Advisor: Dr. Joel Burken
Date & Time: Monday, January 10, 2022 at 8:00 AM
Location (Zoom): https://umsystem.zoom.us/j/95544566757?pwd=OUgxRkE0MUlyRE0vQ2x5RHpWMHBiQT09
Abstract: Owing to the extreme physiochemical characteristics of mine tailings, microbial processes and natural plant growth are generally inhibited. Consequently, vast and numerous tailings sites remain barren for decades and highly susceptible to wind and water erosion to pose environmental concern for the surrounding environment. Phytostabilization is a cost-effective and ecologically productive approach to mitigate the potential transport of the residual metal content; however, tailings revegetation is generally challenging and must often be assisted with soil amendments along with the selection of candidate plant species. When amendments applied individually in this study, greenhouse studies revealed notable improvement in bioenergy crops growth was observed only in biosolids treatments owing to their rich organic matter and nutrient content. Whereas recalcitrant carbon amendments (biochar and humus) showed notable impact only on tailings physichochemical and hydraulic properties. Compared to recalcitrant amendments, biosolids may not support sustained vegetation due to their nutrient lability and rapid decomposition. Therefore, strategies to sustain phytostabilization were evaluated by co-applying biosolids with recalcitrant carbon amendments or biological amendment (mycorrhizal fungi) to synergistically ameliorate tailings characteristics while supporting sustainable growth to stimulate soil formation. Co-applying with biochar exhibited efficient nutrient release while reducing toxic metal bioavailability and uptake. Co-applying with mycorrhizae fungi further improved biomass production while ameliorating tailings characteristics by increasing organic matter input and reducing metal bioavailability and uptake. In addition, a non-destructive and high throughput assessment and cost-effective screening approach was also developed utilizing computer vision and imaging techniques, which allows assessment of plant vitality and vigor throughout the life-cycle of the plants. A wide range of native prairie species was also screened for potential to revegetate mine tailings for greater ecosystem benefit and utilizing the developed approach greatly facilitated quantification of plant responses to phytomanagement strategies for mine-impacts sites and can have application for other blighted lands.
Advisor: Dr. Haiming Wen
Date & Time: Tuesday, January 11, 2022 at 9:00 AM
Location: 268 McNutt Hall
Abstract: Candidate accident tolerant FeCrAl fuel (ATF) claddings for light water reactors (LWRs) need to be thinner than current Zircaloys owing to higher neutronic penalty, demanding an improvement in strength. Therefore, equal channel angular pressing (ECAP), and high pressure torsion (HPT) were used to produce bulk ultra-fine grained and nanocrystalline Kanthal-D [KD; Fe-21Cr-5Al-0.026C (wt.%) alloy] which resulted in an improvement in strength of up to 3 times their nominal strength from grain boundary strengthening, and dislocation strengthening. Dynamic recovery was promoted due to ECAP at 520 C rendering it with a large area fraction of less mobile low angle grain boundaries (LAGBs) which thermally stabilized it up to 500 C, well above the operating temperature of an LWR. FeCrAl alloys suffer from embrittlement after long-term aging around 475 C, due to separation of Cr-enriched α’, which is further accelerated in a nuclear environment because of irradiation induced point defects enhancing diffusion. Nanostructured materials have been shown to have better irradiation tolerance owing to the high volume fraction of GBs acting as effective sinks for irradiation, and thermally induced vacancies. Accordingly, in this study, irradiation and thermally induced α’ precipitation was found to decrease with that of grain size. This study is the first to address this issue from a kinetics perspective as opposed to the existing thermodynamic approach of varying the Cr and Al content to reduce α’ phase separation. This study is also the first to systematically scrutinize the influence of grain size on irradiation and thermally induced α’ precipitation/phase separation in a compositionally homogeneous, and oxide dispersion strengthening (ODS) dispersoid free FeCrAl matrix.
