VictorJuiz/thesis huggingface dataset:
Parallel stochastic particle methods using Markov Chain random walks [electronic resource]

Particle methods, also known as Monte Carlo methods in the statistical community, have become a powerful tool for a variety of research areas such as chemistry, astronomy, and finance, to list a few. This is mainly due to the enormous advances in computational resources in recent years. In this work, we consider an efficient and robust parallel methodology that can be applied to particle methods in a general setting. The parallel methodology proposed in this thesis takes advantage of Markov Chain random walks and corresponding Markov chain theory. We develop parallel stochastic particle methods in two different areas: (1) the optimal filtering problem, and (2) simulation of particle coagulation. In each application, a mathematical proof of convergence as well as a numerical example are provided. After a brief review of Markov Chain random walks and an explanation of the two application areas, the Markov Chain Distributed Particle Filter (MCDPF) algorithm is introduced. The performance of this method is demonstrated with a bearing-only-measurement target-tracking numerical example and is further compared with an existing method, the Distributed Extended Kalman Filter (DEKF), using a flocking model for the target vehicles. We study the convergence of MCDPF to the Centralized Particle Filter (CPF) and the optimal filtering solution by using results from Markov chain theory. In addition, the robustness of the MCDPF method is highlighted for practical problems. As the second application area, we developed a parallel stochastic particle method for the stochastic simulation of Smoluchowski's coagulation equation. This equation is used in many broad areas and for high-dimensional problems the stochastic particle solution is more accurate, stable and computationally cheaper than classical numerical integration schemes. In this application, simulated particles can be considered as representing physical particles. Since more particles result in more accurate and useful solutions, it is desirable to simulate this equation with a greater number of particles. By applying the parallel stochastic particle method, a comparable solution is obtained more efficiently using multiple processors, where one processor maintains many fewer particles by communicating with neighboring processors. A numerical study as well as a theoretical analysis are provided to demonstrate the convergence of the parallel stochastic particle algorithm.

Keywords: Aeronautics and Astronautics
Advisor: Glynn Peter W. primary advisor. Thesis advisor
West Matthew
Alonso Juan José
Lall Sanjay advisor. Thesis advisor
Part I, Symplectic ice, Part II, Global and local Kubota symbols [electronic resource]

My Ph.D. thesis consists of two parts. In the first part I construct an ice-model (a six-vertex model). I show the partition function of this ice model is equal to the product of an irreducible character of the symplectic group and a deformation of the Weyl denominator. A similar result was originally proved by Hamel and King, but the Boltzmann weights (for the vertices at the caps) that I use are different then the ones that are used by Hamel and King. Also, my proof of this result uses Yang-Baxter equation (while the proof of Hamel and King does not). This gives us a 6-vertex models for characters of the symplectic group , but this result can also be interpreted as an example of an exactly solved model, that is, an ice model whose partition function can be computed explicitly (this is of interest to people who work in statistical mechanics). In the second part of my thesis I work with the global and local Kubota symbols. I introduce a local Kubota symbol, and show that it satisfies some properties that are satisfies by the global Kubota symbol; in particular, it satisfies the reciprocity law. Using the parallel between the properties of the global and local Kubota symbols, I give a new proof of Kubota's theorem (for the case when p does not divide n), and then generalize this theorem to the case when p divides n. In the last chapter of my thesis I work with the global Kubota symbol. I investigate the levels for the global Kubota symbols for particular fields, and I obtain new levels for these fields which improve the results of Kubota, and of Bass, Milnor and Serre.

Keywords: Mathematics
Advisor: Bump Daniel
Licata Anthony M. advisor. Thesis advisor
Venkatesh Akshay
Peer-to-peer video streaming with interactive region-of-interest [electronic resource]

