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Articles 1 - 28 of 28
Full-Text Articles in Engineering
Improvements To Micro-Contact Performance And Reliability, Tod V. Laurvick
Improvements To Micro-Contact Performance And Reliability, Tod V. Laurvick
Theses and Dissertations
Microelectromechanical Systems (MEMS) based devices, and specifically microswitches, continue to offer many advantages over competing technologies. To realize the benefits of micro-switches, improvements must be made to address performance and reliability shortfalls which have long been an issue with this application. To improve the performance of these devices, the micro-contacts used in this technology must be understood to allow for design improvements, and offer a means for testing to validate this technology and determine when such improvements are ready for operational environments. To build devices which are more robust and capable of continued operation after billions of cycles requires that …
Integrated Circuit Wear-Out Prediction And Recycling Detection Using Radio-Frequency Distinct Native Attribute Features, Randall D. Deppensmith
Integrated Circuit Wear-Out Prediction And Recycling Detection Using Radio-Frequency Distinct Native Attribute Features, Randall D. Deppensmith
Theses and Dissertations
Radio Frequency Distinct Native Attribute (RF-DNA) has shown promise for detecting differences in Integrated Circuits(IC) using features extracted from a devices Unintentional Radio Emissions (URE). This ability of RF-DNA relies upon process variation imparted to a semiconductor device during manufacturing. However, internal components in modern ICs electronically age and wear out over their operational lifetime. RF-DNA techniques are adopted from prior work and applied to MSP430 URE to address the following research goals: 1) Does device wear-out impact RF-DNA device discriminability?, 2) Can device age be continuously estimated by monitoring changes in RF-DNA features?, and 3) Can device age state …
Physical Layer Defenses Against Primary User Emulation Attacks, Joan A. Betances
Physical Layer Defenses Against Primary User Emulation Attacks, Joan A. Betances
Theses and Dissertations
Cognitive Radio (CR) is a promising technology that works by detecting unused parts of the spectrum and automatically reconfiguring the communication system's parameters in order to operate in the available communication channels while minimizing interference. CR enables efficient use of the Radio Frequency (RF) spectrum by generating waveforms that can coexist with existing users in licensed spectrum bands. Spectrum sensing is one of the most important components of CR systems because it provides awareness of its operating environment, as well as detecting the presence of primary (licensed) users of the spectrum.
Absolute Positioning Using The Earth's Magnetic Anomaly Field, Aaron J. Canciani
Absolute Positioning Using The Earth's Magnetic Anomaly Field, Aaron J. Canciani
Theses and Dissertations
Achieving worldwide alternatives to GPS is a challenging engineering problem. Current GPS alternatives often suffer from limitations such as where and when the systems can operate. Navigation using the Earth's magnetic anomaly field, which is globally available at all times, shows promise to overcome many of these limitations. We present a navigation filter which uses the Earth's magnetic anomaly field as a navigation signal to aid an inertial navigation system (INS) in an aircraft. The filter utilizes highly-accurate optically pumped cesium (OPC) magnetometers to make scalar measurements of the Earth's magnetic field and compare them to a map using a …
Superconducting Quantum Interference Device Array Based High Frequency Direction Finding On An Airborne Platform, Tyrel K. Kvasager
Superconducting Quantum Interference Device Array Based High Frequency Direction Finding On An Airborne Platform, Tyrel K. Kvasager
Theses and Dissertations
This thesis evaluates a new incredibly sensitive highly linear high dynamic range 2D Bi-SQUID array purposed by the dissertation written by Susan Berggren applied to use on an airborne platform for the purposes of HFDF. To evaluate how useful the 2D Bi-SQUID is we explore multiple signals of the same frequency in two different base sensor configurations: Non-uniform phased array and non-colocated Poynting's Theorem based vector sensors. The exploration is performed using the SPIRIT HPC system to calculate the 2D Bi-SQUID output given multiple incident signals. The AoA estimation calculation is performed using the MUSIC algorithm on the signals received …
Utilization Of A Geodesic Sphere And Quadcopter As Two-Way Field Probe For Electro-Magnetic Field Measurements In An Indoor Radar Cross Section Range, Nathan Lett
Theses and Dissertations
