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

Physical Sciences and Mathematics Commons™

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

Theses and Dissertations

Discipline
Institution
Keyword
Publication Year
File Type

Articles 6031 - 6060 of 8341

Full-Text Articles in Physical Sciences and Mathematics

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

Complete Tropical Bezout's Theorem And Intersection Theory In The Tropical Projective Plane, Gretchen Rimmasch Jul 2008

Complete Tropical Bezout's Theorem And Intersection Theory In The Tropical Projective Plane, Gretchen Rimmasch

Theses and Dissertations

In this dissertation we prove a version of the tropical Bezout's theorem which is applicable to all tropical projective plane curves. There is a version of tropical Bezout's theorem presented in other works which applies in special cases, but we provide a proof of the theorem for all tropical projective plane curves. We provide several different definitions of intersection multiplicity and show that they all agree. Finally, we will use a tropical resultant to determine the intersection multiplicity of points of intersection at infinite distance. Using these new definitions of intersection multiplicity we prove the complete tropical Bezout's theorem.

Go to article

Using Live Sequence Chart Specifications For Formal Verification, Rahul Kumar Jul 2008

Using Live Sequence Chart Specifications For Formal Verification, Rahul Kumar

Theses and Dissertations

Formal methods play an important part in the development as well as testing stages of software and hardware systems. A significant and often overlooked part of the process is the development of specifications and correctness requirements for the system under test. Traditionally, English has been used as the specification language, which has resulted in verbose and difficult to use specification documents that are usually abandoned during product development. This research focuses on investigating the use of Live Sequence Charts (LSCs), a graphical and intuitive language directly suited for expressing communication behaviors of a system as the specification language for a …

Go to article

Genetic Analysis Of The Role Of Smpb In Establishing The Reading Frame On Tmrna, Talina Christensen Watts Jul 2008

Genetic Analysis Of The Role Of Smpb In Establishing The Reading Frame On Tmrna, Talina Christensen Watts

Theses and Dissertations

Ribosomes translate the genetic information encoded by mRNA into proteins. Defective mRNAs can cause stalling of translating ribosomes. The molecule tmRNA (transfer-messenger RNA) rescues stalled ribosomes in eubacteria. Together with its protein partner SmpB, tmRNA mimics a tRNA by entering the ribosomal A site and linking an alanine residue to the growing polypeptide chain. The ribosome then abandons the defective mRNA template and resumes translation on tmRNA, adding ten more amino acids to the nascent polypeptide. As a result of tmRNA action, stalled ribosomes are released and recycled, the defective mRNA is destroyed, and the aborted protein product is tagged …

Go to article

Adapting Adtrees For Improved Performance On Large Datasets With High Arity Features, Robert D. Van Dam Jul 2008

Adapting Adtrees For Improved Performance On Large Datasets With High Arity Features, Robert D. Van Dam

Theses and Dissertations

The ADtree, a data structure useful for caching sufficient statistics, has been successfully adapted to grow lazily when memory is limited and to update sequentially with an incrementally updated dataset. However, even these modified forms of the ADtree still exhibit inefficiencies in terms of both space usage and query time, particularly on datasets with very high dimensionality and with high arity features. We propose five modifications to the ADtree, each of which can be used to improve size and query time under specific types of datasets and features. These modifications also provide an increased ability to precisely control how an …

Go to article

Ion Permeation Through Membrane Channels: Molecular Dynamics Simulations Studies, Morad Mustafa Jul 2008

Ion Permeation Through Membrane Channels: Molecular Dynamics Simulations Studies, Morad Mustafa

Theses and Dissertations

Molecular dynamics simulation was used to study ion permeation through different membrane proteins embedded in a lipid bilayer (DMPC) with different saline solutions. The potential of mean force (PMF) for ion transport was obtained by umbrella sampling simulations. A revised MacKerell force field for tryptophan residues was studied using gramicidin A (gA) channel as a test model. The revised force field contribution to the Na+ PMF was consonant with the prediction from the experimental results, but in stark contrast to the prediction of the CHARMM force field, version 22, for the tryptophan side-chain. A new grid-based correction map algorithm by …

Go to article

Early Dynamics Of Ultracold Neutral Plasmas, Adam W. Denning Jul 2008

Early Dynamics Of Ultracold Neutral Plasmas, Adam W. Denning

Theses and Dissertations

We report new studies on the early-time dynamics of ultracold neutral plasmas. We use fluorescence spectroscopy to probe plasma dynamics on the nanosecond time scale. We determine the rms ion velocity during the initial plasma period. The initial ion acceleration is found as the time derivative of the ion velocity. We compare to a theoretical model. The experimental results agree with the model at low plasma densities. However, the ion acceleration is a factor of ten lower than the model at higher densities. The cause of this discrepancy is currently unknown.

