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Articles 49351 - 49380 of 196901

Full-Text Articles in Engineering

An Analysis Of Various Hydrogen Production Methods For Fleet Vehicle Fuel, Eugene J. Denezza Ii Mar 2021

An Analysis Of Various Hydrogen Production Methods For Fleet Vehicle Fuel, Eugene J. Denezza Ii

Theses and Dissertations

As conflict, the environment, and politics cause changes around the world, the United States Air Force is pursuing a diversification of drop-in and alternative fuel sources. Hydrogen fuel cells for vehicles are gaining popularity worldwide. Yet, how to best produce hydrogen gas still remains a question. This thesis will provide an overview of various hydrogen production methods and their respective environmental impacts, costs, efficiencies, and viability; and will perform sensitivity analysis to determine an optimal solution. The optimal production method is Thermolysis followed by Steam Reformation of Landfill or Natural Gas, Coal Gasification, and PEM Electrolysis. Based on varying requirements …

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Utilizing Model Based Systems Engineering To Identify Safety Critical Functions In Airworthiness Certification, Jeffrey C. King Mar 2021

Utilizing Model Based Systems Engineering To Identify Safety Critical Functions In Airworthiness Certification, Jeffrey C. King

Theses and Dissertations

Modern aircraft are complex systems with numerous interacting hardware and software components. To minimize any safety mishaps during operations, new aircraft designs and modifications must go through an airworthiness certification. The current United States Air Force (USAF) airworthiness certification process, captured in MIL-HDBK-516C, is time-consuming and manpower intensive due to extensive documentation. To minimize inefficiencies of this document-based approach, this thesis examined model-based systems engineering (MBSE) to support Safety Critical Function (SCF) thread analysis against criteria found in Section 15 of MIL-HDBK-516C. Within this scope, the research identified an SCF domain-specific profile and style guide using the Systems Modeling Language …

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A Reference Architecture For Rapid Cubesat Development, Sean R. Kelly Mar 2021

A Reference Architecture For Rapid Cubesat Development, Sean R. Kelly

Theses and Dissertations

The CubeSat class of nanosatellites has lowered the barrier of entry to space and has rapidly gained popularity in recent years. To successfully design a CubeSat system in a rapid cycle conducive to academic timelines, a Reference Architecture geared towards University CubeSat development would be helpful. A Reference Architecture would speed up the development process by providing a template, capturing previous work and lessons learned from subject matter experts, providing a framework to focus on the CubeSats design rather than the fine details of modeling software. A Reference Architecture can also add functionality that student teams could use and improve …

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A State-Based Model For Validating Autonomous Munition Behaviors, Dalton J. Miller Mar 2021

A State-Based Model For Validating Autonomous Munition Behaviors, Dalton J. Miller

Theses and Dissertations

Autonomous munitions provide an opportunity for the Department of Defense (DoD) to extend the capabilities of operators in combat situations. However, there is also a need for a high level of trust in the effectiveness and accuracy of these systems. With the advent of model-based standards in autonomy and munitions, there is a need to implement these techniques toward an effective modeling and simulation (MS) capability. By leveraging modern MS tools such as Cameo Systems Modeler and the DoD's Advanced Framework for Simulation, Integration, and Modeling (AFSIM), this thesis proposes a framework for simulating complex autonomy architectures within high fidelity …

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Data- Driven Asset Degradation Modeling: An Enterprise-Wide Roof System Case Study, Kurt R. Lamm Mar 2021

Data- Driven Asset Degradation Modeling: An Enterprise-Wide Roof System Case Study, Kurt R. Lamm

Theses and Dissertations

Organizations with large facility and infrastructure portfolios have used asset management databases for over ten years to collect and standardize asset condition data. Decision makers use this data to predict asset degradation and expected service life, enabling prioritized maintenance, repair, and renovation actions that reduce asset life-cycle costs and achieve organizational objectives. However, these asset condition forecasts are calculated using standardized, self-correcting distribution models that rely on continuous functions. This research presents four step wise asset condition forecast models that utilize historical asset inspection data to improve prediction accuracy: (1) Slope, (2) Weighted Slope, (3) Condition-intelligent Weighted Slope, and (4) …

