Due to its reduced dimensionality, monolayer molybdenum disulfide (MoS2) exhibits many unique optical properties, making it an excellent candidate for future optoelectronic devices. Given the multitude of applications, understanding the optical limitations of MoS2 under intense excitation is essential to optimize its performance. To that end, we investigate the femtosecond laser-induced breakdown of monolayer MoS2 with a variety of techniques. In this study, the substrate is discovered to have a profound effect where the ablation threshold itself can vary by more than one order of magnitude due to a simple interference phenomenon within the monolayer. Via substrate engineering, the ablation threshold can be reduced such that laser patterning using pulse energies less than 100 pJ is possible. Similar to many other optical nonlinearities, absorption measurements and theoretical modeling reveal that avalanche ionization is also enhanced where more than 75% of the generated free carriers at breakdown are due to avalanche ionization alone. Finally, multi-shot studies demonstrate that MoS2 is one of the most optically robust materials with very weak incubation effects. Notably, the onset of optical damage results in the formation of nano-voids where clusters of atoms are removed while the overall integrity of the monolayer remains intact. All these findings help establish MoS2 as a promising candidate for strong field devices and provides foundational knowledge regarding the strong field physics of two-dimensional materials.
New modes of public transportation such as micromobility are rapidly growing in urban areas. Bike sharing and e-scooter sharing, for example, have been advanced to solve the first/last mile problem, providing quick access to bus stops and train stations for their users. This efficiency, however, may come at the cost of transmitting disease since the surfaces on the bicycles or scooters are subject to germs and harmful pathogens when they are left in contaminated places or used by infectious individuals. This dissertation aims to understand various facets of the role of micromobility transportation in the spread of viral disease within dense urban areas. I propose a novel micro-level and spatially-explicit agent-based modeling framework to model the spread of viral infectious diseases through micromobility systems and a baseline population. I use this simulation framework to study the role of micromobility in the spread of viral disease in urban areas by breaking down the problem into three directions. First, I want to study how surfaces on the new micromobility transportation systems contribute to the emergence and dynamics of viral epidemics in urban areas. Second, I seek to find out how geographic space and time are organized concerning the risk of exposure to a viral disease out of using micromobility vehicles. Third, to inform decision-making in response to the spread of viral disease through micromobility systems, I examine what intervention methods and strategies, including random or systematic intervention, are more effective in controlling the spread of infectious diseases through micromobility vehicles. In order to test the proposed model, a case study is conducted in Cook County, Illinois, and uses the Chicago City public bikesharing system. Results show that the emergence of viral disease through micromobility transportation in Cook County is possible, but the overall impact of the system on the disease dynamics in a worst-case scenario, especially with the current size of the system, is rather small. The proposed model, however, provides a better measure to evaluate the role of transportation in spread of disease compared to existing measures. The spatial pattern for the risk of exposure is higher in the central business district and in northern regions, where most of the shared bike transportation occurs. Moreover, the start day of exposure impacts the dynamics of the spread of disease through both micromobility and the baseline population. Finally, intervention success in a full-blown epidemic highly depends on human behavior, availability of disinfection equipment, and strategies to implement control methods. The proposed simulation framework can be used to assess the efficacy of interventions and make trade-offs between these factors when dealing with epidemics of the sort analyzed in this research.
The primary goal of design is to provide effective and innovative solutions for solving design problems. Ideation, an initial idea generation for conceptualizing a design solution, is a key step that can lead design to an innovative design solution in the design process. Idea generation is a process that allows designers to explore many different areas of the design solution space. Due to the importance of ideation, many studies focused on understanding the cognitive processes in idea generation and evaluating ideation. This thesis focuses on the idea generation process based on conceptual similarity in a human-AI collaboration. Co-creative systems in design allow users to collaborate with an AI agent on open-ended creative tasks in the design process. Co-creative systems share the characteristics of both creativity support tools helping users achieve creative goals and algorithms that generate creative content autonomously. Co-creative systems support design creativity by encouraging the exploration of design solutions in the initial idea generation. However, there is a lack of studies about the effect of co-creative systems on the cognitive process during ideation. This thesis posits that the contribution of an AI partner in design is associated with specific properties of ideation such as novelty, variety, quality, and quantity of ideas.
