels prepared from hydrated Al(NO{sub 3}){sub 3} in ethanol were amorphous with microstructures comprised of interconnected spherical particles with diameters in the 5-15 nm range. The difference in microstructure resulted in each type of aerogel displaying distinct physical and mechanical properties. In particular, the alumina aerogels with the weblike microstructure were far more mechanically robust than those with the colloidal network, based on acoustic measurements. Both types of alumina aerogels can be transformed to {gamma}-Al{sub 2}O{sub 3} …
Date:
June 25, 2004
Creator:
Baumann, T. F.; Gash, A. E.; Chinn, S. C.; Sawvel, A. M.; Maxwell, R. S. & Satcher, J. H.
Object Type:
Article
System:
The UNT Digital Library