Physical Sciences and Mathematics Commons^™

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.

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 …

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.

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 …

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, …

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 …

De-2 Observations Of Morningside And Eveningside Plasma Density Depletions In The Equatorial Ionosphere, M. Palmroth, H. Laakso, Bela G. Fejer, R. F. Pfaff

Bela G. Fejer

The occurrence of equatorial density depletions in the nightside F region ionosphere has been investigated by using observations gathered by the polar-orbiting Dynamics Explorer 2 satellite from August 1981 to February 1983. A variety of electric field/plasma drift patterns were observed within these depletions, including updrafting, downdrafting, bifurcating, converging, subsonic, and supersonic flows. The depletions, 116 events in total, are distributed over two groups: group I (eveningside depletions) consists of the events in the 1900–2300 MLT sector, and group II (morningside depletions) are the events in the 2300–0600 MLT sector. A statistical analysis reveals clear differences in the density depletion …

Simulation Of The Prereversalenhancement In The Low Latitude Vertical Drifts, C. G. Fesen, R. G. Noble, A. D. Richmond, G. Crowley, Bela G. Fejer

Bela G. Fejer

Low latitude F region ion motions exhibit strong seasonal and solar cycle dependences. The pre-reversal enhancement (PRE) in the vertical ion drifts is a particularly well-known low latitude electrodynamic feature, exhibited as a sharp upward spike in the velocity shortly after local sunset, which remains poorly understood theoretically. The PRE has been successfully simulated for the first time by a general circulation model, the National Center for Atmospheric Research thermosphere/ionosphere/electrodynamic general circulation model (TIEGCM). The TIEGCM reproduces the zonal and vertical plasma drifts for equinox, June, and December for low, medium, and high solar activity. The crucial parameter in the …

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 …

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, …

An Incoherent Scatter Radar Technique For Determining Two-Dimensional Ionization Structure In Polar Cap F-Region Patches, T. R. Pedersen, Bela G. Fejer, R. A. Doe, E. J. Weber

Bela G. Fejer

We present a technique which combines time series of line-of-sight (LOS) velocity and electron density measurements from the Sondrestrom incoherent scatter radar (74.5° invariant latitude) to reconstruct the large-scale horizontal structure of the F region ionosphere during polar cap patch events. This reconstruction technique provides a new density-based means of examining patch morphology. Its wide region of coverage also facilitates comparison of radar measurements with other observational data sets. For two periods when patches were present and convection conditions in the nightside polar cap could be adequately approximated by the simple velocity model used in this initial implementation of the …

Optical Remote Sensing Of The Thermosphere With Heater Induced Artificial Airglow (Hiaa), P. A. Bernhardt, M. Wong, J. D. Huba, Bela G. Fejer, L. S. Wagner, J. A. Goldstein, C. A. Selcher, V. L. Frolov, E. N. Sergeev

Bela G. Fejer

Optical emissions excited by high-power radio waves in the ionosphere can be used to measure a wide variety of parameters in the thermosphere. Powerful high-frequency (HF) radio waves produce energetic electrons in the region where the waves reflect in the F region. These hot or suprathermal electrons collide with atomic oxygen atoms to produce localized regions of metastable O(1D) and O(1S) atoms. These metastables subsequently radiate 630.0 and 557.7 nm, respectively, to produce clouds of HF pumped artificial airglow (HPAA). The shapes of the HPAA clouds are determined by the structure of large-scale (≈10 km) plasma irregularities that occur naturally …

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.

Low Seasonal Temperatures Promote Life Cycle Synchronization, Janette Lee Jenkins

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

In this paper, we discuss how seasonal temperature variation and dormancy can synchronize the development of exothermic organisms. Using a simple aging model, it is shown that minimal seasonal temperature variation and periods of dormancy during extreme temperature conditions are sufficient to establish stable, univoltine ovipositional cycles. Dormancy, in fact, promotes synchronous oviposition emergence. The mountain pine beetle, an important insect living in extreme temperature conditions and showing no evidence of diapause, invites direct application of this model. Simulations using mountain pine beetle parameters are used to determine temperature regimes for which stable, ovipositional cycles exist.

Pooled And Individual Bycatch Quotas: Exploring Tradeoffs Between Observer Coverage Levels, Bycatch Frequency, Pool Size, And The Precision Of Bycatch Estimates, Landon S. Jensen

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

The North Pacific Ocean is highly productive, hosting many of the world's largest groundfish populations and supporting a thriving fishing industry. Numerous regulations have been implemented to control the incidental take of non-target bycatch. Individual and Pooled Bycatch Quotas have recently been proposed as instruments that could further encourage the avoidance of such bycatch and increase enforceability of bycatch caps at less-than-entire-fishery levels of operation. The recent advent of fishing cooperatives such as the Pacific Whiting Conservation Cooperative and the Pollock Conservation Cooperatives create an additional impetus for examining the characteristics of pool and vessel specific bycatch quotas.

