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Articles 1 - 30 of 96
Full-Text Articles in Physical Sciences and Mathematics
Gravity Wave Heating And Cooling Of The Thermosphere: Sensible Heat Flux And Viscous Flux Of Kinetic Energy, Michael P. Hickey Ph.D., R. L. Walterscheid, G. Schubert
Gravity Wave Heating And Cooling Of The Thermosphere: Sensible Heat Flux And Viscous Flux Of Kinetic Energy, Michael P. Hickey Ph.D., R. L. Walterscheid, G. Schubert
Publications
Total wave heating is the sum of the convergence of the sensible heat flux and the divergence of the viscous flux of wave kinetic energy. Numerical simulations, using a full-wave model of the viscous damping of atmospheric gravity waves propagating in a nonisothermal atmosphere, are carried out to explore the relative contributions of these sources of wave heating as a function of wave properties and altitude. It is shown that the sensible heat flux always dominates in the lower thermosphere, giving a lower region of heating and an upper stronger region of cooling. The heating due to the divergence of …
Fragile Binary Candidates In The Sdss Dr8 Spectroscopic Archive, J. K. Zhao, Terry D. Oswalt, G. Zhao
Fragile Binary Candidates In The Sdss Dr8 Spectroscopic Archive, J. K. Zhao, Terry D. Oswalt, G. Zhao
Publications
We present a catalog of 80 very wide fragile binary candidates (projected separations >10,000 AU) from the Sloan Digital Sky Survey Data Release Eight spectral archive. The pairs were selected based on proper motion, radial velocity, metallicity, and photometric parallax criteria. The angular separations of these pairs range from 3'' to 250''. The peak in the metallicity distribution of these pairs is about −0.5 dex of solar metallicity. Space motions and reduced proper motion diagrams indicate that all these pairs are members of the disk. The chromospheric activity index SHK of each component in 38 binary candidates having spectra …
Orbital Separation Amplification In Fragile Binaries With Evolved Components, K. B. Johnston, Terry D. Oswalt
Orbital Separation Amplification In Fragile Binaries With Evolved Components, K. B. Johnston, Terry D. Oswalt
Publications
The secular stellar mass-loss causes an amplification of the orbital separation in fragile, common proper motion, binary systems with separations of the order of 1000 A.U. In these systems, companions evolve as two independent coeval stars as they experience negligible mutual tidal interactions or mass transfer. We present models for how post-main sequence mass-loss statistically distorts the frequency distribution of separations in fragile binaries. These models demonstrate the expected increase in orbital seapration resulting from stellar mass-loss, as well as a perturbation of associated orbital parameters. Comparisons between our models and observations resulting from the Luyten survey of wide visual …
Application Of Asymptotic Expansions For Maximum Likelihood Estimators' Errors To Gravitational Waves From Inspiraling Binary Systems: The Network Case, Salvatore Vitale, Michele Zanolin
Application Of Asymptotic Expansions For Maximum Likelihood Estimators' Errors To Gravitational Waves From Inspiraling Binary Systems: The Network Case, Salvatore Vitale, Michele Zanolin
Publications
This paper describes the most accurate analytical frequentist assessment to date of the uncertainties in the estimation of physical parameters from gravitational waves generated by nonspinning binary systems and Earth-based networks of laser interferometers. The paper quantifies how the accuracy in estimating the intrinsic parameters mostly depends on the network signal to noise ratio (SNR), but the resolution in the direction of arrival also strongly depends on the network geometry. We compare results for 6 different existing and possible global networks and two different choices of the parameter space. We show how the fraction of the sky where the one …
Book Review: The Cambridge Atlas Of Herschel Objects, T. D. Oswalt
Book Review: The Cambridge Atlas Of Herschel Objects, T. D. Oswalt
Publications
This document is Dr. Oswalt’s review of The Cambridge Atlas of Herschel Objects by James Mullaney and Wil Tirion Cambridge, 2011 183p, 0521138175 $35.00, 9780521138178 $35.00.
