AUETD (Auburn University)
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Enhanced Indirect and Convex Optimization Methods for Generating Minimum-Fuel Low-Thrust Trajectories
Get PDFThe high costs of space missions necessitate optimization across all mission aspects, particularly fuel consumption, which impacts both economic feasibility and payload capacity. Electric propulsion systems, with higher fuel efficiency but lower thrust output (compared to their chemical counterparts), have been used for several decades as a promising alternative propulsion system. To optimize spacecraft equipped with electric propulsion systems, researchers employ two optimization paradigms: indirect and direct methods.
Indirect methods, based on the calculus of variations and Pontryagin’s minimum principle, transform the task of solving an optimization problem into finding the roots of nonlinear boundary-value problems (BVPs). This is achieved by introducing time-varying Lagrange multipliers (a.k.a. costates) and constant Lagrange multipliers. While indirect methods offer high-precision (i.e., with respect to time and resolution) and the solutions are guaranteed to be extremal, the resulting BVPs exhibit high sensitivity to the unknown decision variables (typically costates) and can become challenging to form and solve, when they are applied to constrained nonlinear optimization problems.
Direct methods, on the other hand, discretize variables early, converting the problem into a nonlinear programming (NLP) problem. A convex optimization problem is a specific type of NLP problem where the objective function and constraint set are all ``convex,'' meaning that any local minimum is also a global minimum, making it significantly easier to solve with guaranteed globally optimal solutions, while a general NLP problem can have multiple local minima, making it potentially much harder to find the true optimal solution; essentially, convex optimization is a subset of nonlinear programming with the added benefit of guaranteed global optimality due to its convex structure. By incorporating convexification techniques and leveraging convex optimization tools, direct methods offer a computationally feasible approach. This research proposes methods that alleviate some of the difficulties associated with solving minimum-fuel low-thrust trajectory optimization problems using both indirect and direct methods
Understanding The Relationship Between Performance and Propulsion Mechanics in Collegiate Wheelchair Basketball Athletes
No full textThis dissertation investigated propulsion mechanics used by collegiate wheelchair basketball athletes (WBA) of different performance levels during straight line and pivoting tasks. Two investigations were conducted, focusing on the 1st, 3rd, and 5th pushes during sport-specific movements. Aim I analyzed trunk, shoulder, and wrist displacement in the sagittal plane, as well as push length and push patterns during a linear 20-meter sprint. Aim II examined frontal and sagittal trunk displacement, as well as sagittal shoulder displacement on the pivot and non-pivot side during a change of direction task (CoD).
Results from Aim I revealed significant differences between high-performing (HP) and low-performing (LP) athletes. HP athletes demonstrated a different pattern of trunk control during maximal sprinting compared to LP. HP employed a pattern of a near zero displacement in the sagittal plane during the 3rd and 5th pushes. Asymmetric pushing, particularly during the 3rd push, was associated with faster sprint times. Left-hand push patterns and push length differentiated between performance groups.
Aim II found no statistical significance differences between groups. However, unique propulsion characteristics, frontal trunk displacement and shoulder displacement on the pivot side, were observed, frontal trunk displacement and shoulder displacement on the pivot side. HP athletes utilized lateral trunk flexion and exhibited a gradual shift towards a neutral position during the CoD task, suggesting increased stability and control of their trunk.
These findings provide valuable insights into the sprinting mechanics employed by WBA. This study lays a foundation for developing targeted training interventions and future research directions in para-sport biomechanics
Anxiety Transmission within the Mother-Daughter Relationship: A Phenomenological Qualitative Study
No full textFor children of parents who exhibit symptoms of anxiety, the long-term effects of anxiety on their upbringing can be significant and enduring. Maternal anxiety can adversely impact children’s ability to cope with uncertainty through the modeling of anxious interpretations of ambiguity. The purpose of this qualitative transcendental phenomenological study is to explore how the experiences of being raised by a mother who exhibits symptoms of anxiety affected subsequent anxiety symptomatology for adult daughters. Principles from Bandura’s Social Cognitive Theory of Social Referencing served as the conceptual framework for this study. Data were collected using semistructured interviews and analyzed to determine emergent themes. In addition to contributing to family and child counseling literature, this study can provide information that can help adult daughters of mothers with anxiety understand how their early experiences may have influenced their current anxious thoughts and feelings. The study findings may also be useful to clinicians in fostering more healthy thinking and coping in their female clients who are growing up in homes where anxious affect, cognitions, and behavior are modeled.
