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Articles 1321 - 1350 of 5699
Full-Text Articles in Engineering
The Evaluation Of High Molecular Weight Methacrylate As A Treatment Option For Shrinkage Cracks In Airfield Pavement, Austin R. Hayes
The Evaluation Of High Molecular Weight Methacrylate As A Treatment Option For Shrinkage Cracks In Airfield Pavement, Austin R. Hayes
Theses and Dissertations
Air Force policy dictates that only epoxy can be used as a treatment option for shrinkage cracks in concrete airfield pavement. However, since epoxy is not ideal for shrinkage cracks, this research focuses on the evaluation of high molecular weight methacrylate (HMWM) as a treatment option. Laboratory experiments were performed on four sealants to determine whether they could penetrate a crack 24 inches deep, bond to the concrete, and resist water intrusion. Three HMWMs (TK-2415, Kwik Bond KBP 103, and Castek Transpo T-70) and one epoxy (TK-2110) were assessed. The four sealers were applied to 32 concrete specimens with crack …
Methodology For Including Base Infrastructure In Conceptual System Analysis, Patrick J. Kelly Iv
Methodology For Including Base Infrastructure In Conceptual System Analysis, Patrick J. Kelly Iv
Theses and Dissertations
The 2018 National Defense Strategy defines a transition to agile basing, where the logistics footprint of new conceptual systems can be distributed across a set of airfields, instead of one main operating base. Currently, there is no capability to assess early concepts using airfield data. This research develops a methodology and a tool that assesses system concepts using world-wide civil and military airfield infrastructure, such as runway parameters, parking, munitions, fuel and warehouse storage, and distance to areas of interest. Specifically, the focus of the thesis is on concepts for the Intelligence, Surveillance, and Reconnaissance (ISR) Strike mission. Four concepts …
A Mixed Integer Programming Framework For The Fuel Optimal Guidance Of Complex Spacecraft Rendezvous And Proximity Operation Missions, Andrew S. Levalley
A Mixed Integer Programming Framework For The Fuel Optimal Guidance Of Complex Spacecraft Rendezvous And Proximity Operation Missions, Andrew S. Levalley
Theses and Dissertations
Space is a contested, congested, and competitive environment where space situational awareness (SSA) is a key factor in the long term sustainability of space as a national interest. Space-based SSA conducted by inspector satellites is critical to the detecting, tracking, and attribution of actions in space. Thus, space-based fuel-optimal maneuvers are essential to increasing mission life and improving the capability of inspector satellites working to characterize resident space objects (RSOs) in geosynchronous orbit (GEO). Additionally, on-orbit inspection missions can be characterized by multiple waypoint visits where an inspector is accomplishing a set of proximity operation mission objectives through the visit …
Process Parameter Development Of Additively Manufactured Af9628 Weapons Steel, Erin M. Hager
Process Parameter Development Of Additively Manufactured Af9628 Weapons Steel, Erin M. Hager
Theses and Dissertations
The manufacture of components in Additive Manufacturing processes is limited by the range of materials available. Qualification of materials for Additive Manufacturing is time intensive, and is often specific to a single type of machine. In this study, an approach to selecting power, speed, and hatch spacing values for a newly powderized material, AF9628 weapons steel, is described that results in highly dense (>99.9%) parts on an MLab 200R Cusing. Initial power and speed values used in a weld track study were selected based on a survey of parameters used on similar materials, with a focus on the energy …
Infrared And Electro-Optical Stereo Vision For Automated Aerial Refueling, William E. Dallmann
Infrared And Electro-Optical Stereo Vision For Automated Aerial Refueling, William E. Dallmann
Theses and Dissertations
Currently, Unmanned Aerial Vehicles are unsafe to refuel in-flight due to the communication latency between the UAVs ground operator and the UAV. Providing UAVs with an in-flight refueling capability would improve their functionality by extending their flight duration and increasing their flight payload. Our solution to this problem is Automated Aerial Refueling (AAR) using stereo vision from stereo electro-optical and infrared cameras on a refueling tanker. To simulate a refueling scenario, we use ground vehicles to simulate a pseudo tanker and pseudo receiver UAV. Imagery of the receiver is collected by the cameras on the tanker and processed by a …
Nuclear Data Covariance Analysis Of An Energy Tuning Assembly For Simulating Nuclear Weapon Environments, Nicholas J. Quartemont
Nuclear Data Covariance Analysis Of An Energy Tuning Assembly For Simulating Nuclear Weapon Environments, Nicholas J. Quartemont
