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Full-Text Articles in Engineering

Detecting Near-Earth Objects Using Cross-Correlation With A Point Spread Function, Anthony P. O'Dell Mar 2009

Detecting Near-Earth Objects Using Cross-Correlation With A Point Spread Function, Anthony P. O'Dell

Theses and Dissertations

This thesis describes a process to help discover Near-Earth Objects (NEOs) of larger than 140 meters in diameter from ground based telescopes. The process involves using Nyquist sampling rate to take data from a ground-based telescope and measuring the atmospheric seeing parameter, r0, at the time of data collection. r0 is then used to create a point spread function (PSF) for a NEO at the visual magnitude limit of the telescope and exposure time. This PSF is cross-correlated with the Nyquist sampling rate image from the telescope to reduce the noise and therefore increase the detection probability of …

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Near Real-Time Closed-Loop Optimal Control Feedback For Spacecraft Attitude Maneuvers, C. Douglas Mcfarland Mar 2009

Near Real-Time Closed-Loop Optimal Control Feedback For Spacecraft Attitude Maneuvers, C. Douglas Mcfarland

Theses and Dissertations

Optimization of spacecraft attitude maneuvers can significantly reduce attitude control system size and mass, and extend satellite end-of-life. Optimal control theory has been applied to solve a variety of open-loop optimal control problems for terrestrial, air, and space applications. However, general application of real-time optimal controllers on spacecraft for large slew maneuvers has been limited because open-loop control systems are inherently vulnerable to error and the computation necessary to solve for an optimized control solution is resource intensive. This research effort is focused on developing a near real-time optimal control (RTOC) system for spacecraft attitude maneuvers on the Air Force …

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Second-Order Structural Analysis With One Element Per Member, Jesse William Lyon Mar 2009

Second-Order Structural Analysis With One Element Per Member, Jesse William Lyon

Theses and Dissertations

In this thesis, formulas for the local tangent stiffness matrix of a plane frame member are derived by differentiating the member resistance vector in the displaced position. This approach facilitates an analysis using only one element per member. The formulas are checked by finite difference. The derivation leads to the familiar elastic and geometric stiffness matrices used by other authors plus an additional higher order geometric stiffness matrix. Contributions of each of the three sub-matrices to the tangent stiffness matrix are studied on both the member and structure levels through two numerical examples. These same examples are analyzed three different …

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Vision-Aided Cooperative Navigation For Multiple Unmanned Vehicles, Jason K. Bingham Mar 2009

Vision-Aided Cooperative Navigation For Multiple Unmanned Vehicles, Jason K. Bingham

Theses and Dissertations

In the recent past, a shift has taken place from manned to unmanned Intelligence, Surveillance, and Reconnaissance (ISR) missions. This shift has lead to an increase in the number of unmanned vehicles (UV) operating in a theater. Additionally, removal of the crew allows for a reduction in vehicle scale, which leads to an increased ability to operate in GPS degraded environments. With the loss of GPS signals the vehicles must rely on Inertial Navigation Systems (INS) which when reduced to an appropriate size are inherently inaccurate. This research endeavors to exploit three attributes of increased UV use for ISR missions. …

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Developing A Tool For The Location Optimization Of The Alert Aircraft With Changing Threat Anticipation, Okan Arslan Mar 2009

Developing A Tool For The Location Optimization Of The Alert Aircraft With Changing Threat Anticipation, Okan Arslan

Theses and Dissertations

The threat to the airspace is posed by the outside world in conventional terms as well as hostilities from within the airspace such as hijacked aircraft. Alert aircraft are located with the sole responsibility of responding to any incident. Different regions of the airspace may have different alert states depending on current intelligence input. Due to non-constant states of threat level, the Turkish Air Force must deploy aircraft to cover the more sensitive regions with a greater number of aircraft with a relatively short response time. This research deals with the problem by developing a tool for the location optimization …

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Centralized Cooperative Control For Route Surveillance With Constant Communication, Joseph D. Rosal Mar 2009

Centralized Cooperative Control For Route Surveillance With Constant Communication, Joseph D. Rosal

