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Title: Abstract homomorphisms of algebraic groups : rigidity and group actions
Creator: Ruiter, Joshua
Date: 2022
Collection: Electronic Theses & Dissertations
Description: We investigate two related problems involving abstract homomorphisms between the groups of rational points of algebraic groups. First, we show that under appropriate assumptions, abstract representations of quasi-split special unitary groups associated with quadratic extensions of the field of definition have standard descriptions, i.e. can be factored as a group homomorphism induced by a morphism of algebras, followed by a homomorphism arising from a morphism of algebraic groups. This...
Show moreWe investigate two related problems involving abstract homomorphisms between the groups of rational points of algebraic groups. First, we show that under appropriate assumptions, abstract representations of quasi-split special unitary groups associated with quadratic extensions of the field of definition have standard descriptions, i.e. can be factored as a group homomorphism induced by a morphism of algebras, followed by a homomorphism arising from a morphism of algebraic groups. This establishes a new case of a longstanding conjecture of Borel and Tits. In the second part, we apply existing results on standard descriptions for abstract representations of Chevalley groups to study some rigidity properties of actions of elementary subgroups on algebraic varieties.The thesis is organized as follows. To provide context for the study of abstract homomorphisms, in section 1 we give a historical overview of key developments going back to Cartan's work on homomorphisms of Lie groups. In section 2, we prove our rigidity result for special unitary groups, using a strategy inspired by work of Igor Rapinchuk which depends crucially on the construction of certain algebraic rings associated to abstract representations. In section 3, we apply existing rigidity statements for representations of elementary subgroups of Chevalley groups to study rigidity properties of these groups acting on affine algebraic varieties and projective surfaces. We discuss some open questions and plans for future work in section 4. In the appendices, we collect some relevant background material on algebraic rings, and also provide details on the computations of commutator relations needed for the constructions in section 2.
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Title: NEUTRON SCATTERING AND TRANSPORT STUDIES OF QUANTUM MATERIALS
Creator: Zhang, Heda
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Quantum material is an multi-disciplinary research topic that continues to thrive in recent years. The term \textit{Quantum material} covers all systems which demonstrate physical phenomena beyond the scope of single-particle, semi-classical/quantum theory. Among many sub-fields of quantum materials, topological systems and strongly correlated systems are two topics which have receive growing attention from the scientific community. We begin with a discussion on a van der Waals magnet VI$_3$...
Show moreQuantum material is an multi-disciplinary research topic that continues to thrive in recent years. The term \textit{Quantum material} covers all systems which demonstrate physical phenomena beyond the scope of single-particle, semi-classical/quantum theory. Among many sub-fields of quantum materials, topological systems and strongly correlated systems are two topics which have receive growing attention from the scientific community. We begin with a discussion on a van der Waals magnet VI$_3$ in chapter three. VI$_3$ hosts ferromagnetism on a honeycomb lattice, which was one of the proposed models for topological magnon bands. There have been ample theoretical studies on ferromagnetic honeycomb lattice. However, there has not been any physical realization of such model. In our study, we show that the is a strong anomalous thermal Hall effect in VI$_3$, the underlying mechanism of which is the non-trivial topological nature of the magnon bands.In chapter four, we discuss our transport studies on some magnetic topological metals. The non-zero Berry curvature in the reciprocal space of topological metals can lead to anomalous transverse conductivities ($\kappa^A, \sigma^A, \alpha^A$) in the system. We found large anomalous transverse conductivities in TbMn$_6$Sn$_6$ and verified its intrinsic nature through first-principle calculations. Furthermore, we have found large exchange-bias behavior in TbMn$_6$Sn$_6$, which renders it as a promising system for anomalous Nernst effect based thermoelectric device. We will also discuss the topological Nernst effect observed in Fe$_3$Sn$_2$, which is potentially due to the Skyrmion bubble phase revealed by the Lorentz transmission electron microscopic studies.In chapter five, we discuss our inelastic neutron scattering study on a unique quantum spin chain system in Cu$_2$(OH)$_3$Br. The system hosts alternating ferromagnetic and anti-ferromagnetic spin chains with finite inter-chain couplings. This allows for the coexistence and interactions between magnons and spinons.
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Title: Investigation into the Performance of a Twin-Screw Compressor for Helium Compression
Creator: WILLIAMS, Tasha L.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The screw compressor is a rotary positive displacement compressor, capable of compressing gas, vapors, and refrigerants. It is commonly used in various applications, including building and architecture, food, chemical process, pharmaceutical, metallurgical industries, refrigeration, air conditioning, vehicle superchargers and in cryogenic helium compression applications. The main characteristics that make the screw compressor attractive include high rotational speed, compactness, ability to...
Show moreThe screw compressor is a rotary positive displacement compressor, capable of compressing gas, vapors, and refrigerants. It is commonly used in various applications, including building and architecture, food, chemical process, pharmaceutical, metallurgical industries, refrigeration, air conditioning, vehicle superchargers and in cryogenic helium compression applications. The main characteristics that make the screw compressor attractive include high rotational speed, compactness, ability to maintain high efficiency over a wide range of operating conditions, long service life, and good reliability.An oil-flooded twin screw compressor is selected for investigation in the present work due to its reliability, large capacity, and capability to handle helium’s high heat of compression. Oil-flooded screw compressors refers to the oil being injected into the compression process and mixed with helium. The benefits of injected oil are cooling the helium, creating sealing between rotors, lubrication, and higher performance. In helium systems, the loss of power within the compression system is roughly two-thirds. With such a high loss in power, it is imperative to understand the need for investigating the design and thermodynamic parameters that impact the overall performance of these machines.Initially, a review of different types of compressors is carried out to determine the best suited compressor for helium compression in this current work. A numerical model was created to simulate the compression process of the screw compressor. The model consists of three segments: rotor curve generation, thermodynamic analysis, and performance prediction. The geometric data are a necessary input for the thermodynamic analysis; however, the thermodynamic analysis segment can be used for any rotor geometry. The thermodynamic analysis outputs the thermodynamic parameters as a function of the male rotation angle of helium and oil. The performance prediction determines characteristics of performance such as the volumetric and isothermal efficiencies. The model was validated using a commercial software, which was developed on the basis of extensive screw compressor data. The model predicted performance with reasonable accuracy varying at extreme case with a maximum of a 13\% difference. Using the numerical model, the oil analysis in this thesis determined that the compressor performance is highly dependent on oil injection parameters. The isothermal efficiency spanned from 49.9\% to 56.5\% when adjusting the mass flow rate and oil injection position of the oil. Experimental results determined that the discharge temperature has the biggest impact on compressor performance.
