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Air Force Institute of Technology

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Articles 4141 - 4170 of 5699

Full-Text Articles in Engineering

Monotonic And Fatigue Loading Behavior Of An Oxide/Oxide Ceramic Matrix Composite, Steven G. Steel Mar 2000

Monotonic And Fatigue Loading Behavior Of An Oxide/Oxide Ceramic Matrix Composite, Steven G. Steel

Theses and Dissertations

This thesis evaluates an oxide/oxide ceramic matrix composite, N720/A, for high temperature aerospace applications. The composite consists of a porous alumina matrix reinforced by ten plies of Nextel 720 fibers in a balanced 8 harness satin weave. Monotonic tensile and fatigue tests were performed at room temperature and 1200 °C. The effect of moisture on 1200 °C fatigue life was also examined. Modulus, maximum and minimum strain, and stress-strain hysteresis were monitored to characterized fatigue damage. Retained strength of all specimens that survived 100000 fatigue cycles was tested. Microscopy and fractography were used to examine damage and fracture surfaces. N720/A …

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Optical Metrology Of Adaptive Membrane Mirrors, John W. Wagner Mar 2000

Optical Metrology Of Adaptive Membrane Mirrors, John W. Wagner

Theses and Dissertations

Current space-based imaging platforms are significantly constrained in both size and weight by the launch vehicle. Increased payload size and weight results in increased cost and a decrease in launch responsiveness. The USAF Scientific Advisory Board (SAB) identified "Large lightweight structures for optics and antennas" as a revolutionary primary technology to be developed for the Air Force of the 21st Century. A membrane primary mirror in a space-based imaging system has the ability to overcome current payload constraints and meet evolutionary needs of the future. The challenge of membrane optics in space is the process of implementing adaptive optics technology …

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Simulations Of Flowing Supercritical N-Decane, Jeffery T. Thornburg Mar 2000

Simulations Of Flowing Supercritical N-Decane, Jeffery T. Thornburg

Theses and Dissertations

The Air Force is interested in the research of supercritical jet and rocket fuels, as well as the effects of thermally induced fuel degradation. As future flight vehicles travel at ever increasing Mach numbers, greater heat loads will be imposed upon the fuel. The primary purpose of this study is to develop a computational model for predicting fuel decomposition and bulk fuel temperatures in a stimulated heated flow reactor. The System for Thermal Diagnostic Studies (STDS), located in the Air Force Research Laboratory's Fuels Branch, is used to analyze fuels under supercritical temperatures and pressures. Computational simulations of the STDS …

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Improving Uav Handling Qualities Using Time Delay Compensation, Andrew J. Thurling Mar 2000

Improving Uav Handling Qualities Using Time Delay Compensation, Andrew J. Thurling

Theses and Dissertations

This research investigated control loop time delay and its effect on UAV handling qualities. Compensation techniques to improve handling qualities in the presence of varying amounts of time delay were developed and analyzed. One technique was selected and successfully flight-tested on a UAV. Flight-testing occurred at a constant flight condition with varying levels of additional time delay introduced into the control loop. Research pilots performed a pitch tracking task and gave Cooper-Harper ratings and comments. Tracking errors were used as a quantitative measure of Pilot/Display/UAV system performance. Predictive pitch compensation was found to significantly reduce pilot workload and improve Cooper-Harper …

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Determining The Aircraft Requirement For Turkish Air Mobility System, Mehmet M. Ari Mar 2000

Determining The Aircraft Requirement For Turkish Air Mobility System, Mehmet M. Ari

Theses and Dissertations

Aircraft technology develops very rapidly. To keep up with the modem technology, we should update our systems and material over time. In order to do so, we should keep track of modem technologies, and implement them in our military. Turkish Air Force Command operates a vital logistical system for which routing and scheduling are done on a weekly basis. This research reviewed weekly schedules and determined the average required weekly missions which would be flown during the week. By carefully examining the job - machine formulation, this research devised a method for determining the aircraft required to perform for weekly …

