2,767 Works

Design of Molecules and Materials for Applications in Clean Energy, Catalysis and Molecular Machines Through Quantum Mechanics, Molecular Dynamics and Monte Carlo Simulations

Jose Luis Mendoza-Cortes
We use a multiparadigm, multiscale strategy based on quantum mechanics (QM), first-principles QM-based molecular mechanics (MD) and grand canonical Monte Carlo (GCMC) to rationally design new molecules and materials for clean energy (H2 and CH4 storage), catalysis (O2 evolution, metal organic complexes) and molecular architectures (rotaxanes, hydrogels). This thesis is organized in seven chapters and shows that it is crucial to understand the scale of the system to be studied, the insight obtained can be...

Wire Array Photovoltaics

Daniel B. Turner-Evans
Over the past five years, the cost of solar panels has dropped drastically and, in concert, the number of installed modules has risen exponentially. However, solar electricity is still more than twice as expensive as electricity from a natural gas plant. Fortunately, wire array solar cells have emerged as a promising technology for further lowering the cost of solar. Si wire array solar cells are formed with a unique, low cost growth method and use...

Spatially Resolved Star Formation in Cosmological Zoom-in Simulations: Understanding the Role of Feedback in Scaling Relations

Matthew Edward Orr
To understand the night sky is to understand how galaxies form their stars. Cosmological zoom-in simulations, which self-consistently evolve a small number of galaxies at very high resolution by embedding them within a fully cosmological box, have evolved over the last 25 years to a level of realism where they can begin to tackle questions of spatially resolved star formation within galaxies. Whereas a decade ago simulations faced difficulty in matching even global properties of...

Navigating Earthquake Physics with High-Resolution Array Back-Projection

Lingsen Meng
Understanding earthquake source dynamics is a fundamental goal of geophysics. Progress toward this goal has been slow due to the gap between state-of-art earthquake simulations and the limited source imaging techniques based on conventional low-frequency finite fault inversions. Seismic array processing is an alternative source imaging technique that employs the higher frequency content of the earthquakes and provides finer detail of the source process with few prior assumptions. While the back-projection provides key observations of...

Molecular Design of Side-Group Liquid Crystalline Polymers: Understanding Their Interactions with Small Molecule Liquid Crystal Solvent

Zuleikha Kurji
Liquid crystal (LC) gels – the combination of macromolecules with small molecule LCs – couple the elasticity and mechanical strength of polymers to the order inherent to LCs and are attractive to many researchers hoping to marry liquid crystals' optical and electro-optical responsiveness with polymers' mechanical strength and ease of processing. In particular, side-group liquid crystal polymers (SGLCPs) are flexible-chain polymers that are functionalized with LC side-groups. Here we introduce the concept of polymer dopants:...

Neural and Computational Representations of Decision Variables

Daniel Ciarán McNamee
These studies explore how, where, and when representations of variables critical to decision-making are represented in the brain. In order to produce a decision, humans must first determine the relevant stimuli, actions, and possible outcomes before applying an algorithm that will select an action from those available. When choosing amongst alternative stimuli, the framework of value-based decision-making proposes that values are assigned to the stimuli and that these values are then compared in an abstract...

Electromyographic Signal Processing With Application To Spinal Cord Injury

Zhao Liu
An Electromyogram or Electromyographic (EMG) signal is the recording of the electrical activity produced by muscles. It measures the electric currents generated in muscles during their contraction. The EMG signal provides insight into the neural activation and dynamics of the muscles, and is therefore important for many different applications, such as in clinical investigations that attempt to diagnose neuromuscular deficiencies. In particular, the work in this thesis is motivated by rehabilitation for patients with spinal...

Light and Heat: Nonlocal Aspects in Conformal Field Theories

Murat Koloğlu
This thesis is dedicated to certain nonlocal aspects of conformal quantum field theories (CFTs). Two main directions are the study of CFTs on a particular globally-nontrivial spacetime corresponding to finite temperature, and the study of particular nonlocal CFT observables localized on light-rays. Specifically, we introduce bootstrap techniques for determining finite-temperature data of CFTs, and make novel predictions for the 2+1-dimensional Ising model. We propose the “stringy equivalence principle”, stating that coincident gravitational shocks commute, as...