Theses and Dissertations

The route surveillance mission is a new application of unmanned aircraft systems (UASs) to meet the reconnaissance and surveillance requirements of combatant commanders. The new mission intends to field a UAS consisting of unmanned aerial vehicles (UAVs) that can provide day and night surveillance of convoy routes. This research focuses on developing a solution strategy for the mission based on the application of optimal control and cooperative control theory. The route surveillance controller uses the UAS team size to divide the route into individual sectors for each entity. A specifically designed cost function and path constraints are used to formulate …

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Finite Element Model Optimization Of The Falconsat-5 Structural Engineering Model, Cole C. Doupe Mar 2009

Finite Element Model Optimization Of The Falconsat-5 Structural Engineering Model, Cole C. Doupe

Theses and Dissertations

Space launch vehicles produce tremendously harsh environments for their payloads. One of the worst contributors to this harsh environment is vibration. Launch vehicle contractors require accurate dynamic models in order to perform coupled loads analyses with each payload to mitigate risks. Accurate predictions of the dynamic response of the payload are not achieved easily. The Finite Element (FE) method has proven to be the best approach in creating accurate dynamic models of complex structures. To improve the agreement between an FE model and the structure it represents, a common practice is to `tune' or adjust parameters of the FE model …

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Phosphorus Fractionation And Distribution Across Delta Of Deer Creek Reservoir, Warren C. Casbeer Mar 2009

Phosphorus Fractionation And Distribution Across Delta Of Deer Creek Reservoir, Warren C. Casbeer

Theses and Dissertations

Eutrophication of reservoir systems, which causes deterioration of water quality through increased algal growth, is detrimental to our sustainable water supply and additionally impairs other beneficial reservoir uses. Limiting the amount of phosphorus (P) entering the system has been the key management tool for this problem, as P is the main limiting nutrient for plant and algal growth. These efforts have focused on controlling input of P from point sources, such as effluents from wastewater treatment plants, dairies, and industrial factories. Even in systems (such as reservoirs) with significantly reduced external P loading, however, there has been continued eutrophication and …

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Behavior Of A Full-Scale Pile Cap With Loosely And Densely Compacted Clean Sand Backfill Under Cyclic And Dynamic Loadings, Colin Reuben Cummins Mar 2009

Behavior Of A Full-Scale Pile Cap With Loosely And Densely Compacted Clean Sand Backfill Under Cyclic And Dynamic Loadings, Colin Reuben Cummins

Theses and Dissertations

A series of lateral load tests were performed on a full-scale pile cap with three different backfill conditions, namely: with no backfill present, with densely compacted clean sand in place, and with loosely compacted clean sand in place. In addition to being displaced under a static loading, the pile cap was subjected to low frequency, small displacement loading cycles from load actuators and higher frequency, small displacement, dynamic loading cycles from an eccentric mass shaker. The passive earth pressure from the backfill was found to significantly increase the load capacity of the pile cap. At a displacement of about 46 …

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Correlating Responses Of Portable Field Instruments Used For Testing Aggregate And Soil Pavement Layers, Wendy Melissa Thompson Mar 2009

Correlating Responses Of Portable Field Instruments Used For Testing Aggregate And Soil Pavement Layers, Wendy Melissa Thompson

Theses and Dissertations

This research examined correlations among the responses of five portable aggregate and soil testing devices, including the nuclear density gauge (NDG), dynamic cone penetrometer (DCP), heavy Clegg impact soil tester (CIST), soil stiffness gauge (SSG), and portable falling-weight deflectometer (PFWD). Readings were analyzed from 41 project sites on treated and untreated base, subbase, and subgrade layers representing 15 different material types in Iowa, Louisiana, Utah, and Wyoming. Analyses of the data revealed statistically significant correlations for all six of the possible two-way comparisons involving the DCP, CIST, SSG, and PFWD, and a nomograph was developed for correlating responses among these …

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Uas Collision Avoidance Algorithm That Minimizes The Impact On Route Surveillance, Austin L. Smith Mar 2009

Uas Collision Avoidance Algorithm That Minimizes The Impact On Route Surveillance, Austin L. Smith

