Physical Sciences and Mathematics Commons^™

An Observation Of A Fast External Atmospheric Acoustic-Gravity Wave, J. H. Hecht, R. L. Walterscheid, Michael P. Hickey Ph.D., R. J. Rudy, A. Z. Liu

Publications

In November 1999 a new near-IR airglow imaging system was deployed at the Starfire Optical Range outside of Albuquerque, New Mexico. This system allowed wide angle images of the airglow to be collected, with high signal to noise, every 3 seconds with a one second integration time. At approximately 1000 UT on November 17, 1999, a fast wavelike disturbance was seen propagating through the OH Meinel airglow layer. This wave had an observed period of ≈215 seconds, an observed phase velocity of ≈160 m/s and a horizontal wavelength of ≈35 km. This phase velocity is among the fastest yet reported …

Further Investigations Of A Mesospheric Inversion Layer Observed In The Aloha-93 Campaign, Tai-Yin Huang, Michael P. Hickey Ph.D., Tai-Fu Tuan

Publications

Temperature and wind data obtained from a Na wind/temperature lidar operated by the University of Illinois group during the Airborne Lidar and Observations of the Hawaiian Airglow (ALOHA-93) Campaign, previously analyzed by Huang et al. [1998] using an isothermal Brunt-Va¨isa¨la¨ frequency, have been reexamined to include temperature gradients in the calculation of the Richardson number. In the previous analysis using the isothermal Brunt-Va¨isa¨la¨ frequency the existence of convective instability could not be assessed. New analysis shows that the nonisothermal Richardson number preserves some features found previously, with some striking differences noticable at times between 0900 and 1030 UT. The nonisothermal …

Coupling Of Coamps And Wavetech With Improved Wave Physics, Shahrdad Sajjadi, Pat Fitzpatrick, Gueorgui Mostovoi, Yongzuo Li, Matt Bettencourt

Publications

The Model Coupling Executable Library (MCEL), developed at the University of Southern Mississippi's Center of Higher Learning, has been successfully used to couple the Coupled Ocean/Atmospheric Mesoscale Prediction System (COAMPS) and the ocean wave model WAVEWATCH. An example of its application is shown for Hurricane Gordon, showing that two-way coupling results affects boundary layer physics differently than one-way coupling --- in this case, resulting in larger o z and, consequently, larger surface fluxes and a more intense hurricane. However, since analyzing MCEL is difficult because the wave physics is inaccurate, improvements to the wave algorithms are also part of the …

Identification Of Cool White Dwarfs In The Noao Deep Wide-Field Survey, M. Kilic, Don E. Winget, T. Von Hippel, C.F. Claver

Publications

The chronology of star formation is recorded in the white dwarf luminosity function (WDLF). White dwarf (WD) structure implies a relatively simple connection between WD luminosity and age. First attempts to exploit WDs as chronometers [3,4,6] showed that the WDLF was a map of the history of star formation in the disk, and a significant shortfall of low-luminosity degenerates–the inevitable consequence of the finite age of the disk. The shortfall near log(L/L⊙)≈−4.5 implies a disk age of 6.5–9.5 Gyr [2]. The WDLF from wide common proper motion binaries [5] does not show the shortfall seen by Liebert et al. (1988). …

Search For Oxygen In Cool Dq White Dwarf Atmospheres, M. Kilic, Ted Von Hippel, D. E. Winget, D. F. Lester, D. Saumon

Publications

The existence of carbon in cool He white dwarf (WD) atmospheres has been known for a relatively long time[5]. The presence of carbon in these atmospheres is explained by convective dredge up of interior carbon [6]. Pelletier et al. (1986) presented the first detailed calculations of this process and showed that carbon diffuses upwards from the core into the base of the He-rich envelope where it can be dredged up by a surface convection zone. As the temperature of the star decreases, more carbon diffuses upward, and the base of convection zone moves deeper into the star, further enriching the …

Book Review: Neptune: The Planet, Rings And Satellites, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Neptune : the Planet, Rings and Satellites by Ellis D. Miner and Randii R. Wessen Springer/Praxis, 2002 297p, 1-85233-216-6 $44.95

