AUETD (Auburn University)
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Micro-Diamond Chain: A Lightweight Framework for Controllable AI-Driven Workflows in Industrial Design
No full textThis research addresses the disruptive impact of generative artificial intelligence on traditional industrial design models by proposing and validating a lightweight, AI-adapted design framework: Micro-Diamond Chain (MDC) v1.0. This framework focuses on the "Develop-Deliver" phases of the "Double Diamond" model, utilizing a series of micro-diamond cycles consisting of steps: "Input→Alignment → AI Divergence → Reflection → AI Convergence → Post-AI → Reflection:Output/Cycle." It enhances designers' decision-making capabilities and control over AI tools during both PreAI and PostAI stages. Comparative analysis of two case studies, EcoFusionAI and HomiAI, demonstrates that the MDC framework effectively translates AI's rapid iteration capabilities into concrete, actionable design methods while balancing designer autonomy and efficiency. This research clarifies methodologies for human-AI collaborative design and provides actionable guidance for practical teaching and design applications
An Investigation of Tool Entry in Orthogonal Metal Cutting Using an Optical Quickstop Device and Machine Dynamics Methods
No full textThe entry and steady-state phases of plate orthogonal metal cutting were examined using an improved optical quickstop device (OQSD) in an experimental design that included material, hardness, depth of cut, cutting speed, rake angle, and tool stiffness. The results showed that stress/strain analysis using laser-marked circle deformation may be substituted for etched grain structure with great confidence. Payton’s observation of Merchant’s “direction of crystal elongation” as the direction of shear is proven to be easily measured with the laser-marked circles. The use of circle deformation led to new methods for measuring shear strain, shear strain rate, and shear flow stress, which are compared to previous models. A new empirically derived, statistically based expression for predicting the direction of shear that includes the effect of material properties such as stacking fault and hardness is proposed. A new method of identifying the transition from entry-state to steady-state cutting in orthogonal machining based on deflection and force measurements allows the analyst to analyze the two states individually. The use of modal stiffness as a factor level showed that for lower stiffness tools, the strain rate (̇_snell) increased by 28 percent. The entry-state and steady-state signals were analyzed through nonlinear dynamic methods, specifically employing approximate entropy (ApEn) and the Largest Lyapunov Exponent (LPE). ApEn is higher in steady-state signals than entry-state signals. LPE of the entry-state for thrust deflection showed that the signal changed from linear to nonlinear across the factor levels of material, depth of cut, and cutting speed, but overall was found to be inconclusive in low-speed machining
Investigating the growth cycles of titania and carbonaceous nano dusty plasmas
No full textUnderstanding and controlling dust formation in plasmas — especially from gaseous chemical precursors is a key technological goal, and the overarching theme of this dissertation. Solid nanoparticles (i.e. nano dust) which range in size from ∼ 1 to 500 nm can spontaneously grow from reactive gaseous precursors in non-thermal plasmas. This dissertation studies the particle size, and growth time with and without a background magnetic field in the plasma. Traditionally, studies have focused on the growth of either carbonaceous or silicate dust from either acetylene or silane, respectively. However, recently, there have been a shift towards studying new kinds of dust. For example, recent studies have grown polymers and metallic dust in nonthermal plasmas. This dissertation first introduces and studies the growth of titanium dioxide (a.k.a. titania) dust from the metal-organic vapor precursor of titanium tetraisopropoxide (TTIP). The as-grown materials are of amorphous structure but high temperature annealing crystallizes the samples into anatase and subsequently rutile. Then, the growth of titania dusty plasma is and compared to the growth of carbonaceous dust from acetylene, in argon plasma. They are grown during the presence and absence of weak magnetic fields of ∼ 500 Gauss. Both kinds of dust growth exhibit a growth cycle, which had already been shown for various nano dusty plasma. This occurs because once the dust accumulates a critical radius and mass, they move away from the central region of the plasma, allowing a new generation of growth begins. Ultimately, the new generation of growth also moves away leading to a continuous cycle of particle formation and transport as long as the plasma is on. However, with the presence of the magnetic field, the cycle time decreases, and the spatial distribution of the dust cloud appears differently. For example, titania dust are more concentrated in the middle of the plasma where the field strength is higher but carbonaceous dust appear to move away from the high magnetic field region. Finally, we focus on the growth cycle time of carbonaceous dust and how it decreases with a gradual increase in magnetic field, varying from ∼ 20- 1000 Gauss. We particularly noticed a minimum at ∼ 330 Gauss, which coincides with electron magnetization in the plasma.
