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Articles 1381 - 1410 of 2906

Full-Text Articles in Physical Sciences and Mathematics

Facile Synthesis And Improved Pore Structure Characterization Of Mesoporous Γ-Alumina Catalyst Supports With Tunable Pore Size, Baiyu Huang Mar 2013

Facile Synthesis And Improved Pore Structure Characterization Of Mesoporous Γ-Alumina Catalyst Supports With Tunable Pore Size, Baiyu Huang

Theses and Dissertations

Mesoporous γ-alumina is the most extensively used catalysts support in a wide range of catalytic processes. The usefulness of γ-alumina relies on its favorable combination of physical, textural, thermal, and chemical properties. Pore structure properties are among the most important properties, since high surface area and large pore volume enable higher loading of active catalytic phases, while design of pore size and pore size distribution is critical to optimize pore diffusional transport and product selectivity. In addition, accurate determination of surface area (SA), pore volume (PV) and pore size distribution (PSD) of porous supports, catalysts, and nanomaterials is vital to …

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Experimental Analysis Of Energy-Based Acoustic Arrays For Measurement Of Rocket Noise Fields, Jarom Henry Giraud Mar 2013

Experimental Analysis Of Energy-Based Acoustic Arrays For Measurement Of Rocket Noise Fields, Jarom Henry Giraud

Theses and Dissertations

Microphone arrays are useful for measuring acoustic energy quantities (e.g. acoustic intensity) in the near-field of a full-scale solid rocket motor. Proper characterization of a rocket plume as a noise source will allow for more accurate predictions in engineering models that design for protection of structures, payloads and personnel near the rockets. Acoustic intensity and energy density quantities were measured in three rocket noise fields and have shown that the apparent source region of the rocket becomes smaller and moves upstream as frequency increases. Theoretical results accounting for some scattering and finite-difference errors arising in these types of energy-based measurements …

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Face Tracking User Interfaces Using Vision-Based Consumer Devices, Norman Villaroman Mar 2013

Face Tracking User Interfaces Using Vision-Based Consumer Devices, Norman Villaroman

Theses and Dissertations

Some individuals have difficulty using standard hand-manipulated input devices such as a mouse and a keyboard effectively. For such users who at the same time have sufficient control over face and head movement, a robust perceptual or vision-based user interface that can track face movement can significantly help them. Using vision-based consumer devices makes such a user interface readily available and allows its use to be non-intrusive. Designing this type of user interface presents some significant challenges particularly with accuracy and usability. This research investigates such problems and proposes solutions to create a usable and robust face tracking user interface …

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Online Survey System For Image-Based Clinical Guideline Studies Using The Delphi Method, Todd Martin Harper Mar 2013

Online Survey System For Image-Based Clinical Guideline Studies Using The Delphi Method, Todd Martin Harper

Theses and Dissertations

The increasing use of health information technology (HIT) is due to a rising interest in improving the quality of health care. HIT has the potential to reduce cost and transform services. Proper clinical support systems will contribute to the meaningful use of HIT systems by providing a wide array of data to clinicians for the diagnosis and treatments. Clinical guidelines, created by a consensus of experts, can be put in place to assist physicians in making clinical decisions. Delphi methods are commonly used to create consensus from surveys completed by a team of experts. Image-based studies could create guidelines that …

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Resorcinarene-Based Cavitands: From Structural Design And Synthesis To Separations Applications, Na Li Mar 2013

Resorcinarene-Based Cavitands: From Structural Design And Synthesis To Separations Applications, Na Li

Theses and Dissertations

Resorcinarenes are cyclic tetramers that are synthesized by the condensation of resorcinol and various aldehydes. The upper and lower rims can be modified with substituents that provide specific selectivity and other chemical features. In this work, resorcinarene-based macrocyclic ligands with specific selectivities have been designed, synthesized and applied to chiral amine discrimination and transition metal ion separations.These resorcinarenes fall into two categories. In the first type, the upper rims of resorcinarenes were modified with amino acid groups, including chiral alanine groups. The lower rims were modified with --CH3, or --C11H23 groups. The structures were studied by nuclear magnetic resonance (NMR), …