Light-Bending Tests Of Lorentz Invariance, Quentin G. Bailey, Rhondale Tso
Light-Bending Tests Of Lorentz Invariance, Quentin G. Bailey, Rhondale Tso
Physics & Astronomy - Prescott
Classical light-bending is investigated for weak gravitational fields in the presence of hypothetical local Lorentz violation. Using an effective field theory framework that describes general deviations from local Lorentz invariance, we derive a modified deflection angle for light passing near a massive body. The results include anisotropic effects not present for spherical sources in General Relativity as well as Weak Equivalence Principle violation. We develop an expression for the relative deflection of two distant stars that can be used to analyze data in past and future solar-system observations. The measurement sensitivities of such tests to coefficients for Lorentz violation are …
Cluster Observations Of Bow Shock Energetic Ion Transport Through The Magnetosheath Into The Cusp, K. J. Trattner, S. M. Petrinec, S. A. Fuselier, K. Nykyri, E. Kronberg
Cluster Observations Of Bow Shock Energetic Ion Transport Through The Magnetosheath Into The Cusp, K. J. Trattner, S. M. Petrinec, S. A. Fuselier, K. Nykyri, E. Kronberg
Publications
The observation of energetic particles by polar orbiting satellites in the magnetospheric cusp resulted in a controversy about their source region. It has been suggested that these cusp energetic particles (CEP) with significant fluxes from magnetosheath energies up to several hundred keV/e are accelerated locally in the cusp by the turbulence found in cusp diamagnetic cavities (CDC). As an alternative to the local acceleration region, the quasi‐parallel shock is successful as a source region for CEP events. Energetic ions accelerated at the bow shock can be transported downstream and enter the cusp along newly reconnected field lines. Composition and energy …
Two-Scale Microstructure Dynamics, Arkadi Berezovski, Mihhail Berezovski, Juri Engelbrecht
Two-Scale Microstructure Dynamics, Arkadi Berezovski, Mihhail Berezovski, Juri Engelbrecht
Publications
Wave propagation in materials with embedded two different microstructures is considered. Each microstructure is characterized by its own length scale. The dual internal variables approach is adopted yielding in a Mindlin-type model including both microstructures. Equations of motion for microstructures are coupled with the balance of linear momentum for the macromotion, but not coupled with each other. Corresponding dispersion curves are provided and scale separation is pointed out.
The 25 Parsec Local White Dwarf Population, Jerry B. Holberg, Terry D. Oswalt, Edward M. Sion, George P. Mccook
The 25 Parsec Local White Dwarf Population, Jerry B. Holberg, Terry D. Oswalt, Edward M. Sion, George P. Mccook
Publications
We have extended our detailed survey of the local white dwarf population from 20 pc to 25 pc, effectively doubling the sample volume, which now includes 232 stars. In the process new stars within 20 pc have been added, a more uniform set of distance estimates as well as improved spectral and binary classifications are available. The present 25 pc sample is estimated to be about 68% complete (the corresponding 20 pc sample is now 86% complete). The space density of white dwarfs is unchanged at 4.8 ± 0.5 x 10-3 pc-3. This new study includes a white dwarf mass …
Left Ventricular Assist Devices: Engineering Design Considerations, Marwan A. Simaan, Eduardo Divo, George Faragallah, Yu Wang
Left Ventricular Assist Devices: Engineering Design Considerations, Marwan A. Simaan, Eduardo Divo, George Faragallah, Yu Wang
Publications
Patients with end-stage congestive heart failure awaiting heart transplantation often wait long periods of time (300 days or more on the average) before a suitable donor heart becomes available. The medical community has placed increased emphasis on the use of Left Ventricular Assist Devices or LVADs that can substitute for, or enhance, the function of the natural heart while the patient is waiting for the heart transplant (Poirier, 1997; Frazier & Myers, 1999). Essentially, a rotary LVAD is a pump that operates continuously directing blood from the left ventricle into the aorta by avoiding the aortic valve. Generally speaking, the …
Global Satellite Images For Aviation Operations, Frederick R. Mosher, James Block
Global Satellite Images For Aviation Operations, Frederick R. Mosher, James Block
Applied Aviation Sciences - Daytona Beach
Flight planning and flight following dispatch operations require information on potential flight hazards. Hazards such as thunderstorms, turbulence, icing, fog, volcanic ash, etc., are potential problems which are not always forecast adequately by numerical models. Satellite images are used to monitor the weather conditions causing existing flight hazards, as well as being used to identify the development of new hazards.
