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Title: Ultrafast transient states in nonequilibrium quantum systems
Creator: Hwang, Bin
Date: 2017
Collection: Electronic Theses & Dissertations
Description: Photo-induced phase transitions (PIPT) in quantum systems are the epitome of challenging non-equilibrium many-body phenomena, that also have a wide range of potential applications. Recently interest in light-matter coupled states with an energy gap have yielded evidence for Floquet topological states. In this study we demonstrate nonequilibrium Floquet band formation under ultrafast optical excitation using a one-dimensional topological insulator. As an example, the effects are illustrated...
Show morePhoto-induced phase transitions (PIPT) in quantum systems are the epitome of challenging non-equilibrium many-body phenomena, that also have a wide range of potential applications. Recently interest in light-matter coupled states with an energy gap have yielded evidence for Floquet topological states. In this study we demonstrate nonequilibrium Floquet band formation under ultrafast optical excitation using a one-dimensional topological insulator. As an example, the effects are illustrated using a new Zig-Zag Su-Schrieffer-Heeger model of polyacetylene, which is a paradigmatic Hamiltonian exhibiting nontrivial edge states. Our results indicate short optical pulses feasible in experiments can induce novel topological states, local spectral selection and novel pseudospin textures in polyacetylene. Pump-probe photoemission spectroscopy is able to study these states by measuring Floquet band formation and sizeable energy gaps on femtosecond time scales. We find that optically activated nontrivial variations of sublattice mixing could lead to novel topological phenomenon.The rich variety of states induced by lasers have a wide range of potential applications so that control of these states has become a key objective. We present a computational approach to finding optimal ultrafast laser pulse shapes to induce target states and population inversion in pump-probe PIPT experiments. The Krotov approach for Quantum optimal control theory (QOCT) is combined with a Keldysh Green’s function calculation to describe experimental outcomes such as photoemission, transient single particle density of states and optical responses. Results for a simple model charge density wave (CDW) system are presented, including generation of almost complete population inversion and negative temperature states.
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Title: Understanding Student Experiences in Informal Physics Programs Using the Communities of Practice Framework
Creator: Prefontaine, Brean Elizabeth
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Studies on physics identity have shown that it is one of the main factors that can predict a person’s persistence in the field; therefore, studying physics identity is critical to increase diversity within the field of physics and to understand what changes can allow more women and people of color to identify with the field. Informal physics spaces are not only made up of youth participants, but also facilitators who can be undergraduate or graduate student volunteers. In this work, the...
Show moreStudies on physics identity have shown that it is one of the main factors that can predict a person’s persistence in the field; therefore, studying physics identity is critical to increase diversity within the field of physics and to understand what changes can allow more women and people of color to identify with the field. Informal physics spaces are not only made up of youth participants, but also facilitators who can be undergraduate or graduate student volunteers. In this work, the experiences of facilitators within informal physics programs are investigated as spaces for physics identity development. Thus, the driving question for all of this work is: In what ways can participating as a facilitator within an informal physics program affect identity development? The data for these studies were collected through observations, written artifacts, and semi-structured interviews with those who facilitated the informal physics programs. In order to understand more about the experiences of the facilitators, the informal physics programs were viewed as Communities of Practice (CoP), and the CoP framework was operationalized within the context of these spaces. First, stories from two physics graduate students out of the interview sample are presented to provide a context for testing the feasibility of the extended framework and to identify how experiences within an informal physics program can shape physics identity development. Then, the operationalized CoP framework is used to study three distinct informal physics programs to understand the structures that support physics identity development. Finally, informal programs that combine physics and music/art are examined with the operationalized CoP framework to understand how these blended spaces can form communities of practice and support identity development. Analysis showed that the CoP framework is an effective tool for analyzing informal physics programs and highlights the structures that lead to identity development. These findings indicate that informal physics programs that operate with a CoP structure can provide valuable experiences to undergraduate and graduate facilitators that lead to physics identity growth.
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Title: Understanding adhesion to monitor and control environmental processes : From virus detection to membrane fouling mitigation
Creator: Wang, Xunhao
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Adhesion is a physicochemical process of great importance for various environmental engineering technologies including those that are employed in water treatment facilities Understanding adhesion is the key to elucidating separation mechanisms in unit processes and operations such as flocculation, granular media filtration, membrane separation. The likelihood of adhesion can be quantified in terms of the interfacial energy of interaction between two objects. The first part of this...
Show moreAdhesion is a physicochemical process of great importance for various environmental engineering technologies including those that are employed in water treatment facilities Understanding adhesion is the key to elucidating separation mechanisms in unit processes and operations such as flocculation, granular media filtration, membrane separation. The likelihood of adhesion can be quantified in terms of the interfacial energy of interaction between two objects. The first part of this dissertation is devoted to the study of virus adhesion to surfaces commonly encountered in various indoor settings. Fomites are inanimate surfaces, which can transfer the pathogens to a new human host. Fomite-based transfer is an important pathway of virus transmission, along with direct contact and transmission through aerosols. The study of fomites has traditionally focused on determining whether there is presence of specific pathogenic organisms. In addition to detecting genetic material and viable microbes on fomite surfaces, it is also important to understand the underlying mechanism of virus adhesion and factors that affect the likelihood of transmission between fomites and humans. In this dissertation, Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) is employed to quantify virus attachment to fomites. XDLVO modeling is applied to predict the virus-fomites interactions. Virion size, surface charge and surface energy components as well as surface charge and surface energy components of various fomites were measured and used as inputs to the XDLVO model.The second part of this dissertation describes the study of membrane filter aging due to membrane’s intermittent exposure to foulants and cleaning agents. This study explores how the surface chemistry of polyvinylidene fluoride (PVDF) membranes evolves in challenge tests with humic acid (HA) fouling and sodium hypochlorite (NaClO) employed as a model foulant and cleaning agent, respectively. The evolution of physicochemical properties of the ageing membranes is characterized based on surface energy calculations. The results point to the formation of a chemically irreversible layer of foulants that is conditioned by consecutive exposures to foulants and is comprised of the adsorbed foulant fraction that is hard to oxidize further.