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Title: Numerical Methods for the Evolution of Fields with Applications to Plasmas
Creator: Sands, William A.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: In this dissertation, we present a collection of algorithms for evolving fields in plasmas with applications to the Vlasov-Maxwell system. Maxwell's equations are reformulated in terms of the Lorenz and Coulomb gauge conditions to obtain systems involving wave equations. These wave equations are solved using the methods developed in this thesis and are combined with a particle-in-cell method to simulate plasmas. The particle-in-cell methods developed in this work treat particles using several...
Show moreIn this dissertation, we present a collection of algorithms for evolving fields in plasmas with applications to the Vlasov-Maxwell system. Maxwell's equations are reformulated in terms of the Lorenz and Coulomb gauge conditions to obtain systems involving wave equations. These wave equations are solved using the methods developed in this thesis and are combined with a particle-in-cell method to simulate plasmas. The particle-in-cell methods developed in this work treat particles using several approaches, including the standard Newton-Lorenz equations, as well as a generalized momentum formulation that eliminates the need to compute time derivatives of the field data. In the first part of this thesis, we develop and extend some earlier methods for scalar wave equations, which are used to update the potentials in these formulations. Our developments are based on a class of algorithms known as the MOL$^T$, which combines a dimensional splitting technique with a one-dimensional integral equation method. This results in methods that are unconditionally stable, can address geometry, and are $\mathcal{O}(N)$, where $N$ is the number of mesh points. Our work contributes methods to construct spatial derivatives of the potentials for this class of dimensionally-split algorithms, which are used to evolve particles.The second part of this thesis considers core algorithms used in the MOL$^T$ and the related class of successive convolution methods in the context of high-performance computing environments. We developed a novel domain decomposition approach that ultimately allows the method to be used on distributed memory computing platforms. Shared memory algorithms were developed using the Kokkos performance portability library, which permits a user to write a single code that can be executed on various computing devices with the architecture-dependent details being managed by the library. We optimized predominant loop structures in the code and developed a blocking pattern that prescribes parallelism at multiple levels and is also more cache-friendly. Moreover, the proposed iteration pattern is flexible enough to work with shared memory features available on GPU systems.The final part of this thesis presents the particle-in-cell method for the Vlasov-Maxwell system, which leverages the methods for fields and derivatives developed in this work. The proposed methods are applied to several test problems involving beams. Our results are generally encouraging and demonstrate the capabilities of the proposed field solvers in simulating basic plasma phenomena. Additionally, our results serve to validate the generalized momentum formulation, which will be the foundation of our future work.
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Title: Advancing Field Emission Technology for High Power Injectors Operating in GHz and Beyond
Creator: Schneider, Mitchell E.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: As the next generation of electron injectors pushes to achieve higher gradient fields than ever before (>300 MV/m), they are driven to operate at higher frequencies (C-band through W-band). This shrinks the fabrication dimensions of these cavities, making field emission cathodes (FECs) an electron source of choice. Photoemission and thermionic sources are increasingly less suited as the complex laser transport schemes and heating source powering these injectors cannot provide the necessary...
Show moreAs the next generation of electron injectors pushes to achieve higher gradient fields than ever before (>300 MV/m), they are driven to operate at higher frequencies (C-band through W-band). This shrinks the fabrication dimensions of these cavities, making field emission cathodes (FECs) an electron source of choice. Photoemission and thermionic sources are increasingly less suited as the complex laser transport schemes and heating source powering these injectors cannot provide the necessary beam quality and may cause damage to the cathode or the injector itself. Carbon-based FECs have dominated the field emission sources R&D portfolio at DOD and DOE for the past 30 years across various high-power vacuum electronic device activities. Compared to traditional metal cathode technology, carbon-based technology cathodes are able to produce higher charge at low electric fields. Small intrinsic electron momentum and simple fabrication means these can become a leading technology, e.g., in the case of carbon nanotubes, nanoscale emitters make them attractive for producing high brightness beams. Specifically, diamond-based cathodes can handle extreme temperature and mechanical stresses that can occur under high gradient conditions.Most promising is a unique form of diamond, ultra-nano-crystalline diamond (UNCD) due to its material and electrical properties, which include being the most conductive form of diamond due to having the largest amount of grain boundaries. This cathode material allows us to explore new frontiers of cathode physics research, revealing a new field emission mechanism that diverges from classical Fowler Nordheim, termed space charge dominated Fowler Nordheim. This form of Fowler Nordheim is space charge dominated but can surpass the 1D Child Langmuir limit and approaches the 2D limit. This is not space charge limited Fowler Nordheim. This ability to decouple the extracted current from the space charge effects allows for the production of extremely xiii bright beams. This can be achieved by expanding the current cathode testing facilities beyond L band into C band so as to access these high fields and explore the temporal dynamics of a field emission source. This will yield the new physics knowledge needed to construct the world’s first custom-built injector specifically designed for field emission sources. Furthermore, exploring other forms of diamond cathode such as Diamond Field Emitter Arrays (DFEA) yields insight into the applications of transversely shaped beams for advanced accelerator applications such as emittance exchange beam lines. DFEA’s allow for the exploration of additional materials effects on the cathode performance such as the ballast resistance. This ultimately allows the derivation of a comprehensive concept map for the field emission dynamic regimes needed for the design of RF injectors. Previously, the theoretical assumption was that everything operated under classical Fowler Nordheim without any additional contributions from other materials properties or beam effects.
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Title: IMPROVING INTERACTIONS BETWEEN SELF-MEDICATING CONSUMERS AND OVER-THE-COUNTER PACKAGING WITH FRONT-OF-PACK AND PERSONALIZED LABELING AS STRATEGIES
Creator: LIU, LANQING
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Interactions between self-medicating consumers and the labeling of Over-the-Counter medications (OTC) influence the quality of information processing and hence the appropriateness of medication decisions. Our previous work on human-package interaction yielded evidence that early stages of processing important regulatory information were necessary to improve OTC packaging labeling and human-package interactions, and thus to inform appropriate decisions.Under the framework of Human-Package...
