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Articles 9301 - 9330 of 11196

Full-Text Articles in Aerospace Engineering

Unsteady Numerical Analysis Of A 2-Dimensional, Hydrogen Fueled, Air-Breathing Dual Mode Scramjet Engine, Nathan John Luetke Jul 2006

Unsteady Numerical Analysis Of A 2-Dimensional, Hydrogen Fueled, Air-Breathing Dual Mode Scramjet Engine, Nathan John Luetke

Mechanical & Aerospace Engineering Theses & Dissertations

Upstream interaction in a transient two-dimensional dual-mode scramjet engine is examined. This research is performed to compare completed and verified steady results with unsteady results in order to have a better understanding of the flow field. The flow is solved numerically with a Mach 2.5 free stream and sonic normal injection of hydrogen fuel emanating from facing walls while no symmetry assumptions were made. The free stream is modeled as vitiated air in order to produce comparable flight enthalpies and stagnation properties at the combustor inlet during flight conditions of approximately Mach 7. The vitiated stream consists of water vapor …

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Micron-Level Actuator For Thermal-Fluid Control In Microchannels, Nurhak Erbas Jul 2006

Micron-Level Actuator For Thermal-Fluid Control In Microchannels, Nurhak Erbas

Mechanical & Aerospace Engineering Theses & Dissertations

Effectiveness of an actuator is investigated for thermal-flow control in microchannels. First, simulations of a single actuator in a quiescent external medium are performed in order to study the parameters characterizing the synthetic jet flow from the actuator. For this purpose, a simplified, two-dimensional configuration is considered. The membrane motion is modeled in a realistic manner as a moving boundary in order to accurately compute the flow inside the actuator cavity. The geometric and actuation parameters of the actuator are investigated to define the effectiveness of the jet flow. The study is done initially at macro scales. Then, the flow …

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Reweighting At-Sat To Mitigate Group Score Differences, Andrew R. Dattel, Raymond E. King Jul 2006

Reweighting At-Sat To Mitigate Group Score Differences, Andrew R. Dattel, Raymond E. King

Publications

The Air Traffic Selection and Training (AT-SAT) test battery is the selection tool for applicants for Air Traffic Control Specialist (ATCS) positions within the Federal Aviation Administration (FAA) who have not previously been employed as an air traffic controller. AT-SAT is an aptitude test developed to predict the likelihood of successfully learning ATCS skills. Before operational use, however, concerns were raised about the low passing rate of incumbent (who are fully trained and certified) ATCS personnel (who participated in the initial research) and score differences between groups, which could result in adverse impact (possible unfair discrimination). To address these concerns, …

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Most Probable Point-Based Design Optimization, Akhil R. Tipnis Jul 2006

Most Probable Point-Based Design Optimization, Akhil R. Tipnis

Mechanical & Aerospace Engineering Theses & Dissertations

Modem products ranging from simple components to complex systems should be designed to be optimal and reliable. The challenge of modem engineering is to ensure that manufacturing costs are reduced and design cycle times are minimized while achieving requirements for performance and reliability. If the market for the product is competitive, improved quality and reliability can generate very strong competitive advantages. Reliability based design optimization plays a very important role in designing almost any kind of product. This investigation focuses on the development of the hybrid PMNRIA approach which uses the active-in-reliability concept for reliability based design optimization. The efficiency …

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Incorporating Solid Mechanics Into Biomedical And Life Sciences, Kai-Tak Wan Jul 2006

Incorporating Solid Mechanics Into Biomedical And Life Sciences, Kai-Tak Wan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Integrating and interfacing solid mechanics and life sciences is challenging, but, with effort, the two disciplines can complement one another. This paper describes work ongoing at the Mechanical and Aerospace Engineering Department of the University of Missouri at Rolla on cellular biomechanics and mechanical characterization of single cells. Also discussed is the study of tissue biomechanics in understanding the mechanical aspects of lens accommodation in human vision.

