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Articles 151 - 174 of 174
Full-Text Articles in Engineering
Improvements To Optical Communication Capabilities Achieved Through The Optical Injection Of Semiconductor Lasers, Timothy P. Locke
Improvements To Optical Communication Capabilities Achieved Through The Optical Injection Of Semiconductor Lasers, Timothy P. Locke
Theses and Dissertations
Optically injection locked lasers have shown significant improvement in the modulation capabilities of directly modulated lasers. This research creates a direct-modulated optical communications system to investigate the bit-rate distance improvements achievable using optically injected Fabry-Pérot laser diodes. The injection strength and detuning frequency of the injection signal was varied to determine their impact on the optical communication link's characteristics. This research measured a 25 fold increase in bit-rate distance product using optical injection locking as compared to the injected laser's free-running capability. A 57 fold increase was measured in the bit-rate distance product when signal power is considered in a …
External Verification Of Scada System Embedded Controller Firmware, Lucille R. Mcminn
External Verification Of Scada System Embedded Controller Firmware, Lucille R. Mcminn
Theses and Dissertations
Critical infrastructures such as oil and gas pipelines, the electric power grid, and railways, rely on the proper operation of supervisory control and data acquisition (SCADA) systems. Current SCADA systems, however, do not have sufficient tailored electronic security solutions. Solutions available are developed primarily for information technology (IT) systems. Indeed, the toolkit for SCADA incident prevention and response is unavailing as the operating parameters associated with SCADA systems are different from IT systems. The unique environment necessitates tailored solutions. Consider the programmable logic controllers (PLCs) that directly connect to end physical systems for control and monitoring of operating parameters -- …
Computer Aided Multi-Data Fusion Dismount Modeling, Juan L. Morales
Computer Aided Multi-Data Fusion Dismount Modeling, Juan L. Morales
Theses and Dissertations
Recent research efforts strive to address the growing need for dismount surveillance, dismount tracking and characterization. Current work in this area utilizes hyperspectral and multispectral imaging systems to exploit spectral properties in order to detect areas of exposed skin and clothing characteristics. Because of the large bandwidth and high resolution, hyperspectral imaging systems pose great ability to characterize and detect dismounts. A multi-data dismount modeling system where the development and manipulation of dismount models is a necessity. This thesis demonstrates a computer aided multi-data fused dismount model, which facilitates studies of dismount detection, characterization and identification. The system is created …
Timing Variations In A Magnetic Pulse Compression Circuit, Jeremy S. Oliver
Timing Variations In A Magnetic Pulse Compression Circuit, Jeremy S. Oliver
Theses and Dissertations
The magnetic pulse compression (MPC) circuit uses saturable core inductors and capacitors to compress the width of a pulse. This substantially increases the peak power of the initially applied pulse. The saturable inductor exhibits a hysteresis curve behavior. One particular problem with these MPC circuits is timing variances in the pulse rate of the system. This work models the unique characteristics and signatures of the timing variations of magnetic switches and pulse compressors. The hysteresis curve of the saturable inductor was created by using a nonlinear inductor and a nonlinear resistor in parallel as a substitute for saturable inductors. The …
Near Earth Object Detection Using A Poisson Statistical Model For Detection On Images Modeled From The Panoramic Survey Telescope And Rapid Response System, Curtis J. R. Peterson
Near Earth Object Detection Using A Poisson Statistical Model For Detection On Images Modeled From The Panoramic Survey Telescope And Rapid Response System, Curtis J. R. Peterson
Theses and Dissertations
The purpose of this research effort is to develop, simulate, and test a new algorithm to detect Near Earth Objects (NEOs) using a Likelihood Ratio Test (LRT) based on a Poisson statistical model for the arrival of photons. One detection algorithm currently in use is based on a Gaussian approximation of the arrival of photons, and is compared to the proposed Poisson model. The research includes three key components. The first is a quantitative analysis of the performance of both algorithms. The second is a system model for simulating detection statistics. The last component is a collection of measured data …
All Source Sensor Integration Using An Extended Kalman Filter, Timothy R. Penn
All Source Sensor Integration Using An Extended Kalman Filter, Timothy R. Penn
Theses and Dissertations
