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Articles 2551 - 2580 of 5700
Full-Text Articles in Engineering
Detonation Propagation Through Ducts In A Pulsed Detonation Engine, Jeffrey M. Nielsen
Detonation Propagation Through Ducts In A Pulsed Detonation Engine, Jeffrey M. Nielsen
Theses and Dissertations
Development of a continuously operating pulsed detonation engine (PDE) without a high energy ignition system or a deflagration-to- detonation transition (DDT) device will increase engine efficiency, reduce cost, improve performance, and reduce weight. This report is a study of configurations that allow a consistent and predictable transition of a detonation from one detonation tube to second tube. The intent was, via visualization of detonation propagation through a cross-over tube, to develop a cross-over passage leading to minimization of energy losses and effective and repeatable tube-to-tube initiation. Detonation tube cross-over width, cross-over geometry and fuels were varied to determine their effect …
Cubesat Packaged Electrospray Thruster Evaluation For Enhanced Operationally Responsive Space Capabilities, Scott T. Ober
Cubesat Packaged Electrospray Thruster Evaluation For Enhanced Operationally Responsive Space Capabilities, Scott T. Ober
Theses and Dissertations
A new specialized electrospray thruster with a potential to be used with a 3-U CubeSat was operated. The key difference in this thruster from traditional colloid thrusters is the porous stainless steel surface used for the emission sites. With this porous surface the actual location and number of the Taylor cones formations vary with changing fuel flow. The understanding of these formations is discussed with low, moderate, and high flow rates. The limitations of the experiment and observed system response are discussed. Due to these limitations, the colloid thruster was only able to operate in the low mass flow rate …
Experimental Measurements Of Store Separation Using Dry Ice Models In A Subsonic Flow, Michael C. Paul
Experimental Measurements Of Store Separation Using Dry Ice Models In A Subsonic Flow, Michael C. Paul
Theses and Dissertations
Testing free-drop store separation from a cavity in wind tunnels proves a difficult task because the models are typically destroyed during the test. Furthermore, there is potential for damage to wind tunnel components. Prior work has shown that small dry ice models released within the test section do not cause damage to the AFIT pressure-vacuum wind tunnel components or vacuum chamber. Rather, the dry ice models break apart and sublimate harmlessly into gaseous carbon dioxide. Therefore, this study was undertaken to determine whether dry ice models might prove useful in free-drop store separation testing. A generic aircraft cavity was constructed …
Conceptual Design Tool To Analyze Electrochemically-Powered Micro Air Vehicles, Douglas J. Pederson
Conceptual Design Tool To Analyze Electrochemically-Powered Micro Air Vehicles, Douglas J. Pederson
Theses and Dissertations
A multi-fidelity conceptual design tool was developed to assess electrochemically-powered micro air vehicles(MAVs). The tool utilizes four areas of contributing analyses (CAs): aerodynamics, propulsion, power management, and power sources to determine the endurance duration of a given mission. The low-fidelity aerodynamic CA consisted of drag polar calculations and the high-level CA used a vortex theory code called Athena Vortex Lattice (AVL). The propulsion CA employed QPROP and a MATLAB code that used experimental propeller data and motor constants to predict propeller-motor combination performance for the low- and high-fidelity tracks, respectively. The power management CA determined the percentage of required power …
Sizing Analysis For Aircraft Utilizing Hybrid-Electronic Propulsion Systems, Matthew D. Rippl
Sizing Analysis For Aircraft Utilizing Hybrid-Electronic Propulsion Systems, Matthew D. Rippl
Theses and Dissertations
A submerged inlet investigation, using flow control in the form of discrete blowing, examined proximity and jet directionality to improve compressor face uniformity. The flow control locations were at the head of the ramp and part way down the ramp, providing four configurations under examination. Laser Doppler velocimetry (LDV)measurements at the throat determined the effect of the flow control based on the statistical velocity measurements. Blowing at closer proximity to the throat and targeting the largest velocity deficit region provided the best results. The airspeed and inlet velocity simulated takeoff and landing conditions; velocities ranged from Mach 0.1-0.3 at the …
Estimating Cargo Airdrop Collateral Damage Risk, Vincent R. Cammarano
Estimating Cargo Airdrop Collateral Damage Risk, Vincent R. Cammarano
Theses and Dissertations
The purpose of this research is to determine an appropriate method for estimating cargo airdrop collateral damage risk. Specifically, this thesis answers the question: How can mission planners accurately predict airdrop collateral damage risk? The question is answered through a literature review and a thorough examination of a data set of real world airdrop scoring data. The data were examined to determine critical factors that affect airdrop error risks as well as to determine the characteristics of airdrop error patterns. Through this research it was determined that bivariate normal distributions with parameters pairs determined by empirical data are appropriate for …
Detecting Software Attacks By Monitoring Electric Power Consumption Patterns, Grant A. Jacoby, Nathaniel J. Davis Iv, Randolph C. Marchany