Radar Cross Section (RCS) measurements rely heavily on multiple assumptions. Uncertainty in the final measurement is determined based on these assumptions. One source in particular is the non-homogeneous nature of the transmission path between radar test equipment and a target under test. The following research extends prior research. This thesis intends to provide a unique two-way field probe solution for measuring Electro-magnetic (EM) fluctuations in a test volume. In this thesis, the design, development, and demonstration of a geodesic sphere encased quadcopter two-way probe is explained. The Parrot® Bebop Drone quadcopter was used with a 2v frequency divided geodesic sphere …
Non-Linear Optimization Applied To Angle-Of-Arrival Satellite Based Geo-Localization For Biased And Time Drifting Sensors, Daniel E. Levy
Non-Linear Optimization Applied To Angle-Of-Arrival Satellite Based Geo-Localization For Biased And Time Drifting Sensors, Daniel E. Levy
Theses and Dissertations
Multiple sensors are used in a variety of geolocation systems. Many use Time Difference of Arrival (TDOA) or Received Signal Strength (RSS) measurements to locate the most likely location of a signal. When an object does not emit a classical RF signal, Angle of Arrival (AOA) measurements become more feasible than TDOA or RSS measurements. AOA measurements can be created from any sensor platform with any sort of camera. When location and attitude knowledge of the sensor passive objects can be tracked. A Non-Linear Optimization (NLO) method for calculating the most likely estimate from AOA measurements has been created in …
Characterization For The Development Of The Hybrid Multi-Junction Silicon Germanium Solar Cell, Jimmy J. Lohrman
Characterization For The Development Of The Hybrid Multi-Junction Silicon Germanium Solar Cell, Jimmy J. Lohrman
Theses and Dissertations
Based on the previous development of the hybrid multi-junction silicon (HMJ-Si) solar cell, this work characterized the preceding design for the development of the hybrid multi-junction silicon germanium (HMJ-SiGe) solar cell. Seven focus areas were investigated: diffraction pattern generation, photon propagation, silicon diffusion processing, ohmic contacts, the distributed Bragg reflector (DBR), the Fresnel zone plate (FZP), and the germanium/germanium telluride (Ge/GeTe) pn-junction Diffraction patterns were theoretically examined, and contact grating design characterization for reflectance and transmittance properties was modeled using rigorous coupled wave analysis. An improved silicon diffusion process follower was developed, and theoretical study and experimental assessment were accomplished …
Interference Suppression Using Knowledge-Aided Subarray Pattern Synthesis, David A. New
Interference Suppression Using Knowledge-Aided Subarray Pattern Synthesis, David A. New
Theses and Dissertations
Most phased array systems subarray many antenna elements into far fewer digitized channels. While having more degrees of freedom (DOF) yields better performance, adding channels to create more digital DOF increases system cost and data throughput requirements. A subarray itself constitutes a phased array with as many DOF as it has antenna element weights. Typically, only one degree of freedom is used to steer the maximum gain direction of the subarray pattern. For typical antenna geometries a single subarray will provide many more spatial DOF than there are digitized channels. The inherent DOF of the subarrays could be used to …
Optically Stimulated Luminescence From Ag-Doped Lithium Tetraborate (Li2b4o7), Ember S. Maniego
Optically Stimulated Luminescence From Ag-Doped Lithium Tetraborate (Li2b4o7), Ember S. Maniego
Theses and Dissertations
Silver-doped lithium tetraborate (Li2B4O7) crystals emit optically stimulated luminescence (OSL) in response to stimulating light around 400 nm. Photoluminescence, optical absorption, and electron paramagnetic resonance (EPR) were used to identify the defects in the crystal that cause this OSL. Lithium tetraborate crystals have Ag+ ions at Li+ sites and at interstitial sites. Upon ionization at room temperature via x rays, electron-hole pairs are generated. The electrons are trapped at Ag+ occupying interstitial sites, while the holes are trapped at Ag+ at lithium sites. The trapped electron centers become Ag0 …
Electromagnetic Characterization Of Materials Using A Dual Chambered High Temperature Waveguide, Jeffrey S. Sovern
Electromagnetic Characterization Of Materials Using A Dual Chambered High Temperature Waveguide, Jeffrey S. Sovern
Theses and Dissertations
Measurement of the electromagnetic properties of materials at high temperatures is important for industrial, scientific, medical, and aerospace applications [1]. Current high-temperature electromagnetic material characterization is a time consuming process that typically requires three days to collect data from one material specimen. For example, the standard high-temperature process involving rectangular waveguides [2] requires measurements of the sample (1), the empty waveguide (2), and a metal short standard (3) completed in separate heated runs over three days to perform the Nicolson-Ross-Weir inversion algorithm for computing permittivity and permeability. The technique developed here will reduce the high-temperature measurement process from three days …
