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An Ab Initio Approach Towards Engineering Fischer-Tropsch Surface Chemistry (open access)

An Ab Initio Approach Towards Engineering Fischer-Tropsch Surface Chemistry

As the US seeks to develop an energy strategy that reduces the reliance on foreign oil, there is a renewed interest in research and development of the Fischer Tropsch synthesis of converting syngas into long chain hydrocarbon products. This report investigates some of the basic elementary steps for Fischer-Tropsch synthesis over ideal Co and Ru metal surfaces by using ab initio density functional theoretical calculations. This includes activation of CO of CO, the hydrogenation of CH{sub x} intermediates, and the adsorption and dissociation of water. The activation of CO is studied in detail showing a strong dependence on the surface coverage, defect sites and Co-Ru alloy formation. The barriers for CO activation over the ideal (0001) surfaces are quite high making CO activation at the terrace sites unlikely under operating conditions. The calculations for the overall reaction energies at the step edges indicate that these sites are much more reactive. The hydrogenation of the CHx intermediates occurs in a sequential fashion. CH1 was found to be the most stable intermediate over various surfaces. The barriers to form both CH* as well as CH{sub 4} are both found to be highly activated and potentially difficult steps. Water which is a reaction …
Date: September 11, 2002
Creator: Neurock, Matthew
Object Type: Report
System: The UNT Digital Library
Absorption Spectra of Broadened Sodium Resonance Lines in Presence of Rare Gases (open access)

Absorption Spectra of Broadened Sodium Resonance Lines in Presence of Rare Gases

The pressure broadening of alkali-metal lines is a fundamental problem with numerous applications. For example, the sodium resonance lines broadened by xenon are important in the production of broad spectra emitted in the HPS (High-Pressure Sodium) lamp and they potentially can be used for gas condition diagnostics. Broadened absorption lines of alkali-metal atoms are prominent in the optical spectra of brown dwarfs and understanding the broadening mechanism will help elucidate the chemical composition and atmospheric properties of those stars. The far-line wing spectra of sodium resonance lines broadened by rare gases are found to exhibit molecular characteristics such as satellites and hence the total absorption coefficients for vapors of Na atoms and perturbing rare gas atoms can be modeled as Na-RG (rare gas) molecular absorption spectra. In this work, using carefully chosen interatomic potentials for Na-RG molecules we carry out quantum-mechanical calculations for reduced absorption coefficients for vapors composed of Na-He, Na-Ar, and Na-Xe. Calculated spectra are compared to available experimental results and the agreement is good in the measured satellite positions and shapes.
Date: September 11, 2002
Creator: Chung, H-K; Shurgalin, M & Babb, J F
Object Type: Article
System: The UNT Digital Library
Altus Times (Altus, Okla.), Vol. 104, No. 152, Ed. 1 Wednesday, September 11, 2002 (open access)

Altus Times (Altus, Okla.), Vol. 104, No. 152, Ed. 1 Wednesday, September 11, 2002

Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date: September 11, 2002
Creator: Bush, Michael
Object Type: Newspaper
System: The Gateway to Oklahoma History
The Alvin Advertiser (Alvin, Tex.), Ed. 1 Wednesday, September 11, 2002 (open access)

The Alvin Advertiser (Alvin, Tex.), Ed. 1 Wednesday, September 11, 2002

Weekly newspaper from Alvin, Texas that includes local, state, and national news along with advertising.
Date: September 11, 2002
Creator: Schwind, Jim & Holton, Kathleen
Object Type: Newspaper
System: The Portal to Texas History
Appropriations for FY2003: Military Construction (open access)

Appropriations for FY2003: Military Construction

Appropriations are one part of a complex federal budget process that includes budget resolutions, appropriations (regular, supplemental, and continuing) bills, rescissions, and budget reconciliation bills. This report is a guide to one of the 13 regular appropriations bills that Congress considers each year. It is designed to supplement the information provided by the House and Senate Defense Appropriations Subcommittees.
Date: September 11, 2002
Creator: Else, Daniel H.
Object Type: Report
System: The UNT Digital Library
The Baytown Sun (Baytown, Tex.), Vol. 80, No. 289, Ed. 1 Wednesday, September 11, 2002 (open access)

The Baytown Sun (Baytown, Tex.), Vol. 80, No. 289, Ed. 1 Wednesday, September 11, 2002

