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Air Force Institute of Technology

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Articles 3901 - 3930 of 5699

Full-Text Articles in Engineering

Airborne Radar Interference Suppression Using Adaptive Three-Dimensional Techniques, Todd B. Hale Jun 2002

Airborne Radar Interference Suppression Using Adaptive Three-Dimensional Techniques, Todd B. Hale

Theses and Dissertations

This research advances adaptive interference suppression techniques for airborne radar, addressing the problem of target detection within severe interference environments characterized by high ground clutter levels, levels, noise jammer infiltration, and strong discrete interferers. Two-dimensional (2D) Space-Time Adaptive Processing (STAP) concepts are extended into three-dimensions (3D) by casting each major 2D STAP research area into a 3D framework. The work first develops an appropriate 3D data model with provisions for range ambiguous clutter returns. Adaptive 3D development begins with two factored approaches, 3D Factored Time-Space (3D-FTS) and Elevation-Joint Domain Localized (Elev-JDL). The 3D adaptive development continues with optimal techniques, i.e., …

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Robustness Of Multiple Objective Decision Analysis Preference Functions, William K. Klimack Jun 2002

Robustness Of Multiple Objective Decision Analysis Preference Functions, William K. Klimack

Theses and Dissertations

This research investigated value and utility functions in multiobjective decision analysis to examine the relationship between them in a military decision making context. The impact of these differences was examined to improve implementation efficiency. The robustness of the decision model was examined with respect to the preference functions to reduce the time burden imposed on the decision maker. Data for decision making in a military context supports the distinction between value and utility functions. Relationships between value and utility functions and risk attitudes were found to be complex. Elicitation error was significantly smaller than the difference between value and utility …

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Characterization Of Residual Stress In Microelectromechanical Systems (Mems) Devices Using Raman Spectroscopy, Lavern A. Starman Apr 2002

Characterization Of Residual Stress In Microelectromechanical Systems (Mems) Devices Using Raman Spectroscopy, Lavern A. Starman

Theses and Dissertations

Due to the small scale of MEMS devices, the inherent residual stresses during the deposition processes can affect the functionality and reliability of the fabricated devices. Residual stress often causes device failure due to curling, buckling, or fracture. Currently, few techniques are available to measure the residual stress in MEMS devices. In this dissertation, Raman spectroscopy is used to measure and monitor the residual and induced stresses in MUMPs polysilicon MEMS devices. Raman spectroscopy was selected since it is nondestructive, fast, and provides potential in situ stress monitoring. Raman spectroscopy scans on unreleased and released MEMS fixed-fixed beams, cantilevers, and …

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An Assessment Of Air Force Development Portfolio Management Practices, Michael A. Greiner, Kevin J. Dooley, Dan L. Shunk, Ross T. Mcnutt Apr 2002

An Assessment Of Air Force Development Portfolio Management Practices, Michael A. Greiner, Kevin J. Dooley, Dan L. Shunk, Ross T. Mcnutt

Faculty Publications

Selecting and managing development project portfolios is a critical function within the Air Force’s weapon systems development process. Decision makers must weigh benefits, costs, and mission needs for a variety of proposed new initiatives and current weapon systems programs in order to develop an effective portfolio that provides the best value to the User. This research examines current Air Force development portfolio management practices as perceived by those involved with the decision making process. Research findings indicate several gaps between Air Force practices and those commercial best practices as found in the literature. A general approach for bridging the differences …

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Issues In Modeling Military Space, Peter F. Olsen Mar 2002

Issues In Modeling Military Space, Peter F. Olsen

Theses and Dissertations

Fighter Pilots students undertake an intense 120-day training program. New classes of students enter the training program at regular interval. Students endured rigorous academic, simulator, and aircraft training throughout the program. Squadron schedulers ensure the multiple classes and students are scheduled for the activities. Simulator and aircraft training are scheduled individual for each student. Academic training are taught to the class. Aircraft utilization must also be considered. Aircraft Sortie training are also constrained by daylight hours. Additionally, students are limited to a maximum of three training events in a given day. Squadron schedulers must balance these requirements to ensure students …

