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 1651 - 1680 of 5700

Full-Text Articles in Engineering

Method For Determining Time-Resolved Heat Transfer Coefficient And Adiabatic Effectiveness Waveforms With Unsteady Film Cooling, James L. Rutledge, Jonathan F. Mccall Apr 2016

Method For Determining Time-Resolved Heat Transfer Coefficient And Adiabatic Effectiveness Waveforms With Unsteady Film Cooling, James L. Rutledge, Jonathan F. Mccall

AFIT Patents

A new method for determining heat transfer coefficient (h) and adiabatic effectiveness (η) waveforms h(t) and η(t) from a single test uses a novel inverse heat transfer methodology to use surface temperature histories obtained using prior art approaches to approximate the h(t) and η(t) waveforms. The method best curve fits the data to a pair of truncated Fourier series.

Go to article

Identification Of The Zinc-Oxygen Divacancy In Zno Crystals, Maurio S. Holston, Eric M. Golden, Brant E. Kananen, John W. Mcclory, Nancy C. Giles, Larry E. Halliburton Apr 2016

Identification Of The Zinc-Oxygen Divacancy In Zno Crystals, Maurio S. Holston, Eric M. Golden, Brant E. Kananen, John W. Mcclory, Nancy C. Giles, Larry E. Halliburton

Faculty Publications

An electron paramagnetic resonance (EPR) spectrum in neutron-irradiated ZnO crystals is assigned to the zinc-oxygen divacancy. These divacancies are observed in the bulk of both hydrothermally grown and seeded-chemical-vapor-transport-grown crystals after irradiations with fast neutrons. Neutral nonparamagnetic complexes consisting of adjacent zinc and oxygen vacancies are formed during the irradiation. Subsequent illumination below ∼150 K with 442 nm laser light converts these (V2−Zn − V2+O)0 defects to their EPR-active state (V−Zn − V2+O)+ as electrons are transferred to donors. The resulting photoinduced S = 1/2 spectrum of the …

Go to article

Data Quality Challenges In Distributed Live-Virtual-Constructive Test Environments, Jeremy R. Millar, Douglas D. Hodson, Gilbert L. Peterson, Darryl K. Ahner Apr 2016

Data Quality Challenges In Distributed Live-Virtual-Constructive Test Environments, Jeremy R. Millar, Douglas D. Hodson, Gilbert L. Peterson, Darryl K. Ahner

Faculty Publications

Live-Virtual-Constructive (LVC) simulations are complex systems comprising a combination of live (real people operating real equipment), virtual (real people operating simulated equipment or vice versa), and constructive (wholly simulated) entities. Nodes in the system support the simulation of one or more entities and are often geographically distributed to leverage unique assets (e.g., physical test range space or high-fidelity full motion simulators). Abstract excerpt © ACM

Go to article

Integrity Determination For Image Rendering Vision Navigation, Sean M. Calhoun Mar 2016

Integrity Determination For Image Rendering Vision Navigation, Sean M. Calhoun

Theses and Dissertations

This research addresses the lack of quantitative integrity approaches for vision navigation, relying on the use of image or image rendering techniques. The ability to provide quantifiable integrity is a critical aspect for utilization of vision systems as a viable means of precision navigation. This research describes the development of two unique approaches for determining uncertainty and integrity for a vision based, precision, relative navigation system, and is based on the concept of using a single camera vision system, such as an electro-optical (EO) or infrared imaging (IR) sensor, to monitor for unacceptably large and potentially unsafe relative navigation errors. …

Go to article

Geosynchronous Binary Object Detection, Patrick B. Cunningham Mar 2016

Geosynchronous Binary Object Detection, Patrick B. Cunningham

Theses and Dissertations

This paper will compare competing methods for optically detecting binary objects. This is mostly intended for use in Space Situational Awareness (SSA), though has the potential to be used in other applications. The first method referred to as, “Single Object Detection” is a versatile algorithm which is currently used to detect extraterrestrial objects. However, it does not take into account interference by a nearby object. Therefore a second algorithm is investigated, referred to as “Binary Object Detection”, which does. The binary detection algorithm proved to have a comparable or superior Receiver Operating Characteristic (ROC) curve (based upon the area under …

