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Articles 1 - 30 of 32
Full-Text Articles in Engineering
Ionospheric F-Layer Dipole Flute Instability Effects On Electromagnetic Scattering In A Magnetohydrodynamic Plasma, Andrew J. Knisely
Ionospheric F-Layer Dipole Flute Instability Effects On Electromagnetic Scattering In A Magnetohydrodynamic Plasma, Andrew J. Knisely
Theses and Dissertations
The ionosphere has significant impact on radio frequency (RF) applications such as satellites, over-the-horizon radar, and commercial communication systems. The dynamic processes effecting the behavior of the ionic content leads to a variety of instabilities that adversely affect the quality of RF signals. In the F-layer ionosphere, flute instability persists, appearing as two radial regions of high and low density perturbations elongated along the earth's geomagnetic field lines. The sizes of flute structures are comparable to the wavelengths in the high frequency spectrum. The objective is to characterize the high frequency scattering of an incident field by developing a 3D …
Collaborative All-Source Navigation With Integrity, Jonathon S. Gipson
Collaborative All-Source Navigation With Integrity, Jonathon S. Gipson
Theses and Dissertations
The novel ARMAS-SOM framework fuses collaborative all-source sensor information in a resilient manner with fault detection, exclusion, and integrity solutions recognizable to a GNSS user. This framework uses a multi-filter residual monitoring approach for fault detection and exclusion and is augmented with an additional "observability" EKF sub-layer for resilience. We monitor the a posteriori state covariances in this sub-layer to provide intrinsic awareness when navigation state observability assumptions required for integrity are in danger. This is used to selectively augment the framework with offboard information to preserve resilience. By maintaining split parallel collaborative and proprioceptive estimation instances and employing a …
Characterization Of Anisotropic Materials Using Scattered Field Measurements, Hirsch M. Chizever
Characterization Of Anisotropic Materials Using Scattered Field Measurements, Hirsch M. Chizever
Theses and Dissertations
This research uses monostatic far-zone scattered field measurements to estimate the permittivity of biaxial materials at X-Band. Utilizing Radar Cross Section (RCS) measurement techniques, this effort examines the efficacy of whole-sample TEM illumination in the estimation of anisotropic permittivity, in contrast with traditional subsample illumination methods. The research examines the impact that dielectric supports have on measurement error and uncertainty in permittivity estimates. Following an incremental approach, the research first demonstrates successful estimation of permittivity for isotropic spheres followed by a Teflon isotropic cube. Finally, the method is applied to uniaxial and biaxial cubes whose anisotropic permittivity is validated through …
Evaluating Testing Procedures For Openflow Controller Network Re-Provisioning Time, Steven J. Jensen
Evaluating Testing Procedures For Openflow Controller Network Re-Provisioning Time, Steven J. Jensen
Theses and Dissertations
Software-Defined Networking promises several advantages over traditional networking architectures, but has seen little adoption. Recently codified controller evaluation methodologies have seen little validation without strong statistical analysis of the results. The research developed an environment testing implementing a published Network Re-provisioning Time methodology to evaluate five OpenFlow controllers. The methodology is strong with required parameters but had issues with some edge cases. Further refinement and adding a convergence metric may close the gaps.