Go to article

Rational Schur Rings Over Abelian Groups, Brent L. Kerby Jul 2008

Rational Schur Rings Over Abelian Groups, Brent L. Kerby

Theses and Dissertations

In 1993, Muzychuk showed that the rational S-rings over a cyclic group Z_n are in one-to-one correspondence with sublattices of the divisor lattice of n, or equivalently, with sublattices of the lattice of subgroups of Z_n. This idea is easily extended to show that for any finite group G, sublattices of the lattice of characteristic subgroups of G give rise to rational S-rings over G in a natural way. Our main result is that any finite group may be represented as the automorphism group of such a rational S-ring over an abelian p-group. In order to show this, we first …

Go to article

Ordinal Regression To Evaluate Student Ratings Data, Emily Brooke Bell Jul 2008

Ordinal Regression To Evaluate Student Ratings Data, Emily Brooke Bell

Theses and Dissertations

Student evaluations are the most common and often the only method used to evaluate teachers. In these evaluations, which typically occur at the end of every term, students rate their instructors on criteria accepted as constituting exceptional instruction in addition to an overall assessment. This presentation explores factors that influence student evaluations using the teacher ratings data of Brigham Young University from Fall 2001 to Fall 2006. This project uses ordinal regression to model the probability of an instructor receiving a good, average, or poor rating. Student grade, instructor status, class level, student gender, total enrollment, term, GE class status, …

Go to article

Homomorphisms Into The Fundamental Group Of One-Dimensional And Planar Peano Continua, Curtis Andrew Kent Jul 2008

Homomorphisms Into The Fundamental Group Of One-Dimensional And Planar Peano Continua, Curtis Andrew Kent

Theses and Dissertations

Let X be a planar or one-dimensional Peano continuum. Let E be a Hawaiian Earring with fundamental group H. We show that every homomorphism from H to the fundamental group of X is conjugate to a homomorphism which is induced by a continuous function.

Go to article

Arbitrary Degree T-Splines, Gordon Thomas Finnigan Jul 2008

Arbitrary Degree T-Splines, Gordon Thomas Finnigan

Theses and Dissertations

T-Splines is a freeform surface type similar to NURBS, that allows partial rows of control points. Up until now, T-Splines have only been formally defined for the degree three case. This paper extends the definition to support all odd, even, and mixed degree T-Spline surfaces, making T-Splines a proper superset of all standard NURBS surfaces.

Go to article

Fusion Of Character Tables And Schur Rings Of Dihedral Groups, Long Pham Bao Nguyen Jun 2008

Fusion Of Character Tables And Schur Rings Of Dihedral Groups, Long Pham Bao Nguyen

Theses and Dissertations

A finite group H is said to fuse to a finite group G if the class algebra of G is isomorphic to an S-ring over H which is a subalgebra of the class algebra of H. We will also say that G fuses from H. In this case, the classes and characters of H can fuse to give the character table of G. We investigate the case where H is the dihedral group. In many cases, G can be completely determined. In general, G can be proven to have many interesting properties. The theory is developed in terms of S-ring …

Go to article

Reducing Seed Load In The Bittorrent File Sharing System, Brian T. Sanderson Jun 2008

Reducing Seed Load In The Bittorrent File Sharing System, Brian T. Sanderson

Theses and Dissertations

BitTorrent is an attractive peer-to-peer technology that attempts to reduce load on file sharers by allowing downloaders to share content between themselves. BitTorrent's current focus is to provide users with a fast download, which requires the file sharer to serve a disproportionate amount of the file. We present a modification to the BitTorrent seeding algorithm that reduces the load on BitTorrent file sharers. Essentially, if a block of a file is already available from a significant number of peers, the file sharer refuses to share that block, forcing peers to get it from each other. Using this modification, we show …

Go to article

Generalized Second Price Auctions With Hierarchical Bidding, Kevin Bryan Jun 2008

Generalized Second Price Auctions With Hierarchical Bidding, Kevin Bryan

Theses and Dissertations

The sale of text advertisements on search engines using an auction format called Generalized Second Price (GSP) has become increasingly common. GSP is unique in that it allows bidders to revise their bid if they are unhappy with the result of the auction, and because the auction sells multiple units of a related good simultaneously. We model this sale as a hierarchical game with complete information, allowing one potential bidder to bid in each stage. The hierarchical game has an entirely different set of equilibria from the simultaneous bid game studied in earlier research on this auction. Under hierarchical bidding, …