We have …

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 …

Mean-Square Error Bounds And Perfect Sampling For Conditional Coding, Xiangchen Cui

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In this dissertation, new theoretical results are obtained for bounding convergence and mean-square error in conditional coding. Further new statistical methods for the practical application of conditional coding are developed.

Criteria for the uniform convergence are first examined. Conditional coding Markov chains are aperiodic, π-irreducible, and Harris recurrent. By applying the general theories of uniform ergodicity of Markov chains on general state space, one can conclude that conditional coding Markov chains are uniformly ergodic and further, theoretical convergence rates based on Doeblin's condition can be found.

Conditional coding Markov chains can be also viewed as having finite state space. …

Positive Solutions Obtained As Local Minima Via Symmetries, For Nonlinear Elliptic Equations, Florin Catrina

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In this dissertation, we establish existence and multiplicity of positive solutions for semilinear elliptic equations with subcritical and critical nonlinearities. We treat problems invariant under subgroups of the orthogonal group. Roughly speaking, we prove that if enough "mass " is concentrated around special orbits, then among the functions with prescribed symmetry, there is a solution for the original problem.

Our results can be regarded as a further development of the work of Z.-Q. Wang, where existence of local minima in the space of symmetric functions was studied for the Schrödinger equation. We illustrate the general theory with three examples, all …

A New Perspective On Classification, Guohua Zhao

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The idea of voting multiple decision rules was introduced in to statistics by Breiman. He used bootstrap samples to build different decision rules, and then aggregated them by majority voting (bagging). In regression, bagging gives improved predictors by reducing the variance (random variation), while keeping the bias (systematic error) the same. Breiman introduced the idea of bias and variance for classification to explain how bagging works. However, Friedman showed that for the two-class situation, bias and variance influence the classification error in a very different way than they do in the regression case.

In the first part of …

The Sequence Stratigraphy Of The Middle Cambrian Wheeler Formation In The Drum Mountains Of West Central Utah, Loren P. Schneider

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The majority of the Middle Cambrian Wheeler Formation in the Drum Mountains was deposited during a single 3^rd order sequence. Superimposed onto this sequence are three indistinct 4^th order cycles and twenty distinct 5^th order cycles. These higher order cycles were likely deposited within short intervals of geologic time (204 to 405 ky).

The lower sequence boundary zone occurs within the Swasey Formation. The Transgressive Surface is the contact between the Swasey and Wheeler Formations. The Maximum Flooding Surface is located near the top of the lower Wheeler Formation, which also approximates the base of the Ptychagnostus …

Holocene Tephrostratigraphy, Southern Kenai Peninsula, Lower Cook Inlet, Alaska, Kathleen J. Lemke

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This thesis describes the results of a study of 33 tephra layers found within two peat sections near Anchor Point and Homer, Alaska, on the lower Kenai Peninsula. Numerous lower Cook Inlet volcanoes have been active through the Holocene. Tephra layers found at these two sites provide a partial record of their eruptive activity. The hazards that accompany this activity have increased as populations and commercial activities expand and air traffic over the region increases. The tephras analyzed for this study provide an initial geochemical database for the lower Cook Inlet volcanoes. The database is available in electronic format at …

Rotational Structure Of Extremely Floppy Van Der Waals Complexes: Adiabatic Separation Of Angular And Radial Motion, P. Daniel Ward

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The adiabatic or Born-Oppenheimer approximation is often used in molecular calculations to simplify the solution to the Schrödinger equation. The basis of the approximation is the large difference in the relative motions of the nuclei and electrons in the molecule—the electrons are able to respond almost instantly to the movements of the nuclei. Thus, the nuclei may be regarded as being fixed in a certain position and the Schrödinger equation can then be solved using the potential obtained by solving the electronic problem at fixed nuclear configuration.

