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Articles 1 - 30 of 231
Full-Text Articles in Engineering
Design Of A Miniaturized Cubesat Tt&C Patch Antenna, Thomas A. Butterick
Design Of A Miniaturized Cubesat Tt&C Patch Antenna, Thomas A. Butterick
Theses and Dissertations
This effort explored the design of miniaturized rectangular microstrip patch antennas for application as a telemetry, tracking, and control (TT&C) on a CubeSat. The motivation for this research was the Grissom-P CubeSat mission planned by AFIT. The TT&C antenna selected for the mission exceeded the allotted size by over a factor of two. The studies performed included analyses of simply reducing aperture size, altering substrate permittivity, and layered approaches to antenna miniaturization. The primary approach to miniaturization was based on a virtually shorted patch antenna. Other approaches included an edge-shorted, slotted patch and the use of corner truncations for improved …
Effects Of Calibration Errors On Dropped-Channel Polarimetric Synthetic Aperture Radar, Jacob C. Morrison
Effects Of Calibration Errors On Dropped-Channel Polarimetric Synthetic Aperture Radar, Jacob C. Morrison
Theses and Dissertations
Compressed Sensing (CS) is a mathematical technique that can be applied to sparse data sets to allow for sub-Nyquist sampling. DCPCS is a CS technique that recovers the signal from unmeasured polarisation channels due to antenna crosstalk coupling the information onto the remaining channels. DCPCS reduces data storage/transmission and receiver hardware requirements. This thesis examines the robustness of DCPCS to calibration errors on the antenna crosstalk matrix. Although the antenna design problem is relaxed to a large region of acceptable crosstalk values, very accurate calibration may be required in a monostatic radar. This thesis also looks at the importance of …
Robust Feature Matching For Visual-Based Aerial Navigation Using Registered Imagery, Luis Montenegro
Robust Feature Matching For Visual-Based Aerial Navigation Using Registered Imagery, Luis Montenegro
Theses and Dissertations
This work leverages the SIFT detector along with known robust feature matching techniques for vision-aided sUAS navigation solutions. The proposed algorithm focuses on a sufficient number of features extracted, their quality and their distribution.
Classifying Open-Air Target Measurements Using Simulation-Trained Convolutional Neural Networks, Matthew M. Rofrano
Classifying Open-Air Target Measurements Using Simulation-Trained Convolutional Neural Networks, Matthew M. Rofrano
Theses and Dissertations
No abstract provided.
Comparison Of Federated Kalman Filter And Autonomous Resilient Management Of All-Source Sensors (Armas) Framework For Fault Detection And Exclusion, Flavio Fernandes
Comparison Of Federated Kalman Filter And Autonomous Resilient Management Of All-Source Sensors (Armas) Framework For Fault Detection And Exclusion, Flavio Fernandes
Theses and Dissertations
In recent times, there is a great demand for resilient and robust PNT solutions. Current navigation systems rely heavily on GNSS to provide this solution. This dependence is a major concern and therefore it is prudent to use additional aids to provide the best solution possible. However, traditional methods to address this need require a nontrivial number of Kalman filters to maintain a fault-free solution. The federated filter approach provides an attractive alternative to the current solutions. In this thesis, we examine the use of the federated filter design to address this need in today’s integrated navigation systems. We compared …
Detection And Identification Of Covert Devices Using Infrared And Stacked Optics Detection, Michael A. Reyneke
Detection And Identification Of Covert Devices Using Infrared And Stacked Optics Detection, Michael A. Reyneke
Theses and Dissertations
This work investigates stacked optics detection methodologies to successfully detect and identify observational systems with a cyber-physical sensing tool, ODIN (Observational Device Identification Network). ODIN successfully detected the presence of stacked optics and LiDAR systems using night-vision devices with a 96.32% average accuracy rating, both overt and covertly placed, with objective lens diameters ranging from 17 mm to 50 mm at distances between 1 m to 5 m with and without commonly employed anti-reflective countermeasures. ODIN provides a foundation for counter- measure capabilities of NIR devices and stacked optical systems in stationary environments. Additionally, a pilot study on smartphone LiDAR …
Multichannel Blind Deconvolution Of Circularly Polarized Imagery, Patrick B. Cunningham
Multichannel Blind Deconvolution Of Circularly Polarized Imagery, Patrick B. Cunningham
Theses and Dissertations
Current methods can be used to recreate an expected Stokes polarization vector from measured light for characterization purposes. However, this only applies to three of the Stokes parameters, that is, the linear polarization components. Circular polarization is not currently being utilized for object characterization because the mathematical complexity is greater than for that of linear polarization. This research will analyze a way to expand existing algorithms to include circular polarization and enable the complete reconstruction of the Stokes vector from the measured light into a blind deconvolution algorithm for Stokes estimation and image reconstruction.
