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Articles 1 - 30 of 174
Full-Text Articles in Engineering
Analyzing Systems Integration Best Practices And Assessment In Dod Space Systems Acquisition, Douglas R. Dillon, Enriqueta M. Styres
Analyzing Systems Integration Best Practices And Assessment In Dod Space Systems Acquisition, Douglas R. Dillon, Enriqueta M. Styres
Theses and Dissertations
Senior leadership of the Air Force's Space and Missile Center suggested an investigation of systems integration within the space acquisition community in the fall of 2008. This thesis performs that investigation. A review concluded that while Systems Integration (SI) is extensively discussed as an area deserving considerable attention in the Systems Engineering literature, definitions are weak and methods and tools non-existent. Known SI activities are not being traced and assessed for adequacy throughout system development. Employing the Space System Acquisition Lifecycle Framework as the environment for this research, a method of characterizing and tracing SI throughout a program‘s lifecycle by …
Extending The Strategy Based Risk Model Using The Delphi Method: An Application To The Validation Process For Research And Developmental (R&D) Satellites, Amanda J. Langenbrunner, Mary R. Trautwein
Extending The Strategy Based Risk Model Using The Delphi Method: An Application To The Validation Process For Research And Developmental (R&D) Satellites, Amanda J. Langenbrunner, Mary R. Trautwein
Theses and Dissertations
The validation between a research and developmental satellite and its ground system is critical to ensuring the success on-orbit. However, the exact process for completing validation is not documented, frequently underfunded, and accomplished ad hoc. This leads to debate regarding maintenance of budget and schedule, while ensuring on-orbit success. This thesis examines readiness and on-orbit activities within the U.S. Air Force Space Development and Test Wing's Research Development Test and Evaluation Support Complex. Combining historical data with the consultation of subject matter experts, a validation process was defined. Risks associated with this process were then analyzed using the Strategy Based …
Heat And Current Propagation In Buffered Superconducting And Hyper-Conducting Wire, Jesse L. Lynn
Heat And Current Propagation In Buffered Superconducting And Hyper-Conducting Wire, Jesse L. Lynn
Theses and Dissertations
This research models and analyzes the distribution of heat and current in a buffered superconducting or hyper-conducting wire that shows potential for use in different capacities in multiple Air Force systems including the Active Denial System. The thesis includes a brief background of the reaction-diffusion system of partial differential equations provided by AFRL/RZPG and development of the numerical scheme. It then explores solutions to the model. These solutions indicate some of the various heat-related failures that may be observed in such a wire. The nature of the solutions observed depends on the characteristics of the wire, operating temperature and efficiency …
Laser-Induced Fluorescence And Synthetic Jet Fuel Analysis In The Ultra Compact Combustor, Aaron C. Drenth
Laser-Induced Fluorescence And Synthetic Jet Fuel Analysis In The Ultra Compact Combustor, Aaron C. Drenth
Theses and Dissertations
The Ultra-Compact Combustor (UCC) is currently under investigation at the Air Force Institute of Technology (AFIT) and Air Force Research Laboratory’s Propulsion Directorate. The combustor is a small-scale, axi-symmetric, atmospheric pressure, laboratory combustor with an outer circumferential cavity in which the flame is stabilized by a highly accelerated swirled flow. UCCs will enable aero gas turbine reheat cycle engines and significantly shorten conventional aero gas turbine engines. The experiments of this work utilized the AFIT small-scale combustion diagnostics facility, investigating a sector model of the UCC. The research objectives were to perform an addition to the COAL lab laser diagnostic …
A Physical Model Of Human Skin And Its Application For Search And Rescue, Abel S. Nunez
A Physical Model Of Human Skin And Its Application For Search And Rescue, Abel S. Nunez
Theses and Dissertations
