VictorJuiz/thesis huggingface dataset:
Pulse formation and frequency conversion in dispersion-engineered nonlinear waveguides and resonators
Keywords: Electrical Engineering.

Recent advances in nonlinear photonics have enabled a new class of broadband ultra-stable light sources known as optical frequency combs. These light sources have given rise to an array of new optical devices and systems, spanning applications such as spectroscopy, astronomy, remote sensing, frequency synthesis, attoscience, telecommunications, and optical clockwork. At this time, there are a number of unsolved problems within the field. Optical frequency combs are often constrained to wavelengths within the near-infrared (NIR) due to the limited variety of in mature laser gain media and host glasses, and many applications such as spectroscopy, sensing, and attoscience would benefit from the development of optical frequency combs at longer wavelength ranges such as the mid-infrared (MIR). Furthermore, the generation and stabilization of frequency combs often requires rather complicated nonlinear optical systems, which have prevented these light sources from being used outside of dedicated optics labs. This dissertation considers new approaches to frequency comb generation based on recently discovered nonlinear dynamical processes that occur in quasi-phasematched (QPM) devices with quadratic nonlinearities. A recurring theme is that the interplay of nonlinear optical effects, such as optical parametric amplification and self-phase modulation, with linear optical effects, such as dispersion, can produce qualitatively new dynamical regimes. In many cases, these dynamical regimes exhibit favorable features that potentially solve the problems discussed above. The first half of this thesis considers the pulse formation mechanisms present in optical parametric oscillators (OPOs), and discusses new operating regimes that enable the generation of MIR combs with substantially more bandwidth than the NIR comb used to drive the OPO. These devices can produce few-cycle pulses with conversion efficiencies exceeding 50% while also preserving the coherence of the frequency comb. The latter portion of this thesis studies the dynamics of femtosecond pulses in nanophotonic waveguides. Here, the geometric dispersion associated with sub-wavelength confinement be used to achieve long interaction lengths with femtosecond pulses. Using these effects we are able to achieve saturated SHG with femtojoules of pulse energy, where state-of-the-art devices previously used picojoules. In the limit of phase-mismatched SHG driven with picojoules of pulse energy we observe the formation of a coherent multi-octave supercontinuum comprised of multiple spectrally broadened harmonics. The mechanisms of spectral broadening in this system are shown to be completely unique to dispersion-engineered nanophotonic QPM devices and exhibit a number of desirable features including i) low power requirements, ii) fewer decoherence mechanisms than traditional approaches, and iii) the formation of carrier-envelope-offset beatnotes in the regions of spectral overlap between the harmonics
Quantifying CO2 capillary heterogeneity trapping through experiments, data analysis, and simulation
Keywords: Energy Resources Engineering.

CO2 geologic storage is an integral part of the climate change solutions in that it allows society to transition toward carbon neutral energy while still relying on fossil fuels. Both the primary and secondary trapping mechanisms immobilize the injected CO2 in the reservoir and keep it securely trapped. This work focuses on one such secondary trapping mechanism, residual trapping, which is caused by capillary forces induced by natural geological heterogeneities both at the pore scale and the mesoscale (millimeter scale). To differentiate between residual trapping at the two different scales, we call the former pore-scale residual trapping and the latter capillary heterogeneity trapping. The mechanisms and the various factors affecting pore-scale residual trapping have been extensively studied previously. However, only a handful of studies have examined the role mesoscale heterogeneity plays in capillary heterogeneity trapping. This work mainly focuses on predicting, identifying, and quantifying the CO2 capillary heterogeneity trapping potential of geological formations. We first use coreflooding experiments to investigate which parameter best represents the degree of mesoscale heterogeneity in the context of residual trapping in order to predict the amount of CO2 capillary heterogeneity trapping with an empirical relationship. Then, we use statistical analysis of the data to examine the effects of mesoscale heterogeneity on capillary dominated flow behaviors and to identify and visualize CO2 capillary heterogeneity trapping behavior in sandstone core samples. Finally, we use an improved percolation model to simulate and quantify the effects of mesoscale heterogeneity on residual trapping and the extent of such effects as compared to the pore-scale trapping mechanism. The data analysis results have confirmed that post-imbibition CO2 capillary heterogeneity trapping indeed occurs upstream of capillary barriers. Furthermore, it can also occur within the capillary barriers themselves. Both experiments and simulations have shown that CO2 capillary heterogeneity trapping increases with the degree of mesoscale heterogeneity. Macroscopic percolation simulation results have shown that the capillary heterogeneity trapping contribution can be quite large for heterogeneous rocks with good mesoscale capillary barriers. Experimental results show that the variance in the drainage CO2 saturation fields created under capillary dominated flow conditions can best capture the degree of mesoscale heterogeneity in terms of predicting CO2 capillary heterogeneity trapping
Quantifying geological uncertainty and optimizing technoeconomic decisions for geothermal reservoirs
Keywords: Energy Resources Engineering.

