VictorJuiz/thesis huggingface dataset:
Circuit and layout techniques for soft-error-resilient digital CMOS circuits [electronic resource]
Keywords: Electrical Engineering

Radiation-induced soft errors are a major concern for modern digital circuits, especially memory elements. Unlike large Random Access Memories that can be protected using error-correcting codes and bit interleaving, soft error protection of sequential elements, i.e. latches and flip-flops, is challenging. Traditional techniques for designing soft-error-resilient sequential elements generally address single node errors, or Single Event Upsets (SEUs). However, with technology scaling, the charge deposited by a single particle strike can be simultaneously collected and shared by multiple circuit nodes, resulting in Single Event Multiple Upsets (SEMUs). In this work, we target SEMUs by presenting a design framework for soft-error-resilient sequential cell design with an overview of existing circuit and layout techniques for soft error mitigation, and introducing a new soft error resilience layout design principle called LEAP, or Layout Design through Error-Aware Transistor Positioning. We then discuss our application of LEAP to the SEU-immune Dual Interlocked Storage Cell (DICE) by implementing a new sequential element layout called LEAP-DICE, retaining the original DICE circuit topology. We compare the soft error performance of SEU-immune flip-flops with the LEAP-DICE flip-flop using a test chip in 180nm CMOS under 200-MeV proton radiation and conclude that 1) our LEAP-DICE flip-flop encounters on average 2,000X and 5X fewer errors compared to a conventional D flip-flop and our reference DICE flip-flop, respectively; 2) our LEAP-DICE flip-flop has the best soft error performance among all existing SEU-immune flip-flops; 3) In the evaluation of our design framework, we also discovered new soft error effects related to operating conditions such as voltage scaling, clock frequency setting and radiation dose.
City dwellers and the state [electronic resource] : making modern urbanism in colonial Dakar, 1914-1944
Keywords: History

This dissertation examines the city of Dakar, Senegal, from the mid-1910s to the end of the Second World War, tracing the shaping of the city that occurred on two different planes: the official and the informal. It argues that the official plane faltered as city dwellers created a world that suited them. Three topics anchor this study and are analyzed through urban court records: mobility and residence, diversity and insertion, and money. By shedding light on the transactional culture of city dwellers, court records reveal the hidden sphere of local strategies in Dakarois' everyday lives. In a context of disconnect between people and the state, local norms evolved informally: with neither assistance nor opposition from authorities in a range of areas, city dwellers created solutions that became common across Dakar. This study thus contends that modern-day urban informality and state inefficacy in African cities are rooted in colonialism.
Civil society and interest groups in transitioning regimes [electronic resource]
Keywords: Political Science.

Civil society and the interest groups they engender are key drivers of economic and political activity in states. Amongst other things, it has been argued that a vibrant civil society is essential for economic development (Fukuyama, 2001), democratic transitions (Fatton, 1992), and democratic consolidation (Diamond, 1994). The interconnectedness between markets and civil society has long been a source of debate amongst scholars, from the likes of Adam Smith and Thomas Paine who considered markets the organizing principle of civil society, to Gramsci who thought of civil society as standing between economic structure and the state. In the words of Keane, ``No civil society, no markets...no markets, no civil society." (Keane 2005, 29). This dissertation explores the landscape of civil society and ensuing interest group activity under transitioning economic regime structures, focusing on the case of the transition from a command economy to a free market economy in East and Central Europe. The dissertation argues that the composition of interest groups arising in the post-communist regime is, in part, a function of the groups that existed under the communist regime, and in part a function of transition in the shadow of European Union integration. Four interest groups stand out as prominent actors in the economic policy making arena: Public Labor, Incumbent Management, New Domestic Capital, and Foreign Capital. These groups gain associational representation through bodies such as labor unions and business and employer organizations. The ability of these groups to affect policy, however, lies in their political strength, which, it is argued, varies both cross-sectionally and temporally in the region. Qualitative case study evidence from three case countries, Hungary, Slovakia and Slovenia, coupled with quantitative analysis in the form of Bayesian statistical modeling, provides support for the hypothesized key economic groups and their foundations in the communist command economic structure; variation in the political strengths of these groups in the East and Central European region; and, variation in policy outcomes based on political strengths of these groups.
Class action; community mobilization, race, and the politics of student assignment in San Francisco [electronic resource]
Keywords: Education.

