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Identifying Situational Constraints To Focus Quality Improvement In An Air Force Aerial Port, Timothy J. Pettit
Identifying Situational Constraints To Focus Quality Improvement In An Air Force Aerial Port, Timothy J. Pettit
Theses and Dissertations
This research analyzes the effects of situational constraints on individual performance within an Air Force Aerial Port squadron. Situational constraint research originated with laboratory studies by Peters and O'Connor in 1980 and was investigated in an Air Force field environment in 1984; mixed results were obtained. Laboratory studies identified direct performance inhibitors (Peters et al., 1980); however, field studies found little correlations with job performance (Kane, 1981; O'Connor et al., 1984a). Data collected in June 1995 (Dougherty, 1995) and March 1996, in this study, were used to accomplish a longitudinal analysis. Correlations between constraints and performance were also low in …
Assessing User Requirements For An Automated System To Support Programmed Depot Maintenance Through Use Of A Rapid Prototype In A Group Support System Environment, Floyd A. Gwartney
Assessing User Requirements For An Automated System To Support Programmed Depot Maintenance Through Use Of A Rapid Prototype In A Group Support System Environment, Floyd A. Gwartney
Theses and Dissertations
The purpose of this thesis was to assess user requirements for an automated information system to support programmed depot maintenance (PDM). To accomplish this, the Integrated Technical Information for the Air Logistics Centers (ITI-ALC) program's rapid prototype was evaluated. The evaluation focused on users' perception of how well the prototype met system and human computer interface requirements for PDM technicians and managers. A group support system (GSS) was used as an analysis tool to evaluate the prototype and collect evaluation data. Using the prototype as a requirements baseline for the ITI-ALC system, this thesis had three objectives: to perform an …
A Statistical Analysis Of Variables Related To Officer Retention, Gerald A. Scheuchner
A Statistical Analysis Of Variables Related To Officer Retention, Gerald A. Scheuchner
Theses and Dissertations
The overall objective of this research effort was to statistically analyze survey responses which indicate the extent to which exiting officers say different variables affected their decision to separate. Two surveys were utilized for this analysis. These surveys were administered by the Air Force Personnel and Survey Branch in 1991 and 1993. The first analysis tested whether significant differences existed between rated and non-rated officers with regard to how strongly they feel about each of the variables with respect to their separation decision. The second analysis tested whether significant differences existed between the rated and the non-rated officers respectively, with …
A Model For Successful Reutilization Of A Military Installation: A Case Study Of Gentile Air Force Station, Maria L. Garcia
A Model For Successful Reutilization Of A Military Installation: A Case Study Of Gentile Air Force Station, Maria L. Garcia
Theses and Dissertations
Previous research concerning base closure and reutilization focused on the roles of government agencies and the assistance they provided. This study looks at the community and the impact of installation closure. The process of planning for reuse of an installation is difficult and confusing. The guidance provided by the government has changed drastically since the first closures announced in the 1988 Base Realignment and Closure Committee recommendations. This study focuses on the strategy employed by Kettering, OH to successfully reuse Gentile AFS upon closure. As the final part in a longitudinal study, the research focus was lessons learned and implementation …
Parameter Estimation For Superimposed Weighted Exponentials, Edwards A. Ingham
Parameter Estimation For Superimposed Weighted Exponentials, Edwards A. Ingham
Theses and Dissertations
The approach of modeling measured signals as superimposed exponentials in white Gaussian noise is popular and effective. However, estimating the parameters of the assumed model is challenging, especially when the data record length is short, the signal strength is low, or the parameters are closely spaced. In this dissertation, we first review the most effective parameter estimation scheme for the superimposed exponential model: maximum likelihood. We then provide a historical review of the linear prediction approach to parameter estimation for the same model. After identifying the improvements made to linear prediction and demonstrating their weaknesses, we introduce a completely tractable …
Reaction Based Grasp Force Assignment, Mark W. Hunter
Reaction Based Grasp Force Assignment, Mark W. Hunter
Theses and Dissertations
An iterative method is developed by which the contact forces required to apply an arbitrary wrench (six elements of force and moment) to a stably grasped object may be calculated quickly. The assignment of contact forces, given a required object wrench, is accomplished with the use of fuzzy logic. This concept is referred to as the fuzzy logic reactive system (FLRS). The solution is versatile with respect to goals inherent in the rulebase and the input parameters, and is also applicable for an arbitrary number of contacts. The goal presented in this research, to illustrate the concept of the FLRS, …