Globally, 25% percent of greenhouse gas emissions result from electricity generation that is powered by burning fossil fuels. To mitigate climate change due to these emissions, we must increase the electricity portion generated by low-carbon resources, such as geothermal energy. One of the major barriers for geothermal development is financial risk due to geological uncertainty. Production from a geothermal well highly depends on the unknown location of subsurface geological structures, such as faults. Faults are the most important part of geothermal systems because they host the hydrothermal fluids. In geothermal systems, cold rain-water seeps to hot areas in the subsurface and heats up. This hydrothermal fluid then upwells through subsurface faults towards the surface. Geothermal energy developers need to find these faults to: drill wells to intersect these faults, pump out the hot pressurized water and use the water to turn turbines and generate electricity. Yet, characterizing the structure of faults carrying hydrothermal fluids is extremely difficult and uncertain. Traditionally, geoscientists assess the subsurface structure by collecting many different datasets, interpreting the datasets manually, and creating a single model of fault locations. This method, however, is often inaccurate and does not provide any information about geological uncertainty and ensuing financial risk. In this work, we show that geological uncertainty has been a major challenge for developing geothermal systems, specifically enhanced geothermal systems. Using a synthetic case study, we demonstrate that information about geological uncertainty can influence the process of making decisions regarding reservoir management. we then describe a method for generating geologically realistic structural models of geothermal reservoirs that match observed data and apply this stochastic inversion method on real data from the Patua Geothermal Field in Nevada. To conclude, we provide a case study of how geological uncertainty quantified at Patua Geothermal Field can be used to inform the choice of reservoir development actions
Quantifying the Benefits of New Products: Music Streaming Platforms
Keywords: Streaming
Music Streaming
New Goods
Competition
Merger
Acquisition
Department of Economics
Thesis

The advent of digitization and the entry of music streaming platforms has changed the way music is consumed and discovered. In order to quantify the economic effects of music streaming, I build a structural demand model for music streaming platforms in the United States. To estimate the model, I construct a new market-level dataset with market shares and prices for 2016-2019 and augment this dataset with average consumer demographics to introduce heterogeneity in consumer tastes. I conduct several counterfactual simulations to measure the change in consumer welfare when a product or a set of products is removed from the consumer's choice set. The results from these simulations align with the story that younger populations benefit more from, and hence take to new technology more than the older age groups. I then estimate a multiproduct supply-side model to simulate a Bertrand (Nash) equilibrium and analyze the impact of a possible acquisition of SoundCloud by Spotify. The results support the idea that reduced competition in markets is detrimental to consumers.
Quantum Projection Filter Model for the Coherent Ising Machine
Keywords:  Department of Physics
quantum optics
Gaussian state dynaimcs
Ising model
optical parametric oscillator
quantum projection filter
coherent Ising machine
Thesis

A novel optoelectronic system, the coherent Ising machine (CIM), uses networks of optical parametric oscillators (OPOs) in conjunction with a measurement-based feedback scheme to represent and solve fully-connected Ising spin optimization problems. Solutions to these problems have wide-ranging applicability—data set analysis, circuit design, drug discovery and scheduling. Experimentally, the CIM has been demonstrated to successfully find exact or approximate solutions to a variety of hard optimization problems with up to 2,000 all-to-all connected spins. However, whether the CIM offers any computational advantage over conventional computers is an open question that requires understanding the (potentially quantum) dynamics that govern information processing in the CIM.
As a step towards characterizing CIM system dynamics and formally benchmarking any computational advantage afforded by these dynamics, we describe a model reduction approach that can facilitate scalable numerical studies of the CIM via dynamical simulation. Motivated by the low nonlinearity and high optical losses in the system, we consider the CIM dynamics to be described by a series of time evolutions of the system state on a Gaussian manifold of states, using Gaussian maps to represent the operations performed by beam splitters, measurement, and feedback injections. In particular, to ensure that the propagation of the OPO modes through the χ(2) waveguide is computationally tractable, we employ a quantum projection filter technique to differentially project the quantum dynamics induced by the optical nonlinearity onto the Gaussian manifold. In this work, we present the aforementioned model reduction and derive a set of filter-projected differential equations required for integrating the reduced model into numerical simulations of the CIM with nonlinear pump and signal dynamics. This approach may be useful for describing other photonic systems where nonlinear optical effects coexist with sufficiently strong linear losses.
We also provide a brief review of quantum optics and the Gaussian state formalism, along with a description of the measurement-based CIM and a summary of the important experimental results in the sub-field of CIM research.
Racing engines and cracking fuels : laser-based measurement techniques for challenging environments
Keywords: Mechanical Engineering.