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Global Modeling Of Pitch Damping From Flight Data, Noah M. Favaregh Jul 2006

Global Modeling Of Pitch Damping From Flight Data, Noah M. Favaregh

Mechanical & Aerospace Engineering Theses & Dissertations

Flight testing using a designed experiment was used to model pitch damping in the longitudinal short-period mode of an aircraft. Multi-step elevator maneuvers were flown at different angles of attack and power levels on an electrically powered, propeller-driven UltraStick 120 remotely controlled model A Central Composite Response Surface Design was used to select angle of attack and power levels for each maneuver. During post flight analysis it was discovered that power was not measured correctly for this purpose so advance ratio was selected as a replacement factor. Parameter estimation results for each maneuver were modeled globally using a single response …

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Attribute-Level Neighbor Hierarchy Construction Using Evolved Pattern-Based Knowledge Induction, Thanit Puthpongsiriporn, J. David Porter, Bopaya Bidanda, Ming En Wang, Richard E. Billo Jul 2006

Attribute-Level Neighbor Hierarchy Construction Using Evolved Pattern-Based Knowledge Induction, Thanit Puthpongsiriporn, J. David Porter, Bopaya Bidanda, Ming En Wang, Richard E. Billo

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Neighbor knowledge construction is the foundation for the development of cooperative query answering systems capable of searching for close match or approximate answers when exact match answers are not available. This paper presents a technique for developing neighbor hierarchies at the attribute level. The proposed technique is called the evolved Pattern-based Knowledge Induction (ePKI) technique and allows construction of neighbor hierarchies for nonunique attributes based upon confidences, popularities, and clustering correlations of inferential relationships among attribute values. The technique is applicable for both categorical and numerical (discrete and continuous) attribute values. Attribute value neighbor hierarchies generated by the ePKI technique …

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Investigation Of Particle-In-Cell Acceleration Techniques For Plasma Simulations, David D. Marshall, Douglas B. Vangilder Jun 2006

Investigation Of Particle-In-Cell Acceleration Techniques For Plasma Simulations, David D. Marshall, Douglas B. Vangilder

Aerospace Engineering

COLISEUM is an application framework that integrates plasma propagation schemes and arbitrary 3D surface geometries. Using Particle-in-Cell (PIC) schemes to model the plasma propagation high fidelity modeling of the plasma and its interactions with the surfaces is possible. In order to improve the computational performance of the Particle-in-Cell scheme with Direct Simulation Monte Carlo collision modeling (PIC-DSMC) within COLISEUM, AQUILA, acceleration techniques have been developed that significantly decrease the amount of CPU time needed to obtain a steady-state solution. These techniques have been demonstrated to decrease the CPU time from 3 to 24 times with little appreciable differences in the …

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Filtering Of Acoustic Emission Data Through Principal Frequency Component Extraction, Justin O. Karl Jun 2006

Filtering Of Acoustic Emission Data Through Principal Frequency Component Extraction, Justin O. Karl

Master's Theses - Daytona Beach

Rapid editing of acoustic emission (AE) data is required in order to make real-time acoustic emission flaw growth systems a viable testing method for materials and setups that contain noisy signals. It was hypothesized that extracting major frequency components from the acoustic emission signal would therefore provide a representative acoustic signature of the major waveforms occurring due to defect growth This research has verified that the aforementioned filtering technique does, in fact, extract a representative signal from the composite and metal specimens utilized herein These findings were verified both through visual analysis of the data as well as the low …

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Optimal Geometric Deployment Of A Ground Based Pseudolite Navigation System To Track A Landing Aircraft, Matthew P. Crawford Jun 2006

Optimal Geometric Deployment Of A Ground Based Pseudolite Navigation System To Track A Landing Aircraft, Matthew P. Crawford