For this research we created a human skin reflectance model in the VIS and NIR. We then modeled sensor output for an RGB sensor based on output from the skin reflectance model. The model was also used to create a skin detection algorithm and a skin pigmentation level (skin reflectance at 685nm) estimation algorithm. The average root mean square error across the VIS and NIR between the skin reflectance model and measured data was 2%. The skin reflectance model then allowed us to generate qualitatively accurate responses for an RGB sensor for different biological and lighting conditions. To test the …
Discrete Film Cooling In A Rocket With Curved Walls, Jonathan F. Mccall
Discrete Film Cooling In A Rocket With Curved Walls, Jonathan F. Mccall
Theses and Dissertations
This study quantified the effects of discrete wall-based film cooling in a rocket with curved walls. Simulations and experiments showed decreasing with wall radius of curvature, holding jet diameter constant, improves net heat flux reduction (NHFR) and adiabatic effectiveness (η) for 90˚ compound injected cylindrical jets, though η is reduced at the highest curvature. NHFR and η improved further with a high favorable stream-wise pressure gradient (K=2.1x10-5) at all tested blowing ratios, but were affected little by a high density ratio (DR=1.76) using carbon dioxide as the coolant. Experiments were run at a Reynolds number of 31K and …
Tailored Systems Architecture For Design Of Space Science And Technology Missions Using Dodaf V2.0, Nicholas J. Merski
Tailored Systems Architecture For Design Of Space Science And Technology Missions Using Dodaf V2.0, Nicholas J. Merski
Theses and Dissertations
The use of systems architecture, following a set of integrated descriptions from an architecture framework, has been well codified in Department of Defense acquisition and systems engineering. However, in the Space Science and Technology (S&T) community, this guidance and practice is not commonly adopted. This paper outlines an approach to leverage the changes made in DoD Architecture Framework 2.0 (DoDAF2.0), and the renewed emphasis on data and support to acquisition decision analysis. After decomposing the Space S&T design lifecycle into phases, design milestones and activities using process models, a set of DoDAF prescribed and Fit-for-Purpose views are constructed into a …
Performance Analysis Of Live-Virtual-Constructive And Distributed Virtual Simulations: Defining Requirements In Terms Of Temporal Consistency, Douglas D. Hodson
Performance Analysis Of Live-Virtual-Constructive And Distributed Virtual Simulations: Defining Requirements In Terms Of Temporal Consistency, Douglas D. Hodson
Theses and Dissertations
This research extends the knowledge of live-virtual-constructive (LVC) and distributed virtual simulations (DVS) through a detailed analysis and characterization of their underlying computing architecture. LVCs are characterized as a set of asynchronous simulation applications each serving as both producers and consumers of shared state data. In terms of data aging characteristics, LVCs are found to be first-order linear systems. System performance is quantified via two opposing factors; the consistency of the distributed state space, and the response time or interaction quality of the autonomous simulation applications. A framework is developed that defines temporal data consistency requirements such that the objectives …
Electromagnetic Field Control And Optimization Using Metamaterials, Jeffrey S. Mcguirk
Electromagnetic Field Control And Optimization Using Metamaterials, Jeffrey S. Mcguirk
Theses and Dissertations
Transformation optics has shown the ability to cloak an object from incident electromagnetic radiation is possible. However, the material parameters are inhomogeneous, anisotropic, and, in some instances, singular at various locations. In order for a cloak to be practically realized, simplified parameter sets are required. However, the simplified parameters result in a degradation in the cloaking function. Constitutive parameters for simplified two-dimensional cylindrical cloaks have been developed with two material property constraints. It was initially believed satisfying these two constraints would result in the simplified cylindrical cloaks having the same wave equation as an ideal cloak. Because of this error, …
Investigation Into Contact Resistance And Damage Of Metal Contacts Used In Rf-Mems Switches, Kevin W. Gilbert
