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Bifurcation Analysis Of The Longitudinal Dynamics Of A Simple Powered Lifting Hypersonic Vehicle, Eric E. Fox Dec 1990

Bifurcation Analysis Of The Longitudinal Dynamics Of A Simple Powered Lifting Hypersonic Vehicle, Eric E. Fox

Theses and Dissertations

Bifurcation analysis was used to investigate the nonlinear behavior of a simple powered lifting hypersonic vehicle in circular orbit about a spherical nonrotating Earth with gradients in atmospheric density and pressure and an inverse square law for gravity. Vehicle motion is constrained to a vertical plane so only longitudinal dynamics were modeled. Bifurcation analysis was conducted using the AUTO software package. A simple five-state model with three different thrust laws was derived to describe an unaugmented vehicle whose geometric and aerodynamic characteristics follow those of the literature. A parameter representing a body flap deflection was used to conduct one set …

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Numerical Analysis Of An Axisymmetric Thrust Augmenting Ejector, Kenneth R. Gage Dec 1990

Numerical Analysis Of An Axisymmetric Thrust Augmenting Ejector, Kenneth R. Gage

Theses and Dissertations

Use of an ejector is an effective way to increase the thrust produced by a jet. In this thesis project an axisymmetric ejector concept which had been previously explored by experiment was numerically modeled. An existing axisymmetric, internal flow code based on the explicit MacCormack method was modified to incorporate primary nozzle structure and flow injection within the flowfield. Results were compared qualitatively and quantitatively with experimental results to verify the validity of the model. Internal flow structure, difficult to obtain in experiment, is easily examined. This code may be used for parametric analysis of such ejector performance parameters as …

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Investigation Of Strain Characteristics Of Graphite Polyetherether Ketone Using A Nonlinear Analysis And Experimental Methods, Stephen C. Gould Dec 1990

Investigation Of Strain Characteristics Of Graphite Polyetherether Ketone Using A Nonlinear Analysis And Experimental Methods, Stephen C. Gould

Theses and Dissertations

A geometric nonlinear technique is incorporated in a current finite element program. This nonlinear program allows material nonlinearity for calculating the stresses, strains and failure of composites. The improved program uses an updated Langrangian to calculate the stresses and strains. In addition, it updates the fiber orientation due to displacement in order to calculate the updated stiffness matrix. This method is valuable for large strain values. The analytical data were compared to experimental data obtained from Graphite PolyEtherEther Ketone laminates. To obtain data two geometries were used. Digitized photographs were used to measure the angle change for large strains.

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Modeling And Analysis Of Orthotropic Plate With Circular Cutout And Adhesive Bonded Patch, Mark W. Hunter Dec 1990

Modeling And Analysis Of Orthotropic Plate With Circular Cutout And Adhesive Bonded Patch, Mark W. Hunter

Theses and Dissertations

The purpose of this study was to investigate a modeling technique to simply and adequately model an adhesive bonded patch on an orthotropic plate. This report is limited to linear material behavior. This thesis is also the basis for further work into nonlinear material range and three-dimensional stress states. To further advance aerospace battle damage repair techniques for composite repairs, a finite element model of an orthotropic plate with a hole and patch was constructed to investigate the accuracy of such a model. The fundamental problem in this model is the development of a simple and accurate method of modeling …

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Robustness Of H2 And H∞ Design Techniques In The Design Of A Guided Missile Controller, Steven R. Kolbow Dec 1990

Robustness Of H2 And H∞ Design Techniques In The Design Of A Guided Missile Controller, Steven R. Kolbow

Theses and Dissertations

This work follows Capt. R.L. Riddle's 1989 thesis (ADA216147) which compared conventional, H2 and H∞ controlled guided missiles in simulated flyouts against an airborne target. The simulation results did not clearly demonstrate the H2 and H∞ controller advantages. In this study the missile model and simulation were refined. In addition to simulation runs, performance, noise attenuation, and μ (structural singular value) robustness analyses were conducted. Results showed areas where improvement was needed in the H2 and H∞ controllers used in the study. An H2 and H∞ controller redesign is recommended using the …

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Vortex Bursting Over A Unit Area Aspect Ratio Delta Wing Using Vortex Paneling Methods, Donald A. Lorey Dec 1990

Vortex Bursting Over A Unit Area Aspect Ratio Delta Wing Using Vortex Paneling Methods, Donald A. Lorey

