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Articles 5851 - 5880 of 11510
Full-Text Articles in Engineering
The Fate Of Malathion On Copper And Iron Piping Within A Water Distribution System, Walter R. Lee
The Fate Of Malathion On Copper And Iron Piping Within A Water Distribution System, Walter R. Lee
Theses and Dissertations
Thermogravimetry, the study of mass loss as a function of temperature, has been used for oxidation, decomposition, and solid-state studies. This research used a thermogravimetric analyzer (TGA) coupled with Fourier transform infrared (FT-IR) spectroscopy in the study of copper and iron specimens exposed to malathion. Exposure to the malathion solution created a visible silver coating on copper and graphite-flake particles on iron specimens. Thermogravimetric mass loss curves revealed linear and nonlinear decomposition stages associated with mass loss reactions. Copper specimens exposed to malathion exhibited lower activation energy (Ea) values (2.28 to 4.40 kJ mol-1) than for copper specimens exposed to …
Parametric Estimation Of Load For Air Force Datacenters, Derek P. Molle
Parametric Estimation Of Load For Air Force Datacenters, Derek P. Molle
Theses and Dissertations
The Office of Management and Budget (OMB) has tasked Federal agencies to develop a Data Center Consolidation Plan. Effective planning requires a repeatable method to effectively and efficiently size Air Force Base-level data centers. Review of commercial literature on data center design found emphasis in power efficiency, thermal modeling and cooling, and network speed and availability. The topic of sizing data center processing capacity seems undeveloped. This thesis provides a better, pedigreed solution to the data center sizing problem. By analogy, Erlang's formulae for the probability of blocking and queuing should be applicable to cumulative CPU utilization in a data …
A Comparative Study Of Learning Curve Models In Defense Airframe Cost Estimating, Justin R. Moore
A Comparative Study Of Learning Curve Models In Defense Airframe Cost Estimating, Justin R. Moore
Theses and Dissertations
The goal of this research was to identify which learning curve model is most accurate when applied to Defense acquisition programs. Wright's original learning curve model is widely accepted and used within Defense acquisitions, but the 75+ year old model may be outdated. This study compares Wright's model against three alternative learning curve models using total lot costs for the F-15 C/D & E programs: the Stanford-B model, the DeJong learning formula, and the S-Curve model. However, the results of the study are inconclusive. Two of the three alternative models, the DeJong and S-Curve, rely on the use of an …
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, …
Pragmatic Divestment Of Kc-135 Navigators In The Special Operations Air Refueling Mission, Andrew P. Nation
Pragmatic Divestment Of Kc-135 Navigators In The Special Operations Air Refueling Mission, Andrew P. Nation
Theses and Dissertations
In the late 1990s, the Air Force eliminated over 200 KC-135 navigators, leaving 50 remaining for the aircraft's most complex Special Operations Air Refueling (SOAR) mission. As the Air Force unveils the KC-46 Pegasus, this mission will continue but without a position for the navigator. Instead, navigators will undergo divestment as the SOAR mission transfers to the KC-46. Current plans indicate navigators will not only remain as the KC-46 arrives, but inbound navigators will continue arriving until 2018. This thesis applies the Delphi method, a process eliciting analysis anonymously from a panel of experts, in order to examine the elements …
The Effect Of Malathion On The Activity And Performance Of Activated Sludge, Erik G. Rauglas
The Effect Of Malathion On The Activity And Performance Of Activated Sludge, Erik G. Rauglas
Theses and Dissertations
Decontamination activities following a chemical weapons incident may generate significant quantities of contaminated wash water that may enter the wastewater collection system either intentionally or accidentally. This raises concerns about the effect of chemical warfare agents (CWAs) on the operation of a biological wastewater treatment plant. The goal of the study was to evaluate the effect of malathion on the activity and performance of activated sludge. Malathion is an organophosphate (OP) and is considered an environmental surrogate for VX. This study employed respirometry, short term batch tests, and long term exposure experiments to investigate the effects of different concentrations of …
Low Earth Orbit Satellite Tracking Telescope Network: Collaborative Optical Tracking For Enhanced Space Situational Awareness, Victor A. Salvador
Low Earth Orbit Satellite Tracking Telescope Network: Collaborative Optical Tracking For Enhanced Space Situational Awareness, Victor A. Salvador
Theses and Dissertations
