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Machine Learning Enabled Health Monitoring and\\ Diagnosis of Engineering Systems
Get PDFSystem health monitoring provides valuable insight into the condition of an in-service engineering system, potentially enabling planners to make better, data-informed decisions regarding system maintenance and operation safety. An increasing number of sensors are now utilized to provide real-time feedback on in-service structures, underscoring the need to automate system health monitoring. In principle, machine learning (ML) approaches provide us with such an opportunity, but off-the-shelf methods are challenged by often small, largely-unlabeled, and imbalanced sensor data. Because of these unique data characteristics, existing ML-based studies suffer from generalizability and reproducibility. This dissertation addresses a family of exemplary problems in ML-based system health monitoring and puts forth novel ML-based computational methods that can handle the small and imbalanced data regimes. Unsupervised and semi-supervised ML methods that additionally hybridize concepts and techniques from multi-objective optimization, signal processing, multi-instance learning, and more are shown here to allow mapping the states of a selective compliance articulated robot arm from acoustic monitoring data, detecting road conditions from smartphone accelerometer data, and discovering anomalies from time-series data of diverse sensory types. The methodologies presented in this dissertation advance ML-enabled system health monitoring
Anxiety Problems and Structural Amygdala Volume Differences in Autistic and Non- Autistic Youth
Get PDFAutism is a cluster of highly heterogenous neurodevelopmental conditions that impacts differences in socio-emotional information processing; however, to date, little work has focused on the relevant brain systems involved in anxiety-related emotional processing in autistic youth. Importantly, despite recent efforts in broadening characterizations of the different presentations of autism based on sex assigned at birth, little is known about differences in psychopathological and neurodevelopmental trajectories between autistic girls and autistic boys. The present study interrogated neurodevelopmental differences in bilateral structural amygdala volumes in a sex balanced sample of autistic and nonautistic girls and boys aged 8-17 years old; we tested for effects of sex, IQ, diagnosis, along with anxiety problems and social behavior problems, in addition to interactions among these variables. Overall, between group comparisons did not reveal meaningful statistical differences in normalized left and right amygdala volumes when comparing autistic and typically developing (TD) counterparts. Autistic females (ASDf ) reported significantly greater anxiety problems relative to typically developing females TDf. Additionally, autistic males (ASDm) and ASDf did not differ on anxiety or social behavioral problem measures. As well, ASDf anxiety as a predictor of left or right amygdala volume did not survive statistical significance
Analytical Tools for Modeling and Forecasting Global Maritime Cargo Flows under Changing and Uncertain Conditions
Get PDFGlobal maritime shipping is a backbone of logistic operations for global seaborne trade. These systems are complex, containing hundreds of ports and thousands of shipping routes. Understanding and forecasting the system’s behavior given uncertainty in operational conditions due to weather, climate change impacts, workforce fulfillment levels, new opportunities for crossing the globe, disaster events, and more is important to businesses, shippers, carriers, port stakeholders, regions, and others. This dissertation proposes mathematical models and solution algorithms for estimating and forecasting flows through the maritime system and the system’s performance under changing and uncertain conditions. These conditions arise both from new opportunities, such as the potential to employ Arctic passageways with limited special equipment, and existing and new risks, such as from increased wave heights due to climate change, increased occurrence of disaster events, and concerns about workforce availability. These advancements contribute to an ability to maintain a reliable and resilient global maritime shipping network and the supply chains they support.This dissertation contributes to these modeling and forecasting capabilities in three key areas. Specifically, it presents: (1) A high-fidelity and updatable containerized and bulk cargo shipping network representation with 161 seaports covering 52 countries constructed on publicly available, updatable data sources and mixed-integer linear strategic cargo routing model with combined gradient descent and relax-and-fix decomposition solution methods for estimating global seaborn trade flows. (2) A risk-constrained maritime cargo flow model with exact Benders-branch-and-cut and data-driven Bayesian network solution methodologies for predicting changes in global cargo vessel traffic across a maritime network incorporating Arctic ports and passageways under future reduced-ice shipping scenarios. (3) Quantification of the maritime network’s performance under different disaster events ranging from port-related workforce shortages to natural disasters through a capacity-constrained maritime cargo flow optimization model with workforce level-related scenarios and an Equilibrium Program with Equilibrium Constraints (EPEC) formulation for making coalition-based cross-port investments under natural disaster scenarios, respectively. These analytical tools provide modeling and forecasting capabilities needed to, not only give insights to stakeholders involved in global seaborne trade, but to understand the ramifications of changing trade flows, climate conditions and opportunities on economies, local peoples, the environment, and more
