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Experiential Learning and Technical Debt
No full textExperimental student projects provide a low-barrier opportunity for research universities to both support student learning and to pilot novel presentations of institutional research and data. This is particularly advantageous when students of a minority community are enabled to tell the stories of the research data of that minority community. The unresolved risk, however, is the ongoing stewardship of this work, as such an experimental or pilot project represents an inherited technical debt after the students have graduated. This presentation will describe one such student endeavor as a case study. At the University of Pittsburgh, the University Library System and the School of Computing and Information Science partnered to create a query/visualization tool highlighting a distinctive-collections deposit within the University’s institutional repository of transcriptions of a substantial Chinese village gazetteer collection. The presenter will reflect on successes and challenges of this project and will invite conversation on similar technical management of experimental/pilot student projects which highlight institutional repositories’ research and datasets
Atomic-scale In Situ TEM Investigation of Grain Boundary Deformation Behavior in FCC Gold
No full textThe deformation mechanism of metallic polycrystalline materials is known to transform from dislocation-mediated plasticity into grain boundary (GB)-mediated plasticity when the crystal size decreases to sub-10 nm. Numerous studies have been performed in the past decades to reveal the mechanisms of GB deformation. However, the dynamic process of GB deformation at the atomic scale remains largely unclear due to the lack of real-time experimental observation. In this dissertation, in-situ high-resolution transmission electron microscopy (HRTEM) combined with molecular dynamics (MD) simulations have been employed to investigate the typical GB deformation behavior in face-centered cubic (FCC) gold (Au) nanocrystals at the atomic scale.
Dynamic GB structural transformation arising from reversible facet transformation and GB dissociation was observed during the migration of faceted GBs. It is found that the types of steps/disconnections mediating the migration of GB facets determine which pathway the GB structural transformation follows. Moreover, the loading dependence of GB facet transformation and the roles of GB junctions in accommodating GB migration and structural transformation are clarified.
Regarding the case of mixed tilt-twist GB, two distinct migration patterns showing the opposite signs of shear-coupling factor were observed, and further revealed to be mediated by the motion of GB disconnections with different crystallographic parameters and exhibit different lattice correspondence relations. MD simulation results confirm that the two distinct migration patterns could be activated under different stress/strain states. Furthermore, excess GB sliding and GB plane reorientation were found to accommodate the GB migration in both experiments and simulations, as to establish a point-to-point lattice correspondence during GB migration.
Additionally, the deformation-induced formation and annihilation of a typical HAGB in an Au nanocrystal upon reciprocating bending deformation was investigated. HAGB formation underwent the process of accumulation, alignment, further accumulation, and eventually exhaustion of geometrically necessary dislocations. In comparison, HAGB annihilation was accomplished by the synergic operation of GB structure reconstruction, emission of partial and full dislocations, and twinning.
This dissertation advances the fundamental understanding of atomic-scale GB deformation behavior in FCC materials and provides important guidelines for the future development of ductile nanocrystalline materials and reliable nanocrystal components in nano electromechanical systems devices
Exploring the Wetting Property of Selected 2D Materials
No full textThe wettability of 2D materials is of paramount importance since it is critical to the interaction of 2D materials with liquids, which significantly impacts the performance in a wide array of applications. The fundamental understanding of wettability enables the optimization of 2D materials' functionality by enhancing their capacity to either repel or attract liquids and modulating adhesion properties. In this dissertation, we investigated the wettability of graphene and hexagonal boron nitride (hBN).
The previously proposed wetting transparency of graphene provides a compelling opportunity for multifunctional device design, allowing precise modulation of wettability by selecting an appropriate substrate. However, the graphene's wetting transparency on liquid substrates, which is promising for real-time wettability control, has been rarely studied before; possibly due to serious experimental challenges. To this end, we have developed a method using contact angle measurement, based on Neumann's Triangle model, to directly characterize the wetting transparency of graphene on liquid substrates for the first time. The experimental data suggests that the graphene is nearly wetting transparent on some liquid substrates. We also demonstrated the real-time wettability control with graphene on water-ethanol substrates.