Theses and Dissertations

A unit aspect ratio delta wing is analyzes to determine if an unsteady vortex panel method can calculate the vortex bursting of the vortex developed along the leading edge. A two-dimensional vortex panel method is used to investigate wake splitting schemes of the vortex cores that comprise the vortex sheet, or wake. The worthier of the splitting methods is later implemented into the three-dimensional wake. The weighting values of the Kutta equations are investigated for the leading edges, and are determined to be problem specific. An alternative approach to management of the wake data is presented and implemented. The delta …

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Investigation Of Fatigue Damage Mechanisms In A Metal Matrix Composite Under Elevated Temperature, Barry D. Portner Dec 1990

Investigation Of Fatigue Damage Mechanisms In A Metal Matrix Composite Under Elevated Temperature, Barry D. Portner

Theses and Dissertations

This study investigated the fatigue damage initiation and progression in SCS-6/Ti-15-3 under an environment of fatigue loading at isothermal temperature. This program included two parts. First, an 808 Ultimate Tensile Strength system was set up to accommodate testing at two frequencies of 2.0 and 0.0208 cps at a constant temperature of 427° C. Second, at intervals during the load cycle process, the test specimens were characterized by establishing damage parameters based on changing modulus of elasticity, average strain, strain range, and ultimate tensile strength. Damage progression was documented in the form of failure of the fiber-matrix interface, matrix cracking, fiber …

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Micromechanical Modeling Of The Fiber/Matrix Interface Region In A Metal Matrix Composite, David D. Robertson Dec 1990

Micromechanical Modeling Of The Fiber/Matrix Interface Region In A Metal Matrix Composite, David D. Robertson

Theses and Dissertations

In order to develop reasonable analytical models and to better understand how the integrity of the fiber/matrix interface in high temperature titanium based metal matrix composites effects the overall transverse normal characteristics, a parametric study of various fiber/matrix interface conditions was performed. Analysis methods included both a simplified one-dimensional mathematical model and a finite element analysis using MSC/NASTRAN. First, both strong and weak interfacial bonds were examined. Subsequently, to provide for partial bonding, a model that used an elastic-plastic interphases zone between the fiber and matrix was examined.

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Finite Element Investigation Into The Dynamic Instability Characteristics Of Laminated Composite Panels, Walter W. Taylor Jr. Dec 1990

Finite Element Investigation Into The Dynamic Instability Characteristics Of Laminated Composite Panels, Walter W. Taylor Jr.

Theses and Dissertations

Dynamic instability of a laminated composite panel subjected to a transverse load is studied. Up to cubic variations in the thickness coordinate are included in the inplane displacement field, and only the constant component is kept in the transverse displacement. The transverse shear strains retain only linear displacement terms and vary parabolically through the thickness. The complete quadratic displacement functions are included in the inplane strains. A 36 degree of freedom shell element is used to obtain numerical results. The static snap through load vs displacement curve, as well as the critical collapse load, is examined by invoking the Riks …

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Effect Of Riblets On Pressure Recovery In A Straight-Walled Diffuser, Michael K. Reagan Dec 1990

Effect Of Riblets On Pressure Recovery In A Straight-Walled Diffuser, Michael K. Reagan

Theses and Dissertations

The objective of this thesis was to investigate the effect of riblets on the pressure recovery in a straight-walled diffuser. Previous work has shown that riblets were effective in reducing the viscous drag over surfaces subjected to a turbulent boundary layer. More recently, riblets were shown to delay the flow separation within a subsonic, straight-walled diffuser by as much as 200%. The purpose of this investigation was to determine the effect on the pressure distribution within a diffuser that has had the flow separation point favorably altered by the application of riblets. Investigation results revealed that riblets not only delayed …

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Failure Mechanisms In A Quasi-Isotropic Ceramic Composite Laminate Under Tensile Fatigue Loading, Gregory D. Tracy Dec 1990

Failure Mechanisms In A Quasi-Isotropic Ceramic Composite Laminate Under Tensile Fatigue Loading, Gregory D. Tracy

Theses and Dissertations

A study was conducted to experimentally investigate the tensile fatigue damage mechanisms in a quasi-isotropic ceramic matrix composite (Corning's Nicalon/CASIII). The goals of this study were to (1) develop a grip fixture for a servo-hydraulic MTS test machine and (2) conduct a series of tests with (0/±45/90)s specimens subjected to tensile fatigue loading to study their fatigue damage growth mechanisms. Results showed that when the material was subjected to stresses below 90 MPa, it lasted over 1000000 cycles but when stressed at or above 90 MPa, it failed in less than 1000 cycles.