Multihop Rendezvous Algorithm For Frequency Hopping Cognitive Radio Networks, John A. Pavlik
Multihop Rendezvous Algorithm For Frequency Hopping Cognitive Radio Networks, John A. Pavlik
Theses and Dissertations
Cognitive radios allow the possibility of increasing utilization of the wireless spectrum, but because of their dynamic access nature require new techniques for establishing and joining networks, these are known as rendezvous. Existing rendezvous algorithms assume that rendezvous can be completed in a single round or hop of time. However, cognitive radio networks utilizing frequency hopping that is too fast for synchronization packets to be exchanged in a single hop require a rendezvous algorithm that supports multiple hop rendezvous. We propose the Multiple Hop (MH) rendezvous algorithm based on a pre-shared sequence of random numbers, bounded timing differences, and similar …
Jamming Cognitive Radios, Travis J. Freeman
Jamming Cognitive Radios, Travis J. Freeman
Theses and Dissertations
The goal of this thesis is to identify and evaluate weaknesses in the rendezvous process for Cognitive Radio Networks (CRNs) in the presence of a Cognitive Jammer (CJ). Jamming strategies are suggested and tested for effectiveness. Methods for safe- guarding the Cognitive Radios (CRs) against a CJ are also explored. A simulation is constructed to set up a scenario of two CRs interacting with a CJ. Analysis of the simulation is conducted primarily at the waveform level. A hardware setup is constructed to analyze the system in the physical layer, verify the interactions from the simulation, and test in a …
Neutron Radiation Effects On Ge And Gesn Semiconductors, Christopher T. O'Daniel
Neutron Radiation Effects On Ge And Gesn Semiconductors, Christopher T. O'Daniel
Theses and Dissertations
Two different semiconductor materials received neutron radiation for assessment of radiation damage. The two materials are undoped bulk Ge and epitaxial Ge0.991Sn0.009, which is doped heavily with phosphorous. At room temperature, the Ge sample has direct and indirect bandgaps at 0.78 eV and 0.66 eV, respectively. The Ge0.991Sn0.009 sample has direct and indirect bandgaps at 0.72 eV and 0.63 eV, respectively. Two samples of each material were exposed to research reactor neutrons, delivering a 1 MeV equivalent neutron fluence of 2.52 × 1015 n/cm2. In order to assess the radiation …
Design And Analysis Of A Retroreflective Array For Ir Application, Michael E. Bollinger
Design And Analysis Of A Retroreflective Array For Ir Application, Michael E. Bollinger
Theses and Dissertations
This research investigates the adaptation of a Van Atta style of retrodirective array designed to work at 2 GHz to work in the infrared spectrum of 8-12 μm centered at 30 THz. The Computational Research and Engineering Acquisition Tools and Environments (CREATE) software suite and high performance computing (HPC) resources of the HPC Modernization program were utilized to model and simulate multiple steps of an adaptation process to illustrate and examine the incremental performance changes of frequency scaling the design. Two different substrate materials, germanium and hafnium oxide, are evaluated as the dielectric materials, and a comparison of the broadband …
Geosynchronous Binary Object Detection, Patrick B. Cunningham
Geosynchronous Binary Object Detection, Patrick B. Cunningham
Theses and Dissertations
This paper will compare competing methods for optically detecting binary objects. This is mostly intended for use in Space Situational Awareness (SSA), though has the potential to be used in other applications. The first method referred to as, “Single Object Detection” is a versatile algorithm which is currently used to detect extraterrestrial objects. However, it does not take into account interference by a nearby object. Therefore a second algorithm is investigated, referred to as “Binary Object Detection”, which does. The binary detection algorithm proved to have a comparable or superior Receiver Operating Characteristic (ROC) curve (based upon the area under …
Dynamic Honeypot Configuration For Programmable Logic Controller Emulation, Kyle A. Girtz
Dynamic Honeypot Configuration For Programmable Logic Controller Emulation, Kyle A. Girtz
Theses and Dissertations
Attacks on industrial control systems and critical infrastructure are on the rise. Important systems and devices like programmable logic controllers are at risk due to outdated technology and ad hoc security measures. To mitigate the threat, honeypots are deployed to gather data on malicious intrusions and exploitation techniques. While virtual honeypots mitigate the unreasonable cost of hardware-replicated honeypots, these systems often suffer from a lack of authenticity due to proprietary hardware and network protocols. In addition, virtual honeynets utilizing a proxy to a live device suffer from performance bottlenecks and limited scalability. This research develops an enhanced, application layer emulator …
Implementation And Performance Of Factorized Backprojection On Low-Cost Commercial-Off-The-Shelf Hardware, Alec C. Rasmussen
