VictorJuiz/thesis huggingface dataset:
Biomechanics of hovering vertebrates

Insects, hummingbirds, and nectar bats evolved the ability to hover in front of flowers to get access to energy-rich nectar. It has been established that insects generate up to half of the lift needed to support their body weight during the upstroke. Estimates show that hummingbirds generate at least a quarter of their weight support during the upstroke by inverting their feathered wings more than generalist birds. In contrast, bats evolved membrane wings that they partially fold during the upstroke. While it has been hypothesized that hovering nectar bats generate vertical lift force during the upstroke, the complex structure of their wakes makes it hard to quantify this through flow measurement. To understand how hummingbirds and bats manipulate aerodynamic forces with their wings to perform these feats, we developed a new instrument that accurately measures these aerodynamic forces in vivo. This Aerodynamic Force Platform and an array of 3D-calibrated high-speed cameras simultaneously recorded the vertical aerodynamic forces and wing kinematics. The pressure field generated by the animal travels to the boundaries of the flight volume at the speed of sound. The top and bottom plate mechanically integrate the pressure distribution, which is measured by three force sensors on each plate. By using the Aerodynamic Force Platform to measure these wingbeat-resolved aerodynamic lift forces in vivo, we highlight similarities and differences across species and taxa. While it is known that insects improve efficiency by using elastic recoil for stroke reversal, it is unclear if hummingbirds converged on a similar solution, due to asymmetries in their lift generation and specialized flight muscle apparatus. We measured the aerodynamic force and kinematics of Anna's hummingbirds to resolve wing torque and power within the wingbeat. Comparing wingbeat resolved aerodynamic weight support measurements across species, we find that hummingbirds have low induced power losses similar to flies, much lower than typical for a generalist bird in slow hovering flight. We also show how hummingbirds' early muscle activation furnishes elastic recoil through stroke reversal to stay within the physiological limits of the pectoralis and supracoracoideus flight muscles. Expanding our species of interest, we traveled to Costa Rica with our new measurement device. We resolved the aerodynamic force and wing kinematics of 104 slow hovering hummingbirds and bats across 20 total species in vivo. While all hummingbirds we studied converged on an efficient horizontal wingbeat with an active upstroke to generate lift, the bats did not---they relied on drag to fully support their body weight. Remarkably, the nectar bats generate a significantly elevated vertical force during the upstroke compared to fruit bats---by inverting their wing more like hummingbirds---suggesting convergent evolution.

Keywords: Mechanical Engineering.
Advisor: Lentink David
Dabiri John O. (John Oluseun)
Okamura Allison
Black and white meets blue : race and the social psychology of police-community interactions

In this dissertation, I examine how everyday interactions between police officers and community members build or erode trust along racial lines. In contrast to past social psychological approaches, which have narrowly focused on racial biases in officers' decision making, I advance an alternative framework for understanding these encounters: as institutional interactions. In Chapter 1, I outline this framework, which centers the interactions between institutional agents (e.g., police officers, teachers, doctors), and participants (e.g., citizens, students, patients). Like other intergroup interactions, these encounters bring together perspectives in a dynamic that unfolds across time. However, these interactions are unique in their institutional nature. Police officers are simultaneously individuals and extensions of the state, and act using a combination of their own discretion and departmental guidance. This dual role shapes both officer behavior and citizen experiences in the most common way in which citizens come into contact with the criminal justice system: as the subject of a traffic stop. A distinctive feature of vehicle stops is that the interaction occurs at the officer's discretion; that is, as a result of their decision to pull over a driver. In Chapter 2, I demonstrate that this discretionary context frames interactions in different ways for White and Black community members, shaping their construal of police encounters. In Chapter 3, I analyze racial disparities in the discretionary context of stops, demonstrating that, relative to White drivers, Black drivers are more likely to be stopped in circumstances where the justification for the stop is unclear and the officers' motives more discretionary in nature. I further establish that these disparities vary across departments, and are sensitive to changes in departmental policies. In Chapters 4 and 5, I turn to racial disparities in the content of interactions: how police officers communicate with drivers during traffic stops. In these chapters, I examine racial disparities in the respect that officers' language (Chapter 4) and tone of voice (Chapter 5) connote to drivers, as well as how officers' interpersonal communication influences how citizens' construal of police institutions. To conclude the dissertation, I highlight areas for future research within the institutional interactions framework, along with of implications of the theory for interventions to reduce racial disparities in policing.

