AUETD (Auburn University)
Not a member yet
9771 research outputs found
Sort by
Evaluation of Integrated Weed Control Practices in Conservation Agriculture Legume Row Crops
No full textPeanut (Arachis hypogaea L.) and soybean (Glycine max [L.] Merrell) are vital legume crops facing significant yield losses from weed competition, exacerbated by the rise of herbicide-resistant weeds like Palmer amaranth (Amaranthus palmeri). Conservation tillage systems, while beneficial for soil health, increase reliance on herbicides. This thesis focuses on investigating integrated weed management strategies combining cover crops and reduced tillage with herbicide programs in Alabama. Two field studies were conducted. The first evaluated strip-tilled peanut following cover crops (cereal rye - Secale cereale, wheat - Triticum aestivum, radish - Raphanus sativus, mixture) or fallow (disk-tilled, no-till) combined with four herbicide applications (PRE, POST, PRE+POST, NT) across all temporal and spatial replication. The second study assessed sweep tillage frequencies (single, double, triple pass) following a rolled-crimped cereal rye (Secale cereale) cover crop compared to a PRE+POST herbicide program and winter fallow (NT) in soybean across two locations. Weed biomass, density, visual control, and crop yield were measured. In the peanut study, rye, radish, and the mixture produced substantial biomass (>6000 kg ha⁻¹), providing early season weed suppression. PRE herbicides reduced early weed biomass by approximately 70% compared to NT plots (192 vs 651 kg ha⁻¹). Untimely radish termination led to volunteer radish issues without PRE herbicides. Late-season weed control relied heavily on herbicides; the PRE+POST program significantly reduced weed biomass (e.g., 742 kg ha⁻¹ vs >1300 kg ha⁻¹ for PRE/POST alone at one site) and provided the highest peanut yields (up to 3820 kg ha⁻¹), significantly outperforming NT checks (1333-1640 kg ha⁻¹). In the soybean study, cereal rye (Secale cereale) produced ~6000 kg ha⁻¹ biomass. The PRE+POST herbicide program consistently provided the best weed control (e.g., 79% visual control at 11 WAP) and the highest relative soybean yield (104% at the high weed pressure site, EVS). Sweep tillage efficacy varied; triple sweep provided intermediate control (60% visual rating, 1807 kg ha⁻¹ biomass at EVS 11 WAP), while single sweep often resulted in high late season weed biomass (5956 kg ha⁻¹ at EVS 11 WAP) and density, sometimes exceeding winter fallow. These studies demonstrate that integrating high-biomass cover crops, particularly cereal rye (Secale cereale), with robust, multi-mode-of-action herbicide programs (PRE+POST) enhances weed control and maximizes yield in peanut and soybean conservation systems. While cover crops provide valuable early suppression, their effect diminishes and sweep tillage efficacy is limited and context-dependent, generally not replacing effective herbicide programs, especially under high weed pressure situations
Time-Varying Associations Between Hopelessness, Agitation, Shape/Weight Concerns, Body Connection, Dietary Restraint, and Desire to Kill Self in a Military Sample
No full textSuicidal ideation and dietary restraint are prevalent, especially in military samples. Group-level analyses have identified hopelessness, agitation, weight/shape concerns, and interoceptive deficits as potential risk factors for suicidal ideation and dietary restraint. However, limited research has examined how these risk factors ideographically predict suicidal desire and dietary restraint over time, which is the aim of this study. In our military sample, participants (N = 46, Mage = 35.02, 84.8% White, 97.8% not Hispanic/Latine) completed surveys multiple times each day for a month. Time-varying vector autoregressive models were used to generate unique networks for each participant. To interpret the networks, descriptive and qualitative categories were created. Prediction patterns for suicidal desire and dietary restraint were largely idiographic, even amongst participants with similar symptom trajectories for suicidal desire and dietary restraint across the EMA period. These findings highlight that suicidal desire and dietary restraint are complex systems with predictor patterns that are heterogenous across people and over time
Post-Traumatic Stress Disorder and Self-Injurious Thoughts and Behaviors: Exploratory Network Analysis and Network Comparison Test in Two Trauma-Exposed Samples
Get PDFPre-existing psychopathology, such as post-traumatic stress disorder (PTSD), is a well-established risk factor for self-injurious thoughts and behaviors (SITBs). However, previous studies examining the link between PTSD and SITBs have had mixed results, likely due to their limited ability to capture the complexities of both phenomena. Network analysis is an advanced statistical method that is equipped to account for these complexities. To date, several exploratory networks on PTSD and SITBs have been estimated; however, formal replication of these exploratory network structures has not been conducted. Thus, in the current study, we estimated an exploratory network of DSM-5 PTSD symptoms and SITBs (i.e., suicidal ideation, non-suicidal self-injury, and suicidal behaviors) in a trauma-exposed sample (N=893) and identified relevant bridge symptoms through measures of bridge centrality. Then, we assessed replicability of findings by employing a network comparison test with a second trauma-exposed sample (N=367). Risky or self-destructive behavior and negative beliefs about the self, world, and others emerged as prominent bridge symptoms for PTSD. Suicidal ideation emerged as a prominent bridge symptom for SITBs. Moreover, network comparison test results showed that across all measurement indices, the two networks were not statistically different from each other. Results from our study are consistent with previous studies that have found the PTSD symptoms of risky and self-destructive behaviors and negative beliefs about the self, world, and others to be most related to SITBs, specifically suicidal ideation. This evidence allows for the identification of treatment targets to disrupt the PTSD-SITB symptom presentation
The Effects of High Temperature Ion Implantation in β-Ga2O3
Get PDFDoping electronic oxides is often challenging due to issues like self-compensation, limited solubility, and defect formation. Additionally, there is typically an imbalance in favor of one type of conductivity, most commonly n-type. Another key factor is the impact of post-growth annealing, used for forming contacts or activating dopants, on material conductivity, which depends on the annealing environment. Ion implantation is an appealing technique for device processing because it enables precise control over dopant concentration and spatial distribution, allowing selective doping of specific regions within a material. While the effectiveness of high-temperature ion implantation in SiC is well-documented, this work focuses on investigating its influence on the conductivity and crystal structure of β-Ga2O3. This study highlights the benefits of performing silicon ion (Si+) implantation at elevated temperatures to achieve controlled, heavily doped regions in gallium oxide. Silicon implants were introduced into MBE-grown (010) β-Ga2O3 films at both room temperature (RT, 25 °C) and high temperature (HT, 600 °C) to form approximately 350 nm deep Si-doped layers with average concentrations of around 1.2 × 10^20 cm^-3. While the RT samples were too resistive to measure, the HT samples demonstrated remarkable results, achieving a Si dopant activation efficiency of 82.1%. They also exhibited a high sheet electron concentration of 3.3 × 10^15 cm^-2 and an excellent mobility of 92.8 cm^2/V ·s at room temperature. Additionally, X-ray diffraction analysis revealed that high-temperature implantation minimized the formation of secondary Ga2O3 phases and reduced structural defects and lattice damage. These findings underscore the potential of high-temperature ion implantation for fabricating ultra-low-resistance, heavily doped Ga2O3 layers. In this study, Fe-doped β-Ga2O3 substrates were implanted with Si+ ions at 275 and 425 keV to create a 300 nm thick doping profile, verified by SRIM simulations. Post-implantation annealing was performed at 970 °C and 1050 °C to activate the samples. Ohmic contacts were fabricated using a Ti/Au metal stack, with a 60 nm Ti layer followed by a 150 nm Au layer, and post-deposition annealing was conducted in a high-vacuum chamber at 450 °C for 1 minute. Samples annealed at 970 ◦C exhibited a linear I-V response between -0.2 V and +0.2 V, confirming the formation of ohmic contacts, while samples annealed at 1050 ◦C appeared more resistive. Schottky barrier diodes were also fabricated on in-situ Si-doped samples, showing a rectification ratio of 10^5 and a turn-on voltage of around 1 V. C-V measurements indicated a carrier concentration of 1.9 × 10^17 cm^-3, closely aligning with the target doping level of 2 × 10^17 cm^-3. This study investigates high-temperature (HT) Germanium (Ge) ion implantation to understand its impact on the structural morphology of β-Ga2O3. While prior work on Si ion implantation at 600 ◦C showed reduced lattice deformation compared to room temperature implantation, the influence of implantation-induced defects on material conductivity remains underexplored. Ge was implanted into Fe-doped β-Ga2O3 substrates with (010) orientation at room temperature and 600°C using a dose of 1.5 × 10^15 ions/cm^2. HRXRD analysis revealed that HT implantation resulted in less crystal deformation than room-temperature implantation. STEM analysis further identified dislocations at the interface of the MBE-grown β-Ga2O3 film and substrate, as well as within the film itself. Additional studies are necessary to fully characterize these dislocations and their effects on material properties
An Exploratory Approach of Developing Visually Appealing Furniture Design Concepts by Employing Psychological Effects
No full textThe conscious application of perceptual psychology in furniture design has not been fully explored in shaping user experience. The psychology of perception involves cross-disciplinary applications. Despite extensive research on the use of perception, designers still lack a systematic approach to extend design inspiration in the field of furniture design. The application of perception involves many fields, but how to combine these technologies with furniture design still needs to be explored.
