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Analytical and Numerical Modeling of Solid-Liquid Phase Change Driven by Internal Heat Generation in Cylindrical Coordinates
No full textThe study of liquid-solid phase change has value in a range of applications, including in nuclear power.Nuclear fuel rods are subject to internal heat generation that, during extreme conditions, can result in the fuel becoming partially molten. Understanding of the melting process is critical to the safe design and operation of nuclear power plants. However, analytical work in this area is still limited. Two scenarios of liquid-solid phase change driven by internal heat generation are presented for a cylindrical domain: a case with Constant Surface Temperature (CST), and a case with Constant Surface Heat Flux (CSHF). We conducted an analysis of both scenarios in the form of the Stefan problem, a free boundary problem where the position of the interface between liquid and solid phases can change in time. By assuming constant thermal properties, pure conduction, and a sharp interface, we were able to use the superposition principle to derive closed-form, first-order ordinary differential equations with infinite series describing interface motion for one-dimensional, isothermal phase change. We compared our analytical models against numerical solutions generated through the commercial software Ansys Fluent. This software uses the enthalpy method, which allows the formation of a mushy zone, to solve for temperature, enthalpy, and liquid fraction in the problem domain. Using this model, we were able to check our solutions for mathematical soundness and evaluate the implications of assuming a sharp liquid-solid interface. We performed comparisons between the analytical and numerical models during both melting and solidification scenarios for several values of Stefan number for the CST case and several values of heat flux for the CSHF case. The CST case saw strong agreement in interface position in time for the slower phase change cases. However, during the melting scenarios for these slower speeds, we saw a divergence in temperature profiles characterized by a nonphysical overheating phenomenon at smaller time steps due to the formation of a mushy zone in the numerical model. This issue lessened with higher interface speeds and did not present itself during the solidification cases. Agreement in the CSHF cases was weaker than for the CST cases, with disagreement being most significant when the material was mostly solid. This disagreement was attributed largely to inaccuracy of the theoretical model. At faster phase change speeds, we saw more mushy zone development in the melting cases, with the solidification cases once again showing no mushy zone effects.masters, M.S., Mechanical Engineering -- University of Idaho - College of Graduate Studies, 2021-1
Understanding current and future mountain hydroclimate: consideration of air temperature, snow, and rock glaciers
No full textThe hydroclimate of mountain environments shapes the spatiotemporal distribution of energy and water on scales from local to global. Climate change is inducing rapid changes in mountain hydroclimate in the form of warmer temperatures, reduced snowpack and glacier mass balance, and earlier snowmelt runoff. These changes have large implications for local and downstream ecosystems and societies. However, understanding of current and future mountain hydroclimate is hindered by a paucity of observations and the need for high resolution data and models to capture the effects of topographic complexity. New modeling approaches, tools, and datasets are needed. This dissertation addresses these needs with a focus on three important aspects of mountain hydroclimate: air temperature, snow, and rock glaciers. In the first study, I quantify the error and uncertainty in air temperature lapse rates and outline best practices for lapse rate estimation. In the second study, I develop a novel energy balance snow model and force it with a new high-resolution multitemporal climate dataset to create a dataset of snow and climate metrics for the western United States. In the final study, I employ a machine learning method to understand the response of rock glacier spatial distributions to climate change. This dissertation contributes to scientific understanding of mountain hydroclimate and provides tools and datasets to further develop this understanding.doctoral, Ph.D., Water Resources -- University of Idaho - College of Graduate Studies, 2021-0
Control of Globodera pallida by combining Sinapis alba seed meal extract or 4-hydroxy benzyl alcohol with Brassica juncea seed meal extract or the trap crop Solanum sisymbriifolium
