Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Engineering (144)
- Physical Sciences and Mathematics (83)
- Aerospace Engineering (52)
- Computer Sciences (44)
- Business (30)
-
- Electrical and Computer Engineering (28)
- Operations Research, Systems Engineering and Industrial Engineering (28)
- Information Security (18)
- Operational Research (17)
- Physics (17)
- Social and Behavioral Sciences (15)
- Computer Engineering (14)
- Electrical and Electronics (13)
- Applied Mathematics (10)
- Digital Communications and Networking (9)
- Optics (8)
- Propulsion and Power (8)
- Signal Processing (8)
- Human Resources Management (7)
- Plasma and Beam Physics (7)
- Statistics and Probability (7)
- Aerodynamics and Fluid Mechanics (6)
- Civil and Environmental Engineering (6)
- Law (6)
- Life Sciences (6)
- Operations and Supply Chain Management (6)
- Systems Engineering (6)
- Artificial Intelligence and Robotics (5)
- Government Contracts (5)
- Management Information Systems (5)
- Keyword
-
- #antcenter (20)
- Computer security (14)
- Computer networks--Security measures (10)
- Algorithms (8)
- Drone aircraft (7)
-
- Cyberterrorism (6)
- Data protection (6)
- Composite materials (5)
- Decision making (5)
- Wireless communication systems (5)
- Computer network protocols (4)
- Drone aircraft--Control systems (4)
- Gate array circuits (4)
- Image processing (4)
- Kalman filtering (4)
- Military education (4)
- Reverse engineering (4)
- Airplanes--Scramjet engines (3)
- Artificial satellites--Tracking (3)
- Combat--Computer simulation (3)
- Command and control systems (3)
- Command of troops (3)
- Delphi method (3)
- Finite element method (3)
- Genetic algorithms (3)
- Image processing--Digital techniques (3)
- Knowledge management (3)
- Management information systems (3)
- Navigation (Aeronautics) (3)
- Remote sensing (3)
Articles 1 - 30 of 260
Full-Text Articles in Entire DC Network
Cyber Power In The 21st Century, Joseph M. Elbaum
Cyber Power In The 21st Century, Joseph M. Elbaum
Theses and Dissertations
Historically, the United States Congress has acknowledged that a separate branch of military service is required to exert supremacy over each of the recognized Domains of Operation. Throughout the evolution of modern warfare, leading minds in military theory have come to the conclusion that due to fundamental differences inherent in the theory and tactics that must be employed in order to successfully wage war within a domain’s associated environment, a specialized force was needed - until now. With the recent inclusion of Cyberspace as an operational domain by the Department of Defense, the case should be made that it, too, …
Sub-Circuit Selection And Replacement Algorithms Modeled As Term Rewriting Systems, Eric D. Simonaire
Sub-Circuit Selection And Replacement Algorithms Modeled As Term Rewriting Systems, Eric D. Simonaire
Theses and Dissertations
Intent protection is a model of software obfuscation which, among other criteria, prevents an adversary from understanding the program’s function for use with contextual information. Relating this framework for obfuscation to malware detection, if a malware detector can perfectly normalize a program P and any obfuscation (variant) of the program O(P), the program is not intent protected. The problem of intent protection on programs can also be modeled as intent protection on combinational logic circuits. If a malware detector can perfectly normalize a circuit C and any obfuscation (variant) O(C) of the circuit, the circuit is not intent protected. In …
Integrated Approach To Airborne Laser Communication, James A. Louthain
Integrated Approach To Airborne Laser Communication, James A. Louthain
Theses and Dissertations
Lasers offer tremendous advantages over RF communication systems in bandwidth and security, due to their ultra-high frequency and narrow spatial beamwidth. Atmospheric turbulence causes severe received power variations and high bit error rates (BERs) in airborne laser communication. Airborne optical communication systems require special considerations in size, complexity, power, and weight. Conventional adaptive optics systems correct for the phase only and cannot correct for strong scintillation, but here the two transmission paths are separated sufficiently so that the strong scintillation is \averaged out" by incoherently summing up the two beams in the receiver. This requisite separation distance is derived for …
Optimal Re-Entry Trajectory Terminal State Due To Variations In Waypoint Locations., William J. Karasz
Optimal Re-Entry Trajectory Terminal State Due To Variations In Waypoint Locations., William J. Karasz
Theses and Dissertations
