Physical Sciences and Mathematics Commons^™

Morphology-Properties Studies In Laser Synthesized Nanostructured Materials, Nozomi Shirato

Doctoral Dissertations

Synthesis of well-defined nanostructures by pulsed laser melting is an interesting subject from both a funda- mental and technological point of view. In this thesis, the synthesis and functional properties of potentially useful materials were studied, such as tin dioxide nanostructured arrays, which have potential applications in hydrogen gas sensing, and ferromagnetic Co nanowire and nanomagnets, which are fundamentally im- portant towards understanding magnetism in the nanoscale. First, the formation of 1D periodic tin dioxide nanoarrays was investigated with the goal of forming nanowires for hydrogen sensing. Experimental obser- vations combined with theoretical modeling successfully explained the mechanisms of structure …

Advancements In Modeling Self-Consistent Core-Collapse Supernovae With Chimera, Merek Austin Chertkow

Doctoral Dissertations

Using a sophisticated program named CHIMERA, we perform numerical simulations of the end of a massive star's life when its core can no longer support itself through electron degeneracy pressure. After a violent collapse to super-nuclear densities, the core releases its binding energy (10^53 ergs) in the form of neutrinos. Simulations have shown that a small fraction of these neutrinos' energy is deposited into the matter above the forming neutron star, which drives a delayed explosion. Throughout this process, the oxygen and lighter elements that had composed the star's outer-core and envelope experience shock-driven explosive nucleosynthesis, forming newly synthesized heavy …

The Synthesis And Characterization Of Novel Group 13 Nanostructured Building Block Heterogeneous Silicate Catalysts, Joshua G. Abbott

Doctoral Dissertations

A building block approach and sequential addition methodology were utilized to prepare heterogeneous silicate catalysts containing atomically dispersed group 13 metal (B, Al, Ga) centers. The octa(trimethyltin) silsequioxane, Si8[sub]O12[sub](OSnMe3[sub])8[sub], was used as the building block for the synthesis of these materials. Reaction of the building block with a variety of group 13 metal chlorides led to the formation of cross-linked matrices. All prepared materials were characterized by gravimetric analysis, gas absorption, IR, and NMR. In addition, aluminum and boron samples where characterized by 27[sup]Al and 11[sup]B solid state NMR, and gallium samples were studied using x-ray absorption techniques.

Studies found …

Hard And Soft Error Resilience For One-Sided Dense Linear Algebra Algorithms, Peng Du

Doctoral Dissertations

Dense matrix factorizations, such as LU, Cholesky and QR, are widely used by scientific applications that require solving systems of linear equations, eigenvalues and linear least squares problems. Such computations are normally carried out on supercomputers, whose ever-growing scale induces a fast decline of the Mean Time To Failure (MTTF). This dissertation develops fault tolerance algorithms for one-sided dense matrix factorizations, which handles Both hard and soft errors.

For hard errors, we propose methods based on diskless checkpointing and Algorithm Based Fault Tolerance (ABFT) to provide full matrix protection, including the left and right factor that are normally seen in …

Numerical Analysis Of First And Second Order Unconditional Energy Stable Schemes For Nonlocal Cahn-Hilliard And Allen-Cahn Equations, Zhen Guan

Doctoral Dissertations

This PhD dissertation concentrates on the numerical analysis of a family of fully discrete, energy stable schemes for nonlocal Cahn-Hilliard and Allen-Cahn type equations, which are integro-partial differential equations (IPDEs). These two IPDEs -- along with the evolution equation from dynamical density functional theory (DDFT), which is a generalization of the nonlocal Cahn-Hilliard equation -- are used to model a variety of physical and biological processes such as crystallization, phase transformations, and tumor growth. This dissertation advances the computational state-of-the-art related to this field in the following main contributions: (I) We propose and analyze a family of two-dimensional unconditionally energy …

Numerical Study Of The Transition Metal Oxides And The Transport Properties Of Iron Pnictides, Shuhua Liang

Doctoral Dissertations

Strongly correlated materials such as the manganites and iron pnictides are studied here with several computational techniques. Both types of materials contain transition metals. Thus, our computational models are based on the double exchange mechanism, the super exchange mechanism and the crystal field theory to describe the d electrons. In manganites, we focus on its multiferroic properties induced by the Dzyaloshinskii-Moriya interaction. In the BiFeO3 , we use classical Monte Carlo simulations to study the magnetic critical transition transition. In iron pnictides, we study the interplay between the Fermi surface orbital order and the ground state magnetic order.

