Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Air Force Institute of Technology

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 2971 - 3000 of 5700

Full-Text Articles in Engineering

A Multi-Objective Linear Program Model To Test Hub-And-Spoke Networks As A Potential Air Force Deployment Alternative, Andrew J. Cullen Mar 2008

A Multi-Objective Linear Program Model To Test Hub-And-Spoke Networks As A Potential Air Force Deployment Alternative, Andrew J. Cullen

Theses and Dissertations

The purpose of this research is to develop a multiple-objective mixed-integer linear programming model that determines the feasibility of a new deployment paradigm, which offers greater flexibility to home station and deployed location civil engineers (CE) by applying hub-and-spoke networking. The research covers the histories of CE and Air and Space Expeditionary Force (AEF), current CE deployment needs, multiple-objective decision analysis, hub-and-spoke networking, and organizational behavior benefits of the new paradigm. The methodology section provides details on each objective, explains the model, defines weights, and explains the objective function’s calculation. Next, an analysis of the model’s resulting scenarios helps determine …


Determining The Capability Requirements For A Space Based Optical Sensor To Determine The Trajectory Of An Incoming Antisatellite Weapon, Mesut Gulmus Mar 2008

Determining The Capability Requirements For A Space Based Optical Sensor To Determine The Trajectory Of An Incoming Antisatellite Weapon, Mesut Gulmus

Theses and Dissertations

The goal of this research is to build up a logic to catch and track incoming ASAT weapons by using space-based onboard optical sensors. The satellite orbit and ASAT trajectory of the Chinese test were generated to relate the research to the real world application. These position and velocity values are used to generate simulated observation data for a hypothetical sensor on the targeted satellite. These observation values are assumed to be true, and some representative amounts of error was added to these data. Only two body dynamics are considered; drag effect and other perturbations are neglected. The modern orbit …


Effects Of Environment On Creep Behavior Of Nextel 720/Alumina-Mullite Ceramic Composite At 1200°C, Christopher L. Genelin Mar 2008

Effects Of Environment On Creep Behavior Of Nextel 720/Alumina-Mullite Ceramic Composite At 1200°C, Christopher L. Genelin

Theses and Dissertations

The creep behavior of an oxide-oxide ceramic matrix composite (CMC) was investigated at 1200°C in laboratory air, in steam and in argon. The composite consisted of a porous alumina-mullite matrix reinforced with laminated, woven mullite/alumina (Nextel/720) fibers. The composite had no fiber coating and relied on its porous alumina/mullite matrix for flaw tolerance. Tensile stress-strain behavior was investigated and the tensile properties were measured at 1200°C in laboratory air. Tensile creep behavior of the CMC was examined for creep stress levels of 73, 91, 114 and 136 MPa. Creep run-out, set to 100 h, was achieved for stress levels ≤ …


Direct Initiation Through Detonation Branching In A Pulsed Detonation Engine, Alexander R. Hausman Mar 2008

Direct Initiation Through Detonation Branching In A Pulsed Detonation Engine, Alexander R. Hausman

Theses and Dissertations

Pulsed Detonation Engines are currently limited in operating frequency to the order of 40 Hz due to lengthy ignition and deflagration to detonation transition (DDT) times. An experimental study is conducted to determine the requirements necessary to eliminate these constraints through the concept of direct initiation. A branched detonation crossover setup is constructed and the operational requirements are determined. This research demonstrates the ability to directly initiate a detonation in a vacant tube from a detonation obtained through detonation branching. Using a hydrogen-air mixture, a tail-to-head detonation branching is achieved in which a detonation is seen to propagate from a …


Piv-Based Examination Of Deep Stall On An Oscillating Air Foil, Daniel E. Fredberg Mar 2008

Piv-Based Examination Of Deep Stall On An Oscillating Air Foil, Daniel E. Fredberg