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Title: Understanding free-carrier accumulation in semiconductor nanomaterials : plasmonic behavior, charge storage energetics, and quantum confinement resilience of colloidal indium nitride nanocrystals
Creator: Liu, Zhihui
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Heavily doped semiconductor nanocrystals (NCs) are promising materials that can reversibly and substantially store electrical charges. Indium nitride (InN) is a particularly interesting semiconductor material for studying charge storage processes. Colloidal InN NCs are spontaneously degenerately doped with carrier densities large enough to lead to strong localized surface plasmon resonances (LSPR) in the infrared (IR) part of the spectrum. Unfortunately, many fundamental quantities that...
Show moreHeavily doped semiconductor nanocrystals (NCs) are promising materials that can reversibly and substantially store electrical charges. Indium nitride (InN) is a particularly interesting semiconductor material for studying charge storage processes. Colloidal InN NCs are spontaneously degenerately doped with carrier densities large enough to lead to strong localized surface plasmon resonances (LSPR) in the infrared (IR) part of the spectrum. Unfortunately, many fundamental quantities that ultimately control the behavior of colloidal InN NCs are currently unknown. In this thesis, we focused on advancing our current understanding of the properties of colloidal InN NCs, with special emphasis on the quantification of free electron density, the LSPR behavior, the charge storage ability, the screening effect on phonon behaviors and few other important fundamental quantities such as the electron effective mass, Fermi level, conduction band (CB) edge potential and IR transition oscillator strength.To understand the LSPR behavior of InN NCs, we first evaluated the free carrier density with a direct, model-independent quantification. We found that the number of free electrons per as-prepared InN NC is directly proportional to the NC volume, such that the free electron density is a size-independent quantity. Furthermore, we demonstrated that free electrons in InN NCs can be reversibly extracted with redox species, which leads to a direct way to manipulate the LSPR. Importantly, the LSPR energy in InN NCs barely shifts with free electron density, a behavior strikingly at odds with what is typically observed in other semiconductor plasmonic systems. These unusual plasmonic signatures are shown to arise from the nonparabolicity of the CB dispersion, which leads to a change in the electron effective mass with the number of free electrons per NC, thus mitigating the shift of LSPR in InN NCs.Consequently, we estimated the charge storage capability of InN NCs by pinning the chemical potential of InN NCs to redox-active molecular species. These studies directly yielded precise information on the Fermi level and on the chemical capacitance of InN NCs, which allowed the CB edge potential of InN NCs to be quantitatively determined for the first time. Surprisingly, the CB edge in InN NCs hardly showed any sign of quantum confinement effects, even for NCs sizes that were clearly smaller than the excitonic Bohr radius of InN. This "resilience to quantum confinement" effect was shown to also arise from the same nonparabolic dispersion effects described above.In addition, the light harvesting ability of free electrons in InN NCs was evaluated by calculating the molar absorptivity per free electron. This value directly yielded the optical oscillator strength of LSPR. We found that optical oscillator strength (per free electron) is independent of NC.Finally, the effects of free electrons on lattice vibrations were also explored. We demonstrated that free electrons weakened the A1(LO) phonon mode by screening the Coulombic restoring force induced by the lattice distortion. The A1(LO) mode frequency red-shifted linearly with the increasing free electron density. This relationship provided a fast way to estimate free electron density of InN NCs by measuring Raman spectroscopy.
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Title: Understanding the intersection of loneliness and recovery setting in older cardiac patients
Creator: Macomber, Catherine A.
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "Loneliness has significant negative impact on health. Loneliness is the difference between the amount of social support you expect to receive and the amount you perceive you are getting. Age is one risk factor of loneliness, and life events such as a move to a nursing home or the need for professional care to provide assistance with Activities of Daily Living also increase the risk of loneliness. There is little evidence comparing the experience of loneliness between settings of nursing...
Show more"Loneliness has significant negative impact on health. Loneliness is the difference between the amount of social support you expect to receive and the amount you perceive you are getting. Age is one risk factor of loneliness, and life events such as a move to a nursing home or the need for professional care to provide assistance with Activities of Daily Living also increase the risk of loneliness. There is little evidence comparing the experience of loneliness between settings of nursing homes and at home with home care, and yet much current policy sees aging-in-place, staying in your own home, as the most appropriate setting for growing older. This mixed methods study compares the experience of loneliness in two settings, nursing home and at home, and the influence demographics and social support have on this relationship. The theoretical framework used is the Health Belief Model." -- Abstract.
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Title: Understanding the relationship between work-life flexstyle, job satisfaction, and turnover intention among new professionals in student affairs
Creator: Artale, Paolo
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Attrition amongst new professionals in student affairs has been cited as high as sixty-percent Holmes, Verrier, & Chisholm 1983; Ward, 1995). High rates of employee turnover are problematic for institutions and result in work inefficiencies, costly rehiring processes, and overburdening current employees with increased load (Kantor, 2016). Studies of attrition within student affairs have found several factors that contribute to these high rates of departure including but not limited to heavy...