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Modeling The Effect Of Nonlinear And Rate-Limited Sorption On The Natural Attenuation Of Chlorinated Ethenes, Peter P. Feng Mar 2000

Modeling The Effect Of Nonlinear And Rate-Limited Sorption On The Natural Attenuation Of Chlorinated Ethenes, Peter P. Feng

Theses and Dissertations

Chlorinated solvents like tetrachloroethene (PCE) and trichloroethene (TCE) are the most common detected groundwater contaminants at Department of Defense installations in the United States. Unfortunately, technologies conventionally used to remediate chlorinated solvent-contaminated groundwater often fall short of achieving regulatory goals. Natural attenuation of chlorinated solvents offers an alternative remediation strategy that may achieve goals. However, the processes involved with natural attenuation are not fully understood, and this lack of understanding has hindered acceptance of natural attenuation by regulatory agencies. This study involved use of a numerical model that incorporated the physical, chemical, and biological processes thought to be relevant to …

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Integrating Automated Multi-Disciplinary Optimization In Preliminary Design Of Non-Traditional Aircraft, Mehmet Fidanci, Jeffrey R. Miller, Douglas J. Strauss Mar 2000

Integrating Automated Multi-Disciplinary Optimization In Preliminary Design Of Non-Traditional Aircraft, Mehmet Fidanci, Jeffrey R. Miller, Douglas J. Strauss

Theses and Dissertations

Current methods of aircraft conceptual design lack the ability to quickly generate detailed analysis, particularly of nontraditional designs such as blended wing body craft. This study developed a method to resolve this problem by creating a flexible, parametrically driven conceptual model in an object-oriented, adaptive modeling environment from which analysis and optimization may rapidly be performed. These object-oriented techniques are incorporated into a traditional conceptual design process. All objects inherit dependency-tracking and demand-driven calculations. Design Analysis was performed within the modeling language and utilized interfaces to other software packages. A detailed mesh, suitable for input into finite element analysis programs, …

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A Comparative Analysis Of Cockpit Display Development Tools, Matthew J. Gebhardt Mar 2000

A Comparative Analysis Of Cockpit Display Development Tools, Matthew J. Gebhardt

Theses and Dissertations

Currently, no standard methodology exists that enables cockpit display engineers to evaluate software tools used in the development of graphical cockpit displays. Furthermore, little research has been accomplished in comparing current software development tools with traditional hand-coded methods, This research effort discusses a framework for analyzing cockpit display software development tools and follows through with a detailed analysis comparing today's hand-coding standard, OpenGL, with two of today's cockpit display software development suites, Virtual Application Prototyping System (VAPS) and Display Editor. The comparison exploits the analysis framework establishing the advantages and disadvantages of the three software development suites. The analysis framework …

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Data Warehouse Techniques To Support Global On-Demand Weather Forecast Metrics, Meriellen C. Joga Mar 2000

Data Warehouse Techniques To Support Global On-Demand Weather Forecast Metrics, Meriellen C. Joga

Theses and Dissertations

Air Force pilots and other operators make crucial mission planning decisions based on weather forecasts; therefore, the ability to forecast the weather accurately is a critical issue to Air Force Weather (AFW) and its customers. The goal of this research is to provide Air Force Weather with a methodology to automate statistical data analysis for the purpose of providing on-demand metrics. A data warehousing methodology is developed and applied to the weather metrics problem in order to present an option that will facilitate on-demand metrics. On-line analytical processing (OLAP) and data mining solutions are also discussed.