Show moreInteractions between self-medicating consumers and the labeling of Over-the-Counter medications (OTC) influence the quality of information processing and hence the appropriateness of medication decisions. Our previous work on human-package interaction yielded evidence that early stages of processing important regulatory information were necessary to improve OTC packaging labeling and human-package interactions, and thus to inform appropriate decisions.Under the framework of Human-Package Interaction model (H-PIM) and the types of directiveness of label designs, we proposed two novel labeling strategies: Front-of-Pack (FOP) labeling and personalized FOP labeling. The FOP strategy utilized the concepts of front-of-pack, boxing, grouping, and highlighting (HL), whereas the personalized FOP strategy further combined the concepts of the FOP labeling with augmented user interface and decision-support signals to assist the decision-making process for enhancing human-package interactions. To quantitatively investigate the effectiveness of those FOP labeling strategies, we firstly conducted a change detection test to evaluate the impact of the FOP labeling strategy on consumers’ attention to critical drug information. Additionally, we then developed an absolute judgement test to evaluate the effectiveness of the personalized FOP labeling strategy for assisting decision-making to benchmark the potential benefits of this strategy. The change detection test results indicated that the use of HL was effective and efficient to garner attentions. Specifically, the presence of HL increased change detection accuracy (HL:ME=0.932, SE=0.008; not HL:ME=0.770, SE=0.019; p<0.001)) and shortened the time to correctly detect changes. (HL: ME=3.790, SE=0.200; not HL:ME=5.073, SE=0.268; p<0.001). However, no evidence was found to suggest that the use of FOP labels enhanced the change detection accuracy. Moreover, the presence of FOP labels could prolong the time consumers used to correctly detect changes on the OTC packages than the standard labels. (FOP: ME=4.542, SE=0.238; standard: ME=4.233, SE=0.225; p=<0.001) These results may be caused by factors such as the FOP label location and unbalanced experimental design. Further studies are needed to gain more knowledge of this strategy. The absolute judgement test results supported the effectiveness and efficiency of the personalized FOP strategy on assisting consumer’s decision making. When introduced and educated with the concept of personalized FOP labeling, participants made decisions significantly more accurate (personalized FOP: ME=0.977, SE=0.007; standard: ME=0.933, SE=0.017; p=0.002) and faster (personalized FOP: ME=9.584, SE=0.854; standard: ME=19.052, SE=2.322; p<0.001) with the presence of personalized FOP labels compared to the presence of standard ones. In conclusion, this dissertation extends FOP labeling strategies from non-directive labels to personalized labels. The personalized FOP labeling could act as a very important role in improving the consumer-package interactions in the OTC market. Future studies can explore different designs and presentation modes of personalized labeling to identify the most effective design combination that can assist consumers’ information processing of OTC packaging and medical decision-making. More research is also needed to generalize the effectiveness of personalized labels on medication decision-making to various natural settings, different package types, and other populations.
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Title: Profiles of Student Engagement in Synchronous and Asynchronous Science Instruction
Creator: Schell, Matthew J.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Virtual instruction at the K-12 level is on the rise, yet we know very little about the ways students engage in different types of virtual instruction. The goals of this study were to: 1) describe high school students’ engagement in virtual science courses in terms of behavioral, affective, cognitive-value, and cognitive-self regulatory dimensions; 2) explore whether students’ engagement patterns across these dimensions differed depending on whether science activities were synchronous or...
Show moreVirtual instruction at the K-12 level is on the rise, yet we know very little about the ways students engage in different types of virtual instruction. The goals of this study were to: 1) describe high school students’ engagement in virtual science courses in terms of behavioral, affective, cognitive-value, and cognitive-self regulatory dimensions; 2) explore whether students’ engagement patterns across these dimensions differed depending on whether science activities were synchronous or asynchronous; and 3) examine whether these engagement patterns were associated with students’ final course grades or over-summer retention in a virtual high school. Students enrolled in a range of science courses at virtual high school (n=124) provided multiple reports (n=493) of their engagement during both synchronous and asynchronous learning activities. Latent Profile Analysis (LPA) conducted with these data suggested five distinct situational engagement profiles representing different constellations of the affective, behavioral, cognitive-value, and cognitive-self-regulatory dimensions of engagement. During synchronous instruction, students tended to engage in ways characterized by higher engagement in all dimensions compared with asynchronous instruction. These high engagement profiles were also associated with higher final course grades. There were few differences in the extent to which profiles predicted retention; however, lower self-regulation was associated with higher rates of retention.
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Title: MOLECULAR MECHANISMS INVOLVING PPARY IN THE PLACENTAL PATHOPHYSIOLOGY OF PREECLAMPSIA
Creator: Grimaldi, Brooke A.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Preeclampsia (PE) is a hypertensive disorder of pregnancy that effects 5-7% of all pregnancies and is the main cause of maternal-fetal morbidity and mortality worldwide. Despite significant advancements in obstetric and neonatal care, the prevalence of PE has remained steady over the past thirty years. There is no cure for PE other than placental and fetal delivery. The exact etiology of the PE syndrome remains unclear however, maternal vascular malperfusion and placental ischemia are...
Show morePreeclampsia (PE) is a hypertensive disorder of pregnancy that effects 5-7% of all pregnancies and is the main cause of maternal-fetal morbidity and mortality worldwide. Despite significant advancements in obstetric and neonatal care, the prevalence of PE has remained steady over the past thirty years. There is no cure for PE other than placental and fetal delivery. The exact etiology of the PE syndrome remains unclear however, maternal vascular malperfusion and placental ischemia are prominent features of the PE placenta that cause abnormal trophoblast differentiation and function. PE is considered a two-stage disease due to the ischemic-diseased placenta releasing altered secretion of placental proteins that negatively impact the maternal endothelium causing hypertension and end organ damage. The placental dysfunction is as well characterized by a reduction of the transcription factor, peroxisome proliferator activated receptor γ (PPARγ) which normally promotes trophoblast differentiation and healthy placental function. This dissertation has aimed to understand the link between PPARγ-driven trophoblast dysfunction and the imbalance of secreted proteins in PE. The restoration of these disrupted pathways by PPARγ actions in the placenta could offer potential therapeutic pathways to reverse the disease, extend pregnancy duration, and dampen maternal sequalae. This dissertation has utilized a collection of first trimester and term healthy and preeclamptic placentas in addition to immortalized cell lines to understand the effect of PPARγ activation by the drug, Rosiglitazone, during preeclamptic or in vitro ischemic conditions. These studies revealed several molecules that are regulated by PPARγ in the human placenta, including the anti-angiogenic soluble fms-like tyrosine kinase 1 (sFLT1) and the cytoprotective heme oxygenase (HO1). Both proteins were restored to normal levels in PE by treatment with the PPARγ activating drug, Rosiglitazone. Furthermore, PPARγ activation improved the anti-angiogenic environment in the PE placenta as shown by increasing the pro-angiogenic and growth factor proteins: placental growth factor, fibroblast growth factor 2, follistatin and heparin-binding epidermal growth factor. Placental activation of PPARγ further restored the angiogenic balance in PE through significant reductions in the anti-angiogenic proteins, angiopoietin-2 and soluble endoglin. Using an endothelial cell model representing the maternal response to the placental protein secretion, these works revealed improved angiogenesis in endothelial cells during culture with conditioned medium from Rosiglitazone-treated PE placentas. These studies collectively show the beneficial effects of placental activation of PPARγ to improve placental and vascular function in PE. Future works should aim to understand global changes from PPARγ regulation in the human placenta and focus on compounds that hold promise to be safely used during pregnancy with the goal to improve pregnancy outcomes.
