VictorJuiz/thesis huggingface dataset:
Household sanitation services in sub-Saharan Africa : coverage targets, child health outcomes, and a benefit-cost analysis

A large global health burden has been attributed to a lack of adequate sanitation access. Approximately 2.3 billion people still lacked access to basic sanitation services, a private flush toilet or improved latrine, as of 2015. There remains limited evidence on the effectiveness of shared sanitation facilities for protecting child health. Furthermore, while much research has focused on child health outcomes associated with sanitation improvements, the valuation of non-health benefits has often been neglected. Within this dissertation, I examine household sanitation service options, notably basic and limited sanitation (improved latrines and flush toilets shared by 2 or more households) with regards to child health outcomes and overall benefit values. I also consider the role of community sanitation coverage in child health and drinking water quality as compared to household sanitation access in rural Mali. In Chapter 1, I found the level of sanitation access of surrounding households was more important than private latrine access for protecting water quality and child health. In Chapter 2, I examine the associations between sharing of sanitation facilities and child health outcomes via a combination of matching techniques. Limited and basic sanitation households were not significantly different in stunting prevalence, although basic sanitation indicated greater potential benefits when compared to open defecation and unimproved sanitation. In Chapter 3, I quantify the costs and benefits of basic and limited sanitation options in urban Uganda. Sanitation benefits were an estimated 24 percent of rental value for basic sanitation and 16 percent for limited sanitation shared between 2 and 4 households. The overall benefits and costs in urban settings indicate a potential role for both limited and basic sanitation in increasing sanitation coverage despite minimal health benefits at the household level.

Advisor: Bendavid Eran
Thompson Barton H.
Davis Jenna (Professor)
Pickering Amy (Amy Janel)
How Agricultural Technologies' Development Might Impact U.S. Agricultural Subsidy Policies

In 2017, U.S. farmers received more than $16 billion in subsidies. Critics often point out that these subsidies disproportionately benefit farmers with larger farms. The Food and Agriculture Organization (FAO) predicts that the global population will reach 10 billion by 2050. Experts estimate that the world will need to produce 70% more food to feed this population and that Agricultural Technologies will play a prominent role in increasing production. Besides disrupting the value chain, this shift in technology will also provide a tremendous amount of information and transparency in agri-food production systems. This thesis attempts to answer the following question: how can the information provided by the new technologies change the way the Government subsidizes agricultural commodities?

Keywords:  Public Policy Program
Stanford University
Humanities and Sciences
Public Policy Program
farms subsidy policy
agricultural technologies
cost-benefit analysis
USDA
farming
agriculture
agricultural commodities
food security
data
artificial intelligence
Thesis
Advisor: Rosston Gregory
How do wildfires affect recreation patterns?

The occurrence of large wildfires is an increasing feature of the American West. Despite this, little is known about how these fires affect welfare-relevant outcomes like recreation demand because of the cost of conducting such analyses at a large scale. In this paper, I use the number of photos uploaded to Flickr between 2006-2013 as a costless and scalable proxy for visits to National Parks and Forests in California. Using this dataset, I examine the effect of fires of different sizes, severities, and ages on recreation demand in forests with different types of vegetation over a 30-year period. I find that a fire of average size and severity causes a 9.9% reduction in visits in the long run. Second, the response function of recreation demand to fire occurrence over time is non-monotonic; results suggest that visits drop in response to fires initially, gradually increase, and then drop again towards the end of the 30-year period. Third, while the number of visitors drops in response to fires of all severity levels momentarily, it recovers faster in sites that were burned more severely relative to sites that had milder fires. Lastly, the effect of a wildfire on recreation varies dramatically depending on the vegetation type of a site.

Keywords: wildfires
Flickr
social media
Stanford Economics
thesis
econometrics
recreation
Thesis
How to design and analyze online A/B tests within decentralized organizations

From e-commerce to digital media to social networks, essentially any company that does business online is using A/B tests -- randomized experiments on its customers -- in order to optimize its service. A standard approach to designing and analyzing these experiments, based on classical statistical theory, is ubiquitous in industrial practice. Namely, a sample size for each test should be set in advance, and the data collected should be analyzed in isolation through p-values and confidence intervals that are computed based on a 2-sample t-test of means. This thesis investigates four ways that this default approach proves insufficient, due to the decentralized manner in which A/B tests at these companies are run. For each of the four, we empower experimenters to continue their current behavior, while we offer novel methodology that is simple to implement and ensures inferential reliability. Some of our methods are now in use in industry. We supplement our theoretical results with empirical data from these industrial deployments.

