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Articles 4171 - 4200 of 4850

Full-Text Articles in Engineering

Interior Node Projection Techniques In Sweeping Algorithms, Michael Andrew Scott Nov 2005

Interior Node Projection Techniques In Sweeping Algorithms, Michael Andrew Scott

Theses and Dissertations

The enhancement of node projection techniques in sweeping is the subject of this thesis. Sweeping is a method used to produce all-hexahedral finite element meshes on certain classes of geometry. The placement of nodes in the interior of the geometry during the sweeping process remains a difficult problem. This thesis presents advancements in this area which improve the speed of the algorithm and the resulting element quality. A comparison of existing projection methods was performed. The existing Faceted projection sweeping method was extended to be applicable to more general classes of sweepable geometry. This comparison and extension of node projection …

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A Gasless Method Of Spraying Thermoplastic Resin, Dan T. Rogers Nov 2005

A Gasless Method Of Spraying Thermoplastic Resin, Dan T. Rogers

Theses and Dissertations

This spraying method for thermoplastic resins is a new manufacturing process for applying thermoplastics to a mold or surface in an efficient way that has the potential of reducing cycle time. Spraying thermoplastic resins is similar to spraying other polymers, such as paint, with the differences being higher pressure and temperature. This method uses an injection molding machine with a modified nozzle to spray the plastic material. In this study, temperature, pressure, and nozzle size were factors that influenced the success of this spraying method. The method of spraying in this study proved spraying without a gas is possible, a …

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Object Oriented Cae Software For The Exploration And Design Of Microstructures, Stephen D. Sintay Nov 2005

Object Oriented Cae Software For The Exploration And Design Of Microstructures, Stephen D. Sintay

Theses and Dissertations

Through the use of generalized spherical harmonic basis functions a spectral representation is used to model the microstructure of cubic materials. This model is then used to predict the macroscopic elastic and plastic properties of materials with cubic crystal symmetry and various sample symmetry including triclinic and axial—symmetric. Building on the work of citeN{Barnett-FractureMechanics} the influence that anisotropy has on the fatigue response of the material is also modeled. This is accomplished through using the effective elastic stiffness tensor in the computation of crack extension force G. The resulting material model and macroscopic property calculations are the foundation for …

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Mpsa Effects On Copper Electrodeposition: Understanding Molecular Behavior At The Electrochemical Interface, Clint Gordon Guymon Nov 2005

Mpsa Effects On Copper Electrodeposition: Understanding Molecular Behavior At The Electrochemical Interface, Clint Gordon Guymon

Theses and Dissertations

In this work the structure of the electrochemical metal-liquid interface is determined through use of quantum mechanics, molecular simulation, and experiment. Herein are profiled the molecular dynamics details and results of solid-liquid interfaces at flat non-specific solid surfaces and copper metal electrodes. Ab initio quantum-mechanical calculations are reported and define the interatomic potentials in the simulations. Some of the quantum-mechanical calculations involve small copper clusters interacting with 3-mercaptopropanesulfonic acid (MPSA), sodium, chloride, bisulfate and cuprous ions. In connection with these I develop the electrode charge dynamics (ECD) routine to treat the charge mobility in a metal. ECD bridges the gap …

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Recovery Of The Grain Boundary Character Distribution Through Oblique Double-Sectioning, Brent L. Adams, David T. Fullwood, E. R. Homer Nov 2005

Recovery Of The Grain Boundary Character Distribution Through Oblique Double-Sectioning, Brent L. Adams, David T. Fullwood, E. R. Homer

Faculty Publications

This work was supported primarily by the MRSEC program of the National Science Foundation under DMR-0079996. A method for the retrieval of the complete grain boundary character distribution by oblique double-sectioning is proposed. The method, which is similar to the recovery of the orientation distribution from sets of incomplete pole-figures, is efficient and provides many advantages as compared to calibrated serial sectioning. As compared to standard stereological approaches, the new methodology retains the advantage of direct measurement of the grain boundary inclination parameters. Solutions to the fundamental equation of oblique double-sectioning are provided in the Fourier space, and some specifics …