Theses and Dissertations

With much of the military and civilian communities becoming dependent on GPS technology to navigate it has become imperative that the navigation systems be tested in situations in which GPS does not work. This testing is especially necessary for precise tasks such as landing an aircraft. Currently, research is being conducted into using a pseudolite-based reference system to use as a truth model for the GPS jamming test. Pseudolite systems have been proven to provide sub-centimeter level accuracy in the horizontal plane; however in the vertical plane the position error is still in the decimeter to meter level range. This …

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Maneuver Estimation Model For Geostationary Orbit Determination, Brian J. Hirsch Jun 2006

Maneuver Estimation Model For Geostationary Orbit Determination, Brian J. Hirsch

Theses and Dissertations

As an increasing number of geostationary satellites fill a limited number of orbital slots, collocation of satellites leads to a risk of close approach or misidentification. The ability to detect maneuvers made by these satellites using optical observations can help to prevent these problems. Such a model has already been created and tested using data from the Air Force Maui Optical and Supercomputing site. The goal of this research was to create a more robust model which would reduce the amount of data needed to make accurate maneuver estimations. The Clohessy-Wiltshire equations were used to model the relative motion of …

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Development And Validation Of Reentry Simulation Using Matlab, Robert E. Jameson Jr. Jun 2006

Development And Validation Of Reentry Simulation Using Matlab, Robert E. Jameson Jr.

Theses and Dissertations

This research effort develops a program using MATLAB to solve the equations of motion for atmospheric reentry and analyzes the validity of the program for use as a tool to expeditiously predict reentry profiles. The reentry vehicle is modeled as a point mass with constant aerodynamic properties as defined by the user. The equations of motion for reentry are based on the two-body problem. The atmosphere is modeled as a single layer exponentially decreasing in density. The MATLAB program has the ability to derive the initial trajectory conditions from the position and velocity relative to the rotating surface of the …

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A Wind Tunnel Investigation Of Joined Wing Scissor Morphing, Christopher C. Dike Jun 2006

A Wind Tunnel Investigation Of Joined Wing Scissor Morphing, Christopher C. Dike

Theses and Dissertations

The Air Force Research Laboratory's Munitions Directorate has been looking to extend the range of its small smart bomb. Corneille [6] has conducted tests to determine the aerodynamic characteristics of joined wings on a missile and determine if joined wings are more beneficial than a single wing configuration. The concept of retrofitting wings on the bomb introduced an interesting problem: storage before deployment. This study conducted steady-state low speed wind tunnel testing of a joined wing configuration that morphed from a compact configuration for storage to a full extension. These steady-state tests examine differing sweep angles of the same joined …

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Characterization Of Uav Performance And Development Of A Formation Flight Controller For Multiple Small Uavs, Patrick A. Mccarthy Jun 2006

Characterization Of Uav Performance And Development Of A Formation Flight Controller For Multiple Small Uavs, Patrick A. Mccarthy

Theses and Dissertations

The Air Force Institute of Technology's (AFIT) Advanced Navigation Technology (ANT) Center has recently delved into the research topic of small Unmanned Aerial Vehicles (UAV). One area of particular interest is using multiple small UAVs cooperatively to improve mission efficiency, as well as perform missions that couldn't be performed using vehicles independently. However, many of these missions require that the UAVs operate in close proximity of each other. This research lays the foundation required to use the ANT Center's UAVs for multi-vehicle missions (e.g. cooperatively) by accomplishing two major goals. First, it develops test procedures that can be used to …

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Particle Image Velocimetry Using A Novel, Non-Intrusive Particle Seeding, Charles J. Delapp Ii Jun 2006

Particle Image Velocimetry Using A Novel, Non-Intrusive Particle Seeding, Charles J. Delapp Ii

