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Utah State University

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2000

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Full-Text Articles in Physical Sciences and Mathematics

Ely Disrict Managed Natural And Prescribed Fire Plan, United States Department Of The Interior, Bureau Of Land Management Nov 2000

Ely Disrict Managed Natural And Prescribed Fire Plan, United States Department Of The Interior, Bureau Of Land Management

All U.S. Government Documents (Utah Regional Depository)

No abstract provided.

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Management Guidelines For Sage Grouse And Sagebrush Ecosystems In Nevada, Bureau Of Land Management Oct 2000

Management Guidelines For Sage Grouse And Sagebrush Ecosystems In Nevada, Bureau Of Land Management

All U.S. Government Documents (Utah Regional Depository)

These management guidelines and supportive background information promote the conservation of sage grouse (Centrocercus urophasianus) and their sagebrush (Artemisia spp) habitats on Nevada public lands administered by Bureau of Land Management (BLM). The guidelines are intended to provide interim guidance to field managers, without restricting options currently being explored for regional, state, and local sage grouse/sagebrush conservation planning. The guidelines are a Nevada BLM, habitat-specific, adaptation of the recently updated, and soon to be finalized, Western Association of Wildlife Agencies (WAFWA) Draft Guidelines. The Nevada BLM guidelines apply the most current sage grouse science to BLM activities, within the context …

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Western Rangeland Noxious Weeds: Collecting, Sharing And Using Information, U.S. Department Of Interior, U.S. Department Of Agriculture, Riley Memorial Foundation Sep 2000

Western Rangeland Noxious Weeds: Collecting, Sharing And Using Information, U.S. Department Of Interior, U.S. Department Of Agriculture, Riley Memorial Foundation

All U.S. Government Documents (Utah Regional Depository)

Western rangeland weeds such as yellow starthistle, leafy spurge, Canada thistle and Russian knapweed are causing tremendous losses to agricultural industries, including both crop and livestock production, and to environmental resources on private lands. Concurrently, many public lands managed by federal agencies are being steadily invaded. As a result, these lands held in the public trust are experiencing reductions in commodity yields, recreational opportunities, biodiversity and ecosystem function.

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Utah State University Ground-Based Test Facility For Study Of Electronic Properties Of Spacecraft Materials, W. Y. Chang, John R. Dennison, Neal Nickles, R. E. Davies Sep 2000

Utah State University Ground-Based Test Facility For Study Of Electronic Properties Of Spacecraft Materials, W. Y. Chang, John R. Dennison, Neal Nickles, R. E. Davies

All Physics Faculty Publications

Materials used for spacecraft and space structures in near-Earth orbit are subject to severe environmental effects including high vacuum conditions, hot and cold extremes temperature, strongly oxidizing atomic oxygen environments, and high fluxes of energetic electrons, ions, neutrals and photons. Instrumentation developed at Utah State University is designed to simulate, at least to some level, all of these conditions and to study charged particle and photon interactions with spacecraft surfaces. The facilities are particularly well suited to study electron emission as related to spacecraft charging, including secondary and backscattered yields, energy-spectra, and angleresolved measurements as a function of incident energy, …

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Evolution Of Secondary Electron Emission Characteristics Of Spacecraft Surfaces: Importance To Spacecraft Charging, Robert Davies, John R. Dennison Sep 2000

Evolution Of Secondary Electron Emission Characteristics Of Spacecraft Surfaces: Importance To Spacecraft Charging, Robert Davies, John R. Dennison

All Physics Faculty Publications

A sample of oxidized aluminum was placed inside an ultra-high vacuum (UHV) chamber alongside a piece of PTFE (Teflon®) coated wire and continuously bombarded with 1-3 keV electrons for ~30 hours. The SE yield of the surface was monitored as a function of time throughout the electron bombardment. Oxidized aluminum was chosen as a typical material comprising spacecraft surfaces, while outgassing of the Teflon wire contaminated the UHV environment, simulating the microenvironment surrounding an operating spacecraft. Continuous electron bombardment resulted in two effects—( i) the removal of the oxide layer, and (ii) the deposition of a thin (~1 nm-thick) layer …

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Applications Of Secondary Electron Energy- And Angular-Distributions To Spacecraft Charging, Neal Nickles, R. E. Davies, John R. Dennison Sep 2000

Applications Of Secondary Electron Energy- And Angular-Distributions To Spacecraft Charging, Neal Nickles, R. E. Davies, John R. Dennison

