• Changes in extreme hydroclimate events in Interior Alaskan boreal forest watersheds

      Bennett, Katrina; Hinzman, Larry; Lindsey, Scott; Hiemstra, Christopher; Walsh, John; Cherry, Jessica (2014-12)
      The high latitude regions of the globe are responding to climate change at unprecedented magnitudes and rates. As the climate warms, extreme hydroclimate events are likely to change more than the mean events, and it is the extreme changes that present a risk to society, the economy and the environment of the north. The subarctic boreal forest is one of the largest ecosystems in the world and is greatly understudied with respect to hydroclimate extremes. Thus, defining a baseline for changing extremes is the first step towards planning and implementing adaptation measures to reduce risk and costs associated with the changing extremes. This thesis focuses on quantitative analysis of extreme events using historical data and future model projections of changing temperature, precipitation and streamflow in the Interior forested region of boreal Alaska. Historically, shifts in the climate have resulted in declining magnitudes of peak flow for snow dominated and glacial Interior Alaskan basins. However, changes are variable and dependent upon watershed topography, permafrost conditions, and glacial extents. Therefore, adjacent basins respond in considerably different ways to the same climate drivers. For example, peak streamflow events in the adjacent Salcha and Chena River basins had different responses to changes in climate. In the higher elevation Salcha basin, maximum streamflow increased as spring temperatures increased but in the lower elevation Chena, winter precipitation was a control on increases in maximum streamflow, while both were influenced by the Pacific Decadal Oscillation. Analysis of hydrologic change must take this variability into account to understand extreme hydroclimate responses and correctly account for process shifts. To examine future changes in peak streamflow, the implementation and parameterization of hydrologic models to simulate hydroclimate extremes is required. In the northern latitudes of the world, there is a sparse observational station network that may be used for evaluation and correction of hydrologic models. This presents a limitation to science in these regions of the globe and has led to a paucity of research results and consequently, a lack of understanding of the hydrology of northern landscapes. Input of observations from remote sensing and the implementation of models that contain parameterizations specific to northern regions (i.e. permafrost) is one aim of this thesis. Remote sensing of snow cover extent, an important indicator of climate change in the north, was positively validated at snow telemetry sites across Interior Alaska. Input of the snow cover extent observations into a hydrologic model used by the Alaska Pacific River Forecast Center for streamflow flood forecasting improved discharge estimates for poorly observed basins, whereas the discharge estimates in basins with good quality river discharge observations improved little. Estimates of snow water equivalent were improved compared to station results and the adaptation of the model parameters indicated that the model is more robust, particularly during the snowmelt period when model simulations are error prone. Use of two independent hydrologic models and multiple global climate models (GCMs) and emission scenarios to simulate changes in future hydroclimate extremes indicated that large regime shifts are projected for snowmelt dominated basins of Interior Alaska. The Chena River basin, nearby Fairbanks, Alaska, is projected to be rainfall dominated by the 2080s, with smaller snowmelt peaks. Return intervals for flooding will increase by one-and-one half to double the flow volume magnitude compared to the historical return interval. Frequency of extreme streamflow events will increase five times the mean increase. These changes in extreme streamflow events necessitate further research on the implications for infrastructure, ecology and economy to constrain risk associated with the projected regime shift in boreal forested watersheds of Interior Alaska.
    • Changes in the spring sea ice concentration in the Bering Sea from 1972-2000 in relation to spotted seal (Phoca largha) pregnancy rates

      Picco, Candace M. (2005-08)
      Spotted seals are most dependent on the seasonal sea ice in the Bering Sea during the spring pupping and mating season. Changes in sea ice characteristics, as related to recent documented changes in climate, may have an effect on spotted seal reproduction. This study investigates the relation between changes in the spatial and temporal patterns of the spring sea ice concentration in the Bering Sea from 1972-2000 to changes in the pregnancy rates of the spotted seal (Phoca largha). Multinomial time-series regressions were used to determine the influence of different climatic variables on the sea ice concentration. Different statistical methods were used to compare the ice conditions of defined regions in the Bering Sea and spotted seal pregnancy rates among 20 years from 1964- 2003. The results showed no definitive patterns relating the monthly climatic variables and sea ice concentration averages; however, noticeable trends in sea ice were found. The variability of the seal pregnancy rates coincided with changes in the Bering Sea ecosystem and ice concentration. This study demonstrated that seal pregnancy rates and sea ice concentration varied temporally and spatially, the direct causality of these variations was uncertain.
    • Changes in the value of the Southeast Alaska salmon purse seine limited entry permits following two permit buy back programs

