Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network™

Open Access. Powered by Scholars. Published by Universities.®

Air Force Institute of Technology

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 1111 - 1140 of 8791

Full-Text Articles in Entire DC Network

Verification And Validation Of Radiation Protection Factors From Monte Carlo Simulations, William J. Erwin Sep 2021

Verification And Validation Of Radiation Protection Factors From Monte Carlo Simulations, William J. Erwin

Theses and Dissertations

This dissertation describes the verification and validation of methods for producing radiation protection factors (RPFs) using experiments and Monte Carlo N-Particle 6 (MCNP6) simulations. RPF validation of a steel enclosure using a plutonium-beryllium source produced a validated RPF with statistically significant agreement between neutron MCNP6 models and experiments and a gamma protection factor (GPF) with statistically significant agreement to the measured GPF. Efforts to validate more complex enclosures using the Fast Burst Reactor (FBR) yielded the first-ever direct measurements of this reactor’s prompt gamma emission spectrum and revealed irreconcilable differences between the FBR facility-provided source spectrum and spectrometer measurements, resulting …

Go to article

Pseudospectral Methods Of Robust Optimal Motion Planning For Multi-Aperture Space Systems With Motion And Vibration Compensation, Brian W. Bishop Sep 2021

Pseudospectral Methods Of Robust Optimal Motion Planning For Multi-Aperture Space Systems With Motion And Vibration Compensation, Brian W. Bishop

Theses and Dissertations

For multi-body, flexible systems, the ability to achieve rapid reorientation maneuvers can be impacted by nonlinear dynamics and uncertainty in the model parameters impacting the ability to achieve an optimal trajectory computed using nominal parameter values. Trajectory sensitivity to parameter variations increases final pointing error and residual vibrational energy in the system. This manuscript explores using pseudospectral methods to generate robust optimal control trajectories minimizing trajectory sensitivity to parameter variations and derives maneuvers minimizing residual energy and pointing error. The robustness of open-loop optimal control is compared to a standard maneuver derived using traditional methods demonstrating the ability to simultaneously …

Go to article

Neutron Energy Tuning Assemblies For Nuclear Weapon Environment Applications At The National Ignition Facility, Nicholas J. Quartemont Sep 2021

Neutron Energy Tuning Assemblies For Nuclear Weapon Environment Applications At The National Ignition Facility, Nicholas J. Quartemont

Theses and Dissertations

An energy tuning assembly was developed to spectrally shape the National Ignition Facility deuterium-tritium fusion neutron source to a notional thermonuclear and prompt fission neutron spectrum to fulfill neutron source capability gaps. The experimental neutron environment was characterized with activation dosimetry, neutronics and covariance models, and unfolded to determine the as-fielded neutron spectrum. The first energy tuning assembly was demonstrated to create synthetic spectrally accurate post-detonation fission products, enhancing U.S. technical nuclear forensics capabilities. ATHENA, a second-generation energy tuning assembly, was also optimized to meet similar objectives, but the new platform neutron fluence efficiency was increased by a factor of …

Go to article

Application Of Vortex Tubes To Gas Turbine Film Cooling, Matthew N. Fuqua Sep 2021

Application Of Vortex Tubes To Gas Turbine Film Cooling, Matthew N. Fuqua

Theses and Dissertations

To improve thermal efficiency and reduce fuel consumption, gas turbine engines typically operate at increasingly higher turbine inlet temperatures--well in excess of turbine blade material limits--and film cooling schemes are normally employed to reduce metal temperatures within acceptable limits and prevent structural failure. Cooling requirements vary across a blade surface, but there currently exists no means by which coolant temperatures can be locally adjusted to facilitate optimized usage across a blade. Ranque-Hilsch vortex tubes were investigated as a means of adjusting coolant temperatures solely by fluidic means, induced by the phenomenon of temperature separation. Analytical frameworks were developed to determine …

Go to article

Data-Driven Algorithm To Classify The Degree Of Isotropy In The Bidirectional Reflectance Distribution Function, Anne W. Werkley, Samuel D. Butler, Todd V. Small, Michael A. Marciniak Sep 2021