Show moreAttrition amongst new professionals in student affairs has been cited as high as sixty-percent Holmes, Verrier, & Chisholm 1983; Ward, 1995). High rates of employee turnover are problematic for institutions and result in work inefficiencies, costly rehiring processes, and overburdening current employees with increased load (Kantor, 2016). Studies of attrition within student affairs have found several factors that contribute to these high rates of departure including but not limited to heavy workloads, working long and unusual hours, lack of opportunities for advancement, low levels of pay compared to the private sector, difficulty keeping tasks and emotions that originated at work with those at home (and vice versa), and emotional stress due to being personally invested in the lives of students (Evans, 1988; Lorden, 1998; Marshall, Gardner, Hughes, & Lowery, 2016; Ward, 1995). Within the discussion of meeting combating turnover, the topic of workplace flexibility has emerged. Employees are requiring more latitude to deal with issues such as childcare, elder care, as well as other day-to-day needs. While studies have often referred to policies and formal mechanisms regarding workplace flexibility and the impact it has on retention, there has been a lack of discussion around the role flexstyle plays in employee performance and satisfaction. Flexstyle refers to a way of thinking about the relationships between work and personal life (Kossek & Lautsch, 2008). The purpose of this study was to understand the potential relationship between work-life flexstyle amongst new student affairs professionals and the variables of job satisfaction and turnover intention. To examine the relationship between flexstyle, job satisfaction, and turnover intention, an electronic survey utilizing Kossek, Ruderman, Braddy, and Hannum's (2012) work-nonwork boundary management assessment, Judge, Locke, Durham, and Kluger's (1998) shortened version of Brayfield and Rothe's (1951) Job Satisfaction Schedule, and Bothma and Roodt's (2013) Turnover Intention Scale - 6 (TIS-6) was administered to those who identified as new professionals to members of the National Association of Student Personnel Administrators (NASPA) Knowledge Community for Graduate Students and New Professionals, the American College Personnel Association (ACPA), and the Southern Association of College Student Affairs (SACSA). A total of 287 members provided usable data for use in analysis. Results from the data that utilized ANCOVA showed that significant differences in means existed for behavior factor groups in relation to both job satisfaction and turnover intention. Results from the data that utilized multiple regression showed that significant positive relationships existed between the flexstyle factors of boundary control and work identity with job satisfaction. In addition, data that utilized multiple regression showed that a significant negative relationship existed between the flexstyle factor of boundary control and turnover intention. Implications for student affairs practitioners and researchers and recommendations for future research are also discussed.
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Title: Understanding work with data in summer STEM programs through an experience sampling method approach
Creator: Rosenberg, Joshua M.
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Data-rich activities provide an opportunity to develop core competencies in both science and mathematics identified in curricular standards. Perhaps even more importantly work with data puts learners in the position to use data to ask and answer questions, a potentially empowering capability. Research on work with data has focused on cognitive outcomes and the development of specific practices at the student and classroom levels, and yet, little research has considered learners’ engagement....
Show moreData-rich activities provide an opportunity to develop core competencies in both science and mathematics identified in curricular standards. Perhaps even more importantly work with data puts learners in the position to use data to ask and answer questions, a potentially empowering capability. Research on work with data has focused on cognitive outcomes and the development of specific practices at the student and classroom levels, and yet, little research has considered learners’ engagement. The present study explores learners engagement in work with data in the context of summer STEM programs. The aspects of work with data that are the focus of this study are: asking questions, observing phenomena, constructing measures and generating data, data modeling, and interpreting findings. Data from measures of learners' engagement was collected through the Experience Sampling Method (ESM) that involves asking learners at random intervals to answer short questions about their engagement to discover profiles of learners' engagement.Data was collected from nine summer STEM programs over four weeks in the Northeastern United States. 203 learners reported 2,970 responses via short ESM surveys of how engaged they were (cognitively, behaviorally, and affectively, assessed through separate items) and of their perceptions of themselves (their competence) and the activity (its challenge). These data were used to examine five specific research questions: 1) What is the frequency and nature of opportunities for youth to engage in each of the five aspects of work with data in summer STEM programs? 2) What profiles of engagement emerge from data collected via ESM in the programs? 3) What are sources of variability for the profiles of engagement? 4) How do the five aspects of work with data relate to profiles of engagement? 5) How do youth characteristics relate to profiles of engagement?Findings show that aspects of work with data were fairly common overall, but that work with data was enacted out in varying ways, including some that were possibly highly engaging. Six profiles of youth engagement were identified, representing distinct configurations of the five indicators of engagement. Substantial variability in the profiles was present at the youth level, with less explained by the program youth were in or the nature of the particular instructional episode present at the times when youth were signaled. Relations between the profiles of engagement and each of the aspects of work with data were somewhat small: Notable exceptions were the generating data and data modeling were significantly associated with full engagement. Youth with higher pre-program interest in STEM were more likely to be engaged and competent but not challenged, though other youth characteristics were not highly related to the profiles.I discuss key findings as regards work with data in summer STEM programs and other informal learning environments, the nature of youths' engagement, and what factors can predict engagement. The design and goals of summer STEM programs, which are not (necessarily) focused on activities related to work with data, as well as other limitations including the measures for work with data used and the analytic approach, are identified and described. The role of generating data and modeling data as well as attention to the specifics of how work with data are enacted are presented as implications for practice. I highlight aspects of the findings and the implications for practice with respect to work with data in general and to engagement in informal learning environments, such as summer STEM programs, in both cases with an emphasis on how work with data can serve as a promising context for learning in STEM subject areas.
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Title: Unexpected journeys : at the crossroads of collaborative filmmaking and feminist scholarship
Creator: Von Petersdorff-Campen, Anne Christin
Date: 2018
Collection: Electronic Theses & Dissertations
Description: This hybrid dissertation combines collaborative, creative filmmaking and feminist scholarship grounded in German studies. The written dissertation addresses fundamental issues in feminist filmmaking--body, voice, and collaboration--and is in part conceived as a complement to the travel documentary Wanderlust, cuerpos en tránsito(2017), a bi-autobiographical account of a journey from Egypt to Germany that was co-directed and produced by the author of this dissertation and Maria Pérez-Escalá.

Title: Unraveling Galaxy Evolution Using Numerical Simulations
Creator: Kopenhafer, Claire
Date: 2022
Collection: Electronic Theses & Dissertations
Description: One of the primary concerns in galaxy evolution is how galaxies form their stars: what keeps thatstar formation going over cosmic time, and what causes it to stop in a processes called “quenching”. Galaxies with mass similar to our own Milky Way occupy a sweet spot between abundance and brightness that makes them easy to find in the sky, and such galaxies also populate a transitionary regime in behavior that make them interesting for studying galaxy evolution. Numerical modeling— from semi...
