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Articles 1 - 30 of 56
Full-Text Articles in Physics
Electrical Conductivity Of The Aluminum Oxide Diffusion Barrier Following Catalytic Carbon Nanotube Growth, Berg Daniel Dodson
Electrical Conductivity Of The Aluminum Oxide Diffusion Barrier Following Catalytic Carbon Nanotube Growth, Berg Daniel Dodson
Theses and Dissertations
Carbon nanotube templated microfabrication (CNT-M) is a method that allows high-aspect ratio structures to be made for microelectromechanical systems (MEMS) devices. One concern when making monolithic electrical devices using CNT-M is that the aluminum oxide diffusion barrier will create too large of a resistance in the device. However, in developing CNT based MEMS devices, it has been observed that an electrical DC current is capable of transport from a conductive substrate, across the aluminum oxide, and through to the CNT structure grown on top of it. This thesis attempts to determine the mechanisms responsible for current being able to cross …
Nonlinear Characterizing Of A New Titanium Nitride On Aluminum Oxide Metalens, Michael A. Cumming
Nonlinear Characterizing Of A New Titanium Nitride On Aluminum Oxide Metalens, Michael A. Cumming
Theses and Dissertations
A sample metalens generated from Titanium Nitride deposited onto Aluminum Oxide was designed to focus at 10 microns with a beam centered at 800nm, and when analyzed with high intensity illumination was found to have a focal length of 9.650 ±.003µm at an intensity of 16.93[MW/cm2 ]. Analyzing this change by comparing it to a Fresnel Lens’ physics shows that for this lens, the effective nonlinear index of refraction is certainly greater than the nonlinear index of just Titanium Nitride itself, at −1.6239 × 10−15[m2/W] compared to the materials −1.3 × 10−15[m2 …
Numerical Simulation Of Unstable Laser Resonators With A High Gain Medium, Robert L. Lloyd
Numerical Simulation Of Unstable Laser Resonators With A High Gain Medium, Robert L. Lloyd
Theses and Dissertations
This research focused on the numeric simulation of unstable laser resonators with high gain media. In order to accomplish the research, the modes and eigenvalues for various bare cavity resonator were computed followed by modes of a resonator in the presence of gain. Using a Fourier Split Step Method in a Fox and Li iteration scheme, different laser outputs for various laser cavities with gain were computed. Various parameters defining positive branch confocal unstable resonators were chosen corresponding to four studies. The four studies focused on modifying laser cavity Fresnel number, gain medium parameters, gain cell position, and gain cell …
Digital Holography Efficiency Experiments For Tactical Applications, Douglas E. Thornton
Digital Holography Efficiency Experiments For Tactical Applications, Douglas E. Thornton
Theses and Dissertations
Digital holography (DH) uses coherent detection and offers direct access to the complex-optical field to sense and correct image aberrations in low signal-to-noise environments, which is critical for tactical applications. The performance of DH is compared to a similar, well studied deep-turbulence wavefront sensor, the self-referencing interferometer (SRI), with known efficiency losses. Wave optics simulations with deep-turbulence conditions and noise were conducted and the results show that DH outperforms the SRI by 10's of dB due to DH's strong reference. Additionally, efficiency experiments were conducted to investigate DH system losses. The experimental results show that the mixing efficiency (37%) is …
Targeted Germanium Ion Irradiation Of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistors, Melanie E. Mace
Targeted Germanium Ion Irradiation Of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistors, Melanie E. Mace
Theses and Dissertations
Microscale beams of germanium ions were used to target different locations of aluminum galliumnitride/gallium nitride (AlGaN/GaN) high electron mobility transistors (HEMTs) to determine location dependent radiation effects. 1.7 MeV Ge ions were targeted at the gap between the gate and the drain to observe displacement damage effects while 47 MeV Ge ions were targeted at the gate to observe ionization damage effects. Electrical data was taken pre, during, and post irradiation. To separate transient from permanent degradation, the devices were characterized after a room temperature anneal for at least 30 days. Optical images were also analyzed pre and post irradiation. …
On The Pulsed Laser Ablation Of Metals And Semiconductors, Todd A. Van Woerkom
On The Pulsed Laser Ablation Of Metals And Semiconductors, Todd A. Van Woerkom
Theses and Dissertations
This dissertation covers pulsed laser ablation of Al, Si, Ti, Ge, and InSb, with pulse durations from tens of picosecond to hundreds of microseconds, fluences from ones of J/cm2 to over 10,000 J/cm2, and in ambient air and vacuum. A set of non-dimensional scaling factors was created to interpret the data relative to the laser and material parameters, and it was found that pulse durations shorter than a critical timescale formed craters much larger than the thermal diffusion length, and longer pulse durations created holes much shallower than the thermal diffusion length. Low transverse order Gaussian beams …
Light Scattering In Diffraction Limit Infrared Imaging, Ghazal Azarfar
Light Scattering In Diffraction Limit Infrared Imaging, Ghazal Azarfar