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Title: Hadamard-Babich ansatz and fast Huygens sweeping method for point-source elastic wave equations in an inhomogeneous medium at high frequencies
Creator: Song, Jian
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Asymtotic methods are efficient for solving wave equations in the high frequency regime. In the thesis, we first develop a new asymptotic ansatz for point source elastic wave equations in an inhomogeneous medium. Then, we propose a fast Huygens sweeping method to construct a globally valid Green's functions in the presence of caustics. Finally, an Eulerian partial-differential-equation method is proposed to compute complex-valued eikonals in attenuating media.In Chapter 3, we develop the...
Show moreAsymtotic methods are efficient for solving wave equations in the high frequency regime. In the thesis, we first develop a new asymptotic ansatz for point source elastic wave equations in an inhomogeneous medium. Then, we propose a fast Huygens sweeping method to construct a globally valid Green's functions in the presence of caustics. Finally, an Eulerian partial-differential-equation method is proposed to compute complex-valued eikonals in attenuating media.In Chapter 3, we develop the Hadamard-Babich (H-B) ansatz for frequency-domain point source elastic wave equations in an inhomogeneous medium in the high-frequency regime. First, we develop a novel asymptotic series, dubbed Hadamard’s ansatz, to form the fundamental solution of the Cauchy problem for the time-domain point-source (TDPS) elastic wave equations in the region close to the source. Then, the governing equations for the unknown asymptotics of the ansatz are derived including the traveltime functions and dyadic coefficients. A matching condition is proposed to initialize the data of unknowns at the source. To treat singularity of dyadic coefficients at the source, smoother dyadic coefficients are then introduced. Directly taking the Fourier transform of Hadamard’s ansatz in time, we obtain the H-B ansatz for the frequency-domain point-source (FDPS) elastic wave equations. To verify the feasibility of the new ansatz, we truncate the ansatz to keep only the first two terms to compute the resulting asymptotic solutions. Numerical examples demonstrate the accuracy of our method.In Chapter 4, we propose a new truncated Hadamard-Babich ansatz based globally valid asymptotic method, dubbed the fast Huygens sweeping method, for computing Green's functions of FDPS elastic wave equations in inhomogeneous media in the high-frequency regime and in the presence of caustics. The first novelty of the fast Huygens sweeping method is that the Huygens-Kirchhoff secondary-source principle is used to integrate many locally valid asymptotic solutions to yield a globally valid asymptotic solution so that caustics can be treated automatically and implicitly. The precomputed asymptotic ingredients can be used to construct Green's functions of elastic wave equations for many different point sources and for arbitrary frequencies. The second novelty is that a butterfly algorithm is adapted to accelerate matrix-vector products induced by the discretization of the Huygens-Kirchhoff integral. The computational cost of the butterfly algorithm is O(NlogN) which is in nearly optimal complexity in terms of the total number of mesh points N. The prefactor of the complexity depends only on the specified accuracy and is independent of the frequency parameter. Numerical examples are presented to demonstrate the performance and accuracy of the new method. In Chapter 5, we propose a Eulerian partial-differential-equation method to solve complex-valued eikonals in attenuating media. In the regime of high-frequency asymptotics, a complex-valued eikonal is an essential ingredient for describing wave propagation in attenuating media, where the real and imaginary parts of the eikonal function capture dispersion effects and amplitude attenuation of seismic waves, respectively. Therefore, a unified framework to eulerianize several popular approximate real-space ray-tracing methods for complex-valued eikonals is proposed so that the real and imaginary parts of the eikonal function satisfy the classical real-space eikonal equation and a novel real-space advection equation, respectively, and we dub the resulting method the Eulerian partial-differential-equation method. We further develop highly efficient high-order methods to solve these two equations by using the factorization idea and the Lax-Friedrichs weighted essentially non-oscillatory (WENO) schemes. Numerical examples demonstrate that the proposed method yields highly accurate complex-valued eikonals, analogous to those from ray-tracing methods.
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Title: LISTERIA MONOCYTOGENES PLACENTAL COLONZATION AND CONSEQUENCES FOR PREGNANCY OUTCOME
Creator: Conner, Kayla Nicole
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Listeria monocytogenes (Lm) is a Gram-positive bacterium that causes the severe food-borne disease listeriosis. Listeriosis is particularly problematic in pregnant women as Lm colonizes the placenta, resulting in adverse pregnancy outcomes including stillbirth, miscarriage, and preterm labor. Despite numerous studies of placental listeriosis (PL) in various animal models, the mechanisms driving adverse outcomes following PL are largely uncharacterized. This dissertation addresses some of the...
