Teleoperation Methods for High-Risk, High-Latency Environments

In-Space Servicing, Assembly, and Manufacturing (ISAM) can enable larger-scale and longer-lived infrastructure projects in space, with interest ranging from commercial entities to the US government. Servicing, in particular, has the potential to vastly increase the usable lifetimes of satellites. However, the vast majority of spacecraft on low Earth orbit today were not designed to be serviced on-orbit. As such, several of the manipulations during servicing cannot easily be automated and instead require ground-based teleoperation. Ground-based teleoperation of on-orbit robots brings its own challenges of high latency communications, with telemetry delays of several seconds, and difficulties in visualizing the remote environment due to limited camera views. We explore teleoperation methods to alleviate these difficulties, increase task success, and reduce operator load. First, we investigate a model-based teleoperation interface intended to provide the benefits of direct teleoperation even in the presence of time delay. We evaluate the model-based teleoperation method using professional robot operators, then use feedback from that study to inform the design of a visual planning tool for this task, Interactive Planning and Supervised Execution (IPSE). We describe and evaluate the IPSE system and two interfaces, one 2D using a traditional mouse and keyboard and one 3D using an Intuitive Surgical da Vinci master console. We then describe and evaluate an alternative 3D interface using a Meta Quest head-mounted display. Finally, we describe an extension of IPSE to allow human-in-the-loop planning for a redundant robot. Overall, we find that IPSE improves task success rate and decreases operator workload compared to a conventional teleoperation interface

Building and Evaluating Open-Vocabulary Language Models

Language models have always been a fundamental NLP tool and application. This thesis focuses on open-vocabulary language models, i.e., models that can deal with novel and unknown words at runtime. We will propose both new ways to construct such models as well as use such models in cross-linguistic evaluations to answer questions of difficulty and language-specificity in modern NLP tools. We start by surveying linguistic background as well as past and present NLP approaches to tokenization and open-vocabulary language modeling (Mielke et al., 2021). Thus equipped, we establish desirable principles for such models, both from an engineering mindset as well as a linguistic one and hypothesize a model based on the marriage of neural language modeling and Bayesian nonparametrics to handle a truly infinite vocabulary, boasting attractive theoretical properties and mathematical soundness, but presenting practical implementation difficulties. As a compromise, we thus introduce a word-based two-level language model that still has many desirable characteristics while being highly feasible to run (Mielke and Eisner, 2019). Unlike the more dominant approaches of characters or subword units as one-layer tokenization it uses words; its key feature is the ability to generate novel words in context and in isolation. Moving on to evaluation, we ask: how do such models deal with the wide variety of languages of the world---are they struggling with some languages? Relating this question to a more linguistic one, are some languages inherently more difficult to deal with? Using simple methods, we show that indeed they are, starting with a small pilot study that suggests typological predictors of difficulty (Cotterell et al., 2018). Thus encouraged, we design a far bigger study with more powerful methodology, a principled and highly feasible evaluation and comparison scheme based again on multi-text likelihood (Mielke et al., 2019). This larger study shows that the earlier conclusion of typological predictors is difficult to substantiate, but also offers a new insight on the complexity of Translationese. Following that theme, we end by extending this scheme to machine translation models to answer questions traditional evaluation metrics like BLEU cannot (Bugliarello et al., 2020)

Exploring global change impacts on plant-plant and plant-microbe interactions of grassland species

