Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Electrical and Computer Engineering (2207)
- Mechanical Engineering (1660)
- Aerospace Engineering (1588)
- Civil and Environmental Engineering (1284)
- Operations Research, Systems Engineering and Industrial Engineering (1174)
-
- Physical Sciences and Mathematics (1072)
- Computer Engineering (586)
- Electrical and Electronics (536)
- Operational Research (525)
- Biomedical Engineering and Bioengineering (482)
- Chemical Engineering (470)
- Computer Sciences (465)
- Materials Science and Engineering (442)
- Signal Processing (389)
- Aviation (351)
- Civil Engineering (305)
- Business (235)
- Physics (231)
- Environmental Engineering (228)
- Systems Engineering (216)
- Navigation, Guidance, Control and Dynamics (207)
- Construction Engineering and Management (195)
- Other Operations Research, Systems Engineering and Industrial Engineering (194)
- Engineering Science and Materials (180)
- Aerodynamics and Fluid Mechanics (179)
- Nuclear Engineering (178)
- Digital Communications and Networking (170)
- Space Vehicles (158)
- Electromagnetics and Photonics (144)
- Institution
-
- Air Force Institute of Technology (4613)
- Brigham Young University (2217)
- University of South Carolina (932)
- University of Wisconsin Milwaukee (666)
- Virginia Commonwealth University (623)
-
- Florida Institute of Technology (582)
- Rowan University (300)
- University of Texas Rio Grande Valley (265)
- Mississippi State University (159)
- American University in Cairo (128)
- University for Business and Technology in Kosovo (110)
- University of North Dakota (15)
- Columbus State University (8)
- Illinois State University (8)
- City University of New York (CUNY) (3)
- Pepperdine University (1)
- Keyword
-
- #antcenter (292)
- Optimization (113)
- Machine learning (95)
- FPGA (89)
- Simulation (75)
-
- Modeling (70)
- Applied sciences (63)
- UAV (63)
- Global Positioning System (62)
- Additive manufacturing (60)
- Computer vision (60)
- Image processing (58)
- Machine Learning (54)
- Decision making (52)
- Microelectromechanical systems (51)
- Remote sensing (50)
- Algorithms (49)
- Kalman filtering (49)
- Drone aircraft (47)
- Target acquisition (47)
- Engineering, Chemical Engineering (44)
- Flight control (44)
- Synthetic aperture radar (44)
- Compliant mechanisms (43)
- Reliability (42)
- Composite materials (41)
- Engineering, Mechanical Engineering (41)
- Finite element analysis (41)
- Signal processing (41)
- Deep learning (40)
- Publication Year
Articles 631 - 660 of 10630
Full-Text Articles in Engineering
Cost Estimating Relationships For Recurring T100 Flyaway Costs, Kyrie M. Rojo
Cost Estimating Relationships For Recurring T100 Flyaway Costs, Kyrie M. Rojo
Theses and Dissertations
This research investigates a dataset of over 80 Air Force and Navy aircraft and applies regression techniques to create two cost estimating relationships (CERs) for predicting recurring T100 flyaway costs, depending on where in the acquisition lifecycle the estimate takes place. The first CER explains 89 percent of the variation in the dataset and can be applied prior to Milestone B (MS B). The second CER explains 88 percent of the variation in the dataset and can be applied between MS B and MS C. Significant cost drivers identified include stealth, cohort, empty weight, the natural log of speed, legacy …
Long-Term Asset Prioritization To Support District Planning, Melissa R. Sallberg
Long-Term Asset Prioritization To Support District Planning, Melissa R. Sallberg
Theses and Dissertations
The United States Air Force (USAF) relies on its installations to project military power across the globe. However, due to the deferred infrastructure maintenance and recapitalization backlog of $33 billion as of 2019 (Wilson & Goldfein, 2019), it is more critical than ever for base-level community planners to focus their attention to the projects that will achieve each installation’s long-term goals. The recent incorporation of asset management principles into the USAF District Planning Process allows a unique opportunity to improve the existing scoring model for a holistic look at what matters to enterprise leaders and community planners making the plans …
Designing A Counter-Iads Drone Swarm: Using Evolution To Evaluate Combat Assumptions Underpinning Drone Swarm Target Assignment, Olin H. Kennedy
Designing A Counter-Iads Drone Swarm: Using Evolution To Evaluate Combat Assumptions Underpinning Drone Swarm Target Assignment, Olin H. Kennedy
Theses and Dissertations
The original research goal was to combine the best techniques in the drone swarm literature and model a functional combat drone swarm that conducts a Suppression of Enemy Air Defense (SEAD) mission. However, the body of literature regarding Drone Swarm Target Assignment (DSTA) does not model enemy counteraction and assumes that the drones’ targets are compliant against destruction. Therefore, a model of enemy counteraction against drone swarms is developed, and Novel DSTA (NDSTA) is proposed to respond to the weaknesses of the current DSTA. Both methods of target assignment are combined with a tunable trajectory generation model, and the performance …
