VictorJuiz/thesis huggingface dataset:
Plasma oscillations and associated electron transport within hall thrusters [electronic resource]

The Hall thruster is a type of plasma propulsion system for space vehicle applications. The thrust produced by this device is derived from the momentum of ions, which are accelerated to high exit velocities by the action of an electric field sustained within the plasma. The advantage of the Hall thruster compared to conventional chemical rocket propulsion is a significantly higher exhaust velocity, which leads to better utilization of propellant mass. Since the early days of Hall thruster research, experiments have suggested that the mobility of electrons along the axis of the thruster, perpendicular to an imposed magnetic field, is higher than can be explained by classical collision transfer processes alone. A lack of understanding regarding the mechanism for this enhanced mobility has proved a significant challenge toward the development of reliable simulations capable of predicting the performance of these devices. This thesis examines the role of high frequency plasma oscillations on the electron mobility using a combination of experimental studies on a laboratory Hall thruster, and numerical simulations capable of capturing these oscillations and quantifying their impact on the electron mobility. Two high frequency oscillations were consistently observed in the experiments: a 10MHz mode which appeared strongest in the vicinity of the anode, and a 4.5MHz mode which was strongest in the mid-channel region of the thruster. These were relatively low wave number (long wavelength) oscillations: approximately 6cm for the 4.5MHz oscillation and 3cm for the 10MHz oscillation. The angle of these waves varied considerably depending on the operating conditions of the thruster. They were found to be closely aligned to the axis of the thruster for experiments conducted with Xenon propellant, and were aligned with the circumference of the thruster (in the direction of electron drift) for experiments conducted with Krypton. A Hall thruster simulation, formulated in the axial-azimuthal coordinates of the thruster, was able to capture high frequency oscillations in reasonable agreement with experimental findings: 13MHz near the anode and 5MHz in the mid-channel region of the thruster for 160V discharge conditions. The simulation results demonstrated the crucial role of these oscillations in regulating the electron transport. In the vicinity of these oscillations the electron mobility was increased by a factor of five or more. The central finding of this thesis is that high frequency oscillations in the range 1 - 50MHz can account for the observed discrepancy between classical and experimental electron mobility in the Hall thruster.

Keywords: Mechanical Engineering
Advisor: Cappelli Mark A. (Mark Antony) primary advisor. Thesis advisor
Gascon Nicolas
Iaccarino Gianluca advisor. Thesis advisor
Plasmonic control of light emission [electronic resource] : tailoring light emission properties with metal nanostructures

Enhanced light-matter interactions in light-confining structures (such as optical cavities) have been extensively investigated for both fundamental studies and practical applications. Plasmonic nanostructures, which can confine and manipulate light down to ~1 nm scale, are becoming increasingly important. Many areas of optical physics and devices can benefit from such extreme light concentration and manipulation. For example, fluorescent molecule or quantum dot (QD) emission can be strongly modified and controlled via surface plasmon polariton (SPP) coupling. In this dissertation, we present our theoretical and experimental studies on QD emission in metal nanogap structures that can provide extreme field concentration, enhancing light-matter interactions significantly. We start with a theoretical analysis of dipole emission in metal-dielectric-metal (MDM) waveguide structures. We look at both infinite (i.e. planar) and finite thickness MDM structures. We find that both structures exhibit strong spontaneous emission enhancements due to the tight confinement of modes between two metallic plates and that light emission is dominated by gap SPP coupling. For planar structures we present analytical solutions for the enhanced dipole decay rate, while for finite thickness MDM structures (i.e. nanoslits) we present results from numerical simulations. Next, we present our experiments on the SPP coupling of CdSe/ZnS QD emission in metal nanoslits. First, we observed clear lifetime and polarization state changes of QD emission with slit width due to gap SPP excitation. Second, with optimized side grooves (i.e. combined slit-groove and hole-groove structures), we collimated QD emission vertically into a very narrow angle, achieving an unprecedented level of directionality control, and visualized it with confocal scanning microscopy. Third, by using two metal plates as electrodes, we dynamically modulated the QD emission intensity and wavelength with external voltage. Finally, we extend our dipole emission calculation to several slot waveguide structures. We consider light emission in metal slots, metal-oxide-Si slots, and Si slot waveguides. We find that large spontaneous emission enhancements can be obtained over a broad range of wavelengths and that light emission is strongly funneled into slot waveguide modes. These represent broadband waveguide QED (quantum electro-dynamics) systems, which have unique merits for on-chip light sources and quantum information processing. These theoretical and experimental studies show that the SPP coupling of light emission is a very promising way to control light emission properties and may find broad application in spectroscopy, sensing, optoelectronics, and integrated optics.