Theses and Dissertations
An energy tuning assembly was characterized to spectrally shape the National Ignition Facility neutron source to a notional thermonuclear and prompt fission neutron spectrum to approximate a boosted nuclear device. This research performed nuclear data covariance analysis to predict the performance of the energy tuning assembly to create the objective spectrum, assessed anticipated experimental outcomes, and determine the fission products produced in a highly enriched uranium foil in the sample cavity. Nuclear data covariance impacted the neutron fluence energy distribution by a few percent for a large energy range of the neutron fluence. Neutron flux unfolding techniques provided broad spectral …
Application Of Metamaterials For Multifunctional Satellite Bus Enabled Via Additive Manufacturing, Michael A. Macchia
Application Of Metamaterials For Multifunctional Satellite Bus Enabled Via Additive Manufacturing, Michael A. Macchia
Theses and Dissertations
Space systems require materials with superior stiffness to weight ratios to provide structural integrity while minimizing mass. Additive manufacturing processes enable the design of metamaterials that exceed the performance of naturally occurring materials in addition to allowing the integration of non-structural functions. This research explored the use of a high stiffness, high density, small melt pool track width AM material, Inconel 718, to enable the production of metamaterials with finer features possible than can possibly be created using a lower density aluminum alloy material. Various metamaterials were designed utilizing thin wall triply periodic minimal surface infilled sandwich structures. The performance …
A Focal Plane Array And Electronics Model For Cmos And Ccd Sensors In The Afit Sensor And Scene Emulation Tool (Asset), Fernando D. Fernandez
A Focal Plane Array And Electronics Model For Cmos And Ccd Sensors In The Afit Sensor And Scene Emulation Tool (Asset), Fernando D. Fernandez
Theses and Dissertations
Electro-optical and infrared (EO/IR) sensor models are useful tools that can facilitate understanding a system's behavior without expensive and time-consuming testing of an actual system. EO/IR models are especially important to the military industry where truth data is required but is sometimes impractical to obtain through experimentation due to expense or difficulties in procuring hardware. This work describes implementation of a focal plane array (FPA) model of charge-coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) photodetectors as a component in the Air Force Institute of Technology (AFIT) Sensor and Scene Emulation Tool (ASSET). The FPA model covers conversion of photo-generated …
Optical And Electron Paramagnetic Resonance Characterization Of Point Defects In Semiconductors, Elizabeth M. Scherrer
Optical And Electron Paramagnetic Resonance Characterization Of Point Defects In Semiconductors, Elizabeth M. Scherrer
Theses and Dissertations
Point defects in two semiconductor materials, both with promising optical properties, are investigated. The first material, CdSiP2, is a nonlinear optical material in which absorption bands due to point defects can hinder performance when used in frequency conversion applications in the infrared. The second material, Sn2P2S6, is a photorefractive material where point defects with specific properties are needed to optimize response in dynamic holography applications. Electron paramagnetic resonance (EPR) spectroscopy is used to identify the electronic structure of defects and their charge states. Correlations between EPR spectra and optical absorption allow assignments …
Computational And Experimental Development Of 2d Anisotropic Photonic Crystal Metamaterials, James A. Ethridge
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 …
36% Reduction In Fuel Resupply Using A Hybrid Generator & Battery System For An Austere Location, David J. Chester, Torrey J. Wagner, Douglas S. Dudis
36% Reduction In Fuel Resupply Using A Hybrid Generator & Battery System For An Austere Location, David J. Chester, Torrey J. Wagner, Douglas S. Dudis
Faculty Publications
The DOD energy policy is to increase energy security resiliency, and mitigate costs in the use and management of energy[1] Forward operating bases (FOBs) are remote, austere base camps that support an operationally defined mission with a limited or no ability to draw from an energy grid and have historically relied on diesel-powered generators for the primary production of energy.[2] Generators are sized to meet a theoretical peak demand, but steady state loads are far below this peak, resulting in under-loaded generators.[3] Under-loaded diesel generators decrease efficiency and increase the need for maintenance, affecting the lifespan of …
Evaluation Of Unmanned Aircraft Flying Qualities Using A Stitched Learjet Model, Patrick M. Callaghan
