Climate change is predicted to have many diverse effects on freshwater lakes and reservoirs by increasing both hypolimnetic hypoxia and runoff, which will increase nutrient concentrations and degrade water quality. Hypoxic conditions can trigger the release of metals and nutrients from the sediments, i.e., internal loading, while storms can increase external nutrient loading to a waterbody. One potential solution for combating hypoxia is to use side stream supersaturation (SSS), a novel form of hypolimnetic oxygenation. First, in Chapter 1, I tested the efficacy of SSS operation to improve water quality in Falling Creek Reservoir (FCR), a shallow, eutrophic, drinking water reservoir. I found that SSS operation successfully increased hypolimnetic oxygen concentrations in FCR and suppressed internal loading of iron, manganese, and phosphorus. In Chapter 2, I manipulated inflow volumes to FCR and used SSS as a tool to alter hypolimnetic oxygen conditions in whole-ecosystem manipulations of internal and external nutrient loading. I observed that internal nitrogen and phosphorus loading during hypoxic conditions largely controlled the hypolimnetic mass of nutrients in FCR, regardless of inflow volumes, presumably as a result of the accumulated nutrients in its sediment from historical agriculture. Additionally, FCR consistently functioned as net sink of N and P throughout almost all of the treatments and substantially reduced nutrient export to downstream ecosystems. In summary, my research demonstrates the sensitivity of reservoir water quality to global change. / Master of Science

Yes / Seabed consolidation state is one of important factors for evaluating the foundation stability of the marine structures. Most previous studies focused on the seabed consolidation around breakwaters standing on the seabed surface. In this study, a numerical model, based on Biot’s poro-elasticity theory, is developed to investigate the unsaturated seabed consolidation around a nearshore pile foundation, in which the pile inserted depth leads to a different stress distribution. Seabed instabilities of shear failure by the pile self-weight and the potential liquefaction under the dynamic wave loading are also examined. Results indicate that (1) the presence of the inserted pile foundation increases the effective stresses below the foundation, while increases and decreases the effective stresses around the pile foundation for small (de/R<=3.3) and large (de/R>3.3) inserted depths, respectively, after seabed consolidation, (2) the aforementioned effects are relatively more significant for small inserted depth, large external loading, and small Young’s modulus, (3) the shear failure mainly occurs around the inserted pile foundation, rather than below the foundation as previously found for the located marine structures, and (4) wave-induced momentary liquefaction near the inserted pile foundation significantly increases with the increase of inserted depth, due to the change of seabed consolidation state. / National Natural Science Foundation for Distinguished Young Scholars (51425901), the National Natural Science Foundation of China (51209082, 51209083), the Natural Science Foundation of Jiangsu Province (BK20161509), the Fundamental Research Funds for the Central Universities (2015B15514), Jiangsu Graduate Research and Innovation Plan Grant (#CXLX11_0450) and the 111 project (B12032).

Unintentional injuries present a major threat to the health and welfare of humans. Over 120,000 deaths and over 30,000,000 non-fatal injuries are estimated annually in the United States. The leading causes of nonfatal injuries vary with age, but falls, motor vehicle collisions (occupants), and being struck by or against are among the top 4 leading causes of unintentional injury for all ages. The loading mechanism that cause forces to be transmitted to the body during these events can cause a wide assortment of injury types with a range of severities. Understanding the biomechanical response to loading in these environments can facilitate efforts in injury mitigation. Biomechanical responses can be quantified by performing controlled laboratory experiments with human volunteers and surrogates, such as anthropomorphic test devices (ATDs) and post mortem human surrogates (PMHSs). The overall objective of this dissertation is to quantify the biomechanical response to loading regimes present in motor vehicle collisions, falls, and when being struck by or against an object using human volunteers and surrogates. Specifically, the research will achieve the following: quantify the dynamic responses of human volunteers, Hybrid III ATD, and PMHSs in low-speed frontal sled tests; quantify the neck response of human volunteers and PMHSs in low-speed frontal sled tests; quantify the kinetic and kinematic responses of PMHSs and the Hybrid III ATD in high-speed frontal sled tests; characterize thoracic loading as a result of same level falls using a Hybrid III ATD; and quantify the ability of children to swing sword-like toys and the human kinematic response that could be anticipated as a result of forceful impact using a Hybrid III 6-year old head and neck. / Ph. D.