<p>With increasing global renewable energy demands, there is a need for new materials with improved performance, lower cost, and less toxicity. One such application is photovoltaics, where halide perovskites (HaPs) represent the fastest growing market of absorbers owing to their impressive optoelectronic properties and excellent tunability from composition engineering and structural manipulation. However, the practically infinite composition-structure space of HaPs when considering cation and/or anion site mixing, octahedral distortion and rotation, and other forms of polymorphism, raise considerable challenges when comprehensively exploring their stability and optoelectronic properties. First principles calculations are powerful tools that can investigate large numbers of compounds and structures in a high-throughput fashion. </p><p>In my thesis, I performed high-throughput density functional theory (DFT) computations to generate a HaP dataset within a wide chemical space covering ~500 unique chemical compositions in the (pseudo-)cubic phase, across a 14-dimensional ionic space. This work explored both pure and alloyed compositions, with the latter simulated using the special quasi-random structures approach. Many critical properties were computed using the semi-local GGA-PBE and hybrid non-local HSE06 functionals, including decomposition and mixing energies, electronic band gap, and spectroscopic limited maximum efficiency (SLME), which is a theoretical surrogate for the likely absorption efficiency of the compound when used in a single-junction solar cell. Property screening over this dataset yielded 32 stable perovskite candidates with attractive optoelectronic properties.</p><p>Polymorphism in HaPs is investigated by simulating larger supercell alloys with different ionic ordering, generating compounds with random octahedral distortions and rotations, and optimizing various compositions in non-cubic phases such as tetragonal and orthorhombic. Linear correlation analysis is performed to gain a critical understanding of how properties are influenced by specific cations and anions, their mixing fractions, the perovskite phase, ionic clustering, and amount of strain or distortion in the lattice. Finally, trends, design rules, and predictive insights achieved from the DFT datasets are applied over a much larger set of thousands of hypothetical compounds, resulting in identification of more promising materials and understanding of the most important A-B-X combinations that yield multiple desired objectives.</p><p>Furthermore, a similar DFT workflow is applied for designing transition metal electrocatalysts. DFT simulations are performed to model Hydrogen adsorption, OH adsorption, and the water splitting reaction on Ni3N/Ni and Co2N/Co hybrid structures, to explore their likelihood in being used for Hydrogen Evolution Reaction (HER). The results reveal the excellent catalytic performance of transition metal and transition metal nitride hybrid structures.</p><p><br></p>

Rules which correlate structure and insecticidal activity of pyrethroids have evolved over the last thirty years from the results obtained in the testing of various synthetic pyrethroids. The major portion of these rules have dealt either with the development of new alcohol moieties or variations in the unsaturated side chain of the cyclopropane ring. There has been very little work done concerning modifications of the cyclopropane ring. This study was initiated to discover the affect of substituting an aziridin ring for the cyclopropane ring found in pyrethroids.

This thesis is a description of four-word elaborate expressions in White Hmong, a Hmong-Mienh language spoken in the northern mountains of Southeast Asia. The goal of this work is to describe the behavior, characteristics, and functions of the expressions using data from the White Hmong-English Dictionary (Heimbach 1980). A native speaker helped find 318 examples of elaborate expressions in the dictionary. Elaborate expressions have previously been described as "a balanced group of four words in which the first and third element, and the second and fourth element, are either identical to each other or share a common meaning and often also a common sound" (Jarkey 2010:129). Previous work on elaborate expressions is limited to a full analysis of the Green dialect (Mortensen 2003) and a partial analysis focusing mainly on wordhood in White Hmong (White 2020). After introducing White Hmong and elaborate expressions in chapter 1, I use numerous examples to describe and support the types of concord presented in the analysis. The data is taken from the White Hmong-English Dictionary, which is composed of over 400 pages of definitions with detailed example sentences. Throughout the thesis I offer an analysis based on a previous framework of elaborate expressions depicted in the Green Hmong dialect (Mortensen 2003) to conclude that elaborate expressions offer three types of concord between their parts, namely part of speech, semantic, and phonological.

Understanding the deformation mechanisms and the impact forces generated by landslides on structures is essential for risk assessment and improving the design of mitigation measures. This thesis studies the effect of different basal sliding characteristics of biplanar compound landslides on the post-failure mechanics and the interaction with rigid structures. The Material Point Method (MPM), an advanced numerical tool capable of simulating large deformations, captures the whole instability and the impact process. A simple geometry of a biplanar compound landslide is considered with two different types of biplanar slope transitions along the basal surface – sharp transition (or "kink" geometry) and curved transition (with different radii). A comprehensive parametric study with more than 280 simulations is performed to analyze the landslide post-failure behavior in terms of the radii of transition, the basal friction angle, the distance to the rigid wall, the roughness of the rigid wall, and the scale of the landslide. The results are presented in terms of maximum impact force on the rigid wall and final runout (in the absence of the wall). Results show that the basal characteristics impact the landslide kinetics and energy dissipations, which in turn, influence the impact forces on the rigid wall as well as the final runout of the landslide. The basal friction amplifies the influence of slope geometry on maximum impact forces. In addition, the maximum impact force from numerical results is compared with the predictions from existing semi-empirical approaches. Finally, a preliminary empirical framework is proposed to incorporate the effects of basal sliding characteristics of compound landslides into predicting impact forces on retaining walls. / Master of Science / Landslides and slope failures are a major problem in the geotechnical field that causes significant damage to lives and infrastructure worldwide. It, therefore, becomes essential to understand the mechanisms and the deformation patterns from the standpoint of assessing the impact on infrastructure near the landslide. This thesis studies the effects of the geometry of compound landslides on the maximum impact forces exerted on a rigid structure at a given distance from the landslide. It uses the Material Point Method (MPM), a numerical method that simulates problems involving large deformations. MPM allows the study of the entire instability process from failure initiation to final runout and impact against barriers. Several theoretical models of generic landslides of different radii of slope transition, friction on the sliding surface, and different distances from the wall are presented to study the effects of these parameters on the maximum impact force exerted on the wall. Along with this, the effects of the scale of a landslide on the impact forces are also analyzed. Based on the results, an empirical framework is proposed to help calculate maximum impact forces on a vertical rigid wall while incorporating the basal failure surface characteristics.

Compound aerospike nozzles were designed and tested as part of an ongoing experimental study to determine the feasibility of thrust vectoring an aerospike nozzle with the addition of a secondary port. Earlier phases of the study have indicated that a compound aerospike nozzle could provide sufficient thrust vectoring. The addition of a hole-type secondary port was found to provide effective thrust vectoring. Experiments were carried out to determine the effects of secondary port size, secondary port inlet geometry and compound aerospike nozzle chamber pressure. Results show good predictability, axisymmetric flow, and emphasize the importance of a radius on secondary port inlet geometry.

Prostate cancer is one of the leading causes of death for men in America as approximately 1 in 41 men will have prostate cancer. In this research, we focus on enzalutamide-resistant prostate cancer cells as cell resistance to enzalutamide is a prevalent obstacle in treating prostate cancer. We tested a novel compound library at different doses and observed each compound's efficacy in inducing apoptosis in enzalutamide-resistant cells. Furthermore, we analyzed the mechanism by which apoptosis was induced in compounds that showed a high efficacy at lower doses. Overall, we found that Darapladib shows promising results in treating cells that have acquired enzalutamide resistance.

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