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Air Force Institute of Technology

1998

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Articles 1 - 30 of 75

Full-Text Articles in Engineering

Three-Dimensional Calculation Of Contaminant Transport In Groundwater At A Dover Afb Site, Tariq O. Hashim Dec 1998

Three-Dimensional Calculation Of Contaminant Transport In Groundwater At A Dover Afb Site, Tariq O. Hashim

Theses and Dissertations

Macroscale rate-limited sorption modeling was tested using a production transport code, the GMS/FEMWATER ground-water modeling package. The code (Version 1.1 of FEMWATER. dated 1 August 1995) was applied to a 3D conceptual model developed from a field site at Dover AFB, DE. A simulation was performed of a 200 hour contaminant injection pulse followed by clean water flushing. A moment analysis performed on the resulting breakthrough curve validated code self-consistency. Another injection pulse simulation showed that retardation temporally delays the breakthrough peak. Transport simulations of pulsed clean water pumping of the test cell with a prescribed initial contaminant distribution demonstrated …

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Development Of An Operations Research Software Package For Army Divisions., Blane C. Wilson Dec 1998

Development Of An Operations Research Software Package For Army Divisions., Blane C. Wilson

Theses and Dissertations

There exists great potential for applying operations research techniques to solve specific problems in the areas of operations, installation support, and training at the Army division level. Because of the operational tempo of today's active-duty and reserve component units, command must focus on accomplishing the daily missions. Also, due their limited knowledge of the field, planners may not be aware of how operations research can be used to enhance planning and operations. Time, training funds, resources, safety, personnel, and equipment are all critical factors in this process. Operations research techniques could be used to improve division-level operations by saving time, …

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Design Of The Computer Subsystem For The Afit Simulation Satellite (Simsat), Michael P. Hanke Dec 1998

Design Of The Computer Subsystem For The Afit Simulation Satellite (Simsat), Michael P. Hanke

Theses and Dissertations

This document details the systematic development of the computer subsystem for the AFIT Simulation Satellite (SIMSAT) from Concept Exploration to Implementation. This subsystem design effort was conducted as part of a larger four-phase team design effort to implement a fully functional, user-friendly test facility to meet current AFIT teaching and research requirements. Once SIMSAT system integration is complete, control laws will execute on the free-floating "satellite" to reduce communication systems overhead and its impact on control law execution, thereby allowing for more robust control system development and execution. Control law development, simulation, and interactive control of the system will occur …

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Feature Saliency In Artificial Neural Networks With Application To Modeling Workload, Kelly A. Greene Dec 1998

Feature Saliency In Artificial Neural Networks With Application To Modeling Workload, Kelly A. Greene

Theses and Dissertations

This dissertation research extends the current knowledge of feature saliency in artificial neural networks (ANN). Feature saliency measures allow for the user to rank order the features based upon the saliency, or relative importance, of the features. Selecting a parsimonious set of salient input features is crucial to the success of any ANN model. In this research, several methodologies were developed using the Signal to Noise Ratio (SNR) Feature Screening Method and its associated SNR Saliency Measure for selecting a parsimonious set of salient features to classify pilot workload in addition to air traffic controller workload. Candidate features were derived …

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How To Develop An Interactive Electronic Technical Manual: An Industry Perspective, Ali N. Karabulut, Hilmi Oz Dec 1998

How To Develop An Interactive Electronic Technical Manual: An Industry Perspective, Ali N. Karabulut, Hilmi Oz

Theses and Dissertations

Improvements in technology, especially in computer science, in the last two decades have made it possible, and preferable to develop digital technical manuals. A digital manual, which is called an Interactive Electronic Technical Manual (IETM), is a package of information required for the diagnosis and maintenance of a weapon systems, optimally arranged and formatted for interactive screen presentation to the end-user. Being the largest organization in the U.S., the Department of Defense has pioneered in the development of IETM concept as well as in the establishment of its standards. There have been many researches done about different IETM applications and …

