VictorJuiz/thesis huggingface dataset:
The investigation of online consumer reviews as intentional social actions [electronic resource]

Online reviews play an increasingly important role in consumers' purchase decisions. Such internet-enabled Word-of-Mouth communication offers society a tremendous potential to reduce information asymmetries and in this way, increase the efficiency of electronic and traditional markets (Dellarocas, 2005). Voluntary reporting, however, introduces the potential for reporting biases. In this dissertation, I argue that consumers' willingness to post a review on an online forum is conditioned on the social normative landscape of this public space. I conducted four exploratory investigations of the social dynamics involved in review posting behavior. Given the broadness of the research agenda, these studies focus on different aspects of the research question and, as a result, vary in their levels of analysis and methods. As evidence, I found that review posting behavior was motivated by social obligations and regulated by social norms. Furthermore, these social motives produced systematic biases in review valence distributions. The implications of these findings are clear: Biased distribution of online product reviews can lead to inefficiencies in consumer choice and erroneous conclusions about consumer product preferences.

Advisor: Miller Dale T. primary advisor. Thesis advisor
Flynn Francis J. advisor. Thesis advisor
Mullen Elizabeth advisor. Thesis advisor
Investigations of magmatic end-members [electronic resource] : silicic magma chambers and mafic dikes

Approximately 10% of the global population, some 550 million people, live within 100 km of an active volcano, making it imperative that the causes of magma accumulation in the crust and the factors affecting the scale of subsequent volcanic eruptions are investigated and modeled. This PhD dissertation examines magmatic processes at two scales: silicic calderas represent the large but infrequent end of the continuum, whereas mafic dikes are small in scale but common. Many previous authors have presented hypotheses for how large silicic systems develop. In order to test and refine these hypotheses, I undertook a global compilation that empirically examines how the characteristics of 140 young silicic calderas reflect their crustal-tectonic setting. Results indicate that the size and geochemistry of silicic calderas are affected by the nature of the underlying crust, the tectonic setting, and the local stress regime. For example, large, rhyolitic calderas tend to occur in continental settings under extension. There are, however, few true "rules, " and exceptions may prove useful in analyzing how silicic magma chambers form. Based on this compilation, I present a probabilistic method for determining the tectonic-crustal setting of a given caldera from its diameter, and eruption geochemistry. Focusing specifically on arc settings, this study demonstrates that (1) the abundance of silicic calderas in a given arc is proportional to the trench-normal convergence rate, except in arcs with back-arc spreading; and (2) silicic calderas in continental arcs tend to occur farther behind the volcanic front than do more typical arc volcanoes, possibly because of the abundance of pre-existing structures in continental margins. At the opposite end of the volcanic spectrum, this dissertation examines the intrusion of two mafic dikes. The first lies beneath Mammoth Mountain, California, and was associated with a 1989 seismic swarm. Based on an inversion of leveling data constrained by relocated earthquakes, I propose that a dike 2 km long, 8 km high, with 1 m of opening was intruded at 9 km depth beneath the south side of Mammoth Mountain. The second dike investigation focused on the eruption of Miyakejima, Japan, in 2000, associated with more than 10,000 earthquakes, several small eruptions and progressive caldera collapse. Displacements recorded by GPS stations and pre- and syn- event seismicity were used to determine a geological explanation of the event. In the proposed model, a shallow dike propagated ~30 km away from Miyakejima for one week, stopped propagating laterally after intersecting a pre-existing fault zone, and then continued to open and grow vertically for nearly two months.

Keywords: Geological and Environmental Sciences.
Advisor: Mahood Gail A.
Pollard David D. advisor. Thesis advisor
Segall Paul
In-vitro experimental validation of finite element analysis of blood flow and vessel wall dynamics [electronic resource]