Increasing spatial resolution offered by digital imaging sensors and growing capacities of storage devices are helping the rise of high-spatial-resolution digital video. Such videos offer the possibility of viewing an arbitrary region-of-interest (RoI) interactively. The user can pan/tilt/zoom while watching the video. This allows watching user-selected portions of high-resolution video even on displays of lower spatial resolution. In the case of remote streaming, it avoids transmitting the entire field-of-view in high resolution, thus reducing required data rate. The first main contribution of this thesis is spatial-random-access-enabled video compression. The goal is to encode the video content once such that arbitrary RoIs corresponding to different zoom factors can be extracted from the compressed bit-stream, thus avoiding a dedicated encoder for each user. We explore the trade-off between storage space and mean transmission bit-rate. We show how to choose the slice size for video coding for minimizing the mean transmission bit-rate. Recently, peer-to-peer (P2P) video streaming has shown good potential for enabling large-scale video multicast at much lower cost than currently applied techniques. The second main contribution of this thesis is the design of a P2P live multicast streaming system that allows each user to independently control pan/tilt/zoom while still exploiting the commonalities in their RoIs for delivering content in a P2P manner. We present a distributed P2P protocol, which is run at each client and allows each client to receive and relay relevant data in real time. The protocol is designed by keeping in mind that the overlaps among users' RoIs are highly transient. Our findings indicate that to support the same number of clients as traditional client-server unicast, our P2P approach requires much less server uplink bandwidth. We show how to allocate the server bandwidth for streaming regions that vary in popularity and rate-distortion operating points.

Keywords: Electrical Engineering
Advisor: Girod Bernd primary advisor. Thesis advisor
Gray Robert M.
Singh Jatinder
A penalized matrix decomposition, and its applications [electronic resource]

We present a penalized matrix decomposition, a new framework for computing a low-rank approximation for a matrix. This low-rank approximation is a generalization of the singular value decomposition. While the singular value decomposition usually yields singular vectors that have no elements that are exactly equal to zero, our new decomposition results in sparse singular vectors. This decomposition has a number of applications. When it is applied to a data matrix, it can yield interpretable results. One can apply it to a covariance matrix in order to obtain a new method for sparse principal components, and one can apply it to a crossproducts matrix in order to obtain a new method for sparse canonical correlation analysis. Moreover, when applied to a dissimilarity matrix, this leads to a method for sparse hierarchical clustering, which allows for the clustering of a set of observations using an adaptively chosen subset of the features. Finally, if this decomposition is applied to a between-class covariance matrix then it yields penalized linear discriminant analysis, an extension of Fisher's linear discriminant analysis to the high-dimensional setting.

Keywords: Statistics
Advisor: Tibshirani Robert primary advisor. Thesis advisor
Rajaratnam Balakanapathy advisor. Thesis advisor
Taylor Jonathan E. advisor. Thesis advisor
The performance of justice in imperial Latin literature [electronic resource]

This dissertation investigates the trial scene as a literary topos in early Imperial Latin Literature and how this topos reflects significant changes to the Roman legal system under the emperors. While past scholars have used historical and juristic sources to document what these changes to Roman law were, my dissertation analyzes literary evidence to understand how these changes were viewed by imperial authors. I argue that changes to the legal system are not only manifested in Latin literature but also that a study of the literature can help us better understand the cultural and societal impacts of changes to judicial procedure. Through the analysis and historical contextualization of trial scenes depicted in literature, I assert that imperial authors overwhelmingly represent the emperor in his role as judge (princeps iudex), and I assess accordingly the implications that this new source of legal authority has for a Roman understanding of truth and justice. More broadly, my research aims to bridge the gap between the study of Roman law and Latin literature by revealing that both disciplines evaluate how the Romans engaged in acts of truthseeking and of truthmaking.

Keywords: Classics
Advisor: Barchiesi Alessandro primary advisor. Thesis advisor
Braund Susanna Morton primary advisor. Thesis advisor
Kaesser Christian
Persistence and Recurrence of Internal Armed Conflict

This thesis analyzes factors that affect the duration and relapse of internal armed conflicts. I use a data set containing 173 conflicts that occurred worldwide between 1946 and 2008. I find that ethnically diverse, poor, and populous countries are prone to persistent and recurrent internal conflict. I find that decisive victories tend to be more stable than agreements, which in turn are more stable than conflicts that end due to low activity. My research indicates that peacekeepers are highly effective in reducing the chances that a conflict will relapse. Through a set of case studies focused on recurrence, I determine that countries with a large plurality ethnic group and several smaller groups are prone to recurrent conflict. In a second set of case studies, I argue that exogenous support for rebel organizations is crucial to sustaining many persistent conflicts. I stress that negotiators and policymakers must be acutely aware of the risks of recurrence when mediating internal conflicts. I recommend the deployment of peacekeepers to enforce agreements and the inclusion of ethnic minorities in government, especially in situations at high risk of relapse. Finally, I argue that isolating and neutralizing exogenous support for rebels is critical to ending persistent conflicts.

