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Theses/Dissertations

Air Force Institute of Technology

2013

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Articles 1 - 30 of 131

Full-Text Articles in Engineering

Mems Cantilever Sensor For Thz Photoacoustic Chemical Sensing And Spectroscopy, Nathan E. Glauvitz Dec 2013

Mems Cantilever Sensor For Thz Photoacoustic Chemical Sensing And Spectroscopy, Nathan E. Glauvitz

Theses and Dissertations

Sensitive Microelectromechanical System (MEMS) cantilever designs were modeled, fabricated, and tested to measure the photoacoustic (PA) response of gasses to terahertz (THz) radiation. Surface and bulk micromachining technologies were employed to create the extremely sensitive devices that could detect very small changes in pressure. Fabricated devices were then tested in a custom made THz PA vacuum test chamber where the cantilever deflections caused by the photoacoustic effect were measured with a laser interferometer and iris beam clipped methods. The sensitive cantilever designs achieved a normalized noise equivalent absorption coefficient of 2.83x10-10 cm-1 W Hz-1/2 using a 25 …

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Modeling Reliability Growth In Accelerated Stress Testing, Jason K. Freels Dec 2013

Modeling Reliability Growth In Accelerated Stress Testing, Jason K. Freels

Theses and Dissertations

Qualitative accelerated test methods improve system reliability by identifying and removing initial design flaws. However, schedule and cost constraints often preclude sufficient testing to generate a meaningful reliability estimate from the data obtained in these tests. In this dissertation a modified accelerated life test is proposed to assess the likelihood of attaining a reliability requirement based on tests of early system prototypes. Assuming each prototype contains an unknown number of independent competing failure modes whose respective times to occurrence are governed by a distinct Weibull law, the observed failure data from this qualitative test are shown to follow a poly-Weibull …

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Enhancing Electromagnetic Side-Channel Analysis In An Operational Environment, David P. Montminy Sep 2013

Enhancing Electromagnetic Side-Channel Analysis In An Operational Environment, David P. Montminy

Theses and Dissertations

Side-channel attacks exploit the unintentional emissions from cryptographic devices to determine the secret encryption key. This research identifies methods to make attacks demonstrated in an academic environment more operationally relevant. Algebraic cryptanalysis is used to reconcile redundant information extracted from side-channel attacks on the AES key schedule. A novel thresholding technique is used to select key byte guesses for a satisfiability solver resulting in a 97.5% success rate despite failing for 100% of attacks using standard methods. Two techniques are developed to compensate for differences in emissions from training and test devices dramatically improving the effectiveness of cross device template …

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Trajectory Optimization For Spacecraft Collision Avoidance, James W. Sales Sep 2013

Trajectory Optimization For Spacecraft Collision Avoidance, James W. Sales

Theses and Dissertations

The last several decades have resulted in an unfortunate byproduct of space exploration and development: orbital debris. Satellites in Low Earth Orbit have been required to make an ever increasing number of course corrections in order to avoid collisions. Despite efforts to the contrary, collisions continue to occur, each time creating additional debris and increasing the requirement for the remaining satellites to maneuver. Every required maneuver decreases a satellite's service life. The purpose of this study is to develop a minimum thrust profile to maneuver an orbiting satellite out of its projected error ellipse before a collision occurs. For comparison, …

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Passive Mimo Radar Detection, Daniel E. Hack Sep 2013

Passive Mimo Radar Detection, Daniel E. Hack

Theses and Dissertations

Passive multiple-input multiple-output (MIMO) radar is a sensor network comprised of multiple distributed receivers that detects and localizes targets using the emissions from multiple non-cooperative radio frequency transmitters. This dissertation advances the theory of centralized passive MIMO radar (PMR) detection by proposing two novel generalized likelihood ratio test (GLRT) detectors. The first addresses detection in PMR networks without direct-path signals. The second addresses detection in PMR networks with direct-path signals. The probability distributions of both test statistics are investigated using recent results from random matrix theory. Equivalence is established between PMR networks without direct-path signals and passive source localization (PSL) …

