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Articles 2131 - 2160 of 5700
Full-Text Articles in Engineering
Aerial Networking For The Implementation Of Cooperative Control On Small Unmanned Aerial Systems, Scott A . Songer
Aerial Networking For The Implementation Of Cooperative Control On Small Unmanned Aerial Systems, Scott A . Songer
Theses and Dissertations
The employment of Small Unmanned Aerial Systems (SUAS) for reconnaissance and surveillance missions is a vital capability of the United States military. Cooperative control algorithms for SUAS can enable tactical multi-vehicle configurations for communications extension, intelligent navigation, and a multitude of other applications. Past research at AFIT has designed and simulated a cooperative rover-relay algorithm for extended communications and has investigated its implementation through various modem configurations. This research explores aerial networking options for implementing cooperative control and applies them to an actual SUAS. Using Commercial Off-The-Shelf (COTS) hardware, a system was designed and flight tested to implement the rover-relay …
Power Requirements For Bi-Harmonic Amplitude And Bias Modulation Control Of A Flapping Wing Micro Air Vehicle, Justin R. Carl
Power Requirements For Bi-Harmonic Amplitude And Bias Modulation Control Of A Flapping Wing Micro Air Vehicle, Justin R. Carl
Theses and Dissertations
Flapping wing micro air vehicles (FWMAV) have been a growing field in the research of micro air vehicles, but little emphasis has been placed on control theory. Research is ongoing on how to power FWMAVs where mass is a major area of concern. However, there is little research on the power requirements for the controllers to manipulate the wings of a FWMAV. A novel control theory, BABM, allows two actuators to produce forces and moments in five of the FWMAV's six DOF. Several FWMAV prototypes were constructed and tested on a six-component balance. Data was collected for varying control parameters …
Integration Of An Inter Turbine Burner To A Jet Turbine Engine, Matthew M. Conrad
Integration Of An Inter Turbine Burner To A Jet Turbine Engine, Matthew M. Conrad
Theses and Dissertations
As aircraft power requirements continue to grow, whether for electrical systems or increased thrust, improved engine efficiency must be found. An Ultra-Compact Combustor (UCC) is a proposed apparatus for accomplishing this task by burning in the circumferential direction as a main combustor or an Inter-Turbine Burner (ITB). In order for the UCC to be viable it is important to study the effects of feeding the core and circumferential flows from a common gas reservoir. This research effort has developed a diffuser, for the AFIT Combustion Laboratory, that is capable of 80/20, 70/30, and 60/40 mass flow splits between the core …
Opto-Mechanical Design Of A Chromotomographic Imager Direct-Vision Prism Element, Timothy E. Coon
Opto-Mechanical Design Of A Chromotomographic Imager Direct-Vision Prism Element, Timothy E. Coon
Theses and Dissertations
Chromotomographic Imaging (CTI) offers advantages in remote sensing by resolving intensity distribution spatially, spectrally, and temporally. The Chromotomography Experiment (CTEx) at the Air Force Institute of Technology (AFIT) explores the application of CTI as a space-based observer. Previous work in instrument development has revealed many of the intricacies of component fabrication and how they impact the resolving of image data. The proposed CTEx instrument has as its chromatic dispersion element a direct-vision prism (DVP) that is made to rotate in order to achieve multiple projection angles. Analysis of previous research established the need for a more accurate characterization of the …
Characterization Of Rotating Detonation Engine Exhaust Through Nozzle Guide Vanes, Nick D. Debarmore
Characterization Of Rotating Detonation Engine Exhaust Through Nozzle Guide Vanes, Nick D. Debarmore
Theses and Dissertations
A RDE has higher thermal efficiencies in comparison to its traditional gas turbine counterparts. Thus, as budgets decrease and fuel costs increase, RDEs have become a research focus for the United States Air Force. An integration assembly for attaching the first NGV section from a T63 gas turbine engine to a 6 inch diameter RDE was designed and built for this study. Pressure, temperature, and unsteadiness measurements were completed in this study to characterize the exhaust flow of the RDE through the NGVs. The experiment found that stagnation pressure dropped an average of 4% through the NGVs, and that unsteadiness …
Using Hysteretic Energy To Evaluate Damping Characteristics Of Hard Coating On Titanium, Colin C. Engebretsen
Using Hysteretic Energy To Evaluate Damping Characteristics Of Hard Coating On Titanium, Colin C. Engebretsen
Theses and Dissertations
Current methods of material damping evaluation consist of bending tests involving half-power bandwidth base excitation or free decay methods measured by laser vibrometer. These methods are accompanied by complex, nonlinear strain evaluation; they are vulnerable to undesired air damping; and they require less than commonplace equipment. The measurement of hysteretic energy loss in axial cyclic loading alleviates these difficulties. By using common tensile testing machines, strain is kept linear and air damping is of no concern. Furthermore, the static test section allows for simplified environmental variation for high temperature or high humidity testing. This study set forth to advance and …
Dynamic Constellation Tasking And Management, Steven P. Ingraham
Dynamic Constellation Tasking And Management, Steven P. Ingraham
Theses and Dissertations
Responsive orbits have gained much attention in recent years and many AFIT theses have addressed this topic. Specifically, the following topics have been studied: phasing within an orbit, adjusting time of arrival, avoidance, and maneuver detection. This thesis seeks to determine the feasibility of maneuvering satellites from circular (600 km) orbits to eccentric (600 km by 175 km) orbits in order to collect high resolution images for Earth surveillance. Coverage is calculated for multiple 6-satellite constellations. Perturbations for the subject orbits are analyzed and compared to simulation results.
