Electromagnetics and Photonics Commons^™

Heat And Current Propagation In Buffered Superconducting And Hyper-Conducting Wire, Jesse L. Lynn

Theses and Dissertations

This research models and analyzes the distribution of heat and current in a buffered superconducting or hyper-conducting wire that shows potential for use in different capacities in multiple Air Force systems including the Active Denial System. The thesis includes a brief background of the reaction-diffusion system of partial differential equations provided by AFRL/RZPG and development of the numerical scheme. It then explores solutions to the model. These solutions indicate some of the various heat-related failures that may be observed in such a wire. The nature of the solutions observed depends on the characteristics of the wire, operating temperature and efficiency …

Swept-Frequency Sampled Grating Distributed Bragg Reflector Lasers Optimized For Optical Coherence Tomography Applications, Brandon J. George

Master's Theses

Swept Frequency Source Optical Coherence Tomography (OCT) requires high repetition rate and wide spectral width wavelength tunable sources at a low cost. The sampled grating distributed Bragg reflector (SG-DBR) laser provides wide wavelength tuning range while exhibiting a wavelength switching speed that is among the fastest currently available. The SG-DBR laser is used to generate linear frequency ramps with high repetition rates. Since the SG-DBR laser is currently used for the telecommunications industry in high volume, the price of the system is much lower than current OCT sources. Therefore the SG-DBR laser provides a practical solution for Swept Source OCT. …

Focusing Electromagnetic Radiation In Dielectric Media, Mark A. Migliaccio Jr.

Electrical & Computer Engineering Theses & Dissertations

Bioelectrics and microwave imaging requires an ultra-wideband (UWB) antenna to deliver intense, short electromagnetic pulses into biological targets for the purpose of therapy and imaging. Two antennas with different focal distances, predicted by a two­ dimensional model, have been designed for focusing electromagnetic radiation in the near field.

Focusing is achieved through the use of prolate spheroidal reflector antennas with a conical wave launcher submerged in water. For an ultra-wideband feed signal, with a rise time of 200 picoseconds, the maximum electric field was found to be close to the edge of the reflector, a result that differs from the …

Aerodynamic Analysis Of An Urban Magnetic Levitation Vehicle, John Matthew Wells

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis will detail the aerodynamic qualities of a magnetic levitation concept vehicle designed to be installed on Old Dominion University's campus. The vehicle is representative of a class of small, low-speed Maglev systems commonly referred to as Urban Maglev. A 1:12 scale model underwent testing in Old Dominion's low speed wind tunnel. Force and moment coefficients were measured over a wide range of yaw angles. Results give insight into crosswind effects and how these forces affect vehicle dynamics. An analysis of this type is important in understanding the ride quality and safety of the system. Force Coefficients range from …

Dynamic Interaction Of Elevated Guideway With Uncontrolled Maglev Vehicles, Sumanth Reddy Velma

Mechanical & Aerospace Engineering Theses & Dissertations

A flexible guideway on an elevated foundation is a key to affordable maglev urban transit. The flexible guideway can undergo significant dynamic motion, either when a vehicle solely relies on an open-loop control system or when a vehicle equipped with feedback control system experiences failure, due to fluctuating magnetic forces between the vehicle and the guideway. In an attempt to understand the effect of the uncontrolled vehicle on the structural response of the guideway, its dynamic interaction with maglev vehicles is investigated under various operating conditions. To this end, two vehicle models using Electrodynamic suspension (EDS) and Electromagnetic suspension (EMS) …

Directional Dual-Band Slot Antenna With Dual-Bandgap High-Impedance-Surface Reflector, Xiulong Bao, Giuseppe Ruvio, Max Ammann

Articles

A compact dual-band high-impedance-surface EBG structure is employed as a reflector for a dual-band annular-slot antenna. The reflector comprises an array of miniaturized EBG cells which utilizes square patches augmented by four S-shaped corrugated arms to reduce the resonant frequency of the proposed EBG structure. In order to broaden the bandwidth and adjust the frequency ratio for the dual-band EBG structure, a log-periodic spacing between the S-shaped strips is introduced. The combination of microstrip-fed annular slot and EBG reflector provides directional properties for both frequency bands with reduced size and low-profile.