Show moreOne of the primary concerns in galaxy evolution is how galaxies form their stars: what keeps thatstar formation going over cosmic time, and what causes it to stop in a processes called “quenching”. Galaxies with mass similar to our own Milky Way occupy a sweet spot between abundance and brightness that makes them easy to find in the sky, and such galaxies also populate a transitionary regime in behavior that make them interesting for studying galaxy evolution. Numerical modeling— from semi-analytic models to numerical simulations—are valuable tools for understanding the multiple intersecting physical processes that drive galaxy evolution. These processes act both within and around individual galaxies such that numerical models must necessarily encompass a range of spatial and temporal scales. Multiple approaches are commonly used in order for this modeling to be physically insightful. In this dissertation I will present my efforts to unravel the mechanisms of galaxy evolution affect Milky Way-like galaxies using a variety of numerical models.Addressing the issue of what causes galaxies to stop forming stars, I first investigate an unusualpopulation of galaxies called the “breakBRDs” (Tuttle and Tonnesen 2020). Within the dominant framework for galaxy quenching, galaxies first stop forming stars in their centers and later in their outskirts. This is the “inside-out” quenching paradigm. The breakBRD galaxies possess observa- tional markers that run counter to this narrative. We used the IllustrisTNG cosmological simulation (Pillepich et al. 2018b) to find a set of simulated galaxies that are analogous to the observed breakBRDs in order to better understand their evolution. We found that the breakBRD analogues are galaxies that ultimately become fully quenched, but found no clear cause for the “outside-in” modality. This is not the dominant channel for quenching in the IllustrisTNG simulation, but roughly 10% of quiescent galaxies with 10 < log10 (?∗/M⊙) < 11 had centrally-concentrated star formation similar to the breakBRD analogues.As to what keeps galaxies forming their stars, I used a set of idealized simulations of MilkyWay-like galaxies to study the interactions of the circumgalactic medium (CGM) and its host galaxy. The CGM is an extended volume of gas that accounts for about half of the baryonic matter in a galaxy’s dark matter halo. This gas is also “multiphase,” containing gas at a wide range of densities and temperatures. It may therefore function as a reservoir from which gas may cool, condense, and accrete onto the host galaxy where it can eventually drive star formation and stellar feedback primarily via Type II supernovae. This cycle of condensation and feedback may self-regulate the overall star formation rate of a galaxy. Our idealized simulations include both the CGM and explicit formation of stars but find that stellar feedback can drive outflows that disrupt the CGM with large, hot, low-density cavities. This is true even after we adjust the stellar feedback efficiency to accommodate the “settling” of the initial conditions. We therefore conclude that the picture of star formation self-regulation in Milky Way-like galaxies is missing physical processes at the edge of the galaxy halo that work in tandem with accretion of CGM gas and stellar feedback.The CGM is typically observed via absorption spectra that contain features from numerousmetal ions. In order to better compare the simulated CGM with observations, most simulations need to be post-processed to derive similar information as that extracted from spectra. Therefore, I also present preliminary work quantifying the uncertainties inherent to this post-processing. The results herein focus on the assumption that metals in the CGM follow the abundance pattern of our Sun, which is not physically well-reasoned. We derive plausible alternative abundance patterns using chemical evolution modeling and apply these to a post-processing of the FOGGIE cosmological zoom simulations (Peebles 2020; Simons et al. 2020). We find that adopting a non-Solar abundance affects the column density of CGM absorbers of about ±1 dex.Finally, I present future research directions for all the projects described herein. These includeinvestigating the CGM of the breakBRD analogues from IllustrisTNG, outlining additions to our idealized galaxy simulations that may address the issue of disruptive outflows, and both scaling up our existing uncertainty quantification project as well as including the additional source of uncertainty, ionizing radiation.
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Title: Urban and cluster agglomeration economies's effects on rural households in Asia
Creator: Hu, Chaoran
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "Agglomeration effects play important roles for rural households in participating in farm and nonfarm activities. With the rapid growth of cities of different sizes and the development of food value chain, how these agglomerations of urban effects, networks, and food value chain clusters will affect rural households' participation in nonfarm employment and farm behavior (technology adoption) are not yet well known. The dissertation consists of three chapters that aim to assess the impacts of...
Show more"Agglomeration effects play important roles for rural households in participating in farm and nonfarm activities. With the rapid growth of cities of different sizes and the development of food value chain, how these agglomerations of urban effects, networks, and food value chain clusters will affect rural households' participation in nonfarm employment and farm behavior (technology adoption) are not yet well known. The dissertation consists of three chapters that aim to assess the impacts of these urban and cluster agglomeration economies' on rural households in Asia."--Excerpted from abstract.
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Title: Urban expansion and urban environmental evaluation in Chengdu, China
Creator: Tao, Shiqi
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Environmental consequences resulting from urbanization jeopardize the life quality and social welfare of urban residents. To date, studies have focused on the urban environment by using integrated assessment methods and providing one evaluation result for the whole geographic area within an administrative boundary. These studies lack consideration of spatial heterogeneity, failing to fully understand the urban environmental statuses and dynamics at the pixel scale. Therefore, this research...
Show moreEnvironmental consequences resulting from urbanization jeopardize the life quality and social welfare of urban residents. To date, studies have focused on the urban environment by using integrated assessment methods and providing one evaluation result for the whole geographic area within an administrative boundary. These studies lack consideration of spatial heterogeneity, failing to fully understand the urban environmental statuses and dynamics at the pixel scale. Therefore, this research aims to fill this gap by systematically evaluating the urban environment at every single spatial unit of urban land against the background of urban expansion in Chengdu, a megacity in western China. Guided by a proposed three-dimensional (self, neighborhood and accessibility) theoretical framework, this study uses remote sensing and GIS data and adapts the catastrophe theory to evaluate Chengdu's urban environment in a spatially explicit manner. Results from change detection of the urban area in Chengdu show a high-speed expansion from the urban center towards all directions, especially southwest during 2000-2015. Environmental assessment analysis reveals an improved urban center but degraded outskirts regarding environmental conditions. The regression analysis suggests a negative effect of rapid urban expansion on the environment, while this effect can be alleviated through better planning strategies. Therefore, it is suggested that policy makers should balance the speed of urban expansion and urban environmental planning to provide a better living environment for urban residents in Chengdu. The integration of remote sensing and urban environmental assessment can be applied to other cities in China and elsewhere around the world.