Keywords: Statistics.
Advisor: Johari Ramesh
Efron Bradley 
Owen Art B.
Human operator-autonomous vehicle interactions with system bias and transitions of control

Autonomous vehicles are considered the future of transportation. They offer several potential long-term benefits, including reduction in driving and navigation chores, enhanced mobility for individuals with disabilities, improved safety and decreases in traffic collisions, and reduced infrastructure costs. Currently, however, autonomous vehicle systems in development are still limited by their abilities to detect their surroundings, interpret sensory information, and fully navigate without human input. The human operator needs to both supervise the imperfect system and collaborate with it to navigate the driving environment. The research presented in this dissertation was aimed at better understanding human operator and autonomous vehicle interactions and how they affect system design and implementation. An immersive driving simulator was modified to develop experimental studies that analyzed interactions between the human operator and the autonomous vehicle system. The first part of this research focused on the inherent algorithmic biases present in designing autonomous vehicle systems, and the effects of changes in the system's sensitivity level and autonomy level were analyzed. The results show that a system biased towards lower sensitivity can improve operator vigilance and performance. The results further demonstrate that higher levels of autonomy in vehicles can result in reduced operator performance during potentially fatal events. Subsequent research focused on transitions of control from automation, in which the system hands control of the vehicle over to the human operator because there is a failure in the autonomous driving system. The effect of varying alert frequencies and levels of failure severity on the human operator's ability to successfully navigate a transition was analyzed. Significant differences in operator performance between the presence or lack of an alarm were observed, as well as the fact that an initial system failure's severity level did not seem to affect operator performance in a later failure event. Overall, the results of this work show that engineers and designers of autonomous vehicle systems need to consider a number of scenarios when specifying system actions and responses. This research provides a starting point for further exploration of the implications of system bias, particularly with varying levels of automation. It also provides insights that can help inform the design of transitions of control. A better understanding of human operator and autonomous vehicle interactions remains critical as vehicles with higher levels of automation become more prevalent on the road.

Advisor: Fischer Martin
Leifer Larry J. 
Cutkosky Mark R. 
Sirkin David Andrew
Weyant John P. (John Peter)
Human-computer conflicts in partially-automated driving

Computer systems with independent agency that directly act on the environment or influence behaviors and beliefs now mediate our interactions with the ambient environment—influencing what we believe, and what we can do. We will increasingly come in to conflict with such systems, even if they are helping us pursue our superordinate desires. Moral conflicts, without an objectively correct solution, present a complex challenge and demand empirical investigation as to how people will cope with a human-computer moral conflict, so to inform the design of such systems. To study human-computer moral conflicts, a full-vehicle driving simulator was used to elicit naturalistic driver responses in a set of moral conflict situations, where the computer would steer the participant towards greater danger to self, or would protect them by steering towards vulnerable others. Participants fought more strongly against the computer when it pushed participants towards greater danger to themselves and less when it steered them towards vulnerable others when collisions were impossible and time was available to evaluate the situation and act against the computer's actions. In a time-pressured situation where a collision was inevitable, participants fought more strongly against the system when it steered them to strike a person, and less when it pushed them towards a barrier that would injure them. Ultimately, the circumstances of the situation, time available, and level of perceived threat greatly influence fighting against a computer's actions in the moment, and thus systems need to be designed carefully, as supervisory control may be difficult or impossible in critical situations.

Keywords: Communication.
Advisor: Reeves Byron
Bailenson Jeremy 
Harari Gabriella 
Monin Benoît
Hunting for Special Solutions in Calabi-Yau Compactifications

In this thesis, we discuss approaches to various problems in the field of geometric moduli stabilization in type IIB string theory. We introduce the physics and mathematics of Calabi-Yau compactifications, flux compactifications, and attractor black holes. With these tools we investigate the construction of explicit, analytical flux solutions that generate vacua with small and nonvanishing superpotential and connect these solutions to old ideas in number theory about approximations of irrational numbers. Finally, we detail the statistical theory of vacua in moduli space and cite some new and old results as they pertain to non-supersymmetric vacua and non-BPS attractor black holes.

