VictorJuiz/thesis huggingface dataset:
Aggregate investment and its consequences [electronic resource]
Keywords: Business.

I use financial statement information to examine intertemporal investment decisions by publicly traded firms at the aggregate level. I find that aggregate corporate investment negatively predicts stock market returns in the US and in a number of foreign countries. Corporations invest more when: (i) investor sentiment is higher; (ii) the yield curve is flatter; and (iii) analysts are more optimistic about future earnings. Moreover, higher aggregate investment forecasts: (i) lower aggregate ROA; (ii) lower short-window returns around earnings announcements; (iii) lower returns on growth stocks and a widening of the 'value premium'; and (iv) deteriorating macroeconomic growth and a higher risk of recession. Several dimensions of these findings are difficult to reconcile in an efficient framework and suggest that inefficient investment plays a role in driving prices and fundamentals at the aggregate level.
Aircraft design for reduced climate impact [electronic resource]
Keywords: Aeronautics and Astronautics

Aircraft affect global climate through emissions of greenhouse gases and their precursors and by altering cirrus cloudiness. Changes in operations and design of future aircraft may be necessary to meet goals for limiting climate change. One method for reducing climate impacts involves designing aircraft to fly at altitudes where the impacts of NOx emissions are less severe and persistent contrail formation is less likely. By considering these altitude effects and additionally applying climate mitigation technologies, impacts can be reduced by 45-70% with simultaneous savings in total operating costs. Uncertainty is assessed, demonstrating that relative climate impact savings can be expected despite large scientific uncertainties. Strategies for improving climate performance of existing aircraft are also explored, revealing potential climate impact savings of 20-40%, traded for a 2% increase in total operating costs and reduced maximum range.
Aircraft drag reduction through extended formation flight [electronic resource]
Keywords: Aeronautics and Astronautics

Formation flight has the potential to significantly reduce the fuel consumption of long range flights, even with existing aircraft. This research explores a safer approach to formation flying of transport aircraft, which we term extended formation flight. Extended formations take advantage of the persistence of cruise wakes and extend the streamwise separation between the aircraft by at least five wingspans. Classical aerodynamic theory suggests that the total induced drag of the formation should not change as the streamwise separation is increased, but the large separation distances of extended formation flight violate the simple assumptions of these theorems. At large distances, considerations such as wake rollup, atmospheric effects on circulation decay, and vortex motion become important to consider. We first examine the wake rollup process in the context of extended formations and develop an appropriate physics-based model. Using this model, this dissertation addresses three aspects of formation flight: longitudinally extended formations, compressibility effects, and formations of heterogeneous aircraft. Uncertainty analysis is used to investigate the induced drag savings of extended formations in the presence of variation in atmospheric properties, limitations of positioning accuracy, and uncertainty in model parameters. Next, the methodology is integrated with an Euler solver to assess the impact of compressibility while flying in formation. Finally, we examine the important considerations for optimally arranging formations of non-identical aircraft.
Airfoil aeroacoustics, LES and acoustic analogy predictions [electronic resource]
Keywords: Aeronautics and Astronautics

The development of physics-based noise prediction tools for analysis of aerodynamic noise sources is of paramount importance since noise regulations have become more stringent. Direct simulation of aerodynamic noise remains prohibitively expensive for engineering problems because of the resolution requirements. Therefore, hybrid approaches that consist of predicting nearfield flow quantities by a suitable CFD simulation and farfield sound radiation by aeroacoustic integral methods are more attractive. In this work, we apply the fast multipole method (FMM) to accelerate the solution of boundary integral equation methods such as the boundary element method (BEM) and the Ffowcs Williams & Hawkings (FWH) acoustic analogy formulation. The FMM-BEM is implemented for the solution of acoustic scattering problems and the effects of non-uniform potential flows on acoustic scattering are investigated. The FMM-FWH is implemented for the solution of two and three-dimensional problems of sound propagation. The effects of flow convection and non-linear quadrupole sources are assessed through the study of sound generated by unsteady laminar flows. Finally, a hybrid methodology is applied for the investigation of airfoil noise. This study is important for the design of aerodynamic shapes such as wings and high-lift devices, as well as wind turbine blades, fans and propellers. The present investigation of airfoil self-noise generation and propagation concerns the broadband noise that arises from the interaction of turbulent boundary layers with the airfoil trailing edge and tonal noise that arises from vortex shedding generated by laminar boundary layers. Nearfield acoustic sources are computed using compressible large eddy simulation (LES) and acoustic predictions are performed by the FMM-FWH. Numerical simulations are conducted for a NACA0012 airfoil with tripped boundary layers and blunt rounded trailing edge at different Mach numbers and angles of incidence. The effects of non-linear quadrupole sources and convection are assessed. In order to validate the numerical solutions, flow simulation and acoustic prediction results are compared to experimental data available in the literature and excellent agreement is observed.
An algebraic geometry based approach to decentralized control [electronic resource]
Keywords: Electrical Engineering

