Doctor of Philosophy, The Ohio State University, 2019, Electrical and Computer Engineering

Remote sensing of the ocean surface has become an invaluable technique in advancing the scientific understanding of the Earth and its physical and biological processes. Various land-, sea-, air-, and space-based platforms have been deployed over the years with a wide array of instruments ranging from synthetic aperture radar (SAR) imagers to scatterometers for ocean observing missions. This thesis primarily focuses on two such datasets: a high resolution, high revisit rate L-band SAR dataset collected using the SMAP satellite and a coherent-on-receive X-band dataset collected from a wave-sensing radar using a ship-based platform. Investigations of these datasets presented in this thesis are intended to advance the remote sensing and physical modeling capabilities of ocean surfaces. The SMAP 1 km resolution data collected at a global revisit rate of 2-3 days provides a dramatic improvement on temporal and spatial sampling over previous SAR missions. The backscatter normalized radar cross section (NRCS) measurements in both co- and cross-polarizations are used for sea surface modeling studies using empirical and physical models. The backscatter NRCS predictions made using the two-scale model (TSM) and the second-order small slope approximation (SSA2) under assumed wind-only fully-developed sea surface conditions indicate the presence of swell waves. A wind + swell combined model of the ocean surface is then used to characterize the impact due to swell waves on SMAP NRCS measurements. Results indicate a substantial improvement on backscatter NRCS prediction capability using the combined model over the wind-only model results. The SMAP dataset is further investigated for swell features, while the swell prediction capability is also assessed. A team from The Ohio State University and the University of Michigan developed a low-cost coherent-on-receive X-band wave sensing radar using commercial off-the-shelf (COTS) components for ship-based applications. The radar (open full item for complete abstract)

Committee: Joel Johnson (Advisor); Robert Burkholder (Committee Member); Graeme Smith (Committee Member); Caglar Yardim (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Doctor of Philosophy, The Ohio State University, 2017, Materials Science and Engineering

Titanium alloys are widely used in aerospace engineering due to their high-temperature resistance and high stiffness-to-weight ratio; however, an industrial concern is cold dwell fatigue that could significantly reduce the fatigue life of aerospace components. Researchers have found that one of the metallurgical factors causing cold dwell fatigue is microtexture, which is composed of thousands of alpha grains with similar crystallographic orientation. To satisfy the practical need of microtexture characterization, a nondestructive ultrasonic method is proposed in this study to characterize microtexture regions (MTRs) in titanium alloys. Compared with the traditional characterization approach using electron backscatter diffraction (EBSD), the ultrasonic method has several advantages such as less sample preparation and higher efficiency. Thus, the focus of this study is on the theoretical development and practical application of ultrasonic microstructure characterization. Theoretically, this study extends the second order attenuation (SOA) model with Voigt reference medium to textured polycrystalline materials, and the SOA model is applicable to aggregates with arbitrary texture symmetry and ellipsoidal grains of triclinic symmetry. This development enables us to validate the previous general attenuation model based on the Born approximation and examine the limitation of the Born approximation. This general SOA model also produces phase velocities for the whole frequency range, including quasi-static velocities at the Rayleigh limit. Moreover, the far field approximation (FFA) model, an approximation form of the SOA model but with high computational efficiency, is developed for textured aggregates of triclinic ellipsoidal crystallites. Further comparison between analytical models (SOA and FFA) and the 3D finite element method (FEM) indicates that the SOA and FFA models have excellent agreement with the 3D FEM. Another new element of this study is that the orien (open full item for complete abstract)

Committee: Stanislav Rokhlin (Advisor); Dave Farson (Committee Member); Noriko Katsube (Committee Member) Subjects: Engineering; Materials Science

Doctor of Philosophy, The Ohio State University, 2017, Physics

In this thesis, we present lambda baryon femtoscopy measured by the ALICE collaboration in √sNN = 2.76 TeV Pb-Pb collision. Correlation functions are shown in three centrality ranges for lambda-antilambda and two for the combined lambda-lambda ⊕ antilambda-antilambda results. Femtoscopy is capable of measuring the femtometer-scale spatial and temporal aspects of particle collisions by looking at relative momentum correlations among pairs of particles. In addition, femtoscopy can extract information about the final state interactions of the strong nuclear forces that occur between those particles. The femtoscopic radii and scattering parameters (scattering length and effective range of interaction) of lambda-lambda ⊕ antilambda-antilambda and lambda-antilambda are presented. Following recent measurements of proton-antilambda and antiproton-antiproton, we have expanded the standard femtoscopic fitting process to account for the correlated effects of particles that decay into lambdas. We have estimated the λ parameters that describe the relative contribution of each residual correlation. Residual correlation effects are included in the fitting process by estimating their correlation strength and then smearing the relative momentum of their contribution according to the kinematics of their decay.