No full textThe pale cyst nematode, Globodera pallida, is a highly specialized, economically important pest for potato production. The specialized hatching requirements, ability to adapt, and the loss of effective control strategies such as methyl bromide fumigation increases the challenge to eradicate G. pallida in Idaho. Without a suitable host, this nematode can remain dormant as encysted eggs in soil for up to 20 years. The specificity of G. pallida hatching makes this life stage a potential target for designing efficient integrated control strategies. In this study, first, we demonstrated that Sinapis alba seed meal extract (SME) or 4-hydroxy benzyl alcohol (HBA) under laboratory and greenhouse conditions enhances G. pallida egg hatch when exposed to potato root diffusate (PRD). This hatch enhancement in the presence of PRD is speculated to be due to an increase in egg-shell permeability. This study also aims to determine the efficacy of non-host trap crop Solanum sisymbriifolium or biofumigant Brassica juncea SME to control G. pallida when combined with the hatch enhancement properties of HBA or Sinapis alba SME. For this study, we tested the efficacy of i) S. sisymbriifolium following prior treatment with S. alba SME (0, and 4.48 t/ha) or HBA (0, and 0.12 t/ha) and ii) B. juncea SME (0, 0.14, 0.56, and 1.12 t/ha) following HBA treatment (0, and 4.48 t/ha) on viability and hatch of G. pallida encysted eggs. S. sisymbriifolium alone reduced the number of encysted eggs compared to non-treated control by up to 67%, indicating that this trap crop triggered G. pallida egg hatch. When combined with S. alba SME or HBA, S. sisymbriifolium further significantly reduced egg count, hatch, and viability than S. sisymbriifolium alone. The combination of S. sisymbriifolium with HBA or S. alba SME eliminated G. pallida reproduction on the susceptible potato cultivar, Russet burbank. Treatments with all the tested rates of B. juncea SME alone or with HBA reduced egg hatch and viability compared to the non-treated control. Combining HBA and B. juncea SME further reduced egg hatch and viability than SME alone at rates 0.14, 0.56, and 1.12 t/ha. A lower egg hatch and viability with these combinations indicate that S. alba SME or HBA was able to increase the susceptibility of PCN eggs to the trap crop S. sisymbriifolium or nematicidal effect of B. juncea seed meal extract thus, decreasing G. pallida populations more effectively and rapidly.masters, M.S., Plant, Soil and Entomological Sciences -- University of Idaho - College of Graduate Studies, 2021-1
Centering Indigeneity of 21st Century Shoshone - Bannock & Oglala Lakota Worldviews Through Science & Policy
No full textIn a digital age we are afforded more ways to tell story than text alone. I’m including my defense as it was told to contextualize the four chapters herein as a guide laying the groundwork to what lies ahead. Storytelling of my defense can be found in two formats as a voice only, or video at the attached link here: https://www.northwestknowledge.net/cloud/index.php/s/dSbUzWqMAdgZvI1doctoral, Ph.D., Water Resources -- University of Idaho - College of Graduate Studies, 2021-0
Numerical Simulation of the Nonlinear Magnetic Quantum Response of a Torus
No full textThe nonlinear-optical response of a material leads to novel phenomena and applications. At present, most nonlinear-optical materials are based on the electric susceptibility. This thesis investigates the magnetic susceptibility as an alternative that might lead to a greatly enhanced nonlinear-optical response. To assess the nonlinearity of test systems, the Schrödinger equation and magnetic dipole moment operator are coded in Python using the finite-difference time-domain (FDTD) method to calculate the eigenstates and eigenenergies of a three-dimensional (3D) toroidal potential well, which is chosen as a prototypical magnetic system. The numerical results compare favorably with the analytical solution of the Schrödinger equation for the special case of a quantum wire, thus validating the method. A calculation of the magnetic dipole moment as a function of magnetic field strength demonstrates a nonlinear magnetic response, suggesting that such materials might be candidates for the next generation of nonlinear-optical materials.masters, M.S., Electrical and Computer Engineering -- University of Idaho - College of Graduate Studies, 2021-0
Modeling Deep Infiltration from Irrigated Agriculture to Support Regional Water Management
No full textThroughout the western United States, water managers are facing pressure to account for limited water resources among competing uses. Groundwater is one example of a limited resource that is continually being depleted, especially for areas that use groundwater for irrigated agriculture. In certain hydrologic systems, irrigated agriculture can contribute substantially to aquifer recharge through surface water infiltration, and thus is a significant water balance term for regional groundwater models. This thesis developed a bucket model to estimate deep infiltration by modeling soil water content and root water extraction. The model was calibrated with in-situ soil data from an irrigated alfalfa field and tested for model performance over two subsequent years of field data. The model was applied to a regional scale using test scenarios that account for differences in climate, management, and environmental factors. We show that for sprinkler irrigation methods with improved application efficiency, applied irrigation can contribute between 10-40 percent of deep infiltration losses under dry climate scenarios. While losses may occur at the field scale, these model results describe gains in aquifer recharge at the regional scale. Thus, the model provides an applied tool for more explicit estimates of near-surface boundary conditions for use in regional water management.masters, M.S., Plant, Soil and Entomological Sciences -- University of Idaho - College of Graduate Studies, 2021-1
Quantifying the Effects of Landscape Fragmentation on Biodiversity at Multiple Scales: Community Assembly, Community Diversity, and Population Genetic Diversity