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A Decision-Support System For The Deployment Tasking Process Of U.S. Air Force Civil Engineer Officers, Kenneth A. Neal Mar 2021

A Decision-Support System For The Deployment Tasking Process Of U.S. Air Force Civil Engineer Officers, Kenneth A. Neal

Theses and Dissertations

The Armed Forces frequently deploy their personnel to expeditionary locations around the world. For example, the Air Force tasks its personnel to deploy based on a six-month rotational cycle. In the current tasking process, the deployment makes its way down from combatant commanders to squadron commanders through the chain of command. The commander then has a few days to select an individual from their unit to fill the tasking. The commander may consider an individuals’ dwell time, home-station position, and upcoming significant life events; however, because commanders have little time and information, minimum requirements selection criteria often become the driving …

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Decision Model For Additive Versus Conventional Construction In Remote Locations, Matthew R. Nicholson Mar 2021

Decision Model For Additive Versus Conventional Construction In Remote Locations, Matthew R. Nicholson

Theses and Dissertations

Additive construction is a potential game changing innovative alternative to conventional methods with regards to structural integrity, timeliness, and waste reduction, especially in remote locations. While there have been numerous studies into the material science, additive construction will not be a viable alternative until a cost analysis is performed. This paper details the cost elements for both methods. Breaking down the key variables of material, logistics and transportation, and labor costs garner a better understanding of the cost difference between the two construction methods.

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An Analysis Of Error Structure And Theoretical First Unit Cost In Learning Curve Theory Models, Alexander D. Pollack Mar 2021

An Analysis Of Error Structure And Theoretical First Unit Cost In Learning Curve Theory Models, Alexander D. Pollack

Theses and Dissertations

The dilemma with learning curves and actual costs is "fitting square pegs into round holes." Alternative regression techniques or further modifications to Y=aXb may address discrepancies in modeling observed data with learning curves. Adequate data permits further analysis of the constants, variables, and factors that make up a learning curve model. The analysis involves trying a nonlinear solver on the traditional learning curve models (i.e., Wright's cumulative average theory and Crawford's unit learning curve theory) and changing the theoretical first unit cost (T1) to the actual first unit cost (A1). Mergers and acquisitions in the aircraft industry may have …

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Comparison Of Decision Analysis Methods For A Cubesat Propulsion System, Jared L. Pilcher Mar 2021

Comparison Of Decision Analysis Methods For A Cubesat Propulsion System, Jared L. Pilcher

Theses and Dissertations

Low Earth Orbit (LEO) is becoming an increasingly congested orbital regime. As a result, propulsion systems on CubeSats are becoming a more desirable feature to provide them with collision avoidance capabilities. To date, there have been very few CubeSat launches with a propulsion system on them. Due to the relatively high cost of a propulsion system compared to the budget of small educational organizations, a decision analysis model is needed so that these organizations can make the best decision between whether to purchase a Commercial-Off-The-Shelf (COTS) product or to develop one within the organization. This research applies three decision analysis …

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Assessing The Effectiveness Of Afwerx Ability To Influence Regional Participation Rates And Capture Cluster Specific Technological Innovations, Colin M. Sandor Mar 2021

Assessing The Effectiveness Of Afwerx Ability To Influence Regional Participation Rates And Capture Cluster Specific Technological Innovations, Colin M. Sandor

Theses and Dissertations

The 2018 National Defense Strategy (NDS) emphasized capturing innovation through partnerships with non-traditional defense contractors. Furthermore, the NDS outlined the need to rapidly acquire new technologies to maintain a competitive advantage against our adversaries. The AFWERX program is the Air Forces attempt to accomplish these goals. AFWERX seeks to capture innovations occurring within the private sector of the United States by placing itself geographically within top innovation ecosystems. An approach that creates a setting where the Air Force is one of many investors, who benefit from the learning and investments across the entire network. The research within this paper examines …

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The Effect Of Molar Peroxide Ratio On The Oxidation Of Bisphenol A In An Ultraviolet Light Emitting Diode/Hydrogen Peroxide Advanced Oxidation Process, Megan C. Shade Mar 2021

The Effect Of Molar Peroxide Ratio On The Oxidation Of Bisphenol A In An Ultraviolet Light Emitting Diode/Hydrogen Peroxide Advanced Oxidation Process, Megan C. Shade