Although the wettability of hBN has garnered significant attention, the accurate measurement of water contact angle (WCA) remains challenging; possibly due to sample defect/quality and airborne contamination. We have systematically investigated the effect of airborne hydrocarbons and defects on both static and dynamic WCAs of hBN. Importantly, we have demonstrated that the presence of defects significantly affects the static WCA, indicating previously reported static WCA values do not represent hBN's intrinsic water wettability. Instead, our results showed that the advancing WCA on freshly exfoliated hBN, measured at ~79°, provides the most accurate representation of hBN's intrinsic water wettability since it is not impacted by the defects. We have proposed a qualitative model that elucidates the impact of airborne hydrocarbons and defects on the static and dynamic WCAs of hBN, which aligns well with our experimental findings
Real-time dynamic security assessment of power system using strategic PMU measurements and control technique
No full textThis research presents a comprehensive exploration of adaptive control strategies and data-driven anomaly detection within power systems. At the core of the study lies the investigation of adaptive finite-time tracking control for strict-feedback nonlinear continuous-time
systems. These systems, when influenced by full-state constraints and dead zones, present significant challenges. By harnessing the principles of finite-time stability theory combined with barrier Lyapunov functions, the study introduces a groundbreaking adaptive tracking control strategy. Coupled with the adaptive backstepping method, this approach guarantees that the closed-loop system’s signals remain bounded. Furthermore, it ensures that outputs
adeptly track reference signals, while all system states are confined within predefined compact sets, enhancing system reliability and performance. In parallel, the research unveils an innovative approach to tackle the intricate challenge of anomaly detection in Phasor Measurement Unit (PMU) data. Recognizing the high-dimensional nature of PMU data, an ensemble model, synthesizing the strengths of Gaussian Process Regression (GPR) and Autoencoders,
is proposed. This ensemble not only boasts superior data reconstruction fidelity but also features a Bayesian optimization-driven threshold determination. Such a methodology fosters an adaptive, data-driven anomaly detection process, resulting in heightened specificity and sensitivity. Validation tests conducted on a synthetic dataset, infused with 84 frequency events, attest to the ensemble model’s superior capability in discerning nuanced
anomalies. This superiority is evident both visually and through rigorous quantitative metrics, underscoring the ensemble’s edge over traditional models
Learning Fast Approximations For Nonconvex Optimization Problems Via Deep Learning With Applications To Power Systems
No full textNonlinear convex optimization has provided a great modeling language and a powerful solution tool for the control and analysis of power systems over the last decade. A main challenge today is solving non-convex problems in real-time. However, if an oracle can guess, ahead of time, a high quality initial solution, then most non-convex optimization problems can be solved in a limited number of iterations using off-the-shelf solvers. In this proposal, we study how deep learning can provide good approximations for real-time power system applications. These approximations can act as good initial solutions to any exact algorithm. Alternatively, such approximations could be satisfactory to carry out real-time operations in power systems.
First, we address the problem of joint power system state estimation and bad data identification. We propose a deep learning model that provides high quality approximations in milliseconds.
Second, we address the problem multi-step ahead power system state forecasting and advocate sequence-to-sequence models for better representation.
Lastly, we study the problem of learning fast approximations of the optimal basis of a linear program produced by the simplex algorithm. We cast the problem as a simple classification task and propose a deep learning model
Conditional Activation of Protein Function
No full textThe ability to demonstrate conditional control over biological processes is fundamental to the field of chemical biology and is thoroughly discussed in Chapter 1.0. In this work, I investigated various methods of conditional activation including the modification of small molecule ligands with light, peroxide, or enzymatically activated caging groups as discussed in Chapter 2.1. Peroxide-cleavable functionalities were also utilized for the selective release of the chemotherapeutics pederin, camptothecin, and phorbol in cancerous cell lines as demonstrated in Chapter 5.0. The
natural product rapamycin was modified to include either a photoswitchable arylazopyrazole or a photoactivatable ROS-generating chromophore, further demonstrating light control of small molecule ligands in Chapter 4.0.