Theses and Dissertations

A number of studies suggest that the deep stall flow fields produced by a pure-pitch and a pure-plunge oscillating airfoil are equivalent, when effective angles of attack are matched. This assumption is examined using particle image velocimetry (PIV). Sinusoidal oscillations of a pure-plunge and pure-pitch airfoil with matched reduced frequency k = 3.93 and with kinematically equivalent amplitudes of effective angle of attack are comparatively examined using results of PIV in a free surface water tunnel at AFRL/RB, Wright Patterson AFB. Experiments were conducted at Re = 10,000 and Re = 40,000, based on free stream velocity and airfoil chord, …


Contamination Study Of Micro Pulsed Plasma Thrusters, Ceylan Kesenek Mar 2008

Contamination Study Of Micro Pulsed Plasma Thrusters, Ceylan Kesenek

Theses and Dissertations

Satellite designing trend is progressing towards building smaller satellites. Small satellites require micro propulsion devices for accurate control by the propulsion system. Micro-Pulsed Plasma Thrusters (μPPTs) are highly reliable and simple micro propulsion systems that will offer attitude control, station keeping, constellation flying, and drag compensation for such satellites. As an unfortunate side effect, the plume induces contamination on spacecraft surfaces and may lead to significant problems with sensors and power generation. Solid particulates in the exhaust plume may deposit on spacecraft instrument and the solar array surfaces limiting or reducing the mission capability as well as the lifetime of …


Shi(El)Ds: A Novel Hardware-Based Security Backplane To Enhance Security With Minimal Impact To System Operation, Matthew G. Judge Mar 2008

Shi(El)Ds: A Novel Hardware-Based Security Backplane To Enhance Security With Minimal Impact To System Operation, Matthew G. Judge

Theses and Dissertations

Computer security continues to increase in importance both in the commercial world and within the Air Force. Dedicated hardware for security purposes presents and enhances a number of security capabilities. Hardware enhances both the security of the security system and the quality and trustworthiness of the information being gathered by the security monitors. Hardware reduces avenues of attack on the security system and ensures the trustworthiness of information only through proper design and placement. Without careful system design, security hardware leaves itself vulnerable to many attacks that it is capable of defending against. Our SHI(EL)DS architecture combines these insights into …


Understanding The Emergence Of Disruptive Innovation In The Air Force Science And Technology Organizations, David E. Shahady Mar 2008

Understanding The Emergence Of Disruptive Innovation In The Air Force Science And Technology Organizations, David E. Shahady

Theses and Dissertations

Although innovation is widely discussed in both military and industry venues, many organizations continue to struggle with what it means to be creative as well as maintain a competitive advantage. The United States Air Force has specifically struggled with the balance between improving existing technologies and employing revolutionary technologies. The purpose of this thesis was to study the motivation, focus, barriers, and culture needed to foster disruptive innovation in Air Force Science and Technology (S&T) and to investigate how industry innovation strategies could improve breakthrough Air Force technology emergence. The Air Force Research Laboratory (AFRL), the primary organization responsible for …


Composable Distributed Access Control And Integrity Policies For Query-Based Wireless Sensor Networks, David W. Marsh Mar 2008

Composable Distributed Access Control And Integrity Policies For Query-Based Wireless Sensor Networks, David W. Marsh

Theses and Dissertations

An expected requirement of wireless sensor networks (WSN) is the support of a vast number of users while permitting limited access privileges. While WSN nodes have severe resource constraints, WSNs will need to restrict access to data, enforcing security policies to protect data within WSNs. To date, WSN security has largely been based on encryption and authentication schemes. WSN Authorization Specification Language (WASL) is specified and implemented using tools coded in JavaTM. WASL is a mechanism{independent policy language that can specify arbitrary, composable security policies. The construction, hybridization, and composition of well{known security models is demonstrated and shown to preserve …


Extending Cfd Modeling To Near-Continuum Flows Using Enhanced Thermophysical Modeling, Abram E. Claycomb Mar 2008

Extending Cfd Modeling To Near-Continuum Flows Using Enhanced Thermophysical Modeling, Abram E. Claycomb