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Radio Frequency Based Programmable Logic Controller Anomaly Detection, Samuel J. Stone Sep 2013

Radio Frequency Based Programmable Logic Controller Anomaly Detection, Samuel J. Stone

Theses and Dissertations

The research goal involved developing improved methods for securing Programmable Logic Controller (PLC) devices against unauthorized entry and mitigating the risk of Supervisory Control and Data Acquisition (SCADA) attack by detecting malicious software and/or trojan hardware. A Correlation Based Anomaly Detection (CBAD) process was developed to enable 1) software anomaly detection discriminating between various operating conditions to detect malfunctioning or malicious software, firmware, etc., and 2) hardware component discrimination discriminating between various hardware components to detect malfunctioning or counterfeit, trojan, etc., components.

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Characterizing G-Loading, Swirl Direction And Rayleigh Losses In An Ultra Compact Combustor, Jacob D. Wilson Sep 2013

Characterizing G-Loading, Swirl Direction And Rayleigh Losses In An Ultra Compact Combustor, Jacob D. Wilson

Theses and Dissertations

Previous research has been conducted showing significant benefits on combustion efficiency and stability by creating high centripetally accelerated, also known as g-loaded, combustion environments. Ultra Compact Combustor systems decrease size and weight of the overall engine by burning in a circumferential direction around a hybrid vane row where the high equivalence ratio cavity flow is quick quenched to lean by the core flow. The hybrid vane row integrates the compressor, combustor, and turbine for further length reduction and weight savings. Fuel and air are brought into the cavity and combusted in a high g-loaded environment driven by air injection at …

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Development Of Availability And Sustainability Spares Optimization Models For Aircraft Reparables, Edmund K.W. Pek Sep 2013

Development Of Availability And Sustainability Spares Optimization Models For Aircraft Reparables, Edmund K.W. Pek

Theses and Dissertations

The Republic of Singapore Air Force (RSAF) conducts Logistics Support Analysis (LSA) studies in various engineering and logistics efforts on the myriad of weapon systems. In these studies, inventory spares provisioning, availability and sustainability analyses are key focus areas to ensure asset sustenance. In particular, OPUS10, a commercial-off-the-shelf software, is extensively used to conduct reparable spares optimization in acquisition programs. However, it is limited in its ability to conduct availability and sustainability analyses of time-varying operational demands, crucial in Operations & Support (O&S) and contingency planning. As the RSAF seeks force structure expansion to include more sophisticated weapon systems, the …

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Scattering, Adsorption, And Langmuir-Hinshelwood Desorption Models For Physisorptive And Chemisorptive Gas-Surface Systems, Brook I. Bentley Sep 2013

Scattering, Adsorption, And Langmuir-Hinshelwood Desorption Models For Physisorptive And Chemisorptive Gas-Surface Systems, Brook I. Bentley

Theses and Dissertations

Surface effects limit the performance of hypersonic vehicles, micro-electro-mechanical devices, and directed energy systems. This research develops methods to predict adsorption, scattering, and thermal desorption of molecules on a surface. These methods apply to physisorptive (adsorption and scattering) and chemisorptive (thermal desorption) gas-surface systems, and are developed under the Direct Simulation Monte Carlo construct. The novel adsorption and scattering contribution, the Modified Kisliuk with Scattering method, predicts angular and energy distributions, and adsorption probabilities. These results agree more closely with experiment than the state-of-the-art Cercignani-Lampis-Lord scattering kernel. Super-elastic scattering is predicted. Gas-adlayer interactions are included for the first time. The …

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Image Annotation And Topic Extraction Using Super-Word Latent Dirichlet, George E. Noel Iii Sep 2013

Image Annotation And Topic Extraction Using Super-Word Latent Dirichlet, George E. Noel Iii

Theses and Dissertations

This research presents a multi-domain solution that uses text and images to iteratively improve automated information extraction. Stage I uses local text surrounding an embedded image to provide clues that help rank-order possible image annotations. These annotations are forwarded to Stage II, where the image annotations from Stage I are used as highly-relevant super-words to improve extraction of topics. The model probabilities from the super-words in Stage II are forwarded to Stage III where they are used to refine the automated image annotation developed in Stage I. All stages demonstrate improvement over existing equivalent algorithms in the literature.

