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Air Force Institute of Technology

1995

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Articles 1 - 30 of 141

Full-Text Articles in Engineering

Validation Testing A Contaminant Transport And Natural Attenuation Simulation Model Using Field Data, Steven J. Flier Dec 1995

Validation Testing A Contaminant Transport And Natural Attenuation Simulation Model Using Field Data, Steven J. Flier

Theses and Dissertations

This research extends the work begun by Enyeart (1994) which evaluated the process of intrinsic bioremediation, and which developed a model for predicting the velocity of an aerobic degradation front, as it traverses the length of a JP-4 contaminant plume. It is assumed this aerobic front will traverse the contaminant plume as dissolved oxygen is carried by the ground water through the sorption-retarded contaminant. The ultimate purpose of Enyeart's model is to use it to develop field guidance for assessing the feasibility of intrinsic bioremediation to restore petroleum-contaminated soils. After simulating intrinsic bioremediation many times with a spreadsheet model, results …

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A Decision Tool To Optimally Select Pollution Prevention Projects Within A Constrained Budget, Charlotte Hudson Dec 1995

A Decision Tool To Optimally Select Pollution Prevention Projects Within A Constrained Budget, Charlotte Hudson

Theses and Dissertations

Pollution prevention managers need to select the best environmental projects for an installation within a constrained budget but have no standard way of selecting the optimal mix of projects. This thesis proposes a decision tool to aid decision makers in choosing this optimal mix. The model was built using decision analysis theory which provides a framework to aid the decision maker. Criteria sed in the model for selection was determined using a questionnaire sent to base-level pollution prevention managers. The model ses DPL, a software package designed to build, analyze, and conduct sensitivity analysis of decision problems to perform the …

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Multiple Model Adaptive Control Of The Vista F-16, Michael J. Stepaniak Dec 1995

Multiple Model Adaptive Control Of The Vista F-16, Michael J. Stepaniak

Theses and Dissertations

Multiple model adaptive control (MMAC) is investigated using the high-fidelity, nonlinear, six-degree-of-freedom Simulation Rapid-Prototyping Facility VISTA F-16. Detection of single actuator and sensor failures is considered, with an MMAC algorithm initially pursued which allows a controller specifically designed for each particular failure condition to replace the standard F-16 Block 40 flight control system (FCS) once the failure is detected. The synthesis of certain discrete-time LQG/PI controllers (those using control variables linearly dependent on state derivatives) is shown to be unattainable due to numerical difficulties. A novel control technique, termed control redistribution, is introduced which redistributes control commands (that would normally …

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Methodology For Implementing Fracture Mechanics In Global Structural Design Of Aircraft, Clifton D. Nees Dec 1995

Methodology For Implementing Fracture Mechanics In Global Structural Design Of Aircraft, Clifton D. Nees

Theses and Dissertations

The analysis and design criteria of fracture mechanics are investigated for implementation with the Automated Structural Optimization System (ASTROS) global optimization design tool. The main focus is the optimal design of aircraft wing panels by applying fracture mechanics design criteria within the global finite element model. This effort consists of four main phases: investigation of fracture mechanics analysis methods and design criteria, formulation of a computational technique for damage tolerance design consistent with global optimization requirements, integration of the technique into the ASTROS design tool, and demonstration of the results.

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Fatigue Response Of Cracked Aluminum Panel With Partially Bonded Composite Patch, Jason J. Denney Dec 1995

Fatigue Response Of Cracked Aluminum Panel With Partially Bonded Composite Patch, Jason J. Denney

Theses and Dissertations

More and more aircraft, both commercial and military, are being called upon to fly well beyond their economic and structural service lives. Budget cuts and dwindling new aircraft development has forced the United States Air Force (USAF) to look toward more reliable structural repairs. One of these repair techniques, which was the subject of this study, is the repair of metallic aircraft structures using high strength composite materials. This study investigated the fatigue response of a precracked, 508x1 52x1 mm, 2024-T3 aluminum panel repaired with a partially bonded, unidirectional, three-ply boron/epoxy composite reinforcement with ply lengths of 68, 56 and …

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Adaptive And Fixed Wavelet Features For Narrowband Signal Classification, Anthony J. Pohl Dec 1995