Show moreListeria monocytogenes (Lm) is a Gram-positive bacterium that causes the severe food-borne disease listeriosis. Listeriosis is particularly problematic in pregnant women as Lm colonizes the placenta, resulting in adverse pregnancy outcomes including stillbirth, miscarriage, and preterm labor. Despite numerous studies of placental listeriosis (PL) in various animal models, the mechanisms driving adverse outcomes following PL are largely uncharacterized. This dissertation addresses some of the field’s knowledge gaps by analyzing the changes in placental gene expression and metabolism following infection with Lm and by characterizing a key Lm virulence factor, Internalin P (InlP), which plays a significant role in Lm placental colonization. Chapter 1 gives pertinent background information on the placenta, Lm, and PL and broadly addresses the knowledge gaps to be addressed by the rest of the dissertation. Chapter 2 describes an in vivo study of PL in mice. Infected and control placentas were analyzed for differences in gene expression profiles between the two groups. We identified an enrichment of genes associated with eicosanoid biosynthesis, suggesting perturbations in eicosanoid metabolism in infected tissues. By quantifying placental eicosanoid concentrations through mass spectrometry, we found a significant increase in the concentrations of several eicosanoids with known roles in inflammation and/or labor. This study provides a likely explanation for temporal disruptions of labor following placental infection. Chapters 3 and 4 discuss two studies of the Lm virulence factor InlP, a key player in placental colonization. InlP contributes to Lm’s placental pathogenesis likely by conferring the ability of Lm to transcytose through placental layers. Prior studies reported that no homologs of InlP exist in Listeria species other than Lm. Chapter 3 describes our discovery that at least two other Listeria species, L. ivanovii and L. seeligeri, encode InlP homologs. We characterized the domain architectures and genomic neighborhoods of these homologs and speculated on their implications for Listeria evolution. In chapter 4, I continue discussion of InlP and describe our identification and preliminary characterization of naturally occurring InlP variants. In this study, we used a bioinformatics approach to analyze Lm whole genome sequences (WGS) and identify InlP variants. We uncovered two InlP variants of interest in the Lm population. The first results from a start codon point mutation in the inlP gene, likely resulting in a truncated and potentially nonfunctional InlP protein product. The second is an InlP variant with a PRO to SER substitution in the InlP calcium binding loop, which is hypothesized to play a role in InlP activation or stabilization. These results provide two avenues for further investigation of InlP regulation and function and suggest the potential for InlP-dependent variation in placental colonization potential across Lm isolates. In chapter 5, I summarize this dissertation. This chapter reflects on the results, implications, and challenges of each study outlined in the prior chapters. I discuss the unique challenges faced due to the ongoing COVID-19 pandemic and its effects on my graduate training. Finally, I share concluding remarks and propose future directions for this project and the field of PL. Together, the chapters of this dissertation describe novel findings that contribute to the field by assessing genetic and metabolic changes to the placenta due to listeriosis and further characterizing a known key placental virulence factor.
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Title: STUDIES ON COMPLEX TASK NETWORKS BASED ON CONTEXTUAL SPECIFICS IN ELECTRONIC MEDICAL RECORDS
Creator: Kim, Inkyu
Date: 2022
Collection: Electronic Theses & Dissertations
Description: As organizational processes have become more interconnected and interdependent, contextual factors have become central to both information systems and process management. Despite the importance of context, few studies investigate the influence of contextual factors on the structure of business processes. Thus, in this dissertation, I examine the role of contextual specifics in the structure of the clinical documentation process using data from electronic health records in outpatient clinics....
Show moreAs organizational processes have become more interconnected and interdependent, contextual factors have become central to both information systems and process management. Despite the importance of context, few studies investigate the influence of contextual factors on the structure of business processes. Thus, in this dissertation, I examine the role of contextual specifics in the structure of the clinical documentation process using data from electronic health records in outpatient clinics. The dissertation includes three essays. In the first essay, I address the influence of internal contextual factors on enacted complexity. The findings of the first essay provide a unique opportunity to theorize on the specialization in enacted complexity of process by examining the effects of: 1) the number of roles and 2) specialization index. Contrary to expectations, I find that complexity decreases when a greater number of roles are involved in the clinical process and the roles are highly specialized. In the second essay, I turn my attention to the effects of exogenous shocks: When routines are disrupted, are some patterns of action more likely to be affected than others? I show that cohesion (defined as the consistency of context between pairs of actions) has a particularly strong influence on the persistence of action patterns. In essay three, I suggest a path prediction model in a process based on action sequence and its contextual specifics. The model uses a recurrent neural network that models both the observed sequence of actions and the contextual factors in the process. As expected, the results show that context can improve predictive models. In the case of outpatient medical clinics, the strongest improvement in accuracy comes from two attributes: 1) the workstation (location) where work is performed and 2) whether or not the system has been upgraded. Together, these essays represent a rigorous framework for analyzing the role of context in organizational processes and routines.
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Title: EXAMINING THE RELATIONSHIP AMONG PHYSICAL ACTIVITY, STRESS, DEPRESSION, AND ANXIETY IN COLLEGE STUDENTS
Creator: Hayden, Dorian James
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Mental health challenges have been steadily increasing around college campuses, with consistent findings pointing to ethnic minorities and low socioeconomic groups adversely affected and needing more support than their counterparts. On the other end, physical activity (PA) has consistently been associated with positive mental health outcomes. Therefore, further understanding the relationship among race, socioeconomic status, and PA, as well as college students personal experiences on campuses...
Show moreMental health challenges have been steadily increasing around college campuses, with consistent findings pointing to ethnic minorities and low socioeconomic groups adversely affected and needing more support than their counterparts. On the other end, physical activity (PA) has consistently been associated with positive mental health outcomes. Therefore, further understanding the relationship among race, socioeconomic status, and PA, as well as college students personal experiences on campuses, is of great importance to improve college student well-being. This two-study dissertation sought to address these relationships. Study 1 evaluated differences in mental health across race, parental education (proxy for SES) and PA. Student obstacles to using on-campus mental health and PA resources were examined in a mixed methods design. Most of the data was collected prior to the establishment of COVID-19 restrictions at a large Midwest university. Mental health levels were anticipated to vary between the variables of race, parental education, and PA, which was partially supported. Results showed that low SES participants had significantly higher levels of depression, while PA was associated with lower levels of anxiety and stress. Study 2 sought to replicate findings of study 1 and test the relationships within the context of a diathesis-stress model that includes PA using an expanded sample of students drawn from a large Midwest university and a smaller East Coast university. In addition to replicating study 1 findings, study 2 yielded several themes that revealed common obstacles of college students and how they overcome those obstacles. The hypothesized relationship among race, SES, PA and mental health was partially supported. Specifically, participants whose parents or guardians had lower levels of education reported higher levels of anxiety, while there were significant differences in mental health across different levels of PA. The other goal of this study was to map the above relationship onto a PA moderating model, including variables of race, parental education, depression, stress, and anxiety, based on an adapted diathesis-stress model. This relationship was not supported by the data. Free response answers revealed interesting themes related to the college student experience and campus resources. Focus groups added to this through discussions on topics like the COVID-19 pandemic, mental health, and advice for future students. Data from study 2 was collected while COVID-19 pandemic restrictions were in place. Overall results expanded knowledge on the experience of COVID-19 on college campus and the interconnection between race, parental education, PA, and mental health. Further social relations were important for student wellbeing. Students’ also shared obstacles they faced with the use of on campus mental health and other resources.