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Metrics For Emitter Selection For Multistatic Synthetic Aperture Radar, Sean R. Stevens Sep 2013

Metrics For Emitter Selection For Multistatic Synthetic Aperture Radar, Sean R. Stevens

Theses and Dissertations

A bistatic implementation of synthetic aperture radar (SAR) to form images of the ground from an aircraft makes use of separate emitters and receivers. When not using cooperative emitters, ground based communications systems can provide illumination. One way to improve performance of these waveforms, which are not designed for SAR, is a multistatic implementation, formed from multiple bistatic systems. This leads to the problem of selecting a subset from a potentially large set of emitters to use for image formation. A framework for this selection between sets of emitters is proposed using multiple objective optimization. This approach requires use of …

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Architecting Integrated System Health Management For Airworthiness, Kerwin C. Teong Sep 2013

Architecting Integrated System Health Management For Airworthiness, Kerwin C. Teong

Theses and Dissertations

Integrated System Health Management (ISHM) for Unmanned Aerial Systems (UAS) has been a new area of research - seeking to provide situational awareness to mission and maintenance operations, and for improved decision-making with increased self-autonomy. This research effort developed an analytic architecture and an associated discrete-event simulation using Arena to investigate the potential benefits of ISHM implementation onboard an UAS. The objective of this research is two-fold: firstly, to achieve continued airworthiness by investigating the potential extension of UAS expected lifetime through ISHM implementation, and secondly, to reduce life cycle costs by implementing a Condition-Based Maintenance (CBM) policy with better …

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Design Of A Lighter Than Air Vehicle That Achieves Positive Buoyancy In Air Using A Vacuum, Trent T. Metlen Jun 2013

Design Of A Lighter Than Air Vehicle That Achieves Positive Buoyancy In Air Using A Vacuum, Trent T. Metlen

Theses and Dissertations

Three designs for a Lighter Than Air (LTA) structure that achieve positive buoyancy using a vacuum in place of a lifting gas were proposed and evaluated. The ratio of structure weight to the weight of displaced air was termed Weight/Buoyant Force (W/B) where a W/B1 corresponds to positive buoyancy. Two methods of geometrically stiffening a sphere were investigated and their W/B evaluated. A thin shelled sphere of beryllium stiffened with an isogrid of blade type stiffeners using Ultra High Modulus (UHM) carbon epoxy was predicted to give a W/B= 0.79. A geodesic sphere composed of a frame of cylindrical, UHM, …

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Dynamic Network Topologies, Heather A. Lingg Jun 2013

Dynamic Network Topologies, Heather A. Lingg

Theses and Dissertations

Demand for effective network defense capabilities continues to increase as cyber attacks occur more and more frequently and gain more and more prominence in the media. Current security practices stop after data encryption and network address filtering. Security at the lowest level of network infrastructure allows for greater control of how the network traffic flows around the network. This research details two methods for extending security practices to the physical layer of a network by modifying the network infrastructure. The first method adapts the Advanced Encryption Standard while the second method uses a Steiner tree. After the network connections are …

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Crack Initiation And Growth Behavior At Corrosion Pit In 7075-T6 High Strength Aluminum Alloy, Eric M. Hunt Jun 2013

Crack Initiation And Growth Behavior At Corrosion Pit In 7075-T6 High Strength Aluminum Alloy, Eric M. Hunt

Theses and Dissertations

Research on fatigue crack formation from two types corrosion pits tangent to a circular hole in a 7075-T6 aluminum alloy subjected to uni-axial loads (R = 0.5, lambda = 0) in both an air and saltwater environment provides a method for exploring crack initiation and initial growth rates. This work focuses on a fracture mechanics approach to explore the transition from corrosion pit to crack growth. Specimens with a cylinder shaped through-pit tangent to a circular hole have a closed form solution to predict this delta K that closely resembles the finite element solutions. Specimens with a semi-circular corner-pit tangent …