Go to article

Material Perturbations To Enhance Performance Of The Theile Half-Width Leaky Mode Antenna, Jason A. Girard Jun 2008

Material Perturbations To Enhance Performance Of The Theile Half-Width Leaky Mode Antenna, Jason A. Girard

Theses and Dissertations

Microstrip traveling-wave antennas, often referred to as leaky-wave antennas, have been shown to radiate when the dominant or fundamental mode is suppressed and the first higher-order mode is excited. One such microstrip variation is the Thiele Half-Width (THW) antenna, which operates from 5.9 - 8.2 GHz for this research. Increasing the bandwidth over which the THW antenna radiates is desired, as is a fundamental understanding of the propagation characteristics over this region. This dissertation seeks to vary or perturb the material and physical properties of the THW antenna, including strip-width variations and modifications of the substrate layer, to achieve these …

Go to article

A Naive, Robust And Stable State Estimate, Todd Gordon Remund Jun 2008

A Naive, Robust And Stable State Estimate, Todd Gordon Remund

Theses and Dissertations

A naive approach to filtering for feedback control of dynamic systems that is robust and stable is proposed. Simulations are run on the filters presented to investigate the robustness properties of each filter. Each simulation with the comparison of the filters is carried out using the usual mean squared error. The filters to be included are the classic Kalman filter, Krein space Kalman, two adjustments to the Krein filter with input modeling and a second uncertainty parameter, a newly developed filter called the Naive filter, bias corrected Naive, exponentially weighted moving average (EWMA) Naive, and bias corrected EWMA Naive filter.

Go to article

Geochemistry, Structure, And Tectonic Evolution Of The Eldivan Ophiolite, Ankara Melange, Central Turkey, Anne Dangerfield Jun 2008

Geochemistry, Structure, And Tectonic Evolution Of The Eldivan Ophiolite, Ankara Melange, Central Turkey, Anne Dangerfield

Theses and Dissertations

The Eldivan ophiolite, in the Ankara Mélange, represents the remnant of an ocean basin that developed in the İzmir-Ankara-Erzincan Ocean and collapsed the form the İzmir -Ankara-Erzincan suture zone (İAESZ) through continental block collision. Whole-rock and mineral geochemical evidence show supra-subduction zone tectonomagmatic affinity for the ophiolite, revealing this basin formed in the upper plate of an intra-oceanic subduction zone. Detrital zircon from the ophiolitic mélange sandstone and the overlying Karadağ Formation suggest the ophiolites maximum age is 143.2 (±2) Ma, and the overlying Karadağ Formation is 105.2 (±5) Ma. The angular unconformity between the ophiolite and Karadağ formation reveal …

Go to article

Characterizing Effects And Benefits Of Beam Defocus On High Energy Laser Performance Under Thermal Blooming And Turbulence Conditions For Air-To-Ground Engagements, Scott N. Long Jun 2008

Characterizing Effects And Benefits Of Beam Defocus On High Energy Laser Performance Under Thermal Blooming And Turbulence Conditions For Air-To-Ground Engagements, Scott N. Long

Theses and Dissertations

This dissertation makes contributions towards knowledge of optimizing of laser weapon performance when operating in the air-to-ground (ATG) regime in thermal blooming conditions. Wave optics modeling techniques were used to represent laser weapon performance in a high fidelity sense to allow progress to be made toward improving lower-fidelity scaling laws that can be used in systems level analysis which has need for better representations of thermal blooming. Chemical-oxygen iodine laser (COIL) based weapon systems that operate near the ground will experience thermal blooming due to atmospheric absorption if output power is sufficiently high. The thermal lens in the ATG case …

Go to article

Hardware, Software And Data Analysis Techniques For Sram-Based Field Programmable Gate Array Circuits, Eugene B. Hockenberry Jun 2008

Hardware, Software And Data Analysis Techniques For Sram-Based Field Programmable Gate Array Circuits, Eugene B. Hockenberry

Theses and Dissertations

This work presents a built, tested, and demonstrated test structure that is low-cost, flexible, and re-usable for robust radiation experimentation, primarily to investigate memory, in this case SRAMs and SRAM-based FPGAs. The space environment can induce many kinds of failures due to radiation effects. These failures result in a loss of money, time, intelligence, and information. In order to evaluate technologies for potential failures, a detailed test methodology and associated structure are required. In this solution, an FPGA board was used as the controller platform, with multiple VHDL circuit controllers, data collection and reporting modules. The structure was demonstrated by …

