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Air Force Institute of Technology

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Articles 691 - 720 of 2678

Full-Text Articles in Physical Sciences and Mathematics

Two-Photon Excitation Of Cesium Alkali Metal Vapor 72D, 82D Kinetics And Spectroscopy, Ricardo C. Davila Mar 2018

Two-Photon Excitation Of Cesium Alkali Metal Vapor 72D, 82D Kinetics And Spectroscopy, Ricardo C. Davila

Theses and Dissertations

Pulsed excitation on the two-photon Cs 62S½ → 72D3/2,5/2 transition results in time-resolved fluorescence at 697 nm and 672 nm. The rates for fine structure mixing between the 72D3/2,5/2 states have been measured for helium and argon rare gas collision partners. The mixing rates are very fast, 1.26 ± 0.05 x 10-9 cm3/(atom sec) for He and 1.52 ± 0.05 x 10-10 cm3 /(atom sec) for Ar, driven by the small energy splitting and large radial distribution for the valence electron. …

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The Application Of Text Mining And Data Visualization Techniques To Textual Corpus Exploration, Jeffrey R. Smith Jr. Mar 2018

The Application Of Text Mining And Data Visualization Techniques To Textual Corpus Exploration, Jeffrey R. Smith Jr.

Theses and Dissertations

Unstructured data in the digital universe is growing rapidly and shows no evidence of slowing anytime soon. With the acceleration of growth in digital data being generated and stored on the World Wide Web, the prospect of information overload is much more prevalent now than it has been in the past. As a preemptive analytic measure, organizations across many industries have begun implementing text mining techniques to analyze such large sources of unstructured data. Utilizing various text mining techniques such as n -gram analysis, document and term frequency analysis, correlation analysis, and topic modeling methodologies, this research seeks to develop …

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Improving Annual Fixed Wing Maintenance Cost Estimates Through Cost Estimating Relationships, Kirsten Bunecke Mar 2018

Improving Annual Fixed Wing Maintenance Cost Estimates Through Cost Estimating Relationships, Kirsten Bunecke

Theses and Dissertations

The Air Force executes its mission primarily through the use of fixed-wing aircrafts. Maintaining these aircrafts represents approximately one-third of annual Operating and Support costs; which in turn, make up the majority of Life Cycle Costs. The current approach to estimating aircraft maintenance costs does not take into consideration programmatic data available in the Air Force Total Ownership Cost (AFTOC) database. The four maintenance cost subcategories researched in this thesis are Consumable Materials and Repair Parts, Depot Level Repairables (DLRs), Depot Maintenance, and Contractor Logistic Support. Each of these cost categories must first be standardized to be able to compare …

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Methodology To Analyze Tropical Cyclone Intensity From Microwave Imagery, Matthew W. Perkins Mar 2018

Methodology To Analyze Tropical Cyclone Intensity From Microwave Imagery, Matthew W. Perkins

Theses and Dissertations

Satellites with microwave remote sensing capabilities can be utilized to study atmospheric phenomena through high-level cloud cover (particularly cirrus), an advantage over visible and infrared bands, which only sense cloud tops. This unique capability makes microwave imagery ideal for studying the cloud structures of tropical cyclones (TCs) in detail, and relating these features to TC intensity. Techniques to estimate the intensity of TCs using infrared imagery, such as the Dvorak technique, have been used in TC forecasting for 40 years. However, due to the inherent temporal limitations of microwave imagery, no such similar technique exists for the microwave spectrum. This …

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Integrity Monitoring For Automated Aerial Refueling: A Stereo Vision Approach, Thomas R. Stuart Mar 2018

Integrity Monitoring For Automated Aerial Refueling: A Stereo Vision Approach, Thomas R. Stuart

Theses and Dissertations

Unmanned aerial vehicles (UAVs) increasingly require the capability to y autonomously in close formation including to facilitate automated aerial refueling (AAR). The availability of relative navigation measurements and navigation integrity are essential to autonomous relative navigation. Due to the potential non-availability of the global positioning system (GPS) during military operations, it is highly desirable that relative navigation can be accomplished without the use of GPS. This paper develops two algorithms designed to provide relative navigation measurements solely from a stereo image pair. These algorithms were developed and analyzed in the context of AAR using a stereo camera system modeling that …

