Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Brigham Young University

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 2341 - 2370 of 3436

Full-Text Articles in Physical Sciences and Mathematics

Wolfcampian Development Of The Nose Of The Eastern Shelf Of The Midland Basin, Glasscock, Sterling, And Reagan Counties, Texas, Douglas S. Flamm Nov 2008

Wolfcampian Development Of The Nose Of The Eastern Shelf Of The Midland Basin, Glasscock, Sterling, And Reagan Counties, Texas, Douglas S. Flamm

Theses and Dissertations

The nose of the Eastern shelf of the Midland Basin is a prominent structural and depositional feature present in Glasscock, Sterling, and Howard counties, Texas. This feature has been expressed in many regional maps and mentioned in some literature, but has not otherwise been studied significantly. This study looks at the viability of using an acoustic impedance seismic inversion to interpret the 2nd and 3rd order sequence stratigraphy of the southern portion of the nose of the Eastern shelf along with its shelf to basin transition in Glasscock, Sterling, and Reagan counties during the Wolfcampian (Asselian-Sakmarian) time (Early Permian). The …

Go to article

Extreme-Ultraviolet Polarimeter Utilizing Laser-Generated High-Order Harmonics, Nicole Brimhall, Matthew Turner, Nicholas Herrick, David D. Allred, R. Steven Turley, Michael Ware, Justin Peatross Oct 2008

Extreme-Ultraviolet Polarimeter Utilizing Laser-Generated High-Order Harmonics, Nicole Brimhall, Matthew Turner, Nicholas Herrick, David D. Allred, R. Steven Turley, Michael Ware, Justin Peatross

Faculty Publications

We describe an extreme-ultraviolet (EUV) polarimeter that employs laser-generated high-order harmonics as the light source. The polarimeter is designed to characterize materials and thin films for use with EUV light. Laser high harmonics are highly directional with easily rotatable linear polarization, not typically available with other EUV sources. The harmonics have good wavelength coverage, potentially spanning the entire EUV from a few to a hundred nanometers. Our instrument is configured to measure reflectances from 14 to 30 nm and has ~180 spectral resolution (lambda/delta lambda). The reflection from a sample surface can be measured over a continuous range of incident …

Go to article

Using Vagueness Measures To Re-Rank Documents Retrieved By A Fuzzy Set Information Retrieval Model, Stephen Lynn, Yiu-Kai D. Ng Oct 2008

Using Vagueness Measures To Re-Rank Documents Retrieved By A Fuzzy Set Information Retrieval Model, Stephen Lynn, Yiu-Kai D. Ng

Faculty Publications

Traditional information retrieval (IR) systems evaluate user queries and retrieve/rank documents based on matching keywords in user queries with words in documents. These exact word-matching and ranking approaches ignore too many relevant documents that do not contain the exact keywords as specified in a user query. Instead of considering these traditional approaches, we propose to retrieve documents using a fuzzy set IR model and rank retrieved documents for any vague query using the “vagueness score” of the documents based on the word senses as defined in WordNet. Using the vagueness scores, we rank the most highest “relevant” documents of a …

Go to article

Scalable Multicast Routing For Ad Hoc Networks, Manoj Pandey, Daniel Zappala Oct 2008

Scalable Multicast Routing For Ad Hoc Networks, Manoj Pandey, Daniel Zappala

Faculty Publications

Routing in a mobile ad hoc network is challenging because nodes can move at any time, invalidating a previously-discovered route. Multicast routing is even more challenging, because a source needs to maintain a route to potentially many group members simultaneously. Providing scalable solutions to this problem typically requires building a hierarchy or an overlay network to reduce the cost of route discovery and maintenance. In this paper, we show that a much simpler alternative is possible, by using source specific semantics and relying on the unicast routing protocol to find all routes. This separation of concerns enables the multicast routing …

Go to article

Hop-By-Hop Multicast Transport For Mobile Ad Hoc Wireless Networks, Manoj Pandey, Daniel Zappala Oct 2008

Hop-By-Hop Multicast Transport For Mobile Ad Hoc Wireless Networks, Manoj Pandey, Daniel Zappala