All Physics Faculty Publications

Secondary electron (SE) emission from spacecraft surfaces as a result of energetic electron bombardment is a key process in the electrical charging of spacecraft. It has been suggested that incorporating more complete knowledge of the energy- and angular-distributions of secondary electrons is necessary to fully model how SE emission and spacecraft charging are affected by re-adsorption of low energy electrons in the presence of charge-induced electrostatic fields and ambient magnetic fields in the spacecraft environment. We present data for such energy- and angular-distributions from sputtered, polycrystalline gold surfaces. The data are compared to empirical SE emission models and found to …

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Terdiurnal Oscillations In Oh Meinel Rotational Temperatures For Fall Conditions At Northern Mid-Latitude Sites, W. R. Pendleton Jr., Michael J. Taylor, Larry Gardner Jun 2000

Terdiurnal Oscillations In Oh Meinel Rotational Temperatures For Fall Conditions At Northern Mid-Latitude Sites, W. R. Pendleton Jr., Michael J. Taylor, Larry Gardner

All Physics Faculty Publications

High‐precision (∼0.5 K) measurements of OH Meinel (M) (6,2) rotational temperatures above the Bear Lake Observatory, UT (42°N, 112°W) during October 1996 have revealed an interesting and unexpected mean nocturnal pattern. Ten quality nights (>100 h) of data have been used to form a mean night for autumnal, near‐equinoctial conditions. The mean temperature and RMS variability associated with this mean night were 203 ± 5 K and 2.4 K, respectively, and compare very favorably with expectations based on Na‐lidar measurements of mean tidal temperature perturbations over Urbana, IL (40°N, 88°W) during the fall 1996. Furthermore, this comparison shows that …

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Snapover: Anomalous Plasma Current Collection By Positively Biased Conductors When Surrounded By A Dielectric, Clint Thomson, John R. Dennison May 2000

Snapover: Anomalous Plasma Current Collection By Positively Biased Conductors When Surrounded By A Dielectric, Clint Thomson, John R. Dennison

All Physics Faculty Publications

Over the last decade, high-powered spacecraft have been designed that will operate at voltages greater than 100 V. At these voltages, the solar arrays can undergo both destructive arcing at negative biases, and plasma electron current collection at positive biases. Furthermore, above some critical positive bias voltage (~100 V), the electron current collected by the array interconnects increases dramatically through a phenomenon termed Asnapover@. During snapover, large portions of the solar array cover glass charge positively, and begin to draw electron current from the plasma as if it were a conducting surface. This leads to substantial power losses for the …

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Instrumentation And Measurement Of Secondary Electron Emission For Spacecraft Charging, Neal Nickles, John R. Dennison May 2000

Instrumentation And Measurement Of Secondary Electron Emission For Spacecraft Charging, Neal Nickles, John R. Dennison

All Physics Faculty Publications

Secondary electron emission is an important physical mechanism in the problem of spacecraft charging. The NASA Space Environments and Effects branch is currently revising NASA’s strategy for mitigating damage due to spacecraft charging. In an effort to substantially improve the modeling of spacecraft charging, measurements of secondary electron emission parameters are being made. The design of the apparatus needed to measure these parameters is discussed in detail. Various measurement techniques are explained and conclusions are drawn about the suitability of the final design.

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Effect Of Daily Fluctuations From Flaming Gorge Dam On Ice Processes In The Green River, John W. Hayse, Steven F. Daly, Andrew Tuthill, Richard A. Valdez, Bryan Cowdell, Gary Burton May 2000

Effect Of Daily Fluctuations From Flaming Gorge Dam On Ice Processes In The Green River, John W. Hayse, Steven F. Daly, Andrew Tuthill, Richard A. Valdez, Bryan Cowdell, Gary Burton

All U.S. Government Documents (Utah Regional Depository)

This report provides results and conclusions of a detailed investigation of ice processes in the main channel of the reach of the Green River between the downstream end of Split Mountain (River Mile [RM1] 320) and the Ouray, Utah Bridge (R.M248). The objective of the study was to examine the influence of daily fluctuations in water releases from Flaming Gorge Damon river ice processes in this reach, which serves as an overwintering area for endangered Colorado pikeminnow and razorback sucker. The objective of the study was met through examination of historical records of winter water and air temperatures, flow measurements, …

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Testing Of The New Usgs K Index Algorithm At Bear Lake, Ariel O. Acebal Mar 2000

Testing Of The New Usgs K Index Algorithm At Bear Lake, Ariel O. Acebal

All U.S. Government Documents (Utah Regional Depository)