Although combustion fuels the modern world, much remains unknown about the hydrocarbon chemistry that governs the behavior of fuels and the energy systems used to extract their energy. Many open questions in the field can be traced to the limited diagnostics available to study fuel chemistry and energy-system performance, where relevant processes often occur at millisecond timescales and within inaccessible environments. This work seeks to address the limits of diagnostics in two particularly challenging areas of fuel research and energy-system design: high-temperature fuel pyrolysis and high-performance engines. Part 1 develops new diagnostics for measuring temperature and species in pyrolytic environments, then applies a novel convex-optimization-based technique to the thermal decomposition of ethane and propane to characterize the cracking patterns of these foundational alkane fuels and reveal insights into the governing chemistry. Part 2 shifts gears to present the development of a temperature, pressure, and water-vapor sensor for high-performance-engine applications. The sensor overcomes the challenges of intense vibration, fuel-droplet attenuation, and enclosed geometries to measure intake-runner temperatures, pressures, and water mole fractions with near-crank-angle resolution. Together, these efforts expand the scope of diagnostic capabilities available to kineticists and engine developers to explore new domains, improve predictive modeling capabilities, and ultimately develop more efficient fuels and energy systems for the future
Radial estimate of isotropic pseudo-differential operators via FBI transform
Keywords: Mathematics.

This works aims to prove the propagation of singularities and the radial estimates in smooth isotropic symbol settings. The behavior of the Hamilton vector field of pseudo differential operator symbols and the wave front set of the solutions has been well studied. There are classical results in the standard smooth symbols settings, linking the flow of the Hamilton vector field of the symbol with the operator's regularity propagation by Hörmander. Melrose and Vasy then also establish the regularity behavior of solutions around radial points when it forms a sink or source for the Hamilton vector field. This paper extends such results into the setting of isotropic symbols. First setting up the connections between the isotropic and standard symbols, the paper will then utilize the FBI transform mechanisms, similar to the work of Martinez, to achieve results similar to the standard commutator method. Then we shall refine the results in the isotropic setting from Martinez's FBI estimate. Finally a standard regularization process shall be deployed to establish the more precise high regularity threshold
Rapid computational aerodynamic analysis for multi-rotor aircraft
Keywords: Aeronautics and Astronautics.

In recent years, multi-rotor aircraft have generated significant interest across the aviation industry, resulting in many new aircraft configurations. These aircraft are typically electric or hybrid-electric and leverage the general scale-invariance of distributed electric propulsion. As a result, hundreds of novel multi-rotor vehicle concepts have arisen. In this work, a medium-fidelity simulation capability is developed for multi-rotor aircraft, which solves the Euler equations on a Cartesian mesh with embedded boundaries. The approach is designed to handle arbitrarily-complex geometry and non-linear aerodynamics while retaining a computational cost that is affordable in the preliminary design process. It leverages the integral velocity sampling (IVS) method for angle of attack prediction, resulting in accurate performance estimates for both isolated rotors and full-vehicle DJI Phantom 3 simulations. In addition, this work also investigates algorithmic robustness throughout the solution process, from mesh generation to unsteady flow simulations
Rapid single-crystalline III-V optoelectronics by pulsed laser crystal splitting
Keywords: Materials Science and Engineering.

III-V semiconductors are important electronic materials. We split single-crystalline III-V thin films from their single-crystalline growth substrates using standard lattice-matched III-V epitaxy and unfocused Nd:YAG laser pulses. We collaborate with the National Renewable Energy Laboratory and produce high-efficiency III-V photovoltaics in new ways. The devices are the first of their kind and the crystal ejection process offers tremendous opportunities
Re-assembling radical indigenous autonomy in the Alta California hinterlands : survivance at Puhú
Keywords: Anthropology.

