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Articles 60721 - 60750 of 197987

Full-Text Articles in Engineering

Pedestrian Navigation Using Artificial Neural Networks And Classical Filtering Techniques, David J. Ellis Mar 2020

Pedestrian Navigation Using Artificial Neural Networks And Classical Filtering Techniques, David J. Ellis

Theses and Dissertations

The objective of this thesis is to explore the improvements achieved through using classical filtering methods with Artificial Neural Network (ANN) for pedestrian navigation techniques. ANN have been improving dramatically in their ability to approximate various functions. These neural network solutions have been able to surpass many classical navigation techniques. However, research using ANN to solve problems appears to be solely focused on the ability of neural networks alone. The combination of ANN with classical filtering methods has the potential to bring beneficial aspects of both techniques to increase accuracy in many different applications. Pedestrian navigation is used as a …

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Effects Of Long-Term Evolution Waveform On Synthetic Aperture Radar Image Quality Metrics, Blake M. Colson Mar 2020

Effects Of Long-Term Evolution Waveform On Synthetic Aperture Radar Image Quality Metrics, Blake M. Colson

Theses and Dissertations

As a greater demand by the private sector for bandwidth drives spectrum allocations away from defense, new methods for coexistence in the spectrum are being explored. One of the prominent areas in defense for this coexistence is passive radar. This mode of radar system allows for data collection by referencing signals already established in the environment of interest. Some of the most prolific signals currently available are those used for mobile communication networks. In particular, Long- Term Evolution (LTE) is a common waveform that could be leveraged for discrete collection of image intelligence. Seeking to build a base of knowledge, …

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Use Of Lidar In Automated Aerial Refueling To Improve Stereo Vision Systems, Michael R. Crowl Mar 2020

Use Of Lidar In Automated Aerial Refueling To Improve Stereo Vision Systems, Michael R. Crowl

Theses and Dissertations

The United States Air Force (USAF) executes five Core Missions, four of which depend on increased aircraft range. To better achieve global strike and reconnaissance, unmanned aerial vehicles (UAVs) require aerial refueling for extended missions. However, current aerial refueling capabilities are limited to manned aircraft due to technical difficulties to refuel UAVs mid-flight. The latency between a UAV operator and the UAV is too large to adequately respond for such an operation. To overcome this limitation, the USAF wants to create a capability to guide the refueling boom into the refueling receptacle. This research explores the use of light detection …

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The Design Of A Continuous Wave Molecular Nitrogen Stimulated Raman Laser In The Visible Spectrum, Timothy J. Bate Mar 2020

The Design Of A Continuous Wave Molecular Nitrogen Stimulated Raman Laser In The Visible Spectrum, Timothy J. Bate

Theses and Dissertations

Hollow-core photonic crystal fibers (HCPCFs) shows promise as a hybrid laser with higher nonlinear process limits and small beam size over long gain lengths. This work focuses on the design of a CW molecular nitrogen (N2) stimulated Raman laser. N2 offers Raman gains scaling up to 900 amg, scaling higher than H2. The cavity experiment showed the need to include Rayleigh scattering in the high pressure required for N2 Raman lasing. Even at relatively low pressure ssuch as 1,500 psi, high conversion percentages should be found if the fiber length is chosen based on …

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Laser Induced Thermal Degradation Of Carbon Fiber-Carbon Nanotube Hybrid Laminates, Joshua A. Key Mar 2020

Laser Induced Thermal Degradation Of Carbon Fiber-Carbon Nanotube Hybrid Laminates, Joshua A. Key

Theses and Dissertations

Recent advancements in fiber laser technology have increased interest in target material interactions and the development of thermal protection layers for tactical laser defense. A significant material of interest is carbon fiber reinforced polymers due to their increased use in aircraft construction. In this work, the thermal response of carbon fiber-carbon nanotube (CNT) hybrid composites exposed to average irradiances of 0.87-6.8 W/cm2 were observed using a FLIR sc6900 thermal camera. The camera had a pixel resolution of 640x512 which resulted in a spatial resolution of 0.394x0.383 mm/pixel for the front and 0.463x0.491 mm/pixel for the back. The hybrid samples …

