VictorJuiz/thesis huggingface dataset:
Subgrid-scale turbulence modeling for improved large-eddy simulation of the atmospheric boundary layer [electronic resource]

Large-eddy simulation (LES), as the name suggests, resolves the large eddies in the flow while modeling the effects of smaller motions (turbulence) on those larger eddies. Powerful computers make LES increasingly practical for analyzing a variety of atmospheric behavior in more detail, creating a need for more realistic turbulence models. Advances in describing atmospheric turbulence can impact many disciplines, e.g., weather and climate prediction, wind energy production, ocean dynamics, and, indeed, even computational fluid dynamics itself. Although the turbulence model can significantly affect the accuracy of the LES, simple turbulence models, which are known to be less accurate, are widely used. As an alternative, the Generalized Linear Algebraic Subgrid-Scale (GLASS) model, that actively couples momentum and heat transport, was developed. This model is more complete than conventional LES turbulence models because it accounts for additional transport processes. GLASS includes production, dissipation, pressure redistribution, and buoyancy terms. With the inclusion of an actively coupled turbulent heat flux model, GLASS is applicable to a range of atmospheric stability conditions for the unsaturated atmosphere. LES at various resolutions in a neutrally stratified boundary layer flow indicated that the GLASS model is a more physically complete subgrid-scale turbulence model that provides near-wall anisotropies and yields proper velocity profiles in the logarithmic layer. LES of the moderately convective boundary layer demonstrated that GLASS predicted the evolution of resolved quantities at least as well as the LESs with simple models, while including additional physics. Additional simulations of the stable boundary layer and the transitioning boundary layer highlight that GLASS can be applied to various stability conditions without the need of tuning model coefficients.

Keywords: Civil and Environmental Engineering.
Advisor: Street Robert
Jacobson Mark Z. (Mark Zachary) advisor. Thesis advisor
Sullivan Peter advisor. Thesis advisor
Sufficient statistics for team decision problems [electronic resource]

Decentralized control problems involve multiple controllers, each having access to different measurements but working together to optimize a common objective. Despite being extremely difficult to solve in general, a common thread behind the more tractable cases is the identification of sufficient statistics for each controller, i.e. reductions of the measurements for each controller that do not sacrifice optimal performance. These sufficient statistics serve to greatly reduce the controller search space, thus making the problem easier to solve. In this dissertation, we develop for the first time a general theory of sufficient statistics for team decision problems, a fundamental type of decentralized control problem. We give rigorous definitions for team decisions and team sufficient statistics, and show how team decisions based only on these sufficient statistics do not affect optimal performance. In a similar spirit to the Kalman filter, we also show how to gracefully update the team sufficient statistics as the state evolves and additional measurements are collected. Finally, we show how to compute team sufficient statistics for partially nested problems, a large class of team decision problems that tend to have easier solutions. These team sufficient statistics have intuitive and compelling interpretations. We also show general conditions when these team sufficient statistics can be updated without the state growing in size. To illustrate the results, we give examples for finite-state systems and systems whose variables are jointly Gaussian.

Keywords: Electrical Engineering.
Advisor: Lall Sanjay primary advisor. Thesis advisor
Van Roy Benjamin advisor. Thesis advisor
Ye Yinyu advisor. Thesis advisor
Supersymmetric phenomenology at the large hadron collider [electronic resource]

This work investigates signatures of supersymmetry through the phenomenological Minimal Supersymmetric Standard Model (pMSSM), considering the collider and astrophysical implications that minimal supersymmetry may have. We scan over the 19-dimensional parameter space of the pMSSM, considering both the neutralino and gravitino as candidates for the lightest supersymmetric particle. We explore the sensitivity of the Large Hadron Collider to large sets of pMSSM models, and additionally consider the impact that current and future dark matter direct detection, indirect detection, and neutrino telescope experiments would have in constraining the pMSSM.