Sensor Networks for Geospatial Event Detection - Theory and Applications

Annie Hsin-Wen Liu
This thesis presents theories, analyses, and algorithms for detecting and estimating parameters of geospatial events with today's large, noisy sensor networks. A geospatial event is initiated by a significant change in the state of points in a region in a 3-D space over an interval of time. After the event is initiated it may change the state of points over larger regions and longer periods of time. Networked sensing is a typical approach for geospatial...

Soil Stress Field Around Driven Piles

Marie-Agnes Allard
The description, equipment, and results of a series of pile-driving experiments conducted in a centrifuge using a model pile driven in dry sand are presented. The work was conceived on the basis of the modelling of a soil-structure system under an artificially generated gravitational field, and motivated by the need for experimental data for a better understanding of the complex phenomena involved in the pile-soil interaction during driving. The behavior of the pile itself has...

Topology and Analysis in PWM Inversion, Rectification, and Cycloconversion

Khai Doan The Ngo
Topologies and analysis techniques in switched-mode dc conversion (dc-to-dc), inversion (dc-to-ac), rectification (ac-to-dc), and cycloconversion (ac-to-ac) are unified in this thesis. The buck, boost, buck-boost, and flyback topologies are used to demonstrate that familiar dc converters can be extended into equivalent ac converters. Although some of these are presented as fast-switching circuits, they have also been found in slow-switching applications. Thus, topology is the unifying factor not only over four fields of power electronics, but...

Endoscopic optical coherence tomography : design and application

Jian Ren
This thesis presents an investigation on endoscopic optical coherence tomography (OCT). As a noninvasive imaging modality, OCT emerges as an increasingly important diagnostic tool for many clinical applications. Despite of many of its merits, such as high resolution and depth resolvability, a major limitation is the relatively shallow penetration depth in tissue (about 2∼3 mm). This is mainly due to tissue scattering and absorption. To overcome this limitation, people have been developing many different endoscopic...

Transition Metal Clusters Supported by Multinucleating Ligand Frameworks as Models of Biological Active Sites

Emily Yuan Tsui
This dissertation describes efforts to model biological active sites with small molecule clusters. The approach used took advantage of a multinucleating ligand to control the structure and nuclearity of the product complexes, allowing the study of many different homo- and heterometallic clusters. Chapter 2 describes the synthesis of the multinucleating hexapyridyl trialkoxy ligand used throughout this thesis and the synthesis of trinuclear first row transition metal complexes supported by this framework, with an emphasis on...

Geology of the Ravenna Quadrangle

Richard Henry Jahns
The Vasquez Series, composed of coarse fanglomerates, finer sandstones, and lavas, represents sub-areal deposition in the form of a series of rapidly coalescing alluvial fans. These fans were formed in a basin entirely local in character (confined to the Ravenna and Lang Quadrangles) which was probably caused by faulting, either in late Oligocene or very early Miocene time. The sediments are early or early middle Miocene in age, are very well consolidated, poorly sorted, and...

Cloud Computing for Citizen Science

Michael James Olson
My thesis describes the design and implementation of systems that empower individuals to help their communities respond to critical situations and to participate in research that helps them understand and improve their environments. People want to help their communities respond to threats such as earthquakes, wildfires, mudslides and hurricanes, and they want to participate in research that helps them understand and improve their environment. “Citizen Science” projects that facilitate this interaction include projects that monitor...

Diffraction of a Trapped Wave by a Semi-Infinite Metallic Sheet

Georges G. Weill
[Figure 1; see abstract in PDF for details]. It is a well-known fact that dielectric coated infinite metallic structures such as planes and wires can propagate "surface modes". We are here chiefly concerned with a two-dimensional case. There is no theoretical difficulty in extending our solution to three-dimensional structures. We are dealing here with a grounded dielectric slab of permittivity ε and thickness a. (The case in which the electric wall is replaced by a...

