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Air Force Institute of Technology

2015

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Articles 1 - 30 of 151

Full-Text Articles in Engineering

Optimal Attitude Control Of Agile Spacecraft Using Combined Reaction Wheel And Control Moment Gyroscope Arrays, Cole C. Doupe Dec 2015

Optimal Attitude Control Of Agile Spacecraft Using Combined Reaction Wheel And Control Moment Gyroscope Arrays, Cole C. Doupe

Theses and Dissertations

This dissertation explores the benefits of combined control moment gyroscope (CMG) and reaction wheel array (RWA) actuation for agile spacecraft. Agile spacecraft are capable of slewing to multiple targets in minimum time. CMGs provide the largest torque capability of current momentum exchange actuation devices but also introduce singularity events in operation. RWAs produce less torque capability than CMGs but can achieve greater pointing accuracy. In this research, a combined RWA and CMG (RWCMG) system is evaluated using analytical simulations and hardware experiments. A closed-loop control scheme is developed which takes advantage of the strengths of each actuator set.The CMGs perform …


Effects Of Automation On Aircrew Workload And Situation Awareness In Tactical Airlift Missions, David R. Meyer Dec 2015

Effects Of Automation On Aircrew Workload And Situation Awareness In Tactical Airlift Missions, David R. Meyer

Theses and Dissertations

In tactical aviation, decision superiority brought upon by high situation awareness remains the arbiter of combat effectiveness. The advancement of sophisticated avionics and highly automated cockpits has allowed for the reduction of aircrew size, and in certain platforms, removal of the crew from the aircraft entirely. However, these developments have not reduced the complex and dynamic interaction between situation awareness and crew workload. While many predictive and experimental methods of evaluating workload exist, situation awareness can only be measured by conducting trials with human operators in a functional prototype. This thesis proposes an innovative methodology to predicatively determine situation awareness …


Application Of Executable Architectures In Early Concept Evaluation, Ryan M. Pospisal Dec 2015

Application Of Executable Architectures In Early Concept Evaluation, Ryan M. Pospisal

Theses and Dissertations

This research explores use of executable architectures to guide design decisions in the early stages of system development. Decisions made early in the system development cycle determine a majority of the total lifecycle costs as well as establish a baseline for long term system performance and thus it is vital to program success to choose favorable design alternatives. The development of a representative architecture followed the Architecture Based Evaluation Process as it provides a logical and systematic order of events to produce an architecture sufficient to document and model operational performance. In order to demonstrate the value in the application …


Comparison Of Novel Carboneous Structures To Treat Nitroaromatic Impacted Water, Benjamin M. Doane Dec 2015

Comparison Of Novel Carboneous Structures To Treat Nitroaromatic Impacted Water, Benjamin M. Doane

Theses and Dissertations

Carboneous materials such as carbon nanotube (CNT), granular activated carbon (GAC), and biochar are promising materials for the removal of organic contaminants from aqueous phase solutions. CNTs have astonishing mechanical strength, chemical and thermal stability and high surface area. While biochar, similar to GAC, having an extremely porous structure and high surface area, can be produced in more austere conditions with native materials. In this study, novel CNT-Hybrid structures (CNT-HS), hardwood pellet (HWP) Biochar and standard GAC (F-600 GAC) were used as adsorbents to treat water contaminated by a model nitroaromatic compound, 2,4-dinitrotoluene (DNT).


Demonstration Of Inexact Computing Implemented In The Jpeg Compression Algorithm Using Probabilistic Boolean Logic Applied To Cmos Components, Christopher I. Allen Dec 2015

Demonstration Of Inexact Computing Implemented In The Jpeg Compression Algorithm Using Probabilistic Boolean Logic Applied To Cmos Components, Christopher I. Allen

Theses and Dissertations

Probabilistic computing offers potential improvements in energy, performance, and area compared with traditional digital design. This dissertation quantifies energy and energy-delay tradeoffs in digital adders, multipliers, and the JPEG image compression algorithm. This research shows that energy demand can be cut in half with noisesusceptible16-bit Kogge-Stone adders that deviate from the correct value by an average of 3 in 14 nanometer CMOS FinFET technology, while the energy-delay product (EDP) is reduced by 38 . This is achieved by reducing the power supply voltage which drives the noisy transistors. If a 19 average error is allowed, the adders are 13 times …