Committee: Thomas Humanic (Advisor); Michael Lisa (Committee Member); Yuri Kovchegov (Committee Member); Fengyuan Yang (Committee Member); Michael Bond (Committee Member) Subjects: Physics

Doctor of Philosophy, Case Western Reserve University, 2014, Applied Mathematics

We consider the problem of numerically solving the wave scattering problem in two dimensions, when the scatterer consists of a sound-soft compact scatterer surrounded by a compactly supported scattering medium. The scattering problem in the exterior domain is solved using boundary integral equations, while the solution near the scatterer is best treated by finite element methods. It is well known that these solutions can be glued together using non-reflecting boundary conditions, a common choice being the Dirichlet-to-Neumman (Steklov-Poincare) map. If the support of the scattering medium is large, the interior problem may require a large mesh and become computationally intense. We consider an alternative method based on the idea of invariant imbedding: first numerically solve for the DtN map on a boundary of a small domain merely enclosing the sound-hard scatterer, and then radially propagate the map out of the support of the scattering medium. Special attention needs to be paid to the stability of the propagation scheme that requires a solution of a matrix-valued Riccati equation. It is shown that by applying an appropriate Cayley transform on the matrix, problems arising from resonances can be avoided.

Committee: Erkki Somersalo PhD (Advisor); Daniela Calvetti PhD (Advisor); Steven Izen PhD (Committee Member); Glenn Starkman PhD (Committee Member) Subjects: Mathematics

PhD, University of Cincinnati, 2000, Arts and Sciences : Physics

The research summarized in this thesis was primarily directed towards understanding the microscopic structure of polysiloxanes and their mechanical behavior in different time and length scales using optical and mechanical techniques. This thesis is comprised of two projects. The first was aimed at developing an experimental technique to probe polymer networks based on a mechanical pulse propagation idea. The theory of elastic wave propagation was used to provide a theoretical framework relating the wave speeds to the stress tensor. Molecular models for polymer networks were used to predict the relationship between the speed of propagation and the molecular constitution of networks under deformation. The main objective of this project was to achieve a better understanding of network topology using a propagating pulse as a probe while providing a fast non-destructive method for characterizing networks. These are low frequency measurements (typically ~ 1 KHz) and in these time scales the networks are essentially in the so-called rubbery regime. At much higher frequencies (~ 5 GHz) the networks are almost frozen into a glassy state. At these frequencies Brillouin spectroscopy is a powerful technique to investigate the static and dynamic acoustic properties of polymers. In our second project we used this high-resolution optical technique to study inelastic light scattering studies from phonons in silicones. In these experiments, we probed the molecular-weight dependence, effect of deformation and cross-link dynamics in polysiloxanes. The Brillouin spectra of end-linked poly(dimethylsiloxanes) were obtained using a unique combination of a three-pass tandem Fabry-Perot interferometer in conjunction with a CCD area detector. Longitudinal acoustic phonons of frequency 2 - 6 GHz propagating in the networks were studied at 514.5 nm. From the measured Brillouin shifts, the molecular weight dependence of the velocity and the half-width of the phonons were obtained. The dispersio (open full item for complete abstract)

Committee: Howard Jackson (Advisor) Subjects:

Master of Science, The Ohio State University, 2008, Electrical and Computer Engineering

A new hybrid finite element/rigorous coupled wave analysis formulation is presented for the modeling of electromagnetic wave interactions with dielectric structures which are doubly periodic. The structures under investigation are periodic in two dimensions and have a finite extent in the third dimension. The proposed model can handle dielectric structures which have material properties varying arbitrarily in any of the dimensions. Employment of Fourier series expansion and Floquet's theory in one of the periodic dimensions helps to reduce the dimensions of the mesh grids. Therefore, two-dimensional grids are used rather than three-dimensional meshes of the structures of interest. The periodicity in the other periodic dimension is enforced by the use of phase boundary conditions. Domain truncation in the non-periodic dimension is done by placing Perfectly Matched Layers. Results obtained using alternative methods are used to verify the proposed method's validity.

