Mines Repository (Colorado School of Mines)
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Remote estimation of grain size distribution and simulating grain size effects on debris-flow rheology and post-fire variability of transport by dry ravel
No full textIncludes bibliographical references.2024 Summer.The size distribution of granular material influences the length scale of sediment transport by dry ravel and debris flows. Variability in erosion rates and the grain size distribution of material delivered to channels has been observed due to an increase in the annual areal extent of wildfire in the Western United States. As these changes modify debris-flow hazard, it is essential to constrain the influence of grain size distribution on dry ravel and debris flows, especially in a post-fire setting.
To improve understanding of evolving transport regimes and propose grain-size-dependent constraints on process phenomena, the research presented in this thesis leverages increased access to remotely sensed morphological data and recent advancements in simulations of sediment transport. Here, remotely sensed point cloud data, statistical modeling, and numerical simulation were used to contribute towards the estimation of grain size and the modeling of grain size effects on dry ravel and debris flow.
First, a statistical description of the travel distance exceedance probability distribution of dry ravel was applied to a series of experiments simulating dry ravel with different grain sizes, aspects, and slope angles as a site in the Diablo Range, California recovered from wildfire. The forms of these distributions suggested that the largest naturally occurring grains exhibited a transition from more bounded to more runaway motion during the first year post-fire, after which seasonal changes in vegetation density controlled particle mobility.
Following these efforts, a workflow involving machine learning and a novel clustering approach (termed DBloops) was developed to extract the size distribution of angular cobble and boulder sized clasts from point clouds of nonplanar deposits. This workflow was successfully applied to point clouds of debris-flow and riverbank deposits, reproducing grain size distributions obtained from Wolman pebble counts and outperforming an alternative algorithmic approach.
To achieve the first formal connection between grain size distribution and controlling parameters in the numerical model D-Claw, a compositional mapping of grain size distribution to debris flow permeability and critical volume fraction was implemented. This mapping was found to perform adequately over a range of different compositions by simulating experiments conducted by others at small (2 m) and large (95 m) debris flow flumes.
By integrating knowledge of post-fire changes in the grain size distribution of ravel and the size distributions of the largest particles in debris-flow deposits, a better understanding of the influence of how debris-flow composition changes post-fire will be obtained. By formally implementing grain-size-based parameter selection in D-Claw, these findings will help assess and manage the risk debris-flow hazards present to communities and infrastructure as fire regimes change
Energy optimization of supercapacitors and solar battery energy storage
No full textSolar batteries are currently the most commonly used energy storage device for solar panel energy. The downsides of solar batteries though are their limited lifespan, need for maintenance over those years, and negative environmental impacts from disposing of the batteries. An alternative storage option would be supercapacitors. Supercapacitors are known for their longer lifespans, recyclability, and incredibly high charging rates. Their downside though is that with these high charging speeds, they also have high discharging speeds, not allowing for a lot of storage capability. Supercapacitors have a lot of varying factors determined by the materials that they are made from. The two main types are electrochemical double layer capacitors (EDLCs), or graphene-based, and pseudocapacitors, or non-graphene-based. The goal of this research project is to determine from the three options - solar batteries, graphene-based supercapacitors, or non-graphene-based supercapacitors - what is the most efficient method to store solar energy. To achieve this goal, methods used in this project were online research to complete the Research Learning Outcomes (RLOs). All of the calculations are based on sustaining a 2000 square foot house that runs only on solar energy. Energy costs were calculated for obtaining materials and manufacturing each product. Charge and discharge rates were also calculated for each method. Each storage device has its pros and cons. What is being highly considered today is a hybrid between EDLCs, pseudocapacitors, and batteries. The benefits of this combination are maximizing energy and power density and minimizing energy costs
Analcime with chabazite
No full textPhotographed by Ron Wolf.Blocky vitreous white crystals of analcime with chabazite
Tugtupite (fluorescent)
No full textPhotographed by Ron Wolf.Vitreous white and pink tugtupite (A0179-0414); tugtupite showing fluorescent properties of red and green under ultraviolet light (A0179-0415); two views of tugtupite: top view shows specimen in plain light; bottom view shows fluorescent properties of red and green under ultraviolet light (A0179-0416); Kvanefjeld area, Ilimaussaq complex, Greenland
2D high entropy perovskite oxides for electrocatalysis
No full textA major challenge for next generation dispatchable power sources is transitioning the electrocatalyst from platinum group metals to earth abundant materials while improving durability. The scientific community has found that careful manipulation of both composition and morphology has led to improvements in catalytic efficiency. Emphasis has been placed on the ability to synthesize nanoscale materials and specially-select both chemical composition and morphology of the final products. High entropy oxides (HEOs) (and, by extension, High Entropy Perovskites (HEPs)) are an exciting class of materials that afford earth abundance and tunability towards desired properties, making them an excellent candidate for use in electrocatalysis. This work presents the aerogel synthesis of Ba, Sr, Ca, Co, and Fe in the ABO3 perovskite structure, completed in an autoclave to promote nanomaterial production. Pseudo supercritical drying allowed for solvent removal while circumventing the kinetics of aggregation and the production of a powder product, ready for testing in Symmetric Solid Oxide Fuel Cells (SSOFCs)
High-temperature interactions and property analysis in molten regolith electrolysis: refractory selection and molten oxide behavior
No full textIncludes bibliographical references.2024 Fall.As humanity advances toward sustained lunar and planetary exploration, the development of in-situ resource utilization (ISRU) technologies is crucial for reducing logistical costs and enabling long-term missions. This study contributes to the NASA-funded Molten Aluminum Generation for Manufacturing Additively (MAGMA) LuSTR grant, aimed at extracting metals from lunar regolith for construction purposes. The research focuses on material compatibility between refractory ceramics and molten oxide behavior, including resistivity and viscosity.
Through this work, the viscosity and resistivity of molten lunar regolith simulants at various stages of electrolysis were characterized, providing valuable data for reactor design and tap geometries. A range of refractory materials—including alumina, zirconia, boron nitride, and graphite—were tested for corrosion resistance and wetting behavior with molten oxides. Among these, boron nitride and graphite exhibited the greatest resilience to chemical attack, while alumina failed across all oxide melt compositions.
These insights will inform the design of tap systems for MRE reactors and contribute to the broader goal of advancing ISRU technologies
Celestine on colemanite
No full textPhotographed by Ron Wolf.Pale blue-white glassy celestine with white translucent prisms of colemanite, Billie mine, Ryan district, Death Valley National Park, Inyo County, California