VictorJuiz/thesis huggingface dataset:
Effects of biochemical factors and mechanical loading on chondrogenesis of human adipose-derived stem cells [electronic resource]
Keywords: Mechanical Engineering.

Osteoarthritis (OA), a debilitating musculoskeletal disease that is characterized by cartilage degeneration, is one of the leading causes of disability in older adults. In 2006, it was estimated to affect 27 million adults in the United States, carrying with it a financial burden of over
The effects of ground-based very low frequency transmitters on the ionosphere and magnetosphere [electronic resource]
Keywords: Electrical Engineering.

The effects of ground-based very low frequency (VLF) transmitters on the ionosphere and magnetosphere are investigated. VLF transmitters, used primarily for Naval communications with submarines, are also capable of heating the ionosphere and inducing the precipitation of energetic electrons from the Earth's radiation belts. Controlled modulation experiments are performed with the 21.4 kHz, 424 kW VLF transmitter NPM in Lualualei, Hawaii, and physical effects of the NPM transmissions are studied with sub-ionospherically propagating VLF probe signals. Observed perturbations to the probe signal are not consistent with expectations from transmitter-induced electron precipitation nor to off-path scattering from a concentrated heating region near the transmitter but rather appear to be the result of scattering from extended lateral heating of the ionosphere by the NPM transmitter. A large-scale computational modeling framework confirms theoretically that this form of ionospheric heating can account for the observed probe signal modulations, establishing that the lateral extent of ionospheric heating due to VLF transmitters is several thousand kilometers, significantly greater than previously recognized. The trans-ionospheric propagation of VLF waves is also investigated as updated attenuation estimates are provided for multiple scenarios.
Efficient and high-speed reconfigurable transceiver for miniaturized wirelessly powered implants [electronic resource]
Keywords: Electrical Engineering.

Small and versatile implantable devices that support distributed biosensing and localized operations could revolutionize modern medicine. Implantable systems will soon be an integral part of minimally invasive diagnostic, therapeutic, and surgical treatments to attain more accurate diagnosis and enhance the success rate of complex procedures. Wireless powering in combination with efficient high-speed reconfigurable transceivers that can accommodate a wide variety of biomedical applications and changing environmental conditions are essential for miniaturized medical implants. This thesis presents the detailed description of a wireless system architecture that enables the design of low-power battery-less implants. Wireless power transfer and very efficient high data rate communication techniques will be discussed. System and circuit design for two different miniaturized implantable devices, which were used to demonstrate these techniques, will be presented. The design challenges and tradeoffs of each of the projects will be discussed. The first project demonstrates efficient energy harvesting and forward data transfer as well as actuation for implants by providing up to several milliamps of current to power a magnetohydrodynamic propulsion system. The 3 mm x 4 mm prototype achieves 0.53 cm/sec speeds in fluid with a 0.06 T field using approximately 250 [microwatts], and receives data at up to 25 Mbps from a 2 W 1.86 GHz carrier. The second project illustrates the feasibility of low-power sensing for implants as well as an efficient reverse data link capable of robust operation in changing environmental conditions, which is common for implanted systems. The robustness was achieved through reconfigurable modulating load, pulse width, and data rate making this an attractive solution for a variety of applications, including the target application to develop a 1 mm3 implantable cardiac probe. External interrogator communicates with multiple devices using time domain multiple access. The implantable prototype consists of a 1 mm x 1 mm chip implemented in 65 nm CMOS process integrated with a 3D coil antenna and no other external components and consumes 10 [microwatts] while demonstrating wireless powering and two-way communication through 35 mm of tissue.
Efficient and invisible [electronic resource] : hybrid metal-semiconductor nanoscale photodetectors
Keywords: Materials Science and Engineering.

