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Theses and Dissertations

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Articles 9481 - 9510 of 11503

Full-Text Articles in Engineering

Experimental Results For A High Swirl, Ultra Compact Combustor For Gas Turbine Engines, Ryan J. Quaale Mar 2003

Experimental Results For A High Swirl, Ultra Compact Combustor For Gas Turbine Engines, Ryan J. Quaale

Theses and Dissertations

Laser Doppler Velocimeter (LDV) experiments have been conducted within the cavity of an atmospheric pressure, small scale, Ultra Compact Combustor (UCC). The UCC uses highly swirled flow in a cavity around the outside periphery of the combustor to generate high centripetal acceleration in the fluid. This enhances mixing and leads to a very short axial flame length. Additionally, due to the circumferential velocity, much of the residence time required by the flame is provided by the circumference of the engine rather than axial length as in conventional combustors.

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Nonlinear, Transonic Flutter Prediction For F-16 Stores Configuration Clearance, Raymond G. Toth Mar 2003

Nonlinear, Transonic Flutter Prediction For F-16 Stores Configuration Clearance, Raymond G. Toth

Theses and Dissertations

Wing flutter, or more accurately limit cycle oscillation (LCO), has been an issue for the F-16 since its operational deployment. Different store configurations and the permutations of those configurations after weapons are released will cause LCO to either disappear or appear. Unfortunately, the current method used by engineers for predicting LCO onset is based on linear, subsonic aerodynamic theory with no corrections for transonic effects. Predictions using this method are often good in frequency, but can be far off in predicting onset speed, forcing flutter engineers to rely more on experience and interpolation from similar configurations to design flight test …

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Application Of Maneuver-Based Control In Variable Autonomy Unmanned Combat Aerial Vehicles, Alexander M. G. Walan Mar 2003

Application Of Maneuver-Based Control In Variable Autonomy Unmanned Combat Aerial Vehicles, Alexander M. G. Walan

Theses and Dissertations

The rise in the capability and lethality of unmanned combat aerial vehicles (UCAVs) historically has been paralleled by an increase in the complexity of the command and control of these systems. This trend has continued with the command and control of the current fleet of unmanned aerial vehicles such as the Predator and Global Hawk. The control of these vehicles falls on the extremes on the manual vs autonomous spectrum. As the missions tasked to these vehicles increase in complexity and lethality, operators will increasingly require the ability to tailor the amount of control exercised over the vehicle. Maneuver Based …

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Experimental And Computational Failure Analysis Of Graphite/Bismaleimide Laminated Composite And Carbon Foam In Sandwich Construction, Troy C. Welker Mar 2003

Experimental And Computational Failure Analysis Of Graphite/Bismaleimide Laminated Composite And Carbon Foam In Sandwich Construction, Troy C. Welker

Theses and Dissertations

Sandwich beams consisting of a carbon foam core and graphite/bismaleimide face sheets were constructed and tested. Nine specimens were fabricated using three distinct cross-ply symmetric face sheet layups with a constant core thickness. Four-point bend testing controlled by a constant rate of midspan vertical displacement was used to load the specimens to failure. Displacements and strains from the experiment were compared to analytical sandwich beam theory and displacements and failure loads were compared to a layerwise finite element solution. A phenomenological failure criterion was developed that compares favorably with experimental failure data. The finite element solution gives failure within an …

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Hybrid Control Strategies For Rapid, Large Angle Satellite Slew Maneuvers, David B. French Mar 2003

Hybrid Control Strategies For Rapid, Large Angle Satellite Slew Maneuvers, David B. French

Theses and Dissertations

This research investigated hybrid control strategies for rapid satellite pointing. First, a detailed computer simulation model of AFIT's SIMSAT satellite simulator was constructed. Control strategies were developed to enable the system to perform large-angle, 3-axis slewing maneuvers using a combination of both thrusters and reaction wheels. To handle the non-linear model, a State Dependent Riccati Equation controller was programmed and successfully controlled the computer-modeled satellite for any given slewing maneuver. A simpler PD controller was then programmed and demonstrated on the computer simulation of SIMSAT, using a combination of thruster and reaction wheel control inputs for large-angle single axis maneuvers …

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Development, Fabrication And Ground Test Of An Inflatable Structure Space-Flight Experiment, Thomas L. Philley Jr. Mar 2003

Development, Fabrication And Ground Test Of An Inflatable Structure Space-Flight Experiment, Thomas L. Philley Jr.