Assessing The Effects Of Climate Change And Addressing Solutions At L. F. Wade International Airport, Bermuda, Sebastian Romeo Phillip Brisson
Assessing The Effects Of Climate Change And Addressing Solutions At L. F. Wade International Airport, Bermuda, Sebastian Romeo Phillip Brisson
Doctoral Dissertations and Master's Theses
The purpose of this thesis was to find how past trends and future predictions of climate change and associated factors would affect airport operations at the L. F. Wade International Airport. The Government of Bermuda's plans to build a new terminal were also analyzed to determine potential impacts. Predicted future trends of sea level rise and hurricane activity were assessed by analyzing previous occurrences and studies and depicted using GIS mapping data. Risk of storm surge to the L. F. Wade International Airport has become apparent, especially after Hurricane Fabian of 2003. The results of this study suggest that the …
Particle‐In‐Cell Simulation Of Incoherent Scatter Radar Spectral Distortions Related To Beam‐Plasma Interactions In The Auroral Ionosphere, M. A. Diaz, M. Oppenheim, J. L. Semeter, M. Zettergren
Particle‐In‐Cell Simulation Of Incoherent Scatter Radar Spectral Distortions Related To Beam‐Plasma Interactions In The Auroral Ionosphere, M. A. Diaz, M. Oppenheim, J. L. Semeter, M. Zettergren
Publications
An electrostatic parallel particle‐in‐cell (EPPIC) code that allows for particle beam injections and multiple boundary conditions is used to investigate the beam‐plasma interaction and its manifestations in the incoherent scatter (IS) spectrum. Specifically, the code is used to investigate anomalous enhancements in the ion acoustic line through the destabilization of the plasma by injection (or precipitation) of low‐energy electron beams. This enhancement of the ion acoustic line is a form of IS distortion commonly observed in the vicinity of auroral arcs called the naturally enhanced ion‐acoustic line (NEIAL). Simulations confirm the parametric decay of Langmuir waves as a plausible mechanism, …
Turbulence And Wave Dynamics Across Gas–Liquid Interfaces, Shahrdad Sajjadi, Julian Hunt, Stephen Belcher, Derek Stretch, John Clegg
Turbulence And Wave Dynamics Across Gas–Liquid Interfaces, Shahrdad Sajjadi, Julian Hunt, Stephen Belcher, Derek Stretch, John Clegg
Publications
Mechanisms are reviewed here for the distortion of turbulent flows near thin density interfaces and their effects on transfer processes across them. Firstly the results of rapid distortion calculations show how the in homogeneous eddy structure depends on whether the turbulence is generated above or below the interface, or in both regions. The flow is unstratified and the buoyancy forces are stable and strong enough relative to the inertial forces that the interface is continuous. It is shown that as the surface blocks the vertical turbulent eddy motions, horizontal straining motions are induced which affect the surface viscous layers and …
The Effects Of Eye Gaze Based Control On Operator Performance In Monitoring Multiple Displays, Allison Popola
The Effects Of Eye Gaze Based Control On Operator Performance In Monitoring Multiple Displays, Allison Popola
Doctoral Dissertations and Master's Theses
This study investigated the utility and efficacy of using eye tracking technology as a method for selecting control of a camera within a multiple display configuration. A task analysis with a Keystroke-Level-Model (KLM) was conducted to acquire an estimated time for switching between cameras. KLM estimates suggest that response times are faster using an eye tracker than manual control -indicating a time savings. To confirm these estimates, and test other hypotheses a 2 × 2 within-subjects factorial design was used to examine the effects of Control (Using an eye tracker, or manual) under different Task Loads (Low, High). Dependent variables …
Using A Systemic Model Of Accident For Improving Innovative Technologies: Application And Limitations Of The Stamp Model To A Process For Treatment Of Contaminated Substances, Karim Hardy, Franck Guarnieri
Using A Systemic Model Of Accident For Improving Innovative Technologies: Application And Limitations Of The Stamp Model To A Process For Treatment Of Contaminated Substances, Karim Hardy, Franck Guarnieri
Publications
This paper presents the STAMP accident model, based on systems theory, and describes its application in the context of risk prevention related to the remediation of contaminated materials. The implementation of the model is described, and results are presented both in methodological and technical terms.