Influence Of Solar Heating On The Performance Of Integrated Solar Cell Microstrip Patch Antennas, Maria Roo Ons, S. Shynu, M Seredynski, Max Ammann, Sarah Mccormack, Brian Norton

Articles

The integration of microstrip patch antennas with photovoltaics has been proposed for applications in autonomous wireless communication systems located on building façades. Full integration was achieved using polycrystalline silicon solar cells as both antenna ground plane and direct current power generation in the same device. An overview of the proposed photovoltaic antenna designs is provided and the variation characterised of the electromagnetic properties of the device with temperature and solar radiation. Measurements for both copper and solar antennas are reported on three different commercial laminates with contrasting values for thermal coefficient of the dielectric constant.

Design Of Acousto-Optic Chaos Based Secure Free-Space Optical Communication Links, Anjan K. Ghosh, Pramode K. Verma, Samuel Cheng, Robert C. Huck, Monish Ranjan Chatterjee, Mohammed A. Al-Saedi

Electrical and Computer Engineering Faculty Publications

We discuss the design of an acousto-optic cell based free space optical communication link where the data beam is made secure through chaos encryption. Using external signal modulation of the diffracted light from a hybrid acousto-optic cell chaos (or directly via incorporation in the sound-cell driver's bias voltage) encryption of data is possible. We have shown numerically that decryption of the encoded data is possible by using an identical acousto-optic system in the receiver.

Stability Analysis, Modeling, Simulation And Experimental Testing Of An Ems Maglev System With Structural Flexibility, Aravind M. Hanasoge

Mechanical & Aerospace Engineering Theses & Dissertations

Vehicle-guideway interaction studies of Magnetically Levitated (Maglev) vehicles indicate that structural flexibility can adversely affect the overall stability and performance of such systems. This is one of the reasons why guideways are generally made very rigid. This in turn leads to increased cost of the overall system since guideway construction forms a significant portion of the overall cost. In this dissertation, the influence of structural flexibility on the stability of Electromagnetic Suspension (EMS) Maglev systems is studied. It is shown how inherently unstable and flexible structure EMS Maglev systems can achieve guaranteed stability by using collocated actuators and sensors, along …

Synthetic Aperture Radar Imaging Simulated In Matlab, Matthew Schlutz

Master's Theses

This thesis further develops a method from ongoing thesis projects with the goal of generating images using synthetic aperture radar (SAR) simulations coded in MATLAB. The project is supervised by Dr. John Saghri and sponsored by Raytheon Space and Airborne Systems. SAR is a type of imaging radar in which the relative movement of the antenna with respect to the target is utilized. Through the simultaneous processing of the radar reflections over the movement of the antenna via the range Doppler algorithm (RDA), the superior resolution of a theoretical wider antenna, termed synthetic aperture, is obtained. The long term goal …

Nondestructive Electromagnetic Material Characterization Using A Dual Waveguide Probe: A Full Wave Solution, Milo W. Hyde Iv, James W. Stewart, Michael J. Havrilla, William P. Baker, Edward Rothwell, Dennis P. Nyquist

Faculty Publications

A nondestructive technique for determining the complex permittivity and permeability of a perfect electric conductor backed magnetic shielding material using a dual waveguide probe is presented. The dual waveguide probe allows for the simultaneous collection of reflection and transmission coefficients which distinguishes it from single probe methods common in the literature. Theoretical development of these coefficients, which is accomplished through a coupled magnetic field integral equations formulation using Love's equivalence principle and solved via the method of moments (MOM), is discussed. Evaluation of the resulting MOM impedance matrix elements is performed using complex plane integration leading to enhanced computational efficiency …

Shielding Effectiveness Of Superalloy, Aluminum, And Mumetal Shielding Tapes, Cindy Suit Cheung

Master's Theses

Using MIL-HDBK-419A, MATLAB and Nomographs, Shielding Effectiveness for the Magnetic Field, Electric Field, and Plane Wave were calculated over a frequency range from 10 Hz to 1 GHz. The three shielding tapes used included superalloy, aluminum, and mumetal. Calculations for Shielding Effectiveness involve the computation of Absorption Loss, Reflection Loss, and Re-Reflection Correction Factor. From the outcome of the calculations, it was suitable to conclude that all three metals fulfill the 40 dB Shielding Effectiveness requirements for SGEMP fields for frequencies greater or equal to 1 MHz. Accordingly, all three shielding tapes provide at least 40 dB of shielding to …