Low-Velocity Impact On Composite Sandwich Plates, Eric J. Herup
Low-Velocity Impact On Composite Sandwich Plates, Eric J. Herup
Theses and Dissertations
The objective of the research is to analytically model the response of composite sandwich plates to low velocity impact. A displacement based, plane stress, finite element code is modified for this purpose. Major new algorithms include 5th order Hermitian interpolation, three dimensional equilibrium integration for transverse stress calculations, sandwich core modeling as an elastic plastic foundation, loading by simulated contact with a spherical indentor, adaptive mesh, damage prediction, damage progression via stiffness reduction, and local-global analysis for displacement. An experimental effort is also included in which composite sandwich plates with graphite epoxy facesheets and Nomex honeycomb core are subjected to …
Structures And Techniques For Implementing And Packaging Complex, Large Scale Microelectromechanical Systems Using Foundry Fabrication Processes, John H. Comtois
Structures And Techniques For Implementing And Packaging Complex, Large Scale Microelectromechanical Systems Using Foundry Fabrication Processes, John H. Comtois
Theses and Dissertations
Microelectromechanical Systems, or 'MEMS' is a broad new field of research into devices that range in size from a few microns to a few millimeters. Much of the technology supporting MEMS research is borrowed from the microelectronics industry; so MEMS holds out the promise of batch fabrication of microminiaturized machines that can be easily integrated with electronics. This dissertation research investigated structures and methods for implementing and packaging complex, large scale microelectromechanical devices and systems using commercially available foundry fabrication processes. It specifies methods for creating and packaging large, complex MEM systems, allowing the exploration of new MEMS architectures at …
Formal Transformations From Graphically-Based Object-Oriented Representations To Theory-Based Specifications, Scott A. Deloach
Formal Transformations From Graphically-Based Object-Oriented Representations To Theory-Based Specifications, Scott A. Deloach
Theses and Dissertations
Formal software specification has long been touted as a way to increase the quality and reliability of software; however, it remains an intricate, manually intensive activity. An alternative to using formal specifications is to use graphically-based, semi-formal specifications such as those used in many object-oriented specification methodologies. While semi-formal specifications are generally easier to develop and understand, they lack the rigor and precision of formal specification techniques. The basic premise of this investigation is that formal software specifications can be constructed using correctness preserving transformations from graphically-based object-oriented representations. In this investigation, object-oriented specifications defined using Rumbaugh's Object Modeling Technique …
Electrical Characterization Of Gasb Based Semiconductors For 2-4 Micrometers Diode Laser Applications, Daniel K. Johnstone
Electrical Characterization Of Gasb Based Semiconductors For 2-4 Micrometers Diode Laser Applications, Daniel K. Johnstone
Theses and Dissertations
Deep Level Transient Spectroscopy (DLTS) was used to characterize the band offsets and deep levels in MBE grown GaSb-based semiconductors that are used in 2-4 µm laser diode structures. One of several deep level traps found in AlxGa1-xAsySb1-y (x=0, 0.5, 0.6, 1.0) is a GaSb double acceptor trap. Progress is also made in establishing the model for the DX center in this material. The degree of compensation of the donor related DX center by GaSb affect where donors are situated, giving preference to one configuration over the many other possible configurations. One minority …
Design Of Gradient Index Optical Thin Films, Jeffrey J. Druessel
Design Of Gradient Index Optical Thin Films, Jeffrey J. Druessel
Theses and Dissertations
Gradient index thin films provide greater flexibility for the design of optical coatings than the more conventional 'layer' films. In addition, gradient index films have higher damage thresholds and better adhesion properties. This dissertation presents an enhancement to the existing inverse Fourier transform gradient index design method, and develops a new optimal design method for gradient index films using a generalized Fourier series approach. The inverse Fourier transform method is modified to include use of the phase of the index profile as a variable in rugate filter design. Use of an optimal phase function in Fourier-based filter designs reduces the …
An Investigation Of The Characteristics Of Regenerative Heat Exchangers, Timothy J. Murphy
An Investigation Of The Characteristics Of Regenerative Heat Exchangers, Timothy J. Murphy
Theses and Dissertations
The objective of the current research was to investigate the effects of reducing screen thickness on the volume and compactness factor of stacked, wire-screen regenerators. An improved transient step-change method was devised which integrated experimental data with a numerical model of the flow to determine the heat transfer coefficient and friction factor. The improvements to the approach are: (1) the measured inlet temperature trace is used, (2) the heat transfer coefficient is based on a parameter called the sponge effect delay time, and (3) the important effect of the tube surrounding the matrix is included in the numerical model. The …