The 2009 Samoa And 2010 Chile Tsunamis As Observed In The Ionosphere Using Gps Total Electron Content, David A. Galvan, Attila Komjathy, Michael P. Hickey Ph.D., Anthony J. Mannucci
The 2009 Samoa And 2010 Chile Tsunamis As Observed In The Ionosphere Using Gps Total Electron Content, David A. Galvan, Attila Komjathy, Michael P. Hickey Ph.D., Anthony J. Mannucci
Publications
Ground‐based Global Positioning System (GPS) measurements of ionospheric total electron content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events: the Samoa earthquake of 29 September 2009 and the Chile earthquake of 27 February 2010. Both earthquakes produced ocean tsunamis that were destructive to coastal communities near the epicenters, and both were observed in tidal gauge and buoy measurements throughout the Pacific Ocean. We observe fluctuations in TEC correlated in time, space, and wave properties with these tsunamis using the Jet Propulsion Laboratory’s Global Ionospheric Mapping software. These TEC measurements were …
Group Velocity And Energy Flux In The Thermosphere: Limits On The Validity Of Group Velocity In A Viscous Atmosphere, R. L. Walterscheid, Michael P. Hickey Ph.D.
Group Velocity And Energy Flux In The Thermosphere: Limits On The Validity Of Group Velocity In A Viscous Atmosphere, R. L. Walterscheid, Michael P. Hickey Ph.D.
Publications
The response to wave forcing of finite duration comprises a transient forerunner and the steady state signal (or simply the signal). It is the latter that carries information on the spectral content of the forcing, and the signal velocity is the velocity at which wave energy flows. To the extent that group velocity is a good measure of the energy flow velocity, the ray‐tracing formalism is a valid description of signal propagation. We have examined vertical group velocities as a measure of vertical energy flow velocity for gravity and acoustic waves propagating into the dissipative lower thermosphere. We find that …
On The Origin Of Fluctuations In The Cusp Diamagnetic Cavity, K. Nykyri, A. Otto, E. Adamson, A. Tjulin
On The Origin Of Fluctuations In The Cusp Diamagnetic Cavity, K. Nykyri, A. Otto, E. Adamson, A. Tjulin
Publications
We have analyzed Cluster magnetic field and plasma data during high‐altitude cusp crossing on 14 February 2003. Cluster encountered a diamagnetic cavity (DMC) during northward interplanetary magnetic field (IMF) conditions, and as IMF rotated southward, the spacecraft reencountered the cavity more at the sunward side. The DMC is characterized by a high level of magnetic field fluctuations and high‐energy electrons and protons. Ultralow‐frequency turbulence has been suggested as a mechanism to accelerate particles in DMC. We demonstrate in this paper for the first time that many of the low‐frequency fluctuations in the cavity are back and forth motion of the …
Modelling And Hazard Analysis For Contaminated Sediments Using Stamp Model, Karim Hardy, Franck Guarnieri
Modelling And Hazard Analysis For Contaminated Sediments Using Stamp Model, Karim Hardy, Franck Guarnieri
Publications
Processes for remediation (removal of pollution or contaminants) of contaminated sediments have been very efficient. These technologies, which are particularly complex, call for a comprehensive approach to risk analysis which characterises all threats (to humans, equipment, local residents, the environment, etc.) . The STAMP accident model (Systems-Theoretic Accident Model and Processes) is an example of such a comprehensive approach, and it has been chosen to characterise the risks associated with Novosol (registered trademark), an innovative remediation process.
Interactions And Focusing Of Nonlinear Water Waves, Harihar Khanal, S.C. Mancas, Shahrdad Sajjadi
Interactions And Focusing Of Nonlinear Water Waves, Harihar Khanal, S.C. Mancas, Shahrdad Sajjadi
Publications
A theoretical and computational study is undertaken for the modulational instabilities of a pair of nonlinearly interacting two-dimensional waves in deep water. It has been shown that the full dynamics of these interacting waves gives rise to localized large-amplitude wavepackets (wave focusing). The coupled cubic nonlinear Schrödinger (CNLS) equations are used to derive a nonlinear dispersion equation which give rise to new class of modulational instabilities and demonstrates the dependence of obliqueness of the interacting waves. The computations, due to nonlinear wave-wave interactions, waves that are separately modulationally stable can give rise to the formation of large-amplitude coherent wave packets …