Daily newspaper from Baytown, Texas that includes local, state, and national news along with advertising.
Date: September 11, 2002
Creator: Cash, Wanda Garner
Object Type: Newspaper
System: The Portal to Texas History
Cherokeean/Herald (Rusk, Tex.), Vol. 153, No. 29, Ed. 1 Wednesday, September 11, 2002 (open access)

Cherokeean/Herald (Rusk, Tex.), Vol. 153, No. 29, Ed. 1 Wednesday, September 11, 2002

Weekly newspaper from Rusk, Texas that includes local, state and national news along with extensive advertising.
Date: September 11, 2002
Creator: Whitehead, Marie
Object Type: Newspaper
System: The Portal to Texas History
The Clifton Record (Clifton, Tex.), Vol. 107, No. 73, Ed. 1 Wednesday, September 11, 2002 (open access)

The Clifton Record (Clifton, Tex.), Vol. 107, No. 73, Ed. 1 Wednesday, September 11, 2002

Semi-weekly newspaper from Clifton, Texas that includes local, state, and national news along with advertising.
Date: September 11, 2002
Creator: Smith, W. Leon
Object Type: Newspaper
System: The Portal to Texas History
The Collegian (Hurst, Tex.), Vol. 15, No. 2, Ed. 1 Wednesday, September 11, 2002 (open access)

The Collegian (Hurst, Tex.), Vol. 15, No. 2, Ed. 1 Wednesday, September 11, 2002

Weekly student newspaper published in Hurst, Texas and serving the Tarrant County College District that includes school news and information along with advertising.
Date: September 11, 2002
Creator: unknown
Object Type: Newspaper
System: The Portal to Texas History
The Colony Courier-Leader (The Colony, Tex.), Vol. 21, No. 31, Ed. 1 Wednesday, September 11, 2002 (open access)

The Colony Courier-Leader (The Colony, Tex.), Vol. 21, No. 31, Ed. 1 Wednesday, September 11, 2002

Weekly newspaper from The Colony, Texas that includes local, state, and national news along with advertising.
Date: September 11, 2002
Creator: Shafer, Leah
Object Type: Newspaper
System: The Portal to Texas History
Comparative Dosimetric Estimates of a 25 keV Electron Micro-beam with three Monte Carlo Codes (open access)

Comparative Dosimetric Estimates of a 25 keV Electron Micro-beam with three Monte Carlo Codes

The calculations presented compare the different performances of the three Monte Carlo codes PENELOPE-1999, MCNP-4C and PITS, for the evaluation of Dose profiles from a 25 keV electron micro-beam traversing individual cells. The overall model of a cell is a water cylinder equivalent for the three codes but with a different internal scoring geometry: hollow cylinders for PENELOPE and MCNP, whereas spheres are used for the PITS code. A cylindrical cell geometry with scoring volumes with the shape of hollow cylinders was initially selected for PENELOPE and MCNP because of its superior simulation of the actual shape and dimensions of a cell and for its improved computer-time efficiency if compared to spherical internal volumes. Some of the transfer points and energy transfer that constitute a radiation track may actually fall in the space between spheres, that would be outside the spherical scoring volume. This internal geometry, along with the PENELOPE algorithm, drastically reduced the computer time when using this code if comparing with event-by-event Monte Carlo codes like PITS. This preliminary work has been important to address dosimetric estimates at low electron energies. It demonstrates that codes like PENELOPE can be used for Dose evaluation, even with such small geometries …
Date: September 11, 2002
Creator: Mainardi, Enrico; Donahue, Richard J. & Blakely, Eleanor A.
Object Type: Report
System: The UNT Digital Library
Corrosion Test Results for Inconel 600 vs Inconel-Stainless UG Bellows (open access)

