University of Tennessee Institute of Agriculture
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Impact of Manufacturing Pauses in Additive Friction Stir Deposition Aluminum 7075
Full text linkThis study investigates the effects of manufacturing pauses on the mechanical properties and residual stress evolution in additive friction stir deposition (AFSD) of aluminum alloy 7075 (AA7075). Single-walled builds were produced using a closed-loop temperature control system, with intentional 15- and 100-hour pauses introduced midway. Some builds were reheated to 120 C before resumption; others restarted without preheating. Structured light scanning evaluated base plate deflection, and neutron diffraction characterized residual stresses. Samples were sectioned via wire EDM for surface displacement measurements using a coordinate measurement machine (CMM), followed by tensile testing, hardness mapping, and metallographic analysis.
In continuously deposited material, microhardness in the central region increased over 15 weeks post-deposition due to natural aging, with hardness rising from 113 HV to 147 HV. The base plate beneath the deposit consistently showed lower hardness. In paused builds, the material beneath the pause interface aged prior to resumption, leading to elevated hardness in those layers. For example, the 100-hour pause without reheat yielded initial layer hardness of 100–110 HV, versus 90–100 HV in the no-pause sample.
Tensile testing showed that all samples exhibited yield and ultimate strengths between O-temper and T73 conditions, consistent with W-temper natural aging. Elongation at failure ranged from 1.2\%–9.1\%, with the 100-hour pause without reheat producing the lowest ductility, greatest residual stress, and largest EDM deflection. Neutron diffraction revealed tensile residual stress concentration near the base plate in all builds. Paused builds with warm restarts showed increased tensile stress in pre-pause layers, while cold restarts led to sharp stress variations near the pause. Variations in measured spacing reflected changes in thermal history and microstructural evolution.
This is the first comprehensive evaluation of AFSD AA7075 with manufacturing pauses. Motivated by delamination observed in large-scale builds, the study shows that each new AFSD layer contributes to in-situ heat treatment. A pause interrupts thermal continuity, allowing premature aging and introducing mechanical and microstructural heterogeneity. These insights are critical for ensuring consistent performance in aerospace-grade aluminum components and refining AFSD process control strategies
PLAYING THE CREATIVE ADVANTAGE: CREATIVE ROLE IDENTITY OF FEMALE LEADERS IN SPORTS MEDIA MARKETING
Full text linkThis qualitative study examines how female leaders in sports media marketing define, develop and enact their creative role identity within the organizational context of a historically male-dominated industry. Four guiding research questions offer a foundation to explore how participants define creativity as a part of their role, how creativity extends to their leadership, how their personal and professional journey shaped their leadership, and how the organizational culture and context constrain or support creativity.
One-on-one interviews with 12 female leaders in sport media marketing highlighted competencies to define creativity as a part of their role identity. Growth mindsets were also emphasized as antecedents to enacting creativity within their role identity. Leadership styles that fostered creativity included core components of both transformational and human-centered leadership and were often blended with a situational to achieve results. An emphasis on collaboration, psychological safety, and empowering others was woven into creative leadership approaches. Creative leadership was influenced by personal and professional experiences highlighted as building resilience, the positive influence of mentorship and allies, and the impact of participation in sport. Organizational cultures where authentic value was placed on collaboration and inclusivity aligned with fostering creativity while barriers linked to streamlining and lack of communication limited how leaders enacted creativity.
The findings of this research translate into practical recommendations for female leaders and aspiring female leaders seeking to strengthen and enhance creative thinking within their role identities as well as organizational recommendations to creative inclusive and supporting environments that foster creativity. The findings and practical application support the critical role the self-efficacy and enacting creativity plays in the leadership and professional success of females in sport media marketing, expand the definition of creativity beyond roles, offer insight to enhance creative thinking and female representation in the industry, and highlight the need for organizations to be intentional about creating inclusive and safe environments where creativity can thrive
Steady-State Tools and Algorithms to Enhance Grid Planning Operations
No full textThe electric power grid is undergoing a significant transition towards renewable energy resource. In addition to this, there is a growing energy demand due to increased manufacturing and data center growth. With this in mind, grid planners must develop innovative strategies to accommodate the increased load and renewable energy penetration while maintaining grid reliability in a cost-effective manner. This dissertation proposes several novel tools and algorithms to improve grid planning and address some of the challenges currently faced in power system planning.