Adaptive And Fixed Wavelet Features For Narrowband Signal Classification, Anthony J. Pohl

Theses and Dissertations

The application of the multiresolution analysis developed by Mallat to signal classification by Pati and Krishnaprasad and Szu, et al, is further explored in this thesis. Several different wavelet based feature extraction and classification systems are developed and implemented. Methods which rely on the traditional dyadic wavelet decomposition and on the adaptive wavelet representation are presented. Each of the classification systems is implemented for a labeled data set of narrowband signals. Finally, classification results on the full data set and on low frequency Fourier coefficients are provided as baseline comparisons for our work.

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A Case Study Of The Environmental Impacts Of The Beddown Of The C-17 Globemaster Iii At Charleston Afb, Richard H. Houghton Jr. Dec 1995

A Case Study Of The Environmental Impacts Of The Beddown Of The C-17 Globemaster Iii At Charleston Afb, Richard H. Houghton Jr.

Theses and Dissertations

Unites States Air Force acquisition environmental planning has changed significantly since the passage of the National Environmental Policy Act in 1969. This research examined the role of environmental planning in weapon system acquisition. It focused on environmental planning performed for the C-17 Globemaster III prior to its beddown at Charleston Air Force Base. The case study of the C- 17 beddown included interviews, archival record reviews, and direct observations at the base. Evidence was collected to determine what environmental impacts occurred during the beddown. An environmental postaudit compared actual impacts with those predicted in environmental planning documentation. Impacts were analyzed …

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Design, Fabrication And Characterization Of Micro Opto-Electro-Mechanical Systems, Darren E. Sene Dec 1995

Design, Fabrication And Characterization Of Micro Opto-Electro-Mechanical Systems, Darren E. Sene

Theses and Dissertations

Several micro-opto-electro-mechanical structures were designed using the Multi-User MEMS Process (MUMPS). Specific design techniques were investigated for improving the capabilities of elevating flip up structures. The integration of several flip up microoptical structures into a microoptical system was explored with emphasis on the development of a microinterferometer. The thermal effects on the Modulus of Elasticity were determined by detecting the resonant frequency for a square Flexure Beam Micromirror Device. The resonance of the device was found to match theory to within 0.1 % and the Modulus of Elasticity was found to decrease by 0.041 GPa/K from 290 to 450 K. …

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Comparison Of The Ralph Smith And The Time Domain Flying Qualities Criteria, Lori A. Carlucci Dec 1995

Comparison Of The Ralph Smith And The Time Domain Flying Qualities Criteria, Lori A. Carlucci

Theses and Dissertations

Aircraft pitch response is a crucial element of piloted vehicle flying qualities. The short term pitch response has created controversy over the form and substance of any requirements. Currently there are six different methods for evaluation in MIL-STD-1797A. There are many other methods which have been proposed. The biggest problem is that many of these methods often give conflicting results. The overall goal of the present effort is to compare and contrast the Time Domain criterion and the Ralph Smith criterion. By examining these methods on common grounds, areas of agreement and discrepancies can be found. Parametric studies are performed …

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A Systems Engineering Approach To Aircraft Kinetic Kill Countermeasures Technology: Development Of An Active Aircraft Defense System For The C/Kc-135 Aircraft, Mark C. Cherry, Bruce R. Dewitt, Christopher G. Dusseault, Joel J. Hagan, Brian S. Peterson Dec 1995

A Systems Engineering Approach To Aircraft Kinetic Kill Countermeasures Technology: Development Of An Active Aircraft Defense System For The C/Kc-135 Aircraft, Mark C. Cherry, Bruce R. Dewitt, Christopher G. Dusseault, Joel J. Hagan, Brian S. Peterson

Theses and Dissertations

Modern Surface to Air Missiles (SAMs) present a significant threat to today's military and civilian aircraft. Current countermeasure systems such as flares and chaff rely on decoying the missile threat and do not provide adequate protection against advanced computerized missiles (Schaffer, 1993:1). An aircraft defense system that actively seeks out and defeats an incoming missile by placing a physical barrier in the missile's path offers a promising alternative to current countermeasures technology. This thesis reports the preliminary design of an active aircraft defense system for the protection of the C/KC-135 aircraft from SAMs. The developed system utilizes a kinetic kill …

