Digital Commons Network^™

Prototype Space Fabrication Platform, James A. Bessel, James M. Ceney, David M. Crean, Edward A. Ingham, David J. Pabst

Theses and Dissertations

Current plans for constructing large structures in space entail fabricating the primary components, such as truss segments, on the ground and assembling them in space. This process requires an exorbitant number of support missions, and methods to minimize the number must be considered. Whenever the space shuttle is launched, its external tank is jettisoned and destroyed prior to reaching orbit. This aerospace grade aluminum structure can be carried into orbit and utilized extrusively. The Prototype Space Fabrication Platform SFP fabricates aluminum materials, reduced from external tanks, into functional trusses. The trusses are strong and can be used as the primary …

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 …

Developing Prediction Regions For A Time Series Model For Hurricane Forecasting, William Cheman

Theses and Dissertations

In this thesis, a class of time series models for forecasting a hurricanes future position based on its previous positions and a generalized model of hurricane motion are examined and extended. Results of a literature review suggest that meteorological models continue to increase in complexity while few statistical approaches, such as linear regression, have been successfully applied. An exception is provided by a certain class of time series models that appear to forecast storms almost as well as current meteorological models without their tremendous complexity. A suggestion for enhancing the performance of these time series models is pursued through an …

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 …

Performance Impacts For Actuator Misalignments And Failures In Large- Aperture Adaptive-Optic Telescopes, Timothy D. Hogan

Theses and Dissertations

Large-aperture telescopes require adaptive optics in order to compensate for atmospheric turbulence which would otherwise negate the resolution advantages of using large apertures. This investigation analyzes the impacts of misalignments and failures, in the deformable mirror actuators, upon the performance of such systems. A numerical simulation of a standard adaptive optics system is used to generate characteristic optical transfer function OTF and signal-to-noise ratio SNR performance metrics. The performance impacts of the misalignments are shown to be dependent upon the Fried parameter effective telescope diameter, the source object brightness, and the control system time delay. The degree of performance degradation …

Hyperspectral Analysis Of Space Objects: Signal To Noise Evaluation, Daniel Hrovat

Theses and Dissertations

Hyperspectral analysis of space objects is being considered as a means of enhancing Space Object Identification. SOI capabilities. This study develops a mathematical simulation based on fundamental radiometry principles to evaluate the feasibility of hyperspectral analysis of space objects. The study uses Signal to Noise Ratio SNR as the basis for the feasibility evaluation, and addresses the question Is there enough target signal in narrow wavelength bandwidths to conduct hyperspectral measurements of space objects The analysis characterizes the target signal and noise sources using fundamental radiometry, and develops a flexible radiometry model which calculates the target signal count rate, and …

Objective Image Quality Metrics: Applications For Partially Compensated Images Of Space Objects, David J. Lee

Theses and Dissertations

Digital image reconstruction tasks currently require human intervention for a subjective evaluation of image quality. A method for unsupervised measurement of digital image quality is desired. This research investigated various parameters metrics that can be automatically extracted from a digital image and tested how well they correlated with image quality. Specifically, images of orbiting satellites captured by a partially compensated adaptive optics telescope were dealt with. Two different types of quantities were investigated 1) Fourier spectral parameters, based on the spatial- frequency sensitivities of the HVS; and 2) Histogram shape parameters i.e image statistical moments giving quantitative insight into the …

System Design Analysis Of A Lightweight Laser Satellite Terminal, Brian C. Page

Theses and Dissertations

This study investigated the technological feasibility of a man- portable satellite laser communications system. Areas of interest were an end- to-end system analysis on the communications link evaluation of atmospheric effects and evaluation of semi-conductor lasers as the laser source. A literature search revealed that satellite laser communication research is primarily directed at inter-satellite links. There have been some proposed systems for space-to-ground laser communications systems, but they all utilize large fixed ground stations. The focus of this research effort is directed at a small man-portable ground station capitalizing on recent advances in semiconductor laser devices. Baseline satellite communication systems …

Solving The Ranking And Selection Indifference-Zone Formulation For Normal Distributions Using Computer Software, Catherine A. Poston

Theses and Dissertations

Ranking and selection procedures are statistical methods used to compare and choose the best among a group of similar statistically distributed populations. The two predominant approaches to solving ranking and selection problems are Guptas subset selection formulation and Bechhofers indifference- zone formulation. For the indifference-zone formulation where the populations have equal sample sizes, Barr and Rizvi developed an integral expression of the probability of correct selection PCS. Given appropriate parameters, the integral expression can be solved to determine the common sample size required to attain a desired PCS. Tables with selected solutions to the integral expression are available for a …