Reliability Models For Hpc Applications And A Cloud Economic Model, Thanadech Thanakornworakij

Doctoral Dissertations

With the enormous number of computing resources in HPC and Cloud systems, failures become a major concern. Therefore, failure behaviors such as reliability, failure rate, and mean time to failure need to be understood to manage such a large system efficiently.

This dissertation makes three major contributions in HPC and Cloud studies. First, a reliability model with correlated failures in a k-node system for HPC applications is studied. This model is extended to improve accuracy by accounting for failure correlation. Marshall-Olkin Multivariate Weibull distribution is improved by excess life, conditional Weibull, to better estimate system reliability. Also, the univariate …

Event Shapes In Proton-Proton Collisions At Center Of Mass Energy = 1.96 Tev, Scott Atkins

Doctoral Dissertations

This dissertation presents the analysis of nine different event shapes measured in high energy pp¯ collisions. An event shape can be defined as an event-based quantity that measures how the final energies are distributed in the final event. This analysis will test strong interactions as described by Quantum Chromodynamics (QCD), through their implementation in different Monte Carlo-based models. Each of the event shapes provides information about the flow of energy in QCD events and about the hadronic final states that occur in pp¯ particle collisions, thus allowing the study of the dynamics of QCD multijet events. Any deviation of an …

Study Of Jet Transverse Momentum And Jet Rapidity Dependence Of Dijet Azimuthal Decorrelations With The Dø Detector, Kiran Chakravarthula

Doctoral Dissertations

In a collision experiment involving highly energetic particles such as hadrons, processes at high momentum transfers can provide information useful for many studies involving Quantum Chromodynamics (QCD). One way of analyzing these interactions is through angular distributions. In hadron-hadron collisions, the angular distribution between the two leading jets with the largest transverse momentum (pT) is affected by the production of additional jets. While soft radiation causes small differences in the azimuthal angular distribution of the two leading jets produced in a collision event, additional hard jets produced in the event have more pronounced influence on the distribution of …

The Study Of Pt Dependence Of Dijet Azimuthal Decorrelations In Proton-Proton Collision At Center Of Mass Energy = 7 Tev, Ramasudhakar Dhullipudi

Doctoral Dissertations

The transverse momentum (pT) dependence of azimuthal decorrelations in dijet events is studied with data collected, at an integrated luminosity of [special characters omitted] dt = (36 ± 4) pb−1, from collisions between protons at a center of mass energy of [special characters omitted] = 7 TeV using the ATLAS detector at the Large Hadron Collider. The results of the analysis of jets in a central rapidity of |y| < 0.8 and pT in the range 60 GeV < pT < 1200 GeV are presented. A new observable RΔ&phis;, defined as the fraction of the total dijet cross section corresponding to a particular range of …

Synthesis, Characterization And Self-Assembly Of Amphiphilic Block Copolymers, Xiaojun Wang

Doctoral Dissertations

This dissertation presents a review on state-of-the-art research of well-defined charged block copolymers, including synthesis, characterization, bulk morphology and self-assembly in aqueous solution of amphiphilic block polyelectrolytes. In Chapter 1, as a general introduction, experimental observations and theoretical calculations devoted towards understanding morphological behavior in charged block copolymer systems are reviewed along with some of the new emerging research directions. Further investigation of charged systems is urged in order to fully understand their morphological behavior and to directly target structures for the tremendous potential in technological applications. Following this background, in Chapters 2, 3, 4 and 5 are presented the …

Theoretical Modeling Of The Formation And Functionality Of Low-Dimensional Materials, Hua Chen

Doctoral Dissertations

This dissertation presents a series of work under the topic of designing and modeling novel low-dimensional materials and structures with desired and coherent structural, electronic, and magnetic properties, using a variety of theoretical tools, including first-principles density functional theory (DFT) method, numerical Monte Carlo (MC) method, and analytical phenomenological approaches, etc. The contents are divided into three major topics:

(1) Magnetic properties of n-p codoped materials. The noncompensated n-p codoping method is proposed to increase the density of magnetic dopants in diluted magnetic semiconductors (DMS) while keeping the magnetic coupling strength, which may lead to a …

Characterizing Phyllosilicate Distribution, Abundance, And Origin On Mars, Christina Elizabeth Viviano

Doctoral Dissertations

Secondary phyllosilicates are hydrated minerals formed in the presence of liquid water. On Earth, their formation is often indicative of a neutral, water-rich environment, capable of supporting and preserving organic matter. Different phyllosilicate species may be produced in different pH levels and water-to-rock ratios. The identification of mineralogically diverse phyllosilicates in small, localized exposures on Mars provides a complex record of their formation processes. While discrete outcrops of phyllosilicates have been previously identified in high-resolution visible/near-infrared images of Mars, regional coverage of these phyllosilicate-rich areas at better resolution is limited. Furthermore, spectra of minerals in this wavelength range do not …

A Novel Approach To Assess Environmental Changes In Marine Ecosystems Via Spectroscopic Analyses Of Microalgae, Rebecca Burke Horton

Doctoral Dissertations

Chemical analyses for environmental monitoring encounter many challenges which are imposed by a multitude of chemically complex and interrelated processes. For such investigations, innovative analytical methodologies must be developed which characterize chemical shifts of key environmental parameters in order to deduce insights into their ecological relevance. This dissertation is driven by an analytical chemistry perspective to develop chemical sensing techniques with the ultimate goal of gaining a deeper understanding of environmental changes and their chemical origins.

In order to overcome limitations inherent to any chemical sensor designed for a specific task, new paths are pursued which are based on the …

Laser-Atom Interactions: A Multiresolution Approach, Nicholas Eric Vence

Doctoral Dissertations

Isolated, attosecond laser pulses have allowed real-time measurement and control of electrons on atomic time scales. We present an explicit time-evolution scheme solving the time dependent Schro ̈dinger equation, which employs an adaptive, discontinuous, spectral-element basis that automatically refines to accommodate the requested precision providing efficient computation across many length scales in multiple dimensions. This method is illustrated through time evolution studies of single electron atoms and molecular ions in three and four dimensions under the influence of intense, few-cycle laser pulses.

Improving Analytical Utility Of Surface Enhanced Raman Spectroscopy Through Unique Lithographic Substrate Development, Sabrina Marie Wells

Doctoral Dissertations

Surface enhanced Raman spectroscopy (SERS) has the potential to be a useful analytical technique due to large signal enhancements. Unfortunately, SERS has several drawbacks, including a lack of reproducibility, which inhibits it from being a practical option. These large signals often arise from “hot spots” of extremely high enhancement on nanofeatured metallic substrates, the most common being comprised of aggregated silver colloid. It is difficult to reproducibly create these hot spots due to the randomness of the colloid substrates. However, through controlled substrate fabrication, many problems associated with SERS analysis can be overcome. Electron beam lithography (EBL) combined with reactive-ion …

Development And Experimental Analysis Of Wireless High Accuracy Ultra-Wideband Localization Systems For Indoor Medical Applications, Michael Joseph Kuhn

Doctoral Dissertations

This dissertation addresses several interesting and relevant problems in the field of wireless technologies applied to medical applications and specifically problems related to ultra-wideband high accuracy localization for use in the operating room. This research is cross disciplinary in nature and fundamentally builds upon microwave engineering, software engineering, systems engineering, and biomedical engineering. A good portion of this work has been published in peer reviewed microwave engineering and biomedical engineering conferences and journals. Wireless technologies in medicine are discussed with focus on ultra-wideband positioning in orthopedic surgical navigation. Characterization of the operating room as a medium for ultra-wideband signal transmission …

The Fabrication And Integration Of Pillar Array Channels For Chip Based Separations And Analysis, Lisa Christine Taylor