Theses and Dissertations
Fourier Transform Infrared (FTIR) microspectroscopy is a noninvasive technique for chemical imaging of micrometer size samples. Employing an infrared microscope, an infrared source and FTIR spectrometer coupled to a microscope with an array of detectors (128 x 128 detectors), enables collecting combined spectral and spatial information simultaneously. Wavelength dependent images are collected, that reveal biochemical signatures of disease pathology and cell cycle. Single cell biochemistry can be evaluated with this technique, since the wavelength of light is comparable to the size of the objects of interest, which leads to additional spectral and spatial effects disturb biological signatures and can confound …
A Search For A High-Order Excitation Of Surface Phonon Polaritons On Silicon Carbide Metasurfaces, Md Litan Ali
A Search For A High-Order Excitation Of Surface Phonon Polaritons On Silicon Carbide Metasurfaces, Md Litan Ali
Theses and Dissertations
Metasurfaces promise a control of light in free and confined spaces like optical waveguides using subwavelength-scale nanostructures. In this work, we experimentally investigate a variety control of light in more confined spaces which is localized surface waves of light. A control of surface waves has been challenged because of a lack of efficient nanostructures. For example, conventional and widely used metallic nanostructures have a high coupling efficiency of light due to free charge carriers but the charge carriers induce a high optical power loss. We recently designed and fabricated metal/dielectric multilayer aperture on ionic crystal, which shows a strong resonance …
Enhancing Transport In Classical And Quantum Systems Using Non-Hermiticity, Fatemeh Mostafavi
Enhancing Transport In Classical And Quantum Systems Using Non-Hermiticity, Fatemeh Mostafavi
Theses and Dissertations
Non-Hermiticity, the presence of gain and loss in the structures, provides a flexible platform to utilize the wave propagation in classical and quantum system. Here in this thesis by using this advantage we aim to enhance the transport in both realms.
Scattering In Infrared Microspectroscopy, Alex James Schofield
Scattering In Infrared Microspectroscopy, Alex James Schofield
Theses and Dissertations
Mid-infrared absorbance spectra obtained from spatially inhomogeneous and finite samples often contain scattering effects that undermine the Beer-Lambert law assumption. Such spectra contain generally non-linear contributions from the scattering material’s complex refractive index, which may result in derivative-like bands with shifted peak positions. It is first shown using Mie theory for spherical scatterers, that these band distortions may be interpreted and accurately modeled by Fano theory when the imaginary part of its complex dielectric function is small and Lorentzian in nature—as is the case for many biological media. By fitting Fano line shapes to isolated absorbance bands, recovery of the …
The Conical Diffraction And Adiabatic Elimination In Pt-Symmetric Systems, Mojgan Dehghani
The Conical Diffraction And Adiabatic Elimination In Pt-Symmetric Systems, Mojgan Dehghani
Theses and Dissertations
Dehghani, Mojgan, The Conical Diffraction and Adiabatic Elimination in PT-Symmetric Systems. Master of Science (MS), July, 2019, 75 pp., 32 figures, references, 69 titles. Since almost two decades ago, the non-Hermitian Hamiltonians with combined parity and time-reversal symmetry, having entirely real spectra, have been outstanding candidates for characterizing the features of open systems. In this thesis, we investigate the dynamics of certain PT systems. In chapter I, we present a brief review of the fundamentals of PT-symmetric systems. Chapter II focuses on the conical diffraction in a PT-symmetric waveguide lattice. We explore the evolution of a wave packet, which forms …
Bubble Nucleation And Cooperativity In Duplex Stretching Of A Helicoidal Dna Model, Pawan Kumar Thapaliya
Bubble Nucleation And Cooperativity In Duplex Stretching Of A Helicoidal Dna Model, Pawan Kumar Thapaliya
Theses and Dissertations
Denaturation of DNA means separation of dsDNA into ssDNA due to the breaking of hydrogen bond by the application of heat or another mechanical method to carry out the processes like translation,transcription, and replication. Single-molecule DNA stretching experiments displayed a force-induced transition at a force of 65pN for long dsDNA molecules. In these experiments, double stranded DNA molecules are stretched by a force applied to opposite ends of the DNA, e.g., in anatomic force microscope or an optical tweezers instrument. Here we study the thermal and force-induced denaturation of the helicoidal DNA bubble-in-the middle sequence by Monte-Carlo simulations technique. We …
Optimization Of Information Storage With Quantum Walks, Gui Zhen Lu
Optimization Of Information Storage With Quantum Walks, Gui Zhen Lu
Theses and Dissertations
A four-vertex quantum graph was analyzed with the objective of storing the highest ampli- tude of an incoming qubit. The procedure included the use of phase shifters to allow the user to store and release information when he or she chooses. Several parameters, such as the phase shift, location of the phase shifter, the size and shape of the binding graph and initial incoming state were varied independently to optimize the storage capacity of the graph.