Keywords: Applied Physics
Advisor: Brongersma Mark L. primary advisor. Thesis advisor
Byer R. L. (Robert L.)
Fan Shanhui
Plasmonic metallic nanoparticles: synthesis, experiment, and theory

Metallic nanostructures have unique optical properties due to their ability to support surface plasmons--wave-like oscillations of the free electrons on the surface of a conductor surrounded by a dielectric medium. Optical radiation can be converted into a surface plasmon on a metallic nanostructure, creating intense localized fields or enabling coupling to subwavelength guided modes. A method for synthesizing metallic nanowires through a template-assisted electroplating process is presented. The wire growth has been optimized to produce wires which can act as one dimensional wave-guides for surface plasmons with a resonance in the visible-wavelength range. We explore through experimentation and simulation how light coupled to metallic nanoparticles through surface plasmon resonance produces characteristic scattering spectra.

Keywords: Physics
plasmon
surface plasmons
metallic nanowires
Thesis
Advisor: Brongersma Mark L.
Burchat Patricia
Political participation of indigenous Amazonians in Peru [electronic resource] : the case of the Shipibo-Konibos

Abstract: This study uses theories from anthropology, political science, and sociology, together with an international law framework, to understand the political participation of the Shipibo-Konibos, indigenous Amazonians of eastern Peru. It explains why Peru's native peoples do not follow the generic sequence of indigenous social movements in Latin America in their quest for rights of self-determination. Using an original case study of the Shipibo-Konibo nation, including analyses of the historical record and of data collected using anthropological field methods, I argue: (i) that the politics of equal interaction is a better analytical model than identity politics for understanding indigenous political participation in Peru; (ii) that colonization has weakened Shipibo-Konibo's cultural, social and political customs and their spirit of resistance, resulting in their systematic co-optation by the state, which hindered their autonomous organizational development; (iii) that despite several decades of political activity, the Shipibo-Konibo have not achieved a bona fide social movement (one that is continuous and systematic), but rather have engaged in repeated discrete campaigns or "waves" of social mobilization; (iv) that Shipibo-Konibo identity has been weakened by an array of forces acting over time, and this weakening partially explains the lack of advancement from mobilization to genuine movement; (v) that the new political process of the Shipibo-Konibos — namely, participation in municipal elections — is paradoxical in the sense that they have not yet implemented an indigenous agenda in municipal politics; (vi) that attaining municipal power in the majority of Shipibo-Konibo districts has had both positive and negative effects, empowering their collective identity and cultural revival on the one hand, but resulting in political schisms and disillusionment of the populace due to poor performance by most indigenous mayors, on the other. The thesis contributes to the older political, sociological and anthropological debate about Peru's exceptionalism with regard to indigenous social movements. It also offers a recommendation for indigenous organizations about ways that the long quest for rights of self-determination can be implemented in a realistic manner in Latin America.

Keywords: Anthropological Sciences
Advisor: Durham William H. primary advisor. Thesis advisor
Irvine Dominique advisor. Thesis advisor
Karl Terry Lynn
The politics of security policy [electronic resource] : evidence from language violence in India, 1950-1989

The study of why governments fail to prevent civil violence generally does not consider how domestic political actors impact internal security policy. I argue that governments may avoid measures that would prevent militancy in order to curry favor with the constituencies who have the most to lose from such policies. In this context, the aim of militancy is to convince other interests that share in the costs of violence and repression to put pressure on the government for policy concessions. Civil violence targets the interests of groups that have sufficient political importance to block accommodations during peacetime but are vulnerable to a backlash from other constituencies if the costs of violence escalate. I investigate this model of domestic politics and internal security policy by examining the incidence of language violence in India. Every territorially-concentrated language group in India, in theory, could demand its own state within the country's linguistic federation. Among the scores of Indian languages there are groups that have gained a state peacefully, languages that have achieved statehood only in the wake of violence, and languages that have never mobilized around statehood demands. As suggested above, a critical factor in these differences in militancy and accommodation is the political power of the dominant interests in the existing Indian states. This dissertation demonstrates these patterns using evidence from fieldwork in Northeast India; large-n analysis of the incidence of language violence, including separatist civil wars; and an analysis of Indian parliamentary debates.

