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Full-Text Articles in Physics

Designing Liquid Crystal For Optoacoustic Detection, Michael T. Dela Cruz Mar 2019

Designing Liquid Crystal For Optoacoustic Detection, Michael T. Dela Cruz

Theses and Dissertations

This research impacts the development of a cost-saving, on-chip device that can replace a wide range of costly, bulky sensors for commercial and defense applications. In particular, the goals of this work were to design and test a sensor that uses the optical properties of liquid crystal (LC) to detect acoustic waves. This began with developing a method to fine-tune the optical features of the liquid crystal. Statistical analysis of select experimental variables, or factors, lead to ideal settings of those variables when creating the sensor. A two-factor and three-factor experiment were separately conducted and analyzed as a preliminary demonstration ...


Quantifying Uncertainty Of Ensemble Transport And Dispersion Simulations Using Hysplit, Daniel W. Bazemore Mar 2019

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 ...


Computational And Experimental Development Of 2d Anisotropic Photonic Crystal Metamaterials, James A. Ethridge Mar 2019

Computational And Experimental Development Of 2d Anisotropic Photonic Crystal Metamaterials, James A. Ethridge

Theses and Dissertations

The future of optical devices involves manipulation of nanoscale structure in order to achieve full control over the properties of the device. In fields as diverse as directed energy, remote sensing, optical communications and optical computing, these devices promise to greatly improve performance and efficiency. To advance this further, novel samples that incorporate both photonic crystal (PhC) structure and metamaterial properties, known as PhC metamaterials, are proposed. These PhC metamaterials allow for complete control over the directionality of the light-matter interaction to serve in these new applications. To develop this technology, first, metamaterials with no PhC structure are fabricated using ...


Development Of A Model For 11C Production Via The 14N(P,Α) Reaction Using A Ge Pettrace Cyclotron, Amy C. Hall Mar 2019

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 ...


Global Ionosonde And Gps Radio Occultation Sporadic-E Intensity And Height Comparison, Joshua Y. Gooch Mar 2019

Global Ionosonde And Gps Radio Occultation Sporadic-E Intensity And Height Comparison, Joshua Y. Gooch

Theses and Dissertations

A global, multi-year comparison of low and mid-latitude COSMIC GPS radio occultation (RO) sporadic-E (Es) plasma frequency and altitude and Digisonde blanketing frequency (fbEs) and altitude within 150 km and 30 minutes of each other. RO methods used to estimate the intensity of the Es layer include the scintillation index S4, total electron content (TEC) with both a constant and variable Es cloud thickness, and an Abel transform. The S4 and TEC with varying thickness techniques both under-represent the fbEs values while the TEC with constant thickness and Abel transform better estimate Digisonde fbEs values. All RO ...


Effects Of Sinusoidal Phase Modulation On Signal-To-Noise Ratio In A Digital Holography System, Davin Mao Mar 2019

Effects Of Sinusoidal Phase Modulation On Signal-To-Noise Ratio In A Digital Holography System, Davin Mao

Theses and Dissertations

Digital holography (DH) has been demonstrated to be an effective tool for tactical applications which involve in low signal-to-noise ratios (SNR). In practice, DH uses a strong reference beam from a local oscillator (LO) to scale SNR, however since DH relies on the interference of a signal beam with a mutually coherent LO, the coherence properties of the master oscillator (MO) can degrade system SNR for long range engagements. In this thesis, a digital holography system in the off-axis image plane recording geometry was assembled and used to measure the effects of the coherence properties of the MO on SNR ...


The Non-Mechanical Beam Steering Of Light In Reflective Inverse Diffusion, Eric K. Nagamine Mar 2019

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 ...


Variations Of Heavy Ion Abundances Relative To Proton Abundances In Large Solar Energetic Particle Events, Joseph F. Round Mar 2019

Variations Of Heavy Ion Abundances Relative To Proton Abundances In Large Solar Energetic Particle Events, Joseph F. Round

Theses and Dissertations

Past studies of heavy ions (Z>2) in large (E>10 MeV/nuc) gradual solar energetic particle (SEP) events have focused on elemental abundances relative to those of a single element, such as Fe or O, and have often neglected ionized H (the primary element used for space weather purposes). This work analyzes SEP abundances in a group of 15 large gradual SEP events from 2000 to 2015 across the energy range of 13.5-50.7 MeV. Hourly flux averages of He, C, O, Mg and Fe from the Advanced Composition Explorer/Solar Isotope Spectrometer (ACE/SIS) are compared to ...