To understand the physical factors contributing to observed changes in the growth cycle, we study the growth rate of carbonaceous dust, and plasma potential of the background plasma, as a function of magnetic field. The former is done via scanning electron microscope measurement of the dust size distribution throughout the first growth cycle, and the latter is done using emissive probe measurements in the plasma. Our results suggest that both the growth rate and the plasma potential of the background plasma decreases during weak magnetic fields. Therefore, we conclude that the physics of the plasma changes during the presence of the weak magnetic fields; specifically, the magnitude of the electric field decreases causing smaller dust particles to be levitated in the plasma. However, we also have initial results from optical emission spectroscopy (OES) of the dusty plasma which suggest that the chemistry governing dust formation is changing. For example, we see that the amount of time needed to reach the first maximum peak in intensity of OES increases with an increasing magnetic fields. It is possible that the nucleation and growth rate of the particles are also changing as seen by OES
Examining Negative Body Talk Outcomes in a Dissonance-Based Eating Disorder Prevention Program for Men
No full textPrevious research has shown that engagement in male negative body talk is common and related to muscularity-oriented behaviors and traditional disordered eating pathology, suggesting the importance of targeting male body talk. While dissonance-based (DB) eating disorder prevention programs for men theoretically target negative body talk, DB impacts on negative body talk for adult men remain unexplored. This study examined how a DB eating disorder prevention program impacted negative body talk (i.e., body fat talk and muscle talk) in college-aged, body-dissatisfied men in a randomized controlled trial compared to active control. Participants (N=201) were randomized to the DB intervention or active control condition and completed the Male Body Talk (MBT) scale at four timepoints (baseline, post-intervention, 1-month, and 6-month follow-ups). Contrary to our hypotheses, no condition by time interactions were found and both conditions demonstrated significant and small-medium reductions for Body Fat Talk and medium-large reductions for Muscle Talk. The current study provides preliminary evidence that interventions focused on the harmful impacts of the appearance-ideal, regardless of the inclusion of body talk targets, may be efficacious in reducing engagement in both body fat talk and muscle talk in men. Possible explanations for our findings related to measurement specificity and DB tactics are discussed, highlighting the need for future research regarding the assessment and intervention of male negative body talk
Fisher-KPP Equations And Chemotaxis Models on Metric Graphs
Get PDFThis dissertation is devoted to the study of population dynamics on network-like structures both in the absence and presence of chemical signals that guide population movement. Mathematically, population movement in response to certain chemical signals is often modeled
by so-called Keller-Segel chemotaxis systems. In the absence of chemotaxis sensitivity and assuming logistic population growth, such systems reduce to the so-called Fisher-KPP equation. In this dissertation, we investigate the global existence and dynamical aspects of these models on both bounded and unbounded metric graphs.
The first part of our study is focused on bounded or compact graphs. We start by proving the existence of local classical solutions for parabolic-parabolic and parabolic-elliptic Keller-Segel chemotaxis models with general non-linear coefficients following polynomial growth
assumptions. Next, we prove global uniform boundedness of solutions for Keller-Segel models with logistic source without any condition on the chemotaxis sensitivity. Moreover, we study dynamical aspects of the two chemotaxis systems with a logistic source term on compact metric graphs. It can be easily verified that the positive constant solution of these systems on compact graphs is globally stable in the absence of chemotaxis sensitivity, i.e, χ = 0, in which case the systems reduce to the Fisher-KPP equation. In this dissertation, we determine a threshold value χ*> 0 of the chemotaxis sensitivity parameter that separates the regimes of local asymptotic stability and instability, and, in addition, determine the parameter intervals that facilitate global asymptotic convergence of solutions with positive initial data to constant steady states. In addition, we provide a sequence of bifurcation points for the chemotaxis sensitivity parameter that yields non-constant steady state solutions. In particular, we show that the first bifurcation point coincides with threshold value χ* for a generic compact metric graph. Finally, we supply numerical computation of bifurcation points for several graphs.