Faculty Publications

Multicast transport is a challenging problem because the source must provide congestion control and reliability for a tree, rather than a single path. This problem is made even more difficult in mobile ad hoc networks due to problems caused by contention, spatial reuse, and mobility. In this paper, we design a hop-by-hop multicast transport protocol, which pushes transport functionality into the core of the network. Although this requires per-flow state, a hop-by-hop approach simplifies congestion control, enables local recovery of lost packets, and provides low delay and efficient use of wireless capacity. We use a simulation study to demonstrate the …

Go to article

Enhancement Of Unusual Color In Aerial Video Sequences For Assisting Wilderness Search And Rescue, Bryan S. Morse, Nathan D. Rasmussen, Daniel Thornton Oct 2008

Enhancement Of Unusual Color In Aerial Video Sequences For Assisting Wilderness Search And Rescue, Bryan S. Morse, Nathan D. Rasmussen, Daniel Thornton

Faculty Publications

The use of aerial video for search and surveillance has been popularized by the increased use of camera-equipped unmanned aerial vehicles. For many search applications, objects may also be missed by observers due to their small size, brief visibility, or the inherent monotony of the scene. This paper presents a novel method for automatically emphasizing unusually colored objects to improve their detectability. We use a hue histogram and a local saliency measure to find unusually colored objects, then boost the saturation of these objects while desaturating more common colors, thus drawing the observer’s attention and facilitating video search.

Go to article

Autonomous And Intelligent Radio Switching For Heterogeneous Wireless Networks, Qiuyi Duan, Charles D. Knutson, Lei Wang, Daniel Zappala Sep 2008

Autonomous And Intelligent Radio Switching For Heterogeneous Wireless Networks, Qiuyi Duan, Charles D. Knutson, Lei Wang, Daniel Zappala

Faculty Publications

As wireless devices continue to become more prevalent, heterogeneous wireless networks - in which communicating devices have at their disposal multiple types of radios - will become the norm. Communication between nodes in these networks ought to be as simple as possible; they should be able to seamlessly switch between different radios and network stacks on the fly in order to better serve the user. To make this a possibility, we consider the challenging problems of when two communicating devices should decide to switch to a different radio, and which radio they should choose. We design an Autonomous and Intelligent …

Go to article

Improving Live Sequence Chart To Automata Transformation For Verification, Rahul Kumar, Eric G. Mercer Aug 2008

Improving Live Sequence Chart To Automata Transformation For Verification, Rahul Kumar, Eric G. Mercer

Faculty Publications

This paper presents a Live Sequence Chart (LSC) to automata transformation algorithm that enables the verification of communication protocol implementations. Using this LSC to automata transformation a communication protocol implementation can be verified using a single verification run as opposed to previous techniques that rely on a three stage verification approach. The novelty and simplicity of the transformation algorithm lies in its placement of accept states in the automata generated from the LSC. We present in detail an example of the transformation as well as the transformation algorithm. Further, we present a detailed analysis and an empirical study comparing the …

Go to article

Testing Direct Simulation Monte Carlo Methods Against The Fluid Equations In The Inductively Coupled Plasma Mass Spectrometer, William R. Somers Aug 2008

Testing Direct Simulation Monte Carlo Methods Against The Fluid Equations In The Inductively Coupled Plasma Mass Spectrometer, William R. Somers

Theses and Dissertations

A Direct Simulation Monte Carlo fluid dynamics code named FENIX has been employed to study gas flow-through properties of the inductively coupled plasma mass spectrometer (ICP-MS). Simulation data have been tested against the Navier-Stokes and heat equations in order to see if FENIX functions properly. The Navier-Stokes and heat equations have been constructed from simulation data and are compared term by term. This comparison shows that FENIX is able to correctly reproduce fluid dynamics throughout the ICP-MS simulation, with an exception immediately behind the ICP-MS sampler cone, where the continuum criterion for the Navier-Stokes equation is not met. Testing the …