Development of ultra-compact, silicon-compatible, and functional optoelectronic devices is essential for advancing technologies in emerging areas of optical interconnects solid state lighting, renewable energy. Photodetectors play a key role of interfacing between photonics and electronics but are plagued by a fundamental discrepancy between the dimension of state-of-the-art electronic devices and the optical diffraction limit. As we start to scale optoelectronic devices to the nanoscale dimensions, it is no longer possible to consider the optical properties of the absorbing semiconductor material alone without its surrounding components such as metallic contacts. On the other hand, nanotechnology is enabling the realization of hybrid devices and circuits in which nanoscale metal and semiconductor building blocks are woven together in a highly integrated fashion. Hereby, we will describe several optoelectronic devices for which the geometrical properties of the constituent semiconductor and metallic nanostructures are tuned in conjunction with the materials properties to realize multiple functions in the same physical space. In particular, we will demonstrate a series of photodetectors in which nanoscale semiconductor wires were used to boost light absorption due to excitation of optical resonances and the nanoscale metallic electrical contacts have been designed to either render the device 'invisible' over a broad frequency range, or act as optical antenna which funnels incident light into the device to further enhance efficiency. These structures belongs to a new class of devices that capitalize on the notion that nanostructures have a limited number of resonant, geometrically tunable optical modes whose hybridization and inter-modal interference can be tailored in a myriad of useful ways for enhanced optoelectronic devices with novel functionalities.
An efficient solution procedure for multi-species reacting navier-stokes equations [electronic resource]
Keywords: Aeronautics and Astronautics.

Many countries are planning missions to Mars and the moon, which has made the ability to safely pass the most dangerous phase of the mission -- atmospheric entry -- a research priority. Prediction of the extreme aerodynamic conditions experienced during atmospheric entry is essential for safe mission, but there is currently limited experimental data to base these on. Numerical procedures are heavily used in the design of spacecraft, however, hypersonic flows are extremely challenging and computationally expensive to simulate owing to their complex physics. High temperatures induce chemical reactions in the flow, which ionize the molecular structure of the gas particles into reacting chemical species. In addition, the flow interacts chemically with the surface of the vehicle; the cooler walls of the vehicle act as a catalyst in promoting the recombination reactions which significantly affect the rate of heat transfer from the flow to the surface. These phenomena make the size of the set of governing equations very large, and extremely stiff to solve.
Electrical engineering and project delivery challenges in large-scale photovoltaic systems and data centers [electronic resource]
Keywords: Civil and Environmental Engineering.

There are workflow inefficiencies and engineering knowledge deficits in large-scale photovoltaic system construction projects. This dissertation compiles the results of my doctoral research into (1) identifying and understanding the underlying causes for some of these issues and (2) developing mechanisms to address them. I assert that many workflow inefficiencies stem from sub-optimal organizational constructs--such as extreme project supply chain fragmentation and competitive bidding--prevalent throughout the construction industry. These constructs also retard knowledge development and hence influence knowledge voids in fairly new project types/scopes, such as large-scale photovoltaic systems. In response, I developed new calculation models and analysis methods to fill knowledge voids related to electrical wiring, component layouts, and electric arc-flash safety hazards in these systems. These contributions give engineers better understandings of the performance, reliability, operator safety, and cost implications of the related design choices and facilitate model-based design-analyses. Such analyses facilitate further knowledge development and improved system quality through metric-based optimization, examples of which are presented in this dissertation. This dissertation also communicates workflow inefficiencies and knowledge deficits in data center construction and operation--a project type that is also fairly new and heavily dominated by the electrical construction activities. This secondary focus is a logical extension of my primary research goals and conveys how the sub-optimal organizational constructs negatively impact newly popular construction types other than large-scale photovoltaic projects. As tertiary contributions, I demonstrate the use of systems engineering principles in construction projects and related design-automation software tools to illustrate how these principles can be used to improve stakeholder value and system lifecycle considerations. These contributions are meant to encourage increased use of systems engineering, lean construction, and/or other lifecycle based management processes in construction projects as a means of tackling the sub-optimal organizational constructs. Additionally, I introduce a new method for managing probabilistic uncertainties in popular numerical-based decision-making tools, such as Quality Function Deployment matrices, which are used extensively in systems engineering. This method is meant to increase confidence in the use of such tools and promote further development of (and/or research into) mathematical or scientific decision-making frameworks.
Electrochemical reduction of carbon dioxide on transition metal surfaces [electronic resource]
Keywords: Chemistry.