Evaluation Of Unmanned Aircraft Flying Qualities Using A Stitched Learjet Model, Patrick M. Callaghan
Theses and Dissertations
In recent years, military UAVs have taken over missions that were too dull, dirty, or dangerous for manned aircraft. The increased demand has led to a build-fly-fix-fly development mentality, plaguing the early lifecycle with staggering mishap rates. Currently, MIL-STD-1797 lists flying qualities for UAVs as TBD, and the standards for manned fixed wing are inadequate when applied to UAVs. In an effort to expand the database of UAV flying qualities, an analysis was completed on a Simulink model of an LJ-25D developed from Calspans Variable Stability System aircraft at the United States Test Pilot School. Three maneuvers were simulated: (1) …
Magnetic Field Aided Indoor Navigation, William F. Storms
Magnetic Field Aided Indoor Navigation, William F. Storms
Theses and Dissertations
This research effort examines inertial navigation system aiding using magnetic field intensity data and a Kalman filter in an indoor environment. Many current aiding methods do not work well in an indoor environment, like aiding using the Global Positioning System. The method presented in this research uses magnetic field intensity data from a three-axis magnetometer in order to estimate position using a maximum – likelihood approach. The position measurements are then combined with a motion model using a Kalman filter. The magnetic field navigation algorithm is tested using a combination of simulated and real measurements. These tests are conducted using …
Deep-Turbulence Wavefront Sensing Using Digital Holography In The On-Axis Phase Shifting Recording Geometry With Comparisons To The Self-Referencing Interferometer, Douglas E. Thornton, Mark F. Spencer, Glen P. Perram
Deep-Turbulence Wavefront Sensing Using Digital Holography In The On-Axis Phase Shifting Recording Geometry With Comparisons To The Self-Referencing Interferometer, Douglas E. Thornton, Mark F. Spencer, Glen P. Perram
Faculty Publications
In this paper, we study the use of digital holography in the on-axis phase-shifting recording geometry for the purposes of deep-turbulence wavefront sensing. In particular, we develop closed-form expressions for the field-estimated Strehl ratio and signal-to-noise ratio for three separate phase-shifting strategies—the four-, three-, and two-step methods. These closed-form expressions compare favorably with our detailed wave-optics simulations, which propagate a point-source beacon through deep-turbulence conditions, model digital holography with noise, and calculate the Monte Carlo averages associated with increasing turbulence strengths and decreasing focal-plane array sampling. Overall, the results show the four-step method is the most efficient phase-shifting strategy and …
Improving Regional And Teleseismic Detection For Single-Trace Waveforms Using A Deep Temporal Convolutional Neural Network Trained With An Array-Beam Catalog, Joshua T. Dickey, Brett J. Borghetti, William Junek
Improving Regional And Teleseismic Detection For Single-Trace Waveforms Using A Deep Temporal Convolutional Neural Network Trained With An Array-Beam Catalog, Joshua T. Dickey, Brett J. Borghetti, William Junek
Faculty Publications
The detection of seismic events at regional and teleseismic distances is critical to Nuclear Treaty Monitoring. Traditionally, detecting regional and teleseismic events has required the use of an expensive multi-instrument seismic array; however in this work, we present DeepPick, a novel seismic detection algorithm capable of array-like detection performance from a single-trace. We achieve this performance through three novel steps: First, a high-fidelity dataset is constructed by pairing array-beam catalog arrival-times with single-trace waveforms from the reference instrument of the array. Second, an idealized characteristic function is created, with exponential peaks aligned to the cataloged arrival times. Third, a deep …
A Triaxial Applicator For The Measurement Of The Electromagnetic Properties Of Materials, Saranraj Karuppuswami, Edward Rothwell, Premjeet Chahal, Michael J. Havrilla
A Triaxial Applicator For The Measurement Of The Electromagnetic Properties Of Materials, Saranraj Karuppuswami, Edward Rothwell, Premjeet Chahal, Michael J. Havrilla
Faculty Publications
The design, analysis, and fabrication of a prototype triaxial applicator is described. The applicator provides both reflected and transmitted signals that can be used to characterize the electromagnetic properties of materials in situ. A method for calibrating the probe is outlined and validated using simulated data. Fabrication of the probe is discussed, and measured data for typical absorbing materials and for the probe situated in air are presented. The simulations and measurements suggest that the probe should be useful for measuring the properties of common radar absorbing materials under usual in situ conditions.
