VictorJuiz/thesis huggingface dataset:
Wall-modeled large eddy simulation in an unstructured mesh environment [electronic resource]
Keywords: Mechanical Engineering.

The present study aims at developing and validating a wall-layer model for large eddy simulation of complex turbulent flows at high Reynolds number. To be applicable to complex flows over/inside the complex geometries, a non-equilibrium wall-model based on unsteady three-dimensional Reynolds-averaged Navier-Stokes equations has been implemented in an unstructured mesh environment. This method is similar to that of the wall-model for structured mesh investigated in earlier studies, but it is supplemented by a new dynamic eddy viscosity/conductivity model that corrects the effect of the resolved Reynolds stress (resolved turbulent heat flux) on the skin friction (wall heat flux). This correction is shown to be crucial in predicting the correct level of skin friction. Unlike earlier models, this eddy viscosity/conductivity model does not have a stress-matching procedure or a tunable free parameter, and it shows consistent performance over a wide range of Reynolds numbers. The wall-model is first validated against canonical (attached) transitional and fully turbulent flows at moderate to very high Reynolds numbers. Application to a separated flow over a NACA4412 airfoil operating close to maximum lift is also considered to test the performance of the wall-model in complex non-equilibrium flows. Lastly, the capability of wall-modeled large-eddy simulation for prediction of wall-pressure fluctuations is demonstrated in terms of rms fluctuation, wavenumber-frequency spectra, and two-point correlations in the turbulent channel flow.
Water [electronic resource] : solid and liquid phase structures in "no-man's land"
Keywords: Chemistry.

This thesis will cover a large variety of different techniques and experiments, mainly using x-rays, all of which were performed on MIlliQ (18.2 M [omega] /cm2) water. The techniques range from X-ray Raman Spectroscopy (XRS), to Small Angle X-ray Scattering (SAXS), to Wide Angle X-ray Scattering (WAXS), X-ray Emission Spectroscopy (XES), to Microscopy, to designing a new High Pressure Cell for use with any type of spectroscopy. The results of using these wide variety of techniques measuring water, from near boiling on down to 227K, are tabulated in this Thesis. Primarily we were interested in the effects on the waters structure as we changed the temperature. We have found that as we cool from near boiling to 227K we see a continuous, power law shift in the splitting of the diffraction peaks, which means that at high temperatures our nearest neighbor shells are extremely indistinct, but below 290K we see an incredibly rapid sharpening of the nearest neighbor shells into very well defined shells at 2.8 Å and 4.5 Å as expected of a tetrahedral structure. As a second benefit of measuring the structural properties of very deeply supercooled liquid water, we gain for free structural information on the type of ice that is formed, how fast it is formed, and what shape is takes on when formed at these deeply supercooled temperatures. We found that the type of ice formed was hexagonal ice, not the expected stacking fault or cubic ices, we also found that the nucleation and growth rate were much slower than predicted, and finally we found that the nanoscopic particles of ice had significant anisotropy which also was not predicted.
Wave-equation migration velocity analysis for VTI models with geological and rock physics constraints [electronic resource]
Keywords: Geophysics.

