Physical Sciences and Mathematics Commons^™

The Aging And Impacts Of Atmospheric Soot: Closing The Gap Between Experiments And Models, Ogochukwu Yvonne Enekwizu

Dissertations

The main goal of this dissertation is to generate data and parameterizations to accurately represent soot aerosols in atmospheric models. Soot from incomplete combustion of fossil fuels and biomass burning is a major air pollutant and a significant contributor to climate warming. The environmental impacts of soot are strongly dependent on the particle morphology and mixing state, which evolve continuously during atmospheric transport via a process known as aging. To make predictions of soot impacts on the environment, most atmospheric models adopt simplifications of particle structure and mixing state, which lead to substantial uncertainties. Using an experimentally constrained modeling approach, …

Small-Scale Dynamics Of Photospheric Magnetic Activities And Their Chromospheric Responses, Jiasheng Wang

Dissertations

The evolution of photospheric magnetic fields is considered as the fundamental source of forming atmospheric structures and triggering most solar activities, including flares and mass ejections on various scales (CMEs, jets, etc.). With the implementation of high-resolution observational instruments, small-scale details of magnetic features are recognized that can provide important information regarding the evolution in active regions and the connection between photospheric magnetic reconnection and jet-like ejections in the quiet Sun. This research takes advantage of the exceptionally high-resolution measurements of vector magnetic field and imaging observations by the Goode Solar Telescope, and UV/EUV imaging observations from space-based instruments. The …

Countering Internet Packet Classifiers To Improve User Online Privacy, Sina Fathi-Kazerooni

Dissertations

Internet traffic classification or packet classification is the act of classifying packets using the extracted statistical data from the transmitted packets on a computer network. Internet traffic classification is an essential tool for Internet service providers to manage network traffic, provide users with the intended quality of service (QoS), and perform surveillance. QoS measures prioritize a network's traffic type over other traffic based on preset criteria; for instance, it gives higher priority or bandwidth to video traffic over website browsing traffic. Internet packet classification methods are also used for automated intrusion detection. They analyze incoming traffic patterns and identify malicious …

Blast Shock-Wave Characterization In Experimental Shock Tubes, Sudeepto Kahali

Dissertations

Blast-induced traumatic brain injuries have affected U.S. soldiers deployed for extended periods in the gulf and Afghanistan wars. To identify the biomechanical and biochemical mechanisms of injury, critical in the identification of diagnostic and therapeutic tools, compressed gas-driven shock tubes are used by investigators to study shockwave-animal specimen interactions and its biological consequences. However, shock tubes are designed and operated in a variety of geometry with a range of process parameters, and the quality of shock wave characteristics relevant to field conditions and therefore the study of blast-induced traumatic brain injuries suffered by soldiers is affected by those conditions. Lab-to-lab …

Convergence Of The Boundary Integral Method For Interfacial Stokes Flow, Keyang Zhang

Dissertations

Boundary integral numerical methods are among the most accurate methods for interfacial Stokes flow, and are widely applied. They have the advantage that only the boundary of the domain must be discretized, which reduces the number of discretization points and allows the treatment of complicated interfaces. Despite their popularity, there is no analysis of the convergence of these methods for interfacial Stokes flow. In practice, the stability of discretizations of the boundary integral formulation can depend sensitively on details of the discretization and on the application of numerical filters. A convergence analysis of the boundary integral method for Stokes flow …

Enhancement Of Critical Current In High-Temperature Superconductors By Ion Beam Irradiation Induced Defects, Prashanta Mani Niraula

Dissertations

Particle irradiation is used to induce defects in high-temperature superconducting Y₁Ba₂Cu₃O_7-x (YBCO) coated conductors, containing predominantly c-axis oriented barium zirconate (BZO) nanorods as pre-existing vortex pinning defects. Samples are irradiated with 50.0 MeV Cu ions with doses of 2.5 x 10¹², 2.0 x 10¹², 1.5 x 10¹², 1.0 x 10¹², 0.75 x 10¹², 0.5 x 10¹², 0.05 x 10¹² ions/cm². The dose of 0.5 x 10¹² ions/cm² is found to be the optimal dose with a …

Efficient Time-Stepping Approaches For The Dispersive Shallow Water Equations, Linwan Feng

Dissertations

This dissertation focuses on developing efficient and stable (high order) time-stepping strategies for the dispersive shallow water equations (DSWE) with variable bathymetry. The DSWE extends the regular shallow water equations to include dispersive effects. Dispersion is physically important and can maintain the shape of a wave that would otherwise form a shock in the shallow water system.