Biomechanical forces such as hemodynamic parameters and stress and strain in blood vessel walls have significant effects on the initiation and development of cardiovascular diseases, as well as on the operations of implantable medical devices. Computational fluid dynamics is an emerging powerful numerical tool capable of providing fine temporal and spatial resolutions in the quantifications of these cardiovascular biomechanical forces. The overall goal of this research is to develop tools and methods for conducting in-vitro experiments, and to acquire experimental data for the validation of the computational methods. We first developed a physical Windkessel module which can provide realistic vascular impedances at the outlets of flow phantoms in order to enable in-vitro experiments that mimic in-vivo conditions. We also defined a corresponding analytical model of the Windkessel module, and showed that upon proper characterization, the analytical model can accurately predict the pressure and flow relationships produced by the physical Windkessel module. The precise analytical model can then be prescribed as a boundary condition for the finite element domain, resulting in a direct parallel between the computational description of the physical model and the physical reality. We then performed validation of the numerical method using the Windkessel module, and a rigid, two outlet, patient-derived abdominal aortic aneurysm phantom under resting and light exercise flow and pressure conditions. Physiological pressures within the phantom, and flow waveforms through the two phantom outlets were achieved. Finally, we performed validation of the numerical method incorporating deformable vessel walls, using two compliant flow phantoms under physiological flow, pressure, and deformation conditions. The compliant phantoms mimicked a patent thoracic aorta, and one with an 84% coarctation (by area). The computational predictions of pressure, flow, and velocity patterns compared favorably with experimental measurements in both of the validation studies. The accurate prediction of wave propagation behaviors in the deformable phantom study indicated a faithful prediction of the vessel wall motion. In addition to numerical methods validation, the experimental techniques we have developed can also be used in direct in-vitro evaluations of medical devices.

Keywords: Bioengineering.
Advisor: Taylor Charles A. (Charles Anthony) primary advisor. Thesis advisor
McConnell Michael
Zarins Christopher K. advisor. Thesis advisor
Ion-beam texturing at nucleation [electronic resource] : investigation of the fundamental mechanism of biaxial texture development in ion beam assisted deposition and applications

Low-energy ion-beam irradiation (< 1 keV) during the concurrent deposition of cubic oxide materials results in the growth of crystallographically textured thin films. A model system, magnesium oxide (MgO), has been successfully used as a biaxially textured template fillm for the heteroepitaxial deposition of many materials with texture dependent properties like high temperature superconductors, tunable microwave materials, and ferroelectrics. The ion beam assisted deposition of MgO is unique in that it requires only a few nanometers (< 10nm) at room temperature to develop texture very near that of a single crystal substrate and is substrate independent (glass, metal, etc.). Here, I present data on the nucleation of biaxial crystallographic texture in this model system using a novel in situ quartz crystal microbalance (QCM) substrate combined with in situ reflected high-energy electron diffraction (RHEED). Correlation of mass uptake with the RHEED images of the growing surface shows that the development of crystallographic biaxial texture in this material system occurs suddenly as the initially polycrystalline MgO films reaches a critical film thickness of 2 nm. This texture continues to improve during subsequent growth. I use a combination of in-situ RHEED and ex situ transmission electron microscopy to elucidate the mechanism of this sudden texture formation. I have also investigated these ultra-thin films using synchrotron radiation and report some of the most complete analysis of their in-plane orientation. I present a model to describe this behavior and further explain the role of ion-to-molecule arrival ratio and underlying nucleation surface on texture development. In addition, I will present some empirical rules for selecting new materials for IBAD processing. I will discuss the use of IBAD materials as template layers for several applications. Among these, I have recently developed a new template layer, CaF2, for use in photovoltaic applications. I present my recent effort to develop this system for the deposition of biaxially textured polycrystalline Si and Ge thin films.

Keywords: Materials Science and Engineering
Advisor: Clemens B. M. (Bruce M.) primary advisor. Thesis advisor
Nix William D. advisor. Thesis advisor
Salleo Alberto
It goes without saying [electronic resource] : the importance of creating space for writing talk with African American students

Writing research, primarily done in the 1980s, led to better understanding of writing as a recursive social process and affected change in many language arts classrooms. However, more research is needed to determine what instructional practices around writing are effective in supporting students who struggle with writing, particularly African American students. The achievement gap in American schools is widely documented; this gap is especially wide with regard the writing achievement of African American students. As a group, African Americans scored in the lowest percentile across all grades tested on the 2002 National Assessment of Educational Progress (NAEP) writing exam and the 2007 NAEP writing exam scores continue to show a drop in the percentage of African American students at proficient between eighth and twelfth grade. This is a case study of two middle school English/Language Arts teachers chosen from a larger pool of effective teachers based on value-added measures, and observational data from a prior study. The author investigated the instructional practices of these teachers in one predominantly African American middle school and their impact on the development of students' writing skills and identities as writers. Data included classroom observations, student and teacher interviews, class sets of student writing from the beginning and end of the academic year, and artifacts such as graphic organizers and rubrics. The aim of this study was not to pinpoint one best way of teaching writing, but to develop a better understanding of the ways we can support struggling writers, particularly African American students, to develop their writing skills and a writer's identity. From this work, certain facets of teaching seem particularly supportive during the teaching of writing with African American students: namely, the use of writing talk as a mechanism to bridge between students' and the academic writing required in schools today. This talk creates opportunities for students to engage with models and their peers in ways that support engagement and persistence, and approximate the practice of experienced writers.