Electrochemical carbon dioxide reduction reaction (CO2RR) is a promising way to store energy from intermittent electricity sources (ie. wind and solar) and for the synthesis of carbon-based compounds that are currently derived from fossil fuels. To commercialize this process, catalysts that selectively reduce CO2 at low overpotential are needed. Research in this area is hindered by the experimental difficulty of comparing catalyst activity. This thesis begins with the development of a custom electrolysis cell that can be coupled to product detection with NMR and GC. This method allows for accurate voltage measurement and the quantification of all possible products to give the most complete characterization of CO2RR activity available to date. The CO2RR activity of Cu metal is well-studied, but application of this more sensitive experimental method lead to the identification of five novel products: glyoxal, glycolaldehyde, ethylene glycol, hydroxyacetone, and acetone. The CO2RR product identities and their potential dependence inspired the hypothesis that the enol and diol forms of the products may be the active intermediate species on the electrode surface. CO is believed to be an intermediate of CO2RR to methane and ethylene and the direct electrochemical reduction of CO confirmed that it is also a possible intermediate in the formation of many of the novel products observed as well. After Cu, the activity of Au, Ag, Zn, Ni, Pt, and Fe for CO2RR was also measured using the same experimental method. This represents the most complete dataset of transition metal activity available and reveals several important trends. A plot of CO2RR activity vs. CO binding energy places Au at the top of the volcano, suggesting that it has a near optimal binding energy for CO (and other intermediates) within the pure metals. A strong CO binding energy is also correlated with an early onset potential for HER and methane/methanol formation. The widespread use of CO2RR will require a catalyst with higher activity than any of the pure metals. Efforts to improve activity began by alloying Fe and Ni, which are poor overall CO2RR catalysts individually, but do produce hydrocarbon products. Alloying decreased the overpotential of needed for methane formation, demonstrating that alloying is a promising method of catalyst improvement.
Electrochemistry of oxygen with lithium and protons [electronic resource]
Keywords: Mechanical Engineering.

The focus of this thesis is to identify the fundamental limitations associated with the electrochemistry of oxygen with lithium and protons based on computational modeling of the underlying processes. These have important implications for lithium-air batteries and fuel cells. We have examined three critical questions relating to the practicality of lithium-air batteries namely (i) Cycle efficiency, (ii) Deep discharge and (iii) Rechargeability. The key performance limitations were identified through a close coupling between experiments and theoretical modeling. We have developed a thermodynamic analysis based on density functional theory calculations to understand the reduction of oxygen with protons to water. Based on this analysis, we have identified a fundamental limiting overpotential of 0.37 for this reaction. We also show that this analysis can be used to understand trends in selectivity between the 4e- reduction to water and 2e- reduction to hydrogen peroxide. This analysis has been used to rationalize nearly 30 years of experiments on the catalytic activity of single crystal metal surfaces.
Electronic skin [electronic resource] : flexible and stretchable organic electro-mechanical sensors for robotics, wearable electronics and health monitoring
Keywords: Electrical Engineering.

The natural biological skin's sensor performance presents tremendous challenges to emulate on artificial, electronic systems. High sensitivity, stretchability, and self-repair are salient characteristics of natural skin that, if re-created on artificial electronic skins can empower robotics, wearable devices, and biomedical applications. Organic materials that are inherently soft, flexible, or elastic are useful starting materials to use for artificial electronic skins. In this thesis, we explore the use of soft, elastic rubber as building blocks for force/pressure sensors. In particular, we developed highly sensitive capacitive pressure sensors, and in combination with organic semiconductors, created the first pressure-sensitive organic field effect transistors with unprecedented sensitivity and speed. Our sensors can detect static pressures as small as 3 Pa with milisecond response times. We performed finite element modeling to understand how the shapes of the elastic rubber impacts mechanical sensitivity, and describe the use of soft lithography techniques as a scalable means of manufacturing such elastic shapes. We further developed such organic field effect pressure sensors on flexible substrates that can be integrated onto smart bandages to monitor the human pulse when placed on the radial artery near the wrist. To enable stretchable pressure sensors, we developed a technique to create surface buckling of carbon nanotubes. The buckled nanotube films are highly stretchable and transparent, achieving greater than 2,200 S/cm and stretchable up to 150% strains. In addition, we demonstrate the first repeatably self-healing electronic skin using a supramolecular organic-inorganic composite. We developed the self-healing material using a composite approach, and achieved a conductivity as high as 40 S/cm. The composite material is mechanically flexible, and is capable of sensing tactile and flexion forces. Lastly, we propose using organic transistors to build oscillatory circuits that respond to pressure in a similar fashion to that of biological touch receptors. We call our system Digital Tactile Sensors (DiTACTS). The DiTACT prototype sensor generates a frequency of about 0 - 200 Hz, with the frequency being proportional to the pressure applied. Thus, DiTACTS encodes pressure information using frequency encoding, similar to that of slow-adapting biological touch receptors.
Electronic transport in topological insulator nanostructures [electronic resource]
Keywords: Applied Physics.