Theses and Dissertations

A collision avoidance algorithm is developed and implemented that is applicable to different types of unmanned aerial systems ranging from a single platform with the ability to perform all collision avoidance functions independently to multiple vehicles performing functions as a cooperative group with collision avoidance commands computed at a ground station. The collision avoidance system is exercised and tested using operational hardware and platforms and is demonstrated in representative missions similar to those planned for operational systems. The results presented are the first known flight tests of a global, three-dimensional, geometric collision avoidance system on an unmanned aircraft system. Novel …

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Application Of Kam Theorem To Earth Orbiting Satellites, Bryan D. Little Mar 2009

Application Of Kam Theorem To Earth Orbiting Satellites, Bryan D. Little

Theses and Dissertations

An orbit that lies on a Kolmogorov, Arnold, and Moser (KAM) Torus will remain on that torus until and unless it experiences a force that causes it to leave the torus. Earth satellites that are subject only to the Earth's gravity field may lie on such KAM tori. Analyzing on orbit satellite position data should allow for the identification of the fundamental frequencies needed to define the KAM tori for modeling Earth satellite orbits. KAM Tori are created for the Gravity Recovery and Climate Experience (GRACE) and Jason-1 satellites to model their orbital motion. Precise position data for the satellites …

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Failure Detection Of A Pseudolite-Based Reference System Using Residual Monitoring, Michael A. Ciampa Mar 2009

Failure Detection Of A Pseudolite-Based Reference System Using Residual Monitoring, Michael A. Ciampa

Theses and Dissertations

The 746th TS uses a flight reference system referred to as the Central Inertial and GPS Test Facility (CIGTF) Reference System (CRS). Currently the CRS is the modern standard flight reference system for navigation testing, but high accuracy is dependent on the availability of GPS. A pseudolite system is currently being developed to augment the CRS and supply the capability to maintain high accuracy navigation under normal and jamming conditions. Pseudolite measurements typically contain cycle slips and other errors (such as multipath, tropospheric error, measurement noise) that can affect reliability. Past work relied on the receiver-reported signal-to-noise (SNR) value to …

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Compact Trench Based Bend And Splitter Devices For Silicon-On-Insulator Rib Waveguides, Yusheng Qian Mar 2009

Compact Trench Based Bend And Splitter Devices For Silicon-On-Insulator Rib Waveguides, Yusheng Qian

Theses and Dissertations

Bends and splitters are typically the fundamental limiting waveguide components in reducing the size of planar lightwave circuits (PLCs) based on waveguides that have a low core/clad refractive index contrast, such as silicon-on-insulator (SOI) rib waveguides. This dissertation presents a solution to this problem in the form of trench-based bends (TBBs) and trench-based splitters (TBSs). Emphasis is placed on experimental demonstration of these components and their integration into practical devices exhibiting significant size reduction. First, a compact and low loss silicon-on-insulator rib waveguide 90◦ TBB is demonstrated based on an etched vertical interface and total internal reflection (TIR) realized by …

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Application Of Reliability And Linear Regression To Enterprise Architecture In Support Of The Us Air Force's Capability Review And Risk Assessment, Peter C. Mastro, Richard L. Orcutt Mar 2009

Application Of Reliability And Linear Regression To Enterprise Architecture In Support Of The Us Air Force's Capability Review And Risk Assessment, Peter C. Mastro, Richard L. Orcutt

Theses and Dissertations

This research explored the use of modeling and enterprise architecture in the analysis of Air Force Capabilities. The Air Force accomplishes this through the Capability Review and Risk Assessment (CRRA). The CRRA is currently performed by building architectures which contain Process Sequence Models (PSMs). PSMs are scored by Subject Matter Experts to determine the probability of successfully completing the mission they model and ultimately to determine the risk associated to Air Force capabilities. Two findings were identified. The first is that creating additional architectural viewpoints, some of which are currently being proposed for version 2.0 of the DoD Architecture Framework, …

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Using Shadows To Detect Targets In Synthetic Aperture Radar Imagery, Brian P. Donnell Mar 2009

Using Shadows To Detect Targets In Synthetic Aperture Radar Imagery, Brian P. Donnell