The global positioning system (GPS) has become an ubiquitous source for navigation in the modern age, especially since the removal of selective availability at the beginning of this century. The utility of the GPS is unmatched, however GPS is not available in all environments. Heavy reliance on GPS for navigation makes the warfighter increasingly vulnerability as modern warfare continues to evolve. This research provides a method for incorporating measurements from a massive variety of sensors to mitigate GPS dependence. The result is the integration of sensor sets that encompass those examined in recent literature as well as some custom navigation …
Passive Multistatic Radar Imaging Using An Ofdm Based Signal Of Opportunity, Matthew B. P. Rapson
Passive Multistatic Radar Imaging Using An Ofdm Based Signal Of Opportunity, Matthew B. P. Rapson
Theses and Dissertations
This paper demonstrates a proof of concept in using an OFDM-based signal of opportunity for SAR imaging purposes within a passive, multistatic radar construct. Two signal processing methods have been proposed to create phase history data. The same methods are applied in both a simulated software model and an experimental data collection environment to produce simulated SAR images using the CBP imaging algorithm. The images generated from both the experimental and simulated data were observed to be consistent with each other and with expectations in terms of resolution. Coherent addition of the images results in improved image resolution due to …
Covariance Analysis Of Vision Aided Navigation By Bootstrapping, Andrew L. Relyea
Covariance Analysis Of Vision Aided Navigation By Bootstrapping, Andrew L. Relyea
Theses and Dissertations
Inertial Navigation System (INS) aiding using bearing measurements taken over time of stationary ground features is investigated. A cross country flight, in two and three dimensional space, is considered, as well as a vertical drop in three dimensional space. The objective is to quantify the temporal development of the uncertainty in the navigation states of an aircraft INS which is aided by taking bearing measurements of ground objects which have been geolocated using ownship position. It is shown that during wings level flight at constant speed and a fixed altitude, an aircraft that tracks ground objects and over time sequentially …
Electromagnetic Characterization Of Inhomogeneous Media, Marcus A. Sitterly
Electromagnetic Characterization Of Inhomogeneous Media, Marcus A. Sitterly
Theses and Dissertations
Developed two permittivity profile extraction algorithms for inhomogeneous materials. These two algorithms were created using discrete and continuous approaches. The discrete method used a piece-wise constant permittivity assumption that allowed the use of homogeneous wave equations. Using laboratory data and a theoretical formulation, the permittivity of each piece-wise constant layer within the material was extracted using a root search algorithm. The continuous approach solved the problem using inhomogeneous wave equations. These equations were used to extract a linear permittivity profile using laboratory data and a root search.
Simultaneous Range-Velocity Processing And Snr Analysis Of Afit's Random Noise Radar, T. Joel Thorson
Simultaneous Range-Velocity Processing And Snr Analysis Of Afit's Random Noise Radar, T. Joel Thorson
Theses and Dissertations
This paper presents two research objectives aimed at advancing the AFIT RNR signal processing algorithm and modeling capability toward the overarching goal of performing collision avoidance on an autonomous vehicle. In both research efforts, analytical, simulated, and measured results are provided and used to draw research conclusions. The first research effort is aimed at reducing the memory required for 2D processing in the time domain in order to distribute the processing algorithm across hundreds of processors on a GPU. Distributed processing reduces the overall 2D processing time and the feasibility of a near real-time implementation is studied. The second effort …
Silicon Carbide Capacitive High Temperature Mems Strain Transducer, Richard P. Weisenberger
Silicon Carbide Capacitive High Temperature Mems Strain Transducer, Richard P. Weisenberger
Theses and Dissertations
Air Force Research Lab Air Vehicles directorate performs research on hypersonic vehicles. To verify materials or designs of hypersonic vehicles, they have a need to measure strain at temperatures exceeding 700°C. Strain sensors have the ability to measure strain. Strain is the deformation of materials due to internal stresses in a material. Internal stresses occur when a material is subjected to a force. Traditional strain sensors use Piezoresistive effects to measure strain, which is temperature dependent and making them unusable at high temperatures. This paper discusses a novel strain sensing device, sensing capacitance instead of piezoresistance. The strain sensor is …
A Performance Analysis Of The Optimized Link State Routing Protocol Using Voice Traffic Over Mobile Ad Hoc Networks, André Wolf
Theses and Dissertations