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Simulation Of Sporadic-E Parameters Using Phase Screen Method, Daniel W. Stambovsky Mar 2020

Simulation Of Sporadic-E Parameters Using Phase Screen Method, Daniel W. Stambovsky

Theses and Dissertations

A phase screen simulation experiment is designed and implemented to model radio occultation through sporadic-E ionospheric disturbances between a GPS transmitter operating at the L1 frequency and a second receiving satellite in low earth orbit (LEO). Simulations were made to test the linear relationship between plasma intensity and scintillation S4 index both posited (Arras and Wickert, 2018) and contended (Gooch et al., 2020) in previous literature. Results brought into question both the linear relationship and the use of S4 as a whole and an alternate metric was sought.

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Hybrid Tri-Objective Optimization Of F-15 Fleet Modernization Scheduling, Richard S. Danaher Mar 2020

Hybrid Tri-Objective Optimization Of F-15 Fleet Modernization Scheduling, Richard S. Danaher

Theses and Dissertations

The F-15 weapons system is vital to the Air Forces efforts to obtain air supremacy during conflict. Originally produced almost 50 years ago, technological advancement through systems modifications is necessary to ensure the Eagles lethality and survivability against next-generation adversarial threats. The F-15 Systems Program Office faces challenges to plan aircraft inductions for five fleet modernization programs. Optimal induction schedules are developed using binary-integer linear programming models. Diverse constraints such as manpower, equipment, modification kit availability, minimum operational flight levels, and integration of scheduled depot maintenance reveal that no feasible schedule exists. Two competing objectives representing the value of fully …

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Inherent Jeopardy Of Performance Based Contracting Metrics: A Simulation Experiment, Daniel Cherobini Mar 2020

Inherent Jeopardy Of Performance Based Contracting Metrics: A Simulation Experiment, Daniel Cherobini

Theses and Dissertations

There is a growing trend across the world to adopt Performance Based Contracting strategies to support logistics systems. Using these policies, contract payments are strongly related to the performance achieved compared to prespecified metrics. However, managers are not always confident on what are the most suitable performance goals to use in these agreements. As a consequence, contractors struggle to deliver the desired performance results, while aircraft fleets experience an increase in support costs. And when the results are inadequate, leaders are tempted to impose even more performance targets to contractors, willing to exercise more control over the support organization. In …

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Microturbine Turbojets: Experimental Evaluation Of Commercially Available Engines, Richard A. Depaola Iii Mar 2020

Microturbine Turbojets: Experimental Evaluation Of Commercially Available Engines, Richard A. Depaola Iii

Theses and Dissertations

This research assessed the performance of commercial microturbine turbojets and was the first industry-wide investigation into this class of engine by AFRL's SERL. Four commercial engines of the same thrust class were evaluated for overall and component-level performance. In addition to providing an evaluation of existing systems, the maximum performance for a commercial turbojet was predicted based on component evaluations. This analysis indicated that a commercial turbojet could have comparable thrust performance to a similarly sized military-grade engine, but it is unlikely that commercial engines can achieve the SFC of military engines without upgrading the compressors found in commercial microturbines.

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Cn And C2 Spectroscopy On The Pulsed Ablation Of Graphite In The Visible Spectrum, Brandon A. Pierce Mar 2020

Cn And C2 Spectroscopy On The Pulsed Ablation Of Graphite In The Visible Spectrum, Brandon A. Pierce

Theses and Dissertations

An experimental study was conducted on the nanosecond pulsed laser ablation of graphite using a KrF laser at a fluence of 3.8 J/cm2 in Air, Ar, He, and N2. Optical emissions spectroscopy revealed the C2 Swan sequences and the CN Violet sequences. A spectroscopic model was developed to extract the molecular rotational and vibrational temperatures of each excited species for t=0.5-10 microseconds after laser irradiation. The rovibrational temperatures were found to vary with background gas for the CN Violet; however, only the vibrational temperature varied between He and the other background gases for C2 Swan. …