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Space Range Scheduling And The Lean Aerospace Initiative (Lai), Alan M. Matuszak Mar 2000

Space Range Scheduling And The Lean Aerospace Initiative (Lai), Alan M. Matuszak

Theses and Dissertations

This study describes how lean principles and thinking can be applied to space range operations. The "lean" concepts of the right thing, right place, and the right time are applicable and relevant to this study. The basis for the lean concepts and principles considered is the Lean Aerospace Initiative (LAI). The LAI originated from the International Motor Vehicle Program (IMVP) that was conducted by a team from the Massachusetts Institute of Technology (MIT). The LAI is a collaborative research program involving government, industry, labor, and academia (primarily MIT). The partnership began in 1993 through support of the U.S. Air Force …

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Computational Fluid Dynamics Testing For Drag Reduction Of An Aircraft Laser Turret, Gregory J. Schwabacher Mar 2000

Computational Fluid Dynamics Testing For Drag Reduction Of An Aircraft Laser Turret, Gregory J. Schwabacher

Theses and Dissertations

A computational study was conducted on the use of aft-mounted fairings for passive drag reduction on a sphere at Re=866,000. The sphere dimensions and operating Reynolds number were selected to approximate the flow around a proposed aircraft laser turret for which experimental data was available. To establish the validity of the computational model, flow predictions were compared to sphere data available in the open literature. The model, exercised in both the laminar and turbulent modes, showed good agreement with the published data. Two proposed laser turret fairings were then evaluated computationally: a large fairing (beginning at 49.5 degrees past the …

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Use Of Genetic Algorithms To Characterize Groundwater Contamination Source Areas, Chaz M. Williamson Mar 2000

Use Of Genetic Algorithms To Characterize Groundwater Contamination Source Areas, Chaz M. Williamson

Theses and Dissertations

In this work, genetic algorithms (GAs) were used to help interpret tracer breakthrough curves from partitioning interwell tracer tests (PITTs) conducted at Hill AFB, Utah by researchers from the University of Florida. Two transport models were developed to simulate tracer transport in the test cells. One model assumed the cell consisted of multiple layers, and that transport in each layer could he described by the one-dimensional advective/dispersive equation. The second model also assumed multiple layers, and modeled transport in the individual layers as advective transport through 100 tubes. Transport times were represented by a stochastic (lognormal) distribution. The model solutions …

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The Evaluation Of Competing Classifiers, Stephen G. Alsing Mar 2000

The Evaluation Of Competing Classifiers, Stephen G. Alsing

Theses and Dissertations

This dissertation research makes contributions towards the objective evaluation of competing classifiers, i.e., classification systems (CSs) or pattern recognition algorithms. Automatic CSs have been under development for almost 40 years in a wide range of military and medical applications. During this period, scientists and engineers have developed extensive theory and algorithms for classification, but by comparison have focused little on the testing and evaluation of their systems. Classifier evaluation is very important in the fields of automatic target recognition (ATR) and pilot workload classification. In order for military operators to be confident in new CSs, they must have an objective …

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Tool-Based Integration And Code Generation Of Object Models, Michael Ray Ashby Mar 2000

Tool-Based Integration And Code Generation Of Object Models, Michael Ray Ashby

Theses and Dissertations

Today many organizations are faced with multiple large legacy data stores in different formats and the need to use data from each data store with tools based on the other data stores' formats. This thesis presents a tool-based methodology for integrating object-oriented data models with automatic generation of code. The generated code defines a global data format, generates views of global data in individual integrated data formats, and parses data from individual formats to the global formats and from the global format to the individual formats. This allows for legacy data to be translated into the global format, and all …

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Locating Search And Rescue Stations In The Aegean And Western Mediterranean Regions Of Turkey, Melih M. Basdemir Mar 2000

Locating Search And Rescue Stations In The Aegean And Western Mediterranean Regions Of Turkey, Melih M. Basdemir

Theses and Dissertations

The service of present Search and Rescue (SAR) stations in the Aegean and the Western Mediterranean regions of Turkey are not sufficient to meet the demands of the Turkish Air Force. This research seeks to find the optimum location of new SAR stations. The number of SAR stations required to cover all areas of operation becomes a very decisive element in finding the optimal coverage of the operation area by these stations. The problem of finding the optimum SAR locations can he modeled as a maximal covering location problem (MCLP). Additional constraints are added to set standards on various issues …

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Evaluation Of A Method For Kinematic Gps Carrier-Phase Ambiguity Resolution Using A Network Of Reference Receivers, Brian L. Bracy Mar 2000