The principal goal of the dissertation is to explain the political nature and effect of cultural characterizations on the development of student assignment policy. Cultural characterizations are socially constructed portrayals that become influential when stakeholders mobilize to bring about change. In education, as the professional authority of school boards and superintendents diminishes, community stakeholders are increasingly prominent. They serve as critical producers and providers of cultural characterizations of public education and its beneficiaries. As such, the engagement of community stakeholders with public sector institutions, organizations, and individuals can significantly amplify, modify, or blunt education policy. The dissertation traces the history of community mobilization in San Francisco from 1971 to 2005, during which the federal district court supervised all aspects of the school district's student assignment policy. Cultural characterizations of student assignment were structured by three distinct logics of action: integration, choice, and neighborhood. These logics were stable but not fixed. Changes in the institutional environment coupled with how stakeholders framed, understood, and shaped these logics led to transformations in student assignment policy that ultimately altered the educational experience of multiple generations of public school students. Data are drawn primarily from archival documents from the federal district court, the school district, and community organizations; mainstream and community newspaper articles, letters to the editor, and editorials; and, retrospective interviews with key stakeholders.
Coal energy conversion integrated with deep saline aquifer carbon storage via combustion in supercritical water [electronic resource]
Keywords: Mechanical Engineering

Carbon capture and sequestration (CCS) technologies aim to allow the continued use of fossil fuels by outputting carbon in a form other than atmospheric CO2. Several types of geologic reservoirs are considered as alternatives; of these, deep saline aquifers have the largest potential storage capacity worldwide. Unfortunately, neat CO2 injected into an aquifer is less dense than the native brine. The resulting buoyancy presents a potential for leakage from the storage formation, and, ultimately, to the atmosphere. This work describes a method for using coal to produce electricity that creates a pre-equilibrated brine/CO2 solution for injection into a saline aquifer. Such solutions are more dense than the original brine, and present no potential for buoyancy-driven leakage. A concept is introduced in which coal is oxidized in high-pressure, high-temperature water drawn from a saline aquifer in a process known as supercritical water oxidation (SCWO). Combustion in supercritical water and subsequent aquifer storage of all coal-derived fluid effluent removes the need for CO2 separation and compression steps common in other coal-fired designs with CCS. The properties of supercritical water (T > 647 K, P > 221 bar) are described that make it a suitable combustion medium---in contrast to water at ambient conditions. A conceptual plant is developed that includes systems to manage brine and coal (a solid, complex fuel). The system uses a heat engine for work extraction from hot combustion products, and so may be called a supercritical water oxidation, indirectly-fired combined cycle, or SCWO/IFCC. Next, a thermodynamic model is developed to evaluate the performance of this plant and compare it to other coal-fired designs with CCS. Next, a laboratory-scale combustor, constructed to study flames in supercritical water, is described. This apparatus follows from previous supercritical water reactors that were built to study the destruction of hazardous wastes, but is targeted toward the development of a combustor suitable for use in a power plant. Challenges encountered operating systems that are simultaneously high-pressure and high-temperature are discussed, including the use of several types of metal seals. Autoignition results from initial combustion experiments are presented and compared to previous work.
Coarse-grained structural modeling of molecular motors [electronic resource]
Keywords: Mechanical Engineering

Molecular motors perform central functions in fundamental biological processes, including cell division, DNA replication, muscle contraction, and intracellular transport. Experimental and computational approaches are needed to uncover the mechanisms by which molecular motors convert chemical energy into mechanical work. A software system called Protein Mechanica has been developed to generate structurally realistic models of molecular motor conformations compatible with experimental data from different sources. It facilitates the construction of models of protein geometry from atomic resolution structures, lower-resolution electron microscopy data and parametric solids. Coarse-grained models of molecular structures are constructed by combining groups of atoms into a system of rigid bodies connected by joints. Contacts between rigid bodies enforce excluded volume constraints, and spring potentials model system elasticity. This simplified representation allows the conformations of complex molecular motors to be simulated interactively, providing a tool for hypothesis building and quantitative comparisons between models and experiments. Protein Mechanica was used to build an atomic-resolution model of a mouse brain myosin V, a dimeric cellular transport motor, in pre- and post powerstroke conformations from partial X-ray crystal structures. A mechanical analysis of the head-neck region model was performed using normal mode analyses and molecular dynamics simulations to guide the construction of a coarse-grained models. The coarse-grained model of myosin V enabled examination of its conformations bound to its actin track. Elastic strain energies calculated from simulations are compatible with observations of single myosin V motors traversing suspended actin filaments that infer that the motor uses a combination of 11 subunit and 13 subunit stride sizes. These calculations extend previous simple mechanical models for step size selection and processivity, and provide atomically detailed models for comparison with future experiments. The Protein Mechanica software described in this dissertation provides a new tool for structural modeling of many different molecular machines, basic understanding and engineering design.
Coaxial-tip piezoresistive cantilever probes for high-resolution scanning gate microscopy [electronic resource]
Keywords: Electrical Engineering