Theses and Dissertations

The purpose of this research effort was to study the use of non-intrusive particle seeding for Particle Image Velocimetry (PIV). Current seeding material and techniques involve the use of either solid particles or liquid mixtures which can contaminate or damage closed circuit wind tunnels, and in some cases can introduce a potential fire or explosive hazard. The proposed method is based on creating seed particles utilizing Carbon Dioxide (CO2). The CO2 would be dispensed into the flow as a liquid, immediately condensing to solid seed particles as they leave the spray nozzle. The advantage of using these particles is that …

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An Experimental Study Of A Pulsed Dc Plasma Flow Control Actuator, Jennifer D. Wall Jun 2006

An Experimental Study Of A Pulsed Dc Plasma Flow Control Actuator, Jennifer D. Wall

Theses and Dissertations

An experiment on the effects of a pulsed DC plasma actuator on a separated flow in a low speed wind tunnel was conducted. The actuator consisted of two asymmetric copper electrodes oriented normal to the flow separated by a dielectric barrier and mounted on a flat plate in the center of the tunnel. A contoured insert was constructed and used to create an adverse pressure gradient in the test section comparable to a Pak-B low pressure turbine blade distribution. Suction was applied from the upper wall to induce separation along the flat plate over the electrodes. The DC power supply …

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High Altitude Airship Station-Keeping Analysis, Douglas P. Kondrack Jun 2006

High Altitude Airship Station-Keeping Analysis, Douglas P. Kondrack

Theses and Dissertations

Lighter-than-air vehicles were once widely utilized by most major militaries. The airship’s extended range and flight endurance made them the optimal vehicle for surveillance and reconnaissance. These flight characteristics have created new interest in using lighter-than-air vehicles as high altitude surveillance and communications platforms. Future Department of Defense plans include high altitude airships that will operate at near space altitudes and take advantage of the low wind region in the upper atmosphere located at approximately 24 km. A high altitude airship could provide 24-hour coverage of a target area if operated in this low wind region. This study investigated the …

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Situational Awareness And Synthetic Vision For Unmanned Aerial Vehicle Flight Testing, Joseph M. Dugan Jun 2006

Situational Awareness And Synthetic Vision For Unmanned Aerial Vehicle Flight Testing, Joseph M. Dugan

Theses and Dissertations

The Advanced Navigation Technology (ANT) Center at the Air Force Institute of Technology (AFIT) is currently exploring ways to develop and advance the employment of autonomous Unmanned Aerial Vehicles (UAV) by the Department of Defense for military purposes. The research in this thesis describes the development of a tool that enhances situational awareness and provides synthetic vision in a program called the Aviator Visual Display Simulator (AVDS) during UAV flight. During flight testing, the Situational Awareness and Synthetic Vision Relay Tool (SASVRT) developed provides the test coordinator and pilot, as well as the safety observers, with the most pertinent information …

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Characterizing A Co-Flow Nozzle For Use In A Filtered Rayleigh Scattering System, David S. Miceli Jun 2006

Characterizing A Co-Flow Nozzle For Use In A Filtered Rayleigh Scattering System, David S. Miceli

Theses and Dissertations

Research was conducted on the flow field exiting a co-annular flow nozzle for use in filtered Rayleigh scattering flow visualizations. More specifically, the flow visualizations were of the flow field exiting a coflow nozzle and illuminated by a tunable, nominal 4.2 watt narrow line width Argon laser operating at 514.5nm. ND:YAG lasers are typically used in this application, but some of the properties of a tunable Argon laser make it an attractive alternative. Before generating flow visualizations, the coflow nozzle was characterized both experimentally and computationally. Due to a flow asymmetry in the outer annulus flow field, the nozzle was …

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An Investigation Into Robust Wind Correction Algorithms For Off-The Shelf Unmanned Aerial Vehicle Autopilots, Brent K. Robinson Jun 2006

An Investigation Into Robust Wind Correction Algorithms For Off-The Shelf Unmanned Aerial Vehicle Autopilots, Brent K. Robinson