Theses and Dissertations

Inflatable, rigidizable structures provide a solution to reduce the costs associated with design, fabrication and launch of a space system while simultaneously increasing the deployment reliability and mission success of the system%. This research focused on the follow on design, fabrication, and ground test of the Rigidizable Inflatable Get-Away-Special Experiment (RIGEX). RIGEX is a self-contained experiment that will test the deployment and structural characteristics of three inflatable rigidizable tubes. Once inflated and rigidized, each tube will be excited using piezoelectric transducers in order to collect vibration data for structural characterization. The goal of this research was to collect ground testing …

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Auto Carrier Transporter Loading And Unloading Improvement, Brian M. Miller Mar 2003

Auto Carrier Transporter Loading And Unloading Improvement, Brian M. Miller

Theses and Dissertations

Thousands of vehicles (cars, trucks and vans) are transported every day from one location to another. These vehicles are moved around the country on Auto Carrier Transports (ACTs). Delivering these vehicles involves large quantities of time, money and energy. Any reduction in time and energy will result in a significant savings of money. The intent of this research is to develop an algorithm to solve the Auto Carrier Transport Pickup and Delivery Problem. In doing so, the focus is to limit the total times vehicles are placed on and taken off the carrier, otherwise known as the number of loads, …

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A Simulation-Based Analysis Of The Impact Of In-Sourcing A Major Process Element On The Coast Guard Hh-601 Depot Maintenance Process, Steven E. Vigus Mar 2003

A Simulation-Based Analysis Of The Impact Of In-Sourcing A Major Process Element On The Coast Guard Hh-601 Depot Maintenance Process, Steven E. Vigus

Theses and Dissertations

Leaders at the United States Coast Guard's Aircraft Repair and Service Center (ARSC) in Elizabeth City, North Carolina recently formalized their planning and analysis functions by adding a dedicated branch to their command structure. The Planning and Analysis Branch intends to apply computer modeling and simulation to study the impact of process changes to the various Programmed Depot Maintenance (PDM) lines. This research considers the applicability of this type of modeling and simulation, using ARENA to study the current HH-6OJ PDM process. The contribution of this research is a methodology specific to ARSC needs, an analysis of methodology based on …

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Estimating Engineering And Manufacturing Development Cost Risk Using Logistic And Multiple Regression, John V. Bielecki Mar 2003

Estimating Engineering And Manufacturing Development Cost Risk Using Logistic And Multiple Regression, John V. Bielecki

Theses and Dissertations

Cost Growth in Department of Defense (DoD) major weapon systems has been an on-going problem for more than 30 years. Previous research has demonstrated the use of a two-step logistic and multiple regression methodology to predicting cost growth produces desirable results versus traditional single-step regression. This research effort validates, and further explores the use of a two-step procedure for assessing DoD major weapon system cost growth using historical data, We compile programmatic data from the Selected Acquisition Reports (SARs) between 1990 and 2001 for programs covering all defense departments. Our analysis concentrates on cost growth in the research and development …

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Performance Analysis Of Protocol Independent Multicasting-Dense Mode In Low Earth Orbit Satellite Networks, Mark D. Saeger Mar 2003

Performance Analysis Of Protocol Independent Multicasting-Dense Mode In Low Earth Orbit Satellite Networks, Mark D. Saeger

Theses and Dissertations

This research explored the implementation of Protocol Independent Multicasting - Dense Mode (PIM-DM) in a LEO satellite constellation. PIM-DM is a terrestrial protocol for distributing traffic efficiently between subscriber nodes by combining data streams into a tree-based structure, spreading from the root of the tree to the branches. Using this structure, a minimum number of connections are required to transfer data, decreasing the load on intermediate satellite routers. The PIM-DM protocol was developed for terrestrial systems and this research implemented an adaptation of this protocol in a satellite system. This research examined the PIM-DM performance characteristics which were compared to …