Collecting Unsolicited User-Generated Change Requests, Joseph W. Goldsmith Dec 2015

Collecting Unsolicited User-Generated Change Requests, Joseph W. Goldsmith

Theses and Dissertations

Unlike aircrew directly associated with acquisitions, line operators are not fully engaged in the methods to push materiel hardware or software change requests up the chain, to a decision maker, and then to the engineers. The Air Force trains these end users to logically apply expert systems knowledge to execute the mission but has not fully leveraged this resource for properly identifying and correcting operational shortfalls in an aircraft's design. Focusing on the Remotely Piloted Aircraft (RPA) community, the research goal is to determine if the Air Force should establish a formal program for collecting and prioritizing unsolicited user change …


Feature Selection And Classifier Development For Radio Frequency Device Identification, Trevor J. Bihl Dec 2015

Feature Selection And Classifier Development For Radio Frequency Device Identification, Trevor J. Bihl

Theses and Dissertations

The proliferation of simple and low-cost devices, such as IEEE 802.15.4 ZigBee and Z-Wave, in Critical Infrastructure (CI) increases security concerns. Radio Frequency Distinct Native Attribute (RF-DNA) Fingerprinting facilitates biometric-like identification of electronic devices emissions from variances in device hardware. Developing reliable classifier models using RF-DNA fingerprints is thus important for device discrimination to enable reliable Device Classification (a one-to-many looks most like assessment) and Device ID Verification (a one-to-one looks how much like assessment). AFITs prior RF-DNA work focused on Multiple Discriminant Analysis/Maximum Likelihood (MDA/ML) and Generalized Relevance Learning Vector Quantized Improved (GRLVQI) classifiers. This work 1) introduces a …


Design And Implementation Of A Unified Command And Control Architecture For Multiple Cooperative Unmanned Vehicles Utilizing Commercial Off The Shelf Components, Jeremy Gray Dec 2015

Design And Implementation Of A Unified Command And Control Architecture For Multiple Cooperative Unmanned Vehicles Utilizing Commercial Off The Shelf Components, Jeremy Gray

Theses and Dissertations

Small unmanned systems provide great utility to military applications due to their portable and expendable design. These systems are, however, costly to develop, produce, and maintain, making it desirable to integrate available commercial off the shelf (COTS) components. This research investigates the integration of COTS components through the development of a modular unified command and control (C2) architecture for heterogeneous and homogeneous vehicle teams to accomplish formation flocking and communication relay scenarios. A vehicle agnostic architecture was developed to be applied across different vehicle platforms, different vehicle combination, and different cooperative missions. COTS components consisting primarily of open source hardware …


Continuous Decision Support, Jeremy P. Hendrix Dec 2015

Continuous Decision Support, Jeremy P. Hendrix

Theses and Dissertations

Organizations are often faced with portfolio construction efforts that require them to select one or more alternatives, subject to resource constraints, with the aim of achieving the maximum value possible. This is a well-defined problem with a number of analytically defensible approaches, provided the entire set of alternatives is known when the decision event takes place. Less well treated in the literature is how to approach this problem when the entire set of alternatives is unknown, as when the alternatives arrive over time. This change in the availability of data shifts the problem from one of identifying an optimal subset …


Investigation Of Electromagnetic Signatures Of A Fpga Using An Aprel Em-Isight System, Karynn A. Sutherlin Dec 2015

Investigation Of Electromagnetic Signatures Of A Fpga Using An Aprel Em-Isight System, Karynn A. Sutherlin

Theses and Dissertations

Large military platforms have encountered major performance and reliability issues due to an increased number of incidents with counterfeit electronic parts. This has drawn the attention of Department of Defense (DOD) leadership making detection and avoidance of counterfeit electronic parts a top issue for national defense. More defined regulations and processes for identifying, reporting, and disposing of counterfeit electronic parts are being revised to raise awareness for this aggregating issue, as well as enhance the detection of these parts. Multiple technologies are currently employed throughout the supply chain to detect counterfeit electronic parts. These methods are often costly, time-consuming, and …