Topological insulators are states of quantum matter with an insulating gap in the bulk and gapless surface states. The exotic spin nature of the surface electrons, resulting in topological protection from localization, suggests unconventional applications in electronics as well as fundamental scientific interests. While these exotic states have been investigated via surface-sensitive techniques intensively, electronic transport device, crucial to realize topological electronics, has lagged behind due to material challenges in candidate materials. Topological insulator nanostructure is an attractive candidate for device applications, as the size effect and boundary conditions offer a unique way to enhance / tailor the surface electron transport. In this dissertation, we first describe the design principle of topological insulator nanomaterials, with an emphasis on bismuth selenide. Two major material challenges, dominant bulk electron contribution and low surface mobility due to surface oxidation, are discussed and the solutions via nanomaterial synthesis are achieved. Elemental doping and core-shell heterostructures are developed to suppress bulk carriers and to achieve high surface electron mobility. The high electronic mobility allows us to observe Shubnikov-de Haas oscillations originated from the surface Dirac fermions. In addition to the material development, we also investigate transport properties from helical nature of the surface electrons. 1D modes of surface electrons in bismuth selenide nanowire Aharonov-Bohm interferometers is a unique electronic state providing an opportunity to reveal helical spin nature and topological protection via transport. The helical 1D mode, directly observed near the Dirac point under half magnetic flux quantum, is robust against disorder but fragile against a magnetic field breaking time-reversal-symmetry. The newly discovered 1D helical mode is expected to open a new direction to study topological electronics, as well as future applications.
The emergence of infratactility in live performing arts [electronic resource]
Keywords: Theater and Performance Studies.

This dissertation investigates how contemporary theater and aesthetic performance engage the five senses of both performers and spectators by evoking a feeling of primordial tactility of the human species (regarded both phylogenetically and ontogenetically). More specifically, it seeks out art works that deploy what media theorist Mark Hansen calls "infratactility, " pieces in which the body functions as the framer of information and the "coprocessor" of digital information. Digital coding that has become so prevalent in our lives and art practices simultaneously endanger and enrich the often fragile and elusive material world we tend to think of as live theatrical performance. In analyzing recent live performance works that implement the use of the theremin, robot-administered ingestion, smell-art and contact improvisation or those that − for the first time in the history of theater − were made specifically for (and with) infants, the goal of the dissertation is to suggest the ways live performance responds to the unprecedented threat of total irrelevance that humans face now that their bodies are no longer able to keep pace with the speed of technical vision. The author argues that the performance strategies he discusses serve the recent live performance in reinforcing perceptuomotor activities and expanding the range of perception well beyond the organic-physiological constraints of human embodiment.
Empirical analysis of the impact of tick sizes on exchange efficiency [electronic resource]
Keywords: Management Science and Engineering

The welfare gains that a securities exchange delivers to participants is influenced by regulatory and design decisions. One feature of an exchange that is determined by such decisions, for example, is the tick size. I develop two approaches to empirically analyzing the impact of a tick size reduction on exchange efficiency, measured in terms of average per trader gain. For the first approach, I estimate the impact of a tick size reduction using historical data before and after the reduction. I apply this approach to study the impact of a past tick size change and find that, contrary to the common belief that motivates tick size reductions in many securities markets, the overall exchange efficiency decreased after the tick size reduction. For the second approach, I predict the impact of a tick size reduction on a securities market using historical data from the market under the current tick system together with the incremental gradient method and simulation techniques. I test this approach by using it to predict the changes in efficiency after a historical tick size reduction and comparing the predictions to what can be inferred from historical data. The results show strong correlations between the predictions and the estimates obtained from historical data.