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Articles 1  30 of 106
FullText Articles in Physics
Classification Of Isometry Algebras Of Solutions Of Einstein's Field Equations, Eugene Hwang
Classification Of Isometry Algebras Of Solutions Of Einstein's Field Equations, Eugene Hwang
All Graduate Theses and Dissertations
Since Schwarzschild found the first solution of the Einstein’s equations, more than 800 solutions were found. Solutions of Einstein’s equations are classified according to their Lie algebras of isometries and their isotropy subalgebras. Solutions were taken from the USU electronic library of solutions of Einstein’s field equations and the classification used Maple code developed at USU. This classification adds to the data contained in the library of solutions and provides additional tools for addressing the equivalence problem for solutions to the Einstein field equations. In this thesis, homogeneous spacetimes, hypersurfacehomogeneous spacetimes, RobinsonTrautman solutions, and some famous black ...
Juxtaposition At 45 Km Of Temperatures From RayleighScatter Lidar And Reanalysis Models, David K. Moser
Juxtaposition At 45 Km Of Temperatures From RayleighScatter Lidar And Reanalysis Models, David K. Moser
All Graduate Theses and Dissertations
Weather and climate forecasts are almost exclusively produced by computer models, which use atmospheric measurements as starting points. It is a wellknown and jokedabout fact that model predictions can be incorrect at times. One of the reasons this happens is due to gaps in our knowledge of atmospheric conditions in areas where measurements don’t often taken place, such as the mesosphere, which stretches from roughly 4590 km altitude.
A lidar is a device that can shoot out short bursts of laser light to measure things such as atmospheric thickness at a distance. From this information one can then derive ...
Sensitivity Of The Opal Instrument For Gravity Wave Detection, Kenneth I. Zia
Sensitivity Of The Opal Instrument For Gravity Wave Detection, Kenneth I. Zia
All Graduate Theses and Dissertations
Knowing what goes on in the upper atmosphere (∼80140 km) is very important to the space science community. There are several competing forces that influence the temperature and densities of neutral molecules in that region. OPAL (Optical Profiling of the Atmospheric Limb) is funded by the National Science Foundation (NSF) to measure the temperature there using light from oxygen molecules (∼760 nm). To accomplish this,OPAL is built into a CubeSat (a satellite the size of a loaf of bread) to be launched from the International Space Station (ISS) at an altitude of about 400 km. This vantage point is ...
The Development Of Hydrodynamic And Kinetic Models For The Plasmasphere Refilling Problem Following A Geomagnetic Storm, Kausik Chatterjee
The Development Of Hydrodynamic And Kinetic Models For The Plasmasphere Refilling Problem Following A Geomagnetic Storm, Kausik Chatterjee
All Graduate Theses and Dissertations
The objective of this dissertation is the development of computer simulationbased models for the modeling of upper ionosphere, starting from the first principles. The models were validated by exact analytical benchmarks and are seen to be consistent with experimentally obtained results. This area of research has significant implications in the area of global communication. In addition, these models would lead to a better understanding of the physical processes taking place in the upper ionosphere.
Mesospheric Gravity Wave Climatology And Variances Over The Andes Mountains, Jonathan Rich Pugmire
Mesospheric Gravity Wave Climatology And Variances Over The Andes Mountains, Jonathan Rich Pugmire
All Graduate Theses and Dissertations
Look up! Travelling over your head in the air are waves. They are present all the time in the atmosphere all over the Earth. Now imagine throwing a small rock in a pond and watching the ripples spread out around it. The same thing happens in the atmosphere except the rock is a thunderstorm, the wind blowing over a mountain, or another disturbance. As the wave (known as a gravity wave) travels upwards the thinning air allows the wave to grow larger and larger. Eventually the gravity wave gets too large – and like waves on the beach – it crashes causing ...
