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Articles 2011 - 2040 of 5700
Full-Text Articles in Engineering
Enhanced Vehicle Beddown Approximations For The Improved Theater Distribution Model, Jonathan D. White
Enhanced Vehicle Beddown Approximations For The Improved Theater Distribution Model, Jonathan D. White
Theses and Dissertations
Gathering insight into the theater distribution process can be a complex task, especially when estimating potential beddown solutions. Coming up with a low cost feasible mixture of cargo vehicles that will support distribution of military personnel and goods within theater is currently a high priority for force flow analysts at USTRANSCOM. In the past, analysts used a trial and error simulation process that was iterative and time consuming. Recent research has produced the Improved Theater Distribution Model (ITDM), which presents a less time consuming, more precise method to estimate beddown allocations. Improving on this research, two linear programming methods were …
Applying Lean To The F-15 Maintenance Process For The Royal Saudi Air Force, Mohammad Alamri
Applying Lean To The F-15 Maintenance Process For The Royal Saudi Air Force, Mohammad Alamri
Theses and Dissertations
The thesis was about applying lean to the F-15 maintenance process in Royal Saudi Air Force. The researcher collected the data by using several questionnaires. Researcher used external lean expert recommendation to avoid bias, the F-15 maintenance process improved theoretically.
Ultraviolet Light Emitting Diode Use In Advanced Oxidation Processes, Kelsey L. Duckworth
Ultraviolet Light Emitting Diode Use In Advanced Oxidation Processes, Kelsey L. Duckworth
Theses and Dissertations
Cleanup from a hazardous chemical release can result in large volumes of water containing hazardous materials, such as organophosphates. Unfortunately, this water cannot be treated in a municipal wastewater treatment plant without adversely affecting the performance of the plant. A known method for pretreating this water to prepare it for processing in a traditional treatment plant includes the addition of hydrogen peroxide, followed by ultraviolet (UV) light exposure to form reactive hydroxyl radicals which oxidize the chemical. Light emitting diodes (LEDs) are explored as a UV source as they are durable; compact; can be powered by low voltage, direct current …
Design And Analysis Of An Attitude Determination And Control Subsystem (Adcs) For Afit's 6u Standard Bus, Erin R. Dannemeyer
Design And Analysis Of An Attitude Determination And Control Subsystem (Adcs) For Afit's 6u Standard Bus, Erin R. Dannemeyer
Theses and Dissertations
The design and testing of AFIT's 6U Attitude Determination and Control Subsystem (ADCS) are explored to establish 3-axis attitude control. The development of AFIT's 6U CubeSat standard bus is an on-going research effort designed to create in-house CubeSat bus components and software. The 6U chassis measures approximately 11 x 24 x 37 cu cm and can have a mass up to 12 kg. The larger bus size (as compared to the more common 3U CubeSat) allows for increased power capabilities and potential to host multiple or larger payloads. Individual ADCS hardware components were either commercially purchased or built in-house and …
Influence Of Mach Number And Dynamic Pressure On Cavity Tones And Freedrop Trajectories, Justin D. Merrick
Influence Of Mach Number And Dynamic Pressure On Cavity Tones And Freedrop Trajectories, Justin D. Merrick
Theses and Dissertations
Weapons release at supersonic speeds from an internal weapons bay is a highly desirable capability. To ensure a successful release at multiple Mach numbers, the aerodynamic environment must be well-understood and repeatable, with a robust system for safe testing of store separation. For this reason, experimental methods were used to investigate the characteristics of a scaled WICS bay with a length-to-depth ratio of 4.5 at multiple Mach numbers and stagnation pressures. Three new nozzles were designed, manufactured, and characterized for the AFIT small supersonic tunnel, yielding freestream Mach numbers of 2.22, 1.84, and 1.43. In addition, a control valve was …
Thermal Loss Determination For A Small Internal Combustion Engine, Joshua A. Rittenhouse
Thermal Loss Determination For A Small Internal Combustion Engine, Joshua A. Rittenhouse
Theses and Dissertations
Three analysis techniques were used to measure the heat rejection of a 55 cc air-cooled two-stroke engine. This study was performed as part of a larger effort aimed at extending range and endurance limitations of Group 1 & 2 Remotely Piloted Aircraft (RPA). The engine selected for the study was a 55 cc gasoline-fueled, carbureted, spark-ignition engine made by 3W-Modellmotoren and is representative of RPA engines in these groups. With a surface area to volume ratio of 1.48 1/cm, the engine is in a size region where thermal losses begin to dominate engine efficiency and thermal efficiencies …
An Experimental Evaluation Of Image Quality For Various Scenarios In A Chromotomographic System With A Spinning Prism, Kyle J. Dufaud
An Experimental Evaluation Of Image Quality For Various Scenarios In A Chromotomographic System With A Spinning Prism, Kyle J. Dufaud
Theses and Dissertations
