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Articles 31 - 60 of 134
Full-Text Articles in Engineering
Leveraging External Sensor Data For Enhanced Space Situational Awareness, Charlie T. Bellows
Leveraging External Sensor Data For Enhanced Space Situational Awareness, Charlie T. Bellows
Theses and Dissertations
Reliable Space Situational Awareness (SSA) is a recognized requirement in the current congested, contested, and competitive environment of space operations. A shortage of available sensors and reliable data sources are some current limiting factors for maintaining SSA. Unfortunately, cost constraints prohibit drastically increasing the sensor inventory. Alternative methods are sought to enhance current SSA, including utilizing non-traditional data sources (external sensors) to perform basic SSA catalog maintenance functions. Astronomical data, for example, routinely collects serendipitous satellite streaks in the course of observing deep space; but tactics, techniques, and procedures designed to glean useful information from those collects have yet to …
Integrated Systems Health Management As An Enabler For Condition Based Maintenance And Autonomic Logistics, Robert M. Vandawalker
Integrated Systems Health Management As An Enabler For Condition Based Maintenance And Autonomic Logistics, Robert M. Vandawalker
Theses and Dissertations
Health monitoring systems have demonstrated the ability to detect potential failures in components and predict how long until a critical failure is likely to occur. Implementing these systems on fielded structures, aircraft, or other vehicles is often a struggle to prove cost savings or operational improvements beyond improved safety. A system architecture to identify how the health monitoring systems are integrated into fielded aircraft is developed to assess cost, operations, maintenance, and logistics trade-spaces. The efficiency of a health monitoring system is examined for impacts to the operation of a squadron of cargo aircraft revealing sensitivity to and tolerance for …
System Architecture Of Small Unmanned Aerial System For Flight Beyond Visual Line-Of-Sight, Kwee Siam Seah
System Architecture Of Small Unmanned Aerial System For Flight Beyond Visual Line-Of-Sight, Kwee Siam Seah
Theses and Dissertations
Small Unmanned Aerial Systems (UAS) have increasingly been used in military application. The application in expanding scope of operations has pushed existing small UAS beyond its designed capabilities. This resulted in frequent modifications or new designs. A common requirement in modification or new design of small UAS is to operate beyond visual Line-Of-Sight (LOS) of the ground pilot. Conventional military development for small UAS adopts a design and built approach. Modification of small Remote Control (RC) aircraft, using Commercial-Off-The Shelf (COTS) equipment, offers a more economical alternative with the prospect of shorter development time compared to conventional approach. This research …
Environmental Degradation Of Nickel-Based Superalloys Due To Gypsiferous Desert Dusts, Matthew B. Krisak
Environmental Degradation Of Nickel-Based Superalloys Due To Gypsiferous Desert Dusts, Matthew B. Krisak
Theses and Dissertations
More than twenty-five years of continuous operation in the dusty environments of Southwest Asia have shown that degradation of gas turbine engine components due to particle ingestion is a serious threat to operations. In particular, the continued push for higher engine operating temperatures has brought a new emphasis to the damage mechanisms (for example CMAS glass formation and hot corrosion) caused by ingested particles forming molten deposits on engine components. Despite decades of research little progress has been made to mitigate the effects of CMAS and hot corrosion degradation to engine components. This research focused on hot corrosion specifically. A …
Corrosion Fatigue Crack Growth Behavior At Notched Hole In 7075-T6 Under Biaxial And Uniaxial Fatigue With Different Phases, Ali Khawagi
Theses and Dissertations
This research investigates fatigue crack propagation behavior in both air and saltwater (3.5% NaCl) environments from pre-cracked notched circular hole in a 7075-T6 cruciform specimen. With stress ratio of 0.5, biaxility stress ratio of unity, and frequency of applied load of 10 Hz, the crack growth behavior was investigated under in-plane biaxial tension-tension fatigue with 45⁰, 90⁰ and 180⁰ phase difference conditions and then compared to previous fatigue tests with no phase difference to study the effect of changing the phase differences between the applied loads on the crack growth rate. Finite Element Analysis (FEA) was used to calculate cyclic …
