617 Works

Sediment Mobility in Steep Channels and the Transition to Landsliding

Jeffrey Paul Prancevic
The mobility of sediment in steep mountain rivers controls the denudation rate and height of mountain ranges worldwide. Sediment movement within the steepest terrain often occurs as catastrophic shallow landsliding, posing significant hazards to those living downstream. Despite the importance of steep channels, our observations of sediment transport are mostly limited to rivers with slopes of less than 2°. This prevents us from predicting the runoff required to transport sediment throughout most of the drainage...

Numerical Studies of Topological Phases

Scott D. Geraedts
The topological phases of matter have been a major part of condensed matter physics research since the discovery of the quantum Hall effect in the 1980s. Recently, much of this research has focused on the study of systems of free fermions, such as the integer quantum Hall effect, quantum spin Hall effect, and topological insulator. Though these free fermion systems can play host to a variety of interesting phenomena, the physics of interacting topological phases...

Incipient transport of silt-sized sediments

W. M. Keck Laboratory Of Hydraulics And Water Resources

On the Construction of Higher étale Regulators

Sin Tsun Edward Fan
We present three approaches to define the higher étale regulator maps Φr,net : Hret(X,Z(n)) → HrD(X,Z(n)) for regular arithmetic schemes. The first two approaches construct the maps on the cohomology level, while the third construction provides a morphism of complexes of sheaves on the étale site, along with a technical twist that one needs to replace the Deligne-Beilinson cohomology by the analytic Deligne cohomology inspired by the work of Kerr, Lewis, and Müller-Stach. A vanishing...

Classical and Quantum Effects in Plasmonic Metals

Ana Maii Brown
The field of plasmonics exploits the unique optical properties of metallic nanostructures to concentrate and manipulate light at subwavelength length scales. Metallic nanostructures get their unique properties from their ability to support surface plasmons– coherent wave-like oscillations of the free electrons at the interface between a conductive and dielectric medium. Recent advancements in the ability to fabricate metallic nanostructures with subwavelength length scales have created new possibilities in technology and research in a broad range...

Compilation of alluvial channel data : Laboratory and field

W. M. Keck Laboratory Of Hydraulics And Water Resources

I. Quantal effects in biochemical cooperativity and a proposed mechanism for the differentiation of calcium signaling in synaptic plasticity. II. Evolutionary algorithms for the optimization of methods in computational chemistry

William Chastang Ford
In Part 1 of this thesis, we propose that biochemical cooperativity is a fundamentally non-ideal process. We show quantal effects underlying biochemical cooperativity and highlight apparent ergodic breaking at small volumes. The apparent ergodic breaking manifests itself in a divergence of deterministic and stochastic models. We further predict that this divergence of deterministic and stochastic results is a failure of the deterministic methods rather than an issue of stochastic simulations. Ergodic breaking at small volumes...

Quantifying Earthquake Collapse Risk of Tall Steel Braced Frame Buildings Using Rupture-to-Rafters Simulations

Ramses Mourhatch
This thesis examines collapse risk of tall steel braced frame buildings using rupture-to-rafters simulations due to suite of San Andreas earthquakes. Two key advancements in this work are the development of (i) a rational methodology for assigning scenario earthquake probabilities and (ii) an artificial correction-free approach to broadband ground motion simulation. The work can be divided into the following sections: earthquake source modeling, earthquake probability calculations, ground motion simulations, building response, and performance analysis. As...

Holistic Design In High-Speed Optical Interconnects

Saman Saeedi
Integrated circuit scaling has enabled a huge growth in processing capability, which necessitates a corresponding increase in inter-chip communication bandwidth. As bandwidth requirements for chip-to-chip interconnection scale, deficiencies of electrical channels become more apparent. Optical links present a viable alternative due to their low frequency-dependent loss and higher bandwidth density in the form of wavelength division multiplexing. As integrated photonics and bonding technologies are maturing, commercialization of hybrid-integrated optical links are becoming a reality. Increasing...

Quantifying Earthquake Collapse Risk of Tall Steel Moment Frame Buildings Using Rupture-to-Rafters Simulations

Hemanth Siriki
There is a sparse number of credible source models available from large-magnitude past earthquakes. A stochastic source model generation algorithm thus becomes necessary for robust risk quantification using scenario earthquakes. We present an algorithm that combines the physics of fault ruptures as imaged in laboratory earthquakes with stress estimates on the fault constrained by field observations to generate stochastic source models for large-magnitude (Mw 6.0-8.0) strike-slip earthquakes. The algorithm is validated through a statistical comparison...

The Phonon Thermodynamics of Iron and Cementite

Lisa Mary Mauger
The vibrational properties of materials are essential to understanding material stability and thermodynamics. In this thesis I outline vibrational thermodynamic models and the experimental tools that provide evidence on phonon behavior. The introductory section discusses the history of metallurgy and thermodynamic theory, with an emphasis on the role of iron and cementite, two important components of steels. The thermodynamic framework for understanding vibrational material behavior is provided alongside the growing body of experimental and computational...