Go to article

Biologically Relevant Multiple Sequence Alignment, Hyrum D. Carroll Aug 2008

Biologically Relevant Multiple Sequence Alignment, Hyrum D. Carroll

Theses and Dissertations

Researchers use multiple sequence alignment algorithms to detect conserved regions in genetic sequences and to identify drug docking sites for drug development. In this dissertation, a novel algorithm is presented for using physicochemical properties to increase the accuracy of multiple sequence alignments. Secondary structures are also incorporated in the evaluation function. Additionally, the location of the secondary structures is assimilated into the function. Multiple properties are combined with weights, determined from prediction accuracies of protein secondary structures using artificial neural networks. A new metric, the PPD Score is developed, that captures the average change in physicochemical properties. Using the physicochemical …

Go to article

Implementation Of Optical Spectra Calculations In Fireball: A Local-Orbital Density Functional Theory Approach, Ivan Grigoryevich Okhrimenko Aug 2008

Implementation Of Optical Spectra Calculations In Fireball: A Local-Orbital Density Functional Theory Approach, Ivan Grigoryevich Okhrimenko

Theses and Dissertations

We have expanded the capabilities of the ab initio tight-binding molecular dynamics package FIREBALL to include calculations of optical properties. Basic zero order approximation is based on transitions between Kohn-Sham states. Corrections for electron-electron interactions are based on time dependant density functional theory (TDDFT). Consistent with the FIREBALL approach, we use precalculated integrals and approximations to make the program faster.

Go to article

Recombination Fluorescence In Ultracold Neutral Plasmas, Scott D. Bergeson, F. Robicheaux Aug 2008

Recombination Fluorescence In Ultracold Neutral Plasmas, Scott D. Bergeson, F. Robicheaux

Faculty Publications

We present the first measurements and simulations of recombination fluorescence from ultracold neutral calcium plasmas. This method probes three-body recombination at times less than 1 µs, shorter than previously published time scales. For the lowest initial electron temperatures, the recombination rate scales with the density as n22, significantly slower than the predicted n3. Recombination fluorescence opens a new diagnostic window in ultracold plasmas. In most cases it probes deeply bound level populations that depend critically on electron energetics. However, a perturbation in the calcium 4snd Rydberg series allows our fluorescence measurements to probe the population in weakly bound levels that …

Go to article

Generalized Random Walks, Their Trees, And The Transformation Method Of Option Pricing, Thomas Gordon Stewart Aug 2008

Generalized Random Walks, Their Trees, And The Transformation Method Of Option Pricing, Thomas Gordon Stewart

Theses and Dissertations

The random walk is a powerful model. Chemistry, Physics, and Finance are just a few of the disciplines that model with the random walk. It is clear from its varied uses that despite its simplicity, the simple random walk it very flexible. There is one major drawback, however, to the simple random walk and the geometric random walk. The limiting distribution is either normal, lognormal, or a levy process with infinite variance. This thesis introduces an new random walk aimed at overcoming this drawback. Because the simple random walk and the geometric random walk are special cases of the proposed …

Go to article

An Infrastructure For Performance Measurement And Comparison Of Information Retrieval Solutions, Gary Saunders Aug 2008

An Infrastructure For Performance Measurement And Comparison Of Information Retrieval Solutions, Gary Saunders

Theses and Dissertations

The amount of information available on both public and private networks continues to grow at a phenomenal rate. This information is contained within a wide variety of objects, including documents, e-mail archives, medical records, manuals, pictures and music. To be of any value, this data must be easily searchable and accessible. Information Retrieval (IR) is concerned with the ability to find and gain access to relevant information. As electronic data repositories continue to proliferate, so too, grows the variety of methods used to locate and access the information contained therein. Similarly, the introduction of innovative retrieval strategies—and the optimization of …

Go to article

I. Thermodynamics And Magnetism Of Cu2ocl2 Ii. Repairs To Microcalorimeter The "2"S Are Subscripts, And The Second 2 Is Preceded By A Lower Case L, Not A One, Thomas J. Parry Aug 2008

I. Thermodynamics And Magnetism Of Cu2ocl2 Ii. Repairs To Microcalorimeter The "2"S Are Subscripts, And The Second 2 Is Preceded By A Lower Case L, Not A One, Thomas J. Parry

Theses and Dissertations

Adiabatic calorimetry provides accurate and precise specific heat (Cp) data. From this data, thermodynamic functions may be calculated. Cu2OCl2, melanothallite, became of interest as part of a study of a particular thermochemical cycle. The experimental specific heat data and the calculated thermodynamic functions are reported here. Free energies of formation, calculated from the thermodynamic functions, suggest the particular cycle of interest with this compound as an intermediate is not feasible; uncertainty as to the accuracy of CuO and CuCl2 data used in the calculations indicate further study may be necessary. Upon collection of the specific heat data, an antiferromagnetic transition …

