RSS 1.0Engineering
Recent Submissions
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Effects of vertical earthquake component on columns of reinforced concrete moment frames across different seismic zonesThis thesis investigates the impact of vertical earthquake ground motion on the seismic performance of reinforced concrete (RC) moment-resisting frames. A 12-story RC moment resisting frame, designed in accordance with the NEHRP 2015 seismic provisions for Honolulu, Hawaii, was selected. The building was analyzed using nonlinear time history analysis in OpenSees to capture its seismic response under realistic loading conditions. Earthquake records from four seismically active regions—Kathmandu (Nepal), Anchorage (Alaska), El Centro (California), and Honolulu (Hawaii)—were applied to evaluate the influence of vertical ground motion across different seismic zones. Site-specific amplification and scaling factors were implemented to ensure uniformity in ground motion input. This study compares displacement time histories, moment-displacement relationships, axial force-moment interactions, and stress-strain responses of reinforcement and core concrete under three loading scenarios: horizontal-only, combined horizontal with maximum vertical axial load (P-max), and combined horizontal with minimum vertical axial load (P-min). Results indicate that although vertical ground motion contributes minimally to lateral displacement, it significantly alters axial load variations within columns, thereby affecting flexural strength and strain capacity. Increased axial compression in P-max cases enhances moment capacity but limits deformation, while reduced axial compression in P-min cases decreases moment capacity and allows greater These findings emphasize the importance of incorporating vertical seismic components into structural design and assessment, especially for critical elements in regions subject to strong vertical excitation. This study advances the understanding of vertical earthquake effects on RC moment frames and supports enhanced safety in earthquake-prone areas.
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Effect of climate change on Arctic water qualityClimate change is fundamentally altering Arctic hydrological systems, impacting water quality and posing challenges for communities dependent on these vulnerable sources. This study examines water quality trends across three distinct Arctic contexts: (1) Arctic glaciers, (2) the Yukon River Basin (YRB), encompassing a five-year dataset (2019-2023) of dissolved organic carbon (DOC), sulfate, and stable water isotopes (δ2H, δ18O, and d-excess) across varying permafrost regions and seasons, and (3) Shishmaref, Alaska, where a washeteria-based drinking water system is affected by environmental and seasonal changes triggered by climate change and coastal erosion. By addressing both regional hydrology and community-specific challenges, the study highlights the critical interplay between glacial melt dynamics, permafrost thaw, and water infrastructure vulnerabilities. This study focused on identifying significant spatial and temporal DOC variations, seasonal sulfate patterns, and stable isotope variability across permafrost regions. Additionally, seasonal differences in Shishmaref’s water quality were hypothesized to result from freeze-thaw processes, impacting heavy metals, sulfate, and nitrate levels. The findings reveal distinct biogeochemical and hydrological patterns: DOC fluxes peaked in late summer and fall, particularly in regions with sporadic and "Thick Thin" permafrost, driven by permafrost thaw and organic matter mobilization. Sulfate concentrations exhibited pronounced seasonal variability, with higher levels during peak thaw (June-August) influenced by sulfate-rich soils, glacial melt inputs, and runoff dynamics. Stable isotope enrichment in δ2H and δ18O and declining d-excess during summer reflected evaporation, altered precipitation sources, and shifting hydrological pathways In Shishmaref, seasonal monitoring revealed elevated heavy metal concentrations, such as zinc and copper, during winter due to infrastructure-related leaching and sediment mobilization under freezing conditions. Increased calcium and sodium concentrations during winter were linked to freeze-thaw-induced mineral dissolution and salt deposition. Conversely, DOC and SUVA values showed minimal seasonal variation, indicating consistent organic matter sources. These findings underscore the urgent need for localized water management strategies and long-term monitoring to mitigate the impacts of climate change on Arctic hydrology and community water security. By drawing parallels between Arctic glaciers and the YRB with specific challenges in Shishmaref water quality, this study offers a comprehensive understanding of Arctic water quality dynamics and their broader implications for adaptation and sustainability.