Evaluation Of A Method For Kinematic Gps Carrier-Phase Ambiguity Resolution Using A Network Of Reference Receivers, Brian L. Bracy

Theses and Dissertations

New applications for GPS have driven a demand for increased positioning accuracy. The emerging GPS technology particularly affects the test community. The testing equipment and method must provide a solution that is an order of magnitude more precise than the tested equipment to achieve the desired accuracy. Carrier-phase differential GPS methods using a network of reference receivers can provide the centimeter-level accuracy required over a large geographical area. This thesis evaluates the performance of a 5-receiver network over a 50 km x 120 km area of New Mexico, using a GPS network algorithm called NetAdjust. The percentage of time a …

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Hierarchical Interactive Theater Model (Hitm): An Investigation Into The Relationship Between Strategic Effects And Ooda Loops, Richard K. Bullock Mar 2000

Hierarchical Interactive Theater Model (Hitm): An Investigation Into The Relationship Between Strategic Effects And Ooda Loops, Richard K. Bullock

Theses and Dissertations

Airpower's strength lies in being able to quickly strike the enemy directly where they are vulnerable while being unhampered by geography and surface forces. Airpower theory suggests the effects of these strikes propagate throughout an opponent1s military system yielding catastrophic output or strategic effects. Despite this theory being a cornerstone of US Air Force doctrine, current Air Force models do not seem to capture airpower's inherent strength. Since these models are used to support budgetary decision making, the United States may not be funding the airpower capability it needs.

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Using Rsm, Doe, And Linear Regression To Develop A Metamodel To Predict Cargo Delivery Of A Time Phase Force Deployment Document, Kenneth S. Browne Mar 2000

Using Rsm, Doe, And Linear Regression To Develop A Metamodel To Predict Cargo Delivery Of A Time Phase Force Deployment Document, Kenneth S. Browne

Theses and Dissertations

Air Mobility Command (AMC) uses the Airlift Flow Model as their primary tool to estimate the amount of cargo delivered in a Time Phase Force Deployment Document (TPFDD). The primary objective of this research was an exploratory investigation in the development of a metamodel to predict the amount of cargo delivered from a TPFDD by AMC into a theater. In creating a valid metamodel the analyst would be able to quickly provide the decision-maker with accurate insights should input parameters change. This would save valuable time and replace the need to physically change the input parameters and re-run the simulation. …

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A Decision Support Tool To Aid Campaign Planners In Selecting Combat Aircraft For Theater Crisis, Christopher D. Buzo Mar 2000

A Decision Support Tool To Aid Campaign Planners In Selecting Combat Aircraft For Theater Crisis, Christopher D. Buzo

Theses and Dissertations

One way of comparing alternative deployment plans is to examine how combat aircraft tasked within a deployment plan meet the combat commander's requirements. Both the absolute capabilities and the campaign-specific issues affecting the operational capabilities of those aircraft could assess a set of combat aircraft, unique to a deployment plan. This research-develops a non-absolute, campaign-specific decision Support tool to assess the effect of campaign-specific issues on a set of deployable Air Force combat aircraft. This research is conducted in three phases. Cognitive Task Analysis (CTA) and Multi-Attribute Preference Theory (MAPT) methodologies are applied to in-person and telephone interviews with subject …

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Comparative Analysis Of Mobility Management Schemes In A Low Earth Orbit Satellite Network, Stephen R. Conkling Mar 2000

Comparative Analysis Of Mobility Management Schemes In A Low Earth Orbit Satellite Network, Stephen R. Conkling

Theses and Dissertations

In the 60's the United States and the Union of Soviet Socialist Republics engaged in a "space race" to be the first to put a man on the moon. Today, the space race is between large multinational telecommunication corporations with the winner receiving the financial rewards by providing communication services to the billions without even a simple telephone. Many entrants are using Low Earth Orbit (LEO) satellites to provide the communications infrastructure, but the number of customers a satellite can support is limited by bandwidth available. This resource must be used efficiently, and this involves reducing the management overhead. This …

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Design And Validation Of An Accurate Gps Signal And Receiver Truth Model For Comparing Advanced Receiver Processing Techniques, Phillip Martin Corbell Mar 2000

