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Electrochemical Corrosion Investigation of Structural Materials in Molten Fluoride Eutectic Salts
No full textThis thesis investigates the corrosion behavior of structural materials when exposed to molten fluoride eutectic salts using electrochemical techniques. The research objective is to rank and screen metal structural materials for nuclear reactors based on their performance in determining physical properties, including impedance, corrosion rates, and polarization in FLiNaK salt at 700 °C. The ranking and screening process involved evaluating the materials' performance in these tests and establishing a relative hierarchy. Criteria such as lower corrosion rates, higher impedance values, and increased polarization resistance to corrosion were considered during the analysis. Electrochemical impedance spectroscopy (EIS), Tafel, and polarization resistance (Rp) measurements were conducted for nickel, stainless steel 304, stainless steel 308, Inconel 600, Inconel 617, and HastelloyN. The results revealed variations in the physical properties and corrosion mechanisms of the alloys based on their composition. The EIS analysis provided insights into the corrosion mechanisms and interface properties of the materials, contributing to the development of improved materials in future work. Additionally, the Rp measurement indicated the materials' resistance to corrosion. The findings of this study have significant implications for the design and selection of materials for future high-temperature applications involving molten fluoride eutectic salts, including Gen-IV nuclear reactors and molten salt batteries. The knowledge gained from this research contributes to the development of more durable and efficient materials by delivering important physical property data of metals in molten salts at high temperatures. This knowledge can facilitate the use of these materials as structural components capable of withstanding harsh environments, ultimately enhancing the reliability and safety of high-temperature systems up to 700 °C.masters, M.S., Chemical & Biological Engineering -- University of Idaho - College of Graduate Studies, 2023-0
Hydrologic Modeling to Estimate Peak Streamflow for Post-Fire Forest Management
No full textIn forested ecosystems, wildfires often effect changes in a watershed’s hydrologic response to precipitation. Elevated runoff causes stream discharge to spike during high intensity, short duration rainfall and snowmelt events. This discharge can damage or destroy road infrastructure such as culverts, and make road impassable, resulting in expensive repairs. Forest managers use hydrologic models to identify areas of highest risk to this damage and prescribe treatments to mitigate the risk. We measured peak flow at 12 road crossings following five large wildfires in 2017 in Western Montana and used the data to assess the peak flow estimates of four commonly used hydrologic models: Runoff Curve Number, USGS Regression Equations, WEPPcloud-PEP (Post-fire Erosion Prediction), WEPPcloud-Disturbed. Our data showed that annual peak flow in this region occurs primarily during the spring runoff, though small, isolated rainfall events are capable of producing large spikes in streamflow volume. The Runoff Curve Number method tended to greatly over-estimate peak flows generated by rainfall events we observed and is unable to model runoff events caused by snowmelt. USGS Regression equations underpredicted the changes to post-fire hydrology. When detailed soil information was used, WEPPcloud-Disturbed was able to reasonably predict runoff for both rainfall and snowmelt events which is critical in snowmelt dominated watersheds.masters, M.S., Water Resources -- University of Idaho - College of Graduate Studies, 2023-0
Differentiating Science Motivational Factors of Adolescent College Students by Career Orientation with a Self-Determination Theory Lens on Variables and Voices – an Explanatory Sequential Mixed Methods Study Utilizing the Academic Motivation Scale in Survey and Interviews
No full textThis study investigated how undergraduate college students with different STEM career orientations differ in their motivation toward science education. The purpose of this study was to surface differences in the quality of motivations between groups of students with different orientations toward STEM careers to support them in science education classrooms better. A more in-depth understanding of motivational quality would allow science course instructors to design learning more specific to the types of student motivational profiles. Specifically, five motivational sub-dimensions of the Self-Determination Theory were investigated using the Academic Motivation Scale: amotivation, external, introjected, identified, and intrinsic motivation. This explanatory sequential mixed methods study investigated the the between-groups differences in each motivational sub-dimension quantitatively with a survey and qualitatively with interviews. The researcher conceptualized this study with a critical realist epistemology, applying self-determination theory as theoretical lens of the study. Results show significant differences in intrinsic motivation between all three STEM career orientation groups investigated, those interested in STEM careers, those interested in STEM-related careers, including technical careers and health professions, and those not interested in STEM careers. For all other motivational sub-dimensions, students not interested in STEM careers were significantly different in their motivation from the other two groups. Interviews surfaced the following theme trends for motivational qualities. Students oriented toward STEM careers discussed the challenges of pulling apart dense science concepts to learn as part of their cognitive process to become competent. In contrast, students oriented toward STEM-related careers tended to view the science courses as an externally imposed hurdle toward a career that required learning of knowledge comprised of facts, often not seen as relevant to their career. Overall, the narratives were in line with the empirical results. These outcomes constitute tools for science educators to assess students’ motivational profiles for science alongside authentic perspectives, allowing tangible insight into student views on education and their motivation to learn.doctoral, Ph.D., Education -- University of Idaho - College of Graduate Studies, 2023-0