Utilization Of Characteristic Modal Analysis For Antenna Design Needed For An Afit Satellite, Scott C. Podlogar
Utilization Of Characteristic Modal Analysis For Antenna Design Needed For An Afit Satellite, Scott C. Podlogar
Theses and Dissertations
Antenna design is a pervasive, growing field for electrical engineers. As the number of new materials and techniques increase so too does the demand and requirements pushing forth new innovative ideas. Among these ideas is a leading edge analytic technique called Characteristic Modal Analysis (CMA) originally credited to Garbacz and Turpin. CMA works to break down the current distribution along a structure in a way that can offer great insights into how that structure operates as an antenna. This technique has great merits in post design analytics but it is rarely seen to be integrated into the design process. This …
Towards The Integration Of Ferroelectric Negative Capacitance With Gallium Oxide Semiconductors For High Power Applications, Guillermo A. Salcedo
Towards The Integration Of Ferroelectric Negative Capacitance With Gallium Oxide Semiconductors For High Power Applications, Guillermo A. Salcedo
Theses and Dissertations
Gallium oxide is a relatively new semiconductor material with characteristics auspicious for high frequency and high-voltage applications. Although several research groups have already demonstrated radio-frequency (RF) devices on Ga2O3 with remarkable features, there is still room for improvement. For instance, the operating frequency of RF field-effect transistors (FET) decreases with the parasitic capacitance, which can be counteracted by higher gate capacitance. Implementing ferroelectric dielectrics with suitable parameters in Ga2O3 FET promises to enhance the gate capacitance and therefore increase operating frequency. This work investigated the effect of various factors (film composition, film thickness, TiN …
Feasibility Study Of Radio Frequency Microelectromechanical Filters For Space Operation, Karanvir Singh
Feasibility Study Of Radio Frequency Microelectromechanical Filters For Space Operation, Karanvir Singh
Theses and Dissertations
Piezoelectric contour mode resonator technology has the unique advantage of combining low motional resistance with the ability to define multiple frequencies on the same substrate. Contour mode resonators can be mechanically coupled together to form robust band-pass filters for the next generation of GPS satellites with extreme size reduction compared to electrically coupled filters. Piezoelectric zinc oxide (ZnO) contour mode resonators have the potential for monolithic integration with current ZnO transistor further reducing size, power consumption, and cost of filter modules. Barium strontium titanate (BST) contour mode resonators have incredible frequency tunability due to the fundamental nature of the thin …
Charge Mitigation Technologies For Aircraft Platforms, Mitchell L. Rudy
Charge Mitigation Technologies For Aircraft Platforms, Mitchell L. Rudy
Theses and Dissertations
Research into ion-based advanced propulsion systems, such as air-breathing Hall effect thrusters on high-velocity aircraft and ion-propelled thrusters on spacecraft, necessitates addressing accompanying residual electric charge accumulation on the ungrounded flight platform. An experimental testbed was constructed to assess charge mitigation technologies and their effectiveness on aircraft. A Van de Graaff generator provided static charge accumulation levels exceeding a megavolt when combined with a high voltage direct current source generator. This research attached an isolated airfoil structure to the Van de Graaff generator's lower terminal to measure the induced leakage current under various applied environmental conditions, including up to three …
Robust Scandium Aluminum Nitride Mems Resonators For L Band Operation In Orbital Environments, Israel W. Dunk
Robust Scandium Aluminum Nitride Mems Resonators For L Band Operation In Orbital Environments, Israel W. Dunk
Theses and Dissertations
This thesis investigates AlN alloyed with scandium in a variety of resonator architectures including WEM, overtone WEM, LEM, and SAW that have the potential to achieve high levels of electrical performance and environmental robustness. SAW resonators operating near 370 MHz are fabricated on polycrystalline Sc.37Al.63N, and AlN with the resulting devices compared and conclusions drawn as to the merits of each material. The design and fabrication of SAW devices is discussed in detail, with the operating characteristics of these resonators then tested both electrically and mechanically. Mechanical characterisation includes analysis of vibration and shock effects on …