Go to article

Autonomous And Intelligent Radio Switching, Quiyi Duan Aug 2008

Autonomous And Intelligent Radio Switching, Quiyi Duan

Theses and Dissertations

With the proliferation of mobile applications and the abundance of wireless devices, it is increasingly common for devices to support multiple radios. When two devices are communicating they should choose the best available radio based on user preference and application requirements. This type of “radio switching” should happen automatically, so that the system optimizes performance dynamically. To achieve this objective, we design an Autonomous and Intelligent Radio Switching (AIRS) system to leverage the radio heterogeneity common in today's wireless devices. The AIRS system consists of three key components. First, we design a radio preference evaluation module to dynamically select the …

Go to article

A Radical Conjugate Addition Approach To The Total Synthesis Of Celogentin C, Steven G. Capps Aug 2008

A Radical Conjugate Addition Approach To The Total Synthesis Of Celogentin C, Steven G. Capps

Theses and Dissertations

The synthesis of five chiral DBFOX (dibenzofuran-oxazoline) ligands with either aryl or benzyl substituents will be presented. The requisite amino alcohols were obtained with high enantioselectivity either commercially (DBFOX/Bn), via Sharpless asymmetric aminohydroxylation (DBFOX/Nap, DBFOX/t-BuPh, DBFOX/Pip), or via phase-transfer catalyzed asymmetric alkylation (DBFOX/MeNap). These ligands, complexed with Mg(NTf2)2, were used as Lewis acid promoters of enantioselective radical conjugate additions to α/β-unsaturated nitro-amides/esters. A summary of these results is presented and discussed. These findings led us to believe that our initial binding model between metal, ligand, and substrate was flawed. Thus, we figured that if we started with a functionality known …

Go to article

A Microanalytical Approach To Understanding The Origin Of Cumulate Xenoliths From Mauna Kea, Hawaii, Megan Pickard Aug 2008

A Microanalytical Approach To Understanding The Origin Of Cumulate Xenoliths From Mauna Kea, Hawaii, Megan Pickard

Theses and Dissertations

Cumulate xenoliths erupted with alkalic hawaiite lavas from a postshield cinder cone on Mauna Kea, Hawaii include a variety of mafic and ultramafic rock types. Previous studies of major and trace element compositions of minerals in the xenoliths are interpreted to show transitional to alkalic magma parentages from the postshield stage, although any orthopyroxene-bearing xenoliths are considered to have tholeiitic parents. Major element compositions minerals were analyzed using the electron microprobe and trace element compositions of clinopyroxene grains were analyzed by laser ablation inductively coupled plasma mass spectrometry. In this study, major element compositions of clinopyroxene, olivine and plagioclase grains …

Go to article

On Autonomous Multi-Agent Control In Wilderness Search And Rescue: A Mixed Initiative Approach, Benjamin C. Hardin Aug 2008

On Autonomous Multi-Agent Control In Wilderness Search And Rescue: A Mixed Initiative Approach, Benjamin C. Hardin

Theses and Dissertations

Searching for lost people in a Wilderness Search and Rescue (WiSAR) scenario is a task that can benefit from large numbers of agents, some of whom may be robotic. These agents may have differing levels of autonomy, determined by the set of tasks they are performing. In addition, the level of autonomy that results in the best performance may change due to varying workload or other factors. Allowing a supervisor and a searcher to jointly decide the correct level of autonomy for a given situation (“mixed initiative”) results in better overall performance than giving an agent absolute control over their …

Go to article

Magmatic Sulfur And Chlorine Abundances At Stromboli, Italy And Their Role In The Formation Of Vesicle-Hosted Metal Alloys, Nichelle Lynn Baxter Aug 2008

Magmatic Sulfur And Chlorine Abundances At Stromboli, Italy And Their Role In The Formation Of Vesicle-Hosted Metal Alloys, Nichelle Lynn Baxter

