Digital Commons Network^™

Durability Of Mwcnt Composites Under Electron And Neutron Irradiation, Quan-Hai T. Lu

Theses and Dissertations

Electromagnetic interference shielding effectiveness and conductive properties of carbon nanotube containing composites intended for use as satellite surface materials have been investigated following electron and neutron irradiation. The MWCNT composites were irradiated to fluence levels of 10¹⁶ electrons/cm² with 500 keV electrons. Increase in EMI-SE and conductivity was observed following electron irradiation in two of the samples. The sample with alternating layers of MWCNT and glass had a decrease in conductivity and an increase in EMI-SE post irradiation. This would suggest that the different layered configuration does play a role in the durability of the composite. Having multiple …

Spectral And Spatial Coherent Emission Of Thermal Radiation From Metal-Semiconductor Nanostructures, Shane N. Mcconnell

Theses and Dissertations

The spectral and spatial radiative properties of coherent thermal emission in the mid- and far-IR through the use of micro and nano-structured metal-semiconductor materials were designed and demonstrated experimentally. Using an implementation of the Rigorous Coupled Wave Analysis and Computer Simulation Technology (CST), two structures were designed to selectively emit at mid- and far-IR wavelengths, a 1-D truncated multilayer resonator and a 3-D hybrid photonic crystal (PC)-multilayer. A High Impulse Power Magnetron Sputtering (HIPIMS) deposition technique was used to fabricate two silver-germanium-silver (Ag-Ge-Ag) resonating structures with layer thicknesses of 6-240-160 nm for one sample and 6-700-200 nm for the other. …

Neutron Detection Using Amorphous Boron-Carbide Hetero-Junction Diodes, Thomas P. Mcquary

Theses and Dissertations

The high energy products of the ¹⁰B(n,α)⁷Li neutron capture reaction were explored as a means of thermal neutron detection in thin film amorphous boron carbide (a--B₅C:H_x) on n-type silicon hetero-junction diodes. Pulse height spectroscopy was conducted on the diodes while they were subjected to a moderated plutonium-beryllium (PuBe) source. Neutron capture could not be confirmed experimentally in any of the devices tested. Device modeling was performed to investigate the cause for the diode detector's negative response. A 1.47 MeV α particle produced transient current of 10^-7 A and the induced was 4.7 …

Cesium Absorption Spectrum Perturbed By Argon: Observation Of Non-Lorentzian Far Wings, Gordon E. Lott

Theses and Dissertations

The purpose of this research was to observe the core and far wing absorption spectra of the D₁ and D₂ lines of cesium (Cs) perturbed by argon (Ar). A 1.33 m scanning monochromator with a PMT detector was used to measure the spectra from 8300 Å to 9100 Å. A heat pipe was used to control the Cs concentration and Ar pressure allowing for a broad range of spectra to be collected. Spectra were collected for heat pipe temperatures of 50, 75, 100, 125, 150 and 175 °C, corresponding to Cs concentrations of approximately 6×10¹¹, 4×10 …

Characterization Of A Hyperspectral Chromotomographic Imaging Ground System, Chad B. Su'e

Theses and Dissertations

A field-deployable hyperspectral chromotomographic imager has been developed and tested as a risk-reduction prototype to assist design of a space-based system. The instrument uses a high-speed video camera looking through a rotating direct-vision prism to simultaneously observe the full field of view in all visible wavelength channels. The chromotomographic process multiplexes the spectral and spatial so an advanced reconstruction algorithm is required to separate the spectral channels. A physics-based model of the instrument was developed to assist in future trade-space choices for design of the spaced-based system. Additionally, the model is used for the development and assessment of the filtered …

A Quantitative Analysis Of Solar Flare Characteristics As Observed In The Solar Observing Optical Network And The Global Oscillation Network Group, Thomas M. Wittman

Theses and Dissertations

This study consists of a quantitative comparison of H-alpha solar flare area and brightness as recorded by the Solar Observing Optical Network (SOON) and the Global Oscillation Network Group (GONG) from March 11 through November 30, 2011. The Air Force utilizes the three-site SOON network for H-alpha flare monitoring, while the six-site GONG network, managed by the National Solar Observatory, provides backup H alpha flare monitoring for SOON. A total of 1000 flares were observed and 100 of these were rated larger or brighter than the 0-F category. In the SOON network, 8% of flares observed by two sites had …