Creep And Oxidation Of Hafnium Diboride-Based Ultra High Temperature Ceramics At 1500°C, Anthony J. Degregoria Dec 2015

Creep And Oxidation Of Hafnium Diboride-Based Ultra High Temperature Ceramics At 1500°C, Anthony J. Degregoria

Theses and Dissertations

Ultra high temperature ceramics (UHTCs) are leading candidates for aerospace structural applications in high temperature environments, including the leading edges of hypersonic aircraft and thermal protection systems for atmospheric re-entry vehicles. Before UHTCs can be used in such applications, their structural integrity and environmental durability must be assured, which requires a thorough understanding and characterization of their creep and oxidation behavior at relevant service temperatures.


Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 800°C In Air And In Silicic Acid-Saturated Steam, Scott J. Robertson Dec 2015

Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 800°C In Air And In Silicic Acid-Saturated Steam, Scott J. Robertson

Theses and Dissertations

A facility was demonstrated that successfully resolved problems highlighted by previous attempts to study SiC fibers in steam. Monotonic tension and creep tests were conducted to characterize the fibers. The tensile strength of the fibers showed little dependence on applied stress rate, indicating a resistance to environmentally assisted crack growth. Climb-controlled diffusion in air and grain boundary sliding in silicic acid-saturated steam were the dominant damage mechanisms. Silicic acid-saturated steam had a degrading effect on the mechanical performance of the fibers, but much less than unsaturated steam environments. The Monkman-Grant relationship was demonstrated for Hi-NicalonTM S fibers and may be …


Optimal Uas Assignments And Trajectories For Persistent Surveillance And Data Collection From A Wireless Sensor Network, Nidal M. Jodeh Dec 2015

Optimal Uas Assignments And Trajectories For Persistent Surveillance And Data Collection From A Wireless Sensor Network, Nidal M. Jodeh

Theses and Dissertations

This research developed a method for multiple Unmanned Aircraft Systems (UAS) to efficiently collect data from a Wireless Sensor Networks (WSN). WSN are composed of any number of fixed, ground-based sensors that collect and upload local environmental data to over flying UAS. The three-step method first uniquely assigns aircraft to specific sensors on the ground. Second, an efficient flight path is calculated to minimize the aircraft flight time required to verify their assigned sensors. Finally, sensors reporting relatively higher rates of local environmental activity are re-assigned to dedicated aircraft tasked with concentrating on only those sensors. This work was sponsored …


Creep Behavior In Interlaminar Shear Of A Hi-Nicalon™/Sic-B4c Composite At 1200°C In Air And In Steam, Marina B. Ruggles-Wrenn, Matthew T. Pope Nov 2015

Creep Behavior In Interlaminar Shear Of A Hi-Nicalon™/Sic-B4c Composite At 1200°C In Air And In Steam, Marina B. Ruggles-Wrenn, Matthew T. Pope

Faculty Publications

Creep behavior in interlaminar shear of a non-oxide ceramic composite with a multilayered matrix was investigated at 1200C in laboratory air and in steam environment. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-NicalonTM fibers woven in a five-harness-satin weave. Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. The interlaminar shear properties were measured. The creep behavior was examined for interlaminar shear stresses in the 16–22 MPa range. Primary …


Predicting Public Bicycle Adoption Using The Technology Acceptance Model, Benjamin T. Hazen, Robert E. Overstreet, Yacan Wang Nov 2015

Predicting Public Bicycle Adoption Using The Technology Acceptance Model, Benjamin T. Hazen, Robert E. Overstreet, Yacan Wang

Faculty Publications

Bicycle sharing programs provide a sustainable mode of urban transportation. Although cities across the globe have developed these systems for their citizens and visitors, usage rates are not as high as anticipated. This research uses the technology acceptance model as the basis to understand one’s intention to adopt bicycle sharing programs. Using survey data derived from 421 participants in Beijing, China, the proposed covariance-based structural equation model consisting of perceived quality, perceived convenience, and perceived value is found to predict 50.5% of the variance in adoption intention. The findings of this research contribute to theory and practice in the burgeoning …