Source Term Estimation Of Atmospheric Pollutants Using An Ensemble Of Hysplit Concentration Simulations, Casey L. Zoellick Mar 2019

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 ...


Modeling High-Altitude Nuclear Detonations Using Existing Ionospheric Models, Sophia G. Schwalbe Mar 2019

Modeling High-Altitude Nuclear Detonations Using Existing Ionospheric Models, Sophia G. Schwalbe

Theses and Dissertations

One threat to the United States is a nuclear weapon being detonated at high altitude over the country. The resulting electromagnetic pulse (EMP) could devastate the nation. Despite its destructive nature, the response of the ionosphere to such an event is poorly understood. This study assesses if existing ionospheric models, which are used to nowcast and forecast ionospheric changes, can be used to model the response to a high-altitude nuclear detonation (HAND). After comparing five ionosphere models, the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) was selected and modified to incorporate an array of F10.7 indices to serve as a proxy ...


Investigation Of Endwall Vortex Manipulation In High Lift Turbines Caused By Active Endwall Forcing, Horatio J. Babcock Mar 2019

Investigation Of Endwall Vortex Manipulation In High Lift Turbines Caused By Active Endwall Forcing, Horatio J. Babcock

Theses and Dissertations

With the increased demand for lighter, more fuel efficient and smaller gas turbine engines, the impetus to reduce the weight and size of the turbine has become apparent. One approach to reduce this weight is to reduce the number of blades in the turbine. However, to maintain power output, each blade must be capable of supporting a greater amount of lift. While several high-lift turbine profiles have been detailed in literature, most of these profiles have increased endwall losses, despite their desirable mid-span characteristics. To mitigate this endwall loss, a number of active and passive flow approaches have been studied ...


Direct Numerical Simulation Of Roughness Induced Hypersonic Boundary Layer Transition On A 7° Half-Angle Cone, Tara E. Crouch Mar 2019

Direct Numerical Simulation Of Roughness Induced Hypersonic Boundary Layer Transition On A 7° Half-Angle Cone, Tara E. Crouch

Theses and Dissertations

Direct numerical simulation (DNS) computational fluid dynamic (CFD) calculations were performed on a 30° slice of 7° half-angle cones with increasing nose radii bluntness at Mach 10 while simulating a distributed roughness pattern on the cone surface. These DNS computations were designed to determine if the non-modal transition behavior observed in testing performed at the Arnold Engineering Development Center (AEDC) Hypervelocity Wind Tunnel 9 was induced via distributed surface roughness. When boundary layer transition is dominated by second mode instabilities, an increase in nose radius delays the transition location downstream. However, blunt nose experiments indicated that as the nose radius ...


Analytical Models And Control Design Approaches For A 6 Dof Motion Test Apparatus, Kyra L. Schmidt Mar 2019

Analytical Models And Control Design Approaches For A 6 Dof Motion Test Apparatus, Kyra L. Schmidt

Theses and Dissertations

Wind tunnels play an indispensable role in the process of aircraft design, providing a test bed to produce valuable, accurate data that can be extrapolated to actual flight conditions. Historically, time-averaged data has made up the bulk of wind tunnel research, but modern flight design necessitates the use of dynamic wind tunnel testing to provide time-accurate data for high frequency motion. This research explores the use of a 6 degree of freedom (DOF) motion test apparatus (MTA) in the form of a robotic arm to allow models inside a subsonic wind tunnel to track prescribed trajectories to obtain time-accurate force ...


Schlieren Imaging And Flow Analysis On A Cone/Flare Model In The Afrl Mach 6 Ludwieg Tube Facility, David A. Labuda Mar 2019

Schlieren Imaging And Flow Analysis On A Cone/Flare Model In The Afrl Mach 6 Ludwieg Tube Facility, David A. Labuda

Theses and Dissertations

High-speed Schlieren photography was utilized to visualize flow in the Air Force Research Laboratory Mach 6 Ludwieg tube facility. A 7° half-angle cone/flare model with variable nosetip radius and flare angle options was used in the study. Testing was performed at two driver tube pressures, generating freestream Reynolds numbers of 10.0x106 and 19.8x106 per meter. The variable-angle flare portion of the model provided a method for adjusting the intensity of the adverse pressure gradient at the cone/flare junction. As expected from existing literature, boundary layer separation along the cone frustum occurred further upstream as ...