Wave-equation migration velocity analysis (WEMVA) is a powerful technique for robust velocity model building when the subsurface is complex and the starting model is far from true. However, this traditional isotropic WEMVA technique cannot explain anisotropic wave phenomenon, which has significant effects when the reflectors are steeply dipping and/or the waves are traveling at large angles. Furthermore, errors in the anisotropic parameters cause similar defocusing as errors in isotropic velocity. Any defocusing caused by anisotropy may be translated to false updates in the isotropic velocity, which lead to further mispositioning and misinterpretations. However, simple extension of the isotropic WEMVA to the anisotropic medium cannot provide an unique and reliable solution due to the nonlinear and underdetermined nature of the anisotropic model building problem. Many anisotropic models with vastly different geological interpretations may explain the surface seismic data equally well. This thesis addresses these issues by including anisotropic effects in WEMVA and by integrating other useful information from geology and rock physics to better regularize the inversion. First, I extend the isotropic WEMVA method to the anisotropic medium to evaluate and update the anisotropic Earth models. Instead of the industry standard ray-based tomographic methods, the anisotropic WEMVA technique uses wavefields as information carrier to handle both the complex subsurface and the frequency-dependent behavior of the wave propagation. I include the geological information using steering filters to regularize the gradients. Both synthetic and field 2-D examples show that the anisotropic WEMVA technique can resolve the errors in both velocity and anisotropic parameters. Consequently, the migration images are improved with higher resolution and correct depths for the reflectors. Second, I mitigate the ambiguities among the anisotropic parameters using the rock physics prior information. I model shale anisotropy in the seismic scale from well log measurements and the interpretation results from a previous isotropic processing workflow . By varying the key parameters to the rock physics models, I include different geological scenarios and parameter uncertainties in the rock physics modeling. As a result, multiple realizations of the anisotropic parameters are obtained and used as the rock physics constraints for the seismic data inversion. On a synthetic example, I show the correct rock physics regularization accelerates the convergence of the well constrained parameter and brings extra information for the poorly constrained parameters. Anisotropic WEMVA inversion of a 3-D field data set yields models that are consistent with seismic data, geological knowledge, as well as rock physics information. The migration image based on the inverted models shows better-resolved faulting discontinuities and better imaged reflectors around salt flanks.
Wavelength-modulation spectroscopy for determination of gas properties in hostile environments [electronic resource]
Keywords: Mechanical Engineering.

Over the past 40 years, tunable diode laser absorption spectroscopy (TDLAS) sensors have matured into a practical technology for providing non-intrusive, in-situ measurements of gas properties in a number of hostile energy systems. However, the applicability of TDLAS sensors has been limited by a number of fundamental measurement challenges including: beam-steering, non-absorbing transmission losses, interfering emission, line-of-sight non-uniformities, and broad and blended absorption spectra at high pressures. This work presents the development and demonstration of several novel calibration-free wavelength-modulation spectroscopy (WMS) techniques and sensors that enable high-fidelity measurements of gas properties in highly non-uniform gases and high-pressure gases. These WMS techniques are demonstrated with measurements of gas temperature, H2O, pressure, and velocity in two model scramjet combustors and a pulse detonation combustor.
What motivates people to try to persuade others? Ironic and contradictory determinants of advocacy [electronic resource]
Keywords: Business.

This dissertation explores various factors that influence advocacy. When people seek support for a cause, they typically present the strongest arguments they can muster. The current research departs, however, in identifying the conditions under which (and processes through which) presenting weak arguments can stimulate greater advocacy. Chapter 1 examines this ironic predictor of advocacy. This research also explores the impact of people's lay theories about attitudes on advocacy. People vary in the extent to which they believe attitudes are fixed (entity theorists) or malleable (incremental theorists). Results indicate that entity theories of attitudes simultaneously motivate and demotivate willingness to try to persuade others. Chapter 2 explores the contradictory ways in which these lay theories affect advocacy.
When membranes collide [electronic resource] : studying vesicle fusion using a model system based on DNA hybridization
Keywords: Chemistry.

