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Enthalpy of Formation of the Cyclohexadienyl Radical and the C-H Bond Enthalpy of 1,4-Cyclohexadiene: An Experimental and Computational Re-Evaluation

Description: Article on an experimental and computational re-evaluation and the enthalpy of formation of the cyclohexadienyl radical and the C-H bond enthalpy of 1,4-cyclohexadiene.
Date: June 2, 2009
Creator: Gao, Yide; DeYonker, Nathan J.; Garrett, E. Chauncey; Wilson, Angela K.; Cundari, Thomas R., 1964- & Marshall, Paul
Partner: UNT College of Arts and Sciences

Development of a high-power lithium-ion battery.

Description: Safety is a key concern for a high-power energy storage system such as will be required in a hybrid vehicle. Present lithium-ion technology, which uses a carbon/graphite negative electrode, lacks inherent safety for two main reasons: (1) carbon/graphite intercalates lithium at near lithium potential, and (2) there is no end-of-charge indicator in the voltage profile that can signal the onset of catastrophic oxygen evolution from the cathode (LiCoO{sub 2}). Our approach to solving these safety/life problems is to replace the graphite/carbon negative electrode with an electrode that exhibits stronger two-phase behavior further away from lithium potential, such as Li{sub 4}Ti{sub 5}O{sub 12}. Cycle-life and pulse-power capability data are presented in accordance with the Partnership for a New Generation of Vehicles (PNGV) test procedures, as well as a full-scale design based on a spreadsheet model.
Date: September 2, 1998
Creator: Jansen, A. N.
Partner: UNT Libraries Government Documents Department

Uncertainty Propagation in Calibration of Parallel Kinematic Machines

Description: Over the last decade, multi-axis machine tools and robots based on parallel kinematic mechanisms (PKMs) have been developed and marketed worldwide. Positional accuracy in these machines is controlled by accurate knowledge of the kinematic parameters which consists of the joint center locations and distances between joint pairs. Since these machines tend to be rather large in size, the kinematic parameters (joint center locations, and initial strut lengths) are difficult to determine when these machines are in their fully assembled state. Work recently completed by the University of Florida and Sandia National Laboratories has yielded a method for determining all of the kinematic parameters of an assembled parallel kinematic device. This paper contains a brief synopsis of the calibration method created, an error budget, an uncertainty analysis for the recovered kinematic parameters and the propagation of these uncertainties to the tool tip.
Date: November 2, 1999
Partner: UNT Libraries Government Documents Department

Development of mixed-conducting ceramics for gas separation applications.

Description: Mixed-conducting oxides are used in many applications, including fuel cells, gas separation membranes, sensors, and electrocatalysis. This paper describes mixed-conducting ceramic membranes that are being developed to selectively remove oxygen and hydrogen from gas streams in a nongalvanic mode of operation (i.e., with no electrodes or external power supply). Because of its high combined electronic/ionic conductivity and significant oxygen permeability, the mixed-conducting Sr-Fe-Co oxide (SFC) has been developed for high-purity oxygen separation and/or partial oxidation of methane to synthesis gas, i.e., syngas, a mixture of carbon monoxide and hydrogen. The electronic and ionic conductivities of SFC were found to be comparable in magnitude and are presented as a function of temperature. The oxygen flux through dense SFC tubes during separation of oxygen from air is compared with the oxygen flux during methane conversion. Unlike SFC, in which the ionic and electronic conductivities are nearly equivalent, BaCe{sub 0.80}Y{sub 0.20}O{sub 3} (BCY) exhibits protonic conductivity that is significantly higher than its electronic conductivity. To enhance the electronic conductivity and increase hydrogen permeation, metal powder was combined with the BCY to form a cermet membrane. Nongalvanic permeation of hydrogen through the cermet membrane was demonstrated and characterized as a function of membrane thickness. A sintering aid was developed to avoid interconnected porosity in and improve the mechanical properties of the cermet membrane.
Date: December 2, 1998
Creator: Balachandran, U.
Partner: UNT Libraries Government Documents Department