Data-Driven Algorithm To Classify The Degree Of Isotropy In The Bidirectional Reflectance Distribution Function, Anne W. Werkley, Samuel D. Butler, Todd V. Small, Michael A. Marciniak

Faculty Publications

The bidirectional reflectance distribution function (BRDF) is used to describe reflectances of materials by calculating the ratio of the reflected radiance to the incident irradiance. While it was found that the isotropic models maintained symmetry about ϕs  =  π, such symmetry was not maintained about the θs  =  θi axis, except for close to the specular peak. This led to the development of a data-driven metric for how isotropic a BRDF measurement is. Research efforts centered around developing an algorithm that could determine material anisotropy without having to fit to models. This algorithm was tested using high …

Go to article

Robust Method Of Determining Microfacet Brdf Parameters In The Presence Of Noise Via Recursive Optimization, Michael W. Bishop, Samuel D. Butler, Michael A. Marciniak Sep 2021

Robust Method Of Determining Microfacet Brdf Parameters In The Presence Of Noise Via Recursive Optimization, Michael W. Bishop, Samuel D. Butler, Michael A. Marciniak

Faculty Publications

Accurate bidirectional reflectance distribution function (BRDF) models are essential for computer graphics and remote sensing performance. The popular microfacet class of BRDF models is geometric-optics-based and computationally inexpensive. Fitting microfacet models to scatterometry measurements is a common yet challenging requirement that can result in a model being fit as one of several unique local minima. Final model fit accuracy is therefore largely based on the quality of the initial parameter estimate. This makes for widely varying material parameter estimates and causes inconsistent performance comparisons across microfacet models, as will be shown with synthetic data. We proposed a recursive optimization method …

Go to article

The Impact Of Laser Control On The Porosity And Microstructure Of Selective Laser Melted Nickel Superalloy 718, Travis E. Shelton, Gregory R. Cobb, Carl R. Hartsfield, Benjamin M. Doane, Cayla C. Eckley, Ryan A. Kemnitz Sep 2021

The Impact Of Laser Control On The Porosity And Microstructure Of Selective Laser Melted Nickel Superalloy 718, Travis E. Shelton, Gregory R. Cobb, Carl R. Hartsfield, Benjamin M. Doane, Cayla C. Eckley, Ryan A. Kemnitz

Faculty Publications

Additively manufacturing high performance metals by laser processing represents an exciting opportunity to exploit localized properties by varying input parameters throughout the process. This work explores the solidification and microstructural properties of selectively laser melted (SLM) Inconel 718 (IN718) using unique processing parameters. By employing traditional pulsed laser physics techniques, samples were manufactured with a continuous wave laser to study a potential ubiquitous approach. While the overall power density was controlled, the power, speed, and hatch spacing were varied. The porosity and grain sizes of the samples were characterized by optical and scanning electron microscopes. The influence of processing parameters …

Go to article

Large Eddy Simulations Of Turbulent And Buoyant Flows In Urban And Complex Terrain Areas Using The Aeolus Model, Akshay A. Gowardhan, Dana L. Mcgufffin, Donald L. Lucas, Stephanie J. Neuscamman, Otto Alvarez, Lee G. Glascoe Aug 2021

Large Eddy Simulations Of Turbulent And Buoyant Flows In Urban And Complex Terrain Areas Using The Aeolus Model, Akshay A. Gowardhan, Dana L. Mcgufffin, Donald L. Lucas, Stephanie J. Neuscamman, Otto Alvarez, Lee G. Glascoe

Student Publications

Fast and accurate predictions of the flow and transport of materials in urban and complex terrain areas are challenging because of the heterogeneity of buildings and land features of different shapes and sizes connected by canyons and channels, which results in complex patterns of turbulence that can enhance material concentrations in certain regions. To address this challenge, we have developed an efficient three-dimensional computational fluid dynamics (CFD) code called Aeolus that is based on first principles for predicting transport and dispersion of materials in complex terrain and urban areas. The model can be run in a very efficient Reynolds average …