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Toward A Better Understanding Of Recent Warming Of The Central West Antarctic Ice Sheet From Shallow Firn Cores, Jessica Williams Mar 2013

Toward A Better Understanding Of Recent Warming Of The Central West Antarctic Ice Sheet From Shallow Firn Cores, Jessica Williams

Theses and Dissertations

Previous studies have shown significant warming through the 1990s in the West Antarctic Ice Sheet (WAIS); but the records used in those studies end in early 2000, preventing trend analysis into the latest decade. Fourteen new snowpits and firn cores were collected in 2010 and 2011, which have been combined with previous cores to extend the isotopic records over WAIS. Significance of these isotopic patterns across WAIS was determined and is used to re-evaluate the warming of the West Antarctic interior over recent decades. We find that isotopic records longer than 50 years are needed to assess climate trends due …

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Character Tables Of Metacyclic Groups, Dane Christian Skabelund Mar 2013

Character Tables Of Metacyclic Groups, Dane Christian Skabelund

Theses and Dissertations

We show that any two split metacyclic groups with the same character tables are isomorphic. We then use this to show that among metacyclic groups that are either 2-groups or are of odd order divisible by at most two primes, that the dihedral and generalized quaternion groups of order 2^n, n = 3, are the only pairs that have the same character tables.

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A Hierarchical Multi-Output Nearest Neighbor Model For Multi-Output Dependence Learning, Richard Glenn Morris Mar 2013

A Hierarchical Multi-Output Nearest Neighbor Model For Multi-Output Dependence Learning, Richard Glenn Morris

Theses and Dissertations

Multi-Output Dependence (MOD) learning is a generalization of standard classification problems that allows for multiple outputs that are dependent on each other. A primary issue that arises in the context of MOD learning is that for any given input pattern there can be multiple correct output patterns. This changes the learning task from function approximation to relation approximation. Previous algorithms do not consider this problem, and thus cannot be readily applied to MOD problems. To perform MOD learning, we introduce the Hierarchical Multi-Output Nearest Neighbor model (HMONN) that employs a basic learning model for each output and a modified nearest …

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Toward Scalable Human Interaction With Bio-Inspired Robot Teams, Daniel Sundquist Brown Mar 2013

Toward Scalable Human Interaction With Bio-Inspired Robot Teams, Daniel Sundquist Brown

Theses and Dissertations

Bio-inspired swarming behaviors provide an effective decentralized way of coordinating robot teams. However, as robot swarms increase in size, bandwidth and time constraints limit the number of agents a human can communicate with and control. To facilitate scalable human interaction with large robot swarms it is desirable to monitor and influence the collective behavior of the entire swarm through limited interactions with a small subset of agents. However, it is also desirable to avoid situations where a small number of agent failures can adversely affect the collective behavior of the swarm. We present a bio-inspired model of swarming that exhibits …

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A Classification Tool For Predictive Data Analysis In Healthcare, Mason Lemoyne Victors Mar 2013

A Classification Tool For Predictive Data Analysis In Healthcare, Mason Lemoyne Victors

Theses and Dissertations

Hidden Markov Models (HMMs) have seen widespread use in a variety of applications ranging from speech recognition to gene prediction. While developed over forty years ago, they remain a standard tool for sequential data analysis. More recently, Latent Dirichlet Allocation (LDA) was developed and soon gained widespread popularity as a powerful topic analysis tool for text corpora. We thoroughly develop LDA and a generalization of HMMs and demonstrate the conjunctive use of both methods in predictive data analysis for health care problems. While these two tools (LDA and HMM) have been used in conjunction previously, we use LDA in a …

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The Characterization Of Military Aircraft Jet Noise Using Near-Field Acoustical Holography Methods, Alan Thomas Wall Mar 2013