Membrane fusion consists of a complex rearrangement of lipids and proteins that results in the merger of two lipid bilayers. This fusion reaction is central to many biological processes, including endo- and exocytosis and the transfer of membrane proteins between cellular compartments. The process of vesicle docking and fusion is mediated by formation of the SNARE protein complex, made up of recognition partners on the vesicle and target membranes, with many other accessory proteins assisting or regulating the process. Although extensively studied, essential questions about vesicle fusion, including the number of components involved and the precise physical mechanism, are not well understood. Due to the complexity of the fusion reaction and the proteins involved, reductionist model systems can complement in vivo data to yield a better understanding of this biological process. This dissertation describes the development and study of a reductionist model system that employs synthetic DNA-lipid conjugates as surrogates for the SNARE machinery. This model system affords easy control over DNA sequence, binding geometry, and length—factors less easily probed in SNARE-mediated fusion—and it allows us to examine how fusion proceeds once the vesicle and target membranes are brought close together in the absence of accessory factors. Previous work has demonstrated that hybridization of complementary DNA-lipid pairs on different vesicles can enable fusion between small vesicles in bulk. This dissertation expands upon that previous work to develop assays to study DNA-mediated vesicle fusion on the individual event level. These assays are then used to ask mechanistic questions about the DNA-mediated fusion reaction that were not previously addressable.
Whole-heart magnetic resonance imaging with non-Cartesian trajectories [electronic resource]
Keywords: Electrical Engineering.

The key factor in advancing widespread use of CMRA is the certainty that diagnostic results can be obtained across scanners and across sites. CMRA methods making use of non-Cartesian imaging trajectories, such as the 3D cones trajectory, are prone to errors from deviations in the MR gradient system. By characterizing this system with a linear time-invariant model based on a chirp signal, MR gradient system based errors are reduced. Free-breathing CMRA protocols provide an alternative to breath-held acquisitions which can be difficult for patients to perform. Accurate tracking of the heart is vital in order to ensure that image quality does not suffer from respiratory-based motion. With the development of a variable-density 3D cones trajectory, whole-heart images of the heart are acquired every heartbeat. With this information, the nonrigid motion of the heart can be tracked and corrected in post-processing. The variable-density 3D cones trajectory is also beneficial for increasing the resolution of the CMRA acquisition. Without significantly impacting the scan time, both the spatial and temporal resolution of images are increased. Improved efficiency is also gained by reducing the oversampling of the 3D cones and other non-Cartesian trajectories. With a flexible, numerical framework, time-efficient non-Cartesian trajectories are designed for excitation, improving spatial selectivity, and for imaging.
Wireless powering and communications for mm-sized pacemakers, sensors, neuromodulators, and optogenetics [electronic resource]
Keywords: Electrical Engineering.

Implantable electronic devices provide precise recording or modulation of neurological activity. They promise to be platforms for new treatments and tools for scientific discovery. Two of the key challenges in realizing implantable systems at the millimeter scale are powering and communications. Miniaturizing these devices using wireless technologies would allow the electronics to be delivered into the body using minimally invasive methods such as through a catheter or a hypodermic needle. Power delivery for miniature implants deep within the human body cannot be done safely with inductive coupling at low frequencies. To develop new high frequency power transfer systems through tissue, new instruments are needed. A method for characterizing power receiving microstructures using an optical link is discussed. Midfield powering is introduced which uses a patterned metal plate to transform evanescent waves to propagating waves upon interaction with tissue. A spatially adaptive system is developed that can deliver power through 10~cm of tissue mimicking phantom solution. Next, a pacemaker the size of a grain of rice is developed and powered to pace from the epicardium of a rabbit and the endocardium of a pig. A custom integrated circuit is introduced which contains the main building blocks for efficient power harvesting in tissue and transmission from an implant to outside the body. A pulsed-RF transmitter is designed to harvest energy and transmit RF pulses to an external coupler. Next, wireless technologies are applied to scientific tools for neuroscience experiments in small animals. The challenge of power delivery for neurological experimentation with small animals is that ideally, the animal should be freely moving without any visible sign of an implant. A new approach of wireless powering is introduced for this application which requires no electronics to automatically focus electromagnetic waves to the location of a mouse. A wirelessly powered optogenetic stimulation device is developed that is fully internalized into the animal. Optical stimulation is performed in both the central and peripheral nervous system of untethered, freely moving mice.
Within-nest interactions and the regulation of foraging behavior in harvester ants
Keywords:  Department of Biology
Biology
Stanford
Ecology
Evolution
Gordon Lab
ant behavior
Thesis