Theses and Dissertations

Strand et al. (2002) discovered small metal alloy grains rich in Cu, Co, and Sn (maximum size 150 µm) in vesicles of lava from Kilauea Volcano. These alloys are also found in basaltic rocks of several Italian volcanoes. To better understand the origin of these metal-rich grains, bombs from Stromboli Volcano were examined. Two bomb types were collected from Stromboli: pumiceous bombs and scoriaceous bombs. Bulk rock trace element geochemistry indicates that there are no significant differences in Cu, Co, or Sn (the three major components of the metal alloys) between the pumiceous and scoriaceous bombs. Comparison of olivine melt …

Go to article

Pre-Eruptive Conditions Of The Oligocene Wah Wah Springs Tuff, Southeastern Great Basin Ignimbrite Province, Kurtus Steven Woolf Aug 2008

Pre-Eruptive Conditions Of The Oligocene Wah Wah Springs Tuff, Southeastern Great Basin Ignimbrite Province, Kurtus Steven Woolf

Theses and Dissertations

The Wah Wah Springs Tuff (30.0 Ma) is one of several very large volume ash-flow tuffs (>3200 km³ of erupted magma) that were emplaced near the peak of the flare-up of activity in the Great Basin ignimbrite province of western North America. It can be characterized as a "monotonous intermediate" ignimbrite because of its intermediate concentrations of silica (~63 to ~70 wt. %), apparent uniform chemical and mineralogical characteristics, and crystal-rich nature (32 ± 10 % phenocrysts on a dense rock basis). The major phase assemblage found throughout deposit is similar to other monotonous intermediates with a few exceptions …

Go to article

Regulators Of G-Protein Signaling, Rgs13 And Rgs16, Are Associated With Cxcl12-Mediated Cd4+ T Cell Migration, Lijin Xia Aug 2008

Regulators Of G-Protein Signaling, Rgs13 And Rgs16, Are Associated With Cxcl12-Mediated Cd4+ T Cell Migration, Lijin Xia

Theses and Dissertations

Chemokines are important chemical signals that guide lymphocyte movement within the immune system and promote the organization and functions of germinal centers (GCs) in the secondary lymphoid tissues. Previous studies have shown that GC T cells exhibit high expression of chemokine receptor 4, CXCR4, but that these cells are unable to migrate to the ligand for this receptor, the chemokine CXCL12. This “migratory paralysis” to CXCL12 was found to be correlated with the expression of two Regulators of G-protein Signaling, RGS13 and RGS16 in the GC T cells. The objective of my research was to determine whether RGS13 and RGS16 …

Go to article

Watertight Trimmed Nurbs, Thomas W. Sederberg, Xin Li, Hongwei Lin, Heather Ipson Aug 2008

Watertight Trimmed Nurbs, Thomas W. Sederberg, Xin Li, Hongwei Lin, Heather Ipson

Faculty Publications

This paper addresses the long-standing problem of the unavoidable gaps that arise when expressing the intersection of two NURBS surfaces using conventional trimmed-NURBS representation. The solution converts each trimmed NURBS into an untrimmed T-Spline, and then merges the untrimmed T-Splines into a single, watertight model. The solution enables watertight fillets of NURBS models, as well as arbitrary feature curves that do not have to follow isoparameter curves. The resulting T-Spline representation can be exported without error as a collection of NURBS surfaces.

Go to article

Spectroscopic Study Of Compressible Mobile Phase And Stationary Phase Behavior In Chromatography, Lawrence R. Baker Jul 2008

Spectroscopic Study Of Compressible Mobile Phase And Stationary Phase Behavior In Chromatography, Lawrence R. Baker

Theses and Dissertations

Raman spectroscopy, laser-induced fluorescence, and sum-frequency generation (SFG) spectroscopy are used to investigate the behavior of compressible mobile phases and stationary phases under a variety of chromatographic conditions. Efforts to understand and optimize separations employing compressible mobile phases have been limited by a lack of understanding of the mobile phase density gradient. Mobile phase compressibility leads to gradients in linear velocity and solute retention and affects separation speed and efficiency, especially in packed columns. This work describes on-column density measurement of CO2, a common carrier fluid for SFC and SGC, in packed capillary columns using Raman microspectroscopy. On-column detection by …