Keywords: Education.
Advisor: Grossman Pamela L. (Pamela Lynn)
Darling-Hammond Linda
Lotan Rachel A. advisor. Thesis advisor
Lunsford Andrea A.
Key uncertainties in the risks of future climate change [electronic resource] : insights from a probabilistic analysis of climate change over the past million years

What can we learn from the last million years of Earth history to better characterize important uncertainties in our understanding and predictions of anthropogenic climate change? To investigate this question, I compile a database of over 12,000 reconstructions of sea surface temperature, as well as reconstructions of polar temperatures, deep-sea temperatures, sea level, atmospheric greenhouse gases, and atmospheric dust. I create a probabilistic analysis framework to compare the reconstructions and to quantify numerous sources of uncertainty. Next, I use a Bayesian hierarchical model to assess patterns of sea surface temperature simultaneously over time and space, finding support for a "universal" curve of temperature response with latitude over the past million years. Third, I use the new database to create the first reconstruction of global average surface temperature over the past 800kyr. Previous reconstructions were limited to only a few isolated windows of time or specific locations. I find that climate models very likely (> 90% probability) underpredict global average cooling at the last glacial maximum (19-23kyr ago). I also find a remarkably stable relationship between global temperature and atmospheric carbon dioxide over the past 800kyr. Lastly, I estimate that the Earth's climate sensitivity (change in global temperature in response to a doubling of carbon dioxide concentrations) is 4.1K (2.1K-6.6K, 95% interval) and does not vary with time over the past 450kyr. These results significantly constrain the upper tail of climate sensitivity purely from the paleoclimate record and suggest that climate sensitivity values higher than 7K or less than 2K are not consistent with our current understanding of the Earth's past. Moreover, the median estimate of 4.1K is higher than 16 of the 19 IPCC global climate models. These results have important implications for assessing the risks of future climate change.

Advisor: Field Christopher B.
Schneider Stephen Henry primary advisor. Thesis advisor
Tebaldi Claudia
Dunbar Robert B.
Keyhole diffraction microscopy for semiconductor circuit inspection [electronic resource]

Non-destructive inspection of integrated circuits requires a microscope that features high resolution (< 20 nm) and high penetration (> 0.07mm of silicon substrate), thus suggesting the use of x-ray microscopy. The advent of intense coherent sources of hard (< 1nm wavelength) x-rays has led to the study of x-ray diffraction microscopy in which the image is reconstructed from the far-field diffraction pattern. Atomic resolution is possible with this lensless approach. Because this pattern records only intensity information, additional information, e.g. the phase distribution, is needed for image reconstruction. Here this information is provided by illuminating the sample with a collimated beam of well-defined shape and thus is a form of "keyhole diffraction microscopy". The research featured computer simulations, scaled optical experiments, soft (1.4 nm) x-ray experiments and one hard x-ray experiment. Different reconstruction algorithms were compared. The hybrid input-out (HIO) algorithm followed by a few iterations using the error reduction (ER) algorithm proved to be e±cient. Dynamic support was used to improve the convergence of computation. Samples with complex-valued transmission functions were more difficult to reconstruct. The geometry and periodicity of the sample itself were found to affect the reconstruction. Illumination with asymmetric shapes (such as a triangle) sharply bounded gave the best reconstruction. The results of scaled optical experiment conducted under blind conditions (no a priori knowledge of the sample) suggest that a resolution of 10 nm should be readily achievable at an x-ray wavelength of 0.18 nm.

Keywords: Applied Physics
Advisor: Kasevich Mark A. primary advisor. Thesis advisor
Pease R. (R. Fabian W.) primary advisor. Thesis advisor
Pianetta Piero advisor. Thesis advisor
Kinetic Monte Carlo model of the ionic conduction in bulk yttria-stabilized zirconia [electronic resource]