Grassland plants exist in complex environments, where in addition to coping with environmental conditions, they also interact with other plants in their vicinity as well as with microbes in the soil. How these are affected by global environmental changes need to be better characterized to predict ecosystem functions. My dissertation experimentally explores the global change impacts on plant-plant and plant-microbe interactions in grassland species. In my first chapter, I examined how drought and a soil mutualistic microbe, arbuscular mycorrhizal fungi (AMF), affected the relationship between genetic diversity and productivity of a dominant tallgrass species, using a mesocosm experiment. I found that while genetic diversity and AMF had no effect on productivity, drought differentially affected productivity and functional traits of genotypes of a dominant grass, which implies that drought can have variable outcomes for different genotypes within a same species. In my second chapter, I tested the Stress Gradient Hypothesis, which hypothesizes that plant-plant interactions shift from competition to facilitation with increasing environmental stress. I subjected two co-dominant grasses to drought, elevated CO2, and varying levels of plant-plant interactions. My results demonstrated that plant-plant interactions leaned towards facilitation with decreasing stress gradient, contrary to the stress gradient hypothesis. In the third chapter, I investigated the tripartite relationship among a legume, and two mutualistic microbes, AMF, and rhizobial bacteria, under elevated CO2. I tested the hypothesis that the tripartite relationship depends on the cost of carbon to plants and benefit of nutrients from mutualists, and consequently, elevated CO2 should alter this relationship. I conducted a pot experiment under different CO2 and mutualist treatments. My findings suggest that dual inoculation of the legume with AMF and rhizobia comes with carbon costs, which decreases under elevated CO2. The intricate relationships between global change, plant-plant and plant-microbe interactions collectively shape the response of grassland species to global change. In summary, my dissertation advances our understanding of the context dependency of global change impacts on plant-plant and plant-microbe interactions. This research contributes not only to ecological theory but also to the development of strategies for sustainable grassland ecosystems in a changing world

Institutional Barriers to Innovation in Public Education: A Case Study in Innovation in Public Education in Washington State

Innovation in public education is restricted by the forces of institutionalism, namely mimetic, normative, and coercive isomorphism. As a result, school leaders struggle to find ways to innovative to meet the unique demands of their students, often conforming to district, state, and federal policies that prevent them from designing new school systems and practices. In Tacoma, WA a school leader acted as an educational entrepreneur, designing and opening three high schools inside the third-largest public school district in Washington State over the course of two decades. Using a theory of strong ties, this case study explores the case from its inception in a large comprehensive high school in the mid-1990s to the present day, where the three high schools operate under a school board policy that allows them more freedom to innovate and change. The case study uses qualitative interviews and documents to develop a narrative, social network analysis, and critical event analysis to develop the story of how this school leader was able to create three new high schools inside a large public institution

Self-Regulation in Addressing Math Anxiety in High-Achieving Students in an Affluent Asian American Community

Adolescent learners in a high-achieving school in an affluent, predominantly Asian, and Asian American community in a suburb of Silicon Valley, California, face a myriad of stressors and challenges impacting their math achievement. Existing literature suggests parenting styles, ability-grouping practices, and self-beliefs including math anxiety are a few of the salient factors impacting adolescents’ math achievement. A mixed methods needs assessment was conducted to understand the portrait of a struggling math student through the lens of 16 teachers using a mixed methods design. Results indicated divergent beliefs surrounding math education and a sense of pressure for children to take advanced math classes. Self-regulatory interventions such as mindfulness exercises have been shown to reduce math anxiety. Expressive writing was used as an intervention on math anxiety in 69 7th-grade students in a mixed methods convergent parallel intermittent time series design. Parents (N=16) were interviewed to provide insight on their children’s math learning experiences. Students’ math anxiety levels were not significantly related to the expressive writing. Students’ writing content included themes of parents’ expectations, peer relations, perceptions of math teachers and classrooms, and reflections around math anxiety. A range of themes also appeared in parent interviews including parents’ experiences with schooling in other countries, navigating their children’s school system, and emphasizing performance, well-being, and/or effort in their children. Further research examining antecedents to math anxiety and additional interventions to reduce math anxiety are suggested

Eisenstein Series with Class Number Coefficients Constructed from the Weil Representation

We generalize the work found in the paper [KY10] of Kudla and Yang to the case of Hilbert modular forms that come from the Weil representation associated to a 1-dimensional quadratic space. We also provide a computation of the level groups of certain forms produced this way. To achieve our results, we compute closed-form formulas for quadratic Gauss sums over local fields of characteristic 0. This includes the case of both odd and even residue characteristic

