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Engineering Commons™

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2002

Air Force Institute of Technology

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Articles 1 - 30 of 105

Full-Text Articles in Engineering

Use Of Dimples To Suppress Boundary Layer Separation On A Low Pressure Turbine Blade, Kurt P. Rouser Dec 2002

Use Of Dimples To Suppress Boundary Layer Separation On A Low Pressure Turbine Blade, Kurt P. Rouser

Theses and Dissertations

Flow separation on a low pressure turbine blade is explored at Reynolds numbers of 25k, 45k and 100k. Experimental data is collected in a low-speed, draw-down wind tunnel using a cascade of eight Pak-B blades. Flow is examined from measurements of blade surface pressures, boundary layer parameters, exit velocities, and total pressure losses across the blade. Two recessed dimple shapes are assessed for suppressing flow separation and associated losses. One dimple is spherical, and the second is asymmetric, formed from a full dimple spanwise half-filled. A single row of each dimple shape is tested at 50%, 55% and 65% axial …

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A Framework For Prognostics Reasoning, Thomas C. Clutz Dec 2002

A Framework For Prognostics Reasoning, Thomas C. Clutz

Theses and Dissertations

The use of system data to make predictions about the future system state commonly known as prognostics is a rapidly developing field. Prognostics seeks to build on current diagnostic equipment capabilities for its predictive capability. Many military systems including the Joint Strike Fighter (JSF) are planning to include on-board prognostics systems to enhance system supportability and affordability. Current research efforts supporting these developments tend to focus on developing a prognostic tool for one specific system component. This dissertation research presents a comprehensive literature review of these developing research efforts. It also develops presents a mathematical model for the optimum allocation …

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Electromagnetic Scattering From A Gap In A Magneto-Dielectric Coating On An Infinite Ground Plane, George R. Simpson Nov 2002

Electromagnetic Scattering From A Gap In A Magneto-Dielectric Coating On An Infinite Ground Plane, George R. Simpson

Theses and Dissertations

The electromagnetic scattering from a gap in a magneto-dielectric coating on an infinite ground plane is analyzed. In this context, the gap forms a break only in the magneto-dielectric slab coating while the ground plane is continuous and unbroken. Volume equivalence is used to convert the gap region to one containing unknown volumetric equivalent electric and magnetic currents. The equivalent problem then is one of these currents radiating in the presence of an unbroken grounded magneto-dielectric slab. A Green's function for this geometry is developed consisting of two terms: a direct coupling term and correction term to account for the …

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An Evaluation Of Facility Maintenance And Repair Strategies Of Select Companies, Christopher L. Sharp Sep 2002

An Evaluation Of Facility Maintenance And Repair Strategies Of Select Companies, Christopher L. Sharp

Theses and Dissertations

Although initial construction costs are high, the cost of operation and maintenance over a facilities life-cycle is significantly higher. A common challenge for facility maintenance professionals is balancing the cost of facility Maintenance and Repair (M&R) with the benefits derived from those facilities. This thesis documents how a selection of companies implemented that balance by determining their facilities requirements based on their chosen facility condition level and how they then allocated funds. The research effort consisted of interviews with facility maintenance professionals at each company selected. The data was then used to perform a multiple case study analysis and comparison …

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Automatic Target Recognition Classification System Evaluation Methodology, Christopher Brian Bassham Sep 2002

Automatic Target Recognition Classification System Evaluation Methodology, Christopher Brian Bassham

Theses and Dissertations

This dissertation research makes contributions towards the evaluation of developing Automatic Target Recognition (ATR) technologies through the application of decision analysis (DA) techniques. ATR technology development decisions should rely not only on the measures of performance (MOPs) associated with a given ATR classification system (CS), but also on the expected measures of effectiveness (MOEs). The purpose of this research is to improve the decision-makers in the ATR Technology development. A decision analysis framework that allows decision-makers in the ATR community to synthesize the performance measures, costs, and characteristics of each ATR system with the preferences and values of both the …