Optimal Continuous-Thrust Orbit Transfers, James D. Thorne
Optimal Continuous-Thrust Orbit Transfers, James D. Thorne
Theses and Dissertations
The minimum time orbital transfer problem for spacecraft with steerable, continuous thrust of constant magnitude may be solved using Euler-Lagrange theory, which leads to the optimal control law in terms of Lagrange multipliers. However, the initial values of the Lagrange multipliers are not known from the orbital boundary conditions. Using analytical and empirical results, the optimal initial costates are modeled as functions of the problem parameters which are the initial thrust acceleration, A, and the final orbit radius, H, in canonical units. For circle to circle, coplanar orbit transfers, these approximate initial costate models lead to convergence in the shooting …
Simultaneous Composite Tailoring And Bending Control Optimization For Damping The Torsional Vibration Of A Plate, Douglas W. Dehart
Simultaneous Composite Tailoring And Bending Control Optimization For Damping The Torsional Vibration Of A Plate, Douglas W. Dehart
Theses and Dissertations
A method for the simultaneous structural and control optimization for torsional vibration of a composite plate which simulates a spacecraft solar array structure was developed in this study. Included in the optimization of the plate are the location of the piezoceramic actuators and sensors that provide bending/torsion actuation, the control gains, and the orientation of the graphite fibers in the composite plies. This research included the effects of using composite tailoring to promote the coupling of the twisting-bending mode to enhance the damping system. The plate was modeled by classical lamination plate theory using a linear elastic strain-displacement theory. This …
Direct Measurement Of Skin Friction In High Temperature And Impulsively Started Supersonic Flowfields, David M. Hazelton
Direct Measurement Of Skin Friction In High Temperature And Impulsively Started Supersonic Flowfields, David M. Hazelton
Theses and Dissertations
This study further developed and improved a miniature plastic cantilever floating element gauge for direct measurement of skin friction in shock tunnel tests. Gauge durability and usability were improved, and potential sources of error were quantified. A high frequency 30 kHz gauge (compared to the baseline 10 kHz gauge) was constructed by using an I-beam cantilever rather than a round beam. A directional gauge was developed and demonstrated by measuring the flowfield about a fin in the AFIT shock tunnel. The 10 kHz and 30 kHz gauges were used in two scramjet test sequences conducted at Mach 14 enthalpy (stagnation …
Gain-Scheduled Aircraft Control Using Linear Parameter-Varying Feedback, Martin R. Breton
Gain-Scheduled Aircraft Control Using Linear Parameter-Varying Feedback, Martin R. Breton
Theses and Dissertations
Systems which vary significantly over an operating envelope, such as fighter aircraft, generally cannot be controlled by a single linear time-invariant controller. As a result, gain-scheduling methods are employed to design control laws which can provide the desired performance. This thesis examines a relatively new approach to gain-scheduling, in which the varying controller is designed from the outset to guarantee robust performance, thereby avoiding the disadvantages of point designs. Specifically, the parameter-varying (LPV) aircraft model is linearized using linear fractional transformations (LFT's), and the resulting control problem is characterized as the solution to a set of four linear matrix inequalities …
Effect Of Transient Body Force On The Performance Of An Axial Grooved Heat Pipe, Wen-Lung Wang
Effect Of Transient Body Force On The Performance Of An Axial Grooved Heat Pipe, Wen-Lung Wang
Theses and Dissertations
An experimental investigation was performed to determine the effect of transient body forces on the performance of an ammonia/aluminum axial groove heat pipe. The effects of increased body forces on the dryout and rewet performance were simulated by tilting the heat pipe to different inclination angles. Theoretical calculations predicted the dryout length varied with different final inclination angles. The steady state experimental work was performed by tilting the heat pipe from 0 degrees to different final inclination angles for a long period of time until totally dryout occurred. Then, from the plot of the changing temperature at each location along …
Performance Study Of A Brazilian Air Force Data Communications Network, Oswaldo Zanelli
Performance Study Of A Brazilian Air Force Data Communications Network, Oswaldo Zanelli
Theses and Dissertations
This thesis consists of a performance analysis of two network models using different protocols, the X.25 and Asynchronous Transfer Mode (ATM). X.25 is currently used in the data communications network infrastructure in the Brazilian Air Force. ATM is a high speed network technology. Simulations of both models were performed to compare the two technologies. This study examines the traffic load that each network can handle while still providing a good quality of service (QoS). The X.25 network model proved to have a sufficient capacity to handle the projected workload, but it presented a low QoS when a more intense traffic …
Investigation Of Radio Wave Propagation In The Martian Ionosphere Utilizing Hf Sounding Techniques, Robert J. Yowell