Wiyn Open Cluster Study. Xi. Wiyn 3.5 Meter Deep Photometry Of M35 (Ngc 2168), Ted Von Hippel, Aaron Steinhauer, Ata Sarajedini, Constantine P. Deliyannis

Publications

We present deep BVI observations of the core of M35 and a nearby comparison field obtained at the WIYN 3.5 m telescope under excellent seeing conditions. These observations probe to V > 26 and display the lower main sequence in BV and VI CMDs down to V = 23.3 and 24.6, respectively. At these faint magnitudes the background Galactic field stars are far more numerous than the cluster stars, yet by using a smoothing technique and CMD density distribution subtraction we are able to recover the cluster fiducial main sequence and luminosity function to V = 24.6. We find the location …

Automated Stellar Spectral Classification And Parameterization For The Masses, Ted Von Hippel, Carlos Allende Prieto, Chris Sneden

Publications

Stellar spectroscopic classification has been successfully automated by a number of groups. Automated classification and parameterization work best when applied to a homogeneous data set, and thus these techniques primarily have been developed for and applied to large surveys. While most ongoing large spectroscopic surveys target extragalactic objects, many stellar spectra have been and will be obtained. We briefly summarize past work on automated classification and parameterization, with emphasis on the work done in our group. Accurate automated classification in the spectral type domain and parameterization in the temperature domain have been relatively easy. Automated parameterization in the metallicity domain, …

Metal Abundances And Kinematics Of Bright Metal-Poor Giants Selected From The Lse Survey: Implications For The Metal-Weak Thick Disk, Timothy C. Beers, John S. Drilling, Silvia Rossi, Masashi Chiba, Jaehyon Rhee, Birgit Fṻhrmeister, John E. Norris, Ted Von Hippel

Publications

We report medium-resolution (1–2A ˚ ) spectroscopy and broadband (UBV) photometry for a sample of 39 bright stars (the majority of which are likely to be giants) selected as metal-deficient candidates from an objective-prism survey concentrating on Galactic latitudes below |b| = 30, the Luminous Stars Extension (LSE) survey of Drilling & Bergeron. Although the primary purpose of the LSE survey was to select OB stars (hence the concentration on low latitudes), the small number of bright metal-deficient giant candidates noted during this survey provide interesting information on the metal-weak thick disk (MWTD) population. Metal abundance estimates are obtained from …

The Local Moduli Of Sasakian 3-Manifolds, Brendan Guilfoyle

Publications

The Newman-Penrose-Perjes formalism is applied to Sasakian 3-manifolds and the local form of the metric and contact structure is presented. The local moduli space can be parameterised by a single function of two variables and it is shown that, given any smooth function of two variables, there exists locally a Sasakian structure with scalar curvature equal to this function. The case where the scalar curvature is constant (η-Einstein Sasakian metrics) is completely solved locally. The resulting Sasakian manifolds include S 3, Nil, and SL˜ 2 (ℝ), as well as the Berger spheres. It is also shown that a conformally flat …

Book Review: The Observing Guide To The Messier Marathon: A Handbook And Atlas, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Observing Guide to the Messier Marathon : a Handbook and Atlas by Don Machholz. Cambridge, 2002 157p, 0-521-80386-1 $25.00.

Wiyn Open Cluster Study Xi: Wiyn1 3.5m Deep Photometry Of M35 (Ngc 2168), Ted Von Hippel, Aaron Steinhauer, Ata Sarajedini, Constantine P. Deliyannis

Publications

We present deep BV I observations of the core of M35 and a nearby comparison field obtained at the WIYN 3.5m telescope under excellent seeing conditions. These observations probe to V > 26, and display the lower main sequence in BV and V I CMDs down to V = 23.3 and 24.6, respectively. At these faint magnitudes the background Galactic field stars are far more numerous than the cluster stars, yet by using a smoothing technique and CMD density distribution subtraction we are able to recover the cluster fiducial main sequence and luminosity function to V = 24.6. We find the …

Book Review: Flash!: The Hunt For The Biggest Explosions In The Universe, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Flash! : the hunt for the biggest explosions in the universe by Govert Schilling. tr. by Naomi Greenberg-Slovin Cambridge, 2002 291p, 0-521-80053-6 $28.00

One-Gas Models With Height-Dependent Mean Molecular Weight: Effects On Gravity Wave Propagation, R. L. Walterscheid, Michael P. Hickey Ph.D.

