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Articles 30931 - 30960 of 36659

Full-Text Articles in Physical Sciences and Mathematics

Particle Concentration Characterization For Jet Engine Emissions Under Cruise Conditions, Jonathan D. Paladino, Philip D. Whitefield, Donald E. Hagen, Alfred R. Hopkins, Max B. Trueblood May 1998

Particle Concentration Characterization For Jet Engine Emissions Under Cruise Conditions, Jonathan D. Paladino, Philip D. Whitefield, Donald E. Hagen, Alfred R. Hopkins, Max B. Trueblood

Chemistry Faculty Research & Creative Works

Airborne particle measurements during NASA project SUCCESS have shown that particle concentration profiles serve as good indicators of aircraft exhaust plume encounters. During exhaust plume penetrations there is a strong anticorrelation between the ratio of nonvolatile/total particulates and Nitrogen Oxide (NO) concentrations. an increase in fuel sulfur content was found to increase the total particle emission index, while the nonvolatile emission index remained unchanged. the EI's increased by a factor of 2.6 as the fuel sulfur increased from 70 - 700 ppm. the large particle size distribution (200-400 nm) was seen as a good long term indicator of an aircraft …

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Deep Centers In N-Gan Grown By Reactive Molecular Beam Epitaxy, Z-Q. Fang, David C. Look, W. Kim, Z. Fan, A. Botchkarev, H. Morkoç May 1998

Deep Centers In N-Gan Grown By Reactive Molecular Beam Epitaxy, Z-Q. Fang, David C. Look, W. Kim, Z. Fan, A. Botchkarev, H. Morkoç

Physics Faculty Publications

Deep centers in Si-doped n-GaN layers grown by reactive molecular beam epitaxy have been studied by deep-level transient spectroscopy as a function of growth conditions. Si-doped GaN samples grown on a Si-doped n+-GaN contact layer at 800 °C show a dominant trap C1 with activation energy ET = 0.44 eV and capture cross-section σT = 1.3×10−15 cm−2, while samples grown at 750 °C on an undoped semi-insulating GaN buffer show prominent traps D1 and E1, with ET = 0.20 eV and σT = 8.4×10−17 cm …

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Confocal Microscopy: A Powerful Tool For Biological Research, Amit Singh, K. P. Gopinathan May 1998

Confocal Microscopy: A Powerful Tool For Biological Research, Amit Singh, K. P. Gopinathan

Biology Faculty Publications

Conventional light microscopy allows the observation of living as well as fixed cells and tissues to generate two-dimensional images. The out-of-focus information often obscures the ultrastructural details, especially in thick specimens with overlapping structures. The earliest available light microscopy visualized the objects in hydrated state in two-dimensions during their temporal development. The emergence of electron microscopy (EM) provided superb resolution of ultrastructural details, but it was applicable only for objects in the dehydrated state and thereby potentially introducing handling artifacts. The usefulness of optical methods, however, has been limited by the poor depth discrimination. Often, the fluorescence and reflectance images …

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Discrete-To-Continuum Simulation Approach To Polymer Chain Systems: Subdiffusion, Segregation, And Chain Folding, Grace M. Foo, Ras B. Pandey May 1998

Discrete-To-Continuum Simulation Approach To Polymer Chain Systems: Subdiffusion, Segregation, And Chain Folding, Grace M. Foo, Ras B. Pandey

Faculty Publications

A discrete-to-continuum approach is introduced to study the static and dynamic properties of polymer chain systems with a bead-spring chain model in two dimensions. A finitely extensible nonlinear elastic potential is used for the bond between the consecutive beads with the Lennard-Jones (LJ) potential with smaller (Rc=21/6σ=0.95) and larger (Rc=2.5σ=2.1) values of the upper cutoff for the nonbonding interaction among the neighboring beads. We find that chains segregate at temperature T =1.0 with Rc=2.1 and remain desegregated with Rc=0.95. At low temperature (T=0.2), chains become folded, …

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Thermoconvective Instability Of Paramagnetic Fluids In A Nonuniform Magnetic Field, J. Huang, D. D. Gray, Boyd F. Edwards May 1998

Thermoconvective Instability Of Paramagnetic Fluids In A Nonuniform Magnetic Field, J. Huang, D. D. Gray, Boyd F. Edwards

All Physics Faculty Publications

The effect of a static, nonuniform magnetic field on a laterally unbounded nonconducting paramagnetic fluid layer heated from below or above is studied using a linear stability analysis of the Navier-Stokes equations supplemented by Maxwell’s equations and the appropriate magnetic body force. Buoyancy-driven convection can be controlled by subjecting the layer to a nonuniform magnetic field. Theoretical predictions agree with experimental observations.

