VictorJuiz/thesis huggingface dataset:
Learning to Predict Human Behavior from Video

In recent times, the field of computer vision has made great progress with recognizing and tracking people and their activities in videos. However, for systems designed to interact dynamically with humans, tracking and recognition are insufficient; the ability to predict behavior is requisite. In this thesis, we introduce various general frameworks for predict human behavior at three levels of granularity: events, motion, and dynamics. In Chapter 2, we present a system that is capable of predicting future events. In Chapter 3, we present a system that is capable of personalized prediction of the future motion of multi-agent, adversarial interactions. Finally, in Chapter 4, we present a framework for learning a representation of human dynamics that we can: 1) use to estimate the 3d pose and shape of people moving in videos, and 2) use to hallucinate the motion surrounding a single-frame snapshot. We conclude with several promising future directions for learning to predict human behavior from video.

Advisor: Malik, Jitendra
Navigating Video Using Structured Text

Video has become a primary medium for producing and consuming entertainment, educational content, and documented events. As the cost of recording, sharing, and storing video has decreased, the prevalence of video has increased. Yet, video remains challenging to use as an informative medium because it is difficult to search, browse and skim the underlying content./nUsing a timeline-based video player, users must scrub back-and-forth through a video to gain an overview or locate content of interest. Some video viewing interfaces allow users to search and browse videos by text transcripts or caption files. However, transcribed and captioned speeches or conversations often contain disfluencies and redundancies typical of speech which make the transcripts time-consuming to read and difficult to skim. Further, transcripts and captions lack structure -- transcripts consist of long blocks of text, while captions have a series of short phrases. Without structured organization, it can be difficult for viewers to browse topics or get a high-level overview of the content./nThis thesis explores new ways to search, browse and skim videos through structured text. We aim to create navigable representations of videos that let users ask questions of the video as efficiently and flexibly as possible, and facilitate low cost production. This thesis introduces systems that embody these goals, using structured-text documents aligned to video to enable efficient and flexible video searching, browsing and skimming across three domains: (1) informational lecture videos, (2) films, and (3) casually recorded feedback.

Advisor: Hartmann, Bjoern
Agrawala, Maneesh
Social Class Background and Career Advancement: The Role of Behavioral Signatures

Research has established a strong link between parental social class and individuals’ social class later in life, but less is known about the perceptual processes that govern workplace behaviors and “gatekeeping” interactions (such as interviews) which might advance one’s social class. I propose that people from a lower social class background (e.g., lower household income growing up, less parental education, lower subjective social class) display fewer agentic nonverbal cues in work contexts, thus observers see them as less agentic, and are less willing to hire and promote them. I conducted a field survey (Study 1) which asked mid-career professionals, as well as a minimum of two colleagues, to report on their career advancement and workplace behaviors (n professionals = 215, n raters = 547). A pattern emerged such that professionals from a lower social class background earn less, and also see themselves as behaving less agentically in the workplace. Moreover, self-reported agentic work behaviors fully mediated the relationship between household income growing up and current household income. I then conducted a study of mock job interviews in which undergraduates were videotaped conducting a case interview (n interviewees = 150). Independent judges were invited to make attributions of those interviewees’ underlying traits (n ratings = 1,505, or 10 raters per video), and professional hiring managers were asked to rate their worthiness of career advancement (n ratings = 450, or 3 hiring managers rating each video). I found that students from a lower social class background were seen as less agentic, and thus as less worthy of hire and promotion, than their counterparts from a higher social class background. This can be explained by their reduced display of agentic nonverbal cues such as expanded posture and a confident and factual vocal tone. These findings contribute to the emergent literature on the psychology of social class, particularly highlighting the relationship between social class background, perceptual processes, and career advancement, and ultimately helping to explain the persistence of inequality in intergenerational social mobility.

Advisor: Anderson, Cameron
High temperature studies of electric-field noise in a surface ion trap

Electric-field noise is a major limiting factor in the performance of ion traps and other quantum devices. Despite intensive research over the past decade, the nature and cause of electric field noise near surfaces is not well understood. This dissertation reports the high- temperature dependence of electric-field noise above an Al-Cu surface using a trapped 40Ca+ ion as a probe./nWe employ a novel setup with a surface ion trap mounted on a heater for studies of the temperature dependence of electric-field noise. To characterize the Al-Cu material, we explore the effects of heat treatment through ex situ annealing followed by inspection in a scanning electron microscope. To calibrate the temperature of the trap, we demonstrate the use of thermal imaging for monitoring the temperature of an ion trap in vacuum./nThe temperature and frequency dependence of electric-field noise above the surface is measured using the heating rate of a single ion in a surface-electrode Paul trap. We find that the heating rate saturates at temperatures greater than 450 K. We find that the frequency dependence shows a 1/f behavior, and has a lower frequency scaling exponent at high temperatures than at room temperature. We show that these results are a reflection of the surface-related noise by eliminating other possible sources of noise./nBuilding on historical data for resistance fluctuations in thin films, we develop the thermally-activated fluctuator model to describe the results. We find that a broad distribution of fluctuators with energy barriers peaked around 0.5 eV accurately models both the temperature and frequency dependence of the electric-field noise measured. We present the interpretation of this model as a way to infer that the cause of electric-field noise in the trap is likely defect motion in the metal surface, connecting the problems faced in ion trapping to a large body of work in solid state physics.