Theses and Dissertations

Synthetic Aperture Radar (SAR) can generate high resolution imagery of re- mote scenes by combining the phase information of multiple radar pulses along a given path. SAR based Intelligence, Surveillance, and Reconnaissance (ISR) has the advantage over optical ISR that it can provide usable imagery in adverse weather or nighttime conditions. Certain radar frequencies can even result in foliage or limited soil penetration, enabling imagery to be created of objects of interest that would otherwise be hidden from optical surveillance systems. This thesis demonstrates the capability of locating stationary targets of interest based on the locations of their shadows and …

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An Optical Flow Implementation Comparison Study, John M. Bodily Mar 2009

An Optical Flow Implementation Comparison Study, John M. Bodily

Theses and Dissertations

Optical flow is the apparent motion of brightness patterns within an image scene. Algorithms used to calculate the optical flow for a sequence of images are useful in a variety of applications, including motion detection and obstacle avoidance. Typical optical flow algorithms are computationally intense and run slowly when implemented in software, which is problematic since many potential applications of the algorithm require real-time calculation in order to be useful. To increase performance of the calculation, optical flow has recently been implemented on FPGA and GPU platforms. These devices are able to process optical flow in real-time, but are generally …

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Least-Squares Finite Element Formulation For Fluid-Structure Interaction, Cody C. Rasmussen Mar 2009

Least-Squares Finite Element Formulation For Fluid-Structure Interaction, Cody C. Rasmussen

Theses and Dissertations

Fluid-structure interaction problems prove difficult due to the coupling between fluid and solid behavior. Typically, different theoretical formulations and numerical methods are used to solve fluid and structural problems separately. The least-squares finite element method is capable of accurately solving both fluid and structural problems. This capability allows for a simultaneously coupled fluid structure interaction formulation using a single variational approach to solve complex and nonlinear aeroelasticity problems. The least-squares finite element method was compared to commonly used methods for both structures and fluids individually. The fluid analysis was compared to finite differencing methods and the structural analysis type compared …

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An Investigation Of Shock Wave Physics Via Hybrid Cfd-Bgk Solution Methods For Nonequilibrium Flows, Brook I. Bentley Mar 2009

An Investigation Of Shock Wave Physics Via Hybrid Cfd-Bgk Solution Methods For Nonequilibrium Flows, Brook I. Bentley

Theses and Dissertations

The Unified Flow Solver, a hybrid continuum-rarefied code, is used to investigate the internal structure of a normal shock wave for a Mach range of 1.55 to 9.0 for Argon, and 1.53 to 3.8 for diatomic Nitrogen. Reciprocal shock thickness, density, temperature, heat flux, and the velocity distribution function are calculated for a one-dimensional shock wave and compared with experimental data from Alsmeyer and DSMC results from Bird. Using the Euler, Navier-Stokes, BGK model, and Three-Temperature BGK model schemes, results from UFS compare well with experiment and DSMC. The Euler scheme shows atypical results, possibly resulting from modifications made to …

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Laser Dot Projection Photogrammetry And Force Balance Measurement Techniques For Flapping Wing Micro Air Vehicles, David H. Curtis Mar 2009

Laser Dot Projection Photogrammetry And Force Balance Measurement Techniques For Flapping Wing Micro Air Vehicles, David H. Curtis

Theses and Dissertations

The purpose of this research was to develop testing methods capable of analyzing the performance of a miniature flapping-wing mechanism that can later be adapted to a flapping wing micro air vehicle (MAV). A previously designed and built flapping only mechanism was used for testing, while a previously designed flapping and pitch mechanism was fabricated utilizing an Objet Eden 500V 3-dimensional printer and its operation demonstrated. The flapping mechanism was mounted on a six component force balance. Force and moment data were collected for a variety of wing sets at different flapping frequencies. The testing was conducted using wings composed …

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Development Of Non-Uniform Radiation Solution Methods For Atmospheric Re-Entry Using Detailed Thermal Modeling, Jeffrey R. Komives Mar 2009

Development Of Non-Uniform Radiation Solution Methods For Atmospheric Re-Entry Using Detailed Thermal Modeling, Jeffrey R. Komives