Next, we focus on population dynamics on unbounded graphs. Here, we study the global existence, spreading speed, and traveling wave solutions of the Fisher-KPP equation on unbounded graphs with finitely many edges. Note that there are several studies on front propagation phenomena in bistable equations on unbounded metric graphs with finitely many edges. From these works, it is known that in such equations the network structure of the underlying environment may block the propagation of the fronts. We prove that, unlike the case in bistable
equations, the network structure of the environments doesn’t block the propagation of fronts in Fisher-KPP equations. In particular, we show that the Fisher-KPP equation exhibits the same spreading speed c* as on the real line. Moreover, it admits a generalized traveling wave solution connecting the stable positive constant solution and the trivial solution, with an averaged speed c for any c > c*. We concluded by mentioning current and future works in the study of global existence and long-time dynamics of chemotaxis equations on unbounded graphs
Building Trust in Digital Twins Through Verification and Validation
No full textDigital Twin (DT) is a concept of growing interest, driven by the technological advancements related to Industry 4.0. A DT integrates innovative technologies to create a virtual model that replicates a physical system and enables bi-directional data flow, facilitating real-time monitoring, analysis, and control. These capabilities make DTs increasingly attractive for supporting decision-making in complex environments, especially in manufacturing, where cost and safety are critical. However, the effective adoption of DTs depends on the ability to trust the model and all its components throughout development and deployment. Verification and Validation (V&V) have traditionally been employed to assess the credibility of models, providing a venue for the development of trust. Therefore, V&V are essential foundations for developing DTs that can support decisions in real-world environments.
Through a systematic literature review, this research investigated whether and how V&V practices were employed in DTs developed for manufacturing applications. The findings revealed that relatively few studies reported performing both verification and validation activities, indicating a significant gap in DT credibility methods. The review also examined commonly used V&V techniques, their alignment with DT capability levels, and application domains. Results indicated inconsistencies in V&V terminology, execution, and objectives, as well as the absence of a standard framework to guide V&V in DT development. To address these challenges, this research introduces the Digital Twin V (DTV) framework. The DTV integrates V&V activities across the DT development lifecycle, emphasizing iterative and recursive processes tailored to the unique characteristics of DTs. A case study applying the DTV framework to a fused deposition modeling additive machine illustrates its applicability. The framework’s scalability and potential for adaptation across various DT maturity levels are demonstrated, offering actionable guidelines for practitioners and researchers to enhance the trust and adoption of DTs. Finally, this research also explores the integration of uncertainty quantification techniques into the DTV framework to enhance the understanding of the relationship between virtual and physical systems, as well as to provide a tool to measure the uncertainties in the DT output and how these uncertainties compromise model performance.
Together, this work bridges the gap between theory and practice by uncovering the gaps in current V&V use within DT research, offering a practical methodology to guide future development of trusted DTs with uncertainty quantification considerations
Characterization and Modeling of Temporal Illuminance (Light Intensity) in Naturally-Illuminated Broiler Houses
No full textLighting plays an important role in the welfare, behavior, and productivity of broilers. This thesis investigates the influence of seasonality, sensor orientation and window configurations on light intensity in commercial broiler houses providing natural light. Chapter 1 characterizes light intensity in two GAP-certified naturally illuminated houses with different window configurations over three seasons (winter, summer and fall). Statistical analysis showed that the 2SW treatment resulted in significantly higher light intensities and better uniformity when compared to the 1SW treatment. Chapter 2 explores modeling light intensity in the same natural light broiler houses using empirical models, machine learning algorithms, and physics-based simulations (AGi32). The predictive performance, as well as the pros and cons of using various modeling approaches to predict light intensity in broiler houses are examined
Dense and high degree structures in graphs with chromatic number equal to maximum degree
Get PDFIt is well-known that for any graph , ; Brooks’ Theorem says that all graphs meeting this upper bound must contain either or be an odd cycle. The Borodin-Kostochka Conjecture, from 1977, posits that all graphs with (with ) must contain a . This thesis has two main lines of work, both of which are related to the Borodin-Kostochka Conjecture. In the first, we focus on vertex-critical graphs with and prove that, given some forbidden subgraph conditions, we can get close (in some sense) to containing a . In the second main topic of this thesis, we prove that every graph with (and ) contains either a “high’’ or a “high” odd hole, where ``high'' means that the vertices have average degree at least . This theorem is a weakening of the Borodin-Kostochka Conjecture when ; when there are examples showing that both the high odd hole and the high are needed in the statement of the theorem
Integration of Cellular and Organismal Stress Responses to Light at Night and Simulated Night Shift Work in the Diurnal Zebra Finch and Nocturnal House Mouse
No full textThe presence and absence of light is a fundamental environmental signal leveraged across the tree of life to synchronize internal biological processes to external, predictable environmental conditions. With the rise of artificial lighting sources and everchanging modern lifestyles, humans and wildlife have been faced with a new challenge – disruption in the nighttime environment through exposure to artificial lighting sources at various spectra, types, intensities, and patterns.