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Title: Use of Recycled Aggregate Materials Characteristics in Pavement Design Analyses
Creator: Gheibi, Ida
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Use of recycled materials promotes sustainability in roadway construction by reducing consumption of energy and emission of greenhouse gases associated with mining and the production of natural aggregates. Recycled asphalt pavements (RAP) and recycled concrete aggregates (RCA) have comparable characteristics to natural aggregates that are currently used in roadway base course applications. This study has developed a database for RAP and RCA materials’ characteristics including resilient...
Show moreUse of recycled materials promotes sustainability in roadway construction by reducing consumption of energy and emission of greenhouse gases associated with mining and the production of natural aggregates. Recycled asphalt pavements (RAP) and recycled concrete aggregates (RCA) have comparable characteristics to natural aggregates that are currently used in roadway base course applications. This study has developed a database for RAP and RCA materials’ characteristics including resilient modulus (Mr), California bearing ratio (CBR), gradations along with construction specifications. RAP and RCA relationships with different engineering and index properties were investigated and some trends were proposed such as higher RAP content reveals higher summary of resilient modulus (SMr), higher RCA content causes higher optimum moisture content (OMC) and lower maximum dry unit (MDU).In addition, pavement mechanistic-empirical (ME) analyses have been conducted with the material inputs collected for the database to determine whether different values of different characteristics of RCA and RAP can be used in flexible or rigid pavement designs. Results showed that Mr parameter had the highest impact on pavement distress predictions among gradations and hydraulic conductivity.
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Title: Use of administative claims data to design and emulate a clinical trial in acute stroke patients comparing rehabilitation at inpatient rehabilitation facilities to skilled nursing facilities
Creator: Simmonds, Kent P.
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Stroke affects nearly 800,000 people every year in the United States and is a leading cause of adult disability. After hospitalization half of stroke patients continue to require medical and rehabilitation services provided at inpatient rehabilitation facilities (IRFs) or skilled nursing facilities (SNFs). In general, IRFs provide time-intensive therapy for two to three weeks, while SNFs provide moderately intensive therapy for four- to five-weeks. There is substantial variation in the...
Show moreStroke affects nearly 800,000 people every year in the United States and is a leading cause of adult disability. After hospitalization half of stroke patients continue to require medical and rehabilitation services provided at inpatient rehabilitation facilities (IRFs) or skilled nursing facilities (SNFs). In general, IRFs provide time-intensive therapy for two to three weeks, while SNFs provide moderately intensive therapy for four- to five-weeks. There is substantial variation in the utilization of these alternative rehabilitation settings, but their relative comparative effectiveness remains uncertain. A randomized controlled trial (RCT) would provide an unbiased comparative effectiveness estimate, but the design of such a trial is complicated by several practical and ethical issues. The overarching purpose of this dissertation was to use Medicare claims data to inform the design and to emulate such a trial. In the first aim, we sought to identify patient and hospital level factors that were associated with IRF or SNF discharge and characterize the heterogeneity of hospital effects that influenced discharge to an IRF (vs. SNF). From a retrospective cohort of 145,894 stroke patients, we used multi-level multivariable models to identify several patient- and hospital- level factors that were independently associated with discharge setting. We also showed that hospitals contributed around a third of the variation in IRF (vs. SNF) discharge, but there was substantial variation in the effect that specific hospitals had on influencing IRF discharge. The second aim, was to identify a target trial population that optimized the explanatory-pragmatic balance of a subsequent RCT. To identify this population, we profiled hospitals based on their propensity to discharge stroke patients to IRFs (vs. SNFs) and inferred IRF and SNF referral networks for each hospital. The final target trial population included 44,950 patients (30.8% of the starting sample) who were treated at 441 hospitals (14.5%) and subsequently discharged to 745 IRFs (64.8%) and 5,974 SNFs (48.2%).The third aim was to emulate three alternate RCTs that compared patient outcomes at IRFs vs. SNFs. Trial #1 used the target trial population identified in Aim 2, while trials #2 and 3 excluded increasingly infrequently used IRFs and SNFs. Comparative effectiveness was estimated using a matched propensity score analysis. Overall, on a relative basis, patients treated at IRFs were between 18-35% more likely to be successfully discharged home (i.e., alive and at home for >30 days) and were between 11-15% less likely to die within one year of acute care discharge. The variation in the effect size estimates across the trials was driven by poorer outcomes among patients treated at infrequently used SNFs. Finally, we identified that a moderate sized unmeasured confounder would nullify the observed differences.In conclusion, we identified that referring hospitals are a major driver of IRF or SNF use, and that patients treated at IRFs had better outcomes (relative to SNF patients). However, our results were limited by the inability to adjust for potentially important unmeasured confounders. A pragmatic RCT would eliminate such biases and provide a more valid comparative effectiveness estimate of these two alternative rehabilitation settings.
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Title: Use of water mist to reduce the risk of frost damage in tree fruits
Creator: Rijal, Ishara
Date: 2017
Collection: Electronic Theses & Dissertations
Description: Climate variability and change have been major threats to global food security historically and will almost certainly continue to be threats in the future given the sensitivity of agricultural production systems to their surrounding environment. Recent changes in temperature and seasonality have significantly impacted commercial fruit production in the Great Lakes region. Michigan's sour cherry and apple production in 2012 was reduced by about 90% and 88%, respectively, compared to the...