Go to article

Characterization Of Quad-Copter Positioning Systems And The Effect Of Pose Uncertainties On Field Probe Measurements, James C. Dossett Mar 2016

Characterization Of Quad-Copter Positioning Systems And The Effect Of Pose Uncertainties On Field Probe Measurements, James C. Dossett

Theses and Dissertations

When measuring the Radar Cross Section (RCS) of a test object, many uncertainties must be accounted for, such as the non-homogeneous nature of the medium between the radar test equipment and the platform under test. There are a variety of other error sources, including clutter and Radio Frequency Interference (RFI), motivating the development of techniques to measure and model the uncertainties in RCS measurements. The following research, in unison with prior and current efforts, intends to reduce the impact of these uncertainties by utilizing a unique two-way field probe in the form of a geodesic sphere encompassing a commercial quad-copter …

Go to article

Design And Analysis Of A Retroreflective Array For Ir Application, Michael E. Bollinger Mar 2016

Design And Analysis Of A Retroreflective Array For Ir Application, Michael E. Bollinger

Theses and Dissertations

This research investigates the adaptation of a Van Atta style of retrodirective array designed to work at 2 GHz to work in the infrared spectrum of 8-12 μm centered at 30 THz. The Computational Research and Engineering Acquisition Tools and Environments (CREATE) software suite and high performance computing (HPC) resources of the HPC Modernization program were utilized to model and simulate multiple steps of an adaptation process to illustrate and examine the incremental performance changes of frequency scaling the design. Two different substrate materials, germanium and hafnium oxide, are evaluated as the dielectric materials, and a comparison of the broadband …

Go to article

Towards Automated Aerial Refueling: Real Time Position Estimation With Stereo Vision, Bradley D. Denby Mar 2016

Towards Automated Aerial Refueling: Real Time Position Estimation With Stereo Vision, Bradley D. Denby

Theses and Dissertations

Aerial refueling is essential to the United States Air Force (USAF) core mission of rapid global mobility. However, in-flight refueling is not available to remotely piloted aircraft (RPA) or unmanned aerial systems (UAS). As reliance on drones for intelligence, surveillance, and reconnaissance (ISR) and other USAF core missions grows, the ability to automate aerial refueling for such systems becomes increasingly critical. New refueling platforms include sensors that could be used to estimate the relative position of an approaching aircraft. Relative position estimation is a key component to solving the automated aerial refueling (AAR) problem. Analysis of data from a one-seventh …

Go to article

Satellite Ephemeris Correction Via Remote Site Observation For Star Tracker Navigation Performance Improvement, Jorge E. Diaz Mar 2016

Satellite Ephemeris Correction Via Remote Site Observation For Star Tracker Navigation Performance Improvement, Jorge E. Diaz

Theses and Dissertations

In order for celestial navigation observing satellites to provide accurate positioning estimates, precise ephemerides of the observed satellites are necessary. This work analyzed a method to correct for satellite ephemeris to be used in celestial navigation applications. This correction is the measured angle differences between the expected location of the satellite, which is given by propagating publicly available Two-Line Elements (TLE), and their observed angles from a precisely known reference site. Therefore, the angle difference can be attributed completely to satellite ephemeris error assuming instrument error was accounted for. The intent is to calculate this correction from the reference site …

Go to article

Using Phase Screens To Synthesize Electromagnetic Gaussian-Schell Model Sources With Desired Amplitude, Coherence, And Polarization, Christopher K. Kokoczka Mar 2016

Using Phase Screens To Synthesize Electromagnetic Gaussian-Schell Model Sources With Desired Amplitude, Coherence, And Polarization, Christopher K. Kokoczka

Theses and Dissertations

An electromagnetic Gaussian-Schell model (EGSM) source is built with desired coherence, amplitude, and polarization using correlated phase screens based on re- search conducted in Refs. [2, 9]. A new method of amplitude control is presented and tested using spatial light modulators (SLM). A brief review of theory and concepts is discussed followed by methods of how to build an EGSM source, correlated phase screens, and control amplitude using SLM gratings. The experimental set-up is presented which builds EGSM sources that demonstrate desired amplitude, coherence, and polarization. Irradiance correlation, degree of polarization, and Stokes parameters S0 and S1 are …