One of the key challenges faced by grid planners is the convergence issues encountered in the creation of accurate power flow models that represent the grid under various loading and generation scenarios. To address this convergence issues, three algorithms are developed to achieve power flow convergence in previously non-converging cases. The first algorithm achieves convergence by applying a deep learning neural network initializer to predict better initial conditions for the Newton-Raphson AC power solution method. Next a hot-starting algorithm with switched-shunt control is developed to solve previously non-converging power flow models and third algorithm applies a generator redispatch methodology to converge previously non-converging power flow models. These algorithms were successfully applied to the Electric Reliability Council of Texas (ERCOT) 6102 bus grid system under various operating conditions.
Beyond power flow convergence, this dissertation introduces a hosting capacity tool using an adaptive gradient descent algorithm. It determines the maximum generation capacity a bus can accommodate without violating thermal and voltage constraints, both in base case and N-1 contingency scenarios. Compared to the conventional sequential search method, this algorithm achieved higher accuracy with fewer iterations and was validated on the 243-bus Western Electricity Coordinating Council (WECC) system.
Finally, a steady-state interconnection tool was designed to automate the generation interconnection studies and was applied to a real US power distribution system
Tuning the Processability of Thermal Stimuli-Responsive Lightly Crosslinked Liquid Crystalline Epoxy Networks
Full text linkFunctional liquid crystalline epoxy networks (LCEN) capable of shape memory and self-healing were fabricated according to a variety of novel techniques. These techniques include rheological modification through non-reactive additives, introduction of catalysts to promote dynamic bonding, and curing agent selection to control formation of liquid crystalline domains. The aim of this work is to explore novel, commercially viable methods of fabricating and recycling using techniques to tune and preserve functional properties such as shape memory and self-healing. In this way, functional, smart devices can be produced with LCEN, reducing reliance on critical materials in such devices. Small-angle and wide-angle x-ray scattering, rheometry, and calorimetry were used to determine the functional properties and relate them to the formation of liquid crystalline phases within the epoxy as well as the ability to form and maintain those phases after different processing and reprocessing techniques. The collected works presented demonstrate the viability of tunable LCEN for myriad functional applications
Understanding the Applications of Tetflupyrolimet in Turfgrass Systems
Full text linkTetflupyrolimet, a new herbicide developed by FMC Corporation, targets dihydroorotate dehydrogenase (DHODH), effectively inhibiting de novo pyrimidine biosynthesis in various grass species. This dissertation synthesizes findings from field, greenhouse, and laboratory trials conducted between 2021 and 2024, aimed at better understanding the applications of tetflupyrolimet in turfgrass systems. First, this included assessing turfgrass tolerance to tetflupyrolimet in controlling problematic species such as Poa annua and smooth crabgrass (Digitaria ischaemum). Five turfgrass species relevant to Tennessee were assessed at cutting heights ranging from 3.8 to 12.5 mm across different seasons, revealing that warm-season turfgrasses exhibited no adverse effects to as high as 3200 g ha-1. Response of cool-season grasses varied with an overall trend for cool-season species to be more tolerant to applications made in spring than fall. Efficacy for preemergence (PRE) control of smooth crabgrass fluctuated yearly, but tetflupyrolimet (400 g ha-1) in mixture with pyroxasulfone (128 g ha-1) and rimsulfuron (35 g ha-1) proved effective in controlling herbicide-resistant Poa annua. Additionally, research was conducted to understand the influence of soil texture on tetflupyrolimet activity, revealing significant variations in efficacy between sandy versus clay loam soils, with higher effectiveness with applications made to the coarser textured medium. Data collected suggest that matric potential differences amongst soil-types may explain this response with water being more accessible to seedling weeds in coarser textured mediums with overall moisture content is fixed across soil types. Offering tetflupyrolimet application rates based on soil texture may enhance herbicide performance under various soil-moisture conditions. Furthermore, the lateral movement of tetflupyrolimet was investigated under field capacity and saturated soil-conditions. Regardless of soil moisture content, tetflupyrolimet maximum lateral movement was limited to 1.1 meters, significantly less than pronamide exhibited greater mobility. This experiment indicated that maintaining a buffer of at least 1.1 meters from sensitive grass species could minimize the risk of non-target effects of tetflupyrolimet applications in turfgrass. Overall, the studies support tetflupyrolimet use in turfgrass management, giving managers a novel tool in mitigating herbicide resistance within the troublesome grassy weed, Poa annua