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Wireless Sensor Network Optimization For Radio Tomographic Imaging, Grant T. Nafziger Mar 2020

Wireless Sensor Network Optimization For Radio Tomographic Imaging, Grant T. Nafziger

Theses and Dissertations

Radio tomographic imaging (RTI) is a form of device-free, passive localization (DFPL) that uses a wireless sensor network (WSN) typically made up of affordable, low-power transceivers. The intent for RTI is to have the ability to monitor a given area, localizing and tracking obstructions within. The specific advantages rendered by RTI include the ability to provide imaging, localization, and tracking where other well developed methods like optical surveillance fall short. RTI can function through optical obstructions such as smoke and even physical obstructions like walls. This provides a tool that is particularly valuable for tactical operations like emergency response and …

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Design, Development, And Testing Of A Low Cost, Additively-Manufactured, Centrifugal Compressor, Aaron P. Bauer Mar 2020

Design, Development, And Testing Of A Low Cost, Additively-Manufactured, Centrifugal Compressor, Aaron P. Bauer

Theses and Dissertations

The three objectives of this research were to: 1.) design, build, and test AM compressors to substitute into COTS micro-gas turbine engines, 2.) provide initial correlations between FEA and compressor failure speed, and 3.) characterize the effects of AM on compressor performance. These goals improved the design cycle cost and the design-validation time cycle. ULTEM 9085, 300-AMB, and Onyx-Kevlar temperature-dependent tensile properties were measured. FEA-predicted failure speeds of stock compressor designs led design improvements, potentially fulfilling the original compressor requirements. Physical testing of the stock and ULTEM 9085 compressors occurred. Comparing these compressors' performances demonstrated that low cost, AM materials …

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Design And Analysis Of A Compact Combustor For Integration With A Jetcat P90 Rxi, Daniel Holobeny Mar 2020

Design And Analysis Of A Compact Combustor For Integration With A Jetcat P90 Rxi, Daniel Holobeny

Theses and Dissertations

Ultra Compact Combustors are a novel approach to modern gas turbine combustor designs that look to reduce the overall combustor length and weight. A previous study integrated an Ultra Compact Combustor into a JetCat P90 RXi turbine engine and achieved self-sustained operation with a length savings of 33% relative to the stock combustor. However, that combustor could not operate across the full stock engine performance range due to flameout at increased mass ow rates as reactions were pushed out of the primary zone. To ensure reactions stayed in the primary zone, a new design with a larger combustor volume was …

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Modeling Hybrid Composites Using Tsai-Wu And Hashin Failure Criterion, Candice R. Roberts Mar 2020

Modeling Hybrid Composites Using Tsai-Wu And Hashin Failure Criterion, Candice R. Roberts

Theses and Dissertations

Hybrid composites require further study and testing for future use in various fields. This study focuses on simulating a Hybrid Composite using IM7-977-3 laminae with steel foils in Abaqus under bolt loading by using Hashin and Tsai-Wu failure criterion. Initial simulations contain only the IM7-977-3 composite with cohesive layers. Foil samples were then tested for accurate material properties from which the simulations were then updated to include steel foils. The two models show that Tsai-Wu failure criterion, while great for anisotropic material in tension, does not prove accuracy around the hole of the composite material which is in compression. Hashin …

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Design And Analysis Of A Disk-Oriented Engine Combustor, Bennett M. Staton Mar 2020

Design And Analysis Of A Disk-Oriented Engine Combustor, Bennett M. Staton

Theses and Dissertations

In a novel approach to gas-turbine power production, an engine was designed and analyzed to use both a single-stage centrifugal compressor and single-stage radial in- ow turbine configured back-to-back. This air path reduced the axial length of the engine up to 60%, providing additional modularity in a gas-turbine engine that could be used to improve mobility of ground-based power units or increase the survivability of aircraft through the use of distributive propulsion. This increased modularity was made possible by the use of a circumferential ow combustor that substantially decreased the axial length of the burner and negated the need to …

