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Articles 3421 - 3450 of 4850

Full-Text Articles in Engineering

Microstructure Evolution In 304l Stainless Steel Subjected To Hot Torsion At Elevated Temperature, Jian Lu Sep 2011

Microstructure Evolution In 304l Stainless Steel Subjected To Hot Torsion At Elevated Temperature, Jian Lu

Theses and Dissertations

The current study focus on investigating a relationship between processing variables and microstructure evolution mechanism in 304L stainless steel subjected to hot torsion. The Gleeble 3800 with Mobile Torsion Unit (MTU) is utilized in the current study to conduct hot torsion test of 304L stainless steel. Samples are rotated at 1100℃ in the shear strain rate range of 0.02s-1 to 4.70s-1 and the shear strain range of 0.5 to 4. Orientation imaging microscopy (OIM) technique is used to collect and analyze the microstructure. At low strains (≤1) and strain rate (0.02s-1), average grain size remains relatively constant, but the lengths …

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The Pulled-Macro-Dataflow Model: An Execution Model For Multicore Shared-Memory Computers, Daniel Joseph Richins Sep 2011

The Pulled-Macro-Dataflow Model: An Execution Model For Multicore Shared-Memory Computers, Daniel Joseph Richins

Theses and Dissertations

The macro-dataflow model of execution has been used in scheduling heuristics for directed acyclic graphs. Since this model was developed for the scheduling of parallel applications on distributed computing systems, it is inadequate when applied to the multicore shared-memory computers prevalent in the market today. The pulled-macro-dataflow model is put forth as an alternative to the macro-dataflow model, having been designed specifically to accurately describe the memory bandwidth limitations and request-driven nature of communications characteristic of today's machines. The performance of the common scheduling heuristics DSC and CASS-II are evaluated under the pulled-macro-dataflow model and it is shown that their …

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Vision-Based Path Planning, Collision Avoidance, And Target Tracking For Unmanned Air And Ground Vehicles In Urban Environments, Huili Yu Sep 2011

Vision-Based Path Planning, Collision Avoidance, And Target Tracking For Unmanned Air And Ground Vehicles In Urban Environments, Huili Yu

Theses and Dissertations

Unmanned vehicle systems, specifically Unmanned Air Vehicles (UAVs) and Unmanned Ground Vehicles (UGVs) have found potential use in both military and civilian applications. For many applications, unmanned vehicle systems are required to navigate in urban environments where obstacles with various types and sizes exist. The main contribution of this research is to offer vision-based path planning, collision avoidance, and target tracking strategies for Unmanned Air and Ground vehicles operating in urban environments. Two vision-based local-level frame mapping and planning techniques are first developed for Miniature Air Vehicles (MAVs). The techniques build maps and plan paths in the local-level frame of …

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Optimizing The Use Of Ultrasound To Deliver Chemotherapeutic Agents To Cancer Cells From Polymeric Micelles, Ghaleb A. Husseini, Nabil M. Abdel-Jabbar, Farouq S. Mjalli, William G. Pitt, Ala'a Al-Mousa Sep 2011

Optimizing The Use Of Ultrasound To Deliver Chemotherapeutic Agents To Cancer Cells From Polymeric Micelles, Ghaleb A. Husseini, Nabil M. Abdel-Jabbar, Farouq S. Mjalli, William G. Pitt, Ala'a Al-Mousa

Faculty Publications

In this study, we present an artificial neural network (ANN) model that attempts to predict the dynamic release of doxorubicin (Dox) from P105 micelles under different ultrasonic power densities at 20 kHz. The goal is to utilize the developed ANN model in optimizing the ultrasound application to achieve a target drug release at the tumor site by controlling power density and ultrasound duration via an ANN-based model predictive control. The parameters of the controller are then tuned to achieve good reference signal tracking.