Numerical Investigation of Vertical-Axis Wind Turbines at Low Reynolds Number

Hsieh-Chen Tsai
This thesis is aimed at numerically investigating the aerodynamics and the starting of a vertical-axis wind turbine at low Reynolds number using the immersed boundary method. The influence of the Coriolis effect on dynamic stall is isolated by comparing the rotating airfoil to one undergoing an equivalent planar motion that is composed of surging and pitching motions that produce an equivalent speed and angle of attack variation over a cycle. At lower tip-speed ratios, the...

Quantum Mechanics Studies of Fuel Cell Catalysts and Proton Conducting Ceramics with Validation by Experiment

Ho-Cheng Tsai
We carried out quantum mechanics (QM) studies aimed at improving the performance of hydrogen fuel cells. This led to predictions of improved materials, some of which were subsequently validated with experiments by our collaborators. In part I, the challenge was to find a replacement for the Pt cathode that would lead to improved performance for the Oxygen Reduction Reaction (ORR) while remaining stable under operational conditions and decreasing cost. Our design strategy was to find...

Ferrous Iron Sensing and Responding in Pseudomonas aeruginosa

Naomi N. Kreamer
Controlling iron distribution is important for all organisms, and is key in bacterial pathogenesis. It has long been understood that cystic fibrosis (CF) patient sputum contains elevated iron concentrations. However, anaerobic bacteria have been isolated from CF sputum and hypoxic zones in sputum have been measured. Because ferrous iron [Fe(II)] is stable in reducing, acidic conditions, it could exist in the CF lung. I show that a two-component system, BqsRS, specifically responds to Fe(II) in...

Structural Study of Piezo Channel, a Unique Family of Eukaryotic Mechanosensitive Channel

Aron Kamajaya
Piezo is a unique family of eukaryotic mechanosensitive (MS) channel. With over 2500 amino acids per subunit, intact Piezo channel is one of the largest ion channels known to date. Two versions of Piezo can be found in vertebrates, namely PIEZO1 and PIEZO2. PIEZO1 appears to play roles in processes which control physiological homeostasis, whereas PIEZO2 assumes roles in mechanical somatosensation. A number of mutations mapped onto PIEZO1 or PIEZO2 are found in several hereditary...

Paths Towards High Efficiency Silicon Photovoltaics

Hal S. Emmer
While photovoltaics hold much promise as a sustainable electricity source, continued cost reduction is necessary to continue the current growth in deployment. A promising path to continuing to reduce total system cost is by increasing device efficiency. This thesis explores several silicon-based photovoltaic technologies with the potential to reach high power conversion efficiencies. Silicon microwire arrays, formed by joining millions of micron diameter wires together, were developed as a low cost, low efficiency solar technology....

Dynamics of the Intertropical Convergence Zone

Tobias Bischoff
Previous studies have shown that the latitude of the Intertropical Convergence Zone (ITCZ) is negatively correlated with cross-equatorial atmospheric energy transport and that the ITCZ shifts southward as the northern hemisphere cools and the northward cross-equatorial energy transport strengthens. However, it has remained unclear what controls the sensitivity of the ITCZ position to cross-equatorial energy transport, and what other factors may lead to shifts of the ITCZ position. In this thesis, it is shown how...

Fabrication, Characterization, And Deformation of 3D Structural Meta-Materials

Lauren Christine Montemayor
Current technological advances in fabrication methods have provided pathways to creating architected structural meta-materials similar to those found in natural organisms that are structurally robust and lightweight, such as diatoms. Structural meta-materials are materials with mechanical properties that are determined by material properties at various length scales, which range from the material microstructure (nm) to the macro-scale architecture (μm – mm). It is now possible to exploit material size effect, which emerge at the nanometer...

On the Stability of Supersonic Boundary Layers with Injection

Bryan Eric Schmidt
The problem of supersonic flow over a 5 degree half-angle cone with injection of gas through a porous section on the body into the boundary layer is studied experimentally. Three injected gases are used: helium, nitrogen, and RC318 (octafluorocyclobutane). Experiments are performed in a Mach 4 Ludwieg tube with nitrogen as the free stream gas. Shaping of the injector section relative to the rest of the body is found to admit a "tuned" injection rate...

Optimization and Control of Power Flow in Distribution Networks

Masoud Farivar
Climate change is arguably the most critical issue facing our generation and the next. As we move towards a sustainable future, the grid is rapidly evolving with the integration of more and more renewable energy resources and the emergence of electric vehicles. In particular, large scale adoption of residential and commercial solar photovoltaics (PV) plants is completely changing the traditional slowly-varying unidirectional power flow nature of distribution systems. High share of intermittent renewables pose several...

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  • 2016

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