Go to article

Dynamic Honeypot Configuration For Programmable Logic Controller Emulation, Kyle A. Girtz Mar 2016

Dynamic Honeypot Configuration For Programmable Logic Controller Emulation, Kyle A. Girtz

Theses and Dissertations

Attacks on industrial control systems and critical infrastructure are on the rise. Important systems and devices like programmable logic controllers are at risk due to outdated technology and ad hoc security measures. To mitigate the threat, honeypots are deployed to gather data on malicious intrusions and exploitation techniques. While virtual honeypots mitigate the unreasonable cost of hardware-replicated honeypots, these systems often suffer from a lack of authenticity due to proprietary hardware and network protocols. In addition, virtual honeynets utilizing a proxy to a live device suffer from performance bottlenecks and limited scalability. This research develops an enhanced, application layer emulator …

Go to article

A Practical Wireless Exploitation Framework For Z-Wave Networks, Joseph L. Hall Mar 2016

A Practical Wireless Exploitation Framework For Z-Wave Networks, Joseph L. Hall

Theses and Dissertations

Wireless Sensor Networks (WSN) are a growing subset of the emerging Internet of Things (IoT). WSNs reduce the cost of deployment over wired alternatives; consequently, use is increasing in home automation, critical infrastructure, smart metering, and security solutions. Few published works evaluate the security of proprietary WSN protocols due to the lack of low-cost and effective research tools. One such protocol is ITU-T G.9959-based Z-Wave, which maintains wide acceptance within the IoT market. This research utilizes an open source toolset, presented herein, called EZ-Wave to identify methods for exploiting Z-Wave devices and networks using Software-Defined Radios (SDR). Herein, techniques enabling …

Go to article

Tunable Terahertz Metamaterials With Germanium Telluride Components, Christopher H. Kodama Mar 2016

Tunable Terahertz Metamaterials With Germanium Telluride Components, Christopher H. Kodama

Theses and Dissertations

Terahertz (THz) technology is an emerging field with many exciting applications. THz waves can be used to locate explosives and illicit drugs in security applications, or DNA and other molecule resonances in medical applications. THz frequencies represent the next level of modern, high-speed computing, but they also can be used for covert battlefield communications links. Metamaterials are an integral part of THz technology because they can be used to create exotic material properties—permittivities and permeabilities—in a part of the frequency spectrum that is otherwise rather empty and passive. This work aims to acquire a fuller understanding of THz metamaterials in …

Go to article

Characterization For The Development Of The Hybrid Multi-Junction Silicon Germanium Solar Cell, Jimmy J. Lohrman Mar 2016

Characterization For The Development Of The Hybrid Multi-Junction Silicon Germanium Solar Cell, Jimmy J. Lohrman

Theses and Dissertations

Based on the previous development of the hybrid multi-junction silicon (HMJ-Si) solar cell, this work characterized the preceding design for the development of the hybrid multi-junction silicon germanium (HMJ-SiGe) solar cell. Seven focus areas were investigated: diffraction pattern generation, photon propagation, silicon diffusion processing, ohmic contacts, the distributed Bragg reflector (DBR), the Fresnel zone plate (FZP), and the germanium/germanium telluride (Ge/GeTe) pn-junction Diffraction patterns were theoretically examined, and contact grating design characterization for reflectance and transmittance properties was modeled using rigorous coupled wave analysis. An improved silicon diffusion process follower was developed, and theoretical study and experimental assessment were accomplished …

Go to article

Implementation And Performance Of Factorized Backprojection On Low-Cost Commercial-Off-The-Shelf Hardware, Alec C. Rasmussen Mar 2016

Implementation And Performance Of Factorized Backprojection On Low-Cost Commercial-Off-The-Shelf Hardware, Alec C. Rasmussen