HTS wire irradiation test with 8 GeV protons

Description: The radiation level at High Energy Particle Accelerators (HEPA) is relatively high. Any active component which should be close to the accelerator has to be radiation hard. Since High Temperature Superconductors (HTS) have a great potential to be used in HEPAs (e.g., in superconducting magnets, current leads, RF cavities), it is important to understand the radiation hardness of these materials. A radiation test of HTS wire (Bi-2223) was performed at Fermilab. The HTS sample was irradiated with 8 GeV protons and the relative I{sub c} was measured during the irradiation. The total radiation dose was 10 Mrad, and no I{sub c} degradation was observed.
Date: November 2, 1999
Creator: Feher, S.; Glass, H.; Huang, Y.; Limon, P.J.; Orris, D.F.; Schlabach, P. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the CP violation parameter sin(2{beta}) in B{sup 0} {r_arrow}J/{psi} K{sub s}{sup 0} Decays

Description: A sample of {approximately} 400 B{sub d}{sup 0}/{bar B}{sub d}{sup 0} {r_arrow} J/{psi}K{sub s}{sup 0} decays collected in {bar p}p collisions by the CDF detector is used to directly measure the CP-violation parameter sin (2{beta}). They find sin(2{beta}) = 0.79{sub {minus}0.44}{sup + 0.41}, favoring the standard model expectation of a large CP violation in this B{sup 0} decay mode.
Date: September 2, 1999
Creator: Bauer, G.
Partner: UNT Libraries Government Documents Department

Uniform Strain Elements for Three-Node Triangular and Four-Node Tetrahedral Meshes

Description: A family of uniform strain elements is presented for three-node triangular and four-node tetrahedral meshes. The elements use the linear interpolation functions of the original mesh, but each element is associated with a single node. As a result, a favorable constraint ratio for the volumetric response is obtained for problems in solid mechanics. The uniform strain elements do not require the introduction of additional degrees of freedom and their performance is shown to be significantly better than that of three-node triangular or four-node tetrahedral elements. In addition, nodes inside the boundary of the mesh are observed to exhibit superconvergent behavior for a set of example problems.
Date: March 2, 1999
Creator: Dohrmann, C.R.; Heinstein, M.W.; Jung, J.; Key, S.W. & Witkowski, W.R.
Partner: UNT Libraries Government Documents Department

System for storing cathodic protection measurement data

Description: This paper describes a custom cathodic protection (CP) database, and discusses how this combination of data structure and software improves the ability to analyze cathodic protection. This may be a unique solution to the task of managing CP data, and may have value to others. This paper is primarily about the database design, and not about cathodic protection, per se. Every database project is a balancing act. A developer can create custom software that performs complex opcrafions requiring modest operator skills. On the other hand, custom software is expensive to both create and maintain. The Hanford CP data system will be used primarily by one person, the CP Engineer. It was concluded that this position could be trained to use off-the-shelf, general purpose database to store data, and spreadsheet software to perform analyses. The database product allows flexibility in data reporting, and enforces referential integrity. The spreadsheet allows many display options. Especially useful are the graphics. This solution entailed minimal computer coding and may lend itself to adoption by others. The data structure was designed by a database application developer, with close guidance from the CP engineer. The system will require modest amounts of attention from computer support staff, primarily for new query development. The data structures are provided in this report, and are available electronically.
Date: December 2, 1996
Creator: Bowman, T.J., Westinghouse Hanford
Partner: UNT Libraries Government Documents Department

Parallel FE Electron-Photon Transport Analysis on 2-D Unstructured Mesh

Description: A novel solution method has been developed to solve the coupled electron-photon transport problem on an unstructured triangular mesh. Instead of tackling the first-order form of the linear Boltzmann equation, this approach is based on the second-order form in conjunction with the conventional multi-group discrete-ordinates approximation. The highly forward-peaked electron scattering is modeled with a multigroup Legendre expansion derived from the Goudsmit-Saunderson theory. The finite element method is used to treat the spatial dependence. The solution method is unique in that the space-direction dependence is solved simultaneously, eliminating the need for the conventional inner iterations, a method that is well suited for massively parallel computers.
Date: March 2, 1999
Creator: Drumm, C.R. & Lorenz, J.
Partner: UNT Libraries Government Documents Department

Reactivity estimation for source-driven systems using first-order perturbation theory.