Borrowing in Domestic and International Markets: Crowding Out and Cyclicality

The first chapter studies the effect of government issuance on private issuance during banking crises using transaction-level bond and loan data from 66 countries between 1991 and 2017. Governments rarely issue loans, preferring to issue in bond markets. Firms, on the other hand, receive most of their financing from banks. During banking crises, as the supply of domestic loans decreases, firms switch to issuing bonds in domestic markets. Using a novel instrument based on maturing debt to overcome the potential endogeneity of government issuance, I find that firms must compete with the government for funds in the domestic bond market and are crowded out from this market as a result. This happens not only in developing countries, but in advanced countries as well. I also show that firms with the ability to tap foreign debt markets switch to these markets when crowding out occurs in domestic bond markets. Lastly, I show that more developed domestic bond markets mitigate, but do not eliminate, the degree to which crowding out occurs. The second chapter studies the relationship between firm financing and the business cycle by considering distinct debt components, firm sizes, and country heterogeneities. The paper examines the cyclical patterns of firm financing through both correlation-based and panel data analyses, using a dataset spanning 66 countries over 30 years. I use the financing behavior of firms in United States as a benchmark with which to compare firms of other advanced countries as well as emerging countries. I find that, consistent with previous research, total debt is procyclical for all but the largest firms in the United States. However, firms of all sizes in the United States issue bonds countercyclically and loans procyclically in domestic markets. In other advanced countries, only the largest firms display countercyclical bond and loan issuance domestically, while issuing loans procyclically abroad. Emerging countries do not exhibit any discernible cyclicality patterns. The third paper is joint work with Graciela Kaminsky and Shiyi Wang, and examines the impact of increases in sovereign borrowing on firms' ability to access international capital markets. Our paper analyzes episodes of imperfections in international capital markets, both those that diminish and enhance credit markets. Using a structural VAR approach, we identify shocks to government issuance by imposing that government issuance does not affect contemporaneous GDP growth. This is because we examine longer-term maturity issuance which typically is not used immediately. We identify market imperfections in the financial center as well as those originating in the periphery. The former captures collapses and booms in global liquidity. For the latter, we examine episodes of high and low sovereign credit risk as well as episodes of high and low sovereign debt. We find that, in emerging countries, government issuance decreases the ability of firms to tap international capital markets (crowding out) during collapses in global liquidity and periods of high sovereign risk. In advanced countries, we find that government issuance boosts firm issuance (crowding in) during periods of high sovereign debt and periods of low sovereign risk

Association between same-sex experience and prevalence of subclinical cardiovascular disease among U.S. adults, 1999 – 2004

Background: Previous literature has indicated higher levels of cardiometabolic risk factors and cardiometabolic-associated biomarkers among sexual minorities than heterosexuals. It is thus important to examine if there is a corresponding higher prevalence of subclinical cardiovascular disease among sexual minorities. No previous studies have examined the prevalence of subclinical cardiovascular disease among a representative population of adult sexual minorities. We hypothesized that persons reporting any lifetime same-sex experience (SSE) would have higher burden of subclinical cardiovascular disease than heterosexuals. Methods: We conducted a cross-sectional study of 5,938 participants aged 20 to <60 years without cardiovascular disease in the National Health and Nutrition Examination Survey 1999-2004. We used multivariable logistic regression to evaluate the association of any lifetime SSE with elevated high-sensitivity cardiac troponin T (hs-cTnT), high-sensitivity cardiac troponin I (hs-cTnI), and N-terminal B-type natriuretic peptide (NT-proBNP), biomarkers of cardiovascular disease. Results: The prevalence of SSE was 5%. After adjustment for confounders, we found no statistically significant associations between SSE and elevated levels of hs-cTnT, hs-cTnI, or NT-proBNP. Effect estimates for hs-cTnT were attenuated from the unadjusted model after adjusting for demographics (Model 1 OR 95% CI: 0.48 [0.23, 1.00]) and additional behavioral and cardiometabolic risk factors (Model 2 OR 95% CI: 0.48 [0.23, 1.02]). For hs-cTnI and NT-proBNP, respectively, there were no notable patterns from the unadjusted (OR 95% CI: 0.76 [0.34, 1.69]) to the adjusted models (Model 1 OR 95% CI: 0.78 [0.35, 1.73]; Model 2 OR 95% CI: 0.76 [0.33, 1.74]) and from the unadjusted (OR 95% CI: 0.68 [0.40, 1.15]) to the adjusted models (Model 1 OR 95% CI: 0.68 [0.42, 1.09]; Model 2 OR 95% CI: 0.66 [0.41, 1.05]). Conclusion: Counter to our hypothesis, we did not find evidence to suggest that persons reporting SSE had a higher burden of subclinical cardiovascular disease. Future research is needed to characterize the burden of subclinical cardiovascular disease among sexual minorities using contemporary data collected from a sizable sample of older adults

