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Articles 3241 - 3270 of 4850

Full-Text Articles in Engineering

Comparison Of 3-D Friction Stir Welding Viscoplastic Finite Element Model With Weld Data And Physically-Simulated Data, Maria Posada Dec 2012

Comparison Of 3-D Friction Stir Welding Viscoplastic Finite Element Model With Weld Data And Physically-Simulated Data, Maria Posada

Theses and Dissertations

Models (both physical and numerical) of the friction stir (FS) welding process are used to develop a greater understanding of the influence of independent process parameters on dependent process output variables, such as torque, power, specific weld energy, peak temperature, cooling rates and various metallurgical factors (e.g., grain size and precipitates). An understanding of how the independent process parameters influence output variables and ultimately their effect on resultant properties (e.g., strength, hardness, etc..) is desirable. Most models developed have been validated primarily for aluminum alloys with relatively small amounts of experimental data. Fewer models have been validated for steels or …

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Two-Refinement By Pillowing For Structured Hexahedral Meshes, J. Bruce Malone Dec 2012

Two-Refinement By Pillowing For Structured Hexahedral Meshes, J. Bruce Malone

Theses and Dissertations

A number of methods for adaptation of existing all-hexahedral grids by localized refinement have been developed; however, none ideally fit all refinement needs. This thesis presents the structure to a method of two-refinement developed for conformal, structured, all-hexahedral grids that offers flexibility beyond what has been offered to date. The method is fundamentally based on pillowing pairs of sheets of hexes. This thesis also suggests an implementation of the method, shows the results of examples refined using it and compares these results to results from implementing three-refinement on the same examples.

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Model Development And Application Of Molecular Simulations For The Study Of Proton Transport In Bulk Water And For The Prediction Of Dipole Moments Of Organic Compounds, Abhishek Asthana Dec 2012

Model Development And Application Of Molecular Simulations For The Study Of Proton Transport In Bulk Water And For The Prediction Of Dipole Moments Of Organic Compounds, Abhishek Asthana

Theses and Dissertations

The present work demonstrates the application of molecular simulations (MD) in two different areas: proton transport in bulk water and estimation of the dipole moment of polar organic compounds. In both areas, relatively few successful and robust methodologies exist. In the first part, a new polarizable water model is developed for MD simulations of the proton transport process. The model was parametrized from a combination of quantum chemical calculations and experimental water properties. The model was implemented in MD simulation studies of liquid water at room temperature, as well as with excess protons. For pure water the model gave good …

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Effective Collaboration Through Multi User Cax By Implementing New Methods Of Product Specification And Management, Vonn L. Holyoak Dec 2012

Effective Collaboration Through Multi User Cax By Implementing New Methods Of Product Specification And Management, Vonn L. Holyoak

Theses and Dissertations

This thesis presents a new design process in which design specifications and task distribution are determined from a parallel multi user prospective. Using this method, projects are more easily decomposed into tasks that can be performed concurrently, thus decreasing the design time. Also, a framework is provided to determine the correct distribution of available talent and stakeholders that can be utilized on a given project. The research suggests that by involving the necessary stakeholders in a multi user setting, changes can be made quickly and without additional approval wait time. By including individuals from the various areas of required talent, …

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Seismic Response Of Stiffening Elastic Systems, Andrew Scott Morgan Dec 2012

Seismic Response Of Stiffening Elastic Systems, Andrew Scott Morgan

Theses and Dissertations

Traditional seismic load resisting systems in buildings are designed to undergo inelastic deformations in order to dissipate energy, resulting in residual displacements. This work explores an approach to eliminate these residual displacements. The systems investigated have low initial stiffness which increases at a predefined displacement, and are therefore called stiffening elastic systems. This thesis begins with an examination of single-degree-of-freedom stiffening elastic systems. A case study is presented which suggests that the benefits from stiffening elastic behavior may be limited to systems which would have long periods if designed traditionally. A thorough parameter study is also presented which indicates the …

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Dynamic Modeling, Trajectory Generation And Tracking For Towed Cable Systems, Liang Sun Dec 2012

Dynamic Modeling, Trajectory Generation And Tracking For Towed Cable Systems, Liang Sun

