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Vortex Characterization for Engineering Applications (open access)

Vortex Characterization for Engineering Applications

Realistic engineering simulation data often have features that are not optimally resolved due to practical limitations on mesh resolution. To be useful to application engineers, vortex characterization techniques must be sufficiently robust to handle realistic data with complex vortex topologies. In this paper, we present enhancements to the vortex topology identification component of an existing vortex characterization algorithm. The modified techniques are demonstrated by application to three realistic data sets that illustrate the strengths and weaknesses of our approach.
Date: January 30, 2008
Creator: Jankun-Kelly, M; Thompson, D S; Jiang, M; Shannahan, B & Machiraju, R
System: The UNT Digital Library
Is there a low energy enhancement in the photon strength function in molybdenum? (open access)

Is there a low energy enhancement in the photon strength function in molybdenum?

Recent claims of a low energy enhancement in the photon strength function of {sup 96}Mo are investigated. Using the DANCE detector the gamma-ray spectra following resonance neutron capture was measured. The spectrum fitting method was used to indirectly extract a photon strength function from the gamma-ray spectra. No strong low energy enhancement in the photon strength function was found.
Date: January 30, 2008
Creator: Sheets, S A
System: The UNT Digital Library
Synthesis of a Benzodiazepine-derived Rhodium NHC Complex by C-H Bond Activation (open access)

Synthesis of a Benzodiazepine-derived Rhodium NHC Complex by C-H Bond Activation

The synthesis and characterization of a Rh(I)-NHC complex generated by C-H activation of 1,4-benzodiazepine heterocycle are reported. This complex constitutes a rare example of a carbene tautomer of a 1,4-benzodiazepine aldimine stabilized by transition metal coordination and demonstrates the ability of the catalytically relevant RhCl(PCy{sub 3}){sub 2} fragment to induce NHC-forming tautomerization of heterocycles possessing a single carbene-stabilizing heteroatom. Implications for the synthesis of benzodiazepines and related pharmacophores via C-H functionalization are discussed.
Date: January 30, 2008
Creator: Bergman, Roberg G.; Gribble, Jr., Michael W. & Ellman, Jonathan A.
System: The UNT Digital Library
Searches for the Decays B0 to l+- tau-+ and B+ to l+ nu(L=e,mu) using Hadronic Tag Reconstruction (open access)

Searches for the Decays B0 to l+- tau-+ and B+ to l+ nu(L=e,mu) using Hadronic Tag Reconstruction

We present searches for the leptonic decays B{sup +} {yields} {ell}{sup +}{nu} and the lepton flavor violating decays B{sup 0} {yields} {ell}{sup {+-}}{tau}{sup {-+}}, where {ell} = e, {mu}, with data collected by the BABAR experiment at SLAC. This search demonstrates a novel technique in which we fully reconstruct the accompanying {bar B} in {Upsilon}(4S) {yields} B{bar B} events, and look for a monoenergetic lepton from the signal B decay. The signal yield is extracted from a fit to the signal lepton candidate momentum distribution in the signal B rest frame. Using a data sample of approximately 378 million B{bar B} pairs (342 fb{sup -1}), we find no evidence of signal in any of the decay modes. Branching fraction upper limits of {Beta}(B{sup +} {yields} e{sup +}{nu}) < 5.2 x 10{sup -6}, {Beta}(B{sup +} {yields} {mu}{sup +}{nu}) < 5.6 x 10{sup -6}, {Beta}(B{sup 0} {yields} e{sup +}{tau}{sup -}) < 2.8 x 10{sup -5} and {Beta}(B{sup 0} {yields} {mu}{sup +}{tau}{sup -}) < 2.2 x 10{sup -5}, are obtained at 90% confidence level.
Date: January 30, 2008
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prudent, X. et al.
System: The UNT Digital Library
Active RF Pulse Compression using Electrically Controlled Semiconductor Switches (open access)