Implementation And Performance Of Factorized Backprojection On Low-Cost Commercial-Off-The-Shelf Hardware, Alec C. Rasmussen
Theses and Dissertations
Traditional Synthetic Aperture Radar (SAR) systems are large, complex, and expensive platforms that require significant resources to operate. The size and cost of the platforms limits the potential uses of SAR to strategic level intelligence gathering or large budget research efforts. The purpose of this thesis is to implement the factorized backprojection SAR image processing algorithm in the C++ programming language and test the code's performance on a low cost, low size, weight, and power (SWAP) computer: a Raspberry Pi Model B. For a comparison of performance, a baseline implementation of filtered backprojection is adapted to C++ from pre-existing MATLAB® …
Integrity Determination For Image Rendering Vision Navigation, Sean M. Calhoun
Integrity Determination For Image Rendering Vision Navigation, Sean M. Calhoun
Theses and Dissertations
This research addresses the lack of quantitative integrity approaches for vision navigation, relying on the use of image or image rendering techniques. The ability to provide quantifiable integrity is a critical aspect for utilization of vision systems as a viable means of precision navigation. This research describes the development of two unique approaches for determining uncertainty and integrity for a vision based, precision, relative navigation system, and is based on the concept of using a single camera vision system, such as an electro-optical (EO) or infrared imaging (IR) sensor, to monitor for unacceptably large and potentially unsafe relative navigation errors. …
Characterization Of Quad-Copter Positioning Systems And The Effect Of Pose Uncertainties On Field Probe Measurements, James C. Dossett
Characterization Of Quad-Copter Positioning Systems And The Effect Of Pose Uncertainties On Field Probe Measurements, James C. Dossett
Theses and Dissertations
When measuring the Radar Cross Section (RCS) of a test object, many uncertainties must be accounted for, such as the non-homogeneous nature of the medium between the radar test equipment and the platform under test. There are a variety of other error sources, including clutter and Radio Frequency Interference (RFI), motivating the development of techniques to measure and model the uncertainties in RCS measurements. The following research, in unison with prior and current efforts, intends to reduce the impact of these uncertainties by utilizing a unique two-way field probe in the form of a geodesic sphere encompassing a commercial quad-copter …
Using Phase Screens To Synthesize Electromagnetic Gaussian-Schell Model Sources With Desired Amplitude, Coherence, And Polarization, Christopher K. Kokoczka
Using Phase Screens To Synthesize Electromagnetic Gaussian-Schell Model Sources With Desired Amplitude, Coherence, And Polarization, Christopher K. Kokoczka
Theses and Dissertations
An electromagnetic Gaussian-Schell model (EGSM) source is built with desired coherence, amplitude, and polarization using correlated phase screens based on re- search conducted in Refs. [2, 9]. A new method of amplitude control is presented and tested using spatial light modulators (SLM). A brief review of theory and concepts is discussed followed by methods of how to build an EGSM source, correlated phase screens, and control amplitude using SLM gratings. The experimental set-up is presented which builds EGSM sources that demonstrate desired amplitude, coherence, and polarization. Irradiance correlation, degree of polarization, and Stokes parameters S0 and S1 are …
Hardware Development And Error Characterisation For The Afit Rail Sar System, Dayne A. Schmidt
Hardware Development And Error Characterisation For The Afit Rail Sar System, Dayne A. Schmidt
Theses and Dissertations
This research is focussed on updating the Air Force Institute of Technology (AFIT) Radar Instrumentation Lab (RAIL) Synthetic Aperture Radar (SAR) experimental system. Firstly, this research assesses current hardware limitations and updates the system configuration and methodology to enable collections from a receiver in motion. Secondly, orthogonal frequency-division multiplexing (OFDM) signals are used to form (SAR) images in multiple experimental and simulation configurations. This research analyses, characterises and attempts compensation of relevant SAR image error sources, such as Doppler shift or motion measurement errors (MMEs). Error characterisation is conducted using theoretical, simulated and experimental methods. Final experimental results are presented …
Comparison Of Methods For Radio Position Of Non-Emitting Dismounts, Collin J. Seanor
Comparison Of Methods For Radio Position Of Non-Emitting Dismounts, Collin J. Seanor
Theses and Dissertations
