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Air Force Institute of Technology

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Articles 4741 - 4770 of 5699

Full-Text Articles in Engineering

Tracking Air Force Pallets Using Rfid Technology: A Concept Study, Gary A. Gross Sep 1995

Tracking Air Force Pallets Using Rfid Technology: A Concept Study, Gary A. Gross

Theses and Dissertations

The lack of asset visibility experienced at Aerial Ports of Embarkation (APOEs) during Operation Desert Storm is a phenomenon that has occurred in every major conflict for the last 40 years. The costs associated with this lack of control directly relate to the combat readiness and capability of supported units. This study examined the possibility of installing a Radio Frequency Identification (RF-ID) system to track Department of Defense 463L pallets worldwide. Performance characteristics of commercially available RF-ID systems were summarized, and a conceptual Air Mobility Command (AMC) tracking system was presented. For purposes of concept study, Amtech Corporation's Intellitag RT …


A Performance Analysis Of The Air Force War Time Lean Logistics Pipeline, Craig S. Gaddis, David A. Haase Sep 1995

A Performance Analysis Of The Air Force War Time Lean Logistics Pipeline, Craig S. Gaddis, David A. Haase

Theses and Dissertations

Lean Logistics is an innovative proposal designed to reduce the costs associated with reparable inventory management. The purpose of this thesis is to determine whether a wartime lean logistics pipeline can maintain acceptable aircraft availability rates in response to induced variations of order and ship time (OST) and flying hours for deployed forces. The Dyna-MEIRIC Version 6.4 simulation program was used to evaluate nine different factor-level combinations. The factors, OST and flying hours were varied at three different levels, low, medium, and high. Analysis of the results was accomplished using a two-factor ANOVA. The authors discovered that while increasing OST …


A Review Of Fighter Aircraft Capability For Smart Bombs, David R. King Sep 1995

A Review Of Fighter Aircraft Capability For Smart Bombs, David R. King

Theses and Dissertations

This study examined potential alternatives and decision criteria for inclusion in a Cost and Operational Effectiveness Analysis to recommend an alternative for addressing existing DOD multi-role fighter capability to employ inertially guided smart bombs. A survey of literature and interviews with expens were used to collect required information. An Analytical Hierarchy Process (MIP) decision model was developed for two feasible alternatives and four relevant decision criteriL The two feasible alternatives included either developing the BRU-53 smart bomb rack, or modifying F-15E conformal fuel tanks with additional smart interface wiring. Data on quantitative and qualitative decision criteria were collected to evaluate …


Aligning Demand For Spare Parts With Their Underlying Failure Mode, Steven D. Kephart, Richard C. Roberts Sep 1995

Aligning Demand For Spare Parts With Their Underlying Failure Mode, Steven D. Kephart, Richard C. Roberts

Theses and Dissertations

Current Air Force demand forecasting systems, DO41 and REALM, assume reparable demand is solely flying hour driven. The purpose of this study is to evaluate the relationship between demands, flying hours, and number of sorties at the work unit code level and improve reparable demand forecasting. A three phase methodology is used to analyze the demand, flying hour, and sortie relationship. The first phase uses multiple regression to determine a relationship at various work unit code levels. Multiple regression provides limited correlation between demands, flying hours, and sorties. The second phase uses Poisson regression to evaluate the integer, count nature …


The Effect Of Consolidating Two-Level Reparable Inventories On Aggregate Inventory Requirements And Mission Capability, Glenn R. Barney Sep 1995

The Effect Of Consolidating Two-Level Reparable Inventories On Aggregate Inventory Requirements And Mission Capability, Glenn R. Barney

Theses and Dissertations

One of the proposals of Lean Logistics is the relocation of many inventory assets to Intermediate Supply Points (ISPs). This research investigates the effect of consolidating Two Level Maintenance designated reparable asset inventories. The effects of interest are the potential reduction in aggregate inventory requirement and resulting savings and the effect of delayed issue of the assets on mission capability. The metric selected to measure the effect on mission capability for this study is the Not Mission Capable-Supply (NMCS) rate. A spreadsheet analysis of world-wide Two-Level Maintenance designated reparable asset demands over the study period is used to determine the …