Theses and Dissertations

The line-by-line accurate spectral radiation solver SPRADIAN was integrated with the multi-temperature hypersonic flow-solver NH7Air for the purpose of predicting the radiation incident on the surface of a hypersonic re-entry vehicle. Atomic and molecular radiation mechanisms are considered for chemical species present in an Earth atmosphere re-entry. A new numerical method of radiation propagation is presented that is capable of accurately predicting the radiation propagation through a non-uniform radiation field. This method also introduces a unique treatment of the internal energy of each chemical species, independently tracking the vibrational temperatures of all molecular species. The new radiation propagation method is …

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Using Covert Means To Establish Cybercraft Command And Control, Bradley D. Sevy Mar 2009

Using Covert Means To Establish Cybercraft Command And Control, Bradley D. Sevy

Theses and Dissertations

With the increase in speed and availability of computers, our nation's computer and information systems are being attacked with increased sophistication. The Air Force Research Laboratory (AFRL) Information Directorate (RI) is researching a next generation network defense architecture, called Cybercraft, that provides automated and trusted cyber defense capabilities for AF network assets. This research we consider the issues to protect or obfuscate command and control aspects of Cybercraft. In particular, we present a methodology to hide aspects of Cybercraft platform initialization in context to formation of hierarchical, peer-to-peer groups that collectively form the Cybercraft network. Because malicious code networks (known …

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Design Of A Continuous-Wave Synthetic Aperture Radar System With Analog Dechirp, Matthew C. Edwards Mar 2009

Design Of A Continuous-Wave Synthetic Aperture Radar System With Analog Dechirp, Matthew C. Edwards

Theses and Dissertations

This thesis presents a design methodology for continuous wave (CW) synthetic aperture radar (SAR) systems. The focus is on design considerations specific to small, low-power systems suitable for operation on small aircraft and unmanned aerial vehicles (UAVs). Well-known results which have been derived in other works, such as the radar equation, are explained in the context of low-power, CW systems. Additionally, design issues unique to CW SAR are addressed and the results generalized. A method for controlling feedthrough between antennas is developed, and the resulting limitations on swath width are discussed. Methods are developed which allow an engineer to design …

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Developing Response Surfaces Based On Tool Geometry For A Convex Scrolled Shoulder Step Spiral (Cs4) Friction Stir Processing Tool Used To Weld Al 7075, Bryce K. Nielsen Mar 2009

Developing Response Surfaces Based On Tool Geometry For A Convex Scrolled Shoulder Step Spiral (Cs4) Friction Stir Processing Tool Used To Weld Al 7075, Bryce K. Nielsen

Theses and Dissertations

The purpose of this study is to develop a series of response surfaces that define critical outcomes for welding in Al 7075 based on the tool geometry of a convex scrolled shoulder step spiral (CS4) friction stir processing tool. These response surfaces will be used to find critical minimums in forces which will decrease the required power input for the process. A comprehensive parameterization of the tool geometry is defined in this paper. A pilot study was performed to determine the feasibility of varying certain geometric features. Then a screening experiment eliminated those geometric features that were not as significant …

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The Benefits Of A Network Tasking Order In Combat Search And Rescue Missions, Murat Gocmen Mar 2009

The Benefits Of A Network Tasking Order In Combat Search And Rescue Missions, Murat Gocmen

Theses and Dissertations

Networked communications play a crucial role in United States Armed Forces operations. As the military moves towards more network centric (Net-Centric) operations, it becomes increasingly important to use the network as effectively as possible with respect to the overall mission. This thesis advocates the use of a Network Tasking Order (NTO), which allows operators to reason about the network based on asset movement, capabilities, and communication requirements. These requirements are likely to be derived from the Air Tasking Order (ATO), which gives insight into the plan for physical assets in a military mission. In this research we illustrate the benefit …

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Cooperative Unmanned Aerial Surveillance Control System Architecture, Theodore T. Diamond, Adam L. Rutherford, Jonathan B. Taylor Mar 2009

Cooperative Unmanned Aerial Surveillance Control System Architecture, Theodore T. Diamond, Adam L. Rutherford, Jonathan B. Taylor