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Classification Of Encrypted Web Traffic Using Machine Learning Algorithms, William C. Barto Jun 2013

Classification Of Encrypted Web Traffic Using Machine Learning Algorithms, William C. Barto

Theses and Dissertations

The increasing usage of web services and encrypted network communication makes the network analysis of encrypted web traffic of utmost importance. This research evaluates the feasibility of using ML algorithms to classify web services within encrypted TLS flows. The ML algorithms are compared primarily based on classification accuracy. The runtimes of the classifiers are also considered, as classifiers must be able determine labels quickly in order to be used in near realtime network protection devices. Five ML algorithms are initially considered when analyzing only the first 12 packets: Naive Bayes, NBTree, LibSVM, J4.8, and AdaBoost+J4.8. AdaBoost+J4.8 and J4.8 produce the …

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Side-Channel Analysis Of Subscriber Identity Modules, John A. Hearle Jun 2013

Side-Channel Analysis Of Subscriber Identity Modules, John A. Hearle

Theses and Dissertations

Subscriber identity modules (SIMs) contain useful forensic data but are often locked with a PIN code that restricts access to this data. If an invalid PIN is entered several times, the card locks and may even destroy its stored data. This presents a challenge to the retrieval of data from the SIM when the PIN is unknown. The field of side-channel analysis (SCA) collects, identifies, and processes information leaked via inadvertent channels. One promising side-channel leakage is that of electromagnetic (EM) emanations; by monitoring the SIM's emissions, it may be possible to determine the correct PIN to unlock the card. …

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Improving Multiple Surface Range Estimation Of A 3-Dimensional Flash Ladar In The Presence Of Atmospheric Turbulence, Brian J. Neff Jun 2013

Improving Multiple Surface Range Estimation Of A 3-Dimensional Flash Ladar In The Presence Of Atmospheric Turbulence, Brian J. Neff

Theses and Dissertations

Laser Radar sensors can be designed to provide two-dimensional and three-dimensional (3-D) images of a scene from a single laser pulse. Currently, there are various data recording and presentation techniques being developed for 3-D sensors. While the technology is still being proven, many applications are being explored and suggested. As technological advancements are coupled with enhanced signal processing algorithms, it is possible that this technology will present exciting new military capabilities for sensor users. The goal of this work is to develop an algorithm to enhance the utility of 3-D Laser Radar sensors through accurate ranging to multiple surfaces per …

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The Design And Analysis Of Electrically Large Custom-Shaped Reflector Antennas, Joshua M. Wilson Jun 2013

The Design And Analysis Of Electrically Large Custom-Shaped Reflector Antennas, Joshua M. Wilson

Theses and Dissertations

Designing and analyzing electrically large reflectors poses numerically complex problems because the reflector must be sampled finely to obtain an accurate solution, causing an unwieldy number of samples. In addition to these complexities, a custom-shaped reflector poses a new analysis problem. Previously developed methods and theorems including Geometric Optics, Ray-Tracing, Surface Equivalence Theorems, Image Theory, and Physical Optics can be applied to these custom-shaped reflectors however. These methods all share in common their capability to provide accurate results in the analysis of electrically large structures. In this thesis, two custom-shaped reflector concepts are explored which include a rectangular shaped, spherically …

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Applied Hypergame Theory For Network Defense, Alan S. Gibson Jun 2013

Applied Hypergame Theory For Network Defense, Alan S. Gibson

Theses and Dissertations

Cyber operations are the most important aspect of military conflicts in the 21st century, but unfortunately they are also among the least understood. The continual battle for network dominance between attackers and defenders is considered to be a complex game. Hypergame theory is an extension of game theory that addresses the kind of games where misperception exists, as is often the case in military engagements. Hypergame theory, like game theory, uses a game model to determine strategy selection, but goes beyond game theory by examining subgames that exist within the full game. The inclusion of misperception and misinformation in the …

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Development Of A Model And Localization Algorithm For Received Signal Strength-Based Geolocation, Amanda S. King Jun 2013