No full textWe observe the continued human alteration to natural landscapes around us, fragmenting and isolating populations, yet it remains a challenge to identify the evolutionary processes that are involved and make predictions on the impacts that fragmentation has on community assembly and disassembly processes. These predictions are made increasingly difficult as these impacts are species dependent. In this dissertation I use phylogenetic and genomic tools to quantify the impacts of fragmentation on biodiversity at multiple organizational scales. For this work I have collaborated with researchers to use a combination of techniques, for example, species traits, the relatedness of species to compare species assemblages, and DNA as a tool to be able to infer population level differences. My goal is to quantify the impacts of fragmentation on biodiversity at different scales and identify evolutionary processes that are influencing insular, or seemingly isolated, populations and communities. Further, in my chosen study system of Craters of the Moon National Monument and Preserve (CRMO) in Idaho, I, and my collaborators, can ask and answer questions related to the assembly of communities and the disassembly of communities in fragmented populations. With this work we can inform conservation and restoration efforts, particularly in isolated populations. Thus, science communication and scientific literacy are integral to the scientific process.In Chapter 1, I focus on community level processes, using phylogenies as a tool to quantify the relatedness of species and a trait of interest. Using the community of vascular plants, we compare those species found in insular communities to the species in a larger pool that could potentially inhabit the isolated habitats to test for the impact of a range of factors on the membership of a species in a community. To this end, we use both traditional metrics and a new machine learning approach. With the traditional metrics we inferred neutral processes as important for shaping the insular communities at CRMO. However, with a proposed novel approach we inferred the joint influence of neutral and filtering processes. In Chapter 2, the focus is on the species level impact of fragmentation. Populations of an individual species may be impacted by changes in isolation brought on my fragmentation and may also become isolated genetically. I, along with my collaborators, use DNA as a tool to infer population level changes in a species of crab spider, Mecaphesa celer. This allows us to infer potential impacts to gene flow among separated populations. From this first genome-wide assessment of M. celer at CRMO we do not detect clustering or genetic structure between the isolated populations, so genetically it is as if the spiders are one population. This means high amounts of gene flow exist between the isolated habitats and potentially the neighboring areas as well. In Chapter 3, I describe a community outreach series called Science After Hours that I created and coordinated. I describe its impacts and provide information on the replication of a similar program. As scientists our knowledge is worthless if not shared, as learning does not occur in a vacuum. Sharing our work allows for informed actions and decisions. Science communication is an imperative, integral role for researchers and few low risk, small time commitment opportunities exist. This program filled a need in the Moscow, ID and Pullman, WA community and brought together stakeholders from the community, local businesses, and researchers. Through this work we were able to quantify the impacts of fragmentation on biodiversity at different scales and identify evolutionary processes that are influencing insular, or seemingly isolated, populations and communities at CRMO. Neutral and filtering processes dominate the community assembly process for the vascular plant communities and high amounts of gene flow in M. celer indicate little population structure in the species. By creating a science outreach series, I, along with other researchers in the Moscow and Pullman community were able to fulfill one aspect of our role as a scientist and share the importance of our work.doctoral, Ph.D., Biology -- University of Idaho - College of Graduate Studies, 2021-1
Data-Driven Modeling and Control of Cardiac System
No full textVagus nerve stimulation is an emerging therapy that seeks to offset pathological conditions by electrically stimulating the vagus nerve through cuff electrodes, where the electrical pulse is defined by several parameters such as pulse amplitude, pulse width, and pulse frequency. This electroceutical therapy has been approved for treatment resistant depression, and is currently under investigation for heart failure, heart arrhythmia, hypertension, and gastric motility disorders. Recent studies have shown the ability to selectively activate different fibers in the vagus nerve, thus allowing for a highly specific control of physiological behavior through vagal nerve stimulation. One of the major challenges with the application of this therapy involves a closed loop controller to autonomously control the behavioral responses. This problem becomes additionally challenging when multiple locations and multiple stimulation parameters are considered for optimization. Using a physiological model of a rat heart, this thesis investigates a data-driven control scheme for closed-loop control of the rat cardiac system. In the first section of this thesis, a data-driven modeling approach is used to develop a model that maps vagus nerve stimulation parameter selection to the effect on the physiological variables of heart rate and blood pressure. The second part of this thesis develops a controller that uses the data-driven model by utilizing a model predictive control framework to control the heart rate and the blood pressure in closed-loop simulations of a rat model.masters, M.S., Chemical and Materials Science Engineering -- University of Idaho - College of Graduate Studies, 2021-0