Keywords: Psychology.
Advisor: Eberhardt Jennifer L. (Jennifer Lynn) 
Markus Hazel Rose 
Walton Gregory M. (Gregory Mariotti)
Braindrop : a mixed-signal neuromorphic architecture with a dynamical systems-based programming model

This thesis describes the architecture of Braindrop, a .85 square-millimeter, 4096-neuron, low-power, mixed-signal neuromorphic system. Braindrop is the first such system designed with a comprehensive set of high-level programming abstractions and a synthesis procedure for mapping them to mismatched (and temperature-sensitive) subthreshold analog hardware. This high level of abstraction stands in stark contrast to previous neuromorphic systems, which required expert knowledge (and extensive characterization) of the hardware to use. Braindrop's computations are specified as coupled nonlinear dynamical systems. This program specification is synthesized to the hardware using the Neural Engineering Framework, not just compensating for, but leveraging the fabric of mismatched analog circuit elements as dynamic computational primitives. For typical network configurations, Braindrop achieves an energy per equivalent synaptic operation of 388 fJ.

Keywords: Electrical Engineering.
Advisor: Boahen Kwabena (Kwabena Adu) 
Manohar Rajit 
Olukotun Oyekunle Ayinde
Building a Nanophone: Detecting Surface Acoustic Waves with an Optomechanical Cavity

A technique is presented for detecting surface acoustic waves on a Silicon-on-Oxide chip using a nanomechanical resonator coupled to an optical cavity. Recent advances in cavity optomechanics have generated interest in using on-chip devices for a variety of practical applications, creating a new way to design mass or force sensors, on-chip LIDAR systems, and Bragg cells to name a few. These devices have the dual benefit of being extremely sensitive and relatively easy to integrate with other silicon photonic or electrical components. In this paper, we attempt to photoacoustically excite surface acoustic waves (or SAWs) on chip by focusing a small laser beam on a thin film of aluminum. Then, we try to use a fin cavity device, comprised of an optical waveguide with two mechanical fin resonators on either side, to measure any resulting SAWs. Essentially, we aim to create an extremely sensitive SAW microphone. We determine that it is possible to detect the increased intensity fluctuations on the mechanical resonator due to its interaction with waves generated from a photoacoustic event. However, at this time we cannot prove that we have evidence of SAW detection. There are many promising applications of a SAW microphone; among them is the possibility to resolve individual chemical reaction events by ‘listening’ for their SAW signature. A device that is capable of sensitive SAW measurement would be of great interest to those studying chemical reactions, small biological processes, and RF electronics.

Keywords:  Department of Physics
Cavity
Optomechanics
Optomechanical
Physics
Applied Physics
Surface Acoustic Wave
SAW
detector
fin waveguide
fin
fin cavity
mechanical resonator
photoacoustic
photo
acoustic
Thesis
Advisor: Safavi-Naeini Amir
Hollberg Leo
Building empathy through psychological interventions

Empathy—the ability to share and understand others' emotions—is a social bridge that connects people to one another. It facilitates important outcomes including prosocial behavior, emotional wellbeing, and social centrality, and reduces harmful social forces like prejudice and bullying. Given these benefits, researchers have tried to increase empathy through intervention, often developing a person's empathy-related skills like emotion recognition and empathic communication. But skills-related interventions overlook an essential determinant of empathy: people's desire to empathize. I propose that increasing people's motivation to empathize through psychological intervention can create enduring and generalizable changes in empathy that practically benefit people's social and emotional lives. In this dissertation, I design, administer, and evaluate novel, motivation-based empathy interventions within two populations undergoing significant life changes: college freshmen (chapter 2) and seventh graders (chapter 3). I find that these interventions addressing people's mindsets of empathy or their perceptions of the social normativity of empathy differentially elicit changes in empathy and social behavior in these two groups. These data suggest that shifting motivation related to empathy is a promising new tool for improving social and emotional outcomes during important developmental periods.