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Effects Of Shot-Peening On High Cycle Fretting Fatigue Behavior Of Ti-6al-4v, Halil I. Yuksel Mar 2002

Effects Of Shot-Peening On High Cycle Fretting Fatigue Behavior Of Ti-6al-4v, Halil I. Yuksel

Theses and Dissertations

Effects of Shot-peening on High Cycle Fretting Fatigue behavior of Ti-6Al-4V were investigated. Experiments were performed with 6.35 mm thick specimens which provided S/N curves. After the tests, it was observed that the specimens failed near the trailing edge of contact. Scanning Electron Microscopy showed that cracks initiated on the contact surface for 6.35 mm, and at the depth of specimen ranging from 200 to 300 microns for 3.81 mm thick specimens. Initial crack orientation was around 37 and 42 degrees respectively for 6.35 and 3.81 mm thicknesses. Finite Element Analysis (FEA) was conducted, and using FEA results, Smith-Watson-Topper, Findley, …

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Design Study Of Triggered Isomer Heat Exchanger-Combustion Hybrid Jet Engine For High Altitude Flight, Christopher E. Hamilton Mar 2002

Design Study Of Triggered Isomer Heat Exchanger-Combustion Hybrid Jet Engine For High Altitude Flight, Christopher E. Hamilton

Theses and Dissertations

This study investigated the possibility of utilizing a Triggered Isomer Heat Exchanger (TIHE) within a conventional jet engine in order to increase the endurance of a High Altitude Long Endurance (HALE) Intelligence, Surveillance, and Reconnaissance (ISR) aircraft. Optimizations of the conventional and TIHE engines along with selection of a switchover flight condition, where the aircraft switches from combustion to TIHE operations, were made utilizing engine design and mission analysis software. Radiation shield weights were determined utilizing point source gamma ray shielding methods. The jet engine best suited for the hybrid use, where both combustion and TIHE components located in a …

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Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley Mar 2002

Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley

Theses and Dissertations

This thesis studies selective etching techniques for the development of AlxGa1-xAs micro-opto-electro-mechanical systems (MOEMS). New MEMS technology based on materials such as AlxGa1-xAs enables the development of micro-systems with embedded active micro-optical devices. Tunable micro-lasers and optical switching based on MOEMS technology will improve future wavelength division multiplexing (WDM) systems. WDM vastly increases the speed of military communications and sensor data processing. From my designs, structures are prepared by molecular beam epitaxy. I design a mask set for studies of crystal plane selectivity. I perform a series of experiments on the selective …

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Evaluation And Analysis Of Array Antennas For Passive Coherent Location (Pcl) Systems, Baris Calikoglu Mar 2002

Evaluation And Analysis Of Array Antennas For Passive Coherent Location (Pcl) Systems, Baris Calikoglu

Theses and Dissertations

Passive Coherent Location (PCL) systems use a special form of a radar receiver that exploits the ambient radiation in the environment to detect and track targets. Typical transmissions of opportunity that might be exploited include television and FM radiobroadcasts. PCL implies the use of a non-radar electromagnetic sources of illumination, such as commercial radio or television broadcasts also referred as transmitters of opportunity. The use of such illumination sources means that the receiver needs to process waveforms that are not designed for radar purposes. As a consequence, the receivers for PCL systems must be much more customized than traditional receivers, …

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Analysis Of Ultra Wide Band (Uwb) Technology For An Indoor Geolocation And Physiological Monitoring System, Cengiz Alabacak Mar 2002

Analysis Of Ultra Wide Band (Uwb) Technology For An Indoor Geolocation And Physiological Monitoring System, Cengiz Alabacak

Theses and Dissertations

The goal of this research is to analyze the utility of UWB for indoor geolocation and to evaluate a prototype system, which will send information detailing a person’s position and physiological status to a command center. In a real world environment, geolocation and physiological status information needs to be sent to a command and control center that may be located several miles away from the operational environment. This research analyzes and characterizes the UWB signal in the various operational environments associated with indoor geolocation. Additionally, "typical usage scenarios" for the interaction between UWB and other devices are also tested and …

