VictorJuiz/thesis huggingface dataset:
Composing timbre spaces, composing timbre in space [electronic resource] : an exploration of the possibilities of multidimensional timbre representations and their compositional applications 
Keywords: Music.

This final project is comprised of three works completed over the past two years, and an introductory paper that briefly outlines the approaches to timbre taken in each piece. All three of the compositions approach timbre from a different perspective and explore the possibilities and compositional applications of multidimensional timbre representations. The final project does not present a comprehensive history of timbre, all the research that has been undertaken on the topic, or a complete account of the composers who have used timbre models. Rather, the models and compositions presented here are meant to provide insight into my own compositional thought process. The three original pieces illustrate a trajectory through which composing with timbre yielded new creative insights and compositional techniques. Emergent in these works is a common theme and exploration of "timbre space" and "timbre in space." The first piece presented in this portfolio is Ostiatim, for string quartet. It explores timbre space as a morphing device for sculpting material. Ostiatim was premiered by the Jack Quartet. The second piece, Clocca, for chamber ensemble, examines timbre space as a structuring device. Clocca was premiered by the Talea Ensemble. Finally, the third piece in the collection, Occupied Spaces, for two piano and percussion, explores a series of timbral spaces, presented as "rooms, " which grow, shrink, and continuously shift in shape. Unlike Ostiatim and Clocca, this final piece explores timbre in space. Occupied Spaces was premiered by the ensemble Yarn/Wire.
Composition and temperature effects on minor structural species in aluminosilicate melts and glasses [electronic resource]
Keywords: Geological and Environmental Sciences.

In order to better understand the structure of aluminosilicate glasses and its impact on thermodynamic and transport properties, this work studies the effects of compositional and temperature variations on minor structural species in a series of aluminosilicate glasses. The presence of high-energy minor structural species such as non-bridging oxygen (NBO) and five-coordinated aluminum are not predicted by "standard" models of glass structure along the metaluminous (charge-balanced) join, where they have been observed using aluminum and oxygen nuclear magnetic resonance (NMR) spectroscopy. Two series of calcium aluminosilicate glasses were made along different silica isopleths, crossing the metaluminous join. The rate at which the five-coordinated aluminum content increases in the peraluminous region suggests that the additional aluminum is incorporated into the melt using 3-coordinated oxygen. The presence of NBO into the peraluminous region is confirmed and its value is affected by the Si/Al ratio. A similar, smaller series of potassium aluminosilicate glasses also shows the presence of NBO on the metaluminous join but at a much lower value than observed in the calcium aluminosilicate glasses. However, a series of barium aluminosilicate glasses (at a lower silica content) shows NBO content consistent with similar calcium aluminosilicate glasses; this suggests that the presence of non-stoichiometric NBO along the metaluminous join is driven by cation charge instead of cation field strength, which is confirmed to affect the amount of five-coordinated aluminum. To study the effect of temperature on these minor structural species, the glass-forming calcium aluminosilicate melts were cooled at different rates to sample the glass structure at different fictive temperatures. The five-coordinated aluminum content clearly increased with increasing fictive temperature across all samples studied, while the NBO content showed the clearest increase with increased fictive temperature in the peraluminous and high silica samples. All of these comparisons support the need for decoupled structural reactions to produce NBO and five-coordinated aluminum in these regions. Additionally, the accuracy of oxygen NMR on quantitation of structural species was tested using silicate minerals and glasses, verifying the reliability of these measurements and reaffirming that stoichiometry based methods of predicting NBO in silicate glasses remain valid.
Computational and Experimental Study of Electromagnetic Wave Heating in Magnetized Plasmas
Keywords:  Department of Physics
plasma thruster
wave-particle heating
ion heating
Landau damping
particle-in-cell simulation
Thesis

This thesis summarizes both experimental and computational research efforts concerning the heating of ions in a magnetized plasma. Beginning with the original research objective of constructing a magnetic nozzle plasma thruster, the planning, modeling and construction of the experimental device is described. The key components of the design are motivated, including a discussion of the relevant tradeoffs and challenges. A summary of the current state of the experiment is given. In addition, this work describes a complementary computational research thread studying the efficient heating of ions in magnetized plasmas via particle-in-cell (PIC) simulation. The originally developed codes are motivated, relevant algorithms are discussed, and stability conditions are introduced. The results of the simulations are summarized and possible heating strategies for future experimental applications are inferred. Finally, suggestions for further computational and experimental work on this project are presented.
Congestion control and adaptive routing in large-scale interconnection networks [electronic resource]
Keywords: Electrical Engineering.