In some cases, the DSWE may be simplified when the bathymetry length scales are small (or large) in relation to other length scales in the shallow water system. These simplified DSWE models, which are related to the full DSWEs, are also considered in …

Efficient Approximations For Stationary Single-Channel Calcium Nanodomains, Yinbo Chen

Dissertations

Mathematical and computational modeling plays an important role in the study of local Ca2+ signals underlying many fundamental physiological processes such as synaptic neurotransmitter release and myocyte contraction. Closed-form approximations describing steady-state distribution of Ca2+ in the vicinity of an open Ca2+ channel have proved particularly useful for the qualitative modeling of local Ca2+ signals. This dissertation presents several simple and efficient approximants for the equilibrium Ca2+ concentration near a point source in the presence of a mobile Ca2+ buffer, which achieve great accuracy over a wide range of model parameters. Such approximations provide an efficient method for estimating Ca2+ …

Flare Emission Observed In High Resolution And Comparison With Numerical Modeling, Nengyi Huang

Dissertations

As one of the most intense activities on the solar surface, flares have been extensively observed and studied ever since the first report. The standard model of solar flares has been established and commonly accepted. However, many limitations from the researching tools have left some of the problems unsolved or controversial. For example, the density of electrons in the corona is lower than it is required to activate the observed emission in HXR, and the mechanism that these electron beams can penetrate down to lower chromosphere is unclear. Many theoretical scenarios were suggested, and more observations had been in need. …

Studies Of Two-Phase Flow With Soluble Surfactant, Ryan Peter Atwater

Dissertations

Numerical methods are developed for accurate solution of two-phase flow in the zero Reynolds number limit of Stokes flow, when surfactant is present on a drop interface and in its bulk phase interior. The methods are designed to achieve high accuracy when the bulk Péclet number is large, or equivalently when the bulk phase surfactant has small diffusivity

In the limit of infinite bulk Péclet number the advection-diffusion equation that governs evolution of surfactant concentration in the bulk is singularly perturbed, indicating a separation of spatial scales. A hybrid numerical method based on a leading order asymptotic reduction in this …

Embedded Gold Nanoparticles For Metal Enhanced Photoluminescence, Hasna Alali

Dissertations

Noble metal nanoparticles (MNPs) have attracted great attention in electronics, solar cells and catalysis. Their unique optical properties and biocompatibility makes them useful in biological applications like imaging, drug delivery, therapy and diagnostic. At the surface of MNPs the collective oscillation of free electrons resonates with a particular wavelength of incident light, generating the Localized Surface Plasmons Resonance (LSPR). LSPR results in absorption and scattering of incident light. Scattering results in reflecting photons and absorption leads to enhanced photoluminescence and quenching of fluorophores, if the fluorophore is in the vicinity of MNPs.

Most of the studies in this regard have …

Investigation Of Finite Temperature And Continuum Effects On Nuclear Excitations, Herlik Wibowo

Dissertations

The low-energy nuclear response at finite-temperature significantly affects the radiative neutron capture reaction rates of the r-process nucleosynthesis. In order to address this topic, the first part of this study focuses on the response of compound nuclei or nuclei at finite temperature. The thermal nuclear response satisfies the Bethe-Salpeter equation (BSE) with the static and dynamical kernels of different origins. While the origin of the static kernel is the nearly instantaneous nucleon-meson interaction, the dynamical kernel is induced by the coupling between nucleons and phonons. The presence of singularities in the dynamical kernel makes the BSE unsolvable, however, a time …

Modeling Single Microtubules As A Colloidal System To Measure The Harmonic Interactions Between Tubulin Dimers In Bovine Brain Derived Versus Cancer Cell Derived Microtubules, Arooj Aslam

Dissertations

The local properties of tubulin dimers dictate the properties of the larger microtubule assembly. In order to elucidate this connection, tubulin-tubulin interactions are be modeled as harmonic interactions to map the stiffness matrix along the length of the microtubule. The strength of the interactions are measured by imaging and tracking the movement of segments along the microtubule over time, and then performing a fourier transform to extract the natural vibrational frequencies. Using this method the first ever reported experimental phonon spectrum of the microtubule is reported. This method can also be applied to other biological materials, and opens new doors …

Data Assimilation For Conductance-Based Neuronal Models, Matthew Moye

Dissertations

This dissertation illustrates the use of data assimilation algorithms to estimate unobserved variables and unknown parameters of conductance-based neuronal models. Modern data assimilation (DA) techniques are widely used in climate science and weather prediction, but have only recently begun to be applied in neuroscience. The two main classes of DA techniques are sequential methods and variational methods. Throughout this work, twin experiments, where the data is synthetically generated from output of the model, are used to validate use of these techniques for conductance-based models observing only the voltage trace. In Chapter 1, these techniques are described in detail and the …

Calculating Elastic Properties Of Confined Simple Fluids, Christopher D. Dobrzanski

Dissertations

Confinement in nanoporous materials is known to affect many properties of the fluids confined within their pores. The elastic properties are no exception. This dissertation begins with an overview of the relevant literature on ways of obtaining elastic properties of confined fluids. It outlines some fundamental gaps in our understanding. The chapters following address some of these gaps in understanding elastic properties of the confined fluid, in particular, how the shape of the confining pore matters, how supercriticality effects the properties, how an equation of state designed for confined fluids can be used to calculate elastic properties, and if an …