Tracking Shock Movement On The Surface Of An Oscillating, Straked Semispan Delta Wing, Justin A. Pung Mar 2019

Tracking Shock Movement On The Surface Of An Oscillating, Straked Semispan Delta Wing, Justin A. Pung

Theses and Dissertations

A recent research effort, sponsored by the Air Force Office of Scientific Research, numerically investigated the unsteady aerodynamic flow field around an oscillating, straked, delta wing. The study was centered on determining the importance of the unsteady aerodynamic forces acting as a driver for a nonlinear motion known as limit cycle oscillations. The current effort focused on creating a computational model to compare to the results of previous tests and modeling efforts and discover new information regarding the onset of LCO. The computational model was constructed using the Cartesian overset capabilities of the CREATE-AV™ fixed wing fluid dynamics solver Kestrel ...


Examination Of Flow Dynamics And Passive Cooling In An Ultra Compact Combustor, Tylor C. Rathsack Mar 2019

Examination Of Flow Dynamics And Passive Cooling In An Ultra Compact Combustor, Tylor C. Rathsack

Theses and Dissertations

The Ultra Compact Combustor (UCC) promises to greatly reduce the size of a gas turbine engine’s combustor by altering the manner in which fuel is burnt. Differing from the common axial flow combustor, the UCC utilizes a rotating flow, coaxial to the engine’s primary axis, in an outboard circumferential cavity as the primary combustion zone. The present study investigates two key UCC facets required to further this combustor design. The first area of investigation is cooling of the Hybrid Guide Vane (HGV). This UCC specific hardware acts as a combustor center body that alters the exit flow angle ...


Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, John J. Runco Mar 2019

Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, John J. Runco

Theses and Dissertations

Computational aerothermodynamic analysis is presented for a spacecraft in low Earth orbit performing an atmospheric skip entry maneuver. Typically, atmospheric reentry is a terminal operation signaling mission end-of-life and, in some instances, executed for spacecraft disposal. A variation on reentry – skip entry – is an aeroassisted trans-atmospheric maneuver in which a spacecraft utilizes the effects of aerodynamic drag in order to reduce energy prior to a terminal entry, pinpoint a targeted entry, or change orbital elements such as inclination. Spacecraft performing a skip entry enable new modes of maneuver to enhance operations in nominal or possibly contested mission environments. The present ...


Wall Model Large Eddy Simulation Of A Diffusing Serpentine Inlet Duct, Ryan J. Thompson Mar 2019

Wall Model Large Eddy Simulation Of A Diffusing Serpentine Inlet Duct, Ryan J. Thompson

Theses and Dissertations

The modeling focus on serpentine inlet ducts (S-duct), as with any inlet, is to quantify the total pressure recovery and ow distortion after the inlet, which directly impacts the performance of a turbine engine fed by the inlet. Accurate prediction of S-duct ow has yet to be achieved amongst the computational fluid dynamics (CFD) community to improve the reliance on modeling reducing costly testing. While direct numerical simulation of the turbulent ow in an S-duct is too cost prohibitive due to grid scaling with Reynolds number, wall-modeled large eddy simulation (WM-LES) serves as a tractable alternative. US3D, a hypersonic research ...


Scaling Film Cooling Adiabatic Effectiveness With Mass Transfer And Thermal Experimental Techniques, Luke J. Mcnamara Mar 2019

Scaling Film Cooling Adiabatic Effectiveness With Mass Transfer And Thermal Experimental Techniques, Luke J. Mcnamara

Theses and Dissertations

With increasing engine temperatures, it is becoming more important to design effective film cooling schemes. Low temperature, large scale tests are often implemented in the design process to reduce cost and complexity. A nondimensional adiabatic effectiveness can be used as an indication of the performance of a film cooling scheme. However, the coolant flow rate must be properly scaled between the low temperature tests and engine temperatures to accurately predict film cooling effectiveness. This process is complicated by gas property variation with temperature. Tests are commonly conducted using thermal measurement techniques with infrared thermography (IR), but the use of pressure ...