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Internet Protocol (Ip) Over Link-16, Clinton W. Stinson Mar 2003

Internet Protocol (Ip) Over Link-16, Clinton W. Stinson

Theses and Dissertations

The purpose of Link- 16 is to exchange real-time tactical data among units of the United States and allied forces. Primary Link- 16 functions include exchange of friendly unit position and status data, fl%the dissemination of tactical surveillance track data, and the control/management of air, surface, and subsurface engagements. Because Link- 16 will play an integral role in fl% network-centric Joint Battlespace Infosphere (JBI), the performance of Internet Protocol version six (IPv6) and IP Security (IPSec) over Link-16 needs to be determined. Using OPNET modeling software to simulate a Link- 16 network, the investigation of this research revealed that the …

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Using Future Value Analysis To Select An Optimal Portfolio Of Force Protection Initiatives, Robert P. Eskridge Mar 2003

Using Future Value Analysis To Select An Optimal Portfolio Of Force Protection Initiatives, Robert P. Eskridge

Theses and Dissertations

With the recent increase in terrorist activity, force protection has become a key issue for the Department of Defense, Leading the research for new ideas and concepts in force protection for the US Air Force is the Air Force Force Protection Battlelab (FPB). The FPB is charged with searching out force protection ideas and selecting those most worthy for future consideration. In 2002, a Value-Focused Thinking (VFT) hierarchy was created to help the FPB select those ideas that provided the most value to the Air Force and its force protection goals. This research effort uses the Future Value Analysis (FVA) …

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Long Term Implementation Of A 100 Percent Checked Baggage Screening System: A Value Focused Thinking Approach, Quincy Meade Mar 2003

Long Term Implementation Of A 100 Percent Checked Baggage Screening System: A Value Focused Thinking Approach, Quincy Meade

Theses and Dissertations

The terrorist attacks of 11 September 2001, carried out via aircraft hijackings, clearly demonstrated the massive destruction potential when vulnerabilities in the aviation system are exploited. Airport security measures have since been strengthened and new measures have been set in place. With the passage of the Aviation Transportation and Security Act (ATSA) of 2001 the checked baggage systems at U.S. Airports are now required to screen all checked bags with explosive detection devices. This is a significant increase from the small percentage of bags that were previously screened. The original 2009 deadline was changed to 31 December 2002 and this …

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Optimizing An In Situ Bioremediation Technology To Manage Perchlorate-Contaminated Groundwater, Mark R. Knarr Mar 2003

Optimizing An In Situ Bioremediation Technology To Manage Perchlorate-Contaminated Groundwater, Mark R. Knarr

Theses and Dissertations

Combining horizontal flow treatment wells (HFTWs) with in situ biodegradation is an innovative approach with the potential to remediate perchlorate-contaminated groundwater. A technology model was recently developed that combines the groundwater flow induced by HFTWs with in situ biodegration processes that result from using the HFTWs to mix electron donor into perchlorate-contaminated groundwater. A field demonstration of this approach is planned to begin this year. In order to apply the technology in the field, project managers need to understand how contaminated site conditions and technology design parameters impact technology performance. One way to gain this understanding is to use the …

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A Life Cycle Assessment And Economic Analysis Of Wind Turbines Using Monte Carlo Simulation, Edward J. Liberman Mar 2003

A Life Cycle Assessment And Economic Analysis Of Wind Turbines Using Monte Carlo Simulation, Edward J. Liberman

Theses and Dissertations

The United States depends heavily on nonrenewable fossil fuels to generate electricity. Using renewable energy sources, such as wind, could reduce air emissions and fossil fuel dependency. Previous studies have examined the life cycle costs and environmental impacts of using wind to generate electricity, but results have varied due to inconsistent modeling assumptions. This research uses Monte Carlo simulation to conduct an economic payback analysis and life cycle assessment of 11 modern, utility-scale wind turbines. Hourly meteorological data was used to evaluate 239 U.S. locations. For each location, the wind turbine with the shortest median payback period was assumed to …

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Analysis Of Air Force Civil Engineering Strategic Planning, Francis J. Mondo Jr. Mar 2003

Analysis Of Air Force Civil Engineering Strategic Planning, Francis J. Mondo Jr.

