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Articles 1 - 30 of 1752

Full-Text Articles in Physical Sciences and Mathematics

Nonlinear Optical Characterization Of Solids, Alex Farnsworth Dec 2018

Nonlinear Optical Characterization Of Solids, Alex Farnsworth

Undergraduate Honors Theses

Vibrational Sum Frequency Generation (VSFG) and the similar Second Harmonic Generation (SHG) are both classified as nonlinear optical phenomena, with the hallmark trait being that the input and output frequencies are different. Both of these systems are remarkable tools due to their surface specific nature. Still, there is much that is not known about the response from these systems, especially the nonresonant SFG response. We have worked to better understand SFG signal, specifically the nonresonant temporal profile. We have also collected results that call into question some underlying assumptions about time-based suppression methods when working with single crystal substrates.

As ...


User Attitudes About Duo Two-Factor Authentication At Byu, Jonathan Dutson Dec 2018

User Attitudes About Duo Two-Factor Authentication At Byu, Jonathan Dutson

Undergraduate Honors Theses

Simple password-based authentication provides insufficient protection against increasingly common incidents of online identity theft and data loss. Although two-factor authentication (2FA) provides users with increased protection against attackers, users have mixed feelings about the usability of 2FA. We surveyed the students, faculty, and staff of Brigham Young University (BYU) to measure user sentiment about DUO Security, the 2FA system adopted by BYU in 2017. We find that most users consider DUO to be annoying, and about half of those surveyed expressed a preference for authentication without using a second-factor. About half of all participants reported at least one instance of ...


Divisibility Properties Of Coefficients Of Modular Functions Of Genus Zero Levels, Merrill Warnick Nov 2018

Divisibility Properties Of Coefficients Of Modular Functions Of Genus Zero Levels, Merrill Warnick

Undergraduate Honors Theses

We prove divisibility results for the Fourier coefficients of canonical basis elements for the spaces of weakly holomorphic modular forms of weight 0 and levels 6, 10, 12, 18 with poles only at the cusp at infinity. In addition, we show that these Fourier coefficients satisfy Zagier duality in all weights, and give a general formula for the generating functions of such canonical bases for all genus zero levels. These results originally appeared in a paper of the same title that was accepted by the journal Integers, and was authored by the present author, with Paul Jenkins and Vicki


A Quantitative Study Of The Deployment Of The Sender Policy Framework, Eunice Zsu Tan Oct 2018

A Quantitative Study Of The Deployment Of The Sender Policy Framework, Eunice Zsu Tan

All Theses and Dissertations

Email has become a standard form of communication between businesses. With the prevalent use of email as a form of communication between businesses and customers, phishing emails have emerged as a popular social engineering approach. With phishing, attackers trick users into divulging their personal information through email spoofing. Thus, it is imperative to verify the sender of an email. Anti-spoofing mechanisms such as the Sender Policy Framework (SPF) have been developed as the first line of defense against spoofing by validating the source of an email as well as the presenting options of how to handle emails that fail to ...


Certificate Revocation Table: Leveraging Locality Of Reference In Web Requests To Improve Tls Certificate Revocation, Luke Austin Dickinson Oct 2018

Certificate Revocation Table: Leveraging Locality Of Reference In Web Requests To Improve Tls Certificate Revocation, Luke Austin Dickinson

All Theses and Dissertations

X.509 certificate revocation defends against man-in-the-middle attacks involving a compromised certificate. Certificate revocation strategies face scalability, effectiveness, and deployment challenges as HTTPS adoption rates have soared. We propose Certificate Revocation Table (CRT), a new revocation strategy that is competitive with or exceeds alternative state-of-the-art solutions in effectiveness, efficiency, certificate growth scalability, mass revocation event scalability, revocation timeliness, privacy, and deployment requirements. The CRT periodically checks the revocation status of X.509 certificates recently used by an organization, such as clients on a university's private network. By prechecking the revocation status of each certificate the client is likely to ...