New Methods In Wavelet Analysis For Applications Of The Wavelet Transform, Jeffrey D. Williams
New Methods In Wavelet Analysis For Applications Of The Wavelet Transform, Jeffrey D. Williams
Theses and Dissertations
A commonality in the many applications and domains where signal processing (SP)is applied is the detection of events. Detection in SP requires the identification of the occurrence of an event, within a signal, and distinguishing the occurrence from no event. In a classical application of SP, seismologists seek to detect abnormalities in an electromagnetic (EM) signal to detect or not detect the occurrence of an earthquake, represented as an anomalous EM pulse. Since many signals are noisy, such as those produced by a seismograph, it can be challenging to distinguish a significant EM pulse from incident noise. In SP, smoothing …
Sar Collection Planning And Data Quality Assessment, Jacob M. Brumfield
Sar Collection Planning And Data Quality Assessment, Jacob M. Brumfield
Theses and Dissertations
Radar resource management is an important research topic in the radar community. Identifying the performance of a synthetic aperture radar image early into a data processing chain can improve intelligence collection mission performance. To achieve that goal, separate flags can be presented to a radar technician along a data processing chain to identify various errors within a data collection. Toward the end, this thesis analyzes he radar image processing chain and identifies data quality checks that could be implemented. The first quality check is to identify canonical targets and the necessary Nyquist-Shannon sampling requirements. Then, observations can be made to …
Design And Fabrication Of Zinc Oxide Optofluidic Laser Elements, Kyle T. Bodily
Design And Fabrication Of Zinc Oxide Optofluidic Laser Elements, Kyle T. Bodily
Theses and Dissertations
This thesis systematically goes through the derivation, simulation, and experimentation of Zinc Oxide optofluidic micro laser elements. Single and coupled ring resonators were simulated to show single mode transmission as well as enhanced coupling capabilities when surrounded by high refractive index liquid. Devices with diameters ranging from 100-500 µm were successfully fabricated inexpensively through standard cleanroom procedures. The devices were tested using two different pump laser systems. Testing included such factors as high pump intensity, various angles of excitation, and low temperature. In all cases PL emission was observed and recorded.
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 …
Modeling Aircraft Disturbance Fields For Magnetic Navigation Using Dense Anns And The Novel Manntl Architecture, Kyle A. Emery
Modeling Aircraft Disturbance Fields For Magnetic Navigation Using Dense Anns And The Novel Manntl Architecture, Kyle A. Emery
Theses and Dissertations
The ability to use GPS for navigation is becoming increasingly limited in certain areas of the world. Knowing this, the Air Force Research Labs is constantly looking for ways to improve alternate navigation methods such as magnetic navigation. In the interest of making advancements in aircraft disturbance field modelling, Lieutenant Emery recreates models from previous works to prove results. Lieutenant Emery also introduces a novel model architecture that attempts to mix the filtering properties of Tolles-Lawson with the non-linear capabilities of an artificial neural network. The introduction of this model could present better aircraft disturbance field modelling and in turn, …
Using Motion Capture And Augmented Reality To Test Aar With Boom Occlusion, Vincent J. Bownes
Using Motion Capture And Augmented Reality To Test Aar With Boom Occlusion, Vincent J. Bownes
Theses and Dissertations
The operational capability of drones is limited by their inability to perform aerial refueling. This can be overcome by automating the process with a computer vision solution. Previous work has demonstrated the feasibility of automated aerial refueling (AAR) in simulation. To progress this technique to the real world, this thesis conducts experiments using real images of a physical aircraft replica and a motion capture system for truth data. It also compares the error between the real and virtual experiments to validate the fidelity of the simulation. Results indicate that the current technique is effective on real images and that the …
Automated Find Fix And Track With A Medium Altitude Long Endurance Remotely Piloted Aircraft, Aubrey L. Olson
Automated Find Fix And Track With A Medium Altitude Long Endurance Remotely Piloted Aircraft, Aubrey L. Olson
Theses and Dissertations