Fragility Of The Florida Panhandle's Electrical Transmission Grid To Hurricanes, Zachary D. Schumann
Fragility Of The Florida Panhandle's Electrical Transmission Grid To Hurricanes, Zachary D. Schumann
Theses and Dissertations
The increased frequency and intensity of extreme weather events from climate change necessitates understanding impacts on critical infrastructure, particularly electrical transmission grids. One of the foundational concepts of a grid’s resilience is its robustness to extreme weather events, such as hurricanes. Resilience of the electric grid to high wind speeds is predicated upon the location and physical characteristics of the system components. Previous modeling assessments of electric grid failure were done at the systems level with assumptions on location and type of specific components. To facilitate more explicit adaptation metrics, accurate component-level information is needed. In this study, we build …
An Approximate Dynamic Programming Approach For Solving An Air Combat Maneuvering Problem With Directed Energy Weapons, Elisha A. Palm
An Approximate Dynamic Programming Approach For Solving An Air Combat Maneuvering Problem With Directed Energy Weapons, Elisha A. Palm
Theses and Dissertations
Performing within visual range (WVR) air combat involves the execution of complex air maneuvers and rapid sequential decision making. The complexity of these decisions can increase even further when including additional weapon capabilities. The advancement of unmanned autonomous vehicle technology and weapon capabilities can help combat the hindrance that comes with human limitations. Autonomous unmanned combat aerial vehicles (AUCAVs) and the implementation of advanced weapon capabilities such as Directed Energy Weapons (DEWs) can prove to be vital in a WVR air combat context. This derives the question – Can AUCAV’s possess the proper artificial intelligence and weapon capabilities to attain …
The U.S. Army Officer-To-Unit Assignment Problem, Andrea L. Phillips
The U.S. Army Officer-To-Unit Assignment Problem, Andrea L. Phillips
Theses and Dissertations
Every two to three years, U.S. Army officers must change duty stations, which entails a selection process based on preferences. Currently, officers are assigned to units using a stable-marriage algorithm. Two impracticalities occur within this process. First, officers are required to submit strictly ranked preferences, not allowing indifference among units. Second, the stable-marriage algorithm does not give flexibility to alternative priorities. This research focuses on two modifications to the current model. First, a mixed integer program is created that allows the user, U.S. Army Human Resources Command, to consider other priorities: unit preferences and maximum officer disappointment. Second, generated data …
Overall Effectiveness Superposition Theory For A Film Cooled Leading Edge, Bailey W. Hopkins
Overall Effectiveness Superposition Theory For A Film Cooled Leading Edge, Bailey W. Hopkins
Theses and Dissertations
Film cooling experimentation traditionally reports on the cooling performance of specialty-crafted cooling holes at various angles and array patterns. This is repeated across a variety of model geometries in an effort to provide as much information to the turbine blade designer. While this extensive database of cooling performance is helpful, its true value is found in the designer’s ability to effectively superpose the results on top of each other. One technique for predicting the performance of multiple coolant sources is film cooling superposition theory. This analytical model was employed classically by characterizing the adiabatic effectiveness across a model’s surface; however, …
Anisotropic Characterization Of Additively Manufactured Ti 6-4 Via Tension, Compression, And Three Point Bend Experimentation, James M. Gunderson
Anisotropic Characterization Of Additively Manufactured Ti 6-4 Via Tension, Compression, And Three Point Bend Experimentation, James M. Gunderson
Theses and Dissertations
Titanium's ability to fill existing material gaps because of its higher strength and higher melting temperature compared to other common materials used in aircraft structures requires a need to understand the behavior of the material. Titanium's properties and the development of additive manufacturing also open an opportunity for it to be used in aerospace systems of the future in applications where traditionally manufactured titanium cannot meet the desired system requirements. Compressive, tensile, and three point bend experimental data collected from this research under varying temperatures, print orientations, print layer build heights, and surface finishes were analyzed to determine favorable material …
Gaseous Fuel Combustion In A Small Turbojet, Katherine A. Ashton