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Development Of A Discrete Ordinates Code System For Unstructured Meshes Of Tetrahedral Cells, With Serial And Parallel Implementations, Rodney L. Miller Nov 1998

Development Of A Discrete Ordinates Code System For Unstructured Meshes Of Tetrahedral Cells, With Serial And Parallel Implementations, Rodney L. Miller

Theses and Dissertations

A numerically stable, accurate, and robust form of the exponential characteristic (EC) method, used to solve the time-independent linearized Boltzmann Transport Equation, is derived using direct affine coordinate transformations on unstructured meshes of tetrahedra. This quadrature, as well as the linear characteristic (LC) spatial quadrature, is implemented in our transport code, called TETRAN. This code solves multi-group neutral particle transport problems with anisotropic scattering and was parallelized using High Performance Fortran and angular domain decomposition. A new, parallel algorithm for updating the scattering source is introduced. The EC source and inflow flux coefficients are efficiently evaluated using Broyden's rootsolver, started …

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An Integer Program Decomposition Approach To Combat Planning, John C. Van Hove Sep 1998

An Integer Program Decomposition Approach To Combat Planning, John C. Van Hove

Theses and Dissertations

Over the last two decades, our military forces have been working to incorporate the latest computer technology into the combat planning process. The earliest efforts use word processors, spreadsheets, and databases to organize planning data and to display high level summaries for commanders. Later efforts perform feasibility checks as missions are planned to insure that the necessary resources are available and that the assets requested are capable of meeting the assigned scheduling requirements. Some of the most recent computer planning tools have included the capability to automatically plan individual missions or groups of missions. These automated efforts have been heuristic …

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Data Storage Devices For Air Force Space Command: A Comparative Analysis, Darryl E. Mosley Sep 1998

Data Storage Devices For Air Force Space Command: A Comparative Analysis, Darryl E. Mosley

Theses and Dissertations

Two of Air Force Space Command's primary missions are ballistic missile warning and global navigation, accomplished by commanding and controlling Defense Support Program and Global Positioning System satellites respectively. The computerized ground control system, called the satellite command and control system (CCS) used to perform command and control of the satellites currently uses antiquated peripheral storage devices. These storage devices are critical components, but are often prone to failure, possibly resulting in adverse mission impact. The Air Force must choose an alternative storage device for use in conjunction with CCS in order to accommodate planned operations tempo increases. This thesis …

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A Comparison Of 8-Hour Vs. 12-Hour Shifts On Performance, Health And Safety In A Usaf Aircraft Maintenance Squadron, Kelly J. Scott Sep 1998

A Comparison Of 8-Hour Vs. 12-Hour Shifts On Performance, Health And Safety In A Usaf Aircraft Maintenance Squadron, Kelly J. Scott

Theses and Dissertations

This study examined the effects of converting a large USAF aircraft maintenance squadron from an 8- hour shift system to a 12-hour shift system. In 1996, the squadron converted its 24-hour operations from three 8-hour work shifts, to two 12-hour work shifts with compressed work weeks. The squadron maintained 12-hour shifts for 19 consecutive months. A comparison was made of organizational performance, worker health and safety measures before, during and after 12-hour shift implementation. Findings indicated that changing from 8- to 12-hour shifts resulted in a slight increase in aircraft Mission Capability rates. However, this benefit appears to have come …

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Effects Of Shiftwork On Air Force Aircraft Maintenance Personnel, Craig A. Campbell Sep 1998

Effects Of Shiftwork On Air Force Aircraft Maintenance Personnel, Craig A. Campbell

Theses and Dissertations

This study examined the effects of converting a large aircraft maintenance squadron from 8-hour shifts to 12-hour shifts. The squadron studied converted its 24- hour maintenance work force from three 8-hour work shifts to two 12-hour work shifts incrementally, with one section converting to 12-hour shifts in January, 1996, and the remaining section converting in July, 1996. Both sections remained on 12-hour shifts until September, 1997, when both sections converted back to a three shift 8-hour operation. Health and well being, on- and off-duty accident rates, day shift vs. night shift accident rates, and the effects of stress and fatigue …