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A Multiobjective Approach Applied To The Protein Structure Prediction Problem, Richard O. Day Mar 2002

A Multiobjective Approach Applied To The Protein Structure Prediction Problem, Richard O. Day

Theses and Dissertations

Interest in discovering a methodology for solving the Protein Structure Prediction problem extends into many fields of study including biochemistry, medicine, biology, and numerous engineering and science disciplines. Experimental approaches, such as, x-ray crystallographic studies or solution Nuclear Magnetic Resonance Spectroscopy, to mathematical modeling, such as minimum energy models are used to solve this problem. Recently, Evolutionary Algorithm studies at the Air Force Institute of Technology include the following: Simple Genetic Algorithm (GA), messy GA, fast messy GA, and Linkage Learning GA, as approaches for potential protein energy minimization. Prepackaged software like GENOCOP, GENESIS, and mGA are in use to …

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Compare And Complexity - When Is Compare Not Enough?, Chris E. Greiman Mar 2002

Compare And Complexity - When Is Compare Not Enough?, Chris E. Greiman

Theses and Dissertations

The purpose of this case study research is to determine the utility of COMPARE, the DoD approved software for conducting A-76 competitions, in the more complex world of public-private competition. COMPARE serves as the baseline for establishing cost factors, while two Air Force Depots are used as a basis of comparison. Research questions answered are: 1. What are the baseline cost comparison factors established in COMPARE? 2. What are the common cost factors found in the Air Force Depot public-private competitions? 3. What are the similarities and differences between the cost factors established in COMPARE and those used in the …

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Experimental Vibration Analysis Of Inflatable Beams For An Afit Space Shuttle Experiment, Thomas G. Single Mar 2002

Experimental Vibration Analysis Of Inflatable Beams For An Afit Space Shuttle Experiment, Thomas G. Single

Theses and Dissertations

This study investigated the use of MEMS based devices to control the boundary layer separation from a circular cylinder in cross flow. Velocity profiles were measured experimentally in a low speed wind tunnel. Momentum thickness was measured as the primary way to determine a change in the flow field. The goal was to determine the angular location and frequency of operation that would provide an effect on the boundary layer of the cylinder. A 25% reduction of momentum loss in the cylinder wake was detected with an optimal angle of 69 degrees and an optimal frequency of operation equal to …

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Broadcast Vs Precise Gps Ephemerides: A Historical Perspective, David L. M. Warren Mar 2002

Broadcast Vs Precise Gps Ephemerides: A Historical Perspective, David L. M. Warren

Theses and Dissertations

In most recent years, both high-resolution imagery systems and images were only available to military and national security organizations. Distinctive changes within the commercial image industry allowed space-borne pioneers to provide high-resolution images. Space-borne Image Company's Ikonos satellite provides a 1-meter resolution for the past 3 years. Current development of .5-meter resolution will be offered in the near future. Access of these images is available in ground stations located worldwide in different regions. Studies have shown that these high quality images are eye-catching and may serve a purpose through its design; on contrary high cost and accessibility does not met …

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The Investigation Of Hypervelocity Gouging, David J. Laird Mar 2002

The Investigation Of Hypervelocity Gouging, David J. Laird

Theses and Dissertations

The slipper/rail interface of a hypervelocity rocket sled is subject to immense forces due to dynamic loads and impact of the slipper with the rail, and tremendous heating due to aerodynamic and frictional effects is produced at the interface. Under these severe loading conditions, the material in the rail will sometimes experience large non-linear deformations known as gouging. Hydrocodes are computational solvers designed to handle such non-linear, large deformation, high shock, hydrodynamic applications. The ability of the hydrocode CTH to handle gouge modeling is considered, as well as the manner in which temperature environments affect deformation and plastic strain. The …

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Design And Fabrication Of Micro-Electro-Mechanical Structures For Tunable Micro-Optical Devices, Michael C. Harvey Mar 2002

