VictorJuiz/thesis huggingface dataset:
Electric field-induced conductivity switching in vanadium sesquioxide nanostructures [electronic resource]

Strong interactions, or correlations, between the d or f electrons in transition metal oxides can lead to various types of metal-insulator transitions which may be triggered by external parameters such as temperature, pressure, doping and magnetic field. Recent theoretical and experimental reports have suggested that this transition can also be triggered by a threshold electric field. Fully realized, this effect could lead to an entirely new class of electronic switches based on materials with strongly correlated electron systems. However, significant questions remain about the detailed nature of the experimental results, especially the degree to which Joule heating plays a role. In this work, we present an investigation of time-resolved, voltage-induced conductivity switching in the canonical metal-insulator transition system V2O3. The main findings can be categorized into three parts: film growth, electrical measurement, and electro-thermal modeling. First we discuss the growth, optimization and characterization of high-quality epitaxial V2O3 films, including the effect of oxygen pressure, substrate temperature and substrate material on the film properties. Next we show experimental results on electric field-induced phase transitions in V2O3 nanostructures fabricated by electron beam lithography. We observe that a threshold electric field of approximately 10^7 V/m applied across two-terminal nanostructures causes a metallization of V2O3's low-temperature Mott insulating state, preceded by a nanosecond-scale delay time. Lastly, we explore the feasibility of Joule heating as an explanation for the switching process. After fully accounting for temperature-related feedback and subthreshold nonlinear current-voltage characteristics, we find remarkably good agreement between the predicted and observed threshold voltages and switching delay times as a function of temperature, suggesting the switching mechanism is thermal in origin. We believe these findings have important implications for recent reports of voltage-induced switching in the related materials VO2 and Fe3O4 and will also help to guide future research on this phenomenon.

Keywords: Applied Physics
Advisor: Harris J. S. (James Stewart)
Parkin Stuart S. P.
Goldhaber-Gordon David
Electrothermal properties of nanowire materials for energy conversion systems [electronic resource]

Worldwide energy demand is projected to increase 40% by 2035. Thermoelectric power generators could be a rapid, powerful way to meet the increased need for energy by converting wasted heat energy into useful electrical energy. However, inter-disciplinary factors determining the feasibility of widespread thermoelectric power generation systems have been minimally explored. This work connects materials and manufacturing costs, materials properties, and system level design to identify the factors necessary for successful thermoelectric generators. First, an economic analysis links materials and manufacturing costs with material performance to produce a thermoelectric device cost-performance metric. Current and potential thermoelectric materials are evaluated using this metric to determine which materials are promising candidates. Next, thermoelectric energy system modeling demonstrates the potential for increased energy efficiency in existing energy systems. Thermoelectric waste heat recovery is simulated for three applications: a home water heater, an automotive exhaust system, and an industrial furnace. The impact of system and material parameters on power generation efficiency is determined. Engineering at the nanoscale produces materials with combinations of properties absent in the natural world, enabling tunable and enhanced energy conversion in these systems. In particular, zinc oxide nanowires may offer improved thermoelectric energy conversion. Finally, characterization of electrothermal transport phenomena in single zinc oxide nanowire structures demonstrates the impact of nanowire contacts on the realization of functional nanowire materials.

Keywords: Mechanical Engineering
Advisor: Goodson Kenneth E.
Edwards Christopher
Salleo Alberto
The emergent effects of ocean acidification [electronic resource] : linking individuals to ecosystems