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Methods Of Reverse Engineering A Bitstream For Field Programmable Gate Array Protection, Daniel J. Celebucki Mar 2018

Methods Of Reverse Engineering A Bitstream For Field Programmable Gate Array Protection, Daniel J. Celebucki

Theses and Dissertations

Field Programmable Gate Arrays (FPGAs) are found in numerous industries including consumer electronics, automotive, military and aerospace, and critical infrastructure. The ability to be reprogrammed as well as large computational power and relatively low price make them a good fit for low-volume applications that cannot justify the Non-Recurring Engineering (NRE) costs associated with producing Application-Specific Integrated Circuits (ASICs). FPGAs however, have seen a variety of security issues stemming from the fact that their configuration files are not inherently protected. This research assesses the feasibility of reverse engineering the bitstream format for a previously unexplored FPGA, as well as the utilization …

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Mitigating The Effects Of Boom Occlusion On Automated Aerial Refueling Through Shadow Volumes, Zachary C. Paulson Mar 2018

Mitigating The Effects Of Boom Occlusion On Automated Aerial Refueling Through Shadow Volumes, Zachary C. Paulson

Theses and Dissertations

In flight refueling of Unmanned Aerial Vehicles (UAVs) is critical to the United States Air Force (USAF). However, the large communication latency between a ground-based operator and his/her remote UAV makes docking with a refueling tanker unsafe. This latency may be mitigated by leveraging a tanker-centric stereo vision system. The vision system observes and computes an approaching receiver's relative position and orientation offering a low-latency, high frequency docking solution. Unfortunately, the boom -- an articulated refueling arm responsible for physically pumping fuel into the receiver -- occludes large portions of the receiver especially as the receiver approaches and docks with …

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An Analysis Of The Estimate At Complete For Department Of Defense Contracts, Deborah B. Kim Mar 2018

An Analysis Of The Estimate At Complete For Department Of Defense Contracts, Deborah B. Kim

Theses and Dissertations

When contractors provide timely and reliable information on the status of a contract, both contractors and government program offices can provide an accurate estimate of a contract’s completion costs. This research shows that the cumulative cost performance indices provided by contractors and program offices are high and less accurate than those of previous years and/or that a significant amount of ACWP is being documented in the final portion of a contract. The high performance indices resulted in EACs that were low-balled during the majority of a contract’s life which shows a need to improve the use of EVM metrics for …

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Spatial Resolution And Contrast Of A Focused Diffractive Plenoptic Camera, Carlos D. Diaz Mar 2018

Spatial Resolution And Contrast Of A Focused Diffractive Plenoptic Camera, Carlos D. Diaz

Theses and Dissertations

The conventional Diffractive Plenoptic Camera (DPC) was developed as a system that would capture the spectral and spatial information of a scene in one snapshot. The conventional DPC couples a diffractive optic with plenoptic camera designs that provide snapshot spectral imaging capabilities but produce rendered images with low pixel count. A modified setup of the conventional DPC, the focused DPC, and a modified imaging algorithm, the refocused light field algorithm, were built and tested for the first time, and compared to the conventional DPC as methods that would increase the pixel count and improve rendered image quality. The focused DPC …

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The Geographic Distribution Of Downburst Frequency Across Spaceport Florida, Tania M. Garza Mar 2018

The Geographic Distribution Of Downburst Frequency Across Spaceport Florida, Tania M. Garza

Theses and Dissertations

Strong winds from downbursts pose a significant hazard to personnel and launch operations at Cape Canaveral Air Force Station (CCAFS) and NASA Kennedy Space Center (KSC). The CCAFS/KSC complex has a robust mesonet from which an 18 year (1995-2012) warm-season convective wind climatology (WSCWC) was developed (Koermer 2017). While the frequency of downbursts in the area has been determined, the frequency at the individual tower locations has not. The 5-minute peak wind data from the WSCWC was analyzed to determine the geographic distribution of downburst frequency across Spaceport Florida. For this project a downburst was determined by the threshold of …