Full Envelope Control Of Nonlinear Plants With Parameter Uncertainty By Fuzzy Controller Scheduling, Thomas J. Kobylarz Sep 1995

Full Envelope Control Of Nonlinear Plants With Parameter Uncertainty By Fuzzy Controller Scheduling, Thomas J. Kobylarz

Theses and Dissertations

A full envelope controller synthesis technique is developed for multiple-input single-output (MISO) nonlinear systems with structured parameter uncertainty. The technique maximizes the controller's valid region of operation, while guaranteeing pre-specified transient performance. The resulting controller does not require on-line adaptation, estimation, prediction or model identification. Fuzzy Logic (FL) is used to smoothly schedule independently designed point controllers over the operational envelope and parameter space of the system's model. These point controllers are synthesized using techniques chosen by the designer, thus allowing an unprecedented amount of design freedom. By using established control theory for the point controllers, the resulting nonlinear dynamic …


An Evaluation Of Cost Metrics Used Within Aeronautical Systems Center, Kevin M. Byrne Sep 1995

An Evaluation Of Cost Metrics Used Within Aeronautical Systems Center, Kevin M. Byrne

Theses and Dissertations

Aeronautical Systems Center (ASC) system program offices rely on cost metrics to acquire information on program effectiveness and organizational improvement. This study was an attempt to determine the effectiveness of ASC’s cost metrics. The effectiveness of the metrics were determined by the desirability of the behaviors which are exhibited when individuals utilize the specific metrics. Using an expert panel to evaluate the metrics, data was collected using the Group Research Laboratory for Logistics located in Armstrong Laboratory at Wright Patterson AFB, OH. Metric diagnostic charts were utilized to arrange the data into a format which would provide effectiveness information. The …


Aggregating Organizational Performance Metrics Using The Analytic Hierarchy Process, Bret L. Indermill Sep 1995

Aggregating Organizational Performance Metrics Using The Analytic Hierarchy Process, Bret L. Indermill

Theses and Dissertations

Measurement provides factual information which is necessary for effective control of business processes. Implementing a Total Quality Management (TQM) philosophy is a common process in many organizations today. The United States Air Force is using the Malcolm Baldrige National Quality Award criteria to measure organizational performance in implementing the Quality Air Force (QAF) initiative. Unfortunately, the Baldrige-based unit self-assessment (USA) process is an inconsistent measure due to its subjectivity, and is also time consuming to use. This study determined that a new USA method based on the analytic hierarchy process (AHP) was not a significant improvement over the existing QAF-USA …


A Comparison Of Consistent Versus Inconsistent Scheduling Rules In A Flow Shop Environment, Nicola Gismondi Sep 1995

A Comparison Of Consistent Versus Inconsistent Scheduling Rules In A Flow Shop Environment, Nicola Gismondi

Theses and Dissertations

A consistent scheduling rule is one which will ensure a job's priority (relative to all other job's) will remain constant as it moves from queue to queue in a production system. Previous research concerning flow shop priority scheduling rules focused on comparison of either consistent or inconsistent rules. Conversely, this study sought to provide additional insight by comprising consistent and inconsistent rules in a flow shop environment The Air Force uses both types of rules in maintenance and logistics scheduling. Time and money can be saved if the scheduling managers can better understand the effect of consistency on a system. …


An Empirical Investigation Of The Integrated Weapon System Management Concept Of Seamless Processes, Timothy H. Surabian Sep 1995

An Empirical Investigation Of The Integrated Weapon System Management Concept Of Seamless Processes, Timothy H. Surabian

Theses and Dissertations

This research investigated the way four Air Force Materiel Command (AFMC) single manager organizations operationalized the Integrated Weapon System Management (IWSM) concept of "seamless processes." In this thesis, the IWSM concept of "seamless processes" refers to the degree of integration between acquisition and sustainment organizations. Four SPO organizations were involved in six case studies. This research focused on the way "seamless processes" affect the shifting of the organizational "center of gravity" within or between single manager organizations. An interview questionnaire was administered to 13 Product Center managers and 6 Logistics Center managers. The interview questions focused on IWSM in general, …