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Vehicle Thermal Control With A Variable Area Inlet, Thomas R. Layne Dec 1995

Vehicle Thermal Control With A Variable Area Inlet, Thomas R. Layne

Theses and Dissertations

This study developed a variable area inlet and controller that regulated the temperature of an electrical component with ram air. The intent of the variable area inlet was to reduce vehicle drag by eliminating inefficiencies associated with component cooling and fixed area inlets. These inefficiencies arise from vehicles moving at varying speeds through varying air temperatures. The hardware model consisted of an electrical component mounted inside a right-circular cylindrical duct. The variable area inlet, mounted in the front of the duct, consisted of a butterfly valve that was actuated by a stepper controller acted on the feedback signal of a …

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Investigation Of Aerodynamic Alterations For Improving The Kc-135 Boom Performance During Aerial Refueling, Debra A. Nawrocki Dec 1995

Investigation Of Aerodynamic Alterations For Improving The Kc-135 Boom Performance During Aerial Refueling, Debra A. Nawrocki

Theses and Dissertations

This study investigated the eligibility of the KC-135 air refueling boom for improved capabilities in the areas of control and performance. By using a thick airfoil cross-section for the boom tube, rather than the current circular cross-section, the ability to increase the lift characteristics was verified Prior compiled test data was used for comparison against analytical computer solutions. The possibility and effects of control frequency oscillations were also examined due to the unstable nature of the flow at test conditions. Additionally, the effect of other cross-section shapes, such as the blunt fairing, on the size of the flyable envelope for …

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Influence Of A Moving Endwall On The Tip Clearance Vortex In An Axial Compressor Cascade, Lawrence J. Peter Dec 1995

Influence Of A Moving Endwall On The Tip Clearance Vortex In An Axial Compressor Cascade, Lawrence J. Peter

Theses and Dissertations

This experiment involved the design, construction, validation and testing of a new facility for the investigation of vortices generated by compressor rotor blade tip clearance with a moving endwall. A five-tube pressure rake placed downstream of the trailing edge of a cascade of blades measured the pressure field for flow coefficients ranging from 20 to 1.66 and tip clearances of 0.33, 1.0, 1.7 and 2.4 percent chord. Contour plots of mass averaged pressure loss coefficient appear to show the no-flow tip vortex becomes entrained and diffused by the moving wall boundary layer. The high loss region near the moving wall …

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Experimental Investigation Of Non-Adiabatic Supersonic Slot Injection Into A Supersonic Cross-Flow, Kelly C. Tucker Dec 1995

Experimental Investigation Of Non-Adiabatic Supersonic Slot Injection Into A Supersonic Cross-Flow, Kelly C. Tucker

Theses and Dissertations

Turbulence and mean flow measurements were acquired downstream of a normal, supersonic (M=1.6), two-dimensional, slot injection into Mach 3.0 flow (Re/m = 15x106). Two non-adiabatic cases Ti/T∞ = 1.11 and Ti/T∞ = 0.93) were studied. Multiple overheat anemometry and conventional mean flow analysis, as well as shadowgraph and schlieren photography, were utilized to study the turbulent mixing layer. The mean flow data included the Pitot, cone-static, and Mach number profiles. The measured turbulence data included shear stresses, mass flux, total temperature turbulence intensities, and turbulent heat fluxes. The temperature and density variation …

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The Role Of Frame Selection And Bispectrum Phase Reconstruction For Speckle Imaging Through Atmospheric Turbulence, Elizabeth A. Harpold Dec 1995

The Role Of Frame Selection And Bispectrum Phase Reconstruction For Speckle Imaging Through Atmospheric Turbulence, Elizabeth A. Harpold

Theses and Dissertations

Frame selection using quality sharpness metrics have been shown in previous AFIT theses, to be effective in improving the final product of images obtained using adaptive optics. This thesis extends this idea to noncompensated speckle image data. Speckle image reconstruction is simulated with and without frame selection. Speckle images require the processing of hundreds of data frames. Frame selection is a method of reducing the amount of data required to reconstruct the image. A collection of short exposure image data frames of a single object are sorted based on sharpness metrics. Only the highest quality frames are retained and processed …