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A Comparison Of High Frequency Angle Of Arrival And Ionosonde Data During A Traveling Ionospheric Disturbance, Kalen L. Knippling Mar 2018

A Comparison Of High Frequency Angle Of Arrival And Ionosonde Data During A Traveling Ionospheric Disturbance, Kalen L. Knippling

Theses and Dissertations

High Frequency (HF) geolocation techniques are commonly used to track the source of uncooperative HF emitters. A traveling ionospheric disturbance (TID) makes geolocation particularly difficult due to large perturbations in the local ionospheric electron density profile. Angle of Arrival (AoA) and ionosonde virtual height measurements collected at White Sands Missile Range, New Mexico in January 2014, are analyzed during a medium scale traveling ionospheric disturbance. TID characteristics are extracted from the measurements, and a comparison between the data sets is per- formed to provide a measure of correlation as a function of distance and time between the ionosonde and AoA …

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Impacts Of Sub-Auroral Polarization Streams On High Frequency Operations As A Function Of Modeled Particle Energy Flux, Nathan D. Smith Mar 2018

Impacts Of Sub-Auroral Polarization Streams On High Frequency Operations As A Function Of Modeled Particle Energy Flux, Nathan D. Smith

Theses and Dissertations

Space weather events can cause irregularities within the ionosphere; in particular, this research examines sub-auroral polarization streams (SAPS), as their accompanying irregularities and effects can degrade high-frequency (HF) signal propagation. It is known that the strongest westerly current drifts delineating SAPS are associated with a deep ionospheric trough, which in turn contaminates HF data with clutter from the non-standard ionosphere. Having a methodology to track and identify these occurrences on current computational architecture would provide operators enhanced situational awareness in knowing to expect degradation in HF processes. This study has discovered a weak, yet significant, exponentially decaying correlation between maximum …

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Pulse Height Spectra Analysis Of A Neutron Energy Tuning Assembly, Jason R. Stickney Mar 2018

Pulse Height Spectra Analysis Of A Neutron Energy Tuning Assembly, Jason R. Stickney

Theses and Dissertations

An energy tuning assembly (ETA) was previously designed and built for the purpose of irradiating samples with a combination of a thermonuclear and a prompt fission neutron spectrum. Initial research was performed to characterize the performance of the ETA at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron using 33 MeV deuteron breakup on tantalum as the neutron source. This research analyzes detector responses collected from three EJ-309 detectors used to characterize the ETA generated neutron field. A signal processing chain was developed to reduce the full waveform data into a pulse height spectrum. The primary goal was to develop a …

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Wall-Modeled Large Eddy Simulation Of A Three-Dimensional Shock-Boundary Layer Interaction, Nicholas J. Marco Mar 2018

Wall-Modeled Large Eddy Simulation Of A Three-Dimensional Shock-Boundary Layer Interaction, Nicholas J. Marco

Theses and Dissertations

The direct simulation of turbulent flows is prohibitive at high Reynolds numbers; thus, methods such as RANS and LES are used. However, these methods still require a large number of cells near a solid boundary. To circumvent this issue, a Wall-Modeled Large Eddy Simulation (WM-LES) can be used. Of interest is how these wall models perform in comparison to a Wall-Resolved Large Eddy Simulation (WR-LES) and experimental results of a shock turbulent boundary layer interactions (STBLI) and specifically, whether equilibrium wall models are sufficient to resolve the oscillatory and hence non-equilibrium nature of these flows or whether a non-equilibrium model …

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Behavior Flexibility For Autonomous Unmanned Aerial Systems, Taylor B. Bodin Mar 2018