Design Of A Control Moment Gyroscope Attitude Actuation System For The Attitude Control Subsystem Proving Ground, Samuel C. Johnson
Design Of A Control Moment Gyroscope Attitude Actuation System For The Attitude Control Subsystem Proving Ground, Samuel C. Johnson
Theses and Dissertations
All spacecraft represent a considerable investment of both time and money. To ensure mission success, testing and validation of all vital systems is crucial to the design process. The attitude control subsystem (ACS) is typically tested thoroughly, to include both hardware and control algorithms. Computer simulations offer a simple and relatively cheap method of predicting the performance of the ACS; however, computer simulations cannot provide the assurances necessary to qualify an ACS hardware configuration or control algorithm spaceworthy. For this reason, physical spacecraft simulators must be used to validate ACS dynamics. Previous research showed there is room for significant improvement …
Development Of Optimized Piezoelectric Bending Actuators For Use In An Insect Sized Flapping Wing Micro Air Vehicle, Robert K. Lenzen
Development Of Optimized Piezoelectric Bending Actuators For Use In An Insect Sized Flapping Wing Micro Air Vehicle, Robert K. Lenzen
Theses and Dissertations
Piezoelectric bimorph actuators, as opposed to rotary electric motors, have been suggested as an actuation mechanism for flapping wing micro air vehicles (FWMAVs) because they exhibit favorable characteristics such as low weight, rapidly adaptable frequencies, lower acoustic signature, and controllable flapping amplitudes. Research at the Air Force Research Labs and the Air Force Institute of Technology has shown that by using one actuator per wing, up to five degrees of freedom are possible. However, due to the weight constraints on a FWMAV, the piezoelectric bimorph actuators need to be fully optimized to support free flight. This study focused on three …
Experimental Analysis Of Dampened Breathing Mode Oscillation On Hall Effect Thruster Performance, Christopher D. Vineski
Experimental Analysis Of Dampened Breathing Mode Oscillation On Hall Effect Thruster Performance, Christopher D. Vineski
Theses and Dissertations
Experiments were performed at AFIT to determine the effect of active control of the magnetic field strength to reduce the breathing mode oscillation on the efficiency of a 200W Hall thruster. The breathing mode oscillation amplitude was measured by the root mean square (RMS) variation in the AC portion of the discharge current. Experiments were run using krypton and xenon propellant. Using the xenon propellant control of the RMS improved the propellant utilization efficiency by approximately 2% in two cases, while reducing the magnet current efficiency by about 10%. Control of the RMS's effect on the divergence angle of the …
Firmware Counterfeiting And Modification Attacks On Programmable Logic Controllers, Zachary H. Basnight
Firmware Counterfeiting And Modification Attacks On Programmable Logic Controllers, Zachary H. Basnight
Theses and Dissertations
Recent attacks on industrial control systems (ICSs), like the highly publicized Stuxnet malware, have perpetuated a race to the bottom where lower level attacks have a tactical advantage. Programmable logic controller (PLC) firmware, which provides a software-driven interface between system inputs and physically manifested outputs, is readily open to modification at the user level. Current efforts to protect against firmware attacks are hindered by a lack of prerequisite research regarding details of attack development and implementation. In order to obtain a more complete understanding of the threats posed by PLC firmware counterfeiting and the feasibility of such attacks, this research …
Learning Enterprise Malware Triage From Automatic Dynamic Analysis, Jonathan S. Bristow
Learning Enterprise Malware Triage From Automatic Dynamic Analysis, Jonathan S. Bristow
Theses and Dissertations
Adversaries employ malware against victims of cyber espionage with the intent of gaining unauthorized access to information. To that end, malware authors intentionally attempt to evade defensive countermeasures based on static methods. This thesis analyzes a dynamic analysis methodology for malware triage that applies at the enterprise scale. This study captures behavior reports from 64,987 samples of malware randomly selected from a large collection and 25,591 clean executable files from operating system install media. Function call information in sequences of behavior generate feature vectors from behavior reports from the les. The results of 64 experiment combinations indicate that using more …
Cloud Computing Trace Characterization And Synthetic Workload Generation, Salvatore Capra
Cloud Computing Trace Characterization And Synthetic Workload Generation, Salvatore Capra
Theses and Dissertations