Ants live in colonies that operate without central control. Interactions among individual ants determine how a colony regulates its behavior to conserve water and energy (Greene, et al, 2013). Harvester ants interact in an entrance chamber just inside the nest entrance, as they come in and out of the nest. Whether an outgoing forager leaves the nest depends on its rate of interactions with returning foragers. My work investigates how, during a period of foraging, the number of ants in the entrance chamber and the locations of their interactions change over time. My project examines two aspects of the behavior of the red harvester ant (Pogonomyrmex barbatus): (1) how the rate of returning foragers affects the pool of outgoing foragers by regulating ants moving up to the entrance chamber from the deeper nest, and (2) how the shape of a colony’s entrance chamber determines the density and location of interactions. We created 16 films of 6 different ant colonies and recorded information about the number of ants moving in and out of the entrance chamber from the deeper nest, and also marked where ants were having interactions in the entrance chamber.
We found that the rate of returning foragers does influence the size of the pool of outgoing foragers, because the rate of returning foragers influences the movement of ants in and out of the entrance chamber from the deeper nest. We found a lag of 18 seconds for an ant to descend into the deeper nest after an ant has returned to the entrance chamber from an outside foraging trip. We also found that the descent of an ant into the deeper nest is also associated with an ant coming up from the deeper nest after a mean lag of 38.25 seconds. We also find that ants tend to have most of their interactions around the tunnel entrance and exit of the entrance chamber just inside the nest entrance. These relationships suggest that on a scale of seconds, returning foragers are regulating movement among chambers within a nest and thus changing the outgoing forager numbers. Ants tend to engage in interactions around entrances/exits. But interaction “hotspots” also vary among colonies, as colony nest shape varies.
Wounding the Female Body Politic: Reading the 1580s in The Faerie Queene
Keywords:  Department of English
Department of English
The Faerie Queene
Edmund Spenser
Queen Elizabeth
sixteenth century literature
sixteenth century history
Ireland
wounds
injury
body politic
gender
Thesis

This thesis explores how Edmund Spenser's experience of the 1580s, in conjunction with the events of Queen Elizabeth's reign, shaped his epic The Faerie Queene. In particular, the thesis explores the descriptive detail of wounds in the epic and explores how they reveal Spenser's anxiety about Elizabeth's female body politic.
X-ray spectroscopy of copper surface chemistry for catalysis of carbon dioxide conversion to fuels [electronic resource]
Keywords: Chemical Engineering.

The non-renewable nature of fossil fuels and the environmental impact of related CO2 emissions are two challenges facing mankind in the 21st century. Fossil fuels with their high energy density are predicted to make up ~80% of the global energy portfolio even up to 2040 [U.S. Energy Information Administration]. Renewable energy resources such as solar and wind are attractive because they are virtually inexhaustible energy sources and they have no CO2 emissions once the infrastructure is in place. They do however have the problem of intermittency, and therefore require some form of storage if they are to be used on a large scale as the primary source of energy. Batteries are not yet quire up to the task as they have much lower energy densities than fossil fuels. If it were possible to efficiently convert CO2 to high energy density hydrocarbons using solar and wind energy, this would allow for the storage of the renewable energy in the chemical bonds of the fuels and result in a net zero carbon cycle. Two known methods to convert CO2 to fuels are conventional methanol synthesis and the electrochemical reduction of CO2. The best known catalyst for both reactions is copper but even copper is hardly ideal. In order to design more efficient catalysts, it is important to understand the chemistry of the different surface intermediates present on the copper catalyst in the course of the reactions. The first part of the thesis looks at the interaction of formaldehyde, formate, methanol and methoxy on Cu(111) and Cu(110) in ultra-high vacuum (UHV) using temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS). The second part of the thesis looks at CO2 and CO on the stepped Cu(211) surface in UHV using TPD, XPS and x-ray absorption spectroscopy (XAS). The third part of the thesis looks at the electrochemistry of copper overlayers on a Au(111) surface using XAS.
100-Gbps ethernet over twisted-pairs [electronic resource]
Keywords: Electrical Engineering.