Mobile ad hoc networks (MANETs) have grown in popularity over the past decade and are increasingly considered for time-sensitive multimedia applications. The impact of various routing protocols on voice traffic using different IEEE 802.11 extensions has been investigated via analytical models, simulations and experimental test beds. Many studies determined that optimized link state routing (OLSR) is a suitable routing protocol to support voice over internet protocol (VoIP) conversations. This research expands upon this understanding by determining the point at which voice traffic is no longer feasible in an ad hoc environment and determines which audio codec is best suited for …
Theoretical Study Of The Effects Of Di-Muonic Molecules On Muon-Catalyzed Fusion, Eugene V. Sheely
Theoretical Study Of The Effects Of Di-Muonic Molecules On Muon-Catalyzed Fusion, Eugene V. Sheely
Theses and Dissertations
This document presents a theoretical study di-muonic hydrogen and helium molecules that have the potential of enhancing the muon-catalyzed fusion reaction rate. In order to study these di-muonic molecules a method of non-adiabatic quantum mechanics referred to as a General Particle Orbital (GPO) method was developed. Three mechanisms that have the possibility of enhancing the muon-catalyzed fusion rate were discovered. Two involve the formation of di-muonic hydrogen molecules, and the other uses di-muonic molecules to liberate muons stuck to 3He nuclei. The effects of muon spin on dimuonic hydrogen molecules was studied. The nuclear separation in di-muonic hydrogen molecules …
Using Vft As A Constraint For Goal Programming Models: A Case Study For Turkish Air Force Flying Hour Program, Ahmet Bengoz
Using Vft As A Constraint For Goal Programming Models: A Case Study For Turkish Air Force Flying Hour Program, Ahmet Bengoz
Theses and Dissertations
In its 60-year history, there have been many published documents in the literature about goal programming (GP), but contributions to the literature are still needed. This research intends to add to the literature on goal-programming models by discussing one of the key assumptions of GP regarding linearity, and by discussing some of the issues regarding incommensurability (difference in data types) and weighting. GP requires an interaction between the decision maker (DM) and the analyst to ensure that the model reflects the DM's preferences. However, it may be difficult for them to interact if the mathematical model is very large and …
The Effectiveness Of Using Diversity For Selecting Multiple Classifier Systems, Harris K. Butler
The Effectiveness Of Using Diversity For Selecting Multiple Classifier Systems, Harris K. Butler
Theses and Dissertations
A wealth of approaches exists to perform classification of items of interest. The goal of fusion techniques is to exploit complementary approaches and merge the information provided by these methods to provide a solution superior than any single method. Associated with choosing a fusion algorithm is the choice of algorithm or algorithms that will be fused. This decision is most often referred to as ensemble selection. Historically classifier ensemble accuracy has been used to accomplish this task. More recently research has focused on creating and evaluating diversity metrics to more effectively select ensemble members. This research focuses on the use …
Analysis Of Kc-46 Live-Fire Risk Mitigation Program Testing, Chad N. Chamberlain
Analysis Of Kc-46 Live-Fire Risk Mitigation Program Testing, Chad N. Chamberlain
Theses and Dissertations
Increased emphasis from the Director of Operational Test and Evaluation (DOT&E) over the past few years to include statistical rigor in all testing has brought an augmented look at testing across the Department of Defense. This thesis examines the methodology currently used in live fire testing, particularly in the case of risk mitigation of the KC-46 dry-bay fire test program. The thesis addresses gaps within the methodology and analyzes the results of a statistically rigorous test. The research furthers work on modeling the characterization of ballistic impact flash by validating concurrent models and characterizing the errors prone to these models …
Plume Characterization Of Busek 600w Hall Thruster, Duc Minh Bui
Plume Characterization Of Busek 600w Hall Thruster, Duc Minh Bui
Theses and Dissertations
The BHT-600W thruster has a high potential to place on various commercial and military satellites as a main propulsion system for orbit maintenance and orbit maneuvering. Therefore, the thruster's performance characteristics and parameters were evaluated for various operating conditions. These parameters include thrust, power consumption, mass flow rate, and efficiencies. Various plume properties were measured and characterized for the thruster to include exhaust beam profile and ion species distribution. The faraday probe was used to examine the thruster plume current density while the ion species fractions were determined by the ExB probe. The inverted pendulum thrust stand was also utilized …
Maintenance Operations Degradation Of Airfield Pavement Markings, John C. Jaszkowiak
Maintenance Operations Degradation Of Airfield Pavement Markings, John C. Jaszkowiak
Theses and Dissertations