Keywords: CISAC
Center for International Security and Cooperation
Stanford University
internal conflict
security
Thesis
Advisor: Fearon James
Persistent scatterer interferometry in natural terrain [electronic resource]

Time-series InSAR techniques are designed to estimate the temporal characteristics of surface deformation by combining information from multiple SAR images acquired over time. In many cases, these techniques also enable us to measure deformation signals in locations where conventional InSAR fails and also to reduce the error associated with deformation measurements. Among these techniques, Persistent Scatterer (PS) methods work by identifying the ground resolution elements that are dominated by a single scatterer. A persistent scatterer exhibits reduced baseline and temporal decorrelation due to its stable, point-like scattering mechanism. In PS analysis, a set of interferograms formed with a single master scene are processed at single look resolution in order to maximize the signal-to-clutter ratio (SCR) of the resolution elements containing a single dominant scatterer. In urban terrain, buildings and other man-made structures often act as PS due to their corner reflector-like scattering behavior and high radar reflectivity. Hence, traditional SAR amplitude-based PS-InSAR techniques have proved to be very e ffective in urban terrain. In natural terrain, the absence of bright manmade structures makes reliable estimation of deformation using PS-InSAR techniques a challenging task. The main obstacle is in the phase unwrapping stage, where the solutions are directly dependent on the PS network density. We have developed a two pronged approach to improve the applicability of PS-InSAR techniques to natural terrain - increasing PS network density and improving the reliability of phase unwrapping algorithms. We first present an information theoretic approach to PS pixel selection and demonstrate the ability of these new algorithms in identifying a denser network of PS in natural terrain. We then address the spatio-temporal (three dimensional) phase unwrapping problem applicable to sparse and non-uniformly sampled time-series InSAR data sets, and present two novel phase unwrapping algorithms. We demonstrate the efficacy of our new PS selection technique with experimental results from the San Francisco Bay Area, Lyngen region of Norway and the creeping section of the Central San Andreas Fault. We explain the salient features of our new "edgelist" phase unwrapping algorithm with results from the Central San Andreas Fault region north of Park field, CA. We provide detailed comparisons of the estimated line of sight velocity and deformation time-series with results from other time-series InSAR algorithms developed by research groups based in NORUT, Norway and IREA-CNR, Italy.

Keywords: Electrical Engineering
Advisor: Zebker Howard A. primary advisor. Thesis advisor
Hilley George E. advisor. Thesis advisor
Segall Paul
PET-CT small lesion quantitation and three-dimensional visualization [electronic resource]

Positron Emission Tomography-Computerized Tomography (PET-CT) is a non-invasive molecular imaging technology that plays an important role in thoracic oncology. Currently, PET-CT images are used primarily for cancer staging by assessing the likelihood of malignancy and the likelihood for disease metastasis. More widespread adoption of this modality has been limited by its unreliability for characterizing small lesions affected by the partial volume effect. This dissertation focuses on several novel approaches for combined PET-CT image quantitation in the presence of partial volume effects and three-dimensional visualization to facilitate more accurate characterization of suspicious lung lesions.

Keywords: Bioengineering.
Advisor: Gambhir Sanjiv Sam primary advisor. Thesis advisor
Paik David advisor. Thesis advisor
Pelc Norbert J. advisor. Thesis advisor
Phase-space and related methods in sensor imaging [electronic resource]

This thesis focuses on computations, algorithm development and the analysis of sensor imaging. The work consists of three projects, each of which are inverse problems for the wave equation. In the first project, I introduced and analyzed an inverse filter for improved imaging by small arrays in both homogeneous and random media. In the second project, I introduced and implemented with real data statistical methods for passive sensor localization in a complex scattering medium. In the third project, I developed and analyzed a framework for motion estimation and autofocus within synthetic aperture radar (SAR) imaging. In a broad sense, these three projects address three important issues that could arise in a coherent sensor imaging application. The radio localization problem addresses sensor network awareness that would be a necessary first step in a larger effort to image moving targets within the network. The inverse filter work addresses the fundamental problem of understanding how to maximize the image resolution (or spatial focusing in a time-reversal context) that can be achieved given an array configuration in a homogeneous medium. The SAR project involves both compensating for error in knowledge of the position of the array used for imaging and also tracking of an target when the array is synthetic. While each of these problems is distinct, they all require dealing with noise in a careful and systematic way. In the inverse filter problem, we explicitly quantify the trade-off between the resolution enhancement and the noise amplification when using the inverse filter. For the radio localization problem, standard theory and methods using correlations are not sufficient in a medium that has very strong scattering that results in multiple peaks in the correlation functions. Statistical methods were developed to try to deal with this noisy correlation information. Finally, noise enters the SAR problem through measurement error of the flight platform that must be corrected to reach the image's resolution potential. Phase-space methods are important to the approaches taken to solve each of these problems.