Theses and Dissertations

Bisphenol A is a compound widely used in industry that is detrimental to human health and ecological systems. Ultraviolet light emitting diodes and hydrogen peroxide can be combined t produces hydroxyl radicals. These highly reactive radicals have the potential to degrade contaminants in water. This research utilized 50, 100, 250, 500, and 1000:1 H2O2:BPA molar ratios for analysis. These results illustrated that the reactions at the 50, 100, and 250:1 ratios were hydrogenperoxide limited. The 1000:1 results exhibited evidence of radical scavenging that limited the degradation of BPA.

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Cubesat Development Framework, William D. Sousa Mar 2021

Cubesat Development Framework, William D. Sousa

Theses and Dissertations

AFITs Center for Space Research and Assurance (CSRA) has developed several small satellites without a detailed developmental framework in place but future work will focus on CubeSat development with the intent of managing multiple builds concurrently. With the goal of each satellite being completed in three years, a comprehensive process needs to be established. Research revealed that the Department of Defense (DoD), U.S. Air Force (USAF), and National Aeronautics and Space Administration (NASA) guidance on the acquisition and systems engineering processes require more reviews and deliverables than appropriate for CSRAs projects. The development processes from other universities divulge some aspects …

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Satellite Tracking With Neuromorphic Cameras For Space Domain Awareness, Joseph G. Bacon Jr. Mar 2021

Satellite Tracking With Neuromorphic Cameras For Space Domain Awareness, Joseph G. Bacon Jr.

Theses and Dissertations

A significant number of objects orbit the space around Earth. Each of these objects, be it debris, a functioning satellite, or even a staffed space station, circle the planet at extreme speeds relative to most objects on the Earth's surface. Any collision would result in disaster thanks to the extreme amount of kinetic energy involved. Space Domain Awareness (SDA) includes the detection, identification, cataloging, and tracking of orbiting objects to prevent such catastrophes. SDA is maintained in multiple ways to include radar, lidar, telescopes, and other sensors. This research investigates the maturing technology of neuromorphic cameras to determine their applicability …

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Design And Analysis Of Air-Stiffened Vacuum Lighter-Than-Air Structures, Ruben Adorno-Rodriguez Mar 2021

Design And Analysis Of Air-Stiffened Vacuum Lighter-Than-Air Structures, Ruben Adorno-Rodriguez

Theses and Dissertations

Lighter-than-air (LTA) systems have been developed for numerous applications and have taken several forms. Airships, aerostats, blimps, and balloons are all part of this family of systems, which uses Archimedes principle to achieve neutral and positive buoyancy in air by replacing an air volume with LTA gases. These lifting gases stiffen the otherwise compliant envelope structures, allowing them to sustain the pressure difference brought by the displaced air. The compliance of these structures is a byproduct of the weight requirement, materials and geometrical arrangement of which these structures are built from, typically resulting in dimensionalities that exhibit low or virtually …

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Cubesat Attitude Determination And Control System (Adacs) Characterization And Testing For Rendezvous And Proximity Operations (Rpo), Steven T. Bednarski Mar 2021

Cubesat Attitude Determination And Control System (Adacs) Characterization And Testing For Rendezvous And Proximity Operations (Rpo), Steven T. Bednarski

Theses and Dissertations

This research endeavors to evaluate and characterize the performance of CubeSat specific commercial-off-the-shelf (COTS) Attitude Determination and Control Systems (ADACS) for Mission suitability. To ensure COTS components are capable of meeting CubeSat mission requirements, deliberate performance testing of critical CubeSat subsystems in flight-like conditions is essential. This effort focuses on testing the MAI-401 ADACS subsystem as configured to support the Grissom-1 CubeSat mission, as mounted to an air bearing, residing within a 3-axis Helmholtz Cage, and subjected to a simulated magnetic environment of various orbital parameters.