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Fatigue Behavior Of An Advanced Melt-Infiltrated Sic/Sic Composite With Environmental Barrier Coating At 1200°C In Air And In Steam, Thaddeus M. Williams Mar 2020

Fatigue Behavior Of An Advanced Melt-Infiltrated Sic/Sic Composite With Environmental Barrier Coating At 1200°C In Air And In Steam, Thaddeus M. Williams

Theses and Dissertations

Advanced aerospace applications such as aircraft turbine engine components, hypersonic flight vehicles, and spacecraft reentry thermal protection systems require structural materials that have superior long-term mechanical properties under high temperature, high pressure, and varying environmental factors, such as moisture. Because of their low density, high strength and fracture toughness at high temperatures SiC fiber-reinforced SiC matrix composites are being evaluated for aircraft engine hot-section components. In these applications the composites will be subjected to various types of mechanical loadings at elevated temperatures in oxidizing environments. Because their constituents are intrinsically oxidation-prone, the most significant problem hindering SiC/SiC composites is oxidation …

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Development Of A Drone-Mounted Wireless Attack Platform, Nathan V. Barker Mar 2020

Development Of A Drone-Mounted Wireless Attack Platform, Nathan V. Barker

Theses and Dissertations

The commercial drone market has grown rapidly due to the increasing utility and capabilities of drones. This new found popularity has made it possible for inexpensive drones capable of impressive carry capacities and flight times to reach the consumer market. These new features also offer an invaluable resource to wireless hackers. Capitalizing on their mobility, a wireless hacker can equip a drone with hacking tools to surpass physical security (e.g. fences) with relative ease and reach wireless networks. This research seeks to experimentally evaluate the ability of a drone-mounted wireless attack platform equipped with a directional antenna to conduct wireless …

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Human Performance Modeling: Analysis Of The Effects Of Manned-Unmanned Teaming On Pilot Workload And Mission Performance, Jinan M. Andrews Mar 2020

Human Performance Modeling: Analysis Of The Effects Of Manned-Unmanned Teaming On Pilot Workload And Mission Performance, Jinan M. Andrews

Theses and Dissertations

Due to the advent of autonomous technology coupled with the extreme expense of manned aircraft, the Department of Defense (DoD) has increased interest in developing affordable, expendable Unmanned Aerial Vehicles (UAVs) to become autonomous wingmen for jet fighters in mosaic warfare. Like a mosaic that forms a whole picture out of smaller pieces, battlefield commanders can utilize disaggregated capabilities, such as Manned-Unmanned Teaming (MUM-T), to operate in contested environments. With a single pilot controlling both the UAVs and manned aircraft, it may be challenging for pilots to manage all systems should the system design not be conducive to a steady …

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A Life-Cycle Analysis Of The Thermal Energy Transfer In Prototypical Air Force Office Building Construction Using Best Value Insulation Standards, Michael E. Canfield Mar 2020

A Life-Cycle Analysis Of The Thermal Energy Transfer In Prototypical Air Force Office Building Construction Using Best Value Insulation Standards, Michael E. Canfield

Theses and Dissertations

The United States Department of Defense (DoD) possesses over 560,000 buildings and structures around the world which require electricity to maintain and operate. The energy costs associated with the operations of these building is approximately $4 billion per year. Sustainable infrastructure management is a crucial opportunity to improve and establish a prudent, manageable, and successful DoD budget. This research identified, modeled, and simulated thermal energy-efficient standards in building construction in order to recognize the best value standards as opportunities for potential cost savings. EnergyPlus and OpenStudio Building Performance Simulation (BPS) software was used to model the energy flow into and …

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The Effects Of Funding Gaps On Depot Maintenance Hours, Carlo S. D'Amato Mar 2020