A lab and eld based hyperspectral chromotomographic imager has been developed at the Air Force Institute of Technology. It is a prototype used to study the requirements for a space-based system. The imager uses a high speed visible band camera behind a direct-vision prism to image both spatial dimensions and the spectral dimension at the same time. Capturing all 3 simultaneously allows for the hyperspectral imaging of transient events. The prism multiplexes the spectral and spatial information, so tomographic reconstruction algorithms must be used to separate hyperspectral channels. Experiments were conducted to compare reconstructed image quality as a function of …
Polarimetric Calibration And Characterization Of The Telops Field Portable Polarimetric-Hyperspectral Imager, Joel G. Holder
Polarimetric Calibration And Characterization Of The Telops Field Portable Polarimetric-Hyperspectral Imager, Joel G. Holder
Theses and Dissertations
The Telops polarimetric-hyperspectral imager combines polarimetric and hyperspectral technologies to enable enhanced scene characterization. The Defense Threat Reduction Agency funded research at AFIT to leverage this capability to provide more accurate scene information to radiation transport models that will allow for more effective location of radiation sources within a region of interest. To support the objectives of the DTRA effort, there is a requirement for highly accurate radiometric, polarimetric, and spectral data on a pixel-by-pixel basis. The complex nature of the Telops instrument combined with working in the thermal IR waveband makes achieving this accuracy a challenge. This thesis develops …
Comparative Analysis Of Reconstructed Image Quality In A Simulated Chromotomographic Imager, Ryan L. Tervo
Comparative Analysis Of Reconstructed Image Quality In A Simulated Chromotomographic Imager, Ryan L. Tervo
Theses and Dissertations
A hyperspectral chromotomographic instrument has been developed to determine the spatial and spectral distribution of a target. It does this by recording the dispersed images produced by a rotating direct vision prism with a high speed camera. The recorded images are processed through a tomographic reconstruction algorithm to produce a reconstructed hypercube. A physics-based system model was developed to investigate three areas. The first was how the prism angle selection and range of angles used impacted the reconstructed image quality. The second was an assessment of a new iterative reconstruction algorithm developed to remove artifacts produced in the Back Projection …
Neutral Nitrogen Acceptors In Zno: The 67Zn Hyperfine Interactions, Eric M. Golden, S. M. Evans, Larry E. Halliburton, Nancy C. Giles
Neutral Nitrogen Acceptors In Zno: The 67Zn Hyperfine Interactions, Eric M. Golden, S. M. Evans, Larry E. Halliburton, Nancy C. Giles
Faculty Publications
Electron paramagnetic resonance (EPR) is used to characterize the 67Zn hyperfine interactions associated with neutral nitrogen acceptors in zinc oxide. Data are obtained from an n-type bulk crystal grown by the seeded chemical vapor transport method. Singly ionized nitrogen acceptors (N−) initially present in the crystal are converted to their paramagnetic neutral charge state (N0) during exposure at low temperature to 442 or 633 nm laser light. The EPR signals from these N0 acceptors are best observed near 5 K. Nitrogen substitutes for oxygen ions and has four nearest-neighbor cations. The zinc ion …
Opportunistic Access In Frequency Hopping Cognitive Radio Networks, Ethan S. Hennessey
Opportunistic Access In Frequency Hopping Cognitive Radio Networks, Ethan S. Hennessey
Theses and Dissertations
Researchers in the area of cognitive radio often investigate the utility of dynamic spectrum access as a means to make more efficient use of the radio frequency spectrum. Many studies have been conducted to find ways in which a secondary user can occupy spectrum licensed to a primary user in a manner which does not disrupt the primary user's performance. This research investigates the use of opportunistic access in a frequency hopping radio to mitigate the interference caused by other transmitters in a contentious environment such as the unlicensed 2.4 GHz region. Additionally, this work demonstrates how dynamic spectrum access …
Triplet Ground State Of The Neutral Oxygen-Vacancy Donor In Rutile Tio2, A. T. Brant, Eric M. Golden, Nancy C. Giles, Shan Yang, M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton
Triplet Ground State Of The Neutral Oxygen-Vacancy Donor In Rutile Tio2, A. T. Brant, Eric M. Golden, Nancy C. Giles, Shan Yang, M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton
Faculty Publications
Electron paramagnetic resonance (EPR) is used to investigate the triplet (S = 1) ground state of the neutral oxygen vacancy in bulk rutile TiO2 crystals. This shallow donor consists of an oxygen vacancy with two nearest-neighbor, exchange-coupled 3+ ions located along the [001] direction and equidistant from the vacancy. The spins of the two trapped electrons, one at each 3+ ion, align parallel to give the S = 1 state. These neutral oxygen vacancies are formed near 25 K in as-grown oxidized TiO2 crystals by illuminating with sub-band-gap 442 nm laser light. The angular dependence of the EPR …
A Systematic Study Of The Optical And Electrical Properties Of Ge1-YSnY And Ge1-X-YSiXSnY Semiconductor Alloys, Thomas R. Harris