      Shriver, Jennifer Christine (2014-12)
      The Southeast Alaska salmon purse seine fishery (S01A) is an Alaska state waters limited entry fishery. When initially limited by the Commercial Fisheries Entry Commission in 1975, 419 permanent permits were issued. As salmon prices dropped in the late 1990s, current and expected future revenues also dropped leading to a decline in the market value of permit. This led permitees to look at different ways to improve their economic position. Reduction of permit numbers through the buyback and permanent retirement of some permits emerged as a preferred option for the S01A fishery; it was motivated as the best means to improve economic conditions in the fishery. After a very long road of regulatory changes at the state and federal level, 35 permits were bought and retired in 2008 using funds provided under a federal grant. A second buyback in 2012, based on a federally backed fishery reduction loan led to the retirement of 65 additional permits. Basic economic principles suggest that resulting decrease in supply of limited entry permits would lead to an increase in the market value of remaining permits. An important policy question is: whether the increased value to permitees is sufficient to offset the cost to taxpayers of financing the buyback. However, conducting that cost-benefit assessment is made difficult because of unrelated but concomitant changes in exvessel prices and catch volumes. During the same time that permits were being removed through the buyback, the exvessel value of salmon increased as did the volume of Southeast Alaska salmon harvests, per-vessel average exvessel gross earnings, and the market value of S01A permits. Econometric analyses based on Alaska Commercial Fisheries Entry Commission (CFEC) time series data on S01A permit values, estimated gross earnings, and salmon prices indicate that the buybacks led to statistically significant increases in the asset value of S01A LEPs. In light of the program's stated goals, the buyback was a qualified success in increasing the asset value of S01A permits and removing latent fishing capacity from returning to the fishery as exvessel prices increased. The buyback did not change the fundamental conditions that precondition the Alaska salmon LEP program to systematic vulnerabilities inherent in a management system that does not counter the pernicious race for fish motivations of participants.
    • Changing police culture: raising awareness of the importance of mental health

      Dombroski, Mary; Daku, Mike; Duke, J. Robert; May, Jeff; Boldt, Frank (2017-08)
      The suicide rate involving police officers has produced alarming statistics for decades. Until recently, however, little has been done to prevent suicide in law enforcement and even fewer efforts have been made to change the root of the problem. This paper reviews why a law enforcement officer may choose to take their life, looks at preexisting programs and resources that departments can choose to embrace, and supplies departments with a new approach to destigmatizing suicide within the police culture starting at the academy level.
    • Changing strategies in Seward Peninsula reindeer (Rangifer tarandus tarandus) management

      Oleson, Heather J. (2005-12)
      Reindeer (Rangifer tarandus tarandus) management techniques have changed since the founding of the reindeer industry on the Seward Peninsula in 1891. From 1891-1915, herds were small and management was intensive. Between 1915 and 1944, community herds and joint stock companies were formed. Herd management was extensive and herds were large and relatively free roaming. A period of re-privatization followed from 1944 to 1960, during which a limited number of moderately stocked ranges were established. The era after 1960 saw the introduction of several new forms of technology, some of which became catalysts for broad changes in reindeer management. Snow machines (c. 1960s), helicopters (c. 1970s), radio telemetry (c. 1980s), and Internet use became an integral part of how reindeer were managed. Most recently, satellite telemetry and online mapping have been developed as herd management tools. Combining telemetry, mapping programs, and the Internet allows herders to monitor range use, herd movement, and whether their animals need to be moved to refuge areas to prevent mixing with caribou. Equipped with this knowledge, herders can more effectively use ATV's and aircraft to manage their herds.
    • The changing vista of the northern Northwest Coast Indian Deer Ritual

      Austin, Kenneth Frank (1999-08)
      From time immemorial until the start of the 20th century, when disputing Tlingits decided to end a conflict, Tlingit clan leaders and elders met in council and negotiated an equitable peace settlement. After reaching a satisfactory negotiation, a peace dance took place to validate the settlement. Besides the Tlingits, the neighboring Indian groups in Southeast Alaska and British Columbia practiced this custom. When the European and Western powers assumed governance, the deer ritual--a judicial function of the Pacific Northwest Coast Indians--was modified, and new forms appeared. Presently, while elders know their regional history, many do not remember the protocol and formalities of the rite that was performed. This thesis undertakes a step into the past when the rite had an active and viable purpose in settling disputes and validating agreements
    • Changing Winds: National Politics And Its Role In Funding For Rural Development In Alaska