Keywords: Political Science
Advisor: Laitin David D. primary advisor. Thesis advisor
Fearon James D. advisor. Thesis advisor
Jha Saumitra advisor. Thesis advisor
Wilkinson Steven
Weinstein Jeremy M. advisor. Thesis advisor
Polyphase deformation and metamorphism [electronic resource] : a geochronologic perspective

The use of combined geochronology, structural geology, petrology and geochemistry on exhumed deep crustal rocks can be used to unravel protracted histories of tectonic events that create and modify continental crust. The highly extended Basin and Range province of western U.S. contains countless exposures of mid-lower crustal rocks that offer an excellent opportunity to study deep crustal processes. Two examples of this approach are described here: The Albion-Raft River-Grouse Creek (ARG) metamorphic core complex of southern Idaho and northern Utah, and the Ivanpah Mountains of the Mojave crustal province of southeastern California. The lower plate of the ARG metamorphic core complex consists of deformed and metamorphosed 2.56 Ga crystalline basement and highly attenuated, Neoproterozoic supracrustal rocks that were intruded by 32-25 Ma syn-extensional plutons of the greater Cassia batholith. Crystallization temperatures of these plutons based on Ti concentrations in zircon range from 603-812 °C, and are mostly below 700 °C, suggesting hydrous melt conditions. Very low negative whole rock [epsilon]Nd values of the Oligocene granites ([epsilon]Nd = -25 to -36) and abundant, Late Archean inherited zircons contained within them indicate that the Cassia batholith formed from melting of late Archean crust that underlies the region. Deformation occurred in the country rocks to these plutons during sillimanite grade metamorphism, ductile attenuation and normal-sense shear along the Middle Mountain shear zone. Detailed study of an attenuated section of the country rocks to the Oligocene plutons revealed protracted (32-26 Ma) monazite growth and indicates an older period of metamorphism (~ 140 Ma) as preserved in monazite cores and metamorphic zircon rims on detrital grains. In the Ivanpah Mountains, exposures of Paleoproterozoic banded gneisses have been exhumed from deep crustal levels by Basin and Range extension. The granulite facies rocks preserved here contain a record of multiple tectonic events related to crustal formation of the North American continent. Orthogneisses and paragneisses are strongly deformed, partially melted and isoclinally folded with a penetrative, N-S-trending folding and migmatitic layering that dips steeply to the west. Samples of metaigneous and metasedimentary rocks were analyzed for U-Pb geochronology of zircon and monazite using the SHRIMP-RG. I use trace elements in zircon, in situ monazite dating, and thermobarometry to show that copious garnet growth and the formation of the dominant, N/S striking fabric developed under metamorphic conditions of 4-6 kb and ~750 °C during the final metamorphic event at ~1.67-1.66 Ga.

Keywords: Geological and Environmental Sciences.
Advisor: Miller Elizabeth primary advisor. Thesis advisor
Graham S. A. (Stephan Alan)
Wooden Joseph L. advisor. Thesis advisor
Post-silicon bug localization in processors [electronic resource]

For complex integrated circuits, pre-silicon verification alone is inadequate in ensuring that manufactured chips do not contain logic and electrical bugs. Post-silicon validation, which operates samples of manufactured chips in application environments to validate correct behaviors across specified operating conditions, is essential. According to industry reports, post-silicon validation is becoming very expensive. A major bottleneck in post-silicon validation is the bug localization step which involves identifying hardware bug locations and short functional stimuli that can expose detected bugs. For example, it may take several days to weeks to localize an electrical bug that may arise due to incorrect interactions between a design and the operating conditions. This dissertation presents IFRA (Instruction Footprint Recording & Analysis), a new technique for post-silicon bug localization in processors, which overcomes cost and scalability challenges of existing techniques. During normal operation of a processor in a post-silicon validation setup, special on-chip recorders collect information about flows of instructions through the processor and what the instructions did as they passed through various design blocks. Upon system failure, such as a crash, the recorded information is scanned out and analyzed offline using special self-consistency-based analysis techniques to localize hardware bugs. IFRA provides two major benefits over traditional techniques: (1) it does not require bugs to be reproduced at the system-level and (2) it does not require system-level simulation. Evaluation of IFRA on an open-source microarchitectural simulator modeling Alpha 21264 demonstrates high bug localization accuracy (96%) at low area overhead (1%). Applying IFRA to new microarchitectures can be challenging because it requires some degree of manual effort. This dissertation will also present a new BLoG (Bug Localization Graph) technique which is a step towards automated application of IFRA. Evaluation of BLoG-assisted IFRA on an industrial microarchitectural simulator modeling Intel Core i7, a state-of-the-art complex commercial processor, demonstrates its effectiveness (90% bug localization accuracy) and practicality.