Decentralized control has been one of the important problems in systems and control engineering. Computing an optimal decentralized controller for general linear systems, however, is known to be a very challenging task. In particular, designing an optimal decentralized controller in the standard framework of a linear system with quadratic cost and Gaussian noise is well known to be extremely hard even in very simple and small sized problems. Because of this fact, previous work has focused on characterizing several different classes of problems for which an optimal decentralized controller may be efficiently computed. The set of quadratically invariant problems is one of the largest known class of such problems. This dissertation provides a novel, general, and powerful framework for addressing decentralized control by introducing the idea of using rational elimination theory of algebraic geometry. We show that, in certain cases, this approach reduces the set of closed-loop maps of decentralized control to the solution set of a collection of linear equations. We show how to use these linear equations to find an optimal decentralized controller. We also prove that if a system is quadratically invariant then under an appropriate technical condition the resulting elimination set is affine. We further illustrate that our approach can be well applied to a strictly larger class of decentralized control problem than the quadratically invariant one by presenting a simple example: the example shows that there are problems which are not quadratically invariant but for which the resulting elimination description is affine.
Algebraic space-time block codes with manageable complexity of maximum-likelihood detection [electronic resource]
Keywords: Electrical Engineering

Multiple-input multiple-output (MIMO) wireless systems provide tremendous throughput and reliability gains by utilizing multiple antennas at the transmitters and receivers. As a result, numerous papers have addressed communication and signal-processing topics like space-time code design and signal detection theory. However, today's industry still faces problems with integrating MIMO into products owing to the implementation complexity. Management of complexity is therefore essential to realize the promise of MIMO technology. Previous research on designing space-time block codes was mostly concerned with maximizing transmit diversity and coding gains, and with achieving the optimal diversity-multiplexing trade-off. In contrast, this thesis aims at designing new transmission strategies that can be efficiently decoded while retaining or approaching the optimal performance. The first part of this thesis proposes a new set of rate-1 space-time block codes in systems with 2^n-transmit antennas. These designs achieve the full spatial diversity in quadrature amplitude modulation (QAM). Furthermore, the column vectors of each code matrix can be partitioned into two classes such that any two vectors from different classes are orthogonal. As a result, the maximum-likelihood (ML) detection can be implemented in reduced time complexity. For a system with four transmit antennas, the proposed encoders attain the optimal bit error rate (BER) in QAM without the necessity of extra modulation. These results will be extended to new rate-1 codes employing four transmit antennas for which the ML detection can be determined in linear time. These codes similarly achieve the full diversity in QAM, and moreover in 4M-phase-shift keying (4M-PSK), while the corresponding ML detection can be accomplished by independently decoding each symbol. The reduction in detection complexity simply necessitates an increment of 0.21 dB in the signal-to-noise ratio (SNR) for sustaining the same BER.
Algorithms and strategies for web advertising [electronic resource]
Keywords: Electrical Engineering

Web advertising is a multi-billion dollar business and the main revenue source of the most popular web sites such as Google, Yahoo and Facebook. Web advertisers reach their potential customers mainly through two different channels: sponsored search, the display of textual ads next to the search engine organic results and display advertising, the display of graphical ads as part of web pages. In the simplest form of web advertising three parties are involved: the advertisers, the medium, i.e., the search engine or the publisher, and the users. Their interactions can be grouped in three steps: (a) Bidding: The advertisers provide the medium with their ads, their bids, and some preferences regarding the users of interest; (b) Delivery: Given the ads and a user in a particular context, i.e., a query or a web page, the medium selects an ad that respects advertiser preferences and maximizes its own expected profit; (c) Response: The user sees the selected ad and he either ignores it or proceeds to an action related to it, e.g., he clicks a link or buys a product. Such actions fulfill the advertiser goals and, consequently, they drive the whole procedure. In this thesis we study each of these steps and we propose new algorithms and strategies that tackle inefficiencies of current solutions. In bidding, we introduce output URL bidding, a new bidding mechanism for sponsored search, where advertisers bid on search result URLs, as opposed to keywords in the input query. For example, an advertiser may want his ad to appear whenever the search result includes the sites www.imdb.com and en.wikipedia.org, instead of bidding on keywords that lead to these sites, e.g., particular movie titles or actor names. We have shown that output bidding can provide a more concise language among advertisers and the search engine and it can increase the recall of relevant queries. In ad selection, we introduce sponsored search auctions with conflicts. In such auctions, advertisers can condition their bids on the non-appearance of certain undesired ads on the results page. With such constraints the ad selection becomes computationally challenging. However, we introduce algorithms that can deal with the computational cost, while providing advertisers with higher utility and the search engine with increased revenue. Finally, our work includes also novel ways to quantify the user response. Using a field experiment we have measured the impact of display advertising on user search behavior. Our results show that display ads can increase the volume of queries that are related to an ad by 5% to 25% for a two-week period. Surprisingly, the impact of advertising is not limited to exposed users but also to their social friends.
Algorithms for congestion control and bandwidth-partitioning in data centers [electronic resource]
Keywords: Electrical Engineering