Detecting Software Attacks By Monitoring Electric Power Consumption Patterns, Grant A. Jacoby, Nathaniel J. Davis Iv, Randolph C. Marchany
AFIT Patents
Software attacks such as worms and viruses are detected in an electronic device by monitoring power consumption patterns. In a first embodiment, software attacks are detected by an increase in power consumption. The increased power consumption can be caused by increased network traffic, or by increased activity in the microprocessor. Monitoring power consumption is particularly effective for detecting DOS/flooding attacks when the electronic device is in an idle state. In a second embodiment, a power consumption signal is converted to the frequency domain (e.g., by fast Fourier transform). The highest amplitude frequencies are identified. Specific software attacks produce characteristic frequencies …
Electro-Luminescent Display With Power Line Voltage Compensation, Michael E. Miller, Michael J. Murdoch, John W. Harmer
Electro-Luminescent Display With Power Line Voltage Compensation, Michael E. Miller, Michael J. Murdoch, John W. Harmer
AFIT Patents
An active matrix electro-luminescent display system, comprising: a display composed of an array of regions of light-emitting elements, pixel driving circuits for independently controlling the current to each light-emitting element, one or more display drivers for receiving an input image signal for data to drive the pixel driving circuits and generating a converted image signal for driving the light emitting elements in each region of the display through signals provided through data lines and select lines, wherein the one or more display drivers sequentially receive the input image signal for driving the light emitting elements within each region of the …
Mh-53j/M Pave Low Iii/Iv Systems Engineering Case Study, Air Force Center For Systems Engineering, William Albery, Raymond L. Robb, Lee Anderson
Mh-53j/M Pave Low Iii/Iv Systems Engineering Case Study, Air Force Center For Systems Engineering, William Albery, Raymond L. Robb, Lee Anderson
AFIT Documents
No abstract provided.
Afit Graduate School Of Engineering And Management Catalog 2011–2012, Graduate School Of Engineering And Management, Air Force Institute Of Technology
Afit Graduate School Of Engineering And Management Catalog 2011–2012, Graduate School Of Engineering And Management, Air Force Institute Of Technology
AFIT Documents
The Graduate Catalog represents the offerings, programs, and requirements in effect at the time of publication.
An Fpga-Based System For Tracking Digital Information Transmitted Via Peer-To-Peer Protocols, Karl R. Schrader, Barry E. Mullins, Gilbert L. Peterson, Robert F. Mills
An Fpga-Based System For Tracking Digital Information Transmitted Via Peer-To-Peer Protocols, Karl R. Schrader, Barry E. Mullins, Gilbert L. Peterson, Robert F. Mills
Faculty Publications
This paper presents a Field Programmable Gate Array (FPGA)-based tool designed to process file transfers using the BitTorrent Peer-to-Peer (P2P) protocol and VoIP phone calls made using the Session Initiation Protocol (SIP). The tool searches selected control messages in real time and compares the unique identifier of the shared file or phone number against a list of known contraband files or phone numbers. Results show the FPGA tool processes P2P packets of interest 92% faster than a software-only configuration and is 97.6% accurate at capturing and processing messages at a traffic load of 89.6 Mbps.
Fatigue Behavior Of A Sic/Sic Composite At 1000⁰C In Air And In Steam, Michael W. Knauf
Fatigue Behavior Of A Sic/Sic Composite At 1000⁰C In Air And In Steam, Michael W. Knauf
Theses and Dissertations
Tension-tension fatigue behavior of a prototype Silicon Carbide/Silicon Carbide (SiC/SiC) ceramic matrix composite (CMC) material was investigated at 1000°C in laboratory air and in steam environments. The material consists of a SiC matrix reinforced with CG NICALON™ fibers woven in an eight harness satin weave (8HSW) and coated with a BN/SiC dual-layer interphase. The composite was manufactured by a Polymer Infiltration and Pyrolysis (PIP) process. A seal coat of SiC and elemental boron was applied to the test specimens after machining. The tensile stress-strain behavior was investigated and the tensile properties were measured at 1000°C. Tension-tension fatigue behavior was studied …
Flow Control Application On A Submerged Inlet Characterized By Three-Component Ldv, Tina H. Reynolds
Flow Control Application On A Submerged Inlet Characterized By Three-Component Ldv, Tina H. Reynolds
Theses and Dissertations
A submerged inlet investigation, using flow control in the form of discrete blowing, examined proximity and jet directionality to improve compressor face uniformity. The flow control locations were at the head of the ramp and part way down the ramp, providing four configurations under examination. Laser Doppler velocimetry (LDV)measurements at the throat determined the effect of the flow control based on the statistical velocity measurements. Blowing at closer proximity to the throat and targeting the largest velocity deficit region provided the best results. The airspeed and inlet velocity simulated takeoff and landing conditions; velocities ranged from Mach 0.1-0.3 at the …
Performance Characterization Of A Three-Axis Hall Effect Thruster, Spencer E. Temkin
Performance Characterization Of A Three-Axis Hall Effect Thruster, Spencer E. Temkin
Theses and Dissertations
No abstract provided.