Local Histograms For Per-Pixel Classification, Melody L. Massar

Theses and Dissertations

We introduce a rigorous mathematical theory for the analysis of local histograms, and study how they interact with textures that can be modeled as occlusions of simpler components. We first show how local histograms can be computed as a system of convolutions and discuss some basic local histogram properties. We then introduce a probabilistic, occlusion-based model for textures and formally demonstrate that local histogram transforms are natural tools for analyzing the textures produced by our model. Next, we characterize all nonlinear transforms which satisfy the three key properties of local histograms and consider the appropriateness of local histogram features in …

Using Vft As A Constraint For Goal Programming Models: A Case Study For Turkish Air Force Flying Hour Program, Ahmet Bengoz

Theses and Dissertations

In its 60-year history, there have been many published documents in the literature about goal programming (GP), but contributions to the literature are still needed. This research intends to add to the literature on goal-programming models by discussing one of the key assumptions of GP regarding linearity, and by discussing some of the issues regarding incommensurability (difference in data types) and weighting. GP requires an interaction between the decision maker (DM) and the analyst to ensure that the model reflects the DM's preferences. However, it may be difficult for them to interact if the mathematical model is very large and …

Cubesat Attitude Determination And Helmholtz Cage Design, Megan R. Brewer

Theses and Dissertations

A method of 3-axis satellite attitude determination utilizing six body-fixed light sensors and a 3-axis magnetometer is analyzed. A Helmholtz cage is designed, built, and tested to provide a dynamic, 3-axis, uniform magnetic field to cancel the Earth's magnetic field and create an environment similar to the geomagnetic field a satellite would experience on-orbit. A CubeSat is provided the inertial magnetic vector and Sun vector, which are combined with data from the light sensors and magnetometer in a CubeSat. Attitude is estimated on-board the CubeSat via the optimal fast quaternion estimation algorithm. The capabilities of the Helmholtz cage, including the …

Conceptual Layout Of Wing Structure Using Topology Optimization For Morphing Micro Air Vehicles In A Perching Maneuver, James R. Elgersma

Theses and Dissertations

A topology optimization model for conceptual wing structure layouts of morphing micro air vehicles (MAVs) has been developed and implemented in MATLAB. Specifically, a six degree-of-freedom finite element (FE) model with a general quadrilateral discretization scheme was created by superposition of a known simple linear plane membrane element and a Kirchhoff plate bending element derived herein. The purpose of the six degree-offreedom model was to accommodate in-plane and out-of-plane aerodynamic loading combinations. The FE model was validated and the MATLAB implementation was verified with classical beam and plate solutions. A compliance minimization optimization objective was then formulated with the Solid …

Accurate Modeling Of Stability And Control Properties For Fighter Aircraft From Cfd, Jedediah H. Butler

Theses and Dissertations

Difficulties in obtaining accurate Stability and Control (S&C) data for nonlinear regions in the flight envelope early in the design phase often lead to costly fixes late in the acquisition process. Work examined herein addresses this problem by utilizing recent advances in Computational Fluid Dynamics (CFD) to create a high-fidelity database before any parts have to be physically produced. In combination with CFD, System Identification (SID) is used to characterize the S&C characteristics of aircraft by some Reduced Order Model (ROM). The method of obtaining enough data in the right places, via some optimized maneuver, to create an accurate ROM …

Hybrid Solution Of Stochastic Optimal Control Problems Using Gauss Pseudospectral Method And Generalized Polynomial Chaos Algorithms, Gerald C. Cottrill

Theses and Dissertations

Two numerical methods, Gauss Pseudospectral Method and Generalized Polynomial Chaos Algorithm, were combined to form a hybrid algorithm for solving nonlinear optimal control and optimal path planning problems with uncertain parameters. The algorithm was applied to two concept demonstration problems: a nonlinear optimal control problem with multiplicative uncertain elements and a mission planning problem sponsored by USSTRATCOM. The mission planning scenario was constructed to find the path that minimizes the probability of being killed by lethal threats whose locations are uncertain to statistically quantify the effects those uncertainties have on the flight path solution, and to use the statistical properties …