Pavement markings are an essential element in the navigational aids subsystem for any airfield. Most airfields still use waterborne paint as the primary marking material, although there are other materials in use on roadways that airfield managers could use to save time and money. An airfield experiences a host of maintenance operations that cause degradation of the pavement markings. Of particular concern are rubber removal operations, sweeping operations, and snowplowing operations. This research focuses on chemical rubber removal operations and sweeping operations. The study evaluates waterborne paint markings and thermoplastic marking strips to determine if these marking materials perform differently …
A Programmable Liquid Collimator For Both Coded Aperture Adaptive Imaging And Multiplexed Compton Scatter Tomography, Jack G. M. Fitzgerald
A Programmable Liquid Collimator For Both Coded Aperture Adaptive Imaging And Multiplexed Compton Scatter Tomography, Jack G. M. Fitzgerald
Theses and Dissertations
A novel, fully reconfigurable collimator device for gamma-ray and X-ray imaging was built and tested as a coded aperture. The device consisted of 10x10, 5x5x5 mm3 chambers. Each chamber either was filled with an attenuating liquid, stopping photons, or evacuated of the attenuating liquid, allowing the photons to pass through. As the pattern of on and off chambers was manipulated, different, semi-independent views of the gamma-ray source were found. Noise in reconstructed images decreased in all tests. Image reconstruction was performed with correlation methods and Maximum Likelihood Expectation Maximization (ML-EM). Using 10 mask patterns, the signal-to-noise ratio (SNR) in …
Agent Based Modeling And Simulation Framework For Supply Chain Risk Management, Tiffany J. Harper
Agent Based Modeling And Simulation Framework For Supply Chain Risk Management, Tiffany J. Harper
Theses and Dissertations
This research develops a flexible agent-based modeling and simulation (ABMS) framework for supply chain risk management with significant enhancements to standard ABMS methods and supply chain risk modeling. Our framework starts with the use of software agents to gather and process input data for use in our simulation model. For our simulation model, we extend an existing mathematical framework for discrete event simulation (DES) to ABMS and then implement the concepts of variable resolution modeling from the DES domain to ABMS and provide further guidelines for aggregation and disaggregation of supply chain models. Existing supply chain risk management research focuses …
Modeling Small Unmanned Aerial System Mishaps Using Logistics Regression And Artificial Neural Networks, Sean E. Wolf
Modeling Small Unmanned Aerial System Mishaps Using Logistics Regression And Artificial Neural Networks, Sean E. Wolf
Theses and Dissertations
A dataset of 854 small unmanned aerial system (SUAS) flight experiments from 2005-2009 is analyzed to determine significant factors that contribute to mishaps. The data from 29 airframes of different designs and technology readiness levels were aggregated. 20 measured parameters from each flight experiment are investigated, including wind speed, pilot experience, number of prior flights, pilot currency, etc. Outcomes of failures (loss of flight data) and damage (injury to airframe) are classified by logistic regression modeling and artificial neural network analysis. From the analysis, it can be concluded that SUAS damage is a random event that cannot be predicted with …
The Effect Of Elevated Temperature On The Inelastic Deformation Behavior Of Pmr-15 Solid Polymer, Chad E. C. Ryther
The Effect Of Elevated Temperature On The Inelastic Deformation Behavior Of Pmr-15 Solid Polymer, Chad E. C. Ryther
Theses and Dissertations
The inelastic deformation behavior of PMR-15 neat resin, a high-temperature thermoset polymer, was investigated at temperatures in the 274-316°C range. The experimental program was developed to explore the influence of temperature on tensile loading, relaxation and creep behaviors of PMR-15. The results demonstrate that the mechanical behavior of PMR-15 exhibits a strong dependence on temperature. During strain-controlled tensile loading, the slope of the stress-strain curve in the quasi-elastic region decreases and the flow stress level decreases with increasing temperature. During relaxation, the amount of the stress drop decreases with increasing temperature. Based on experimental results the Viscoplasticity Based on Overstress …
Large Aircraft Infrared Countermeasures (Laircm) Systems Engineering Case Study, Air Force Center For Systems Engineering, William Albery
Large Aircraft Infrared Countermeasures (Laircm) Systems Engineering Case Study, Air Force Center For Systems Engineering, William Albery
AFIT Documents
No abstract provided.
Afit Graduate School Of Engineering And Management Catalog 2012-2013, Graduate School Of Engineering And Management, Air Force Institute Of Technology
Afit Graduate School Of Engineering And Management Catalog 2012-2013, Graduate School Of Engineering And Management, Air Force Institute Of Technology
AFIT Documents
The Graduate Catalog represents the offerings, programs, and requirements in effect at the time of publication.