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Air Force Institute of Technology

Theses and Dissertations

1993

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Full-Text Articles in Engineering

Modeling Of A Large Undamped Space Structure Using Time Domain Techniques, Anthony R. Nash Dec 1993

Modeling Of A Large Undamped Space Structure Using Time Domain Techniques, Anthony R. Nash

Theses and Dissertations

The first phase of this project was the selection of accurate time domain state space modeling techniques by comparing the models generated by various methods, against a known system. The techniques selected were the Eigensystem Realization Algorithm and the Backward Least Squares method. These modeling techniques were applied to the vibration data from the PACOSS dynamic test article. The resulting model transfer function was then compared to the frequency response function of the actual system, and was found to be an accurate match for the system poles, but not for the system zeros. Large Space structures, Dynamic Control, System Mode …

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Steady Motions Of Rigid Body Satellites In A Central Gravitational Field, Cynthia A. Provost Dec 1993

Steady Motions Of Rigid Body Satellites In A Central Gravitational Field, Cynthia A. Provost

Theses and Dissertations

Numerous studies have been conducted on equilibrium orientations of objects moving under the influence of a central gravitational field. The results of many of these studies conclude that equilibrium conditions exist only when one of the principal axes coincides with the radius vector. Furthermore, these results assume that the center of force is located within the orbit plane, thereby tracing a great circle orbit. While these previous works have approximated the gravitational potential, this study examines relative equilibrium obtained by retaining an exact expression for the potential of a spherical primary body, as shown in a recent paper by Wang, …

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The Modal Solution To The Moon's Orbit Using Canonical Floquet Perturbation Theory, Kurt A. Vogel Dec 1993

The Modal Solution To The Moon's Orbit Using Canonical Floquet Perturbation Theory, Kurt A. Vogel

Theses and Dissertations

Using the restricted three body problem, the equations of motion EOM and Hamiltonian are computed for the moons orbit in physical variables. A periodic orbit is found in the vicinity of the moons orbit, and classical Floquet theory is applied to the periodic orbit to give stability information and the complete solution to the equations of variation. Floquet theory also supplies a transformation from physical variables to modal variables. This transformation to modal variables is made canonical by constraining the initial transformation matrix to be symplectic. Actual lunar data is used to calculate the modes for the real moons orbit. …

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Control Of A Large Space Structure Using Multiple Model Adaptive Estimation And Control Techniques, Gregory J. Schiller Dec 1993

Control Of A Large Space Structure Using Multiple Model Adaptive Estimation And Control Techniques, Gregory J. Schiller

Theses and Dissertations

The purpose of this thesis is to apply moving-bank multiple model adaptive estimation and control MMAEMMAC algorithms to an actual space structure SPICE being examined at Phillips Laboratory at Kirtland AFB, NM. The structure consists of a large platform and a smaller platform connected by three legs in a tripod fashion. Kalman filtering and LQG control techniques are utilized as the primary design tool. Implementing a bank of filters increases the robustness of the LQG controller when uncertainties exist in the system model, whereas the moving bank is utilized to reduce the computational load. Several reduced-order models are developed from …

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The Effect Of Cutout Dimensionality On The Collapse Characteristics Of Cylindrical Composite Shells Of Varying Thickness, John C. Del Barga Dec 1993

The Effect Of Cutout Dimensionality On The Collapse Characteristics Of Cylindrical Composite Shells Of Varying Thickness, John C. Del Barga

Theses and Dissertations

This study involved a numerical and experimental investigation of the (geometric instability of graphite/epoxy cylindrical panels with free vertical edges undergoing axial compression. Symmetric quasi-isotropic laminates with five different size centralized cutouts, were investigated for two axial lengths of panels and three thicknesses. The study compared experimental data to results from SHELL, a geometrically nonlinear finite-element program which incorporates a parabolic transverse shear strain distribution through the thickness. The research verified that the SHELL program will provide good predictions of the collapse characteristics of a panel with large cutouts of varying dimensions undergoing large displacements and rotations. The best correlation …

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Rendering Of Three-Dimensional Data Sets Derived From Finite-Difference And Spectral Methods, Paul A. Schubert Dec 1993