Corrosion Test Results for Inconel 600 vs Inconel-Stainless UG Bellows

The Conversion Project (CP) of the Molten Salt Reactor Experiment at Oak Ridge National Laboratory (ORNL) involves converting slightly less than 40 kg of {sup 233}U to a stable form for safe storage. The operation is performed within a few vessels interconnected by valves and 1/2-in. metal tubing. During this conversion, a particularly toxic and corrosive by-product is formed, namely aqueous hydrofluoric acid (HF). The production of HF is a result of the hydrolysis of UF{sub 6} and subsequent steam treatments of UO{sub 2}F{sub 2}. For each mole of UF{sub 6} converted, 6 mol of HF are produced. The HF that forms during conversion combines with water to produce approximately 1.5 L of 33 wt % HF. As this mixture is transferred within the process system, the tubing and valves are exposed to high concentrations of HF in liquid and vapor form. Of particular concern in the system are the almost 30 valves that have the potential for exposure to HF. For these valves, a vendor-supplied UG valve was installed. UG valves consist of an Alloy 400 (Monel) body and stem tip and Alloy 600 (Inconel) bellows. These valves have been used under experimental conditions that simulate the CP. It …
Date: September 11, 2002
Creator: Osborne, P. E.
Object Type: Report
System: The UNT Digital Library
The Cuero Record (Cuero, Tex.), Vol. 108, No. 37, Ed. 1 Wednesday, September 11, 2002 (open access)

The Cuero Record (Cuero, Tex.), Vol. 108, No. 37, Ed. 1 Wednesday, September 11, 2002

Weekly newspaper from Cuero, Texas that includes local, state, and national news along with advertising.
Date: September 11, 2002
Creator: Rea, Glenn
Object Type: Newspaper
System: The Portal to Texas History
Daily Journal (Perry, Okla.), Vol. 109, No. 179, Ed. 1 Wednesday, September 11, 2002 (open access)

Daily Journal (Perry, Okla.), Vol. 109, No. 179, Ed. 1 Wednesday, September 11, 2002

Daily newspaper from Perry, Oklahoma that includes local, state, and national news along with advertising.
Date: September 11, 2002
Creator: Brown, Gloria
Object Type: Newspaper
System: The Gateway to Oklahoma History
Effects of landscape disturbance on ecohydrologic systems (open access)

Effects of landscape disturbance on ecohydrologic systems

None
Date: September 11, 2002
Creator: Newman, Brent D.; Allen, Craig Daniel; Breshears, David D. & Wilson, Cathy J.
Object Type: Article
System: The UNT Digital Library
Electrophilic metal alkyl chemistry in new ligand environments (open access)

Electrophilic metal alkyl chemistry in new ligand environments

Cationic group 4 and actinide Cp{sub 2}MR{sup +} metallocenes, and isolobal neutral group 3 and lanthanide Cp{sub 2}MR analogs, are exceptionally reactive in insertion and {sigma}-bond metathesis processes, and have been exploited extensively in catalysis and synthesis, most notably single-site olefin polymerization. The objectives of recent work were to design new electrophilic metal alkyls based on non-Cp{sub 2}M structures, and to exploit these systems in fundamental and applied studies related to olefin polymerization and other catalytic reactions. Key results are reported in the following areas: discrete non-metallocene cationic group 4 alkyls, activation of non-metallocene compounds with methylalumoxane, and cationic aluminum alkyl compounds. Numerous structural formulas are included.
Date: September 11, 2002
Creator: Jordan, Richard F.
Object Type: Report
System: The UNT Digital Library
The Express-Star (Chickasha, Okla.), Ed. 1 Wednesday, September 11, 2002 (open access)

The Express-Star (Chickasha, Okla.), Ed. 1 Wednesday, September 11, 2002

Daily newspaper from Chickasha, Oklahoma that includes local, state, and national news along with advertising.
Date: September 11, 2002
Creator: Bush, Kent
Object Type: Newspaper
System: The Gateway to Oklahoma History
F-22 Raptor Aircraft Program (open access)

F-22 Raptor Aircraft Program

This report discusses the background information, analysis and the recent developments in the F-22 Raptor Aircraft Program. The F-22 program raises questions about its cost and the need for this aircraft, the capabilities it would have, and the number of these planes needed to meet military requirements. The F-22 has had strong congressional support, although some have criticized the program on grounds of cost, requirements, and coordination with other tactical aircraft programs. Deletion of procurement funds in the FY2000 defense appropriation bill passed by the House made the future of the program a major issue for House and Senate conferees in 1999.
Date: September 11, 2002
Creator: Bolkcom, Christopher
Object Type: Report
System: The UNT Digital Library
Fine-grain authorization for resource management in the Grid environment (open access)