The Characterization Of Military Aircraft Jet Noise Using Near-Field Acoustical Holography Methods, Alan Thomas Wall

Theses and Dissertations

The noise emissions of jets from full-scale engines installed on military aircraft pose a significant hearing loss risk to military personnel. Noise reduction technologies and the development of operational procedures that minimize noise exposure to personnel are enhanced by the accurate characterization of noise sources within a jet. Hence, more than six decades of research have gone into jet noise measurement and prediction. In the past decade, the noise-source visualization tool near-field acoustical holography (NAH) has been applied to jets. NAH fits a weighted set of expansion wave functions, typically planar, cylindrical, or spherical, to measured sound pressures in the …

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Cliff Walls: Threats To Validity In Empirical Studies Of Open Source Forges, Landon James Pratt Feb 2013

Cliff Walls: Threats To Validity In Empirical Studies Of Open Source Forges, Landon James Pratt

Theses and Dissertations

Artifact-based research provides a mechanism whereby researchers may study the creation of software yet avoid many of the difficulties of direct observation and experimentation. Open source software forges are of great value to the software researcher, because they expose many of the artifacts of software development. However, many challenges affect the quality of artifact-based studies, especially those studies examining software evolution. This thesis addresses one of these threats: the presence of very large commits, which we refer to as "Cliff Walls." Cliff walls are a threat to studies of software evolution because they do not appear to represent incremental development. …

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Optimized Simulation Of Granular Materials, Seth R. Holladay Feb 2013

Optimized Simulation Of Granular Materials, Seth R. Holladay

Theses and Dissertations

Visual effects for film and animation often require simulated granular materials, such as sand, wheat, or dirt, to meet a director's needs. Simulating granular materials can be time consuming, in both computation and labor, as these particulate materials have complex behavior and an enormous amount of small-scale detail. Furthermore, a single cubic meter of granular material, where each grain is a cubic millimeter, would contain a billion granules, and simulating all such interacting granules would take an impractical amount of time for productions. This calls for a simplified model for granular materials that retains high surface detail and granular behavior …

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An Optimized R5rs Macro Expander, Sean P. Reque Feb 2013

An Optimized R5rs Macro Expander, Sean P. Reque

Theses and Dissertations

Macro systems allow programmers abstractions over the syntax of a programming language. This gives the programmer some of the same power posessed by a programming language designer, namely, the ability to extend the programming language to meet the needs of the programmer. The value of such systems has been demonstrated by their continued adoption in more languages and platforms. However, several barriers to widespread adoption of macro systems still exist. The language Racket defines a small core of primitive language constructs, including a powerful macro system, upon which all other features are built. Because of this design, many features of …

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Animating Non-Rigid Bodies Using Motion Capture, Jie Long Jan 2013

Animating Non-Rigid Bodies Using Motion Capture, Jie Long

Theses and Dissertations

Simulating the motion of a non-rigid body under external forces is a difficult problem because of the complexity and flexibility of the non-rigid geometry and its associated dynamics. Physically based animation of objects moving in the wind is computationally expensive, so simulation-based approaches oversimplify the model by ignoring important effects, such as tree's sheltering. Motion capture records actual responses of a non-rigid body to external forces and helps solve these problems. Mainly focusing on natural trees and ropes as instances of non-rigid bodies, we present a new approach to building motion for objects in wind using incomplete motion capture data …

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Metallization Of Dna And Dna Origami Using A Pd Seeding Method, Yanli Geng Jan 2013

Metallization Of Dna And Dna Origami Using A Pd Seeding Method, Yanli Geng

Theses and Dissertations

In this dissertation, I developed a Pd seeding method in association with electroless plating, to successfully metallize both lambda DNA and DNA origami templates on different surfaces. On mica surfaces, this method offered a fast, simple process, and the ability to obtain a relatively high yield of metallized DNA nanostructures. When using lambda DNA as the templates, I studied the effect of Pd(II) activation time on the seed height and density, and an optimal activation time between 10 and 30 min was obtained. Based on the Pd seeds formed on DNA, as well as a Pd electroless plating solution, continuous …