Exhaust Composition In A Small Internal Combustion Engine Using Ftir Spectroscopy, Kevin P. Horn
Exhaust Composition In A Small Internal Combustion Engine Using Ftir Spectroscopy, Kevin P. Horn
Theses and Dissertations
The mission-specific needs of small, remotely piloted aircraft demand lighter, more efficient engines with increased performance for their propulsion systems. A wide range of experimental efforts were undertaken to further the ability to obtain performance data on small engines as well as to develop understanding of their operation. Data were collected to quantify friction losses present in the dynamometer drivetrain on the small engine research bench. A correction and calibration model was developed for brake power collected by the dynamometer. Mechanical efficiencies for 28 cm3, 55 cm3 and 85 cm3 engines were 92.4%, 91.3% and 89.7%, respectively. Maximum fuel conversion …
Orbit Estimation Of Non-Cooperative Maneuvering Spacecraft, Gary M. Goff
Orbit Estimation Of Non-Cooperative Maneuvering Spacecraft, Gary M. Goff
Theses and Dissertations
Due to the ever increasing congestion of the space environment, there is an increased demand for real-time situation awareness of all objects in space. An unknown spacecraft maneuver changes the predicted orbit, complicates tracking, and degrades estimate accuracies. Traditional orbit estimation routines are implemented, tested, and compared to a multiple model format that adaptively handles unknown maneuvers. Multiple Model Adaptive Estimation is implemented in an original way to track a non-cooperative satellite by covariance inflation and filtering-through a maneuver. Parameters for successful instantaneous maneuver reconstruction are analyzed. Variable State Dimension estimation of a continuously maneuvering spacecraft is investigated. A requirements …
Effect Of Prior Exposure At Elevated Temperatures On Tensile Properties And Stress-Strain Behavior Of Four Non-Oxide Ceramic Matrix Composites, Sarah M. Wallentine
Effect Of Prior Exposure At Elevated Temperatures On Tensile Properties And Stress-Strain Behavior Of Four Non-Oxide Ceramic Matrix Composites, Sarah M. Wallentine
Theses and Dissertations
Thermal stability of four non-oxide ceramic matrix composites was studied. The materials studied were commercially available composites: SiC/SiNC; C/SiC; C/SiC-B4C (C/HYPR-SiCTM); and SiC/SiC-B4C (SiC/HYPR-SiCTM). COI Ceramics manufactured the SiC/SiNC and C/SiC composites using polymer infiltration and pyrolysis (PIP). The C/HYPR-SiCTM and SiC/HYPR-SiCTM CMCs were manufactured by Hyper-Therm High-Temperature Composites using chemical vapor infiltration (CVI). All four composites rely on a dense matrix for strength, stiffness, and oxidation protection. Fiber coating provides a fiber-matrix interface that allows fiber-matrix debonding and fiber pullout to occur, imparting fracture toughness to the CMC. The SiC/SiNC, C/SiC, and C/HYPR-SiC …
Simulation Of Metal Particulates In High Energetic Materials, Eduardo Nieto
Simulation Of Metal Particulates In High Energetic Materials, Eduardo Nieto
Theses and Dissertations
This research focused on analyzing the effects of aluminum in high explosives such as PBX9501 using the MPEXS computational simulation code for a wide range of metalized explosive cases. The varying parameters are aluminum particle diameter and mass fraction of aluminum. The addition of metal particulates in explosive mixtures increases the density of the shock wave, causing a higher pressure in the shock. It was concluded that pressure and density steadily increases as the Al particle diameter increases, and pressure and density decreases when Al mass fraction increases. The concentrated pressures will dissipate quickly due to the high density, providing …
A Method To Predict Compressor Stall In The Tf34-100 Turbofan Engine Utilizing Real-Time Performance Data, Shuxiang A. Li, Trevor G. Jones
A Method To Predict Compressor Stall In The Tf34-100 Turbofan Engine Utilizing Real-Time Performance Data, Shuxiang A. Li, Trevor G. Jones
Theses and Dissertations
The Air Force current operations continue to undergo significant changes compelled by decreasing fiscal appropriations, aging aircraft, and personnel drawdown. The Air Force must effectively improve current maintenance operations in part to deal with these challenges. This study will explore the area of the A-10 aircraft fleet's TF34-100 high-pass turbo-fan engine sensor data to seek its deterioration modelling and prognostics capability. In futurity this will allow for achievement of greater confidence in predicting the compressor stall which leads to engine performance deterioration and a costly repair in maintenance. By utilizing an innovative method to forecast the probability of compressor stall, …
