VictorJuiz/thesis huggingface dataset:
Optimal Control for Learning with Applications in Dynamic MRI

Unknown parameters in models of dynamical systems can be learned reliably only when the system is excited such that the measured output data is informative. Given a statistical model that specifies the dependence of the measured data on the state of the dynamical system, the design of maximally informative inputs to the system can be formulated as a mathematical optimization problem using the Fisher information as an objective function./nOptimal design in the time domain is hard in general, but efficient approximation algorithms have been developed in some special cases. In this dissertation, we present new approaches to solving this problem using optimal control algorithms based on convex relaxations, and exploiting geometric structure in the underlying optimization problem./nMagnetic resonance imaging (MRI) serves as a motivating application problem throughout. We highlight two successes of these methods in the design of dynamic MRI experiments: magnetic resonance fingerprinting (MRF) for accelerated anatomic imaging, and hyperpolarized carbon-13 MRI for noninvasively monitoring cancer metabolism. In particular, we use optimal experiment design algorithms to compute optimized flip angle sequences for MRF and hyperpolarized carbon-13 acquisitions as well as optimized tracer injection inputs for estimating metabolic rate parameters in hyperpolarized carbon-13 acquisitions. In the final chapter, we present results on constrained reconstruction of metabolism maps from experimental data, closing the path from experiment design to data collection to synthesis of interpretable information.

Advisor: Arcak, Murat
Eulerian Simulation of Elastic Membranes and Shells

The simulation of the dynamics of thin elastic surfaces is an essential component in applications ranging from cardiovascular medicine to flapping wing aerospace engineering. In this thesis we introduce a fully Eulerian method for accurately simulating elastic surfaces. Our approach can be applied to membranes and shells with nonlinear elastic properties, either moving under their own dynamics or immersed in a Fluid. By representing the surface with a level set function and a set of advected reference coordinates, we are able to evaluate the full elastic surface forces. Our approach is compatible with compatible with implicit interface representations, including level set techniques, and can make use of high-order finite difference stencils or more sophisticated techniques. We introduce our method and its implementation, including new solution techniques for several problems associated with immersed interface representations. We demonstrate second order accurate numerical results for a range of model problems in two and three dimensions.

Advisor: Sethian, James
Synthesis and Applications of Graphene Nanoribbons and Heterostructures from Molecular Precursors

Graphene nanoribbons (GNRs), nanometer wide strips of graphene with extraordinary/nelectronic and physical properties, represent the cutting edge of post-silicon electronics development./nThese nanomaterials boast potential solutions to downsizing of future electronics/nin both size and energy consumption, as well as opening the door to faster processing. Novel/nGNRs of varied width and heteroatom incorporation were synthesized in a surface assisted/nbottom-up fashion from novel small molecule precursors (Chapter 2). The advancement of/nGNR based technologies to new and advanced architectures requires the controlled formation/nof functional GNR heterostructures, and to this end, a GNR-porphyrin-GNR heterostructure/nwas designed and developed which is shown to self-assemble on functionalized surfaces/n(Chapter 3). Furthermore, bulk GNRs are shown to have practical applications beyond the/nsingle ribbon scale, acting as functional support materials for inorganic nanoparticles (Chapter/n4). This work advances both the development and applications of bottom-up synthesized/nGNRs.

Advisor: Fischer, Felix R
Electrophysiology of inhibition and auditory prediction mechanisms in human cortex

One of the core problems the brain has to solve is how to navigate and interact with the external world. This requires a complex analysis of sensory input, the translation of perceptual input to goal-directed behavior, followed by motor planning and execution. In this thesis we investigated two crucial aspects of this perception-action cycle. First, we examined the underlying neural mechanisms that support response inhibition. Here, novel sensory information is integrated on very short time-scales to cancel an already planned action. The frontal cortex is believed to play a crucial role in the temporal organization of goal-directed behavior and cognitive control and is implicated in stopping a motor response. Using the high spatiotemporal resolution of electrocorticography (ECoG), we found evidence for two distinct processes localized to the middle frontal gyrus (MFG). High-frequency band (HFB) power increased in stop-trials before the stop-signal reaction time (SSRT), showing no difference between successful and unsuccessful stops. We interpret this activation as contributing to the stopping process, either by signaling the stop-signal itself, or by implementing attentional control. A second HFB activation was observed after the go and stop processes have finished, and was larger for unsuccessful stops, and is likely related to behavioral monitoring. Our results support the notion that frontal cortex implements different functions related to stopping./nImplementing the perception-action cycle not only involves re-acting to novel information from the senses in a bottom-up manner. It is believed that the brain also implements a strategy anticipating future events based on prior knowledge. Here we investigated how anticipation of sounds influences auditory processing. Using both EEG and ECoG, we employed a task with omissions of expected sounds, thereby isolating endogenous responses to expectations in auditory cortex. We found that a subset of auditory active electrodes in lateral superior temporal gyrus (STG) and superior temporal sulcus (STS) showing HFB power increases to omissions. We were able to successfully decode whether the subject heard the syllable ‘Ba’ or ‘Ga’. However, which sound was omitted could not be decoded from auditory active sites, nor from the omission HFB increase specifically. We also observed a negative ERP in posterior STG in the intracranial data, which may be related to an auditory cortical generator of the N2 component. In a separate EEG studies we also observed both an N2 negativity, as well as a negativity occurring before the intracranial negativity, the source of which may be in A1, a region which we could not access intracranially. Finally, a P3a ERP was observed in EEG, which points to both the HFB and ERP effects in posterior STG to be signatures of auditory-specific salience or mismatch detection.