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Cell Speed Is Independent Of Force In A Mathematical Model Of Amoeboidal Cell Motion With Random Switching Terms., J. C. Dallon, Emily J. Evans, Christopher Grant, William V. Smith Jan 2013

Cell Speed Is Independent Of Force In A Mathematical Model Of Amoeboidal Cell Motion With Random Switching Terms., J. C. Dallon, Emily J. Evans, Christopher Grant, William V. Smith

Faculty Publications

In this paper the motion of a single cell is modeled as a nucleus and multiple integrin based adhesion sites. Numerical simulations and analysis of the model indicate that when the stochastic nature of the adhesion sites is a memoryless and force independent random process, the cell speed is independent of the force these adhesion sites exert on the cell. Furthermore, understanding the dynamics of the attachment and detachment of the adhesion sites is key to predicting cell speed. We introduce a differential equation describing the cell motion and then introduce a conjecture about the expected drift of the cell, …

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Versatile Rb Vapor Cells With Long Lifetimes, John F. Hulbert, Matthieu Giraud-Carrier, Tom Wall, Aaron R. Hawkins, Scott D. Bergeson, Jennifer Black, Holger Schmidt Jan 2013

Versatile Rb Vapor Cells With Long Lifetimes, John F. Hulbert, Matthieu Giraud-Carrier, Tom Wall, Aaron R. Hawkins, Scott D. Bergeson, Jennifer Black, Holger Schmidt

Faculty Publications

The authors report on an approach to the construction of long-lasting rubidium atomic vapor cells. The method uses pinch-off copper cold-welds, low temperature solders, and electroplated copper to create long-lasting hermetic seals between containment chambers of dissimilar geometries and materials. High temperature epoxy, eutectic lead/tin solder, and indium solder were considered as sealing materials. These seals were analyzed using accelerated lifetime testing techniques. Vapor cells with epoxy and bare metal solder seals had a decrease in the rubidium atomic density within days after being heated to elevated temperatures. They also exhibited broadened spectra as a result of rubidium reacting with …

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A Force Based Model Of Individual Cell Migration With Discrete Attachment Sites And Random Switching Terms, J. C. Dallon, Matthew Scott, William V. Smith Jan 2013

A Force Based Model Of Individual Cell Migration With Discrete Attachment Sites And Random Switching Terms, J. C. Dallon, Matthew Scott, William V. Smith

Faculty Publications

A force based model of cell migration is presented which gives new insight into the importance of the dynamics of cell binding to the substrate. The main features of the model are the focus on discrete attachment dynamics, the treatment of the cellular forces as springs, and an incorporation of the stochastic nature of the attachment sites. One goal of the model is to capture the effect of the random binding and unbinding of cell attachments on global cell motion. Simulations reveal one of the most important factor influencing cell speed is the duration of the attachment to the substrate. …

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Limit Of Strong Ion Coupling Due To Electron Shielding, M. Lyon, Scott D. Bergeson, M. S. Murillo Jan 2013

Limit Of Strong Ion Coupling Due To Electron Shielding, M. Lyon, Scott D. Bergeson, M. S. Murillo

Faculty Publications

We show that strong coupling between ions in an ultracold neutral plasma is limited by electron screening. While electron screening reduces the quasiequilibrium ion temperature, it also reduces the ion-ion electrical potential energy. The net result is that the ratio of nearest-neighbor potential energy to kinetic energy in quasiequilibrium is constant and limited to approximately 1 unless the electrons are heated by some external source. We support these conclusions by reporting measurements of the ion velocity distribution in an ultracold neutral calcium plasma. These results match previously reported simulations of Yukawa systems. Theoretical considerations are used to determine the screened …