Ocean acidification represents a pervasive environmental change that could impact a wide range of species and cause extensive changes in marine ecosystems. An understanding of the potential emergent effects of acidification requires an integrated knowledge of the impacts on single species, species interactions, community structure, and ecosystem function. By using meta-analysis and field experiments in a naturally acidified ecosystem, this dissertation investigates how the responses of individual species to ocean acidification combine to affect the community and ecosystem. This research highlights the key role of species interactions in the emergent effects of ocean acidification. While meta-analyses underline the sensitivity of a wide range of species that build their shells or skeletons of calcium carbonate to acidification, field experiments in a naturally acidified ecosystem suggest that the loss or reduced abundance of the sensitive calcareous species in acidified conditions is compensated by an increased abundance of more tolerant species, resulting in an entire reorganization of the community. Analyses of succession patterns of the benthic rocky reef communities in the naturally acidified ecosystem suggest the reduced abundance of some calcareous species is linked to the increased abundance of fleshy seaweeds. While some calcareous species are able to recruit and grow at similar rates in non-acidified and acidified conditions during early stages of succession, their abundance is limited by the rapid growth of fleshy seaweeds in acidified conditions during the later stages of succession. Furthermore, analyses of recovery patterns suggest the role of calcareous herbivores is altered in acidified conditions. While recovery from disturbance in non-acidified conditions is highly variable and contingent on grazing by calcareous herbivores, the effects of grazing are not apparent in acidified conditions. Instead, recovery patterns in acidified conditions are canalized and consistently result in similar assemblages dominated by fleshy seaweed. Together, the results from this dissertation suggest ocean acidification causes a reorganization of a benthic rocky reef community, resulting in assemblages dominated by fleshy seaweeds with reduced diversity, invertebrate biomass, and trophic complexity. Furthermore, acidification affects the temporal and spatial dynamics of benthic rocky reef communities, leading to reduced habitat patchiness and diversity at the landscape scale.

Keywords: Biology.
Advisor: Micheli Fiorenza primary advisor. Thesis advisor
Dunbar Robert advisor. Thesis advisor
Palumbi Stephen R. advisor. Thesis advisor
Emerging immunosuppressants [electronic resource] : the identification, characterization and in vivo application of orai channel inhibitors

Store-operated calcium (SOC) entry and channel play a central role in regulating intracellular calcium concentrations in a variety of cell types. SOC is critical for many physiological processes, most notably activation of the immune system, where its lack of function is known to cause severe combined immunodeficiency (SCID) in human patients. In lymphocytes, where SOC has been extensively studied, it has been shown that SOC is mediated by the calcium channel Orai that is activated by its direct binding to STIM, a calcium sensor localized in the endoplasmic reticulum. While it was previously thought that SOC serves an important role only in immune and non-excitable cells, it is now clear that SOC and the proteins that regulate its function are ubiquitously expressed in variety of tissues, including muscle and the nervous system, and serve a diverse set of biological functions. More recently, SOC has been shown to act in a several pathological processes, ranging from muscular dystrophy to cancer, underscoring the significance of gaining a better understanding of its mechanism of action. Here we set out to develop pharmacological blockers of SOC, in order to gain insights into its molecular mechanism and physiological role. Such blockers could allow for acute inhibition of SOC, allowing for a temporal control that is essential for mechanistic studies. If successfully developed, such reagents could also be of therapeutic use as immunosuppressants or anti thrombotic agents in human patients. We designed a novel methodology for generating SOC blockers based on the identification and targeting of minimal functional domains (MFDs) of STIM and Orai. Using this approach, we identified small molecule blockers that can inhibit SOC at high nanomolar concentrations and can also block T cell activation in vitro and in vivo. These studies not only provide an important set of tools for better understanding STIM and Orai function, but also identify compounds that could potentially be developed into therapeutic agents for the treatment of pathological conditions such as autoimmune disease.