Polynomial Fitting, R. Steven Turley Sep 2018

Polynomial Fitting, R. Steven Turley

All Faculty Publications

This article reviews the theory and some good practice for fitting polynomials to data. I show by theory and example why fitting using a basis of orthogonal polynomials rather than monomials is desirable. I also show how to scale the independent variable for a more stable fit. I also demonstrate how to compute the uncertainty in the fit parameters. Finally, I discuss regression analysis: how to determine whether adding an additional term to the fit is justified.


Linear Least Squares Curve Fitting, R. Steven Turley Sep 2018

Linear Least Squares Curve Fitting, R. Steven Turley

All Faculty Publications

This article is a review of the theory and practice behind linear least squares curve fitting. It outlines how to find the optimal parameters to match experimental data with theory and how to estimate the uncertainty in those parameters. The article demonstrates and validates these calculations in Excel, MATLAB, Mathematica, Python, and Julia.


Fitting Parameter Uncertainties In Least Squares Fitting, R. Steven Turley Sep 2018

Fitting Parameter Uncertainties In Least Squares Fitting, R. Steven Turley

All Faculty Publications

This article review the theory and practice of computing uncertainties in the fit parameters in least squares fits. It shows how to estimate the uncertainties and gives some numerical examples in Julia of their use. Examples are given and validated for both linear and nonlinear fits.


Cubic Interpolation With Irregularly-Spaced Points In Julia 1.0, R. Steven Turley Aug 2018

Cubic Interpolation With Irregularly-Spaced Points In Julia 1.0, R. Steven Turley

All Faculty Publications

This article shows how to interpolate between regularly- or irregularly-spaced points in Julia 1.0. It has derivations of the theory behind cubic splines, and piece-wise cubic hermite polynomial interpolation. The spline interpolants are continuous and have continuous first and second derivatives. The hermite polynomial interpolants are continuous and have continuous first derivatives. Three techniques are implemented to determine the slope at the data points for the interpolation (knots). One uses the average slope of the neighboring segments. Another use the quadratic polynomial passing through the point and its two neighbors. The third, PCHIP, is similar to the first method ...


Adding Limit Points To Bass-Serre Graphs Of Groups, Alexander Jin Shumway Jul 2018

Adding Limit Points To Bass-Serre Graphs Of Groups, Alexander Jin Shumway

All Theses and Dissertations

We give a brief overview of Bass-Serre theory and introduce a method of adding a limit point to graphs of groups. We explore a basic example of this method, and find that while the fundamental theorem of Bass-Serre theory no longer applies in this case we still recover a group action on a covering space of sorts with a subgroup isomorphic to the fundamental group of our new base space with added limit point. We also quantify how much larger the fundamental group of a graph of groups becomes after this construction, and discuss the effects of adding and identifying ...


Congruences For Fourier Coefficients Of Modular Functions Of Levels 2 And 4, Eric Brandon Moss Jul 2018

Congruences For Fourier Coefficients Of Modular Functions Of Levels 2 And 4, Eric Brandon Moss

All Theses and Dissertations

We give congruences modulo powers of 2 for the Fourier coefficients of certain level 2 modular functions with poles only at 0, answering a question posed by Andersen and Jenkins. The congruences involve a modulus that depends on the binary expansion of the modular form's order of vanishing at infinity. We also demonstrate congruences for Fourier coefficients of some level 4 modular functions.


Data Assimilation In The Boussinesq Approximation For Mantle Convection, Shane Alexander Mcquarrie Jul 2018

Data Assimilation In The Boussinesq Approximation For Mantle Convection, Shane Alexander Mcquarrie

All Theses and Dissertations

Many highly developed physical models poorly approximate actual physical systems due to natural random noise. For example, convection in the earth's mantle—a fundamental process for understanding the geochemical makeup of the earth's crust and the geologic history of the earth—exhibits chaotic behavior, so it is difficult to model accurately. In addition, it is impossible to directly measure temperature and fluid viscosity in the mantle, and any indirect measurements are not guaranteed to be highly accurate. Over the last 50 years, mathematicians have developed a rigorous framework for reconciling noisy observations with reasonable physical models, a technique ...