Surface Defect Detection In Aircraft Skin & Visual Navigation Based On Forced Feature Selection Through Segmentation, Tyler B. Hussey
Surface Defect Detection In Aircraft Skin & Visual Navigation Based On Forced Feature Selection Through Segmentation, Tyler B. Hussey
Theses and Dissertations
Visual inspection of aircraft skin for surface defects is an area of maintenance that is particularly intensive for time and manpower. One novel way to combat this problem is through the use of computer vision and the advent of Artificial Neural Networks (ANN), or more specifically, semantic segmentation via Convolutional Neural Networks (CNN). The research in the paper explores the use of semantic segmentation of aerial imagery as a way to force feature selection onto key areas of an image that might be more likely to correspond under seasonal variations. Utilizing feature selection and matching on the masked aerial image …
Supporting Space Domain Awareness Through The Development And Analysis Of Space Object Detection Algorithms Employed By Ground-Based Telescopes, Connor A. Paw
Theses and Dissertations
Detection algorithms are instrumental in maintaining space domain awareness, specifically in the observation, monitoring, and categorization of unknown space objects. State of the art detection algorithms utilize a matched filter or a spatial correlator on long exposure image data to make pixel-wise detection decisions. This thesis investigates the advantages and practical potential of two different post-processing detection algorithms that can be employed by ground-based telescopes. The first algorithm explored is based on a long exposure Fourier domain processing technique, while the second is centered around frame selection from a series of short exposure images. The results of the experiments performed …
Commuting Compositions For Quantum Circuit Reduction, Brenna R. Cole
Commuting Compositions For Quantum Circuit Reduction, Brenna R. Cole
Theses and Dissertations
The US Air Force has been increasing the use of automation in its weapon systems to include the remotely piloted aircraft (RPA) platforms. The RPA career field has had issues with poor pilot retention due to job stressors. For example, RPA operators spend a lot of time and attention surveilling a suspect on the ground for many hours, so adding automation to this activity could help improve pilot retention. The research problem in this thesis attempted to automate the process of observing a ground target. This thesis presents a method termed conic ray tracing for determining visibility and occlusion of …
Monte Carlo Tree Search Applied To A Modified Pursuit/Evasion Scotland Yard Game With Rendezvous Spaceflight Operation Applications, Joshua A. Daughtery
Monte Carlo Tree Search Applied To A Modified Pursuit/Evasion Scotland Yard Game With Rendezvous Spaceflight Operation Applications, Joshua A. Daughtery
Theses and Dissertations
This thesis takes the Scotland Yard board game and modifies its rules to mimic important aspects of space in order to facilitate the creation of artificial intelligence for space asset pursuit/evasion scenarios. Space has become a physical warfighting domain. To combat threats, an understanding of the tactics, techniques, and procedures must be captured and studied. Games and simulations are effective tools to capture data lacking historical context. Artificial intelligence and machine learning models can use simulations to develop proper defensive and offensive tactics, techniques, and procedures capable of protecting systems against potential threats. Monte Carlo Tree Search is a bandit-based …
Near Real-Time Zigbee Device Discrimination Using Cb-Dna Features, Yousuke Z. Matsui
Near Real-Time Zigbee Device Discrimination Using Cb-Dna Features, Yousuke Z. Matsui
Theses and Dissertations
Currently, Low-Rate Wireless Personal Area Networks (LR-WPAN) based on the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 standard are at risk due to open-source tools which allow bad actors to exploit unauthorized network access through various cyberattacks by falsifying bit-level credentials. This research investigates implementing a Radio Frequency (RF) air monitor to perform Near RealTime (NRT) discrimination of Zigbee devices using the IEEE 802.15.4 standard. The air monitor employed a Multiple Discriminant Analysis/Euclidean Distance classifier to discriminate Zigbee devices based upon Constellation-Based Distinct Native Attribute (CB-DNA) fingerprints. Through the use of CB-DNA fingerprints, Physical Layer (PHY) characteristics unique to …
A Non-Destructive Evaluation Application Using Software Defined Radios And Bandwidth Expansion, Nicholas J. O'Brien