Advisor: Knight, Robert T
Thinking Danger with Jean-Jacques Rousseau

This dissertation discusses danger as of one the central concepts of Jean-Jacques Rousseau’s thought. While many classic inquiries have emphasized metaphysical themes like “evil” in Rousseau’s work, I focus on danger as it pertains to the relationship between man and the built environment, as distinct from interhuman relationships. I argue that dangerousness is most visible for Rousseau in human creative activities like architecture, urban planning, and other material makings, subjects poorly treated in Rousseauian criticism. Although some theorists of risk and danger like Georges-Yves Kerven have briefly touched on this problematic in Rousseau, literary and philosophical approaches have not, thus weakening our grasp on the totality of Rousseau’s thought. Thus, in classic readings such as Derrida’s as well as more recent studies like Rudy Le Mentheour’s Manufacture des maladies, danger is either kept on a secondary plan or has been largely limited to psycho-political approaches. Through readings of texts such as the Lettre sur le désastre de Lisbonne, the Discours sur l’origine de l’inégalité, and the Lettre à d’Alembert, this dissertation seeks to fill a gap in the Rousseauian criticism by showing that Rousseau offers a true « riskology », one that has no counterpart either in earlier thinkers such as Hobbes or in contemporaries like Voltaire. I believe that this dissertation will render Rousseau and his thought more accessible to non-literary and non-philosophical thinkers who cannot dialogue with Rousseau within the classical critical frames.

Advisor: Paige, Nicholas D
Prosodic Prominence in Karuk

This study focuses on word-level prosodic prominence in Karuk (kyh), a Hokan isolate of Northern California. Prosodic prominence in Karuk is made up of sparse tone and stress, and there are two main influences on its placement: the alignment of high tone and certain syllable structures, and the use of prosodic prominence to mark stem edges. These influences are at times in conflict, with the resolution depending on criteria specific to particular sets of morphology. The study is based on analysis of a corpus combining recent fieldwork and historical data. Specific findings include: 1) the placement of prominence in a Karuk word is largely dependent on CV-skeleton syllable structure and far more predictable than previ- ously thought; 2) while one tone-syllable alignment is the unmarked output of constraints, a different tone-syllable alignment on the input blocks its surfacing; 3) various sets of morphol- ogy interfere with the basic placement of prominence by triggering stem-final prominence; and 4) the predictable placement of basic prominence only applies within the prosodic stem, from which certain morphemes are excluded./nThe prosodic system of Karuk bears some striking resemblances to those of other lan- guages known as accent languages, but has important differences and added complexities. An unmarked high-tone-before-long-vowel alignment in Karuk is typologically unusual, as is a dispreferred high-tone-on-CVC alignment. Although tone and stress generally coincide, reference to both tone and metrical structure is required in defining preferred and avoided structures./nThe complexity of Karuk word prosody poses a challenge for approaches which seek to limit the role of morphology to either the phonology or the syntax, as well as for those which seek to implement a wholly parallel or a wholly derivational model of the phonology- morphology interface. The Karuk case shows that phonology and morphology must be interleaved, and I find that a cophonology approach best accounts for the complex patterns seen. Other challenges for an Optimality Theoretic approach raised by the Karuk data are opacity in a non-surface-apparent constraint driving placement of prosody, and the need for special faithfulness to account for the protected status of a particular tone-syllable alignment.

