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John, P. K.Charged particle escape from a steady state plasma in a mirror magnetic field /
Doctor of Philosophy, The Ohio State University, 1963, Graduate School

Committee:

Not Provided (Other)

Subjects:

Physics

Keywords:

Plasma ;Electromagnetism;Electric discharges through gases

Chakrabarti, SuryarghyaModeling of 3D Magnetostrictive Systems with Application to Galfenol and Terfenol-D Transducers
Doctor of Philosophy, The Ohio State University, 2011, Mechanical Engineering

Magnetostrictive materials deform in response to applied magnetic fields and change their magnetic state when stressed. Because these processes are due to moment realignments, magnetostrictive materials are ideally suited for sensing and actuation mechanisms with a bandwidth of a few kHz. Significant research effort has been focused on two magnetostrictive alloys: Terfenol-D (an alloy of terbium, iron and dysprosium) and Galfenol (an iron gallium alloy), for their ability to produce giant magnetostrictive strains at moderate fields. Terfenol-D has higher energy density and magnetomechanical coupling factor than Galfenol but it is brittle and suffers from poor machinability. Galfenol on the other hand has excellent structural properties. It can be machined, welded, extruded into complex shapes for use in transducers with 3D functionality.

Advanced modeling tools are necessary for analyzing magnetostrictive transducers because these materials exhibit nonlinear coupling between the magnetic and mechanical domains. Also, system level electromagnetic coupling is present through Maxwell's equations. This work addresses the development of a unified modeling framework to serve as a design tool for 3D, dynamic magnetostrictive transducers. Maxwell's equations for electromagnetics and Navier's equations for mechanical systems are formulated in weak form and coupled using a generic constitutive law. The overall system is approximated hierarchically; first, piecewise linearization is used to describe quasistatic responses and perform magnetic bias calculations. A linear dynamic solution with piezomagnetic coefficients computed at the bias point describes the system dynamics for moderate inputs. Dynamic responses at large inputs are obtained through an implicit time integration algorithm. The framework simultaneously describes the effect of magneto-structural dynamics, flux leakages, eddy currents, and transducer geometry. Being a fully coupled formulation, it yields system level input-output relationships and is applicable to both actuators and sensors.

An anhysteretic 3D discrete energy-averaged constitutive law for Galfenol is incorporated into the framework to describe the dynamic performance of Galfenol transducers. A parameter identification algorithm is developed which takes as input the 1D material characterization curves and calculates the 3D constitutive model parameters. The algorithm is embedded within the finite element model such that the only inputs required are the constitutive parameters for passive materials (permeability, conductivity, Young's modulus etc.), the transducer geometry, and the 1D magnetostrictive material characterization curves. A case study on a Galfenol unimorph actuator illustrates the model's ability to accurately describe the dynamic mechanical and magnetic response of Galfenol transducers. A new energy-averaged model is formulated for Terfenol-D based on an implicit definition of domain volume fractions and a weighted anisotropy energy. The model is shown to simultaneously describe the strain-field and magnetization-stress behavior of Terfenol-D. The 3D finite element model is reduced to a 2D axisymmetric form to exploit the axisymmetric geometry of Terfenol-D transducers. The model describes the dynamic mechanical and electrical response of a hydraulically amplified Terfenol-D mount actuator. A parametric study on the actuator shows the applicability of the model to transducer design optimization.

Committee:

Marcelo Dapino, PhD (Advisor); Ahet Kahraman, PhD (Committee Member); Junmin Wang, PhD (Committee Member); Rajendra Singh, PhD (Committee Member)

Subjects:

Electromagnetics; Electromagnetism; Mechanical Engineering; Mechanics

Keywords:

magnetostriction; electromagnetism; eddy currents; finite element modeling; magnetostrictive transducers; engine mount actuator; nonlinear constitutive modeling; magnetomechanical coupling

Maschino, Tyler StephenFREQUENCY-SELECTIVE DESIGN OF WIRELESS POWER TRANSFER SYSTEMS FOR CONTROLLED ACCESS APPLICATIONS
Master of Science, Miami University, 2016, Computational Science and Engineering
Wireless power transfer (WPT) has become a common way to charge or power many types of devices, ranging from cell phones to electric toothbrushes. WPT became popular through the introduction of a transmission mode known as strongly coupled magnetic resonance (SCMR). This means of transmission is non-radiative and enables mid-range WPT. Shortly after the development of WPT via SCMR, a group of researchers introduced the concept of resonant repeaters, which allows power to hop from the source to the device. These repeaters are in resonance with the WPT system, which enables them to propagate the power wirelessly with minimal losses to the environment. Resonant repeaters have rekindled the dream of ubiquitous wireless power. Inherent risks come with the realization of such a dream. One of the most prominent risks, which we set out in this thesis to address, is that of accessibility to the WPT system. We propose the incorporation of a controlled access schema within a WPT system to prevent unwarranted use of wireless power. Our thesis discusses the history of electromagnetism, examines the inception of WPT via SCMR, evaluates recent developments in WPT, and further elaborates on the controlled access schema we wish to contribute to the field.