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Global Finish Curvature Matched Machining, Jianguo Wang Nov 2005

Global Finish Curvature Matched Machining, Jianguo Wang

Theses and Dissertations

As competition grows among manufacturing companies, greater emphasis has recently been placed on product aesthetics and decreasing the product development time. This is promoting and standardizing widespread use of sculptured surface styling within product design. Therefore, industries are looking for high efficiency machining strategies for sculptured surface machining (SSM). Many researchers have produced various methods in tool path generation for SSM. Five-axis curvature matched machining (CM2) is the most efficient. With the widespread use of 5-axis mill in industries, CM2 is a better solution for improving the machining efficiency for product concept models. CM2 has very good performance for global …

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A Provacative Test To Determine Brain Compliance In The Management Of Patients With Hydrocephalus, Preston K. Manwaring Nov 2005

A Provacative Test To Determine Brain Compliance In The Management Of Patients With Hydrocephalus, Preston K. Manwaring

Theses and Dissertations

Non-invasive techniques to explore intracranial compliance and pressure have been extensively explored in recent years. Previous techniques have used expensive technologies to make these measurements, often with difficulty. We present a novel, inexpensive provocative test to observe trends in intracranial compliance measurement targeted towards the treatment and management of hydrocephalus. Two techniques are proposed which derive data from the digital and supraorbital arteries as well as tympanic membrane displacement. This requires the use of two photo-plethysmographic sensors and a TMD sensor. A common tilt table apparatus is used to methodically and artificially increase intracranial pressure to stress the cranial system …

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High Voltage Analog Design In A Standard Digital Cmos Process, Riley D. Beck Nov 2005

High Voltage Analog Design In A Standard Digital Cmos Process, Riley D. Beck

Theses and Dissertations

This thesis introduces high-voltage approaches that are implemented in an analog Hall-effect sensor interface. This interface has been realized in a modified 5V 0.6um CMOS process using 40V high-voltage MOS transistors that do not affect low-voltage device functionality. These circuits include a high-voltage, low-offset current sense amplifier, which achieves a common-mode input range that is within a Vtp of Vdd using a bulk-driven differential input stage. The amplifier also uses high voltage cascode devices to protect low-voltage devices that have been placed in critical matching areas to achieve a low input offset voltage of 500uV without the use of trim. …

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Highly Efficient Fluorescence Detection In Picoliter Volume Liquid-Core Waveguides, Aaron R. Hawkins, John P. Barber, Dongliang Yin Nov 2005

Highly Efficient Fluorescence Detection In Picoliter Volume Liquid-Core Waveguides, Aaron R. Hawkins, John P. Barber, Dongliang Yin

Faculty Publications

We report loss improvement and fluorescence detection in integrated antiresonant reflecting optical waveguides with liquid cores. The minimum waveguide loss is reduced to 0.33/cm by compensating for thickness variations in the fabrication process. We demonstrate fluorescence detection from as few as 490 molecules in a 57 pl core using these optimized waveguides. We measure angular fluorescence collection factors as high as 15% per facet in good agreement with theory. This demonstrates the potential of integrated hollow-core waveguides as optical sensors for single-molecule spectroscopy.

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Effects Of Reclaimed Asphalt Pavement On Mechanical Properties Of Base Materials, Dane A. Cooley Nov 2005

Effects Of Reclaimed Asphalt Pavement On Mechanical Properties Of Base Materials, Dane A. Cooley

Theses and Dissertations

Reuse of reclaimed asphalt pavement (RAP) in the full-depth recycling (FDR) process is a cost-effective and environmentally responsible method of asphalt pavement reconstruction. Although FDR has been used for several years in some locations, the effect of RAP on the mechanical properties of recycled base materials has not been well documented. The purpose of this research was to investigate the influence of RAP on the mechanical properties of recycled base materials typical of northern Utah. Two sources of RAP, two sources of base, and RAP contents of 0, 25, 50, 75, and 100 percent were utilized in a full-factorial experimental …