Large-scale lossless interconnection networks are widely used in high-throughput, low-latency systems such supercomputers or data centers. In addition to bandwidth and latency, managing congestion is a critical component to guarantee network performance. Congestion in a lossless network is worsened by the effect of tree saturation, where a single point of congestion can spread through the network. This can have severe and global impact on the performance of the entire system. As the size of networks continues to expand, traditional congestion control algorithms, such as Explicit Congestion Notification (ECN) and traditional adaptive routing algorithms, are no longer adequate for large-scale networks. In this thesis, I describe two solutions for eliminating network congestion caused by different types of traffic. For congestion within the network fabric, I introduce Indirect Adaptive Routing (IAR), a new class of adaptive routing algorithms designed to improve channel load balance in a large-scale high-radix network. Each IAR algorithm uses a different mechanism to determine the level of congestion on non-local channels near a router's vicinity. Both local and remote network congestion information are then used to improve the adaptive routing decisions for network packets, load balancing the network under arbitrary admissible traffic patterns. The Speculative Reservation Protocol (SRP) resolves congestion caused by inadmissible or in-cast traffic at the network endpoints. SRP uses end-to-end reservations to ensure that no destination in the network is overloaded. To reduce reservation overhead, SRP allows sources to send packets speculatively while awaiting reservation replies. These speculative data packets can be dropped by the otherwise lossless network if congestion begins to form. By taking a proactive approach, SRP is able to react significantly faster to the onset of network congestion compared to reactive protocols used in systems today. While IAR and SRP each targets a specific area of network congestion, they can also be combined to create a single comprehensive congestion solution. I show that these two protocols work in complement and are able to resolve congestion caused by arbitrary traffic configurations in a large-scale network.
Constructing a motile cell [electronic resource] : how extrinsic information and intrinsic self-organization coordinate the mechanics of cellular behavior
Keywords: Biochemistry.

The actin-based crawling motility of eukaryotic cells is a vital example of emergent cellular behavior arising from the mechanical output of thousands to millions of individual chemical reactions occurring every second. In this work, I describe a set of experimental and analytical results that seek to reveal the underlying organization and operations of this micron sized biological machine. We found that the morphology of crawling cells is quantitatively dictated by the cytoskeletal elements that produce motility. Each cell is unique in its organization and behavior, and across a population of cells this variation could largely be reduced to a single dimension. Globally perturbing the biochemical reaction rates that drive motility with changes in temperature forced individual cells out of their steady state behavior along this same single dimension of variation. In addition individual cells fluctuated harmonically around their steady state behavior, suggesting a mechanical oscillator arising from the coupling of the processes of actin meshwork assembly and disassembly. Flickers of elevated intracellular concentration of the canonical secondary messenger calcium were seen, but these calcium flickers were not required for cell motion nor were they correlated with any measured change in cell behavior. The orientation of motion, similar to the rate of motion, is directly coupled to the cytoskeletal organization and cellular shape. To change their direction of migration, cells develop asymmetries in the interwoven actions of myosin contractility and adhesion to the substrate at the rear of the cell creating asymmetric centripetal actin flow. This system of controlling orientation was responsive to external cues from electric fields secondary to electrophoretic redistribution of charged membrane components extending into the extracellular space.
Constructing culture [electronic resource] : architecture and contemporary islamic identity in northern Ghana
Keywords: Art and Art History.

This dissertation is a multi-disciplinary project that explores the methods through which Islamic identity in northern Ghana is being remodeled in the modern period, using architectural form as its primary methodological tool. As the principal mode through which individuals organize their physical reality, architecture is not only able to articulate cultural identity, but also response to shifts in its trajectory through subsequent changes in an architectural landscape. Taking as a case study the village of Larabanga, a small but spiritually significant Islamic community in Northern Ghana, this project explores how contemporary heritage initiatives, tourism, and the improvement of technological capabilities, as well as issues of climate, available materials, and the current socio-political environment, have modified traditional Afro-Islamic architectural systems in this area and in the process articulated the current condition of Larabanga as existing in a state of cultural and spiritual flux.
Continuum and atomistic aspects of dislocation dynamics [electronic resource]
Keywords: Materials Science and Engineering.

