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Air Force Institute of Technology

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Articles 4471 - 4500 of 5699

Full-Text Articles in Engineering

Applying Cross-Decking And Activity-Based Costing To Military Distribution Centers: A Proposed Framework, Jonathan P. Elliott, Dwight H. Hintz Jr. Sep 1997

Applying Cross-Decking And Activity-Based Costing To Military Distribution Centers: A Proposed Framework, Jonathan P. Elliott, Dwight H. Hintz Jr.

Theses and Dissertations

Current events and fiscal constraints have focused DoD planners' attention on reducing logistics costs and improving efficiency while maintaining effective combat operations support. Military leaders are seeking private industry best practices that may help the DoD achieve these goals. Two commercially successful business practices that may help the DoD achieve its goals are cross-docking and Activity-Based Costing (ABC). Cross-docking is a commercially proven approach to material distribution through a distribution center that can help reduce inventories, speed material flows, and cut related logistics activity costs. However, the DoD is faced with the challenge of costing current and potential logistics processes …

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Reorientations Of Flexible Spacecraft Using Momentum Exchange Devices, Kevin A. Ford Sep 1997

Reorientations Of Flexible Spacecraft Using Momentum Exchange Devices, Kevin A. Ford

Theses and Dissertations

We study rest-to-rest reorientations of flexible spacecraft using momentum exchange devices. A new and concise form of the equations of motion for a rigid body containing a cluster of gimbaled momentum wheels is developed using the Euler-Newton approach. Special restrictions of the gimbaled momentum wheel equations yield equations of motion for the momentum wheel cluster and the control moment gyroscope cluster. A mathematical model of a free spacecraft with Euler-Bernoulli appendages is developed. Using the assumed modes method, a complete set of equations is developed which describes the dynamics of a spacecraft with flexible appendages and gimbaled momentum wheels. Special …

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Predicting Mishap Rates At Closing Usaf Maintenance Depots, Douglas E. Mcclain Sep 1997

Predicting Mishap Rates At Closing Usaf Maintenance Depots, Douglas E. Mcclain

Theses and Dissertations

It is clear that the Department of Defense and the USAF, in an effort to cut costs, will continue to reduce infrastructure through base closures. This has particular implications to the civilian employee who will likely lose his or her job. The purpose of this study was to review the most recent literature relating to safety and industrial facility closures and develop a theoretical model for predicting accident or mishap rates. From the literature reviewed, a theoretical model is proposed containing five candidate variables intended to measure; perceived adequacy of employee safety training, perceived safety culture, perceived safety climate, self-reported …

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Comparison Of Effects Of Change From 8 To 12 Hour Shifts On Air Force Aircraft Maintenance Workers, Daniel W. Overland Sep 1997

Comparison Of Effects Of Change From 8 To 12 Hour Shifts On Air Force Aircraft Maintenance Workers, Daniel W. Overland

Theses and Dissertations

This study examined the effects of converting from an 8 hour shift system to a 12 hour system on aircraft maintenance personnel. The squadron had converted its 24 hour operations from an 8 hour shift schedule to a 12 hour shift schedule in stages, changing one group first and then another. A smaller third group of workers remained on 8 hour shifts. Individual differences in job related outcomes and situational constraints were measured for all three groups. Results showed that changing from 8 to 12 hour shifts affected worker well-being and morale, as indicated by an increase in hospital visits …

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Parameter Estimation For Real Filtered Sinusoids, Daniel R. Zahirniak Sep 1997

Parameter Estimation For Real Filtered Sinusoids, Daniel R. Zahirniak

Theses and Dissertations

This research develops theoretical methods for parameter estimation of filtered, pulsed sinusoids in noise and demonstrates their effectiveness for Electronic Warfare EW applications. Within the context of stochastic modeling, a new linear model, parameterized by a set of Linear Prediction LP coefficients, is derived for estimating the frequencies of filtered sinusoids. This model is an improvement over previous modeling techniques since the effects of the filter and the coefficients upon the noise statistics are properly accounted for during model development. From this linear model, a relationship between LP coefficient estimation and Maximum Likelihood ML frequency estimation is derived and several …