Go to article

Active Attestation Of Embedded Systems, Mark M. Stephenson, Patrick A. Reber, Patrick J. Sweeney, Scott R. Graham Aug 2021

Active Attestation Of Embedded Systems, Mark M. Stephenson, Patrick A. Reber, Patrick J. Sweeney, Scott R. Graham

AFIT Patents

An active attestation apparatus verifies at runtime the integrity of untrusted machine code of an embedded system residing in a memory device while it is being run/used with while slowing the processing time less than other methods. The apparatus uses an integrated circuit chip containing a microcontroller and a reprogrammable logic device, such as a field programmable gate array (FPGA), to implement software attestation at runtime and in less time than is typically possible with comparable attestation approaches, while not requiring any halt of the processor in the microcontroller. The reprogrammable logic device includes functionality to load an encrypted version …

Go to article

Re-Visiting Acoustic Sounding To Advance The Measurement Of Optical Turbulence, Steven T. Fiorino, Santasri Bose-Pillai, Kevin J. Keefer Aug 2021

Re-Visiting Acoustic Sounding To Advance The Measurement Of Optical Turbulence, Steven T. Fiorino, Santasri Bose-Pillai, Kevin J. Keefer

Faculty Publications

Optical turbulence, as determined by the widely accepted practice of profiling the temperature structure constant, C2T, via the measurement of ambient atmospheric temperature gradients, can be found to differ quite significantly when characterizing such gradients via thermal-couple differential temperature sensors as compared to doing so with acoustic probes such as those commonly used in sonic anemometry. Similar inconsistencies are observed when comparing optical turbulence strength derived via C2T as compared to those through direct optical or imaging measurements of small fluctuations of the index of refraction of air (i.e., scintillation). These irregularities are especially apparent …

Go to article

Analysis Of The Effects Of Spatiotemporal Demand Data Aggregation Methods On Distance And Volume Errors, Zachary Hornberger, Bruce A. Cox, Raymond R. Hill Aug 2021

Analysis Of The Effects Of Spatiotemporal Demand Data Aggregation Methods On Distance And Volume Errors, Zachary Hornberger, Bruce A. Cox, Raymond R. Hill

Faculty Publications

Purpose — Large/stochastic spatiotemporal demand data sets can prove intractable for location optimization problems, motivating the need for aggregation. However, demand aggregation induces errors. Significant theoretical research has been performed related to the modifiable areal unit problem and the zone definition problem. Minimal research has been accomplished related to the specific issues inherent to spatiotemporal demand data, such as search and rescue (SAR) data. This study provides a quantitative comparison of various aggregation methodologies and their relation to distance and volume based aggregation errors. Design/methodology/approach — This paper introduces and applies a framework for comparing both deterministic and stochastic aggregation …

Go to article

Augmenting The Space Domain Awareness Ground Architecture Via Decision Analysis And Multi-Objective Optimization, Albert R. Vasso, Richard G. Cobb, John M. Colombi, Bryan D. Little, David R. Meyer Aug 2021

Augmenting The Space Domain Awareness Ground Architecture Via Decision Analysis And Multi-Objective Optimization, Albert R. Vasso, Richard G. Cobb, John M. Colombi, Bryan D. Little, David R. Meyer

Faculty Publications

Purpose — The US Government is challenged to maintain pace as the world’s de facto provider of space object cataloging data. Augmenting capabilities with nontraditional sensors present an expeditious and low-cost improvement. However, the large tradespace and unexplored system of systems performance requirements pose a challenge to successful capitalization. This paper aims to better define and assess the utility of augmentation via a multi-disiplinary study. Design/methodology/approach — Hypothetical telescope architectures are modeled and simulated on two separate days, then evaluated against performance measures and constraints using multi-objective optimization in a heuristic algorithm. Decision analysis and Pareto optimality identifies a set …

Go to article

Multi-Gaussian Random Variables For Modeling Optical Phenomena, Olga Korotkova, Milo W. Hyde Iv Aug 2021