A limitation in RPA ISR operations is loss of target track if the command link is severed. For an RPA to effectively execute the ISR mission without a command link, it needs the capability to F2T targets autonomously. Automated Find Fix and Track (AFFTRAC) was developed to help solve this problem by demonstrating a proof of concept tactical autopilot. Monocular stereo vision was used to process sequential images acquired during orbit to produce a partial structural point cloud of the original structure. This partial structural point cloud was then exploited to create a holding area density for the aircraft to …
The Wargaming Commodity Course Of Action Automated Analysis Method, William T. Deberry
The Wargaming Commodity Course Of Action Automated Analysis Method, William T. Deberry
Theses and Dissertations
This research presents the Wargaming Commodity Course of Action Automated Analysis Method (WCCAAM), a novel approach to assist wargame commanders in developing and analyzing courses of action (COAs) through semi-automation of the Military Decision Making Process (MDMP). MDMP is a seven-step iterative method that commanders and mission partners follow to build an operational course of action to achieve strategic objectives. MDMP requires time, resources, and coordination – all competing items the commander weighs to make the optimal decision. WCCAAM receives the MDMP's Mission Analysis phase as input, converts the wargame into a directed graph, processes a multi-commodity flow algorithm on …
An Analysis Of X-Band Radiation For Space Based Wireless Power Transmission, Noah W. Friz
An Analysis Of X-Band Radiation For Space Based Wireless Power Transmission, Noah W. Friz
Theses and Dissertations
The USAF is interested in developing a solar powered satellite power beaming system using X-Band radiation. To determine the expected level of transmission efficiency of the system, an atmospheric characterization and radiative transfer modeling system called LEEDR was employed. A study was conducted to validate LEEDRs performance while working with microwave frequencies by replicating brightness temperatures measured by a 10.7 GHz radiometer above the Pacific Ocean in 1999. The results were inconclusive. Brightness temperature vs. rain rate curves developed within other studies for X-Band radiation curves could be replicated within LEEDR, and therefore the associated path transmission and extinction values. …
Optimal Defense Of High Value Airborne Assets, Isaac E. Weintraub
Optimal Defense Of High Value Airborne Assets, Isaac E. Weintraub
Theses and Dissertations
Optimal control theory and differential game theory is applied to the study of the defense of high value airborne assets, particularly in the case of a single threat such as an adversarial aircraft or missile. Rather than utilizing onboard defenses of the high value airborne asset, defense is proposed using a teamed unmanned combat air vehicle. The common scenario throughout this dissertation involves the defense of a high value airborne asset (evader) teamed with an unmanned combat vehicle (defender) against a single threat (pursuer). The unmanned combat air vehicle (defender), provides defense in one of two ways: kinetic or directed …
Indoor Navigation Using Convolutional Neural Networks And Floor Plans, Ricky D. Anderson
Indoor Navigation Using Convolutional Neural Networks And Floor Plans, Ricky D. Anderson
Theses and Dissertations
The goal of this thesis is to evaluate a new indoor navigation technique by incorporating floor plans along with monocular camera images into a CNN as a potential means for identifying camera position. Building floor plans are widely available and provide potential information for localizing within the building. This work sets out to determine if a CNN can learn the architectural features of a floor plan and use that information to determine a location. In this work, a simulated indoor data set is created and used to train two CNNs. A classification CNN, which breaks up the floor plan into …
Comparison Of Conic Ray Tracing For Occlusion Determination On 3d Point Cloud Data, Henry Cho
Comparison Of Conic Ray Tracing For Occlusion Determination On 3d Point Cloud Data, Henry Cho
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 …
Mitigating The Multipath Effects On Radio Tomographic Imaging, Destinee N. Battle
Mitigating The Multipath Effects On Radio Tomographic Imaging, Destinee N. Battle
Theses and Dissertations
Various radio tomographic imaging (RTI) models and reconstruction methods are equipped with capabilities to mitigate the effects of multipath interference. This thesis combined the network shadowing (NeSh) and weighting-g models in conjunction with Tikhonov regularization and low-rank and sparse decomposition (LRSD). MATLAB was used to implement the four combinations for six experimental data sets and produce attenuation images. The attenuation images were analyzed qualitatively and quantitatively to accomplish the goal of determining which combination performed best at locating human targets. After analyzing the results, it was determined that no single combination outperformed the others for at least three out of …