      Langenberg-Miller, Edwina C.; Pullar, Gordon; Knecht, Rick (2010)
      The combination of the election of Senator Mark Begich in 2008, an increased emphasis on transparency, and a growing movement away from congressionally-directed spending (earmarks) and toward competitively-awarded and formula-based funding has the potential to drastically reduce federal funding for rural development in Alaska. Alaska's basic needs for infrastructure remain equivalent to those of some of the least developed nations of the world. Rural development projects in Alaska, however, fight an uphill battle for federal funding because rural populations are low in numbers and remote, costs of rural development in Alaska far exceed similar projects in the "lower 48," and changes in the U.S. Congress have drastically reduced Alaskans' ability to circumvent formula-based and competitively-awarded funding avenues. This thesis is an analysis of recent changes that affect rural development funding in Alaska, and it hypothesizes how rural development funding for Alaska may continue to change.
    • Characteristic behavior of the dayside aurora in the minutes leading up to substorm onset: evidence for external triggering of substorms by the interplanetary magnetic field

      Andersen, Carl Stephen (2005-12)
      Two meridian scanning photometers, one located in Alaska and one in Svalbard, are used to examine the behavior of the dayside aurora just before the onset of the expansion phase of 61 substorms. In a strong majority of cases (80%), a poleward movement of the dayside aurora is seen in the minutes preceding sub storm onset. For the cases examined where a poleward movement of the dayside aurora is seen, a northward turning of the (generally southward) IMF is usually, but not always, seen. This suggests that for a majority of substorms, the 'trigger' is, or is related to, a northward turning of the IMF which can be seen by the motions of the dayside aurora. The observed movements of the dayside aurora and supposed onset triggers begin, on average, 12 minutes before substorm onset, which is the period before on-set during which nightside 'auroral fading' is known to happen. Two opposite but not necessarily exclusive behaviors of ionospheric convection have also been reported to occur during this period before onset, namely a decrease and/or an increase in polar cap convection velocities. Radar measurements of ionospheric convection are examined for these events but do not show an easily identifiable characteristic behavior.
    • Characteristics And Variability Of Storm Tracks In The North Pacific, Bering Sea And Alaska

      Dos Santos Mesquita, Michel (2009)
      Storm activity in the North Pacific, Bering Sea and Alaska regions is investigated using various automated storm tracking and parameter extraction algorithms. Specific, novel details of storm activity throughout the year are presented. The influence of major climatic drivers is considered, including the Pacific/North American Index and sea ice variability. Details of synoptic-scale forcing on a specific, severe storm event are considered in the context of how different tracking algorithms are able to depict the event. New storm climatology results show that the inter-seasonal variability is not as large during spring and autumn as it is in winter. Most storm variables exhibited a maxima pattern that was oriented along a zonal axis. From season to season this axis underwent a north-south shift and, in some cases, a rotation to the northeast. Barotropic processes have an influence in shaping the downstream end of storm tracks and, together with the blocking influence of the coastal orography of northwest North America, result in high lysis concentrations, effectively making the Gulf of Alaska the "graveyard" of Pacific storms. Summer storms tended to be longest in duration. Temporal trends tended to be weak over the study area. Sea surface temperature did not emerge as a major cyclogenesis control in the Gulf of Alaska. Positive sea-ice anomalies in the Sea of Okhotsk were found to decrease secondary cyclogenesis, shift cyclolysis locations westward, and alter the North Pacific subtropical jet. In the Atlantic, a negative North-Atlantic-Oscillation-like pattern is observed; these results were confirmed by experiments on the ECHAM5 Atmospheric Global Circulation Model driven with sea-ice anomalies in the Sea of Okhotsk. The destructive west Alaska storm of autumn 1992, which flooded Nome, was investigated using two storm tracking algorithms: NOAA's (National Oceanic and Atmospheric Administration) current operational algorithm and the Melbourne algorithm. Manual tracking was performed as a control. The main storm location features were captured by both algorithms, but differed in the genesis and lysis location. The NOAA algorithm broke the event into two. This storm was shown to have been affected by a blocking high that influenced how the tracking algorithms handled the event.
    • Characteristics of Arctic storms and their influence on surface climate