Keywords: Physics.
Advisor: Hewett JoAnne L. primary advisor. Thesis advisor
Peskin Michael Edward
Rizzo Thomas
Wacker Jay advisor. Thesis advisor
Supersymmetry at the large hadron collider [electronic resource]

Supersymmetry is a well-motivated extension of the Standard Model that can exhibit a wide range of phenomenology. This dissertation explores various supersymmetric models with distinct signatures and discusses the prospects for discovering them using data from the Large Hadron Collider.

Keywords: Physics.
Advisor: Dimopoulos Savas
Graham Peter (Peter Wickelgren) advisor. Thesis advisor
Wacker Jay advisor. Thesis advisor
Surface-normal germanium quantum well modulators for free-space optical interconnects to silicon [electronic resource]

Today's computer systems are constrained by the high power consumption and limited bandwidth of inter- and intra-chip electrical interconnections. Optical links could alleviate these problems, provided that the optical and electronic elements are tightly integrated. Most present optical modulators use materials systems that are incompatible with CMOS device fabrication, or rely on weak electrooptic effects that are difficult to utilize for vertical incidence devices. The extremely high communications bandwidth demands of future silicon chips may ultimately require massively parallel free-space optical links based on array integration of such vertical incidence modulators. We have investigated the suitability of surface-normal asymmetric Fabry-Perot electroabsorption modulators for short-distance optical interconnections between silicon chips. These modulators should be made as small as possible to minimize device capacitance; however, size-dependent optical properties impose constraints on the dimensions. We have thus performed simulations that demonstrate how the optical performance of the modulators depends on both the spot size of the incident beam and the dimensions of the device. We also discuss the tolerance to nonidealities such as surface roughness and beam misalignment. The particular modulators considered here are structures based upon the quantum-confined Stark effect in Ge/SiGe quantum wells. We present device designs that have predicted extinction ratios greater than 7 dB and switching energies as low as 10 fF/bit, which suggests that these CMOS-compatible devices can enable high interconnect bandwidths without the need for wavelength division multiplexing. Next, we present experimental results from these Ge/SiGe asymmetric Fabry-Perot modulators. Several approaches were investigated for forming resonant cavities using high-index-contrast Bragg mirrors around the Ge/SiGe quantum well active regions. These include fabrication on double-silicon-on-insulator reflecting substrates, a layer transfer and etch-back process using anodic bonding, and alkaline etching the backside of the Si substrate to leave suspended SiGe membranes. We present results from each of these modulator structures. The best performance is achieved from the SiGe membrane modulators, which are the first surface-normal resonant-cavity reflection modulators fabricated entirely on standard silicon substrates. Electroabsorption and electrorefraction both contribute to the reflectance modulation. The devices exhibit greater than 10 dB extinction ratio with low insertion loss of 1.3 dB. High-speed modulation with a 3 dB bandwidth of 4 GHz is demonstrated. The moderate-Q cavity (Q~600) yields an operating bandwidth of more than 1 nm and permits operation without active thermal stabilization.

Keywords: Electrical Engineering.
Advisor: Miller D. A. B. primary advisor. Thesis advisor
Brongersma Mark L. advisor. Thesis advisor
Saraswat Krishna advisor. Thesis advisor
Symbolic wages and identity taxes [electronic resource] : upward mobility and middle-class narratives in Chicana/o and Black cultural production