Fine-grain authorization for resource management in the Grid environment

In this document we describe our work-in-progress for enabling fine-grain authorization of resource management. In particular we address the needs of Virtual Organizations (VOs) to enforce their own polices in addition to those of the resource owners 1.
Date: September 11, 2002
Creator: Keahey, K. & Welch, V.
Object Type: Article
System: The UNT Digital Library
Grid and Zone Selection for AMR and ALE Schemes (open access)

Grid and Zone Selection for AMR and ALE Schemes

Numerical algorithms are based fundamentally on polynomial interpolation. In regions of the computational domain where a low order polynomial fits the data well one will find small errors in the computed quantities. Therefore, in order to design robust methods for grid selection for AMR schemes or zone selection for ALE schemes, one needs some information on the local polynomial structure of the fields being computed. We provide here algorithms and software for selecting zones based on local estimates of polynomial interpolation error. The algorithms are based on multiresolution and wavelet analysis.
Date: September 11, 2002
Creator: Jameson, L; Johnson, J; Bihari, B; Eliason, D & Peyser, T
Object Type: Report
System: The UNT Digital Library
Hydrofluoric Acid Corrosion Study of High-Alloy Materials (open access)

Hydrofluoric Acid Corrosion Study of High-Alloy Materials

A corrosion study involving high-alloy materials and concentrated hydrofluoric acid (HF) was conducted in support of the Molten Salt Reactor Experiment Conversion Project (CP). The purpose of the test was to obtain a greater understanding of the corrosion rates of materials of construction currently used in the CP vs those of proposed replacement parts. Results of the study will help formulate a change-out schedule for CP parts. The CP will convert slightly less than 40 kg of {sup 233}U from a gas (UF{sub 6}) sorbed on sodium fluoride pellets to a more stable oxide (U{sub 3}O{sub 8}). One by-product of the conversion is the formation of concentrated HF. Six moles of highly corrosive HF are produced for each mole of UF{sub 6} converted. This acid is particularly corrosive to most metals, elastomers, and silica-containing materials. A common impurity found in {sup 233}U is {sup 232}U. This impurity isotope has several daughters that make the handling of the {sup 233}U difficult. Traps of {sup 233}U may have radiation fields of up to 400 R at contact, a situation that makes the process of changing valves or working on the CP more challenging. It is also for this reason that a comprehensive …
Date: September 11, 2002
Creator: Osborne, P. E.
Object Type: Report
System: The UNT Digital Library
Illustrated Paperboy (Cleveland, Tex.), Vol. 10, No. 25, Ed. 1 Wednesday, September 11, 2002 (open access)

Illustrated Paperboy (Cleveland, Tex.), Vol. 10, No. 25, Ed. 1 Wednesday, September 11, 2002

Weekly newspaper from Cleveland, Texas that includes local, county, and state news along with extensive advertising.
Date: September 11, 2002
Creator: unknown
Object Type: Newspaper
System: The Portal to Texas History
Investigation of passive vibration damping methods for the Advanced Photon Source storage ring girders. (open access)

Investigation of passive vibration damping methods for the Advanced Photon Source storage ring girders.

Beam stability is a major concern for the operation of the APS. One of the many contributing factors to electron-beam instability is mechanical vibration of the accelerator components especially the focusing magnets. The electron beam should be stable to 5% of its rms size to maintain the specified photon beam stability. The APS uses steel girders to support the conventional magnets and vacuum chambers in the storage ring (SR). Three pedestal and jack assemblies support the girders. Damping pads are presently installed between the pedestals and the jacks. These damping pads have been shown to be very effective in reducing the fundamental girder-vibration mode. The horizontal vibration levels of the SR quadrupole magnets are presently within specification at between two and four times the ground motion, i.e., 50-100 nm rms (4-50 Hz). Future improvements to the APS beam quality would require a further reduction in girder vibration. Several options for reducing the vibration of the girders and magnets are discussed, and the measurement results are presented.
Date: September 11, 2002
Creator: Sharma, S. & Doose, C.
Object Type: Article
System: The UNT Digital Library
Iran: Current Developments and U.S. Policy (open access)

Iran: Current Developments and U.S. Policy

Report discussing the most recent political developments in Iran, including who the country offers support to and opposes. The report also makes note of U.S. policy regarding these developments, as well as the measures put in place to ensure continued peaceful relations between the two countries.
Date: September 11, 2002
Creator: Katzman, Kenneth
Object Type: Report
System: The UNT Digital Library