      Yang, Yang; Zhang, Xiangdong; Danielson, Seth; Fochesatto, Javier; Hock, Regine (2020-05)
      Impacts of intense synoptic storms on Chukchi Sea and Beaufort Sea surface environmental conditions are examined, focusing on storms moving into the regions with northward and eastward pathways. Both storms alter the prevailing northeasterly wind to southerly and southwesterly wind. The storms moving from the East Siberian Sea that follow a west to east route are most active in summer and have the longest duration. Increasing southwesterly wind plays a key role in the decline of thin sea ice within the warm season. Storms traveling from the relatively warm Pacific Ocean into the Arctic over the Bering Strait are more common in winter, and are typically more intense than the summer storms that propagate west to east. Downward longwave radiation increases considerably with the passage of intense winter storms over the ice-covered Chukchi Sea; the sea ice concentration decreases accordingly. The impact of different sea ice conditions on Arctic synoptic storm systems in autumn are investigated in the North Pacific and Atlantic sectors, based on the ten ensembles of hindcast simulations from coupled regional climate model HIRHAM-NAOSIM. In both the Pacific and Atlantic sectors, greater transfers of heat and moisture fluxes from the open ocean to the atmosphere occur in low sea ice years than in high sea ice years. The largest increase of upward heat fluxes and baroclinicity occurs over the Laptev, southern Chukchi and Beaufort Seas in the Pacific sector, and over the southern Greenland and Barents Seas in the Atlantic sector. Enhanced baroclinity plays a dominant role in the development of intense storm systems. Therefore, storms in reduced sea ice years are more intense than in enhanced sea ice years in both Atlantic and Pacific sectors. The storm count also increases over locations exhibiting high baroclinicity. Sea ice volume anomalies are significantly correlated with synoptic storm counts based on maximum covariance analysis (MCA) leading modes of covariance between sea ice volume and storm count over Pacific and Atlantic sectors are identified respectively. The results are consistent with our findings in the composite analysis. In the Pacific sector, the first pattern of the MCA demonstrates that increasing storm counts over the Laptev Sea corresponds to decreasing sea ice volume over that region. In the Atlantic sector, the decrease of sea ice volume is highly correlated with decreasing storm counts over the northern Greenland Sea. Connection of storm activity over the North Pacific Ocean with the tropical stratosphere quasi-biennial oscillation (QBO) is investigated following a composite analysis of intense storm vertical cross sections. An observed stronger potential vorticity anomaly of intense storms is associated with the QBO west phase and results in enhanced warm air advection near the surface. A warm core structure forms over the east or northeast direction relative to the surface low center, which bows the isentropes downward. Upward motion following the isentropes reduces the surface low pressure, which in turn, facilitate storms to keep propagating in east and northeast directions. Under the QBO east phase, a weak surface warm core forms to the southeast of the storm center, resulting in a slow development of the storms, and these storms tend to move southeastward.
    • Characteristics of dayside auroral displays in relation to magnetospheric processes

      Minow, Joseph I.; Smith, Roger W. (1997)
      The use of dayside aurorae as a ground based monitor of magnetopause activity is explored in this thesis. The origin of diffuse (OI) 630.0 nm emissions in the midday auroral oval is considered first. Analysis of low altitude satellite records of precipitating charged particles within the cusp show an unstructured electron component that will produce a 0.5-1 kR 630.0 nm emission throughout the cusp. Distribution of the electrons is controlled by the requirement of charge neutrality in the cusp, predicting a diffuse 630.0 nm background even if the magnetosheath plasma is introduced into the magnetosphere in discrete merging events. Cusp electron fluxes also contain a structured component characterized by enhancements in the electron energy and energy flux over background values in narrow regions a few 10's of kilometers in width. These structured features are identified as the source of the transient midday arcs. An auroral model is developed to study the morphology of (OI) 630.0 nm auroral emissions produced by the transient arcs. The model demonstrates that a diffuse 630.0 nm background emission is produced by transient arcs due to the long lifetime of the O$(\sp1D)$ state. Two sources of diffuse 630.0 nm background emissions exist in the cusp which may originate in discrete merging events. The conclusion is that persistent 630.0 nm emissions cannot be interpreted as prima facie evidence for continuous particle transport from the magnetosheath across the magnetopause boundary and into the polar cusp. The second subject that is considered is the analysis of temporal and spatial variations of the diffuse 557.7 nm pulsating aurora in relation to the 630.0 nm dominated transient aurora. Temporal variations at the poleward boundary of the diffuse 557.7 nm aurora correlate with the formation of the 630.0 nm transient aurorae suggesting that the two events are related. The character of the auroral variations is consistent with the behavior of particle populations reported during satellite observations of flux transfer events near the dayside magnetopause. An interpretation of the events in terms of impulsive magnetic reconnection yields a new observation that relates the poleward moving transient auroral arcs in the midday sector to the flux transfer events.
    • Characteristics of the Sulukna River spawning population of inconnu, Yukon River drainage, Alaska