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Development of a versatile ground station for satellite communicationsThe purpose of this project is to create a communication link from a Student Ground Station at the NOAA facility in Fox to the Cubesat Communication Platform (CCP) Cubesat . The Student Ground Station will send Commands (Uplink) and receive Telemetry (Downlink). The radio onboard of the CCP Cubesat is the GOMSpace AX100, which is a Commercial off the shelf system. The GOMSpace AX100 uses Cubesat Space Protocol and AX.25 standards for their packet structure. The GOMspace AX100 uses Frequency Shift Keying (FSK) for modulation. My project will use a Software Defined Radio (SDR) that was coded in Matlab to communicate with the GOMSpace AX100. For Uplink, I will receive bits from COSMOS and conform to Cubesat Space Protocol and AX.25 standards. After I have Cubesat Space Protocol and AX.25 encoded bits, I perform FSK modulation on the bits and send the voltages to the SDR. In Downlink, I will receive samples from the SDR and perform FSK demodulation. After I have bits from demodulation, I will perform AX.25 decoding, then Cubesat Space Protocol decoding. The payload is then extracted from the decoded bits, then the payload data is sent to COSMOS for interpretation. I was able to successfully send commands to the GOMSpace AX100 and I was able to decode Telemetry packets sent by the AX100, which means I was are able to establish a communication link to the AX100.
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Geotechnical investigation of sand flow slides, Haines, AlaskaThe Lutak Spur (LS) - a prominent glacio-deltaic landform located near Haines, Alaska - formed during the retreat of the Cordilleran Ice Sheet during the Last Glacial Maximum. This study evaluates its geologic evolution, soil development, and hydrologic-slope stability response to a December 2020 atmospheric river (AR) event, which triggered multiple slope failures. Geologic mapping and interpretation of previous work suggest that the LS formed as an ice contact kame delta at the margin of a retreating valley glacier. Following deglaciation, post glacial isostatic adjustment and sea-level changes exposed the LS surface, allowing for the development of Spodosols with iron-cemented (Fe-cemented) horizons beneath forest vegetation. We used field observations, laboratory testing, and surface drainage mapping to assess slope behavior. Laboratory tests indicated that the Fe-cemented layers contribute cohesion to the strength of near-surface soils with a cohesion of 80 kPa, an average friction angle of 30.9°, and a hydraulic conductivity of 7.6x10-3 cm/s, while the underlying stratified sand exhibited an average friction angle of 36.4°, and an average hydraulic conductivity of 9x10-3 cm/s. Based on measured precipitation and NOAA Atlas 14 precipitation frequency estimates (PFE), the December 2020 AR event approached the intensity of a 1,000-year storm. Hydrologic modeling using HEC-HMS indicated that peak discharges during this extreme precipitation event were approximately three times greater than those produced by a modeled 100-year storm. Seepage modeling in SEEP/W demonstrated that infiltration during the December 2020 AR event elevated groundwater levels and pore-water pressures. Slope stability modeling in SLOPE/W indicated dry slopes were stable, but removal of the organic mat and Fe-cemented layers reduced the factor of safety (FS). Under saturated conditions, the FS dropped below 1.0, consistent with the occurrence of slope failures in 2020. Field evidence, residents’ observations, and modeling results support our hypothesis that tree throw at the slope crest disrupted the Fe-cemented sand stabilizing layer, triggering failures during the AR event. These results suggest that extreme precipitation, in combination with tree throw and surface disturbance, reduced slope stability through transient increases in pore-water pressure and loss of near-surface strength.
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Development of low-profile wideband microstrip antennas for CubeSat phased-array applicationsCubeSat missions rely heavily on effective communication systems in order to transmit and receive large amounts of data quickly and efficiently. The total throughput is limited by the capacity of the channel - a quantity dependent upon the signal quality and bandwidth of the link. Volume and power constraints on a CubeSat impede overall capacity in a fixed bandwidth channel. Phased-array antennas provide a more power efficient solution to improving signal quality by optimizing the spatial properties of the link, rather than broadcasting higher signal power over a broader area through power amplification alone. In order to take advantage of a larger antenna gain without having to mechanically rotate, the array must be controlled properly such that the radiated power is focused in the desired direction. The appropriate steering vector can be determined autonomously through Retrodirective beamforming - a process where the characteristics of arriving signals are used to determine the direction of arrival, and the resulting array directivity is maximized in that direction. In order to accommodate enough bandwidth to transmit and receive at separate frequencies, a low-profile antenna element was developed in this work and arrayed for a 1U CubeSat. The individual circularly-polarized antenna element shows a wide measured impedance bandwidth of 21% (for a 2:1 VSWR) at a low profile of 0.34λ0 × 0.39λ0 × 0.025λ0. The resulting gain of the circularly polarized array averaged a realized gain of ~10-dBic between 2.0 and 2.3-GHz, yielding roughly twice the gain of traditional planar CubeSat antennas at these frequencies, with the added bonus of an array interface for potential beam-steerability.
