Digital Commons Network^™

Evaluating The Resiliency Of Industrial Internet Of Things Process Control Using Protocol Agnostic Attacks, Hector L. Roldan

Theses and Dissertations

Improving and defending our nation's critical infrastructure has been a challenge for quite some time. A malfunctioning or stoppage of any one of these systems could result in hazardous conditions on its supporting populace leading to widespread damage, injury, and even death. The protection of such systems has been mandated by the Office of the President of the United States of America in Presidential Policy Directive Order 21. Current research now focuses on securing and improving the management and efficiency of Industrial Control Systems (ICS). IIoT promises a solution in enhancement of efficiency in ICS. However, the presence of IIoT …

Analytic Non-Adiabatic Derivative Coupling Terms For Spin-Orbit Mrci Wavefunctions. Ii. Derivative Coupling Terms And Coupling Angle For Khe (A2Π1/2) ⇔ Khe B2Σ1/2), Lachlan T. Belcher, Charlton D. Lewis, Gary S. Kedziora, David E. Weeks

Faculty Publications

A method for calculating the analytic nonadiabatic derivative coupling terms (DCTs) for spin-orbit multi-reference configuration interaction wavefunctions is reviewed. The results of a sample calculation using a Stuttgart basis for KHe are presented. Additionally, the DCTs are compared with a simple calculation based on the Nikitin’s 3 × 3 description of the coupling between the Σ and Π surfaces, as well as a method based on Werner’s analysis of configuration interaction coefficients. The nonadiabatic coupling angle calculated by integrating the radial analytic DCTs using these different techniques matches extremely well. The resultant nonadiabatic energy surfaces for KHe are presented.

An Agent Based Model Of Passenger Boarding For Examining Commercial Aircraft Boarding Strategies, Frank W. Ciarallo, Raymond R. Hill, Kerry K. Ward

Faculty Publications

We use an agent-based simulation methodology to study airline passenger boarding using measures that reflect both the customer experience and airline efficiency perspective. This approach supports exploration of models of actual aircraft used in practice and detailed modeling of passenger dynamics. This paper discusses the modeling approach and a set of experiments comparing several boarding strategies from practical settings as well as the literature.

Deep Donors And Acceptors In Β-Ga2O3 Crystals: Determination Of The Fe2+/3+ Level By A Noncontact Method, Christopher A. Lenyk, Timothy D. Gustafson, Larry E. Halliburton, Nancy C. Giles

Faculty Publications

Electron paramagnetic resonance (EPR), infrared absorption, and thermoluminescence (TL) are used to determine the Fe^2+/3+ level in Fe-doped β-Ga₂O₃ crystals. With these noncontact spectroscopy methods, a value of 0.84 ± 0.05 eV below the conduction band is obtained for this level. Our results clearly establish that the E2 level observed in deep level transient spectroscopy (DLTS) experiments is due to the thermal release of electrons from Fe²⁺ ions. The crystals used in this investigation were grown by the Czochralski method and contained large concentrations of Fe acceptors and Ir donors, and trace amounts of Cr …

E700xd Portable Doppler Radar Energy Systems Analysis, Brandon M. Bailey, Torrey J. Wagner, Jada Williams

Faculty Publications

Occurring in industrialized nations, inexpensive and abundantly available power is routinely taken for granted. However, energy resilience and to a lesser extent price are key concerns when considering potential solutions for disaster response, disaster relief, or military operations. The Department of Defense (DoD) currently uses a 5 kW generator to power the E700XD portable Doppler radar system when grid power is unavailable [1]. While the radar has an approximate power consumption of 2.5 kW, there is a potential for higher demand due to weather conditions [2]. This paper examines the cost of operating a currently installed generator, compared to the …

Gamma-Ray Radiation Effects In Graphene-Based Transistors With H-Bn Nanometer Film Substrates, E. J. Cazalas, Michael R. Hogsed, S. R. Vangala, Michael R. Snure, John W. Mcclory

Faculty Publications

Radiation effects on graphene field effect transistors (GFETs) with hexagonal boron nitride (h-BN) thin film substrates are investigated using 60Co gamma-ray radiation. This study examines the radiation response using many samples with varying h-BN film thicknesses (1.6 and 20 nm thickness) and graphene channel lengths (5 and 10 μm). These samples were exposed to a total ionizing dose of approximately 1 Mrad(Si). I-V measurements were taken at fixed time intervals between irradiations and postirradiation. Dirac point voltage and current are extracted from the I-V measurements, as well as mobility, Dirac voltage hysteresis, and the total number of GFETs that remain …