Scanning probe techniques provide a wealth of information about the nanoscale properties of materials and devices. In scanning gate microscopy (SGM), the current through a sample is recorded as a sharp, conductive tip that modifies the local electrostatic potential is scanned above the surface. SGM has been used to map current flow, carrier density and potential barriers. Existing, unshielded SGM probes have significant stray capacitance, resulting in poor lateral resolution when they are used to image nanostructures. Thus, there is a need for a probe that minimizes stray capacitance to produce highly-localized electric fields. This probe must also self-sense topography for tip-sample alignment, as the conventional laser-based detection methods can disturb photosensitive samples. In this thesis, we present a new scanning probe that integrates a coaxial tip on a piezoresistive cantilever. The coaxial tip is comprised of a heavily-doped silicon inner conductor and an aluminum outer shield, separated by a silicon dioxide insulator. By shielding the inner conductor up to the tip apex, this tip configuration minimizes stray capacitance to produce narrow electrostatic potential profiles. A piezoresistor is embedded at the root of the cantilever and enables electrical measurement of deflection at the free end. Scanning gate microscopy is commonly performed at room temperature (room-T) and low temperature (low-T). We discuss the design of piezoresistive cantilevers for atomic force microscopy (AFM) under both temperature regimes. We introduce a numerical optimizer that we used to identify 12 cantilever designs for use at room-T and low-T for hard, semiconductor samples and soft, biological samples. We show the results of finite-element analysis used to predict the electrostatic potential profiles produced by unshielded and coaxial tips. We investigate how the full-width at half-maximum (FWHM) of the coaxial tip perturbation varies with lift height and tip geometry. We discuss the development of a 7-mask process to fabricate scanning probes with both a coaxial tip and a piezoresistor. We compare two methods to create sub-micron tip apertures with focused ion beam milling, and provide a recipe that can repeatably produce openings with a radius of 30 nm. We describe the characterization of the piezoresistive cantilevers at room-T on a commercial AFM and at low-T on a home-built cryogenic scanning system. Finally, we provide images of the potential profile from the coaxial tip, obtained using a quantum point contact at low-T. In a measurement bandwidth from 1 Hz to 10 kHz, our scanning probes achieve a vertical displacement resolution of 2.8 A at 293 K and 82 A at 2 K, where the low temperature performance is limited by amplifier noise. When the coaxial tip is 100 nm above a sample, the FWHM of the electrostatic potential profile it produces at the surface is less than 240 nm, representing a 2.3x improvement in the lateral resolution of SGM over unshielded tips.
Code generation for embedded convex optimization [electronic resource]
Keywords: Electrical Engineering

Convex optimization is widely used, in many fields, but is nearly always constrained to problems solved in a few minutes or seconds, and even then, nearly always with a human in the loop. The advent of parser-solvers has made convex optimization simpler and more accessible, and greatly increased the number of people using convex optimization. Most current applications, however, are for the design of systems or analysis of data. It is possible to use convex optimization for real-time or embedded applications, where the optimization solver is a part of a larger system. Here, the optimization algorithm must find solutions much faster than a generic solver, and often has a hard, real-time deadline. Use in embedded applications additionally means that the solver cannot fail, and must be robust even in the presence of relatively poor quality data. For ease of embedding, the solver should be simple, and have minimal dependencies on external libraries. Convex optimization has been successfully applied in such settings in the past. However, they have usually necessitated a custom, hand-written solver. This requires signficant time and expertise, and has been a major factor preventing the adoption of convex optimization in embedded applications. This work describes the implementation and use of a prototype code generator for convex optimization, CVXGEN, that creates high-speed solvers automatically. Using the principles of disciplined convex programming, CVXGEN allows the user to describe an optimization problem in a convenient, high-level language, then receive code for compilation into an extremely fast, robust, embeddable solver.
Collective atom-cavity interactions in a high-finesse dual-wavelength cavity [electronic resource]
Keywords: Applied Physics

We developed a high-finesse single-wavelength cavity with a large collective cooperativity to achieve pseudospin squeezing and study collective atom-cavity interactions. We observed collective normal mode splitting, providing evidence for a large collective cooperativity that can result in better spin-squeezing. We observed ~13dB large anti-spin-squeezing but little spin-squeezing because of the inhomogeneous atom-cavity coupling, limiting the atomic coherence. In order to achieve identically coupled atoms to a cavity mode, we developed a high-finesse dual-wavelength cavity with a 1560nm cavity lattice and a 780nm cavity probe. Optically trapped atoms in the lattice are in-phase with the cavity probe at the cavity center, and we obtained spatially identical atom-cavity coupling. We studied macroscopic self-trapping behavior of two hyperfine levels experimentally and theoretically, and in-phase atom registration in the dual-wavelength cavity enables us to treat the trapped atoms as one macroscopic ensemble of atoms. At the mid-point of a full Rabi oscillation, the collective atom-cavity interaction interrupts the coherent evolution of the macroscopic ensemble of atoms. We demonstrated a free-running Raman laser in our cavity system using 87Rb atoms as the gain medium, which has atypical lasing threshold behavior and tunable gain properties. The intermode laser linewidth is as low as 80Hz.
Collective quantum behavior of atomic ensembles in high-finesse optical cavities [electronic resource]
Keywords: Applied Physics