The K index was developed by Bartels in 1939 as an estimate of the level of geomagnetic activity caused by the Sun. This index was computed manually every three hours at geomagnetic observatories using the magnetic traces of the surface planetary magnetic field. In 1991, the International Association of Geomagnetism and Aeronomy approved four additional methods to compute the K index; all of them were computer algorithms. One of the approved methods, the Wilson code, recently underwent some modifications. The new algorithm is now part of a Windows-based computer program being developed by the United States Geological Survey (USGS). After …

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Selenium Poisoning Of Wildlife And Western Agriculture: Cause And Effect, N. E. Korte Feb 2000

Selenium Poisoning Of Wildlife And Western Agriculture: Cause And Effect, N. E. Korte

All U.S. Government Documents (Utah Regional Depository)

This project examined the hypothesis that selenium contamination is not the principal cause of the decline of endemic fish species in the Upper Colorado Basin. Activities employed to test this hypothesis included a reconnaissance of locations altered by recent road construction, a reinterpretation of available literature regarding selenium toxicity, and the interpretation of unpublished data obtained from the Upper Colorado Basin Fish Recovery Program. The project demonstrates that most of the evidence implicating selenium is circumstantial. Specifically, this research demonstrates that neither the historical record nor the technical literature consistently supports the emphasis given selenium toxicity. For example, many locations …

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Surface Core-Level Phonon Broadening Of Li(110), D. Mark Riffe, G. K. Wertheim Jan 2000

Surface Core-Level Phonon Broadening Of Li(110), D. Mark Riffe, G. K. Wertheim

All Physics Faculty Publications

High-resolution core-level photoemission data from the 1s level of Li(110) have been obtained between 77 and 280 K. Analysis of the data reveals a significant difference in the zero-temperature phonon broadening between the bulk and surface atoms but only a small difference in the effective surface and bulk Debye temperatures. This latter result is in good agreement with an embedded-atom-method calculation of the bulk and surface Debye temperatures of Li. Implications of these results to surface core-level phonon broadening and surface lattice dynamics of the heavier alkali metals are discussed.

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Utah Fire Amendment: Environmental Assessment, Pam Gardiner Jan 2000

Utah Fire Amendment: Environmental Assessment, Pam Gardiner

Elusive Documents

No abstract provided.

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Value Engineering: Final Report- Bear River Migratory Bird Refuge Headquarters And Education Complex, U.S. Bureau Of Reclamation Jan 2000

Value Engineering: Final Report- Bear River Migratory Bird Refuge Headquarters And Education Complex, U.S. Bureau Of Reclamation

Elusive Documents

No abstract provided.

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Effect Of Daily Fluctuations From Flaming Gorge Dam On Ice Processes In The Green River, John W. Hayse, Steven F. Daly, Andrew Tuthill, Richard A. Valdez, Bryan Cowdell, Gary Burton Jan 2000

Effect Of Daily Fluctuations From Flaming Gorge Dam On Ice Processes In The Green River, John W. Hayse, Steven F. Daly, Andrew Tuthill, Richard A. Valdez, Bryan Cowdell, Gary Burton

Elusive Documents

No abstract provided.

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Utah Stream Team Appendices, John Geiger, Nancy Mesner Jan 2000

Utah Stream Team Appendices, John Geiger, Nancy Mesner

All Archived Publications

No abstract provided.

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Group Invariant Solutions Without Transversality, Ian M. Anderson, Mark E. Fels, Charles G. Torre Jan 2000

Group Invariant Solutions Without Transversality, Ian M. Anderson, Mark E. Fels, Charles G. Torre

All Physics Faculty Publications

We present a generalization of Lie's method for finding the group invariant solutions to a system of partial differential equations. Our generalization relaxes the standard transversality assumption and encompasses the common situation where the reduced differential equations for the group invariant solutions involve both fewer dependent and independent variables. The theoretical basis for our method is provided by a general existence theorem for the invariant sections, both local and global, of a bundle on which a finite dimensional Lie group acts. A simple and natural extension of our characterization of invariant sections leads to an intrinsic characterization of the reduced …

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Actions For Biconformal Matter, Andre Wehner, James Thomas Wheeler Jan 2000

Actions For Biconformal Matter, Andre Wehner, James Thomas Wheeler

All Physics Faculty Publications

We extend 2n-dim biconformal gauge theory by including Lorentz-scalar matter fields of arbitrary conformal weight. For a massless scalar field of conformal weight zero in a torsion-free biconformal geometry, the solution is determined by the Einstein equation on an n-dim submanifold, with the stress-energy tensor of the scalar field as source. The matter field satisfies the n-dim Klein-Gordon equation.