The Air Force's Prompt Global Reach concept describes the desire to have a capability to reach any target within a 9000 nautical mile radius within two hours of launch. To meet this objective, much effort is being devoted to hypersonics and re-entry vehicles. Given the limited maneuverability of hypersonic vehicles, computational modeling is used to generate trajectories before launch to strike intended targets. In addition to endpoint (target) constraints, additional waypoints may constrain the trajectory. This research finds the optimal trajectory which satisfies the endpoint and waypoint constraints, and then investigates where else the vehicle can go while still meeting …
Secureqemu: Emulation-Based Software Protection Providing Encrypted Code Execution And Page Granularity Code Signing, William B. Kimball
Secureqemu: Emulation-Based Software Protection Providing Encrypted Code Execution And Page Granularity Code Signing, William B. Kimball
Theses and Dissertations
This research presents an original emulation-based software protection scheme providing protection from reverse code engineering (RCE) and software exploitation using encrypted code execution and page-granularity code signing, respectively. Protection mechanisms execute in trusted emulators while remaining out-of-band of untrusted systems being emulated. This protection scheme is called SecureQEMU and is based on a modified version of Quick Emulator (QEMU) [5]. RCE is a process that uncovers the internal workings of a program. It is used during vulnerability and intellectual property (IP) discovery. To protect from RCE program code may have anti-disassembly, anti-debugging, and obfuscation techniques incorporated. These techniques slow the …
Dynamic Supersonic Base Store Ejection Simulation Using Beggar, Michael D. Johnson
Dynamic Supersonic Base Store Ejection Simulation Using Beggar, Michael D. Johnson
Theses and Dissertations
Static and dynamic conditions throughout various aft supersonic store separation events are examined using the Beggar Computational Fluid Dynamics (CFD) code from Air Force SEEK Eagle Office at Eglin Air Force Base, FL. An 8.9 deg half angle sphere cone is used for the carrier vehicle with an identically shaped store stowed within a hollow compartment in the aft section of the carrier body. Dynamic store separation simulations are implemented at a free-stream Mach of 2.9 with a Reynolds number of Re = 6.9 x 106/m referenced against carrier base diameter. Analysis covers multiple dynamic separation events along …
Nondestructive Evaluation Of Aircraft Composites Using Terahertz Time Domain Spectroscopy, Christopher D. Stoik
Nondestructive Evaluation Of Aircraft Composites Using Terahertz Time Domain Spectroscopy, Christopher D. Stoik
Theses and Dissertations
Terahertz (THz) time domain spectroscopy (TDS) was assessed as a nondestructive evaluation technique for aircraft composites. Material properties of glass fiber composite were measured using both transmission and reflection configuration. The interaction of THz with a glass fiber composite was then analyzed, including the effects of scattering, absorption, and the index of refraction, as well as effective medium approximations. THz TDS, in both transmission and reflection configuration, was used to study composite damage, including voids, delaminations, mechanical damage, and heat damage. Measurement of the material properties on samples with localized heat damage showed that burning did not change the refractive …
Flexible Twist For Pitch Control In A High Altitude Long Endurance Aircraft With Nonlinear Response, Vanessa L. Bond
Flexible Twist For Pitch Control In A High Altitude Long Endurance Aircraft With Nonlinear Response, Vanessa L. Bond
Theses and Dissertations
Information dominance is the key motivator for employing high-altitude long-endurance (HALE) aircraft to provide continuous coverage in the theaters of operation. A joined-wing configuration of such a craft gives the advantage of a platform for higher resolution sensors. Design challenges emerge with structural flexibility that arise from a long-endurance aircraft design. The goal was to demonstrate that scaling the nonlinear response of a full-scale finite element model of a high-altitude long-endurance (HALE) aircraft was possible if the model was aeroelastically and "nonlinearly" scaled. A straight-forward method of scaling the first three natural vibration frequencies and mode shapes, and the first …
Modeling The Economic Impacts Of Large Deployments On Local Communities, Aaron L. Gregory
Modeling The Economic Impacts Of Large Deployments On Local Communities, Aaron L. Gregory
Theses and Dissertations