Suite Of Standards For Electromagnetic Material Characterization Using Mode Matching Theory, Brian J. Witthoeft

Theses and Dissertations

The objective of this research is to determine if an acceptable standard can be developed to access the accuracy and precision of measurements taken using waveguide systems. Tiny changes in material fabrication, processing, and environment can cause problems with accuracy and precision in measurement. There is a great deal of research on uncertainty analysis in the literature. A large portion of the effort will be to determine the levels of uncertainty caused by each of the dimensions of the waveguide insert and to develop a suitable standard capable of verifying system performance. The Mode-Matching Technique will be used to extract …

Advanced Radiometry For High Discrimination Explosive Fireball Discrimination, Steven E. Slagle

Theses and Dissertations

The high explosive fireball phenomenological model for the mid wave infrared spectrum, developed by AFIT, performs classification from spectral signatures was modified to use radiometric intensities. Five bands were sequentially fit to derive the five physical fit parameters describing the fireball's temperature, size, soot absorption coefficient within 16% and emissions from the H₂O and CO₂ concentrations within 333% of the spectral model. This was improved by changing the model's band sizes, center, and fitting methods where all five fit parameters were matched to within 17% of spectral model. This demonstrated that a combination of radiometric intensities could …

Analysis And Application Of The Bi-Directional Scatter Distribution Function Of Photonic Crystals, Robert B. Lamott

Theses and Dissertations

Photonic crystals (PCs) are periodic structures built from materials with different refractive indices repeated at sub-wavelength intervals, which results in unusual optical characteristics, including narrowband laser protection, and zero reflectance and high absorption anomalies. Most of the research into the optical properties of PCs has concentrated only on the small range of wavelengths and angles where these effects occur. To better understand where all light leaving a PC is scattered, a Complete Angle Scatter Instrument was used to analyze the scatter from three Guided Mode Resonance Filters designed for laser protection. In the plane of incidence, measurements of the scatter …

Retroreflector For Photonic Doppler Velocimetry, Thomas J. Lagoski

Theses and Dissertations

In order to meet the goals of the Department of Defense (DoD) for smaller and more accurate weapons, the Munitions Directorate of the Air Force Research Laboratory (AFRL/RW) has numerous projects investigating the miniaturization of weapons and munition fuze components. One of these efforts is to characterize the performance of small detonators. The velocity of the flyer, the key component needed to initiate a detonation sequence, can be measured using a photonic Doppler velocimeter (PDV). The purpose of this research was to develop a microelectromechanical system (MEMS) device that would act as an optimal retroreflective surface for the PDV. Two …

Power Scaling Of Large Mode Area Thulium Fiber Lasers In Various Spectral And Temporal Regimes, Timothy Mccomb

Electronic Theses and Dissertations

High power thulium fiber lasers are interesting for a myriad of applications due to their potential for high average output power, excellent beam quality, compactness, portability, high operating efficiency and broad, eye-safe spectral range from 1.8-2.1 microns. Currently, the majority of thulium laser research effort is being invested into scaling average output powers; however, such output powers are being scaled with no degree of control on laser system output spectrum or temporal behavior. Thulium fiber laser technology is not useful for many of its most important applications without implementation of techniques enabling tunable, narrow spectral widths with appropriate pulse durations …

Digital Camera Photographing In Measuring Propagation Loss Properties Of Ion2exchange Planar Optical Waveguides, Ling-Hua Jia, Feng Qiu, Jian Ying, Ti Yun-Jiang, Jie Z|Heng, Pengfei Wang, Gerald Farrell

Articles

The digital photographs of propagation lines of ion-exchange planar glass optical waveguides were taken by a common digital camera.According to the profile of light intensity of propagation lines,the attenuation curves were fitted and the propagation losses of the waveguides were calculated.The waveguides were treated by annealing process,and propagation losses properties were studied before and after annealing,respectively.The results show that the loss of waveguide increases with the mode.The loss in 0 mode decreases from 2.148 9 dB·cm－1 to 0.746 0 dB·cm－1.