The Communication Preferences and Science Communicator Identities of University of Idaho Extension Faculty and Educators
No full textThis study explored what relationship existed between UI Extension educators and faculty’s social identity as science communicators and the communication types they most commonly used. The findings from this study can help UI Extension, and the Cooperative Extension Service increase their communication and programming impact to new and changing audiences through specifically tailored research-based information that is disseminated effectively. This non-experimental, sequential, mixed-method study with a qualitative priority utilized surveys and interviews to gather data. The data found in the surveys described how UI Extension educators and faculty communicate with constituents. Data were analyzed using descriptive statistics, paired t-tests, and Wilcoxon-Signed Ranks tests. UI Extension educators and faculty’s most preferred communication channels were walk-in, phone calls, and emails. Their constituents preferred walk-in, email, and phone calls. There was significant increase in time spent communicating during COVID as compared to before, and the utilization of mass communication also significantly increased. Interviews were used to understand their social identities as science communicators. Participants were selected for interviews through stratified purposive sampling based upon their location, urban or rural county, and communication type most commonly used. Interviews were recorded, transcribed verbatim, broken into meaning units, and open coded. Five main themes were identified: Continual development, technology, research dissemination, evaluation and motivation, and community relationships. These two sets of information were then mixed using cross case comparison to find significant relationships. This study found a significant relationship between an individual’s most commonly used communication type and their social identity as science communicators.masters, M.S., Agricultural Education & 4H Youth Development -- University of Idaho - College of Graduate Studies, 2021-1
A Procedure for the Generation of Material for Flat-Joint Models and the Simulation of Rock Testing using PFC2D
No full textThe overall behavior of rock mass is effectively controlled by the micro properties of its constituent particles and the bonds between the particles. Unfortunately, the micro-scale properties are difficult to measure with routine laboratory tests. This study, using Discrete Element Methods (DEM), investigated the influence of these micro-scale bonding properties on typical parameters which may be measured in a uniaxial compression test. This research used the DEM software: “PFC2D” (Itasca 2019) to investigate the influence of the micro-scale bond properties. PFC2D is a popular DEM simulation program that can be used to study the behavior of rock made up of discrete particles. It creates discontinuous bodies, balls, clusters, and clumps in the model and bonds them together as a rigid body. However, the material properties to be assigned in the model are bond properties, and not typical material properties. “Inverse modeling"" is used to essentially back-calculate appropriate bond properties that will match laboratory material properties. Calibrating the material without studying the consequence of assigning bond parameters is not practical. So, this research provided a parametric study of four bond parameters: (1) normal to shear stress ratio (kratio), (2) tensile strength (fj_ten), (3) effective modulus (emod), and (4) cohesion (fj_coh). The parameter labels, such as kratio, correspond to the names defined for use in PFC2D. These selected parameters were varied for a total of 108 uniaxial compressive and 108 direct tension simulations to see which parameters should be adjusted and calibrated first to match lab tests. The recommended procedure for generating material for flat-joint models starts with adjusting the four bond parameters in the following preferred order: (1) kratio to match the material's, Poisson's ratio, (2) fj_ten to match the material's tensile strength, (3) emod to match the material's Young's modulus, and (4) fj_coh to match the material's compressive strength. This procedure was found to be most effective because the last parameter's calibration does not affect the previously calibrated parameters. The bond's friction angle was assumed to equal the material's friction angle for all cases. Because the calibrated, simulated material behaves identically to the real specimen, the development of cracks during loading was also studied. Interestingly, the study demonstrates that the material cracks in a small portion of the linear elastic zone before entering the nonlinear zone. Additionally, we discovered that the inclusion of rock lineations, with different properties, resulted in a range of compressive strength, Young's modulus, and ultimate axial strain, depending on the angles. The compressive strength, Young's modulus, and axial strain of materials with lineation acting at a 30-degree angle to the maximum principal stress produced the lowest values.masters, M.S., Civil Engineering -- University of Idaho - College of Graduate Studies, 2021-0