Development Of A Model And Localization Algorithm For Received Signal Strength-Based Geolocation, Amanda S. King

Theses and Dissertations

Location-Based Services (LBS), also called geolocation, have become increasingly popular in the past decades. They have several uses ranging from assisting emergency personnel, military reconnaissance and applications in social media. In geolocation a group of sensors estimate the location of transmitters using position and Radio Frequency (RF) information. A review of the literature revealed that a majority of the Received Signal Strength (RSS) techniques used made erroneous assumptions about the distribution or ignored effects of multiple transmitters, noise and multiple antennas. Further, the corresponding algorithms are often mathematically complex and computationally expensive. To address the issues this dissertation focused on …

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Evaluation Of Cyber Sensors For Enhancing Situational Awareness In The Ics Environment, Jeremy R. Otis Jun 2013

Evaluation Of Cyber Sensors For Enhancing Situational Awareness In The Ics Environment, Jeremy R. Otis

Theses and Dissertations

Industrial Control Systems (ICS) monitor and control operations associated with the national critical infrastructure (e.g., electric power grid, oil and gas pipelines and water treatment facilities). These systems rely on technologies and architectures that were designed for system reliability and availability. Security associated with ICS was never an inherent concern, primarily due to the protections afforded by network isolation. However, a trend in ICS operations is to migrate to commercial networks via TCP/IP in order to leverage commodity benefits and cost savings. As a result, system vulnerabilities are now exposed to the online community. Indeed, recent research has demonstrated that …

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Kernel Extended Real-Valued Negative Selection Algorithm (Kernsa), Brett A . Smith Jun 2013

Kernel Extended Real-Valued Negative Selection Algorithm (Kernsa), Brett A . Smith

Theses and Dissertations

Artificial Immune Systems (AISs) are a type of statistical Machine Learning (ML) algorithm based on the Biological Immune System (BIS) applied to classification problems. Inspired by increased performance in other ML algorithms when combined with kernel methods, this research explores using kernel methods as the distance measure for a specific AIS algorithm, the Real-valued Negative Selection Algorithm (RNSA). This research also demonstrates that the hard binary decision from the traditional RNSA can be relaxed to a continuous output, while maintaining the ability to map back to the original RNSA decision boundary if necessary. Continuous output is used in this research …

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Space Debris Mitigation Conops Development, Earl B. Alejandro Jun 2013

Space Debris Mitigation Conops Development, Earl B. Alejandro

Theses and Dissertations

Space debris remains an unsolved hazard for space operators and astronomers alike. Passive debris mitigation techniques have been enumerated and codified by the UNCOPUOS and IADC and several proposals for actively mitigating space debris have been presented. However, the space debris problem requires reframing. On the way to developing a viable CONOPS, a multi-disciplinary construct for building solution sets to tackle the space debris problem must be created. It must be shaped by building blocks of active and passive debris mitigation techniques, debris characterization and law. Central considerations must be taken. First, targeting of space debris for removal must be …

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Evaluation Of The Thorax Of Manduca Sexta For Flapping Wing Micro Air Vehicle Applications, Brian C. Cranston Mar 2013

Evaluation Of The Thorax Of Manduca Sexta For Flapping Wing Micro Air Vehicle Applications, Brian C. Cranston

Theses and Dissertations

The tobacco hornworm hawkmoth (Manduca sexta) provides an excellent model from which to gather knowledge pertaining to the development of a Flapping Wing Micro Air Vehicle (FWMAV). One of the major challenges in design of a FWMAV is the energy demanding nature of low Reynolds number flapping flight. Therefore, an understanding of the power required by the flight muscles to actuate the wings is essential for the design of a FWMAV. The M.sexta wing/thorax mechanism was evaluated as a mechanical system in order to gain insight to the mechanical power required to produce the full natural wing stroke. A unique …

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Computational Simulation Of Explosively Generated Pulsed Power Devices, Mollie C. Drumm Mar 2013

Computational Simulation Of Explosively Generated Pulsed Power Devices, Mollie C. Drumm