Behavior Flexibility For Autonomous Unmanned Aerial Systems, Taylor B. Bodin

Theses and Dissertations

Autonomous unmanned aerial systems (UAS) could supplement and eventually subsume a substantial portion of the mission set currently executed by remote pilots, making UAS more robust, responsive, and numerous than permitted by teleoperation alone. Unfortunately, the development of robust autonomous systems is difficult, costly, and time-consuming. Furthermore, the resulting systems often make little reuse of proven software components and offer limited adaptability for new tasks. This work presents a development platform for UAS which promotes behavioral flexibility. The platform incorporates the Unified Behavior Framework (a modular, extensible autonomy framework), the Robotic Operating System (a RSF), and PX4 (an open- source …

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Progressive Network Deployment, Performance, And Control With Software-Defined Networking, Daniel J. Casey Mar 2018

Progressive Network Deployment, Performance, And Control With Software-Defined Networking, Daniel J. Casey

Theses and Dissertations

The inflexible nature of traditional computer networks has led to tightly-integrated systems that are inherently difficult to manage and secure. New designs move low-level network control into software creating software-defined networks (SDN). Augmenting an existing network with these enhancements can be expensive and complex. This research investigates solutions to these problems. It is hypothesized that an add-on device, or "shim" could be used to make a traditional switch behave as an OpenFlow SDN switch while maintaining reasonable performance. A design prototype is found to cause approximately 1.5% reduction in throughput for one ow and less than double increase in latency, …

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Target Detection Using Convolutional Neural Networks, Robert P. Loibl Mar 2018

Target Detection Using Convolutional Neural Networks, Robert P. Loibl

Theses and Dissertations

This research explores the use of Convolutional Neural Networks (CNNs) to classify targets of interest within satellite imagery. Methods were specifically devised for the classification of airports within Landsat-8 scenes. A novel automated dataset generation technique was developed to create labeled datasets from satellite imagery using only coordinate metadata. Using this approach a very large dataset of over 132,000 labeled images was created without human input. This dataset was used to evaluate the effects of color and resolution on airport classification accuracy. Two experiments were run with the first experiment classifying large airports with 96.8% accuracy, and the second classifying …

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Passive Radiolocation Of Ieee 802.11 Emitters Using Directional Antennae, Bradford E. Law Mar 2018

Passive Radiolocation Of Ieee 802.11 Emitters Using Directional Antennae, Bradford E. Law

Theses and Dissertations

Low-cost commodity hardware and cheaper, more capable consumer-grade drones make the threat of home-made, inexpensive drone-mounted wireless attack platforms (DWAPs) greater than ever. Fences and physical security do little to impede a drone from approaching private, commercial, or government wireless access points (WAPs) and conducting wireless attacks. At the same time, unmanned aerial vehicles (UAVs) present a valuable tool for network defenders conducting site surveys and emulating threats. These platforms present near-term dangers and opportunities for corporations and governments. Despite the vast leaps in technology these capabilities represent, UAVs are noisy and consequently difficult to conceal as they approach a …

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Stereo Vision: A Comparison Of Synthetic Imagery Vs. Real World Imagery For The Automated Aerial Refueling Problem, Nicholas J. Seydel Mar 2018

Stereo Vision: A Comparison Of Synthetic Imagery Vs. Real World Imagery For The Automated Aerial Refueling Problem, Nicholas J. Seydel

Theses and Dissertations

Missions using unmanned aerial vehicles have increased in the past decade. Currently, there is no way to refuel these aircraft. Accomplishing automated aerial refueling can be made possible using the stereo vision system on a tanker. Real world experiments for the automated aerial refueling problem are expensive and time consuming. Currently, simulations performed in a virtual world have shown promising results using computer vision. It is possible to use the virtual world as a substitute environment for the real world. This research compares the performance of stereo vision algorithms on synthetic and real world imagery.