The Global War on Terrorism has required the large scale deployment of active-duty troops to support operations in Afghanistan and Iraq. This thesis presents an economic analysis of the impacts these deployments have had on local communities as measured by changes in local retail sales. County level data from Colorado, Kansas, North Carolina, and Tennessee were combined with open source deployment information to construct panel models. Panel model analysis is a form of regression that combines cross-sectional and time-series dimensions. Seasonality and general economic conditions were also incorporated into the model. The goal of this research is to provide an …
Limitations Of A True Random Number Generator In A Field Programmable Gate Array, Jennifer L. Brady
Limitations Of A True Random Number Generator In A Field Programmable Gate Array, Jennifer L. Brady
Theses and Dissertations
Random number generators are used in many areas of engineering, computer science, most notably in simulations and cryptographic applications. There are true random number generators (TRNG) and pseudo random number generators (PRNG). Only a true random number generator is secure because the output bits are non-repeating and nonreproducible. As society has become more dependent on electronic technology the need for true random number generators has increased due to processes that require encryption in everyday use. A fast true random number generator on a field programmable gate array presents digital designers with the ability to have the generator on chip. Since …
Extension Of Viscoplasticity Based On Overstress To Capture The Effects Of Prior Aging On The Time Dependent Deformation Behavior Of A High-Temperature Polymer: Experiments And Modeling, Amber J. W. Mcclung
Extension Of Viscoplasticity Based On Overstress To Capture The Effects Of Prior Aging On The Time Dependent Deformation Behavior Of A High-Temperature Polymer: Experiments And Modeling, Amber J. W. Mcclung
Theses and Dissertations
The inelastic deformation behavior of PMR-15 neat resin, a high-temperature thermoset polymer, was investigated at 288 degrees C. The experimental program was designed to explore the influence of strain rate on tensile loading, unloading, and strain recovery behaviors. In addition, the effect of the prior strain rate on the relaxation response of the material, as well as on the creep behavior following strain controlled loading were examined. The experimental data were modeled with the Viscoplasticity Based on Overstress (VBO) theory. A systematic procedure for determining model parameters was developed and the model was employed to predict the response of the …
Application Of Optimization Techniques To Spectrally Modulated, Spectrally Encoded Waveform Design, Todd W. Beard
Application Of Optimization Techniques To Spectrally Modulated, Spectrally Encoded Waveform Design, Todd W. Beard
Theses and Dissertations
A design process is demonstrated for a coexistent scenario containing Spectrally Modulated, Spectrally Encoded (SMSE) and Direct Sequence Spread Spectrum (DSSS) signals. Coexistent SMSE-DSSS designs are addressed under both perfect and imperfect DSSS code tracking conditions using a non-coherent delay-lock loop (DLL). Under both conditions, the number of SMSE subcarriers and subcarrier spacing are the optimization variables of interest. For perfect DLL code tracking conditions, the GA and RSM optimization processes are considered independently with the objective function being end-to-end DSSS bit error rate. A hybrid GA-RSM optimization process is used under more realistic imperfect DLL code tracking conditions. In …
Pylon Effects On A Scramjet Cavity Flameholder Flowfield, Andrew B. Freeborn
Pylon Effects On A Scramjet Cavity Flameholder Flowfield, Andrew B. Freeborn
Theses and Dissertations
Cavity flameholders in supersonic combustion ramjet (scramjet) combustors, while effective, fail to take advantage of the full combustor volume. Adding a pylon to the leading edge of a cavity flameholder generates a flowfield increasing mass exchange between the cavity and main combustor flow, increasing the mixing interface between flameholder products and main combustor flow, and exhibiting minimal Reynolds number effects. To demonstrate this modified flowfield driven by supersonic expansion behind the pylon, pylon-cavity flameholder flowfield data were obtained through a combination of wind tunnel experimentation and steady-state computational fluid dynamics (CFD). Flowfield effects of the pylon-cavity were examined at a …
Hypermixer Pylon Fuel Injection For Scramjet Combustors, Jason C. Doster
Hypermixer Pylon Fuel Injection For Scramjet Combustors, Jason C. Doster
Theses and Dissertations