Committee:

Dmitriy Garmatyuk, PhD (Advisor); Mark Scott, PhD (Committee Member); Herbert Jaeger, PhD (Committee Member)

Subjects:

Computer Engineering; Electrical Engineering; Electromagnetics; Electromagnetism; Engineering

Keywords:

wireless power transfer; WPT; resonance; magnetic resonance; electromagnetism; power security; power encryption; wireless power transfer security; wireless power transfer encryption; SCMR; strongly coupled magnetic resonance; power transfer;

Kwa, Kiam HeongLaser-Driven Charged Particles as a Dynamical System
Doctor of Philosophy, The Ohio State University, 2009, Mathematics

Based on Lagrangian formulations of the Lorentz equations of motion, we investigate the relativistic orbit of a classical charged particle in response to a generic electromagnetic field in the four dimensional Minkowski space. Within the context of classical mechanics, the results are relativistically and mathematically exact. With the application to laser-particle interaction in mind, our primary focus is on the particle dynamics in a generic plane wave field.

Taking advantage of the fact that the particle motion in the direction transverse to the wave propagation direction is cyclic, we use the classical Routh's procedure to reduce the number of degrees of freedom of the motion and to manifest the observation that the longitudinal motion of the particle controls every aspect of the particle dynamics under the influence of a generic plane wave field. In fact, we show that the particle longitudinal motion is a generalized natural mechanical system in the sense that it has a Lagrangian consists of the difference of a metric based kinetic energy and a potential function. A corollary of this is the culmination of this work, that is, the geodesic variational principle.

The geodesic variational principle implies that longitudinally, the particle moves along a timelike geodesic in a curved two dimensional Lorentzian spacetime whose metric is determined by the plane wave field. In other words, the effect of the field on the particle dynamics gets replaced by the effect of the geometry and its curvature on the geodesics of a two-dimensional manifold. This gives rise to a geometrization of the laser-particle interaction.

We also use the geodesic variational principle to establish a Lorentzian law of refraction in which the particle, in response to the plane wave field, gets refracted by the field in the same way that light rays get refracted by a medium permeating Euclidean space. The plane wave field acts as a refractive medium with a characteristic Lorentzian refractive index. Introducing the notion of the rapidity of the particle, this gives rise to a Lorentzian Snell's law.

Finally, we apply the law of refraction to study particle scattering process in two counter-propagating trains of square pulses. We discretize the particle dynamics by introducing the notions of the itinerary and the refraction sequence of a particle orbit. As illustrations, we discuss various properties of periodic orbits and construct a class of periodic orbits and a class of unbounded orbits explicitly with the aid of these notions.

Committee:

Ulrich Gerlach (Advisor); Ovidiu Costin (Committee Member); David Terman (Committee Member)

Subjects:

Mathematics

Keywords:

Dynamical system; Calculus of variations; Lagrangian Mechanics; Geodesic variational principle; Geometrization of electromagnetism; Laser-matter interaction; Law of refraction in spacetime; Snell's law in spacetime; Particle scattering

Gross, Francis B.Characterization of electromagnetic backscatter from moving tracked vehicles /
Doctor of Philosophy, The Ohio State University, 1982, Graduate School

Committee:

Not Provided (Other)

Subjects:

Mathematics

Keywords:

Backscattering;Electromagnetism;Tracking radar

Bulman, Warren EugeneUtilization of photoconductivity in electromagnetics /
Doctor of Philosophy, The Ohio State University, 1958, Graduate School

Committee:

Not Provided (Other)

Subjects:

Engineering

Keywords:

Electromagnetism;Photoconductivity

Gupta, Inder JeetRelationship between the adaptive performance of antenna arrays and their underlying electromagnetic characteristics /
Doctor of Philosophy, The Ohio State University, 1982, Graduate School

Committee:

Not Provided (Other)

Subjects:

Engineering

Keywords:

Antenna arrays;Electromagnetism

Hagenlocker, Edward EmersonTwo-phase radio frequency heating of a plasma confined in a magnetic mirror system /
Doctor of Philosophy, The Ohio State University, 1964, Graduate School

Committee:

Not Provided (Other)

Subjects:

Physics

Keywords:

Plasma ;Electromagnetism

Via, Michelle FrancesAtmospheric Effects on Radar/Ladar Detection of Seismic Activity
Master of Science (MS), Wright State University, 2015, Earth and Environmental Sciences
This thesis investigates how well ground vibrations can be detected at ladar or radar wavelengths and how the atmosphere may impact the observation of such activity. First understanding atmospheric hindrances at each of these wavelengths is helpful to prioritize by those yielding best transmission results. A prerequisite to the outdoor field experiment performed for this study involves analyzing atmospheric effects characterization at six probable wavelengths using the Laser Environmental Effects Definition and Reference tool (LEEDR) developed by the Air Force Institute of Technology’s (AFIT) Center for Directed Energy (CDE). These wavelengths, selected from the shortwave infrared and microwave portions of the electromagnetic (EM) spectrum, are assessed to determine which provides optimal path transmission results allowing a sensor platform at an altitude of 1525 meters to sense induced ground vibrations. Selecting an altitude just above the typical atmospheric boundary layer (BL) allows further investigation of precipitation and cloud impacts on potential path transmission. The objective of performing the outdoor field experiment is to induce surface vibrations tracked by a 12 channel geophone spread linked to a seismograph at various locations along a horizontal path to determine if the signal can be detected by a 35 GHz radar. The contributory goal of this research is to realize new ways of monitoring otherwise invisible illegal or terrorist-like activities for the security of this nation. Additionally, the use of LEEDR could allow the atmospheric effects measured in the microwave part of the spectrum to be scaled for various platform altitudes and applied for atmospheric correction in other parts of the spectrum such as the visible, near-infrared, infrared, or submillimeter ranges. Experimental results indicate a 35 GHz radar is optimal and capable of detecting ground vibrations across short ranges when using a retro-reflector. How well seismic activity can be detected and the impacts of estimating atmospheric transmission in various weather conditions is presented and discussed.

Committee:

Ernest Hauser, Ph.D. (Committee Chair); Steven Fiorino, Ph.D. (Committee Member); Douglas Petkie, Ph.D. (Committee Member)

Subjects:

Atmosphere; Atmospheric Sciences; Electromagnetism; Energy; Environmental Geology; Environmental Science; Environmental Studies; Experiments; Geology; Geophysical; Geophysics; Physics; Remote Sensing

Keywords:

atmospheric sciences;atmosphere;electromagnetism;energy;environmental geology;environmental science;environmental studies;experiments;geophysical;geophysics;geology;physics;remote sensing

Lemberger, Benjamin KurtThe one place we're trying to get to is just where we can't get: algebraic speciality and gravito-electromagnetism in Bianchi type IX
BA, Oberlin College, 2014, Physics and Astronomy

Einstein's theory of General Relativity, put forward in 1915, predicts that space and time do not form a fixed background, but instead are malleable and dynamic quantities themselves. Their union forms something called spacetime, which when curved causes gravitational effects. This framework has led to models of the universe which match observations that the entire universe is expanding. Running these models backwards in time leads to a 'big bang', which is a single point from which the entire known universe came from. This single point is a singularity, a place where the theory breaks down, rendering questions like 'what happened before the big bang' meaningless. However, we can use General Relativity to study what happens near these singularities, which can have profound implications for whatever theory will succeed General Relativity, which will need to explain singularities, and will presumably be a quantum theory of gravity.

In 1970, Belinsky, Khalatnikov, and Lifshitz made a conjecture about the nature of spacetime near any singularity. They proposed that as one asymptotically approaches a singularity, each spatial point decouples from the points around it, and therefore acts like an independent homogeneous universe. An important homogeneous universe is the 'Mixmaster Universe', and in many cases, numerical simulations show that, on approaches to singularities, each point begins to act like its own Mixmaster Universe. The Mixmaster universe features chaotic, oscillatory behavior known as 'Mixmaster Dynamics'.

Mixmaster dynamics are fairly well understood, but in this thesis I will study them in a new way, utilizing an alternative language for understand the curvature of spacetime called Gravito-Electromagnetism. In electromagnetism, the electric and magnetic fields are decomposed from a single quantity which contains all the information of the electromagnetic field. A similar decomposition can be done to the gravitational analogue of the full field quantity, giving rise to the Gravito-Electric and Gravito-Magnetic fields, which have relatively simple physical interpretations, making them ideal for the visualization of spacetimes. Additionally, I will explore the Mixmaster Universe using a related algebraic classification commonly used in General Relativity called the Petrov Classification. While the Mixmaster Universe is known to not be algebraically special according to this classification, we use a recently developed measurement of the 'nearness' of a spacetime to algebraic speciality to gain more insight into Mixmaster Dynamics.

Committee:

Rob Owen, Dr. (Advisor)

Subjects:

Physics

Keywords:

General Relativity;Gravito-Electromagnetism;Mixmaster;Singularity