Advisor: Garrett, Andrew
Inkelas, Sharon
Modeling and Analysis of Elements in Structural Mechanics

The focus of this work is to advance the theoretical and modeling techniques for the fields of hybrid simulation and multi-slider friction pendulum systems (MSFPs). Hybrid Simulation is a simulation technique involving the integration of a physical system and a computational system with the use of actuators and sensors. This method has a strong foundation in the experimental mechanics community where it has been used for many years. The hybrid simulation experiments are performed with the assumption of an accurate result as long as the main causes of error are reduced. However, the theoretical background on hybrid testing needs to be developed in order validate these findings using this technique. To achieve this objective, a model for hybrid simulation is developed and applied to three test cases: an Euler-Bernoulli beam, a nonlinear damped, driven pendulum, and a boom crane structure. Due to the complex dynamics that these three test cases exhibit, L2 norms, Lyapunov exponents, and Lyapunov dimensions, as well as correlation exponents were utilized to analyze the error in hybrid simulation tests. From these three test cases it was found that hybrid simulations are highly dependent on the natural frequencies of the dynamical system as well as how and where the hybrid split is located. Thus, proper care must be taken when conducting a hybrid experiment in order to guarantee reliable results./nMulti-stage friction pendulum systems (MSFPs), such as the triple friction pendulum (TFP), are currently being developed as seismic isolators. However, all current analytical models are inadequate in modeling many facets of these devices. Either the model can only handle uni-directional ground motions while incorporating the kinetics of the TFP system, or the model ignores the kinetics and can handle bi-directional motion. And in all cases, the model is linearized to simplify the equations. The second part of this dissertation presents an all-in-one model that incorporates the full nonlinear kinetics of the TFP system, while allowing for bi-directional ground motion. In this way, the model presented here is the most complete single model currently available. It was found that the non-linear model can more accurately predict the experimental results for large displacements due to the nonlinear kinematics used to describe the system. The model is also able to successfully predict the experimental results for bi-directional ground motions.

Advisor: Govindjee, Sanjay
O'Reilly, Oliver
Integers that can be written as the sum of two rational cubes.

We are interested in finding for which positive integers D we have rational solutions for the equation x^3+y^3=D. The aim of this thesis is to compute the value of the L-function L(E_D, 1), for E_D: x^3+y^3=D. For the case of D prime D=1 mod 9, two formulas have been computed by Rodriguez-Villegas and Zagier. We have computed several formulas that relate $L(E_D, 1)$ to the trace of a modular function at a CM point. This offers a criterion for when the integer D is the sum of two rational cubes. Furthermore, when L(E_D, 1) is nonzero we get a formula for the number of elements in the Tate-Shafarevich group of E_D.

Advisor: Yuan, Xinyi
Serious Play: Formal Innovation and Politics in French Literature from the 1950s to the Present

Serious Play: Formal Innovation and Politics in French literature from the 1950s to the present investigates how 20th- and 21st-century French authors play with literary form as a means of engaging with contemporary history and politics. Authors like Georges Perec, Monique Wittig, and Jacques Jouet often treat the practice of writing like a game with fixed rules, imposing constraints on when, where, or how they write. They play with literary form by eliminating letters and pronouns; by using only certain genders, or by writing in specific times and spaces. While such alterations of the French language may appear strange or even trivial, by experimenting with new language systems, these authors probe into how political subjects—both individual and collective—are formed in language. The meticulous way in which they approach form challenges unspoken assumptions about which cultural practices are granted political authority and by whom. This investigation is grounded in specific historical circumstances: the student worker-strike of May ’68 and the Algerian War, the rise of and competition between early feminist collectives, and the failure of communism and the rise of the right-wing extremism in 21st-century France. Analysis of pronominal subjects in Perec and Wittig shows how they interrogate power struggles during May ’68; both authors imagine shared textual production as the bedrock of new political communities. Moving into the 21st century, Jouet stages various “bad” communists, in order to pay tribute to dying communist communities and to unpack the ongoing legacy of communism’s collapse. In the end, formal play offers an antidote to 20th- and 21st-century crises of community by creating virtual communities through the text itself.