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Applied Reachability Analysis For Time-Optimal Spacecraft Attitude Reorientations, Layne C. Barrett Mar 2021

Applied Reachability Analysis For Time-Optimal Spacecraft Attitude Reorientations, Layne C. Barrett

Theses and Dissertations

Satellite attitude reorientation has been of significant interest in astronautical engineering, and being able to reorient in a time-optimal manner has been of exceeding interest since the 1970s. Ensuring a spacecraft mission set can be conducted within a certain amount of time begs the question of whether or not a certain maneuver can be completed with a bounded control. This thesis answers that question by using the concept of reachability to provide reachable sets for different spacecraft reorientation scenarios. The reachable sets generated provide a range of initial states that guarantee a satellite reach a desired end orientation given a …

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Cislunar Debris Propagation Following A Catastrophic Spacecraft Mishap, Nathan R. Boone Mar 2021

Cislunar Debris Propagation Following A Catastrophic Spacecraft Mishap, Nathan R. Boone

Theses and Dissertations

This research involves theoretical analysis of the short- and long-term motion of space debris in cislunar trajectories following a spacecraft catastrophic mishap. Specifically, the research formulates a debris propagation model using four-body dynamics and determines debris trajectories following breakup events for a variety of different initial orbital positions. A spacecraft survivability model is then used to quantify the risks from the debris to other cislunar spacecraft. First, a study of the risks due to natural debris comprising the Kordylewski clouds at the Earth-Moon ��4 and ��5 Lagrange points is conducted as an introduction to cislunar debris propagation. Next, …

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Scaling Gas Turbine Film Cooling Adiabatic Effectiveness Through Simultaneous Matching Of Momentum Flux Ratio And Advective Capacity Ratio, Evan C. Glowiak Mar 2021

Scaling Gas Turbine Film Cooling Adiabatic Effectiveness Through Simultaneous Matching Of Momentum Flux Ratio And Advective Capacity Ratio, Evan C. Glowiak

Theses and Dissertations

The study of gas turbine engine performance improvement requires extracting usable work from the hot section turbine. To prevent heat damage to turbine blades, film cooling is employed. Low temperature tests are conducted at ambient pressure on scale models to analyze the effects of gas flow parameters on scaling adiabatic effectiveness at easily repeatable conditions. This research aims to determine how matching coolant flow rate parameters Momentum Flux Ratio (I) and Advective Capacity Ratio (ACR) can scale adiabatic effectiveness on flat plate and leading edge geometries between air and carbon dioxide gas. Results indicate improvement in scaling adiabatic effectiveness when …

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A Reduced Order Model Of The Celestial Icosahedron As The Substructure For A Lighter Than Air Vehicle, Torin C. Quick Mar 2021

A Reduced Order Model Of The Celestial Icosahedron As The Substructure For A Lighter Than Air Vehicle, Torin C. Quick

Theses and Dissertations

A finite element approach was used to investigate a novel reduced order model to determine the minimum structure dimensionality to support vacuum for a VLTAV. This modeling technique represented the individual segments of the substructure as curved beams with clamped radially-resisted boundary conditions. The full structure was then modeled as a bare structure and structure with skin to validate the results of the reduced order model. The beam geometry for the material Ultem 9085 was determined through this process leading to the 3-D printing of the structure. It was then experimentally tested under uniaxial compression complimented with a FEA model.

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Safe Spacecraft Rendezvous And Proximity Operations Via Reachability Analysis, Paul A. Grossi Mar 2021

Safe Spacecraft Rendezvous And Proximity Operations Via Reachability Analysis, Paul A. Grossi

Theses and Dissertations

The rapid expansion of the utilization of space by nations and industry has presented new challenges and opportunities to operate efficiently and responsibly. Reachability analysis is the process of computing the set of states that can be reached given all admissible controls and can be a valuable component in an autonomous mission planning system if conducted efficiently. In the current research, reachability analysis is used with several relative motion models to show that all ranges of orbits can be computed in milliseconds, and that it is a feasible approach for on-board autonomous mission planning. Reachability analysis is then combined with …

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Hybridized Spacecraft Attitude Control Via Reinforcement Learning Using Control Moment Gyroscope Arrays, Cecily C. Agu Mar 2021

Hybridized Spacecraft Attitude Control Via Reinforcement Learning Using Control Moment Gyroscope Arrays, Cecily C. Agu

Theses and Dissertations

Machine learning techniques in the form of reinforcement learning (RL) can solve complex nonlinear problems found within spacecraft attitude determination and control systems (ADCS). Three CMG arrays were implemented in two simulated spacecraft environments using a reinforcement learning controller. The performance of the controllers were evaluated using target profiles from traditional control law implementations, singularity measure, and variable initial state values. The current research demonstrates that while RL techniques can be implemented, further exploration is needed to investigate the operational efficacy of an approach for producing comparable performance attributes with respect to traditional control laws.