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Utilizing An Improved Rotorcraft Dynamic Model In State Estimation, Timothy Mclain, Randal W. Beard, Robert C. Leishman, John Macdonald, Jeffrey L. Ferrin, Stephen C. Quebe Sep 2011

Utilizing An Improved Rotorcraft Dynamic Model In State Estimation, Timothy Mclain, Randal W. Beard, Robert C. Leishman, John Macdonald, Jeffrey L. Ferrin, Stephen C. Quebe

Faculty Publications

Multirotor aircraft have become a popular platform for indoor flight. To navigate these vehicles indoors through an unknown environment requires the use of a SLAM algorithm, which can be processing intensive. However, their size, weight, and power capacity limit the processing capabilities available onboard. In this paper, we describe an approach to state estimation that helps to alleviate this problem. By using an improved dynamic model we show how to more accurately estimate the aircraft states than can be done with the traditional approach of integrating IMU measurements. The estimation is done with relatively infrequent corrections from accelerometers (40Hz) and …

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Differential Flatness Based Control Of A Rotorcraft For Aggressive Maneuvers, Timothy Mclain, Randal W. Beard, Robert C. Leishman, Jeffrey L. Ferrin Sep 2011

Differential Flatness Based Control Of A Rotorcraft For Aggressive Maneuvers, Timothy Mclain, Randal W. Beard, Robert C. Leishman, Jeffrey L. Ferrin

Faculty Publications

We propose a new method to control a multi-rotor aerial vehicle. We show that the system dynamics are differentially flat. We utilize the differential flatness of the system to provide a feed forward input. The system model derived allows for arbitrary changes in yaw and is not limited to small roll and pitch angles. We demonstrate in hardware the ability to follow a highly maneuverable path while tracking a time-varying heading command.

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Active Impedance Matching And Sensitivity Optimized Phased Array Feed Design For Radio Astronomy, David E. Carter Aug 2011

Active Impedance Matching And Sensitivity Optimized Phased Array Feed Design For Radio Astronomy, David E. Carter

Theses and Dissertations

One of the many challenges in radio astronomy is the ability to make accurate measurements quickly. In recent years engineers and astronomers have begun implementing phased array feeds (PAFs) as a way to negate the long observation times required by single antenna feeds. Unfortunately, large mutual coupling and other loss terms result in low sensitivity, restricting PAF usefulness in on dish observation. This thesis addresses several ways to reduce mutual coupling and maximize sensitivity for PAFs in radio astronomy. Antenna design of this magnitude requires accurate modeling capabilities. To this end, electromagnetic software models and low loss component designs are …

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Expanding Lamina Emergent Mechanism (Lem) Capabilities: Spherical Lems, Lem Joints, And Lem Applications, Samuel E. Wilding Aug 2011

Expanding Lamina Emergent Mechanism (Lem) Capabilities: Spherical Lems, Lem Joints, And Lem Applications, Samuel E. Wilding

Theses and Dissertations

Lamina Emergent Mechanisms (LEMs) are a class of compliant mechanisms that can be manufactured from sheet goods and possess motion out of the plane of fabrication. LEMs can be designed to perform sophisticated motions. This thesis expands LEM understanding and increases the ability to utilize them in applications by introducing the fundamentals of spherical LEMs, creating joints suitable for LEMs, and providing an example of a LEM application. In this thesis, the fundamentals of spherical LEMs are developed. This includes classification of all possible spherical 4R LEMs and a discussion of the motion characteristics of the various mechanisms. The motion …

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Comparison Of Analysis And Optimization Methods For Core-Megacolumn-Outrigger Skyscrapers, James B. Peterson Aug 2011

Comparison Of Analysis And Optimization Methods For Core-Megacolumn-Outrigger Skyscrapers, James B. Peterson

Theses and Dissertations

The goal of this research is to compare performance of three analysis methods and three optimization methods for core-megacolumn-outrigger, or CMO skyscrapers. The three analysis methods include a 1D stick analysis, 2D frame analysis, and 3D finite element analysis. The three optimization methods include a trial and error optimization, optimality criteria optimization, and genetic algorithm. Each of these methods was compared by applying an example CMO skyscraper. The 1D stick analysis proved to be the most accurate when compared with the 3D finite element results. The genetic algorithm was recommended as the best optimization method in this research. The 1D …

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Analytical Comparison Of Multimicrophone Probes In Measuring Acoustic Intensity, Curtis P. Wiederhold Aug 2011

Analytical Comparison Of Multimicrophone Probes In Measuring Acoustic Intensity, Curtis P. Wiederhold