Advisor: Lucey, Michael
Creating Community Among Leaders: Leveraging Shared Practices for School Improvement

Principals work within a complex context where multiple stakeholders make many competing demands of them. Chief among these demands includes district initiatives, which serve to create leadership expectations but often do not contain clear methods or practices for implementation. Additionally, demands of the local community and interests of teachers and students create layers of complexity which can confound and isolate leaders. While principals may feel cut off from their peers dealing with these intricacies, the reality is, regardless of initiative or priority, principals have many common problems of practice. Establishing highly effective teacher collaborative groups, is an example of an implementation most principals come to face./nThe Early Release Wednesday Toolkit was developed to support leadership practices for implementing highly effective collaborative teacher groups. To create the toolkit, a sample of principals engaged in a co-development process to capture effective practices already in place, and share them with the larger principal group. In so doing, the principal Community of Practice was strengthened. The findings of this study suggest that principals gain from relying on each other for problem solving where their leadership is concerned, and may serve to inform other leaders about effective ways to learn from one another. This design study is centered on action research and includes two primary research elements, evaluation of the design outcome and assessment of the design process.

Advisor: Gifford, Bernard
Theoretical Approaches to Measuring the Welfare Effects of Asset Transfers

Millions of low-income households have received large one-time transfers of capital as part of private and public anti-poverty programs. Economists have studied the effect of such transfers in a wide variety of settings to understand their effect on household welfare and poverty rates. The standard metric used to study these effects is aggregate consumption, measured in price-adjusted dollars per capita per day, which in turn gets used to define the global poverty lines at $2 and $1.25. In this dissertation, I discuss some of the theoretical and practical issues that these measures face, and then suggest some alternatives pulled from a model of consumer demand. I demonstrate how they can be used to expand our understanding of two programs of direct capital transfers to poor households, with the broad goal of bringing insights from economic theory farther into the practice of impact evaluation./nThis dissertation has as its chapters three papers, each written so that they stand alone for those interested in a particular part of the overall project. The first chapter develops a Frischian model of household expenditures, and uses this model to derive estimates of an individual household’s marginal utility in expenditures at any given time, log λit, which serves as the central welfare metric in each chapter. The application of this model to measure the welfare effects of asset transfers is illustrated using the early results of a pilot in South Sudan of the so-called “Targeting the Ultra-Poor” (TUP) program. It concludes that the large asset transfers improved welfare in the short-run.1/nChapter 2 uses the methods in Chapter 1 to reanalyze the first large experimental evaluation of the TUP framework in Bangladesh, previously studied in Bandiera et al. (2017). It goes on to estimate a flexible direct utility function which allows one to estimate welfare in a way that accounts for the immiserating effects of uncertainty faced by poor households. It concludes that this TUP program improved household welfare years after the transfers, and that this benefit was accompanied by a lower level of risk./nFinally, Chapter 3 goes on to study the experiment in South Sudan in more detail. It compares the TUP treatment to an experimental cash transfer, and showcases the practical value of the methods in Chapter 1 by continuing to cost-effectively monitor household welfare/nafter the long-form panel survey was completed. It then briefly speaks to how participation in the TUP program may have affected households’ response to the outbreak of violent civil conflict in 2014. The results show that both cash and asset transfers improved household welfare only in the short run, but the asset transfers had a sustained positive impact on households’ total stock of assets, which may have reduced the likelihood that those households were left without recourse upon the onset of violence.

Advisor: Ligon, Ethan
Land Grabs in Urban Frontiers: Producing Inequality in Senegal's Dakar Region

This dissertation examines urban political struggles surrounding the proliferation of middle-class and elite housing estates in Senegal, where urban real estate developments have emerged as a center of political friction and commercial dynamism. Utilizing a variety of methods, including ethnographic fieldwork and textual analysis of secondary sources, this project explores two case studies of large-scale land conflicts in sites of middle-class and elite housing developments in Senegal’s Dakar Region. Through five empirical chapters, I explore how the social, political, and economic context of neoliberalism in urban Senegal has not only produced urban land grabs, but has also fundamentally reconfigured how land is governed and urban politics are practiced./nIn focusing on urban land governance, my project examines changes in the cartography of political relationships between and within central/local governments, farmer associations, housing cooperatives, traditional leaders, and international institutions. This dissertation consequently deepens spatial readings on civil society and state relations in sub-Saharan Africa, using conflicts produced through urban land grabs as a lens to examine the spatial logics of in/formal housing, territorial patronage relations, political decentralization reforms, and contentious politics in Senegal’s Dakar Region. This dissertation also throws fresh light on research documenting a recent increase in land conflicts in sub-Saharan Africa, drawing attention to how coalitions brokered by farmer associations negotiate legal settlements to land conflicts by relying on private mapping projects, Senegalese courts, formal land laws, and public protests. In studying the outcomes of these urban protests and legal settlements, this research describes how the rise of a new and powerful African middle-class is not only reshaping urban political life, but producing new landscapes of urban inequality.

Advisor: Watts, Michael