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Feasibility Study On The Use Of The Internet For Traffic Of Unclassified Data, Alexandre L. Guerra, Luiz Gustavo F. P. Silva Sep 1998

Feasibility Study On The Use Of The Internet For Traffic Of Unclassified Data, Alexandre L. Guerra, Luiz Gustavo F. P. Silva

Theses and Dissertations

This research compares two possible networking methods for connecting all Brazilian Air Force Materiel Command units responsible for support and operation of Brazilian Air Force's weapons systems. The network includes the use of dedicated X.25 links, and the use of a virtual Private Network using the Internet (TCP/IP) as the medium of transmission. The Brazilian Air Force Materiel Command, responsible to support operating units over a very large sparse territory, lacks an efficient media of computer communications, which makes it difficult to control the supply chain channels of materiel present in each unit, depots, and warehouses. We studied the network …

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Automatic Target Cueing Of Hyperspectral Image Data, Terry A. Wilson Sep 1998

Automatic Target Cueing Of Hyperspectral Image Data, Terry A. Wilson

Theses and Dissertations

Modern imaging sensors produce vast amounts data, overwhelming human analysts. One such sensor is the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) hyperspectral sensor. The AVIRIS sensor simultaneously collects data in 224 spectral bands that range from 0.4µm to 2.5µm in approximately 10nm increments, producing 224 images, each representing a single spectral band. Autonomous systems are required that can fuse "important" spectral bands and then classify regions of interest if all of this data is to be exploited. This dissertation presents a comprehensive solution that consists of a new physiologically motivated fusion algorithm and a novel Bayes optimal self-architecting classifier …

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Value Of Increased Use Of Scheduled Maintenance On Aircraft Availability And Maintenance Cost Of The C-5, William T. Webb Sep 1998

Value Of Increased Use Of Scheduled Maintenance On Aircraft Availability And Maintenance Cost Of The C-5, William T. Webb

Theses and Dissertations

The C-5 consistently performs below its established mission capable rate of 75 percent. The purpose of this study was to investigate whether or not mission capable rates and maintenance costs can be improved by increased use of scheduled maintenance. Nine C-5 components were studied. Availability and cost were compared when scheduled replacement occurred at ten, twenty, and thirty percent before their respective mean time between failure and actual failure times. Actual failure times were not available so they were generated using simulation. The trade-off of using preventive maintenance is the decreased cost of sending fewer maintenance repair teams and increased …

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The Effects Of Three Media Presentation Systems On Maintenance Task Performance, John W. Chastain Sep 1998

The Effects Of Three Media Presentation Systems On Maintenance Task Performance, John W. Chastain

Theses and Dissertations

Wearable computers and Portable Maintenance Aids (PMAs) may soon be the normal way of doing aircraft maintenance in the Air Force. Currently, the Air Force uses the paper form of Technical Orders (TO's) while doing aircraft maintenance. The purpose of this thesis was to compare the effects of three different media presentations of the information used during aircraft maintenance. The three different presentations compared are the current paper form, a Head Mounted Display (HMD), and an auditory mode. An experiment was conducted to determine if there was a significant difference between the systems (in terms of task completion times and …

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Analysis Of Usaf Medium And Heavylift Space Launch Mission Reliability Requirements, Arthur R. Dawkins Sep 1998

Analysis Of Usaf Medium And Heavylift Space Launch Mission Reliability Requirements, Arthur R. Dawkins

Theses and Dissertations

The launch services that the USAF procures to carry DOD payloads into orbit are characterized by high risks and high costs. If a launch vehicle experiences a catastrophic failure, the cost of the entire launch vehicle, the launch processing, and the payload are completely lost (often in excess of 1,5 billion dollars.) Despite this enormous risk for the payload customer, and indeed the launch provider, launch success rates around the world are not much above 90 percent. The current USAF medium and heavylift launch systems are often based on technology that is 20 years old and older. Furthermore, little historical …