Rendering Of Three-Dimensional Data Sets Derived From Finite-Difference And Spectral Methods, Paul A. Schubert

Theses and Dissertations

The timely visualization of three-dimensional data sets and the advantages of using a spectral method solution versus a finite-difference method solution in rendering isosurfaces is described. The Beam-Warming numerical algorithm, which uses implicit-approximate-factorization, is used to generate the steady-state solutions for a model diffusion-convection problem. The Chebyshev collocation operator is used to evaluate the right-hand side of the Beam-Warming algorithm for the spectral solution. Comparing the model problem results with the exact solution, the spectral series solution is truncated to the same degree of accuracy as the finite-difference for comparison of rendering times. The rendering algorithm employs octrees to efficiently …

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Design Of A Parallel Discrete Event Simulation Coprocessor, Jacob L. Berlin Dec 1993

Design Of A Parallel Discrete Event Simulation Coprocessor, Jacob L. Berlin

Theses and Dissertations

A Parallel Discrete Event Simulation Coprocessor was designed to off- load the synchronization overhead from the processors executing the application. In a multiprocessor architecture, one coprocessor executes the synchronization routines for each host processor. Speedup can be achieved when the host processor executes the application and the coprocessor concurrently executes synchronization routines. The coprocessor uses a programmable microcode control store to guarantee flexibility in the synchronization routines. The coprocessor uses an Extreme Search Associative Memory to support fast Next Event Queue NEQ management. This associative memory uses bit-serial word-parallel search logic to provide 01 insert and retrieval time of events …

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Object Imaging Accomplished With An Integrated Circuit Robotic Tactile Sensor Incorporating A Piezoelectric Polyvinylidene Fluoride Thin Film, John M. Emmert Dec 1993

Object Imaging Accomplished With An Integrated Circuit Robotic Tactile Sensor Incorporating A Piezoelectric Polyvinylidene Fluoride Thin Film, John M. Emmert

Theses and Dissertations

The purpose of this research effort was to investigate the performance of a piezoelectric tactile sensor design and appropriately refine it. The sensor was fabricated from an 8 x 8 electrode array MOS integrated circuit. Each taxel in the array was 400 microns x 400 microns. A 6 mm x 6 mm piece of piezoelectric polyvinylidene fluoride was adhered to the electrode array using a urethane dielectric adhesive to form the active sensing area of the sensor. An amplifier was investigated to enhance the range of the tactile sensor's output signal. The amplifier is a high input' impedance differential amplifier …

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A Physics-Based Heterojunction Bipolar Transistor Model For Integrated Circuit Simulation, James A. Fellows Dec 1993

A Physics-Based Heterojunction Bipolar Transistor Model For Integrated Circuit Simulation, James A. Fellows

Theses and Dissertations

The purpose of this research effort was to derive a physics-based dc model for a Heterojunction Bipolar Transistor HBT. The dc model was then linearized to arrive at a small-signal model that accurately predicts the devices electrical behavior at microwave frequencies. This new model offers features not found in previous analytical or physics-based HBT models such as consideration of a cylindrical emitter-base geometry and is direct implementation into SPICE Simulation Program with Integrated Circuit Emphasis. The device model parameters were determined from a knowledge of the device material, geometry, and fabrication process. The model was then developed by using semiconductor …

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Incorporation Of Carrier Phase Global Positioning System Measurements Into The Navigation Reference System For Improved Performance, Neil P. Hansen Dec 1993

Incorporation Of Carrier Phase Global Positioning System Measurements Into The Navigation Reference System For Improved Performance, Neil P. Hansen

Theses and Dissertations

In order to quantify the performance and accuracy of existing navigation systems, the U.S. Air Force has been using the Completely Integrated Reference Instrumentation System (CIRIS) as a baseline. CIRIS combines information from an inertial navigation unit, a barometric altimeter, and a range/range-rate system of ground transponders to obtain a navigation solution. This research explores the possibilities of enhancing CIRIS by adding measurements obtained from the Global Position System (GPS). Pure pseudorange measurement updates to the CIRIS Extended Kalman Filter form the basis of the Navigation Reference System (NRS). Applying differential corrections to the pseudorange measurements forms the basis of …