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Adaptive Harmonic Balance Method For Unsteady, Nonlinear, One-Dimensional Periodic Flows, Raymond C. Maple Sep 2002

Adaptive Harmonic Balance Method For Unsteady, Nonlinear, One-Dimensional Periodic Flows, Raymond C. Maple

Theses and Dissertations

A new adaptive split-domain harmonic balance computational fluid dynamics (CFD) method is developed to solve highly nonlinear time-periodic flows such as those found in turbomachinery. The basic harmonic balance CFD method transforms an unsteady time-periodic problem into a steady-state problem by assuming a solution in the form of a Fourier series in time. The new method employs a unique multi-domain split-operator solution technique to remove a large-series stability restriction present in previous harmonic balance CFD approaches. In addition, the new method adapts the frequency content to the flow, starting with a small number of Fourier frequencies and augmenting the frequency …

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Congruent Weak Conformance, Ronald W. Brower Sep 2002

Congruent Weak Conformance, Ronald W. Brower

Theses and Dissertations

This research addresses the problem of verifying implementations against specifications through an innovative logic approach. Congruent weak conformance, a formal relationship between agents and specifications, has been developed and proven to be a congruent partial order. This property arises from a set of relations called weak conformations. The largest, called weak conformance, is analogous to Milner's observational equivalence. Weak conformance is not an equivalence, however, but rather an ordering relation among processes. Weak conformance allows behaviors in the implementation that are unreachable in the specification. Furthermore, it exploits output concurrencies and allows interleaving of extraneous output actions in the implementation. …

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Mean Performance Optimization Of An Orbiting Distributed Aperture By Warped Aperture Image Plane Comparisons, Timothy W. Parker Sep 2002

Mean Performance Optimization Of An Orbiting Distributed Aperture By Warped Aperture Image Plane Comparisons, Timothy W. Parker

Theses and Dissertations

This work models the aggregate performance of satellite receiver formations functioning as orbiting interferometers as compared to filled apertures of similar geometries. These models facilitate selecting initial conditions for formations such that their control-free dynamics yield interferometry performance with minimal errors as compared to the filled apertures. The solution method draws on the dynamic models of an orbiting planar satellite formation to define the size and shape of a reference aperture and to define the degrees of freedom for the formation members. The paths of formation elements yield geometries for which the aggregate performance of the array of discrete receivers …

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Analysis For Cooperative Behavior Effectiveness Of Autonomous Wide Area Search Munitions, Sang M. Park Aug 2002

Analysis For Cooperative Behavior Effectiveness Of Autonomous Wide Area Search Munitions, Sang M. Park

Theses and Dissertations

The purpose of this study is to investigate how a simulation model can accurately represent the performance of the autonomous wide area search munitions, and to find the effectiveness of the cooperative behavior on the autonomous munitions. Though it does not provide a practical solution for the development of the autonomous wide area search munitions, this research will show some meaningful allocations of the munitions tasks that are applicable to the development of the autonomous munitions. For the first phase, this thesis presents how accurately a simplified simulation model can represent a proposed weapon system by comparing the simulation results …

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A Combined Adaptive Tabu Search And Set Partitioning Approach For The Crew Scheduling Problem With An Air Tanker Crew Application, Todd E. Combs Aug 2002

A Combined Adaptive Tabu Search And Set Partitioning Approach For The Crew Scheduling Problem With An Air Tanker Crew Application, Todd E. Combs

Theses and Dissertations

This research develops the first metaheuristic approach to the complete air crew scheduling problem. It develops the first dynamic, integrated, set-partitioning based vocabulary scheme for metaheuristic search. Since no benchmark flight schedules exist for the tanker crew scheduling problem, this research defines and develops a Java™ based flight schedule generator. The robustness of the tabu search algorithms is judged by testing them using designed experiments. An integer program is developed to calculate lower bounds for the tanker crew scheduling problem objectives and to measure the overall quality of solutions produced by the developed algorithms.

