Physical Sciences and Mathematics Commons^™

Droplet-Based Fuel Property Measurements, Wanjun Dang

LSU Doctoral Dissertations

Ongoing work to find renewable biofuels to function as drop-in replacements or blending components with gasoline has identified a large number of fuel candidates. Given the vast number of potential biomass-derived fuel molecules and limited sample sizes, screening tools are required to down-select candidate fuels having desired physical properties to ensure good engine performance. This work investigates approaches for rapid screening of candidate fuels using micro-liter sample sizes targeting four properties -- surface tension, viscosity, heat of vaporization (HOV), and vapor pressure. Measurement techniques for fuel properties are developed based on unit phenomena for liquid fuel droplets including droplet oscillation …

Functional Structure Of Biomacromolecules In Plant Biomass Using Solid-State Nmr And Dynamic Nuclear Polarization, Alex Kipchirchir Kirui

LSU Doctoral Dissertations

This dissertation summarizes the recent findings on complex biomacromolecules in cell wall of plants and fungi which perform important roles in cell recognition, structural build up, and energy storage. Because of the technical difficulty in characterizing these biomacromolecules, which are often polymorphic and disordered in structure, the functional structure of these biomacromolecules remains elusive. In this dissertation, I present two solid-state nuclear magnetic resonance (ssNMR) and dynamic nuclear polarization (DNP) studies of carbohydrate-rich biosystems: the energy-rich plant biomass and disease-relevant, pathogenic fungi.

First, we have investigated the secondary cell wall of plant biomass which is a carbohydrate-rich biosystem using solid …

Limits On Parameter Estimation Of Quantum Channels, Vishal Katariya

LSU Doctoral Dissertations

The aim of this thesis is to develop a theoretical framework to study parameter estimation of quantum channels. We begin by describing the classical task of parameter estimation that we build upon. In its most basic form, parameter estimation is the task of obtaining an estimate of an unknown parameter from some experimental data. This experimental data can be seen as a number of samples of a parameterized probability distribution. In general, the goal of such a task is to obtain an estimate of the unknown parameter while minimizing its error.

We study the task of estimating unknown parameters which …

Non-Adiabatic Excited State Molecular Dynamics Using Ehrenfest And Modulated X-Ray Absorption In Titania, Alexander Matthew Meyer

LSU Doctoral Dissertations

This dissertation contains two separate sections aside from an introduction (Chapter 1): theory and methods (Chapter 2), time dependent density functional theory with Ehrenfest for excited state lifetimes in materials (Chapter 3), and simulated field modulated X-ray absorption in titania (Chapter 4).

Excited state lifetime in insulators and semiconductors can be difficult to compute using quantum chemistry due to their dense excited states. Non-radiative decay in these materials requires the use of non-adiabatic effects to dissipate energy through the means of electron-nuclear coupling such as coherent phonon generation. One method of approaching this challenge in these materials is using Ehrenfest …

Congruences Between Coefficients Of A Class Of Eta-Quotients And Their Applications To Combinatorics, Shashika Petta Mestrige

LSU Doctoral Dissertations

Ramanujan in $1920$s discovered remarkable congruence properties of the partition function $p(n)$. Later, Watson and Atkin proved these congruences using the theory of modular forms. Atkin, Gordon, and Hughes extended these works to $k$-colored partition functions. In $2010$, Folsom-Kent-Ono and Boylan-Webb proved the congruences of $p(n)$ by studying a $\ell$-adic module associated with a certain sequence of modular functions which are related to $p(n)$.

Primary goal of this thesis is to generalize the work of Atkin, Gordon, Hughes, Folsom-Kent-Ono, and Boylan-Webb about the partition function to a larger class of partition functions. For this purpose we study a closely related …

System Design And Optimization For Efficient Flash-Based Caching In Data Centers, Jian Liu

LSU Doctoral Dissertations

Modern data centers are the backbone of today’s Internet-based services and applications. With the explosive growth of the Internet data and a wider range of data-intensive applications being deployed, it is increasingly challenging for data centers to satisfy the ever-increasing demand for high-quality data services. To relieve the heavy burden on data center systems and accelerate data processing, a popular cost-efficient solution is to deploy high-speed, large-capacity flash-based cache systems. However, we are facing multiple critical challenges from device hardware, systems, to application workloads. In this dissertation, we focus on designing highly efficient caching solutions to cope with the explosive …