In addition to the use of small molecule ligands, a variety of photoactivatable unnatural amino acids were utilized throughout Chapters 2.2 and 3.0 to directly render proteins conditionally activatable, specifically for the selective control of MAPK signaling and antibody-directed enzyme
prodrug therapies. The unnatural amino acids utilized herein fall under two major categories: 1) photocaging, in which irradiation activates protein function or 2) photoswitchable, in which irradiation with two different wavelengths of light control protein function in a reversible manner. In either case, the unnatural amino acid was typically introduced to the protein via genetic code expansion, a concept which has been widely utilized by the Deiters lab in order to control and
study various biological processes as demonstrated in this work and the work of previous lab members
Of Victims and Survivors: Representing Collective and Individual Rape Trauma
No full textThe female victim-survivor of sexual and gendered violence is seldom theorized in scholarly accounts of such violence on screen. The presumed audience for much scholarship in the fields of film studies, feminist studies, and trauma studies as they intersect with cultural production is one that must first be informed of the horrors of rape and abuse, must be touched by a film in a way that they have not been in real life. This dissertation, by contrast, assumes that the audience for representations of rape and abuse in cultural production—literary, poetic, filmic, to name a few—has personal, lived experience with sexual and gendered violence. By theorizing media through the rape victim-survivor, and then creating media based on that theory, this dissertation and accompanying film work to disrupt common-sense notions of who is and is not allowed to speak as a victim, how victim-survivors are constructed and exist in the world, and what possible ways forward may exist in the realm of imagining better futures. I begin with a study of rape in cinema, surveying the 1910s and ‘20s forward, with case studies from the 1960s and ‘70s rape-revenge film cycle. From there I expand out to analyses of current fiction film trends, poetry (written and spoken word), music, art, documentary, and memoir. This dissertation closes on a discussion of digital media and where representations of rape victim-survivors intersect online with real-world conditions
Seeking Self-Determination for Black Communities: Toward Revolutionary Place-based Community Engagement
No full textBlack self-determination and freedom is the goal of Black communities who have faced the oppressive and violent hand of white supremacy in America and throughout the world. Higher education is rooted in the European University and was not created for Black people. Historically, predominantly white higher education institutions (PWHEIs) maintained the social order. As racialized organizations, various PWHEIs created place-based Community Engagement Centers (CECs) located within marginalized communities, including the University of Pittsburgh (Pitt). Pitt’s first CEC opened in Homewood in October 2018 with a 15-year long-term commitment of “staffing infrastructure, and coordination to facilitate mutually beneficial collaborations between Pitt and the local community” (University of Pittsburgh, 2023a). Homewood is a predominantly Black neighborhood located in Pittsburgh’s East End. Black residents face challenges including underemployment and poverty, dilapidated housing stock, lower life expectancy and failing schools. Despite this, its residents have displayed resiliency and a desire to thrive. Though distrust of Pitt by community members loomed, Homewood’s leadership, reflected through the Homewood Community Development Collaborative, continued to partner with Pitt and other anchor institutions to improve the community’s conditions. This evaluative dissertation in practice examined the perception of Pitt in Homewood and whether the institution’s place-based practices were in alignment with principles of Black self-determination and freedom. The ideology of Kawaida (Karenga, 1993, 1998), an African American and social philosophy, and its central values the Nguzo Saba (The Seven Principles; Karenga, 1998) are examined and reimagined as a value-system which centers Blackness and could result in community-university partnerships and praxis aimed at supporting Homewood’s ability to define, defend, and develop itself
A Biomarker-based Reconstruction and Comparison of The Microbial Ecology of Ancient Lake Magadi and Modern Nasikie Engida in the East African Rift Valley
No full textIt is important to understand the system dynamics of equatorial saline alkaline (soda) lakes in order to expand our understanding of lake biogeochemical dynamics around the world. Little is known about equatorial soda lakes over geologic time despite their high modern production rates and unique microbial assemblages. Here, biomarkers are used to trace microbial diversity in Lakes Nasikie Engida and Magadi over the past 2.8 and 456 kyr respectively. I used the recalcitrant lipids in methane cycling archaea, pigments in algae and bacteria, and leaf waxes from aquatic and terrestrial plants to reconstruct paleoenvironments and microbial community variations in lakes Nasikie Engida and Magadi. The results from this project have filled gaps in our understanding of lake microbial ecosystems and biogeochemical processes in soda lakes of the East African Rift Valley in the Middle to Late Pleistocene