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Electro-Mechanical Fatigue Behavior Of A Quasi-Isotropic Laminate With An Embedded Piezoelectric Actuator, Tse Lin Hsu Sep 1998

Electro-Mechanical Fatigue Behavior Of A Quasi-Isotropic Laminate With An Embedded Piezoelectric Actuator, Tse Lin Hsu

Theses and Dissertations

This study primarily investigated the electro-mechanical fatigue behavior of the embedded piezoelectric actuators in graphite/epoxy laminate with a lay-up of 0 | ± 45 | 90s. A secondary focus was the investigation of the mechanical fatigue effects of the 0 | 0 | ± 45 | 0 | 0 | 90s laminate with embedded PZT under tensile loading. All the fatigue tests were conducted with a triangular loading waveform which had a frequency of 10 Hz and with R=0. 1. In the electro-mechanical testing, the embedded actuator was excited by a -10 V to -100 V or a 10 V …

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An Examination Of The United States Air Service's Logistics Operations, Andrew W. Hunt Sep 1998

An Examination Of The United States Air Service's Logistics Operations, Andrew W. Hunt

Theses and Dissertations

This historical study details the U.S. Air Service's logistics operations at home and abroad in an attempt to determine the relationship between the process and more recently established logistic principles. The information in the study was collected through an extensive review of both first hand accounts and historical compilations of the nature of World War I aviation logistics. Information regarding the production of the De Haviland DH-4 and Liberty Engine serve as the primary case examples of the operation of the logistics system. The established principles required for comparison were extracted from the writings of a number of expert military …

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Monotonic And Fatigue Behavior Of 2-D Woven Ceramic Matrix Composite At Room And Elevated Temperatures (Blackglas/Nextel 312), Musa Al-Hussein Sep 1998

Monotonic And Fatigue Behavior Of 2-D Woven Ceramic Matrix Composite At Room And Elevated Temperatures (Blackglas/Nextel 312), Musa Al-Hussein

Theses and Dissertations

This study investigated the monotonic tension and compression and the tension-tension and tension-compression fatigue loading of Blackglas/Nextel 312 woven CMC at room temperature and at 760 degrees centigrade. Young's Modulus and strain variation were evaluated. S-N curves were obtained for room and elevated temperatures. The ultimate tensile stress was lower at the elevated temperature and it was higher in the compression test. Failure-strain was higher at the elevated temperature in both tension and compression tests. There was no significant change in Young's Modulus at the elevated temperature. Also, there was no difference in the number of cycles to failure at …

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Global Positioning System (Gps) Receiver Design For Multipaths Mitigation, El-Sayed Abdel-Salam Gadallah Aug 1998

Global Positioning System (Gps) Receiver Design For Multipaths Mitigation, El-Sayed Abdel-Salam Gadallah

Theses and Dissertations

Multipath effects are a source of error degrading the accuracy of DGPS signal processing. The statistical models of multipath are determined by user location and, in addition are time varying. There is no unified statistical model for the multipath signal. Therefore the solution of the multipath problem using statistical models is difficult. This research introduces a new estimator that can detect the presence of multipath, can determine the unknown number of multipath components and can estimate multipath parameters in the GPS receiver (time delay and attenuation coefficients). Furthermore the multipath signal parameters are estimated at any instant of observation. The …

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Representations, Approximations, And Algorithms For Mathematical Speech Processing, Laura R. Suzuki Jun 1998

Representations, Approximations, And Algorithms For Mathematical Speech Processing, Laura R. Suzuki

Theses and Dissertations

Representing speech signals such that specific characteristics of speech are included is essential in many Air Force and DoD signal processing applications. A mathematical construct called a frame is presented which captures the important time-varying characteristic of speech. Roughly speaking, frames generalize the idea of an orthogonal basis in a Hilbert space, Specific spaces applicable to speech are L2(R) and the Hardy spaces Hp(D) for p> 1 where D is the unit disk in the complex plane. Results are given for representations in the Hardy spaces involving Carleson's inequalities (and its extensions), …