Description: Applicability of the first-order perturbation (FOP) theory method to reactivity estimation for source-driven systems is examined in this paper. First, the formally exact point kinetics equations have been derived from the space-dependent kinetics equations and the kinetics parameters including the dynamic reactivity have been defined. For the dynamic reactivity, exact and first-order perturbation theory expressions for the reactivity change have been formulated for source-driven systems. It has been also shown that the external source perturbation itself does not change the reactivity if the initial {lambda}-mode adjoint flux is used as the weight function. Using two source-driven benchmark problems, the reactivity change has been estimated with the FOP theory method for various perturbations. By comparing the resulting reactivity changes with the exact dynamic reactivity changes determined from the space-dependent kinetics solutions, it has been shown that the accuracy of the FOP theory method for the accelerator-driven system (ADS) is reasonably good and comparable to that for the critical reactors. The adiabatic assumption has also been shown to be a good approximation for the ADS kinetics analyses.
Date: July 2, 2002
Creator: Kim, Y.; Yang, W. S.; Taiwo, T. A. & Hill, R. N.
Partner: UNT Libraries Government Documents Department

Microwave radar detection of gas pipeline leaks.

Description: We are developing a microwave radar sensing and imaging system to detect and locate gas leaks in natural gas pipelines. The underlying detection principle is radar backscattering from the index-of-refraction inhomogeneities introduced by the dispersion of methane in air. An essential first step in the development effort is modeling to estimate the radar cross section. This paper describes the modeling results and the experimental efforts underway to validate the model. For the case of leaks from small holes in a pressurized gas pipeline, we modeled the gas dynamics of the leak jet to determine the plume geometry and the variation of methane concentration in air as a function of distance from the leak source. From the static and dynamic changes in the index of refraction in the turbulent plume, the radar backscatter cross sections were calculated. The results show that the radar cross sections of the leak plumes should be detectable by special-purpose radars.
Date: October 2, 2002
Creator: Gopalsami, N.; Kanareykin, D. B.; Asanov, V. D; Bakhtiari, S. & Raptis, A. C.
Partner: UNT Libraries Government Documents Department


Description: The very clean Schottky spectra of gold beams in RHIC allow an accurate measurement of potential well distortion. By observing the variation in the small amplitude, incoherent synchrotron tune with intensity and bunch length, the intensity dependent longitudinal force can be measured. Dynamical effects associated with coherent motion are not important though some new dynamical effects appear. Measurements were carried out both at injection energy and store, which allowed the space charge and wall contributions to be individually determined.
Date: June 2, 2002
Partner: UNT Libraries Government Documents Department


Description: Beam stability up the ramp requires the appropriate sign and magnitude of the chromaticity. We developed a way to measure the chromaticity using the PLL (Phase Locked Loop) tune-meter. Since, the accuracy of the PLL tune-meter with properly adjusted loop gain is better than {approx} 0.0001 in tune units, the radial loop needs only be changed by a small amount of 0.2mm at a 1Hz rate. Thus, we can achieve fast chromaticity measurements in 1 sec. Except during the very beginning of the ramp where there are snapback effects and the gamma changes very rapidly, we can have good chromaticcity measurements along the ramp. This leads to the possibility of correcting the chromaticity during the ramp using a feedback system.
Date: June 2, 2002
Partner: UNT Libraries Government Documents Department

Time-resolved measurement of a self-amplified free-electron laser.

Description: We report on a time-resolved measurement of self-amplified spontaneous emission (SASE) free-electron laser (FEL) pulses. We observed that the spikes in the output of such free-electron laser pulses have an intrinsic positive chirp and the energy chirp in the electron bunch mapped directly into the FEL output. The measurement also provides rich information on the statistics of the FEL output.
Date: October 2, 2002
Creator: Li, Y.; Lewellen, J.; Huang, Z.; Sajaev, V. & Milton, S. V.
Partner: UNT Libraries Government Documents Department

Materials for low temperature SOFCs.

Description: Solid oxide fuel cells (SOFCs) are one of the potentially most efficient and clean energy conversion technologies for electric utility applications. Laboratory cells have shown extraordinary durability, and actual utility-scale prototypes have worked very well. The main obstacle to commercialization has been the relatively high manufacturing cost. To reduce these costs, efforts have been underway for several years to adapt manufacturing technology from the semiconductor industry to the SOFCs; however, tape casting, screen printing and similar methods are more applicable to planar configurations than to the more proven tubular ones. In planar cells the bipolar plate and edge seals become more critical elements, and material selection may have repercussions for the other fuel cell components. Ferritic stainless steel bipolar plates may be a good choice for reducing the cost of the stacks, but ferritic steels oxidize rapidly at temperatures above 800 C. Inexorably, one is led to the conclusion that anodes, cathodes and electrolytes operating below 800 C need to be found. Another motivation for developing planar SOFCs operating at reduced temperature is the prospect of new non-utility applications. The U.S. Department of Energy has initiated the Solid State Energy Conversion Alliance (SECA) program for developing small modular stacks ranging in capacity from 5 to 10 kW{sup (1)}. This size range meets the power requirements of auxiliary power units for heavy and perhaps even light-duty vehicles, and also for remote stationary applications. In terms of electric capacity, the distributed electric utility market may well exceed the potential market for APUs, but the number of units produced could be higher for the latter, yielding cost benefits related to mass production. On the other hand, the fuel for use in transportation or remote stationary applications will consist of gasoline, diesel or propane, which contain higher sulfur levels than natural gas. Anodes with ...
Date: August 2, 2002
Creator: Krumpelt, M.; Ralph, J.; Cruse, T. & Bae, J.-M.
Partner: UNT Libraries Government Documents Department