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 …
Laser Illuminated Imaging: Beam And Scene Deconvolution Algorithm, Benjamin W. Davis
Laser Illuminated Imaging: Beam And Scene Deconvolution Algorithm, Benjamin W. Davis
Theses and Dissertations
Laser illuminated imaging systems deal with several physical challenges that must be overcome to achieve high-resolution images of the target. Noise sources like background noise, photon counting noise, and laser speckle noise will all greatly affect the imaging systems ability to produce a high-resolution image. An even bigger challenge to laser illuminated imaging systems is atmospheric turbulence and the effect that it will have on the imaging system. The illuminating beam will experience tilt, causing the beam to wander off the center of the target during propagation. The light returning to the detector will similarly be affected by turbulence, and …
Development Of A Testbed For Foot Mounted Based Pedestrian Dead Reckoning (Pdr) Systems, Jordan E. Eldridge
Development Of A Testbed For Foot Mounted Based Pedestrian Dead Reckoning (Pdr) Systems, Jordan E. Eldridge
Theses and Dissertations
Over the last several years of research into the field of Pedestrian Dead Reckoning (PDR), there have been varying degrees of success in providing a viable individual navigation system. The PDR solutions developed utilize everything from a single Inertial Measurement Units (IMU) to several IMUs with additional sensors. One specific PDR solution identified that by utilizing a micro-mechanical Inertial Measurement Unit (IMU) on each foot (along with the application of Zero Velocity Updates (ZUPT) and foot-to-foot range measurements) a reliable method of PDR tracking could be accomplished. Their study concludes that further evaluation is required for this foot-mounted solution to …
Optical Study Of 2-D Detonation Wave Stability, Eulaine T. Grodner
Optical Study Of 2-D Detonation Wave Stability, Eulaine T. Grodner
Theses and Dissertations
Fundamental optical detonation study of detonations constricted to a 2-d plane propagation, and detonations propagating around a curve. All images were processed using modern image processing techniques. The optical techniques used were shadowgraph, Schlieren, and chemiluminescence. In the 2-Dstraight channels, it was determined wave stability was a factor of cell size. It was also determined the detonation wave thickness (area between the combustion and shockwave) was a factor of how much heat available for the detonation. For the detonations propagating around a curve, it was determined the three main classifications of wave stability were stable, unstable, and detonation wave restart. …
Spatially Separable Blind Deconvolution Of Long Exposure Astronomical Imagery, Justin S. Lee
Spatially Separable Blind Deconvolution Of Long Exposure Astronomical Imagery, Justin S. Lee
Theses and Dissertations
In this thesis, a spatially separable blind deconvolution algorithm is demonstrated that achieves a significantly faster processing time and superior sensitivity when processing long-exposure image data of unresolvable objects from a ground-based telescope. The proposed approach takes advantage of the structure of the long exposure point spread functions radial symmetric characteristics to approximate it as a product of one dimensional horizontal and vertical intensity distributions. Objects at geosynchronous or geostationary orbit also can be well approximated as being spatially separable as they are, in general non-resolvable. The algorithms performance is measured by computing the mean-squared error compared with the true …
Utilizing Software Defined Radios For Increased Bandwidth In Satellite Communications, Brian M. Wright
Utilizing Software Defined Radios For Increased Bandwidth In Satellite Communications, Brian M. Wright
Theses and Dissertations
This research explores the background and future possibilities of using cooperative satellites equipped with Software Defined Radios (SDRs) to combine their bandwidth and increase their signal reliability. Software Defined Radios are a potential solution to realize various software applications that support a reconfigurable and adaptive communication system without altering any hardware devices or features. This benefit, along with others that are offered by SDRs and the ongoing improvements in commercial digital electronics have sparked an interest in developing small satellites for advanced communications. This research effort sets out to prove if a high bandwidth signal can be generated by using …
Simulating A Mobile Wireless Sensor Network Monitoring The Air Force Marathon, Matthew D. Eilertson
