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2009

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Articles 2071 - 2100 of 4158

Full-Text Articles in Engineering

Suite Of Standards For Electromagnetic Material Characterization Using Mode Matching Theory, Brian J. Witthoeft Mar 2009

Suite Of Standards For Electromagnetic Material Characterization Using Mode Matching Theory, Brian J. Witthoeft

Theses and Dissertations

The objective of this research is to determine if an acceptable standard can be developed to access the accuracy and precision of measurements taken using waveguide systems. Tiny changes in material fabrication, processing, and environment can cause problems with accuracy and precision in measurement. There is a great deal of research on uncertainty analysis in the literature. A large portion of the effort will be to determine the levels of uncertainty caused by each of the dimensions of the waveguide insert and to develop a suitable standard capable of verifying system performance. The Mode-Matching Technique will be used to extract …


Implementation Of Collaborative Rf Localization Using A Software-Defined Radio Network, Augustine A. Honore Mar 2009

Implementation Of Collaborative Rf Localization Using A Software-Defined Radio Network, Augustine A. Honore

Theses and Dissertations

This thesis investigates the use of collaboration between sensor nodes that were tasked with localizing a radio frequency emitter. Localization is a necessary component for dynamic spectrum access. Using a set of software-defined radios as our sensors and a received signal strength-based maximum likelihood localization algorithm, we successfully localized transmitting nodes based on their received signal strength. Our experiment was conducted outdoors using a flexible topology that could be shaped into 21 sub-topologies that varied in size, and orientation with respect to the transmitters. This was made possible through application of a time shift concept and a post-processing technique. We …


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 …


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 …


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. …


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 …


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 …


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 …


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 …


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 …


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 …


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 …


Frsmc Design For The Steering Control And Diving Control Of Underwater Vehicles, Tzu-Chun Kuo, Ying-Jeh Huang, Hung-Hsiu Yu Mar 2009

Frsmc Design For The Steering Control And Diving Control Of Underwater Vehicles, Tzu-Chun Kuo, Ying-Jeh Huang, Hung-Hsiu Yu

Journal of Marine Science and Technology–Taiwan

A robust control method is proposed for the steering and diving control systems of autonomous underwater vehicles. Heading angle and heave position tracking are achieved. All the closed-loop poles in the sliding mode can be placed by using the sliding mode and root locus techniques. Fuzzy logic technique is further employed to effectively tune the control law. Parameter variation and external disturbance such as various vehicle speeds and the ocean current effect are overcome.


Lateral Buckling Analysis Of Angled Frames With Thin-Walled I-Beams, Jong-Dar Yau Mar 2009

Lateral Buckling Analysis Of Angled Frames With Thin-Walled I-Beams, Jong-Dar Yau

Journal of Marine Science and Technology–Taiwan

With the inclusion of warping deformations, lateral buckling behavior for angled frames with I-beams under the action of in-plan bending moments will be conducted in this paper. By adopting the joint equilibrium for the angled frame and the force-displacement relations for the members defined at the buckled position (rather than the initial position), the analytical solutions for buckling moments of an angled frame with simply supported ends are presented in closed form. The computed results indicate that for symmetric buckling, the buckling resistance to resist positive moments can be strengthened along with the increase of inclined angle of the member …


Lmi Robustly Decentralized H Output Feedback Controller Design For Stochastic Large-Scale Uncertain Systems With Time-Delays, Wen-Ben Wu, Pang-Chia Chen, Min-Hsiung Hung, Koan-Yuh Chang, Wen-Jer Chang Mar 2009

Lmi Robustly Decentralized H Output Feedback Controller Design For Stochastic Large-Scale Uncertain Systems With Time-Delays, Wen-Ben Wu, Pang-Chia Chen, Min-Hsiung Hung, Koan-Yuh Chang, Wen-Jer Chang

Journal of Marine Science and Technology–Taiwan

The present paper investigates the problem of robustly decentralized H∞ output feedback controller design for a class of stochastic large-scale uncertain systems with time-delays. The considered time-delay parameters appear in the interconnections between individual subsystems and uncertainties are allowed to be unstructured but time-varying and norm-bounded. The sufficient conditions of the desired output feedback controller are based on the Lyapunov-Krasovskii stability theory and utilizing the decentralized scheme to be derived in terms of linear matrix inequalities (LMIs). The effectiveness of the proposed approach is illustrated by a numerical example.


Vibroacoustic Attenuation Effect Of Sandwich Damping Material On Pipe Flow Noise, Wei-Yu Lu, Wei-Hui Wang Mar 2009

Vibroacoustic Attenuation Effect Of Sandwich Damping Material On Pipe Flow Noise, Wei-Yu Lu, Wei-Hui Wang

Journal of Marine Science and Technology–Taiwan

The attenuation effects of a number of sheathing materials on pipe flow noise are assessed by numerical simulations of the sound pressure field around pipe wall and the transfer mobility function of pipe wall vibration. The simulation model is established by using the finite element method (FEM) and the boundary element method (BEM), in which solid elements are used for the pipe wall and the sheathing material. Between pipe wall and sheathing material , contact elements are adopted. The frequency dependent loss factors of the sheathing material are determined by the experimental modal analysis (EMA) based on the half power …


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 …


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 …


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 …


Novel Design Of Multiphase Reactors For Biomass-To-Liquid Synthesis, Ahmed Youssef, Milorad Dudukovic, Muthanna H. Al-Dahhan Mar 2009

Novel Design Of Multiphase Reactors For Biomass-To-Liquid Synthesis, Ahmed Youssef, Milorad Dudukovic, Muthanna H. Al-Dahhan

Chemical and Biochemical Engineering Faculty Research & Creative Works

Generation of liquid fuels from renewable sources such as biomass has been practiced since early 1900’s. In view of the skyrocketing oil prices and the depleting reserves of natural gas, it has gained further interest. The Fischer-Tropsch synthesis is one of the main processes considered. It involves the reaction of syngas in presence of a catalyst to produce liquid fuels. Syngas sources are numerous ranging from waste gasification, anaerobic digestion to clean coal. The reactor of choice for gas to liquid conversion is a slurry bubble column. Although, these multiphase reactors offer several advantages including good heat and mass transfer, …


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 …


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, …


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 …


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 …


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 …


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 …


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 …


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 …


Synthesis Of Magnetic Porous Hollow Silica Nanotubes For Drug Delivery, H. Ma, J. Tarr, M. A. Decoster, J. Mcnamara, D. Caruntu, J. F. Chen, Charles J. O'Connor, Weilie Zhou Mar 2009

Synthesis Of Magnetic Porous Hollow Silica Nanotubes For Drug Delivery, H. Ma, J. Tarr, M. A. Decoster, J. Mcnamara, D. Caruntu, J. F. Chen, Charles J. O'Connor, Weilie Zhou

Chemistry Faculty Publications

In this paper, we report a synthesis of magnetic porous hollow silica nanotubes (MPHSNTs) using sol-gel method. The MPHSNTs were fabricated by coating Fe(3)O(4) nanoparticles and silica on surfactant hexadecyltrimethylammonium bromide (CTAB) modified CaCO(3) nanoneedles surface under alkaline condition. CaCO(3) nanoneedles and surfactant CTAB are introduced as nanotemplates to form the hollow and porous structures, respectively. After removing CTAB by calcination and etching CaCO(3) nanoneedles away in diluted acetic acid, magnetic porous hollow silica nanotubes with Fe(3)O(4) nanoparticles embedded in the silica shell were achieved. The products were characterized by scanning electron microscopy, transmission electron microscopy, and N(2) adsorption-desorption isotherms. …


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 …