https://etd.auburn.edu/handle/10415/1 2026-08-15T11:59:41Z https://etd.auburn.edu/handle/10415/10646 Development of a Non-Equilibrium Plasma Coupled Rapid Compression Machine for Advanced Ignition Studies Bopaiah, Karan A plasma-coupled rapid compression machine (PRCM) was developed to investigate plasma-assisted combustion (PAC) under elevated-pressure and elevated-temperature conditions representative of end-of-compression (EOC) engine environments. The facility enables controlled comparison of autoignition, conventional spark ignition (CSI), and nanosecond pulsed discharge (ns-PD) ignition. The experimental approach combines time-resolved pressure measurements, synchronized electrical diagnostics (voltage, current, and energy deposition), and high-speed CH* chemiluminescence imaging to quantify early flame evolution and flame propagation. Baseline autoignition experiments established mixture reactivity under identical thermodynamic conditions. Methane exhibited single-stage ignition with monotonic reduction in ignition delay with increasing temperature, while n-butane showed two-stage ignition with a distinct negative temperature coefficient (NTC) regime, consistent with low-temperature chain-branching chemistry. Ignition experiments at 10 bar and 664 K were performed using CSI and ns-PD systems. Flame development time (FDT) and flame propagation time (FPT) were extracted from pressure traces to separate kernel formation from subsequent flame growth. CSI results show that ignition improvement is primarily governed by early breakdown energy and voltage rise rate, while additional dwell time increases post-kernel energy deposition with limited impact on FPT, indicating diminishing returns once a self-sustaining kernel is formed. Nanosecond pulsed discharge ignition was investigated using three geometries to understand the contribution of distinct glow and spark regimes towards ignition enhancement. Experiments were performed over pulse repetition frequencies (1–100 kHz), voltages (24–29 kV), and pulse counts up to 100 pulses, with selected cases held at constant total energy (~95 mJ) to isolate inter-pulse coupling effects. Compared to CSI, ns-PD ignition reduced both FDT and FPT, with performance strongly dependent on discharge morphology. High-speed CH* chemiluminescence imaging at 25 kHz was used to resolve ignition kernel evolution and flame propagation. Results show that spark-containing discharges produce larger initial kernels due to rapid thermalization, while glow-dominated discharges exhibit slower initial growth but accelerated late-stage flame propagation. Area-averaged emission reveals an initial post-discharge decay in CSI and spark systems due to relaxation of excited species, whereas glow-dominated discharges show smoother evolution due to sustained radical production. Lean-burn experiments demonstrated improved ignition robustness for ns-PD systems relative to CSI, extending the practical lean limit to φ = 0.45 with improved cycle-to-cycle variability. Collectively, these studies advance the experimental understanding of plasma-assisted combustion by establishing the relationships between discharge morphology, energy deposition, inter-pulse coupling towards combustion enhancement. The resulting database provides a comprehensive benchmark for the development, validation, and refinement of plasma-assisted combustion models and PAC-specific chemical kinetic mechanisms applicable to practical high-pressure combustion systems. 2026-08-14T00:00:00Z https://etd.auburn.edu/handle/10415/10645 Evaluating Emerging Food Production Systems Through Product Quality and Consumer Research: Aquaponic Tomato Production, Poultry Stunning Technologies, and the Role of Information Depth Dees, Jacob Emerging food production and processing systems must be evaluated not only by their technical performance, but also by the quality of the products they produce and the way consumers understand and respond to them. This thesis evaluated two emerging food system contexts: aquaponic cherry tomato production and controlled atmosphere stunning (CAS) in poultry processing. The first study examined the effects of aquaponic system design and harvest timing on cherry tomato quality using instrumental color and texture analysis, trained descriptive sensory analysis, and electronic nose volatile profiling. Tomatoes were harvested once per week at the red-ripe stage over five weeks from four aquaponic treatments differing in hydraulic configurations and light exposure: light-coupled (LC), light-decoupled (LD), dark-coupled (DC), and dark-decoupled (DD) systems. Hydroponic reference samples were included when available between weeks 2-5. Instrumental color and hardness showed intermittent treatment differences, but subtle differences between individual harvest weeks had the most influence on measured tomato attributes. Trained sensory panel results showed limited treatment separation across most attributes, although green aroma significantly declined across harvest weeks in aquaponic treatments. Electronic nose analysis showed that volatile fingerprints varied by harvest week and production system, but targeted, green-associated volatile measures were not significantly correlated with sensory green aroma. These findings indicate that aquaponic tomato quality is multidimensional and that instrumental, sensory, and volatile measures can provide complementary information. The second study evaluated how information depth influenced consumer understanding, perceptions, acceptance, and WTP for aquaponic tomato production and CAS poultry processing. A randomized online survey was conducted with 1,064 U.S. respondents, including 580 respondents in the tomato branch and 484 in the poultry branch. Within each branch, respondents were assigned Control, Basic, or Detailed system information conditions. Detailed system information improved aquaponic knowledge, perceived information understanding, expected quality, perceived sustainability, and acceptance, but did not significantly increase aquaponic WTP. In the poultry branch, information depth improved CAS and electrical stunning knowledge, perceived understanding, and information quality, but did not significantly affect CAS acceptance, WTP, or perspectives on the humaneness of each system. Across both branches, choice likelihood of either system within the branch was more strongly associated with purchase comfort, expected product quality, and perceived sustainability/ humaneness of the system than with understanding of the provided information alone. CATA and ranking results further showed that respondents prioritized familiar and outcome-based attributes, including food safety, reduced pesticide use, efficient water use, healthy birds, and reduced pain. 