A Non-Destructive Evaluation Application Using Software Defined Radios And Bandwidth Expansion, Nicholas J. O'Brien
Theses and Dissertations
The development of low-complexity, lightweight and low-cost Non-Destructive Evaluation (NDE) equipment for microwave device testing is desirable from a maintenance efficiency and operational availability perspective. Current NDE equipment tends to be custom-designed, cumbersome and expensive. Software Defined Radio (SDR) technology, and a bandwidth expansion technique that exploits a priori transmit signal knowledge and auto-correlation provides a solution. This research investigated the reconstruction of simultaneous SDR receiver instantaneous bandwidth (sub-band) collections using single, dual and multiple SDR receivers. The adjacent sub-bands, collectively spanning a transmit signal bandwidth were auto-correlated with a replica transmit signal to restore frequency and phase offsets. The …
Characterization And Sensitivity Analysis Of 6 Meter Cassegrain Antenna, James L. Harris
Characterization And Sensitivity Analysis Of 6 Meter Cassegrain Antenna, James L. Harris
Theses and Dissertations
This paper will characterize a 6 meter in diameter cassegrain antenna. The cassegrain antenna is a special form of a dual reflector antenna which uses a main reflector following a parabolic curve and a sub reflector which follows a hyperbolic curve. Cassegrain style antennas have multiple parameters which can be tuned to achieve specific design goals. Performing a sensitivity analysis will establish relationships between design parameters, directivity, side lobe levels, and effects of strut geometry. The initial design parameters will be assumed based on typical values. Results from the sensitivity analysis will be used to provide a performance band for …
Development Of A Drone-Mounted Wireless Attack Platform, Nathan V. Barker
Development Of A Drone-Mounted Wireless Attack Platform, Nathan V. Barker
Theses and Dissertations
The commercial drone market has grown rapidly due to the increasing utility and capabilities of drones. This new found popularity has made it possible for inexpensive drones capable of impressive carry capacities and flight times to reach the consumer market. These new features also offer an invaluable resource to wireless hackers. Capitalizing on their mobility, a wireless hacker can equip a drone with hacking tools to surpass physical security (e.g. fences) with relative ease and reach wireless networks. This research seeks to experimentally evaluate the ability of a drone-mounted wireless attack platform equipped with a directional antenna to conduct wireless …
Improved Ground-Based Monocular Visual Odometry Estimation Using Inertially-Aided Convolutional Neural Networks, Josiah D. Watson
Improved Ground-Based Monocular Visual Odometry Estimation Using Inertially-Aided Convolutional Neural Networks, Josiah D. Watson
Theses and Dissertations
While Convolutional Neural Networks (CNNs) can estimate frame-to-frame (F2F) motion even with monocular images, additional inputs can improve Visual Odometry (VO) predictions. In this thesis, a FlowNetS-based [1] CNN architecture estimates VO using sequential images from the KITTI Odometry dataset [2]. For each of three output types (full six degrees of freedom (6-DoF), Cartesian translation, and transitional scale), a baseline network with only image pair input is compared with a nearly identical architecture that is also given an additional rotation estimate such as from an Inertial Navigation System (INS). The inertially-aided networks show an order of magnitude improvement over the …
Adaptive-Hybrid Redundancy For Radiation Hardening, Nicolas S. Hamilton
Adaptive-Hybrid Redundancy For Radiation Hardening, Nicolas S. Hamilton
Theses and Dissertations
An Adaptive-Hybrid Redundancy (AHR) mitigation strategy is proposed to mitigate the effects of Single Event Upset (SEU) and Single Event Transient (SET) radiation effects. AHR is adaptive because it switches between Triple Modular Redundancy (TMR) and Temporal Software Redundancy (TSR). AHR is hybrid because it uses hardware and software redundancy. AHR is demonstrated to run faster than TSR and use less energy than TMR. Furthermore, AHR allows space vehicle designers, mission planners, and operators the flexibility to determine how much time is spent in TMR and TSR. TMR mode provides faster processing at the expense of greater energy usage. TSR …
Non-Destructive Characterization Of Rotated Uniaxial Anisotropic Materials, Alexander G. Knisely
Non-Destructive Characterization Of Rotated Uniaxial Anisotropic Materials, Alexander G. Knisely
Theses and Dissertations