Theses and Dissertations

Traditional Synthetic Aperture Radar (SAR) systems are large, complex, and expensive platforms that require significant resources to operate. The size and cost of the platforms limits the potential uses of SAR to strategic level intelligence gathering or large budget research efforts. The purpose of this thesis is to implement the factorized backprojection SAR image processing algorithm in the C++ programming language and test the code's performance on a low cost, low size, weight, and power (SWAP) computer: a Raspberry Pi Model B. For a comparison of performance, a baseline implementation of filtered backprojection is adapted to C++ from pre-existing MATLAB® …

Go to article

Visual-Ins Using A Human Operator And Converted Measurements, Turner J. Montgomery Mar 2016

Visual-Ins Using A Human Operator And Converted Measurements, Turner J. Montgomery

Theses and Dissertations

A method human operated INS aiding is explored in which the pilot identifies and tracks a ground feature of unknown position over a short measurement epoch using an E/O sensor. One then refers to Visual-INS. In contrast to current research trends, a human operator is entrusted with visually tracking the ground feature. In addition, a less conventional measurement linearization technique is applied to generate “converted” measurements. A linear regression algorithm is then applied to the converted measurements providing an estimate of the INS horizontal velocity error and accelerometer biases. At the completion of the measurement epoch, the INS is corrected …

Go to article

Electromagnetic Characterization Of Materials Using A Dual Chambered High Temperature Waveguide, Jeffrey S. Sovern Mar 2016

Electromagnetic Characterization Of Materials Using A Dual Chambered High Temperature Waveguide, Jeffrey S. Sovern

Theses and Dissertations

Measurement of the electromagnetic properties of materials at high temperatures is important for industrial, scientific, medical, and aerospace applications [1]. Current high-temperature electromagnetic material characterization is a time consuming process that typically requires three days to collect data from one material specimen. For example, the standard high-temperature process involving rectangular waveguides [2] requires measurements of the sample (1), the empty waveguide (2), and a metal short standard (3) completed in separate heated runs over three days to perform the Nicolson-Ross-Weir inversion algorithm for computing permittivity and permeability. The technique developed here will reduce the high-temperature measurement process from three days …

Go to article

Dynamic Network Security Control Using Software Defined Networking, Michael C. Todd Mar 2016

Dynamic Network Security Control Using Software Defined Networking, Michael C. Todd

Theses and Dissertations

This thesis develops and implements a process to rapidly respond to host level security events using a host agent, Software Defined Networking and OpenFlow updates, role based flow classes, and Advanced Messaging Queuing Protocol to automatically update configuration of switching devices and block malicious traffic. Results show flow table updates are made for all tested levels in less than 5.27 milliseconds and event completion time increased with treatment level as expected. As the number of events increases from 1,000 to 50,000, the design scales logarithmically caused mainly by message delivery time. Event processing throughput is limited primarily by the message …

Go to article

Field-Based Phase Retrieval Using Under-Sampled Data, Tatsuki L. Watts Mar 2016

Field-Based Phase Retrieval Using Under-Sampled Data, Tatsuki L. Watts

Theses and Dissertations

A phase retrieval algorithm designed for use with under-sampled astronomical data is developed in this thesis. Blind-deconvolution, Gerchberg Saxton (GS), and a field-based compass search are combined into an algorithm capable of recovering Zernike coefficients 4 through 11 from single frames of noisy, under-sampled data without the need to unwrap the recovered phase. The performance of the algorithm in data under-sampled by a factor of 2 is compared the performance of the algorithm on Nyquist-sampled data. In simulation trials, the magnitudes of all 8 estimated Zernike coefficients converged to within half a wave of the true values for 98% of …

Go to article

Radiation Response From A Novel Uo2 Crystal, Stephan A. Varga Mar 2016

Radiation Response From A Novel Uo2 Crystal, Stephan A. Varga

Theses and Dissertations

The radiation response of a novel, single-crystalline UO2 sample was analyzed using several types of radiation. The crystal was exposed to alpha, gamma, and neutron radiation under various environmental conditions and the electronic response of the crystal was measured using a pulse shape discrimination algorithm. The distributions of pulse amplitude (Vmax) and pulse decay times (τ) were used to compare the output. This research revealed that the crystal radiation response is exceptionally sensitive to surface conditions, specifically humidity, which tends to alter the time dependent currents resulting from the radiation interactions. The pulse τ can be made to …