      Esse, David Andrews; Margraf, F. Joseph; Sutton, Trent M.; Brown, Randy J. (2011-12)
      Inconnu Stenodus leucichthys are large migratory whitefish harvested in subsistence and sport fisheries in Alaska. Research on the Sulukna River spawning population of inconnu was conducted in September and early October from 2007 to 2009. Samples were collected to verify maturity and spawning readiness, and to determine age distributions of mature males and females. Spawning abundance was estimated and post-spawning migration timing was identified. Otoliths were analyzed optically to determine age and chemically to determine amphidromy. Maturity sampling indicated that all sampled fish were in spawning condition or had recently spawned. Abundance estimates were 2,079 and 3,531 inconnu in 2008 and 2009, respectively. Post-spawning downstream migration timing was nearly identical between years, with the majority of fish moving downstream between September 30 and October 9. In both years, migrating inconnu displayed a nocturnal migration pattern, with 96% migrating between 10:00 pm and 9:00 am hours daily. Age estimates ranged between 6 and 26 years. Chemical analysis indicated that some Sulukna River inconnu were amphidromous, making migrations of over 1,300 km to the sea. This information indicates that the Sulukna River spawning population of inconnu has a large and variable abundance, in which amphidromy is facultative.
    • Characterization and delineation of caribou habitat on Unimak Island using remote sensing techniques

      Atkinson, Brian M.; Harris, Norman R.; Finstad, Greg L.; Verbyla, David L. (2014-08)
      The assessment of herbivore habitat quality is traditionally based on quantifying the forages available to the animal across their home range through ground-based techniques. While these methods are highly accurate, they can be time-consuming and highly expensive, especially for herbivores that occupy vast spatial landscapes. The Unimak Island caribou herd has been decreasing in the last decade at rates that have prompted discussion of management intervention. Frequent inclement weather in this region of Alaska has provided for little opportunity to study the caribou forage habitat on Unimak Island. The overall objectives of this study were two-fold 1) to assess the feasibility of using high-resolution color and near-infrared aerial imagery to map the forage distribution of caribou habitat on Unimak Island and 2) to assess the use of a new high-resolution multispectral satellite imagery platform, RapidEye, and use of the "red-edge" spectral band on vegetation classification accuracy. Maximum likelihood classification algorithms were used to create land cover maps in aerial and satellite imagery. Accuracy assessments and transformed divergence values were produced to assess vegetative spectral information and classification accuracy. By using RapidEye and aerial digital imagery in a hierarchical supervised classification technique, we were able to produce a high resolution land cover map of Unimak Island. We obtained overall accuracy rates of 71.4 percent which are comparable to other land cover maps using RapidEye imagery. The "red-edge" spectral band included in the RapidEye imagery provides additional spectral information that allows for a more accurate overall classification, raising overall accuracy 5.2 percent.
    • Characterization and diagnostic methods for geomagnetic auroral infrasound waves