The Relationship between Dietary Intakes of Magnesium, Copper, Iron, Omega-3, and Selenium and Depression among College Students Aged 18-24 Years at George Mason University
Get PDFBackground: Depression is a common illness that leads to serious outcomes ranging from poor functional performance at work, school, and in family roles, to suicide. Young adult (18-29 years old) depression is a serious health problem. Over twenty percent of young adults have reported depression symptoms in the United States1. Around seventeen percent of American college students are depressed2. For college students, mental health is important for their education and quality of life. About sixty percent of people who have committed suicide previously reported mood disorders such as major depression, bipolar disorder, and dysthymia3. According to WHO (2020)1, suicide is the second leading cause of death among the individuals aged 15-29 years, which is the age when people typically attend college. Nutrition is a modifiable factor that plays an essential role in human psychological health4. It could be a sustainable treatment method for depression with low cost and minimal side effects. Nutrients, such as selenium, copper, iron, magnesium, and omega-3, are reported to have an association with depression. However, studies regarding the intakes of these nutrients and depression are inconclusive. Few studies focused on college students. Thus, the overall purpose of this study is to investigate the relationship between dietary nutrient intakes and depression level among college students at George Mason University by 1) evaluating the dietary intakes of selenium, magnesium, copper, iron, and omega-3 among George Mason University college students with different depression levels; and 2) examining whether the extent of dietary intake of these nutrients is related to the severity of depression. Method: This is a cross-sectional study. In total, 205 participants were eligible to be included in this study from the 2019 population of the Mason: Health Starts Here cohort study. The participants were first-year college students aged 18-24 years at George Mason University. Demographic information such as gender, race, BMI, and financial support were collected, and dietary nutrient intake was measured using Dietary History Questionnaire (DHQ-III). Depression level was evaluated by utilizing Patient-Reported Outcomes Measurement Information System (PROMIS). Physical activity level was assessed using International Physical Activity Questionnaire (IPAQ) - short version. SPSS version 28.0 was used to do the statistical analysis. ANOVA was used to compare the differences between the average nutrient intakes and depression levels. Linear regression was to analyze the relationship between dietary nutrient intakes and depression levels. Results: There were no significant differences between depression levels in race, gender, body mass index, physical activity level, and financial support. Compared to the mild and the moderate/severe groups, the none to slight depression group had the highest percentage of the participants (68.1%) with normal BMI. The moderate/severe depression group had the highest percentage of underweight (11.9%) and obese (11.9%) participants. Finally, the mild depression group had the highest percentage of participants being overweight (25%). A greater proportion of participants had low physical activity level as the depression level increased, from 17.6% in the none to slight group to 31.0% in the moderate/severe group. The percentage of participants with high physical activity was higher in the none to slight depressed group (56.3%) compared to the other two groups (mild 40.9% and moderate/severe 50%). Dietary intakes of magnesium, iron, copper, selenium, and omega-3 were not significantly related to depression level. The average intakes of examined nutrients were not significantly different between depression groups. Conclusion: The present study did not find significant between-group differences of the average dietary intakes of magnesium, copper, iron, omega-3, and selenium; nor a significant relationship between dietary intakes of selenium, iron, copper, magnesium, and omega-3 and depression level among freshmen college students aged 18-24 years at George Mason University.This thesis has been embargoed for 2 years. It will not be available until December 2024 at the earliest
Crisis and Stability: Examining the Effects of Remittances on the Macroeconomy