Go to article

Improved Performance By The Tie-Gcm With The Inclusion Of Helium As A Major Species, Fredrick R. Schmidt Mar 2016

Improved Performance By The Tie-Gcm With The Inclusion Of Helium As A Major Species, Fredrick R. Schmidt

Theses and Dissertations

When considering the neutral constituents in the upper thermosphere and exosphere, helium needs to be accounted for as a major species. As detailed by Emmert [2015], most first-principle models do not consider helium a major species when solving for diffusion and collisions within the atmosphere. First-principle, physics-based models hold a distinct advantage of seasonal variations and spatial resolution over empirical models which leads to a more realistic depiction of the atmosphere. The National Center for Atmospheric Research’s (NCAR) self-consistent, physics-based Thermosphere-Ionosphere-Electrodynamic General Circulation Model (TIE-GCM) has been updated to take into account this neutral constituent in its calculations. The major …

Go to article

Heterogeneous Air Defense Battery Location: A Game Theoretic Approach, Nicholas T. Boardman Mar 2016

Heterogeneous Air Defense Battery Location: A Game Theoretic Approach, Nicholas T. Boardman

Theses and Dissertations

The Unites States and its allies confront a persistent and evolving threat from missile attacks as nations around the world continue to invest and advance their current capabilities. Within the air defense context of a missile-and-interceptor engagement, a challenge for the defender is that surface to air interceptor missile batteries often must be located to protect high-value targets dispersed over a vast area, subject to an attacker observing the disposition of batteries prior to developing and implementing an attack plan. To model this scenario, we formulate a two-player, three-stage, perfect information, sequential move, zero-sum game that accounts for, respectively, a …

Go to article

Simulation Of Modeling Sortie Generation Process In Turaf, Bahadir Aykiri Mar 2016

Simulation Of Modeling Sortie Generation Process In Turaf, Bahadir Aykiri

Theses and Dissertations

Simulation is a useful technique for engineers and operations researchers. One of the primary advantages of simulation models is that they are able to provide users with practical feedback when analyzing real-world systems. This thesis builds a discrete event simulation of the sortıe generatıon process, to help decision makers in performing analyses regarding quantity of manpower, bottlenecks in supply and maintenance activities; as well as utilization of maintenance manpower, cost and number of sorties produced in a specific time. We only model one aircraft system with four Line Replacement Units (LRU), but any system and its LRUs can be included …

Go to article

Determination Of Fire Control Policies Via Approximate Dynamic Programming, Michael T. Davis Mar 2016

Determination Of Fire Control Policies Via Approximate Dynamic Programming, Michael T. Davis

Theses and Dissertations

Given the ubiquitous nature of both offensive and defensive missile systems, the catastrophe-causing potential they represent, and the limited resources available to countries for missile defense, optimizing the defensive response to a missile attack is a necessary endeavor. For a single salvo of offensive missiles launched at a set of targets, a missile defense system protecting those targets must decide how many interceptors to fire at each incoming missile. Since such missile engagements often involve the firing of more than one attack salvo, we develop a Markov decision process (MDP) model to examine the optimal fire control policy for the …

Go to article

A Response Surface Validation Of A Quantum Key Distribution Model, Jacob M. Ehrlich Mar 2016

A Response Surface Validation Of A Quantum Key Distribution Model, Jacob M. Ehrlich

Theses and Dissertations

The need for secure communication in the presence of an adversary introduced the field of cryptology -- the practice and study of techniques for secure communication. A common method to secure communication is to distribute a secret key among authorized parties so they can encrypt and decrypt messages between each other. By doing so, ideally, any messages intercepted by a third party are meaningless. An innovative technique to distribute a shared key is Quantum Key Distribution (QKD). QKD uses laws of quantum mechanics to generate and distribute such keys. The purpose of this thesis is to validate an existing mathematical …