The Effects Of Funding Gaps On Depot Maintenance Hours, Carlo S. D'Amato

Theses and Dissertations

The relationship between expenditures and readiness level is a topic of interest to military senior leaders, defense resource planners, and the American taxpayer alike. Senior leaders within the Air Force (AF) justify increased defense budgets by pointing to the potential adverse effects that decreased funding could have on military readiness. Resource planners within the AF are then tasked with the responsibility of ensuring that budgets are allocated most effectively to maximize the AF's ability to project airpower across a variety of contingency operations. This thesis investigates the relationship between budgets and readiness by examining the relationship between depot level funding …

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Vote Forecasting Using Multi-Objective Decision Analysis, Connor G. Crandall Mar 2020

Vote Forecasting Using Multi-Objective Decision Analysis, Connor G. Crandall

Theses and Dissertations

In December 2018, the United States Federal Government began what would become the longest government shutdown in U.S. history. This was the 21st shutdown since the adoption of the current appropriations process and 4th of the last decade. These shutdowns occur after government departments and agencies submit budget requests to Congress and the legislature is unable to come to an agreement to pass an appropriations bill. There is no clear solution to this problem. But this study hypothesizes that government departments and agencies could benefit from considering the political viability of their own budget requests prior to submitting them to …

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A Reference Architecture For Cubesat Development, Luke J. Farrell Mar 2020

A Reference Architecture For Cubesat Development, Luke J. Farrell

Theses and Dissertations

Developing a space vehicle is a complex and detailed process, and while CubeSats are smaller and more accessible than traditional satellites the design process is relatively unchanged. Creating a viable space vehicle design requires detailed analysis of a set of mission needs in order to define the mission, with this need set used to then create the specific mission requirements. These requirements are used to formulate a concept of operations, and then move into developing a physical system for executing the mission. The successful production of CubeSats within an organization is contingent upon the accurate execution of the general CubeSat …

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Investigating Lifecycle Costs Of Optimized Battery-Photovoltaic Systems On A Forward Operating Base, Neal S. Fennell Mar 2020

Investigating Lifecycle Costs Of Optimized Battery-Photovoltaic Systems On A Forward Operating Base, Neal S. Fennell

Theses and Dissertations

The purpose of this research was to investigate the total life-cycle cost of using utility-scale battery systems to increase the energy efficiency of forward operating bases, thereby reducing the burden of diesel fuel logistics. Specifically, this thesis answered three research questions addressing optimal sizing for various battery types connected with photovoltaic grids, logistical parameters directly impacting total cost, and the cost of increasing the energy resilience of the network. The research questions were answered through a review of literature, modeling, and data analysis. The model determines an optimal size and area for a Vanadium redox flow, Lithium-ion, or Lead-acid battery …

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Preliminary Study Of Communication Network Characterization Towards Improved Organizational Behavior, Taylor F. Flaxington Mar 2020

Preliminary Study Of Communication Network Characterization Towards Improved Organizational Behavior, Taylor F. Flaxington

Theses and Dissertations

Nearly one third of the Air Force acquisition system’s large programs are over cost and half are over budget; performance must improve. This research applies a systems perspective to this challenge and frames the acquisition system as a complex system of systems. It is a system composed of people in multiple organizations; organizations interacting with one another to develop, acquire and sustain weapon programs. The system’s performance is an emergent behavior of its components (people), structure and processes. Communication networks are a view of a system’s structure, revealing the flows and interactions between components (people) as the system accomplishes its …

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A Comparison Of Sbir Investment Methods: Afwerx Vs Legacy, Evan A. Gist Mar 2020

A Comparison Of Sbir Investment Methods: Afwerx Vs Legacy, Evan A. Gist

Theses and Dissertations

The AFWERX Open Topic (AOT) program uses funding from the United States Air Force’s (USAF) Small Business Innovation and Research (SBIR) budget to adapt commercial technology to USAF needs. The AOT approach to small business investment is markedly different from that of legacy SBIR investment methods. This research is a comparison of processes and outcomes for AOT and legacy SBIR. The first axis of comparison is on commercialization rates. Applying a legacy definition of commercialization on a sample of AOT contracts, we found AOT’s commercialization to be 37% (compared to an 8.8% for legacy SBIR). We caveat this finding by …