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Array Analysis Of Radio Frequency Interference Cancelation Requirements For A Land Mine Detection System, Devin Baker Pratt Nov 2005

Array Analysis Of Radio Frequency Interference Cancelation Requirements For A Land Mine Detection System, Devin Baker Pratt

Theses and Dissertations

Land mines are a major humanitarian problem with millions of active mines in place around the world. Since these mines can have little metal in them, novel detection techniques are needed. Nuclear Quadrupole Resonance (NQR) is one such technique. Unfortunately, NQR is highly succeptible to radio frequency interference (RFI). A significant contribution of this thesis is the development of a custom, experimental data acquisition system designed and built specifically for capturing RFI at frequencies significant to NQR land mine detection systems. Another major contribution is the development of data analysis techniques for determining the number of reference antennas required to …

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Development Of Commercial Applications For Recycled Plastics Using Finite Element Analysis, Nanjunda Narasimhamurthy Nov 2005

Development Of Commercial Applications For Recycled Plastics Using Finite Element Analysis, Nanjunda Narasimhamurthy

Theses and Dissertations

This thesis investigates the suitability of thermo-kinetically recycled plastics for use in commercial product applications using finite element analysis and statistics. Different recycled material blends were tested and evaluated for their use in commercial product applications. There are six different blends of thermo-kinetically recycled plastics used for testing and CATIA is used for finite element analysis. The different types of thermo-kinetically recycled plastics blends are: pop bottles made of PolyethyleneTeraphthalate (PET), milk jugs made of High-Density Polyethylene (HDPE), Vinyl seats made of Poly Vinyl Chloride (PVC) and small amount of Polypropylene (PP) and Urethane, electronic scrap made of engineering resins …

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Piezoresistive Sensing Of Bistable Micro Mechansim State, Jeffrey K. Anderson Nov 2005

Piezoresistive Sensing Of Bistable Micro Mechansim State, Jeffrey K. Anderson

Theses and Dissertations

The objective of this work is to demonstrate the feasibility of on-chip sensing of bistable mechanism state using the piezoresistive properties of polysilicon, thus eliminating the need for electrical contacts. Changes in position are detected by observing changes in resistance across the mechanism. Sensing the state of bistable mechanisms is critical in their various applications. The research in this thesis advances the modeling techniques of MEMS devices which use piezoresistivity for position sensing. A fully compliant bistable micro mechanism was designed, fabricated, and tested to demonstrate the feasibility of this sensing technique. Testing results from two fabrication processes, Fairchild's SUMMiT …

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Evolution Of Turbine Blade Deposits In An Accelerated Deposition Facility: Roughness And Thermal Analysis, James Edward Wammack Nov 2005

Evolution Of Turbine Blade Deposits In An Accelerated Deposition Facility: Roughness And Thermal Analysis, James Edward Wammack

Theses and Dissertations

During the operation of a gas turbine, ingested contaminants present in the air form deposits on the surfaces of the turbine blades. These deposits grow over time, resulting in an increasingly rough surface. This gradual increase in roughness results in several negative consequences, among which is an increase in the rate of heat transfer to the blade which shortens blade life. This thesis presents research in which deposits were evolved on three different turbine blade coupons and their evolution was studied. A trend in roughness change over time was discovered. Also, an attempt was made to find the effect of …

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An Automated Three-Dimensional Unstructured Mesh Generation Algorithm For Groundwater Modeling, James Edward Greer Nov 2005

An Automated Three-Dimensional Unstructured Mesh Generation Algorithm For Groundwater Modeling, James Edward Greer

Theses and Dissertations

This thesis describes a new method to create three-dimensional finite element meshes using the horizons to mesh algorithm. The algorithm uses available geologic data and user-defined inputs to guide the mesh generation process. This new approach allows for material layer pinch outs and many different layer refinement options to create well-formed elements that better represent hydrogeologic formations. Two case studies are presented that demonstrate the application of the algorithm's options and capabilities. A graphical interface for the algorithm was developed in the Groundwater Modeling System.