Investigating The Climatology Of Mesospheric And Thermospheric Gravity Waves At High Northern Latitudes, Michael Negale
Investigating The Climatology Of Mesospheric And Thermospheric Gravity Waves At High Northern Latitudes, Michael Negale
All Graduate Theses and Dissertations
An important property of the Earth's atmosphere is its ability to support wave motions, and indeed, waves exist throughout the Earth's atmosphere at all times and all locations. What is the importance of these waves? Imagine standing on the beach as water waves come crashing into you. In this case, the waves transport energy and momentum to you, knocking you off balance. Similarly, waves in the atmosphere crash, known as breaking, but what do they crash into? They crash into the atmosphere knocking the atmosphere off balance in terms of the winds and temperatures. Although the Earth's ...
The Role Of Recoverable And NonRecoverable Defects In Dc Electrical Aging Of Highly Disordered Insulating Materials, Allen Andersen
The Role Of Recoverable And NonRecoverable Defects In Dc Electrical Aging Of Highly Disordered Insulating Materials, Allen Andersen
All Graduate Theses and Dissertations
Electrical insulation under high voltage can eventually fail, causing critical damage to electronics. Such electrostatic discharge (ESD) is the primary source of anomalies or failures on spacecraft due to charged particles from the Sun or planetary radiation belts accumulating in spacecraft insulators. Highvoltage direct current power distribution is another example of a growing industry that needs to estimate the operational lifetime of electrical insulation. My research compares laboratory tests of ESD events in common insulating materials to a physicsbased model of breakdown. This model of breakdown is based on the approximation that there are two primary types of defects in ...
The Investigation Of Gravity Waves In The Mesosphere / Lower Thermosphere And Their Effect On Sporadic Sodium Layer, Xuguang Cai
The Investigation Of Gravity Waves In The Mesosphere / Lower Thermosphere And Their Effect On Sporadic Sodium Layer, Xuguang Cai
All Graduate Theses and Dissertations
Gravity waves in the atmosphere are the waves with gravity and buoyancy force as the restoring forces. Gravity waves will significantly impact the Mesosphere Lower / Thermosphere (MLT), and the breaking of gravity waves is the key factor to cause the cool summer and warm winter in the Mesopause region. Therefore, it is important for us to investigate gravity waves. In this dissertation, we mainly use USU Na lidar data to explore gravity waves in the MLT. The exploration is made up of two projects. One is the investigation of gravity wave breaking and the associated dynamic instability by USU Na ...
29Day Analysis Of Scale Heights And The Inference Of The Topside Ionosphere Over Millstone Hill During The 2002 Incoherent Scatter Radar Campaign, Jennifer L. Meehan
29Day Analysis Of Scale Heights And The Inference Of The Topside Ionosphere Over Millstone Hill During The 2002 Incoherent Scatter Radar Campaign, Jennifer L. Meehan
All Graduate Theses and Dissertations
Ionospheric scale height is a measure of the topside altitude dependence of electron density and is a key ionospheric parameter due to its intrinsic connection to ionospheric dynamics, plasma temperature, and composition. A longtime problem has been that information on the bottomside ionospheric profile is readily available, but the observation of the topside ionosphere is still challenging. Despite numerous data techniques to characterize the topside ionosphere, the knowledge of the behavior of the topside ionosphere and its subsequent scale heights remains insufficient. The goal of this study is to evaluate whether or not we can characterize the topside ionospheric density ...
Design And Characterization Of A TimeOfFlight Mass Spectrometer For Composition Measurements In The Upper Atmosphere, E. Addison Everett
Design And Characterization Of A TimeOfFlight Mass Spectrometer For Composition Measurements In The Upper Atmosphere, E. Addison Everett
All Graduate Theses and Dissertations
Insitu composition measurements of the mesosphere/lower thermosphere (MLT) are challenging; this region is only accessible via highspeed sounding rockets, ambient pressures extend into the 10^{3} Torr range, and particles of interest range in mass from electrons to meteoric smoke and dust particles. Timeofflight mass spectrometers (TOFMS) are capable of making fast, accurate measurements over a wide mass range. However, since they rely on pressuresensitive microchannel plate (MCP) detectors and high voltages, they have rarely been applied at these altitudes. A new TOFMS for making insitu composition measurements in the MLT has been developed at the Space Dynamics Laboratory ...