Investigation Into Contact Resistance And Damage Of Metal Contacts Used In Rf-Mems Switches, Kevin W. Gilbert
Theses and Dissertations
This research examines the physical and electrical processes involved in lifecycle failure of Microelectromechanical (MEMS) Radio-Frequency (RF) cantilever beam ohmic contact switches. Failures of these switches generally occur at the contact, but complete details of performance of microcontacts are difficult to measure and have not been previously reported. This study investigated the mechanics of microcontact behavior by designing and constructing a novel experimental setup. Three representative contact materials of varying microstructure (Au, Au5%Ru, Au4%V2O5) were tested and parameters of contact during cycling were measured. The Au4%V2O5, a dispersion strengthened material developed at …
Fatigue Behavior Of An Advanced Sic/Sic Composite At Elevated Temperature In Air And In Steam, Devon T. Christensen
Fatigue Behavior Of An Advanced Sic/Sic Composite At Elevated Temperature In Air And In Steam, Devon T. Christensen
Theses and Dissertations
The fatigue behavior of an advanced Silicon Carbide/Silicon Carbide (SiC/SiC) ceramic matrix composite (CMC) was investigated at 1200 ˚C in laboratory air and in steam environments. The composite consisted of a SiC matrix reinforced with Boron Nitride (BN) coated Hi-Nicalon fibers woven into eight-harness-satin (8HS) weave plies. Tensile stress-strain behavior and tensile properties were also evaluated at 1200 ˚C. Tension-tension fatigue tests were conducted in both laboratory air and in steam at 1200 ˚C at frequencies of 0.1 Hz, 1.0 Hz, and 10 Hz. The tension-tension fatigue tests had a ratio of minimum stress to maximum stress of R = …
Flow Visualization Study Of Passive Flow Control Features On A Film-Cooled Turbine Blade Leading Edge, Daniel R. Carroll
Flow Visualization Study Of Passive Flow Control Features On A Film-Cooled Turbine Blade Leading Edge, Daniel R. Carroll
Theses and Dissertations
A flow visualization study was conducted on a model of a film-cooled turbine blade leading edge in a closed-loop water channel at ReD = 30k. The model consisted of an 8.89 cm diameter half-cylinder with flat afterbody joined at the ninety degree point. A single radial coolant hole (dc / D = 0.054) drilled 21.5° from the stagnation line, angled 20° to the surface and 90° to the flow direction generated a coolant jet transverse to the freestream. Water channel testing assessed the hydrodynamic effects of 16 passive flow control features, to include a variety of …
Flow Measurements Using Particle Image Velocimetry In The Ultra Compact Combustor, Levi M. Thomas
Flow Measurements Using Particle Image Velocimetry In The Ultra Compact Combustor, Levi M. Thomas
Theses and Dissertations
Velocity measurements were performed using the Particle Image Velocimetry (PIV) technique on the Ultra Compact Combustor (UCC) test rig at the Air Force Institute of Technology (AFIT). Velocity patterns and time-averaged turbulence statistics were calculated for data taken with the UCC burning hydrogen fuel in the straight cavity vane and curved cavity vane configurations. The equivalence ratio was varied from 0.7 to 1.5, while the ratio of cavity air to main air was varied from 5% to 20% in testing performed on the straight vane configuration. Spanwise velocity was observed to decrease linearly with distance from the cavity vane over …
Structured P2p Technologies For Distributed Command And Control, Daniel R. Karrels, Gilbert L. Peterson, Barry E. Mullins
Structured P2p Technologies For Distributed Command And Control, Daniel R. Karrels, Gilbert L. Peterson, Barry E. Mullins
Faculty Publications
The utility of Peer-to-Peer (P2P) systems extends far beyond traditional file sharing. This paper provides an overview of how P2P systems are capable of providing robust command and control for Distributed Multi-Agent Systems (DMASs). Specifically, this article presents the evolution of P2P architectures to date by discussing supporting technologies and applicability of each generation of P2P systems. It provides a detailed survey of fundamental design approaches found in modern large-scale P2P systems highlighting design considerations for building and deploying scalable P2P applications. The survey includes unstructured P2P systems, content retrieval systems, communications structured P2P systems, flat structured P2P systems and …