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Satellite Studies Of Mid- And Low-Latitude Ionospheric Disturbancezonal Plasma Drifts, L. Scherliess, Bela G. Fejer May 1998

Satellite Studies Of Mid- And Low-Latitude Ionospheric Disturbancezonal Plasma Drifts, L. Scherliess, Bela G. Fejer

Bela G. Fejer

We use low- and mid-latitude zonal ion drift observations from the DE-2 satellite and auroral electrojet indices to study the temporal and latitudinal variations of F-region perturbation drifts during magnetically disturbed conditions. These perturbation drifts are driven by magnetospheric and ionospheric disturbance dynamo electric fields with time constants from less than one to several hours. We determine, initially, the drift patterns due to the prompt penetration of magnetospheric electric fields and of longer lasting disturbances. In this study, we concentrate on the properties of the longer lasting perturbations which occur with latitude-dependent time delays after enhancements in the high-latitude ionospheric …

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Invariant Representations Of Finite Rotation Matrices And Some Applications, N. L. Manakov, A. V. Meremianin, Anthony F. Starace May 1998

Invariant Representations Of Finite Rotation Matrices And Some Applications, N. L. Manakov, A. V. Meremianin, Anthony F. Starace

Anthony F. Starace Publications

Standard representations of finite rotation matrices (FRM) are defined by expressions that are wedded to two particular coordinate frames such as, e.g., are involved in the definition of Euler angles. We present here representations for the FRM in invariant tensor forms comprised of vectors defined in a space-fixed coordinate frame K. Three explicit expressions for a FRM are presented: First, in terms of tensor products of the spherical or Cartesian basis vectors of frame K, second in a differential form containing the tensor products of gradient operators, and, third, as the superposition of so-called “minimal” bipolar harmonics depending …

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The New Aleph Silicon Vertex Detector, D. Creanza, Manoj Thulasidas May 1998

The New Aleph Silicon Vertex Detector, D. Creanza, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

The ALEPH collaboration, in view of the importance of effective vertex detection for the Higgs boson search at LEP 2, decided to upgrade the previous vertex detector. Main changes were an increased length (+/- 20 cm), a higher granularity for r phi view (50 mu m), a new preamplifier (MX7 rad hard chip), a polymide (upilex) fan-out on z side to carry the signals from the strips to the front-end electronics outside the fiducial region reducing consequently the passive material in the central region by a factor of two. The detector, the running experience and its performance will be described. …

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All-Sky Measurements Of The Mesospheric "Frontal Events" From Bear Lake Observatory, Utah, Seon-Hee Seo May 1998

All-Sky Measurements Of The Mesospheric "Frontal Events" From Bear Lake Observatory, Utah, Seon-Hee Seo

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Studies of internal gravity waves in the earth's upper atmosphere are of considerable interest. These waves play a very important role in the dynamics of the mesosphere and lower thermosphere (ML T) region where they can transfer large amounts of energy and momentum from the lower atmosphere via wave saturation and dissipation. In particular, small-scale short-period ( < 1 hour) waves of the type regularly recorded by all-sky nightglow imagers operated by Utah State University (USU) are known to be very important contributors. In this thesis attention is focused on a subset of small-scale wave phenomena recently discovered using such image data, the so called "frontal events." Frontal events have distinguishable characteristics from usual short-period ( < 1 hour) gravity waves. The principal characteristics are a well defined leading "front, " which exhibits a sharp change in intensity followed by a coherent wave trail (often extending from horizon to horizon) and relatively high phase speeds ( > 50ms-1) Another unusual characteristic of "frontal events" is an apparent reversal in contrast of the wave structures as imaged in the hydroxyl (OH) emission (peak altitude - 87 km) when compared with the oxygen (OJ) "green line" (557.7 nm) emission (peak …