Active RF Pulse Compression using Electrically Controlled Semiconductor Switches

In this paper, we will present our recent results on the research of the ultra-fast high power RF switches based on silicon. We have developed a switch module at X-band which can use a silicon window as the switch. The switching is realized by generation of carriers in the bulk silicon. The carriers can be generated electrically or/and optically. The electrically controlled switches use PIN diodes to inject carrier. We have built the PIN diode switches at X-band, with <300ns switching time. The optically controlled switches use powerful lasers to excite carriers. By combining the laser excitation and electrical carrier generation, significant reduction in the required power of both the laser and the electrical driver is expected. High power test is under going.
Date: January 30, 2008
Creator: Guo, J. & Tantawi, S. G.
System: The UNT Digital Library
Fabrication and Characterization of Nanolayer Capacitors (open access)

Fabrication and Characterization of Nanolayer Capacitors

None
Date: January 30, 2008
Creator: Chow, R & Ellis, A D
System: The UNT Digital Library
Oxidation Kinetics of High Strength Low Alloy Steels at Elevated Temperatures (open access)

Oxidation Kinetics of High Strength Low Alloy Steels at Elevated Temperatures

None
Date: January 30, 2008
Creator: Talekar, Anjali; Chandra, Dhanesh; Chellappa, Raja; Daemen, Jaak; Tamura, Nobumichi & Kunz, Martin
System: The UNT Digital Library
Tilt sensitivity of the two-grating interferometer (open access)

Tilt sensitivity of the two-grating interferometer

Fringe formation in the two-grating interferometer is analyzed in the presence of a small parallelism error between the diffraction gratings assumed in the direction of grating shear. Our analysis shows that with partially coherent illumination, fringe contrast in the interference plane is reduced in the presence of nonzero grating tilt with the effect proportional to the grating tilt angle and the grating spatial frequencies. Our analysis also shows that for a given angle between the gratings there is an angle between the final grating and the interference plane that optimizes fringe contrast across the field.
Date: January 30, 2008
Creator: Anderson, Christopher N. & Naulleau, Patrick P.
System: The UNT Digital Library
Surrogate Reactions in the Actinide Region (open access)

Surrogate Reactions in the Actinide Region

Over the past three years we have studied various surrogate reactions (d,p), ({sup 3}He,t), ({alpha},{alpha}{prime}) on several uranium isotopes {sup 234}U, {sup 235}U, {sup 236}U, and {sup 238}U. An overview of the STARS/LIBERACE surrogate research program as it pertains to the actinides is discussed. A summary of results to date will be presented along with a discussion of experimental difficulties encountered in surrogate experiments and future research directions.
Date: January 30, 2008
Creator: Burke, J. T.; Bernstein, L. A.; Scielzo, N. D.; Bleuel, D. L.; Lesher, S. R.; Escher, J. et al.
System: The UNT Digital Library
Observation of Multi-GeV Breakdown Thresholds in Dielectric Wakefield Structures (open access)

Observation of Multi-GeV Breakdown Thresholds in Dielectric Wakefield Structures

An experiment designed to test the breakdown threshold of a dielectric subjected to the GV/m-scale electric-fields of an intense electron-beam has been completed. In this experiment at the Final Focus Test Beam (FFTB) facility, the 28.5 GeV SLAC electron beam was focused down and propagated through short fused-silica capillary-tubes with internal diameters of as little as 100 {micro}m. The electric field at the inner surface of the tubes was varied from about 1 GV/m to 22 GV/m by adjusting the longitudinal compression of the electron bunch. We observed a sharp increase in optical emissions from the capillaries in the middle part of this surface field range which we believe indicates the transition between sustainable field levels and breakdown. If this initial interpretation is correct, the multi-GV/m surfaced fields that were sustained equate to on axis accelerating field of several GV/m.
Date: January 30, 2008
Creator: Thompson, M. C.; /LLNL, Livermore; Yoder, R. B.; /Manhattan Coll., Riverdale; Hogan, M. J.; Ischebeck, R. et al.
System: The UNT Digital Library