A Model For Forecasting Pollution Prevention Life Cycle Costs For Air Force Major Weapon Systems, Mark E. Garner, Jennifer S. Kirchoffer Sep 1995

A Model For Forecasting Pollution Prevention Life Cycle Costs For Air Force Major Weapon Systems, Mark E. Garner, Jennifer S. Kirchoffer

Theses and Dissertations

This research effort developed a modification to the HAZMAT program so that the program could provide the user with the capability to generate an estimate during the concept exploration and design phases for the total costs associated with hazardous materials usage in a major weapon system. Using the HAZMAT database, a spreadsheet was developed which projects a cost for a weapon system based on its total surface area and the number of aircraft to be produced by performing an analogy with a similar weapon system. The modification uses algorithm which are based on the hazardous material substances rather than processes …


A Study Of The Structural Limitation Affecting Implementation Of The Government Performance And Results Act In Air Force Materiel Command Logistics, Darwina M. Liguori Sep 1995

A Study Of The Structural Limitation Affecting Implementation Of The Government Performance And Results Act In Air Force Materiel Command Logistics, Darwina M. Liguori

Theses and Dissertations

This thesis provides an in-depth discussion of the Government Performance and Results Act (GPRA) of 1993. The GPRA is a new law that mandates strategic management be conducted in all federal government agencies. Soon all federal government agencies will be directed to comply with the requirements of the law and implement strategic management within their organizations. This study selected Air Force Materiel Command Headquarters (AFMC) logistics organizations and subordinate units as the test organization. Interviews were conducted with headquarters AFMC logistics and strategic planning personnel, as well as 88th Logistics Group personnel to evaluate several issues within their organization: (1) …


Optical Characterization Of Indium Arsenide Antimonide Semiconductors Grown By Molecular Beam Epitaxy, Michael A. Marciniak Sep 1995

Optical Characterization Of Indium Arsenide Antimonide Semiconductors Grown By Molecular Beam Epitaxy, Michael A. Marciniak

Theses and Dissertations

The material parameters and crystalline quality of undoped, MBE-grown InAs1-xSbx nearly lattice-matched to (100) GaSb (-0.617% ≤ Δ a-a ≤ +0.708%) similar to material used for mid-infrared semiconductor lasers were determined by optical characterization. Absorption measurements at temperatures between 6-295 K determined the energy gap and wavelength-dependent absorption coefficient for each sample. The compositional dependence of the energy gap was anomalous when compared to previously reported data, suggesting phase separation existed in the material. The samples were also studied by temperature- and excitation-dependent photoluminescence (PL), which, for the majority of cases, showed only a single band-edge peak, …


Nonlinear Geometric And Material Behavior Of Composite Shells With Large Strains, Scott A. Schimmels Aug 1995

Nonlinear Geometric And Material Behavior Of Composite Shells With Large Strains, Scott A. Schimmels

Theses and Dissertations

A two-dimensional, geometrically and materially nonlinear shell theory applicable to arbitrary geometries described by orthogonal curvilinear coordinates and encompassing large displacements, moderate rotations for large strain situations has been developed. Additionally, the theory includes Jacobian transformation matrices, based upon displacement parameters, for the Cauchy - 2nd Piola-Kirchhoff stress-state and the Cauchy (Almansi) - Green strain-state transformations, and a layered material approach is included for the elastoplastic analysis to allow for variation of plasticity through-the-thickness. Doubly curved 20, 28, and 36 degree-of-freedom finite elements are defined based on specialization of the theory to spherical coordinates. The computer program includes algorithms for …


Methods For Monitoring Process Control And Capability In The Presence Of Autocorrelation, Daniel J. Zalewski Aug 1995

Methods For Monitoring Process Control And Capability In The Presence Of Autocorrelation, Daniel J. Zalewski

Theses and Dissertations

When standard control charts are applied to a process whose measurements of quality exhibit autocorrelation, the performance of those charts can be considerably different than that expected when no autocorrelation is present. To model this performance, the existing definitions of assignable and chance causes of variation are extended to account for the variation induced by the autocorrelation structure. The application of statistical thinking toward continuous process improvement using the proposed taxonomy is discussed. A method to select control limits which yield a specified average run length in the absence of assignable causes of variation and which is suitable for use …