Topology Optimization Of An Aircraft Wing, David L. Walker
Topology Optimization Of An Aircraft Wing, David L. Walker
Theses and Dissertations
A Topology Optimization (TO) was conducted on an aircraft wing in order to mathematically determine an ideal structural case for future aircraft. TO generally involves iteratively reducing individual elemental density until the desired mass or volume constraint is met. Two different TO styles where approached: a global three-dimensional concept and a more traditional two-dimensional rib and spar optimization which more closely mimics the baseline model. All optimizations were compared against a baseline wing for von-Mises stress, displacement, and buckling. The objective of this research was to develop a design procedure maintaining the baseline structural integrity of the wing while reducing …
Generation Of Strategies For Environmental Deception In Two-Player Normal-Form Games, Howard E. Poston
Generation Of Strategies For Environmental Deception In Two-Player Normal-Form Games, Howard E. Poston
Theses and Dissertations
Methods of performing and defending against deceptive actions are a popular field of study in game theory; however, the focus is mostly on action deception in turn-based games. This work focuses on developing strategies for performing environmental deception in two-player, strategic-form games. Environmental deception is defined as deception where one player has the ability to change the other's perception of the state of the game through modification of their perception of the game's payoff matrix, similar to the use of camouflage. The main contributions of this research are an expansion of the definition of the stability of a Nash equilibrium …
Coupling Nuclear Induced Phonon Propagation With Conversion Electron Mössbauer Spectroscopy, Michael J. Parker
Coupling Nuclear Induced Phonon Propagation With Conversion Electron Mössbauer Spectroscopy, Michael J. Parker
Theses and Dissertations
Mössbauer spectroscopy is a very sensitive measurement technique (10-8 eV) which prompted motivation for the experiment described in this thesis. Namely, can a sensitive detection system be developed to detect nuclear recoils on the order of 10 to 100 of eVs? The hypothesis that this thesis tests is: Nuclear induced phonon bursts caused by Rutherford scattered alphas, decayed from 241Am, in a type-310 stainless steel material can couple with 7.3 keV conversion electron Mössbauer events at the other end of the material which will have a statistically significant effect on a Mössbauer spectrum. The phonon bursts produced by …
Supply Chain Interoperability Measurement, Christos E. Chalyvidis
Supply Chain Interoperability Measurement, Christos E. Chalyvidis
Theses and Dissertations
Academia recognizes that although supply chains have an inherent need to be validated for their performance, supply chain performance measurement systems are still inadequate and one of the major barriers to successful supply chain collaboration. In this research, theory of Systems Architecture is used to make the first step towards an innovative supply chain performance measure defined as supply chain interoperability. Interoperability is considered a similarity metric with regard to a set of deterministic and stochastic characters (criteria) describing supply chain participants, a methodology that adapts and expands an interoperability measurement tool initially developed in and for a military context. …
A System Dynamics Approach To The Efficacy Of Oxime Therapy In Sub Lethal Exposure To Sarin Gas, Daniel J. Droste
A System Dynamics Approach To The Efficacy Of Oxime Therapy In Sub Lethal Exposure To Sarin Gas, Daniel J. Droste
Theses and Dissertations
The 2010 National Security Strategy states, The effective dissemination of a lethal agent would endanger the lives of thousands of people and have unprecedented economic, societal, and political consequences. We must continue to work at home with first responders and health officials to reduce the risk associated with high-consequence threats . Nerve agents, such as Sarin gas, are considered high consequence threats. The threat of use of agents such as Sarin is as much a threat today as any other time in our history. However, the suggested treatment protocol is not as precise as it could be. Debate exists over …
An Assessment Of The Effectiveness Of Air Force Risk Management Practices In Program Acquisition Using Survey Instrument Analysis, Michael J. Maroney Jr.