Effects Of Prior Aging At 274⁰C In Argon On Inelastic Deformation Behavior Of Pmr-15 Polymer At 288⁰C: Experiment And Modeling, Joseph A. Wahlquist
Effects Of Prior Aging At 274⁰C In Argon On Inelastic Deformation Behavior Of Pmr-15 Polymer At 288⁰C: Experiment And Modeling, Joseph A. Wahlquist
Theses and Dissertations
No abstract provided.
A Space Acquisition Leading Indicator Based On System Interoperation Maturity, Jason T. Shibata
A Space Acquisition Leading Indicator Based On System Interoperation Maturity, Jason T. Shibata
Theses and Dissertations
The Department of Defense‘s space acquisition enterprise has experienced numerous challenges since the advent of space power. Space borne capabilities are needed more than ever, but space acquisition frequently fails to meet its goals. The decades of space acquisition experience form a rich history that can be used to build a leading indicator of success to enable effective program execution. First, the space acquisition areas of greatest concern were determined to be cost, schedule and requirements. These areas are considered as systems composed of the people, processes and products that execute the program. Second, the vital interoperation characteristics, or attributes …
Network Security Toolkit Including Heuristic Solutions For Trust System Placement And Network Obfuscation, Gabriel H. Greve
Network Security Toolkit Including Heuristic Solutions For Trust System Placement And Network Obfuscation, Gabriel H. Greve
Theses and Dissertations
For Part I, a supervisory control and data acquisition (SCADA) network consists of a group stations and substations in a portion of the power grid. The use of Internet technology in SCADA communications as well as other factors has caused vulnerabilities. One idea to help mitigate this risk is to strategically place trust nodes to compartmentalize and secure the SCADA systems without disturbing its finely honed processes. The trust nodes combine firewall and intrusion detection technology to provide more secure communication. An optimal solution to this problem has already been developed using a mixed-integer linear programming model. Because the problem …
Navigation With Limited Prior Information Using Time Difference Of Arrival Measurements From Signals Of Opportunity, Christopher M. Rondeau
Navigation With Limited Prior Information Using Time Difference Of Arrival Measurements From Signals Of Opportunity, Christopher M. Rondeau
Theses and Dissertations
The Global Positioning System (GPS) provides world-wide availability to high-accuracy navigation and positioning information. However, the threats to GPS are increasing, and many limitations of GPS are being encountered. Simultaneously, systems previously considered as viable backups or supplements to GPS are being shut down. This creates the need for system alternatives. Navigation using signals of opportunity (SoOP) exploits any signal that is available in a given area, regardless of whether or not the original intent of the signal was for navigation. Common techniques to compute a position estimate using SoOP include received signal strength, angle of arrival, time of arrival, …
A Linear Combination Of Heuristics Approach To Spatial Sampling Hyperspectral Data For Target Tracking, Barry R. Secrest
A Linear Combination Of Heuristics Approach To Spatial Sampling Hyperspectral Data For Target Tracking, Barry R. Secrest
Theses and Dissertations
Persistent surveillance of the battlespace results in better battlespace awareness which aids in obtaining air superiority, winning battles, and saving friendly lives. Although hyperspectral imagery (HSI) data has proven useful for discriminating targets, it presents many challenges as a useful tool in persistent surveillance. A new sensor under development has the potential of overcoming these challenges and transforming our persistent surveillance capability by providing HSI data for a limited number of pixels and grayscale video for the remainder. The challenge of exploiting this new sensor is determining where the HSI data in the sensor's field of view will be the …
Conceptual Design And Analysis Of Service Oriented Architecture (Soa) For Command And Control Of Space Assets, Eric B. Snyder
Conceptual Design And Analysis Of Service Oriented Architecture (Soa) For Command And Control Of Space Assets, Eric B. Snyder
Theses and Dissertations
The mission-unique model that has dominated the DoD satellite Command and Control community is costly and inefficient. It requires repeatedly “reinventing” established common C2 components for each program, unnecessarily inflating budgets and delivery schedules. The effective utilization of standards is scarce, and proprietary, non-open solutions are commonplace. IT professionals have trumpeted Service Oriented Architectures (SOAs) as the solution to large enterprise situations where multiple, functionally redundant but non-compatible information systems create large recurring development, test, maintenance, and tech refresh costs. This thesis describes the current state of Service Oriented Architectures as related to satellite operations and presents a functional analysis …