Rooted in an interdisciplinary methodology, Symbolic Wages and Identity Taxes establishes a comparative framework for understanding representations of upward mobility and middle-class status in Chicana/o and black cultural production. By examining novels as well as more widely disseminated media like television and film, I focus on how artists represent upward mobility as a process that illuminates the symbolic and material value of identity. Major works in whiteness studies (Roediger, Harris, Lipsitz, etc.) all focus on whiteness as a form of currency, or wages, that have historically enabled whites to own more property than people of color, assert an elevated social status, and pursue paths of upward mobility. I argue, in contrast, that membership in the middle class for racial minorities can impose a kind of tax in the form of social dues paid when negotiating dual membership in the mainstream and in a racial community. On one hand, the identity tax reveals the impossibility or undesirability of straight-line assimilation into the white mainstream. On the other hand, this tax is also an aesthetic opportunity, as ethnic writers create new kinds of narratives specifically about racialized upward mobility. In chapter one, I examine Dorothy West's The Living Is Easy (1948), Paule Marshall's Brown Girl Brownstones (1957), and Gloria Naylor's Linden Hills (1985) to show how black female writers developed status seeking and artistic figures to represent intergenerational social mobility while questioning its accompanying symbols of success. Chapter two continues to analyze the representation of status along with how upward mobility evokes ambivalence in minority texts. First, I offer three reasons for why there have been so few representations of middle-class status in Chicana/o texts. I then analyze Richard Rodriguez's Hunger of Memory (1982), The George Lopez Show (2001-2007), and Michele Serros's Honey Blonde Chica (2006) as texts that narrate the psychic stresses that accompany minority middle-class identity. In chapter three, I demonstrate how Helena María Viramontes' Under the Feet of Jesus (1994) allegorizes the process that becomes the foundation for a politically conscious upward mobility. Chapter four explicates how three Chicano films--The Gatekeeper (2002), Sleep Dealer (2008), and Machete (2010)-- reinterpret the "sellout" narrative to depict immigration and NAFTA as issues that, by forging ethnic solidarity, can transcend the divisions created by social class. My last chapter examines how Percival Everett's novel, Erasure (2001) imagines a re-emergent "passing" narrative as a template for exploring the experiential and commercial value placed on black lower-class identity. Ultimately, my dissertation reveals how authors have created characters and plotlines to reflect the increasing heterogeneity of ethnic populations while also theorizing the relationship between individual identity and group affiliation.

Advisor: Moya Paula M. L.
Saldívar Ramón
Elam Michele
Jones Gavin Roger
Synchronization in rhythmic performance with delay [electronic resource]

In the last few years, musicians have been exploring ways to perform with people in different parts of a city, a country or the world. New technologies for the Internet have been developed that are already high-quality in terms of audio experience. There is, however, a persistent problem: telecommunications delay. Even though these latencies are presently down to approximately 150 milliseconds from opposites sites of the globe, we know that delays of 20 milliseconds are already problematic for musical performance. This research presents an experimental analysis of the rhythmic strategies that humans use to stay synchronized with different delay conditions, similar to the ones encountered in present day networked music performance concerts. The vast majority of experimental studies of sensorimotor synchronization involve humans synchronizing to machines, usually some sort of tapping experiments. Likewise, rhythmic tracking has overwhelmingly focused on the analysis of one musical source, but not on the interaction of performing musicians. This research's focus is on the latter. The results show that performers are able to adapt to different delay conditions anticipating each other's beats. This anticipation is believed to be an intrinsic aspect of beat perception. The results are compared to earlier studies and new metrics are proposed that consider the alternating interaction between musicians. This approach also adopts phase dynamics using stroboscopic mapping. An integrated model for tracking and generating rhythmic interactions between two performers is also presented. This model uses coupled adaptive oscillators and includes an anticipation and reaction parameter that is shown to be critical to understand rhythmic synchronization with delay. We show how this model compares to the experimental data and use it to explain some common observations in rhythmic performance with delay.

Keywords: Music.
Advisor: Chafe Chris primary advisor. Thesis advisor
Abel Jonathan (Jonathan Stuart) advisor. Thesis advisor
Fujioka Takako advisor. Thesis advisor
Synthesis and organization of nanomaterials using biomolecules [electronic resource]