Development, Construction, and Operation of a Non-Nuclear Microreactor Experimental Capability
No full textIdaho National Laboratory has constructed the microreactor non-nuclear experimental test bed (MAGNET) to reduce uncertainty and risk for microreactor developers, users, and regulators. MAGNET will provide verification and validation data for dynamic models and system scaling allowing demonstration and validation of microreactor systems, components, and auxiliary systems. The system was designed around typical air-Brayton parameters with a hot design temperature of 650°C and a maximum allowable working pressure of 22 bar. The differential temperature through the microreactor test article was assumed to be 290°C. MAGNET is compatible with compressed air, nitrogen, or helium as the cooling fluids. Testing to date comprises a single heat pipe proof of concept test and a prototype helium-to-air heat exchanger test for a commercial developer.masters, M.S., Mechanical Engineering -- University of Idaho - College of Graduate Studies, 2023-0
The Optimization of Biochar for the Removal of Phosphorus from Water
No full textPhosphorous (P) pollution from anthropogenic activities is contributing to increases in eutrophication in freshwater systems. In addition, the demand for plant-available P sources continues to increase globally. Biochar, a substance created through biomass pyrolysis, has shown potential for removing P from wastewater. Numerous published studies indicate that chemically modified biochar is more effective at P removal than unmodified biochar. To identify the most suitable type of biochar for future modification for P removal and storage, several characterization experiments were conducted. After conducting the characterization experiments on fourteen biochar types, four were chosen for further experimentation. These biochars were then chemically altered to optimize P adsorption. The modification agents used were Ca, Mg, Fe cations, and cationic polymers. 4% Fe-modified biochar was determined to be the best and it was incorporated into a bench scale continuous flow reactor with dairy effluent wastewater to simulate real wastewater treatment applications. The biochar was then recovered from the reactor and experiments were done to determine the quantity of recoverable plant available P and total P. The Fe-modified biochar treatment had a significant increase in plant available P from 27 to 138 mg/kg. However, this was still lower than the initial value of unmodified biochar, which was 646 mg/kg and increased to 680 mg/kg after treatment. Total P was highest in the Fe-biochar post-treatment with the flow reactor at 1224 mg/kg, while the unmodified biochar had a total P of 993 mg/kg. Results from the research will enable P recycling using modified biochars that can be used as a soil amendment. To test biochar use for P recycling, a pilot study was conducted at Elk Mountain Farms, Idaho, to assess the effectiveness of Fe-modified biochar in removing P from groundwater impacted by agriculture. The University of Idaho Clean Water Machine, which uses reactive filtration technology, was utilized to remove and recover P from groundwater. The water samples showed that for 4% Fe-modified Pacific Biochar, total P in the water dropped from 0.166 mg/L to 0.019 mg/L between the influent and effluent samples, while ortho-phosphate decreased from 0.102 mg/L to 0.008 mg/L. Total P for the unmodified biochar dropped from 0.091 mg/L to 0.025 mg/L between the influent and effluent samples, and ortho-phosphate decreased from 0.049 mg/L to 0.003 mg/L. Both the unmodified biochar and the Fe-modified treatment showed an increase in total P after being used in the reactive filtration. The unused unmodified biochar had an initial P amount of 725 mg/kg, which increased to 1108 mg/kg after water treatment. Similarly, the Fe-modified treatment had an initial P amount of 614 mg/kg, which increased to 995 mg/kg after water treatment. These results indicate that biochar has the potential to be used to remove P from water, especially if the biochar is modified to do so.masters, M.S., Soil & Water Systems -- University of Idaho - College of Graduate Studies, 2023-0
BARLEY YIELD AND PROTEIN RESPONSE TO NITROGEN AND SULFUR FERTILIZER RATES AND APPLICATION TIMING
No full textThe introduction of new barley varieties and changes in management practices necessitate re-evaluating nitrogen (N) and sulfur (S) nutrient management and application timing guidelines. Nitrogen has a significant impact on barley grain quality and yield. However, overapplication of N can result in yield reduction, groundwater pollution, and high protein content, resulting in lower end-use quality of barley, while underapplication of N results in reduced grain quality and yield. Because S improves N utilization and enhances protein synthesis and split N application improves yield and N use efficiency in winter barley, split N application timing and the interaction of N and S may be a valuable tool to reduce N loss, increase yield, improve grain quality, and improve N use efficiency for agronomically optimal spring barley production. In a bid to provide barley growers in the Western US with an optimal N application timing, as well as appropriate N and S rates for improved yields and grain quality and reduced input costs and environmental contamination, we evaluated