VictorJuiz/thesis huggingface dataset:
Using a physical metaphor to scale up communication in virtual worlds [electronic resource]

This dissertation argues that application-level messaging in virtual worlds must have five properties to enable scalability while avoiding the undesirable limitations of existing systems: recipient selection, minimum quality of service, graceful degradation, fine-grained multiplexing and high utilization. To address these issues, the Sirikata system architecture, a new virtual world back-end system, was developed that achieves these five properties. Sirikata's key insight is to leverage the geometric nature of virtual worlds by applying a physical metaphor to communication. Object communication follows an inverse square law, behaving similarly to point-source radio transmitters and receivers. The theoretical scalability results are proven, and some valid approximations are investigated. Then an implementation of a message forwarder that supports a large number of objects and prioritizes traffic using such an inverse square falloff is introduced. Evaluations of Sirikata show that it satisfies the stated requirements, performs better than current virtual worlds, and can closely follow the real-world radio communication analogy. Finally, a range of sample application demonstrates the effectiveness of this approach. Each sample application is coded in the world and studied when the system is loaded.

Advisor: Hanrahan P. M. (Patrick Matthew) primary advisor. Thesis advisor
Levis Philip advisor. Thesis advisor
Rosenblum Mendel advisor. Thesis advisor
Using influence to understand complex systems [electronic resource]

This thesis is concerned with understanding the behavior of complex systems, particularly in the common case where instrumentation data is noisy or incomplete. We begin with an empirical study of logs from production systems, which characterizes the content of those logs and the challenges associated with analyzing them automatically, and present an algorithm for identifying surprising messages in such logs. The principal contribution is a method, called influence, that identifies relationships among components---even when the underlying mechanism of interaction is unknown---by looking for correlated surprise. Two components are said to share an influence if they tend to exhibit surprising behavior that is correlated in time. We represent the behavior of components as surprise (deviation from typical or expected behavior) over time and use signal-processing techniques to find correlations. The method makes few assumptions about the underlying systems or the data they generate, so it is applicable to a variety of unmodified production systems, including supercomputers, clusters, and autonomous vehicles. We then extend the idea of influence by presenting a query language and online implementation, which allow the method to scale to systems with hundreds of thousands of signals. In collaboration with system administrators, we applied these tools to real systems and discovered correlated problems, failure cascades, skewed clocks, and performance bugs. According to the administrators, it also generated information useful for diagnosing and fixing these issues.

Advisor: Aiken Alexander primary advisor. Thesis advisor
Engler Dawson R. advisor. Thesis advisor
Ousterhout John K. advisor. Thesis advisor
Using meaningful interpretation and chunking to improve memory [electronic resource] : the case of Chinese characters learning

Learning and retaining Chinese characters are often considered to be the most challenging elements in learning Chinese as a foreign language. Applying the theory of meaningful interpretation, the chunking mnemonic technique, and the linguistic features of Chinese characters, this study examines whether the method of meaningful interpretation and chunking (MIC) can promote learners' immediate learning and retention of Chinese characters. Mandarin Chinese learners at two high schools were randomized into a treatment and a control group. Students varied by language level of study (second, third, and fourth year of Mandarin) and whether they were heritage learners of Mandarin or not. Students in the treatment group learned Chinese characters with the MIC method, whereas their peers in the control group learned characters by the traditional method of rote repetition according to the stroke order. Four balanced character sets were introduced each day for 4 continuous days with 3 different interventions: teacher-instructed method on Day 1, teacher-cued method on Day 2, and students' independent work on Day 3 and Day 4. Students' learning outcomes of the characters were measured with (a) immediate quizzes given each day after instruction, (b) a retention test (after 1 week) that integrated all immediate quizzes, and (c) an application test administered 2 months after the experiment to determine whether the students could apply the MIC method to their own learning of Chinese characters. The findings suggest that meaningful interpretation and chunking enhances learners' immediate learning and retention of Chinese characters. Additionally, the teacher-cuedmethod and familiar independent work were more effective for learning and retaining Chinese characters than the teacher-instructed method and unfamiliar independent work. However, the treatment effect of the MIC method disappeared in the application test when students were tested 2 months following the study. Furthermore, the treatment effect also varied across the measurement components (meaning versus perception), levels of instruction, and heritage versus non-heritage groups. Based on these findings, implications for future research and teaching practices are suggested.