      Oldham, Justin J.; Szuberla, Curt A. (2015-12)
      Infrasonic perturbations resulting from auroral activity have been observed since the 1950's. In the last decade advances in infrasonic microphone sensitivity, high latitude sensor coverage, time series analysis methods and computational efficiency have elucidated new types of auroral infrasound. Persistent periods of infrasonic activity associated with geomagnetic sub-storms have been termed geomagnetic auroral infrasound waves [GAIW]. We consider 63 GAIW events recorded by the Fairbanks, AK infrasonic array I53US ranging from 2003 to 2014 and encompassing a complete solar cycle. We make observations of the acoustic features of these events alongside magnetometer, riometer, and all-sky camera data in an effort to quantify the ionospheric conditions suitable for infrasound generation. We find that, on average, the generation mechanism for GAIW is confined to a region centered about ~60° longitude east of the anti-Sun-Earth line and at ~77° North latitude. We note furthermore that in all cases considered wherein imaging riometer data are available, that dynamic regions of heightened ionospheric conductivity periodically cross the overhead zenith. Consistent features in concurrent magnetometer conditions are also noted, with irregular oscillations in the horizontal component of the field ubiquitous in all cases. In an effort to produce ionosphere based infrasound free from the clutter and unknowns typical of geophysical observations, an experiment was undertaken at the High Frequency Active Auroral Research Program [HAARP] facility in 2012. Infrasonic signals appearing to originate from a source region overhead were observed briefly on 9 August 2012. The signals were observed during a period when an electrojet current was presumed to have passed overhead and while the facilities radio transmitter was periodically heating the lower ionosphere. Our results suggest dynamic auroral electrojet currents as primary sources of much of the observed infrasound, with modulation of the electrojets due to energetic particle precipitation, dispersion due to coupling with gravity waves, and reflection and refraction effects in the intervening atmosphere all potential factors in the shaping of the waveforms observed.
    • Characterization and fluid flow properties of frozen rock systems of Umiat Oil Field, Alaska

      Godabrelidze, Vasil (2010-12)
      The Umiat field, located in northwestern Alaska between the Brooks Range and the Arctic Ocean, potentially contains the largest accumulation of oil in Naval Petroleum Reserve No.4. Most of the oil is found within the permafrost zone. The main oil-producing zones in the Umiat field are marine sandstones in the Grandstand Formation of the Cretaceous Nanushuk group. Although the temperatures are close to freezing, the oil in the Umiat field remains unfrozen due to its very high API gravity. However, this results in a very unique pore space containing frozen water and oil, posing a particular challenge to characterization and measurement of fluid flow properties necessary for production. The unsteady-state gas-oil relative permeability measurement experiments were conducted in order to obtain critical information about the properties of two-phase fluid flow through the Umiat porous medium. Fluid flow experiments at 22°C and -10°C on representative core samples from the Umiat field showed 61% average decline in oil relative permeability as a result of freezing irreducible water. Capillary pressure measurement experiments were also carried out on selected core samples with an intention of characterizing their pore size distribution. Subsequently obtained data indicates fairly wide range of pore size for Umiat cores.
    • Characterization and implementation of stress dependent resilient modulus of asphalt treated base for flexible pavement design