Go to article

Developing Network Situational Awareness Through Visualization Of Fused Intrusion Detection System Alerts, Serafin A. Avitia V Jun 2008

Developing Network Situational Awareness Through Visualization Of Fused Intrusion Detection System Alerts, Serafin A. Avitia V

Theses and Dissertations

With networks increasing in physical size, bandwidth, traffic volume, and malicious activity, network analysts are experiencing greater difficulty in developing network situational awareness. Traditionally, network analysts have used Intrusion Detection Systems to gain awareness but this method is outdated when analysts are unable to process the alerts at the rate they are being generated. Analysts are unwittingly placing the computer assets they are charged to protect at risk when they are unable to detect these network attacks. This research effort examines the theory, application, and results of using visualizations of fused alert data to develop network situational awareness. The fused …

Go to article

Interactive Part Selection For Mesh And Point Models Using Hierarchical Graph-Cut Partitioning, Steven W. Brown Jun 2008

Interactive Part Selection For Mesh And Point Models Using Hierarchical Graph-Cut Partitioning, Steven W. Brown

Theses and Dissertations

This thesis presents a method for interactive part selection for mesh and point set surface models that combines scribble-based selection methods with hierarchically accelerated graph-cut segmentation. Using graph-cut segmentation to determine optimal intuitive part boundaries enables easy part selection on complex geometries and allows for a simple, scribble-based interface that focuses on selecting within visible parts instead of precisely defining part boundaries that may be in difficult or occluded regions. Hierarchical acceleration is used to maintain interactive speeds with large models and to determine connectivity when extending the technique to point set models.

Go to article

Lifting Galois Representations In A Conjecture Of Figueiredo, Wayne Bennett Rosengren Jun 2008

Lifting Galois Representations In A Conjecture Of Figueiredo, Wayne Bennett Rosengren

Theses and Dissertations

In 1987, Jean-Pierre Serre gave a conjecture on the correspondence between degree 2 odd irreducible representations of the absolute Galois group of Q and modular forms. Letting M be an imaginary quadratic field, L.M. Figueiredo gave a related conjecture concerning degree 2 irreducible representations of the absolute Galois group of M and their correspondence to homology classes. He experimentally confirmed his conjecture for three representations arising from PSL(2,3)-polynomials, but only up to a sign because he did not lift them to SL(2,3)-polynomials. In this paper we compute explicit lifts and give further evidence that his conjecture is accurate.

Go to article

A Secure And Efficient Communications Architecture For Global Information Grid Users Via Cooperating Space Assets, Victor P. Hubenko Jun 2008

A Secure And Efficient Communications Architecture For Global Information Grid Users Via Cooperating Space Assets, Victor P. Hubenko

Theses and Dissertations

With the Information Age in full and rapid development, users expect to have global, seamless, ubiquitous, secure, and efficient communications capable of providing access to real-time applications and collaboration. The United States Department of Defense’s (DoD) Network-Centric Enterprise Services initiative, along with the notion of pushing the “power to the edge,” aims to provide end-users with maximum situational awareness, a comprehensive view of the battlespace, all within a secure networking environment. Building from previous AFIT research efforts, this research developed a novel security framework architecture to address the lack of efficient and scalable secure multicasting in the low earth orbit …

Go to article

Statistical Methods For Image Registration And Denoising, Matthew D. Sambora Jun 2008

Statistical Methods For Image Registration And Denoising, Matthew D. Sambora

Theses and Dissertations

This dissertation describes research into image processing techniques that enhance military operational and support activities. The research extends existing work on image registration by introducing a novel method that exploits local correlations to improve the performance of projection-based image registration algorithms. The dissertation also extends the bounds on image registration performance for both projection-based and full-frame image registration algorithms and extends the Barankin bound from the one-dimensional case to the problem of two-dimensional image registration. It is demonstrated that in some instances, the Cramer-Rao lower bound is an overly-optimistic predictor of image registration performance and that under some conditions, the …

Go to article

An Analysis Of Botnet Vulnerabilities, Sean W. Hudson Jun 2008

An Analysis Of Botnet Vulnerabilities, Sean W. Hudson

Theses and Dissertations

Botnets are a significant threat to computer networks and data stored on networked computers. The ability to inhibit communication between servers controlling the botnet and individual hosts would be an effective countermeasure. The objective of this research was to find vulnerabilities in Unreal IRCd that could be used to shut down the server. Analysis revealed that Unreal IRCd is a very mature and stable IRC server and no significant vulnerabilities were found. While this research does not eliminate the possibility that a critical vulnerability is present in the Unreal IRCd software, none were identified during this effort.

Go to article

First Prev Next Last