Gaseous Fuel Combustion In A Small Turbojet, Katherine A. Ashton
Theses and Dissertations
This project set out to test the suitability of natural gas as an aviation fuel by comparing how a small turbojet performed when run on traditional jet fuel versus methane. A JetCat P400, originally designed for jet fuel, was modified to run on methane. The modifications made did not succeed at getting the engine to run at normal operating speed on methane, but did get the engine to run at normal operating speeds using ethylene and ethane. It was determined a fuel and air mixing problem was hindering the engine performance when run on methane Future studies improving the fuel …
Shock Induced Trailing Edge Separation Effect On F-16 Limit-Cycle Oscillation, Eric D. Stubblefield
Shock Induced Trailing Edge Separation Effect On F-16 Limit-Cycle Oscillation, Eric D. Stubblefield
Theses and Dissertations
No abstract provided.
Debris Survivability Study For Mega-Constellation Architectures, Joseph C. Canoy
Debris Survivability Study For Mega-Constellation Architectures, Joseph C. Canoy
Theses and Dissertations
The analysis for the overall theoretical debris survivabilty of mega-constellation architectures, with an emphasis on space-based ballistic missile defense constellation (SB-BMD), is explored via three extensive different Monte Carlo simulations: preliminary analysis of low Earth Orbit (LEO) mega-constellation survivabilty following a fragmentation event within the constellation, analysis of LEO mega-constellation survivability with a fragmentation event occurring on a satellite performing a maneuver to insert itself within the constellation, and the analysis of LEO mega-constellation survivabilty after a fragmentation event resulting from the destruction of a missile. The LEO mega-constellations represent the SB-BMD constellation. The first two analysis sections will include …
Direct Collocation Methods For Comparison Of Aerothermodynamic Models Effect On Hypersonic Trajectory Optimization By The Process Of Continuation, Noor K. Khan
Theses and Dissertations
An algorithm was created to optimize trajectories of hypersonic glide vehicles with selected cost functions by applying the process of continuation to direct orthogonal collocation methods. The trajectory was optimized to maximize the range of launch position given a fixed terminal location. The hypersonic glide vehicle system dynamics were modeled with three-dimensional, three degree of freedom equations of motion assuming no thrust and a non-rotating Earth with the control as bank angle. Three aerothermodynamic models were compared when input as path constraints to calculate the stagnation point heating rate at the nose as well as integrated for heat load. Use …
Critical Infrastructure System Resiliency Modeling Using Multi-Layer Network Optimization, Spencer R. Figge
Critical Infrastructure System Resiliency Modeling Using Multi-Layer Network Optimization, Spencer R. Figge
Theses and Dissertations
ccurately modeling the interdependent operation of critical infrastructure systems is an effective and efficient way of proactively evaluating system vulnerabilities and resiliency. Infrastructure systems are designed to transport essential commodities from where they are produced to where they are consumed and network flow-based models are one of the most effective ways to simulate and quantify infrastructure performance. The literature is populated with proposed models that must balance accuracy of interdependent operations, capability to include real-world considerations, and computational cost. This research proposes an alternative network-flow based model called the Critical Infrastructure System Resiliency Model (CISRM) that focuses on modeling a …
Development Of Novel Turbomachinery Manufacturing Methods, Timothy P. Winkler
Development Of Novel Turbomachinery Manufacturing Methods, Timothy P. Winkler
Theses and Dissertations
Compact turbine engines are of increasing interest as a means of propulsion for small, lightweight, low cost, unmanned aerial systems. This study looks to leverage advancements in novel manufacturing technology to produce turbomachinery components while simultaneously reducing costs and manufacturing time. To determine the feasibility of drop-in replacements for stock components this study focused on several research areas. This included materials research on both polymer-reinforced and ceramic materials, specimen tensile testing to determine temperature-dependent material properties, finite element analysis of multiple candidate materials, design and fabrication of a spin test rig, and physical spin testing of manufactured components to predict …
Classifying Open-Air Target Measurements Using Simulation-Trained Convolutional Neural Networks, Matthew M. Rofrano
Classifying Open-Air Target Measurements Using Simulation-Trained Convolutional Neural Networks, Matthew M. Rofrano
Theses and Dissertations
No abstract provided.