An Algorithm For Symbolic Computing Of Singular Limits Of Dynamical Systems, Dane Jordan Bjork Jul 2018

An Algorithm For Symbolic Computing Of Singular Limits Of Dynamical Systems, Dane Jordan Bjork

All Theses and Dissertations

The manifold boundary approximation method, MBAM is a new technique used in approximating systems of equations using parameter reduction. This method and other approximation methods are introduced and described. Several current issues in performing MBAM are discussed in further detail. These issues significantly slow down the process of MBAM and create a barrier of entry for those wishing to use the method without a strong background in mathematics. A solution is proposed to automatically reparameterize models and evaluate specific types of variables approaching limits -- significantly speeding up the process of MBAM. An implementation of the solution is discussed.


Machine Learning For Inspired, Structured, Lyrical Music Composition, Paul Mark Bodily Jul 2018

Machine Learning For Inspired, Structured, Lyrical Music Composition, Paul Mark Bodily

All Theses and Dissertations

Computational creativity has been called the "final frontier" of artificial intelligence due to the difficulty inherent in defining and implementing creativity in computational systems. Despite this difficulty computer creativity is becoming a more significant part of our everyday lives, in particular music. This is observed in the prevalence of music recommendation systems, co-creational music software packages, smart playlists, and procedurally-generated video games. Significant progress can be seen in the advances in industrial applications such as Spotify, Pandora, Apple Music, etc., but several problems persist. Of more general interest, however, is the question of whether or not computers can exhibit autonomous ...


Finding Torsion-Free Groups Which Do Not Have The Unique Product Property, Lindsay Jennae Soelberg Jul 2018

Finding Torsion-Free Groups Which Do Not Have The Unique Product Property, Lindsay Jennae Soelberg

All Theses and Dissertations

This thesis discusses the Kaplansky zero divisor conjecture. The conjecture states that a group ring of a torsion-free group over a field has no nonzero zero divisors. There are situations for which this conjecture is known to hold, such as linearly orderable groups, unique product groups, solvable groups, and elementary amenable groups. This paper considers the possibility that the conjecture is false and there is some counterexample in existence. The approach to searching for such a counterexample discussed here is to first find a torsion-free group that has subsets A and B such that AB has no unique product. We ...


Euclidean Domains, Vandy Jade Tombs Jul 2018

Euclidean Domains, Vandy Jade Tombs

All Theses and Dissertations

In the usual definition of a Euclidean domain, a ring has a norm function whose codomain is the positive integers. It was noticed by Motzkin in 1949 that the codomain could be replaced by any well-ordered set. This motivated the study of transfinite Euclidean domains in which the codomain of the norm function is replaced by the class of ordinals. We prove that there exists a (transfinitely valued) Euclidean Domain with Euclidean order type for every indecomposable ordinal. Modifying the construction, we prove that there exists a Euclidean Domain with no multiplicative norm. Following a definition of Clark and Murty ...


Use Of Phase And Amplitude Gradient Estimation For Acoustic Source Characterization And Localization, Joseph Scott Lawrence Jul 2018

Use Of Phase And Amplitude Gradient Estimation For Acoustic Source Characterization And Localization, Joseph Scott Lawrence

All Theses and Dissertations

Energy-based acoustic quantities provide vital information about acoustic fields and the characterization of acoustic sources. Recently, the phase and amplitude gradient estimator (PAGE) method has been developed to reduce error and extend bandwidth of energy-based quantity estimates. To inform uses and applications of the method, analytical and experimental characterizations of the method are presented. Analytical PAGE method bias errors are compared with those of traditional estimation for two- and three-microphone one-dimensional probes. For a monopole field when phase unwrapping is possible, zero bias error is achieved for active intensity using three-microphone PAGE and for specific acoustic impedance using two-microphone PAGE ...


Ion Friction At Small Values Of The Coulomb Logarithm, Robert Tucker Sprenkle Jul 2018

Ion Friction At Small Values Of The Coulomb Logarithm, Robert Tucker Sprenkle

All Theses and Dissertations

We create a dual-species ultracold neutral plasma (UNP) by photo-ionizing Yb and Ca atoms in a dual-species magneto-optical trap. Unlike single-species UNP expansion, these plasmas are well outside of the collisionless (Vlasov) approximation. We observe the mutual interaction of the Yb and Ca ions by measuring the velocity distribution for each ion species separately. We model the expansion using a fluid code including ion-ion friction and compare with experimental results to obtain a value of the Coulomb logarithm of Λ= 0.04.