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Methodology For Determining The Variance Of The Taylor Factor: Application In Fe-3%Si, Craig P. Przybyla Nov 2005

Methodology For Determining The Variance Of The Taylor Factor: Application In Fe-3%Si, Craig P. Przybyla

Theses and Dissertations

The variance of the Taylor factor due to variations in the microstructure and window size is explored using both a random sampling method and a previously developed statistical relationship. The results from the random sampling method correlated well with the statistical variance relationship when the magnitude of the variance was greater than that of the numerical errors observed in the statistical calculation. An empirical relation was developed to model the results and the constants for this relationship were determined for pseudo-three dimensional Fe-3%Si. Implementation of the statistical variance relationship in true 3D microstructures is not limited by material opacity, since …

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Grain Boundary Character Distribution In The Haz Of Friction Stir-Processed Al 7075 T7, John A. Basinger Nov 2005

Grain Boundary Character Distribution In The Haz Of Friction Stir-Processed Al 7075 T7, John A. Basinger

Theses and Dissertations

The heat affected zone (HAZ) of friction stir welded Al 7075 T7 shows diminished corrosion resistance properties when compared with the parent material. Corrosion attack in this region of the weld is primarily intergranular and is associated with the presence of precipitate free zones. Current TEM research conducted at Brigham Young University by Dr. Bin Cai finds a correlation between precipitate free zone (PFZ) width and grain boundary geometry. As both grain boundary geometry and the PFZ are associated with modes of failure in 7XXX aluminum, this paper makes a comparison of grain boundary character distributions (GBCD) in the HAZ …

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Percolation In Two-Dimensional Grain Boundary Structures And Polycrystal Property Closures, David T. Fullwood Nov 2005

Percolation In Two-Dimensional Grain Boundary Structures And Polycrystal Property Closures, David T. Fullwood

Theses and Dissertations

The thesis addresses two topics in the study of material properties as determined by the microstructure. The first topic involves percolation as a tool in relating the grain boundary structure to global properties such as fracture and corrosion resistance. The second investigates optimization techniques in order to find the space of values that properties of a material can take, from consideration of the microstructure. In part I, the applicability of standard lattice percolation models to a random 2-D grain structure is explored. A random network based on the triangle lattice is proposed as a more appropriate model, and results in …

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Social Utility Functions-Part Ii: Applications, Wynn C. Stirling, Richard L. Frost Nov 2005

Social Utility Functions-Part Ii: Applications, Wynn C. Stirling, Richard L. Frost

Faculty Publications

Social utilities account for agent preferences and, thus, can characterize complex interrelationships, such as cooperation, compromise, negotiation, and altruism, that can exist between agents. Satisficing game theory, which is based on social utilities, offers a framework within which to design sophisticated multiagent systems. Key features of this approach are: a) an N-agent system may be represented by a 2N-dimensional Bayesian network, called a praxeic network; b) the theory accommodates a notion of situational altruism (a willingness to defer to others in a controlled way if so doing would actually benefit others under the condition that others wish to take advantage …

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A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell Nov 2005

A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell

Faculty Publications

This paper presents the compliant contact-aided revolute (CCAR) joint, a planar mechanism capable of performing the functions of a bearing and a spring. The pseudo-rigid-body model is used to predict the behavior of the CCAR joint, and this model is validated through the use of finite element analysis and prototype testing. The CCAR joint is shown to have high maximum rotation and lateral stiffness. A case study is presented, and manufacturing considerations are discussed for the macro, meso, and micro scales.