The Air Force Institute of Technology has spent the last seven years conducting research on orbit identification and object characterization of space objects through the use of commercial-off-the-shelf hardware systems controlled via custom software routines, referred to simply as TeleTrak. Year after year, depending on the research objectives, students have added or modified the system's hardware and software to achieve their individual research objectives. In the last year, due to operating system and software upgrades, TeleTrak became inoperable. Furthermore, due to a lack of student overlap, knowledge of the basic operation of the TeleTrak deteriorated. This research re-establishes the basic …
Army Information Technology Procurement: A Business Process Analysis, Alexander M. Vukcevic
Army Information Technology Procurement: A Business Process Analysis, Alexander M. Vukcevic
Theses and Dissertations
This thesis presents a business process analysis of the Army's ICT procurement system. The research identified several inefficiencies and proposes several potential solutions. the contributions of this research include a unified taxonomy, a method to prioritize requests, and system architecture products for development of an automated and sustainable collaboration interface for the CIO/G6 to streamline their IT acquisition process. Development of a centralized system would reduce waste in the request process from submission to formal accounting, hasten the movement of requests between stakeholders, maintain a digital signature authorization for each approval authority, provide a reporting database to recognize reprogramming thresholds, …
Error Characterization Of Flight Trajectories Reconstructed Using Structure From Motion, Daniel C. Alix
Error Characterization Of Flight Trajectories Reconstructed Using Structure From Motion, Daniel C. Alix
Theses and Dissertations
This research effort assessed the accuracy of Structure from Motion (SFM) algorithms in replicating aircraft fight trajectories. Structure from Motion techniques can be used to estimate aircraft trajectory by determining the position and pose of an aircraft mounted camera from a sequential series of images taken during flight. An algorithm is proposed and implemented that successfully reconstructed aircraft trajectory using only a known starting position and a sequential series of images. The error in and reliability of the algorithm was found to be a function of image resolution as well as the amount of overlap and angular separation between sequential …
Impacts Of Severe Weather, Climate Zone, And Energy Factors On Base Realignment And Closure (Brac), Christopher L. Teke
Impacts Of Severe Weather, Climate Zone, And Energy Factors On Base Realignment And Closure (Brac), Christopher L. Teke
Theses and Dissertations
The Air Force is in a period of downsizing, both aircraft and personnel. In recent years, the service has cut hundreds of aircraft from its fleet and decreased military end-strength, but has not substantially reduced its infrastructure. Consequently, the cost to operate and maintain Air Force Bases is not decreasing. Mitigation methods are needed to manage the costly burden of excess infrastructure. A new Base Realignment and Closure (BRAC) round will help the Air Force reduce unnecessary infrastructure and alleviate precious resources necessary for weapon modernization and improved readiness. Cost savings through BRAC can help the Air Force achieve reduced …
Methods Of Measuring Stress Relaxation In Composite Tape Springs, Justin T. Heppe
Methods Of Measuring Stress Relaxation In Composite Tape Springs, Justin T. Heppe
Theses and Dissertations
Composite tape springs present an opportunity to use stored energy for the deployment of space structures. Concern has risen over the dissipation of strain energy during storage due to viscoelasticity inherent in polymeric materials commonly used as the composite matrix. Tests to measure the internal behavior of a composite tape spring over time are conducted along with methods of analyzing and fitting the resulting data. The three constant strain configurations tested were compression force of the cross section, a restraining force of a longitudinal fold, and the change in shape of a folded section. While the shape changing test did …
Navigation Constellation Design Using A Multi-Objective Genetic Algorithm, Heather C. Diniz
Navigation Constellation Design Using A Multi-Objective Genetic Algorithm, Heather C. Diniz
Theses and Dissertations
In satellite constellation design, performance and cost of the system drive the design process. The Global Positioning System (GPS) constellation is currently used to provide positioning and timing worldwide. As satellite technology has improved over the years, the cost to develop and maintain the satellites has increased. Using a constellation design tool, it is possible to analyze the tradeoffs of new navigation constellation designs (Pareto fronts) that illustrate the tradeoffs between position dilution of precision (PDOP) and system cost. This thesis utilized Satellite Tool Kit (STK) to calculate PDOP values of navigation constellations, and the Unmanned Spacecraft Cost Model (USCM) …