Effect Of Ar(3p54p; 2p)+M -> Ar(3p54s; 1s)+M Branching Ratio On Optically Pumped Rare Gas Laser Performance, Daniel J. Emmons Ii, David E. Weeks

Faculty Publications

Optically pumped rare gas laser performance is analyzed as a function of the Ar(3p⁵4p; 2p) + M → Ar(3p⁵4s; 1s) + M branching ratios. Due to the uncertainty in the branching ratios, a sensitivity study is performed to determine the effect on output and absorbed pump laser intensities. The analysis is performed using a radio frequency dielectric barrier discharge as the source of metastable production for a variety of Argon in Helium mixtures over pressures ranging from 200 to 500 Torr. Peak output laser intensities show a factor of 7 increase as the branching ratio is …

Development Of Cislunar Space Logistics Networks For Satellite Constellation Support Using Event-Driven Generalized Multi-Commodity Network Flows, Alexander R. Collins

Theses and Dissertations

As space becomes an increasingly congested domain, the risk of damage to satellite constellations is increasing. In response, there is an increasing need for capabilities for unmanned repair, refueling, and reconstitution (R3) of those constellations. Cislunar orbits offer a promising storage and low-cost transfer solution for on-orbit service vehicles and replacement satellites to leverage those capabilities. This research makes use of mixed-integer linear programming-based logistics models to determine the situations in which a cislunar mission architecture would offer a cost-effective alternative to Earth-based R3. The network models presented in this research make use of the latest developments in Event-Driven Generalized …

Measurement Of Electron Density And Temperature From Laser-Induced Nitrogen Plasma At Elevated Pressure (1–6 Bar), Ashwin P. Rao, Mark Gragston, Anil K. Patnaik, Paul S. Hsu, Michael B. Shattan

Faculty Publications

Laser-induced plasmas experience Stark broadening and shifts of spectral lines carrying spectral signatures of plasma properties. In this paper, we report time-resolved Stark broadening measurements of a nitrogen triplet emission line at 1–6 bar ambient pressure in a pure nitrogen cell. Electron densities are calculated using the Stark broadening for different pressure conditions, which are shown to linearly increase with pressure. Additionally, using a Boltzmann fit for the triplet, the electron temperature is calculated and shown to decrease with increasing pressure. The rate of plasma cooling is observed to increase with pressure. The reported Stark broadening based plasma diagnostics in …

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[m^{2 …}

Air Force Space Programs: Comparing Estimates To Final Development Budgets, Christopher Elworth, Edward D. White, Jonathan D. Ritschel, Gregory E. Brown

Faculty Publications

This article analyzes how development budget estimates, as reported in the Selected Acquisition Reports, change over time for primarily Air Force space programs. Government acquisition policy emphasizes the importance of developing an accurate point estimate for programs to ensure program budget efficiency; however, statistics imply space programs tend to underspend at the beginning of the program and to overspend at the end of Initial Operational Capability. This suggests new phasing methods that reflect the unique needs of space and perhaps other developmental-type programs by allocating more of the budget in later years rather than at the beginning of the program, …

Generating Electromagnetic Schell-Model Sources Using Complex Screens With Spatially Varying Auto- And Cross-Correlation Functions, Milo W. Hyde Iv

Faculty Publications

We present a method to generate any physically realizable electromagnetic Schell-model source. Our technique can be directly implemented on existing vector-beam generators that utilize spatial light modulators for coherence control, beam shaping, and relative phasing. This work significantly extends published research on the subject, where control over the partially coherent source’s cross-spectral density matrix was limited. We begin by presenting the statistical optics theory necessary to derive and implement our method. We then apply our technique, both analytically and in simulation, to produce two electromagnetic Schell-model sources from the literature. We demonstrate control over the full cross-spectral density matrices of …

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 …

Target Detection In Heterogeneous Clutter With Low Resolution Radar, Kyle G. Stankowski

Theses and Dissertations

This thesis develops a framework for SAR target detection and super-resolution in low-resolution environments. The primary focus in this research is the background clutter heterogeneity that often accompanies low range and cross-range resolutions. A corrective model which accounts for clutter replacement is developed to define the detection and false alarm rates of the detector more accurately than a traditional model in which the radar return from the target supplements the existing clutter. In a heterogeneous clutter cell, the clutter replacement model leverages the different scattering distributions among the individual clutter types to generate a probability distribution function for the areas …