This study addresses this gap by proposing an exploratory framework that systematically utilizes psychological effects to produce visually compelling furniture concepts. Analyzing the principle of perception combined with perception of furniture design will allow the development of guidelines that will aid in the design and understanding of furniture that utilizes the principles of perception. Doing so will help designers move from emotional selection and analysis to prototyping. The analysis of the perception principle helps the designer to extract the elements that play a role in different perceptions and combine them with the characteristics of the furniture. In the guidelines, a set of concrete design schemes is proposed. Using this process, the designer can specify the design by the desired effect, allowing the designer to fully explore the application of perceptual psychology in enhancing visual appeal.
This study hopes to provide practical exploration methods for designers that enables designers to go beyond traditional design themes and add design inspiration for the perception aspect. The guidelines allow designers to effectively combine psychology with furniture and explore eye-catching furniture designs. By connecting cognitive psychology and industrial design, this work demonstrates the transformative potential of perception as a scaffold for innovation, a paradigm shift from traditional design thinking to perception-driven furniture design
Early Childhood Bedtime Routines and Adolescent Objective Sleep: Facilitators, Barriers, and Mechanisms
No full textImproving sleep is a public health need, given the implications poor sleep has for the health of children and the wide disparities in sleep based on race and economic class (Hale et al., 2020). Consistent bedtime routines started before the age of five have been identified as one of the most beneficial practices for children's sleep and are often used in interventions and recommended by pediatricians (Mindell & Williamson, 2018). However, many parents experiencing poverty can find maintaining a bedtime routine challenging due to employment constraints and other factors (Adams et al., 2024). Moreover, adolescence is a period of increased vulnerability to sleep disturbances (Crowley et al., 2019), and the self-regulation fostered by early childhood bedtime routines may help preserve sleep quality and improve health (Staples et al., 2015).
This dissertation examines predictors, mediators, and objective sleep outcomes of early childhood bedtime routines using data from Years 3, 9, and 15 of the Future of Families and Child Wellbeing Study (FFCWS), a birth-cohort study primarily focused on children born to unmarried parents. Bedtime routines at Year 3 were assessed through maternal-reported bedtime routine use, consistency, and four bedtime routine activity categories: physical contact, communication, hygiene, and nutrition.
The first study tests maternal non-standard employment (i.e., night, weekend, variable shifts), child externalizing behavior, and maternal social capital as predictors and moderators of bedtime routine use, consistency, and activity type at age three. Results showed that maternal non-standard employment was associated with a lower probability of using a bedtime routine and communication activities. However, higher levels of social capital mitigated these differences, with greater social capital being linked to a higher probability of bedtime routine use and engagement in hygiene activities. Additionally, children with higher levels of externalizing behavior were more likely to have bedtime routines and use hygiene and nutrition activities.