Get PDFRemittances, money sent from migrant workers to families in their home countries, have increased considerably since the 1990s and represent a large source of international capital flows for many developing countries. Generally, remittances are a remarkably stable source of income and are countercyclical to the recipient-country, to compensate for lower economic growth. This dissertation examines the effects of remittances on the macroeconomy of developing countries, and its role in managing risks of crises and promoting growth and stability. Chapter one considers the role of remittances as a source of stable foreign exchange reserves, and how they can enhance stability in the macroeconomy. I ask the question: can the flow of remittances help to decrease the likelihood of a financial crisis? To evaluate this question, I identify a financial crisis as a banking and currency crisis and estimate the effect of remittance flows on each crisis using logit and probit techniques. I find robust evidence for a sample of remittance-recipient countries that remittances have a statistically significant effect on financial crises. By increasing the foreign exchange reserves of a central bank, remittances improve the capacity of the central bank to manage the risk of a financial crisis. Thereby, remittances decrease the likelihood of a banking and currency crisis occurring. The academic literature has devoted much attention to discerning the institutions and policies affecting economic growth. Chapter two considers the nature of this problem and develops a case study to highlight the role remittances can play in boosting growth. This chapter, co-authored with Carlos D. Ramirez and published in Applied Economics Letters (2022), examines the effects of remittances on output for Lebanon, a case with a unique setting: remittances to Lebanon are primarily from workers located in oil-producing Gulf States and thus influenced by oil prices. This setting enables us to estimate a structural vector autoregression (VAR) model using the price of oil as an instrument. Our results suggest that the adoption of policies that facilitate remittance flows should be encouraged, as they likely stimulate economic growth. Chapter three investigates the impact of remittance flows on monetary policy decisions in a small-open economy – Lebanon. Lebanon maintains a fixed exchange rate, with its currency pegged to the US dollar, and remittances comprise approximately a quarter of its gross domestic product. I study whether the policies of the Lebanese central bank are endogenous to remittance flows. To address this question, I perform a VAR analysis and evaluate orthogonalized impulse response functions of remittances on Lebanon's money supply (M1). The results indicate that there is a causal relationship between the money supply and remittance inflows in Lebanon: as remittance levels increase, M1 levels decrease. The findings suggest that monetary policy in Lebanon is endogenous, and remittances influence the decisions of the central bank
MENGER VS. CHARTALISM ON THE ORIGINS OF MONEY: THEORY AND HISTORY
Get PDFThe dissertation begins by rebutting the Chartalist criticism that Menger’s theory of money cannot explain credit existing before money. The second chapter is an application of the first to late 4th Millennium BC Mesopotamia which Chartalists claim falsify the Mengerian account. The third chapter argues the evidence from Mesopotamia from the early 3rd Millennium BC to 330 BC supports a Neo-Mengerian account on the origins of money and defends the application of standard price theory to Ancient Mesopotamia. The first chapter begins discussing how credit-theory proponents, such as A. Mitchell Innes and his contemporaries, argue Carl Menger's timeline for the origin of money, accepted by most economists, is wrong. Rather than credit coming into existence after money has emerged as a means of eliminating a barter system’s need for a double coincidence of wants, credit-theory proponents argue credit precedes barter. Thus, Menger is historically said to be false. What the followers of A. Mitchell Innes miss, however, is that barter may occur intertemporally—credit may be extended and repaid in goods rather than in money. The incorporation of intertemporal barter into Menger's account on the emergence of money strengthens his story: goods which are more portable, uniform, durable, and divisible will be more suitable for intertemporal transactions than goods that are not. Further, the origin of money is not necessarily grounded in a commodity, but in a scarce good with nonmonetary value. The second chapter is an application of the first chapter to the late 4th Millennium BC. Chartalists, followers of Karl Polanyi, proponents of the credit-theory of money, and others argue the evidence from Mesopotamia in the 4th Millennium BC falsifies the Mengerian account on the origins of money. As a result, Menger’s account is conjectural and ahistorical without much, if any, historical evidence. Following Denise Schmandt-Besserat’s seminal interpretation on the purpose of clay tokens in Mesopotamia, Chartalists argue such tokens were accounting tools, which preceded any common medium of exchange, did not emerge out of any market or voluntary exchange, and best fit the state and credit theories of money articulated by Georg F. Knapp and A. Mitchell