Throughout my PhD, I aimed to elucidate how birds and mammals respond to perturbations in the nighttime environment through aperiodic and alternating lighting conditions, particularly focusing on the physiological costs associated with unnatural light/dark cycles. Birds and mammals offer interesting insights on the role of circadian rhythm disruption due to 1) differences in their ability to receive and relay light information and 2) distinct physiological differences.
Zebra finches (Taeniopygia guttata castanotis) are an opportunistic, diurnal social songbird native to Australia, with well-charactered stress physiology and neurobiology. They are generally insensitive to changes in the photoperiod, meaning that we can disentangle unique physiological responses in response to photoperiod manipulations that mimic human patterns without activating alternate pathways sensitive to photoperiodism associated with life-history transitions. Therefore, zebra finches are the ideal model to evaluate the mechanisms underlying physiological and metabolic effects to altered lighting conditions.
The nocturnal mouse (Mus musculus) has been the prime model to examine the theoretical and mechanistic basis of circadian rhythm biology. Indeed, the ability to easily manipulate their genome to ask targeted questions regarding the pathogenesis of diseases related to circadian rhythm disruption, in combination with other important factors such as diet and exercise has proven extremely useful. Yet, artificial selection may have removed vital components involved in mediating their physiological and behavioral response to stressors, particularly by making strains more docile, and more reproductively capable. Consequently, the genotypes of many lab strains are virtually the same, and common lab rodents used in circadian rhythm research are done in some strains unable to produce melatonin, a key hormone related to biological timekeeping. Thus, studies capitalizing on the wild-derived house mouse that retains natural sensitivity to stressors bridges together the strength of genetic heterogeneity and plasticity, with the utility of controlled laboratory environments to further evaluate nighttime light disturbances on physiology will prove useful.
These ecologically relevant models are at the forefront of my dissertation, in which I explored neuroendocrine, metabolic, and morphological effects of light at night across four data chapters. In chapters 2 and 3, I examined the role of stress resilience by exposing zebra finches to high intensity constant light and allowing a recovery period. I collected samples to address transient and persistent changes in hypothalamic-pituitary-adrenal (HPA) axis and glucose regulation, body mass, and the abundance of glucocorticoid receptors (Chapter 2).
To further evaluate physiological costs to constant light, I investigated the capacity to which zebra finches displayed ephemeral or persistent cellular damage by measuring a suite of damage markers related to DNA, lipids, and proteins across the blood, liver, and skeletal muscle (Chapter 3). To identify the mechanism(s) associated with cellular damage outcomes, I leveraged data collected from Chapter 2 to perform path analysis, synonymous to structural equation modelling (SEM), to reveal how light at night altered the physiological regulatory network after exposure and a recovery period.
In Chapter 4, I investigated the bioenergetic mechanisms related to sex and tissue-specific responses to constant light and darkness in the wild-derived house mouse. While HPA axis function could be a mechanism underlying metabolic or cellular damage outcomes to altered lighting conditions, two alternative mechanisms are declines in mitochondrial respiratory function and resting metabolic rate, both of which, are heavily involved in maintaining metabolic homeostasis and underlie metabolic diseases.
In the last data chapter, to bridge together experimental paradigms and findings from chapters 2-4, I exposed zebra finches to simulated night shift work conditions commonly experienced by human shift workers and experimentally done in rodent models. Here, I extended upon hypothalamic-pituitary-adrenal (HPA) regulation by including negative feedback efficiency, the ability to terminate the adrenocortical response to avoid a long duration of elevated glucocorticoid. Moreover, I evaluated circadian rhythmicity of two key hormones reflective of circadian alignment: corticosterone and melatonin.
In Chapter 2, I found that there were time-dependent effects of constant light on the morphology and physiology of zebra finches in addition to varying degrees of stress resilience. Body mass marginally increased after 3 days of constant light, but after 23 days of exposure to constant light, body mass was significantly higher in treatment birds compared to controls. In contrast, baseline glucose levels decreased over the duration of the experiment, yet these effects were transient, as both body mass and glucose levels rebounded to pretreatment levels after the recovery period, indicating stress resilience. Yet, the glucose stress response was blunted due to constant light, and remained blunted after the recovery period, indicating a persistent effect and a lack of stress resilience. Interestingly, there were no changes in circulating baseline corticosterone, the reactivity of the HPA axis, or the abundance of glucocorticoid receptors in the liver. These data suggest that there is variation in the capacity for different traits to rebound after recovery from a chronic stressor. Yet, questions remain as to if these trends are the result of prioritization of recovery between different traits or is dependent on the length of the recovery period.