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Multicast Routing Algorithms And Failure Analyses For Low Earth Orbit Satellite Communication Networks, Jae Soong Lee Aug 2002

Multicast Routing Algorithms And Failure Analyses For Low Earth Orbit Satellite Communication Networks, Jae Soong Lee

Theses and Dissertations

In the rapidly changing environment of mobile communications, the importance of the mobile satellite (e,g,, low earth orbit satellites (LEOsats)) networks will increase due to their global visibility and connection. Multicasting is an effective communication method in terms of frequency spectrum usage for a LEO network. It is devised to provide lower network traffic (i,e,, one-to-many transmissions). This research examines the system performance of two dissimilar terrestrially-based multicasting protocols: the Distance Vector Multicast Routing Protocol (DVMRP) and the On Demand Multicast Routing Protocol (ODMRP). These two protocols are simulated in large group membership density and in the presence of satellite …

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Propagation Of Detonation Waves In Tubes Split From A Pde Thrust Tube, August J. Rolling, Paul I. King, Fred R. Schauer Jul 2002

Propagation Of Detonation Waves In Tubes Split From A Pde Thrust Tube, August J. Rolling, Paul I. King, Fred R. Schauer

Faculty Publications

A Pulse Detonation Engine (PDE) combusts a fuel air mixture through detonation. Existing designs require spark plugs in each separate thrust tube to ignite premixed reactants. A single thrust tube could require the spark plug to fire hundreds of times per second for long durations. This paper reports on the use of a continuously propagating detonation wave as both a thrust producer and a single ignition source for a multi-tube system. The goal was to minimize ignition complexity and increase reliability by limiting the number of ignition sources. The work includes a systematic investigation of single tube geometric effects on …

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Robustness Of Multiple Objective Decision Analysis Preference Functions, William K. Klimack Jun 2002

Robustness Of Multiple Objective Decision Analysis Preference Functions, William K. Klimack

Theses and Dissertations

This research investigated value and utility functions in multiobjective decision analysis to examine the relationship between them in a military decision making context. The impact of these differences was examined to improve implementation efficiency. The robustness of the decision model was examined with respect to the preference functions to reduce the time burden imposed on the decision maker. Data for decision making in a military context supports the distinction between value and utility functions. Relationships between value and utility functions and risk attitudes were found to be complex. Elicitation error was significantly smaller than the difference between value and utility …

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Airborne Radar Interference Suppression Using Adaptive Three-Dimensional Techniques, Todd B. Hale Jun 2002

Airborne Radar Interference Suppression Using Adaptive Three-Dimensional Techniques, Todd B. Hale

Theses and Dissertations

This research advances adaptive interference suppression techniques for airborne radar, addressing the problem of target detection within severe interference environments characterized by high ground clutter levels, levels, noise jammer infiltration, and strong discrete interferers. Two-dimensional (2D) Space-Time Adaptive Processing (STAP) concepts are extended into three-dimensions (3D) by casting each major 2D STAP research area into a 3D framework. The work first develops an appropriate 3D data model with provisions for range ambiguous clutter returns. Adaptive 3D development begins with two factored approaches, 3D Factored Time-Space (3D-FTS) and Elevation-Joint Domain Localized (Elev-JDL). The 3D adaptive development continues with optimal techniques, i.e., …

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Characterization Of Residual Stress In Microelectromechanical Systems (Mems) Devices Using Raman Spectroscopy, Lavern A. Starman Apr 2002

Characterization Of Residual Stress In Microelectromechanical Systems (Mems) Devices Using Raman Spectroscopy, Lavern A. Starman

Theses and Dissertations

Due to the small scale of MEMS devices, the inherent residual stresses during the deposition processes can affect the functionality and reliability of the fabricated devices. Residual stress often causes device failure due to curling, buckling, or fracture. Currently, few techniques are available to measure the residual stress in MEMS devices. In this dissertation, Raman spectroscopy is used to measure and monitor the residual and induced stresses in MUMPs polysilicon MEMS devices. Raman spectroscopy was selected since it is nondestructive, fast, and provides potential in situ stress monitoring. Raman spectroscopy scans on unreleased and released MEMS fixed-fixed beams, cantilevers, and …