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Title: COMPOSITION AND FUNCTION : UNRAVELING THE ROLE OF GROUP B STREPTOCOCCAL MEMBRANE VESICLES
Creator: McCutcheon, Cole Ross
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Group B Streptococcus (GBS) is an opportunistic pathogen that asymptomatically colonizes the vaginal tract of approximately 30% of women. In individuals with an altered immune state such as the elderly, pregnant women, and neonates, GBS can cause invasive infections. During pregnancy, GBS frequently contributes to infections in utero that can result in chorioamnionitis, preterm birth, or miscarriage. The bacterial factors that promote these adverse outcomes, however, are under studied. For...
Show moreGroup B Streptococcus (GBS) is an opportunistic pathogen that asymptomatically colonizes the vaginal tract of approximately 30% of women. In individuals with an altered immune state such as the elderly, pregnant women, and neonates, GBS can cause invasive infections. During pregnancy, GBS frequently contributes to infections in utero that can result in chorioamnionitis, preterm birth, or miscarriage. The bacterial factors that promote these adverse outcomes, however, are under studied. For instance, previous reports have demonstrated that GBS produces membrane vesicles (MVs), which have been linked to adverse pregnancy outcomes in a murine model. Nonetheless, little is known about the composition of GBS MVs and their role in pathogenesis and impact on the immune response. Therefore, using genotypically diverse strains of GBS, I sought to examine MV production and composition, as well as their impact on ascending infection in vivo to better understand their role in GBS disease. While MVs contain a variety of immunomodulatory virulence factors, including hyaluronidase, C5a peptidase, and sialidase, the relative abundance of these virulence factors varies in a lineage dependent manner. With this information in hand, I then assessed the host response to GBS derived MVs using human THP-1 derived macrophages. I found that regardless of strain, MVs induce a potent proinflammatory immune response characterized by the production of proinflammatory cytokines and chemokines. Notably, many neutrophil chemokines were highly upregulated in response to MVs, which is consistent with observations seen during murine challenge with MVs. I went on to demonstrate that MVs, in the absence of t, induce a potent IL-1ß response, which is dependent on caspase-1 and NLRP3, suggesting that the NLRP3 inflammasome is a sensor of GBS derived MVs. Previous data had suggested that MVs induce inflammation at the maternal-fetal interface. We have confirmed these findings and identified a potential mechanism for this inflammatory response. Furthermore, others utilized models of intra-amniotic injection that bypasses many immune defenses such as the extraplacental membranes and the cervix, which may prevent this response, while we assessed the role of MVs during vaginal challenge with GBS. However, we found that the addition of exogenous MVs does not promote ascending infection in vivo. While bacteria were able to ascend from the vaginal tract into gestational tissues, similar levels of bacteria were found regardless of the addition of exogenous MVs. Consistent with this observation, using flow cytometry we showed that neither exogenous MVs supplemented at the time of infection nor vaginal supplementation of MVs alone alter inflammatory responses at the maternal-fetal interface, suggesting that these innate barriers are capable of blocking MV mediated effects. The work presented here dramatically alters our understanding of the composition and host-pathogen interactions of GBS MVs, by substantially increasing our knowledge of both their composition and function during infection.
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Title: INVESTIGATING THE RELATIONSHIP BETWEEN WELLBEING AND GRAZING MANAGEMENT DECISIONS ON MICHIGAN’S PASTURE-BASED BEEF FARMS
Creator: MathisonSlee, Morgan
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Livestock producers around the world are concerned about land degradation and the increase in extreme weather events such as more frequent flooding and droughts, as well as current rates of biodiversity loss, soil erosion, and desertification. One suggested change that could improve grassland sustainability is the use of adaptive grazing management approaches, however the ramifications of using an adaptive grazing approach have been understudied from a social perspective. In this dissertation...
Show moreLivestock producers around the world are concerned about land degradation and the increase in extreme weather events such as more frequent flooding and droughts, as well as current rates of biodiversity loss, soil erosion, and desertification. One suggested change that could improve grassland sustainability is the use of adaptive grazing management approaches, however the ramifications of using an adaptive grazing approach have been understudied from a social perspective. In this dissertation I used a social-ecological systems approach to investigate the relationship between grazing management style and farmer wellbeing in Michigan’s pasture-based beef farms. I created a novel theoretical framework which integrated the Theory of Planned Behavior with the Theory of Basic Human Values at an individual farm scale to understand why farmers manage their animals the way they do. Further,. I explored the relationship between management style and the physical, psychological, and social wellbeing of farmers to better understand if certain management practices result in higher farmer wellbeing. I investigated wellbeing from a benefits-challenges perspective to acknowledge there will always be tradeoffs in the system. This focus on wellbeing is necessary because farmers often suffer from higher-than-average rates of mental illness and are one of the top three occupations most likely to die by suicide. Thus, it is imperative we determine if there are any management techniques that bolster wellbeing.I used a sequential mixed methods approach by coupling an online survey with follow up interviews from a subsample of the participants to better understand the range of grazing management practices being used on Michigan’s pasture-based beef farms, particularly how perceptions of control, attitudes, norms, and values influence the farmer’s choice of grazing management behaviors. I found pasture-based beef farmers managed their grazing animals either rotationally or adaptively, and that my theoretical framework can explain why there are differences in what drives the adoption of different grazing management styles. If we want to understand the adoption of adaptive grazing management as a tool for grassland restoration it is important to know what management strategies are used on the ground. Farmers who were managing rotationally were more likely to be a generational, family farm and the adaptive farmers were more likely to be an independent startup farm. Additionally, there were differences in the role of diversification between the two groups, mainly, adaptive farmers are more confident in their ability to create a highly diversified farm than their rotational counterparts I also found that Michigan’s pasture-based beef farmers did not report the low levels of wellbeing I expected, rather farmers across the management spectrum have high physical and psychological wellbeing. The largest challenge to wellbeing was in the social dimension where many farmers expressed feeling isolated. However, when the COVID-19 pandemic emerged farmers coped in ways that supported their wellbeing, including receiving financial support and spending additional time outdoors. These findings and my theoretical framework serve as an initial exploration into the wellbeing and management decisions of pasture-based beef farmers in Michigan that will hopefully be useful for future research on the wellbeing of farmers across the state and beyond.