Design And Fabrication Of Micro-Electro-Mechanical Structures For Tunable Micro-Optical Devices, Michael C. Harvey

Theses and Dissertations

Tunable micro-optical devices are expected to be vital for future military optical communication systems. In this research I seek to optimize the design of a microelectromechanical (MEM) structure integrated with a III-V semiconductor micro-optical device. The resonant frequency of an integrated optical device, consisting of a Fabry-Perot etalon or vertical cavity surface emitting laser (VCSEL), may be tuned by applying an actuation voltage to the MEM Flexure, thereby altering the device's optical cavity length. From my analysis I demonstrate tunable devices compatible with conventional silicon 5V integrated circuit technology. My design for a Fabry-Perot etalon has a theoretical tuning range …

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Fretting Fatigue Behavior Of A Titanium Alloy Ti-6al-4v At Elevated Temperature, Onder Sahan Mar 2002

Fretting Fatigue Behavior Of A Titanium Alloy Ti-6al-4v At Elevated Temperature, Onder Sahan

Theses and Dissertations

The purpose of this research is to investigate the fretting fatigue behavior of the titanium alloy Ti-6Al-4V at elevated temperature is investigated. Fretting and plain fatigue experiments are conducted at 260 °C. Crack initiation location and crack initiation orientation is measured and fretting and plain fatigue life data of the specimens from these tests are obtained. Fatigue parameters capable of predicting the number of cycles to specimen failure, the crack location and the crack orientation along the contact surface are analyzed. The parameters are calculated by using the computed stresses and strains obtained from the finite element analysis. The mechanisms …

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An Analytical Study Of T-38 Drag Reduction In Tight Formation Flight, Eugene H. Wagner Jr. Mar 2002

An Analytical Study Of T-38 Drag Reduction In Tight Formation Flight, Eugene H. Wagner Jr.

Theses and Dissertations

This thesis explores the benefits of flying in a tight formation, mimicking the natural behavior of migratory birds such as geese. The first phase of the research was to determine an optimal position for the wingman of a tight formation flight of T-38 Talon aircraft using the HASC95 vortex lattice code. A second wingman was then added to determine the benefit derived by increasing formation size. The second wingman was predicted to derive an even greater induced drag benefit than the first wingman for T-38s operating at Mach 0.54 at a 10,000-foot altitude. The predicted values were 17.5% savings for …

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Orbital Maneuvering Using Electrodynamic Tethers, Hakan San Mar 2002

Orbital Maneuvering Using Electrodynamic Tethers, Hakan San

Theses and Dissertations

Considerably short electrodynamic tethers can be used as a low-thrust propulsion system with minimum or no mass expenditure. The propulsive force is generated by inducing a current flow through the tether which interacts with the magnetosphere of the planet (i.e. Earth, Jupiter and other planetary bodies with magnetosphere). The basics of electrodynamic tether systems have been studied and successful experiments such as boost and de-boost of spacecraft have been conducted in the past. This study presents a simple guidance scheme for the current in the tether in order to perform orbital maneuvers. The general perturbation equations are used to develop …

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Estimating Engineering Cost Risk Using Logistic And Multiple Regression, Vincent P. Sipple Mar 2002

Estimating Engineering Cost Risk Using Logistic And Multiple Regression, Vincent P. Sipple

Theses and Dissertations

This study explores a two-step procedure for assessing defense acquisition program cost growth using historical data. Specifically, we seek to predict whether a program will experience cost growth and, if applicable, how much costs will increase. We compile programmatic data from the Selected Acquisition Reports (SARs) between 1990 and 2000 for programs from all defense departments. We focus our analysis on cost growth in research and development dollars for the Engineering Manufacturing Development phase of acquisition. We further limit our study to only one of the seven SAR categories of cost growth engineering cost growth. We explore the use of …

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A Life Cycle Cost Analysis Of The Proposed Replacement Of Pope Air Force Base's C-130e Fleet Using A Fleet Replacement Model, Lance R. French Mar 2002