Dislocation dynamics (DD) simulations have been developed to link the plastic deformation of single crystals with the microscopic dynamics of dislocations. Most of the existing DD simulation programs are limited to isotropic elasticity, even though most single crystals are elastically anisotropic. Understanding the connection between DD and plasticity under these conditions requires an efficient DD simulation program that can account for anisotropic elasticity. Cross-slip is also an aspect of dislocation dynamics, which plays an important role in the plastic deformation of FCC metals, leading to hardening and dynamic recovery. However, a satisfactory cross-slip model has not yet been implemented in DD simulations, which accurately reflects the dependence of energy barrier on the local stress. To enable efficient computation of forces on dislocation segments in an anisotropic linear elastic medium, several alternative approaches are investigated and explicit expressions are derived for self-stress and self-force. These can be used to compute short range stress fields in DD simulations. To compute long-range interactions between distant dislocation segments, the fast multipole method (FMM) proves to be efficient; however, FMM has not yet been applied to three dimensional DD simulations which take into account anisotropic elasticity. A systematic procedure is demonstrated to establish this capability by first obtaining the derivatives of the elastic Green's function to arbitrary order for a medium of general anisotropy. Then the stress fields of dislocation segments are computed using multipole expansions based on these derivatives. These algorithm advances enable efficient calculations of both short range and long range stress fields in DD simulations. Both continuum and atomistic study of dislocation cross-slip is performed. To construct a cross-slip rate function of the local stress state, the line tension model following Stroh and Escaig is studied and the cross-slip energy barriers are computed numerically. To provide an atomistic understanding of cross-slip mechanism, molecular dynamics (MD) simulations are performed to investigate the phenomenon under different stress conditions. Cross-slip energy barriers are evaluated and are compared with numerical results given by the line tension model. These studies lead to cross slip rate predictions as a function of local stress, which are suitable for use in DD simulations.
Continuum and atomistic modeling of lipid membranes [electronic resource] : biophysics of hair cell mechanotransduction
Keywords: Mechanical Engineering.

A lipid bilayer membrane is not just a simple inert barrier of cells, but a dynamic structure which plays a crucial role in cell functioning. A force conveying role of the lipid membrane for the mechanosensitive ion channels is now an accepted phenomenon across various mechanoreceptors. However, such a mechanism has not been established for mechanotransduction in the hair bundle of the auditory sensory hair cell. A major goal of this theoretical study is to investigate the role of the lipid membrane in the hair bundle mechanotransduction in the auditory system, especially in generating the nonlinear bundle force vs. displacement measurements -- one of the main features of auditory mechanotransduction. To this end we developed a hair bundle model which reproduces the lipid membrane tented deformation in the stereocilia. To analyze the membrane deformation, the conventional Helfrich theory for the lipid membrane is modified and solved by a novel numerical method using Fourier series. Our hair bundle model, incorporating membrane elasticity with bundle rigid body kinematics and lipid flow components, reproduces nonlinear bundle force measurements and in so doing potentially elucidates aspects of hair cell transduction for which the physical basis has been elusive for three decades. The nonlinear force vs. displacement calculation of the tented membrane, the central goal of this analysis, is further supported by the nonlinear finite element (FE) formulation. This Galerkin finite element method uses the B-spline basis function and Newton's method to solve the nonlinear equation system. By repeating the tenting problem with the finite element method, the consistency of the force vs. displacement calculation compared to our previous approach is demonstrated. The validity of the continuum analysis is also investigated though atomistic modeling of the lipid membrane. The coarse-grained molecular dynamics simulation of the tented lipid membrane is performed. Generating similar nonlinearity validates our previous continuum analysis of the membrane based on the Helfrich theory and supports the role of the lipid membrane in generating nonlinear hair bundle mechanics.
Contributions to microeconomic theory [electronic resource]
Keywords: Business.

This dissertation consists of contributions to three different "waves" or "eras" of microeconomic theory from around 1950 until today. All three contributions concern environments featuring uncertainty. In the first of these three eras, the focus was largely on choice theory, both individual and social, and on equilibrium in perfectly competitive markets. My first chapter contributes to the theory of individual choice. I provide axiomatic foundations for supermodularity and quasisupermodularity of Bernoulli utility functions in the context of choice over lotteries. In the second of the eras, the focus shifted to game theory and to its application to information economics and mechanism design. In Chapter 2, I provide a contribution to this literature: I analyze the problem of designing dynamic mechanisms for agents who learn about a common component of their valuation through experience, and privately: Whoever gets a unit today acquires a private signal about the common value, aside from enjoying immediate surplus. Thus, allocating a unit today creates an informational asymmetry tomorrow. This problem resembles economic environments where parties interacting over time privately gather socially valuable information, and when this information acquisition is a result of the outcome of their interaction, rather than being exogenously given. Recently, microeconomic theorists have begun to turn their attention towards behavioral economics, and towards problems where are boundedly rational is some fashion, and hence they are unable to find the "optimal" course of action in the complex environment that they inhabit. Chapter 3 concerns the second type of behavioral problem. A decision maker faces a finite set of alternatives and every period chooses a subset from this set. The values of the alternatives are drawn from an unknown distribution, and the decision maker only observes the realized values of those alternatives in the chosen subset. Due to the information structure of this problem, we are unable to fully characterize optimal strategies. Instead, I propose and analyze heuristics.
The control of metal-insulator transition in vanadium dioxide [electronic resource]
Keywords: Materials Science and Engineering.