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A Comparison Of Boltzmann And Gibbs Definitions Of Microcanonical Entropy For Small Systems, Randall B. Shirts Dec 2012

A Comparison Of Boltzmann And Gibbs Definitions Of Microcanonical Entropy For Small Systems, Randall B. Shirts

Faculty Publications

Two different definitions of entropy, S= klnW, in the microcanonical ensemble have been competing for over 100 years. The Boltzmann/Planck definition is that W is the number of states accessible to the system at its energy E (also called the surface entropy). The Gibbs/Hertz definition is that W is the number of states of the system up to the energy E (also called the volume entropy). These two definitions agree for large systems but differ by terms of order N-1 for small systems, where N is the number of particles in the system. For three analytical …

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Investigation Of Low-Stress Silicon Nitride As A Replacement Material For Beryllium X-Ray Windows, David B. Brough Dec 2012

Investigation Of Low-Stress Silicon Nitride As A Replacement Material For Beryllium X-Ray Windows, David B. Brough

Theses and Dissertations

The material properties of low stress silicon nitride make it a possible replacement material for beryllium in X-ray windows. In this study, X-ray windows made of LPCVD deposited low stress silicon nitride are fabricated and characterized. The Young's modulus of the LPCVD low stress silicon nitride are characterized and found to be 226±23 GPa. The residual stress is characterized using two different methods and is found to be 127±25 MPa and 141±0.28 MPa. Two support structure geometries for the low stress silicon nitride X-ray windows are used. X-ray windows with thicknesses of 100 nm and 200 nm are suspended on …

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Thin Films Of Carbon Nanotubes And Nanotube/Polymer Composites, Anthony D. Willey Dec 2012

Thin Films Of Carbon Nanotubes And Nanotube/Polymer Composites, Anthony D. Willey

Theses and Dissertations

A method is described for ultrasonically spraying thin films of carbon nanotubes that have been suspended in organic solvents. Nanotubes were sonicated in N-Methyl-2-pyrrolidone or N-Cyclohexyl-2-pyrrolidone and then sprayed onto a heated substrate using an ultrasonic spray nozzle. The solvent quickly evaporated, leaving a thin film of randomly oriented nanotubes. Film thickness was controlled by the spray time and ranged between 200-500 nm, with RMS roughness of about 40 nm. Also described is a method for creating thin (300 nm) conductive freestanding nanotube/polymer composite films by infiltrating sprayed nanotube films with polyimide.

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Comparing Theory And Experiment For Analyte Transport In The First Vacuum Stage Of The Inductively Coupled Plasma Mass Spectrometer, Matthew R. Zachreson Dec 2012

Comparing Theory And Experiment For Analyte Transport In The First Vacuum Stage Of The Inductively Coupled Plasma Mass Spectrometer, Matthew R. Zachreson

Theses and Dissertations

The Direct Simulation Monte Carlo algorithm as coded in FENIX is used to model the transport of trace ions in the first vacuum stage of the inductively coupled plasma mass spectrometer. Haibin Ma of the Farnsworth group at Brigham Young University measured two radial trace density profiles: one 0.7 mm upstream of the sampling cone and the other 10 mm downstream. We compare simulation results from FENIX with the experimental results. We find that gas dynamic convection and diffusion are unable to account for the experimentally-measured profile changes from upstream to downstream. Including discharge quenching and ambipolar electric fields, however, …

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Modeling Radial Bernstein Modes In A Finite-Length Axisymmetric Non-Neutral Plasma, Mark Andrew Hutchison Dec 2012

Modeling Radial Bernstein Modes In A Finite-Length Axisymmetric Non-Neutral Plasma, Mark Andrew Hutchison

Theses and Dissertations

Axisymmetric radial Bernstein modes are known to exist in non-neutral plasmas and have been studied theoretically and computationally in 1D, but detection of these modes has still proven to be difficult due to self-shielding. To help advance the work on this front we created a 2D particle-in-cell (PIC) code that simulates a non-neutral plasma in a Malmberg-Penning trap. A detailed description of the PIC code itself has been included that highlights the benefits of using an $r^2$--$z$ grid and how it can be tested. The focus of the PIC simulation was to discover how best to drive and detect these …