Interface-Induced Lattice Structure And Magnetism In Ultrathin Transition Metal Oxide Trilayers, David Howe

LSU Doctoral Dissertations

The study of magnetism has been a rich playground in condensed matter physics due to the multiple mechanisms capable of producing the effect and its relationship to multiple characteristics of a material. Transition metal oxides (TMOs) have been of particular interest for ongoing research into magnetic phenomenon due to the abundance of interesting physical phenomena found in member systems such as colossal magnetoresistance, skyrmion formation, and interface-driven 2D electron gases. Thin films introduce an additional thickness-dependent element, where reduction below a critical thickness eliminates the magnetic coherence of a system and FM order is lost. The atomic structure of these …

Floodplain Forests Vegetation Dynamics Driven By Water Deficits Across Scales, Nga Thanh Nguyen

LSU Doctoral Dissertations

Restoration of floodplain ecosystems relies on identifying the most crucial hydrologic process which has been altered by human and climate. Flooding is a well-known dominant hydrologic process for floodplain ecosystems, but surprisingly little is known about drought's role in structuring ecosystems. In addition, several issues remained uncertain, such as the nature of drought within floodplains and the sensitivity of floodplain species-specific growth to climate. These gaps of understanding have in common in missing observations of mechanistic pathways of vegetation response to water deficits at multiple scales in time and space.Generally, this research contributed to floodplain management by expanding our understanding …

Classifying Soft X-Ray Objects In The Galactic Bulge, Joshua D. Wetuski

LSU Doctoral Dissertations

The Galactic Bulge Survey (GBS) is a broad and shallow X-ray survey designed to detect quiescent X-ray binary systems in the direction of the Milky Way bulge, which include objects such as low-mass X-ray binaries, cataclysmic variables, and symbiotic binaries. LMXBs can provide constraints to the neutron star equation of state and symbiotic systems and are likely progenitors of double white dwarf systems which are themselves candidate progenitors to type Ia supernova. We seek to improve identification and classification of optical counterparts to GBS in several ways. By improving upon the original GBS, an updated catalog was created to help …

Rigid Connections On The Projective Line With Elliptic Toral Singularities, Alisina Azhang

LSU Doctoral Dissertations

We generalize two studies of rigid $G$-connections on $\pp$ which have an irregular singularity at origin and a regular singularity at infinity with unipotent monodromy: one is the work of Kamgarpour-Sage which classifies rigid homogeneous Coxeter $G$-connections with slope $\frac{r}{h}$, where $h$ is the Coxeter number of $G$, and the other is the work of Chen, which proves the existence of rigid homogeneous elliptic regular $G$-connections with slope $\frac{1}{m}$, where $m$ is an elliptic number for $G$. In our work, similar to Chen, we look for rigid homogeneous elliptic regular $G$-connections, but we allow the slope to have a numerator …

Electromagnetic Transitions And Beta Decays In Nuclei From The Ab Initio Symmetry-Adapted No-Core Shell Model, Grigor Sargsyan

LSU Doctoral Dissertations

Nuclear physics today is a diverse field, involving research that extends from the minus- cule scales of neutrons and protons to the colossal dimensions of astrophysical objects in the universe. And since the ab initio methods in nuclear physics use realistic internucleon interactions, nuclear modeling has gained predictive capabilities that enable us to probe ever more deeply into the fundamental nature of matter. One of these models – the symmetry- adapted no-core shell model (SA-NCSM) – is capable of reaching the medium-mass region of the chart of the nuclides, by exploiting the emergent symmetries of nuclei, and is therefore well-suited …

Effects Of Structure, Crystallographic Orientation, And Dimensionality On Emergent Properties Of Transition Metal Oxide Thin Films, Prahald Siwakoti

LSU Doctoral Dissertations

SrRuO₃ is the only example of ferromagnetic perovskite oxide of a 4d transition metal, wherein the electron -electron correlation is still relevant while the heavier 4d ion (Ru) gives it a larger spin-orbit coupling strength which makes it an interesting material to study. In this thesis, we present our investigation of the structure and properties of SrRuO₃ thin films of varying thickness grown on [001] and [111] crystallographic orientation of the SrTiO3 substrate. For SrRuO₃(001), we present microscopically the presence of 90◦ in-plane rotated structural domains that are identified by the difference in octahedral rotations and …