This thesis presents a co-creative system that enhances design creativity in the initial idea generation process. The Collaborative Ideation Partner (CIP) is a co-creative design system that selects and presents inspirational images based on their conceptual similarity to the design task while the designer is sketching. This thesis addresses how the conceptual similarity of the contribution of the AI partner influences design ideation in a co-creative system. This thesis presents an experiment with a control condition in which the images are selected randomly from a curated database for inspiration and a treatment condition in which conceptual similarity is the basis for selecting the next inspiring image. To evaluate the ideation during the use of CIP, this thesis employed an aggregate analysis and a temporal analysis. The findings show that the AI model of conceptual similarity used in the treatment condition has a significant effect on the novelty, variety, and quantity of ideas during human design ideation.
Since the 1954 Brown v. Board of Education ruling against school segregation, Black women teachers (BWTs) have had perpetually high rates of attrition, despite their legacy of providing high quality, emancipatory education. Thus, the purpose of this study was to contextualize the attrition of critical BWTs to better understand the factors that would support their sustainability in urban schools. Specifically, I investigated (a) the relationship between Black women’s intersectional identities and their experiences as critical educators in urban schools, (b) the compounding factors that led to their ultimate departure, and (c) the complexities of their decision to leave the profession.
Using Black feminist thought and cognitive dissonance theory as my framework, I employed sista circle methodology to study fifteen post-service critical Black women teachers. Each participant engaged in an individual interview, one of three sista circles, and a written reflection. Data analysis revealed three major themes that offer rich context and a complex narrative of why critical BWTs love and leave the classroom: instinct vs. opposition, commitments vs. personal needs, and dissonance-reduction strategies. As they are examined, these themes suggest several actions that can be taken by key stakeholders to support their professional sustainability.
As the number of minority students in public schools increases in the U.S., the teacher workforce and administration remain majority White. Increased access to service-learning will help mitigate opportunity gaps that exist in marginalized communities. Service-learning combines academic coursework with volunteer community service experiences, which can be beneficial to in-service and pre-service teachers. Changing the structure of service-learning opportunities to include the voices of African American women is critical to expanding the structure of volunteer efforts, specifically within urban school environments. Using Seidman’s In-Depth Interview Protocol, this research explores the experiences of African American women educators with service-learning and volunteering in local communities and schools. The study examines how Black women educators saw service-learning and volunteering as part of their identities. The findings indicate that service is central to their definitions of social justice work in education and beyond through the concepts of: (a) giving back, (b) serving, (c) family, (d) Black womanhood, (e) leadership and (f) spirituality. The results of this study illustrate how educators’ lived experiences expand conceptions of service. The participants viewed service-learning as being crucial to student and teacher success in urban environments.
Keywords: service-learning, critical service-learning pedagogy, social justice, volunteerism
The task of visually tracking multiple objects remains an active field of algorithm development even after several decades of research in the computer vision community. It remains an active research area because identifying and maintaining the location of multiple targets in a video recording can be approached from several perspectives. Another reason is simply that the general problem of automated tracking can be very challenging. Challenges within visual tracking collectively manifest into three broader design decisions often faced by multiple object tracking (MOT) algorithms. First is how to handle what one could think of as "easy" and "hard" regions of a trajectory. The second is how to handle the sheer number of possible explanations of the data. The third is how do you model certainty. This dissertation aims to better model the uncertainty among possible answers to the tracking data in offline tracking scenarios. Furthermore, the method does so in a way that utilizes the information within the "hard to track" regions — information that is typically not used. The way we do this results in accurate tracking that is better suited for video analysis pipelines that may need to filter or correct any tracking errors.