Prediction Of Persistent Post-Traumatic Headache With Long Short-Term Memory Networks, Todd C. Campo
Prediction Of Persistent Post-Traumatic Headache With Long Short-Term Memory Networks, Todd C. Campo
Theses and Dissertations
Military members in combat situations are at a high risk for experiencing a Traumatic Brain Injury (TBI), often leaving them with Post-Traumatic Headache (PTH). There is currently a poor understanding of what factors predict if a patient will endure acute (short-term) PTH or Persistent PTH (PPTH). The Concussion Assessment, Research, and Education (CARE) Consortium dataset contains a variety of pre-and-post-injury concussion assessments taken by NCAA athletes and service academy cadets between 2014 and 2018. Participants in this study (n = 1769) suffered a TBI. Using this longitudinal data, three models were constructed: an LSTM model using the raw assessment scores, …
Arctic Construction Under Climatological Constraints: A Decision Support System For Expeditionary Construction Site Selection In The Arctic Environment, Zachary S. Wontrop
Arctic Construction Under Climatological Constraints: A Decision Support System For Expeditionary Construction Site Selection In The Arctic Environment, Zachary S. Wontrop
Theses and Dissertations
The natural physical barriers present in the Arctic are being eroded by climate change, increasing near peer adversaries' abilities to exploit this region for strategic and economic gain. To maintain the Arctic as a region of strategic and economic international cooperation, increased infrastructure investment by the United States and its allies are required. No methodology currently exists to quantify construction-limiting climatological factors over time and space. Decision support systems can provide actionable information to guide decision makers during site selection. This research employs geographic, and time-coded historical climatology applied to a project case study, to develop a site selection decision …
U.S. Army Force Structure Optimization And Sufficiency Analysis, Francis P. Gargin
U.S. Army Force Structure Optimization And Sufficiency Analysis, Francis P. Gargin
Theses and Dissertations
The United States Army perpetually deploys rotational forces across the globe in support of the National Security Strategy. These forces meet a set of discrete mission demands over an extended time period before redeploying, modernizing, and preparing for the next deployment. The U.S. Army now utilizes the Regionally Aligned Readiness and Modernization Model to execute these cyclical stages for unit deployments. Specific emphasis is placed on aligning forces against a Geographic Combatant Command, which allows units to build readiness and lethality oriented towards the same series of threats, physical terrain, and civilian considerations. This research provides an Integer Programming model …
Analysis And Optimization Of Contract Data Schema, Franklin Sun
Analysis And Optimization Of Contract Data Schema, Franklin Sun
Theses and Dissertations
agement, development, and growth of U.S Air Force assets demand extensive organizational communication and structuring. These interactions yield substantial amounts of contracting and administrative information. Over 4 million such contracts as a means towards obtaining valuable insights on Department of Defense resource usage. This set of contracting data is largely not optimized for backend service in an analytics environment. To this end, the following research evaluates the efficiency and performance of various data structuring methods. Evaluated designs include a baseline unstructured schema, a Data Mart schema, and a snowflake schema. Overall design success metrics include ease of use by end …
Concept Of Operations Of Cislunar Mirror Satellites To Provide Augmented Lighting Of Dim Space-Based Objects, Alec E. Cook
Concept Of Operations Of Cislunar Mirror Satellites To Provide Augmented Lighting Of Dim Space-Based Objects, Alec E. Cook
Theses and Dissertations
The imaging and inspection of Resident Space Objects (RSOs) is an increasingly important mission as space-faring nations and commercial enterprises alike seek to develop means to repair and refuel spacecraft, as well as de-orbit RSOs to reduce orbital debris. Lighting conditions are not always advantageous for an imaging/inspection or repair/refuel spacecraft; therefore, the use of mirror spacecraft to reflect solar energy is proposed to illuminate dimly lit RSOs. The present research investigates the efficacy of space-based reflectors at examining spacecraft in the cislunar environment. Specific assessments include target spacecraft in geosynchronous Earth orbit and periodic orbits around selected Lagrange points, …