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Development And Packaging Of Microsystems Using Foundry Services, Jeffrey T. Butler Jun 1998

Development And Packaging Of Microsystems Using Foundry Services, Jeffrey T. Butler

Theses and Dissertations

Micro-electro-mechanical systems (MEMS) are a new and rapidly growing field of research. Several advances to the MEMS state of the art were achieved through design and characterization of novel devices. Empirical and theoretical model of polysilicon thermal actuators were developed to understand their behavior. The most extensive investigation of the Multi-User MEMS Processes (MUMPs) polysilicon resistivity was also performed. The first published value for the thermal coefficient of resistivity (TCR) of the MUMPs Poly 1 layer was determined as 1.25 x 10(exp -3)/K. The sheet resistance of the MUMPs polysilicon layers was found to be dependent on linewidth due to …

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High Amplitude Tracking Control, Joseph W. Mcnamee Jun 1998

High Amplitude Tracking Control, Joseph W. Mcnamee

Theses and Dissertations

The problem of tracking control in the face of high amplitude dynamic reference signals, hard state and control constraints, and open-loop unstable plants is investigated. Saturation effects mitigation is a current research topic, and a large body of literature exists which addresses this problem. However, with a few notable exceptions, little work has been accomplished which is applicable to the problem of high amplitude dynamic reference signal tracking in the face of hard state and control constraints, and open-loop unstable plants. Moreover, methods that do address the stated problem generally limit the exogenous reference signal to statically admissible values to …

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Wind Tunnel Testing For Drag Reduction Of An Aircraft Laser Turret, Christopher H. Snyder Jun 1998

Wind Tunnel Testing For Drag Reduction Of An Aircraft Laser Turret, Christopher H. Snyder

Theses and Dissertations

This study investigated the use of aft-mounted fairings and splitter plates to reduce the drag of a half-scale aircraft laser turret. Forces, moments, and pressure distributions were measured in the AFIT 1.5-m (5-ft) wind tunnel at Reynolds numbers between 3x10 to the 5th power and 9x10 to the 5th power based on the turret diameter. Oil traces indicated the nature of the flow near the surface of the unmodified turret and the surrounding area. Tufts placed on the turret, fairings, and splitter plates showed changes in separation regions when configurations were changed. The flow around the turret was characterized by …

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Singularity Avoidance Strategies For Satellite Mounted Manipulators Using Attitude Control, Nathan A. Titus Jun 1998

Singularity Avoidance Strategies For Satellite Mounted Manipulators Using Attitude Control, Nathan A. Titus

Theses and Dissertations

Control concepts for satellite mounted manipulators (SMM) are examined. The primary focus is on base actuated concepts, which eliminate singularity problems associated with free floating SMMs. A new form of the equations of motion for an n-link SMM is developed using a quasi coordinate form of Lagrange's Equation. Alternative free floating SMM designs are presented which eliminate dynamic singularities, but still experience difficulties due to the unactuated base. A new generic SMM controller is developed as a framework for various control concepts with and without base actuation. Momentum constrained Jacobians are shown to produce better SMM tracking than fixed base …

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Effects Of Clutter Height Distribution On Adaptive Clutter Erasure Performance, Kelce Steven Wilson Jun 1998

Effects Of Clutter Height Distribution On Adaptive Clutter Erasure Performance, Kelce Steven Wilson

Theses and Dissertations

A new real beam interferometric processing technique, called Adaptive Clutter Erasure (ACE), is investigated for applicability to ground clutter suppression in airborne radar systems. By analysis and simulation, the viability of the ACE concept as a next generation clutter suppression technique is demonstrated to achieve performance enhancements commensurate with currently implemented techniques. Research results indicate the ACE concept provides a reliably consistent 10dB Signal-to-Clutter Ratio (SCR) advantage over the APG-63, an operational radar system used for baseline comparison. ACE system concept development and performance predictions are conducted in conformity with the physical and operational design parameters of the APG-63, namely …