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Monitoring surficial change and forecasting subsurface thermal properties of frozen debris lobesFrozen debris lobes (FDLs) warrant a multi-faceted research approach due to their complexity as large scale, slow-moving, soil-based landslides located on paraglacial permafrost slopes. Since 2008, University of Alaska Fairbanks-based (UAF) researchers have been monitoring these features due to their increasing rates of downslope movement and proximity to linear infrastructure. The majority of FDLs within Alaska have been observed and/or monitored south of the Continental Divide in the south-central Brooks Range; FDL-A has been studied most extensively because of its proximity to the Dalton Highway and Trans Alaska Pipeline System (TAPS). This thesis synthesizes two research approaches: first, quantification of the detected mass movement of nine FDLs from 2011 to 2023 between discrete digital terrain model (DTM) time steps; and second, thermal modeling of FDL-A with four surface vegetation scenarios from 1970 through 2070. Change detection indicated a net volume loss of FDLs through time, while also highlighting that some FDLs advanced up to 4.1×105 m3 of material near their toes. Sediment disturbance from FDL surface runoff and accumulation also was observed from FDLs -D, -C, -A, and -7. Refined thermal modeling of FDL-A demonstrated that vegetation cover significantly drives permafrost temperature, influencing subsurface stability both now and during a warmer future. Projections indicate that if the surface cover declines, FDL-A could develop taliks and warm above -0.2 °C by 2070. The workflows presented herein provide snapshots of current FDL conditions across their surfaces (via change detection) and at depth (via thermal modeling), serving as useful tools for understanding FDL permafrost dynamics and informing mitigation strategies as FDLs continue to advance downslope.
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An analysis of vulnerable road user crashes in Alaska using spatio-temporal methodsThis study presents a two-part investigation into the spatial patterns of crashes and safety of vulnerable road users (VRUs). VRUs, cyclists and pedestrians in this context, represent approximately 18% of traffic fatalities in Alaska annually. However, existing studies on VRU safety in Alaska are limited and causal factors and effects of safety projects are not well understood making it difficult to implement targeted and strategic approaches to improve VRU safety. To that end, the objectives of this research are two-fold: 1) analyze spatial interactions of VRU crashes involving risk tolerant behaviors; and 2) evaluate the effectiveness of Highway Safety Improvement Program (HSIP) projects in achieving VRU safety outcomes. First, risk-tolerant behaviors among VRUs, namely alcohol consumption, suspected drug use, and lack of safety gear, are considered using Anchorage as a case study. Network-based spatial methods such as kernel density estimation, nearest neighborhood and K-function analysis, along with other network functions were employed to identify crash clustering and spatial dependencies. Results suggest statistically significant clustering is exhibited by crashes involving alcohol or drug use for both cyclists and pedestrians. Results also revealed spatial dependence between cyclist crashes and pedestrian crashes for the same risk-tolerant behaviors. Moreover, crashes involving cyclists who were not wearing helmets or safety gear exhibited significant spatial clustering. Second, explicit and implicit safety benefits of HSIP projects were evaluated using a before-after approach to determine the extent to which safety projects were successful in reducing crashes. Frequency and injury severity for VRUs. The analysis found mixed results. Some projects and project types demonstrated clear safety benefits while others showed neutral or negative outcomes. Additionally, VRU-specific project types were found to have more explicit safety benefits for cyclists than they did for pedestrians and that non-VRU specific project types seemed to exhibit more implicit safety benefits for pedestrians when compared to cyclists. These findings offer valuable insights for improving VRU safety in Alaska and serve to better inform the HSIP process including more robust methods for network safety screening, introduces new variables for consideration in the project selection process, and presents a more comprehensive approach for post-project evaluation.
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Analysis of a persistant early winter open water zone within the ice-covered Tanana River near Fairbanks, Alaska using field studies, remote sensing, and hydraulic modelingFrozen rivers serve as important transportation corridors for Alaskans during winter. Open water zones (OWZs, i.e., open leads) in otherwise ice-covered rivers present a hazard because their location and causes are poorly understood. I studied one persistent OWZ on the Tanana River near Fairbanks using field studies, remote sensing, and hydraulic modeling. Interannual occurrence and duration of the OWZ was identified from 2014 to 2023 using optical satellite images and synthetic aperture radar. In eight out of ten years, an OWZ zone formed when an ice jam occurred at an upstream channel constriction during freeze-up. In the other two years, a partial ice cover developed downstream of the reach and no OWZ formed. I suspected this initial ice jam where the channel narrowed played an important role in OWZ formation. To test this, I performed simulations of various ice covers and discharges in HEC-RAS to evaluate flow hydraulics restrictive or conducive to ice cover formation. Model results demonstrated that initial ice jam locations influence a range of potential velocities that may prevent ice formation. Long term records showing increasing discharge on the Tanana during freeze-up may impact the formation of persistent OWZs and future river ice regimes. My findings indicate that channel form, discharge, and ice jams may explain the occurrence of many OWZs in otherwise ice- covered rivers. Thus, considering channel form, hydrology, and ice-affected flow hydraulics will allow for better prediction of current and future river ice conditions, leading to improved winter travel safety across Alaska.