Design And Validation Of An Accurate Gps Signal And Receiver Truth Model For Comparing Advanced Receiver Processing Techniques, Phillip Martin Corbell

Theses and Dissertations

Recent increases in the computational power of computers and digital signal processors have made possible new, novel signal tracking techniques in GPS receivers. One such technique is known as Direct Correlators Output Processing (DCOP). This technique replaces individual traditional tracking loops with a single Kalman Filter, which jointly processes the received signals while exploiting their correlated noises. DCOP is innovative in its potential to replace the tried and true classical signal tracking loops. It is also an enabling technology for ultra-tightly coupled GPS/INS (Global Positioning System/Inertial Navigation System). Potential benefits of these new tracking techniques include an order-of-magnitude improvement in …

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Modeling Piezoceramic Twist Actuation In Single-Cell Anisotropic Torque Box Of Low-Observable Uav Wing, Peter Cseke Jr. Mar 2000

Modeling Piezoceramic Twist Actuation In Single-Cell Anisotropic Torque Box Of Low-Observable Uav Wing, Peter Cseke Jr.

Theses and Dissertations

The reduction of an aircraft's radar cross section can increase its survivability in hostile airspace by making it more difficult to locate and track by enemy radar. Replacing articulated flight control surfaces with adaptive controls will reduce surface discontinuities, and enhance low observability. Actuation of the aerodynamic surfaces is achieved by an electric field applied to PZT actuators embedded in the top and bottom skins, creating differential strain and shear in the host substrate. This creates torsion about the elastic axis, and a change in the wing lift coefficient. The torsion of the designed baseline UAV's wing torquebox was modeled …

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An Experimental Investigation On Periodic Forced Vibrations Of A Bladed Disk, Colin J. Duffield Mar 2000

An Experimental Investigation On Periodic Forced Vibrations Of A Bladed Disk, Colin J. Duffield

Theses and Dissertations

Aircraft engine blades are subject to harmonic forcing produced from periodic wakes created by fixed stators. Prolong or repeated exposure at blade resonant frequencies can cause vibration-induced fatigue, otherwise known as High Cycle Fatigue (HCF). Structural mistuning coupled with HCF causes premature blade failures, excessive operational costs and increased engine servicing. This study offered a novel approach to characterize mistuning effects on bladed disk forced vibration behavior. A model fan reduced in dynamic scale from an operational jet engine fan and with weak inter-blade coupling was fabricated. Aerodynamic disturbances produced by the stators were replicated by magnets attached to a …

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Effects Of Moisture Content In Solid Waste Landfills, Craig P. Eck Mar 2000

Effects Of Moisture Content In Solid Waste Landfills, Craig P. Eck

Theses and Dissertations

Solid waste landfills are an extremely complex and heterogeneous environment. Modeling the biodegradation processes within a landfill must involve an understanding of how environmental factors affect these processes. Arguably, the most important environmental factor influencing biodegradation processes is solid waste moisture content. This research effort, which is an extension of a system dynamics model previously presented by Colborn (1997) and amended by Benter (1999), attempts to understand and model the effects of moisture content on waste degradation and landfill gas generation. The new moisture structure that was added to the previous models provides a better representation of the impact of …

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Multi-Objective Evaluation Of Target Sets In A Logistics Network, Paul D. Emslie Mar 2000

Multi-Objective Evaluation Of Target Sets In A Logistics Network, Paul D. Emslie

Theses and Dissertations

This thesis addresses the selection of target sets to disrupt an adversary's logistics network in a wartime environment. In the presence of many objectives--such as reducing maximum flow, lengthening routes, avoiding collateral damage, all at minimal risk to our pilots--the problem of determining the best target set is complex. Previous efforts have not adequately considered the value of the remaining network functionality after target destruction. In addition, current network targeting procedures optimize target sets with respect to only a single metric. This thesis uses a multi-objective decision analysis framework capturing actual targeting decision-maker values and preferences to evaluate and analyze …