In this thesis, I develop an ab-initio based kinetic Monte Carlo (kMC) model to simulate the vacancy diffusion in Yttria-stabilized Zirconia (YSZ), a popular solid electrolyte. As a fundamental input to kMC simulation, the energy barrier model is constructed. Density Functional Theory (DFT) calculations in large supercells are combined with the cluster expansion method to account for the interactions between ions in energy barrier model, which has not been fully covered by previous works. Developed energy barrier model is implemented into the kMC model. I perform kinetic Monte Carlo simulations to predict the electrical impedance to study the effect of yttria doping concentration to the ionic conductivity of bulk YSZ when yttrium ions are randomly distributed. These kMC simulations validate the developed model and quantify two competing mechanisms of ionic conduction in YSZ. I also perform kinetic Monte Carlo simulations to predict the impedance when the distribution of yttrium ions is not random and formulate two design principles to rearrange yttrium ions to enhance the ionic conductivity. It is predicted that the conductivity is maximized when yttrium ions are distributed in < 100> lines forming a 2D superlattice.

Keywords: Mechanical Engineering
Advisor: Cai Wei
Cui Yi
Prinz F. B. advisor. Thesis advisor
Knockout tournament design [electronic resource] : a computational approach

Knockout tournaments constitute a very common and important form of social institution. They are perhaps best known in sporting competitions, but also play a key role in other social and commercial settings as they model a specific type of election scheme (namely, sequential pairwise elimination election). In such tournaments the organizer controls the shape of the tournament (a binary tree) and the seeding of the players (their assignment to the tree leaves). A tournament can involve millions of people and billions of dollars, and yet there is no consensus on how it should be organized. It is usually dependent on arbitrary decisions of the organizers, and it remains unclear why one design receives precedence over another. The question turns out to be surprisingly subtle. It depends among other things on (a) the objective, (b) the model of the players, (c) the constraints on the structure of the tournament, and (d) whether one considers only ordinal solutions or also cardinal ones. We investigate the problem of finding a good or optimal tournament design across various settings. We first focus on the problem of tournament schedule control, i.e., designing a tournament that maximizes the winning probability of a target player. While the complexity of the general problem is still unknown, various constraints -- all naturally occurring in practice -- serve to push the problem to one side or the other: easy (polynomial) or hard (NP-complete). We then address the question of how to find a fair tournament. We consider two alternative fairness criteria, adapted from the literature: envy-freeness and order preservation. For each setting, we provide either impossibility results or algorithms (either exact or heuristic) to find such a fair tournament. We show through experiments that our heuristics are both efficient and effective. Finally, using a combination of analytic and experimental tools we investigate the optimality of ordinal solutions for three objective functions: maximizing the predictive power, maximizing the expected value of the winner, and maximizing the revenue of the tournament. The analysis relies on innovative upper bounds that allow us to evaluate the optimality of any seeding, even when the number of possible seedings is extremely large.

Advisor: Shoham Yoav primary advisor. Thesis advisor
Jackson Matthew O. advisor. Thesis advisor
Roughgarden Tim advisor. Thesis advisor
Laboring in Los Angeles [electronic resource] : Chicano autoworkers, community activism, and union leadership, 1965-1988

This dissertation chronicles the rise to leadership of Chicano labor activists within the United Auto Workers union who led the fight to keep Los Angeles-area auto plants open during the economic contraction of the 1970s. They joined the union in increasing numbers in the 1950s after the "second shifts" were added to the General Motors plants in South Gate and Van Nuys. By the early 1960s, they were transformed into "union men" with bedrock socialization into labor politics that enhanced their sense of masculine pride in their working abilities, which in turn emboldened them in their exchanges with GM managers and corporate officers as they executed union business. As the Chicano Movement took hold in Los Angeles, Chicano UAW leaders were engulfed into its politics as well as into the larger civil rights discourse around economic liberation, especially as it came to be symbolized for Chicanos by the farmworker movement of the United Farm Workers (UFW) union. This study analyzes the process by which Chicano unionists used their political training and leadership experience from the civil rights era, particularly their experience with direct-action resistance from the UFW's grape strike and boycott, to challenge declining union provisions within the UAW and what they believed to be corporate encroachment on workers' rights during the economic contractions of the 1970s and 1980s. Chicano autoworkers brought their steadfast, community-centered, class-conscious politics to bear on Los Angeles locals of the UAW during the 1970s, rising to elected positions in their own union due to their political experience and the appeal of their anti-corporate platforms as the domestic automobile industry was de-industrialized in the 1970s and 1980s. Following the closure of their plants, an important set of former UAW leaders carried this work into the 1990s and beyond, remaining active in Los Angeles politics.

Keywords: History.
Advisor: Camarillo Albert primary advisor. Thesis advisor
Freedman Estelle B.
Ruíz Vicki advisor. Thesis advisor