Innes. However, Menger’s account is not contradicted by Schmandt-Besserat’s thesis once more recent ‘Neo-Mengerian’ scholarship is brought to attention. Specifically, when the crux of Menger’s story is on the marketability and the original nonmonetary use of the thing which becomes money, rather than his historical timeline. Finally, the third chapter surveys the scholarship on Ancient Mesopotamia. Chartalists and the scholarship in the tradition of Karl Polanyi believe Menger’s theory of money and standard price theory is inapplicable to Ancient Mesopotamian history, especially before the 2nd Millennium. Here the evidence between 2700 BC to 330 BC is considered regarding what Neo-Mengerian monetary theory and standard price theory would expect to find. The history, especially newer scholarship, confirms the traditional Mengerian account and the universal applicability of standard price theory to wherever there exists constrained choice
The Empire's City: A Global History of Salem, Massachusetts, 1783-1820
Get PDFWhile best known for its infamous Witch Trials of the 1690s, this dissertation explores another history of Salem, Massachusetts: a global city and trading port from 1783-1820. In the wake of the American Revolution, Salem merchants began sending ships to trade in ports throughout the Indian and Pacific Oceans. This new commerce reflected Americans’ expansive visions for their country’s future. Trade with Asia changed Salem’s local and global economy, architecture and material culture, public life, race relations, and historical memory. Global trade catapulted Salem’s merchant elite to new levels of wealth but furthered their complicity with slavery. Salem merchants had supported Caribbean plantation owners since the 1600s by selling them food for enslaved people and now began shipping Chinese tea and India textiles to the West Indies. Salem builders added Chinese latticework to local homes and the Salem East India Marine Society, a local organization for ship captains, opened a museum and sponsored an annual parade featuring cultural objects collected overseas. All Salem residents, including women, poor whites, and Black sailors, purchased imported consumer goods and participated in the city’s global economy. Trade with Asia also brought Salem’s white merchants into contact with foreign peoples and facilitated the migration of a diverse community of sailors to Salem. These interactions prompted new questions and conclusions about race and the social order. Trade with Asia changed not only Salem’s demographics but also its material culture as captains built homes and buildings decorated with interpretations of Chinese designs. Salem public life was additionally altered by the Salem East India Marine Society which, after its founding in 1799, cultivated a civic identity of “merchant explorer” for its members by celebrating not their wealth but their newfound knowledge of Asia represented in Society’s museum of objects collected while conducting business overseas. Paradoxically, as Salem’s volume of trade with Asia declined in the 1820s and 1830s, its cultural power grew. Salem residents attempted to replace the city’s “Witch Trials” identity with a new one, “global trading port,” by adopting an official city seal in 1839 which depicted a Salem ship, an Indonesian merchant, and the motto “To the farthest port of the rich East.” Salem’s local context reveals how American culture was shaped by global exchanges
Measuring Food Preparation Equipment in the Home: Developing and Field Testing an Instrument for Use in a Pediatric Obesity Intervention
Get PDFBackground: Hispanic children are disproportionately affected by obesity in the United States. Interventions targeting the home food environment of obese Hispanic children may contribute to reductions in obesity in both the short term and the long term. One component of the home food environment that has not been studied is food preparation equipment present in the homes of obese Hispanic children. Objectives: To develop and field test an instrument for the collection of data about food preparation equipment present in the homes of obese children of Spanish-speaking Central American immigrants living in the Woodbridge area of Northern Virginia. Method: A multi-stage process was used to develop and field test the instrument: A literature review was conducted to identify any existing instruments that could be used to collect data on the home food preparation equipment of the target population. Since no appropriate instrument was identified from this review, an instrument in the form of a checklist was developed. Face validity of the checklist was assessed using a review by a native Spanish speaker with experience working with the target population. Content validity of the checklist was assessed through its use in field tests that occurred in the homes of two members of the target population. Both quantitative and qualitative data were collected from these reviews and analyzed using descriptive statistics and NVivo software. Results: Face validity assessment revealed the need to include a photographic image of each item next to it on the checklist. With two limited exceptions, the checklist demonstrated good content validity. Descriptive analysis of