A Systematic Study Of The Optical And Electrical Properties Of Ge1-YSnY And Ge1-X-YSiXSnY Semiconductor Alloys, Thomas R. Harris
Theses and Dissertations
In order to fully utilize newly developed Ge1-ySny and Ge1-x-ySixSny materials for new novel optoelectronic devices, the optical and electrical properties of these alloys were investigated using photoluminescence (PL) and Hall-effect measurements. Direct bandgap PL emission was observed from almost all the samples, making them very promising candidates for Si-based light emitting devices. T-dependent PL studies also indicate that the indirect-to-direct bandgap transition of Ge1-ySny alloys might take place at a much lower Sn content than the theory predicts. T-dependent Hall-effect measurements showed both degenerate parallel conducting layers as …
Digital Display With Integrated Computing Circuit, Ronald S. Cok, John W. Harmer, Michael E. Miller
Digital Display With Integrated Computing Circuit, Ronald S. Cok, John W. Harmer, Michael E. Miller
AFIT Patents
A digital display device includes a display substrate; an array of pixels formed on the display substrate; an array of driving circuits located on the display substrate, each driving circuit electrically connected to one or more pixels for controlling a pixel current provided to each pixel; an array of computing circuits located on the display substrate, each computing circuit including circuits for signal or image processing and for communicating with neighboring computing circuits; a plurality of electrical conductors formed on the display substrate and connected to each of the driving circuits and digital computing circuits, wherein each computing circuit is …
Graduate School Of Engineering And Management Catalog 2014-2015, Graduate School Of Engineering And Management, Air Force Institute Of Technology
Graduate School Of Engineering And Management Catalog 2014-2015, 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.
Structure Health Monitoring (Shm) System Trade Space Analysis, Salman A. Albinali, David R. Jacques
Structure Health Monitoring (Shm) System Trade Space Analysis, Salman A. Albinali, David R. Jacques
Faculty Publications
An analytic approach to exploring the tradespace associated with Structural Health Monitoring (SHM) systems is presented. Modeling and simulation of the life cycle of a legacy aircraft and the expected operational and maintenance events that could occur is shown. A focus on the SHM system detection of a significant crack length and the possibility of False Alarm (FA), miss detection and mishap events is investigated. The modeling approach allows researchers to explore the tradespace associated with safe and critical crack lengths, sensor thresholds, scheduled maintenance intervals, falsely triggered maintenance actions, and mishaps due to missed detections. As one might expect, …
Using Software-Based Decision Procedures To Control Instruction-Level Execution, William B. Kimball
Using Software-Based Decision Procedures To Control Instruction-Level Execution, William B. Kimball
AFIT Patents
An apparatus, method and program product are provided for securing a computer system. A digital signature of an application is checked, which is loaded into a memory of the computer system configured to contain memory pages. In response to finding a valid digital signature, memory pages containing instructions of the application are set as executable and memory pages other than those containing instructions of the application are set as non-executable. Instructions in executable memory pages are executed. Instructions in non-executable memory pages are prevented from being executed. A page fault is generated in response to an attempt to execute an …
Mems Cantilever Sensor For Thz Photoacoustic Chemical Sensing And Spectroscopy, Nathan E. Glauvitz
Mems Cantilever Sensor For Thz Photoacoustic Chemical Sensing And Spectroscopy, Nathan E. Glauvitz
Theses and Dissertations
Sensitive Microelectromechanical System (MEMS) cantilever designs were modeled, fabricated, and tested to measure the photoacoustic (PA) response of gasses to terahertz (THz) radiation. Surface and bulk micromachining technologies were employed to create the extremely sensitive devices that could detect very small changes in pressure. Fabricated devices were then tested in a custom made THz PA vacuum test chamber where the cantilever deflections caused by the photoacoustic effect were measured with a laser interferometer and iris beam clipped methods. The sensitive cantilever designs achieved a normalized noise equivalent absorption coefficient of 2.83x10-10 cm-1 W Hz-1/2 using a 25 …
Modeling Reliability Growth In Accelerated Stress Testing, Jason K. Freels
Modeling Reliability Growth In Accelerated Stress Testing, Jason K. Freels
Theses and Dissertations
Qualitative accelerated test methods improve system reliability by identifying and removing initial design flaws. However, schedule and cost constraints often preclude sufficient testing to generate a meaningful reliability estimate from the data obtained in these tests. In this dissertation a modified accelerated life test is proposed to assess the likelihood of attaining a reliability requirement based on tests of early system prototypes. Assuming each prototype contains an unknown number of independent competing failure modes whose respective times to occurrence are governed by a distinct Weibull law, the observed failure data from this qualitative test are shown to follow a poly-Weibull …
