Dissertation Defense Announcements

Candidate Name: Taryn Greene
 November 04, 2021  12:00 PM
Location: Virtual (Zoom)

Background: Current popular conceptualizations of the psychological process Repetitive Thought (RT) appear of limited accuracy due to ample construct proliferation (e.g. equating RT with rumination or worry), tautological definitions, and the construct being studied primarily in mentally disordered populations. This paper sought to unite current disparate lines of research surrounding RT, in order to illuminate and clarify the nature of RT.

Methods: Two studies were completed: First, a systematic literature review was conducted in order to develop a more comprehensive and conceptually coherent model of RT. Second, the structural validity of the model produced by the first study was empirically tested using factor analytic and multiple regression techniques.

Results: Partially Exploratory Factor Analyses revealed a strong general Repetitive Thinking factor, as well as a three-factor model that was empirically most appropriate (Intrusive Repetitive Thought, Deliberate Processing, and Self-Conscious Repetitive Thought). Additional validation analyses confirmed these findings.

Conclusions: This study contributes to our understanding of the nature of Repetitive Thought. Importantly, the three RT factors can be conceptualized as independent dimensions that are all part of a larger RT trait. The empirical and applied implications of the conceptualization of RT, as well as development of a preliminary measure of RT, are discussed.

Candidate Name: Peyman Razi
Title: Numerical Simulations and Low-Order Models of the Two-Way Interaction between Ocean Current Turbines and the Background Flow
 November 15, 2021  11:00 AM
Location: https://uncc.zoom.us/j/95188333283

Ocean Current Turbines (OCTs), which function similarly to wind and tidal turbines, represent a promising technology for harnessing the energy from oceanic currents such as the Gulf Stream. In planning the deployment of arrays of OCT devices, it is critical to consider the two-way interactions between the turbines and the ocean environment: temporally and spatially nonuniform flow fields are expected in the dynamic flow environments of western boundary currents, and include the presence of upstream shear and turbulence. These nonuniform flow conditions will affect power extraction, and the efficiency of the turbines when operating in isolation or as part of an array. Furthermore, models that are used in a predictive capability to compute the levelized cost of energy obtainable from such devices, or to optimize the layout of an array of turbines must be modified to account for the effects of such spatially and temporally inhomogeneous conditions. Similarly, the operation of OCT arrays can in turn influence the background flow in two significant ways, namely by contributing to the production of turbulence and through the generation of internal gravity waves that are radiated away from the point of origin. In this thesis, we have studied using detailed numerical simulations, the above two-way interaction between arrays of OCTs and the ocean environment. Insights developed from the simulations have guided the development of low-order wake interaction models capable of describing the effects of inhomogeneous flow conditions on array performance.
A new, wake interaction modeling framework capable of capturing the detailed effects of turbulence and upstream shear on various performance parameters associated with OCTs arranged in any arbitrary configuration has been developed. The model accounts for the effects of turbulence and shear on the structure of the turbine wakes, specifically the extents of near- and far-wake regions. The analytical description for turbine wake is combined with an existing wake interaction model, the Unrestricted Wind Farm Layout Optimization model to predict the global power output from an array of OCTs. The resulting modelling framework accurately captures the effect of inlet turbulence and shear on the OCT farm power and efficiency, and can be applied to any array configuration. Results from the model were validated against both Large Eddy Simulations and Reynolds Averaged Navier-Stokes simulations, in which the OCTs were modeled using a Blade Element Momentum model. The dispersion of OCT wake turbulence through the background stratification of the ocean was investigated using Large Eddy Simulations for different levels of the density stratification. The effects of varying the strength of the stratification as well as the turbulent forcing were studied. Finally, the wake turbulence associated with OCT operation can drive the formation and radiation of internal gravity waves in the density-stratified background flow of ocean currents. Through detailed numerical simulations, the effect of the propagation of the internal waves on the background turbulent diffusivity was studied, and found to alter the transport properties of the ambient flow. The properties of the internal wave field, and its impact on background turbulent mixing was found to depend both on the Richardson number and the ambient, upstream turbulence.