Simulating A Mobile Wireless Sensor Network Monitoring The Air Force Marathon, Matthew D. Eilertson
Theses and Dissertations
This thesis explores the feasibility of deploying a mobile Wireless Sensor Networks (WSN) to the Air Force (AF) Marathon in support of Air Force Research Laboratory (AFRL) research of sensor and networking infrastructure in denied or degraded environments. A simulation called MarathonSim is developed in the Objective Modular Network Testbed in C++ (OMNeT++) Discrete Event Simulator to test the performance of a mobile WSN. A full factorial design using numbers of runners, transmission powers, and routing protocols is executed to measure Packet Delivery Ratio (PDR) to a central database, average end-to-end delay of application packets, and average power consumed per …
Performance Analysis Of Long-Term Evoluution Signals In Passive Bistatic Radar Applications Using Reduced Dimension Space-Time Adaptive Processing Techniques, Sureshan Suntharalingam
Performance Analysis Of Long-Term Evoluution Signals In Passive Bistatic Radar Applications Using Reduced Dimension Space-Time Adaptive Processing Techniques, Sureshan Suntharalingam
Theses and Dissertations
Widespread availability of long term evolution (LTE) signals makes them potential for use in passive bistatic radar (PBR) applications. However, their utility in such applications is yet to be fully explored. This research focuses on the key LTE signal attributes, such as subcarrier modulation schemes and bandwidth, and their effect on PBR application. space-time adaptive processing (STAP) concepts, both full dimension STAP (FD-STAP) reduced dimension STAP (RD-STAP), were employed to evaluate and compare the effects of varying these signal attributes, in terms of signal to interference-plus-noise ratio (SINR) loss metrics. Simulation results concluded that decreasing LTE signal's bandwidth and increasing …
Real-Time Aerial Magnetic And Vision-Aided Navigation, Daniel J. Clarke
Real-Time Aerial Magnetic And Vision-Aided Navigation, Daniel J. Clarke
Theses and Dissertations
Aerial magnetic navigation has shown to be a viable alternative navigation method that has the potential for world-wide availability, to include over oceans. Obtaining GPS-level accuracy using magnetic navigation alone is challenging, but magnetic navigation can be combined with other alternative navigation methods that are more posed to obtaining GPS-level accuracy in their current state. This research presents an aerial navigation solution combining magnetic navigation and vision-aided navigation to aid an inertial navigation system (INS). The navigation solution was demonstrated in real-time playback using simulated magnetic field measurements and flight-test captured visual imagery. Additionally, the navigation solution was flight-tested on …
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 …
Computational Electromagnetic Modeling Of Metasurface Optical Devices With Defect Study, Carlos D. Diaz
Computational Electromagnetic Modeling Of Metasurface Optical Devices With Defect Study, Carlos D. Diaz
Theses and Dissertations
One of the first fabricated metasurface optical devices, the in-plane V-antenna lenses, were plagued by a fundamental transmission limit (<25 >). Two distinct sets of Out-of-Plane phase elements were designed with improved transmission (~60 ). These were fabricated as beamsteerers and characterized in terms of their Bidirectional Transmittance Distribution Function measured as a function of scatter angle. Experimental data from the beamsteerers was analyzed via simulations using a finite element method (FEM). The measurements showed the designed beamsteering, but also a strong zero-order diffraction not present in the simulations, which motivated this study to understand what was causing these differences. …
Studying The Conditions For Magnetic Reconnection In Solar Flares With And Without Precursor Flares, Seth H. Garland
Studying The Conditions For Magnetic Reconnection In Solar Flares With And Without Precursor Flares, Seth H. Garland
Theses and Dissertations
Forecasting of solar flares remains a challenge due to the limited understanding of the triggering mechanisms associated with magnetic reconnection, the primary physical phenomenon connected to these events. Consequently, methods continue to rely on the climatology of solar flare events as opposed to the underlying physics principles. Models of magnetic reconnection in the solar atmosphere places the null point of the reconnection within the corona. Though as of now the coronal magnetic field cannot be directly measured, the field is tied to the photospheric magnetic field, which can be. This study utilized data from the Solar Dynamics Observatory Helioseismic and …
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 …