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Trade-Space Analysis Of A Small Unmanned Vehicle System For Radiological Search Missions, Sam B. Harriger Mar 2020

Trade-Space Analysis Of A Small Unmanned Vehicle System For Radiological Search Missions, Sam B. Harriger

Theses and Dissertations

Nuclear and radiological terrorism is a persistent threat to United States national security. The research and development of new technological capabilities is vital to bolstering emergency response and prevention capabilities in support of national security initiatives. This research characterized the applicable trade-space for a system of unmanned vehicles deployed for search, detection, and identification of radiological source material. Exploration included the development of a CONOPS, a functional decomposition and physical allocation, design considerations, and an analysis of feasibility and utility. The concept system comprises of a ground control station, ground vehicle, hybrid-electric multirotor, and fixed-wing vehicle with an open architecture …

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Civil Engineer Company Grade Officer Competency-Based Education Modeling, Scott R. Guerin Mar 2020

Civil Engineer Company Grade Officer Competency-Based Education Modeling, Scott R. Guerin

Theses and Dissertations

The importance of continuing education for professionals cannot be understated. This importance is doubly true for Air Force Civil Engineer Company Grade Officers who are members of not only the profession of engineering, but also the profession of arms. Air Force senior leaders understand this importance and required an update to the existing developmental education model, with a paradigm shift toward competency-based education and credentialing. Unfortunately, the Air Force Civil Engineer career field does not currently possess the required information to create a model in compliance with the senior leader directives. This research aims at establishing the required characteristics of …

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An Analysis Of The Viability Of 3d-Printed Construction As An Alternative To Conventional Construction Methods In The Expeditionary Environment, Jeneé A. Jagoda Mar 2020

An Analysis Of The Viability Of 3d-Printed Construction As An Alternative To Conventional Construction Methods In The Expeditionary Environment, Jeneé A. Jagoda

Theses and Dissertations

Conventional construction is believed by some to have reached its technological limit of performance, making it increasingly difficult for conventional construction methods to meet the U.S. military’s core standards of quality, cost, and timeliness in the expeditionary environment. While still in its infancy, 3D-printed construction has the potential to revolutionize the way the military performs construction in deployed environments. This research conducts a systematic review of the viability of 3D-printed construction to investigate whether or not it is now or could be a viable replacement for conventional construction methods, specifically in remote environments where conventional construction capability may be limited. …

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Evaluation Framework For Cislunar Space Domain Awareness (Sda) Systems, Simon R. Knister Mar 2020

Evaluation Framework For Cislunar Space Domain Awareness (Sda) Systems, Simon R. Knister

Theses and Dissertations

Modern space missions are increasingly transiting cislunar space, requiring expansion of existing Space Traffic Management (STM) functions. Legacy Space Domain Awareness (SDA) systems were not purpose-built to detect and track cislunar objects, which could require acquisition of a new system of systems. There are numerous parameters that could be varied for each system, as well as the type and location of systems across the architecture. This research attempts to solve this problem by applying a model-based systems engineering (MBSE) approach to assess the performance and financial burden of a given system of systems. Fitness metrics are developed based upon the …

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The Impact Of Changing The Size Of Aircraft Radar Displays On Visual Search In The Cockpit, Justin R. Marsh Mar 2020

The Impact Of Changing The Size Of Aircraft Radar Displays On Visual Search In The Cockpit, Justin R. Marsh

Theses and Dissertations

Advances in sensor technology have enabled our fighter aircraft to find, fix, track, target, engage (F2T2E) at greater distances, providing the operator with more data within the battlefield. Modern aircraft are designed with larger displays while our legacy aircraft are being retrofitted with larger cockpit displays to enable display of the increased data. While this modification has been shown to enable improvements in human performance of many cockpit tasks, this effect is often not measured nor fully understood at a more generalizable level. This research outlines an approach to comparing human performance across two display sizes in future F-16 cockpits. …

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