Show moreClimate variability and change have been major threats to global food security historically and will almost certainly continue to be threats in the future given the sensitivity of agricultural production systems to their surrounding environment. Recent changes in temperature and seasonality have significantly impacted commercial fruit production in the Great Lakes region. Michigan's sour cherry and apple production in 2012 was reduced by about 90% and 88%, respectively, compared to the previous year's production due to a series of spring freeze events (USDA, 2013). The timing of the seasonal warm up in the spring and resulting onset of phenological development is a key factor in determining potential cold damage risk for overwintering perennial tree fruit crops, as the vulnerability of vegetation to freeze injury increases rapidly with the stage of development. Application of water prior to the onset of growth has been used in the past to delay early vegetative development of temperate tree fruit crops. Evaporative cooling associated with this approach effectively reduces plant tissue temperature, slowing the rate of growth and leaving it less vulnerable to freezing temperatures. There are several potential drawbacks, however, including consumption of large quantities of water that could increase nutrient leaching along with elevated risks of plant disease risk. This study examined the potential effectiveness of water applied as a spray mist via a new plant management technology, the solid set canopy delivery system (SSCD), to suppress tree fruit bud temperatures and delay the phenological development of the buds. There were two major portions: 1) A detailed collection of field-based phenological and physiological observations associated with the operation of a prototype SSCD cooling system and: 2) Development of a deterministic model of tree fruit bud temperature that was used to examine the potential of water-based cooling of buds in Michigan. The observational study aimed to identify the timing and discharge rate of mist applications on cherry and apple trees was carried out in a growth chamber and at five Michigan orchards (apple at St. Joseph, Charlotte, and Hillsdale, sweet cherry at SWMREC, and sour cherry at Traverse City,) during the 2014, 2015, and 2016 growing seasons with automated instrumentation to monitor and control the water mist flow rate based on environmental conditions. Water mist was applied to apple and cherry buds via the SSCD system after the end of endo-dormancy until king bloom in the non-misted buds based on ambient air temperature and relative humidity. Overall, in three years of the field study misting delayed bloom by 4-9 days in apple and 7- 11 days in cherry, all using substantially less water than that reported in earlier studies; 8.4 to 26 cm/ha in apple and 5.5 to 10.8 cm/ ha in sweet cherry. The deterministic heat transfer model of a tree fruit bud was developed with observational data from growth chamber, potted plant and field-based studies. The model was calibrated using growth chamber data and validated using potted plant and field data. In a model validation study, model simulated one-minute bud temperatures were generally found to be in good agreement with observed bud temperatures, with overall mean average differences of -0.5±0.30C (lab observations) and -0.3±0.15 0C (field observations), mean absolute differences less than 10C and R-square values of 0.80 or greater. The model was then run with ten years of hourly climate data at three locations in major fruit-producing regions of Michigan (2006-2015). Overall, the model estimated a delay in bloom of misted buds by more than a week compared to non-misted buds, which translates into a potential reduction in the frequency of damaging freeze events of 50-75 %, and decrease in freeze injury severity by 10-60 % in misted apple buds and 45-100% in misted cherry buds. Collectively, the results suggest that the spray mist technique has promise as a straightforward and effective indirect frost control strategy with relatively few environmental impacts.
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Title: Using Eventual Consistency to Improve the Performance of Distributed Graph Computation In Key-Value Stores
Creator: Nguyen, Duong Ngoc
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Key-value stores have gained increasing popularity due to their fast performance and simple data model. A key-value store usually consists of multiple replicas located in different geographical regions to provide higher availability and fault tolerance. Consequently, a protocol is employed to ensure that data are consistent across the replicas.The CAP theorem states the impossibility of simultaneously achieving three desirable properties in a distributed system, namely consistency,...
Show moreKey-value stores have gained increasing popularity due to their fast performance and simple data model. A key-value store usually consists of multiple replicas located in different geographical regions to provide higher availability and fault tolerance. Consequently, a protocol is employed to ensure that data are consistent across the replicas.The CAP theorem states the impossibility of simultaneously achieving three desirable properties in a distributed system, namely consistency, availability, and network partition tolerance. Since failures are a norm in distributed systems and the capability to maintain the service at an acceptable level in the presence of failures is a critical dependability and business requirement of any system, the partition tolerance property is a necessity. Consequently, the trade-off between consistency and availability (performance) is inevitable. Strong consistency is attained at the cost of slow performance and fast performance is attained at the cost of weak consistency, resulting in a spectrum of consistency models suitable for different needs. Among the consistency models, sequential consistency and eventual consistency are two common ones. The former is easier to program with but suffers from poor performance whereas the latter suffers from potential data anomalies while providing higher performance.In this dissertation, we focus on the problem of what a designer should do if he/she is asked to solve a problem on a key-value store that provides eventual consistency. Specifically, we are interested in the approaches that allow the designer to run his/her applications on an eventually consistent key-value store and handle data anomalies if they occur during the computation. To that end, we investigate two options: (1) Using detect-rollback approach, and (2) Using stabilization approach. In the first option, the designer identifies a correctness predicate, say $\Phi$, and continues to run the application as if it was running on sequential consistency, as our system monitors $\Phi$. If $\Phi$ is violated (because the underlying key-value store provides eventual consistency), the system rolls back to a state where $\Phi$ holds and the computation is resumed from there. In the second option, the data anomalies are treated as state perturbations and handled by the convergence property of stabilizing algorithms.We choose LinkedIn's Voldemort key-value store as the example key-value store for our study. We run experiments with several graph-based applications on Amazon AWS platform to evaluate the benefits of the two approaches. From the experiment results, we observe that overall, both approaches provide benefits to the applications when compared to running the applications on sequential consistency. However, stabilization provides higher benefits, especially in the aggressive stabilization mode which trades more perturbations for no locking overhead.The results suggest that while there is some cost associated with making an algorithm stabilizing, there may be a substantial benefit in revising an existing algorithm for the problem at hand to make it stabilizing and reduce the overall runtime under eventual consistency.There are several directions of extension. For the detect-rollback approach, we are working to develop a more general rollback mechanism for the applications and improve the efficiency and accuracy of the monitors. For the stabilization approach, we are working to develop an analytical model for the benefits of eventual consistency in stabilizing programs. Our current work focuses on silent stabilization and we plan to extend our approach to other variations of stabilization.
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Title: Using Semantic Structure of the Data and Knowledge in Question Answering Systems
Creator: Zheng, Chen
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Understanding and reasoning over natural language is one of the most crucial and long-standing challenges in Artificial Intelligence (AI). Question answering (QA) is the task of automatically answering questions posed by humans in a natural language form. It is an important criterion to evaluate the language understanding and reasoning capabilities of AI systems. Though machine learning systems on Question Answering (QA) have shown tremendous success in language understanding, they still...