the effects of N and S fertilizer rates and application timing on malt, feed, and food barley grain yield and quality for four site-years in Aberdeen and Kimberly Research and Extension Centers and Brigham Young University-Idaho in Idaho for the 2021 and 2022 growing seasons. Three barley varieties: malt (Moravian 179), feed (Claymore), and food (Julie) were grown at 1,980,000 seeds ha-1. Nitrogen fertilizer treatments included urea (46-0-0) applied at 0, 45, 90, 135, or 180 kg N ha-1 at planting or a split application of 45 kg N ha-1 done at planting and top-dressed with 23, 45, or 90 kg N ha-1 at heading. Sulfur fertilizer treatments included three S rates of potassium sulfate (0-0-53-18) fertilizer applied at 0, 17, or 34 kg S ha-1 at planting. Data was collected on grain yield, protein concentration, plant height, harvest heads, test weight, kernel plumpness, and N use efficiency.We investigated fertilizer rates for N and S, but S did not affect yield and yield components due to the high S concentration in the irrigation water. Plant height, harvest heads, and grain yield increased with increasing N rate for all varieties except at the Aberdeen 2021 field site, where grain yield was non-responsive to N due to the high preplant N at this location. The linear responses indicate N fertilizer insufficiency to maximize yield. Claymore had a quadratic response at Rexburg, with a maximum yield at approximately 120 kg N ha-1 rate. At the Aberdeen 2021 site, Julie responded to N and had a quadratic response with a maximum yield between 135-180 kg N ha-1. Grain protein concentration, test weight, and kernel plumpness were similar to those reported for Moravian 179, Claymore, and Julie in the southeastern and southcentral Idaho variety trials. Single N application produced similar or greater yields than split N application, contributing a 6-46% yield advantage over split N application across all varieties. Similarly, single N applications improved N use efficiency compared to split N applications and contributed a 9-25% N use efficiency advantage. For malt barley at Kimberly and Rexburg, split N application produced grains with 0.6-1.4% higher protein concentrations than acceptable for malting, suggesting an economic loss for growers as grains are sold as feed. This study demonstrated how pre-plant soil N content and N treatment timing affect spring barley yield and quality responses to N. Furthermore, we showed that the high S concentration in the irrigation water in this area negates the need for additional S fertilizer to maximize barley productivity and quality on the Snake River Plain. Split N applications are not an efficient way to increase yield, and N use efficiency for spring barley production and should be avoided in favor of a single N application at planting.masters, M.S., Plant Sciences -- University of Idaho - College of Graduate Studies, 2023-0
Abelian Surfaces with Complex Multiplication Admitting Nonprincipal Polarizations
No full textThe theory of complex multiplication of abelian varieties is a useful field of study with applications ranging from the explicit construction of abelian extensions CM-fields to the explicit description of L-functions of abelian varieties in ways which are much easier to carry out than the more general case. In the literature the most commonly studied abelian surfaces are those with a principal polarization. In the present thesis we extend this analysis to describe abelian surfaces with complex multiplication which carry a nonprincipal polarization. We provide a complete characterization of which types of polarizations are possible on abelian surfaces which have complex multiplication by a given quartic CM-field K as well as how to construct them when they do exist. We also derive several necessary conditions for such abelian surfaces to exist as well as provide an existence theorem in limited circumstances.doctoral, Ph.D., Mathematics & Statistical Sci -- University of Idaho - College of Graduate Studies, 2023-0
Integrating Water, Energy and Climate Change: Irrigation Modernization in Chile’s Elqui Watershed
No full textThis research critically analyzes socioenvironmental dynamics surrounding the water-energy-climate change interface in Chile’s Elqui River Valley, located in the semi-arid Coquimbo Region. Specifically, the project investigates processes linked to irrigation modernization, an emerging phenomenon aimed at addressing water allocation inefficiencies, rescaling operations, and incorporating renewable energy in water-dependent landscapes. Irrigated agriculture is a key driver of water and energy provision practices. However, Chile’s water and electricity codes operate within separate legal frameworks, despite the increasingly codependent nature of these resources. Consequently, disparities exist between national policies and empirical outcomes in a water-scarce environment, creating tensions that are being exacerbated as climate change impacts manifest. Chile is attempting to alleviate these incongruities through adaptive and integrative water/energy decision-making, central components of emerging national legislation, specifically the Energía2050 Initiative and National Climate Change Action Plan. Still, landscapes such as the Elqui Watershed are being shaped by disparities between power concentration from the neoliberal agribusiness complex, enshrined in the current constitution, and operating at the expense of small-scale entities and natural resource conservation. Such trends are a result of inconsistencies between national policies and on-the-ground socioenvironmental patterns interrogated in this project. The research seeks to understand such paradoxes by critically investigating how irrigation modernization reflects broader systems and ideologies surrounding water and energy resource management. Globalized agribusiness, highly developed through Chile’s irrigated central corridor, has supported