Physics Commons^™

Near-Field Measurements On Contrail Properties From Fuels With Different Sulfur Content, Andreas Petzold, Reinhold Busen, Franz Peter Schroder, Robert Baumann, Markus Kuhn, Johan Strom, Donald E. Hagen, Philip D. Whitefield, Darrel G. Baumgardner, Frank Arnold, Stephan Borrmann, Ulrich Schumann

Physics Faculty Research & Creative Works

Microphysical properties of jet exhaust aerosol and contrails were studied in the near field of the emitting aircraft for different fuel sulfur contents. Measurements were performed behind two different aircraft (ATTAS test aircraft of type VFW 614 and Airbus A310-300) using fuels with sulfur contents of 6 ppm and 2700 ppm, respectively. At closest approach (plume age < 1 s), the total number concentrations exceeded the measuring range of the condensation particle counter, i.e., N > 10⁵ cm^-3. The concentration of the dry accumulation mode aerosol, i.e., predominantly soot particles, was not affected by the fuel sulfur content. At a plume age of 10 s, an increase in total number concentration (Dp > 0.01 μm) by a …

Hybrid Quantum And Molecular Mechanics Embedded Cluster Models For Chemistry On Silicon And Silicon Carbide Surfaces, James R. Shoemaker

Theses and Dissertations

Fabrication of silicon carbide SiC semiconductor devices are of interest for aerospace applications because of their high-temperature tolerance. Growth of an insulating SiO₂ layer on SiC is a poorly understood process, and sometimes produces interface defects that degrade device performance. Accurate theoretical models of surface chemistry, using quantum mechanics QM, do not exist because of the huge computational cost of solving Schroedingers equation for a molecular cluster large enough to represent a surface. Molecular mechanics MM, which describes a molecule as a collection of atoms interacting through classical potentials, is a fast computational method, good at predicting molecular structure, …

Segregation Of Bismuth To Triple Junctions In Copper, K.-M. Yin, Alexander H. King, T.E. Hsieh, F.-R. Chen, J.J. Kai, L. Chang

Alexander H. King

Bismuth segregation in copper has been studied using energy-dispersive X-ray spectrometry (EDX) in a JEOL 2010F transmission electron microscope. In addition to the expected solute enrichment at grain boundaries, we have observed extremely high concentrations of bismuth at certain triple junctions, with significantly greater enrichment factors than in the adjacent grain boundaries. It is shown here that the triple junction segregation is a function of the parameters of the grain boundaries at the triple line, and existence of this type of segregation implies that the affected triple junctions embody excess free energy. At least one of the observed triple junctions …

39th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Preliminary program and registration information for the 39th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 3-7, 1997.

Nondipole Resonant X-Ray-Raman Spectroscopy: Polarized Inelastic Scattering At The K Edge Of Cl2, J. D. Mills, J. A. Sheehy, T. A. Ferrett, S. H. Southworth, R. Mayer, Dennis W. Lindle, P. W. Langhoff

Chemistry and Biochemistry Faculty Research

Experimental and theoretical studies are reported on the inelastic (Raman) scattering of wavelength-selected polarized x rays from the K edge of gas-phase chlorine molecules. The polarized emission spectra exhibit prominent nondipole features consequent of phase variations of the incident and emitted radiation over molecular dimensions, as predicted by the Kramers-Heisenberg scattering formalism. Issues pursuant to the detection of core-hole localization by resonant Raman scattering from homonuclear diatomic molecules are critically examined. [S0031-9007(97)03486-8]

Breakdown Of The Independent Particle Approximation In High-Energy Photoionization, E. W. B. Dias, H. S. Chakraborty, P. C. Deshmukh, S. T. Manson, Oliver Hemmers, P. Glans, D. Hansen, H. Wang, S. B. Whitfield, Dennis W. Lindle, R. Wehlitz, Jon C. Levin, I. A. Sellin

Environmental Studies Faculty Publications

The independent particle approximation is shown to break down for the photoionization of both inner and outer nℓ (ℓ>0) electrons of all atoms, at high enough energy, owing to interchannel interactions with the nearby ns photoionization channels. The effect is illustrated for Ne 2p in the 1 keV photon energy range through a comparison of theory and experiment. The implications for x-ray photoelectron spectroscopy of molecules and condensed matter are discussed.

Computer Modeling Of Molecular Vibration Frequencies And Its Application To The Modeling Of Silane Compounds, Ryan T. Merrell

Honors Capstone Projects and Theses

No abstract provided.