Keywords: Psychology.
Advisor: Zaki Jamil
Dweck Carol S.
Gross James J.
Building markets within authoritarian institutions : the political economy of banking development in China

This dissertation studies the development of the banking system in China, the world's largest. Specifically, it examines why and how the banking market has become diverse and competitive, and the economic consequences of this process. The case is puzzling and important for political science because contrary to the existing literature, none of the formal institutions commonly associated with financial development—those that credibly constrain state power—is present. I argue that what happened in China is an outcome not of financial liberalization but of state engineering. In lieu of full-fledged market opening, Beijing mobilized and incentivized its local state agents to enter the banking market as competitors. While the new local state banks (LSBs) are distinct profit-maximizing players, their organizational structure and institutional missions are modeled explicitly after those owned by the central state. I call this model of banking market development "organizational spinoff." Through this approach, the Chinese state has managed to capture gains from a more competitive albeit internal market while maintaining political monopoly over it. In essence, organizational spinoff has enabled the state to avoid the conventional commitment game with private financiers, which would have required tying its own hands to entice market entry while risking losing financial control. This dissertation makes several contributions to the study of political economy and Chinese politics. Substantively, it contributes to our understanding of market development in autocracies. Analytically, it highlights the limits of modeling autocracies as unitary actors and shows the utility of an organizational approach. Methodologically, it introduces spatial and experimental methods to the study of the political economy of finance. Finally, it is the first to systematically trace the evolution of China's banking system, the complexity of which has thus far been masked by the simple term "state-owned, " thereby shedding new light on policy making and central--local politics in reform China.

Keywords: Political Science.
Advisor: Oi Jean C. (Jean Chun) 
Haber Stephen H.
Lipscy Phillip Y.
Bureaucracy and networks : the politics of career mobility in large organizational systems

Career mobility in state bureaucracy is an important topic with key implications for policy, development, and labor market dynamics. Existing literature on organizations emphasizes the importance of experience and network connections, whereas careers develop as linear progression in internal labor markets. The standard theories, however, commonly suffer from three issues. First, whereas network research focuses on static effects of connections, I point out the dynamic impacts of connections: the same tie that used to bring career benefits can carry inherent risks in an evolving authority structure. Second, whereas the assumption of linear job ladders prevails in internal labor market theories, I find that such functional ladders rarely exist in large bureaucracies. Third, one of the most challenging issues in organizational research is the limited scope condition, as studies typically focus on a single market or institutional setting. Using unique administrative data from the state bureaucracy of China and the Indian Administrative Service, I tackle these theoretical problems with novel empirical strategies, combining techniques from network analysis, quasi-experiment, and stochastic models. The findings challenge the standard theories, bringing out the contextual variations between organizations in different political systems.

Keywords: Sociology.
Advisor: Walder Andrew G. (Andrew George)
Zhou Xueguang
Jackson Matthew O. 
Powell Walter W.
Call Collect: Enabling any journalist to gather audio from the public

Call Collect is an open source web application for gathering audio. It helps journalists quickly create call-in numbers and simple web widgets where people can record themselves. It's designed so that any newsroom can set up its own copy of the software easily and affordably.