Dynamic Response Analysis Of An Icosahedron Shaped Lighter Than Air Vehicle, Lucas W. Just
Dynamic Response Analysis Of An Icosahedron Shaped Lighter Than Air Vehicle, Lucas W. Just
Theses and Dissertations
The creation of a lighter than air vehicle using an inner vacuum instead of a lifting gas is considered. Specifically, the icosahedron shape is investigated as a design that will enable the structure to achieve positive buoyancy while resisting collapse from the atmospheric pressure applied. This research analyzes the dynamic response characteristics of the design, and examines the accuracy of the finite element model used in previous research by conducting experimental testing. The techniques incorporated in the finite element model are confirmed based on the experimental results using a modal analysis. The experimental setup designed will allow future research on …
Optimized Flight Path For Localization Using Line Of Bearing, Namkyu Kim
Optimized Flight Path For Localization Using Line Of Bearing, Namkyu Kim
Theses and Dissertations
This research develops optimized flight paths for localization of a target using LOB measurements. The target area is expressed as an error ellipse using the measurement errors of the LOBs. The optimization approach is focused on minimizing the size of the error ellipse. The algorithm for the optimized path is generated and compared with typical flight paths. The optimization routine is based on the results revised from previous similar research in the literature. A geometrical method to estimate the error ellipse is combined with optimal control in this research. Each LOB gives a possible target area and this target area …
Reflections Of A Wave: An Analysis Of Photonic Doppler Velocimetry Systems, Brian K. Lagrange
Reflections Of A Wave: An Analysis Of Photonic Doppler Velocimetry Systems, Brian K. Lagrange
Theses and Dissertations
Munitions are one of the Air Force's most effective weapons in eliminating targets, but also one of the most expensive. Due to the inherent high-cost in deploying munitions, munition shock wave detonation must be better observed and quantified for munitions to be more cost-efficient. PDV systems have the potential to achieve this quantification of shock wave properties on a molecular scale during solid-against-solid impacts. The overall goal of this research was to determine whether the current photonic Doppler velocimetry (PDV) system at Eglin Air Force Base is prepared for future explosive sensitivity testing. This determination was done through an uncertainty …
A Monocular Slam Method To Estimate Relative Pose During Satellite Proximity Operations, Scott J. Kelly
A Monocular Slam Method To Estimate Relative Pose During Satellite Proximity Operations, Scott J. Kelly
Theses and Dissertations
Automated satellite proximity operations is an increasingly relevant area of mission operations for the US Air Force with potential to significantly enhance space situational awareness (SSA). Simultaneous localization and mapping (SLAM) is a computer vision method of constructing and updating a 3D map while keeping track of the location and orientation of the imaging agent inside the map. The main objective of this research effort is to design a monocular SLAM method customized for the space environment. The method developed in this research will be implemented in an indoor proximity operations simulation laboratory. A run-time analysis is performed, showing near …
A Cubesat Mission For Mapping Spot Beams Of Geostationary Communications Satellites, Jacob A. Lasarge
A Cubesat Mission For Mapping Spot Beams Of Geostationary Communications Satellites, Jacob A. Lasarge
Theses and Dissertations
As space-rated technologies become more compact and more readily available over time, the concept of accomplishing space missions with smaller nanosatellite-class spacecraft becomes increasingly feasible. This research focuses specifically on a CubeSat mission to assist with radio frequency (RF) domain verification; that of characterizing and mapping K-band spot beams from communications satellites in geostationary orbit. By flying a constellation of CubeSats through the edges of spot beams originating from geostationary communication satellites, the spot beam's coverage area will be characterized. This research conducts a mission feasibility assessment, identifies the principle mission requirements to complete a spot beam mapping CubeSat mission, …
Tension-Compression Fatigue Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature In Air And Steam Environments, Richard L. Lanser
Tension-Compression Fatigue Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature In Air And Steam Environments, Richard L. Lanser
Theses and Dissertations