Fueling the core airflow of a circular or elliptical scramjet combustor cross-section often requires intrusive geometries. Intrusive geometries can distribute the fuel evenly across the combustor cross-section and act as a flameholder for the fuel/air mixture. Compared to conventional transverse or angled wall injection, intrusive geometries allow easier penetration into the core combustor airflow and reduced fuel injection pressures. The design and testing of an intrusive pylon geometry for scramjet combustor fueling is the subject of this research. Three pylon configurations are compared: a basic pylon, a ramp pylon, and an alternating wedge pylon. All three pylon configurations exhibit the …
A Novel Method Characterizing The Impact Response Of Functionally Graded Plates, Reid A. Larson
A Novel Method Characterizing The Impact Response Of Functionally Graded Plates, Reid A. Larson
Theses and Dissertations
Functionally graded material (FGM) plates are advanced composites with properties that vary continuously through the thickness of the plate. Metal-ceramic FGM plates have been proposed for use in thermal protection systems where a metal-rich interior surface of the plate gradually transitions to a ceramic-rich exterior surface of the plate. The ability of FGMs to resist impact loads must be demonstrated before using them in high-temperature environments in service. This dissertation presents a novel technique by which the impact response of FGM plates is characterized for low-velocity, low- to medium-energy impact loads. An experiment was designed where strain histories in FGM …
Closed-Loop Adaptive Optics Control In Strong Atmospheric Turbulence, Todd M. Venema
Closed-Loop Adaptive Optics Control In Strong Atmospheric Turbulence, Todd M. Venema
Theses and Dissertations
A self-referencing interferometer based closed-loop adaptive optics controller is developed which is designed to operate effectively under strong turbulence conditions. The aberrated optical field is modeled stochastically and then estimates of the state of the system are developed using a steady-state, fixed-gain Kalman filter. The phase of the optical field is considered the state of the system which is wrapped in a limited range of (-π, π]. This phase is unwrapped through the use of a least-squares reconstructor which has been modified to work effectively in the presence of branch points associated with strong turbulence. The conjugate of the optical …
Electronic State Distributions Of Y Ba2Cu3O7-X Laser Ablated Plumes, Patrick D. Kee
Electronic State Distributions Of Y Ba2Cu3O7-X Laser Ablated Plumes, Patrick D. Kee
Theses and Dissertations
The application of spectral and imagery diagnostics to YBa2Cu3O7 (YBCO) laser-ablated plumes was systematically studied to determine their effectiveness for process control. Emission signatures were collected for plumes created by ablating bulk YBCO with a pulsed laser source. A KrF (λ=248 nm) laser source operating at 4-10 J/cm2 at a 4-10 Hz pulse repetition frequency was used to ablate a bulk YBCO target at O2 background pressures ranging from 50 to 400 mTorr. Emission spectra were collected over the 500 to 860 nm bandpass at distances from the target ranging from 31.4 to …
A Study Of The Irradiance-And-Temperature-Dependence Of Mid-Wave-Infrared (Mwir)Absorption In Indium Antimonide (Insb), John M. Callahan
A Study Of The Irradiance-And-Temperature-Dependence Of Mid-Wave-Infrared (Mwir)Absorption In Indium Antimonide (Insb), John M. Callahan
Theses and Dissertations
This work entails further investigation of the absorption of photons in indium antimonide (InSb). Previously work at the Air Force Institute of Technology (AFIT) attributed laser blooming effects in InSb focal plane arrays (FPA’s) to the Burstein-Moss effect. The contributing effect is from a decrease in the absorption of the InSb material, such that the transmitted optical energy scatters off the integrated circuitry beneath the InSb thin film back into the optical system. To evaluate this, irradiance-dependent laser-absorption experiments were performed on thinned, InSb wafers prior to their FPA fabrication. The samples were illuminated with a focused CO2 laser at …
Software Acquisition Improvement In The Aeronautical Systems Center, William A. Pogorzelski
Software Acquisition Improvement In The Aeronautical Systems Center, William A. Pogorzelski
Theses and Dissertations
In the past 20 years, over 150 recommendations have been made to improve software systems development by organizations such as the Defense Science Board, National Research Council and the U.S. General Accountability Office. It has been discovered that many of these recommendation have remained unimplemented. This research had the purpose of confirming the application of these previous recommendations to improve software acquisition in the Aeronautical Systems Center. This was accomplished through interviews with 20 software practitioners in the acquisition community and the review of relevant literature. Through the analysis of the interviews and literature, this research was able to confirm …