Theses and Dissertations

The constitutive relations found in traditional Navier-Stokes-based computational fluid dynamics solvers are known to be limited in altitude. The presence of nonequilibrium phenomena beyond what these methods are able to predict becomes more prevalent at higher altitudes, or increasing Knudsen number. The bulk viscosity, normally assumed to be zero in most computational fluid dynamics applications, is examined as a means of increasing the range of applicability of computational fluid dynamics. The bulk viscosity model used was from recent calculations available in the literature, from a new anisotropic potential energy surface, and is restricted to temperatures below 2000 K. The normal …


Damage Detection Analysis Using Lamb Waves In Restricted Geometry For Aerospace Applications, Roman T. Underwood Mar 2008

Damage Detection Analysis Using Lamb Waves In Restricted Geometry For Aerospace Applications, Roman T. Underwood

Theses and Dissertations

Today many USAF aircraft are approaching the end of their projected service life. However, those aircraft, such as the F-15 Eagle, are still being operated to accomplish the mission of the USAF. As the F-15 ages the required maintenance increases, as does the risk of structural failure. A goal of structural health monitoring (SHM) programs is to increase aircraft safety by monitoring areas known to have structural failures. Currently, time intensive manual inspections are used to monitor failure “hotspots” decreasing the readiness of the F-15 fleet. The lead ziconate titanate (PZT) is a commonly used piezoelectric transducer that has shown …


Advanced Cathodes For Next Generation Electric Propulsion Technology, Dustin J. Warner Mar 2008

Advanced Cathodes For Next Generation Electric Propulsion Technology, Dustin J. Warner

Theses and Dissertations

The research presented here investigated the feasibility of 6.4 mm Lanthanum Hexaboride (LaB6) and Cerium Hexaboride (CeB6) hollow cathodes for low power electric propulsion applications (100-300W). Two orifice geometries, one anode configuration, several anode and keeper currents, and a range of xenon flow rates were tested for the LaB6 cathode. The CeB6 cathode underwent the same tests, with the exception of the second orifice geometry due to time constraints. An oscilloscope measured waveform behavior and a single Langmuir probe for plasma properties. Infrared imaging studied the thermal characteristics of both cathodes and electron microscopy …


Dialable Cryptography For Wireless Networks, Marnita T. Eaddie Mar 2008

Dialable Cryptography For Wireless Networks, Marnita T. Eaddie

Theses and Dissertations

The objective of this research is to develop an adaptive cryptographic protocol, which allows users to select an optimal cryptographic strength and algorithm based upon the hardware and bandwidth available and allows users to reason about the level of security versus the system throughput. In this constantly technically-improving society, the ability to communicate via wireless technology provides an avenue for delivering information at anytime nearly anywhere. Sensitive or classified information can be transferred wirelessly across unsecured channels by using cryptographic algorithms. The research presented will focus on dynamically selecting optimal cryptographic algorithms and cryptographic strengths based upon the hardware and …


Constellation Design Of Geosynchronous Navigation Satellites Which Maximizes Availability And Accuracy Over A Specified Region Of The Earth, Halil Ibrahim Ozdemir Mar 2008

Constellation Design Of Geosynchronous Navigation Satellites Which Maximizes Availability And Accuracy Over A Specified Region Of The Earth, Halil Ibrahim Ozdemir

Theses and Dissertations

Currently, there are four Global Navigation Satellite Systems (GNSS) either being developed or in existence-GPS, GLONASS, Compass, and Galileo. Additionally, there are several Regional Navigation Satellite Systems (RNSS) planned or in existence, as well as numerous augmentation systems (which require a GNSS for operation). It can be anticipated that there will be interest in developing additional independent regional navigation satellite systems to cover areas of interest to particular countries or regions, who want to have their own system. In this paper, a genetic algorithm is used in an effort to determine near-optimal RNSS constellations. First, a cost function is setup, …


Increasing Combat Aircraft Survivability Through Coherent Self-Protection Jammers, Soner Ozer Mar 2008

Increasing Combat Aircraft Survivability Through Coherent Self-Protection Jammers, Soner Ozer