Laser Surface Treatment And Laser Powder Bed Fusion Additive Manufacturing Study Using Custom Designed 3d Printer And The Application Of Machine Learning In Materials Science, Hao Wen

LSU Doctoral Dissertations

Selective Laser Melting (SLM) is a laser powder bed fusion (L-PBF) based additive manufacturing (AM) method, which uses a laser beam to melt the selected areas of the metal powder bed. A customized SLM 3D printer that can handle a small quantity of metal powders was built in the lab to achieve versatile research purposes. The hardware design, electrical diagrams, and software functions are introduced in Chapter 2. Several laser surface engineering and SLM experiments were conducted using this customized machine which showed the functionality of the machine and some prospective fields that this machine can be utilized. Chapter 3 …

Learning To Interpret Fluid Type Phenomena Via Images, Simron Thapa

LSU Doctoral Dissertations

Learning to interpret fluid-type phenomena via images is a long-standing challenging problem in computer vision. The problem becomes even more challenging when the fluid medium is highly dynamic and refractive due to its transparent nature. Here, we consider imaging through such refractive fluid media like water and air. For water, we design novel supervised learning-based algorithms to recover its 3D surface as well as the highly distorted underground patterns. For air, we design a state-of-the-art unsupervised learning algorithm to predict the distortion-free image given a short sequence of turbulent images. Specifically, we design a deep neural network that estimates the …

Palynology And Paleoclimatology Of The Chicxulub Impact Crater In The Early Paleogene, Vann Smith

LSU Doctoral Dissertations

At the end of the Cretaceous Period, a large bolide impacted the Earth and formed the Chicxulub impact crater in the Yucatán Peninsula, Mexico. In 2016, International Ocean Discovery Program (IODP) Expedition 364 Site M0077 drilled into the buried peak ring of the crater, recovering a marine Paleocene to early Eocene post-impact section deposited on top of the impact breccia. Palynological analysis of 195 samples from the post-impact section has yielded the first pre-Holocene vegetational record from inside the Chicxulub impact crater and the first palynological record of the recovery of life following the end-Cretaceous mass extinction from inside the …

Algorithms Related To Triangle Groups, Bao The Pham

LSU Doctoral Dissertations

Given a finite index subgroup of $\PSL_2(\Z)$, one can talk about the different properties of this subgroup. These properties have been studied extensively in an attempt to classify these subgroups. Tim Hsu created an algorithm to determine whether a subgroup is a congruence subgroup by using permutations \cite{hsu}. Lang, Lim, and Tan also created an algorithm to determine if a subgroup is a congruence subgroup by using Farey Symbols \cite{llt}. Sebbar classified torsion-free congruence subgroups of genus 0 \cite{sebbar}. Pauli and Cummins computed and tabulated all congruence subgroups of genus less than 24 \cite{ps}. However, there are still some problems …

Computer Simulations Of Diffusional Isotope Effects And Dynamical Properties Of Silicate Melts, Haiyang Luo

LSU Doctoral Dissertations

Silicate melts have served as transport agents in the chemical and thermal evolution of Earth. Diffusional isotope effect in silicate melts is the key to interpret isotope variations in lots of geological samples. Isotopic mass dependence of diffusion is commonly expressed as (Di/Dj)=(mj/mi)^β, where Di and Dj are diffusion coefficients of two isotopes whose masses are mi and mj. However, how the dimensionless empirical parameter β depends on temperature, pressure, and composition remains poorly constrained. Viscosity and electrical conductivity are two fundamental dynamical properties of silicate melts needed to constrain melt distribution in Earth's interior but remain unclear for most …

Effect Of Forage Management Strategies And Land Use Change On Nitrogen Budget And Soil Health Parameters In Pasture Systems, Yili Meng