Electromagnetic material characterization of anisotropic media requires measurement diversity, minimal measurement uncertainty and insight into sample symmetry. Additionally, non-destructive characterization techniques are valued over legacy measurement techniques because a destructive approach requires sample preparation to execute a measurement. A Single Port Waveguide Probe (SPWP) non-destructive material characterization technique is proposed to accommodate measuring a metal backed, known thickness, rotated uniaxial anisotropic material. A rotated uniaxial sample possesses unique transverse constitutive components and a longitudinal constitutive component which is the same as one of the transverse values. The SPWP consists of a rectangular waveguide aperture cut in the center of a …
Segmented Control Of Electrostatically Actuated Bimorph Micromirrors, Kullen W. Waggoner
Segmented Control Of Electrostatically Actuated Bimorph Micromirrors, Kullen W. Waggoner
Theses and Dissertations
Electrostatic actuating bimorph beams are a MEMS device that can be used to control arrays of small micromirrors for optical beam scanning. Previous research has demonstrated that creating high-angle deflection using long repeating arms of bimorph beams is possible. The current devices lack precise control and measurement of the mirror deflection. A solution to improve control and measurement is by using segmented bias channels to control separate portions of the actuation arm. The amount of mirror deflection will vary depending on which segments of the arm are actuated. This thesis discusses the results of FEA modeling and testing.
Engineered Surfaces To Control Secondary Electron Yield For Multipactor Suppression, James M. Sattler
Engineered Surfaces To Control Secondary Electron Yield For Multipactor Suppression, James M. Sattler
Theses and Dissertations
A significant problem for satellites, vacuum electron devices, and particle accelerators is multipactor: an avalanche of electrons caused by recurring secondary electron emission (SEE) in a time-varying electric field. The consequences of multipactor range from temporary to permanent device failure. This research studied how surface topography can be engineered to minimize SEE and suppress multipactor. Two new semi-empirical models (one based on a 2D pore, the other based on a 3D pore) were developed to predict the secondary electron yield (SEY) of a porous surface based on pore aspect ratio and porosity. The models were validated with experimental SEY measurements …
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 …
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 …
Investigation Of Electromagnetic Signatures Of A Fpga Using An Aprel Em-Isight System, Karynn A. Sutherlin
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 …
Multi-Mode Analysis Of Dual Ridged Waveguide Systems For Material Characterization, Jason G. Crosby
Multi-Mode Analysis Of Dual Ridged Waveguide Systems For Material Characterization, Jason G. Crosby
Theses and Dissertations
In this dissertation, two nondestructive dual ridged waveguide (DRWG) material characterization systems are investigated. The single and clamped DRWG probe geometries were analyzed in previous work; however, that research only incorporated the dominant DRWG mode. Here, that restriction is removed and the existence of evanescent higher- order modes is considered. Theoretical analysis of the single and clamped DRWG probes is presented and discussed. The approach taken here is similar to that presented in previous research: Love's equivalence theorem is used to remove the DRWG apertures which are replaced with equivalent magnetic currents radiating in the presence of the background parallel-plate …
Novel Applications Of A Thermally Tunable Bistable Buckling Silicon-On-Insulator (Soi) Microfabricated Membrane, Robert A. Lake
Novel Applications Of A Thermally Tunable Bistable Buckling Silicon-On-Insulator (Soi) Microfabricated Membrane, Robert A. Lake
Theses and Dissertations
Buckled membranes are commonly used microelectromechanical systems (MEMS) structures. Recent work has demonstrated that the deflection and stiffness of these membranes can be tuned through localized joule heating. These devices were implemented into the design and fabrication of two novel device applications, a tunable pressure sensor and a steerable micromirror. A differential pressure across the membrane causes de reflection, up or down, which can be measured and related to a specific pressure. By tuning the stiffness of the membrane, its pressure response is varied providing a wider range of application for the pressure sensor. A 2.0mm by 2.0mm square membrane …