The Arithmetic Of Modular Grids, Grant Steven Molnar Jul 2018

The Arithmetic Of Modular Grids, Grant Steven Molnar

All Theses and Dissertations

Let Mk(∞) (Gamma, nu) denote the space of weight k weakly holomorphic weight modular forms with poles only at the cusp (∞), and let widehat Mk(∞) (Gamma, nu) subseteq Mk(∞) (Gamma, nu) denote the space of weight k weakly holomorphic modular forms in Mk(∞) (Gamma, nu) which vanish at every cusp other than (∞). We construct canonical bases for these spaces in terms of Maass--Poincaré series, and show that the coefficients of these bases satisfy Zagier duality.


Examining Multimorbidities Using Association Rule Learning, Kaylee Dudley Jun 2018

Examining Multimorbidities Using Association Rule Learning, Kaylee Dudley

Undergraduate Honors Theses

All insurance companies, regardless of the kind of insurance they offer, do their best to predict the future by comparing current to historical information. Any statistically significant correlation, regardless of expectations and hidden factors, can help to actuarially model future behavior. Using deidentified data from over 6 million health insurance policies over one year, we looked for any significant groupings of medical issues. The medical issues are defined based on the commercial “Episode Treatment Groups” (ETGs) classification, and our claims contain 347 different ETGs. We performed different kinds of analysis, including Bayesian posterior cluster analysis, k-means cluster analysis, and association ...


Application Of The Entropy Concept To Thermodynamics And Life Sciences: Evolution Parallels Thermodynamics, Cellulose Hydrolysis Thermodynamics, And Ordered And Disordered Vacancies Thermodynamics, Marko Popovic Jun 2018

Application Of The Entropy Concept To Thermodynamics And Life Sciences: Evolution Parallels Thermodynamics, Cellulose Hydrolysis Thermodynamics, And Ordered And Disordered Vacancies Thermodynamics, Marko Popovic

All Theses and Dissertations

Entropy, first introduced in thermodynamics, is used in a wide range of fields. Chapter 1 discusses some important theoretical and practical aspects of entropy: what is entropy, is it subjective or objective, and how to properly apply it to living organisms. Chapter 2 presents applications of entropy to evolution. Chapter 3 shows how cellulosic biofuel production can be improved. Chapter 4 shows how lattice vacancies influence the thermodynamic properties of materials. To determine the nature of thermodynamic entropy, Chapters 1 and 2 describe the roots, the conceptual history of entropy, as well as its path of development and application. From ...


Probabilistic Programming For Theory Of Mind For Autonomous Decision Making, Iris Rubi Seaman Jun 2018

Probabilistic Programming For Theory Of Mind For Autonomous Decision Making, Iris Rubi Seaman

All Theses and Dissertations

As autonomous agents (such as unmanned aerial vehicles, or UAVs) become more ubiquitous, they are being used for increasingly complex tasks. Eventually, they will have to reason about the mental state of other agents, including those agents' beliefs, desires and goals – so-called Theory of Mind – and make decisions based on that reasoning. We describe increasingly complex theory of mind models of a UAV pursuing an intruder, and show that (1) there is a natural Bayesian formulation to reasoning about the uncertainty inherent in our estimate of another agent's mental state, and that (2) probabilistic programming is a natural way ...


Network Specializations, Symmetries, And Spectral Properties, Dallas C. Smith Jun 2018

Network Specializations, Symmetries, And Spectral Properties, Dallas C. Smith

All Theses and Dissertations

In this dissertation, we introduce three techniques for network sciences. The first of these techniques is a series of new models for describing network growth. These models, called network specialization models, are built with the idea that networks grow by specializing the function of subnetworks. Using these models we create theoretical networks which exhibit well-known properties of real networks. We also demonstrate how the spectral properties are preserved as the models grow. The second technique we describe is a method for decomposing networks that contain automorphisms in a way that preserves the spectrum of the original graph. This method for ...