Radio Tomographic Imaging (RTI) is a form of Device Free Passive Localization (DFPL) that utilizes the Received Signal Strength (RSS) values from a collection of wireless transceivers to produce an image in order to localize a subject within a Wireless Sensor Network (WSN). Radio Mapping is another form of DFPL that can utilize the same RSS values from a WSN to localize a subject by comparing recent values to a set of calibration data. RTI and Radio Mapping have never been directly compared to one another as a means of localization within a WSN. The goal of this research is …
A Comparative Analysis Of Ieee 802.15.4 Adapters For Wireless Range Finding, Andrew P. Seitz
A Comparative Analysis Of Ieee 802.15.4 Adapters For Wireless Range Finding, Andrew P. Seitz
Theses and Dissertations
ZigBee wireless networks have become increasingly prevalent over the past decade. Based on the IEEE 802.15.4 low data rate wireless standard, ZigBee offers low-cost mesh connectivity in hospitals, refineries, building automation, and critical infrastructure. This thesis explores two ZigBee Received Signal Strength Indicator (RSSI)-based rangefinding tool sets used for assessing wireless network security: Z-Ranger and Zbfind. Z-Ranger is a new tool set developed herein for the Microchip Zena Wireless Adapter that offers configurable distance estimating parameters and a RSSI resolution of 256 values. Zbfind is an application developed for the Atmel RZUSBstick with no configurable distance estimating parameters and a …
Field-Based Phase Retrieval Using Under-Sampled Data, Tatsuki L. Watts
Field-Based Phase Retrieval Using Under-Sampled Data, Tatsuki L. Watts
Theses and Dissertations
A phase retrieval algorithm designed for use with under-sampled astronomical data is developed in this thesis. Blind-deconvolution, Gerchberg Saxton (GS), and a field-based compass search are combined into an algorithm capable of recovering Zernike coefficients 4 through 11 from single frames of noisy, under-sampled data without the need to unwrap the recovered phase. The performance of the algorithm in data under-sampled by a factor of 2 is compared the performance of the algorithm on Nyquist-sampled data. In simulation trials, the magnitudes of all 8 estimated Zernike coefficients converged to within half a wave of the true values for 98% of …
An Openeaagles Framework Extension For Hardware-In-The-Loop Swarm Simulation, Derek B. Worth
An Openeaagles Framework Extension For Hardware-In-The-Loop Swarm Simulation, Derek B. Worth
Theses and Dissertations
Unmanned Aerial Vehicle (UAV) swarm applications, algorithms, and control strategies have experienced steady growth and development over the past 15 years. Yet, to this day, most swarm development efforts have gone untested and thus unimplemented. Cost of aircraft systems, government imposed airspace restrictions, and the lack of adequate modeling and simulation tools are some of the major inhibitors to successful swarm implementation. This thesis examines how the OpenEaagles simulation framework can be extended to bridge this gap. This research aims to utilize Hardware-in-the-Loop (HIL) simulation to provide developers a functional capability to develop and test the behaviors of scalable and …
Comparison Of Radio Frequency Distinct Native Attribute And Matched Filtering Techniques For Device Discrimination And Operation Identification, Barron D. Stone
Comparison Of Radio Frequency Distinct Native Attribute And Matched Filtering Techniques For Device Discrimination And Operation Identification, Barron D. Stone
Theses and Dissertations
The research presented here provides a comparison of classification, verification, and computational time for three techniques used to analyze Unintentional Radio- Frequency (RF) Emissions (URE) from semiconductor devices for the purposes of device discrimination and operation identification. URE from ten MSP430F5529 16-bit microcontrollers were analyzed using: 1) RF Distinct Native Attribute (RFDNA) fingerprints paired with Multiple Discriminant Analysis/Maximum Likelihood (MDA/ML) classification, 2) RF-DNA fingerprints paired with Generalized Relevance Learning Vector Quantized-Improved (GRLVQI) classification, and 3) Time Domain (TD) signals paired with matched filtering. These techniques were considered for potential applications to detect counterfeit/Trojan hardware infiltrating supply chains and to defend …
Automated Sunspot Classification And Tracking Using Sdo/Hmi Imagery, Maclane A. Townsend
Automated Sunspot Classification And Tracking Using Sdo/Hmi Imagery, Maclane A. Townsend
Theses and Dissertations
Verification of an automated sunspot detection and classification algorithm is conducted utilizing two years of solar imagery from NASA's Solar Dynamics Observatory (SDO) satellite. Automated McIntosh classifications are compared against sunspot reports from the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center (SWPC) using a three-tiered comparison metric. Statistical confidence is demonstrated for algorithm performance and consistency when compared against the SWPC data set, suggesting future applications of the algorithm will perform similarly. A sunspot tracking algorithm is added to the existing code and demonstrates reliable feature tracking for time periods out to four days between consecutive images. …