Recent advances in materials synthesis have revealed unique properties that occur at the nanoscale; however, organization of nanomaterials into hierarchical three-dimensional structures remains an unmet challenge. In striking contrast, Nature exhibits control over precise nanoscale processing which leads to highly organized and complex three-dimensional structures. This control is achieved through the action of many molecules, especially a wide array of proteins, that direct the synthesis, morphology, and organization of the many organic and inorganic materials found in Nature. Understanding and applying insights from these natural processes offers a promising new way forward for the manipulation and organization of materials at the nanoscale. This thesis focuses on understanding the unique self-assembling protein clathrin and developing strategies to modify self-assembled clathrin scaffolds for the synthesis and organization of inorganic nanomaterials. I have studied clathrin as an example of a robustly self-assembling protein to gain insight into how self-assembly is achieved in natural systems. I have designed and used bi-functional peptides for functionalization of self-assembled clathrin cage scaffolds through site-specific molecular recognition to generate complexes for the synthesis of two classes of inorganic nanomaterials, metal oxides and noble metals. Additionally, I have demonstrated that a single clathrin-based biomolecular complex can be used to generate distinct arrangements of gold nanoparticles. I have extended the peptide design strategy to design components that will direct hierarchical organization and have demonstrated the importance of considering the effect of multivalent interactions in peptide-mediated assembly. Taken together, the results presented provide insight to aid in the design of novel biomimetic systems for the tunable control over nanoscale synthesis and organization.

Keywords: Materials Science and Engineering.
Advisor: Heilshorn Sarah primary advisor. Thesis advisor
Melosh Nicholas A. advisor. Thesis advisor
Spakowitz Andrew James advisor. Thesis advisor
Synthesis of microfluidic chips [electronic resource]

Microfluidic chips are devices that allow one to manipulate nano- and pico-liters of fluids and microscopic objects, such as cells and complex molecules, and are widely employed in bioengineering, molecular biology, chemistry and adjacent fields. We focus our work on soft lithography technology used to create microfluidic chips in a number of bio labs. The growing complexity of these chips increases the probability and the cost of a design mistake, thus making them harder to design and debug. In this thesis, we address these challenges by introducing appropriate design tools. First, we will present a robust compact modelling framework that enables rapid simulations of microfluidic chips via existing circuit simulators, such as SPICE, and validate these models on two simple devices, a long channel and a pump. Then, we frame our model as a geometric program, enabling us to perform fast and global optimizations of complete chip designs. Finally, we introduce a synthesis tool that conceives a design of a chip using parameterized building blocks and optimizes its performance.

Keywords: Electrical Engineering.
Advisor: Horowitz Mark (Mark Alan) primary advisor. Thesis advisor
Boyd Stephen P. advisor. Thesis advisor
Weaver James
Synthesizing patterns using factor graphs [electronic resource]

In computer graphics, we are interested in recreating the richness and beauty of the world we see around us. We are also interested in helping artists create novel work. Even though the arrangement of design elements can vary greatly in patterns, we may still often characterize the relationships between design elements in the same kind of patterns. Previous pattern synthesis methods consist mainly of procedural and optimization techniques. Procedural techniques are good for generating a collection of models using a set of predefined rules and parameters. However, they are difficult to control. Optimization methods generate the best model given a cost function defined by a set of constraints. How do we combine the strength of the two methods such that we can generate a collection of models that satisfy both hard and soft constraints? That is, we want a system where preferred models are more likely to be generated. In this dissertation, we propose to use factor graphs, a type of graphical model, to encode the constraints present in patterns for computer graphics. We then model the design space for possible patterns as a generative probabilistic distribution. We also demonstrate how we can use factor graphs to set up the probabilistic distributions and develop synthesis algorithms for two classes of pattern synthesis problems: example- based tiled patterns and scene synthesis. In example-based tiled patterns, the patterns are grid-based and the size of a tiled pattern is fixed (i.e., a closed world). We learn the factor functions from the examples. Because of the hard constraints that the adjacent pairs of tiles must adjoin seamlessly, the distribution has high probability states that are isolated into disconnected regions. To address this challenge, we propose a search algorithm for tilings that is an extension of MC-SAT. Next, we consider the problem of scene synthesis. In scene synthesis, we relax the grid restriction and allow the number of objects to vary in the scene (i.e., an open world). The resulting distribution is transdimensional. Such a setting is useful when the number of objects is not known a priori. We propose a reversible jump Markov chain Monte Carlo method (LARJ-MCMC) that uses localized annealing. We also show through experimentation that the proposed MCMC sampler better adapts to the change in energy landscape when the dimensionality changes. Both algorithms exploit the factor graph formulation to synthesize layouts more efficiently.