Theses and Dissertations

In the late 1970s, a method was developed to estimate acoustic intensity in one dimension by taking the cross-spectral density of two closely-spaced microphone signals. Since then, multimicrophone probes have been developed to measure three-dimensional intensity as well as energy density. Their usefulness has led to the design of various types of multimicrophone probes, the most common being the four-microphone orthogonal, the four-microphone regular tetrahedron, and the six-microphone designs. These designs generally either consist of microphones suspended in space near each other or mounted on the surface of a sphere. This work analytically compares the relative merits of each probe …

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Influence Of Subglottic Geometry On Computational And Synthetic Vocal Fold Model Vibration, Simeon L. Smith Aug 2011

Influence Of Subglottic Geometry On Computational And Synthetic Vocal Fold Model Vibration, Simeon L. Smith

Theses and Dissertations

The voice plays a vital role in human communication. The purpose of voice research is to advance the understanding of voice production physics, with the ultimate goal of leading to improved voice care. In this research computational and synthetic vocal fold models were used to explore the role of subglottal geometry in vocal fold vibration. Three specific studies were performed. First, the effect of the inferior vocal fold surface angle on voice production was investigated using a two-dimensional self-oscillating finite element vocal fold model. Varying the inferior angle resulted in significant changes to model vibratory motion, glottal width, flow rate, …

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Smb-Interp: An N-Th Order Accurate, Distributed Interpolation Library, Stephen Mardson Mcquay Aug 2011

Smb-Interp: An N-Th Order Accurate, Distributed Interpolation Library, Stephen Mardson Mcquay

Theses and Dissertations

The research contained herein yielded an open source interpolation library implemented in and designed for use with the Python programming language. This library, named smbinterp, provides an interpolation to an arbitrary degree of accuracy. The library is parametric in that is can take input from the user to adjust the underlying interpolation mechanism. The characteristics and behavior of the library according to the adjustment of these parameters is presented herein, as well as the results of a mesh resolution study depicting the accuracy obtained by the library. The smbinterp library was designed with parallel computing environments in mind. The library …

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Flow-Induced Responses Of Normal, Bowed, And Augmented Synthetic Vocal Fold Models, Preston Roylance Murray Aug 2011

Flow-Induced Responses Of Normal, Bowed, And Augmented Synthetic Vocal Fold Models, Preston Roylance Murray

Theses and Dissertations

The voice is the primary mode of communication for humans. Because the voice is so important, voice disorders tend to severely diminish quality of life. A better understanding of the physics of voice production can help to improve treatment of voice disorders. For this thesis research a self-oscillating synthetic vocal fold model was developed, compared with previous synthetic vocal fold models, and used to explore the physical effects of augmentation injections on vibration dynamics. The research was conducted in two stages. First, four vocal fold models were evaluated by quantifying onset pressure, frequency, maximum glottal gap, flow rate, and medial …

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Tailoring The Spectral Transmission Of Optofluidic Waveguides, Brian S. Phillips Aug 2011

Tailoring The Spectral Transmission Of Optofluidic Waveguides, Brian S. Phillips

Theses and Dissertations

Optofluidics is a relatively new and exciting field that includes the integration of optical waveguides into microfluidic platforms. The purpose of this field of study is to miniaturize previously developed optical systems used for biological and chemical analysis with the end goal of placing bench-top optics into microscopic packages. Mundane optical alignment and sample manipulation procedures would then be intrinsic to the platform and allow measurements to be completed quickly and with reduced human interaction. Biosensors based on AntiResonant Reflecting Optical Waveguides (ARROWs) consist of hollow-core waveguides used for fluid sample manipulation and analysis, as well as solid-core waveguides used …

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Collaborative Products: A Design Methodology With Application To Engineering-Based Poverty Alleviation, Jacob S. Morrise Aug 2011

Collaborative Products: A Design Methodology With Application To Engineering-Based Poverty Alleviation, Jacob S. Morrise

Theses and Dissertations

Collaborative products are created when physical components from two or more products are temporarily recombined to form another product capable of performing entirely new tasks. The method for designing collaborative products is useful in developing products with reduced cost, weight, and size. These reductions are valued in the developing world because collaborative products have a favorable task-per-cost ratio. In this paper, a method for designing collaborative products is introduced. The method identifies a set of products capable of being recombined into a collaborative product. These products are then designed to allow for this recombination. Three examples are provided to illustrate …