Multi-Gaussian Random Variables For Modeling Optical Phenomena, Olga Korotkova, Milo W. Hyde Iv

Faculty Publications

A generalization of the classic Gaussian random variable to the family of multi-Gaussian (MG) random variables characterized by shape parameter M > 0, in addition to the mean and the standard deviation, is introduced. The probability density function (PDF) of the MG family members is an alternating series of Gaussian functions with suitably chosen heights and widths. In particular, for integer values of M, the series has a finite number of terms and leads to flattened profiles, while reducing to the classic Gaussian PDF for M = 1. For non-integer, positive values of M, a convergent infinite series of …

Go to article

Generalized Deep Learning Eeg Models For Cross-Participant And Cross-Task Detection Of The Vigilance Decrement In Sustained Attention Tasks, Alexander J. Kamrud, Brett J. Borghetti, Christine M. Schubert Kabban, Michael E. Miller Aug 2021

Generalized Deep Learning Eeg Models For Cross-Participant And Cross-Task Detection Of The Vigilance Decrement In Sustained Attention Tasks, Alexander J. Kamrud, Brett J. Borghetti, Christine M. Schubert Kabban, Michael E. Miller

Faculty Publications

Tasks which require sustained attention over a lengthy period of time have been a focal point of cognitive fatigue research for decades, with these tasks including air traffic control, watchkeeping, baggage inspection, and many others. Recent research into physiological markers of mental fatigue indicate that markers exist which extend across all individuals and all types of vigilance tasks. This suggests that it would be possible to build an EEG model which detects these markers and the subsequent vigilance decrement in any task (i.e., a task-generic model) and in any person (i.e., a cross-participant model). However, thus far, no task-generic EEG …

Go to article

Thematic Analysis Of Military Medical Ethics Publications From 2000 To 2020—A Bibliometric Approach, Zachary Bailey [*], Peter Mahoney, Marina Miron, Martin Bricknell Jul 2021

Thematic Analysis Of Military Medical Ethics Publications From 2000 To 2020—A Bibliometric Approach, Zachary Bailey [*], Peter Mahoney, Marina Miron, Martin Bricknell

Student Publications

There has been external criticism of the compliance of military health personnel with internationally agreed principles in military medical ethics (MME). In response, a number of authors have called for clarity on the principles and topics within the domain of MME. This complements an increased acknowledgment of the need for education in MME for military health personnel. Our paper utilizes bibliometric techniques to identify key themes in MME to inform the development of a curriculum for this subject.

Go to article

Investigation And Statistical Modeling Of The Mechanical Properties Of Additively Manufactured Lattices, Derek G. Spear, Anthony N. Palazotto Jul 2021

Investigation And Statistical Modeling Of The Mechanical Properties Of Additively Manufactured Lattices, Derek G. Spear, Anthony N. Palazotto

Faculty Publications

This paper describes the background, test methodology, and experimental results associated with the testing and analysis of quasi-static compression testing of additively manufactured open-cell lattice structures. The study aims to examine the effect of lattice topology, cell size, cell density, and surface thickness on the mechanical properties of lattice structures. Three lattice designs were chosen, the Diamond, I-WP, and Primitive Triply Periodic Minimal Surfaces (TPMSs). Uniaxial compression tests were conducted for every combination of the three lattice designs, three cell sizes, three cell densities, and three surface thicknesses. In order to perform an efficient experiment and gain the most information …

Go to article

Efficient, Dual-Particle Directional Detection System Using A Rotating Scatter Mask, Robert Olesen, Bryan V. Egner, Darren E. Holland, Valerie Martin, James E. Bevins, Larry W. Burggraf, Buckley E. O'Day Iii Jul 2021

Efficient, Dual-Particle Directional Detection System Using A Rotating Scatter Mask, Robert Olesen, Bryan V. Egner, Darren E. Holland, Valerie Martin, James E. Bevins, Larry W. Burggraf, Buckley E. O'Day Iii