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A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell Nov 2005

A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell

Faculty Publications

This paper presents the compliant contact-aided revolute (CCAR) joint, a planar mechanism capable of performing the functions of a bearing and a spring. The pseudo-rigid-body model is used to predict the behavior of the CCAR joint, and this model is validated through the use of finite element analysis and prototype testing. The CCAR joint is shown to have high maximum rotation and lateral stiffness. A case study is presented, and manufacturing considerations are discussed for the macro, meso, and micro scales.

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Social Utility Functions-Part I: Theory, Wynn C. Stirling Nov 2005

Social Utility Functions-Part I: Theory, Wynn C. Stirling

Faculty Publications

The dominant approaches to utility-based multiagent decision theory rely on the premise of individual rationality-the doctrine that each individual is committed to achieving the best outcome for itself, regardless of the effect doing so has on others. This fundamentally asocial concept is the basis of conventional von Neumann-Morgenstern (vN-M) utilities but is inadequate to characterize truly cooperative artificial systems. Social utility functions differ from conventional vN-M utilities in that they are functions of multiple decision-maker preferences, rather than actions, and thus permit individuals to expand their spheres of interest beyond the self. A logical basis for coherent reasoning in multiagent …

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Properties Model For Aqueous Sodium Chloride Solutions Near The Critical Point Of Water, Bing Liu Oct 2005

Properties Model For Aqueous Sodium Chloride Solutions Near The Critical Point Of Water, Bing Liu

Theses and Dissertations

Traditional excess Gibbs energy models in terms of temperature, pressure, and concentration become progressively less effective in describing the thermodynamics of aqueous solutions at temperatures above 300 ¢ªC, and are totally inadequate in the critical region of water. This deficiency is due to the strong ion association and the large property fluctuations (such as density) with small variations in pressure, temperature, and solute concentration around the critical point of water. In this work, a speciation-based model has been developed to describe the thermodynamic properties of aqueous sodium chloride solutions in the critical region of water. The anomalous fluctuation problem is …

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The Role Of Cavitation In Acoustically Activated Drug Delivery, Mario A. Diaz, Ghaleb A. Husseini, William G. Pitt, Eric S. Richardson, Douglas A. Christensen Oct 2005

The Role Of Cavitation In Acoustically Activated Drug Delivery, Mario A. Diaz, Ghaleb A. Husseini, William G. Pitt, Eric S. Richardson, Douglas A. Christensen

Faculty Publications

The triblock copolymer, Pluronic P105, has been found to be an ideal ultrasonically activated drug delivery vehicle because it forms micelles with hydrophobic polypropylene oxide cores that sequester hydrophobic drugs (Fig. 1). These micelles release their contents upon the application of low frequency ultrasound [1]such that drugs can be released specifically at the ultrasonicated region (Fig. 2). Such ultrasonically controlled release has been effective against cancer cells in vitro [2] and in vivo [3]. This poster presents our results showing that collapse cavitation is associated with drug release. Cavitation is generally divided into two types of behavior. Stable cavitation is …

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Compliant Ortho-Planar Spring Behavior Under Complex Loads, Nathan Oliver Rasmussen Sep 2005

Compliant Ortho-Planar Spring Behavior Under Complex Loads, Nathan Oliver Rasmussen

Theses and Dissertations

This thesis presents research on the feasibility of applying compliant-ortho-planar springs (COPS) to rotational applications. The primary motivation of this research is the application of COPS to a continuously variable transmission (CVT). The design space limitations, loading conditions, stresses, stress concentrations, and limitations of current design tools, such as pseudo-rigid-body models (PRBM) for COPS, are discussed. A new 3D PRBM is presented along with a discussion on the possible applications of such to a rotating COPS. Stress stiffening and lateral stability are two major phenomena occurring in a rotating COPS. Both phenomena are a direct result of the inertial loads …

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Experimental Measurements Of Longitudinal Load Distributions On Friction Stir Weld Pin Tools, Aaron L. Stahl Sep 2005

Experimental Measurements Of Longitudinal Load Distributions On Friction Stir Weld Pin Tools, Aaron L. Stahl

