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Articles 69001 - 69030 of 77677

Full-Text Articles in Engineering

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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A Study Of Two Dimensional Tapered Periodic Edge Treatments To Reduce Wideband Edge Diffraction, Russell A. Burleson Dec 1993

A Study Of Two Dimensional Tapered Periodic Edge Treatments To Reduce Wideband Edge Diffraction, Russell A. Burleson

Theses and Dissertations

This is a brief summary of a study to reduce diffraction from an infinite two dimensional edge using tapered periodic surfaces. The concept is to use the impedance characteristics of a periodic surface to create a tapered impedance much like a tapered resistance commonly used for diffraction reduction. This approach has several advantages over. tapered resistive treatments to include ease of fabrication, better engineering control of the impedance and negligible loss absorbed by the ta per. In this study, four periodic tapers were design, built and tested. These tapers were also modeled using a variety of numerical techniques. The results …

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Satellite Attitude Determination Using Linear Combination Of Models, Martin S. Chin Dec 1993

Satellite Attitude Determination Using Linear Combination Of Models, Martin S. Chin

Theses and Dissertations

In satellite analysis, it is often necessary to determine the attitude of a satellite from a two dimensional image of the satellite. This thesis describes work performed to determine the attitude of a satellite relative to a reference position. The attitude is described in terms of the scaling, rotation and translation of the reference that will result in a pose that can be projected to form the image of interest. The techniques used are based on finding coefficients for the linear combination of basis images and decomposition of a composite transformation matrix. The methods were initially modeled in Mathematica and …

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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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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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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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Analysis And Simulation Of A Gps Receiver Design Using Combined Delay-Lock And Modified Tanlock Loops, George D. Harris Dec 1993

Analysis And Simulation Of A Gps Receiver Design Using Combined Delay-Lock And Modified Tanlock Loops, George D. Harris

Theses and Dissertations

The purpose of this thesis was to investigate the performance of two types of tracking loops used in Global Positioning System (GPS) receivers. The first loop, the Delay-Lock Loop (DLL), is responsible for maintaining synchronization with the received PN sequence. The second loop, the Modified Tanlock Loop (MTLL), is responsible for maintaining synchronization with the carrier signal. The performance of the two loops is investigated first separately then their performance is evaluated when operated together. This thesis is an investigation on the ability of these two loops to overcome corruption of the input signal due to noise. Expanding the dynamic …

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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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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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Investigation Into Model-Based Fuzzy Logic Control, Michael W. Logan Dec 1993

Investigation Into Model-Based Fuzzy Logic Control, Michael W. Logan

Theses and Dissertations

This thesis investigates the feasibility of a proposed hybrid linear/Fuzzy controller for nonlinear plants. The proposed controller concept is based on the use of multiple linearizations of a nonlinear plant, which describe the dynamics of perturbations about equilibrium points throughout the desired envelope of operation. A bank of linear compensators is developed, each corresponding to a linearized plant about a different equilibrium. The multiple control signals generated by the bank of compensators are then weighted and summed using Fuzzy Logic to produce a composite control perturbation signal, which is used to drive the nonlinear plant. Experiments were conducted to test …

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Development Of A Performance Evaluation Tool (Mmsofe) For Detection Of Failures With Multiple Model Adaptive Estimation (Mmae), Robert L. Nielsen Dec 1993

Development Of A Performance Evaluation Tool (Mmsofe) For Detection Of Failures With Multiple Model Adaptive Estimation (Mmae), Robert L. Nielsen

Theses and Dissertations

Multiple model Kalman Filter (KF) techniques are used extensively for Multiple Model Adaptive Estimation (MMAE), Multiple Model Adaptive Control (MMAC), and Distributed Kalman Filter (DKF) applications to determine Bayesian- blended optimal estimates of states, uncertain parameters, and optimal control signals. Multiple model methods are used for sensor management, Failure Detection and Isolation (FDI), and other Guidance and Control (G and C) applications. A simulation tool called the Multiple Model Simulation for Optimal Filter Evaluation (MMSOFE) has been in this research. MMSOFE is based on the well-benchmarked single Kalman filter tool called Multimode Simulation for Optimal Filter Evaluation (MSOFE). MMSOFE is …

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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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Design Of A Subsonic Envelope Flight Control System For The Vista F-16 Using Quantitative Feedback Theory, Odell R. Reynolds Dec 1993

Design Of A Subsonic Envelope Flight Control System For The Vista F-16 Using Quantitative Feedback Theory, Odell R. Reynolds

Theses and Dissertations

A controlled plant's characteristics can vary widely throughout its operational envelope. This is a major problem in nominal plant-based control system design. Hence, gain scheduling is often used for full envelop design. In this paper, it is proposed to address the plant's variability using robust control design concepts. In particular, the frequency domain based Quantitative Feedback Theory Multiple-Input Multiple-Output robust control design method is employed for the synthesis of a full envelop flight control system for an F-16 derivative. Compensators for the aircraft's pitch and lateral directional channels are designed, and the designs are validated using linear simulations.