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Record Of Decision Based On The Final Environmental Impact Statement For The South Manti Timber Salvage, United States Forest Service Jan 2000

Record Of Decision Based On The Final Environmental Impact Statement For The South Manti Timber Salvage, United States Forest Service

Record of Decisions (UT)

This project was initiated in response to epidemic spruce beetle (Dendroctonus rufipennis) activity across the South Manti landscape. The Final Environmental Impact Statement (FEIS) summarizes potential direct, indirect, and cumulative effects of corresponding site-specific forest management alternatives on portions of the Ferron-Price and Sanpete Ranger Districts of the Manti-La Sal National Forest.

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South Manti Timber Salvage Final Environmental Impact Statement, United States Forest Service Jan 2000

South Manti Timber Salvage Final Environmental Impact Statement, United States Forest Service

Final environmental Impact Statements (UT)

This project was initiated in response to epidemic spruce beetle (Dendroctonus rufipennis) activity across approximately 24,597 acres of National Forest System lands within the southern portion of the Wasatch Plateau (Townships 19, 20, and 21 South; Range 4 East; SLM). The South Manti project area is located on the Manti-La Sal National Forest approximately 45 miles southwest of Price, Utah.

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Modeling The Evolution Of Meso-Scale Ionospheric Irregularities At High Latitudes, Jan Josef Sojka, L. Zhu, M. David, Robert W. Schunk Jan 2000

Modeling The Evolution Of Meso-Scale Ionospheric Irregularities At High Latitudes, Jan Josef Sojka, L. Zhu, M. David, Robert W. Schunk

All Physics Faculty Publications

The modeling of ionospheric plasma density irregularities (ΔN/N) is a necessary first step towards forecasting ionospheric scintillation effects. This modeling challenge is difficult not only because the linear‐nonlinear saturation levels of instabilities are not completely understood but also because ΔN/N often evolves on time scales which are long compared to the characteristic time constants of the instability drivers. In this study, the linear 1‐D gradient drift instability (GDI) is used in a high latitude simulation of ΔN/N evolution. For the first time snapshots (maps) of ΔN/N are presented demonstrating that it is possible to use …

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Model Study Of Ionospheric Dynamics During A Substorm, Lie Zhu, Robert W. Schunk, Jan Josef Sojka, Michael David Jan 2000

Model Study Of Ionospheric Dynamics During A Substorm, Lie Zhu, Robert W. Schunk, Jan Josef Sojka, Michael David

All Physics Faculty Publications

A global substorm electrodynamic model and a global ionospheric model were coupled in order to study ionospheric dynamics during substorms, with the focus on small-scale substorm electrodynamic and plasma structures. The simulation results show that in the expansion phase, structured precipitation and channeled field-aligned currents quickly develop in the substorm onset region. The Hall and Pedersen conductance ratio in the region increases significantly, and the magnetospheric field-aligned currents are mainly closed by highly structured Hall currents. Correspondingly, the plasma in the ionosphere also undergoes significant changes during a substorm and is highly structured in both the horizontal and vertical directions. …

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Measurements Of Electronic Properties Of Conducting Spacecraft Materials With Application To The Modeling Of Spacecraft Charging, W. Y. Chang, John R. Dennison, Parker Judd Jan 2000

Measurements Of Electronic Properties Of Conducting Spacecraft Materials With Application To The Modeling Of Spacecraft Charging, W. Y. Chang, John R. Dennison, Parker Judd

All Physics Faculty Publications

This paper describes the results of the first stage of this project, measurements of the electronic properties of conducting spacecraft materials. We begin with a description of the required measurements and specifics of the experimental methods used. A complete list of the conducting materials studied, justification of their selection for study, and a summary of the important results of the measurements is presented. This is followed by detailed measurements and analysis for one representative conductor, namely polycrystalline Au. We end with a description of incorporation of these measurements into the NASCAP database.

