Engineering Commons^™

Exploring Soil Microbial Dynamics In Southern Appalachian Forests: A Systems Biology Approach To Prescribed Fire Impacts, Saad Abd Ar Rafie

Doctoral Dissertations

Prescribed fires in Southern Appalachian forests are vital in ecosystem management and wildfire risk mitigation. However, understanding the intricate dynamics between these fires, soil microbial communities, and overall ecosystem health remains challenging. This dissertation addresses this knowledge gap by exploring selected aspects of this complex relationship across three interconnected chapters.

The first chapter investigates the immediate effects of prescribed fires on soil microbial communities. It reveals subtle shifts in porewater chemistry and significant increases in microbial species richness. These findings offer valuable insights into the interplay between soil properties and microbial responses during the early stages following a prescribed fire. …

The Synthesis And Optimization Of Sulfide And Halide Solid Electrolytes For All Solid-State Batteries, Teerth Brahmbhatt

Doctoral Dissertations

Countries and organizations around the world have established ambitious targets to transition away from fossil fuel-based energy sources and devices. The transition is focused on cleaning up power generation by converting coal, natural gas, and oil-based power generation to renewables and nuclear energy. Decarbonizing other sectors of energy use, transportation for example, will require broader electrification. To drive this move away from fossil fuel powered transportation will require portable energy storage devices. Conventional lithium-ion batteries are a popular candidate to lead this shift. However, these batteries often rely on flammable liquid electrolytes and carbon anodes that suffer from low energy …

Heat Pump Integrated Thermal Storage For Building Demand Response And Decarbonization, Sara Sultan

Doctoral Dissertations

This work presents a novel thermal energy storage (TES) integrated with existing residential heat pump (HP). The research focuses on controls and configuration for energy, demand, cost and carbon emissions savings for residential buildings’ energy consumption. This work will be significant in developing a framework especially for reduced energy demand and carbon emissions associated with space heating and cooling in residential buildings. Since buildings account for about 40% primary energy consumption in U.S. and half of that is associated with HP.

An existing air source HP in integrated with a phase change material (PCM) based TES via active configuration where …

Understanding And Simulating Wildfire Changes Using Advanced Statical And Process-Oriented Models, Rongyun Tang

Doctoral Dissertations

This study aims to investigate the spatiotemporal dynamic of global wildfires, their underlying climate-driving mechanisms, and their predictability by utilizing multiple data sources (both process-based model simulations and satellite-based observations) and multiple analytical methods including machine learning techniques (MLTs).

We first explored the global wildfire interannual variability (IAV) and its climate sensitivity across nine biomes from 1997 to 2018, leveraging the state-of-art U.S. Department of Energy’s Energy Exascale Earth System Model (E3SM) land component (ELM-v1) simulations with six sets of climate forcings. Results indicate that 1) ELM simulations could reproduce the IAV of wildfire in terms of magnitudes, distribution, bio-regional …

A Connectivity Framework To Explore The Role Of Anthropogenic Activity And Climate On The Propagation Of Water And Sediment At The Catchment Scale, Christos Giannopoulos

Doctoral Dissertations

Anthropogenic disturbance in intensively managed landscapes (IMLs) has dramatically altered critical zone processes, resulting in fundamental changes in material fluxes. Mitigating the negative effects of anthropogenic disturbance and making informed decisions for optimal placement and assessment of best management practices (BMPs) requires fundamental understanding of how different practices affect the connectivity or lack thereof of governing transport processes and resulting material fluxes across different landscape compartments within the hillslope-channel continuum of IMLs. However, there are no models operating at the event timescale that can accurately predict material flux transport from the hillslope to the catchment scale capturing the spatial and …

Susceptibility Of Riverine Fishes To Anthropogenically-Linked Trauma: Strikes From Hydropower Turbine Blades, Ryan K. Saylor

Doctoral Dissertations

Hydropower accounts for nearly 40% of renewable electricity generation in the US; however, dams significantly impact the surrounding aquatic ecosystems. One of the most visible impacts of hydropower―beyond the dam itself―is the direct negative impacts (injury or death) to fish populations that must pass through hydropower turbines to access desired downstream habitat. During passage, fishes face many potential stressors that can cause severe injuries and often leads to high rates of mortality. In this dissertation, I have focused on quantifying how fishes respond to impacts from turbine blades that may occur during turbine passage. Laboratory research into blade strike impact …

Development Of High-Performing Polydimethylsiloxane-Based Membranes For Carbon Dioxide Separation, Tao Hong

Doctoral Dissertations

Membrane separation is highlighted as one of the most promising approaches to mitigate the excessive CO₂ [carbon dioxide] emission, due to its significant reduction of energy cost compared with many conventional separation techniques. Unfortunately, the separation performance of current membranes does not meet the practical CO₂/N₂ [nitrogen] separation requirements. And due to the huge volume of industrial flue gas, membranes with exceptionally high permeability are needed for practical reasons.