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Optimizing power fluid in jet pump oil wellsA method for optimizing power fluid to a network of jet pump wells is established. Jet pump performance is modeled by numerically solving a system of equations for specific throat and nozzle geometries. An upper boundary is established of the most efficient geometries for each well which creates a continuous function relating power fluid to oil production. Jet pump oil wells are segregated into networks which share a common power fluid surface pump. These boundaries are added together to create a non-linear objective function. To solve power fluid distribution in a network, a reduced Newton method is applied that incorporates active constraints. System constraints are that the total network power fluid is at or below surface pump capacity and that each power fluid rate is non-negative. Upon successful convergence, the power fluid estimate per well is passed to a discrete algorithm to choose between either a high or low power fluid jet pump. A computer program is developed capable of implementing the optimization method. This program is successfully tested on an eight well network, determining whether an additional well can be supported with existing equipment. The continuous optimization is fast, converging in four iterations to an answer. Any engineer can run this program, providing the benefit of a unified approach to decision making. This is a significant improvement, since no previous methods have been found in literature on how to distribute power fluid across a jet pump network.
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Data-driven simulation of sustainable residential HVAC systems in Fairbanks, AKResidential heating comes at extremely high costs and with harmful air pollution in many Alaskan communities. In Fairbanks, the issue of air pollution has received special attention in recent years, specifically due to the high concentration of small particulate matter resulting from residential space heating. This thesis aims to address energy insecurity and air pollution in Fairbanks by proposing an improved residential HVAC system. A computer simulation was developed to model the operations of several different HVAC configurations for comparison with standard heating oil boiler and portable air conditioner systems. This Python model provided a means of simulating one year of heating and cooling using TMY3 weather data, performance data from commercially available HVAC equipment, and historic energy pricing. The proposed HVAC system integrated a hybrid source heat pump with thermal storage, radiative sky cooling, and solar evacuated tube heating technology. Other tested systems included single and dual air source heat pumps, and water source heat pumps integrated with thermal storage, radiative sky cooling, and solar evacuated tube heating technology. Each of the tested systems were fitted with a backup boiler to meet the heating requirement in Fairbanks at the ASHRAE design temperature. A boiler and portable AC unit were also simulated in operation as a baseline for comparison to the tested systems. Each tested system was found to greatly reduce the operational cost, heating oil consumption, and associated CO2 and PM2.5 emissions compared to the baseline system. The proposed hybrid source heat pump system saw the greatest of these operational benefits, demonstrating operational cost savings of 19.12% and heating oil consumption reduction of 43.1% as compared to the heating oil boiler and portable AC unit. A benefit-cost analysis revealed that while each tested system showed operational benefits from the baseline, the increased maintenance costs associated with these complex systems outweighed the operational benefits. Furthermore, the capital costs were found to increase substantially with system complexity, creating a barrier to entry for users. While each tested system was found to lower operational costs and increase social benefit by reducing CO2 and PM2.5 emissions, the disproportionate capital and maintenance costs of these systems resulted in economic nonviability. This research highlighted the need for sustainable HVAC solutions for residential homes in Fairbanks. While these results showcased a modern-day application of the developed model in Fairbanks, the key contribution of this thesis was the development of a powerful, adaptable model which can simulate the operation of a variety of HVAC systems in different locations. The structure of the model allows the user to simply upload new location specific data to perform a one-year HVAC simulation in any location where this data is available. While this thesis uses a sample Fairbanks home in simulation, the simulated building’s construction geometry and material properties are easily adaptable, allowing the user to fully specify the desired building for analysis. Similarly, the selected HVAC equipment is easily adaptable, allowing the user to specify performance data for commercially available equipment, or even test new technology in a variety of locations and building applications. This adaptability allows the model to be applied for both residential and commercial buildings and used to simulate HVAC operations across a variety of locations for cost analysis, research and development.