Fast Engineering Model For Defect Production In Magnesium Oxide, Henry R. Little
Fast Engineering Model For Defect Production In Magnesium Oxide, Henry R. Little
Theses and Dissertations
Defect production from irradiation of materials with thicknesses much less than the mean free path for neutron interaction is explored. A model is developed using the Monte Carlo N-Particle transport code from Los Alamos National Laboratory, experimental data from irradiations at the Oak Ridge High Flux Isotope Reactor, defect production theory, and atomistic simulation results to predict the total number of F-centers resulting from neutron irradiation of a MgO rod. This model accurately predicts the concentration of atomic defects under conditions closely matching experiments at long timescales, for large geometries, and requiring only 6.9 minutes on a single CPU. Results …
Towards An Understanding Of The Thermodynamic Properties Of Crtao4: A Computational Perspective, Tanner B. Gordon
Towards An Understanding Of The Thermodynamic Properties Of Crtao4: A Computational Perspective, Tanner B. Gordon
Theses and Dissertations
Materials that can withstand higher temperatures are paramount for next-generation aircraft design. Hypersonic capabilities and jet-turbine engines operate in extreme environments. Choosing materials that have high thermal stability and oxidation resistance for these applications can increase engine efficiency, reduce size, weight and power (SWaP), and increase the maneuverability of the aircraft. The mixed oxide CrTaO4 has been experimentally observed to significantly contribute to oxidation resistance at high temperatures. However, and despite its significance, its properties remain largely unknown. This work explores the thermal properties of this material from a multi-scale approach, by obtaining an accurate description of the thermodynamics …
Characterizing Gesn Alloys By Sem/Eds And Photoluminescence Spectroscopy, Christopher M. Sutphin
Characterizing Gesn Alloys By Sem/Eds And Photoluminescence Spectroscopy, Christopher M. Sutphin
Theses and Dissertations
Germanium tin (GeSn) alloys are being studied as potential transition metal (Group IV) photoelectric semiconductors or optical detectors. GeSn alloys could be employed as an optically active material within a computer. Compared to current technologies, a direct band gap GeSn alloy can be engineered to operate with higher thermal stability and efficiency. The GeSn alloy studied was composed of Ge and Si substrates with various Sn percentages grown using remote plasma-enhanced chemical vapor deposition (RPECVD). Photoluminescence spectroscopy (PL) techniques were initially used to determine the GeSn properties, including the band gap. The Ge91.2Sn8.8 PL spectra suggested the …
Material Property Dependence Of Nanoparticle Silicon Carbide Alloying In Additively Manufactured Molybdenum, Andrew P. Mason
Material Property Dependence Of Nanoparticle Silicon Carbide Alloying In Additively Manufactured Molybdenum, Andrew P. Mason
Theses and Dissertations
The structural performance of additively manufactured Mo printed by LPBF can be significantly improved by nanoparticle alloying. Previous AFIT studies of SiC nanoparticle addition conducted by Ellsworth (2022) et al. demonstrated increased powder consolidation, leading to reduced porosity, increased microhardness, and a shift in atomic defect concentrations. The addition of defected SiC particles is proposed to reduce in situ oxidation by acting as a sacrificial oxidizing agent and contributing to the formation of Mo disilicide secondary phases. This study investigated the relationship between laser powder bed fusion Mo microscale and nanoscale properties with varying SiC particle size while maintaining a …
Simulation Of Neutron Generation From Laser-Driven Fusion In A Liquid D2o Sheet Using Novel Warpx Module, Colton R. Stoner
Simulation Of Neutron Generation From Laser-Driven Fusion In A Liquid D2o Sheet Using Novel Warpx Module, Colton R. Stoner
Theses and Dissertations
Using WarpX’s new nuclear fusion module, this work attempts to model an experimental system at the ELL at the AFIT with WarpX and draw conclusions about fusion products from resulting simulations. Recently, a table-top, high repetition rate, mixed radiation source was demonstrated at the ELL employing a HIL to fuse the deuterium nuclei present in a unique liquid target of heavy water. Analysis of the simulations predicted an isotropic output of neutrons from deuterium-deuterium fusion. These simulated neutrons were created in tens of femtoseconds from dense bodies of deuterons that were perturbed by the laser. However, it was found that …