Range Precision Of Ladar Systems, Steven E. Johnson
Range Precision Of Ladar Systems, Steven E. Johnson
Theses and Dissertations
A key application of Laser Detection and Ranging (LADAR) systems is measurement of range to a target. Many modern LADAR systems are capable of transmitting laser pulses that are less than a few nanoseconds in duration. These short-duration pulses provide excellent range precision. However, randomness in the detected laser signals places limits on the precision. The goal of this dissertation is to quantify the range precision limits of LADAR systems. The randomness in the time between photon arrivals, which is called shot noise, is discussed in depth. System-dependent noise sources such as dark current and detector gain variation are considered. …
The Roc Curves Of Fused Independent Classification Systems, Michael B. Walsh
The Roc Curves Of Fused Independent Classification Systems, Michael B. Walsh
Theses and Dissertations
The need for optimal target detection arises in many different fields. Due to the complexity of many targets, it is thought that the combination of multiple classification systems, which can be tuned to several individual target attributes or features, might lead to more optimal target detection performance. The ROC curves of fused independent two-label classification systems may be generated by the mathematical combination of their ROC curves to achieve optimal classifier performance without the need to test every Boolean combination. The monotonic combination of two-label independent classification systems which assign labels to the same target types results in a lattice …
Hall Thruster Plume Diagnostics Utilizing Microwave Interferometry, Vipul Sharma
Hall Thruster Plume Diagnostics Utilizing Microwave Interferometry, Vipul Sharma
Theses and Dissertations
The fatigue behavior of two woven SiC-SiNC ceramic matrix composites (CMCs) was investigated at 1300 °C in laboratory air and in steam. The first composite (C1) consists of a PIP SiNC matrix reinforced with Sylramic (Syl) fibers woven in a five-harness satin weave fabric and coated with a proprietary dual-layer interface. The second composite (C2) consists of a modified PIP SiNC matrix reinforced with Sylramic-iBN (Syl-iBN) fibers woven in a five-harness satin weave fabric and coated with a proprietary dual-layer interface. The tensile stress-strain behavior was investigated and the tensile properties measured at 1300°C. Tension-tension fatigue behavior was studied for …
Creep Behavior Of Oxide/Oxide Composites With Monazite Fiber Coating At 1100°C In Air And In Steam Environments, Tufan Yeleser
Creep Behavior Of Oxide/Oxide Composites With Monazite Fiber Coating At 1100°C In Air And In Steam Environments, Tufan Yeleser
Theses and Dissertations
The creep behavior of six oxide-oxide ceramic-matrix composites (CMCs) was investigated at 1100 °C in laboratory air and in steam environments. The six CMC systems had an alumina ( Al2O3 ) matrix reinforced with NextelTM610 fibers. The CMC systems C1, C2 and C3 were reinforced with 10 uni-directional fiber layers in a symmetric cross-ply (0°/90°/0°/90°/0°)s orientation. In the case of composites C2 and C3, monazite (LaPO4) fiber coating was applied to the fibers. Composite C1 contained no fiber coating. In the case of composites C1 and C2, alumina matrix was infiltrated with monazite. The CMC systems …
A Constraint Based Approach For Building Operationally Responsive Satellites, Mesut O. Kahraman
A Constraint Based Approach For Building Operationally Responsive Satellites, Mesut O. Kahraman
Theses and Dissertations
The Operational Responsive Space (ORS) program requires flexible and responsive satellites to meet user’s needs. Traditional satellite design methods are typically iterative processes that optimize individual components, subsystems, and ultimately the entire satellite. This study focuses on developing a new approach for creating Responsive Satellites (RS) from Plug-and-Play (PnP) components. The aim is to create an approach that quickly evaluates a wide variety of possible satellite configurations and identify the best configurations that meet the user’s needs and constraints. Satellite configurations are created by matching locations on the satellite structure with PnP components. Various constraints are derived from the user’s …
Combat Identification Using Multiple Tuav Swarm, Younin Kang
Combat Identification Using Multiple Tuav Swarm, Younin Kang
Theses and Dissertations