Monoclinic Optical Constants, Birefringence, And Dichroism Of Slanted Titanium Nanocolumns Determined By Generalized Ellipsometry, Daniel Schmidt, Benjamin Booso, Tino Hofmann, Eva Schubert, Andrew Sarangan, Mathias Schubert

Electrical and Computer Engineering Faculty Publications

Generalized spectroscopic ellipsometry determines the principal monoclinic optical constants of thin films consisting of slanted titanium nanocolumns deposited by glancing angle deposition under 85° incidence and tilted from the surface normal by 47°. Form birefringence measured for wavelengths from 500 to 1000 nm renders the Ti nanocolumns monoclinic absorbing crystals with c-axis along the nanocolumns, b-axis parallel to the film interface, and 67.5° monoclinic angle between the aand c-axes. The columnar thin film reveals anomalous optical dispersion, extreme birefringence, strong dichroism, and differs completely from bulk titanium. Characteristic bulk interband transitions are absent in the spectral range investigated.

Zero-Broadening Measurement In Brillouin Based Slow-Light Delays, Andrzej Wiatrek, Ronny Henker, Stefan Preußler, Max Ammann, Andreas Schwarzbacher, Thomas Schneider

Articles

A novel method for the achievement of zero-broadening in a SBS based slow-light system is discussed in theory and demonstrated experimentally. The system is realized just with a single broadened Brillouin gain. It is shown, that if the gain bandwidth is much broader than the initial pulse width, the output pulse width decreases with increasing pump power. A compression of approximately 90 % of the initial pulse width was achieved in simulation and experiment.

Application And Extension Of Glauber Ising-Spin Dynamics In The Context Of A Single Chain Magnet System, Ryan Tucker Kristensen

Legacy Theses & Dissertations (2009 - 2024)

The Glauber Ising-spin dynamic with a local equilibrium approximation is applied to infinite and finite one-dimensional (anti-)ferromagnetic Ising chains with classic nearest neighbor interactions. The application of the Glauber dynamic and local equilibrium approximation is then extended to the one-dimensional ferrimagnetic chain with nearest neighbor interactions. Time dependant behavior and equilibrium states of the one-dimensional ferrimagnetic chain are then discussed in terms of the single chain magnet referred to as CoPhOMe, whose behavior empirical data to date suggest is consistent with a one-dimensional Ising ferrimagnet.

Feynman’S Relativistic Electrodynamics Paradox And The Aharonov-Bohm Effect, Adam Caprez, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

An analysis is done of a relativistic paradox posed in the Feynman Lectures of Physics involving two interacting charges. The physical system presented is compared with similar systems that also lead to relativistic paradoxes. The momentum conservation problem for these systems is presented. The relation between the presented analysis and the ongoing debates on momentum conservation in the Aharonov-Bohm problem is discussed.

Dense Spectral Beam Combining With Volume Bragg Gratings In Photo-Thermo-Refractive Glass, Oleksiy Andrusyak

Electronic Theses and Dissertations

Beam combining techniques have become an important tool in the design of high-power high-brightness laser systems. Spectral beam combining (SBC) is an incoherent combining technique that does not require phase control of sources, allowing for a stable and robust system. Using SBC, beams from an array of lasers with each element operated at a different wavelength are combined into a single near-diffraction-limited beam with the same aperture using dispersive optical elements. SBC by means of volume Bragg gratings (VBGs) utilizes unique spectral response of VBGs: diffraction efficiency is close to unity when the Bragg condition is satisfied and is close …

Analysis And Design Of Wide-Angle Foveated Optical Systems, George Curatu

Electronic Theses and Dissertations

The development of compact imaging systems capable of transmitting high-resolution images in real-time while covering a wide field-of-view (FOV) is critical in a variety of military and civilian applications: surveillance, threat detection, target acquisition, tracking, remote operation of unmanned vehicles, etc. Recently, optical foveated imaging using liquid crystal (LC) spatial light modulators (SLM) has received considerable attention as a potential approach to reducing size and complexity in fast wide-angle lenses. The fundamental concept behind optical foveated imaging is reducing the number of elements in a fast wide-angle lens by placing a phase SLM at the pupil stop to dynamically compensate …

Design, Analysis, And Optimization Of Diffractive Optical Elements Under High Numerical Aperture Focusing, Toufic Jabbour