Conducted in a community-based participatory research (CBPR) framework in partnership with Tongva, Acjachemen, (Blas Adobe Aguliar Museum, Juaneño--Acjachemen Culture Center) and Payómkawichum (Pechanga Band of Luiseno Mission Indians) peoples, this dissertation is an Indigenous Archaeology study of the California Historic Landmark (CHL#217; CA-ORA-132 and CA-ORA-317) Black Star Canyon Puhú Village site in the Santa Ana Mountains of Orange County, California. The landmark memorializes the 1832 CE "Battle in Cañón de los Indios". Indigenous occupants of the Puhú village were accused of stealing horses from local colonial settlers over several months, after which, the village was razed by hired American frontiersmen. I integrate perspectives from descendant collaborators, Indigenous survivance, philosophies of historicity, guerilla resistance, Practice Theory, and Assemblage Theory in the analysis of archaeological and ethnohistorical data collected from five years of interviews, archival research, surveys, excavations, and laboratory research under the Black Star Canyon Archaeology Project (BSCAP). The result of my archaeological and ethnoarchival research reveals how the Puhú occupants exercised economic and political traditions within and beyond the village to exceed a condition of bare survival or micropolitical resistance after colonization. This study facilitates new attention to enduring communal scale Indigenous traditions associated with macropolitical forms of autonomy and prosperity in the Los Angeles Basin proximal colonial hinterlands. In doing so, the archaeological study is envisioned as facilitating a mode of Indigenous survivance-storytelling by challenging the foundations of colonial historiography associated with the landmark
Reconstructing Indian territory : federal vs. native power and the contested expansion of American sovereignty, 1861 - 1907
Keywords: History.

Reconstructing Indian Territory is a history of Indian Territory as a critical site of Reconstruction: the multifaceted federal project to rebuild a unified American nation-state committed to free labor, private property ownership, and a homogenous citizenry. Based on U.S. and Native government sources, this project explains how Reconstruction politics and priorities transformed Indian Territory as part of the growth of federal supremacy throughout the continental United States. Federal policymakers sought to reconstruct the Five Tribes of Indian Territory through a variety of legislative and legal reforms, including the Reconstruction Treaties of 1866, the expansion of federal jurisdiction, the allotment of tribal land, and the dissolution of Native governments in favor of single statehood. While piecemeal and often disjointed, this darker side of Reconstruction achieved many more of its aims than its southern sister project, securing the plenary power of the U.S. Congress over Indian affairs at the price of tribal sovereignty. Reconstruction has long been a southern narrative, but this project demonstrates that we cannot fully account for the successes and failures of the multiregional and multinational project of Reconstruction without Indian Territory
Reconstructing past events : a study of engineering failure investigations
Keywords: Philosophy.

When a major engineering product failed, a failure investigation is often conducted to prevent similar failures in the future. In this dissertation, I propose an account of the epistemology and methodology of engineering failure investigations, based on a close examination of five major plane crash investigations conducted by the National Transportation Safety Board (NTSB). The dissertation is divided into three parts. The first part consists of the five case studies. In each case study, I summarize the entire investigation process, focusing on articulating the questions that arise and the evidential reasoning that helped resolve each question. The second part examines how the investigators infer causes of failure events. The type of causal inference used in failure investigations typically proceeds from effects to causes, hence it is called reverse causal inference. I identify three types of reverse causal inference in engineering failure investigations: feature dependence, additional outcomes, and process tracing. The third part examines how the investigators construct narratives of failure events and support them with evidence. I argue that both the construction and the justification of a narrative of a failure event depend on the question-and-answer process in the investigation, which I call the question dynamics of the investigation. I examine three main components of the question dynamics: the resolution of questions, the significance of questions, and the arising of questions. I conclude the dissertation with an account of the coherence of narratives, which captures the intuitive idea that the pieces of a coherent narrative "fit together" very well
Regulating the Regulators: Whether User Fees for Prescription Drug Reviews within the FDA Approval Process are a Cause for Concern
Keywords: drug reviews
new drug applications
user fees
PDUFA
FDA
agency capture
Thesis

This paper studied the potential adverse impact of the Prescription Drug User Fee Act (PDUFA) on the integrity of the U.S. Food and Drug Administration (FDA) drug application review process. The concern was that PDUFA-established user fees could result in agency capture by the pharmaceutical drug industry. To determine the validity of this concern, the paper analyzed public data detailing the submission date of a new drug application and the subsequent date of approval. The data was then used to calculate the average drug review time for each manufacturer and establish whether those with more total user fee contributions experienced quicker review times. External factors were controlled for given a variety of confounding variables. If the firms were found to receive preferential treatment for greater user fee contributions to the FDA, it would be a sign of potential agency capture. Although a great deal more research is needed to verify the results, the analysis suggested that there is little, if any, association between the cumulative fees paid by a sponsor and the review times of its new drug applications. These findings may be good news for the FDA and other agencies who charge, or may want to charge, user fees to supplement their funding.