The Dependence Of The Time-Asymptotic Structure Of 3-D Vortex Breakdown On Boundary And Initial Conditions, Jeffrey C. Tromp Jul 1995

The Dependence Of The Time-Asymptotic Structure Of 3-D Vortex Breakdown On Boundary And Initial Conditions, Jeffrey C. Tromp

Theses and Dissertations

The three-dimensional, compressible Navier-Stokes equations are solved numerically to simulate vortex breakdown in tubes. Time integration is performed with an implicit Beam-Warming algorithm, which uses fourth-order compact operators to discretize spatial derivatives. Initial conditions are obtained by solving the steady, compressible, and axisymmetric form of the Navier-Stokes equations using Newton's method. Stability of the axisymmetric initial conditions is assessed through 3-D time integration. Unique axisymmetric solutions at a Reynolds number of 250 lose stability to 3-D disturbances at a critical value of vortex strength, resulting in 3-D and time-periodic flow. Axisymmetric solutions at a Reynolds number of 1000 contain regions …


Tolerance Theory Of Periodic Surfaces, James A. Godsey Jul 1995

Tolerance Theory Of Periodic Surfaces, James A. Godsey

Theses and Dissertations

Two formulations for the far field statistical average power pattern of a strip grating with errors in strip and slit width are presented. The first formulation utilizes the Born approximation in which the unknown aperture fields are replaced by the incident fields. The second formulation utilizes an approximation which satisfies the edge condition. Approximations for the scattered fields are first derived using PEC surface equivalence for a TEz polarized plane wave incident upon a strip grating consisting of an infinite PEC screen cut by a number of infinitely long slits. Babinet's principle is then used to obtain approximations for the …


Ohmic Contact To Ion Implanted Gallium Arsenide Antimonide For Application To Indium Aluminum Arsenide-Gallium Arsenide Antimonide Heterostructure Insulated-Gate Field Effect Transistors, Kenneth G. Merkel Ii Jul 1995

Ohmic Contact To Ion Implanted Gallium Arsenide Antimonide For Application To Indium Aluminum Arsenide-Gallium Arsenide Antimonide Heterostructure Insulated-Gate Field Effect Transistors, Kenneth G. Merkel Ii

Theses and Dissertations

The p-channel In0.52Al0.48As-GaAs1-xSbx heterostructure insulated-gate field effect transistor (p-HIGFET) is a candidate for complementary integrated circuits due to superior cutoff characteristics and low gate leakage current. Advancement of the In0.52Al0.48As-GaAs1-xSbx p-HIGFET requires improved source-drain design. Five main tasks were accomplished to achieve this goal. First, thermal limits of the In0.52Al0.48As-GaAs0.51Sb0.49 HIGFET were investigated. Second, the temperature dependence of band gap and impurity energies were determined for beryllium doped In0.52Al0.48. Third, high acceptor concentrations were obtained …


Effects Of Blowing Ratios On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Fu-Jung Chen Jun 1995

Effects Of Blowing Ratios On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Fu-Jung Chen

Theses and Dissertations

The effects of transpiration cooling on heat transfer in the throat region of a porous-walled nozzle were investigated. The experiments were performed in the AFIT low speed shock tube fitted with a Mach 2 nozzle. A blowing region was limited to the area from 1.3 cm prior to the throat to 1.2 cm downstream of the throat. The blowing ratios from -0.0002 (suction) to 0.0117 (blowing) of the main stream flow were studied. Heat flux data were taken from both sides of the nozzle. One side was transpiration cooled by secondary air injection through a porous wall, while the other …


Scattering From Finite By Infinite Periodic Arrays With Arbitrary Piecewise-Linear Slot Elements, Paul R. Barre Jun 1995

Scattering From Finite By Infinite Periodic Arrays With Arbitrary Piecewise-Linear Slot Elements, Paul R. Barre