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Analysis And Interpretation Of Ion Data Associated With Neutral Gas Releases In The Earth's Ionosphere, Timothy M. Shadid Dec 1995

Analysis And Interpretation Of Ion Data Associated With Neutral Gas Releases In The Earth's Ionosphere, Timothy M. Shadid

Theses and Dissertations

Barium and strontium release experiments were conducted throughout 1991 from the Combined Release and Radiation Effects Satellite (CRRES) to study both natural and man-made disturbances in the earth's ionosphere. A mass spectrometer on the spacecraft counted the Ba and Sr ions as the cloud expanded. In this study, data from the G-1 (in sunlight) and G-11b (in darkness) releases were modeled to understand the source of the ion signals. The model reproduced the Ba+ sun data well assuming photoionization (τ = 28 s) was the primary ionization mechanism. However, it was not able to account for the remaining ion …

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Validation Of Operational Multiscale Environment Model With Grid Adaptivity (Omega), Gordon R. Taylor Dec 1995

Validation Of Operational Multiscale Environment Model With Grid Adaptivity (Omega), Gordon R. Taylor

Theses and Dissertations

The Defense Nuclear Agency (DNA) is improving the military's capability to forecast dosage and hazard levels due to release of chemical, biological, and nuclear agents. During Operation DESERT STORM the military realized the need for models to predict risk levels for military personnel assigned proximate to missile attacks. One project associated with this is the continuing development of the Operational Multiscale Environmental Model with Grid Adaptivity (OMEGA). DNA has sponsored AFIT to validate OMEGA with focus on incorporating weather data obtained from Air Force Combat Climatology Center for the period of the Chernobyl Nuclear Accident. The physics of the model …

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The Effect Of Meteorological Data Averaging Times On Plume Concentrations From Explosive Ordnance Disposal Open Burning Operations, Ida L. Widmann Dec 1995

The Effect Of Meteorological Data Averaging Times On Plume Concentrations From Explosive Ordnance Disposal Open Burning Operations, Ida L. Widmann

Theses and Dissertations

Explosive Ordnance Disposal (EOD) Open Burning (OB) operations are performed to treat and dispose of unserviceable munitions in the Department of Defense (DOD) inventory. Air pollution modeling of OB operations is an Environmental Protection Agency requirement for permit issuance at OB sites. Specific OB regulation is still in its infancy; therefore, establishment of OB modeling techniques is still in the early stages. This thesis effort sought to develop a computer model, based upon the Gaussian Puff Equation. The model varies from standard plume modeling practices by not making the assumption that the wind direction, wind speed and turbulence are uniform …

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A Differential Gps Aided Ins For Aircraft Landings, Ryan L. Britton Dec 1995

A Differential Gps Aided Ins For Aircraft Landings, Ryan L. Britton

Theses and Dissertations

The Department of Defense (DOD) and the commercial airline industry are in the process of replacing the instrument landing system (ILS) for aircraft precision approach landings. The use of differential Global Positioning System (DGPS) is thought to be a viable replacement for ILS precision approaches. This thesis explores the integration of an INS, DGPS, Barometric Altimeter, Pseudolite, and Radar Altimeter for a tanker type and a single engine aircraft precision approach. These devices are integrated using an extended Kalman filter (EKF). For the tanker type aircraft federal Aviation Administration (FAA) requirements for a Category I and a Category II precision …

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Design And Fabrication Of A Micromechanical Gyroscope, Richard M. Kuhns Dec 1995

Design And Fabrication Of A Micromechanical Gyroscope, Richard M. Kuhns

Theses and Dissertations

Both size and cost of mechanical and optical inertial navigation systems (INS) have prevented their use in many applications. By developing a micromachined gyroscope and combining it with existing micromachined accelerometer designs to form a low sensitivity INS, the cost would be reduced by a factor of 10 or more. The lower per unit cost would open new areas for INS use. A second advantage of the micromachined INS would be its size. A micromachined INS would weigh only a few ounces and take significantly less space, allowing more room for electronics and the weight reduction would lead to longer …