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Developing a proof-of-concept non-scalable active vacuum insulated building envelope prototypeHeating and cooling buildings consumes around 17% of global energy demand. Improved thermal insulation can reduce much of this consumption with positive implications for energy security and economic opportunity. For over 25 years vacuum insulation panels (VIPs) have been considered a highly promising thermal insulation solution for building envelopes. VIPs can potentially provide an order of magnitude greater insulative performance than common insulation materials with the same thickness. However, the adoption of VIPs in buildings is hindered by many factors: their relatively high costs, installation challenges due to fragility, inalterability, and limited dimensions; limited service life in comparison to buildings due to loss of vacuum over time; susceptibility to thermal bridging along their edges; and other issues. An innovative concept in vacuum insulation technology, active vacuum insulation, is being developed to address many of these challenges. Incorporating a connection to a vacuum pump enables use of cheaper materials and equipment for on-site assembly and evacuation of customizable, large (for example, a whole wall) active vacuum insulation panels (active-VIPs). Vacuum can be extended indefinitely through occasional reactivation of the vacuum pump. For the project described in this thesis, a proof-of-concept active vacuum insulated building envelope prototype was developed. Large active-VIPs were produced and integrated with a vacuum assembly that created, monitored, and maintained internal vacuum. Over a one month trial period an average pressure of about 68 mTorr was maintained and the average R-value per inch of the active-VIPs was around 50 hr∙ft2∙°F∕Btu∕in. This was achieved using a minimal amount of electrical energy for the vacuum pump, representing less than 5% of the thermal energy saved thanks to the vacuum pump. These results indicate that active vacuum insulation is a worthwhile innovation for continued investment in research and development.
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Performance and viability of air source heat pumps for residential heating in cold climatesWith an ever-increasing concern for Earth’s climate, solutions to mitigate further climate change caused by greenhouse gas emissions are continuously being investigated, one of which is heating buildings using air source heat pumps (ASHP) rather than traditional fossil fuel systems such as a furnace. The benefits of heat pumps over other heating methods such as resistive heating is their ability to transfer multiple times greater heat using the same amount of electricity by utilizing the phase change of a refrigerant and different inside and outside temperatures through use of the vapor-compression cycle. This also provides an advantage over fossil fuel-based systems by operating on electric power rather than burning fuel, greatly reducing greenhouse gas emissions. While heat pumps are a superior choice for many heating needs, heat pumps suffer performance issues when outside temperatures are low. This low coefficient of performance (COP) in cold climates has limited the widespread use of heat pumps to provide heat in the winter. The first section of this thesis will review heat pump technology and research on cold climate performance, including discussions on refrigerants, environmental impacts, and the economic cost of using a heat pump. A field test in Fairbanks, Alaska was performed and collected data on heat pump performance of a commercially available (CA) R410A-based ASHP and a prototype ASHP with new technologies and R32 refrigerant. Results of these tests revealed a 53.8% increase in COP of the prototype heat pump from -30°C to -35°C compared to the CA unit with a 26.7% average increase in COP over the 0°C to -35°C range, with increases to heating output seen as well. An economic comparison of a furnace heating system compared to both heat pumps also revealed generally lower operating costs for the heat pumps, with a potential hybrid heating system resulting in cost savings of 33% to 57% for the prototype unit and 17% to 45% for the CA unit. Year-long projections were performed for Fairbanks, AK as well as Boston, MA and Fargo, ND to evaluate performance, cost, and environmental impact in regions with different weather conditions and energy costs. Across all three locations, cost savings were seen from utilizing heat pumps over a furnace, with the Fargo location being more cost effective to use a heat pump 100% of the time. An analysis on levelized cost of heating was calculated for each location to evaluate long-term costs, with a discussion at the end about possible errors in calculations and projections.