Adaptive-Hybrid Redundancy For Radiation Hardening, Nicolas S. Hamilton

Theses and Dissertations

An Adaptive-Hybrid Redundancy (AHR) mitigation strategy is proposed to mitigate the effects of Single Event Upset (SEU) and Single Event Transient (SET) radiation effects. AHR is adaptive because it switches between Triple Modular Redundancy (TMR) and Temporal Software Redundancy (TSR). AHR is hybrid because it uses hardware and software redundancy. AHR is demonstrated to run faster than TSR and use less energy than TMR. Furthermore, AHR allows space vehicle designers, mission planners, and operators the flexibility to determine how much time is spent in TMR and TSR. TMR mode provides faster processing at the expense of greater energy usage. TSR …

A Study Of Onboarding And Turnover Mediating Variables In U.S. Air Force Officers, Brett S. Bowers

Theses and Dissertations

Employee retention, while always a concern in the workplace, has become a greater challenge for organizations in recent years. Today’s working class has displayed a propensity to change jobs more rapidly than previous generations, exacerbating not only turnover rates but also the costs associated with them (Frankel, 2016). This challenge is especially relevant to the United States Air Force, which has experienced difficulty retaining young officers in recent years. The problems resulting from this voluntary turnover are exceedingly impactful to the military command structure, as senior leaders must work their way up from the lowest ranks. As such, the Air …

Statistical L-Moment And L-Moment Ratio Estimation And Their Applicability In Network Analysis, Timothy S. Anderson

Theses and Dissertations

This research centers on finding the statistical moments, network measures, and statistical tests that are most sensitive to various node degradations for the Barabási-Albert, Erdös-Rényi, and Watts-Strogratz network models. Thirty-five different graph structures were simulated for each of the random graph generation algorithms, and sensitivity analysis was undertaken on three different network measures: degree, betweenness, and closeness. In an effort to find the statistical moments that are the most sensitive to degradation within each network, four traditional moments: mean, variance, skewness, and kurtosis as well as three non-traditional moments: L-variance, L-skewness, and L-kurtosis were examined. Each of these moments were …

The Afit Engineer, Volume 1, Quarter 3, Graduate School Of Engineering And Management, Air Force Institute Of Technology

AFIT Documents

In this issue:

• Graduate School Welcomes 264 New Students
• AFIT Re-designated by NSA and DHS
• Centennial Day Symposium
• AFIT Offers Systems Engineering Certificate Program
• Advanced Cyber Education (ACE) Program Develops Cadets’ Cybersecurity Skills
• ...and more.

Autonomous And Resilient Management Of All-Source Sensors For Navigation Assurance, Juan D. Jurado

Theses and Dissertations

All-source navigation has become increasingly relevant over the past decade with the development of viable alternative sensor technologies. However, as the number and type of sensors informing a system increases, so does the probability of corrupting the system with sensor modeling errors, signal interference, and undetected faults. Though the latter of these has been extensively researched, the majority of existing approaches have constrained faults to biases, and designed algorithms centered around the assumption of simultaneously redundant, synchronous sensors with valid measurement models, none of which are guaranteed for all-source systems. This research aims to provide all-source multi-sensor resiliency, assurance, and …

Nondestructive Electromagnetic Characterization Of Perfect-Electric-Conductor-Backed Uniaxial Materials, Adam L. Brooks

Theses and Dissertations

As the use of anisotropic materials in electromagnetic applications continues to proliferate, it becomes increasingly important to develop non-destructive evaluation methods for those materials in their installed configuration. In many applications, these materials are permanently affixed onto conducting bodies to reduce unwanted reflections, making it impossible to collect S₂₁ or S₁₂ transmission measurements as used in many techniques based on the well-known Nicolson-Ross-Weir algorithm. It also makes it impractical to reorient the sample to collect orthogonal measurements aligned with the optical axes of the anisotropic material. The goal of this research is to develop a two-reflection coefficient measurement …

Sample Size Requirements And Considerations For Models To Assess Human-Machine System Performance, Jennifer S. G. Lopez

Theses and Dissertations

Hierarchical Linear Models (HLMs), also known as multi-level models, are an extension of multiple regression analysis and can aid in the understanding of human and machine workloads of a system. These models allow for prediction and testing in systems with hierarchies of two or more levels. The complex interrelated variability of these multi-level models exists in operational settings, such as the Air Force Distributed Common Ground System Full Motion Video (AF DCGS FMV) community which is composed of individuals (Level-1), groups (Level-2), units (Level-3), and organizations (Level-4). Through the development of sample size requirements and considerations for multi-level models, this …