Subjective perceptions of social mobility are critical for defending societal system and maintain political stability (Day and Fiske 2017; Houle 2019). This dissertation enhances our understanding of factors that shape beliefs in opportunity for upward mobility by focusing on the living environments in American neighborhoods. Inspired by the research from psychology and development economics, I developed and tested the Opportunity Beliefs Theory to explain how the built environment in neighborhoods affects individuals’ opportunity beliefs. The theory aims to elucidate how environmental factors psychologically affect people’s beliefs and behavior. The Opportunity Beliefs theory argues that the living environment can rouse positive or negative emotions. These emotional incentives shape residents’ self-efficacy. These emotions and self-efficacy largely affect people’s expectations for the future. According to the Opportunity Beliefs Theory, for people with low/middle income, those who live in a neighborhood with a better-maintained built environment are more likely to possess positive emotions and hold a high-level of self-efficacy. Furthermore, these residents will perceive more opportunities for themselves and their children for getting ahead in life, and they are more likely to agree that the opportunities are distributed equally in the society.
I have designed three studies which can support each other to explore the valid causal inferences between the built environment in neighborhoods and opportunity beliefs. First, In order to understand how the built environment in neighborhoods affects Americans’ opportunity beliefs, I designed a conventional survey which can obtain samples nation-wide and has high external validity. Next, I conducted two-round survey experiments to explore the causal inference. The results support my hypotheses.
This dissertation explores the interaction between the living environment and human psychological states and enriches the knowledge of emotions, self-efficacy, and opportunity beliefs. This research has important implications for poverty reduction and redistributive policy.
It is so rewarding to help someone to achieve their desires for their health care. The feeling of helping to empower others to know the choices that they have available to them while they can make those choices is profound. It is also gratifying to advocate for others to have a proactive role in the decisions related to their health care.
Registered nurses working in North Carolina each day have ample opportunities to engage with patients, caregivers, and community members on the topic of advance care planning and advance directives. The importance of ensuring that nurses receive education and awareness on these topics cannot be overstated. Improving a nurse’s education and awareness can impact a nurse’s ability and comfort level to discuss these topics with others. In addition to providing education and awareness, it is also important to allow for time of reflection on a nurse’s unique experiences and perceptions on barriers related to advance care planning and advance directive completion.
Through participants completing an initial survey, educational training including open-ended questions and post-survey, this DNP Scholarly Project seeks to look at nurses’ knowledge, attitudes, experiences, perceptions, and self-efficacy related to advance care planning and advance directives while also gaining awareness to nurses’ thoughts on perceived barriers to advance care planning and advance directives and if nurses feel the educational training offered as part of this project would benefit other nurses.
The antibiotic resistance genes (ARGs) have been increasing over time in the environment due to human activities and antibiotic use. According to CDC, antibiotic resistance (AR) causes casual infections untreatable and result in high socioeconomic costs and health care burdens. This study focuses on targeting ARGs origination, distribution, and expression in the water system under anthropogenic effects. Investigation of ARGs takes following goals: 1) Optimization of conventional and new technologies for ARG detection using quantitative polymerase chain reaction (qPCR) and droplet digital PCR (qPCR), 2) Comparison of performance between qPCR and ddPCR on ARGs, 3) Measurement of ARG abundance throughout different types of water bodies such as a lake, river, wetland, underground aquifer across the U.S. water system under anthropogenic effects, and 4) metagenomic bacterial and ARG expression analysis under a stressed environment with metal-laden industrial flue gas desulfurization (FGD) wastewater. This study helps improve surveillance and develop mitigation plans for AR and ARGs in the water system globally. And add knowledge to have better control in tracking, treatment, and containment protecting the health of humans and the ecosystem.
Expectations regarding leadership practices are changing and evolving as the expectations for school leaders and, thus, central office leaders, to lead and support the creation of equitable outcomes for all students. School systems are recognizing methods to acquire and strengthen a critical lens for identifying the inequities within their school systems so that they can tackle barriers to advancement and root causes more directly (Cheatham et al., 2020). Central office leaders should exemplify specific critical roles for school reform (Rorrer et al., 2008). For this phenomenological study, six equity officers from five urban districts were interviewed about their perceptions of how they define equity-driven central office leadership and their perception of the skills needed for central office leaders to actualize their definition of equity-driven central office leadership and to also reflect upon their roles as equity officers. Districts may benefit from learning more about the practical core skills, behaviors, and comprehensive leadership development practices to develop equity-driven central office leaders who impact equitable outcomes for students. The findings indicate that when equity officers have support from the district, including time, financial resources, and access to school leaders, they believe they can have a more significant impact on schools and leaders.