On The Propagation Of Atmospheric Gravity Waves In A NonUniform Wind Field: Introducing A Modified AcousticGravity Wave Equation, Ahmad Talaei
All Graduate Plan B and other Reports
Atmospheric gravity waves play fundamental roles in a broadrange of dynamical processes extending throughout the Earth’s neutral atmosphere and ionosphere. In this paper, we present a modified form for the acousticgravity wave equation and its dispersion relationships for a compressible and nonstationary atmosphere in hydrostatic balance. Importantly, the solutions have been achieved without the use of the wellknown Boussinesq approximation which have been used extensively in previous studies.
We utilize the complete set of governing equations for a compressible atmosphere with nonuniform airflows to determine an equation for vertical velocity of possible atmospheric waves. This intricate wave equation is ...
Investigating The Effect Of Carbon Nanotube Functionalization In A Polydimethylsiloxane Composite Through Use Of A Stepped Bar Apparatus, Matthew I. Ralphs
Investigating The Effect Of Carbon Nanotube Functionalization In A Polydimethylsiloxane Composite Through Use Of A Stepped Bar Apparatus, Matthew I. Ralphs
All Graduate Theses and Dissertations
Thermal interface materials (TIMs) are used as an aid in transporting heat away from a circuit or electronic module. Composite materials are a popular research area for TIMs because they allow the desired properties from the individual constituents to be combined. The composite selected for this study uses carbon nanotubes (CNT) as the filler and an elastomeric polymer for the matrix, specifically a multiwalled carbon nanotube (MWCNT) / polydimethylsiloxane (PDMS) composite. Additionally, functionalization of the CNT may affect the composites’ thermal conductivity because of its effect on the CNT dispersion in the polymer matrix and its effect on the CNTpolymer interface ...
Thermal Property Measurement Of Thin Fibers By Complementary Methods, Troy Robert Munro
Thermal Property Measurement Of Thin Fibers By Complementary Methods, Troy Robert Munro
All Graduate Theses and Dissertations
To improve measurement reliability and repeatability and resolve the orders of magnitude discrepancy between the two different measurements (via reduced model transient electrothermal and lockin IR thermography), this dissertation details the development of three complementary methods to accurately measure the thermal properties of the natural and synthetic Nephila (N.) clavipes spider dragline fibers. The thermal conductivity and diffusivity of the dragline silk of the N. clavipes spider has been characterized by one research group to be 151416 W m−1 K −1 and 6.412.3 ×10−5 m2 s −1 , respectively, for samples with low to high strains (zero ...
RayleighScatter Lidar Measurements Of The Mesosphere And Thermosphere And Their Connections To Sudden Stratospheric Warmings, Leda Sox
All Graduate Theses and Dissertations
The Earth’s middle atmosphere is comprised of the stratosphere, mesosphere and thermosphere, from approximately 10 to 110 km, or approximately 6 to 68 miles. An understanding of the dynamics and climatological conditions in this region is of vital importance to the aerospace industry and military, which both launch aircraft and spacecraft into this region, as well as researchers who study climate change and the interactions between the atmosphere and the Earth, oceans, and space.
Measurements of atmospheric properties (density, temperature, and pressure) in this region are relatively difficult to gather as the middle atmosphere’s altitudes are both too ...
Cryostat System For Spacecraft Materials Testing, Justin Dekany
Cryostat System For Spacecraft Materials Testing, Justin Dekany
All Graduate Theses and Dissertations
The main cause of spacecraft failures is due to the harsh space environment; therefore, rigorous testing of materials used in modern spacecraft is imperative to ensure proper operation during the life span of the mission. Enhancing the capabilities of groundbased test facilities allows for more accurate measurements to be taken as it better simulates the environment to which spacecraft will be exposed. The range of temperature measurements has been significantly extended for an existing space environment simulation test chamber used in the study of electron emission, sample charging and discharge, electrostatic discharge and arcing, electron transport, and luminescence of spacecraft ...