An Analysis Of The Root Causes Of Delays And Deficiencies In The Development Of Embedded Software For Air Force Weapon Systems, Jay R. Hopkins, Curtis De Keyrel

Theses and Dissertations

The importance of embedded software, used in every subsystem of ah major weapon systems used by the United States Air Force, has increased drastically over the last decades. However, in spite of the regulations currently in existence, developing and acquiring software which meets the user requirements within the original cost and schedule estimates continues to be difficult. At the same time, the Air Force has pushed to improve the development process with the Total Quality Management TQM program. The primary method used to improve the process has been to create metrics, collect data on these metrics, and then perform a …

Local Area Network Implementation At The 4950th Test Wing: A Study Of The Relationship Between Individual Factors And The Effectiveness Of A Local Area Network, Doyle F. Cone, David J. Donahoo

Theses and Dissertations

This research investigated the individual factors which directly impacted the effectiveness of the 4950th Test Wing local area network (LAN). Areas of interest included the relationships between demographic and user attitude factors and LAN effectiveness. A literature review provided the basis for: 1) operationally defining effectiveness as a subjective measure of user satisfaction; 2) identifying specific factors which impact information system effectiveness; and 3) developing a research instrument to measure user attitudes and user satisfaction. A questionnaire was administered to 342 LAN users 173 were returned (a response rate of 51 percent). Sixteen factors (eight demographic factors and eight attitude …

The Development And Use Of An Evaluation Mechanism For The Assessment Of Software Configuration Management Tools, Wayne M. Descheneau, Neil W. Robinson

Theses and Dissertations

This study investigated the development of a mechanism for use in the evaluation of Software Configuration Management SCM tools. An examination of applicable DoD standards identified the SCM requirements that could be levied on a development contractor, and a literature search revealed the functionality common to various automated tools. These two sets of information were organized into a matrix, and for each requirement that was met, the intersection on the matrix of the requirement and each functionality used to meet that requirement was checked. In addition to the matrix, the mechanism consisted of general information about a given tool and …

Demonstration Of Improved Software Support Labor Estimation For Air Force Operational Flight Programs Through Functional Orientation, Ronald R. Warner Jr., Darrel L. Wright

Theses and Dissertations

This study demonstrated two approaches to improve current software support effort estimation models for aircraft software. Both approaches involved a functional orientation not used by existing models. The first approach demonstrated how to orient a model to reflect the block change cycle modification process and how to represent support effort changes over time in order to improve effort estimation accuracy. Current software models do not reflect the support environment or the temporal characteristics of aircraft software support. The second approach demonstrated how to calibrate a model by properly selecting source data in order to increase accuracy. Support calibration is not …

Predictors Of Success On The Uniform Certified Public Accountant Examination, Mark E. Skean

Theses and Dissertations

The purposes of this study were to identify personal and intellectual characteristics associated with successful performance of first-time candidates on the uniform Certified Public {CPA) Examination and to develop prediction equations for success on each of the four exam sections.

CPA candidates who received undergraduate degrees from the University of North Dakota and who wrote the exam in 1988, 1989, or May 1990 were eligible for the study. Data for the 39 characteristics were gathered from candidate questionnaires and the university registrar.

Exam success was measured in several ways. An individual with a higher score, a passing grade on an …

Do Computers Enhance Student Involvement, Darcy J. Santangelo

Theses and Dissertations

No abstract provided.

A Non-Homogeneous, Spatio-Temporal, Wavelet Multiresolution Analysis And Its Application To The Analysis Of Motion, Thomas J. Burns

Theses and Dissertations

This research presents a multiresolution wavelet analysis tool for analyzing motion in time sequential imagery. A theoretical framework is developed for constructing an L2R wavelet multiresolution analysis from three non-identical spatial and temporal L2R wavelet multiresolution analyses. This framework provides the flexibility to tailor the spatio-temporal frequency characteristics of the three dimensional wavelet filter to match the frequency behavior of the analyzed signal. An unconventional, discrete multiresolution wavelet decomposition algorithm is developed which yields a rich set of independent spatio-temporally oriented frequency channels for analyzing, the size and speed characteristics of moving objects. Unlike conventional wavelet decomposition methods, this algorithm …

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 …

Spectroscopic And Vibrational Energy Transfer Studies In Molecular Bromine, Courtney D. Holmberg