An Assessment Of The Effectiveness Of Air Force Risk Management Practices In Program Acquisition Using Survey Instrument Analysis, Michael J. Maroney Jr.
Theses and Dissertations
Air Force acquisition programs invest a large amount of resources to develop and field systems. Many of these resources go to risk management in order to help ensure those programs finish successfully with respect to cost, schedule, and technical performance goals. The question arises as to whether this is a sound investment. Although risk management has been shown to be effective in industry, scant empirical evidence exists for its effectiveness within the Air Force. Correlation and regression analysis of survey data show that a positive relationship does exist between specific risk practices and project success. Furthermore, the analysis suggests that …
Analysis Of The Effectiveness Of The F-15e Risk Management During Peacetime Operations, Elliot B. Vasquez
Analysis Of The Effectiveness Of The F-15e Risk Management During Peacetime Operations, Elliot B. Vasquez
Theses and Dissertations
Human factors are causal or contributory in 80% of Class A mishaps in the Air Force. Risk management tools are used throughout the service in every aircraft to help mitigate the risk of those human factors occurring. The F-15E Strike Eagle community was selected for analysis on the effectiveness of its risk management program but the data was comprised on Class A mishaps from Accident Investigation Boards since 2000 between the F-15 (all models), F-16 (all models), and F-22. Cases were selected if there were human factors root causes or contributory. A fault tree analysis coupled with the Department of …
Modal Characterization Of A Piezoelectric Shaker Table, Randall J. Hodkin
Modal Characterization Of A Piezoelectric Shaker Table, Randall J. Hodkin
Theses and Dissertations
Piezoelectric actuated shaker tables are often used for high frequency fatigue testing. Since natural frequencies can appear in the operating range of these shaker tables, it is necessary to conduct modal characterization of the system before testing. This thesis describes the design and experimental validation of a mechanical model used for modal analysis of a piezoelectric shaker table. A commercially available three-dimensional scanning device was used to produce a point cloud model of the surface geometry, which was converted to a solid model and imported into a Finite Element Analysis (FEA) package for modal analysis. Using a laser vibrometer to …
Creep Of Sylramic-Ibn Fiber Tows At Elevated Temperature In Air And In Silicic Acid-Saturated Steam, Kevin B. Sprinkle
Creep Of Sylramic-Ibn Fiber Tows At Elevated Temperature In Air And In Silicic Acid-Saturated Steam, Kevin B. Sprinkle
Theses and Dissertations
Stressed oxidation experiments on Sylramic-iBN fiber tows were performed to evaluate the novel fiber's mechanical performance, creep behavior, and creep mechanisms. This research effort investigated creep response of Sylramic-iBN fiber tows at elevated temperatures in both air and in silicic acid-saturated steam environments. Creep experiments were conducted at creep stresses ranging from 127 to 762 MPa at 400°C and 500°C in order to examine the mechanical behavior of the Sylramic-iBN fiber tows at temperatures below and above the melting point of boria (450°C). Sylramic-iBN fibers are known to have excellent creep resistance, better than most other non-oxide fibers and significantly …
Improving The Performance Of The Space Surveillance Telescope As A Function Of Seeing Parameter, Jae H. Jeon
Improving The Performance Of The Space Surveillance Telescope As A Function Of Seeing Parameter, Jae H. Jeon
Theses and Dissertations
This research paper investigates ways to improve the detection capability and predict the performance of the Space Surveillance Telescope (SST) system when it's relocated to Exmouth, Australia. The dataset collected by the SST observing the Geosynchronous Earth Orbit (GEO) satellite, ANIK-F1, entering the earth's eclipse is used to test the performance of the three existing and one new detection algorithm. The three existing algorithms are the point detection (Binary Hypothesis Test (BHT)), correlation detection (CD-BHT), and Multi-hypothesis Test using ten hypotheses (MHT10), and the new detection algorithm is the Multi-hypothesis Test using six hypotheses (MHT6). To improve the accuracy and …
Static Scene Statistical Non-Uniformity Correction, Adrian M. Catarius
Static Scene Statistical Non-Uniformity Correction, Adrian M. Catarius
Theses and Dissertations