Spin-squeezed states (SSS) are collective atomic states whose Heisenberg uncertainty properties have been altered, either by state transfer from squeezed light, or, as presented here, by a quantum non-demolition (QND) measurement of a light field after it has probed the atomic system. These states are of interest for their potentially large increases in measurement precision in atom-based experiments, and for the study of many-particle entanglement. The body of work related to generating these novel states through measurement of a non-destructive probe (after interaction with the atomic system) can be split into two general groups: Those using atoms in free space, and those using optical cavities. This dissertation will focus on the approach using optical cavities, increasing the effective optical depth, and therefore the interaction strength between the atoms and the light. The first experiment will describe a quantum nondemolition measurement to probe the collective pseudospin of an atomic ensemble in a high-finesse optical cavity. We analyze the backaction antisqueezing produced by the measurement process to show that our protocol could create conditional spin squeezing in the atomic ensemble. However, technical measurement noise and residual variations in atom-cavity coupling limit our ability to observe squeezing while preserving coherence. In the second experiment we attempt to remove these main sources of noise by trapping the atoms in a far red-detuned optical lattice with twice the wavelength of the probe light. This wavelength configuration ensures that lattice antinodes, where the atoms are trapped, are always overlapped with probe antinodes, ensuring maximum coupling between the atoms and the probe field. The trapping also prevents atoms from exploring the cavity mode, eliminating noise due to variations in atom-cavity coupling. Finally, I will describe a third experiment (unrelated to spin squeezing) in which we experimentally realized a Raman laser in a high-finesse optical cavity. The large collective cooperativity of the atom-cavity system manifests in some interesting threshold behavior of the cavity output power, which we can describe using a simple model. Although not directly related to spin squeezing, a lasing system with the highly configurable gain medium presented here could have applications as a light source in precision measurement.
Colloidal nanoparticles for phase change memory applications [electronic resource]
Keywords: Chemistry

Phase change (PC) memory has emerged as a leading candidate for next generation information storage technology. Based on the reversible amorphous-crystalline phase transition of chalcogenide materials, PC technology has already been commercialized through the optical disk industry and is currently being evaluated for non-volatile electronic data storage as phase change random access memory (PCRAM). In either the optical or electronic application, device performance relies on the material properties of the active phase change material (PCM). Traditionally deposited through physio-chemical routes such as sputtering or chemical vapor deposition, the PCM fundamentally limits PC scaling potential as it is expected that key properties will change as the volume of PCM decreases. Colloidal nanoparticle systems provide a unique opportunity to systematically study the properties of materials in the nanosize regime due to the potential for exquisite composition and size control. In this talk, I will present the first colloidal nanoparticle system of a known phase change material. Colloidal GeTe nanoparticles 1.4-4nm in diameter were synthesized through a co-precipitation route and characterized by transmission electron microscopy, energy dispersive x-ray spectroscopy and x-ray diffraction. Nuclear magnetic resonance spectroscopy (1H and 31P) was used to elucidate the molecular species involved in the reaction pathway and found that a metal center mediated proton transfer is necessary to mediate the relative reactivity of the reactants. In addition, a post-synthetic size selective procedure was developed to separate the nanoparticles into distinct size ranges. Using in-situ heating, the size dependent crystallization temperature was measured by XRD and was found to increase with decreasing nanoparticle diameter suggesting favorable improvements in lifetime data retention for scaled PCRAM cells. To evaluate the potential use in PCRAM devices, electrical measurements were also collected on nanoparticle films. Resistance versus temperature measurements revealed that nanoparticle films retained the high resistive contrast between the amorphous and crystalline phases necessary for PCRAM operation. After design optimization, PCRAM cells were fabricated utilizing the nanoparticles as a solution processable precursor to the PCM. Completed cells showed reversible switching, including threshold switching, characteristic of PCRAM operation. Cycling up to 200 times, the cells are the best performing solution processed PCRAM devices reported to date, suggesting that colloidal nanoparticles are a viable route to PCMs.