Theses and Dissertations

Several organizations within the Department of Defense, including the Air Force Civil Engineer, are actively engaged in strategic planning in an effort to create a roadmap for future capabilities and performance. The objective of this research was to analyze the strategic planning process of the Air Force Civil Engineer (CE) as well as the effectiveness of the Civil Engineer Strategic Plan (CESP). The methodology used to complete this analysis was conducted in two distinct phases: 1) process modeling and evaluation, and 2) performance measure evaluation. The first phase compared the CE strategic planning process to a theoretical planning model developed …

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Ultra Wide Band Multiple Access Performance Using Th-Ppm And Ds-Bpsk Modulations, Courtney M. Canadeo Mar 2003

Ultra Wide Band Multiple Access Performance Using Th-Ppm And Ds-Bpsk Modulations, Courtney M. Canadeo

Theses and Dissertations

The increasing demand for portable, high data rate communications has focused much attention on wireless technology. Ultra Wide Band (UWB) waveforms have the ability to deliver megabits of information while maintaining low average power consumption. In accordance with recent FCC ruling, UWB systems are now allowed to operate in the unlicensed spectrum of 3.1 to 10.6 GHz, motivating renewed interest in the forty year old concept of impulse radio. Gaussian monocycles produce UWB waveforms occupying large bandwidths with multiple access (MA) capability enabled by spread spectrum techniques. Time Hopping (TH) and Direct Sequence (DS) modulations are considered here for UWB …

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Mechanical Computing In Microelectromechanical Systems (Mems), Kenneth C. Bradley Mar 2003

Mechanical Computing In Microelectromechanical Systems (Mems), Kenneth C. Bradley

Theses and Dissertations

Mechanical computing devices in polysilicon-based microelectromechanical systems (MEMS) were designed with the goal of developing computing devices for harsh environments, such as those with high dose radiation and high temperatures, as well as devices that may be able to interface with molecular or biological computer systems. The devices that were designed include both analog and digital computing devices. The analog devices include integrators, differentials (summers), multipliers, and those that perform trigonometric functions. The digital devices that were designed are inverters, NAND, NOR, and XOR logic gates. Analog-to-digital (A-to-D) and digital-to-analog (D-to-A) converters were also designed. The designs were submitted to …

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Theoretical Analysis Of Information Watermarking In Wavelet-Based Video Compression, Brendan K. Casey Mar 2003

Theoretical Analysis Of Information Watermarking In Wavelet-Based Video Compression, Brendan K. Casey

Theses and Dissertations

Embedding audio bits into images for transmission of video data alleviates the synchronization problem common in video transmission techniques. We continue work combining audio or other information bits and images into one file using digital watermarking techniques to correct the synchronization problem. The system compresses the file by using wavelet image coefficients and implementing bit plane coding. Our research encompasses incorporating five free variables into the watermark/compression technique. These variables are watermark robustness, number of coding iterations, number of image coefficients, number of watermarked information bits, and number of watermarked error correcting bits. By altering these variables, four measurements of …

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Tightly-Coupled Image-Aided Inertial Navigation System Via A Kalman Filter, Michael G. Giebner Mar 2003

Tightly-Coupled Image-Aided Inertial Navigation System Via A Kalman Filter, Michael G. Giebner

Theses and Dissertations

Inertial navigation systems and GPS systems have revolutionized the world of navigation. Inertial systems are incapable of being jammed and are the backbone of most navigation systems. GPS is highly accurate over long periods of time, and it is an excellent aid to inertial navigation systems. However, as a military force we must be prepared to deal with the denial of the GPS signal. This thesis seeks to determine it, via simulation, it is viable to aid an INS with visual measurements.