Computational Analysis And Characterization Of Rc-135 External Aerodynamics, Michael G. Chenery

Theses and Dissertations

Both the RC-135V/W Rivet Joint (RJ) and the RC-135U Combat Sent (CS) aircraft are United States Air Force (USAF) electronics reconnaissance platforms. The RJ is the USAF's standard airborne signals intelligence (SIGINT) gathering platform, while the CS is designed to collect technical intelligence on adversary radar emitter systems. Both aircraft are extensively modified C-135's characterized by protruding cheek fairings along the sides of the fuselage forward of the wings as well as the addition of numerous antennas along the top and bottom of the fuselage. The major distinguishing feature between the two variants is the nose radome, wherein the RJ …

Electromagnetic Interference Behavior Of Multiwall Carbon Nanotubes And Carbon Nanofibers Composites Under Fatigue, Peter A. Hunt

Theses and Dissertations

The United States military is researching the use of nanocomposite materials for structural applications on space vehicle systems. To reduce vehicle weight and mitigate the electromagnetic interference (EMI) brought on by the harsh space environment, today's space vehicles are made of composites coated with expensive conductive materials. Research on composites made of carbon nanotubes (CNT) and carbon nanofibers (CNF) has shown better EMI shielding performance with these materials compared to the current composites coated with expensive conductive materials. Thus, CNTs and CNFs offer the potential to replace the current composites. This study evaluated the effects of EMI behavior on one …

Validation Of The Chemistry Module For The Euler Solver In Unified Flow Solver, William C. Humphrey Jr.

Theses and Dissertations

In the world of computational fluid dynamics (CFD), three main types of flow regimes exist: continuum, rarified, and free molecular. Of these regimes, the rarified regime is the most difficult to model because the continuum equations don't apply and using the Boltzmann equation is too computationally expensive to use. The Unified Flow Solver (UFS) is currently being developed to solve this problem by using the kinetic continuum Euler equations where valid, and only using the Boltzmann equation where necessary, thus reducing the computational cost. The use of the kinetic Euler equations helps to aid in the coupling of the Euler …

Gravitational Lens: Deep Space Probe Design, Berkley R. Davis

Theses and Dissertations

A number of interstellar precursor missions have been designed, but they have all made use of unproven future technologies. This research focuses on designing an interstellar precursor mission to the gravitational lens that can be manufactured solely with today's technology. The design includes an examination of trip time and trajectory, a system trade between subsystems, a launch vehicle analysis and an overall spacecraft performance analysis. The trip time was found to be approximately 108 years using the NEXT thruster and GPHS power source. The GPHS provided approximately 4 kW of power at BOL. The communications subsystem relied on a 12 …

Development Of A Star Tracker-Based Reference System For Accurate Attitude Determination Of A Simulated Spacecraft, Jorge G. Padro

Theses and Dissertations

The goal of this research effort is to investigate the analysis, design, integration, testing, and validation of a complete star tracker and star field simulator system concept for AFIT's satellite simulator, SimSat. Previous research has shown that while laboratory-based satellite simulators benefit from star trackers, the approach of designing the star field can contribute significant error if the star field is generated on a flat surface. To facilitate a star pattern that better represents a celestial sky, a partially hemispherical dome surface is suspended above SimSat and populated with a system of light emitting diodes of various intensities and angles …

Application Of Multi-Input Multi-Output Feedback Control For F-16 Ventral Fin Buffet Alleviation Using Piezoelectric Actuators, Tomoyuki D. Ono

Theses and Dissertations

Control of structural vibrations has been a popular topic. Use of MFC piezoelectric actuators and co-located sensors allows for an active rather than passive control method. The F-16 ventral fin is susceptible to buffet induced vibrations and is a perfect test structure for active vibration control for flight-testing. The research follows the previous ACTIVE FIN project and improves on the design by increasing the number of actuator layers, available actuator power, and using multi-input multi-output (MIMO) control algorithms. The research involved experimental identification of the ventral fin and its principle strain directions, selection of system components, determination of mathematical plant …