Publications

Many models of the thermosphere employ the one-gas approximation where the governing equations apply only to the total gas and the physical properties of the gas that depend on composition (mean molecular weight and specific heats) are height-dependent. It is further assumed that the physical properties of the gas are locally constant; thus motion-induced perturbations are nil. However, motion in a diffusively separated atmosphere perturbs local values of mean molecular weight and specific heats. These motion-induced changes are opposed by mutual diffusion of the constituent gases, which attempts to restore diffusive equilibrium. Assuming that composition is locally constant is equivalent …

Reflection Of A Long-Period Gravity Wave Observed In The Nightglow Over Arecibo On May 8–9, 1989?, Michael P. Hickey Ph.D.

Publications

During the Arecibo Initiative for Dynamics of the Atmosphere (AIDA) campaign in 1989 a characteristic of gravity wave perturbations observed in mesopause region airglow emissions was that airglow brightness fluctuations and airglow-derived temperature fluctuations often occurred either in phase or in antiphase. This stimulated the development of a theory suggesting that such in-phase fluctuations were most probably the result of strong reflections occurring in the mesosphere and lower thermosphere region. Recent examination of a particular wave event and application of simple WKB-type theory has appeared to support this hypothesis. Here we use a full-wave model and a WKB-type model, each …

Three-Dimensional Spectral Classification Of Low-Metallicity Stars Using Artificial Neural Networks, Shawn Snider, Ted Von Hippel, Et Al.

Publications

We explore the application of artificial neural networks (ANNs) for the estimation of atmospheric parameters (T_eff, log g, and [Fe/H]) for Galactic F- and G-type stars. The ANNs are fed with medium-resolution (Δλ ~ 1-2 Å) non-flux-calibrated spectroscopic observations. From a sample of 279 stars with previous high-resolution determinations of metallicity and a set of (external) estimates of temperature and surface gravity, our ANNs are able to predict T_eff with an accuracy of σ(T_eff) = 135-150 K over the range 4250 ≤ T_eff ≤ 6500 K, log g with an accuracy …

Acoustic Wave Heating Of The Thermosphere, Michael P. Hickey Ph.D., G. Schubert, R. L. Walterscheid

Publications

A numerical model is used to study the dissipation in the thermosphere of upward propagating acoustic waves. Whereas dissipating gravity waves can cool the upper atmosphere through the effects of sensible heat flux divergence, it is found that acoustic waves mainly heat the thermosphere by viscous dissipation. Though the amplitudes of acoustic waves in the atmosphere are poorly constrained, the calculations suggest that dissipating acoustic waves can locally heat the thermosphere at rates of tens of kelvins per day and thereby contribute to the thermospheric energy balance. It is shown that viscous heating cannot be calculated from the divergence of …

Plasma Transport At The Magnetospheric Boundary Due To Reconnection In Kelvin-Helmholtz Vortices, K. Nykyri, A. Otto

Publications

The Kelvin-Helmholtz( KH) mode has long been considered for viscous interaction at the magnetospheric boundary but it is not expected to produce significant mass transport. The presented results indicate that the Kelvin- Helmholtz instability can indeed cause a transfer of mass into the magnetotail during times of northward IMF. The vortex motion of KH waves can generate a strongly twisted magnetic field with multiple current layers. Magnetic reconnection in the strong current layers inside the vortices can detach high density plasma filaments from the magnetosheath. This may explain observed high density and low temperature filaments in the magnetosphere and the …

Airglow Variations Associated With Nonideal Ducting Of Gravity Waves In The Lower Thermosphere Region, Michael P. Hickey Ph.D.