Keywords: anxiety, mother, daughters, family, parenting, information processing biases, social referencin
Valorization of Loblolly Pine (Pinus taeda) Downed Timber: Degradation and Recovery of Natural Polymers to Improve Bioeconomy Strategies
No full textIn the aftermath of events such as hurricanes, downed timber's economic impact can reach billions. Accurate forecasting of stumpage prices post-events is crucial yet challenging due to data nature. This study innovatively applies wavelet analysis in forestry economic analysis to uncover relationships between timber market indices and hurricane seasons. Combining traditional correlation and wavelet coherence analysis deepens the understanding of timber market dynamics and the effects of hurricanes. The study highlights recent advancements in wavelet methodology, leveraging open-source R packages like WaveletComp and Wavelet-ARIMA. The Wavelet-ARIMA model effectively reduces noise, enhancing prediction accuracy across an extensive dataset encompassing various indices.
Simultaneously, the study investigates hurricane-downed timber degradation in Alabama using near-infrared spectroscopy (NIR) and acoustic technology. Analyzing 30 loblolly pine trees, the research focuses on wood composition analysis, employing nonlinear techniques, smoothing optimization, and first derivative as a mathematical pretreatment, coupled with Box-Behnken (BB) experimental design. Utilizing 15 core samples, the models demonstrate efficiency comparable to complete sets, showcasing the potential for resource-efficient wood composition prediction. Spectral pretreatment investigations underscore the first derivative's efficacy and the balanced distribution of explained variance. Support Vector Machines (SVM) models exhibit superior predictive performances, particularly with a polynomial kernel. This innovative approach, combining reduced sample sizes and simplified spectral treatments, not only presents a promising avenue for wood composition prediction but also offers streamlined methodologies for scalability in forestry and wood industry practices, with implications for research and practical applications.
Moreover, the study unveils distinct temporal patterns in sound-wave propagation and NIR measurements. NIR data’s principal component analysis (PCA) captures temporal phases, while transverse sound-wave measurements indicate consistent stress wave velocity variations. Thermogravimetric analysis (TGA) reveals significant shifts, emphasizing temporal dynamics, and chemical characterization highlights variations in lignin and carbohydrate fractions. The findings underscore the dynamic degradation process of hurricane-downed timber, emphasizing potential applications in timber quality assessment and biorefinery operations. Contributing to resilient and sustainable timber utilization post-natural disasters, the study enriches understanding of composition changes over time and the weathering process.
Furthermore, the study delves into the weathering effects on downed timber over 12 months, mainly focusing on lignin and carbohydrate composition changes. The model study with harvested loblolly pine trees reveals gradual increases in Klason lignin content over time, indicating potential improvements in recovery operations. Changes in Fourier transform infrared (FTIR) spectra and Thermogravimetric analysis (TGA) demonstrate alterations in chemical composition, structure, and thermal properties of co-solvent enhanced lignin fractionation (CELF) lignin samples. Differential scanning calorimetry (DSC) analysis provided specific glass transition temperature (Tg) values, while Gel-permeation chromatography (GPC) indicated differences in molecular weight distribution consistent with expected natural degradation. Nuclear magnetic resonance (NMR) of the cell wall composition and CELF lignin obtained corroborate the observations. This comprehensive investigation contributes to understanding the intricate weathering effects on timber, offering valuable insights for sustainable utilization and recovery operations post-natural disasters.
The consistency in lignin quality suggests the robustness and reliability of the CELF process in effectively isolating lignin from different stages of timber degradation. The process appears to be resilient to variations in the structural integrity and chemical composition of the starting material, ensuring that the resulting lignin maintains similar characteristics regardless of the initial state of the downed timber
Multilingual Learners and Agricultural Education: A three-article dissertation exploring the needs of both instructor and learner
Get PDFThis study examined the instructional preparedness and professional development needs
of high school agricultural education (SBAE) teachers in California's Central Region to support
multilingual learners (MLs). Using culturally responsive teaching, the sheltered instruction
observation protocol (SIOP), and andragogy as theoretical frameworks, the research explored
SBAE teacher qualifications, language proficiency, and familiarity with strategies for MLs.
Findings revealed that while teachers were confident in teaching fluent English speakers, they
faced challenges in addressing the needs of beginning-level ML students, primarily due to
limited professional development specifically tailored for MLs. Many educators recognized
strategies like translation tools and scaffolding but struggled with consistent implementation. The
predominantly White, monolingual teaching group highlighted barriers, including limited
training and challenges in adapting to students' linguistic and cultural diversity.