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Attitude Control And Multimedia Representation Of Air Force Institute Of Technology’S (Afit’S) Simulation Satellite (Simsat), Joseph M. Fulton Mar 2000

Attitude Control And Multimedia Representation Of Air Force Institute Of Technology’S (Afit’S) Simulation Satellite (Simsat), Joseph M. Fulton

Theses and Dissertations

This document describes the systematic construction of the AFIT-sponsored program to develop a laboratory-based satellite simulator. The simulation satellite (SIMSAT) system will provide a useful tool for resident staff while teaching attitude control concepts. A brief overview of attitude control theory is provided as well as a discussion of the benefits of multimedia use in education. A detailed discussion of the satellite's components allows the reader to become familiar with each piece of SIMSAT. Software control models are provided as well as a multimedia lesson plan on satellite attitude control. Also included in this document are potential experimental uses in …

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Analysis Of Uh-60 Blackhawk Safety Controls Using Value Focused Thinking And Monte Carlo Simulation, Roger D. Gallan Jr. Mar 2000

Analysis Of Uh-60 Blackhawk Safety Controls Using Value Focused Thinking And Monte Carlo Simulation, Roger D. Gallan Jr.

Theses and Dissertations

In the past few years, Army aviation accidents have been on the rise, due largely to increases in mission frequency and complexity, and diminishing resources. The magnitude of the resulting losses (casualties, dollars, equipment) has prompted the Commanding General of the Army Safety Center to demand a complete examination of the way safety hazards and subsequent safety controls are evaluated and selected. This project integrates value focused thinking, Monte Carlo simulation, and integer programming in response to this demand by developing and using a methodology that effectively identifies and evaluates portfolios of controls. An integer program generates portfolios of controls …

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A Group Theoretic Tabu Search Approach To The Traveling Salesman Problem, Shane N. Hall Mar 2000

A Group Theoretic Tabu Search Approach To The Traveling Salesman Problem, Shane N. Hall

Theses and Dissertations

The traveling salesman problem (TSP) is a combinatorial optimization problem that is mathematically modeled as a binary integer program. The TSP is a very important problem for the operations research academician and practitioner. This research demonstrates a Group Theoretic Tabu Search (GTTS) Java algorithm for the TSP. The tabu search metaheuristic continuously finds near-optimal solutions to the TSP under various different implementations. Algebraic group theory offers a more formal mathematical setting to study the TSP providing a theoretical foundation for describing tabu search. Specifically, this thesis uses the Symmetric Group on n letters, S(n), which is the set of all …

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Modelling Information Assurance: A Value Focused Thinking Approach, Jonathan Todd Hamill Mar 2000

Modelling Information Assurance: A Value Focused Thinking Approach, Jonathan Todd Hamill

Theses and Dissertations

The information revolution has brought forth new and improved capabilities to rapidly disseminate and employ information in decision-making. These capabilities are critical to the civilian and military infrastructures of the United States, and act as force enhancers and enablers for the Armed Forces. These capabilities, however, often rely upon systems interconnected throughout the world, resulting in potentially increased vulnerability to attack. To add to this problem, elusive, threatening forces (national and transnational) originating from anywhere on the globe are likely to offer opponents less reliant on information technology an asymmetric advantage over information-reliant nations like the United States. To date, …

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A Java Universal Vehicle Router In Support Of Routing Unmanned Aerial Vehicles, Robert W. Harder Mar 2000

A Java Universal Vehicle Router In Support Of Routing Unmanned Aerial Vehicles, Robert W. Harder

Theses and Dissertations

Unmanned Aerial Vehicles (UAVs) help the military gather information in times of peace and war. During a mission, typically 100 sites or more, a UAV will frequently be re-tasked to visit a pop-up threat, leaving the operator to determine the best way to finish the day's list of sites after the re-tasking. I develop a prototype application to serve the needs of a specific customer, the 11th Reconnaissance Squadron, by helping them preplan missions and dynamically re-task UAVs. This prototype application is built on a reusable airframe router called the core AFIT Router, which can later be added to more …

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