Go to article

Analysis Of Military Entry Control Point Queueing, Justin J. Dwyer Mar 2016

Analysis Of Military Entry Control Point Queueing, Justin J. Dwyer

Theses and Dissertations

Military Entry Control Facilities (ECFs) are unique service queues that are constrained by space, receive high peak traffic flow, and have a customer base that must receive service. Due to complexity of the interactions within the system, simulations provide input that would be impractical for quantitative experimentation. Our research examines relationships within the ECF in order to develop insights that could lead to more efficient daily operations. We focus the research on interactions that generate a queue length that would interfere with traffic flow surrounding the base. Examining the interactions between multiple arrival rates and service times as well as …

Go to article

Epidemiology, Cost, And Aircraft Choice For Aeromedical Evacuation In Africom, Daniel A. Griffith Mar 2016

Epidemiology, Cost, And Aircraft Choice For Aeromedical Evacuation In Africom, Daniel A. Griffith

Theses and Dissertations

A significant shortfall exists in the medical capability provided to US Service members deployed to the African Area of Responsibility because of unknown epidemiology, large distances, limited resources, and high patient movement cost. The first step in closing this gap is to understand the types, demographics, diagnoses, and distribution of the patients requiring aeromedical evacuation. This research examined the DoD’s aeromedical evacuation missions from Africa between 2010 and 2014. Of the 274 patients and 170 missions identified from available data, a gap is evident in aeromedical evacuation capability with over 23% of Priority patients and almost 10% of Urgent patients …

Go to article

An Examination Of Economic Metrics As Indicators Of Air Force Retention, Helen L. Jantscher Mar 2016

An Examination Of Economic Metrics As Indicators Of Air Force Retention, Helen L. Jantscher

Theses and Dissertations

Fluctuations in the economy can cause military recruitment and retention plans to go awry. By focusing on various economic metrics, it is possible to anticipate changes in retention rates for specific Air Force Specialty Codes (AFSCs). To address the challenge of maintaining a robust and mission capable Air Force, a correlation analysis is employed to determine the relationship between certain economic indicators and AFSC retention rates. As one might suspect, retention rates follow the trend of decreasing when the economy is strong. Of interest, we found two AFSCs which go against this trend. Namely, the retention rates for officers in …

Go to article

Overhaul Facility Planning And Control Tool Selection And Implementation Analysis, Santiago L. Martin Mar 2016

Overhaul Facility Planning And Control Tool Selection And Implementation Analysis, Santiago L. Martin

Theses and Dissertations

The Argentine Air Force Materiel General Directorate (AAFMGD) has initiated an effort to assure logistical support and to gradually increase the productivity and efficiency of related processes. Within the efforts of increased productivity and efficiency over the AAF Overhauling Facilities, the Planning and Control Departments (PCD) became targets for improvements. These departments are tasked with providing the best certainty and visibility of all assets within their facilities to feed the logistics pipeline, and better support air operations. This thesis, sponsored by the MGD, is focused on achieving improvements in the PCD processes, through an academically rigorous evaluation of confounding factors …

Go to article

A "Big Bang" Versus A "Small Bang" Approach: A Case Study Of The Expeditionary Combat Support System (Ecss) And The Maintenance, Repair, And Overhaul Initiative (Mroi), George B. Lafiguera Mar 2016

A "Big Bang" Versus A "Small Bang" Approach: A Case Study Of The Expeditionary Combat Support System (Ecss) And The Maintenance, Repair, And Overhaul Initiative (Mroi), George B. Lafiguera

Theses and Dissertations

In 2003, the United States Air Force embarked on one of the largest and most comprehensive logistical transformation to delineate the logistics community’s strategy for supporting the warfighter. A key aspect of this campaign plan was to leverage information technology through an enterprise resource planning (ERP) solution called the Expeditionary Combat Support System (ECSS), a “big-bang” approach. In early 2012, the ECSS program was cancelled mainly due to uncontrollable increases in costs and schedule overruns. In late 2012, the Air Force Sustainment Center (AFSC) launched the Maintenance, Repair, and Overhaul initiative (MROi), a “small-bang” approach, to increase enterprise visibility and …

Go to article

First Prev Next Last