Investigations Of Point Defects In Kh2Po4 Crystals Using Ab Initio Quantum Methods, Tabitha E. R. Dodson

Theses and Dissertations

Potassium dihydrogen phosphate (KH₂PO₄, or commonly called KDP) crystals can be grown to large sizes and are used for many important devices (fast optical switches, frequency conversion, polarization rotation) for high powered lasers. The nonlinear optical material has a wide intrinsic transparency range. Intrinsic point defects are responsible for several short-lived absorption bands in the visible and ultraviolet regions that affect high-power pulsed laser propagation. The primary intrinsic defects have been experimentally detected in KDP using electron paramagnetic resonance (EPR) experiments. The defect models established thus far include (i) self-trapped holes, (ii) oxygen vacancies, and (iii) …

Effects Of Carbon-Based Ablation Products On Hypersonic Boundary Layer Stability, Olivia S. Elliott

Theses and Dissertations

Hypersonic vehicles require an accurate prediction of the transition of the boundary layer for the design of the thermal protection system due to the high heating rates under turbulent flow. Many thermal protection systems are carbon-based and introduce new species, specifically CO₂, into the boundary layer flow which are known to dampen the instabilities that lead to transition for hypersonic vehicles. A Computation Fluid Dynamics study was accomplished examining the concentration of CO₂ required to impact boundary layer transition over both sharp and blunt cones. These results were used in conjunction with air-carbon ablation models models to …

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 …

Ion Software-Defined Radio Metadata Standard Final Report, Sanjeev Gunawardena, Alexander Rugamer, Muhammad Subhan Hameed, Markel Arizabaleta, Thomas Pany, Javier Arribas

Faculty Publications

The ION GNSS SDR Metadata Standard describes the formatting and other essential PNT-related parameters of sampled data streams and files. This allows processors to seamlessly consume such data without the need to input these parameters manually. The technical development phase of the initial version of the standard has now been deemed complete and is currently undergoing the last remaining procedural steps towards adoption as a formal standard by the Institute of Navigation. This paper reports on the activities of the working group since September 2018 and summarizes the final products of the standard. It also reports on examples of early …

Quantitative Analysis Of Cerium-Gallium Alloys Using A Hand-Held Laser Induced Breakdown Spectroscopy Device, Ashwin P. Rao, Matthew Cook, Howard L. Hall, Michael B. Shattan

Faculty Publications

A hand-held laser-induced breakdown spectroscopy device was used to acquire spectral emission data from laser-induced plasmas created on the surface of cerium-gallium alloy samples with Ga concentrations ranging from 0–3 weight percent. Ionic and neutral emission lines of the two constituent elements were then extracted and used to generate calibration curves relating the emission line intensity ratios to the gallium concentration of the alloy. The Ga I 287.4-nm emission line was determined to be superior for the purposes of Ga detection and concentration determination. A limit of detection below 0.25%was achieved using a multivariate regression model of the Ga I …

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

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 …

Near-Field Effects On Partially Coherent Light Scattered By An Aperture, Milo W. Hyde Iv, Michael J. Havrilla

Faculty Publications

We investigate how the near field affects partially coherent light scattered from an aperture in an opaque screen. Prior work on this subject has focused on the role of surface plasmons, and how they affect spatial coherence is well documented. Here, we consider other near-field effects that might impact spatial coherence. We do this by examining the statistics of the near-zone field scattered from an aperture in a perfect electric conductor plane—a structure that does not support surface plasmons. We derive the near-field statistics (in particular, cross-spectral density functions) by applying electromagnetic equivalence theorems and the Method of Moments. We …

Controlling The Spatial Coherence Of An Optical Source Using A Spatial Filter, Milo W. Hyde Iv

Faculty Publications

This paper presents the theory for controlling the spectral degree of coherence via spatial filtering. Starting with a quasi-homogeneous partially coherent source, the cross-spectral density function of the field at the output of the spatial filter is found by applying Fourier and statistical optics theory. The key relation obtained from this analysis is a closed-form expression for the filter function in terms of the desired output spectral degree of coherence. This theory is verified with Monte Carlo wave-optics simulations of spatial coherence control and beam shaping for potential use in free-space optical communications and directed energy applications. The simulated results …