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Foreign Military Sales Supply Support: Is There A Better Way?, Eric G. Ellmyer, Won Joon Jang Sep 1997

Foreign Military Sales Supply Support: Is There A Better Way?, Eric G. Ellmyer, Won Joon Jang

Theses and Dissertations

In today's world of declining defense budgets, there is an increasing need for South Korea to ensure they obtain the best dollar value when procuring defense articles. With the increasing financial situation, the purpose of this thesis is to research a surrogate third party firm and determine to what degree South Korea and other foreign military sales customers obtain the best value for their money for follow-on support item procurements. South Korea has participated in the Parts and Repair Ordering System program since its inception. However, South Korea has received little, if any, feedback regarding lead time and cost performance …

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A Comparison Of The Military's Organic Movement And Commercial Express Carriers, Travis E. Condon, Kirk A. Patterson Sep 1997

A Comparison Of The Military's Organic Movement And Commercial Express Carriers, Travis E. Condon, Kirk A. Patterson

Theses and Dissertations

The DoD has begun outsourcing airlift in order to expedite high priority cargo movement. However, are commercial express carriers more expedient in the cargo delivery than the Air Force organic transportation system? Although anecdotal evidence suggests commercial carriers are faster, little empirical research has been conducted on this subject. This study compares the military's organic transportation system with Federal Express in the delivery of high priority cargo to Spangdahlem Air Base, Germany. The Large Sample Test of Hypothesis was used to determine if there was a significant difference between the cargo transit times of the two. The mean delivery time …

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Modeling Intelligent Control Of Distributed Cooperative Inferencing, Edward M. Williams Sep 1997

Modeling Intelligent Control Of Distributed Cooperative Inferencing, Edward M. Williams

Theses and Dissertations

The ability to harness different problem-solving methods together into a cooperative system has the potential for significantly improving the performance of systems for solving NP-hard problems. The need exists for an intelligent controller that is able to effectively combine radically different problem-solving techniques with anytime and anywhere properties into a distributed cooperative environment. This controller requires models of the component algorithms in conjunction with feedback from those algorithms during run-time to manage a dynamic combination of tasks effectively. This research develops a domain-independent method for creating these models as well as a model for the controller itself. These models provide …

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Experimental Investigation Of Nonlinear Dynamics In Single Mode Semiconductor Laser Diodes With Phase Conjugate Feedback, Gordon T. Hengst Aug 1997

Experimental Investigation Of Nonlinear Dynamics In Single Mode Semiconductor Laser Diodes With Phase Conjugate Feedback, Gordon T. Hengst

Theses and Dissertations

The semiconductor laser diode offers a unique system to investigate nonlinear dynamics when optical feedback is applied. Although there is extensive research of laser diodes with optical feedback from normal dielectric mirrors, very little has been done experimentally to analyze the effects of degenerate phase conjugate feedback from a BaTiO3 crystal. This research experimentally investigated the dynamics of a single-mode laser diode with weak phase conjugate feedback using both the self-pumped and double phase conjugate geometries. The experimental results validated a mathematical model which numerically evaluates the Lang-Kobayahsi coupled differential equations. The model simulated the nonlinear behavior of a …

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A Value Function Approach To Information Operations Moe's: A Preliminary Study, Michael P. Doyle, Richard F. Deckro, Jack M. Kloeber Jr., Jack A. Jackson Jr., Center For Modeling, Simulation, And Analysis, Air Force Institute Of Technology Jul 1997

A Value Function Approach To Information Operations Moe's: A Preliminary Study, Michael P. Doyle, Richard F. Deckro, Jack M. Kloeber Jr., Jack A. Jackson Jr., Center For Modeling, Simulation, And Analysis, Air Force Institute Of Technology