Recommendations emphasized the need for targeted professional development in culturally
responsive teaching, SIOP, and academic vocabulary to strengthen instructional practices. Future
research should assess the impact of ongoing training on teacher preparedness and the
educational outcomes for MLs in agricultural programs
Designing Sustainability with Emotions by Communities Who Care
No full textThe fashion industry has been increasingly scrutinized for its environmentally damaging operations, but fashion companies are not implementing sustainable solutions fast enough to counterbalance the negative environmental and social impacts of the rapidly growing fashion industry. This netnographic study focused on exploring the emotion-based communication of a not-for-profit Facebook (FB) group in the natural setting of an online sharing platform for the implications of apparel sustainable practice. This study identified the emotional elements that are influential to sharing behavior in this FB community and captured the possibility for sustainable practice in everyday settings. The researcher served as a member that was a complete observer of the group and captured data (word for word content) for over one year. Thematic analysis was used to identify, analyze, and report themes in the data. No photos or personal identification was disclosed. Findings include group members having integrity make the online system of sharing work. Participating in their way to this group brought members the sense of autonomy and a cooperative spirit of kindness. The analysis found that the key factors of this group’s emotions to be trust, sincerity, empathy, compassion, benevolence, vulnerability, and sensitivity, and the members’ communicated emotions and the acts of generosity, reciprocity, gratitude, and altruism are associated with the sharing of apparel. These attitudes regarding sharing are in line with other studies that support emotions that can affect challenging social issues such as sustainability. This research aimed to not only identify the emotional elements of the online community but also capture the implication that those communicational elements have for understanding apparel sustainability in real-life practice
Pyrolysis of Woody Biomass and Waste from Additive Manufacturing for the Synthesis of Chemicals and Transportation Fuels
No full textGenerating fuels and chemicals using renewable sources is paramount to mitigate the depletion of energy sources and global warming. Pyrolysis produces bio-oil from the thermochemical conversion of biomass, which can be used for resin and bio-fuel synthesis. This study investigated the effects of the different woody biomass (Douglas fir, eucalyptus, and hybrid poplar) on the properties of pyrolysis products. Poplar bio-oil was found to be the best candidate for resin synthesis applications because of its higher hydroxyl concentration and carbon content. Furthermore, the optimization of the pyrolysis reactor was done using the Box-Behnken response surface methodology to determine the effects of operating parameters. The feed rate and square of temperature significantly affected the bio-oil yield whereas, temperature and the interaction between feed rate and bed height-to-diameter ratio were significant for hydroxyl concentration. Additionally, ex-situ catalytic pyrolysis was carried out to study the effect of catalyst (Cu/Al2O3) on bio-oil. Catalytic pyrolysis increased the amount of carbon, alkyl phenol (from 7.72 to 22.52 area %), and hydrocarbons (from 1.59 to 11.28%) in the bio-oil, which were attributed to deoxygenation and alkylation reactions.
Pyrolysis bio-oil needs further catalytic hydrodeoxygenation for its suitability in fuel applications. However, catalysts screened so far suffer from coke formation. Thus, the effects of Cu-based catalysts on the severe hydrogen treatment of pyrolysis bio-oil were investigated. Cu/Al2O3 catalyst yielded maximum treated oil (50.5%) with higher carbon conversion (67.64%) than conventional catalysts. Additionally, the coke formation was less than 3% for Cu-based catalysts which could be attributed to the lower acidity of Cu-based catalysts.
In addition to fuel, pyrolysis bio-oil could be used to prepare the resin for additive manufacturing. Investigating the circularity of any process is necessary to determine its sustainability. This study further investigated the application of pyrolysis in maintaining the circularity of additive manufacturing. It was observed that sodium silicate in the composite waste of additive manufacturing acts as a catalyst during the pyrolysis, increasing the selectivity towards the generation of hydrocarbons and alkyl phenols. Additionally, sodium silicate increased the phenolic hydroxyl concentration by assisting the degradation of lignin. This proved the applicability of pyrolysis in upcycling additive manufacturing waste to bio-fuel and resin
An Assessment of Alabama Food Pantry Nutrition Environments
Get PDFThe US Dietary Guidelines recommend following a nutrient-dense dietary pattern while limiting added sugars, sodium, and saturated fat for all to maintain a healthy lifestyle and prevent diet-related disease. However, a growing number of US adults have inadequate access to these foods. Similar to retail environments in limited-resource communities, such as grocery outlets and farmers markets, food pantries are increasingly studied sites for healthy food availability and access interventions to support healthy choices among consumers and clients.