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Computational Investigation Of Circulation Control Turbulence Modeling, T. Bryan Scruggs Dec 1990

Computational Investigation Of Circulation Control Turbulence Modeling, T. Bryan Scruggs

Theses and Dissertations

A computational study of the turbulence model parameters and the effect on the flow field of a circulation control airfoil was conducted. A Beam- Warming algorithm with a modified Baldwin-Lomax turbulence model was used to solve the Navier-Stokes equations. A comparison between the effects of the Bradshaw constant on the flow field about the cylinder and the flow field about an airfoil were to be made. The lack of a steady 'converged' solution for the cylinder precluded the analysis of the flow field about a cylinder. For the airfoil, the separation point moves rearward and an enhanced vortex pattern is …

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Directing An Original Script: "The Only Woman Awake Is The Woman Who Has Heard The Flute", Denise A. Heiman Dec 1990

Directing An Original Script: "The Only Woman Awake Is The Woman Who Has Heard The Flute", Denise A. Heiman

Theses and Dissertations

No abstract provided.

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Investigating The Application Of The Theory Of Constraints To The Scheduling Environment Of The Iaf's Depots, Lewis S. Trigger Dec 1990

Investigating The Application Of The Theory Of Constraints To The Scheduling Environment Of The Iaf's Depots, Lewis S. Trigger

Theses and Dissertations

This research investigated the application and merits of the Theory of Constraints (TOC) to the scheduling environment of the Israeli Air Force's (IAF) maintenance depots. TOC was extensively reviewed including an elaboration of the TOC paradigm and the scheduling procedures developed for a commercial manufacturing setting. Background information was also presented on the IAF depots and traditional scheduling rules. An experiment was designed and conducted that simulated a simplified version of the process flow of the armaments depot. the simulation compared the terms of lower inventory and makespan. The experiment did not conclusively show any difference in standard throughput hours …

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Nonlinear Analysis Of A Spinning Symmetric Satellite In An Elliptical Orbit, Michael Ulisse Dec 1990

Nonlinear Analysis Of A Spinning Symmetric Satellite In An Elliptical Orbit, Michael Ulisse

Theses and Dissertations

Controlled and uncontrolled equations of motion for a spinning symmetric satellite in an elliptical orbit are analysed using Floquet theory, Poincare maps, and continuation. The equations of motion for the uncontrolled system are derived via energy methods. A simple feedback controller design and one based on Floquet theory are presented. Parameters varied in the equations of motion include the spin about the symmetry axis of the satellite, the inertia ratio of the satellite, the eccentricity of the orbit, and the controller gains. Floquet analyses determine local stability and bifurcation points. Poincare maps exhibit some interesting and complex structure in the …

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An Evolution Operator Solution For A Nonlinear Beam Equation, Carl E. Crockett Dec 1990

An Evolution Operator Solution For A Nonlinear Beam Equation, Carl E. Crockett

Theses and Dissertations

A nonlinear partial differential equation, motivated by the transverse vibration of a beam, is shown to have a unique solution. The existence theory, which is in the setting of semigroups and evolution operators, is a composite and synthesis of theorems of Kato. The formulation of the problem and the verification that the formulation leads to a solution are new. The introductory chapter provides background on the topic generally. Chapter 2 provides detailed formulations for the constant coefficient case. Chapter 3 describes nonautonomous cases. The general theorem is presented here. In Chapter 4, a more general case is considered. Namely, Kelvin …

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Characterization Of Multilayer Perceptrons And Their Application To Multisensor Automatic Target Detection, Dennis W. Ruck Dec 1990

Characterization Of Multilayer Perceptrons And Their Application To Multisensor Automatic Target Detection, Dennis W. Ruck

Theses and Dissertations

The multilayer perceptron was extensively analyzed. A technique for analyzing the multilayer perceptron, the saliency measure, was developed which provides a measure of the importance of inputs. The method was compared to the conventional statistical technique of best features and shown to provide similar rankings of the input. Using the saliency measure, it is shown that the multilayer perceptron effectively ignores useless inputs and that whether it is trained using backpropagation or extended Kalman filtering, the weighting of the inputs is the same. The backpropagation training algorithm is shown to be a degenerate version of the extended Kalman filter. The …

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Analysis Of Periodic Orbits About The Martian Moons By Continuation Techniques, Frank Luria Dec 1990

Analysis Of Periodic Orbits About The Martian Moons By Continuation Techniques, Frank Luria

Theses and Dissertations

From a few known periodic orbits of Phobos and Deimos, continuation techniques were used to find entire families of stable orbits. These techniques involved varying a parameter, the Hamiltonian, of the system and analyzing how the orbital behavior changed with the parameter. Floquet multipliers, for stability analysis, were also computed. AUTO86, a continuation/bifurcation software package, was used in this study. Artificial energy dissipation had to be added to the conservative Hamiltonian system to enable use of AUTO.