Candidate Name: Shreya Goyal
 October 18, 2021  12:00 PM
Location: Zoom

Careful control of intracellular signaling pathways plays an important role in a cell’s ability to maintain stable internal conditions in the face of an ever-changing extracellular environment. This is particularly true as it relates to the process of cellular self-eating or autophagy. Macroautophagy (herein referred to as autophagy) is a catabolic process by which unneeded or damaged cellular components are sequestered as cargo into unique double-membrane vesicles called autophagosomes which fuse to the vacuole (yeast lysosome) to be metabolized. The autophagy-related (Atg) proteins that mediate and regulate the process are evolutionarily conserved across all autophagy pathways, including starvation-induced bulk autophagy and cargo-selective autophagy pathways. The central theme of this thesis is to understand how autophagy is affected by lipids and regulatory proteins in yeast. In this thesis, we have summarized the field’s understanding of lipid homeostasis and trafficking during autophagy and autophagosome formation. Furthermore, we have extended this knowledge by discovering a clear interplay between autophagy and the SNX-BAR protein subfamily. In recent years, the SNX-BARs have been reported to have emerging roles in autophagy, however, such mechanisms of action have been primarily indirect. In this thesis, we have characterized a novel SNX-BAR protein, we have termed Vps501 and have found it directly affects autophagy which brings to light a new role of SNX-BAR proteins in autophagy regulation.

Candidate Name: Bo Qiu
Title: Travel Time Forecasting on a Freeway Corridor: a Dynamic Information Fusion Model based on the Machine Learning Approach
 November 10, 2021  1:00 PM
Location: TRB

The metropolitan areas suffer more traffic, the change in travel time is very complex as it can be influenced by various factors, many of which are also unpredictable. Random forest was applied in the travel time prediction application to overcome the overfitting problem. Furthermore, the attention mechanism is implemented by developing the neural network to capture the inner relationship within the traffic data. The proposed long short memory neural network with attention mechanism method achieves its superior capability for TTP longer than 15 minutes (30 min to 60 min), overcoming the performance issue through long temporal dependency and memory blocks. To validate the accuracy and reliability of proposed models, the proposed approaches are tested using a freeway corridor in Charlotte, North Carolina, using the probe vehicle-based traffic data. Detailed information about the input variables and data preprocessing was presented. The results indicate that all proposed TTP models predicting in 15 minutes show better prediction performance over the other time horizons. A comparison with other prediction methods validates that the proposed hybrid LSTM and RF method can achieve a better prediction performance in accuracy and efficiency, proving its deployment is one of the successful solutions to critical, real-world transportation challenges.

Candidate Name: Karla Natalia Villatoro Godoy
Title: Three Essays on Corporate Financial Policies
 October 29, 2021  2:00 PM
Location: Virtual

Candidate Name: William Ray Leach
Title: Ambiguous Loss and Parental Traumatic Brain Injury
 November 04, 2021  12:00 PM
Location: Virtual- Email for Zoom Link


WILLIAM RAY LEACH. Ambiguous Loss and Parental Traumatic Brain Injury
(Under the direction of DR. DREW POLLY)

Parental traumatic brain injury (PTBI) and the effect it has on adolescents living in the home has been mostly avoided in the current literature. Even more rare in the literature is the idea of ambiguous loss, coined by Boss (1991). An ambiguous loss refers to a loss of someone who has not died, but who is also not the same person as before the injury, physically or mentally. Consequently, the loss is unclear and requires constant recalibration by the uninjured family members to accept their ever-changing injured family member. Together, no researcher has ever studied ambiguous loss as it relates to PTBI.
This study focused on three research questions:
Research Question 1: As it pertains to PTBI, what is the influence of ambiguous loss when experienced during adolescence?
Research Question 2: When PTBI is experienced in adolescence, how does the perception of ambiguous loss result in tangible consequences later in life?
Research Question 3: In what ways do adolescents experiencing ambiguous loss from PTBI describe their family, self, and situation? 
Using a qualitative approach, this phenomenological dissertation found that ambiguous loss affects adolescents in different ways and at different times after the injury has occurred. Ambiguous loss can also result in tangible consequences later in their life. The time since the injury can affect the severity of feelings of ambiguous loss, however, this study also found that PTBI adolescents can exhibit traits of resilience through their experience.

Candidate Name: Morium B. Bably
Title: Infant Feeding Practices and Weight Status among WIC Participants
 October 29, 2021  1:00 PM
Location: https://uncc.zoom.us/j/9760036795