A similar argument can be used to decouple the angular and radial motions …

Comparing Nonlinear And Nonparametric Modeling Techniques For Mapping And Stratification In Forest Inventories Of The Interior Western Usa, Gretchen Gengenbach Moisen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Recent emphasis has been placed on merging regional forest inventory data with satellite-based information both to improve the efficiency of estimates of population totals, and to produce regional maps of forest variables. There are numerous ways in which forest class and structure variables may be modeled as functions of remotely sensed variables, yet surprisingly little work has been directed at surveying modem statistical techniques to determine which tools are best suited to the tasks given multiple objectives and logistical constraints. Here, a series of analyses to compare nonlinear and nonparametric modeling techniques for mapping a variety of forest variables, and …

Theoretical Studies Of Penetration Of Magnetospheric Electric Fields To The Ionosphere, Stanislav Sazykin

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Ionospheric disturbance electric fields of magnetospheric origin play an important role in determining the global morphology and dynamics of the ionosphere of the Earth. In this work, we present a number of numerical simulations of the transient electric fields in the middle and inner magnetosphere and the ionosphere equatorward of the auroral zone caused by idealized changes in the magnetospheric driving parameters. For these studies, we use the Rice Convection Model (RCM), a large computer code of the magnetosphere-ionosphere coupling which consistently computes the electric fields, currents, and plasma densities in the magnetosphere and the electric field and currents in …

Studies On The Roles Of Atp In Nitrogenase Catalysis, Wei Wu

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Nitrogenase is the enzyme that catalyzes the reduction of nitrogen to ammonia in a reaction requiring MgATP hydrolysis. Two component proteins of nitrogenase are the iron protein (Fe protein) and the molybdenum-iron protein (MoFe protein).

Nitrogenase contains two nucleotide binding sites. During catalysis, the Fe protein binds two MgATP first. The conformational changes induced upon MgATP binding allow the Fe protein to associate with the MoFe protein. After the formation of the Fe protein-MoFe protein complex, a single electron is transferred from the Fe protein to the MoFe protein, an event that is coupled to MgATP hydrolysis in the Fe …

Responses Of Sphagnum And Carex Peatlands To Ultraviolet-B Radiation, And A Meta-Analysis Of Uv-B Effects On Vascular Plants, Peter S. Searles

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The severity of stratospheric ozone depletion in the temperate and polar latitudes has raised concerns about the sensitivity of terrestrial vegetation and ecosystems to solar ultraviolet (UV-B) radiation. This dissertation examined the responses of plants and microbes to solar UV-B for 3 years in Tierra del Fuego, Argentina (55° S). This region is under the influence of the Antarctic "ozone hole" during the austral spring. Additionally, a quantitative review of the UV-B literature was conducted using a set of statistical techniques known as meta-analysis.

For the field studies in Tierra del Fuego, plots were established in a Sphagnum moss peatland …

Debris-Flow Activity In Canyon Of Lodore, Colorado: Implications For Debris-Fan Formation And Evolution, Jennifer A. Martin

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Large-scale characteristics of Ladore Canyon debris fans are dependent upon the bedrock and lithology of the mainstem and tributary canyons. The largest fans occur in the widest section of the mainstem canyon, which typically correlates with the location of large faults. The steepest fans are found at the mouths of tributaries where cliffs are formed by resistant lithologies. Smaller-scale fan characteristics are dependent upon the magnitude and frequency of events from the respective drainage basin, which is controlled primarily by climate. Three distinct deposit ages (oldest, intermediate, youngest) were distinguished on individual fans and were tentatively correlated throughout the canyon …

Late Quaternary Glacier Fluctuations And Vegetation Change In The Northwestern Ahklun Mountains, Southwestern Alaska, Yarrow L. Axford

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This research examines moraine and lacustrine records of glacier fluctuations, in combination with palynological records of vegetation change, from the previously unstudied northwestern Ahklun Mountains in southwestern Alaska.

Moraine mapping reveals that ice-cap outlet glaciers in the study area extended ca. 60 km from the center of the Ahklun Mountians ice dome during the early Wisconsin (sensu lato), and ca. 40 km during the late Wisconsin. Correlations with well-studied moraines in the southern Ahklun Mountains indicate an asymmetry of glaciation over the range, with ice-cap outlet glaciers more extensive to the south. This asymmetry was more striking during …

A Survey Of The Taniyama-Shimura Conjecture, Kady Schneiter

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Perhaps the most famous problem in all of mathematics is the theorem that states that the equation aⁿ + bⁿ = cⁿ has no non-trivial solutions for integers a, b, and c, and n ≥ 2. This theorem was proposed by a seventeenth century French mathematician named Pierre de Fermat. Though the theorem is easy to understand, the proof has been elusive. Over the past 350 years many mathematicians have attempted to prove Fermat's theorem. They have used a variety of methods and many have been successful in proving the theorem in specific cases. …

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 …