Publications

A numerical full-wave model is used to study the response of the O2 atmospheric airglow to ducted gravity waves in the mesopause region. For an isothermal, quasi-adiabatic, and motionless background atmosphere the calculated phase differences between airglow brightness fluctuations and fluctuations of temperatures derived from the airglow, as given by Krassovsky's ratio, are in good agreement with the predictions of published theory. Significant departures from the predictions of the basic theory are obtained when we consider ducting in the presence of the eddy and molecular diffusion of heat and momentum in a nonisothermal background atmosphere. Wind shears also affect the …

Simulation Of Engineering Systems Described By High-Index Dae And Discontinuous Ode Using Single Step Methods, Marc Compere

Publications

This dissertation presents numerical methods for solving two classes of or-dinary diferential equations (ODE) based on single-step integration meth-ods. The first class of equations addressed describes the mechanical dynamics of constrained multibody systems. These equations are ordinary differential equations (ODE) subject to algebraic constraints. Accordinly they are called differential-algebraic equations (DAE).

Specific contributions made in this area include an explicit transforma-tion between the Hessenberg index-3 form for constrained mechanical systems to a canonical state-space form used in the nonlinear control communities. A hybrid solution method was developed that incorporates both sliding-mode control (SMC) from the controls literature and post-stabilization from …

Aurora Working Group: Dsr Front End Lvcsr Evaluation — Baseline Recognition System Description, Naveen Parihar, Joseph Picone

Publications

In this document we describe the features of the baseline system to be used in the Distributed Speech Recognition (DSR) front end large vocabulary continuous speech recognition (LVCSR) evaluations being conducted by the Aurora Working Group of the European Telecommunications Standards Institute (ETSI). The objective of these evaluations is to determine the robustness of different front ends for use in client/server type telecommunications applications. As such, our experiments are designed to test the following focus conditions on the DARPA Wall Street Journal (WSJ0) corpus using a 5000-word closed-loop vocabulary and a bigram language model:

1. Additive Noise: six noise conditions …

Three-Dimensional Spectral Classification Of Low-Metallicity Stars Using Artificial Neural Networks, Shawn Snider, Ted Von Hippel, Carlos Allende Prieto, Timothy C. Beers, Christopher Sneden, Et Al.

Publications

We explore the application of artificial neural networks (ANNs) for the estimation of atmospheric parameters (Teff, log g, and [Fe/H]) for Galactic F- and G-type stars. The ANNs are fed with medium-resolution (Δλ ~ 1-2 Å) non-flux-calibrated spectroscopic observations. From a sample of 279 stars with previous high-resolution determinations of metallicity and a set of (external) estimates of temperature and surface gravity, our ANNs are able to predict Teff with an accuracy of σ(Teff) = 135-150 K over the range 4250 ≤ Teff ≤ 6500 K, log g with an accuracy of σ(log …

Interfering Solutions Of A Nonhomogeneous Hamiltonian System, Gregory S. Spradlin

Publications

A Hamiltonian system is studied which has a term approaching a constant at an exponential rate at infinity. A minimax argument is used to show that the equation has a positive homoclinic solution. The proof employs the interaction between translated solutions of the corresponding homogeneous equation. What distinguishes this result from its few predecessors is that the equation has a nonhomogeneous nonlinearity.

Cluster Computing In The Classroom: Topics, Guidelines, And Experiences, Amy Apon, Rajkumar Buyya, Hai Jin, Jens Mache

Publications

With the progress of research on cluster computing, more and more universities have begun to offer various courses covering cluster computing. A wide variety of content can be taught in these courses. Because of this, a difficulty that arises is the selection of appropriate course material. The selection is complicated by the fact that some content in cluster computing is also covered by other courses such as operating systems, networking, or computer architecture. In addition, the background of students enrolled in cluster computing courses varies. These aspects of cluster computing make the development of good course material difficult. Combining our …

Climatology And Modeling Of Quasi-Monochromatic Atmospheric Gravity Waves Observed Over Urbana Illinois, J. H. Hecht, R. L. Walterscheid, Michael P. Hickey Ph.D., S. J. Franke

Publications

From analyzing nine months of airglow imaging observations of atmospheric gravity waves (AGWs) over Adelaide, Australia (35°S) [Walterscheid et al., 1999] have proposed that many of the quasi-monochromatic waves seen in the images were primarily thermally ducted. Here are presented 15 months of observations, from February 1996 to May 1997, for AGW frequency and propagation direction from a northern latitude site, Urbana Illinois (40°N). As Adelaide, Urbana is geographically distant from large orographic features. Similar to what was found in Adelaide, the AGWs seem to originate from a preferred location during the time period around summer solstice. In …

Gravity Wave Propagation Directions Inferred From Satellite Observations Including Smearing Effects, Jason S. Brown, Michael P. Hickey Ph.D.