Measurement And Modeling Of Infrared Nonlinear Absorption Coefficients And Laser-Induced Damage Thresholds In Ge And Gasb, Torrey J. Wagner, Matthew J. Bohn, Ronald A. Coutu Jr., L. P. Gonzales, J. M. Murray, K. L. Schepler, S. Guha
Measurement And Modeling Of Infrared Nonlinear Absorption Coefficients And Laser-Induced Damage Thresholds In Ge And Gasb, Torrey J. Wagner, Matthew J. Bohn, Ronald A. Coutu Jr., L. P. Gonzales, J. M. Murray, K. L. Schepler, S. Guha
Faculty Publications
Using a simultaneous fitting technique to extract nonlinear absorption coefficients from data at two pulse widths, we measure two-photon and free-carrier absorption coefficients for Ge and GaSb at 2.05 and 2.5 µm for the first time, to our knowledge. Results agreed well with published theory. Single-shot damage thresholds were also measured at 2.5 µm and agreed well with modeled thresholds using experimentally determined parameters including nonlinear absorption coefficients and temperature dependent linear absorption. The damage threshold for a single-layer Al2O3 anti-reflective coating on Ge was 55% or 35% lower than the uncoated threshold for picosecond or nanosecond …
Improving The Quality Of Service And Security Of Military Networks With A Network Tasking Order Process, Matthew D. Compton
Improving The Quality Of Service And Security Of Military Networks With A Network Tasking Order Process, Matthew D. Compton
Theses and Dissertations
This research presents a Network Tasking Order process that collects mission plans, network capabilities, and historical records to build a Network Tasking Order (NTO). The NTO document directs the form and usage of the network, much like an Air Tasking Order (ATO) directs the usage of air power. The NTO process is fleshed out with the content and format of the NTO given herein for the first time. Tools such as topology control algorithms are then shown through simulation to improve the quality of service of the network by finding favorable ways to connect the assets identified during the NTO …
Improving Range Estimation Of A 3d Flash Ladar Via Blind Deconvolution, Jason R. Mcmahon
Improving Range Estimation Of A 3d Flash Ladar Via Blind Deconvolution, Jason R. Mcmahon
Theses and Dissertations
The purpose of this research effort is to improve and characterize range estimation in a three-dimensional FLASH LAser Detection And Ranging (3D FLASH LADAR) by investigating spatial dimension blurring effects. The myriad of emerging applications for 3D FLASH LADAR both as primary and supplemental sensor necessitate superior performance including accurate range estimates. Along with range information, this sensor also provides an imaging or laser vision capability. Consequently, accurate range estimates would also greatly aid in image quality of a target or remote scene under interrogation. Unlike previous efforts, this research accounts for pixel coupling by defining the range image mathematical …
Determining The Index Of Refraction Of An Unknown Object Using Passive Polarimetric Imagery Degraded By Atmospheric Turbulence, Milo W. Hyde Iv
Determining The Index Of Refraction Of An Unknown Object Using Passive Polarimetric Imagery Degraded By Atmospheric Turbulence, Milo W. Hyde Iv
Theses and Dissertations
In this research, an algorithm is developed to estimate the index of refraction of an unknown object using passive polarimetric images degraded by atmospheric turbulence. The algorithm uses a variant of the maximum-likelihood blind-deconvolution algorithm developed by LeMaster and Cain to recover the true object (i.e., the first Stokes parameter), the degree of linear polarization, and the polarimetric-image point spread functions. Nonlinear least squares is then used to find the value of the complex index of refraction which best fits the theoretical degree of linear polarization, derived using a polarimetric bidirectional reflectance distribution function, to the turbulence-corrected degree of linear …
Hijacking User Uploads To Online Persistent Data Repositories For Covert Data Exfiltration, Curtis P. Barnard
Hijacking User Uploads To Online Persistent Data Repositories For Covert Data Exfiltration, Curtis P. Barnard
Theses and Dissertations
As malware has evolved over the years, it has gone from harmless programs that copy themselves into other executables to modern day botnets that perform bank fraud and identity theft. Modern malware often has a need to communicate back to the author, or other machines that are also infected. Several techniques for transmitting this data covertly have been developed over the years which vary significantly in their level of sophistication. This research creates a new covert channel technique for stealing information from a network by piggybacking on user-generated network traffic. Specifically, steganography drop boxes and passive covert channels are merged …