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Evaluation of hybrid enhanced oil recovery strategies for Ugnu heavy oil reservoirs in the Alaska North SlopeThe Alaska North Slope (ANS) holds a vast reserve of heavy oil, primarily in the Ugnu formation, estimated at 12-18 billion barrels. However, the recovery of these resources presents challenges due to high oil viscosity and proximity to continuous permafrost, which precludes thermal recovery methods that could cause disastrous environmental damage. Recently, low-salinity water flooding (LSWF) and low-salinity water with polymer (LSP) have been considered for enhancing oil recovery from moderately viscous oil reservoirs on the slope. This study explores non-thermal hybrid enhanced oil recovery (cEOR) techniques, focusing on solvent pre-treatment (e.g., CO2) and low-salinity water (LSW) within a Water Alternating Gas (WAG) injection method. Commercial silica sand packed in cylindrical sandpacks was used throughout the study to evaluate the recovery performance of the proposed methods on both dead and live Ugnu heavy oil. Various injection modes were also examined to optimize recovery performance. Cumulative oil production and pressure drops were measured and recorded, while oil recovery factors and residual oil saturation after each flooding were determined based on material balance. The displacement test results reveal that combining liquid CO2 with LSW in a WAG process significantly enhances recovery, achieving up to 83.5% of original oil in place (OOIP), more than double that of continuous LSW flooding. This improvement is attributed to CO2-induced viscosity reduction and swelling, with additional benefits of CO2 storage in the reservoir. Hydrocarbon lean gas (HLG) was also evaluated as an alternative solvent, but the performance was lower (68.4% of OOIP) compared to liquid CO2 due to differences in mass transfer and live oil interactions. Simulation studies optimized key parameters for the CO2-WAG process, such as soaking time and CO2 slug volume, highlighting the potential for maximizing recovery while sequestering greenhouse gases. Another promising approach, CO2-saturated low-salinity water (CWI), demonstrated substantial recovery benefits, achieving an additional 36% OOIP beyond secondary LSW injection and 40% in tertiary stages. The effectiveness of CWI lies in viscosity reduction and solubility trapping of CO2 in residual oil, with 28-41% of injected CO2 stored during the process. However, integrating low-salinity water polymer (LSWP) in tertiary recovery was less effective due to polymer degradation. Overall, these studies underscore the significant potential of CO2-based cEOR methods, particularly liquid CO2-WAG and CWI, for Ugnu heavy oil recovery. These techniques not only improve oil recovery but also contribute to greenhouse gas mitigation through efficient CO2 utilization and storage.
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At the crossroads of technology, policy, and society: energy transitions in rural AlaskaThe future of energy in remote and rural communities is shaped by a complex interplay of technology, policy, and social structures. This dissertation explores why some regions--despite facing similar economic, geographic, and environmental constraints--have successfully developed renewable energy systems while others have struggled. Focusing on rural Alaska, this research examines the factors that drive or inhibit local energy transitions, considering historical institutionalism, governance structures, policy interventions, and economic incentives. Through a mixed-methods approach including case studies, qualitative comparative analysis, and statistical methods, this dissertation examines how energy subsidies and the pooling of resources--whether through shared infrastructure, cooperative utilities, or other forms of regional collaboration-- shape energy costs, innovation, and renewable energy adoption in isolated communities. The findings highlight the pooling of resources as a key driver of successful energy transitions and offer insights applicable to other Arctic and remote regions. By bridging engineering, policy, and social science, this work challenges dominant narratives that view energy transitions as purely technological or economic shifts and argues that sustainable energy futures emerge from balancing past wisdom and innovation. Informed by diverse perspectives including those of communities, utilities, and Alaska's Indigenous knowledge systems, this dissertation reframes the approach to energy transitions, emphasizing the integration of historical wisdom, policy adaptation, and local agency. Rather than discarding old systems for new ones, integrating historical knowledge with modern solutions is key to building resilient, affordable, and community-driven energy systems. The findings contribute to ongoing discussions in academia, policymaking, and practical decision making, offering insights relevant to scholars, practitioners, and leaders working on rural and Arctic energy transitions.
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Mechanical properties of biofilms in water distribution and bioremediation systemsThis dissertation explores biofilm dynamics in water distribution and acid mine drainage (AMD) treatment, focusing on their roles in resource recovery and public health. Biofilms consist of microbial communities in a self-produced extracellular polymeric substance (EPS) matrix, which influences their mechanical and structural properties based on EPS composition, environmental conditions, and biofilm age. In drinking water distribution systems (DWDS), biofilms pose health hazards as they harbor pathogens and encourage metal corrosion. The composition of extracellular polymeric substances (EPS), particularly its high protein content, is noted in downstream areas, facilitating biofilm development in conditions of reduced chlorine and higher temperature turbidity. Traditional antimicrobial strategies often fail due to the protective EPS matrix, highlighting the need for targeted biofilm control strategies. On the other hand, biofilms show promise in AMD treatment, where biofilm-based bioreactors utilizing sulfate-reducing bacteria (SRB) effectively neutralize acidity and recover valuable metals, including rare earth elements. SRB bioreactors demonstrated sulfate reduction rates of up to 92.8% and near-complete removal of essential metals, showcasing the ability of biofilms to facilitate precipitation and biosorption under extreme conditions. The mechanical properties (as Young’s modulus) of biofilms were observed to vary with environmental conditions and biofilm age, influencing their resilience to mechanical stress. In DWDS, these properties impact biofilm control and removal efforts, while in AMD treatment, increased biofilm stiffness supports structural stability for effective metal removal. Advanced techniques like confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM) assessed biofilm characteristics, emphasizing the need for site-specific management strategies. Findings indicate that successful biofilm management necessitates an understanding of mechanics, EPS composition, and environmental factors. Future research should enhance biofilm control technologies and explore enzyme-based disruptors, balancing sustainability and public health concerns while optimizing resource recovery.