A Life Cycle Cost Analysis Of The Proposed Replacement Of Pope Air Force Base's C-130e Fleet Using A Fleet Replacement Model, Lance R. French

Theses and Dissertations

The 43rd Airlift Wing at Pope AFB, NC, possesses 33 E-model C-130 aircraft. The airplanes range in age from 30-36 years old. Current plans call for replacing Pope's aging fleet of tactical airlifters with new C-130J model planes in FY11. There are two replacement alternatives proposed in this research. The first is to calls for replacing the C-130Es with C-130Js now. The second option is upgrade the C-130Es to C-130Xs and replace them in 10 years with the C-130J. The results indicate that the least cost solution is to upgrade Pope's fleet of C-130Es to C-130Xs now. However, after conducting …

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The Management Of Energy Savings Performance Contracts (Espcs), Ericka M. Dailey Mar 2002

The Management Of Energy Savings Performance Contracts (Espcs), Ericka M. Dailey

Theses and Dissertations

Energy Savings Performance Contracts (ESPCs) originated to accomplish several objectives: (1) to meet energy efficiency goals mandated by executive orders and energy policies; (2) to improve federal government facilities using funds allocated for utility bills; and (3) to receive repayment of expenditures through energy savings reflected in reduced utility bills. In ESPC's, the contractor guarantees savings to the federal government agency. 10 CFR 436 limits the time necessary for payback. However, this regulation and others were written prior to the deregulation of utility companies. This theory is based on the underlying premise that the contractor payback is a direct result …

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A System Dynamics Approach To Modeling Aircraft System Production Break Costs, John J. Dubelko Mar 2002

A System Dynamics Approach To Modeling Aircraft System Production Break Costs, John J. Dubelko

Theses and Dissertations

This research effort employs a System Dynamics methodology to model Air Force aircraft production break costs. The Air Force currently used the Anderlohr, Modified Anderlohr, and Retrograde methods for the estimation of aircraft production breaks. These methods offer little insight into the dynamic behavior of an aircraft production break. System Dynamics offers a unique way of capturing expert opinions in this area and dynamically presenting behaviors of an Air Force aircraft production line during a production break. Development of this model followed a four-step process of conceptualization, formulation, testing, and implementation. Five Air Force aircraft production break experts in were …

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Spectrum Management And The Global Positioning System: A Case Study In Interagency Coordination, John A. Enis Mar 2002

Spectrum Management And The Global Positioning System: A Case Study In Interagency Coordination, John A. Enis

Theses and Dissertations

At the 2000 World Radio Conference (WRC), a European initiative resulted in the approval of resolutions 605 and 606 (agenda item 1.15), which the United States opposed. These resolutions established provisional power flux density (PFD) limits on the L2 and L5 frequencies of the Global Positioning System. These limits will negatively affect the $1.2B GPS modernization. The United States will have to present its positions and rationale regarding the PFD limits to international meetings, including the 2003 World Radio Conference, to persuade the international community to adopt that U.S. view. Developing the U.S. view and conducting the supporting technical work …

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Admissions Criteria And Academic Performance In The Afit Graduate Cost Analysis Program, Kenneth R. Garwood Mar 2002

Admissions Criteria And Academic Performance In The Afit Graduate Cost Analysis Program, Kenneth R. Garwood

Theses and Dissertations

This research examined the admissions criteria used by the Air Force Institute of Technology (AFIT) to determine academic eligibility for the in-residence Graduate Cost Analysis (GCA) master's degree program. Using the cumulative graduate grade point average earned at AFIT as the measure of academic performance, comparisons were made between the predictive capability of the current criteria and other potential factors. Factors considered included scores from the Graduate Record Examination (GRE) and the Graduate Management Admissions Test (GMAT), undergraduate cumulative and math grade point averages, applicant's age and gender, ratings of the undergraduate school's admissions competitiveness, undergraduate degree type, and various …

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An Evaluation Of Public And Private Sector Housing Alternatives For Military Families, Lawrence P. Kokocha Jr. Mar 2002

An Evaluation Of Public And Private Sector Housing Alternatives For Military Families, Lawrence P. Kokocha Jr.