ASSESSING THE PROVISION AND EQUITABILITY OF PRIMARY CARE IN A LOW-RESOURCE SETTING

Introduction: To inform policies to promote well-being and eliminate health inequities in all settings, this dissertation focuses on an often-cited necessity for population health and heath equity—primary care—by pursuing the following aims: 1) conducting a review of the literature on the impact of primary care features on health access inequities 2) investigating the association between primary care experience (PCE) and the likelihood of hospitalization for chronic ambulatory care sensitive conditions (ACSCs) & inequities in the likelihood of hospitalization for chronic ACSCs among adults in rural Bihar, one of India’s socioeconomically backward states; and 3) investigating the association between the quality of local primary care—measured as average provider competence—and an individual’s self-rated health (SRH) & inequities in SRH in rural Bihar, India. Methods: The 1st aim uses the scoping review approach. The 2nd and 3rd aims analyze data collected through household and provider surveys conducted under a parent study set in Bihar, India, using logistic regressions to model the odds of hospitalization and poor SRH as a functions of PCE and average provider competence, respectively, including interactions with markers of inequity. Results: Primary care interventions are largely associated with improvements along the health access continuum for disadvantaged and advantaged populations, oftentimes with greater improvements for disadvantaged populations. Better PCE is associated with reduced likelihood of hospitalization for chronic ACSCs among adults. Individuals in the poorest wealth quintile with better PCE experienced the largest drop in the likelihood of hospitalization, compared to higher wealth quintiles. Better quality of local primary care, beyond a threshold, is associated with better individual-level SRH, although improvements in SRH appear to inequitable by gender and age. Conclusion: This dissertation provides support for the strengthening of primary care systems, particularly in LMICs to tackle the burden of chronic primary care sensitive conditions and health inequities. Findings also highlight the importance of ensuring that the local quality of primary care is of an adequate standard to promote population health. More studies are needed to evaluate the quality of primary care and the reasons behind inequities in access to primary care in lower income countries

Unveiling Frustrated Magnetism and Topological Phenomena in Rare-Earth Pyrochlores through Inelastic Light Scattering

In this dissertation, we present a comprehensive investigation into the magnetic and electronic properties of pyrochlore materials, with a focus on three different compounds: Pr2Zr2O7, Pr2Ir2O7, and Nd2Ir2O7. Utilizing Raman scattering spectroscopy, this study delves into the complex magnetic behaviors exhibited by these materials, elucidating the underlying mechanisms that govern their magnetic interactions. The first part of the thesis focuses on Pr2Zr2O7 and Pr2Ir2O7, examining the coupling between lattice, electronic, and magnetic degrees of freedom in these compounds. The comparison of Raman phonon spectra unveils magnetoelastic coupling in Pr2Zr2O7 and characterizes phonon-electron scattering in the semimetallic Pr2Ir2O7. The second part explores the dynamic interactions between the crystal lattice and magnetic degrees of freedom in Pr2Zr2O7. We investigate crystal electric field excitations and observe unconventional behavior in the splitting of the non-Kramers ground state doublet of Pr3+. The results suggest the possibility of static or dynamic deviations of Pr3+ from the ideal crystal structure position as the origin of this effect. Finally, the third part uncovers the unique magnetic behavior of Nd2Ir2O7, showcasing the lowest temperature of all-in-all-out (AIAO) Ir moments ordering and the highest temperature at which AIAO order of rare-earth Nd ions is detected. The presence of characteristic spin ice fluctuations in the temperature range between 14 K and 33 K suggests a strong enhancement of magnetic interactions between Nd ions, resulting from the interplay of spin-orbit coupling, electronic correlations, and geometric frustration. Raman spectroscopy reveals specific one-magnon Raman modes associated with the AIAO order and a broad mode characteristic of spinon continuum arising from Nd spin ice fluctuations