      Li, Peng; 鹏 李; Liu, Juanyu; Connor, William; Zhang, Xiang; Shur, Yuri; Saboundjian, Stephan (2013-08)
      Asphalt treated base (ATB) is the most commonly used type of stabilized material in pavements because of material availability and relatively low cost in Alaska. The treatment enhances the material's properties to overcome deficiencies in some marginal materials. Resilient modulus (MR) of these materials is an essential pavement design input. Currently, in the Alaska Flexible Pavement Design (AKFPD) Manual, MRS of ATBs were back calculated using testing results of falling weight deflectometer (FWD). There is a need for an accurate laboratory characterization of these materials. In this study, the MRS of hot asphalt treated base (HATB), emulsifed asphalt treated base (EATB), foamed asphalt treated base (FATB), and a mixture of reclaimed asphalt pavement (RAP) and D-1 aggregate at a 50: 50 ratio (RAP 50:50) were measured using repeated triaxial tests. D-1 granular materials used for base course construction were collected from three regions in Alaska. HATB specimens were compacted using Superpave gyratory compactor and three binder contents were used: 2.5%, 3.5% and 4.5%. EATB and FATB specimens were compacted according to ASTM D1557 and three residual binder contents were used: 1.5%, 2.5% and 3.5%. RAP 50:50 was also compacted according to ASTM D1557 and no additional additives were added. MR was measured at three temperatures (i.e. -10°C, 0°C, 20°C for HATB, EATB and FATB; -10°C, -2°C, 20°C for RAP 50:50). The stress-dependent property of MR was successfully characterized by the modified universal soil model, in which the MR was expressed as a function of bulk stress (θ) and octahedral shear stress (τoct). Generally, MR increased with an increase of θ and decreased with an increase of τoct. Stress-dependent patterns of each type of ATB were analyzed and discussed. Predictive equations for MR were developed for all types of ATBs investigated in this study. The equations were based on the modified universal soil model. The material properties (i.e. binder content and percentage fracture surface), temperature and the interactions among them were incorporated into equations. The developed predictive equations had very high coefficient of determination (R²). The R² s of equations HATB_10, EATB_10, FATB_10 and RAP_9, in which the influencing factors and second order interactions among factors were included, were all greater than 99%. These equations can be also used to estimate nonlinear elastic constants of ATBs in the modified universal soil model (i.e. k₁, k₂ and k₃). The stress dependent property of MR was incorporated into pavement structural analysis using the finite element method (FEM) program Abaqus through user defined material that was programmed in the user subroutine. Comparisons were made between pavement responses obtained from nonlinear FEM and traditional linear elastic layered system. The representative MR of ATBs were determined and recommended based on the equivalent critical pavement response of the typical Alaska flexible pavement structure. Predictive equations were developed to estimate the critical pavement responses. The equations were developed through regression analyses using a database generated from 16,848 nonlinear pavement FEM analyses, which covered a variety of pavement structure combinations. These nonlinear pavement analyses were implemented through the function of a parametric study provided in Abaqus FEM package. In total 9 independent variables were included, which were the thickness of the surface course, base course, and subbase, moduli of HMA, subbase and subgrade, and nonlinear elastic constants of ATB (i.e. k₁ k₂ k₃) in the MR model. The interactions among these variables were also included. The R²s of predictive equations were at least 0.9725. The predictive equations can be used for routine pavement analysis and design purposes.
    • Characterization And Interpretation Of Volcanic Activity At Redoubt, Bezymianny And Karymsky Volcanoes Through Direct And Remote Measurements Of Volcanic Emissions

      Lopez, Taryn M.; Cahill, Catherine; Dehn, Jonathan; Newberry, Rainer; Simpson, William; Werner, Cynthia (2013)
      Surface measurements of volcanic emissions can provide critical insight into subsurface processes at active volcanoes such as the influx or ascent of magma, changes in conduit permeability, and relative eruption size. In this dissertation I employ direct and remote measurements of volcanic emissions to characterize activity and elucidate subsurface processes at three active volcanoes around the North Pacific. The 2009 eruption of Redoubt Volcano, Alaska, produced elevated SO2 emissions that were detected by the Ozone Monitoring Instrument (OMI) satellite sensor for over three months. This provided a rare opportunity to characterize Redoubt's daily SO2 emissions and to validate the OMI measurements. Order of magnitude variations in daily SO2 mass were observed, with over half of the cumulative SO2 emissions released during the explosive phase of the eruption. Correlations among OMI daily SO2 mass, tephra mass and acoustic energies during the explosive phase suggest that OMI data may be used to infer eruption size and explosivity. From 2007 through 2010 direct and remote measurements of volcanic gas composition and flux were measured at Bezymianny Volcano, Kamchatka, Russia. During this period Bezymianny underwent five explosive eruptions. Estimates of passive and eruptive SO2 emissions suggest that the majority of SO2 is released passively. Order of magnitude variations in total volatile flux observed throughout the study period were attributed to changes in the depth of gas exsolution and separation from the melt at the time of sample collection. These findings suggest that exsolved gas composition may be used to detect magma ascent prior to eruption at Bezymianny Volcano. Karymsky Volcano, Kamchatka, Russia, is a dynamic volcano which exhibited four end-member activity types during field campaigns in 2011 and 2012, including: discrete ash explosions, pulsatory degassing, gas jetting, and explosive eruption. These activity types were characterized quantitatively and uniquely distinguished using a multiparameter dataset based on infrasound, thermal imagery, and volcanic emissions. These observations suggest a decoupling between exsolved volatiles and magma at depth. I propose that variations in magma degassing depth influence the flux and proportions of decompression- and crystallization-induced degassing, as well as conduit permeability, can explain the variations in volcanic activity.
    • Characterization and optimization of the magnetron directional amplifier