Keywords: Education.
Advisor: Padilla Amado M. primary advisor. Thesis advisor
Hakuta Kenji advisor. Thesis advisor
Schwartz Daniel L. advisor. Thesis advisor
The validity of classical nucleation theory and its application to dislocation nucleation [electronic resource]

Nucleation has been the subject of intense research because it plays an important role in the dynamics of most first-order phase transitions. The standard theory to describe the nucleation phenomena is the classical nucleation theory (CNT) because it correctly captures the qualitative features of the nucleation process. However potential problems with CNT have been suggested by previous studies. We systematically test the individual components of CNT by computer simulations of the Ising model and find that it accurately predicts the nucleation rate if the correct droplet free energy computed by umbrella sampling is provided as input. This validates the fundamental assumption of CNT that the system can be coarse grained into a one dimensional Markov chain with the largest droplet size as the reaction coordinate. Employing similar simulation techniques, we study the dislocation nucleation which is essential to our understanding of plastic deformation, ductility, and mechanical strength of crystalline materials. We show that dislocation nucleation rates can be accurately predicted over a wide range of conditions using CNT with the activation free energy determined by umbrella sampling. Our data reveal very large activation entropies, which contribute a multiplicative factor of many orders of magnitude to the nucleation rate. The activation entropy at constant strain is caused by thermal expansion, with negligible contribution from the vibrational entropy. The activation entropy at constant stress is significantly larger than that at constant strain, as a result of thermal softening. The large activation entropies are caused by anharmonic effects, showing the limitations of the harmonic approximation widely used for rate estimation in solids. Similar behaviors are expected to occur in other nucleation processes in solids.

Keywords: Physics
Advisor: Cai Wei
Osheroff Douglas D. primary advisor. Thesis advisor
McIntyre Paul Cameron advisor. Thesis advisor
Nix William D. advisor. Thesis advisor
Validity of value-added estimation [electronic resource] : investigations into meaning and measure

Despite the growing use of "value-added" estimation to capture the contribution of a specific school or teacher to student achievement, there is still much debate about what exactly value-added estimates capture, and if these estimates are reliable enough to use for policy-purposes. As a whole, my dissertation examines the implications of choices we make as researchers about value-added modeling, especially for use in education accountability policies. Rarely do the details of statistical modeling play such a direct role in shaping policy. Producing valid value-added estimates is crucial to both the perceived fairness and ultimate success of any policy that relies on these measures. Here, a blunt use of statistics can undermine the efforts of struggling schools or teachers and hinder our ability as researchers to learn from places that do actually stimulate large growth in student learning. Thus, it is the crucial role of researchers in this field to both develop and be critical of the methods for obtaining valid value added estimates. In my dissertation, I explore three facets of value-added modeling, which together generate a deeper knowledge of how such measures should be created and used.

Keywords: Education.
Advisor: Reardon Sean F. primary advisor. Thesis advisor
Bryk Anthony S. advisor. Thesis advisor
Loeb Susanna advisor. Thesis advisor
Variational analysis of electrowetting on dielectric configurations [electronic resource]

This thesis considers a perfectly conducting fluid drop resting on a dielectric in the presence of an applied electric field. We first review background concepts, emphasizing the central role of mean curvature and Young's equation in capillarity. We then review prior work on this problem, which includes the classical Young-Lippmann equation as well as more modern approaches. Our analysis of this problem uses techniques from the calculus of variations to find the minimum energy configuration. In this way, we rigorously show that the fluid height and the electrostatic potential satisfy a pair of coupled differential equations. Our approach allows us to interpret the equation for fluid height geometrically; in particular, we analyze the effects of dielectric breakdown, finite volume, and the divergent field on the mean curvature of the fluid. We compare our analysis to a simplified spherical cap model and then develop the theory of partially conducting drops. Finally we construct an iterative algorithm to successively approximate both the drop shape and electric field, and we develop estimates for important parameters. The algorithm numerically finds that the contact angle saturates with increasing applied voltage, an improvement over the classical Young-Lippmann theory which does not predict saturation. We compare our results with current experiments and find in general qualitative agreement.