Keywords: Electrical Engineering
Advisor: Mitra Subhasish primary advisor. Thesis advisor
Dill David L. advisor. Thesis advisor
Kozyrakis Christoforos
Post-social prescriptions [electronic resource] : medical welfare in Mozambique

Based on twenty-four months of fieldwork, this dissertation explores how welfare -- the provision of social goods and supports -- is being configured through transnational medical intervention and public health policy in Mozambique. My research was concerned with how a variety of techniques, diagnoses, and criteria were used to mediate families' access to care and social supports as well as with the kinds of social and material opportunities these interventions made available. In a context marked by material scarcity far beyond the well-defined clinical criteria through which medical welfare supports were channeled, I was interested in how a variety of differently situated actors -- including health planners, donors, psychologists, counselors, and nurses, members of patients associations, volunteers, family members and patients -- defined, diagnosed, and accessed welfare needs. I also aimed to trace how legal and ethical norms structured and emerged out of these new welfare assemblages, and asked why and how contested, gendered family relationships came to be a privileged locus for these medical-social interventions. I investigated how planners, workers, patients and families negotiated institutional and everyday practices of care in order to understand how new modes of diagnosis, treatment, care, and social support for children and patients are taken up across a range of institutional and non-institutional sites. Based on this research, I argue that medical welfare interventions instantiate a new mode of governance in Mozambique, one in which the state not only provides services but also (even primarily) coordinates non-governmental endeavors and constitutes individuals and communities as available for humanitarian intervention. As a result, new forms of claims-making and claims-denying, including and beyond citizenship claims, are emerging in medical welfare spaces, as diagnoses of individual and community "vulnerability" become means of mobilizing new forms of care and material resources. Crucially, I suggest, these dynamics are shaped not only by contemporary development practice but also by historical legacies of colonialism, conflict and intervention that have shaped the politics of biomedical knowledge and transnational aid in contemporary Mozambique.

Keywords: Anthropology
Advisor: Ferguson James
Malkki Liisa H. (Liisa Helena) advisor. Thesis advisor
Yanagisako Sylvia Junko
Presenting personalized recommendations [electronic resource] : how interfaces should reveal what they know about users

The present age of digital commerce affords many of the key wins of the previous two stages (local and mass) and also allows new opportunities to provide a personalized experience to consumers. Abstracting the key elements of the interaction between retailers and customers that make it feel personalized offers a guiding framework for taking digital commerce to its apex: 1) Gather user information and needs, 2) Build user model and profile, 3) Match user with appropriate available content, and 4) Present personalized content. This framework offers an approach for extracting the lessons learned from the two previous stages of media evolution as well as from social science and human-computer interaction to make digital consumer experiences feel more personal. This dissertation focuses on the last step of this personalization cycle and details empirical evidence tackling how interfaces should reveal what they know about users in the context of affective computing systems for emotion-based adaptation. The first experiment uncovered how a personalized interface should respond to users when it has detected they are feeling either happy or sad and the consequences for revealing it has made an inaccurate assessment. Experiment 1 was a 2 (Mood Induced: happy or sad) by 2 (Feedback Accuracy about Emotion Detection: accurate or inaccurate) by 2 (Recommendation Sentiment: happy or sad) between-subjects experiment on the web (N = 96). The results illuminated that feedback accuracy and the congruency of recommendation sentiment have different effects for happy and sad users. The second experiment investigated how a personalized interface should respond to frustrated users. Experiment 2 was a 2 (Source: internal or third party) by 2 (Blame Attribution: user or system) by 2 (Recommendation Difficulty: easy or hard) between-subjects experiment on the web (N = 96). The results stress that it is critical for systems to avoid patronizing users when they are frustrated. These experiments and the larger personalization framework offer design implications for the numerous cross-functional teams working in this space. They also suggest directions for future research aiming to uncover insights to advance the user experience of personalized recommendation systems.

Keywords: Communication
Advisor: Nass Clifford Ivar primary advisor. Thesis advisor
Bailenson Jeremy advisor. Thesis advisor
Fogg Brian J. advisor. Thesis advisor
Reeves Byron
Preservation of transport properties trend [electronic resource] : computational rock physics approach

Computational rock physics is a rapidly evolving field and as such requires careful quantitative analysis of the components of this technology: resolution, digital sample size, thresholding of the image, as well as the effects of the scale of the computational simulation. In this thesis we address these issues by utilizing various mathematical and statistical techniques. We use 3D CT-scan images of three different samples to determine the effect of resolution. sample size and thresholding of these images have on transport properties trend, specifically porosity-permeability and porosity-formation factor. We compare these trends with laboratory measured trends and theoretical trends. We find that although the absolute transport properties change as we change these parameters, however the trend formed by these transport properties remains unchanged. These results imply that, we can obtain physically meaningful trend from these non-optimally generated samples e.g., by using non-optimal sample size, non-optimal thresholding or non-optimal resolution. However, our analysis is not exhaustive. For example, our range of sample sizes varies only from core scale to micro-pore structure. Also, the samples used in this study are fairly homogeneous sandstones.

Keywords: Geophysics
Advisor: Mavko Gary
Mukerji Tapan
Dvorkin Jack