Engineering Commons^™

An Object-Oriented Database Implementation Of The Magic Vlsi Layout Design System, Timothy M. Jacobs

Theses and Dissertations

This thesis attempts to prove that the commercially available Object Store data management system provide the performance and functionality necessary to support a complex engineering design system. This is accomplished by modifying the Magic VLSI circuit layout design system to eliminate its current Unix file data management system and replace it with Object Store. The approach to this research effort includes a design recovery of the Magic system and identification of its ket data management functions. These functions are then modified to take advantage of the database management facilities of Object Store. Additional code is added to instrument performance measurement …

A Comparative Analysis Of Computer End-User Support In The Air Force And Civilian Organizations, Maureen C. Casey, Douglas A. Kveene

Theses and Dissertations

This study compared end-user computing support provided by the Air Force to support provided by civilian organizations with information centers and those without. Factors measured included the end user's demographics, applications used, the effect of computing on perceived confidence, productivity, quality and quantity of output, the importance of various types of support, and satisfaction with the support received from different sources. A survey was administered to 450 Air Force and 265 civilian end users; 416 were returned (response rate of 58.18%). Although there were significant demographic differences between end users, there were no differences in types of support required. Training, …

Crack Growth Rate Modeling Of A Titanium-Aluminide Alloy Under Thermal-Mechanical Cycling, John J. Pernot

Theses and Dissertations

In this study, a model is developed to predict crack growth rates in a titanium-aluminide alloy under thermal-mechanical fatigue (TMF). This TMF crack growth rate prediction model, which requires only isothermal data to define its parameters, is distinguished from earlier models in two ways. First, it accounts for mechanical-fatigue and environmental crack growth rate contributions while it also considers a retardation mechanism thought to be caused by creep blunting of the crack tip. This is the first study to account for such a retardation mechanism during TMF. The second uniqueness of the model is that its general form can account …

High-Resolution Tvd Schemes For The Analysis Of 1. Inviscid Supersonic And Transonic Flows. 2. Viscous Flows With Shock-Induced Separation And Heat Transfer, Mark A. Driver

Theses and Dissertations

Application of TVD schemes to both inviscid and viscous flows is considered. The mathematical and physical bases of TVD schemes are discussed. First and second-order accurate TVD schemes and a second-order accurate Lax- Wendroff scheme are used to compute solutions to the Riemann problem in order to investigate the capability of each to resolve shocks, rarefactions, and contact surfaces. Second-order finite-volume and finite-difference TVD schemes are used to obtain solutions to inviscid supersonic and transonic cascade flow problems. TVD schemes are shown to be superior to the Lax-Wendroff family of schemes for both transient and steady-state computations. TVD methodology is …

An Analysis Of The Information Requirements Of Conus Based Deputy Commanders For Maintenance, Daniel J. Green

Theses and Dissertations

The purpose of this research was to identify the information requirements of Air Force Deputy Commanders for Maintenance. It had three basic objectives: (1) identify the critical success factors that they monitor on a continuous basis, (2) identify similarities in those requirements for all DGMs and across major commands, and (3) determine if the application of information technology would enhance their decision making. Surveys were sent to all CONUS based Deputy Commanders for Maintenance. The study found that there were nine critical success factors that were used by a majority of all respondents. In addition, nine command-specific critical success factors …

Thermal Nonequilibrium Effects On Turbine Cascade Aerodynamics, Jill L. R. Shaw

Theses and Dissertations

The AFIT Total Variation Diminishing Euler Code (ATEC) was modified to include a thermal nonequilibrium model to investigate high temperature effects associated with vibrational relaxation in a transonic turbine cascade. Incorporation of this model into ATEC and creating ANTEC (AFIT Nonequilibrium TVD Euler Code) was accomplished in three steps. Steady-state solutions obtained with ANTEC were compared with those obtained with ATEC for various inlet and exit conditions. The Courant-Friedrichs-Levy criterion was held constant to ATEC; however, it required variation for ANTEC. Blade temperature profiles, temperature difference contours in the vicinity of the trailing edge and the value of the ratio …