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Title: Efficient and Secure Message Passing for Machine Learning
Creator: Liu, Xiaorui
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Machine learning (ML) techniques have brought revolutionary impact to human society, and they will continue to act as technological innovators in the future. To broaden its impact, it is urgent to solve the emerging and critical challenges in machine learning, such as efficiency and security issues. On the one hand, ML models have become increasingly powerful due to big data and models, but it also brings tremendous challenges in designing efficient optimization algorithms to train the big ML...
Show moreMachine learning (ML) techniques have brought revolutionary impact to human society, and they will continue to act as technological innovators in the future. To broaden its impact, it is urgent to solve the emerging and critical challenges in machine learning, such as efficiency and security issues. On the one hand, ML models have become increasingly powerful due to big data and models, but it also brings tremendous challenges in designing efficient optimization algorithms to train the big ML models from big data. The most effective way for large-scale ML is to parallelize the computation tasks on distributed systems composed of many computational devices. However, in practice, the scalability and efficiency of the systems are greatly limited by information synchronization since the message passing between the devices dominates the total running time. In other words, the major bottleneck lies in the high communication cost between devices, especially when the scale of the system and the models becomes larger while the communication bandwidth is relatively limited. This communication bottleneck often limits the practical speedup of distributed ML systems. On the other hand, recent research has generally revealed that many ML models suffer from security vulnerabilities. In particular, deep learning models can be easily deceived by the unnoticeable perturbations in data. Meanwhile, graph is a kind of prevalent data structure for many real-world data that encodes pairwise relations between entities such as social networks, transportation networks, and chemical molecules. Graph neural networks (GNNs) generalize and extend the representation learning power of traditional deep neural networks (DNNs) from regular grids, such as image, video, and text, to irregular graph-structured data through message passing frameworks. Therefore, many important applications on these data can be treated as computational tasks on graphs, such as recommender systems, social network analysis, traffic prediction, etc. Unfortunately, the vulnerability of deep learning models also translates to GNNs, which raises significant concerns about their applications, especially in safety-critical areas. Therefore, it is critical to design intrinsically secure ML models for graph-structured data.The primary objective of this dissertation is to figure out the solutions to solve these challenges via innovative research and principled methods. In particular, we propose multiple distributed optimization algorithms with efficient message passing to mitigate the communication bottleneck and speed up ML model training in distributed ML systems. We also propose multiple secure message passing schemes as the building blocks of graph neural networks aiming to significantly improve the security and robustness of ML models.
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Title: AI ACCELERATED COLLISIONAL CROSS SECTION PREDICTION FOR HIGH THROUGHPUT METABOLITE IDENTIFICATION
Creator: Tanemura, Kiyoto Aramis
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Metabolomics refers to the collective characterization of small organic molecules in a biological sample. While instrumentation and software continues to improve for metabolomics studies, the fraction of annotated signals in untargeted metabolomics experiments remain small. Translating features to metabolite identities present a major bottleneck, confounded by the lack of authentic standards to build comprehensive experimental databases. I illustrate the development of collisional cross...
Show moreMetabolomics refers to the collective characterization of small organic molecules in a biological sample. While instrumentation and software continues to improve for metabolomics studies, the fraction of annotated signals in untargeted metabolomics experiments remain small. Translating features to metabolite identities present a major bottleneck, confounded by the lack of authentic standards to build comprehensive experimental databases. I illustrate the development of collisional cross section (CCS) prediction methods through deduction from theory and induction from available data. The theoretical CCS prediction involves multistep modeling of conformational ensemble followed by simulation of ion mobility. The advanced computational chemistry operations were automated using the AutoGraph conformational clustering protocol and implementation of the workflow in Snakemake. In a complementary approach, I applied a graph convolutional deep Bayesian neural net to predict CCS values and their uncertainty values. The quantified uncertainty was used to guide ab initio prediction of CCS values in an active learning strategy. The developed methodologies lay the foundation to a continuously refining in silico CCS library to aid in metabolite annotation.
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Title: THE ROLE OF DISTRICT AND UNION SUPPORT IN PURSUING THREE-DIMENSIONAL SCIENCE TEACHING PROFESSIONAL COMMUNITIES
Creator: Thomas, Christie Morrison
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This qualitative study compares four public school districts in a state to investigate how Next Generation Science Standards-aligned, three-dimensional science classroom teaching and learning in biology classrooms could become normal, instead of exceptional. Interview data were collected through two rounds of interviews – one year apart – with teachers, district science coordinators, and teachers’ union staff and leaders in districts using Carbon TIME instructional resources in high school...
Show moreThis qualitative study compares four public school districts in a state to investigate how Next Generation Science Standards-aligned, three-dimensional science classroom teaching and learning in biology classrooms could become normal, instead of exceptional. Interview data were collected through two rounds of interviews – one year apart – with teachers, district science coordinators, and teachers’ union staff and leaders in districts using Carbon TIME instructional resources in high school biology. Results are shared through district-level identifying stories of current realities (actual identities) and future plans and goals (designated identities).Each of the four school districts described similar interacting communities of practice – teachers’ classrooms; teachers’ course-based (biology) professional communities; and district administrators and local union leaders. The study’s analytical framework addresses roles, responsibilities, and professional actions of teachers, union leaders, and administrators and district science coordinators relevant to teachers’ course-based professional communities. Attention was given to professional actions that could “cross the classroom door,” connecting what teachers do together in their course-based (biology) professional communities with their own classroom communities. Two orientations of the identifying stories varied across school districts in ways that influence three-dimensional science classroom teaching and learning: collective (versus individual) orientations and three-dimensional science (versus one-dimensional science) orientations. Identifying stories in districts with collective and three-dimensional science orientations described teachers’ professional community work as necessary to realizing classroom goals for students’ three-dimensional science experiences and performances. District and union leaders endorsed teachers’ professional community work as integral to classroom instruction and supported such work through mitigating transaction and conflict costs. Teachers’ professional actions within their course-based (biology) professional communities included selecting, developing, and revising common three-dimensional instructional resources and making sense of their classroom science instruction using evidence of student learning. Differently, in districts with identifying stories as individually and non-three-dimensional-science oriented professional communities, participants described teachers with individual classroom goals and teachers’ professional communities with traditional norms of non-interference and egalitarian beliefs. District and union leaders endorsed teachers’ independent expertise and classroom autonomy. Teachers’ work with their course-based (biology) professional community was described connecting in optional ways or as not connected to teachers’ individual classroom communities. This study suggests that collectively oriented professional communities can help all classroom communities engage in three-dimensional science teaching and learning. Districts and local teachers’ unions can play important roles in reducing transaction and conflict costs and endorsing identifying stories that support collective orientations.