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Quantum-Statistical Properties Of Two Coupled Modes Of Electromagnetic Field, Serguei Y. Kalmykov, Mikhail E. Veisman Apr 1998

Quantum-Statistical Properties Of Two Coupled Modes Of Electromagnetic Field, Serguei Y. Kalmykov, Mikhail E. Veisman

Serge Youri Kalmykov

Squeezing the quantum fluctuations of the two-mode light due to the nonstationary coupling between the quadrature components q_1 and q_2 is examined. The delta-function and step-function mode couplings are considered. The conditions of weak and strong step-function coupling are distinguished, the latter being the condition of the instability for the classical counterpart of the quantum system under study. Under the conditions of weak coupling the quadrature squeezing is established in both a two-mode electromagnetic noise in thermal equilibrium (the thermal state) and a two- mode correlated coherent state (CCS). Squeezing in the thermal state is suppressed at a high temperature. …

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Two-Body B Meson Decays To Η And Η′: Observation Of B→Η′K, B. H. Behrens, Kenneth A. Bloom, Cleo Collaboration Apr 1998

Two-Body B Meson Decays To Η And Η′: Observation Of B→Η′K, B. H. Behrens, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

In a sample of 6.6 X 106 produced B mesons we have observed decays B → η′K, with branching fractions Ɓ(B+ → η′K) = 6.5-1.4+1.5± 0.9) X 10-5 and Ɓ(B0 → η′K0) = 4.7-2.0+2.7 ± 0.9) X 10-5. We have searched with comparable sensitivity for 17 related decays to final states containing an η or η′ meson accompanied by a single particle or low-lying resonance. Our upper limits for these constrain theoretical interpretations of the B → η′K signal.

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X-Ray Spectroscopic Mapping Of Three Unusual Active Galaxies (Ngc 4258, Ngc 1097, And Ngc 1068), Jeremy Kotter '98 Apr 1998

X-Ray Spectroscopic Mapping Of Three Unusual Active Galaxies (Ngc 4258, Ngc 1097, And Ngc 1068), Jeremy Kotter '98

Honors Projects

One enigmatic class of objects whose structures are interesting and only recently explored are active galactic nuclei (AGN). These are galaxies in which massive black holes sit at the center and accrete matter. The term "active" refers to energetic processes which are not directly attributable to stars and which occur in the innermost portions of galaxies. Astrophysicists have developed general descriptions of AGN, but details about these objects remain incomplete. Notably, the thermal and ionization structures of AGN accretion disks and the geometries of the circum-source clouds which surround the black hole and comprise an important portion of the energy …

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Evidence For A Scalar Kappa(900) Resonance In Pi-K Scattering, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Francesco Sannino Apr 1998

Evidence For A Scalar Kappa(900) Resonance In Pi-K Scattering, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Francesco Sannino

Physics - All Scholarship

Motivated by the 1/N_c\ expansion, we study a simple model in which the pi-K scattering amplitude is the sum of a current-algebra contact term and resonance pole exchanges. This phenomenological model is crossing symmetric and, when a putative light strange scalar meson, kappa, is included, satisfies the unitarity bounds to well above 1 GeV. The model also features chiral dynamics, vector meson dominance and appropriate interference between the established scalar K*(1430) resonance and its predicted background. We briefly discuss the physical significance of the results and directions for further work.

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Measurement Of B(D0 → K-Π+) Using Partial Reconstruction Of B̅ → D*+Xℓ- Ν̅, M. Artuso, Kenneth A. Bloom, Cleo Collaboration Apr 1998

Measurement Of B(D0 → K-Π+) Using Partial Reconstruction Of B̅ → D*+Xℓ- Ν̅, M. Artuso, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We present a measurement of the absolute branching fraction for D0 → K-π+ using the reconstruction of the decay chain B̅ → D*+Xℓ- ν̅ where only the lepton and the low-momentum pion from the D*+ are detected. With data collected by the CLEO II detector at the Cornell Electron Storage Ring, we have determined Ɓ(D0 → K-π+)= [3.81 ± 0.15(stat) ± 0.16(syst)]%.