LSU Doctoral Dissertations

Pastures produce hay for livestock, and they conserve soil, water, and air resources. However, high nitrogen (N) fertilizer demands in pasture production have significant implication on greenhouse gas emission and environmental pollution. Appropriate forage management strategies can reduce environmental N loss and improve soil health, to enhance the long-term pasture productivity. Therefore, this study was carried out to investigate the effects of management strategies on N budgets and soil health parameters in subtropical pastures. Both field and laboratory experiments were conducted to evaluate the effects of N stabilizers including urease inhibitor and nitrification inhibitor on pasture yield, greenhouse gas emission, …

Numerical And Field Study Of Tidal And Subtidal Dynamics In A Bar-Built Estuary: Barataria Bay, Gulf Of Mexico, Ali Reza Payandeh

LSU Doctoral Dissertations

This study investigated tidal and subtidal dynamics of water level, currents, and suspended sediment concentration (SSC) in Barataria Bay, a shallow bar-built estuary of the Northern Gulf of Mexico. First, the local and remote wind forcing contribution on subtidal water level and current variability were examined using three different methods: (i) statistical analysis of observed data, (ii) an analytical model and (iii) a 2-D barotropic numerical model. Results suggested that the remote and local wind effects were equally important at the bay mouth, however local winds were the dominant forcing driver inside the bay. The amplitudes of subtidal fluctuations induced …

Simulation Of Compound Flood Events In Low-Gradient Coastal Watershed, Felix Luis Santiago-Collazo

LSU Doctoral Dissertations

Low-gradient coastal watersheds are susceptible to flooding caused by various flows such as rainfall, tides, and storm surge. Compound flooding occurs when at least two of these mechanisms happen simultaneously or in close succession. Different inundation models, observed data, and/or a combination of these are coupled through varying techniques involving one-way, loosely, tightly, or fully coupled approaches to assess compound flooding. This study presents a one-dimensional (1-D), fully coupled compound inundation model based on the Shallow Water equations. This model approach simultaneously simulates the free water surface variations in the ocean domain (i.e., tide and storm surge modeling), rainfall-runoff in …

Investigation On The Structure And Dynamics Of Lithium Ion Solvation Shell By Linear And Non-Linear Infrared Spectroscopy, Xiaobing Chen

LSU Doctoral Dissertations

Lithium ion battery (LIB) is a lightweight, rechargeable and powerful battery that is used widely from mobile phones to laptops to electric cars. It has many exceptional advantages such as high energy density, high output power, relatively low self-discharge, etc. However, it has some disadvantages such as safety issues, capacity loss, and expensive manufacture. LIB is composed of three main components: electrolytes, positive and negative electrodes. Researchers have been working on improving the performance of LIB for the past decade, but only a few have focused on investigating the electrolytes at the molecular level. In addition, the molecular mechanisms behind …

A Generalized, Modular Approach To Treating Moving Tumors With Ion Beams, Michelle Jennifer Lis

LSU Doctoral Dissertations

Despite advancements in cancer therapy, certain indications continue to have a poor prognosis, including cancers of the thorax. Existing methods for treating moving tumors with carbon ions have shown promise, but require technologically complex facilities and still have inherent limitations to mitigating tumor motion. The goal of this dissertation was to develop and test a safe, portable, and modular motion-synchronized dose delivery system (M-DDS) and its peripheral components as a framework for studying motion mitigation with ion beams.

We designed and integrated a motion-synchronized radiotherapy approach, called multi-phase 4D delivery (MP4D), as modular units of a clinical dose delivery system. …

An Equivalence Between Contact Gluing Maps In Sutured Floer Homology: A Conjecture Of Zarev, Charles Ryan Leigon

LSU Doctoral Dissertations

We show that the contact gluing map of Honda, Kazez, and Matic has a natural algebraic description in bordered sutured Floer homology. In particular, we establish Zarev's conjecture that his gluing map on sutured Floer homology is equivalent, in the appropriate sense, to the contact gluing map. This further solidifies the relationship between bordered Floer theory and contact geometry.