AFIT Patents

A directional radiation detection system and an omnidirectional radiation detector. The omnidirectional radiation detector detects radiation comprising at least one of: (i) gamma rays; and (ii) neutron particles. A radiation scatter mask (RSM) of the radiation detection system includes a rotating sleeve received over the omnidirectional radiation detector and rotating about a longitudinal axis. The RSM further includes: (i) a fin extending longitudinally from one side of the rotating sleeve; and (ii) a wall extending from the rotating sleeve and spaced apart from the fin having an upper end distally positioned on the rotating sleeve spaced apart or next to …

Go to article

Classical And Neural Network Machine Learning To Determine The Risk Of Marijuana Use, Laura Zoboroski, Torrey J. Wagner, Brent T. Langhals Jul 2021

Classical And Neural Network Machine Learning To Determine The Risk Of Marijuana Use, Laura Zoboroski, Torrey J. Wagner, Brent T. Langhals

Faculty Publications

Marijuana is the most commonly abused drug for military personnel tested at the Air Force Drug Testing Laboratory. A publicly available dataset of drug use, personality trait scores and demographic data was modeled with logistic regression, decision tree and neural network models to determine the extent to which marijuana use can be predicted using personality traits. While the logistic regression model had lower performance than the neural network model, it matched the sensitivity of prior work (0.80), achieved a high level of significance (p < 0.05) and yielded valuable inferences. It implied that younger, less educated individuals who exhibit sensation-seeking behavior and are open to experience tend to be at higher risk for THC use. A method for performing an iterative multidimensional neural network hyperparameter search is presented, and two iterations of a 6-dimensional search were performed. Metrics were used to select a family of 8 promising models from a cohort of 4600 models, and the best NN model’s 0.87 sensitivity improved upon the literature. The model met an f1 overfitting threshold on the test and holdout datasets, and an accuracy sensitivity analysis on a holdout-equivalent dataset yielded a 95% CI of 0.86 ± 0.04. These results have the potential to increase the efficacy of drug prevention and intervention programs.

Go to article

En At A Glance, Academic Year 2020-2021, Graduate School Of Engineering And Management, Air Force Institute Of Technology Jul 2021

En At A Glance, Academic Year 2020-2021, Graduate School Of Engineering And Management, Air Force Institute Of Technology

AFIT Documents

No abstract provided.

Go to article

Uranium Integral Fission Product Yields For A Spectrally-Shaped 14.1 Mev Neutron Source At The National Ignition Facility, Nicholas J. Quartemont, N. Gharibyan, K. Moody, James E. Bevins Jul 2021

Uranium Integral Fission Product Yields For A Spectrally-Shaped 14.1 Mev Neutron Source At The National Ignition Facility, Nicholas J. Quartemont, N. Gharibyan, K. Moody, James E. Bevins

Faculty Publications

This paper describes the experimental results for an energy tuning assembly created to modify the National Ignition Facility deuterium–tritium fusion neutron source into a notional thermonuclear and prompt fission neutron spectrum, which has applications in integral measurements, nuclear data benchmarks, and radiation effects on microelectronics. The Monte Carlo neutron transport utilized MCNP5 to estimate the ETA-modified fluence using the ENDF-B/VIII.0 and IRDFF-II continuous energy nuclear data libraries, and SCALE Sampler was used to estimate the systematic nuclear data covariance using ENDF-B/VII.1 and IRDFF-II in a 252-group structure. The experiment fielded eight activation foils and a highly enriched uranium sample. This …

Go to article

Estimating Turbulence Distribution Over A Heterogeneous Path Using Time‐Lapse Imagery From Dual Cameras, Benjamin Wilson, Santasri Bose-Pillai, Jack E. Mccrae, Kevin J. Keefer, Steven T. Fiorino Jul 2021

Estimating Turbulence Distribution Over A Heterogeneous Path Using Time‐Lapse Imagery From Dual Cameras, Benjamin Wilson, Santasri Bose-Pillai, Jack E. Mccrae, Kevin J. Keefer, Steven T. Fiorino