A Comparative Study Of Numerical Versus Analytical Waverider Solutions, Gregory O. Stecklein

Theses and Dissertations

The WL/FIMM explicit, Roe flux-splitting Euler algorithm is applied to the inviscid hypersonic flow over a parabolic-top waverider configuration optimized for Mach 10 at zero degrees angle of attack. An on-design grid refinement study is conducted to determine the asymptotic nature of the optimized flight parameter L/D. A parametric study of off-design conditions is conducted to determine flow perturbation effects on HSDT waverider theory. A validation of the Euler code is conducted through a comparison of the numerical data to analytical results derived by Rasmussen. The grid refinement study shows little effect on the inviscid calculation of the optimized parameter …

Analysis Of An Advanced Fighter Aircraft Using Jet Flap Techniques And The Vortex Lattice Method, Steven P. Snyder

Theses and Dissertations

A computer code using the vortex lattice method with modified boundary conditions was used to determine the induced aerodynamic characteristics of high aspect ratio, vectoring, exhaust nozzles located at the wing root of a canard configured fighter aircraft. Comparison with existing wind tunnel data verified results of the method. The exhaust was modeled as a singularly blown jet flap at deflection angles of -10, 0, 10, 20, 30, and 40 degrees. Jet momentum coefficients were based on gross engine thrust for maximum afterburner and military power settings at a Mach number of 0.6 and an altitude of 20,000 ft. Lift, …

Robust Grasp Design Using Grasp Force Focus Positioning, Freddie D. Zayas

Theses and Dissertations

A three-finger precision grasp is used to rotate a cylindrical object about a threaded post. Three fingered grasps are unique in that the homogeneous solution for the contact forces produces a grasp force focus. Mapping of focus points which meet grasp stability and joint torque criteria results in a usable focus region. The effects of applied torque, contact location, and object position and orientation on usable regions are presented. Stability behavior about the region is also examined. Results are used to demonstrate a technique for robust grasp design. The versatility of robotic hands permit fine motion manipulation on a wide …

An Experimental Study Of A Sting-Mounted Circulation Control Wing, Steven J. Lacher

Theses and Dissertations

This wind tunnel study investigated the lift, drag, and pitching moment of a 20% thick, 8.5% camber, partial elliptical cross-section, single blowing slot, 2.325 aspect ratio, rectangular circulation control wing. The AFIT 5-foot wind tunnel was used. Lift and drag were referenced to the wind axis. The Reynolds number was 500,000 for all tests. Angle of attack was varied from -6 to 16 degrees and the effects of pulsed blowing were investigated. Effects of tripping the Coanda jet with a small flow barrier attached spanwise along the Coanda surface were also studied. Results indicate that there is a limit on …

Experimental Investigation Into The Effects Of Riblets On Compressor Cascade Performance, James A. Rothenflue

Theses and Dissertations

The effects of adding riblets to the blades of a subsonic, linear compressor cascade were investigated at the Air Force Institute of Technology. Three blade configurations were tested, including a set of unmodified NACA 64- A905 series blades, a set with riblets applied to the suction surface, and a set with riblets on the pressure surface. Performance was evaluated over a wide range of Reynolds numbers, and at low and high free stream turbulence levels. Cascade performance was evaluated in terms of total pressure loss coefficient, turning angle, and static pressure rise. No riblet configuration offered robust cascade performance improvements; …

The Effect Of Angle Of Incidence And Reynolds Number On Heat Transfer In A Linear Turbine Cascade, Steven G. Meschwitz

Theses and Dissertations

The AFIT linear Turbine Cascade Test Facility was used to study the effect of the small changes in the angle of incidence on turbine blade convective heat transfer. Other parameters studied were the model Reynolds number and the freestream turbulence level. Characterization tests, performed to determine the feasibility of the study were followed by a series of tests designed to separate the effects of the angle of incidence, Reynolds number, and freestream turbulence level on convective heat transfer. For any given freestream turbulence level or angle of incidence, there is an increase in the heat transfer coefficient for an increase …