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Friction Anisotropy And Asymmetry Of A Compliant Monolayer Induced By A Small Molecular Tilt, Nancy Burnham, M Liley, D. Gourdon, Dimitrios Stamou, U Meseth, T Fischer, C Lautz, H Stahlberg, H Vogel, C Duschl Apr 1998

Friction Anisotropy And Asymmetry Of A Compliant Monolayer Induced By A Small Molecular Tilt, Nancy Burnham, M Liley, D. Gourdon, Dimitrios Stamou, U Meseth, T Fischer, C Lautz, H Stahlberg, H Vogel, C Duschl

Nancy A. Burnham

Lateral force microscopy in the wearless regime was used to study the friction behavior of a lipid monolayer on mica. In the monolayer, condensed domains with long-range orientational order of the lipid molecules were present. The domains revealed unexpectedly strong friction anisotropies and non-negligible friction asymmetries. The angular dependency of these effects correlated well with the tilt direction of the alkyl chains of the monolayer, as determined by electron diffraction and Brewster angle microscopy. The molecular tilt causing these frictional effects was less than 15 degrees, demonstrating that even small molecular tilts can make a major contribution to friction.

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Cross Sections Spring 1998, Department Of Physics And Astronomy Apr 1998

Cross Sections Spring 1998, Department Of Physics And Astronomy

Cross Sections

No abstract provided.

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Search For The Decay B→DS1+(2536)X, M. Bishai, Kenneth A. Bloom, Cleo Collaboration Apr 1998

Search For The Decay B→DS1+(2536)X, M. Bishai, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We have searched for the decay B→Ds1+ (2536)X and measured an upper limit for the inclusive branching fraction of B(B→Ds1+X) < 0.96% at the 90% confidence level. This limit is small compared with the total expected B→D‾(*)D(*) KX rate. Assuming factorization, the Ds1+ 1 decay constant is constrained to be fDs1+ < 114 MeV at the 90% confidence level, at least 2.5 times smaller than that of Ds.

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Measurement Of The Branching Fractions Of ΛC+→Pk̅N (Π), M. S. Alam, Kenneth A. Bloom, Cleo Collaboration Apr 1998

Measurement Of The Branching Fractions Of ΛC+→Pk̅N (Π), M. S. Alam, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using data recorded by the CLEO-II detector at CESR, we report new measurements of the branching fractions for the decays of the charmed baryon Λc+ into pK-π+π0, pK0, pK0π+π-, and pK0π0, all measured relative to pK-π+. The relative branching fractions are 0.67±0.04±0.11,0.46±0.02±0.04,0.52±0.04±0.05, and 0.66±0.05±0.07, respectively.

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Intermediate- To High-Energy Positrons Scattered By Alkali-Metal Atoms, David D. Reid, J. M. Wadehra Apr 1998

Intermediate- To High-Energy Positrons Scattered By Alkali-Metal Atoms, David D. Reid, J. M. Wadehra

Physics and Astronomy Faculty Research Publications

We present calculations of the differential, integrated elastic, and total cross sections for positrons scattered from alkali-metal atoms. The energy of the positrons ranges from 10 eV to 1000 eV. In the calculations we use parameter-free model potentials for the correlation-polarization and absorption interactions. The absorption potential used for positron scattering is based on a quasifree model that we recently proposed and tested for the noble-gas targets. For positron–alkali-metal scattering the model potentials have produced reliable scattering cross sections over the extended range of impact energies when compared against the available experimental data.