The external control of the conductivity of correlated oxides is one of the most promising avenues towards realizing energy-efficient electronic devices. One of the prime candidates for such devices, vanadium dioxide (VO2), undergoes a temperature-driven metal-insulator transition (MIT) near room temperature (~340 K) with a concomitant change in crystal symmetry. First, using epitaxial strain provided by a variable thickness RuO2 buffer layer, we vary the MIT transition temperature of VO2 (001) films continuously from ~285 to ~345 K. We show, using strain-, polarization- and temperature-dependent x-ray absorption spectroscopy, in conjunction with x-ray diffraction and electrical transport measurements, that the transition temperature (TMIT) of VO2 is controlled by the orbital occupancy in its metallic state. Our results furthermore indicate that the magnitude of the structural distortion across the transition is also directly related to the orbital occupation in the metallic state. This work opens up the possibility of controlling the nature of the conducting state in atomically thin VO2 layers by manipulating the orbital occupancy by, for example, hetero-structural engineering. In a related study, we have used a combination of electron-beam and optical lithography to fabricate lateral two-terminal nano-devices from VO2 films deposited on TiO2 (001) substrates without RuO2 buffer layers. In these devices, we show that the transition can also be engendered by the application of modest electric fields, several orders of magnitude below the electric breakdown field, making this phenomenon potentially useful for two or three terminal switches. The delay time before switching is found to decrease with increasing electric field and temperature. We discuss whether these results indicate the transition is dominated by electronic or by Joule heating effects. These results demonstrate the possibility of triggering an MIT at low voltages and, therefore, at low energies, which is essential for device applications. Finally, we also discuss MIT in VO2-TiO2 based hetero-structures. We show that the temperature-driven MIT persists in VO2 films as thin as 1.8 nm.
Controlling injection and propagation of domain walls in magnetic nanowires [electronic resource]
Keywords: Electrical Engineering.

Magnetic domain walls (DWs) are regions where the magnetization changes rapidly from one orientation to another. These magnetic textures are of considerable interest both scientifically as well as technologically with potential applications in novel memory and logic devices based on their controlled creation and manipulation under magnetic field and current. We consider the injection and propagation of DWs in two different materials systems, namely in permalloy (Ni81Fe19) nanowires where the magnetization points in the film plane and in Co/Ni multilayers where the magnetization points perpendicular to the film plane. DWs in permalloy nanowires can be considered as composite objects composed of elementary topological bulk and edge defects with integer and fractional winding numbers, respectively; whose relative spatial arrangement determines the chirality of the DW. Here we show how we can understand and control the trajectory of DWs in magnetic branched networks, composed of connected nanowires, by a consideration of their fractional elementary topological defects and how they interact with those innate to the network. We also demonstrate a highly reliable mechanism for the injection of a DW of a given chirality into a nanowire and show that its chirality determines which branch the DW follows at a symmetric Y-shaped magnetic junction - the fundamental building block of the network. Using these concepts, we unravel the origin of the one-dimensional nature of magnetization reversal of connected artificial spin ice systems that have been observed in the form of Dirac strings. In the second part of this work, we demonstrate that by irradiating small regions in perpendicularly magnetized nanowires to induce in-plane magnetic anisotropy, and thereby creating a 90° DW, we can significantly decrease the energy needed for DW creation. In fact, due to the presence of a 90° DW at the injection site, the process of creating a DW in the nanowire in reality involves extraction of the 90° DW to the perpendicularly magnetized region. We show that this can not only be done by conventional means of creating local magnetic fields near the injection site but more importantly, by exploiting the giant spin transfer torque obtained at the 90° DW (due to the abrupt change in the magnetization), we can inject a series of domain walls using nano-second long, uni-polar current pulses through the nanowire which use much lower energy than conventional techniques.