Theses and Dissertations

In this dissertation, we focus on the strategy that places and stabilizes the path of an aerial drogue, which is towed by a mothership aircraft using a long flexible cable, onto a horizontally flat orbit by maneuvering the mothership in the presence of wind. To achieve this goal, several studies for towed cable systems are conducted, which include the dynamic modeling for the cable, trajectory generation strategies for the mothership, trajectory-tracking control law design, and simulation and flight test implementations. First, a discretized approximation method based on finite element and lumped mass is employed to establish the mathematical model for …

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Filtering Techniques For Pose Estimation With Applications To Unmanned Air Vehicles, Bryce Benson Ready Nov 2012

Filtering Techniques For Pose Estimation With Applications To Unmanned Air Vehicles, Bryce Benson Ready

Theses and Dissertations

This work presents two novel methods of estimating the state of a dynamic system in a Kalman Filtering framework. The first is an application specific method for use with systems performing Visual Odometry in a mostly planar scene. Because a Visual Odometry method inherently provides relative information about the pose of a platform, we use this system as part of the time update in a Kalman Filtering framework, and develop a novel way to propagate the uncertainty of the pose through this time update method. Our initial results show that this method is able to reduce localization error significantly with …

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Site-Specific Metallization Of Multiple Metals On A Single Dna Origami Template, Bibek Uprety Nov 2012

Site-Specific Metallization Of Multiple Metals On A Single Dna Origami Template, Bibek Uprety

Theses and Dissertations

This work examines the selective deposition of two different metals on the same DNA origami template for nanofabrication. DNA, with adjustable size and shape serves as a suitable template for fabricating metal junctions in the nanometer domain via bottom-up assembly. Bottom-up assembly utilizes the recognition capability of molecules like DNA to self-assemble and form structures. In this regard, DNA origami provides a useful means for forming nanostructures by folding single-stranded DNA into different two and three dimensional shapes. Selective deposition of metal on specific locations of a DNA template is essential for making DNA-templated electronic circuits.Site-specific metallization of DNA origami …

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An Optimization-Based Method Of Traversing Dynamic S-Pareto Frontiers, Patrick K. Lewis Nov 2012

An Optimization-Based Method Of Traversing Dynamic S-Pareto Frontiers, Patrick K. Lewis

Theses and Dissertations

The use of multiobjective optimization in identifying systems that account for changes in customer needs, operating environments, system design concepts, and analysis models over time is generally not explored. Providing solutions that anticipate, account for, and allow for these changes over time is a significant challenge to manufacturers and design engineers. Products that adapt to these changes through the addition and/or subtraction of modules can reduce production costs through product commonality, and cater to customization and adaptation. In terms of identifying sets of non-dominated designs, these changes result in the concept of dynamic Pareto frontiers, or dynamic s-Pareto frontiers …

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Measurement Of Thermal Diffusivities Using The Distributed Source, Finite Absorption Model, James B. Hall Nov 2012

Measurement Of Thermal Diffusivities Using The Distributed Source, Finite Absorption Model, James B. Hall

Theses and Dissertations

Thermal diffusivity in an important thermophysical property that quantifies the ratio of the rate at which heat is conducted through a material to the amount of energy stored in a material. The pulsed laser diffusion (PLD) method is a widely used technique for measuring thermal diffusivities of materials. This technique is based on the fact that the diffusivity of a sample may be inferred from measurement of the time-dependent temperature profile at a point on the surface of a sample that has been exposed to a pulse of radiant energy from a laser or flash lamp. An accepted standard approach …

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Reactive Rayleigh–Taylor Turbulent Mixing: A One-Dimensional-Turbulence Study, E.D. Gonzalez-Juez, A.R. Kerstein, D.O. Lignell Nov 2012

Reactive Rayleigh–Taylor Turbulent Mixing: A One-Dimensional-Turbulence Study, E.D. Gonzalez-Juez, A.R. Kerstein, D.O. Lignell