Electronic Theses and Dissertations

The demand for high optical resolution has brought researchers to explore the use of beam shaping diffractive optical elements (DOEs) for improving performance of high numerical aperture (NA) optical systems. DOEs can be designed to modulate the amplitude, phase and/or polarization of a laser beam such that it focuses into a targeted irradiance distribution, or point spread function (PSF). The focused PSF can be reshaped in both the transverse focal plane and along the optical axis. Optical lithography, microscopy and direct laser writing are but a few of the many applications in which a properly designed DOE can significantly improve …

Temperature-Induced Phenomena In Systems Of Magnetic Nanoparticles, Abdul Wazed Bhuiya

Open Access Theses & Dissertations

Magnetic nanoparticle ensembles have received a lot of attention, stemming in part from their current and potential applications in biomedicine and in the development of high-density magnetic storage media. Key to the functionality of these systems are microscopic structures and mechanisms that make them exhibit unique properties and behave differently from their bulk counterparts.

We studied microscopic structures and processes that dictate macroscopic properties, behavior and functionality of magnetic nanoparticle ensembles. As the temperature T strongly influences the magnetic behavior of these systems, we studied temperature dependent magnetic properties using AC-susceptibility and DC-magnetization measurements carried out over a broad range …

The Effect Of Copt Crystallinity And Grain Texturing On Properties Of Exchange-Coupled Fe/Copt Systems, H. Oguchi, A. Zambano, M. Yu, Jason R. Hattrick-Simpers, D. Banerjee, Y. Liu, Z. L. Wang, J. P. Liu, S. E. Lofland, D. Josell, I. Takeuchi

Faculty Publications

The effect of the crystallinity and the grain texturing of CoPt hard layers on exchange coupled Fe/CoPt soft/hard magnetic systems was studied using gradient thickness multilayer thin films. We have studied the hard layer structures by transmission electron microscopy and x-ray diffraction, and characterized the exchange coupling interaction through magnetization loops obtained by the magneto-optical Kerr effect measurement. We found that exchange coupling strongly depends on the crystalline characteristics of the CoPt hard layer. There is correlation between the mixture of different grain orientations of the CoPt hard layer and coupling efficiency. In particular, interlayer coupling is enhanced when there …

Analysis Of Possible Use Of Identification Technologies In Disassembly, Vukica Jovanović, Sreten Filipović, Gordana Ostojić, Stevan Stankovski, Milovan Lazarević

Engineering Technology Faculty Publications

The barcodes and Radio Frequency Identification tags that are being used during manufacturing, assembly, warehousing, and distribution could also be reused at the end of the product lifecycle for an identification of the correct disassembly process that would result in recycling of its components. The barcodes or RFID tags can be helpful in identifying objects in terms of sustainable development, regarding disassembly, recycling and reuse. In this paper, the analysis of the current applications of RFID Technology in the final phase of the product lifecycle will be presented. The simulation of the disassembly process supported by both barcode and RFID-enabled …

Silicon Carbide And Agile Optics Based Sensors For Power Plant Gas Turbines, Laser Beam Analysis And Biomedicine, Mumtaz Sheikh

Electronic Theses and Dissertations

Proposed are novel sensors for extreme environment power plants, laser beam analysis and biomedicine. A hybrid wireless-wired extreme environment temperature sensor using a thick single-crystal Silicon Carbide (SiC) chip embedded inside a sintered SiC probe design is investigated and experimentally demonstrated. The sensor probe employs the SiC chip as a Fabry-Perot (FP) interferometer to measure the change in refractive index and thickness of SiC with temperature. A novel temperature sensing method that combines wavelength-tuned signal processing for coarse measurements and classical FP etalon peak shift for fine measurements is proposed and demonstrated. This method gives direct unambiguous temperature measurements with …

Wavefront Sensor For Eye Aberrations Measurements, Costin Curatu

Electronic Theses and Dissertations

Ocular wavefront sensing is vital to improving our understanding of the human eye and to developing advanced vision correction methods, such as adaptive optics, customized contact lenses, and customized laser refractive surgery. It is also a necessary technique for high-resolution imaging of the retina. The most commonly used wavefront sensing method is based on the Shack-Hartmann wavefront sensor. Since Junzhong Liang's first application of Shack-Hartmann wavefront sensing for the human eye in 1994, the method has quickly gained acceptance and popularity in the ophthalmic industry. Several commercial Shack-Hartmann eye aberrometers are currently available. While the existing aberrometers offer reasonable measurement …