In modern warfare, Tactical Unmanned Aerial Vehicles (TUAVs) are rapidly taking on a leading role in traditional and non-traditional ISR, to include Automatic Target Recognition (ATR). However, additional advancements in processors and sensors on TUAVs are still needed before they can be widely employed as a primary source for positive identification in the Combat Identification (CID) process. Cost is a driving factor for operating an ATR system using multiple TUAVs. The cost of high quality sensors appropriate for a single TUAV can be significantly higher than less sophisticated sensors suitable for deployment on a group, or swarm, of coordinated TUAVs. …
A Confidence Paradigm For Classification Systems, Nathan J. Leap
A Confidence Paradigm For Classification Systems, Nathan J. Leap
Theses and Dissertations
There is no universally accepted methodology to determine how much confidence one should have in a classifier output. This research proposes a framework to determine the level of confidence in an indication from a classifier system where the output is or can be transformed into a posterior probability estimate. This is a theoretical framework that attempts to unite the viewpoints of the classification system developer (or engineer) and the classification system user (or war-fighter). The paradigm is based on the assumptions that the system confidence acts like, or can be modeled as a value and that indication confidence can be …
Interoperability Measurement, Thomas C. Ford
Interoperability Measurement, Thomas C. Ford
Theses and Dissertations
This research presents an inaugural general method of measuring the collaborative and confrontational interoperability of a heterogeneous set of systems in the context of an operational process. The method is holistic, fundamental, flexible, and mathematical in nature and accommodates all types of systems and interoperations. The method relates the interoperability measurement to measures of operational effectiveness for confrontational operational processes. Extant leveling methods of describing interoperability are shown to be a special case of the more general method given in this research and the general interoperability measurement method is demonstrated through the presentation of coalition interoperability, suppression of enemy air …
Distribution Iteration: A Robust Alternative To Source Iteration For Solving The Discrete Ordinates Radiation Transport Equations In Slab And Xy- Geometries, Nicholas J. Prins
Distribution Iteration: A Robust Alternative To Source Iteration For Solving The Discrete Ordinates Radiation Transport Equations In Slab And Xy- Geometries, Nicholas J. Prins
Theses and Dissertations
The discrete ordinates method is widely used to solve the Boltzmann transport equation for neutral particle transport for many engineering applications. Source iteration is used to solve the discrete ordinates system of equations, but can be slow to converge in highly scattering problems. Synthetic acceleration techniques have been developed to address this shortcoming; however, recent research has shown synthetic acceleration to lose effectiveness or diverge for certain problems. LTC Wager introduced an alternative to source iteration and demonstrated it in slab geometry. Here the method is further developed, enhancing efficiency in various ways, and demonstrated in XY-geometry as well as …
On Graph Isomorphism And The Pagerank Algorithm, Christopher J. Augeri
On Graph Isomorphism And The Pagerank Algorithm, Christopher J. Augeri
Theses and Dissertations
A graph is a key construct for expressing relationships among objects, such as the radio connectivity between nodes contained in an unmanned vehicle swarm. The study of such networks may include ranking nodes based on importance, for example, by applying the PageRank algorithm used in some search engines to order their query responses. The PageRank values correspond to a unique eigenvector typically computed by applying the power method, an iterative technique based on matrix multiplication. The first new result described herein is a lower bound on the execution time of the PageRank algorithm that is derived by applying standard assumptions …
Statistical Methods For Polarimetric Imagery, Daniel A. Lemaster
Statistical Methods For Polarimetric Imagery, Daniel A. Lemaster
Theses and Dissertations
Estimation theory is applied to a physical model of incoherent polarized light to address problems in polarimetric image registration, restoration, and analysis for electro-optical imaging systems. In the image registration case, the Cramer-Rao lower bound on unbiased joint estimates of the registration parameters and the underlying scene is derived, simplified using matrix methods, and used to explain the behavior of multi-channel linear polarimetric imagers. In the image restoration case, a polarimetric maximum likelihood blind deconvolution algorithm is derived and tested using laboratory and simulated imagery. Finally, a principal components analysis is derived for polarization imaging systems. This analysis expands upon …