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Design Of A Flight Controller For An Unmanned Research Vehicle With Control Surface Failures Using Quantitative Feedback Theory, Mark S. Keating Dec 1993

Design Of A Flight Controller For An Unmanned Research Vehicle With Control Surface Failures Using Quantitative Feedback Theory, Mark S. Keating

Theses and Dissertations

This thesis describes the application of the multiple-input multiple- output (MIMO) Quantitative Feedback Theory (QFT) design technique to the design of a digital flight control system for the Lambda Unmanned Research Vehicle (URV). The QFT technique allows the synthesis of a control system which is robust in the presence of structured plant uncertainties. Uncertainties considered in this design are the aircraft's plant variation within the flight envelope and the effects of damage to aircraft control surfaces. Mathematical models of control surface failure effects on aircraft dynamics are derived and used to modify an existing small perturbation model of the Lambda. …

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The Afit Multielectrode Array For Neural Recording And Simulation: Design, Testing, And Encapsulation, James R. Reid Jr Dec 1993

The Afit Multielectrode Array For Neural Recording And Simulation: Design, Testing, And Encapsulation, James R. Reid Jr

Theses and Dissertations

A two-dimensional, X-Y addressable, multiplexed array of 256 electrodes (16 x 16) has been fabricated using conventional semiconductor processing techniques. The individual electrodes are 16O microns x 160 microns, approximating the size of the cortical columns; the overall array size is 3910 microns x 3910 microns. The array has been fitted to a chronically implantable package and tested for several days in a simulated neural environment. EEG-like data were collected successfully from individual electrodes in the array. This array improves on a previous design of a 16 electrode (4 x 4) array that was chronically implanted on the cortex of …

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Development Of Computer Software To Aid Environmental Decision Makers In The Education And Training Of Air Force Remedial Project Managers, Roger R. Ouellette, Bruce K. Lyman Dec 1993

Development Of Computer Software To Aid Environmental Decision Makers In The Education And Training Of Air Force Remedial Project Managers, Roger R. Ouellette, Bruce K. Lyman

Theses and Dissertations

By the end of Fiscal Year 1991, the Air Force had identified 4,354 contaminated sites. Much like the 177 toxic sites at McClellan AFB, bases across the country and throughput the world are filled with chrome, lead, paint solvents and many other toxics that are rendering water supplies unusable and endangering the health of millions of people living in and around these bases. Air Force officials continue to identify contaminated sites with no end in sight. Since the cleanup of these toxic materials involves diverse, complex activities, the Air Force created the duty position of Remedial Project Manager to manage …

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Automating Satellite Range Scheduling, S. Michael Schalck Dec 1993

Automating Satellite Range Scheduling, S. Michael Schalck

Theses and Dissertations

The objective of this study was to develop a computer based satellite range scheduling SRS algorithm to create a 24 hour satellite support schedule. The algorithms goal was to schedule as many satellite support requests as possible. An iterative heuristic approach was used to schedule satellite support requests in three successive sub problems. The first sub problem involves scheduling low altitude satellite support requests using a mixed integer programming approach. The next two sub problems each involve scheduling 12 hour blocks of medium and high altitude satellite support requests, again using a mixed integer programming approach. Fourteen 24 hour schedules …

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Simultaneous Design Of Active Vibration Control And Passive Damping, Michele Lynn Devereaux Gaudreault Dec 1993

Simultaneous Design Of Active Vibration Control And Passive Damping, Michele Lynn Devereaux Gaudreault

Theses and Dissertations

A modified form of the standard linear quadratic regulator LQR cost functional is used to optimally blend active vibration control and passive structural damping, whether viscous or viscoelastic. Viscoelastic damping is first modelled by a standard linear model, and then by a fractional derivative model. For the viscous damping case and the classically modelled viscoelastic damping case, a sub-optimal closed form solution is derived that is independent of the initial conditions. An iterative technique that minimizes the average value of the cost functional and one that minimizes the maximum value are developed. Both techniques are applicable to viscous and viscoelastic …