Keywords: Electrical Engineering
Advisor: Finn Robert
Dutton Robert W. advisor. Thesis advisor
Solgaard Olav advisor. Thesis advisor
Variation-aware design of carbon nanotube digital VLSI circuits [electronic resource]

Carbon Nanotube Field Effect Transistors (CNFETs) are excellent candidates for building highly energy-efficient future electronic systems. Variations specific to carbon nanotubes (CNTs) pose major obstacles to energy-efficient and robust CNFET digital VLSI. CNFET circuits can suffer from large performance variations, reduced yield, and increased susceptibility to noise. CNT processing techniques alone are inadequate to overcome these challenges. We present an integrated approach, combining CNFET modeling, processing and circuit design, to create VLSI circuits tolerant to CNT variations. Probabilistic models, calibrated using experimental data, are used to analyze the effects of two major sources of CNT variations: metallic CNTs (CNTs with no / very small bandgaps) and grown CNT density variations (due to the non-uniformity in CNT positioning). Using these models, we create a probabilistic framework to derive simple yet useful CNFET processing and circuit design guidelines to overcome CNT variations. The effectiveness of this approach is demonstrated using two examples: 1. CNT variations result in functional failures of CNFET circuits. The failure probability may be reduced through CNFET sizing but at substantial energy costs. A new layout design technique, which engineers correlation among various CNFETs, reduces CNFET circuit failure probability at significantly lower costs. 2. For the first time, the impact of CNT variations on delay variations of CNFET circuits is quantified. We explore the space of CNFET sizing, together with various possibilities to improve CNFET processing, to minimize circuit delay variations at low energy costs.

Keywords: Electrical Engineering
Advisor: Mitra Subhasish primary advisor. Thesis advisor
Howe Roger Thomas advisor. Thesis advisor
Wong Hon-Sum Philip
View inside the barrel [electronic resource] : insights into the group II chaperonin folding mechanism

Chaperonins are a unique class of molecular chaperone that assist in the folding of newly synthesized, partially folded, and misfolded proteins. The importance of these folding machines is evident by their conservation across all three branches of life. The general structure of the chaperonins consists of 14-18 subunits, which form two back-to-back cavities. Unfolded polypeptide substrate is captured in one of the two cavities, and assisted to its native conformation in an ATP dependent fashion. The chaperonins can be separated into two, related, but unique groups. The group I chaperonins, typified by GroEL from bacteria, are fairly well understood, however, there are substantial gaps in our knowledge of the group II chaperonins, such as TRiC from the eukaryotic cytosol. Gaining a mechanistic understanding of the group II chaperonins is of great importance, as it has been shown that TRiC malfunction is associated with a variety of diseases. Toward this end the group II chaperonin conformation cycle, ATPase, and substrate folding mechanism have been investigated. This work elucidates key components of the folding cycle and greatly increases our understanding of these folding machines.

Keywords: Biological Sciences
Advisor: Frydman Judith primary advisor. Thesis advisor
Nelson W. J. (W. James) advisor. Thesis advisor
Puglisi Joseph D. advisor. Thesis advisor
Wandless Thomas advisor. Thesis advisor
Viewing the Han Empire from the edge [electronic resource]

This dissertation examines in the continental context the building and maintenance of the Han state, which existed in the Yellow and Yangtze Rivers regions roughly from the second century B.C.E. to the second century C.E. It surveys the trajectory that transformed the Han state from a regional polity confined to the Yellow and Yangtze Rivers regions to a trans-regional superpower, exerting its influence across East Eurasia. I focus specifically on the interstate interaction between the Yellow River region (the Han), on the steppe (the Xiongnu), and in the Tarim Basin (multiple oasis-states) from the beginning of the second century B.C.E. to the early first century C.E. as my case study. Making use of both transmitted and excavated Han texts, I demonstrate that two major mechanisms facilitated the transformative process of the Han state in the political landscape of East Eurasia. One was horizontal kin ties between the Han emperor and peer rulers. The other was the vertically-structured imperial bureaucracy that organized communities in the Yellow and Yangtze Rivers regions for imperial power-building. In particular, the imperial bureaucracy evolved into the nodal mechanism to sustain imperial initiatives. On the one hand, it vertically incorporated into its writing-based system individuals of diverse social, cultural, and geographic backgrounds in the Yellow and Yangtze Rivers regions as the support base of the Han emperor. On the other hand, it horizontally facilitated the emperor's kinship-based alliance network across East Eurasia. This bureaucratic mechanism became the backbone that continued to weave together complex communities in the Yellow and Yangtze Rivers regions regardless of the rise and fall of ruling houses.