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Satellite Communications In The V And W Band: Tropospheric Effects, Bertus A. Shelters Mar 2018

Satellite Communications In The V And W Band: Tropospheric Effects, Bertus A. Shelters

Theses and Dissertations

An investigation into the use of Weather Cubes compiled by the atmospheric characterization package, Laser Environmental Effects Definition and Reference (LEEDR), to develop accurate, long-term attenuation statistics for link-budget analysis is presented. A Weather Cube is a three-dimensional mesh of numerical weather prediction (NWP) data plus LEEDR calculations that allows for the quantification of rain, cloud, aerosol, and molecular effects at any UV to RF wavelength on any path contained within the cube. The development of this methodology is motivated by the potential use of V (40-75 GHz) and W (75-110 GHz) band frequencies for the satellite communication application, as …

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Analysis Of A Voting Method For Ranking Network Centrality Measures On A Node-Aligned Multiplex Network, Kyle S. Wilkinson Mar 2018

Analysis Of A Voting Method For Ranking Network Centrality Measures On A Node-Aligned Multiplex Network, Kyle S. Wilkinson

Theses and Dissertations

Identifying relevant actors using information gleaned from multiple networks is a key goal within the context of human aspects of military operations. The application of a voting theory methodology for determining nodes of critical importance—in ranked order of importance—for a node-aligned multiplex network is demonstrated. Both statistical and qualitative analyses on the differences of ranking outcomes under this methodology is provided. As a corollary, a multilayer network reduction algorithm is investigated within the context of the proposed ranking methodology. The application of the methodology detailed in this thesis will allow meaningful rankings of relevant actors to be produced on a …

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Modeling A Space-Based Quantum Link, Alexander W. Duchane Mar 2018

Modeling A Space-Based Quantum Link, Alexander W. Duchane

Theses and Dissertations

Quantum sources and single photon detectors have improved, allowing quantum algorithms for communication, encryption, computing, and sensing to transition from theory and small-scale laboratory experiments to field experiments. One such quantum algorithm, Quantum Key Distribution, uses optical pulses to generate shared random bit strings between two locations. These shared bit strings can be turned into encryption keys to be used as a one-time-pad or integrated with symmetric encryption techniques such as the Advanced Encryption Standard. This method of key generation and encryption is resistant to future advances in quantum computing which significantly degrade the effectiveness of current asymmetric key sharing …

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The Impact Of Changing Requirements, James C. Ellis Mar 2018

The Impact Of Changing Requirements, James C. Ellis

Theses and Dissertations

The fundamental purpose of an Engineering Change Proposal (ECP) is to change the requirements of a contract. To build in flexibility, the acquisition practice is to estimate a dollar value to hold in reserve after the contract is awarded. There appears to be no empirical-based method for estimating this ECP withhold in the literature. Using the Cost Assessment Data Enterprise (CADE) database, 533 contracts were randomly selected to build two regression models: one to predict the likelihood of a contract experiencing an ECP, and the other to determine the expected median percent increase in baseline contract cost if an ECP …

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Radial Basis Function Generated Finite Differences For The Nonlinear Schrodinger Equation, Justin Ng Mar 2018

Radial Basis Function Generated Finite Differences For The Nonlinear Schrodinger Equation, Justin Ng

Theses and Dissertations

Solutions to the one-dimensional and two-dimensional nonlinear Schrodinger (NLS) equation are obtained numerically using methods based on radial basis functions (RBFs). Periodic boundary conditions are enforced with a non-periodic initial condition over varying domain sizes. The spatial structure of the solutions is represented using RBFs while several explicit and implicit iterative methods for solving ordinary differential equations (ODEs) are used in temporal discretization for the approximate solutions to the NLS equation. Splitting schemes, integration factors and hyperviscosity are used to stabilize the time-stepping schemes and are compared with one another in terms of computational efficiency and accuracy. This thesis shows …

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Shortest Path Across Stochastic Network With Correlated Random Arcs, Stephanie M. Boone Mar 2018

Shortest Path Across Stochastic Network With Correlated Random Arcs, Stephanie M. Boone

Theses and Dissertations

This paper introduces a new approach to identify the shortest path across a stochastic network with correlated random arcs utilizing nonparametric samples of arc lengths. This approach is applied to find optimal aircraft routes that minimize expected fuel consumption for a given airspeed utilizing predicted wind output from NWP ensemble models. Results from this new methodology are then compared to the current fuel minimization route planning method that utilizes deterministic NWP wind data for arc lengths. Comparisons are also made to other previously proposed alternative fuel minimization methodologies that utilize mean and median wind data calculated from NWP ensemble wind …