Go to article

Assessing Multivariate Heritability Through Nonparametric Methods, Benjamin Alan Carper Jul 2008

Assessing Multivariate Heritability Through Nonparametric Methods, Benjamin Alan Carper

Theses and Dissertations

The similarities between generations of living subjects are often quantified by heritability. By distinguishing genotypic variation, or variation due to parental pairings, from phenotypic variation, or normal intraspecies variation, the heritability of traits can be estimated. Due to the multivariate nature of many traits, such as size and shape, computation of heritability can be difficult. Also, assessment of the variation of the heritability estimate is extremely difficult. This study uses nonparametric methods, namely the randomization test and the bootstrap, to obtain both a measure of the extremity of the observed heritability and an assessment of the uncertainty.

Go to article

Theory And Estimation Of Acoustic Intensity And Energy Density, Derek C. Thomas Jul 2008

Theory And Estimation Of Acoustic Intensity And Energy Density, Derek C. Thomas

Theses and Dissertations

In order to facilitate the acquisition and accurate interpretation of intensity and energy density data in high-amplitude pressure fields, the expressions for intensity and energy density are examined to ascertain the impact of nonlinear processes on the standard expressions. Measurement techniques for estimating acoustic particle velocity are presented. The finite-difference method is developed in an alternate manner and presented along with bias and confidence estimates. Additionally, two new methods for estimating the local particle velocity are presented. These methods appears to eliminate the errors and bias associated with the finite-difference technique for certain cases.

Go to article

Lyapunov Exponents And Invariant Manifold For Random Dynamical Systems In A Banach Space, Zeng Lian Jul 2008

Lyapunov Exponents And Invariant Manifold For Random Dynamical Systems In A Banach Space, Zeng Lian

Theses and Dissertations

We study the Lyapunov exponents and their associated invariant subspaces for infinite dimensional random dynamical systems in a Banach space, which are generated by, for example, stochastic or random partial differential equations. We prove a multiplicative ergodic theorem. Then, we use this theorem to establish the stable and unstable manifold theorem for nonuniformly hyperbolic random invariant sets.

Go to article

The Tropical Jacobian Of A Tropical Elliptic Curve Is S^1(Q), Darryl Gene Wade Jul 2008

The Tropical Jacobian Of A Tropical Elliptic Curve Is S^1(Q), Darryl Gene Wade

Theses and Dissertations

We establish consistent definitions for divisors, principal divisors, and Jacobians of a tropical elliptic curve and show that for a tropical elliptic cubic C , the associated Jacobian (or zero divisor class group) is the group S^1(Q).

Go to article

Predicting The Longevity Of Dvdr Media By Periodic Analysis Of Parity, Jitter, And Ecc Performance Parameters, Daniel Patrick Wells Jul 2008

Predicting The Longevity Of Dvdr Media By Periodic Analysis Of Parity, Jitter, And Ecc Performance Parameters, Daniel Patrick Wells

Theses and Dissertations

For the last ten years, DVD-R media have played an important role in the storage of large amounts of digital data throughout the world. During this time it was assumed that the DVD-R was as long-lasting and stable as its predecessor, the CD-R. Several reports have surfaced over the last few years questioning the DVD-R's ability to maintain many of its claims regarding archival quality life spans. These reports have shown a wide range of longevity between the different brands. While some DVD-Rs may last a while, others may result in an early and unexpected failure. Compounding this problem is …

Go to article

Simple, Secure, Selective Delegation In Online Identify Systems, Bryant Gordon Cutler Jul 2008

Simple, Secure, Selective Delegation In Online Identify Systems, Bryant Gordon Cutler

Theses and Dissertations

The ability to delegate privileges to others is so important to users of online identity systems that users create ad hoc delegation systems by sharing authentication credentials if no other easy delegation mechanism is available. With the rise of internet-scale relationship-based single sign-on protocols like OpenID, the security risks of password sharing are unacceptable. We therefore propose SimpleAuth, a simple modification to relationship-based authentication protocols that gives users a secure way to selectively delegate subsets of their privileges, making identity systems more flexible and increasing user security. We also present a proof-of-concept implementation of the SimpleAuth pattern using the sSRP …

Go to article

First Prev Next Last