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The Scheduling Process In A Depot From The Brazilian Air Force, Fabricio J. Saito Jun 1998

The Scheduling Process In A Depot From The Brazilian Air Force, Fabricio J. Saito

Theses and Dissertations

The Brazilian Air Force (BAF) in its logistic structure contains 5 Air Logistic Centers (depots). This thesis concentrates its analysis on one of the most important BAF depots located at Sao Paulo (PAMASP). This thesis explores the scheduling process currently used in PAMASP. This thesis adopted a managerial approach in a sense that it looked to take a big picture of the current process. The researcher performed field interviews with the goal of describing the process. During the visit to PAMASP, the researcher also gathered problems related to the process. The recommendations stated on this study were based on the …

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The T-27 "Tucano" Engine Pipeline Of The Brazilian Air Force: A Managerial Approach, Jorge Barros Santos Jun 1998

The T-27 "Tucano" Engine Pipeline Of The Brazilian Air Force: A Managerial Approach, Jorge Barros Santos

Theses and Dissertations

The T-27 is a Brazilian-made aircraft, manufactured by "Empresa Brasileira de Aeronautica - EMBRAER". The purpose of this study is to describe the processes that take place in the logistic pipeline of the T-27 Engine. With the objective of identifying any existent bottlenecks and suggests managerial approaches to improve the overall system performance.

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Trigonometric Transforms For Image Reconstruction, Thomas M. Foltz Jun 1998

Trigonometric Transforms For Image Reconstruction, Thomas M. Foltz

Theses and Dissertations

This dissertation demonstrates how the symmetric convolution-multiplication property of discrete trigonometric transforms can be applied to traditional problems in image reconstruction with slightly better performance than Fourier techniques and increased savings in computational complexity for symmetric point spread functions. The fact that the discrete Fourier transform a circulant matrix provides an alternate way to derive the symmetric convolution-multiplication property for discrete trigonometric transforms. Derived in this manner, the symmetric convolution-multiplication property extends easily to multiple dimensions and generalizes to multidimensional asymmetric sequences. The symmetric convolution-multiplication property allows for linear filtering of degraded images via point-by-point multiplication in the transform domain …

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Parallel Implementation Of An Artificial Neural Network Integrated Feature And Architecture Selection Algorithm, Craig W. Rizzo Mar 1998

Parallel Implementation Of An Artificial Neural Network Integrated Feature And Architecture Selection Algorithm, Craig W. Rizzo

Theses and Dissertations

The selection of salient features and an appropriate hidden layer architecture contributes significantly to the performance of a neural network. A number of metrics and methodologies exist for estimating these parameters. This research builds on recent efforts to integrate feature and architecture selection for the multilayer perceptron. In the first stage of work a current algorithm is developed in a parallel environment, significantly improving its efficiency and utility. In the second stage, improvements to the algorithm are proposed. With regards to feature selection, a common random number (CRN) addition is proposed. Two new methods of architecture selection are examined, to …

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The Application Of Statistical Sampling Techniques To The Operational Readiness Inspection, Troy L. Dixon, Timothy S. Madgett Mar 1998

The Application Of Statistical Sampling Techniques To The Operational Readiness Inspection, Troy L. Dixon, Timothy S. Madgett

Theses and Dissertations

A Blue Ribbon Commission report to the Air Force Chief of Staff in February 1997 makes several specific recommendations on the conduct of Operational Readiness Inspections. This thesis develops a solution to one of the recommendations of that report; utilize scientifically based sampling techniques to reduce the footprint of the inspection on an evaluated unit. Acceptance sampling, common in industry, is developed for use in the environment of the Operational Readiness Inspection. The time saved from this more efficient sampling practice reduces Inspector General time at an evaluation, decreases the footprint, and answers the specific recommendations of the Blue Ribbon …

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