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Static Fatigue Of Hi-Nicalon S Fiber Tows At 500°C In Air And In Silicic Acid-Saturated Steam, Richard J. Reinink Mar 2021

Static Fatigue Of Hi-Nicalon S Fiber Tows At 500°C In Air And In Silicic Acid-Saturated Steam, Richard J. Reinink

Theses and Dissertations

Recent developments in aerospace propulsion systems, along with emerging interest in hypersonic air vehicles has emphasized the need for materials which can withstand extreme service environments. The leading candidates for the structural components expected to operate in these environments are SiC-based ceramic matrix composites (CMCs). When a CMC component is subjected to thermomechanical loads in an aggressive environment during service, surface cracks form. As steam penetrates cracks in the SiC matrix, it becomes saturated with silicic acid, (SI(OH)4) and attacks the SiC fibers. The interaction between the Hi-Nicalon™ S SiC fibers and the (SI(OH)4)-saturated steam is …

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Shock Migration On An Oscillating Straked Delta Wing Using An Unsteady Euler Solver, Alexander J. Brown Mar 2021

Shock Migration On An Oscillating Straked Delta Wing Using An Unsteady Euler Solver, Alexander J. Brown

Theses and Dissertations

This research contributes to the understanding of Shock Induced Trailing Edge Separation (SITES) as a driver of Limit Cycle Oscillation (LCO) by performing a computational investigation of nonlinear aerodynamic phenomena on a straked delta wing in transonic flow, oscillating in pitch. ZEUS, an Euler-based aeroelastic solver with a boundary layer coupling scheme meant to capture viscous flow effects within the boundary layer, was used to analyze aerodynamic flow around the wing for various mean incidence angles, oscillation amplitudes, and Mach numbers within the transonic region. The dynamic characteristics of the airflow around the wing were investigated in order to characterize …

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Optimizing Design Parameters For Active Flow Control Boundary-Layer Fence Performance Enhancement On A Delta Wing, Nathan L. Tedder Mar 2021

Optimizing Design Parameters For Active Flow Control Boundary-Layer Fence Performance Enhancement On A Delta Wing, Nathan L. Tedder

Theses and Dissertations

Utilizing computational fluid dynamic (CFD) simulations, the presented study is able to further the investigation of replicating and improving upon the performance of a NACA 0012 cropped half-span delta-wing at high angles-of-attack with an active flow control fluidic fence via wall-normal, steady blowing from an optimized single chordwise slot located at z/b = 70%,. The data is generated using CREATE-AV Kestrel v10.1rc5 CFD software on the Department of Defense High Performance Computing systems. The flight regime is held constant at a Mach number of 0.18 and a Reynolds number (Re) of 5.0 x 105, based on the root …

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A Survey Of The Strategic Alternate Sourcing Program Offices Management Of United States Air Force Diminishing Manufacturing Sources And Material Shortages Subject Matter Experts, David E. Portée Mar 2021

A Survey Of The Strategic Alternate Sourcing Program Offices Management Of United States Air Force Diminishing Manufacturing Sources And Material Shortages Subject Matter Experts, David E. Portée

Theses and Dissertations

The office designated by the Air Force to be DMSMS subject expert program office is known as the Strategic Alternate Sourcing Program Office (SASPO). Aided by the USAF Program Offices and DMSMS Subject Matter Experts, the SASPO is responsible for sourcing DMSMS resolutions as well as the organizing, training, and equipping of the Program Offices DMSMS Programs. Using quantitative research, this study conducts a survey, with the USAF Program Offices as the unit of analysis, to gain insight as to where the SASPO is doing well and where gaps exist in their program management. The analysis and conclusion identify where …

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Simulating A Mobile Wireless Sensor Network Monitoring The Air Force Marathon, Matthew D. Eilertson Mar 2021