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Electric power regulation for a novel riverine hydrokinetic energy conversion systemTransportation of diesel fuel used to produce electricity for Alaska remote communities is highly expensive. Thus, people living in those remote areas pay a high rate for electric energy compared to the national average cost. The availability of renewable energy resources may help to minimize these high expenses. As many rural Alaskans live near rivers, hydrokinetic energy could be used as a renewable source of electric power. This renewable resource, if successfully harvested, has immense potential to help power Alaska remote communities and significantly reduce electric energy costs. This project aims to investigate the implementation of an energy conversion system to harvest riverine power by utilization of a novel hydrokinetic energy harvesting system through field testing and modelling. An electrical power generator, specifically a permanent magnet synchronous generator (PMSG), was selected to be used for mechanical-to-electrical energy conversion within a low-speed range. Unregulated electric power produced by the generator was rectified and filtered to produce smooth DC power. A maximum power point tracking (MPPT) current controller was implemented in the Simulink® environment to demonstrate how to extract the maximum power available at the generator output under different water velocities and load conditions.
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Seismic site response, liquefaction-induced lateral spreading and impact of seasonal frost on pile foundations in cold regionsPermafrost sites are experiencing significant changes due to anthropogenic activities and climate change, leading to substantial variations in soil dynamic properties and increased seismic risks. The associated geohazards, including differential settlement, slope instability, and liquefaction of degraded, unconsolidated materials in seismically active warm permafrost regions, pose substantial threats to the built infrastructure. This study aims to assess the seismic site response of warm permafrost sites and analyze the impact of seasonal frost on liquefaction-induced lateral spreading and pile foundation behavior in cold regions. Northway Airport, Alaska, was used as the study site to characterize permafrost conditions, while the Slana River site and the newly constructed bridge along the Tok Cut-Off were selected as the prototype for investigating liquefaction-induced lateral spread and its impact on pile foundations. Geophysical testing methods, including Multichannel Analysis of Surface Waves (MASW), Horizontal-to-Vertical Spectra Ratio (HVSR) method of ambient noise, and Electrical Resistivity Tomography (ERT), were used to map the shear wave velocity profiles. A one-dimensional equivalent linear analysis assesses site response across multiple seismic hazard levels, accounting for frozen and thawed conditions. Meanwhile, a three-dimensional finite element modeling approach, i.e., OpenSees, simulates ground liquefaction and the interactions between pile foundations and liquefiable soils under varying conditions of seasonal frost depth and soil properties. The results from this study show that, in degraded permafrost areas, changes in shear wave velocity (Vs) due to thawing significantly influence ground motion characteristics during seismic events. Seasonal frost depth and soil permeability emerged as critical factors in affecting liquefaction-induced lateral ground spreading, with lower soil permeability and greater frost thickness increasing liquefaction susceptibility and resulting in a larger amount of ground lateral spread. Furthermore, this study demonstrates that seasonal frost can substantially reduce ground lateral spreading. However, it can also increase internal forces such as shear force and bending moment in bridge pile foundations and form additional plastic hinges, complicating the seismic design of deep foundations. These findings highlight the need to understand comprehensively permafrost degradation-induced changes in soil dynamic properties in cold regions. This study proposes a framework for assessing permafrost degradation's impact on the seismic site response. It offers new insights for engineers and policymakers to develop effective strategies for constructing and retrofitting resilient infrastructure and mitigating the hazards in seismically active cold regions.