Tension-compression fatigue behavior of an oxide-oxide ceramic matrix composite was investigated at 1200°C in air and steam. The composite is comprised of an alumina matrix reinforced with Nextel 720 fibers woven in an eight harness satin weave. The composite relies on a porous matrix for damage tolerance. Compression and tension tests to failure were conducted to characterize basic mechanical properties. Tension-compression fatigue tests were performed at 1 Hz frequency with a ratio of minimum to maximum stress of -1. Maximum stresses ranged from 60-120 MPa. Fatigue run-out (defined as 105 cycles) was achieved in air at 80 MPa and in …
Computer Modeling Of A Rotating Detonation Engine In A Rocket Configuration, Nihar Shah
Computer Modeling Of A Rotating Detonation Engine In A Rocket Configuration, Nihar Shah
Theses and Dissertations
Detonation-based combustors leverage the higher thermodynamic efficiency of the Atkinson cycle compared to the traditional deflagration-based combustion of the Brayton cycle. The rotating detonation engine (RDE) has one or more shock waves rotating around an annulus. The RDE can theoretically be 20% more thermally efficient than a traditional deflagration-based cycle. A RDE was modeled in Numerical Propulsion System Simulation (NPSS) based on a model developed in Microsoft Excel. The thermodynamic analysis of the RDE in these models is broken into four streams. Empirical models were used to find the percentage of the total flow in each stream. The pre-detonation pressure …
Characterization Of A Robotic Manipulator For Dynamic Wind Tunnel Applications, James C. Lancaster
Characterization Of A Robotic Manipulator For Dynamic Wind Tunnel Applications, James C. Lancaster
Theses and Dissertations
The newly acquired 6-DOF Motion Test Apparatus (MTA) was installed to perform dynamic wind tunnel testing in the AFIT Low Speed Wind Tunnel. Several complex motions revealed that the overall performance of the test rig needed improvement especially during small motions. The motions exposed that further enhancements would need to be performed individually for each joint. This research effort focused on the improvement of the MTA wrist roll motor and controller using a pitch oscillation. The controller software was improved using position feedback because the MTA wrist roll motor and controller exhibited reduced signal bias and amplitude attenuation. The enhanced …
Design And Test Of An Attitude Determination And Control System For A 6u Cubesat Using Afit's Cubesat Testbed, Michael L. Tibbs
Design And Test Of An Attitude Determination And Control System For A 6u Cubesat Using Afit's Cubesat Testbed, Michael L. Tibbs
Theses and Dissertations
The design and test of a 6U CubeSat Attitude Determination and Control System (ADCS) are explored to establish single-axis control using AFIT's CubeSat testbed consisting of a Helmholtz cage and hemi-spherical air bearing. The Helmholtz cage produces a near-uniform magnetic field inside the cage while the air bearing provides a near-frictionless surface for ADCS testing. The ADCS testbed includes a four wheel pyramid reaction wheel array (RWA) for actuation and an inertial measurement unit (IMU) for attitude determination. Along with the ADCS hardware, the ADCS testbed also includes an Electrical Power System (EPS) and Command and Data Handling (CDH) for …
Simulation Of Locking Space Truss Deployments For A Large Deployable Sparse Aperture Reflector, Dylan M. Van Dyne
Simulation Of Locking Space Truss Deployments For A Large Deployable Sparse Aperture Reflector, Dylan M. Van Dyne
Theses and Dissertations
Large deployable space structures require an inordinate amount of effort to fully design and test on Earth. To aid in the determination of the feasibility of the reflector, a method to simulate the structure's deployment was developed using COMSOL. The simulation model is comprised of a locking hinge truss that constitutes the partial reflector structure. To meet computational and temporal restrictions, the structure is simplified to use simple beams with square cross sections and is meshed to a sufficient accuracy with second order elements. The geometry is modeled in the truss's stowed configuration, with the connecting hinges and applied forces …
Advancements Of In-Flight Mass Moment Of Inertia And Structural Deflection Algorithms For Satellite Attitude Simulators, Jonathan W. Wright
Advancements Of In-Flight Mass Moment Of Inertia And Structural Deflection Algorithms For Satellite Attitude Simulators, Jonathan W. Wright
Theses and Dissertations
Experimental satellite attitude simulators have been used to test and analyze control algorithms; driving down risk before implementation on operational satellites. Ideally, the dynamic response of a terrestrial-based experimental satellite attitude simulator matches that of an on-orbit satellite. Unfortunately, gravitational disturbance torques and poorly characterized moments of inertia introduce uncertainty into the system dynamics leading to questionable experimental results. This research consists of three distinct, but related contributions to the field of developing robust satellite attitude simulators. First, existing approaches to estimate mass moments and products of inertia are evaluated followed by a proposition and evaluation of a new approach …