Simulating A Mobile Wireless Sensor Network Monitoring The Air Force Marathon, Matthew D. Eilertson

Theses and Dissertations

This thesis explores the feasibility of deploying a mobile Wireless Sensor Networks (WSN) to the Air Force (AF) Marathon in support of Air Force Research Laboratory (AFRL) research of sensor and networking infrastructure in denied or degraded environments. A simulation called MarathonSim is developed in the Objective Modular Network Testbed in C++ (OMNeT++) Discrete Event Simulator to test the performance of a mobile WSN. A full factorial design using numbers of runners, transmission powers, and routing protocols is executed to measure Packet Delivery Ratio (PDR) to a central database, average end-to-end delay of application packets, and average power consumed per …

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Performance Analysis Of Long-Term Evoluution Signals In Passive Bistatic Radar Applications Using Reduced Dimension Space-Time Adaptive Processing Techniques, Sureshan Suntharalingam Mar 2021

Performance Analysis Of Long-Term Evoluution Signals In Passive Bistatic Radar Applications Using Reduced Dimension Space-Time Adaptive Processing Techniques, Sureshan Suntharalingam

Theses and Dissertations

Widespread availability of long term evolution (LTE) signals makes them potential for use in passive bistatic radar (PBR) applications. However, their utility in such applications is yet to be fully explored. This research focuses on the key LTE signal attributes, such as subcarrier modulation schemes and bandwidth, and their effect on PBR application. space-time adaptive processing (STAP) concepts, both full dimension STAP (FD-STAP) reduced dimension STAP (RD-STAP), were employed to evaluate and compare the effects of varying these signal attributes, in terms of signal to interference-plus-noise ratio (SINR) loss metrics. Simulation results concluded that decreasing LTE signal's bandwidth and increasing …

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Remote Monitoring Of Memory Data Structures For Malware Detection In A Talos Ii Architecture, Robert A. Willburn Mar 2021

Remote Monitoring Of Memory Data Structures For Malware Detection In A Talos Ii Architecture, Robert A. Willburn

Theses and Dissertations

New forms of malware, namely xC;leless malware and rootkits, pose a threat to traditional anti-malware. In particular, Rootkits have the capacity to obscure the present state of memory from the user space of a target machine. If thishappens, anti-malware running in the user space of an axB;ected machine cannot be trusted to operate properly. To combat this threat, this research proposes the remote monitoring of memory from a second, secure processor runningOpenBMC, serving as a baseboard management controller for a POWER9 processor, which is assumed vulnerable to exploitation. The baseboard management controller includes an application called pdbg, used for debugging …

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The Impact Of Threat Levels At The Casualty Collection Point On Military Medical Evacuation System Performance, Nathaniel C. Dennie Mar 2021

The Impact Of Threat Levels At The Casualty Collection Point On Military Medical Evacuation System Performance, Nathaniel C. Dennie

Theses and Dissertations

One of the primary duties of the Military Health System is to provide effective and efficient medical evacuation (MEDEVAC) to injured battlefield personnel. To accomplish this, military medical planners seek to develop high-quality dispatching policies that dictate how deployed MEDEVAC assets are utilized throughout combat operations. This thesis seeks to determine dispatching policies that improve the performance of the MEDEVAC system. A discounted, infinite-horizon continuous-time Markov decision process (MDP) model is developed to examine the MEDEVAC dispatching problem. The model incorporates problem features that are not considered under the current dispatching policy (e.g., myopic policy), which tasks the closest-available MEDEVAC …

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Using Motion Capture And Augmented Reality To Test Aar With Boom Occlusion, Vincent J. Bownes Mar 2021

Using Motion Capture And Augmented Reality To Test Aar With Boom Occlusion, Vincent J. Bownes

Theses and Dissertations

The operational capability of drones is limited by their inability to perform aerial refueling. This can be overcome by automating the process with a computer vision solution. Previous work has demonstrated the feasibility of automated aerial refueling (AAR) in simulation. To progress this technique to the real world, this thesis conducts experiments using real images of a physical aircraft replica and a motion capture system for truth data. It also compares the error between the real and virtual experiments to validate the fidelity of the simulation. Results indicate that the current technique is effective on real images and that the …

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