Graduate School Of Engineering And Management Catalog 2019-2020, Graduate School Of Engineering And Management, Air Force Institute Of Technology
Graduate School Of Engineering And Management Catalog 2019-2020, Graduate School Of Engineering And Management, Air Force Institute Of Technology
AFIT Documents
The Graduate Catalog represents the offerings, programs, and requirements in effect at the time of publication.
A Case For Open Mission Systems In Dod Aircraft Avionics, Michael J. Brown, R. David Fass, Jonathan D. Ritschel
A Case For Open Mission Systems In Dod Aircraft Avionics, Michael J. Brown, R. David Fass, Jonathan D. Ritschel
Faculty Publications
The DOD is adopting open mission systems (OMS) as the future in the military aviation environment. OMS proponents promise reduced costs and truncated schedules through increased competition in the marketplace and reduced coding efforts. To the best of our knowledge, no studies have examined the success of these open architectures in the DOD. Therefore, we investigate costs and schedule for a recent DOD avionics OMS demonstration platform in comparison to 13 historically analogous programs.
A Sustainable Prototype For Renewable Energy: Optimized Prime-Power Generator Solar Array Replacement, Nathan Thomsen, Torrey J. Wagner, Andrew J. Hoisington, Steven J. Schuldt
A Sustainable Prototype For Renewable Energy: Optimized Prime-Power Generator Solar Array Replacement, Nathan Thomsen, Torrey J. Wagner, Andrew J. Hoisington, Steven J. Schuldt
Faculty Publications
Remote locations such as disaster relief camps, isolated arctic communities, and military forward operating bases are disconnected from traditional power grids forcing them to rely on diesel generators with a total installed capacity of 10,000 MW worldwide. The generators require a constant resupply of fuel, resulting in increased operating costs, negative environmental impacts, and challenging fuel logistics. To enhance remote site sustainability, planners can develop stand-alone photovoltaic-battery systems to replace existing prime power generators. This paper presents the development of a novel cost-performance model capable of optimizing solar array and Li-ion battery storage size by generating tradeoffs between minimizing initial …
Real-Time Path Planning In Constrained, Uncertain Environments, Randall Christensen, Robert C. Leishman
Real-Time Path Planning In Constrained, Uncertain Environments, Randall Christensen, Robert C. Leishman
Faculty Publications
A key enabler of autonomous vehicles is the ability to plan the path of the vehicle to accomplish mission objectives. To be robust to realistic environments, path planners must account for uncertainty in the trajectory of the vehicle as well as uncertainty in the location of obstacles. The uncertainty in the trajectory of the vehicle is a difficult quantity to estimate, and is influenced by coupling between the vehicle dynamics, guidance, navigation, and control system as well as any disturbances acting on the vehicle. Monte Carlo analysis is the conventional approach to determine vehicle dispersion, while accounting for the coupled …
Real-Time Heuristics And Metaheuristics For Static And Dynamic Weapon Target Assignments, Alexander G. Kline
Real-Time Heuristics And Metaheuristics For Static And Dynamic Weapon Target Assignments, Alexander G. Kline
Theses and Dissertations
The problem of targeting and engaging individual missiles (targets) with an arsenal of interceptors (weapons) is known as the weapon target assignment problem. This problem has been well-researched since the seminal work in 1958. There are two distinct categories of the weapon target assignment problem: static and dynamic. The static weapon target assignment problem considers a single instance in which a known number of incoming missiles is to be engaged with a finite number of interceptors. By contrast, the dynamic weapon target assignment problem considers either follow on engagement(s) should the first engagement(s) fail, a subsequent salvo of incoming missiles, …
Improving Detection Of Dim Targets: Optimization Of A Moment-Based Detection Algorithm, Shannon R. Young
Improving Detection Of Dim Targets: Optimization Of A Moment-Based Detection Algorithm, Shannon R. Young
Theses and Dissertations