Theses and Dissertations

The research effort focuses on developing methods to design efficient wind correction algorithms to "piggyback" on current off-the-shelf Unmanned Aerial Vehicle (UAV) autopilots. Autonomous flight is certainly the near future for the aerospace industry and there exists great interest in defining a system that can guide and control aircraft with high levels of accuracy. The primary systems required to command the vehicles are already in place, but with only moderate abilities to adjust for dynamic environments (i.e. wind effects), if at all. The goal of this research is to develop a systematic procedure for implementing efficient and robust wind effects …

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The Determination Of Remaining Satellite Propellant Using Measured Moments Of Inertia, Jason W. Geitgey Jun 2006

The Determination Of Remaining Satellite Propellant Using Measured Moments Of Inertia, Jason W. Geitgey

Theses and Dissertations

This research is designed to demonstrate that a change in satellite propellant can be determined using measured moments of inertia (MOI) from a satellite. Because satellites are currently incapable of being refueled in orbit it is important to have multiple methods to determine the remaining fuel onboard. This research can also support satellite operator selection of control-system gains to improve performance or recover the spacecraft. To meet the research objectives, new mathematical models of the Air Force Institute of Technology's Simulated Satellite (SimSat) were developed. These models were created using dynamic response analysis techniques on the reaction wheel and SimSat …

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Theoretical Modeling Of The Transient Effects Of A Towline Using The Method Of Characteristics, Christopher A. Hill Jun 2006

Theoretical Modeling Of The Transient Effects Of A Towline Using The Method Of Characteristics, Christopher A. Hill

Theses and Dissertations

The use of decoys in combat has become more advanced in recent years. Some of the newest military aircraft, such as the US Navy's F/A-18E/F Superhornet, have the capability to deploy a towline with an attached decoy when entering hostile territory as a defense mechanism against enemy threats. In steady state, the towline extends behind and below the aircraft. A major concern is the position of the towline, as aircraft maneuvers can cause the line to enter the engine plume. The high exhaust heat can cause problems, such as damaging electrical equipment and severing the line. In order to better …

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Experimental Investigation Of The Aerodynamic Ground Effect Of A Tailless Lambda-Shaped Ucav With Wing Flaps, Jason T. Mostaccio Jun 2006

Experimental Investigation Of The Aerodynamic Ground Effect Of A Tailless Lambda-Shaped Ucav With Wing Flaps, Jason T. Mostaccio

Theses and Dissertations

This experimental study adequately identified the ground effect region of a lambda-shaped unmanned combat air vehicle (UCAV). The lambda planform used in this study was originally tested in a previous experiment to determine the stability and control characteristics generated out-of-ground-effect. The following study extends the existing database by analyzing the inherent aerodynamic behavior that is produced by employing trailing edge flap deflections while flying in-ground-effect (IGE). To accomplish this objective, static ground effect tests were performed in the AFIT 3? x 3? subsonic wind tunnel where a ground plane was used to simulate the forces and moments on the UCAV …

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A Comparative Analysis Of Single-Stage-To-Orbit Rocket And Air-Breathing Vehicles, Benjamin S. Orloff Jun 2006

A Comparative Analysis Of Single-Stage-To-Orbit Rocket And Air-Breathing Vehicles, Benjamin S. Orloff

Theses and Dissertations

This study compares and contrasts the performance of a variety of rocket and air breathing, single-stage-to-orbit, reusable launch vehicles. Fuels considered include bi-propellant and tri-propellant combinations of hydrogen and hydrocarbon fuels. Astrox Corporation's HySIDE code was used to model the vehicles and predict their characteristics and performance. Vehicle empty mass, wetted area and growth rates were used as figures of merit to predict the procurement, operational and maintenance cost trends of a vehicle system as well as the system's practicality. Results were compared to those of two-stage-to-orbit reusable launch systems using similar modeling methods. The study found that single-stage-to-orbit vehicles …