Doctoral Dissertations

The fundamental motivations for scaling existing technological platforms down to lab on chip dimensions are applicable in nearly all scientific disciplines. These motivations include decreasing waste, improving throughput, and decreasing time consumption. Analytical tools, such as chromatographic separation devices, can additionally benefit from system miniaturization by utilizing wafer-level fabrication technology, allowing for the rational design and precise control of variables which ultimately affect separation performance. With the use of microfabrication techniques, we have developed an original processing sequence for the fabrication of silicon oxide enclosed pillar arrays integrated within a fluidic channel. These pillar arrays create a highly uniform submicron …

Atomistic Simulations Of The Fusion-Plasma Material Interface, Mostafa Jon Dadras

Doctoral Dissertations

A key issue for the successful performance of current and future fusion reactors is understanding chemical and physical processes at the Plasma Material Interface (PMI). The material surfaces may be bombarded by plasma particles in a range of impact energies (1 eV - a few keV) and kept at a range of temperatures (300 - 1000 K). The dominant processes at the PMI are reflection and retention of impacting particles and sputtering (chemical and physical). Sputtering leads to surface erosion and pollution of the plasma, both of which degrade reactor performance. Retention influences the recycling of the plasma, and in …

The Itinerant Position Of Yttrium As Evidenced By Carboxylic Acid Extractions, Dustin C Collier

Doctoral Dissertations

The rare-earth elements Y and La-Lu share many similar physical and chemical properties. These similarities are reflected by the difficulty in the complete separation of the rare earths, often requiring hundreds to thousands of stages for the production of pure rare earths. Yttrium, traditionally known to be separated with Ho, has also been observed to be separated with other elements within the lanthanide series, and even outside the bounds of the lanthanide series itself. Previous publications by several authors have indicated that steric factors could influence the position of Y in solvent extractions of the rare earths using carboxylic acid …

A Framework For File Format Fuzzing With Genetic Algorithms, Roger Lee Seagle Jr.

Doctoral Dissertations

Secure software, meaning software free from vulnerabilities, is desirable in today's marketplace. Consumers are beginning to value a product's security posture as well as its functionality. Software development companies are recognizing this trend, and they are factoring security into their entire software development lifecycle. Secure development practices like threat modeling, static analysis, safe programming libraries, run-time protections, and software verification are being mandated during product development. Mandating these practices improves a product's security posture before customer delivery, and these practices increase the difficulty of discovering and exploiting vulnerabilities.

Since the 1980's, security researchers have uncovered software defects by fuzz testing …

Experimental Studies Of Nuclei Near Doubly Magic 100sn And 78ni, Lucia Cartegni

Doctoral Dissertations

The experimental study of exotic nuclei is very important for our understanding of nuclear structure. In this work the nuclei near doubly magic nuclei 100Sn and 78Ni were studied in two separate experiments. The first one was performed at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. This experiment searched for the alpha decay of 112Cs, in order to establish the proton separation energy of 104Sb. Although the alpha decay of 112Cs was not observed, the upper limit of the alpha branching ratio was set at 0.26%. The improved statistics enabled an improved half-lives measurement of …

Towards Sustainable Development Of Nanomanufacturing, Sasikumar Ramdas Naidu

Doctoral Dissertations

"Sustainability" is a buzz word these days not just among regulatory agencies but even with corporations, as evident by the release of annual sustainability report by a large number of firms. Companies are starting to portray profit making along with corporate environmental responsibility.

Nanotechnology and nanomanufacturing which holds a lot of promise for development in a multitude of fields in science and engineering is the new kid on the block and carries a lot of apprehension due to public concern about their potential unwanted side effects that may result in the case of an untoward incident or lack of oversight. …

Dome Formation During Crustal Extension In The Himalaya: Kinematic And Pressure-Temperature-Time-Deformation Constraints On Extensional Exhumation Along The Southern Margin Of The Tibetan Plateau, Jackie M. Langille

Doctoral Dissertations

The Himalaya and Tibetan Plateau were built by a combination of south-directed thrusting, north-directed extension, and generally east-west-directed extension within the Himalaya and Tibetan Plateau all to accommodate convergence between the Indian and Eurasian plates that began in the Eocene. Normal-sense shear zones that accommodate roughly east-west-directed extension across the southern margin of the Himalaya have exhumed young metamorphic domes across the Himalayan front. These metamorphic domes contain high-grade metamorphic rocks bound by normal-sense shear zones. The purpose of this study is to evaluate how these normal-sense shear zones develop and how they exhume metamorphic domes, which remains poorly understood …