Mechanically Scanned Interference Pattern Structured Illumination Imaging, Jarom Silver Jackson
Mechanically Scanned Interference Pattern Structured Illumination Imaging, Jarom Silver Jackson
Theses and Dissertations
A method of lensless, single pixel imaging is presented. This method, referred to as MAS-IPSII, is theoretically capable of resolutions as small as one quarter of the wavelength of the imaging light. The resolution is not limited by the aperture of any optic, making high resolutions (including subwavelength) feasible even at very large (greater than a meter) distances. Imaging requires only flat optics and a coherent source, making it a good candidate for imaging with extreme wavelengths in the UV and x-ray regimes. The method is demonstrated by the imaging of various test targets. Both real and complex imaging (i.e. …
Analytical Expressions For Acoustic Radiation Modes Of Simple Curved Structures, Caleb Burley Goates
Analytical Expressions For Acoustic Radiation Modes Of Simple Curved Structures, Caleb Burley Goates
Theses and Dissertations
The search for a convenient connection between vibration patterns on a structure and the sound radiated from that structure is ongoing in structural acoustics literature. Common techniques are wavenumber domain methods, or representation of the vibration in terms of some basis, such as structural modes or elementary radiators, and calculating the sound radiation in terms of the basis. Most choices for a basis in this situation exhibit strong coupling between the basis functions, but there is one choice which does not: Acoustic radiation modes are by definition the basis that orthogonalizes the radiation operator, meaning the radiation modes do not …
Nuclear Magnetic Resonance Characterization Of Dynamics In Novel Electrochemical Materials, Christopher T. Mallia
Nuclear Magnetic Resonance Characterization Of Dynamics In Novel Electrochemical Materials, Christopher T. Mallia
Theses and Dissertations
As our daily use of electronics and electronic technology grows, so does the societal need for sustainable, renewable and portable electrical power. To this end, materials of interest in the electrochemical world are needed to advance the frontier of battery science and energy storage technologies so that a safer, more efficient and reliable electrical future can be realized. This work focuses on characterization of materials primarily of interest for use as electrolytes in rechargeable Lithium-Ion Batteries (LIBs). Despite their extraordinary power, LIB application in certain fields, such as in electric vehicles, has been limited due to performance and safety concerns. …
Optimizing Advanced Ligo's Scientific Output With Fast, Accurate, Clean Calibration, Aaron Daniel Viets
Optimizing Advanced Ligo's Scientific Output With Fast, Accurate, Clean Calibration, Aaron Daniel Viets
Theses and Dissertations
Since 2015, the direct observation of gravitational waves has opened a new window to observe the universe and made strong-field tests of Einstein's general theory of relativity possible for the first time. During the first two observing runs of the Advanced gravitational-wave detector network, the Laser Interferometer Gravitational-wave Observatory (LIGO) and the Virgo detector have made 10 detections of binary black hole mergers and one detection of a binary neutron star merger with a coincident gamma-ray burst. This dissertation discusses methods used in low and high latency to produce Advanced LIGO's calibrated strain data, highlighting improvements to accuracy, latency, and …
Object Enhancement, Noise Reduction, Conversion And Collection Of Spatiotemporal Image Data, Michael Izaguirre Jr.
Object Enhancement, Noise Reduction, Conversion And Collection Of Spatiotemporal Image Data, Michael Izaguirre Jr.
Theses and Dissertations
In this report, a variety of cellular dynamics are enhanced and analyzed utilizing various algorithms and filter for contrast enhancement. This report will also illustrate the underlying complexities of processing compressed data received from certain type of sensors, their default applications, various methods in converting compressed data to compatible universal uncompressed formats allowed in scientific applications, various methods of image and video capture, guidelines in ethical image manipulation, various methods of frame extraction, and analyzing/processing video images. These methods and processes purposely utilize freeware and public domain software to lower the cost of reproducibility for all.