substantial socioeconomic growth. However, existing market models are being disrupted by rapidly accelerating water scarcity and energy insecurity despite initiatives promoting a transition toward democratic and sustainable resource governance. To date, little evidence supports the discourse of a comprehensive movement. In fact, Chile is still largely reliant on large, centralized power generation and water diversion to support mining and heavy industry. When analyzed through a lens of scalar interplay, agriculture and hydropower represent salient examples of the interrelated dynamics of water, energy, and climate change that are at the forefront of resource policy. Irrigation practices demand significant water and energy, yet also reflect landscapes of opportunity to implement efficiency strategies and increase infrastructural resilience. However, a severe lack of empirical evidence limits understanding of how these adaptations are developing and how outcomes for stakeholders are playing out. Therefore, this research is grounded in a theoretical framework that meshes elements of scale, energy geography, and political ecology to analyze nuances that are emerging throughout a rapidly shifting watershed. This approach seeks to build on previous scholarship looking at uneven dynamics of resource provision under neoliberal economic models and dominant Chilean public policy, applying such principles to a new phenomenon. A suite of mixed methods is employed to holistically understand the complexities underlying relationships between stakeholders including environmental organizations, governmental representatives, irrigation district managers, local agricultural entities (both large and small), regional scholars/scientists, and water user associations. Takeaways will help advance insights into the role of modernized irrigation in mitigating climate change impacts and either supporting or disrupting existing power structures within the watershed. Such discoveries can help inform the greater landscape of water and energy governance in agricultural regions across the globe as climate change impacts accelerate.doctoral, Ph.D., Geography & Geological Science -- University of Idaho - College of Graduate Studies, 2023-0
LIMING FOR IMPROVED NUTRIENT UTILIZATION AND WEED MANAGEMENT
No full textMajor yield setbacks due to invasive weed species population and soil acidity have been recorded in various regions of the United States. Estimated yield loss due to weed competition was approximately 12.3% in the Pacific Northwest. Similarly, it is estimated that there is a 40 to 70% reduction in yield when small grains are grown on acidic soils worldwide. One way to simultaneously improve the productivity of Idaho soils while increasing crop competitiveness is through liming. Agricultural lime applications increase soil pH which may improve crop competitiveness and make soil conditions unsuitable for certain weed species. Lime requirement (LR) analyses can be performed by reacting varying concentrations of lime with soil to provide calibrated equations for estimating how much lime is required to increase the pH of that soil to the desired level. Unfortunately, no known calibration testing has been conducted using soils from southern Idaho. The current University of Idaho and soil testing lab lime recommendations are based on testing mostly done in the 1980s on soils from Midwestern states, Washington, and northern Idaho. These calibrations do not reflect the climate or chemical and physical properties of acidic and trending acidic soils in southern Idaho. The overall aim for this paper was to evaluate the effect of liming acidic soils on soil properties, crop growth, and weed density, and b) to develop lime requirement equations for Idaho soils using lab incubations and field trial results. Generally, linear soil pH and Al responses were observed to lime rates, but there were no recorded significant effects on grain quality metrics or weed growth. Sikora (R2=0.99) and the Adams-Evans buffer (R2=0.92 to 0.97) methods were best suited for predicting the LR for Idaho soils compared to the calcium hydroxide buffer method (R2=0.02 to 0.11). The insights gained from this thesis on the potential benefits of lime application can be of great value to farmers and other stakeholders in Idaho's agricultural industry who seek to optimize crop yield and improve soil health.masters, M.S., Plant Sciences -- University of Idaho - College of Graduate Studies, 2023-0
Differing Sources: Comparing the Historical and Archaeological Data of Fort Hoskins, and Fort Yamhill
No full textBetween the years 1856 to 1866, the Forts of Hoskins and Yamhill monitored and policed newly created reservations in Oregon. As with any bureaucratic institution, an abundance of records was left behind. As historical archaeologists, we rely on documentary and archaeological evidence to piece together the story of an archaeological site. This work intends to examine how the archaeological and historical records compare and contrast, showing how diverse sources can complement each other and provide distinct information about the past.Initially, the intent was to produce a case study on clothing at Fort Yamhill and Hoskins, using both digitized historical administrative records and archaeological data and artifacts. However, lab closures due to the Covid-19 pandemic prevented access to the archaeologically recovered material. A partial workaround to the archaeological data access challenges was Justin Eichelberger’s 2019 dissertation and James Shane’s 2019 MA thesis which provided catalogs of the pertinent artifacts and have proven to be invaluable sources of data and information to build on. As such, my focus shifted to examining how the larger historical and archaeological datasets and sources intersect and relate.masters, M.A., Letters Arts & Social Sciences -- University of Idaho - College of Graduate Studies, 2023-0