University of Tennessee Institute of Agriculture
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Neural Mechanisms of Visual Stability
No full textWe examined the mechanisms that support processes of transsaccadic visual stability by measuring hemodynamic activity across cortical areas associated with spatial working memory and saccade updating during a transsasccadic change detection task. Participants were presented with a saccade target and instructed to execute a saccade to the target. In some trials, the color of the saccade target would change during the saccade, and participants were asked to report whether they detected a change in a two-alternative forced choice task. Further, we used the postsaccadic blanking paradigm, where the saccade target briefly disappears upon saccade onset and reappears after 250ms, to manipulate stability in half of the trials. To examine how stability processes generalize to non-target information, we further included a session where the item probed for report was a peripheral target, rather than the target of the saccade. The results demonstrated that blanking significantly improved sensitivity to changes of the target object during the saccade, both for the saccade target object and the peripheral target object. Neuroimaging data further demonstrated that both spatial memory mechanisms and saccade updating mechanisms were recruited across the task, however the saccade updating mechanisms were particularly recruited for disruptions of visual stability of the saccade target object and maintained stability for a peripheral target. Thus, while disruptions to visual stability result in similar behavioral results for the saccade target and a peripheral target item, the mechanisms of stability appear to differ, possibly due to differences in storage of information across the saccade or different attentional mechanisms
Filtered Angular Discretizations in Radiation Transport
No full textThis dissertation focuses on angular approximations of the radiation transport equation (RTE), which governs the evolution of particle density in space, angle, and time. We investigate the spherical harmonics and discrete ordinates methods, two widely used angular discretizations known for their spectral convergence. While spectral convergence offers high accuracy for smooth solutions, its performance deteriorates in the context of non-smooth solutions.
To address this limitation, we explore a regularization strategy known as filtering, which modifies angular discretizations by introducing a dissipative operator that damps high-frequency, angular modes.
We derive an error estimate of the filtered spherical harmonic solution using the theory of hypocoercivity, which characterizes decay to equilibrium, even in the absence of coercivity. This analysis highlights the trade-off between stability and consistency in filtered regularization.
We propose a novel approach for tuning the filter strength of the filtered spherical harmonic method locally, in space and time. The filter strength is modeled by a neural network, whose input features include local moment information and material properties. The network parameters are determined by solving a PDE-constrained minimization problem. This adaptive approach suppresses nonphysical oscillations, while preserving the accuracy of the spherical harmonic solution in smooth regions. Numerical experiments demonstrate that this method can substantially reduce the error of the original filtered spherical harmonic method with constant filter strength.
We study filtered approximations in the context of thermal radiative transfer (TRT), where the discrete ordinates method is employed. The variable Eddington factor (VEF) method couples the first two angular moments of the transport equation with the TRT equations. We develop a filtering strategy that maintains consistency between the discrete ordinates equations and the moment equations. Numerical experiments demonstrate that this filtering strategy significantly improves the quality of the TRT approximation, particularly when the solution lacks regularity
The Effect of Motor, Cognitive, and Combined Fatigue on Motor Performance, Retention, and Transfer.
No full textThis dissertation aimed to synthesize existing literature on acute state motor and cognitive fatigue within a military population. Significant effort has aimed to explore the underpinnings of human fatigue, how it is perceived and appraised, and subsequent impacts on motor performance capabilities. Despite extensive exploration, a notable gap exists in exploring the combined effects of fatigue on subsequent motor performance within a controlled laboratory setting. To our knowledge, no study has examined the interaction between performance and learning under a state of combined fatigue, nor the transferability of skills acquired in practice to combat-specific environments.
Study one served as a foundational study and aimed to compare the effects of isolated fatigue (motor, cognitive fatigue) and combined fatigue on subsequent motor performance. In support of previous findings, results demonstrated that isolated motor and cognitive fatigue resulted in slower anticipatory reaction time. Notably, findings demonstrated the compounding effect of simultaneous motor and cognitive fatigue, resulting in performance deterioration that exceeded the additive effects of isolated fatigue alone.