Data Center Networks represent the convergence of computing and networking, of data and storage networks, and of packet transport mechanisms in Layers 2 and 4. These networks provide a rich opportunity for developing new algorithms and architectures. In this thesis, we propose a Layer 2 congestion management algorithm called QCN (Quantized Congestion Notification), which we have developed for the IEEE 802.1Qau Congestion Notification standard for Data Center Ethernet. QCN has been designed to be stable, responsive, and simple to implement. This thesis also introduces ECN-hat, a slightly modified version of the TCP algorithm that mimics QCN's multi-bit rate cuts, leading to significantly higher utilization and lower latency. It does this by using the ECN marks in the acks of packets in a non-traditional way, one which extracts more information about the congestion in network. We also show how QCN and Data Center TCP (DCTCP) can be easily extended via light-weight switch modifications to provide programmable bandwidth partitioning in multi-tenanted Cloud Computing and Data Center environments. Our Approximately Fair extensions, AF-QCN and AF-DCTCP, achieve weighted fairness at the granularity of a few milliseconds while retaining the good properties of QCN and DCTCP (stability, responsiveness, and simplicity).
Americans and climate change [electronic resource] : understanding elite perceptions of the gap between science and action
Keywords: Political Science.

This dissertation explores why, given the widespread and longstanding assessment of scientific and other experts that climate change is an urgent problem requiring a large-scale policy remedy, such governmental action not transpired to date. It reports and interprets the diagnoses offered by 111 elite "informants" to explain this inaction and their judgments on what interventions might be designed and executed to produce action. The dissertation further evaluates their experientially derived, case-specific insights against social scientific findings on the question of what leads citizens, and their democratic institutions, to take effective action on some issues and not others. An intervening variable of particular interest in this research is that of public pressure, including elite understandings of its role and how it can be generated. Because climate change is an arena of robust scientific consensus, it provides a particularly useful test case of citizen and governmental competence. Informants included participant-observers from the following eight domains, each of whom describe how the incentives operating in their respective domain influence how scientific knowledge about climate change is defined, framed, communicated, propagated, absorbed, interpreted and translated into action or inaction: science; news media; religion & ethics; politics; entertainment & advertising; education; business & finance; environmentalists & civil society. Patterns and interactive effects cutting across the domains are also considered, including a revealed diffusion of responsibility that has created a vacuum of elite leadership on climate change. Given the time signature of risks associated with unabated climate change, the informants are shown to generally prefer interventions that are inherently faster to execute but not necessarily more effective in terms of producing durable attitude change or the intended inducement to action. The dissertation additionally finds that "real-world cues" -- broadly construed to include empirical observations of climate change impacts from the present and future-oriented information garnered through credible modeling -- remains a "sleeping giant" appropriate for greater use in persuasive strategies to promote climate change action. It also finds that the authoritative and "settled" nature of climate change science has created a temptation among informants to overvalue one-way, top-down communications efforts, rather than to mount civic engagement initiatives that emphasize peer-to-peer networking and group deliberation. The role of terminal values are also considered, including the lack of a terminal value associated with preservation of civilization against unabated climate change that is capable of competing with a value that has been advanced in opposition to policy action on climate change, that of economic freedom from government oppression in the form of environmental regulation nominally, but on a presumed slippery slope to confiscation of private property.
America's teachers, do management practices in public schools provide incentives for quality teaching? [electronic resource]
Keywords: Business.