High-Powered Led Assembly As Replacement For Conventional Hbo Lamps In High Resolution, High Magnification Microscopy System, Christian Y. Miranda Solis
High-Powered Led Assembly As Replacement For Conventional Hbo Lamps In High Resolution, High Magnification Microscopy System, Christian Y. Miranda Solis
Theses and Dissertations
Through decades, fluorescence microscopy has relied on mercury vapor lamps as its main light source due to their high power, broad spectrum, and bright bands generated. The use of mercury vapor lamps has remained fundamentally associated with the required lighting equipment of research laboratories. However, as time progresses, mercury vapor lamps have been slowly replaced with technologies that offered longer lifetimes, less hazardous waste, and output light at similar intensities. LED technology has been actively used in biological research, but was limited by price, lower intensities, and stability. The recent development of LED technology has allowed for further understanding and …
Nominalization And Interpretation: A Critique Of Global Nominalization Criteria, Jason Alen Dewitt
Nominalization And Interpretation: A Critique Of Global Nominalization Criteria, Jason Alen Dewitt
Theses and Dissertations
Nominalization is the process which removes abstract objects from our scientific theories. But what makes a proposed nominalization a good or successful one? In the paper “Is It Possible to Nominalize Quantum Mechanics,” Otávio Bueno develops criteria for any successful nominalization. In the present work, I discuss one of these criteria that I call the “interpretation criterion.” It claims that a nominalization of a scientific theory should be neutral with regards to the interpretations of that theory. I argue that the interpretation criterion is problematic, and that it should be replaced with an alternative criterion of nominalization. I first explicate …
Weak Turbulence Closures In Incompressible Magnetohydrodynamics, Augustus Antanas Azelis
Weak Turbulence Closures In Incompressible Magnetohydrodynamics, Augustus Antanas Azelis
Theses and Dissertations
In this work we apply the weak turbulence closure to the governing equation of incompressible homogeneous magnetohydrodynamics (MHD). It was originally thought that the method lacked applicability to linearly dispersive waves however MHD presents a unique exception to this notion. A perturbative scheme is used in combination with multiple scale analysis to find a dynamic equation for the wavenumber energy spectrum corresponding to weakly non-linear shear Alfv´enic turbulence. We begin by deriving an equation describing the time evolution of the Fourier transformed Els¨asser fields associated with linear propagation and non-linear interactions between counter-propagating Alfv´en waves. A cumulant hierarchy is then …
Noise Control Of Vacuum-Assisted Toilets, Michael Thomas Rose
Noise Control Of Vacuum-Assisted Toilets, Michael Thomas Rose
Theses and Dissertations
Vacuum-assisted toilets make use of a large pressure difference between the ambient pressure and a vacuum tank to transport waste from the toilet bowl to the septic tank. This process requires 98% less water per flush making it an attractive product for transport vehicles such as airplanes, cruise ships, and trains. Unfortunately, the water savings come at the cost of high noise levels. This thesis investigates the acoustic characteristics of a vacuum-assisted toilet flush and several methods to reduce the radiated noise. Some methods include changing rinse parameters such as rinse pressure, rinse length, and rinse timing, adding structural damping …
A Model Independent Measurement Of The Cross Section Ratio, R_Σ = Σ(Ν_Μ N → Μ^− P) / Σ(Ν_Μ N → 2track), Barnali Chowdhury
A Model Independent Measurement Of The Cross Section Ratio, R_Σ = Σ(Ν_Μ N → Μ^− P) / Σ(Ν_Μ N → 2track), Barnali Chowdhury
Theses and Dissertations
NOνA (NuMI Off-Axis νe Appearance) experiment is a long-baseline neutrino and anti-neutrino oscillation experiment, designed to study the neutrino mass ordering and to search for the effects of the CP violating phase angle δ. Extraction of the νµ and νe oscillation parameters requires knowledge of the energy of the neutrino interacting in the detector. The reactions of neutrinos with matter produce charged and neutral particles in the detector. How well we are able to measure the energy of the incoming neutrino is directly related to the final state particles, seen in the detector. Inaccurate …
Linear Theory Of Alfvén Wave Reflections At A Density Discontinuity, Shane Marcus
Linear Theory Of Alfvén Wave Reflections At A Density Discontinuity, Shane Marcus
Theses and Dissertations
One of the most important outstanding problems in solar physics is explaining why the corona is much hotter than the surrounding solar atmosphere, called the Coronal Heating Problem (CHP). There has been much work in trying to understand the origin of this issue, as it contradicts what one may think when it comes to basic thermodynamics. One such theory is Alfv´en wave turbulence. These waves are a form of low frequency electromagnetic waves that have been proposed as a suitable heating mechanism behind the CHP. There is a thin layer that separates the chromosphere and the corona, known as the …