Orbital Tori Construction Using Trajectory Following Spectral Methods, Ralph E. Bordner Iii
Orbital Tori Construction Using Trajectory Following Spectral Methods, Ralph E. Bordner Iii
Theses and Dissertations
By assuming the motion of a satellite about the earth’s geopotential mimics the known Kolmogorov-Arnold-Moser (KAM) solution of a lightly perturbed integrable Hamiltonian system, this research focused on applying trajectory following spectral methods to estimate orbital tori from sampled orbital data. From an estimated basis frequency set, orbital data was decomposed into multi-periodic Fourier series, essentially compressing ephemerides for long-term use. Real-world Global Positioning System (GPS) orbital tracks were decomposed and reconstructed with error from as low as few kilometers per coordinate axis over a 10-week span to tens of kilometers per coordinate axis over the same time period, depending …
Providing A Theoretical Basis For Nanotoxicity Risk Analysis Departing From Traditional Physiologically-Based Pharmacokinetic (Pbpk) Modeling, Dirk P. Yamamoto
Providing A Theoretical Basis For Nanotoxicity Risk Analysis Departing From Traditional Physiologically-Based Pharmacokinetic (Pbpk) Modeling, Dirk P. Yamamoto
Theses and Dissertations
The same novel properties of engineered nanoparticles that make them attractive may also present unique exposure risks. But, the traditional physiologically-based pharmacokinetic (PBPK) modeling assumption of instantaneous equilibration likely does not apply to nanoparticles. This simulation-based research begins with development of a model that includes diffusion, active transport, and carrier mediated transport. An eigenvalue analysis methodology was developed to examine model behavior to focus future research. Simulations using the physicochemical properties of size, shape, surface coating, and surface charge were performed and an equation was determined which estimates area under the curve for arterial blood concentration, which is a surrogate …
Exploring The Effects Of International Traffic In Arms Regulations Restrictions On Innovation In The U.S. Space Industrial Base, Kalliroi L. Landry
Exploring The Effects Of International Traffic In Arms Regulations Restrictions On Innovation In The U.S. Space Industrial Base, Kalliroi L. Landry
Theses and Dissertations
The International Traffic in Arms Regulations (ITAR) are used to protect United States (U.S.) military technologies. However, changes to ITAR export controls regarding space technologies have had a major impact to the U.S. space industry. The literature mentions a concern for the health of lower-tier firms because they are a major source of innovation, but there is no additional information considering the effects of ITAR on space innovation at those lower tiers. The purpose of this thesis was to explore the implications of continuing the current ITAR restrictions with regard to innovation in the space industry. This research used a …
Knowledge-Based Decision Support In Department Of Defense Acquisitions, Clifton L. Hicks
Knowledge-Based Decision Support In Department Of Defense Acquisitions, Clifton L. Hicks
Theses and Dissertations
Despite numerous reform efforts over the past 30 years, acquisition programs in the Department of Defense (DoD) continue to experience cost overruns and schedule delays. One contributing factor is the decision-making process used by defense officials. The General Accounting Office (GAO) has stated that ‘poor program outcomes are the lack of widespread adoption of a knowledge-based acquisition process within DoD despite polices that support such a process. A knowledge-based business case at the outset of each program would alleviate overpromising on cost, schedule, and performance and would empower program managers.’ Effective decision-making for acquisition programs is very important. It not …
Satellite Capabilities Mapping - Utilizing Small Satellites, David A. Grigsby
Satellite Capabilities Mapping - Utilizing Small Satellites, David A. Grigsby
Theses and Dissertations
The cost and schedule advantages small satellites have over larger legacy systems have been studied, but there has been very little experimentation performed to determine whether small satellites can actually deliver the capabilities of larger spacecraft. To date, a desired operational capability has not been fully realized by a scalable satellite design. Advances in sensor technology have led to significant reductions in size, weight, and power (SWaP) presenting an opportunity to exploit the evolution of space operations by using small satellites to perform specific missions. This paper describes a methodology that maps a specific set of large space vehicle capabilities …