Initial Stage Of Fluid-Structure Interaction Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, Dustin P. Graves Mar 2019

Initial Stage Of Fluid-Structure Interaction Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, Dustin P. Graves

Theses and Dissertations

The analysis of a celestial icosahedron geometry is considered as a potential design for a Vacuum Lighter than Air Vehicle (VLTAV). The goal of the analysis is ultimately to understand the initial fluid-structure interaction of the VLTAV and the surrounding airflow. Up to this point, previous research analyzed the celestial icosahedron VLTAV in relation to withstanding a symmetric sea-level pressure applied to the membrane of the structure. This scenario simulates an internal vacuum being applied in the worst-case atmospheric environmental condition. The next step in analysis is to determine the aerodynamic effects of the geometry. The experimental setup for obtaining ...


Electrical Characterization Of Crystalline Uo2, Tho2 And U0.71Th0.29O2, Christina L. Dugan Dec 2018

Electrical Characterization Of Crystalline Uo2, Tho2 And U0.71Th0.29O2, Christina L. Dugan

Theses and Dissertations

Uranium dioxide (UO2), thorium dioxide (ThO2), and UxTh1-xO2 alloys are characterized for suitability in uranium-based neutron detectors. ThO2 was studied for an envisioned UO2/ThO2 heterojunction. A U0.71Th0.29O2 alloy was studied because of its resistance to oxidation and potential use in surface passivation. The U0.71Th0.29O2 effective Debye temperature of 217± 24 K was measured using temperature-dependent x-ray photoemission spectroscopy (XPS). The specific heat capacity for the U0.71Th0.29O2 alloy was ...


Kinetics Of Higher Lying Potassium States After Excitation Of The D2 Transition In The Presence Of Helium, Austin J. Wallerstein Dec 2018

Kinetics Of Higher Lying Potassium States After Excitation Of The D2 Transition In The Presence Of Helium, Austin J. Wallerstein

Theses and Dissertations

A kinetic model for the performance of a potassium Diode Pumped Alkali Laser (DPAL), including the role of higher lying states is developed to assess the impact on device efficiency and performance. A rate package for a nine level kinetic model including recommended rate parameters is solved under steady-state conditions. Energy pooling and far wing absorption populates higher lying states, with single photon and Penning ionization leading to modest potassium (K) dimer ion concentrations. The fraction of the population removed from the basic three levels associated with the standard model is less than 10% for all reasonable laser conditions, including ...


Design And Optimization Of A 3-D Plasmonic Huygens Metasurface For Highly-Efficient Flat Optics, Bryan M. Adomanis Sep 2018

Design And Optimization Of A 3-D Plasmonic Huygens Metasurface For Highly-Efficient Flat Optics, Bryan M. Adomanis

Theses and Dissertations

For miniaturization of future USAF unmanned aerial and space systems to become feasible, accompanying sensor components of these systems must also be reduced in size, weight and power (SWaP). Metasurfaces can act as planar equivalents to bulk optics, and thus possess a high potential to meet these low-SWaP requirements. However, functional efficiencies of plasmonic metasurface architectures have been too low for practical application in the infrared (IR) regime. Huygens-like forward-scattering inclusions may provide a solution to this deficiency, but there is no academic consensus on an optimal plasmonic architecture for obtaining efficient phase control at high frequencies. This dissertation asks ...


Reconstruction Of The 3d Temperature And Species Concentration Spatial Distribution Of A Jet Engine Exhaust Plume Using An Infrared Fourier Transform Spectrometer Hyperspectral Imager, Mason D. Paulec Sep 2018

Reconstruction Of The 3d Temperature And Species Concentration Spatial Distribution Of A Jet Engine Exhaust Plume Using An Infrared Fourier Transform Spectrometer Hyperspectral Imager, Mason D. Paulec

Theses and Dissertations

The measurement of combustion byproducts is useful for determining pollution of any fuel burning application, efficiency of combustion, and determining detectability of aircraft exhausts. Both intrusive and non-intrusive techniques have been utilized to measure these quantities. For the majority of the non-intrusive techniques, the absorption and emission spectra of the gases are utilized for measurements. For this research, the use of the Telops Infrared Fourier Transform Spectrometer (IFTS) Hyperspectral Imager (HSI) was explored within the scope of combustion diagnostic methods, as an option for remote measurements of a jet turbine to determine concentration of species and temperature of the combustion ...