Failure Characteristics Of Scs-6/Ti-24al-11nb Composite With A Circular Hole At Room And Elevated Temperatures, Joseph E. Overbeck

Theses and Dissertations

Off-axis loading of eight ply, unidirectional specimens with and without a circular hole determined the ultimate tensile strength of SCS-6/Ti- 24A1-11Nb composite at temperatures of 25°C and 650°C and fiber orientations of 0 degrees, 15 degrees, 45 degrees. Longitudinal moduli of the tested orientations compared closely to the rule of mixtures calculated values, and strengths compared closely to those predicted by the Tsai-Wu failure theory. The small diameter hole does not act as a stress concentrator, but merely reduces the material's strength in proportion to area loss. This result differs from those predicted by linear finite element analysis and orthotropic …

Analysis Of The Effects Of Removing Nose Ballast From The F-15 Eagle, Richard L. Bennett

Theses and Dissertations

This study investigated the results of removing lead ballast from the nose section of the F-15 Air Superiority fighter. The goal of the investigation was to determine if aircraft handling qualities remained acceptable with the ballast removed, and also to determine what improvements in aircraft nose pointing authority resulted. Actual F-15 weight reports were used to calculate the worst case aft center of gravity location shift due to the ballast removal. Several configurations with different center of gravity locations (based on various amounts of lead weights removed) were used for comparison to the baseline aircraft. Moments of inertia were calculated …

Thermomechanical Fatigue Of Scs-6/Β21-S [0/90]2s Composite, Dana G. Hanson

Theses and Dissertations

The objective of this study was to investigate the material behavior of SCS-6/β21-S [0/90]_2s in a thermomechanical fatigue environment. Samples of the SCS-6/β21-S composite were subjected to in-phase and out-of-phase cyclic loading; four samples were tested under in-phase conditions and eight samples were tested under out-of-phase conditions. Stress, temperature, and total strain values were acquired during the test sequence and analyzed for indication of possible trends. Experimental results indicated in-phase specimen possessed shorter fatigue lives then their out-of-phase counterparts above the static first ply failure of the matrix. The out-of-phase specimen showed a shorter fatigue life below the first …

Illustrative Examples Based On The Asce Standard Specification For The Design Of Cold-Formed Stainless Steel Structural Members, Shin-Hua Lin, Wei-Wen Yu, Theodore V. Galambos

CCFSS Library (1939 - present)

PREFACE During the past four years, two methods were developed for the design of stainless steel structural members at the University of Missouri-Rolla with consultation of Professor T. V. Galambos at the University of Minnesota. One of the methods is based on the load and resistance factor design (LRFD) and the other is based on the allowable stress design (ASD). Both design methods are now included in the new ASCE Standard 8-90, Specification for the Design of Cold-Formed Stainless Steel Structural Members. At the September 21, 1990 meeting of the Control Group of the ASCE Stainless Steel Cold-Formed Section Standards …

Material Handling In A Flexible Manufacturing Systems Processing Part Families, Paul Savory, Gerald Mackulak, Jeff Cochran

Department of Industrial and Management Systems Engineering: Faculty Publications

The objective of this simulation study is to analyze the system performance of a six machine flexible manufacturing system cell in which a material handling system is to be incorporated. The analysis focuses on determining the production potential of the cell by grouping common parts into "families". To accomplish this, computer simulation models are developed using the SIMAN simulation language.

Initially the manufacturing cell is modeled with no material handling system to get an upper bound estimate of production output. We next explore the impact that an automatic guided vehicle (AGV) has on system performance of the manufacturing system cell. …

Construction Evaluation Of Hydraway Edge Drains And Outlet Pipes On Interstate 64, L. John Fleckenstein, David L. Allen

Kentucky Transportation Center Research Report

This report documents the installation of the Hydraway edge drain (version two) on 1-64 in Franklin·Woodford-Scott and Fayette Counties. The edge drain was placed on the back side of the trench against the shoulder and backfilled with a sand/slurry.