Faculty Publications

Knowledge of turbulence distribution along an experimental path can help in effective turbulence compensation and mitigation. Although scintillometers are traditionally used to measure the strength of turbulence, they provide a path-integrated measurement and have limited operational ranges. A technique to profile turbulence using time-lapse imagery of a distant target from spatially separated cameras is presented here. The method uses the turbulence induced differential motion between pairs of point features on a target, sensed at a single camera and between cameras to extract turbulence distribution along the path. The method is successfully demonstrated on a 511 m almost horizontal path going …

Go to article

Strengthening Criteria Independence Through Optimization Of Alternative Value Ratio Comparisons, Joseph P. Kristbaum, Frank W. Ciarallo Jun 2021

Strengthening Criteria Independence Through Optimization Of Alternative Value Ratio Comparisons, Joseph P. Kristbaum, Frank W. Ciarallo

Faculty Publications

Every decision maker’s internal scale is different based on a myriad of possible factors unique to that decision maker. Conflicting criteria within and between alternatives in multicriteria decision making can create negative effects within the weighting schemes and amplify preference biases and scale disparities between decision makers in a group decision context. Additionally, the weighting of group decision-making frameworks can intensify the already skewed criteria values. When making judgments against requirements, it may be preferable to reduce scale trend distortions between decision makers as much as possible. Previous research supports that certain information presentation modes can significantly reduce preference bias …

Go to article

Synthetic Aperture Radar Image Recognition Of Armored Vehicles, Christopher Szul, Torrey J. Wagner, Brent T. Langhals Jun 2021

Synthetic Aperture Radar Image Recognition Of Armored Vehicles, Christopher Szul, Torrey J. Wagner, Brent T. Langhals

Faculty Publications

Synthetic Aperture Radar (SAR) imagery is not affected by weather and allows for day-and-night observations, however it can be difficult to interpret. This work applies classical and neural network machine learning techniques to perform image classification of SAR imagery. The Moving and Stationary Target Acquisition and Recognition dataset from the Air Force Research Laboratory was used, which contained 2,987 total observations of the BMP-2, BTR-70, and T-72 vehicles. Using a 75%/25% train/test split, the classical model achieved an average multi-class image recognition accuracy of 70%, while a convolutional neural network was able to achieve a 97% accuracy with lower model …

Go to article

Design And Fabrication Of Zinc Oxide Optofluidic Laser Elements, Kyle T. Bodily Jun 2021

Design And Fabrication Of Zinc Oxide Optofluidic Laser Elements, Kyle T. Bodily

Theses and Dissertations

This thesis systematically goes through the derivation, simulation, and experimentation of Zinc Oxide optofluidic micro laser elements. Single and coupled ring resonators were simulated to show single mode transmission as well as enhanced coupling capabilities when surrounded by high refractive index liquid. Devices with diameters ranging from 100-500 µm were successfully fabricated inexpensively through standard cleanroom procedures. The devices were tested using two different pump laser systems. Testing included such factors as high pump intensity, various angles of excitation, and low temperature. In all cases PL emission was observed and recorded.

Go to article

Evolutionary Generation Of Diversity In Embedded Binary Executables For Cyber Resiliency, Mitchell D. I. Hirschfeld Jun 2021

Evolutionary Generation Of Diversity In Embedded Binary Executables For Cyber Resiliency, Mitchell D. I. Hirschfeld

Theses and Dissertations

Hardening avionics systems against cyber attack is difficult and expensive. Attackers benefit from a "break one, break all" advantage due to the dominant mono-culture of automated systems. Also, undecidability of behavioral equivalence for arbitrary algorithms prevents the provable absence of undesired behaviors within the original specification. This research presents results of computational experiments using bio-inspired genetic programming to generate diverse implementations of executable software and thereby disrupt the mono-culture. Diversity is measured using the SSDeep context triggered piecewise hashing algorithm. Experiments are divided into two phases. Phase I explores the use of semantically-equivalent alterations that retain the specified behavior of …

Go to article

Feasibility Study Of Radio Frequency Microelectromechanical Filters For Space Operation, Karanvir Singh Jun 2021

Feasibility Study Of Radio Frequency Microelectromechanical Filters For Space Operation, Karanvir Singh