Faculty Publications

We study the problem of reactive Rayleigh–Taylor turbulence in the Boussinesq framework using one-dimensional-turbulence (ODT) simulations. In this problem a reaction zone between overlying heavy/cold reactants and underlying light/hot products moves against gravity. First, we show that ODT results for global quantities in non-reactive Rayleigh–Taylor turbulence are within those from direct numerical simulations (DNS). This comparison give us confidence in using ODT to study unexplored flow regimes in the reactive case. Then, we show how ODT predicts an early stage of reactive Rayleigh–Taylor turbulence that behaves similarly to the non-reactive case, as observed in previous DNS. More importantly, ODT indicates …

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Fib/Sem-Based Calculation Of Tortuosity In A Porous Licoo2 Cathode For A Li-Ion Battery, T. Hutzenlaub, A. Asthana, J. Becker, D. R. Wheeler, R. Zengerle, S. Thiele Nov 2012

Fib/Sem-Based Calculation Of Tortuosity In A Porous Licoo2 Cathode For A Li-Ion Battery, T. Hutzenlaub, A. Asthana, J. Becker, D. R. Wheeler, R. Zengerle, S. Thiele

Faculty Publications

We present a new method to quantify tortuosity in the porous, LiCoO2 cathode of a Li-ion battery. The starting point is a previously published 3D reconstruction from FIB/SEM images with three phases, the active material domain, carbon-binder domain and pore space. Based on this geometrical configuration, we compute effective diffusivities, from which we in turn derive tortuosity values for the pore space ranging between 5 and 11.6 for the three spatial directions. In a next step, we compare our approach to an imaging method that employs back-filling material. These methods do not differentiate between the carbon-binder domain and the pore …

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Fpga Floor-Planning Impact On Implementation Results, Jaren Tyler Lamprecht Nov 2012

Fpga Floor-Planning Impact On Implementation Results, Jaren Tyler Lamprecht

Theses and Dissertations

The field programmable gate array (FPGA) is an attractive computational platform for many applications because of its customizable nature and modest development cost, in terms of both time and money. As FPGAs scale to increased logical capacities, designers have increased flexibility. However, the FPGA placement problem becomes more difficult at increased sizes. Increasingly, designers are encouraged to structure designs hierarchically and floor-plan. Floor planning is a manual process which maps specified design submodules to selected physical regions of the FPGA device fabric. This thesis explores several of the effects that floor-planning has on submodules and the designs they comprise. A …

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Ultrasound-Induced Phase Change Of Emulsion Droplets For Targeted Gene And Drug Delivery, James R. Lattin Nov 2012

Ultrasound-Induced Phase Change Of Emulsion Droplets For Targeted Gene And Drug Delivery, James R. Lattin

Theses and Dissertations

This dissertation explores the potential of using perfluorocarbon emulsion droplets to add an ultrasound-sensitive element to drug delivery systems. These emulsion droplets may be induced to vaporize with ultrasound; during the rarefactional phase of an ultrasound wave, the pressure around the droplets may fall below the vapor pressure of the liquid forming the emulsion, providing a thermodynamic potential for vaporization. This ultrasound-induced phase change of the emulsion droplet could release therapeutics attached to the droplet surface or aid in drug delivery due to mechanical effects associated with vaporization and expansion, similar to the ability of cavitating bubbles to aid in …

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Developing A Guidance Law For A Small-Scale Controllable Projectile Using Backstepping And Adaptive Control Techniques And A Hardware System Implementation For A Uav And A Ugv To Track A Moving Ground Target, Kevin Christopher Meier Nov 2012

Developing A Guidance Law For A Small-Scale Controllable Projectile Using Backstepping And Adaptive Control Techniques And A Hardware System Implementation For A Uav And A Ugv To Track A Moving Ground Target, Kevin Christopher Meier

Theses and Dissertations

The work in this thesis is on two topics. The first topic focuses on collaboration between a UAV and a UGV to track a moving ground target. The second topic focuses on deriving a guidance law for a small-scale controllable projectile to be guided into a target. For the first topic, we implement a path planning algorithm in a hardware system for a UAV and UGV to track a ground target. The algorithm is designed for urban environments where it is common for objects to obstruct sensors located on the UAV and the UGV. During the hardware system's implementation, multiple …