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Crossover From Pure Ising To Random-Exchange Dominated Behavior Of The Two-Dimensional Antiferromagnet Rb2Co1-XMgXF4, Christian Binek, Wolfgang Kleemann, David P. Belanger Apr 1998

Crossover From Pure Ising To Random-Exchange Dominated Behavior Of The Two-Dimensional Antiferromagnet Rb2Co1-XMgXF4, Christian Binek, Wolfgang Kleemann, David P. Belanger

Christian Binek Publications

The temperature dependence of the uniform susceptibility χ of diluted two-dimensional Ising antiferromagnets Rb2Co1-xMgxF4, 0<~xN(x), but also in relation to the “local” phase transition temperatures TN′ throughout the Griffiths regime, TN(x)<~TN′<~TN(0), a satisfactory quantitative description of χ vs T is deduced for any x above the percolation threshold. ©1998 The American Physical Society

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Nonlocal Theory Of Dissociative Electron Attachment To H2 And Hf Molecules, Gordon A. Gallup, Y. [Yuanguang] Xu, Ilya I. Fabrikant Apr 1998

Nonlocal Theory Of Dissociative Electron Attachment To H2 And Hf Molecules, Gordon A. Gallup, Y. [Yuanguang] Xu, Ilya I. Fabrikant

Gordon Gallup Publications

We develop a method for calculation of dissociative electron attachment cross sections based on the Fano- Feshbach projection-operator approach. The coupling between the diabatic state and electron continuum is calculated with the inclusion of orthogonality scattering and long-range electron-molecule interaction. The dynamics of nuclear motion in the non-local complex potential is treated by semiclassical theory. We apply the theory to the calculation of dissociative attachment to the H2 and HF molecules. Our results for attachment to ground-state hydrogen molecules and the near-threshold vibrational enhancement of H2 are essentially the same as previous non-local results. However, the shape of …

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Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei, Xii: Ground-Based Monitoring Of 3c 390.3, M. Dietrich, Bradley M. Peterson, P. Albrecht, M. Altmann, A. J. Barth, P. J. Bennie, R. Bertram, N. G. Bochkarev, H. Bock, J. M. Braun, A. Burenkov, S. Collier, L.-Z. Fang, O. P. Francis, A. V. Filippenko, C. B. Foltz, W. Gassler, C. Martin Gaskell, M. Geffert, K. K. Ghosh, R. W. Hilditch, R.K. Honeycutt, K. Horne, J. P. Huchra, Shai Kaspi, M. Kummel, K. M. Leighly, D. C, Leonard, Yu. F. Malkov, V. Mikhailov, H. Richard Miller, A. C. Morrill, J. Noble, Paul T. O'Brien, T. D. Oswalt, S. P. Pebley, M. Pfeiffer, V. I. Pronik, B.-C. Qian, J. W. Robertson, A. Robinson, Kenneth S. Rumstay, J. Schmoll, S. G. Sergeev, E. A. Sergeeva, A. I. Shapovalova, D. R. Skillman, Stephanie A. Snedden, S. Soundararajaperumal, G. M. Stirpe, J. Tao, G. W. Turner, R. M. Wagner, S. J. Wagner, J. Y. Wei, H. Wu, W. Zheng, Z. L. Zhou Apr 1998

Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei, Xii: Ground-Based Monitoring Of 3c 390.3, M. Dietrich, Bradley M. Peterson, P. Albrecht, M. Altmann, A. J. Barth, P. J. Bennie, R. Bertram, N. G. Bochkarev, H. Bock, J. M. Braun, A. Burenkov, S. Collier, L.-Z. Fang, O. P. Francis, A. V. Filippenko, C. B. Foltz, W. Gassler, C. Martin Gaskell, M. Geffert, K. K. Ghosh, R. W. Hilditch, R.K. Honeycutt, K. Horne, J. P. Huchra, Shai Kaspi, M. Kummel, K. M. Leighly, D. C, Leonard, Yu. F. Malkov, V. Mikhailov, H. Richard Miller, A. C. Morrill, J. Noble, Paul T. O'Brien, T. D. Oswalt, S. P. Pebley, M. Pfeiffer, V. I. Pronik, B.-C. Qian, J. W. Robertson, A. Robinson, Kenneth S. Rumstay, J. Schmoll, S. G. Sergeev, E. A. Sergeeva, A. I. Shapovalova, D. R. Skillman, Stephanie A. Snedden, S. Soundararajaperumal, G. M. Stirpe, J. Tao, G. W. Turner, R. M. Wagner, S. J. Wagner, J. Y. Wei, H. Wu, W. Zheng, Z. L. Zhou