From observations on this project and several previous projects, the sand/slurry backfill helps to insure the integrity of the drainage system during initial backfilling. It is apparent that the sand slurry backfill provides a better installation in comparison to previous methods using excavated trench material. Notable trench settlement did occur on this project. It is apparent that insufficient water was used …

Seat Belt Attitudinal Survey, Kenneth R. Agent

Kentucky Transportation Center Research Report

The primary objective of this study was to conduct a statewide survey to determine public opinion of a statewide mandatory safety belt law. The survey was conducted so that opinions could be analyzed by areas of the state. The method used to separate the state into geographic regions was to use the boundaries of the 15 Area Development Districts (ADD). A mail survey was conducted with 1,000 questionnaires sent to each ADD. A response rate of 51 percent was obtained.

The respondents were in favor of a statewide law requiring use of safety belts. The statewide percentage in favor of …

Part 1 Of The Mcmaster University Laboratory Test Program On Brick Veneer/Steel Stud Wall Systems, Robert G. Drysdale, Normand Breton

CCFSS Library (1939 - present)

The behaviour of steel stud backup wall panels subjected to lateral loads was investigated experimentally and analytically. In addition, various steel stud to track connections were investigated experimentally.

The experimental work consisted of the fabrication and testing of 109 steel stud to track connections. Thirty-two full size steel stud backup wall panels were also tested. Some of the panels were braced with various types of commonly used steel bridging while others were braced with gypsum board sheathing or Styrofoam SM insulation. Twelve beam tests were also performed in order to establish the flexural bending capacity of the steel studs tested. …

Function Prediction Using Recurrent Neural Networks, Randall L. Lindsey

Theses and Dissertations

A fully recurrent neural network was applied to the function prediction problem. The real-time recurrent learning (RTRL) algorithm was modified and tested for use as a viable function predictor. The modification gave the algorithm a variable learning rate and a linear/sigmoidal output selection. Verifying the networks ability to temporally learn both the classic exclusive-OR (XOR) problem and the internal state problem, the network was then used to simulate the frequency response of a second order IIR lowpass Butterworth filter. The recurrent network was then applied to two problems: head position tracking, and voice date reconstruction. The accuracy at which the …

Verification And Validation Of The Comprehensive Operational Support Evaluation Model For Space, Lawrence A. Cooper

Theses and Dissertations

This study details the verification and validation (V and V) of the Comprehensive Operational Support Evaluation Model for Space (COSEMS). COSEMS is an Ada-based simulation which models spacecraft constellation support concepts such as support from the ground and on-orbit support. While the model is intended for use in analyzing Strategic Defense System concepts, it can easily evaluate non-military satellite constellations. The V&V was confined to a subset of the over 200 subprograms which comprise COSEMS. This subset covered random number generation, reliability, orbital mechanics, and mission planning functions. The study used traces and comparison to other models to perform the …

Swatter (Space-Based Weapons Against Tactical Terrestrial-Based Resources): A Design For Integrating Space Into A Theater Level Wargame, Duane R. Cozadd

Theses and Dissertations

This thesis provides the foundation to expand the newly developed theater level computerized wargame, SABER, at the Air Force Wargaming Center, Maxwell AFB, Alabama to include space conflict at the theater level of simulation. Building upon the recently completed SABER, this thesis effort expands the conceptual framework of the model by integrating the dynamics of space warfare into the current theater level model. This expansion forms a new game called SWATTER. This thesis adds the space units required to integrate the land and air battles with the possible interactions from space. This thesis expands the stochastic attrition processes to include …

A Time-Dependent Adaptive Filter For Cochannel Interference Reduction, Matthew H. Foster

Theses and Dissertations

This thesis presents a Time Dependent Adaptive Filter (TDAF) which exploits the cyclostationarity of digitally modulated communications signals and seeks to improve the Signal to Interference Ratio (SIR) and Signal to Noise Ratio (SNR) of such signals. The TDAF is embedded in a computer simulation of a simple communication system consisting of a data source, data formatter, pulse shaping filter, BPSK modulator, and demodulator. In the simulation the TDAF and a Time Independent Adaptive Filter (TIAF) attempt to extract the Signal of Interest (SOI) from noise or interference. the criteria of Mean Squared Error (MSE) is used as the primary …