Keywords:  Department of Communication
Stanford
communication
department of communication
journalism
audience engagement
audience participation
hotline
vox populi
call
call-in
audio
podcast
radio
recording
collect
crowdsource
crowdsourcing
Thesis
Advisor: Nguyen Dan
Camera design optimization using image systems simulation [electronic resource]

In this thesis I use physically accurate, end-to-end camera simulation environment to explore different imaging system architectures and to co-optimize the acquisition hardware with computational imaging and computer vision algorithms. The simulation tools use 3D modeling to create different scene models. Scene images that are projected onto the sensor are computed with ray tracing tools. Finally, realistic sensor and camera pipeline simulators compute pixel values that can be used by subsequent computational photography or vision algorithms. I use the simulation tools to optimize the spectral characteristics of cameras and lights used to collect data for inverse estimation methods that characterize surface spectral properties. I show that appropriately selected narrowband lights improve the performance of pixel based surface classification. I also propose a new algorithm that extends beyond narrowband light selection by computing the spectral power distribution of light that is optimal for such classification tasks. I further use simulations to guide and optimize the design of a system that characterizes fluorescent materials which interact with incident light in more complex ways than simple reflection. Spectral illuminant optimization is also useful in consumer photography. I describe a spectrally tunable flash and computational algorithms that can be used to efficiently estimate the ambient illuminant spectrum and to improve the color reproduction of captured images. Such flash is particularly useful when capturing images under extreme ambient lights, for example in underwater photography. The end-to-end nature of the simulation tools makes it possible to explore how viewing conditions (e.g. light level, spectral content, depth), hardware components of an imaging system (e.g. optics, sensor QE, filters, pixel and noise properties) and image processing pipelines affect both the perceived image quality of camera images and the ability of machine learning algorithms to detect and classify objects. I use simulation to render large collections of images in order to evaluate the object detection performance of convolutional neural networks (CNNs) . I demonstrate that the performance of CNNs trained using images that are generated by simplified image processing pipelines (ISP) is similar to the performance of CNNs trained using images generated by more complex and time-consuming ISPs optimized for consumer photography. I also explore and quantify the robustness and performance bounds of detection methods against fundamental algorithms controlling camera exposure and focus.

Keywords: Electrical Engineering.
Advisor: Wandell Brian A. primary advisor. Thesis advisor
Farrell Joyce E.
Girod Bernd advisor. Thesis advisor
Wetzstein Gordon advisor. Thesis advisor
Capoeira and Community in Grupo Besouro

Capoeira is seen as a martial art, a dance, a game, and a music. Shaped by slavery and official repression throughout the 19th and early 20th century in Brazil, it is uniquely Brazilian, but at the same time, many capoeiristas acknowledge its afro-centricity. Often called a jogo, or game, two players use kicks, evasive maneuvers, leg sweeps, counterattacks and balances on their hands and head to resist the other’s advances while an instrument ensemble plays capoeira music and sings around them. Through my thesis, I argue that Capoeira Besouro, a capoeira school in Rio de Janeiro, Brazil, functions as a For Us, By Us community center that strengthens the surrounding community and creates community leaders. Furthermore, the capoeira school serves as an grassroots alternative educational space that passes on a black-centric narrative, passing on Afro-Brazilian musical, cultural, and artistic traditions. For my Senior Thesis in CSRE, I will be using the framework of Django Paris and H. Samy Alim’s theory of Culturally Sustaining Pedagogies to explore and offer insights into the community practices of Grupo de Capoeira Besouro.

Keywords: Capoeira
Culturally Sustaining Pedagogies
Brazil
Rio de Janeiro
CSRE
Comparative Studies for Race and Ethnicity
Stanford University
IDA
Institute for Diversity in the Arts
Thesis
Capturing human behavior and language for interactive systems

From smart homes that prepare coffee when we wake, to phones that know not to interrupt us during important conversations, our collective visions of human-computer interaction (HCI) imagine a future in which computers understand a broad range of human behaviors. Today our systems fall short of these visions, however, because this range of behaviors is too large for designers or programmers to capture manually. In this thesis I will present three systems that mine and operationalize an understanding of human life from large text corpora. The first system, Augur, focuses on what people do in daily life: capturing many thousands of relationships between human activities (e.g., taking a phone call, using a computer, going to a meeting) and the scene context that surrounds them. The second system, Empath, focuses on what people say: capturing hundreds of linguistic signals through a set of pre-generated lexicons, and allowing computational social scientists to create new lexicons on demand. The final system, Codex, explores how similar models can empower an understanding of emergent programming practice across millions of lines of open source code. Between these projects, I will demonstrate how semi-supervised and unsupervised learning can enable many new applications and analyses for interactive systems.