Ever-increasing network and internet traffic, coupled with continued growth in server capacity, puts higher and higher requirements on interconnections between equipment in data centers. Ethernet over twisted-pair cabling (Base-T) has traditionally been the method of choice for these connections. To be able to meet those higher requirements, a next-generation Base-T technology should ideally be capable of delivering a maximum throughput of up to an order of magnitude higher than today. New techniques are proposed here to increase the data rates achievable over twisted-pairs. A model based on multi-conductor transmission line theory is expanded and used at frequencies up to a few GHz to characterize existing cables, as well as to suggest guidelines for improvements in the future. Lab measurements are then used to both validate this model, as well as to compute data rates achieved by using common-mode (as opposed to the conventional differential-only) signaling in twisted-pairs. It is shown that there is a potential for a significant increase in data rates by exploiting all available modes of energy transfer in this medium. More specifically, under the stated assumptions in Chapter 4, it is shown that only through the use of single-ended signaling is a rate of 100Gbps achievable at 30m with a single cable, and at 100m with four cables.
3D finite-difference frequency-domain method for plasmonics and nanophotonics [electronic resource]
Keywords: Electrical Engineering.

The finite-difference frequency-domain (FDFD) method is a conceptually simple method to solve time-dependent differential equations for steady-state solutions. In solving Maxwell's equations in three-dimensional (3D) space, however, the FDFD method has not been a popular method due to the slow convergence of iterative methods of solving a large system of linear equations Ax = b constructed by the FDFD method. In this dissertation, we show that the convergence speed can be greatly accelerated for plasmonic and nanophotonic systems by carefully modifying the properties of A. First, we make the matrix A significantly better-conditioned by using the stretched-coordinate perfectly matched layer (SC-PML) rather than the more commonly used uniaxial PML (UPML) as an absorbing boundary. Second, we eliminate the high multiplicity of near-zero eigenvalues of A by utilizing the continuity equation. By combining these two techniques, we achieve 300-fold acceleration in the convergence of iterative methods for an example 3D plasmonic system. We also demonstrate successful application of the acceleration techniques to a real-world engineering problem of designing novel integrated optical circuit components, namely broadband sharp 90-degree bends and T-splitters, in plasmonic coaxial waveguides.
A Body of Work: Anatomy of an Eating Disorder
Keywords: eating disorders
memoir
college students
body image
eating disorders-therapy and treatment
interviews
mental and physical health
Stanford University Program in Feminist Gender and Sexuality Studies
Thesis

Abstract from Introduction:
How do you recover a broken body?
"In the spring of my junior year, this question sparked the flame that became my thesis. I did not
know the answer to my question or what form my answer might take. I did not know where I
would begin or where, and with what, I intended to end. Like a child running away from home,
all I had attached to the stick over my shoulder was the will to write and a story to tell. I wanted
to share my own experience with an eating disorder. I wanted to use my struggle and the lessons
I learned to help others who are also struggling. “What if my thesis had the power to inspire
desire?” I wrote to myself at the beginning of the project. “What if someone who was struggling
with an eating disorder read it and found herself in the words, found a flame in the words to
warm her hands by?”
With this question to guide me, I set off on my research: “How do you recover a broken
body?” I began by interviewing other writers. To poets, novelists, and memoirists, I asked how
you create a narrative arc, how you articulate pain through language, and how you find the
bravery to share your work. I asked if they were recovering in any way. I also interviewed
medical professionals including doctors, therapists, researchers, and nutritionists. We spoke
about the challenges and rewards of working with adolescents with eating disorders, and they
shared their stories and their definitions of recovery. Having spent so long in a hospital bed,
during these interviews I had an understanding for the first time of what it might be like to stand
over the bed, read the charts, make the diagnosis, and witness the struggle."