Cryostat System For Spacecraft Materials Testing, Justin Dekany
Cryostat System For Spacecraft Materials Testing, Justin Dekany
Theses and Dissertations
The main cause of spacecraft failures is due to the harsh space environment; therefore, rigorous testing of materials used in modern spacecraft is imperative to ensure proper operation during the life span of the mission. Enhancing the capabilities of groundbased test facilities allows for more accurate measurements to be taken as it better simulates the environment to which spacecraft will be exposed. The range of temperature measurements has been significantly extended for an existing space environment simulation test chamber used in the study of electron emission, sample charging and discharge, electrostatic discharge and arcing, electron transport, and luminescence of spacecraft ...
Explicit Construction Of First Integrals For The Toda Flow On A Classical Simple Lie Algebra, Patrick Seegmiller
Explicit Construction Of First Integrals For The Toda Flow On A Classical Simple Lie Algebra, Patrick Seegmiller
All Graduate Theses and Dissertations
The Toda flow is a Hamiltonian system which evolves on the dual of the Borel subalgebra of a complex Lie algebra g. The dual of the Borel subalgebra can be identified with an affine subspace of its negative plus the element given by the sum of the simple root vectors in g. The system has been proven completely integrable in the Liouville sense on a generic coadjoint orbit for the Borel subgroup. This paper gives a verification of integrability of the Toda flow on classical simple Lie algebras and describes a method for the construction of a complete collection of ...
The Role Of Thermospheric Neutral Winds In The MidLatitude Ionospheric Evening Anomalies, Levan Lomidze
The Role Of Thermospheric Neutral Winds In The MidLatitude Ionospheric Evening Anomalies, Levan Lomidze
All Graduate Theses and Dissertations
One of the intriguing features of the Fregion ionosphere are anomalous evening enhancements of the electron density over certain midlatitude sites. The most prominent example of this enhancement is the Weddell Sea Anomaly. Although the evening anomalies have been known for several decades, their generation mechanisms are still under debate and their accurate modeling remains a challenge. In this dissertation, the role of thermospheric neutral winds in the generation of these anomalies is investigated.
Thermospheric winds play an important role in the dynamics of the Fregion ionosphere, and, as it will be shown, in the generation of the evening anomalies ...
A Study Of The Dayside HighLattitude Ionospheric Electrodynamics During Extended Solar Minimum, Janelle V. Jenniges
A Study Of The Dayside HighLattitude Ionospheric Electrodynamics During Extended Solar Minimum, Janelle V. Jenniges
All Graduate Theses and Dissertations
The highlatitude electric eld fallo region connects convection in the polar cap to the region where ring currents modify the penetration electric field equatorward of the polar cap boundary. This region is often overlooked because it falls between the limits of low latitude and highlatitude ionospheric models. However, penetrating electric fields cause large changes in ion composition; and therefore, correctly modeling the electric fields and plasma drift in this region aids in correctly specifying the ionosphere. Many ionospheric models use the Kp index as a physical driver, and so the latitude dependence of the plasma drift in the fallo region ...
Altitudinal Variability Of QuietTime Plasma Drifts In The Equatorial Ionosphere, Debrup Hui
Altitudinal Variability Of QuietTime Plasma Drifts In The Equatorial Ionosphere, Debrup Hui
All Graduate Theses and Dissertations
The plasma drifts or electric fields and their structures in the ionosphere affect the accuracy of the presentday spacebased systems. For the first time, we have used ionospheric plasma drift data from Jicamarca radar measurements to study the climatology of altitudinal variations of vertical and zonal plasma drifts in low latitudes during daytime. We used data from 1998 to 2014 to derive these climatological values in bimonthly bins from 150 km to 600 km. For the vertical plasma drifts, we observed the drifts increasing with altitudes in the morning and slowly changing to drifts decreasing with altitude in the afternoon ...