MICROBIAL INTERACTIONS IN AN ANTARCTIC DESERT: RESPONSES TO ENVIRONMENTAL CHANGE AND TOOLS FOR LIFE DETECTION
Full text linkCryosphere microorganisms can provide fundamental insights into individual and community response to a changing climate, and how we may detect past or present life on other planets. The polar desert of the McMurdo Dry Valleys (MDV), the largest ice-free region in Antarctica, supports microbially-dominated ecosystems that experience extremes of temperature, salinity, nutrient availability, and solar radiation. A changing Antarctic climate leads to alteration of these natural gradients, thus, studying how organisms respond to changing stressors can inform predictions of future impacts to ecosystems. This dissertation elucidates how MDV microorganisms interact with their environment through culture-based and multi-omics techniques performed on both environmental materials and bacterial isolates. We describe the ecophysiology of a red pigmented strain of Massilia frigida (strain DJPM01) isolated from a microbial mat. Through genomic analyses, adaptations to cold and saline environments, and biosynthesis genes for the pigment prodigiosin were identified. The synthesis of prodigiosin was confirmed using mass spectrometry, and breakdown of this pigment was observed when DJPM01 cultures were incubated under ultraviolet light, a relevant stressor for polar bacteria. To investigate the impact of salinity on whole communities and individual species, we leveraged samples from a natural salinity gradient in MDV soils that forms from permafrost melt. Environmental soil DNA was sequenced to examine differences in community structure and potential correlations with salinity. We then identified changes in transcription and metabolite production in a potentially novel Gillisia sp., isolated from this soil gradient, under elevated salt concentrations. A Shewanella sp. BF02_Schw, isolated from a Mars analog feature known as Blood Falls, was used to describe biosignatures produced during iron reduction, a plausible metabolic strategy for life on early Earth and Mars. Employing instrumentation relevant to both in situ and sample return Mars missions, we identified mineral and molecular biosignatures produced under high iron concentration and confirmed the biogenicity of these signatures via transcriptomics. Collectively, this dissertation describes specific ways that MDV microorganisms interact with their environment that provide insight into the impact of climatic change on Antarctic communities and inform strategies for the detection of life on other planets
Graduate Instructors at Work: A Narrative Inquiry into the Development of Writing Assessment Literacy
Full text linkWriting assessment shapes what students learn and the extent to which they invest in their writing development, with lasting consequences on academic growth, literacy development, and retention. University writing programs often rely on Graduate Teaching Associates (GTAs) to teach first-year composition (FYC) courses and assess student writing; however, GTAs often receive incomplete or inadequate training in writing assessment theory and practice. English Departments that provide writing pedagogy education have not yet fully considered how GTAs learn to assess writing nor the assessment challenges they face in the FYC classroom, creating a significant gap between the importance of effective writing assessment and the often-minimal preparation instructors receive to deliver that assessment. To address this gap, this qualitative study examined how new GTAs developed writing assessment literacy. Using narrative inquiry as a research methodology, I followed eight GTAs during their first year teaching FYC courses as instructors of record at the University of Tennessee, Knoxville (UTK). I collected stories through a series of three interviews with each participant over the 2023–2024 academic year, triangulating interview data with focus groups and assessment materials. Then, I composed eight individual narratives that document and analyze GTAs’ writing assessment literacy. Based on the narratives and thematic analysis, I developed an expanded conceptual model for tracing writing assessment literacy development that emphasizes lived experience, prior knowledge, affect, and labor in teacher learning. I use the results to redefine the development of writing assessment literacy as literacy labor to draw attention to the material, intellectual, affective, and embodied dimensions of GTA development. Key findings suggest that the conditions that most impacted writing assessment literacy were peer support, classroom teaching experience, and prior knowledge and experience. The formal aspects of writing pedagogy education that most influenced writing assessment literacy development were ranked as teaching assistantship, tutoring, composition pedagogy coursework, and departmental workshops. Based on these findings, I suggest that writing program administrators refocus writing pedagogy education to foster the development of writing assessment literacy. Graduate student instructors need experiential learning, guided reflection, and ongoing support beyond the first year to thrive as they teach and assess writing
The Quest for Queer Authenticity: The Roles of Spirituality, Self-Compassion, and Psychological Flexibility