Computational Electromagnetic Studies For Low-Frequency Compensation Of The Reflector Impulse-Radiating Antenna, Casey E. Fillmore
Computational Electromagnetic Studies For Low-Frequency Compensation Of The Reflector Impulse-Radiating Antenna, Casey E. Fillmore
Theses and Dissertations
The reflector impulse-radiating antenna (IRA) is considered to meet the requirement for a wideband, directional antenna with short temporal response and small electrical footprint. Standard reflector IRA designs are modeled and performance is simulated using full-wave computational electromagnetic (CEM) software. Characterization of the standard designs reveals the possible existence of wide, frequency-independent backlobes containing nearly 40% of the radiated power at high frequencies. These undesirable backlobes have never been hypothesized, predicted or measured, likely due in part to their alignment outside the primary measurement planes. At the lowest operating frequencies, the reflector IRA is unaffected by backlobes, but is characterized …
Precision Relative Positioning For Automated Aerial Refueling From A Stereo Imaging System, Kyle P. Werner
Precision Relative Positioning For Automated Aerial Refueling From A Stereo Imaging System, Kyle P. Werner
Theses and Dissertations
The United States Air Force relies upon aerial refueling to fulfill its missions. Unmanned aerial systems (UAS) and remotely piloted aircraft (RPA) do not currently have access to this capability due to the lack of an on-board pilot to safely maintain a refueling position. This research examines stereo vision for precision relative navigation in order to accomplish the Automated Aerial Refueling (AAR) task. Previous work toward an AAR solution has involved the use of Differential Global Positioning (DGPS), Light Detection and Ranging (LiDAR), and monocular vision. This research aims to leverage organic systems in future aircraft to compliment these solutions. …
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 - …
A Predictive Logistic Regression Model Of World Conflict Using Open Source Data, Benjamin C. Boekestein
A Predictive Logistic Regression Model Of World Conflict Using Open Source Data, Benjamin C. Boekestein
Theses and Dissertations
Nations transitioning into conflict is an issue of national interest. This study considers various data for inclusion in a statistical model that predicts the future state of the world where nations will either be in a state of violent conflict or not in violent conflict based on available historical data. Logistic regression is used to construct and test various models to produce a parsimonious world model with 15 variables. Further analysis shows that nations differ significantly by geographical area. Therefore six sub-models are constructed for differing geographical areas of the world. The dominant variables for each sub-model vary, suggesting a …
Ethical Behavior And Ajzen’S Theory Of Planned Behavior Applied To The Decision To Obtain Professional Credentials, Sarajo Paluch
Ethical Behavior And Ajzen’S Theory Of Planned Behavior Applied To The Decision To Obtain Professional Credentials, Sarajo Paluch
Theses and Dissertations
Currently, the requirement to obtain and maintain professional credentials within the engineering discipline varies among the five military departments within the U.S. Department of Defense (DoD). However, there may be an ethical requirement to do so. The purpose of this research was to investigate ethical theory and behavior theory, and their influence on the decision to obtain and maintain professional credentials. Individual Moral Philosophy (IMP) is one approach describing ethical thought. The Ethics Position Questionnaire (EPQ) measures the two dimensions of IMP: idealism and relativism. The Theory of Planned Behavior (ToPB) is used in research to predict behavior intentions and …
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 …
Subtractive Plasma-Assisted-Etch Process For Developing High Performance Nanocrystalline Zinc-Oxide Thin-Film-Transistors, Thomas M. Donigan
Subtractive Plasma-Assisted-Etch Process For Developing High Performance Nanocrystalline Zinc-Oxide Thin-Film-Transistors, Thomas M. Donigan
Theses and Dissertations
Thin-Film-Transistors (TFTs) employing undoped zinc-oxide (ZnO) thin-films are currently being investigated by the Air Force for microwave switching applications. Since the on-resistance (R(on)) of the device scales with channel length (LC), ZnO TFT optimization should be focused on reducing LC, therefore minimizing the associated insertion losses. In this research, deep sub-micron scaling of ZnO TFTs was undertaken using a subtractive reactive-ion-etch (RIE) process. Under optimum processing conditions, ZnO TFTs with LC as small as 155 nm were successfully demonstrated. The active ZnO channels of the TFTs were patterned by selective SF6-RIE of a tungsten ohmic film through electron-beam defined openings …