Show moreUnderstanding and reasoning over natural language is one of the most crucial and long-standing challenges in Artificial Intelligence (AI). Question answering (QA) is the task of automatically answering questions posed by humans in a natural language form. It is an important criterion to evaluate the language understanding and reasoning capabilities of AI systems. Though machine learning systems on Question Answering (QA) have shown tremendous success in language understanding, they still suffer from a lack of interpretability and generalizability, in particular, when complex reasoning is required to answer the questions. In this dissertation, we aim to build novel QA architectures that answer complex questions using the explicit relational structure of the raw data, that is, text and image, and exploiting external knowledge. We investigate a variety of problems, including answering natural language questions when the answer can be found in multiple modalities, including 1) Textual documents (Document-level QA), 2) Images (Cross-Modality QA), 3) Knowledge graphs (Commonsense QA) and, 4) Combination of text and knowledge graphs. First, for Document-level QA, we develop a new technique, Semantic Role Labeling Graph Reasoning Network (SRLGRN), via which the explicit semantic structure of multiple textual documents is used. In particular, based on semantic role labeling, we form a multi-relational graph that jointly learns to find cross-paragraph reasoning paths and answers multi-hop reasoning questions. Second, for the type of QA that requires causal reasoning over textual documents, we propose a new technique, Relational Gating Network (RGN), that jointly learns to extract the entities and their relations to help highlight the important entity chains and find how those affect each other. Third, for the type of questions that require complex reasoning over language and vision modalities (Cross-Modality QA), we propose a new technique, Cross-Modality Relevance (CMR). This technique considers the relevance between textual tokens and visual objects by aligning the two modalities. Fourth, for answering questions based on given Knowledge Graphs (KG), we propose a new technique, Dynamic Relevance Graph Network (DRGN). This technique is based on a graph neural network and re-scales the importance of the neighbor nodes in the graph dynamically by training a relevance matrix. The new neighborhoods trained by relevance help fill in the knowledge gaps in the KG for more effective knowledge-based reasoning. Fifth, for answering questions using a combination of textual documents and an external knowledge graph, we propose a new technique, Multi-hop Reasoning Network over Relevant Commonsense Subgraphs (MRRG). MRRG technique extracts the most relevant KG subgraph for each question and document and uses that subgraph combined with the textual content and question representations for answering complex questions. We improve the performance, interpretability, and generalizability of various challenging QA benchmarks based on different modalities. Our ideas have proven to be effective in multi-hop reasoning, causal reasoning, cross-modality reasoning, and knowledge-based reasoning for question answering.
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Title: Using cover crops in wheat-corn rotations to provide forage while improving soil
Creator: Gerdes, Sabra Lynn
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "The time window after wheat harvest in a wheat (Triticum aestivum L.)- corn (Zea mays L.) rotation could be used to grow cover crops (CC) to provide forage while protecting soil from erosion. Field experiments were initiated in East Lansing, MI to determine the consequences of partial removal of CC biomass on soil improvement and crop yield and quality. Soft red winter wheat ('Hopewell' 03360336and 03360336'Red 03360336Dragon') was planted in October of 2013 and 2014 and harvested in July...
Show more"The time window after wheat harvest in a wheat (Triticum aestivum L.)- corn (Zea mays L.) rotation could be used to grow cover crops (CC) to provide forage while protecting soil from erosion. Field experiments were initiated in East Lansing, MI to determine the consequences of partial removal of CC biomass on soil improvement and crop yield and quality. Soft red winter wheat ('Hopewell' 03360336and 03360336'Red 03360336Dragon') was planted in October of 2013 and 2014 and harvested in July 2014 and 2015. Cover crops included: frost-seeded red clover, and summer-seeded alfalfa, cowpea, sunn hemp, radish, oat/field pea mixture, sudangrass, sorghum x sudangrass, and teffgrass. Half of each CC plot was mechanically harvested eight weeks after planting. Harvested forage dry matter yield was greatest for red clover (4.3 Mg ha-1 ); oat-pea mix (2.5 Mg ha-1 ), sudangrass/sudex (1.8 Mg ha-1 ) and radish (1.2 Mg ha-1 ) (P < 0.01) yielded less. Corn grain yield harvested in October averaged 13.7 Mg ha-1 and did not differ across CC species or forage harvest treatment (P > 0.05). Harvesting forage reduced total N removal (TNR) in subsequent corn for red clover only; harvesting forage did not affect TNR after any other CC (CC x harvest interaction, P < 0.05). In the harvested system, TNR did not differ (P > 0.05) between for any CC, but unharvested RCL (374 kg N ha-1 ) had greater (P < 0.01) TNR than oat-pea mix (338 kg N ha-1 ). There were no differences among treatments for soil permanganate oxidizable carbon POXC (P > 0.05). Harvesting cover crops for forage after winter wheat harvest in Michigan can give harvestable forage and acceptable nutritive value."--Page ii.
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Title: Using video modeling to teach typical adolescents to interact socially with peers with ASD
Creator: MacFarland, Mari Cris
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Researchers have found that video modeling can be an effective procedure for training teachers, behavioral technicians, and paraeducators to administer evidence-based practices to children with autism spectrum disorder (Brock & Carter, 2013; Catania et al., 2009; Digennaro‐Reed, Codding, Catania, & Maguire, 2010; Lipschultz, Vladescu, Reeve, Reeve, & Dipsey, 2015; Moore & Fisher, 2007; Rosales et al., 2015; Vladescu, Carroll, Paden, & Kodak, 2012; Weldy, Rapp, & Capocasa, 2014). Video...