Theses and Dissertations

A numerical model for analyzing electromagnetic scattering from a planar Frequency Selective Surface (FSS) is developed. The model can represent an FSS with multiple arrays of arbitrary piecewise linear scatterers in a stratified dielectric medium. The FSS's arrays are finite by infinite, accounting for edge effects, where a periodic array element is formed from the piecewise linear connection of thin slots in a groundplane. The stratified dielectric medium is defined as an arbitrary stack of lossless dielectric slabs that sandwich the user defined arrays, simulating an FSS. The Surface Equivalence theorem is used to construct an equivalent problem based on …


Optimal Mixed-Norm Control Synthesis For Discrete-Time Linear Systems, David R. Jacques Jun 1995

Optimal Mixed-Norm Control Synthesis For Discrete-Time Linear Systems, David R. Jacques

Theses and Dissertations

A mixed-norm approach to control synthesis for discrete time linear systems is developed. Specifically, the problem of minimizing the H2 norm of a transfer function, subject to a combination of ℓ1 and-or H∞ norm constraints on dissimilar but related transfer functions is considered. The uniqueness of the optimal solution is shown, and numerical methods for approximating the optimal solution to within arbitrary accuracy are developed. These methods generally result in high order compensators which can not be implemented in most practical applications. In response to this, a numerical method is developed which solves for suboptimal solutions of …


Determination Of The Temperature Coefficients Of Selected Material Constants Of Dilithium Tetraborate, Gregory S. Weaver Jun 1995

Determination Of The Temperature Coefficients Of Selected Material Constants Of Dilithium Tetraborate, Gregory S. Weaver

Theses and Dissertations

The first and second order temperature coefficients of the material constants cE11, cE12, cE44, cE66, and e15 of dilithium tetraborate (Li2B4O7) have been measured over a temperature range of 20°C to 150°C. An improved resonator method was used to measure the fundamental zero mass loading antiresonant frequencies of selected pure-mode orientations of Li2B4O7. Material constants extraction was performed using a linear least squares matrix method. The resulting material constant curves were fit with a third …


Design, Fabrication, Modeling, And Testing Of Surface-Micromachined Micromirror Devices, M. Adrian Michalicek Jun 1995

Design, Fabrication, Modeling, And Testing Of Surface-Micromachined Micromirror Devices, M. Adrian Michalicek

Theses and Dissertations

The Flexure-Beam Micromirror Device (FBMD) is a phase-only piston style spatial light modulator demonstrating properties which can be used for phase adaptive- corrective optics. This thesis presents a complete study of new designs of FBMDs and other micromirror devices, from original design considerations through final device testing and verification of ideal and advanced models. The models relate the electrical and mechanical properties of the device by equating the electrostatic force of a parallel- plate capacitor with the counteracting spring force of the device's support flexures. For the advanced model of the Flexure-Beam micromirror device, the capacitor solution is derived via …


Design And Development Of Microswitches For Micro-Electro-Mechanical Relay Matrices, Mark W. Phipps Jun 1995

Design And Development Of Microswitches For Micro-Electro-Mechanical Relay Matrices, Mark W. Phipps

Theses and Dissertations

Many different micro-electro-mechanical switches were designed in the Multi-User MEMS processes (MUMPs) and deep x-ray lithography and electroforming (LIGA) processes. The switches were composed of actuators that operated based upon either electrostatic forces or thermal forces. A thermally activated beam flexure actuator that operated based upon differential heating was used extensively. This actuator, which was fabricated in the MUMPs process, was able to deflect up to 12 microns with a total input power of less than 25 mW. The thermal resistance, which was needed to model this actuator, was determined from a material constant, 1.9 ± 0.08 m1.5-°C-W …


Identification And Evaluation Of Monitoring Techniques For The Performance Of A Communication Network, Maureen E. Borgia May 1995

Identification And Evaluation Of Monitoring Techniques For The Performance Of A Communication Network, Maureen E. Borgia

Theses and Dissertations

This study investigates the application of statistical process control methods to monitoring the performance of a communication network. The methods applied include four different types of control charts. The literature search uncovered only one previous study that used a control chart to monitor a communication network. Using a case study of a communication network, four important issues for proper control chart usage are emphasized. These issues are: proper data collection rate due to autocorrelation, proper subgrouping of the data, ensuring that count data conforms to the assumptions of the binomial probability model before implementing p or np control charts, and …