Keywords: Electrical Engineering.
Advisor: Hanrahan P. M. (Patrick Matthew) primary advisor. Thesis advisor
Goodman Noah (Noah D.) advisor. Thesis advisor
Guibas Leonidas J. advisor. Thesis advisor
Synthetic and mechanistic investigations of a diruthenium-catalyzed C-H amination reaction [electronic resource]

The development of efficient and selective rhodium-catalyzed C--H and [pi]-bond amination processes makes possible unprecedented C--N bond disconnections in the synthesis of complex molecules. The oxidizing conditions of the reaction, however, have limited a broad utilization of catalyst structures beyond the well-documented bimetallic tetracarboxylates. Our desire to uncover catalyst systems tolerant of a wider range of ligand architectures inspired an evaluation of a congeneric class of diruthenium complexes that feature higher oxidation potentials. These studies have culminated in the identification of a family of efficacious amination catalysts crafted from a diruthenium core. Empirical examinations have demonstrated exceptional performance for the strapped carboxylate catalyst [Ru2(esp)2]SbF6 in amination reactions, and a unique proclivity for allylic C--H bond oxidation exacted by the tetrakis-oxypyridinate complex [Ru2(hp)4Cl]. Density functional calculations on this latter catalyst have implicated a mechanism for C--H insertion that operates via an H-atom abstraction/radical rebound sequence, contrasting the body of work on intramolecular amination by dirhodium systems. Experimental studies were undertaken to corroborate the stepwise nature of the catalytic reaction and to dissect the details of the insertion event. Investigations of alternative pathways operating in parallel to productive turnover have unveiled a host of processes that effect substrate or product consumption, oxidant depletion, and global catalyst reorganization. With the assistance of desorption electrospray ionization mass spectrometry (DESI-MS), a wealth of mechanistic data has been amassed, including evidence of critical, short-lived reaction intermediates. The collective data provide a detailed mechanistic framework for diruthenium-mediated amination reactions that should assist the continued development of effective and varied C--H amination technologies.

Keywords: Chemistry.
Advisor: Du Bois Justin primary advisor. Thesis advisor
Stack T. (T. Daniel P.)
Wender Paul A. advisor. Thesis advisor
Synthetic routes toward scalable, tunable carbon nanotube ensembles for use in devices [electronic resource]

Studies of carbon nanotube forests, carbon nanotube transistors and wire bundles, and carbon nanotube doping are carried out. A synthesis technique called "synergetic carbon nanotube growth" is developed in which enhanced growth rates are induced in catalyst areas of micron-scale feature size using asymmetric catalyst designs. This technique is used to fabricate carbon nanotube wire bundles with fair alignment which have resistivities of 1.4-2.2 Ohm*cm. Control of the chirality distribution in carbon nanotube growths is attained using alcohol chemical vapor deposition. Spectroscopic measurements and statistical analysis of transistor device measurements show that the semiconducting fraction in carbon nanotube ensembles can be tuned from 69% to 85% by varying growth temperature. The use of a precursor, triethylamine, is demonstrated to achieve in situ nitrogen doping in carbon nanotube growth at levels of approximately 0.2%, measured by X-ray photoelectron spectroscopy measurements and corroborated by Raman spectroscopy measurements. This work shows that mechanistic explanations ascribing to a surface-mediated process of carbon nanotube growth are correct.

Keywords: Electrical Engineering.
Advisor: Wong Hon-Sum Philip
Goodson Kenneth E.
McVittie James P. advisor. Thesis advisor
Nishi Yoshio