In Chapter 3, there were no transient or persistent effects of constant light on global DNA damage in the red blood cells. Furthermore, constant light at night did not result in persistent oxidative damage in the liver or skeletal muscle, measured through protein carbonyls and 4-hydroxynonaneal. However, by leveraging data from chapter 2, a phenotypic integration approach via path analysis revealed interesting associations between traits and their relationship with damage outcomes that were dependent on treatment groups. In control birds, path analysis revealed that HPA axis function was a condition-dependent trait, such that individuals with greater body mass mounted stronger stress responses. Moreover, birds that mounted stronger HPA axis responses also had stronger downstream glucose responses. However, exposure to constant light uncoupled condition-dependency of the stress phenotype, such that after a recovery period, birds previously exposed to light at night had no relationship between body mass, HPA axis function, and the glucose stress response. These data suggest that prior stress history (i.e., exposure and recovery from light at night) may have persistent effects by modifying physiological network linkage between traits within the physiological regulatory network which may underlie damage outcomes.
In Chapter 4, there was a sex and tissue-specific response relating to constant light, but not constant darkness. Specifically, state 3 maximum mitochondrial respiratory function was higher in the liver of female mice exposed to constant light, compared to controls and females under constant darkness. There was not a similar trend in the mitochondrial respiratory response in the male livers, or the skeletal muscles of either sex. While females had greater mitochondrial respiratory function, they did not suffer from greater lipid peroxidation in the liver, indicating that the common assumption between enhanced oxidative phosphorylation capacity and cellular damage is not supported. There were no significant changes in body mass, fat pads, or the resting metabolic rates of mice under constant light or darkness. These data contrast many studies that investigate the effects of light at night in laboratory rodents, emphasizing the importance of individual variation and plasticity. Furthermore, these data highlight that the bioenergetic underpinning of metabolism could improve upon our understanding of metabolic disease to circadian disruption.
In Chapter 5, I found that 24-h corticosterone profiles were inverted an inversion of corticosterone profiles after 63 days of simulated night shift work. There was a similar trend suggesting inversion of melatonin profiles, however, lack of biological samples and statistical power inhibited my ability to capture this effect. I also found that simulated night shift work suppressed HPA axis reactivity, but not negative feedback efficiency. Moreover, simulated night shift work enhanced fatty acid metabolism, indicated by greater number of circulating β-hydroxybutyrate, yet this did not result in changes to body mass or subcutaneous fat deposits. There were no differences in superoxide dismutase 1 or abundance of 4-hydroxynonaneal adducts in the liver. In contrast, there were lower amounts of relative protein abundance of superoxide dismutase 1 in the brain, but no difference between groups in 4-hydroxynonaneal damage in the brain. Overall, the data gathered here indicate plasticity in circadian mechanisms in response to alternating patterns of light at night that mimic night shift work in humans. Such plasticity was able to alleviate some of the physiological costs to simulated night shift work, indicating resilience to alternating patterns of light
Non-Steroidal Intra-Articular Therapeutics for the Management of Canine Osteoarthritis: A Survey for Canine Practitioners and a Scoping Review of Current Literature
No full textNon-steroidal intra-articular therapeutics (NSIATs) are increasingly used in the multimodal management of canine osteoarthritis (OA). This thesis comprised two projects.
The first involved a survey of 174 practitioners to explore clinical use, decision-making, and perceived outcomes associated with NSIATs. Of these, 164 participants performed intra-articular (IA) injections and 144 reported using NSIATs. Platelet-rich plasma (PRP) and viscosupplements were the most commonly administered NSIATs. Over 50% of participants using PRP and viscosupplements subjectively noted either some or substantial clinical improvement with these therapies.
The second project was a scoping review that identified 148 studies on NSIATs. Cellular therapeutics, PRP, and viscosupplements were the most frequently studied. Research in this area has grown over the past decade; however, most studies are non-randomized and lack control, which limits the overall quality of the evidence due to potential bias. Further randomized controlled trials are needed.
These findings provide meaningful insight into the current use and evidence base for NSIATs in the management of canine OA