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Effects Of Shot-Peening On High Cycle Fretting Fatigue Behavior Of Ti-6al-4v, Halil I. Yuksel Mar 2002

Effects Of Shot-Peening On High Cycle Fretting Fatigue Behavior Of Ti-6al-4v, Halil I. Yuksel

Theses and Dissertations

Effects of Shot-peening on High Cycle Fretting Fatigue behavior of Ti-6Al-4V were investigated. Experiments were performed with 6.35 mm thick specimens which provided S/N curves. After the tests, it was observed that the specimens failed near the trailing edge of contact. Scanning Electron Microscopy showed that cracks initiated on the contact surface for 6.35 mm, and at the depth of specimen ranging from 200 to 300 microns for 3.81 mm thick specimens. Initial crack orientation was around 37 and 42 degrees respectively for 6.35 and 3.81 mm thicknesses. Finite Element Analysis (FEA) was conducted, and using FEA results, Smith-Watson-Topper, Findley, …

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Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley Mar 2002

Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley

Theses and Dissertations

This thesis studies selective etching techniques for the development of AlxGa1-xAs micro-opto-electro-mechanical systems (MOEMS). New MEMS technology based on materials such as AlxGa1-xAs enables the development of micro-systems with embedded active micro-optical devices. Tunable micro-lasers and optical switching based on MOEMS technology will improve future wavelength division multiplexing (WDM) systems. WDM vastly increases the speed of military communications and sensor data processing. From my designs, structures are prepared by molecular beam epitaxy. I design a mask set for studies of crystal plane selectivity. I perform a series of experiments on the selective …

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Design Study Of Triggered Isomer Heat Exchanger-Combustion Hybrid Jet Engine For High Altitude Flight, Christopher E. Hamilton Mar 2002

Design Study Of Triggered Isomer Heat Exchanger-Combustion Hybrid Jet Engine For High Altitude Flight, Christopher E. Hamilton

Theses and Dissertations

This study investigated the possibility of utilizing a Triggered Isomer Heat Exchanger (TIHE) within a conventional jet engine in order to increase the endurance of a High Altitude Long Endurance (HALE) Intelligence, Surveillance, and Reconnaissance (ISR) aircraft. Optimizations of the conventional and TIHE engines along with selection of a switchover flight condition, where the aircraft switches from combustion to TIHE operations, were made utilizing engine design and mission analysis software. Radiation shield weights were determined utilizing point source gamma ray shielding methods. The jet engine best suited for the hybrid use, where both combustion and TIHE components located in a …

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Issues In Modeling Military Space, Peter F. Olsen Mar 2002

Issues In Modeling Military Space, Peter F. Olsen

Theses and Dissertations

Fighter Pilots students undertake an intense 120-day training program. New classes of students enter the training program at regular interval. Students endured rigorous academic, simulator, and aircraft training throughout the program. Squadron schedulers ensure the multiple classes and students are scheduled for the activities. Simulator and aircraft training are scheduled individual for each student. Academic training are taught to the class. Aircraft utilization must also be considered. Aircraft Sortie training are also constrained by daylight hours. Additionally, students are limited to a maximum of three training events in a given day. Squadron schedulers must balance these requirements to ensure students …

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Evaluation And Analysis Of Array Antennas For Passive Coherent Location (Pcl) Systems, Baris Calikoglu Mar 2002

Evaluation And Analysis Of Array Antennas For Passive Coherent Location (Pcl) Systems, Baris Calikoglu

Theses and Dissertations

Passive Coherent Location (PCL) systems use a special form of a radar receiver that exploits the ambient radiation in the environment to detect and track targets. Typical transmissions of opportunity that might be exploited include television and FM radiobroadcasts. PCL implies the use of a non-radar electromagnetic sources of illumination, such as commercial radio or television broadcasts also referred as transmitters of opportunity. The use of such illumination sources means that the receiver needs to process waveforms that are not designed for radar purposes. As a consequence, the receivers for PCL systems must be much more customized than traditional receivers, …