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Effects Of Jamming And Excision Filtering Upon Error Rates And Detectability Of A Spread Spectrum Communication System, Christopher B. Madden Dec 1995

Effects Of Jamming And Excision Filtering Upon Error Rates And Detectability Of A Spread Spectrum Communication System, Christopher B. Madden

Theses and Dissertations

This thesis examines the effects of a digital excision filter (DEF) upon the error rates and detectability of a Direct Sequence Binary Phase Shift Keyed communication signal in the presence of both continuous wave (CW) and pulsed jammers. Simulations were performed using the Comdisco Signal Processing Worksystem. Detector models used were the wideband radiometer and two forms of the chip-rate detector. Twelve jamming scenarios were used to test the performance of the DEF in the presence of the CW and pulsed jammers. In addition, the effects of the CW jammer frequency, the pulsed jammer duty cycle, and the pulsed jammer …

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Two-Wavelength Neodymium Based Lasers, Scott H. Mccracken Dec 1995

Two-Wavelength Neodymium Based Lasers, Scott H. Mccracken

Theses and Dissertations

A dual wavelength Q switched laser cavity has been successfully designed and assembled to evaluate the new neodymium (Nd) based materials. Initial characterization has been achieved for Nd:YAG and Nd:YLF. The results indicate that for a fixed pulse repetition frequency, the delay time can be used to adjust the relative energy between the 1.06 and 1.32 micrometer pulses. Any deficiency in the performance of one transition can be made up by performance in the other simply by changing the relative amount of time the population inversion is allowed to build up for each pulse. The best performance was obtained using …

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Design Of Flight Control Laws For Aircraft With Flexible Wings Using Quantitative Feedback Theory, Christina L. Osmon Dec 1995

Design Of Flight Control Laws For Aircraft With Flexible Wings Using Quantitative Feedback Theory, Christina L. Osmon

Theses and Dissertations

Aircraft composed of lightweight composite materials are extremely enticing since their structural weight is greatly reduced. However, the control of these aircraft is complicated by the resultant flexibility of the wings. Two avenues of approach are possible; stiffen the wings thus losing some of the weight reduction benefits, or design the lateral/directional flight control system cognizant of the wing's flexibility. In this thesis the second approach is taken. The design of three lateral/directional flight control systems for the sub-sonic flight envelope of the F-18 is presented. The Quantitative Feedback Theory (QFT) robust control design technique is used. These designs incorporate …

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Optimal Formation Flight Control, Shawn B. Mccamish Dec 1995

Optimal Formation Flight Control, Shawn B. Mccamish

Theses and Dissertations

Automatic formation flight involves controlling multiple wing aircraft equipped with standard Mach-hold, altitude-hold, and heading-hold autopilots in order to maintain a desired position relative to a lead aircraft throughout formation maneuvers. Changes in the lead aircraft's states, including formation heading, velocity, altitude, and geometry changes, are treated as disturbance and are rejected by the formation flight control system. The work in this thesis is a continuation of five previous theses, dealing with the design of formation flight control systems. The goal of the optimal formation flight control design is to achieve robust formation maintenance in the face of formation maneuvers …

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Electroencephalography: Subdural Multi-Electrode Brain Chip, John E. Rosenstengel Dec 1995

Electroencephalography: Subdural Multi-Electrode Brain Chip, John E. Rosenstengel

Theses and Dissertations

In October 1995, a CMOS brain chip consisting of two 8 x 17 multiplexed sub-arrays designed to measure electrical potentials at the cortical column level, was implanted on the somatosensory cortex of a laboratory rhesus monkey. Electroencephalograph (EEG) and averaged evoked response (AEG) data were taken over a period of 40 minutes. The brain chip was replaced with an identical chip, and data were again taken for 40 minutes. In both instances AEG signals of approximately 150 µVpp were recorded. Additionally, the first implanted chip recorded three phases of data: (1) AEG; (2) large clock noise (during a period …

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Thermo-Mechanical Fatigue Behavior Of Cross-Ply Ceramic Matrix Composite Under Tension-Tension Loading, Dana G. Allen Dec 1995