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Beyond Gel Electrophoresis: Microfluidic Separations, Fluorescence Burst Analysis, And Dna Stretching, Kevin D. Dorfman, Scott B. King, Daniel W. Olson, Joel D. P. Thomas, Douglas R. Tree Nov 2012

Beyond Gel Electrophoresis: Microfluidic Separations, Fluorescence Burst Analysis, And Dna Stretching, Kevin D. Dorfman, Scott B. King, Daniel W. Olson, Joel D. P. Thomas, Douglas R. Tree

Faculty Publications

This review addresses methods for obtaining sequence information directly from unamplified genomic length DNA. Our generic starting point is a large piece of DNA that contains many thousands of base pairs (kilobase pairs, kbp) or even millions of base pairs (megabase pairs, Mbp). We would like to determine the genomic distance between two repeats of a given sequence, indicated by the red dots on the coiled DNA molecule in Figure 1. Let us consider the case where these sequences are restriction sites, which can be selectively cut using proteins known as restriction enzymes. For decades, gel electrophoresis served as the …

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A Hybrid Bishop-Hill Model For Microstructure Sensitive Design, Ribeka Takahashi Nov 2012

A Hybrid Bishop-Hill Model For Microstructure Sensitive Design, Ribeka Takahashi

Theses and Dissertations

A method is presented for adapting the classical Bishop-Hill model to the requirements of elastic/yield-limited design in metals of arbitrary crystallographic texture. The proposed Hybrid Bishop-Hill (HBH) model, which will be applied to ductile FCC metals, retains the `stress corners' of the polyhedral Bishop-Hill yield surface. However, it replaces the `maximum work criterion' with a criterion that minimizes the Euclidean distance between the applicable local corner stress state and the macroscopic stress state. This compromise leads to a model that is much more accessible to yield-limited design problems. Demonstration of performance for the HBH model is presented for an extensive …

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Functionalization Of In-Plane Photonic Microcantilever Arrays For Biosensing Applications, Stanley J. Ness Oct 2012

Functionalization Of In-Plane Photonic Microcantilever Arrays For Biosensing Applications, Stanley J. Ness

Theses and Dissertations

Microcantilevers have been investigated as high sensitivity, label free biosensors for approximately 15 years. In nearly all cases, a thin gold film deposited on the microcantilevers is used as an intermediate attachment layer because of the convenience of thiol-gold chemistry. Unfortunately, this attachment chemistry can be unstable when used with complex sample media such as blood plasma. The Nordin group at BYU has recently developed an all-silicon in-plane photonic microcantilever (PMCL) technology to serve as a platform for label-free biosensing. It has the advantage of being readily scalable to simultaneous readout of many PMCLs in array format, and allows integration …

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Syngas Impurity Effects On Cell Growth, Enzymatic Activities And Ethanol Production Via Fermentation, Deshun Xu Oct 2012

Syngas Impurity Effects On Cell Growth, Enzymatic Activities And Ethanol Production Via Fermentation, Deshun Xu

Theses and Dissertations

A syngas compositional database with focus on trace impurities was established. For this work, ammonia (NH3) and benzene (C6H6) effects on cell growth, enzymatic activities of hydrogenase and alcohol dehydrogenase (ADH), and product formation were studied. NH3, after entering media, will be converted rapidly to NH4+, which will raise the total osmolarity of the media. NH3, as a common nutrient for the cell growth, is not the real culprit for cell growth inhibition. In essence, it is the high osmolarity resulting from the accumulation of NH4+ in the media which disrupts the normal regulation of the cells. It was concluded …

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Thermodynamic Kinetics And Efficiency Analysis Of Methyl Viologen, Chang Chen Oct 2012

Thermodynamic Kinetics And Efficiency Analysis Of Methyl Viologen, Chang Chen

Theses and Dissertations

Methyl Viologen (MV) is an electron mediator that has great possibilities to be used with an electrode system in which the electrode system provides electrons towards reducing MV species. MV has three redox states and they can be converted to each other via redox reactions on the surface of the electrode. The concentration of the three species of MV was related to the voltage potential applied to the system through a thermodynamic model. With the thermodynamic model the concentration of the three species can be predicted with different applied voltage potentials towards providing guidance for controlling the redox state of …