Shaped Mems Contact, Ronald A. Coutu Jr., Paul E. Kladitis, Robert L. Crane
Shaped Mems Contact, Ronald A. Coutu Jr., Paul E. Kladitis, Robert L. Crane
AFIT Patents
A MEMS switch fabrication process and apparatus inclusive of a bulbous rounded surface movable contact assembly that is integral with the switch movable element and achieving of long contact wear life with low contact electrical resistance. The disclosed process is compatible with semiconductor integrated circuit fabrication materials and procedures and includes an unusual photoresist reflow step in which the bulbous contact shape is quickly defined in three dimensions from more easily achieved integrated circuit mask and etching-defined precursor shapes. A plurality of differing photoresist materials are used in the process. A large part of the contact and contact spring formation …
Precision Navigation Using Pre-Georegistered Map Data, Frederick C. Webber
Precision Navigation Using Pre-Georegistered Map Data, Frederick C. Webber
Theses and Dissertations
Navigation performance in small unmanned aerial vehicles (UAVs) is adversely affected by limitations in current sensor technology for small, lightweight sensors. Because most UAVs are equipped with cameras for mission-related purposes, it is advantageous to utilize the camera to improve the navigation solution. This research improves navigation by matching camera images to a priori georegistered image data and combining this update with existing image-aided navigation technology. The georegistration matching is done by projecting the images into the same plane, extracting features using the techniques Scale Invariant Feature Transform (SIFT) [5] and Speeded-Up Robust Features (SURF) [3]. The features are matched …
Least-Squares, Continuous Sensitivity Analysis For Nonlinear Fluid-Structure Interaction, Douglas P. Wickert
Least-Squares, Continuous Sensitivity Analysis For Nonlinear Fluid-Structure Interaction, Douglas P. Wickert
Theses and Dissertations
A least-squares, continuous sensitivity analysis method is developed for transient aeroelastic gust response problems to support computationally efficient analysis and optimization of aeroelastic design problems. A key distinction between the local and total derivative forms of the sensitivity system is introduced. The continuous sensitivity equations and sensitivity boundary conditions are derived in local derivative form which is shown to be superior for several applications. The analysis and sensitivity problems are both posed in a first-order form which is amenable to a solution using the least-squares finite element method. Several example and validation problems are presented and solved, including elasticity, fluid, …
F-16 Ventral Fin Buffet Alleviation Using Piezoelectric Actuators, Joseph S. Browning
F-16 Ventral Fin Buffet Alleviation Using Piezoelectric Actuators, Joseph S. Browning
Theses and Dissertations
Buffet-induced vibrations can have a disastrous impact on aircraft structures. Early attempts at combating buffet vibrations included passive methods such as structural enhancements and leading edge fences. Active methods have shown greater promise, including active airflow control, control surface modulation, and active structural control using piezoelectric actuators. Surface mounted piezoelectric actuators impart directional strain reducing the negative effects associated with harmful vibration. The Block-15 F-16 ventral fin represents an aircraft structure prone to failure when subjected to the buffet field from the wake of a LANTIRN pod. This research takes advantage of the susceptibility to buffet vibration of the Block …
Pulsed Film Cooling On A Turbine Blade Leading Edge, James L. Rutledge
Pulsed Film Cooling On A Turbine Blade Leading Edge, James L. Rutledge
Theses and Dissertations
Unsteadiness in gas turbine film cooling jets may arise due to inherent unsteadiness of the flow through an engine or may be induced as a means of flow control. The traditional technique used to evaluate the performance of a steady film cooling scheme is demonstrated to be insufficient for use with unsteady film cooling and is modified to account for the cross coupling of the time dependent adiabatic effectiveness and heat transfer coefficient. The addition of a single term to the traditional steady form of the net heat flux reduction equation with time averaged quantities accounts for the unsteady effects. …