From The Mantle To The Moon: Studies Of Kimberlitic Ilmenites, Meteorite Fusion-Crusts, And The Moscoviense Basin On The Moon, Kevin Glenn Thaisen

Doctoral Dissertations

I have explored a variety of geologic problems in the course of the chapters contained within this dissertation. These include a study relating to the fusion crusts on meteorites, an impact basin of the Moon, and Siberian kimberlitic ilmenites. The first chapter explores two assumptions commonly employed in meteorite analysis; that fusion crust compositions represent the bulk-rock chemistry of the entire meteorite and that the vesicles within the fusion crust result from the release of implanted solar-wind volatiles. Neither of these assumptions was found to hold true in that study. The second chapter explores the unusual nature of the Moscoviense …

Theoretical Study On Spontaneous Symmetry Breaking In Strongly Correlated Electrons, Xiaotian Zhang

Doctoral Dissertations

In the early days of condensed matter physics, the single electron approximation was considered to be a very good approach in order to explore the properties of many systems. However, as time goes on, a variety of new systems have been discovered and many of them, such as high temperature superconductors and manganites, show phenomenas that evidently can not be explained by single electron theories. Spontaneous symmetry breaking is a very important and famous concept in physics, from the Higgs mechanism in particle physics to the spin density wave in condensed matter physics. The present text describes the detailed studies …

Measurement Of Production And Decay Properties Of Bs Mesons Decaying Into J/Psi Phi With The Cms Detector At The Lhc, Giordano Cerizza

Doctoral Dissertations

The production of hadrons containing b-quarks has been measured in proton anti-proton collisions up to center-of-massenergies of 1.96 TeV at the Tevatron. Information at lower energy is provided by electron-positron collision experiments.The underlying theory of hadronic interactions is tuned to those data but cannot reliably predict reaction rates from first principlesfor higher energies. Therefore, it is important to test the extrapolations and optimize model parameters for the new energy regime at the LHC. The b-hadrons from proton-proton collisions are a major source of background in searches for the Higgs boson andother heavy not-yet-discovered particles. Hence, it is important to quantify …

Derivation Of Correction Terms To The Eikonal Approximations In The Formulation Of Analytical Abrasion-Ablation Model, Santosh Bhatt

Doctoral Dissertations

Analytical models for the quantitative predictions of spectra from the neutrons and light ions produced from the high energy, heavy ion (HZE) reactions are extremely important in assessment of the radiation damage during long duration deep space missions, and for various accelerator applications. The fundamental physics of the secondary particle production and transport from these HZE reactions is described using the abrasion-ablation model. The abrasion part of the model is based on the Glauber multiple scattering theory while the ablation process is based on statistical decay based on an evaporation model. The current formulations for the abrasion process are based …

Analysis Of Solvability And Applications Of Stochastic Optimal Control Problems Through Systems Of Forward-Backward Stochastic Differential Equations., Kirill Yevgenyevich Yakovlev

Doctoral Dissertations

A stochastic metapopulation model is investigated. The model is motivated by a deterministic model previously presented to model the black bear population of the Great Smoky Mountains in east Tennessee. The new model involves randomness and the associated methods and results differ greatly from the deterministic analogue. A stochastic differential equation is studied and the associated results are stated and proved. Connections between a parabolic partial differential equation and a system of forward-backward stochastic differential equations is analyzed.

A "four-step" numerical scheme and a Markovian type iterative numerical scheme are implemented. Algorithms and programs in the programming languages C and …

Generalized Branching In Circle Packing, James Russell Ashe

Doctoral Dissertations

Circle packings are configurations of circle with prescribed patterns of tangency. They relate to a surprisingly diverse array of topics. Connections to Riemann surfaces, Apollonian packings, random walks, Brownian motion, and many other topics have been discovered. Of these none has garnered more interest than circle packings' relationship to analytical functions. With a high degree of faithfulness, maps between circle packings exhibit essentially the same geometric properties as seen in classical analytical functions. With this as motivation, an entire theory of discrete analytic function theory has been developed. However limitations in this theory due to the discreteness of circle packings …