Advisor: Papanicolaou George primary advisor. Thesis advisor
Garapon Pierre advisor. Thesis advisor
Ryzhik Leonid advisor. Thesis advisor
Photo and dark current mechanisms in organic heterojunction solar cells [electronic resource]

Organic photovoltaic (OPV) cells can potentially become the renewable energy source of choice because of their advantages such as flexibility and low-cost. Over the past decade, extensive research attention has focused on increasing the power conversion efficiency of OPV cells with record efficiencies near 6%, still falling far short of the efficiency achieved in traditional inorganic solar cells. Further improvements in OPV cell performance will require a thorough understanding of the physical processes that govern photocurrent generation. It is usually assumed that non-geminate recombination is the most important loss mechanism that can be minimized by increasing the carrier mobilities. We have modeled the separation of the geminate charge-pair at a donor-acceptor interface of arbitrary geometry using kinetic Monte Carlo simulations. We find that the geminate carrier recombination process that takes place at the donor-acceptor immediately following exciton dissociation determines the shape of the photocurrent-voltage characteristics and contributes significantly to losses in organic donor-acceptor solar cells. The ratio of the electron mobility in the acceptor material over the hole mobility of the donor material (or vice versa), and not the absolute carrier mobility, determines the geminate separation probability and fill factor. These results are confirmed by intensity, voltage, intentional doping, and temperature dependent photocurrent measurements on planar and bulk heterojunctions. We performed capacitance-voltage measurements on simple bilayer organic solar cells as a function of temperature. These measurements provide information about the electrically active doping concentration and the ionization energy of these dopants. Band structures were calculated for the doping density and ionization energy typically found for various temperatures, and Monte Carlo simulations of the geminate pair separation process were performed, providing a complete model for photocurrent generation that matches experimental observations closely. The Shockley diode equation has been used extensively to explain the dark current in donor-acceptor organic heterojunctions, but without thorough justification. We show experimentally that these devices cannot be modeled accurately using Shockley's model. The fit to Shockley's diode equation is coincidental and holds for a single temperature only. A new model was proposed and shown to fit experimental data. The work provides precise guidelines for increasing the efficiency of organic heterojunction photovoltaic cells.

Keywords: Materials Science and Engineering
Advisor: Peumans Peter
Brongersma Mark L. advisor. Thesis advisor
McGehee Michael
Pipelined analog-to-digital conversion using class-AB amplifiers [electronic resource]

In high-performance pipelined analog-to-digital converters (ADCs), the residue amplifiers dissipate the majority of the overall converter power. Therefore, finding alternatives to the relatively inefficient, conventional class-A circuit realization is an active area of research. One option for improvement is to employ class-AB amplifiers, which can, in principle, provide large drive currents on demand and improve the efficiency of residue amplification. Unfortunately, due to the simultaneous demand for high speed and high gain in pipelined ADCs, the improvements seen in class-AB designs have so far been limited. This dissertation presents the design of an efficient class-AB amplification scheme based on a pseudo-differential, single-stage and cascode-free architecture. Nonlinear errors due to finite DC gain are addressed using a deterministic digital background calibration that measures the circuit imperfections in time intervals between normal conversion cycles of the ADC. As a proof of concept, a 12-bit 30-MS/s pipelined ADC was realized using class-AB amplifiers with the proposed digital calibration. The prototype ADC occupies an active area of 0.36 mm2 in 90-nm CMOS. It dissipates 2.95 mW from a 1.2-V supply and achieves an SNDR of 64.5 dB for inputs near the Nyquist frequency. The corresponding figure of merit is 72 fJ/conversion-step.

Keywords: Electrical Engineering
Advisor: Murmann Boris primary advisor. Thesis advisor
Wong S. advisor. Thesis advisor
Wooley Bruce A.