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Efficient, Accurate, And Non-Gaussian Error Propagation Through Nonlinear, Closed-Form, Analytical System Models, Travis V. Anderson Jul 2011

Efficient, Accurate, And Non-Gaussian Error Propagation Through Nonlinear, Closed-Form, Analytical System Models, Travis V. Anderson

Theses and Dissertations

Uncertainty analysis is an important part of system design. The formula for error propagation through a system model that is most-often cited in literature is based on a first-order Taylor series. This formula makes several important assumptions and has several important limitations that are often ignored. This thesis explores these assumptions and addresses two of the major limitations. First, the results obtained from propagating error through nonlinear systems can be wrong by one or more orders of magnitude, due to the linearization inherent in a first-order Taylor series. This thesis presents a method for overcoming that inaccuracy that is capable …

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Simulation Of Dna Extension In Nanochannels, Yanwei Wang, Douglas R. Tree, Kevin D. Dorfman Jul 2011

Simulation Of Dna Extension In Nanochannels, Yanwei Wang, Douglas R. Tree, Kevin D. Dorfman

Faculty Publications

We have used a realistic model for double-stranded DNA and Monte Carlo simulations to compute the extension (mean span) of a DNA molecule confined in a nanochannel over the full range of confinement in a high ionic strength buffer. The simulation data for square nanochannels resolve the apparent contradiction between prior simulation studies and the predictions from Flory theory, demonstrating the existence of two transition regimes between weak confinement (the de Gennes regime) and strong confinement (the Odijk regime). The simulation data for rectangular nanochannels support the use of the geometric mean for mapping data obtained in rectangular channels onto …

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Desorption Kinetics Of An Alternative Monoethanolamine Based Co2 Capture Process, Morris D. Argyle, Zhuoyan Sun, Maohong Fan Jul 2011

Desorption Kinetics Of An Alternative Monoethanolamine Based Co2 Capture Process, Morris D. Argyle, Zhuoyan Sun, Maohong Fan

Faculty Publications

Supported monoethanolamine (MEA) sorbents are promising materials for CO2 separation due to their low energy demands. Like any other CO2 separation technologies, CO2 desorption from supported MEA sorbents is the most energy-expensive step in the overall CO2 separation process. The presence of water during CO2 desorption process leads to a significant increase in energy consumption. Therefore, CO2 desorption in the absence of water is an important method to reduce energy consumption of CO2 separation using supported MEA, which is determined by several major factors, including desorption kinetics. However, study on CO2 desorption kinetics of supported MEA is lacking. This research …

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Direct Numerical Simulation Of Transonic Wake Flow In The Presence Of An Adverse Pressure Gradient And Streamline Curvature, Jeffrey Reed Gibson Jul 2011

Direct Numerical Simulation Of Transonic Wake Flow In The Presence Of An Adverse Pressure Gradient And Streamline Curvature, Jeffrey Reed Gibson

Theses and Dissertations

Wakes are present in many engineering flows. These flows include internal flows such as mixing chambers and turbomachinery as well as external flows like flow over high-lift or multi-element airfoils. Many times these wakes are exposed to flow conditions such as adverse pressure gradients and streamline curvature that alter the mean flow and turbulent structure of the wake. The ability to understand how pressure gradients and streamline curvature affects the structure of the wake is essential to predicting how the wake will affect the performance of the application in which it is found. The effects of pressure gradients and curvature …

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Design And Analysis Of A Flapping Wing Mechanism For Optimization, Ryan Brandon George Jul 2011

Design And Analysis Of A Flapping Wing Mechanism For Optimization, Ryan Brandon George

Theses and Dissertations

Furthering our understanding of the physics of flapping flight has the potential to benefit the field of micro air vehicles. Advancements in micro air vehicles can benefit applications such as surveillance, reconnaissance, and search and rescue. In this research, flapping kinematics of a ladybug was explored using a direct linear transformation. A flapping mechanism design is presented that was capable of executing ladybug or other species-specific kinematics. The mechanism was based on a differential gear design, had two wings, and could flap in harsh environments. This mechanism served as a test bed for force analysis and optimization studies. The first …