Using Information-Theoretic Principles To Analyze And Evaluate Complex Adaptive Supply Network Architectures, Joshua V. Rodewald, John M. Colombi, Kyle F. Oyama, Alan W. Johnson Oct 2015

Using Information-Theoretic Principles To Analyze And Evaluate Complex Adaptive Supply Network Architectures, Joshua V. Rodewald, John M. Colombi, Kyle F. Oyama, Alan W. Johnson

Faculty Publications

Information-theoretic principles can be applied to the study of complex adaptive supply networks (CASN). Previous modeling efforts of CASN were impeded by the complex, dynamic nature of the systems. However, information theory provides a model-free approach to the problem removing many of those barriers. Understanding how principles such as transfer entropy, excess entropy/predictive information, information storage, and separable information apply in the context of supply networks opens up new ways of studying these complex systems. Additionally, these principles provide the potential for new business analytics which give managers of CASN new insights into the system's health, behavior, and eventual control …


Modeling Napl Dissolution From Pendular Rings In Idealized Porous Media, Junqi Huang, John A. Christ, Mark N. Goltz, Avery H. Demond Oct 2015

Modeling Napl Dissolution From Pendular Rings In Idealized Porous Media, Junqi Huang, John A. Christ, Mark N. Goltz, Avery H. Demond

Faculty Publications

The dissolution rate of nonaqueous phase liquid (NAPL) often governs the remediation time frame at subsurface hazardous waste sites. Most formulations for estimating this rate are empirical and assume that the NAPL is the nonwetting fluid. However, field evidence suggests that some waste sites might be organic wet. Thus, formulations that assume the NAPL is nonwetting may be inappropriate for estimating the rates of NAPL dissolution. An exact solution to the Young‐Laplace equation, assuming NAPL resides as pendular rings around the contact points of porous media idealized as spherical particles in a hexagonal close packing arrangement, is presented in this …


Finite Element Analysis And Experimentation Of An Icosahedron Frame Under Compression, Mohammed Alghofaily Sep 2015

Finite Element Analysis And Experimentation Of An Icosahedron Frame Under Compression, Mohammed Alghofaily

Theses and Dissertations

A nonlinear analysis of a 3D icosahedron frame was conducted using ABAQUS, under a compressive load in which collapse occurs. The frame was created in SolidWorks using the material properties of the 3D plastic building material VeroBlue. Two considerations were made: the computational features of the frame, and the comparison between the experimental solution to the numerical solution. Two studies were also considered in this research: The first study was a comparison between the seven-inch and the four-inch icosahedron model with identical weight to buoyancy ratios; and the second study was a comparison between the seven-inch icosahedrons frame, with the …


Adaptive Automation Design And Implementation, Jason M. Bindewald Sep 2015

Adaptive Automation Design And Implementation, Jason M. Bindewald

Theses and Dissertations

Automations allow us to reduce the need for humans in certain environments, such as auto-pilot features on unmanned aerial vehicles. However, some situations still require human intervention. Adaptive automation is a research field that enables computer systems to adjust the amount of automation by taking over tasks from or giving tasks back to the user. This research develops processes and insights for adaptive automation designers to take theoretical adaptive automation ideas and develop them into real-world adaptive automation system. These allow developers to design better automation systems that recognize the limits of computers systems, enabling better designs for systems in …


Characterization Of Point Defects In Lithium Aluminate (Lialo2) Single Crystals, Maurio S. Holston Sep 2015

Characterization Of Point Defects In Lithium Aluminate (Lialo2) Single Crystals, Maurio S. Holston

Theses and Dissertations

Lithium aluminate (LiAlO2) is an insulating wide-band gap material currently under development for tritium breeding and radiation detection and dosimetry applications. Point defects are imperfections in a crystal lattice localized over a few atomic lengths that can alter the electrical, mechanical, or optical properties of materials. An understanding of point defect behavior is a necessary precursor for optimizing lithium aluminate for nuclear applications. This dissertation has identified and characterized the major point defects created and induced through x-ray and neutron radiation using electron paramagnetic resonance and fluorescence spectroscopy, thermoluminescence, and optical absorption. This dissertation explains for the first …