This thesis researches cloud computing workload characteristics and synthetic workload generation. A heuristic presented in the work guides the process of workload trace characterization and synthetic workload generation. Analysis of a cloud trace provides insight into client request behaviors and statistical parameters. A versatile workload generation tool creates client connections, controls request rates, defines number of jobs, produces tasks within each job, and manages task durations. The test system consists of multiple clients creating workloads and a server receiving request, all contained within a virtual machine environment. Statistical analysis verifies the synthetic workload experimental results are consistent with real workload …
Creep Of Hi-Nicalon S Fiber Tows At Elevated Temperature In Air And In Steam, Theodore R. Shillig
Creep Of Hi-Nicalon S Fiber Tows At Elevated Temperature In Air And In Steam, Theodore R. Shillig
Theses and Dissertations
Structural aerospace components require materials that have superior long-term mechanical properties and can withstand severe environmental conditions, such as high temperatures, high pressures and moisture. Ceramic-matrix composites (CMCs) are capable of maintaining excellent strength and creep resistance at high temperatures, which makes them attractive candidate materials for aerospace applications, particularly in propulsion components. Silicon Carbide (SiC) ceramic fibers have been used as constituent materials in CMCs, although oxidation of the SiC to SiO2 has been a known fiber degradation mechanism. Recently developed near stoichiometric Hi-Nicalon-S fibers have shown significant improvements in thermo-chemical stability. Creep of the Hi-Nicalon-S fibers at elevated …
Estimating And Measuring Application Latency Of Typical Distributed Interactive Simulation (Dis) - Based Simulation Architecture, Ryan L. Drinkwater
Estimating And Measuring Application Latency Of Typical Distributed Interactive Simulation (Dis) - Based Simulation Architecture, Ryan L. Drinkwater
Theses and Dissertations
One of the challenges in a distributed virtual environment stems from the requirement to simultaneously execute the simulations in realtime to support human interaction, in conjunction with maintaining a consistent view of the shared simulated environment. Maintaining a consistent set of simulation state data in the presence of network latency is difficult if individual data items are updated frequently. The principle application of DIS-based simulation environments has been in the domain of training where a consistent view or its correctness is often judged in subjective terms such as the simulation looking and feeling correct. New application areas for these systems …
Examining Application Components To Reveal Android Malware, John B. Guptill
Examining Application Components To Reveal Android Malware, John B. Guptill
Theses and Dissertations
Smartphones are becoming ubiquitous in everyday life and malware is exploiting these devices. Therefore, a means to identify the threats of malicious applications is necessary. This paper presents a method to classify and analyze Android malware through application component analysis. The experiment parses select portions from Android packages to collect features using byte sequences and permissions of the application. Multiple machine learning algorithms classify the samples of malware based on these features. The experiment utilizes instance based learner, naive Bayes, decision trees, sequential minimal optimization, boosted naive Bayes, and boosted decision trees to identify the best components that reveal malware …
Mobile Network Defense Interface For Cyber Defense And Situational Awareness, James C. Hannan
Mobile Network Defense Interface For Cyber Defense And Situational Awareness, James C. Hannan
Theses and Dissertations
Today's computer networks are under constant attack. In order to deal with this constant threat, network administrators rely on intrusion detection and prevention services (IDS) (IPS). Most IDS and IPS implement static rule sets to automatically alert administrators and resolve intrusions. Network administrators face a difficult challenge, identifying attacks against a vast number of benign network transactions. Also after a threat is identified making even the smallest policy change to the security software potentially has far-reaching and unanticipated consequences. Finally, because the administrator is primarily responding to alerts they may lose situational awareness of the network. During this research a …
All-Optical Logic Gates And Wavelength Conversion Via The Injection-Locking Of A Fabry-Perot Semiconductor Laser, Evan P. Harvey
All-Optical Logic Gates And Wavelength Conversion Via The Injection-Locking Of A Fabry-Perot Semiconductor Laser, Evan P. Harvey
Theses and Dissertations
This work investigates the implementation of all-optical wavelength conversion and logic gates based on optical injection locking (OIL). All-optical inverting, NOR, and NAND gates are experimentally demonstrated using two distributed feedback (DFB) lasers, a multi-mode Fabry-Perot laser diode (MMFP-LD), and a optical band-pass filter (BPF). The DFB lasers are externally modulated to represent logic inputs into the cavity of the MMFP-LD slave laser. The master lasers' wavelengths are aligned with the longitudinal modes of the MMFP-LD slave laser and their optical power is used to modulate the injection conditions in the slave laser. The optical BPF is used to select …