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Force Optimization And Flow Field Characterization From A Flapping Wing Mechanism, Nathaniel Stephen Naegle Oct 2012

Force Optimization And Flow Field Characterization From A Flapping Wing Mechanism, Nathaniel Stephen Naegle

Theses and Dissertations

Flapping flight shows promise for micro air vehicle design because flapping wings provide superior aerodynamic performance than that of fixed wings and rotors at low Reynolds numbers. In these flight regimes, unsteady effects become increasingly important. This thesis explores some of the unsteady effects that provide additional lift to flapping wings through an experiment-based optimization of the kinematics of a flapping wing mechanism in a water tunnel. The mechanism wings and flow environment were scaled to simulate the flight of the hawkmoth (Manduca sexta) at hovering or near-hovering speeds. The optimization was repeated using rigid and flexible wings …

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Spherical Lamina Emergent Mechanisms, Samuel E. Wilding, Larry L. Howell, Spencer P. Magleby Oct 2012

Spherical Lamina Emergent Mechanisms, Samuel E. Wilding, Larry L. Howell, Spencer P. Magleby

Faculty Publications

Lamina emergent mechanisms (LEMs) are compliant mechanisms that can be manufactured from planar materials and are capable of motion out of the plane of manufacture. Spherical LEMs combine the unique motion of spherical mechanisms with the compactness and simple topology of LEMs. The fundamentals of spherical LEMs are discussed in this work. It is found that 21 of the 33 possible spherical 4R types can be spherical LEMs. A classification based on these 21 possible types is developed. This classification is used to predict motion capabilities of spherical 6R, and Equintet mechanisms. It is also applied to arrays of spherical …

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Introduction Of Planar Compliant Joints Designed For Combined Bending And Axial Loading Conditions In Lamina Emergent Mechanisms, Samuel E. Wilding, Larry L. Howell, Spencer P. Magleby Oct 2012

Introduction Of Planar Compliant Joints Designed For Combined Bending And Axial Loading Conditions In Lamina Emergent Mechanisms, Samuel E. Wilding, Larry L. Howell, Spencer P. Magleby

Faculty Publications

This work introduces three joints to allow motion in lamina emergent mechanisms (LEMs) that were designed to have minimal parasitic motion under tension, compression, and a combination of tension and compression loading. Closed-form models of the joints were developed and combined with optimization algorithms for maximum flexibility in bending and then modeled using finite element analysis (FEA). The FEA results were used to predict the stiffness of the joints in bending, tension, and compression. As a baseline, lamina emergent torsional (LET) joints were designed to match the bending stiffness of each of the joints, so that the tensile-compressive performance could …

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Thermal And Mechanical Properties Of Nitrate Thermal Storage Salts In The Solid-Phase, Brian D. Iverson, Scott T. Broome, Alan M. Kruizenga, Joseph G. Cordaro Oct 2012

Thermal And Mechanical Properties Of Nitrate Thermal Storage Salts In The Solid-Phase, Brian D. Iverson, Scott T. Broome, Alan M. Kruizenga, Joseph G. Cordaro

Faculty Publications

Implementation of molten salt compounds as the heat transfer fluid and energy storage medium provides specific benefits to energy collection and conversion. Nitrate salts have been identified as a strong candidate for energy transfer and storage and have been demonstrated for use in these applications over time. As nitrate salts have solidification temperatures above ambient, concern for recovery from salt freezing events has instigated efforts to understand and predict this behavior. Accurate information of salt property behavior in the solid-phase is necessary for understanding recovery from a freeze event as well as for phase change thermal energy storage applications. Thermal …

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Application Of Seawinds Scatterometer Data To The Study Of Antarctic Icebergs, Keith Mitchell Stuart Sep 2012

Application Of Seawinds Scatterometer Data To The Study Of Antarctic Icebergs, Keith Mitchell Stuart

