Doctor of Philosophy, The Ohio State University, 2012, Nuclear Engineering

Utilities operating nuclear power plants in the United States are required to demonstrate that their plants comply with the safety requirements set by the U.S. Nuclear Regulatory Commission (NRC). How to show adherence to these limits through the use of computer code surrogates is not always straightforward, and different techniques have been proposed and approved by the regulator. The issue of compliance with regulatory limits is examined by rephrasing the problem in terms of hypothesis testing. By using this more rigorous framework, guidance is proposed to choose techniques to increase the probability of arriving at the correct conclusion of the analysis. The findings of this study show that the most straightforward way to achieve this goal is to reduce the variance of the output result of the computer code experiments. By analyzing different variance reduction techniques, and different methods of satisfying the NRC's requirements, recommendations can be made about the best-practices, that would result in a more accurate and precise result. This study began with an investigation into the point estimate of the 0.95-quantile using traditional sampling methods, and new orthogonal designs. From there, new work on how to establish confidence intervals for the outputs of experiments designed using variance reduction techniques was compared to current, regulator-approved methods. Lastly, a more direct interpretation of the regulator's probability requirement was used, and confidence intervals were established for the probability of exceeding a safety limit. From there, efforts were made at combining methods, in order to take advantage of positive aspects of different techniques. The results of this analysis show that these variance reduction techniques can provide a more accurate and precise result compared to current methods. This means an increased probability of arriving at the correct conclusion, and a more accurate characterization of the risk associated with even (open full item for complete abstract)

Committee: Tunc Aldemir PhD (Advisor); Richard Denning PhD (Committee Member); Marvin Nakayama PhD (Committee Member); Alper Yilmaz PhD (Committee Member) Subjects: Nuclear Engineering; Statistics

Master of Science (MS), Bowling Green State University, 2019, Biological Sciences

Understanding responses of food webs to climate change is vital, especially when those food webs influence important ecosystem services, like pollination, valued at over $3 billion globally. Historically the focus has been on single factors (e.g. temperature) and mechanisms (e.g. change in mortality). However, global climate change is predicted to alter temperature and moisture simultaneously. Additionally, thermal and hygric physiological performance and species interactions are both likely mechanisms underlying food web responses to changing climate. The current lack of a synergistic, mechanistic understanding of how food webs respond to key aspects of global climate change is a major research gap. Here we questioned how changes in temperature and moisture may alter food web composition through filtering of sensitive taxa (physiological limits) or by modifying consumption (trophic interactions). We placed bumblebees (Bombus impatiens) and tomato plants (Solanum lycopersicum) in 32 mesocosms within a greenhouse in Bowling Green, OH in July 2018. We explored differences in fruit set and tomato quality by excluding half of the flowers from buzz-pollination via bags. Additionally, all mesocosms were categorized in four abiotic treatments (cool/dry, cool/moist, hot/dry, hot/moist), and were paired based on predator presence (with or without Green Lynx spiders (Peucetia viridans)). We found that predatory spider body temperature was significantly higher when more moisture was available in the environment (SE=0.779, df=28.0, t-ratio=-3.661, p=0.005). Our findings also indicate that if predatory spiders are more hydrated, they change their behavior and expose themselves more to heat (χ2=4.028, df=1, p= 0.045). Furthermore, this behavioral change influences spider consumption of bumblebees. When more moisture was available in the environment, spiders ate significantly more bumblebees (χ2=8.924, df=1, p=0.003). However, there were no significant differences between the h (open full item for complete abstract)

Committee: Kevin McCluney Dr. (Advisor); Helen Michaels Dr. (Committee Member); Daniel Wiegmann Dr. (Committee Member) Subjects: Behavioral Sciences; Biology; Climate Change; Conservation; Ecology; Entomology