Study two aimed to extend these findings by examining whether the observed effects would generalize to the military population, enhancing the ecological validity and increasing the applicability to real-world military operations. Consistent with study one, results demonstrated decreased military marksmanship performance following isolated motor and cognitive fatigue. Additionally, results demonstrated a negative, additive effect on marksmanship accuracy and effect when compared to isolated fatigue.
Study three aimed to expand these results further by exploring the impact of fatigue during practice on skill performance, acquisition, and transfer to real-world combat tasks. Results indicated that practice that incorporates similar demands of the performance environment resulted in improved skill acquisition and transfer. For instance, participants who practiced under fatigued conditions outperformed those who trained without fatigue when assessed during retention and transfer testing conducted under fatigue. These findings suggest that skill learning and transfer are context-dependent and contingent on the similarity of training to performance environments.
This dissertation not only contributes to the mechanistic influence of fatigue, but more importantly, demonstrates the importance of nesting task-specific training to improve motor performance, learning, and transfer
Computational Characterization of Unsteady Three-dimensional Corner Effects in a Scramjet Isolator Flow Path for Early Unstart Detection
No full textThe complexity of a scramjet isolator flowfield is magnified by the presence of wall-bounded intersecting no-slip walls that introduce secondary flows, vortical structures, and turbulent boundary layers interacting with the shock structure of the primary flowfield. Experimental studies have shown that the onset and magnitude of corner flow separation can have a significant impact on primary centerline separation in the presence of strong Shock Boundary Layer Interactions (SBLI). A computational study of the three-dimensional characteristics of a scramjet isolator flow path is conducted to gain an understanding of how viscous corner interactions influence the formation and stability of the isolator shock train. This work leverages a multi-fidelity computational fluid dynamics (CFD) campaign with an experimental study to identify the underlying physics introduced by the viscous corner region affecting the primary flowfield. A cylindrical rod was inserted into the flow downstream of the isolator to simulate pressure rises associated with combustion-induced effects that can lead to upstream shock propagation, premature mode transition, and potential unstart. This enables the experimental facility to fine-tune the onset and position of the pre-combustion shock train (PCST) and track the conditions that can lead to the detection of the unstart process. The experimental data are collected via static pressure probes, Kulite pressure probes, and Background Oriented Schlieren (BOS) imaging to give a quantitative and qualitative analysis of the flowfield. This CFD study employs an Improved Delayed Detached Eddy Simulation (IDDES) to capture the flow mechanisms that drive the formation and upstream propagation of the pre-combustion shock train (PCST) within the scramjet isolator. The mechanisms and flow physics investigated include downstream flow blockage, shock train behavior, and viscous corner interactions with the shock train. Focus is placed on the viscous corner regions, where three-dimensional secondary flows are tracked throughout the extent of the shock train. These corner interactions are analyzed to characterize and assess their influence on the unsteady behavior of the shock system. The magnitude and structure of the corner vortices are found to vary in response to the shock train position, where correlations are identified between vortex evolution and shock train unsteadiness
Improving Independent Purchasing Skills in Postsecondary Students with Disabilities
No full textPostsecondary educational opportunities for transition-age students with disabilities have increased through the creation and expansion of inclusive postsecondary education (IPSE) programs. One of the primary purposes of IPSE programs is to improve their students’ employability and independent daily living skills (Grigal et al., 2019). Having proficient purchasing skills is an important daily living skill that can improve the long-term outcomes of individuals with disabilities.
This dissertation includes three chapters. Chapter One provides an overview of inclusive postsecondary education (IPSE) programs, academic skill level of students with disabilities, the instructional hierarchical model of skill acquisition, previous purchasing skill intervention, use of student response cards during group instruction, and the benefits of student response cards for students with disabilities. Chapter Two details a study in which a researcher-developed, classroom-based purchasing skill intervention was implemented with postsecondary students with intellectual and/or developmental disabilities (IDD) to teach them the one dollar more strategy when counting money for price values up to $39. The intervention included eight modules with explicit, small-group instruction and learning trials with multiple exemplars using student response cards. Chapter Three discusses the results of the current study which included statistical analyses, intervention teach data, and an overview of individual score changes between the pretest and posttest measures. Chapter Four discusses the implications and limitations of using a classroom-room based purchasing skill intervention to enhance students’ acquisition of the one dollar more strategy to count money. This third chapter also offers considerations for future research endeavors in this area
Implementing a Multimodal Pain Management Best Practice Alert for Pediatric Orthopedic Injury Patients in an Adolescent Medical-Surgical Unit
Get PDFBACKGROUND: One in five children is at risk for orthopedic injury, and 80% of emergency department visits involve pain. Evidence concludes a multimodal approach improves pain management satisfaction in this population. This project aimed to implement a standardized, multimodal pain management process for pediatric orthopedic patients.