Emulation Of Industrial Control Field Device Protocols, Robert M. Jaromin
Emulation Of Industrial Control Field Device Protocols, Robert M. Jaromin
Theses and Dissertations
It has been shown that thousands of industrial control devices are exposed to the Internet, however, the extent and nature of attacks on such devices remains unknown. The first step to understanding security problems that face modern supervisory control and data acquisition (SCADA) and industrial controls networks is to understand the various attacks launched on Internet-connected field devices. This thesis describes the design and implementation of an industrial control emulator on a Gumstix single-board computer as a solution. This emulator acts as a decoy field device, or honeypot, intended to be probed and attacked via an Internet connection. Evaluation techniques …
Information Encoding On A Pseudo Random Noise Radar Waveform, Joshua A . Hardin
Information Encoding On A Pseudo Random Noise Radar Waveform, Joshua A . Hardin
Theses and Dissertations
Navigation requires knowledge of current location and a planned destination. This is true with manned vehicles and unmanned vehicles. There are many ways to acquire the current location, including global positioning system (GPS), triangulation, radar, and dead reckoning. Today GPS is the most reliable and accurate navigation technique when there is a clear, unobstructed view of the satellite constellation. Various sensors can be used to perform indoor navigation; however, when the vehicle is autonomous the sensors need to provide the exact location to the system. This research determined if using a template replay strategy has the same RNR performance as …
Development Of A Response Planner Using The Uct Algorithm For Cyber Defense, Michael P. Knight
Development Of A Response Planner Using The Uct Algorithm For Cyber Defense, Michael P. Knight
Theses and Dissertations
A need for a quick response to cyber attacks is a prevalent problem for computer network operators today. There is a small window to respond to a cyber attack when it occurs to prevent significant damage to a computer network. Automated response planners offer one solution to resolve this issue. This work presents Network Defense Planner System (NDPS), a planner dependent on the effectiveness of the detection of the cyber attack. This research first explores making classification of network attacks faster for real-time detection, the basic function Intrusion Detection System (IDS) provides. After identifying the type of attack, learning the …
Constitutive Parameter Measurement Using Double Ridge Waveguide, Nathan J. Lehman
Constitutive Parameter Measurement Using Double Ridge Waveguide, Nathan J. Lehman
Theses and Dissertations
Electromagnetic materials characterization is important in the design of systems that interact with electromagnetic waves. Determining the constitutive parameters of a material is a vast area of research and practice. For this paper, discussion will focus on a destructive method using waveguides in the frequency range of 6-18 GHz. Traditional methods to perform similar measurements include using coaxial cable, stripline, focus beam and rectangular waveguides. This work will use Double Ridged Waveguide (DRWG) to compare to these other methods and will discuss the attributes and drawbacks of this new approach. The most similar method utilizes rectangular waveguide, so the primary …
An Architecture For Coexistence With Multiple Users In Frequency Hopping Cognitive Radio Networks, Ryan K. Mclean
An Architecture For Coexistence With Multiple Users In Frequency Hopping Cognitive Radio Networks, Ryan K. Mclean
Theses and Dissertations
The radio frequency (RF) spectrum is a limited resource. Spectrum allotment disputes stem from this scarcity as many radio devices are con confined to a fixed frequency or frequency sequence. One alternative is to incorporate cognition within a configurable radio platform, therefore enabling the radio to adapt to dynamic RF spectrum environments. In this way, the radio is able to actively observe the RF spectrum, orient itself to the current RF environment, decide on a mode of operation, and act accordingly, thereby sharing the spectrum and operating in more flexible manner. This research presents a novel framework for incorporating several …
Spectral Detection Of Acute Mental Stress With Vis-Swir Hyperspectral Imagery, Elizabeth K. Norvell
Spectral Detection Of Acute Mental Stress With Vis-Swir Hyperspectral Imagery, Elizabeth K. Norvell
Theses and Dissertations
The ability to identify a stressed person is becoming an important aspect across different work environments. Especially in higher-stress career fields, such as first responders and air traffic controllers, mental stress can inhibit a person's ability to accomplish their job. A person's efficiency and psychological state in the work environment can be impeded due to poor mental health. Stress can result in harmful effects on the body, both physically and mentally, including depression, lack of sleep, and fatigue, which can lead to reduced work productivity. Research is being conducted to detect stress in workload-intensive environments. This thesis implements an imaging …