Do management practices in America's public schools provide incentives for quality teaching? This dissertation argues that (i) current pay practices in teaching do not provide incentives for the most able individuals to become teachers and (ii) the changed management practices that accompanied the introduction of accountability programs improved the quality of teaching in poorly performing schools. Using data from Florida, Illinois, North Carolina, Texas, Virginia, Pennsylvania, and Wisconsin, the structure of pay in public schools during 1993 through 2003 is compared to the structure of pay in other occupations requiring a college degree. Those who leave teaching during this period earn much less after leaving, even after several years. This suggests that pay practices in teaching have not been successful in attracting the most able individuals to teaching. (Otherwise, at least some individuals would exit teaching for higher pay when outside opportunities improved, as they did in the late 1990s.) The management practices that accompanied the introduction of accountability likely improved the quality of teaching in poorly performing schools through two channels: (i) existing teachers made more effort, and (ii) many of the worst teachers left teaching. Moonlighting (working a second job) is used as an inverse proxy for effort because a full-time worker is likely exerting only limited effort if she is moonlighting. Teachers in public schools exposed to performance pressure from a state accountability system were much less likely to moonlight and much more likely to leave teaching. Those who left teaching did not fare well in the broader labor market; they earned less than they did as teachers, even after several years. Data from three states that implemented demanding accountability systems in the 1990s (Florida, Illinois, and North Carolina) are used. Taken together, these results suggest that accountability did help to improve the quality of teaching in poorly performing schools.
An Analysis of the Credit Union for Migrant Workers in Thailand
Keywords:  Department of Economics
Stanford Department of Economics
microfinance
interest rate
microloan
migrant workers
financial exclusion
Thesis

Along the Thai-Burmese border region of the Sangkhlaburi District, Kanchanaburi province, Thailand, there reside displaced ethnic communities who migrated from Burma. These people have been deprived of access to commercial banks or any other formal financial services because they do not carry Thai identification cards. This form of financial exclusion acts as a barrier to development for this local community. In order to analyze the effectiveness of one institution, the Pattanarak Credit Union (PCU), that addresses the financial needs of this community in terms of meeting legitimate financial needs of the migrant workers, I test if the PCU charges competitive rates and provides much-needed loans to the members of the group. This paper proposes a financial model to study the effectiveness of the PCU and analyzes the savings and borrowing mechanisms of its microcredit program. My honors thesis shows that the PCU’s mechanisms have been effective in keeping the default rate at zero and withdrawal rate low. This study also finds that the interest rates charged on borrowers should be raised to maximize dividends distributed back to members of the credit union, which is in keeping with the PCU’s social mission.
Analysis and synthesis of three-dimensional illumination using partial coherence [electronic resource]
Keywords: Electrical Engineering

There exists many devices that generate three-dimensional illumination patterns. Analysis of the capabilities of three major device families using measures of partial coherence reveals specific illumination patterns that cannot be generated by each device family. Ray-based devices cannot achieve patterns with high resolution, coherent holographic devices cannot achieve certain intensity patterns, even in the two-dimensional case, and volumetric devices cannot simulate occlusions and suffer from out-of-focus blur. Synthesis of more versatile illumination patterns is proposed by computing the mutual intensity representation of a desired partially coherent beam from application specifications and then generating the beam using time-multiplexing methods based on coherent modes. The mutual intensity can be computed directly from a simple scene description, or it can be computed through a novel algorithm using nonlinear conjugate gradients from a desired three-dimensional intensity volume. Equivalent coherent mode decomposition representations for the same mutual intensity will be considered in terms of optimality in efficiency. For cases when the computed mutual intensity is fairly incoherent, a new "quasi-Schell" mode decomposition is proposed to reduce the number of patterns needed at the SLM by introducing partially coherent sources. Use of arbitrary partially coherent beams for three-dimensional illumination enables the versatile generation of light patterns not possible with current devices and is a promising new field for exploration.
Analytical goal-driven learning of procedural knowledge by observation [electronic resource]
Keywords: Electrical Engineering

Knowledge-based approaches to planning and control offer benefits over classical techniques in applications that involve large yet structured state spaces. However, knowledge bases are time consuming and costly to construct. In this dissertation I introduce a framework for analytical learning that enables the agent to acquire generalizable, domain-specific procedural knowledge in the form of goal-indexed hierarchical task networks by observing a small number of successful demonstrations of goal-driven tasks. I discuss how, in contrast with most algorithms for learning by observation, my approach can learn from unannotated input demonstrations by automatically inferring the purpose of each solution step using the background knowledge about the domain. I discuss the role of hierarchical structure, distributed applicability conditions, and goals in the generalizability of the acquired knowledge. I also introduce an approach for adaptively determining the structure of the acquired knowledge that strikes a balance between generality and operationality, and for making the algorithm robust to changes in the structure of background knowledge. This involves resolving interdependencies among goals using temporal information. I present experimental studies on a number of domains which demonstrate that the quality of acquired knowledge is comparable to handcrafted content in terms of both coverage and complexity. In closing, I review related work and directions for future research.