Noncommutative Tensor Triangular Geometry And Its Applications To Representation Theory, Kent Barton Vashaw

LSU Doctoral Dissertations

One of the cornerstones of the representation theory of Hopf algebras and finite tensor categories is the theory of support varieties. Balmer introduced tensor triangular geometry for symmetric monoidal triangulated categories, which united various support variety theories coming from disparate areas such as homotopy theory, algebraic geometry, and representation theory. In this thesis a noncommutative version will be introduced and developed. We show that this noncommutative analogue of Balmer's theory can be determined in many concrete situations via the theory of abstract support data, and can be used to classify thick tensor ideals. We prove an analogue of prime ideal …

On Properties Of Weil Sums Of Binomials, Liem P. Nguyen

LSU Doctoral Dissertations

This dissertation explores questions regarding the Weil sum of binomials, a finite field character sum originated from information theory. The Weil spectrum counts distinct values of the Weil sum through invertible elements in the finite field. The value of these sums and the size of the Weil spectrum are of particular interest, as they link problems in information theory, coding theory, and cryptography to other areas of math such as number theory and arithmetic geometry. In the setting of Niho exponents, we prove the Vanishing Conjecture of Helleseth ($1971$) on the presence of zero values in the Weil spectrum and …

Applications Of Nonstandard Analysis In Probability And Measure Theory, Irfan Alam

LSU Doctoral Dissertations

This dissertation broadly deals with two areas of probability theory and investigates how methods from nonstandard analysis may provide new perspectives in these topics. In particular, we use nonstandard analysis to prove new results in the topics of limiting spherical integrals and of exchangeability.

In the former area, our methods allow us to represent finite dimensional Gaussian measures in terms of marginals of measures on hyperfinite-dimensional spheres in a certain strong sense, thus generalizing some previously known results on Gaussian Radon transforms as limits of spherical integrals. This first area has roots in the kinetic theory of gases, which is …

Characterizing The Northern Hemisphere Circumpolar Vortex Through Space And Time, Nazla Bushra

LSU Doctoral Dissertations

This hemispheric-scale, steering atmospheric circulation represented by the circumpolar vortices (CPVs) are the middle- and upper-tropospheric wind belts circumnavigating the poles. Variability in the CPV area, shape, and position are important topics in geoenvironmental sciences because of the many links to environmental features. However, a means of characterizing the CPV has remained elusive. The goal of this research is to (i) identify the Northern Hemisphere CPV (NHCPV) and its morphometric characteristics, (ii) understand the daily characteristics of NHCPV area and circularity over time, (iii) identify and analyze spatiotemporal variability in the NHCPV’s centroid, and (iv) analyze how CPV features relate …

Machine Learning Methods For Depression Detection Using Smri And Rs-Fmri Images, Marzieh Sadat Mousavian

LSU Doctoral Dissertations

Major Depression Disorder (MDD) is a common disease throughout the world that negatively influences people’s lives. Early diagnosis of MDD is beneficial, so detecting practical biomarkers would aid clinicians in the diagnosis of MDD. Having an automated method to find biomarkers for MDD is helpful even though it is difficult. The main aim of this research is to generate a method for detecting discriminative features for MDD diagnosis based on Magnetic Resonance Imaging (MRI) data.

In this research, representational similarity analysis provides a framework to compare distributed patterns and obtain the similarity/dissimilarity of brain regions. Regions are obtained by either …

Quantifying Feature Overlaps In Deep Neural Networks And Their Applications In Unsupervised Learning And Generative Adversarial Networks, Edward Collier

LSU Doctoral Dissertations

Deep neural network learn a wide range of features from the input data. These features take many different forms from, structural to textural, and can be very scale invariant. The complexity of these features also differs from layer to layer. Much like the human brain, this behavior in deep neural networks can also be used to cluster and separate classes. Applicability in deep neural networks is the quantitative measurement of the networks ability to differentiate between clusters in feature space. Applicability can measure the differentiation between clusters of sets of classes, single classes, or even within the same class. In …

Musical Gesture Through The Human Computer Interface: An Investigation Using Information Theory, Michael Vincent Blandino

LSU Doctoral Dissertations

This study applies information theory to investigate human ability to communicate using continuous control sensors with a particular focus on informing the design of digital musical instruments. There is an active practice of building and evaluating such instruments, for instance, in the New Interfaces for Musical Expression (NIME) conference community. The fidelity of the instruments can depend on the included sensors, and although much anecdotal evidence and craft experience informs the use of these sensors, relatively little is known about the ability of humans to control them accurately. This dissertation addresses this issue and related concerns, including continuous control performance …