The second study tests whether mother-child closeness at Year 9 mediates the relationship between bedtime routines at age three and objective sleep and sleep variability at age 15. Mother-child closeness was reported by the child using a single-item measure at Years 9 and 15. Adolescent sleep was measured at Year 15 using actigraphy. Findings did not support a direct effect of mother-child closeness on adolescent sleep or a mediation effect between bedtime routines and sleep outcomes. However, results showed that engagement in communication activities (e.g. reading) at age three was associated with a more consistent sleep schedule at age 15, as reflected in less variability in time in bed and total sleep minutes. Communication activities were also marginally associated with less variability in wake after sleep onset (WASO). Additionally, physical contact activities at age three (e.g., cuddling) were associated with significantly better average sleep quality, including higher sleep efficiency and lower WASO, at age 15. Taken together, the current study illustrates that bedtime routines are sensitive to family contexts and a useful tool for promoting sleep across development
Tactical Piety: Heretical Piracy and Catholic Rhetoric in Colonial Quito, Panama, and Guatemala
Get PDFDuring the sixteenth and seventeenth century, Francis Drake and other English corsairs attacked Spanish coastal cities and ports. In response to the attacks, Spanish functionaries devised a religious rhetoric as an offensive and defensive strategy. While recent studies have analyzed colonial poetry and the influence of religion on piracy, not many have paid attention to official administrative correspondence. This thesis focuses on three particular archival sources from three different locations that experienced pirate attacks: Quito, Panama, and Guatemala. I use Bruno Latour’s Actor-Network Theory to examine the religious rhetoric of written correspondence and other documents by Spanish administrators who attempted to create a network of Catholic combatants. I argue that the Catholic rhetoric embedded in the three documents reveals an administrative use of religiosity with the purpose of persuasion both to build identity and show a united front against pirates
Reliability and Degradation of Bulk and Interfacial Properties in Electronic Packages under Extreme Operating Conditions
No full textThe durability of electronic packages used in harsh environments is of vital importance to the automotive underhood electronics, aerospace, and high-performance computing industries. Such applications demand materials capable of withstanding long-term exposure to elevated temperatures, humidity, and mechanical stressors without degrading structural integrity and thermal performance. Underfills, thermal interface materials (TIMs), and epoxy mold compounds (EMCs) are key materials that help reduce thermomechanical stresses, enhance structural integrity, and facilitate better heat dissipation in electronic packages. Yet, the materials' deteriorating properties over time result in accelerated stress accumulation, interfacial delamination, and premature failure of packages. The dissertation elaborates on the development of underfill properties under isothermal aging and hygrothermal conditions and examines their influence on packaging's long-term reliability. The development of mechanical and thermal properties of the underfills is assessed using dynamic mechanical analysis (DMA), polarized optical microscopy, and finite element modeling (FEM) to analyze their performance under different environmental conditions. The findings indicate that underfill oxidation has a significant influence on mechanical behavior, including package warpage, stress distribution, and reliability.
The research incorporates conventional and non-PFAS underfills, with an emphasis on viscoelastic behavior and oxidation resistance. The comparative study of conventional and non-PFAS underfills highlights the advantages and limitations of novel materials for application in next-generation packaging. The study provides new information on material selection strategies where mechanical property retention and environmental resistance are paramount in determining long-term performance.
A competing risk model is established for estimating the collective impact of multiple degradation mechanisms on package failure. The model integrates the non-linear viscoelastic behavior of underfills from DMA tests and linear properties of TIMs into finite element models of FCBGA packages. By considering concurrent effects such as linear and non-linear properties of underfills, the model is a good foundation for reliability prediction. Furthermore, the research investigates the fracture behavior of TIM/copper and EMC/substrate interfaces using experimental fatigue and monotonic test methods. The moisture diffusivity, activation energy, and acceleration factors are extracted to project the long-term stability of these materials under conditions that mimic actual environments. Furthermore, data from accelerated life testing is coupled with predictive models to enhance the knowledge of time-dependent failure mechanisms and thereby connect laboratory experiments to actual operating conditions.
Aside from the reliability predictions, actual geometry modeling of QFN packages is accomplished with X-ray Micro-CT. In contrast to conventional idealized models, incorporating actual manufacturing variations in FEM simulations improves accuracy in prediction by taking into account realistic material distributions and defects. Surface Evolver techniques are used for modeling actual solder ball shapes, incorporating the actual geometry in interconnects that influence stress concentrations and fatigue life.