Network Interdependency Modeling For Risk Assessment On Built Infrastructure Systems, Vhance V. Valencia
Network Interdependency Modeling For Risk Assessment On Built Infrastructure Systems, Vhance V. Valencia
Theses and Dissertations
As modern infrastructures become more interconnected, the decision-making process becomes more difficult because of the increased complexity resulting from infrastructure interdependencies. Simulation and network modeling provide a way to understand system behavior as a result of interdependencies. One area within the asset management literature that is not well covered is infrastructure system decay and risks associated with that decay. This research presents an enhanced version of Haimes' input-output inoperability model (IIM) in the analysis of built infrastructure systems. Previous applications of the IIM characterized infrastructure at the national level utilizing large economic databases. This study develops a three-phased approach that …
Situational Awareness/Triage Tool For Use In A Chemical, Biological, Radiological Nuclear Explosive (Cbrne) Environment, John N. Scarlett, Heather L. Gallup, David A. Smith
Situational Awareness/Triage Tool For Use In A Chemical, Biological, Radiological Nuclear Explosive (Cbrne) Environment, John N. Scarlett, Heather L. Gallup, David A. Smith
AFIT Patents
A method of managing patient care and emergency response following a Chemical, Biological, Radiological, or Nuclear Explosive (CBRNE) attack and maintaining compliance with the Health Insurance Portability and Accountability Act (HIPAA). The method including identifying each patient with a unique patient identifier, the identifier based upon the geospatial location of the patient, the geospatial location including at least the latitude and longitude of the patient when first treated, the unique patient identifier being part of patient data. Providing a collection point of patient data to form a patient data database where in the patient location data may be used to …
Aerodynamic Performance And Particle Image Velocimetery Of Piezo Actuated Biomimetic Manduca Sexta Engineered Wings Towards The Design And Application Of A Flapping Wing Flight Vehicle, Anthony M. Deluca
Theses and Dissertations
Considerable research and investigation has been conducted on the aerodynamic performance, and the predominate flow physics of the Manduca sexta size of biomimetically designed and fabricated wings as part of the AFIT FWMAV design project. Despite a burgeoning interest and research into the diverse field of flapping wing flight and biomimicry, the aerodynamics of flapping wing flight remains a nebulous field of science with considerable variance into the theoretical abstractions surrounding aerodynamic mechanisms responsible for aerial performance. Traditional FWMAV flight models assume a form of a quasi-steady approximation of wing aerodynamics based on an infinite wing element model (BEM). An …
Enhancing Ground Based Telescope Performance With Image Processing, John C. Zingarelli
Enhancing Ground Based Telescope Performance With Image Processing, John C. Zingarelli
Theses and Dissertations
The Space Surveillance Telescope (SST) is a Defense Advanced Research Projects Agency (DARPA) program designed to detect objects in space like Near Earth Asteroids (NEAs) and space debris in the Geosynchronous Earth Orbit (GEO) belt. Binary hypothesis tests (BHTs) have historically been used to facilitate the detection of new objects in space. In this dissertation, a multi-hypothesis test (MHT) detection strategy is introduced to improve the detection performance of the SST. In this context, the MHT determines if an unresolvable point source is in the center, corner or side of a pixel in contrast to a BHT, which only tests …
Tonescale Compression For Electroluminescent Display, Michael E. Miller, Christopher J. White
Tonescale Compression For Electroluminescent Display, Michael E. Miller, Christopher J. White
AFIT Patents
A method for controlling an electroluminescent display to produce an image for display that has reduced luminance to reduce burn-in on the display while maintaining visible contrast, includes providing the electroluminescent (EL) display having a plurality of EL emitters, the luminance of the light produced by each EL emitter being responsive to a respective drive signal; receiving a respective input image signal for each EL emitter; and transforming the input image signals to a plurality of drive signals that have a reduced peak frame luminance value but maintains contrast in the displayed image to reduce burn-in by adjusting the drive …
Coded Aperture Aided Navigation And Geolocation Systems, Jamie R. Morrison, John F. Raquet, Michael J. Veth
Coded Aperture Aided Navigation And Geolocation Systems, Jamie R. Morrison, John F. Raquet, Michael J. Veth
AFIT Patents
A micro air vehicle having a navigation system with a single camera to determine position and attitude of the vehicle using changes the direction to the observed features. The difference between the expected directions to the observed features versus the measured direction to the observed features is used to correct a navigation solution.