Ladar Performance Simulations With A High Spectral Resolution Atmospheric Transmittance And Radiance Model- Leedr, Benjamin D. Roth

Theses and Dissertations

In this study of atmospheric effects on Geiger Mode laser ranging and detection (LADAR), the parameter space is explored primarily using the Air Force Institute of Technology Center for Directed Energy's (AFIT/CDE) Laser Environmental Effects Definition and Reference (LEEDR) code. The LADAR system is assessed at operationally representative wavelengths of 1.064, 1.56 and 2.039 μm with several up and down looking engagement geometries at locations worldwide. Results computed with LEEDR are compared to standard atmosphere and Fast Atmospheric Signature Code (FASCODE) assessments. Results show significant climate dependence, but large variances between climatological and standard atmosphere assessments. An overall average absolute …

A Finite Element Analysis Of A Carbon Fiber Composite Micro Air Vehicle Wing, Theodore A. Szelag

Theses and Dissertations

Micro-air vehicles (MAV)s provide a valuable and low observable way to do the jobs that the Air Force deems to be dull, dirty and dangerous. Basing the design of an MAV wing on that of a biological counterpart will provide a proven design that is capable of achieving the mission requirements. This research is designed to analyze the design and manufacturing of a wing based off the Manduca Sexta.

Inaccuracies in the fiber orientation can result in substantial changes in the material properties. Experimental vibration data of composite material samples manufactured using a three-ply [0/90/0] small non-homogenous fiber composite provided …

Boundary Layer Measurements In The Trisonic Gas-Dynamics Facility Using Particle Image Velocimetry With Co₂ Seeding, Daniel B. Wolfe

Theses and Dissertations

Particle image velocimetry (PIV) is utilized with solid carbon dioxide (CO₂) seeding material to conduct boundary layer measurements in the test section of the Air Force Research Laboratory's Trisonic Gas-dynamics Facility (TGF), which has a 24 inch by 24 inch cross-section. Freestream velocity was set at Mach 0.3, Mach 0.5, or Mach 0.8 while stagnation pressure ranged from 500 to 2400 pounds per square foot (psf). High pressure liquid CO₂ was directed through expansion nozzles into shroud tubes which led to solidified particles in the wind tunnel stagnation chamber. Two different sets of shroud tubes were used …

Trajectory Control And Optimization For Responsive Spacecraft, Costantinos Zagaris

Theses and Dissertations

The concept of responsive space has been gaining interest, and growing to include systems that can be re-tasked to complete multiple missions within their lifetime. The purpose of this study is to develop an algorithm that produces a maneuver trajectory that will cause a spacecraft to arrive at a particular location within its orbit earlier than expected. The time difference, delta t, is used as a metric to quantify the effects of the maneuver. Two separate algorithms are developed. The first algorithm is an optimal control method and is developed through Optimal Control Theory. The second algorithm is a feedback …

Empirical Analysis Of Optical Attenuator Performance In Quantum Key Distribution Systems Using A Particle Model, Thomas C. Adams

Theses and Dissertations

Quantum key distribution networks currently represent an active area of development and software modeling to address the security of future communications. One of the components used in quantum key distribution implementations is an optical attenuator. Its role in the system is necessary to reach the single photon per bit necessary to maintain theoretically perfect secrecy. How the photon pulse is modeled has a significant impact on the accuracy and performance of quantum channel components like the optical attenuator. Classical physics describe light using Maxwell's wave equations for electromagnetism. Quantum physics has demonstrated light also behaves as discrete particles referred to …

Optimum Concentration Ratio Analysis Using Dynamic Thermal Model For Concentrated Photovoltaic System, John T. Avrett