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Using Binary Star Observations To Bound The Mass Of The Graviton, Shane L. Larson, William A. Hiscock Jan 2000

Using Binary Star Observations To Bound The Mass Of The Graviton, Shane L. Larson, William A. Hiscock

All Physics Faculty Publications

Interacting white dwarf binary star systems, including helium cataclysmic variable (HeCV) systems, are expected to be strong sources of gravitational radiation, and should be detectable by proposed space-based laser interferometer gravitational wave observatories such as LISA. Several HeCV star systems are presently known and can be studied optically, which will allow electromagnetic and gravitational wave observations to be correlated. Comparisons of the phases of a gravitational wave signal and the orbital light curve from an interacting binary white dwarf star system can be used to bound the mass of the graviton. Observations of typical HeCV systems by LISA could potentially …

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A Comprehensive Study Of Dielectric-Conductor Junctions In Low Density Plasmas, B. V. Vayner, J. T. Galofaro, D. C. Ferguson, W. A. De Groot, C. D. Thomson, John R. Dennison, R. E. Davies Jan 2000

A Comprehensive Study Of Dielectric-Conductor Junctions In Low Density Plasmas, B. V. Vayner, J. T. Galofaro, D. C. Ferguson, W. A. De Groot, C. D. Thomson, John R. Dennison, R. E. Davies

All Physics Faculty Publications

In this paper, results are presented of an experimental and theoretical study of snapover, glow discharge, and arc phenomena for different materials immersed in argon or xenon plasmas. The effect of snapover is investigated for several metal-dielectric junctions: copper-teflon, copper-Kapton, copper-glass, aluminum-teflon, aluminum-Kapton, steel-teflon, anodized aluminum with pinholes, and copper-ceramics. I-V curves are measured, and snapover inception voltages, essential parameters (increase in current and collection area due to secondary electrons), and glow discharge inception thresholds are determined. Optical spectra are obtained for glow discharges in both argon and xenon plasmas. These spectra provide information regarding atomic species entrapped in the …

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Measurement Of Silicon Surface Recombination Velocity Using Ultrafast Pump-Probe Reflectivityin The Near Infrared, A. J. Sabbah, D. Mark Riffe Jan 2000

Measurement Of Silicon Surface Recombination Velocity Using Ultrafast Pump-Probe Reflectivityin The Near Infrared, A. J. Sabbah, D. Mark Riffe

All Physics Faculty Publications

We demonstrate that ultrafast pump–probe reflectivity measurements from bulk Si samples using a Ti:sapphire femtosecond oscillator (λ=800 nm) can be used to measure the Si surface recombination velocity. The technique is sensitive to recombination velocities greater than ∼104 cm s−1

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Extended Conformal Symmetry, James Thomas Wheeler Jan 2000

Extended Conformal Symmetry, James Thomas Wheeler

All Physics Faculty Publications

We show that the grading of fields by conformal weight, when built into the initial group symmetry, provides a discrete, non-central conformal extension of any group containing dilatations. We find a faithful vector representation of the extended conformal group and show that it has a scale-invariant scalar product and satisfies a closed commutator algebra. The commutator algebra contains the infinite Heisenberg and Virasoro algebras. In contrast to the classical treatment of scale invariance, covariant derivatives and gauge transformations automatically incorporate the correct conformal weights when the extended symmetry is gauged.

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Inception Of Snapover And Gas Induced Glow Discharges, J. T. Galofaro, B. V. Vayner, D. C. Ferguson, W. A. Degroot, C. D. Thomson, John R. Dennison, R. E. Davies Jan 2000

Inception Of Snapover And Gas Induced Glow Discharges, J. T. Galofaro, B. V. Vayner, D. C. Ferguson, W. A. Degroot, C. D. Thomson, John R. Dennison, R. E. Davies

All Physics Faculty Publications

Ground based experiments of the snapover phenomenon were conducted in the large vertical simulation chamber at the Glenn Research Center (GRC) Plasma Interaction Facility (PIF). Two Penning sources provided both argon and xenon plasmas for the experiments. The sources were used to simulate a variety of ionospheric densities pertaining to a spacecraft in a Low Earth Orbital (LEO) environment. Secondary electron emission is believed responsible for dielectric surface charging, and all subsequent snapover phenomena observed. Voltage sweeps of conductor potentials versus collected current were recorded in order to examine the specific charging history of each sample. The average time constant …

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Effects Of Evolving Surface Contamination On Spacecraft Charging, W. Y. Chang, John R. Dennison, Jason Kite, R. E. Davies Jan 2000

Effects Of Evolving Surface Contamination On Spacecraft Charging, W. Y. Chang, John R. Dennison, Jason Kite, R. E. Davies

All Physics Faculty Publications

The effects of evolving surface contamination on spacecraft charging have been investigated through (i) ground-based measurements of the change in electron emission properties of a conducting surface undergoing contamination and (ii) modeling of the charging of such surfaces using the NASCAP code. Specifically, we studied a Au surface as adsorbed species were removed and a very thin disordered carbon film was deposited as a result of exposure to an intense, normal incidence electron beam. As a result of this contamination, we found an ~50% decrease in secondary electron yield and an ~20% reduction in backscattered yield. The type and rates …

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