Investigation Of Radio Wave Propagation In The Martian Ionosphere Utilizing Hf Sounding Techniques, Robert J. Yowell
Theses and Dissertations
This thesis presents a preliminary design of an ionospheric sounder to be carried aboard one or more of NASA's Mars Surveyor landers. Past Russian and American probes have indicated the existence of an ionosphere, but none of these missions remotely sensed this atmospheric layer from the surface. The rationale for utilizing a surface-based Martian ionospheric sounder is discussed. Based on NASA's choice of launch vehicle and power source, a low-weight, low-powered Chirp sounder using a horizontally-polarized dipole antenna is recommended for the sounder experiment. The sounder experiment should be conducted for at least one Martian year, in order to investigate …
Characteristic Spatial Quadratures For Discrete Ordinates Neutral Particle Transport On Arbitrary Tetrahedral Meshes, Charles R. Brennan
Characteristic Spatial Quadratures For Discrete Ordinates Neutral Particle Transport On Arbitrary Tetrahedral Meshes, Charles R. Brennan
Theses and Dissertations
Characteristic spatial quadratures for discrete ordinates calculations on meshes of arbitrary tetrahedra are derived and tested, including the step (SC), linear (LC), and exponential (EC) characteristic quadratures and variants that assume constant distributions on cell faces. Tetrahedral meshes accurately model curved surfaces with few cells. A split cell approach subdivides tetrahedra along the streaming direction, reducing the transport to one dimension. Assumed forms of the cell source and entering flux distributions have sufficient parameters to match the zeroth and first spatial moments. These parameters are determined by analytically inverting a linear system (LC), or by numerical inversion using Newton's method …
Residual Strength After Fatigue Of Unidirectional And Cross-Ply Metal Matrix Composites At Elevated Temperature, Sen-Tzer Chiou
Residual Strength After Fatigue Of Unidirectional And Cross-Ply Metal Matrix Composites At Elevated Temperature, Sen-Tzer Chiou
Theses and Dissertations
This study investigated the residual strength of the unidirectional and cross-ply laminates of SCS-6 / Ti-15-3, metal matrix composite at elevated temperature 427°C (800°F) after under tension-tension load controlled mode. For this purpose, several specimens were fatigued to various fractions of the fatigue life and then loaded monotonically to failure. The purpose of this study was to determine the effects of different levels of fatigue damage on the composite's strength. The unidirectional specimens were cycled at a 900 MPa maximum stress at a frequency of 10 Hz, while, the cross-ply specimens were tested at both 300 MPa and 450 MPa …
A Methodology For Reengineering Relational Databases To An Object-Oriented Database, Pedro A. Linhares Lima
A Methodology For Reengineering Relational Databases To An Object-Oriented Database, Pedro A. Linhares Lima
Theses and Dissertations
This research proposes and evaluates a methodology for reengineering a relational database to an object-oriented database. We applied this methodology to reengineering the Air Force Institute of Technology Student Information System (AFITSIS) as our test case. With this test case, we could verify the applicability of the proposed methodology, especially because AFITSIS comes from an old version of Oracle RDBMS. We had the opportunity to implement part of the object model using an object-oriented database, and we present some peculiarities encountered during this implementation. The most important result of this research is that it demonstrated that the proposed methodology can …
Characterization Of Spatial And Temporal Anisotropy In Turbulent Mixing Layers Using Optical Techniques, Patrick J. Gardner
Characterization Of Spatial And Temporal Anisotropy In Turbulent Mixing Layers Using Optical Techniques, Patrick J. Gardner
Theses and Dissertations
The optical aberrations induced by mixing layers of dissimilar gases are recorded and analyzed in order to characterize the spatial and temporal properties of the flow. Laser light was propagated through a mixing layer of Helium and Nitrogen gas, having velocities of 8.5 m/sec and 1.5 m/sec, respectively. The light was propagated in a direction perpendicular to the plane of the mixing layer. The mixing layer was evaluated in two experimental regimes: free turbulent mixing, where the mixing layer spreads into the surrounding air; and channel flow, where the mixing layer is confined to a rectangular channel. The optical perturbations …
Nonlinear Analysis Of Airfoil Flutter At Transonic Speeds, Scott A. Morton
Nonlinear Analysis Of Airfoil Flutter At Transonic Speeds, Scott A. Morton
Theses and Dissertations
Hopf-bifurcation analysis is used to determine flutter boundaries of a pitch and plunge airfoil (PAPA) at transonic Mach number conditions. The PAPA model is a coupling of the Euler equations and a two-degree-of-freedom structural model composed of linear and torsional springs. The Euler equations are discretized using an upwind total variation diminishing scheme (TVD) of Harten and Yee. Equilibrium solutions of the PAPA model are computed using Newton's method and dynamic solutions are explicitly integrated in time with first-order accuracy. The Hopf-bifurcation point, which models the flutter condition, is computed directly by solving an extended system of equilibrium equations following …