Keywords: Chemical and Systems Biology.
Advisor: Dolmetsch Ricardo E. primary advisor. Thesis advisor
Lewis Richard (Richard Sheridan) advisor. Thesis advisor
Mochly-Rosen Daria advisor. Thesis advisor
Wandless Thomas advisor. Thesis advisor
Emotions are relational [electronic resource] : positioning and the use of affective linguistic resources

To understand human beings is to understand the variety and complexity of emotional experiences they have. Understanding how language is both shaped by and used in creating and coping with these experiences is the focus of this dissertation. It offers three case studies about affective linguistic resources, advancing a theoretical framework (positioning) and a series of quantitative methodologies that grow out of information-theoretic approaches to language. The first case study shows how many different linguistic resources have prominent affective aspects by examining a single emotional relationship conversation between two friends, showing how we might confidently make claims that one section of conversation is more emotionally intense than another and how we might get experimental data about connected discourse rather than being stuck in analyses of disconnected individual sentences. The second case study focuses on the word "little", which allows speakers to position themselves closer to their audiences and others through affectionate uses, allows them to hedge positions they aren't prepared to give full illocutionary force to, and which can also be used to demean and be-little. I show the factors important to determining "little"'s meaning through three experiments and analysis of seven conversational corpora. I look at the socio-pragmatics of its use, focusing especially on power and gender. In the third case study I show that emoticons occur in about 10% of posts on Twitter that are sent by people that are actually involved in real interactions (that is, they are sending messages and receiving messages back from at least four but no more than 100 other users). In addition to describing who uses which emoticons and how, I use the emoticons to describe the major dimensions of affective meaning in Twitter using hierarchical cluster analysis, factor analysis, and topic modeling. These dimensions—positivity/negativity, immediacy, teasing, and flirting—are all positional in nature. People use language to position themselves, their audiences, and their topics relative to one another. Expressions of emotions are more than internal states made visible, they are actions that have particular interpersonal causes and consequences, which are understood linguistically ("I'm mad/happy/scared") and which collective add up. This has important ramifications for any given interaction and at a more general level, these linguistic actions reveal and perturb the affective aspects of the cultural and cognitive systems they are part of.

Keywords: Linguistics
Advisor: Eckert Penelope primary advisor. Thesis advisor
Jurafsky Dan
Potts Christopher
Rickford John R.
An empire of camps [electronic resource] : British imperialism and the concentration of civilians, 1876-1903

This dissertation looks to the origins of the concentration camp as a technology of British imperial rule. Concentrated civilian camps first emerged in British India in the 1870s and 1890s to care for and control famine refugees and plague "suspects." During the South African War (1899-1902) the technology of the camp was applied in a wartime setting. Forging imperial connections across the Indian Ocean, a group of "camp experts" traveled from India to South Africa to administer the camps. Concentration camps were afflicted with high rates of mortality that resulted in a political scandal, but British officials successfully reformed living conditions using the lessons of earlier episodes of encampment. In doing so, they helped legitimize the camp as a tenable procedure of imperial warfare and welfare.

Keywords: History.
Advisor: Satia Priya primary advisor. Thesis advisor
Daughton J. P. (James Patrick) advisor. Thesis advisor
Stansky Peter
Empirical studies of demand signal processing in supply chains [electronic resource]

This dissertation studies "demand signal processing, " how demand information flows through supply chains. We begin with the bullwhip effect, the topic most commonly associated with demand signal processing. After, we study demand signal processing in new context: as a means to infer unobserved operational metrics. The bullwhip effect---a byproduct of demand signal processing---is the amplification of demand variability along a supply chain: a company bullwhips if it purchases from suppliers more variably than it sells to customers. We investigate the bullwhip effect in a sample of 4,689 public U.S. companies over 1974-2008. Overall, we find about two thirds of firms bullwhip. Decomposing the bullwhip by information transmission lead time, we find that demand signals firms observe with more than three quarters' notice drive 30% of the bullwhip, and those firms observe with less than one quarter's notice drive 51%. Demand signal processing, however, is broader than the bullwhip effect: it is a rich process that indicates much about supply chain operations. We develop an empirical supply chain model that enables empiricists to derive operational metrics from patterns in demand signal processing, and perform corresponding counterfactual analyses. The metrics illuminate previously-obscure supply chain aspects, and the counterfactuals permit related "what if" studies. We demonstrate our methodology with six studies and firm-level Compustat data, analyzing (1) whether firms consider their supplier's inventory costs, (2) the convexity of production cost functions, (3) the replenishment rate of depleted inventories, (4) the drivers of the bullwhip effect, (5) the degree to which supply chain alignment mitigates the bullwhip effect, and (6) whether demand forecast accuracy constitutes a supply chain externality.