C. Martin Gaskell Publications

Results of a ground-based optical monitoring campaign on 3C 390.3 in 1994-1995 are presented. The broadband fluxes (B, V , R, and I), the spectrophotometric optical continuum flux Fλ(5177 Å), integrated emission-line fluxes of Hα, Hβ, Hγ, He I λ5876, and He II λ4686 all show a nearly monotonic increase with episodes of milder short-term variations superposed. The amplitude of the continuum variations increases with decreasing wavelength (4400-9000 Å). The optical continuum variations follow the variations in the ultraviolet and X-ray with time delays, measured from the centroids of the crosscorrelation functions, typically around …

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Scaling Studies Of Spheromak Formation And Equilibrium, Cameron G. R. Geddes , '97, Thomas W. Kornack , '98, Michael R. Brown Apr 1998

Scaling Studies Of Spheromak Formation And Equilibrium, Cameron G. R. Geddes , '97, Thomas W. Kornack , '98, Michael R. Brown

Physics & Astronomy Faculty Works

Formation and equilibrium studies have been performed on the Swarthmore Spheromak Experiment (SSX). Spheromaks are formed with a magnetized coaxial plasma gun and equilibrium is established in both small (d(small)=0.16 m) and large (d(large)=3d(small)=0.50 m) copper flux conservers. Using magnetic probe arrays it has been verified that spheromak formation is governed solely by gun physics (in particular the ratio of gun current to flux, mu(0)I(gun)/Phi(gun)) and is independent of the flux conserver dimensions. It has also been verified that equilibrium is well described by the force free condition del xB=lambda B (lambda=constant), particularly early in decay. Departures from the force-free …

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Solvable Model Of Two-Dimensional Dilaton Gravity Coupled To A Massless Scalar Field, Marco Cavaglia Apr 1998

Solvable Model Of Two-Dimensional Dilaton Gravity Coupled To A Massless Scalar Field, Marco Cavaglia

Physics Faculty Research & Creative Works

We present a solvable model of two-dimensional dilaton-gravity coupled to a massless scalar field. We locally integrate the field equations and briefly discuss the properties of the solutions. For a particular choice of the coupling between the dilaton and the scalar field the model can be interpreted as the two-dimensional effective theory of 2+1 cylindrical gravity minimally coupled to a massless scalar field.

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Electrophoretic Deposition Of Polymer Chains On An Adsorbing Surface In (2+1) Dimensions: Conformational Anisotropy And Nonuniversal Coverage, Grace M. Foo, Ras B. Pandey Apr 1998

Electrophoretic Deposition Of Polymer Chains On An Adsorbing Surface In (2+1) Dimensions: Conformational Anisotropy And Nonuniversal Coverage, Grace M. Foo, Ras B. Pandey

Faculty Publications

Electrophoretic deposition of polymer chains flowing in a (2 + 1)-dimensional system is studied by computer simulations. Steady-state surface coverage θj is found to decay with the chain's length, i.e., θj∼Lc-a with a nonuniversal exponent α≃0.0-0.9 depending on the magnitude of driving field and temperature. Conformational crossover occurs for chains from a surface or wall to an adjacent bulk region with different scaling exponents for their longitudinal and transverse spread.

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Dynamic And Chemical Aspects Of The Mesospheric Na ‘Wall’ Event On 9 October 1993 During The Aloha Campaign, G. R. Swenson, J. Qian, J. M.C. Plane, P. J. Espy, Michael J. Taylor, D. N. Turnbull, R. P. Lowe Apr 1998

Dynamic And Chemical Aspects Of The Mesospheric Na ‘Wall’ Event On 9 October 1993 During The Aloha Campaign, G. R. Swenson, J. Qian, J. M.C. Plane, P. J. Espy, Michael J. Taylor, D. N. Turnbull, R. P. Lowe

All Physics Faculty Publications

On October 9, 1993, observations were made from the National Center for Atmospheric Research Electra aircraft during a flight from Maui, Hawaii, toward a low-pressure system NW of the island, a flight of 7 hours in total. The leading edge (wall) of a bright airglow layer was observed 900 km NW of Maui at 0815 UT, which was traveling at 75 m s−1 toward the SE, reaching Haleakala, Maui, about 3.25 hours later [see Swenson and Espy, 1995]. An intriguing feature associated with the event was the large increase in the mesospheric Na column density at the wall (∼180%). The …