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A Numerical Investigation Of The Series Reversion/Inversion And Series Reversion Of Lambert's Time Function, Michael P. Ward Dec 1990

A Numerical Investigation Of The Series Reversion/Inversion And Series Reversion Of Lambert's Time Function, Michael P. Ward

Theses and Dissertations

An expression for the semi-major axis as a function of time may be determined by performing a series reversion and inversion of Lambert's Time Function. Since the resulting series contains a singularity, it is desirable to perform only a reversion on the original series to obtain an expression for the inverse of the semi-major axis. Using a Lagrange expansion to obtain the coefficients for this series is very computer intensive. Therefore, alternative methods are presented. Also, each series was expanded into a continued fraction which provided greater accuracy than the series using the same number of coefficients. The accuracy was …

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Material Properties Of Silicon Carbide Fibers With Continuously Applied Sol-Gel Alumina Coatings, Christian C. Daehnick Dec 1990

Material Properties Of Silicon Carbide Fibers With Continuously Applied Sol-Gel Alumina Coatings, Christian C. Daehnick

Theses and Dissertations

An investigation was conducted to determine the effect of non-alpha- alumina coatings applied under varying conditions on some of the properties of silicon carbide fibers. Limited characterization of the coating by optical, scanning electron, and transmitted electron microscopy as well as energy- dispersive x-ray analysis was performed. Tensile tests were used to determine changes in elastic modulus, ultimate strength, and strain to failure of the coated fibers relative to uncoated fibers. The coatings were found to lower the mean value of the measured properties as their thickness increased, but the measurements were not accurate enough to determine if this corresponded …

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A Low-Cost Part-Task Flight Training System: An Application Of A Head Mounted Display, David A. Dahn Dec 1990

A Low-Cost Part-Task Flight Training System: An Application Of A Head Mounted Display, David A. Dahn

Theses and Dissertations

To investigate the feasibility of using head-mounted display(HMD) and Computer Image Generators(CIG) in a low cost part-task trainer, we created a prototype system. Our approach was to build a virtual world interface using a HMD to an existing flight simulator application. This allowed a CIG with only one graphics channel to drive the display. To investigate which class of computing platform was suitable for use as the CIG, a cooperative thesis effort was launched to host the simulator on a mini-computer and micro-computer platform. The appropriate CIG could then be determined through demonstration and comparison between the systems. A software …

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An Empirical Evaluation Of Analytical Models For Parallel Relational Database Queries, Mark C. Denham Dec 1990

An Empirical Evaluation Of Analytical Models For Parallel Relational Database Queries, Mark C. Denham

Theses and Dissertations

This thesis documents the design and implementation of three parallel join algorithms to be used in the verification of analytical models developed by Kearns. Kearns developed a set of analytical models for a variety of relational database queries. These models serve as tools for the design of parallel relational database system. Each of Kearns' models is classified as either single step or multiple step. The single step models reflect queries that require only one operation while the multiple step models reflect queries that require multiple operations. Three parallel join algorithms were implemented based upon Kearns' models. Two are based upon …

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Recursive Optimization Of Digital Circuits, John Knutson Dec 1990

Recursive Optimization Of Digital Circuits, John Knutson

Theses and Dissertations

The goal of this thesis is twofold: first, to identify the advantages and disadvantages of existing optimization systems and second, to develop an optimization system that uses Boolean principles to generate a recursive realization of combinational logic. Current multi-level optimization systems fall into two categories: local optimization which removes redundancy by pattern matching on a local scale and global optimization which works with the equations that specify a circuit rather than with the circuit implementation itself. While global systems are very flexible and can produce near-optimal solutions, they are inherently complex. This research effort demonstrates that an effective global optimization …

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Model-Based Reasoning In Electronic Repair, Kenneth B. Cohen Dec 1990

Model-Based Reasoning In Electronic Repair, Kenneth B. Cohen

Theses and Dissertations

Diagnosis is the process of identifying the cause for an observed behavior of a system. Model-based reasoning uses knowledge of the behavior of the component and the interconnection of the components to diagnose a system. This thesis investigates the application of model-based reasoning to the problem of isolating faulty components of an analog electronic circuit. More specifically, this thesis describes an architecture for a model-based diagnostic system for electronic modules, implements an assumption-based truth maintenance system (one of the component parts of a model-based diagnostic system), and creates the interface between the truth maintenance system and the diagnostic system.