AFIT Documents

A value focused thinking approach is applied to information operations. A preliminary value hierarchy for information operations is constructed by extracting the values of senior military leadership from existing doctrine. To identify these key values for information operations, applicable existing doctrine was reviewed and summarized. Additionally, hierarchical representations of the values represented within each reviewed doctrine are developed. A value hierarchy requires that supporting objectives be mutually exclusive and collectively exhaustive. Within this analysis, these requirements are enforced, in part, by developed definitions which serve as tests to maintain mutual exclusivity. An exhaustive set of supporting values is also guaranteed …

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Diffraction Analysis And Tactical Applications Of Signal Propagation Over Rough Terrain, You-Cheol Jang Jun 1997

Diffraction Analysis And Tactical Applications Of Signal Propagation Over Rough Terrain, You-Cheol Jang

Theses and Dissertations

The free space propagation model is inadequate to predict the mean path-loss in ground wireless communication. Also, many existing propagation channel models do not adequately predict path-loss in rough terrain because most of them were based on measurements in urban areas. Hence, a channel model that estimates mean path-loss over many different kinds of terrain conditions is desired. In this thesis, two new propagation channel models, Real Terrain Diffraction Model (RTDMOD) and Universal Terrain Channel Model (UTCMOD), were developed. Other geometric theory of diffraction (GTD) methods (Epstein-Peterson (EP) and Deygout (DG)) agree within 5 % from 3 MHz to 3GHz …

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Analysis Of Tethers In Sampling Near Earth Objects, John W. Wong Jun 1997

Analysis Of Tethers In Sampling Near Earth Objects, John W. Wong

Theses and Dissertations

This study investigated the feasibility of a SAIC proposal to sample Near Earth Objects (NEOs) from an orbiting spacecraft using a tethered landing device. The parameters for suitable targets were derived from an analysis of a proposed point design as applied to current knowledge of NEOs. Tether strength and lifetime for the point design were also assessed. First order modeling of tether dynamics showed that deployment and attachment to a NEO are feasible. The dynamics of retrieving a sample via a crawler unit which crawls up the tether requires further exploration.

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Thickness Effects On A Cracked Aluminum Plate With Composite Patch Repair, Joel J. Schubbe Jun 1997

Thickness Effects On A Cracked Aluminum Plate With Composite Patch Repair, Joel J. Schubbe

Theses and Dissertations

Post-repair fatigue crack growth was investigated in 3.175, 4.826, and 6.35 mm thick aluminum panels asymmetrically repaired with boron/epoxy composite patches bonded to the plates with FM73 sheet adhesive. Patches were uniaxial with patch to panel stiffness ratios ranging from 0.46 to 1.3. Experimental fatigue tests were carried out at 120 MPa, R=0.1, and 10 Hz (sinusoidal) to measure patched and unpatched face crack lengths, center crack opening displacements, and selected strains. Crack growth data was acquired using optical, eddy current, and post-test analysis methods. Crack growth rates were calculated using the incremental polynomial method. A three-layer Mindlin plate finite …

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Stepped Tip Gap Effects On A Transonic Axial-Flow Compressor Rotor, Donald W. Thompson Jun 1997

Stepped Tip Gap Effects On A Transonic Axial-Flow Compressor Rotor, Donald W. Thompson

Theses and Dissertations

The effects of stepped tip gaps and clearance levels on the performance, flowfield, and stall characteristics of a transonic axial-flow compressor rotor were experimentally and numerically determined. A theory and mechanism for relocation of blockage in the rotor tip region was developed. A two-stage compressor with no inlet guide vanes was tested in the Wright Laboratories Compressor Research Facility located at Wright-Patterson Air Force Base, Ohio. The first-stage rotor was unswept and was tested for an optimum tip clearance with variations in stepped gaps machined into the casing near the aft tip region of the rotor. Nine casing geometries were …

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Estimating Kc-137 Aircraft Ownership Costs In The Brazilian Air Force, Ulisses O. Bonasser Jun 1997

Estimating Kc-137 Aircraft Ownership Costs In The Brazilian Air Force, Ulisses O. Bonasser

Theses and Dissertations

This research addresses the estimation of operation and support (O&S) costs of the Brazilian Air Force KC-137 aircraft. BAF lacks an established set of procedures for computing ownership costs of such aircraft, which prejudices the elaboration of cost-benefit analysis and allocation of budget resources. The purpose of the study is to develop an O&S cost breakdown structure and a set of cost estimating equations that will be used to estimate the ownership costs of the KC-137 aircraft during their expected service life.