Theses and Dissertations

When the battlefields were within the visual range, the objective of deception tactics in warfare was to deceive the human senses. In the battlefield of electromagnetic spectrum, the objective of deception is to deceive the sensors of the enemy weapon systems. The survivability of the aircraft operating in hostile environment is of prime importance to the mission planner. If the aircraft can deny its location information to the tracking radar of the radar guided threat missile system, this, in return, may increase its survivability. The deception, a tactic which stems from the wisdom of ancient battles, incarnated in the form …


Microfluidic Power Generation, Aaron J. Sprecher Mar 2008

Microfluidic Power Generation, Aaron J. Sprecher

Theses and Dissertations

This thesis includes the detailed mathematical calculations used to determine the feasibility of harnessing electrical energy from the blood flow through human capillaries. The designs are inspired by human physiology and well established electromagnetic energy harvesting techniques and the fabrication methods have been proposed for the various components of the device. The fabrication and the design of these components have also been extensively analyzed using calculations based on the governing principles of microfluidics, kinetics, and electromagnetics. The analysis has confirmed that this design can produce sufficient energy to power a MEMS device using non-standard materials and fabrication methods. The designs …


Anti-Tamper Method For Field Programmable Gate Arrays Through Dynamic Reconfiguration And Decoy Circuits, Samuel J. Stone Mar 2008

Anti-Tamper Method For Field Programmable Gate Arrays Through Dynamic Reconfiguration And Decoy Circuits, Samuel J. Stone

Theses and Dissertations

As Field Programmable Gate Arrays (FPGAs) become more widely used, security concerns have been raised regarding FPGA use for cryptographic, sensitive, or proprietary data. Storing or implementing proprietary code and designs on FPGAs could result in the compromise of sensitive information if the FPGA device was physically relinquished or remotely accessible to adversaries seeking to obtain the information. Although multiple defensive measures have been implemented (and overcome), the possibility exists to create a secure design through the implementation of polymorphic Dynamically Reconfigurable FPGA (DRFPGA) circuits. Using polymorphic DRFPGAs removes the static attributes from their design; thus, substantially increasing the difficulty …


Construction And Testing Of Broadband High Impedance Ground Planes (Higps) For Surface Mount Antennas, Bora Cakiroglu Mar 2008

Construction And Testing Of Broadband High Impedance Ground Planes (Higps) For Surface Mount Antennas, Bora Cakiroglu

Theses and Dissertations

The purpose of this research was to design and build appropriate broadband high impedance ground planes for surface mount antennas. Broadband, low-profile antennas, such as spirals, log-periodics, and bow-ties, suffer substantially in gain and bandwidth performance when they are brought close to a conducting surface. Thus, when standard broadband antenna designs are conformally placed on vehicle bodies, they can no longer achieve the high data rates required by modern communication. A simple remedy for this has been to place an absorber lined cavity behind the antenna to preserve some bandwidth, at the expense of reduced gain. However, recently introduced high …


Improvement Of Ecm Techniques Through Implementation Of A Genetic Algorithm, James D. Townsend Mar 2008

Improvement Of Ecm Techniques Through Implementation Of A Genetic Algorithm, James D. Townsend

Theses and Dissertations

This research effective effort develops the necessary interfaces between the radar signal processing components and an optimization routine, such as genetic algorithms, to develop Electronic Countermeasure (ECM) waveforms under a Hardware-in-the-Loop (HILS) architecture. The various ECM waveforms are stored in an ECM library, where an operator selects the desired function to use against a particular system. This optimization works with modular components, compared to previous research that embedded a genetic algorithm into the Range Gate Pull-off (RGPO) waveform optimization loop, which can be interchanged based upon the operator's desired hardware/ software testing setup. The ECM library's first entries contain the …


Sensitivity Analysis Of Algan/Gan Hemts To Process Variation, Adam J. Liddle Mar 2008

Sensitivity Analysis Of Algan/Gan Hemts To Process Variation, Adam J. Liddle

Theses and Dissertations

A sensitivity analysis of AlGaN/GaN HEMT performance on material and process variations was performed. Aluminum mole fraction, barrier thickness, and gate length were varied ± 5% over nominal values to determine how sensitive simulated device performance was to changes in these 3 parameters. Simulated data was generated with the Synopsys TCAD software suite using a physics-based HEMT model. To validate model performance, simulated data was correlated with experimental data, which consisted of wafer epilayer characterization data as well as DC and small-signal RF device performance data from 1-26 GHz. Trends were observed in the experimental data due to variations in …