An Investigation Of Learning Curves And Their Use In Simulation, Jennie H. Lommel
An Investigation Of Learning Curves And Their Use In Simulation, Jennie H. Lommel
Theses and Dissertations
In 1995, the C-17 Factory Simulation Model (FSM) was developed to enable analysts to address 'what-if' questions about the resources required to build future aircraft, and is based on learning curve models that are used to both portray and simulate future aircraft production. In this thesis, we examine and develop alternate learning curve models that also utilize a small amount of initial production data to portray the relationship between the number of aircraft built and the resources required to build them. The goal is to identify a model which not only provides a good fit and forecast based on a …
Generalized Hidden Filter Markov Models Applied To Speaker Recognition, John M. Colombi
Generalized Hidden Filter Markov Models Applied To Speaker Recognition, John M. Colombi
Theses and Dissertations
Classification of time series has wide Air Force, DoD and commercial interest, from automatic target recognition systems on munitions to recognition of speakers in diverse environments. The ability to effectively model the temporal information contained in a sequence is of paramount importance. Toward this goal, this research develops theoretical extensions to a class of stochastic models and demonstrates their effectiveness on the problem of text-independent (language constrained) speaker recognition. Specifically within the hidden Markov model architecture, additional constraints are implemented which better incorporate observation correlations and context, where standard approaches fail. Two methods of modeling correlations are developed, and their …
A Generic Intelligent Architecture For Computer-Aided Training Of Procedural Knowledge, Freeman A. Kilpatrick Jr.
A Generic Intelligent Architecture For Computer-Aided Training Of Procedural Knowledge, Freeman A. Kilpatrick Jr.
Theses and Dissertations
Intelligent Tutoring System (ITS) development is a knowledge-intensive task, suffering from the same knowledge acquisition bottleneck that plagues most Artificial Intelligence (AI) systems. This research presents an architecture that requires knowledge only in the form of a shallow knowledge base and a simulation to produce a training system. The knowledge base provides the basic procedural knowledge while the simulation provides context. The remainder of the knowledge required for training is learned through the interaction of these components in a state-space scenario exploration process and inductive machine learning. These knowledge components are used only at the interface level, allowing the internal …
Linear And Non-Linear Preprocessing Of Wavefront Sensor Slope Measurements For Improved Adaptive Optics Performance, Dennis A. Montera
Linear And Non-Linear Preprocessing Of Wavefront Sensor Slope Measurements For Improved Adaptive Optics Performance, Dennis A. Montera
Theses and Dissertations
New methods for preprocessing wavefront sensor (WFS) slope measurements are presented. Methods are developed to improve the accuracy of WFS slope measurements, as well as estimating key atmospheric and system parameters from the slope signals. Both statistical and artificial neural network solutions are investigated. Also, new atmospheric models for generating slope and phase data with the proper spatial and temporal statistics are developed. The experiments in improving the accuracy of WFS slope measurements include reducing the WFS slope measurement error and compensating for adaptive optics system time delay through temporal slope prediction. The experiments in key parameter estimation include estimating …
A Crosstalk Correcting Router That Uses Online Noise Simulation To Route High-Speed Multichip Modules, Kenneth J. Mcclellan Jr.
A Crosstalk Correcting Router That Uses Online Noise Simulation To Route High-Speed Multichip Modules, Kenneth J. Mcclellan Jr.
Theses and Dissertations
Existing Multi Chip Module (MCM) auto-routers either ignore crosstalk or use over-simplified crosstalk approximations. Of the routers that do consider crosstalk, very few have the capability to correct crosstalk problems after they occur. This dissertation describes a router that not only has an internal crosstalk model for high speed MCMs which is more accurate than that of other existing routers, but also has the capability to use an online simulator to more accurately determine noise levels. After crosstalk problems occur, the router has the ability to correct these problems. Through memory usage reductions and routing efficiency improvements, this maze router …
Structural Damage Identification From Limited Measurement Data, Richard G. Cobb
Structural Damage Identification From Limited Measurement Data, Richard G. Cobb
Theses and Dissertations
The research focused on the development of a new method to identify damaged structural elements from a large flexible space structure on-orbit, using limited measured modal data. Limited measured modal data is loosely defined as measured data containing only a few modal frequencies and less than 10% of the total structural degrees-of-freedom. This effort was decomposed into four specific tasks. The first is the identification of partial modal properties from measured data of the nominal space structure. Second, the finite element model must be adjusted to match the measured nominal partial data. The third task is an analysis of the …