ScholarWorks

ScholarWorks is an open access repository for the capture of the intellectual work of Montana State University (MSU) in support of its teaching, research and service missions. MSU ScholarWorks is a central point of discovery for accessing, collecting, sharing, preserving, and distributing knowledge to the Montana State University community and the world.

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Scholarship & Research

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Polarimetric and range selective digital holography for stationary and vibrating objects
(Montana State University - Bozeman, College of Letters & Science, 2025)
Goodman, Matthew Aaron
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Chairperson, Graduate Committee: Wm. Randall Babbitt
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This is a manuscript style paper that includes co-authored chapters.
Digital holography (DH) is an advanced technique that improves upon traditional imaging by providing phase information in addition to magnitude information about the object being imaged. One of the two uses of DH demonstrated in this thesis is to obtain phase information about light scattered off of an object. An off-axis digital holographic imaging polarimeter was developed to estimate the Jones matrices of an object. The Jones vector image of the electric field returned from the object is determined from a single holographic recording using the interference between the dual, nearly orthogonal, reference beams. The technique compensated for phase variations in the optical beam paths between the recorded holograms and relaxed the need to generate orthogonal illumination polarization states. A minimization algorithm was developed for computing an estimation of the Jones matrix image of the object based on a set of measured Jones vector images. The other distinct use of DH is to use phase sensitivity of digital holography to perform range selective imaging. For traditional DH the depth of field is the axial distance around the focused object plane over which the image in acceptably sharp focus. Objects within the depth of field (DOF) of the selected focal distance will appear in focus, while those beyond the DOF are blurred. The integration of FMCW or chirped frequency modulated continuous wave (FMCW) lidar techniques into digital holography enabled range selective holographic imaging well beyond the depth of field of the system. By frequency shifting the reference beam to compensate for the typical beat frequency associated with a particular range, temporally stable holograms were formed for objects at the selected range. The holograms associated with objects at all other ranges oscillate and integrate towards zero. Experimental demonstrations showing enhanced imaging of objects at different ranges and cancellation of obscuring objects are presented. For vibrating objects, longitudinal movements of the object greater than half of an optical wavelength during the exposure time of the sensor array induce phase shifts that can wash out the hologram. An analog feedback system was designed and constructed whereby a lidar subassembly provides real time phase compensation information to a DH subassembly in order to stabilize the range selective digital holographic recording of the object. The design and characterization of the feedback system, as well as the results demonstrating the performance for vibrating objects that move over 17 wavelengths during the sensor exposure are shown.
Assessing the accuracy and variability of estimating snow water equivalent from lake water pressure
(Montana State University - Bozeman, College of Letters & Science, 2025)
Schreier, Erich Stefan
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Chairperson, Graduate Committee: Eric A. Sproles
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This is a manuscript style paper that includes co-authored chapters.
Seasonal snowpack is a crucial global water resource, but measuring it accurately poses challenges. Measurements of snow water equivalent (SWE) from existing instruments are susceptible to significant bias and often provide data only at the point scale. The global network of SWE sensors is sparse and bias towards lower elevations in the mountains, limiting their effectiveness in informing hydrologic models and forecasts. A promising new method has been proposed to estimate SWE from lake pressure in frozen alpine lakes. To gain a more complete understanding of the capabilities of this method, we conducted an alpine study site at Mystic Lake (45.54, -110.93) in Southwest Montana, USA. We present how noise in the water pressure signal can add significant uncertainty to SWE methods, and we present methods for smoothing the data to achieve more reliable estimates in employing this method to measure SWE. We find that there is substantial variability between SWE observed over the ice surface and adjacent ground surfaces during the study period, underscoring the challenges of measuring snow in the mountains. The results of this study demonstrate that estimating SWE from lake water pressure can provide valuable insights into basin hydrology and easy-to-implement observations of SWE. However, careful consideration and site-specific planning are requisite for accurate and representative SWE estimates.
A multi-geochronologic approach to identify the focus of erosion in the Kosi Basin, Nepal
(Montana State University - Bozeman, College of Letters & Science, 2025)
Zehner, Jessica Nash
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Chairperson, Graduate Committee: Devon A. Orme