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Using The Gps To Improve Trajectory Position And Velocity Determination During Real-Time Ejection Seat Design, Test And Evaluation, Christina G. Schutte Mar 2003

Using The Gps To Improve Trajectory Position And Velocity Determination During Real-Time Ejection Seat Design, Test And Evaluation, Christina G. Schutte

Theses and Dissertations

Test and evaluation of the United States Air Force’s latest aircraft escape system technology requires accurate position and velocity profiles during each test to determine the relative positions between the aircraft, ejection seat, manikin and the ground. Current rocket sled testing relies on expensive ground based multiple camera systems to determine the position and velocity profiles. While these systems are satisfactory at determining seat and manikin trajectories for sled testing, their accuracy decreases when they are used for in-flight testing, especially at high altitudes. This research presents the design and test results from a new GPS-based system capable of monitoring …

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Redundant Discrete Wavelet Transform Based Super-Resolution Using Sub-Pixel Image Registration, Daniel L. Ward Mar 2003

Redundant Discrete Wavelet Transform Based Super-Resolution Using Sub-Pixel Image Registration, Daniel L. Ward

Theses and Dissertations

The limited resolution of video imagery taken by aircraft, over geographical areas of interest, hinders the accurate extraction of useful information. The frame resolution of the video is determined by the camera that created it. Information exists about the camera which can be used to increase frame resolution beyond the resolution capability of the camera. This is achieved by a process called super-resolution, which uses multiple low-resolution video frames to create one high-resolution image.

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Development Of Variable Slope Piecewise-Based Brown Symbols For Application To Nonlinear Ambiguity Suppression, John Kurian Mar 2003

Development Of Variable Slope Piecewise-Based Brown Symbols For Application To Nonlinear Ambiguity Suppression, John Kurian

Theses and Dissertations

In 1962, Palermo used two conjugate Linear Frequency Modulated (LFM) pulses to demonstrate a Non-linear Ambiguity Suppression (NLAS) technique to reduce ambiguous energy in radar returns. Using conjugate LFM pulse coding does not readily extend to larger symbol families and thus is severely limited for M-channel (M> 2) NLAS applications. Larger families of optimal mutually dispersible codes with bigger time bandwidth products are needed to achieve the desired M-fold range ambiguity reduction. Using correlation function the time duration as an optimization metric, the recently proposed Brown's theorem formulates a deterministic process for designing optimal mutually dispersible symbol sets of arbitrary …

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Gaussian Mixture Reduction Of Tracking Multiple Maneuvering Targets In Clutter, Jason L. Williams Mar 2003

Gaussian Mixture Reduction Of Tracking Multiple Maneuvering Targets In Clutter, Jason L. Williams

Theses and Dissertations

The problem of tracking multiple maneuvering targets in clutter naturally leads to a Gaussian mixture representation of the Provability Density Function (PDF) of the target state vector. State-of-the-art Multiple Hypothesis Tracking (MHT) techniques maintain the mean, covariance and probability weight corresponding to each hypothesis, yet they rely on ad hoc merging and pruning rules to control the growth of hypotheses.

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Outsourcing Information Technology And The Insider Threat, Valerie L. Caruso Mar 2003

Outsourcing Information Technology And The Insider Threat, Valerie L. Caruso

Theses and Dissertations

As one of our nation's top critical infrastructures, telecommunications is an essential element of many aspects of our lives upon which we, as a society, are becoming increasingly dependent. Computers, digital telephone switches, and interconnected information technology (IT) systems impact finances, travel, infrastructure management, and missions of national defense. This research examined whether the trend in increased outsourcing of information technology systems is a significant contributing factor to a reportedly increasing amount of insider attacks. In light of changing social, global economic, and technological conditions, the paradigm in which risk analysis, management practices, and operational and personnel security practices are …

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Characterizing Data Streams Over Ieee 802.11b Ad-Hoc Wireless Networks, John T. Wagnon Mar 2003