Evaluating The Usability Of Two-Factor Authentication, Kendall Ray Reese Jun 2018

Evaluating The Usability Of Two-Factor Authentication, Kendall Ray Reese

All Theses and Dissertations

Passwords are the dominant form of authentication on the web today. However,many users choose weak passwords and reuse the same password on multiple sites, thus increasing their vulnerability to having their credentials leaked or stolen. Two-factor authentication strengthens existing password authentication schemes against impersonation attacks and makes it more difficult for attackers to reuse stolen credentials on other websites. Despite the added security benefits of two-factor authentication, there are still many open questions about its usability. Many two-factor authentication systems in widespread usage today have not yet been subjected to adequate usability testing. Previous comparative studies have demonstrated significant ...


Adaptive Fluid Simulation Using A Linear Octree Structure, Sean A. Flynn May 2018

Adaptive Fluid Simulation Using A Linear Octree Structure, Sean A. Flynn

All Theses and Dissertations

An Eulerian approach to fluid flow provides an efficient, stable paradigm for realistic fluid simulation. However, its traditional reliance on a fixed-resolution grid is not ideal for simulations that simultaneously exhibit both large and small-scale fluid phenomena. Octree-based fluid simulation approaches have provided the needed adaptivity, but the inherent weakness of a pointer-based tree structure has limited their effectiveness. We present a linear octree structure that provides a significant runtime speedup using these octree-based simulation algorithms. As memory prices continue to decline, we leverage additional memory when compared to traditional octree structures to provide this improvement. In addition to reducing ...


Addressing The Regulator's Dilemma: A Self Drive Framework For Balancing Safety And Innovation, Craig Maughan May 2018

Addressing The Regulator's Dilemma: A Self Drive Framework For Balancing Safety And Innovation, Craig Maughan

Brigham Young University Prelaw Review

Policymakers are tasked with creating regulations that responsibly oversee the growth and deployment of emerging technologies. I argue that the SELF DRIVE Act, currently being deliberated in Congress, offers one such intelligent regulatory structure for autonomous vehicles: it prioritizes public safety over adherence to outdated requirements, giving innovators greater freedom to field-test new designs. More importantly, I examine how key principles of the SELF DRIVE Act should be applied to other emerging technologies currently facing regulatory roadblock. Specifically, I suggest the drone industry be subject to regulatory changes that incentivize safety, allow exploration, and anticipate future growth. Such regulations allow ...


Signal Structure For A Class Of Nonlinear Dynamic Systems, Meilan Jin May 2018

Signal Structure For A Class Of Nonlinear Dynamic Systems, Meilan Jin

All Theses and Dissertations

The signal structure is a partial structure representation for dynamic systems. It characterizes the causal relationship between manifest variables and is depicted in a weighted graph, where the weights are dynamic operators. Earlier work has defined signal structure for linear time-invariant systems through dynamical structure function. This thesis focuses on the search for the signal structure of nonlinear systems and proves that the signal structure reduces to the linear definition when the systems are linear. Specifically, this work: (1) Defines the complete computational structure for nonlinear systems. (2) Provides a process to find the complete computational structure given a state ...


Fitting Als Reflectance Data Using Python, R. Steven Turley Apr 2018

Fitting Als Reflectance Data Using Python, R. Steven Turley

All Faculty Publications

This article describes how to use the python refl library in https://bitbucket.org/steve_turley/reflectance-fitting to fit thin film reflectance data from the Advanced Light Source (ALS) at Lawrence Berkeley National Labs. It uses data taken for a thin film of aluminum capped by a thin film of aluminum fluoride on a silicon nitride substrate. The single fit in the example shown here shows the importance of taking into account the oxidation of the aluminum layer as part of the fit.


Blockchain: Technical Review, Evan D. Poff Apr 2018

Blockchain: Technical Review, Evan D. Poff

Marriott Student Review

This review of blockchain technology accompanies the article "Strategic Implications of Blockchain."


Buzzwords, Evan D. Poff Apr 2018

Buzzwords, Evan D. Poff

Marriott Student Review

This feature will explain the following buzzwords:

  • Blockchain
  • Cryptocurrency
  • Work-Life Integration
  • Passive Equities
  • Risk-Adjusted Returns