In Situ Observations Of Air Traffic Emission Signatures In The North Atlantic Flight Corridor, Hans Schlager, Paul Konopka, P. Schulte, U. Schumann, H. Ziereis, F. Arnold, M. Klemm, Donald E. Hagen, Philip D. Whitefield, J. Ovarlez

Physics Faculty Research & Creative Works

Focussed aircraft measurements have been carried out over the eastern North Atlantic to search for signals of air traffic emissions in the flight corridor region. Observations include NO, NO₂, HNO₃, SO₂, O₃, H₂O, total condensation nuclei (CN), and meteorological parameters. A flight pattern with constant-altitude north-south legs across the major North Atlantic air traffic tracks was flown. Signatures of air traffic emissions were clearly detected for NO_x, SO₂, and CN with peak concentrations of 2 ppbv, 0.25 ppbv, and 500 cm^-3, respectively, exceeding background …

Magnetic And Structural Properties Of Nd₂Fe₁₇₋ₓmnₓ Solid Solutions, Peter C. Ezekwenna, G. K. Marasinghe, William Joseph James, Oran Allan Pringle, Gary J. Long, H. Luo, Z. Hu, William B. Yelon, Ph. I'Héritier

Chemistry Faculty Research & Creative Works

A series of Nd₂Fe_17-xMn_x solid solutions with x values between 0 and and 6 were prepared and analyzed using magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. All of the Nd₂Fe_17-xMn_x samples crystallized in the Th₂Zn_17-x-type rhombohedral structure. The lattice parameters and unit cell volumes decrease with increasing manganese content up to ∼ x equal to 2, and then increase for higher manganese content. The magnetizations of Nd₂Fe_17-xMn_x decrease with increasing manganese content and Nd₂Fe_17-xMn_x is paramagnetic …

Studies Of V, Nb, Cr, And Zr Substituted 2:17 Compounds And Their Carbides Using Neutron Diffraction, H. Luo, Z. Hu, Muguo Chen, William B. Yelon, G. K. Marasinghe, Peter C. Ezekwenna, William Joseph James, W. C. Chang, S. H. Tsai

Physics Faculty Research & Creative Works

Samples of Nd₂Fe_17-xT_xC_y with T=V, Nb, Cr, and Zr were prepared by melting of the constituent elements including C and studied by neutron diffraction. Comparing with their uncarbided counterparts, we found that the substituents transfer, more or less, from the 6c site to the 18f and 18h sites with the introduction of C atoms. This behavior appears to relate to the electronegativities between the C atoms and the early transition series elements because the 18f and 18h sites are near neighbors of the interstitial C site. However, the C effects in the V. …

Microwave Plasma Chemical Vapor Deposited Diamond Tips For Scanning Tunneling Microscopy, Sacharia Albin, Jianli Zheng, John B. Cooper, Weihai Fu, Arnel C. Lavarias

Electrical & Computer Engineering Faculty Publications

Diamond microparticles were grown on etched tungsten wires using a microwave plasma-assisted chemical vapor deposition process. The apexes on cubo-octahedral particles bound by {100} and {111} facets were effectively used as tunneling tips for scanning tunneling microscopy. The atomically resolved surface image of highly oriented pyrolytic graphite was acquired. Tunneling characteristics revealed a higher electron emission from the diamond tips than that from the platinum–iridium tips. The same diamond tips were used to produce surface indentation and its image. © 1997 American Institute of Physics.

Observation Of Upper Tropospheric Sulfur Dioxide- And Acetone-Pollution: Potential Implications For Hydroxyl Radical And Aerosol Formation, F. Arnold, J. Schneider, K. Gollinger, H. Schlager, P. Schulte, Donald E. Hagen, Philip D. Whitefield, Peter F. J. Van Velthoven

Physics Faculty Research & Creative Works

Aircraft-based measurements of sulfur dioxide, acetone, carbon dioxide, and condensation nuclei (CN) were made over the north-eastern Atlantic at upper tropospheric altitudes, around 9000 m. On October 14, 1993, strong SO ₂- and acetone-pollution (both up to 3 ppbv) were observed, which were accompanied by a CO ₂-enhancement of up to 6 ppmv, and large CN-concentrations of up to about 1500 cm ^-3 (for radii ≥ 6 nm). CN, excess CO ₂, and to a lesser degree also acetone, were positively correlated with SO ₂. Air mass trajectory analyses indicate, that most of the air masses …

Microstructural Characterization Of An Ultra-High-Performance Polyimide, April Heather Baugher

Dissertations, Theses, and Masters Projects

The motivation for this study was to further characterize a relatively new high-temperature polymer for application as a matrix resin for carbon fiber composites. The two primary questions addressed in this study dealt with the structural and chemical changes occurring in these polymers on exposure to high temperature.;To investigate the structural changes in the heat-treated samples, a positron annihilation lifetime spectrometer was designed, built and optimized. Because the lifetime of a positron in a material reflects the electronic structure of the material in which it annihilates, measurements by positron annihilation lifetime spectroscopy can be used to investigate changes in a …

Characterization Of Iron Oxides And Atmospheric Corrosion Of Steel, Sei Jin Oh

Physics Theses & Dissertations

The study of corrosion behavior was performed using three different analytical techniques, which provided information on the formation, development and layering of iron oxides on the corrosion products as a function of atmospheric conditions, exposure time and type of steel. In particular, the protective layer formed on weathering steel was investigated as a function of different amounts of alloying elements in the steel, atmospheric conditions and exposure times. Combined together, the results provided a better understanding of the atmospheric corrosion behavior of steel, and formed a part of database of the atmospheric corrosion characteristics.

Accurate characterization of the iron oxides …