The findings of the current study are important for the development of valid predictive models for electronic package reliability and offer fundamental knowledge of underfills, TIMs, EMCs, and interface behavior under harsh operating conditions. By combining experimental characterization, data-driven modeling, and cutting-edge simulation techniques, this research offers a unified platform with the vision of optimizing packaging materials. The platform is employed to guide the pursuit of sustainable and robust solutions for high-performance electronic applications. The outcomes derived from this research will allow design for reliability (DfR) practices for future semiconductor packaging technologies to be improved and therefore facilitate the creation of more reliable and thermally stable electronic products
Caught in a Digital Trap: The Effects of Technostress on Work-Family Conflict and The Moderating Role of Attentional Resources
Get PDFAs technology becomes increasingly embedded in the modern workplace, understanding its psychological effects on employees is critical for reducing work-family conflict and promoting well-being. This study investigates how technostress - specifically, techno-overload and techno-invasion - contributes to work-family conflict (WFC), and whether these relationships are mediated by psychological detachment from work. Drawing on the Stressor Detachment Model-Revised (SDM-R), this study also examines attentional resources as a moderating factor in the detachment process. Using a multi-wave design, the findings reveal that both techno-overload and techno-invasion are significantly associated with higher levels of WFC. Notably, psychological detachment mediates the relationship between techno-invasion and WFC, but not between techno-overload and WFC. Furthermore, attentional resources moderate the indirect effects of techno-invasion on WFC, such that individuals with lower attentional resources experience greater difficulty detaching from work, intensifying the impact of technostress on WFC. These results contribute to the theoretical development of the SDM-R by identifying attentional resources as a critical personal buffer and highlight the need for organizations to consider both technological job demands and employee cognitive capacities when developing strategies to support work-life balance in digitally demanding work environments
Reliability Investigation of Power Sources and Additively Printed Electronics for Flexible and Miniaturized Form Factors
No full textOver the past three decades, consumer electronics demand has surged, with products like smartphones, laptops, smartwatches, and VR headsets becoming widespread. These devices have evolved to become sleeker and more powerful. Concurrently, rising carbon emissions have prompted a shift towards sustainable manufacturing processes. This dual drive led to the adoption of li-ion battery technology in the early 2000s, now widely used across various sectors including automotive and healthcare. Additionally, the push for sustainability and miniaturization has spurred growth in printed electronics, particularly in the automotive and aerospace industries, due to their lighter, more eco-friendly designs.
Li-ion batteries became the popular choice among power sources for applications in consumer electronics devices owing to their combination of high specific capacity and specific energy density along with several other benefits such as long cycle life and ability to be charged rapidly. However, owing to their inability to tolerate overcharge as well as deep discharge, li-ion batteries require stringent control during operation via a battery management system which also needs to inform the user of the battery’s available capacity to prompt recharge as well as battery health to prompt battery replacement. Moreover, li-ion batteries are sensitive to operation at higher charge currents as well as higher temperatures owing to their susceptibility to thermal runaway, they must be qualified for operation under these conditions and the battery life under such conditions must be examined. In this work, two li-ion coin cells and one li-ion pouch cell have been subjected accelerated life cycle testing along with different electrical and environmental parameters to quantify their lifetimes as a response to the selected use parameters. Apart from this, the cells have also been subjected to calendar aging tests and knee-point tests to evaluate the effect of various degradation modes that the battery encounters not only when use in a device, but throughout its lifetime. The gathered data from the accelerated life test has then been used to model the battery state of health considering battery use parameters for individual cells. Post model generation, the models were then evaluated on quasi-real-world randomized use battery datasets to investigate model robustness and a combined model for all the three cells was proposed.
Li-ion batteries of the ultra-thin flexible pouch cell configuration are also finding applications in wearable electronic devices such as e-textiles, fitness trackers, and biomedical sensors, as well as in rollable displays. In such applications, the ultra-thin pouch cells are expected to undergo and endure mechanical flexing during operation, which can have critical effects on battery capacity degradation as well as safety. In this work, an ultra-thin flexible pouch cell has been subjected to static as well as dynamic flexing to investigate the effects of parameters such flex radius, orientation, and speed along with accelerated life cycling so as to investigate the effect on battery life. Furthermore, an investigation of battery lamination for integration with printed electronics has also been conducted while investigating the effect of laminating conditions on battery cycle life performance.
In modern consumer electronics, a major component of the power supply system apart from the battery, is the battery management system which has traditionally been employed on a rigid PCB format which contributed to the overall weight and bulk of the device. Transitioning the BMS from a rigid PCB format to a flexible format can allow for further device miniaturization, weight reduction of the device and such an effort has been made in this work by fabricating linear and buck topology charging circuits on flexible substrates using printed electronics techniques. The printed circuits have been fabricated with various inks and interconnect materials as an effort to compare the performance of sustainable materials for printed electronics with traditional non-sustainable materials. The fabricated circuits have also been tested for their reliability by subjecting them to repeated cycling. Finally, sustainable materials for printed electronics have been further explored for different printing techniques via different circuit designs. The application of printed electronics for developing in-mold-electronics which are thermoformed circuits for applications in the automotive industry has also been explored