Wide area motion imagery (WAMI) sensor technology is advancing rapidly. Increases in frame rates and detector array sizes have led to a dramatic increase in the volume of data that can be acquired. Without a corresponding increase in analytical manpower, much of these data remain underutilized. This creates a need for fast, automated, and robust methods for detecting dim, moving signals of interest. Current approaches fall into two categories: detect-before-track (DBT) and track-before-detect (TBD) methods. The DBT methods use thresholding to reduce the quantity of data to be processed, making real time implementation practical but at the cost of the …
Carbon Nanotube Fibers: Mechanical Behavior And The Effects Of The Space Environment, Ryan A. Kemnitz
Carbon Nanotube Fibers: Mechanical Behavior And The Effects Of The Space Environment, Ryan A. Kemnitz
Theses and Dissertations
Carbon nanotube materials are promising multifunctional materials for incorporation into aerospace structures because of their high tensile strength, high electrical conductivity, and low density. This research aimed to characterize the mechanical failure mechanisms of carbon nanotube fibers and examine the effects of the space environment on their material properties. Tensile tests were conducted at varying strain rates and on fibers of varying gage lengths to examine the underlying molecular failure mechanisms and impact of defects on fiber strength. Tensile strength and elastic modulus were observed to increase with increasing strain rate and decrease with increasing gage lengths. The observed effects …
Thermal Management Of Satellite Electronics Via Gallium Phase Change Heat Sink Devices, Brian O. Palmer
Thermal Management Of Satellite Electronics Via Gallium Phase Change Heat Sink Devices, Brian O. Palmer
Theses and Dissertations
The purpose of this research was to determine the effectiveness and feasibility of additively manufactured heat sinks using gallium as a phase change material in the thermal management of satellite electronics. A design was created based on the footprint of an Astronautical Development, LLC Lithium 1 UHF radio and six heat sinks were additively manufactured; two each of stainless steel 316, Inconel 718, and ULTEM 9085. Each heat sink was filled with gallium for testing purposes. Models were created to simulate the behavior of the heat transfer and phase change processes occurring within the heat sink. Additionally, laboratory data was …
Experimental And Computational Analysis Of The Interaction Of Carbon And Silicon Ablation Products In Expanding Hypersonic Flows, Brian E. Donegan
Experimental And Computational Analysis Of The Interaction Of Carbon And Silicon Ablation Products In Expanding Hypersonic Flows, Brian E. Donegan
Theses and Dissertations
Thermal protection is required for vehicles entering planetary atmospheres to protect against the severe heating loads experienced. Characterization of candidate materials is often done utilizing plasma or arc-jet facilities, which provide steady-state testing of the thermal environments experienced during hypersonic flight, but do not correctly simulate hypersonic flowfields. Conversely, impulse facilities can reproduce flight velocities and enthalpies but have extremely short test times, prohibiting testing of thermal response. Modeling ablation and heating rates, particularly in the wake region, remains a significant challenge due to the complexity of the flowfield. To better understand this complex phenomenon and provide data to validate …
Mems Variable Area Capacitor For Room Temperature Electrometry, George C. Underwood, Tod V. Laurvick
Mems Variable Area Capacitor For Room Temperature Electrometry, George C. Underwood, Tod V. Laurvick
Faculty Publications
This paper introduces a new way to detect charge using MEMS variable capacitors for extremely sensitive, room temperature electrometry. It is largely based on the electrometers introduced by Riehl et al. [1] except variable capacitance is created by a changing area, not a changing gap. The new scheme will improve MEMS electrometers by eliminating the effects of squeeze-film damping and by theoretically increasing the maximum charge resolution by 70%. The charge conversion gain (the increase in output voltage per input unit charge) for this system is derived. The result show good agreement with MATLAB calculations.