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Multiple Model Adaptive Control Of A Large Flexible Space Structure With Purposeful Dither For Enhanced Identifiability, James A. Fitch Dec 1993

Multiple Model Adaptive Control Of A Large Flexible Space Structure With Purposeful Dither For Enhanced Identifiability, James A. Fitch

Theses and Dissertations

Dithering techniques for enhancing uncertain parameter identification with moving-bank Multiple Model Adaptive Estimation MMAE and Control MMAC algorithms are analyzed in this thesis. The dithering techniques and multiple- model adaptive algorithms are applied to the SPICE 2 flexible space structure. The dithering techniques studied include purposefully constructed square wave, sine wave fixed and swept frequency and wide-band noise wave forms. Purposeful rigid-body slew commands are also used in order to excite the structures flexible bending modes. Dither inputs into the structure are performed in an effort to enhance the open-loop identifiability of the uncertain parameter, namely a scalar multiplier on …

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Modal Control Of A Satellite In An Unstable Periodic Orbit About The Earth-Sun Interior Lagrange Point, Douglas J. Hopper Dec 1993

Modal Control Of A Satellite In An Unstable Periodic Orbit About The Earth-Sun Interior Lagrange Point, Douglas J. Hopper

Theses and Dissertations

A periodic halo orbit which exists about the interior Lagrange point for the Earth-sun system was decomposed using Floquet theory into modal variables, which are dynamically decoupled subspaces for the six degree of freedom system. Modal control consisted of evaluating the diverging mode and maneuvering to counteract its divergence. In the unperturbed system, this was successful. Control costs were low, and the significance is that the controller did nothing to suppress modes that were oscillatory or converging. The effect of the moons motion allowed the scheme to operate with reasonable control costs, but the effect of eccentricity caused divergence in …

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Evaluation Of A Concentration Probe For Application In A Supersonic Flow Field, John S. Alsup Dec 1993

Evaluation Of A Concentration Probe For Application In A Supersonic Flow Field, John S. Alsup

Theses and Dissertations

Aspirating, concentration probes are used to measure binary gas concentrations in a supersonic flow. In the past, a tank discharge method has been used to calibrate concentration probes. An alternate calibration method has been developed and tested on a probe in a steady, subsonic/sonic flow. This study evaluated the calibration and performance of a concentration probe in a steady, supersonic flow over a range of mixture ratios of air and helium. The results of this study and a comparison of the two calibration methods are presented.

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Development And Implementation Of A Scramjet Cycle Analysis Code With A Finite-Rate-Chemistry Combustion Model For Use On A Personal Computer, Clarence F. Chenault Dec 1993

Development And Implementation Of A Scramjet Cycle Analysis Code With A Finite-Rate-Chemistry Combustion Model For Use On A Personal Computer, Clarence F. Chenault

Theses and Dissertations

This study compared the performance of an equilibrium combustion model to a finite-rate-chemistry combustion model for a fixed geometry Scramjet flying at the flight conditions of Mach 12, 15, and 18 with a constant dynamic pressure of 50,000 Pa. An integrated PC-based code, developed specifically for this study, models the combustor as an equilibrium combustion process or as finite-rate-chemistry combustion process. This integrated program is based on two existing programs, Ramjet Performance Analysis (RJPA) and 3 STREAM. The effects of mixing schedule, combustor length, and combustor exit area were investigated. The results of this study indicate that inefficient mixing is …

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Influence Of Embedded Optical Fibers On Compressive Strength Of Advanced Composites, Stefan B. Dosedel Dec 1993

Influence Of Embedded Optical Fibers On Compressive Strength Of Advanced Composites, Stefan B. Dosedel

Theses and Dissertations

This study investigated the effects of embedding optical fibers into advanced composite materials. This combination was meant to simulate 'smart structures' that have been shown to sense several different variables in the composite including strain, temperature, and damage. A laminate orientation taken from an existing aircraft structure was used to fabricate sixteen groups of specimens which were subjected to compression testing in an IITRI fixture to determine the ultimate compressive strength and modulus of elasticity. Ten of these groups were fabricated with optical fibers while the other six were control groups and contained no optical fibers. This study showed that …