Advisor: Dr. John P. Hogan
Date & Time: Tuesday, January 11, 2022 at 10:00 AM
Location : McNutt Hall, Room 249
Abstract: The Jurassic to Eocene Sevier fold-thrust belt is the subject of continued scientific curiosity in tectonics, stratigraphy, and industry. Understanding its development in southwest Utah is hindered in part due to the multiple origins proposed for the Kanarra anticline, a major leading edge structure—a drag fold along the Hurricane fault, Laramide monocline, Sevier fault propagation fold, or a combination of these—which have confused its tectonic significance and regional context. This confusion results from the structural complexity of its exposed eastern limb, as well as displacement and burial of its crest and western limb beneath Neogene sediments and volcanics along the Hurricane fault. New, detailed bedrock geologic mapping of the central portion of the fold near Kanarraville, Utah and geologic cross sections restored to Cretaceous time (i.e., pre-Basin and Range extension) demonstrate the formation of a composite anticline-syncline pair and fold accommodation thrust faulting are linked in the development of this Sevier structure. A previously unrecognized thrust, the Red Rock Trail thrust, formed due to fold tightening as a "break thrust" in a favorable position to link with the basal detachment. The traditional "Kanarra anticline" is more appropriately termed the "Kanarra fold-thrust system" considering the formation of the Red Rock Trail thrust and other thrusts on the fold. The east verging Red Rock Trail thrust locally presents as a distinctive cataclasite zone in the Navajo Sandstone, which is thrust over the Jurassic Carmel and younger Cretaceous strata. Traceable from Kanarraville to Parowan Gap, this thrust is the leading edge of the Sevier fold-thrust belt in southwest Utah. Stratigraphic relationships constrain the development of the Kanarra fold-thrust system to the Late Cretaceous to Early Eocene (~80 to 50 Ma). Thus the Red Rock Trail thrust records eastward advancement of the Sevier deformation front from the Iron Springs thrust (~100 Ma, Quick et al. (2020)), coinciding with magmatic flare-ups in the Cordilleran arc and indicating close correspondence between arc-related processes and foreland deformation.
Advisor: Dr. Mohamed ElGawady
Date & Time: Friday, January 14, 2022 at 10:30 AM
Location: Butler-Carlton Hall, Room 312
Abstract: This study has investigated the feasibility of using locally available fly ashes (FAs) to synthesize alkali-activated concrete (AAC) for different structural and repair applications. Using AAC made of 100% FA reduces global CO2 emissions, saves energy, and decreases raw material consumption during the production process of ordinary Portland cement. Class C FAs, sourced from Labadie, City, Kansas City, Thomas Hill, and Sikeston power plants in the state of Missouri, were used to synthesize the AAC. Two different alkali activators (Alk) were used in this study: sodium silicate (SS), Na2SiO3, and sodium hydroxide (SH), NaOH. Slag, crumb rubber, and air-entraining admixture (AEA) were used in a few mixtures as additives to improve the durability of the AAC. The mixing procedure, water/FA, Alk/FA, SS/SH, curing regime, fresh properties, mechanical properties, durability, repair applicability, and cost analysis of the AAC were investigated in this study. Approximately 300 mortar and concrete mixtures were tested. A 5000 psi MoDOT conventional concrete (CC) mixture was prepared and tested for comparison purposes. Three curing regimes (oven, ambient, and moist) were applied to the AAC. This study revealed that AAC can be used as a replacement for CC. AAC showed good workability and adequate compressive strength for structural applications ranging from 3,660 psi to 7,465 psi based on the curing regime and source of FA. Some AAC mixtures successfully passed 300 cycles of freeze and thaw per ASTM C666-15 procedures A and B. AAC also presents higher corrosion resistance compared to CC. AAC mixtures have a low to moderate permeability and chloride ion penetrability, while the CC mixture showed a high permeability and chloride ion penetrability. AAC can be used as a repair material for existing concrete structures. The bond between AAC as a repair material and CC as a host material was adequate and comparable to the bond between CC and CC. The relationships between the compressive strength of AAC and splitting tensile strength, flexural strength, and modulus of elasticity are similar to those used by current codes and standards such ACI 318-14.
Advisor: Dr. William Fahrenholtz
Date & Time: Tuesday, January 18, 2022 at 10:00 AM
Location: 268 McNutt Hall
Abstract: The role of cobalt in trivalent chromium passivations (TCPs) to improve corrosion resistance of γ-ZnNi coated steel and aluminum is based on its effect on hexavalent chromium content in the passive layer. Investigations of both a cobalt-containing and cobalt-free TCP on SAE 1008 steel indicated that both passivations protect well for up to 1000 hours in neutral salt spray exposure (SSE). A repetition on Al 6061-T6 alloy indicated that TCP performed much better than cobalt-free TCP implicating the underlying substrate. Optical and electron micrographs indicated physical changes such as crack thickness, crack density, passivation porosity, and passivation thickness existed between the TCP and cobalt-free TCPs but had contradictory results on corrosion performance. Electrochemical differences between the TCPs on both substrates were consistent and scribed specimens on the Al 6061-T6 specimens showed active protection from TCP and not cobalt-free TCP indicating a chemical rather than physical difference. Confounding factors of electroless nickel (EN) between the substrate and γ-ZnNi coating and heat treatments led to Al 6061-T6 panels that were heat treated and steel panels with EN layers. The EN layer had no significant effect and heat treatments had inconsistent performance. Direct measurements of Cr(VI) content found some correlation between the amount of Cr(VI) and corrosion performance. XPS analysis of the surface Cr(VI) content revealed that Cr(VI) is needed for corrosion protection but that there must be an interaction with physical aspects of the coating to explain the inconsistent results. The TCPs were found to perform better because the divalent cobalt in TCPs facilitated production of Cr(VI) during corrosion.