Keywords:  Department of Physics
string theory
Calabi-Yau manifolds
moduli stabilization
Thesis
Advisor: Kachru Shamit
Raghu Sri
A hybrid approach to automatic program parallelization via efficient tasking with composable data partitioning

Despite the decades of research, distributed programming is still a painful task and programming systems designed to improve productivity fall short in practice. Auto-parallelizing compilers simplify distributed programming by parallelizing sequential programs automatically for distributed execution. However, their applicability is severely limited due to the fundamental undecidability of their static analysis problem. Runtime systems for implicit parallelism can handle a broader class of programs via an expressive programming model, but their runtime overhead often becomes a performance bottleneck. To design a practical system for productive distributed programming, one must combine the strengths of different parallelization paradigms to overcome their weaknesses when used in isolation. This dissertation presents a hybrid approach to automatic program parallelization, which combines an auto-parallelizing compiler with an implicitly parallel tasking system. Our approach parallelizes programs in two steps. First, the auto-parallelizer materializes data parallelism in a program into task parallelism. Next, the tasking system dynamically analyzes dependencies between tasks and executes independent tasks in parallel. This two-stage process gives programmers a second chance when the auto-parallelizer "fails": When a part of a program is not amenable to the compiler auto-parallelization, the programmer can gracefully fall back to the run- time parallelization by writing that part directly with task parallelism. Furthermore, hand-written tasks can be seamlessly integrated with the auto-parallelized part via composable data partitioning enabled by our auto-parallelizer, which allows them to share the partitioning strategy and thereby avoid excessive communication. Key to the success of this hybrid approach is to minimize the overhead of the tasking system. To achieve this goal, we introduce dynamic tracing, a runtime mechanism for efficient tasking. The most expensive component in the tasking system is dynamic dependence analysis. Although this dynamic analysis is necessary when applications exhibit true dynamic behavior, the analysis is redundant for common cases where dependencies are (mostly) unchanging. Dynamic tracing eliminates this redundancy in dynamic dependence analysis by recording the dependence analysis of an execution trace and then replaying the recording for the subsequent occurrences of the same trace. To guarantee that a recording of a trace correctly replaces the trace's original analysis, dynamic tracing also records memory locations that hold valid data when it records a trace and replays the recording only when those locations are still valid. Dynamic tracing significantly improves the efficiency of tasking, and thereby brings the strong scalability of explicit parallelism to implicit task parallelism

Advisor: Aiken Alexander 
Mitchell John C. 
Olukotun Oyekunle Ayinde
Hydrodynamics of condensed matter

Symmetries control the late time physics of classical and quantum systems that thermalize; hydrodynamics is the framework that describes this physics. The first part of this thesis establishes the hydrodynamic description of several archetypal systems of modern condensed matter physics: anomalous metals, Wigner crystals and fractional quantum Hall materials. A hydrodynamic theory describing the elusive bad metallic phase of high temperature superconductors is proposed. The second part of this thesis lays out several developments in the theoretical framework itself. It is shown that the symmetry algebra alone (as opposed to how it is realized) determines the hydrodynamic description of a system. A systematic theory of hydrodynamic fluctuations is presented and used to determine universal corrections to diffusion. Finally, bounds on transport coefficients are derived from microscopic positivity conditions.

Keywords: Physics.
Advisor: Hartnoll Sean
Kivelson Steven 
Senatore Leonardo
Hydrogen bond dynamics and directional interactions in nanostructured condensed phases

The hydrogen bond is a key intermolecular interaction in chemistry, biology, geology, and materials science, with its energy tuned for a perfect balance between structural rigidity and rapid dynamic rearrangements around ambient conditions. Ultrafast infrared spectroscopic methods are described that can interrogate the dynamics and intermolecular interactions of the hydroxyl stretch mode, a sensitive reporter of hydrogen bonding environments, of water and alcohols in complex environments far removed from the bulk liquids. New methodology for conducting noncollinear two-dimensional infrared experiments in a rotating frame to accelerate data acquisition is described. Water confined in polyacrylamide hydrogels is found to slow as one population as the size of the water pool decreases. The lack of any water with bulk-like dynamics is surprising and attributed to the continuity of hydrogen bond network between the water pool and confining polymer. Room temperature ionic liquids, a family of tunable, non-volatile, and non-flammable solvents composed entirely of cations and anions, are structured at the nanoscale by charge ordering as well as the possibility of other motifs, such as segregation of polar and apolar groups. Water and alcohols isolated in ionic liquids, as representative solutes or cosolvents, experience hydrogen bond interactions with the solvating ions. A rich hierarchy of dynamical processes in the randomization of their orientations and intermolecular interactions is observed, ranging from less than 100 femtoseconds to sometimes over 100 picoseconds. The hydrogen bond interactions are highly directional, leading to distinct forms in the polarization dependence of ultrafast IR measurements of structural dynamics (spectral diffusion), particularly in ionic liquids. Theory is developed to characterize these directional interactions and dynamics quantitatively and separate the reorientation-induced spectral diffusion (RISD) processes, arising through rotation of the tracer, from spectral diffusion that is due to the randomization of the surroundings. Related theories of RISD are presented that are appropriate for carbon dioxide, a highly symmetrical vibrational probe, as well as fluorescent probe molecules undergoing time-dependent Stokes shift with highly directional interactions that determine the absorption and emission frequencies. Measurements of the dynamics of water confined in the nanoscale pores of amorphous silica are presented. Several techniques to overcome the inherent scatter from silica particles (sand) were combined, including phase cycling, polarization control, and spatial filtering, and their individual merits are discussed. The slowdown in dynamics of water in the silica pore are compared to previous measurements of the dynamics of selenocyanate, an anion that H-bonds to the surrounding water in the pore.