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A Study Of Graphite Peek Composite With Central Elliptical Holes Under Tension, Bill J. Lau Dec 1993

A Study Of Graphite Peek Composite With Central Elliptical Holes Under Tension, Bill J. Lau

Theses and Dissertations

This study investigated the stress-strain response and failure modes of Graphite/Polyetheretherketone (Gr/PEEK) tension specimens containing a central elliptical hole. Both experiments and finite element numerical analyses were conducted. Test specimens included seven layups and three hole geometries; three of each combination were tested. The holes consisted of an ellipse with major axis aligned with the load axis, an ellipse with major axis transverse to the load axis, and a circle. Strain gages were located adjacent to the hole and midway between the hole and tab on all specimens. Strain data was used to plot stress-strain response. The analysis utilized a …

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Partitioning Structural Vhdl Circuits For Parallel Execution On Hypercubes, Kevin L. Kapp Dec 1993

Partitioning Structural Vhdl Circuits For Parallel Execution On Hypercubes, Kevin L. Kapp

Theses and Dissertations

Distributing simulations among multiple processors is one approach to reducing VHDL simulation time for large VLSI circuit designs. However, parallel simulation introduces the problem of how to partition the logic gates and system behaviors among the available processors in order to obtain maximum speedup. This research investigates deliberate partitioning algorithms that account for the complex inter-dependency structure of the circuit behaviors. Once an initial partition has been obtained, a border annealing algorithm is used to iteratively improve the partition. In addition, methods of measuring the cost of a partition and relating it to the resulting simulation performance are investigated. Structural …

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An Object-Oriented Database Interface For Ada, Anthony D. Moyers Dec 1993

An Object-Oriented Database Interface For Ada, Anthony D. Moyers

Theses and Dissertations

Object data management ODM is currently at the forefront of research and development efforts in the database community. In order to take advantage of ODM technology, the Department of Defense DoD needs to ensure that these systems are accessible to Ada programmers. The Air Force Institute of Technology AFIT is conducting research towards the development of an Ada ODM interface to existing ODM systems. The design goals are portability, transparency, and completeness for Ada programmers. Portability means that the ODM system can be changed without affecting any existing application programs. Transparency means that Ada programmers can use the interface without …

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Radar Cross Section Visualization Using Sample Buffer Progressive Refinement Volume Rendering, Alain L. Jones Dec 1993

Radar Cross Section Visualization Using Sample Buffer Progressive Refinement Volume Rendering, Alain L. Jones

Theses and Dissertations

This study developed a prototype for an interactive radar cross section visualization software system. The system, hosted on a Silicon Graphics workstation, is intended to support aircrews, mission planners, aircraft designers, and others who require an understanding of aircraft radar cross section characteristics. The input to the system is a set of radar cross section samples taken at various aspect angles. A pre-processor developed as part of this study transforms the input radar cross section data into a three-dimensional cuberille data volume. This data volume is then visualized using an interactive volume renderer. The interactive volume renderer implements progressive image …

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Evaluation Of Moderate Angle Of Attack Roll Of A Dual Engine, Thrust Vectoring Aircraft Using Quantitative Feedback Theory, Kevin E. Boyum Dec 1993

Evaluation Of Moderate Angle Of Attack Roll Of A Dual Engine, Thrust Vectoring Aircraft Using Quantitative Feedback Theory, Kevin E. Boyum

Theses and Dissertations

This thesis develops an innovative approach to the design of a flight control system for performing the large-amplitude velocity vector roll maneuver at high angles of attack AOAs. A six degree of freedom aircraft model is developed from the fundamental nine-state equations of motion using a modified linearization technique. The MIMO multiple-input multiple-output Quantitative Feedback Theory QFT robust control design technique is then used to jointly address the system nonlinearities present in this maneuver and the changes in the system parameters due to changes in flight condition, treating them as structured uncertainty in the design of a three-axis rate-commanded control …

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Analyzing Adaptive Beamformer Performance In A Stable Multipath Environment, Mark Godino Dec 1993

Analyzing Adaptive Beamformer Performance In A Stable Multipath Environment, Mark Godino