Theses and Dissertations

Technology and size constraints have limited the development of the end game mechanisms of today's modern military weapons. A smaller, more efficient means of powering these devices is needed, and explosive pulsed power devices could be that answer. While most prior research has been in the experimental field, there is a need for more theory-based research and a computer modeling capability. The objective of this research was to use experimental data collected by the US Army at Redstone Arsenal from their ferroelectric generator (FEG) design in combination with the ALEGRA-EMMA code to develop a computer model that can accurately represent …

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Experimental Characterization Of The Structural Dynamics And Aero-Structural Sensitivity Of A Hawkmoth Wing Toward The Development Of Design Rules For Flapping Wing Micro Air Vehicles, Aaron G. Norris Mar 2013

Experimental Characterization Of The Structural Dynamics And Aero-Structural Sensitivity Of A Hawkmoth Wing Toward The Development Of Design Rules For Flapping Wing Micro Air Vehicles, Aaron G. Norris

Theses and Dissertations

A case is made for why the structures discipline must take on a more central role in the research and design of flapping-wing micro-air-vehicles, especially if research trends continue toward bio-inspired, insect-sized flexible wing designs. In making the case, the eigenstructure of the wing emerges as a key structural metric for consideration. But with virtually no structural dynamic data available for actual insect wings, both engineered and computational wing models that have been inspired by biological analogs have no structural truth models to which they can be anchored. An experimental framework is therefore developed herein for performing system identification testing …

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Porous Emitter Colloid Thruster Performance Characterization Using Optical Techniques, Eric T. Wolf Mar 2013

Porous Emitter Colloid Thruster Performance Characterization Using Optical Techniques, Eric T. Wolf

Theses and Dissertations

This research focuses on experimentally characterizing the performance parameters of a colloid thruster with porous emitters through optical techniques. Porous emitters are different than traditional needle emitters in how they allow a variation in the number and size of Taylor Cones throughout a range of propellant volumetric flow rate conditions. An algorithm is created to calculate the estimated minimum and maximum number of emitter sites based on magnified images of the porous emitter heads. Theoretical thruster performance parameters are then established from the estimated number of emitter sites. Experimental techniques for measuring the thrust and exhaust exit velocity are proposed. …

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Characterization Of Metal-Insulator-Transition (Mit) Phase Change Materials (Pcm) For Reconfigurable Components, Circuits, And Systems, Brent L. Danner Mar 2013

Characterization Of Metal-Insulator-Transition (Mit) Phase Change Materials (Pcm) For Reconfigurable Components, Circuits, And Systems, Brent L. Danner

Theses and Dissertations

Many microelectromechanical systems (MEMS) use metal contact micro-switches as part of their reconfigurable device design. These devices utilize a mechanical component that can wear down and fail over time. Metal insulator transition (MIT) materials, also known as phase change materials (PCMs), exhibit a reversible transition that can be used to replace the mechanical component in reconfigurable devices. In the presence of a thermal or electric field stimuli, the PCMs will transition back and forth between a crystalline and amorphous state. During this transformation, the resistivity, reflectivity, and Young's modulus of the material drastically change. This research effort focuses on characterizing …

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Using Rf-Dna Fingerprints To Discriminate Zigbee Devices In An Operational Environment, Clay K. Dubendorfer Mar 2013

Using Rf-Dna Fingerprints To Discriminate Zigbee Devices In An Operational Environment, Clay K. Dubendorfer

Theses and Dissertations

This research was performed to expand AFIT's Radio Frequency Distinct Native Attribute (RF-DNA) fingerprinting process to support IEEE 802.15.4 ZigBee communication network applications. Current ZigBee bit-level security measures include use of network keys and MAC lists which can be subverted through interception and spoofing using open-source hacking tools. This work addresses device discrimination using Physical (PHY) waveform alternatives to augment existing bit-level security mechanisms. ZigBee network vulnerability to outsider threats was assessed using Receiver Operating Characteristic (ROC) curves to characterize both Authorized Device ID Verification performance (granting network access to authorized users presenting true bit-level credentials) and Rogue Device Rejection …

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