Theses and Dissertations

The longitudinal forces generated from the Friction Stir Welding process are substantial. An understanding of these forces is critical to proper tool design. This study describes a technique to measure the longitudinal force distribution on a friction stir weld pin tool. Total longitudinal forces were recorded on a dynamometer while welding 6061 aluminum with non-threaded pins that varied in length and diameter. A model was developed that characterizes pin force as a function of pin length and diameter. Results suggest that force generally increases with pin length, while forces remain relatively constant with pin diameter. Unexpected force variation was found …

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The Development Of A Small Scale Radio Astronomy Image Synthesis Array For Research In Radio Frequency Interference Mitigation, Jacob L. Campbell Sep 2005

The Development Of A Small Scale Radio Astronomy Image Synthesis Array For Research In Radio Frequency Interference Mitigation, Jacob L. Campbell

Theses and Dissertations

Radio astronomy synthesis imaging arrays are composed of many parabolic reflector antennas. These antennas are designed to be extremely sensitive to detect faint emissions from astronomical sources. Unfortunately, this also makes them susceptible to radio frequency interference (RFI) from man made sources such as orbiting satellites. The radio astronomy research group at Brigham Young University (BYU) is investigating methods to mitigate the effects of RFI in radio astronomy synthesis imaging. Though real-time RFI mitigation has been demonstrated for a large single dish telescope, for synthesis imaging arrays our prior work has consisted solely of algorithm development and computer simulations. To …

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Superdirectivity In Mimo Systems, Michael A. Jensen, Matthew L. Morris, Jon W. Wallace Sep 2005

Superdirectivity In Mimo Systems, Michael A. Jensen, Matthew L. Morris, Jon W. Wallace

Faculty Publications

Multiantenna systems such as devices for multiple-input-multiple-output (MIMO) communication can theoretically use array superdirectivity to optimally exploit the propagation channel. In traditional analyses of MIMO systems, such superdirectivity is not observed due to the commonly applied constraint that limits the excitation current magnitudes. However, when an electromagnetically appropriate constraint on the power radiated by the array is applied, the computed capacity can include effects of transmit superdirectivity. A similar result occurs at the receiver for spatially colored noise. This paper formulates the MIMO system capacity under these circumstances and provides a framework for computing this capacity when the level of …

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Static And Dynamic Obstacle Avoidance For Miniature Air Vehicles, Jeffery Brian Saunders, Brandon Call, Andrew Curtis, Randal W. Beard, Timothy W. Mclain Sep 2005

Static And Dynamic Obstacle Avoidance For Miniature Air Vehicles, Jeffery Brian Saunders, Brandon Call, Andrew Curtis, Randal W. Beard, Timothy W. Mclain

Faculty Publications

Small unmanned air vehicles are limited in sensor weight and power such that detection and avoidance of unknown obstacles during flight is difficult. This paper presents a low power low weight method of detection using a laser range finder. In addition, a rapidly-exploring random tree algorithm to generate waypoint paths around obstacles known a priori is presented, and a dynamic geometric algorithm to generate paths around detected obstacles is derived. The algorithms are demonstrated in simulation and in flight tests on a fixed-wing miniature air vehicle (MAV).

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Embedded Slanted Grating Coupler For Vertical Coupling Between Fibers And Silicon-On-Insulator Planar Waveguides, Gregory P. Nordin, J. Jiang, B. Wang Sep 2005

Embedded Slanted Grating Coupler For Vertical Coupling Between Fibers And Silicon-On-Insulator Planar Waveguides, Gregory P. Nordin, J. Jiang, B. Wang

Faculty Publications

We propose a compact and efficient grating coupler for vertical coupling between optical fibers and planar waveguides. A grating with a parallelogram shape is designed to be etched through the entire high-index waveguide core. The coupler is optimized using a microgenetic algorithm coupled with a two-dimensional finite-difference time-domain method. Simulations show that up to 75.8% coupling efficiency can be obtained between a single-mode fiber and a 240-nm-thick silicon-on-insulator planar waveguide.

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