Publications

We simulate space-based, sublimb viewing observations of airglow brightness fluctuations caused by atmospheric gravity wave interactions with the O2 atmospheric airglow, and we demonstrate that because of the geometry associated with such observations, the brightness fluctuations observed for the optically thick 0–0 band emission will always appear stronger for waves traveling toward the observer (the satellite). The effect should be most noticeable for waves having relatively small vertical wavelengths (∼10 km) and horizontal wavelengths of 50 km or greater. For waves of short (∼100 km) horizontal wavelength, the brightness fluctuation anisotropy with respect to viewing direction may also be evident …

Secular Variations Of Oi 5577 Å Airglow In The Mesopause Region Induced By Transient Gravity Wave Packets, Michael P. Hickey Ph.D., R. L. Walterscheid

Publications

We employ a 2-dimensional, time-dependent, fully nonlinear model of minor species in the mesopause region and our Spectral Full-Wave Model to simulate the response of minor species and the OI 5577 Å airglow to a gravity wave packet in the mesopause region. Gravity waves affect the time-averaged distribution of minor species in the mesosphere and lower thermosphere (MLT) region through constituent fluxes induced by violation of the non-acceleration conditions due to wave transience and dissipation. In addition, wave perturbed chemistry can induce a flux of chemically active species. Simulations are performed with nominal values of eddy diffusion coefficients in the …

A Determination Of The Local Density Of White Dwarf Stars, J. B. Holberg, Terry D. Oswalt, E. M. Sion

Publications

The most recent version of the Catalog of Spectroscopically Identified White Dwarfs lists 2249 white dwarf stars. Among these stars are 109 white dwarfs that have either reliable trigonometric parallaxes or color-based distance moduli that place them at a distance within 20 pc of the Sun. Most of these nearby white dwarfs are isolated stars, but 28 (25% of the sample) are in binary systems, including such well-known systems as Sirius A/B and Procyon A/B. There are also three double degenerate systems in this sample of the local white dwarf population. The sample of local white dwarfs is largely complete …

Fabricating And Imaging Carbon-Fiber Immobilized Enzyme Ultramicroelectrodes With Scanning Electrochemical Microscopy, David O. Wipf, Fuyun Ge, Robert C. Tenent

Publications

The scanning electrochemical microscope (SECM) is used to image the activity of enzymes immobilized on the surfaces of disk-shaped carbon-fiber electrodes. SECM was used to map the concentration of enzymatically produced hydroquinone or hydrogen peroxide at the surface of a 33-mm diameter disk-shaped carbon-fiber electrode modified by an immobilized glucose-oxidase layer. Sub-monolayer coverage of the enzyme at the electrode surface could be detected with micrometer resolution. The SECM was also employed as a surface modification tool to produce microscopic regions of enzyme activity by using a variety of methods. One method is a gold-masking process in which microscopic gold patterns …

Two Photon Absorption In Chromophore Doped Solid Matrices, S.C. Mancas, Michael Canva, Yves Levy, Kathleen A. Richardson, Giselle Roger

Publications

Over the past decades organic materials have shown an important potential for applications in the field of nonlinear optics. Two-photon absorbing materials can be optically addressed in three dimensions of space, which make them unique for many new applications, including 3D displays, optical memories, bio-sensors, etc. Fluorescent organic chromophores can be synthesized with structures especially optimized for this nonlinear optical property. Yet, for some applications, they have to be incorporated in solid state matrices. We especially investigate hybrid organic/inorganic doped matrices synthesized by solgel process. However , the linear transmission for such molecules is often significantly less than unity. Two-photon …