Evaluation And Quantification Of Diffractive Plenoptic Camera Algorithm Performance, Jack A. Shepherd Iii Sep 2018

Evaluation And Quantification Of Diffractive Plenoptic Camera Algorithm Performance, Jack A. Shepherd Iii

Theses and Dissertations

A diffractive plenoptic camera is a novel approach to the traditional plenoptic camera which replaces the main optic with a Fresnel zone plate making the camera sensitive to wavelength instead of range. However, algorithms are necessary to reconstruct the image produced by plenoptic cameras. While many algorithms exist for traditional plenoptic cameras, their ability to create spectral images in a diffractive plenoptic camera is unknown. This paper evaluates digital refocusing, super resolution, and 3D deconvolution through a Richardson-Lucy algorithm as well as a new Gaussian smoothing algorithm. All of the algorithms worked well near the Fresnel zone plate design wavelength ...


Application Of Spectral Solution And Neural Network Techniques In Plasma Modeling For Electric Propulsion, Joseph R. Whitman Sep 2018

Application Of Spectral Solution And Neural Network Techniques In Plasma Modeling For Electric Propulsion, Joseph R. Whitman

Theses and Dissertations

A solver for Poisson's equation was developed using the Radix-2 FFT method first invented by Carl Friedrich Gauss. Its performance was characterized using simulated data and identical boundary conditions to those found in a Hall Effect Thruster. The characterization showed errors below machine-zero with noise-free data, and above 20% noise-to-signal strength, the error increased linearly with the noise. This solver can be implemented into AFRL's plasma simulator, the Thermophysics Universal Research Framework (TURF) and used to quickly and accurately compute the electric field based on charge distributions. The validity of a machine learning approach and data-based complex system ...


Techniques For Improved Space Object Detection Performance From Ground-Based Telescope Systems Using Long And Short Exposure Images, David J. Becker Aug 2018

Techniques For Improved Space Object Detection Performance From Ground-Based Telescope Systems Using Long And Short Exposure Images, David J. Becker

Theses and Dissertations

Space object detection is of great importance in the highly dependent yet competitive and congested space domain. Detection algorithms employed play a crucial role in fulfilling the detection component in the space situational awareness mission to detect, track, characterize and catalog unknown space objects. Many current space detection algorithms use a matched filter or a spatial correlator on long exposure data to make a detection decision at a single pixel point of a spatial image based on the assumption that the data follows a Gaussian distribution. This research focuses on improving current space object detection algorithms and developing new algorithms ...


Automating Mobile Device File Format Analysis, Richard A. Dill Aug 2018

Automating Mobile Device File Format Analysis, Richard A. Dill

Theses and Dissertations

Forensic tools assist examiners in extracting evidence from application files from mobile devices. If the file format for the file of interest is known, this process is straightforward, otherwise it requires the examiner to manually reverse engineer the data structures resident in the file. This research presents the Automated Data Structure Slayer (ADSS), which automates the process to reverse engineer unknown file for- mats of Android applications. After statically parsing and preparing an application, ADSS dynamically runs it, injecting hooks at selected methods to uncover the data structures used to store and process data before writing to media. The resultant ...


Efficient Phase Retrieval For Off-Axis Point Spread Functions, Salome Esteban Carrasco Jun 2018

Efficient Phase Retrieval For Off-Axis Point Spread Functions, Salome Esteban Carrasco

Theses and Dissertations

A novel pairing of phase retrieval tools allows for efficient estimation of pupil phase in optical systems from images of point spread functions (PSFs). The phase retrieval algorithm uses correlation of modeled phase in the focal plane to decouple aberrations that are difficult to identify in complex PSFs. The use of a phase kernel that departs from the Fresnel approximation for off-axis PSFs is a more accurate representation of wavefront phase in finite conjugate imaging. The combination of the approximation and phase correlation algorithm can be more efficient and accurate than generic algorithms.


Investigation Of Scramjet Flowfield Temperatures At The Boundary Layer With Hyperspectral Imaging, Amy M. Kerst Jun 2018

Investigation Of Scramjet Flowfield Temperatures At The Boundary Layer With Hyperspectral Imaging, Amy M. Kerst

Theses and Dissertations

Within the domain of chemical propulsion, the fields of combustion diagnostics and computational fluid dynamics each have a long history, and both have led to a better understanding of complex phenomena yielding practical improvements in propulsion systems. As more exotic forms of propulsion are developed, the importance of -- and often the challenges with -- both diagnostic and simulation capabilities also increase. In the case of scramjet combustion, these challenges primarily arise from the highly turbulent environment in the combustion cavity, and the high-speed, compressible nature of the flowfield. Efforts are underway to develop computer models of scramjet combustion environments to better ...