Non-Uniformity Correction (NUC) is required to normalize imaging detector Focal-Plane Array (FPA) outputs due to differences in the end-to-end photoelectric responses between pixels. Currently, multi-point NUC methods require static, uniform target scenes of a known intensity for calibration. Conversely, scene-based NUC methods do not require a priori knowledge of the target but the target scene must be dynamic. The new Static Scene Statistical Non-Uniformity Correction (S3NUC) algorithm was developed to address an application gap left by current NUC methods. S3NUC requires the use of two data sets of a static scene at different mean intensities but does not require a …
Theoretical Limits Of Lunar Vision Aided Navigation With Inertial Navigation System, David W. Jones
Theoretical Limits Of Lunar Vision Aided Navigation With Inertial Navigation System, David W. Jones
Theses and Dissertations
The precision navigation capabilities of the Global Positioning System (GPS) are used extensively within US military operations. However, GPS is highly vulnerable to intentional and unintentional external interference. Therefore, a need exists to develop a non-GPS precision navigation method to operate in GPS degraded environments. This research effort presents the theoretical limits of a precision navigation method based on an inertial navigation system (INS) aided by angle measurements with respect to lunar surface features observed by a fixed camera. To accomplish this task, an extended Kalman filter (EKF) was implemented to estimate INS drift errors and bring in simulated lunar …
Non-Linear Optimization Applied To Angle-Of-Arrival Satellite-Based Geolocation With Correlated Measurements, Joshua S. Sprang
Non-Linear Optimization Applied To Angle-Of-Arrival Satellite-Based Geolocation With Correlated Measurements, Joshua S. Sprang
Theses and Dissertations
A common remote sensing application is producing geolocation estimates for an object of interest from multiple sensor platforms. Geolocation estimates are desired to help improve situational awareness when dealing with space objects that do not actively broadcast their location. A depiction of the error parameters are calculated in conjunction with the positional estimates. Problems occur when multiple measurements from a single sensor are used to estimate a location due to correlations in sensor error. A non-linear optimization approach is presented for determining geolocation estimates and their associated error parameters. The error parameters directly reflect the error present on the individual …
Surface Geometry And Chemistry Of Hydrothermally Synthesized Single Crystal Thorium Dioxide, Scott W. Key
Surface Geometry And Chemistry Of Hydrothermally Synthesized Single Crystal Thorium Dioxide, Scott W. Key
Theses and Dissertations
The surface chemistry and geometry of hydrothermally grown, single crystal ThO2 was studied using X-ray Photoemission Spectroscopy (XPS) and Atomic Force Microscopy (AFM). The crystal was studied before and after sputter etching with Ar+, heating up to 675 K, and dehydration with dry nitrogen. The hydrothermal growth technique incorporated Cs and F into the near surface bulk. Heating to 675 K drove off the F, but did not the Cs. Sputtering with Ar+ at 75° cleaned the crystal and created a more uniform surface geometry. The Th 4f peak resolution, as measured by XPS improved by …
Pulsed Ultraviolet Light Emitting Diodes For Advanced Oxidation Of Tartrazine, Patrick M. Mudimbi
Pulsed Ultraviolet Light Emitting Diodes For Advanced Oxidation Of Tartrazine, Patrick M. Mudimbi
Theses and Dissertations
A study was conducted to evaluate the advanced oxidation of organic contaminants using pulsed ultraviolet light emitted diode (UV LED). Tartrazine was used as a surrogate organic compound. Low pressure Mercury-based lamps currently used in the treatment of water pose potential health risks if broken and create final disposal issues at the end of their service life. UV LED offers an alternative solution due to its non-toxicity, flexible design, and longer operating life compared to the mercury-based lamps. The apparent first order reaction rate constant for tartrazine degradation increased linearly with increasing duty cycle. At a continuous 100% duty cycle, …
Effect Of Prior Exposure At Elevated Temperatures On Tensile Properties And Stress-Strain Behavior Of Three Oxide/Oxide Ceramic Matrix Composites, Christopher J. Hull
Effect Of Prior Exposure At Elevated Temperatures On Tensile Properties And Stress-Strain Behavior Of Three Oxide/Oxide Ceramic Matrix Composites, Christopher J. Hull