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The Highly-Automated Airplane: Its Impact On Aviation Safety And An Analysis Of Training Philosophy, Kuo K. Liu Jun 1997

The Highly-Automated Airplane: Its Impact On Aviation Safety And An Analysis Of Training Philosophy, Kuo K. Liu

Theses and Dissertations

Two Airbus accidents at Nagoya, Japan and Toulouse, France in April and June 1994 highlighted the problem of the highly-automated airplane and its interface with pilots. As technologies in the engineering design progress so quickly in airplane automation, training philosophies toward the 'glass cockpit' may need to be re-evaluated. Many pilots, young and old, praise the advantages brought by the new technology. On the other hand, many have complained about the increasing workload and the danger of automation features which are not in their control. In this thesis, I evaluate the accidents of the highly-automated airplane and the probable solutions …

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Optimization Considerations For Adaptive Optics Digital Imagery Systems, Robert T. Brigantic Jun 1997

Optimization Considerations For Adaptive Optics Digital Imagery Systems, Robert T. Brigantic

Theses and Dissertations

This dissertation had three objectives. The first objective was to develop image quality metrics that characterize Adaptive Optics System (AOS) performance. The second objective was to delineate control settings that maximize AOS performance. The third objective was to identify and characterize trade-offs between fully and partially compensated adaptive. For the first objective, three candidate image quality metrics were considered: the Strehl ratio, a novel metric that modifies the Strehl ratio by integrating the modulus of the average system optical transfer function to a 'noise-effective-cutoff' frequency at which some specified image spectrum signal-to-noise-ratio level is attained, and the noise-effective-cutoff frequency. It …

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Control Of Nonlinear Systems Via State Feedback State-Dependent Riccati Equation Techniques, Kelly D. Hammett Jun 1997

Control Of Nonlinear Systems Via State Feedback State-Dependent Riccati Equation Techniques, Kelly D. Hammett

Theses and Dissertations

Nonlinear regulation and nonlinear H-infinity control via state-dependent Riccati equation (SDRE) techniques are considered. Relationships between SDREs and Hamilton-Jacobi/Bellman inequalities/equations are examined, and a necessary condition for existence of solutions involving nonlinear stabilizability is derived. A single additional necessary criterion is given for the SDRE methods to yield the optimal control or guaranteed induced L2 gain properties. Pointwise stabilizability and detectability of factorizations prove necessary and sufficient, respectively, for well-posedness of standard numerical implementations of suboptimal SDRE regulators, but neither proves necessary if analytical solutions are allowed. For scalar analytic systems or those with full rank constant control input matrices, …

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Residual Strength After Fatigue Of A Cross-Ply Metal Matrix Composite At Elevated Temperature, Alvin N. Ruiz Jun 1997

Residual Strength After Fatigue Of A Cross-Ply Metal Matrix Composite At Elevated Temperature, Alvin N. Ruiz

Theses and Dissertations

The objective of this study was to investigate the residual strength of a cross-ply, SCS-6/Ti-15-3, metal matrix composite (MMC) at elevated temperature (427 °C) when exposed to fatigue loading. Several specimens were subjected to a strain-controlled, fully reversed loading (R=-1), at various strain levels. The specimens were fatigued up to a portion of their life expectancy and then loaded to failure. Stress and strain data obtained during the test provided useful information for the macro-mechanical behavior of the material. It was determined that the residual strength was directly related to the amount of damage present in the matrix, meanwhile, the …

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A Framework For An Automated Compilation System For Reconfigurable Architectures, George R. Roelke Iv Mar 1997

A Framework For An Automated Compilation System For Reconfigurable Architectures, George R. Roelke Iv