Thermo-Mechanical Fatigue Behavior Of Cross-Ply Ceramic Matrix Composite Under Tension-Tension Loading, Dana G. Allen

Theses and Dissertations

The purpose of this study was to investigate the combined effect of cyclic temperature and loading on the fatigue life of a ceramic matrix composite with a cross ply lay-up. The material used in this study was a potassium borosilicate glass (BSG) doped magnesium aluminosilicate (MAS) cordierite matrix reinforced with Nicalon (silicon carbide, SiC) fibers in a [0/90]4s lay-up. Thermomechanical fatigue (TMF) tests were performed with a period of 180 seconds/cycle, or 0.00556 Hz, and a triangular wave-form. The temperature was cycled between 566°C and l093°C, and the stress levels varied between 60 MPa and 145 MPa. All tests …

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Stress/Strain Ratio Effects On Fatigue Response Of A Scs-6/Ti-15-3 Metal Matrix Composite At Elevated Temperature, Sean C. Jackson Dec 1995

Stress/Strain Ratio Effects On Fatigue Response Of A Scs-6/Ti-15-3 Metal Matrix Composite At Elevated Temperature, Sean C. Jackson

Theses and Dissertations

This study investigated the fatigue life and damage mechanisms of a [0]8, SCS-6/Ti-15-3, metal matrix composite at 427°C for three different stress/strain ratios, R = -1, 0 and 0.5. Fatigue life and damage mechanism comparisons were made for the varying R ratios and between the load and strain control modes. Fatigue life comparisons show that on a maximum stress/strain basis as R is increased fatigue life increases while on a stress/strain range basis as R increases fatigue life decreases. Similar damage mechanisms were found between the R = -1 and R = 0 tests conducted at the same …

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Frequency Effects On Fatigue Behavior Of A Unidirectional Metal Matrix Composite At Elevated Temperature, Robert N. Pittman Dec 1995

Frequency Effects On Fatigue Behavior Of A Unidirectional Metal Matrix Composite At Elevated Temperature, Robert N. Pittman

Theses and Dissertations

The fatigue response and life of a unidirectional SCS-6/Ti-6-4 metal-matrix composite were examined under tension-tension, load-controlled conditions at elevated temperatures and different frequencies. Composite specimens were fatigued at frequencies of 0.01, 0.1, 1 and 10 Hz, and at three stress levels. Plots of cycles to failure versus maximum stress and test frequency showed that fatigue life was more cycle-dependent at higher frequencies and more time-dependent at lower frequencies. Comparisons of tests at 427°C with their counterparts at 370°C and 538°C showed that these frequency effects were magnified as temperature increased: lower frequency tests at 538°C exhibited greater time-dependence than tests …

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Effects Of Base Cavity Depth On A Free Spinning Wrap-Around Fin Missile Configuration, Jon A. Struck Dec 1995

Effects Of Base Cavity Depth On A Free Spinning Wrap-Around Fin Missile Configuration, Jon A. Struck

Theses and Dissertations

This study investigated the role base cavity depth plays in altering the overall subsonic aerodynamic forces on a free spinning axisymmetric body with wrap around fins. Wind tunnel usage allowed the forces to be monitored for varying base cavity depths and angles of attack. A base cavity depth analysis was also performed on a non-spinning axisymmetric body for comparison. Oil visualizations were conducted on the non-spinning configuration to further describe airflow patterns around the body and within the cavity. Results revealed that the aerodynamic forces, mostly drag, changed with increasing cavity depth but not to the extent previously believed. The …

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Applications Of Nonlinear Control Using The State-Dependent Riccati Equation, David K. Parrish Dec 1995

Applications Of Nonlinear Control Using The State-Dependent Riccati Equation, David K. Parrish

Theses and Dissertations

This thesis examines the relatively new theory of nonlinear control using state dependent coefficient factorizations to mimic linear state space systems. The control theory is a nonlinear quadratic approach, analogous to linear quadratic regulation. All implementations examined in this thesis are done strictly numerically. This thesis is meant to provide a proof of concept for both satellite control and for an artificial pancreas to regulate blood glucose levels in diabetics by automatic insulin injection. These simulations represent only a first step towards practical use of the NQR method, and do not address noise rejection or robustness issues.

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