A Nonequilibrium Finite-Rate Carbon Ablation Model For Radiating Earth Re-Entry Flows, Christopher R. Alba Sep 2015

A Nonequilibrium Finite-Rate Carbon Ablation Model For Radiating Earth Re-Entry Flows, Christopher R. Alba

Theses and Dissertations

Vehicles entering planetary atmospheres at high speed require an ablative heat shield in order to withstand the high thermal energy flux to the body. The interaction between the ablative products and the flow field is not well characterized. Numerical simulations were conducted to investigate the influence of carbon ablation on shock layer radiation. Data collected from experiments performed in the X-2 expansion tunnel at the University of Queensland was used to compare to the simulations. The model was a short half-cylinder made of isomolded graphite and was tested in 8.6 km/s Earth entry flow. The model surface was heated within …


Modular Heat Dissipation Technique For A Cubesat, Melih Eken Sep 2015

Modular Heat Dissipation Technique For A Cubesat, Melih Eken

Theses and Dissertations

In recent years, due to their many advantages, interest in larger scale CubeSats, such as 3U and 6U, has been increased. Correspondingly, dissipating the heat from the heat generating components in the CubeSat has become a challenge for thermal control. In this research, a modular approach was developed to dissipate heat from the overheating components in a CubeSat. To accomplish this, both experimental and computational methodologies were used. A 6U CubeSat was computationally modeled and the model correlated by experimental test results. Subsequently, validated CubeSat thermal model was used to design a modular heat dissipater. Validation and performance experiments of …


System Architecture Of Small Unmanned Aerial System For Flight Beyond Visual Line-Of-Sight, Kwee Siam Seah Sep 2015

System Architecture Of Small Unmanned Aerial System For Flight Beyond Visual Line-Of-Sight, Kwee Siam Seah

Theses and Dissertations

Small Unmanned Aerial Systems (UAS) have increasingly been used in military application. The application in expanding scope of operations has pushed existing small UAS beyond its designed capabilities. This resulted in frequent modifications or new designs. A common requirement in modification or new design of small UAS is to operate beyond visual Line-Of-Sight (LOS) of the ground pilot. Conventional military development for small UAS adopts a design and built approach. Modification of small Remote Control (RC) aircraft, using Commercial-Off-The Shelf (COTS) equipment, offers a more economical alternative with the prospect of shorter development time compared to conventional approach. This research …


Network Analysis With Stochastic Grammars, Alan C. Lin Sep 2015

Network Analysis With Stochastic Grammars, Alan C. Lin

Theses and Dissertations

Digital forensics requires significant manual effort to identify items of evidentiary interest from the ever-increasing volume of data in modern computing systems. One of the tasks digital forensic examiners conduct is mentally extracting and constructing insights from unstructured sequences of events. This research assists examiners with the association and individualization analysis processes that make up this task with the development of a Stochastic Context -Free Grammars (SCFG) knowledge representation for digital forensics analysis of computer network traffic. SCFG is leveraged to provide context to the low-level data collected as evidence and to build behavior profiles. Upon discovering patterns, the analyst …


Tension-Compression Fatigue Behavior Of 2d And 3d Polymer Matrix Composites At Elevated Temperature, Saleh A. Alnatifat Sep 2015

Tension-Compression Fatigue Behavior Of 2d And 3d Polymer Matrix Composites At Elevated Temperature, Saleh A. Alnatifat

Theses and Dissertations

In this Research effort, the tension-compression fatigue behavior of the 3D and 2D PMCs with 0/90˚ fiber orientation (newly developed) was investigated. These polymer composites consist of an NRPE (high-temperature polyimide) matrix with carbon fiber reinforcement. Compressive properties were assessed at (1) room temperature and (2) elevated temperature with one side, Tright, at 329˚C and the other side open to the ambient air. Tension-compression fatigue tests were conducted at elevated temperature with a frequency of 1 Hz and a ratio of minimum to maximum stress of -1.