Theses and Dissertations

Piezoelectric contour mode resonator technology has the unique advantage of combining low motional resistance with the ability to define multiple frequencies on the same substrate. Contour mode resonators can be mechanically coupled together to form robust band-pass filters for the next generation of GPS satellites with extreme size reduction compared to electrically coupled filters. Piezoelectric zinc oxide (ZnO) contour mode resonators have the potential for monolithic integration with current ZnO transistor further reducing size, power consumption, and cost of filter modules. Barium strontium titanate (BST) contour mode resonators have incredible frequency tunability due to the fundamental nature of the thin …

Go to article

One Dimensional Study Of Magnetoplasmadynamic Thrusters For A Potential New Class Of Heavy Ion Drivers For Plasma Jet Driven Magnetoinertial Fusion, Patrick M. Brown Jun 2021

One Dimensional Study Of Magnetoplasmadynamic Thrusters For A Potential New Class Of Heavy Ion Drivers For Plasma Jet Driven Magnetoinertial Fusion, Patrick M. Brown

Theses and Dissertations

Plasma Jet Driven Magnetoinertial Fusion (PJMIF) requires high velocity heavy ion drivers in order to compress a magnetized target to fusion conditions. Previous work with heavy ion drivers has revealed sub-par accelerations due to plasma instabilities; thus, it is necessary to investigate new methods of heavy ion plasma acceleration. One such method is Magnetoplasmadynamic (MPD) thrusters. Past studies of these thrusters have been conducted at an initial temperature at or below the energy of full ionization. Here MPD thrusters are investigated using a Godunov type MHD solver with a Harten-Lax van Leer-D (HLLD) flux solving scheme assuming the plasma is …

Go to article

Examining The Influence Of Source Dependence On Supplier Performance In The Usaf Organic Supply Chain, Thomas A. Counter Jun 2021

Examining The Influence Of Source Dependence On Supplier Performance In The Usaf Organic Supply Chain, Thomas A. Counter

Theses and Dissertations

The purpose of this study is to examine the U.S. Air Force's dependence toward sole sourcing and how that influences procurement outcomes in terms of supplier performance. This research used linear regression to explain the effect of source dependence and supplier size on performance categories for 326 suppliers. The five supplier performance categories in the study included timeliness, cost control, quality, business relations, and regulatory compliance. The research found that the USAFs dependence on sole sourcing had a small but statistically significant influence on all five aspects of supplier performance, with timeliness being the most adversely impacted.

Go to article

A Quantitative Argument For Autonomous Aerial Defense Overembedded Missile Systems To Thwart Cruise Threats, Andrew R. Davis Jun 2021

A Quantitative Argument For Autonomous Aerial Defense Overembedded Missile Systems To Thwart Cruise Threats, Andrew R. Davis

Theses and Dissertations

Given the high cost of missile defense systems, their ability to be overwhelmed, and rising tensions between the U.S. and adversaries in the Indo-Pacific region, a new modeled is proposed to investigate a new approach to missile defense. The Autonomous Aerial Defense Against Missiles (AADAM) system leverages reusable, small-scale UAVs to propose a cheaper, more effective system in defending against cruise missile threats. The aim of this system is to provide and additional layer in current missile defense strategies at lower-cost. This modeled system is found to outperform a modeled Patriot system in close-range interception of designated assets, with no …

Go to article

Developing A Basic Formal Supply Chain Ontology To Improve Communication And Interoperability, David Morrow Jun 2021

Developing A Basic Formal Supply Chain Ontology To Improve Communication And Interoperability, David Morrow

Theses and Dissertations

Information is crucial to supply chain performance because it is used to make decisions and trigger actions. Organizations across world-class supply chains increasingly use information technology to analyze and process supply chain data. However, supply chain management lacks a common language, making information exchange difficult. An ontology can provide a standardized framework that organizes a given knowledge domain. This research proposes a common language for developing a supply chain ontology that can be built into a basic formal ontology understood by both humans and computers. According to current research, an established and widely used supply chain framework is a good …

Go to article

First Prev Next Last