Characterizing Data Streams Over Ieee 802.11b Ad-Hoc Wireless Networks, John T. Wagnon

Theses and Dissertations

Soon, advancements in data encryption technology will make real-time decryption of the contents of network packets virtually impossible. This research anticipates this development and extracts useful information based on packet level characteristics. Distinguishing characteristics from e-mail, HTTP, print, and FTP applications are identified and analyzed. The analysis of collected data from an ad-hoc wireless network reveals that distinguishing characteristics of network traffic do indeed exist. These characteristics include packet size, packet frequency, inter-packet correlation, and channel utilization. Without knowing the contents of packets or the direction of the traffic flow, the applications accessing the wireless network can be determined.

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Detection Of Special Nuclear Material With High Purity Germanium (Hpge) And Mercuric Iodide (Hgi2) Gamma Detectors, Michael B. Nelson Mar 2003

Detection Of Special Nuclear Material With High Purity Germanium (Hpge) And Mercuric Iodide (Hgi2) Gamma Detectors, Michael B. Nelson

Theses and Dissertations

The Defense Threat Reduction Agency (DTRA) contracted for two gamma radiation detectors: mercuric iodide (HgI2) and electromechanically cooled (EMC) high purity germanium (HPGe) to support arms control inspection efforts. This project investigated whether these detectors could measure the quality and quantity of special nuclear material (SNM), particularly Pu-239 for the treaty verification mission. The project investigated two areas of detector capabilities: 1) HgI2 and HPGe detector performance necessary to characterize the quality of plutonium and the presence of shielding materials and 2) HgI2 and EMC HPGe detector performance degradation by high noise levels and EMC HPGe …

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Investigation Of A Passive, Temporal, Neutron Monitoring System That Functions Within The Confines Of Start I, Stephanie Vaughn Mar 2003

Investigation Of A Passive, Temporal, Neutron Monitoring System That Functions Within The Confines Of Start I, Stephanie Vaughn

Theses and Dissertations

This study is an investigation of the theoretical and experimental possibilities of using activation foils to detect and monitor special nuclear material for treaty monitoring purposes. None of the experiments demonstrated sufficient sensitivity to detect the target flux of 0.5 neutrons/cu cm--sec. The target flux could be detectable, if the limit of detection had been reduced by a factor of 4 to 6. However, many issues identified could enhance the sensitivity including: increasing foil size, increasing detector efficiency, and optimizing foil selection. The theoretical portion focused on gold, silver, indium, europium, and gadolinium foils and determined the minimum flux detectable, …

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Assessing The Treatment Of Airborne Tactical High Energy Lasers In Combat Simulations, Maurice C. Azar Mar 2003

Assessing The Treatment Of Airborne Tactical High Energy Lasers In Combat Simulations, Maurice C. Azar

Theses and Dissertations

In March 2000, the High Energy Laser Executive Review Panel presented the Department of Defense Laser Master Plan, which reported that HEL weapons are ready for offensive and defensive applications. One candidate platform capable of performing some of the reported applications is the Advanced Tactical Laser (ATL), an Advanced Concept Technology Demonstration program which places a high energy laser weapon on a tactical aircraft, such as the V-22, C-130, or H-47. A way of assessing the utility of a new weapon system and the benefits of its inclusion in the force structure is the use of combat models. This research …

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Simulation Of Autonomic Logistics System (Als) Sortie Generation, Paul D. Faas Mar 2003

Simulation Of Autonomic Logistics System (Als) Sortie Generation, Paul D. Faas

Theses and Dissertations

The Air Force needs tools for analysis and evaluation of new logistic operational concepts. The purpose of this research was to conflict a discrete event simulation model of the aircraft sortie generation process to permit what-if analyses of these concepts. The current Air Force logistics operations system is reactive in nature meaning that after the aircraft detects a part failure, the maintenance person must perform fault isolation procedures and then steps are taken to repair or replace the faulty item. The Autonomic Logistics System (ALS) concept changes the reactive process into a proactive one with the employment of technologies such …

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