Jet algorithms at D0

Description: The D0 experiment at the Fermilab Tevatron proton-antiproton collider ({radical}s = 1.8 TeV) accumulated a large sample of high energy jet production data during Run 1 (1992-1996). Since March 2001, D0 has engaged in continuous data collection with an upgraded detector equipped for the higher energy ({radical}s = 1.96 TeV) and luminosity conditions of the Run 2 Tevatron. We summarize here pivotal measurements of Run 1 and consider their comparison to theoretical predictions and to other experiments. These factors elucidate D0's jet clustering algorithm strategy for Run 2 jet measurements. Preliminary measurements of jets from the Run 2 D0 experiment are also presented.
Date: January 2, 2003
Creator: Gallas, Elizabeth
Partner: UNT Libraries Government Documents Department

Top: Latest results from the Tevatron - Cross section and mass

Description: The Tevatron is presently the world's only source of top quark production. This presentation summarizes the latest Run II results on top physics obtained by the CDF and D0 collaborations, using data taken until mid-January 2003. The first cross section measurements at 1.96 TeV in dilepton and lepton+jets channels agree with the NLO (Next-to-Leading-Order) theoretical predictions. Two top mass measurements, one by CDF using Run II data and another by D0 using an improved technique anticipate the improvements to come in the near future.
Date: September 2, 2003
Creator: Coca, M.
Partner: UNT Libraries Government Documents Department


Description: The RHIC 2001-2 Au and polarized proton runs used several different low-beta optics configurations. Low-beta squeezes were routinely performed through the Au acceleration ramp to optimize injection and transition optics; the polarized proton run injected and accelerated with constant low-beta optics to optimize polarization preservation. This paper summarizes tools, methods and results for linear optics measurement and correction during these runs as well as future plans.
Date: June 2, 2002
Partner: UNT Libraries Government Documents Department

Imaging columns of the light elements carbon, nitrogen and oxygen with sub angstrom resolution

Description: It is reported that lattice imaging with a 300 kV field emission microscope in combination with numerical reconstruction procedures can be used to reach an interpretable resolution of about 80 pm for the first time. A retrieval of the electron exit wave from focal series allows for the resolution of single atomic columns of the light elements carbon, nitrogen, and oxygen at a projected nearest neighbor spacing down to 85 pm. Lens aberrations are corrected on-line during the experiment and by hardware such that resulting image distortions are below 80 pm. Consequently, the imaging can be aberration-free to this extent. The resolution enhancement results from increased electrical and mechanical stability's of the instrument coupled with a low spherical aberration coefficient of 0.595 + 0.005 mm.
Date: January 2, 2000
Creator: Kisielowski, C.; Hetherington, C.J.D.; Wang, Y.C.; Kilaas, R.; O'Keefe, M.A. & Thust, A.
Partner: UNT Libraries Government Documents Department

Search for eta b at CDF

Description: The {eta}{sub b} (1S) is the J{sup PC} = 0{sup {-+}} b{bar b} ground state, and has not yet been experimentally observed. Theorists have recently suggested that it could be observed at the Fermilab Tevatron through its decay to J/{psi}J/{psi}, if not in the 1992-96 (''Run 1'') dataset, then in Run 2. This article describes a search for this particle at CDF in Run 1 using this decay channel. A small cluster is seen, with 7 events where 1.8 events are expected from background. The statistical significance is estimated to be 2.2{sigma}, and an upper limit is set on the product of cross section and branching fractions.
Date: January 2, 2003
Creator: Tseng, J.
Partner: UNT Libraries Government Documents Department