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Analysis Of Ultra Wide Band (Uwb) Technology For An Indoor Geolocation And Physiological Monitoring System, Cengiz Alabacak Mar 2002

Analysis Of Ultra Wide Band (Uwb) Technology For An Indoor Geolocation And Physiological Monitoring System, Cengiz Alabacak

Theses and Dissertations

The goal of this research is to analyze the utility of UWB for indoor geolocation and to evaluate a prototype system, which will send information detailing a person’s position and physiological status to a command center. In a real world environment, geolocation and physiological status information needs to be sent to a command and control center that may be located several miles away from the operational environment. This research analyzes and characterizes the UWB signal in the various operational environments associated with indoor geolocation. Additionally, "typical usage scenarios" for the interaction between UWB and other devices are also tested and …

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A Multiobjective Approach Applied To The Protein Structure Prediction Problem, Richard O. Day Mar 2002

A Multiobjective Approach Applied To The Protein Structure Prediction Problem, Richard O. Day

Theses and Dissertations

Interest in discovering a methodology for solving the Protein Structure Prediction problem extends into many fields of study including biochemistry, medicine, biology, and numerous engineering and science disciplines. Experimental approaches, such as, x-ray crystallographic studies or solution Nuclear Magnetic Resonance Spectroscopy, to mathematical modeling, such as minimum energy models are used to solve this problem. Recently, Evolutionary Algorithm studies at the Air Force Institute of Technology include the following: Simple Genetic Algorithm (GA), messy GA, fast messy GA, and Linkage Learning GA, as approaches for potential protein energy minimization. Prepackaged software like GENOCOP, GENESIS, and mGA are in use to …

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Compare And Complexity - When Is Compare Not Enough?, Chris E. Greiman Mar 2002

Compare And Complexity - When Is Compare Not Enough?, Chris E. Greiman

Theses and Dissertations

The purpose of this case study research is to determine the utility of COMPARE, the DoD approved software for conducting A-76 competitions, in the more complex world of public-private competition. COMPARE serves as the baseline for establishing cost factors, while two Air Force Depots are used as a basis of comparison. Research questions answered are: 1. What are the baseline cost comparison factors established in COMPARE? 2. What are the common cost factors found in the Air Force Depot public-private competitions? 3. What are the similarities and differences between the cost factors established in COMPARE and those used in the …

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A Study Of Satellite Navigation, Dilution Of Precision, And Positioning Techniques For Use On And Around The Moon, John H. Macnicol Mar 2002

A Study Of Satellite Navigation, Dilution Of Precision, And Positioning Techniques For Use On And Around The Moon, John H. Macnicol

Theses and Dissertations

The National Aeronautics and Space Agency is examining several approaches to meet navigational requirements for spacecraft in lunar orbit, in transit to or from the moon, and for personnel on the lunar surface requiring an accurate, real-time, on-board navigation capability. This work addresses one possible solution to the navigation problem in the vicinity of the moon using a lunar satellite navigation system. Dilution of precision is the figure of merit used to determine if a candidate lunar satellite navigation system can meet accuracy specifications based on a given satellite constellation and the measurement types used. Ten satellite constellations, using two …

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Decision Analysis With Value-Focused Thinking As A Methodology In Structuring The Civil Engineer Operations Flight, Dee Jay Katzer Mar 2002

Decision Analysis With Value-Focused Thinking As A Methodology In Structuring The Civil Engineer Operations Flight, Dee Jay Katzer

Theses and Dissertations

The civil engineer operations flight organizational structure has been in a state of change since the flight's inception and is currently prescribed only to the element level. Therefore, an operations flight commander must determine the organizational structure best suited for their unique situation without any guidance or support. To provide insight and defensible support for an operations flight commander faced with this decision, a value-focused thinking process was used to create a value model that aids in evaluating possible organizational structures. To ensure that the results of this research are applicable across the Air Force, the value model was created …

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Flight Control Failure Detection And Control Redistribution Using Multiple Model Adaptive Estimation With Filter Spawning, Michael L. Torres Jr. Mar 2002

Flight Control Failure Detection And Control Redistribution Using Multiple Model Adaptive Estimation With Filter Spawning, Michael L. Torres Jr.