Validation Of Digital System Models, James R. Winton
Validation Of Digital System Models, James R. Winton
Theses and Dissertations
The Department of Defense is undergoing a Digital Transformation driven by Digital Engineering and Model-Based Systems Engineering. Document-based processes are being replaced by digital artifacts, pedigreed data, and an Authoritative Source of Truth for a system across its life cycle. As traditional Design-Build-Test transitions to a Model-Analyze-Build methodology, digital models will proliferate throughout the enterprise and require novel validation processes earlier in the development timeline. A new definition for digital system model validation is proposed to address the identified shortcomings in existing guidance. The proposed validation framework leverages the Systems Modeling Language, use cases, requirements, test cases, and a custom …
Investigation Of Hypersonic Near-Wake Relaminarization Over A 7 Degree Half-Angle Cone, Jesse L. Roberts
Investigation Of Hypersonic Near-Wake Relaminarization Over A 7 Degree Half-Angle Cone, Jesse L. Roberts
Theses and Dissertations
To investigate the potential for relaminarization in the near-wake of a 7-degree half-angle cone, a series of hypersonic wake experiments were conducted in the Air Force Research Laboratory Mach 6.1 Ludwieg tube. Relaminarization is a spatial phenomenon that occurs when a turbulent flow reverts to a laminar-like state at a downstream location, where turbulent fluctuations negligibly contribute to average flow properties. Although relaminarization has been documented in subsonic and supersonic flows, the current body of knowledge related to the occurrence of, and mechanisms that drive, relaminarization at hypersonic speeds is sparse. Measurements were obtained across a range of freestream unit …
Assessment Of Emergency Cooling Requirement For Nuclear Reactor Loss-Of-Coolant Accidents, Michael T. Lindsay
Assessment Of Emergency Cooling Requirement For Nuclear Reactor Loss-Of-Coolant Accidents, Michael T. Lindsay
Theses and Dissertations
The 2022 Russia-Ukraine War marks the first time in modern history of conventional military forces targeting and seizing control of an operational nuclear power plant. Power supply and operational cooling systems are critical to avert reactor loss-of-coolant accidents (LOCA) in the event of emergency shutdown, or SCRAM. A wartime non-design based reactor accident causing loss of reactor power and coolant supply would require an emergency heat exchange via coolant to mitigate reactor core heat. At present, the military does not have a well-defined model which characterizes this requirement for operational planning should such an event occur. SCALE 6.2.4 is used …
A Systems Modeling Approach To Support Human-Agent Team Performance For Combat Identification, Clayton W. Couch
A Systems Modeling Approach To Support Human-Agent Team Performance For Combat Identification, Clayton W. Couch
Theses and Dissertations
Combat Identification (CID) in an air-to-air combat context is a highly complex cognitive task that requires the operator to make rapid, high consequence decisions. To accomplish CID, fighter aircrew must attend to and perceive a broad range of information while concurrently building situation awareness (SA) and conducting other tasks. While existing automated agents are available to help fighter aircrew with this CID task, they are designed for a very narrow subset of the overall task and are not well suited for human-agent teaming. An interdependence analysis of the human operator and supporting machine agents conducted for this task support the …
Illuminating The Unknown: A Mixed Methods Exploration Of The Dod Software Factory Ecosystem, Zachary O. Ryan
Illuminating The Unknown: A Mixed Methods Exploration Of The Dod Software Factory Ecosystem, Zachary O. Ryan
Theses and Dissertations
The Department of Defense’s (DoD) software factories are a collection of modern software acquisition programs that commonly employ the agile, network-based business strategies often found within commercial industries. Having been formally recognized by senior leaders for their revolutionary software development approaches, the software factories highlight a cultural shift within the DoD away from traditional organizational practices. As a result of the factories demonstrated successes, the number of programs employing non-traditional strategies is expanding. While this is notable, it also presents a challenge because a comprehensive understanding of the characteristics, structures, and behaviors of the DoD’s software factories does not currently …