Theses and Dissertations

This study explored the three primary housing alternatives along with their associated benefits and costs for military members at Robins Air Force Base. Using a case study methodology, qualitative and quantitative data were collected from contract documents, cost records, statements and testimonies to Congress, literature, census data, and interviews with civil engineering, contracting, financial management and legal professionals. This data was analyzed to determine which housing alternative seems to provide the best benefits at the lowest costs for military members and the government. The results of the study indicated that private sector alternatives are less expensive than government provided housing. …

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An Empirical Investigation Of Critical Factors Affecting The Ability Of Public Entities To Compete In Public Private Competitions, Timothy J. Gilbride Mar 2002

An Empirical Investigation Of Critical Factors Affecting The Ability Of Public Entities To Compete In Public Private Competitions, Timothy J. Gilbride

Theses and Dissertations

In 1996, the Commandant of the U.S. Coast Guard initiated the largest ever service acquisition program to re-capitalize Coast Guard assets. Called the Integrated Deepwater System or IDS, this acquisition effort seeks to renovate, modernize, and or replace the Coast Guard s entire portfolio of ships, aircraft, and support facilities. The IDS contractor will be responsible for designing and constructing the system, as well as, sharing responsibility for supporting and disposing of it. This poses a significant threat to the USCG Aircraft Repair and Supply Center (AR&SC), the Coast Guard s aircraft depot located in Elizabeth City, North Carolina. The …

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How Can The Air Force Maximize The Value Of Reverse Auctioning As A Pricing Technique?, Cynthia L. Marion-Mullins Mar 2002

How Can The Air Force Maximize The Value Of Reverse Auctioning As A Pricing Technique?, Cynthia L. Marion-Mullins

Theses and Dissertations

This research examines the pricing tool reverse auctioning. In a reverse auction buyers state the item they wish to buy and the sellers compete with each other for the sale, driving the price steadily down until no seller is willing to go any lower. Darleen A. Druyun, Principal Deputy Assistant Secretary of the Air Force for Acquisition and Management, Washington, D.C., launched the Air Force acquisition reform "Lightning Bolts" initiatives. These initiatives jump-start acquisition reform to find processes leading towards a better, faster, and cheaper way of conducting business. A reverse auction is one of these processes. A review of …

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The Predictive Validity Of The Afit Graduate Engineering And Environmental (Geem) Admission Requirements, Charles C. Zitzmann Mar 2002

The Predictive Validity Of The Afit Graduate Engineering And Environmental (Geem) Admission Requirements, Charles C. Zitzmann

Theses and Dissertations

Recognizing that a strong commitment to advanced technical and management education (Van Scotter, 1993, p. 1) serves to maintain the capability and strength of the United States Air Force (USAF), the Air Force Institute of Technology (AFIT) Graduate School of Engineering and Management (GSEM) offers a full-time, eighteen-month, Graduate Engineering and Environmental Management (GEEM) program to military officers and Department of Defense (DoD) civilian employees. The AFIT uses the applicant's undergraduate grade-point average (UGPA), Graduate Record Examination (GRE) General Test verbal and quantitative scores, and undergraduate mathematics course grade-point average (UMGPA) to select applicants for admission. This study analyzed how …

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Integrated Manet Mutual Authentication System, Jason T. Ballah Mar 2002

Integrated Manet Mutual Authentication System, Jason T. Ballah

Theses and Dissertations

The Integrated MANET Mutual Authentication System (IMMAS) provides implied mutual authentication of all routing and data traffic within a Mobile Ad Hoc Network (MANET) by combining Elliptic Curve Cryptography, a public-key cryptosystem, with the Dynamic Source Routing (DSR) Protocol. IMMAS provides security by effectively hiding network topology from adversaries while reducing the potential for, among other things, traffic analysis and data tampering, all while providing a graceful degradation for each of the authentication components. Current research in MANETs tends to focus primarily on routing issues leaving topics such as security and authentication for future research. IMMAS focuses on achieving a …

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