Alternative Methods To Standby Gain Scheduling Following Air Data System Failure, Matthew W. Coldsnow
Alternative Methods To Standby Gain Scheduling Following Air Data System Failure, Matthew W. Coldsnow
Theses and Dissertations
The United States Air Force has advanced fighter aircraft that lose the ability to operate in a large portion of their operating flight envelope when an air data system failure is experienced. These aircraft are reverted to a fixed set of standby-gains that limit their maneuverability, degrade handling qualities, and increase susceptibility to departure. The purpose of this research was to determine if three alternative methods of standby-gain-scheduling could provide robust control with minimal performance degradation despite the lack of air data. To accomplish this, three methods of standby-gain-scheduling were developed, integrated, and tested in the Infinity Cube simulator at …
Thermo-Mechanical Characterization Of Silicon Carbide-Silicon Carbide Composites At Elevated Temperatures Using A Unique Combustion Facility, Ted T. Kim
Theses and Dissertations
This research investigated four different types of CMCs in a simulated gas turbine engine hot section condition that involved the simultaneous application of a combustion environment and mechanical fatigue loading using a unique burner rig facility developed for this study at AFIT. Three of the materials were woven Melt-Infiltrated (MI) BN/SiC reinforced by Hi-Nicalon Type S (Hi-Nic-S), Sylramic (Syl) and Sylramic with insitu BN coating (Syl-iBN) fibers, respectively. They were made by the slurry cast method. The other CMC was MI Hi-Nic-S/BN/SiC made using the prepreg MI processing. Prepreg MI CMC and Sylramic-iBN fiber reinforced CMC showed better resistance to …
Electronic Image Stabilization For Mobile Robotic Vision Systems, Michael John Smith
Electronic Image Stabilization For Mobile Robotic Vision Systems, Michael John Smith
Theses and Dissertations
When a camera is affixed on a dynamic mobile robot, image stabilization is the first step towards more complex analysis on the video feed. This thesis presents a novel electronic image stabilization (EIS) algorithm for small inexpensive highly dynamic mobile robotic platforms with onboard camera systems. The algorithm combines optical flow motion parameter estimation with angular rate data provided by a strapdown inertial measurement unit (IMU). A discrete Kalman filter in feedforward configuration is used for optimal fusion of the two data sources. Performance evaluations are conducted by a simulated video truth model (capturing the effects of image translation, rotation, …
The Navigation Potential Of Ground Feature Tracking, Guner Mutlu
The Navigation Potential Of Ground Feature Tracking, Guner Mutlu
Theses and Dissertations
This research effort examines the reduction of error in inertial navigation aided by vision. This is part of an effort focused on navigation in a GPS denied environment. The navigation concept examined here consists of two main steps. First, extract the position of a tracked ground object using vision and geo-locate it in 3 dimensional navigation frame. In this first step multiple positions of the UAV are assumed known; think of a synthetic aperture. The only information about the tracked ground objects/features is the unit vector that points to the objects from the center of the camera. Two such vectors …
Synthesis, Interdiction, And Protection Of Layered Networks, Kevin T. Kennedy
Synthesis, Interdiction, And Protection Of Layered Networks, Kevin T. Kennedy
Theses and Dissertations
This research developed the foundation, theory, and framework for a set of analysis techniques to assist decision makers in analyzing questions regarding the synthesis, interdiction, and protection of infrastructure networks. This includes extension of traditional network interdiction to directly model nodal interdiction; new techniques to identify potential targets in social networks based on extensions of shortest path network interdiction; extension of traditional network interdiction to include layered network formulations; and develops models/techniques to design robust layered networks while considering trade-offs with cost. These approaches identify the maximum protection/disruption possible across layered networks with limited resources, find the most robust layered …