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Two-Dimensional Hydrodynamics Of Swimming Rainbow Trout Using Navier-Stokes And Large Eddy Simulation Models, Donovan R. Chipman Jul 2011

Two-Dimensional Hydrodynamics Of Swimming Rainbow Trout Using Navier-Stokes And Large Eddy Simulation Models, Donovan R. Chipman

Theses and Dissertations

Energy efficiency and propulsive characteristics of a 10 cm undulatory rainbow trout (oncorhynchus mykiss) swimming in a stationary position are considered. Two CFD simulations are performed utilizing dynamic grid meshing (FLUENT 6.3). The first simulation uses a laminar flow model with an added hydrofoil shape in order to test if thrust and drag can be brought to unity. The second simulation uses a Large-Eddy Simulation (LES) turbulence model to determine if transition to turbulence along the fish's surface leads to boundary layer separation. The expected results caused by adding these two features to earlier simulations do not occur. …

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Automated Multidisciplinary Optimizations Of Conceptual Rocket Fairings, Ronald S. Smart Jul 2011

Automated Multidisciplinary Optimizations Of Conceptual Rocket Fairings, Ronald S. Smart

Theses and Dissertations

The purpose of this research is to develop and architect a preliminary multidisciplinary design optimization (MDO) tool that creates multiple types of generalized rocket fairing models. These models are sized relative to input geometric models and are analyzed and optimized, taking into account the primary objectives, namely the structural, thermal, and aerodynamic aspects of standard rocket flights. A variety of standard nose cone shapes is used as optimization proof of concept examples, being sized and compared to determine optimal choices based on the input specifications, such as the rocket body geometry and the specified trajectory paths. Any input models can …

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Analytical Modeling And Optimization Of A Thermoelectric Heat Conversion System Operating Betweeen Fluid Streams, Stephen H. Taylor Jul 2011

Analytical Modeling And Optimization Of A Thermoelectric Heat Conversion System Operating Betweeen Fluid Streams, Stephen H. Taylor

Theses and Dissertations

Analytical, closed-form solutions governing thermoelectric behavior are derived. An analytical model utilizing a thermal circuit is presented involving heat transfer into, through, out of, and around a thermoelectric device. A nondimensionalization of the model is presented. Linear heat transfer theory is applied to the model to obtain a series of closed form equations predicting net power output for the thermoelectric device. Fluid streams flowing through shrouded heat sinks with square pin fins are considered for the thermal pathways to and from the device. Heat transfer and pressure drop are characterized in a manner conducive to an analytical model using previously …

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Mapping And Modeling Chlorophyll-A Concentrations In Utah Lake Using Landsat 7 Etm+ Imagery, Victor Nii Afum Narteh Jul 2011

Mapping And Modeling Chlorophyll-A Concentrations In Utah Lake Using Landsat 7 Etm+ Imagery, Victor Nii Afum Narteh

Theses and Dissertations

This study shows the results of testing previous research that used remote sensing techniques to determine chlorophyll-a concentrations in turbid surface waters, and developing similar methods and models for Utah Lake using Landsat 7 ETM+ satellite imagery and field measured concentrations of chlorophyll-a. The data for the study included images acquired on June 22 and July 8, 2009. The field data included ground measurements taken on June 22 and July 6, 2009 from seven water quality sampling locations. The 48 hour time difference between the Landsat image acquisition (July 8) and the field measurement (July 6), and the small sample …

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Automated Fixed-Point Analysis And Bit Width Selection In Digital Signal Processing Circuits Using Ptolemy, Derrick S. Gibelyou Jul 2011

Automated Fixed-Point Analysis And Bit Width Selection In Digital Signal Processing Circuits Using Ptolemy, Derrick S. Gibelyou

Theses and Dissertations

When designing custom hardware to implement signal processing algorithms, it is important to select bitwidths that meet the minimum error requirements while minimizing implementation area. Larger bitwidths reduce error, but increase area, while selecting smaller bitwidths does the opposite. Finding the set of bitwidths that produces the smallest area that still meets the error requirements has been shown to be NP-hard. To address this problem, many heuristics have been developed. Unfortunately, they are not always well documented and do not have available source code. It is also di cult to know which algorithm to try to use. This thesis addresses …