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Characterization Of Silicon Ion Exposure On Deinococcus Radiodurans, Richard F. Daughtry Mar 2018

Characterization Of Silicon Ion Exposure On Deinococcus Radiodurans, Richard F. Daughtry

Theses and Dissertations

Deinococcus radiodurans is a robust bacterium that is known for its extraordinary resistance to ionizing radiation. In general, many of the investigations of this bacterium's resistance have revolved around low linear energy transfer radiation, such as gamma and electron radiation. This study explored Deinococcus radiodurans's ability to survive high linear energy transfer radiation, specifically proton and neutron radiation. Deinococcus radiodurans was dehydrated to reduce the effects of low linear energy transfer radiation. The bacteria were exposed to both neutron and proton radiation of varying amounts and rehydrated. The resulting colonies were counted and compared to colonies of non-irradiated control samples …

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Pattern-Of-Life Modeling Using Data Leakage In Smart Homes, Steven M. Beyer Mar 2018

Pattern-Of-Life Modeling Using Data Leakage In Smart Homes, Steven M. Beyer

Theses and Dissertations

This work investigates data leakage in smart homes by providing a Smart Home Automation Architecture (SHAA) and a device classifier and pattern-of-life analysis tool, CITIoT (Classify, Identify, and Track Internet of things). CITIoT was able to capture traffic from SHAA and classify 17 of 18 devices, identify 95% of the events that occurred, and track when users were home or away with near 100% accuracy. Additionally, a mitigation tool, MIoTL (Mitigation of IoT Leakage) is provided to defend against smart home data leakage. With mitigation, CITIoT was unable to identify motion and camera devices and was inundated with an average …

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Estimating Defensive Cyber Operator Decision Confidence, Markus M. Borneman Mar 2018

Estimating Defensive Cyber Operator Decision Confidence, Markus M. Borneman

Theses and Dissertations

As technology continues to advance the domain of cyber defense, signature and heuristic detection mechanisms continue to require human operators to make judgements about the correctness of machine decisions. Human cyber defense operators rely on their experience, expertise, and understanding of network security, when conducting cyber-based investigations, in order to detect and respond to cyber alerts. Ever growing quantities of cyber alerts and network traffic, coupled with systemic manpower issues, mean no one has the time to review or change decisions made by operators. Since these cyber alert decisions ultimately do not get reviewed again, an inaccurate decision could cause …

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Assured Android Execution Environments, Brandon P. Froberg Mar 2018

Assured Android Execution Environments, Brandon P. Froberg

Theses and Dissertations

Current cybersecurity best practices, techniques, tactics and procedures are insufficient to ensure the protection of Android systems. Software tools leveraging formal methods use mathematical means to assure both a design and implementation for a system and these methods can be used to provide security assurances. The goal of this research is to determine methods of assuring isolation when executing Android software in a contained environment. Specifically, this research demonstrates security properties relevant to Android software containers can be formally captured and validated, and that an implementation can be formally verified to satisfy a corresponding specification. A three-stage methodology called "The …

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Special Perturbations On The Jetson Tx1 And Tx2 Computers, Tyler M. Moore Mar 2018

Special Perturbations On The Jetson Tx1 And Tx2 Computers, Tyler M. Moore

Theses and Dissertations

Simplified General Perturbations Number 4 (SGP4) has been the traditional algorithm for performing Orbit Determination (OD) onboard orbiting spacecraft. However, the recent rise of high-performance computers with low Size, Weight, and Power (SWAP) factors has provided the opportunity to use Special Perturbations (SP), a more accurate algorithm to perform onboard OD. This research evaluates the most efficient way to implement SP on NVIDIA’s Jetson TX series of integrated Graphical Processing Units (GPUs). An initial serial version was implemented on the Jetson TX1 and TX2's Central Processing Units (CPUs). The runtimes of the initial version are the benchmark that the runtimes …

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