Theses and Dissertations

The advent of the Field Programmable Gate Array has allowed the implementation of runtime reconfigurable computer systems. These systems are capable of configuring their hardware to provide custom hardware support for software applications. Since these architectures can be reconfigured during operation, they are able to provide hardware support for a variety of applications, without removal from the system. The Air Force is currently investigating reconfigurable architectures for avionics and signal processing applications. This thesis investigates the problem of automating the application development process for reconfigurable architectures. The lack of automated development support is a major limiting factor in the use …

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A Decision Support System For Joint Force Air Component Commander (Jfacc) Combat Planning, Donald W. Hinton Mar 1997

A Decision Support System For Joint Force Air Component Commander (Jfacc) Combat Planning, Donald W. Hinton

Theses and Dissertations

This system allows assessment of the Master Air Attack Plan (MAAP) during construction and at completion. The system functions around a relational database management system providing a decision support tool for the Guidance, Apportionment, & Targeting (GAT) cell of Central Command's JFACC Combat Plans. A Microsoft Access application is programmed to provide PC-based, real time evaluation of air campaign goals and constraints. The decision support system was validated in February 1997 by the CENTAF combat plans staff at Blue Flag 97-1. The software and user's manual are maintained at HQ ACC/XP-Studies and Analysis Squadron.

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Linking Procurement Dollars To An Alternative Force Structures' Combat Capability Using Response Surface Methodology, James B. Grier Mar 1997

Linking Procurement Dollars To An Alternative Force Structures' Combat Capability Using Response Surface Methodology, James B. Grier

Theses and Dissertations

A General Officer Steering Group, chaired by HQ USAF/XOM tasked action to develop and implement evaluation and analysis support to lead turn' the Program Objective Memorandum (POM) and Joint Warfare Capability Assessment (JWCA) process. This evaluation process should be designed to supply measures of the 'health' of the Air Force program in light of the Defense Planning Guidance (DPG) and the Chairman's Program Assessment (CPA). The Air Force needs to be able to quickly evaluate various alternative force structures with regards to its combat capability, measured in terms of theater level campaign objectives (CO). HQ USAF/XOM tasked HQ USAF/XPY to …

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Ranking And Generating Alternatives For The National Air Intelligence Center's (Naic) Resource Allocation Strategy, Steven M. Cox Mar 1997

Ranking And Generating Alternatives For The National Air Intelligence Center's (Naic) Resource Allocation Strategy, Steven M. Cox

Theses and Dissertations

Allocating resources is never an easy task, especially when requirements call for more resources than those available. It gets more difficult when the availability of resources shrinks from year to year. This is the case at the National Air Intelligence Center (NAIC). In each of the past five years, NAIC has been forced to make their resource allocation decision with fewer dollars and less manpower. This decision has been time consuming, manpower intensive, and sometimes very heated. In an effort to lessen these three consequences, a resource allocation model, based upon the NAIC Commander's values and preferences, was developed. The …

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Statistical Modeling And Optimization Of Nuclear Waste Vitrification, Todd E. Combs Mar 1997

Statistical Modeling And Optimization Of Nuclear Waste Vitrification, Todd E. Combs

Theses and Dissertations

This thesis describes the development of a methodology to minimize the cost of vitrifying nuclear waste. Pacific Northwest Laboratory (PNL) regression models are used as baseline equations for modeling glass properties such as viscosity, electrical conductivity, and two types of durability. Revised PNL regression models are developed that eliminate insignificant variables from the original models. The Revised PNL regression model for electrical conductivity is shown to better predict electrical conductivity than the original PNL regression model. Neural networks are developed for viscosity and the two types of durability, PCT-B and MCC-1 B. The neural network models are shown to outperform …

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Simulation Model Of Fighter Pilot Assignment Process, Anthony J. Hutfles Mar 1997