Keywords: Chemistry.
Advisor: Fayer Michael D. 
Markland Thomas E.
Zare Richard N.
A hydrologic and slope stability analysis of a steep, tropical watershed : an integrated modeling approach

The abundance of water lies at the heart of many of the risks facing the tropics, including hazards such as floods and landslides. This region is subject to some of the highest intensities of land cover disturbance through forest removal and is also particularly vulnerable to climate change. However, there are few detailed hydrologic studies of tropical environments relative to their temperate counterparts, and the extent to which knowledge gleaned from detailed studies of temperate watersheds can be applied to the tropics remains unclear. We use ParFlow.CLM, a three-dimensional, integrated hydrologic model to advance our understanding of the hydrologic and slope-stability response of watersheds in the Northern Range of Trinidad, a tropical island in the Caribbean. Despite a low frequency of extreme storms, this location has one of the highest incidences of reported landslides. This dissertation includes a collection of sensitivity experiments at the scale of a single hillslope, as well as the watershed scale. We investigate under what conditions a series of short-duration rainfall events leads to slope instability. Even though a fully coupled approach is computationally expensive to implement, our results demonstrate that using a simple, 1D hydrologic model without lateral flow and heterogeneity to simulate slope failures can lead to non-conservative results, particularly in the case of multiple short duration rainfall events. We also perform a collection of experiments to analyze the effect of model discretization, hydraulic conductivity heterogeneity, and land cover change on hydrologic model response. We show that coarsening the spatial discretization at grid cell sizes less than 100 m results in sizable differences in the magnitude of the evapotranspiration flux. Changes in subsurface storage and surface runoff obtained with ParFlow.CLM are of the same order of magnitude as HRU based models such as SWAT which have become the de facto standard for analyzing the effects of land-cover changes on the water budget.

Advisor: Freyberg David L. 
Gorelick Steven
Koseff Jeffrey Russell
Hydrologic change and muskrat population dynamics in the Peace-Athabasca Delta, Canada

Empirical and anecdotal reports suggest that muskrat are in decline across North America, including in the 5500 square km Peace-Athabasca Delta ("Delta"), Canada, part of a World Heritage Site with 'in Danger' status pending. This dissertation is concerned with the effects of rapid hydrologic change on the Delta's muskrat population. Analysis of a Landsat-derived record of inundation for the Delta (1972-2017), together with 21 years of muskrat survey records, show that the catastrophic decline in the Delta's muskrat population is synchronous with loss of critical habitat. Results suggest that loss of wetland habitat could be the cause of the observed, but as yet unexplained, decline of muskrat across North America. Conceptual and quantitative agent models of the muskrat population at a model floodplain lake region of the Delta illustrate mechanisms controlling muskrat abundance. Model results show that shoreline habitat and muskrat intensive herbivory are key mechanisms controlling muskrat abundance, while trapping intensity is not a primary factor. This is a key finding as muskrat trapping continues to be an important practice for Indigenous communities with traditional territory in the Delta. Ecological agent modeling, dynamic habitat maps driven by hydrologic change, and landscape genetic analysis are brought together to assess spatio-temporal characteristics of population dynamics for muskrat on the Delta floodplain. Results show that the Delta undergoes dramatic transitions from a network of population sources, to a network of population sinks, on an interannual basis in years following floodwater inputs. Notably, this network of sources and sinks is less prominent following the most recent flood in 2014, suggesting a reduced footprint of the muskrat population on the Delta floodplain, a change with broad implications for the ecological integrity of the Delta ecosystem. Together, the findings from this dissertation lay the groundwork for use of muskrat as an indicator species for the impacts of hydrologic change on wetland ecosystems, particularly in subarctic and arctic delta regions where the hydrologic effects of climate change are pronounced.

Keywords: Earth System Science.
Advisor: Gorelick Steven M. 
Hadly Elizabeth Anne
Lambin Eric F.