A Robust Method Of Solving Nonlinear Boundary Value Problems Via Modified Compromise Programming, John L. Zornick May 1995

A Robust Method Of Solving Nonlinear Boundary Value Problems Via Modified Compromise Programming, John L. Zornick

Theses and Dissertations

This study is an extension of Ng's previous work in which goal programming was used to determine an approximate solution to a boundary value problem. This approach follows the same basic approach developed by Ng in which the method of collocation was recast as a compromise programming model. Hence, instead of solving a system of simultaneous nonlinear equations, one seeks a compromise solution which minimizes (in a weighted residual sense) a vector norm of the differential equation residuals. A difference in this approach is that it makes use of a genetic algorithm as the optimizing engine as opposed to the …


Compressible Turbulence Measurement In Low-Angle Injection Into A Supersonic Flow, Gregory J. Mccann Mar 1995

Compressible Turbulence Measurement In Low-Angle Injection Into A Supersonic Flow, Gregory J. Mccann

Theses and Dissertations

Mean flow and compressible turbulence measurements have been obtained at two stations downstream of low-angle supersonic injection into a Mach 3.0 flow (Re/m = 15 x 106). Data were collected using conventional Pitot and cone-static probes, single and multiple overheat cross-wire anemometry, and flow visualization techniques (shadowgraphs and schlierens). A direct measure of total Reynolds shear stress was accomplished using a turbulence transformation of the Reynolds-averaged Navier-Stokes equations. Results show compressibility effects, indicated by density fluctuations, to be large relative to the velocity fluctuations and on the same order in all three components. Compressibility appears to account for …


Selecting Optimal Experiments For Feedforward Multilayer Perceptrons, Lisa M. Belue Mar 1995

Selecting Optimal Experiments For Feedforward Multilayer Perceptrons, Lisa M. Belue

Theses and Dissertations

Where should a researcher conduct experiments to provide training data for a multilayer perceptron? This question is investigated and a statistically-based method for optimally selecting experimental design points for multilayer perceptrons is introduced. Specifically, a criterion is developed based on the size of an estimated confidence ellipsoid for the weights in the multilayer perceptron. This criterion is minimized over a set of exemplars to find optimal design points. Initially, single output networks are examined. An example is used to demonstrate the superiority of optimally selected design points over randomly chosen points and points chosen in a grid pattern. Also, two …


Applications Of Statistical Process Control In Monitoring Aircrew Bombing Proficiency, Kirk G. Horton Mar 1995

Applications Of Statistical Process Control In Monitoring Aircrew Bombing Proficiency, Kirk G. Horton

Theses and Dissertations

The current tools used by squadron supervisors to monitor the bombing performance of aircrews flying F-111E aircraft are monthly reports that have little predictive capability. No real-time methodology exists for monitoring and predicting aircrew bombing performance and preventing bombing problems that might cause an individual to become unqualified. It has been suggested that Statistical process Control (SPC) can be applied to the bombing process to develop tools for managing the process, correcting problems, and improve the bombing performance of a squadron. This study investigates the application of SPC to the bombing process. It examines data taken from an F-111E Fighter …


Life-Cycle Cost Analysis For Radioactive Waste Remediation Alternatives, Thomas P. White, Ronald J. Toland, Dorian Y. Buitrago Mar 1995

Life-Cycle Cost Analysis For Radioactive Waste Remediation Alternatives, Thomas P. White, Ronald J. Toland, Dorian Y. Buitrago

Theses and Dissertations

This research has two primary objectives. The first is to develop a generic, interactive, spreadsheet-based life-cycle cost model that uses net present value and risk analysis techniques for cost comparison. The second is to apply the model specifically to the vitrification and cementation methods of waste remediation. By using spreadsheet analysis and graphics capabilities, the model will provide direct and objective comparisons of remediation alternatives. Since vitrification is a new technology, the plant design and operations are conceptual. Therefore, computer simulation and engineering judgement are integral to the vitrification LCC estimate.