Theses and Dissertations

Vibrational transfer and electronic quenching in the lower vibrational levels (v' < 3) of the B³π(0_u⁺) state of ⁷⁹Br₂ were investigated using spectrally resolved, temporally resolved laser induced fluorescence techniques. Spectrally resolved emissions from collisionally populated Br₂(B) vibrational levels were observed for Br₂ and rare gas collision partners. Vibrational transfer was efficient in the non-predissociative vibrational levels and was adequately described by the Montroll-Shuler model for harmonic oscillators. A single fundamental rate coefficient for vibrational transfer from v' = 1 to v' = 0, k_v(1,0), characterizes vibrational relaxation. For Br₂, the …

Air Pollution Transport Modeling, David M. Paal

Theses and Dissertations

This research effort addresses modeling of the transportation of air pollution in the atmosphere and the numerical analysis of the partial differential equations used in such modeling. Three Gaussian models are examined and compared using example problems. Several finite difference schemes are developed to solve the partial differential equations used in air pollution transport modeling. This study examines three Gaussian models SCREEN, AFTOX, and the program GAUSPLUM. The model GAUSPLUM is developed in this study and uses the Ada programming language and the analytic solution to the advection- diffusion equation. Numerical analysis of the partial differential equations PDE used in …

Binaural Room Simulation, Brian A. Smith

Theses and Dissertations

Research in binaural and spatial hearing is of particular interest to the Air Force. Applications in cockpit communication, target recognition, and aircraft navigation are being explored. This thesis examines human auditory localization cues and develops a mathematical model for the transfer function of a sound signal traveling from an isotropic point source through a rectangular room to both ears of a listener. Using this model as a guide, non-head coupled binaural sound signals are generated in a binaural room simulation. Reflection and attenuation cues included in the computer generated signals are varied in order to determine which cues enhance the …

Design And Construction Of The Aerobot Robotic Manipulator (Arm), William L. Cochran

Theses and Dissertations

This thesis designed, constructed, and tested a robotic arm for the Aerobot Aerial Robot. The main purpose of the ARM is to enable the Aerobot to retrieve objects for use in an annual robotics competition. Design of the ARM involved synthesizing the characteristics of simplicity, weight, strength, and size. The result was a three-degree-of-freedom manipulator that uses electric motors, cable linkages, and telescoping tubes to access a work space below the Aerobot. Forward and inverse kinematics were investigated to enable automation of the ARM. Data was collected from infrared sensors to validate the model. Manipulation of the ARM is presently …

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 …

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 …

An Approximate Solution For The Spinup Dynamics Of Near Axisymmetric Axial Gyrostats Using The Method Of Multiple Scales, Stewart J. Kowall

Theses and Dissertations

Approximate solutions for the spinup of a near axisymmetric gyrostat are derived using the straightforward expansion method and the method of multiple scales. Two method of multiple scale solutions are presented. The first is derived using cartesian coordinates while the second is derived using cylindrical coordinates. The multiple scales solutions are compared to numerically integrated results for oblate and prolate configurations. A comparison for flat spin recovery is also accomplished. Excellent results are obtained for oblate configurations. Trajectory separatrix crossings hindered the results for prolate configurations and flat spin recoveries.

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 …

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, …

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. …

A Numerical Study Of High-Speed Missile Configurations Using A Block- Structured Parallel Algorithm, Douglas C. Blake

Theses and Dissertations

A numerical analysis of the aerodynamic phenomena associated with the high-speed flight of a sharp-nosed, four-finned, high-fineness ratio missile using a block-structured, parallel computer algorithm is presented. The algorithm, PANS-3EM, utilizes a second-order-accurate, shock-capturing, Total Variation Diminishing scheme and incorporates a Baldwin-Lomax turbulence model. PANS-3EM allows for extreme flexibility in the choice of computational domain decomposition and computing machine of implementation. Developmental work consists of conceptualization and verification of the algorithm as well as parallel performance and scalability studies conducted on a variety of computing platforms. Using PANS-3EM, the aerodynamic characteristics of the missile are investigated. Drag and pitching moment …

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 …

Comparison Of The Dynamic Behavior Of Composite Plates And Shells Incorporating Green's Strain Terms With The Von Karman And Donnell Models, Arthur E. Forral

Theses and Dissertations

The dynamic collapse behavior of thin, composite cylindrical shells subjected to transverse point loads is considered. The dynamic behavior of the undamped cylindrical shells of varying radii is analyzed with a finite element formulation that incorporates all nonlinear Green's strain terms in the in-plane directions; transverse strains are linear and vary parabolically through the shell thickness. This formulation is denoted as the simplified large displacement/rotation (SLR) theory. Graphical representations are used extensively to examine dynamic behaviors not noted in similar research that utilized the DSHELL finite element code. Composite plate behavior is also explored. Comparison of the higher-order formulations to …