Evaporation From Lakes

Nephi Willard Cummings
Evaporation can be determined by the aid of the first law of thermodynamics in such a way that wind velocity need not enter the calculation. Air temperature and humidity enter only as terms in a correction which can have a relatively small average value under typical conditions. A method of finding the difference between incoming and outgoing radiation, from observations on a well insulated pan is described, and also a method of finding the ratio...

Statistical Models of the Protein Fitness Landscape: Applications to Protein Evolution and Engineering

Philip Anthony Romero
Understanding the protein fitness landscape is important for describing how natural proteins evolve and for engineering new proteins with useful properties. This mapping from protein sequence to protein function involves an extraordinarily complex balance of numerous physical interactions, many of which are still not well understood. Directed evolution circumvents our ignorance of how a protein’s sequence encodes its function by using iterative rounds of random mutation and artificial selection. The selection criteria is based on...

Proximal-Field Radiation Sensors for Dynamically Controllable and Self-Correcting Integrated Radiators

Amirreza Safaripour Tabbalvandani
One of the major challenges in the design of integrated radiators at mm-wave frequencies is the generation of surface waves in the dielectric substrate by the on-chip antennas. Since dielectric substrates are excellent surface waveguides with a fundamental mode with no cutoff frequency, there is always some energy trapped in them due to the surface waves and the excited substrate modes. This phenomenon is a significant cause of reduced radiation efficiency for mm-wave integrated radiators....

Fast Numerical Methods for Mixed, Singular Helmholtz Boundary Value Problems and Laplace Eigenvalue Problems - with Applications to Antenna Design, Sloshing, Electromagnetic Scattering and Spectral Geometry

Eldar Akhmetgaliyev
This thesis presents a novel class of algorithms for the solution of scattering and eigenvalue problems on general two-dimensional domains under a variety of boundary conditions, including non-smooth domains and certain "Zaremba" boundary conditions - for which Dirichlet and Neumann conditions are specified on various portions of the domain boundary. The theoretical basis of the methods for the Zaremba problems on smooth domains concern detailed information, which is put forth for the first time in...

Robot Navigation in Dense Crowds: Statistical Models and Experimental Studies of Human Robot Cooperation

Peter Trautman
This thesis explores the problem of mobile robot navigation in dense human crowds. We begin by considering a fundamental impediment to classical motion planning algorithms called the freezing robot problem: once the environment surpasses a certain level of complexity, the planner decides that all forward paths are unsafe, and the robot freezes in place (or performs unnecessary maneuvers) to avoid collisions. Since a feasible path typically exists, this behavior is suboptimal. Existing approaches have focused...

Advancements in Jet Turbulence and Noise Modeling: Accurate One-way Solutions and Empirical Evaluation of the Nonlinear Forcing of Wavepackets

Aaron S. Towne
Jet noise reduction is an important goal within both commercial and military aviation. Although large-scale numerical simulations are now able to simultaneously compute turbulent jets and their radiated sound, lost-cost, physically-motivated models are needed to guide noise-reduction efforts. A particularly promising modeling approach centers around certain large-scale coherent structures, called wavepackets, that are observed in jets and their radiated sound. The typical approach to modeling wavepackets is to approximate them as linear modal solutions of...

Dielectric Properties of a Lattice of Anisotropic Particles

Zohrab A. Kaprielian
The dielectric properties of lattices composed of identical metallic or dielectric elements of various geometries, such as spheres, discs and strips have been investigated from a molecular point of view by Kock, Corkura and others. These investigations have treated two cases, in both of which, the element size and spacings are small compared to the wave length. The first applies to the case where the spacings are large compared to element size and which therefore...

Exact Treatment of Antenna Current Wave Reflection at the End of a Tube-Shaped Cylindrical Antenna

Erik Hallén
Antennas, whose radiating body has a cross section which is small in comparison to the length of the antenna and to the wave length, i. e. antennas consisting of wires and rods, are to a very wide extent treated with the help of a linearized integral equation, the invention of the author (Hallén 1930, eqn. 20a, b; Hallén 1938, eqn. 24; Hallén 1953, eqn. 35.31). In this equation the distance between two points on the...

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