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Dynamic Nonlinear Bending And Torsion Of A Cantilever Beam, Michael S. Whiting Jun 2006

Dynamic Nonlinear Bending And Torsion Of A Cantilever Beam, Michael S. Whiting

Theses and Dissertations

This effort sought to measure the dynamic nonlinear bending and torsion response of a cantilever beam. The natural frequencies of a cantilever beam in both chord and flap directions were measured at different static root pitch angles with varying levels of weights attached at the free end. The results were compared with previous experimentation to validate the data and testing procedures while lowering the associated error bands. Additionally, methodology for measuring mode shapes was set forth and mode shapes were measured for a few test cases with zero degrees of root pitch.

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Technology For Exploration, Robert J. Twiggs May 2006

Technology For Exploration, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A published article that included Professor Bob Twiggs titled "Technology for Exploration" from May 12, 2006.

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Experiences In Accurately Predicting Time-Dependent Flows, Russell M. Cummings, Scott A. Morton, David R. Mcdaniel May 2006

Experiences In Accurately Predicting Time-Dependent Flows, Russell M. Cummings, Scott A. Morton, David R. Mcdaniel

Aerospace Engineering

As computational fluid dynamics matures, researchers attempt to perform numerical simulations on increasingly complex aerodynamic flows. One type of flow that has become feasible to simulate is massively separated flow fields, which exhibit high levels of flow unsteadiness. While traditional computational fluid dynamic approaches may be able to simulate these flows, it is not obvious what restrictions should be followed in order to insure that the numerical simulations are accurate and trustworthy. Our research group has considerable experience in computing massively separated flow fields about various aircraft configurations, which has led us to examine the factors necessary for making high-quality …

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Air Jet Impingement For Levitation, James Frederick Huber May 2006

Air Jet Impingement For Levitation, James Frederick Huber

Mechanical and Aerospace Engineering Theses - Archive

Traditional part acquisition methods such as vacuum cups and robotic grippers do not meet the handling needs of truly fragile materials, because both of these methods require surface contact. An alternative to these traditional approaches is the use of air jet impingement for levitation. This technique confines impinged air to a thin disk above the target to form radial diffuser. The Bernoulli Effect causes a pressure difference between the fast-moving impinged air above the surface and ambient air below it. The net pressure difference is sufficient to lift objects weighing more than one kilogram using standard shop air. This method …

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Frequency Response Approximation Methods Of The Dissipative Model Of Fluid Transmission Lines, John King May 2006

Frequency Response Approximation Methods Of The Dissipative Model Of Fluid Transmission Lines, John King

Mechanical and Aerospace Engineering Theses - Archive

This thesis introduces an accurate and efficient method of obtaining a linear approximation for a nonlinear model of a complete fluid transmission line system using Matlab® Signal Processing Toolbox and Symbolic Math Toolbox programs. This technique is then packaged in a Graphical User Interface program to streamline the process of analyzing a total system. The method of approximating the frequency response of a fluid transmission line with a rational polynomial transfer function using the Matlab® 'invfreqs' least squares curve fitting algorithm has already been introduced. This research improves the technique by applying the 'invfreqs' command to a total system rather …

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Structural Optimization Using Femlab And Smooth Support Vector Regression, Divija Odapally May 2006

Structural Optimization Using Femlab And Smooth Support Vector Regression, Divija Odapally

Mechanical and Aerospace Engineering Theses - Archive

In recent years support vector machine (SVM) has been emerging as a popular tool for function approximation. Application of SVM for approximation of mathematical functions and complex engineering analysis has been represented by Palancz et al and Clarke et al, respectively. However the training of the original SVM involves the solution of a quadratic programming (QP) problem. This makes the application of SVM to large problem computationally expensive. To circumvent this difficulty, Lee et al developed a more efficient SVM formulation namely epsilon-SSVR which drastically improved the training efficiency of SVM. In this research the SSVR is used to build …

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