Analysis Of Hypersonic Vehicle Wakes, Matthew A. Kania Sep 2015

Analysis Of Hypersonic Vehicle Wakes, Matthew A. Kania

Theses and Dissertations

As advancements are made with ballistic missiles, particularly in the area of hypersonic bodies, there is a growing need to advance the methods of detecting these new ballistic weapons. As a result, the National Air and Space Intelligence Center has asked the Air Force Institute of Technology to examine the wake region behind hypersonic bodies. A thorough understanding of the aerothermal phenomena and the chemical reactions occurring in the wake region will enable an advancement of tracking hypersonic bodies. This research examined the wake region behind a hypersonic body using computational fluid dynamics.
This study used Pointwise® to develop a …


A Feasibility Study On The Application Of The Scriptgene Framework As An Anomaly Detection System In Industrial Control Systems, Charito M. Corvin Sep 2015

A Feasibility Study On The Application Of The Scriptgene Framework As An Anomaly Detection System In Industrial Control Systems, Charito M. Corvin

Theses and Dissertations

Recent events such as Stuxnet and the Shamoon Aramco have brought to light how vulnerable industrial control systems (ICSs) are to cyber attacks. Modern society relies heavily on critical infrastructure, including the electric power grid, water treatment facilities, and nuclear energy plants. Malicious attempts to disrupt, destroy and disable such systems can have devastating effects on a populations way of life, possibly leading to loss of life. The need to implement security controls in the ICS environment is more vital than ever. ICSs were not originally designed with network security in mind. Today, intrusion detection systems are employed to detect …


An Analysis Of Conus Based Deployment Of Pseudolites For Positioning, Navigation And Timing (Pnt) Systems, Justin H. Deifel, Albert J. Pena Sep 2015

An Analysis Of Conus Based Deployment Of Pseudolites For Positioning, Navigation And Timing (Pnt) Systems, Justin H. Deifel, Albert J. Pena

Theses and Dissertations

The Global Positioning System (GPS) developed and operated by the United States Air Force (USAF) provides a way for users to determine position, navigation and timing (PNT). GPS provides an extraordinary capability that has become instrumental in all aspects of our day to day lives. As new technologies such as automated vehicles and unmanned aircraft continue to be developed, a reliable back up to GPS is required to ensure the PNT data generated in these systems is accurate. This research studies a potential architecture for deploying a nationwide network of ground based pseudolites that would act to supplement and backup …


Leveraging External Sensor Data For Enhanced Space Situational Awareness, Charlie T. Bellows Sep 2015

Leveraging External Sensor Data For Enhanced Space Situational Awareness, Charlie T. Bellows

Theses and Dissertations

Reliable Space Situational Awareness (SSA) is a recognized requirement in the current congested, contested, and competitive environment of space operations. A shortage of available sensors and reliable data sources are some current limiting factors for maintaining SSA. Unfortunately, cost constraints prohibit drastically increasing the sensor inventory. Alternative methods are sought to enhance current SSA, including utilizing non-traditional data sources (external sensors) to perform basic SSA catalog maintenance functions. Astronomical data, for example, routinely collects serendipitous satellite streaks in the course of observing deep space; but tactics, techniques, and procedures designed to glean useful information from those collects have yet to …


Environmental Degradation Of Nickel-Based Superalloys Due To Gypsiferous Desert Dusts, Matthew B. Krisak Sep 2015

Environmental Degradation Of Nickel-Based Superalloys Due To Gypsiferous Desert Dusts, Matthew B. Krisak

Theses and Dissertations

More than twenty-five years of continuous operation in the dusty environments of Southwest Asia have shown that degradation of gas turbine engine components due to particle ingestion is a serious threat to operations. In particular, the continued push for higher engine operating temperatures has brought a new emphasis to the damage mechanisms (for example CMAS glass formation and hot corrosion) caused by ingested particles forming molten deposits on engine components. Despite decades of research little progress has been made to mitigate the effects of CMAS and hot corrosion degradation to engine components. This research focused on hot corrosion specifically. A …