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Neural Networks For Dynamic Flight Control, Ronald E. Setzer Dec 1993

Neural Networks For Dynamic Flight Control, Ronald E. Setzer

Theses and Dissertations

This thesis examines the application of artificial neural networks (NNs) to the problem of dynamic flight control. The specific application is the control of a flying model helicopter. The control interface is provided through a hardware and software test bed called the Fast Adaptive Maneuvering Experiment (FAME). The NN design approach uses two NNs: one trained as an emulator of the plant and the other trained to control the emulator. The emulator neural network is designed to reproduce the flight dynamics of the experimental plant. The controller is then designed to produce the appropriate control inputs to drive the emulator …

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An Analysis Of Fm Jamming And Noise Quality Measures, Timothy N. Taylor Dec 1993

An Analysis Of Fm Jamming And Noise Quality Measures, Timothy N. Taylor

Theses and Dissertations

This thesis provides a description of FM-by-noise jamming, both at RF and at the output of the radar receiver, in terms of spectra, time-domain waveforms, and univariate probability density of amplitude. Particular emphasis is given to the case where the peak frequency deviation of the FM modulator is sufficiently small that Woodward's Theorem does not provide a good approximation of the RF spectrum. Additionally, noise quality measures which have been used to measure noise quality of radar jammers are considered theoretically and experimentally, and it is concluded that a noise measure which incorporates both a spectral measure and a probability …

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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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Color Image Segmentation, Kimberley A. Mccrae Dec 1993

Color Image Segmentation, Kimberley A. Mccrae

Theses and Dissertations

The most difficult stage of automated target recognition ATR is segmentation. Current AFIT segmentation problems include faces and tactical targets previous efforts to segment these objects have used intensity and motion cues. This thesis develops a color preprocessing scheme to be used with the other segmentation techniques. A neural network is trained to identify the color of a desired object, eliminating all but that color from the scene. Gabor correlations and 2D wavelet transformations will be performed on stationary images and 3D wavelet transforms on multispectral data will incorporate color and motion detection into the machine visual system. The thesis …

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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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Prototype Space Fabrication Platform, James A. Bessel, James M. Ceney, David M. Crean, Edward A. Ingham, David J. Pabst Dec 1993

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 …

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Design Analysis Of A Combined Optical-Ladar Deep-Space Surveillance Satellite, Bradley K. Fournier Dec 1993

Design Analysis Of A Combined Optical-Ladar Deep-Space Surveillance Satellite, Bradley K. Fournier

Theses and Dissertations

This research determines the performance requirements of a combined optical LADAR space-based system in order to detect and track deep-space satellites from a near-earth orbit satellite. The research derives the necessary equations to compare both direct and heterodyne detection techniques. The selection of the candidate laser systems is based on current space developed LADAR technology. The selection of the detector, detector size, and optic size are determined in order to maximize the signal-to-noise ratio. The analysis includes the effects of beam truncation, obscuration, pixel geometry, and background radiance. The results indicate that the direct detection technique with a GaA1As semiconductor …

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Hyperspectral Analysis Of Space Objects: Signal To Noise Evaluation, Daniel Hrovat Dec 1993

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 …

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Shielded Coil Electrodynamic Propulsion (Scep). A Feasibility Study, Richard J. R. Ladouceur Dec 1993

Shielded Coil Electrodynamic Propulsion (Scep). A Feasibility Study, Richard J. R. Ladouceur

Theses and Dissertations

This study investigated Shielded Coil Electrodynamic Propulsion SCEP. The use of the earths magnetic field as a propulsion source has been previously investigated. It was found that a significant amount of power and long conductors were required. A more compact propulsion concept which requires significantly less power is proposed. This concept relies on the feasibility of significantly reducing the magnetic force induced by the earths magnetic field on selected segments of a coil. An experiment design to support the theoretical findings was conducted. The experiment results support the theoretical model.