Appropriate infant and child feeding practices and balanced nutrition can significantly reduce malnutrition and can contribute to optimal physical, mental, and developmental growth of children. Childhood obesity is a major public health concern in the United States and is associated with both physical and psychological consequences and decreased health-related quality of life. Early life feeding practices and nutrients intake starting from birth to 2 years can significantly contribute to the development of obesity. This dissertation aimed to develop three manuscripts to understand the association between infant feeding practices including bottle feeding practices, initiation of added sugar and added sugar intake, and children’s BMI-for-age percentile at 36 months old among Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) participants. First manuscript examined the association between added sugar consumption at young age and BMI-for-age percentile at 36 months old among WIC participants. Second manuscript examined factors associated with initiation of added sugar among WIC participants. Third manuscript examined the association between usual daily intake of added sugar at young age and BMI-for-age percentile at 36 months old among WIC participants. Data were from the WIC Infant and Toddler Feeding Practices Study-2 (ITFPS-2). The ITFPS-2, a longitudinal study of WIC participants (mothers and their children) began in 2013. First, Cox proportional hazards model was used to identify factors associated with bottle cessation, and multivariate linear regression to examine the association between age of bottle cessation and BMI. Second, Cox proportional hazards model examined factors associated with introducing added sugar. Third, bivariate analysis was used to examine the association between usual daily intake of added sugar before age 2 years old and BMI-for-age-percentile at 36 months old. The first research study indicates about 34% of children used a bottle longer than 12 months, and 13% longer than 18 months. Bottle cessation at older ages was associated with Hispanic ethnicity, multiparity, low income, low education, higher caregiver weight, and not initiating breastfeeding, and adjusted children’s BMI-for-age percentile at age 36 months increased by 0.47 for each additional month of bottle use. The second research study indicates about 25% of children initiated added sugar at or before 7 months. Contributing factors were caregiver’s race/ethnicity, education, employment, weight status, parity, child sex, and premature birth (all p<0.05). The third research study indicates the mean added sugar intake ≤7 months, 8-13 months, and 14-24 months were 0.23 teaspoon (tsp), 3.44 tsp, and 11 tsp, respectively. Bivariate analysis indicates added sugar intake before 2 years old is associated with children’s BMI-for-age-percentile at 36 months old. These research studies indicate a need for health care advocacy programs and intervention to educate the caregivers to practice appropriate feeding practices among infants and children aged 2 or younger.

Candidate Name: Wen Zhang
Title: Stress wave propagation and tunability in 1D granular systems
 November 03, 2021  9:00 AM
Location: Zoom: https://uncc.zoom.us/j/7690604878?pwd=M0FnakcyNmVCVkJsYXhwQ1RCSFpDQT09

Stress wave propagation in granular materials subjected to dynamic loadings has attracted much attention for exploring new physical phenomena. One-dimensional (1D) granular systems, a type of artificially designed granular materials consisting of periodically aligned discrete particles, are demonstrated to produce unprecedented wave properties that are notably different from conventional engineering materials. By designing the critical characteristics of 1D granular systems, a remarkable tunability can be achieved, which yields various engineering applications. Therefore, it is of great significance to fundamentally investigate the stress wave propagation and tunability in 1D granular systems.
Firstly, the solitary wave propagation within 1D granular crystals based on composite cylinders is systematically investigated via experiments, numerical simulations, and theoretical analysis. Next, we investigate the properties of Nesterenko solitary wave supported by one-dimensional granular chains and achieve an equivalent wave transmission among various materials and dimensions. Furthermore, we develop efficient and controllable stress wave attenuation approaches by considering I. Strain-softening behaviors; II. Kirigami-based structures. Finally, we design a 1D cylindrical granular system and comprehensively investigate solitary wave tuning strategies based on the system through mass, modulus, and thickness mismatch. Results unlock the unique solitary wave tuning mechanism and provide design guidance for next-generation signal measurement and monitoring systems.

Candidate Name: Alicia D. Dervin
Title: Exploring Diasporic Dialects for Black Women in College Composition and Communication: A Critical Reflective Narrative Inquiry
 September 17, 2021  11:00 AM
Location: Virtual (Zoom)

Historically, standard English language ideologies have been perpetually ingrained in American educational practices and policies (Smitherman, 2017; Wong & Teuben-Rowe, 1997). These practices are not limited to K-12 studies and maintain a position of dominance in higher education (Álvarez-Mosquera & Marín-Gutiérrez, 2020). Calls for diversity in curriculum and pedagogical practices currently involve increasing demands for linguistic inclusion that reflects the diversity of student populations (CCCC, 2020). This study explores how Black women students across the diaspora who use home and/or native languages, dialects, and accents navigate their identities in academic spaces of higher learning where standard English language ideologies are often the only acceptable language varieties that are valued or encouraged. Data was collected through the use of virtual semi-structured interviews using Seidman’s (2006) method of three 90-minute interviews. A single focus group interview with all three participants was conducted as well. All interviews took place during the summer of 2021. Data was analyzed using a qualitative, narrative-based approach that included emphasis on both small stories (De Fina and Georgakopoulou, 2012) and dominant narratives (Lyotard, 1984). This research suggests the experiences of Black women in college composition and communications include themes like feelings of rejection, inadequacies, pressure to conform, and a lack of linguistic agency.