Cost Performance Index Stability: Insights From Environmental Remediation Projects, Denis S. Clayson, Edward D. White, Alfred E. Thal Jr.
Cost Performance Index Stability: Insights From Environmental Remediation Projects, Denis S. Clayson, Edward D. White, Alfred E. Thal Jr.
Faculty Publications
The purpose of this study was to investigate the stability of the cost performance index (CPI) for environmental remediation projects as the topic is not addressed in the literature. CPI is defined as the earned value of work performed divided by the actual cost of the work, and CPI stability represents the point in time in a project after which the CPI varies by less than 20 percent (measured in different ways).
Evaluation Of Eu:Licaf For Neutron Detection Utilizing Sipms And Portable Electronics, Michael A. Ford, Buckley E. O'Day Iii, John W. Mcclory, Manish K. Sharma, Areg Danagoulian
Evaluation Of Eu:Licaf For Neutron Detection Utilizing Sipms And Portable Electronics, Michael A. Ford, Buckley E. O'Day Iii, John W. Mcclory, Manish K. Sharma, Areg Danagoulian
Faculty Publications
With the increasing cost and decreasing availability of 3He, there have been many efforts to find alternative neutron detection materials. Lithium calcium aluminum fluoride (LiCAF) enriched to 95% 6Li doped with europium was evaluated here as a replacement material for 3He. Wafers 0.5 cm thick, consisting of LiCAF crystals in a rubberized matrix, were embedded with wavelength shifting fibers (WSF) and mated to silicon photo-multipliers (SiPMs) to measure the photon response in a flux of neutrons from a DD neutron generator. Excellent discrimination was realized between neutrons and gammas, and both pulse-height discrimination and pulse-shape analysis were …
Delineating Operating And Support Costs In Aircraft Platforms, Garrett B. O'Hanlon, Jonathan D. Ritschel, Edward D. White, Gregory E. Brown
Delineating Operating And Support Costs In Aircraft Platforms, Garrett B. O'Hanlon, Jonathan D. Ritschel, Edward D. White, Gregory E. Brown
Faculty Publications
As the costs of Department of Defense (DoD) Weapon Systems increase, the ability to estimate the Operating and Support (O&S) costs accurately for the various weapon systems has become vital to long-term affordability. This research focuses on the O&S costs of the Air Force fixed-wing arsenal (i.e., platforms) for 1996–2016. First, the Cost Element Structure (CES) for 52 aircraft platforms and seven operational mission categories is analyzed to derive the descriptive statistics per aircraft category through examination of actual historical costs. Second, testing to identify statistical differences within the O&S CES construct across various Air Force aircraft categories is conducted. …
A Deterministic-Stochastic Method For Computing The Boltzmann Collision Integral In O(Mn) Operations, Alexander Alekseenko, Truong Nguyen, Aihua W. Wood
A Deterministic-Stochastic Method For Computing The Boltzmann Collision Integral In O(Mn) Operations, Alexander Alekseenko, Truong Nguyen, Aihua W. Wood
Faculty Publications
We developed and implemented a numerical algorithm for evaluating the Boltzmann collision integral with O(MN) operations, where N is the number of the discrete velocity points and M < N. At the base of the algorithm are nodal-discontinuous Galerkin discretizations of the collision operator on uniform grids and a bilinear convolution form of the Galerkin projection of the collision operator. Efficiency of the algorithm is achieved by applying singular value decomposition compression of the discrete collision kernel and by approximating the kinetic solution by a sum of Maxwellian streams using a stochastic likelihood maximization algorithm. Accuracy of the method is …