Advisor: Haeffner, Hartmut
Computations of the cohomological Brauer group of some algebraic stacks

The theme of this dissertation is the Brauer group of algebraic stacks. Antieau and Meier showed that if $k$ is an algebraically closed field of $\on{char} k \ne 2$, then $\Br(\ms{M}_{1,1,k}) = 0$, where $\ms{M}_{1,1}$ is the moduli stack of elliptic curves. We show that if $\on{char} k = 2$ then $\Br(\ms{M}_{1,1,k}) = \Z/(2)$. In another direction, we compute the cohomological Brauer group of $\G_{m}$-gerbes; this is an analogue of a result of Gabber which computes the cohomological Brauer group of Brauer-Severi schemes. We also discuss two kinds of algebraic stacks $X$ for which not all torsion classes in $\H_{\et}^{2}(X,\G_{m})$ are represented by Azumaya algebras on $X$ (i.e. $\Br \ne \Br'$).

Advisor: Olsson, Martin C
New Probes of Axions and Ultra-Heavy Dark Matter

The Standard Model of particle physics is known to be incomplete, and many extensions and modifications have been proposed to resolve outstanding issues. In order to discriminate which of these many ideas may be correct, we seek novel approaches to acquire new data and apply old data. The research in this dissertation advances these efforts, probing physics beyond the Standard Model in three distinct ways. First, we propose a novel design of a laboratory search for axions based on photon regeneration with superconducting radiofrequency resonant cavities. We use a confined static magnetic field to avoid degrading the large resonant quality factors. After analysis of fundamental issues and limitations, we conclude this design can potentially probe axion-photon couplings beyond astrophysical limits, comparable and complementary to next generation optical experiments. Second, we demonstrate that rotational superradiance can be efficient in millisecond pulsars. We use measurements from the two fastest known pulsars to place bounds on bosons with masses below 10^−11 eV and Yukawa couplings to neutrons, exceeding fifth force constraints by 3 orders of magnitude for masses near the pulsar rotation rates. For certain neutron star equations of state, these measurements also constrain the QCD axion. Third, we consider dark matter (DM) candidates that heat white dwarfs through the production of high-energy Standard Model (SM) particles, and show that such particles will efficiently thermalize the stellar medium and ignite type Ia supernovae. Based on the existence of long-lived white dwarfs and the observed supernovae rate, we derive new constraints on DM with masses greater than 10^16 GeV which produce SM particles through DM-DM annihilations, DM decays, and DM-SM scattering interactions in the stellar medium.

Advisor: Rajendran, Surjeet
Mapping a Chemical Journey through the United States Chemical Management System

Since the phase-out of the historically-used polybrominated diphenyl ethers because of growing evidence of their negative health and environmental impacts, current-use organophosphate flame retardants have re-emerged to replace polybrominated diphenyl ethers. However, very little is known about organophosphate flame retardants. This process of replacing suspected harmful chemicals with understudied alternatives is common. Many chemicals are largely unstudied before they are introduced to consumer products and the environment, and are unregulated. Scientific research has revealed potential negative associations between health and certain chemicals, such as flame retardants. Subsequently, these chemicals are either banned or phased out. Other chemicals with unknown health repercussions potentially replace their banned or phased out predecessors (legacy chemicals) and are often structurally similar to the previous iteration or are structurally similar to other chemicals with adverse impacts on health./nThis dissertation maps a typical chemical’s path within the United States chemical management system. I chart this process, focusing on flame retardants, by measuring the level of contamination of the legacy flame retardants, polybrominated diphenyl ethers, and the re-emerging organophosphate flame retardants in fire station dust across the United States. Then, I evaluate the association between maternal urinary levels of organophosphate flame retardant metabolites and their effect on sex hormones in male children at age 12. Finally, I present what the electronics industry is currently doing to avoid regrettable substitutions and discuss the need to combine risk assessments with alternatives assessments.