the data collected with the checklist showed that the homes of both persons participating in the field testing were adequately stocked with the minimum number of items needed to store and prepare foods for home consumption. Qualitative analysis showed that both of these individuals regularly prepared balanced, healthy meals for their families. Both also showed interest in food and the process of cooking, although convenience was an important consideration. The reliance by one individual on the use of social media to obtain information about food and cooking skills suggests that efforts to promote home cooking as part of a family- and home-based obesity intervention must take these new ways of transmitting information into account. Overall, the checklist achieved the purpose for which it was developed. Field testing also suggested that the checklist was adaptable and could be used other populations of interest with some modification as appropriate to reflect their unique foodways
Self-Protection Through Dynamic Reconfigurations
No full textModern computer systems have become more complex over time and traditional resilience mechanisms built around static configurations may no longer adequately protect them against cyberattacks and failures. To address these limitations, systems have to become more dynamic to increase their resilience and adaptability to environmental changes. Adaptation through dynamic reconfiguration can improve quality of service, increase fault-tolerance, help recover from failures, prevent and recover from cyberattacks. A major challenge of dynamic reconfiguration is the performance and availability degradation that may occur during system reconfiguration. Dynamic reconfiguration is primarily a mechanism that reconfigures one or more of a system's resources. Although multiple dynamic reconfiguration techniques have been described in the literature, there is no comprehensive method to quantify their tradeoffs due to reconfiguration overhead. Therefore, a quantification framework for dynamic reconfiguration is needed to formally analyze and optimize performance tradeoffs. This dissertation formalizes the problem of dynamic reconfiguration and demonstrates several theorems regarding the use of dynamic reconfiguration to reduce the incidence of cyberattacks and protect from failures.This work defines functions that capture the effect of dynamic reconfigurations on a system's resilience to cyberattacks and failures. Metrics are also developed that capture the impact of reconfigurations on a system's execution time and on the probability of cyberattacks and failure. This work also derives analytic models for predicting the effect of dynamic reconfigurations on execution time and resilience to cyberattacks and failures. Several theorems regarding the tradeoff between resilience and performance and availability are presented. An optimization problem is defined, formalized with the help of these theorems, to determine the optimal reconfiguration frequency to meet performance-resilience tradeoffs. This dissertation also applied an approach inspired by Moving Target Defense (MTDs) to increase workflow-based applications robustness to cyberattacks. This approach is based on dynamic reconfigurations of workflow tasks to reduce an attacker's probability of succeeding in completing the reconnaissance phase of a workflow before launching an attack. To determine the impact of task reconfigurations on a workflow's execution time and resilience against cyberattacks, this work designed recursive algorithms for computing the execution time of a workflow and the reconnaissance function of a workflow, and derived an analytic model that captures the tradeoff between security and execution time of workflow-based applications. To validate the result the experiments used a trace-driven simulation analysis of 6,000 workflows from the Workflow Trace Archive consisting of real-life workflow traces from three different domains: scientific computing, engineering, and industrial
Astraea Underground
No full textThis thesis has been embargoed for 10 years and will not be available until April 2032 at the earliest.This thesis project, Astraea Underground, contains spaceships; reader beware. It is a family-oriented sci-fi novel that tells the story of three characters who are forced by fifteen years of political turmoil to consider whether it is permissible to keep things from those they love and when the costs of betrayal and obligations of loyalty are too high to bear. The novel grapples with how personal trauma compounds into geopolitical instability while exploring the individual and societal impacts of untreated PTSD and addiction. These traumas burden the story’s relationships and drive much of its plot. Though the lens of tomorrow, the story examines issues relevant today, including corporate influence on and power in politics, xenophobia, nationalism, the treatment of immigrants and political dissidents, and the power of media in shaping popular opinion, and features a multi-generational and diverse cast of characters who depict complex, unconventional familial relationships. In these pages, even sworn enemies must work together to survive in the inhospitable environments of life beyond Earth.2032-04-2