Changes In Structural Health Monitoring System Capability Due To Aircraft Environmental Factors, Jeffrey D. Kuhn
Changes In Structural Health Monitoring System Capability Due To Aircraft Environmental Factors, Jeffrey D. Kuhn
Theses and Dissertations
Structural Health Monitoring (SHM) promises to decrease the maintenance cost and increase the availability of aging aircraft fleets by fundamentally changing the way structural inspections are performed. But this promise can only be realized through the consistent and predictable performance of a SHM system throughout the entire remaining life of an aircraft. In a sensor-based SHM system, sensor signal changes are analyzed and interpreted to identify structural flaws. But aircraft environmental factors such as temperature fluctuations, cyclic strain and exposure to various aircraft fluids also have the potential to change SHM sensor signals, raising questions about long term SHM system …
Analysis And Modeling Of Motor Vehicle Crashes Involving Air Force Military Personnel, Antonios Markopoulos
Analysis And Modeling Of Motor Vehicle Crashes Involving Air Force Military Personnel, Antonios Markopoulos
Theses and Dissertations
The primary purpose of this thesis was to improve the data analysis of Motor Vehicle Crashes (MVCs). This thesis employed the Air Force Safety Center (AFSC) data, collected over 20 years, of MVCs in which US Air Force (USAF) military personnel are involved when off duty and off base. Categorical Data Analysis and Analysis of Variance (ANOVA) were applied to identify risk factors related to MVCs and influence the severity of injuries and those factors associated with the alcohol consumption before driving, and affect the number of lost workdays resulting from MVCs. Categorical Data Analysis showed that male USAF members …
Formation Flight Of Earth Satellites On Kam Tori, Christopher T. Craft
Formation Flight Of Earth Satellites On Kam Tori, Christopher T. Craft
Theses and Dissertations
Kolmogorov, Arnold and Moser (KAM) theory provides that orbits of satellites whose dynamics are representable by an integrable Hamiltonian plus a small, real perturbation lie on tori in phase space and remain on the KAM tori for all time, unless acted upon by a non-conservative force. A refined technique for constructing KAM tori for Earth-orbiting satellites is developed and implemented using numerically integrated orbital data for hypothetical satellites and involving methods of Fourier analysis and spectral decomposition. Definition of satellite formations on the KAM tori is performed and analyses conducted to investigate both constellations with large separations and clusters with …
Kc-135 Simulator Systems Engineering Case Study, Air Force Center For Systems Engineering, Macaulay-Brown, Inc., Don Chrislaghi, Richard Dyer, Free Jay
Kc-135 Simulator Systems Engineering Case Study, Air Force Center For Systems Engineering, Macaulay-Brown, Inc., Don Chrislaghi, Richard Dyer, Free Jay
AFIT Documents
No abstract provided.
Global Hawk Systems Engineering Case Study, Air Force Center For Systems Engineering, Bill Kinzig
Global Hawk Systems Engineering Case Study, Air Force Center For Systems Engineering, Bill Kinzig
AFIT Documents
No abstract provided.
Abstracting Gis Layers From Hyperspectral Imagery, Torsten E. Howard, Michael J. Mendenhall, Gilbert L. Peterson
Abstracting Gis Layers From Hyperspectral Imagery, Torsten E. Howard, Michael J. Mendenhall, Gilbert L. Peterson
Faculty Publications
The spectral-spatial relationship of materials in a hyperspectral image cube is exploited to partially automate the creation of Geographic Information System (GIS) layers. The topological neighborhood preservation property of the Self Organizing Map (SOM) is clustered into six (partially overlapping) neighborhoods that are mapped into the image domain to locate in-scene structures of similar material type. GIS layers are abstracted through spatial logical and morphological operations on the six image domain material maps and a novel road finding algorithm connects road segments under significant tree-occlusion resulting in a contiguous road network. It is assumed that specific knowledge of the scene …