Optical Characterization Of Carbon Nanotube Forests, Brian D. Wood
Optical Characterization Of Carbon Nanotube Forests, Brian D. Wood
All Graduate Theses and Dissertations
Carbon nanotube forests are vertically grown tubular formations of graphene. Samples were grown with an injection chemical vapor deposition method on substrates of silicon with various deposited layers and bare fused silica. The morphology of the forest is characterized by the height, density, and presence of defects. Total diffuse reflectance and transmittance measurements were taken in the 216 �m spectral range and correlated to the forest’s specific morphology. From these correlations, the conditions necessary to maximize the absorption of the forest were found and exploited to cater sample growth for specific substrates to make ideal absorbers. From the transmittance ...
Gravitational Wave Astrophysics With Compact Binary Systems, Eric Addison
Gravitational Wave Astrophysics With Compact Binary Systems, Eric Addison
All Graduate Theses and Dissertations
In this dissertation, I present two studies in the field of gravitational wave astrophysics applied to compact binary systems. In the first project, I investigate simulated encounters between a binary system comprised of two stellar mass black holes with a galactic supermassive black hole. It is found that binaries disrupted by the supermassive black hole form extreme mass ratio inspirals (EMRIs), which would begin with very high eccentricity, e ≈ 1 − O(10−2), but circularize dramatically by the emission of gravitational wave radiation. At the time when the stable orbit turns over to a plunge orbit, the EMRIs still have ...
Conformal Gravity And Time, Jeffrey Shafiq Hazboun
Conformal Gravity And Time, Jeffrey Shafiq Hazboun
All Graduate Theses and Dissertations
Cartan geometry provides a rich formalism from which to look at various geometrically motivated extensions to general relativity. In this manuscript, we start by motivating reasons to extend the theory of general relativity. We then introduce the reader to our technique, called the quotient manifold method, for extending the geometry of spacetime. We will specifically look at the class of theories formed from the various quotients of the conformal group. Starting with the conformal symmetries of Euclidean space, we construct a manifold where time manifests as a part of the geometry. Though there is no matter present in the geometry ...
Modeling The Defect Density Of States Of Disordered Sio2 Through Cathodoluminescence, Amberly Evans Jensen
Modeling The Defect Density Of States Of Disordered Sio2 Through Cathodoluminescence, Amberly Evans Jensen
All Graduate Theses and Dissertations
This study measures the electroninduced luminescence (cathodoluminescence) for various samples of fused silica. With a band gap of ~8.9 eV, visible and nearIR (NIR) luminescence occurs only if there are states (localized defect or trap states) within the forbidden band gap for electrons to occupy. A model is presented based on the electronic band structure and defect density of states—used to explain electron transport in highly disordered insulating materials—which has been extended to describe the relative cathodoluminescent intensity and spectral bands as a function of incident beam energy and current density, sample temperatures, and emitted photon wavelength ...
Modeling The Defect Density Of States Of Disordered Sio2 Through Cathodoluminescence, Amberly Evans Jensen
Modeling The Defect Density Of States Of Disordered Sio2 Through Cathodoluminescence, Amberly Evans Jensen
Theses and Dissertations
Spacecraft charging is the accumulation of an electrical charge on orbiting spacecraft induced by the space plasma environment and has harmful effects on the electrical functionality of a spacecraft. This is studied extensively, particularly in the Materials Physics Group (MPG) at Utah State University (USU). During charging studies performed by the MPG, another potentially problematic effect of the space plasma environment on spacecraft was observed: light emanating from the sample undergoing electron beam bombardment. Spacebased observatories are one type of spacecraft on which this luminescence may occur. If the luminescence from the material caused by the space plasma is within ...