Laser Diagnostic System Validation And Ultra-Compact Combustor Characterization, Terry B. Hankins Mar 2008

Laser Diagnostic System Validation And Ultra-Compact Combustor Characterization, Terry B. Hankins

Theses and Dissertations

The AFIT combustion optimization and analysis laser (COAL) lab is now completely operational and is state-of-the-art in combustion diagnostics. The objective of this research is to perform a validation of a laser diagnostic system and to begin the characterization of a small-scale model of an ultra-compact combustor (UCC). Validation of the laser system was accomplished by using planar laser induced fluorescence (PLIF) on a laminar premixed hydrogen-air flame produced by a Hencken burner. OH species concentrations are measured. Flame temperatures are determined with a two line fluorescence technique using different transitions in the (1,0) band of the OH (A-X) electronic …


Digital Signal Processing Leveraged For Intrusion Detection, Theodore J. Erickson Mar 2008

Digital Signal Processing Leveraged For Intrusion Detection, Theodore J. Erickson

Theses and Dissertations

This thesis describes the development and evaluation of a novel system called the Network Attack Characterization Tool (NACT). The NACT employs digital signal processing to detect network intrusions, by exploiting the Lomb-Scargle periodogram method to obtain a spectrum for sampled network traffic. The Lomb-Scargle method for generating a periodogram allows for the processing of unevenly sampled network data. This method for determining a periodogram has not yet been used for intrusion detection. The spectrum is examined to determine if features exist above a significance level chosen by the user. These features are considered an attack, triggering an alarm. Two traffic …


Priority Based Buffering Over Multiple Lossy Links Using Tcp Aware Layer Buffering, Kevin J. Savidge Mar 2008

Priority Based Buffering Over Multiple Lossy Links Using Tcp Aware Layer Buffering, Kevin J. Savidge

Theses and Dissertations

Wireless military information systems require high reliability, which is difficult to achieve in adverse conditions. To provide high reliability, one must overcome packet loss across multiple wireless hops. Buffering packets in a lossy environment is well explored; however, the ability to selectively buffer TCP traffic across multiple lossy links is a new area of research. This document seeks to explore the delivery of high priority traffic in a lossy environment and conclude that prioritized buffing can increase the probability that a high priority download will finish, where others will fail. It is shown that buffering provides six times the throughput …


Mission Impact Analysis Visualization For Enhanced Situational Awareness, Sean C. M. Carroll Mar 2008

Mission Impact Analysis Visualization For Enhanced Situational Awareness, Sean C. M. Carroll

Theses and Dissertations

This research effort examines the creation of mission impact analysis visualizations to enhance situational awareness. It focuses on using prefuse to create a visualization that allows the user to quickly understand the impact of the failure of any element needed directly or indirectly for a mission. The visualization correctly identifies the direct or indirect impact on physical requirements such as network links and servers as well as non-physical elements such as the generation of a report, or ability to perform a task. The visualization provides an overview of the situation, as well as including enhancements to allow for greater detail …


Evaluating Security And Quality Of Service Considerations In Critical Infrastructure Communication Networks, Gregory R. Roberts Mar 2008

Evaluating Security And Quality Of Service Considerations In Critical Infrastructure Communication Networks, Gregory R. Roberts

Theses and Dissertations

This thesis demonstrates the benefits of utility communication based on Internet technology, some dangers in using Internet technology in establishing a utility intranet connecting protection and control systems, and compares three different approaches to making reservations for routing traffic in the utility intranet based on different levels of background traffic. A model of expected background traffic on a national utility intranet is presented. The Utility Communication Architecture 2.0 and the International Electrotechnical Commission (IEC) 61850 began laying the groundwork in 2002 in establishing an infrastructure allowing power substations, program logic controllers, remote terminal units, intelligent electronic devices, and other devices …


Hot Swapping Protocol Implementations In The Opnet Modeler Development Environment, Mark E. Coyne Mar 2008