Keywords: Business.
Advisor: Mendelson Haim primary advisor. Thesis advisor
Lee Hau Leung advisor. Thesis advisor
Whang Seungjin advisor. Thesis advisor
End-to-End Text Recognition with Convolutional Neural Networks

Full end-to-end text recognition in natural images is a challenging problem that has recently received much attention in computer vision and machine learning. Traditional systems in this area have relied on elaborate models that incorporate carefully hand-engineered features or large amounts of prior knowledge. In this thesis, I describe an alternative approach that combines the representational power of large, multilayer neural networks with recent developments in unsupervised feature learning. This particular approach enables us to train highly accurate text detection and character recognition modules. Because of the high degree of accuracy and robustness of these detection and recognition modules, it becomes possible to integrate them into a full end-to-end, lexicon-driven, scene text recognition system using only simple off-the-shelf techniques. In doing so, we demonstrate state-of-the-art performance on standard benchmarks in both cropped-word recognition as well as full end-to-end text recognition.

Keywords: Computer Science.
Neural networks (Computer science)
Text processing (Computer science)
Thesis
Advisor: Ng Andrew Y.
Energy efficient floating-point unit design [electronic resource]

Energy-efficient computation is critical for increasing performance in power limited systems. Floating-point performance is of particular interest because of its importance in scientific computing, graphics and multimedia processing. For floating-point applications that have large amounts of data parallelism one should optimize the throughput/sqmm given a power density constraint. We present a method for creating a trade-off curve that can be used to estimate the maximum floating-point performance given a set of area and power constraints. These throughput optimized designs turn out to be different from latency optimized ones and more energy efficient. Looking at floating-point multiply-add units and ignoring register and memory overheads, we find that in a 90nm CMOS technology at 1W/sqmm, one can achieve a performance of 27 GFlops/sqmm single-precision, and 7.5 GFlops/sqmm double-precision. Adding register file overheads reduces the throughput by less than 50% if the compute intensity is high. Since the energy of the basic gates is no longer scaling rapidly, to maintain constant power density with scaling requires moving the overall floating-point architecture to a lower energy/performance point using lower supply voltage, shallower pipelines and more relaxed gate sizing. A 1W/sqmm design at 90nm is a "high-energy" design, so scaling it to a lower energy design in 45 nm still yields a 7x performance gain, while a more balanced 0.1W/sqmm design only speeds up by 3.5x when scaled to 45 nm. Performance scaling below 45 nm rapidly decreases, with a projected improvement of only 2-3x for both power densities when scaling to a 22 nm technology. On the other hand, some floating-point units employed for single threaded performance such as CPU designs are latency sensitive. For such designs a different optimization in the implementation of fused floating-point multiply-add operations can be utilized. By realizing that the average latency of all operations going through the unit is what matters most, an optimized cascade design can reduce the accumulation dependent latency by 2x over a fused design, at a cost of a 13% increase in non-accumulation dependent latency. A simple in-order execution model shows this design is superior in most applications, providing 12% average reduction in floating-point instructions stalls, and improves performance by up to 6%. Simulations of superscalar out-of-order machines show 4% average CPI improvement in 2-way machines and 4.6% in 4-way machines. This feat is achieved by a design architecture called cascade where the addition operation is cascaded after multiplication in comparison to traditional architectures. The cascade design has the same area and energy budget as a traditional FMA.