Currently, the separation mechanism of most polymeric membranes is based on size-sieving. However, this method is not sufficient for CO₂/N₂ separations due to the …

Lattice Boltzmann Methods For Wind Energy Analysis, Stephen Lloyd Wood

Doctoral Dissertations

An estimate of the United States wind potential conducted in 2011 found that the energy available at an altitude of 80 meters is approximately triple the wind energy available 50 meters above ground. In 2012, 43% of all new electricity generation installed in the U.S. (13.1 GW) came from wind power. The majority of this power, 79%, comes from large utility scale turbines that are being manufactured at unprecedented sizes. Existing wind plants operate with a capacity factor of only approximately 30%. Measurements have shown that the turbulent wake of a turbine persists for many rotor diameters, inducing increased vibration …

Lignin-Based Li-Ion Anode Materials Synthesized From Low-Cost Renewable Resources, Nicholas William Mcnutt

Doctoral Dissertations

In today’s world, the demand for novel methods of energy storage is increasing rapidly, particularly with the rise of portable electronic devices, electric vehicles, and the personal consumption and storage of solar energy. While other technologies have arguably improved at a rate that is exponential in accordance with Moore’s law, battery technology has lagged behind largely due to the difficulty in devising new electric storage systems that are simultaneously high performing, inexpensive, and safe.

In order to tackle these challenges, novel Li-ion battery anodes have been developed at Oak Ridge National Laboratory that are made from lignin, a low-cost, renewable …

Impacts Of Climate Change On The Evolution Of The Electrical Grid, Melissa Ree Allen

Doctoral Dissertations

Maintaining interdependent infrastructures exposed to a changing climate requires understanding 1) the local impact on power assets; 2) how the infrastructure will evolve as the demand for infrastructure changes location and volume and; 3) what vulnerabilities are introduced by these changing infrastructure topologies. This dissertation attempts to develop a methodology that will a) downscale the climate direct effect on the infrastructure; b) allow population to redistribute in response to increasing extreme events that will increase under climate impacts; and c) project new distributions of electricity demand in the mid-21^st century.

The research was structured in three parts. The first …

Stability, Erosion, And Morphology Considerations For Sustainable Slope Design, Isaac Andres Jeldes Halty

Doctoral Dissertations

The construction of more natural and sustainable earth slopes requires the consideration of erosion and runoff characteristics as an integral part of the design. These effects not only result in high costs for removal of sediment, but also a profound damage to the ecosystem. In this dissertation, innovative techniques are developed such that more natural appearing slopes can be designed to minimize sediment delivery, while meeting mechanical equilibrium requirements. This was accomplished by: a) examining the fundamental failure modes of slopes built with minimum compaction (FRA) to enhance quick establishment of forest, b) investigating the geomechanical and erosion stability of …

Towards Sustainable Development Of Nanomanufacturing, Sasikumar Ramdas Naidu

Doctoral Dissertations

"Sustainability" is a buzz word these days not just among regulatory agencies but even with corporations, as evident by the release of annual sustainability report by a large number of firms. Companies are starting to portray profit making along with corporate environmental responsibility.

Nanotechnology and nanomanufacturing which holds a lot of promise for development in a multitude of fields in science and engineering is the new kid on the block and carries a lot of apprehension due to public concern about their potential unwanted side effects that may result in the case of an untoward incident or lack of oversight. …

Effects Of 2000-2050 Global Climate Change On Ozone And Particulate Matter Air Quality In The United States Using Models-3/Cmaq System, Yun-Fat Lam

Doctoral Dissertations

The Models-3/Community Multi-scale Air Quality modeling system (CMAQ), coupled with Goddard Institute for Space Studies (GISS) atmospheric General Circulation Model (GCM), fifth Generation Mesoscale Model system (MM5), and Goddard Earth Observing System-CHEMistry (GEOS-Chem), was used to simulate atmospheric concentration of ozone and particulate matter over the continental United States 12-km and 36-km (CONUS) domains at year 2000 and year 2050. In the study, GISS GCM model outputs interfaced with MM5 were utilized to supply the current and future meteorological conditions for CMAQ. The conventional CMAQ profile initial and boundary conditions were replaced by time-varied and layer-varied GEOS-Chem outputs. The future …