Theses and Dissertations

Intelligence, surveillance and reconnaissance (ISR) is a high-demand Department of Defense mission performed by unmanned aircraft systems (UASs) at the tactical and theater levels. Coordinating UASs through cooperative control offers the advantages of persistence, distributed and adaptable sensor coverage, and reduced revisit time on points of interest. The purpose of this thesis is to apply systems engineering principles to the problem of developing a flexible, common control system for cooperative UAS surveillance at the tactical level. The AFIT team developed a concept of operations (CONOPS) encompassing various users and surveillance tasks. The team then used the scenarios in the CONOPS …

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Laminar And Turbulent Flow Of A Liquid Through Channels With Superhydrophobic Walls Exhibiting Alternating Ribs And Cavities, Brady L. Woolford Mar 2009

Laminar And Turbulent Flow Of A Liquid Through Channels With Superhydrophobic Walls Exhibiting Alternating Ribs And Cavities, Brady L. Woolford

Theses and Dissertations

There is significant interest in reducing the frictional resistance that occurs along a surface in contact with a liquid. A novel approach to reducing the frictional resistance across a liquid-solid interface is the use of superhydrophobic surfaces. superhydrophobic surfaces are created in this work by the use of micro-fabrication techniques where systematic roughness is fabricated on a substrate surface which is subsequently treated with a hydrophobic coating. This work reports an experimental study of superhydrophobic surfaces used to reduce drag in both laminar and turbulent channel flows. In the laminar flow regime reductions in frictional resistance greater than 55% were …

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A Tailored Systems Engineering Framework For Science And Technology Projects, Stephen M. Behm, J. Bradford Pitzer, Jane F. White Mar 2009

A Tailored Systems Engineering Framework For Science And Technology Projects, Stephen M. Behm, J. Bradford Pitzer, Jane F. White

Theses and Dissertations

As government and industry becomes subject to a wider range of technology initiatives, science and technology (S&T) research project leadership recognizes the need to incorporate more systems engineering (SE) rigor into their projects. The objective of this research is to develop a tailorable systems engineering framework for S&T project planning, execution, assessment and transition. The key deliverable is an Excel-based tool instantiating the SE framework for a wide range of S&T projects in technology development organizations. It includes a report with tailored methods based on programmatic discriminants.
To develop this framework, a comprehensive understanding of SE principles is applied to …

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Fusion Of Inertial Sensors And Orthogonal Frequency Division Multiplexed (Ofdm) Signals Of Opportunity For Unassisted Navigation, Jason G. Crosby Mar 2009

Fusion Of Inertial Sensors And Orthogonal Frequency Division Multiplexed (Ofdm) Signals Of Opportunity For Unassisted Navigation, Jason G. Crosby

Theses and Dissertations

The advent of the global positioning system (GPS) has provided worldwide high-accuracy position measurements. However, GPS may be rendered unavailable by jamming, disruption of satellites, or simply by signal shadowing in urban environments. Thus, this thesis considers fusion of Inertial Navigation Systems (INS) and Orthogonal Frequency Division Multiplexed (OFDM) signals of opportunity (SOOP) for navigation. Typical signal of opportunity navigation involves the use of a reference receiver and uses time difference of arrival (TDOA) measurements. However, by exploiting the block structure of OFDM communication signals, the need for the reference receiver is reduced or possibly removed entirely. This research uses …

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Evaluation Of An Opnet Model For Unmanned Aerial Vehicle Networks, Clifton M. Durham Mar 2009

Evaluation Of An Opnet Model For Unmanned Aerial Vehicle Networks, Clifton M. Durham

Theses and Dissertations

The concept of Unmanned Aerial Vehicles (UAVs) was first used as early as the American Civil War, when the North and the South unsuccessfully attempted to launch balloons with explosive devices. Since the American Civil War, the UAV concept has been used in all subsequent military operations. Over the last few years, there has been an explosion in the use of UAVs in military operations, as well as civilian and commercial applications. UAV Mobile Ad Hoc Networks (MANETs) are fast becoming essential to conducting Network-Centric Warfare (NCW). As of October 2006, coalition UAVs, exclusive of hand-launched systems, had flown almost …

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