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Application Of Tomographic Inversion In Studying Airglow In The Mesopause Region, T. Nygren, Michael J. Taylor, M. S. Lehtinen, M. Markkanen Apr 1998

Application Of Tomographic Inversion In Studying Airglow In The Mesopause Region, T. Nygren, Michael J. Taylor, M. S. Lehtinen, M. Markkanen

All Physics Faculty Publications

It is pointed out that observations of periodic nightglow structures give excellent information on atmospheric gravity waves in the mesosphere and lower thermosphere. The periods, the horizontal wavelengths and the phase speeds of the waves can be determined from airglow images and, using several cameras, the approximate altitude of the luminous layer can also be determined by triangulation. In this paper the possibility of applying tomographic methods for reconstructing the airglow structures is investigated using numerical simulations. A ground-based chain of cameras is assumed, two-dimensional airglow models in the vertical plane above the chain are constructed, and simulated data are …

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Neutral Dissociation Of Hydrogen Following Photoexcitation Of Hcl At The Chlorine K Edge, D. L. Hansen, J. Cotter, G. R. Fisher, K. T. Leung, R. Martin, Paul Neill, Rupert C. Perera, I. A. Sellin, Marc Simon, Y. Uehara, B. Vanderford, S. B. Whitfield Apr 1998

Neutral Dissociation Of Hydrogen Following Photoexcitation Of Hcl At The Chlorine K Edge, D. L. Hansen, J. Cotter, G. R. Fisher, K. T. Leung, R. Martin, Paul Neill, Rupert C. Perera, I. A. Sellin, Marc Simon, Y. Uehara, B. Vanderford, S. B. Whitfield

Chemistry and Biochemistry Faculty Research

Time-of-flight mass spectroscopy was used to study the relaxation dynamics of HCl following photoexcitation in the vicinity of the Cl K edge (~2.8 keV) using monochromatic synchrotron radiation. At the lowest resonant excitation to the 6ơ* antibonding orbital, almost half of the excited molecules decay by emission of a neutral H atom, mostly in coincidence with a highly charged Cln1 ion. The present work demonstrates that neutral-atom emission can be a significant decay channel for excited states with very short lifetimes (1 fs). [S1050-2947(98)03604-X]

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Thermal Lattice Boltzmann Simulations Of Variable Prandtl Number Turbulent Flows, Min Soe, George Vahala, Pavol Pavlo, Linda L. Vahala, Hudong Chen Apr 1998

Thermal Lattice Boltzmann Simulations Of Variable Prandtl Number Turbulent Flows, Min Soe, George Vahala, Pavol Pavlo, Linda L. Vahala, Hudong Chen

Electrical & Computer Engineering Faculty Publications

Thermal lattice Boltzmann (TLBE) models that utilize the single relaxation time scalar Bhatnagar, Gross, and Krook collision operator have an invariant Prandtl number. For flows with arbitrary Prandtl number, a matrix collision operator is introduced. The relaxation parameters are generalized so that the transport coefficients become density independent. TLBE simulations are presented for two-dimensional free decaying turbulence induced by a strongly perturbed double velocity shear layer for various Prandtl numbers.

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The Effects Of Fabry-Perot Fringing On The Sensitivity Of A Wavelength Modulation Experiment, Patrick C. Shea Apr 1998

The Effects Of Fabry-Perot Fringing On The Sensitivity Of A Wavelength Modulation Experiment, Patrick C. Shea

Electrical & Computer Engineering Theses & Dissertations

Parasitic Fabry-Perot etaloning plagues many experiments which use wavelength modulation spectroscopy. This fringing, which is an artifact that almost always appears in such experiments, arises from multiple reflections in the optical elements in the experimental apparatus. The etaloning plays a detrimental role and limits the ultimate sensitivity of wavelength modulation spectroscopy experiments. The research described in this thesis investigates this phenomenon. Experimental results are presented which show that when the Q-factor of the parasitic etalon is smaller that that of the absorption line being measured, significant improvement in the Signal to Fringe Noise Ratio can be obtained through the use …

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