Advisor: Dr. Xiong Zhang
Date & Time: Wednesday, January 26, 2022 at 2:00 PM
Location: 312 Butler-Carlton Hall & https://umsystem.zoom.us/j/96450907284
Abstract: Unsaturated soils are often used as a construction material in transportation infrastructures; in which it is subjected to cyclic traffic loadings and/or seasonal wetting-drying cycles. While mechanical hysteresis is a common feature of soils in general, hydraulic hysteresis is associated with unsaturated soils. Most existing constitutive models paid limited attention to unsaturated soils' mechanical and hydraulic hysteresis behavior. This research presents a consistent three-dimensional elasto-plastic model to study unsaturated soil behavior with consideration of coupled hydro-mechanical hysteresis. The model was first formulated under isotropic conditions with special consideration to the non-linearity of the hydraulic behavior. Only one yield curve is used to represent the yielding of both mechanical and hydraulic behaviors. Later, the model is extended to general three-dimensional stress conditions. It was formulated in a way that a smooth transition between the saturated and unsaturated soil states is guaranteed. The model provides consistent predictions for different soil phases that is considered a significant limitation in many existing models. One of the characteristic features of the proposed model is the ability to represent the hydro-mechanical coupling during shearing. Conventional oedometer and direct shear tests apparatus for saturated soils are then modified to fully characterize and model the strength-stiffness behavior of unsaturated soils under cyclic undrained loading conditions. The model was validated, qualitatively and quantitatively, through comparing the model predictions with the measured behavior under undrained conditions (from this research) and drained conditions (data collected from the literature). The model response was consistent and satisfactory, indicating its powerfulness and robustness. In addition, a new model was developed to simulate the chemomechanical behavior of contaminated saturated clayey soil by modifying the Barcelona basic model (BBM) for unsaturated soils. This model accounts for most of the associated strength and stiffness complex features related to the chemomechanical coupling behavior of saturated soils. The model was verified by comparing its strength/ stiffness predictions with the measured results for saturated red clay contaminated with different concentrations of urea solution.
Advisor: Dr. Henry Pernicka
Date & Time: Friday, January 28, 2022 at 3:00 PM
Location (Zoom): https://umsystem.zoom.us/j/99328298464?pwd=M2VsalFKWksyL3dKYmk0elRyVFgvZz09
Abstract: Spaceflight systems can enable advanced mission concepts that can help expand our understanding of the universe. To achieve the objectives of these missions, spaceflight systems typically leverage guidance and control systems to maintain some desired path and/or orientation of their scientific instrumentation. A deep understanding of the natural dynamics of the environment in which these spaceflight systems operate is required to design control systems capable of achieving the desired scientific objectives. However, mitigating strategies are critically important when these dynamics are unknown or poorly understood and/or modelled. This research introduces two neural network methodologies to control the translation and rotation dynamics of spaceflight systems. The first method uses a neural network to perform nonlinear estimation in the control space for both translational and attitude control. The second method uses an observer with a neural network to perform estimation outside the control space, and input-output feedback linearization using the estimated dynamics for both translational and attitude control. The methods are demonstrated for attitude control through simulation and hardware testing on the Wallops Arc-Second Pointer, a high-altitude balloon-borne spaceflight system. Results show that the two new methodologies can provide improved attitude control performance over the heritage control system. The methods are also demonstrated for translational and attitude control of two small spacecraft in a deep space environment, where they provide improved position and attitude control performance as compared to a traditional control method. This work demonstrates, through simulation and hardware testing, that the two neural network methods presented can offer improved translational and attitude control performance of spaceflight systems where the dynamic environment may be unknown or poorly understood and/or modelled.