Mems Fabrication Process Base On Su-8 Masking Layers, Scott A. Ostrow, Ronald A. Coutu Jr.
Mems Fabrication Process Base On Su-8 Masking Layers, Scott A. Ostrow, Ronald A. Coutu Jr.
AFIT Patents
A novel fabrication process uses a combination of negative and positive photoresists with positive tone photomasks, resulting in masking layers suitable for bulk micromachining high-aspect ratio microelectromechanical systems (MEMS) devices. This technique allows the use of positive photomasks with negative resists, opening the door to an ability to create complementary mechanical structures without the fabrication delays and costs associated with having to obtain a negative photomask. In addition, whereas an SU-8 mask would normally be left in place after processing, a technique utilizing a positive photoresist as a release layer has been developed so that the SU-8 masking material can …
Deployed Communications In An Austere Environment: A Delphi Study, Andrew Soine, James Harker, Alan R. Heminger
Deployed Communications In An Austere Environment: A Delphi Study, Andrew Soine, James Harker, Alan R. Heminger
Faculty Publications
The information and communications technology (ICT) field is undergoing a period of tremendous change. The exponential growth rate of ICT capability in recent decades, which has had an undeniable effect on every aspect of our society, will likely have ramifications for military operations in austere environments. 1 The Air Force’s 689th Combat Communications Wing commissioned a study to forecast the future of mobile ICT in such environments. Researchers at the Air Force Institute of Technology chose to employ the Delphi technique as the methodology for executing this task. The following scenario, based on the results of that study, demonstrates how …
A Clamped Dual-Ridged Waveguide Measurement System For The Broadband, Nondestructive Characterization Of Sheet Materials, Milo W. Hyde Iv, Michael J. Havrilla
A Clamped Dual-Ridged Waveguide Measurement System For The Broadband, Nondestructive Characterization Of Sheet Materials, Milo W. Hyde Iv, Michael J. Havrilla
Faculty Publications
A novel two-port probe which uses dual-ridged waveguides for the nondestructive, broadband characterization of sheet materials is presented. The new probe is shown to possess approximately 2 to 3 times the bandwidth of traditional coaxial and rectangular/circular waveguide probe systems while maintaining the structural robustness characteristic of rectangular/circular waveguide probe systems. The theoretical development of the probe is presented, namely, by applying Love’s equivalence theorem and enforcing the continuity of transverse fields at the dual-ridged waveguide apertures, a system of coupled magnetic field integral equations is derived. The system of coupled magnetic field integral equations is solved using the method …
Development Of Availability And Sustainability Spares Optimization Models For Aircraft Reparables, Edmund K. W. Pek
Development Of Availability And Sustainability Spares Optimization Models For Aircraft Reparables, Edmund K. W. Pek
Theses and Dissertations
The Republic of Singapore Air Force (RSAF) conducts Logistics Support Analysis (LSA) studies in various engineering and logistics efforts on the myriad of weapon systems. In these studies, inventory spares provisioning, availability and sustainability analyses are key focus areas to ensure asset sustenance. In particular, OPUS10, a commercial-off-the-shelf software, is extensively used to conduct reparable spares optimization in acquisition programs. However, it is limited in its ability to conduct availability and sustainability analyses of time-varying operational demands, crucial in Operations & Support (O&S) and contingency planning. As the RSAF seeks force structure expansion to include more sophisticated weapon systems, the …
Architecting Integrated System Health Management For Airworthiness, Kerwin C. Teong
Architecting Integrated System Health Management For Airworthiness, Kerwin C. Teong
Theses and Dissertations
Integrated System Health Management (ISHM) for Unmanned Aerial Systems (UAS) has been a new area of research - seeking to provide situational awareness to mission and maintenance operations, and for improved decision-making with increased self-autonomy. This research effort developed an analytic architecture and an associated discrete-event simulation using Arena® to investigate the potential benefits of ISHM implementation onboard an UAS. The objective of this research is two-fold: firstly, to achieve continued airworthiness by investigating the potential extension of UAS expected lifetime through ISHM implementation, and secondly, to reduce life cycle costs by implementing a Condition-Based Maintenance (CBM) policy with better …