      Hatfield, Michael Craig; Hawkins, Joseph G. (1999)
      Many applications of microwave wireless power transmission (WPT) are dependent upon a high-powered electronically-steerable phased array composed of many radiating modules. The phase output from the high-gain amplifier in each module must be accurately controlled if the beam is to be properly steered. A highly reliable, rugged, and inexpensive design is essential for making WPT applications practical. A conventional microwave oven magnetron may be combined with a ferrite circulator and other external circuitry to create such a system. By converting it into a two-port amplifier, the magnetron is capable of delivering at least 30 dB of power gain while remaining phase-locked to the input signal over a wide frequency range. The use of the magnetron in this manner is referred to as a MDA (Magnetron Directional Amplifier). The MDA may be integrated with an inexpensive slotted waveguide array (SWA) antenna to form the Electronically-Steerable Phased Array Module (ESPAM). The ESPAM provides a building block approach to creating phased arrays for WPT. The size and shape of the phased array may be tailored to satisfy a diverse range of applications. This study provided an in depth examination into the capabilities of the MDA/ESPAM. The basic behavior of the MDA was already understood, as well as its potential applicability to WPT. The primary objective of this effort was to quantify how well the MDA could perform in this capacity. Subordinate tasks included characterizing the MDA behavior in terms of its system inputs, optimizing its performance, performing sensitivity analyses, and identifying operating limitations. A secondary portion of this study examined the suitability of the ESPAM in satisfying system requirements for the solar power satellite (SPS). Supporting tasks included an analysis of SPS requirements, modeling of the SWA antenna, and the demonstration of a simplified phased array constructed of ESPAM elements. The MDA/ESPAM is well suited for use as an amplifier or an element in a WPT phased array, providing over 75% efficiency and a fractional bandwidth exceeding 1.7% at 2.45 GHz. The results of this effort provide the WPT design engineer with tools to predict the MDA's optimum performance and limitations.
    • Characterization of Alaska North Slope oils for wax deposition

      Anyanwu, Okechukwu Ndubuisi; Zhu, Tao; Chukwu, Godwin A.; Dandekar, Abhijit; Zhou, Wendy (2007-08)
      Wax deposition during crude oil production is a major problem that has plagued the oil industry for decades especially in cold environments such as Alaska North Slope (ANS) fields, with adverse consequences in huge mitigation cost and lost production. It is therefore imperative to adequately and accurately identify the conditions for wax precipitation and deposition in order to optimize operation of the production systems of ANS. In order to assess ANS crude's potential for wax precipitation, Viscometry and Cross Polarization Microscopy (CPM) are used to determine the temperature at which paraffins begin to precipitate from ANS dead oils. Wax dissolution temperatures (WDT) are also determined by CPM. Results show that wax precipitation is possible at temperatures as high as 41°C (106°F) while it takes up to 50°C (122°F) to get all waxes back into solution. The CPM technique was more sensitive while Viscometry results did not provide a high level of certainty in some samples and therefore appear over-estimated relative to CPM results. Previous thermal history was observed to influence test results. Pour point, viscosity, density and specific gravity have also been measured. Pour point results indicate that oil could form gel in the temperature range 12°C (53.6°C) to less than -31°C ( -23.8°F).
    • Characterization of host-pathogen interactions in two model pathogens: Francisella tularensis and simian virus SV40

      Smith, Lisa K.; Hueffer, Karsten; Khun, Thomas; Runstadler, Jonathan (2012-05)
      We sought to elucidate the molecular mechanisms of host-pathogen interaction. The bacterium Francisella tularensis and simian virus SV40 represent two ideal model systems. Francisella tularensis is a facultative intracellular bacterium known to dampen the host immune response to infection. The Francisella pathogenicity island (FPI) encodes a cluster of 19 genes essential for full virulence and the observed change in immune response. We investigated the role of two FPI encoded proteins, PdpC and PdpD, on immune response. While both proteins affect a change, the effect of PdpD is more pronounced, and appears to play a role in modulation of host immune responses. SV40 is a DNA polyoma virus that targets GM1 receptors for entry into cells. The GM I receptor is localized to cholesterol-rich membrane microdomains, termed lipid rafts. Disruption of lipid rafts using the cholesterol chelator methyl-P-cyclodextrin prevents SV40 entry into cells. We investigated whether natural product alternatives would similarly disrupt lipid raft integrity and prevent viral entry. The triterpenoid ursolic acid, present in many plants, has been shown to possess antimicrobial properties and was used to treat cells prior to infection with SV40. We found ursolic acid to have no effect on the viral infectivity of SV40.