The Himalayan orogen represents a convergent tectonic setting in which two continental tectonic plates collided, forcing material upwards and forming a chain of high elevation peaks. This setting is also host to the Indian Summer Monsoon, which hammers the region with heavy seasonal rainfall. The respective roles of tectonics and climate in shaping this dramatic landscape remain a subject of debate. Our research approaches this gap in understanding by investigating sediment routing in Nepal's Kosi basin. The Kosi watershed is a well-suited basin to study this phenomenon, as it captures many of the key geologic structures and climatic conditions that are characteristic of the region. We sampled modern rivers to understand the sediment profile in the Kosi basin. We then utilized two radioactive dating methods to fingerprint sediment grains and understand their origin in the watershed. Detrital zircon U-Pb geochronology dates when a crystal formed and utilizes large sample sizes to match detrital age spectra to known bedrock profiles. Alternatively, (U-Th)/He low-temperature thermochronology dates when an individual zircon grain cooled to the surface. These detrital cooling dates are in turn matched to areas known to have cooled at similar times. We applied both methods to our modern river samples. Using our new geochronological and thermochronological datasets, we completed two statistical analyses to pinpoint accelerated areas of erosion: inverse monte-carlo mixture modeling and multi-dimensional scaling nearest-neighbor analysis. Our results suggest that each major geologic unit and sub-basin in the watershed contributes to the sediment load in the Kosi River to some extent. Furthermore, U-Pb mixing model results and young helium cooling ages both highlight an over representation of grains in the center of the watershed, by latitude. Integrating our datasets, these results suggest that erosion is focused north of the dominant precipitation band and south of the largest glacial cover. We propose that these findings support a model of landscape evolution in which structural geometry at depth, specifically duplexing along a midcrustal ramp, plays a critical role in shaping surface topography.
The heart of Winnett: rural schools face teacher recruitment & retention challenges
(Montana State University - Bozeman, College of Arts & Architecture, 2025)
Ehmke, Marit Charlotte Lanier
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Chairperson, Graduate Committee: Hugo R. Sindelar
There is a critical teacher shortage in America, and it is most acute in U.S. rural communities. The three teachers profiled in this film teach at Winnett School in Winnett, MT, with a K-12 enrollment of less than 100 students in one building; these teachers exhibit what it means to be truly dedicated to their students, their profession, and their community despite facing challenges unique to rural educators. There's the K-12 shop teacher, Adam Tholt, who has been teaching for more than two decades in Winnett; Nicole Tholt, the 3rd/4th grade teacher and Adam's wife; and Haley Kiehl, the 5th/6th grade teacher who has held various roles at the school over the last decade. The film chronicles their observations and attempts to bring to light some of the issues rural teachers face on a day-to-day basis. This document expands on the elements pertaining to The Heart of Winnett, including the filmmaker's background and connection to the topic, research, the artistic approach, theoretical elements, and dissemination information, including a budget and distribution plan.
Molten salt torrefied biomass as a soil nutrient amendment
(Montana State University - Bozeman, College of Engineering, 2025)
Pritchard, Hayden Harlow
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Chairperson, Graduate Committee: Dilpreet S. Bajwa
Torrefaction is a thermal pretreatment process that decreases moisture content and increases energy density in an organic feedstock. This is useful for decreasing the transportation cost of biomass resources while increasing their shelf life. Molten salt torrefaction (MST) results in greater carbonization and lignification than traditional, inert gas torrefaction at the same temperature due to salt's catalytic and heat transfer properties. Biochar, a stable, carbon-rich solid material, can be produced using torrefaction. The charcoal-like characteristics of biochar are valuable not only for fuel use but also for soil amendment. Biochar has a history of use in agricultural applications, including hydrology, nutrient retention, and pH regulation. The separation of biochar from salt used in the molten salt torrefaction process produces nitrate-rich wash water, which also has potential as a soil nutrient amendment. The present study aims to compare the influence of traditional biochar, molten salt-torrefied biochar and wash water on soil nutrient availability and plant responses. Molten salt torrefied biochar formulations were processed in binary and ternary blends of Calcium, Potassium and Lithium Nitrates. Biochar was characterized by its mass yield, lignocellulosic composition, pH, water uptake, chemical composition and electrical conductivity. Processing conditions of sweep gas, temperature, time, lithium content, salt to biomass ratio and particle size were evaluated for their effects on the biochar's characteristics. Biochar composition was found to be most sensitive to temperature, time and lithium content processing conditions. Soil responses to biochar treatment included increased soil pH and nutrient availability. Substantial amounts of lithium and nitrates from the molten salt torrefaction process were retained in both the treated biochar and soil. Durum wheat (Triticum turgidum ssp. durum) was potted with medium-texture soil and switchgrass biochar (Panicum virgatum), applied at 1.5% by weight. The harvested wheat was measured for leaf and root mass yield, plant height and germination. Biochar treatments did not elucidate statistically significant effects in the potted plants. However, plants treated with the wash water had earlier growth and greater root mass, albeit a decreased germination rate. The average root mass nearly doubled with the wash water treatment (64.4mg) compared to the control treatment (35.7mg).