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Advanced Numerical Methods In General Relativistic Magnetohydrodynamics, Michael J. Besselman Dec 2012

Advanced Numerical Methods In General Relativistic Magnetohydrodynamics, Michael J. Besselman

Theses and Dissertations

We show our work to refine the process of evolutions in general relativistic magnetohydrodynamics. We investigate several areas in order to improve the overall accuracy of our results. We test several versions of conversion methodologies between different sets of variables. We compare both single equation and two equations solvers to do the conversion. We find no significant improvement for multiple equation conversion solvers when compared to single equation solvers. We also investigate the construction of initial data and the conversion of coordinate systems between initial data code and evolution code. In addition to the conversion work, we have improved some …

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Website Adaptive Navigation Effects On User Experiences, James C. Speirs Dec 2012

Website Adaptive Navigation Effects On User Experiences, James C. Speirs

Theses and Dissertations

The information search process within a website can often be frustrating and confusing for website visitors. Navigational structures are often complex and multitiered, hiding links with several layers of navigation that user's might be interested in. Poor navigation causes user frustration. Adaptive navigation can be used to improve the user's navigational experience by flattening the navigational structure and reducing the number of accessible links to only those that the user would be interested in. This examines the effects on a user's navigational experience, of using adaptive navigation as the main navigational structure on a website. This study measured these effects …

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Microfluidic Devices With Integrated Sample Preparation For Improved Analysis Of Protein Biomarkers, Pamela Nsang Nge Dec 2012

Microfluidic Devices With Integrated Sample Preparation For Improved Analysis Of Protein Biomarkers, Pamela Nsang Nge

Theses and Dissertations

Biomarkers present a non-invasive means of detecting cancer because they can be obtained from body fluids. They can also be used for prognosis and assessing response to treatment. To limit interferences it is essential to pretreat biological samples before analysis. Sample preparation methods include extraction of analyte from an unsuitable matrix, purification, concentration or dilution and labeling. The many advantages offered by microfluidics include portability, speed, automation and integration. Because of the difficulties encountered in integrating this step in microfluidic devices most sample preparation methods are often carried out off-chip. In the fabrication of micro-total analysis systems it is important …

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Researching Effective Methods For Teaching The Phases Of The Moon, Heather Patti Jones Dec 2012

Researching Effective Methods For Teaching The Phases Of The Moon, Heather Patti Jones

Theses and Dissertations

This study investigated the effectiveness of commonly used instructional methods for teaching the phases of the Moon to fifth and sixth grade students. The instructional methods investigated were the use of diagrams, animations, and models. The effectiveness of each method was tested by measuring students' understanding of Moon phases with a pre and post-assessment after receiving instruction with a specific method or combination of methods. These methods were then evaluated for their ability to help students learn essential concepts, reinforce relevant vocabulary and discourage misconceptions. Results showed that students had better scores with less prevalence of misconception when they were …

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Necessary And Sufficient Informativity Conditions For Robust Network Reconstruction Using Dynamical Structure Functions, Vasu Nephi Chetty Dec 2012

Necessary And Sufficient Informativity Conditions For Robust Network Reconstruction Using Dynamical Structure Functions, Vasu Nephi Chetty

Theses and Dissertations

Dynamical structure functions were developed as a partial structure representation of linear time-invariant systems to be used in the reconstruction of biological networks. Dynamical structure functions contain more information about structure than a system's transfer function, while requiring less a priori information for reconstruction than the complete computational structure associated with the state space realization. Early sufficient conditions for network reconstruction with dynamical structure functions severely restricted the possible applications of the reconstruction process to networks where each input independently controls a measured state. The first contribution of this thesis is to extend the previously established sufficient conditions to incorporate …

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