Theses and Dissertations

Knowledge of iceberg location and size is important for safety reasons as well as for understanding many geophysical and biological processes. This dissertation analyzes large tabular icebergs in the Southern Ocean using the SeaWinds scatterometer. SeaWinds is a spaceborne radar designed to measure the microwave backscatter from the Earth's surface. Using resolution-enhancement techniques, backscatter measurements are processed into backscatter images in which icebergs can be observed. An iceberg detection methodology is formalized using daily scatterometer images. Radar profiles from common Antarctic scatterers are quantified and an iceberg detection methodology is formalized using daily scatterometer images. Iceberg positions are determined in …

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Liquid Jet Impingement Experiments On Micro Rib And Cavity Patterned Superhydrophobic Surfaces In Both Cassie And Wenzel States, Michael G. Johnson Sep 2012

Liquid Jet Impingement Experiments On Micro Rib And Cavity Patterned Superhydrophobic Surfaces In Both Cassie And Wenzel States, Michael G. Johnson

Theses and Dissertations

Experiments were performed to characterize hydraulic jumps that form due to liquid jet impingement on superhydrophobic surfaces with alternating micro-ribs and cavities. If the surface is unimmersed, a surface tension based transition into droplets occurs, so a known depth of water was imposed downstream from the hydraulic jump to ensure the existence of a hydraulic jump. The surfaces are characterized by the cavity fraction, which is defined as the width of a cavity divided by the combined width of a cavity and an adjoining rib. Four different surface designs were studied, with respective cavity fractions of 0 (smooth surface), 0.5, …

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Effects Of Haptic And 3d Audio Feedback On Pilot Performance And Workload For Quadrotor Uavs In Indoor Environments, Robert Mark Philbrick Sep 2012

Effects Of Haptic And 3d Audio Feedback On Pilot Performance And Workload For Quadrotor Uavs In Indoor Environments, Robert Mark Philbrick

Theses and Dissertations

Indoor flight of unmanned aerial vehicles (UAVs) has many applications in environments in which it is undesirable or dangerous for humans to be, such as military reconnaissance or searching for trapped victims in a collapsed building. However, limited visual feedback makes it difficult to pilot UAVs in cluttered and enclosed spaces. Haptic feedback combined with visual feedback has shown to reduce the number of collisions of UAVs in indoor environments; however, it has increased the mental workload of the operator. This thesis investigates the potential of combining novel haptic and 3D audio feedback to provide additional information to operators of …

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Technical Note On Manipulating Multivariate Gaussian Distributions, John C. Macdonald Sep 2012

Technical Note On Manipulating Multivariate Gaussian Distributions, John C. Macdonald

Student Works

In this technical note we present some derivations treating conditional, marginal, and joint distributions for Gaussian random vectors.

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Defining The Role Of Ultrasound In Drug Delivery, William G. Pitt Sep 2012

Defining The Role Of Ultrasound In Drug Delivery, William G. Pitt

Faculty Publications

Ultrasound is a very effective modality for drug delivery because energy that is noninvasively transmitted through the skin can be focused on a specific location and employed to release drug at that site. Most of the drug delivery techniques employ one or both of the results of ultrasonic insonation – the generation of thermal energy, called hyperthermia, or the oscillation of gas bubbles, called acoustic cavitation. Cavitation perturbs cell membrane structures via several modes and increases the permeability to drugs or other solutes. Microconvection, caused by stable cavitation, shears cell membranes. The shock waves and fluid jets of inertial cavitation …

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Phase Transitions Of Nanoemulsions Using Ultrasound: Experimental Observations, Ram Singh, Ghaleb A. Husseini, William G. Pitt Sep 2012

Phase Transitions Of Nanoemulsions Using Ultrasound: Experimental Observations, Ram Singh, Ghaleb A. Husseini, William G. Pitt

Faculty Publications

The ultrasound-induced transformation of perfluorocarbon liquids to gases is of interest in the area of drug and gene delivery. In this study, three independent parameters (temperature, size, and perfluorocarbon species) were selected to investigate the effects of 476-kHz and 20-kHz ultrasound on nanoemulsion phase transition. Two levels of each factor (low and high) were considered at each frequency. The acoustic intensities at gas bubble formation and at the onset of inertial cavitation were recorded and subsequently correlated with the acoustic parameters. Experimental data showed that low frequencies are more effective in forming and collapsing a bubble. Additionally, as the size …

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