Advisor: Bernstein Michael S.
Agrawala Maneesh 
Horvitz Eric J. (Eric Joel)
Carlo: Harnessing the Power of Teacher Feedback Through Improving the Writing Cycle

Students often struggle to implement teacher feedback on their writing, and teachers report that they provide the same feedback time and again. In order to successfully teach the craft of writing, teachers must both provide meaningful feedback to their students and assist them in implementing the feedback they’ve provided. Carlo is an online feedback tool that collects teacher annotations on student writing and generates powerful data visualizations about an individual’s or a class’s areas of strength and growth over time. With Carlo, teachers are able to guide their students in implementing feedback and students are provided the necessary tools to improve their craft and build positive self-identification as writers.

Keywords: Graduate School of Education
Learning Design &amp; Technology
Julia Rubin
formative assessment
feedback
writing development
literacy
learning sciences
Thesis
Catalytic enantioselective dihalogenation of allylic alcohols [electronic resource]

Enantioselective dihalogenation is an important method for the total synthesis of stereocomplex polyhalogenated natural products, but only a few methods with significant limitations currently exist for this transformation. In 2015, we developed the chemo-, regio- and enantioselective bromochlorination of allylic alcohols featuring a titanium half-salen catalyst to help address this problem. The utility of this method has been demonstrated by the enantioselective total syntheses of 11 halogenated natural products to date by our lab, each of which was directly enabled by this method. Following development, we applied the enantioselective bromochlorination to various new substrates including homoallylic alcohols, which resulted in the total synthesis of (--)-anverene, a polyhalogenated marine natural product with modest but selective antibiotic activity. Computational and experimental mechanistic work was undertaken to better understand the catalytic enantioselective bromochlorination, as well as the enantiospecific solvolysis of resulting enantioenriched bromochlorides. The enantioselective dihalogenation catalyst system has also been extended to new reactions using other electrophile-nucleophile pairs, including haloazidation, which uses TMSN3 as the nucleophilic azide source.

Keywords: Chemistry.
Advisor: Burns Noah
Kool Eric T. advisor. Thesis advisor
Trost Barry M. advisor. Thesis advisor
Channel power and rate optimization of nonlinear optical fiber networks

Channel power and rate optimization objectives are examined in nonlinear long-haul optical communication networks. Problems of maximizing the minimum channel margin and maximizing fiber capacity are found to have convex forms. The Kerr nonlinear inter- and intra-channel nonlinear interference is initially modelled via the Gaussian noise nonlinearity model. Valuable performance benefits are obtained in inhomogeneous scenarios including mesh networks. The inhomogeneity introduced by the additional nonlinear impairment of stimulated Raman scattering makes the optimization objective non-convex, but also provides inherent inhomogeneity that supports performance benefits from power optimization. The discrete-rate optimization objective is formulated for maximizing the real-world capacity of optical communication systems with discrete code rates. Efficient heuristic methods are proposed that make use of a sequence of calls to solve the minimum-margin channel power optimization problem. Lastly, the channel power optimization problem is generalized with a model that applies beyond the dispersion-uncompensated domain of the Gaussian noise model. A first-order perturbation-based approach is used for the nonlinear interference modelling.

Keywords: Electrical Engineering.
Advisor: Kahn Joseph M. (Joseph Mardell) 
Lall Sanjay 
Miller D. A. B.