2026-08-14T00:00:00Z https://etd.auburn.edu/handle/10415/10644 Eco-epidemiological Study of Ixodidae at the Interface of Humans, Domestic Animals, and Wildlife in Eastern Central Alabama Wright, Isabella Ixodidae, the family of hard ticks, are obligatory hematophagous ectoparasites of vertebrates and efficient vectors of a wide variety of pathogens affecting wildlife, domestic livestock, companion animals and humans. Ticks and tick-borne diseases pose persistent and growing challenges to human and animal health worldwide, but there remains minimal research in Alabama on their phenology, host interactions and associated pathogens. To address this gap in knowledge, my overarching goal was to assess the interactions between ticks, hosts and their pathogens within the environment using a variety of sampling methods. Sampling methods included both opportunistic host-tick collection for assessing tick diversity and tick dragging as the primary method for investigating phenology. I sampled vertebrate populations for host-tick collection including raccoons (Procyon lotor), wild pigs (Sus scrofa), white-tailed deer (Odocoileus virginianus), and coyotes (Canis latranis). Environmental sampling took place across eight sites for approximately eight months while host-tick collection occurred opportunistically through collaboration with ongoing projects. Following collection, tick samples were identified by species and then screened for pathogens using molecular methods. I documented the presence of six known tick species in Alabama including Amblyomma americanum, Amblyomma maculatum, Dermacentor albipictus, Dermacentor variabilis, Ixodes scapularis and Rhipicephalus sanguineus. One of the major findings of this study was that habitat and host availability influence the complex dynamics of tick populations, resulting in phenological differences across regions. These regional differences were strongly associated with habitat characteristics, as tick abundance was positively correlated with shaded, moist forests and negatively associated with open grassy fields. Following pathogen screening, the presence of babesiosis, ehrlichiosis, rickettsiosis and Heartland virus (HRTV) were detected in the samples. Because HRTV has only been detected once before in this region, these results indicate that ticks and their diseases may be expanding. The findings from this study can be used to address existing gaps in research and inform public health surveillance for tick-borne disease in Alabama. 2026-08-14T00:00:00Z https://etd.auburn.edu/handle/10415/10643 Identifying and Mitigating the Effects of the Covid-19 Pandemic on Primary Care Clinics Using Lean Tools and Simulation Wilson, Anna Lean Systems have provided the healthcare industry with a set of tools to identify, reduce and eliminate waste (delays, re-work, waiting, unnecessary movement, etc.) from their processes. These tools have been useful during the Covid-19 pandemic era, when all non-acute healthcare services were pressured to quickly switch completely to telehealth operations to reduce disease transmission. However, in the literature, there has been little discussion on using Lean Systems to measure the effect of the pandemic on operational processes and how to mitigate that impact in the outpatient setting. This dissertation addresses this gap by applying lean methodologies such as Value Stream Mapping (VSM), Voice of the Process (VoP), Control Charts, and Time Motion Studies (TMS) in combination with agent-based simulation to evaluate the operational, organizational, and human impacts of the Covid-19 pandemic in an outpatient primary care clinic. The research is organized into three complementary contributions that combine lean Engineering methodologies with agent-based simulation to develop evidence-based recommendations for future public health emergencies. This dissertation addresses this gap by applying lean methodologies such as Value Stream Mapping (VSM), Voice of the Process (VoP), Control Charts, and Time Motion Studies (TMS) in combination with agent-based simulation to evaluate the operational, organizational, and human impacts of the Covid-19 pandemic in an outpatient primary care clinic. The research is organized into three complementary contributions that combine lean Engineering methodologies with agent-based simulation to develop evidence-based recommendations for future public health emergencies. The first contribution identified and quantified the effects of the Covid-19 pandemic on operational process waste using Lean methodologies. By comparing pre-pandemic workflows with pandemic workflows, the study identified wastes that increased, remained unchanged, decreased, or emerged as a direct result of Covid-19-related operational changes. The findings demonstrate how lean tools can be used not only to identify process inefficiencies but also to support rapid workflow redesign during major healthcare disruptions. The second contribution assessed actual and perceived occupational risk associated with Covid-19 and evaluated its relationship to provider and clinical staff stress and burnout. Voice of the Process interviews and organizational-wide surveys were used to examine how rapidly changing clinical protocols affected healthcare workers throughout multiple stages of the pandemic. The results identified organizational and clinical practices that reduced occupational risk while improving employee well-being and maintaining patient care. The third contribution developed and validated an agent-based simulation of an outpatient primary care clinic to evaluate alternative clinical and organizational protocols under pandemic conditions. The simulation incorporated real clinic workflows, staffing patterns, patient movement, infection transmission, and mitigation strategies, including masking, social distancing, and symptom screening. Multiple experimental scenarios were used to evaluate the effects of these protocols on workflow efficiency, patient wait times, provider utilization, and infection transmission. The simulation provides healthcare organizations with a decision-support framework for balancing operational efficiency, employee safety, and quality patient care during future infectious disease outbreaks. Overall, this dissertation demonstrates that integrating Lean Engineering methodologies with agent-based simulation provides a comprehensive approach for identifying operational waste, evaluating occupational risk, and optimizing healthcare workflows. The results contribute new knowledge to the limited body of research on outpatient primary care during the Covid-19 pandemic and provide practical guidance for healthcare organizations seeking to improve resilience and preparedness for future public health emergencies. 2026-08-12T00:00:00Z