This two-study dissertation aims to describe and evaluate a food pantry nutrition environment intervention in a convenience sample of Alabama pantries (n = 55). Supplemental Nutrition Assistance Program – Education (SNAP-Ed) educators provided technical assistance designed to improve a pantry’s nutrition environment. We used a validated assessment tool to determine changes in the environment. We found Alabama pantries demonstrate lower nutrition environments when compared to US averages. We also found technical assistance provided by SNAP-Ed translated into positive significant changes in pantry nutrition environments. Finally, we observed associations among environment changes with pantry and neighborhood characteristics. We also assessed food pantry manager nutrition knowledge, beliefs, and behaviors (n = 44). Managers demonstrated positive nutrition beliefs and behaviors, and average to low-average nutrition knowledge. Data were not associated with pantry nutrition environments. We found pantry characteristics were more strongly associated with a pantry’s nutrition environment score than manager perceptions of nutrition. Our findings demonstrate a continued opportunity to support Alabama pantries in improving healthy food availability and access for clients. Identifying solutions for infrastructural barriers to healthy food distribution may be more influential predictors of healthy pantry practices
Design and development of novel selective LXR/PPAR dual agonists for Alzheimer’s Disease.
Get PDFAlzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of insoluble protein aggregates, i.e., amyloid beta and Tau. Genetic predispositions in amyloid beta (A) and Tau protein processing correlate strongly with disease prevalence. However, pathological hallmarks of AD can exist independently of each other. Additionally, patients with a genetic predisposition may never develop AD, indicating that epigenetic influences and lifestyle choices significantly impact disease initiation and progression.
Mutations in Apolipoprotein E (APOE) constitute the single most significant genetic risk factor for developing AD—the most commonly occurring mutations for APOE result in three different phenotypes: APOE2, APOE3, and APOE4. APOE2 and APOE3 are frequently referred to as neutral alleles, with the former being protective in certain studies. It is the APOE4 allele that poses the most significant risk for AD development, as cholesterol transport is most dramatically altered in these patients, resulting in an increased rate of blood-brain barrier (BBB) degradation and neurovascular dysfunction.
APOE transports lipids in the form of protein complexes that vary in size, density, and function, i.e., HDL, LDL, VLDL, etc. APOE is most abundantly expressed within the brain by astrocytes, a non-neuronal cell type responsible for many regulatory functions, including maintenance of the BBB, formation of myelin, regulation of nutrients, and removal of harmful metabolites, e.g., A and Tau. Current therapeutic applications that modulate APOE target patients with atherosclerotic plaques and promote the removal of lipids from the peripheral tissues, transporting them back to the liver for subsequent elimination. In so doing, HDL (“healthy” cholesterol) is increased, and LDL (“bad” cholesterol) is lowered in a process known as reverse cholesterol transport (RCT).
In the paradigm of RCT-mediated therapeutic benefit, Peroxisome-proliferator-activated receptors (PPARs) and liver-X receptors (LXRs) are enticing targets, as they can directly modulate APOE regulation to improve associated deficits in patients with AD. PPAR/LXRs transcriptionally regulate various genes related to energy regulation, lipid metabolism, and cholesterol clearance through RCT mechanisms. While PPAR and LXR-specific agonists have shown promise in different transgenic animal models with atherosclerosis and AD, they perform poorly in human clinical trials and have failed to achieve FDA approval due to systemic toxicities such as steatosis, neutropenia, edema, and cardiotoxicity. Complicating this issue is the difficulty of attaining therapeutic specificity amongst PPAR/LXR isoform variability and function to prevent undesirable off-target activity in healthy tissue types.
Therefore, our computational design for novel PPAR/LXR compounds has centered around profiling selective ligand interactions across all isoforms of these receptors to gather surface activity relationships and mechanical details that identify novel ligands with improved therapeutic efficacy
Applying the Visual Analysis and Design Principles of Postwar American Modern Furniture to Contemporary Home Living Furniture Design
Get PDFThis thesis discusses how to incorporate the visual analysis of Post War American Modern Furniture into the design of furniture that better suits contemporary lifestyles. Post War American Modern Furniture, also known as Mid-Century American Modern Furniture, holds a classic status in furniture history, and its work from that era remain popular in today's market. The article covers the development of Post War American Modern Furniture, analyzing its design style, elements, features, and concepts, including some classic design pieces. It also explores the differences between modern and post-war life, proposing guiding principles and methods to help designers apply this style to contemporary furniture design. The research results suggest that designing furniture aligned with modern life using the visual analysis of Post War American Modern Furniture is feasible. The thesis concludes by summarizing and condensing the methods, providing designers with a practical tool for successfully creating contemporary home living furniture reflecting the visual analysis of Post War American Modern Furniture