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Title: Language Ideologies and Practices, Transnationalism, and Identity in Multilingual Families
Creator: Reichmuth, Heather Lyn
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This three-paper formatted dissertation is a qualitative case study of one intermarried Korean-English speaking family residing in South Korea. Data was drawn from in-depth, semi-structured interviews, participant journals, and video documentation of familial interactions, including discussions of family member’s language portraits, family mealtimes, and familial time spent playing board and card games. The first of the three articles examines the language ideologies and practices of the...
Show moreThis three-paper formatted dissertation is a qualitative case study of one intermarried Korean-English speaking family residing in South Korea. Data was drawn from in-depth, semi-structured interviews, participant journals, and video documentation of familial interactions, including discussions of family member’s language portraits, family mealtimes, and familial time spent playing board and card games. The first of the three articles examines the language ideologies and practices of the intermarried family and argues that a translanguaging stance needs to be taken up by caregivers in a bilingual home to support bilingual children and push back on monolingual ideologies placed on bilingual children. The second article looks at the influence of transnational knowledge that the parent members of the family possessed and how this knowledge alongside their ethnotheories of childrearing influenced their bonding and language practices in the home. The third paper examines the practiced and positioned identities of the four family members in Korea. The findings of this dissertation suggest that: 1) multiple and conflicting language ideologies and practices can exist in multilingual homes, 2) a translanguaging stance among caregivers of bilingual children is important to support their evolving bilingual identities, 3) transnational knowledge and ethnotheories are present in the decision making of family language policies and practices in intermarried families, and 4) practiced identities may conflict with positioned identities, especially those of multilingual and multiracial children in the Korean context.
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Title: Tool Wear Study in Turning Ti-6Al-4V and Edge Trimming of Carbon Fiber Reinforced Plastics (CFRP)
Creator: Khawarizmi, Ryan Muhammad
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Lightweight materials such as titanium alloys and carbon fiber reinforced plastics (CFRP) are highly desirable due to their low density and high strength properties for many aerospace, chemical, petroleum, automotive, and sports applications. However, both materials are considered difficult to machine due to various factors.In machining titanium alloys, the low thermal conductivity and highly reactive nature of titanium with cutting tools cause the temperature to rise quickly, producing a...
Show moreLightweight materials such as titanium alloys and carbon fiber reinforced plastics (CFRP) are highly desirable due to their low density and high strength properties for many aerospace, chemical, petroleum, automotive, and sports applications. However, both materials are considered difficult to machine due to various factors.In machining titanium alloys, the low thermal conductivity and highly reactive nature of titanium with cutting tools cause the temperature to rise quickly, producing a segmented or “saw-tooth” chip. Chip segmentation caused a periodic loading on the tool and affected the cutting process. Ti-6Al-4V depending on the heat treatment, produces four distinct types, elongated (ELO), mill-annealed (MIL), solution treated and aged (STA), and lamellar (LAM). In this dissertation, four different microstructures of Ti64, ELO, MIL, STA, and LAM, are machined at 61, 91, and 122 m/min. The machining chips were collected and characterized to study the impact of the microstructure. In addition, the crater wear for different types of Ti64 was measured and compared. A finite element numerical simulation was developed using the chip morphology measured, which enables estimating the cutting temperature for Ti64-STA. Electron backscatter images of the cutting chips (EBSD) and crater wear surfaces were also analyzed to verify the wear mechanism. The findings suggested a high interface temperature during cutting enables faster tool diffusion. Another machinability study of turning Ti64-STA using a variety of coated tools was conducted. The coated tool materials include TiAlN, AlTiN, AlMgB14(BAM), ZrN, and (AlCrSi/Ti)N. The performance of these cutting tools was assessed using cutting force data, flank wear, and crater wear measurements. In conjunction with the coating experiments, another machining study was conducted in minimum quantity lubrication (MQL) using oil mixed with solid additives such as hBN, WS2, MoS2, and xGnP. For CFRP, the abrasion from the fibers was the leading cause of tool wear. Three distinctly different types of CFRPs with T300 PAN-based carbon fibers as standard modulus (SM), IM-7 PAN-based carbon fibers as intermediate modulus (IM), and K13312 pitch-based carbon fibers as high modulus (HM) are used. Tool wear during the edge-trimming process of three types of CFRP laminates is analyzed for four different ply angles, namely 0°, 45°, 90°, 135°, to investigate the interactions between the fiber type and the fiber orientation.
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Title: Monetary Policy and Labor Supply
Creator: Burke, Patrick
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The first chapter gives an overview of the current literature on participation in the labor market. Special attention is paid to trends in participation since 2000. The role of demographic change in those trends is compared against other explanations. With the increasing focus on labor market participation at the United States Federal Reserve, the history of monetary policy changes and participation is also examined. The second chapter estimates a labor market matching model to get a more...
Show moreThe first chapter gives an overview of the current literature on participation in the labor market. Special attention is paid to trends in participation since 2000. The role of demographic change in those trends is compared against other explanations. With the increasing focus on labor market participation at the United States Federal Reserve, the history of monetary policy changes and participation is also examined. The second chapter estimates a labor market matching model to get a more accurate measure of the market tightness elasticity of the job finding rate and unexplained residual. The estimation strategy in the second chapter follows the approach in Borowczyk-Martins et al. (2013) which models the autocorrelation structure of the unobserved component in the matching function to address simultaneity bias. This chapter then uses asset data present in the Survey of Income and Program Participation. This allows for the use of average household debt as an additional instrument to correct for measurement error. These results help characterize the recent shifts in the Beveridge curve and the decline of the matching rate between job seekers and job openings between 2008-2013. How important is labor supply for the ability of monetary policy to influence inflation and employment? Hiring costs alter the response of inflation to monetary policy. As shown in Kurozumi and Van Zandweghe (2010), adjustments in employment can make it difficult for monetary policy to reach its price stability and full employment targets. As the policy response is more vigorous in maintaining inflation around a target, that target becomes impossible to maintain. Recent fluctuations in the participation rate have led to a growing concern about the role of labor supply in monetary policy. This chapter shows that as labor supply becomes more elastic, the monetary authority is more likely to be able to stabilize the economy around its steady state targets. The central bank's response to cyclical unemployment is important for price level stability regardless of business cycle goals. Journal of Economic Literature codes: E12 E24 E31 E32 E52.
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