LOCAL PROBLEM: The project site was a 24-bed adolescent medical-surgical unit at a Magnet-designated pediatric level one trauma and teaching hospital in St. Louis, MO. Inadequate pain management after orthopedic injuries or surgery was a consistent issue. An informal survey of unit nursing staff notably revealed that 100% of nurses felt pain management was insufficient.
METHODS: Guided by the Evidence-Based Practice Improvement (EBPI) model, the project involved unit nursing staff, pediatric orthopedic patients aged 3–18 with acute orthopedic injuries (fractures, trauma, sports injuries), their families, and therapy personnel. Interventions were tailored to educational needs and aimed to standardize pain management. Change was evaluated through chart reviews, surveys, and pre-/post-implementation data on knowledge, pain scores, and satisfaction.
INTERVENTIONS: The intervention introduced a standardized pain management process over nine weeks using a stepwise approach: pre-BPA satisfaction survey, rounding-based satisfaction survey, pre-tip sheet knowledge survey (pharmacologic and non-pharmacologic), tip sheet implementation, post-tip sheet knowledge survey, BPA implementation, and post-BPA satisfaction survey to evaluate system performance and address identified issues.
RESULTS: Pediatric orthopedic patients received non-pharmacological or multimodal pain management more often than pharmacological methods alone, with multimodal approaches linked to lower pain scores. Implementing tip sheets and BPAs significantly improved nursing knowledge and patient satisfaction, highlighting the effectiveness of the educational interventions.
CONCLUSIONS: Implementing a standardized multimodal pain management BPA tool and tip sheets improved patient satisfaction, pain control, and staff knowledge. This approach supports patient- and family-centered care, enhances the healthcare experience, and is recommended for broader use. An educational binder on each inpatient unit is advised to promote sustainability
The Creating Opportunities for Personal Empowerment (COPE) Program: An Evidence-Based Practice Improvement Project to Improve Adolescent Depression
Get PDFBACKGROUND: Depression rates in adolescents are rising, while screening and treatment rates remain minimal. Untreated depression leads to poor outcomes related to self-harm and suicide, physical health, education, relationships, and decision making.
LOCAL PROBLEM: A rural Ohio middle school identified increases in mental health issues across its adolescent population. The school did not previously screen all students with a standardized screening tool or teach a mental health program.
METHODS: A Doctor of Nursing Practice (DNP) student developed a project to increase depression screening and improve depression symptoms through implementation of a standardized screening tool and cognitive-behavioral therapy (CBT)-based skill building program. The guiding framework of this project was the evidence-based practice improvement (EBPI) model.
INTERVENTIONS: The Creating Opportunities for Personal Empowerment (COPE) program, a manualized cognitive-behavioral program, was implemented in seven weekly sessions. The Patient Health Questionnaire Modified for Adolescents (PHQ-A) was administered before the first session, immediately after completion of the last session, and two-months post-program completion time periods to monitor depression scores. Students who screen positive for depression in the moderate range or above were referred for further assessment and referral.
RESULTS: Implementation of the PHQ-A increased depression screening and referral rates at the site. Screening scores throughout COPE completion displayed decreases for both the entire sample as well as students who were identified as having depression at baseline. Both groups had clinically significant decreases from the pre-to-post-COPE and post-COPE-to-follow-up scores, as well as clinically and statistically significant decreases from pre-COPE-to-follow-up scores.
CONCLUSIONS: Implementing a manualized cognitive-behavioral therapy-based program and standardized screening tool in the classroom setting can improve depression screening and adolescent coping skills