Non-Local Spin Valve Interferometer: Experimental Observation Of Superconducting Spin Current And Spin Aharonov-Bohm Effect, Ning Lu
Theses and Dissertations
An electron interferometer was designed and fabricated via a normal metal (supercon- ductor)/insulator/ferromagnet non-local lateral spin valve with a ring-shaped normal metal/insulator spacer, and spin current interference was observed. At 4.2 K, a very high spin signal of 200 mΩ was found in a device with 2 µm injector-detector dis- tance and magnetic field swept parallel to the plane. With a perpendicular magnetic field sweep, a Hanle effect measurement showed both spin precession and h/e oscil- lation. Because of the non-adiabatic nature of the precessing spins at low fields as they traverse the normal metal ring, this is an …
Using Symmetry To Accelerate Materials Discovery, Wiley Spencer Morgan
Using Symmetry To Accelerate Materials Discovery, Wiley Spencer Morgan
Theses and Dissertations
Computational methods are commonly used by materials scientists to make predictions about materials. These methods can achieve in hours what would take days or weeks to accomplish in a lab. However, there are limits to what computational methods can do and how accurate the predictions are.A limiting factor for computational materials science is the size of the search space. The space of potential materials is infinite. Selecting specific systems of elements on a fixed lattice to study reduces the number of possible arrangements of atoms in the lattice to a finite number. However, this number can still be very large. …
Source Term Estimation Of Atmospheric Pollutants Using An Ensemble Of Hysplit Concentration Simulations, Casey L. Zoellick
Source Term Estimation Of Atmospheric Pollutants Using An Ensemble Of Hysplit Concentration Simulations, Casey L. Zoellick
Theses and Dissertations
In support of Comprehensive Nuclear-Test-Ban Treaty (CTBT) monitoring and nuclear event detection, this study works toward source term estimation (STE) of dispersive pollutants using a novel method|an ensemble of forward trajectory concentration simulations using a meteorology-coupled dispersion model. Traditionally a mathematically and physically rigorous problem, STE of a plume of atmospheric pollutants can be solved in a variety of ways depending on what is known regarding the emission, but little has been studied on the sensitivity between the horizontal resolution of the meteorology data in relation to the dispersion model and the results derived from known concentrations at multiple locations. …
The Non-Mechanical Beam Steering Of Light In Reflective Inverse Diffusion, Eric K. Nagamine
The Non-Mechanical Beam Steering Of Light In Reflective Inverse Diffusion, Eric K. Nagamine
Theses and Dissertations
Wavefront shaping is a technique that uses spatial light modulators to conjugate the phase of light incident on a rough surface, such that the light will refocus after reflection. This refocusing effect is called reflective inverse diffusion. There currently are two different approaches used to achieve reflective inverse diffusion: iterative methods and matrix methods. Iterative methods find one phase mask which allows for reflected light to be focused at a single, specific position, with results that are immediately available and continuously improving. Matrix methods calculate the complex matrix which describes the rough surface and allows for reflected light to be …
Quantifying Uncertainty Of Ensemble Transport And Dispersion Simulations Using Hysplit, Daniel W. Bazemore
Quantifying Uncertainty Of Ensemble Transport And Dispersion Simulations Using Hysplit, Daniel W. Bazemore
Theses and Dissertations
Uncertainty associated with determining the source location of nuclear pollutants in the atmosphere after a nuclear fallout using a numerical model is difficult to determine. Uncertainty can originate from input data (meteorological and emissions), internal model error, physics parameterizations, and stochastic processes. This study uses the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model with data from the 1983 Cross Appalachian Tracer Experiment (CAPTEX) (Ferber et al. 1986) and simulating six nuclear detonations (Rolph et al. 2014) to quantify and communicate uncertainty in ensemble dispersion simulations. This is accomplished by utilizing an ensemble of forward trajectory simulations varying initial conditions …
Development Of A Model For 11C Production Via The 14N(P,Α) Reaction Using A Ge Pettrace Cyclotron, Amy C. Hall
Development Of A Model For 11C Production Via The 14N(P,Α) Reaction Using A Ge Pettrace Cyclotron, Amy C. Hall
Theses and Dissertations
The GE PETtrace 800 Series cyclotron at the Missouri University Research Reactor (MURR) facility is used extensively for medical and research radioisotope production. However, no model exists of its radioisotope production performance, and the energy, full intensity, and spatial profile of the cyclotron proton beam has never been measured. To improve production planning for research and medical isotopes, a MCNP6 model of the isotope production process was developed to maximize efficiency in target design and better understand irradiation conditions. Since the cyclotron beam energy and profile has a significant impact on the types of reactions that take place and the …