Advisor: Hammond, Sally K.
Tropical plant hydraulics in a changing climate: importance for species distribution and vulnerability to drought

Amazonian droughts are becoming more frequent and intense, having a profound effect on water availability for plants. However, we still have limited abilities to predict the effect of climate change on plant species survival and distribution in mega-diverse systems like the Amazon. Plant hydraulic traits coupled with the assessment of environmental characteristics emerge as an important tool to assess species physiological performance and resilience, especially during extreme climatic events. Here we investigate plant hydraulic strategies and physiological performance of tropical tree species (i) across contrasting environments, (ii) during an extreme drought event and (iii) during the course of a day to understand how water availability may shape species distribution and plant vulnerability to drought in the Amazon Basin./nIn the first chapter, I investigate if the current patterns of species’ distribution in the main Amazonian habitats can be explained by species hydraulic strategies and how variation in the hydraulic properties of Amazonian forests influences species-specific vulnerability to drought across different habitat types. I found strong segregation between species from wet vs. dry environments in relation to their functional traits, suggesting that water availability could be a strong predictor of species functional composition in the different Amazonian environments. Also, the xylem of dry-habitat species are more embolism resistant, but it may not be correct to assume that these species will be the ones performing better under a warmer and drier climate./nThe second chapter assesses plant physiological performance during a strong El Niño. This is the first study in the Amazon to measure in situ tree physiological stress before, during and after a natural drought event. I show that the warmer and drier conditions imposed by the El Niño greatly amplified trees’ physiological stress and could affect growth, phenology and potentially lead to tree mortality. Given the extreme nature of the this El Niño and that temperatures are predicted to increase in the tropics, this work can serve as a case study of the possible impact climate warming can have on tropical trees./nIn the third chapter, I analyzed the diurnal patterns of stomatal conductance, water potential, and sap velocity during the dry season and investigate how they change with canopy temperature and vapor pressure deficit. I found that unlike preview reported, plants have a re-hydration period during the hottest time of the day probably due to an imbalance between stem sap-velocity and leaf transpiration rates. This study helps to elucidate the array of processes influencing diurnal patterns of plant-water balance in tropical trees.

Advisor: Dawson, Todd E
Implementation of a Rotationally Symmetric Ring Ion Trap and Coherent Control of Rotational States

In this thesis, I present the design, implementation, and characterization of a novel, rotationally symmetric ion trap. Our compact design creates a toroidal trapping potential for charged atoms that has a radius that is much smaller than the height at which the ions are positioned above the surface of the trap. We trap ions at a height of 385~$\mu$m and a radius of 45~$\mu$m as expected from simulation. We demonstrate that this ring is rotationally symmetric with imperfections in the potential of much less than 3~mK./nWith two ions contained in a point Paul trap, we demonstrate the creation of a 100~kHz rotating ring using a rotating quadrupole. By releasing the quadrupole potential, we demonstrate the ability to create superpositions of rotational states using the modulation of the laser light produced by the classical rotation of the crystal in a symmetric potential. Superpositions of rotational states differing by up to four quanta are observed./nWith these rotational superpositions, we describe an experiment capable of observing the identical nature of two ions in a Coulomb crystal. By creating a rotational interferometer, one can coherently exchange two particles and observe their interference upon recombination. We describe what this interference signature would be and how particle indistinguishability would affect it. We present experimental efforts towards realizing this exchange and reflect on our unexpectedly short rotational superposition coherence times.

Advisor: Haeffner, Hartmut
Reconsidering Dispute Resolution in Saudi Arabia: A Comparative Study of Consumer Arbitration and Class Action’s Mechanism

Consumer arbitration can act as a vehicle for bringing justice against corporate misconduct. There is a proliferating global trend toward confirming an unprejudiced system of collective redress. In the context of consumer arbitration, class action is a prime example of a legal mechanism that supports the weaker party by giving a group of people an option to present their claims in front of an arbitral tribunal. Enabling consumers to use this mechanism can cultivate a just system with a healthy balance between businesses and consumers. The purpose of this paper is to define an adequate device that can be fair to consumers while also protecting the interests of businesses. The ultimate goal is for such a framework to be incorporated in Saudi Arabia./nThe current framework is not as effective as consumers in Saudi prefer to use social media as an outlet instead of adjudicating disputes. Through a comparative analysis methodology, this paper conducts a search for a compromise that can protect consumers’ rights while also acting as an incentive to attract foreign investment. There are two distinct paradigmatic approaches to the areas of consumer arbitration and collective action. Some jurisdictions’ practices could be viewed as favoring businesses at the expense of consumers by focusing on enforcing a pre-dispute arbitration clause. Moreover, such contracts mostly exclude the use of class action. On the other end of the spectrum, other jurisdictions concentrate on the protection of consumers from the misuse of contracts of adhesion by businesses, and they even consider arbitration unfair if the clause was not negotiated after the dispute. In view of these points, the best choice is seemingly to default to arbitration with an opt-out option in addition to an implemented class-action mechanism. These objectives are proposed to further economic and legal development in Saudi Arabia.