Keywords: History.
Advisor: Lewis Mark primary advisor. Thesis advisor
Sommer Matthew Harvey
Vinograd Richard Ellis advisor. Thesis advisor
Violent order [electronic resource] : rebel organization and Liberia's civil war

Rebel groups exhibit significant variation in their treatment of civilians, with profound humanitarian consequences. This dissertation proposes a new theory of rebel behavior and cohesion based on the internal dynamics of rebel groups. Rebel leaders have incentives to provide security, but are often unable to prevent group members from abusing civilians. Leaders exert effective control over their troops when they can offer cash payments and credible future rewards to their top commanders. Leaders who cannot offer these incentives allow their forces to loot locals in exchange for a minimal level of loyalty. The leader's ability to offer incentives that allow local security to prevail depends on partnerships with external actors such as diaspora communities and foreign governments. When these patrons have a stake in the group's success, they are motivated to supply financial resources to qualified, trusted leaders. Other patrons have goals that conflict with those of the rebel client. These patrons exert leverage over the rebels by supporting low quality leaders and withholding resources that could strengthen leader control, resulting in more abusive, faction-prone groups. The type of partnership available depends on factors beyond the group's control. The dissertation formalizes this theory and tests the implications in various ways, using an original cross-national dataset of rebel groups, 1980-2003, as well as a micro-level dataset of crop area during Liberia's war, derived through remote sensing. The dissertation also traces the model's logic through a detailed analysis of Liberia's rebel groups, based on fourteen months of fieldwork and interviews with nearly all surviving rebel leaders and top commanders who participated in Liberia's war, 1989-2003.

Keywords: Political Science
Advisor: Laitin David D. primary advisor. Thesis advisor
Fearon James D. advisor. Thesis advisor
Weinstein Jeremy M. advisor. Thesis advisor
Visitors encounter the dust [electronic resource] : how people think with objects in a history museum exhibition

The role objects play in a museum visitor's experience is much debated (Conn, 2010). This study offers an empirical look at how visitors think with objects in a history museum exhibition. To study the phenomenon a new method, called the "head camera protocol, " was introduced. Participants in the study wore a hat outfitted with a video camera and microphone, and were instructed to think aloud as they explored an exhibition. The resulting video constituted the head camera protocols that were analyzed. The exhibition studied was called Elegy in the Dust: September 11th and the Chelsea Jeans Memorial. On display at the New-York Historical Society in 2006-2007, it was built around a primary object called the Chelsea Jeans Memorial—a portion of a jeans store covered in dust and ash from the events of September 11th. The exhibition also contained photographs of September 11th and its aftermath, as well as video of the store owner who donated the Chelsea Jeans Memorial to the Historical Society. This study profiles seven participants who walked through the exhibition. Among them were two material culture historians, two tourists, and three Ground Zero volunteers. The findings show how visitors think with their bodies and their multiple selves. The study also offers an empirical look at how visitors interact with Walter Benjamin's notion of an object's "aura" (1935/1968). "Historical thinking with objects" is defined and a visitor--object interaction model is proposed. Finally, implications for the design of learning environments generally, and history museums specifically, are addressed.

Keywords: Education.
Advisor: Wineburg Samuel S. primary advisor. Thesis advisor
Barron Brigid advisor. Thesis advisor
Goldman Shelley V. advisor. Thesis advisor
Pea Roy D. advisor. Thesis advisor
The visual consequences of language comprehension [electronic resource]

How do we understand language? What kinds of representations do people form when hearing a story or when reading a paragraph? In this dissertation, I will explore how people make meaning out of the language that they read or hear. One possibility is that the words we read or hear engage perceptuomotor representations, and language comprehension arises from modality-specific simulation or imagery of the linguistic content. Strong versions of the modality-specific approach assume complete overlap between the representations generated by language and those generated by perception and action. Perhaps representations brought about by language only partially overlap and interact with perception and action, with clear limits, and with important differences along the continuum from concrete to abstract language. The studies presented in this dissertation aim to delineate where perception and language understanding share representations and processing resources, and where they diverge. The findings suggest that language understanding affects visuospatial processing (Chapter 2) and visual motion processing (Chapter 3), but to a lesser extent than does perception itself.

Keywords: Psychology
Advisor: Boroditsky Lera primary advisor. Thesis advisor
Clark Herbert H. advisor. Thesis advisor
McClelland James L. advisor. Thesis advisor