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Automatic Determination Of Recommended Test Combinations For Ada Compilers, James S. Marr Dec 1990

Automatic Determination Of Recommended Test Combinations For Ada Compilers, James S. Marr

Theses and Dissertations

Ada compilers are validated using the Ada Compiler Validation Capability (ACVC) test suit, containing over 4000 individual test programs. Each test program focuses, to the extent possible, on a single language feature. Despite the advantages of this atomic testing methodology, it is often the unexpected interactions between language features that result in compilation problems. This research investigated techniques to automatically identify recommended combinations of Ada language features for compiler testing. A prototype program was developed to analyze the Ada language grammar specification and generate a list of recommended of features to be tested. The output from this program will be …

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Computer Generated Holography As A Three-Dimensional Display Medium, Bryant L. Stuart Dec 1990

Computer Generated Holography As A Three-Dimensional Display Medium, Bryant L. Stuart

Theses and Dissertations

A process was developed to produce three dimensional images using computer generated holography (CGH). This process consisted of a series of steps that began with a geometric description of an object and concluded with a three dimensional holographic image being computed from a synthetic wavefront. The objects used in this series of steps (or CGH pipeline) were described geometrically as a collection of three dimensional points. The modular nature of the CGH pipeline provided a flexible platform from which to evaluate various object geometries, interference calculations algorithms, and interference pattern recording and reduction techniques. This system was implemented with general …

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A Hypermedia Implementation For Reusable Software Component Representation, Gary G. Worrall Dec 1990

A Hypermedia Implementation For Reusable Software Component Representation, Gary G. Worrall

Theses and Dissertations

This study investigated software component representation methods. Hypermedia was chosen as the implementation method to represent a collection of reusable software components. The hypermedia implementation organizes knowledge about the component collection into a web of small information chunks called frames. The set of software components was represented using a hybrid classification scheme composed of enumerated and faceted parts. The enumerated part enables the user to progress along a path in a taxonomic tree, narrowing the scope of eligible components. Each leaf node in this tree denotes a class of components, members of which are distinguished by their time and space …

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An Empirical Study Of Combining Communicating Processes In A Parallel Discrete Event Simulation, Ann K. Lee Dec 1990

An Empirical Study Of Combining Communicating Processes In A Parallel Discrete Event Simulation, Ann K. Lee

Theses and Dissertations

The primary goal of distributed discrete event simulations is to achieve speedup in simulation execution time by distributing the processing of the simulation over multiple processors. When partitioned for distribution in this fashion, simulations are typically partitioned such that there are more processes than processors. This thesis reviews existing methods for distributed discrete event simulations, and proposes general guidelines for efficient partitioning for a given communications topology based on empirical evidence. A performance analysis is conducted for two approaches to partitioning the system. The first method chosen is a mapping of multiple processes to a processor and the second approach …

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A Study Of The Effects Of Noise Jamming On Radar Receivers, Paul E. Bishop Dec 1990

A Study Of The Effects Of Noise Jamming On Radar Receivers, Paul E. Bishop

Theses and Dissertations

A comprehensive study of the effects of noise jamming on various pulsed radar receiver types is proposed. First, a literature review on the sources of electrical noise and various jamming waveforms is presented. The power spectra for three noise jamming waveforms are rigorously derived. These cases are shot noise in a parallel-plate diode, a series of pulses with random amplitudes and intervals, and for a series of pulses with random amplitudes, spacing and phases. Next, the probability density functions for the output of linear and quadratic detectors are developed. For each detector type, the probability density functions for the cases …

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Interference Cancellation In Rf Signals Using Adaptive Array Techniques, Mark E. Brown Dec 1990

Interference Cancellation In Rf Signals Using Adaptive Array Techniques, Mark E. Brown

Theses and Dissertations

This study investigated the effectiveness of the Least Means Squared (LMS) algorithm against various types of common jammers. The LMS algorithm was implemented using the Block Oriented Systems Simulator (BOSS). The LMS algorithm was inserted at the output of a two element antenna array. The array was configured so as to have one-half wavelength spacing. A quadrature hybrid signal structure was used. The array was then tested against a barrage and sweep jammer. The barrage jammer testing consisted of varying each of the three available jammer parameters; power, frequency and angle of arrival individually. The sweep jammer testing consisted of …

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