Unified Model Of Charge Transport In Insulating Polymeric Materials, Alec Sim
Unified Model Of Charge Transport In Insulating Polymeric Materials, Alec Sim
All Graduate Theses and Dissertations
Charge transport, charging, and subsequent electrostatic discharge due to interactions with the space environment are primary concerns of spacecraft designers. Developing a physical understanding of the interactions of charge with the multitude of materials that spacecraft are composed of is a critical step in understanding and mitigating both shortterm and longterm spacecraft degradation. In particular, the study of charge transport in highly insulating materials is critical as they store charge longer, with higher capacity, and with greater destructive capability than other materials.
The Utah State University Materials Physics Group, with the funding of the NASA James Webb Space Telescope project ...
Lunar Tidal Effects In The Electrodynamics Of The LowLatitude Ionosphere, Brian David Tracy
Lunar Tidal Effects In The Electrodynamics Of The LowLatitude Ionosphere, Brian David Tracy
All Graduate Theses and Dissertations
We used extensive measurements made by the Jicamarca Unattended LongTerm Investigations of the Ionosphere and Atmosphere (JULIA) and Incoherent Scatter Radar (ISR) systems at Jicamarca, Peru during geomagnetic quiet conditions to determine the climatologies of lunar tidal effects on equatorial vertical plasma drifts. We use, for the first time, the expectation maximization (EM) algorithm to derive the amplitudes and phases of the semimonthly and monthly lunar tidal perturbations. Our results indicate, as expected, lunar tidal effects can significantly modulate the equatorial plasma drifts. The local time and seasonal dependent phase progression has been studied in much more detail than previously ...
Carrier Dynamics In Ingaas/Gaas Quantum Dots Excited By Femtosecond Laser Pulses, Kripa Nidhan Chauhan
Carrier Dynamics In Ingaas/Gaas Quantum Dots Excited By Femtosecond Laser Pulses, Kripa Nidhan Chauhan
All Graduate Theses and Dissertations
Ultrafast carrier dynamics studies have been carried out on samples with single layers of selfassembled In_{0.4}Ga_{0.6}As/GaAs quantum dots (QDs). Measurements were made using femtosecond degenerate pumpprobe differential reflectivity with an 800nm, 28fs Tisapphire oscillator as the source. The QDs were grown via modified StranskiKrastanov growth. This modified growth process consists of two steps: lowtemperature growth and hightemperature annealing. Specifically, the InGaAs QD structures are fabricated on ntype GaAs(001) using molecular beam epitaxy. The InGaAs layer is deposited at 3503700C followed by QD self assembly at 4204900C. Finally, these QDs are capped with ...
Parallel Heat Transport In Magnetized Plasma, Mukta Sharma
Parallel Heat Transport In Magnetized Plasma, Mukta Sharma
All Graduate Theses and Dissertations
A code that solves the coupled electron drift kinetic and temperature equations has been written to study the effects of collisionality and particle trapping on temperature equilibration along magnetic field lines. A ChapmanEnskoglike approach is adopted with the timedependent distribution function written as the sum of a dynamic Maxwellian and a kinetic distortion expanded in Legendre polynomials. The drift kinetic equation is solved on a discrete grid in normalized speed, and an FFT algorithm is used to treat the onedimensional spatial domain along the magnetic field. The dependence of the steadystate temperature on collisionality and magnetic well depths is discussed ...
A Numerical Algorithm For Simulating Two Species Plasma, Richard F. Datwyler
A Numerical Algorithm For Simulating Two Species Plasma, Richard F. Datwyler
All Graduate Theses and Dissertations
An algorithm for modeling two species plasmas, which evolves the number density, flow velocity, and temperature equations coupled to Maxwell's electric and magnetic field equations, is discussed. Charge separation effects and the displacement current are retained. Mathematical derivations of normal modes in cold and hot plasmas, as represented by dispersion relations resulting from a linear analysis of the two fluid equations, are presented. In addition, numerical theory in relation to the ideas of geometry, temporal and spatial discretization, linearization of the fluid equations, and an expansion using finite elements is given. Numerical results generated by this algorithm compare favorably ...