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Extraction of rare earth elements from coal ash using supercritical CO₂The increasing demand for rare earth elements (REEs) as critical components in modern technologies has led to growing interest in their efficient recovery from alternative sources. Coal ash, a waste product generated from coal combustion, has been identified as a potential reservoir of valuable REEs with reported REE concentrations varying between 270 and 1480 ppm. In this research paper, we investigate the recovery of REEs from three coal ashes: anthracite, bituminous, sub-bituminous using environmentally benign supercritical fluid (SCF) carbon dioxide (CO2). Additionally, the effect of tributyl phosphate (TBP) and nitric acid (HNO3) as complexing agents is explored to enhance the extraction efficiency. The advantage of this option over conventional solvent extraction methods includes minimization of liquid waste generation, solute separation, and rapid reaction rates. Supercritical fluids (SCFs) can penetrate and transport solutes from different matrices due to its high diffusivity, low viscosity, and liquid-like solvating. CO2 provides a good option as an efficient solvent since it has the benefit of being easy to obtain and has a medium critical constant (Tc = 31.1oC and Pc = 7.38 MPa), as compared to other solvents. Additionally, CO2 is inert and stable (chemically and radio chemically), inexpensive, easy to supply at high purity, and it is environmentally friendly and widely used. The experimental work involved the optimization of process parameters, including temperature, pressure, and solvent-to-solid ratio, to ensure maximum REE recovery while minimizing environmental impact. The optimum extraction conditions for anthracite ash were determined to be 60°C, 1100 psi, 120 minutes residence time, 250 rpm agitation rate, solid to chelating agent ratio 1:10 and TBP to HNO3 ratio 1:1, with corresponding 80% extraction efficiency which is 230 ppm. The optimum extraction conditions for bituminous ash were determined to be 60°C, 1100 psi, 120 minutes residence time, 250 rpm agitation rate, solid to chelating agent ratio 1:10 and TBP to HNO3 ratio 1:1, with corresponding 49% extraction efficiency which is 290 ppm. The optimum extraction conditions for sub-bituminous ash were determined to be 60°C, 1835 psi, 120 minutes residence time, 250 rpm agitation rate, solid to chelating agent ratio 1:10 and TBP to HNO3 ratio 1:2, with corresponding 58% extraction efficiency which is 149 ppm.
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Identification and future susceptibility of permafrost degradation near Red Dog MinePermafrost degradation is a major concern in the Arctic region, and its impacts on infrastructure, ecosystems, and global climate are significant. Within recent years, 2018 to present, the level of Total Dissolved Solids (TDS) has been elevated in Ikalukrok Creek in Northwest Alaska, made evident by creek discolorations known as river rusting. The current analyses indicate that changes in permafrost regimes can trigger the observed rise in TDS. Data visualization, remote sensing, and permafrost modeling were used to understand the physical mechanisms involved in the increase of TDS and to identify regions susceptible to permafrost degradation. This comprehensive approach integrates various datasets to capture the spatiotemporal characteristics of talik formation near Ikalukrok Creek. The permafrost models incorporate a variety of data such as soil temperature, soil type, vegetation, snow cover, and topography. Spatially distributed 1-D models utilize vegetation as a proxy to parameterize ground thermal properties. All models are validated using ground temperature measurements. The study aims to investigate the correlation between changes in TDS and climatic factors, particularly how variations in air temperature influence TDS concentrations in river water. Additionally, it seeks to understand the mechanisms driving river rusting, monitor hydrological and permafrost changes using remote sensing and modeling. By utilizing remote sensing images, it is possible to identify and map the visual extent of river rusting and to investigate the relationship between river rusting concentration, climatic events, and talik formation. This study presents a better understanding of the factors driving talik formation and the increase of TDS. Understanding talik formation and increases in TDS is critical for the mitigation of pollution in the environment. This research provides a foundation for other researchers to build upon, as we learn more about river rusting, it is hoped that policymakers will be able to utilize this information or similar insights.
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Modeling rate of penetration in a south Texas oil field with aggregated well data in a supercomputing frameworkThe objective of this work is to develop an accurate and practical tool for drilling engineers supporting operations to predict rate of penetration (ROP) in the tangent section of the wellbore using easily obtainable data. Historically, tacit knowledge has been used to predict both ROP and the ideal parameters. Such a tool is valuable for planners seeking to adjust rig schedules. Further, this tool could easily be modified to also optimize parameters. This work was comprised of two major efforts: data acquisition and wrangling, and modeling. Data was obtained from three distinct sources: well files, drilling logs, and survey logs. Data on bit geometry or formation was not available. This data was manually downloaded and imported into Python. Due to the size of the data, a university-owned high-performance computer (HPC) was required to process the data. Special care was given to optimizing for memory efficiencies that allowed the HPC to perform these operations. A test data set of 5 wells was used to pilot the data wrangling process and initial linear regression models. Four different model types were produced and evaluated: linear regression, polynomial regression, nonlinear regression, and neural networks. Neural networks provided the best prediction with a R2 of 0.85. The most important variables affecting ROP in the tangent section in descending order are: total pump output, rotary speed, hook load, differential pressure, and bit type. To the best of our knowledge, this is the largest dataset of ROP data found in literature; containing over 350 wells and 30 million rows of data. This workflow can be adopted to create other field-specific models or adapted to evaluate other sections of the wellbore. More immediately, this work creates a large database ready to be utilized for developing other models undergirded by different computational methodologies.