Metamaterial Structure Design Optimization: A Study Of The Cylindrical Cloak, Jason V. Paul
Metamaterial Structure Design Optimization: A Study Of The Cylindrical Cloak, Jason V. Paul
Theses and Dissertations
Previously, Transformational Optics (TO) has been used as a foundation for designing cylindrical cloaks. The TO method uses a coordinate transform to dictate an anisotropic material parameter gradient in a cylinder coating that guides waves around the cylinder to reduce the Radar Cross Section (RCS). The problem is that the material parameters required for the TO cloak are not physically realizable and thus must be approximated. This problem is compounded by the fact that any approximation deviates from the ideal design and will allow fields to penetrate the cloak layer and interact with the object to be cloaked. Since the …
Atmospheric Impact On Long Pulse Laser Detection And Ranging (Ladar) Systems, Isaac B. Putnam
Atmospheric Impact On Long Pulse Laser Detection And Ranging (Ladar) Systems, Isaac B. Putnam
Theses and Dissertations
For conventional imaging systems, GEO space objects cannot be resolved due to their 40 Mm distance. There exists a strong need to obtain high resolution images of GEO objects and to accomplish this task, investigation into the suitability of ISAL is currently underway. A critical component in determining this suitability is to accurately model the atmospheric impacts on LADAR pulses. Conventional knowledge says that while the atmosphere churns, wind is the predominant cause of temporal evolution which simplifies all modeling and simulation into the frozen flow hypothesis. The concern is that the frozen flow hypothesis based phase screen generation techniques …
Inertial Navigation System Aiding Using Vision, James O. Quarmyne
Inertial Navigation System Aiding Using Vision, James O. Quarmyne
Theses and Dissertations
The aiding of an INS using measurements over time of the line of sight of ground features as they come into view of an onboard camera is investigated. The objective is to quantify the reduction in the navigation states' errors by using bearings-only measurements over time of terrain features in the aircraft's field of view. INS aiding is achieved through the use of a Kalman Filter. The design of the Kalman Filter is presented and it is shown that during a long range, wings level cruising flight at constant velocity and altitude, a 90% reduction in the aided INS-calculated navigation …
A Multi Agent System For Flow-Based Intrusion Detection, David A . Ryan
A Multi Agent System For Flow-Based Intrusion Detection, David A . Ryan
Theses and Dissertations
The detection and elimination of threats to cyber security is essential for system functionality, protection of valuable information, and preventing costly destruction of assets. This thesis presents a Mobile Multi-Agent Flow-Based IDS called MFIREv3 that provides network anomaly detection of intrusions and automated defense. This version of the MFIRE system includes the development and testing of a Multi-Objective Evolutionary Algorithm (MOEA) for feature selection that provides agents with the optimal set of features for classifying the state of the network. Feature selection provides separable data points for the selected attacks: Worm, Distributed Denial of Service, Man-in-the-Middle, Scan, and Trojan. This …
Material Characterization Using Passive Multispectral Polarimetric Imagery, Melissa A . Sawyer
Material Characterization Using Passive Multispectral Polarimetric Imagery, Melissa A . Sawyer
Theses and Dissertations
A new method for characterization of unknown targets using passive multispectral polarimetric imagery is presented. Previous work makes use of a pBRDF derived equation for the degree of linear polarization and with the aid of measurements at multiple incident angles estimates refractive index and reflection angle. This work uses known incident and reflection angles along with dispersion equations and polarimetric data at multiple wavelengths to recover the index of refraction. Although imagery is collected with a division of time polarimeter and a spectral filter wheel in iterative, manual steps, the new algorithm could be applied to any set of registered …
Airborne Network Data Availability Using Peer To Peer Database Replication On A Distributed Hash Table, Trevor J. Vranicar
Airborne Network Data Availability Using Peer To Peer Database Replication On A Distributed Hash Table, Trevor J. Vranicar
Theses and Dissertations
The concept of distributing one complex task to several smaller, simpler Unmanned Aerial Vehicles (UAVs) as opposed to one complex UAV is the way of the future for a vast number of surveillance and data collection tasks. One objective for this type of application is to be able to maintain an operational picture of the overall environment. Due to high bandwidth costs, centralizing all data may not be possible, necessitating a distributed storage system such as mobile Distributed Hash Table (DHT). A difficulty with this maintenance is that for an Airborne Network (AN), nodes are vehicles and travel at high …