Show moreResearchers have found that video modeling can be an effective procedure for training teachers, behavioral technicians, and paraeducators to administer evidence-based practices to children with autism spectrum disorder (Brock & Carter, 2013; Catania et al., 2009; Digennaro‐Reed, Codding, Catania, & Maguire, 2010; Lipschultz, Vladescu, Reeve, Reeve, & Dipsey, 2015; Moore & Fisher, 2007; Rosales et al., 2015; Vladescu, Carroll, Paden, & Kodak, 2012; Weldy, Rapp, & Capocasa, 2014). Video modeling has not yet been evaluated to teach typical adolescents to deliver evidence-based practices. The purpose of the present study was to extend previous research on the use of video modeling as a training tool by teaching typical adolescents to administer naturalistic evidence-based practices to adolescents and young adults with autism spectrum disorder (ASD). This was accomplished by: (a) examining the effects of video modeling training on typical adolescents’ performance of peer mediated social interaction (PMSI), a 10-step procedure comprised of simplified behavioral practices, during roleplay with an adult actor , (b) examining the effects of video modeling training on the generalization of PMSI from an actor to adolescents with ASD, and (c) determining the social meaningfulness of video modeling training via pre- and post-intervention measures of social interaction for youth with ASD.A multiple probe design across participants was used to evaluate the effects of training via video modeling on delivery of PMSI by five typical adolescents. The dependent variable was the percentage of steps performed correctly by the typical adolescent for each step of PMSI. All participants demonstrated an immediate increase in PMSI as video modeling was systematically applied. Typical adolescents also generalized delivery to adolescents with ASD. These findings demonstrate a clear functional relation between video modeling training (VMT) and improved performance of PMSI. In addition, the present data extend the results of previous VMT research conducted with adult service providers (Catania et al., 2009; Lipschultz et al., 2015; Vladescu et al., 2012) by demonstrating similar outcomes with typical adolescents.An analysis of social interaction was conducted to ensure that teaching PMSI was likely to be of benefit to individuals with ASD. Social interaction consisted of: (a) being within 3 ft of and physically orienting toward peers, (b) interacting verbally or with gestures with one or more peers, and (c) engaging in an activity consistent with the peer hangout group. Social interaction between two youths with ASD and typical adolescent participants was evaluated within a peer mediated setting before and after VMT. Pre-intervention measures were compared to post-intervention measures. Social interaction for both youths with ASD improved following VMT.
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Title: VALIDATION OF A FELINE FEMORAL BONE SURROGATE WITH MECHANICAL AND CLINICAL EVALUATION OF FELINE ORTHOPEDIC IMPLANTS
Creator: Marturello, Danielle Marie
Date: 2021
Collection: Electronic Theses & Dissertations
Description: A bone surrogate was developed and subsequently used to evaluate the mechanical behavior of two novel feline interlocking nails against plate controls in vitro, in an attempt to evaluate their safety and efficacy. Following testing in both torsion and 4-point bending, the I-Loc nail was evaluated in 30 clinical feline trauma cases.Fracture gap constructs were implanted with an I-Loc (3 or 4 mm), Targon (2.5 or 3.0 mm) or LCP (2.0 or 2.4 mm) and mechanically compared. Additionally, explanted...
Show moreA bone surrogate was developed and subsequently used to evaluate the mechanical behavior of two novel feline interlocking nails against plate controls in vitro, in an attempt to evaluate their safety and efficacy. Following testing in both torsion and 4-point bending, the I-Loc nail was evaluated in 30 clinical feline trauma cases.Fracture gap constructs were implanted with an I-Loc (3 or 4 mm), Targon (2.5 or 3.0 mm) or LCP (2.0 or 2.4 mm) and mechanically compared. Additionally, explanted surrogates with implant specific pilot holes were failed to assess the effect of implant removal on bone surrogate strength. Finally, a prospective clinical case series of 30 feline fractures were evaluated for time to clinical union, return to function and complications following repair using the I-Loc nail. The I-Loc 3 and 4 mm nails overall were mechanically stronger than either the Targon nails or locking plates, including explanted specimens. All cats in the clinical study were weight bearing within 2 days of surgery and reached clinical union in a mean time of 7.2 weeks. All returned to full limb function. No major complications were encountered. These studies suggest that the I-Loc may represent a safe and effective alternative to other available feline osteosynthesis options
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Title: VISIONING THE AGRICULTURE BLOCKCHAIN : THE ROLE AND RISE OF BLOCKCHAIN IN THE COMMERCIAL POULTRY INDUSTRY
Creator: Fennell, Chris
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Blockchain is an emerging technology that is being explored by technologists and industry leaders as a way to revolutionize the agriculture supply chain. The problem is that human and ecological insights are needed to understand the complexities of how blockchain could fulfill these visions. In this work, I assert how the blockchain's promising vision of traceability, immutability and distributed properties presents advancements and challenges to rural farming. This work wrestles with the...
Show moreBlockchain is an emerging technology that is being explored by technologists and industry leaders as a way to revolutionize the agriculture supply chain. The problem is that human and ecological insights are needed to understand the complexities of how blockchain could fulfill these visions. In this work, I assert how the blockchain's promising vision of traceability, immutability and distributed properties presents advancements and challenges to rural farming. This work wrestles with the more subtle ways the blockchain technology would be integrated into the existing infrastructure. Through interviews and participatory design workshops, I talked with an expansive set of stakeholders including Amish farmers, contract growers, senior leadership and field supervisors. This research illuminates that commercial poultry farming is such a complex and diffuse system that any overhaul of its core infrastructure will be difficult to ``roll back'' once blockchain is ``rolled out.'' Through an HCI and sociotechnical system perspective, drawing particular insights from Science and Technology Studies theories of infrastructure and breakdown, this dissertation asserts three main concerns. First, this dissertation uncovers the dominant narratives on the farm around revision and ``roll back'' of blockchain, connecting to theories of version control from computer science. Second, this work uncovers that a core concern of the poultry supply chain is death and I reveal the sociotechnical and material implications for the integration of blockchain. Finally, this dissertation discusses the meaning of ``security’’ for the poultry supply chain in which biosecurity is prioritized over cybersecurity and how blockchain impacts these concerns. Together these findings point to significant implications for designers of blockchain infrastructure and how rural workers will integrate the technology into the supply chain.
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