Theses and Dissertations

In the current research, the MMAE with Filter Spawning and Control Redistribution (MMAE/FS/CR) are used together to identify failures and apply appropriate corrections. This effort explores the performance of the MMAE/FS/CR in different regions of the flight envelope using model and gain scheduling. The MMAE/FS/CR is able to detect complete and partial actuator/surface failures, as well as complete sensor failures. Once the actuator/surface failure is identified and the effectiveness is determined in the case of partial failures, proper control is applied in order to accomplish the desired pilot command. Improvements in the algorithm are required in order to enhance the …

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Commercial Regional Space/Airborne Imaging, Ugur Akyazi, Ali Durmus, Birce Boga Bakirli, Arif Arin Mar 2002

Commercial Regional Space/Airborne Imaging, Ugur Akyazi, Ali Durmus, Birce Boga Bakirli, Arif Arin

Theses and Dissertations

In this work goal programming is used to solve a minimum cost multicommodity network flow problem with multiple goals. A single telecommunication network with multiple commodities (e.g., voice, video, data, etc.) flowing over it is analyzed. This network consists of: linear objective function, linear cost arcs, fixed capacities, specific origin-destination pairs for each commodity. A multicommodity network flow problem with goals can be successfully modeled using linear goal programming techniques. When properly modeled, network flow techniques may be employed to exploit the pure network structure of a multicommodity network flow problem with goals. Lagrangian relaxation captures the essence of the …

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An Analysis Of Mutually Dispersive Brown Symbols For Non-Linear Ambiguity Suppression, Matthew J. Papaphotis Mar 2002

An Analysis Of Mutually Dispersive Brown Symbols For Non-Linear Ambiguity Suppression, Matthew J. Papaphotis

Theses and Dissertations

This thesis significantly advances research towards the implementation of optimal Non-linear Ambiguity Suppression (NLS) waveforms by analyzing the Brown theorem. The Brown theorem is reintroduced with the use of simplified linear algebraic notation. A methodology for Brown symbol design and digitization is provided, and the concept of dispersive gain is introduced. Numerical methods are utilized to design, synthesize, and analyze Brown symbol performance. The theoretical performance in compression and dispersion of Brown symbols is demonstrated and is shown to exhibit significant improvement compared to discrete codes. As a result of this research a process is derived for the design of …

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Smart Structures For Control Of Optical Surfaces, D. Michael Sobers Jr. Mar 2002

Smart Structures For Control Of Optical Surfaces, D. Michael Sobers Jr.

Theses and Dissertations

The development of lightweight, large-aperture optics is of vital importance to the Department of Defense and the US Air Force for advancing remote sensing applications and improving current capabilities. Synthetic polymer optics offer weight and flexibility advantages over current generation glass mirrors, but require active control to maintain tight surface figure tolerances. This research explores the feasibility of using imbedded piezoelectric materials to control optical surfaces. Membrane-based and stiff piezo-controlled mirrors were constructed to develop and validate control techniques. Test results verified that surface control on the order of tens of wavelengths is possible using these systems.

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Alternative Pulse Detonation Engine Ignition System Investigation Through Detonation Splitting, August J. Rolling Mar 2002

Alternative Pulse Detonation Engine Ignition System Investigation Through Detonation Splitting, August J. Rolling

Theses and Dissertations

A Pulse Detonation Engine (PDE) combusts fuel air mixtures through a form of combustion: detonation. Recent PDE research has focused on designing working subsystems. This investigation continued this trend by examining ignition system alternatives. Existing designs required spark plugs in each separate thrust tube to ignite premixed reactants. A single thrust tube could require the spark plug to fire hundreds of times per second for long durations. The goal was to minimize hardware and increase reliability by limiting the number of ignition sources. This research used a continuously propagating detonation wave as both a thrust mechanism and an ignition system …

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