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Objective Image Quality Metrics: Applications For Partially Compensated Images Of Space Objects, David J. Lee Dec 1993

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 …

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System Design Analysis Of A Lightweight Laser Satellite Terminal, Brian C. Page Dec 1993

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 …

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A Methodology To Assess The Impact Of The Global Positioning System On Air Combat Outcomes, Stephen F. Sovaiko Dec 1993

A Methodology To Assess The Impact Of The Global Positioning System On Air Combat Outcomes, Stephen F. Sovaiko

Theses and Dissertations

The Air Force has a requirement to quantify the force enhancement effects of military space systems, but no methodology currently exists for the measurement of their contribution to air combat outcome. This research examines the Global Positioning System GPS and models its influence on air-to-ground combat. The decision analysis technique of influence diagrams is used to identify the effects of GPS launch decisions and constellation size on the navigation accuracy available to air combatants. The effect of accuracy variations on combat outcome is shown by using a value tree to identify the affected campaign Measures of Effectiveness. The study reveals …

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Measuring User Satisfaction Of The Electronic Mail System At Air Force Materiel Command Headquarters As An Indicator Of The System's Effectiveness, Randall R. Bradford Dec 1993

Measuring User Satisfaction Of The Electronic Mail System At Air Force Materiel Command Headquarters As An Indicator Of The System's Effectiveness, Randall R. Bradford

Theses and Dissertations

The purpose of this study was to evaluate the effectiveness of the electronic mail system at the Air Force Materiel Command Headquarters. User satisfaction was measured as an indicator of the systems effectiveness. In order to provide an objective measurement of system effectiveness, the following research questions were addressed: (1) What is system effectiveness in relation to this particular electronic mail system, and how should it be measured? (2) What measurement instruments can be adapted, modified, or created to measure effectiveness as it is defined for problem? (3) If a measurement instrument is administered what do the results of the …

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Guidelines For Ensuring Software Supportability In Systems Developed Under The Integrated Weapon System Management Concept, Forrest F. Butts Iii, Anthony C. Johndro Dec 1993

Guidelines For Ensuring Software Supportability In Systems Developed Under The Integrated Weapon System Management Concept, Forrest F. Butts Iii, Anthony C. Johndro

Theses and Dissertations

This thesis studied the software maintenance planning and practices of the pilot Integrated Weapon System Management IWSM programs. Before IWSM, a System Program Office SPO acquired an Air Force weapon system then passed it to an Air Logistics Center ALC for follow-on support. The ALC was forced to maintain the software despite its questionable maintainability. The SPO de- emphasized maintainability because maintenance was an ALC responsibility and building maintainable software increased development costs and lengthened schedules. The IWSM philosophy closes the gap between development and maintenance. A System Program Director SPD, who oversees both system development and maintenance, has an …

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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 Dec 1993

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 …

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An Evaluation Of The Software Engineering Institute's Capability Maturity Model As A Framework For Software Process Improvement At Three Air Logistics Centers, Brian G. Hermann, Raymond J. Lewis Jr. Dec 1993

An Evaluation Of The Software Engineering Institute's Capability Maturity Model As A Framework For Software Process Improvement At Three Air Logistics Centers, Brian G. Hermann, Raymond J. Lewis Jr.

Theses and Dissertations

This research sought to determine whether a relationship exists between the maturity level of the software process, as determined by the Software Engineering Institutes Capability Maturity Model SEI CMM, and the actual success of particular software projects at three US Air Force Air Logistics Centers. Project success is defined in terms of cost, schedule, and quality criteria. In addition, each organizations acceptance of the SEI assessment as well as its effectiveness in setting up follow-on process improvement programs were evaluated. Finally, the process improvement programs were reviewed individually inasmuch as these programs are the mechanisms for achieving improved quality, lower …

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An Assessment Of The Appropriateness To The Royal Australian Air Force Of A Masters Level Professional Program In Information Systems, Ralph G. L. Kettle, Joseph R. Taylor Dec 1993

An Assessment Of The Appropriateness To The Royal Australian Air Force Of A Masters Level Professional Program In Information Systems, Ralph G. L. Kettle, Joseph R. Taylor

Theses and Dissertations

This study assessed the appropriateness, to the Royal Australian Air Force RAAF, of a graduate professional program in Information Systems (IS) based on the Association for Computing Machinery’s ACM curriculum model. The ACM curriculum model is an archetype of graduate education in IS. Programs based on this model produce graduates with knowledge, skills, and abilities (KSAs) that are required by IS practitioners. The usefulness of twenty KSAs that underlie the ACM curriculum model were evaluated by 33 incumbents of RAAF information Systems Agencies and Directorate of Communications and Information Systems - Air Force. Although uncertain about the educational background suited …

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