Theses and Dissertations
Thermal stability of three oxide-oxide ceramic matrix composites was studied. The materials studied were NextelTM610/aluminosilicate (N610/AS), NextelTM720/aluminosilicate (N720/AS), and NextelTM720/Alumina (N720/A), commercially available oxide-oxide ceramic composites (COI Ceramics, San Diego, CA). The N610/AS composite consists of a porous aluminosilicate matrix reinforced with laminated woven alumina N610 fibers. The N720/AS and N720/A composites consist of a porous oxide matrix reinforced with laminated, woven mullite/alumina (NextelTM720) fibers. The matrix materials are aluminosilicate in N720/AS and alumina in N720/A. All three composites have no interface between the fibers and matrix, and rely on the porous …
Detection And Characterization Of Malathion Adherence To Piping Materials Used In Water Distribution Systems, William D. Flemings
Detection And Characterization Of Malathion Adherence To Piping Materials Used In Water Distribution Systems, William D. Flemings
Theses and Dissertations
Protection of the public water supply is a national security priority, and as such, it is important to better understand the fate of a chemical weapons agent injection into a public water distribution system. This study investigated the adherence of malathion to pipe materials that are used in public water distribution systems, with malathion serving as a chemical representative of the organophosphorus nerve agent VX. Copper and iron specimen were exposed to malathion solutions for periods of 4, 8, and 24 hours and then tested for evidence of chemical adherence to the metal surfaces. Nonlinear desiccation profiles revealed total mass …
Investigation Of The High-Cycle Fatigue Life Of Selective Laser Melted And Hot Isostatically Pressed Ti-6al-4v, Kevin D. Rekedal
Investigation Of The High-Cycle Fatigue Life Of Selective Laser Melted And Hot Isostatically Pressed Ti-6al-4v, Kevin D. Rekedal
Theses and Dissertations
Experimental research was conducted on the effectiveness of Hot Isostatic Pressing (HIP) to improve the high-cycle fatigue life of Selective Laser Melted Ti-6Al-4v (SLM Ti-64). A thorough understanding of the fatigue life performance for additively manufactured parts is necessary before such parts are utilized in an operational capacity in Department of Defense (DoD) systems. Such applications include the rapid, on-demand fabrication of replacement parts during contingency operations or the production of light-weight topology-optimized components. This research assesses the fatigue life of SLM Ti-64 test specimens built directly to net dimensions without any subsequent surface machining. The configuration is designed as …
Fatigue Behavior Of Im7/Bmi 5250-4 Composite At Room And Elevated Temperatures, James T. Tipton
Fatigue Behavior Of Im7/Bmi 5250-4 Composite At Room And Elevated Temperatures, James T. Tipton
Theses and Dissertations
The tension-tension fatigue and tension-compression fatigue behaviors of the IM7/BMI 5250-4 composite were investigated. The tension-tension fatigue of the composite with 0/90 and ±45 fiber orientations was studied at 23, 170, and 190°C. The tension-compression fatigue of the composite with 0/90 fiber orientation was examined at 23°C. The tensile and compressive properties of the composite were also evaluated at room and elevated temperatures for both 0/90 and ±45 fiber orientations. Elevated temperature had little effect on the tensile properties of the 0/90 fiber orientation, but strongly influenced the ±45 tensile properties as well as the compressive properties of both fiber …
Non-Destructive Techniques For Classifying Aircraft Coating Degradation, Kody A. Wilson
Non-Destructive Techniques For Classifying Aircraft Coating Degradation, Kody A. Wilson
Theses and Dissertations
In this research non-destructive techniques were examined as possible methods of determining aircraft coating degradation. Single Value Decomposition(SVD)-Linear Discriminant Analysis(LDA) algorithms were applied to measured spectra. When applied to infrared emittance spectra only 52% classification accuracy was achieved. When applied to Raman spectroscopy a higher classification accuracy of 70.4% is attained when using the same SVD-LDA algorithm. However the best performing measurement was using infrared reflectance classification accuracies were 100%, 99.83% and 94.4% when using the Bomem FTS, DRIFTS and Telops respectively for one of the sample sets. For DRIFTS data a more accurate fingerprint region was identified 865.6 - …