Hot Swapping Protocol Implementations In The Opnet Modeler Development Environment, Mark E. Coyne

Theses and Dissertations

This research effort demonstrates hot swapping protocol implementations in OPNET via the building of a dependency injection testing framework. The thesis demonstrates the externalization (compiling as stand-alone code) of OPNET process models, and their inclusion into custom DLL's (Dynamically Linked Libraries). A framework then utilizes these process model DLL's, to specify, or “inject,” process implementations post-compile time into an OPNET simulation. Two separate applications demonstrate this mechanism. The first application is a toolkit that allows for the testing of multiple routing related protocols in various combinations without code re-compilation or scenario re-generation. The toolkit produced similar results as the same …


Multi-Reference Frame Image Registration For Rotation, Translation, And Scale, Christopher S. Costello Mar 2008

Multi-Reference Frame Image Registration For Rotation, Translation, And Scale, Christopher S. Costello

Theses and Dissertations

This thesis investigates applications of multi-reference frame image registration for image sets with various translation, rotation, and scale combinations. It focuses on registration accuracy improvement over traditional pairwise registration, and also compares the quality of scene estimation from frame averaging. Three experiments are developed which use cross-correlation to estimate translation, the Radon transform to estimate translation and rotation, and the Fourier-Mellin transform to estimate translation, rotation, and scale. Results from applying multi-reference frame registration in these experiments show distinct improvements in both registration accuracy and quality of frame averaging compared to single-reference frame registration. Furthermore, it is shown that the …


Characterization And Implementation Of A Real-World Target Tracking Algorithm On Field Programmable Gate Arrays With Kalman Filter Test Case, Benjamin D. Hancey Mar 2008

Characterization And Implementation Of A Real-World Target Tracking Algorithm On Field Programmable Gate Arrays With Kalman Filter Test Case, Benjamin D. Hancey

Theses and Dissertations

A one dimensional Kalman Filter algorithm provided in Matlab is used as the basis for a Very High Speed Integrated Circuit Hardware Description Language (VHDL) model. The JAVA programming language is used to create the VHDL code that describes the Kalman filter in hardware which allows for maximum flexibility. A one-dimensional behavioral model of the Kalman Filter is described, as well as a one-dimensional and synthesizable register transfer level (RTL) model with optimizations for speed, area, and power. These optimizations are achieved by a focus on parallelization as well as careful Kalman filter sub-module algorithm selection. Newton-Raphson reciprocal is the …


Effects Of Multipath And Oversampling On Navigation Using Orthogonal Frequency Division Multiplexed Signals Of Opportunity, Christopher M. Schexnayder Mar 2008

Effects Of Multipath And Oversampling On Navigation Using Orthogonal Frequency Division Multiplexed Signals Of Opportunity, Christopher M. Schexnayder

Theses and Dissertations

The Global Positioning System (GPS) has become the primary system for navigation and precise positioning. GPS has limitations, though, and is not suitable in environments where a line-of-site (LOS) path to multiple satellites is not available. Reliable alternatives need to be developed to provide GPS-like positioning when GPS is unavailable. One such alternative is to use signals of opportunity (SoOP). This concept refers to navigation using signals which inherently exist in the environment and were developed for non-navigation applications. This research focuses on exploiting the Orthogonal Frequency Division Multiplexed (OFDM) signal for the purpose of navigation. An algorithm was developed …


Hardware Algorithm Implementation For Mission Specific Processing, Jason W. Shirley Mar 2008

Hardware Algorithm Implementation For Mission Specific Processing, Jason W. Shirley

Theses and Dissertations

There is a need to expedite the process of designing military hardware to stay ahead of the adversary. The core of this project was to build reusable, synthesizeable libraries to make this a possibility. In order to build these libraries, Matlab® commands and functions, such as Conv2, Round, Floor, Pinv, etc., had to be converted into reusable VHDL modules. These modules make up reusable libraries for the Mission Specific Process (MSP) which will support AFRL/RY. The MSP allows the VLSI design process to be completed in a mere matter of days or months using an FPGA or ASIC design, as …