Theses and Dissertations

Fighter aircraft equipped with X-Band radars having an adaptive beamforming capability exhibit degraded performance due to radome multipath reflection (RMR). The reflections from the radome into the antenna array degrade the pattern and cause the formation of large sidelobes. This phenomenon makes detection of LO targets difficult when jamming enters the high RMR sidelobes. Actual radomes are curved and cause reflected wavefronts to be nonplanar. Analyzing beamformer performance under these conditions is difficult, since the beamformer response is defined as the amplitude and phase change experienced by a complex plane wave as a function of frequency and location. To work …

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Development Of A 4-Bit Parallel Analog-To-Digital Converter And A Four- Quadrant Double-Balanced Mixer Using Heterojunction Bipolar Transistor Technology, Scott F. Jokerst Dec 1993

Development Of A 4-Bit Parallel Analog-To-Digital Converter And A Four- Quadrant Double-Balanced Mixer Using Heterojunction Bipolar Transistor Technology, Scott F. Jokerst

Theses and Dissertations

A 4-bit parallel analog-to-digital converter (ADC) and a four- quadrant double-balanced mixer were designed and simulated using heterojunction bipolar transistor (HBT) technology to test the dc and high-frequency characteristics of HBTs. HSPICE simulations of small-scale components and the large-scale ADC operated within expected ranges. The ADC implemented with the Rockwell HBT model operated at a sampling rate of over 1 GHz, and the Fellows model also operated at a 1 GHz sampling rate. The mixer produced an intermediate frequency (IF) signal using radio frequency (RF) and local oscillator (LO) inputs. The circuit produced a +9 dB power gain with less …

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Optical Wavelet Transform For Fingerprint Identification, Robert P. Macdonald Dec 1993

Optical Wavelet Transform For Fingerprint Identification, Robert P. Macdonald

Theses and Dissertations

The Federal Bureau of Investigation FBI has recently sanctioned a wavelet fingerprint image compression algorithm developed for reducing storage requirements of digitized fingerprints. This research implements an optical wavelet transform of a fingerprint image, as the first step in an optical fingerprint identification process. Wavelet filters are created from computer generated holograms of biorthogonal wavelets, the same wavelets implemented in the FBI algorithm. Using a detour phase holographic technique, a complex binary filter mask is created with both symmetry and linear phase. The wavelet transform is implemented with continuous shift using an optical correlation between binarized fingerprints written on a …

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Creation Of Prototype Aircrew Protection Equipment Based On Face Anthropometry, Martin E. Piccus, Gary A. Smith, Brian K. Standley, Tami L. Volk, Linda B. Wildes Dec 1993

Creation Of Prototype Aircrew Protection Equipment Based On Face Anthropometry, Martin E. Piccus, Gary A. Smith, Brian K. Standley, Tami L. Volk, Linda B. Wildes

Theses and Dissertations

The objective of this research is to develop a process which will analyze and group human faces, concentrating on the oxygen mask seal area, into a minimum number of generic yet distinct face types. The shape and size, or form, of the face is described by bending energies. This bending energy provides the features for the grouping of similar face types, while distinguishing representatives for each cluster. The face tariffs are the percentage of faces grouped under a representative face. The representative faces are then transformed Into three-dimensional solids using computer-aided design. A rapid prototype creates the solids or plugs …

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Filtering, Coding, And Compression With Malvar Wavelets, Stephen R. Hall Dec 1993

Filtering, Coding, And Compression With Malvar Wavelets, Stephen R. Hall

Theses and Dissertations

This thesis develops and evaluates a number of new concepts and tools for the analysis of signals using Malvar wavelets lapped orthogonal transforms . Windowing, often employed as a spectral estimation technique, can result in irreparable distortions in the transformed signal. By utilizing the Malvar wavelet, any signal distortion resulting from the transformation can be eliminated or cancelled during reconstruction. This is accomplished by placing conditions on the window and the basis function and then incorporating the window into the orthonormal representation. Paradigms for both a complex-valued and a real-valued Malvar wavelet are summarized. I-lie algorithms for the wavelets were …

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