Theses and Dissertations

Concentrated photovoltaic (PV) technology represents a growing market in the field of terrestrial solar energy production. As the demand for renewable energy technologies increases, further importance is placed upon the modeling, design, and simulation of these systems. Given the U.S. Air Force cultural shift towards energy awareness and conservation, several concentrated PV systems have been installed on Air Force installations across the country. However, there has been a dearth of research within the Air Force devoted to understanding these systems in order to possibly improve the existing technologies. This research presents a new model for a simple concentrated PV system. …

A Black Hole Attack Model For Reactive Ad-Hoc Protocols, Christopher W. Badenhop

Theses and Dissertations

Net-Centric Warfare places the network in the center of all operations, making it a critical resource to attack and defend during wartime. This thesis examines one particular network attack, the Black Hole attack, to determine if an analytical model can be used to predict the impact of this attack on ad-hoc networks. An analytical Black Hole attack model is developed for reactive ad-hoc network protocols DSR and AODV. To simplify topology analysis, a hypercube topology is used to approximate ad-hoc topologies that have the same average node degree. An experiment is conducted to compare the predicted results of the analytical …

Context Aware Routing Management Architecture For Airborne Networks, Joan A. Betances

Theses and Dissertations

This thesis advocates the use of Kalman filters in conjunction with network topology information derived from the Air Tasking Order (ATO) during the planning phase for military missions. This approach is the basis for an algorithm that implements network controls that optimize network performance for Mobile Ad hoc Networks (MANET). The trajectories of relevant nodes (airborne platforms) participating in the MANET can be forecasted by parsing key information contained in the ATO. This information is used to develop optimum network routes that can significantly improve MANET performance. Improved MANET performance in the battlefield enables decision makers to access information from …

Detector Design Considerations In High-Dimensional Artificial Immune Systems, Jason M. Bindewald

Theses and Dissertations

This research lays the groundwork for a network intrusion detection system that can operate with only knowledge of normal network traffic, using a process known as anomaly detection. Real-valued negative selection (RNS) is a specific anomaly detection algorithm that can be used to perform two-class classification when only one class is available for training. Researchers have shown fundamental problems with the most common detector shape, hyperspheres, in high-dimensional space. The research contained herein shows that the second most common detector type, hypercubes, can also cause problems due to biasing certain features in high dimensions. To address these problems, a new …

Trade-Offs In A 1 Tbps Mimo Communication System Between An Airship And An Array Of Ground Receive Antennas, Adam R. Brueggen

Theses and Dissertations

As demand for higher data-rate wireless communications increases, so will the interest in multiple-input and multiple-output (MIMO) systems. In a single transmitter, single receiver communication system, there is a fundamental limit to the data-rate capacity of the system proportional to the systems bandwidth. Since increasing the bandwidth is expensive and limited, another option is increasing the system's capacity by adding multiple antennas at the transmitter and receiver to create a MIMO communication system. With a T transmitter, R receiver MIMO communication system, TR channels are created which allow extremely high data-rates. MIMO systems are attractive because they are extremely robust …

Understanding How Reverse Engineers Make Sense Of Programs From Assembly Language Representations, Adam R. Bryant

Theses and Dissertations

This dissertation develops a theory of the conceptual and procedural aspects involved with how reverse engineers make sense of executable programs. Software reverse engineering is a complex set of tasks which require a person to understand the structure and functionality of a program from its assembly language representation, typically without having access to the program's source code. This dissertation describes the reverse engineering process as a type of sensemaking, in which a person combines reasoning and information foraging behaviors to develop a mental model of the program. The structure of knowledge elements used in making sense of executable programs are …

Towards Quantifying Programmable Logic Controller Resilience Against Intentional Exploits, Henry W. Bushey

Theses and Dissertations

Supervisory Control and Data Acquisition (SCADA) systems control and monitor services for the nation's critical infrastructure. Recent cyber induced events (e.g., Stuxnet) provide an example of a targeted, covert cyber attack against a SCADA system that resulted in physical effects. Of particular note is how Stuxnet exploited the trust relationship between the human machine interface (HMI) and programmable logic controllers (PLCs). Current methods for validating system operating parameters rely on message exchange and network communications protocols, generally observed at the HMI. Although sufficient at the macro level, this method does not provide detection of malware that exhibits physical effects via …