Full text linkRecent research has identified authenticity as an aspect of lesbian, gay, and bisexual (LGB+) positive identity that is distinct from coming out. Authenticity refers to an inner sense of peace and comfort with one’s LGB+ identity and is consistently linked to positive psychological outcomes in this population. However, there is limited research on how authenticity can be facilitated among LGB+ adults. Spirituality may be a potential source of support for LGB+ individuals that can reduce the negative effects of minority stress and promote authenticity by facilitating greater self-compassion and psychological flexibility. The present study aimed to examine the relationship between spirituality and authenticity, as mediated by self-compassion, psychological inflexibility, and internalized heterosexism, in a sample of LGB+ adults. Participants (n = 577) completed an online survey with self-report measures on spirituality, self-compassion, psychological inflexibility, internalized heterosexism, and authenticity. Results from a structural equation modeling analysis indicated that spirituality was indirectly linked to authenticity through serial meditation, such that self-compassion mediated the relationship between spirituality and psychological inflexibility, which in turn mediated the relationship between self-compassion and internalized heterosexism, which in turn mediated the relationship between psychological inflexibility and authenticity. These findings have important implications for interventions designed to support the well-being and identity development of LGB+ individuals
Inactivation of foodborne viruses dried and as bio-aerosolized droplets on food-contact surfaces by ultraviolet light
Full text linkTransmission of foodborne pathogens can occur in food-processing environments through contaminated food-contact surfaces and aerosols leading to foodborne outbreaks. Improved sanitation approaches including ultraviolet (UV-C)-light technologies for optimal dose delivery to inactivate microorganisms are being researched. The objectives of this research were to determine the effects of UV-C LED at 255 and 279 nm and traditional 254 nm-UV-C against surface-dried and bio-aerosolized (UV-C LEDs only) hepatitis A virus (HAV), feline calicivirus (FCV) and Aichi virus (bioaerosols only) on model food-contact surfaces. Each surface-spread or bioaerosol-deposited virus on sterile ceramic (surface-spread only), stainless-steel, or glass surfaces were UV-C treated for up to 3.75 min (surface dose=0-48.83 mJ/cm2 (surface-spread) and 0-76.5 mJ/cm2 (bioaerosols) for HAV; 0-16.28 mJ/cm2 (surface-spread) and 0-51.0 mJ/cm2 (bioaerosols) for FCV and AiV). Recovered plaque counts from three treatments assayed twice were statistically analyzed using mixed model analysis of variance (MMAOV). The D-10 values (dose) for surface-spread HAV were 9.48±0.34, 14.53±2.52, and 7.26±1.93 mJ/cm2 using 254 nm-UV-C, were 4.60±0.91, 6.85±1.16, and 8.24±1.03 mJ/cm2 with 255 nm UV-C LED, and were 19.72±2.45, 26.05±0.60, and 9.12±2.08 mJ/cm2 with 279 nm UV-C LED on stainless-steel, ceramic, and glass, respectively. Surface-treated FCV showed D-10-values with 254 nm-UV-C of 3.65±0.06, 6.25±1.90, and 4.69±0.03 mJ/cm2, with 255 nm UV-C LED of 5.79 ±0.67, 5.97±0.32, and 5.25±2.01mJ/cm2, and with 279 nm UV-C LED of 7.53±2.11, 8.67±2.12, and 7.88±0.86 mJ/cm2, on stainless-steel, ceramic, and glass, respectively. The 279 nm UV-C LED D-10 values of bioaerosol-deposited HAV were 6.60±0.27 and 5.57±0.74 mJ/cm2, were 4.12±0.50 and 3.95±0.50 mJ/cm2 for FCV, and were 3.97±0.03 and 3.64±0.43 mJ/cm2 for AiV; and with 255 nm-UV-C LED were 47.39±7.40 and 40.0±2.94 mJ/cm2 for HAV, 35.36±4.04 and ii 40.16±7.95 mJ/cm2 for FCV, and 27.70±4.36 and 31.45±7.47 mJ/cm2 for AiV on stainless-steel and glass, respectively. These data indicate that generally higher 279 nm UV-C LED doses are needed for foodborne viral inactivation on food-contact surfaces compared to 255 nm-UV-C systems, and that viral-bioaerosols are more resistant to 255 nm-UV-C treatment than surfacedried viruses. These linear-model UV-C doses for viral inactivation on surfaces and as bioaerosol-deposits are useful for designing optimal UV-C systems for microbial inactivation
News Media Constructions of School Shootings in the Contemporary United States
Full text linkThe occurrence of school shootings has been a significant issue within the United States. The occurrence of school shootings within the United States is rising, and the media coverage of these school shootings is declining. This study examines the shift of media attention towards school shootings from 1999 to 2024 by analyzing the number of articles being published in The New York Times and The Washington Post regarding six school shootings - Columbine (1999), Red Lake (2005), Marjory Stoneman Douglas (2018), Santa Fe (2018), Oxford (2021), and Apalachee (2024). This study also qualitatively analyzes six articles from The New York Times to understand how the articles construct the trajectory of events and their associated effects. This qualitative examination of these six articles suggests that the media guides readers toward a redemptive closure. Together, these findings suggest that the media attention towards school shootings is declining, and news media may favor redemptive closure in the aftermath of such shootings