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Unintended Social And Economic Consequences Resulting From The Implementation Of New Construction Technologies In The Developing World, Andrew J. South Jul 2011

Unintended Social And Economic Consequences Resulting From The Implementation Of New Construction Technologies In The Developing World, Andrew J. South

Theses and Dissertations

One of the key components of international development is to provide adequate shelter for citizens of developing countries. This is often accomplished by governmental, non- governmental, and private organizations that seek to lower the cost, increase the quality, and expand the availability of safe, sustainable housing through the use of innovative technologies. These new technologies can affect the social and/or economic structure within communities. This paper is a case study resulting from the construction of a seventy-one-home village, including infrastructure, near Yogyakarta, Indonesia by a foreign, aid-based non-governmental organization (NGO). The village was relocated less than two kilometers from its …

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Development Of An Experimental Phased-Array Feed System And Algorithms For Radio Astronomy, Jonathan Charles Landon Jul 2011

Development Of An Experimental Phased-Array Feed System And Algorithms For Radio Astronomy, Jonathan Charles Landon

Theses and Dissertations

Phased array feeds (PAFs) are a promising new technology for astronomical radio telescopes. While PAFs have been used in other fields, the demanding sensitivity and calibration requirements in astronomy present unique new challenges. This dissertation presents some of the first astronomical PAF results demonstrating the lowest noise temperature and highest sensitivity at the time (66 Kelvin and 3.3 m^2/K, respectively), obtained using a narrowband (425 kHz bandwidth) prototype array of 19 linear co-polarized L-band dipoles mounted at the focus of the Green Bank 20 Meter Telescope at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. Results include …

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Robust Signaling, Scheduling And Authentication In The Multi-User Multiple-Input-Multiple-Output Channel, Yan Shi Jul 2011

Robust Signaling, Scheduling And Authentication In The Multi-User Multiple-Input-Multiple-Output Channel, Yan Shi

Theses and Dissertations

Multiple-input multiple-output (MIMO) networks are known to be able to achieve throughput performance superior to that available from single-input single-output (SISO) systems. However, when applying MIMO in multi-user networks, achieving this throughput advantage requires efficient precoding and optimal network scheduling. Furthermore, MIMO radios can help ensure security in a multi-user network. Previous work has proposed various precoding techniques for the MIMO broadcast channel, based either on channel state information (CSI) or channel distribution information (CDI), which achieve optimal or near- optimal MIMO channel throughput. The performance of these techniques largely depends on the availability of the channel information at the …

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Spinal Implant With Customized And Non-Linear Stiffness, Eric Ray Dodgen Jul 2011

Spinal Implant With Customized And Non-Linear Stiffness, Eric Ray Dodgen

Theses and Dissertations

There is a need for spinal implants that have nonlinear stiffness to provide stabilization if the spine loses stiffness through injury, degeneration, or surgery. There is also a need for spinal implants to be customizable for individual needs, and to be small enough to be unobtrusive once implanted. Past and ongoing work that defines the effects of degeneration on the torque rotation curve of a functional spinal unit (FSU) were used to produce a spinal implant which could meet these requirements. This thesis proposes contact-aided inserts to be used with the FlexSuRe™ spinal implant to create a nonlinear stiffness. Moreover, …

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Eddy Impaction As An Ash Deposition Mechanism: A Theoretical And Experimental Investigation, Minmin Li Jul 2011

Eddy Impaction As An Ash Deposition Mechanism: A Theoretical And Experimental Investigation, Minmin Li

Theses and Dissertations

The eddy impaction ash deposition model derived and validated in this document predicts eddy impaction rates as a function of turbulence intensity, boundary layer thickness, and gas velocity. The experimental apparatus introduces small particles (200 nm, 25 µm, and 500 µm diameter) into a gas stream flowing through a horizontal pipe (Re 2,300-8,000). The particles deposit on the pipe wall and the total mass of impacted particles provides a measure of collection efficiency. Experimental results indicate deposition velocity increases with Reynolds number, consistent with eddy impaction theory and based on increased turbulent energy. Eddy impaction also increases with particle size …

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