Simulation Model Of Fighter Pilot Assignment Process, Anthony J. Hutfles

Theses and Dissertations

This thesis analyzes the effect Continental United States (CONUS) Time on Station (TOS) has on filling critical rated assignments. A SIMSCRIPT II.5 simulation model of the F15 and F16 pilots assignment process was developed. The simulation tested the effect of changing CONUS TOS from 3 years to 6 years in half year increments. Analysis of the number of unfilled rated assignments from simulation runs of 10 years in length indicated that changing CONUS TOS by itself has no statistically significant effect on model's output. The analysis was expanded to a 2(2) factorial experimental design using CONUS TOS and Total Active …

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A Comparison Of Circular Error Probable Estimators For Small Samples, Charles E. Williams Mar 1997

A Comparison Of Circular Error Probable Estimators For Small Samples, Charles E. Williams

Theses and Dissertations

Several previous studies investigated the performance of competing circular error probable (CEP) estimators for small samples. This estimation is important in ICBM analysis because, due to expense, there are a limited number of ICBM test launches. In the most recent previous study (1993), Tongue considered five CEP estimators in a simulation test, attempting to determine the behavior of these estimators for populations of various bias, ellipticity, correlation, and sample size. In this paper, we build on Tongue's findings in three ways: (1) The number of estimators compared is expanded to eight. (2) Different factors and factor levels are used. (3) …

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Modeling Mirv Footprint Constraints In The Weapons Assignment Model, Elliot T. Fair Mar 1997

Modeling Mirv Footprint Constraints In The Weapons Assignment Model, Elliot T. Fair

Theses and Dissertations

US Strategic Command (USSTRATCOM) is developing a new linear programming model called the Weapons Assignment Model (WAM) to perform weapons assignment for the Strategic Integrated Operations Plan (SIOP). One of the major improvements WAM will have over its predecessor is the ability to include Multiple Independently Targetable Reentry Vehicle (MIRV) footprinting constraints in the optimization process. In order to include MIRV footprint constraints in WAM, a methodology is needed to model the MIRV footprints in a manner that is consistent with the limitations of linear programming. Two techniques for modeling MIRV footprints were developed. The first, Geometric Approximation (GA), uses …

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Decision Boundary Analysis Feature Selection For Breast Cancer Diagnosis, Daniel W. Gregg Mar 1997

Decision Boundary Analysis Feature Selection For Breast Cancer Diagnosis, Daniel W. Gregg

Theses and Dissertations

The general pattern recognition problem always involves the extraction of features to be used in pattern classification. There are no theoretical limitations to the number of features which can be obtained for a given pattern recognition problem. This research will develop a correlation procedure for screening a large feature set without the use of a trained classifier. The results will be compared to established saliency metrics such as the Fisher ratio and derivative-based techniques such as Ruck's saliency.

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System Comparison Procedures For Automatic Target Recognition Systems, Anne E. Catlin Mar 1997

System Comparison Procedures For Automatic Target Recognition Systems, Anne E. Catlin

Theses and Dissertations

Estimating the performance of an automatic target recognition (ATR) system in terms of probability of successful target identification involves extensive image collection and processing, which can be very time-consuming and expensive. We investigate the Wald sequential test for the difference in two proportions as a sample size-reducing alternative to ranking and selection and the classical method of comparing binomial confidence intervals. The test is modified for the multiple pairwise comparison of four systems, and is applied to actual data to compare different configurations of the Moving and Stationary Target Acquisition and Recognition (MSTAR) System.

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Analyzing And Improving Stochastic Network Security: A Multicriteria Prescriptive Risk Analysis Model, David L. Lyle Mar 1997

Analyzing And Improving Stochastic Network Security: A Multicriteria Prescriptive Risk Analysis Model, David L. Lyle

Theses and Dissertations

This research optimized two measures of network security by hardening components and improving their reliability. A common measure of effectiveness (MOE) for networks is statistical reliability, which ignores the effects of hostile actions. A new MOE which includes hostile actions was developed. Both measures require component reliability functions, derived using fault trees. Fuzzy Logic and Monte Carlo simulation were used to quantify uncertainty. Results from the model are compared to traditional Risk Assessment results.

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