Keywords: Electrical Engineering
Advisor: Dally William
Horowitz Mark (Mark Alan) primary advisor. Thesis advisor
Olukotun Oyekunle Ayinde advisor. Thesis advisor
Energy recovery from waste nitrogen through N₂O decomposition [electronic resource] : the coupled aerobic-anoxic nitrous decomposition operation (CANDO)

Human alteration of the global nitrogen cycle poses one of the greatest threats to the environment today. Anthropogenic production of reactive forms of nitrogen, namely ammonia (NH4+) via the Haber Bosch process, has nearly doubled the rate of terrestrial nitrogen deposition and resulted in an array of public health and environmental problems including ammonia toxicity to aquatic life, eutrophication of nutrient limited natural water bodies, oxygen depletion (hypoxia), and over 400 documented "dead zones" worldwide. As a result, dual pressures of increasingly stringent nitrogen discharge regulation and rising energy costs have made efficient removal of nitrogen polluted water streams one of the most pressing water quality issues facing treatment facilities. While many processes recover energy from waste organics, no known process recovers energy from waste nitrogen. This research work introduces a new process that improves the efficiency of nitrogen (NH4+) removal from wastewater by lowering energy inputs and enabling energy recovery from waste nitrogen itself. This process is termed the Coupled Aerobic-anoxic Nitrous Decomposition Operation (CANDO) and is based on three principal steps: (1) biological oxidation of NH4+ to NO2-; (2) biological or chemical reduction of NO2- to N2O gas; and (3) N2O conversion to N2 with energy recovery via decomposition or combustion with a fuel (biogas). The development of CANDO was inspired by prior research on the use of N2O as a "green" propellant in propulsion applications and the realization that N2O could be a renewable feedstock, generated by waste nitrogen. This research is presented in three parts: (1) development of thrusters based on N2O catalytic decomposition that achieve high performance and a self-sustaining reaction; (2) theoretical studies of N2O decomposition over Rh2O3 catalyst, using Density Functional Theory (DFT), that reveal high reactivity of stable surfaces of Rh2O3 and key N2O reaction mechanisms; and (3) experimental studies on the conversion of NO2- to N2O (the novel and previously unexplored step in CANDO) via two pathways - biotic partial denitrification by oxidation of intracellular polyhydroxybutyrate (PHB), and abiotic chemical reaction driven by Fe(II).

Keywords: Mechanical Engineering
Advisor: Cantwell Brian primary advisor. Thesis advisor
Criddle Craig advisor. Thesis advisor
Wilcox Jennifer
Energy-efficient flow control for on-chip networks [electronic resource]

With the emergence of on-chip networks, the power consumed by router buffers has become a primary concern. Bufferless flow control has been proposed to address this issue by removing router buffers and handling contention by dropping or deflecting flits. In this thesis, we compare virtual-channel (buffered) and deflection (packet-switched bufferless) flow control. Our study shows that unless process constraints lead to excessively costly buffers, the performance, cost and increased complexity of deflection flow control outweigh its potential gains. To provide buffering in the network but without the cost and timing overhead of router buffers, we propose elastic buffer (EB) flow control which adds simple control logic in the channels to use pipeline flip-flops (FFs) as EBs with two storage locations. This way, channels act as distributed FIFOs and input buffers as well as the complexity for virtual channels (VCs) are no longer required. Therefore, EB networks have a shorter cycle time and offer more throughput per unit power than VC networks. We also propose a hybrid EB-VC router which is used to provide traffic separation for a number of traffic classes large enough for duplicate physical channels to be inefficient. These hybrid routers offer more throughput per unit power than both EB and VC routers. Finally, this thesis proposes packet chaining, which addresses the tradeoff between allocation quality and cycle time traditionally present in routers with VCs. Packet chaining is a simple and effective method to increase allocator matching efficiency to be comparable or superior to more complex and slower allocators without extending cycle time, particularly suited to networks with short packets.

Keywords: Electrical Engineering
Advisor: Dally William
Kozyrakis Christoforos
McKeown Nick advisor. Thesis advisor