Advisor: Tyler, Amanda
Leveraging Mobile Technology and Financial Incentives to Increase Non-Communicable Disease Screening Rates in Tanzania

The epidemiological transition has resulted in an increased burden of non-communicable diseases throughout lower- and middle-income countries (LMICs). As countries adapt to this new environment, they must find cost-effective ways of screening for and treating these diseases. With the proliferation of mobile technology as well as the increased evidence for the effectiveness of cash transfers, a randomized-controlled trial in rural Tanzania was conducted to examine the usage of an SMS-based approach of informing individuals of the dangers of non-communicable diseases and offering financial incentives for hypertension screening. The study originally included 961 participants randomized into two treatment arms and a control arm across three villages. The treatment arms received text messages notifying them of the importance and availability of screening at their local dispensary. One treatment arm also received two thousand Tanzanian shillings if they came in for a visit. The study was rolled out to the three villages over the course of seven weeks. Beyond estimating the overall impact of this program and the utility of negative prices, the study design enabled the measure of spillover to individuals who were not initially enrolled in the experiment. Further, information on social networks was leveraged to estimate the impact of not being treated but knowing someone who was. Without accounting for spillover when analyzing the impact of the intervention, impact is significantly underestimated. The results that lack any control for network or spillover effects show a six to eight percentage point change in screening behavior, whereas accounting for them shows a thirty percentage point impact. This effect is largest for those in the cash arm who knew other people in the same treatment arm. There is also a negative effect on screening for individuals in the cash arm who knew people in the information arm. Therefore, the study suggests both the potential viability of using SMS-based approaches with cash transfers to increase non-communicable disease screening as well as a need to better understand the network effects associated with such a program. Importantly those designing randomized controlled trials should account for the possibility of network interactions when selecting their samples.

Advisor: Gertler, Paul
Injection and Plasma Waveguides for Multi-Stage Laser Plasma Acceleration

Laser plasma accelerators (LPAs) have shown promise as the next generation of compact particle accelerators. When a high intensity laser pulse propagates through a plasma, the laser can drive a large-amplitude wave which supports accelerating and focusing electric fields. Acceleration gradients three orders of magnitude greater than those found in conventional accelerators have been demonstrated. However, before an LPA-based high energy collider can be built, several advancements are still necessary, including further increases in beam energy and improvements in beam quality./nWhile electron beams have been accelerated to 8 GeV in a 20 cm LPA, the energy gain in a single LPA stage is limited by the laser energy available. To reach the energies needed for high energy physics, coupling of many LPAs is required. In addition, the beams must be injected and accelerated with high beam quality to reach the luminosities needed at the collision point to produce enough events to search for new physics. While enormous progress has been seen in the acceleration of electrons, positron acceleration is more challenging because most of the existing LPA structures are less suitable for positively charged particles./nIn this thesis, we demonstrate staging of two laser plasma accelerators, injecting electrons in one stage and post-accelerating them in a second. We discuss the development of a high-quality injector stage and demonstrate techniques for controlling the injected electron beam parameters by modifying the plasma density profile. Finally, we detail a novel LPA structure which has demonstrated low-power laser guiding and has the potential to accelerate both electrons and positrons with high quality.

Advisor: Leemans, Wim
Shapiro, Marjorie
Approximation and Hardness: Beyond P and NP

The theory of NP-hardness of approximation has led to numerous tight characterizations of approximability of hard combinatorial optimization problems. Nonetheless, there are many fundamental problems which are out of reach for these techniques, such as problems that can be solved (or approximated) in quasi-polynomial time, parameterized problems and problems in P./nThis dissertation continues the line of work that develops techniques to show inapproximability results for these problems. In the process, we provide hardness of approximation results for the following problems./n- Problems Between P and NP: Dense Constraint Satisfaction Problems (CSPs), Densest k-Subgraph with Perfect Completeness, VC Dimension, and Littlestone's Dimension./n- Parameterized Problems: k-Dominating Set, k-Clique, k-Biclique, Densest k-Subgraph, Parameterized 2-CSPs, Directed Steiner Network, k-Even Set, and k-Shortest Vector./n- Problems in P: Closest Pair, and Maximum Inner Product./nSome of our results, such as those for Densest k-Subgraph, Directed Steiner Network and Parameterized 2-CSP, also present the best known inapproximability factors for the problems, even in the (believed) NP-hard regime. Furthermore, our results for k-Dominating Set and k-Even Set resolve two long-standing open questions in the field of parameterized complexity.

Advisor: Trevisan, Luca
Raghavendra, Prasad