Committee: Robert Lee Prof. (Advisor); Fernando L. Teixeira Prof. (Committee Member); Can Emre Koksal Prof. (Committee Member) Subjects: Electrical Engineering

PHD, Kent State University, 2012, College of Arts and Sciences / Department of Physics

The main focus of this dissertation was a phenomenological study of baryon spectroscopy involving N* and ¿¿¿¿¿¿¿* resonances. Our main goal was to extract of reliable information about the resonance properties by carrying out unitary, multichannel fits of partial-wave amplitudes of πN reactions. We began by performing single-energy partial-wave analyses of πN -> ηN and πN -> KΛ and obtained the corresponding partial-wave amplitudes by binning all available data for these reactions in c.m. energy bins of width 30 MeV. In addition to these reactions, the other πN reactions included in the fits were πN -> πN, πN -> ππN, and γN -> πN, for which previously published partial-wave amplitudes were used. The multichannel fits used an energy-dependent parametrization consistent with unitarity of the partial-wave S-matrix. The final fits resulted in highly constrained energy-dependent amplitudes, which allowed us to extract N* and ¿¿¿¿¿¿¿* resonance parameters. These resonance parameters were compared with results of other groups and with quark-model predictions.

Committee: Dr. Mark Manley (Advisor); Dr. Declan Keane (Committee Member); Dr. John Portman (Committee Member); Dr. Alexander Seed (Committee Member); Dr. Anatoly Khritin (Committee Member) Subjects: Nuclear Physics; Particle Physics

PHD, Kent State University, 2012, College of Arts and Sciences / Department of Physics

Asymmetry measurements were conducted in Jefferson Lab's experimental Hall A through electron scattering from a polarized 3He target in the quasi-elastic 3He(e, e′n) reaction. Measurements were made with the target polarized in the longitudinal direction with respect to the incoming electrons (AL), in a transverse direction that was orthogonal to the beam-line and parallel to the q-vector (AT), and in a vertical direction that was orthogonal to both the beam-line and the q-vector (Ay0). The experiment measured Ay0 at four-momentum transfer squared (Q2) of 0.127 (GeV/c)2, 0.456 (GeV/c)2, and 0.953 (GeV/c)2. The AT and AL asymmetries were both measured at Q2 of 0.505 (GeV/c)2 and 0.953 (GeV/c)2. This is the first time that three orthogonal asymmetries have been measured simultaneously. Results from this experiment are compared with the plane wave impulse approximation (PWIA) and Faddeev calculations. These results provide important tests of models that use 3He as an effective neutron target and show that the PWIA holds above Q2 of 0.953 (GeV/c)2.

Committee: Bryon Anderson (Advisor); Douglas Higinbotham (Advisor) Subjects: Nuclear Physics; Particle Physics

PHD, Kent State University, 2008, College of Arts and Sciences / Department of Physics

The main goal of this dissertation is the experimental and phenomenological study of hyperon spectroscopy. In this work, we focus on the strangeness -1 hyperon resonances, the Λ* and Σ*s. Our ultimate goal is to obtain more reliable information about the properties of Λ* and Σ* resonances by carrying out a multichannel partial-wave analysis of KN scattering. Most prior energy-dependent partial-wave analyses of KN scattering assumed a simple parametrization for the partial-wave amplitudes. Such a parametrization introduces a model-dependent bias and results in a violation of unitarity of the partial-wave S-matrix.Thus, one objective of our work is to reduce this bias as much as possible by carrying out a constrained single-energy partial-wave analysis. The Crystal Ball Collaboration recently measured several important KN reactions. These high quality data have also fostered part of the motivation for our new partial-wave analysis. In this dissertation, we initialized our single-energy analysis of KN scattering using results of a global fit of previously published partial-wave amplitudes. Thereafter, we performed a multichannel fit of our single-energy amplitudes to determine an energy-dependent solution that is consistent with S-matrix unitarity. We iterated between single-energy and energy-dependent fits until we obtained an energy-dependent solution that agrees with the initial data. Our research included all available data for KN → KN, KN → π Λ, and KN → π Σ reactions, covering the c. m. energy range 1480 to 2170 MeV.

Committee: D. Mark Manley (Advisor); Declan Keane (Committee Member); Peter C. Tandy (Committee Member); Carmen C. Almasan (Committee Member); Paul Sampson (Committee Member); Alfred S. Cavaretta (Other) Subjects: Physics