Wave Propagation In A Randomly Inhomogeneous Medium - A Study Of The Problem, Kyle Hunter

Theses and Dissertations

The problem of calculating the scintillation index of an atmospherically propagating spherical wave is examined. The fourth statistical moment of the complex field is obtained by using Feynman (path) integral techniques applied to the stochastic parabolic equation. The general trajectory of each Feynman integral is approximated by a truncated Fourier-sine series and the infinite-fold integration of the Feynman integral is reduced to a three-fold Riemann integral which is shown to match results derived under different assumptions. This thesis is highly tutorial.

Infrared Target Recognition, Brian D. Singstock

Theses and Dissertations

In this thesis, three approaches were used for Automatic Target Recognition (ATR). These approaches were shape, moment and Fourier generated features, Karhunen-Loeve transform (KLT) generated features and Discrete Cosine Transform (DCT) generated features. The KLT approach was modelled after the face recognition research by Suarez, AFIT, and Turk and Pentland, MIT. A KLT is taken of a reduced covariance matrix, composed all three classes of targets, and the resulting eigenimages are used to reconstruct the original images. The reconstruction coefficients for each original image are found by taking the dot product of the original image with each eigenimage. These reconstruction …

Finite Element Analysis Of A Riveted Repair On A Curved Composite Panel, Scott A. Hamilton

Theses and Dissertations

To analyze the current Aircraft Battle Damage Repair (ABDR) techniques, a finite element model (FEM) of a curved composite panel with a center cutout section was developed and verified against previously obtained modal test results. The FEM was modified using different methods to exhibit the effects of riveting on an aluminum patch to repair the section. The different methods were contrasted against each other and previously obtained modal test results. The panel, a (0/-45/+45/90) sub s layup of AS4/3501 graphite epoxy measuring 12 inches in height and 12.19 inches across its arc length with a 2 by 4 inch cutout …

Static Pressure Measurements Of A Low Power Arcjet, Kevin P. Talley

Theses and Dissertations

The NASA Lewis 1.2 kilowatt arcjet has been used for a number of performance and lifetime studies. This design was modified to obtain static pressure measurements at several locations along the arcjet nozzle. These measurements were taken at various propellant flow rates over most of the operational envelope of the thruster. Measured static pressure distributions are considerably higher than predicted by ID models and are proportional to the arc power. A simple thermodynamic model is also compared to the data, and is shown to match the slope of the data while overpredicting the pressure.

A Standardized Software Reliability Measurement Methodology, Joseph J. Stanko

Theses and Dissertations

Current Air Force practice is to perform Operational Test and Evaluation (OT and E) for each new weapons system. In support of this, Headquarters Air Force Operational Test and Evaluation Center (HQ AFOTEC) is responsible for measuring both suitability and effectiveness. While suitability is adequately measured, the current effort only addresses hardware effectiveness, or at best, system effectiveness. Since tools and metrics are in place for software suitability assessments related to OT and E (for example, software maintainability), there should be some effective way of measuring the operational effectiveness of software. Currently, HQ AFOTEC/LG5 has a data collection tool for …

A Walsh-Domain Adaptive Filter, Larry J. Duvall

Theses and Dissertations

Two Walsh-domain dyadic convolution adaptive filters are developed using a circular convolution frequency-domain filter (FDF1) and the Fast LMS adaptive filter (FDF2): WDF1 and WDF2 respectively. General theory of time- domain adaptive filters and a theoretical analysis of the FDF1, FDF2, WDF1, and WDF2 filters are presented. WDF1 and WDF2 software implementation are shown to be error free. A time-domain filter (TDF) and a FDF2 frequency-domain filter (FDF) are implemented for comparison testing. The WDF1, WDF2, TDF, and FDF filters are tested using time-shifted sinusoidal and rectangular noisy and noiseless signals. WDF1 and WDF2 are shown to converge faster and …